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Biomedical subjects

S Strickland

Publications and source records attributed to S Strickland.

At least 109 records · Page 6Linked to original sources
PubMed1980

The culture of hormone-dependent epithelial cells from the rat ventral prostate.

This paper describes a method for obtaining cultures of rat ventral prostate epithelial cells. The prostate is first perfused with a collagenase solution before removal from the animal; subsequent mincing and incubation in vitro produces a suspension of alveolar cell clumps. Upon incubation, these clumps attach to the surface of the culture dish and spread into discrete epithelial cell colonies, which both retain differentiated morphology, and secrete a species of plasminogen activator that is characteristic of prostatic tissue. These properties were not observed in cultures prepared from single cell suspensions of the same organ. Maintenance of epithelial colony integrity and secretory activity specifically required the continued presence of stromal cells, glucocorticoids and insulin. Androgenic steroids were much less effective than glucocorticoids in stimulating plasminogen activator secretion and in maintaining colony integrity, in spite of the well-established androgen dependence of prostatic tissue morphology in vivo and in organ culture. Furthermore, no effects of prolactin were observed, either when this hormone was tested alone or in conjunction with steroid hormones. Of 3 retinoids tested, retinal was highly cytotoxic at concentrations in the range of 1 microM, whereas retinol and retinoic acid were without detectable effect.

Animals↗
PubMed1979

Antigenicity of venous allografts.

With isolated exceptions, the clinical use of venous allografts has been disappointing. Considerable evidence indicates that allograft antigenicity plays a major role in the failure of venous allografts when used as arterial replacements. Recent reports suggest that DMSO-cryopreservation of venous allografts may reduce allograft antigenicity while preserving allograft viability. The present study examines the effect of modifications of vein allografts on subsequent allograft antigenicity. Skin grafts were transplanted from ACI to Lewis inbred strains of male rats. Primary skin graft rejection occurred in 9.0 +/- 1.0 days. Subcutaneous implantation of fresh inferior vena cava from ACI rate into Lewis rats resulted in subsequent skin graft rejection in 5.0 +/- 1.0 days, confirming the antigenicity of venous tissue. Cryopreservation of ACI inferior vena cava for seven days prior to implantation, with or without 15% DMSO, resulted in subsequent skin graft rejection in 5.0 +/- 1.0 days. Treatment of ACI inferior vena cava with 0.30% gluteraldehyde for 20 minutes prior to implantation in Lewis rats resulted in skin graft rejection in 9.0 +/- 1.0 days, the same time as a first set rejection. This study indicates that unmodified veins are normally antigenic and that this antigenicity is not eliminated by cryopreservation with or without DMSO. Gluteraldehyde treatment appears to reduce allograft antigenicity, but results in a nonviable graft. At the present time, there is no known way to reduce the antigenicity of viable venous allografts.

Animals↗
PubMed1979

Corticosteroid-potentiated vascular responses of the equine digit: a possible pharmacologic basis for laminitis.

Spirally cut digital arteries and veins were mounted isotonically in organ baths containing oxygenated Krebs' Q-Henseleit solution. Twelve arterial and 12 venous preparations all contracted dose dependently when epinephrine, norepinephrine, serotonin, or histamine were added to the bathing fluid. Addition of hydrocortisone or betamethasone alone did not cause contractions in any of the tissues tested. However, when hydrocortisone or betamethasone was added to vessel strips that were partially contracted (40% to 60% maximal) by epinephrine, norepinephrine, or serotonin, each vessel strip invariably underwent an additional contraction. In venous and arterial strips, dose-response curves to epinephrine, norepinephrine, serotonin, or histamine were established in the absence and in the presence of corticosteroid. Effects of the amines, except histamine, were markedly potentiated. The degree of corticosteroid/amine potentiation was greater for epinephrine than for norepinephrine and greater in the digital vein than in the corresponding artery from the same animal. Betamethasone was more potent than hydrocortisone.

Adrenal Cortex Hormones↗
PubMed1978

A cell culture assay for follicle-stimulating hormone.

Cultured rat ovarian granulosa cells respond to follicle-stimulating hormone (FSH) by synthesizing and secreting plasminogen activator. The specificity of the response for FSH prompted us to explore the use of this system as an in vitro bioassay for FSH. The release of FSH by pituitary cell cultures has been examined by this method, as have been preparations of FSH of known biological activity. The results indicate that the granulosa cell system allows accurate, rapid, and convenient determinations of FSH activity. Furthermore, the method obviates metabolic clearance problems associated with whole animal assays and it is extremely sensitive: as little as 10(-15) mol (approximately 100 micronIU) of FSH can be detected.

Animals↗
PubMed1978

The induction of differentiation in teratocarcinoma stem cells by retinoic acid.

Embryonal carcinoma cells, the stem cells of teratocarcinomas, usually undergo extensive differentiation in vivo and in vitro to a wide variety of cell types. There exist, however, several embryonal carcinoma cell lines that have almost completely lost the capacity to differentiate, so that the cells are propagated primarily as the stem cells. Using one such cell line, F9, we have found that retinoic acid at concentrations as low as 10(-9) M induces multiple phenotypic changes in the cultures in vitro. These changes include morphological alteration at the resolution of the light microscope, elevated levels of plasminogen activator production, sensitivity to cyclic AMP compounds and increased synthesis of collagen-like proteins. The nature of these changes, as well as their independence of the continued presence of retinoic acid, are consistent with the proposition that retinoic acid induces differentiation of embryonal carcinoma cells into endoderm.

Acetylglucosaminidase↗
PubMed1976

Studies on the role of plasminogen activator in ovulation. In vitro response of granulosa cells to gonadotropins, cyclic nucleotides, and prostaglandins.

A quantitative method is described for measuring the amount of plasminogen activator produced by rat ovarian granulosa cells following exposure to hormones in vivo or in vitro. The results confirm the previously reported observation (Beers, W. H., Strickland, S., and Reich, E. (1975) Cell 6, (387-394) that granulosa cells in vivo produce increasing amounts of plasminogen activator as the time of ovulation approaches and that the enzyme is produced only be cells obtained from follicles destined to ovulate. Inactive cells can be stimulated in vitro by gonadotropins to produce plasminogen activator. This response is time- and dose-dependent, and results in an increase of intracellular and extracellular enzyme. Studies of the specificity of this response indicate that preparations of follicle-stimulating hormone are much more effective than corresponding preparations of luteinizing hormone. The effect of other pituitary hormones is also presented. Molecules other than gonadotropins are also capable of stimulating the cells to produce the enzyme. Prostaglandins E1 and E2 and analogues of cAMP effectively stimulated the cells to produce plasminogen activator, cGMP and its analogues and prostaglandins F1a and F2a were without effect as were the six steroids studied. The inactive compounds also did not inhibit the response of the cells to gonadotropins. The granulosa cell plasminogen activator has been analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and has an apparent molecular weight of 75,000. By this and other criteria, the granulosa cell enzyme is similar to one of the species of plasminogen activators obtained from cultures of simian virus 40-transformed rat embryo fibroblasts.

Animals↗
PubMed1976

Plasminogen activator in early embryogenesis: enzyme production by trophoblast and parietal endoderm.

We have surveyed the early stages in the development and differentiation of cultured mouse embryos for plasminogen activator production. This enzyme is first detectable by the sixth equivalent gestation day. Thereafter, cultured blastocysts produce plasminogen activator with a biphasic time course: in the first phase, enzyme secretion rises to a maximum at about the eighth day and then decreases; a second phase, during which more enzyme accumulates, begins somewhat later and continues to at least the fifteenth day. By fractionating the blastocyst into its constituent cell types, we have identified the trophoblast as the cells responsible for the first phase of enzyme synthesis. The pattern of enzyme production by the trophoblast is closely correlated with the invasive period of these cells in vivo and implies that plasminogen activator is involved in embryo implantation. The second phase of plasminogen activator production is due to parietal endoderm, which initiates enzyme synthesis upon differentiation from the inner cell mass. The properties of the parietal endoderm suggest that plasminogen activator may participate in the migration of these cells and/or in the metabolism of Reichert's membrane which accompanies embryo growth. These results are consistent with the concept, deveolped from work on other cell types, that plasminogen activator may represent a generalized mechanism for tissue remodeling and cell migration.

Animals↗
PubMed1976

Differentiation of early mouse embryonic and teratocarcinoma cells in vitro: plasminogen activator production.

Cultured mouse blastocysts produce plasminogen activator, a protease that converts the zymogen plasminogen into the trypsin-like enzyme, plasmin. We have fractionated the blastocyst and cultured the constituent cell types. Trophoblast outgrowths free of inner cell mass derivatives secrete plasminogen activator during a time period that closely parallels the invasive phase of trophoblast cells in utero. Isolated inner cell masses also produce plasminogen activator; further fractionation of the inner cell mass as well as studies with primary cultures obtained from midgestation tissues demonstrate that enzyme formation is restricted entirely to parietal endoderm cells. Secretion of the enzyme may facilitate the migration of parietal endoderm cells along the trophoblast layer as the yolk sac cavity enlarges during gestation. F9 embryonal carcinoma cells do not secrete detectable amounts of plasminogen activator. However, when these cells are induced to differentiate, the resulting parietal endoderm-like cells are capable of producing the enzyme. These results are consistent with previous findings suggesting that plasminogen activator production may be a characteristic of invasive and/or migratory cells.

Blastocyst↗
PubMed1975

Kinetic and mechanistic studies on the reaction of melilotate hydroxylase with deuterated melilotate.

Melilotate has been synthesized from melilotate by iodiantion followed by reductive deiodination in the presence of deuterated hydrazine. The deuterated melilotate has been employed in investigations of the reaction mechanism of melilotate hydroxylase. Stopped-flow spectrophotometry has revealed no isotope effect in the formation or decay of the oxygenated intermediate which is observed when reduced melilotate hydroxylase reacts with molecular oxygen. Steady-state analysis has corroborated this result, and in addition shows that there is no isotope effect in the reductive cycle of the enzyme mechanism. This analysis does reveal a reproducible 8% decrease in Vmax for the enzyme when using deuterated melilotate. These observations are compatible with the thesis that the above intermediate is an oxygenated form of the reduced flavine prosthetic group and that the last step of the proposed mechanism is rapid and involves a primary isotope effect. The existence of the NIH shift mechanism has been studied using combined gas chromatography-mass spectrometry. No evidence could be obtained for intramolecular migration of deuterium during the hydroxylation reaction. However, the small amount of migration expected when phenols are hydroxylated precludes elimination of the NIH shift as a possibility.

Chromatography, Gas↗
PubMed1975

Fibrin overlay methods for the detection of single transformed cells and colonies of transformed cells.

Fibrin overlay methods are described which can detect the plasminogen activator produced by single transformed cells or small colonies of transformed cells. These methods were applied to malignant cells derived from humans, mice, hamsters, rats, and chicks. The lysis observed was plasminogen dependent. Transformation of chicken cells by Rous sarcoma virus was detected 4 days after infection. The number of lysis zones produced was proportional to the virus inoculum and was identical to the number of morphologically determined foci. These methods may also have application in model systems for scoring transformation by chemicals. Transformed mouse and chicken cells were detected at the single cell level and the number of lysis zones produced was dependent on the number of cells present, the time of incubation, and the concentration of plasminogen.

Animals↗
PubMed1975

Ovarian plasminogen activator: relationship to ovulation and hormonal regulation.

A technique is described for detecting fibrinolytic activity of single cells in culture. This method was applied to the analysis of rat ovarian granulosa cells. Cells obtained from follicules shortly before ovulation show high levels of fibrinolytic activity. This activity is plasminogen-dependent, indicating that it is due to plasminogen activator. The appearance of this activity is correlated with ovulation by temporal and functional criteria, and can be demonstrated both in immature animals primed with hormones and in mature cycling animals. Granulosa cell cultures can be stimulated to release plasminogen activator by exposure in vitro either to luteinizing hormone or to dibutyryl cyclic AMP.

Animals↗