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Biomedical subjects

W Johnson

Publications and source records attributed to W Johnson.

At least 19 recordsLinked to original sources
PubMed1999

Effect of intensive therapy for heart failure on the vasodilator response to exercise.

OBJECTIVES: The purpose of the study was to evaluate the lower extremity vascular responsiveness to metabolic stimuli in patients with heart failure and to determine whether these responses improve acutely after intensive medical therapy. BACKGROUND: Metabolic regulation of vascular tone is an important determinant of blood flow, and may be abnormal in heart failure. METHODS: The leg blood flow responses were measured in 11 patients with nonedematous class III-IV heart failure before and after inpatient medical therapy and in 10 normal subjects. Venous occlusion plethysmography was used to measure peak blood flow and total hyperemia in the calf after arterial occlusion and also after isotonic ankle exercise. Measurements were repeated following short-term inpatient treatment with vasodilators and diuretics administered to decrease right atrial pressure (18+/-2 to 7+/-1 mm Hg), pulmonary wedge pressure (32+/-3 to 15+/-2 mm Hg), and systemic vascular resistance (1581+/-200 to 938+/-63 dynes.s.cm(-5), all p < 0.02). RESULTS: Leg blood flow at rest, after exercise, and during reactive hyperemia was less in heart failure patients than in control subjects. Resting leg blood flow did not increase significantly after medical therapy, but peak flow after the high level of exercise increased by 59% (p = 0.009). Total hyperemic volume in the recovery period increased by 73% (p = 0.03). Similarly, the peak leg blood flow response to ischemia increased by 88% (p = 0.04), whereas hyperemic volume rose by 98% (p = 0.1). CONCLUSIONS: The calf blood flow responses to metabolic stimuli are blunted in patients with severe heart failure, and improve rapidly with intensive medical therapy.

Blood Flow Velocity↗
PubMed1999

Analysis of Legionella pneumophila serogroup 1 isolates by pulsed-field gel electrophoresis.

At a hospital in Halifax, Nova Scotia, Canada, three strains of Legionella pneumophila were detectable based on plasmid content, while the isolates collected at another hospital in Halifax had no plasmids. Genomic DNA was digested with BssHII, SalI, and SpeI and subjected to pulsed-field gel electrophoresis (PFGE). We found no relationship between plasmid profile and PFGE pattern.

Bacterial Typing Techniques↗
PubMed1999

Repeat tear of postoperative meniscus: potential MR imaging signs.

PURPOSE: To determine the usefulness of five magnetic resonance (MR) signs of repeat tears of the postoperative meniscus. MATERIALS AND METHODS: Fat-saturated proton-density-weighted and T2-weighted MR images in 20 patients who had undergone at least two knee surgeries were reviewed. Second-look arthroscopic confirmation of meniscal status was available in all patients. MR images of 39 menisci (10 repeat tears, 11 postoperative menisci without repeat tears, three tears in previously normal menisci, and 15 normal menisci) were evaluated for (a) a linear area of abnormal signal intensity extending to an articular surface on intermediate-weighted images, (b) abnormal meniscal morphology, (c) likelihood of a typical postoperative appearance, (d) fluid extending into the linear area on T2-weighted images, and (e) cartilage defects. Two radiologists rated their confidence on a five-point scale for the presence of these signs and were compared for level of agreement. RESULTS: The intraclass correlation coefficient (range, 0.75-0.91) indicated a high level of agreement. Areas under the receiver operating characteristic curves were large (range, 0.70-0.87) for all five signs, with a line (grade 3 signal intensity) and fluid within a line having the highest areas. These two signs also had the highest statistical scores (chi 2 = 14.12 and 13.30; P < .002; odds ratio, 1.588 and 1.599 for the line and the fluid within the line, respectively). CONCLUSION: The two best MR signs of repeat tear of the postoperative meniscus were the presence of a line and fluid within the line extending to an articular surface.

Adult↗
PubMed1998

Targeting bacteriophage to mammalian cell surface receptors for gene delivery.

Filamentous bacteriophages represent one of nature's most elegant ways of packaging and delivering DNA. In an effort to develop novel methods for ligand discovery via phage gene delivery, we conferred mammalian cell tropism to filamentous bacteriophages by attaching basic fibroblast growth factor (FGF2), transferrin, or epidermal growth factor (EGF) to their coat proteins and measuring CMV promoter-driven reporter gene expression in target cells. In this system, FGF2 was a more effective targeting agent than transferrin or EGF. The detection of green fluorescent protein (GFP) or beta-galactosidase (beta-Gal) activity in cells required FGF2 targeting and was phage concentration dependent. Specificity of the targeting for high-affinity FGF receptors was demonstrated by competing the targeted phage with FGF2, by the failure of FGF2-targeted bacteriophage to transduce high-affinity FGF receptor-negative cells, and by their ability to transduce these same cells when stably transfected with FGFR1, a high-affinity FGF receptor. Long-term transgene expression was established by selecting colonies for G418 resistance, suggesting that with the appropriate targeted tropism, filamentous bacteriophage can serve as a vehicle for targeted gene delivery to mammalian cells.

Animals↗
PubMed1998

Establishing the level of digitization for wrist and hand radiographs for the third National Health and Nutrition Examination Survey.

In the third National Health and Nutrition Examination Survey (NHANES III) conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention, radiographs of the hands and knees were taken of participants 60 years and older as part of the study of arthritis and musculoskeletal conditions. The purpose of the study was to decide the digitizing resolution to be used for these radiographs. A set of wrist and hand radiographs (N = 49) was graded by two radiologists for degree of bone erosions and served as a "gold standard." The radiographs were then digitized at three resolution levels; low-resolution 150 microns (2001 x 1634 x 12 bit matrix); intermediate-resolution 100 microns (3000 x 2400 x 12 bit matrix); and high-resolution 50 microns (4900 x 3000 x 12 bit matrix). A comparison of the digital images versus the gold standard reading was made at the three resolutions by two radiologists. Kappa statistics suggested fair (K > .4) to excellent (K > .75) agreement between the gold standard and the images at all levels. Intraclass correlation coefficient suggested high agreement between readers (ICC > .5), with minimal individual reader effect. Variance component estimates showed that the major contribution (78-83%) to scoring came from variability in the images themselves, not from the readers. The 100 microns resolution was selected over the 150 and 50 microns on the basis of practical considerations such as storage requirements, display time, and easier manipulation of the digital images by the readers.

Arizona↗
PubMed1998

Sensitivities and specificities of premier E. coli O157 and premier EHEC enzyme immunoassays for diagnosis of infection with verotxin (Shiga-like toxin)-producing Escherichia coli. The SYNSORB Pk Study investigators.

This study describes the performance of two rapid enzyme immunoassays, Premier E. coli O157 and Premier EHEC (Meridian Diagnostics Inc., Cincinnati, Ohio) for the detection in stools of Escherichia coli O157 and verotoxins (Shiga-like toxins), respectively. Both tests were performed on stools from 876 children presenting to eight emergency departments with diarrhea. Standard culture, including E. coli O157:H7 isolation, was performed, and paired sera were taken for anti-O157-lipopolysaccharide antibody determination. Stools from patients enrolled in the study, and those yielding discordant results, were sent to a reference laboratory for repeat testing and further investigation, including cytotoxicity and non-O157 verotoxin-producing E. coli culture. Results were classified as field results (obtained in the eight site laboratories) and resolved results (obtained after repeat testing in the central laboratory). The "gold standard" for sensitivity of both tests and for specificity of Premier E. coli O157 was isolation of E. coli O157:H7 or a fourfold anti-O157 antibody rise. Specimens positive by the Premier EHEC test and negative for E. coli O157 culture were examined for non-O157 verotoxin-producing E. coli. The field sensitivity of Premier E. coli O157 was 86%, that of Premier EHEC was 89%, and the specificity of Premier E. coli O157 was 98%. Ten of 13 discordant Premier E. coli O157 results were reassigned as true results after repeat testing. Ten non-O157 verotoxin-producing E. coli isolates were recovered from Premier EHEC-positive, E. coli O157 culture-negative stools. Only one specimen gave an unequivocally false-positive Premier EHEC result. Both tests are highly sensitive and are specific if correctly performed. The Premier EHEC test will be particularly valuable as a practical routine test for the detection of non-O157 verotoxin-producing E. coli.

Antibodies, Bacterial↗
PubMed1998

The effects of noncontingent and contingent attention for self-injury, manding, and collateral responses.

To date, most functional analysis studies have focused on the effects of treatment contingencies on specific targeted aberrant and alternative responses. In the current investigation, the main and collateral effects of the assessment and treatment of attention-maintained self-injury were assessed. Specifically, we evaluated the effects of noncontingent and contingent social attention on four categories of behavior: self-injury, a novel mand, preexisting prosocial responses (e.g., babbling and reaching out), and other aberrant responses (i.e., aggression and destruction). Results suggested that self-injury, prosocial responses, and other aberrant behaviors were within the same functional response class. Possible impact of these results when selecting mands for functional communication training is discussed.

Attention↗
PubMed1998

The thyroid hormone receptor variant alpha2 is a weak antagonist because it is deficient in interactions with nuclear receptor corepressors.

The thyroid hormone receptor splice variant, alpha2, is unable to bind thyroid hormone (T3) and has been proposed to function as an endogenous inhibitor of T3 action. In this report, we examined further the DNA sequence requirements for alpha2 binding to thyroid hormone response elements (TREs) in an attempt to identify response elements that mediate potent inhibition by alpha2. Heterodimers of alpha2 and retinoid X receptor were found to bind to a subset of TREs (DR4, direct repeats spaced by 4 bp) in which selected flanking and spacer sequences enhanced interactions with the AGGTCA core binding sequence. Despite the optimization of the TRE-binding sites, alpha2 remained a weak dominant negative inhibitor of TRE-driven transcription. A promoter interference assay was also developed for testing inhibition by alpha2. In these studies, alpha2 blocked gene transcription, but it required cotransfected retinoid X receptor, and it was not as potent as unliganded thyroid hormone receptors. These results led to the hypothesis that alpha2 might be deficient in interactions with nuclear receptor corepressors. Consistent with this view, alpha2 did not silence basal transcription in its native form or when linked to Gal4. Alpha2 also failed to interact with corepressors (NCoR and SMRT) in both gel shift assays and mammalian two-hybrid assays. We conclude that alpha2 is a weak antagonist of thyroid hormone action because it binds weakly to a limited repertoire of response elements, and it does not interact with corepressors. Thus, alpha2 may be able to compete with thyroid hormone receptors for binding to a limited group of target sites, but it is not able to actively inhibit transcription.

Binding Sites↗
PubMed1998

Salmonella typhimurium DT104: a virulent and drug-resistant pathogen.

Salmonella typhimurium phage type (PT) or definitive type (DT) 104 is a virulent pathogen for humans and animals, particularly cattle. It has been isolated increasingly from humans and animals in the United Kingdom and several other European countries and, more recently, in the United States and Canada. Humans may acquire the infection from foods of animal origin contaminated with the infective organism. Farm families are particularly at risk of acquiring the infection by contact with infected animals or by drinking unpasteurized milk. The symptoms in cattle are watery to bloody diarrhea, a drop in milk production, pyrexia, anorexia, dehydration and depression. Infection may result in septicemic salmonellosis and, upon necropsy, a fibrinonecrotic enterocolitis may be observed. The infection occurs more commonly in the calving season than at other times. Feedlot cattle and pigs may also be affected. Prolonged carriage and shedding of the pathogen may occur. Symptoms in humans consist of diarrhea, fever, headache, nausea, abdominal pain, vomiting, and, less frequently, blood in the stool. Salmonella typhimurium DT104 strains are commonly resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline.

Agricultural Workers' Diseases↗
PubMed1998

Serving up food safety.

Explore the source record for details and available documents.

Centers for Disease Control and Prevention, U.S.↗
PubMed1997

Regulation of the human chorionic gonadotropin alpha- and beta-subunit promoters by AP-2.

Production of the placental hormone, chorionic gonadotropin (CG), increases dramatically as cytotrophoblasts fuse to form syncytiotrophoblasts. The CG alpha- and beta-promoters are both responsive to cAMP, although the kinetics of cAMP stimulation are different. In an effort to understand the mechanisms of coordinate induction of these genes, AP-2 binding sites were identified in the promoter regions of the alpha and CGbeta genes. AP-2 bound to the upstream regulatory element (-186 to -156 base pairs (bp)) in the alpha-promoter and to several different regions of the CGbeta promoter, including footprints 2 and 4B (FP2, -311 to -279 bp; FP4B, 221 to -200 bp). AP-2 antibodies induced supershifts of these complexes, confirming the identity of the protein-DNA complex. In JEG-3 cells, which contain abundant AP-2, mutations in these CGbeta AP-2 sites reduced basal activity and decreased cAMP stimulation. In AP-2-deficient Hep-G2 cells, co-transfection of AP-2 stimulated expression of the CGbeta promoter 10-20-fold, and the alpha-promoter was induced by 3-6-fold. Mutations that eliminate AP-2 binding to CGbeta FP4B reduced AP-2 stimulation by more than 80%, whereas mutations in FP2 reduced AP-2 stimulation by less than 50%. Analyses of AP-2 mutants revealed a requirement for the DNA binding/dimerization domain and the amino-terminal proline-rich and acid-rich transactivation domains for stimulation of the CGbeta promoter. Primary cultures of placental cytotrophoblasts were differentiated into syncytiotrophoblasts in vitro to examine AP-2 expression by reverse transcriptase-polymerase chain reaction. AP-2 mRNA levels increased by day 2 and continued to rise in parallel with a marked increase in alpha and CGbeta gene expression. We conclude that both the alpha and CGbeta promoters contain binding sites for AP-2 and suggest that this transcription factor provides a mechanism for coordinating the induction of these genes during placental cell differentiation.

Cell Nucleus↗
PubMed1997

The effect of dietary flavonoids on DNA damage (strand breaks and oxidised pyrimdines) and growth in human cells.

The effects of the flavonoids quercetin, myricetin and silymarin on DNA damage and cytotoxicity in human cells were investigated. DNA strand breaks and oxidised pyrimidines were determined using alkaline single cell gel electrophoresis (the comet assay). Inhibition of cell growth was also measured. Caco-2 (colon), HepG2 (liver), HeLa (epithelial) cells and normal human lymphocytes showed different, dose-dependent susceptibilities (in terms of strand breakage) to the various flavonoids, quercetin being the most damaging. This agreed well with the ability of the flavonoids to inhibit cell growth. None of the flavonoids induced DNA base oxidation above background levels. All of the flavonoids under investigation caused depletion of reduced glutathione, which, in the case of quercetin, occurred prior to cell death. Neither cytotoxicity nor genotoxicity was associated with the antioxidant enzyme capacity (glutathione, glutathione reductase, glutathione peroxidase and catalase) of the cells.

Adenocarcinoma↗
PubMed1997

Cardiovascular effects of different infusion rates of sufentanil in patients undergoing coronary surgery.

OBJECTIVE: Pharmacokinetics and haemodynamic effects of a total dose of 15 micrograms.kg-1 sufentanil, an opioid anaesthetic agent, were studied in patients undergoing aortocoronary bypass surgery at three infusion rates of 30 (group I), 5 (group II), and 2 (group III) micrograms.kg-1.min-1, respectively. RESULTS: Plasma concentrations of sufentanil could be optimally characterized by a linear biexponential pharmacokinetic model. Non-compartmental analyses indicated that there was no significant difference in the values of clearance (11.6, 13.3, 14.3 ml.min-1.kg-1), steady-state volume of distribution (0.220, 0.255 and 0.331 l.kg-1) and mean residence time (18.8, 13.3 and 14.3 min) among the groups. The observed mean Cmax values of 421 (group I), 125 (group II), and 53 (group III) ng.ml-1 and observed mean AUC values from 0 to 3 min were all consistent with the dosing regimens. There were large inter-individual variations in haemo-dynamic response. Compared to plasma data, a delay in haemodynamic effects was found. Times to reach peak haemodynamic effect ranged from 4.3 to 4.9 min for group I, from 4.6 to 6.1 min for group II, and from 9.9 to 11.3 for group III. Except heart rate, peak haemodynamic effects in these study patients generally ranged from 20.9% to 35.2%. Significant reductions in the area under the effect-time profiles of mean arterial blood pressure and systemic vascular resistance were observed in group II and group III, but not in group I. Significant reductions in the area under the effect-time profiles of left ventricular stroke work index were observed in group III only. No effect on heart rate was found in any group. CONCLUSION: Our findings suggested that a slower infusion rate of sufentanil at a dose of 15 micrograms.kg-1 tends to give a greater reduction in mean arterial blood pressure, systemic vascular resistance, and left ventricular stroke work index than does a faster infusion rate.

Analgesics, Opioid↗
PubMed1997

Baker's cysts mimicking the symptoms of deep vein thrombosis: diagnosis with venous duplex scanning.

PURPOSE: The purpose of this study was to determine the incidence and characteristics of Baker's cysts discovered during venous duplex examinations to rule out deep vein thrombosis (DVT). METHODS: We reviewed the vascular laboratory charts of patients found to have Baker's cysts during venous duplex studies to rule out DVT from October 1988 through December 1995. RESULTS: Ninety-five (3.1%) of 3072 patients who underwent venous duplex studies were found to have 111 Baker's cysts. Seven of the 95 had coexistent DVT. Ten patients had ruptured cysts, whereas six patients had cysts that compressed the popliteal vein. CONCLUSION: The presentation of DVT and that of a Baker's cyst are similar enough to be difficult to distinguish by clinical examination. Careful examination of the popliteal fossa should be performed during venous duplex examinations regardless of the indication for the study.

Adult↗