摘要:

It has been proposed that the cervical flexure of vertebrate embryos arises from the normal morphogenesis of the heart. This hypothesis is based on experiments in which the heart tube is removed or disrupted in early chick embryos. It has been reported that, in normal atmosphere, these embryos continued normal morphogenesis except for cervical flexure formation. In the present study, we performed similar experiments. In contrast to previous work, however, only one set of our heart-deprived chick embryos was reincubated in normal air. The other sets were reincubated in oxygen-enriched air. Under normoxia, heart removal resulted not only in prevention of the cervical flexure, but also in mesenchymal defects, and in a remarkable hypoplasia of the craniocervical region. Under hyperoxia, heart-deprived embryos developed no severe mesenchymal defects and the growth of the upper body portion was more normal, with the hypoplasia confined to the cranial region. The formation of the cervical flexure was now normalized. These results show that cervical flexure formation is not directly dependent on normal morphogenesis of the heart, but does depend on a sufficient oxygen supply to the cervical region. During early development, the craniocervical region of a chick embryo is more sensitive to circulatory failure than the trunk.

ISSN:1422-6405    

DOI:10.1159/000147677

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The interactive effects of clomiphene citrate (CC) and exogenous oestrogen (E2) or progesterone (P4), on the vaginal epithelium of ovariectomised rats were examined using scanning electron microscopy and light microscopy. Results were compared with P4E2 treatment. Statistical analysis showed no significant difference between the two combination CC treatments. All treatment groups had the ability to stimulate a dormant epithelium and cause surface modifications in the form of individually elongated microvilli and rosette formations. The results of this study indicate that v/hile P4 enhances the oestrogenicity of CC, there is no cumulative oestrogenic effect when E2 and CC are combined, but there is modification of cell surface organisation and evidence of anti-oestrogenic activity.

ISSN:1422-6405    

DOI:10.1159/000147678

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In transgenic mice with cerebral expression of foreign GH, pituitary GH production is profoundly disturbed, blood IGF-I levels are decreased and growth is retarded. Adenohypophysial morphology in these transgenic mice (6 males and 6 females) was studied by immunocytochemistry, in situ hybridization and electron microscopy. In both sexes, GH immunoreactive cells were smaller, and reduced in number by about 50% compared to controls; the decrease of GH mRNA signal was stronger in males than in females and by electron microscopy, the somatotrophs had the features consistent with suppressed endocrine activity. In both sexes, PRL immunoreactive cells were slightly decreased in number; in male pituitaries PRL mRNA signal was weak and ultrastructurally, only lactotrophs with small secretory granules were found. In the adenohypophyses of females, the intensity of hybridization signal for PRL mRNA was unchanged and ultrastructurally, the lactotrophs were slightly decreased in size and contained increased number of phagolysosomes. The number of ACTH immunoreactive cells was increased in males; however, the intensity of POMC mRNA was unchanged. The increase in number of LH immunoreactive cells appeared to be more pronounced in males. These changes resemble but are less prominent than those seen in mice transgenic for MT/hGH in which hGH is produced in many tissues, blood hGH and IGF-I are elevated and gigantism develops. Pituitary alterations are attributed to the indirect effects of hGH which is both somatotropic and lactogenic in mice.

ISSN:1422-6405    

DOI:10.1159/000147679

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Thyrotrophs were studied by quantitative immunohistochemistry in the pituitary gland of young (4 months), old (20 months) and very old (29 months) male rats. An attempt was also made to correlate morphometric parameters with serum levels of thyrotropin (TSH), thyroxine (T4) and triiodothyronine (T3). Cells were immunostained by the peroxidase-antiperoxidase method and hormones were measured in serum by specific radioimmunoassays. There was a marked age-related reduction in TSH cell number, volume density and surface density but a significant increase in TSH cell area and perimeter. Basal serum levels of TSH increased, T4 decreased and T3 remained unchanged with age. There was a highly significant (p < 0.001) negative correlation between serum TSH and T4, but no significant correlation was found between TSH and morphometric parameters. The present results suggest that aged rats possess a reduced but functionally preserved thyrotrophic cell population. The coexistence of high circulating levels of TSH with reduced serum T4 suggests that aging brings about a progressive desensitization of the thyroid to TSH.

ISSN:1422-6405    

DOI:10.1159/000147680

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Male Sprague-Dawley rats aged 3 weeks that were maintained on an iron-deficient diet for 4-5 weeks developed severe anemia with markedly reduced hemoglobin levels (4.11 ± 0.20 Hb g% versus controls 12.74 ± 0.15 Hb g%). On sacrifice, the adrenal glands were removed and processed for light and transmission electron microscopy and enzyme cytochemistry. The major histological and ultrastructural changes in the adrenal cortex in response to the iron deficiency were seen in cells of the zona fasciculata, especially in its outer region, and to a lesser degree in cells of the zona reticularis. Structural changes were seen in the mitochondria of these cells, which often became grossly enlarged and developed unusual electron-dense inclusions. In addition, the lipid droplets in the iron-deficient cells of these regions were much less developed and less prominent compared with controls. Quantitative cytochemical localization of succinic dehy-drogenase (SDH) activity in the adrenal glands showed that in iron-deficient rats there was an increase in SDH activity in the zona fasciculata (46%) and in the zona reticularis (74%), whereas there was a reduction of approximately 41% in SDH activity in the zona glomerulosa. Serum corticosterone levels were significantly raised in the iron-deficient rats compared with the control rats. Our results indicate that severe nutritional iron deficiency in rats causes ultrastructural and cytochemical changes in the mitochondria of the adrenal cortex accompanied by increased secretion of corticosteron

ISSN:1422-6405    

DOI:10.1159/000147681

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The endothelium of the high endothelial venules (HEVs) of lymph nodes is normally considered to inhibit an association with neutrophils. The present paper shows that for a few weeks after birth, however, neutrophils are commonly associated with the walls of HEVs, the extent depending on the site of the lymph node. Overall, neutrophils increase in numbers in rat nodes from birth until about day 11, and vanish progressively thereafter. Moreover, neutrophils are more abundant in the nodes of standard neonates than in the nodes of pathogen-free neonates raised in an aseptic milieu. It is concluded that the postnatal recruitment of neutrophils by nodal HEVs relates to the then prevailing state of immaturity of the immune system. An explanation is proposed as to why neonatal HEVs of nodes recruit neutrophils and not only lymphocytes, as is the case later in ontogeny.

ISSN:1422-6405    

DOI:10.1159/000147682

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The purpose of this study was to determine the effect of surgical induction of anterior disk displacement (ADD) on fibronectin amount and distribution in the rabbit craniomandibular joint (CMJ) tissues using an immunohistochemical technique. The right CMJ was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left CMJ served as a sham-operated control. Ten additional joints were used as nonoperated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) following surgery. Disks, bilaminar zones, condyles and articular eminences were excised. Condyles and articular eminences were decalcified in EDTA. All tissues were sectioned at 10 µm in a cryostat. Sections were incubated with monoclonal antibodies directed against fibronectin. Following incubation in the appropriate FITC-labeled secondary antibodies, tissue sections were studied under the fluorescence microscope. The results showed that at 2 weeks following induction of ADD, there was a reduction in fibronectin immunostaining in the condyle, articular eminence and articular disk. Depletion of fibronectin in these tissues was followed by restoration of its immunostaining at 6 weeks. Also, there was a progressive increase in fibronectin immunostaining in the bilaminar zone at 2 and 6 weeks. It was concluded that surgical induction of ADD in rabbit CMJ leads to alteration in the amount and distribution of fibronectin

ISSN:1422-6405    

DOI:10.1159/000147683

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Alteration of hip joint angle, while keeping the knee position constant, changes the orientation of the biarticular rat semimembranosus lateralis muscle with respect to the bony origin at the pelvis. Geometrical and length-force characteristics of the muscle were determined in two experimental groups, each with a different orientation: angles between the muscle and line of origin were set at 68.1 ± 5.3° (condition 68) and 121.9 ± 9.1 ° (condition 122). For muscles of condition 68 and condition 122, the number of sarcomeres in series was similar in both proximal fibers (11,436 ± 356 and 11,555 ± 175, respectively) and distal fibers (12,585 ± 844 and 12,787 ± 288, respectively). At similar distal fiber lengths, the sarcomere length in proximal fibers was higher in condition 122 than in condition 68, indicating a change in heterogeneity of fiber sarcomere lengths in the muscle. Hence, length-force relationships of proximal and distal sarcomeres were more scattered with respect to muscle length in condition 122 than in condition 68. Range of distal fiber length between optimum and zero muscle force was increased by 2.7 mm (13%) in condition 122. These data indicate that biarticular muscles with bony origins can exhibit different length-force characteristics at similar distal fiber lengths. During hip joint movements and fiber shortening, muscle fibers of such biarticular muscles use shifting fiber length-force relationships with respect to muscle

ISSN:1422-6405    

DOI:10.1159/000147684

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In order to help avoid complications of parotid surgery, we investigated the relationship between the facial nerve and the retromandibular vein. Fifty dissections were performed on 30 cadavers. In 45 (90%) of the cases the retromandibular vein was located on the medial side of the upper and lower trunks of the facial nerve, and in 5 (10%), the course of the retromandibular vein was lateral to the lower trunks and medial to the upper trunks. These variations were divided into subgroups. The most commonly encountered variation was that the retromandibular vein crossed the facial nerve from the medial (34 cases) or lateral side (3 cases) at a point between the bifurcation and ramification points of the lower facial trunk. In one case, the retromandibular vein was detected on the lateral side of the facial nerve at the bifurcation. In 3 cases (15%), the course of the retromandibular vein was different on the right and left sides of the face in the same cadaver.

ISSN:1422-6405    

DOI:10.1159/000147685

出版商:S. Karger AG    

年代:1995

数据来源: Karger