摘要:

The role of microtubules in the early development of the chick embryo heart was studied. The microtubules were disrupted by treatment of the embryos with colchicine. The embryos were divided for study into three groups: (I) before the fusion of the paired cardiac primordia; (II) before the starting of the cardiac loop, and (III) during the formation of the looping process. Colchicine did not impair the fusion of the paired heart primordia nor the acquisition of an asymmetric C-shaped form. However, the normal counterclockwise movement of the heart loop was prevented. From these results we conclude that the formation of the tubular heart and its looping are independent of the integrity of the microtubular system. Under the effects of colchicine the developing myocytes rounded up bulging into the pericardial cavity. The cell contours became scarcely discernible and the individual cell surfaces gave rise to blebs and ruffles of different sizes. In older embryos, clefts of different sizes appeared between the myocardial cells. The effects of colchicine on the pulsatile activity of the heart were recorded. These effects, as well as those on the cell surface characteristics, were found to be age dependent. The more mature the hearts were, the more resistant to colchicine they became. The developmental significance of the results reported here is discussed.

ISSN:1422-6405    

DOI:10.1159/000145855

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

A population of catecholamine-containing cells, broadly belonging to the class of small intensely fluorescent (SIF) cells, was observed in the ganglionated plexus and around blood vessels of the guinea pig gallbladder. Their morphological features were studied by fluorescence and electron microscopy. Some cells were closely associated with ganglion neurons within the ganglionated plexus. Others were clustered into small groups located along blood vessels. Counts carried out on the whole gallbladder showed that these cells varied greatly in number between individuals and that they were most numerous shortly after birth (on average 230 cells). In the adult, their average number was about 30.

ISSN:1422-6405    

DOI:10.1159/000145856

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The cytological structure of the Hofbauer cells was investigated in human placentas of the first and second trimesters of gestation. These cells are found in the stromal channel system of the chorionic villi core. Their walls, which are supported by collagen fiber bundles, are produced by reticulum cells and fibroblasts. The cytoplasmic processes of the Hofbauer cells are in contact with the walls of the channels without being associated with them by desmosomal complexes. Some of these cells have features in common with macrophages, such as cytoplasmic processes, larger vacuoles, many pinocytotic vesicles and intracytoplasmic granules. This system of vacuoles and vesicles enables micropinocytotic activity and phagocytosis. This type of Hofbauer cell resembles the typical macrophages. These cells may play a role in the regulation of stromal water content, transportation of ions and the flow of interstitial fluid. The most original finding of this study are long tubes observed in some Hofbauer cells and extending between the nucleus and the extracellular ground substance through the cytoplasm. One of these tubular formations resembles a cilium in structure with three limiting membranes and is filled with a slightly electron-dense substance. This type of Hofbauer cell may transport information between the nucleus and the extracellular ground substance by means of these tubular structures.

ISSN:1422-6405    

DOI:10.1159/000145857

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The surface of the conjunctiva was investigated in goats, sheep and bovines. The lid-facing surface of the nictitating membrane carries a serrated crest. At a low magnification the areas covered by a stratified squamous epithelium appear as a mosaic. In the superior and inferior conjunctival fornices the mucous membrane has a uniform appearance. Areas of goblet cells have an irregular appearance. Four functional stages can be observed in the goblet cells. At a high magnification the superficial cells of the palpebral and bulbar conjunctiva are covered by microplicae. In the fornix conjunctival microvilli project over the superficial cells.

ISSN:1422-6405    

DOI:10.1159/000145858

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

We studied 27 embryos of 5–12 weeks gestational age where pregnancy was interrupted due to paramedical reasons, in order to find the developmental stages at which matrix vesicles appear in cartilage, and whether they are involved in the mineralization process. Specimens of long bones, lumbar and thoracic vertebral column were prepared for light, transmission and scanning electron microscopic studies. In the cartilaginous models of long bones, matrix vesicles were found amongst maturing and hypertrophic chondrocytes already by the 6th week after fertilization. By that stage, bone rudiments consisted of only cartilage that was not yet mineralized. In the vertebral column matrix, vesicles were found in the vertebral bodies amongst maturing and hypertrophic chondrocytes at the beginning of the 8th week. At that stage, although hypertrophy of chondrocytes was observed, mineralization was still absent. No matrix vesicles were found in the perichondrium, investing mesenchyme and intervertebral discs. Mineralization of cartilage in long bone rudiments started in the form of hydroxyapatite crystals within or around the matrix vesicles at 7 weeks of age and in the vertebral column at 11 weeks. As mineralization progressed, more hydroxyapatite crystals were observed around the matrix vesicles, forming typical calcospherites. Mineralization then progressed in the form described in other animal

ISSN:1422-6405    

DOI:10.1159/000145859

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Based on dissection of 20 adult specimens the anatomy of the knee joint of the cat is described. An attempt is made to include all functionally relevant structures such as bones, ligaments, menisci, joint capsule and capsular reinforcements. A comparison with the human knee joint is made. There is a high resemblance in construction with the main differences occurring in the proportions of the constituent elements. A comparison of the semimembranosus and biceps femoris receives particular attention. These descriptions lead to functional considerations in relation to the stability and force transmission of the knee joint in the cat.

ISSN:1422-6405    

DOI:10.1159/000145860

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The distribution of adrenergic fibres in the ganglionated plexuses of the porcine small intestine has been made on air-dried stretch preparations using the glyoxylic acid fluorescence method. Adrenergic fluorescent fibres occur in the ganglia and internodal strands of the three fundamental ganglionated plexuses: the myenteric plexus (Auerbach) and the two superimposed meshworks of the plexus submucosus, i.e. the plexus submucosus externus (Schabadasch) and the plexus submucosus internus (Meissner). The plexus Auerbach consists of densely glyoxylic acid induced fluorescent (GIF) elongated ganglia with in general a longitudinal axis running parallel to the circular muscle layer and large dense interconnecting fibre tracts with primary, secondary and tertiary subdivisions. In the ganglia, the fibres are varicose, forming large fluorescent ‘baskets’ which might be related to the occurrence of well defined enteric neurones. The plexus Schabadasch can be distinguished from the plexus Meissner by its size, strongly fluorescent ganglia and broad densely fluorescent internodal strands. The pattern of fluorescing ring-like formations at the margin and out of the nodes, clearly present in the Auerbach and Schabadasch plexuses, completely lack in the plexus Meissner, the latter being narrow-meshed with smaller fluorescent ‘baskets’, indicating that the corresponding neurones are smaller in size. In the ganglionic nodes of all three plexuses the axons display comparatively more varicosities than in the fibre tracts. Each of the three main ganglionated enteric plexuses are quite different with regard to the pattern of the adrenergic network both in the ganglia and in the

ISSN:1422-6405    

DOI:10.1159/000145861

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The ratio between the length of the anterior and posterior cruciate ligaments and the distance between their femoral and tibial attachments in the canine and equine knee joint reveals that these structures form a Tchebychev mechanism for parallel motion.

ISSN:1422-6405    

DOI:10.1159/000145862

出版商:S. Karger AG    

年代:1984

数据来源: Karger