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S L Bullock

Publications and source records attributed to S L Bullock.

14 recordsLinked to original sources
PubMed2001

Conserved signals and machinery for RNA transport in Drosophila oogenesis and embryogenesis.

Localization of cytoplasmic messenger RNA transcripts is widely used to target proteins within cells. For many transcripts, localization depends on cis-acting elements within the transcripts and on microtubule-based motors; however, little is known about other components of the transport machinery or how these components recognize specific RNA cargoes. Here, we show that in Drosophila the same machinery and RNA signals drive specific accumulation of maternal RNAs in the early oocyte and apical transcript localization in blastoderm embryos. We demonstrate in vivo that Egalitarian (Egl) and Bicaudal D (BicD), maternal proteins required for oocyte determination, are selectively recruited by, and co-transported with, localizing transcripts in blastoderm embryos, and that interfering with the activities of Egl and BicD blocks apical localization. We propose that Egl and BicD are core components of a selective dynein motor complex that drives transcript localization in a variety of tissues.

Animals↗
PubMed2001

The molecular phenotype of heparan sulfate in the Hs2st-/- mutant mouse.

Heparan sulfate (HS) is a co-receptor for a number of growth factors, morphogens, and adhesion proteins. HS biosynthetic modifications may determine the strength and outcome of HS-ligand interactions. We previously described the phenotype of mice with a gene-trap mutation in Hs2st, encoding the key HS 2-O-sulfotransferase enzyme in HS polymer modification. In contrast to the early developmental failure of embryos lacking HS, the onset of abnormalities in the Hs2st(-/-) mice occurs only after midgestation, the most dramatic being the complete failure of kidney development. Uronate 2-O-sulfates were not detected in the mutant HS, indicating a complete loss of function of Hs2st. However, the domain structure of the mutant HS is conserved, and compensatory increases in N- and 6-O-sulfation maintain the overall charge density. The apparent affinities of the mutant HS for hepatocyte growth factor/scatter factor and fibronectin were unchanged but were reduced for fibroblast growth factor-1 and -2. Surprisingly, the Hs2st(-/-) cells were able to mount an apparently normal signaling response to fibroblast growth factor-1 and -2 as well as to hepatocyte growth factor/scatter factor.

Animals↗
PubMed2001

A gene trap insertion reveals that amyloid precursor protein expression is a very early event in murine embryogenesis.

Although it is known that aberrant processing of amyloid precursor protein (APP) in the adult is associated with Alzheimer's disease, the normal roles of APP in neuronal and embryonic development are not clear yet. As part of a gene trap screen undertaken to identify genes coding for secreted proteins involved in mouse gastrulation, we have obtained a mouse line in which the gene encoding APP is mutated by insertion of the lacZ reporter gene. This study shows that App expression is detected as early as gastrulation. In addition, although widely distributed at later stages, APP expression appears dynamically regulated during development.

Amyloid beta-Protein Precursor↗
PubMed1998

Renal agenesis in mice homozygous for a gene trap mutation in the gene encoding heparan sulfate 2-sulfotransferase.

Heparan sulfate proteoglycans have been implicated in the presentation of a number of secreted signaling molecules to their signal-transducing receptors. We have characterized a gene trap mutation in the gene encoding a heparan sulfate biosynthetic enzyme, heparan sulfate 2-sulfotransferase (HS2ST). Transgenic mice were generated from embryonic stem cells harboring this insertion. lacZ reporter gene activity in heterozygous embryos demonstrates that the gene is expressed differentially during embryogenesis, presumably directing dynamic changes in heparan sulfate structure. Moreover, mice homozygous for the Hs2st gene trap allele die in the neonatal period, exhibiting bilateral renal agenesis and defects of the eye and the skeleton. Analysis of kidney development in Hs2st mutants reveals that the gene is not required for two early events-ureteric bud outgrowth from the Wolffian duct and initial induction of Pax-2 expression in the metanephric mesenchyme. It is required, however, for mesenchymal condensation around the ureteric bud and initiation of branching morphogenesis. Because 2-O-sulfation has been shown to influence the functional interactions of ligands with heparan sulfate in vitro, we discuss the possibility that the Hs2st mutant phenotype is a consequence of compromised interactions between growth factors and their signal-transducing receptors. These data provide the first genetic evidence that the regulated synthesis of differentially glycosylated proteoglycans can affect morphogenesis during vertebrate development.

Amino Acid Sequence↗
PubMed1998

Condom use among Aboriginal people in Ontario, Canada.

A survey of 658 Aboriginal men and women living in 11 reserve communities in Ontario, Canada, was utilized to collect data on patterns of condom use. Individuals who had sexual intercourse in the previous 12 months were included in the analysis (n=400). Descriptive statistics and multiple logistic regression were used to analyse condom use in the previous 12 months. Eight per cent always, 31% sometimes, and 61% never used condoms. Rates of condom use differed with the number of sex partners in the last year, age, gender, having a steady sex partner, and marital status. Multiple logistic regression revealed that people most likely to use condoms were under the age of 30, male, did not have a long-term steady sex partner, had more than one sex partner, worried about pregnancy, were knowledgeable about HIV/AIDS, and were not embarrassed to obtain condoms. Condom users who were knowledgeable about HIV/AIDS and who knew someone with HIV/AIDS were more likely to always use condoms. The most common reason for not using a condom was 'I was with my steady sex partner'. These results have implications for STD prevention efforts and for future research of sexual and STD preventive behaviour among Aboriginal people.

Adolescent↗
PubMed1997

Differences in sexual risk-taking behavior with state of inebriation in an aboriginal population in Ontario, Canada.

OBJECTIVE: This article describes the self-reported use of substances, participation in unprotected intercourse and differences in sexual risk-taking behavior with state of inebriation among a group of aboriginal (First Nations) people in Ontario. And, in so doing, attempts to answer some of the questions about the association between the use of alcohol and sexual risk taking in this population. METHOD: The project was developed in a partnership between an aboriginal steering committee and university researchers. Data were collected via interview from 658 randomly selected status First Nations people living within 11 reserve communities in the province. RESULTS: Of the 426 individuals included in the within subject analysis 9.6% reported variation in their participation in sex, 13.8% variation in their participation in intercourse and 10.3% variation in their participation in unprotected intercourse with inebriation. An examination of individual behavior across "sober" and "drunk or high" states showed that there were almost equal proportions of respondents who only participated in unsafe sex when sober and respondents who only participated in unsafe sex when drunk or high. Where significant differences occurred, individuals were more likely to report a shift towards no sex or no intercourse with inebriation, not towards unprotected intercourse. CONCLUSIONS: Since a large proportion of individuals in this study engage in unprotected intercourse, the small proportion of individuals reporting different sexual behavior were more likely to report participation in a safe activity rather than an unsafe activity while "drunk or high." Stereotypes and assumptions may lead educators and researchers to feel the need to focus their messages on the relationship between drug and alcohol consumption and unsafe sex; however, the amount of unsafe sexual intercourse that occurs only while individuals are inebriated suggests that this focus is not of principal concern.

Adolescent↗
PubMed1992

HIV, substance use and related behaviour of gay and bisexual men: an examination of the talking sex project cohort.

This paper reports on the substance use of 612 gay and bisexual men who participated in an HIV risk reduction project. Use/non-use, level of substance use, and reported frequency of use prior to sexual activity were examined in relation to number of sexual partners, sexual activities, HIV antibody test seeking behaviour and known HIV status. The use of substances among the study cohort appear to be higher than in a comparable heterosexual male group. An association was found between substance use, and both number of sexual partners and sexual activities. However, no significant difference was found in substance use between men participating in protected versus unprotected anal sex. Similarly, no significant difference was found in the reported frequency of substance use prior to sex by those participating in protected and unprotected anal intercourse. Greater drug use was reported among those who were known to be HIV antibody positive. These findings raise issues for further research. The high use of alcohol and drugs by gay and bisexual men may pose significant health risks for this group of men.

AIDS Serodiagnosis↗
PubMed1979

Ethyl acetate as a substitute for diethyl ether in the formalin-ether sedimentation technique.

Ethyl acetate appears to be a satisfactory subsitute solvent for diethyl ether in the Formalin-ether sedimentation technique. In comparative studies, concentration of organisms with ethyl acetate was equal to or greater than that with diethyl ether. No distortion or alteration of morphology was observed with eigher solvent, and preparations were comparable in appearance and ease of examination. In addition, ethyl acetate is less flammable and less hazardous to use than diethyl ether.

Acetates↗
PubMed1977

Evaluation of some of the parameters of the enzyme-linked immunospecific assay.

In an attempt to standardize the procedure for the enzyme-linked immunospecific assay, several parameters were examined. It was determined that horseradish peroxidase was the enzyme of choice and that several brands of polystyrene tubes and plates could be used. The test was considerably shortened by omitting long incubation steps previously used for eliminating background fixation of conjugate. The reproducibility of the procedure proved to be excellent, but reactivity curves indicated that use of a single dilution is not adequate for quantitative tests. A "standard" procedure was proposed.

Enzyme-Linked Immunosorbent Assay↗
PubMed1977

Use of the enzyme-linked immunosorbent assay (ELISA) and its microadaptation for the serodiagnosis of toxoplasmosis.

The enzyme-linked immunosorbent assay (ELISA) has proved to be a sensitive and specific quantitative procedure for the serodiagnosis of toxoplasmosis. Using the toxoplasma model, several parameters of the test were investigated. Day-to-day reproducibility was 90% within one twofold dilution and 98% specific when tested against batteries of sera from other diseases. Both the tube method and the microtitration method were used successfully. ELISA results are equivalent to those found in the indirect immunofluorescence test, yet the ELISA procedure is simpler and more rapid to perform.

Diagnosis, Differential↗
PubMedDate not supplied

Sexual partnering and risk of HIV/STD among Aboriginals.

OBJECTIVE: To examine the contribution of patterns of sexual partnering to the spread of HIV/STD infection between communities. METHODS: 651 randomly selected Aboriginals from 11 reserve communities in Ontario were interviewed. This analysis included those who had sex in the previous 12 months. Descriptive statistics and multivariate analyses identified associations with patterns of sexual partnering. RESULTS: 22% reported having partners from both within and outside the community, 51% from within only, and 27% from outside only. Those with partners from both within and outside were more likely to be male, unmarried, from a remote community, have more sexual partners and perceive that their behaviour placed them at higher risk of HIV/STD infection. They were least likely to perceive their community to be at risk from their behaviour. CONCLUSIONS: Findings suggest that Aboriginal communities are not insulated and that HIV could spread rapidly if introduced.

Adolescent↗
PubMedDate not supplied

The Talking Sex Project: descriptions of the study population and correlates of sexual practices at baseline.

The Talking Sex Project is an HIV risk reduction education project for gay and bisexual men. It was developed to evaluate two types of small discussion groups using a randomized control study design. This paper reports on the baseline measures of knowledge, attitudes and sexual practices. The 612 subjects had a mean age of 32 years, were all English speaking and were relatively highly educated. Bivariate analyses found that younger men, those in a relationship, those reporting bisexual activity and those with higher levels of substance use were significantly more likely to have unprotected anal intercourse. While overall knowledge was not associated with sexual behaviour, a significant relationship was found with knowledge of risk of anal sex. Attitudes, in particular, the belief in the efficacy of condoms and the enjoyment of safer sex were found to have the strongest associations with protected anal intercourse. The paper provides an understanding of some of the factors which may be important to behaviour change and clues for the targeting of programs.

Adolescent↗