• Activity of brainstem cholinergic neurons during 22 kHz ultrasonic vocalization in rats /

      Iku, Nwamaka.; Department of Biological Sciences (Brock University, 2007-06-09)
      Adult rats emit 22 kHz ultrasonic alann calls in aversive situations. This type of call IS a component of defensive behaviour and it functions predominantly to warn conspecifics about predators. Production of these calls is dependent on the central cholinergic system. The laterodorsal tegmental nucleus (LDT) and pedunculopontine tegmental nucleus (PPT) contain largely cholinergic neurons, which create a continuous column in the brainstem. The LDT projects to structures in the forebrain, and it has been implicated in the initiation of 22 kHz alarm calls. It was hypothesized that release of acetylcholine from the ascending LDT terminals in mesencephalic and diencephalic areas initiates 22 kHz alarm vocalization. Therefore, the tegmental cholinergic neurons should be more active during emission of alarm calls. The aim of this study was to demonstrate increased activity of LDT cholinergic neurons during emission of 22 kHz calls induced by air puff stimuli. Immunohistochemical staining of the enzyme choline acetyltransferase identified cell bodies of cholinergic neurons, and c-Fos immunolabeling identified active cells. Double labeled cells were regarded as active cholinergic cells. There were significantly more (p<O.05) c-Fos labeled cells in the LDT of vocalizing animals than in control (non-vocalizing air puffed and naIve non-airpuffed) animals. Although the numbers were low, there were also significantly more (p<O.05) doublelabeled neurons in the LDT of vocalizing animals than in the non-vocalizing controls. Such a difference between vocalizing and control animals was not found in the neighbouring PPT nucleus. Results suggest that there are cholinergic and non-cholinergic cells, which are selectively active in the LDT during emission of 22 kHz alarm calls.
    • Alicaligenes faecalis : identification and study of its antagonistic properties against Botrytis cinerea

      González, Dagoberto Rodriguez.; Department of Biological Sciences (Brock University, 1998-07-09)
      A Gram negative aerobic flagellated bacterium with fungal growth inhibitory properties was isolated from a culture of Trichoderma harzianum. According to its cultural characteristics and biochemical properties it was identified as a strain of Alcaligenes (aeca/is Castellani and Chalmers. Antisera prepared in Balbc mice injected with live and heat-killed bacterial cells gave strong reactions with the homologous immunogen and with ATCC 15554, the type strain of A. taeca/is, but not with Escherichia coli or Enterobacter aerogens in immunoprecipitation and dot immunobinding assays. Growth of Botrytis cinerea Pers. and several other fungi was significantly affected when co-cultured with A. taeca/is on solid media. Its detrimental effect on germination and growth of B. cinerea has been found to be associated with antifungal substances produced by the bacterium and released into the growth medium. A biotest for the antibiotic substances, based on their inhibitory effect on germination of B. cinerea conidia, was developed. This biotest was used to study the properties of these substances, the conditions in which they are produced, and to monitor the steps of their separation during extraction procedures. It has been found that at least two substances could be involved in the antagonistic interaction. One of these is a basic volatile substance and has been identified as ammonia. The other substance is a nonvolatile, dialysable, heat stable, polar compound released into the growth medium. After separation of growth medium samples by Sephadex G-10 column chromatography a single peak with a molecular weight below 700 Daltons exhibited inhibitory activity. From its behaviour in electrophoretic separation in agarose gels it seems that this is a neutral or slightly positively charged.
    • Alloparental care in a solitary bee

      Lewis, Vern, R.E.; Department of Biological Sciences (Brock University, 2014-08-18)
      Research into the evolutionary origins of sociality in insect colonies is changing emphasis from understanding how eusociality is maintained to how insects transition from solitary to social lifestyles. The pygmy carpenter bees (Ceratina spp.) offer an excellent model for investigating such factors as they have been historically thought of as solitary but have recently been shown to be socially polymorphic, which may indicate that they are currently in a transitive phase. By utilizing behavioural observation and experimental removal protocols, I show that extended parental care, as well as sibling care in Ceratina calcarata plays an important role in offspring development. I found, upon removal of the mother, that specifically produced ‘dwarf’ female offspring take over parental care roles in the nest. The existence of alloparental care and generational overlap suggests that although they are classified as solitary bees, C. calcarata possess the prerequisite behavioural repertoire for sociality.
    • Amino acid transport : the special case of a H/L-glutamate cotransport system in Asparagus sprengeri mesophyll cells /

      McCutcheon, Steve L.; Department of Biological Sciences (Brock University, 1987-06-09)
      The addition of L-Glutamate (L-GLU) and L-Hethionine ~ulfoximine (L-HSO) to mechanically isolated. photosynthetically competent, Asparagus sprengeri mesophyll cells ~u~pended in 1mM CaS04 cau~ed an immediate transient alkalinization of the cell su~pension medium in both the light and dark. The alkalinization response was specific and stereospecific as none of the L-isomers of the other 19 protein amino acids tested or D-GLU gave this response. Uptake of 14C-L-GLU was stimulated by the light. The addition of non-radioactive L-GLU. or L-GLU analogs together with 14C-L-GLU showed that only L-GLU and L-HSO stimulated alkalinization whilst inhibiting the uptake of 14C-L-GLU. Both the L-GLU dependent alkalinization and the upt~ke of 14C-L-GLU were stimulated when the external pH was decreased from 6.5 to 5.5. Increasing external K+ concentrations inhibited the uptake of 14C-L-GLU. Fusicoccin (FC) stimulated uptake. The L-GLU dependent alkalinization re~ponse exhibited monophasic saturation kinetics while the uptake of 14C-L-GLU exhibited biphasic saturation kinetics. In addition to a saturable component. the uptake kinetics also showed a linear component of uptake. Addition of L-GLU and L-MSO caused internal acidification of the cell as measured by a change in the distribution of 14C-DMO. There was no change in K+ efflux when L-GLU was added. A H+ to L-GLUinflux stoichiometry of 3:1 wa~ mea~ured at an external I.-GLU concentration of O.5mM and increased with increasing external 13 L-QLU concentration. Metabolism of L-GLU was detected manometrlcally by observing an increase in COa evolution upon the addition of L-QLU and by detection of i*C02 evolution upon the addition of »*C-L-GLU. »*C02 evolution was higher in the dark than in the light. The data are consistent with the operation of a H+/L-QLO cotransport system. The data also show that attempts to quantify the stoichlometry of the process were complicated by the metabolism of L-GLU.
    • Amplification of the DFR1 gene in Saccaromyces cerevisiae

      Ondrusek, Nancy K.; Department of Biological Sciences (Brock University, 1987-07-09)
      A new system was employed to study amplification of t,he DHF'R gene DFB,1 ) in Sa<,:;charoillYCB§. .Q~~Yi...S!i<;1~. . This system consists of a series of yeast strains containing a casset,te which encodes t he yeast, D..ERl gene ttghtly linked tjO a f usion of the yeast 1EU2. regulat,ory region wi tJ1 the LAQZ str ctural gene from E. cO.1-1 (,) . M. Clement , unpubl i,::;hed) . Th's casset;t e was shown t.o be integrat,ed int o a unj que chromosomal l ocati on in each strain . Yeast cells were se l ected for MTX-resistance and overproduction of ~ galac t osi d se ( B-gal ). Since the inserted DF'Rl and ~ACZ genes are independently regulated, it was thought that cel l s with this phenotype probably contain e d ampl if ications of the cassette. A lar ge variat ion in the f requn y o f MTX-resistance was found between the di ff e r ent str ains. These freqlen c ~ es r anged from about 2 x 10 - 7 fo r a population of cells containing the cassette integrated at, the BI J2.l gene in t,he middle of the long arm of chromosome V, to about 5 x 10-4 for a strain with the cassette i nserted in the r DNA cluster Abo It 85% of the MTX- res i stcmt iso l ates examined showed enhanced B·-gal act i v ity rel a t ive t o the parental strain . For the ma jorit y of strains, the mean B- gal activity in drug-r sistant clones was about 3 times that o f the parent following a single se l ect i on step . I n con t r ast, primary MTX-resistant derivat~ves of cells with the cassette inserted 3 at the rDNA cluster showed inc r eases in B- gal activity ranging from 9 - 14 f old r elative to the parent. Analysis of the latte r s train by Southe rn hybr idization indicated that the cassette was inde e d amplified several fold in MTX-re sistant derivatives. A sing l e strain, in which the cassette was inserted at the !lEA;], loc u.s , was used to examine in more detai 1 , the parameters affecting DFRl gene amplificat~ion in yeast . The mean B- gal activity in drug-resistant derivatives of this strain could be increased from 3 to 6 or 7 fold relative to the parent, by stepwise sel ection using increasing MTX concentrations. B-gal overproduction was found to be un stable in all primary and highly -resistant isolates examined. There was no indication, h owever, of a decrease i n growth r a t e in MTX-res i s tant cells which overproduced B - gal.
    • Amputation and heat induced protein synthesis in the regenerating forelimb of Notophthalmus viridescens

      Fraser, Gordon Andrew Donald.; Department of Biological Sciences (Brock University, 1989-07-09)
      This thesis compares the responses of regenerating forelimb tissues of the newt Notophthalmu..f vlridescens to the stresses of hyperthermia and ID.echanical injury of amputation. In particular, both quantitative and qualitative changes in the synthesis of soluble proteins in stump tissues, including those of the heat shock protein family (HSP70-1ike) were examined. Results from SDS-PAGEfluorography indicate that the trauma of amputation mimics the heat shock response both quantitatively and temporally in its transient repression of the synthesis of most normal cellular proteins, and qualitatively. in the locaJized expression of two unique proteins (hsp30 and hsp70). Fluorography of proteins separated by twodimensional gets revealed that thelCl4:alizedt amputation induced 70kDa protein (amp70) was distinct from the more basic newt hsp/hsc70 isoforms. Although limb amputation resulted in an increase in the synthesis of HSP70 mRNA analogous to that induced by heat 3.b.OCKf amp70 did not cross-react with murine monoclonal antibodies directed against both the inducible and cognate HSP70 proteins of the human. Thus, the possible relationship of amp70 to other members of the HSP70-1ike protein family remains unclear. Western analyses indicated that the levels of the constitutive form of HSP70 (hsc70) were found to be regulated in a stage-dependent manner in the distal stump tissues of the regen,erating forelimb of the newt. The highest levels were found in the mid-late bud stage, a period during which rapidly dividing blastema cells begin to redifferentiate in a proximodistal direction. Immediately after amputation) hsc70 synthesis and accumulation was depressed below steady-state levels measured in the unamputated limb~ The results are discussed in light of a possible role for HSPs and amputatio~ induced proteins in the epimorphic regeneration of the amphibian limb.
    • Analysis of a temperature sensitive mutation affecting aldehyde oxidase activity in Drosophila melanogaster

      Paterson, Roger C.; Department of Biological Sciences (Brock University, 1984-07-09)
      A strain of Drosophila melanogaster (mid america stock culture no. hl16) has been reported to be deficient in aldehyde oxidase activity (Hickey and Singh 1982). This strain was characterized during the course of this study and compared to other mutant strains known to be deficient in aldehyde oxidase activity. During the course of this investigation, the hl16 strain was found to be temperature sensitive in its viability. It was found that the two phenotypes, the enzyme deficiency, and the temperature sensitive lethality were the result of two different mutations, both mapping to the X-chromosome. These two mutations were found to be separable by recombination. The enzyme deficiency was found to map to the same locus as the cinnamon mutation, another mutation which affects aldehyde oxidase production. The developmental profile of aldehyde oxidase in the hl16 strain was compared to the developmental profile in the Canton S wild type strain. The aldehyde oxidase activity in adult hl16 individuals was also compared to that of various other strains. It was also found that the aldehyde oxidase activity was temperature sensitive in the adult flies. The temperature sensitive lethality mutation was mapped to position 1-0.1.
    • Analysis of cellular responses to microwave irradiation in E. coli and change of oxygen level and culture medium in human cancer cell lines using RNA-seq based transcriptomic profiling

      Hilson, Eunike Ilona; Department of Biological Sciences
      RNA sequencing (RNA-seq) is one of the applications of next-generation sequencing (NGS) with differential gene expression (DGE) analysis at the transcriptomic level as its primary objective. Among the NGS technologies, the Illumina platforms are the current standard for RNA-seq analysis for their best cost efficiency and sequencing accuracy. In this study, we employed Illumina-based RNA-seq to examine the gene expression profile change in E. coli cells after exposure to microwave irradiation (MWI) and in cancer cell lines in response to different culture conditions using breast cancer cell lines (MCF7) and prostate cancer cell lines (PC3) as the models. Our results in examining the gene expression change in E. coli showed that the non-thermal effects of MWI led to E. coli cells entering the stationary phase with most of the downregulated genes involved in metabolic and biosynthesis pathways. MWI also upregulated the expression of genes important for the maintenance of membrane integrity and adhesion associated with bacterial motility. In comparison with other similar studies, our methodology allowed us to observe the impact of non-thermal effects of MWI at 2.45 GHz via simultaneous cooling. Our results in examining the transcriptomic profile of MCF7 and PC3 cells in response to oxygen level and culture medium change showed that gene expression in MCF7 is highly affected by oxygen level and culture medium changes when compared to PC3, especially in DMEM at 18% O2. DNA replication, cell-cycle, and viral carcinogenesis are the most affected pathways observed from different culture conditions in both cell lines. In PC3, only the legionellosis seems to be most impacted by culture medium changes at 5% O2, involving 8 differentially expressed genes (DEGs), important for cancer cell development. DGE analysis also provides the transcriptomic profile of MCF7 and PC3, showing that different nutrient composition (between DMEM and Plasmax) and oxygen levels (5% O2 and 18% O2) changes the metabolism and various signaling pathways in both cell lines differently suggesting that the oxygen level and culture medium are important factors impacting the outcome of cell culture-based experiments in cell type-specific fashion.
    • The analysis of gene transcripts associated with conidiation in the insect pathogenic fungus, Metarhizium anisopliae /

      Small, Cherrie-Lee.; Department of Biological Sciences (Brock University, 2004-05-21)
      Conidia of the insect pathogenic fungus, Metarhizium anisopliae play an important role in pathogenicity because they are the infective propagules that adhere to the surface of the insect, then germinate and give rise to hyphal penetration of the insect cuticle. Conidia are produced in the final stages of insect infection as the mycelia emerge from the insect cadaver. The genes associated with conidiation have not yet been studied in this fiingus. hi this study we used the PCR-based technique, suppression subtractive hybridization (SSH) to selectively amplify conidial-associated genes in M. anisopliae. We then identified the presence of these differentially expressed genes using the National Center for Biotechnology Information database. One of the transcripts encoded an extracellular subtilisin-like protease, Prl, which plays a fundamental role in cuticular protein degradation. Analysis of the patterns of gene expression of the transcripts using RT-PCR indicated that conidial-associated cDNAs are expressed during the development of the mature conidium. RT-PCR analysis was also performed to examine in vivo expression of Prl during infection of waxworm larvae {Galleria mellonelld). Results showed expression of Prl as mycelia emerge and produce conidia on the surface of the cadaver. It is well documented that Prl is produced during the initial stages of transcuticular penetration by M. anisopliae. We suggest that upregulation of Prl is part of the mechanism by which reverse (from inside to the outside of the host) transcuticular penetration of the insect cuticle allows subsequent conidiation on the cadaver.
    • Analysis of the feeding behaviour of the mosquito Culex pipiens L. (Diptera: Culicidae) in relation to West Nile virus

      Russell, Curtis B.; Department of Biological Sciences (Brock University, 2007-05-28)
      The goal ofthis literature review is to inform the reader on several aspects of West Nile Virus (WNV) transmission by its mosquito vector, Culex pipiens and to elucidate how Cx. pipiens and WNV are intertwined. The first few sections of the literature review describe the life cycle and blood feeding behaviours ofmosquitoes so that baseline data ofmosquito biology are established. In addition to explaining how and why a mosquito blood feeds, the section on "Blood Meal Analysis" describes the different methods for determining the vertebrate source of mosquito blood meals and a brief history of these testing methods. Since this thesis looks at the feeding behaviour of Cx. pipiens, it is important to know how to determine what they are feeding upon. Discussion on other mosquito-borne diseases related to WNV gives a broader perspective to the thesis, and examines other diseases that have occurred in Ontario in the past. This is followed by background information on WNV and theories on how this virus came to North America and how it relates to Cx. pipiens. The final sections discuss Cx. pipiens and give background information to how this species of mosquito exists and behaves within North America.
    • Annual Variation in Bee Community Structure in the Context of Disturbance (Niagara Region, South-Western Ontario)

      Cordero, Rodrigo Leon; Department of Biological Sciences (Brock University, 2013-04-01)
      This study examined annual variation in phenology, abundance and diversity of a bee community during 2003, 2004, 2006, and 2008 in recovered landscapes at the southern end of St. Catharines, Ontario, Canada. Overall, 8139 individuals were collected from 26 genera and sub-genera and at least 57 species. These individuals belonged to the 5 families found in eastern North America (Andrenidae, Apidae, Colletidae, Halictidae and Megachilidae). The bee community was characterized by three distinct periods of flight activity over the four years studied (early spring, late spring/early summer, and late summer). The number of bees collected in spring was significantly higher than those collected in summer. In 2003 and 2006 abundance was higher, seasons started earlier and lasted longer than in 2004 and 2008, as a result of annual rainfall fluctuations. Differences in abundance for low and high disturbance sites decreased with years. Annual trends of generic richness resembled those detected for species. Likewise, similarity in genus and species composition decreased with time. Abundant and common taxa (13 genera and 18 species) were more persistent than rarer taxa being largely responsible for the annual fluctuations of the overall community. Numerous species were sporadic or newly introduced. The invasive species Anthidium oblongatum was first recorded in Niagara in 2006 and 2008. Previously detected seasonal variation patterns were confirmed. Furthermore, this study contributed to improve our knowledge of temporal dynamics of bee communities. Understanding temporal variation in bee communities is relevant to assessing impacts caused on their habitats by diverse disturbances.
    • The application of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates in biological samples /|nby David J. LeBlanc. -- 260 St. Catharines [Ont. : s. n.],

      LeBlanc, David J.; Department of Biological Sciences (Brock University, 1976-07-09)
      A study was undertaken' to determine the applicability of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates from biological samples. A new method of silylation involving dimethylsulfoxide, hexamethyldisilazane, trimethylchlorosilane and cyclohexane (1:0.2:0.1:1) which rapidly silylated sugars and sugar phosphates was developed. Subsequent chromatography on a 5% SE-52 column gave good resolution of the sugar and sugar phosphate samples. Sugar phosphates decomposed during chromatography and were lost at the 7 x 10-3 ~mole level. Acidic ethanol extraction of yeast samples revealed background contamination from the yeast sample, the culture medium and the silylation reagents which would further limit the level of detection obtainable with the glc for sugars in biological samples to the 3 x 10-4 ~mole level.
    • Aspects of the hemes and modulation of hydrogen donors in catalases from bovine liver, yeast, and escherichia coli

      Hillar, Alexander P.; Department of Biological Sciences (Brock University, 1993-07-09)
      Catalase is the enzyme which decomposes hydrogen peroxide to water and oxygen. Escherichia coli contains two catalases. Hydroperoxidase I (HPI) is a bifunctional catalase-peroxidase. Hydroperoxidase II (HPII) is only catalytically active toward H202. Expression of the genes encoding these proteins is controlled by different regimes. HPJI is thought to be a hexamer, having one heme d cis group per enzymatic subunit. HPII wild type protein and heme containing mutant proteins were obtained from the laboratory of P. Loewen (Univ. of Manitoba). Mutants constructed by oligonucleotidedirected mutagenesis were targeted for replacement of either the His128 residue or the Asn201 residue in the vicinity of the HPII heme crevice. His128 is the residue thought to be analogous to the His74 distal axial ligand of the heme in the bovine liver enzyme, and Asn201 is believed to be a residue critical to the function of the enzyme because of its role in orienting and interacting with the substrate molecule. Investigation of the nature of the hemes via absorption spectroscopy of the unmodified catalase proteins and their derived pyridine hemochromes showed that while the bovine and Saccharomyces cerevisiae catalase enzymes are protoheme-containing, the HPII wild type protein contains heme d, and the mutant proteins contain either solely protoheme, or heme d-protoheme mixtures. Cyanide binding studies supported this, as ligand binding was monophasic for the bovine, Saccharomyces cerevisiae, and wild type HPII enzymes, but biphasic for several of the HPII mutant proteins. Several mammalian catalases, and at least two prokaryotic catalases, are known to be NADPH binding. The function of this cofactor appears to be the prevention of inactivation of the enzyme, which occurs via formation of the inactive secondary catalase peroxide compound (compound II). No physiologically plausible scheme has yet been proposed for the NADPH mediation of catalase activity. This study has shown, via fluorescence and affinity chromatography techniques, that NADPH binds to the T (Typical) and A (Atypical) catalases of Saccharomyces cerevisiae, and that wild type HPII apparently does not bind NADPH. This study has also shown that NADPH is unlike any other hydrogen donor to catalase, and addresses its features as a unique donor by proposing a mechanism whereby NADPH is oxidized and catalase is protected from inactivation via the formation of protein radical species. Migration of this radical to a position close to the NADPH is also proposed as an adjunct hypothesis, based on similar electron migrations that are known to occur within metmyoglobin and cytochrome c peroxidase when reacted with H202. Validation of these hypotheses may be obtained in appropriate future experiments.
    • Assessing the influence of irrigation and fertigation on fruit composition, vine performance and wine quality in a cool, humid climate /

      Lowrey, Wesley D.; Department of Biological Sciences (Brock University, 2004-07-14)
      A study was devised to evaluate influences of irrigation and fertigation practices on Vitis vinifera and Vitis labruscana grapes in the Niagara Peninsula. A modified FAO Penman- Monteith evapotranspiration formula was used to calculate water budgets and schedule irrigations. Five deficit irrigation treatments (non-irrigated control; deficits imposed postbloom, lag phase, and veraison; fiiU season irrigation) were employed in a Chardonnay vineyard. Transpiration rate (4-7 /xg H20/cmVs) and soil moisture data demonstrated that the control and early deficit treatments were under water stress throughout the season. The fiiU season irrigation treatment showed an 18% (2001) and 19% (2002) increase in yield over control due to increased berry weight. Soluble solids and wine quality were not compromised, and the fiiU season treatment showed similar or higher °Brix than all other treatments. Berry titratable acidity andpH also fell within acceptable levels for all five treatments. Irrigation/fertigation timing trials were conducted on Concord and Niagara vines in 2001- 02. The six Concord treatments consisted of a non-irrigated control, irrigation fi^om Eichhom and Lorenz (EL) stage 12 to harvest, and four fertigation treatments which applied 70 kg/ha urea. The nine Niagara treatments included a non-irrigated control, two irrigated treatments (ceasing at veraison and harvest, respectively) and six fertigation treatments of various durations. Slight yield increases (ca. 10% in Concord; 29% in Niagara) were accompanied by small decreases in soluble solids (1.5°Brix), and methyl anthranilate concentrations. Transpiration rate and soil moisture (1 1.9-16.3%) data suggested that severe water stress was present in these Toledo clay based vineyards.
    • Assessment of chromatin activity in mouse and human tissues

      Winter, Karen Judith.; Department of Biological Sciences (Brock University, 1985-07-09)
      Pancreatic deoxyribonuclease preferentially digests active genes during all phases of the cell cycle including mitosis. Recently, a DNAse I-directed in ~ nick translation technique has been used to demonstrate differences in the DNAse I sensitivity of euchromatic and heterochromatic regions of mitotic chromosomes. This ill ~ technique has been used in this study to ask whether facultative heterochromatin of the inactive X chromosome can be distinguished from the active X chromosome in mouse and human tissues. In addition to this, in ~ nick translation has been used to distinguish constitutive heterochromatin in mouse and human mitotic chromosomes. Based on relative levels of DNAse I sensitivity, the inactive X chromosome could not be distinguished from the active X chromosome in either mouse or human tissues but regions of constitutive heterochromatin could be distinguished by their relative DNAse I insensitivity. The use of !D situ nick translation was also applied to tissue sections of 7.5 day mouse embryos to ask whether differing levels of DNAse I sensitivity could be detected between different tissue types. Differences in DNAse I sensitivities were detected in three tissues examined; embryonic ectoderm, an embryo-derived tissue, and two extraembryonic tissues, extraembryonic ectoderm and ectoplacental cone. Embryonic ectoderm and extraembryonic ectoderm nuclei possessed comparable levels of DNAse I sensitivity while ectoplacental cone was significantly less DNAse I sensitive. This suggests that tissue-specific mechanisms such as chromatin structure may be involved in the regulation of gene activity in certain tissue types. This may also shed some light on possible tissue specific mechanisms regulating X chromosome activity in the developing mouse embryo.
    • Attractive silences in cricket courtship song : mate choice using a short-range signal /

      Fitzpatrick, Mark Jeffrey.; Department of Biological Sciences (Brock University, 2000-05-21)
      Matings systems using signals for sexual communication have been studied extensively and results commonly suggest that females use these signals for locating males, species-identification, and mate choice. Although numerous mating systems employ multiple signals, research has generally focused on long-range signals perhaps due to their prominence and ease of study. This study focused on the short-range acoustic courtship song of crickets. The results presented here suggest this signal is under selection by female choice. Females mated preferentially with males having shorter silences between the two types of ticks within the song. The length of these silences (Gap 1) was correlated with male condition such that males having long silences were significantly lower in mass with respect to body size when compared to males having short silences. Both Gap 1 length and male condition were significantly repeatable within males over time suggesting the possibility these traits have a genetic basis. This study is the first empirical study to test female preferences within the natural variation of the courtship song. It now appears, at least in crickets, that both the longand short-range signals of a multi-signal mating system may contribute to male mating success.
    • Bacteriophages of Erwinia amylovora and their potential use in biological control

      Gill, Jason J.; Department of Biological Sciences (Brock University, 2000-11-04)
      Forty-four bacteriophage isolates of Erwinia amy/ovora, the causal agent of fire blight, were collected from sites in and around the Niagara Region of Southern Ontario in the summer of 1998. Phages were isolated only from sites where fire blight was present. Thirty-seven of these phages were isolated from the soil surrounding infected trees, with the remainder isolated from aerial plant tissue samples. A mixture of six E. amy/ovora bacterial host strains was used to enrich field samples in order to avoid the selection bias of a single-host system. Molecular characterization of the phages with a combination of peR and restriction endonuclease digestions showed that six distinct phage types were isolated. Ten phage isolates related to the previously characterized E. amy/ovora phage PEa1 were isolated, with some divergence of molecular markers between phages isolated from different sites. The host ranges of the phages revealed that certain types were unable to efficiently lyse some E. amy/ovora strains, and that some types were able to lyse the epiphytic bacterium Pantoea agg/omerans. Biological control of E. amy/ovora by the bacteriophages was assessed in a bioassay using discs of immature pear fruit. Twenty-three phage isolates were able to significantly suppress the incidence of bacterial exudate on the pear disc surface. Quantification of the bacterial population remaining on the disc surface indicated that population reductions of up to 97% were obtainable by phage treatment, but that elimination of bacteria from the surface was not possible with this model system.
    • Bee Communities in Restored Landfill Sites of Niagara Region

      Kutby, Rola; Department of Biological Sciences (Brock University, 2013-11-25)
      This study examined the impact of habitat restoration on bee communities (Hymenoptera: Apidae) of the Niagara Region, Ontario, Canada. Bee abundance and diversity was studied in three restored landfill sites: the Glenridge Quarry Naturalization Site (GQNS) in St. Catharines, Elm Street Naturalization Site in Port Colborne, and Station Road Naturalization Site in Wainfleet during 2011 and 2012. GQNS represented older sites restored from 2001-2003. Elm and Station sites represented newly restored landfills as of 2011. These sites were compared to control sites at Brock University where bee communities are well established and again to other landfills where no stable habitat was available before restoration. The objective of this study is to investigate the impact of restoration level on bee abundance and diversity in restored landfill sites of the Niagara Region. Based on the increased disturbance hypothesis (InDH) and the intermediate disturbance hypothesis (IDH), I hypothesized that bee abundance and diversity will follow two patterns. First pattern according to InDH suggest that as the disturbance decrease the bee abundance and diversity will increased. Second pattern according to the IDH bee abundance and diversity will be the highest at the intermediate level of disturbance. A total of 7 173 bees were collected using pan traps and flower collections, from May to October 2011 and 2012. Bees were classified to five families, 21 genera and sub-genera, containing at least 78 species. In 2011 bee abundance was not significantly different among restoration levels while in 2012 bee abundance was significant difference among restoration level. According to family there were no significant difference in Halictidae and Apidae abundance among restoration level while Colletidae and Megachilidae abundance were varied among restoration levels. The bee species richness was highest in the newly restored sites followed by restored control sites, and then the control site. The current study demonstrates that habitat restoration results in rapid increases in bee abundance and diversity for newly restored sites, and, further, that it takes only 2-3 years for bee assemblages in newly restored sites to arrive at the same levels of abundance and diversity as in nearby control sites where bee communities are well established.
    • The bees of Niagara: a test of the intermediate disturbance hypothesis /

      Rutgers-Kelly, Amy Christine.; Department of Biological Sciences (Brock University, 2005-06-29)
      This study examined the bee fauna of the Carolinian Zone in Ontario, Canada. In 2003, 15687 individuals from 152 species of bees were collected. Tliere were many rare species but few abundant species. There were three distinct bee seasons. The Niagara bee assemblage was less diverse compared to other Carolinian Zone assemblages and types of landscapes. This study also examined how anthropogenic disturbance affects the diversity of bee assemblages. The intermediate disturbance hypothesis (IDH) was tested by selecting field sites subject to low, intermediate, and high disturbance. Intermediate disturbance had the highest species richness (SR=1 15) and most bees (N=556I), followed by low disturbance (SR= 100, N=2975), then high disturbance (SR=72, N=1364), supporting the IDH. Increased species richness in areas of intermediate disturbance was due to higher abundance, possibly because more blooming flowers were found there. Bees were larger in high disturbance areas but smaller in areas of high and intermediate disturbance.
    • Behavioural and neural correlates of operant conditioning in Lymnaea stagnalis : role of previous experience during development /

      Khan, Abdullah Mohammad.; Department of Biological Sciences (Brock University, 2006-06-04)
      The freshwater mollusc Lymnaea stagnalis was utilized in this study to further the understanding of how network properties change as a result of associative learning, and to determine whether or not this plasticity is dependent on previous experience during development. The respiratory and neural correlates of operant conditioning were first determined in normally reared Lymnaea. The same procedure was then applied to differentially reared Lymnaea, that is, animals that had never experienced aerial respiration during their development. The aim was to determine whether these animals would demonstrate the same responses to the training paradigm. In normally reared animals, a behavioural reduction in aerial respiration was accompanied by numerous changes within the neural network. Specifically, I provide evidence of changes at the level of the respiratory central pattern generator and the motor output. In the differentially reared animals, there was little behavioural data to suggest learning and memory. There were, however, significant differences in the network parameters, similar to those observed in normally reared animals. This demonstrated an effect of operant conditioning on differentially reared animals. In this thesis, I have identified additional correlates of operant conditioning in normally reared animals and provide evidence of associative learning in differentially reared animals. I conclude plasticity is not dependent on previous experience, but is rather ontogenetically programmed within the neural network.