Fluid mechanics of bloodmeal uptake by Leishmania-infected sandflies.

The fluid mechanics of blood flow in the pharynx and cibarium of Phlebotomus papatasi are described using a simple static model. The flow is characterized as viscous laminar. The Hagen-Poiseuille equation is used to assess the effects of attached parasites in the foregut of Leishmania-infected sandflies on blood flow. The reductions in flow rate imposed by parasite colonization of the pharynx and cibarium will reduce the ability of an infected fly to take a bloodmeal, thus encouraging further probing, enhancing transmission. Regurgitation of the contents of the foregut is also possible. This will aid the deposition of infective forms from the foregut. Transmission by means of regurgitation of parasites from the midgut is considered unlikely.

Mechanoreceptor--trypanosome interactions in the labrum of Glossina: fluid mechanics.

The fluid mechanics of the flow of blood through the labrum of Glossina is described in uninfected and trypanosome infected flies. The flow is characterised by the Reynolds number, and a frequency parameter for the pulsating flow and non-newtonian viscosity effects are considered. The effects of colonies of trypanosomes on the flow rate in the labrum and the interactions between colonies of Trypanosoma (Nannomonas) congolense and Trypanosoma (Trypanozoon) brucei and mechanoreceptors in the proximal third of the labrum are described. The direct association between trypanosomes and mechanoreceptors and the reduction in flow rate imposed by trypanosome colonies in the food canal distal to the mechanoreceptors will impair detection of stimuli by them. The epidemiological implications of these and earlier observations are discussed.

IGF-1 and IGFBP-3 screening for disorders of growth hormone secretion.

AIM: To assess the value of plasma assays of insulin like growth factor (IGF-1) and insulin like growth factor binding protein 3 (IGFBP-3) in the diagnosis of growth hormone disorders in children and adults. METHODS: Plasma IGF-1 and IGFBP-3 were measured in 47 children referred for the assessment of short stature, 26 adult subjects with hypopituitarism and in 10 adult subjects with acromegaly. Findings were compared with results obtained in 148 normal children and 124 normal adult subjects who comprised the reference range. RESULTS: Levels of both growth factors and especially IGF-1 are highly age dependent in normal children and adults. Six of 47 short children had growth hormone deficiency and in these cases both IGF-1 and IGFBP-3 were close to the lower limit or below the normal reference range. In young children ( < 10 yr) IGFBP-3 was more informative than IGF-1, distinguishing normal short children from those with growth hormone deficiency. IGF-1 levels were raised in all 10 acromegalic adults, eight of whom had normal levels of IGFBP-3. Similarly growth hormone deficient adults were better identified (23 of 26 patients) by IGF-1 whereas IGFBP-3 was subnormal in only eight cases. CONCLUSIONS: Provided results are reviewed in relation to an age related normal reference range, both IGF-1 and IGFBP-3 are simple and convenient screening tests for assessing growth hormone deficiency in children. In adults plasma IGF-1 is the diagnostic test for a disorder of growth hormone excess. Low IGF-1 in an adult with a history of pituitary disease strongly suggests the presence of growth hormone deficiency.

Are we using the right irrigation system?

The relationships between bladder pressure and irrigant fluid flow rate were tested using two commonly used supply systems and a 27 FG Storz resectoscope. Simple and inexpensive modifications would enable transurethral prostatectomy to be carried out with reduced intravesical pressure and less risk of fluid absorption. With a continuous suction resectoscope, the modified system allows accurate balance of the inflow and outflow of the irrigant fluid.

Feeding behaviour of tsetse flies infected with salivarian trypanosomes.

Although much is known about factors which determine infection rates of salivarian trypanosomes (subgenera Nannomonas, Duttonella and Tryanozoon) in the tsetse fly Glossina, it is not clear why infection rates of Trypanozoon are high in mammalian hosts but low in wild-caught Glossina and why trypanosomiasis occurs where Glossina is not readily detectable. We report here that the feeding behaviour of trypanosome-infected Glossina differed from that of uninfected control flies. Infected flies probed more frequently and fed more voraciously. We describe a specific relationship between trypanosomes and the mechanoreceptors responsible for detecting the rate of blood flow, and show how infection affects that rate in the labrum. We suggest that the observed differences in feeding behaviour result from impaired function of the labral mechanoreceptors in infected Glossina.