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Biomedical subjects

S Morton

Publications and source records attributed to S Morton.

At least 19 recordsLinked to original sources
PubMed2004

Regulatory roles of leptin at the hypothalamic-hypophyseal axis before and after sexual maturation in cattle.

Studies assessed, either directly or indirectly, the role of GnRH in leptin-mediated stimulation of LH release in cattle before and after sexual maturation. In experiment 1, the objectives were to determine whether leptin could acutely accelerate the frequency of LH pulses, and putatively GnRH pulses, in prepubertal heifers at different stages of development. In experiment 2, we determined directly whether acute, leptin-mediated increases in LH secretion in the fasted, mature female are accompanied by an increase in GnRH secretion. Ten-month-old prepubertal heifers (experiment 1) fed normal- (n = 5) and restricted-growth (n = 5) diets received three injections of saline or recombinant ovine leptin (oleptin; 0.2 microg/kg body weight, i.v.) at hourly intervals during 5-h experiments conducted every 5 wk until all normal-growth heifers were pubertal. Leptin increased mean concentrations of circulating LH regardless of diet, but pulse characteristics were not altered at any age. In experiment 2, ovariectomized, estradiol-implanted cows (n = 5) were fasted twice for 72 h and treated with either saline or oleptin i.v. (as in experiment 1) on Day 3 of each fast. Leptin increased plasma concentrations of LH and third ventricle cerebrospinal fluid concentrations of GnRH, and increased the amplitude of LH and the size of GnRH pulses, respectively, on Day 3 of fasting compared to saline. Overall, results indicate that leptin is unable to accelerate the pulse generator in heifers at any developmental stage. However, leptin-mediated augmentation of LH concentrations and pulse amplitude in the nutritionally stressed, mature female are associated with modifications in GnRH secretory dynamics.

Animals↗
PubMed2003

Effects of leptin on basal and GHRH-stimulated GH secretion from the bovine adenohypophysis are dependent upon nutritional status.

We have shown recently that leptin modulates at least two aspects of anterior pituitary LH release in ruminants: basal and GnRH-mediated release. To test the hypothesis that leptin directly affects basal and GHRH-mediated GH secretion from the adenohypophysis, we examined the effects of various doses of recombinant ovine leptin (oleptin) on perifused adenohypophyseal (AP) explants and compared responses of tIssues from control and fasted cows. Ten mature, ovariectomized and estradiol-implanted cows were assigned to one of two dietary groups: (1) normal-fed (n=5) and (2) fasted for 72 h (n=5). At the end of the fasting period, cows were euthanized and pituitaries were collected. Adenohypophyseal explants were perifused for a total of 6.5 h, including a 2-h treatment at 2.5 h with Krebs-Ringer bicarbonate buffer containing 0, 5, 10, 50, or 100 ng/ml oleptin, and a challenge with GHRH at 4.5 h. All doses of oleptin greater than 5 ng/ml decreased (P<0.01) basal GH secretion compared with controls in tIssues collected from normal-fed cows. In contrast, GH release from AP explants from fasted cows treated with the lowest dose of oleptin was 28% (P<0.002) higher than control explants, but larger doses had no effect. Leptin caused an inversely related, dose-dependent increase in GHRH-mediated GH release in tIssues from normal-fed cows. Marked increases (P<0.01-P<0.001) in GH release were observed for the 5 and 10 ng/ml oleptin, with lesser (P<0.08) and no effects observed at the 50 and 100 ng/ml doses respectively. In fasted cows, oleptin had no stimulatory effect on GHRH-induced GH release. Results show that leptin can act directly at the anterior pituitary level to modulate GH release, and this effect is dependent upon nutritional history.

Animals↗
PubMed2002

Dinitrogen oxide detection for process failure early warning systems.

A number of experiments were conducted in order to establish whether the concentration of N2O in the off-gas from an activated sludge pilot plant could be used as a indicator for monitoring the nitrification process and as an early indication of ammonia appearing in the plant effluent. A strong correlation was found between ammonia shock loads and the concentration of N20 in the off-gas from the aeration tank for ammonia shock loads and dissolved oxygen depletion. When subjecting the experimental setup to doses of a nitrification inhibitor (allylthiourea) a similar pattern was seen with a correlation between nitrite build up in the aeration tank and concentration increase of N2O in the off-gas from the aeration tank. The results from this work suggest the concentration and the changes in the concentration of N2O in the exhaust gas from a nitrifying process may be a useful parameter for monitoring nitrifying activated sludge processes.

Ammonia↗
PubMed2001

Predictors of sleep-disordered breathing in children with a history of tonsillectomy and/or adenoidectomy.

STUDY OBJECTIVES: To identify predictors of sleep-disordered breathing (SDB) in children who have undergone self-reported tonsillectomy and/or adenoidectomy (TA). DESIGN: Observational study of pediatric participants in a longitudinal genetic-epidemiological cohort study of SDB. SETTING: Community-based; studies conducted at participants' homes PARTICIPANTS: 577 children age <18 (10.8+/-4.2 SD) years; 53% female; 48% Black; 76% with a family member identified with SDB. INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: Medical history assessed by questionnaire. Physical measures made directly. SDB was assessed with overnight inhome cardio-respiratory monitoring. 10% of children (n=60) had had aTA 5.5+/-4.6 yrs previously. An Apnea-Hypopnea Index (AHI, events/hr) > or =5 was found in a higher proportion of children with a reported TA than in children with no history of out surgery (35% vs. 13.7%, p<.001). A TA was reported more frequently for non-Blacks than for Blacks (13.6% non-Blacks, 6.9% Blacks, p=.02). Among children who had a TA, significant predictors of SDB (AHI> or =5) were: Black ethnicity (SDB in 57% vs. 24% of Blacks vs. non-Blacks; adjusted odds ratio (OR): 3.85; 95% CI: 1.11, 13.33) and obesity (OR 3.98; 95% Cl: 1.05, 15.08). SDB also tended to be greater in children with a family member with SDB (OR 2.87; 95% CI: 0.65, 12.07). CONCLUSIONS: Black children were less likely to have undergone TA but more likely to have SDB after TA surgery. These findings underscore the need to follow children post-TA and for evidence-based studies that define the role of TA in the management of pediatric adenotonsillar disease.

Adenoidectomy↗
PubMed2001

Changes in subjective quality of life among homeless adults who obtain housing: a prospective examination.

BACKGROUND: The aim of this present study is to examine whether overall subjective quality of life and specific domains of quality of life change among homeless adults after they become housed, and if so, what factors predict changes in satisfaction. METHODS: The data analysed here were collected through face-to-face interviews with a sample of 485 homeless adults who were interviewed as often as bi-monthly over a 16-month period. Bivariate analyses examined initial differences between three groups: homeless people who did not exit from homelessness; those with an exit from homelessness to dependent housing; and those with an exit to independent housing. Bivariate analyses also examined differences in subjective quality of life before and after an exit from homelessness among the three groups. Multivariate analyses identified predictors of changes in quality of life before and after exit. RESULTS: This study has three main findings. First, homeless people who obtained independent housing had the largest positive and significant improvements in satisfaction with overall quality of life, and in satisfaction with housing, leisure and money. Second, becoming housed was not a predictor of changes in overall quality of life perceived by homeless people, nor in their satisfaction with leisure, clothing, food, and social life. Furthermore, a positive change in housing satisfaction was not associated with all types of exits from homelessness; only a move into independent housing predicted such a change, but a move into dependent housing did not. Finally, of all the covariates included as predictors at baseline, only two variables seemed to consistently predict changes in satisfaction; namely, self-assessed general health and self-assessed self-help skills. CONCLUSIONS: This study suggested that becoming independently housed may improve some aspects of quality of life for homeless people, but not others. The results suggest that homeless people prefer to be independently housed relative to remaining homeless or staying in a dependent housing situation, but that independent housing does not necessarily improve other aspects of their lives.

Adult↗
PubMed2001

Relationship between 24-H blood pressure and sleep disordered breathing in a normotensive community sample.

Sleep disordered breathing (SDB) and hypertension are commonly associated. In this study, we assessed how longitudinal measures of SDB predict a 24-h ambulatory blood pressure monitoring (ABPM) profile. Participants (n = 82) were recruited from a community-based urban (26% African American) sample and included family members of patients with laboratory diagnosed SDB (cases) and family members of neighborhood control subjects evaluated at baseline and at 5 years. Nearly all participants were normotensive and were not receiving therapy for SDB. During both examinations, the respiratory distress index (RDI) was assessed with overnight in-home polysomnography. Seated blood pressure (BP) was assessed at a baseline examination (t,) and after a 5-year follow-up period (t5), when 24-h ABPM also was performed. The change in RDI (t5-t1) over 5 years was significantly associated with 24-h mean systolic blood pressure (SBP) (P = .04), 24-h maximum diastolic blood pressure (DBP) (P = .03), sleep mean SBP (P = .05), sleep mean DBP (P < .05), and sleep maximum SBP (P = .02). Regression analysis revealed that average 24-h mean arterial pressure (MAP) and mean 24-h DBP were each best predicted by change in RDI, explaining 5% of the variance in these 24-h BP readings, and by current smoking status. After accounting for these variables, BP was not predicted by any of the other potential confounders (all P > .10). Mean RDI (averaged between t5 and t1) was associated with mean MAP, mean SBP, and maximal SBP measured during sleep. This study documents for the first time the association between changes in sleep apnea activity and BP and in a community-based normotensive sample. Further long-term evaluation of the effects of these findings and the long-term consequences of hypertension are needed.

Adult↗
PubMed2001

Sensitive LH and FSH assays for monitoring low serum levels in men undergoing steroidal contraception.

BACKGROUND AND OBJECTIVES: Current immunoassays for detecting serum FSH and LH are not sufficiently sensitive to detect the markedly reduced levels in men undergoing steroidal hormonal treatment for contraceptive purposes. The purpose of this study was to increase the sensitivity of available LH and FSH immunofluorometric (Delfia) assays in order to allow a better understanding of the importance of gonadotrophin suppression in achieving the optimal suppression of sperm count. DESIGN AND PATIENTS: Assay conditions were modified by increasing serum sample volume, the inclusion of either FSH- or LH-depleted serum to reduce the resulting matrix effects and extending incubation times. The microassays were applied to serum from 10 men administered testosterone enanthate with or without depot medroxyprogesterone acetate for 12 weeks as part of a contraceptive trial. RESULTS: The assay sensitivities were increased to 0.005 IU/l for LH and 0.010 IU/l for FSH, representing a five- to six-fold increase in sensitivity compared with existing assays. In the clinical trial, serum LH levels were suppressed to near or below the level of assay detection (mean 0.014 IU/l < 0.4% of pretreatment values) while in eight of 10 men, plasma FSH levels were detectable (0.04-0.07 IU/l, 1-5% of pretreatment values). These FSH levels would not have been detected by current assays. CONCLUSIONS: The increased sensitivities of the LH and FSH assays enabled the detection of gonadotrophins that were < 0.4% of pretreatment serum levels. Using these methods, serum LH was suppressed to nondetectable or near nondetectable levels while serum FSH was highly suppressed but still detectable in the majority of men undergoing steroidal treatment for contraceptive purposes.

Contraceptive Agents, Male↗
PubMed2001

'Oh it's a wonderful practice... you can talk to them': a qualitative study of patients' and health professionals' views on the management of type 2 diabetes.

This paper uses 85 semistructured interviews with people with type 2 diabetes, and with the health professionals who deliver their diabetes care, to explore the issues that they perceive as central to effective management of diabetes, primarily within a primary care setting. Attention is especially focused on the nature of the patient-practitioner relationship, and on the implications of this for patient empowerment and the effective self-management of diabetes. The paper is organized around five key concepts identified in the qualitative analysis: the importance of having sufficient time for consultations, the significance of continuity of care through a named individual, the need for patients to have an opportunity to ask questions during a consultation, the extent to which patients feel that they are listened to by health professionals, and the variability of each patient's individual experience of living with diabetes. In conclusion, these themes are briefly related to key issues in the geography of health.

Aged↗
PubMed2001

Phosphorus availability for beneficial use in biosolids products.

It has become necessary to identify accurately the availability of phosphorus in biosolids products applied to land. The fertiliser value of these products must be quantified not only to satisfy the customer but also to ensure the best use of phosphorus when considering the need to avoid excess concentrations in the wider environment, With the advent of chemical phosphorus removal at more wastewater treatment works, the impact of iron and phosphate availability is particularly important. Existing research has indicated that there is a correlation between phosphate availability, and factors such as biosolids pH and iron concentration. However, it has not yet been possible to draw any firm conclusions, which can be used as a tool to manage the availability of phosphate in practice. Through a joint research programme for Anglian Water, involving literature investigation, laboratory tests on biosolid/soil interactions, and benchmarking phosphate availability over time, the study uses the best available input and output data to indicate the parts of the land bank most at risk from over-enrichment.

Agriculture↗
PubMed2001

Classification and identification of Pfiesteria and Pfiesteria-like species.

Dinoflagellates can be classified both botanically and zoologically; however, they are typically put in the botanical division Pyrrhophyta. As a group they appear most related to the protistan ciliates and apicomplexans at the ultrastructure level. Within the Pyrrhophyta are both unarmored and armored forms of the dominant, motile flagellated stage. Unarmored dinoflagellates do not have thecal or wall plates arranged in specific series, whereas armored species have plates that vary in thickness but are specific in number and arrangement. In armored dinoflagellates, the plate pattern and tabulation is a diagnostic character at the family, subfamily, and even genus levels. In most cases, the molecular characterization of dinoflagellates confirms the taxonomy on the basis of external morphology; this has been demonstrated for several groups. Together, both genetic and morphological criteria are becoming increasingly important for the characterization, separation, and identification of dinoflagellates species. Pfiesteria and Pfiesteria-like species are thinly armored forms with motile dinospore stages characterized by their distinct plate formulae. Pfiesteria piscicida is the best-known member of the genus; however, there is at least one other species. Other genetically and morphologically related genera, now grouped under the common names of "Lucy," "Shepherd's crook," and cryptoperidiniopsoid, are being studied and described in separate works. All these other heterotrophic dinoflagellate groups, many of which are thought to be benign, co-occur in estuarine waters where Pfiesteria has been found.

Animals↗
PubMed2001

Simultaneous activated sludge wastewater treatment and odour control.

Lab-scale tests were used to determine the amount of H2S that can be treated using a range of different activated sludges. Static vessels were used to study the effects of different H2S concentrations (5, 25, 50 and 75 ppm). The data indicated that odour control may be carried out using certain types of sludge, but sludge type, e.g. carbonaceous, nitrifying, with or without coagulant, affects removal efficiency. The presence of the biomass resulted in greater H2S removal than the use of wet scrubbing and the adverse effects on mixed liquor were negligible. A pilot plant was used to study the removal efficiencies of activated sludge diffusion using a typical wastewater treatment plant H2S concentration and investigated the effects that the diffusion of H2S had on the process performance. Results indicated that the levels of H2S produced by other unit processes on a wastewater treatment site (approximately 5 ppm) can be treated using activated sludge diffusion without compromising the performance of the wastewater treatment process. The only effects on the activated sludge plant observed were: (1) nitrification was interrupted briefly as H2S diffusion commenced and (2) the species' diversity in the sludge decreased.

Air Pollution↗
PubMed2000

Prevalence and predictors of highly active antiretroviral therapy use in patients with HIV infection in the united states. HCSUS Consortium. HIV Cost and Services Utilization.

BACKGROUND: Highly active antiretroviral therapy (HAART) became standard for HIV in 1996. Studies at that time showed that most people infected with HIV had initiated HAART, but that members of minority groups and poor people had lower HAART use. It is not known whether high levels of HAART use have been sustained or whether socioeconomic and racial disparities have diminished over time. OBJECTIVES: To determine the proportion of patients who had received and were receiving HAART by January 1998, and to evaluate predictors of HAART receipt. DESIGN AND PARTICIPANTS: Prospective cohort study of a national probability sample of 2267 adults receiving HIV care who completed baseline, first follow-up, and second follow-up interviews from January 1996 to January 1998. MAIN OUTCOME VARIABLES: Proportion currently using HAART at second follow-up (August 1997 to January 1998), contrasted with the cumulative proportions using HAART at any time before January 1998 and before December 1996. ANALYSES: Bivariate and multiple logistic regression analysis of population characteristics predicting current use of HAART at the time of the second follow-up interview. RESULTS: The proportion of patients ever having received HAART increased from 37% in December 1996 to 71% by January 1998, but only 53% of people were receiving HAART at the time of the second follow-up interview. Differences between sociodemographic groups in ever using HAART narrowed after 1996. In bivariate analysis, several groups remained significantly less likely to be using HAART at the time of the second follow-up interview: blacks, male and female drug users, female heterosexuals, people with less education, those uninsured and insured by Medicaid, those in the Northeast, and those with CD4 counts of >/=500 cells/microl (all p <.05). Using multiple logistic regression analysis, low CD4 count (for CD4 <50 cells/microl: odds ratio [OR], 3.20; p <.001) remained a significant predictor of current HAART use at the time of the second follow-up interview, but lack of insurance (OR, 0.71; p <.05) predicted not receiving HAART. CONCLUSIONS: The proportion of persons under HIV care in the United States who had ever received HAART increased to over 70% of the affected population by January 1998 and the disparities in use between groups narrowed but did not disappear. However, nearly half of those eligible for HAART according to the U.S. Department of Health and Human Services guidelines were not actually receiving it nearly 2 years after these medications were first introduced. Strategies to promote the initiation and continuation of HAART are needed for those without contraindications and those who can tolerate it.

Adolescent↗
PubMed2000

Delayed medical care after diagnosis in a US national probability sample of persons infected with human immunodeficiency virus.

OBJECTIVE: To identify health care and patient factors associated with delayed initial medical care for human immunodeficiency virus (HIV) infection. DESIGN: Survey of a national probability sample of persons with HIV in care. SETTING: Medical practices in the contiguous United States. PATIENTS: Cohort A (N = 1540) was diagnosed by February 1993 and was in care within 3 years; cohort B (N = 1960) was diagnosed by February 1995 and was in care within 1 year of diagnosis. MAIN OUTCOME MEASURE: More than 3- or 6-month delay. RESULTS: Delay of more than 3 months occurred for 29% of cohort A (median, 1 year) and 17% of cohort B. Having a usual source of care at diagnosis reduced delay, with adjusted odds ratios (ORs) of 0.61 (95% confidence interval [CI], 0.48-0.77) in cohort A and 0. 70 (95% CI, 0.50-0.99) in cohort B. Medicaid coverage at diagnosis showed lower adjusted ORs of delay compared with private insurance (cohort A: adjusted OR, 0.52; 95% CI, 0.30-0.92; cohort B: adjusted OR, 0.48; 95% CI, 0.27-0.85). Compared with whites, Latinos had 53% and 95% higher adjusted ORs of delay (P<.05) in cohorts A and B, respectively, and African Americans had a higher adjusted OR in cohort A (1.56; 95% CI, 1.19-2.04). The health care factors showed similar effects on delay of greater than 6 months. CONCLUSIONS: Medicaid insurance and a usual source of care were protective against delay after HIV diagnosis. After full adjustment, delay was still greater for Latinos and, to a lesser extent, African Americans compared with whites.

Adult↗
PubMed2000

Composition of alveolar surfactant changes with training in humans.

OBJECTIVE: We test the hypothesis that the changes we observed previously in the relative amounts of disaturated phospholipids (DSP), cholesterol (CHOL), and surfactant protein-A (SP-A) in human alveolar surfactant in response to acute exercise, and which were related to fitness, can be induced by training. METHODOLOGY: We examine the effect of 7 weeks' training on these major surfactant components, together with surfactant protein-B (SP-B), in bronchoalveolar lavage fluid harvested from 17 males, both at rest and after acute exercise. Fitness was assessed as workload/heart rate achieved during cycling for 30 min at 90% of theoretical maximal heart rate, and was increased in all subjects following training (mean increase 22.2+/-3.91%; P = 0.001). RESULTS: Training significantly increased the SP-A/DSP, SP-B/DSP, SP-A/CHOL and SP-A/SP-B ratios in whole surfactant harvested from subjects both at rest and immediately following exercise. Training also increased the SP-B/CHOL ratio at rest. Changes were particularly marked at rest in the SP-A/DSP, SP-A/CHOL, and SP-B/CHOL ratios in the tubular myelin-rich fraction, and after exercise in the SP-A/DSP, SP-A/CHOL, and SP-A/SP-B ratios in the tubular myelin-poor fraction. CONCLUSION: We conclude that training markedly alters the composition of alveolar surfactant both at rest and with exercise; the physiological significance of these changes remains to be determined.

Adolescent↗
PubMed2000

Violence victimization after HIV infection in a US probability sample of adult patients in primary care.

OBJECTIVES: This study estimated the proportion of HIV-infected adults who have been assaulted by a partner or someone important to them since their HIV diagnosis and the extent to which they reported HIV-seropositive status as a cause of the violence. METHODS: Study participants were from a nationally representative probability sample of 2864 HIV-infected adults who were receiving medical care and were enrolled in the HIV Costs and Service Utilization Study. All interviews (91% in person, 9% by telephone) were conducted with computer-assisted personal interviewing instruments. Interviews began in January 1996 and ended 15 months later. RESULTS: Overall, 20.5% of the women, 11.5% of the men who reported having sex with men, and 7.5% of the heterosexual men reported physical harm since diagnosis, of whom nearly half reported HIV-seropositive status as a cause of violent episodes. CONCLUSIONS: HIV-related care is an appropriate setting for routine assessment of violence. Programs to cross-train staff in antiviolence agencies and HIV care facilities need to be developed for men and women with HIV infection.

Adolescent↗