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Biomedical subjects

B Stewart

Publications and source records attributed to B Stewart.

At least 19 recordsLinked to original sources
PubMed1998

An evaluation of the marmoset Callithrix jacchus (sagüi) as an experimental model for the dyslipoproteinemia of human Schistosomiasis mansoni.

Human infection with the parasite Schistosoma mansoni is a relatively common occurrence in regions of South America and is associated with liver dysfunction and dyslipoproteinemia. Specifically, the activity of plasma lecithin:cholesterol acyltransferase (LCAT) activity is reduced, the concentration of plasma cholesterol esters falls, phospholipid concentrations are elevated and erythrocyte membranes become cholesterol enriched. Previous studies have utilized rodents (rats and mice) as experimental models to study the dyslipoproteinemia induced by S. mansoni infection. However, the plasma lipoprotein profiles in these animals is very different from humans and infection is not accompanied by decreases in LCAT activity or cholesterol enrichment of their erythrocyte membranes. Here we have evaluated the suitability of the marmoset Callithrix jacchus (sagüi) which is small and readily available in Brazil, as a potential animal model for the study of the dyslipoproteinemia of S. mansoni infections. The plasma lipoprotein compositions and distributions in sagüi, unlike rats or mice, approximate those of man with the LDL representing a major lipoprotein species. The molecular species of phospholipids, cholesterol esters and triglycerides present in sagüi plasma are also very similar to man, whereas those of rats and mice favor the longer chain more unsaturated species, Sagüi, like rodents, can be successfully infected with S. mansoni and after 60 days, this results in a 50% reduction in plasma LCAT activity, an 11% reduction in plasma cholesterol esters, an absolute increase of 46% in plasma phospholipids and an 18% increase in the cholesterol content of erythrocyte membranes. These changes are qualitatively and quantitatively very similar to those previously reported following human infections. Based upon these changes, and the observation that the plasma lipoprotein profile of sagüi and human is similar, we conclude that C. jacchus (sagüi) is an appropriate animal model for the study of dyslipoproteinemia associated with S. mansoni infections.

Animals↗
PubMed1998

Screening of chlorpropamide in horse plasma by high-performance liquid chromatography with ultraviolet absorbance detection, and confirmation by gas chromatography-mass spectrometry.

A chromatographic method was developed to detect and confirm the presence of chlorpropamide (I) in horse plasma samples, for antidoping control. The plasma sample (1 ml) was extracted with dichloromethane and screened by high-performance liquid chromatography, and confirmation of the drug's presence was accomplished by using gas chromatography-mass spectrometry (GC-MS). The limit of detection was found to be 3.5 ng/ml at a signal-to-noise ratio of three. Derivatization of I with N,O-bis-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane allowed for highly stable, accurate and sensitive GC-MS analysis. Plasma samples collected after the administration of diabinese were positive for I (one-five days) in all samples analysed.

Animals↗
PubMed1998

The participation of families of homeless persons with severe mental illness in an outreach intervention.

OBJECTIVES: This study describes how an Assertive Community Treatment (ACT) team which employs a family outreach worker (FOW) interacts with homeless persons with severe mental illness and their families. METHODS: The team's ratings of the frequency and importance of clients' and treatment team's family contact are summarized and compared with independent research reports on patients' satisfaction with family relations, housing and hospitalization outcomes. RESULTS: 73% of clients had contact with their families. ACT worked with families of 61% of clients. ACT had less contact with the families of men (p < .01) and substance abusers (p < .01). Client days in stable housing were associated with increased ACT family contact (p < .05). CONCLUSIONS: Most ACT clients had significant family contact. ACT established contact with most families, and the work with families appeared to be associated with higher levels of satisfaction with family relations and housing. The role of the FOW should be explored further.

Adult↗
PubMed1998

Contamination of embryo transfer catheter and treatment outcome in in vitro fertilization.

PURPOSE: The effect of embryo transfer (ET) catheter contamination with mucus and/or blood on treatment outcome in an in vitro fertilization (IVF) program was evaluated. METHODS: One thousand four ET procedures in 877 patients having conventional IVF in the long (1189 cycle) and short (15 cycles) protocol were analyzed to determine the impact of catheter contamination on the incidence of retained embryos and the clinical pregnancy rate. RESULTS: Catheter contamination with mucus and/or blood is a feature of difficult ET. Embryos were significantly more likely to be retained when the transfer catheter was contaminated with mucus (17.8 versus 3.3%) or blood (12 versus 3.3%). When the catheter was contaminated and an embryo(s) was retained and immediately retransferred, the pregnancy rate was not compromised. The pregnancy rate was significantly reduced when the ET catheter was contaminated with blood (15.5 versus 27.1%; P = 0.002), but no embryo was retained in the catheter set. CONCLUSIONS: Catheter contamination compromises the treatment outcome in IVF only when there is no associated retained embryo(s). As increased vigilance in searching for extruded embryos may not be practical, we suggest that cervical mucus should be routinely aspirated and ET performed as atraumatically as possible.

Adult↗
PubMed1998

The importance of water quality for media preparation.

The variability in pregnancy rates achieved among in-vitro fertilization (IVF) clinics may be partially attributable to the disparate quality of the water used in the preparation of culture media. The removal of contaminants in the water is of paramount importance since water constitutes the predominant component in any media formulation. To assist in the selection, operation and maintenance of a water purification system, the level of contaminants must be carefully monitored. Conductivity and resistance are used to measure the purity of natural and ultrapure water respectively. Feed water is analysed by an assortment of direct chemical means to determine the necessary system filtration steps. In general, high quality water can be produced by combined reverse osmosis and electrodeionization of treated tap water. Processed water is supplied to an ultrapure water system to provide final polished water. A detailed water processing protocol is presented along with quality assurance guidelines to ensure the consistent production of high quality ultrapure water suitable for in-vitro human embryo culture.

Animals↗
PubMed1998

Restoration of the severely worn dentition using a systematized approach for a predictable prognosis.

Dental literature supports the concept that vertical dimension of occlusion is normally not lost in severely worn dentition, and the bite should generally not be opened to facilitate dental reconstruction. However, restoration of a periodontally sound but severely worn dentition, at existing vertical dimension, frequently presents unique challenges in patient management, diagnosis, treatment planning, and restorative methodology. This report reviews and demonstrates an integrated and planned approach to this complex treatment situation that can lead to a favorable and predictable prognosis. The approach also allows a practitioner free use of various techniques if certain goals of occlusion are followed.

Crowns↗
PubMed1997

The recognition of haemoglobin by antibodies raised for the immunoassay of beta-amyloid.

Canine and porcine cerebrospinal fluid (CSF) were fractionated by size exclusion chromatography and analysed by a luminescence enzyme linked immunosorbent assay (ELISA) configured to detect beta-amyloid. A peak of activity was observed in the CSF consistent with the molecular weight of beta-amyloid. When CSF contaminated with blood was analysed an additional peak of immunoreactivity at a higher molecular weight was observed. The peak of activity was found to be derived from cross-reactivity of the immunoglobulins employed in the ELISA with haemoglobin. These findings are discussed with reference to primary and structural sequence homology between beta-amyloid and haemoglobin from a number of species, the known properties of beta-amyloid and recent clinical reports.

Amyloid beta-Peptides↗
PubMed1997

Among young adults, college students and graduates practiced more healthful habits and made more healthful food choices than did nonstudents.

OBJECTIVES: Health-related characteristics and habits and food choices of young adults were compared for three groups: college students, college graduates, and nonstudents. DESIGN: Subjects completed a mailed survey that included questions about demographics, attitudes, and behaviors and a food frequency questionnaire. Main outcome measures were health-related characteristics and habits and food choices. SUBJECTS: Female (n = 758) and male (n = 580) 18- to 24-year-olds in nine states who were selected randomly by zip code in each state. The response rate averaged 43% for all states. STATISTICAL ANALYSES PERFORMED: Analysis of variance of chi 2 tests were applied to health-related personal characteristic variables and the Kruskal-Wallis analysis of variance was applied to food consumption variables for women and men separately. RESULTS: According to self-reported heights and weights, female nonstudents were more often overweight than female students or graduates. Nonstudents of both genders reported smoking more often than students or graduates. College students and graduates ate more grain foods high in dietary fiber, more fruits and dark-green vegetables, and more lower-fat milk and meats than nonstudents. CONCLUSIONS/APPLICATIONS: Nonstudents were at greater health risk for some chronic illnesses, because of poorer health habits and food choices, than were college students and graduates. The behavior of nonstudents implies weaker response to messages promoting weight control, smoking cessation, and observance of the Dietary Guidelines for Americans than behavior exhibited by students or college graduates. Health promotion efforts could be enhanced by identifying demographic, educational, situational, and formative influences on positive health and dietary behaviors of young adults.

Adolescent↗
PubMed1997

Multiple attempts at embryo transfer: does this affect in-vitro fertilization treatment outcome?

In this study, we retrospectively analysed data from 877 patients who had 1204 embryo transfer procedures following in-vitro fertilization (IVF) at Midland Fertility Services, UK, between January 1991 and December 1995 to investigate the factors contributing to failure of embryo transfer at first attempt and the impact of immediate retransfer of retained embryos on the treatment outcome. Embryos were significantly more likely to be retained when the embryo transfer catheter was contaminated with mucus (3.3 versus 17.8%, P = 0.000001) or blood (3.3 versus 12%, P = 0.00001) and when the transfer procedure was difficult compared with when it was easy (20.3 versus 0.8%, P = 0.00001). There was no significant difference in the clinical pregnancy rate between those who had all their embryos transferred at the first attempt (24.7%) and those who required more than one attempt (23.2%). The types of embryo transfer catheter used in the unit did not show any difference in terms of embryo retention. Although we recommend aspiration of cervical mucus in order to reduce the rate of retained embryos, there is no evidence from our study to suggest that pregnancy rate is compromised when embryos are retained, provided they are discovered and immediately retransferred into the uterine cavity. Immediate retransfer is more convenient to the patients and reduces the laboratory workload without compromising the treatment outcome.

Adult↗
PubMed1996

An office system for organizing preventive services: a report by the American Cancer Society Advisory Group on Preventive Health Care Reminder Systems.

Despite increasing recognition of the importance of preventive services, such services are not provided in primary care practice as often as recommended. One of the most important reasons is the lack of a systematic, organized approach within practices. The American Cancer Society Ad Hoc Advisory Group on Preventive Health Care Reminder Systems reviewed evidence-based reports and expert opinion to summarize current knowledge about office systems for clinical preventive services. This article describes the process of developing an office system for preventive care, beginning with writing a practice policy, auditing charts for baseline performance, developing and implementing a plan for efficient delivery of preventive care, involving office staff, and monitoring progress. Strategies for dissemination of this approach to a wide range of primary care practices may involve professional medical organizations and managed care companies.

Ambulatory Care Information Systems↗
PubMed1996

Response of growing swine to dietary exposure to pure fumonisin B1 during an eight-week period: growth and clinical parameters.

Consumption of corn or corn-based products contaminated with Fusarium moniliforme/fumonisins has been associated with a variety of animal and human diseases and is a major food/feed safety issue. This study focused on the clinical toxicity and performance parameters in growing swing exposed to low to moderate levels of pure fumonisin B1 (FB.) for 8 weeks. Male (castrated) and female pigs were fed diets containing 0,0.1,1.0, and 10 mg FB1/kg diet (ppm). Weight gains and feed consumption were measured weekly. Blood samples were collected throughout the study, and various clinical and hematological parameters were measured. Because fumonisins are potent inhibitors of sphingolipid biosynthesis, sphinganine and sphingosine concentrations were determined in the liver, lung, and kidney. Organ weights and carcass quality were measured at the end of the trial. In general, male pigs were more adversely affected by FB1 in the diet than females. The average daily gain for males decreased by 8% for pigs fed 1.0 ppm and by 11% at 10.0 ppm, when compared to the control (0 ppm). Males fed 0.1 ppm showed an erratic growth pattern during the first 5 weeks of the experiment. Feed consumption for the same animals was somewhat higher than that of the controls during each of the first 4 weeks but thereafter was 6-7% lower each week as compared to controls. Female pigs fed FB1-diets showed a general enhancement of feed consumption until week 4. Among clinical chemistry parameters, cholesterol increased in males for the 1.0 and 10.0 ppm diets as compared to controls after 2 weeks, while the levels in both sexes were elevated for the 1.0 ppm diet only by the end of the experiment. Serum liver enzyme concentrations were altered during week 2 only. Changes were observed in the weight of the pancreas and adrenals for male pigs fed FB1 diets as compared to controls. The free sphinganine to free sphingosine ratio (biomarker of exposure in FB1-consuming animals) increased in all three organs for the 10 ppm diet, regardless of sex. The study indicated that FB1 can cause different effects at each dose level, at concentrations as low as 0.1 ppm (showing erratic growth) followed by a reduced growth and biochemical abnormalities in blood (1.0 ppm) and sphingolipid alterations in tissues (10.0 ppm). Some of these effects occurred below the exposure level that caused alteration in sphingolipid metabolism.

Adrenal Glands↗
PubMed1995

Sexual dimorphism in the metabolic response to the calcium channel antagonists, diltiazem and clentiazem, by hyperlipidemic JCR:LA-cp rats.

The JCR:LA-cp rat is obese, insulin resistant, and hypertriglyceridemic. The obese male rats spontaneously develop atherosclerosis and ischemic myocardial lesions that are prevented by treatment with the calcium channel antagonist, nifedipine. Male and female JCR:LA-cp rats were treated with the calcium channel antagonist, diltiazem, and a closely related compound, clentiazem (at 30 mg/kg). Clentiazem, but not diltiazem, caused a significant increase in body weight of both sexes in the presence of decreased food consumption. Serum triacylglycerols were decreased by half by both drugs in male rats only, reflecting decreased very-low-density lipoprotein (VLDL) secretion. Females did not respond with lower concentrations of triacylglycerol (although VLDL secretion rate was decreased) and showed increased concentrations of cholesterol in the high-density lipoprotein (HDL) fraction. Diltiazem-treated male rats showed decreased VLDL particle size, together with a shift to shorter-chain fatty acids in the triacylglycerols. This effect was not seen with clentiazem treatment. There was no effect on insulin and glucose metabolism in these insulin-resistant animals. Calcium channel antagonists have complex metabolic effects in the hypertriglyceridemic rats, with highly beneficial hypolipidemic effects in the males that are not seen in the females. The sexual dimorphism of these responses is sex linked, but appears not to be due to the steroid sex hormones. These results suggest caution in the chronic treatment of human females with these agents and the importance of detailed human studies in females and individuals with the insulin-resistant/hypertriglyceridemic/obese syndrome.

Animals↗