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Biomedical subjects

T Chapman

Publications and source records attributed to T Chapman.

At least 37 records · Page 2Linked to original sources
PubMed2000

Behavioral risk reduction in a declining HIV epidemic: injection drug users in New York City, 1990-1997.

OBJECTIVES: This study assessed trends in HIV risk behaviors among injection drug users in New York City from 1990 to 1997. METHODS: Injection drug users were recruited continuously from a large drug detoxification treatment program (N = 2588) and a research storefront located in a high-drug-use area (N = 2701). Informed consent was obtained, and a trained interviewer administered a structured interview covering sociodemographics, drug use history, HIV risk behavior, and participation in syringe exchange. RESULTS: Trends were assessed for 5 risk behaviors in the 6-month period before the interview. The 3 injection risk behaviors declined significantly over time at each site (all P < .01). When data were pooled across sites, all 5 risk behaviors declined significantly over time (all P < .01). Participation in syringe exchange programs and in HIV counseling and testing increased greatly from 1990 to 1997. CONCLUSIONS: The continuing risk reduction among injection drug users indicates a "declining phase" in the large HIV epidemic in New York City. HIV prevention programs appear to be making an important contribution to the declining phase.

Adult↗
PubMed1999

Mating-induced inhibition of remating in female Mediterranean fruit flies Ceratitis capitata.

Mechanisms producing inhibition of remating in mated female Mediterranean fruit flies Ceratitis capitata, were investigated by matings with surgically altered males. Comparison of remating by females mated with either intact control males or males with a shortened penis, showed that ejaculate or a physical stimulus of penis insertion caused remating inhibition for at least 10 days after first mating. Remating frequency at two days after mating was significantly higher in females mated to castrated (spermless) males than in females mated to sham-operated control males. This difference disappeared by day four after mating, indicating that sperm cause a shorter-term inhibition of remating than does a normal first mating. Other factors in addition to sperm must therefore play a role in inhibition of remating.

Journal Article↗
PubMed1999

A neuromorphic hair sensor model of wind-mediated escape in the cricket.

Crickets are able to extract directional information about a wind stimulus through the filiform hairs located on their cerci. This paper describes the design and testing of a neuromorphic sensor that aims to achieve a close correlation with both the physical and functional properties of these hairs. An integrate and fire neural network is used to process the sensory information in real time. The resulting system is shown to be capable of extracting directional information from a wind stimulus and producing an appropriate motor control pattern.

Action Potentials↗
PubMed1998

Interactions of mating, egg production and death rates in females of the Mediterranean fruit fly, Ceratitis capitata.

Costs of reproduction include costs of producing eggs and of mating itself. In the present study, we made an experimental investigation of costs of reproduction in the Mediterranean fruit fly (medfly, Ceratitis capitata). We demonstrated that virgins live longer than non-virgin females. However, in strong contrast to most findings within the Diptera, non-virginity had no detectable effect on egg production. Therefore the increased longevity of the virgin females cannot be attributed to an increase in egg production in non-virgin females, and instead indicates a cost of mating. A comparison of the life spans of normal females and those sterilized by low doses of X-irradiation, revealed an additional cost of egg production. There were no significant differences in remating levels between females that did and did not lay eggs, showing that the cost of producing eggs is independent of mating frequency. Medfly females therefore suffer a decrease in survival as a result of egg production and of mating, and these costs are independent of one another. To put our results into context, we reviewed the existing literature on the effects of mating on longevity, egg production and sexual receptivity for 64 species of Diptera, and examined the pattern of mating effects that emerged.

Animals↗
PubMed1998

Sex-specific selection on time to remate in Drosophila melanogaster.

Female Drosophila melanogaster were artificially selected for fast and slow time to remate (denoted 'high' and 'low' selection regimes, respectively). Both selection regimes and a control were replicated three times. Correlated responses to selection in females and in males were measured. A significant direct response to selection for time to remating was found in females from both selection regimes. Remating frequency of females showed a correlated response only in the females from the lines selected for faster time to remating. Time to first mating of virgin females showed no correlated response in either selection regime. No correlated response was found in males for time to remate, remating frequency or time to first mating of virgins, indicating that genetic correlations between the sexes do not influence the evolution of these traits in this population of D. melanogaster. There was no direct response to artificial selection for the ability of first males to deter females from remating. However, we found that the genotype of the first male to mate with a female could influence her time to remate; base stock males were better at deterring females from remating than were males from any of the selection lines. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Some reflections on cultural and social considerations in mental health nursing.

This article critiques the contribution of two main theoretical perspectives on mental health care and ethnicity, with particular reference to Asian women. It considers the work of those who highlight the impact of culture on the health and illness experience (Kleinman 1980, Rack 1982, Fernando 1989) and the work of authors who argue that the impact of broader socio-economic structures must be considered (Donovan 1989, Pearson 1989, Ahmad 1993). It is posited that the emphasis on cultural difference results in crude monolithic generalizations about Asian culture and operates as a smokescreen for the impact of poverty and racism. The backdrop to this article is provided by an assessment of the problematic conceptual framework of Western mental health and the role it plays in perpetuating stereotypes. It is concluded that mental health nurses need a thorough understanding of the complexity of the cultural and social factors that influence health and illness; an understanding which falls somewhere between these two theoretical perspectives. Such an approach needs to be grounded in the experience of mental health clients themselves if it is to be appropriate.

Attitude to Health↗
PubMed1998

Declining seroprevalence in a very large HIV epidemic: injecting drug users in New York City, 1991 to 1996.

OBJECTIVES: This study assessed recent trends in HIV seroprevalence among injecting drug users in New York City. METHODS: We analyzed temporal trends in HIV seroprevalence from 1991 through 1996 in 5 studies of injecting drug users recruited from a detoxification program, a methadone maintenance program, research storefronts in the Lower East Side and Harlem areas, and a citywide network of sexually transmitted disease clinics. A total of 11,334 serum samples were tested. RESULTS: From 1991 through 1996, HIV seroprevalence declined substantially among subjects in all 5 studies: from 53% to 36% in the detoxification program, from 45% to 29% in the methadone program, from 44% to 22% at the Lower East Side storefront, from 48% to 21% at the Harlem storefront, and from 30% to 21% in the sexually transmitted disease clinics (all P < .002 by chi 2 tests for trend). CONCLUSIONS: The reductions in HIV seroprevalence seen among injecting drug users in New York City from 1991 through 1996 indicate a new phase in this large HIV epidemic. Potential explanatory factors include the loss of HIV-seropositive individuals through disability and death and lower rates of risk behavior leading to low HIV incidence.

Adult↗
PubMed1997

Mating and hormonal triggers regulate accessory gland gene expression in male Drosophila.

Drosophila melanogaster males transfer accessory gland proteins, as part of their seminal fluid, to females during each mating. Since accessory gland proteins are important for male reproductive success, it is important that the male replenish the proteins he transferred during mating. Previous studies had shown that mating induces the resynthesis of accessory gland proteins, but since mating includes a set of stereotyped behavior patterns as well as the act of copulation, it was not known which aspect of the mating process induces accessory gland protein synthesis. By exposing males to females whose ovipositors had been sealed shut, we have shown that resynthesis of accessory gland proteins occurs only when seminal fluid is transferred to females. By applying juvenile hormone or 20-hydroxyecdysone topically to the cuticle of male flies, we showed that these hormones can act in vivo to stimulate the synthesis of accessory gland proteins to levels similar to those observed after mating.

Journal Article↗
PubMed1997

Panic disorder and quality of life: variables predictive of functional impairment.

OBJECTIVE: The authors sought to characterize the functional impairment in patients with panic disorder, specifically the variance in impairment explained by demographic and clinical variables. METHOD: Sixty-two patients with panic disorder and 61 comparison subjects from three primary care clinic sites were assessed with an adapted form of the Structured Clinical Interview for DSM-III-R. Impairment was assessed according to three measures from the 36-item Short-Form Health Survey (general health perception, mental health, and physical functioning) as well as a principal component factor of the survey. Subjects were also compared with respect to personality variables, presence and severity of chronic medical illness, and demographic characteristics. Stepwise multiple regressions with and without pairwise interactions were used to construct models of disability in the patients with panic disorder. RESULTS: The patients with panic disorder were more impaired than comparison subjects on each measure of the Short-Form Health Survey. The panic disorder diagnosis combined with major depression, increasing neuroticism and age, less education, and an interaction between panic disorder and age accounted for 48%-77% of the variance in impairment scores. Gender and ethnicity contributed modestly to the variance in impairment in physical functioning, whereas no contribution was demonstrated for chronic medical illness or city of residence. CONCLUSIONS: Factors in addition to panic phenomena contribute to the severe impairment seen in patients with panic disorder. Further research about factors that affect impairment may help improve clinical approaches to this illness.

Adult↗
PubMed1996

Female fitness in Drosophila melanogaster: an interaction between the effect of nutrition and of encounter rate with males.

Female Drosophila melanogaster were maintained at five levels of nutrition, with either continuous or intermittent exposure to males. Remaining frequency increased with nutrition and was higher with continuous exposure to males. Age-specific and lifetime egg production increased with increasing nutrition, but lifespan peaked at intermediate nutrition. Females on the three highest nutritional levels showed a cost of mating in reduced survival, but only at the highest food level did this reduced lifespan lead to a significant cost of mating for lifetime egg production. The data suggest that remating frequencies in laboratory cultures may evolve to a low enough level for the cost of mating to be only weakly expressed, if at all. Further data are required to assess the importance of the cost of mating in natural populations, where the evolution of low remating frequencies might be expected to be opposed by other costs.

Animal Nutritional Physiological Phenomena↗
PubMed1996

The respiratory chain of Helicobacter pylori: identification of cytochromes and the effects of oxygen on cytochrome and menaquinone levels.

The quinone and cytochrome components of the respiratory chain of the microaerophilic bacterium Helicobacter pylori have been investigated. The major isoprenoid quinone was menaquinone-6, with traces of menaquinone-4; no methyl-substituted or unusual menaquinone species were found. Cell yield was highest after growth at 10% (v/v) oxygen and menaquinone levels (per dry cell mass) were maximal at 5-10% (v/v) oxygen. Helicobacter pylori cells and membranes contained b- and c-type cytochromes, but not terminal oxidases of the a- or d-types, as judged by reduced minus oxidised difference spectra. Spectra consistent with the presence of a CO-binding terminal oxidase of the cytochrome b- or o-type were obtained. The soluble fraction from disrupted cells also contained cytochrome c. There were no significant qualitative differences in the cytochrome complements of cells grown at oxygen concentrations in the range 2-15% (v/v) but putative oxidases were highest in cells grown at 5-10% (v/v) oxygen.

Cytochromes↗
PubMed1996

New segregation analysis of panic disorder.

We performed simple segregation analyses of panic disorder using 126 families of probands with DSM-III-R panic disorder who were ascertained for a family study of anxiety disorders at an anxiety disorders research clinic. We present parameter estimates for dominant, recessive, and arbitrary single major locus models without sex effects, as well as for a nongenetic transmission model, and compare these models to each other and to models obtained by other investigators. We rejected the nongenetic transmission model when comparing it to the recessive model. Consistent with some previous reports, we find comparable support for dominant and recessive models, and in both cases estimate nonzero phenocopy rates. The effect of restricting the analysis to families of probands without any lifetime history of comorbid major depression (MDD) was also examined. No notable differences in parameter estimates were found in that subsample, although the power of that analysis was low. Consistency between the findings in our sample and in another independently collected sample suggests the possibility of pooling such samples in the future in order to achieve the necessary power for more complex analyses.

Adult↗
PubMed1996

The DSM-IV panic disorder field trial: panic attack frequency and functional disability.

The goal of the DSM-IV panic disorder field trial was to provide an empirical basis for choosing between alternate proposals (DSM-III-R and proposed DSM-IV) for the diagnostic threshold for panic disorder, in particular the number and frequency of panic attacks required for diagnosis. The two criteria sets were compared with respect to their ability to identify individuals whose panic attacks were associated with distress, impairment, or help-seeking. Subjects were a convenience sample screened in three geographically diverse primary care clinics for presence (past 6 months) or absence (lifetime) of panic attacks. Each underwent a clinician-administered semistructured interview which included assessment of panic frequency, panic-related impairment, psychiatric diagnosis, health services utilization, and medical illness. Self-perceived health-related quality of life was assessed using the Medical Outcome Study SF-36 Health Survey Questionnaire. Although both proposals diagnosed the same proportion of panic-impaired individuals, they were not completely overlapping. Twenty percent of subjects diagnosed by each criteria set were excluded by the other. Subjects who had been excluded by the DSM-III-R but included by the DSM-IV proposal were those with fewer than 4 attacks in 4 weeks who also denied worry about the "next" attack. Broadening the worry criterion to include concerns about the health implications of attacks enabled diagnosis of this group. Subjects who met DSM-III-R, but not the proposed DSM-IV criteria, had 4 attacks in 4 weeks but denied any panic related worry. Modification of the DSM-IV proposal to include a month of worry or "a significant change in behavior related to the attacks" allowed inclusion of this group in the diagnostic category. These data suggest that the finalized DSM-IV panic disorder criteria will diagnose a greater proportion of individuals whose panic attacks are associated with impairment without inflating the diagnostic category or significantly reducing specificity.

Adult↗
PubMed1996

How is lean body mass conserved with the very-low protein diet regimen?

Eight CRF patients (GFR = 18.8 +/- 2.7 ml/min) underwent a crossover comparison of a very-low-protein diet (VLPD) providing 0.28 g protein and 35 kcal/kg/day, plus an isomolar mixture of ketoacids (KA) or essential amino acids (EAA). During each dietary period, a 5-day nitrogen balance (BN) was performed and whole-body protein turnover (WBPT) was measured during fasting and feeding using intravenous [1-13C]leucine and intragastric [5,5,5-2H3]leucine. Although the VLPD/KA regimen contained 15% less nitrogen, BN was neutral and did not differ between the regimens. Similarly, rates of WBPT did not differ between the KA or EAA regimens, and neutral BN was achieved by a marked suppression of amino acid oxidation and postprandial inhibition of protein degradation (PD). Participants were then discharged on the VLPD/KA regimen and monitored as outpatients for > or = 1 year. Repeat BN was neutral and rates of WBPT did not differ from baseline values. Thus, the adaptive responses to dietary protein restriction are sustained during long-term therapy.

Adult↗
PubMed1996

CFTR chloride channels in human and simian heart.

OBJECTIVES: The cAMP-dependent Cl- conductance in heart is believed to be due to cardiac expression of the cystic fibrosis transmembrane conductance regulator (CFTR). While CFTR expressed in rabbit and guinea-pig heart (CFTRcardiac) is an alternatively spliced isoform of the epithelial gene product, little information is known regarding possible expression of CFTR in primate heart. In this study, we examined molecular expression of CFTR in human and simian atrium and ventricle and functional expression of cAMP-dependent Cl- currents in isolated human atrial and simian ventricular cells. METHODS: The reverse transcription polymerase chain reaction (RT-PCR) was performed on human and simian atrial and ventricular mRNA using primers designed to border regions of the CFTR gene product corresponding to transmembrane segments I-VI (TSI-VI), the first nucleotide binding domain (NBD1), transmembrane segments VII-XII (TSVII-XII), and the large cytoplasmic domain which includes the regulatory (R) domain and NBD1. Functional expression of CFTR Cl- channels in human atrial and simian ventricular myocytes was determined using whole-cell and giant inside-out patch-clamp techniques. RESULTS: Southern blot analysis of these RT-PCR products demonstrated expression of CFTR transcripts in human and simian atrial and ventricular tissue and revealed a novel pattern of expression compared to most animal species studies: both the exon 5 plus (unspliced) and exon 5 minus (spliced) CFTR transcripts are co-expressed in human and simian atrium and ventricle. Whole-cell experiments demonstrated a Cl- sensitive time-independent background conductance in both human atrial and simian ventricular myocytes that was activated by forskolin (FSK) and insensitive to 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). In inside-out patches utilizing the giant patch technique on human atrial myocytes, unitary Cl- sensitive channels resembling CFTR Cl- channels (approximately 14 pS conductance) were activated by the catalytic subunit of protein kinase A (PKA) in 3/12 patches examined. CONCLUSIONS: These results clearly demonstrate the molecular expression of CFTR Cl- channels and provide electrophysiological evidence consistent with functional expression of these channels in human atrial and simian ventricular myocardium.

Aged↗
PubMed1995

Cost of mating in Drosophila melanogaster females is mediated by male accessory gland products.

Female Drosophila melanogaster with environmentally or genetically elevated rates of mating die younger than controls. This cost of mating is not attributable to receipt of sperm. We demonstrate here that seminal fluid products from the main cells of the male accessory gland are responsible for the cost of mating in females, and that increasing exposure to these products increases female death rate. Main-cell products are also involved in elevating the rate of female egg-laying, in reducing female receptivity to further matings and in removing or destroying sperm of previous mates. The cost of mating to females may therefore represent a side-effect of evolutionary conflict between males.

Animals↗