Biomedical subjects

K J Johnson

Publications and source records attributed to K J Johnson.

At least 127 records · Page 7Linked to original sources

PubMed1991

Experimental obliterative cholangitis. A model for the study of biliary atresia.

Noninfectious obliterative cholangitis results from biliary tract inflammation in clinical conditions such as biliary atresia and sclerosing cholangitis. The purpose of this study was to develop an animal model of noninfectious biliary tract inflammation and fibrosis. An implantable osmotic pump was connected to a catheter placed into the gallbladder of hamsters. Phorbol myristate acetate (PMA) was infused into the biliary tract for periods of 6 hours to 28 days. After 7 days the animals developed neutrophil infiltration, cellular necrosis, and edema of the biliary ducts. After 14 days, the animals demonstrated intrahepatic cholestasis with bile duct fibrosis and acute and chronic inflammatory cell infiltration. By 28 days pronounced portal fibrosis was present, some of which created an early bridging cirrhosis pattern. In addition there was evidence of neocholangiogenesis. We conclude that long-term PMA infusion into the biliary tract generates an inflammatory response characterized by obliterative cholangitis and fibrosis, sharing many of the histologic features of human biliary atresia. This model may provide a relatively simple technique for investigating the process of nonpyogenic biliary tract inflammation.

Animals↗

PubMed1991

Amino acid protection of cultured kidney tubule cells against calcium ionophore-induced lethal cell injury.

Treatment of two cultured renal tubule epithelial cell lines, MDCK and LLC-PK1, with ionomycin produced rapidly evolving models of lethal cell injury characterized by increases of cytosolic free calcium to the microM level within 15 minutes followed by lactate dehydrogenase release and failure to exclude vital dyes that began between 30 and 60 minutes and became extensive after 60 minutes. The pattern of injury was similar when the mitochondrial uncoupler, carbonyl cyanide-m-chlorophenylhydrazone, was added to ionomycin. Carbonyl cyanide-m-chlorophenylhydrazone alone produced severe ATP depletion but not lactate dehydrogenase release. Inclusion of glycine in the experimental medium at concentrations ranging from 0.25 mM to 5 mM did not affect the increases of cytosolic free calcium or ATP depletion but was protective against enzyme release and failure to exclude vital dyes for 180 minutes. Maximal protection was achieved at glycine concentrations between 1 and 5 mM. Several other small neutral amino acids including alanine, beta-alanine, L-serine, 1-aminocyclopropane-1-carboxylic acid, and alpha-aminoisobutyric acid also had protective effects but, glucose, pyruvate, glutamate, glutamine, leucine, valine, and taurine did not. These data indicate that potent protective effects of glycine and other small neutral amino acids previously shown in fresh tubule preparations are fully expressed in cultured tubule cells of diverse origin when appropriate acute injury models are used and the protective effects are sustained for long durations. The suitability of cultured cell lines for prolonged exposure studies will provide a powerful way of further exploring mechanisms of these effects.

Adenosine Triphosphate↗

PubMed1991

Effects of all-trans retinoic acid on neutrophil-mediated endothelial cell injury in vitro and immune complex injury in rats.

All-trans retinoic acid (RA) has beneficial effects when used in a variety of inflammatory skin conditions. In this study, the authors found that RA inhibited superoxide anion production and proteolytic enzyme release by human and rat neutrophils. Concomitantly, the authors found that RA-treated neutrophils were less able than untreated neutrophils to injure endothelial cells in culture even though the adhesion of the RA-treated neutrophils to endothelial cell monolayers was not diminished. Inhibition of cytotoxicity occurred over the same range of concentrations that inhibited oxygen radical formation and protease release. In additional studies, it was observed that pretreatment of endothelial cells with RA-induced resistance to subsequent injury by activated neutrophils. Finally, in vivo studies showed that pretreatment of rats for 3 days with RA (1-10 mg/day, IP) reduced the degree of injury in the lungs and skin sites after treatment with bovine serum albumin and antibodies to bovine serum albumin in the reverse-passive Arthus reaction. Thus, RA can modulate neutrophil-mediated endothelial cell injury by an effect on both the neutrophils and their target cells. Together, these effects may underlie the reduction in immune complex-mediated injury seen in experimental animals. The beneficial effects that retinoids have in a variety of inflammatory skin diseases may likewise be a reflection of their effects on the physiology of both neutrophils and endothelial cells.

Animals↗

PubMed1991

The MEL gene: a new member of the RAB/YPT class of RAS-related genes.

The MEL gene was identified following transfection of NIH3T3 mouse fibroblasts with DNA from a human melanoma cell line. The human MEL gene has been localized to 19cen-p13.2, a region in which translocation breakpoints occur in a number of malignancies. We have identified and sequenced human and mouse MEL cDNA clones which show homology of 92% and 96% at the nucleotide and amino acid levels respectively. The predicted human MEL protein shows only six amino acid differences between it and the recently described dog RAB8 protein. All of these changes occur in the 30 amino acids at the C-terminal of these proteins. MEL is similar to the RAB/YPT proteins in the region corresponding to the putative effector domain, suggesting that they may interact with the same cellular substrates. However, MEL contains a C-terminal CAAX motif in common with the majority of the RAS superfamily, unlike YPT1 and the majority of the RAB proteins.

Amino Acid Sequence↗

PubMed1991

Infrared thermometry of newborn infants.

An infrared thermometer, the FirstTemp, was tested among newborn infants by comparing tympanic membrane temperature measurements in three operating modes, "Cal-tympanic," "Cal-surface," and "Cor-tympanic," with nearly simultaneous tympanic membrane, rectal, and axillary temperature measurements using other standard methods. The FirstTemp underestimated other measurements of body temperature in the "Cal-tympanic" mode and overestimated them in the "Cor-tympanic" mode. In the "Cal-surface" mode, the First-Temp readings were significantly lower than tympanic membrane temperatures measured with a thermistor probe and electronic thermometer (mean difference 0.2 degrees C) but not significantly different from rectal or axillary temperatures. According to these results, the FirstTemp can be used reliably in the "Cal-surface" mode but not in the "Cal-tympanic" or "Cor-tympanic" mode. Its speed and ease of operation offer significant advantages over traditional clinical methods of temperature measurement.

Axilla↗

PubMed1990

Time-dependent inhibition of oxygen radical induced lung injury.

Experimental acute lung injury mediated by reactive metabolites of oxygen can be inhibited by the antioxidant enzymes catalase and superoxide dismutase (SOD). However, the specific time interval during which these enzymes must be present in order to cause protection is not well defined. Using two experimental models of oxidant-dependent acute lung injury, one involving the intratracheal injection of glucose, glucose oxidase, and lactoperoxidase and the other involving the intravenous injection of cobra venom factor (CVF), we investigated the effects of delaying antioxidant administration on the outcome of the inflammatory response. In both cases, the protective effects of catalase and SOD were rapidly attenuated when their administration was delayed for a short period of time. For example, intratracheal catalase resulted in 98% protection when given simultaneously with the glucose oxidase and lactoperoxidase, but only 13% protection when the catalase was delayed 4 min. Likewise, in the CVF-induced lung injury model, intravenous catalase resulted in 40% protection when given simultaneously with the CVF, but only 2% protection when the catalase was delayed 20 min, even though the peak of the injury occurred hours after the initiation of the injury. A similar time dependence was seen with SOD. These results indicate that antioxidant therapy is required early in the course of oxygen radical-mediated acute lung injury for effective protection.

Animals↗

PubMed1990

Variability of abdominal circumference of premature infants.

Serial measurements of abdominal circumference were made in 27 premature infants 1 hour before feeding, immediately before and after feeding, and 1 and 2 hours after feeding. In some infants these measurements were repeated for 2 (n = 18) or 3 (n = 3) consecutive days. All 258 measurements were performed by the same examiner; 124 were also repeated blindly by another examiner to test interobserver reliability. The coefficient of variation of repeated measurements of any one infant by the same examiner on a single day was 2.7%. Ninety percent of repeated measurements agreed within 1.5 cm. The interobserver reliability was 0.99. Abdominal circumference was positively correlated with birth weight (P = .0001) and time from last defecation (P = .0001) and negatively correlated with time from last feeding (P = .04). Increases in abdominal circumference of less than 1.5 cm occur normally and, in the absence of other clinical signs, should not be considered indicative of disease.

Abdomen↗

PubMed1990

Establishment of the mouse chromosome 7 region with homology to the myotonic dystrophy region of human chromosome 19q.

A number of genetic markers, including ATP1A3, TGFB, CKMM, and PRKCG, define the genetic region on human chromosome 19 containing the myotonic dystrophy locus. These and a number of other DNA probes have been mapped to mouse chromosome 7 utilizing a mouse Mus domesticus/Mus spretus interspecific backcross segregating for the genetic markers pink-eye dilution (p) and chinchilla (cch). The establishment of a highly syntenic group conserved between mouse chromosome 7 and human chromosome 19q indicates the likely position of the homologous gene locus to the human myotonic dystrophy gene on proximal mouse chromosome 7. In addition, we have mapped the muscle ryanodine receptor gene (Ryr) to mouse chromosome 7 and demonstrated its close linkage to the Atpa-2, Tgfb-1, and Ckmm cluster of genes. In humans, the malignant hyperthermia susceptibility locus (MHS) also maps close to this gene cluster. The comparative mapping data support Ryr as a candidate gene for MHS.

Animals↗

PubMed1990

Role of O2- in neutrophil recruitment into sites of dermal and pulmonary vasculitis.

Using analogous models of acute dermal vasculitis and alveolitis in rats, we have examined the role of oxygen-derived metabolities in the tissue damage associated with neutrophil influx into sites of immune complex deposition. In the lung, as previously reported, catalase and deferoxamine are highly protective, while superoxide dismutase (SOD) has a transient protective effect. The xanthine oxidase inhibitors, allopurinol, and lodoxamide, are also protective. In the skin, neither catalase (which has been covalently linked to the antibody) nor deferoxamine is protective, suggesting that H2O2 and iron are not absolutely required for the development of dermal vasculitis. In the skin, SOD, as well as the inhibitors of xanthine oxidase, have protective effects. These data suggest that the neutrophil-mediated pathways of immune complex injury in the dermal and pulmonary microvascular compartments are fundamentally different. As a measurement of neutrophil accumulation, measurements of myeloperoxidase in tissue extracts have been employed. In both the lung and skin, the protective effects of SOD and the xanthine oxidase inhibitors are paralleled by reductions in neutrophil influx into sites of injury. In contrast, catalase and deferoxamine have no effect on neutrophil accumulation. These data suggest that vascular beds in rat skin and lung are fundamentally different with respect to mechanisms of acute immune complex mediated injury. The data also provide evidence that O2- contributes significantly to the accumulation of neutrophils.

Allopurinol↗

PubMed1990

Alterations in influenza A virus specific immune injury in mice anesthetized with halothane or ketamine.

CD-1 mice infected with a sublethal dose of influenza A virus were anesthetized for 2 h with halothane. These mice were compared to a control group which was similarly infected using ketamine sedation. Mice anesthetized with halothane showed less physical signs of illness and demonstrated less lung histopathology than the control group of mice. Virus titers were reduced in the group of animals exposed to halothane 12 h after infection, but were the same as the infected controls at all other times measured (1-12 days after infection). Morphometric analysis of lung tissue demonstrated a delayed appearance of both neutrophils and monocytes in the halothane-exposed mice. These results suggest that the halogenated volatile anesthetic halothane decreases the pulmonary pathogenesis of influenza A virus by altering the recruitment of immunological effector cells during the course of the infection.

Animals↗

PubMed1990

PAF and immune complex-induced injury.

Acute immune complex-mediated dermal vasculitis and pulmonary alveolitis have been induced in rats by the intradermal injection or intrapulmonary instillation of rabbit polyclonal antibody to bovine serum albumin (BSA), followed by intravenous injection of antigen. In the dermis, using reconstitution experiments in neutrophil-depleted rats and platelet-activating factor (PAF) receptor antagonists, we have shown that accessibility of PAF receptors on neutrophils is required for the full expression of dermal vascular injury. In the lung, intratracheal instillation of PAF receptor antagonists (with anti-BSA) results in a 54% suppression of pulmonary vascular leakage, suggesting that PAF receptors are necessary for the full expression of injury. These data suggest that in immune complex-induced tissue damage in which neutrophils and their oxygen radicals and proteases play a key role, there is an interplay of PAF and neutrophils required for the full expression of injury. The possible mechanisms involved will be discussed.

Animals↗

PubMed1989

Confirmation and refinement of the localisation of the c-MEL locus on chromosome 19 by physical and genetic mapping.

The human gene locus c-MEL was identified following transfection of genomic DNA from the human melanoma cell line NK14; it has previously been assigned to chromosome 19 (p13.2-q13.2) by analysis of somatic cell hybrids. We have further refined the position of this gene to the proximal region of 19p (cen-p13.2), using cell hybrids containing only fragments of human chromosome 19. We have confirmed this physical localisation by linkage analysis with a recently described restriction fragment length polymorphism for the c-MEL gene, and mapped the locus within the region of the low density lipoprotein receptor gene (LDLR) (Lod 4.43, theta = 0.10) and the anonymous marker D19S11 (13.1.25) (Lod 9.33, theta = 0). This gene thus maps to a region of chromosome 19 involved in karyotypic abnormalities in a variety of malignancies including melanomas and leukaemias.

Cell Line↗

PubMed1989

Failure of antioxidant therapy (polyethylene glycol-conjugated catalase) in acute pancreatitis.

Previous studies have demonstrated that intravenous catalase infusion protects against the formation of pancreatic edema in cerulein-induced acute pancreatitis; however, polyethylene glycol (PEG)-conjugated catalase given as a bolus was not protective. Using radiolabeled catalase and PEG-catalase in subtherapeutic tracer doses, the pancreas tissue distributions of each were determined in rats with and without pancreatitis. Rats with cerulein-induced pancreatitis developed tissue concentrations of catalase within the pancreas that were three times those of PEG-catalase. The relatively low levels of PEG-catalase in the pancreas outside of the vascular compartment suggest that the failure to prevent edema formation may result from inability of PEG-catalase to reach extravascular sites of injury because of the large molecular size.

Acute Disease↗

PubMed1989

Signal transduction events in stimulated rat neutrophils: effects of adenine nucleotides.

When rat neutrophils were stimulated with chemotactic peptide N-formyl-Met-Leu-Phe; fMLP), phorbol myristate acetate (PMA), or immune complexes in the presence of homologous platelets, O2- responses were enhanced. Secretion products of thrombin-stimulated platelets as well as ATP, ATP gamma S, or ADP enhanced O2- responses of fMLP-stimulated neutrophils, although these nucleotides did not, by themselves, initiate an O2- response. Calcium transients were measured in neutrophils which were stimulated with fMLP under a variety of conditions (+/- ATP gamma S, +/- cytochalasin B) which enhance O2- responses. Neutrophils incubated with ATP gamma S alone developed brief calcium transients similar to those produced by fMLP. As compared to changes in intracellular calcium in fMLP-stimulated neutrophils, the copresence of ATP gamma S with fMLP did not cause a statistically significant difference in the calcium transients, even though O2- production was enhanced. In contrast, in the presence of cytochalasin B, the addition of ATP gamma S to fMLP-stimulated neutrophils produced greatly sustained and protracted elevations in intracellular calcium, correlating with further enhancement of O2- responses. In fMLP-stimulated neutrophils the latter phases of the calcium transients appeared to be dependent in part on the availability of extracellular calcium. These data suggest that ATP gamma S-induced enhancement of O2- responses in fMLP-stimulated rat neutrophils may be related to two mechanisms, one being independent of fMLP-induced intracellular calcium transients and the other, which is related to the presence of cytochalasin B, being linked to sustained elevations in intracellular calcium associated with mobilization of extracellular calcium.

Adenine Nucleotides↗

PubMed1989

Vascular endothelial cell killing by combinations of membrane-active agents and hydrogen peroxide.

Previous studies have demonstrated that a number of membrane-active agents are capable of binding to the surface of polymorphonuclear leukocytes (PMN) resulting in an augmentation of superoxide anion and hydrogen peroxide (H2O2) production in response to soluble stimuli. It is now demonstrated that these same membrane-active agents can bind to the surface of endothelial cells and enhance their susceptibility to killing by H2O2. Membrane-active agents which are capable of synergizing with H2O2 include cationic proteins, cationic poly-amino acids, lysophosphatides and enzymes which are capable of degrading membrane phospholipids (e.g., phospholipase C, phospholipase A2 and streptolysin S). In each case, treatment of the target cells with the membrane-active agent and H2O2 produces greater damage than the sum of the damage produced by either agent separately. Since inflammatory lesions, particularly sites of bacterial infection, may contain a rich mixture of cationic substances, phospholipases and phospholipid breakdown products, these substances may contribute to the tissue damage observed at sites of inflammation by enhancing endothelial cell sensitivity to PMN-generated H2O2 as well as by augmenting the generation of H2O2 by PMNs.

Animals↗

PubMed1989

Modification of disease by preventing free radical formation: a new concept in pharmacological intervention.

There is considerable clinical and both in vivo and in vitro experimental evidence that toxic oxygen radicals contribute to the development of tissue injury associated with the inflammatory response. There is also strong evidence that cell injury caused by activation of phagocytic cells is iron dependent. Several of the clinical studies and in vivo and in vitro experimental models supporting these conclusions and suggesting mechanisms through which iron may participate in inflammation are discussed.

Animals↗

PubMed1989

Neutrophil-dependent, oxygen-radical mediated lung injury associated with acute pancreatitis.

Cerulein-induced acute pancreatitis in rats is associated with a reversible lung injury that is characterized by alveolar capillary endothelial-cell injury, increased microvascular permeability, interstitial edema formation, and intraalveolar hemorrhage and fibrin deposition. The role of mediators in this injury was analyzed using gravimetric data, microvascular permeability indices, electron microscopy, and a quantitative morphometric analysis. Neutrophil depletion induced by a specific antibody was highly protective against lung injury. Interruption of the complement pathway (using low dose Naja naja cobra venom factor) also protected against lung injury. Catalase and superoxide dismutase were also protective. The iron chelator deferoxamine and the hydroxyl radical scavenger, dimethylsulfoxide, were not protective against acute lung injury. These data suggest that complement, neutrophils, and neutrophil-derived (H2O2-dependent) oxygen products mediate lung injury that occurs secondary to cerulein-induced pancreatitis. In contrast to other models of neutrophil-dependent, oxygen-radical-mediated lung injury, this lung injury does not appear to be an iron-dependent and hydroxyl-radical mediated injury. We postulate that the process of acute pancreatitis leads to complement activation followed by neutrophil recruitment, sequestration, and adherence to alveolar capillary endothelial cells. Ultimately lung injury appears to result from local endothelial-cell injury secondary to neutrophil-generated oxygen products that may be myeloperoxidase dependent.

Acute Disease↗

PubMed1989

Evidence for the role of platelet-activating factor in immune complex vasculitis in the rat.

These studies were designed to determine the role of platelet-activating factor (PAF) in the pathogenesis of immune complex (IgG) induced dermal vasculitis in the rat. In vitro, very low (pM and nM) concentrations of PAF "primed" rat neutrophils for enhanced O2-. responses to IgG immune complexes while higher concentrations were directly stimulatory. The PAF receptor antagonist, L-652,731, blocked responses (O2-. production and enzyme release) of rat neutrophils stimulated with PAF but did not block responses triggered by immune complexes, formyl chemotactic peptide or opsonized zymosan particles. When L-652,731 was added to the antibody employed in the reversed passive Arthus reaction, the injury resulting from immune complex-induced vasculitis was significantly attenuated. In order to determine if in vivo protection provided by L-652,731 was related to neutrophils, we developed a new model in which rats are systemically depleted of neutrophils by cyclophosphamide and then locally reconstituted with intact neutrophils in a manner that allows restoration of immune complex-induced vascular injury. With this model, we demonstrated that the effects of neutrophil reconstitution are substantially diminished if the cells are pretreated with L-652,731 and then washed. By priming neutrophils with substimulatory concentrations of PAF, we have also provided in vivo evidence that neutrophil priming can increase the magnitude of vascular injury. These data provide evidence that vascular injury associated with immune complex dermal vasculitis is related to availability of PAF receptors on neutrophils, suggesting a mechanism through which PAF may function as a mediator in the pathogenesis of immune complex vasculitis.

Animals↗