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Biomedical subjects

N Bersch

Publications and source records attributed to N Bersch.

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

Growth without growth hormone: evidence for a potent circulating human growth factor.

A potent growth factor was detected in the serum of a child with growth hormone (GH) deficiency and early growth delay whose growth velocity spontaneously increased to supranormal levels despite persistent GH deficiency by both radioimmunoassay (RIA) and radioreceptor assay. Thyroid function, prolactin, insulin response to oral glucose, glucose response to intravenous insulin, and computerised tomography of the head were all normal. Whilst somatomedin-C levels measured by RIA were low or low-normal, in vitro somatomedin bioactivity measured by bioassay was normal, suggesting the presence of a growth factor other than somatomedin-C. By way of confirmation, the patient's serum was incubated with erythroid progenitor cells from peripheral blood of a normal individual and a Laron dwarf. In this system, proliferation of normal erythroid progenitors was almost double that obtained with physiological concentrations of GH or control sera, and Laron erythroid progenitors, which were completely resistant to added GH, also responded strongly to the patient's serum. The patient's growth is therefore independent of GH and other known growth factors.

Child↗
PubMed1986

T cell-derived migration-inhibitory factor and colony-stimulating factor share common structural elements.

Migration-inhibitory factor (MIF) is a lymphokine that acts to localize mononuclear phagocytes (monocytes and macrophages) and perhaps to activate them. Mo cells are a human T cell leukemia virus II-infected T cell line previously shown to secrete large quantities of MIF upon stimulation with phytohemagglutinin and phorbol myristate acetate. MIF was purified from Mo cell-conditioned medium by gel filtration, phenyl-Sepharose affinity chromatography, isoelectrofocusing, and reverse-phase high-performance liquid chromatography (RP-HPLC). Overall purification was 6,000-fold. The purified MIF fraction was found to display potent colony-stimulating factor (CSF) activity when assayed on human bone marrow cells. The double peak of MIF activity as shown by C 18-RP-HPLC coincided with the double peak of CSF activity. A monoclonal antibody selected for its anti-MIF activity absorbed both the CSF and the MIF activity. These findings indicate that MIF and CSF are either identical molecules or closely related molecules with common structural elements.

Cell Line↗
PubMed1986

Persistence of insulin resistance in polycystic ovarian disease after inhibition of ovarian steroid secretion.

Six nonobese women with polycystic ovarian disease (PCOD) showed significant hyperinsulinemia, compared with controls after oral glucose (P less than 0.05). As an indicator of insulin sensitivity, in vitro proliferation of erythrocyte progenitor cells of PCOD subjects exposed to physiologic concentrations of insulin was significantly blunted (P less than 0.001). Monocyte insulin receptor binding was not impaired in the PCOD subjects. Three of the PCOD patients were treated with a long-acting gonadotropin-releasing hormone agonist for 6 months, which resulted in marked suppression of ovarian androgen secretion but no demonstrable changes in in vivo or in vitro indicators of insulin resistance. Thus insulin resistance in PCOD subjects appears to be unrelated to ovarian hyperandrogenism (or acanthosis or obesity). Although certain tissues are insulin-resistant in PCOD patients, the ovary may remain sensitive and overproduce androgens in response to high circulating insulin levels.

Adult↗
PubMed1985

Diminished in vitro responsiveness of circulating erythroid progenitor cells to insulin as an indicator of insulin resistance.

While insulin resistance is considered characteristic of extreme obesity, it may be more difficult to demonstrate in less severe forms of obesity. We studied five moderately obese individuals [mean body mass index (MBMI), 34.1 +/- 1.85 (+/- SE) kg/m2], one massively obese patient (BMI, 50.2 kg/m2), and seven age-matched normal subjects (MBMI, 22.4 +/- 0.93 kg/m2). While two of the obese patients had normal glucose tolerance, all had fasting hyperinsulinemia (P less than 0.02 vs. normal subjects) and exaggerated insulin responses after oral glucose challenge, as defined by area under the 3-h insulin response curve (P less than 0.01 vs. normal subjects). That this hyperinsulinemia represented in vivo insulin resistance was supported by the glucose and insulin responses in four individuals to an iv glucose bolus analyzed by the minimal modeling technique. Study of monocyte insulin receptors revealed no reduction in total insulin binding in the four obese patients tested. Since physiological concentrations of insulin stimulate the in vitro growth of normal human erythroid progenitor cells (EPC), we reasoned that this response might be blunted in cells from individuals with endogenous insulin resistance. The mean peak EPC proliferative response (26.7 +/- 9.11% above baseline) in the obese hyperinsulinemic group was significantly less than the corresponding mean value in the control group (92.6 +/- 5.24% above baseline, P less than 0.001). These results suggest that the minimal modeling technique is a sensitive method for the in vivo demonstration of insulin resistance in moderately obese individuals and that EPC responsiveness to physiological concentrations of insulin reflects in vivo insulin sensitivity and may be used as an in vitro indicator of insulin resistance.

Adolescent↗
PubMed1985

Characterization of purified human erythroid-potentiating activity.

Erythroid-potentiating activity (EPA), purified from serum-free medium conditioned by the Mo human T-lymphoblast cell line, is a 28,000 dalton glycoprotein. Removal of carbohydrate from EPA by digestion with endoglycosidase F generates a protein with an apparent molecular weight of 18,000. We have used purified EPA to develop rabbit antisera which neutralize the burst-promoting activity of purified EPA. These antisera immunoprecipitate a 28,000-dalton glycoprotein from metabolically labeled Mo cells. Purified EPA stimulates murine and human BFU-E and CFU-E but not myeloid or macrophage colonies.

Animals↗
PubMed1983

Production of migration-inhibitory factor by a human T-lymphoblast cell line.

Migration-inhibitory-factor (MIF) activity was detected in culture supernatants of the human T-lymphoblast cell line Mo after stimulation with phytohemagglutinin and phorbol myristate acetate. MIF activity was not detected in unstimulated cultures reconstituted with phytohemagglutinin and phorbol myristate acetate. Conditioned medium from the cell line Mo was fractionated by Sephadex G-100 gel filtration. MIF-containing Sephadex fractions corresponding to a Mr of 60,000 to 70,000 were further fractionated by isoelectrofocusing, resulting in a sharp peak of activity with a pI of 4.6 to 5.2. This MIF species constitutes a major form secreted by Mo cells; it adheres to Con A-Sepharose, is trypsin-resistant, and is denser than pure protein as determined by CsCl density gradient centrifugation. These are the same physicochemical characteristics previously established for second-day pH5-MIF from peripheral blood mononuclear cells (W.Y. Weiser et al., J. Immunol. 126, 1958, 1981). In contrast, Sephadex fractions corresponding to larger molecules (Mr 70,000-90,000) contain at least two additional MIF species. These larger MIF forms have a pI of 3.0 to 3.5 and of 4.6 to 5.2 and lack affinity to Con A Sepharose. Thus, the Mo T-cell line produces large quantities of at least three different species of human MIF.

Cell Line↗
PubMed1983

A unique growth factor in patients with acromegaloidism.

Acromegaloidism is a syndrome characterized by features of acromegaly without biochemical evidence of excessive GH or somatomedin production. We searched for a growth factor in the serum of patients with this syndrome. Growth-promoting activity was measured by determining the stimulatory effect of whole and fractionated serum on colony formation by human erythroid progenitors in vitro. Sera from five subjects with acromegaloidism gave a mean (+/- SEM) stimulated colony growth of 211 +/- 4.0 colonies, in contrast to normal sera which yielded a mean colony growth of 100 +/- 11.0 (n = 9; P less than 0.001). When serum was chromatographed on a Sephadex G-200 column, the maximal stimulation of colony growth was found in the fractions coinciding with the descending slope of the second protein peak. Based on gel filtration chromatography, the estimated molecular weight was 70,000 daltons. Epidermal growth factor, nerve growth factor, fibroblast growth factor, and platelet-derived growth factor resulted in no substantial stimulation of colony growth under the conditions used. Although the erythroid progenitor cells of a Laron dwarf were unresponsive to 200 ng/ml human GH, they were clearly stimulated by serum from a patient with acromegaloidism. The present study describes the presence of a heretofore unidentified growth factor in the serum of subjects with acromegaloidism. This factor also stimulated the erythroid precursor cells of a Laron dwarf whose cells were unresponsive to GH. The physiological role of this growth factor in normal man as well as its pathogenic role in subjects with acromegaloidism remain to be established.

Acromegaly↗
PubMed1982

Natural and biosynthetic insulin stimulates the growth of human erythroid progenitors in vitro.

High concentrations of insulin are known to augment the growth of various cell types in vitro. We examined the effect of a purified porcine insulin and biosynthetic human insulin produced in E. coli on the growth of human erythroid progenitors in vitro. Both insulins stimulated peripheral blood erythroid colony formation within the physiological range. An approximately 2-fold augmentation in colony formation was seen at insulin concentrations of 8 ng/ml, and as little as 0.1 ng/ml (0.17 nM) caused detectable stimulation of colony formation. The effect of subnanomolar concentrations of insulin or erythropoiesis in vitro suggests that insulin could modulate erythropoiesis in vitro. Human responsiveness to insulin's growth-promoting activity can be directly assayed in vitro using peripheral blood.

Adult↗
PubMed1980

Production of erythroid-potentiating activity by a human T-lymphoblast cell line.

We derived a human T-lymphoblast cell line (Mo) that constitutively elaborates certain lymphokines. The Mo cells produce a colony-stimulating factor necessary for the growth of human granulocyte-monocyte precursors in vitro as well as an erythroid-potentiating activity (EPA) that enhances the proliferation of human erythroid progenitors in vitro. In the presence of serum, the EPA in Mo-conditioned medium stimulated the growth of small and large erythroid colonies almost 2-fold. EPA was also produced in serum-free medium, and, when assayed in serum-free cultures of human erythroid progenitors, it stimulated colony growth about 3-fold. The EPA produced by the Mo cell line did not stimulate normal murine erythroid progenitors (CFU-E) or Friend erythroleukemia cell growth in vitro. EPA was inactivated by protease treatment but was remarkably heat stable, with most of the activity recovered after boiling for 15 min. Preliminary biochemical characterization suggests that EPA is an acidic glycoprotein with molecular weight approximately 45,000. EPA is clearly separable from colony-stimulating factor on the basis of heat stability and gel-filtration chromatography. The present observations provide strong support for the concept that activated T cells produce humoral factors important in the regulation of erythropoiesis. The availability of a cell line producing human EPA should facilitate the characterization of the protein and permit definitive studies of its biologic effects.

Cell Line↗
PubMed1979

Transformation of DBA/2 mouse fetal liver cells infected in vitro by the anemic strain of Friend leukemia virus.

Fetal liver cells of DBA/2 mice were infected with the anemic strain of Friend leukemia virus (FLV-A), which has no spleen focus-forming virus (SFFV) activity. The infected cells were grown in medium with or without erythropoietin. Transformed lines were isolated only from the infected cultures that had been treated with erythropoietin at the time of their initiation. The properties of three permanent cell lines in serial passage for over 2 years are described. Each has an aneuploid karyotype. Only the immature hematopoietic cells of the first line have metacentric chromosomes. They grow in suspension, as do the erythroleukemic lines derived from leukemic spleens of FLV-infected mice, and clone on agar. They produce tumors resembling reticulum cell sarcomas upon subcutaneous inoculation into syngeneic hosts. Stimulation of differentiation induced after treatment with dimethyl sulfoxide identifies the cells of the first line as being erythroid in origin. The two other lines are adherent and epithelioid in appearance. These lines may have originated from the nonhematopoietic cells present in fetal liver. No tumors were produced after the subcutaneous inoculation of 10(6) cells. All three lines synthesize virus. The virus is attenuated for leukemogenicity and has no SFFV activity. The transforming event appears to be specific, because fetal liver cells from C57BL/6 mice, which are resistant to the induction of leukemia by FLV, were not affected by the virus. Malignant transformation of erythroid cells by FLV-A in vitro confirms the in vivo findings that SFFV may not be a necessary prerequisite for the induction of erythroleukemia in susceptible hosts.

Anemia↗
PubMed1979

Detection of glucocorticoid receptors on Friend erythroleukemia cells.

The inhibition of dimethyl sulfoxide-induced differentiation of Friend erythroleukemia cells by steroids led us to examine these cells for the presence of glucocorticoid receptors. Direct assessement of dexamethasone binding revealed high-affinity dexamethasone receptors on the untreated cells. The specific binding of [3H]dexamethasone was dose dependent. At a concentration of 10(-8) M, almost all binding sites were occupied. The mean number of binding sites per cell in two separate experiments was 8045 and 7191, respectively, and the Kd varied between 3.38 and 3.49 x 10(-9) M. Dimethyl sulfoxide treatment led to a decrease in the number of dexamethasone binding sites on the cells induced to differentiate. After 5 days of treatment, the mean number of sites per cell was reduced to 1216 and 896 in two experiments, with a Kd of 5 x 10(-9) M. Dexamethasone treatment resulted in a moderate decrease in the efficiency of colony formation within 72 hr after the cells were plated in methylcellulose. The mechanism of this inhibitory effect is unknown. However, it was also dose dependent and could be abrogated by appropriate concentrations of progesterone or 11-deoxycortisone. These results suggest that the steroid effects on growth and differentiation of the erythroleukemia cells may be mediated via glucocorticoid receptors.

Animals↗
PubMed1978

Growth hormone modulation of murine erythroleukemia cell growth in vitro.

There are few studies showing a biological effect of growth hormone (somatotropin) on cell proliferation in vitro at physiological concentrations. We report here that Friend virus-infected erythroleukemia cells are responsive to growth hormone in vitro. Using a serum-free clonogenic assay we found as little as 0.1 ng of human growth hormone per ml caused a prominent stimulation of cell proliferation. Peak activity of human growth hormone occurred at 200 ng/ml, resulting in a 2-fold increase in cloning. Human chorionic somatomammotropin and the Cys(Cam)53-hGH(1-134) fragment of human growth hormone were also active, but a biologically inert oxidized human growth hormone had no growth-promoting effect in vitro. Cell proliferation was stimulated by insulin with peak potentiation occurring at 1 ng/ml, and prolactin had a demonstrable stimulatory effect between 50 and 100 ng/ml. These observations indicate that growth hormone and related polypeptides have a direct effect on the in vitro proliferation of erythroleukemia cells in the absence of serum. The results confirm a direct action of growth hormone on mammalian cells and suggest that pituitary hormones may affect leukemic cell growth.

Animals↗
PubMed1978

Trimethoprim and sulphamethoxazole inhibition of haematopoiesis in vitro.

The effect of trimethoprim and sulphamethoxazole on haematopoiesis was studied in vitro using cloning techniques for human and murine erythroid and granulocytic precursor cells. Trimethoprim was found to inhibit granulopoiesis and erythropoiesis in vitro in a dose-dependent fashion with approximately 50% inhibition of human erythroid and granulocytic colonies at a therapeutically achievable concentration of 7 micrograms/ml. Sulphamethoxazole was also shown to impair haematopoiesis in vitro. The inhibition caused by both these constituents of co-trimoxazole was completely reversed by folinic acid. The data suggest that co-trimoxazole can impair human haematopoiesis by inhibition of tetrahydrofolate synthesis. These observations suggest that the clinical haematopoietic toxicity of trimethoprim-sulphamethoxazole can be abrogated by simultaneous administration of folinic acid.

Adult↗
PubMed1977

Growth hormone: species-specific stimulation of erythropoiesis in vitro.

The effects of purifed bovine and human growth hormone were tested in vitro with murine and human bone marrow by means of granulocyte-monocyte and erythroid progenitor cloning techniques. Nanogram concentrations of the growth hormones potentiated erythropoietin-stimulated erythropoiesis, but not granulopoiesis, in a species-specific manner.

Animals↗
PubMed1977

Thyroid hormones stimulate erythropoiesis in vitro.

Thyroid hormones have important effects on erythropoiesis in man and animals. We performed in vitro culture studies with murine and human bone marrow in order to define the interaction of these hormones with erythroid and granulocyte-monocyte progenitor cells. The methylcellulose clonogenic assay was used with the appropriate addition of erythropoietin or colony-stimulating activity. L-thyroxine, D-thyroxine and L-triiodothyronine potentiated erythropoientin-stimulated erythroid colony formation in concentrations of 50-100 ng/ml. These hormones had no effect on granulocyte-monocyte colony formation at concentrations up to 500 ng/ml. Testing of various thyroid analogues showed no clear correlation between potentiation of erythropoiesis and known calorigenic potency. Reverse triiodothyronine also had potentiating activity in this system. The active thyroid hormones stimulated erythroid colony formation at several concentrations of erythropoietin but could not substitute for erythropoietin. These data suggest that thyroid hormones have a direct effect on erythroid precursor proliferative capacity, a finding which may have relevance to the mechanism of erythropoietic dysfunction in human thyroid disease.

Animals↗
PubMed1977

Polycythemia vera: hormonal modulation of erythropoiesis in vitro.

We performed in vitro culture studies examining the interaction of erythropoietin with red cell progenitors in polycythemia vera. Bone marrow was obtained from five patients with typical disease and from five healthy volunteers, and assayed for erythroid colony formation (CFU-E) by the methylcellulose technique. In cultures without added erythropoietin, a mean eightfold greater cloning efficiency was noted with the polycythemia vera marrows, as compared to normal. There was prominent stimulation of colony formation by erythropoietin, and the shape of the erythropoietin dose-response cruves appeared to be similar in both patients and controls. Anti-erythropoietin antibody reduced the number of CFU-E in cultures not containing added erythropoietin, but did not eliminate them. Dexamethasone (10(-9) M) caused a consistent increase in CFU-E in the patients' cultures. These studies provide evidence for functional erythropoietin and glucocorticosteroid receptor mechanisms on erythroid precursors in polycythemia vera. The observations are consistent with a concept of this disease as a disorder of hematopoietic stem cells in which peripheral erythrocytosis is caused by an expanded erythroid progenitor compartment which maintains responsiveness to hormonal modulation.

Antibodies↗