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S T Hoffstein

Publications and source records attributed to S T Hoffstein.

32 records · Page 2Linked to original sources
PubMed1981

Thyrotropin-releasing hormone stimulation of prolactin release from clonal rat pituitary cells: evidence for action independent of extracellular calcium.

Thyrotropin-releasing hormone (TRH) stimulates prolactin release and (45)Ca(2+) efflux from GH(3) cells, a clonal strain of rat pituitary cells. Elevation of extracellular K(+) also induces prolactin release and increases (45)Ca(2+) efflux from these cells. In this report, we distinguish between TRH and high K(+) as secretagogues and show that TRH-induced release of prolactin and (45)Ca(2+) is independent of the extracellular Ca(2+) concentration, but the effect of high K(+) on prolactin release and (45)Ca(2+) efflux is dependent on the concentration of Ca(2+) in the medium. The increment in (45)Ca(2+) efflux induced by 50 mM K(+) during perifusion was reduced in a concentration-dependent manner by lowering extracellular Ca(2+) from 1,500 to 0.02 muM (by adding EGTA), whereas 1 muM TRH enhanced (45)Ca(2+) efflux similarly over the entire range of extracellular Ca(2+) concentrations. Although 50 mM K(+) caused release of 150 ng prolactin from 40 x 10(6) GH(3) cells exposed to 1,500 muM Ca(2+) (control), reduction of extracellular Ca(2+) to 2.8 muM decreased prolactin release caused by high K(+) to <3% of controls and no prolactin release was detected after exposure to 50 mM K(+) in medium with 0.02 muM free Ca(2+). In contrast, TRH caused release of 64 ng of prolactin from 40 x 10(6) GH(3) cells exposed to medium with 1,500 muM Ca(2+), and release caused by TRH was still 50 and 35% of control in medium with 2.8 and 0.02 muM Ca(2+), respectively. Furthermore, TRH transiently increased by 10-fold the fractional efflux of (45)Ca(2+) from GH(3) cells in static incubations with 1,500 or 3.5 muM Ca(2+), hereby confirming that the enhanced (45)Ca(2+) efflux caused by TRH in both low and high Ca(2+) medium was not an artifact of the perifusion system.Data obtained with chlortetracycline (CTC), a probe of membrane-bound Ca(2+), were concordant with those obtained by measuring (45)Ca(2+) efflux. Cellular fluorescence of CTC varied with the extracellular Ca(2+) concentration and the duration of incubation. TRH decreased the fluorescence of cell-associated CTC in a manner strongly suggesting stimulus-induced mobilization of Ca(2+), and this effect was still demonstrable in GH(3) cells incubated in 50 mM K(+). These data suggest that TRH acts to mobilize sequestered cell-associated Ca(2+) reflected as a (45)Ca(2+) efflux which is independent of the extracellular Ca(2+) concentration. Mobilization of sequestered Ca(2+) into the cytoplasm may elevate free intracellular Ca(2+) and serve to couple stimulation by TRH to secretion of prolactin.

Animals↗
PubMed1981

Inverse correlation between neutrophil microtubule numbers and enhanced random migration.

The random migration of neutrophils under agarose as measured by the number of cells leaving the well, is enhanced when the pH or the osmolality of the medium is reduced or when microtubule agents are used. Concentrations of colchicine above 5 x 10-7 M increased the number of cells migrating and decreased the mean number of centriolar microtubules in a dose-dependent fashion from 16 to 4 per 4 micron 2 at 10-5 M. The distance that colchicine-treated neutrophils migrated from the well was not different from the control. Lowering the pH from 7.4 to 6.0 also increased random migration and decreased pericentriolar microtubules from a mean of 16 to a mean of 10. At pH 6.0, both the number of cells that migrated and the distance the cells forming the leading edge travelled from the well were increased. Since peripheral microtubules may play a greater role in cell migration than centiolar ones, we examined the numerical density of microtubules in the peripheral cytoplasm. Lowering the medium pH reduced the mean number of microtubules per 10 micron 2 from 6 to 2. Colchicine reduced micro-tubules in the same area to I. At the low pH, colchicine reduced even further the numbers of both centriole-associated and peripheral microtubules but the migration pattern was the same as that seen at pH 6.0 without colchicine. Lowering medium osmolality from 280 to 230 m-osmol increased random migration but did not affect microtubule numbers. The addition of colchicine to this system decreased microtubule numbers and increased migration even further. Conditions that enhanced neutrophil migration also affected cell shape. Whereas cells at pH 7.4 were generally fan-shaped with a broad, smooth leading edge, cells at pH 6.0 with or without colchicine were long and narrow. Neutrophils at pH 7.4 but 230 m-osmol had a scalloped edge, which often appeared thickened. This too was not altered by colchicine. The morphology of cells treated with colchicine was similar to controls except for the more frequent presence of long retraction fibres. Each of these treatments thus appears to act on a different aspect of the cell's locomotory apparatus. The mechanisms by which colchicine and lowered ph enhance migration may partially overlap since both significantly decrease peripheral microtubules. The data suggest that microtubules play a constraining role within the cell, limiting the ability of the cell to move and change direction.

Adult↗
PubMed1981

Fibonectin is a component of the surface coat of human neutrophils.

Although adherence to surfaces is central to neutrophil function many of the determinants of neutrophil adherence are still unknown. The possible involvement of cell surface material, fibronectin in particular, was therefore studied. Surface coat material was visualized ultrastructurally by the ferrocyanide--reduced osmium technique of Karnovsky (1971). Loosely attached surface coat material was seen distributed uniformly on cells in suspension. Indirect immunofluorescence indicated the presence of fibronectin on the neutrophil surface. Distribution of fibronectin as determined by indirect immunoferritin localization corresponded with the distribution of cell coat material. Some, if not all, of this fibronectin was synthesized by neutrophils themselves since metabolically labelled fibronectin could be obtained by immunoprecipitation after short-term culture with [36S]methionine. Neutrophils also adhere to Sepharose beads to which gelatin is covalently linked (GS) but not to plain Sepharose beads (PS). In the process they transfer surface coat material to GS but not PS. Similar transfer was seen when cells were permitted to adhere to glass or plastic coverslips. Indirect immunofluorescence showed that fibronectin-containing material was transferred from neutrophils to GS but not PS. Parallel studies with antisera to 2 other plasma proteins, factor VIIIR and alpha 1-antitrypsin showed that neutrophils did not transfer these to either GS or PS beads. The data suggest that material antigenically and functionally related to fibronectin is associated with the extracellular coat of neutrophils and is transferred with cell surface material to surfaces to which neutrophils adhere.

Cell Adhesion↗
PubMed1980

Anion channel blockers inhibit lysosomal enzyme secretion from human neutrophils without affecting generation of superoxide anion.

The role of permeant anions in lysosomal enzyme secretion from human neutrophils was investigated by means of anion-channel-blocking agents: 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), and pyridoxal phosphate. Lysosomal enzyme release from cytochalasin B-treated human neutrophils stimulated by immune complexes (bovine serum albumin and IgG anti-bovine serum albumin) was inhibited by DIDS, SITS, and pyridoxal phosphate at concentrations that inhibited sulfate fluxes. Enzyme secretion triggered by calcium ionophore A23187 was also inhibited by DIDS and SITS; these agents acted on secretory events subsequent to Ca2+ influx. Neither the species of permeant anion(s) nor the role of anion fluxes in degranulation was identified, although influxes of chloride, hydroxide, or phosphate ions were not critical. In contrast to degranulation, generation of superoxide anions (O2.-) stimulated by immune complex or A23187 was not inhibited by these agents. Ultrastructural cytochemical studies demonstrated that, although lysosomal contents were not discharged from stimulated cells, vacuole formation and lysosome-lysosome fusion were unaffected by SITS or DIDS. Data suggest that anion channel blockers specifically inhibit fusion of lysosomes with the plasma membrane or its invaginations.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1979

Induction of liver cell haem oxygenase in iron-overloaded rats.

Rats were chronically iron-overloaded by intraperitonel injections of iron-dextran. Electron microscopy revealed that the excess iron was deposited in ferritin-like particles packed in lysosomes and scattered in hepatic cytoplasm. No mitochondrial iron deposition or damage was seen. Furthermore, mitochondrial preparations from chronically iron-overloaded animals were found to be contaminated with lysosomes, which could explain previously reported increases in mitochondrial iron by chemical analysis. Mitochondrial function, as measured by cytochromes a-a3, b and c concentrations as well as activity of the rate-limiting enzyme of haem synthesis, delta-aminolaevulinate synthetase, was not diminished by chronic iron-overloading. Microsomal haem was decreased by 30% at the time that haem oxygenase, the rate-limiting enzyme of haem degradation, was increased approx. 3-fold. Animals were given a single intraperitoneal injection of iron-dextran and the activities of delta-aminolaevulinate synthetase and haem oxygenase were measured over 24 h. delta-Aminolaevulinate synthetase activity increased approx. 2-fold in these acutely iron-overloaded rat livers, but at a time after the increase in haem oxygenase. These results suggest that an early consequence of excess iron in liver is acceleration of the rate of haem degradation, possible by haem oxygenase.

5-Aminolevulinate Synthetase↗
PubMed1978

Cellular heterogeneity in primary monolayer cultures of mouse pituitary thyrotropic tumors: separation of thyrotrophs.

Primary monolayer cultures of cells derived by enzymatic dispersion from mouse pituitary thyrotropic tumors were demonstrated to be comprised of at least 2 cell types and were separated by selective culture techniques. Suspension cultures of spherical cells had the morphological characteristics of thyrotrophs and produced large quantities of TSH. Separated monolayer cultures of spreading, planar cells produced collagen but almost no TSH. These observations indicate that primary monolayer cultures of cells derived from thyrotropic tumors are heterogeneous, containing only a small proportion of thyrotrophs.

Animals↗
PubMed1975

Mechanisms of lysosomal enzyme release from human polymorphonuclear leukocytes. Effects of phorbol myristate acetate.

PMA enhanced release of the azurophil granule enzyme, beta-glucuronidase, as well as lysozyme, from cytochalasin B-treated PMN's exposed to either zymosan particles or C5a. PMA was active at nanomolar concentrations, was not toxic to the cells, and was most effective when present for brief durations (0-1 min) before exposure of the cells to the stimuli. Beta-glucuronidase was not released in significant amounts from PMN's exposed to PMA alone, in the absence of stimuli such as zymosan or C5a. In contrast, only the specific granule enzyme, lysozyme, was released from unstimulated cells. Electron micrographs of cells exposed to PMA revealed an increase in the number of visible cytoplasmic microtubules as compared to control cells. Enhancement of lysosomal enzyme (beta-glucuronidase) release by PMA appears to be independent of effects on release of specific granule enzymes (lysozyme), but rather is likely due to PMA-induced elevations of cellular cGMP.

Complement C5↗
PubMed1975

Influence of divalent cations upon complement-mediated enzyme release from human polymorphonuclear leukocytes.

The complement component, C5a provokes the selective release of granule-associated enzymes from the intact, viable cytochalasin B-treated human polymorphonuclear leukocytes (PMN) in the absence of phagocytosis or cellular adherence to surfaces. Consquently, in this experimental system the influence of divalent cations on these two processes can be disregarded and their effects on enzymes secretion can be studied directly. Cytochalasin B-treated PMN exposed to C5a in calcium and magnesium-free media consistently secreted significant amounts of the granule-associated enzymes, beta-glucuronidase and lysozyme. The basal secretory response was not diminished if cells were preincubated with 5.0 mM EDTA, nor was it influenced if 1.0 mm or 2.0 mM EDTA were present in the reaction mixtures. The addition of calcium (up to 1.5 to 2.0 mM) produced a concentration-dependent enhancement of beta-glucuronidase release, whereas increasing amounts of calcium (above 2.0 mM) inhibited secretion of this enzyme. Lysozyme release was similarly enhanced by the addition of calcium, but inhibition with high concentrations was not observed. Calcium per se, in the absence of C5a, provoked only the release of lysozyme from these cells. The effects of calcium upon enzyme release were not associated with alterations in the state of assembly of cytoplasmic microtubules. These findings provide another example of the role of calcium in "stimulus-secretion coupling" and provide evidence that exocytosis of various granules in human PMN is regulated by independent mechanisms involving calcium.

Adult↗
PubMedDate not supplied

Leukotriene D4 (LTD4) induces mucus secretion from goblet cells in the guinea pig respiratory epithelium.

To study the potential role of leukotriene (LTD4) as a mucus secretagogue, anesthetized and spontaneously breathing guinea pigs were intubated and challenged with various concentrations of an LTD4 aerosol. The resulting changes in airway resistance and compliance were then observed for 20 min, after which the animals were euthanized and the lower respiratory tract airways fixed for morphometric evaluation. Sections for these airways were stained with alcian blue-periodic acid Schiff (AB-PAS), photographed, and the content of AB-PAS positive granules in the epithelium of the extrapulmonary bronchi quantified. The fractional volume of mucus granules in the respiratory epithelial volume. Aerosol LTD4 produced a dose-dependent decrease in the granule fractional volume (GFV) over the range of 0.1 to 1 microgram/ml when compared with epithelia challenged with saline aerosols. Increasing the concentration of administered LTD4 from 1 microgram to 3 micrograms/ml produced further bronchoconstriction but had no further effect on the GFV. Decreases in GFV did not appear to be secondary to smooth muscle contraction since aerosols of other agonists (0.05% histamine and 1% acetylcholine), which yielded resistance changes similar to those of LTD4, did not effect the GFV. Pretreatment with an aerosol of the specific LTD4 receptor antagonist SK&F 104353-Z2 produced a dose-dependent inhibition of the changes in both the airway resistance and GFV. The data suggest that LTD4 mediates epithelial mucus secretion as well as bronchoconstriction in the guinea pig airway and may provide an additional therapeutic use for specific LTD4 receptor antagonists in the treatment of obstructive pulmonary disease.

Animals↗