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Biomedical subjects

D Lagunoff

Publications and source records attributed to D Lagunoff.

At least 55 records · Page 3Linked to original sources
PubMed1984

Ethchlorvynol-induced pulmonary edema in rats. An ultrastructural study.

Studies of ethchlorvynol (ECV)-induced pulmonary edema were undertaken for determination of the structural basis of increased microvascular permeability. Rats were administered an intravenous bolus dose of 15 mg/kg ECV and killed at time intervals between 5 minutes and 72 hours. Oyster glycogen and ferritin were used as permeability probes for identification of the sites of altered microvascular permeability. Edema fluid containing ferritin begins to accumulate in the alveolar interstitium 10 minutes after EVC . Thirty minutes after ECV, marked intersitial edema fluid is present containing both permeability probes. The absence of any appreciable transendothelial movement of either probe via vesicles and the presence of open endothelial junctions led the authors to propose the latter as the principal determinant of the increase in permeability. In addition to open endothelial junctions, prominent subendothelial blebs occur. These blebs develop in an otherwise intact endothelium and increase in frequency and size with time following their appearance at 10 minutes. Ferritin and glycogen progressively accumulate within the blebs. At 15 minutes the concentration of ferritin in blebs appears to equal that in plasma, whereas glycogen is absent or sparsely present in a few blebs. At 60 minutes both permeability probes have become concentrated in the blebs. The mechanism of formation of the blebs and concentration in them of the permeability probes cannot yet be specified. The lesion caused by ECV is completely reversible, so that by 72 hours after ECV there is complete resolution of interstitial edema, disappearance of the subendothelial blebs, and closure of endothelial junctions. A small amount of exudate remaining in the alveoli is cleared by 72 hours.

Animals↗
PubMed1983

Evidence for control of mast cell granule protease in situ by low pH.

The second order rate constant, k2, for the inhibition of mast cell protease I by phenylmethanesulfonyl fluoride (PMSF) is lower for intact mast cells and isolated granules with intact membranes than for granules stripped of their membranes and suspended in medium at pH 7.1. In order to test the hypothesis that the decreased activity of the protease in intact granules is attributable to low pH, two agents capable of lowering pH in intracellular compartments similar to mast cell granules were tested. Ammonium chloride increased k2 of the protease in isolated granules with intact membranes and mast cells and wash out of the salt partially reversed this effect. Treatment of cells with nigericin also substantially increased the rate of protease inactivation by PMSF. These results are consistent with the proposal that the observed k2 is determined in whole or part by a low pH of the granule in situ or isolated with intact membranes. If the low k2 in situ is solely dependent on low pH, then the rate of protease inhibition can be utilized as an endogenous probe of granule pH. On this basis we have estimated the pH of the intracellular granule as 5.2 and that of the isolated granule with its membrane intact as 6.0. The value for the pH of granules in situ is lower than that previously estimated, and we have considered possible bases for this discrepancy.

Ammonium Chloride↗
PubMed1983

Histidine uptake by isolated rat peritoneal mast cells. Effect of inhibition of histidine decarboxylase by alpha-fluoromethylhistidine.

Preincubation with (S)-alpha-fluoromethylhistidine, an irreversible inhibitor of histidine decarboxylase, was found to markedly reduce, but not eliminate, the uptake of [3H]histidine by rat peritoneal mast cells. The Vmax for histidine transport for cells in which decarboxylation of histidine had been completely inhibited was 11.9 pmoles per min per 10(6) cells, compared to a Vmax of 18.9 pmoles per min per 10(6) cells in the presence of active mast cell histidine decarboxylase. The Km of uptake was 139 microM in the presence of alpha-fluoromethylhistidine, several times higher than the Km of 44.0 microM in the uninhibited cell. alpha-Fluoromethylhistidine did not inhibit mast cell uptake of phenylalanine, a competitive inhibitor of histidine uptake but not a substrate for histidine decarboxylase; nor did it inhibit the uptake of histidine by non-mast cells, which lack histidine decarboxylase. Levels of intracellular [3H]histidine in mast cells were similar in the presence and absence of the decarboxylase inhibitor. Based on these observations, we propose that intracellular decarboxylation of histidine in the mast cell serves to specifically enhance the uptake of histidine by the relatively non-specific amino acid transporter present in the plasma membrane of the cell.

Animals↗
PubMed1983

Periodic, multimodal distribution of granule volumes in mast cells.

The areas of 2327 mast cell granules in transmission electron micrographs of sections of peritoneal mast cells from adult rats were measured by digitized planimetry. A histogram constructed using equivalent volumes calculated from the measured areas assuming approximation of the granules to spheres showed a periodic multimodal distribution in which the modes fell at volumes that were successively larger integral multiples of the volume at the first mode. Application of a moving-bin technique to the data confirmed the presence of the modes. We propose a mechanism of fusion of unit sized granules to account for the multimodal distribution. The presence of pear- and dumbbell-shaped granules in mast cells is consistent with this mechanism.

Animals↗
PubMed1983

The role of mast cells in asthma.

Mast cells store or generate a number of substances, such as histamine, leukotrienes, specific chemotactic factors, and proteases, which have potent inflammatory effects. Mast cells are present in mammalian lung in the bronchial wall, in the epithelium itself, and in airway lumens. Evidence implicating mast cells in the induction of airway muscle constriction and mucosal inflammation includes direct studies of mast cell secretion, measurement of histamine release, and inhibition of asthmatic reactions with antihistamines and with the inhibitor of mast cell degranulation, sodium cromoglycate. Definitive evaluation of the role of the mast cell in asthma remains elusive, in part because of the general hyperactivity of airway smooth muscle in asthmatics.

Animals↗
PubMed1982

Rat mast cell phospholipase A2: activity toward exogenous phosphatidylserine and inhibiton by N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylserine.

The presence of phospholipase A2 in intact rat peritoneal mast cells was investigated by using two synthetic radiolabeled phosphatidylserine (PS) substrates. Incubation of intact cells with 1-oleoyl-2-[3H]oleoyl-PS resulted in the release of a considerable quantity of [3H]oleic acid from the substrate. To establish that [3H]oleic acid release was mediated via direct enzymatic attack at the sn-2 position, we measured release of the [3H]serine moiety from the glycerol backbone of 1,2-dimyristoylphosphatidyl[3H]serine. This activity, which represents the combined actions of phospholipases C and D, was 10-fold lower than [3H]oleic acid release, indicating that neither of these enzymes is required for the release of the preponderance of [3H]oleic acid. These results establish the existence in intact rat mast cells of a phospholipase A2 active toward exogenous PS. Over the concentration range at which exogenous PS activates mast cell secretion, intact mast cells and broken cells possessed nearly equal levels of phospholipase A2 activity, and enzyme activity was 3--4-fold higher toward PS than phosphatidylcholine. Several agents were tested for their ability to inhibit phospholipase A2 in intact mast cells. Of the agents tested, an N-substituted derivative of PS previously identified as an inhibitor of mast cell secretion was shown to be a particularly potent and efficacious inhibitor of mast cell phospholipase A2. The concentration dependence of enzyme inhibition paralleled inhibition of histamine secretion, providing a strong positive correlation between the level of phospholipase A2 in mast cells and the capacity for secretion.

4-Chloro-7-nitrobenzofurazan↗
PubMed1981

Secretion from rat basophilic leukaemia cells induced by calcium ionophores. Effect of pH and metabolic inhibition.

Previous experiments on the functional properties of rat basophilic leukaemia cells showed a major anomaly when compared to normal mast cells: though IgE-mediated secretion was dependent on external Ca2+ with both types of cells, substantial non-cytotoxic release with ionophore A23187 could be demonstrated with the normal cells but not with the tumour cells. We now show that when the pH of the incubation medium is increased to 8 it is possible to obtain excellent Ca-dependent, non-cytotoxic secretion from tumour basophils with the ionophores A23187 and ionomycin. These results provide further evidence that secretion from the tumour cells occurs via a mechanism similar to that used by normal mast cells and basophils. Experiments with metabolically inhibited tumour cells suggest that their unusual sensitivity to the cytotoxic effects of Ca2+ ionophores may be related to their ability to sequester intracellular calcium. Changes in the conditions of cell culture appeared to produce substantial and at least partially reversible changes in responsiveness to IgE-mediated triggering and ionophores.

Animals↗
PubMed1981

Effect of age on mast cell granules.

Padawer has proposed that rat mast cells in the peritoneal cavity have an extended lifespan and under normal conditions exhibit little turnover of their secretory granules. We have examined several constituents of the granules as part of a study of the structure and function of these organelles. The previously described increase in volume of mast cells with age of the rats from which the cells are obtained is associated with an increase in the quantity of histamine, heparin, beta-glucuronidase and mast cell protease. While the former 3 granule components increase in parallel with mast cell volume, the increase in protease between 3- and 6-month-old rats is in excess of cell volume and the other 3 granule component. Granules from rats 1 month or less in age tend to be more difficult to isolate with their surrounding membranes intact.

Aging↗
PubMed1981

Mast cell restoration. A study of the rat peritoneal mast cells after depletion with polymyxin B.

The recovery of mast cells in adult rats after depletion induced by polymyxin-B has been studied. At days 17-18 after depletion the number of identifiable mast cells in the peritoneal fluid reached 3 X 10(6) cells/rat. Mast cell granule constituents such as histamine, heparin, mast cell protease and beta-glucuronidase increased steadily during the observation period, whereas the amount of N-acetyl-beta-glucosaminidase decreased during the first 2 weeks and was thereafter constant. At 2 weeks after depletion the peritoneal mast cells were biochemically restored. From 14 to 34 days (end of experimental period) cell growth occurred with a simultaneous accumulation of the various mast cell granule constituents.

Acetylglucosaminidase↗
PubMed1980

The presence of mast cell granules in rat parotid secretory granule preparations.

Rat parotid secretory granule preparations contain, in addition to the acinar secretory granules, a second type of granule. Whereas the acinar granules lyse under hypotonic conditions, this second type of granule does not, thus providing a means for obtaining a fraction sufficiently enriched in these granules to allow for their characterization. In the present study, these granules are shown to possess demonstrable chymotrypsin-like enzyme activity. In the intact rat parotid, such activity is shown by histochemical methods to be present in the numerous mast cells residing in the connective tissue stroma, but no such activity exists in any of the parenchymal cells. On the basis of their electron microscopic appearance, enzyme activity, and physical characteristics it is concluded that the second type of granule present in rat parotid secretory granule preparations originates from stromal mast cells rather than from parenchymal cells.

Animals↗