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Biomedical subjects

G D Bloom

Publications and source records attributed to G D Bloom.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effects of norepinephrine on transmembrane calcium transport in rat mast cells.

The effect of norepinephrine on transmembrane passage of calcium in rat peritoneal mast cells, was studied in an in vitro system. It was found the histamine release from mast cells induced by the ionophore A 23 187 in normal calcium medium and compound 48/80 in a calcium-free medium was suppressed by 10(-3) M norepinephrine but not at concentrations in the range 10(-5)-10(-4) M. When the secretory process is totally dependent on the presence of calcium in the incubation medium, i.e. calcium-depleted cells, 10(-5) M norepinephrine suppresses the histamine release induced by low concentrations of compound 48/80. The effect of norepinephrine (10(-5) M) on strontium-induced "spontaneous' histamine release was also studied. It was found that norepinephrine (10(-5) M) totally inhibits the progressive histamine release induced by strontium. It is possible to evoke secretion in a calcium-free medium, and subsequent introduction of Ca2+ will result in optimal histamine release. This demonstrates a secretory process in which we can distinguish between utilization of endogenous versus exogenous calcium. The release that is dependent on extracellular calcium is inhibited by norepinephrine (10(-5) M). These data indicate that the suppressive effect of norepinephrine (concentrations less than 10(-3) M) on histamine release from rat mast cells is due to an interference in transmembrane passage of calcium.

Animals↗
PubMed1979

Effect of norepinephrine on in vitro histamine release from rat mast cells.

The effect of norepinephrine on compound 48/80-induced histamine release from rat peritoneal mast cells, was studied in an in vitro system. It was found that norepinephrine, within the concentration range 10(-5)--10(-3) M, exerts a significant, dose-related, repressive effect. This effect is greatly potentiated by the beta-antagonist practolol (10(-3) M), throughout the concentration range of 10(-11)--10(-3) M norepinephrine. Methoxyamine, a selective alpha-adrenergic agonist, also represses histamine release in a dose-dependent manner; however, it is not as potent as norepinephrine. The present results would seem to suggest that the repressive effect on histamine release, observed within a low concentration range of norepinephrine, may be due to alpha-adrenoceptor mechanisms.

Animals↗
PubMed1979

Enigma of disodium cromoglycate action on mast cells.

In rat peritoneal mast cells, disodium cromoglycate showed no inhibitory effect on histamine release values if the cells were preincubated with the drug for 40 min prior to stimulation with antigen, compound 48/80 or ATP. If the drug was added simultaneously with antigen or a low dose of compound 48/80, a repression of histamine release occurred. No such effect was noted if ATP was employed as histamine liberator.

Adenosine Triphosphate↗
PubMed1979

Quantitative structural analysis and the secretory behaviour of the rat parotid gland after long and short term isoprenaline treatment.

Isoprenaline (IPR) was administered as daily subcutaneous injections into newborn rats for a period of 9 weeks (long-term treatment) and into 8 week-old rats for 10 days (short-term treatment). Both the parotid and the submandibular glands increased five- to six-fold in weight in the two groups due to hypoertrophy as well as to hyperplasia. The parotid glands were subjected to electron microscopic stereological analyses and to in vitro secretory studies. The results were compared with non-treated controls. Whereas mean total cell volume in the latter was 807 microns 3 it amounted to 5804 microns 3 in glands from long-term IPR-treated rats. A striking increase in size and number of cytoplasmic granules was noted after IPR treatment; there was also a marked decrease in granule electron density as compared with control cells. Granule volume density was 31.2 +/- 1.8% in controls and 58.0 +/- 1.5% in long-term IPR-treated rats. The increase in volume density, however, was accompanied by a relative decrease in amylase and cyclic AMP contents. On a percentage basis, the basal secretion of amylase from incubated IPR-treated parotid glands was markedly higher (roughly twice) than that of control glands; the absolute release of amylase into the medium, however, was only slightly increased. Basal secretion was not energy requiring, which would suggest a passive diffusion. Stimulation by beta-adrenoceptor agonists, including beta 1 and beta 2 selective agents, had no or only a small stimulatory effect in vitro on IPR-treated glands. Dibutyryl cyclic AMP was effective in controls but not in treated glands. Cholinergic stimulation caused a considerable amylase release from glands of IPR-treated rats; this release was comparable to that obtained in controls. The results suggest that superstimulation of the beta-adrenoceptor leads to a decreased sensitivity for adrenergic agonists. This may be due to membrane changes (e.g. modified receptor sites) and/or to an altered intracellular metabolism (e.g. a modified turnover of cyclic nucleotides).

Adrenergic beta-Agonists↗
PubMed1978

Mast cells of the Mongolian gerbil (Meriones unguiculatus). Morphology, histamine content and role of calcium in the histamine release process.

The fine structure, histamine conten;, and role of calcium in the histamine release process were studied in peritoneal mast cells of the Mongolian gerbil (Meriones unguiculatus). Stereological methods were applied to obtain quantitative data on their structure. The findings were compared with results obtained from the same type of cells in the rat. The gerbil mast cells were smaller in size (mean volume 242 micrometer3 vs 684 micrometer3 in the rat), and the nuclei were also smaller (55 micrometer3 vs 102 micrometer3). There were fewer granules in the gerbil mast cells and their diameter averaged 0.54 micrometer as compared with 0.78 micrometer in the rat). Only 20% of the cytoplasm of the gerbil mast cell was occupied by granules. This figure is approximately one third of that obtained in rat mast cells. The mean total histamine content per cell was 9 pg as compared to an estimated 30 pg/cell in rats. Calculated molar concentration of histamine in the mast granules, however, was higher in the gerbil than in the rat (2.3 M vs. 0.9 M). The mast cells of the gerbil were much more sensitive to the histamine-releasing agent compound 48/80 and in contrast to rat mast cells they were entirely dependent on calcium for their amine release. The fine cellular structure of both species showed multitudinous plasma membrane folds on their surfaces. In addition gerbil mast cells showed extensive surface invaginations. Apart from this were no major differences at the ultrastructural level between unstimulated cells of the two species. During histamine release, however, the mast cells of the gerbil showed a much greater tendency to form large, intracytoplasmic vacuoles and a decreased propensity for fusion of perigranular and plasma membranes (exocytosis) as compared with the corresponding cells in the rat.

Animals↗
PubMed1977

Distribution of mucosubstances in adenoid cystic carcinoma.

The distribution of mucosubstances in adenoid cystic carcinoma was investigated, and an attempt was made to characterize histochemically the various mucosubstances present. For these purposes the high iron diamine technique (HID), as well as the Astra blue, aldehyde fuchsin and Alcian blue staining methods were employed. Alcian blue was further combined with the periodic acid-Schiff (PAS) technique, the Alcian blue being applied at pH levels between 0.5 and 2.5. In addition the effect of neuraminidase and hyaluronidase treatment as well as methylation and acid hydrolysis procedures on the staining qualities were studied. Acidic mucosubstances with varying histochemical properties were present in different structures of the neoplasm. The characteristic pseudocyst, a major structural component of the neoplasm, stained strongly with HID, Astra blue, aldehyde fuchsin and Alcian blue at low pH. These staining reactions were markedly suppressed by hyaluronidase treatment, and are apparently attributable to the presence of chondroitin 4- and/or 6-sulfate. Employing the Alcian blue-critical electrolyte concentration technique, the basophilia of the pseudocysts was suppressed at a concentration of 0.5-0.6 M MgCl2, which might indicate polysaccharides of relatively low degree of sulfation. An additional, non-sulfated acid mucin could also be demonstrated in these structures. In certain duct and gland like structures of the tumours, a change in staining pattern from blue or blue-red to red could be observed after exposure of the sections to neuraminidase and subsequent staining with the Alcian blue (pH 2.5)-PAS sequence. Similar observations were also made when the pH of the Alcian blue was lowered to 1.5-1.0, as well as after acid hydrolysis. These findings afford evidence for the presence of a neuraminidase susceptive sialomucin in certain epithelial secretions of the tumor. At the ultrastructural level the replicated basement lamina of the pseudocysts displayed a strong positive reaction with the PA-CrA-silver staining technique. Furthermore, amorphous material within the lumina of small duct like structures also displayed a positive reaction. The amorphous material of the cystic compartments was less reactive.

Carcinoma, Adenoid Cystic↗
PubMed1977

Ultrastructural cytochemistry of the secretory granules of the hamster submandibular gland.

The ultrastructure and cytochemistry of the secretory granules of the male hamster submandibular salivary gland were studied; After fixation in glutaraldehyde followed by osmium tetroxide the granules exhibit a characteristic bipartite substructure, with an electron lucid crescenteric rim and a more dense central core. A differentiation into two regions of the granules could also be visualized in specimens primarily fixed in Millonig's osmium tetroxide or in potassium permanganate. The electron lucid peripheral portion of the membrane bounded secretory granules further displays a strong positive reaction after staining of ultrathin sections with the periodic acid-chromic acid-(PA-CrA)-silver technique. The strong periodate reactivity of the rim relative to the core, suggests a difference in mucin composition of the two granule regions. With the PA-CrA-silver straining technique a positive reaction was also observed within the Golgi apparatus of the acinar cells.

Animals↗
PubMed1977

Some ultrastructural features of acinic cell carcinoma.

The ultrastructure of an acinic cell carcinoma, occurring in the left parotid gland of a 52-year-old woman and causing a total facial nerve paralysis, is described. Histologically the tumour consisted of numerous granulated cells arranged around lumen-like openings and resembling a secretory system. Furthermore, areas with agranulated cells growing in a solid pattern were also encountered. In the electron microscope the cytoplasmic granules of the tumour cells displayed a varied appearance. Granules of a dense homogeneous type, as well as granules with a more electron lucid appearance were observed. Furthermore, numerous cytoplasmic granules displayed a bipartite structure with a dense central and a more electron lucid outer zone. In specimens primarily fixed in OSO4 or KMnO4 the granules displayed a 'leached out' appearance. The membrane-bounded of the tumour cells also showed a strong positive staining with the periodic acid-chromic silver technique of Rambourg et al. (1969). Other characteristic ultrastructural features of the tumour cells studied were: Smooth cell surfaces, the presence of subplasmalemmal bands of electron dense material, desmosome-like attachment areas between cells and grossly altered mitochondria.

Carcinoma↗
PubMed1977

Glucose-stimulated and La3+-nondisplaceable Ca2+ pool in pancreatic islets.

To study intracellular pools of calcium tissue specimens from noninbred ob/ob mice were labeled with 45Ca2+ and subsequently washed with La3+. D-glucose, 20 mM, enhanced the labeling of the La3+-nondisplaceable calcium in pancreatic islets but not in pieces of exocrine pancreas or liver. The disappearance of 45Ca2+ from labeled islets was accelerated by the ionophore, X-537A, but not by dibutyryl cyclic AMP, theophylline, or pentobarbital. On fractionation of 45Ca2+-labeled islets, the greatest radioactivity per unit of protein occured in a fraction rich in insulin secretory granules. The radioactivity of this fraction was higher after the islets had been loaded with 45Ca2+ in the presence of 20 mM glucose as compared to 3 mM glucose. It is concluded that the secretory granules make up a considerable part of the glucose-sensitive calcium store in the beta-cells.

Animals↗
PubMed1977

Intra-acinar nerve terminals in four rodent parotid glands.

The distribution of autonomic nerves was studied at the ultrastructural level in guinea pig, hamster, mouse and rat parotid glands employing potassium permanganate fixation/staining technique. In the periacinar connective tissue numerous unmyelinated nerves were observed in all the glands examined. Two types of axonal enlargements were encountered, one contained small, dense-cored vesicles (500-600 A in diameter) as well as a few large (approximately 1,000 A in diameter), the other exhibited numerous agranular vesicles (500-600 A in diameter). In all glands, axons devoid of Schwann cell investment were visualized at the base of the acinar cells, inside the basement membrane and in intimate contact with gland cells. In addition, axonal enlargements of both types were encountered in the intervening space between neighbouring acinar cells. Whereas nerve terminals within the gland epithelium were extremely common in the rat, mouse and hamster, their frequency was much lower in the guinea pig. In addition, only parenchymal varicosities of the adrenergic (dense-cored vesicles) type were encountered in the latter species. No intraepithelial nerves were observed in the striated ducts. However, axonal enlargements were present in the subepithelial connective tissue and were most numerous in the hamster parotid gland. The above findings confirm the dual innervation of the serous acinar cells of the guinea pig, hamster, mouse and rat parotid glands by both parasympathetic and sympathetic nerves. Furthermore, there exists a close membrane-to-membrane contact between autonomic nerves and salivary gland cells.

Animals↗
PubMed1976

An electron microscopic study on the autonomic innervation of the rabbit parotid gland.

As visualized in the electron microscope, the parotid gland of the rabbit has a dual innervation. Both adrenergic and cholinergic nerves are equally distributed in the parenchyma and often run together within the same nerve bundle. Nerve terminals are observed not only subjacent to the basement membrane but interposed between the latter and the acinar cells, where they establish a close membrane to membrane contact with the latter.

Animals↗
PubMed1976

Effect of cholecystokinin-pancreozymin (CCK-PZ) on glycoprotein secretion from mouse gallbladder epithelium: an ultrastructural and cytochemical study.

Structural changes in the gallbladder epithelial cells of the mouse were studied following in vivo and in vitro stimulation of the gallbladder with the gastrointestinal hormone cholecystokinin-pancreozymin (CCK-PZ). Signs of increased secretory activity were observed within the first 2-3 min after hormone administration. At the ultrastructural level, best visualized with the PA-CrA-silver technique, granule discharge was observed, as was an overall increase in size of the granules. After prolonged in vitro incubation or repeated in vivo stimulation, there was an almost total depletion of secretory granules. This phenomenon is accompanied by an enhanced uptake of extracellular thorium dioxide by endocytotic vesicles at the apical cell surface. An exocytosis-endocytosis coupling mechanism may be important for membrane conservation in the gallbladder epithelial cells. The findings establish that the hormone CCK-PZ stimulates the secretion of glycoproteins from the mouse gallbladder epithelium.

Animals↗
PubMed1976

Autolysis of Neisseria gonorrhoeae.

Autolysis of Neisseria gonorrhoeae was studied under different conditions. It was found that low pH and temperature, as well as the presence of divalent cations, spermine, sucrose, and polyvinylpyrrolidone, stabilized nongrowing gonococci. Ethylenediaminetetraacetic acid alone promoted lysis, whereas lysozyme had only a limited additive effect. The autolytic behavior of gonococci appears to be connected with their prolonged cell division process. The relative dependence on the outer membrane and the peptidoglycan layer for the mechanical stability of gonococci is discussed.

Bacteriolysis↗
PubMed1976

Septum formation-defective mutant of Escherichia coli.

Mutants of Escherichia coli defective in septum initiation, as well as in septum formation were obtained spontaneously, without mutagenic treatment, by selection of rifampin-tolerant mutants of an antibiotic-permeable strain carrying the envA mutation. The disturbed phenotype was in all mutants aggrevated the low incubation temperatures. One allele, sefA1, was studied in detail. Septum initiation, as well as septum formation, was promoted by high cell densities or by the addition of low concentrations of certain antibiotics, e.g., rifampin and chloramphenicol, to low-density cultures. The observed rifampicin depencence was studied in detail. These experiments indicated that a very modest shift-down situation suppressed the phenotype and enabled constrictions to proceed to cell separation. The rifampicin sensitivity of the partially purified deoxyribonucleic acid polymerase was not affected by the sefA1 allele, which is located close to proA and is thus distinct from envA. Growth parameters during the shift to 25 degrees C were followed in a transductant carrying HE SEFA1 allele. This constriction was characteristically blunt and did not lead to cell separation. At the time of formation of these frozen constrictions, clear zones representing a separation of wall from cytoplasmic membrane appeared. These polar tips did not inhibit expansion of the cell envelope. The phenotype of cells carrying the sefA1 allele suggests a disturbed relationship among protoplasm expansion, envelope growth, and septum formation. It is thought that the blunt constrictions observed are caused by an inability of the two septal peptidoglycan layers to fuse during an early stage of septation.

Cell Division↗
PubMed1976

Cell envelope of Neisseria gonorrhoeae. A comparative study with Escherichia coli.

The cell envelope of Neisseria gonorrhoeae was studied and compared to that of Escherichia coli. Outer membranes (OM) from both species were isolated by an identical method, and subjected to biochemical analysis. Differences in OM structure were sought that might explain the dissimilarity in OM permeability of these two species. The most pronounced difference appeared to reside in the OM proteins as judged by gel electrophoresis. Moreover, gonococcal OM proteins appeared to be more hydrophilic than those of E. coli.

Bacterial Proteins↗
PubMed1976

Effects of fasting and refeeding on secretory granules of the mouse gallbladder epithelium. A quantitative electron microscopic study.

Mouse gallbladder epithelial cells were studied with the electron microscope during fasting and refeeding. Morphometric data were obtained from randomly selected epithelial cells of normal starved (12, 24, and 48 hr) and refed (12 hr) mice. Deprivation of food significantly diminishes the volume density of the mucinous secretory granules by about 70% after 48 hr of fasting. Upon refeeding, this secretory granule parameter increases significantly ( 2.5 times). Stereological measurements were also performed on nuclei, mitochondria, and lysosomes, but no major morphometric changes were observed in these organelles. The findings suggest that a basal secretion of mucin granules occur in the mouse gallbladder, irrespective of the animal's nutritional state and that this discharge during starvation exceeds the formation of new granule material. The findings are discussed in relation to effects of fasting and refeeding on other secretory cell systems.

Animals↗
PubMed1975

Dopamine-induced amylase secretion from guinea-pig submandibular gland.

1. The effects of dopamine, 5-hydroxydopamine (5-OHDA) and noradrenaline on amylase secretion from the guinea-pig submandibular gland were investigated under in vitro conditions. 2. All three amines greatly enhanced amylase secretion. Blockade of dopamine beta-hydroxylase did not inhibit the response to dopamine. 3. Noradrenaline and dopamine stimulated amylase release from salivary glands of reserpine-treated animals, whereas 5-OHDA had no stimulatory effect on secretion in guinea-pigs pretreated with reserpine. 4. Haloperidol completely inhibited dopamine-induced enzyme discharge, but did not affect noradrenaline-initiated secretion. 5. Apomorphine caused a slight enzyme release by itself; it diminished the dopamine secretory effect, but did not modify that of noradrenaline. 6. Pimozide and fluspirilene attenuated the dopamine-induced enzyme discharge, but compared with haloperidol they were less effective. 7. It is concluded that dopamine exerts a secretagogic action different from that of noradrenaline. The possible presence of a specific dopamine receptor in salivary glands is discussed.

Amylases↗