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Biomedical subjects

R B Johnson

Publications and source records attributed to R B Johnson.

214 records · Page 12Linked to original sources
PubMedDate not supplied

Effects of doxorubicin on human dental pulp cells in vitro.

There is substantial information concerning the effects of continuous exposure to supratherapeutic or therapeutic concentrations of doxorubicin on human molar pulpal cells; the effects of continuous exposure to subtherapeutic concentrations of this agent are undetermined. To this end, we studied the proliferation of human fibroblasts and pulpal cells and their pattern of mineralized nodule deposition in vitro. Cell proliferation was assessed at 1, 3, 5, and 7 days from populations with either no exposure (control) or exposure to 10(-6)-10(-9) mol/L doxorubicin. Mineralized nodule deposition and calcium-45 incorporation were assessed at 7 and 21 days of culture. Data were compared by factorial ANOVA and a post-hoc Tukey test. 10(-6) and 10(-7) mol/L doxorubicin significantly reduced the total number of viable pulpal cells in cultures from days 1 to 3 (p < 0.05); doxorubicin 10(-6)-10(-9) mol/L significantly inhibited cell proliferation (p < 0.05) and DNA synthesis 5 days after plating (p < 0.001). After 21 days, doxorubicin 10(-6)-10(-8) mol/L significantly decreased calcium-45 incorporation into pulpal cultures (p < 0.001); all dilutions significantly reduced the number of mineralized nodules within the 21-day pulpal cultures (p < 0.05). In addition, all dilutions of doxorubicin significantly inhibited fibroblast cell proliferation and incorporation of [(3)H]thymidine. In contrast, the fibroblast cultures did not produce mineralized nodules, suggesting that the mineralized nodules within the pulpal cell cultures did not result from dystrophic calcification. Thus, exposure to subtheraputic doxorubicin concentrations has potential adverse effects on mineralized tissue formation within the pulp, which could affect the rates of reparative dentin deposition within the tooth pulps of patients receiving this chemotherapeutic agent.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

Recovery from disuse osteopenia coincident to restoration of muscle strength in mdx mice.

The objective of this study was to compare the tibial structure and the strength of the tibia during muscle weakness and after recovery in mdx mice (which demonstrate X-linked muscular dystrophy and subsequent muscle regeneration) and age-matched control mice. The extent of disuse atrophy produced by muscle weakness and recovery following restoration of normal muscle strength could then be determined. The tibiae adjacent to weakened tibialis anterior muscles of 4-week-old mdx mice had significantly reduced radiographic density (p < 0.05) and cortical thickness (p < 0.001), and increased porosity (p < 0.001) compared to age-matched controls, suggesting development of disuse osteopenia. Significantly less force was required to break mdx tibiae than age-matched control tibiae (p < 0.05). In addition, Sharpey's fiber density was reduced (p < 0.001), suggesting a weakened attachment of the tibialis anterior muscle to bone. At 12 weeks, during the period of muscle regeneration, mdx tibial cortical thickness (p < 0.001) and porosity (p < 0.01) remained significantly lower, but percent calcium and Sharpey's fiber and radiographic densities were significantly greater (p < 0.001) than in age-matched controls, suggesting that bone mineralization and muscle attachment strength had increased to above normal levels in parallel with recovery of strength by the attached muscle. By 18 weeks, mdx tibial cross-sectional area, cortical thickness, and porosity remained significantly less (p < 0.001) than normal. Although Sharpey's fiber density was greater than in age-matched controls (p < 0.001) by 18 weeks, mdx tibial percent calcium (p < 0.005) and Sharpey's fiber density (p < 0.001) were significantly reduced from levels in 12-week-old mdx animals. There was significantly less deformation of the tibia prior to fracture in mdx than control tibiae at 18 weeks of age, suggesting tibial brittleness. Thus, at the site of attachment of mdx muscle to osteopenic bone, the remodelling which accompanies recovery of muscle strength is atypical, and produces an attachment of greater strength than function appears to require. These observations suggest that data are needed regarding bone mass and muscle-bone attachments in humans with disuse osteopenia, DMD, and other neuromuscular diseases.

Animals↗
PubMedDate not supplied

Single dose azithromycin treatment of gonorrhea and infections caused by C. trachomatis and U. urealyticum in men.

BACKGROUND AND OBJECTIVES: Single dose regimens have advantages in the treatment of STD. Azithromycin has unique pharmacokinetics that may make single dose regimens feasible. Treatment with a single 1 g dose of azithromycin was compared to 100 mg doxycycline twice daily for seven days. STUDY DESIGN: This was a randomized third-party blinded study on 183 male patients, 176 of whom could be evaluated for efficacy. RESULTS: Chlamydia trachomatis was cultured from 148 patients, 79 receiving azithromycin and 69 receiving doxycycline. Six patients receiving azithromycin had positive cultures on follow-up, four were known to have had sexual intercourse with infected partners. Fifty-one patients had gonorrhea; 28 were treated with azithromycin and 23 with doxycycline. Neisseria gonorrhoeae was eradicated from all patients except one receiving azithromycin. He denied sexual exposure during follow-up. Sixty patients were infected with Ureaplasma urealyticum, 35 were treated with azithromycin and 25 with doxycycline. Five patients in each group had positive cultures on follow up. Three patients receiving azithromycin and two receiving doxycycline were known to have had sexual exposure during follow-up. CONCLUSION: A single dose of azithromycin showed similar effectiveness as a 7-day regimen of doxycycline.

Adolescent↗
PubMedDate not supplied

Polymeric IgA antibody to gliadin in the serum of patients with coeliac disease.

Secretory component (SC) binding assays which detect polymeric IgA (pIgA) in serum were used to measure serum antigliadin pIgA and total pIgA in patients with coeliac disease. Total IgA antigliadin antibody in serum and intestinal fluid was measured by enzyme linked immunosorbent assay (ELISA). The relationship of pIgA antibody to dietary gluten and the antigliadin IgA antibody in intestinal fluid was examined. Twenty-nine serum samples were assayed, twelve from patients ingesting gluten and seventeen from patients who had excluded gluten from their diet for 6 months. Eight of these were paired samples from 4 adults on and off gluten. In addition, paired samples of both intestinal fluid and serum were obtained from 7 children on and off gluten. Polymeric IgA antibody to gliadin was detected in 11 of 12 subjects on gluten but in only 3 of 17 who had excluded gluten. Three of the four adults from whom paired serum samples were obtained had pIgA antigliadin, but only while on gluten. Three of the seven children in whom intestinal and serum antibody were assayed had pIgA to gliadin, which could not be detected after exclusion of gluten, although their intestinal antibody level remained elevated. There was no change in total pIgA levels with diet although the levels were higher than those seen in normal subjects. We conclude that pIgA antibody to gliadin is frequently found in the serum of coeliac patients ingesting gluten. It disappears with gluten elimination at a time when the IgA antigliadin antibody in intestinal fluid has not altered.

Celiac Disease↗
PubMedDate not supplied

The neutralizing characteristics of strains of infectious bronchitis virus as measured by the constant-virus variable-serum method in chicken tracheal cultures.

The constant-virus variable-serum neutralization test in chicken tracheal organ cultures was employed in cross-neutralization tests with the following infectious bronchitis viruses: Massachusetts 41, Connecticut, Iowa 97, Iowa 609, Holte, JMK, Clark 333, SE 17, Florida, and Arkansas 99. These viruses all proved serologically distinct by this method. Chickens immunized with the Connecticut strain and later challenged with Arkansas 99 were not protected against it.

Animals↗
PubMedDate not supplied

New strains of infectious bronchitis virus isolated in Maine.

Twelve IBV isolants from diseased chickens in Maine were studied by serum-neutralization tests in chicken tracheal culture. Six isolants were neutralized by Mass-type antisera. The serum-neutralizing characteristics of six other isolants from vaccine breaks differed from any of the standard IBV viruses and appear to comprise three new strains, Maine 209, 212,and 246. The data provide additional evidence that strains of IBV responsible for disease probably vary from region to region and that the strains present must be known for a regional vaccination program to be effective.

Animals↗
PubMedDate not supplied

Strains of infectious bronchitis virus on the Delmarva peninsula and in Arkansas.

The constant-virus variable-serum neutralization test in chicken tracheal cultures was used to serotype infectious bronchitis virus (IBV) isolants from the Delmarva peninsula and Arkansas. Of 106 isolants obtained from Delmarva in 1971-1974, 93 were found to be the JMK strain, 5 Massachusetts (Mass), 5 Connecticut (Conn), 2 a new strain designated Maryland (Md) 27, and 1 a new strain designated Md 31. Of 26 isolants obtained from Arkansas between October, 1971, and February, 1973, 17 were Arkansas (Ark) 99, 4 Mass, 1 Conn, and 1 an additional new strain, designated Ark 155. Antisera produced against 2 more isolants each neutralized both Ark 99 and Mass viruses. Antiserum against another isolant neutralized both Ark 155 and Conn viruses. The neutralizing characteristics of the new strains are described.

Animals↗
PubMedDate not supplied

An indirect enzyme-linked immunosorbent assay (ELISA) for measuring antibodies in chickens infected with infectious bursal disease virus.

An immuno-enzyme assay for measuring infectious bursal disease antibodies in chickens is described. The test is performed rapidly after coating plates overnight with partially purified antigen prepared in cell culture. Coated plates can be stored for at last 4 months. The chromatographically purified rabbit anti-chicken immunoglobulin-G, conjugated to horseradish peroxidase, was used optimally at a dilution of 1:3,000. It could be stored for at least 10 months without a reduction in titer. The test is safe, highly reproducible, specific, and sensitive. Results can be read visually or by spectrophotometry. Antibodies could be detected as early as 4 days postinfection. Serum titers rose rapidly to high levels, ranging from 1:1,600 to 1:25,600 by one week postinfection. High titers persisted for up to one year. The results of this assay compare favorably with results obtained with the agar-gel precipitin and virus-neutralization tests.

Animals↗