摘要:

The so-called tracheo-esophageal septum is in fact the curved primitive floor that results from the ventrocaudal out-growth of the respiratory primordium from the caudal end of the laryngeal sulcus of the foregut. This floor, which separates the openings of the respiratory diverticulum and esophagus, is apparent in transverse sections as a bridge of tissue separating the lumina. The respiratory and hepatic primordia are contiguous initially, but they are separated very early by the rapid growth of the heart and liver, and the resultant stretching of the slower-growing foregut. The portion of foregut between the primordia is drawn out into a narrowing tube that develops into the esophagus and stomach. The respiratory primordium is drawn cranialward; it proliferates, dilates, bifurcates, and grows caudally, dragging out a stalk from the ventral aspect of the foregut. Most of the stalk above the bifurcation will develop into the trachea.

ISSN:1422-6405    

DOI:10.1159/000145574

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Experimental intimal hyperplasia was obtained by microvascular surgery. A segment of the left common carotid artery of rat was grafted by means of end-to-end anastomosis onto the right common carotid artery of the same animal. 3 months after surgery, hyperplasia was observed in the intima of the grafted arterial segment formed by modified smooth muscle cells: myointimal cells. These cells do not present ultrastructural changes and they are connected by gap and tight junctions. The gap junctions are the predominant type of junction between myointimal cells in our experimental model.

ISSN:1422-6405    

DOI:10.1159/000145575

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The anatomy of the duodenum of the West Indian manatee has both macroscopic and microscopic features that are unusual when compared to other mammalian forms. Macroscopically, the voluminous duodenal ampulla and the paired duodenal diverticula are distinctive. The general microscopic structure of the manatee duodenum is not unusual, but the duodenal glands secrete an acid mucin (sialomucin). The cells of these glands appear to be intermediate between classical serous and mucous cell types. These cells also contain granules with regions of high peripheral electron density. The overall structure of tlie manatee duodenum most strongly resembles that of the dugong, another member of the order Sirenia.

ISSN:1422-6405    

DOI:10.1159/000145576

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The response of capillary pericytes to thermal lesion in the inguinal fat pad of 10-day-old rats was observed with the light and electron microscope. Samples were taken from the necrotic area and the immediately surrounding tissue at various time intervals from 1 h to 10 days post-lesion. The initial physical disruption and swelling of the capillary resulted in the liberation of some pericytes near the necrotic zone. Most pericytes remained, however, in the basal lamina and went through a period of activation that peaked at 48 h. Pericyte activation consisted of a noticeable increase in rough endoplasmic reticulum with the cisternae containing granular, electron-opaque material. There was evidence of migration of these activated cells from the capillary basal lamina between 24 and 72 h. By 72 h, fibroblast-like cells possessing different nuclear and cytoplasmic morphology were oriented along distinct bands of extracellular fibrin and necrotic tissue. These cells produced limited amounts of collagen. Differentiation into immature adipocytes occurred 5 days after the lesion. Small, unilocular adipocytes were located in the necrotic zone by 7 days. Complete restoration of the lesion area was accomplished by 10 days. It is proposed that pericytes act as a reserve cell in the recovery of the rat inguinal fat pad after thermal lesion.

ISSN:1422-6405    

DOI:10.1159/000145577

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The morphogenesis and maturation of the coronal suture in C57B1-strain mice was studied histologically using light microscopy from day 15 postconception through day 71 postpartum. Early differentiation of the osteoid precursors proceeds centrally within the 7- to 8-cell-thick fibrous ectomeninx beginning in the regions of the ossification centers and extends peripherally toward the future sutural margin. Differentiation into osteogenic cellular elements is marked morphologically by an increased nuclear: cytoplasmic ratio, dark-staining nucleoli and a granular chromatin pattern. This zone of cells, designated the osteogenic induction front (OIF), extends in advance of any identifiable accumulation of osteoid matrix or biomineralization. As the OIFs of the parietal and frontal bones approach, but prior to any physical overlap, they lie in different planes dorsoventrally; the parietal OIF located dorsal to the frontal OIF, a pattern maintained throughout subsequent sutural morphogenesis. Upon physical overlapping of the parietal and frontal OIFs, the fibrous capsule thickens dorsoventrally assuming a ‘fusiform’ configuration. This morphological event, referred to as the ‘fusiform blastema’, has been suggested to presage sutural location and determine the relative vertical position of the bony plates comprising the suture. Our results suggest that this is actually a secondary event, the structure of the suture having already been established with the relative physical overlapping of the respecti

ISSN:1422-6405    

DOI:10.1159/000145578

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

An 8-week human embryo with cystic dilation of the right renal pelvis and ampullar portions of collecting tubules was found among 2,500 conceptuses (including 76 with urogenital malformations) obtained through unduced abortion. This observation presents further evidence that some cases of renal cysts are not secondary to ureteric atresia or nonunion of primitive collecting and secretory tubules but are the primary anomaly of ureteric bud branching and nehphron induction.

ISSN:1422-6405    

DOI:10.1159/000145579

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Lactotrophs in the adenohypophysis have the apparent inherent capability to produce simultaneous secretion of prolactin from individual cells. There are two possibilities to account for this synchronized, discrete pulsatile secretion: (1) humoral communication, or (2) cell-to-cell syncytial communication. As a first step in examining the second possibility, we searched for ultrastructural evidence of intercellular contacts. The presence of desmosomes, the conventional junctions that serve to anchor adjacent cells, would be the first step in proving contact between homologous cells. In order to increase the observation of desmosomes, the population of lactotrophs in the adenohypophysis was increased by implantation of capsules containing estradiol in male Sprague-Dawley rats. The adenohypophyses were then examined by electron microscopy for indications of these intercellular bridges. Desmosomes were discovered between lactotrophs, indicating that cell-to-cell contact does exist, and suggesting that the desmosome may help the formation of a syncytium among lactotrophs, either directly or indirectly. Since an ectopic pituitary without direct help from the hypothalamus can secrete prolactin in a pulsatile fashion and since there are desmosomes between lactotrophs, it is possible that the synchronized prolactin release occurs through a direct cell-to-cell communication system which is linked by the desmosomes.

ISSN:1422-6405    

DOI:10.1159/000145580

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Porcine calcitonin (CT) (0.5 MRC unit daily) was administered intraperitoneally to house shrews, Suncus murinus, for 42 days. The changes in serum calcium and phosphate levels as well as the light microscopical alterations of the parathyroid and calcitonin cells (C cells) between the 1st and 42nd day of treatment were recorded. The serum calcium level shows a fall up to the 7th day of treatment and thereafter it increases to normal values. The hypophosphataemic effect of CT increases progressively throughout the experiment continuing even after the loss of the hypocalcaemic effect. CT administration inhibits the release of secretory granules of C cells up to 21 days. Hyperplasia and degranulation of C cells is observed at 28, 35 and 42 days of treatment. C cells with collapsed membrane are also encountered in the lumina of the thyroid follicles. From the 28th day onwards the parathyroid chief cells of treated animals show hypertrophy and loss of staining reaction.

ISSN:1422-6405    

DOI:10.1159/000145581

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Anterior pituitary cells of the adult rat were studied by scanning electron microscopy after 3, 6 and 8 days in culture. Epithelial (parenchymal) cells and fibroblasts could be differentiated by their characteristic cell surface structures and by their associations with each other. The surface of solitary and grouped epithelial cells is uneven and rich in smaller or larger blebs, wrinkles and microvilli. A few solitary cilia were found on the surface of some cells. The individual cells forming epithelial cell groups adhere to each other with numerous, parallel, slender extensions. The fibroblasts found in monolayers have extensions with various lengths contacting other cells or the inert substratum. Microvilli arise in various frequency from their smooth surface. Transmission electron microscopy confirmed the presence of the surface structures detected in the scanning electron microscope.

ISSN:1422-6405    

DOI:10.1159/000145582

出版商:S. Karger AG    

年代:1982

数据来源: Karger