摘要:

The processes of elevation and convergence of the spinal neural folds were analyzed in normal (+/+; Lp/+) and abnormal (Lp/Lp) embryos of the loop-tail mutant mouse in order to determine possible mechanisms underlying the dysraphic defect characterized by a failure of the neural fold to close in this mutant. The results indicate that the neural folds are already defective during very early phases of elevation, with greater distances between the apical points of the paired walls of the neural groove, larger ventral angles and higher ratios of luminal/basal linear distances occurring in the abnormal embryos relative to those in normal embryos. The cross-sectional area of the neuroepithelium is also greater in abnormals, suggesting that faulty elongation of the neuraxis may contribute to the dysraphic condition.

ISSN:1422-6405    

DOI:10.1159/000147234

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Iron-deficient female Wistar rats were fed a diet, which contained 0.5% trimethylhexanoylferrocene, over a 56-week period. This dietary iron loading resulted in a progressive siderosis and enlargement of the liver with a maximum iron content of 947.0 ± 148.0 mg (vs. 0.07 ± 0.04 mg in iron deficiency) and a maximum organ weight of 39.4 ± 6.6 g (vs. 6.9 ± 1.4 g in iron-deficient control rats). Up to 43 weeks, whole liver iron rose by increase in iron concentration (max. 28.0 ± 6.1 mg/g wet weight, w.w.) as well as by enlargement of the organ. Afterwards whole liver iron increased solely by ongoing hepatomegaly. At the commencement of iron loading, stainable iron was almost exclusively stored by hepatocytes equally throughout all areas of the liver lobule. Later, the distribution of iron-loaded hepatocytes became strikingly periportal, and, in addition, Kupffer cells as well as sinus-lining endothelia began to store iron. Animals with a liver iron concentration of more than 10.4 ± 0.75 mg/g w.w. showed no further increase in ferritin and haemosiderin within hepatocytes. Iron-burdened Kupffer cells/macrophages, however, accumulated permanently, hereby forming intrasinusoidal and portal siderotic nodules and areas. First signs of liver damage such as necrosis of single hepatocytes and mild fibrosis began at a liver iron concentration of 14.7 ± 1.4 mg/g w.w. With advancement of iron loading, focal necrosis of hepatocytes and iron-burdened macrophages took place, and significant perisinusoidal as well as portal fibrosis developed. Cirrhosis, however, the final stage of impairment in iron overload of the liver in humans, could not be induced in this animal model up

ISSN:1422-6405    

DOI:10.1159/000147235

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The three-dimensional relationship between the epithelial cell layer and the underlying connective tissue core (CTC) of the foliate papilla of the rabbit tongue was studied by scanning electron microscopy after removal of the epithelial cell layer. The foliate papillae were fixed in Karnovsky’s fixative, and the epithelial cell layers were exposed to long-term hydrochloric acid treatment (3.5 N HCl for 2-3 weeks at room temperature). The foliate papillae consisted of ridges and grooves located on the posterolateral margin of the tongue. They appeared as linear projections or ridges of lingual mucosa roughly perpendicular to the longitudinal axis of the tongue. These projections or ridges were parallel to one another and separated by grooves. After removal of the epithelium, two kinds of CTC folds appeared: one was the septal fold of CTC which runs in the central portion under each linear projection or ridge, and the other consisted of two sheets of groove side folds of CTC which run along both sides of the former and face the groove side epithelium. It was revealed that there are two sheets of septal epithelial processes, and each of them fits in between each septal fold and groove side fold of CTC. Numerous taste buds were located in the groove side epithelia, and their pores faced the surface of the groove. On the hollow surfaces that appeared on the surface of the groove side fold of CTC after removal of the epithelial cells with taste buds, nerve-terminal-like structures were encountered. Some openings of the ducts of small lingual glands were arranged linearly on the underside of the basal portion of each groove side epitheliu

ISSN:1422-6405    

DOI:10.1159/000147236

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Prolactin (PRL) cells of the goat adenohypophysis have been identified by the IgG-gold procedure with anti-sheep PRL serum. The secretion of these cells show differences in size and labelling in the three reproductive stages under study. Cells containing PRL can be grouped into low secretory activity cells (PRL-I) and high secretory activity cells (PRL-II) regarding their ultrastructure and functional significance. PRL-I were the most frequent cells in animals at the anoestrus stage, presenting numerous secretory granules and scarce development of the rough endoplasmic reticulum (RER) and Golgi complex (GC). At anoestrus and pregnancy stages there are frequent granule fusions, and the hormonal content partially disappears, perhaps by digestion. PRL-II cells were the most numerous at the lactating stage, presenting a moderate number of secretory granules and well-developed GC and RER. Some PRL-II cells of lactating animals exhibited scarce granules and numerous exocytosis suggesting a high secretory activity. In both anoestrus and pregnancy stages most granules range in diameter from 450 to 750 nm, in contrast to the lactating stage in which most granules range in diameter from 150 to 450 nm.

ISSN:1422-6405    

DOI:10.1159/000147237

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

This study among South African Negroids was undertaken, firstly, to determine the convergence of the facial muscles at the angle of the mouth and, secondly, to determine the presence or absence of a connective tissue nodule at the junction of the above-mentioned muscles (modiolus).

ISSN:1422-6405    

DOI:10.1159/000147238

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The structure, distribution and formation of accessory canals in the developing and mature molar teeth of rat mandibular jaws were investigated with scanning electron microscopy and with three-dimensional image analysis using serial light-microscopic sections. In the initial stage of the accessory canal formation, most of the canals appeared in the gaps of the epithelial root sheaths formed by their approaching each other in the initial stage of the root formation. However, some of the canals appeared in the slits which may be formed by the destruction of the epithelial root sheath in the root apex regions. When the gaps and slits were invaded by blood vessels, the regions surrounding the vessels did not mineralize but became accessory canals. Usually, an accessory canal with one blood vessel connected the periodontal ligament to the dental pulp; however, in some cases, the canals were broken off midway following the destruction of the vessels.

ISSN:1422-6405    

DOI:10.1159/000147239

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The aim of the present study was to examine the effects of mesenchyme on the cytodifferentiation of the Dunning tumor (DT, R3327), a transplantable rat prostatic adenocarcinoma developed spontaneously from the dorsolateral prostate of a Copenhagen rat. Small pieces of DT were combined with mesenchyme of the rat urogenital sinus (18-day fetal, UGM) or seminal vesicle (0-day neonatal, SVM). Both types of combinations were grown under the kidney capsule of male athymic nude mice for 4 weeks. At harvest, the tissue recombinants were fixed and processed for electron microscopy. Grafts of parental DT were similarly processed for electron microscopy. The tumor was characterized by tubules lined by 2-3 layers of undifferentiated cells lacking secretory granules. The basal lamina was reduplicated, and epithelioid cells traversing gaps in the basal lamina were frequently observed. The stroma was composed of a mixture of fibroblastic and large epithelioid cells derived from the ductal lining epithelium through a process of micrometastasis. In UGM or SVM+DT combinations the mesenchyme influenced the differentiation and secretory activity of the DT epithelium. The induced DT epithelial cells exhibited a well-developed granular endoplasmic reticulum, a large Golgi apparatus and prominent secretory granules which were never observed in the parental DT. The basal lamina returned to normal, while the incidence of micrometastasis was decreased. The collagen content of the stroma was increased with a concurrent appearance of smooth muscle cells surrounding those tubules where secretory cytodiff erentiation had occurred. While the mechanism involved in the mesenchyme-induced change in cytodiff erentiation remains unknown, it is evident that the DT epithelial cells when associated with normal embryonic or neonatal mesenchyme can express a more normal cytodifferentiation and function. It is concluded (a) that the DT cells can be induced by mesenchyme to express more highly differentiated ultrastructural patterns and secretory cytodifferentiation, (b) that the induced secretory cytodifferentiation is associated with a reduction in invasiveness (micrometastasis) and a more normal-appearing basal lamina and (c) that the increased abundance of collagen fibers and the differentiation of smooth muscle in the stromal compartment are associated with secretory cytodifferentiation suggesting that reciprocal epithelial-mesenchymal interactions are involved in the regulation of the pathobiology of the DT.

ISSN:1422-6405    

DOI:10.1159/000147240

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Laser photocoagulation is associated with paradoxical results: it causes obliteration of vessels, but leads also to the formation of new ones. In an attempt to better understand this dual vascular response we conducted an ultrastructure study of the choroidal vascular repair following krypton laser injury in rats. Three processes were observed: recanalization, neovascularization, and atrophy of both recanalized and newly formed capillaries. Post-lasering repair of the choroidal vasculature can therefore be described as a remodeling process, characterized by both regeneration and involution. The latter appears to be a secondary process of atrophy, contributing to permanent vascular obliteration. These mechanisms might explain why, in spite of initial vascular regeneration, laser photocoagulation treatment has a beneficial effect on choroidal subretinal neovascularization.

ISSN:1422-6405    

DOI:10.1159/000147241

出版商:S. Karger AG    

年代:1992

数据来源: Karger

ISSN:1422-6405    

DOI:10.1159/000147242

出版商:S. Karger AG    

年代:1992

数据来源: Karger