小鼠肾血管球滤过膜发育的电镜研究

目的研究发育中小鼠血管球滤过膜的变化。方法应用透射电镜观察胚胎和新生小鼠血管球滤过膜的超微结构。结果在肾小体的发育过程中,足细胞形状明显变薄,足突数量逐渐增多,其形状逐渐窄小,足突间裂孔和裂孔膜出现;足细胞下、内皮细胞下先后出现基膜,而后两种基膜融合形成一层较厚的基膜。随着毛细血管袢的不断增生,在足细胞下方出现新合成的环状或袋状的基膜片段;内皮细胞形状也明显变薄。出现大量内皮孔。结论在小鼠肾小体的发育过程中,足细胞和内皮细胞逐渐分化成熟,基膜最早来源于足细胞。随后内皮也参与合成基膜,发育晚期基膜的合成和更新主要由足细胞来完成。     

Genetics of nephrotic syndrome: new insights into molecules acting at the glomerular filtration barrier

Nephrotic syndrome is caused by increased permeability of the glomerular filtration barrier for macromolecules. The identification of mutations of various podocyte-expressed proteins as causes of familial nephrotic syndrome has significantly contributed to shedding light into the molecular pathogenesis of nephrotic proteinuria and into the physiology of the glomerular sieve. More recent findings have changed our conception of the glomerular filtration barrier from a relatively static structure to a highly dynamic one. Both the multiprotein slit diaphragm complex around nephrin and the integrin receptor complex that mediates binding of the podocyte to the glomerular basement membrane, may translate outside–inside signaling and lead to podocyte actin cytoskeleton rearrangement. This may enable the podocyte network to adapt to environmental changes and respond to injury. Disturbance in these processes may not only be involved in the pathogenesis of hereditary nephrotic syndrome but also in that of more common acquired proteinuric diseases. Elucidation of the molecular mechanisms involved will possibly open the way to new therapeutic approaches.     

An integral approach to the measurement of glomerular filtration rate

The paper presents a method for the accurate clinical measurement of kidney glomerular filtration rate using a single injection of tracer and the collection of plasma and urine samples. The method is based on an integral-equation approach and is implemented by computerised curve fitting of the plasma-concentration data. The urine-collection procedures are simplified, and errors are reduced. Plasma-only methods are shown to be special cases of the general integral equation, and their limitations are stated.     

The myorelaxant effect of theophylline on smooth muscle cells of the afferent arterioles and glomerular tuft

Theophylline, infused i.v. into rats increased the diameter of the glomerular afferent arterioles by 35.78%; when added to a suspension of isolated glomeruli, it increased the diameter of the capillary tuft within the glomerulus by 25-30%. These variations in diameter can be explained by the myorelaxant effect of theophylline on the smooth contractile fibers present in the arteriolar cells and in certain glomerular cells, such as the mesangial cells. These observations explain, in part, the marked changes in glomerular hemodynamics caused by the injection of theophylline.     

Morphometry of the kidney in rat pups from uninephrectomized mothers

Background: The present study was designed to explore whether maternal renal dysfunction affects fetal kidney development and if the effects are lasting during the postnatal development. Methods: Kidneys of 1-day-old and 6-week-old pups from mothers which were uninephrectomized on day 5 of gestation were studied. Results: One day after birth, both the number of immature glomeruli and average volume of mature glomeruli of the neonates from uninephrectomized mothers were significantly larger than those from sham-operated mothers. Six weeks after birth, no significant differences in parameters of the kidney were observed between the pups from uninephrectomized and those from sham-operated mothers. Furthermore, blood urea nitrogen (BUN) concentration in adult female rats was determined at various days after uninephrectomy. BUN concentration in uninephrectomized rats was significantly higher than that in sham-operated ones. Conclusions: These results suggest that the fetal kidney development is accelerated by the elevated BUN level following maternal uninephrectomy and that the renotropic activity does not last during the postnatal developmental period. © 1994 Wiley-Liss, Inc.     

Electron microscopic localization of nerve growth factor receptor (p75)-immunoreactivity in pars caudalis / medullary dorsal horn of the cat

Previous studies have demonstrated the presence of nerve growth factor receptor [NGFr(p75)]-immunoreactivity (IR) in the spinal trigeminal nucleus of both 8–10 week-old kittens and mature cats. Most of the NGFr(p75)-IR is lost following retrogasserian rhizotomy, indicating that the majority of the NGFr(p75)-IR within the spinal trigeminal nucleus is of trigeminal primary afferent origin. Here, we examined the ultrastructural localization of NGFr(p75)-IR within lamina II outer of pars caudalis/medullary dorsal horn in the mature cat. Lamina II outer represents a location where dense NGFr(p75)-IR is seen with the light microscope. The NGFr(p75)-IR identified with the electron microscope was located within small thinly myelinated and unmyelinated axons and within axon terminals. The terminals with NGFr(p75)-IR typically formed asymmetric synaptic specializations onto dendritic profiles and at times were postsynaptic to other axon terminals at symmetric synaptic specializations. The terminals with NGFr(p75)-IR were either simple (associated with a single profile) or more complex, such as those that typically formed the central element in synaptic glomeruli. The NGFr(p75)-IR in terminals was especially prominent on microtubules and the plasmalemma and these findings are consistent with proposed roles for NGFr(p75) in axoplasmic/neuronal transport and as a membrane protein, respectively. The profiles with NGFr(p75)-IR seen with the electron microscope indicate a primary afferent origin and show some similarities when compared to other markers of primary afferent fibers such as calcitonin gene-related peptide. In addition, a possible role for NGFr(p75) in the transmission of nociceptive stimuli is also discussed.     

The differential staining patterns of two lectins in the accessory olfactory bulb of the rat

We examined the binding sites of Bandeiraea simplicifolia lectin I (BSL-I) and Vicia villosa agglutinin (VVA) which bind to the vomeronasal nerve of the rat. BSL-I stained the whole vomeronasal nerve and glomerular layers. VVA strongly stained the posterior 2/3, but weakly stained the anterior 1/3 of the glomerular layer. These results indicate that the glomeruli of the rat AOB have two subdivisions revealed by lectin histochemistry using BSL-I and VVA.     

Olfactory nerves and their excitatory action in the olfactory bulb

Summary Extracellular field potentials were recorded from the rabbit olfactory bulb following stimulation of the surface and the lateral olfactory tract. Experiments were also performed on olfactory nerve rootlets and a conduction velocity of .34 m/sec and an absolute refractory period of 2.7 msec were obtained. Stimulation of the surface of the bulb produced in a nearby surface recording electrode an initial sharp triphasic potential followed by two slow negative waves and a later positive wave. It was concluded that the initial triphasic potential represents the compound action potential of the olfactory nerves. The first slow negative wave is due to the postsynaptic excitation of the dendrites of secondary neurons by the olfactory nerves. The second negative wave is due to the synaptic depolarization of the granule cell processes by the dendrites of secondary neurons. The later positive wave represents the inhibitory postsynaptic potentials generated in the relay neurons by the granule cell processes.     

Scanning electron microscopy of podocytes of the renal glomerulus of rats with nephrotoxic serum nephritis

Summary Nephrotoxic serum nephritis was produced in rats by intraperitoneal injections of rabbit nephrotoxic serum. Heterologous and autologous phases of nephritis were demonstrated by immunofluorescence and ultrastructural studies. Scanning electron microscopy showed changes in the surface of the podocytes, swelling of the arm-like cytoplasmic processes, and disappearance of the pedicles. The podocyte alterations are discussed.