Random versus volunteer selection for a community-based study

BACKGROUND: Selection methods vary greatly in ease and cost-effectiveness. The effects of selection factors associated with subjects' recruitment into studies can introduce bias and seriously limit the generalizability of results. METHODS: For an epidemiologic study, we recruited an age-stratified random sample of 1,422 community-dwelling individuals aged 65+ years from the voter registration lists in a rural area of southwestern Pennsylvania. The first 1,366 of these were accrued through intensive recruitment efforts; the last 56 of them responded to a single mailing. To increase sample size for future risk factor analyses, we also recruited by direct advertisement a sample of 259 volunteers from the same area. The three groups were compared on selected baseline characteristics and subsequent mortality. RESULTS: The two subgroups of the random sample were not significantly different on any of the variables we examined. Compared to the random sample, in cross-sectional analyses, volunteers were significantly more likely to be women, more educated, and less likely to have used several health and human services. Volunteers also had higher cognitive test scores and Instrumental Activities of Daily Living (IADL) ability. Over 6-8 years (10,861 person-years) of follow-up, volunteers had significantly lower mortality rates than randomly selected subjects. CONCLUSIONS: Health-related studies with populations composed partly or entirely of volunteers should take potential volunteer bias into account when analyzing and interpreting data.     

Two distinct pathways exist for down-regulation of the TCR

TCR down-regulation plays an important role in modulating T cell responses both during T cell development and in mature T cells. Down-regulation of the TCR is induced by engagement of the TCR by specific ligands and/or by activation of protein kinase C (PKC). We report here that ligand- and PKC-induced TCR down-regulation is mediated by two distinct, independent mechanisms. Ligand-induced TCR down-regulation is dependent on the protein tyrosine kinases p56(lck) and p59(fyn) but independent of PKC and the CD3gamma leucine-based (L-based) internalization motif. In contrast, PKC-induced TCR down-regulation is dependent on the CD3gamma L-based internalization motif but independent of p56(lck) and p59(fyn). Finally, our data indicate that in the absence of TCR ligation, TCR expression levels can be finely regulated via the CD3gamma L-based motif by the balance between PKC and serine/threonine protein phosphatase activities. Such a TCR ligation-independent regulation of TCR expression levels could probably be important in determining the activation threshold of T cells in their encounter with APC.     

In vitro quantification of radiofrequency ablation lesion size using intracardiac echocardiography in dogs

It was shown that L-arginine (up to 0.5 mM) competitively inhibits the NADPH-diaphorase activity in drosophila melanogaster. The value of inhibition constant is equal to 103 microM. In the presence of higher concentration of L-arginine total NADPH-diaphorase activity includes not only the L-arginine inhibited component, but also the non-inhibited one.     

What do patients express as their preferences in advance directives?

Hydrochlorothiazide-induced pulmonary edema is an unusual but life-threatening adverse reaction. It causes hypoxemia, hypotension, tachycardia, fever, and occasionally electrocardiographic and echocardiographic abnormalities. The mechanism of production is, probably, idiosyncratic.     

Declining rates of oropharyngeal candidiasis and carriage of Candida albicans associated with trends toward reduced rates of carriage of fluconazole-resistant C. albicans in human immunodeficiency virus-infected patients

In order to determine the current prevalence and incidence of fluconazole-resistant oropharyngeal candidiasis among human immunodeficiency virus (HIV)-infected patients, we conducted a prospective observational study of a consecutive series of HIV-infected patients. Of 128 enrolled patients, 70 patients completed four quarterly follow-up visits over a period of 1 year. Over this period, declining rates of carriage of Candida albicans (from 61% to 39%; P = .008) and of oropharyngeal candidiasis (from 30% to 4%; P < .001) were documented. Trends toward reduction in the frequency of fluconazole-resistant isolates (MIC, > or = 64 micrograms/mL) were also seen. During the survey period, the mean (median) number of antiretroviral agents used per patient rose from 0.5 (0) to 1.8 (2) (P < .001). Thus, rather than progression, we observed declining rates of oropharyngeal candidiasis, C. albicans carriage, and fluconazole-resistant C. albicans in a cohort of HIV-infected patients treated with increasingly effective antiretroviral therapy.     

Public veterinary medicine: public health. Serologic evaluation of vesicular stomatitis virus exposure in horses and cattle in 1996

OBJECTIVE: To determine potential risk factors for vesicular stomatitis (VS) in Colorado livestock in 1995 and evaluate VS virus (VSV) exposure of Colorado livestock in 1996. DESIGN: Retrospective case-control study of VS risk factors and seroprevalence evaluation. SAMPLE POPULATION: Premises included 52 that had VS-positive animals and 33 that did not have VS-positive animals during the 1995 epidemic, and 8 in the vicinity of premises that had VS-positive animals during the 1995 epidemic. PROCEDURE: Layout and management data for premises were collected during site visits in 1996. Signalment and management data were collected for animals from which samples were obtained, and samples were tested by serologic examination and virus isolation. The VSV seroprevalence rate was estimated for Colorado, using serum obtained for equine infectious anemia testing and from the Market Cattle Identification program in Colorado. RESULTS: At least 1 animal was seropositive for VSV on 35 of 52 (67%) premises, and 71 of 228 (31%) animals tested were seropositive for VSV. Seroprevalence was 63 of 170 (37%) for horses and 8 of 54 (15%) for cattle. Seroprevalence of VSV in animals from non-study premises in Colorado in 1996 was estimated to be 1.1% in cattle and 0.8% in horses. CLINICAL IMPLICATIONS: Overall VSV seroprevalence in Colorado livestock was less than seroprevalence in epidemic areas, and seroprevalence rates in epidemic areas were greater for horses than cattle. Results may indicate that some animals had subclinical VSV infection during epidemics and that animals may be exposed to VSV between epidemics.     

A canine model of acute hydrocephalus with MR correlation

Within 3 hours of induction of acute hydrocephalus in a canine model, lateral ventricular CSF pressure increased from an initial average of 14.6 +/- 2.8 cm H2O to 40.2 +/- 5.7 cm H2O. Ventricular volumes, as measured from MR images, increased 1.45 +/- 0.94 cm3, 1.92 +/- 0.82 cm3, and 2.24 +/- 0.60 cm3 after 6, 24, and 48 hours, of hydrocephalus, respectively. This canine model was reliable and consistent with clinical conditions.     

Capillary isotachophoresis with fiber-optic Raman spectroscopic detection. Performance and application to ribonucleotides

A fiber-optic Raman probe fitted with a microscope objective was used to obtain on-line normal Raman spectra of adenosine 5'-monophosphate, cytidine 5'-monophosphate, guanosine 5'-monophosphate and uridine 5'-monophosphate separated by capillary isotachophoresis. With multimode optical fiber, the system interrograted a 40-micron length of capillary. Fiber-optic coupling facilitated use of an unmodified spectrograph and conventional capillary mounting systems. Raman spectra were excited with a 2W 532 nm NdYVO4, laser as the excitation source, with collection of 1 spectrum per second. Even at 2.10(-5) M initial concentration, Raman spectra were obtained at a good signal-to-noise ratio.