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Biomedical subjects

M A Blankenstein

Publications and source records attributed to M A Blankenstein.

At least 55 records · Page 3Linked to original sources
PubMed1996

Lack of islet amyloid polypeptide/amylin-immunoreactivity in urine collected from healthy volunteers after ingestion of a carbohydrate-rich meal.

Islet amyloid polypeptide (IAPP), or amylin, is synthesized by beta cells in the islets of Langerhans of the pancreas. Plasma IAPP levels are highly elevated in patients with advanced renal failure. To investigate the involvement of the kidney in the clearance of IAPP, the response of plasma and urinary IAPP to a carbohydrate-rich meal was investigated in 14 healthy volunteers. Although plasma IAPP levels increased severalfold after the meal, no IAPP-immunoreactivity was detected in the urine samples up to 4 hours after the meal. This might be due to the fact that urinary IAPP levels are under the detection limit of the assay or, assuming the presence of IAPP in the primary urine, immunoreactive IAPP molecules may be processed by renal mechanisms in such a way that they are no longer recognized by the antibodies used in the radioimmunoassay. Processed IAPP molecules may be reabsorbed in the proximal tubules of the kidney and/or excreted.

Adult↗
PubMed1996

A comparative study of risk factors for hyperplasia and cancer of the endometrium.

A cohort study has been carried out to investigate risk factors for cancer as well as hyperplasia of the endometrium. Over the 13 years for which we followed 25,000 women aged 40-65 (who took part in a population-based screening programme for breast cancer), 111 cases of endometrial cancer and 109 cases of endometrial hyperplasia were diagnosed. A comparison of the outcome between the two disease entities revealed that large body weight among postmenopausal women and the use of oestrogenic drugs at all ages were risk factors for both cancer and hyperplasia of the endometrium. However, reproductive histories and premenopausal steroid profiles differed. Steroid excretion determinations in urine samples collected years before diagnosis provided further evidence in favour of the hypothesis of unopposed action of oestrogens in the aetiology of endometrial cancer. In women who were to develop endometrial hyperplasia or cancer the obesity-oestrogen relationship was stronger than in those who remained free of endometrial disease during the period of follow-up. The possible significance of differences in aromatase activity among the obese is considered.

Adult↗
PubMed1996

Disrupted co-ordination of Pax-8 and thyroid transcription factor-1 gene expression in a dedifferentiated rat thyroid tumour cell line derived from FRTL-5.

The mutant rat thyroid cell line FRTL-5/TA, isolated from a non-functional tumour which originated spontaneously from wild-type FRTL-5 cells, shows autonomous TSH-independent growth and loss of the thyroid-specific phenotype, lacking thyroid-specific expression of thyroglobulin (Tg) and thyroid peroxidase (TPO) genes. To investigate the role of the transcription factors Pax-8 and thyroid transcription factor-1 (TTF-1) in rat thyroid tumorigenesis, RNA expression of these two thyroid-specific nuclear factors was measured in FRTL-5/TA tumour cells and compared with the expression in wild-type FRTL-5 cells. TTF-1 gene expression was similar to that in wild-type FRTL-5, and showed a similar down-regulation after stimulation with TSH. The finding suggested normal TTF-1 mRNA and protein expression in both cell lines. By contrast, Pax-8 mRNA transcript signal was markedly reduced in FRTL-5/TA cells, reaching levels as low as 8% of the normal, basal level in FRTL-5 cells. These data indicated that the loss of thyroid-specific expression of Tg and TPO genes in FRTL-5/TA cells was not related to changes in TTF-1 gene expression but rather to reduced Pax-8 gene expression. It was concluded that a disruption of the co-ordinated expression of TTF-1 and Pax-8 is implicated in the loss of thyroid phenotype of FRTL-5/TA cells in terms of reduced Tg and TPO expression.

Animals↗
PubMed1996

Large discrepancy between prostate-specific antigen results from different assays during longitudinal follow-up of a prostate cancer patient.

A case is presented of a patient with stage D prostatic carcinoma, from whom a serum sample proved to be an outlier in a correlation study performed with a 2nd-generation prostate-specific antigen (PSA) assay on the Immulite system (6.4 micrograms/L) and IMx (101 micrograms/L). Clearly, the PSA result reported by Immulite was falsely low. For nine longitudinal samples, Immulite results were approximately 20-fold lower than the IMx value (range of IMx results 5-275 micrograms/L). A selection of the samples was analyzed with the ACS:180, ES-600, and IMx (all > 180 micrograms/L); Immulite, DPC Coat-A-Count IRMA, Immuno 1, AIA-pack, and Tandem-R (all <70 micrograms/L); and Immulite free PSA assay (41 micrograms/L). Gel filtration demonstrated that apart from the alpha1-antichymotrypsin (ACT) complex, no other complexes were found. However, the sample consisted of 53% free PSA (IMx). Possibly, a change of conformation of the PSA molecule resulted in a decreased binding to ACT and a reduced affinity of the antibodies used in the affected assays.

Aged↗
PubMed1995

Progestin receptors in meningiomas. Comparison of cytosolic assays with immunocytochemical identification in cryostat and paraffin sections.

The results are reported of ligand binding and enzyme immunoassays in tumour cytosols, and of immunoperoxidase assays in cryostat and paraffin sections measuring oestrogen (ER) and progestin receptors (PR) in 22 meningiomas and three non-meningioma tumours (two neurinomas and one haemangiopericytoma). With regard to the meningioma tissues, cytochemical immunoperoxidase PR-staining was present in all cryostat sections and in all but one of the paraffin sections. There was a good degree of qualitative accordance between all assay methods; they revealed the picture of "typical" meningioma: high PR and low ER. In this series, immunoperoxidase staining for the detection of PR-receptors, both in cryostat and paraffin sections, rendered encouraging results, thus offering a method for the detection of progestin receptors, which can compete with cytosolic methods.

Adult↗
PubMed1995

Oestrogen receptor independent expression of progestin receptors in human meningioma--a review.

Human meningiomas are rich in progestin receptors (PR), which are expressed in this tissue in an oestrogen independent fashion. In the search for an explanation of this observation, the existence of a protein in human meningioma cytosol which is capable of binding to a synthetic oestrogen responsive element (ERE) has been demonstrated. Using reverse transcriptase, PCR mRNA encoding for the wild-type oestrogen receptor (ER) was found. In addition, several splice variants of ER mRNA have been identified in human meningioma tissue, including variants lacking exons 4, 5 and 7. We found the ER delta 4 protein to have no transcriptional activity and the ER delta 7 protein reportedly is dominant negative. These mutants therefore probably are not responsible for the autonomous PR synthesis in human meningioma. The ER delta 5 protein, by contrast, has been reported to have oestrogen independent transcriptional activity and it is tempting to speculate that this protein is similar or identical to the ERE binding protein we have found in human meningioma. The role of wild type ER mRNA is presently unclear. Activation of other signal transduction pathways in meningioma does not lead to an increased PR concentration. The promoter area of the meningioma PR gene should be investigated for the possible sensitivity to other transcription factors.

Base Sequence↗
PubMed1995

Expression of the gene encoding growth hormone in the human mammary gland.

Progestins cause a syndrome of growth hormone (GH) excess and enhanced mammary tumorigenesis in the dog. This has been regarded as being specific for the dog. Recently we reported that progestin-induced GH excess originates from foci of hyperplastic ductular epithelium of the mammary gland in the dog. In the present report we demonstrate by reverse-transcriptase PCR and immunohistochemistry that a main factor involved in tissue growth, i.e. GH, is also expressed in normal and neoplastic human mammary glands. The gene expressed in the human mammary gland proved to be identical to the gene encoding GH in the pituitary gland. The role of progesterone in the GH expression of the human mammary gland needs, however, to be proven. It is hypothesized that this locally produced hGH may play a pathogenetic role in breast cancer.

Adolescent↗
PubMed1995

A patient with a progesterone-producing adrenal adenoma who presented with primary amenorrhea.

A case report is presented of a patient with a primary amenorrhea due to a progesterone-producing adrenocortical adenoma. Clinical and endocrinological abnormalities disappeared after removal of the tumor, and the patient experienced her menarche. To our knowledge, a predominantly progesterone-producing adrenal adenoma--in this patient associated with the clinical picture of primary amenorrhea--has not previously been described.

Adenoma↗
PubMed1995

The presence of progesterone receptors in arachnoid granulations and in the lining of arachnoid cysts: its relevance to expression of progesterone receptors in meningiomas.

Progesterone receptors (PR) were identified with an enzyme immunoassay in cytosols from human arachnoid granulations and arachnoid cysts. Meningiomas presumably originate from subdural endothelium which is abundantly present in these structures. In the three cases studied, oestrogen receptors were absent. The presence of PR in subdural endothelium may provide further ground for the expression of PR in meningiomas.

Adult↗
PubMed1994

Expression of epidermal growth factor receptor (EGFR) in non-affected and tumorous mammary tissue of female dogs.

Epidermal growth factor (EGFR), oestrogen (ER), and progestin (PR) receptor concentrations were determined by radioligand binding assay in non-affected mammary tissues (n = 13) and benign (n = 11) and primary/locally recurrent malignant proliferative mammary lesions (n = 45) and metastases (n = 19) in 65 female dogs. The number of specimens expressing EGFR was not significantly different among these tissues, but EGFR concentration was lower in metastases (P = 0.02) than in benign or primary/locally recurrent malignant lesions not mixed with non-affected mammary tissue. The presence of non-affected mammary tissue in primary cancer specimens was noticed as a factor that may influence results of receptor measurements. No relation was found between the expression of EGFR and that of ER or PR in non-affected or in tumorous mammary tissues. It was concluded that in the dog mammary gland EGFR expression is not associated with conditions of steroid receptor absence of biological agressiveness of neoplastic growth.

Animals↗
PubMed1994

Functional analysis of an alternatively spliced estrogen receptor lacking exon 4 isolated from MCF-7 breast cancer cells and meningioma tissue.

An alternatively spliced mRNA coding for a variant estrogen receptor (ER) missing exon 4 (ERdelta4) was detected in the breast tumor cell line MCF7 and meningioma tissue by using the reversed transcriptase PCR technique. The trans-activational properties of this mutant ER were assessed in embryo carcinoma P19EC and human choriocarcinoma JEG3 cells by co-transfection of the ERdelta4 expression vector with an oxytocin promoter construct containing an estrogen-responsive element. ERdelta4 did not trans-activate the oxytocin promoter in either a hormone-dependent or -independent manner. Co-transfection of ERdelta4 together with the wtER did not show any interference of ERdelta4 on the stimulation of the oxytocin promoter by the wtER. ERdelta4 was translated in vitro. Its capacity to bind estradiol, and the binding of the variant to a synthetic estrogen-responsive element were compared to those of the wild-type receptor. ERdelta4 did not bind to a synthetic estrogen-responsive element, nor did it bind estradiol. Hence, ERdelta4 appears to be a silent variant and we speculate that it is without any role in tumor progression.

Alternative Splicing↗
PubMed1994

An improved method for the determination of islet amyloid polypeptide levels in plasma.

We describe an improved method for the determination of islet amyloid polypeptide (IAPP) levels in plasma. Plasma is first extracted with acid-acetone, followed by a specific and sensitive radioimmunoassay (RIA) for IAPP using rabbit-anti-human-IAPP serum. Recovery of synthetic IAPP from plasma was 82 +/- 6% (n = 16). Standard samples, prepared in 'hormone-free' serum, were also extracted with acid-acetone. Displacement curves of serially diluted acid-acetone extracted plasma samples were parallel to the standard curve. The lower detection limit of the RIA was 2.3 +/- 0.1 fmol/sample (n = 5). Intra-assay variations for IAPP concentrations of 4, 17 and 32 pM were 16.3% (n = 10), 9.2% (n = 10) and 6.2% (n = 10); interassay variations were 35.9% (n = 14), 19.9% (n = 15) and 15.4% (n = 15), respectively. Non-stimulated IAPP levels ranged from 2.4 to 12 pM (mean 6 +/- 4 pM, n = 10) in healthy control subjects. IAPP was not detectable in type 1 (insulin-dependent) diabetic patients before and after glucagon administration. In type 2 (non-insulin-dependent) diabetic patients basal levels ranged from 2.2 to 14.5 pM and glucagon-stimulated levels ranged from 2.2 to 38.9 pM. The increase in IAPP varied from 0 to 24.4 pM. The anti-human-IAPP serum had full cross-reactivity with rat IAPP (= mouse IAPP). Transgenic mice overexpressing the human IAPP gene showed elevated plasma IAPP levels as compared to (non-transgenic) control mice. It is concluded that the method presented for the determination of IAPP in plasma is reliable and easy to perform, yielding reproducible results.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid↗
PubMed1994

Tumor markers. Consensus Conference on Diagnosis and Prognostic Parameters in Localized Prostate Cancer. Stockholm, Sweden, May 12-13, 1993.

This chapter mainly deals with biochemical aspects on prostate specific antigen (PSA) and its clinical value. To a limited extent, also other tumor markers, which might be of importance in the evaluation of patients with prostate cancer are discussed. In serum, PSA exists in a free form or bound to antichymotrypsin. Interestingly, only 10% of PSA secreted from cancer cells seems to exist in a free form, as compared to 30% of PSA secreted from cells in benign prostatic hyperplasia (BPH). PSA seems to be closely, but not absolutely, related to tumor grade and stage. The mean value of PSA in patients with tumors dominated by Gleason grades 3 or below, was 10 ng/ml, compared to 29 ng/ml in those with higher grades. Patients with PSA values of 50 ng/ml or above almost exclusively had tumor of Gleason grades 4 or 5, and this limit usually reflected a generalized disease. Patients with PSA-values below 10 ng/ml almost exclusively had tumors confined to the prostate gland. In countries where screening for prostate cancer is believed in, it is important to understand that normal cut-off values are related to patient's age. The upper normal limit of males below 50 years of age should be set at 2.5 ng/ml, as compared to 6.5 ng/ml for men over 70 years of age. To improve the value of PSA determination and for scientific purposes, the standardization of the assay is urgently needed and under way. Prostate acid phosphatase (PAP) has in most centres been replaced by PSA. An elevated PAP value, as measured by the enzymatic method, invariably indicates a generalized disease and could thus be used as a complementary informative assay to PSA. Other markers have been used mainly to achieve additional prognostic information. In a multivariate analysis, the non-specific tumor marker neopterin, which reflects the host response to tumor antigens, was closely related to short-term prognosis. Neopterin was followed by thymidine kinase, a protein reflecting the cell turn-over and tumor grade. Also PSA at diagnosis seemed to add some prognostic information, whereas other markers did not.

Adult↗
PubMed1993

Species specificity of triphenylethylene derivatives and of compounds with a steroidal backbone for human and rat liver antioestrogen binding site (AEBS).

The binding affinity of derivatives of the triphenylethylene (TPE) antioestrogen tamoxifen and of steroidal compounds for human liver antioestrogen binding sites (AEBS) was compared with their binding affinity for rat liver AEBS. Despite the observation of some quantitative differences overall a highly significant correlation between the relative binding affinity (RBA) for human and rat liver AEBS was found for all compounds tested (r = 0.93, N = 19, P < 0.001). This was more pronounced for TPE derivatives (r = 0.83, N = 12, P < 0.01) than for cholesterol derived compounds (r = 0.64, N = 7, not significant). We conclude that AEBS from rat liver can be used instead of human livers as a model to study the interactions of antioestrogens with AEBS.

Animals↗
PubMed1993

Inhibition of the in vivo conversion of androstenedione to estrone by the aromatase inhibitor vorozole in healthy postmenopausal women.

Vorozole is a new, potent, and highly selective nonsteroidal aromatase inhibitor, which in animal and human studies was found to be about 1000-fold more potent than aminoglutethimide. Almost all aromatase-inhibiting activity resides in the dextro-enantiomer currently undergoing clinical trials. A marked decrease in circulating estrogens was found in several studies of healthy premenopausal women and male volunteers treated with the racemate, referred to as vorozole racemate. To further evaluate the aromatase-inhibiting potency of this drug, the in vivo conversion of androstenedione to estrone was studied in 12 healthy postmenopausal women. Four h after a single oral dose of vorozole racemate, [14C]androstenedione and [3H]estrone were infused at a constant rate for 2 h. Women were randomized to receive vorozole racemate orally in one of three different doses, i.e., 1, 2.5, and 5 mg, in a double-blind protocol. Each woman acted as her own control in an identical experiment with a placebo carried out 2-4 weeks either before or after the test with vorozole racemate. In the urine, collected for 4 days after each experiment, estrogens were extracted and purified until a constant 3H/14C ratio of estrone was achieved. The percentage conversion of androstenedione to estrone in the 12 placebo experiments was 2.19 +/- 0.60% (mean +/- SD, n = 12). Following a single administration of vorozole racemate, the conversion decreased to 0.14 +/- 0.04%. The percentage inhibition was 93.0 +/- 2.5 (n = 4) following administration of 1 mg vorozole racemate; administration of 2.5 or 5 mg resulted in an inhibition percentage of 93.2 +/- 1.6 or 94.4 +/- 1.2, respectively. It is concluded that a single oral dose of 1-5 mg vorozole racemate results in an almost complete inhibition of in vivo aromatase activity.

Aged↗
PubMed1993

Effect of culture conditions on androgen sensitivity of the human prostatic cancer cell line LNCaP.

Several effects of androgens on LNCaP-FGC prostate tumor cells showed a biphasic pattern. Stimulation of growth and inhibition of secretion of prostatic acid phosphatase (PAP) was observed at low androgen concentrations (below 1 nM of the synthetic androgen R1881), and inhibition of growth and stimulation of PAP secretion was observed at higher concentrations. In contrast, prostate specific antigen (PSA) secretion did not show this biphasic response pattern. Comparable effects were found for two sublines of the LNCaP-FGC cells: an early (passage 20, androgen-dependent) and relatively late (passage 70, androgen-sensitive) passage of the cells. Culturing of both sublines in the presence of a high concentration of androgens (10 nM R1881) resulted initially in a decrease in growth rate, but the cells started to proliferate within 3 weeks. These cells became less sensitive to androgens, lost their biphasic response pattern, and showed reduced androgen receptor levels. Three weeks after removal of the excess of androgens, the passage 70 cells regained a biphasic growth response to androgens. Culture in medium without steroids but with EGF resulted in a decrease of both androgen sensitivity and androgen receptor level. In conclusion, rapid changes of the androgen sensitivity and receptor level of the LNCaP cells occurred under the influence of culture conditions. These changes were partly reversible and, therefore, were most likely due to adaptation of the cells.

Acid Phosphatase↗