RESUMEN
During development of the mouse urogenital complex, the gonads undergo changes in three-dimensional structure, body position and spatial relationship with the mesonephric ducts, kidneys and adrenals. The complexity of genital ridge development obscures potential connections between morphogenesis and gonadal sex determination. To characterize the morphogenic processes implicated in regulating gonad shape and fate, we used whole-embryo tissue clearing and light sheet microscopy to assemble a time course of gonad development in native form and context. Analysis revealed that gonad morphology is determined through anterior-to-posterior patterns as well as increased rates of growth, rotation and separation in the central domain that may contribute to regionalization of the gonad. We report a close alignment of gonad and mesonephric duct movements as well as delayed duct development in a gonad dysgenesis mutant, which together support a mechanical dependency linking gonad and mesonephric duct morphogenesis.
Asunto(s)
Gónadas/fisiología , Morfogénesis/fisiología , Conductos Mesonéfricos/fisiología , Animales , Embrión de Mamíferos/fisiología , Femenino , Edad Gestacional , Riñón/fisiología , Masculino , Mesonefro/fisiología , Ratones , Ratones Endogámicos C57BL , Diferenciación Sexual/fisiologíaRESUMEN
Meiotic initiation of germ cells at 13.5 dpc (days post-coitus) indicates female sex determination in mice. Recent studies reveal that mesonephroi-derived retinoic acid (RA) is the key signal for induction of meiosis. However, whether the mesonephroi is dispensable for meiosis is unclear and the role of the ovary in this meiotic process remains to be clarified. This study provides data that RA derived from fetal ovaries is sufficient to induce germ cell meiosis in a fetal ovary culture system. When fetal ovaries were collected from 11.5 to 13.5 dpc fetuses, isolated and cultured in vitro, germ cells enter meiosis in the absence of mesonephroi. To exclude RA sourcing from mesonephroi, 11.5 dpc urogenital ridges (UGRs; mesonephroi and ovary complexes) were treated with diethylaminobenzaldehyde (DEAB) to block retinaldehyde dehydrogenase (RALDH) activity in the mesonephros and the ovary. Meiosis occurred when DEAB was withdrawn and the mesonephros was removed 2 days later. Furthermore, RALDH1, rather than RALDH2, serves as the major RA synthetase in UGRs from 12.5 to 15.5 dpc. DEAB treatment to the ovary alone was able to block germ cell meiotic entry. We also found that exogenously supplied RA dose-dependently reduced germ cell numbers in ovaries by accelerating the entry into meiosis. These results suggest that ovary-derived RA is responsible for meiosis initiation.
Asunto(s)
Meiosis/fisiología , Ovario/embriología , Ovario/fisiología , Tretinoina/fisiología , Familia de Aldehído Deshidrogenasa 1 , Animales , Benzaldehídos/farmacología , Inhibidores Enzimáticos/farmacología , Femenino , Isoenzimas/antagonistas & inhibidores , Isoenzimas/metabolismo , Masculino , Mesonefro/efectos de los fármacos , Mesonefro/embriología , Mesonefro/fisiología , Ratones , Ovario/efectos de los fármacos , Óvulo/efectos de los fármacos , Óvulo/crecimiento & desarrollo , Óvulo/fisiología , Embarazo , Retinal-Deshidrogenasa/antagonistas & inhibidores , Retinal-Deshidrogenasa/metabolismo , Procesos de Determinación del Sexo/fisiología , Técnicas de Cultivo de Tejidos , Tretinoina/administración & dosificaciónRESUMEN
The metanephros is the functional organ in adult amniotes while the mesonephros degenerates. However, parallel tubulogenetic events are thought to exist between mesonephros and metanephros. Mesonephric tubules are retained in males and differentiate into efferent ducts of the male reproductive tract. By examining the murine mesonephric expression of markers of distinct stages and regions of metanephric nephrons during tubule formation and patterning, we provide further evidence to support this common morphogenetic mechanism. Renal vesicle, early proximal and distal tubule, loop of Henle, and renal corpuscle genes were expressed by mesonephric tubules. Vip, Slc6a20b, and Slc18a1 were male-specific. In contrast, mining of the GUDMAP database identified candidate late mesonephros-specific genes, 10 of which were restricted to the male. Among the male-specific genes are candidates for regulating ion/fluid balance within the efferent ducts, thereby regulating sperm maturation and genes marking tubule-associated neurons potentially critical for normal male reproductive tract function.
Asunto(s)
Diferenciación Celular/genética , Genes del Desarrollo , Mesonefro/embriología , Nefronas/embriología , Nefronas/metabolismo , Animales , Tipificación del Cuerpo/genética , Femenino , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Masculino , Mesonefro/citología , Mesonefro/metabolismo , Mesonefro/fisiología , Ratones , Modelos Biológicos , Organogénesis/genética , Organogénesis/fisiología , Distribución TisularRESUMEN
GATA-2 is an essential transcription factor in the hematopoietic system that is expressed in hematopoietic stem cells (HSCs) and progenitors. Complete deficiency of GATA-2 in the mouse leads to severe anemia and embryonic lethality. The role of GATA-2 and dosage effects of this transcription factor in HSC development within the embryo and adult are largely unexplored. Here we examined the effects of GATA-2 gene dosage on the generation and expansion of HSCs in several hematopoietic sites throughout mouse development. We show that a haploid dose of GATA-2 severely reduces production and expansion of HSCs specifically in the aorta-gonad-mesonephros region (which autonomously generates the first HSCs), whereas quantitative reduction of HSCs is minimal or unchanged in yolk sac, fetal liver, and adult bone marrow. However, HSCs in all these ontogenically distinct anatomical sites are qualitatively defective in serial or competitive transplantation assays. Also, cytotoxic drug-induced regeneration studies show a clear GATA-2 dose-related proliferation defect in adult bone marrow. Thus, GATA-2 plays at least two functionally distinct roles during ontogeny of HSCs: the production and expansion of HSCs in the aorta-gonad-mesonephros and the proliferation of HSCs in the adult bone marrow.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Dosificación de Gen , Células Madre Hematopoyéticas/fisiología , Factores de Transcripción/fisiología , Animales , Aorta/fisiología , Médula Ósea/fisiología , Radioisótopos de Cesio , Proteínas de Unión al ADN/genética , Femenino , Citometría de Flujo , Factor de Transcripción GATA2 , Gónadas/fisiología , Inmunohistoquímica , Mesonefro/fisiología , Ratones , Ratones Endogámicos C57BL , Microscopía Confocal , Reacción en Cadena de la Polimerasa/métodos , Bazo/anatomía & histología , Factores de Tiempo , Factores de Transcripción/genéticaRESUMEN
BACKGROUND: The hemangioblast is a bi-potential precursor cell with the capacity to differentiate into hematopoietic and vascular cells. In mouse E7.0-7.5 embryos, the hemangioblast can be identified by a clonal blast colony-forming cell (BL-CFC) assay or single cell OP9 co-culture. However, the ontogeny of the hemangioblast in mid-gestation embryos is poorly defined. DESIGN AND METHODS: The BL-CFC assay and the OP9 system were combined to illustrate the hemangioblast with lymphomyeloid and vascular potential in the mouse aorta-gonad-mesonephros region. The colony-forming assay, reverse transcriptase polymerase chain reaction analysis, immunostaining and flow cytometry were used to identify the hematopoietic potential, and Matrigel- or OP9-based methods were employed to evaluate endothelial progenitor activity. RESULTS: Functionally, the aorta-gonad-mesonephros-derived BL-CFC produced erythroid/myeloid progenitors, CD19(+) B lymphocytes, and CD3(+)TCRbeta(+) T lymphocytes. Meanwhile, the BL-CFC-derived adherent cells generated CD31(+) tube-like structures on OP9 stromal cells, validating the endothelial progenitor potential. The aorta-gonad-mesonephros-derived hemangioblast was greatly enriched in CD31(+), endomucin(+) and CD105(+) subpopulations, which collectively pinpoints the endothelial layer as the main location. Interestingly, the BL-CFC was not detected in yolk sac, placenta, fetal liver or embryonic circulation. Screening of candidate cytokines revealed that interleukin-3 was remarkable in expanding the BL-CFC in a dose-dependent manner through the JAK2/STAT5 and MAPK/ERK pathways. Neutralizing interleukin-3 in the aorta-gonad-mesonephros region resulted in reduced numbers of BL-CFC, indicating the physiological requirement for this cytokine. Both hematopoietic and endothelial differentiation potential were significantly increased in interleukin-3-treated BL-CFC, suggesting a persistent positive influence. Intriguingly, interleukin-3 markedly amplified primitive erythroid and macrophage precursors in E7.5 embryos. Quantitative polymerase chain reaction analysis demonstrated declined Flk-1 and elevated Scl and von Willebrand factor transcription upon interleukin-3 stimulation, indicating accelerated hemangiopoiesis. CONCLUSIONS: The hemangioblast with lymphomyeloid potential is one of the precursors of definitive hematopoiesis in the mouse aorta-gonad-mesonephros region. Interleukin-3 has a regulatory role with regards to both the number and capacity of the dual-potential hemangioblast.
Asunto(s)
Aorta/fisiología , Gónadas/fisiología , Hemangioblastos/fisiología , Interleucina-3/fisiología , Mesonefro/fisiología , Animales , Aorta/citología , Aorta/embriología , Células Cultivadas , Técnicas de Cocultivo , Gónadas/citología , Gónadas/embriología , Hemangioblastos/citología , Hematopoyesis/fisiología , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/fisiología , Humanos , Mesonefro/citología , Mesonefro/embriología , Ratones , Células del Estroma/citología , Células del Estroma/fisiologíaRESUMEN
Although renal regeneration is limited to repair of the proximal tubule in mammals, some bony fish are capable of renal regeneration through nephron neogenesis in the event of renal injury. We previously reported that nephron development in the medaka mesonephros is characterized by four histologically distinct stages, generally referred to as condensed mesenchyme, nephrogenic body, relatively small nephron, and the mature nephron. Developing nephrons are positive for wt1 expression during the first three of these stages. In the present study, we examined the regenerative response to renal injury, artificially induced by the administration of sublethal amounts of gentamicin in adult medaka. Similar to previous reports in other animals, the renal tubular epithelium and the glomerulus of the medaka kidney exhibited severe damage after exposure to this agent. However, kidneys showed substantial recovery after gentamicin administration, and a significant number of developing nephrons appeared 14 days after gentamicin administration (P < 0.01). Similarly, the expression of wt1 in developing nephrons also indicated the early stages of nephrogenesis. These findings show that medaka has the ability to regenerate kidney through nephron neogenesis during adulthood and that wt1 is a suitable marker for detecting nephrogenesis.
Asunto(s)
Mesonefro/fisiología , Nefronas/fisiología , Regeneración/fisiología , Células Madre Adultas/fisiología , Animales , Biomarcadores , División Celular , Gentamicinas/toxicidad , Masculino , Mesonefro/química , Mesonefro/efectos de los fármacos , Nefronas/química , Oryzias , Especificidad de la Especie , Proteínas WT1/análisisRESUMEN
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.
Asunto(s)
Mesonefro/fisiología , Ovario/embriología , Testículo/embriología , Animales , Técnicas de Cultivo , Inducción Embrionaria , Femenino , Edad Gestacional , Masculino , Ratones , Conductos Paramesonéfricos/fisiología , Diferenciación Sexual , Conductos Mesonéfricos/fisiologíaRESUMEN
Testicular Leydig cells produce testosterone and provide the hormonal environment required for male virilization and spermatogenesis. In utero, fetal Leydig cells (FLCs) are necessary for the development of the Wolffian duct and male external genitalia. Steroidogenic factor 1 (Sf1) is a transcriptional regulator of hormone biosynthesis genes, thus serving a central role in the Leydig cell. Desert hedgehog (Dhh), a Sertoli cell product, specifies the FLC lineage in the primordial gonad through a paracrine signaling mechanism. Postnatally, FLCs are replaced in the testis by morphologically distinct adult Leydig cells (ALCs). To study a putative interaction between Sf1 and Dhh, we crossed Sf1 heterozygous mutant mice with Dhh homozygous null mice to test the function of these two genes in vivo. All of the compound Sf1(+/-); Dhh(-/-) mutants failed to masculinize and were externally female. However, embryonic gonads contained anastomotic testis cords with Sertoli cells and germ cells, indicating that sex reversal was not attributable to a fate switch of the early gonad. Instead, external feminization was attributable to the absence of differentiated FLCs in XY compound mutant mice. ALCs also failed to develop, suggesting either a dependence of ALCs on the prenatal establishment of Leydig cell precursors or that Sf1 and Dhh are both required for ALC maturation. In summary, this study provides genetic evidence that combinatorial expression of the paracrine factor Dhh and nuclear transcription factor Sf1 is required for Leydig cell development.
Asunto(s)
Proteínas Hedgehog/metabolismo , Proteínas de Homeodominio/metabolismo , Células Intersticiales del Testículo/fisiología , Receptores Citoplasmáticos y Nucleares/metabolismo , Testículo/embriología , Testículo/fisiología , Factores de Transcripción/metabolismo , Animales , Hormona Antimülleriana , Enzima de Desdoblamiento de la Cadena Lateral del Colesterol/metabolismo , Trastornos del Desarrollo Sexual , Femenino , Regulación del Desarrollo de la Expresión Génica/fisiología , Células Germinativas/citología , Células Germinativas/fisiología , Glicoproteínas/metabolismo , Proteínas Hedgehog/genética , Proteínas de Homeodominio/genética , Células Intersticiales del Testículo/citología , Masculino , Mesonefro/embriología , Mesonefro/fisiología , Ratones , Ratones Endogámicos , Ratones Mutantes , Mitosis , Embarazo , Receptores Citoplasmáticos y Nucleares/genética , Diferenciación Sexual/fisiología , Factor Esteroidogénico 1 , Hormonas Testiculares/metabolismo , Testículo/citología , Factores de Transcripción/genéticaRESUMEN
During embryogenesis there is a sequential, temporal appearance of increasingly more-complex hematopoietic cells beginning with unipotential progenitors, proceeding to multipotential (myeloid, erythroid and lymphoid) progenitors and culminating with adult-repopulating hematopoietic stem cells. Current research has established an important role for the aorta-gonads-mesonephros region of the mouse embryo in the generation of multipotential progenitors and hematopoietic stem cells. Comparisons of normal and hematopoietic-cell-mutant mouse embryos have revealed several genes pivotal in hematopoietic stem cell generation/function. Other genes have been implicated in the critical generation of lymphoid lineage potential. Thus, an understanding of the cellular and molecular interactions within the midgestation aorta-gonads-mesonephros region offers insight into the mechanisms of hematopoietic lineage specification during ontogeny and perhaps will lead to a more complete knowledge of the adult hematopoietic system.
Asunto(s)
Sistema Hematopoyético/embriología , Tejido Linfoide/embriología , Mesonefro/embriología , Proteínas Proto-Oncogénicas , Animales , Aorta/citología , Aorta/embriología , Diferenciación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal , Proteínas de Unión al ADN/fisiología , Gónadas/citología , Gónadas/embriología , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/fisiología , Sistema Hematopoyético/citología , Sistema Hematopoyético/fisiología , Factor de Transcripción Ikaros , Tejido Linfoide/citología , Tejido Linfoide/fisiología , Mesonefro/citología , Mesonefro/fisiología , Ratones , Morfogénesis , Mutación , Factores de Transcripción/fisiología , Saco Vitelino/embriología , Saco Vitelino/fisiologíaRESUMEN
Fibroblast growth factor 9 (FGF9) signal has a role in organogenesis of the mammalian testis by controlling migration of mesonephric cells to the XY gonad, but neither it nor the FGF receptors is expressed sex-specifically. Of the Sprouty genes encoding antagonists of receptor tyrosine kinases including FGFr, mSprouty2 expression was confined to the developing testis and mesonephros. Gain of SPROUTY2 function in the male genital ridge and mesonephros malformed the vas deferens and epididymis, and diminished the number of seminiferous tubules and interstitium associating with reduced mesonephric cell migration and Fgf9 expression in embryonic testis, whereas exogenous FGF9 signaling recovered mesonephric cell migration inhibited by SPROUTY2. These phenotypes associated also with the decreased expression of Sox9, Desert hedgehog, Hsd3beta, Platelet/endothelial cell adhesion molecule, and alpha-smooth muscle actin, which are markers of the Sertoli, Leydig, endothelial, and peritubular myoid cells of the developing testis. Based on these data, we propose that the Sprouty proteins are involved normally in mediating the sexually dimorphic signaling of FGF9 and controlling cell migration from the mesonephros during testis development.
Asunto(s)
Factor 9 de Crecimiento de Fibroblastos/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas/metabolismo , Testículo/embriología , Testículo/fisiología , 3-Hidroxiesteroide Deshidrogenasas/genética , Proteínas Adaptadoras Transductoras de Señales , Animales , Movimiento Celular/fisiología , Células Endoteliales/fisiología , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Femenino , Factor 9 de Crecimiento de Fibroblastos/metabolismo , Proteínas de Homeodominio/genética , Péptidos y Proteínas de Señalización Intracelular , Proteínas con Homeodominio LIM , Laminina/genética , Células Intersticiales del Testículo/fisiología , Masculino , Proteínas de la Membrana , Mesonefro/citología , Mesonefro/embriología , Mesonefro/fisiología , Ratones , Ratones Endogámicos , Ratones Transgénicos , Miocitos del Músculo Liso/fisiología , Técnicas de Cultivo de Órganos , Factor de Transcripción PAX2/genética , Embarazo , Regiones Promotoras Genéticas/fisiología , Proteínas Serina-Treonina Quinasas , Proteínas/genética , Proteínas Proto-Oncogénicas/genética , Diferenciación Sexual/fisiología , Testículo/citología , Factores de Transcripción , Proteínas Wnt/genética , Proteína Wnt4 , Conductos Mesonéfricos/citología , Conductos Mesonéfricos/embriología , Conductos Mesonéfricos/fisiologíaRESUMEN
The aorta-gonad-mesonephros (AGM) region contains intra-aortic clusters (IACs) thought to have acquired hematopoietic stem cell (HSC) potential in vertebrate embryos. To assess extrinsic regulation of IACs in the AGM region, we employed mouse embryos harboring a Sall1-GFP reporter gene, which allows identification of mesonephros cells based on GFP expression. Analysis of AGM region tissue sections confirmed mesonephros GFP expression. Mesonephric cells sorted at E10.5 expressed mRNA encoding Csf1, a hematopoietic cytokine, and corresponding protein, based on real-time PCR and immunocytochemistry, respectively. Further analysis indicated that some IACs express the CSF1 receptor, CSF1R. Expression of Cebpa and Irf8 mRNAs was higher in CSF1R-positive IACs, whereas that of Cebpε and Gfi1 mRNAs was lower relative to CSF1R-negative IACs, suggesting that CSF1/CSF1R signaling functions in IAC myeloid differentiation by modulating expression of these transcription factors. Colony formation assays using CSF1R-positive IACs revealed increased numbers of myeloid colonies in the presence of CSF1. Analysis using an intra-cellular signaling array indicated the greatest fold increase of Cleaved Caspase-3 in AGM cells in the presence of CSF1. Immunohistochemistry revealed that Cleaved Caspase-3 is primarily expressed in IACs in the AGM region, and incubation of IACs with CSF1 up-regulated Cleaved Caspase-3. Overall, our findings suggest that CSF1 secreted from mesonephros accelerates IAC myeloid differentiation in the AGM region, possibly via Caspase-3 cleavage.
Asunto(s)
Aorta/metabolismo , Aorta/fisiología , Diferenciación Celular/fisiología , Factor Estimulante de Colonias de Macrófagos/metabolismo , Mesonefro/metabolismo , Células Mieloides/fisiología , Animales , Proteínas Potenciadoras de Unión a CCAAT/metabolismo , Caspasa 3/metabolismo , Factores Reguladores del Interferón/metabolismo , Mesonefro/fisiología , Ratones , Ratones Endogámicos C57BL , Células Mieloides/metabolismo , ARN Mensajero/metabolismo , Receptores de Factor Estimulante de Colonias de Granulocitos y Macrófagos/metabolismo , Transducción de Señal/fisiología , Factores de Transcripción/metabolismoRESUMEN
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.
Asunto(s)
Células Intersticiales del Testículo/citología , Mesonefro/fisiología , Células de Sertoli/citología , Testículo/embriología , Animales , Diferenciación Celular/fisiología , Masculino , Ratones , Morfogénesis/fisiología , Técnicas de Cultivo de Órganos , Testículo/citología , Testosterona/análisisRESUMEN
We investigated mesonephric tubular-derived efferent ductules in female wild-type (WT) and estrogen receptor-alpha knockout (ERalphaKO) mice from late fetal to adult life. On gestational day 17, efferent ductules in both fetal WT and ERalphaKO females were well developed and morphologically similar, although one third the size of the male counterpart. Unexpectedly, efferent ductules with a ciliated epithelium were still present on postnatal day 10 in WT and ERalphaKO females. By day 23, however, marked phenotypic differences occurred in efferent ductules of WT and ERbetaKO vs. ERalphaKO female mice. In the latter, efferent ductules became hypertrophied and dilated, whereas only small tubules remained in WT and ERbetaKO adult mice. The serum testosterone concentrations were similar in 21- to 25-day-old ERalphaKO, heterozygous, and WT female mice, suggesting that increased testosterone was not inducing enlargement of efferent ductules in ERalphaKO females. In conclusion, remnants of efferent ductules persisted in normal adult female mice, although these structures were greatly reduced in size compared with efferent ductules in ERalphaKO female mice. The underlying mechanism inducing hypertrophy and dilation of efferent ductules in ERalphaKO females is not clear, but secretory and/or reabsorptive function of female efferent ductules may involve ERalpha.
Asunto(s)
Mesonefro/fisiología , Receptores de Estrógenos/fisiología , Animales , Animales Recién Nacidos/sangre , Dihidrotestosterona/farmacología , Receptor alfa de Estrógeno , Receptor beta de Estrógeno , Femenino , Mesonefro/efectos de los fármacos , Mesonefro/ultraestructura , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos , Ratones Noqueados/genética , Concentración Osmolar , Receptores de Estrógenos/genética , Testosterona/sangreRESUMEN
Cardiac output (CO), heart rate (HR), stroke volume (SV), dorsal aortic blood flow (DABF), dorsal aortic blood pressure (PDA) and plasma electrolytes were monitored in stanniectomized and sham-operated freshwater eels over a 3-week period; branchial shunting and systemic resistance (RSYS) were estimated. DABF was significantly reduced by 45% from 11.72 +/- 0.48 (control) to 6.55 +/- 0.41 (n = 6; day 21) ml.min-1.kg-1 within 3 weeks after the removal of the corpuscles of Stannius. This large reduction in blood flow was due to a 25% decrease in CO and a 100% increase in estimated branchial shunting which preceded the fall in CO. CO was decreased from 16.07 +/- 0.31 (control) to 11.91 +/- 1 (n = 6; day 21) ml.min-1.kg-1 through a reduction in SV; there was no significant change in HR. Estimated branchial shunting, a relative measure of branchial arterio-venous blood flow, corresponded to 2.53 +/- 0.18 ml.min-1.kg-1 (control; n = 12), which represents 16% of baseline CO. Ventral and dorsal aortic pulse flows also decreased following stanniectomy. The decrease in DABF occurred in conjunction with a reduction in PDA which was measured for 12 days in a separate group of eels. Baseline PDA (3.03 +/- 0.1 kPa) significantly decreased by 15% to 2.55 +/- 0.13 kPa 4 days after stanniectomy. However, this fall in PDA was transient and accompanied by an elevation in derived RSYS. These results support the hypothesis that the corpuscles of Stannius are closely linked to cardiovascular regulation in freshwater eels. Electrolyte changes (hypercalcemia, hypomagnesia, hyperkalemia and hyponatremia) were temporally coupled to the changes in blood flows. Impaired cardiovascular function and altered patterns of blood flow to osmoregulatory organs such as the gills, kidney and skin may have led to some or all of the electrolyte disturbances which followed stanniectomy.
Asunto(s)
Fenómenos Fisiológicos Cardiovasculares , Anguilas/fisiología , Mesonefro/fisiología , Animales , Velocidad del Flujo Sanguíneo , Presión Sanguínea/fisiología , Gasto Cardíaco/fisiología , Femenino , Frecuencia Cardíaca/fisiología , Mesonefro/cirugía , Flujo Sanguíneo Regional/fisiología , Volumen Sistólico/fisiologíaRESUMEN
Peroxisomes in three forms of vertebrate kidney (pronephros, mesonephros, and metanephros), as permanent or provisional kidney, are summarized concerning their ultrastructure and developmental changes. Because the peroxisome is known to be diverse in mammalian metanephros, and species difference is its distinctive feature among cell organelles, information should be obtained on each kidney of each species. The ultrastructural and biochemical features of peroxisomes have at least been partly delineated in the metanephros and mesonephros, but nothing is known about the pronephros. Ultrastructural studies of the metanephric peroxisomes are present in mammals, birds, and reptiles, but information on their development is restricted to mammals and birds. As for the mesonephric peroxisomes, both ultrastructural and developmental data have been accumulating on mammals and amphibians, and ultrastructural information is present on fishes, but not on birds and reptiles. At present, studies on peroxisomes of provisional kidney have been restricted to mammalian mesonephros. The common features of renal peroxisomes previously examined are that they are spherical cell organelles with a single limiting membrane in ultrastructure, and are positive for catalase. Information on the ultrastructure and enzymes is not sufficient at present for comparing the ontogenesis of renal peroxisomes with their phylogenesis.
Asunto(s)
Riñón/fisiología , Mesonefro/fisiología , Peroxisomas/fisiología , Animales , Humanos , Riñón/embriología , Riñón/ultraestructura , Mesonefro/ultraestructura , FilogeniaRESUMEN
The ability of the many cell types within the adult blood system to be constantly replenished and renewed from hematopoietic stem cells is an interesting problem in development and differentiation and has led to questions concerning how, when and where these stem cells for the adult hematopoietic system are generated within the embryo. During embryonic development many mature hematopoietic cells appear before adult-type hematopoietic stem cells thus the notion of a conventional hematopoietic hierarchy is challenged. Experiments probing the development of hematopoietic stem cells in the mouse embryo strongly suggest that at least two independent hematopoietic sites generate blood cells during development; the yolk sac, which produces the transient embryonic hematopoietic system, and the AGM (aorta-gonad-mesonephros) region, which initiates the long-lived adult hematopoietic system.
Asunto(s)
Desarrollo Embrionario y Fetal , Hematopoyesis/fisiología , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/fisiología , Animales , Aorta/embriología , Gónadas/embriología , Mesonefro/fisiología , Ratones , Saco Vitelino/fisiologíaRESUMEN
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.
Asunto(s)
Matriz Extracelular/fisiología , Mesonefro/fisiología , Diferenciación Sexual , Animales , Colágeno/farmacología , Combinación de Medicamentos , Femenino , Laminina/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos ICR , Técnicas de Cultivo de Órganos , Embarazo , Proteoglicanos/farmacología , Vimentina/análisisRESUMEN
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.
Asunto(s)
Embrión de Pollo/fisiología , Mesonefro/fisiología , Nefronas/embriología , Animales , Factores de TiempoRESUMEN
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.
Asunto(s)
Hibernación/fisiología , Mesonefro/fisiología , Mesonefro/ultraestructura , Rana esculenta/anatomía & histología , Rana esculenta/fisiología , 4-Nitrofenilfosfatasa/metabolismo , Fosfatasa Alcalina/metabolismo , Animales , Femenino , Histocitoquímica , Túbulos Renales Colectores/ultraestructura , Túbulos Renales Proximales/ultraestructura , Masculino , Mesonefro/enzimología , Microscopía Electrónica , Reacción del Ácido Peryódico de Schiff , Rana esculenta/metabolismo , Estaciones del Año , Succinato Deshidrogenasa/metabolismoRESUMEN
Renal tubule epithelial cells can regenerate in response to acute injury. Although this process remains poorly understood, it appears to involve the reactivation of pathways that are operative during embryonic kidney formation. A better understanding of renal regeneration may lead to the development of new therapies that can attenuate acute kidney injury or expedite recovery. The zebrafish is being used as a model to understand renal regeneration. In this review, we summarize the current knowledge on zebrafish kidney formation, describe methods for inducing acute injury, and focus on the unique capacity of the zebrafish adult kidney to undergo de novo nephron formation in response to damage.