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Biomedical subjects

J S Kesner

Publications and source records attributed to J S Kesner.

48 records · Page 3Linked to original sources
PubMed1980

Growth hormone, glucocorticoid and thyroxine response to duration, intensity and wavelength of light in prepubertal bulls.

Effects of duration, intensity and wavelength of light on growth hormone (GH), glucocorticoids, thyrotropin (TSH) and thyroxine (T4) concentrations in serum were determined in prepubertal bulls maintained at 18 to 22 C and 60 tp 70% relative humidity. Mean GH was 8.3 +/- .8, 9.5 +/- 2.2 and 13.8 +/- 2.2 ng/ml (P greater than .10) during 6 weeks of exposure to 8 hr of light: 16 hr of dark (8L:16D), 16L:8D and 20L:4D, respectively. However, concentrations of GH were more variable (P less than .01) in bulle exposed to 16L:8D and 20L:4D than in bulls exposed to 8L:16D. Concentrations of GH averaged 10.6 +/- 1.3 and 13.6 +/- 2.6 ng/ml (P greater than .10) when intensities of light exposures were 22 and 540 lux. Variability of GH was greater (P less than .01) in bulls exposed to 540 lux. Increase in the duration of light by the addition of 8 hr of red (550 to 750 nm) or 8 of blue (300 to 427 nm) light to 8 hr of white (300 to 750 nm) light did not affect (P greater than .10) mean GH concentrations. Among experiments, concentrations of glucocorticoids decreased by 29 to 58% (P less than .05) when daily light exposures were increased from 8 to 15.7, 16 or 20 hours. Conversely, glucocorticoids increased by 118% (P less than .05) when light was decreased from 15.7 to 8 hr daily. Duration of light exposures did not effect concentrations of TSH or T4. Similarly, intensities of 22 and 540 lux and blue and red wavelengths of light did not affect average concentrations of glucocorticoids or T4. Injection of 33 microgram thyrotropin releasing hormone (TRH)/100 kg body weight increased (P less than .05) GH two- to five-fold above average basal values; however, duration, intensity and wavelength of light did not influence peak GH concentration or area of GH response curves after injection of TRH. We conclude that in comparison with 8 L, 16 L increased variance of GH without affecting average concentrations of GH, TSH or T4. In contrast, 16 L suppressed serum glococorticoids.

Animals↗
PubMed1980

The hypothalamo-pituitary gonadotrophic axis of suckled and nonsuckled dairy cows postpartum.

The objective was to determine whether the suckling-induced delay in return to estrus postpartum could be explained by changes in hypothalamic LHRH content or ability of the pituitary to release LH and FSH in response to LHRH or 59 mM K+ in vitro. In addition, serum concentrations of several other hormones were measured. Nine Holstein cows were suckled ad libitum by two calves and milked by machine twice daily and eight were milked by machine only from calving until slaughter on day 14 postpartum. On day 13 postpartum, blood was collected at 15-min intervals from 0815 to 1200 hr and from 2015 to 2400 hours. Suckled cows had lower (P less than .05) mean serum LH concentrations on day 13 postpartum than did nonsuckled controls. This decrease resulted from a 60% reduction in frequency and a 40% reduction in amplitude of episodic LH peaks. Suckling did not affect body weight change postpartum or serum concentrations of progesterone, estradiol-17 beta, total glucocorticoids, prolactin or FSH during the first 14 days postpartum. The suckling-induced decrease in serum LH was not reflected by a reduction in hypothalamic LHRH or pituitary LH on day 14 postpartum. However, pituitary explants from suckled cows on day 14 postpartum secreted 50% less (P less than .01) LH in response to LHRH (25 ng/ml for 30 min) or K+ (59 mM for 30 min) in vitro than did those from nonsuckled cows. Secretion of FSH was increased 20-fold by LHRH and K+ in vitro, but differences due to suckling treatment were not significant. Decreased frequency and amplitude of episodic LH secretion in vivo and reduced capacity of pituitaries to respond to LHRH may be the cause of suckling-induced inhibition of postpartum ovulation in cattle.

Animals↗
PubMedDate not supplied

Stability of urinary female reproductive hormones stored under various conditions.

Urinary reproductive hormones afford specific and sensitive evaluation of female reproductive potential in epidemiologic and clinical settings. The goal of this study was to characterize the stability of urinary luteinizing hormone, follicle stimulating hormone, estrone 3-glucuronide, pregnanediol 3-glucuronide, and creatinine during storage as functions of time, temperature, and additives. After 2 weeks with no additives, activity of the four analytes, relative to initial concentrations, ranged from 91.9 to 102.8% at 4 degrees C, 35.1 to 89.6% at 25 degrees C, and 7.5 to 66.9% at 37 degrees C. Antimicrobial additives did not consistently improve stability. Analyte activity for samples stored with no additives for 24 weeks at -80 degrees C ranged from 69.0 to 101.2%. Glycerol and bovine serum albumin improved analyte stability; activity ranged from 91.1 to 106.3%. Other additives were ineffective. These results reveal conditions for storing reproductive hormone analytes in urine during epidemiologic field studies.

Adult↗
PubMedDate not supplied

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. II. Female reproductive disorders.

Members of the workgroup on female reproductive disorders discussed methods to evaluate five principal functions: menstrual dysfunction, infertility, pregnancy loss, lactation disorders, and pregnancy complications. To test each function, a nested strategy was considered, based on progressive levels of effort available to conduct field investigations. This strategy was analogous to the three-tier classification of biomarkers used by other workshops. The lowest level of effort, corresponding to Tier 1, consists only of questionnaires, diaries, and reviews of maternal and infant medical records. The medium level of effort (Tier 2) collects data from questionnaires and diaries, and some biologic specimens. Suggested laboratory analyses included measurement of progesterone in saliva and several glycoprotein hormones in urine that evaluate menstrual dysfunction, infertility, and pregnancy loss. The highest level of effort (Tier 3) involves prospective collection of diary information and simultaneous collection of biological specimens.

Abortion, Spontaneous↗
PubMedDate not supplied

Herbicides and adjuvants: an evolving view.

The present report examines the in vitro genotoxicity (micronucleus assay) of herbicides and adjuvants and reports on an in vivo human study on potential endocrine effects of pesticides, including herbicides. Adjuvants are used in conjunction with 2,4-dichlorophenoxy acetic acid (2,4-D) and other herbicides. Earlier pesticide applier survey results (n = 709) show that 59% of the applicators used adjuvants, and the majority of this group used paraffinic oils and/or surfactant mixtures. As a beginning effort to explore the role of adjuvants and herbicides in hormonally based reproductive effects, a prospective, controlled study was performed to analyze blood specimens from three different exposure groups (applicators using herbicides only; applicators using both herbicides and insecticides; and applicators using fumigants in addition to herbicides and insecticides; and a control group composed of other agricultural workers including organic farmers). The applicators and controls were age- and smoking-matched. Study subjects (n = 78) were tested before, during, and after completion of pesticide application season for the effects of pesticide products on hormone levels in the bloodstream. Of the applicator exposure groups examined, only the herbicide group showed significant endocrinologic differences from controls. Free testosterone levels were significantly elevated in post-season measurements (p = 0.032), and follicle-stimulating hormone (FSH) was significantly decreased at the height of the season (p = 0.016) and in the post-season (p = 0.010) as compared to controls. These endocrinologic findings are discussed in terms of their possible relationship to potential endocrine effects of herbicides, herbicide contaminants, and adjuvants. In vitro genotoxicity examination compared four different commercially available surfactant mixtures with 12 different commercial herbicide products, including six different chlorophenoxy herbicides. Only one herbicide yielded a significant dose-response curve. All four adjuvants showed positive dose-response effects. These preliminary data suggest that adjuvants are not inert but are toxicologically active components added to herbicide mixtures. Whether adjuvant toxicant effects are additive or are independent of herbicide effects is poorly understood.

Adult↗