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K J Johnson

Publications and source records attributed to K J Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1997

Reduced sensitivity of fa/fa Zucker rats to adrenomedullin.

Rat adrenomedullin is a peptide vasodepressor that may be of importance in the pathogenesis of hypertensive disease. Because of the known link between obesity and hypertension, we hypothesized that decreased responsiveness to adrenomedullin might be seen in an obese rodent model. In this study, the in vivo vasodilator actions of exogenous adrenomedullin were compared in anesthetized lean (n = 7) and obese (fa/fa) Zucker rats (n = 8). Adrenomedullin dose dependently lowered mean arterial pressure in both phenotypes, but the half-maximal dose (ID50) was 2-fold higher in fa/fa rats (1.7 +/- 0.22 vs. 0.83 +/- 0.06 nmol/kg). Moreover, the duration of effect was markedly reduced in the fa/fa rats, to 1-2 min from about 5 min in the lean animals. There was no evidence for an increased rate of degradation of adrenomedullin in the fa/fa rats. Although the rats used in this study were not hypertensive, adrenomedullin had reduced sensitivity and duration of action. The evidence suggests possible defects at the target receptor or altered metabolism of adrenomedullin in obesity.

Adrenomedullin↗
PubMed1996

Glomerular inflammation induces resistance to tubular injury in the rat. A novel form of acquired, heme oxygenase-dependent resistance to renal injury.

Considerable attention is directed to a surprising biologic phenomenon wherein tissues exposed to one insult acquire resistance to another. We identify a novel example of acquired resistance to acute renal failure and a mechanism that contributes to such resistance. Nephrotoxic serum, administered to rats 24 h before the induction of glycerol-induced acute renal failure, reduces functional and structural injury that occurs in this model. Since heme oxygenase, the rate-limiting enzyme in heme degradation, protects against heme protein-induced renal injury, we questioned whether induction of heme oxygenase underlies the protection afforded by nephrotoxic serum. Kidney heme oxygenase (HO-1) mRNA was induced 6 h after nephrotoxic serum and renal tubules were identified as the site of expression of heme oxygenase protein. Induction of heme oxygenase was accompanied by increased renal content of ferritin but not by induction of other antioxidant enzymes. Inhibition of heme oxygenase prevented the protection afforded by nephrotoxic serum. Nephrotoxic serum did not protect against ischemic acute renal failure, a model in which heme oxygenase is not induced. Thus, nephrotoxic serum protects against glycerol-induced acute renal failure by inducing heme oxygenase in tubules. This study provides the first demonstration of resistance to tubular injury acquired from glomerular inflammation, uncovers a mechanism for such resistance, and exposes the dialogue that occurs between glomeruli and tubules.

Acute Kidney Injury↗
PubMed1996

Requirement and role of C5a in acute lung inflammatory injury in rats.

The complement activation product, C5a, may play a key role in the acute inflammatory response. Polyclonal antibody to rat C5a was used to define the requirements for C5a in neutrophil-dependent inflammatory lung injury after systemic activation of complement by cobra venom factor (CVF) or after intrapulmonary deposition of IgG immune complexes. In the CVF model, intravenous infusion (but not intratracheal instillation) of anti-C5a produced a dose-dependent reduction in lung permeability and in lung content of myeloperoxidase. In C6-deficient rats, CVF infusion caused the same level of lung injury (measured by leak of 125I-albumin) as found in C6-sufficient rats. In the IgG immune complex model of lung injury, anti-C5a administered intratracheally (but not intravenously) reduced in a dose-dependent manner both the increase in lung vascular permeability as well as the buildup of lung myeloperoxidase. Treatment with anti-C5a greatly suppressed upregulation of lung vascular intercellular adhesion molecule-1 (ICAM-1). This was correlated with a substantial drop in levels of TNFalpha in bronchoalveolar fluids. These data demonstrate the requirement for C5a in the two models of injury. In the IgG immune complex model, C5a is required for the full production of TNFalpha and the corresponding upregulation of lung vascular ICAM-1.

Animals↗
PubMed1996

Cloning of the human SIX1 gene and its assignment to chromosome 14.

The recently described murine homeobox genes, Six1 and Six2, which are expressed during development in limb tendons, have also been shown to be expressed in skeletal and smooth muscle, respectively. We have cloned and sequenced a human SIX1 cDNA and shown by Northern blotting that it is expressed in adult skeletal muscle. The cDNA sequence and predicted protein sequence of SIX1 and Six1 are highly homologous, with 98% similarity over the entire predicted amino acid sequence. SIX1 was mapped to human chromosome 14 using a rodent/human somatic cell hybrid panel.

Adult↗
PubMed1996

Ligand recognition by murine anti-DNA autoantibodies. II. Genetic analysis and pathogenicity.

Although anti-DNA autoantibodies are an important hallmark of lupus, the relationships among anti-DNA structure, reactivity, and pathogenicity have not been fully elucidated. To further investigate these relationships, we compare the variable genes and primary structure of eight anti-DNA mAbs previously obtained from an MRL/MpJ-lpr/lpr mouse along with the ability of three representative mAbs to induce nephritis in nonautoimmune mice using established adoptive transfer protocols. One monospecific anti-single-stranded (ss) DNA (11F8) induces severe diffuse proliferative glomerulonephritis in nonautoimmune mice whereas another anti-ssDNA with apparently similar in vitro binding properties (9F11) and an anti-double-stranded DNA (4B2) are essentially benign. These results establish a murine model of anti-DNA-induced glomerular injury resembling the severe nephritis seen in lupus patients and provide direct evidence that anti-ssDNA can be more pathogenic than anti-double-stranded DNA. In vitro binding experiments using both protein-DNA complexes and naive kidney tissue indicate that glomerular localization of 11F8 may occur by recognition of a planted antigen in vivo. Binding to this antigen is DNase sensitive which suggests that DNA or a DNA-containing molecule is being recognized.

Amino Acid Sequence↗
PubMed1996

Common subtypes of idiopathic generalized epilepsies: lack of linkage to D20S19 close to candidate loci (EBN1, EEGV1) on chromosome 20.

Hereditary factors play a major role in the etiology of idiopathic generalized epilepsies (IGEs). A trait locus (EBN1) for a rare subtype of IGEs, the benign neonatal familial convulsions, and a susceptibility gene (EEGV1) for the common human low-voltage electroencephalogram have been mapped close together with D20S19 to the chromosomal region 20q13.2. Both loci are potential candidates for the susceptibility to IGE spectra with age-related onset beyond the neonatal period. The present study tested the hypothesis that a putative susceptibility locus linked to D20S19 predisposes to spectra of IGEs with age-related onset from childhood to adolescence. Linkage analyses were conducted in 60 families ascertained through IGE patients with juvenile myoclonic epilepsy, juvenile absence epilepsy or childhood absence epilepsy. Our results provide evidence against linkage of a putative susceptibility gene for four hierarchically broadened IGE spectra with D20S19 assuming tentative single-locus genetic models. The extent of an "exclusion region" (lod scores below-2) varied from 0.5 cM up to 22 cM on either side of D20S19 depending on the trait assumed. These results are contrary to the expectation that a susceptibility gene in vicinity to D20S19 confers a common major gene effect to the expression of IGE spectra with age-related onset from childhood to adolescence.

Chromosome Mapping↗
PubMed1996

Exclusion of linkage between idiopathic generalized epilepsies and the GABAA receptor alpha 1 and gamma 2 subunit gene cluster on chromosome 5.

Hereditary factors play a major role in the etiology of idiopathic generalized epilepsies (IGEs). The pivotal function of ionotropic gamma-aminobutyric acid type A receptors (GABRs) in inhibitory neurotransmission in the mammalian central nervous system suggests that they may be involved in epileptogenesis and genetic predisposition to IGEs. Dinucleotide repeat polymorphisms associated with the human GABAA receptor alpha 1 (GABRA1) and gamma 2 subunit (GABRG2) gene cluster on chromosome 5q32-q35 offer the opportunity to test whether these candidate genes confer susceptibility to IGEs. Our linkage analyses in 63 families ascertained through IGE patients with either juvenile myoclonic epilepsy, juvenile absence epilepsy or childhood absence epilepsy do not support the hypothesis that variants within the GABRA1 and GABRG2 gene cluster contribute a frequent major gene effect to the expression of the common familial IGEs.

Base Sequence↗
PubMed1996

Kinesin localizes to the trans-Golgi network regardless of microtubule organization.

Knowledge of the mechanisms of intracellular membrane trafficking is critical for understanding cell function. Here, the microtubule motor kinesin is localized to the Sertoli cell trans-Golgi network with the SUK4 kinesin monoclonal antibody. Using immunoelectron and immunofluorescence microscopy, kinesin was shown to localize to the trans-Golgi network in primary Sertoli cell cultures. Kinesin immunostaining was not observed in brefeldin A-induced trans-Golgi network-derived membrane tubules and remained associated with trans-Golgi network remnants. Despite dramatic differences in microtubule organization between Sertoli cells in vivo and in vitro, kinesin immunostaining was consistently associated with the trans-Golgi network. In cryosections of control testis and testis treated with colchicine to disrupt microtubules, kinesin immunostaining was juxtaposed with immunostaining for a Golgi cisternal protein; however, brefeldin A exposure partitioned the kinesin immunostaining from the Golgi cisternal protein, indicating that kinesin was associated with the trans-Golgi network of Sertoli cells in vivo. These results are discussed in relation to known Golgi-associated microtubule-dependent transport events in other cell types and suggest that kinesin functions locally at the Sertoli cell trans-Golgi network.

Animals↗
PubMed1995

Mechanism of drug-induced lupus. I. Cloned Th2 cells modified with DNA methylation inhibitors in vitro cause autoimmunity in vivo.

Treating activated CD4+ T cells with DNA methyltransferase inhibitors modifies gene expression and induces autoreactivity. Adoptive transfer of viable polyclonal autoreactive cells causes a lupus-like disease, most likely because of one or more effector functions expressed by the autoreactive cells. However, the number of potential effector mechanisms expressed by polyclonal cells is large. To more readily identify responsible mechanisms, we asked if autoimmunity can be induced by using the conalbumin-reactive, cloned Th2 cell line D10.G4.1, treated with 5-azacytidine (5-azaC) or procainamide (Pca). Treated, but not untreated, cells responded to syngeneic APCs without Ag, overexpressed LFA-1, spontaneously lysed syngeneic macrophages, and secreted relatively large amounts of IL-6, small amounts of IL-4, and no detectable IL-2 nor IFN-gamma. Adoptive transfer of treated, but not untreated, cells induced a severe immune complex glomerulonephritis, pulmonary alveolitis, central nervous system abnormalities including fibrinoid necrosis, karyorrhexis, and meningitis, and bile duct proliferation with periportal inflammatory cell infiltration resembling primary biliary cirrhosis. Anti-ssDNA, anti-dsDNA, and anti-histone Abs were also found. These experiments demonstrate that modification of this cloned T cell line with DNA methyltransferase inhibitors is sufficient to cause an autoimmune disease, with features of lupus as well as autoimmune liver disease. The results also raise the possibility that macrophage lysis, IL-6 secretion, and LFA-1 overexpression could contribute to the disease process. This system may be useful in testing the role of these and other pathologic mechanisms in the development of specific autoimmune lesions.

Animals↗
PubMed1995

Volatile anesthetic modulation of lung injury and outcome in a murine model of multiple organ dysfunction syndrome.

General anesthesia has been shown to have a significant impact on the inflammatory response. We hypothesized that lung pathophysiology will be attenuated in a mouse model of secondary multiple organ dysfunction syndrome (MODS) elicited by intraperitoneal zymosan suspension in saline. CD-1 mice were anesthetized for 6 h with either 1% halothane or 1.5% isoflurane in 30% oxygen in N2 carrier gas. Another group of mice was exposed to 30% oxygen in N2 carrier gas only. The inflammatory response to zymosan was quantified by measuring lung myeloperoxidase activity (neutrophil recruitment). Lung injury was estimated by determining the degree of lung permeability to radioactive albumin (permeability index). Unanesthetized injured mice exhibited maximal lung myeloperoxidase activity 2 h after zymosan injection (.671 +/- .07 delta OD.min-1), which was significantly attenuated (p < .01) in injured mice anesthetized with halothane (.369 +/- .054) and isoflurane (.324 +/- .055). The maximum lung permeability index occurred 8 h after injection in the unanesthetized, injured mice (.398 +/- .019), and was attenuated (p < .01) in injured mice anesthetized with halothane (.255 +/- .02) and isoflurane (.224 +/- .019). Histopathological findings corresponded to the quantitative myeloperoxidase and permeability index values. Halothane and isoflurane attenuate lung inflammation and injury in this mouse model of multiple organ dysfunction syndrome. This attenuation may be related to modulation of the inflammatory response by volatile anesthetics.

Anesthetics, Inhalation↗
PubMed1995

All-trans retinoic acid inhibits fluctuations in intracellular Ca2+ resulting from changes in extracellular Ca2+.

Previous studies have shown that all-trans retinoic acid (RA) preserves fibroblast viability and stimulates their proliferation, in part, by reducing the extracellular Ca2+ requirement (Am J Pathol 1990, 130:1275). Based on this observation, we have in the present study examined the effects of RA on Ca2+ mobilization in human dermal fibroblasts. For these studies we used the Ca(2+)-binding dyes, Fluo-3 and Indo-1. Using fluorescence of Fluo-3-loaded cells or Indo-1-loaded cells as indicators of intracellular free Ca2+, we observed that treatment of the cells with RA did no, by itself, alter the concentration of intracellular Ca2+. Nor did it interfere with the rapid, transient rise in intracellular Ca2+ induced by treatment with ionomycin. However, treatment of the cells with RA prevented re-equilibration of intracellular Ca2+ when the cells were initially equilibrated in low Ca2+ (0.15 mmol/L) culture medium and then switched to high Ca2+ (1.4 mmol/L) medium or when cells were first equilibrated in high Ca2+ medium and then switched to low Ca2+ medium. This effect of RA could be seen within seconds after treatment and the effect was observed 1 day after treatment (longest time point examined). The effect was concentration dependent and concentrations of RA that modulated Ca2+ re-equilibration (0.3 to 3.0 mumol/L) were the same as those that have previously been shown to promote fibroblast survival and growth. A biologically inactive retinoid did not have this effect. Specificity of the response was suggested by the finding that concentrations of RA that modulated Ca2+ movement had no effect on Ba2+ transport. These data suggest that RA prevents re-equilibration of intracellular Ca2+ in human dermal fibroblasts by interfering with Ca2+ movement across the plasma membrane.

Aniline Compounds↗
PubMed1995

Renal structure and function effects after low dose cyclosporine in psoriasis patients: a preliminary report.

Our studies on the treatment of psoriasis with cyclosporine A (CSA) have demonstrated efficacy at doses < 5 mg/kg/day. However, the nephrotoxicity of CSA at these low doses is not known and is the focus of this current study. Twenty-nine patients prospectively had pretherapy assessment of renal function including serum creatinine and glomerular filtration rate (GFR). GFR was also measured while receiving CSA as well as posttherapy. These functional studies were compared with renal biopsies taken one month after discontinuing the drug. Pretherapy GFR values were normal in all of our subjects. However, by midstudy GFR values had dropped significantly in many patients. This trend continued so that at the end of the study mean GFR values had decreased by 12% with slightly over one quarter of the patients having reductions in GFR of at least 25%. Renal biopsy findings correlated well with the functional studies in particular the GFR, with those patients having the greatest reduction in GFR showing the most renal scarring. Thus, CSA at doses < 5 mg/kg/day induces variable chronic renal injury which correlates most closely with changes in the GFR.

Adult↗
PubMed1995

Human skin in organ culture. Elaboration of proteolytic enzymes in the presence and absence of exogenous growth factors.

Proteinase levels were assessed in organ culture fluids from human neonatal foreskin maintained under growth factor-free conditions and in the presence of a combination of growth factors (ie, epidermal growth factor, insulin, hydrocortisone, pituitary extract, and all-trans-retinoic acid). Analysis of culture fluids by gelatin zymography revealed the presence of 92-kd and 72-kd gelatinases. There was a greater amount of 92-kd gelatinase activity in the presence of growth factors whereas the levels of 72-kd gelatinase were similar in growth factor-free and growth factor-containing media. Experiments with keratinocytes and fibroblasts in monolayer culture and with isolated dermal tissue in organ culture indicated that the epithelial component was responsible for most of the 92-kd gelatinase activity whereas fibroblasts were primarily responsible for the 72-kd gelatinase activity. Activation with aminophenyl mercuric acetate, requirement for divalent cations, inhibition with EDTA, and insensitivity to inhibition with phenylmethyl sulfonyl fluoride indicated that both gelatinases were metalloproteinases. In additional studies, culture fluids were examined for the presence of plasminogen activator activity. This was detected in culture fluids from tissues maintained under both conditions but was increased in the growth factor-containing medium. The increased amount seen in the growth factor-containing medium appeared to be due almost entirely to a single factor, ie, all-trans-retinoic acid. In monolayer culture, both keratinocytes and fibroblasts produced plasminogen activator; the level was higher in keratinocyte culture fluids than in culture fluids from fibroblasts.

Cells, Cultured↗
PubMed1995

New concepts in the pathogenesis of drug-induced lupus.

Although the importance of DNA methylation in normal cellular development and hereditary disease states has been appreciated for some time, the role of environmental agents in causing DNA methylation abnormalities and the effects of DNA hypomethylation on T cells have only recently been examined. This review summarizes current knowledge about the role of DNA methylation in regulating T function and gene expression and highlights a novel mechanism causing autoimmunity, in which epigenetic modification of T cell DNA by environmental agents plays an important role in triggering lupus-like diseases. The observations that DNA methylation inhibitors modify gene expression and induce autoreactivity in cloned, Ag-specific CD4+ cells in vitro, that the modified cells cause autoimmunity in vivo, and that similar changes are found in patients with active lupus provide a new approach to understanding how some forms of autoimmunity develop and may lead to new and more effective treatments.

Acetylation↗
PubMed1995

Multiple organ dysfunction syndrome: end organ and systemic inflammatory response in a mouse model of nonseptic origin.

The authors measured the peripheral blood pro-inflammatory cytokine responses (tumor necrosis factor-alpha [TNF-alpha] and interleukin-6 [IL-6]) and related end organ responses ti intraperitoneal zymosan-saline suspension over 5 days in CD-1 mice. Other indicators of local and systemic inflammation included wet:dry weight ratios of lung, liver, kidneys, spleen, and bowel; peripheral blood hematocrit, white blood cell count, and platelet count; lung myeloperoxidase activity; lung protein leak; and bacterial translocation to liver, spleen, and mesenteric lymph nodes. The initial event in responses to zymosan A injection was a sharp rise in the peripheral blood TNF-alpha level, which crested within 1 h of injection. This response was followed by a peripheral blood leukocytosis also within 1 h, and a peak lung myeloperoxidase activity within 1-2 h of injection. The maximum lung permeability index occurred 8 h after injection (zymosan, .398 +/- .019 [n = 10]; saline vehicle, .266 +/- .007 [n = 10], p < .001) followed by the maximum lung wet:dry weight ratio, which occurred 18 h after injection. The peak wet:dry weight ratios for the other organs occurred between 12 and 24 h after injection as well. Peripheral blood IL-6 maxima followed TNF-a maxima after lags of several hours. The release of pre-formed TNF-a is likely the most proximal event following injection of zymosan, and may set in motion the processes that result in end-organ injury and secondary multiple organ dysfunction, particularly activation of leukocytes. The precise roles of TNF-alpha and IL-6 in the pathogenesis of end-organ injury, however, are not addressed.

Animals↗