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Biomedical subjects

A J Johnson

Publications and source records attributed to A J Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1984

The effect of exercise and fasting on the myocardial protein and lipid metabolism in experimental bacterial myocarditis.

A generally nonlethal Salmonella typhimurium infection in weanling rats produced bacterial myocarditis and myocardial hyperplasia. Myocardial lesions were characterized by focal infiltrates of inflammatory cells (predominantly mononuclear), segmental myocyte necrosis, and incipient fibrosis. Although bacterial infections are infrequently associated with myocarditis, the S. typhimurium infection in young rats produced a new experimental model of diffuse myocardial inflammatory foci. Biochemical changes in the myocardium included great increases in total myocardial contents of protein (23%), RNA (39%) and DNA (43%) and several lipid fractions (35-55%) as well as in tissue activities of acid hydrolases, such as cathepsin D (124%) and beta-glucuronidase (135%), all of which contrasted with the relatively limited areas of histologic involvement (1.5%). To study the effects of additional stress in this model infection, some rats were exercised by forced running in wheels for 2 hours and others were fasted for 24 hours before samples were obtained. The short period of forced exercise in this infection caused an additional increase of myocardial protein content (47%) but with no additional change in histology. The expected fasting-induced degradation of protein as well as an infection-associated increase in myocardial lipids were each prevented when rats were fasted during ongoing acute infection. Protein degradation, as reflected by heightened acid hydrolase activities, seemed to occur at a similar rate regardless of other stresses, whereas the rate of myocardial protein synthesis appeared to be alterable.

Animals↗
PubMed1984

Sequential metabolic alterations in the myocardium during influenza and tularemia in mice.

Mice with generalized influenza or tularemia of similar lethality were studied in an effort to compare biochemical responses of the myocardium during infections of viral and bacterial etiology. A progressive loss of body weight characterized the course of both infections. Accompanying this, the myocardial content of protein and the activities of lactate dehydrogenase, citrate synthase, and cytochrome c oxidase all decreased. However, myocardial protein degradation appeared earlier and was more pronounced in influenza, and the protein changes were accompanied by a rapid decline of myocardial RNA. Activation of acid hydrolases, such as cathepsin D and beta-glucuronidase, occurred in tularemia but not in influenza, whereas leakage of beta-glucuronidase into the plasma occurred in both infections. Conversely, there was a considerably greater activation of myocardial catalase in influenza. These findings suggested that different control mechanisms or metabolic pathways were operative in the degradation of myocardial constituents in influenza as compared with tularemia. The absence of histological signs of myocarditis in either infection appeared to exclude any direct local effects of an inflammatory process on myocardial cells. Since the infections were of comparable lethality (based upon the inoculated dose of organisms), the observed differences in pattern and extent of metabolic responses of the myocardium to these infections may be attributed to different pathophysiological mechanisms evoked by the different microorganisms.

Animals↗
PubMed1984

Modifying effects of exercise on clinical course and biochemical response of the myocardium in influenza and tularemia in mice.

For a study of the interactions of strenuous physical exercise (daily swimming to exhaustion) and a viral as compared with a bacterial infection with regard to the clinical course and the biochemical response of the myocardium, influenza and tularemia of similar lethality were used in mice. In both infections, expected infection-induced catabolic alterations in the ventricular myocardium were evident 2 days before median lethality was achieved, with a more pronounced wasting in influenza than in tularemia. Exercise before inoculation (preconditioning) was beneficial in that the catabolic effects of both infections were limited and lethality in influenza was reduced. Thus, the myocardial protein-degrading effect of influenza did not occur with preconditioning, and oxidative tissue enzyme activities decreased less. In tularemia, cytochrome c oxidase activity was fully preserved with preconditioning, and activation of catalase was less pronounced. Exercise during ongoing infection counteracted the infection-induced decrease in the activities of glycolytic and oxidative enzymes in tularemia, but lethality and bacterial counts in the spleen were uninfluenced. Conversely, exhaustive exercise in influenza increased lethality and had no significant effect on cardiac enzymes. These exercise models caused no major alterations in activation of lysosomal enzymes (beta-glucuronidase and cathepsin D).

Animals↗
PubMed1984

Visceral leishmaniasis in the German shepherd dog. I. Infection, clinical disease, and clinical pathology.

Two groups of three German shepherd dogs each were inoculated with Leishmania chagasi or Leishmania donovani amastigotes and the infection was followed for 82 days. The dogs developed a persistent infection, became thin, and developed splenomegaly and lymphadenomegaly by 55 days after inoculation. All dogs developed a normocytic, normochromic anemia of increasing severity. Thrombocytopenia and leukopenia occasionally occurred. Blood tryptophan levels were decreased significantly in infected dogs. Increased total serum protein, with hypergammaglobulinemia and hypoalbuminemia, was present in all dogs to various degrees. There was a marked increase in gamma globulins, with smaller increases in alpha and beta globulins. Many of the clinicopathologic changes observed in these dogs were similar to the disease as it occurs in man. The German shepherd dog may be a useful laboratory model for the study of visceral leishmaniasis.

Anemia↗
PubMed1984

Visceral leishmaniasis in the German shepherd dog. II. Pathology.

Three German shepherd dogs were inoculated with Leishmania chagasi and three with Leishmania donovani and the infection was followed for 82 days. All infected dogs developed splenomegaly and lymphadenomegaly. In lymph nodes there was a reduction in lymphocyte population in paracortical areas, extensive proliferation of macrophages in paracortical areas and medullary cords, follicular hyperplasia, and increased numbers of plasma cells. The spleen had decreased numbers of lymphocytes in periarteriolar lymphoid sheaths, proliferation of macrophages in these regions, follicular hyperplasia, and enlargement of the red pulp with clusters of macrophages and plasma cells. The morphology of the tonsil was similar to the lymph nodes. Clusters of macrophages, often containing Leishmania spp, were present in liver, bone marrow, lung, and the intestines. The morphologic changes in lymph nodes and spleen were suggestive of a suppressed cell-mediated immunity and an active humoral immunity. The German shepherd dog may be a useful laboratory model for the study of immunopathologic changes in visceral leishmaniasis.

Animals↗
PubMed1984

Approaches to plasma fractionation for improved recovery and the development of potentially useful clinical factors.

World-wide use of large amounts of highly purified Factor VIII and Factor IX concentrates has increased steadily over the last decade. The increase has resulted in more effective treatment of patients with haemophilia, especially those patients on home care and 'demand' therapy, those on prophylactic therapy for chronic bleeding or those on maintenance therapy for the suppression of inhibitors. Changing socioeconomic conditions have also contributed to greater use of the concentrates. The trend is putting an increasing strain on conventional methods for collecting and fractionating plasma. These include the donor, the nature of the anticoagulant, methods for purification of the clotting factors, procedures for denaturation and/or separation of viral contaminants and patterns of clinical usage. As a result, it is essential that we upgrade the quantity and quality of plasma collected and utilize the most effective new methods for increasing the yield and purity of the plasma fractions. Of special significance are recently described procedures for heat inactivation and/or separation of viral contaminants from the fractions and the long-term promise of genetically engineered proteins.

Antibody Formation↗
PubMed1982

Response to infusions of polyelectrolyte fractionated human factor VIII concentrate in human haemophilia A and von Willebrand's disease.

Factor VIII was purified from cryoprecipitate by ion exchange chromatography on solid phase polyelectrolyte E-5 (PE-E5). The product was highly purified (3.5 u VIII:C/mg protein) compared to conventional concentrate (0.3 u VIII:C/mg protein) with low fibrinogen, low isoagglutinin titre, and a ratio of factor VIII coagulant activity (VIII:C) to factor VII related antigen (VIIIR:Ag) of 16:1. Trial infusions of this material (PE VIII) were given to three patients with severe haemophilia A and one patient with homozygous von Willebrand's disease. These patients also each received separate infusions of intermediate purity concentrate (IPC) for comparison. There were no adverse effects. The mean half life of VIII:C after PE VIII infusion in the haemophiliacs was 10.9 h and after IPC was 12.1 h, a statistically insignificant difference. The survival of factor VIII coagulant antigen (VIII:CAg) was similar to that of VIII:C. In contrast, the half life of VIII:C and of VIII:CAg was very short after infusion of PE VIII in the patient wih von Willebrand's disease (2.4 h). IPC when infused in this patient produced a typical secondary rise of VIII:C. Two bleeding episodes in severe haemophiliacs were satisfactorily treated with PE VIII. PE-E5 deserves further study as a means of preparing clinical concentrates of factor VIII.

Antigens↗
PubMed1981

Partial purification of biologically active, low molecular weight, human antihemophilic factor free of Von Willebrand factor. I. Partial characterization and evidence for disulfide bond(s) susceptible to limited reduction.

Partially purified (approx. 5000-fold), low molecular weight human antihemophilic factor, free of detectable Von Willebrand factor (ristocetin cofactor activity or Von Willebrand antigen), was prepared from fresh citrated plasma by limited reduction with 1 mM dithiothreitol and chromatography on Sepharose CL-4B, Sephadex G-100, and polyelectrolyte E-5. The ratio of antihemophilic factor activity to Von Willebrand factor activity or antigen was greater than 27 000 : 1. The antihemophilic factor activity could be neutralized with homologous antibody and could be further increased with thrombin. The Mr (approx. 116 000) was determined by calibrated gel permeation chromatography, electrophoresis in 5% polyacrylamide gels with sodium dodecyl sulfate and by electrophoresis in large-pore acrylamide gels without it. Since the low Mr antihemophilic factor could be prepared by treating fresh rather than fresh-frozen plasma with dithiothreitol, it was concluded that partial reduction of the antihemophilic factor with this reagent helped to maintain the antihemophilic factor in a low Mr form. When iodo[l-14C]acetamide was used to alkylate the reduced plasma proteins prior to purification, the molecular weight of the purified antihemophilic factor remained low despite numerous purification steps. By this means, one of four radioactive proteins (Mr 116 000) in the final preparation was bound specifically to homologous antihemophilic factor antibody and attributed to 14C-labeled antihemophilic factor. While the data suggest that antihemophilic factor in fresh plasma contains one or more dithiothreitol-sensitive intramolecular disulfide bonds, the possibility of disulfide linkages with other proteins(s) cannot be excluded.

Chemical Phenomena↗
PubMed1981

Partial purification of biologically active, low molecular weight, human antihemophilic factor free of Von Willebrand factor. II. Further purification with thiol-disulfide interchange chromatography and additional evidence for disulfide bonds susceptible to limited reduction.

Thiol-disulfide interchange chromatography was used in the preparation of partially purified (approx. 17 000-fold) low molecular weight, Mr approximately or equal to 115 000, human antihemophilic factor essentially free of Von Willebrand factor. This antihemophilic factor was prepared from fresh plasma which had undergone limited reduction with 1 mM dithiothreitol and was subsequently reacted with 2,2'-dipyridyl disulfide, a sulfhydryl reagent which readily undergoes disulfide exchange. Exchange of protein-2-pyridyl mixed disulfide with thiopropyl-Sepharose resulted in the chromatographic adsorption of approx. 96% of the coagulant activity, of which approx. 20% subsequently eluted with 1.0 mM dithiothreitol. After reductive displacement from the thiopropyl-Sepharose the antihemophilic factor could be S-alkylated with iodo-[1-14]acetamide. The ratio of coagulant activity to Von Willebrand factor-antigen activity was greater than 30 000 : 1. In contrast, reduced antihemophilic factor was alkylated with iodoacetamide prior to chromatography as a control, and showed no exchange with the thiopropyl-Sepharose, eluting quantitatively in the breakthrough volume. These studies reinforce our previous results (Harris, R.B., Newman, J. and Johnson, A.J. (1981) Biochim. Biophys. Acta 668, 456-470) that partial reduction with dithiothreitol exposes critical sulfhydryl groups which, when alkylated, maintains the antihemophilic factor in a low molecular weight form without inactivating procoagulant activity.

Chromatography↗
PubMed1981

Comparison of multiple puncture liquid tuberculin test with Mantoux test.

Two studies were performed to compare the disposable liquid tuberculin PPD 'Imotest' with the Mantoux test. While there was a tester effect in the first study indicating the need for accurate application of the imotest, the results of the second study showed that the two tests were comparable in selecting truly positive and negative tuberculin reactors. Results were compared both by conventional methods and by a method new to tuberculin testing, the maximum likelihood technique. This method gives a more accurate estimate of false reaction rates. A significant difference was found between reading at 48 and 72 h for both tests. The acceptability and ease of reading of the imotest, with a tuberculin selectivity comparable to the Mantoux method, make it a suitable alternative tuberculin test, especially for screening large populations.

False Negative Reactions↗
PubMed1980

Isolation of fibrinogen-fibrin related antigen from human plasma by immuno-affinity chromatography: its characterization in normal subjects and in defibrinating patients with abruptio placentae and disseminated cancer.

Highly purified fibrinogen-fibrin related antigen (FR-antigen) was isolated with good recovery from 1.0--2.0 ml of human plasma, by immuno-affinity chromatography with antibody specific for fibrinogen and fibrin, and plasmin degradation products X, Y, D and D-D dimer. In FR-antigen from defibrinating patients there was evidence for thrombin activity alone (mainly disseminated cancer) or both plasmin and thrombin (mainly abruptio placentae). Thus, the molar ratio of N-terminal Gly-Tyr in the FR-antigen of 18 of 20 patients strongly suggested thrombin activity (95th percentile). In addition, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) on unreduced samples frequently showed bands similar in mol wt to fragments X, Y and D, and in the reduced samples A alpha and B beta chain degradation, both indicating plasmin activity. 'N-terminal beta chain Ala' was elevated in the antigen of four of 20 patients, also suggesting plasmin activity (99th percentile). Combined thrombin, plasmin and factor-XIII activity, as shown with high levels of serum FR-antigen (greater than 10 mg/dl). In some defibrinating patients, especially those with disseminated cancer, heterogeneity of unreduced FR-antigen and A alpha chain degradation, both indicators of mild plasmin-like activity which are commonly seen in normals, were absent.

Abruptio Placentae↗
PubMed1979

Quantitative N-terminal analysis of fibrinogen-fibrin-related antigen [FR antigen] from human plasma.

Fibrinogen-fibrin-related antigen (FR antigen) was isolated from as little as 1 ml of human plasma by immuno-affinity chromatography with agarose-bound antibody to human fibrinogen. N-terminal analysis was performed to determine the nature and extent of proteolytic degradation of the FR antigen in patients with disseminated intravascular coagulation and in normal subjects. Thrombin cleavage of the A- and B-peptides from fibrinogen in vitro was monitored by the appearance of N-terminal glycine, and an increase in glycine was shown in the FR antigen of patients with disseminated intravascular coagulation. As plasmin progressively degraded fibrinogen, increases in N-terminal alanine, aspartic acid and lysine were observed, corresponding to the known plasmin-cleavage points of fibrinogen; increases in these N-terminal amino acids were also found in the patients' FR antigen. Thrombin treatment in vitro was used to remove fibrinopeptide A (N-terminal alanine) from the samples and to reflect specifically the N-terminal alanine at the plasmin-cleavage point (Arg-42-Ala-43) of the B beta-chain on assay; this alanine was increased progressively in the FR antigen of a patient during urokinase therapy, and was high in other patients when the FR antigen was examined by this procedure.

Alanine↗