Search PubMed⌕ Search

Biomedical subjects

R E Johnson

Publications and source records attributed to R E Johnson.

At least 253 records · Page 14Linked to original sources
PubMed1982

Proactive effects in memory for stories.

Selective omissions in the recall of longer prose passages have been interpreted as evidence of abstractive processes during encoding. Presumably, the additional information in longer passages produces an information overload which necessitates selective attention. Learners in three experiments were tested on their recognition or recall of a short passage that either was or was not preceded by a long introductory segment. An encoding-based view predicts that increased passage length should diminish both recognition and recall. However, increased passage length decreased recall, but not recognition, demonstrating that passage length effects are dependent upon the type of cues available during retrieval. A further study demonstrated that ideas of greater thematic importance were recognized better than ideas of lesser thematic importance, even after a negligible retention interval. Abstractive processes deal with the relative importance of ideas but not the amount of information.

Humans↗
PubMed1982

Response to exercise in patients taking psychotropic drugs. Arrhythmias and the QT interval (QT wave peak).

Psychotropic drugs may prolong the QT interval, potentially predisposing to ventricular arrhythmias and/or sudden death. Exercise prescribed as therapy for depression may also prolong the QT interval and augment arrhythmia risk. To determine QT-interval (QT wave peak, or QTPK) response to exercise in patients receiving psychotropic drugs, treadmill exercise testing was performed on 20 mentally competent psychiatric inpatients clinically free of heart disease. Twenty-four-hour ambulatory ECGs were performed within one day of exercise testing to detect arrhythmias during routine daily activities. Exercise test results for psychiatric patients were compared with those of normal subjects receiving no medication. Separate regression lines relating heart rate of QTPK interval, calculated for each group, showed no significant difference. No serious arrhythmias occurred during routine daily activities or exercise. Patients without heart disease taking psychotropic drugs have appropriate QTPK-interval shortening with exercise.

Adult↗
PubMed1982

Melanotic neuroectodermal tumor of infancy: a malignant tumor of the femur.

An 18-month-old white girl had a malignant melanotic neuroectodermal tumor of infancy of the left femur. Light microscopic findings of a biopsy specimen of the femoral lesion demonstrated the characteristic histologic features, that is, nests of small cells with hyperchromatic nuclei and scant cytoplasm lying within cleftlike spaces lined by cuboidal, melanin-producing cells. Electron microscopy confirmed both neuroblastic and melanocytic differentiation. Despite radiation and chemotherapy, an extensive pelvic tumor developed, which prompted laparotomy 20 months after the femoral biopsy, The apparently metastatic tumor was largely necrotic, but viable nests of undifferentiated small cells and rare individual melanin-containing cells were identified. The patient died 4 months later, at 3 years of age. This case is of particular importance because it is the first example of this tumor found in a long bone. No similar lesions were seen in 17,000 primary tumors of bone treated and seen in consultation at this institution. Its aggressively malignant clinical course is also unusual; only 6 of the 159 cases of melanotic neuroectodermal tumor of infancy reported to date have expressed malignant behavior.

Female↗
PubMed1982

Wilson's disease. Electron microscopic, x-ray energy spectroscopic, and atomic absorption spectroscopic studies of corneal copper deposition and distribution.

The eyes from three patients with Wilson's disease and bilateral circumferential Kayser-Fleischer rings were obtained at autopsy. The cornea from one eye of each of the patients was divided into five anatomic regions--superior, inferior, medial, lateral, and central--and each area was examined by x-ray energy spectroscopy interfaced with transmission electron microscopy and by atomic absorption spectrophotometry. The cornea of the second eye was examined by light microscopy. Electron-dense granules, rich in copper and sulfur, were present in both the peripheral and the central region of the cornea but were more numerous at the periphery. The total copper concentration, determined by atomic absorption spectrophotometry, was high in both the peripheral and the central area of the cornea. The association of copper with sulfur suggests that a sulfur-containing moiety functions in binding copper. The distribution of the copper granules correlates with the clinical appearance of the Kayser-Fleischer ring, but no correlation exists between the total copper content and the Kayser-Fleischer ring. This suggests that sulfur-copper binding results in aggregation of copper granules and production of the first clinically detectable corneal lesion in Wilson's disease.

Adolescent↗
PubMed1982

Cardioplegic infusion: the safe limits of pressure and temperature.

In patients with coronary artery disease, infusion of very cold cardioplegic solutions at elevated pressures may facilitate homogeneous cooling and cardioplegia. This study was designed to determine if very high infusion pressures or very low temperatures of the cardioplegic solution damages normal myocardium. In a hemodynamically controlled canine right heart bypass preparation, a crystalloid solution (Plasma-Lyte 148 with 30 mEq/L potassium chloride, 0 degree to 2 degrees C) was infused with separate control of the infusion pressures in the left anterior descending and circumflex arteries. A sonomicrometer measured regional myocardial function in each area. During a 100 minute arrest period, cardioplegic solution was reinfused every 20 minutes and reduced myocardial temperatures to an average of 9.4 degrees +/- 2.2 degrees C. In a comparison of infusion pressures of 50 versus 100 mm Hg and 100 versus 150 mm Hg, postarrest regional myocardial function was unchanged from prearrest. However, in a comparison of infusion pressures of 150 to 200 mm Hg, a significant fall in regional myocardial function was noted with the higher pressures (106% and 64% recovery, respectively, p less than 0.02, n = 6). Excluding the areas perfused at 200 mm Hg, comparison of regions cooled to less than 8 degrees C and to greater than 8 degrees C demonstrated no difference in recovery of regional myocardial function. In this study, elevation of cardioplegic infusion pressures to 150 mm Hg and lowering of myocardial temperatures to less than 8 degrees C caused no impairment of regional myocardial function.

Animals↗
PubMed1981

Thermodynamics of dihexanoylphosphatidylcholine aggregation.

Heats of dilution of aqueous solutions of dihexanoylphosphatidylcholine were determined by use of a flow microcalorimeter to monitor an exponential dilution gradient. Three different models of micelle formation were tested: monomer in equilibrium with micelles of fixed size, with micelles of varied size, or with small aggregates and micelles. The heat of dilution data for low solute concentration could be fit only by assuming the existence of premicellar aggregates. The critical micelle concentration determined calorimetrically is 0.016 +/- 0.002 M and is independent of the model. The enthalpy change for transfer of monomer into the micelle is 1.6 +/- 0.2 kcal/mol; about one-third of this heat effect is produced in formation of the premicellar aggregation. Comparison of the calorimetric measurements with results obtained by using other methods indicates the complexity of the micellization process.

Chemical Phenomena↗
PubMed1981

Evidence for a change in the structure of glutamate dehydrogenase during its catalytic cycle under cryogenic conditions.

Glutamate dehydrogenase binds alpha-ketoglutarate and NADPH to form a ternary complex whose ultraviolet difference spectrum exhibits a blue-shifted coenzyme absorption band and a distinctive aromatic amino acid perturbation. When ammonia is added to this complex at -42 degrees C in 50% methanol, initiating the enzymatic reaction, these two spectral features disappear at different rates. The kinetic independence of these two features is especially evident in the presence of excess L-glutamate. We propose that, under cryogenic conditions at least, there are two forms of the enzyme. The blue shift of the coenzyme absorption band reflects only the physical presence of an alpha-ketoglutarate molecule at the active site, while the distinctive aromatic amino acid perturbation reflects a change in enzyme structure caused by alpha-ketoglutarate binding which may persist in the absence of any bound alpha-ketoglutarate molecule. Simple red and blue shifts of model tyrosine and tryptophan compounds cannot be used to simulate the observed aromatic amino acid perturbation.

Acetates↗
PubMed1981

The cytotoxic effect of ethylnitrosourea on the developing rat cerebellum. Morphologic observations.

A single i.p. injection of 240 mg/kg of ethylnitrosourea (ENU) into rats in the perinatal period resulted in lethal damage to the proliferating external granular cells of the developing cerebellar cortex. Lethally damaged cells of the external granular layer were also observed in fetal rats at 20 days of gestation after transplacental administration of the same dose of ENU. The percentage of susceptible cells affected remained constant throughout the period investigated. Light microscopy showed large numbers of randomly distributed pyknotic nuclei and complete inhibition of mitotic activity 6 h after ENU administration. Electron-microscopic examination showed that damaged granular cells had clumping of chromatin along the nuclear membrane. Cell organelles were morphologically distorted and unidentifiable; lysosomal bodies accumulated in the cytoplasm. Nonproliferating Purkinje cells were not lethally affected; however, dilatation of the Golgi apparatus and an increase in the number of lysosomes were commonly observed cytoplasmic changes.

Animals↗
PubMed1981

Synthesis and antibacterial activity of 1-(arylamino)-1H-pyrroles and 4-(1H-pyrrol-1-ylimino)-2,5-cyclohexadienes.

The syntheses of 1-(arylamino)-1H-pyrroles and 4-(1H-pyrrol-1-ylimino)-2-5-cyclohexadienes are described. Several of these compounds express in vitro antibacterial activity or can be metabolized to show in vitro antibacterial activity, and a few examples have shown efficacy against tuberculosis in mice. One compound, N,N'-(2,5-cyclohexadiene-1,4-diylidene)bis-1H-pyrrol-1-amine, is completely effective at 6.25 mg/kg against Mycobacterium tuberculosis H37Rv.

Animals↗
PubMed1981

The risk of hip fracture in postmenopausal females with or without estrogen drug exposure.

This study estimated the risk of hip fracture among postmenopausal females with and without estrogen drug exposure. The Kaiser-Permanente Medical Care Program in Portland, Oregon served as the setting and medical records the source of data. A retrospective case-control method that matched each female member hospitalized with a hip fracture (N = 168) between 1965-1975 with two control female members hospitalized for reasons other than a hip fracture was used. The estrogen exposure rate of cases was 29.2 per cent and of controls 36.0 per cent. The risk of hip fracture was reduced with postmenopausal and prefracture estrogen exposure (RML = 0.72, 95 per cent CL: 0.48-1.09). However, the number of cases was sufficient only to detect a reduction in risk of about 50 per cent or greater. A possible protective effect from estrogens was also suggested with oral estrogen exposure and with longer lengths of estrogen exposure.

Activities of Daily Living↗