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Biomedical subjects

J Johnson

Publications and source records attributed to J Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1998

A rapid method for detecting the predominant Ashkenazi Jewish mutation in the Bloom's syndrome gene.

Bloom's syndrome (BS) is a rare, autosomal recessive disease characterized by sun sensitivity, short stature, and predisposition to cancer. Although rare in the general population, BS is more common in the Ashkenazi Jewish population (German, 1993). The isolation of the gene for BS, known as BLM, has permitted the identification of mutations within the gene and the discovery that most BS individuals of Ashkenazi Jewish origin carry the identical 6-bp deletioin/7-bp insertion at position 2,281 of BLM (blmAsh). We have developed a rapid method for detecting blmAsh based on restriction enzyme digestion of a PCR product containing the mutation. blmAsh creates a restriction site within the amplified fragment allowing distinction of normal and mutant DNAs. This method has been designed for use with genomic DNA or cDNA.

Adenosine Triphosphatases↗
PubMed1998

Susceptibility of European respiratory tract isolates to trovafloxacin, ciprofloxacin, clarithromycin, azithromycin and ampicillin.

As part of the Artemis project, 11500 isolates (3000 from patients with respiratory tract infections) were collected throughout six European countries between 1994 and 1996. Twenty-seven hospitals or laboratories participated in this first phase of the study. The activities of three classes of antimicrobial agents (fluoroquinolones, beta-lactam agents, macrolides) are presented for the six most frequently isolated pathogens (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, Klebsiella pneumoniae). Overall, trovafloxacin and ciprofloxacin activities were similar for Haemophilus influenzae, Moraxella catarrhalis and Klebsiella pneumoniae isolates. Of the Streptococcus pneumoniae isolates, 6% were resistant to penicillin. Trovafloxacin had the highest activity against the Streptococcus pneumoniae isolates, with a minimum inhibitory concentration of 0.25 mg/l for 90% of isolates (MIC90); all strains tested were susceptible to trovafloxacin. The MIC90 of ciprofloxacin for Streptococcus pneumoniae was 3 mg/l, and overall 52% of the strains were susceptible; 9% were resistant. Azithromycin and clarithromycin exhibited similar activity against all collected pathogens, except Haemophilus influenzae. All strains of Haemophilus influenzae were susceptible to azithromycin compared with 79% for clarithromycin, with respective MIC90s of 2 and 16 mg/l. The data presented demonstrate differences in the susceptibility patterns of six major respiratory tract pathogens in Europe.

Ampicillin↗
PubMed1998

Differentiation of oral Actinomyces species by 16S ribosomal DNA polymerase chain reaction-restriction fragment length polymorphism.

16S rDNA polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to generate restriction profiles of the reference strains, including the American Type Culture Collection type strains, of oral Actinomyces spp., i.e., A. israelii, A. gerencseriae, A. naeslundii genospecies 1 and 2, A. odontolyticus, A. meyeri and A. georgiae, and 23 Actinomyces strains isolated from human dental plaque. The 16S rRNA gene sequences from isolated genomic DNA samples were amplified by PCR. The PCR products were purified and characterized by single digestion with four restriction endonucleases, i.e., MnlI, HaeIII, CfoI, or HpaII. Among them, MnlI was found to discriminate the respective reference strains. The clinical isolates were assigned to one of the species, i.e., A. gerencseriae, A. naeslundii genospecies 1 and 2 and A. odontolyticus, on the basis of their restriction profiles by single digestion with MnlI. Thus, 16S rDNA PCR-RFLP, using MnlI, is a rapid and reliable method for the differentiation of oral Actinomyces spp.

Actinomyces↗
PubMed1998

Production and characterisation of monoclonal antibodies to phytoene synthase of Lycopersicon esculentum.

Monoclonal antibodies have been prepared against the tomato (Lycopersicon esculentum Mill.) fruit ripening-enhanced phytoene synthase (PSY1). The antigen was prepared as a beta-galactosidase fusion protein by cloning a 1.13 kb fragment of Psy1 cDNA into pUR291, followed by transformation of E. coli. The fusion protein, induced by IPTG, was purified by preparative SDS-PAGE and used to elicit an immune response. The cell lines were screened for cross-reactivity against beta-galactosidase-phytoene synthase fusion protein in E. coli extracts using western blotting and ELISA detection procedures. Positive clones were further screened for their ability to cross-react with the mature phytoene synthase protein on western blots as well as their ability to inhibit enzyme activity. Eleven monoclonal lines were obtained. Nine of these, all of the IgM isotype, exhibited strong responses to phytoene synthase of ripe tomato fruit on western blots, but did not inhibit enzyme activity effectively. The other two lines (IgG/la 2 isotypes) inhibited phytoene synthase activity in ripe tomato stroma, but produced a poor response to the protein on western blots. The monoclonals identified a ripe fruit phytoene synthase of 38 kDa, exclusively located in the chromoplast. In contrast, antibodies were unable to detect microbial phytoene synthases, nor phytoene synthase of maize leaf, tomato chloroplast or mango fruit extracts, either on western blots or from inhibition of phytoene synthase activity. However, they did cross-react with a 44 kDa protein from carrot leaf stroma and with three different proteins (44, 41, and 37 kDa) in carrot root. Cross-reactivity was also found with a 37 kDa protein from pumpkin fruit stroma.

Alkyl and Aryl Transferases↗
PubMed1998

Comparison of three composite compliance indices in a trial of self-administered preventive therapy for tuberculosis in HIV-infected Ugandan adults. Uganda-Case Western Reserve University Research Collaboration.

Compliance with tuberculosis preventive therapy in a randomized placebo-controlled trial in 2736 HIV-infected Ugandans was measured using urinary isoniazid metabolite testing, clinic attendance, and self-report. Overall, 77% of urine tests were positive, subjects kept 85% of their scheduled visits while on therapy, and 69% reportedly never forgot to take their medication. Different strategies were used for constructing three composite compliance indices in active arms: (1) an unweighted index of the summed scores on scaled compliance measures; (2) a weighted index using weights obtained from a survey of experts on tuberculosis; and (3) a statistically weighted index using principal components analysis. Composite indices were evaluated for reliability, validity, and practical utility. Understanding of the regimen, study arm, subsequent follow-up, tuberculosis status, and urine spot-check result were associated with composite compliance scores. The unweighted index in this study performed as well as the weighted indices.

AIDS-Related Opportunistic Infections↗
PubMed1998

Influence of image processing on chest radiograph interpretation and decision changes.

RATIONALE AND OBJECTIVES: The authors investigate the effect of image processing on diagnostic performance in the reading of computed chest radiographs. MATERIALS AND METHODS: Six radiologists read 168 chest images with and without the use of image processing. Diagnostic performance was measured by means of receiver operating characteristic analysis, and changes made in diagnostic decisions with the use of image processing were evaluated. RESULTS: There were no statistically significant differences between reader performance with image processing and reader performance without image processing (P < .05). Readers' decisions were just as likely to change from false-negative to true-positive as from true-positive to false-negative with the use of image processing. More decisions changed from true-negative to false-positive than from false-positive to true-negative with processing, CONCLUSION: The effect of image processing does not greatly influence diagnostic performance in chest radiography.

Attitude of Health Personnel↗
PubMed1998

Effects of ischemic tolerance on mRNA levels of IP3R1, beta-actin, and neuron-specific enolase in hippocampal CA1 area of the gerbil brain.

Global cerebral ischemia induced to Mongolian gerbils by ligation of common carotid arteries (CCAs) is known to result in injury to the hippocampal CA1 region. In this study, we examined whether neuronal injury can be depicted by measuring levels of mRNA encoding inositol 1,4,5-trisphosphate receptor type 1 (IP3R1), neuron specific enolase (NSE) and beta-actin and whether these measurements can be use to assess ischemic tolerance. Gerbils were subjected either to cerebral ischemia induced by ligation of both CCAs for 5 min, or to an ischemic tolerance paradigm in which a 2 min ischemic preconditioning was performed 24 hr prior to the 5 min ischemia. At 48 hr after the 5 min ischemic insult, significant decreases in mRNA levels for IP3R1 (26%), NSE (38%) and beta-actin (50%) could be observed in the hippocampal CA1 region. Although levels of mRNA in the preconditioning group were decreased as compared to the sham control, the levels were significantly higher than those in the ischemic group. These results indicate the feasibility of using mRNA measurement as a parameter to assess cerebral ischemic damage. In addition, based on the differences in the decline in mRNA levels between the ischemia group and the preconditioned ischemia group, it can be concluded that this ischemic tolerance paradigm could offer partial protection (around 45%) against the injury due to the 5 min cerebral ischemic insult.

Actins↗
PubMed1998

Guidelines for anal cytology--to make cytological diagnosis and follow up much more reliable.

Anal intraepithelial neoplasia is a difficult diagnostic and management problem, particularly when it occurs in women with synchronous or metachronous genital intraepithelial neoplasia. Diagnosis and follow up by colposcopy is too specialized for widespread use, and although anal cytology has been used before it has been thought of as too inconsistent for practical application. This study standardized collection of specimens and investigated interobserver variation. The aim of the study was to determine whether observers could reliably distinguish high grade anal intraepithelial neoplasia from other conditions. Standardized collection of anal preparations was achieved in the host centre. A meeting of experienced cytopathologists was convened to agree guidelines for anal cytology. These guidelines were sent to the panel of six observers who were subsequently circulated with 30 cytopathological preparations in random order and asked to report them all. The results were collected and processed centrally. Four individuals were in complete agreement about those preparations which were inadequate for reporting, but two others had a lower threshold for rejecting preparations as inadequate. There was agreement between the observers in over 95% of cases in distinguishing high grade intraepithelial neoplasia from other cytological conditions. Kappa values range from 0.66 to 1.00. This study demonstrates that the provision of guidelines for the interpretation of anal cytopathological preparations can result in a high degree of interobserver agreement about the clinically important distinction between high grade anal intraepithelial neoplasia and other conditions. Anal cytology is a more useful technique for diagnosis and follow up of 'at risk' individuals than has previously been suggested, and should be utilized more widely in this group of patients.

Anal Canal↗
PubMed1998

Nurses' perceptions of gross self-neglect amongst older people living in the community.

Self-neglect in older people has an established medical literature but receives surprisingly little attention in the nursing literature. Hospital and community nurses were interviewed using a semistructured questionnaire. All the nurses were able to identify patients who had shown features of 'gross self-neglect'. Poor nutrition was a prominent feature: links with the literature are explored.

Aged↗
PubMed1998

Protected-site phosphorylation of protein kinase C in hippocampal long-term potentiation.

One important aspect of synaptic plasticity is that transient stimulation of neuronal cell surface receptors can lead to long-lasting biochemical and physiological effects in neurons. In long-term potentiation (LTP), generation of autonomously active protein kinase C (PKC) is one biochemical effect persisting beyond the NMDA receptor activation that triggers plasticity. We previously observed that the expression of early LTP is associated with a phosphatase-reversible alteration in PKC immunoreactivity, suggesting that autophosphorylation of PKC might be elevated in LTP. In the present studies we tested the hypothesis that PKC phosphorylation is persistently increased in the early maintenance of LTP. We generated an antiserum that selectively recognizes the alpha and betaII isoforms of PKC autophosphorylated in the C-terminal domain. Using western blotting with this antiserum we observed an NMDA receptor-mediated increase in phosphorylation of PKC 1 h after LTP was induced. How is the increased phosphorylation maintained in the cell in the face of ongoing phosphatase activity? We observed that dephosphorylation of PKC in vitro requires the presence of cofactors normally serving to activate PKC, i.e., Ca2+, phosphatidylserine, and diacylglycerol. Based on these observations and computer modeling of the three-dimensional structure of the PKC catalytic core, we propose a "protected site" model of PKC autophosphorylation, whereby the conformation of PKC regulates accessibility of the phosphates to phosphatase. Although we have proposed the protected site model based on our studies of PKC phosphorylation in LTP, phosphorylation of protected sites might be a general biochemical mechanism for the generation of stable, long-lasting physiologic changes.

Amino Acid Sequence↗
PubMed1998

A placebo-controlled trial of ranitidine in patients with early human immunodeficiency virus infection.

Previous uncontrolled reports have suggested that H2-antagonists may possess immunomodulatory activity in human immunodeficiency virus (HIV)-infected patients. Such trials reported improvements in HIV-related symptoms, increased absolute CD4 cell numbers, and improvements in other measures of host immunity. The present trial was a randomized, placebo-controlled, double-blind trial of ranitidine 300 mg (orally twice daily) in subjects with early HIV infection (absolute CD4 cells, 400-700/mm3). Eighty-one subjects entered the trial and 73 completed 16 weeks on study medications. There were no significant differences in the time-weighted average change from baseline between the 2 treatment groups in absolute CD4 cell number, plasma HIV RNA level, or most other surrogate markers of HIV infection. Serum beta2-microglobulin levels were significantly lower in placebo than ranitidine recipients. Ranitidine should not be recommended for the treatment of HIV-infected patients unless it is used for established indications.

Adult↗
PubMed1998

Phase III trial of modulation of cisplatin/fluorouracil chemotherapy by interferon alfa-2b in patients with recurrent or metastatic head and neck cancer. Head and Neck Interferon Cooperative Study Group.

PURPOSE: In preclinical experiments, interferon alfa modulates the anticancer activity of fluorouracil (5-FU) and cisplatin (CDDP). To test this effect clinically in patients with recurrent or metastatic head and neck cancer (RMHNC), a multicenter randomized controlled trial with CDDP and 5-FU with or without interferon alfa-2b (IFNalpha) was performed. PATIENTS AND METHODS: Eligible patients had histologically confirmed RMHNC; a good performance status; measurable disease; adequate bone marrow, hepatic, and renal function; no prior chemotherapy for recurrent or metastatic disease; only one chemotherapy regimen administered with previous local therapy; and a treatment-free interval of at least 3 months following previous local therapy. Patients were randomized and stratified according to treatment center, and prior radiotherapy and chemotherapy. The treatment regimen consisted of CDDP 100 mg/m2 on day 1 and 5-FU 1,000 mg/m2/d by continuous infusion for 96 hours (days 1 to 4), without (arm A) or with (arm B) IFNg alpha 3 x 10(6) U/d subcutaneously on days 1 to 5. Cycles were repeated every 21 days. RESULTS: One hundred twenty-two patients were entered on each arm. The response rate (RR) was similar in both arms (arm A: complete response [CR] 10.7%, partial response [PR] 36.4%; arm B: CR 6.8%, PR 31.6%) (.70 < P < .50). There was no difference in median survival between the two arms (arm A 6.3 months v arm B 6.0 months; P = .49). Anorexia, fever, leukopenia, and thrombocytopenia grade III to IV were significantly more frequent in the IFNalpha arm. CONCLUSION: Modulation of CDDP and 5-FU with IFNalpha as used in this study does not improve the RR or the median survival in patients with RMHNC. Patients on both study arms had a poor prognosis, which indicates the need for novel therapies.

Adult↗
PubMed1998

HIV risk behaviors associated with the injection process: multiperson use of drug injection equipment and paraphernalia in injection drug user networks.

This study examines drug acquisition and multiperson use of paraphernalia, drugs, and needles/syringes. Ethnographers observed 54 injection episodes in which IDUs were linked by HIV risk behaviors, and developed a typology of higher-risk, lower-risk, and nonsharing-risk networks. Multiperson use of injection paraphernalia or drug solution occurred in most injection events (94%). Serial use of syringes/needles occurred infrequently (14%) relative to "backloading" (37%) and reuse of paraphernalia (cookers 84%, cotton 77%, water 77%). Higher-risk injection networks were characterized by larger size and pooling of resources for drugs. Prevention messages must include avoiding reuse of injection paraphernalia and transfer of drug solution.

Anthropology, Cultural↗
PubMed1998

Butyrate inhibits colon carcinoma cell growth through two distinct pathways.

BACKGROUND: Dietary fiber and the resultant increase in colonic butyrate levels protect against colon carcinogenesis. Previous studies have shown that p21 and histone hyperacetylation are important in basal growth inhibition by butyrate. This study was designed to elucidate other mechanism underlying the butyrate effects on cell growth. METHODS: HT-29 colon carcinoma cells (standard medium or medium lacking serum) were treated with sodium butyrate (NaBu), epidermal growth factor (EGF), or both. Northern blot analyses were performed with cDNA probes specific for c-fos, c-jun, and actin. Cell growth was measured by 3H-thymidine incorporation. Enzyme-linked immunosorbent assay (ELISA) was used to quantify EGF receptor levels. RESULTS: Butyrate and serum starvation (SS) both induced a cell cycle withdrawal by 24 hours. In response to EGF treatment, SS cells exhibited a growth spurt and induced c-fos and c-jun proto-oncogene expression, whereas butyrate-treated cells exhibited minimal growth response to EGF. This relative unresponsiveness to EGF in butyrate-treated cells corresponded to a dramatic decline in EGF receptor levels when compared to untreated controls. CONCLUSIONS: Butyrate appears to inhibit colon cancer cell growth by two mechanisms, one involving histone hyperacetylation and p21 induction and the other related to impaired EGF-responsiveness.

Actins↗
PubMed1998

Pharyngeal colonisation, ADNB response and development of cardiac lesions in mice following intranasal inoculation with group A beta haemolytic streptococcus M type 18.

Swiss albino mice from a randomly bred colony were inoculated intranasally with 1.6, 2 or 2.4 x 10(7) colony forming units of a mid-logarithmic phase culture of group A beta haemolytic streptococcus M type 18 for 3 days, 6 days or once a week respectively for three weeks. Pharyngeal colonisation could be observed in 67 (59.8%) of 112 mice on 4th day after inoculation and 14 (38%) of the 37 mice on 21st day. Out of 27 mice tested for determination of antibodies to deoxyribonuclease B at regular intervals for 98 days, 15 (55.5%) showed responses, with maximum titers varying from 50 units to 4800 units in individual mice. Histopathological evidence for cardiac lesions were seen in five (3.03%) of the 165 animals studied. These included one case of severe endocarditis, two cases of endocarditis with valvular lesions and one case with non-specific lymphocyte infiltration in the heart. One other animal showed subendocardial oval nodular aggregates. Although the cellular nature of these lesions were not determined, this study shows that Swiss albino mice can serve as suitable animal models to study experimental streptococcal infections. However these are preliminary observations and are to be confirmed and revalidated by further controlled experiments.

Animals↗