Search PubMed⌕ Search

Biomedical subjects

G G Johnson

Publications and source records attributed to G G Johnson.

At least 19 recordsLinked to original sources
PubMed1999

Anti-CD43 monoclonal antibody L11 blocks migration of T cells to inflamed pancreatic islets and prevents development of diabetes in nonobese diabetic mice.

Nonobese diabetic mice are a well-known model for human insulin-dependent diabetes mellitus. These mice develop autoimmune-mediated inflammation of the pancreatic islets, followed by destruction of the insulin-producing beta cells and development of diabetes. Nonobese diabetic mice also have salivary gland inflammation, and serve as a model for human Sjogren's syndrome. T cells are a prominent component of the inflammatory infiltrate in these sites, and T cell recruitment from the blood is thought to be essential for the initiation and maintenance of pathologic tissue damage. A unique mAb to murine CD43, L11, has recently been shown to block the migration of T cells from blood into organized lymphoid tissues. Here we demonstrate that L11 significantly inhibits T cell migration from blood into inflamed islets and salivary glands. Treatment of nonobese diabetic mice with L11 from 1 to 4 or 8 to 12 wk of age led to significant protection against the development of diabetes. Moreover, protection was long-lived, with decreased incidence of diabetes even months after cessation of Ab administration. When treatment was started at 1 wk of age, L11 inhibited the development of inflammation in pancreatic islets and salivary glands. L11 treatment had no long-term effect on numbers or phenotypes of peripheral lymphocytes. These data indicate that anti-CD43 Abs that block T cell migration may be useful agents for the prevention or treatment of autoimmune diseases including insulin-dependent diabetes mellitus and Sjogren's syndrome.

Adoptive Transfer↗
PubMed1999

L11, a unique anti-CD43 monoclonal antibody, inhibits the adoptive transfer of diabetes and pancreatic islet, salivary gland, and lacrimal gland inflammation in NOD/scid mice.

L11 is an anti-murine CD43 monoclonal antibody that blocks the migration of T cells from blood into lymphoid tissues. We used a T-cell-mediated adoptive transfer model to evaluate the ability of L11 to inhibit inflammation and destruction in extranodal tissues in the nonobese diabetic (NOD) mouse. Splenocytes from diabetic NOD mice were transferred intravenously into NOD/scid mice. The host mice were treated with L11, negative control antibody, or saline for the first 8 days after transfer. L11 treatment significantly delayed the onset of diabetes and inhibited the development of inflammation in pancreatic islets, salivary gland, and lacrimal gland. These results suggest that L11 may be a useful immunotherapeutic tool for the prevention of T-cell-mediated autoimmune diseases.

Adoptive Transfer↗
PubMed1999

Commentary: a personal view on palliative and hospice care in correctional facilities.

Author notes that the provision of palliative and hospice care in correctional settings requires a multidisciplinary team approach, involving not only health care providers, but also corrections managers and their employees. All facets of an inmate's life must be reviewed in terms of end-of-life decisions, management, and palliative care.

Health Policy↗
PubMed1996

Superior mesenteric artery blood flow and indomethacin-induced intestinal injury and inflammation.

Intestinal injury caused by nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with increased mucosal permeability, microvascular injury, focal intravascular thrombus formation, fibrin deposition, and neutrophil infiltration. Ulcerations and adhesions are also prominent feature of this injury. Although NSAID-induced inhibition of prostaglandin formation has been suggested to produce ischemic injury and inflammation, no studies have directly assessed intestinal blood flow in experimental NSAID-induced enteropathy. This study tested the hypothesis that indomethacin-induced small bowel injury and inflammation result from intestinal ischemia. With the use of pulsed Doppler flowmetry, superior mesenteric artery blood flow was continuously monitored in conscious rats after doses of indomethacin known to promote acute and then chronic small bowel inflammation (7.5 mg/kg, 2 sc doses spaced 24 h apart). After 72 h, rats were anesthetized and a section of small bowel was removed for histology and intestinal myeloperoxidase activity measurements. Mean arterial blood pressure was not affected until 32 h after indomethacin, when it decreased 20% (P < 0.05) to P < 0.01). Sustained blood flow changes first occurred at 20 h, when an increase of 15% (P < 0.01) was observed, whereas flow resistance decreased. Flow resistance continued to decrease for the remainder of the 72-h period, and there was an accompanying blood flow increase to +40% (P < 0.05 to P < 0.01). Intestinal ulcers developed in 86% of indomethacin-treated rats. Adhesions, dilation, and thickening of the distal jejunum and proximal ileum were observed in most indomethacin-treated rats. Histological grading of intestinal injury yielded scores of 7.1 +/- 1.2 and zero for indomethacin-treated and vehicle-injected rats, respectively (P < 0.01). Myeloperoxidase activity was greater in indomethacin-treated rats (6.7 +/- 1.9 vs. 1.8 +/- 0.3 U/cm, P < 0.05). These results suggest that indomethacin-induced enteropathy is associated with an increase, not a decrease, in superior mesenteric artery blood flow. Therefore, ischemia dose not appear to be a mechanism by which subcutaneous indomethacin administration produces small intestinal injury and inflammation.

Animals↗
PubMed1995

I1-imidazoline receptors. Definition, characterization, distribution, and transmembrane signaling.

Data were presented showing that I1-imidazoline sites show a unique ligand specificity that differs markedly from that of any of the alpha 2-adrenergic subtypes or the I2-imidazoline sites labeled by [3H]idazoxan. On the other hand, the ligand specificity of I1-imidazoline sites is maintained across mammalian species (cow, rat, dog, and human) and between different tissues and cell types. I1-Imidazoline sites can be further distinguished from I2 sites because the latter, unlike I1 sites, were not present in RVLM membranes from bovine brain stem. Furthermore, I1-imidazoline sites were modulated by guanine nucleotides with a specificity appropriate for a receptor coupled to G-protein and were mainly localized to plasma membranes. I1-Imidazoline sites show a unique pattern of distribution between diverse tissues and cell types and appear to be a neuroepithelial marker as well as being present in secretory cells of the pancreatic islets. The widespread distribution of I1-imidazoline sites implies that the functional significance of this putative receptor may have been underestimated. The signaling pathway associated with the I1-imidazoline receptor remains to be fully elucidated, but is likely that activation of phospholipase A2 leading to release of arachidonic acid and subsequent generation of prostaglandins plays a major role.

Animals↗
PubMed1995

Nitric oxide synthase in circulating vs. extravasated polymorphonuclear leukocytes.

It is becoming increasingly apparent that certain forms of acute and chronic inflammation are associated with enhanced production of nitric oxide (NO). Although substantial information has been obtained describing the regulation of NO synthase (NOS) in macrophages, little information is available regarding the biochemistry and molecular biology of NOS in circulating vs. extravasated polymorphonuclear leukocytes (PMNs). The objective of this study was to characterize the molecular and biochemical properties of the inducible NO synthase (iNOS) in circulating vs. extravasated rat and human PMNs. Circulating rat and human PMNs were purified from peripheral blood and extravasated PMNs were elicited in rats by intraperitoneal injection of 1% oyster glycogen or in humans by peritoneal dialysis of patients with peritonitis. Inducible NOS mRNA from circulating and elicited PMNs was quantified using slot blot hybridization analysis with a cDNA probe specific for iNOS. iNOS protein was identified using Western immunoblot analysis, and NOS activity was quantified by measuring the NG-monomethyl-L-arginine (L-NMMA)-inhibitable conversion of 14C-labeled L-arginine to L-[14C]citrulline. In a separate series of experiments, circulating or extravasated PMNs were cultured for 4 h and the accumulation of L-NMMA-inhibitable nitrite (NO2-) in the supernatant was determined and used as a measure of NO production in vitro. We found that circulating PMNs (rat or human) contained no iNOS mRNA, protein, or enzymatic activity. Furthermore, circulating rat or human PMNs (2 x 10(6) cells/well) were unable to generate significant amounts of NO2- when cultured for 4 h in vitro. In contrast, iNOS mRNA levels in 4- and 6-h elicited rat PMNs increased 21- and 42-fold, respectively, when compared with circulating cells. Western blot analysis revealed the presence of iNOS protein in the elicited rat PMNs and iNOS enzymatic activity increased from normally undetectable levels in circulating rat PMNs to 81 and 285 pmol/min/mg for the 4- and 6-h elicited rat PMNs, respectively. Approximately 20-30% of the total iNOS activity was Ca(2+)-dependent. Nitrite formation by elicited rat PMNs in the absence of any exogenous stimuli increased from normally undetectable amounts for circulating PMNs to approximately 8 and 11 microM/10(6) cells for the 4- and 6-h elicited PMNs, respectively. Highly enriched preparations of extravasated human PMNs contained neither message, protein nor iNOS enzymatic activity. Taken together our data demonstrate that inflammation-induced extravasation of rat PMNs upregulates the transcription and translation of iNOS in a time-dependent fashion and that 20-30% of the total inducible NOS is Ca(2+)-dependent. In contrast, neither circulating nor extravasated human PMNs contained iNOS message, protein, or enzymatic activity. These data suggest that the human PMN iNOS gene is under very different regulation than is the rat gene.

Animals↗
PubMed1988

Altered turnover of allelic variants of hypoxanthine phosphoribosyltransferase is associated with N-terminal amino acid sequence variation.

The results of our previous studies suggested that differences in the primary structures of the hypoxanthine phosphoribosyltransferase (HPRT) A and B proteins (EC 2.4.2.8) of mice are associated with altered turnover of these proteins in reticulocytes. On the basis of nucleotide sequence comparisons of their corresponding cDNAs, we show here that the HPRT A and B proteins differ at two positions; there is an alanine/proline substitution at amino acid position 2 and a valine/alanine substitution at amino acid position 29 (HPRT A/B proteins, respectively; total protein length, 218 amino acids). On the basis of results obtained from sequencing of the N termini of the purified HPRT A and B proteins, we also show that these amino acid substitutions are associated with differences in processing of the proteins; HPRT B, which is encoded as N-terminal Met-Pro, has a free N-terminal proline residue; HPRT A, which is encoded as N-terminal Met-Ala, lacks a free N-terminal alpha-amino group and is presumed to be acetylated following removal of the N-terminal methionine (i.e. AcO-Ala). These observations are discussed in reference to the idea that the N terminus of a protein plays a role in determining the rate at which the protein is degraded in erythroid cells.

Alleles↗
PubMed1987

Altered turnover of hypoxanthine phosphoribosyltransferase in erythroid cells of mice expressing Hprt a and Hprt b alleles.

We have previously shown that mice expressing Hprt a allele(s) have erythrocyte hypoxanthine phosphoribosyltransferase (HPRT) levels that are approximately 25-fold (Mus musculus castaneus) and 70-fold (Mus spretus) higher than in mice that express the Hprt b allele (Mus musculus domesticus; C57BI/6J; C3H/HeHa), and that these differences in erythrocyte HPRT levels are due to differences in the turnover rates of the HPRT A and B proteins as reticulocytes mature to erythrocytes. We show here that: the taxonomic subgroups of the genus Mus are essentially monomorphic for the occurrence of either the Hprt a or the Hprt b allele, with Hprt a being common in the aboriginal species (M. spretus, Mus hortulanus and Mus abbotti) and in several commensal species (Mus musculus musculus, M. m. castaneus, Mus musculus molossinus), while Hprt b is common in feral M. m. domesticus populations as well as in all inbred strains of mice tested; in all these diverse Mus subgroups there is a strict association of Hprt a with high and Hprt b with low levels of erythrocyte HPRT; and, the association between the occurrence of the Hprt a allele and elevated erythrocyte HPRT levels is retained following repeated backcrosses of wild-derived Hprt a allele(s) into the genetic background of inbred strains of mice with the Hprt b allele. Collectively, these observations indicate that the elevated and low levels of erythrocyte HPRT are specified by differences in the Hprt a and b structural genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1987

Gamma-interferon in aplastic anemia: inability to detect significant levels in sera or demonstrate hematopoietic suppressing activity.

A radioimmunoassay (RIA) was used to quantitate biologically active gamma interferon (INF-gamma) in sera and in supernatants of cultured mononuclear cells obtained from 50 patients with aplastic anemia. Only five of the 50 serum samples had INF-gamma levels above background (greater than 0 less than 0.5 units per mL). Detectable levels of spontaneous INF-gamma (0.3 to 868 U/mL) were found in 18 of the 50 mononuclear cell supernatants tested. The addition of patient sera or INF-gamma positive supernatants to cultures of normal hematopoietic colonies did not result in reduced colony growth. Flow cytofluorimetric analysis of mononuclear cells failed to establish a correlation between the presence of INF-gamma in supernatants and the number of activated T cells or natural killer (NK) cells in the mononuclear cell population. However, a significant correlation did exist between the presence of monocytes and the production of INF-gamma. Contrary to previous reports, our data suggest that patients with aplastic anemia do not have high circulating levels of INF-gamma. Unstimulated mononuclear cells from some patients will produce significant levels of INF-gamma, but this does not result in decreased in vitro hematopoiesis.

Anemia, Aplastic↗
PubMed1985

Elevated levels of erythrocyte hypoxanthine phosphoribosyltransferase associated with allelic variation of murine Hprt.

Murine stocks with wild-derived hypoxanthine phosphoribosyltransferase (HPRT) A alleles (Hprt a) have erythrocyte HPRT activity levels that are approximately 25-fold (Mus musculus castaneus) and 70-fold (Mus spretus) higher than those of laboratory strains of mice with the common Hprt b allele (Mus musculus: C3H/HeHa or C57B1/6). Since the purified HPRT A and B enzymes have substantially similar maximal specific activities (64 and 46 units/mg of protein, respectively), we infer that these HPRT activity levels closely approximate the relative levels of HPRT protein in these cells. Red blood cells of HPRT A and B mice have similar levels of adenine phosphoribosyltransferase activity (APRT; EC 2.4.2.7) and reticulocyte percentages, which suggests that the elevated levels of HPRT in erythrocytes of HPRT A mice are not secondary consequences of abnormal erythroid cell development. The HPRT activity levels in reticulocytes of HPRT B mice are approximately 35-fold higher than the levels in their erythrocytes and approach the HPRT activity levels in reticulocytes of HPRT A mice. Thus, the marked differences in the levels of HPRT protein in erythrocytes of HPRT A and B mice result from differences in the extent to which the HPRT A and B proteins are retained as reticulocytes mature to erythrocytes. The substantial and preferential loss of HPRT B activity from reticulocytes is paralleled by an equivalent loss of HPRT immunoreactive protein (i.e., CRM) from that cell, and we infer that the HPRT B protein is degraded or extruded as reticulocytes mature to erythrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1983

Hypoxanthine-guanine phosphoribosyltransferase in human erythroid cells: properties of the isozymes.

We have previously given evidence that the hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) isozymes in human erythroid cells result from posttranslational modifications of a single gene product [Johnson, G. G., et al. (1982). Biochemistry 21: 960]. In the present work we compare the properties of the unmodified and two major modified isozymes, which collectively account for 90% of the HGPRT enzyme activity in cell lysates. The modified isozymes differ from the parent molecule in the pH dependence of activity and in the relative utilization of the two purine base substrates, hypoxanthine and guanine. In contrast to the changes in the catalytic properties of the enzyme, the modifications have no detectable effects on the heat stability or on the equilibrium between enzyme dimers and enzyme tetramers.

Erythrocytes↗
PubMed1983

Hypoxanthine-guanine phosphoribosyltransferase in human erythroid cells: degradation of the enzyme.

In a previous report we provided evidence that the three major hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) isozymes in human erythroid cells are derived by posttranslational modification of a single enzyme [Johnson, G. G. et al. (1982). Biochemistry 21: 960]. In the experiments reported here we provide further evidence that the modified isozymes have a catalytic activity that is at least as great as that of the unmodified enzyme. However, we also show that the total HGPRT activity decrease with red-cell age, by a factor of approximately 4, and that this decrease in activity is paralleled by a loss in HGPRT immunoreactive protein. We estimate that the loss of HGPRT activity and immunoreactive protein as well as the changes in the relative abundances of the major isozymes occur early in the cell's life.

Cell Survival↗