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PubMed1993

[Ontogeny of the pronephros and mesonephros in the South African clawed frog, Xenopus laevis Daudin, with special reference to the appearance and movement of the renin-immunopositive cells].

Development of the pronephros and mesonephros of Xenopus laevis was morphologically studied in the larvae immediately after hatch (stage 35/36) to the end of metamorphosis (stage 66) together with the appearance of renin-immunopositive cells. The pronephros consisted of 3 pairs of pronephric tubules at stage 35/36 and became functional at stage 37/38 with the opening of the pronephric ducts to the cloaca. It increased thereafter in volume, but became degenerative at stage 56, lost a part of the pronephric ducts at stage 60, and completely disappeared at stage 64. The mesonephros displayed its anlage at stage 42, and gained the immature renal corpuscles at stage 48. At stage 49, it was equipped with the matured nephrons. The mesonephric tubules differentiated into the neck, proximal, intermediate and distal parts. The collecting tubules and ducts were also observed at this stage. At stage 56, a part of the mesonephric tubules degenerated and were displaced by newly formed tubules. Reorganization of the mesonephros was not completed at the end of metamorphosis. Renin-immunopositive cells did not appear in the pronephros, but were observed at the diverging part of the renal artery from the dorsal aorta, and in the walls of arteries and afferent arterioles within the mesonephros in a low frequency of appearance.

Animals↗
PubMed1996

Immunohistochemical localization of the epidermal growth factor, transforming growth factor alpha, and their receptor in the human mesonephros and metanephros.

The distribution of epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha), and EGF/TGF alpha receptor were studied by means of immunohistochemical methods starting from the very early stages of human embryonic kidney development. Mesonephros and metanephros were examined in order to detect immunoreactive staining in serial sectioned embryos and fetal kidneys. Anti-EGF immunoprecipitates were found in the S-shaped mesonephric vesicles of 6-week old embryos as well as in the mesonephric duct albeit with a lower degree of reactivity. Intense reactivity was observed in the metanephros within the blastemic caps of the same gestational period; the reaction was weaker within the ureteric bud branches. Bowman's capsule, proximal tubules, and collecting ducts were also reactive in the fetal kidney to varying degrees. The distribution of TGF alpha reactivity in the mesonephros was similar to that observed for EGF but with a lower intensity. In contrast, there was no reactivity in the metanephros, at least during the embyronic periods examined. By the 11th week of gestation, an intense reactivity for TGF alpha polipeptide was shown in the fetal kidney at the level of the proximal tubules and Bowman's capsule; distal tubules as well as all urinary structures from the collecting ducts to the pelvis were less reactive. Finally, EGF/TGF alpha receptor reactivity was identified by the 6th week of development, being more intense in the mesonephros at the level of the mesonephric duct cells. In the metanephros, the ureteric bud-derived branches were reactive, whereas most of the blastemic tissue did not stain. By the 11th week, only the collecting ducts and the remaining urinary structures contained reaction products: Reactivity was distributed to the tissues originating from the ureteric bud branching. Taking into account recent advances in knowledge about the biology of growth factors, the hypothesis is proposed that the secretory components (vesicles, glomerulus, and tubules) of renal anlagen might release the growth factors while the cells of the urinary tract (i.e., collecting duct, pelvis, etc.) may be their targets.

Epidermal Growth Factor↗
PubMed1995

FGF-2 mRNA and its antisense message are expressed in a developmentally specific manner in the chick limb bud and mesonephros.

FGF-2 protein is present in the ectoderm and mesoderm of the developing chick limb bud. Its importance has been shown by the ability of ectopically applied FGF-2 to replace the apical ectodermal ridge, allowing complete outgrowth and subsequent pattern formation of the limb bud. The first goal of this study was to determine whether FGF-2 mRNA was present in the same ectodermal and mesodermal regions of the chick embryo as FGF-2 protein. FGF-2 also has an antisense message that is convergently transcribed from the opposite DNA strand (Kimelman and Kirschner [1989] Cell 59:687-696; Volk et al. [1989] EMBO J. 8:2983-2988). The second goal was to demonstrate the expression and distribution of the antisense message. Using RNAse protection assays we detected a full length protected fragment that corresponds to chick embryo FGF-2 mRNA, and a partially protected fragment that corresponds to the antisense message. We used in situ hybridization to show that FGF-2 mRNA was present in the ectoderm and subjacent mesoderm of the chick wing bud. FGF-2 mRNA was also present in body ectoderm and undifferentiated mesoderm throughout the embryo, and in muscle cells, dorsal neural tube, and mesonephros. In situ hybridization also revealed evidence for the presence of the natural antisense message in the embryo in most, but not all, of the same regions as the FGF-2 mRNA. FGF-2 mRNA and its antisense message colocalized in undifferentiated limb mesoderm; however, antisense message was not detected in differentiated muscle or cartilage. It is important to note that FGF-2 mRNA was always present in the mesonephros but that the antisense message was never observed in the mesonephros, thereby providing an internal control for non-specific signal. Although little is known about its function, Kimelman and Kirschner ([1989] Cell 59: 687-696) proposed that the antisense message may increase turnover of FGF-2 mRNA. When we compared the in situ hybridization data of both mRNAs with levels of FGF-2 protein (Savage et al. [1994] Dev. Dyn. 198:159-170), interesting tissue specific patterns emerged that support this hypothesis.

Animals↗
PubMed1982

Preliminary observations on the role of the mesonephros in the development of the adrenal cortex.

The interrelationship between mesonephros, adrenal cortex, and gonads was studied in 28- and 31-day old sheep fetuses by means of light microscopy on plastic sections. At these stages, the adrenal cortex is just beginning to develop and mesonephros is undergoing involution; its regression is accompanied by mobilization of cells from the glomerulus of a peculiar nephron situated in the proximal third of the organ, and referred to as "giant" because of its large size. The mobilized cells egress from this glomerulus organized in trabeculae, some of which reach the cranial extremity of the adrenal cortex while others coalesce into a prominent cellular formation which extends uninterrupted toward and into the developing gonads. In previous studies we have shown that the mesonephric cells which colonize the gonads differentiate into sustentacular and interstitial steroidogenic cells; the presence of an analogous cellular migration from the mesonephros to the adrenal cortex now suggests that also the adrenal cortical cells may be of mesonephric origin.

Adrenal Cortex↗
PubMed2001

Comparative immunohistochemical analysis of the expression of cytokeratins, vimentin and alpha-smooth muscle actin in human foetal mesonephros and metanephros.

The human mesonephros is currently regarded as a simplified version of the foetal metanephros, primarily due to the close morphological resemblance between these two structures. The aim of the present study was to define whether human mesonephric and foetal metanephric nephrons share immunophenotypical traits in their corresponding structures (glomeruli, proximal and distal tubules). For this purpose we first investigated immunohistochemically the overall expression and topographical distribution of cytokeratins 7, 8, 18, 19, and 20, vimentin and alpha-smooth muscle actin in mature mesonephric nephrons and compared the results with those obtained in maturing-stage foetal metanephric nephrons. No expression of cytokeratins 7 and 20 was found. Cytokeratins 8, 18, and 19 and vimentin showed a restricted and basically coincident expression along the different components of both mesonephric and metanephric nephrons. These findings indicate that the intermediate filament protein profile of human mature mesonephric nephrons closely recapitulates that observed in developing metanephros and thereby strengthens the concept that human mesonephros, a transient ontogenic structure, is largely similar to the foetal metanephros. The sole difference between human mesonephros and foetal metanephros was the divergent expression of alpha-smooth muscle actin. This protein exhibited an increasingly accentuated mesangial expression paralleling the morphological maturation of metanephric glomerulus, whereas it was absent from the mesonephric one. This would suggest that the mesangial cells in these two renal structures have a different function during the foetal life.

Actins↗
PubMed2001

Functional glucocorticoid receptors in the mesonephros of the ovine fetus.

BACKGROUND: At 27 days of gestation in the ovine fetus (term = 145 to 150 days), the only kidney is the mesonephros, and allantoic fluid represents fetal urine. The hypothesis tested in this study was that functional glucocorticoid receptors (GRs) are present in this early mesonephric kidney. METHODS: Pregnant ewes, between 26 and 30 days, were infused with saline, dexamethasone (0.48 mg/hour), cortisol (5 mg/hour), or aldosterone (10 microg/hour) for 48 hours and were then killed for collection of fetuses and fetal fluids. GR mRNA was measured by real-time polymerase chain reaction in whole fetuses, and the location of gene expression was determined by hybridization histochemistry. RESULTS: Significant changes in allantoic fluid composition were produced by the exposure of the fetus to maternally infused synthetic (dexamethasone) and natural (cortisol) glucocorticoids, over a period of two days, compared with fetuses of ewes infused with vehicle (isotonic saline; N = 8) or aldosterone (N = 8). Volume of fluid was unchanged by any treatment, but both dexamethasone (N = 10) and cortisol (N = 8) caused significant (P < 0.05) decreases in sodium and chloride concentrations and increases in concentrations of potassium, urea, glucose, and fructose. GR mRNA was detected in equivalent concentrations in the whole fetuses of saline, dexamethasone, and cortisol treatments. The GR mRNA levels were significantly decreased in the aldosterone group. By hybridization histochemistry, GR mRNA was detected in most of the tubular cells of the mesonephros. CONCLUSION: These results suggest that functional GRs are present in the early ovine mesonephros.

Allantois↗
PubMed1997

The developmental relation among mesonephros, gonad and external genitalia in the fetus of goat (Capra prisca).

The mesonephros, the gonad, the external genitalia and the developmental relationships between them were examined on 21 goat fetuses, 29 to 92 days old. Three fetuses were not sexually differentiated, however 11 were males and 7 females. The development of the gonad could be divided in a not differentiated stage and a gonadal and external genitalia differentiation stage. A close relationship between the fetal gonad and the mesonephros was found during the stage of differentiation. The epicenter of this relation is the giant mesonephric nephron, a peculiar structure of mesonephros, from which epithelial cells presumably migrate into the gonad.

Animals↗
PubMed2002

Patterns of apoptosis during degeneration of the pronephros and mesonephros.

PURPOSE: The adult mammalian kidney is preceded developmentally by 2 primitive kidneys. We determine whether apoptosis is involved in the regression of these primitive organs and document its temporospatial characteristics. MATERIALS AND METHODS: Timed pregnant rats were sacrificed at 11 to 16 days of gestation inclusively. The fetuses were histologically examined to determine the timing and pattern of apoptosis in the primitive kidneys, including pronephros and mesonephros. RESULTS: Apoptosis of the pronephros occurred primarily at 12 days of gestation. Apoptosis of the distal mesonephros occurred primarily at 13 days and was completed by 14, which left the proximal mesonephros a functioning kidney during the early period of development. The location and timing of apoptosis were consistent and specific. CONCLUSIONS: Apoptosis appears to be an important mechanism of the normal regression of the primitive kidney and follows a strict temporospatial pattern.

Animals↗
PubMed1979

Morphological observations on the mesonephros in the postnatal opossum, Didelphis virginiana.

The mesonephros of the opossum persists for 3-4 weeks into the postnatal period. Based on our observations of its structure, and the vital dye experiments of others, it appears that the opossum mesonephros is functional during the first 10 days of the postnatal period. The mesonephros of the newborn opossum consists of 35-45 nephron units which are structurally very similar to metanephric nephrons except that they lack a loop of Henle. By the end of the first postnatal week, regression which proceeds in a craniocaudal direction, is observed. By the end of the second week most nephrons show some signs of regression. The regressing mesonephric nephrons are replaced by connective tissue.

Animals↗
PubMed1981

[Chick embryo ovarian differentiation after experimental mesonephros agenesis (author's transl)].

Agenesis of the mesonephros was obtained by preventing its early induction by the Wolffian duct. In the older embryos (14 to 19 days) studied, the ovaries differentiated in the absence of the underlying mesonephros, but were reduced in size. Their different cell populations (somatic and germinal) were however present and showed typical cytological features. Nevertheless, both components of the ovary, the medulla and the cortex, demonstrated lack of harmonious development. The medulla contained much larger lacunae; the cortex was shrunken with less secondary cords. At these stages, the gonocytes are not yet in premeiosis. These results are discussed in relation to the role of the mesonephros in gonadogenesis and in initiation of meiosis.

Animals↗
PubMed1993

Blood supply to the amphibian mesonephros.

The purpose of the present study was to describe geometry of branching, topography and sources of blood vessels supplying the mesonephros of three different species of amphibia and to infere from the results their common and species-specific features. The detailed information on arrangement of portal and arterial blood supply to mesonephros is necessary for better understanding of the conditions under which these kidneys function. For this reason the blood vessels of the mesonephros of adult Hynobius Keyserlingi, Triturus vulgaris and Rana temporaria were injected with stained gelatin. The urodelian kidneys were shown to be supplied by numerous segmental arteries. Three types of arterial supply to glomeruli were distinguished: those mediated by short, medium and long branches, which create different physical conditions for the glomerular filtration in pertinent nephrons--as the blood pressure necessarily decreases with the increasing distance from the aorta. The tributaries to the renal portal vein were identified in all three species as the veins draining hind limbs, tail, pelvis and body wall. It is being suggested that the purpose of this large drainage area is to secure a sufficient volume of blood to the peritubular network.

Amphibians↗
PubMed1993

The role of the mesonephros in cell differentiation and morphogenesis of the mouse fetal testis.

In mouse fetal gonads, the adjacent mesonephros is required for seminiferous cord formation in vitro (Buehr et al., Development 117: 273-281, 1993). Here, we have investigated the role of mesonephric cells in seminiferous cord formation and in differentiation of Sertoli and Leydig cells. Undifferentiated male gonads with and without mesonephros at 11.5 dpc were cultured and immunocytochemical staining of Müllerian-inhibiting substance (MIS) was used as the criterion for Sertoli cell differentiation. For Leydig cells, testosterone (T) radioimmunoassay and cytochemical detection of delta 5-3 beta-hydroxysteroid-dehidrogenase (HSD) were undertaken. An ultrastructural study was also performed. In our culture conditions, the timing of differentiation of both Sertoli and Leydig cells was similar to that in the fetus. Although mesonephros is required for seminiferous cord formation, differentiation of Sertoli and Leydig cells proceeds in its absence at 11.5 dpc. Moreover, when 3H-thymidine labeled mesonephroi were grafted to unlabeled gonads, endothelial and peritubular myoid-like cells migrated into the gonad. We propose that these cells might be the mesonephric cells required for seminiferous cord formation.

Animals↗
PubMed1975

The problem of sampling homologous groups of nephrons during development of the chick mesonephros.

With the aim of defining homologous groups of nephrons in the chick mesonephros at different stages of development, we opened the abdominal wall of 295 White Leghorn embryos at stage HH 26 and marked off 6 segments of equal length at different levels of the organ by Seichert's plastic linear marking method (Seichert 1965), using marks previously introduced into the vertebral column at the same levels as a guide. The embryos were removed after 2-6 days, weighed and classified according to weight. The primordia of the marked vertebrae were identified. The length of the artificially defined segments or their relationships to both poles of the mesonephros were evaluated in projections. The portion of the mesonephros above Th 3 level shorten during the period of observation, while the more caudal segments grow in a craniocaudal gradient. Homologous groups of nephrons can be identified only by the marking technique, except for those at Th 7 level, whose distance from the caudal pole does not alter up to the 11th embryonic day.

Animals↗
PubMed1997

Afferent portal venous system in the mesonephros and metanephros of chick embryos: development and degeneration.

BACKGROUND: In the chick embryo, both mesonephros and metanephros have a renal portal system. The classical literature gives uncertain answers about the development and degeneration of the meso- and metanephric portal venous system. Some mesonephric vessels present angiogenic processes to colonize the metanephros, while others show signs of degeneration and disappear together with the mesonephros. The adult avian kidney has a conspicuously placed valve, the renal portal valve. The development of this functionally important renal portal valve has not yet been studied in detail. METHODS: Scanning electron microscopy of vascular corrosion casts has been used in this study. Strong mesonephric degeneration as well as metanephric growth and maturation occur in the developmental stages selected for this investigation (7.5, 9, 11, 14, and 21 days of incubation). RESULTS: The mesonephric afferent venous system in the chick embryo is supplied by two vessels, the posterior and the anterior mesonephric portal veins. The posterior mesonephric portal veins show a similar pattern to the anuran (amphibian) kidney. The anterior mesonephric portal vein has not previously been described. Constrictions were found in this vessel, a probable sign of subsequent degeneration. The metanephric afferent venous system is also supplied by two vessels: the caudal and cranial metanephric portal veins. The caudal metanephric portal vein is derived from the postcardinal vein. The cranial metanephric portal vein grows independently throughout the development of the mesonephric vascular system. It is connected to the vertebral venous sinus already at the beginning of its development. The renal portal valve first appears as a capillary network that communicates with the developing afferent and efferent metanephric venous systems. This capillary network later develops to a venous valve. The metanephric afferent venous system shows typical angiogenic signs in corrosion cast, such as nodular protrusions, holes, and enlarged vessels. CONCLUSIONS: The postcardinal vein first supplies only the mesonephric tissue as a portal vessel. Then it becomes a common source for both kidney generations. Finally it supplies only the metanephric tissue with venous blood. However, two independent vessels were found to supply the cranial renal regions: the anterior mesonephric portal vein and the cranial metanephric portal vein.

Animals↗
PubMed1995

Development and degeneration of the arterial system in the mesonephros and metanephros of chicken embryos.

BACKGROUND: The general morphology of the mesonephric and metanephric arteries in chicken embryos has already been described previously. Moreover, the general basis of glomerulogenesis has also been established. However, the degeneration of the mesonephric vascular system, and especially glomerular degeneration, have not been well established yet. Also the morphology of the metanephric angiogenic buds has not been studied yet. METHODS: Scanning electron microscopy of vascular corrosion casts and critical point dried specimens as well as light microscopy of serially sectioned material has been used in this study. Mesonephric degeneration coincides in time with metanephros growth and maturation in the developmental stages of chicken embryos chosen for this investigation (7.5, 9, 11, and 14 days of incubation). RESULTS: The arterial system of the mesonephros in embryonic chicken is similar to that of the anuran kidney, as described in the literature. The morphology of the degenerating mesonephric glomeruli shows that the glomerular capillaries are more thick, tortuous, and numerous than those in normal glomeruli. The podocytes also show degeneration. The arterial system of the metanephros grows directly from the aorta and from the mesonephric arterial system. During these stages of rapid growth, the metanephros shows angiogenic buds. These angiogenic buds can be either pointed or round blind endings. CONCLUSIONS: The distribution and topography of the mesonephric and metanephric arteries is in general accordance with the literature. The process of glomerular degeneration in the mesonephros seems similar to glomerular senescence in man but is different from that of the aged rat glomeruli. The round angiogenic buds observed in the metanephros resemble tumoral angiogenic buds in some aspects. However, both angiogenesis and the degenerative phenomena are part of the normal developmental process. Consequently, the involved mechanisms are probably under sole genetic control. The system studied here offers therefore the possibility to study vascular growth and degeneration on the same model in physiological conditions without application of vasoactive or pathological agents.

Animals↗
PubMed1993

The development of the caudal ligaments of the mesonephros and of the gonads: a contribution to the development of the human gubernaculum (Hunteri).

The formation of the two caudal mesonephric folds is described. The plica uropelvina becomes the plica urogenitalis as soon as the paramesonephric (Müllerian) duct grows, and the plica inguinalis runs over the ridge of the umbilical artery to the ventral abdominal wall. Within the plica inguinalis the inguinal or caudal mesonephric ligament is formed directly subjacent to the coelomic epithelium. It interacts intensively with the mesenchyme sheath of the paramesonephric (Müllerian) duct in stage 21. It is separated by loose mesenchyme from the subjacent mesonephros and mesonephric (Wolffian) duct which therefore it does not pass beneath. In stage 23, and during the early fetal period, the caudal gonadal ligament is formed. It arises from the caudal pole of the gonads and proliferates in the space between the two genital ducts. Only the duct not destined to disappear associates with it. Therefore, in males the gubernaculum consists of the inguinal ligament of the mesonephros only. Its significance for the descent of the testis is discussed. In females the inguinal and the caudal gonadal ligaments fuse into a single strand and together form the gubernaculum.

Female↗
PubMed1981

Formation of the chick mesonephros. 4. Course and architecture of the developing nephrons.

Using colour microinjections the course of mesonephric nephrons was visualized in embryos of White Leghorn chicks on days 5-18. From the stage of the S-shaped body until their full maturity, the nephrons generally retain the S-shaped form, with two main flexures. The first flexure is formed at the point where the tubule runs closest to the Wolffian duct, the second, more distal flexure, at the site of juxtaposition to Bowman's capsule. The cranial, narrow part of the mesonephros contains rudimentary nephrons with mostly obliterated tubules and short nephrons often exhibiting an irregular course. Nephrons of the caudal part of the mesonephros grow rapidly in length forming secondary and tertiary infoldings. The nephrons situated ventrally are segmentally arranged in planes perpendicular to the long axis of the organ, whereas the dorsal nephrons are situated in various planes and their tubules are folded within narrow spaces of approximately ovoid form. Among the rare anomalies "two-headed" nephrons and nephrons lacking the main flexures are described.

Animals↗
PubMed1990

Histochemical detection of sugar residues in the chick embryo mesonephros with lectin-horseradish peroxidase conjugates.

Fragments of mesonephros were taken from chick embryos and studied from the 4th to the 21st day of incubation. A battery of seven different horseradish peroxidase-labelled lectins was used to study the distribution of carbohydrate residues in glycoconjugates along the mesonephric nephron during the period of excretory activity and the period of involution. ConA and WGA reacted at every site of the nephron thus showing the ubiquitous presence of alpha-D-mannose and N-acetyl-D-glucosamine. SBA was a good marker of the proximal tubule. Other lectins, such as PNA and LTA, reacted only for a short time at some sites during the considered period of incubation. The presence of sialic acid was detected in the podocytes, capillary wall and mesangial cells. From the 10th-11th day of incubation changes were noted in the proximal tubule as shown by PNA reactivity. This may be significant as regards the exact stage of incubation during which the involution of mesonephros begins.

Acetylglucosamine↗