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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 433 records · Page 24Linked to original sources
PubMed1975

Postreplication repair gap filling in an Escherichia coli strain deficient in dnaB gene product.

Gaps in daughter-strand DNA synthesized after exposure of Escherichia coli E279 to ultraviolet light are filled during reincubation at 30 degrees C for 20 min. Escherichia coli E279 is phenotypically DnaB- when incubated at 43 degrees C. Cells incubated at 43 degrees C were tested for their ability to complete postreplication repair gap filling. It is concluded that the dnaB gene product is essential for postreplication repair gap filling and that the inhibition seen is not initially the result of degradation.

Centrifugation, Density Gradient↗
PubMed1975

Effect of pretreatment with Mycobacterium bovis (strain BCG) and immune syphilitic serum on rabbit resistance to Treponema pallidum.

Stimulation of the rabbit reticuloendothelial system with viable Mycobacterium bovis (strain BCG), and other agents, had no effect on the development of syphilitic lesions after intradermal or intravenous inoculation with graded doses of Treponema pallidum (virulent Nichol's strain; mean infective doses less than 10). The simultaneous administration of immune syphilitic rabbit serum retarded the development of lesions, but this appeared to be due solely to the immune serum, suggesting no synergism between the activated reticuloendothelial system and the anti-T. pallidum antibodies. The administration of two doses of BCG enhanced syphilitic lesion development in the rabbit.

Animals↗
PubMed1975

Retention of motility and virulence of Treponema pallidum (Nichols strain) in vitro.

A maintenance medium for Treponema pallidum was designed to hold its Eh at the optimum for that organism, -10 to -110 mV. After 100% motile (freshly harvested) T. pallidum was inoculated into the medium, the motility of the treponemes decreased to 80% after 2 days, 50% after 3.5 days, and 0% after 9 days during incubation at 34 C. Full virulence was retained for 2 days, but it dropped rapidly thereafter, and the treponemes became avirulent by day 5.

Animals↗
PubMed1975

Antileptospiral activity in lower-vertebrate sera.

Normal serum from the painted turtle (Chrysemys picta), the snapping turtle (Chelydra serpentina), and the frog (Rana pipiens) were found to possess bactericidal activity towards Leptospira. Leptospires from both the parasitic and biflexa complexes were killed by these sera at high dilutions. This pattern differs from that of mammalian serum, as generally only the biflexa complex leptospires are killed by normal mammalian serum. The activity in C. picta serum was characterized as being complement dependent and not mediated by basic proteins. Because comple-inactivated C. picta serum regained leptospiricidal activity after the addition of fresh rabbit serum, antibody is also likely to participate in the killing activity. Further support that C. picta serum contained leptospiral antibodies was found by the detection of serotype-specific agglutinins.

Animals↗
PubMed1975

The lipids of four unusual non-pathogenic host-associated spirochetes.

The lipid compositions of two spirochetes isolated from the human oral cavity and two isolated from pig feces were examined. These isolates were unusual in that they did not require long-chain fatty acids for growth, as do the other host-associated spirochetes, but rather required isobutyric and valeric acids. Therefore, they could be cultured in a medium free of serum or fatty acid - albumin supplements. The major fatty acids synthesized were normal and iso fatty acids with 14 and 16 carbons. No unsaturated fatty acids were detected, nor were chain lengths longer than 16 carbons. The major complex lipids found were monogalactosyl diglyceride, phosphatidyl glycerol, and bis-phosphatidyl glycerol. Nitrogenous phospholipids, present in Treponema and Leptospira, were not synthesized by these novel strains. The data indicate an intermediate position of these isolates between Treponema and free-living Spriochaeta.

Animals↗
PubMed1975

Cognitive abilities: use of family data as a control to assess sex and age differences in two ethnic groups.

Four cognitive factors were extracted from test data obtained on 997 families (3,268 individuals) in Hawaii. Factor loading profiles for the two largest ethnic groups (Caucasians and Japanese) are nearly identical, as are profiles for three different age groups. Age curves are presented for factor scores and for four specific cognitive tests. The younger respondents on the age curves are biological offspring of older respondents represented on the same curves, facilitating an unusual control for between-family variance. When the data were stratified by ethnicity, differential rates of cognitive development were indicated.

Adolescent↗
PubMed1975

Recognition of streptococcal pharyngitis in adults.

In order to devise a strategy for the management of acute pharyngitis, the clinical features of 418 adults with sore throat were noted and throat cultures were obtained. Patients with cultures positive for group A beta-hemolytic streptococci had a significantly higher (P less than or equal to .01) frequency of recent exposure to streptococcal infection, pharyngeal exudate, enlarged or tender cervical nodes, and high fever (greater than or equal to 38.3 C [101 F]. Patients with negative cultures complained more frequently of cough. On the basis of these symptoms and signs, a clinical algorithm was developed and discriminant function scores were computed that identify patient populations with different probabilities of having streptococcal pharyngitis. The patients with moderate and high probabilities included 91% of patients with positive cultures but only 67% of the total patient population. These methods could be the basis for more efficient evaluation of adults with sore throat.

Adolescent↗
PubMed1975

Immune plasma-dependent cytotoxicity of immune and non-immune peripheral lymphoid cells for target cells coated with bacterial outer unit membrane.

The development of a model system for use in the study of lymphoid cell cytotoxicity to bacterial membrane antigens was attempted. In this system 51 Cr-labelled chicken red blood target cells were coated with pieces of the outer unit membrane of leptospirae rather than with soluble antigens. Using the model system to study dog peripheral immune lymphoid cell cytotoxicity to coated target cells we found that both immune and non-immune lymphocytes are antibody dependent for the expression of their cytotoxicity. It was also found that the unit membrane preparation from leptospirae can serve as a good antigenic stimulant to immune dog lymphoid cells as measured by increased [3H]thymidine uptake.

Animals↗
PubMed1974

Near identity of cognitive structure in two ethnic groups.

As part of a large-scale family study in Hawaii, Americans of either Japanese or European ancestry were administered a battery of 15 cognitive tests. Principal component analyses (varimax rotations) yielded the same four major cognitive factors for each of the two ethnic groups, and these factors are defined by strikingly similar factor loadings.

Asian People↗