Older donors and kidney transplantation

Reluctance to use kidneys from older donors (>50 years of age) is based on reports of inferior results. We reviewed our experience with 45 kidneys transplanted from older donors. Primary nonfunction, immediate graft function, and 1-, 2- and 3-year graft survival rates were similar to those obtained with kidneys transplanted from donors aged between 20 and 40 years. Renal function at 1 year (as measured by serum creatinine) was poorer in kidneys from older donors. No beneficial effect with respect to graft survival was noted with cyclosporin therapy compared to conventional immunosuppression; however, the numbers are small. We conclude that kidneys from older donors are a valuable source for transplantation.     

Fluoride uptake and retention at various stages of rat molar enamel development

Suckling rat pups were given intraperitoneal fluoride injections at selected ages so that we could study fluoride uptake in the enamel of the maxillary first molar at various stages of enamel development. Plasma fluoride levels in six-day-old and 11-day-old pups were monitored following the intraperitoneal injection of fluoride. The findings indicate that: (1) fluoride was more easily taken up and retained during the early stages of enamel formation, but fluoride uptake can occur during all stages of enamel formation; (2) when injections were started early in enamel formation, more fluoride was contained in the enamel of the maxillary first molar at 13 days of age; and (3) the same dose of fluoride per gram body weight resulted in greater exposure to elevated plasma fluoride levels in six-day-old pups than in 11-day-old pups.     

Measles in developing countries. Part II. The predicted impact of mass vaccination

A mathematical model is developed to mimic the transmission dynamics of the measles virus in communities in the developing world with high population growth rates and high case fatality rates. The model is used to compare the impacts of different mass vaccination programmes upon morbidity and mortality arising from infection by measles virus. Analyses identify three conclusions of practical significance to the design of optimal vaccination programmes. First, there is no single optimum age at which to vaccinate children for all urban and rural communities in developing countries. For a given community the best age at which to vaccinate depends critically on the age distribution of cases of infection prior to the introduction of control measures. Second, numerical studies predict that the introduction of mass vaccination will induce a temporary phase of very low incidence of infection before the system settles to a new pattern of recurrent epidemics. Mass vaccination acts to lengthen the inter-epidemic period in the post-vaccination period when compared with that prevailing prior to control. Third, numerical simulations suggest that two-phase and two-stage vaccination programmes are of less benefit than one-stage programmes (achieving comparable coverage) aimed at young children. The paper ends with a discussion of the needs for: improved programmes of data collection; monitoring of the impact of current vaccination programmes; and the development of models that take account of viral transmission dynamics, host demography and economic factors.     

Retinoblastoma. The relationship of proliferating cells to blood vessels

In 150 retinoblastomas the authors found a uniform thickness of the cuff of viable retinoblastoma cells that surrounds blood vessels. The mean thickness was 98.7 microns with a standard deviation of 11.9 microns. The cross-sectional area of the cuff was negatively correlated with the mitotic activity in the cuff and positively correlated with the diameter of the central vessel. The mitotic activity in the cuff of cells was inversely related to the distance from the central blood vessel. When the cuff was divided into three concentric rings, the inner ring contained a mean of 6.2 mitotic figures, the middle ring contained a mean of 2.9 mitotic figures, and the outer ring contained a mean of 0.6 mitotic figures. This pattern of growth is similar to that observed in other rapidly growing neoplasms in humans and experimental animals. In these tumors this pattern results from reduction in oxygen tension with increased distance from the central blood vessel.     

Conversion of choledochojejunostomy stents to jejunal feeding tubes for postoperative enteral alimentation

The problem of protein calorie malnutrition following major gastrointestinal surgery can be treated with central venous or enteric alimentation, with the latter being preferred. The authors describe a simple technique for the conversion of biliary stents placed after pancreaticoduodenal surgery into jejunal feeding tubes when the stenting function is no longer needed. Three illustrative cases are presented. In each case, the procedure took less than 30 min and had no associated morbidity. This technique allows early conversion from central venous to enteric alimentation without the need to create a second surgical enterostomy.