Search PubMed⌕ Search

Biomedical subjects

G Bennett

Publications and source records attributed to G Bennett.

At least 109 records · Page 6Linked to original sources
PubMed1987

Synthesis and migration of 3H-fucose-labeled glycoproteins in the retinal pigment epithelium of albino rats, as visualized by radioautography.

3H-fucose was injected into the vitreous body of the eye(s) of 250-gm rats, which were then killed by means of an intracardiac perfusion with glutaraldehyde after intervals of 10 min, 1 and 4 hr, and 1 and 7 days. The eyes were removed and further fixed, and pieces of retina were processed for light and electron microscope radioautography. Light microscope radioautography showed that the pigment epithelial cells actively incorporated 3H-fucose label. The intensity of reaction peaked at 4 hr after injection of the label and then slowly declined. Quantitative electron microscope radioautography revealed that, at 10 min after 3H-fucose injection, over 70% of the label was localized to the Golgi apparatus, indicating that fucose residues are added to newly synthesized glycoproteins principally at this site. With time the proportion of label associated with the Golgi apparatus decreased, but that assigned to the infolded basal plasma membrane, the apical microvilli, and various apical lysosomes increased. These results indicate that in retinal pigment epithelial cells newly synthesized glycoproteins continuously migrate from the Golgi apparatus to lysosomes and to various regions of the plasma membrane. In this case, the membrane glycoproteins may play specific roles in receptor functions of the basal plasma membrane or phagocytic activities at the apical surface. Very little label migrated to Bruch's membrane, indicating either a very slow turnover or a paucity of fucose-containing glycoproteins at this site.

Animals↗
PubMed1987

Loss of microtubules and alteration of glycoprotein migration in organ cultures of mouse intestine exposed to nocodazole or colchicine.

Explants from mouse jejunum were cultured for 3-7 h in the absence (control) or presence of colchicine (100 micrograms/ml) or nocodazole (10 micrograms/ml). In recovery experiments, explants were cultured in fresh medium for an additional period. To label glycoproteins, 3H-fucose was added during the last 3 or 6 h of the initial culture or recovery period. Subcellular fractionation studies revealed that colchicine and nocodazole inhibited migration of labelled glycoproteins to the brush border (P2) by 40-45%. Radioautographic studies of absorptive cells showed that colchicine and nocodazole inhibited labelling of the microvillous border by 67% and 87%, while labelling of the basolateral plasma membrane increased by 114% and 275%. Immunocytochemical studies revealed that both colchicine and nocodazole caused the virtual disappearance of the microtubular network in the absorptive cells. It is possible that some glycoproteins normally destined for the microvillous border are rerouted to the basolateral membrane. The observed loss of microtubules after drug treatment suggests that microtubules may play a role in the intracellular migration of membrane glycoproteins. Additional support for this concept is provided by the fact that in recovery experiments the distribution of label returned to control values after the microtubular network became re-established.

Animals↗
PubMed1987

Effect of monensin on cell ultrastructure and glycoprotein migration in adult mouse jejunal epithelium in organ culture.

Explants from adult mouse jejunum were cultured for 3 h in a medium which contained both 3H-fucose (10 or 25 microCi/ml) and monensin (100 microM) or 3H-fucose only (control). Radiochemical analysis of cell fractions showed that 3H-fucose labelling of the brush border fraction decreased 42% in monensin-treated explants, suggesting that in absorptive cells the intracellular transport of newly synthesized glycoproteins to the apical plasma membrane had been inhibited. Electron-microscopic examination of treated explants revealed a variation in response to the drug from region to region. In some areas, both absorptive and goblet cells exhibited little alteration. In others, the Golgi cisternae of both absorptive and goblet cells were entirely replaced by large vacuoles, and in the latter cell type, the cisternae of the rough endoplasmic reticulum were greatly distended. Electron-microscopic radioautographic analysis showed that in absorptive and goblet cells exhibiting little morphological change, intracellular transport of newly synthesized glycoproteins was similar to that in controls. In regions where absorptive cells exhibited extensive Golgi modifications, intracellular transport remained normal in some cases; more often-however, there was a marked inhibition (over 70%) of transport of labelled glycoproteins to the apical surface. Transport to the basolateral membrane was never affected. In goblet cells exhibiting modifications of the Golgi apparatus and rough endoplasmic reticulum, no incorporation of 3H-fucose label in the Golgi apparatus occurred, suggesting a block of intracellular transport proximal to the site at which 3H-fucose is added. In absorptive cells, this does not appear to be the case, since the level of 3H-fucose incorporation in all treated cells remained similar to that in controls.

Animals↗
PubMed1987

Face burn reconstruction--does early excision and autografting improve aesthetic appearance?

Despite improvements in functional rehabilitation secondary to better control of scar and contractures, aesthetic rehabilitation of the extensively burned face has remained a difficult problem. This study was undertaken to evaluate both technique and aesthetic results of early excision and split thickness autografting (STAG) of full skin thickness face burns. Twenty-five patients with full skin thickness face burns were operated on between days 4 and 14 post-burn. Thirteen patients had excision and STAG in one stage. Twelve patients had a two-stage procedure-excision and coverage with a biological dressing followed 24-72 h later by STAG. Seven of these patients had a pressure dressing in the form of a silicone face mask applied at the second stage. Early cosmetic results were encouraging in all patients. Twenty-five per cent of patients later required either contracture release or skin resurfacing. Preliminary results are encouraging and warrant evaluation by surgeons at other centres. When early excision of full skin thickness face burns is undertaken, cautious optimism as to the ultimate aesthetic result, both by the surgeon and the patient, is advisable.

Adolescent↗
PubMed1987

Autoradiographic demonstration of in vivo sialylation of endogenous acceptors at the microvillar surface of intestinal columnar cells after intraluminal administration of CMP-[3H]-sialic acid.

To investigate the presence of glycosyltransferase activity at the apical surfaces of columnar cells in small intestine, CMP-[3H]-sialic acid was injected into the lumen of a ligated segment of rat jejunum; 5 min later the tissue was fixed and processed for light microscopic autoradiography. After a 3-6-month exposure, an autoradiographic reaction appeared over the microvillar surfaces of columnar cells, indicating the presence of surface sialyltransferase activity accompanied by endogenous acceptors. When CMP-[3H]-sialic acid was injected into the posterior chamber of rat eye or the lumen of mouse gallbladder, no autoradiographic reaction was observed at the surfaces of the cells facing these cavities. After injection of UDP-[3H]-galactose into the same three sites, an autoradiographic reaction was observed in the Golgi regions of the various epithelial cells, but not along their apical surfaces. Competition experiments using unlabeled galactose indicated that [3H]-galactose had been released from the nucleotide and had entered the cells to be incorporated into the Golgi apparatus.

Animals↗
PubMed1987

Memory clinics.

Explore the source record for details and available documents.

Alzheimer Disease↗
PubMed1987

Correlative clinical biochemistry and hematological profiles of laboratory-bred Bolivian squirrel monkeys (Saimiri sciureus).

Twenty-five clinical and biochemical parameters were determined on 17 normal, male, laboratory-bred Bolivian squirrel monkeys (Saimiri sciureus). Parallel hematologic parameters were conducted. The correlation of biochemical and hematological observations and the distribution characteristics, range, and standard error of the mean were determined. The purpose of the present communication is to establish baseline biochemical values for laboratory-bred squirrel monkeys and to present a correlative comparison between selected cellular elements and major blood electrolytes.

Animals↗
PubMed1986

Radioimmunoassay of relaxin in pregnancy with an analogue of human relaxin.

A radioimmunoassay for relaxin was developed in which a synthetic analogue of human relaxin was used as standard, tracer, and immunogen. Relaxin could not be measured in sera from men or non-pregnant women, but was measurable in pregnant women from the tenth week of gestation until term. Concentrations ranged from 0.19-1.18 ng/ml, with highest levels measured in the first trimester.

Animals↗
PubMed1986

Synthesis and migration of 3H-fucose-labeled glycoproteins in the ciliary epithelium of the eye: effects of microtubule-disrupting drugs.

3H-fucose was injected intravenously or intravitreously into albino rats. After time intervals of 10, 40, and 50 min, 1, 1.5, and 4 hr, 1, 3, and 7 days, and 1, 2, and 4 weeks after injection, the animals were sacrificed by intracardiac perfusion with glutaraldehyde. Samples of the ciliary body were prepared for light and electron microscope radioautography. Light microscope autoradiographs showed that the cells of both the inner and outer layers of ciliary epithelium actively incorporated 3H-fucose label in a reaction that peaked in intensity at 4 hr after injection, and then progressively declined. Electron microscope radioautographs revealed that, at early time intervals, most of the label was localized to the Golgi apparatus. With time, the plasma membrane of both cell types became increasingly labeled, and accounted for 60-70% of the total silver grains at 4 hr after injection. Adjacent to the basal cell surface of the inner layer cells, the fibers of the zonula became increasingly labeled from 1.5 hr onwards, providing strong evidence that these cells secrete glycoproteins to the zonula. When vinblastine was administered 30 min before 3H-fucose injection, followed by sacrifice 1.5 hr later, a much larger proportion of label remained localized to the Golgi apparatus than in controls, and the plasma membrane and zonula were much less labeled. These results suggest that, as documented in other cell types, microtubules may play a role in the intracellular transport of membrane and secretory glycoproteins in these cells.

Animals↗
PubMed1986

Presence of glycoproteins in the cell nucleus as shown by radioautographic studies after administration of [3H]fucose and [3H]galactose.

Dorsal root ganglia were removed from adult bullfrogs and incubated with [3H]fucose for intervals from 15 min to 1 h, followed by fixation. Some ganglia were post-incubated in the absence of [3H]fucose for up to 17 h. In additional in vivo experiments, young frogs were injected with [3H]fucose, and killed 30 min or 1 h later, and then ganglia were removed and fixed. Electron microscope radioautographs of the ganglia revealed an intense radioautographic reaction over the nuclei of Schwann and satellite cells as early as 5 min after initial exposure to [3H]fucose. At time intervals up to 2 h after initial exposure to [3H]fucose, the silver grains were evenly distributed over both the periphery and internal regions of the nucleus, while at 18 h they were localized to the cell periphery. In occasional cells, the perinuclear space was expanded in some areas and was the site of reaction. In young rats, injected with [3H]galactose and killed 15 min to 5 h later, electron microscope radioautographs revealed heavy reaction over the nuclei of duodenal villous and crypt columnar cells, in which the grains were evenly distributed over both the peripheral and internal regions. In mitotic cells, grains appeared to be associated with the condensed chromatin of forming chromosomes. These results provide strong evidence that glycoproteins exist in the nuclei of the above cell types and that they are actively renewed. The rapid appearance of nuclear reaction after initial exposure to [3H]fucose or [3H]galactose indicates that either these sugars are added to glycoproteins within the nucleus itself or that they migrate rapidly to this site after having been glycosylated elsewhere.

Animals↗
PubMed1985

Hematologic values of normal Bolivian squirrel monkeys (Saimiri sciureus): a comparison between wild-caught and laboratory-bred male animals.

Complete and differential blood counts were conducted on 23 male squirrel monkeys (Saimiri sciureus) of Bolivian origin. The sample included 9 laboratory-bred and 14 wild-caught adult monkeys weighing between 600 and 1,500 g. The means of total white blood cell (WBC) counts, total hemoglobin and hematocrits of laboratory-bred animals were found to be significantly different from those of wild-caught monkeys (p less than 0.01). Other hematologic parameters showed no significant differences between the two experimental groups. 3 of 14 (21.0%) wild-caught animals each had 1 reactive lymphocyte and 7% of the same group had 10 nucleated erythrocytes per 100 WBC. No reactive lymphocytes or nucleated erythrocytes were observed in laboratory-bred animals. The importance of these baseline data and the basis for the differences observed between laboratory and wild-caught monkeys are discussed within the context of experimental studies involving primates in which hematologic parameters are valuable.

Animals↗
PubMed1984

Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: I. Inhibition of glycoprotein migration in various rat cell types as shown by light microscope radioautography after injection of 3H-fucose.

Previous studies have shown that colchicine and vinblastine inhibit secretion in many cell types by interrupting the normal intracellular migration of secretory products. In the present work, radioautography has been used to study the effects of these drugs on migration of membrane and secretory glycoproteins in a variety of cell types. Young (40 gm) rats were given a single intravenous injection of colchicine (4.0 mg) or vinblastine (2.0 mg). At 10 min after colchicine and 30 min after vinblastine administration, the rats were injected with 3H-fucose. Control rats received 3H-fucose only. All rats were sacrificed 90 min after 3H-fucose injection and their tissues processed for light microscope radioautography. Examination of secretory cell types such as ameloblasts and thyroid follicular cells in control animals revealed reactions of approximately equal intensity over the Golgi region and over extracellular secretion products, while in drug-treated rats most of the reaction was confined to the Golgi region. In a variety of other cell types, including endocrine cells (e.g., hepatocytes) and cells generally considered as nonsecretory (e.g., intestinal columnar cells), reaction in control animals occurred both over the Golgi region and over various portions of the cell surface. In drug-treated animals, a strong Golgi reaction was present, but reaction over the cell surface was weak or absent. These results indicate that in many cell types, colchicine and vinblastine inhibit migration out of the Golgi region not only of secretory glycoproteins, but also of membrane glycoproteins destined for the plasma membrane.

Animals↗