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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 415 records · Page 23Linked to original sources
PubMed1977

Isolation of spontaneously derived mutants of Caulobacter crescentus.

Caulobacter crescentus has a penicillinase which precludes the use of penicillin for mutant enrichment. However, two other antibiotics, fosfomycin and D-cycloserine, can be enrich for C. crescentus mutants. In enrichment procedures for C. crescentus auxotrophs, spontaneously derived mutants occur at a frequency of 5-10% among the survivors of an enrichment procedure. Consequently, large numbers of mutants are readily obtained without any need for mutagenesis. These mutants are heterogeneous both with regard to the type of mutation and to the nutritional requirement. A similar procedure has been used to isolate temperature-sensitive mutants.

Anti-Bacterial Agents↗
PubMed1977

Chronic active hepatitis and cirrhosis in Wilson's disease.

A 32-year-old woman was found to have chronic active hepatitis and cirrhosis after exploratory celiotomy resulted in hepatic decompensation. Subsequent investigation confirmed the diagnosis of Wilson's disease. This case demonstrates that Wilson's disease may manifest itself as chronic active hepatitis as late as the fourth decade of life without neurologic symptoms or findings. Wilson's disease should be actively considered in patients with chronic active hepatitis or cirrhosis, even in older age groups and despite the absence of central nervous system manifestations.

Adult↗
PubMed1977

Interaction of Treponema pallidum (Nichols strain) with cultured mammalian cells: effects of oxygen, reducing agents, serum supplements, and different cell types.

Cultured mammalian cells extend the time of survival of Treponema pallidum (Nichols strain). Various parameters that have been previously shown to enhance treponemal survival in vitro were examined for influences on the interaction of T. pallidum with cultured cells. With cells derived from normal rabbit testes, the time of retention of treponemal virulence was extended in an atmosphere containing reduced concentrations of oxygen. Glutathione and cysteine, when added to the basal tissue culture medium, prolonged treponemal survival. In an assessment of various tissue culture medium supplements, normal rabbit serum was equivalent to fetal bovine serum and superior to bovine serum albumin fraction V (BSA), fatty acid-poor BSA, and lipid-pooed for TRK-2, HSE, NRK, and C6 cells. Dithiotreitol, as an additional reducing agent, sharply enhanced treponemal survival. With SF1Ep NBL-11 cells and basal tissue culture medium containing glutathione, cysteine, and dithiothreitol, in an atmosphere of approximately 3% oxygen, T. pallidum was maintained without detectable decreases in the number of virulent organisms for 6 days.

Blood↗
PubMed1977

Characterization of the attachment of Treponema pallidum (Nichols strain) to cultured mammalian cells and the potential relationship of attachment to pathogenicity.

The interaction of Treponema pallidum (Nichols strain) with 19 different cultured mammalian cell types was examined. These types included cells derived from testis, kidney, spleen, lung, epidermis, cervix, urethra, and nerve tissue of human, rabbit, or rat origins. They represented normal and malignant cells, epithelial and fibroblastic morphology, cell lines, and cell strains, Large numbers of organisms attached to the cultured cells; this attachment prolonged the time of retention of active treponemal motility. Attachment was examined in terms of the number of treponemes inoculated, cultured cells present, and actively growing versus stationary cultured cells; the motility of the treponemes; the viability of the cultured cells; and the different cell passages. In sharp contrast to the attachment of T. pallidum, 11 nonpathogenic treponemes failed to attach to cultured cells. Immune syphilitic rabbit serum prevented the attachment of T. pallidum to cultured cells, as indicated by phase contrast microscopy and rabbit inoculations. This blockage of attachment by immune serum occurred without interfering with active motility of the organisms. Results are discussed in terms of the potential relationship of attachment to the pathogenicity of T pallidum.

Antibodies, Bacterial↗
PubMed1977

Scanning electron microscopy of Treponema pallidum (Nichols strain) attached to cultured mammalian cells.

This paper describes the attachment of Treponema pallidum (Nichols strain) to cultured mammalian cells as a visualized by scanning electron microscopy. Treponemes were incubated for 3 hr with cultured cells derived from normal rabbit testes or human skin epithelium, then fixed, processed with critical-point drying, and examined with a Cambridge Mark 2A scanning electron microscope. Large numbers of treponemes became attached to the cultured cells without altering the morphological integrity of the cultured cells. Attachment appeared to involve a very close physical proximity of treponemes to the cultured cells; at the site of attachment, no changes such as swelling or indentation of the cultured cell surface were observed. The addition of ruthenium red to the fixatives produced a treponemal-associated surface precipitate. This material, which is probably mucopolysaccharide and/or phospholipid, may be important in protecting the organisms against host defense mechanisms; in addition, it may be involved in the serological unresponsiveness of freshly prepared suspensions of T. pallidum.

Animals↗
PubMed1977

The spirochetes.

Explore the source record for details and available documents.

Borrelia↗
PubMed1976

Level of functioning of siblings and parents of probands of varying degrees of retardation.

A further analysis of already published data supports the position that retardates of low ability level less frequently have retarded siblings, retarded parents, and parents low in occupational level than do retardates higher in ability level. The analysis supports the position that there are two types of retarded individuals, persons retarded as a result of gene or chromosomal anomalies, brain injury, etc., who more frequently occur in the lower-level retardate group, and persons whose retardation represents polygenic segregation, who more frequently occur in the higher-level group.

Humans↗
PubMed1976

Binding of squalene, lanosterol, desmosterol, and cholesterol to proteins in brain and liver 105,000 g supernatant fractions: evidence for specific binding sites.

The binding of squalene, lanosterol, desmosterol, and cholesterol to proteins in 105,000 g supernatant fraction (S105) from brain and liver of rats was investigated. The S105 fractions from both tissues contain specific binding sites for sterols, which are sensitive to trypsin. The dissociation constants for squalene and sterol protein complexes were in the range of 10(-6) M and were not appreciably different for proteins in brain and liver S105. Competition studies revealed that both brain and liver S105 contain one receptor protein which binds lanosterol and is specific for methyl sterols, and a second receptor which binds both desmosterol and cholesterol. Binding of 7-dehydrocholesterol reported by others must occur at a third independent site since this compound does not interfere with the binding of lanosterol, desmosterol, or cholesterol. Although binding of squalene to proteins in brain and liver S105 does occur, we were unable to show the specificity of squalene binding. The concentration of desmosterol and cholesterol binding sites, which ranged from 6 to 10 nmol/mg protein, was 3- to 5-fold higher than the concentration of squalene and lanosterol binding sites (1.6-2.3 nmol/mg protein). The brain S105 from suckling rats contained fewer binding sites for desmosterol and cholesterol than the brain S105 from weaned rats. However, the concentration of lanosterol binding sites in brain S105 did not show an age-dependent change. The receptor proteins in brain and liver appear to be identical.

Animals↗
PubMed1976

Effects of a short heat pulse on phenomena related to DNA repair in ultraviolet-irradiated Escherichia coli.

Mutational synergism between heat and UV light in Escherichia coli was examined for evidence supporting various possible synergistic mechanisms. UV and heat lethality were only additive or slightly synergistic after 30 sec at 50 degrees C. The order of treatment did not affect the mutational synergism. Synergism is not peculiar to induction of mutation from streptomycin sensitivity to resistance. Neither DNA breakage nor alteration of post-replication repair rates was seen after a 5 min 50 degrees C heat pulse. Synergism was observed with temperatures as low as 43 degrees C. A strain deficient in excision repair but not post-replication repair exhibited mutational synergism, suggesting that synergism may involve the differential heat alteration of the error-prone post-replication repair process.

DNA Repair↗
PubMed1976

The absence of caffeine inhibition of post-replication repair in excision deficient strains of Escherichia coli B and K12.

The effect of caffeine on postreplication repair, as seen in alkaline sucrose gradients, conjugation, and ultraviolet light (UV) survival, was studied in excision deficient strains of Escherichia coli K12 and B. A caffeine concentration of 2 mg/ml was chosen for the study which did not inhibit colony formation. Both E. coli K12 AB2500 and E. coli B WWP2 were more sensitive to UV when plated on caffeine plates. Conjugation was not inhibited in the E. coli K12 strain; however, the same procedure confirmed caffeine inhibition in the E. coli B strain [17]. Caffeine did not inhibit postreplication repair in either strain, as determined by sedimentation profile studies of DNA on alkaline sucrose gradients. No strand breakage or degradation was observed in parental or post-UV replicated DNA for as long as 50 min incubation in caffeine. Thus caffeine concentrations that inhibited two recA gene product related phenomena did not cause immediate changes in size of DNA or inhibit the rate of a DNA gap generating postreplication type of DNA repair.

Caffeine↗
PubMed1976

Treponeme outer envelope: chemical analysis.

The chemical composition of the outer envelope (OE) of Treponema phagedenis biovar Kazan 5 was investigated. After cultivation in a lipid-defined medium, the OE was removed from the cells with 0.7 mM sodium dodecyl sulfate. The solubilized OE was reaggregated by dialysis against 20 mM MgCl2, washed, lyophilized, and subjected to chemical analysis. The average yield of OE was 14.6% of the whole cell (WC) dry weight. The magnesium content was 0.683 mug/mg OE. Peptidoglycan components such as muramic acid and ornithine were detected in the WC but not in the OE, and diaminopimelic acid was absent in both WC and OE. The OE contained protein (60-73%), carbohydrate (1-2%), and lipid (4-5%), primarily polar lipid. The major polar lipids were monogalactosyldiglyceride (43%) and phospholipid (57%), of which phosphatidylcholine was the main phospholipid component, with phosphatidylethanolamine present in lesser amounts.

Amino Acids↗
PubMed1976

Accidental laboratory infection with Treponema pallidum, Nichols strain.

This case report describes a laboratory-acquired infection with Treponema pallidum, Nichols strain. The specific details of the accidental exposure are presented, along with a description of the clinical observations. This infection indicates that the rabbit adapted Nichols strain of T pallidum retains its capability to infect humans. In addition, aerosols of concentrated preparations of these organisms, generated within the laboratory, represent a definite biohazard.

Aerosols↗