PubMed Health⌕ Search

Biomedical subjects

R Oosterom

Publications and source records attributed to R Oosterom.

64 records · Page 4Linked to original sources
PubMed1981

Studies on the mechanism of action of human thymic epithelial conditioned medium on mouse thymocytes. Evidence for induction of immune competence.

It has been shown that addition of human thymic epithelial conditioned medium (HTECM) leads to an increased response of mouse thymocytes to concanavalin A and phytohemagglutinin. HTECM caused a maximal potentiating effect when added to thymocyte cultures at the time of their initiation. Addition at later times had a smaller enhancing effect and after 24 hr no effect of HTECM could be measured. Responses to mitogen were higher at all time periods measured and peak responses were shifted to later times in the presence of HTECM. Determination of cell viability made it highly unlikely that the effect of HTECM was simple due to enhanced numbers of viable cells in culture. These data support the view that HTECM induces T-lymphocyte maturation.

Animals↗
PubMed1981

A met-enkephalin analog inhibits adrenocorticotropin secretion by cultured pituitary cells from a patient with Nelson's syndrome.

ACTH excretion by cultured nonenzymatically dispersed pituitary tumor cells from a patient with Nelson's syndrome was studied. Hormone release was suppressed by 74 +/- 6% by the addition of 1 microM of the met-enkephalin analog FK 33824, while naloxone (1 microM) stimulated ACTH release by 70 +/- 5%. Somatostatin, dexamethasone, bromocriptine, and cyproheptadine in a concentration of 1 microM each inhibited ACTH release by 25 +/- 2%, 35 +/- 2%, 52 +/- 2%, and 61 +/- 4%, respectively, while lysine vasopressin (0.1 microM) and dibutyryl cAMP (5 mM) stimulated ACTH release by 112 +/- 8% and 220 +/- 4%, respectively. In conclusion, it was shown that the stimuli mentioned above directly affect ACTH secretion by the pituitary tumor cells. The inhibitory action of the met-enkephalin analog and the stimulatory action of naloxone on ACTH secretion make the presence of opiate receptors on this type of tumor likely.

Adenoma↗
PubMed1979

Presence of thymosin-like factors in human thymic epithelium conditioned medium.

The objective of the present study was to determine whether or not thymosin and conditioned medium from human thymus epithelial cultures (HTECM) contain similar fractions, capable of inducing T-cell differentiation. Therefore we tested the ability of rabbit antisera to different thymosin fractions (thymosin fractions 5, 6 and alpha 1) of both bovine and human origin to block the stimulatory effect of HTECM on Con A and PHA response of mouse thymocytes. We also looked for reactivity of the antisera toward tissues of man, mouse and calf, and to tissue cultures of man and mouse. Anti-thymosin fraction 5 and 6, but not anti-thymosin-alpha 1, were found to inhibit the stimulatory effect of HTECM on both Con A and PHA responses. This cannot be attributed to cytostatic or cytotoxic effects of the antisera on thymocytes. No effect was seen when using antiserum to kidney fraction 5 or normal rabbit serum. In both tissue sections and tissue cultures of the different species tested, anti-thymosin reacts only with thymus epithelial cells. The reactivity is blocked by neutralizing the antisera with thymosin fraction 5 but not by kidney fraction 5. The reactivity is also strongly diminished by neutralizing the antisera with HTECM but not with supernatants of conditioned media from non-thymic tissues. The observations are highly suggestive for the presence of similar fractions in HTECM and thymosin, and that both are secreted by thymus epithelial cells.

Animals↗