Nephrogenic Tissue Research Articles

Microanatomy and Ultrastructure of the Mesonephros of Cyprinids Inhabiting the Territory of Kazakhstan

The ultrastructure of three species of cyprinids inhabiting the territory of Kazakhstan has been studied. It is shown that the microanatomy of the trunk bud of the Kushakevich char Iskandaria kuschakewitschi, the common marinka Schizothorax intermedius and the Tibetan char Noemacheilus stoliczkai has a common body plan with freshwater cyprinids. Larger area of nephrogenic tissue, greater number of mitochondria on sections of proximal tubules and leukocyte sections, three types of vesicles in cells with radially arranged vesicles, larger diameter of distal tubules, diversity of mitochondria of epitheliocytes of distal tubules of the studied species, compared with previously studied representatives of carp reservoirs of the Upper Volga, testify to the adaptive ability of the cellular structures of the mesonephros to maintain water-salt homeostasis, as well as the functioning of the cellular link of immunity in the life of the rivers of Kazakhstan with a seasonal increase in water temperature up to 27°C. The diversity of the ultrastructure of granules of neutrophils and eosinophils depends on the stage of the life cycle and the characteristics of the functional activity of cells.

New Data on Nephron Microanatomy and Ultrastructure of Senegal Bichir (Polypterus senegalus).

Simple SummaryTransitional forms of animals between Pisces and Amphibia are interesting to study, as they are the first to begin the development of a new environment - terrestrial. Such a transitional form are amphibious fish. The study of the structure of the nephron, the main structure that performs an osmoregulatory function, makes it possible to build evolutionary series that describe the processes of transition from the aquatic environment to the terrestrial one. Bichirs is a monophyletic group that arose in the Devonian and formed a species complex only in the Neogene. They share features with lungfish and amphibians, which formed convergently in the early stages of evolution. Therefore Bichirs are of great interest as a transitional form of animals. This study presents new data on the nephron age of Polypterus senegalus. Two groups of features are described. The first group consists of ancestral traits that have been preserved in the modern population of P. senegalus and are associated with habitat conditions in the aquatic environment. The second group is a complex of characters associated with the adaptation of P. senegalus to air breathing and periodic ground migrations.This study presents new data on the microanatomy and ultrastructure of Polypterus senegalus nephrons. It was shown that the diameter and ultrastructure of renal corpuscles, a well-developed neck segment, and ultrastructure of two types of epithelial cells of the proximal tubule are ancestral signs of the modern population of P. senegalus associated with habitat conditions in the aquatic environment. The outer diameter of the tubules, the height of the epitheliocytes, the presence of two types of epithelial cells of the intermediate and distal tubules of the corresponding ultrastructure, and a large area of nephrogenic tissue are progressive features of the modern population of P. senegalus, associated with adaptation to air respiration and periodic terrestrial migrations, which were formed at the early stages of evolution of P. senegalus convergently with lungfish and amphibians.

Multilocular Cystic Nephroma. Kidney Disease Difficult To Diagnose Before Surgery: A Case Report

Cystic nephroma is a benign renal lesion. It is a benign and rare cystic tumor of the kidney whose diagnosis needs renal specimen after nephrectomy. We report an observation of 62-year-old woman, obese with a history of type 2 diabetes who consults for left lumbar pain without hematuria. The examination found no lumbar contact or signs of urinary tract infection. The first exploration by an abdominal echotomographic shows the existence of an inferior medieval and polar lesion of 84mm of the large axis, heterogeneous with multiple anechoic zones within it of small sizes. The interpretation made by the radiologist retained 3 possible diagnoses, namely: a renal mass suspected of malignancy, a heterogeneous multicystic lesion and a hydatid cyst stage III of Gerbi. The computed tomography found a heterodyne left medieval tumor process and lower polar poorly limited with several areas of necrosis of 80mm of large diameter taking the contrast and interpreted as a malignant lesion, without hilar lymphadenopathies or retroperitoneal visible. The rest of the extension balance sheet was free of anomalies. Hydatid serology was performed and returned negative. The patient was operated on with the diagnosis of kidney cancer. The intraoperative exploration showed the existence of a left kidney increased in volume in its compartment, the accidental break-in of the latter allowed even the multilocular cystic appearance of small infracentimetric sizes of this lesion. An enlarged total nephrectomy was realized. Macroscopic examination of the part reveals a kidney carrying multiple cystic lesions arranged one against the other without nephrogenic tissue in the septic letting out a clear liquid. The pathology study showed the appearance of a multilocular cystic nephroma. Our patient is alive at 48months and in well health.

Morphological examination of the possible criteria for a simple renal cyst recurrence after sclerotherapy 96° ethanol

Nowadays kidneys’ cysts are widely spread in adult and old persons, they are usually revealed during screening ultrasonic control of population. Cysts’ sclerotherapy is one of the common mini invasive ways of their treatment. Recurrent kidney cysts appear in 12,5-33 % after sclerotherapy. The morphological signs of recurrent cysts have to be determined. Investigation of histological samples of recurrent kidney cyst (n=21) was carried out in the course of the work. The obtained data were compared with the primarily diagnosed kidneys’ cysts (n=40).For the microscopic study the histological samples were stained by hematoxilin and eosin, by the solution of alcyan blue (pH 2,6) and after Van-Gyzon. It is settled that the wall of the cyst turns thinner after conducting of sclerotherapy with 960 ethanol in comparison with the primarily diagnosed kidneys’ cyst (349,04±19,92 μm and 263,64±16,54 μm after sclerotherapy and 618±17,21 μm и 557,5±54,55 μm in compared group, respectively). This fact takes place mostly because of the enormous tissue fibrosis after sclerotherapy. The structure of the recurrent kidneys’ cyst was characterized by unequal thickness of the wall, by an enormous fibrosis, increasing of the arterial wall thickness, lymphatic vessels’ obliteration, sclerosis of the nephrogenic tissue, glomerular deformation and thickening of their walls, tubular deformation and hyaline cylinders inside, large lymphocyte’s and hemorrhagic infiltrates and hemosiderin infiltrates. Interstitial edema, which was caused by venous blood stasis and capillary thrombosis, impairs the basal membrane and interstitial fluid followed by protein component passes into the cavity of the cyst and causes the recurrent cyst development.

Nephroblastomatosis: imaging challenges

Nephroblastomatosis is a rare pre-neoplastic lesion defined as the presence of multiple nephrogenic rests. These are abnormal foci of persistent embryonal cells beyond 36 weeks’ gestation that are thought to be precursors for the development of Wilms tumor. Nephrogenic rests are seen in approximately 1% of pediatric autopsy series. Nephrogenic rests and nephroblastomatosis represent a spectrum of the same disease and the distinction between the two is somewhat arbitrary. There are no formal quantitative criteria that determine how many nephrogenic rests constitute nephroblastomatosis. The nephrogenic rests are divided into four categories in the pathology literature: perilobar, intralobar, combined and diffuse, depending on their location within the renal parenchyma. On imaging, nephroblastomatosis is best classified as multifocal or diffuse. Virtually all cases of bilateral Wilms tumor have associated multifocal nephroblastomatosis. Advances in imaging have increased our ability to detect small renal lesions in situ and, therefore, have played an increasingly significant role in the preoperative diagnosis and postoperative management of nephroblastomatosis and Wilms tumor. Imaging studies are essential in the diagnosis of these lesions and their evaluation over time to detect transformation into Wilms tumor. State-ofthe-art imaging with contrast-enhanced CT and MRI routinely detects lesions as small as 5 mm in diameter. Nephroblastomatosis is considered a predisposing condition to Wilms tumor development both in the ipsilateral and contralateral kidney. Identifying and distinguishing between nephroblastomatosis and Wilms tumor is critical because they imply distinct prognoses and treatment decisions. Differentiation between Wilms tumor and nephroblastomatosis is based on histological evaluation of biopsy combined with imaging studies. Fine-needle aspiration cytology is of limited value in the assessment of these lesions, as cytology is not able to distinguish nephroblastomatosis from Wilms tumor. The anatomical location of nephrogenic rests varies as well as the pattern of their distribution. Importantly, multifocal nephroblastomatosis has a stronger association with Wilms tumor than the diffuse type. The diffusely hyperplastic perilobar nephroblastomatosis has a characteristic appearance that is identified as peripheral confluent masses distorting and compressing the kidney with a thick rind of uniform abnormal tissue. On CT and MR imaging, both types appear similar to the renal cortex on nonenhanced scans. After contrast administration, NRs become markedly hypodense on CT and hypointense on MRI in comparison with the intensely enhancing renal parenchyma. Although there are no absolute imaging criteria to differentiate nephrogenic rests and nephroblastomatosis from Wilms tumor, nephrogenic rests and nephroblastomatosis can be differentiated from Wilms tumor in the same kidney, as Wilms tumors tend to be larger and more heterogeneous and demonstrate some contrast enhancement. Gadolinium-enhanced T1-weighted MRI is currently touted as the optimal imaging approach for detecting nephrogenic tissue, although US and CT are commonly Disclaimer Dr. Grattan-Smith has no financial interests, investigational or off-label uses to disclose.

Congenital solitary kidney with three renal arteries. An MDCT angiographyc study

Congenital solitay kidney (CSK) is one of the most rare renal malformations. CSK has usually a single renal artery. The MDCT angiography of 1700 clinical cases revealed 4 with CSK. Among these only one case with right CSK (male) presented besides the main renal artery also two additional arteries. The main renal artery with origin in the abdominal part of aorta (APA) at the level of L1‐L2 intervertebral disc, with a diameter at origin of 0.53cm, a length of 3.51cm gives rise at three segmentat arteries (SA) (superior, anterior‐superior and posterior superior). The first additional artery originated in the APA at the level of 1/3 lower of L2 vertebra, with a diameter at origin of 0.34cm, and a length of 3.70cm gives rise to two SA (anterior‐inferior and inferior). The second additional renal artery originated in the APA at the level of 1/3 lower of L3 vertebra, with a diameter at origin of 0.32cm and a length of 4.77cm gives rise to a single SA (posterior‐inferior). This association of CSK with the presence of the additional renal arteries involves two distinctive embryologic mechanisms: non‐development of the nephrogenic tissue in the left part, with the persistence of the mesonephric arteries in the right. The knowlwdge of these aspects is important when performing partial kidney resections. (Supported by Grant CNMP 42097/2008).

Diffuse Hyperplastic Perilobar Nephroblastomatosis

Nephroblastomatosis is a rare preneoplastic lesion defined as the presence of diffuse or multifocal nephrogenic rests. They are divided into 4 categories: perilobar, intralobar, combined, and universal. The aim of this report is to describe a case of diffuse hyperplastic perilobar nephroblastomatosis. A 1-year-old boy presented with an abdominal mass on the left side. Computed tomography scan showed a homogeneous, isointense enlarged left kidney. A fine needle aspiration cytology was reported as Wilms tumor. After chemotherapy, the left kidney was excised. Nephrectomy specimen presented a thick cortical rim of hyperplastic nephrogenic tissue, well delineated from preserved renal parenchyma without pseudocapsule. Nephroblastomatosis is a rare condition affecting renal parenchyma. Diagnosis is based on imaging studies, such as ultrasound, computed tomography scan, and magnetic resonance imaging. Fine needle aspiration cytology is of limited value. Therapeutic management is controversial. Chemotherapy is used preoperatively, and surgical excision may be an alternative for refractory cases.

Calpastatin overexpression prevents progression of S-1,2-dichlorovinyl-l-cysteine (DCVC)-initiated acute renal injury and renal failure (ARF) in diabetes

Previously we have shown that 90% of streptozotocin (STZ)-induced type-1 diabetic (DB) mice survive from acute renal failure (ARF) and death induced by a normally LD(90) dose (75 mg/kg, i.p.) of the nephrotoxicant S-1,2-dichlorovinyl-l-cysteine (DCVC). This remarkable protection is due to a combination of slower progression of DCVC-initiated renal injury and increased compensatory nephrogenic tissue repair in the DB kidneys. BRDU immunohistochemistry revealed that the DB condition led to 4-fold higher number of proximal tubular cells (PTC) entering S-phase of cell cycle. In the present study, we tested the hypothesis that DB-induced augmentation of PTC into S-phase is accompanied by overexpression of the calpain-inhibitor calpastatin, which endogenously prevents the progression of DCVC-initiated renal injury mediated by the calpain escaping out of damaged PTCs. Immunohistochemical detection of renal calpain and its activity in the urine, over a time course after treatment with the LD(90) dose of DCVC, indicated progressive increase in leakage of calpain into the extracellular spaces of the injured PTCs of the non-diabetic (NDB) kidneys as compared to the DB kidneys. Calpastatin expression was minimally detected in the NDB kidneys, using immunohistochemistry, over the time course. On the other hand, consistently higher number of tubules in the DB kidney showed calpastatin expression over the time course. The lower leakage of calpain in the DB kidneys was commensurate with constitutively higher expression of calpastatin in the S-phase-laden PTCs of these mice. To test the protective role of newly divided/dividing PTCs, DB mice were given the anti-mitotic agent colchicine (CLC) (2 mg/kg and 1.5 mg/kg, i.p., on days 8 and 10 after STZ injection) prior to challenge with a LD(90) dose of DCVC, which led to 100% mortality by 48 h. Mortality was due to rapid progression of DCVC-initiated renal injury, suggesting that newly divided/dividing cells are instrumental in mitigating the progression of DCVC-initiated renal injury in DB. The anti-mitotic effect of CLC in DB kidney is associated with lower expression of calpastatin and higher leakage of calpain in the injured tubules. These findings suggest that constitutively higher cell division in the DB kidney is associated with overexpression of calpastatin, which reduces the progression of DCVC-initiated renal injury mediated by calpain on the one hand and accelerates nephrogenic tissue repair on the other, thereby restoring renal structure and function.

Diabetic mice are protected from normally lethal nephrotoxicity of S-1,2-dichlorovinyl-l-cysteine (DCVC): role of nephrogenic tissue repair

Streptozotocin (STZ)-induced diabetic (DB) rats are protected from nephrotoxicity of gentamicin, cisplatin and mercuric chloride, although the mechanisms remain unclear. Ninety percent of DB mice receiving a LD90 dose (75 mg/kg, ip) of S-1,2-dichlorovinyl-l-cysteine (DCVC) survived in contrast to only 10% of the nondiabetic (NDB) mice surviving the same dose. We tested the hypothesis that the mechanism of protection is upregulated tissue repair. In the NDB mice, DCVC produced steep temporal increases in blood urea nitrogen (BUN) and plasma creatinine, which were associated with proximal tubular cell (PTC) necrosis, acute renal failure (ARF), and death within 48 h. In contrast, in the DB mice, BUN and creatinine increased less steeply, declining after 36 h to completely resolve by 96 h. HPLC analysis of plasma and urine revealed that DB did not alter the toxicokinetics of DCVC. Furthermore, activity of renal cysteine conjugate beta-lyase, the enzyme that bio-activates DCVC, was unaltered in DB mice, undermining the possibility of lower bioactivation of DCVC leading to lower injury. [3H]-thymidine pulse labeling and PCNA analysis indicated an early onset and sustained nephrogenic tissue repair in DCVC-treated DB mice. BRDU immunohistochemistry revealed a fourfold increase in the number of cells in S-phase in the DB kidneys even without exposure to DCVC. Blocking the entry of cells into S-phase by antimitotic intervention using colchicine abolished stimulated nephrogenic tissue repair and nephro-protection. These findings suggest that pre-placement of S-phase cells in the kidney due to diabetes is critical in mitigating the progression of DCVC-initiated renal injury by upregulation of tissue repair, leading to survival of the DB mice by avoiding acute renal failure.

Diagnosis of the human fetal age based on the development of the normal kidney

Background and aims: The diagnosis of human fetal age is usually estimated based on the measurement of crown-rump length or crown-heel length and the weight of the fetus. However, this estimate is not totally accurate and sometimes is necessary to combine other data to determine the fetal age. An analysis of the normal embryological development of the kidney may assist in this determination. The histology of this process, although well described, lacks photographic documentation. We intend to fill this gap by providing histologists and pathologists, especially inexperienced ones, with information about the staging of the renal development through microphotography. The objective of the present study was to achieve greater accuracy for the diagnosis of human fetal age through the proposed classification and the photographic documentation presented. Material and methods: Normal embryological development of the human kidney was studied by light microscopy. The fetal period from 6 to 40 weeks of gestation was observed according the stage of maturity of glomeruli and tubules; localization of glomeruli, occurrence of nephrogenic tissue and cortico-medullary differentiation. At least 5 different exams were observed from each week of development. Two hundred four exams were analyzed in the whole study. The histological characteristics were quantified and the process was documented by microphotography. Results and final considerations: The fetal development of the kidney was divided into 8 stages, which was documented through microphotography. Nephron structural formation occurred until the 34th week of prenatal development. From the 35th week on, tubules and glomeruli continued to mature without the formation of new nephrons. The proposed classification intends to improve the accuracy of the fetal age diagnosis.

Clinicopathologic features of nephrogenic rests and nephroblastomatosis.

Nephrogenic rests are the consequence of residual metanephric tissue in a fully developed kidney. They usually occur along the perimeter of a mature renal lobe (i.e., perilobar), within the lobe itself (i.e., intralobar), or both (i.e., combined). Nephrogenic rests can be grossly obvious or microscopically discrete. Nephroblastomatosis designates nephrogenic rests that are multifocal or diffuse, and implies more extensive disease. Universal (panlobar) nephroblastomatosis denotes complete replacement of the renal lobe by nephrogenic tissue. The fate of nephrogenic rests and nephroblastomatosis varies and includes obsolescence, sclerosis, dormancy, hyperplasia, or neoplasia. Evidence strongly suggests that neoplastic transformation of nephrogenic rests results in Wilms' tumor (nephroblastoma). Nephrogenic rests almost always occur in the setting of Wilms' tumor; perilobar rests show a strong association with synchronous bilateral Wilms' tumors, whereas intralobar rests are more strongly associated with metachronous tumors. Genetic studies have shown that nephrogenic rests often share many of the same chromosomal defects as Wilms' tumor, which provides further evidence that they are precursors to nephroblastoma. Thus, nephrogenic rests are recognized as clinically significant entities requiring adequate detection and close surveillance. Heightened awareness regarding the clinical relevance of nephrogenic rests and nephroblastomatosis (1) has led to improved detection of these precancerous lesions, (2) fostered more intensive investigation into their biologic behavior, and (3) initiated in-depth discussions about potentially new treatment regimens. The pathologists' ability to identify and detect nephrogenic rests has benefited from the more efficient Beckwith classification. Radiologists have deployed high-resolution radiologic/imaging modalities to improve detection of nephrogenic rests in situ. Clinicians and surgeons are more aware of the impact that nephrogenic rests have upon patient management. Despite this progress, more data is needed to further define these lesions.

Expression of angiotensin II AT2 receptor mRNA during development of rat kidney and adrenal gland.

The angiotensin II (ANG II) receptors have been pharmacologically classified into two major distinct types, designated AT1 and AT2. A high transient expression of AT2 receptors in the fetal tissues has been previously demonstrated. This study describes the cellular distribution of AT2 receptor mRNA in the developing rat kidney and adrenal gland by in situ hybridization with 35S-labeled cRNA probes. From day 12 of fetal life (F12) to day 15 postpartum (D15) AT2 mRNA was detected in the undifferentiated nephrogenic mesenchymal tissue but not in the immature and mature glomeruli and tubules of the kidney. No AT2 mRNA was observed in the kidney after D22. The adrenal gland also expressed AT2 receptor mRNA early during development from F12 but, unlike the kidney, continuously expressed the mRNA at high levels through to adulthood. The disappearance of AT2 mRNA in the kidney was synchronous with the completion of nephrogenesis and suggests that ANG II might act through this receptor as a differentiation/growth factor during nephron development. In the adrenal gland ANG II could act as a hormone and also as a differentiation/growth factor via the AT2 receptor.

Expression of transcription factor HNF-4 in the extraembryonic endoderm, gut, and nephrogenic tissue of the developing mouse embryo: HNF-4 is a marker for primary endoderm in the implanting blastocyst.

The expression of HNF-4 (hepatocyte nuclear factor 4) mRNA in postimplantation mouse embryos was analyzed by in situ hybridization. Expression was found in the primary endoderm at embryonic day 4.5 and was restricted to the columnar visceral endoderm cells of the yolk sac from day 5.5 to day 8.5. HNF-4 mRNA was first detected in embryonic tissues at day 8.5, in the liver diverticulum and the hindgut. At later times HNF-4 transcripts were observed in the mesonephric tubules, pancreas, stomach, and intestine and, still later, in the metanephric tubules of the developing kidney. This expression pattern suggests that HNF-4 has a role in the earliest stages of murine postimplantation development as well as in organogenesis.

Differential expression of the laminin A and B chains in chimeric kidneys

The expression of laminin in embryonic kidneys growing in ovo is followed with mouse-specific, affinity-purified antibodies against the laminin A and B chains. In mouse kidneys growing on the chicken chorioallantoic membrane, the epithelium and nephrogenic mesenchyme are derived from mouse and the vasculature from chicken chorioallantoic vessels. Hence, with the mouse-specific antibodies, it is possible to analyze the deposition of laminin chains by the nephrogenic tissue, because laminin derived from the chicken vasculature remains unstained. In these chimeras, only the laminin B chain, but not the A chain, is expressed in the undifferentiated nephrogenic mesenchyme. The basement membrane around the ureter bud is labeled by the antibodies against both laminin A and B chains. In the mesenchyme, the laminin A chain appears when the mesenchyme converts into tubules. The results suggest that the laminin A and B chains are synthesized differentially in the embryonic nephrogenic tissue.

The Origin of the Ectodermal Ring in Staged Human Embryos of the First 5 Weeks

Seven embryos of stages 10-16 (3-5 weeks) were studied for their external form by means of graphic reconstructions. This is the first systematic report on the general surface anatomy of the early human embryo. The brain has been described and illustrated in a previous publication, and the present article is concerned particularly with an important although neglected feature: the ectodermal ring, described by Schmitt [Morph. Arb., Jena 8: 236-303, 1898] and named by Blechschmidt [Funktionsentwicklung. I. Mechanische Gegenwirkungen. Musterschmidt, Göttingen 1948]. Late in stage 10, three longitudinal bands can be seen on the surface: somitic, intermediate, and lateral plate. The intermediate band, which partly overlies nephrogenic tissue, is the site of the future ectodermal ring, which begins as an inverted U at stage 11 and is completed caudally in stage 12. The ectodermal ring, which may well be an important example of epithelial-mesenchymal interaction, comprises six parts: (a) rostral part, containing the situs neuroporicus, and olfactory and lens discs; (b) pharyngeal part, the covering of the pharyngeal arches; (c) occipital and cervicothoracic parts, related at first to the four occipital somites and later to the cervicothoracic junction; (d) membral part, represented by a preliminary ectodermal thickening, followed within 2 days by the apical ectodermal ridge; (e) intermembral part, related at first to the underlying coelom, and mesonephric duct and ridge; (f) caudal part, containing the cloacal membrane and a temporary 'caudal ectodermal ridge'. It is stressed that the incorrectly named 'Milchstreifen' is merely the intermembral part, in which the mammary crest ('Milchlinie' or 'Milchleiste') appears 1 week later.

Development of the renal corpuscle during metamorphosis in the lamprey.

The renal corpuscle of the adult lamprey, Petromyzon marinus L., is formed during the programmed period of metamorphosis. Development is initiated early in this metamorphic period and is marked by the synchronous formation and growth of rudimentary nephron units (RNU) from longitudinal cord of nephrogenictissue extending from the posterior tip of the degenerating larval kidney to the cloaca and connected to the peritoneal epithelium. Detachment of the RNU from the peritoneum involves autolysis and cell death and is accompanied by their branching into five or six hexagonally-arranged nephrons which radiate from the original point of attachment. Differentiation of the epithelial cells at the proximal ends of the nephrons is preceded by the widening of lateral intercellular spaces, the formation of tubular lumina (primitive urinary spaces), the loss of apical cell junctions, and the development of a capillary network with its associated mesangium. With the extension of the capillaries and mesangium between the proximal ends of adjacent undifferentiated nephrons, visceral epithelial cells (podocytes), with long cell processes (trabeculae) and slit membranes, make their appearance. The urinary spaces resulting from this form of development are lined by the epithelium of the dilated ends of the nephrons (nephric capsules). The cells of these capsules differentiate mainly into podocytes, but a few parietal cells connect to the draining tubule. This method of development explains the unique form of the renal corpuscle in the adult lamprey. Despite the type of morphogenesis, this renal corpuscle possesses the fine-structural features seen in the renal corpuscles of other vertebrates.

Implantation growth of nephrogenic tissue and tubular epithelium of the renal nephron culturedin vivo

Implantation growth of nephrogenic tissue of a 17-day rat embryo and of the epithelium from the nephron of animals aged 1 month was compared. Nephrogenic tissue in implantsin vivo showed appearances characteristic of its histogenesis. The tubular epithelium from the nephron of month-old animals showed manifestations of tissue growth and formed atypical kidney structures, reflecting its ability to undergo tissue and organotypical differentiation. It is concluded that the epithelium of the renal nephron has a wide range of reactive and plastic properties and is capable of organotypical determination.

Benign epithelial nephroblastoma

The occurrence of a malignant Wilms'tumor in the right kidney and of a benign epithelial nephroblastoma in the left kidney of a 5-year-old girl is reported. Both kidneys contained foci of persistent well differentiated blastema. In the left kidney a direct transformation of the primitive metanephric epithelium into a benign nephroblastoma is shown. This finding suggests an origin of epithelial nephroblastoma from persistent nephrogenic tissue and indicates that the former represents the benign counterpart of the malignant Wilms'tumor.

Growth of the opisthonephric kidney during larval life in the anadromous sea lamprey, Petromyzon marinus L.

Light microscopy, autoradiography, and gross anatomical measurements are used to study the growth of the larval opisthonephric kidneys of anadromous sea lamprey, Petromyzon marinus. Linear regression analysis of kidney lengths of the ammocoetes, ranging in length from 13 mm to 151 mm, reveals six natural groups of ammocoetes, year classes 0 to V, with each group demonstrating a definite growth pattern of the kidneys.Within the year classes 0 to III, the nephron rudiments at the posterior tip of the kidney differentiate periodically into functional nephrons as the larval opisthonephros lengthens in an anterior lo posterior direction. Labelling of cells with [3H]thymidine occurs in the differentiating nephrons and in the adjoining nephrogenic tissue. In contrast, the growth of the opisthonephric kidney in the year classes IV and V appears to result from the elongation of existing nephrons by cell proliferation.The length of the kidneys appears to be a valuable asset to our present means of age classification of the ammocoetes of anadromous P. marinus. The ammocoetes provide a unique opportunity to study growth and differentiation of a vertebrate kidney over a long period of time.

Metanephric hamartomas and nephroblastomatosis in siblings.

The occurrence of unusual renal lesions in 2 siblings, the second and fourth child of a young Yemenite woman, is reported. One of the siblings, a male infant, died 48 hours after birth and multiple metanephric hamartomas were found in his normal-sized kidneys. The second sibling, a stillborn delivered 3 years later, had both kidneys enlarged by multiple nodules of neoplastic nephrogenic tissue similar to that observed in Wilms' tumor and corresponding to the picture of diffuse nephroblastomatosis. The presence of these 2 lesions in siblings may be considered as support for the origin of Wilms' tumor from embryonic nephrogenic tissue.