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Biomedical subjects

H Bojar

Publications and source records attributed to H Bojar.

At least 55 records · Page 3Linked to original sources
PubMed1979

The endocrine background of human renal cell carcinoma. IV. Glucocorticoid receptors as possible mediators of progestogen action.

In order to investigate whether progestins may trigger tumour regression by a mechanism involving the glucocorticoid receptor, human renal cell carcinomas obtained from 15 patients were analysed for cytoplasmic glucocorticoid-binding components, using [3H] dexamethasone. The existence of glucocorticoid binders could be demonstrated in 10 out of 15 tumours studied. The average binding capacity was calculated and found to be 7.1 fmol/mg of cytosol protein. The apparent dissociation specificity experiments clearly cell-free system amounted to 1.9 X 10(-8) mol/l. The ligand specificity experiments clearly indicated that binding to these receptors is not restricted to glucocorticoids alone. Progesterone and aldosterone turned out to be moderate competitors for dexamethasone binding. Medroxyprogesterone acetate, the compound widely used in hormone therapy of advanced renal cancer in man, was demonstrated to be one of the strongest inhibitors of [3H] dexamethasone. It is concluded that binding of medroxyprogesterone acetate to glucocorticoid receptors might represent the primary mechanism of action of the compound in causing tumour regression.

Adenocarcinoma↗
PubMed1979

[Viable cells from human renal cell carcinoma: isolation procedure and analysis of hormone sensitivity (author's transl)].

An enzymatic procedure for the isolation of metabolically active tumour cells from human renal cell carcinoma is described. The cells were suspended by a multistep incubation procedure of the tissue in the presence of collagenase (10 mg enzyme/g tumour wet weight) dissolved in a calcium-free buffer solution. About 90% of the isolated tumour cells were viable, as judged by routine trypan blue staining. Electron microscopic examination revealed tumour cells in various stages of dedifferentiation. The cells had retained their capability of protein synthesis. In short term experiments the effects of 17 beta-oestradiol and progesterone on the incorporation of [U - C] L-leucine into cellular proteins was studied; Progesterone was found to exhibit a slight tumour antianabolic or catabolic action. A 17 beta-oestradiol-dependent modulation of the rates of protein synthesis was not observed.

Adenocarcinoma↗
PubMed1977

Distribution of oestradiol receptor molecules in human kidney.

Experiments were performed to determine the distribution of oestrogen receptors in normal human kidney. Cytosols prepared from renal medulla and cortex were separately analyzed for oestrogen receptor molecules aga gel electrophoresis. Oestrogen receptors could be demonstrated in both compartments of the organ. However, the experiments reveal that the medulla is the main locus of oestrogen receptor in human kidney.

Aged↗
PubMed1977

[Sex specific action of insulin on the glucose metabolism of lymphatic tissue of rats and humans (author's transl)].

Glucose metabolism of lymphoid cells isolated from thymus and spleen of Wistar rats, weighing 140-150 g, was found to be sensitive to insulin. The influence of insulin on glucose uptake by isolated cells from both lymphoid tissues displayed a significant sex specificity. Insulin at 0.1-10 nmol/1 stimulated glucose uptake of cells from male rats, whereas in cells from females, inhibition of glucose uptake was observed. However, lactate production was enhanced in lymphoid cells of both sexes. Cortisol (100 nmol/1) displayed a significant anti-insulin action on glucose uptake and lactate release by thymocytes of male rats. In contrast, in cells from females, cortisol and insulin both exhibited an inhibitory action on glucose uptake, whereas the hormones were found to antagonise lactate production. The sex specific stimualtory influence of insulin on glucose uptake by thymocytes of male rats was reversed and the hormone became inhibitory when animals were castrated. The action of insulin on glucose uptake was also shown to be age-dependent. In experiments with rats weighing either about 10 g or 40 g, sex-specific effects on glucose influx were found, that were similar to those of rats weighing 140-150 g. However, stimulation of glucose uptake was found with thymocytes from rats of both sexes weighing about 80 g. Comparable results were obtained with isolated thymocytes from immature humans (2 months-10 years old). Incubation of thymocytes from males with insulin (10 nmol/1) stimulated glucose uptake and lactate release, whereas insulin caused an inhibition of glucose uptake and an enhancement of lactate production in thymocytes from female. Age dependence and sex specificity of insulin action on glucose metabolism in lymphoid cells and tissues may explain the contradictory results reported by other authors.

Age Factors↗
PubMed1976

Identification and partial characterization of specific oestrogen-binding components in human kidney.

In normal human kidney from adult males cytoplasmic components which bound 17beta-estradiol specifically and with high affinity were demonstrated by dextran-coated charcoal assay, sucrose gradient centrifugation and agar gel electrophoresis. The dissociation constant of the oestradiol-binder complex amounted to 2.2 +/- 0.1 x 10(-9) mol/l. The binding capacity was limited to 34.0 +/- 9.7 fmol/mg of cytosol protein. Sedimentation in sucrose gradient revealed the bulk of these components to be in the 4S region. The binding entities could be clearly separated from sex hormone-binding globulin by agar gel electrophoresis. The ligand specificity for binding to these components indicated a requirement for oestrogens. The fact that an excess of aldosterone had no competitive effect on oestradiol binding suggests that the oestrogen-binding sites are independent of mineralocorticoid receptors. It is concluded that the specific binding components in human kidney have the properties of oestrogen receptors.

Aged↗
PubMed1976

Oestrogen-binding components in human renal cell carcinoma.

Specific binding of [3H]oestradiol-17beta by the cytosol fraction of human renal cell carcinoma was studied. The binding reaction displayed marked ligand specificity and high affinity of binding. Unlabelled oestradiol, oestriol and oestrone inhibited the binding of [3H]oestradiol-17beta to the cytosol binding sites, wehereas all other steroids tested turned out to be only weak or insignificant competitors for the oestrogen binding sites. Scatchard analyses suggested the existence of a single class of binding sites. The dissociation constant of the oestradiol-binding complex was found to be 2.51 +/¿.75 x 10(-9) mol/l. The number of binding sites was limited (17.5 +/- 3.8 fmoles per mg of cytosol protein). Sucrose gradient centrifugation revealed these binding components to be macromolecules either displaying a complex sedimentation pattern (peaks at 3.5 S, 4S, 5.7S and, in addition, high molecular weight aggregates) or sedimenting in the 4S region alone. By agar gel electrophoresis it could be demonstrated that the oestradiol-inding components migrated into the receptor region of the gel. Binding of [3H]oestradiol-17beta to these entities was markedly reduced, when the cytosol was heated (60 min at 45 degrees C) prior to the reaction with the labelled hormone. Since the specific binding components exhibit properties of oestradiol receptors in target tissues, a direct effect of oestradiol on human renal cell carcinoma is suggested.

Adenocarcinoma↗
PubMed1976

Preparation of parenchymal and non-parenchymal cells from adult human liver--morphological and biochemical characteristics.

By perfusion of the isolated human liver with collagenase and hyaluronidase a mixed suspension of various cell types was obtained. Pure parenchymal cells were prepared by differential centrifugation, pure non-parenchymal cells by the use of pronase and subsequent isopycnic centrifugation on metrizamide gradients (50-300 g/l). About 90% of the parenchymal and non-parenchymal cells were viable as judged by trypan blue staining. Non-parenchymal cells were not capable fo gluconeogenesis but at high rates. Parenchymal cells retained their ability to form glucose and to accumulate glycogen from fructose greater than lactate/pyruvate greater than alanine. Studies on binding of 125I-labelled insulin by isolated parenchymal cells were performed at 30 degrees C. The binding data may fit with a minimum of two classes of binding sites: (a) high affinity--low capacity sties (Kd approximately 6.6 nmol/l, capacity approximately 16 000 insulin molecules per cell) and (b) low affinity-high capacity sites (Kd approsimately 0.37 mumol/l, capacity approximately 646 000 molecules per cell).

Adult↗
PubMed1975

[Isolation of intact liver parenchymal cells by a modified enzymatic method].

An enzymatic method is described for isolating intact parenchymal cells from rat livers. 3--4 g cells (wet weight) could be isolated from livers of rats weighing 180--230 g. After an in vitro preperfusion of 15 minutes with a Ca-free buffer, collagenase (200 mg/1) and calcium chloride (5.2 mmol/1) were added. Perfusion was continued for another 15 minutes at 37 degrees C. Micromorphological integrity of cell membranes was demonstrated by scanning electron microscopy. With regard to rates of gluconeogenesis and protein synthesis, parenchymal cells isolated according to our method were found to be superior to liver slices and cells isolated by other methods. Ratios of ATP/ADP (5.69) and of lactate/pyruvate (8.64) as parameters of the energetic situation and the redox state resp. were found within the physiological range. Integrity of cell surface receptors was proved by their sensitivity to epinephrine, glucagon and insulin. Glucagon (0.3 mumol/1) and epinephrine (1 mumol/1) and reduced glycogen deposition in hepatocytes of fasted rats by 84.9 % and 95.9 % resp. Both hormones stimulated glycogenolysis in parenchymal cells of fed rats to a similar extent. Urea synthesis was stimulated 29.5 % by glucagon (1 mumol/1), and inhibited 28.0 % by insulin (10 nmol/1). The stimulatory effect of glucagon (1 mumol/1) was abolished by insulin (10 nmol/1).

Adenosine Diphosphate↗
PubMed1975

[An enzymatic method for the isolation of tubules and cells from human kidney cortex].

The isolation of tubules and cells from human kidney cortex was realized by an enzymatic method. Tubules and cells were released from slices of kidney cortex by collagenase. The yield amounted to 80 % of the wet weight of incubated cortex slices. Thus numerous experiments with isolated tubules from one organ could be performed. Glucose production from different substrates was measured in order to test the biochemical integrity of the isolated cells. The highest rates of glucose formation were obtained with fructose as precursor. Glucose production was higher from lactate than from pyruvate. With proline and glutamine as substrates only small amounts of glucose were produced. Glucose formation from 10 mmol/1 pyruvate was linear with time up to 80 minutes. Ado-3':5'-P stimulated glucose formation at 10 mumolar concentration and inhibited gluconeogenesis at 1 mmolar, 0.1 mmolar and 1 mumolar concentrations.

Calcium↗
PubMedDate not supplied

Effects of high-dose medroxyprogesterone acetate and various other steroid hormones on plasma membrane lipid mobility in CAMA-1 mammary cancer cells.

The influence of medroxyprogesterone acetate (MPA) and various other steroid hormones on the lateral diffusion of the fluorescent lipid probe 1-acyl-2-(N-4-nitrobenzo-2-oxa-1.3-diazolyl)-aminocarpropylphos phatidylcholine (NBD-PC) in the plasma membrane of intact mammary cancer cells (CAMA-1 cell line) has been studied by fluorescence recovery after photobleaching technique. Incubation of cells with MPA in serum free medium at ambient temperature for 1 hr led to a significant decrease in the lateral diffusion coefficient of NBD-PC. MPA induced this change over a limited concentration range with 10(-7)-10(-5) mol/l near-maximal or maximal effects, and 10(-8) mol/l exhibiting no effect. Exposure of the CAMA-1 cells to 10(-7) mol/l MPA in undiluted serum induced a significant effect following 1.5 hr of treatment with no increase in effectiveness up to 4 hr of incubation. As compared to MPA, the other steroids tested were less effective or ineffective. The influence on lateral lipid mobility diminished as follows: MPA greater than progesterone greater than 5a-DHT approximately 17 beta-estradiol greater than dexamethasone, and roughly seems to parallel their lipid solubility as estimated by partition coefficients in an n-octanol-water system. Any involvement of classical steroid hormone receptors in the mechanism of membrane action could be excluded. Nongenomic steroid effects on the plasma membrane are assumed. As the structure and function of biomembranes are modulated by lipid-bilayer fluidity and membranes crucially participate in nearly all aspects of cell biology, it is concluded that direct interactions of MPA with membranes potentially play a role in the antitumor activity of the compound.

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