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Biomedical subjects

L Johnson

Publications and source records attributed to L Johnson.

At least 415 records · Page 23Linked to original sources
PubMed1982

A revised classification of retinopathy of prematurity.

We have developed a classification system for the acute phases of retinopathy of prematurity based on more than 13,000 ophthalmoscopic examinations of more than 3,400 premature infants between 1968 and 1982. Two forms of the active disease exist. Retinopathy of prematurity is a relatively common mild disease and retinopathy of prematurity plus is characterized by rapid progression and posterior pole vascular tortuosity and dilation. The five grades progress from peripheral vascular abnormalities (Grade 1) through a demarcation line (Grade 2) and extraretinal neovascularization (Grade 3) to partial (Grade 4) or total (Grade 5) retinal detachment. The persistence of abnormal retinal vessels during the first year of life is considered "transitional" retinopathy of prematurity unless unequivocal cicatricial changes with macular distortion develop.

Humans↗
PubMed1982

A re-evaluation of daily sperm output of men.

The daily sperm output (DSO) was reevaluated and urinary loss of sperm was determined. Ejaculates were immediately fixed with glutaraldehyde, stored, and homogenized in a blender to produce a cell suspension. The number of sperm per ejaculate was determined by phase-contrast cytometry. Based on the average number of sperm per ejaculate for the last three of five daily ejaculates, the DSO was 166 +/- 29 X 10(6) sperm for nine men aged 26 to 38 years. Two successive daily ejaculates were sufficient to stabilize extragonadal sperm reserves following accumulation or depletion of epididymal sperm. Sperm were found in urine of three men, and less than 2% of their DSO appeared in the 24-hour urine. Few sperm were voided in the urine of men ejaculating daily; however, the DSO exceeds previous estimates.

Adult↗
PubMed1982

Vitamin E supplementation and the retinopathy of prematurity.

The effect of high-dosage E treatment (Rx) initiated at the stage of 3-plus active disease (target serum E levels, 5-6 mg/dl) was evaluated by a standardized scoring system of visual morbidity at the one to two year eye exam among infants cared for in the University of Pennsylvania Neonatal Complex (1976-1978). The incidence of legal blindness in both eyes or worse was decreased from 71 to 40% in E Rx (n = 10) as compared to non-E Rx (n = 14) infants, and the number of infants with minimal visual morbidity was increased. Pilot studies (1972-76; target serum E level, 1.5 and 3.0 mg/dl) of the prophylactic effect of E Rx from birth on showed a decrease in mean severity of acute stage disease and a decrease in sequelae at one to two years. A strikingly difference in visual morbidity following resolved low-grade ROP was seen when prestudy infants (1968-72) who were fed early iron supplements and given formulas with low E:PUFA ratios were compared to non-E Rx as well as to E Rx 1972-76 infants. Vitamin E seems to exert a beneficial effect at all stages of ROP, perhaps because of its broadly based regulatory role.

Animals↗
PubMed1982

A semiquantitative histological method to estimate acute and chronic radiation injury in the small intestine of the cat.

To study the radiation injury in the small bowel of the cat after doses close to and above the threshold for chronic radiation injury (15 Gy), an attempt was made to quantify these changes. For this purpose a semiquantitative method was developed by using 13 different histological alterations that were considered to mirror the acute and chronic radiation changes in the mucosa. Fibrosis was difficult to quantify; micrometric measurements of the bowel wall and its different layers were therefore carried out. The histological alterations were tabulated in increasing degree of severity. The sum of points of registered alterations in the specimen yielded scores that together with the micrometric measurements made it possible to differentiate specimens irradiated with high doses from those irradiated with low doses. The method may be valuable in estimating radiation injury in surgical specimens and in experimental studies of radiation injury.

Animals↗
PubMed1981

Mouse liver glutathione S-transferases. Biochemical and immunological characterization.

Three major forms of cytosolic glutathione S-transferase (designated F1, F2, and F3 transferases according to increasing isoelectric points) were purified to homogeneity from liver of DBA/2J mice, primarily by CM-cellulose and hydroxylapatite chromatography. The purified enzymes were shown to have specific activities of 104, 281, and 143 units/mg, respectively, when assayed with 1 mM each of 1-chloro-2,4-dinitrobenzene and reduced glutathione. Antisera against these three forms of mouse transferase were raised separately in rabbits. F1 and F2 transferases showed complete immunological identity either by double immunodiffusion or enzyme immunoinactivation tests. No cross-reactivity was observed between the antisera to F1 (or F2) transferase an F3 transferase or between the antisera to F3 transferase and F1 (or F2) transferase. F1 and F2 transferases were shown to be homodimers with an identical molecular weight of 44,000 +/- 1,000, whereas F3 transferase has a dimeric molecular weight of 51,000 +/- 2,000. The amino acid composition and tryptic peptide map of F1 transferase are similar to those of F2 transferase, but are distinct from those of F3 transferase. In addition to these major forms, a minor form of mouse transferase (F4) with a high isoelectric point (greater than 9.5) was shown to be a mixture of interconvertible isomers of F2 and F3 transferase. Different forms of mouse transferase were studied extensively with respect to their biochemical properties, including Michaelis constants, substrate specificity, thermal stability, and fluorometric ligand binding. The results of this study suggest great species variations regarding the multiple forms as well as the substrate specificity of this family of enzymes.

Amino Acids↗
PubMed1981

Neuroendocrine measures in psychiatric patients: course and outcome with ECT.

Measures of neuroendocrine function--plasma cortisol and its response to dexamethasone, and plasma thyroid-stimulating hormone (TSH) and its response to thyrotropin-releasing hormone (TRH)--were employed in 50 hospitalized male veteran psychiatric patients with diagnoses of unipolar or bipolar melancholia, secondary depression, or schizophrenia. Of 20 cases of unipolar melancholia, 17 (85%) exhibited hypercortisolism; 14 (70%) failed to suppress plasma cortisol after dexamethasone; and 4 (31%) of 13 tested had an abnormal TSH response to intravenous TRH. Two patients with secondary depression also exhibited hypercortisolism; no other patients evinced abnormal neuroendocrine test results. These measures were repeated in 14 unipolar depressed patients after a course of electroconvulsive therapy (ECT). Improvement in psychopathology was directly related to normalization of measures of hypothalamic-pituitary-adrenal (HPA) function. The TSH response to TRH was not systematically altered. After a followup period of 1 to 9 months, there was a good correlation between the measures of HPA function and the clinical outcome. These findings encourage further study of HPA function measures as outcome criteria for depressed patients receiving ECT.

Adult↗
PubMed1981

[Evidence for the presence of glucocorticoid receptors in heart contractile cells].

Using 3H-labelled glucocorticoids, the receptor activity of heart and liver cytosol preparations from various animal classes and species, the distribution of receptors in the myocardium from different divisions of rat heart and the number of glucocorticoid receptors in the myocyte preparations isolated from adult rat hearts after treatment of cardiac tissue with hyaluronidase and collagenase have been studied. The specific binding of 3H-dexametasone to bovine fetal heart endothelial cells as well as to some other cell cultures was investigated. The data obtained suggest that the bulk of the total receptor activity of the heart is accounted for contractile cells of the myocardium. The number of specific sites of glucocorticoid binding by whole myocyte cells (per 1 mg of protein) or by "crude nuclear fraction" (per 1 mg of DNA) is comparable to that for some other cell types, which are believed to be hormone-sensitive. However, by the number of receptors per single cell myocytes surpass all the other cell types under study.

Animals↗
PubMed1980

Multiple forms of Drosophila hexokinase. Purification, biochemical and immunological characterization.

Major forms of hexokinases (Hex A and Hex C) in Drosophila melanogaster were purified to homogeneity by utilizing affinity chromatography and preparative isoelectric focusing column as the key steps. Three different affinity ligands immobilized on Sepharose (3-amino pyridine adenine dinucleotide, glucosamine, and 8-(6-aminohexyl)-amino-ATP) were employed during different stages of enzyme purification. Antisera against purified Hex A and Hex C were raised in rabbits. Hex A, the major form in adults, and Hex B, the predominant form in larvae, showed complete immunological identity by double immunodiffusion and enzyme immunoinactivation studies. No cross-reactivity was observed between the antiserum to Hex A and Hex C or between the antiserum to Hex C and Hex A. By gel filtration chromatography and sodium dodecyl sulfate-acrylamide gel electrophoresis, all of the Drosophila hexokinases were shown to be monomers of molecular weights ranging from 40,000 to 50,000. Multiple forms of Drosophila hexokinase were studied extensively with respect to their biochemical properties including Michaelis constants, substrate and coenzyme specificities, pH-dependent activity, and thermal stability. Consistent with previous genetic evidence, the results of our studies also suggest that Hex A and Hex B (with subforms B1 and B2) are products of a single structural gene but are modified post-translationally, whereas the allelic forms of Hex C (C1 and C2) are derived from a different structural gene from that of Hex A and Hex B.

Animals↗