Stress propagation in a concentrated colloidal suspension under shear.

The stress propagation in a concentrated attractive colloidal suspension under shear is studied using numerical simulations. The spatial correlations of the intercolloidal stress field are studied and an inertia-like tensor is defined in order to characterize the anisotropic nature of the stress field. It is shown that the colloids remain in a liquid order, the intercolloidal stress is strongly anisotropic. A transition under flow is observed: during a transient regime at low deformation, the stress propagates along the compression direction of the shear, whereas at larger deformations, the stress is organized into layers parallel to the (flow, vorticity) plane.

Using the national registry of HIV-infected veterans in research: lessons for the development of disease registries.

Disease-specific registries have many important applications in epidemiologic, clinical and health services research. Since 1989 the Department of Veterans Affairs has maintained a national HIV registry. VA's HIV registry is national in scope, it contains longitudinal data and detailed resource utilization and clinical information. To describe the structure, function, and limitations of VA's national HIV registry, and to test its accuracy and completeness. The VA's national HIV registry contains data that are electronically extracted from VA's computerized comprehensive clinical and administrative databases, called Veterans Integrated Health Systems Technology and Architecture (VISTA). We examined the number of AIDS patients and the number of new patients identified to the registry, by year, through December 1996. We verified data elements against information obtained from the medical records at five VA sites. By December 1996, 40,000 HIV-infected patients had been identified to the registry. We encountered missing data and problems with data classification. Missing data occurred for some elements related to the computer programming that creates the registry (e.g., pharmacy files), and for other elements because manual entry is required (e.g., ethnicity). Lack of a standardized data classification system was a problem, especially for the pharmacy and laboratory files. In using VA's national HIV registry we have learned important lessons, which, if taken into account in the future, could lead to the creation of model disease-specific registries.

IMPI: Making MPI Interoperable.

The Message Passing Interface (MPI) is the de facto standard for writing parallel scientific applications in the message passing programming paradigm. Implementations of MPI were not designed to interoperate, thereby limiting the environments in which parallel jobs could be run. We briefly describe a set of protocols, designed by a steering committee of current implementors of MPI, that enable two or more implementations of MPI to interoperate within a single application. Specifically, we introduce the set of protocols collectively called Interoperable MPI (IMPI). These protocols make use of novel techniques to handle difficult requirements such as maintaining interoperability among all IMPI implementations while also allowing for the independent evolution of the collective communication algorithms used in IMPI. Our contribution to this effort has been as a facilitator for meetings, editor of the IMPI Specification document, and as an early testbed for implementations of IMPI. This testbed is in the form of an IMPI conformance tester, a system that can verify the correct operation of an IMPI-enabled version of MPI.

Accelerating Scientific Discovery Through Computation and Visualization.

The rate of scientific discovery can be accelerated through computation and visualization. This acceleration results from the synergy of expertise, computing tools, and hardware for enabling high-performance computation, information science, and visualization that is provided by a team of computation and visualization scientists collaborating in a peer-to-peer effort with the research scientists. In the context of this discussion, high performance refers to capabilities beyond the current state of the art in desktop computing. To be effective in this arena, a team comprising a critical mass of talent, parallel computing techniques, visualization algorithms, advanced visualization hardware, and a recurring investment is required to stay beyond the desktop capabilities. This article describes, through examples, how the Scientific Applications and Visualization Group (SAVG) at NIST has utilized high performance parallel computing and visualization to accelerate condensate modeling, (2) fluid flow in porous materials and in other complex geometries, (3) flows in suspensions, (4) x-ray absorption, (5) dielectric breakdown modeling, and (6) dendritic growth in alloys.

Constitutional symptoms and health-related quality of life in patients with symptomatic HIV disease.

PURPOSE: To assess the severity of constitutional symptoms in persons with human immunodeficiency virus (HIV) infection, and their relationship to health-related quality of life (HRQOL). PATIENTS AND METHODS: Two hundred five HIV-infected patients (93% male, 26% African American, 28% Latino, 39% white, 7% other ethnicity) with diarrhea, fever, or weight loss were studied at a county hospital and a Veterans Administration hospital in southern California. Consenting subjects were administered a battery that included 11 scales measuring various aspects of health-related quality of life and detailed questions about six constitutional symptoms or symptom complexes (myalgias, exhaustion, anorexia/nausea/vomiting, night sweats, fever, and weight loss) as well as about other manifestations of HIV disease. RESULTS: Constitutional symptoms except weight loss were all strongly related to all measures of quality of life. On 0 (worst) to 100 (best) point scales, mean scores ranged from 34 (for individuals having all five symptoms other than weight loss) to 78 (for those with none) for physical function, 43 to 79 for emotional well-being, and 36 to 73 for social function. Adjustment for helper T-lymphocyte counts, duration of illness, and demographic characteristics did not diminish these associations. CONCLUSION: The presence, number, and severity of constitutional symptoms in HIV disease is strongly related to health-related quality of life in symptomatic HIV-infected individuals. Identifying and treating these very common symptoms has the potential to improve quality of life in these patients.

Long-term follow-up of symptomatic HIV-infected patients originally randomized to early versus later zidovudine treatment; report of a Veterans Affairs Cooperative Study. VA Cooperative Study Group on AIDS Treatment.

Following a 4-year controlled trial comparing early and later zidovudine treatment, we conducted an additional 3-year follow-up. Of the original 338 patients, 275 participated. Clinical outcome measures were AIDS and death. In the early therapy group (n = 170), 67 patients progressed to AIDS compared with 85 in the later therapy group (n = 168); the relative risk (RR) comparing early with later therapy was 0.72% (95% confidence interval [CI] 0.52-0.99; p = 0.044). The early therapy group had 74 deaths compared with 73 in the later therapy (RR = 0.98; 95% CI, 0.71-1.36; p = 0.91). The early group had a peak CD4+ count increase at 1-2 months and a delay of 1 year before CD4+ counts fell below baseline. For patients who received zidovudine for more than the median duration (20.3 months) before their first AIDS diagnosis, the RR for death was 2.08 (95% CI, 1.36-3.19, p = 0.001). Additional factors independently associated with poor prognosis following AIDS were a CD4+ count of < 100 cells/mm3 and increased severity of the first AIDS diagnosis, whereas use of another antiretroviral agent was associated with improved survival. We conclude that early zidovudine therapy delays progression to AIDS but does not affect survival. Patients who progress to AIDS while on prolonged zidovudine monotherapy many benefit from a change to other antiretroviral therapy(ies).

Relationship between procedures and health insurance for critically ill patients with Pneumocystis carinii pneumonia.

The objective of the present study was to assess the association between type of health insurance coverage and use of diagnostic tests and therapies among patients with AIDS-related Pneumocystis carinii pneumonia (PCP). Fifty-six private, public, and community hospitals in Chicago, Los Angeles, and Miami were selected for the study, and the charts of 890 patients with empirically treated or cytologically confirmed PCP, hospitalized during 1987 to 1990 were retrospectively reviewed. Patients were classified by insurance status: self-pay (n = 56), Medicaid (n = 254), or private insurance, including health maintenance organizations and Medicare (n = 580). Primary outcomes were the use and timing of bronchoscopy, the type and timing of PCP therapy, and in-hospital mortality. The results indicate that Medicaid patients were less likely than privately insured patients to undergo bronchoscopy (relative odds = 0.61; 95% CI = 0.40, 0.93; p = 0.02) or to have their diagnosis of PCP confirmed (relative odds = 0.51; 95% CI = 0.33, 0.77), after adjusting for patient, severity of illness, and hospital characteristics. Medicaid patients were approximately three-fourths more likely than privately insured patients (relative odds = 1.73; 95% CI = 1.01, 2.96; p = 0.04) to die in-hospital, after adjusting for patient, severity of illness, and hospital characteristics. However, with further adjustment for confirmation of PCP, Medicaid patients no longer had a significantly higher likelihood of dying in-hospital. We conclude that Medicaid patients are less likely to receive diagnostic bronchoscopy than privately insured or self-insured patients, more likely to be empirically treated for PCP, and more likely to die in-hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Empirically treated Pneumocystis carinii pneumonia in Los Angeles, Chicago, and Miami: 1987-1990.

Many patients infected with the human immunodeficiency virus (HIV) with symptoms suggestive of pneumonia are treated empirically for Pneumocystis carinii pneumonia (PCP), although other bacterial infections (e.g., tuberculosis) and pulmonary Kaposi's sarcoma may cause identical symptoms. Empiric treatment for PCP may result in misdiagnosis and mistreatment. When the outcomes of cytologically confirmed versus empirically treated PCP cases were evaluated, the most important predictors of in-hospital mortality were severity of illness and use of bronchoscopy. Persons who did not undergo bronchoscopy had higher mortality rates than patients negative by bronchoscopy or cytologically confirmed as positive for PCP (22% vs. 11% vs. 14%, P < .01), although severity of illness and timing of anti-PCP medications did not differ significantly. Compared with cytologically confirmed cases, persons who did not have bronchoscopy were more likely to die than were bronchoscopy-negative patients (P < .05), after adjusting for severity of illness. Bronchoscopy use may have contributed to better outcomes for persons treated for HIV-related PCP.

A rapid preadmission method for predicting inpatient course of disease for patients with HIV-related Pneumocystis carinii pneumonia.

Pneumocystis carinii pneumonia (PCP) has been the most common reason for hospitalization and the most common cause of death for persons with HIV infection. Hospital mortality rates for PCP range from 10 to 60%. Studies that evaluate differences in hospital mortality rates must control for differences in patient severity of illness. We developed a simple staging system for categorizing severity of illness in patients with PCP. We analyzed the relation between clinical factors and in-hospital mortality for 576 hospitalized patients with HIV-related PCP treated at 56 hospitals for the years 1987 to 1990. Four stages of PCP could be identified based on three routinely measured clinical variables: alveolar-arterial oxygen difference, total lymphocyte count, and body mass index. The mortality rate increased by stage: 1% for Stage 1, 8% for Stage 2, 23% for Stage 3, and 48% for Stage 4. The four-stage severity system compared well with previous models developed for AIDS and for PCP, and is easier to use in clinical practice. Our staging system identifies patients with a high and low risk of in-hospital death upon admission. Physicians may benefit from consideration of PCP stage in deciding on management strategies. In addition, researchers involved in clinical trials of new agents for PCP might consider stratification by PCP stage in order to define homogenous groups.

A controlled trial of early versus late treatment with zidovudine in symptomatic human immunodeficiency virus infection. Results of the Veterans Affairs Cooperative Study.

BACKGROUND: Zidovudine is recommended for asymptomatic and early symptomatic human immunodeficiency virus (HIV) infection. The best time to initiate zidovudine treatment remains uncertain, however, and whether early treatment improves survival has not been established. METHODS: We conducted a multicenter, randomized, double-blind trial that compared early zidovudine therapy (beginning at 1500 mg per day) with late therapy in HIV-infected patients who were symptomatic and had CD4+ counts between 0.2 x 10(9) and 0.5 x 10(9) cells per liter (200 to 500 per cubic millimeter) at entry. Those assigned to late therapy initially received placebo and began zidovudine when their CD4+ counts fell below 0.2 x 10(9) per liter (200 per cubic millimeter) or when the acquired immunodeficiency syndrome (AIDS) developed. RESULTS: During a mean follow-up period of more than two years, there were 23 deaths in the early-therapy group (n = 170) and 20 deaths in the late-therapy group (n = 168) (P = 0.48; relative risk [late vs. early], 0.81; 95 percent confidence interval, 0.44 to 1.59). In the early-therapy group, 28 patients progressed to AIDS, as compared with 48 in the late-therapy group (P = 0.02; relative risk, 1.76; 95 percent confidence interval, 1.1 to 2.8). Early therapy increased the time until CD4+ counts fell below 0.2 x 10(9) per liter (200 per cubic millimeter), and it produced more conversions from positive to negative for serum p24 antigen. Early therapy was associated with more anemia, leukopenia, nausea, vomiting, and diarrhea, whereas late therapy was associated with more skin rash. CONCLUSIONS: In symptomatic patients with HIV infection, early treatment with zidovudine delays progression to AIDS, but in this controlled study it did not improve survival, and it was associated with more side effects.

Effect of iron on production of a possible virulence factor by Plesiomonas shigelloides.

Plesiomonas shigelloides, when grown in an iron-poor medium (syncase), produces a substances that causes elongation of Chinese hamster ovary (CHO) cells similar to that produced by cholera toxin. When syncase is supplemented with iron, the ability of P. shigelloides (but not of Vibrio cholerae) to produce this elongation of CHO cells is lost. Iron depletion of the growth medium appears to be essential for the CHO cell elongation produced by P. shigelloides but is not essential for the production of toxin by V. cholerae. The possible role of iron regulation of this potential virulence factor warrants further study.

Spirochete-like organisms in the human gastrointestinal tract.

Spirochete-like organisms were first detected in human feces in 1884. In the century since that observation an appreciable amount of epidemiologic and morphologic information has been published; nevertheless, it is not known how many species of cultivable human intestinal spirochetes exist, nor is the role of these organisms in health and disease known. Recent advances in microbiologic techniques, coupled with the recognition that the rate of carriage of such spirochetes in certain populations is approximately 30%-40%, should provide the impetus for careful scientific study of these organisms and of their importance-if any-to human health.

A multicenter, double-blind, trimethoprim-sulfamethoxazole controlled study of enoxacin in the treatment of patients with complicated urinary tract infections.

In a double-blind, randomized, controlled trial, 249 patients with complicated urinary tract infections received either 400 mg. enoxacin or 160 mg. trimethoprim plus 800 mg. sulfamethoxazole orally every 12 hours for 14 days. The clinical outcome at the end of treatment revealed that all 89 evaluable patients (100 per cent) in the enoxacin group and 88 of 90 (98 per cent) in the trimethoprim-sulfamethoxazole group had satisfactory clinical responses (cure or improvement). Bacteriological effectiveness was measured cumulatively based on responses during and at the end of treatment, and 7 days later at followup. Satisfactory bacteriological responses (eradication or superinfection at all evaluations throughout the study) were achieved in significantly more (p equals 0.03) patients treated with enoxacin (93 per cent) than in those treated with trimethoprim-sulfamethoxazole (83 per cent). Both study medications were well tolerated. These results indicate that oral enoxacin was more effective clinically and bacteriologically (the latter statistically so) than trimethoprim-sulfamethoxazole when given as empiric therapy in the treatment of complicated urinary tract infections.

Disseminated infection caused by urease-negative Cryptococcus neoformans.

We report a case of fungemia and disseminated disease caused by a urease-negative strain of Cryptococcus neoformans in a patient with the acquired immune deficiency syndrome. Except for failure to hydrolyze urea, the microbiological characteristics of the isolate were typical of C. neoformans. Laboratory specialists should be aware of the occurrence of atypical strains of C. neoformans, particularly those recovered from patients with the acquired immune deficiency syndrome.

Suppurative thrombophlebitis due to Aeromonas.

A patient developed lethal suppurative thrombophlebitis and adjacent soft-tissue infection caused by Aeromonas. Potential risk factors included corticosteroid therapy and the use of warm tap water compresses at the site of intravenous catheter-related phlebitis. This case demonstrates the rapidly invasive characteristics of Aeromonas and the need for early surgical intervention in suppurative thrombophlebitis.

Effect of incubation temperature on growth and soluble protein profiles of motile Aeromonas strains.

Motile Aeromonas spp. are said to have an optimal growth temperature of 28 degrees C. We performed growth studies on 24 isolates at 29 and 37 degrees C and found that the optimal growth temperature was not necessarily 28 degrees C. We also detected temperature-dependent differences in soluble protein production in some of these strains.

In vitro production of cholera toxin-like activity by Plesiomonas shigelloides.

Although Plesiomonas shigelloides is considered to cause diarrhea in humans, the mechanisms by which it might do so are not known. Enteric pathogens such as Vibrio cholerae and some strains of Escherichia coli produce enterotoxins that activate adenylate cyclase, increase production of cyclic AMP, and thereby cause elongation of Chinese hamster ovary (CHO) cells in tissue culture. We grew 28 strains of P. shigelloides and the type strain in an iron-depleted medium, and sterile filtrates were examined in CHO cell culture. Filtrates from 24 of the 29 strains produced elongation of CHO cells. These changes could be prevented by heating or by preincubation of the filtrate with cholera antitoxin. These data indicate that P. shigelloides elaborates a cholera-like toxin; such a substance might be important in the pathogenesis of P. shigelloides-associated diarrhea.

Intravenous catheter-associated Malassezia furfur fungemia.

Malassezia furfur, a lipophilic yeast that is the etiologic agent of tinea versicolor, has not been considered as a cause of serious illness in adults in the past. Two adults are described in whom Malassezia furfur fungemia developed while receiving total parenteral nutrition supplemented with lipids. The organism was identified in blood cultures from both patients only after isolation media were supplemented with a source of fatty acids. Because M. furfur will grow only in media supplemented with fatty acids, clinicians should alert the laboratory whenever a lipophilic organism is suspected to be present in blood cultures.