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H Bojar

Publications and source records attributed to H Bojar.

At least 37 records · Page 2Linked to original sources
PubMed1986

Abbott monoclonal enzyme immunoassay measurement of estrogen receptors in human breast cancer: a European multicenter study.

A new enzyme immunoassay (Abbott ER-EIA Monoclonal) for the determination of estrogen receptor in cytosols from breast tumor specimens has been developed by Abbott Laboratories. To establish the correlation of the results from this new technique with currently existing steroid binding methods, a multicenter study was conducted in eight European laboratories. All participants followed the same protocol consisting of a familiarization phase, a proficiency evaluation, and a comparison of existing steroid binding methods with the new immunoassay using panel samples and clinical specimens. ER-EIA was compared with the multipoint dextran coated charcoal assay in six laboratories, four of which followed the EORTC protocol; of the remaining two laboratories, one used a single saturating dose assay, the other an isoelectric focusing assay. The results show no significant difference between reducing agents when used in the ER-EIA. Reproducibility for the immunoassay (interassay coefficient of variation, 6%, interlaboratory coefficient of variation, 11-19%) was somewhat better than that for the steroid binding methods (interlaboratory coefficient of variation, 12-32%). The correlation between the methods was dependent on the origin of the lyophilized specimens. In breast tumor samples, an excellent correlation, (not statistically different from 1) was found between the ER-EIA and the steroid binding method in six laboratories. One laboratory showed a slope of 1.1 for the correlation line; the laboratory using isoelectric focusing showed a slope of 1.9. The mean value determined by the enzyme immunoassay in premenopausal women was 74 fmol/mg cytosol protein, and in postmenopausal women it was 187 fmol/mg cytosol protein with no significant difference in the slope of the correlation line. Results suggest the usefulness of the new standardized enzyme immunoassay for routine use in the clinical laboratory.

Antibodies, Monoclonal↗
PubMed1986

Quality control requirements in estrogen receptor determination.

The clinical significance of estrogen receptor (ER) levels determined in breast cancer tissue depends on the quality of the ER assay procedure itself as well as on several critical factors beyond the direct responsibility of the receptor laboratory. A novel immunobiochemical assay (ER-EIA) has been made available by Abbott Laboratories. In comparison to the classical radioligand binding assay, the use of ER-EIA resulted in lower intra- and interassay as well as interlaboratory coefficients of variation. This may be explained by the complete standardization of ER-EIA as compared to ER radioligand binding assay. Considerable attention must be paid to the source of origin of quality control material if identical ER levels are to be obtained by both methods, as the monoclonal antibodies of ER-EIA bind less avidly to cytosolic ER of calf uterus and, in contrast to routine ER radioligand binding assay, are able to recognize occupied ER.

Antibodies, Monoclonal↗
PubMed1985

Insulin effect on translational diffusion of lipids and proteins in the plasma membrane of isolated rat hepatocytes.

The effects of insulin (10(-10)-10(-8) mol/l) on lateral diffusion of three fluorescent lipid probes, 1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)aminocaproyl phosphatidylcholine (NBD-PC), 5-(N-hexadecanoyl)aminofluorescein (F-C16), 5-(N-dodecanoyl)aminofluorescein (F-C12), and of fluorescein isothiocyanate-labeled proteins in the plasma membrane of intact rat hepatocytes were studied by the technique of fluorescence recovery after photobleaching. The absolute lateral diffusion coefficients of the lipid analogues NBD-PC, F-C16 and F-C12 at 21 degrees C were 2.5 X 10(-9) cm2/s, 5.4 X 10(-9) cm2/s and 19 X 10(-9) cm2/s, respectively. The diffusion coefficient mean of proteins labeled with fluorescein isothiocyanate was 6.4 X 10(-10) cm2/s. Insulin at 10(-9) and 10(-8) mol/l reduced the lateral diffusion coefficient for F-C12- and F-C16-labeled cells by 20% and for NBD-PC-labeled cells by 30% (P less than 0.025). The insulin effect was specific as tested by cell incubation with proinsulin and desoctapeptide insulin (10(-8) mol/l) and was detectable after 7 min of insulin preincubation. In contrast to lateral diffusion of lipid probes, lateral mobility of unselected membrane proteins was not altered by insulin. The observed modulation of lipid dynamics in the plasma membrane of intact hepatocytes, by which a variety of membrane functions can be influenced, may be an important step in the mechanism of insulin action.

Animals↗
PubMed1985

Steroid receptor status of human testicular tumors.

Biopsies of 9 testicular tumors were examined for the presence of cytoplasmic receptor proteins for estrogens, progestins, androgens, and glucocorticoids. Using an arbitrary threshold value of 10 fmol/mg cytosol protein for a postive assay, only 1 of 9 tumors was estrogen-receptor positive. However, no receptor-specific 8S binding could be detected by low salt sucrose gradient centrifugation. 1 tumor was progesterone-receptor positive. No androgen receptors could be demonstrated. In contrast, 8 of 9 neoplasms contained significant quantities of glucocorticoid receptors exclusively sedimenting at 8S. Our findings suggest that androgens, estrogens, and progestins are unlikely to play a major role in the natural history of testicular tumors. The presence of glucocorticoid receptors might offer a chance for endocrine manipulation of the development and growth of these neoplasms by glucocorticoids.

Adolescent↗
PubMed1984

Steroid receptor status of focal-nodular hyperplasia of the human liver.

As with normal human liver, both focal nodular hyperplasia (FNH) of the liver and a hepatocellular carcinoma were found to contain low levels of high affinity estrogen-binding components. In low-salt sucrose gradients the estrogen binders sedimented at 4S and 8S. Specificity studies indicated a requirement for estrogenic hormones. Progestin-binding studies using labeled and unlabeled ORG 2058 revealed high levels of specific binding in FNH and normal liver cytosol, whereas only insignificant amounts of ORG 2058 binding was found in the hepatocellular carcinoma. As judged by the high apparent dissociation constant (4-14 X 10(-8) mol/l) of the ORG 2058 - binder complex, the apparent lack of 8S binding in low-salt sucrose gradients and the atypical ligand specificity, the progestin receptor nature of these binding entities is unlikely. In contrast, normal liver, FNH, and the hepatocellular carcinoma were found to contain significant quantities of glucocorticoid receptors.

Adult↗
PubMed1980

Investigation on the thermostability of steroid hormone receptors in lyophilized calf uterine tissue powder.

Powdered calf uteri were lyophilized and sealed in a vacuum. The effects of lyophilization and the thermostability of the binding activity of uterine steroid hormone receptors were studied. The lyophilized powder was analyzed for its ability to bind estrogen, progestin, androgen, and glucocorticoid steroids. Lyophilization had no deleterious effects on the binding activity. Storage of the lyophilized powder at +20 C for more than 14 days did not reduce the binding activity. No reduction of the binding capacity was also observed when the storage temperature was at +30 C for 16 hours. However, a slight loss of specific binding sites was observed for 17 beta-estradiol (-12%) at the storage temperature of +40 C, but the other steroid binding proteins were more stable. When the storage temperature was at +60 C for 16 hours, a loss of about 24% was observed for the specific estrogen binding sites, whereas the binding capacity of progestin, androgen, and glucocorticoid receptors was reduced by only less than 10%. Storage at the high temperature of +80 C for 16 hours resulted in a loss of only 36% for the estrogen binding capacity and less than 30% loss for the other binding proteins. The freeze-dried uterine powders can be useful quality control specimens for steroid receptor assays.

Animals↗
PubMed1980

The endocrine background of human renal cell carcinoma. V. Binding of the highly potent androgen methyltrienolone (R 1881) by tumour cytosol.

The binding of methyltrienolone (R 1881, 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-trien-3-one), a highly active synthetic androgen, by cytosol preparations from human renal cell carcinoma was investigated. High-affinity, low-capacity binding components for R 1881 were detected in 3 out of 8 tumours analysed. The apparent dissociation constant of the R 1881-binder complexes was found to be in the range of 1.1-2.3 x 10(-9) mol/l. The number of binding sites in the positive tumours varied from 2.1 to 9.7 fmol/mg cytosol protein. Studies of binding specificity indicated a requirement for androgens. It is concluded that these binding components may be hormone receptors. If in consecutive studies this hypothesis holds true, progestins, most widely used in hormonal therapy of metastatic renal cancer, may possibly act on the tumour tissue by inhibiting the secretion of gonadotropins, thus lowering the blood levels of eventually growth-promoting.

Adenocarcinoma↗
PubMed1980

Identification and partial characterization of glucocorticoid receptors in human liver.

In normal human liver from adult males and females cytoplasmatic components which bind dexamethasone specifically and with high affinity, were demonstrated via dextran-coated charcoal assay, agar gel electrophoresis, isoelectric focusing and sucrose gradient centrifugation. The apparent dissociation constant of the dexamethasone-binder complex was found to be 1.7 +/- 0.3 x 10-(8) mol/l. The binding capacity was limited to 67.5 +/- 5.3 fmol/mg of cytosol protein. The ligand specificity for binding to these components indicated the requirement for glucocorticoids. It was shown by means of agar gel electrophoresis that the dexamethasone-binding entities migrate to the receptor region of the gel. The isoelectric point of the binding components in human liver cytosol was found to be pH 6.3. Sedimentation in sucrose gradients revealed the bulk of these components to be in the 7S region. It is concluded that the specific dexamethasone-binding entities in human liver have all the properties of glucocorticoid receptors.

Adolescent↗
PubMed1980

Detection and partial characterization of glucocorticoid-binding components in hepatic metastases of human bronchial and gastric carcinoid tumors.

Metastases of human carcinoid tumors of bronchial and gastric origin have been analysed for glucocorticoid receptors using the fluorinated compound [3H] dexamethasone. In both tumors high concentrations of glucocorticoid-binding components were detected which based on several physicochemical characteristics were identified as glucocorticoid receptors in nature. The apparent dissociation constant of the dexamethasone-binder complex was found to be 1.8 x 10(-8) mol/l for the bronchial and 2.8 x 10(-8) mol/l for the gastric carcinoid tumor. Sedimentation in sucrose gradients disclosed the binding components to be macromolecules, sedimenting at about 7.S. By agar gel electrophoresis the molecular species binding dexamethasone were found to exhibit the same electrophoretic mobility as glucocorticoid receptors from well-known target organs. The ligand specificity for binding to these components indicated a requirement of active glucocorticoids as well as anti-glucocorticoids. A regulatory function of glucocorticoids in serotonin biosyntheses is discussed, which may be of potential clinical significance.

Binding, Competitive↗
PubMed1979

The endocrine background of human renal cell carcinoma. I. Binding of the highly potent progestin R 5020 by tumour cytosol.

Based on the potential sensitivity of the growth of human renal cell carcinoma, tumour tissue from 88 patients was analysed for progestin receptors. With the dextran-coated charcoal assay, cytoplasmic components which bound the potent progestin R 5020 specifically and with high affinity could be detected in 42% of the carcinomas. The apparent dissociation constant of the R-5020-binder complex amounted to 3.1 +/- 1.2 X 10(-8) mol/l. Sedimentation in sucrose gradients revealed the bulk of these components to be in the 4-S region. The ligand specificity for binding to these sites indicated a requirement for progestins. Despite the enormous case material investigated, we were unable to confirm the presence of the high receptor concentrations reported in the literature.

Adenocarcinoma↗
PubMed1979

The endocrine background of human renal cell carcinoma. II. Attempt to induce the R-5020-binding components by oestrogens.

In an attempt to elevate the concentration of progestin-binding components in human renal cell carcinoma, 24 patients were treated prior to tumour nephrectomy with various doses of oestrogens, potent inducers of progestin receptor synthesis. Low-dose oestrogen treatment was found to be insufficient to significantly induce progestin-binder synthesis in the tumour tissue. In the carcinoma of patients receiving high-dose oestrogen treatment, the average concentration of R-5020-binding sites did not differ from that of the low-dose group. However, 2 out of these patients (12.5%) exhibited R-5020-binder concentrations in the tumour tissue which exceeded the highest quantities of progestin-binding components found in 88 untreated controls previously analysed in our laboratory.

Adenocarcinoma↗
PubMed1979

The endocrine background of human renal cell carcinoma. III. Role of inhibitors of R 5020 binding in tumour cytosol.

Cytosol preparations obtained from 9 different human renal cell carcinomas were investigated for the eventual presence of progestin-binding inhibitors which might offer an explanation for the previous failure to demonstrate high receptor levels in the tumour tissue. The inhibitory potency of these preparations was estimated by measuring the decrease of R 5020 binding to uterine progestin receptors in the presence of tumour cytosol. Interestingly, cytosol from human renal cell carcinoma was found to contain progestin-binding inhibitors. The average inhibition of R-5020-receptor interaction amounted to 46%. In only 1 out of 9 cases, binding was completely suppressed. In order to circumvent the inhibitory reaction potentially occurring in cell-free systems, R-5020-binding studies additionally were performed in cell suspension. Out of 7 carcinomas studied using this assay system, 5 did not contain any specific progestin-binding entities. In 1 tumour, receptor-atypical non-saturable binding was observed. Only in isolated cells prepared from 1 other carcinoma, could slight indications for the presence of low concentrations of progestin receptors be detected.

Adenocarcinoma↗