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Biomedical subjects

M A Lieberman

Publications and source records attributed to M A Lieberman.

At least 55 records · Page 3Linked to original sources
PubMed1988

Growth factor production by a human megakaryocytic tumor cell line.

A recently described human megakaryocytic tumor cell line was analyzed for the presence of growth factor activity and was found to produce large quantities of transforming growth factor beta-like (TGF-beta) and basic fibroblast growth factor-like (bFGF) activities. Growth factor activities were identified using a radioreceptor assay for the TGF-beta-like activity, a heparin-binding assay for the b-FGF-like activity, and a demonstration of distinct biological activities for each type of factor. Tumor poly-A+ RNA revealed strong signals when probed with complementary DNA corresponding to bovine basic FGF and human TGF-beta and weak signals when probed with cDNA corresponding to epidermal growth factor (EGF) and TGF-alpha. The levels of EGF and TGF-alpha produced in the tumor line were too low to be detected by radioreceptor assays. Relative levels of messenger RNA encoding each of the growth factors reflected the relative levels of each of the respective factors tested. These data represent the first definitive identification of FGF-like activities in megakaryocytic-like cell lines. Interestingly, the line displayed little activity similar to platelet-derived growth factor (PDGF) when assayed either biochemically or by poly-A+ RNA analysis.

Animals↗
PubMed1988

The neuronal cell-surface molecule mitogenic for Schwann cells is a heparin-binding protein.

The cell surface of embryonic peripheral neurons provides a mitogenic stimulus for Schwann cells. We report (i) the solubilization of this mitogenic activity from rat dorsal root ganglion neurons grown in tissue culture and (ii) the solubilization and partial purification of mitogenic activity from neonatal rat brains. Extracted mitogenic activity is peripheral rather than intrinsic to the membrane, stable after extraction, and active as a mitogen in the absence of serum (the most stringent criterion defining the neuronal mitogen). We have previously provided evidence suggesting that a neuronal cell-surface heparan sulfate proteoglycan is required for expression of the neurons' mitogenic activity. We now show that mitogenic activity can be extracted from the membrane dissociated from proteoglycan as assayed by its ability to bind to immobilized heparin. After dissociation, low concentrations of heparin (1 micrograms/ml) inhibit the ability of the mitogen to stimulate Schwann cell division. Basic fibroblast growth factor (FGF) is weakly mitogenic for Schwann cells, but it is not present in mitogenic brain extracts (based on immunoblotting). Immunodepletion experiments with specific antibodies to FGF indicate that the mitogenic activity extracted from neurons is not a form of this heparin-binding mitogen. Acidic FGF is not mitogenic for Schwann cells and is not present in mitogenic brain extracts. We suggest that these and previous data indicate the neurite mitogen is a proteoglycan-growth factor complex that limits mitogenic activity to the axonal surface, protects mitogen against inactivation by other proteoglycans, and provides for effective presentation of mitogen to the Schwann cell.

Animals↗
PubMed1987

Differential effects of epidermal growth factor and transforming growth factor-beta on synthesis of Mr = 35,000 surfactant-associated protein in fetal lung.

Differentiation of pulmonary Type II epithelial cells in late gestation is associated with the synthesis of pulmonary surfactant required for adaptation to air breathing at birth. In the present work, induction of synthesis of a Type II epithelial cell protein, surfactant-associated glycoprotein of Mr = 35,000 (SAP-35) was studied in human fetal lung tissue obtained at 15-24 weeks of gestation. SAP-35 content increased during organ culture in the absence of exogenous hormones. Epidermal growth factor or triiodothyronine stimulated the induction of SAP-35 synthesis during culture. Stimulation by epidermal growth factor (EGF) was detected as early as 2 days and persisted for up to 5 days in culture. Response to EGF was dose-dependent (0.01-10 ng/ml) and was associated with enhanced incorporation of [35S]methionine into immunoprecipitable SAP-35. Increased SAP-35 synthesis was associated with increased SAP-35 RNA as assessed by Northern blot and hybridization assays with human SAP-35 cDNA. Effects of EGF were comparable to the induction of SAP-35 synthesis by 8-bromo-cAMP. In contrast to the stimulatory effect of EGF and triiodothyronine, SAP-35 content was inhibited by transforming growth factor-beta. Both the stimulatory and inhibitory effects of these agents on SAP-35 content were associated with concomitant changes in SAP-35 synthesis. These findings demonstrate multihormonal control of SAP-35 expression and strongly implicate both EGF and transforming growth factor-beta in the regulation of surfactant apoprotein synthesis.

DNA↗
PubMed1987

Heparin potentiates the action of plasma membrane-associated growth stimulatory activity.

Plasma membranes prepared from mouse liver have been previously shown to contain growth stimulatory activity as determined with cultured mouse fibroblasts. This growth stimulatory activity, termed plasma membrane-associated growth stimulatory activity (PMGA), is highly mitogenic in the presence of platelet-poor plasma. We now demonstrate that the growth stimulatory action of PMGA is dramatically enhanced by the addition of heparin. The half-maximal effect of heparin was observed at 1-3 micrograms/ml. The synergistic effect was seen in two distinct assays; the stimulation of DNA synthesis in quiescent cells, and an increase of cell number over a 3-day culture period. Heparin, by itself, does not have any measurable influence on the growth of fibroblasts. The action of heparin is not unique to this glycosaminoglycan, as several other highly sulfated polysaccharides, including dextran sulfate, pentosan polysulfate, and fucoidan, also exhibited the highly synergistic effect. Among other glycosaminoglycans examined, chondroitin sulfate B and heparan sulfate had a small, but significant, effect on enhancing the growth stimulatory action of PMGA. Chondroitin sulfate A, chondroitin sulfate C, hyaluronic acid dextran, and poly-L-glutamic acid, however, had no detectable effect. Further experiments suggested that the effect of heparin is twofold, namely, both a potentiation of growth stimulatory activity and a protection of PMGA activity. The data presented here suggest that the association of various cell surface components, such as PMGA and specific proteoglycans, can modulate the growth potential of a cell.

Animals↗
PubMed1987

Growth-stimulatory action of plasma membrane-associated growth factor. A synergistic effect with platelet-poor plasma.

Growth factor activity was partially purified from mouse liver plasma membranes and its growth-stimulatory action on cultured mouse fibroblasts was studied. The plasma membrane-associated growth factor (PMGF) was unable to support the proliferation of mouse fibroblasts in monolayer when added as the sole source of growth factor. However, it stimulated the growth of fibroblasts in the presence of CM-Sephadex-treated human platelet-poor plasma (h-CMP) which by itself is not growth-stimulatory. The stimulation of DNA synthesis in quiescent fibroblasts was also observed upon the addition of PMGF and h-CMP. Under the same conditions, both platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) showed the same effect as did PMGF. The synergistic action of h-CMP with PMGF on quiescent cells was partially reproduced by insulin at microgram quantities or by insulin-like growth factor I(IGF-I) at nanogram quantities. Thus, the data presented here indicates that the action of PMGF is similar to that of the family of growth factors termed 'competence factor', and distinct from that of plasma growth factors termed 'progression factor'.

Animals↗
PubMed1987

Effects of large group awareness training on participants' psychiatric status.

The impact of large group awareness training on psychiatric status was evaluated in two cohorts of participants. Clinical and Diagnostic Interview Schedule interviews were used to specify impact; a small number of stress reactions and no psychiatric casualties were identified in the more than 300 subjects studied.

Adult↗
PubMed1986

Reproducibility of occlusal marking techniques.

Our study was designed to (1) test clinically the reproducibility of the NPT by comparing two consecutive occlusal records and records made at 1-month intervals (2) test the reproducibility of a color-marking technique under the same conditions, and (3) compare the location of occlusal contacts as registered by these two techniques. Results showed that neither technique is highly reproducible. However, the NPT is more reproducible than the CMT. The advantages and disadvantages of the NPT and the CMT were described. It was suggested that more research should be conducted to improve the accuracy of occlusal record techniques.

Dental Articulators↗
PubMed1985

Inhibition of lymphocyte proliferation by detergent-solubilized mouse liver membranes.

The role of phenomena analogous to fibroblast contact inhibition in lymphocyte growth regulation is controversial, although it is clear that direct cell-cell contact is vital to immunoregulation and accessory cell function. An extract of mouse liver plasma membrane proteins, referred to as suppressive liver extract (SLE), that suppresses the growth of 3T3 fibroblasts also inhibited the mitogen-induced proliferation of murine lymphocytes. A dose of 20 micrograms/ml SLE was less than 95% suppressive of proliferation in both mouse T and mouse B cells treated with a variety of mitogens. B cell growth factor, while increasing DNA synthesis overall in mitogen-stimulated B cells, did not change the extent of SLE suppression, which suggests that the SLE does not interfere with lymphocyte-growth factor interactions. In exploring a sequence of B cell activation events, we discovered that SLE had no effect on the early activation event of increased phosphatidylinositol turnover. Blastogenesis, however, was inhibited in mitogen-stimulated, SLE-treated B cells. The maximum suppressive effect was observed if the SLE was added within 8-12 h of the mitogenic stimulus. SLE did not affect the viability of cells in culture. These results point to a possible unity of regulatory mechanisms between contact inhibition in fibroblasts and the processes of immunoregulation.

Animals↗
PubMed1985

Mandibular dysfunction in 10-18 year old school children as related to morphological malocclusion.

An association was sought between certain morphologic characteristics of malocclusion--Angle classification, over-bite, over-jet, open-bite, cross-bite and crowding--and the presence or absence of three cardinal symptoms of mandibular dysfunction--joint sounds, joint sensitivity to palpation and muscle sensitivity--in a sample of 369 Israeli school children. In addition, two additional independent variables, 'occlusal wear' and 'previous orthodontic treatment' were introduced into the statistical analysis. Occlusal wear and abnormal overbite were the only factors found to increase significantly the presence of dysfunction symptoms.

Adolescent↗
PubMed1984

The presence of both growth inhibitory and growth stimulatory factors on membranes prepared from mouse liver.

Plasma membrane fractions from mouse livers were examined for the presence of growth regulatory peptides. Both growth inhibitory and growth stimulatory factors were found on these membranes. The growth inhibitory component could be enriched by extractions with both dimethylmaleic anhydride and octylglucoside. The growth stimulatory component could be removed from the membrane by either freeze-thaw, high salt, protease or pyrophosphate treatment, indicating that this factor is an extrinsic membrane protein. The existence of these factors on liver membranes provides an easily obtainable source for the large-scale purification of these molecules and may indicate a possible role in normal tissue growth.

Animals↗
PubMed1983

Mitogenic proteins of the 3T3 plasma membrane.

A mitogenic factor from 3T3 plasma membranes has been identified and partially characterized. The factor appears to be a peripheral membrane protein that can be released by mild trypsin, chymotrypsin, or plasmin treatment. This component is sensitive to heat and acid, and has a molecular weight in the range of 150,000-200,000 daltons as determined by gel filtration. A similar mitogenic activity has also been found on the membranes of both SV-40-transformed 3T3 cells and human fibroblasts. The factor appears to be distinct from all previously described mitogenic components.

Animals↗
PubMed1982

Binding of isolated 3T3 surface membranes to growing 3T3 cells and their effect on cell growth.

We have quantitated by autoradiography the binding of [125I]labeled 3T3 plasma membrane fragments to 3T3 cells growing on the surface of plastic dishes; ie, the same conditions in which these membranes specifically arrest the growth of 3T3 cells early in the G1 phase of the cell cycle. We have been able to demonstrate that binding of membranes to cells is coincidental with the expression of the growth inhibitory activity of protein(s) present in the membrane fragments. Treatments that reduce binding (heat denaturation of the membranes or culture in the presence of high serum) also reduce growth inhibitory activity. [125I]labeled membranes bound to cells are located primarily on the cell surface (as determined by electron microscope autoradiography) and are exchangeable with unlabeled membranes. We conclude that binding of membranes to cells is necessary but may not be sufficient for the expression of the growth inhibitory activity of these membranes. This approach provides information not only on the average level of binding of membranes to cells, but also provides a quantitative assessment of the variation of the level of membrane to cell binding between different cells in the population.

Animals↗