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Biomedical subjects

S M Rogers

Publications and source records attributed to S M Rogers.

At least 19 recordsLinked to original sources
PubMed2006

Linkage maps of the dwarf and Normal lake whitefish (Coregonus clupeaformis) species complex and their hybrids reveal the genetic architecture of population divergence.

Elucidating the genetic architecture of population divergence may reveal the evolution of reproductive barriers and the genomic regions implicated in the process. We assembled genetic linkage maps for the dwarf and Normal lake whitefish species complex and their hybrids. A total of 877 AFLP loci and 30 microsatellites were positioned. The homology of mapped loci between families supported the existence of 34 linkage groups (of 40n expected) exhibiting 83% colinearity among linked loci between these two families. Classes of AFLP markers were not randomly distributed among linkage groups. Both AFLP and microsatellites exhibited deviations from Mendelian expectations, with 30.4% exhibiting significant segregation distortion across 28 linkage groups of the four linkage maps in both families (P < 0.00001). Eight loci distributed over seven homologous linkage groups were significantly distorted in both families and the level of distortion, when comparing homologous loci of the same phase between families, was correlated (Spearman R = 0.378, P = 0.0021). These results suggest that substantial divergence incurred during allopatric glacial separation and subsequent sympatric ecological specialization has resulted in several genomic regions that are no longer complementary between dwarf and Normal populations issued from different evolutionary glacial lineages.

Animals↗
PubMed2006

The genetic basis of intrinsic and extrinsic post-zygotic reproductive isolation jointly promoting speciation in the lake whitefish species complex (Coregonus clupeaformis).

Understanding the genetic architecture of reproductive barriers and the evolutionary forces that drove their divergence represents a considerable challenge towards understanding speciation. The objective of this study was to determine the genetic basis of intrinsic and extrinsic post-zygotic isolation in diverging populations of dwarf and normal lake whitefish with allopatric glacial origins. We found that the rate of embryonic mortality was 5.3-6.5 times higher in dwarf-normal hybrid backcrosses during development than in F1 dwarf and normal crosses. When comparing embryos that died during development against larvae that successfully hatched, patterns of Mendelian segregation at 101 loci whose linkage is known identified 13 loci distributed over seven linkage groups that exhibited significant shifts in segregation ratios leading to significant segregation distortion at these loci in the surviving progeny. Controlled crosses and quantitative trait loci analysis revealed a significant genetic basis for developmental time until emergence, a trait critical to fish larval survival in nature. Hatching backcross progeny exhibited asynchronous emergence and transgressive segregation, suggesting that extrinsic post-zygotic isolation may select against hybridization in specific environmental contexts. Evidence of a genetic basis for increased embryonic mortality followed by asynchronous emergence indicated that intrinsic and extrinsic mechanisms are not mutually exclusive in the formation and maintenance of reproductive isolation, but may be jointly promoting population divergence and ultimately speciation.

Animals↗
PubMed2005

Integrating QTL mapping and genome scans towards the characterization of candidate loci under parallel selection in the lake whitefish (Coregonus clupeaformis).

As natural selection must act on underlying genetic variation, discovering the number and location of loci under the influence of selection is imperative towards understanding adaptive divergence in evolving populations. Studies employing genome scans have hypothesized that the action of divergent selection should reduce gene flow at the genomic locations implicated in adaptation and speciation among natural populations, yet once 'outlier' patterns of variation have been identified the function and role of such loci needs to be confirmed. We integrated adaptive QTL mapping and genomic scans among diverging sympatric pairs of the lake whitefish (Coregonus clupeaformis) species complex in order to test the hypothesis that differentiation between dwarf and normal ecotypes at growth-associated QTL was maintained by directional selection. We found evidence of significantly high levels of molecular divergence among eight growth QTL where two of the strongest candidate loci under the influence of directional selection exhibited parallel reductions of gene flow over multiple populations.

Adaptation, Biological↗
PubMed2005

Monitoring STI prevalence using telephone surveys and mailed urine specimens: a pilot test.

OBJECTIVES: This pilot test assessed the feasibility of a cost effective population based approach to STI monitoring using automated telephone interviews, urine specimen collection kits sent out and returned by US Postal Service mail, and monetary incentives to motivate participation. METHODS: 100 residents of Baltimore, MD, USA, completed an automated telephone survey and agreed to mail in a urine specimen to be tested for chlamydia and gonorrhoea. Participants were paid dollar 10 for completing the survey and dollar 40 for mailing the specimen. RESULTS: 86% of survey participants mailed in a urine specimen for testing. CONCLUSIONS: Automated telephone surveys linked with testing of mailed-in urine specimens may be a feasible lower cost (relative to household surveys) method of estimating infection prevalences in a population.

Adolescent↗
PubMed2005

Audio computer assisted interviewing to measure HIV risk behaviours in a clinic population.

OBJECTIVES: To examine whether audio computer assisted survey interviewing (ACASI) influenced responses to sensitive HIV risk behaviour questions, relative to interviewer administration of those questions (IAQ), among patients attending a sexually transmitted infection (STI) clinic and whether the impact of interview mode on reporting of risk behaviours was homogeneous across subgroups of patients (defined by age, sex, and previous STI clinic experience). METHODS: 1350 clinic patients were assigned to complete a detailed behavioural survey on sexual risk practices, previous STIs and symptoms, condom use, and drug and alcohol use using either ACASI or IAQ. RESULTS: Respondents assigned to ACASI were more likely to report recent risk behaviours such as sex without a condom in the past 24 hours (adjusted OR = 1.9), anal sex (adjusted OR = 2.0), and one or more new partners in the past 6 months (adjusted OR = 1.5) compared to those interviewed by IAQ. The impact of ACASI varied by sex but, contrary to expectations, not by whether the patient had previously visited an STI clinic. Mode of survey administration made little difference within this population in reports of STI knowledge, previous STIs, STI symptoms, or illicit drug use. CONCLUSION: ACASI provides a useful tool for improving the quality of behavioural data in clinical environments.

Adolescent↗
PubMed2003

LCR testing for gonorrhoea and chlamydia in population surveys and other screenings of low prevalence populations: coping with decreased positive predictive value.

OBJECTIVE: Nucleic acid amplification tests have facilitated field based STD studies and increased screening activities. However, even with highly specific tests, the positive predictive value (PPV) of such tests may be lower than desirable in low prevalence populations. We estimated PPVs for a single LCR test in a population survey in which positive specimens were retested. METHODS: The Baltimore STD and Behavior Survey (BSBS) was a population based behavioural survey of adults which included collecting urine specimens to assess the prevalence of gonorrhoea and chlamydial infection. Gonorrhoea and chlamydial infection were diagnosed by ligase chain reaction (LCR). Nearly all positive results were retested by LCR. Because of cost considerations, negative results were not confirmed. Predicted curves for the PPV were calculated for a single testing assuming an LCR test sensitivity of 95%, and test specificities in the range 95.0%-99.9%, for disease prevalences between 1% and 10%. Positive specimens were retested to derive empirical estimates of the PPV of a positive result on a single LCR test. RESULTS: 579 participants age 18-35 provided urine specimens. 20 (3.5%) subjects initially tested positive for chlamydial infection, and 39 (6.7%) tested positive for gonococcal infection. If positive results on the repeat LCR are taken as confirmation of a "true" infection, the observed PPV for the first LCR testing was 89.5% for chlamydial infection and 83.3% for gonorrhoea. This is within the range of theoretical PPVs calculated from the assumed sensitivities and specificities of the LCR assays. CONCLUSIONS: Empirical performance of a single LCR testing approximated the theoretically predicted PPV in this field study. This result demonstrates the need to take account of the lower PPVs obtained when such tests are used in field studies or clinical screening of low prevalence populations. Repeat testing of specimens, preferably with a different assay (for example, polymerase chain reaction), and disclosure of the non-trivial potential for false positive test results would seem appropriate in all such studies.

Adolescent↗
PubMed2001

Combining the analyses of introgressive hybridisation and linkage mapping to investigate the genetic architecture of population divergence in the lake whitefish (Coregonus clupeaformis, Mitchill).

Adaptation and reproductive isolation, the engines of biological diversity, are still elusive when discussing the genetic bases of speciation. Namely, the number of genes and magnitude of selection acting positively or negatively on genomic traits implicated in speciation is contentious. Here, we describe the first steps of an ongoing research program aimed at understanding the genetic bases of population divergence and reproductive isolation in the lake whitefish (Coregonus clupeaformis). A preliminary linkage map originating from a hybrid cross between dwarf and normal ecotypes is presented, whereby some of the segregating AFLP markers were found to be conserved among natural populations. Maximum-likelihood was used to estimate hybrid indices from non-diagnostic markers at 998 AFLP loci. This allowed identification of the most likely candidate loci that have been under the influence of selection during the natural hybridisation of whitefish originating from different glacial races. As some of these loci could be identified on the linkage map, the possibility that selection of traits in natural populations may eventually be correlated to specific chromosomal regions was demonstrated. The future prospects and potential of these approaches to elucidate the genetic bases of adaptation and reproductive isolation among sympatric ecotypes of lake whitefish is discussed.

Animals↗
PubMed2000

Parallel somatotopic maps of gustatory and mechanosensory neurons in the central nervous system of an insect.

Relatively little is still known about the sense of taste, or contact chemoreception, compared with other sensory modalities, despite its importance to many aspects of animal behaviour. The central projections of the sensory neurons from bimodal contact chemoreceptors (basiconic sensilla) were compared with those from mechanosensory tactile hairs located on similar regions of the middle leg of the locust. Basiconic sensilla are multiply innervated, containing one mechanosensory and several chemosensory neurons, whereas tactile hairs are innervated by a single mechanosensory neuron. We show that the sensory neurons from tactile hairs form a complete 3-dimensional somatotopic map in the mesothoracic ganglion. Sensory neurons from hairs located on the coxa projected to a region near the midline of the ganglion with neurons from hairs located on progressively more distal parts of the leg arborizing in successively more lateral regions of neuropil. All the neurons from basiconic sensilla, both mechanosensory and chemosensory, also projected in a similar, strictly somatotopic, manner, and the arbors from these neurons overlapped considerably with those from tactile hairs on equivalent parts of the leg to form a continuous region. Thus, the position of a receptor on the leg is preserved in the central nervous system not only for the mechanosensory neurons from both tactile hairs and basiconic sensilla but also for chemosensory neurons. We could observe no anatomical features or small differences in projection region between sensory neurons from individual basiconic sensilla consistent with differences in modality.

Animals↗
PubMed2000

Local movements evoked by chemical stimulation of the hind leg in the locust Schistocerca gregaria.

The behavioural responses of desert locusts, Schistocerca gregaria, to solutions of four behaviourally relevant chemicals (sodium chloride, sucrose, nicotine hydrogen tartrate and lysine glutamate) applied as droplets to the hind tarsus were analysed. All responses following within 1 s of chemical stimulation were local leg avoidance reflexes, and the probability of eliciting such a response increased in a dose-dependent manner with increasing concentration for all the chemicals tested. Chemical identity, however, critically determined the concentration threshold at which the different chemicals became an effective stimulus. For example, a 2.5 mmol l(-)(1) concentration of the secondary plant metabolite nicotine hydrogen tartrate (NHT), a potent feeding deterrent to locusts, was sufficient to evoke avoidance responses in 50 % of cases, whilst for the nutrients, sucrose and lysine glutamate, 250-500 mmol l(-)(1) of the chemical was needed to induce avoidance behaviour in 50 % of the locusts. NaCl was of intermediate effectiveness, with a 50 % response rate occurring at a concentration of approximately 50 mmol l(-)(1). The latency to the start of the response following stimulation was negatively correlated with the concentration of NaCl, but for the other chemicals concentration had no effect on latency. The duration of the avoidance behaviour decreased with increasing concentration for NaCl and more weakly for NHT, but not for the other chemicals. Adding a subthreshold concentration of sucrose to 50 mmol l(-)(1) NaCl decreased the incidence of response compared with 50 mmol l(-)(1) NaCl on its own. Experiments with other mixtures combining NaCl, sucrose and NHT indicate that the frequency and dynamics of the responses to chemical mixtures cannot be simply predicted from the responses to their individual constituents.

Animals↗
PubMed1998

Adolescent sexual behavior, drug use, and violence: increased reporting with computer survey technology.

Surveys of risk behaviors have been hobbled by their reliance on respondents to report accurately about engaging in behaviors that are highly sensitive and may be illegal. An audio computer-assisted self-interviewing (audio-CASI) technology for measuring those behaviors was tested with 1690 respondents in the 1995 National Survey of Adolescent Males. The respondents were randomly assigned to answer questions using either audio-CASI or a more traditional self-administered questionnaire. Estimates of the prevalence of male-male sex, injection drug use, and sexual contact with intravenous drug users were higher by factors of 3 or more when audio-CASI was used. Increased reporting was also found for several other risk behaviors.

Adolescent↗
PubMed1998

Effects of interview mode on bias in survey measurements of drug use: do respondent characteristics make a difference?

Three recent empirical studies have provided strong evidence that self-administered questionnaires (SAQs), compared with interviewer questioning, substantially improve the reporting of drug use in population surveys. Specifically, SAQs appear to diminish underreporting bias. Two of these studies previously reported that this effect of interview mode varied significantly across gender, race/ethnicity, and age. Data from a randomized experiment embedded in the 1990 National Household Survey of Drug Abuse (NHSDA) field test were reanalyzed to test for those interaction effects. To better replicate prior studies, the NHSDA field test sample was restricted to people ages 18 to 45 (N = 1,877). The results of our statistical analyses generally replicated the finding of a main effect of SAQs on the reporting of drug use. However, only weak evidence was found to support the hypothesis that the advantage of SAQs varies substantially by the gender, race/ethnicity, or age of the respondent.

Adolescent↗
PubMed1997

Thermoregulation during exercise in women who are taking oral contraceptives.

Thermoregulation during exercise was studied in seven women who were taking oral contraceptive pills for 3 weeks of each month. The subjects were studied once in the 3rd week of taking the pill (P) and once during the following week when they took no pil (N). Rectal temperature (Tre), heart rate (fc) and evaporative water loss (EWL, ventilated capsule technique) were measured while they walked on a treadmill for 60 min at 4.8 km.h-1 at a 10% gradient. Ambient temperature was 22 degrees C. A venous blood sample was drawn 30 min before each experiment for measurement of hematocrit (packed cell volume, PCV), plasma osmolality (Osmpl), and plasma levels of the endogenous pyrogens interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6). Resting Tre was 0.31 degree C higher in P than in N (P < 0.01) and Tre remained higher in P throughout the entire exercise period (P < 0.01). Threshold Tre for the onset of EWL was 0.32 degree C higher in P than in N (P < 0.01). Exercise fc was 6.5 beats.min-1 higher in P than in N (P < 0.01). There was no significant difference in PCV, Osmpl, IL-1 beta or IL-6 between P and N. It was concluded that the administration of synthetic progestins in oral contraceptives causes an upward shift in the threshold for heat loss responses, resulting in higher body core temperatures both at rest and during exercise. There was no evidence that these alterations in thermoregulation were mediated by changes in body fluid balance or in plasma levels of IL-1 beta or IL-6.

Adult↗
PubMed1994

Neurologic health outcomes and Agent Orange: Institute of Medicine report.

The National Academy of Sciences' Institute of Medicine conducted an independent scientific investigation to evaluate the strength of evidence for human health effects among veterans exposed to herbicides used in Vietnam and to suggest future research recommendations. Neurologic domains where multiple studies had been performed in military, occupational, or environmental situations were (1) cognitive and neuropsychiatric effects, (2) motor/coordination dysfunction and other central nervous system disorders, and (3) peripheral neuropathy. In all categories, no strong evidence established an association between herbicides used in Vietnam and clinical neurologic disorders. Methodologic weaknesses, long durations between exposure and assessments, and poor exposure measures limited many studies. The committee concluded that the available evidence was insufficient to determine an association between neurologic disorders and exposure to herbicides used in Vietnam. Neurotoxicologic studies available did not suggest strong biological plausibility for neurologic alterations related to herbicide exposure. Furthermore, given the large uncertainties in the epidemiologic studies reviewed and inadequate control for important confounders, the committee could not quantify a degree of risk for neurologic disorders from herbicide exposure likely to be experienced by Vietnam veterans. Although not part of the neurologic report, the risk of brain tumors was considered in the cancer analysis, and the committee concluded that there is limited/suggestive evidence of no association between exposure to herbicides and brain tumors.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1990

Eye banking: the Minnesota experience.

We present a brief report on the activities of the Minnesota Lions Eye Bank. This eye bank receives and supplies tissue to several midwestern states. In addition, it plays a vital role in providing tissue for research and training at the University of Minnesota. In association with the Department of Ophthalmology, the eye bank is also actively involved in the research and development of various corneal preservation systems. Included below is information relative to procedures used in the eye bank for the selection and collection of donor material; the decontamination, preparation, and storage of corneas; cost of eye bank services; and staff coverage. Also included is some data on the number of eyes received and processed and the eventual uses of the tissues, during the last ten years.

Corneal Transplantation↗
PubMed1989

Emergency presentation of coalescent mastoiditis.

Since the introduction of sulfonamides in the late 1930s, coalescent mastoiditis is an uncommon complication of otitis media. Swelling, erythema, and tenderness over the mastoid area with associated anterior displacement of the auricle are classic signs and symptoms of coalescent mastoiditis with formation of a subperiosteal abscess. Early recognition of this entity is essential to prevent its complications. Prompt otolaryngologic consultation is indicated and inpatient antibiotic therapy should be begun. Surgical treatment is also needed and may obviate further complications.

Ceftizoxime↗
PubMed1988

A comparison of two cause-of-death classification systems for deaths among women of reproductive age in Menoufia, Egypt.

Mortality data ascertained from sources other than a death registration system can validate the accuracy of the system, but this information is rarely obtained. Data on 1979 deaths among reproductive age women were collected in the 1981-1983 Reproductive Age Mortality Survey (RAMOS) in the governorate of Menoufia, Egypt, and compared with data on these deaths as recorded by the Egyptian death registration system. Although the distribution of the causes of death were similar, there were substantial differences between classification systems for deaths due to particular causes. Over half of the deaths classified differently by the systems were those assigned to circulatory disease on the death certificate. In contrast, there was a high rate of agreement between systems in the classification of trauma deaths. About half (52.4%) of cancer deaths had the same site-specific cancer diagnosis assigned by RAMOS. The percentage of deaths assigned to maternal causes was three times higher in RAMOS (19.2%) than on death certificates (6.1%). Reported mortality rates for this often-preventable cause of death have been substantially underestimated in national death registration systems. Such underreporting masks the need for additional prenatal care and maternal health programmes.

Adolescent↗