Thrombin activity by intrinsic activation of plasma in-vitro accelerates with increasing age of the donor.

Thrombotic diseases increase in incidence with advancing years and this might be partly due to an increased propensity for fibrin formation in older individuals. Accordingly we decided to investigate whether the time taken to generate 50% thrombin activity in vitro varied with the age of the plasma donor. Coagulation was initiated in defibrinated, diluted plasma by contact activation and thrombin activity measured using the chromogenic substrate, S2238. The rate of thrombin generation was assessed by measuring the time taken to reach 50% maximal activity (T50/s). There was a highly significant negative correlation between T50 and age, T50 declining from 93 s at 19 years to 71 s at 65 years (r = -0.637, p less than 0.0001). A strong negative correlation was demonstrated between T50 and FVII level (r = -0.415, p = 0.0007) and FVIII:C level (r = -0.465, p = 0.0001). Although FVII concentration correlated with age (r = 0.307, p = 0.014) no relationship was seen between age and FVIII:C. These data suggest that coagulation rates in plasma accelerate with age.     

AIDS and South Africa--towards a comprehensive strategy. Part II. Screening and control

In this, the second of a three-part series of articles in which we propose steps towards a comprehensive strategy for the control of HIV infection, we consider controversies relating to screening for HIV, the indications for and desirability of mandatory testing of certain groups at risk, and the place of voluntary testing in the control of HIV transmission and infection. Key recommendations are that mandatory testing of donors of blood and other vital tissues, patients on haemodialysis and haemodialysis unit staff is justified, and that children put up for adoption may require testing. We make further recommendations regarding HIV testing as a prerequisite for life insurance and recommend that voluntary testing be offered, supported by adequate pre- and post-test counselling. We consider that all health care workers should accept as their moral obligation the care and management of HIV-infected individuals, and that they should be adequately educated and skilled in such work. These recommendations were reached largely by consensus, although there were occasions when individual authors condoned recommendations with which they did not personally agree.     

Characterization of a YAC containing part or all of the Norrie disease locus

It has been shown from pulsed-field gel electrophoresis (PFGE)that the monoamine oxidase genes A and B (MAOA & MAOB) andDXS7 loci are physically very close. We have therefore extendedstudies on their relationship through the characterisation ofa 650 kb YAC isolated using L1.28 (recognising the DXS7 locus)as a probe. Restriction mapping of the YAC indicates that itcontains both MAOA and MAOB genes in addition to the DXS7 locus.The map derived from the YL1.28-YAC is compatible both withthe map from an independently derived YAC carrying MAOA andB genes and with the long range genomic map for the region.A series of subclones prepared from a 'phage library (lambdaDASH II) of the YAC have been characterised and have been employedto determine the end point of the deletion of a Norrie disease(NDP) patient who has been shown to lack both DXS7 and MAO codingsequences. The pattern of retention of subclones in the deletionpatient place the end point of the deletion within 30–130kb of the proximal end of the YAC. By combining the data withestablished recombination analysis, we provide evidence thatall or part of the NDP lies in the interval of approximately250kb within the YAC.