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Biomedical subjects

L E Johnson

Publications and source records attributed to L E Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1985

Acute hemodynamic effects of hydralazine in dogs with chronic mitral regurgitation.

The hemodynamic response to hydralazine administration was evaluated in 6 conscious small dogs with chronic mitral regurgitation. All dogs underwent invasive and noninvasive hemodynamic monitoring before and after hydralazine administration. Cardiac output and pulmonary capillary wedge pressure were measured with a Swan-Ganz thermodilution catheter. Systemic arterial blood pressure (AP) was measured directly by inserting a needle into the femoral artery. Standard M-mode echocardiograms and thoracic radiographs were obtained. Other hemodynamic variables were calculated. Base-line hemodynamic variables were altered severely in all dogs. Hydralazine decreased mean arterial blood pressure from 104 +/- 18 (mean +/- SD) to 78 +/- 12 mm of Hg (P less than 0.005), total systemic resistance index from 2,946 +/- 625 to 1,261 +/- 420 dynes-s-cm-5m2 (P less than 0.005), and pulmonary capillary wedge pressure from 40 +/- 5 to 26 +/- 3 mm of Hg, (P less than 0.005). Cardiac index increased from 2.92 +/- 0.72 to 5.36 +/- 1.67 L/min/m2 of body surface area (P less than 0.005). Mixed venous oxygen tension (PvO2) increased from 28.4 +/- 4.3 to 41.2 +/- 5.2 mm of Hg (P less than 0.001). Pulmonary edema resolved, as determined on thoracic radiographs. Mixed venous oxygen tension correlated well with the cardiac index (r = 0.92; P less than 0.001). It was concluded that hydralazine administration caused a small decrease in end diastolic diameter (4.8 +/- 0.9 to 4.5 +/- 0.8 cm, P less than 0.05) and end systolic diameter (2.6 +/- 0.8 to 2.3 +/- 0.7 cm, P less than 0.05). Fractional shortening and heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Anorexia nervosa and bulimia in female adolescents with insulin dependent diabetes mellitus: a systematic study.

An unselected sample of 46 female adolescents with insulin-dependent diabetes mellitus (IDDM) for more than one year were assessed systematically for the presence of anorexia nervosa and bulimia. These disorders and their partial syndromes were found in 19.5% of this population. Anorexia nervosa and bulimia diagnosed on the basis of DSM-III criteria were each found in 6.5% of the population representing approximately a 6-fold and 2-fold increase respectively in the expected prevalence for similar nondiabetic individuals. Bulimic symptoms were associated with poor metabolic control as reflected in blood levels of glycosylated hemoglobin (HbAl). These findings have important implications both for the pathogenesis of anorexia nervosa and bulimia and for the management of some cases of IDDM with unstable metabolic control.

Adolescent↗
PubMed1984

Vocal responses to left visual stimuli following forebrain commissurotomy.

Four forebrain commissurotomized patients, 12-15 yr post-surgery, along with one partially commissurotomized and three normal control subjects, were presented with a variety of stimuli to either the LVF (left visual field) or RVF. Three of four "split-brain" patients could name LVF numbers and two of four could name LVF letters. Irrespective of their accuracy, and unlike control subjects, all "split-brain" patients named LVF stimuli about twice as slowly as RVF stimuli. In addition, three of four patients could vocally categorize LVF stimuli into two classes (yes-no, odd-even, more or less than five). In this case, like the control subjects, they respond to LVG stimuli as quickly as to RVF stimuli. The results support an hypothesis that "split-brain" patients may transfer information from the right to the left cerebral hemisphere when making two-choice verbal categorizations of LVF stimuli, but are able to name some simple LVF stimuli directly from the right hemisphere. Combining categorization and naming tasks, however, can elicit interference, suggesting that the two tasks are not completely autonomous.

Brain↗
PubMed1984

Bilateral visual cross-integration by human forebrain commissurotomy subjects.

Four forebrain commissurotomized patients were compared with one partially commissurotomized control subjects on their ability to cross-compare simultaneously flashed bilateral visual stimuli (colors, schematic faces, numbers, letters, patterns) as same or different, or to name the two stimuli. Two of the four patients were able to cross-compare some or all of the stimuli verbally, while another patient could name the two stimuli but not separately determine same-difference. It is hypothesized that (1) each cerebral hemisphere is capable of making separate verbal naming responses, and (2) brainstem interconnections between the 'disconnected' hemispheres allow some patients to integrate bilateral visual stimuli and make accurate same-different judgments.

Brain↗
PubMed1984

Tissue cultures derived from ineffective root nodules of alfalfa : callus initiation and enzymic comparisons.

Callus tissue cultures were developed from apical meristem regions of tumor-like ineffective root nodules of alfalfa. Callus growth was a function of tissue source and hormone composition and concentration. Callus derived from ineffective nodules also were shown not to contain Rhizobium meliloti.Glutamate dehydrogenase, glutamine synthetase, glutamate synthase, glutamate oxaloacetate transaminase and phosphoenolpyruvate carboxylase activities were present in callus cultures and in the respective nodule source used for callus induction. The mean specific activity of all enzymes evaluated was higher in callus cultures than in ineffective nodules. Quantitative but not qualitative differences in enzyme activities were evident between ineffective nodules and callus derived from these nodules. Tissue cultures derived from ineffective nodules may provide a model system to evaluate host plant-Rhizobium interactions.

Journal Article↗
PubMed1983

Filicidal behavior: behavioral correlates and role of sensory systems.

The administration of para-chloro-D,L-phenylalanine (PCPA) produces a high incidence of filicidal (pup-killing) behavior in female rodents. The present series of experiments determined the major behavioral, sensory, and temporal correlates of filicidal behavior in nulliparous adult Sprague-Dawley female rats. In Experiment 1, behavioral episodes involving the interaction of test pups and PCPA-induced filicidal females were videotaped, and subsequent analyses of behaviors related to locating, carrying, mauling, attacking, gnawing, and consuming the prey object were performed. Analysis indicated that the primary behavioral correlates in the PCPA animals included location, initiation of the attack (mauling), and killing of the pup (filicide). Only location was observed in control animals. Experiment 2 evaluated the effects of sensory impairments on location, mauling, and filicide. Sensory impairment occurred at 24 days of age for enucleation and 62 days of age for olfactory bulbectomies and/or auditory destruction. Animals were injected either at 110 or 130 days of age with PCPA for three consecutive days and tested for filicide for five additional days. Locating of the test pup was not affected by sensory impairment. Mauling was reduced significantly in the enucleation/auditory destructed animals. Filicide was significantly lower in animals with visual/auditory destruction, and, compared to controls, was reduced in all sensory impaired groups.

Aggression↗
PubMed1979

Nitrogen Fixation, Nodule Development, and Vegetative Regrowth of Alfalfa (Medicago sativa L.) following Harvest.

Nitrogenase-dependent acetylene reduction, nodule function, and nodule regrowth were studied during vegetative regrowth of harvested (detopped) alfalfa (Medicago sativa L.) seedlings grown in the glasshouse. Compared with controls, harvesting caused an 88% decline in acetylene reduction capacity of detached root systems within 24 hours. Acetylene reduction in harvested plants remained low for 13 days, then increased to a level comparable to the controls by day 18.Protease activity increased in nodules from harvested plants, reached a maximum at day 7 after harvest, and then declined to a level almost equal to the control by day 22 after harvest. Soluble protein and leghemoglobin decreased in nodules from harvested plants in an inverse relationship to protease activity.Nitrate reductase activity of nodules from harvested plants increased significantly within 24 hours and was inversely associated with acetylene reduction. The difference in nitrate reductase between nodules from harvested plants and control plants became less evident as shoot regrowth occurred and as acetylene reduction increased in the harvested plants.No massive loss of nodules occurred after harvest as evidenced by little net change in nodule fresh weight. There was, however, a rapid localized senescence which occurred in nodules of harvested plants. Histology of nodules from harvested plants showed that they degenerated at the proximal end after harvest. Starch in the nodule was depleted by 10 days after harvest. The meristem and vascular bundles of nodules from harvested plants remained intact. The senescent nodules began to regrow and fix nitrogen after shoot growth resumed.

Journal Article↗
PubMed1975

A test of time invariance in models of ferrokinetics.

Application of a particular mathematical property of time-invariant systems to experimental data obtained from injection and infusion of radioactive tracer iron in normal subjects is used to show that the generally applied assumption of time invariance to ferrokinetic systems is unjustified and may lead to substantial errors in analysis.

Adult↗