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Biomedical subjects

G E Crawford

Publications and source records attributed to G E Crawford.

11 recordsLinked to original sources
PubMed1987

Viscoelastic relaxation of bilayer lipid membranes. Frequency-dependent tension and membrane viscosity.

Photon correlation spectroscopy has been used to study capillary waves on black lipid membranes of glycerol monooleate at temperatures above the lipid transition. For the first time the tension and viscosity of solvent-free bilayers have been observed to display a frequency dependence. The variations of both parameters can be accounted for by a Maxwell viscoelastic fluid model having a relaxation time of 37 microseconds. The equilibrium (omega = 0) tension is compatible with literature values. The present results do not suffice to precisely define the specific molecular processes involved, but relaxation times similar to the present are associated with certain phenomena in phospholipid vesicles. Bilayers containing hydrocarbon solvent do not show such relaxation, presumably due to their weaker intermolecular interactions.

Elasticity↗
PubMed1986

Phase transitions in monoglyceride bilayers. A light scattering study.

Thermotropic phase transitions in single planar bilayers of glycerol mono-oleate have been investigated using quasi-elastic light scattering from thermally excited membrane fluctuations. In certain cases both spectroscopic and intensity information were derived from the observations. For solvent-free bilayers transitional changes were observed in several membrane parameters: in tension, viscosity and thickness, in a combination of lipid orientational order parameter and dielectric anisotropy, and in the lateral compression modulus. These changes, particularly those in membrane thickness and in the anisotropy/order combination, were clearly indicative of a chain-melting transition in the lipid molecules. The chain-melting transition temperature was identified as 16.6 +/- 0.03 degrees C (delta T 1/2 = 1.5 degrees C). The other changes tended to cluster around 12.5 and 16.6 degrees C, suggesting that a two-stage transition was involved. Analysis of pretransitional fluctuations in membrane viscosity, based on a Landau approach, suggested that at the transition the membrane was close to a critical point (T = 12.7 degrees C). Less information was accessible for membranes containing n-decane within their structure. In this case, the change in membrane tension was much smaller than in the solvent-free case and the transition was considerably broadened. These effects accord with an increase in 'interactive volume' within the bilayer due to solvent inclusion.

Glycerides↗
PubMed1984

Photon correlation spectroscopy as a probe of planar lipid bilayer phase transitions.

Photon correlation spectroscopy has been applied to study phase transitions of planar bilayer membranes. The membrane tension and one specific membrane viscosity are probed. Difficulties arising in the measurement of the temperature dependence of these properties are discussed and a servo-control system to overcome them is described. Typical data are presented for monoglyceride bilayers. Membranes incorporating cholesterol display effects below the lipid transition temperature which are interpreted in terms of separation within the membrane into cholesterol-rich fluid regions and regions of lipid in the gel phase. Some of the cholesterol-rich regions are apparently of macroscopic extent.

Cholesterol↗
PubMed1981

Measles pneumonia in young adults. An analysis of 106 cases.

Measles occurred in 3,220 Air Force recruits between January 1976 and July 1979 and was complicated by pneumonia in 106 cases (3.3 percent). Although no deaths occurred, the illness was characterized as clinically severe with high fever and prolonged hospitalization (mean, 14.5 days). Bacterial superinfection as documented by transtracheal aspiration occurred in 35 cases (30.3 percent) and was caused by Hemophilus influenzae (18), Hemophilus parainfluenzae (two), Neisseria meningitidis (nine), Streptococcus pneumoniae (three), Streptococcus pyogenes (two) and Moraxella kingae (one). Clinical evidence of bronchospasm was present in 18 patients (17 percent) and required bronchodilators in six. Other complications included liver function abnormalities (31 percent), otitis media (29 percent) and sinusitis (25 percent). Measles pneumonia in adolescents is clinically severe with a generally benign outcome.

Adolescent↗
PubMed1981

Epidemic measles and rubella in air force recruits: impact of immunization.

The safety of attenuated viral vaccines against measles and rubella and their efficacy in controlling a massive outbreak of these two diseases in air force recruits at Lackland Air Force Base, Texas, were studied. Recorded cases of measles declined from a high of 1,345 in 1976 to a low of 227 in 1979. Similarly, rubella cases declined from a peak before the immunization program of 1,361 in 1977 to a low of 67 in 1979. A controlled study of morbidity related to immunization revealed that there is less immediate local morbidity from immunizations against measles and rubella than with other routine immunizations. Recruits who received the attenuated viral vaccines reported fever, myalgias, and diarrhea only slightly more frequently than did recruits in the concurrent control group. The present data indicate that measles and rubella, increasingly consequential diseases among young adults, can be safely and effectively controlled with attenuated viral vaccines.

Disease Outbreaks↗
PubMed1978

Necrotizing fasciitis associated with Haemophilus aphrophilus. Report of a case.

Necrotizing fasciitis, a serious infection requiring prompt antibiotic and surgical therapy, previously has not been associated with Haemophilus aphrophilus. We report a case of necrotizing fasciitis associated with methylphenidate abuse from which H aphrophilus was isolated. Surgical and antibiotic therapy based on in vitro susceptibility testing resulted in eradication of the infection.

Adult↗