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Biomedical subjects

R L Johnson

Publications and source records attributed to R L Johnson.

At least 343 records · Page 19Linked to original sources
PubMed1980

An automated method for studying stereotyped gnawing.

Stereotyped behavior in rats, consisting of compulsive, repetitive sniffing and gnawing, caused by high doses of amphetamine-like psychostimulants, may serve as an animal model for psychosis. Previous methods for measuring behavioral stereotypies of this kind have required continuous observation and rating of the behaviors or semiquantitative techniques that fail to produce a continuous record of the behaviors. The present paper describes a simple automated method that provides a continuous quantitative record of the specific gnawing behavior induced in rats by methylphenidate, an amphetamine-like psychostimulant. The apparatus described and the test procedures developed are compatible with a wide variety of common counters and recorders.

Animals↗
PubMed1980

N-(alpha-Hydroxyalkanoyl) derivatives of Leu-Val-Phe-OCH3 as inhibitors of renin.

The following N-(alpha-hydroxylakanoyl) derivatives of Leu-Val-Phe-OCH3 were synthesized and tested for their ability to inhibit human amniotic renin: D- and L-alpha-hydroxyisocaproyl-Leu-Val-Phe-OCH3, D- and L-alpha-hydroxyisovaleryl-Leu-Val-Phe-OCH3, L-2-hydroxy-3-phenylpropanoyl-Leu-Val-Phe-OCH3, and D- and L-alpha-hydroxyphenylacetyl-Leu-Val-Phe-OCH3. Analysis of the compounds through the use of Dixion plots showed all of the compounds to be competitive inhibitors of renin. All but D-alpha-hydroxyisovaleryl-Leu-Val-Phe-OCH3 were found to be more active than the known tetrapeptide inhibitor Leu-Leu-Val-Phe-OCH3 (1). The two most active compounds of the series were L-alpha-hydroxyisocaproyl-Leu-Val-Phe-OCH3 (Ki = 0.23 mM) and L-alpha-hydroxyisovaleryl-Leu-Val-Phe-OCH3 (Ki = 0.3 mM).

Amnion↗
PubMed1980

Hysteresis in the relation between diffusing capacity of the lung and lung volume.

The diffusing capacity of the lung for carbon monoxide (DLCO) varies directly with lung volume (VA) when measured during a breath-holding interval. DLCO measured during a slow exhalation from total lung capacity (TLC) to functional residual capacity (FRC) does not vary as VA changes. Since VA is reached by inhaling during breath holding and by exhaling during the slow exhalation maneuver, we hypothesized that the variability in the relation between DLCO and VA was due to hysteresis. To test this hypothesis, breath-holding measurements of DLCO were made at three lung volumes, both when VA was reached by inhaling from residual volume (RV) and when Va was reached by exhaling from TLC. At 72% TLC, DLCO was 22% higher when VA was reached by exhalation compared to inhalation (P < 0.02). At 52% TLC, DLCO was 19% higher when VA was reached by exhalation compared to exhalation (P < 0.005). DCLO measured during a slow exhalation fell on the exhalation limb of the CLCO/VA curve. these data indicate that there is hysteresis in DLCO with respect to lung volume.

Adult↗
PubMed1980

The caterpillar and the butterfly: despite regulation, the system thrives.

Although battered and buffeted by increasing regulations, hospitals will survive as important institutions. Hospitals must take steps to ensure that the federal government does not concentrate solely on regulating inpatient services, but applies controls equitably to ambulatory services as well.

Ambulatory Care↗
PubMed1980

Mitogen-activated human mononuclear cells suppress calcium binding by sarcoplasmic reticulum.

Weakness in inflammatory myopathy is commonly more prominent than is muscle fiber necrosis, suggesting additional explanations for its origin. Recent studies reveal that cell-mediated immune mechanisms are active in PMS-DMS. In experiments reported here, the effect of human mononuclear cell-derived mediator-rich supernatant upon calcium accumulation by SR membranes was examined. SR, by triggered binding and release of calcium in the vicinity of myofibrils, plays a key role in regulation of skeletal muscle contraction and relaxation. SR was derived from Lewis and Sprague-Dawley rat pelvic girdle muscles. Mediator-rich supernatants were generated by exposure of Hypaque-Ficoll-purified human mononuclear cells to PHA-P and Con-A during 72 hr of incubation in RPMl 1640 medium containing 10% autologous serum. Mitogens alone were without effect on SR. Suppression of ATP-dependent calcium accumulation was demonstrable within 40 min of exposure of SR to mediator-rich supernatants. The factor(s) producing suppression of calcium binding was nondialyzable, stable on storage at -70 degrees C, and active upon SR at physiologic calcium-loading levels. These findings may have important implications for understanding of the mechanism of weakness in inflammatory myopathies.

Animals↗
PubMed1980

Case reports. Intrauterine echovirus type II infection.

The case described herein represents the first laboratory-confirmed case indicating intrauterine infection due to echovirus type II. The virus was recovered from the vagina of the mother and from the blood from the umbilical cord and nasopharynx of an apathetic newborn (all cultures were taken within 60 minutes of birth in the delivery room) with a generalized maculopapular exanthem. When the infant was 15 days of age, results of all laboratory tests and physical examinations were normal.

Adult↗
PubMed1979

Revisiting "the wobbly three legged stool".

Examination of both the similarities and dissimilarities of the use of the corporate organizational model in the typical hospital has led to the conclusion that the model can, at best, be only a loose fit.

Attitude↗
PubMed1979

Diffusing capacity at different lung volumes during breath holding and rebreathing.

Single-breath diffusing capacity of the lung for carbon monoxide (DLCO) increases as lung volume increases above functional residual capacity (FRC). However, the physiological mechanism responsible for this increase remains controversial. This volume dependence of diffusing capacity could reflect changing regional distribution of inspired air as lung volume increases rather than a change in capillary blood volume or surface area for gas exchange. We measured DLCO during breath holding and during rebreathing with a technique employed to mix respired gases throughout the lung thereby minimizing regional distribution differences. Measurements were made 1,500 ml above FRC and near total lung capacity (TLC). Breath holding DLCO was 18% higher near TLC than at 1,500 ml above FRC (P less than 0.05). Rebreathing DLCO was 16% higher near TCL than at 1,500 ml above FRC (P less than 0.01). Equality of results by the two techniques indicates that changes in DLCO with lung volume are not a consequence of the changing distribution of inspired air. Our results are compatible with the hypothesis that effective surface area of the lung increases as lung volume expands.

Adult↗
PubMed1979

Cardiovascular effects of positive-pressure ventilation in normal subjects.

In normal subjects during 15-min positive-pressure ventilation with 10 cmH2O end-expiratory pressure (PEEP), cardiac output fell 19% due to a fall in stroke volume. Transmural mean right atrial pressure rose 3.1 cmH2O and right ventricular end-diastolic diameter increased 15%. Simultaneously, left ventricular end-diastolic diameter decreased 21%, ejection time increased 11%, and velocity of circumferential fiber shortening fell 30%. Thus, right ventricular filling increased and left ventricular filling decreased. The function of the right ventricle was impaired and the function of the left ventricle may have been impaired. Cardiac output gradually increased due to a 7% increase in heart rate as PEEP was continued for 1 h and transmural mean right atrial pressure also increased further by 2.4 cmH2O. Compensation for the reduced stroke volume occurred as filling pressures and heart rate rose, but ventricular function remained impaired for the entire duration of PEEP. On resuming spontaneous breathing, cardiac output and ventricular function returned to base-line levels. We conclude that the reduced cardiac output during PEEP is not due to a direct mechanical reduction in right ventricular filling.

Adult↗