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Biomedical subjects

K J Johnson

Publications and source records attributed to K J Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1994

Mechanisms of hyperacute rejection in porcine liver transplantation. Antibody-mediated endothelial injury.

Hyperacute rejection after OLT is an unusual event. We have demonstrated previously that hepatic hyperacute rejection can occur in the presence of high titers of donor-specific cytotoxic antibody. This study addresses the issues of antibody localization within the allograft and the consequences of antibody deposition and complement activation within the transplanted organ. A porcine model of liver transplantation was used and 3 experimental groups were studied. Group I recipients (n = 6) were specifically sensitized to their liver donors with skin grafts from their liver donors before hepatic grafting. Group II recipients (n = 6) underwent third-party skin graft sensitization before liver transplantation. Group III recipients (n = 6) underwent liver grafting without prior sensitization. After liver transplantation, serum complement (CH50) levels declined promptly in all groups; a statistically significant drop as compared with control animals was seen only in group I (P < 0.05). Liver biopsies from donor-specific sensitized recipients showed massive injury by light microscopy within 30 min of revascularization, demonstrating fibrinoid necrosis of vessels and neutrophil influx. On immunofluorescent examination, liver specimens from donor-specific sensitized animals showed intense IgG, IgM, and C3 deposition in the vessels of the portal triads. Antibody deposition was not seen in third-party sensitized animals or control animals. On electron microscopy, control animals and third-party sensitized animals showed minimal ultrastructural alterations. In comparison, livers from donor-specific sensitized animals showed severe microvascular injury with destruction of endothelial cells, edema, hemorrhage, and hepatocyte necrosis. In a passive serum transfer experiment carried out by infusing serum from a skin graft-sensitized pig directly into the portal vein of the skin graft donor, severe liver injury was evident, with identification of antibody deposition by light and electron microscopy and by immunofluorescence. These studies demonstrate that tissue injury in hyperacute hepatic rejection is mediated by antibody deposition within the grafted liver and is associated with systemic activation of the complement cascade.

Acute Disease↗
PubMed1994

Further evidence for clustering of human GABAA receptor subunit genes: localization of the alpha 6-subunit gene (GABRA6) to distal chromosome 5q by linkage analysis.

GABAA receptors are hetero-oligomeric ion-channel complexes that are composed of combinations of alpha, beta, gamma, and delta subunits and play a major role in inhibitory neuro-transmission in the mammalian brain. We report here a microsatellite polymorphism within the human alpha 6-subunit gene (GABRA6). Mapping of this marker in a human-hamster hybrid cell-line panel and typing of the repeat in the Centre d'Etude du Polymorphisme Human (CEPH) reference families enabled the localization of this gene to chromosome 5q and established its linkage to the GABAA receptor alpha 1-subunit gene (GA-BRA1) with a maximum lod score (Zmax) of 39.87 at a theta of 0.069 (males) and 0.100 (females). These results reveal the clustering of GABRA6, GABRA1, and the GABAA receptor gamma 2-subunit gene (GABRG2) on distal chromosome 5q.

Animals↗
PubMed1994

Fas ligation triggers apoptosis in macrophages but not endothelial cells.

The reticuloendothelial system includes macrophages and endothelial cells. These cells are produced and destroyed in vivo with a precision that implies the existence of homeostatic mechanisms. The stimuli for endothelial cell proliferation and monocyte production are becoming well characterized. However, the mechanisms involved in eliminating these cells are poorly understood. One mechanism involved in cellular elimination is apoptosis, which can be triggered in some cells by ligation of the Fas molecule. In this report we have investigated whether macrophages and endothelial cells express the Fas molecule, and whether Fas transmits an apoptosis-inducing signal in these cells. We demonstrate that macrophages express Fas and readily undergo apoptosis when cultured with anti-Fas. In contrast, while endothelial cells can express the Fas molecule, Fas ligation is insufficient to induce apoptosis. These results suggest differential regulation of Fas function among cells of the reticuloendothelial system, and imply different mechanisms of homeostasis.

Antigens, Surface↗
PubMed1994

A prospective study of renal structure and function in psoriasis patients treated with cyclosporin.

The impact of long-term cyclosporin therapy on kidney structure and function was evaluated in psoriasis patients with normal baseline renal function. Patients received cyclosporin at an average dose 3.9 mg/kg/day for up to three years and underwent serial kidney biopsies and measurements of iothalamate clearance and serum creatinine concentration. Kidney biopsy specimens (assessed on a scale of 0 to 4 where 0 = normal and 4 = severe) from 19 cyclosporin-treated patients as compared to 38 age-matched transplant donors showed increased interstitial fibrosis (1.9 +/- 0.2 vs. 0.3 +/- 0.1, P < 0.0001) and tubular atrophy (1.6 +/- 0.2 vs. 0.3 +/- 0.1, P < 0.0001) at one year. Eleven patients had a second biopsy after an additional two years of cyclosporin treatment demonstrating additional interstitial fibrosis (1.8 +/- 0.2 to 2.4 +/- 0.3, P = 0.002) and tubular atrophy (1.4 +/- 0.2 to 1.9 +/- 0.2, P = 0.053), and the onset of cyclosporin-associated arteriolopathy (0 to 0.5 +/- 0.2, P = 0.02). Quantitative digital morphometric analysis of trichrome-stained specimens also showed increased interstitial fibrosis (22.5 +/- 1.5 to 32.0 +/- 2.0% of interstitial area, P = 0.0008). Iothalamate clearance declined at an average rate of -3.1 ml/min/1.73 m2 per year (95% CI -5.8, -0.3) during the period of cyclosporin treatment. The slope of reciprocal serum creatinine declined by -0.06 dl/mg per year (95% CI -0.08, -0.04). Chronic cyclosporin treatment of otherwise healthy psoriasis patients is associated with progressive renal structural injury and reduced glomerular filtration rate.

Adult↗
PubMed1994

Analysis of GABAA receptor subunit genes in multiplex pedigrees with manic depression.

The gamma-aminobutyric acid (GABA) neurotransmitter system has been implicated in the pathogenesis of manic depression. Tests of this hypothesis can now be carried out due to the recent characterization of simple sequence repeat polymorphisms for the GABAA receptor alpha 1, alpha 2, alpha 4, alpha 5, alpha 6, beta 1, beta 3 and gamma 2 subunit genes. Using both parametric and non-parametric methods, we tested for linkage between manic depression and these polymorphisms in six multi-generational pedigrees. No evidence of linkage was found.

Adolescent↗
PubMed1994

The SON gene encodes a conserved DNA binding protein mapping to human chromosome 21.

We report the identification and characterization of a clone for the DNA binding protein SON, which we have isolated from a human keratinocyte cDNA library. Using this clone we have found that the SON gene is expressed in different cell types and that homologous sequences can be detected in vertebrate and insect genomic DNA. Using the polymerase chain reaction (PCR) to amplify SON sequences from a panel of somatic cell hybrids we have assigned the gene encoding human SON to chromosome 21. By use of hybrids containing regions of chromosome 21 the localization has been refined to 21q 22.1-q22.2.

Amino Acid Sequence↗
PubMed1994

C5a-induced expression of P-selectin in endothelial cells.

Human umbilical vein endothelial cells have recently been shown to respond to C5a with increases in intracellular Ca2+, production of D-myo-inositol 1,4,5-triphosphate and superoxide anion generation. In the current studies, C5a had been found to cause in a time- and dose-dependent manner rapid expression of endothelial P-selectin, secretion of von Willebrand factor, and adhesiveness for human neutrophils. The effects of C5a in P-selectin expression and adhesiveness of neutrophils were similar to the effects of histamine and thrombin on endothelial cells. The adhesiveness of C5a-stimulated endothelium for neutrophils was blocked by anti-P-selectin, but not by antibodies to intercellular adhesion molecule 1, E-selectin, or CD18. A cell-based ELISA technique has confirmed upregulation of P-selectin in endothelial cells exposed to C5a. Binding of C5a to endothelial cells has been demonstrated, with molecules bound being approximately 10% of those binding to neutrophils. By a reverse transcriptase-PCR technique, endothelial cells have been shown to contain mRNA for the C5a receptor. These data suggest that C5a may be an important inflammatory mediator for the early adhesive interactions between neutrophils and endothelial cells in the acute inflammatory response.

Cell Adhesion↗
PubMed1994

Immune complex vasculitis with secondary ulcerative dermatitis in aged C57BL/6NNia mice.

A spontaneous, severely pruritic ulcerative dermatitis was initially observed in 33/201 (16.4%) aged C57BL/6NNia mice obtained from the National Institute of Aging. This ulcerative dermatitis also developed in 21/98 (21%) aged C57BL/6 mice in a subsequent experimental group obtained from the same source. The average age of onset in the initial group was 20 months. These animals were negative for ectoparasite infestation and primary bacterial or fungal infection. The lesions varied from acute epidermal excoriation and ulceration to chronic ulceration with marked dermal fibrosis. In the affected animals, leukocytoclastic vasculitis was present in the dermis in both areas of ulceration and areas covered by normal intact epidermis. Immunofluorescent staining of the skin was positive for deposition of IgG, IgM, and fibrinogen in the dermal vessels of the affected mice. Leukocytoclastic vasculitis was not observed in unaffected animals, nor were deposits of immunoglobulin or fibrinogen present in the skin of the control animals. This study provides strong evidence that the ulcerative dermatitis is caused by an immune complex-induced vasculitis. The elucidation of the pathogenesis of this disease is important because of the significant percentage of animals affected and because the C57BL/6 mouse may be a useful model to study human vasculitides.

Age Factors↗
PubMed1994

Myotonic disorders and periodic paralysis.

The myotonias are a diverse set of diseases, variable in presentation, often difficult to diagnose and, until now, treated with only a limited degree of success. Recent genetic advances have pinpointed many of the mutations that underlie these disorders and have demonstrated that there may be different causative genetic mutations underlying the same phenotype. This chapter summarizes the genetic data currently available for these disorders and attempts to link these to their clinical features. In some instances this is conceptually relatively straightforward but in others, particularly DM, the manner in which the mutation leads to the observed phenotype is very unclear and can be used as a paradigm for some of the more puzzling aspects of modern human genetics. Some suggestions are put forward on how the unusual mutation seen in DM can lead to highly variable symptoms between individual patients, and how the mutation can be transmitted unstably through a pedigree.

Humans↗
PubMed1993

In vivo suppression of immune complex-induced alveolitis by secretory leukoproteinase inhibitor and tissue inhibitor of metalloproteinases 2.

The pulmonary tree is exposed to neutrophil-derived serine proteinases and matrix metalloproteinases in inflammatory lung diseases, but the degree to which these enzymes participate in tissue injury remains undefined, as does the therapeutic utility of antiproteinase-based interventions. To address these issues, an in vivo rat model was examined in which the intrapulmonary deposition of immune complexes initiates a neutrophil-mediated acute alveolitis. In vitro studies demonstrated that rat neutrophils can release neutrophil elastase and cathepsin G as well as a neutrophil progelatinase, which was subsequently activated by either chlorinated oxidants or serine proteinases. Based on structural homologies that exist between rat and human neutrophil proteinases, rat neutrophil elastase and cathepsin G activities could be specifically regulated in vitro by recombinant human secretory leukoproteinase inhibitor, and rat neutrophil gelatinase activity proved sensitive to inhibition by recombinant human tissue inhibitor of metalloproteinases 2. When either of the recombinant antiproteinases were instilled intratracheally, in vivo lung damage as assessed by increased permeability or hemorrhage was significantly reduced. Furthermore, the coadministration of the serine and matrix metalloproteinase inhibitors almost completely prevented pulmonary damage while effecting only a modest decrease in neutrophil influx. These data support a critical role for neutrophil-derived proteinases in acute lung damage in vivo and identify recombinant human secretory leukoproteinase and recombinant human tissue inhibitor of metalloproteinases 2 as potentially efficacious interventions in inflammatory disease states.

Animals↗
PubMed1993

Isolation and analysis of the gene and cDNA for a human Mu class glutathione S-transferase, GSTM4.

We have isolated the human gene and cDNA that encode the fourth member of the Mu class glutathione S-transferases (GSTs). The complete gene sequence (GenBank M96233) and the cDNA sequence (M96234) are reported and named GSTM4. The gene, located on chromosome 1, is comprised of eight exons with an organization similar to that of other Mu class genes. GSTM4 differs from a partial gene sequence, termed GSTmu2 (Taylor, J. B., Oliver, J., Sherrington, R., and Pemble, S. E. (1991) Biochem. J. 274, 587-593), in exons 3 through 5 by only 11 nucleotides within introns. The cDNA for GSTM4 was isolated from a library derived from the cervical carcinoma cell line, HeLa. Northern blots demonstrate the presence of GSTM4 mRNA in human heart, placenta, lung, brain, liver, skeletal muscle, pancreas, testis, cerebral cortex, uterus, ovary, a lymphoblastoid cell line, and four carcinoma cell lines. The deduced amino acid sequence of GSTM4 is 87% (GSTM1), 83% (GSTM2), and 70% (GSTM3) identical to the previously described human Mu class GSTs. The polypeptide encoded by the GSTM4 cDNA, produced in a bacterial expression system, conjugates 1-chloro-2,4-dinitrobenzene to GSH with a specific activity of 1.39 +/- 0.21 mumol/min/mg.

Amino Acid Sequence↗
PubMed1993

Evidence that macrophages are programmed to die after activating autologous, cloned, antigen-specific, CD4+ T cells.

The bone marrow produces large numbers of monocytes daily, but the mechanisms balancing production and elimination are unknown. In this report we demonstrate that macrophages (M phi) undergo apoptosis after activating autologous CD4+ cells. Since apoptosis is a genetically programmed response, these results argue that M phi death can be part of a normal immune response. This event may have relevance to monocyte/M phi homeostasis, as well as immune response regulation and host defenses to intracellular organisms.

Antigen-Presenting Cells↗
PubMed1993

Colchicine disrupts the cytoskeleton of rat testis seminiferous epithelium in a stage-dependent manner.

Sertoli cell microtubules play an important role in the process of spermatogenesis. We investigated the effects of colchicine, a microtubule-disrupting agent, on the seminiferous epithelium. Rats were injected intratesticularly with 0.004-40 micrograms colchicine/testis. Colchicine had a dose-related effect on seminiferous tubule fluid secretion and completely blocked secretion at a dose of 40 micrograms colchicine/testis. Colchicine also resulted in a dose-related decrease in testes weight 2 and 8 wk after injection. When 40 micrograms colchicine/testis was used, testis morphology showed a time-dependent increase in the incidence of sloughing over a time course of 1, 3, 6, and 16 h. Quantitative analysis demonstrated that stage IX-XIV seminiferous tubules were most sensitive to sloughing. Changes in the distribution of tubulin immunostaining within Sertoli cells occurred preferentially in stage VII-VIII seminiferous tubules, which were most resistant to sloughing. In addition, colchicine resulted in disruption of vimentin filaments in stage IX-XIV seminiferous tubules, which correlated with the stage-dependent sensitivity of sloughing. We propose that the stage dependence of colchicine-induced effects reflects the dynamic and stage-dependent role of microtubules in spermatogenesis. Furthermore, cellular structures other than microtubules, such as vimentin filaments, may be important for maintaining the structural integrity of the seminiferous epithelium.

Animals↗
PubMed1993

Halothane-oxidant interactions in the ex vivo perfused rabbit lung. Fluid conductance and eicosanoid production.

BACKGROUND: The present studies were undertaken to determine the interactions between halothane and oxidative injury with respect to endothelial integrity, as measured by pulmonary capillary filtration coefficient (Kfc), and production of arachidonic acid-derived mediators, in perfused rabbit lungs challenged with the oxidant tert-butyl-hydroperoxide (t-bu-OOH). METHODS: Isolated lungs were prepared from 27 New Zealand white rabbits (2-3 kg) and were perfused with Ca(2+)-free Krebs-Henseleit buffer solution. In group A (n = 9), lungs were ventilated with halothane 2.5% in carrier gas (5% CO2 in air); in group B (n = 9), with carrier gas alone; and in group C (n = 9), with carrier gas, but without injury. The lungs in the two injury groups (A and B) received four infusions of t-bu-OOH, 200 microM, over 1 min, directly into the pulmonary artery. The uninjured lungs received four infusions of vehicle (normal saline). Kfc was determined after each t-bu-OOH infusion. Concentrations of thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha were measured in samples of effluent perfusate obtained before and 30 s after the end of each infusion of t-bu-OOH. The wet/dry weight ratio of each pair of lungs was determined at the end of each experiment. RESULTS: Kfc progressively increased after each infusion of oxidant in group A when compared with the other two groups. Lung wet/dry ratios were elevated in group A (14.3 +/- 0.7) and group B (13.2 +/- 0.2) compared with group C (12.1 +/- 1.1). TxB2 production in group A (2206 +/- 263 pg.min-1.g-1 dry lung tissue) was greater than in group B (1413 +/- 127) by the final infusion of t-bu-OOH. CONCLUSIONS: Ex vivo perfused rabbit lungs ventilated with halothane exhibited, simultaneously, evidence of greater fluid conductance across the pulmonary capillary bed and production of thromboxane A2 when challenged with oxidant than did lungs ventilated with carrier gas. Both of these effects may be mediated by halothane-related enhancement of intracellular endothelial Ca2+ mobilization stimulated by intrapulmonary infusion of oxidant.

Animals↗
PubMed1993

Postischemic renal injury due to oxygen radicals.

Ischemia-reperfusion injury occurs in many organs and is the underlying cause of many disease processes, including myocardial infarction, stroke, and acute renal failure, which in total are responsible for the majority of deaths seen in developed countries. Most of the injury seen with this process is associated with the reperfusion phase in which the blood flow to the ischemic tissues is reinstituted. This reperfusion phase is associated with the formation of reactive oxygen species (ROS) in the tissues, and the sources of these oxidants are both the neutrophil as well as parenchymal cells such as endothelium. In the kidney as well as other organs, antioxidant therapy is protective, suggesting an important role for these agents. However, there is emerging evidence that ROS are not solely responsible for the reperfusion injury. In many of the kidney models of ischemia-reperfusion, antioxidants are only partially effective in ameliorating the functional and morphologic alterations. Furthermore, in vitro, ROS do not appear to be primarily involved in the killing of renal tubular epithelial cells, which is the morphologic hallmark of acute renal failure. Thus, reperfusion injury, like other types of tissue injury, appears to be mediated by more than one class of inflammatory mediator.

Animals↗
PubMed1993

The genetics of malignant hyperthermia.

Malignant hyperthermia susceptibility remains the commonest cause of death owing to general anaesthesia. This is despite the availability of presymptomatic testing, admittedly by a highly invasive method, and a recognised treatment for implementation immediately a patient shows signs of developing a crisis. Recently the finding of linkage to markers from chromosome 19q13.1-13.2 and the identification of mutations in a candidate gene held out hope of genetic diagnosis being available. However, it is likely that only about 50% of families have a mutation of the skeletal muscle calcium release channel gene. With this degree of genetic heterogeneity, presymptomatic testing based on DNA markers can only be offered at present to a limited number of families where linkage to markers from 19q13.1-13.2 has been clearly shown.

Animals↗
PubMed1993

Requirements for leukocyte adhesion molecules in nephrotoxic nephritis.

Requirements for leukocyte adhesion molecules as well as cytokines have been determined in the rat model of acute nephrotoxic nephritis. Proteinuria (at 24 h) and neutrophil accumulation in renal glomeruli (at 6 h) have been used as the endpoints. For full accumulation in glomeruli of neutrophils as well as full development of proteinuria, requirements have been demonstrated for TNF alpha, (but not IL-1), CD11b (but not CD11a), very late arising-4 (CD49d/CD29), and intercellular adhesion molecule-1 but not endothelial leukocyte adhesion molecule-1 (E-selectin). By immunohistochemical approaches, infusion of antibody to glomerular basement membrane induced glomerular upregulation of intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, and vascular adhesion molecule-1. Treatment of rats with anti-TNF alpha or soluble recombinant human TNF receptor-1 blocked this expression. Renal arterial infusion of TNF alpha induced glomerular expression of all three endothelial adhesion molecules, but infusion of IL-1 beta did not. These data suggest that, in neutrophil and complement-dependent anti-glomerular basement membrane-induced acute nephritis in rats, there are selective requirements for cytokines, beta 1 and beta 2 integrins, and endothelial adhesion molecules. These requirements contrast with those found in other vascular beds in which complement and neutrophil-induced vascular injury has been induced by deposition of immune complexes.

Acute Disease↗