Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mesonephros”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2001

Morphogenesis of the bovine rete testis: extratesticular rete, mesonephros and establishment of the definitive urogenital junction.

The development of the extratesticular rete, the regression of the mesonephros and the establishment of the urogenital junction between rete testis and efferent ductules were investigated in 67 bovine embryos and fetuses collected in the period from day 29 through day 250 post conception. The results were obtained by immunohistochemistry and by the study of semithin sections. At about day 30, the large mesonephros contains a peculiar Malpighian body in its cranial part, generally referred to as the mesonephric giant corpuscle, which is connected to the Wolffian duct by a series of well-developed and functioning mesonephric tubules. This set of primary mesonephric tubules, however, will not participate in the formation of the definitive urogenital junction, but will regress and soon disappear completely. The efferent ductules in the bovine are represented by another set of secondary mesonephric tubules that grow out from the dorsal aspect of the mesonephric giant corpuscle at about day 50. Transiently, the lumina of the sprouting efferent ductules are plugged by invading intraductular blood vessels, probably representing rudimentary glomeruli. The proximal portions of the newly-formed efferent ductules establish side-to-end contacts with extensions of the extratesticular rete that has bypassed the regressing giant corpuscle. At 85 days, the efferent ductules have reached the Wolffian duct and open into it. At 150 days, the channels of the extratesticular rete display a patent lumen and now form end-to-end anastomoses with the efferent ductules. The proliferating mesenchymal cells surrounding the epithelia of the efferent ductules have arranged in several concentric layers at about 85 days. These mesenchymal cells are the precursors of the periductular musculature and are reached by the first nerve fibers at about day 130.

Animals↗
PubMed1994

Cloning and characterization of a full-length cDNA coding for ovine aldolase B from fetal mesonephros.

An ovine aldolase B cDNA was isolated from mesonephros (29 d pc). The sequence covers 1649 nucleotides. Comparison with human liver aldolase B cDNA shows a homology of about 86%. The deduced amino acid sequence is composed of 364 residues and exhibits 92% homology to the human protein. Northern blot analysis and in situ hybridization data show that during the first third of gestation in sheep, aldolase B expression is restricted to the mesonephros.

Amino Acid Sequence↗
PubMed2004

Expression of natriuretic peptides, nitric oxide synthase, and guanylate cyclase activity in frog mesonephros during the annual cycle.

Natriuretic peptides (NPs), a family of structurally related hormones and nitric oxide (NO), generated by nitric oxide synthase (NOS), are believed to be involved in the regulation of fluid balance and sodium homeostasis. Differential expression and regulation of these factors depend on both physiological and pathological conditions. Both NPs and NO act in target organs through the activation of guanylate cyclase (GC) and the generation of guanosine 3',5'-cyclic monophosphate (cGMP), which is considered a common messenger for the action of these factors. The present study was designed to investigate--by histochemical methods--the expression of some NPs (proANP and ANP) and isoforms of NOS (neuronal NOS, nNOS, and inducible NOS, iNOS) in the mesonephros of Rana esculenta in different periods of the year including hibernation, to evaluate possible seasonal changes in their expression. We also studied the enzyme activity of NOS-related nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) and of GC. The experiments were performed on pieces of kidney of R. esculenta collected in their natural environment during active and hibernating life. The study was carried out using immunohistochemical techniques to demonstrate proANP, ANP, and some NOS isoforms. Antigen capture by enzyme linked immunosorbent assay (ELISA) was also performed to determine the presence of NPs in the frog kidney extract. Enzyme histochemistry was used to demonstrate the NOS-related NADPHd activity at light microscopy; GC activity was visualized at the electron microscope, using cerium as capture agent. The application of the immunohistochemical techniques demonstrated that frog mesonephros tubules express different patterns of distribution and/or expression of ANP and NOS during the annual cycle. Comparing the results obtained on active and hibernating frogs has provided interesting data; the NOS/NADPHd and GC activities showed some variations as well. Furthermore, the presence of NPs in the frog kidney extract was evidenced by dose-dependent response in the ELISA. The data suggest that both ANP and NO are intra-renal paracrine and/or autocrine factors which may modulate the adaptations of frog renal functions to seasonal changes through the action of the cGMP generated from GC activity.

Animals↗
PubMed1995

Distribution of extracellular matrix glycoproteins in the human mesonephros.

We analyzed the expression and distribution of collagen types IV and VI, laminin and fibronectin during the development and regression of the mesonephros in human embryos and fetuses ranging from 6 to 12 weeks of gestation by indirect immunoperoxidase methods. Type IV collagen, laminin and fibronectin were detected along the glomerular, tubular and capsular basement membranes of developing and mature nephrons. Only type IV collagen and fibronectin were found in the mesangium. Type VI collagen formed a delicate interstitial fibrillar network and a continuous basement membrane-like structure along the mesonephric nephrons. Basement membranes (GBM) of developing and mature glomeruli showed a distinct continuous staining for this collagen. The mesangial matrix was rich in type VI collagen. Mesonephric involution started during the 8th week of gestation and coincided with a moderate expansion of mesangial matrix and progressive collapse of the capillary walls, while the tubules became thinner and shorter. Staining for all extracellular matrix glycoproteins studied showed GBM wrinkling, gradual disintegration of some capillary loops and glomerulosclerosis. The sclerotic glomeruli were strongly positive for type IV collagen and less positive for type VI collagen and fibronectin. Laminin was absent. Our results indicate that collagen types IV, VI, laminin and fibronectin may be involved in the development and regression of the human mesonephros.

Collagen↗
PubMed1996

An ultrastructural and cytochemical study of the mesonephros of Rana esculenta during activity and hibernation.

The biological cycle of most amphibians undergoes seasonal variations. In this study, we investigated the mesonephros of Rana esculenta during active life and the natural hibernation period. The ultrastructural morphology of the different tracts constituting the nephron was analysed. Moreover, to evaluate the effect of seasonal temperature variations on the mesonephros function, the activity of some enzymes linked to membrane transport and playing regulatory roles in various metabolic pathways was investigated in different tracts of the frog nephron. During hibernation the glomerular filtration barrier appeared thicker than in the active life, lysosomes and paraplasmatic material, mostly glycogen, being accumulated in the proximal and distal tubule cells respectively. Cytoplasmic organelles, i.e., mitochondria, endoplasmic reticulum were observed in segregated areas. At the same time, changes in some enzyme activities were noted. The activity of some membrane-transport enzymes (5' nucleotidase and K+-p-nitrophenyl phosphatase) and of energetic metabolism (succinic dehydrogenase) was reduced. Nevertheless the alkaline phosphatase activity was not changed significantly, and this suggests that some metabolic activities were preserved in the hibernating samples. These results indicate morpho-functional adaptations of the kidney cells that preserve their role in osmoregulation and some metabolic processes, even during unfavourable seasons.

4-Nitrophenylphosphatase↗
PubMed1992

Effects of He-Ne laser irradiation on chick embryo mesonephros.

A study on the effects of He-Ne laser irradiation on glomeruli and renal tubules of the chick embryo mesonephros at 7 days of in ovo development was made. To this purpose, He-Ne laser irradiation (potency: 5 mW, wavelength: 632.8 nm) was beamed for 5 minutes through a window opened in the egg shell, and the eggs were maintained aseptically for 24 h in an incubator. Mesonephros were dissected out and processed for hematoxylin/eosin, periodic acid-Schiff, and Alcian blue at pH 2.5 and 1.0, toluidine Blue at pH 3.8. In controls, the glomeruli were formed by coiled capillaries with a homogeneous basement membrane, the proximal tubules presented a high cubic epithelium with acidophilic cytoplasm and a developed brush border. Distal and collecting segments were lined by cubic epithelium. An alcianophilic and PAS-positive reaction stood out at the membrane coats of the proximal tubules and tubular and glomerular basement membranes. No glomerular alterations were observed during the experiment. However, there was a marked enlargement of the tubular interstitium, with edema and lymphohistiocytic inflammatory infiltration. Some tubular cells desquamated to the lumen. Other cells presented a raveled apical surface. Some nuclei were dispersed out, and mixing with chromatin, formed diminutive granules. Pyknotic nuclei were seen occasionally. Epithelial necrosis and cytoplasmic debris in the lumen were also noted. For mucins, some zones showed brush border coats of the proximal tubules as discontinuous.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Human testicular development and the role of the mesonephros in the origin of a dual Sertoli cell system.

Some aspects of the development of the human testis (and overy) are discussed and the main theories regarding gonadal differentiation summarized. The major part of this review deals with the origin and differentiation of the three groups of somatic cellular content: Sertoli cells, Leydig cells and peritubular cells. The most important role of the mesonephros in gonadal development is described. Under the influence of the mesonephros, a second type of meiosis-inducing Sertoli cell differentiates and becomes the opponent of a meiosis-preventing type of Sertoli cell which derives from the coelomic epithelium. All somatic cells are pooled in the central gonadal blastema which is part of the medulla. They migrate via the rete blastema to the sites of their final differentiation. Included are the precursors of the Leydig cells and the peritubular cells.

Cell Differentiation↗
PubMed1981

Feminizing effect of mesonephros on cultured differentiating mouse gonads and ducts.

Gonads were removed from fetal mice at about the time that gonadal sex differentiation occurs. The gonads were cultured in vitro with or without their mesonephric tissue. When gonads and ducts removed from sexually undifferentiated fetuses were cultured together, the gonads of both sexes developed female characteristics, whereas gonads cultured without mesonephros developed according to the sex of the fetus from which they were removed. Gonads of sexually differentiated fetuses developed whether they were cultured with or without the mesonephros.

Animals↗
PubMed1982

Influence of mesonephros on foetal and neonatal rabbit gonads. I. Sex-steroid release by the testis in vitro.

The experiments were performed to study the influence of mesonephros on gonadal sex hormone release. Foetal and neonatal rabbit testes were cultured for 5 days, with and without their mesonephric tissue. The culture media were harvested every day and analyzed by RIA for the content of testosterone, progesterone and oestradiol. The development of the tissues were evaluated microscopically after culturing. The results show that between day 20 pc and day 1 pp the mesonephric tissue lowered the amounts of testosterone in co-cultures with testis. This effect disappears when the mesonephric derived cells develop the capacity to synthesize a meiosis inducing substance (MIS). A relationship between decrease of testosterone and secretion of MIS is discussed. It is concluded that the steroid producing cells of the testis, the Leydig cells, originate or are heavily influenced by mesonephros during early testicular organogenesis.

Animals↗
PubMed1977

The role of cellular locomotion in leukemic infiltration. An organ culture study on penetration of L 5222 rat leukemia cells into the chick embryo mesonephros.

The significance of cellular locomotion for leukemic infiltration was investigated using L 5222 rat leukemia cells. Previous cinemicrographic studies have shown that these cells are able to locomote only after formation of a uropod-like posterior extension. This characteristic locomotive configuration of L 5222 cells is easily recognizable in scanning electron micrographs and appropriate sections. Leukemia cells were inoculated on slices of chick embryo mesonephros incubated for 24h; at this time the fragments are completely encapsulated. Leukemic infiltration is found to begin within the first 2 h and to increase gradually up to the end of the observation period at 72 h. Spread of leukemia cells occurs mainly in the intertubular spaces; the tubular epithelium is only rarely affected. In all stages of infiltration, L5222 cells with the characteristic locomotive configuration are frequently recorded. Besides this strong although indirect indication for the significance of locomotion, further evidence was provided by experiments performed at 25 degrees C and 18 degrees C. In accordance with the previous cinemicrographic finding that at these temperatures L 5222 cells are unable to produce their posterior extension, no leukemic infiltration mesonephros fragments is recognizable at subnormal temperatures.

Animals↗
PubMedDate not supplied

[Succinate dehydrogenase activity in the mesonephros in the process of development of chick embryos].

The activity of succinate dehydrogenase in the mesonephros tissue of chick embryos is rather high on the 6th day of embryonal development and is not subjected to significant changes up to the 17th day. The absence of wide variations in the activity of this enzyme during the period of degeneration of the mesonephros may be due to a parallel decrease in the organ's mass and in the number of its mitochondria.

Animals↗
PubMed2004

[Expression of VEGFA, VEGFC, angiopoietin-1, angiopoietin-2 and their receptors on yolk sac blood island, aorta-gonad-mesonephros (AGM) region of human embryo].

The study was to investigate the expression of VEGFA, VEGFC, angiopoietin-1, angiopoietin-2 and their receptors on yolk sac blood island, AGM region during gestation of 3th-12th weeks of human embryo. Human embryo contingently aborted at 3 - 12 weeks of gestation were collected with signed agreements of the pregnant women suffered from accidental abortions. The specimens were fixed by 4% paraformaldehyde and embedded by paraffin. 5 micro m serial sections were made. HE and immunohistochemistry method (SABC) and light-microscope were employed. The results showed that VEGFA and its receptors flt1/flk-1, VEGFC and its receptor flt-4, angiopoietin-2 and its receptor tie-2 proteins were expressed strongly and angiopoietin-1 was weakly expressed by hematopoietic cells and vascular endothelial cells of blood island at 21 and 25 days of gestation. In the 4th week of gestation, immuno-positive reaction of these factors and their receptors appeared in the aorta and mesonephros deposited in larger, rounded and nucleated cells which represented hematopoietic cells. Up to 7th week, positive hematopoietic cells in the regions were much abundant. The number of positive cells decreased at 8th week. Up to 12th week, almost all blood cells were immuno-negative. VEGFA, flt-1, flt-4, angiopoietin-1, angiopoietin-2 and Tie-2 protein were expressed mainly by gonad at 6 - 8 weeks, but it did not express VEGFC and flk-1. The immuno-reaction of the factors and their receptors could not detected in vascular endothelial cells during 3-12th weeks of gestation. It is concluded that hematopoietic cells and endothelial cells in blood island of yolk sac, mesonephros and dorsal aorta co-expressed some factors and their receptors in relation to vasculogenesis and hematopoiesis. Intraembryonic hematopoiesis began in the 4th week of gestation.

Angiopoietin-1↗
PubMed1999

Detailed characterization of the human aorta-gonad-mesonephros region reveals morphological polarity resembling a hematopoietic stromal layer.

The definitive long-term repopulating human hematopoietic stem cell, which seeds the adult blood system, was previously thought to derive from the extra-embryonic yolk sac. However, there is now considerable evidence that in both avian and murine systems, yolk sac hematopoietic cells are largely a transient, embryonic population and the definitive stem cell, in fact, derives from a distinct region within the embryonic mesoderm, the aorta-gonad-mesonephros region. In the human embryo, an analogous region has been found to contain a cluster of cells distinct from, but closely associated with, the ventral endothelium of the dorsal aorta, the appearance of which is restricted both spatially and temporally. We have used antibodies recognising hematopoietic regulatory factors to further characterise this region in the human embryo. These studies indicate that all factors examined, including vascular endothelial growth factor and its receptor FLK-1, Flt-3 ligand and its receptor STK-1, and stem cell leukemia transcription factor, are expressed by both hematopoietic cells in the cluster and endothelial cells. However, there is some discontinuity in cells directly underlying the cluster. Furthermore, we have identified a morphologically distinct region of densely-packed, rounded cells in the mesenchyme directly beneath the ventral wall of the dorsal aorta, and running along its entire length. In the preumbilical AGM region, directly underlying the hematopoietic cluster, but not at more rostral and caudal levels, this region of mesenchyme expresses tenascin-C, an extracellular matrix glycoprotein known to facilitate cell-cell interactions and migration. This region of cells may therefore provide the microenvironmental support for the intraembryonic development of definitive hematopoietic stem cells, a process in which tenascin-C may play a pivotal role.

Antigens, CD34↗
PubMed1982

The contribution of the mesonephros to the development of the sheep fetal testis.

In this study, which was performed on 52 sheep fetuses aged 24 to 85 days, we examined the relationship between testicular development and the "giant" mesonephric nephron, a peculiar structure consisting of a large glomerulus and multiple tubules. The development of the testis occurred in two phases. The preparatory phase began at day 24 of gestation, evolved simultaneously with the involution of the glomerulus of the giant nephron, and was characterized by mobilization of the glomerular cells and by their colonization of the genital ridge. By day 31, a prominent mass of migrating mesonephric cells had developed; it extended uninterrupted from the giant glomerulus into the gonad where the mesonephric cells associated with the germinal cells forming the cellular template from which the testicular cords later became assembled. At complete involution of the glomerulus (day 52), the migratory mass implanted on the tubules of the giant nephron, which thus became continuous with the gonad. During the organizational phase, which began at day 29 with the formation of the tunica albuginea, the various components of this continuum became progressively organized along a testis-to-mesonephros direction into seminiferous cords, tubuli recti, the cords of the rete testis, and the ductules efferentes. These observations show that, in the sheep, the precursors of the Sertoli cells are mesonephric in origin, and that the genital tract proximal to the epididymis differentiates from a single mesonephric nephron.

Animals↗
PubMed1994

Expression patterns of ammonia-metabolizing enzymes in the liver, mesonephros, and gut of human embryos and their possible implications.

Human and ungulate embryos can catabolize amino acids for energy production, whereas rodent embryos cannot, raising the question whether studies of rodent model systems are suitable for extrapolation to the human situation. Therefore, we investigated the expression of the amino acid- and ammonia-metabolizing enzymes glutaminase, glutamate dehydrogenase, glutamine synthase, carbamoylphosphate synthase, and arginase immunohistochemically in a graded series of human embryos and fetuses. During human development the expression of these enzymes is first seen in the liver, then in the mesonephric kidney, and finally in the small intestine. Such a simultaneous expression of nitrogen-metabolizing enzymes was not seen in any other organ. The early appearance of the enzymes involved in amino acid and ammonia metabolism in the human liver, compared to, for example, the rat liver, suggests that catabolism of amino acids may provide an important supply of metabolic energy for the human embryo. The coexpression of glutaminase, glutamate dehydrogenase, and carbamoylphosphate synthase, but not of arginase, in the mesonephros and the small intestine suggests that these organs are involved in the biosynthesis of intermediates of the ornithine cycle, e.g., arginine or citrulline. From a comparison of the developmental appearance of ornithine cycle enzymes in different mammalian species we postulate that an early appearance of these enzymes is generally associated with a relatively slow prenatal growth rate and the use of amino acids as metabolic fuel.

Amino Acids↗
PubMed1995

Effects of extracellular matrix on differentiation of mouse fetal gonads in the absence of mesonephros in vitro.

The influence of mesonephric tissues and the extracellular matrix on mouse gonadal differentiation was examined in vitro. Gonadal ridges, with or without the adjacent mesonephric region, were removed from mouse embryos on day 12 post coitum (p.c.), and cultured in the presence or absence of reconstituted basement membrane (matrigel) for 5 days. Culturing control undifferentiated testes with mesonephric tissues induced normal testicular differentiation. When testes without mesonephric tissues were cultured in the absence of matrigel, testicular cord formation was not observed in the explants. Sertoli cells were irregularly arranged in the testicular parenchyma, and no continuous basal lamina was formed around the Sertoli cells. However, when testes without mesonephric tissues were embedded in matrigel and cultured for 5 days, the Sertoli cells were organized into testicular cord-like structures. The Sertoli cells positioned at the base of the cord-like structures were closely connected to the matrigel at their basal surface, and showed a polarized distribution of vimentin filaments in their basal cytoplasm. Leydig cells, on the other hand, were differentiated in all testicular explants. In all ovarian explants, germ cells normally entered meiotic prophase. Therefore, these findings indicate that the extracellular matrix permits testicular differentiation in the absence of the mesonephros, and that removal of mesonephric tissues leads to developmental failure of cord formation because the components of the extracellular matrix around pre-Sertoli cells are incomplete.

Animals↗
PubMed2000

The AML1 transcription factor functions to develop and maintain hematogenic precursor cells in the embryonic aorta-gonad-mesonephros region.

We examined the role of the AML1 transcription factor in the development of hematopoiesis in the paraaortic splanchnopleural (P-Sp) and the aorta-gonad-mesonephros (AGM) regions of mouse embryos. The activity of colony-forming units of colonies from the P-Sp/AGM region was reduced severalfold by heterozygous disruption of the AML1 gene, indicating that AML1 functioned in a dosage-dependent manner to generate hematopoietic progenitors. In addition, no hematopoietic progenitor activity was detected in the P-Sp/AGM region of embryos with an AML1 null mutation. Similar results were obtained when a dispersed culture was first prepared from the P-Sp/AGM region before assay of the activity of the colony-forming units. In a culture of cells with the AML1(+/+) genotype, both hematopoietic and endothelial-like cell types emerged, but in a culture of cells with the AML1(-/-) genotype, only endothelial-like cells emerged. Interestingly, introduction of AML1 cDNA into the P-Sp/AGM culture with the AML1(-/-) genotype partially restored the production of hematopoietic cells. This restoration was observed for cultures prepared from 9.5-day postcoitum (dpc) embryos but not for cultures prepared from 11.5-dpc embryos. Therefore, the population of endothelial-like cells capable of growing in the AML1(-/-) culture would appear to contain inert but nonetheless competent hematogenic precursor cells up until at least the 9.5-dpc period. All these results support the notion that the AML1 transcription factor functions to develop and maintain hematogenic precursor cells in the embryonic P-Sp/AGM region.

Animals↗
PubMed1991

Renal carbonic anhydrase in the quail Coturnix coturnix japonica. II. Changes of enzyme activity in developing and regressing mesonephros.

Carbonic anhydrase activity was studied during development and regression of the quail mesonephros by in situ and extra situm investigation. A close correlation was noted between enzyme expression and tissue morphofunctional state. Carbonic anhydrase appears in early development; its highest activity is reached when the kidney is actively secreting, followed by a decrease concomitant with tissue involution. The main localization of the reaction product is the distal tubule showing strongly positive cells intercalated with clear, negative ones. In the functional organ, staining was found at the level of transitional and connecting segments and Wolffian duct. The comparison with the histochemical pattern of the quail metanephros suggests that the functional meaning of renal carbonic anhydrase might be the same both in transitory and in permanent kidney.

Animals↗