HIV-1 and HIV-2 antibodies in pregnant women in the City of Maputo, Mozambique. A comparative study between 1982/1983 and 1990

The seroprevalence of HIV-1 and HIV-2 among pregnant women in Maputo, the capital of Mozambique, was compared between the years 1982/83, 1988 and 1990. None of the 432 serum samples collected in 1982/83 was positive for HIV antibodies whereas in 1988 the HIV-1 and HIV-2 seroprevalence was 0.4% (2/500) and 0.6% (3/500), respectively, and in 1990 0.6% (12/2014) and 0.2% (4/2014), respectively. These results indicate that HIV infection has been introduced recently in Maputo and is spreading at a slow rate among women.     

Ignition of powder materials under friction

It is shown that ignition may occur under light frictional pressure. In the case of friction applied to a powder, there are two limits of ignition in terms of the frictional pressure. A frictional approach permits a high degree of compaction of powder at low frictional pressure (∼10 kg/cm²). The influence of the material of the frictional body on sample heating and ignition is investigated. Activation of chemically active powder under the action of friction is observed. A discussion of the results is presented. Institute of Structural Macrokinetics, Russian Academy of Sciences, Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 6, pp. 14–19, November–December, 1995.     

A 13-week subchronic toxicity study of josamycin in F344 rats

A 13-week subchronic toxicity study of josamycin was performed in male and female F344 rats to determine the maximum tolerable dose (MTD) for subsequent investigation of the carcinogenicity. As animals refused to take diet containing 5.0% josamycin in our preliminary study, dose levels in the present study were determined as 0, 0.16, 0.32, 0.63, 125 and 2.5% in diet. Rats were randomly allocated to 6 groups, each consisting of 10 males and 10 females. No animal died during the administration period and no group showed significant changes in body weight gain. Definite toxicity of josamycin was not noted in hematological and serum biochemical examinations. Histopathological examinations revealed no particular findings related to josamycin administration except cecal enlargement in the 1.25 and 2.5% groups. based on the results of the present study, it was concluded that the MTD of josamycin in 2.5% in diet, because the dietary dose level of 2.5% proved to exert no significant toxicological signs.     

Contribution of cadherins to directional cell migration and histogenesis in Xenopus embryos

Perturbation of adhesion mediated by cadherins was achieved by over-expressing truncated forms of E- and EP-cadherins (in which the extracellular domain was deleted) in different blastomeres of stage 6 Xenopus laevis embryos. Injections of mRNA encoding truncated E- and EP-cadherins into A1A2 blastomeres resulted in inhibition of cell adhesion and, at later stages, in morphogenetic defects in the anterior neural tissues to which they mainly contribute. In addition, truncated EP-cadherin mRNA produced a duplication of the dorso-posterior axis in a significant number of cases. The expression of truncated E- and EP-cadherins in blastomeres involved in gastrulation and neural induction (B1B2 and C1), led to the duplication of the dorso-posterior axis as well as to defects in anterior structures. Morphogenetic defects obtained with truncated EP-cadherin were more severe than those induced with truncated E-cadherin. Cells derived from blastomeres injected with truncated EP-cadherin mRNA, dispersed more readily at the blastula and gastrula stages than the cells derived from the blastomeres expressing truncated E-cadherin. Presumptive mesodermal cells expressing truncated cadherins did not engage in coherent directional migration. The alteration of cadherin-mediated cell adhesion led directly to the perturbation of the convergent-extension movements during gastrulation as shown in the animal cap assays and indirectly to perturbation of neural induction. Although the cytoplasmic domains of type I cadherins share a high degree of sequence identity, the over-expression of their cytoplasmic domains induces a distinct pattern of perturbations, strongly suggesting that in vivo, each cadherin may transduce a specific adhesive signal. These graded perturbations may in part result from the relative ability of each cadherin cytoplasmic domain to titer the beta-catenin.     

Characterization of solid-phase welds between Ti---6A1---2Sn---4Zr---2Mo---0.1Si and Ti---13.5A1---21.5Nb titanium aluminide

Dissimilar-alloy welds have been produced between Ti---6Al---2Sn---Z4---2Mo---0.1Si (wt. %) and Ti---13.5Al---21.5 NB (wt.%) titanium aluminde using the three different solid-phase welding processes that create significantly different thermo-mechanical conditions at the weld interface. Exposure to supertransus temperatures, appreciable deformation and rapid cooling of the weld interface region during linear-friction welding promote dynamic recrystallization of beta grains and beta decomposition to fine martensitic products. In contrast, diffusion welding at temperatures below the base metal beta transus temperatures and at relatively low pressures minimizes deformation and microstructural variations in the weld interface region relative to the unaffected base metal. During capacitor-discharge resistance spot welding, extremely rapid heating of the weld interface region to near-solidus temperatures, and subsequent rapid cooling, result in the formation of a metastable, ordered-beta microstructure in the Ti---s13.5Al---21.6Nb and fine alpha-prime martensite in the Ti---6Al---2Sn---4Zr---2Mo-0.1Si.     

Effect of alloying elements on the solidification characteristics and microstructure of Al- Si- Cu- Mg- Fe 380 alloy

The effect of varying the major alloying elements within the limits of specification on the solidification behavior, fluidity, and microstructure of a 380 alloy has been studied at two cooling rates. The thermal analysis technique has been used to study the solidification behavior. The alloying elements investigated ranged from 3.22 to 4.09 pct copper, 1.01 to 1.70 pct iron, 0.06 to 0.50 pct magnesium, 1.69 to 3.00 pct zinc, and 0.16 to 0.46 pct manganese. The results show that the solidification behavior of the 380 alloys is complicated, and the cooling curve at 0.4 ‡C/s indicates six reactions taking place during the process of solidification. Cooling curves obtained for each of the alloying element additions, their analysis, and the resultant microstructures are discussed.     

Oxidation of boron silicide and materials based on it

Boron silicide and compounds based on it containing titanium, chromium, nickel, and yttrium and scandium oxides are studied for their oxidation in air from room temperature to 1300°C. It is shown that chromium boride markedly improves the heat resistance of B₄Si over a wide temperature range (700–1300°C) probably as a result chromium-oxide dissolution in borosilicate glass and alteration of its structure. A favorable effect of yttrium and scandium oxides as well of nickel silicide appears at above 100°C as a result of forming complex oxide compounds in the scale.