• The identification and characterization of inter- and intra-species genetic diversity derived from retrotransposons in humans

      Tang, Wanxiangfu; Department of Biological Sciences (Brock University, 2013-01-14)
      Retrotransposons, which used to be considered as “junk DNA”, have begun to reveal their immense value to genome evolution and human biology due to recent studies. They consist of at least ~45% of the human genome and are more or less the same in other mammalian genomes. Retrotransposon elements (REs) are known to affect the human genome through many different mechanisms, such as generating insertion mutations, genomic instability, and alteration in gene expression. Previous studies have suggested several RE subfamilies, such as Alu, L1, SVA and LTR, are currently active in the human genome, and they are an important source of genetic diversity between human and other primates, as well as among humans. Although several groups had used Retrotransposon Insertion Polymorphisms (RIPs) as markers in studying primate evolutionary history, no study specifically focused on identifying Human-Specific Retrotransposon Element (HS-RE) and their roles in human genome evolution. In this study, by computationally comparing the human genome to 4 primate genomes, we identified a total of 18,860 HS-REs, among which are 11,664 Alus, 4,887 L1s, 1,526 SVAs and 783 LTRs (222 full length entries), representing the largest and most comprehensive list of HS-REs generated to date. Together, these HS-REs contributed a total of 14.2Mb sequence increase from the inserted REs and Target Site Duplications (TSDs), 71.6Kb increase from transductions, and 268.2 Kb sequence deletion of from insertion-mediated deletion, leading to a net increase of ~14 Mb sequences to the human genome. Furthermore, we observed for the first time that Y chromosome might be a hot target for new retrotransposon insertions in general and particularly for LTRs. The data also allowed for the first time the survey of frequency of TE insertions inside other TEs in comparison with TE insertion into none-TE regions. In summary, our data suggest that retrotransposon elements have played a significant role in the evolution of Homo sapiens.
    • Identification and characterization of polymorphic mobile elements (MEs) in humans

      Dahi, Zakia; Department of Biological Sciences
      Retrotransposons are mobile elements (MEs) that propagate in a “copy and paste” fashion in the genomes via RNA intermediates. In the human genome, retrotransposons consist of long terminal repeats (LTRs), long interspersed elements (LINEs), short interspersed elements (SINEs), SINE-VNTR- Alus (SVAs), and processed pseudogenes (PPSGs), and they collectively contribute close to 50% of the genome. Some members of these MEs continue to undergo retrotransposition, thereby generating a type of structural variations (SVs) within and between human populations by the presence and absence of ME insertions at specific genomic locations. A large number of such polymorphic MEs have been previously reported and documented, including cases associated with diseases, but with limited sequence characterization and genotype analysis. In this study, we performed extensive computational analysis and compilation of polymorphic MEs from multiple sources. We focused on characterization of complete sequences representing the insertion alleles and pre-integration alleles of ME polymorphic loci, using methods including local sequence assembly based on rich personal genome sequence data for many entries. Further, we performed in silico genotyping and population distribution for these polymorphic MEs for 2600 human subjects representing 28 well recognized populations around the world, as well as phylogenetic analysis of these human subjects using these polymorphic MEs as markers. We identified a total of 4400 polymorphic MEs with full sequence characterization for both the pre-integration and insertion alleles. Among these, 1267 entries represent new insertions not previously documented in the Database of Retrotransposon Insertion Polymorphisms in humans (dbRIP), and 1777 entries represent ME insertions outside the current human reference genome. By individual populations and all samples as whole, all 5 ME types displayed a similar allele distribution pattern with the majority having an allele frequency at 0.5, while differences across ME types are also seen at the very low frequency range. Nevertheless, polymorphic MEs do show substantial geographic differentiation, with numerous continent-specific loci identified. Polymorphic ME-based clustering of human subjects seems to correlate well with what we know about the history and relationship of human populations, indicating the usefulness of polymorphic MEs as markers for studying human evolution. Furthermore, polymorphic MEs were found to participate in both coding and regulatory sequences, signifying their potential contribution to the phenotypic diversity present among human populations and individuals. In conclusion, polymorphic MEs represent a significant source of human genetic diversity with potentials on impacting the structure, function, and evolution of the human genome.
    • Identification of transcripts associated with postharvest withering in Vitis vinifera L. ‘Cabernet Franc’ grape berry

      Cathline, Kimberley; Department of Biological Sciences
      The withering of grape berries following harvest is known in Italian as appassimento, and it used as a tool to alter the composition of the berries prior to winemaking. Specific gene expression patterns were determined by RNA Sequencing in the red-skinned berries of Vitis vinifera L. ‘Cabernet Franc’ for three time points during withering, at both slow and fast rates, up to 40.7 and 31.2 percent cluster weight loss respectively, with a target of 29 + 1 oBrix. Slow withering was associated with a higher number of differentially expressed genes, and those commonly up-regulated across all time points were associated with a higher number of gene ontology categories, including phenylpropanoid and cellular aromatic compound metabolism and biosynthesis. Commonly up-regulated genes across fast drying were only related to response to abiotic and biotic stimuli terms. Both slow and fast withering were associated with an up-regulation of numerous WRKY and MYB transcription factors, as well as stilbene synthase, phenylalanine ammonia lyase and trehalose-phosphate phosphatase. With respect to anthocyanin biosynthesis, there was no change in expression for MYBA genes, and UDP-glucose:flavonoid 3-O-glucosyltransferase was down-regulated transiently in fast withering and showed no change in expression in slow. Slow withering was also associated with an up-regulation of a dehydrin and the CBF3 gene. The results of the present study suggest that fast withering may be associated with primarily an intense stress response, while slow withering may be associated with a senescence or over-ripening, in combination with a gradual adaptation to a less intense dehydration stress. As such, the influence of rate during withering will likely have a strong impact on the final berry composition, and thus will influence the characteristics of the resulting wines.
    • Identifying the effect of clone and rootstock on viticultural performance, fruit composition and winemaking potential for Pinot Noir, Chardonnay and Riesling, in Niagara, Ontario.

      Barker, Andrea; Department of Biological Sciences
      Previous research globally has demonstrated that the performance of grapevine clone and rootstock combinations on vine performance and fruit quality are region-specific. Consequently, it is imperative for the Ontario wine industry to have locally-relevant information on the performance of vine combinations before these selections are purchased and established in vineyards. The objective of this research is to identify the influence of clone and rootstock combination on vine performance, fruit composition and oenological potential for core Ontario varieties: Pinot noir (clones: 113, 114, 115 and 777 on rootstock Riparia Gloire), Chardonnay (clones: 548, 96, 95 and 76 on rootstock Selektion Oppenheim 4), and Riesling (clones 9, 12 and 21 on rootstock SO4; clones 239, 49 and 21 on rootstock SO4; rootstocks 101-14, SO4 and 5C on clone 9; and rootstocks 3309C and SO4 on clone 21) over the course of multiple growing seasons and vintages, 2017 and 2018. Replicated blocks for each treatment were established in one of three commercial vineyards within the Niagara region. Vine performance was measured by timing of phenological stages, yield components, vine balance, disease and winter injury. Fruit composition was determined by measuring acid and soluble solid content of 100-berry samples taken from sentinel vines. Fruit was harvested from select research blocks and fermented into wine to evaluate oenological potential through must composition analysis, fermentation kinetics and finished wine composition analysis. Results indicate significant (p≤0.05) differences in all cultivars in both years, for the effects of clone and rootstock on vine performance, fruit composition and oenological potential in Niagara. However, trends were generally not consistent across years, indicating further vintages will be required to eliminate the weather-related differences between years. This project is limited by its duration of two years. Research from additional vintages is required in order to further understand the effects of clone and rootstock selection under Niagara vineyard conditions.
    • Immuno-cytochemical localization of glycoproteins involved in recognition and attachment in a mycoparatism

      Su, Longcheng.; Department of Biological Sciences (Brock University, 1992-07-09)
      Polyclonal antibodies prepared against the two glycoproteins (Mr 100 and 85 kDa) involved in recognition and attachment of the mycoparasite, Piptocephalis virginiana, to its hosts, Mortierella pusilla and Phascolomyces articulosus, susceptible and resistant, respectively, were employed to localize the antigens at their cell surfaces. Indirect immunocytochemical technique using secondary antibodies labelled with either FITC or gold particles as probes, were used. FITC-Iabelled antibodies revealed a discontinous pattern of fluorescence on the hyphae of MortlerelLa pusilla and no fluorescence on the hyphae of Phascolomyces articulosus. Intensity of fluorescence was high in the germinating spores of both the fungi. Fluoresence could be observed on P. articulosus hyphae pretreated with a commercial proteinase. Fluorescence was not observed on either hyphae or germinating spores of the nonhost M0 r tie re11 a ca ndelabrum and the mycoparasite P. virginiana. Antibodies labelled with gold conjugate showed a different pattern of antigen localization on the hyphal walls of the susceptible and resistant hosts. Patches of gold particles were observed allover the whole cell wall of the susceptible host but only on the inner cell wall layer of the resistant host. Cell wall fragments of the susceptible host but not those of the resistant host, previously incubated with the antibodies inhibited attachment of the mycoparasite. Implications of preferential localization of the antigen in the resistant host and its absence in the nonhost are described.
    • Immuno-gluorescence study of five zygomycetous fungi with two chitin-binding probes

      Sahai, Amarpal S.; Department of Biological Sciences (Brock University, 1993-07-09)
      A polyclonal antiserum was prepared against a purified microsomal chitinase isolated from the fungus Choanephora cucurbitarum. Indirect immunofluorescence was used to localize chitinase at various developmental stages of five zygomycetous fungi and during abiotrophic mycoparasite interaction with a susceptible and resistant host. This was compared to localization of oligomers of N-acetylglucosamine with the lectin wheat germ agglutinin (WGA). Dotimmunoblot and Western blot techniques revealed that the anti-serum reacted strongly with the antigen from which it was derived. Cross reactivity of the antiserum was found with WGA and another chitin binding lectin, Phyto/acca americana agglutinin (PAA). Immuno-fluorescence results showed the direct involvement of chitinase in spore swelling, germination, sporangium development and response during mechanical injury. There appeared to be no involvement of chitinase during apical hyphal growth or new branch initiation in any of the fungi tested despite mild proteolysis and permeabilization of the cell surface prior to labelling. Binding with WGA revealed similar patterns of fluorescence to that of chitinase localization but differed by showing fluorescence and therefore chitin localization at the apex and new branch initiation when tested at different developmental stages. There was no difference between chitinase localization and binding with WGA in a susceptible host and resistant host challenged with the mycoparasite, Piptocephalis virginiana. Differences in binding ability of antichitinase and lectin WGA suggests that the latter is not a suitable indicator for indirect localization of the lytic enzyme, chitinase.
    • Immunohistochemical study of laterodorsal tegmental neurons active during 22kHz vocalization /

      Savoy, Alison E.; Department of Biological Sciences (Brock University, 2005-06-29)
      An ascending cholinergic projection, which originates in the laterodorsal tegmental nucleus (LDT), was implicated in the initiation of ultrasonic vocalization. The goal of this study was to histochemically examine the activity the LDT following ultrasonic calls induced by two methods. It was hypothesized that cholinergic LDT cells would be more active during air puffinduced vocalization than carbachol-induced one. Choline acetyltransferase (ChAT), and cFos protein were visualized histochemically as markers of cholinergic calls and cellular activity, respectively. Results indicated that animals vocalizing after carbachol, but not after air puff, had a significantly higher number of Fos labeled nuclei within the LDT than non vocalizing controls. A significantly higher number of doublelabeled neurons were discovered in the LDT of vocalizing animals (in both groups) as compared to control conditions. Thus, there were significantly more active cholinergic cells in the LDT of vocalizing than non-vocalizing rats for both methods of call induction.
    • The impact of the Multicolor Asian Lady Beetle (Harmonia axyridis) on wine quality /

      Lin, Yong.; Department of Biological Sciences (Brock University, 2004-06-29)
      The Impact of the Multicolor Asian Lady Beetle (Harmonia axyridis) on Niagara Wine Quality The possible influence of Harmonia axyridis (the Multicolored Asian Lady Beetle) on the sensory properties of wine was investigated. H. axyridis beetles were added to white and red grape musts at a rate of 0, 1 or 10 per L, and a trained panel evaluated the finished wines using flavor-profiling techniques. Significant modification of both wine aroma and flavor characteristics were observed in the 10 beetlelL treatments, with smaller effects noted at the 1 beetlelL rate. Vinification in the presence of H. axyridis gave higher intensity scores for peanut, bell pepper and asparagus aromas and flavors in the white wines, and peanut, asparagus/bell pepper, and earthy/herbaceous aromas and flavors in the red wines. In addition, sweet, acid and bitter tastes were affected in red wines, and a general trend of decreasing fruit and floral intensities with increasing beetle rate was observed in both white and red wines. 15 ngIL Isopropylmethoxypyrazine was added to control wines and sensory profiles similar to high beetle treatments were obtained, supporting the hypothesis that methoxypyrazines from beetles are implicated in the taint. A trained panel evaluated the treated wines after 10 months of aging using the same sensory methods described above. Sensory profiles were very similar. Fennenting in the presence of Harmonia Axyridis (HA) had little influence on the chemical composition of the ftnished wine. The notable exception IS Isopropylmethoxypyrazine content, which was assessed usmg GC-MS analysis and showed increased concentration with increasing beetle nwnber for both white and red wmes. The influence of potential remedial treatments on the sensory properties of white and red wines tainted by Harmonia axyridis were also investigated. Bentonite, activated charcoal, oak chips, de-odorized oak chips, and UV or light irradiation were applied to tainted wine, and these wines evaluated chemically and sensorially. Both white and red wines treated with oak chips had strong oak characteristics, which masked the Harmonia axyridis-associated aroma and flavour attributes. In red wine, asparagus/bell pepper characteristics were decreased by bentonite and charcoal treatments. Only activated charcoal significantly decreased methoxypyrazine levels and only in white wine.
    • The impact of wine closure and packaging type, and light and temperature exposure on the concentration of 3-alkyl-2 -methoxypyrazines and other key constituents of wine

      Blake, Amy J.; Department of Biological Sciences (Brock University, 2009-02-16)
      3-alkyl-2-methoxypyrazines (MPs) are grape- and insect-derived odor-active compounds responsible for vegetative percepts that are detrimental to wine quality when elevated. This study tested both the effect of closure/packaging types and light/temperature storage conditions on MPs (isopropyl-, secbutyl-, and isobutyl-MP) in wine. An MP-emiched wine rapidly (after 140 hours) and significantly decreased in MP concentration after natural and synthetic cork contact (immersion of closures in wine). This decrease was greatest with synthetic closures (70% - 89% reduction) and secbutyl-MP. Subsequently storage trials tested the effects of commercial closure/packaging options (natural cork, agglomerate cork, synthetic corks, screwcaps and TetraPak® cartons) on MPs in MP-emiched Riesling and Cabernet Franc over 18 months. Regardless of packaging, isobutyl-MP was the most altered from bottling. Notably, all MP levels tended to decrease to the greatest extent in TetraPak® cartons (~34% for all MPs) and there was evidence of contribution ofisoproyl- and secbutyl-MP from cork-based closures (i.e. ~30% increase in secbutyl-MP after 6 months) or from an unidentified wine constituent. To test the effects of various light/temperature conditions (light exposed at ambient temperature in three different bottle hues, light excluded at ambient temperature and light excluded at a "cellar" temperature (14°C)), MP-emiched Riesling and Cabernet Franc were also analyzed for MP concentrations over 12 months. MPs did not vary consistently with light or temperature. Other odorants and physico-chemical properties were tested in all wines during storage trials and closely agree with previous literature. These results provide novel insights into MPs during ageing, interactions with packaging and storage conditions, and assist in the selection of storage conditions/packaging for optimal wine quality.
    • The Implications of Forager Behaviour for Social Organisation in a Socially Polymorphic Carpenter Bee (Xylocopa virginica)

      Course, Chris; Department of Biological Sciences (2013-04-01)
      In social Hymenoptera, the division of labour is a major step in the evolution of sociality. Bees, which express many different kinds of sociality, can be classified according to how individuals share or do not share foraging and reproductive activities (Michener, 1974). The large carpenter bee, Xylocopa virginica, lives in populations with both solitary and social nests. In social nests, reproduction is controlled by the dominant female, who does all of her own foraging and egg-laying, while the subordinates guard the nest only. This study examined foraging behaviour as a way to classify the social hierarchy. Individual females were marked, measured and intensely observed for the foraging season. It was found that a large number of subordinates forage and likely obtain more reproductive fitness than previously thought. The dominance hierarchy is very likely a social queue, in which bees take turns foraging and egg-laying.
    • Incidence of resistance to benzimidazole fungicides in a field population of Venturia inaequalis /

      Moftah, Housain Gadmoor.; Department of Biological Sciences (Brock University, 2000-05-21)
      The allele-specific polymerase chain reaction (PCR) was used to screen for the presence of benomyl resistance, and to characterize their levels and frequencies in field populations of Venturia inaequalis during two seasons. Three hundred isolates of V. inaequalis were collected each season from infected leaves of MalusX domestica. Borkh c.v. Mcintosh. The trees used were sprayed in the year prior to collection with five applications of benomyl, its homologue Azindoyle, or water. Monoconidial isolates of V. inaequalis were grown on 2% potato dextrose agar (PDA) for four weeks. Each isolate was taken from a single lesion from a single leaf. Total genomic DNA was extracted from the four week old colonies of V. inaequalis, prepared and used as a template in PCR reactions. PCR reactions were achieved by utilizing allele-specific primers. Each primer was designed to amplify fragments from a specific allele. Primer Vin was specific for mutations conferring the ben^^"^ phenotype. It was expected to amplify a 171 bp. DNA fragment from the ben^"^ alleles only. Primers BenHR and BenMR were specific for mutations conferring the ben"" and ben'^'' phenotypes, respectively. They were expected to amplify 172 bp. and 165 bp. DNA fragments from the ben"" and ben"^" alleles, respectively. Of the 953 isolates tested, 414 (69.9%) were benomyl sensitive (ben^) and 179 (30.1%) were benomyl resistant. All the benomyl resistant alleles were ben^"", since neither the ben"" nor the ben"" alleles were detected. Frequencies of benomyl resistance were 23%, 24%, and 23% for the 1997 collections, and were 46%, 26% and 38% for the 1998 collections for benomyl, Azindoyle and water treatments, respectively. Growth assay was performed to evaluate the applicability of using PCR in monitoring benomyl resistance in fungal field populations. Tests were performed on 14 isolates representing the two phenotypes (ben^ and ben^"'' alleles) characterized by PCR. Results of those tests were in agreement with PCR results. Enzyme digestion was also used to evaluate the accuracy and reliability of PCR products. The mutation associated with the ben^"'' phenotype creates a unique site for the endonuclease enzyme Bsh^236^ allowing the use of enzyme digestion. Isolates characterized by PCR as ben^'^'^ alleles had this restriction site for the SsA7l2361 enzyme. The most time consuming aspect of this study was growing fungal isolates on culture media for DNA extraction. In addition, the risk of contamination or losing the fungus during growth processes was relatively high. A technique for extracting DNA directly from lesions on leaves has been used (Luck and Gillings 1 995). In order to apply this technique in experiments designed to monitor fungicide resistance, a lesion has to be homogeneous for fungicide sensitivity. For this purpose, PCR protocol was used to determine lesion homogeneity. One hundred monoconidial isolates of V. inaequalis from 10 lesions (10-conidia/ lesion) were tested for their phenotypes with respect to benomyl sensitivity. Conidia of six lesions were homogeneous, while conidia of the remaining lesions were mixtures of ben^ and ben^ phenotypes. Neither the ben" nor the ben' phenotype was detected.
    • Individual differences and factors affecting male behaviour in field crickets

      Wyatt, David Ross.; Department of Biological Sciences (Brock University, 1981-07-09)
      Individual differences in male sexual behav~our and the factors influencing calling behaviour were studied in the field crickets Gryllus 2 integer and Q. veletis. In a large (13m) outdoor arena individually numbered adult male ~~ integer started calling at three to five days of age but thereafter the age of individual G. integer males did not affect nightly calling duration. Calling also did not correlate with individual weight. In this study individual male calling was continuously distributed from 0 hrs. per night to 3.5 hrs. per night, on average. A temporal effect on the number of G. integer males calling was observed. The number of males calling through the night was uniform, but a sharp increase in the number calling was observed in the early morning. No difference in calling times was observed between the night and dawn callers. AlsC)' males calling at dawn usually didnotc'all during the preceeding night. Calling and reproductive success in 1979 demonstrated a negative logarithmic relationship while in the 1980(initial) population a negative linear relationship was observed. No relationship was seen in the 1980 high density population. The ratio of non-callers to callers also affected the mating of individuals in the 1979 and1980(initial) densities:-non~callers (males calling .5 hrs. per night, on average, or less) obtained more females when the population contained a high number of callers, this being a negative logarithmic relationship to, No such relationship was observed in the 1980 high density population. Individual displacement varied nightly and was not correlated to amount of calling or reproductive success of individual G. integer males. G. integer males were displa~ed more when in a higher density in the outdoor arena Male G. integer and G. veletis behaviours were also observed in an indoor arena at different densities and, in G. veletis, with respect to female presence. When females were present in the arena, in G. veletis, male calling was reduced. Males of both species called less, on average, when in ~ higher density, than when they were in a lower density. Male displacement of both species increased on average when in a higher density as compared to displacement in a lower density. Aggression was measured by aggressive call-ing and fighting and was studied in regards to density.G. integer demonstrated less aggression in all but one comparison at higher density. No difference was observed in the ratio of aggressive calling to f.ighting comparison in G. integer. G. veletis demonstrated mixed results. No difference in aggression between densities was observed in comparisons. Less.aggression did occur in higher densities when comparisons invol.ved fighting behaviour. Male behaviour represents a competitive strategy against ot~er males, strategy being defined as a genetic (in part) alternative to other strategies. In this sense, the factors of time, density, male-male aggression, and female presence are conditions demonstrated to affect male behaviour in G. integer and G. veletis. Individual male differences and other considerations suggest that alternative male behaviours are represented by at least two conditional strategies. This possibility, and the transient 'or stable nature of genetic polymorphisms in field cricket behaviour are considered.
    • The influence of carbon dioxide on growth and metabolism of etiolated Avena sativa 1 coleoptiles

      Thein, Aung.; Department of Biological Sciences (Brock University, 1972-07-09)
      The influence of carbon dioxide on growth and protein synthesis of etiolated Avena coleoptiles was investigated. Evidence is presented that 0.03% carbon dioxide stimulated both these processes; and that carbon dioxide stimulated growth depends on carbon dioxide stimulated protein synthesis, In addition the evidence indicates that carbon dioxide stimulated growth is mediated by metabolism, and that carbon dioxide stimulates growth through a dark fixation process. Growth studies also demonstrated that IAA and carbon dioxide stimulated growth in a synergistic manner.
    • Influence of dietary nutrients on life history-related traits of black flies and mosquitoes

      Antwi-Amoabeng, Daniel; Department of Biological Sciences (Brock University, 2013-02-22)
      The sugar-feeding ecology of dipteran vectors has recently been targeted because it presents opportunities to inoculate common food sources for these dipterans with entomopathogenic bacteria as a means of controlling the population of host-seeking adult dipteran vectors. Whereas this approach to vector control holds some promise, differences in the nutrient composition and concentration in sugary food sources can influence the food selection pattern of dipteran vectors and potentially confound the outcomes of field trials on the efficacy of entomopathogenic bacteria as vector control agents. Further, nutrient components of bacteria-inoculated artificial diets may present unintended effects of extending the survivorship or fecundity of the target population and potentially render the whole approach counterproductive. The present study investigated the diet-specific factors that influence the foraging decisions of female Simulium venustum/verecundum (Diptera: Simuliidae) and female Anopheles stephensi (Diptera: Culicidae) on artificial nectar and honeydew. Paired choice experiments showed that the black flies forage more frequently from high calorie diets, which contained melezitose, or those diets that contained amino acids, compared to low calorie melezitose-free diets or amino acid-free diets. The mosquitoes however displayed a more random diet selection pattern. The effects of sugary diets on certain life-history traits considered to be important to the ecological fitness of the black flies and mosquitoes were also investigated. Sugary diets had no significant effect on the survivorship and fecundity of the black flies, but they influenced the resistance of Leucocytozoon-infected flies to the parasite. Amino acid-containing diets appeared to extend the survival of mosquitoes, and also allowed them to take more vertebrate blood when they blood fed.
    • The influence of investigator disturbance on aggressive behaviour and breeding success of ring-billed gulls (Larus delawarensis) /

      Brown, Kevin M.; Department of Biological Sciences (Brock University, 1992-05-21)
      Increased losses of eggs and chicks resulting from human intrusion (investigator or other) into seabird colonies has been well documented. In 1990/91, I studied the effects of investigator disturbance on aggressive behaviour and breeding success of individual pairs of ring-billed gulls nesting at two colonies near Port Colborne, Ontario. The insular colony was on an artificial breakwall, associated with the Welland Ship Canal, approximately 1 km off the north shore of Lake Erie. The mainland colony was adjacent to the canal approximately 1 km east of the breakwall. The frequencies of adult threat and assault behaviours, chick movement and adult attacks on chicks were recorded by continuous scan sampling 30 min prior to, 30 min during and 60 (2 X 30) min after investigator disturbance. The frequency of threat and assault behaviours increased during the period of investigator activity in the colony while the duration of wingpulls and beakpulls decreased. Significantly more chicks ran ("runners") from their natal territories during disturbances and "runners" were more frequently attacked than "territorial" chicks. No chicks were fatally attacked during disturbance and "runners" returned to their natal territories quickly after disturbance. Breeding success was determined for pairs nesting in study plots subjected to two levels of disturbance (normal and moderate). The disturbance level of each plot differed in visitation frequency and activities performed on each visit. Investigator disturbance had no effect on the hatching success or fledging success (taken as 21 days of age) of ring-billed gull study pairs at either colony.
    • The Influence of Male Diet on Life History Traits of Female Mosquitoes

      Abraham, Ben; Department of Biological Sciences (Brock University, 2014-01-08)
      In the field, mosquitoes characteristically feed on sugars soon after emergence and intermittently during their adult lives. Sugar meals are commonly derived from plant nectar and homopteran honeydew, and without them, adults can only survive for a few days on larval reserves. In addition to sugar, females of most species rely on blood for the initiation and maintenance of egg development; thus their reproductive success depends to some extent on the availability of blood hosts. Males, on the other hand, feed exclusively on sugars. Consequently, their sexual maturation and reproductive success is largely dependent upon access to sugar sources. Plant nectar and homopteran honeydew are the two main sugar sources utilized by mosquitoes in the wild. Previous laboratory studies had shown that differences between nectar sources can affect the survivorship and biting frequency of disease vectoring mosquitoes. However, little is known on how sugar composition influence the reproductive processes in male mosquitoes. Male mosquitoes transfer accessory gland proteins and other hormones to their mates along with sperm during mating. In the female, these seminal fluid constituents exert their influence on reproductive genes that control ovulation and vitellogenesis. The present study tests the hypothesis that the mates of males consuming different sugar meals will exhibit varying levels of induction of vitellogenin (a gene which regulates the expression of egg yolk precursor proteins). Real-time quantitative RT-PCR was used to investigate how each sugar meal indirectly influences vitellogenin mRNA abundance in female Anopheles stephensi following mating. Results indicate that mates of nectar-fed males exhibit 2-fold greater change in vitellogenin expression than the mates of honeydew-fed males. However, this response did not occur in non-blood fed controls. These findings suggest that the stimulatory effect of mating on vitellogenesis in blood meal-reliant (i.e. anautogenous) mosquitoes may only be synergistic in nature. The present study also sought to compare the potential fitness costs of mating incurred by females that do not necessarily require a blood meal to initiate a reproductive cycle (i.e., exhibit autogeny). Females of the facultatively autogenous mosquito, Culex molestus were allowed to mate with males sustained on either nectar or honedyew. Mean lifetime fecundity and survivorship of females under the two different mating regimes were then recorded. Additionally, one-dimensional gel electrophoresis was used to verify the transfer of male accessory gland proteins to the sperm storage organs of females during mating.While there was no significant difference in survival between the test treatments, the mates of nectar-fed males produced 11% more eggs on average than mates of honeydew-fed males. However, additional data are needed to justify the extrapolation of these findings to natural settings. These findings prompt further investigation as the differences caused by diet variation in males may be reflected across other life history traits such as mating frequency and insemination capacity.
    • Influence of temperature and photoperiod upon ionic regulation in rainbow trout Salmo gairdneri

      Murphy, Patrick George Francis.; Department of Biological Sciences (Brock University, 1977-07-09)
      Interactions of photoperiod and temperature upon waterelectrolyte balance were examined in rainbow trout acclimated to six combinations of two photoperiods {18h light: 6h dark, o 6h light: l8h dark) and three temperatures (2, 10 and 18 C). The influence of temperature and photoperiod upon plasma, skeletal muscle, cardiac muscle and liver levels of sodium, potassium, magnesi.um, calcium, chloride, water content, water distribution and cellular ion concentrations was determined by a one way analysis of variance. Significant (p < 0.05 or better) temperature effects at common photoperiods were observed in 70% of the analyses performed, showing no bias toward either photoperiod. Significant photoperiod effects occured in 57% of the analyses performed at common temperatures. The influence of photoperiod was most prevalent at reduced temperatures. Potassium and magnesium appeared to be particularly thermosensitive, while sodium and calcium were the most photosensitive of the electrolytes. The ionic composition of all tissues studied were relatively thermosensitive, with liver apparently being the most sensitive. On the other hand; the ionic composition of skeletal and cardiac muscle appear to be the mos.t photosensitive of the tissues examined. Water content and distribution in skeletal muscle and liver were significantly influenced by temperature in 50% of the analyses performed showing a very strong bias toward UwinterU animals. Photoperiod effects were significant in 56% of the water parameters measured with a strong bias toward the two lower temperatures. Body weight was of significant influence in 16% of the 174 analyses performed. These data are discussed in terms of the effect of temperature upon ionregulatory mechanisms and the possible impact of photoperiod variations on endocrine systems influencing water-electrolyte metabolism.
    • The influence of water on the glucose affinity of hexokinase

      Reid, Charles Robert.; Department of Biological Sciences (Brock University, 1995-07-09)
      In the present thesis, the role of hydration during the glucose induced conformational change of hexokinase is investigated. This is accomplished by applying the osmotic stress technique. The osmotic stress technique is founded on varying of the activity of water in a system in order to determine ifs effects. This is accomplished by adding inert solute molecules that are excluded from the system under study. The solute molecules used within the present investigation are Polyethylene glycols (PEGs). PEGs aid in the removal of water from hexokinase by exerting osmotic pressure. The osmotic pressures of the PEG solutions are also measured with both vapour pressure osmometry and secondary osmometry with phospholipids. An interesting discovery is made in that the osmotic pressures of PEG and co-solute solutions are non-additive. This indicates that PEG concentrates co-solutes in solution by making a certain proportion of the water inaccessible. Glucose binding was measured fluorometrically and the glucose equilibrium dissociation constant (GEDC) of hexokinase is measured in solutions containing the different MW PEGs. Changes in the sensitivity of the glucose affinity with osmotic pressure allows the calculation of the change in the numbers of polymer-inaccessible water molecules upon the binding of glucose to hexokinase ~Nw. It was determined the ~Nw decreases with increases in osmotic pressure in the presence of all MW PEGs. ~Nw decreases from values between 45-290 water molecules at low pressure to approximately 15 at high pressure. There is also a molecular weight dependence observed. There are large decreases in ~Nw with osmotic pressure in the presence of PEGs above MW 1000. However, below MW 1500 changes in ~Nw with osmotic pressure are relatively small. These findings are interpreted with respect to two possible mechanisms involving changes in the conformation of hexokinase u~der osmotic pressure and the access of the PEG molecules to water surrounding hexokinase.
    • Interactions between the cholinergic and dopaminergic system during the production of ultrasonic vocalizations in rats

      Silkstone, Michael; Department of Biological Sciences (Brock University, 2012-10-11)
      Rats produce ultrasonic vocalizations that can be categorized into two types of ultrasonic calls based on their sonographic structure. One group contains 22-kHz ultrasonic vocalization (USVs), characterized by relatively constant (flat) frequency with peak frequency ranging from 19 to 28-kHz, and a call duration ranging between 100 – 3000 ms. These vocalization can be induced by cholinomimetic agents injected into the ascending mesolimbic cholinergic system that terminates in the anterior hypothalamic-preoptic area (AH-MPO) and lateral septum (LS). The other group of USVs contains 50-kHz USVs, characterized by high peak frequency, ranging from 39 to 90-kHz, short duration ranging from 10-90 ms, and varying frequency and complex sonographic morphology. These vocalizations can be induced by dopaminergic agents injected into the nucleus accumbens, the target area for the mesolimbic dopaminergic system. 22-kHz USVs are emitted in situations that are highly aversive, such as proximity of a predator or anticipation of a foot shock, while 50 kHz USVs are emitted in rewarding and appetitive situations, such as juvenile play behaviour or anticipation of rewarding electrical brain stimulation. The activities of these two mesolimbic systems were postulated to be antagonistic to each other. The current thesis is focused on the interaction of these systems indexed by emission of relevant USVs. It was hypothesized that emission of 22 kHz USVs will be antagonized by prior activation of the dopaminergic system while emission of 50 kHz will be antagonized by prior activation of the cholinergic system. It was found that injection of apomorphine into the shell of the nucleus accumbens significantly decreased the number of carbachol-induced 22 kHz USVs from both AH-MPO and LS. Injection of carbachol into the LS significantly decreased the number of apomorphine-induced 50 kHz USVs from the shell of the nucleus accumbens. The results of the study supported the main hypotheses that the mesolimbic dopaminergic and cholinergic systems function in antagonism to each other.
    • Interactions between the cholinergic and dopaminergic systems during the production of ultrasonic vocalizations in rats

      Silkstone, Michael; Department of Biological Sciences (Brock University, 2012-09-18)
      Rats produce ultrasonic vocalizations that can be categorized into two types of ultrasonic calls based on their sonographic structure. One group contains 22-kHz ultrasonic vocalization (USVs), characterized by relatively constant (flat) frequency with peak frequency ranging from 19 to 28-kHz, and a call duration ranging between 100 – 3000 ms. These vocalization can be induced by cholinomimetic agents injected into the ascending mesolimbic cholinergic system that terminates in the anterior hypothalamic-preoptic area (AH-MPO) and lateral septum (LS). The other group of USVs contains 50-kHz USVs, characterized by high peak frequency, ranging from 39 to 90-kHz, short duration ranging from 10-90 ms, and varying frequency and complex sonographic morphology. These vocalizations can be induced by dopaminergic agents injected into the nucleus accumbens, the target area for the mesolimbic dopaminergic system. 22-kHz USVs are emitted in situations that are highly aversive, such as proximity of a predator or anticipation of a foot shock, while 50 kHz USVs are emitted in rewarding and appetitive situations, such as juvenile play behaviour or anticipation of rewarding electrical brain stimulation. The activities of these two mesolimbic systems were postulated to be antagonistic to each other. The current thesis is focused on the interaction of these systems indexed by emission of relevant USVs. It was hypothesized that emission of 22 kHz USVs will be antagonized by prior activation of the dopaminergic system while emission of 50 kHz will be antagonized by prior activation of the cholinergic system. It was found that injection of apomorphine into the shell of the nucleus accumbens significantly decreased the number of carbachol-induced 22 kHz USVs from both AH-MPO and LS. Injection of carbachol into the LS significantly decreased the number of apomorphine-induced 50 kHz USVs from the shell of the nucleus accumbens. The results of the study supported the main hypotheses that the mesolimbic dopaminergic and cholinergic systems function in antagonism to each other.