Biomedical subjects

E M Sternberg

Publications and source records attributed to E M Sternberg.

75 records · Page 5Linked to original sources

PubMedDate not supplied

The estrous cycle and pituitary-ovarian function in Lewis and Fischer rats.

We have characterized the estrous cycle by obtaining vaginal smears, and quantitating estradiol (E), progesterone (P), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) plasma levels at different phases of the estrous cycle in Lewis (LEW/N) and Fischer (F344/N) rats. Comparison of the duration of the component phases of estrous showed LEW/N metestrous to be significantly longer than in F344/N rats while diestrous and estrous were significantly shorter; proestrous was identical. E levels in LEW/N rats were significantly greater than in F344/N rats only in the estrous phase of the cycle. P levels were significantly greater in LEW/N rats in all phases. LH and FSH levels in the two strains did not differ. Elevated E and P levels would be expected to be associated with increased corticosterone through inhibition of the glucocorticoid negative-feedback pathway. The data reported suggest that other modulating factors in corticotropin-releasing-factor synthesis/release could be overriding both the E and P effects upon hypothalamic-pituitary-adrenal axis responsiveness.

Animals↗

PubMedDate not supplied

Inflammatory responses to carrageenan injection in LEW/N and F344/N rats: LEW/N rats show sex- and age-dependent changes in inflammatory reactions.

We studied the inflammatory responses of LEW/N and F344/N inbred rat strains after peripheral injection of carrageenan. The inflammatory responses were assessed in terms of volume, relative and total white blood cell counts of the exudates. Moreover, in both strains, blood CD4, CD8, CD25, naive CD4 (CD4/CD45RC) cell and B (CD45R) cell counts and plasma corticosterone levels, constituents of systemic inflammatory responses to carrageenan were evaluated. In general, LEW/N rats are highly responsive to challenge with carrageenan, whereas F344 rats are not. The strong local inflammatory responses to carrageenan are primarily exhibited by female LEW/N rats. The intensity of local inflammatory responses of LEW/N rats changes with the rat age, the highest exhibited by LEW/N rats up to 3 months of age, thereafter the carrageenan-induced inflammatory responses decline. Our results indicate that peripheral injection of carrageenan induces strong systemic immune component. After carrageenan injection, increases in CD8 and naive CD4 blood lymphocytes are seen. Although the carrageenan challenge does not change CD4 blood lymphocytes in both LEW/N and F344/N rat strains, LEW/N rats exhibit higher levels of CD4 cells than F344/N rats. Additionally, LEW/N rats demonstrated lower levels of B cells and higher naive CD4 lymphocytes. Carrageenan challenges induce significant increases in plasma corticosterone response in F344/N rats, as well as increases in LEW/N rats 1 h after injection. Our data stress the importance of rat age and gender in experiments studying inflammatory responses.

Age Factors↗

PubMedDate not supplied

Intracerebroventricularly transplanted embryonic neuronal tissue from inflammatory-resistant F344/N rats decreases acoustic startle responses in inflammatory-susceptible LEW/N rats.

Recently, we have shown that intracerebral transplantation of fetal F344/N hypothalamic tissue into LEW/N rats converts the LEW/N inflammatory-susceptible phenotype into an inflammatory-resistant phenotype in LEW/N hosts. Because LEW/N rats also exhibit relatively high acoustic startle responses (ASRs) compared to F344/N rats, in the present study we examined the effects on ASR of transplantation of F344/N hypothalamic tissue into the third ventricle of LEW/N rats. Dissected neuronal tissue from F344/N rats (Day E15-16) was implanted into the third ventricle of LEW/N rats. After 4 wk of postoperative survival, the animals' responses to acoustic startle stimuli were tested. Compared to naive and sham-operated animals, LEW/N rats transplanted with hypothalamic tissue exhibited significant decreases in ASR amplitudes. A similar decrease in ASR amplitude was observed in the group of LEW/N rats transplanted with embryonic striatal tissue. Our results indicate that the third ventricular neuronal grafts may modulate behavioral responses in the LEW/N rats. Although the mechanism of this effect is unknown, these studies suggest that intracerebral neuronal transplantation is a viable method with which to explore mechanisms of behavioral, neuroendocrine, and inflammatory response associations.

Acoustic Stimulation↗