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Biomedical subjects

S R White

Publications and source records attributed to S R White.

117 records · Page 7Linked to original sources
PubMed1977

Characterization of proteins transported at different rates by axoplasmic flow in the dorsal root afferents of rats.

Proteins synthesized by soma located in L4 dorsal root ganglia and supplied to the axonal branches extending centrally in the dorsal root and peripherally towards the sciatic nerve were analyzed for radioactivity following injections of [3H] leucine into the L4 dorsal root ganglia. All proteins located in the dorsal root and sciatic nerve were analyzed by SDS acrylamide gel electrophoresis at various times post injection. The differences in radioactivity between the dorsal root and sciatic nerve proteins were mainly quantitative and not qualitative, with many proteins of various molecular weight ranges being transported into both segments. Generally, it appears that in both axonal branches the high molecular weight proteins are transported at the highest rate, medium weights slower and low molecular weight proteins slowest. More proteins of high and low molecular weights are transported into the dorsal root whereas more of those of medium molecular weight are transported towards the sciatic nerve.

Animals↗
PubMed1976

Physical fitness levels vs selected coronary risk factors. A cross-sectional study.

Several studies show significant correlations of blood variables, weight, abnormal electrocardiograms, and blood pressure with the incidence of coronary heart disease, but the quantification of fitness and its correlation with coronary heart disease is more difficult. In this study, approximately 3,000 men, average age of 44.6 years, were examined for blood and lipid profile, pulmonary function, percent body fat determination, and Balke maximal performance treadmill stress testing with multilead ECG monitoring. Five age-adjusted cardiorespiratory fitness categories were determined from treadmill times. A consistent inverse relationship among physical fitness categories and resting heart rate, body weight, percent body fat, serum levels of cholesterol and triglycerides, glucose, and systolic blood pressure, was observed. Forced vital capacity was directly related to levels of fitness. These results, although cross-sectional, imply that physical fitness is related to lower coronary risk factors.

Adult↗
PubMed1976

A comparative analysis of four protocols for maximal treadmill stress testing.

The purpose of this investigation was to compare the results from four commonly used maximal treadmill stress tests: Balke, Bruce, Ellestad, and a continuous multistage running protocol. The results compared serial and maximal heart rate, metabolic demands, and ECG determinations. Fifty-one healthy men, 35 to 55 years of age, volunteered for this study and were dichotomized into trained and untrained subjects. Regression analyses showed all the tests to correlate highly. No significant differences were found between tests at maximum for V02, heart rate, and blood pressure, except for V02 for the Balke as compared to the running protocol (39 vs. 41 ml./Kg-min). The Balke protocol showed lower values at maximum in VE and RP than the other three tests as well as the most gradual rate of progression in MET cost (0.5 METS per minute). The increase for the Bruce and Ellestad tests was from 1 to 1.5 METS per minute, and a rapid initial increase (9 METS in the first 3 minutes) made the running test undesirable as a screening method. Although serial plots of heart rate and MET costs were similar to those previously reported for different population samples, the present data further refined these values. Finally, a nomograph comparing treadmill time and V02, max. for the Balke, Bruce, and Ellestad tests was developed from these data.

Adult↗
PubMed1975

Spinal and spino-bulbo-spinal reflexes in rats with experimental allergic encephalomyelitis.

Experimental allergic encephalomyelitis (EAE) often produces complete hindlimb paralysis in rats. Stimulating the dorsal root at L5 was found to produce hindleg twitches in EAE rats with complete hindlimb paralysis. In addition, it was possible to record a monosynaptic response from the ventral root at L5 after stimulating the ipsilateral dorsal root (L5) in these rats. It was also possible to elicit a reflex at L5 which was shown to involve the central nervous system above the spinal cord level. These experiments demonstrated that the motoneurons and the muscles of the hindlimbs and the spinal cord segment innervating the hindlimbs remain functional in EAE paralyzed rats. This suggests that the paralysis may be caused by dysfunction of descending pathways of supraspinal origin.

Animals↗
PubMedDate not supplied

Migration of 3T3 and lung fibroblasts in response to calcitonin gene-related peptide and bombesin.

Neuropeptides found in airways, such as bombesin and calcitonin gene-related peptide (CGRP), are known to elicit proliferation of several cell types, including fibroblasts and epithelial cells in culture and in vivo. However, the effects of these neuropeptides on fibroblast migration, which may also be a necessary part of airway repair, have not been well established. To determine if these peptides could stimulate fibroblast chemotaxis, we grew NIH 3T3 and IM R-90 cells in culture and studied migration using 48-well blindwell chambers. 3T3 cells were treated with 10(-14) to 10(-7) M bombesin or 10(-14) to 10(-7) M CGRP and permitted to migrate through a gelatin-coated filter for 2-24 hours. Both bombesin and CGRP elicited 3T3 migration which was both time and concentration dependent. After 6 hours, migration of 3T3 cells treated with 10(-7) M bombesin was 33.9 +/- 4.4 cells versus control migration of 4.0 +/- 1.2 cells per 10 high-power fields (hpf) (P < .01, n = 4). Migration of 3T3 cells treated with 10(-9) M CGRP was 30.2 +/- 5.4 cells versus control migration of 10.7 +/- 1.4 cells per 10 hpf (P < 0.02, n = 6). IMR-90 cells migrated in a similar manner in response to CGRP and bombesin. The response to each neuropeptide was both chemotactic and chemokinetic, and could be blocked completely with an appropriate receptor antagonist. We demonstrate that both bombesin and CGRP are chemotactic for 3T3 and IMR-90 fibroblasts in culture. These peptides therefore may have multiple roles in repair and healing of airway injury.

3T3 Cells↗
PubMedDate not supplied

In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene.

Microencapsulated healing agents that possess adequate strength, long shelf-life and excellent bonding to the host material are required for self-healing materials. Urea-formaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 microm in diameter were produced by appropriate selection of agitation rate in the range of 200-2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160-220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80-90%) of a free flowing powder of spherical microcapsules were produced with a fill content of 83-92 wt% as determined by CHN analysis.

Capsules↗