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Biomedical subjects

R Weinstein

Publications and source records attributed to R Weinstein.

At least 127 records · Page 7Linked to original sources
PubMed1985

The stimulation of normal human melanocyte proliferation in vitro by melanocyte growth factor from bovine brain.

Cell culture conditions for the selective growth and serial propagation of normal human melanocytes from epidermal tissue are described. In addition to the presence of 2% fetal bovine serum, the human melanocyte cell culture environment contains the following growth factor supplements: epidermal growth factor (10 ng/ml), triiodothyronine (10(-9) M), hydrocortisone, (5 X 10(-5) M), insulin (10 micrograms/ml), transferrin (10 micrograms/ml), 7S nerve growth factor (100 ng/ml) cholera toxin (10(-10) M), and bovine brain extract (150 micrograms/ml). The ability to establish selectively the human melanocyte in vitro has been attributed to the contrast between human epidermal keratinocytes and melanocytes for attachment to fibronectin, while the growth of the human melanocyte has been attributed to the mitogenic activity of the growth factor-supplemented medium. Human melanocytes can be cultivated for at least 15 cumulative population doublings and are capable of [3H]-Dopa incorporation. The growth factor-supplemented medium contains a neutral extract from bovine brain that is a potent source of a human melanocyte mitogen. The biological activity of melanocyte growth factor is described as a heat and alkaline-labile mitogen with an estimated molecular weight of 30,000 by gel exclusion chromatography and a weakly cationic isoelectric point. The mitogen is capable of stimulating the growth of quiescent populations of human melanocytes in vitro. The ability to isolate and propagate normal human melanocytes in vitro permitted an examination of the expression of fibronectin and tissue plasminogen activator. Human epidermal melanocytes established in culture do not contain either tissue plasminogen activator or fibronectin. In contrast, human melanoma cell lines contain immunologically detectable fibronectin and tissue plasminogen activator. The absence of tissue plasminogen activator and fibronectin in normal human melanocytes also occurs under conditions of co-cultivation with human melanoma cells. These contrasts between normal human melanocytes and human melanoma cells may be relevant to the metastatic capabilities of human melanoma.

Animals↗
PubMed1985

Alterations of excitation-contraction coupling by platelet-derived growth factor in enzymatically isolated and cultured vascular smooth muscle cells.

We studied stimulus-specific alterations of the excitation-contraction coupling pathway in freshly isolated contractile and subcultured non-contractile vascular smooth muscle cells. Using the calcium indicator aequorin, we detected physiological increases in cytoplasmic free calcium [( Ca2+]i) in subcultured smooth muscle cells subjected to angiotensin or 33 mM potassium depolarization. These increases were qualitatively identical to those previously measured in intact vascular strips. Platelet-derived growth factor (PDGF) induced a slow, sustained [Ca2+]i increase when applied to the subcultured smooth muscle cells at low picomolar concentrations. Freshly isolated, contractile vascular smooth muscle cells, prepared by a novel technique, exhibited a slow shortening of 20% of resting length in response to PDGF. PDGF also markedly potentiated smooth muscle cell shortening in response to an ED50 dose of phenylephrine. This effect was PDGF concentration dependent. The time course of shortening induced by PDGF alone was consistent with the time course of the PDGF-induced [Ca2+]i increase in the cultured smooth muscle cells. These data suggest that agonists which induce [Ca2+]i changes in contractile smooth muscle cells may retain this ability with respect to cultured smooth muscle cells. PDGF, a peptide mitogen for proliferative smooth muscle cells, may also serve to modulate vascular tone by modestly raising [Ca2+]i in contractile smooth muscle cell and, therefore, sensitizing the cells to alpha adrenergic agonists.

Aequorin↗
PubMed1985

Cell cycle-dependent repair of double-strand DNA breaks in a gamma-ray-sensitive Chinese hamster cell.

A Chinese hamster cell mutant has been isolated which is extremely sensitive to killing by gamma-irradiation in the G1 and early S phases of the cell cycle (LD50 of 20 vs. 250 rads for parent), but which has nearly normal resistance in late S. The mutant cell is able to repair single-stranded DNA breaks introduced by gamma-radiation. However, in comparison to its parental cell, the mutant is deficient in the repair of double-stranded DNA breaks produced by gamma-irradiation during the sensitive G1-early S period, while in the resistant late S period, the repair is nearly the same for both cell types. This correlation between gamma-ray sensitivity and repair strongly suggests that an inability to repair double-strand DNA breaks in G1 is the basis for the hypersensitivity of the mutant to killing by gamma-rays in this phase of the cell cycle. It also provides direct evidence in mammalian cells that the ability to repair double-strand DNA breaks induced by ionizing radiation is an important biochemical function in cell survival and supports the hypothesis that unrepaired double-strand breaks are a major lethal lesion in mammalian cells. A plausible explanation for the appearance of the cell cycle phenotype of the mutant is that in normal cells there are at least two pathways for the repair of double-strand breaks, one of which functions primarily in late S phase, and the other, either throughout the cell cycle or only in the G1 and early S phases.

Animals↗
PubMed1984

Acquired immunodeficiency syndrome (AIDS) associated with transfusions.

Of 2157 patients with the acquired immunodeficiency syndrome (AIDS) whose cases were reported to the Centers for Disease Control by August 22, 1983, 64 (3 per cent) with AIDS and Pneumocystis carinii pneumonia had no recognized risk factors for AIDS. Eighteen of these (28 per cent) had received blood components within five years before the onset of illness. These patients with transfusion-associated AIDS were more likely to be white (P = 0.00008) and older (P = 0.0013) than other patients with no known risk factors. They had received blood 15 to 57 months (median, 27.5) before the diagnosis of AIDS, from 2 to 48 donors (median, 14). At least one high-risk donor was identified by interview or T-cell-subset analysis in each of the seven cases in which investigation of the donors was complete; five of the six high-risk donors identified during interview also had low T-cell helper/suppressor ratios, and four had generalized lymphadenopathy according to history or examination. These findings strengthen the evidence that AIDS may be transmitted in blood.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Characterization and partial purification of keratinocyte growth factor from the hypothalamus.

An extract of bovine hypothalamus is known to be mitogenic for human keratinocytes in vitro. In order to identify the responsible substance(s), biochemical characterization and subsequent bioassay of the extract in a serum-free culture system were performed. The keratinocyte growth-promoting activity of the hypothalamic extract was unaffected by heating (100 degrees C, 10 min); acidification to pH 3.3; or by exposure to lipase, RNAase, or proteolytic enzymes; but was abolished by alkalinization to pH 11. An approximate molecular weight of 1,700 daltons was determined by elution on a calibrated Sephadex G-25 column, and an approximate pl of 3.5 was determined by isoelectric focusing. Optimal concentrations of the crude extract (150-300 micrograms/ml) increased keratinocyte growth approximately 50-fold compared to control cultures lacking the extract. Partial purification resulted in a preparation biologically active at 30 ng/ml protein equivalent and was consistent with the presence of a single mitogen which we have termed keratinocyte growth factor (KGF). Mitogenic activity for human melanocytes, dermal fibroblasts, and endothelial cells, present in the crude hypothalamic extract, was lacking in heat-treated preparations that contained KGF. Optimal concentrations of purified epidermal growth factor and ethanolamine, the only remotely similar substances previously reported to augment keratinocyte growth in vitro, could not substitute for KGF in the serum-free culture system. Keratinocyte growth-promoting activity comparable to that observed in bovine hypothalamic extracts was present in human hypothalamic extracts prepared in the same manner.

Animals↗
PubMed1984

Timing of mutation-fixation events in ethyl methane sulfonate-treated Chinese hamster cells.

Exposure of single Chinese hamster ovary (CHO) cells to the mutagen, ethyl methane sulfonate, produces two types of mutant colonies lacking glucose-6-phosphate dehydrogenase activity: colonies uniformly deficient in enzyme activity, and mosaic colonies containing both mutant and nonmutant cell phenotypes in various relative proportions and sectored patterns (1/8, 1/4, 1/2). We find that the relative size of the mutant sector in these mosaic colonies primarily reflects the cell division at which the mutation was genetically fixed. Thus, the mutation-fixation event occurs before the first cell division in 1/2 sector and pure mutant colonies, between the first and second divisions for 1/4 sectors, and between the second and third divisions for 1/8 sectors. Delay in the formation of mutations could also explain the phenomenon of "mutation expression time" which is observed when drug resistance is used to select for mutants. Colony sectoring offers for the first time in mammalian cells the opportunity to observe an agent's effect on the timing of the mutational process.

Animals↗
PubMed1983

Isolation of cell cycle-dependent gamma ray-sensitive Chinese hamster ovary cell.

A technique for the isolation of gamma ray-sensitive Chinese hamster ovary (CHO) cell mutants is described, which uses nylon cloth replica plating and photography with dark-field illumination to directly monitor colonies for growth after gamma irradiation. Two gamma ray-sensitive mutants were isolated using this method. One of these cells (XR-1) had a two-slope survival curve: an initial steep slope and then a flattening of the curve at about 10% survival. Subsequently, it was found that this cell is sensitive to gamma irradiation in G1, early S, and late G2 phases of the cell cycle, whereas in the resistant phase (late S phase) its survival approaches that of the parental cells. The D37 in the sensitive G1 period is approximately 30 rads, compared with 300 rads of the parental cell. This mutant cell is also sensitive to killing by the DNA breaking agent, bleomycin, but is relatively insensitive to UV light and ethyl methane sulfonate, suggesting that the defect is specific for agents that produce DNA strand breakage.

Animals↗
PubMed1983

Antibacterial mechanisms of antibody to mannose-sensitive pili of Escherichia coli.

To identify mechanisms whereby antibody to mannose-sensitive pili of Escherichia coli might enhance host defenses, we evaluated the activity of antibody to pili in four antibacterial immune processes. Antiserum to pili and Fab' fragments of IgG antibody to pili inhibited the ability of homologous piliated organisms to adhere to buccal epithelial cells. However, this antiserum did not enhance intravascular clearance, complement-dependent bacteriolysis, or opsonophagocytosis. The addition of antiserum to pili to polymorphonuclear leukocytes and piliated E. coli reduced the rate of killing from 52% to 5%. The addition of complement restored the rate to 52%, but this was much less than the 99% rate achieved with polymorphonuclear leukocytes and either fresh serum or antibody to the whole bacteria. These observations suggest that the principal anti-bacterial property of antibody to mannose-sensitive pili of E. coli is inhibition of bacterial attachment. Whether the anti-opsonic effect of antibody to pili is detrimental to host defense remains to be determined.

Adhesiveness↗
PubMed1983

Human warts permanently removed by static electricity.

The CED was found to be a highly effective, safe, inexpensive, and simple device to use for complete wart removal with no regrowth or scarring. The warts are shed in the same manner as the surface epithelium exfoliates or sloughs off. Plantar warts cause a great deal of pain in walking and surgical procedures are warranted in some cases. Since these warts tend to become very large and to extend deeply into the dermis, when they are removed surgically the patient is incapacitated for a period of time. Opening the area to bacteria may cause additional infection, and the surgery may result in tender scar formation. According to our study group, the CED offers an effective alternate means of therapy for removing warts and alleviating the pain associated with them.

Electric Stimulation Therapy↗
PubMed1982

High and low molecular weight forms of endothelial cell growth factor.

Endothelial cell growth factor (ECGF) is a neural-derived mitogen capable of stimulating the proliferation of quiescent populations of human umbilical vein endothelial cells (HUV-EC). ECGF has been isolated from bovine hypothalamus in two forms: a high molecular weight from (high Mr ECGF, greater than 70,000) and a low molecular weight form form (low Mr ECGF, 17,000 to 25,000). Isoelectric focusing of high Mr ECGF and low Mr ECGF revealed that both Mr forms possess similar anionic isoelectric points (pI 4 to 6). High Mr ECGF can be converted into low Mr ECGF by mild acidification of the high Mr ECGF complex. Low Mr ECGF prepared by the high Mr to low Mr transition procedure is biologically active at 100 ng/ml in the low density HUV-EC growth assay and is capable of stimulating DNA synthesis in Balb/c 3T3 cells at 10 ng/ml. The two Mr forms of ECGF are related since they (i) share similar biological activity, (ii) possess similar isoelectric points, and (iii) high Mr ECGF can be converted into low Mr ECGF by mild treatment with acetic acid. Furthermore, the high Mr and low Mr forms of ECGF are not related to the cationic bovine brain fibroblast growth factor.

Animals↗
PubMed1982

Growth of human foreskin fibroblasts in a serum-free, defined medium without platelet-derived growth factor.

The hormones which support growth, in vitro, of normal, neonatal human foreskin fibroblasts were determined. Whereas thrombin and hydrocortisone were major growth stimulants, platelet-derived growth factor was not. Human foreskin fibroblasts grew in a serum-free, biochemically defined medium consisting of epidermal growth factor (100 ng/ml), insulin (100 ng/ml), transferrin 10 micrograms/ml), thrombin (1 microgram/ml), ascorbic acid (10 micrograms/ml), and hydrocortisone (5 x 10(-5) M) in a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12, supplemented with ovalbumin (1 mg/ml) and trace elements. The growth achieved was comparable to that achieved with 5% fetal bovine serum. Neither platelet-derived growth factor, fibroblast growth factor, nor somatomedin activity increased proliferation. This serum-free medium, designated Defined Medium F, provides a biochemically defined system for growth and limited subcultivation of human foreskin fibroblasts in vitro.

Blood Platelets↗