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Biomedical subjects

D Feldman

Publications and source records attributed to D Feldman.

At least 235 records · Page 13Linked to original sources
PubMed1981

Ultrastructural study of rat liver and liver neoplasms after long-term treatment with phenobarbital.

The purpose of this investigation is to study the ultrastructure of liver and liver neoplasms after long-term administration of phenobarbital. Liver from female Charles River rats treated with 0.1% sodium phenobarbital by dietary admix for 60, 180, or 113 weeks was examined; liver neoplasms present at 108 or 113 weeks were also examined. At 60 weeks, an outstanding feature of most hepatocytes was the extensive proliferation of smooth endoplasmic reticulum, increase in autophage vacuoles, lysosomes, blebbing, and Kupffer cells containing phagosomes. At 108 or 113 weeks, additional changes in liver included an abundance of myelin figures in vacuoles, sinusoids, and bile canaliculi and the occasional appearance of whorls of smooth endoplasmic reticulum. Hepatocytes from liver neoplasms, all identified as well-differentiated hepatic cell neoplasms, contained voluminous whorls and large phagosomes filled with whorls, myelin figures, and cellular debris. The phagosomes were present both intracytoplasmic and intrasinusoidal, either partially or completely surrounded by Kupffer cell extensions. These cellular alterations are interpreted as evidence of adaptive cellular responses.

Age Factors↗
PubMed1980

Nuclear translocation of the 1,25-dihydroxycholecalciferol receptor in mouse kidney.

We have recently demonstrated that cytosol from mouse kidney contains a receptor-like binding protein for 1,25-dihydroxycholecalciferol (1,25-(OH)2D3). The present studies were undertaken to investigate whether this component undergoes nuclear translocation, thus adding support to the contention that this binding moiety represents a receptor for 1,25-(OH)2D3. Kidney slices from vitamin D-deficient mice were incubated with 1,25-(OH)2[3H]D3 and specific binding was assessed in cytosol and 0.3 M KCl extracts of isolated nuclei. The appearance of specific nuclear-bound 1,25-(OH)2[3H]D3 exhibited a saturation time course and the increase in nuclear binding was accompanied by a concomitant decrease in cytoplasmic binding such that, by 120 min, approximately 80% of specifically bound 1,25-(OH)2[3H]D3 was associated with the nuclear fraction and approximately 20% remained in the cytoplasmic compartment. The nuclear transfer was found to be temperature-dependent and specific for the dihydroxy metabolite. Both the cytoplasmic and nuclear receptors sedimented at 3.2 S in 0.3 M KCl sucrose density gradients. However, under low salt conditions, the cytoplasmic receptor was transformed to yield an approximately 5.4 S peak while the nuclear receptor sedimented unchanged t 3.2 S. In summary, the cytoplasmic 1,25-(OH)2D3 receptor in mammalian kidney undergoes temperature-dependent nuclear translocation and the cytoplasmic and nuclear forms of the receptor can be distinguished by their sedimentation properties.

Animals↗
PubMed1980

In vitro gamma irradiation of leukemic cells in mice, rats, and guinea pigs.

In vitro gamma irradiation of virus-induced (Gross) mouse leukemia cells at doses of 350-1600 rads (1 rad = 0.01 gray) had no effect on their ability to induce leukemia, usually within 2 weeks, after transplantation into syngeneic mice. However, when cells irradiated at doses of 2000-20,000 rads were transplanted, they induced leukemia after a latency period exceeding 2.5 months, similar to the results observed in mice inoculated with filtered mouse leukemia extracts. Similar results were also obtained after irradiation of leukemic cells derived from rats in which leukemia had been induced by rat-adapted mouse leukemia virus. Apparently, gamma irradiation at a dose of, or exceeding, 2000 rads, inhibits the ability of mouse and rat leukemic cells to induce leukemia after transplantation into syngeneic hosts; however, it does not inactivate the virus carried by such cells nor prevent it from inducing leukemia. [In previous experiments, doses of more than 4,500,000 rads were needed to inactivate the passage A (Gross) leukemia virus carried in either mouse or rat leukemic cells.] In vitro gamma irradiation of L2C guinea pig leukemic cells at doses of 750-2500 rads had no apparent effect on their ability to induce leukemia after transplantation effect on their ability to induce leukemia after transplantation into strain 2 guinea pigs. However, irradiation at doses of 3250-20,000 rads inactivated their ability to do so. The morphology of mouse, rat, and guinea pig leukemic cells and the virus particles present in such cells was not affected by irradiation at doses of 20,000 rads.

Animals↗
PubMed1980

Elimination of excess smooth endoplasmic reticulum after phenobarbital administration.

Livers from Charles River rats during and after treatment with phenobarbital were studied in order to investigate possible mechanisms involved in the elimination of excess smooth endoplasmic reticulum. The most pronounced structural change during compound administration was proliferation of smooth endoplasmic reticulum; depletion of glycogen and an increase in lipid deposits were also observed. After termination of treatment, these changes were reversed. The appearance of an increased number of autophage vacuoles and lysosomes plus the localization of acid phosphatase reaction product in these bodies suggests autophagy as one possible mechanism for the elimination of excess smooth endoplasmic reticulum. Cytoplasmic blebs and fragments replete with smooth endoplasmic reticulum were observed within the sinusoids. The presence of Kupffer cell cytoplasmic extensions surrounding these fragments and acid phosphatase reaction product within Kupffer cell inclusions suggests heterophagy as another process participating in the removal of excess smooth endoplasmic reticulum.

Animals↗
PubMed1980

Demonstration of glucocorticoid receptors in the adrenal cortex: evidence for a direct dexamethasone suppressive effect on the rat adrenal gland.

The adrenal cortex was evaluated for the presence of glucocorticoid receptors and functions. Substantial binding of [3H]dexamethasone was observed in aminoglutethimide-treated, hypophysectomized, and intact rats. Further studies demonstrated binding in cultured bovine adrenocortical cells and in Y-1 cells, a cloned murine cell line of adrenal cortical origin. Scatchard analysis of specific binding data in cytosol from hypophysectomized rats revealed an apparent Kd of approximately 15 nM and a receptor content (Nmax) of 123 fmol/mg cytosol protein. Analysis of Y-1 cell cytosol showed a Kd of approximately 17 nM and Nmax of 190 fmol/mg protein. The binding site in hypophysectomized rats had the following steroid specificities: high affinity for dexamethasone, corticosterone, and progesterone; moderate affinity for 11 beta-cortisol, and low affinity for testosterone, estradiol, pregnenolone, and 11 alpha-cortisol. Sedimentation in sucrose density gradients revealed 8S binding peaks in cytosols prepared from intact rat adrenal glands, Y-1 cells, and cultured bovine adrenocortical cells. Time- and temperature-dependent nuclear uptake of [3H]dexamethasone in Y-1 cells was demonstrated. In vivo treatment of hypophysectomized rats with dexamethasone significantly enhanced the rate of adrenal atrophy. ACTH stimulation tests in hypophysectomized rats showed a decreased corticosterone response in dexamethasone-treated rats compared to that in control animals. However, in vitro, there was no evidence for an effect of dexamethasone on ACTH-stimulated corticosterone production. The data indicate that the adrenal cortex possesses a high affinity binding site that fulfills the criteria for a glucocorticoid receptor. Glucocorticoid administration enhances adrenal atrophy and impairs adrenal function. We speculate that this action contributes to the suppressive effect of glucocorticoids on the pituitary-adrenal axis.

Adrenal Cortex↗
PubMed1980

Heterogenetiy of glucocorticoid binders: a high affinity triamcinolone acetonide binder in bovine serum.

While investigating glucocorticoid-binding proteins in bovine tissues, a new binder was found in fresh bovine serum which exhibited high affinity for certain synthetic glucocorticoids. This serum binder was characterized using [3H]triamcinolone acetonide (TA) as the ligand. On sucrose gradients, the [3H]TA peak sedimented at 8S, which was easily distinguishable from the [3H]cortisol-transcortin peak at 4S. Unlike the tissue receptor, which showed ionically dependent transformation from 8S in equilibrium or formed from 4S, the serum binder sedimented at 8S in both hypo- and hypertonic gradients. Binding properties were evaluated employing sephadex G-50 chromatography to separate bound from free steroid. Scatchard analysis of specific [3H]TA binding data revealed a straight line. The apparent equilibrium dissociation constant (Kd) was 7.8 +/- 0.7 X 10(-8) M, and the binding capacity was 772 +/- 70 fmol/mg serum protein. Hormonal specificity was determined by a competitive binding assay and revealed the following sequence: TA (100%) > betamethasone (47%) > triamcinolone (33%) > dexamethasone (2%) = cortisol = progesterone; aldosterone, estradiol, and testosterone exhibited negligible competitive activity. The serum binder was very stable, withstanding heating to 37 C for 60 min and long term storage in the frozen state. However, binding was significantly destroyed by trypsin. The binder was absent from fresh samples of chicken, mouse, rat, rabbit, dog, monkey, and human sera and frozen horse and porcine sera, but was clearly present in commercially available frozen calf, fetal calf, and lamb sera. At this time, we are unable to define the function of this binder, although its existence in both ovine and bovine sera suggests a possible role in ruminants. However, since bovine serum is routinely employed in tissue culture studies, the presence of this glucocorticoid binder might significantly influence many experiments.

Animals↗
PubMed1980

Demonstration of 1,25-dihydroxyvitamin D3 receptors in human skin biopsies.

In this study we report the demonstration of receptors for 1,25-(OH)2 vitamin D3 in fresh and cultured human skin. Cultured fibroblasts grown from infant foreskin exhibit a binding site which by Scatchard analysis had a Kd for [3H]1,25-(OH)2D3 of 0.2 nM and an Nmax of approximately 40 fmol/mg cytosol protein. On sucrose density gradients the receptor sediments at 3.2S. Receptors could also be identified in skin biopsies from adult patients when assayed either in fresh epidermis or cultured keratinocytes and dermal fibroblasts. The human receptors are similar to rodent receptors assessed in classical target organs such as intestine, bone and kidney. The findings that receptors can be measured in cultured human skin after several arterial passages indicates that skin biopsy may provide a means of assessing the 1,25-(OH)2D3 receptor status of patients.

Adult↗
PubMed1979

A receptor-like binding macromolecule for 1 alpha, 25-dihydroxycholecalciferol in cultured mouse bone cells.

1alpha, 25-Dihydroxycholecalciferol (1,25-(OH)2D3), the active form of vitamin D, like other steroid hormones, initiates its action by binding to cytoplasmic receptors in target cells. Although the 1,25-(OH)2D3 receptor has been well studied in intestine, little information beyond sucrose gradient analyses is presently available from mammalian bone. We, therefore, employed primary cultures of mouse calvarial cells to characterize the mammalian receptor in bone. A hypertonic molybdate-containing buffer was found to protect receptor binding. On hypertonic sucrose gradients, the 1,25-(OH)2-[3H]D3 binder sedimented at 3.2 S. Scatchard analysis of specific 1,25-(OH)2[3H]D3 binding sites at 0 degrees C yielded an apparent Kd of 0.26 nM and an Nmax of 75 fmol/mg of cytosol protein. Competitive binding experiments revealed the receptor to prefer 1,25-(OH)2D3 greater than 25-(OH)-D3 = 1 alpha-(OH)-D3 greater than 24R,25-(OH)2D3; vitamin D3, dihydrotachysterol, sex steroids, and glucocorticoids exhibited negligible binding. As shown in other systems, the receptor could be distinguished from a 25-(OH)-[3H]D3 binder which sedimented at approximately 6 S. In summary, cultured mouse calvarial cells possess a macromolecule with receptor-like properties. This system appears to be an ideal model for the investigation of 1,25-(OH)2D3 receptor binding and action in mammalian bone.

Animals↗
PubMed1979

Glucocorticoid and estrogen regulation of corticosteroid-binding globulin production by rat liver.

We have recently demonstrated that rat liver can synthesize and secrete corticosteroid-binding globulin (CBG). The present study extends these observations and examines the hormonal regulation of hepatic CBG production. Male rats were pretreated by adrenalectomy and/or glucocorticoid or estrogen administration and the rate of CBG production was measured in vitro. The production rates were assessed by the generation of specific corticosterone binding sites in both a liver-slice preparation and in an isolated perfused liver. The two techniques showed qualitatively similar results. Adrenalectomy enhanced and glucorticoid administration inhibited the rate of CBG production and secretion. Pretreatment of male rats with estradiol stimulated the rate of CBG production. The production rates were 20- to 40-fold higher in the perfused liver demonstrating its superiority over the liver-slice system. The livers from intact rats secreted CBG binding sites at a rate of approximately 18 pmol/g liver per hours, generating an estimated 20% of the total CBG content of a rat each day. The possible clinical implications of the therapeutic use of glucocorticoids that bind to CBG, yet inhibit CBG production, are discussed.

Adrenalectomy↗
PubMed1979

Synthesis and secretion of corticosteroid-binding globulin by rat liver. A source of heterogeneity of hepatic corticosteroid-binders.

Classical glucocorticoid receptors (type II) have a high affinity for synthetic and natural glucocorticoids. We have previously demonstrated an additional binding site in kidney cytosol (type III) which has a high affinity for corticosterone but a low affinity for dexamethasone. In many ways, this binder resembles plasma corticosteroid-binding globulin (CBG). The first goal of this study was to determine the organ distribution of the type III binding sites. Cytosol was prepared from isolated cells to avoid plasma contamination. Of the tissues examined, type III sites were found only in liver and kidney; sites were absent from thymocytes, IM-9 lymphocytes, adipocytes, and bone cells. The second goal of this study was to ascertain whether CBG is synthesized in liver and kidney. Liver and kidney slices were incubated in vitro and the concentration of type III sites was seen to rise in hepatic cytosol and incubating medium but not kidney. To verify the impression that liver was synthesizing and secreting CBG, the following experiments were performed: (a) To demonstrate that type III sites were CBG, steroid-binding profiles and migration on polyacrylamide gel electrophoresis were shown to be identical for hepatic type III sites and serum. (b) To indicate that the rise in type III sites was dependent on protein synthesis, it was shown that cycloheximide blocked the appearance of new type III sites. (c) To establish that the type III sites were being secreted, in situ liver perfusion experiments showed time-dependent release of new sites into the perfusate. In conclusion, liver synthesizes and secretes type III sites, a finding previously suspected but never proved. The presence of type III sites in kidney remains to be explained.

Animals↗
PubMed1979

Glucocorticoid receptors and actions in subpopulations of cultured rat bone cells. Mechanism of dexamethasone potentiation of parathyroid hormone-stimulated cyclic AMP production.

We have previously shown that bone cells possess glucocorticoid receptors and that, in addition to being inhibitory to cell growth, glucocorticoid treatment potentiates the ability of parathyroid hormone (PTH) to stimulate cyclic AMP (cAMP) formation. This study extends those observations to specific subpopulations of bone cells and explores the mechanism of the cAMP augmentation. Subpopulations of cultured bone cells derived from 20-d-old fetal rat calvaria were enriched for "osteoblast-like" (OB) and "osteoclast-like" (OC) cells by sequential collagenase digestion. OC cells released during the first 30 min of collagenase digestion were characterized by low alkaline phosphatase activity, a cAMP response to salmon calcitonin (CT), but only a small cAMP response to bovine PTH. In contrast, OB cells released between 30 and 120 min of collagenase digestion, possessed high alkaline phosphatase activity, responded with a large cAMP rise to PTH, but exhibited no response to CT. Glucocorticoid receptors, with similar properties, were demonstrated in both populations (K(d) congruent with 5 nM, N(maximum) congruent with 400 fmol/mg cytosol protein). Dexamethasone equivalently inhibited cell growth and alkaline phosphatase activity in both populations. Dexamethasone potentiation of cAMP generation occurred after PTH but not CT stimulation. A greater enhancement of cAMP generation observed in OB cells appears to result from two glucocorticoid actions: (a) stimulation of adenylate cyclase and (b) inhibition of phosphodiesterase. Only the latter mechanism was found in OC cells. Dexamethasone-treated cells showed an increase in both sensitivity and maximal response of cAMP to PTH. The possible relationship of these actions to the mechanism of glucocorticoid-induced osteopenia is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Demonstration of a 1,25-dihydroxycholecalciferol cytoplasmic receptor-like binder in mouse kidney.

Isolated mouse renal tubule cells have been employed to demonstrate the presence of a specific high affinity cytoplasmic binding protein for 1,25-dihydroxycholecalciferol (1,25(OH)2D3) in kidney. This receptor-like macromolecule sedimented at 3.2 S in hypertonic sucrose density gradients. Scatchard analysis of [3H]1,25-(OH)2D3 binding at O C revealed an apparent Kd of 0.2 nM and a concentration of binding sites of 50 fmol/mg cytosol protein. In competition experiments, the binder exhibited a low affinity for other vitamin D3 metabolites; the order of potency was 1,25(OH)2D3 greater than 250HD3 greater than u alpha OHD3 greater than 24R,25(OH)2D3. The sedimentation properties, binding affinity, and specificity of this 1,25(OH)2D3 binding protein are strikingly similar to the receptors in rat intestine, mouse bone, and human intestine. The demonstration of a renal receptor-like binder adds further support to the concept that the kidney is a 1,25(OH)2D3 target organ.

Animals↗
PubMed1979

Virus particles in the basal plate of rhesus monkey and baboon placenta.

C-type virus particles and particles, approximately 35 nm in diameter, were present in the region of the basal plate from the placenta of a rhesus monkey and two baboons. Both particles appeared to bud from the plasma membrane of the cytotrophoblast: large, pleomorphic cells with cytoplasmic extensions, indented nuclei, well-developed endoplasmic reticulum, and glycogen deposits. Extracellular particles were enmeshed within a fibrous matrix. Particles were also observed in the junctional zone, but not in the decidua. C-type virus particles from the rhesus monkey and baboons differed in ultrastructure from each other and from C-type mouse leukemia virus particles. The 35-nm-type particle was spherical with a dense central core.

Animals↗