Comparison of two pumping speed measuring methods of oil diffusion pumps

This paper presents a comparative study of two pumping speed measurement methods recommended for oil diffusion pumps. The methods used are the test dome method and the conductance tube method with an auxiliary pumping system which is used at very low pressures when the throughput is below 10^?5 Nm s^?1 (～ 0.1 μl s^?1). It is found that, in order to obtain the comparative results in the overlapping pressure region on the speed measurement of oil diffusion pumps by these two methods, the conductance tube in the conductance tube method should be located at a height 1.2 D from the pump mouth when the position of the inlet gauge is at a distance D/2 from the pump flange, i.e. at the same position as recommended in the dome method to obtain the intrinsic speed of the pump.     

Vaccination of pregnant macaques protects newborns against mucosal simian immunodeficiency virus infection

Simian immunodeficiency virus (SIV) infection of newborn rhesus macaques is a rapid, sensitive animal model of human pediatric AIDS. Newborn macaques were readily infected by uncloned SIVmac following oral-conjunctival exposure and had persistently high viremia and rapid development of AIDS. In contrast, when 3 pregnant macaques were vaccinated against SIV, 2 of the newborns that had transplacentally acquired antiviral antibodies were protected against mucosal SIV infection at birth. These results suggest that intervention strategies such as active immunization of human immunodeficiency virus (HIV)-infected pregnant women and anti-HIV immunoglobulin administration may decrease the rate of perinatal HIV infection.     

Preventing perinatal transmission of HIV--costs and effectiveness of a recommended intervention

OBJECTIVE: To calculate the national costs of reducing perinatal transmission of human immunodeficiency virus through counseling and voluntary testing of pregnant women and zidovudine treatment of infected women and their infants, as recommended by the Public Health Service, and to compare these costs with the savings from reducing the number of pediatric infections. METHOD: The authors analyzed the estimated costs of the intervention and the estimated cost savings from reducing the number of pediatric infections. The outcome measures are the number of infections prevented by the intervention and the net cost (cost of intervention minus the savings from a reduced number of pediatric HIV infections). The base model assumed that intervention participation and outcomes would resemble those found in the AIDS Clinical Trials Group Protocol 076. Assumptions were varied regarding maternal seroprevalence, participation by HIV-infected women, the proportion of infected women who accepted and completed the treatment, and the efficacy of zidovudine to illustrate the effect of these assumptions on infections prevented and net cost. RESULTS: Without the intervention, a perinatal HIV transmission rate of 25% would result in 1750 HIV-infected infants born annually in the United States, with lifetime medical-care costs estimated at $282 million. The cost of the intervention (counseling, testing, and zidovudine treatment) was estimated to be $ 67.6 million. In the base model, the intervention would prevent 656 pediatric HIV infections with a medical care cost saving of $105.6 million. The net cost saving of the intervention was $38.1 million. CONCLUSION: Voluntary HIV screening of pregnant women and ziovudine treatment for infected women and their infants resulted in cost savings under most of the assumptions used in this analysis. These results strongly support implementation of the Public Health Service recommendations for this intervention.     

Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses

Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight (P < 0.05). From pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1, maximal O2 uptake (VO2max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group, VO2max was 29% higher (151 +/- 2 ml.kg-1.min-1 in both C and OLT groups) than pretraining values. There was no significant reduction in VO2max until after 6 wk detraining when VO2max was 137 +/- 2 ml.kg-1.min-1. By 12 wk detraining, mean VO2max was 134 +/- 2 ml.kg-1.min-1, still 15% above pretraining values. When overtraining developed, VO2max was not different between C and OLT groups, but maximal values for CO2 production (147 vs. 159 ml.kg-1.min-1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease in VO2max and, after prolonged training, decreases in VO2max occurred slowly during detraining.     

Racial differences in rate of CD4 decline in HIV-1-infected homosexual men

OBJECTIVE: To determine whether racial differences exist in the rate of CD4 lymphocyte decline in HIV-1-infected homosexual men. DESIGN: Prospective cohort study. STUDY POPULATION: Non-Hispanic white (n = 321) and black (n = 102) HIV-1-seropositive homosexual and bisexual men were recruited from the Baltimore/Washington, DC metropolitan areas between 1984-1985 and 1987-1990, and evaluated semiannually. MAIN MEASUREMENTS: Changes in CD4 lymphocyte count and CD4 percentage over time were analysed using linear regression methods for the 271 white and 69 black participants who had at least four semiannual CD4 lymphocyte measurements. RESULTS: Rate of decline in CD4 lymphocyte count over 6 months was much slower among black than white seroprevalent men at all levels of baseline CD4 count (baseline 201-400 x 10(6)/l: + 0.24 versus -17.7 x 10(6)/l; 401-600 x 10(6)/l: -11.3 versus -23.9 x 10(6)/l; 601-800 x 10(6)/l: -15.1 versus -35.2 x 10(6)/l; > 800 x 10(6)/l: -4.3 versus -42.7 x 10(6)/l for black versus white, respectively), although this was only statistically significant for the lowest and highest strata of baseline CD4 count. These racial differences persisted after adjustment for recruitment period (1984-1985 or 1987-1990), follow-up duration, age and zidovudine therapy or Pneumocystis carinii pneumonia prophylaxis. Similar findings were observed among the 70 white and 11 black seroconverters. Black participants were also less likely than a subgroup of white participants matched on baseline CD4 lymphocyte count to be HIV-1 p24 antigen-positive. However, after acid dissociation of samples initially p24 antigen-negative, there were no significant differences in the prevalence of p24 antigenemia at enrollment or after 1 year of follow-up. CONCLUSIONS: This analysis suggests a more gradual decline in CD4 lymphocyte count among black than white Americans. The clinical significance of and reasons for this are unclear, but the lower prevalence of p24 antigenemia due to immune complexing among black Americans suggests that racial differences in the immune response to HIV may exist. Additional studies are needed to validate these findings in a larger cohort of non-whites, and to assess their relationship with other measures of cell-mediated immune function.     

Amplification of 16S rRNA genes from Frankia strains in root nodules of Ceanothus griseus, Coriaria arborea, Coriaria plumosa, Discaria toumatou, and Purshia tridentata

To study the global diversity of plant-symbiotic nitrogen-fixing Frankia strains, a rapid method was used to isolate DNA from these actinomycetes in root nodules. The procedure used involved dissecting the symbiont from nodule lobes; ascorbic acid was used to maintain plant phenolic compounds in the reduced state. Genes for the small-subunit rRNA (16S ribosomal DNA) were amplified by the PCR, and the amplicons were cycle sequenced. Less than 1 mg (fresh weight) of nodule tissue and fewer than 10 vesicle clusters could serve as the starting material for template preparation. Partial sequences were obtained from symbionts residing in nodules from Ceanothus griseus, Coriaria arborea, Coriaria plumosa, Discaria toumatou, and Purshia tridentata. The sequences obtained from Ceonothus griseus and P. tridentata nodules were identical to the sequence previously reported for the endophyte of Dryas drummondii. The sequences from Frankia strains in Coriaria arborea and Coriaria plumosa nodules were identical to one another and indicate a separate lineage for these strains. The Frankia strains in Discaria toumatou nodules yielded a unique sequence that places them in a lineage close to bacteria that infect members of the Elaeagnaceae.     

Use of synthetic material in sling surgery: a minimally invasive approach

Traditionally, autologous material has been favored over synthetic material in the construction of pubovaginal slings for the treatment of female stress urinary incontinence (SUI). This preference arose largely because of concern about an increased incidence of infection or sling erosion when synthetic materials are used. However, when care is taken to minimize the amount of synthetic material, reduce total operative time, and limit exposure of the material to the operative field, female SUI can be treated effectively with synthetic material with an acceptably low complication rate. Furthermore, utilization of slings constructed with artificial graft material can be minimally invasive, cost effective, and well tolerated.