Renal morphology of the hook-lipped African rhinoceros, Diceros bicornis, Linnaeus

The kidney of Diceros bicornis has about 60 lobes, all appearing peripherally. These are separated by interlobar septa, except for small septal defects through which tubules pass. Renal capsule and interlobar septa are fibromuscular and contain small blood vessels. The kidney is about 65% cortex. It contains about 12.5 x 10(6) glomeruli, which form about 7% of the cortical mass and 4.6% of the renal mass. Diameter of a glomerular capsule is about 244 microns, there being no difference in size across the cortex in these adults. The ureter bifurcates into a cephalic and a caudal, fibromuscular, urothelial-lined conduit, into which open about 23 urothelial-lined infundibula. The common large collecting duct, or tubus maximus, of every lobe opens at the apex of its infundibulum. Two tubi may join into one infundibulum. The tubi and their terminal collecting ducts (of Bellini) are part of the inner medulla. Musculature of conduits and infundibula is largely longitudinal. The calyx may be represented by a circular muscle bundle near the apex of every infundibulum. The large intralobar veins are partly adherent to their infundibulum and calyx and receive arcuate veins via valved orifices. Most branches of the renal artery enter via the interlobar septa. Within a septum they branch again and also supply numerous perforators, which thence enter the cortex. Remaining branches of the renal artery enter cortex directly from without. A fibromuscular scaffolding lies deep to arcuate veins where they contact medulla. Where these veins contact cortical tubules; however, their walls become merely endothelium, like the walls of the interlobular veins.     

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.     

Gene expression in the normal adult human kidney assessed by complementary DNA microarray

The kidney is a highly specialized organ with a complex, stereotyped architecture and a great diversity of functions and cell types. Because the microscopic organization of the nephron, the functional unit of the kidney, has a consistent relationship to the macroscopic anatomy of the kidney, knowledge of the characteristic patterns of gene expression in different compartments of the kidney could provide insight into the functions and functional organization of the normal nephron. We studied gene expression in dissected renal lobes of five adult human kidneys using cDNA microarrays representing approximately 30,000 different human genes. Total RNA was isolated from sections of the inner and outer cortex, inner and outer medulla, papillary tips, and renal pelvis and from glomeruli isolated by sieving. The results revealed unique and highly distinctive patterns of gene expression for glomeruli, cortex, medulla, papillary tips, and pelvic samples. Immunohistochemical staining using selected antisera confirmed differential expression of several cognate proteins and provided histological localization of expression within the nephron. The distinctive patterns of gene expression in discrete portions of the kidney may serve as a resource for further understanding of renal physiology and the molecular and cellular organization of the nephron.     

Neural networks in the mushroom bodies of the honeybee

The Kenyon cells (K cells) or intrinsic neurones of the honeybee's mushroom bodies are organised as a series of arrays. In the calyces the arrays form concentric rings that are represented by rectilinear layers in the α and β lobes. The inputs to the calyces have been revealed by intraneuropilar cobalt injection into the optic and antennal lobes. Neurones from the medulla project to the collar neuropil of the calyx while the relay neurones of the antennal lobe project to the lip neuropil of the calyx. Extrinsic neurones of unknown polarity penetrating the α and β lobes have branching patterns that reflect the layered pattern of the intrinsic neurones. The study illustrates the feasibility of producing a fine grain map of the optic lobe and antennal lobe inputs to the mushroom bodies. It is suggested that the map could be produced by making cobalt injections into individual identified antennal glomeruli and at known sites in the medulla retinotopic mosaic.     

Anatomy of the renal pelvis in the hamster.

The hamster renal pelvis has been studied by means of low-power light microscopy, scanning electron microscopy and morphometric analyses. The results of this study are highly suggestive that the contact of pelvic urine with the other medulla as well as with the inner medulla may be an important aspect of final urine formation. The outer medulla constituted nearly 50% of the total pelvic surface area, with the inner stripe of the outer medulla more than twice the pelvic surface area of the outer stripe of the outer medulla. The large outer medullary pelvic surface area was accounted for by the elaboration of the upper pelvic walls into peripelvic columns, opercula ("secondary pyramids"), fornices and secondary pouches. A thin simple-squamous to low cuboidal pelvic epithelium separated pelvic urine from outer medullary parenchyma. The inner medulla which constituted about one quarter of the total pelvic surface area was covered by a cuboidal to columnar pelvic epithelium which appeared morphologically similar to the papillary collecting duct epithelium. Tubules and capillaries of the inner medulla did not appear as closely juxtaposed to the pelvic epithelium as did those of the outer medulla. Cortical tissue comprised only 11.7% of the total pelvic surface area and was covered by transitional epithelium similar to that of ureter and bladder. The previously reported impermeability of this epithelium suggests that pelvic urine contact with the cortex is unimportant in final urine formation. The rich layer of smooth muscle under the transitional epithelium probably functions to move urine into and out of the pelvis during pelvic peristalsis, which has been observed in vivo.     

Modification of genital kidney nephrons for sperm transport in a plethodontid salamander,Eurycea longicauda

Salamanders possess kidneys with two distinct regions: a caudal pelvic portion and cranial genital portion. Nephrons of the pelvic region are responsible for urine formation and transport. Nephrons of the genital region transport sperm from testes to Wolffian ducts; however, nephrons of the genital region possess all the same functional regions found in pelvic kidney nephrons that are involved with urine formation and transport (renal corpuscles, proximal tubules, distal tubules, and collecting ducts). Morphological similarities between pelvic and genital regions stimulated past researchers to hypothesize that nephrons of genital kidneys possess dual function; that is, sperm transport and urine formation/transport. Considering size of glomeruli is directly related to the total amount of blood plasma filtered into the Bowman's space, we tested the hypothesis that nephrons of genital kidneys have reduced urine formation function by comparing glomerular size between nephrons of pelvic and genital kidney regions in Eurycea longicauda with general histological techniques. Light microscopy analysis revealed that glomeruli of pelvic kidneys were significantly larger than those measured from genital kidneys. Transmission electron microscopy analysis also revealed modifications in genital kidney nephrons when compared to pelvic kidney nephrons that suggested a decrease in urine formation function in genital kidneys. Such modifications included a decrease in basal and lateral plasma membrane folding in genital kidney proximal and distal tubules compared to that of pelvic kidney proximal and distal tubules. Genital kidney proximal tubules were also ciliated, which was not observed in pelvic kidney proximal tubules. In conclusion, although structurally similar at the histological level, it appears that nephrons of genital kidneys have decreased urine formation function based on glomerular size comparison and nephron ultrastructure.     

Neuronal architecture of the antennal lobe in Drosophila melanogaster

Summary Computer reconstruction of the antennal lobe of Drosophila melanogaster has revealed a total of 35 glomeruli, of which 30 are located in the periphery of the lobe and 5 in its center. Several prominent glomeruli are recognizable by their location, size, and shape; others are identifiable only by their positions relative to prominent glomeruli. No obvious sexual dimorphism of the glomerular architecture was observed. Golgi impregnations revealed: (1) Five of the glomeruli are exclusive targets for ipsilateral antennal input, whereas all others receive afferents from both antennae. Unilateral amputation of the third antennal segment led to a loss of about 1000 fibers in the antennal commissure. Hence, about 5/6 of the approximately 1200 antennal afferents per side have a process that extends into the contralateral lobe. (2) Afferents from maxillary palps (most likely from basiconic sensilla) project into both ipsi-and contralateral antennal lobes, yet their target glomeruli are apparently not the same as those of antennal basiconic sensilla. (3) Afferents in the antennal lobe may also stem from pharyngeal sensilla. (4) The most prominent types of interneurons with arborizations in the antennal lobe are: (i) local interneurons ramifying in the entire lobe, (ii) unilateral relay interneurons that extend from single glomeruli into the calyx and the lateral protocerebrum (LPR), (iii) unilateral interneurons that connect several glomeruli with the LPR only, (iv) bilateral interneurons that link a small number of glomeruli in both antennal lobes with the calyx and LPR, (v) giant bilateral interneurons characterized by extensive ramifications in both antennal lobes and the posterior brain and a cell body situated in the midline of the suboesophageal ganglion, and (vi) a unilateral interneuron with extensive arborization in one antennal lobe and the posterior brain and a process that extends into the thorax. These structural results are discussed in the context of the available functional and behavioral data.Abbreviations AC antennal commissure - AMMC antennal mechanosensory and motor center - iACT, mACT, oACT inner/middle/outer antenno-cerebral tract - bACTI, uACTI bilateral/unilateral ACT relay interneuron - AN antennal nerve - AST antenno-suboesophageal tract - FAI fine arborization relay interneuron - GSI giant symmetric relay interneuron - LI local interneuron - LPR lateral protocerebrum - SOG suboesophageal ganglion - TI thoracic relay interneuron - bVI bilateral V-relay interneuron     

Ultrastructural organization of the hamster renal pelvis.

The renal pelvis of the hamster has been studied by light microscopy (epoxy resin sections), transmission electron microscopy, and morphometric analysis of electron micrographs. Three morphologically distinct epithelia line the pelvis, and each covers a different zone of the kidney. A thin epithelium covering the outer medulla (OM) consists of two cell types: (1) granular cells are most numerous and have apically positioned granules which stain intensely with toluidine blue, are membrane-bound, and contain a fine particulate matter that stains light grey to black in electron micrographs. (2) Basal cells do not have granules, are confined to the basal lamina region, and do not reach the mucosal epithelial surface. The inner medulla (IM) is covered by a pelvic epithelium morphologically similar to collecting duct epithelium of IM. Some cells in this portion of the pelvic epithelium (IM) stain intensely dark with toluidine blue, osmium tetroxide, lead, and uranyl acetate. Transitional epithelium, which separates cortex (C) from pelvic urine, has an asymmetric luminal plasma membrane and discoid vesicles, each of which is similar to those previously observed in mammalian ureter and urinary bladder epithelia. Based on morphological comparisons with other epithelia, the IM and OM pelvic epithelia would appear permeable to solutes and/or water, while the transitional epithelium covering the C appears relatively impermeable. It would also appear that the exchange of solutes and water between pelvic urine and OM would involve capillaries, primarily, since morphometric analysis showed that both fenestrated and continuous capillaries of the OM were extremely abundant (greater than 60% of OM pelvic surface area) just under the thin pelvic epithelium.     

The activity of mitochondrial alpha-glycerophosphate dehydrogenase in the rat nephron following triiodo-L-thyronine treatment: a histochemical study.

The effect of triiodo-L-thyronine (T3) treatment (15 mug/100 g body weight daily for 10 days) on the activity of mitochondrial alpha-glycerophosphate dehydrogenase (GPOX) in different nephron segments of the male rat was investigated by a histochemical staining method. The study showed marked segmental differences regarding the response to T3-treatment: 1. The first two proximal segments were unstained in the control rats and intensely stained following treatment. 2. The third proximal segments, the thick ascending limbs of Henle's loop and the distal convolted tubules showed a strong or moderate reaction in controls and a moderate increase after T3-treatment. 3. The high activity of collecting ducts in the cortex and outer zone of the medulla in controls was slightly increased by treatment. 4. Faintly reacting glomeruli and negative thin limbs of Henle's loop and collecting ducts in the inner medulla (papilla) were unaffected by T3-treatment. The results are discussed in relation to biochemical and physiological data.     

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.     

Tissue injury after lithium treatment in human and rat postnatal kidney involves glycogen synthase kinase-3β-positive epithelium

It was hypothesized that lithium causes accelerated and permanent injury to the postnatally developing kidney through entry into epithelial cells of the distal nephron and inhibition of glycogen synthase kinase-3β (GSK-3β). GSK-3β immunoreactivity was associated with glomeruli, the thick ascending limb of Henle's loop, and collecting ducts in the developing and adult human and rat kidney. In rats, the abundance of inactive, phosphorylated GSK-3β (pGSK-3β) protein decreased during postnatal development. After feeding of dams with litters lithium [50 mmol Li/kg chow, postnatal (P) days 7-28], the offspring showed plasma lithium concentration of 1.0 mmol/l. Kidneys from lithium-treated rat pups exhibited dilated distal nephron segments with microcysts. Stereological analysis showed reduced cortex and outer medullary volumes. Lithium increased pGSK-3β and the proliferation marker proliferating cell nuclear antigen (PCNA) protein abundances in the cortex and medulla. After lithium treatment, pGSK-3β-immunopositive cells exhibited restricted distribution and were associated primarily with subsets of cells in dilated and microcystic segments of cortical collecting ducts. After 6 wk of lithium discontinuation, adult rats exhibited attenuated urine concentration capacity and diminished outer medullary volume. Histological sections of two nephrectomy samples and a biopsy from three long-term lithium-treated patients showed multiple cortical microcysts that originated from normally appearing tubules. Microcysts were lined by a cuboidal PCNA-, GSK-3β-, and pGSK-3β-immunopositive epithelium. The postnatal rat kidney may serve as an experimental model for the study of lithium-induced human kidney injury. The data are compatible with a causal relationship between epithelial entry of lithium into cells of the aldosterone-sensitive distal nephron, inactivation of GSK-3β, proliferation, and microcysts.     

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)     

Cobalt sulphide staining of optic fibres in the brain of the cricket,Gryllus campestris

Neuronal projections from one optic lobe to other parts of the brain were stained in the cricket Gryllus campestris using the cobalt sulphide technique and Timm's sulphide-silver method. The results are: Four tracts directly connect the medulla with the lobula and medulla of the contralateral optic lobe. Direct medullar projections end mainly in the non-glomerular neuropile of the protocerebrum, but also penetrate the calyx of the mushroom bodies, pons and central body in small numbers. A few somata which send fibres into the medulla lie in the pars intercerebralis, in the protocerebrum ventral to the opposite beta-lobe, the outer margin of the medulla of the contralateral optic lobe and between deuto- and tritocerebrum. The anatomical and physiological relevance of the stained connections is discussed.     

Localization of S-adenosylhomocysteine hydrolase in the rat kidney.

S-adenosylhomocysteine (SAH) hydrolase is a cytosolic enzyme present in the kidney. Enzyme activities of SAH hydrolase were measured in the kidney in isolated glomeruli and tubules. SAH hydrolase activity was 0.62 +/- 0.02 mU/mg in the kidney, 0.32 +/- 0.03 mU/mg in the glomeruli, and 0.50 +/- 0.02 mU/mg in isolated tubules. Using immunohistochemical methods, we describe the localization of the enzyme SAH hydrolase in rat kidney with a highly specific antibody raised in rabbits against purified SAH hydrolase from bovine kidney. This antibody crossreacts to almost the same extent with the SAH hydrolase from different species such as rat, pig, and human. Using light microscopy, SAH hydrolase was visualized by the biotin-streptavidin-alkaline phosphatase immunohistochemical procedure. SAH hydrolase immunostaining was observed in glomeruli and in the epithelium of the proximal and distal tubules. The collecting ducts of the cortex and medulla were homogeneously stained. By using double immunofluorescence staining and two-channel immunofluorescence confocal laser scanning microscopy, we differentiated the glomerular cells (endothelium, mesangium, podocytes) and found intensive staining of podocytes. Our results show that the enzyme SAH hydrolase is found ubiquitously in the rat kidney. The prominent staining of SAH hydrolase in the podocytes may reflect high rates of transmethylation. (J Histochem Cytochem 48:211-218, 2000)     

Immunocytochemical localization of carbonic anhydrase on ultrathin frozen sections with protein A-gold

The protein A-gold technique was used to localize carbonic anhydrase isozymes on ultrathin frozen sections of kidney collecting duct epithelial cells and erythrocytes. The particulate nature of the gold marker gives a more precise appreciation of the intracellular distribution of this enzyme than has been previously possible, and allows the intensity of the labeling to be quantified. Intercalated cells showed four times more labeling over the cytosol than adjacent principal cells in collecting ducts from the inner stripe of the outer medulla: by double-labeling using protein A-gold particles of different sizes, carbonic anhydrase isozymes B and C were simultaneously localized in erythrocytes.     

Aldose reductase and sorbitol dehydrogenase distribution in rat kidney.

The sorbitol pathway catalyzes the conversion of glucose to fructose via the intermediate sorbitol. It consists of aldose reductase (AR) and sorbitol dehydrogenase (SDH). In adult (44 day) kidney zones, AR was highest in the outer medulla. In substructures AR was highest in distal convoluted tubule. The AR was greatest in newborn and 8-day zones of developing rat kidney. Acute alloxan diabetes was associated with decreased AR in small arteries, but not glomeruli. The SDH was lowest in outer medulla. It was most active in glomeruli and distal convoluted tubules. The diabetic state leads to no change of SDH in arteries but an increase in glomeruli. SDH increased with development. This study demonstrates AR and SDH in substructures of the kidney. The pathway is present in developing kidney. In diabetes the enzymatic changes would tend to decrease accumulation of sorbitol.     

Stem cell marker TRA-1-60 is expressed in foetal and adult kidney and upregulated in tubulo-interstitial disease

The kidney has an intrinsic ability to repair itself when injured. Epithelial cells of distal tubules may participate in regeneration. Stem cell marker, TRA-1-60 is linked to pluripotency in human embryonic stem cells and is lost upon differentiation. TRA-1-60 expression was mapped and quantified in serial sections of human foetal, adult and diseased kidneys. In 8- to 10-week human foetal kidney, the epitope was abundantly expressed on ureteric bud and structures derived therefrom including collecting duct epithelium. In adult kidney inner medulla/papilla, comparisons with reactivity to epithelial membrane antigen, aquaporin-2 and Tamm–Horsfall protein, confirmed extensive expression of TRA-1-60 in cells lining collecting ducts and thin limb of the loop of Henle, which may be significant since the papillae were proposed to harbour slow cycling cells involved in kidney homeostasis and repair. In the outer medulla and cortex there was rare, sporadic expression in tubular cells of the collecting ducts and nephron, with positive cells confined to the thin limb and thick ascending limb and distal convoluted tubules. Remarkably, in cortex displaying tubulo-interstitial injury, there was a dramatic increase in number of TRA-1-60 expressing individual cells and in small groups of cells in distal tubules. Dual staining showed that TRA-1-60 positive cells co-expressed Pax-2 and Ki-67, markers of tubular regeneration. Given the localization in foetal kidney and the distribution patterns in adults, it is tempting to speculate that TRA-1-60 may identify a population of cells contributing to repair of distal tubules in adult kidney.     

Histochemical and immunohistochemical localization of hexokinase isoenzymes in rat kidney

Summary Histochemical and immunohistochemical staining techniques have been used to investigate the localization of hexokinase isoenzymes within rat kidney tissue. Hexokinase type I was shown to be the major isoenzyme present. It was located mainly in the thin and thick limbs of loops of Henle, in distal tubules and in the transitional or dark cells in the initial portions of collecting ducts. The smooth muscle cells of arteries and arterioles, peripheral nerves and the transitional epithelial cells lining the renal pyramid also contained large amounts of the isoenzyme while smaller quantities were present in glomeruli and in collecting tubules near the papillary tip. The distribution pattern obtained in tubular epithelia agrees well with that demonstrated in earlier microdissection studies. It is also consistent with the suggestion that glycolysis provides the majority of the energy fuelling the sodium transport mechanisms which form such an essential feature of the countercurrent urine concentration system present within the renal medulla.