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Biomedical subjects

L L Johnson

Publications and source records attributed to L L Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1982

Two per cent glutaraldehyde: a disinfectant in arthroscopy and arthroscopic surgery.

Arthroscopes and some instruments for arthroscopic surgery were prepared for use by soaking them for fifteen minutes in a cold solution of 2 per cent glutaraldehyde. This method was practical, economical, safe, and effective. Over a eight-year period we performed 12,505 arthroscopic procedures with an infection rate of 0.04 per cent. Although technically classified as a disinfectant, 2 per cent glutaraldehyde used under these conditions proved to be an effective method of preparing arthroscopic surgical instruments and was less damaging to these instruments than methods involving sterilization by steam.

Aldehydes↗
PubMed1982

Impact of diagnostic arthroscopy on the clinical judgement of an experienced arthroscopist.

This study explores the impact of a careful analysis of 1000 consecutive cases of diagnostic arthroscopy conducted by the author. The cases are evaluated to determine whether there is a tendency to clinically misdiagnose certain lesions. The findings furthered knowledge in regards to other possible diagnoses for specific symptom complexes. Diagnostic arthroscopy has allowed surgeons to " fine tune" their preoperative diagnostic ability and can be a very useful enhancement to the armamentarium of clinical evaluations, laboratory tests, plain radiographs, and double contrast arthrograms as diagnostic tools for knee problems. An "audit" procedure is outlined that could benefit any surgeon who is concerned about increasing their diagnostic ability.

Adolescent↗
PubMed1981

Genetics of histocompatibility in mice. IV. Detection of certain minor (non-H-2) H antigens in selected organs by the popliteal node test.

The H-Y antigen and minor H antigens defined by eight C57BL/6By (B6) congenic mouse strains were studied for their distribution among 13 different tissues. Antigen expression was detected by implanting B6 recipients with organ fragments from congenic strain donors that had been previously grafted with B6 bone marrow to minimize the number of allogeneic passenger leukocytes. Successfully immunized recipients were identified by the enlargement of their popliteal lymph nodes following footpad challenge with spleen cells of the donor type. No two strains had identical patterns of expression of their distinguishing antigens. The data provide evidence for differences in levels of minor H-antigen expression among different tissues.

Animals↗
PubMed1981

Genetics of histocompatibility in mice. III. Characteristics of the popliteal lymph-node response to minor (non-H-2) H antigens.

The response to spleen cells incompatible at defined histocompatibility, H, loci was studied using the popliteal lymph-node enlargement test to establish its applicability as a method for detecting minor H antigens. This test was able to detect H-2 and H-Y antigens as well as most of the minor H antigens represented by 23 different strains congenic with C57BL/6By. Responses of both naive and immunized recipients were examined, and time-courses of the response were obtained for ten donor strains. These curves revealed that different antigens elicited responses that differed in timing and magnitude of peak enlargements, and that the two parameters were not closely correlated. Both the peak magnitude and the slope of the primary response were correlated with skin-graft rejection, however. The response to individual minor antigens did not appear to be dose-dependent above a threshold. Irradiation of donor cells had strain-dependent effects on the elicited response. Irradiation of recipients appeared to abrogate the primary response but not the responses of previously primed recipients in the combination tested. None of the responses studied had any demonstrable graft-versus-host component.

Animals↗
PubMed1981

Comparison of two radionuclide techniques for detecting disease of right and left coronary arteries.

Radionuclide angiography and thallium-201 myocardial perfusion scintigraphy were compared in 31 patients with coronary artery disease studied at rest and during exercise. Seventeen of the 31 patients had perfusion defects on thallium-201 redistribution scans (61%); 16 of these had prior transmural infarction. Six other patients with prior inferior infarction had no defects on thallium-201 redistribution scans. During treadmill exercise, 28 of 31 patients (90%) developed new or larger thallium-201 perfusion defects, a significantly higher percentage of patients than those that developed ST segment abnormalities during exercise (74%). During bicycle exercise left ventricular ejection fraction decreased in 27 of the 31 patients (87%); the average change in left ventricular ejection fraction was from 54 +/- 16+ to 48 +/- 14% (p less than 0.1). Twenty-three of the 31 patients had abnormalities of regional ejection fraction at rest (74%), while 30 of the 31 had abnormalities during exercise (97%). The number of patients who developed new regional ejection fraction abnormalities during exercise (28 of 31) was not significantly different from the number of patients who developed new or larger thallium-201 myocardial perfusion defects during exercise. In order to compare the two radionuclide techniques with respect to identification of vessel involvement, the patients were separated into those with disease of the right coronary system, disease of the left coronary system, or both. Thallium-201 scintigraphy correctly identified ten of 14 patients with involvement of only the right or left system; radionuclide angiography correctly identified six of 14. However, radionuclide angiography identified more patients with right and left system involvement (15/17) than did thallium-201 scintigraphy (6/17), p less than .01. These data suggest radionuclide angiography is more useful for identifying patients with disease of both the right and left coronary arteries.

Adult↗
PubMed1980

Analysis of courtship sequences of the hybrids between Drosophila melanogaster and Drosophila simulans.

Several transitions between sequential male courtship elements were analyzed for Drosophila melanogaster, its close relative D. simulans, and two types of hybrid males. Hybrid males from special reciprocal crosses did not differ. While D. melanogaster and D. simulans males differed markedly for the majority of transitions studied, hybrid males showed no consistent pattern with the parent species, being indistinguishable from D. simulans males, indistinguishable from D. melanogaster, or intermediate between them, depending on the trait observed. This suggests independent genetic control of these transitions during male courtship.

Animals↗
PubMed1980

Genetics of histocompatibility in mice. II. Survey for interactions between minor (non-H-2) antigens by skin grafting.

Twenty-five congenic mouse strains differing at distinguishable minor (non-H-2) histocompatibility loci were paired in 71 different combinations. F1 offspring were used as skin-graft donors for more than 4000 recipients to test whether immune responses to parental strain antigens were statistically independent. Thirty-four (48 percent) of the 71 combinations were predicted adequately by an independent response hypothesis. A simple additive model was consistent with 39 (55 percent) of the observed responses, although 18 of these were among those in agreement with the independent hypothesis. A synergistic response faster than that predicted by either the independent or additive response model was seen in 12 (17 percent) of the combinations. The remaining 5 percent were not well described by any of these models. No strain was represented with unusual frequency among those involved in synergistic interactions.

Animals↗
PubMed1980

Improved exercise ejection fraction with long-term prazosin therapy in patients with heart failure.

To study the effect of prazosin therapy on left ventricular function in patients with chronic stable heart failure, first pass radionuclide angiography at rest and during exercise was performed in 15 patients before the administration of prazosin and after seven to 12 weeks of prazosin therapy. There was no significant change in resting ejection fraction before and during prazosin therapy (36 +/- 14 per cent versus 37 +/- 14 per cent) (mean +/- standard deviation). However, exercise ejection fraction increased from 34 +/- 14 per cent to 42 +/- 17 per cent (p less than 0.01). The difference in ejection fraction from rest to exercise (ejection fraction response) changed significantly from -2 +/- 6 per cent before prazosin therapy to +5 +/- 7 per cent during prazosin therapy (p less than 0.01). Exercise duration increased from 368 +/- 82 seconds to 476 +/- 82 seconds (p less than 0.01). Total work capacity measured in kilojoules increased from 12.6 +/- 8.3 to 18.6 +/- 10.4 (p less than 0.01). The improved ejection fraction response during prazosin therapy correlated with the improved work capacity (r = 0.69, p less than 0.01) and exercise duration (p = 0.59, p less than 0.05). This improvement occurred despite a significant weight gain with prazosin from 72.2 +/- 20.8 kg to 73.5 +/- 20.8 kg (p less than 0.01). These data suggest that long-term prazosin therapy is effective in the treatment of heart failure. However, the beneficial effects of prazosin, an alpha 1 blocking agent, may be evident only during exercise.

Adult↗
PubMed1980

Adrenocortical response to novelty stress in rats with dentate gyrus lesions.

Male rats exposed to a novel environment exhibited a marked rise of plasma corticosterone in response to the initial exposure. These animals showed a significant but not complete habituation of their adrenal response after 18 exposures. Following their first exposure to a novel environment, animals with bilateral lesions in the dentate gyrus of the hippocampus had plasma corticosterone concentrations which were significantly lower than those observed for the control animals. Whereas the control groups demonstrated a significant decrease in their adrenal response following 18 exposures (habituation), there was no decrease of the adrenocortical response to novelty stress within the dentate-lesioned group between trials 1 and 18. The effect of the dentate lesions appeared to be specific to the behavioral stress: dentate lesions failed to alter resting levels, or the animal's adrenal responses to laparotomy stress and ether inhalation.

Adrenal Cortex↗
PubMed1979

[Not Available].

Explore the source record for details and available documents.

Argentina↗
PubMed1979

Comparison of intraoperative nitroprusside unloading in mitral and aortic regurgitation.

To compare the hemodynamic effect of vasodilator therapy on different regurgitant lesions, we infused sodium nitroprusside intraooperatively in 12 patients with mitral regurgitation and 15 with aortic regurgitation. During the critical period preceding establishment of cardiopulmonary bypass, both groups had developed intense vasoconstriction and cardiac decompensation. All demonstrated improved cardiac function with vasodilator therapy; however, the degree of improvement with nitroprusside differed in the two groups. Stroke volume increased 10 ml. per beat per meter squared in those patients with aortic regurgitation and only 6 ml. per beat per meter squared in those with mitral regurgitation (p less than 0.05). The percent increase in stoke volume induced by nitroprusside was inversely correlated to the preoperative left ventricular ejection fraction (r = 0.44, p less than 0.02). Patients with aortic regurgitation had lower preoperative left ventricular ejection fractions than those with mitral regurgitation (0.53 versus 0.63, p less than 0.02). Therefore, we conclude that patients with aortic regurgitation derived greater intraoperative hemodynamic benefit from unloading with nitroprusside, because they came to surgery with greater impairment of left ventricular contractility. Although nitroprusside improved cardiac function in both groups, only the patients with aortic regurgitation achieved normal pulmonary artery pressure (17 torr) and pulmonary vascular resistance (2.1 units) as a result of unloading. Those with mitral regurgitation continued to have pulmonary hypertension (28 torr) and increased pulmonary vascular resistance (3.9 units) despite vasodilator therapy. Thus the data suggest that patients with mitral regurgitation derived less hemodynamic benefit from intraoperative nitroprusside therapy because they were also limited by right ventricular dysfunction and a less responsive pulmonary vasculature.

Adult↗
PubMed1978

In vitro analysis of pre- and early postimplantation development of lethal yellow (Ay/Ay) mouse embryos.

Preimplantation embryos from matings between yellow heterozygous (Ay/a) mice were recovered at 56 hours post coitum, cultured for five days, and compared with the development of embryos from three control matings (Ay/a female X a/a male, a/a female X Ay/a male, a/a female X a/a male). Most embryos were at the 8-cell stage at recovery; however fewer embryos from the experimental cross had developed to the 8-cell stage than embryos of control matings, indicating a developmental lag of experimental embryos (P less than 0.01). The yellow (Ay/a) uterus did not contribute (P = 0.05) to delayed development. Experimental and control embryos were equally capable of successful development in culture to the morula stage with no distinct morphological characteristics identifying the class of Ay/Ay mutants. However, significant differences were observed in the development from morulae to blastocysts; 9.4% (10/106) of the morulae in experimental crosses failed to undergo blastocyst formation as compared with 2.5% (10/398) of morulae in pooled control crosses (P = 0.010-0.025). In the experimental cross 25.0% (24/96) of embryos that developed successfully to the blastocyst stage failed to hatch from the zona pellucida; these are presumed to include the class of lethal yellow homozygotes. Abnormalities seen in cultured embryos consisted primarily of blastomere disintegration, blastomere arrest and exclusion, and embryo fragmentation.

Animals↗