Biomedical subjects
Publications and source records attributed to B J Barnett.
We report the case of a human immunodeficiency virus-negative woman who developed native valve endocarditis of the aortic valve due to Bartonell henselae infection. The diagnosis was established using serology and PCR analysis of excised aortic valve tissue.
Findings that decision makers can come to different conclusions depending on the order in which they receive information have been termed the "information order bias." When trained, experienced individuals exhibit similar behaviors; however, it has been argued that this result is not a bias, but rather, a pattern-matching process. This study provides a critical examination of this claim. It also assesses both experts' susceptibility to an outcome framing bias and the effects of varying task loads on judgment. Using a simulation of state-of-the-art ship defensive systems operated by experienced, active-duty U.S. Navy officers, we found no evidence of a framing bias, while task load had a minor, but systematic effect. The order in which information was received had a significant impact, with the effect being consistent with a judgment bias. Nonetheless, we note that pattern-matching processes, similar to those that produce inferential and reconstructive effects on memory, could also explain our results. Actual or potential applications of this research include decision support system interfaces or training programs that might be developed to reduce judgment bias.
The health of travelers returning home from developing countries has received increased attention in recent years. Much of this attention has centered on immunizations, malaria chemoprophylaxis and treatment of traveler's diarrhea. In contrast, there are very few data on the health problems of international travelers to developed countries such as the United States. We studied the experience of two corporate medical assistance clinics established for both national and international travelers to Atlanta, Georgia during the Centennial Summer Olympic Games in 1996.
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The influence of infection-control practices on bloodstream infection (BSI) risk was examined in a home health care setting in which three needleless devices were used consecutively. A case-control study and a retrospective cohort study were conducted. Risk factors for BSI included lower education level, younger age, having a central venous catheter (CVC) with multiple ports, or having a tunneled CVC. Among patients with a tunneled CVC, those at greatest risk had been allowed to shower rather than bathe and to get their exit site wet (P<.01). A high proportion (49%) of isolates were hydrophilic gram-negative bacteria, suggesting water sources of infection. In the cohort study, the BSI rate decreased as the frequency of changing the needleless device end cap increased from once weekly up to every 2 days, suggesting that the mechanism for BSI may involve contamination from the end cap. These findings may help to develop infection-control measures specific to home health care.
Governments often provide grants or low-interest loans to disaster victims. Yet these programmes have proven to be quite costly. In addition, questions have been raised about associated behavioural incentives. Conceptually, government disaster insurance programmes should be more efficient, consistent and equitable than ex post facto disaster relief in the form of grants and loans. Yet the performance of government disaster insurance programmes has been mixed, at best. This article reviews the history of US federal natural disaster assistance to individuals and concludes with a recommendation for a new government role in the provision of disaster insurance.
The global resurgence of malaria has raised concerns of the possible reintroduction of indigenous transmission in the United States. The Centers for Disease Control and Prevention's National Malaria Surveillance System, using data supplied by state and local health departments (SLHDs), is maintained to detect local malaria transmission and monitor trends in imported cases. To determine the completeness of reporting of malaria cases to SLHDs, cases identified by local surveillance systems were compared with those identified through active case detection conducted at all laboratories that receive clinical specimens from 11 metropolitan areas in Arizona, California, New Mexico, and Texas. Of the 61 malaria cases identified through either local surveillance or active case detection, 43 (70%) were identified by SLHDs (range by metropolitan area = 50-100%) and 56 (92%) through active case detection. High percentages of cases were identified by SLHDs in New Mexico (80%) and San Diego County (88%), where laboratories are required to send positive blood smears to the SLHD laboratory for confirmation. Completeness of reporting, calculated using the Lincoln-Peterson Capture-Recapture technique, was 69% for SLHD surveillance systems and 89% for laboratory-based active case detection. The high percentage of cases identified by the 11 SLHDs suggests that the National Malaria Surveillance System provides trends that accurately reflect the epidemiology of malaria in the United States. Case identification may be improved by promoting confirmatory testing in SLHD laboratories and incorporating laboratory-based reporting into local surveillance systems.
The number of Salmonella agona isolates reported annually in Texas from 1992 through 1994 ranged from 14 to 21. An increase in incidence of S. agona infections was noted in the fall of 1995. Pulsed-field gel electrophoresis (PFGE) analysis identified prospectively two possible cryptic outbreaks caused by an indistinguishable strain which was isolated from 18 of 59 patients who were culture positive from March through December 1995. These 18 patients had onset of illness from 20 May through 3 October 1995. Eight individuals resided in the Austin area, eight resided in San Antonio, and two resided in Houston; none had attended a common social gathering or owned common pets. Six patients in San Antonio and one patient from Houston recalled eating food items from the same Mexican food restaurant in San Antonio. S. agona organisms with the same PFGE profile were isolated from machacado, an air-dried, raw beef product prepared at the restaurant. The machacado had been shredded in a kitchen blender which was the probable source for cross-contamination of other food items. Five patients in Austin reported eating at a popular Mexican food restaurant in Austin. Improperly prepared machacado also may have been served at the Austin restaurant; however, sufficient quantities of machacado were not available for analysis. PFGE was essential in determining whether the cases constituted outbreaks and was invaluable in guiding the epidemiological investigation.
Urinary tract infection (UTI) remains very common. As many as 50% of women report having had at least one UTI in their lifetimes. Urinary tract infection is the most common cause of infection in nursing home residents and the most common source of bacteremia in the elderly population. Urinary tract infection occurs in patients with structurally or functionally abnormal urinary tracts (complicated UTI) and in patients with anatomically normal urinary tracts (uncomplicated UTI). Escherichia coli (E coli) is the most common cause of uncomplicated UTI, whereas antibiotic-resistant Enterobacteriaceae, enterococci, and Candida species often are the causes of complicated UTI. In this article we review current concepts of the epidemiology, microbiology, pathophysiology, clinical manifestations, diagnosis, and treatment of urinary tract infection.
In 1994 a Texas prison containing a population of mentally retarded inmates experienced a large tuberculosis outbreak. Fifteen cases of tuberculosis were identified (8 confirmed by positive cultures for Mycobacterium tuberculosis) and more than 100 inmates became infected. The culture-confirmed patients were infected with an identical strain of tuberculosis as demonstrated by polymerase chain reaction (PCR) based DNA fingerprinting technique. The prison followed standard tuberculosis infection control policies, but these controls were inadequate to prevent tuberculosis transmission in this special population. Two hundred and thirty inmates (119 inmates showing evidence of new tuberculosis infection or active disease and 111 healthy controls) were enrolled in the investigation. Inmate cell assignments, job duties, and educational classes were identified and medical chart reviews were conducted on all inmates. Tuberculosis transmission was associated with residing on the D Wing of the prison (OR = 25.84, P < 0.01), attending school in Classroom A (OR = 8.34, P = 0.01) and working on the prison utility work crew (OR = 2.52, P < 0.01). The index case in the outbreak had been prescribed 6 months of isoniazid (INH) chemoprophylaxis in 1988.
Ribonuclease T1 has two disulfide bonds linking cysteine residues 2-10 and 6-103. We have prepared a derivative of ribonuclease T1 in which one disulfide bond is broken and the cysteine residues carboxymethylated, (2-10)-RCM-T1, and three derivatives in which both disulfides are broken and the cysteine residues reduced, R-T1, carboxamidomethylated, RCAM-T1, or carboxymethylated, RCM-T1. The RNA hydrolyzing activity of these proteins has been measured, and urea and thermal denaturation studies have been used to determine conformational stability. The activity, melting temperature, and conformational stability of the proteins are: ribonuclease T1 (100%, 59.3 degrees C, 10.2 kcal/mol), (2-10)-RCM-T1 (86%, 53.3 degrees C, 6.8 kcal/mol), R-T1 (53%, 27.2 degrees C, 3.0 kcal/mol), RCAM-T1 (43%, 21.2 degrees C, 1.5 kcal/mol), and RCM-T1 (35%, 16.6 degrees C, 0.9 kcal/mol). Thus, the conformational stability is decreased by 3.4 kcal/mol when one disulfide bond is broken and by 7.2-9.3 kcal/mol when both disulfide bonds are broken. It is quite remarkable that RNase T1 can fold and function with both disulfide bonds broken and the cysteine residues carboxymethylated. The large decrease in the stability is due mainly to an increase in the conformational entropy of the unfolded protein which results when the constraints of the disulfide bonds on the flexibility are removed. We propose a new equation for predicting the effect of a cross-link on the conformational entropy of a protein: delta Sconf = -2.1 - (3/2)R 1n n, where n is the number of residues between the side chains which are cross-linked. This equation gives much better agreement with experimental results than other forms of this equation which have been used previously.
An improved method for purifying ribonuclease T1 from Aspergillus oryzae is described. The method uses gradient elution from DEAE-cellulose and sulfopropyl-Sephadex columns followed by gel filtration on Sephadex G-50 to give almost 100 mg (50% yield) of ribonuclease T1 from 100 g of starting material in less than 5 days.
A growth assay was conducted for six consecutive 28-day periods by using triplicate groups of 110 rainbow trout with an average initial body weight of 3.0 g. Ergocalciferol (vitamin D2 or D2) and cholecalciferol (vitamin D3 or D3) were included to provide levels of 200, 400 and 800 iu/kg in a semipurified casein, gelatin diet. Further treatments with 0 vitamin D and 1600 IU/kg of D3 were also included. The resulting growth curves were significant for parallelism. Statistical analysis showed that D3 was 3.27 times as potent as D2 (limits 2.33 to 4.58). The dietary requirement for D3 was found to be in excess of 800 iu/kg of diet. Vitamin D-deficient fish showed no change in bone ash but exhibited clinical manifestations of tetany with no hypocalcemia. A complete absence of tetany was seen only in the groups fed 800 and 1600 IU of D3 per kilogram. None of the levels of D2 used were sufficient to completely alleviate symptoms of this disorder. These studies of rainbow trout provide evidence that vitamin D is required for the normal functioning of white muscle without altering the calcium content of the plasma or epaxial musculature.
Dietary 25-hydroxycholecalciferol (25-hydroxycholecalciferol (25-OH-D3) and 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] showed vitamin D activity in rainbow trout. However, inclusion of dietary cholecalciferol (vitamin D3 or D3), ergocalciferol (vitamin D2 or D2), 25-OH-D3 or 1,25-(OH)2D3 did not result in the presence of detectable levels of vitamin D or 25-OH-D in the blood plasma of the fish. Fish fed the diet devoid of vitamin D over an extended period of time showed symptoms of a droopy-tail or "lordosis-like" syndrome that appeared to be related to muscle weakness since x-ray examination indicated no abnormality in vertebral development. The requirement for vitamin D as cholecalciferol was in excess of 1600 IU/kg diet and may be as high as, or higher than 2400 IU/kg diet.