Initial morphological symmetry breaking in the foregut and development of the omental bursa in human embryos.

Bilaterally symmetrical primordia of visceral organs undergo asymmetrical morphogenesis leading to typical arrangement of visceral organs in the adult. Asymmetrical morphogenesis within the upper abdomen leads, among others, to the formation of the omental bursa dorsally to the rotated stomach. A widespread view of this process assumes kinking of thin mesenteries as a main mechanism. This view is based on a theory proposed already by Johannes Müller in 1830 and was repeatedly criticized, but some of the most plausible alternative views (initially proposed by Swaen in 1897 and Broman in 1904) still remain to be proven. Here, we analyzed serial histological sections of human embryos between stages 12 and 15 at high light microscopical resolution to reveal the succession of events giving rise to the development of the omental bursa and its relation to the emerging stomach asymmetry. Our analysis indicates that morphological symmetry breaking in the upper abdomen occurs within a wide mesenchymal plate called here mesenteric septum and is based on differential behavior of the coelomic epithelium which causes asymmetric paragastric recess formation and, importantly, precedes initial rotation of stomach. Our results thus provide the first histological evidence of breaking the symmetry of the early foregut anlage in the human embryo and pave the way for experimental studies of left-right symmetry breaking in the upper abdomen in experimental model organisms.

The Lesser Sac and Foramen of Winslow: Anatomy, Embryology, and CT Appearance of Pathologic Processes.

OBJECTIVE. This article reviews the embryologic development, relevant anatomy, and imaging features, on CT, of pathologic processes involving the lesser sac and foramen of Winslow. CONCLUSION. The lesser peritoneal sac is an intricate anatomic region involved in many disease processes. It is a significant conduit for the spread of disease within the peritoneal cavity. The spectrum of pathologic processes pertaining to the lesser sac can be classified on the basis of the type of involvement, such as a fluid collection (e.g., transudate, exudate, bile, and blood), a mass (e.g., neoplastic or nonneoplastic conditions and lymphadenopathy), or an internal hernia into the lesser sac.

Three-dimensional morphogenesis of the omental bursa from four recesses in staged human embryos.

The omental bursa (OB) is a complex upper abdominal structure in adults. Its morphological complexity stems from embryonic development. Approximately 200 years ago, the first theory regarding OB development was reported, describing that the OB developed from changes in the position of the stomach and its dorsal mesentery. Thereafter, the second theory reported that the OB originated from three recesses: the right pneumato-enteric recess (rPER), hepato-enteric recess (HER), and pancreatico-enteric recess (PaER). However, the first theory, focusing on the rotation of the stomach, is still described in certain modern embryology textbooks. These two coexisting embryological theories deter the understanding of the anatomical complexity of the OB. This study aimed to unify these two theories into realistic illustrations. Approximately 10 samples per stage among Carnegie stage (CS) 13 and CS21 were microscopically observed and histological serial sections of the representative samples were aligned using the new automatic alignment method. The aligned images were segmented computationally and reconstructed into 3D models. The rPER and the HER encompassed the right half circumference of the esophagus and the stomach at CS13 and CS14, the PaER spread dorsal to the stomach and formed a discoid shape at CS15 and CS16, the infracardiac bursa (ICB) was separated by the diaphragm at CS17 and CS18, and the fourth recess, which we called the greater omental recess (GOR), extended caudally from the PaER among CS19 and CS21. The present results indicate that the fourth recess is also the origin of the OB. These two theories over 200 years can be generally unified into one embryological description indicating a new recess as the origin of the OB.

Congenital Filariasis Caused by Setaria bidentata (Nematoda: Filarioidea) in the Red Brocket Deer (Mazama americana).

The filarial nematode Setaria bidentata was found in 10 of 31 fetuses of the red brocket deer ( Mazama americana ) from the Loreto region of the Peruvian Amazon. A total of 25 specimens were collected and morphologically identified as S. bidentata. Filarial nematodes were found in the peritoneal cavity of 9 deer fetuses and the thoracic cavity of 1 fetus. Most specimens were adult stage. In this report, we provide morphometric data for these filarial specimens. This is the first study to demonstrate prenatal S. bidentata infection in cervid fetuses. Also, the finding of S. bidentata in Peru expands the geographic range of this parasite.

Morphology of the ligament of Treitz likely depends on its fetal topographical relationship with the left adrenal gland and liver caudate lobe as well as the developing lymphatic tissues: a histological study using human fetuses.

To investigate the factors affecting the development of the ligament of Treitz, we examined sagittal and frontal histological sections of 35 human fetuses with a crown-rump length of 100-300 mm (approximately 16-38 weeks of gestation). The retropancreatic fascia consistently extended in a layer behind the pancreatic body and the splenic artery and vein, and also in front of the left renal vein and left adrenal. In 18 specimens, a connective tissue band was seen originating from the diaphragmatic crus around the esophageal opening and ending at the retropancreatic fascia to the left of the origin of the celiac artery. In 10 of these 18 specimens, these putative upper parts of the ligament contained striated muscles, or so-called Hilfsmuskel. Although most of other 17 specimens were larger fetuses, the left adrenal, the liver caudate lobe and the celiac ganglion made space for the ligament very limited. In 22 specimens including the above 18, the retropancreatic fascia extended inferiorly to approach the fourth portion of the duodenum (D4) or the duodenojejunal junction (DJJ). However, in 11 of the 22 examples of the putative lower part of the ligament, the connection between the duodenal muscle coat and the fascia was interrupted by developing lymphatic tissues. Consequently, the ligament of Treitz seemed to develop from both pleuroperitoneal membrane-derived cells and the retropancreatic fusion fascia, although the morphology was markedly modified by adjacent structures such as the adrenal gland. The ligament may "recover" after the adrenal becomes reduced in size after birth.

Fetal topographical anatomy of the upper abdominal lymphatics: its specific features in comparison with other abdominopelvic regions.

Using semiserial sections from 19 human fetuses of 8-30 weeks gestation, we examined the topohistology of the upper abdominal lymphatics and compared it with that of the lower abdominal and pelvic lymphatics. The upper abdominal lymphatics were characterized by an intimate relationship with the peritoneal lining, a common mesentery for the celiac trunk and superior mesenteric artery (SMA). Lymphatic connections from the upper abdominal viscera to the paraaortic and paracaval areas followed two routes: (1) from the intestinal mesentery, along the peritoneum on the left aspect of the proximal SMA, via the chain of lymph follicles (LFs) lying along the retropancreatic fusion fascia, to drain into the LFs around the left renal vein; (2) from sites along the peritoneum on the posterior wall of the omental bursa, via the root of the hepatoduodenal ligament, to drain into LFs around the vena cava. The development of these two posterior drainage routes seemed to be promoted by the peritoneum or a peritoneal remnant (i.e., fusion fascia) attaching to the great vessels, and inhibited or impeded by the developing nerves and diaphragm. No paraaortic, paracaval, or pelvic LFs lay along the peritoneum. The pelvic LFs were usually located along the bundle of lymphatic vessels originating from the femoral canal.

Identification and characterization of engrafted human cells in human/goat xenogeneic transplantation chimerism.

We have injected human CD34+lin- cells derived from cord blood (CB) into the goat fetuses via in utero at 45-55 days gestation under guidance of B-scan ultrasonograph. Sixty out of 68 fetuses injected survived to full term. The long-term survival of the human cells in transplant goat has been tested by various experimental methods, including FACS analysis, real-time PCR, RT-PCR, Southern-blot hybridization, FISH, as well as immunohistochemical assays. All the 60 transplant goats demonstrated engrafted human cells, including myeloid, B-lymphoid, and erythroid lineages. The yield of the human CD34+ cells varied, but was not linked with sex and age. High numbers of human cells could be detected for at least 16 months after birth. Immunohistochemical analyses revealed that the human cells were present not only in blood but also in other tissues, such as liver, of the transplant goats. In addition, a human-specific serum albumin and the hepatocyte nuclear factor (hHNF-3beta) mRNAs specific to human hepato-antigen could be readily detected in the livers of the transplant goats. Our results demonstrate that this in utero xenograft model should be useful for expansion of human HSC and possibly for the evaluating the effectiveness of prenatal treatment of human genetic diseases.

In utero transplantation of human hematopoetic stem cells into fetal goats under B-type ultrasonographic scan: an experimental model for the study of potential prenatal therapy.

OBJECTIVE: Using fetal goats as animal models, to establish the methodology of in utero transplantation of human hematopoeitic stem cell (HSC) under B-scan ultrasonographic guidance for prenatal therapy. STUDY DESIGN: Human HSC were directly injected into the peritoneal cavities of the recipient fetal goats at 45-55 days of gestation (term: 145 days) under the guidance of B-type ultrasound scan. After birth, the peripheral blood was collected for fluorescence assisted cell sorting (FACS), quantitative real-time PCR and fluorescence in situ hybridization (FISH) to detect and analyze the presence of human cells in the recipients. RESULTS: The 32 recipients were born alive except one miscarriage. To test for the presence of human-goat chimeras, cells from 13 randomly selected transplanted goats were collected. FACS analyses showed the presence of human cells in all the transplanted goats tested. The average proportion of CD34+ cells and GPA+(glycophorin A) cells in the peripheral blood were 1.34 +/- 1.10% and 2.80 +/- 2.10%, respectively. No CD34+ or GPA+ cells were found in the non-transplanted goats tested. The results of the quantitative real-time PCR in three engraftment goats were 1.2 x 10(4), 2.9 x 10(4), and 3.2 x 10(4) copies of human GPA DNA per mug of genomic DNA. FISH experiments showed that cells containing human specific alpha-satellite DNA sequence were present in the peripheral blood of the transplanted goats. CONCLUSIONS: The method described herein is safe and reliable, with low miscarriage risk and high chimerism rate. This approach may provide a promising animal model for potential prenatal treatment.

The persisting pneumatoenteric recess and the infracardiac bursa: possible role in the pathogenesis of right hydrothorax complicating peritoneal dialysis.

Hydrothorax, an uncommon complication of peritoneal dialysis (PD), results from the migration of dialysis fluid under pressure from the peritoneal cavity into the pleural space. The exact site of the transdiaphragmatic fluid leak remains obscure, but the right-sided predominance of the hydrothorax points to the presence of abnormalities in the right hemidiaphragm. Such abnormalities have occasionally been described. In a recent case of acute massive right hydrothorax at the start of PD, the autopsy revealed extensive changes of amyloidosis that were comparable in both hemidiaphragms, prompting us to revisit the accepted explanation for right hydrothorax. We propose that an embryonic remnant--namely, the persisting pneumatoenteric recess and the infracardiac bursa--provides a passage connecting the peritoneal cavity to the right pleural space. The potential presence of this mechanism is consistent with the recognized clinical features of right hydrothorax complicating PD. This proposed route for dialysis fluid to form a right hydrothorax during PD can be investigated by currently available high-definition imaging techniques. This novel mechanism may also be involved in the pathogenesis of right hydrothorax observed in other medical conditions with tense ascites (liver cirrhosis, Meigs syndrome).

[Inguinal symptoms of acute abdomen]. / Manifestaciones inguinales del abdomen agudo.

INTRODUCTION: We describe a syndrome in which empty hernial sac, in its role of peritoneal recess, becomes distended with pus during or after general peritonitis, usually caused by acute appendicitis. Until 1998, only 14 pediatric cases were described in the literature. MATERIALS, METHODS, AND RESULTS: We presented here eight cases of patients who experienced inguinal symptoms. In four, appendectomy was performed; in four, this was secondary to necrotizing enterocolitis. Inguinal complaints, pain, and flogosis were present in first group, while pneumoperitoneum and visible duct vaginalis were present in second group. CONCLUSIONS: These cases demonstrated that persistent patent processus vaginalis may predispose to inguinal pathology secondary to intraabdominal sepsis and represent a unique complication.

Generation of live fry from intraperitoneally transplanted primordial germ cells in rainbow trout.

Germ cell transplantation has tremendous applications in transgenic animal production, assisted reproductive technology, and germline stem cell research. Here, we report for the first time the production of individuals from intraperitoneally transplanted primordial germ cells (PGCs) in animals. To trace the behavior of exogenous PGCs in recipients, PGCs visualized by a green fluorescent protein gene were used as donors. The PGCs prepared from the genital ridges of hatching embryos were transplanted into recipients at various developmental stages. The PGCs injected into the peritoneal cavities of hatching embryos had the ability to migrate toward, and to colonize, the genital ridges of recipient embryos. Furthermore, donor-derived PGCs proliferated and differentiated into mature eggs and sperm in the allogenic gonads; the resulting gametes produced live fry, showing the donor-derived phenotype, through fertilization. Combined with in vitro culture, genetic modification, and cryopreservation of PGCs, this technique provides new approaches for fish bioengineering.

[Differences in the structure of the posterior parietal (lumbar) lymphatic bed of the peritoneal cavity in human fetuses and newborns]. / Razlichiia v stroenii zadnego parietal'nogo (poiasnichnogo) limfaticheskogo rusla briushnoi polosti u plodov i novorozhdennykh cheloveka.

The study was performed in 150 corpses of human 8.5-36 wks old fetuses and 10 newborns using the complex of macro-microscopic methods. Primary lymphatic structures of lumbar region (sacs and canals) are transformed into lymphatic plexuses (9.5-10.5 wks) with the following formation of anlages of lumbar lymph nodes inside the invaginations. Variants of lumbar tracts and trunks structure arise during magistralization of lymphatic plexuses (14.5-19.5 wks) and reflect its depth and topographic variant. In intensive, medium and weak magistralization monomagistral, intermediate and plexiform forms develop. Topographic variant of magistralization provides the appearance of right-sided (20%), left-sided (20%) and relatively even bilateral (60% cases) organization of lumbar lymphatic bed on the whole.

An ultrasound-guided procedure to administer a label of DNA synthesis into fetal sheep.

A novel technique was developed to deliver a bolus dose of a DNA label into the peritoneal cavity of fetal sheep at 85-130 days gestation. Use of markers to identify the site of injection in fetuses from litters up to quadruplets, and immunohistochemistry to detect the DNA label, 5-bromo-2'-deoxyuridine (BrdU), confirmed the procedure was successful in 85% of cases. Duration of the procedure was (mean +/- SD) 44 +/- 16 min, and recovery from anaesthesia was rapid and uneventful in all cases. Fetal weight was estimated with a high degree of accuracy (residual standard deviation (RSD) = 297 g and r2 = 0.93, P<0.001) and the dose of label administered (110 +/- 33 mg BrdU/kg fetal weight) was adequate in all cases. BrdU detected in fetal nuclei following injection into amniotic fluid highlights the need for positive identification of the injection site in timed, short-term studies, and suggests potential to further develop the technique to investigate cellular events in fetal sheep younger than 85 days of gestation. The results demonstrate that the procedure can be used to determine in vivo whether or not nuclei have entered the S-phase of the cell cycle.

Development of diaphragmatic lymphatics: the process of their direct connection to the peritoneal cavity.

The development of the lymphatic system in the rat diaphragm was studied from embryonic day 16 to 25 weeks after birth by histochemistry for 5'-nucleotidase, scanning electron microscopy of KOH-treated or intact tissues, and transmission electron microscopy of thin sections. On embryonic day 16, distinct lymphatics were noted in the subpleural space of the diaphragm periphery. The endothelial cells at this stage contained an abundance of rough endoplasmic reticulum, a developed Golgi apparatus and mitochondria, and fewer pinocytotic vesicles than those in adults. The subpleural lymphatics subsequently increased and formed a polygonal network. They possessed many valves, and by postnatal week 6, some thick collecting lymphatics became endowed with smooth muscle cells. On embryonic day 19, some lymphatics appeared in the subperitoneal space. They extended centripetally and had many lateral projections that subsequently became elongated and connected with those from adjacent lymphatics, thus forming a lattice-like network. During the early postnatal days, the subperitoneal lymphatics projected many bulges that subsequently became elongated, and came into contact with the pores among the mesothelial cells, thus forming lymphatic stomata connecting the lymphatic lacunae to the peritoneal cavity. The lymphatic stomata increased until postnatal week 10. The results show that lymphatics appear as early as embryonic day 16 in the subpleural space of the diaphragm periphery, and develop with age by sprouting to form networks in both the subpleural and the subperitoneal spaces, and that the direct connection of the lymphatic lacunae to the peritoneal cavity is formed after birth.

Peritoneal lymphatic stomata of the diaphragm in the mouse: process of their formation.

BACKGROUND: Lymphatic stomata are channels connecting the peritoneal cavity with the lymphatics in the diaphragm. The process of sequential formation of the stomata has not been studied. The objective of this study was to examine the morphogenesis of the lymphatic stomata in mice. METHODS: Ultrathin sections of diaphragms from ddY mice obtained on embryonic day 18 and postnatal days 0, 4, and 10 were observed with a transmission electron microscope. RESULTS: By embryonic day 18 and postnatal day 0, lymphatics were already observed in the submesothelial connective tissue on the peritoneal side of the fetal diaphragm. The lymphatic endothelial cells, but not the mesothelial cells covering the diaphragm, protruded short cytoplasmic processes into the submesothelial connective tissue, and these almost reached the basal surfaces of individual mesothelial cells. By postnatal days 4 and 10, the lymphatic endothelial cells frequently protruded cytoplasmic processes into the submesothelial connective tissue, and the endothelial cell processes broke the continuity of both the basal lamina beneath the mesothelial cells and the submesothelial connective tissue. Neighboring endothelial processes formed a pair of U-shaped folds that were connected with each other via intercellular junctions at the apexes of the U-shaped folds. The disassembly of the intercellular junctions between the U-shaped folds was observed, and the basal surface of the mesothelial cell faced the lymphatic lumen. Dehiscence of the intercellular junctions between the mesothelial cells overlaying the lymphatics was observed, and lymphatic stomata were present. On the pleural side of the diaphragm, lymphatics were already present on embryonic day 18, but it was not observed that the endothelial process spanned the submesothelial connective tissue to the basal surface of the mesothelial cell. CONCLUSIONS: These results suggest the following process of the formation of the lymphatic stomata. (1) Neighboring lymphatic endothelial cells span the submesothelial connective tissue to the basal surfaces of mesothelial cells. (2) The lymphatic stomata are formed by the disassembly of the intercellular junctions between the neighboring endothelial cells and between the mesothelial cells overlying the endothelial cells.

Utility of fetal intraperitoneal saline infusion in the prenatal evaluation of diaphragmatic hernia.

The diagnosis of a diaphragmatic hernia at 18 weeks gestation by instillation of normal saline into the fetal peritoneal cavity under ultrasound guidance is described. The procedure established the diaphragmatic defect with certainty, outlined the contents of the hernia within the thorax, and demonstrated the degree of secondary lung compression.

Growth curve of the foetal dog and the morphometry of its internal cavities and organs.

In the present study we determined the foetal growth curve of the greyhound. Using an LKB 2250 PMV cryomicrotome, we studied selected sagittal sections from 15 foetuses of the same breed of dog and described the expansion and development of the thoracic and abdominal cavities, the lungs, the liver and (in part) the heart and the thymus. Drawings of the sections were measured by means of a Vids II image analyser and its fractional area programme.

Mononuclear cells in the extraembryonic and intraembryonic coelom of the mouse embryo: a semithin light microscopic cytometry.

Mononuclear cells in the extraembryonic and intraembryonic spaces of mice were examined qualitatively and quantitatively by semithin light microscopy. At 9 and 10 days of gestation, the extraembryonic serous cavities contained a small number of mononuclear free cells. These cells had an elongated or kidney-shaped nucleus and the cell surface showed many villous projections. The cytoplasm occasionally contained small lucent vesicles but no phagocytic vacuoles. The average cell diameter was 8.4 +/- 0.9 microns and N-C ratio, 0.51 +/- 0.21. Cell larger than 10 microns in diameter constituted only 0.4% of the total. In vitelline vessels at 9 days, mononuclear cells bearing a close morphological resemblance to extraembryonic free cells were observed. At 12 days of gestation, extraembryonic and peritoneal cavities contained mature macrophages and a few small mononuclears which had the same morphological features as those in the extraembryonic coelom and vitelline vessels.

A semithin light microscopic study of peritoneal cells of the mouse embryo.

Using semithin plastic sections, sequential changes in the mouse peritoneal cells during their intrauterine life were observed by light microscopy. At 11-13 days of gestation, the peritoneal cavity contained a small number of free mononuclear cells, singly scattered. Most of them were 9 to 12 micron in cell diameter, and the N-C (nucleocytoplasmic) ratio was smaller than 0.7. The cytoplasm contained large phagocytic vacuoles, and long processes extended from the cell surface. These cells were considered mature macrophages. After 15 days, the peritoneal cavity contained small-sized mononuclear cells in addition to mature macrophages. The small mononuclear cells were 5-10 micron in cell diameter, and formed the major cell type at this time. The cytoplasm contained occasional small vesicles but no phagocytic vacuoles. The small mononuclear cells showed a larger N-C ratio, 0.8-1.7. In 18-day-old fetuses, the peritoneal cells consisted of mononuclear cells, 79.5%, and mast cells, 20.5%. During the initial 18 days of embryonic life, small lymphocytes, neutrophils and eosinophils were not contained in the mouse peritoneal space.