Honeycomb-like intra-axonal tubular structures in irradiated rat cerebella

Summary In the cerebella of all (5) 30-days old rats, whose cerebellar region was irradiated with 1000 r at the 2nd day of life, honeycomblike tubular arrays were found in myelinated axons, identical with those described by others in a variety of conditions.

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Zusammenfassung Im Kleinhirn aller (5) 30 Tage alter Ratten, deren Kleinhirnregion mit 1000r am Ende des 2. Lebenstages bestrahlt worden war, fanden sich honigwabenartige tubuläre Formationen in den bemarkten Axonen, die den von anderen Autoren bei verschiedenen Bedingungen beschriebenen Veränderungen entsprechen.

     

分离纯化肾小管基底膜的改进方法

本实验采用分样筛、磁性分离和密度梯度离心综合法分离猪肾皮质的肾小管基底膜。相差显微镜观察肾小管的纯度可达97％以上。磁性分离后用超声震碎细胞核,再经密度梯度离心,即可获得高纯度的肾小管基底膜。     

The visual fields of the tawny owl, Strix aluco L

The uniocular retinal field of Strix aluco is highly asymmetrical. The maximum width of 124 degrees is less than that recorded in any other vertebrate. Maximum retinal binocular field width equals 48 degrees and the optic axes diverge by 55 degrees. Maximum binocularity occurs above the bill whose tip lies outside of the visual field. The cyclopean retinal field has a maximum width of 201 degrees. Limited data on the visual fields of the pigeon are also presented. All of these data are compared with visual field widths in other species and the significance of the owl eye's tubular shape, its nasad asymmetry, and the possible factors influencing binocular field width are discussed.     

Effects of obstruction on renal functions

Following ureteral obstruction there is a progressive fall in glomerular filtration rate (GFR) due to a reduction in single nephron glomerular filtration rate (SNGFR) and a reduced number of filtering nephrons. Renal plasma flow also declines after a transient, prostaglandin-dependent increase, due to afferent and efferent arteriolar vasoconstriction. The vasoactive hormones thromboxane A₂ and angiotensin II are implicated in the pathogenesis of the vasoconstriction following ureteral obstruction and they also reduce the glomerular ultrafiltration coefficient by causing mesangial contraction. Ureteral obstruction also leads to profound changes in renal tubular cell function. These include altered sodium and water handling resulting in a post-obstructive diuresis and natriuresis and a failure to dilute or concentrate the urine. Potassium and divalent cation exchange is also affected, as is urinary acidification. Furthermore, the response of the tubule to hormones such as antidiuretic hormone and parathyroid hormone is impaired. The pathophysiology of these alterations in renal function is discussed.     

A simple method for estimating tubular and net glomerular capillary pressures in the isolated perfused kidney

To estimate glomerular filter resistance it is necessary to measure net glomerular capillary pressure, tubular pressure, and glomerular filtration rate. Net glomerular capillary pressure is defined as the difference between glomerular capillary hydrostatic and oncotic pressures. A method has been developed for estimating both tubular pressure and net glomerular capillary pressure for the whole kidney from the time course of the rise in ureteral pressure on ureteral occlusion. Pressure and flow relations which apply in the kidney during ureteral occlusion have been represented by a simple mathematical model. Estimates of tubular pressure and net glomerular capillary pressure are made by representing the first 60 s of the rise in ureteral pressure as the linear combination of two exponential terms. These estimates compare favourably with corresponding results obtained from a more general numerical analysis. Direct measurements of tubular pressure and net glomerular capillary pressure made by micropuncture of early proximal tubules have been compared with analytical estimates from subsequent ureteral occulusion. There was no significant difference between results obtained using either method for a wide range of perfusion pressures.     

Evidence for redistribution of filtrate among nephrons after beta-adrenergic stimulation and blockade

Summary Renal excretion of fluid and electrolytes, total kidney GFR and superficial nephron GFR were determined in 42 Sprague Dawley rats after beta-adrenergic stimulation with isoprenaline and beta-adrenergic blockade with propranolol. Isoprenaline (0.3 g/kg · min i. v.) decreased urine volume, sodium and potassium excretion and increased urinary sodium and potassium concentration and urine osmolarity. These effects were reversed by injection of propranolol (2.2 mg/kg i.v.). Propranolol alone increased renal sodium and potassium excretion and urinary sodium concentration. Total kidney GFR did not change after both substances, whereas superficial nephron GFR increased after propranolol by 35% and decreased after isoprenaline by 35%. A redistribution of glomerular filtration rates among nephrons therefore must have occured with a shift of the GFR to deep nephrons after isoprenaline and to superficial nephrons after propranolol. The redistribution of glomerular filtration rates is thought to the related to the changes in urinary excretion of electrolytes. Additionally, isoprenaline increased fractional fluid reabsorption of superficial proximal convoluted tubules by 12.3%.     

Fine structure of intercellular junctions and blood vessels in medulloblastomas

Summary Six medulloblastomas were studied by electron microscopy. Two features were found which seem to be constant and essential characteristics of medulloblastoma. First, cell junctions are abundant between tumor cells. These are mostly desmosome-like but other, closer junctions, were also seen. Second, the capillary endothelia contain frequent tubular bodies and other inclusions which may be related to them.     

Preexistence of chronic tubular damage in cases of renal cell cancer after long and high exposure to trichloroethylene

 Substantially more cases of tubular damage were found among renal cell carcinoma patients who had been exposed to high levels of trichloroethylene over many years than among renal cell carcinoma patients who had not been exposed to trichloroethylene. This supports the hypothesis (Goeptar et al. 1995) that chronic tubular damage may be regarded as a necessary precondition for trichloroethylene to exert a nephrocarcinogenic effect. The findings also indicate that the urine protein patterns identified with SDS-PAGE may represent a valuable parameter for effect biomonitoring of persons exposed to high levels of trichloroethylene over many years. Received: 20 June 1995/Accepted: 21 August 1995