Biomedical subjects

J S Main

Publications and source records attributed to J S Main.

4 recordsLinked to original sources

PubMed1996

Interactive brain atlas with the Visible Human Project data: development methods and techniques.

A prototype of an interactive digital brain atlas was developed by using the Visible Human Project data set of the National Library of Medicine. This data set provides corresponding axial magnetic resonance images, computed tomographic images, and cryosections of the brain. The prototype was developed to demonstrate the techniques and methods that will be used throughout the development process of the atlas. The atlas has a graphical user interface, supports user interaction with various representations of the brain (i.e., two-dimensional and three-dimensional [3D]), and displays multiple images simultaneously. Motion sequences of the 3D brain were incorporated in the atlas to provide an important link between two-dimensional brain slices and volume-rendered 3D anatomic structures. Volume visualization tools were used to interactively render, rotate, and reslice the volumetric brain data. The brain was segmented with manual tracing, thresholding, and morphologic algorithms and then rendered with volume-rendering tools.

Anatomy, Cross-Sectional↗

PubMed1991

Inhibitory role of the coronary arterial endothelium to alpha-adrenergic stimulation in experimental heart failure.

The role of the endothelium in regulating coronary alpha-adrenergic tone was evaluated in isolated coronary arterial rings from dogs with and without pacing-induced congestive heart failure (CHF). The maximal contractile response to methoxamine was attenuated approximately 43% (p less than 0.05) in both intact and denuded CHF rings compared with control. Conversely, norepinephrine-induced contractions were diminished 58% in intact CHF vessels and 39% in denuded CHF vessels (p less than 0.05). Denudation did not alter responses to methoxamine but significantly (p less than 0.05) augmented the tension generated by norepinephrine in both control (1.7-fold) and CHF (2.4-fold) arteries. In both intact control and CHF coronary arteries, norepinephrine elicited rapid, transient relaxations that preceded slow, sustained contractions; the initial relaxation phase was endothelium dependent, because denudation eliminated the response. Relaxations to the selective alpha 2-adrenoceptor agonist BHT 920 were also dependent on the presence of an endothelium. At peak CHF, endothelium-dependent relaxations to norepinephrine and BHT 920 were enhanced, whereas relaxations to nitroglycerin and acetylcholine were unaltered. The data suggest that alpha-adrenergic tone in canine coronary arteries is diminished by pacing-induced CHF because of a decrease in alpha 1-adrenoceptor-mediated constriction and an enhanced capacity of the endothelium to antagonize the direct vascular smooth muscle response of norepinephrine through endothelium-dependent, alpha 2-adrenoceptor-mediated relaxations.

Acetylcholine↗

PubMed1990

Endothelium modulation of the effects of nitroglycerin on blood vessels from dogs with pacing-induced heart failure.

1. The relaxant actions of nitroglycerin (previously considered to be an endothelium-independent relaxing agent) and acetylcholine (an endothelium-dependent relaxing agent) were compared on 4 vascular preparations (dorsal pedal artery, saphenous vein, left anterior descending coronary artery and circumflex coronary artery) from dogs with and without pacing-induced congestive heart failure (CHF). 2. Responses of the coronary arteries to acetylcholine were unaltered in endothelium-intact rings from dogs with and without heart failure. Similarly no such changes were observed in the peripheral vessels. The maximum relaxation produced by acetylcholine was always greater in the coronary vessels compared to the peripheral vessels. 3. Before heart failure, the coronary vessels were more sensitive and reactive to nitroglycerin compared to the peripheral vessels. 4. Removal of the endothelium in both the control (dogs without CHF) and experimental (dogs with CHF) rings enhanced the relaxant effects of nitroglycerin, such that the EC50 for nitroglycerin became significantly lower in all denuded rings, with the exception of the saphenous vein and the left anterior descending coronary artery, before the development of CHF. 5. When CHF was maximally developed, vascular sensitivity to nitroglycerin was increased in peripheral vessels with an intact endothelium, but not in the coronary vessels. 6. These findings indicate that relaxation produced by nitroglycerin cannot be considered as entirely endothelium-independent but should be considered endothelium-modulated.

Acetylcholine↗

PubMed1975

Studies on lipopolysaccharides isolated from strains of Neisseria gonorrhoeae.

Lipopolysaccharides, extracted by phenol-water from five strains fo Neisseria gonorrhoeae, were purified by treatment with ribonuclease followed by multiple washes. These preparations were fatal to mice when administered in submicrogram amounts with actinomycin D, the LD50 values varying from 4 to 16 mug/kg. Analyses showed that all preparations contained glucose, galactose, glucosamine, heptose, 2-keto-3-deoxyoctonic acid and phosphate. All the lipopolysaccharides contained the same fatty acids, namely beta-OH-10:0, beta-OH-12:0, beta-OH-14:0, 12:0, 14:0,16:0, 16:1, 18:0 and 18:1. We were unable to detect significant differences between the lipopolysaccharides of virulent and avirulent gonococci or between penicillin-sensitive and resistant strains. Gonococcal lipopolysaccharides appeared to lack O-antigen side chains.

Animals↗