A ß-galactosidase probe for the detection of cellular senescence by mass cytometry.

Mass cytometry (MC) is a powerful method that combines the cellular resolution of flow cytometry with the isotopic resolution of inductively coupled plasma mass spectrometry (ICP-MS). This combination theoretically allows for the simultaneous quantification of >80 different parameters at the single cell level, in turn allowing for the deep profiling of heterogeneous cell populations. The majority of available reagents for MC are antibodies labeled with heavy metal isotopes, allowing for the quantification of static biomarkers. To complement these reagents, we aim to develop small molecule reporters of cellular metabolism that are compatible with MC. Here we report a probe of ß-galactosidase activity capable of detecting cellular senescence. The galactoside probe contains a tellurophene reporter group and, when hydrolyzed, generates a quinone alkide. This reactive alkylating agent forms covalent tellurophene bearing conjugates with local nucleophiles, allowing for the quantification of ß-galactosidase activity in individual cells. Difluoromethyl and monofluoroethyl quinone alkide generating warheads were examined for their activities and compared in vitro and in vivo. We showed that the difluoromethyl derivative gave higher tellurium labelling in vitro and that the quinone methide was more reactive towards thiols than amines. In vivo the difluoromethyl derivative successfully labeled senescent cells with comparable selectivity to the commonly used fluorescent senescence probe C12FDG.

HBV infection: prevalence of core antibody and other markers in urban based, black school children in Kenya.

This paper reports a study of 279 sera obtained from children attending five schools in Nairobi, the capital of Kenya which is situated in a non-malarious zone. Their ages ranged from six to 16 years. The surface antigen of hepatitis B virus (HBV) was detected in 13 children (4.7%) including seven boys and six girls. The core and surface antibodies were measured by radioimmunoassay on 125 of the samples to study the pattern of infection in childhood and the interrelationships of different parameters of the infection. The core antibody by itself was observed in four children (3.2%). A total of 31 samples (24.8%) had both core and surface antibodies, 19 (15.2%) had only surface antibody. Thus, 48% of all school children tested had serological evidence of past exposure to the virus. The implications of these findings are discussed.