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Biomedical subjects

C A Thomas

Publications and source records attributed to C A Thomas.

151 records · Page 9Linked to original sources
PubMedDate not supplied

PTH excess may promote weight gain by impeding catecholamine-induced lipolysis-implications for the impact of calcium, vitamin D, and alcohol on body weight.

Increased free intracellular calcium ([Ca(2+)](i)) in adipocytes blunts the lipolytic response to catecholamines by activating phosphodiesterase 3B - the same enzyme that mediates the antilipolytic effect of insulin - while also compromising the efficiency of insulin-stimulated glucose uptake. Physiological increases in parathyroid hormone (PTH) have been shown to increase [Ca(2+)](i) in adipocytes. These considerations may rationalize recent evidence that high dietary intakes of calcium and/or dairy products may reduce risk for obesity, diabetes, and insulin-resistance syndrome, and they predict that other dietary measures which down-regulate PTH - such as good vitamin D status, and moderation in phosphate and salt intakes - may likewise be beneficial in these respects. Consistent with this position are reports that body weight is elevated in elderly subjects with both primary and secondary hyperparathyroidism; furthermore, insulin resistance is a well-known complication of both forms of hyperparathyroidism. The fact that regular alcohol consumption is associated with decreased PTH secretion may help to explain why moderate drinkers are less prone to insulin resistance, diabetes, and - in women - obesity. Down-regulation of PTH cannot be expected to promote dramatic weight loss, but in the long-term it may lessen risk for significant weight gain and diabetes, and conceivably may potentiate the fat loss achievable with caloric restriction and/or exercise.

Adipocytes↗
PubMedDate not supplied

Mobile and portable dentistry: alternative treatment services for the elderly.

With the rapidly expanding geriatric population in the United States, the demand for geriatric dentistry is rising. With the financial, transportation, and motivational barriers the geriatric population faces, it can be difficult for them to seek dental treatment in a traditional setting. Mobile and portable dental units can be used as alternative methods to provide dental care to the geriatric population. Mobile and portable dental units offer advantages such as providing community outreach, increasing personal satisfaction for geriatric clients and dental professionals, and providing dental care to those who would otherwise not receive treatment due to some of the barriers. Although mobile and portable dental units are ideal for long-term facilities, disadvantages do exist in implementing the use of these systems. These include the initial cost of implementing such a unit, limitation of treatment options, the number of clients seen in a day, and maintenance for the unit. Until more research can be done to find ways to improve the quality of dental care for the geriatric population, these units seem to be a reasonable alternative to the traditional approach to providing the elderly with the dental care they require.

Aged↗
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Post-thaw bovine spermatozoal quality estimated from fresh samples.

Comparisons were made among flow cytometrically quantified populations of fresh and cryopreserved bovine spermatozoa, tri-stained with fluorophores rhodamine 123 (R123), 5- (and 6-) carboxy-4',5'-dimethylfluorescein diacetate (CMFDA), and propidium iodide (PI), and analyzed by dual parameter flow cytometry. The purpose was to find parameters in fresh semen samples that were potentially predictive of frozen sample parameters so that bulls with marginal cryopreservation capacity could be identified. Fresh and cryopreserved aliquots of semen from two sets of six bulls were semen processed in either milk (bulls 1-6) or egg yolk citrate (bulls 11-16). Membrane-damaged red (PI) and intact green (CMFDA + R123) populations were evaluated as percentages of 10,000-cell samples or numbers per straw. In milk, gated central subsets of membrane-damaged sperm cells in fresh samples and moribund cells in post-thaw samples were significantly correlated for sample percentages (r = 0.90, P = 0.014) and cell numbers per straw (r = 0.94, P = 0.006). In egg yolk citrate, fresh and frozen membrane-damaged populations were correlated (percentages: r = 0.81, P = 0.048; numbers: r = 0.88, P = 0.019). Additionally, post-thaw motility estimated by a photographic method was correlated with the number of sperm cells per straw in the intact central green subset (r = 0.98, P = 0.0006). These findings suggest that partitioning red and gree populations into smaller, central subset populations reveals significant relationships between fresh and cryopreserved bull ejaculates. The proportion of membrane-damaged spermatozoa in fresh semen seems to be predictive of the proportion of post-thaw membrane-damaged or moribund spermatozoa. The data consistently showed ejaculates of bulls 1 and 12 as having the greatest cryopreservation potentials, and bulls 4 and 16 the least. Thus, flow cytometric evaluation of fresh semen may be useful for identifying young sires with relatively poor fertilizing potential.

Analysis of Variance↗
PubMedDate not supplied

Effect of semen dilution on bovine sperm viability as determined by dual-DNA staining and flow cytometry.

Living and dead spermatozoa were examined for the effects of sperm concentration level on sperm viability. Semen was collected from two different bulls on each of four collection dates. A ninth bull was collected on all four collection dates as a control for effects of collection date. The ejaculates from these nine bulls were diluted to 30 x 10(6) spermatozoa/0.5 ml and then serially diluted to 20, 10, 5, or 1 x 10(6) spermatozoa/0.5 ml French straw. One-half of the straws for each dilution series was stored 24 hours at 5 degrees C, while the other half was cryopreserved. Spermatozoa were stained with SYBR-14 and propidium iodide (PI) to assess viability. Flow cytometry yielded dot plots showing three distinct sperm populations: dead red-stained spermatozoa (PI), viable green-stained spermatozoa (SYBR-14), and moribund spermatozoa that stained both red and green (doubly-stained). Populations were expressed and analyzed in terms of mean percentage of viable spermatozoa and by actual numbers of viable spermatozoa per insemination dose. The mean percentage of living spermatozoa decreased linearly with decreasing sperm concentration; whereas the decrease was parabolic when those same samples were expressed as the mean number of living spermatozoa per insemination dose. The percentage of SYBR-14-stained spermatozoa differed among concentration levels and among bulls (P < 0.01). There were no differences among straws from the same ejaculate. The total volume of ejaculated semen and the concentration of spermatozoa in that ejaculate were both significantly positively correlated with the percentage of SYBR-14-stained spermatozoa in that semen when it was cryopreserved and diluted to < 10 x 10(6) spermatozoa/0.5 ml. In contrast, there were no significant correlations between the initial ejaculate characteristics and the proportion of SYBR-14-stained spermatozoa in the 24-hour-stored samples at any concentration. In conclusion, the percentage of viable spermatozoa in an ejaculate significantly decreased with increasing dilution. Further, in cryopreserved samples, the percentage of living spermatozoa < 10 x 10(6) spermatozoa/0.5 ml depended on the original volume and the sperm concentration of that particular ejaculate.

Analysis of Variance↗