Survey of the morphology of the dog kidney.

Dogs are frequent subjects in experimental studies of renal physiology and pathology in spite of the paucity of information on their normal renal morphology. In this study, gross morphology, light microscopy, and scanning and transmission electron microscopy were used to describe dog renal anatomy. The dog has a multilobed kidney with the medulla fused into an elongate crest and a renal pelvis of elaborate shape. The outer zone of the medulla lacks a definitive outer stripe. The proximal tubule consists of four distinct anatomical segments. Dark cells are abundant in the collecting duct of the inner medulla. The majority of the nephron segments demonstrate remarkable similarities to those of the human kidney and less to those of the kidney of the laboratory rat.     

Glutamine synthetase and glutamyltransferase in the kidney of man, dog, and rat.

Glutamine synthetase (GS) is known to exist in the kidney of the rat, guinea pig, rabbit, and sheep but not in that of the dog, pig, cat, or pigeon. No data is available in man. Assay of histologically normal renal tissue obtained in human subjects during surgery for abdominal vascular disease failed to demonstrate significant GS activity. In addition, L-glutamine gamma-glutamyltransferase (GT) activity was also very low. The same results were observed in the dog, in which both GS and GT activities did not exceed 15% of those found in the kidney of the normal rat. In the latter animal both GS and GT activities are higher in the outer medulla (312 and 1,165 mumol/h per g wet wt, respectively) than in the cortex (230 and 844, respectively). During metabolic acidosis, GT activity did not change but GS activity decreased in the outer medulla by 40%. When renal cortex slices from normal rats were incubated in the presence of ammonia, glutamate, and octanoate (as a source of ATP), net synthesis of glutamine was readily demonstrated in contrast to slices from normal DOGS. The present studies demonstrate that the kidney of man, like that of the dog, is devoid of significant glutamine synthetase and glutamine gamma-glutamyltransferase activities. In the rat, we have confirmed the functional significance of GS activity in the kidney. We have also shown that renal GT activity is ammoniagenic in vitro in this animal, but the contribution of this system to total ammonia production in vivo remains to be demonstrated.     

The pelvic epithelium of the rat kidney: A scanning and transmission electron microscopic study

The renal pelvis of the rat is characterized by extensions called specialized fornices that penetrate into the outer zone of the outer medulla (a type II as classified by Pfeiffer, 1968, 1970). The renal pelvic epithelium, therefore, covers areas of the kidney from the inner medulla, the inner and outer stripe of the outer medulla, and the cortex. The renal pelves of seven rats were studied by transmission and scanning electron microscopy. The transitional epithelium on the nonparenchymal surface of the pelvis was three to four cell layers thick (zone 0–1). This epithelium became thinner where it covered the renal cortex (zone 1–2) or the outer medulla. Although the apical cells of the epithelium retained the asymmetric luminal unit-membrane plaques, the number of cytoplasmic fusiform vesicles decreased as one studied the epithelium progressing over the zones from cortex toward papilla. Scanning electron microscopy demonstrated a small number of surface cells of a different morphology that were characterized by apical microvilli. The number of these microvillous lining cells increased as the epithelium covering the outer (zone 2–3) and inner (zone 3–4) stripe regions of the outer medulla was viewed, until the inner medulla was entirely covered by this cell type. In a reciprocal manner, the cells with the asymmetric apical plaques decreased in numbers and in their morphologic specialization in each successive region. The epithelium surrounding the inner medulla (zone 6–7) was completely devoid of this transitional cell type. Judging from the morphologic characteristics of the epithelia, one could surmise that little exchange of urea, water, and salts would occur with the extrarenal connective tissue or the cortical parenchyma. Recycling of urea might become more important physiologically with the outer stripe parenchyma, and even more so with the increased surfaces of the inner stripe parenchyma that lined the secondary pyramid, as well as with the epithelium lining the inner medulla.     

Outer medullary circulatory defect in ischemic acute renal failure.

Changes in medullary circulation may contribute significantly to the pathogenesis of ischemic acute renal failure. The microcirculation of the outer medulla of the rat kidney was studied by morphometry, carbon injection, and scanning electron microscopy of vascular casts after temporary renal ischemia. Morphometry showed a markedly reduced vascular area and an increased tubular epithelial cell area in the outer stripe of the medulla 2 hours after blood reflow. Maximum diminution in vascular area occurred 24-48 hours after reflow, with swollen and later necrotic tubular epithelium compressing the surrounding vascular compartment. Outflow blockade of venous vasa recta in the outer stripe caused congestion of the inner stripe. Carbon injection and scanning electron microscopy of vascular casts confirmed the perfusion defects of the outer stripe. These results suggest that decreased blood reflow to the outer stripe of the medulla secondary to tubular epithelial cell swelling and necrosis plays a significant role in the pathogenesis of ischemic acute renal failure in the rat.     

Intrarenal distribution of citrate in the dog during antidiuresis and diuresis

Summary The intrarenal distribution of citrate was evaluated in the dog during antidiuresis and osmotic diuresis, by using the specific citrate assay method of Moellering and Gruber. The measurements were made on tissue samples taken from four different regions throughout the kidney: cortex, outer and inner medulla, and papilla. During antidiuresis, a characteristic distribution of citrate was observed with highest levels in the papilla and lowest ones in the outer medulla. A medullary concentration gradient for citrate was found. Mannitol greatly decreased papillary citrate and sodium, but no changes in outer and inner medullary citrate occured. The results could not be explained by the citrate contained either in the trapped urine or blood in the tissue. It is suggested that citrate accumulation in the inner regions of renal medulla may be accounted for by countercurrent mechanisms or regional differences in renal citrate metabolism.Supported by grants from I.N.S.E.R.M. (n^o 72.1.062.5) and Fondation pour la Recherche Médicale.     

小鼠长髓襻肾单位在髓质的分布

目的 肾髓质渗透梯度的形成与髓襻走行及转运功能关系密切,本研究拟建立长髓袢肾单位在髓质的走行规律。方法C57BL6/J小鼠3只,灌流固定后取肾组织块,树脂812包埋,垂直肾长轴连续半薄切片,从肾被膜到内髓,共得到2 000张2.5μm厚的连续切片,显微镜下获取数字图像,计算机配准,C语言编程,进而追踪26条长髓襻肾单位。结果 长髓襻肾单位来自中层和近髓质区的皮质,其髓襻襻曲分布在内髓不同水平,最深的可达肾乳头。通过数字追踪发现,在外髓内带外侧区,髓襻降支细段起始部高度盘曲走行,其盘曲部分的长度是其直线距离的2倍。在盘曲走行中,与同源的髓襻升支粗段间隔排列。最长的长髓襻升支粗段走行在外髓内带的血管丛。在外髓内带的内侧区,髓襻降支细段与髓襻升支粗段紧密相邻,直行进入内髓。结论 降支细段在外髓内带高度盘曲走行,在增加了这一节段长度的同时,也增加了这一节段的转运功能,提示此结构特征对该区域的渗透梯度形成可能产生重要影响。     

Morphological study of the desert heteromyid kidney with emphasis on the genus Perognathus.

The renal morphology of three species of desert dwelling Perognathus rodents were compared to Dipodomys and two species of sympatric cricetid rodents. Perognathus has a highly adapted unipolar kidney capable of urine concentration up to 7,500 mOsm/KgH2O. Two major modifications were observed in these kidneys. (1) There is elongation of both the inner and outer medulla. When the thickness of the regions in P. penicillatus are factored by kidney weight it is found that the outer medulla is 3.8 and the inner medulla is 2.2 times greater in length than the extensively studied Dipodomys merriami. (2) There is great variance in glomerular size with approximately 20% of the glomeruli being very large and located in the juxta medullary region. These glomeruli are 1.5--1.6 times greater in diameter than the more numerous superficial glomeruli. These structural modifications are quantitated and the functional implications are discussed particularly in relation to urine concentrating ability in these desert inhabitants.     

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.     

A morphological and biochemical study of the effects of L-cysteine on the renal uptake and nephrotoxicity of cadmium.

In JCLR and Wistar-Porton rats renal concentrations of Cd2+ were maximal (21-22 micrograms Cd2+/g wet wt tissue) at 1 and 4 h respectively after the administration of CdCl2 (10 micromol, 1-12 mg Cd2+/kg body wt) together with L-cysteine (5 mmol/kg body wt). Synthesis of metallothionein in the kidney in response to the uptake of Cd2+, which occurred between 2 and 7 h after treatment in the Wistar-Porton rat, affected the distribution of Cd2+ between proteins of the renal soluble fraction, but not between the particulate components and, at both times, about 40% of the total Cd2+ was associated with the heterogeneous nuclei + cell debris fraction. Autoradiographic studies with 109CdCl2 revealed that Cd2+, accumulated by the kidney under these conditions, was not uniformly distributed throughout the renal cortex, but was concentrated unevenly in proximal tubules in the outer stripe of the outer zone of the medulla. Pathological changes, which were correlated with the concentrations of accumulated Cd2+ and were limited to the S3 segments of the proximal tubules, were apparent by light microscopy at 4 h after the administration of Cd2+ + cysteine and progressed with time. Thus by 7 h the lesion had extended to include almost the whole of the outer stripe of the outer zone of the medulla and, by 24 h the cells of the affected epithelia showed extensive necrosis and karyorrhexis. At this, as at earlier times, the cortex appeared to be undamaged. Neither these nor other morphological changes were observed in the kidneys of animals that had been dosed with either Cd2+, or L-cysteine alone. Within 60 min of the administration of Cd2+ + cysteine an increase in the number of endocytotic vesicles in the apical cytoplasm of the proximal tubular epithelium was observed by electron microscopy. Subsequent cytoplasmic vesiculation, which was conspicuous at 2 h, was extensive and widespread in both the apical and basal regions of the cytoplasm at 4 h. In some cells at this time the nuclei were irregular in shape; the mitochondria were swollen and their cristae were disorganized. As, after the administration of either Cd2+ or cadmium-metallothionein, damage is known to occur in the S1 and S2 segments of proximal tubules throughout the cortex, the Cd2+ + cysteine combination does not provide an exact model which reproduces in a short time the effects of long-term, low level exposure to Cd2+. Nevertheless it is suggested that the toxic mechanisms are the same after either treatment with Cd2+ + cysteine or continual exposure to Cd2+, but are limited to different segments of the proximal tubules. Possible mechanisms of toxicity are discussed.     

Morphological study of the desert heteromyid kidney with emphasis on the genus perognathus

The renal morphology of three species of desert dwelling Perognathus rodents were compared to Dipodomys and two species of sympatric cricetid rodents. Perognathus has a highly adapted unipolar kidney capable of urine concentration up to 7,500 mOsm/KgH₂O. Two major modifications were observed in these kidneys. (1) There is elongation of both the inner and outer medulla. When the thickness of the regions in P. penicillatus are factored by kidney weight it is found that the outer medulla is 3.8 and the inner medulla is 2.2 times greater in length than the extensively studied Dipodomys merriami. (2) There is great variance in glomerular size with approximately 20% of the glomeruli being very large and located in the juxta medullary region. These glomeruli are 1.5-1.6 times greater in diameter than the more numerous superficial glomeruli. These structural modifications are quantitated and the functional implications are discussed particularly in relation to urine concentrating ability in these desert inhabitants.     

Blood supply and drainage of the outer medulla of the rat kidney: scanning electron microscopy of microvascular casts

Blood supply and drainage of the outer medulla of the rat kidney were studied by scanning electron microscopy of vascular casts, using both arterial (n = 10) and venous (n = 10) injections of resin. Both outer and inner stripes of the outer medulla were supplied through different arterial capillary networks arising from efferent arterioles and arterial (descending) vasa recta. In contrast to previous studies using silicone rubber and light microscopy, a rich arterial capillary network supplying the outer stripe was demonstrated. Capillaries in the outer stripe and outer part of the inner stripe drained into venous vasa recta between vascular bundles, while capillaries in the inner part of the inner stripe drained into venous vasa recta within the bundles. The results indicate that each zone in the outer medulla is supplied through separate capillary networks. The demonstration of a rich capillary network in the outer stripe of the outer medulla suggests that the predilection of this zone for tubular necrosis with ischemic or toxic injury is not related to a sparse capillary blood supply.     

Morphologic and functional evidence for oxygen deficiency in the isolated perfused rat kidney

Morphologic and functional studies were undertaken in the isolated rat kidney, perfused with an albumin-Krebs-Henseleit solution, to which 5% human erythrocytes and/or various amino acids had been added. Perfused only with the albumin-Krebs-Henseleit solution, the kidneys displayed a characteristic pattern of cell necrosis after 2 hours of perfusion, which was confined to the interbundle region of the outer medulla and was not evident in either the cortex or the inner medulla. In the outer stripe only those proximal straight tubules (P3 segments) farthest from the vascular bundles were damaged. In the inner stripe only those thick ascending loops of Henle at the periphery of the vascular bundles escaped damage; all thick ascending loops of Henle lying farthest from the bundles were severely damaged. The number of damaged tubules increased toward the border to the inner medulla. Necroses in both segments, P3 and thick ascending loops of Henle, could be prevented by perfusion with the erythrocyte-albumin-Krebs-Henseleit solution but not by the addition of glutathione, in the absence of erythrocytes. Perfusion with the erythrocyte medium also significantly improved glomerular filtration rate and sodium and glucose reabsorption. It is concluded that, in the isolated, erythrocyte-free perfused kidney, the oxygen content of the "arterial" vasa recta in the vascular bundles is only sufficient to supply the tubules in the immediate surroundings. Countercurrent exchange in the vascular bundles between arterial and "venous" vasa recta progressively lowers the arterial oxygen content as the inner stripe of the outer medulla is approached and with it the number of tubules receiving an adequate oxygen supply.     

The effects of asphyxia on afferent activity recorded from the cervical vagus in the duck

Summary The rats with chronic renal hypertension caused by constricting one renal artery, exhibit a decrease in the activity of Na–K-ATPase in the outer medulla of the untouched kidney, as compared to this activity in the kidneys of intact normotensive rats and in the untouched kidney of the rats where renal artery constriction did not result in hypertension.There were no differences between the control normotensive Wistar rats and the spontaneously hypertensive rats (SHR) in the prehypertensive and early hypertensive stages (at the age of 6–8 weeks) as far as the activities of Na–K-ATPase and oxidoreductases (SDH and LDH) in the renal cortex, the outer and inner medulla are concerned. The spontaneously hypertensive rats with chronic hypertension had at the age of 16–20 and 27–29 weeks lower activity of Na–K-ATPase, SDH, and LDH in the outer renal medulla than the control normotensive Wistar rats.The experimental results indicate that in chronic arterial hypertension there is a decrease in the activity of Na–K-ATPase, in the outer renal medulla, which suggests a reduction in the resorption capabilities of the ascending Henle's loop with respect to sodium and water.     

Response of the medullary thick ascending limb to hypothyroidism in the rat.

Hypothyroidism in the rat is associated with a decrease in kidney size and weight. We have shown previously that this decrease involves all nephron segments in the cortex and outer medulla and is especially pronounced in the medullary thick ascending limb (mTAL). Therefore, the present study was undertaken for examination of the effect of hypothyroidism on the ultrastructure of the rat mTAL. Hypothyroidism was induced by feeding aminotriazole (ATZ), 0.5 g/kg of food, for 4 weeks. A second group of animals received ATZ plus a daily injection of L-thyroxine (T4). A third group was fed a normal diet only and served as control animals. The kidneys were preserved by in vivo perfusion with 3% glutaraldehyde, and tissue from the inner and outer stripe of the outer medulla was processed for electron microscopy. Morphometric analysis revealed a significant decrease in the cross-sectional area of the mTAL in both the inner and outer stripe of the outer medulla in hypothyroid animals. No changes were observed in the surface density of either the apical or basolateral plasma membranes following ATZ treatment. However, when calculated per millimeter tubule, there was a significant decrease in the surface area (SL) of both the apical and basolateral plasma membranes of the mTAL of hypothyroid animals in comparison with control animals. Simultaneous treatment with T4 prevented the ATZ-induced reduction in both tubule cross-sectional area and in the SL of the plasma membrane. These findings suggest that the observed changes in SL of the plasma membrane of the mTAL are due to a regulatory role of thyroid hormone in membrane proliferation as well as in cell growth in general.     

Postnatal development of the interstitial tissue of the rat kidney

Summary To study the ontogenetic development of the interstitial tissue of the kidney, rats were investigated 1, 3, 7, 14, 21 and 28 days after birth. Kidneys perfusionfixed with glutaraldehyde were studied with light- and electron microscopy. Cryostate sections from kidneys immediately frozen in liquid nitrogen were studied with respect to the expression of MHC class II antigen using the monoclonal antibody OX6. The interstitial space of both the renal cortex and the outer and inner medulla was prominent during the first days postnatally. The relative interstitital volume of the cortex and outer part of the medulla then decreased in conjunction with the outgrowth and maturation of the superficial nephrons while the inner medullary interstitium remained wide. During the first postnatal days, the abundant interstitial cells of the cortex were connected via cytoplasmic processes to form a loose network which later became less well defined. The lipid-laden interstitial cells of the inner medulla showed essentially the same ultrastructure in the newborn as in the adult animal. Strong expression of class II antigen first appeared on epithelial cells of the thick ascending limb of Henle’s loop about 7 days postnatally, and became weak at 28 days. From 21 days, a weak staining of the proximal tubules was also observed. While interstitial cells in the inner medulla were always negative, cortical and outer medullary interstitial cells became strongly positive for class II antigen from day 21 post partum.     

Regional expression of inducible nitric oxide synthase in the kidney stimulated by lipopolysaccharide in the rat

The renal medulla contains more mRNA of the inducible isoform of nitric oxide synthase (iNOS) than the cortex, which may be important in preventing ischaemic injury, since blood flow and tissue oxygen tension are normally low in this region. We examined the effects of the bacterial endotoxin E. coli lipopolysaccharide (LPS) on renal function and regional expression of iNOS in male Sprague-Dawley rats. In six rats, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were 0.95 +/- 0.09 ml min(-1) g(-1) and 3.36 +/- 0.20 ml min(-1) g(-1), respectively, and decreased significantly to 0.35 +/- 0.09 and 1.74 +/- 0.54 ml min(-1) g(-1), respectively, 1 h after administration of LPS. In an additional seven rats, GFR and ERPF were 0.91 +/- 0.07 and 2.97 +/- 0.30 ml min(-1) g(-1), respectively, 18 h after LPS administration; these values were similar to those in control rats. In all rats, arterial pressure was stable throughout all study periods. In control rats, immunoblot analysis revealed expression of the iNOS protein in the cortex and more pronounced expression in the medulla. In rats studied 18 h after LPS treatment, there was a striking increase in the iNOS expression in the outer medulla. Immunohistochemical examination in the LPS-treated rats showed limited iNOS immunostaining in the cortex, localised to the vascular endothelium and macula densa; however, intense and widespread staining was noted in the tubular and vascular structures of the outer medulla. These findings demonstrated a differential constitutive expression of iNOS protein in different regions of the rat kidney, and marked augmentation of iNOS expression in the outer medulla by LPS.     

Renal vasculature of the trout demonstrated by scanning electron microscopy,compared with canine glomerular vessels

In order to gain additional information regarding renal circulatory patterns, we have used both ink and resin injections to study the arterial supply to the mesonephric kidney of trout. Arterial injections through the dorsal aorta with ink were made for histological preparations in which the length, termination and relationship of glomerular vessels were examined. Similar injections with methyl methacrylate were made in preparation of corrosion casts to provide us with gross replicas of the aortic branches to the kidney as well as casts of glomerular structure for scanning electron microscopy. The sequence of vessels through which arterial blood passed to the renal corpuscle and ultimately to the uriniferous tubules was traced. Each afferent arteriole was found to terminate in three to six brancehs which formed anastomosing circuits of capillaries; these vessels reunited at the hilum to form a single efferent arteriole. The efferent arterioles in turn traveled a short distance to peritubular capillary beds and sinusoids. Morphological evidence was found for preglomerular sphincter-like action only. The glomerular vessels were found to be similar to, although less complex than, those of the outer and mid-cortical regions of the dog kidney.     

Magnetic resonance histology of age-related nephropathy in the Sprague Dawley rat

Magnetic resonance histology (MRH) has become a valuable tool in evaluating drug-induced toxicity in preclinical models. However, its application in renal injury has been limited. This study tested the hypothesis that MRH could detect image-based biomarkers of chronic disease, inflammation, or age-related degeneration in the kidney, laying the foundation for more extensive use in evaluating drug toxicity. We examined the entire intact kidney in a spontaneous model of chronic progressive nephropathy. Kidneys from male Sprague Dawley rats were imaged at 8 weeks (n = 4) and 52 weeks (n =4) on a 9.4 T system dedicated to MR microscopy. Several potential contrast mechanisms were explored to optimize the scanning protocols. Full coverage of the entire kidney was achieved with isotropic spatial resolution at 31 microns (voxel volume = 30 pL) using a gradient recalled echo sequence. Isotropic spatial resolution of 15 microns (voxel volume < 4 pL) was achieved in a biopsy core specimen. Qualitative age-related structural changes, such as renal cortical microvasculature, tubular dilation, interstitial fibrosis, and glomerular architecture, were apparent. The nondestructive 3D images allowed measurement of quantitative differences of kidney volume, pelvis volume, main vessel volume, glomerular size, as well as thickness of the cortex, outer medulla, and inner medulla.     

Passage of plasma through the kidney studied by external counting and autoradiography

Summary At different times after injection into the renal artery of¹³¹I-albumin, the distribution of the tracer in kidneys of the rabbit and the dog was illustrated by a series of autoradiograms. In order to determine the mean circulation time for albumin in the kidney, the radioactivity over the kidney was simultaneously registered by external monitoring. A short mean circulation time was measured for albumin (plasma) passing cortex, and a longer one for that fraction of the albumin that passed through medulla, papillae, and capsule. The investigation rendered probable that the mean circulation time for blood through the kidney determined by the external technique applies to blood passing cortex. The circulation times for blood through medulla, papillae, and capsule are not included in the calculation of the mean circulation time.The work was supported by a grant from King Christian X's Foundation     

Adaptation of the rat kidney to altered water intake and urine concentration

Previous experiments in Brattleboro rats with hereditary diabetes insipidus revealed that absence of ADH led to several alterations in kidney anatomy, which could be reversed by chronic ADH treatment. Present experiments were undertaken to determine if similar alterations were observable in normal Wistar rats when endogenous ADH level was varied by manipulating water intake or when exogenous ADH was infused. Water intake was increased by giving food with a high water content ad libitum and offering 5% glucose solution to drink (HWI rats), or decreased by reducing water intake to 1/3 of spontaneous intake (RWI rats). An additional group received chronic ADH infusion with Alzet osmotic minipumps (ADH rats). Results were compared to those obtained in control rats (CON) drinking ad libitum. RWI, CON, and ADH rats ate dry pellets ad libitum. After 6 weeks on these regimens kidneys were perfusion fixed and serial sections were cut for morphometric measurements by light microscopy. Results in the four groups showed that kidney weight relative to body weight was influenced by the operation of urinary concentrating mechanism, with HWI相似文献