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Biomedical subjects

L W Johnson

Publications and source records attributed to L W Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Serologic and clinical responses of premunized, vaccinated, and previously infected cattle to challenge exposure by two different Anaplasma marginale isolates.

Two Anaplasma marginale isolates, one originating in Florida (FAM) and the other from Virginia (VAM), were compared immunologically by cross-challenge exposure of 14 Anaplasma carrier cattle, 8 previously infected cattle, and 6 splenectomized carrier calves. In addition, 28 cattle vaccinated with a commercially available adjuvant killed vaccine and 22 nonvaccinated cattle were challenge exposed with either FAM or VAM. A detectable clinical response was not produced by either FAM or VAM challenge exposure in carrier and previously infected cattle; however, evidence of A marginale growth as characterized by low percentages of parasitemia and increased serum complement-fixation titers was seen in carrier cattle given a heterologous challenge organism and in previously infected cattle inoculated with either homologous or heterologous organisms. Among splenectomized calves, there was virtually no cross protection to the heterologous challenge exposure, whereas a homologous challenge failed to elicit any detectable response. Vaccinated cattle were resistant to VAM exposure, but the clinical response to FAM exposure was severe with a 47% mortality. Most of these cattle displayed typical acute anaplasmosis that was only marginally less severe than that encountered in nonvaccinated cattle.

Anaplasma↗
PubMed1983

Supraventricular arrhythmias following coronary artery bypass. The effect of preoperative digitalis.

Supraventricular arrhythmias continue to complicate the postoperative course of patients undergoing myocardial revascularization. In a previous study, we showed a decrease in arrhythmias if patients were given digitalis prior to operation. Since that time we have made two changes-- propranolol is no longer discontinued prior to operation and cold hyperkalemic cardioplegic solution is routinely used. To assess the affect of these changes on arrhythmias, we repeated the previous study. One hundred twenty patients all receiving preoperative and postoperative propranolol were randomized into a control group and a digitalis-treated group. The incidence of supraventricular arrhythmia postoperatively was 21.4% in the control group and 3.1% in the digitalis group (p less than 0.005). Therefore, we continue to advise preoperative digitalization in patients requiring coronary artery bypass and continue to maintain beta blocker and digitalis therapy in the postoperative period.

Arrhythmias, Cardiac↗
PubMed1982

Clinical and clinicopathologic features of transport tetany of feedlot lambs.

Clinical and clinicopathologic features of transport tetany in 9 feedlot lambs were investigated. The lambs became recumbent within 10 days after arrival in the feedlot. The mean serum calcium concentration, mean magnesium concentration, and calcium:phosphorus ratio were significantly (P less than 0.01) less in affected lambs than in 6 unaffected lambs from the same feedlot. The mean serum phosphorus concentration was significantly (P less than 0.05) greater in the group of affected lambs. High activities of serum glutamic oxalacetic transaminase, creatine kinase, and lactate dehydrogenase in the serum of affected lambs indicated muscle necrosis, which was confirmed by histologic examination. Blood pH, HCO-3, and total carbon dioxide were significantly greater in affected lambs (P less than 0.01) than in unaffected lambs.

Animals↗
PubMed1982

Heritabilities for regression and progression of rous sarcomas in the chicken.

Variance components for hatch, line, and sire expressed as percentages of the total variance for each parameter of regression and progression of Rous sarcomas in chickens were obtained. Some parameters measured specific stages of regression or progression, and other parameters measured the entire process of regression or progression of Rous sarcomas. Heritabilities of each parameter were estimated. Additive genetic variation is strongly implicated in the defense of the chicken against early tumor growth and during the entire process of regression. Environmental variation is important in influencing the point in time of tumor growth when the first reduction in size of tumor occurs. There is evidence of genetic variation exclusive of the R-Rs-1 gene locus that assists the chicken to resist tumor growth. The coefficient of variation for each of the parameters is very large as compared with the coefficient of variation for economic traits such as body weight at broiler age.

Animals↗
PubMed1982

Responses to prolonged selection for resistance and susceptibility to acute cecal coccidiosis in the auburn strain single comb white leghorn.

Selection in the parental Auburn Strain Leghorn (A line) for resistance (R line, 13 filial generations) and susceptibility (S line, 7 filial generations) to acute cecal coccidiosis (ACC) caused by Eimeria tenella resulted in a sixfold difference in the ACC mortality rates of the two lines. Relaxation of selection for resistance in line RR, derived entirely from R line, resulted in gradual regression of the ACC mortality rate toward that of the parental A line nonselected control. Progress of selection in R line based on the same low dose of oocysts employed in S line neared a plateau of low mortality after six generations. Average ACC mortality in the first four generations of S line was 50% greater than that in A line. Before infection, chicks of S line were smaller than those of lines A, R, and RR. After infection, growth of S line survivors was inferior to that of survivors of the other lines. Uninfected controls of S line and A line grew at similar rates; those of R line grew at a significantly lower rate. In R line, large doses of oocysts caused high mortality. The largest dose caused mortality approaching 90% in both sexes; at lower doses, males died at higher rates than females. Among the survivors, growth rates of females were inferior to those of males; the difference increased with increasing dose. Large doses of oocysts resulted in spreading of the infection beyond the typical site. In R line, severe infection occurred in the necks of the cecal pouches and rectum with comparatively mild infection in the bulbar portion of the pouches. In contrast, the chief focus of infection remained in the bulbar pouches in S line. Selection for resistance seemingly disrupted the typical host tissue specificity of E. tenella. Thus, genes mediating the response of the host to ACC are possibly identical or complementary to genes controlling tissue specificity.

Animals↗
PubMed1982

Preventing heat stroke.

High temperature, mental status changes and anhidrosis constitute the classic triad of the heat stroke syndrome. Prevention should be the foremost concern. For athletes, this means gradual acclimation to a warm environment, liberal water replacement and use of the wet-bulb thermometer as a guide to activity. Other precautionary measures include preseason history and physical examination, records of pre- and post-exercise body weights, proper clothing and education. These principles are adaptable to nonathletes.

Acclimatization↗
PubMed1982

Ischemia: a cause of hepatic telangiectasis in cattle.

We histologically examined (i) 73 bovine livers condemned by packing house inspectors for telangiectasis, (ii) 15 bovine livers passed by the same inspectors as normal, and (iii) 8 livers from cattle given an injection into their mesenteric veins: 6 with a suspension of agar particles containing viable Haemophilus somnus and 2 with diluent only. The injected cattle were killed and necropsied 2 to 12 days after the inoculations. Of the 73 telangiectatic livers, 57 (78%) had thrombosed and occluded or contracted and empty portal veins (venopathies), whereas 1 of the 15 normal livers contained one microscopic focus of telangiectasis and nearby venopathy. Of the 6 livers injected with suspended particles, all had venopathies and telangiectasis and the 2 control livers had neither.

Animals↗
PubMed1981

Tissue reaction to suture materials in infected surgical wounds--a histopathologic evaluation.

Suture materials are foreign bodies which induce and prolong tissue reaction in the wound area. Cellular responses to infected wounds containing 7 suture materials (braided polyglycolic acid [BPGA, Dexon], multifilament stainless steel, monofilament nylon, black braided silk, braided Dacron [Mersilene], and plain and chromic catgut) were studied at 6, 10, 20, and 40 days. Cellular reaction varied with different suture materials. In general, neutrophils were the predominant cells in acute infection, but later, macrophages and fibroblasts predominated. Occasionally, plasma cells, lymphocytes, eosinophils, and giant cells were present. In the infected wounds with implants of plain catgut, chromic catgut, silk, and braided Dacron, there were large numbers of neutrophils even in chronic implantation, indicating persistence of local infection. With nylon, steel, and BPGA, the number of neutrophils rapidly decreased. Although BPGA induced intense acute reaction, the response was mild in chronic implantation. It appeared to be absorbed more slowly than plain or chromic catgut, and tissue reaction was minimal in the absorption stages. A reaction similar to the Splendore-Hoeppli phenomenon was seen around multifilament silk strands in chronic stages of implantation.

Animals↗
PubMed1981

Further studies with polyglycolic acid (Dexon) and other sutures in infected experimental wounds.

Seven suture materials (braided polyglycolic acid [BPGA, Dexon], multifilament stainless steel, monofilament nylon, black braided silk, braided Dacron (BD, Mersilene], and plain and chromic catgut) were implanted in surgical wounds which were inoculated with 3 dilutions of Staphylococcus aureus. The degree of swelling was measured at 6, 10, 20, and 40 days. Monofilament nylon and multifilament steel produced the least amount of swelling; plain and chromic catgut produced the most. The BPGA, BD, and silk caused swellings that were intermediate in degree. In chronic implantations, inflammatory reactions to the various suture materials differed from those occurring soon after implantation. Response to steel and nylon remained minimal; that to silk was gradual, but overall became the most severe. There was slightly less response with BD. The catguts varied little from each other in their responses. Intense reaction was induced by BPGA in the early stages, but the response was mild in chronic implantations.

Animals↗
PubMed1980

Monosaccharide transport across microvillous membrane of human placenta.

Transport through the microvillous membrane of the syncytium is the first step in placental transfer of nutrients. We have therefore studied glucose transport by isolated microvillous membrane vesicles. Transport occurred by selective and rapid facilitated diffusion, which was inhibited by phloridzin, phloretin, cytochalasin B, and HgCl2. Nonmediated diffusion of the substrate was found by three independent methods to be very slow. Competition studies showed that aldohexoses in the C-1 chair conformation were the preferred substrates. Transport was independent of sodium gradients and was not modulated by insulin. However, several steroids inhibited transport including estriol and progesterone, which are abundant in utero. Kinetic analysis by equilibrium exchange demonstrated a Km of 31 mM and a Vmax of 120 nmol . s-1 . mg protein-1. The Km and Vmax suggest a large capacity in relation to calculated fetal needs. In consequence of this capacity, intrasyncytial concentrations of glucose are probably maintained near those of maternal blood. Augmentation of transport at this membrane by hormones or other agents is unlikely to increase fetal supply of glucose, but down regulation by steroids may serve a regulatory function.

Biological Transport↗
PubMed1980

Immunization of cattle with a Babesia bigemina antigen in Freund's complete adjuvant.

Three adult intact cattle and five splenetomized calves were immunized against Babesia bigemina by the subcutaneous injection of an adjuvant-vaccine given twice at 3- and 4-week intervals, respectively. The antigen consisted of B bigemina parasites and erythrocytic stroma. The vaccinated adults plus one control, and the vaccinated splenectomized calves plus four comparable controls were challenge exposed at 67 and 33 days, respectively, after the last vaccine injection. All control animals died of acute babesiosis. The intact vaccinated adult cows showed only minimal response and little or no drop in packed cell volume. Three of five vaccinated splenectomized calves showed a moderate response to challenge exposure and recovered rapidly.

Animals↗
PubMed1979

Changes in human amniotic fluid lecithin/sphingomyelin ratio and dipalmitoyl lecithin associated with maternal betamethasone therapy.

In an effort to understand the biochemical changes responsible for the decreased incidence of neonatal RDS observed in premature infants delivered after maternal glucocorticoid therapy we have compared quantitative changes in L/S ratio and qualitative changes in dipalmitoyl lecithin in serial amniotic fluid samples from 20 pregnant women treated with betamethasone and 11 patients who had repeated amniocentesis at similar gestational age but did not receive glucocorticoids. Initial L/S ratio values were not significantly different between treated (1.24 +/- 0.24 [S.D.]) and control (1.09 +/- 0.29 [S.D.]) groups but the values obtained within 1 week after therapy (1.49 +/- 0.21 [S.D.]) were significantly higher (t=3.8; p less than 0.01) than those obtained after a similar period in the untreated group (1.24+/- 0.29 [S.D.]). However, only one of the treated patients reached a mature L/S ratio (2.0 or more). Simultaneously, 10 of 17 treated patients exhibited increases in the amount of dipalmitoyl lecithin within the first week after treatment, wheras no change was detected in serial samples from six control patients (p = 0.016). These results indicate that qualitative changes in amniotic fluid lecithin composition are a part of the fetal response to glucocorticoids which may be responsible for the decreased incidence of RDS observed after treatment.

Amniocentesis↗
PubMed1979

Pseudocorpus luteum insufficiency: a local defect of progesterone action on endometrial stroma.

A 23-yr-old woman whose initial complaint was infertility demonstrated glandular stromal dissociation with failure of the endometrial stroma to undergo pseudodecidualization in repeated endometrial biopsies taken late in the luteal phase. As the clinical presentation was consistent with the inadequate corpus luteum syndrome, hormone measurements were performed. The endometrial biopsy was abnormal during cycles in which the serum pattern of progesterone, estradiol, FSH, and LH was normal. Exogenous progesterone did not correct the abnormality. The patient, by in vitro studies, has approximately one half the number of high affinity progesterone-binding sites in the cytosol fraction of her endometrium compared to preparations from two normal control subjects. Since her cytosol-binding protein was qualitatively identical to two control subjects, the incomplete maturation of her endometrial stroma may represent an absence or reduced number of stromal cytosol receptors and/or a resistance to specific hormone action in an individual target tissue.

Adult↗