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Biomedical subjects

R C Hunt

Publications and source records attributed to R C Hunt.

At least 73 records · Page 4Linked to original sources
PubMed1978

Lectins.

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Agglutination↗
PubMed1976

Asymmetric distribution of phosphatidylethanolamine in the membrane of vesicular stomatitis virus.

The membrane-impermeable reagent trinitrobenzenesulfonate has been shown to react only with the surface components of vesicular stomatitis virus (VSV) membranes. When the amount of phosphatidylethanolamine (PE) available to modification by trinitrobenzenesulfonate in intact virions was determined, it was found that 36% of the total membrane PE was converted to the trinitrophenyl derivative. The same proportion of the total membrane PE was reactive after removal of the surface glycoprotein by trypsin digestion, but disruption of the virus membrane by sonication rendered all of the PE reactive. These results indicate that PE is asymmetrically distributed in the VSV membrane; 36% is present in the outer lipid leaflet, whereas 64% is found on the inner layer.

Lactoperoxidase↗
PubMed1976

Identification of a high molecular weight trans-membrane protein in mouse L cells.

We have developed a new method for identifying proteins which span the plasma membrane ("trans-membrane" proteins) of mammalian cells grown in tissue culture. The method involves labeling proteins exposed on the cell surface with 125I by the lactoperoxidase technique and then preparing sealed, "inside-out" membrane vesicles (phagosomes) from the labeled cells using the polystyrene latex bead procedure. These inside-out vesicles are then treated briefly with trypsin and analyzed by SDS-polyacrylamide gel electrophoresis for the presence of 125I-labeled protein species which were degraded by proteolytic attack. Such proteins must be exposed on both the outer and inner membrane surfaces and, therefore, they must pass through the lipid barrier. This method is a general one in the sense that it is suitable for use with a wide variety of cell types, and here we show how it has been employed to prove that a particular high molecular weight polypeptide, called band 1, spans the plasma membrane of mouse L cells. Further studies of the band 1 polypeptide have demonstrated that it is preferentially exposed on the L cell surface during G1 phase of the cell cycle. Progression of cells from G1 to S is accompanied by a marked decrease in the availability of band 1 to iodination and it remains unavailable until cells re-enter G1. It is suggested that the band 1 polypeptide may be functionally involved in the regulation of cell proliferation.

Cell Membrane↗
PubMed1975

Cell cycle dependent exposure of a high molecular weight protein on the surface of mouse L cells.

The non-penetrating lactoperoxidase iodination probe has been employed in conjunction with synchronously dividing populations of mouse L cells to identify a high molecular weight protein is preferentially exposed on the L cell surface during G1 phase of the cell cycle. Progression of cells from G1 to S is accompanied by a marked decrease in tha availability of this structure, called band 1, to lactoperoxidase-catalyzed iodination and it remains unavailable until cells re-enter G1. It is suggested that the band 1 polypeptide may be functionally involved in the regulation of L cell growth.

Animals↗
PubMed1975

Isolation of a concanavalin A receptor from mouse L cells.

A cell surface glycoprotein receptor for concanavalin A (Con A) has been isolated from mouse L cells. The isolation procedure involved dissolving whole L cells in 0.3 M lithium diiodosalicylate and extracting with aqueous phenol. The Con A receptor, which was found in the aqueous phase of this extract, was further purified by affinity chromatography on a column of Con A-Sepharose; the receptor was adsorbed to Con A-Sepharose and eluted with 0.1 M methyl alpha-D-glucopyranoside or with 0.1 M methyl alpha-D-mannopyranoside, but not with other monosaccharides. The cell surface location of the Con A receptor purified in this way was confirmed by showing that it can be isolated from purified L cell plasma membranes and by demonstrating that it can be labeled from the exterior surface of intact L cells by the nonpenetrating galactose oxidase-KB3H4 system. Biochemical studies of the Con A receptor have shown that it migrates on sodium dodecyl sulfate-polyacrylamide gels as a single component having an apparent molecular weight of approximately 100,000. Its N-terminal amino acid is valine and it has carbohydrate attached at several (at least five) different sites along the polypeptide chain.

Amino Acid Sequence↗
PubMedDate not supplied

Use of local climatic data to determine if weather precludes the operation of an air medical system.

INTRODUCTION: Weather is one of many factors that affect safety in an air medical program. Syracuse, New York, has notoriously bad weather, and some have questioned whether an air medical service is practical given central New York's climate. This study was undertaken to determine the extent to which the area's climate could be expected to limit the availability of an air medical service. METHODS: CAMTS weather minimums for rotor-wing programs were compared with 1996-1997 hourly weather observations from the Northeastern Regional Climate Center (NRCC) and sunrise/sunset data from the United States Naval Observatory to determine how frequently weather conditions could be expected to preclude an air medical response in the greater Syracuse area. RESULTS: Exactly 17,544 hourly observations were made. CAMTS weather minimums would have precluded local flights for 606 (3.5%) of these hours and cross-country flights for 1111 (6.3%) hours. Cross-country flights were more likely to be precluded than local flights (P = .001), and both local and cross-country flights were more likely to be precluded at nighttime than in the daytime (P = .001). All flights were more likely to be precluded during winter months than during summer months (P = .000). CONCLUSION: The weather in central New York generally does not preclude the operation of an air medical services system.

Air Ambulances↗
PubMedDate not supplied

Rural vs urban motor vehicle crash death rates: 20 years of FARS data.

OBJECTIVES: Historically, motor vehicle crash (MVC)-related mortality is higher in rural areas than in urban areas. The authors evaluated whether the difference in rural and urban MVC deaths is persisting, and whether the frequency of patients being found dead at the scene, particularly in rural areas, is increasing. METHODS: Fatal Accident Reporting System (FARS) data for 1977 through 1996 were reviewed. The authors determined the frequency with which crash deaths occurred, and calculated population-based and vehicle-miles-traveled-based crash death rates. They compared rates for urban and rural areas. RESULTS: A total of 875,405 crash deaths were included in the analysis. Both population-based and vehicle-miles-traveled-based MVC deaths have decreased over the last 20 years, but rural rates remain significantly higher than urban rates. Dead-at-scene rates may be increasing, and the rural dead-at-scene rate is higher than the urban rate. CONCLUSION: While MVC death rates are declining, the rural MVC death rate is still higher than the urban rate. Although these data may indicate some positive movement in the area of MVC-related deaths, differences in the rural and urban rates and the number of patients found dead on-scene remain as issues that require attention.

Accidents, Traffic↗
PubMedDate not supplied

Do warning lights and sirens reduce ambulance response times?

OBJECTIVE: To determine the time saving associated with lights and siren (L&S) use during emergency response in an urban EMS system. METHODS: This prospective study evaluated ambulance response times from the location at time of dispatch to the scene of an emergency in an urban area. A control group of responses using L&S was compared with an experimental group that did not use L&S. An observer was assigned to ride along with ambulance crews and record actual times for all L&S responses. At a later date, an observer and an off-duty paramedic in an identical ambulance retraced the route--at the same time of day on the same day of the week--without using L&S and recorded the travel time. Response times for the two groups were compared using paired t-test. RESULTS: The 32 responses with L&S averaged 105.8 seconds (1 minute, 46 seconds) faster than those without (95% confidence interval: 60.2 to 151.5 seconds, p = 0.0001). The time difference ranged from 425 seconds (7 minutes, 5 seconds) faster with L&S to 210 seconds (3 minutes, 30 seconds) slower with L&S. CONCLUSION: In this urban EMS system, L&S reduce ambulance response times by an average of 1 minute, 46 seconds. Although statistically significant, this time saving is likely to be clinically relevant in only a very few cases. A large-scale multicenter L&S trial may help address this issue on a national level.

Ambulances↗