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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 379 records · Page 21Linked to original sources
PubMed1979

Anesthesia for cesarean section: further studies.

This study was designed to re-evaluate neonatal condition at birth following elective cesarean section performed with epidural anesthesia and a modified technique of general anesthesia. Two groups of 20 patients were studied. Twenty received epidural anesthesia with 2 per cent lidocaine-carbon dioxide-epinephrine, and 20 patients were given general anesthesia. Modifications of our previous general anesthetic technique included the administration, to the mother, of high inspired concentrations of oxygen (66 per cent) prior to delivery, short induction-to-delivery intervals, and positioning of the mother in a 20 degrees left lateral tilt position. No significant differences in oxygen tension and acid-base balance in umbilical venous and arterial blood were demonstrated between the two sets of neonates. One-and five-minute Apgar scores and time to sustained respiration were similar in both groups. Our observations of the infants immediately after delivery led us to conclude that either anesthesia technique is acceptable for elective cesarean section.

Acid-Base Equilibrium↗
PubMed1979

Hemispheric efficiency in middle and later adulthood.

Right and left hemisphere efficiency, as measured by dichotic memory for numbers, was assessed in a sample of older adults in Experiment I. Right hemisphere efficiency dropped off sharply with age, while left hemisphere efficiency did not show a significant decline. A second group of subjects was tested on a musical note recognition task in Experiment II. Regression analyses revealed significant age decrements in performance, regardless of ear/hemisphere involved. The writers suggested that the reported decline with age in spatial ability may result from an age related decline in right hemispheric functioning, even on tasks that are right hemisphere dominant. The lack of decline reported for verbal ability may be a consequence of the lack of decline in left hemisphere efficiency with regard to left hemisphere dominant tasks.

Adult↗
PubMed1979

Surface mucopolysaccharides of Treponema pallidum.

The viscous mucoid fluid that accumulates within syphilitic lesions may be due to breakdown of host tissue during infection, or may be synthesized by Treponema pallidum. Experiments were performed to investigate the acidic mucopolysaccharides that occur at the surface of T. pallidum (Nichols strain). These mucopolysaccharides were demonstrated by reaction with acidified bovine serum albumin and by agglutination with wheat germ agglutinin and soybean agglutinin. The polycations ruthenium red and toluidine blue influenced treponemal survival. Concentrations of both compounds at 200 mug/ml inhibited survival, whereas concentrations at 0.1mug/ml enhanced survival. The mucopolysaccharide concentration within the mucoid fluid that accumulates during intratesticular infection was determined by reaction with acidified bovine serum albumin; it ranged from 10,000 mug/ml to less than 8 mug/ml. The addition of this mucoid fluid to treponemal suspensions resulted in differing effects on T. pallidum survival. Some preparations were inhibitory, and others were stimulatory. Commercial preparations of hyaluronic acid and chondroitin sulfate at 400, 200, 100, and 50 mug/ml were detrimental to treponemal survival. The organisms exhibited pronounced clumping in the presence of the higher concentrations of hyaluronic acid. These clumps of treponemes were comprised of mucopolysaccharides as shown by acidified bovine serum albumin and toluidine blue reactions and by hyaluronidase degradation. Results are discussed in terms of the derivation and potential role of acidic mucopolysaccharides at the surface of T. pallidum.

Animals↗
PubMed1979

Relationship of Treponema pallidum to acidic mucopolysaccharides.

Attempts were made to relate Treponema pallidum to the acidic mucopolysaccharides that occur in vivo within host ground substance and in vitro on the surface of cultured testicular cells. Infected testicular tissue was fixed and processed for transmission electron microscopy in the presence of ruthenium red. The use of this inorganic dye demonstrated the large quantity of mucopolysaccharide within testicular tissue and the intimate association of treponemes with this material. Wheat germ agglutinin and soybean agglutinin agglutinated freshly harvested trypsinized testicular cells and trypsinized cultured cells derived from normal rabbit testes (NRT). When stained with toluidine blue, both cell preparations were metachromatic. Prior treatment of cultured NRT cells with hyaluronidase slightly decreased their sensitivity to agglutination by wheat germ agglutinin and soybean agglutinin. Lectin agglutination, metachromasia, and hyaluronidase susceptibility indicated that freshly harvested testicular cells and NRT cells have surface-associated acidic mucopolysaccharides that are probably hyaluronic acid and chondroitin sulfate. A rabbit erythrocyte "sandwich" technique was devised to show that hyaluronidase removed wheat germ agglutinin receptors from the cultured NRT cells. Prior incubation of NRT cells with hyaluronidase, followed by the addition of T. pallidum, resulted in a reduction in numbers of treponemes attached to the NRT cells. The attachment of T. pallidum appears to be mediated through the acidic mucopolysaccharides on the surface of NRT cells. The findings are discussed in terms of the importance of host ground substance mucopolysaccharide to the syphilitic infective process.

Animals↗
PubMed1979

Mucopolysaccharidase of Treponema pallidum.

Treponema pallidum (Nichols strain) exhibited mucopolysaccharidase activity. Acidic mucopolysaccharides were broken down more rapidly by viable treponemes than by heat-inactivated treponemes or membrane filtrates of treponemal suspensions. Ouchterlony immunodiffusion demonstrated the occurrence of antibodies to the hyaluronidase-like enzyme within syphilitic sera. After intratesticular inoculation of 2 x 10(7) to 6 x 10(7) treponemes, these anti-mucopolysaccharidase antibodies were detected between 9 and 35 days postinoculation. In addition, acidic mucopolysaccharides were present in the serum of infected animals 9 and 16 days postinoculation. Immune serum that contained antibodies to the mucopolysaccharidase restricted treponemal breakdown of acidic mucopolysaccharides. It has been previously demonstrated that immune rabbit serum contains a factor that blocks attachment of T. pallidum (Nichols strain) to cultured mammalian cells. This factor was effectively absorbed by prior incubation with bovine hyaluronidase. It is postulated that T. pallidum attaches to acidic mucopolysaccharides on the surface of cultured cells through the mucopolysaccharidase enzyme at the surface of the organisms. These findings are discussed in terms of the histopathogenesis of T. pallidum with applications to the healing immune response.

Glycosaminoglycans↗
PubMed1979

Suppression of lymphocyte response to concanavalin A by mucopolysaccharide material from Treponema pallidum-infected rabbits.

The testicular fluid and serum from rabbits infected intratesticularly with Treponema pallidum inhibited the mitogenic response of normal rabbit peripheral blood lymphocytes to concanavalin A. Mucopolysaccharide material present in the testicular fluid and serum was associated with the lymphocyte-inhibitory activity. Degradation of the mucopolysaccharide material with hyaluronidase resulted in the loss of the inhibitory activity of testicular fluid and serum of T. pallidu-infected rabbits.

Animals↗
PubMed1979

Analysis of nonmotile mutants of the dimorphic bacterium Caulobacter crescentus.

A total of 69 spontaneous nonmotile mutants were isolated from the dimorphic bacterium Caulobacter crescentus. The majority of the mutants were unable to assemble a flagellar filament (Fla-), although eight were able to synthesize a short stub of a flagellum. A third mutant class assembled flagella of normal morphology but were nonmotile (Mot-). Genetic analysis by phiCr30-mediated transduction revealed 27 linkage groups for the fla and stub-forming mutations, and three linkage groups for the mot mutations. Intracellular flagellin detected by immunodiffusion was at the limit of detectability in most of the Fla- and stub-forming mutants but normal in the Mot- mutants. The Fla- and stub-forming mutants also showed decreased sensitivity to the swarmer-specific phages phiCbK and phiCb5 and phiCr40. One additional strain was totally resistant to phiCbK, and the mutation in this strain has been designated pleA. Each of the mutants containing mot mutations showed wild-type sensitivity to all of the phages tested.

Bacteria↗
PubMed1979

Flagellar hook and basal complex of Caulobacter crescentus.

Intact bacterial flagella possessing a membrane-free hook and basal complex were purified from Caulobacter crescentus CB15, as well as from mutants which synthesize incomplete flagella. The basal body consisted of five rings mounted on a rod. Two rings were in the hook-proximal upper set, and three rings (two narrow and one wide) were in the lower set. The diameters of the two upper rings differed, being 32 and 21 nm, respectively. The lower rings were all approximately 21 nm in diameter, although they varied significantly in width. During the normal course of the C. crescentus cell cycle, the polar flagellum with hook and rod was shed into the culture medium without the basal rings. Similarly, hooks with attached rods were shed from nonflagellate mutants, and these structures also lacked the basal rings. The hook structure was purified from nonflagellated mutants and found to be composed of a 70,000-molecular-weight protein component.

Bacteria↗
PubMed1979

Endocardial alterations in myocardial infarction.

Transmural infarcts of the ventrolateral wall of canine left ventricle were produced by ligation of the ventral interventricular (anterior descending) branch of the left coronary artery. Endocardium from these infarcted hearts was sampled at sites corresponding to the infarct center and periphery, and to uninfarcted (normal) area at 24 and 48 hours after ligation, and examined by correlative scanning and transmission electron microscopy and by light microscopy. Endocardial samples from sham-ligated hearts were included as a further control. Striking alterations were observed in the endocardium that lined infarcted myocardium. There was endothelial desquamation coextensive with leukocytic invasion. Leukocytes appeared to initiate sloughing by separating the endothelial cells from their basal lamina and partially from one another. The latter cells desquamated in sheets, leaving behind a denuded basal lamina. Although altered in form, the individual endothelial cells seemed to remain largely intact. Denuded subendothelial surfaces only rarely contained thrombi. In areas where the cardiac endothelium was altered, the subjacent subendocardium, myocardium, and usually the remainder of the endocardium also showed leukocytic exudate. Samples from uninfarcted regions showed an intact, leukocyte-free endocardium, as did the sham-ligated controls. The appearance of abnormal endocardium was qualitatively similar wherever found, whether in different areas of the same heart or from one heart to another, and regardless of age of infarct. In 48-hour infarcts, almost all of the central and most of the peripheral samples exhibited the changes described. The data suggested a similar pattern for hearts with 24-hour infarcts. By locating biopsy sites in frozen cardiac sections processed for histologic staining and 201-thallium autoradiography, the electron microscopy results were shown to correlate with the intramural histopathologic topography of the infarcts. The alterations described here represent the endocardial manifestation of the inflammatory stage of transmural infarcts, known to be well developed in 1- and 2-day-old lesions.

Animals↗
PubMed1978

Parent-offspring resemblance for specific cognitive abilities in Korea.

Regressions of offspring on midparent value for tests of specific cognitive abilities in Korea were considerably higher than those for Americans of Japanese ancestry or Americans of European ancestry tested in Hawaii. This greater parent-offspring resemblance in Korea may be due to the particular method of test administration or to an increased genetic variance resulting from assortative mating. The pattern of parent-child correlations for three relatively pure tests of spatial ability and for the spatial factor did not conform to that of a sex-linked recessive character.

Adolescent↗