Ventral Primordia Research Articles

Morphology and divisional morphogenesis of Nudiamphisiella interrupta Foissner, Agatha & Berger, 2002 (Ciliophora: Stichotrichia) based on a Brazilian strain

The morphology and divisional morphogenesis of a Brazilian strain of Nudiamphisiella interrupta were characterized. The organisms were investigated after protargol impregnation. Interphase cells of N. interrupta fitted the original description. Stomatogenesis in dividing cells occurred apokinetally, left of the amphisiellid cirral row, and the ventral ciliature was derived from five ventral primordia; primordium IV was absent. The dorsal kineties replicated intrakinetally, with the exception of kinety 4, which is interpreted as a dorso-marginal row, since it originates in association with the right marginal row. The nuclear apparatus divided as usual in non-urostylid stichotrichs, exhibiting complete fusion of the macronuclear nodules in middle dividers.

Unusual fusion between ventral and dorsal primordia causes anomalous pancreaticobiliary junction

Anomalous pancreaticobiliary junction (APBJ) is a congenital anomaly in which the pancreatic duct joins the common bile duct proximal to the sphincter of Oddi. Anatomical and immunohistochemical examination of the pancreas with APBJ has rarely been performed. A 72-year-old woman with gallbladder cancer and APBJ died of respiratory failure. Macroscopic features of the pancreas were examined in detail. Immunohistochemistry using anti-pancreatic polypeptide (anti-PP) antibody was done to discriminate ventral and dorsal pancreas. Macroscopically the inferior part of the head of the pancreas was smaller than normal. The posterior surface of the head was obliquely grooved. Part of the pancreatic head protruded into the posterior side of the pancreatic head. A PP-rich region was located in the superioposterior position of the pancreas head. Considering the relationship between the ventral and dorsal pancreas, it was inferred that the ventral primordium could obliquely fuse with the dorsal primordium during embryological development. As a result, APBJ occurs through an abnormal fusion between ventral and dorsal primordia.

GABA immunoreactivity in the developing rat thalamus and Otx2 homeoprotein expression in migrating neurons

We investigated the expression of gamma-aminobutyric acid (GABA) in the developing rat thalamus by immunohistochemistry, using light, confocal and electron microscopy. We also examined the relationship between the expression of the homeoprotein Otx2, a transcription factor implicated in brain regionalization, and the radial and non-radial migration of early generated thalamic neurons, identified by the neuronal markers calretinin (CR) and GABA. The earliest thalamic neurons generated between embryonic days (E) 13 and 15 include those of the reticular nucleus, entirely composed by GABAergic neurons. GABA immunoreactivity appeared at E14 in immature neurons and processes laterally to the neuroepithelium of the diencephalic vesicle. The embryonic and perinatal periods were characterized by the presence of abundant GABA-immunoreactive fibers, mostly tangentially oriented, and of growth cones. At E15 and E16, GABA was expressed in radially and non-radially oriented neurons in the region of the reticular thalamic migration, between the dorsal and ventral thalamic primordia, and within the dorsal thalamus. At these embryonic stages, some CR- and GABA-immunoreactive migrating-like neurons, located in the migratory stream and in the dorsal thalamus, expressed the homeoprotein Otx2. In the perinatal period, the preponderance of GABAergic neurons was restricted to the reticular nucleus and several GABAergic fibers were still detectable throughout the thalamus. The immunolabeling of fibers progressively decreased and was no longer visible by postnatal day 10, when the adult configuration of GABA immunostaining was achieved. These results reveal the spatio-temporal features of GABA expression in the developing thalamus and suggest a novel role of Otx2 in thalamic cell migration.

Persistence of the left part of the ventral pancreas may cause congenital biliary dilatation.

Congenital biliary dilatation (CBD) is a congenital anomaly by which pancreaticobiliary maljunction (PBMJ) is accompanied in most patients. The etiology of these conditions is unknown. AIMS To clarify the pattern of fusion between the ventral and dorsal parts of the pancreas. We examined the pancreases from five patients who had PBMJ with or without CBD and five control subjects, and we detected pancreatic polypeptide (PP) immunohistochemically. In cases of CBD, the pancreatic head was huge, while the uncinate process was undetectable. The dorsal portion of the head was formed by the ventral pancreas macroscopically. It was divided into PP-rich and PP-poor portions immunohistochemically. In cases of PBMJ without CBD, the uncinate process was relatively small. The PP-rich portion (ventral pancreas) was situated obliquely dorsal to the PP-poor portion (dorsal pancreas). In case of CBD, the PP-rich and PP-poor portions of the ventral pancreas may be derived from the right and left parts of the ventral primordia, respectively. CBD may occur when the remnant of the left part of the ventral primordium prevents normal recanalization of the common bile duct, resulting in dilatation of the duct. In cases of PBMJ without CBD, PBMJ without CBD may be caused by abnormal fusion between the ventral and dorsal primordia.

Anatomical segmentectomy of the head of the pancreas along the embryological fusion plane: A feasible procedure?

Background. Less extensive resection of the head of the pancreas has been the procedure of choice recently for low-grade malignant neoplasms. The anatomical detail of the head of the pancreas is currently insufficient for segmental resection along the embryological fusion plane. Methods. The anatomy of the head of the pancreas was analyzed in 31 consecutive autopsy specimens. An anterior (n = 10) or posterior (n = 10) segmentectomy of the head of each pancreas was performed along the macroscopically found fusion plane. The pancreatic arteries, the portal vein, the bile duct, and the pancreatic duct were visualized by injecting 3 silicon dyes of different colors. Another 11 specimens were examined by pancreatography before and after anterior (n = 5) or posterior (n = 6) segmentectomy. Eight of these 11 specimens were stained immunohistochemically to reveal the distribution of pancreatic polypeptide cells after segmentectomy. Results. The cleavage between the anterior and posterior segments was discovered at the anterior inferior edge or at the posterior superior edge of the head of the pancreas. Anterior segmentectomy was accomplished while preserving the anterior and posterior pancreaticoduodenal arcades and the lower bile duct in the posterior segment. Posterior segmentectomy involved the removal of the lower bile duct and the posterior pancreaticoduodenal arcades. Pancreatography after segmentectomy showed the division of the ducts of Wirsung and Santorini with the peripheral branches. The immunohistochemical boundary of pancreatic polypeptide cells coincided with the surgical plane. These results showed the anterior and posterior segments were originated from the embryologically dorsal and ventral primordia, respectively. Conclusions. The current anterior or posterior segmentectomy of the head of the pancreas corresponded to the resection of the embryologically dorsal or ventral primordium, respectively. Anterior segmentectomy of the head of the pancreas might be a clinically applicable procedure; however, posterior segmentectomy involving the resection of the lower bile duct may be impractical. (Surgery 2000;128:822-31.)

Ultrastructure and morphogenesis of the marine epibenthic ciliate Epiclintes ambiguus (Epiclintidae, n. fam.; Ciliophora)

Epiclintes ambiguus, a highly contractile marine ciliate, has ventral cirri in oblique and marginal rows, and three rows of dorsal cilia, thus is at the hypotrich structural grade. We use light microscopy of living and protargol stained specimens and both scanning and transmission electron microscopy to describe cortical morphogenesis through cell division and interphase cortical structure of E. ambiguus. Cortical morphogenesis proceeds in 2 oblique developmental zones and is based on 4 kinds of primordia: oral, frontal, somatic, and a specialized ventral primordium. Thirteen to fifteen oblique rows of ventral cirri arise primarily from somatic (within-row) primordia (producing the anterior complement of cirral rows) and the ventral primordia (producing the posterior complement of cirral rows); frontal ciliature is limited to one or two short cirral rows. A longitudinal series of transverse cirri differentiate from posterior kinetosomes in (1) frontal streaks, (2) ventral (within-row) streaks, and (3) streaks that develop from ventral primordia. Stomatogenesis in the opisthe begins near the cell surface, then continues within a cortical pit which lengthens posteriorly. Stomatogenesis in the proter occurs dorsally to the parental buccal membranelles. The ultrastructural organization of membranelies and cirri of Epiclintes is consistent with the general structural pattern within the Spirotricha. Dorsal ciliary complexes are dikinetids with the anterior kinetosome ciliated, the posterior nonciliated; each dorsal cilium protrudes from a cylindrical cortical papilla. Dikinetids have postciliary, transverse, and nematodesmal microtubules as well as a kinetodesmal fiber. Nematodesmal granules (d = 55 nm) lie beside nematodesmal microtubules. A system of multilayered, membrane-like materials lie within the cortex. Stomatogenesis, deployment of somatic ciliature, and general organization of microtubular structures in Epiclintes suggest an evolutionary relationship with Kahliella and other members of the Stichotrichina. Morphogenetic and structural specializations however justify inclusion of Epiclintes in a new family, the Epiclintidae.

Variants of pancreatic duct system of importance in endoscopic retrograde cholangiopancreatography. Observations on autopsy specimens.

A postmortem radiographic investigation of 330 pancreas specimens showed a total frequency of 10 per cent for the 3 variants of the pancreatic duct system, in which the main pancreatic duct drained to the minor duodenal papilla (type III). In no instance did the main duct drain into the duodenum distal to the major papilla, onto which the common bile duct drained as usual. In the most common variant, type III-B, a separate accessory duct drained part of the pancreatic head onto the major papilla. In the remaining cases either an analogous accessory duct existed, communicating with the main duct (type III-A) or no accessory duct at all (type III-C). The different features of the accessory and main duct systems of type III in the pancreatic head varied widely. In types III-A and III-B, the corresponding ventral and dorsal pancreatic primordia formed more or less of mainly the posterior and anterior parts of the pancreatic head, respectively.

Development of the glycogen body through the whole length of the chick spinal cord.

The development of the glycogen body was studied throughout the entire length of the chick spinal cord. The glycogen body cells first appeared at stage 31 on each side of the ependymal septum from the 26th to 28th segments of the spinal cord. by stage 34 the paired primordia of the glycogen body extended from the 25th to 29th segments. In the middle of the structure described classically as the glycogen body (i.e., the portion restricted to the level of the spinal nerves 26-29), these primordia were fused dorsally at stage 34 and had fused completely by stage 37. The paired primordia extended from the cervical enlargement to the lumbosacral portion of the spinal cord by stage 36 and extended to the upper cervical segments by stage 38. They were totally fused throughout the entire length of the spinal cord by stage 42. The glycogen-containin cells, in the classical glycogen body level, appeared ventrolateral to the central canal at stage 35. Thereafter they increased in number and glycogen content, and extended rostrad and caudad from the classical glycogen body level. They fused to each other and then fused with the glycogen body. Therefore, the bilateral clusters of the glycogen containing cells are considered as the ventral paired primordia of the glycogen body. The development of the glycogen body is essentially the same pattern as in the classical glycogen body throughout the entire length of the spinal cord.