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Biomedical subjects

M A Blankenstein

Publications and source records attributed to M A Blankenstein.

At least 73 records · Page 4Linked to original sources
PubMed1993

The cardiovascular risk factor plasminogen activator inhibitor type 1 is related to insulin resistance.

The cardiovascular risk factor plasminogen activator inhibitor type 1 (PAI-1) has been associated with abdominal obesity, hypertension, hypertriglyceridemia, hyperinsulinemia, glucose intolerance, and type II diabetes, conditions known to be linked with insulin resistance. To determine whether PAI-1 is related to insulin resistance, we studied nine obese nondiabetics and 10 obese type II diabetics by means of a sequential hyperinsulinemic euglycemic clamp study. Plasma PAI-1 antigen (Ag) correlated significantly with peripheral insulin resistance, represented by the insulin level at which peripheral glucose uptake (PGU) is half-maximal ([ED50PGU] r = .87, P < .001). Multiple regression analysis including indices of hepatic and peripheral insulin action, fasting plasma insulin levels, triglyceride levels, blood pressure (BP), waist to hip ratio (WHR), and body mass index (BMI) disclosed ED50PGU to account for 76% of the variance of PAI-1 Ag. We suggest that PAI-1 contributes to the increased cardiovascular risk encountered with insulin resistance.

Antigens↗
PubMed1993

Local aromatase activity in human breast tissues.

The presence of oestradiol in malignant breast cells is considered to be an important factor in the promotion of growth of the tumor. Therefore the regulation of the local high intra-tissue oestradiol concentrations, regardless of plasma concentrations, has been investigated. Experimental evidence suggests that in situ biosynthesis of oestrogens is at least partly responsible for the local accumulation of these steroids. In this paper we report further data on measurements in fatty and tumor tissues of local aromatase activities and of concentrations of substrates and products of this enzyme. Data are given on localization of aromatase and on steroid concentrations in tumors and in adipose tissues dissected from different quadrants of breasts with malignant tumors. In adipose tissues small variations in steroid concentrations in fatty tissues were found. No tumor-directed gradients in the adipose tissue-concentrations of the androgens dehydro-epiandrosterone, 5-androstene-3 beta, 17 beta-diol, 4-androstene-3,17-dione and testosterone and of the oestrogens oestradiol, oestrone and their sulfates could be detected. Furthermore no consistent pattern could be recognized in the aromatase activities in the fatty tissues dissected from tumor-bearing and non-affected quadrants of the same breast. No correlations between aromatase activity measured in vitro and product concentrations in vivo were found. Therefore the mechanisms for regulation of the local oestradiol levels in breast tissues remain unknown.

Adipose Tissue↗
PubMed1993

Wild type and alternatively spliced estrogen receptor messenger RNA in human meningioma tissue and MCF7 breast cancer cells.

Human meningiomas are rich in progesterone receptors (PR), which appear to be expressed autonomously. To investigate whether estrogen receptor (ER) variants which do not bind the ligand, but may constitutively induce PR expression, prevail in meningioma, we amplified cDNA by PCR in order to detect mRNA coding for the ER in meningioma which were ER-negative/PR-positive at the protein level. We screened for a portion of the ER which includes the DNA binding domain, the hinge region and the ligand binding domain. For this part of the ER we found a wild type mRNA in all 8 meningiomas tested. No mutations were detected. Apart from this transcript we found two alternatively spliced products missing exons 4 and 7, respectively in 8/8 meningioma specimens. These two products were not exclusive for meningioma, since they were also detected in the MCF7 breast cancer cell line which was used as control. ER deletion mutants missing exon 7 have already been reported [Ref. 1; Molec. Endocr. 5 (1991) 1571-1577]. These are dominant negative. To our knowledge, this is the first report on ER mutants missing exon 4. The presence of ER variants missing exon 4, which is probably not able to bind heat shock protein 90 and therefore may be constitutively active, might explain the autonomous expression of PR in meningioma.

Alternative Splicing↗
PubMed1993

Detection of an oestrogen receptor-like protein in human meningiomas by band shift assay using a synthetic oestrogen responsive element (ERE).

When a ligand binding or enzyme immunoassay is used, meningiomas are found to be rich in progestin receptors (PR) whereas oestrogen receptors (ER) are virtually undetectable. A protein that can bind to an oestrogen responsive element (ERE) was detected in meningiomas, by using the band-shift assay. The binding of ER to the ERE is inhibited by the anti-ER monoclonal antibody ER-P31, which is directed to the A/B domain of the ER, indicating that the binding protein is an ER-like protein.

Antibodies, Monoclonal↗
PubMed1992

Comparative affinity of steroidal and non-steroidal antioestrogens, cholesterol derivatives and compounds with a dialkylamino side chain for the rat liver antioestrogen binding site.

Steroidal and non-steroidal antioestrogens, steroidal compounds with (disubstituted) dialkyl amino side chain, cholesterol derivatives, histaminic and (anti)-progestational compounds were tested for their ability to compete with [3H]tamoxifen for the specific antioestrogen binding site (AEBS) in the post-mitochondrial fraction of rat liver homogenates. Relative binding affinity was highest for compounds with diethylamino or pyrrolidino ethoxy side chains. Affinity decreased with shortening of this side chain. No connection could be established between the carbon backbone of the compound and affinity, except for the presence of (sometimes aromatic) ring structures. Steroidal ring structures do not seem to be necessary for binding. The cholesterol derivatives, tested in our laboratory, showed very little affinity for the rat liver AEBS. Histamine, melatonin and the (anti)-progestational compounds showed no affinity for the AEBS; and we therefore conclude that the AEBS is not identical to receptors for these compounds. Results of these experiments could be useful in other investigations on the development of resistance of breast cancer to antioestrogens.

Animals↗
PubMed1992

Effect of wheat bran on excretion of radioactively labeled estradiol-17 beta and estrone-glucuronide injected intravenously in male rats.

Urinary and fecal estrogen excretion were studied in male rats fed a non-fiber wheat starch diet (dietary fiber less than 1%; NF group; n = 4), a low-fiber wheat flour diet (dietary fiber 2%; LF group; n = 4) or a high-fiber wheat bran diet (dietary fiber 11.6%; HF group; n = 3). Short-term effects of the experimental diet on estrogen excretion were studied after i.v. injection of 5 microCi (0.185 MBq) of [14C]estradiol-17 beta (E2) into the tail vein of the rats fed the diets for 2 days. After 3 weeks on the experimental diets, the long-term effects were studied after injection of 5 microCi of [14C]E2 and 10 microCi of [3H]estrone-3-glucuronide (E1-gluc). The diet was found to affect estrogen excretion. The short-term effect indicated that rats fed the HF diet excreted a relatively large amount of labeled compounds in the feces during the first day after injection, while rats fed the NF or the LF diets excreted about half that amount over the same period. On the other hand, urinary excretion of labeled compounds was significantly higher in the NF and LF rats. The long-term effect resulted in steeper slopes (P less than 0.05) of the fecal excretion profiles of rats fed the HF diet as compared with rats fed the NF and LF diets, indicating an accelerated fecal excretion of labeled compounds in the HF rats. The kinetic profiles of 14C and 3H radioactivity in blood plasma indicated a fast decrease (t1/2 of less than 2 min) for both [14C]E2 and [3H]E1-gluc. It was concluded that, owing to the short-term effect of wheat bran intake, during the first 24 h after i.v. administration relatively large amounts of radioactively labeled compounds are excreted in feces of rats fed the HF diet. In contrast, excretion is lower in urine of these rats. When the microflora is adapted to the experimental diet the wheat bran diet still results in an accelerated fecal excretion of labeled compounds, which might be attributed to an interruption of the enterohepatic circulation of estrogens. This might result in lowered plasma and/or tissue estrogen levels and hence a decreased exposure of estrogen-sensitive tissue to estrogens, which might decrease risk on mammary (breast) cancer development.

Animals↗
PubMed1992

Aberrant oestrogen receptor species in human meningioma tissue.

Meningiomas are very rich in progestin receptors (PR) whereas oestrogen receptors (ER) are seldomly found and only at low concentrations. These tumours might possess an ER which is defective in oestrogen binding but still functional in stimulating oestrogen-responsive genes such as PR. In human meningiomas a polymerase chain reaction fragment including the DNA binding domain, the hinge region and the ligand binding domain of ER was amplified. The size of the fragment obtained was as expected from wild type mRNA sequences. Moreover, a variant, which was overexpressed in meningiomas, with a major deletion in exons 2-6 was detected.

Base Sequence↗
PubMed1992

Tissue androgens and the endocrine autonomy of breast cancer.

To evaluate whether a tumour-directed gradient in androgen levels in fatty tissue can account for the maintenance of intra-tissue oestradiol levels, androstenedione (Adione), dehydroepiandrosterone (DHEA), testosterone (Testo) and androstenediol (Adiol) were assayed in breast tumour tissues and in fatty tissue taken at different distances from the tumour. The concentration of Adione was significantly lower in tumour tissue (5.6 +/- 1.5 pmol/g tissue; mean +/- SEM; n = 14) than in the adjacent fatty tissue (20.4 +/- 2.2; P less than 0.005). Testo, by contrast, occurred in equal concentrations in tumour (0.80 +/- 0.11) and in adjacent fatty tissue (0.70 +/- 0.07). Adione levels tended to be lower after the menopause only in fatty tissue, not in the tumour tissue; for Testo no differences were observed between samples from pre- and postmenopausal patients. Tumour DHEA levels (57 +/- 12 pmol/g tissue) were lower than those in fatty tissue (117 +/- 17; P less than 0.02). As with Adione, fatty tissue DHEA concentrations tended to be higher in pre- than in postmenopausal patients. Adiol showed a similar pattern as Testo. For none of the aromatase substrates nor their precursors a tumour-directed gradient was observed. The concentration of Adione in breast cancer tissue is much lower than the reported Km of the aromatase system for Adione. We have concluded, therefore, that the maintenance of oestradiol concentrations in tumour tissues is not substrate-driven.

Adipose Tissue↗
PubMed1992

On the significance of in situ production of oestrogens in human breast cancer tissue.

We have previously shown that human breast cancer is autonomous in the regulation of its intra-tissue oestradiol concentration. Breast fatty tissue does not have this capacity, but rather reflects changes in the peripheral oestradiol concentration. To further evaluate the relative contribution of breast cancer and fatty tissue to the maintenance of tumour oestradiol we investigated whether a tumour-directed gradient in aromatase activity and oestrogen levels existed in mastectomy specimens. No such gradient was found, however, for aromatase, oestrone, oestradiol and their sulphates. Aromatase activity (expressed per gram of tissue) and the concentrations of oestradiol, oestradiol sulphate and oestrone sulphate were higher in tumour than in breast fatty tissue. Fatty tissue had a higher oestrone concentration. It is tentatively concluded that breast tumour aromatase activity is more important for the maintenance of tumour oestradiol levels than aromatase in breast fatty tissue.

Adipose Tissue↗
PubMed1992

High affinity growth hormone binding protein in plasma of patients with acromegaly and the effect of octreotide treatment.

OBJECTIVE: The objective of this study was to investigate the effect of plasma GH-levels on the high affinity growth hormone binding protein (GHBP). PATIENTS: We studied plasma samples of eight patients with acromegaly and eight age and sex matched healthy subjects. DESIGN: Patients with acromegaly were treated with octreotide administered by continuous subcutaneous infusion. Levels of growth hormone binding protein (GHBP) were measured in plasma samples before therapy and 3, 6 and 12 months after starting treatment. During this period, octreotide was administered in doses of 300-800 micrograms/day. The mean dose per patient over the study period ranged from 300 to 575 micrograms/24 h. The GHBP levels of patients with acromegaly were compared with those in the healthy subjects. MEASUREMENTS: Bound and free 125I-GH in plasma were measured using FPLC gel chromatography on a Superose 12 column, after an overnight incubation period. The binding data were used for a Scatchard plot analysis. Wilcoxon's signed rank test was used for statistical analysis. RESULTS: We found lower GHBP levels in acromegalic patients (P = 0.01) than in the control subjects. Octreotide treatment resulted in IGF-I levels < 300 micrograms/l in four patients. In these patients GHBP levels increased. CONCLUSIONS: We conclude that growth hormone binding protein levels are down regulated in acromegaly, indicating an important role for GH in the regulation of this protein.

Acromegaly↗
PubMed1992

Estrogens in plasma and fatty tissue from breast cancer patients and women undergoing surgery for non-oncological reasons.

Breast cancer tissue is able to maintain the tissue estradiol level in spite of the massive decrease in plasma estradiol associated with menopause, whereas fatty tissue from breasts with malignancies more closely reflects the changes in plasma. In the present study estrone and estradiol levels in fatty tissues from different origins were compared to evaluate the capacity of distant fatty tissues to act as estrogen reservoirs. Abdominal fat was obtained from 25 premenopausal and 20 postmenopausal women who underwent surgery for non-oncological reasons. Estrone and estradiol levels in these tissues were compared to those in breast fatty tissue from breast cancer patients. Plasma estrogen levels were not different in the two groups. In both groups, median plasma estradiol levels dropped sharply with menopause (from 363 to 40 pmol/l in breast cancer patients; from 280 to 45 pmol/l in the non-oncological patients; p less than 0.002), whereas a significant decrease in plasma estrone was observed only in the breast cancer patients (from 238 to 140 pmol/l; p less than 0.02). In premenopausal women, median estrone and estradiol levels in breast fatty tissue (1135 and 375 fmol/g, respectively) and abdominal tissue (1390 and 470 fmol/g, respectively) were not different. In postmenopausal women, however, significantly higher estrone levels (663 vs. 508 fmol/g; p less than 0.01) and estradiol levels (245 vs. 187 fmol/g; p less than 0.02) were found in abdominal fatty tissue. In view of the absolute estrogen levels in breast and abdominal fatty tissue and in plasma, we conclude, however, that it is unlikely that remote fat contributes substantially to the maintenance of estrogen levels in breast cancer tissue.

Abdomen↗
PubMed1991

Endogenous steroid hormones and local aromatase activity in the breast.

To test the hypothesis of an increased activity of the enzyme aromatase in adipose tissue from affected when compared with non-affected quadrants of patients with breast cancer, the aromatase activity has been measured in tumour and fatty tissues dissected at specific sites from the breasts of 16 patients. Activity was measured after extensive purification of the product formed. Results, expressed in fmol/g of tissue, did not show a higher activity in the affected vs the non-affected quadrants. In the tumours, higher activities were found when expressed per g of tissue. Per mg of DNA, an indicator of the number of cells, tumour enzymatic activity was lower than in fatty tissues. The relations between the products of aromatase, oestrone and oestradiol in the various tissues point to the importance of additional enzymatic processes, especially of the reductive 17 beta-oestradiol dehydrogenase, in the accumulation of high quantities of oestradiol in the malignant tissue.

Adipose Tissue↗
PubMed1991

Tamoxifen and oestrogen both protect the rat muscle against physiological damage.

Tamoxifen (TX), an oestrogen antagonist, was used to characterize the protective effect of oestradiol (E2) on exercise-related creatine kinase (CK) release from skeletal muscle of the rat. Subcutaneous administration of TX for 3 weeks in female rats had a profound antioestrogen effect as evidenced by a reduced weight of the uterus. The CK release after electrical stimulation of the isolated soleus muscle, previously shown to be E2-dependent, was markedly reduced (30-50%) after treatment with TX; this observation points to an E2-like protective action of TX instead of E2-antagonism. This effect was dose-dependent (0.25-1.00 mg/kg) and was not seen when TX was given shortly (24 h) before the experiments. In ovariectomized females, that show more CK leakage due to the lack of circulating E2, both E2- and TX-treatment resulted in a 60% reduction of the CK leakage. Muscles from male rats, treated with TX, showed a similar response: after contractions the CK release was significantly lower. We conclude that TX, like E2, reduces contraction-induced muscle damage in the rat and, thus, has E2-agonistic properties on skeletal rat muscle.

Animals↗
PubMed1991

The origin of estrogens, progesterone, androgens and sex hormone binding globulin in peritoneal fluid in the immediate postovulatory period in normal ovulating women.

In 20 women with proven fertility, one menstrual cycle was monitored by ovarian ultrasonography, laparoscopy and estimation of 17 beta-estradiol (E2), estrone (E1), progesterone, testosterone, androstenedione (Adion), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), and sex hormone binding globulin (SHBG) in serum and peritoneal fluid. Three groups were studied, in which the peritoneal fluid was collected within 1, 3 and 5 days after ovulation. E1, E2 and progesterone levels in peritoneal fluid were highest shortly after ovulation and decreased with time. Testosterone and Adion in peritoneal fluid showed no changes, but peritoneal fluid levels were always higher than serum levels. No differences were found between the peritoneal fluid and serum levels of DHEA and DHEAS. SHBG in serum was always higher than in peritoneal fluid. The results are compared with reported steroid levels in follicular fluid from the literature and factors complicating the interpretation of steroid levels in peritoneal fluid are discussed.

Adult↗
PubMed1991

Steroid receptors in mammary tumours of the cat.

The capacity of steroidal regulatory influence on benign and malignant mammary tissue in cats was investigated. Estrogen, progestin, and (in some cats) androgen receptor levels in the cytosol were measured by a multiconcentration dextran-coated charcoal method in non-affected mammary tissue (NAMT) and in benign and malignant mammary lesions from 34 cats. Receptor levels less than 5 fmol/mg protein were considered negative. Since 3 out of 4 NAMT samples had low-positive estrogen receptor and progestin receptor levels, we considered specimens in which tumour cells were intermeshed with NAMT separate from "pure" tumour specimens. The variation in estrogen receptor expression between the different tissues was moderate, there being 9/17 malignant lesions (without NAMT) estrogen receptor+ as compared with 6/6 benign lesions (without NAMT) (p less than 0.05). The variation in progestin receptor expression was greater (p less than 0.02), with only 5/17 malignant lesions-(without NAMT) progestin receptor+ as compared with 6/6 benign lesions (without NAMT). The difference in progestin receptor levels between these 2 groups was also statistically significant. In 5 cats metastases were also assayed and 2 had a low-positive estrogen receptor level, whereas 1 had a low-positive progestin receptor level. Two of 9 malignant lesions (without NAMT) had positive androgen receptor levels. Comparison of the steroid receptor expression of human and feline mammary cancer indicates that estrogen receptor and progestin receptor levels are lower in the latter. This may indicate that loss of steroid hormone dependency occurs at an earlier stage of the disease in feline mammary cancer than in human breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Comparison of breast cancer mucin (BCM) and CA 15-3 in human breast cancer.

The Breast Cancer Mucin (BCM) enzyme immunoassay utilizes two monoclonal antibodies (Mab), M85/34 and F36/22, for the identification of a mucin-like glycoprotein in serum of breast cancer patients. We have compared BCM with CA 15-3, another member of the human mammary epithelial antigen family. Serum BCM was evaluated in 151 and CA 15-3 in 134 patients with breast cancer, in 30 normal controls, in 9 pregnant women, and in 13 cancer patients (non-breast). Neither the normal controls nor the pregnant women had BCM levels greater than 25 U/ml. In contrast, 87 of 115 patients (75%) with metastatic breast cancer had BCM levels greater than 25 U/ml. All control persons had CA 15-3 levels less than 25 U/ml, but 2 out of 9 pregnant women (22%) had levels greater than 25 U/ml. Seventy-four out of 97 patients (76%) with metastatic breast cancer had CA 15-3 levels greater than 25 U/ml. A statistically significant correlation was found between BCM and CA 15-3 in the breast cancer patient group (r = 0.883, p less than 0.001, n = 134) and in the normal control group (r = 0.743, p less than 0.001, n = 30). BCM and CA 15.3 both showed no correlation with CEA in breast cancer patients (r = 0.060, n = 81; and r = 0.146, n = 78, respectively). BCM had a range of sensitivity similar to that of the CA 15-3 RIA. Our results suggest that BCM may be a useful new marker for monitoring the clinical course of patients with breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Neoplasm↗
PubMed1990

Comparison of ligand binding assay and enzyme immunoassay of oestrogen receptor in human breast cancer cytosols. Experience of the E.O.R.T.C. Receptor Group.

Nine laboratories cooperating in the Receptor Study Group of the EORTC compared results of ligand binding assay supplemented with Scatchard plot analysis (LBA) and enzyme immunoassay (EIA) for the assessment of oestrogen receptors in 1665 breast cancer cytosols. An excellent agreement was observed between results of Scatchard plot analysis and EIA in each laboratory. Linear correlation coefficients of log-transformed data (log [(ER + 10)/10]) ranged from 0.839 to 0.977 (n = 52-373; P less than 0.001); Spearman's R ranged from 0.797 to 0.972 (P less than 0.001). Orthogonal regression analysis on log-transformed data revealed slopes of 0.794 to 1.141 and intercepts of -0.057 to 0.154 corresponding to -1.2 to 4.3 fmole/mg protein. Both assays compared equally well for pre- as well as postmenopausal patients, which confirms that occupied receptors are not extracted during the preparation of cytosol. The percentage discordance in the classification of tumours as ER positive or negative varied from 4.1 to 13.3 when a cut-off value of 10 fmol/mg protein was used, and from 1.4 to 7.5 at a cut-off level of 20. Considerable variations were observed in the actual receptor levels reported by each laboratory. Since these differences occurred in the results of both methods, they are attributed to differences in tissue handling. It is concluded that the ER-EIA is an excellent alternative to Scatchard plot analysis for the assay of oestrogen receptors. It is recommended, however, that laboratories performing assays on samples obtained from patients who are eligible for entrance in EORTC clinical trials and who wish to use the EIA should validate this assay against the Scatchard plot assay in their own setting.

Adult↗