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Biomedical subjects

R B Johnson

Publications and source records attributed to R B Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1996

Chlamydial cervicitis and urethritis: single dose treatment compared with doxycycline for seven days in community based practises.

STUDY GOAL: To compare the efficacy and safety of single 1 g oral azithromycin with doxycycline, 100 mg twice daily for seven days for treatment of uncomplicated urogenital chlamydial infection. STUDY DESIGN: Randomised, unblinded, comparative trial, involving 597 patients demonstrating clinical evidence of genital chlamydia and a positive non-culture assay for Chlamydia trachomatis. RESULTS: Among the azithromycin- and doxycycline-treated patients 61% and 60%, respectively, were asymptomatic within one week after the first dose. At two weeks, these figures increased to 86% and 83%, respectively. Bacteriological eradication, based on a negative assay, occurred in 338 (97%) of 347 azithromycin-treated patients and 161 (99%) of 163 doxycycline-treated patients. CONCLUSION: Treatment of uncomplicated chlamydial cervicitis and urethritis with single 1 g oral azithromycin is equivalent to standard therapy with doxycycline. Drug-related adverse events were approximately twice as common as previously reported for both drugs.

Adolescent↗
PubMed1996

Azithromycin.

Explore the source record for details and available documents.

Anti-Bacterial Agents↗
PubMed1996

Mercury release during autoclave sterilization of amalgam.

Natural teeth are an invaluable teaching tool for preclinical instruction in operative dentistry and endodontic techniques. Cavity preparation in teeth containing amalgam restorations is a realistic simulation of an often experienced clinical situation. As various pathogens are contained in saliva, teeth must be disinfected before use by students. The purpose of this study is to indirectly evaluate whether mercury vapor is released from amalgam restorations in such teeth during steam autoclave sterilization. Mercury vapor detection, sample mass changes and x-ray fluorescence data were collected from experimental steam autoclave sterilization of amalgam samples sealed in autoclave bags. All of the data showed evidence of mercury vapor generation coincident to steam autoclave sterilization. Mercury vapor levels within the room where amalgam was exposed to steam autoclave sterilization reached levels that constitute an unnecessary health risk to dental personnel. The volume of amalgam tested simulated that contained in 175 amalgam restored teeth. Initial venting of the autoclave chamber produced mercury vapor concentrations significantly in excess of OSHA vapor concentration ceiling levels. Thus, the use of a steam autoclave for sterilization of amalgam containing teeth for use in preclinical laboratory exercises may be harmful to personnel involved.

Air Pollutants, Occupational↗
PubMed1996

Digital x-ray imaging: a diagnostic aid for the clinician and a technological instrument for the researcher.

Digital x-ray imaging is a relatively new technology which may have potential for both the oral health care practitioner and the oral researcher. The ability to acquire low x-ray dose images is extremely important to patient care. Additionally, the ability to manipulate these images provides valuable clinical and research information which can enhance overall patient care.

Dental Research↗
PubMed1995

The effects of smokeless tobacco extract on bone nodule formation and mineralization by chick osteoblasts in vitro.

Short-term exposure to smokeless tobacco extracts (STE) reportedly inhibits osteoblast metabolism. The objective of this study was to determine the effects of serial dilutions of a water-soluble extract of smokeless tobacco on osteoblast proliferation and their potential to form and mineralize bone nodules. STE significantly stimulated cell proliferation when diluted 10(2)-10(4) times; 10(3) and 10(4) dilutions produced the greatest effect. 10(2)-10(4) STE dilutions significantly increased alkaline phosphatase activity at day 7 but 10(6) STE dilutions significantly decreased it. 10(3) and 10(4) dilutions significantly increased bone nodule formation, but inhibited their mineralization. In contrast, 10(5) and 10(6) dilutions significantly decreased bone nodule formation, but increased their mineralization. Stimulation of in vitro bone nodule formation by STE was similar to that produced by 10(-7) M insulin-like growth factor 1 (IGF-1) in vivo. Heat and acid treatment of STE significantly reduced its beneficial effect on cell proliferation, suggesting that a peptide within STE may be responsible for enhancement of osteogenic cell proliferation. Thus, STE may contain a peptide capable of significantly stimulating osteoblast proliferation, differentiation and metabolism, similar to the effects of IGF-1. This peptide could have potential therapeutic benefits.

Analysis of Variance↗
PubMed1995

Effectiveness of ethylene oxide for sterilization of dental handpieces.

Ethylene oxide gas has been utilized as an alternative method for sterilization of dental handpieces, as it is less corrosive than steam. However, its effectiveness for sterilization of the internal components of dental handpieces has not been established. The objective of this study was to compare the effectiveness of ethylene oxide and steam for sterilization of dental handpieces. Unused handpieces and handpieces which had been exposed to clinical dental procedures ('clinical') were contaminated with Streptococcus mutans, exposed to steam or ethylene oxide, and flushed with sterile saline. Washings were plated on mitis-salivarius agar, and colonies identified and counted. No viable colonies could be established from washings from 'clinical' or 'unused' handpieces exposed to steam. However, viable colonies could be established from 'clinical' handpieces exposed to ethylene oxide. This data suggests that a substance entrapped within 'clinical' handpieces (possibly the biofilm) may protect bacteria from ethylene oxide gas, preventing adequate sterilization.

Biofilms↗
PubMed1995

Comparison of azithromycin and ceftriaxone for the treatment of chancroid.

We conducted a randomized, unblinded, prospective study designed to determine the efficacy of single-dose azithromycin for the treatment of chancroid. Men and women 16 years of age and older who had darkfield-negative genital ulcers that were clinically suspected to be caused by Haemophilus ducreyi and who attended urban sexually transmitted disease clinics or presented to hospital emergency departments were enrolled in the study. Patients were randomized to receive 250 mg of ceftriaxone im or 1 g of azithromycin orally, both given as a single dose. They were followed for up to 23 days after treatment. For 65 patients, cultures were positive for H. ducreyi; there were 68 patients whose cultures were negative for both H. ducreyi and herpes simplex virus and who had no evidence of syphilis. All 133 patients returned for at least one follow-up visit. At the time of the last follow-up visit, all 32 patients whose cultures were positive for H. ducreyi and who were treated with azithromycin were clinically cured. In all 33 culture-positive cases in which ceftriaxone was used, there was either clinical improvement or cure at the time of the patient's last follow-up visit. In addition, azithromycin and ceftriaxone were equally effective in healing ulcers for which cultures were negative. We conclude that a single 1-g oral dose of azithromycin is as effective as a 250-mg im dose of ceftriaxone for the treatment of chancroid.

Administration, Oral↗
PubMed1995

Gingival interleukin-6 concentration following phase I therapy.

There is little information available on the effects of periodontal therapy on tissue levels of interleukin-6 (IL-6). This study compares IL-6 concentrations in gingiva and gingival crevicular fluid (GCF) from patients requiring surgical procedures following Phase I periodontal therapy. Sites requiring surgery due to "unresolved" intrabony pockets were compared to sites not requiring surgery ("resolved") in each patient. Resolved sites had minimal histologic evidence of chronic inflammation and IL-6 accumulation; unresolved sites contained a substantial number of chronic inflammatory cells and IL-6 was widely distributed. IL-6 levels in GCF were significantly greater at resolved than at unresolved gingival sites (P < 0.001); however, IL-6 tissue levels were significantly greater at unresolved than in resolved gingival sites (P < 0.01). These results suggest that IL-6 levels were elevated in gingival connective tissue adjacent to intrabony pockets which had not been resolved following Phase I therapy. Thus, intrabony pocket resolution may be affected by accumulation of IL-6 in the adjacent gingival connective tissue, which may result from increased rates of synthesis or reduced rates of release from gingiva into the GCF.

Adult↗
PubMed1994

Pilot study of azithromycin for treatment of primary and secondary syphilis.

Azithromycin has in vitro activity against Treponema pallidum and is effective against experimental syphilis in rabbits. We undertook an open, noncomparative pilot study of oral azithromycin (500 mg once daily for 10 days) to treat 16 patients with primary or secondary syphilis who were seronegative for human immunodeficiency virus. Cure was documented for 11 of 13 patients observed > or = 3 months; three patients were lost to follow-up. The serological response of one patient with secondary syphilis was indeterminate, and one patient with primary syphilis had either relapse or reinfection. Four patients had mild gastrointestinal side effects, and another patient had an episode of nausea and vomiting; all side effects occurred in the first 3 days and resolved spontaneously as treatment continued. Azithromycin shows promise as an alternative agent for treatment of early syphilis; controlled trials and assessment of other dosage regimens are indicated.

Administration, Oral↗
PubMed1994

MDS1, a dosage suppressor of an mck1 mutant, encodes a putative yeast homolog of glycogen synthase kinase 3.

The yeast gene MCK1 encodes a serine/threonine protein kinase that is thought to function in regulating kinetochore activity and entry into meiosis. Disruption of MCK1 confers a cold-sensitive phenotype, a temperature-sensitive phenotype, and sensitivity to the microtubule-destabilizing drug benomyl and leads to loss of chromosomes during growth on benomyl. A dosage suppression selection was used to identify genes that, when present at high copy number, could suppress the cold-sensitive phenotype of mck1::HIS3 mutant cells. Several unique classes of clones were identified, and one of these, designated MDS1, has been characterized in some detail. Nucleotide sequence data reveal that MDS1 encodes a serine/threonine protein kinase that is highly homologous to the shaggy/zw3 kinase in Drosophila melanogaster and its functional homolog, glycogen synthase kinase 3, in rats. The presence of MDS1 in high copy number rescues both the cold-sensitive and the temperature-sensitive phenotypes, but not the benomyl-sensitive phenotype, associated with the disruption of MCK1. Analysis of strains harboring an mds1 null mutation demonstrates that MDS1 is not essential during normal vegetative growth but appears to be required for meiosis. Finally, in vitro experiments indicate that the proteins encoded by both MCK1 and MDS1 possess protein kinase activity with substrate specificity similar to that of mammalian glycogen synthase kinase 3.

Amino Acid Sequence↗
PubMed1994

Public hospitals and managed care.

Managed health care is used increasingly in the public and private sectors to control rising health-care costs and to assure quality of care. While current proposals for health-care reform promote even wider application of managed care as a component in cost control, the formal use of managed care by public hospitals has not been fully explored. This article identifies possible reasons for providing managed care within a public-hospital system, explores the implications of managed care for public hospitals and their patients, and addresses some of the barriers to implementing managed care in a traditional public-hospital setting.

Cost Control↗
PubMed1994

Comparative metabolism of 3H-glucosamine by fibroblast populations exposed to cyclosporine.

Cyclosporine and nifedipine therapy produces gingival overgrowth in many patients. Neither the mechanism underlying this undesirable side effect nor the possibility of synergism between these drugs is known, although many renal transplant patients receive both drugs. This study compared the rates of 3H-glucosamine utilization by three groups of fibroblasts: untreated gingival fibroblasts, fibroblasts from gingival overgrowth tissue of a patient receiving both cyclosporine and nifedipine, and normal gingival fibroblasts exposed to cyclosporine-A in vitro. Significant differences in the rates of deposition of 3H-glucosamine into the extracellular matrix by each group of gingival fibroblasts were demonstrated, suggesting that increased rates of deposition of proteoglycans into the gingival extracellular matrix by fibroblasts should be further investigated as a biologic mechanism for gingival overgrowth.

Adult↗
PubMed1993

In vitro changes in platelet function and metabolism following increasing doses of ultraviolet-B irradiation.

Ultraviolet-B (UV-B) irradiation of platelet concentrates (PCs) may prevent the development of posttransfusion HLA alloimmunization. This study evaluated the effect of increasing doses of UV-B radiation on stored PCs. Pooled PCs were irradiated at UV-B doses of 600, 2400 or 10,000 mJ per cm2 and stored up to 96 hours under standard blood bank conditions. Compared to nonirradiated room-temperature and 37 degrees C controls, the irradiated units showed no significant changes in platelet count, white cell count, discharge of lactate dehydrogenase, release of beta-thromboglobulin, metabolism of ATP, ADP, ammonia, glutamine, glutamate, hypoxanthine, pCO2, or pO2 at any time of storage following any of the three UV-B doses. However, after a dose of 10,000 mJ per cm2, there were significant decreases in in vitro assays of platelet function-specifically, osmotic recovery and morphology score. Some metabolic systems were also affected by the 10,000 mJ per cm2 radiation dose, as shown by a decline in pH and bicarbonate and an increase in glucose consumption and lactate production (p < 0.05). The changes in these latter assays appeared only after 96 hours of postirradiation storage. Such changes were not seen in either the room-temperature or 37 degrees C control groups. Thus, heat generated during irradiation, per se, did not appear responsible for the observed in vitro changes in platelet function and metabolism. On the basis of the assays analyzed, it is concluded that UV-B irradiation of PCs at doses up to 10,000 mJ per cm2 does not induce significant metabolic or functional derangements following short-term storage (24-48 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1993

Selection of dose regimens of azithromycin .

The unique pharmacokinetics of azithromycin are characterized by high, sustained tissue concentrations. The concentrations of azithromycin were predicted, following various multiple dose regimens, from concentrations in tonsillar, prostatic, and uterine tissues following single oral doses. Following a five-day treatment regimen (500 mg on day 1, followed by 250 mg on days 2-5), or a three-day regimen (500 mg daily for three days), concentrations of azithromycin in tonsillar tissue, representative of respiratory tract tissues, will continuously be greater than the MICs for key target pathogens (Streptococcus pyogenes, Haemophilus influenzae, Staphylococcus aureus) in infections of the respiratory tract for up to 10 days. Since tissue concentrations above the MICs for infecting organisms were correlated with efficacy in animal models of infection, short treatment regimens consisting of once-daily oral administration of azithromycin should be effective in the treatment of a variety of infections. A single 1 g oral dose will provide concentrations in the uterus and prostate, representing urogenital tissues, above the MIC for Chlamydia trachomatis for approximately 10 days. Thus, this regimen should be effective in the treatment of chlamydial infections of the genital tract.

Administration, Oral↗
PubMed1993

Health care reform: what it might mean to urban public hospitals.

Health care reform proposals may affect public hospitals in a number of ways. To insure that such proposals benefit the underserved communities within which public hospitals operate, reform initiatives should be evaluated against 10 criteria that emphasize prevention and primary care, community health education, cost control, tort reform, and community values.

Cost-Benefit Analysis↗