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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 343 records · Page 19Linked to original sources
PubMed1982

Control of Tn5 transposition in Escherichia coli is mediated by protein from the right repeat.

The right repeat in Tn5, which encodes protein absolutely required for transposition, is also capable of inhibiting Tn5 transposition. Analysis of Tn5 mutants indicates that the left repeat is defective in supplying the transposition-inhibition function because of the sequence difference between the repeats located at nucleotide 1443; that the transposition-inhibition activity is a function of the quantity of right-repeat protein synthesis; that the smaller of the right-repeat proteins, protein 2, is sufficient for supplying the transposition-inhibition function (but not for the transposase activity); and that the transposition-inhibition function can act in trans, as opposed to the transposase activity, which functions efficiently only in cis. Gene fusion experiments indicate that the transposition-inhibition activity cannot be explained by autogenous regulation of right-repeat protein synthesis. Finally, immunoprecipitation assays of right-repeat protein-lacZ fusion proteins indicate that protein 2 is synthesized in significantly greater amounts than protein 1 in whole cells. This synthetic ratio may ber important with respect to the control of Tn5 transposition.

Bacterial Proteins↗
PubMed1982

Opsonic requirements for phagocytosis of Borrelia hermsii by human polymorphonuclear leukocytes.

Opsonic requirements for phagocytosis by human polymorphonuclear leukocytes (PMNLs) of a laboratory strain of Borrelia hermsii were examined. Intracellular localization of spirochetes was confirmed by electron microscopy and cinephotomicroscopy. Phagocytosis of 3H-labeled spirochetes was increased with higher concentrations of pooled human serum or greater ratios of spirochetes to PMNLs and was unaffected by diminished classical complement pathway activity. Immune rabbit serum markedly increased phagocytosis of spirochetes beyond levels observed with preimmune rabbit serum. Immune rabbit serum also demonstrated direct activity against B. hermsii, which decreased the motility and viability and increased agglutination of the spirochetes independently of complement. Both the direct activity against B. hermsii and the opsonic activity of immune rabbit serum were eliminated by immunoabsorption of immunoglobulins. These observations suggest a role for the alternative complement pathway and for immunoglobulins in the opsonization of spirochetes for phagocytosis by PMNLs. Immunoglobulins may also play a role in the direct clearance of spirochetes.

Animals↗
PubMed1982

Comparison of the activities of ceftriaxone and penicillin G against experimentally induced syphilis in rabbits.

The activity of ceftriaxone, a newly developed cephalosporin, against early cutaneous infections with Treponema pallidum in rabbits was compared with that of equimolar doses of penicillin G. Activity was related to the time required for cutaneous lesions to become dark-field negative, serological response, and the disappearance of T. pallidum from the popliteal lymph nodes. Both antibiotics were very effective in the treatment of syphilis in this animal model. The 50% curative dose for penicillin G was 0.8 mumol/kg (0.29 mg or 480 U/kg) and for ceftriaxone, it was 1.45 mumol/kg (0.96 mg/kg). Overall, ceftriaxone was slightly less effective than penicillin G was. Transmission and scanning electron microscopy studies of testicular aspirates obtained from rabbits treated with ceftriaxone revealed alterations in the treponeme surface which apparently resulted in changes in cell permeability and morphology.

Animals↗
PubMed1982

Leptospiral vaccines in dogs: immunogenicity of whole cell and outer envelope vaccines prepared in protein-free medium.

The immunogenicity of leptospires cultivated in modified bovine albumin-polysorbate 80 medium and those cultivated in protein-free medium were quantitatively evaluated in the dog. Vaccine preparations, whole cell or outer envelope, prevented leptospiremia; however, kidney culture data revealed that 1 of 4 dogs vaccinated with 0.1 to 1 mg of whole cell prepared from leptospires cultivated in the modified bovine albumin-polysorbate 80 medium was positive for Leptospira, whereas dogs vaccinated with whole cells prepared in protein-free medium were not. Dogs vaccinated with greater than or equal to 0.5 mg of outer envelope were refractory to infection after challenge exposure.

Animals↗
PubMed1982

Immunogenicity and humoral and cell-mediated immune responses to leptospiral whole cell, outer envelope, and protoplasmic cylinder vaccines in hamsters and dogs.

The immunogenicity of 2 leptospiral cell structural components, the outer envelope (OE) and protoplasmic cylinder (PC), as well as the leptospire whole cell (WC), was compared in hamsters and dogs. The 50% protective dose for hamsters against death (PD50D) and kidney infection (PD50k) was evaluated for Leptospira interrogans serovars canicola, icterohaemorrhagiae, pomona, and grippotyphosa. All 3 immunogens had similar PD50D values. However, the PD50K values for OE and WC vaccines ranged from 0.05 to 0.80 micrograms (dry weight), whereas the PC vaccines ranged from 7.0 to 14.0 micrograms. Cellular and humoral responses of dogs to serovar canicola WC, OE, and PC vaccines were monitored for 21 weeks. Little difference was observed among the canine humoral responses to the different preparations. Protoplasmic cylinder vaccines sensitized the greater population of lymphoid cells followed by OE and WC. Cross-reactivity was greater in the blastogenic response of lymphoid cell populations than in the humoral response.

Animals↗
PubMed1981

Localization of the Tn5 transposase promoter using the cycling reaction of RNA polymerase.

RNA polymerase is known to undergo a cycling process during initiation of transcription in vitro in which large amounts of small oligonucleotides are released. We have used this cycling reaction to determine the 5' end of the RNA synthesized from the outer ends of the Tn5 inverted repeats. By analyzing the size of the radiolabeled oligonucleotides synthesized using different labeled nucleoside triphosphates and in reactions deficient for a particular nucleoside triphosphate, the partial 5' sequence was obtained. This sequence was correlated with the DNA sequence of the region and an unambiguous origin for the mRNA was determined. The start site for the RNA, which is located at 97 base pairs from the outer ends of the inverted repeats, was confirmed by digesting gamma-32 P-ATP labeled full length (run off) transcripts with ribonuclease T1. The resulting gamma-labeled T1 generated oligonucleotide corresponded to the predicted size determined using the cycling reaction. With the knowledge of the RNA start site, the probable translation start sites for the protein(s) known to be required for Tn5 transposition can be predicted. Possible implications of the DNA sequence with respect to the regulation of the transposase are also discussed.

Base Sequence↗
PubMed1981

Personality attributes of males and females marrying within vs. across racial/ethnic groups.

As part of a larger study, Adjective Check List scores were obtained from 543 couples in Hawaii who had married within their own ethnic group and 83 who had not. Females who married across ethnic groups generally scored higher in one domain of personality (dominance) than did females who married within their own ethnic group. Males who married cross-ethnically also differed in dominance from those who did not, but in different directions in different ethnic groups. In the group that had the highest status (Caucasian) in the decades in which these subjects married, they were less dominant; in the other groups, to varying degrees, they were more dominant. In general, males and females in cross-ethnic matings were more similar in personality test scores than males and females who married within their own ethnic groups. Spouse correlations were generally positive but trivial in magnitude, with very little difference in personality between homogamous and heterogamous couples. The average difference in personality between those who married within and outside their own ethnic group was associated with the rarity of outmarriage for the sex and ethnic group concerned.

Cross-Cultural Comparison↗
PubMed1981

A family study of lactose tolerance.

Survey data from 38 families consisting of both parents and at least one biological offspring provided no support for the belief that lactose tolerance resulted from having at least one dominant gene on an autosomal gene pair and did not support the belief that Caucasians are more frequently tolerant of lactose than are persons of Oriental or of mixed Caucasian-Oriental ancestry.

Adult↗
PubMed1981

Endoscopic evaluation of 125 cases of upper gastrointestinal bleeding.

The fiberoptic panendoscope has been shown to be superior to the UGI series in diagnosing the site(s) of upper gastrointestinal bleeding (UGIB). Recent data has shown that gastritis has replaced peptic ulcer disease (PUD) as the leading cause of UGIB since the diagnosis can now be made with the endoscope. Our clinical experience differs from this. One hundred twenty five cases of UGIB from December 1975 to December 1978 were reviewed. The patients ranged in age from 11 to 91 years. There were 83 males and 42 females included in the study. Twenty-four per cent of the patients were actively bleeding at the time of endoscopic examination, and 62% received two or more units of blood. Endoscopic examination was technically successful in all patients, and there were no deaths or complications. One hundred twenty three lesions were found in 117 patients for a diagnostic accuracy of 93.9%. In eight patients, no bleeding site was found, resulting in a failure rate of 6.1%. PUD accounted for 74.9% of the bleeding sites, while gastritis accounted for only 0.8%. Mallory-Weiss tears of the esophagus accounted for 9.8% and esophageal varices for 4.9%. Thirty-five per cent of the patients had associated lesions, with gastritis and esophagitis being the most common. Eighteen patients (14.4%) required surgical intervention. Seventeen patients had PUD. There was one death, for a mortality rate of 5.5%. The medical mortality rate was 0.9%. The benefits of endoscopy in UGIB are still controversial. An important subgroup of patients with the "visible vessel" in the ulcer bed has been identified recently by others. If not bleeding at the time of endoscopy, 70% will rebleed. It is our opinion that it is important to identify this patient, as well as to know if one is treating gastritis, PUD, or varices. Finally, electrocoagulation of bleeding points, as well as the development of the laser and application of adhesives or clotting agents through the endoscope, will change the management of UGIB.

Adolescent↗