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Biomedical subjects

V L Herzberg

Publications and source records attributed to V L Herzberg.

9 recordsLinked to original sources
PubMed1987

T cell growth without serum.

Most in vitro T cell proliferation experiments are performed by using serum-supplemented medium, yet the actual contributions of serum components to cell cycle progression remain ill-defined, thus complicating attempts to fully define requirements for cell division. By utilizing a functional separation between T cell receptor-triggered "competence" and IL 2-promoted "progression" to independently assess serum requirements during each cell cycle stage, it was shown that serum serves an essential, active role only during the early events of the competence phase (G0-G1 transition) of T cell activation. Serum is required for optimal IL 2 production and the cell surface expression of IL 2 receptors after the stimulation of the T3/Ti antigen receptor complex. In contrast, serum does not function actively during IL 2-mediated progression through the G1 phase of the cycle. Serum proteins serve only a passive role at this stage, preventing the adsorption of IL 2. This same effect can be provided by any number of proteins including IL 2 itself, or even a high cell concentration. Supplementation of serum-free T cell cultures solely with IL 2 and transferrin is sufficient for maximal T cell proliferation, although the time of the peak response is delayed owing to a suboptimal rate of IL 2 receptor expression. Accordingly, the realization that serum is only necessary for the earliest stage of T cell activation will now enable studies designed to identify the critical individual serum components and to define their mechanism of action.

Blood↗
PubMed1986

Secretion of vasopressin, oxytocin, and two neurophysins from rat hypothalamo-neurohypophyseal explants in organ culture.

Secretion of the neurohypophyseal principles arginine vasopressin, oxytocin, vasopressin-neurophysin, and oxytocin-neurophysin by hypothalamic-neurohypophyseal explants in organ culture was studied. The viability of explant cultures was tested on day 6 by their ability to incorporate 3H-amino acid into acid-precipitable protein, specifically vasopressin-neurophysin. The explants released all four neurosecretory products in a controlled manner during 8 successive days of culture. In addition, these substances were all present in neural lobes and hypothalami at the end of the culture period. Although the tissue retained a 1:1 molar ratio between the hormone and corresponding neurophysin, the levels of neurophysins in culture media were much higher than the levels of hormones. Through immunoprecipitation techniques we determined that both arginine vasopressin and oxytocin were unstable in culture media containing explants or in medium containing 10% heat-inactivated fetal calf serum. This suggests that neurophysins are more stable indicators of secretion by explants than are the corresponding hormones. An increased release of arginine vasopressin, oxytocin, vasopressin-neurophysin, and oxytocin-neurophysin occurred in response to elevated K+ and to increased sodium ions in the medium, and these four substances were released in different molecular proportions. The results indicate that explant cultures may be useful for comparisons of secretion of the two neurophysins and, to a more limited extent, of the two hormones in response to such stimuli.

Animals↗
PubMed1986

Increased water excretion in hyperprolactinemic rats.

The role of PRL in mammalian salt and water balance remains controversial. To avoid the methodological problems of exogenous PRL administration, endogenous hyperprolactinemia was established in normal rats by implantation of extra anterior pituitary glands under the kidney capsule. To eliminate excess glucocorticoid secretion in these rats, they were adrenalectomized, implanted with corticosterone replacement pellets, and given 0.9% saline drinking fluid. A highly significant increase in urine flow was found in pituitary-grafted male Fischer rats compared to control rats (38.9 +/- 3.8 vs. 20.7 +/- 1.6 ml/24 h X 100 g BW; P less than 0.0005). Urine osmolality was lower in pituitary-grafted rats, but sodium and potassium excretion were not abnormal. Although fluid intake was also greater in hyperprolactinemic rats, the urine flow remained elevated when adjusted for fluid intake. Renal binding sites for radioactive PRL were not decreased in pituitary-grafted rats. Thus, the hyperprolactinemic rat has increased water excretion that may be attributed to a direct renal effect rather than to glucocorticoid excess or a primary change in thirst. Since it is possible that water absorption in the gut is also increased by PRL, multiple effects of PRL may be responsible for the diuresis observed in hyperprolactinemic rats.

Animals↗
PubMed1985

Characterization of insulin receptor carbohydrate by comparison of chemical and enzymatic deglycosylation.

To characterize the carbohydrate moieties of the insulin receptor on IM-9 lymphocytes, the cells were surface iodinated and solubilized, and the insulin receptors were precipitated with anti-receptor antibody. The precipitates were resuspended, subjected to either enzymatic digestion or chemical treatment with trifluoromethanesulfonic acid and the relative mobilities of the alpha and beta subunits before and after treatment were analyzed by polyacrylamide gel electrophoresis and autoradiography. The results indicate that the alpha subunit possesses primarily N-linked carbohydrate which is both complex (Endoglycosidase F sensitive) and polymannose (Endoglycosidase H sensitive). The beta subunit also contains polymannose oligosaccharide units and has, in addition, a substantial amount of carbohydrate which is removed by chemical treatment but is not susceptible to Endoglycosidase F, suggesting the presence of O-linked saccharides. The apparent molecular weights of the core protein of the mature alpha and beta subunits as determined by gel electrophoresis following complete deglycosylation are 98 kDa and 80 kDa, respectively.

Carbohydrates↗
PubMed1983

Studies of anterior pituitary-grafted rats: II. Normal growth hormone secretion.

Of the various animal models used to study chronic hyperprolactinemia, the otherwise intact rat implanted with extra anterior pituitary glands (AP) under the kidney capsule is assumed to be normal except for excess circulating prolactin (PRL). Since the ectopic glands contain numerous somatotropes in addition to abundant and active lactotropes, it was important to assess growth hormone (GH) secretion as well in this model of hyperprolactinemia. The structural and functional similarities of PRL and GH are such that it is necessary to demonstrate that metabolic abnormalities noted in AP-implanted rats are due to hyperprolactinemia and not to altered GH secretion. AP-implanted female rats have significantly higher resting serum PRL concentrations when compared to sham-operated control rats, but baseline serum GH levels are similar in normal and pituitary-grafted rats. Suppression of GH by insulin and clonidine is comparable in AP-implanted and control rats. The intrasellar pituitary GH concentration is also similar (ca. 20 micrograms/mg wet weight) in hyperprolactinemic and normal rats. We conclude that GH secretion is normal in the non-hypophysectomized AP-implanted rat, in contrast to the hypophysectomized AP-implanted rat model which has been reported to have diminished GH secretion. Despite the presence of recognizable somatotropes, the ectopic anterior pituitary does not appear to secrete significant amounts of GH, making the intact rat bearing multiple pituitary grafts an excellent model of chronic hyperprolactinemia.

Animals↗
PubMed1980

125I-insulin receptor binding to cord blood erythrocytes of varying gestational age and comparison with adult values.

The measurement of 125I-insulin binding to erythrocytes from 34 samples of cord blood (% B/T = 11.2 +/- 3.8) showed statistically significant differences when compared to adult erythrocytes (% B/T = 6.6 +/- 1.7). Preterm erythrocytes (% B/T = 14.7 +/- 3.4) bound significantly more insulin when compared to term erythrocytes (% B/T = 10.1 +/- 3.2). The negative correlation (r = -0.613; P = 0.001) between insulin binding and gestational age indicates that the trend during the final trimester of gestation is toward the lower binding observed for adult cells. The major differences in binding between adult and term cord blood erythrocytes may be primarily attributed to differences in the number of binding sites per cell. Additionally, there are small differences in both affinity and number of sites per cell in preterm as compared to term and adult erythrocytes.

Adult↗
PubMedDate not supplied

Human T lymphocytes require lipid as either lipoprotein or nonesterified fatty acid for in vitro activation.

Serum, which is required for activation of T cells in vitro, was fractionated to isolate and identify major supportive components. The serum activity concentrated exclusively with the lipoprotein fractions LDL and HDL. Furthermore, oleic and linoleic acids were equally active supplements, suggesting that resting T cells may require exogenous lipid because they are incapable of synthesizing fatty acid. A survey of fatty acids disclosed that all were capable of some degree of support. Titration delineated the narrow concentration range of lipid supplements successful in supporting T cell proliferation and demonstrated that concentrations must be rigidly controlled to optimize cell proliferation.

Adult↗