摘要:

AbstractLight microscopic, scanning electron microscopic, and transmission electron microscopic studies of the early developmental stages of chick embryonic bone marrow disclose characteristic associations of the first hematopoietic cells with stromal cells. The first hematopoietic cells, large basophilic cells that we have termed presumptive stem cells, segregate into erythropoietic and granulopoietic regions. Intravascular erythropoietic cells associate with sinusoidal endothelial cells, while granulopoietic cells associate with extravascular reticular cells. Extensive, intimate contacts between erythroid and endothelial cells are maintained, in part, by marginal arrays of microtubules, which promote a flattening of the adherent erythroid cell surface. In addition, cell surface components of opposing cells, visualized by ruthenium red staining, appear to merge and possibly to interact. Granulopoietic cells establish intimate but less extensive associations with reticular cells through cell‐surface interactions. Stationary granuloid cells appear to be held in place by small, thin processes emanating from the sheet‐like reticular cells. Granuloid cells are capable of moving within the extravascular region, using reticular cell surfaces as a substrate. Intimate associations also occur among granulopoietic cells, the significance of which is unclear. Thus, sinusoidal endothelial cells and reticular cells comprise the critical non‐hematopoietic or stromal elements of avian bone marrow, where they have a putative role in segregating presumptive stem cells into erythrocytic and granulocytic compartments. They serve as an architectual, and possibly regulatory, framework on which hematopoiesis o

ISSN:0003-276X    

DOI:10.1002/ar.1091970102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractTestosterone capsules implanted in hypophysectomized rats prevented tubulobulbar complexes from forming in many late spermatids. These spermatids also displayed an accumulation of cytoplasm (swelling) in the perinuclear region of the head. Other spermatids with normal or near‐normal numbers of tubulobulbar complexes showed a typical perinuclear space. The results indicate, but do not prove, that development of tubulobulbar complexes (and their subsequent phagocytosis) is essential for the normal elimination of cytoplasm that takes place prior to sperm releas

ISSN:0003-276X    

DOI:10.1002/ar.1091970103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe three‐dimensional arrangement of mitochondria and endoplasmic reticulum in the red muscle fiber was studied both in thick sections of the rat diaphragm fixed in glutaraldehyde and impregnated with uranyl acetate followed by lead and copper citrate, and in thin sections of glutaraldehyde fixed tissue treated with ferrocyanide‐reduced osmium. The mitochondria were located either at the periphery of the fiber, where they were spherical, or between the myofibrils, where they formed longitudinal columns of rectangular, slightly flattened elements. From both types of mitochondria, thin, elongated branches arose at right angles that formed transversely oriented mitochondrial pairs at the I band level. At the periphery of the fiber, the endoplasmic reticulum took the appearance of a subsarcolemmal network of tubular cisternae oriented parallel to the cell surface. In the juxtanuclear region, it was made up of spherical masses composed of tightly knitted tubules that were interconnected by more loosely anastomosed tubules. In between the myofibrils, it was composed of longitudinally oriented repetitive units whose structure varied according to their position in front of the A or I bands of the myofibrils. In front of the A band, the endoplasmic reticulum appeared as a single sheet of anastomotic tubules compressed between the adjacent myofibrils, whereas at the I band level, its tubular elements passed in front and behind the transverse expansions of the mitochondria to form an intricate multilayered network in front of the Z l

ISSN:0003-276X    

DOI:10.1002/ar.1091970104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractUltrastructural histochemical procedures were employed to determine the carbohydrate components and their contributions to the rodent and amphibian surfactant systems. Zirconium stained the rodent (rat) cytoplasm surrounding the multilamellar bodies, the Golgi, and was associated with the membrane structures of the compact lamellae of alveolar multilamellar bodies. In the rodent and amphibian (Rana pipiens), ruthenium red stain was observed within all tubular myelin surfactant matricies. The “gutters” tubular myelin surfactant matrix, and intratubular myelin surfactant matrix materials all demonstrated a positive reaction product. The periodic acid‐chromic acid‐silver procedure revealed irregular channels extending from the multilamellar bodies to the surface of the rodent great alveolar pneumocyte.The extra‐pulmonary and respiratory surfaces in both species were additionally studied by stereoscanning electron microscopy. The respiratory anatomy of the rodent was corroborated. The amphibian lung demonstrated three orders of septa, and in the expired state, tertiary septal pits. The amphibian primary septa were hollow, blind tubules containing respiratory

ISSN:0003-276X    

DOI:10.1002/ar.1091970105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractLung tissues from the Indian dove,Scardafella inca, desert spiny lizard,Sceloporus magister, and the Taiwan golden skink lizard,Mabuya aurates, were studied by transmission electron microscopy utilizing ruthenium red as a carbohydrate stain and with the so‐called lipid‐carbohydrate retention procedures to elucidate the morphology of the surfactant systems. Stereoscopic scanning electron microscopic procedures were utilized for a comparative anatomical study of these three species, and the results were compared with the rat and frog in the companion article. The avian lung tissues demonstrated several peculiarities. The ciliated epithelial cells of the bronchus had cytoplasmic ciliated projections between the boundaries of mucus secreting cells. The discrete morphology of the main bronchus, secondary bronchi, parabronchi, and the air capillaries, and their three‐dimensional morphologic perspective were elucidated. The skink illustrated an arrangement of primary, secondary, and tertiary septa, with elaborate tertiary septal pits, similar to the amphibian. All septa contained a solid connective tissue core. The desert lizard was similar to the skink except the tertiary septal pits were rudimentary. All three species had a modified great alveolar pneumocyte and a laminated surfactant which included a carbohydrate matrix material between layered phospholipid‐based membranes. The ruthenium red additionally stained the homogeneous surface‐lining material. A comparative analysis of the surfactant systems of these three species with each other, and with the rodent and amphibian in the companion article, were discussed in terms of phylogenet

ISSN:0003-276X    

DOI:10.1002/ar.1091970106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractAsymmetric‐unit‐membrane (AUM) plaques are major components of the luminal surface of superficial cells in mammalian urinary bladder. We have now demonstrated ultrastructurally identical AUM plaques in intraepithelial locations, at the lateral and basal surfaces of superficial cells and at the apical surfaces of intermediate epithelial cells in the urinary bladder. Typically, luminal apposing AUM plaques are present in clusters. Similar plaque clusters are present on apposing surfaces of cell pairs within the epithelium. These intraepithelial plaque clusters are in register, although often separated by a wide interspace. In areas where they come into closer apposition, they form membrane complexes resembling but distinctly different from certain types of cell‐to‐cell junctions. Both luminal and intraepithelial AUM plaques serve as membrane attachment sites for cytoplasmic microfilaments. Their intraepithelial location and association with microfilaments support the hypothesis that AUM plaques serve a mechanical function and modulate cell surface area during the urinary bladder distention‐contract

ISSN:0003-276X    

DOI:10.1002/ar.1091970107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractIntramedullary Schwann cells have been observed following x‐irradiation of lumbosacral spinal cords in immature rats. The present investigation was designed to determine whether or not the development of intramedullary Schwann cells within the spinal cord could be influenced by the portion of the spinal cord exposed to radiation. Three groups of rats were irradiated when three days of age. In one group the irradiated zone was limited to a 5 mm length of mid‐thoracic spinal cord (T only), in another group the irradiation was limited to a 5 mm length of lumbosacral spinal cord (L only), and in a third group 5 mm lengths of both mid‐thoracic and lumbosacral spinal cord (T/L) were irradiated. All of these animals received a single exposure to 4000 R of soft x‐rays (HVL 0.16 mm Al). Sham‐irradiated littermates served as control animals. Groups of rats were killed at intervals from 9 through 60 days following irradiation, and the spinal cords were prepared for light microscopic examination. Schwann cells appeared in the lateral portion of the lumbosacral dorsal funiculi of L only and T/L irradiated spinal cords as early as 9 days post‐irradiation. By 19 days post‐irradiation Schwann cells occupied the lateral, medial, and deep medial portions of the dorsal funiculi in the lumbosacral areas. By 25 days post‐irradiation Schwann cells were also observed in the dorsal gray horns. In contrast, Schwann cells were not observed in the midthoracic regions of T only and T/L irradiated rats until 11 days post‐irradiation. The accumulation of these cells was not extensive, and, in general, the Schwann cells were confined to the lateral portion of the dorsal funiculi in all animals. These findings indicate that intramedullary Schwann cell development is influenced by the region of spinal cord irradiated

ISSN:0003-276X    

DOI:10.1002/ar.1091970108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe mechanisms underlying directed axonal movement in the developing central nervous system are largely unknown. Histochemical methods for transmission and scanning electron microscopy were used to study the surface of the developing optic tectum in the chick embryo at the time of optic fiber ingrowth.A highly structured extracellular matrix consisting of fibrillar and granular components was seen in normal and in uninnervated specimens that had been fixed in solutions containing the cationic dyes Alcian blue, ruthenium red, or safranin O. The strong affinity of these stains for glycosaminoglycans suggests that the matrix contains such macromolecular aggregates. With routine fixation methods the matrix was not seen, but empty extracellular spaces were apparent.The tectal matrix was particularly prominent ahead of the growing front of optic fibers. Its location was thus appropriate for interacting with pioneering axons that cross the surface of the developing tectum along its anteriorposterior axis. Matrix fibrils were organized in a stacked alignment predominantly parallel to the tectal surface, but otherwise their orientation appeared random. The matrix possibly bears on the guidance of optic fibers. However, its geometry suggests that this may involve a mechanism more specific than mechanical contact guidance.

ISSN:0003-276X    

DOI:10.1002/ar.1091970109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091970101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY