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Biomedical subjects

W Johnson

Publications and source records attributed to W Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1996

Risk behavior and HIV seroincidence among out-of-treatment injection drug users: a four-year prospective study.

We monitored trends in HIV risk behaviors and seroconversion among out-of-treatment injection drug users (IDUs) receiving street-based outreach intervention. Beginning in 1988, 641 HIV-seronegative IDUs were recruited by targeted sampling methods to reflect broader IDU populations and were followed for 4 years (1988-1992). All were active injectors not in treatment when recruited. Cohort members were targets of HIV-prevention outreach. The intervention was guided by the Indigenous Leader Outreach Model: Exaddicts deliver HIV-prevention services targeting IDU social networks in community settings. Primary outcome measures were HIV seroconversion and HIV risk behaviors. Observed incidence of HIV infection decreased, from 8.4 to 2.4 per 100 person-years. Prevalence of drug risk behaviors also decreased, from 100 to 14%. Seroconversion was associated with injection risk behavior [risk ratio (RR) = 9.8]. Sex risk behavior also decreased, but less dramatically, from 71 to 45%. Out-of-treatment IDUs in Chicago have reduced their rates of new HIV infection by reducing their injection risk behavior. New infections were strongly associated with injection risk behavior but not with sex risk behavior.

Adolescent↗
PubMed1996

Pityriasis rubra pilaris with acantholysis.

Two patients developed a papulosquamous eruption in a widespread distribution which progressed with islands of sparing of uninvolved skin characteristic clinically of adult-onset pityriasis rubra pilaris (PRP). Biopsies from both patients showed multiple areas of nonfollicular and follicular suprabasilar and intra-epidermal acantholysis with minimal dyskeratosis. They also showed the usual histologic features of PRP with a thickened orthokeratosis and parakeratosis, a retained and sometimes thickened granular cell layer, and psoriasiform epidermal hyperplasia with a perivascular lymphohistiocytic infiltrate in the superficial dermis. Two previous patients with PRP have been reported with nonfollicular, focal acantholytic dyskeratosis and both were interpreted as most likely representing an incidental finding. We believe the acantholysis in these two cases is related to the disease process, and in our second patient, was helpful in establishing the diagnosis.

Acantholysis↗
PubMed1996

Interaction of Legionella pneumophila with Acanthamoeba castellanii: uptake by coiling phagocytosis and inhibition of phagosome-lysosome fusion.

Legionella pneumophila is a facultative intracellular parasite able to survive within both human monocytes and amoebae. We have demonstrated that processing of L. pneumophila by the free-living amoeba Acanthamoeba castellanii shows many similarities to the processing of L. pneumophila by monocytes. These similarities include uptake of L. pneumophila by coiling phagocytosis and the subsequent confinement of L. pneumophila in a ribosome-studded phagosome. In addition, as in monocytes, inhibition of lysosomal fusion with phagosomes containing L. pneumophila was detected in amoebae. With all clinical isolates, inhibition of phagosomes-lysosome fusion correlated with virulence. However, with one of the environmental isolates tested, no significant difference in phagosome-lysosome fusion was observed between the virulent and avirulent forms. These results indicate that the avirulent form of this isolate differed from the virulent form in some other respect critical to intracellular survival. Therefore, intracellular multiplication of L. pneumophila within A. castellanii may not be solely dependent upon the inhibition of lysosomal fusion.

Acanthamoeba↗
PubMed1996

Pulpal response to dentin etched with 10% phosphoric acid.

PURPOSE: To histopathologically evaluate the effect of etching sound dentin with 10% phosphoric acid, in cavities prepared just within the DEJ on young patients. MATERIALS AND METHODS: Twenty-four orthodontic patients who required premolar extractions were selected for the study. Each of the patients had facial Class V resin composite restorations placed in two maxillary premolars selected for extraction. Each preparation was cut circular, 2 mm in circumference and 0.5 mm into dentin. The dentin of one maxillary premolar preparation, randomly selected, was etched with 10% phosphoric acid (Bisco) for 20 seconds. This was followed by the placement of a dentin bonding agent (All-Bond 2) and a microfilled composite restoration (Silux). The contralateral maxillary premolar, received a similar preparation, but the dentin surface was lined with a light-cured glass ionomer liner before etching of the enamel, followed by placement of a dentin bonding agent and a microfilled resin composite restoration. One of the mandibular premolars was randomly selected as a negative control, having no treatment. Fourteen days after the placement of the restorations, the teeth were extracted, and histologically examined for insult to the pulpal tissues. Injury to the pulp was evaluated by quantitative measures of histopathology, including necrosis, infiltration by inflammatory cells, and other indicators of tissue injury. RESULTS: Using a Kruskal-Wallis analysis, there was no statistically significant difference in pulpal histopathology of the teeth with etched dentin versus teeth with dentin protected by a liner or the negative control teeth (P < 0.05).

Acid Etching, Dental↗
PubMed1995

Testing independence when the form of the bivariate distribution is unspecified.

We address the problem of testing for independence between X and Y in two situations. In the first we assume that the joint distribution of X and Y is unknown but the observations on X and Y are identifiable. In the second case we assume that the distribution of (X, Y) is exchangeable. Here we consider both when (X, Y) are identifiable and when they are not. We illustrate applications to the testing of independence in DNA databases and in twin studies.

Adult↗
PubMed1995

A prolonged outbreak of exfoliative toxin A-producing Staphylococcus aureus in a newborn nursery.

An outbreak of erythromycin-resistant, exfoliative toxin-producing Staphylococcus aureus infection in a neonatal unit is described. The organism was coagulase positive but staphyloslide negative, and this unusual phenotype facilitated early recognition of the organism in the routine laboratory. In the initial outbreak there were 77 probable or confirmed cases, with a peak attack rate of 66%. Increased infection control measures were put in place and attempts were made to identify a staff carrier. No carriers were found and the major outbreak subsided. Sporadic cases occurred over the following 10 months, until May 1992, when a colonized staffperson was discovered. She was treated and no further cases occurred. The causative organism was subjected to typing by phage, enterobacterial repetitive intergenic consensus sequence polymerase chain reaction, and pulsed-field gel electrophoresis with two separate enzymes. The phage typing and genomic tests confirmed the presence of the same clone in the unit for 9 months. The organism possessed genes encoding exfoliative toxin A as determined by polymerase chain reaction.

Bacterial Toxins↗
PubMed1995

Potable water and nosocomial Legionnaires' disease--check water from all rooms in which patient has stayed.

We studied 7 patients with nosocomial Legionnaires' disease to determine the relationship between isolates of Legionella pneumophila recovered from potable water and those recovered from patients. Potable water was cultured from all rooms in which patients had stayed prior to the diagnosis of Legionnaires' disease. The 38 isolates of L. pneumophila (31 environmental, 7 patient) were resolved into 9 distinct patterns by pulse-field gel electrophoresis (PFGE), 3 by plasmid content and 2 each with monoclonal antibodies and conventional agarose gel electrophoresis of small fragments of DNA. Using PFGE it was determined that 4 of the 7 patients were infected with L. pneumophila identical to an isolate recovered from the potable water supply in one of the rooms each had occupied prior to the diagnosis of Legionnaires' disease. Patients had resided in a mean of 3.57 rooms before a diagnosis of nosocomial Legionnaires' disease. We conclude that in the setting of contaminated potable water and nosocomial Legionnaires' disease water from all the rooms which the patient has occupied prior to this diagnosis should be cultured. PFGE of large DNA fragments discriminated best among the isolates of L. pneumophila.

Antibodies, Monoclonal↗
PubMed1995

Antibody-independent binding of complement component C1q by Legionella pneumophila.

Incubation of Legionella pneumophila Philadelphia 1 in normal human serum depleted of either classical-pathway component C1q or alternative-pathway component factor B resulted in activation of the complement system. Experiments focused on the role of the classical pathway in complement activation revealed that legionellae bound C1q independently of antibody. Purified preparations of L. pneumophila major outer membrane protein but not serogroup 1 lipopolysaccharide bound C1q independently of antibody. This suggests that antibody-independent binding of C1q by L. pneumophila can result in activation of the classical pathway in normal human serum and that major outer membrane protein may be a C1q acceptor on the L. pneumophila cell surface.

Antibodies, Bacterial↗
PubMed1995

Sorbitol-negative phenotype among enterohemorrhagic Escherichia coli strains of different serotypes and from different sources.

Enterohemorrhagic Escherichia coli (EHEC) strains detected with DNA probes (for virulence plasmid and Shiga-like toxins) from subjects with hemolytic-uremic syndrome (n = 19) or diarrhea (n = 41) or asymptomatic carriers (n = 29) were examined for sorbitol fermentability, as were enterotoxigenic (n = 40), enteropathogenic (n = 40), and enteroinvasive (n = 40) E. coli and urinary tract infection (n = 40) strains and normal flora E. coli strains (n = 40). Sorbitol negativity was common only in EHEC, particularly among strains from severe clinical infections. All 19 EHEC strains from patients with hemolytic-uremic syndrome, irrespective of O:H serotype or Shiga-like toxin genotype, were sorbitol negative.

Carrier State↗
PubMed1995

Identification of fat-cell enhancer activity in Drosophila melanogaster using P-element enhancer traps.

To identify genes important in fat-cell metabolism and development, we have screened Drosophila stocks carrying an engineered transposable element that can reveal the presence of nearby enhancer elements. We have identified those "enhancer-trap lines" that contain transposable P elements integrated near fat-cell specific enhancer elements. We anticipate that the genes associated with these enhancers will provide information concerning fat-cell function and serve as target genes for studying fat-cell specific gene expression. Furthermore, the identification of enhancer-trap lines active in the developing fat cell should provide an entry point into the molecular and genetic analysis of early fat-cell development. Analysis of two lines has revealed that the transcription factors svp, a steroid-hormone receptor, and Kr, a zinc-finger protein, are present in the fat body; these factors are likely to be involved in fat-cell gene expression. In two other lines, beta-galactosidase was detected in a subset of adepithelial cells that may be the precursors to the adult fat cell. And finally, in a single line transgene activity is present in the progenitor cells of the embryonic fat body. The genes associated with these enhancer-trap lines may be involved in fat-cell development.

Animals↗
PubMed1995

Inhibition of collagen cross-linking: effects on fibrillar collagen and ventricular diastolic function.

The fibrillar collagen network is postulated to be a primary determinant of left ventricular diastolic stiffness. This hypothesis was tested by examining the structural and physiological effects of a reduction in fibrillar collagen content and cross-linking in the intact left ventricle. Collagen cross-linking was inhibited by treating five normal adult pigs with beta-aminopropionitrile (BAPN; 10 g/day po) for 6 wk; five normal untreated pigs served as controls. Left ventricular volume, mass, and function were determined by simultaneous echocardiography and catheterization. Chamber stiffness, defined by pressure vs. volume data, and myocardial stiffness, defined by stress vs. dimension data, were determined from variably loaded beats during dextran infusion. Collagen distribution (% area) and integrity (% confluence) were determined by light microscopy. Collagen content was measured by hydroxyproline assay, and collagen cross-linking was measured by salt extraction. BAPN decreased collagen distribution (% area decreased from 12 +/- 1% in control to 7 +/- 1% in BAPN, P < 0.05), collagen integrity (% confluence decreased from 8 +/- 1% in control to 4 +/- 1% in BAPN, P < 0.05), collagen content (from 36 +/- 2 mg/g dry wt in control to 27 +/- 2 mg/g dry wt in BAPN, P < 0.05), and collagen cross-linking (extractable collagen increased from 21 +/- 2% in control to 28 +/- 2% in BAPN, P < 0.05). BAPN decreased chamber stiffness (0.13 +/- 0.02 in control to 0.06 +/- 0.01 in BAPN, P < 0.05) and myocardial stiffness (10.4 +/- 0.5 in control to 6.6 +/- 0.5 in BAPN, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminopropionitrile↗
PubMed1995

No evidence for association of familial Parkinson's disease with CAG repeat expansion.

In some kindreds, familial Parkinson's disease (PD) exhibits genetic anticipation. Thus, we postulated that familial PD in certain kindreds may be associated with a CAG repeat expansion. However, using the repeat expansion detection method, we found no significant increase in the frequency of CAG repeat expansion among 46 unrelated PD probands compared with controls. Nor did we find evidence for CAG repeat expansion between generations in 11 different PD families that exhibit anticipation in age at onset.

Adult↗
PubMed1995

Retrospective appraisals of fathers' effectiveness and psychological health of adults.

Previous research has shown fathers' self-reports of their effectiveness to be positively correlated with their children's psychological health. To assess the relationship between adults' retrospective appraisals of fathers' effectiveness using a modified version of the Seven Secrets Survey and rated their current psychological health on the Personality Assessment Questionnaire. Total scores on the two measures correlated - .37. Three of the six Seven Secrets Survey scales, Knowing your Child, Consistency, and Protecting/Providing, were also correlated with total scores on the Personality Assessment Questionnaire.

Adaptation, Psychological↗
PubMed1995

Clozapine-caused eosinophilic colitis.

Four patients with diarrhea and eosinophilia associated with clozapine therapy are presented. In two cases clozapine therapy was interrupted but then restarted; all patients eventually tolerated clozapine well. A syndrome of clozapine-induced eosinophilic colitis is suggested.

Adult↗
PubMed1995

Differential regulation of a glial fibrillary acidic protein-LacZ transgene in retinal astrocytes and Müller cells.

PURPOSE: Glial fibrillary acidic protein (GFAP) is normally expressed in astrocytes, but not in Müller cells, in the mouse retina. In response to retinal injury or photoreceptor degeneration, however, GFAP gene transcription is strongly activated in the Müller cell. To identify the genetic elements involved in GFAP gene induction, the authors have studied gene expression in transgenic mice in which beta-galactosidase (beta-gal) expression is under control of GFAP regulatory sequences. METHODS: Histochemical methods were used to study gene expression. The transgene expression was followed by x-gal staining, whereas GFAP expression was monitored by immunostaining with GFAP antibody. RESULTS: In GFAP-LacZ transgenic mice, beta-gal activity and GFAP immunostaining were found in retinal astrocytes. Transgene expression showed the same developmental pattern as that of endogenous GFAP in retinal astrocytes. In addition, beta-gal staining also was observed in lens epithelial cells. Neither GFAP nor beta-gal expression was seen in Müller cells in the adult or developing retina. When focal retinal lesions were introduced into the retina, strong GFAP immunostaining was observed in Müller cells throughout the retina. No beta-gal staining was seen in Müller cells in these retinas. In astrocytes, however, beta-gal and GFAP both were present. CONCLUSIONS: The observations suggest that cis elements responsible for GFAP expression in retinal astrocytes are present in 5' flanking region of the GFAP gene, whereas the regulatory elements involved in GFAP induction in Müller cells are located elsewhere.

Animals↗
PubMed1994

Role of sensory and cognitive information in the enhancement of certainty and liking for novel and familiar foods.

Expected and actual liking for novel and familiar foods were examined under various conditions of sensory and verbal information with 121 subjects who differed in food neophobia. The possible mediating roles of uncertainty about product identity and resemblance to familiar foods were also investigated. Subjects were divided into three verbal information groups (no information; product name; ingredient and use information) balanced for neophobia, age and gender. All groups rated test samples under three sensory conditions: (1) appearance only, (2) appearance and smell and (3) appearance, smell and taste. Neophilics rated novel foods more favorably than did neophobics. Accumulating sensory experience (appearance, smell, taste) decreased liking for novel foods but increased liking for familiar foods. Verbal information generally increased liking for all samples. Liking and certainty of product identity were curvilinearly related for novel foods, but linearly related for familiar foods. Liking for products judged to closely resemble the test product predicted up to 64% of the variability in expected and actual liking. Eight weeks later, subjects rated one of the two novel foods higher than in the first exposure, but no other exposure effects were observed. Our data suggest that information (possibly via reduced uncertainty), resemblance to more familiar foods, and exposure contribute to reducing initially negative responses to novel foods; furthermore, neophobia decreases liking for novel foods similarly at all levels of sensory input (visual, smell and taste).

Adult↗