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G Bennett

Publications and source records attributed to G Bennett.

At least 37 records · Page 2Linked to original sources
PubMed1989

Morphological and functional characteristics of myocytes isolated from human left ventricular aneurysms.

Isolated single myocytes were prepared from myocardium of developing ventricular aneurysms and from myocardium within the scar of chronic ventricular aneurysms. The morphology and function of the individual cells were compared. The cells from developing aneurysms were rod-shaped, with a distinct sarcomeric structure, but did not contract even in the presence of high calcium concentrations. The sarcomere length was significantly higher than that of cells from chronic aneurysms and approached the theoretical point at which no contraction can occur. Cells from chronic aneurysms were either rod-shaped and contractile, or rounded due to hypercontracture of the myofilaments. Electron microscopy of cells from developing aneurysms confirmed the presence of elongated sarcomeres, a loss of the actin-myosin interdigitation, and damage to the contractile proteins which was particularly evident in the thin filaments. Cells with similar characteristics have also been isolated from a ruptured, ischaemic papillary muscle. These changes, which are due either to ischaemia or to overstretching of cells, may account for the weakness of the wall of developing aneurysms and be a cause of rupture or enlargement.

Adult↗
PubMed1989

Ultrastructural localization of CMPase, TPPase, and NADPase activity in neurons, satellite cells, and Schwann cells in frog dorsal root ganglia.

Sections of bullfrog dorsal root ganglia were analyzed for cytidine monophosphatase (CMPase), thiamine pyrophosphatase (TPPase), and nicotinamide adenine dinucleotide phosphatase (NADPase) activity, and the distributions of these enzymatic activities were compared with those traditionally found in other cell types (e.g., CMPase: Golgi trans-sacculotubular network; TPPase: trans-Golgi saccule(s); NADPase: intermediate Golgi saccules). In the present study, CMPase activity in neurons was localized mainly to the Golgi trans-sacculotubular network and lysosomes, but sometimes also occurred at the ends of the trans and most distal intermediate Golgi saccules. A similar distribution was found in satellite and Schwann cells. TPPase activity in neurons occurred not only in the trans-Golgi saccule but also in the trans-sacculotubular network, lysosomes, and scattered tubular elements. In satellite and Schwann cells, activity was found in both the trans saccule and trans-sacculotubular network, and substantial activity often appeared in the more distal of the intermediate saccules. NADPase activity in neurons was usually absent from the intermediate Golgi saccules and was confined to the trans-sacculotubular network and lysosomes; however, activity was sometimes also found in the intermediate and/or trans-Golgi saccules. In satellite and Schwann cells, activity appeared consistently in both the trans-sacculotubular network and intermediate saccules, as well as in lysosomes. These distributions, especially in the case of TPPase and NADPase, differ substantially from the most frequently reported localizations of the above enzymes, indicating that the Golgi complex may exhibit considerable plasticity of structure and function in different cell types.

Animals↗
PubMed1989

An enzyme-linked immunosorbent assay to study human relaxin in human pregnancy and in pregnant rhesus monkeys.

A sensitive and specific double-antibody enzyme-linked immunoassay, using a synthetic analogue of human relaxin for standard and immunogen, was developed for the measurement of human relaxin (hRLX) in serum and plasma. No cross-reactivity was observed for human insulin, human insulin-like growth factor-I, hGH, human chorionic gonadotropin, hFSH, hLH or human prolactin. The assay was used to monitor RLX concentrations in samples from men, non-pregnant and pregnant women, and in pregnant rhesus monkeys infused with hRLX. RLX was not detected in serum from men nor from non-pregnant women, while a concentration of 600 ng/l was measured in pooled sera from two pregnant women (pregnancies achieved by in-vitro fertilization). Immunoreactive RLX (1.1 micrograms/g) was found in human corpora lutea taken from ectopic pregnancies at 7 weeks. In an experiment with a pregnant rhesus monkey infused with human RLX analogue, less than 1.5% of the maternal concentration was measured in the fetal circulation. Even though preliminary, these data suggest a low level of transfer of human analogue relaxin across the placenta in a rhesus monkey. Further studies of the physiology of RLX in human pregnancy will be facilitated by the availability of this immunoassay.

Amino Acid Sequence↗
PubMed1989

The assessment.

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Adult↗
PubMed1988

Synthesis of lens capsule and plasma membrane glycoproteins by lens epithelial cells and fibers in the rat.

The lens of the eye possesses a capsule which is a greatly hypertrophied basement membrane. To investigate the synthesis of glycoproteins destined for this capsule, 3H-fucose was injected into the vitreous body of intact rats weighing approximately 200 gm. The animals were killed from 10 min to 14.5 months later, and their lenses were processed for electron microscope radioautography. At 10 min after injection, more than 58% of the silver grains were localized to the Golgi apparatus of the lens epithelial cells. By day 1, the heaviest sites of reaction were the plasma membrane (more than 50% of total label), the basal cytoplasm, and the adjacent lens capsule, where a heavy band of reaction was seen. The remainder of the capsule exhibited a lighter diffuse reaction. In the lens fibers, the label was at first localized to clusters of vesicles but then migrated to the plasma membrane and to the region of the capsule adjacent to the basal surface of these fibers. Light microscope radioautographs of the lens capsule at later time intervals revealed that by 1 month after injection the diffuse reaction had disappeared, and only the strongly labeled band remained. By 14.5 months after injection, this band had migrated partially across the lens capsule, but the capsule itself had increased considerably in thickness. On the other hand, the distance between the labeled band and the free edge of the capsule had decreased from that seen at the time of injection.

Animals↗
PubMed1988

Mutations in human lymphocytes studied by an HLA selection system.

Human lymphocytes mutated at the HLA-A2 or HLA-A3 alleles were enumerated and studied by primary selection using antibody and complement, followed by limiting dilution cloning and secondary selection using immunofluorescence or antibody and complement. The geometric mean frequency of in vivo mutant lymphocytes was 3.08 X 10(-5) for the HLA-A2 allele and 4.68 X 10(-6) for the HLA-A3 allele. Mutagenesis by X-radiation or mitomycin produced a dose-related increase in mutant frequency. HLA-B phenotyping and Southern Analysis of the HLA-A gene suggested that mutation was frequently due to gene deletion, which was often substantial.

Alleles↗
PubMed1988

Radioautographic and cytochemical studies on the synthesis and intracellular transport of glycoproteins.

SUBCOMPARTMENTALIZATION OF GOLGI APPARATUS. There is much evidence that the Golgi apparatus may consist of various subcompartments which differ from one another in morphology, biochemical content and function. These subcompartments do not always have the same properties in different cell types, however, and may change properties in one cell type at different times. Important glycosyltransferases are distributed throughout the Golgi stack in some cell types, indicating that subcompartmentalization is not essential for the process of glycosylation in this organelle. PRESENCE OF GLYCOPROTEINS OUTSIDE OF THE SECRETORY-ENDOCYTIC PATHWAY. Preliminary biochemical, cytochemical and radioautographic evidence indicates that glycoproteins may exist outside of the secretory-endocytic pathway. The presence of radioautographic reaction over the nucleoplasm of Schwann and satellite cells as early as 5 minutes after 3H-fucose administration suggest either that fucosylated glycoproteins must migrate very rapidly to this location or that fucosylation occurs within the nucleoplasm itself.

Animals↗
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.

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Alzheimer Disease↗