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PubMed1983

The pig mesonephros. II. The proximal tubule: SEM, TEM and freeze-fracture images.

The ultrastructure of the proximal tubule of mature mesonephric nephrons was studied in perfusion-fixed pig embryos of the 41st gestational day. Despite its 8-12 mm long course, the proximal tubule possesses no cytologically different subsegments except its very last cells at the abrupt transition into the distal tubule. The first brush-bordered proximal tubule cells stand considerably within Bowman's capsule, abuting its attenuated cells. In SEM specimens, the average luminal cell diameters are 8 X 13 micron. The cells are 6-11 micron in height with overlying microvilli 2-4 micron long. Lateral faces of perfectly disjoined cells exhibit plate-like interdigitating processes projecting more than 5 micron deep into the neighboring cells. The basal cell face is completely covered with microvilli. The TEM pictures reveal an endocytic apparatus largely matching its metanephric counterpart. Mitochondria account for 23% of the cytoplasm and together with the many basolateral cell membranes indicate a high capacity for energy-dependent transport processes. Small basal lipid droplets represent a species peculiarity. Freeze-fracture specimens show an electrocoupling of the cells by gap junctions. The tight junction, with only 1-2 strands, characterizes a "leaky" epithelium. In most features, this tissue is as mature as its metanephric counterpart.

Animals↗
PubMed2002

Vasculogenesis and angiogenesis in the subcardinal venous plexus of quail mesonephros: spatial and temporal morphological analysis.

Vasculogenesis and angiogenesis are involved in a coordinated program for the development of the mesonephric subcardinal venous plexus of quail embryo. Vasculogenesis occurs between days 3 and 4 of incubation, while angiogenesis takes place from day 5 to day 7. Examination of vascular corrosion casts and whole mounts, and tissue sections labelled with specific markers to hemangioblast lineage (QH1, LEP100 and AcPase activity), allowed us to distinguish six phases in the formation of subcardinal plexus. (1) Appearance of isolated angioblast-like cells where the subcardinal plexus will form. (2) Alignment of angioblast-like cells into cellular strands. (3) Formation of compact vascular cords by association of angioblast-like strands. (4) Polygonal interconnection of vascular cords to constitute the primary subcardinal plexus. In this stage, isolated angioblast-like cells were present inside inter-vascular spaces. (5) The splitting of primary inter-vascular spaces by angiogenic sprouts to form secondary subcardinal plexus (outward angiogenesis). Isolated angioblast-like cells were not present in this stage. (6) Expansion of the secondary subcardinal plexus by insertion of slender transcapillary tissue pillars (inward angiogenesis) and angiogenic sprouts. We also describe three morphogenetic gradients during the development of the subcardinal plexus: ventral-to-dorsal, cranial-to-caudal and lateral-to-medial.

Animals↗
PubMed2005

Quantitative analysis of embryonic kidney impairment by confocal microscopy and stereology: effect of 1,2-dibromoethane in the chick mesonephros.

1. Chick embryos in ovo were treated with a teratogenic dose of 1,2-dibromoethane (DBE) on embryonic day (ED) 3. On ED 6 and 10, histological sections of whole embryos were prepared for confocal microscopy. In parallel, mesonephroi of 10-d-old embryos were dissected for in situ staining with acridine orange (AO), a fluorescence probe for lysosomes. 2. DBE impaired differentiation of renal vessels which manifested as a delay in rearrangement of primitive renal vascular architecture on ED 6 and a significant reduction of the mesonephric vascularisation on ED 10. This was accompanied by delayed functional maturation of embryonic kidney, as suggested by staining with AO. 3. Renal vessels appeared to be more susceptible to DBE than tubules. Unequal growth of these renal components might be a cause of DBE-induced spatial disorganisation of tubular apparatus. 4. Nephrotoxic effects of DBE during the embryonic period are associated primarily with damage to the renal blood supply. 5. Confocal microscopy, stereological methods and three-dimensional reconstruction of developing tissues are useful tools to investigate pathogenic processes during embryonic development.

Animals↗
PubMed1983

Paravaginal wolffian duct (mesonephros) adenocarcinoma: a light and electron microscopic study.

This is a report of an adenocarcinoma of mesonephric origin studied by light microscopy, electron microscopy, and immunocytochemistry. Unlike previous reports, our lesion was located paravaginally and not in the leaves of the broad ligament or in the cervix. The light microscopic features are similar to those of previous cases in the literature. Although not specific, the ultrastructural features of the tumor are similar to those of mesonephric structures and different from those of müllerian structures. The diagnosis always should be considered when a tumor occurs at the site where mesonephric remnants may be found and after exclusion of a carcinoma of other pelvic organs or a metastasis from a primary neoplasm elsewhere.

Adult↗
PubMed2002

Quantitative developmental anatomy of definitive haematopoietic stem cells/long-term repopulating units (HSC/RUs): role of the aorta-gonad-mesonephros (AGM) region and the yolk sac in colonisation of the mouse embryonic liver.

In the developing mouse embryo the first definitive (transplantable-into-the-adult) haematopoietic stem cells/long-term repopulating units (HSC/RUs) emerge in the AGM region and umbilical vessels on 10-11 days post coitum (d.p.c.). Here, by limiting dilution analysis, we anatomically map the development of definitive HSC/RUs in different embryonic tissues during early colonisation of the liver. We show that by day 12 p.c. the mouse embryo contains about 66 definitive HSC/RUs (53 in the liver, 13 in other tissues), whereas on the previous day the total number of definitive HSC/RUs in the entire conceptus is only about 3. Owing to the length of the cell cycle this dramatic increase in the number of definitive HSC/RUs in only 24 hours is unlikely to be explained purely by cell division. Therefore, extensive maturation of pre-definitive HSCs to a state when they become definitive must take place in the day 11-12 embryo. Here we firstly identify the numbers of HSCs in various organs at 11-13 d.p.c. and secondly, using an organ culture approach, we quantitatively assess the potential of the aorta-gonadmesonephros (AGM) region and the yolk sac to produce/expand definitive HSC/RUs during days 11-12 of embryogenesis. We show that the capacity of the AGM region to generate definitive HSC/RUs is high on 11 d.p.c. but significantly reduced by 12 d.p.c. Conversely, at 12 d.p.c. the YS acquires the capacity to expand and/or generate definitive HSCs/RUs, whereas it is unable to do so on 11 d.p.c. Thus, the final steps in development of definitive HSC/RUs may occur not only within the AGM region, as was previously thought, but also in the yolk sac microenvironment. Our estimates indicate that the cumulative activity of the AGM region and the yolk sac is sufficient to provide the day 12 liver with a large number of definitive HSC/RUs, suggesting that the large pool of definitive HSC/RUs in day 12 foetal liver is formed predominantly by recruiting 'ready-to-use' definitive HSC/RUs from extra-hepatic sources. In accordance with this we observe growing numbers of definitive HSC/RUs in the circulation during days 11-13 of gestation, suggesting a route via which these HSCs migrate.

Animals↗