Medullary rays. Visualization during excretory urography.

The medullary rays are well-defined anatomic structures consisting of bundles of renal tubules which form in the renal cortex and continue through the renal medulla as the medullary striations. These structures are occasionally visualized during excretory urography in abnormal physiologic states characterized by tubular stasis and hyperconcentration of contrast material. Under these conditions, fine striations are visualized which correspond in position and orientation to these structures. The work of others has shown that in tubular stasis, contrast material is hyperconcentrated in the tubules. On microradiography in normal and obstructed kidneys, the highest concentrations of contrast material are seen in the lumen of collecting ducts. Lastly, retrograde injection of contrast material into the medullary rays produces a roentgen image similar to our illustrated cases.     

Pneumothorax: a complication of percutaneous aspiration of upper pole renal masses.

Pneumothorax is a rare complication of percutaneous needle aspiration of suspected upper pole renal cysts. This complication is of particular concern in elderly patients with compromised cardiopulmonary reserve who undergo this procedure on an outpatient basis. An upright expiratory chest film is recommended following needle aspiration of upper pole lesions for detection of asymptomatic pneumothorax.     

Cajal beyond the gut: interstitial cells in the urinary system--towards general regulatory mechanisms of smooth muscle contractility?

Interstitial cells of Cajal (ICC), similar to GI pacemakers have been identified throughout the urinary system. Although each part of the system serves a different function, ranging from peristalsis of the ureters, storage of urine by the bladder, and a sphincteric action by the urethra, they share a common mechanism in being able to generate phasic myogenic contractions. Even the urethra, often considered to be a 'tonic' smooth muscle, achieves an apparently sustained contraction by averaging numerous small asynchronous 'phasic' contractions. This activity can occur in the absence of any neural input, implying the presence of an intrinsic pacemaker. Intracellular microelectrode recordings from urethral muscle strips reveal electrical slow waves similar to those of the GI tract. To study this further, we isolated single cells from rabbit urethra and found not only smooth muscle cells (SMC), but a second cell type comprising -10% of the total. The latter cells were branched and non-contractile and closely resembled intestinal ICC. Electrophyiological studies revealed that, while the isolated smooth muscle cells were electrically quiescent, the 'ICC' fired electrical slow waves similar to those observed in the whole tissue. The basis of this difference was the presence of a large pacemaker current involving the activation of calcium-activated Cl channels by spontaneous intracellular Ca2+ waves. These, in turn, have been shown to be modulated by neurotransmitters such as nitric oxide, noradrenaline and ATP, thus providing a possible mechanism whereby neural regulation of the urethra, as well as spontaneous tone, may be mediated via ICC.     

Identification of potyviral amorphous inclusion protein as a nonstructural, virus-specific protein related to helper component

Antisera to amorphous inclusion (AI) proteins associated with infections by pepper mottle virus (PeMV) and the watermelon mosaic virus-1 strain of papaya ringspot virus (PRSV-W) were used to probe in vitro translation products of the viral RNAs. The major translation product of PeMV RNA in the rabbit reticulocyte lysate (RRL) system was a previously reported polypeptide of apparent molecular weight 78,000 (Mr 78K). It reacted with anti-AI serum, whereas the major translation product in the wheat germ (WG) system was a 30K polypeptide that did not react with the antiserum. These results, the Mr values, and analyses of peptides generated by partial digestion with proteinase indicate that the amino acid sequences of the 30K polypeptide and the (Mr) 51K AI protein are distinct subsets of the 78K polypeptide amino acid sequence. Similar results were obtained with PRSV-W except that the Mr values of the corresponding translation products are 110K (RRL) and 60K (WG). Thus the 5'-most region of the PeMV and PRSV-W RNAs (corresponding to 78K and 110K, respectively) appears to encode two proteins rather than one as previously supposed on the basis of RRL translation products. Reciprocal serological tests revealed that the tobacco vein mottling virus aphid transmission helper component protein was related to AI protein. There is direct evidence that the AI represent another potyviral-coded nonstructural protein and the first evidence that a biologically functional protein is related to a component of a potyviral inclusion.     

Detection of picogram quantities of potyviruses using a dot blot immunobinding assay

Highly sensitive direct visual detection of potyviruses was achieved using a dot blot immunobinding assay (DBIA). The small sample volumes required permit the detection of as little as 0.5 pg virus in purified preparations. The binding of rabbit antibodies could be visualized using goat anti-rabbit IgG (GAR) conjugated to alkaline phosphatase, beta-D-galactosidase, glucose oxidase, or horseradish peroxidase and histochemical substrates. The avidin-biotin system was also useful, but somewhat less sensitive than GAR-enzyme conjugates. Detection of potyviruses in an aphid vector was also attempted, but without success due to endogenous aphid enzymes.     

Ca2+ signalling in urethral interstitial cells of Cajal

Interstitial cells of Cajal (ICC) in the urethra have been proposed as specialized pacemakers that are involved in the generation of urethral tone and therefore the maintenance of urinary continence. Recent studies on freshly dispersed ICC from the urethra of rabbits have demonstrated that pacemaker activity in urethra ICC is characterized by spontaneous transient depolarizations (STDs) under current clamp and spontaneous transient inward currents (STICs) under voltage clamp. When these events were simultaneously recorded with changes in intracellular Ca²⁺ (using a Nipkow spinning disk confocal microscope) they were found to be associated with global Ca²⁺ oscillations. In this short review we will consider some of these recent findings regarding the contribution of intracellular Ca²⁺ stores and Ca²⁺ influx to the generation of pacemaker activity in urethral ICC with particular emphasis on the contribution of reverse Na⁺/Ca²⁺ exchange (NCX).     

Clarification of glycosylphosphatidylinositol anchorage of OTOANCORIN and human OTOA variants associated with deafness

Otoancorin (OTOA), encoded by OTOA, is required for the development of the tectorial membrane in the inner ear. Mutations in this gene cause nonsyndromic hearing loss (DFNB22). The molecular mechanisms underlying most DFNB22 remain poorly understood. Disruption of glycosylphosphatidylinositol (GPI) anchorage has been assumed to be the pathophysiology mandating experimental validation. From a Korean deaf family, we identified two trans OTOA variants (c.1320 + 5 G>C and p.Gln589ArgfsX55 [NM_144672.3]) . The pathogenic potential of c.1320 + 5 G>C was confirmed by a minigene splicing assay. To experimentally determine the GPI anchorage, wild‐type (WT) and mutant OTOA harboring p.Gln589ArgfsX55 were expressed in HEK293T cells. The mutant OTOA with p.Gln589ArgfsX55 resulted in an uncontrolled release of OTOA into the medium in contrast with phosphatidylinositol‐specific phospholipase C‐induced controlled release of WT OTOA from the cell surface. Together, the results of this reverse translational study confirmed GPI‐anchorage of OTOA and showed that downstream sequences from the 589th amino acid are critical for GPI‐anchorage.