Kidney of the sumatran rhinoceros,Dicerorhinus sumatrensis

The kidney of Diceros sumatrensis has the rhinocerotic form and lobation. The ureter divides intrarenally into two fibromuscular conduits which receive, at separate loci, the terminal collecting ducts of the lobes. The kidney is 67% cortex. Total renal mass is 0.46% of body mass. There are about 34 lobes and 23 primary orifices at the conduits. Glomeruli are relatively small and of the same size across the cortex. They number about 14.6 million in one kidney but the glomerular mass is relatively low. Unlike other rhinocerotic species, the kidney of D. sumatrensis lacks interlobar septa. The interlobar arteries nevertheless enter the renal parenchymas as in the other rhinoceroses, i.e., between the cortices of adjacent lobes rather than in the common mammalian manner between cortex and medulla. Thus, internal “perforator” arteries pass from cortical periphery to interior giving off cortical twigs on their way to the corticomedullary border, along which they branch while releasing centrifugal arteries back toward the cortical periphery. The arcuate veins are wide centrally where they enter the paraconduital veins. The latter form prominent central anastomoses between the large interlobar veins. © 1993 Wiley-Liss, Inc.     

Kidney of the great Indian rhino Rhinoceros unicornis, Linnaeus

The kidney of R. unicornis has almost 80 closely apposed lobes, all appearing peripherally. Every lobe, almost enclosed by a collagenous septum, resembles a deformed truncated cone. The pelvis proper is a small pouch which divides into a cephalic and a caudal urothelial-lined fibromuscular conduit. The terminal collecting ducts of every lobe open into a tubus maximus. This is lined by cuboidal cells and otherwise has no wall. There is no papilla. All lobes finally empty through the 18 primary infundibular orifices at the pelvic conduits. A primary fibromuscular infundibulum typically yields a secondary one supplying an adjacent lobe. Two or three lobes can use a common tubus maximus by "convergence" of their medullae. Tubus maximus, terminal collecting ducts and deep outer medulla are embraced by a fibromuscular calyx which is the peripheral extension of an infundibulum and is fused to the outer medulla. There is thus no vault between medulla and calyx. Large intralobar veins are fused to the outer wall of the calyx. The possible significance of this is discussed. The cortex is the only part of a lobe which has contact with infundibulum, pelvic conduits, or pelvis proper. The kidney has about 16 million glomeruli which form 5.8% of the adult's cortical mass. Many adult mammals, from mouse to rhinoceros, fit into the log10-log10 slope relating number of glomeruli per kidney to body-mass. Neonatal rhinos at term have mature glomeruli throughout the cortex. The small size of the glomeruli and the large number per field allow 16 million in an 118-gm kidney.     

Sinus-parenchyma border of the human kidney as the site of origin of intracanalicular and extravascular diffusion of fluids

Injecting fluids into the kidney against the physiological direction of flow leads to a passage of liquid across the border-line between the renal sinus and the parenchyma. This event, caused by a sudden raising of pressure during the injection is called pyelorenal backflow. It can be divided into a number of subtypes, as there are: pyelocanalicular backflow, pyelosinous backflow, pyelovenous backflow, pyelolymphatic backflow. Among all these phenomena only the pyelocanalicular backflow can be interpreted as a genuine backflow in the fullest sense of the word, while the others never can happen before the fornix had been mutilated. In the case of pyelocanalicular backflow, the contents of the renal pelvis regurgitate into the Ducts of Bellini, but the fluid never goes beyond the collecting ducts in the pyramids. Neither a rupture of the tubuli, followed by an interstitial spreading up to under the capsule, nor a direct penetration into the medullary veins are possible, because the pressure necessary for it causes a rupture of the fornix earlier. This rupture happens step by step as an oblique dissection of the calyx from the papilla. The big calices at the poles show an increased tendency to rupture because they are attached along a line which is shaped like an "8" or like a clover leaf, and so do calices the angle of which is acute. Depending on whether a vein is torn simultaneously with the fornix or not, the contents of the pelvis transflow into the vein (pyelovenous backflow) or into the sinus (pyelosinous backflow). In spite of a previous pyelocanalicular backflow the pelvis is not relieved of pressure to such an extent that there could not occur an additional rupture of the fornix, nevertheless. The pyelosinous backflow leads to a sinus-extravasation which can ascend towards the parenchyma and descend towards the hilum. The ascending sinus-extravasation spreads out within the vascular canals of the kidney. These canals, strictly situated between cortex and medulla, enclose a pyramid (Canales peripyramidales) and contain the interlobar and arcuate bloodvessels. The space between the bloodvessels and the wall of a peripyramidal canal (perivascular space) is filled with connective tissue consisting of 3 components: tunica adventitia of the bloodvessels themselves and fibres originating from the inner capsule and the wall of the calyx. The ascending sinus-extravasation proceeds into the perivascular space by pushing off the bloodvessels from the medulla.(ABSTRACT TRUNCATED AT 400 WORDS)     

GABA-immunoreactive structures in rat kidney.

We examined the distribution of gamma-aminobutyric acid-like immunoreactivity (GABA-LI) in the rat kidney by light and electron microscopy. In vibratome sections, GABA-LI was present in both the renal medulla and cortex. The inner stripe of the outer medulla was most heavily and almost homogeneously labeled, whereas GABA-LI in the cortex was mainly confined only to some tubules. GABA-positive structures involved the epithelial cells of the thin and the thick ascending limbs of the loop of Henle, the connecting tubules, and the collecting ducts. In GABA-positive connecting tubules and collecting ducts the immunoreactivity was present in the cytoplasm of about half of the epithelial cells. As revealed by electron microscopy, the labeled cells in the collecting tubules were the light (principal) cells. No GABA-LI occurred in neuronal structures. These findings are consistent with the presence of a non-neuronal GABA system in the rat kidney. Furthermore, the specific distribution of GABA in the tubular epithelium suggests a functional significance of this amino acid in tubular transport processes.     

The fibromuscular basket (Sporta perimedullaris musculosa) in renculi of kidneys from the ringed seal, Phoca hispida (Pinnipedia)

The medulla of renculi from kidneys of Ringed seals (Phoca hispida) is completely enclosed by cortex except at the hilum. Within the renculus, the fibromuscular coat of the calyx separates from the transitional epithelium at the level of the corticomedullary junction, where the intrarencular arteries also diverge into the parenchyma. Flat ribbons of this stromal tissue form an arborized framework near the medullary side of the intrarencular arteries and the larger of the arcuate arteries derived from them. The ribbons, which are clearly distinct from periarterial connective tissue, are composed of coarse collagenous fibers, elastic fibers, and smooth muscle cells, all oriented in the direction of the long axes of the ribbons, and myofibroblasts. The proportion of smooth muscle cells decreases and that of myofibroblasts increases with increasing distance from the calyx. At the base of the medullary pyramid, the elements of the framework diminish in width and ultimately blend with the surrounding interstitial tissue. The stromal framework, or basket, is homologous with the Sporta perimedullaris musculosa of cetacean kidneys.     

Identification of noradrenergic nerve terminals immunoreactive for neuropeptide Y and vasoactive intestinal peptide in the rat kidney

Cryostat- and vibratome-cut sections of rat kidneys were singly or doubly labeled to visualize immunoreactive tyrosine hydroxylase (THI), dopamine beta-hydroxylase (DBHI), vasoactive intestinal peptide (VIPI), and neuropeptide Y (NPYI). Rats were perfusion fixed with 2-4% paraformaldehyde with or without 0.15% picric acid and rinsed in buffer for 18-48 hr. Single antigens were labeled with horseradish peroxidase in vibratome sections, whereas cryostat sections were used to label one antigen with peroxidase and another with a fluorophore in the same tissue section. A dense plexus of DBHI noradrenergic nerves innervates the renal arterial tree, and such nerves innervate the interlobar veins and renal calyx as well. Immunoreactive NPY is colocalized in most of these nerves, but some intrarenal noradrenergic nerves do not contain NPY but do contain VIP immunoreactivity. The distribution of NPYI nerves resembles that of DBHI nerves, whereas most perivascular noradrenergic nerves immunoreactive for VIP innervate selected arcuate and interlobular arteries. A small population of nonadrenergic, VIPI nerves innervates the renal calyx.     

The stroma of the thymus of the rat: morphology and antigen diffusion, a reconsideration

This work reconsiders aspects of the morphology of the capsule, of the blood vasculature, of the distribution of reticular fibers, and of the diffusion of intramediastinally injected antigens in the stroma of the thymus of the rat. This was done by an analysis of standard sections of normal thymuses, of sections of thymuses perfused with colloidal carbon, of silver-impregnated sections, and of sections of thymuses of rats injected intramediastinally with a fluorescent antigen or intravenously with Trypan blue, and by electron microscopy of the thymic capsule. The capsule consisted of two layers: an outer layer covering the entire periphery of a thymic lobe, and an inner layer which outlined the entire convoluted peripheral cortex of a lobe. Cortical vessels entered the capsule and septa in which they formed a capillary network. These capsular capillaries were fenestrated and leukocytes were often present near them. Adipocytes were also seen near these vessels in some areas of the capsule, and often at the bases of septa and trabeculae. Furthermore, much of the medulla had a dense network of coarse reticular fibers, whereas the remainder of the medulla and the cortex contained a loose network of fine fibers stretching out from the capsule, septa, and trabeculae. Intramediastinally injected fluorescent antigens were observed to spread in the capsule and septa and to diffuse in the fiber networks stretched across the cortex and the medulla. Fluorescence also highlighted cortical reticular cells but not the thymocytes. Intravenously injected Trypan blue stained the capsule, the septa, the cortical reticular cells, and the autofluorescent cells outlining the corticomedullary junction of each lobule. The unusual penetration of capillaries from the thymic parenchyma into the thymic capsule suggested that the capsular capillaries participate in peculiar thymic events, such as the recruitment of blood stem-cells. It is concluded that small amounts of blood antigens normally exude from capsular capillaries and diffuse into the fibers extending from the capsule across the cortex. The phenomenon would be increased under conditions causing thymic involution. An explanation is proposed to account for the development of involution which involves the exudation of antigens from the capsular capillaries. A comparable mechanism could also account for the development of a particular experimental immune tolerance.     

Angiotensin converting enzyme predominates in the inner cortex and medulla of the rat kidney

Regional distribution of angiotensin converting enzyme(ACE) in the rat kidney was studied. The ACE activities in the inner cortex and outer medulla were about 10 and 5 times those in the outer cortex, respectively. The activity in the inner medulla or papilla was much the same as that in the outer cortex. Immunofluorescence was greatest in the proximal tubules in the inner cortex, while the outer medulla and the inner medulla or papilla showed a weak fluorescence. The brush border membranes isolated from the inner cortex also possessed about 10 times the ACE activity seen in the outer cortex. The results indicate that the major source of renal ACE is not the proximal convoluted tubules in the outer cortex, but rather the brush border membranes of proximal tubules in the inner cortex. The contribution of ACE in the inner cortex would therefore be predominant.     

Microvasculature of the feline renal medulla

The microvascular pattern of the feline renal medulla was studied by scanning electron microscopy using corrosion casts. At the corticomedullary junction, numerous efferent arterioles were observed giving rise to peritubular capillary plexuses and arteriole rectae. Considerable differences in vessel diameters were seen. Arteriolae rectae coursed around interlobar veins before returning to the corticomedullary area, as venulae rectae. Diffuse capillary papillary plexuses were seen protruding into the renal pelvis.     

Localization of thyroxine 5'-monodeiodinase activity in the renal proximal tubules in rabbits and rats

To determine the localization of T4 5'-monodeiodinase activity in rabbit and rat nephron segments, the formation of tri-iodothyronine (T3) from thyroxine (T4) was measured in kidney homogenate and in isolated nephron segments obtained by the microdissection method. In order of decreasing activity, homogenates of rabbit renal cortex, outer medulla and inner medulla were capable of converting T4 to T3. In the isolated nephron segments of the rabbit cortex, the activities were noted in both proximal convoluted and proximal straight tubules. On the other hand, the activities were not detected in segments including the cortical thick ascending limb of Henle's loop, the distal convoluted tubule, the connecting tubule, and the cortical collecting tubule. It is concluded that both the convoluted and the straight tubules are the sites of T3 production in the kidney.     

The cellular localization of increased atrial natriuretic peptide mRNA and immunoreactivity in diabetic rat kidneys.

Increased intrarenal atrial natriuretic peptide (ANP) mRNA expression has been reported in several disorders. To further investigate the action of renal ANP, we need to elucidate the exact site of its alteration in diseased kidneys. ANP mRNA and ANP were detected by in situ hybridization and immunohistochemistry in the kidneys from five normal and five diabetic rats. Renal ANP mRNA in eight normal and nine diabetic rats was measured by RT-PCR with Southern blot hybridization. In normal and diabetic rats, the distribution of ANP mRNA and ANP-like peptide was mainly located in proximal, distal, and collecting tubules. However, diabetic rats had significant enhancement of ANP mRNA and ANP-immunoreactive staining in the proximal straight tubules, medullary thick ascending limbs, and medullary collecting ducts. ANP mRNA in the outer and inner medulla of nine diabetic rats increased 5.5-fold and 3.5-fold, but only 1.8-fold in the renal cortex. This preliminary study showed that ANP mRNA and ANP immunoreactivity in proximal straight tubules, medullary thick ascending limb, and medullary collecting ducts apparently increased in diabetic kidneys. These findings imply that ANP synthesis in these nephrons may involve in adaptations of renal function in diabetes.     

Estrogen upregulates renal angiotensin II AT1 and AT2 receptors in the rat

We studied renal AT1 and AT2 receptors in male, female, ovariectomized and ovariectomized-estrogen-treated Wistar-Hanover and Wistar-Kyoto rats. AT1 receptors and AT1A receptor mRNA predominated, with no significant differences between males and females. AT2 receptor expression was restricted in female rats to the capsule, the transition zone between outer and inner medulla, the endothelium lining the papilla, and arcuate arteries and veins. There were no AT2 receptors in male rats, while male mice express substantial numbers of estrogen-dependent AT2 receptors. Arcuate arteries and veins expressed AT1B mRNA in males and females, and AT2 mRNA in females only. AT1 receptor and AT2 receptor expression were estrogen-dependent, with increases in AT1 and AT2 receptor expression after estrogen treatment in ovariectomized rats. Estrogen treatment increased prostaglandin E2 (PGE2) and cGMP concentrations in the renal medulla, and eNOS expression in cortical arteries. In rodents, expression of renal Angiotensin II receptor types is estrogen-dependent, with significant species, strain and area differences. Our results support an important role for AT2 receptors in the regulation of renal function and in the protective effects of estrogen in the kidney.     

High- and low-affinity binding sites for vasoactive intestinal peptide (VIP) in the rat kidney revealed by light microscopic autoradiography

The distribution of VIP binding sites in rat kidney and adrenal gland has been examined by light microscopic autoradiography. A fully characterized mono-iodinated molecular form of VIP (M-125-I-VIP) which maintains the biological activity of the native peptide, was used for this study. Two types of VIP binding sites, with high and low affinity, have been identified. High affinity sites are associated with (i) glomerular structures in the cortex, (ii) the inner stripe of the outer medulla, possibly corresponding to Henle's loops and distal tubules, (iii) radiated structures in the inner zone of the medulla, likely to represent labeling of collecting ducts and/or vascular bundles and (iv) the adrenal cortex. Autoradiographic grains associated with low affinity sites are present diffusely throughout the renal cortex, possibly corresponding to labeling of tubular and/or vascular structures, and throughout the adrenal gland. These observations further delineate a role of VIP in renal and neuroendocrine function.     

Isolation of a cDNA for rat CHIP28 water channel: high mRNA expression in kidney cortex and inner medulla.

The cDNA coding for the rat CHIP28 water channel was isolated from a kidney library. At the amino acid level, rat CHIP28 is 93% identical to the recently published human protein (1). Expression of rat CHIP28 mRNA was highest in the renal inner medulla, unchanged during antidiuresis and twice the level expressed in outer cortex, with lower expression levels also apparent in parotid gland, urinary bladder and prostate. The evidence suggests that CHIP28 water channels in the ADH-sensitive collecting tubules are identical to those of the ADH-insensitive proximal convoluted tubules and possibly other tissues specialised in fluid transport.     

Renal anatomy in sparrows from different environments

The renal anatomy of three species of sparrows, two from mesic areas, the House Sparrow (Passer domesticus) and Song Sparrow (Melospiza melodia), and one salt marsh species, the Savannah Sparrow (Passerculus sandwichensis) was examined. Electron microscopy was used to describe the ultrastructure of the nephron. In addition, stereology was used to quantify the volumes of cortex, medulla, and major vasculature of the kidneys, and the volumes and surface areas occupied by individual nephron components. There appeared to be no differences in the ultrastructural anatomy of the nephrons among the sparrows. Proximal tubules contained both narrow and wide intercellular spaces filled with interdigitations of the basolateral membrane. The thin limbs of Henle contained very wide intercellular spaces which were absent in the thick limbs of Henle. The distal tubule cells contained short, apical microvilli and infoldings of the basolateral membrane. In cross section, the medullary cones of all birds display an outer ring of thick limbs of Henle which surround an inner ring of collecting ducts, which in turn surround a central core of thin limbs of Henle. The Savannah Sparrow has a significantly higher volume of medulla compared to the two more mesic species. Within the cortex, the Savannah Sparrow also has a significantly higher volume of proximal tubules but a significantly lower volume of distal tubules than the other species. Within the medulla, the Savannah Sparrow has a significantly higher volume and surface area of capillaries, and a significantly higher surface area of thick limbs of Henle and collecting ducts than the mesic species. These data suggest that the salt marsh Savannah Sparrow has the renal morphology necessary to produce a more highly concentrated urine than the mesic zone species.     

华鲮泌尿系统组织学的初步观察

2004年3月至9月采用常规组织学方法对华鲮泌尿系统作了研究,结果表明：华鲮泌尿系统包括中肾、输尿管、膀胱。中肾由肾小体和肾小管组成,无皮质、髓质之分,有肾小体聚集现象;肾小管可分为颈段、第一近曲小管、第二近曲小管、远曲小管、集合管。肾中散布有大量淋巴髓样组织,还有甲状腺滤泡和斯坦尼氏小体,显然华鲮的肾脏是一个具有多种生理功能的复合器官。输尿管位于两肾叶腹侧,其上皮为似复层,缺黏膜下层,无纵肌,外膜甚薄。左右输尿管在后端合并,稍微扩大,形成膀胱,膀胱内壁具有发达的绒毛,绒毛表面为变移上皮。     

CFTR and TNR-CFTR expression and function in the kidney

The cystic fibrosis transmembrane conductance regulator (CFTR) is abundantly expressed in the kidney. CFTR mRNA is detected in all nephron segments of rats and humans and its expression is higher in the renal cortex and outer medulla than in the inner medulla. CFTR protein is detected at the apical surface of both proximal and distal tubules of rat kidney but not in the outer medullary collecting ducts. The localization of CFTR in the proximal tubules is compatible with that of endosomes, suggesting that CFTR might regulate pH in endocytic vesicles by equilibrating H⁺ accumulation due to H⁺-ATPase activity. Many studies have also demonstrated that CFTR also regulates channel pore opening and the transport of sodium, chloride and potassium. The kidneys also express a CFTR splicing variant, called TNR-CFTR, in a tissue-specific manner, primarily in the renal medulla. This splicing variant conserves the functional characteristics of wild-type CFTR. The functional significance of TNR-CFTR remains to be elucidated, but our group proposes that TNR-CFTR may have a basic function in intracellular organelles, rather than in the plasma membrane. Also, this splicing variant is able to partially substitute CFTR functions in the renal medulla of Cftr^-/- mice and CF patients. In this review we discuss the major functions that have been proposed for CFTR and TNR-CFTR in the kidney.     

The intrarenal and pericapsular venous systems of kidneys of the ringed seal, Phoca hispida

The kidneys of Phoca hispida are comprised of many closely adherent renculi, each of which is a small kidney, functionally independent of its neighbours except with respect to venous drainage. Venous blood from the rencular parenchyma drains to the periphery through interlobular veins. These interlobular veins empty into a perirencular plexus comprised of subcapsular veins on the free surface of the renculus, interrencular veins on adjoined surfaces, and marginal subcapsular veins lying in the furrows between adjoined renculi. A pericapsular plexus of large veins overlies the marginal subcapsular veins and has frequent connections with them. Blood drains from the pericapsular plexus into large superficial collecting veins that converge over the surface of the kidney toward the divided hilum and connect directly to the paired trunks of the posterior vena cava. There are also connections to other major venous systems of the region. There is no arcuate venous system, no major vein at the rencular hilum, and no vein of consequence emerging from the renal hilum. Venous outflow is virtually entirely directed to the peripheral plexuses. The venous pattern differs from that of most mammals in which blood drains from the renal parenchyma to arcuate veins and leaves the kidney through a renal vein, or veins, emerging from the hilum. The walls of veins in the kidney are remarkably thin in comparison to their size. Subcapsular veins up to 0.5 mm wide have walls on the parenchymal side that in places consist only of a thin, fenestrated endothelium and a basal lamina.     

<Emphasis Type="Italic">Miconia rondoniensis</Emphasis> (Melastomataceae), a new species from the Southern Amazon of Brazil

Miconia rondoniensis occurs in secondary upland (terra firme) moist open forest in the Brazilian states of Rondônia, Mato Grosso and Amazonas. It can be recognized by the tree habit, large leaves with rounded to obtuse or subcordate bases and 5+2 basal veins (five main veins plus a faint submarginal pair), large inflorescences with proximal paraclades bearing quaternary branches and distal paraclades bearing tertiary branches, persistent hemi-elliptic bracteoles, short persistent calyx lobes, and capitate stigmas. The most striking feature of this new species is the thick pubescence on the branches and petioles, composed of trichomes having a long axis and short arms at the base, but inflated and lacking arms at the apex, resulting in a sorus-like surface covered with globose structures.     

塔里木兔肾脏水通道蛋白在适应干旱环境中的作用

We measured the expression of aquaporin (AQP)1 -3 in kidneys of yarkand hares (Lepus yarcandensis )to understand the role of AQPs in adaptation to drought environment. We used H. E staining methods for detecting the histological structure of kidneys,and immunohistochemistry and western blotting for detecting expression of AQP1 - 3 in kidneys,
and also compared the results with those from domestic rabbits. Results showed that AQP1 is localized in capillary endothelial cell cytoplasm in glomeruli,and continued uninterrupted from proximal straight tubules into descending thin limbs in the outer medulla. AQP2 is observed in epithelial cells membrane in collecting ducts. AQP3 is localized in connecting tubules of the cortex and the outer medulla and epithelial cell basal membrane in collecting ducts. The expression of AQP1 -3 in kidneys is greater and the protein content is higher in yarkand hares than in domestic rabbits. These results indicate that the yarkand hare has increased the expression of aquaporins in kidneys,strengthened renal reabsorption of water and the ability for concentrating the urine,improving the ability for adaptation to arid environment.