Biomedical subjects

R C Zimmermann

Publications and source records attributed to R C Zimmermann.

22 records · Page 2Linked to original sources

PubMed1989

Is follicular fluid steroid content representative of follicular steroid secretion?

Nine oestrogen-active (E-A) and seven oestrogen-inactive (E-I) bovine follicles were superfused for 10 h. Levels of oestradiol (E2), testosterone (T) and progesterone (P4) were measured in superfusate and follicular fluid. No correlation between intrafollicular steroid concentrations of E2, T and P4 and the amount of these steroids detected in the superfusate was found in oestrogen-active follicles, i.e. follicular fluid E2, T or P4 levels did not allow for any prediction of superfusate E2, T and P4 concentrations and vice versa. In contrast, E-I follicles showed a close correlation between intrafollicular and superfusate T and P, but not E2 levels. It is speculated that an alteration in intrafollicular regulatory mechanisms might explain the different findings for these two classes of follicles.

Animals↗

PubMed1987

In-vitro steroid secretion of tertiary atretic bovine follicles in a superfusion system correlated to their histological features.

In monotocus mammals most of the tertiary follicles are atretic. The experimental design of a blind study was used to evaluate the steroid secretion pattern and histological features of atretic bovine follicles. Steroidogenesis of the vesicles was studied with the aid of a superfusion system, and the superfused follicles were evaluated independently using the histological classification elaborated by Marion et al. Twelve single atretic follicles removed during the follicular and luteal phases of twelve cows were superfused for 10 h and then histologically processed. Follicles in early and definite contracting atresia secreted predominantly testosterone, whereas follicles in definite cystic, advanced contracting and late atresia secreted predominantly progesterone. Such secretion was independent of the stage of the oestrus cycle of the animal, so that follicles with the same histological pattern had a characteristic steroid secretion pattern, which was not influenced by the stage of the oestrus cycle at the time of follicular removal. In conclusion, atretic follicles should be considered significant endocrine organs.

Animals↗

PubMed1975

Evaluation of University of Florida split-course technique for various head and neck squamous cell carcinomas.

A retrospective evaluation was made of 260 patients with squamous carcinoma of various head and neck sites in order to determine the relative value of continuous vs. split-course irradiation techniques. There was no obvious difference in local control or survival in early-stage cases. The continuous technique resulted in a better local control and survival rate in moderately advanced and advanced stages. Complications were less severe in the split-course cases.

Carcinoma, Squamous Cell↗

PubMedDate not supplied

Prolonged inhibition of presynaptic catecholamine synthesis with alpha-methyl-para-tyrosine attenuates the circadian rhythm of human TSH secretion.

OBJECTIVE: Originating from the pituitary gland, TSH secretion is regulated predominantly by thyroid-releasing hormone (TRH) neurons located in the hypothalamus. Norepinephrine and dopamine have important effects in modulation of TSH secretion. An inhibitor of catecholamine synthesis, alpha-methyl-para-tyrosine (AMPT) has been used in several studies of the regulation of human TSH secretion. The short-term effects (<8 hours) of low doses of AMPT include stimulation of pituitary TSH secretion by selective lowering of brain dopamine levels. After prolonged administration of AMPT (>24 hours), theoretically both dopamine and norepinephrine levels are lowered significantly in the brain, although this has not been reported previously. METHODS: Nine subjects (five women and four men) received a total of five 1-g doses of AMPT or five 50-mg doses of promethazine (active placebo) over 28 hours in a randomized, double-blind, placebo-controlled crossover design in which the active and control tests were separated by 4-6 weeks. Blood samples were obtained over 24 hours (18 time points) on day 2 of each condition. RESULTS: Changes in prolactin secretion and 6-hydroxymelatonin sulfate excretion indirectly showed the effects of AMPT on dopamine and norepinephrine. The typical circadian rhythm of TSH secretion was blunted by AMPT throughout the night; at ten time points, the difference between the two groups was statistically significant (P <.01). The long-term effects of repeated doses of AMPT were inhibition of TSH secretion and significant attenuation of the circadian rhythm of TSH. Additionally, AMPT induced low norepinephrine levels, which counteracted the stimulatory effect of low dopamine levels on TSH. CONCLUSION: Through its inhibitory effect on TRH, norepinephrine appeared to be involved in the regulation of TSH.

Adult↗