Evaluation of Doppler ultrasonography and dynamic contrast-enhanced CT in acute and chronic renal obstruction.

The development of a reliable, minimally invasive method of distinguishing physiologically significant renal obstruction from dilation without obstruction would have important clinical implications. As it is well known that renal blood flow decreases over time in the presence of obstruction, we investigated the ability of color flow Doppler ultrasonography and dynamic contrast-enhanced CT scanning to detect changes in blood flow in unilaterally obstructed porcine kidneys. In the initial phase of this study, the effect of acute unilateral obstruction were studied in nine pigs. The resistive index (RI) was measured with Doppler ultrasonography, and renal blood flow was quantitated with dynamic CT using tracer kinetic principles and deconvolution. The RI measurements were unable to distinguish between the obstructed kidneys and their controls. Dynamic CT scanning demonstrated a greater fall in blood flow in the obstructed kidney, and this change was significantly different from baseline. The same findings were supported by radiolabelled microsphere blood-flow measurement. In the chronic portion of the study, after surgical creation of a partial ureteric obstruction, the kidneys were studied by both techniques at 1, 2, and 3 weeks. Again, RI was unable to demonstrate any difference between obstructed and unobstructed kidneys, while CT showed a progressive fall in blood flow in each successive week that was statistically significant. Dynamic contrast-enhanced CT scanning is a promising diagnostic tool that might be used to distinguish a functionally significant renal obstruction from nonobstructive dilation. Further clinical studies to validate this technique are warranted.

A low cost microprocessor-controlled electrofusion and electroporation system.

An important recent development in the field of biotechnology has been the use of high electric fields to render cell membranes temporarily permeable (electroporation). Cells in this state are receptive to gene transfer or can be induced to fuse with each other (electrofusion) to form hybrid cells containing the combined characteristics of the parent cells. A major reason for fusing cells is to form hybridoma cells which secrete monoclonal antibodies. A problem for research workers has been the high price of some of the electrofusion equipment. This problem has been addressed by designing a device that is inexpensive (less than $800 Canadian) and can be assembled by an electronics technician. The system uses a Radio Shack CoCo III microcomputer which is programmed in BASIC and controls the electroporation voltage pulse amplitude (25-500 V) and duration (2-275 microseconds) to an electrofusion chamber; this yields electric field strengths of 0.25-5 kV cm-1 for a 0.1 cm electrode spacing. The system is capable of delivering pulse currents up to 3 A. This paper provides technical details on how to construct an instrument that has greater flexibility at less cost than comparable commercially available instruments.

[Perinatal intracranial hemorrhage due to immune thrombocytopenia]. / Hemorragia intracraneal perinatal por trombocitopenia inmune.

INTRODUCTION: Immune neonatal thrombocytopenia is caused by maternal antibodies (IgG) passing across the placenta, with subsequent destruction of foetal platelets. There are two forms, the iso-aloimmune forms, with an incidence of intracranial hemorrhage (ICH) in the neonatal period of 10-20%, and the autoimmune form with an incidence of only 1%. OBJECTIVE: To review the patients with this condition in a neonatal unit. CLINICAL CASES: During the past 12 years, three patients with ICH due to immune thrombocytopenia were attended in the neonatal unit. Three newborn babies had ICH (two intrauterine, at 30 and 33 weeks of gestation, and one postnatal) secondary to immune thrombocytopenia (two aloimmune and one autoimmune). Two births were by caesarean section and one was vaginal. All three had thrombocytopenia at birth (12,000; 23,000 and 56,000 platelets/mm3). Immunological study of the platelets from the patients with aloimmune thrombocytopenia showed the absence of HPA-1a in their mothers. The patients were treated with gammaglobulins and platelets. Intracranial hemorrhage was confirmed on neuroimaging in all cases. A porencephalic cyst was seen to have formed in two cases. The clinical course was satisfactory in two patients. However, the third patient had severe motor impairment and died 9 months later. In all three patients the PEV were altered and two had reduced visual acuity. CONCLUSIONS: 1. Perinatal ICH due to immune thrombocytopenia is uncommon, but potentially serious. 2. We suggest that cranial ecographic studies should be done in all newborn babies with immune thrombocytopenia even when no neurological disorder is seen. 3. Early diagnosis and suitable treatment may help to reduce the neurological sequelae. 4. The neurological complications are due to intraparenchymatous hemorrhage, and visual sequelae are frequent.

Isometric dynamic response of mammalian heart muscle due to step changes in the calcium concentration of the perfusing medium.

The isometric tension transient response of isolated kitten papillary muscle was found to exhibit direction-dependent dynamics when subjected to step changes in the calcium concentration of the bathing medium. The tension transient curves could be resolved into a minimum of two to three exponential components, which could be considered to indicate different calcium compounds or compartments within the muscle. However, a model relating calcium diffusion across the muscle to the dose-response curve indicates that the exponential components of the tension transient curves are due to the properties of calcium diffusion through the extracellular space, and that the direction-dependent dynamics are caused by the nonlinearity of the dose-response curve.