Low-energy supersymmetry and the Tevatron bottom-quark cross section.

A long-standing discrepancy between the bottom-quark production cross section and predictions of perturbative quantum chromodynamics is addressed. We show that pair production of light gluinos, of mass 12 to 16 GeV, with two-body decays into bottom quarks and light bottom squarks, yields a bottom-quark production rate in agreement with hadron collider data. We examine constraints on this scenario from low-energy data and make predictions that may be tested at the next run of the Fermilab Tevatron collider.

Prevalence of chronic hepatitis B virus infection in pregnant black women living in Soweto.

Urban black children have an appreciably lower hepatitis B virus (HBV) carrier rate than rural Black children. The purpose of this study was to determine the carrier rate in the preceding generation of urban-born Blacks, in order to establish how rapidly the reduction in carrier rate following urbanization has occurred. HBV markers were measured by radioimmunoassay in the serum of 616 urban-born and 618 rural-born pregnant Black women living in Soweto. HBV carriage was significantly less frequent in the urban-born (1.3%) than in the rural-born women (4.0%; P less than 0.05). Total HBV exposure was also less common in the urban-born women (35.2% compared with 44.7%; P less than 0.001). HBV carrier rates were the same in women whose mothers were urban-born (1.31%) and those with rural-born mothers (1.68%). Only three rural-born and no urban-born women had replicative HBV infection. These findings suggest that the decrease in the HBV carrier rate with urbanization is abrupt, occurring in the first generation born in the urban environment.

The value of serum concentrations of tissue polypeptide antigen in the diagnosis of hepatocellular carcinoma.

Tissue polypeptide antigen (TPA) is a polypeptide isolated from malignant cells and found in high concentration in the serum of patients with various tumors. No information is available with respect to hepatocellular carcinoma (HCC). Serum TPA concentrations were measured in 290 patients with HCC, 85 healthy controls, 33 patients with amebic hepatic abscesses, 43 with chronic hepatitis or cirrhosis, and 39 with acute hepatitis. Raised values were found in 96% of the HCC patients, but also in 61% of patients with amebic abscesses, 86% with chronic hepatic parenchymal disease, and 90% with acute hepatitis. If a cut-off level of 500 IU/L was used, this reduced the sensitivity of TPA in HCC to 46%, but still left 46% of patients with acute hepatitis with raised values. TPA is comparable in sensitivity with alpha-fetoprotein as a marker for HCC, but its lack of specificity severely limits its clinical usefulness.

Prevalence of hepatitis B virus infection among black children in Soweto.

Roughly 15% of black children in rural areas of southern Africa are carriers of the hepatitis B virus. The purpose of the present study was to determine the prevalence of chronic hepatitis B virus infection among urban black children born and growing up in Soweto. A total of 2364 children were studied, ranging in age from 3 to 19 years, and of these, 1319 (56%) were girls. The children were drawn from the highest and the lowest socioeconomic classes. Serum samples were tested for all hepatitis B virus markers as well as IgG antibody against hepatitis A virus. HBsAg was detected in 23 (0.97%) of the children, anti-HBc and anti-HBs together in 155 (6.6%), anti-HBc alone in 17 (0.7%), and anti-HBs alone in 72 (3%). Of the 2364 children, 2097 (88.5%) were negative for all hepatitis B virus markers. IgG antibody to hepatitis A virus was present in 175 (97%) of a sample of 179 children. There was no difference in prevalence of hepatitis B virus markers between children from the upper and lower socioeconomic classes. HBsAg was more common in boys (16 out of 1043 (1.5%) than girls (seven out of 1321 (0.57%), and the prevalence of all hepatitis B virus markers increased with age. The youngest carrier of hepatitis B virus was 7 years old. The remarkable difference in the hepatitis B virus carrier rate between urban and rural black children offers a unique opportunity to investigate the favourable influences operating in an urban environment to limit the prevalence of hepatitis B virus infection.