Effect of alpha thalassaemia on the rheology of homozygous sickle cell disease

A study of rheological determinants (plasma viscosity, whole-blood viscosity, and erythrocyte deformability) was made in 24 matched pairs of patients with homozygous sickle cell disease, with and without homozygous x-thalassaemia. Patients with coexisting x-thalassaemia showed a significant increase in erythrocyte deformability measured as filtration of washed erythrocytes through 5 um diameter pores and also as viscosity of whole blood at high shear rate (230s-1) and standard haematocrit (0.45). This rheological advantage may explain the beneficial effect of x-thalassaemia 2 on haematological parameters and clinical events in homozygous sickle cell disease (AU)

Evaluation of a membrane (Nuclepore) filtration method using capillary blood for the detection of microfilariae

The efficacy of a membrane (Nuclepore) filtration technique using capillary blood (100 mm 3) for the detection of blood-circulating microfilariae was investigated during a prevalence survey for Wuchereria bancrofti and Mansonella ozzardi in north Trinidad by comparing results thus obtained with results from conventional thick smear preparations (25mm3) and from membrane (Nuclepore) filtration of venous blood (1 ml). Prevalence rates of W. bancrofti were 14 percent by thick smear, 17 percent by filtration of capillary blood and 6 percent by filtratioon of venous blood. For M. ozzardi the corresponding rates were 27 percent, 29 percent and 31 percent. A total of 389 persons was examined by all three methods. Microfilaria detection rates for both of the filtration techniques were significantly higher than by thick smear preparation, with the exception of results for M. ozzardi obtained by filtration of capillary blood. There was no significant difference between the number of positive persons detected by filtration of capillary blood and filtration of venous blood. Significantly higher microfilaria densities per unit volume of blood were recorded by thick smear preparation and filtration of capillary blood than by filtration of venous blood. Whereas results for the two capillary blood techniques were similar. In the detection of low density microfilaraemias, membrane filtration of capillary blood provides a practical and sensitive alternative to venous blood filtration and has the additional advantage of capilary blood collection rather than venepuncture.(AU)

Direct filtration for recovery of Schistosoma mansoni carcariae in the field

The recovery of schistosome cercariae from natural waters has been limited by variations in turbidity and in the accuracy of recovery with different techniques. A modification of the Rowan vacuum paper filtration method employing a battery-operated pumping system, a glass-silicone plate filter, and a specially designed filter holder is described and evaluated. Field tests of St. Lucia indicate a mean filtration volume of 12.2 litres per filters at a mean turbidity of 20.3 Jackson turbidity units. Overall, 86 percent of the volumes filtred per filter were in excess of 6 litres. Particle size, rather than turbidity, was found to be the main factor influencing filter blockage, reading time, and accuracy. Recoveries of 0.01 cercaria (Schistosoma mansoni) per litre sampled were obtained, but the practical limit of the method is considered to be closer to 0.1 cercaria per litre sampled.(AU)

Effect of seasonal effluent chlorination on coliforms in Jamaica Bay

Quite frequently, the need for chlorinating effluents discharged to receiving waters not used for recreational purposes is questioned. A study was undertaken to demonstrate that chlorination of wastewater treatment plant effluents that, by volume, represented less than 0.5 percent of the receiving water volume, would significantly improve the bacteriological quality of Jamaica Bay. This estuary was an ideal site for such an investigation because more than 99 percent of the treated effluents being discharged to the Bay are chlorinated on a seasonal basis only- May 15 to September 30. (AU)