Biomedical subjects

R H Johnson

Publications and source records attributed to R H Johnson.

At least 217 records · Page 12Linked to original sources

PubMed1975

Clinical and pharmacological evaluation of the effects of piribedil in patients with parkinsonism.

Nine patients with Parkinsonism were studied before and after treatment with piribedil, a dopamine-receptor stimulator. Piribedil appeared to have a slight anti-Parkinsonism effect upon bradykinesia, and possibly upon tremor, but did not improve rigidity. The chief toxic effects were drowsiness and confusion, and two patients experienced nausea. Changes in homovanillic acid in the cerebrospinal fluid indicated that the drug reduced the turnover of endogenous dopamine. In spite of this definite neuropharmacological action, no clear-cut associated clinical benefit was demonstrated. The significance of these findings is discussed.

Aged↗

PubMed1975

The effect of naftidrofuryl on the metabolic response to exercise in man.

We have designed this investigation to determine whether naftidrofuryl has an effect upon metabolism in vivo in man. Five subjects were studied during and after steady exercise on a bicycle ergometer. On the first occasion they received naftidrofuryl (300 mg orally) 20-40 min before exercise; and on the second they exercised without the drug to provide control observations. Blood samples were taken for the estimation of glucose, pyruvate, lactate, glycerol, acetoacetate and 3-hydroxybutyrate. Exercise with naftidrofuryl caused a significantly greater rise in blood pyruvate concentration during the exercise and post-exercise period compared with the controls. Changes in glucose, lactate, glycerol and ketone-bodies were not significantly different from the control values. Lactate/pyruvate ratios were significantly reduced with naftidrofuryl during the post-exercise period. Exercise causes a rise in intracellular anaerobic metabolism with associated increases in blood lactate/pyruvate ratios. This is followed by enhanced oxidative capacity during the recovery period as adduced from falling lactate/pyruvate ratios. The greater decline in lactate/pyruvate ratios with naftidrofuryl during the post-exercise period is evidence that naftidrofuryl is able to enhance cellular oxidative activity in vivo in man. Further studies in clinical situations are therefore indicated.

Acetoacetates↗

PubMed1975

Studies on the effects of infectious bovine rhinotracheitis virus on reproduction in heifers.

Natural venereal infection of heifers with IBR virus resulted in vulvovaginal lesions in 9 of 12 heifers at 3 weeks after introducttion to bulls, and virus was isolated from 5 of the 9 affected animals. The infection was not associated with any effect on conception. Experimental nasal and conjunctival infection of 18 heifers pregnant for 3, 5 or 7 months with a genital strain of IBR virus caused mild rhinitis or conjunctivitis in all inoculated animals and virus was recovered from 14 animals at 8 days after inoculation. No effects on pregnancy were recorded.

Animals↗

PubMed1975

Characterization of group A streptococcal R-28 antigen purified by hydroxyapatite column chromatography.

Purified R-28 antigen from an M-protein-poor, R-antigen-rich strain of group A Streptococcus was prepared by sequential treatment of an acid extract of whole cells with ammonium sulfate fractionation and hydroxylapatite (HA) column chromatography. Purified R-28 antigen was eluted only with 0.10 M sodium phosphate, pH 6.7. Findings on quantitative amino acid composition, polyacrylamide gel electrophoresis pattern, and HA column elution pattern were similar but not identical to those previously reported for streptococcal M-proteins. Rabbits immunized with either HA-purified R-28 antigen or heat-killed cells developed two pepsin-sensitive, trypsin-resistant immunodiffusion lines of identity against HA-purified R-28 antigen but failed to form bactericidal antibody. One of these two lines formed a line of identity with R-28 antigen prepared by trypsinization of whole cells. The other line remained undefined, although it appeared not to be either streptococcal group A carbohydrate, M-protein, T-antigen, polyglycerophosphate, E4 antigen, or M-associated protein; by enzymatic criteria it is an R-antigen. Polyacrylamide gel electrophoresis of HA-purified R-28 antigen revealed multiple serologically active charge and size isomers. These findings suggest possible structural similarities between group A streptococcal M-proteins and R-antigens and also indicate that the same purification techniques may be utilized to study these protein antigens if the proper strain of Streptococcus is chosen.

Amino Acids↗

PubMed1975

Orthostatic hypotension associated with paroxysmal ventricular tachycardia.

Two patients (aged 46 and 49 years) are presented who gave a history of several years' duration of unsteadiness, dizziness, and syncopal attacks on standing. Both had orthostatic hypotension which was associated with the development of a unifocal paroxysmal ventricular tachycardia. There was no evidence of organic heart disease. In one of the patients the symptoms usually developed when standing after working in a crouched position. He responded to treatment with beta-adrenergic blockade. The other patient developed her symptoms on standing, after exercise or other stress. The paroxysmal ventricular tachycardia, which occurred in the upright position only, was accompanied by a marked rise in plasma adrenaline. In this patient one contributory factor was a low blood volume and she responded to plasma volume expansion. We wish to draw attention to the common neurological symptoms with which paroxysmal ventricular tachycardia may present. We suggest that paroxysmal ventricular tachycardia may result from ventricular sensitivity to circulating adrenaline and not due to aberrant innervation of the heart as has been suggested previously.

Autonomic Nervous System↗

PubMed1975

N-6-(delta-2-isopentenyl) adenosine: hydrolysis by a mucleosidase isolated from Lactobacillus acidophilus cells.

A nucleosidase activity has been isolated from Lactobacillus acidophilus which rapidly hydrolyses N-6 (delta-2-isopentenyl) adenosine to its corresponding base, N-6(delta-2-isopentenyl) adenine. The activity can be distinguished from the spleen exzyme (EC. 2.4.2.1), a purine nucleoside transferase, on the basis of its substrate specificity, electrophoretic behavior, and nondependence on phosphate. The bacterial enzyme hydrolyzes both inosine and isopentenyl adenosine, giving Km values of 63.3muM and 177 muM respectively. The presence of this enzyme in bacteria counts for the rapid conversion of the parent nucleoside to isopentenyl adenine, which has been observed in these cells. The enzyme thus assumes importance as one of the catabolic activities available to the cell for metabolizing the cytokinin, N-6-(delta-2-isopentenyl) adenosine.

Adenosine↗

PubMed1975