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Biomedical subjects

K Johnson

Publications and source records attributed to K Johnson.

At least 415 records · Page 23Linked to original sources
PubMed1988

Expression and secretion of the cloned Pseudomonas aeruginosa exotoxin A by Escherichia coli.

The exotoxin A gene from Pseudomonas aeruginosa PAK was expressed in Escherichia coli from recombinant plasmids when transcription was initiated from a promoter in the cloning vector. The exotoxin A polypeptide synthesized was found to have an electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels of 66,000 daltons, identical in size to the mature exotoxin A made by P. aeruginosa. Analysis of the location of exotoxin A in various bacterial compartments by immunoblotting revealed that exotoxin A was exported by E. coli into its periplasmic space. Several functional assays, including analyses of disulfide bond formation, potentiation of ADP-ribosyltransferase activity, and HeLa cell cytotoxicity, were used to establish that the conformation of exotoxin A isolated from the E. coli periplasmic space is identical to that of exotoxin exported by P. aeruginosa to its extracellular space. Previous studies with recombinant plasmids expressing exotoxin A from P. aeruginosa PA103 (G. D. Gray, D. Smith, J. Baldridge, R. Markins, M. Vasil, E. Chen, and M. Heyneker, Proc. Natl. Acad. Sci. USA 81:2645-2649, 1984) showed a complete lack of processing and export of pre-exotoxin A in E. coli, differing from results reported here. These discrepancies may be explained by observed differences in the sequence of signal peptides encoded by the exotoxin A genes of PAK and PA103 strains of P. aeruginosa.

ADP Ribose Transferases↗
PubMed1988

Molecular heterogeneity in lysosomal storage diseases. Alpha-fucosidase and N-acetyl-beta-D-hexosaminidase deficiency variants.

The availability of specific antibodies and cDNA probes for lysosomal hydrolases has revealed unexpected heterogeneity among the human inherited lysosomal storage diseases. Using alpha-fucosidase and N-acetyl-beta-D-hexosaminidase deficiency variants as examples, it has been determined that a lysosomal hydrolase deficiency can result from DNA deletion mutations, failure to synthesize mRNA because of defective splicing, posttranslational defects in assembly, and synthesis of a precursor enzyme that is prematurely proteolytically degraded through lack of a protective protein. In some cases (fucosidosis), the different genotypes cannot be distinguished phenotypically, whereas in others (beta-hexosaminidoses) the phenotypes can range from infantile neurodegeneration through juvenile motor neuron disease to adult neurodysfunction. Biochemical studies on both diseases have revealed several distinct genotypes. We show that some forms of fucosidosis result from unstable enzyme that can be stabilized by protease inhibitors, whereas partial beta-hexosaminidase deficiencies cannot be corrected by these protease inhibitors.

Cells, Cultured↗
PubMed1988

Pediatric central auditory dysfunction. Comparison of children with confirmed lesions versus suspected processing disorders.

This study compared and contrasted results on pure tone audiometry, acoustic reflexes, and the Pediatric Speech Intelligibility Test in children with either documented or suspected central auditory dysfunction. Ages ranged from 3 years, 2 months, to 8 years, 4 months. In children with confirmed CNS lesions, results were consistently normal for children with lesions in nonauditory areas of the brain and consistently abnormal for children with lesions in areas of the brain important for auditory perceptual function. The patterns of abnormality were consistent with previous findings in adults. In children with suspected central auditory processing disorders (CAPDs), audiometric findings typically showed normal hearing sensitivity, abnormal (rising) audiometric contours, normal acoustic reflexes, normal degraded monotic speech perception, and abnormal dichotic speech perception. This pattern of results was similar to findings in children with confirmed temporal lobe lesions. Overall, results supported an auditory perceptual, rather than a linguistic, basis for CAPDs.

Auditory Diseases, Central↗
PubMed1988

Potentiation of aminoglycoside nephrotoxicity by vitamin-D-induced hypercalcemia.

The effect of 1,25(OH)2 vitamin D3-induced hypercalcemia on the course of aminoglycoside nephrotoxicity in the rat was studied. Daily gentamicin, 100 mg/kg body weight, was administered subcutaneously concomitant with 1,25(OH)2 vitamin D3, 50 ng s.c. to male Sprague-Dawley rats. This group was compared to rats injected with gentamicin alone, 1,25(OH)2 vitamin D3 alone, and an ethanol vehicle as a control. Structural and functional parameters of acute renal failure were assessed following 4, 6 and 7 days of treatment. Severe morphologic evidence of tubular injury was documented on day 6 in the group injected with gentamicin and 1,25(OH)2 vitamin D3. Correlative functional and metabolic evidence of tubular cell deterioration occurred in this group on day 7 as represented by an elevated blood urea nitrogen (BUN), 198 +/- 14 mg/dl (p less than 0.001 compared to all other groups), a heightened mean renal cortical homogenate calcium, 1,028.3 +/- 304.8 nmol/mg protein (p less than 0.05 or better compared to all other groups), and significantly increased mean cortical mitochondrial calcium content, 796.3 +/- 116.5 nmol/mg protein (p less than 0.01 in relation to all other groups). Elevated total serum calcium to a level of 11.9 +/- 0.2 mg/dl (p less than 0.001 compared to control group) developed in the gentamicin/1,25(OH)2 vitamin D3 group on day 4, 2 days prior to pronounced structural damage, and continued to be elevated through day 7. No difference in serum phosphorus levels, however, developed between control and gentamicin-plus-vitamin-D-treated animals except on day 7 when severe renal failure developed in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Cytokine-dependent granulocytic differentiation. Regulation of proliferative and differentiative responses in a murine progenitor cell line.

Human granulocyte colony stimulating factor (G-CSF) can support the survival and short term proliferation of the interleukin 3 (IL 3)-dependent diploid murine hemopoietic progenitor cell line 32D C13. After 8 days in the presence of 30 U/ml of G-CSF and in the absence of IL 3, the great majority of 32D C13 cells becomes positive for myeloperoxidase (a marker that appears at the promyelocytic stage of the granulocytic lineage) and progressively differentiates into lactoferrin-containing neutrophilic granulocytes. Myeloperoxidase mRNA rapidly increases after 24 to 48 hr of treatment with G-CSF, peaks at day 6 and is no longer detectable at day 9 and 12, paralleling the appearance of myeloperoxidase-positive promyelocytes and myelocytes in the culture. After 12 days, 100% of the cells terminally differentiate, and clonogenic assays in IL 3-containing semisolid media indicate that the whole population has irreversibly lost proliferative capability. By using varying concentrations of both murine IL 3 and recombinant human G-CSF, the cultures develop an heterogeneous population of cells representing all the differentiation stages of the myeloid lineage, and the relative ratios of immature proliferating precursors and terminally differentiated cells present in the cultures can be modulated by modifying the concentrations of IL 3 or recombinant human G-CSF. Isobolic curves indicate that IL 3 and G-CSF have an antagonistic effect on the proliferation of 32D C13 cells. Thus, these cells represent a simplified in vitro model of normal granulocytic differentiation whose extent may be modulated completely in the presence of serum by two well-defined growth and differentiation factors: IL 3 and G-CSF.

Animals↗
PubMed1987

Electrophoretic analysis of genetic linkage in Scots pine (Pinus sylvestris L.).

Eighty megagametophytes from each of 24 Scots pines (Pinus sylvestris L.) were subjected to horizontal starch gel electrophoresis. The trees were from crosses among widely separated provenances, and each was polymorphic for 8 to 14 loci. Evidence for linkage among 275 two-locus combinations was tested using chi-square analysis. Data from different trees were pooled to calculate map distances for the species. Nineteen of the twenty-nine loci tested were linked in one of six groups; the groups varied in size from two to seven loci. Similarities in linkage relationships among Scots pine, other pines, and other species within the Pinaceae support karyological research that suggests extensive conservation of the conifer genome.

Electrophoresis, Starch Gel↗
PubMed1987

Giant cell reparative granuloma of the hand.

A case of recurrent giant cell reparative granuloma of the hand is reported. The radiographs showed a lytic, expansile lesion that extended from the secondary ossification center proximally to the articular surface distally. Treatment consisted of excision of the involved proximal phalanx and interposition bone graft. The histopathologic findings were typical for this benign, nonneoplastic process: a cellular fibrous stroma with many giant cells. The differentiation of giant cell reparative granuloma from giant cell tumor, aneurysmal bone cyst, and brown tumor of hyperparathyroidism is reviewed.

Adolescent↗
PubMed1987

Lack of effect of deferoxamine, dimethyl sulfoxide, and catalase on monocrotaline pyrrole pulmonary injury.

Monocrotaline pyrrole (MCTP) is a reactive metabolite of the pyrrolizidine alkaloid monocrotaline. MCTP given intravenously to rats causes pulmonary hypertension and right ventricular hypertrophy. Lesions in lungs after MCTP treatment contain macrophages and neutrophils, which may contribute to the damage by generation of reactive oxygen metabolites. Rats were treated with MCTP and agents known to protect against oxygen radical-mediated damage in acute models of neutrophil-dependent lung injury. Rats received MCTP and deferoxamine mesylate (DF), dimethyl sulfoxide (DMSO), or polyethylene glycol-coupled catalase (PEG-CAT). MCTP/vehicle-treated controls developed lung injury manifested as increased lung weight, release of lactate dehydrogenase into the airway, and sequestration of 125I-labeled bovine serum albumin in the lungs. Cotreatment of rats with DF, DMSO, or PEG-CAT did not protect against the injury due to MCTP. These results suggest that toxic oxygen metabolites do not play an important role in the pathogenesis of MCTP-induced pulmonary injury.

Animals↗
PubMed1987

Characterization of Pseudomonas aeruginosa mutants with altered piliation.

The pilus-specific Pseudomonas aeruginosa bacteriophage P04 was used to select spontaneous mutants of strain PAK which have altered piliation. The largest class of phage-resistant mutants synthesized the pilin polypeptide, but did not assemble pili. These mutants are likely to contain mutations in genes required for pilus assembly and not mutations in the pilin structural gene, as they could not be complemented by a normal copy of the pilin gene. In addition, two alterations in pilin gene transcription were found among the mutants--hyperpiliated mutants which overproduce pilin mRNA, and a mutant with temperature-sensitive pilin gene transcription. We also present a model for the regulation of pilin gene transcription by a feedback mechanism sensitive to the relative rates of pilus assembly and disassembly.

Bacterial Outer Membrane Proteins↗
PubMed1987

Akathisia in idiopathic Parkinson's disease.

Akathisia is a little-studied symptom of Parkinson's disease. Interviews of 100 patients with idiopathic Parkinson's disease indicated that 68% periodically experienced the need to move and inability to remain still, usually because of well-defined causes such as parkinsonism and sensory complaints. Twenty-six patients could not explain the inability to remain still, a state of true akathisia. This disputes the common belief that akathisia represents simply the need to move for relief of discomfort imposed by rigidity or lack of movement, and emphasizes the need to distinguish between true akathisia and other, more common causes for the need to move experienced by parkinsonian patients.

Aged↗
PubMed1987

Differentiation between two African arenaviruses (Lassa and Mozambique) by plaque assay.

The biological characteristics of Lassa and Mozambique viruses were compared by plaque assay. Both viruses produced plaques under the same conditions, however, Lassa virus plaques measured on average 2 mm in diameter being twice as large as the Mozambique virus plaques. By plaque reduction tests, cross protection was demonstrated between both viruses showing that Lassa and Mozambique viruses are distinct but related.

Animals↗