Your browser does not allow saving data (e.g. private mode): bookmarks will be lost when the tab closes.
Search PubMed
Keywords, author, journal, years — results from PubMed, abstracts with Russian translation, bookmarks in your browser.
Found: 5 469
Page 197 of 547-
Fine structure of cells and their histologic organization within internodal pathways of the heart: clinical and electrocardiographic implications.
The fine structure of the normal internodal pathways was studied in 1 human and 2 canine hearts and correlated with histologic observations on more than 100 human and 10 canine hearts. From the electron microscopic studies six different kinds of myocardial cells were classified from two locations: the Eustachian ridge (posterior internodal pathway) and the Bachmann bundle (anterior internodal pathway). Five of the six kinds of cells (working myocardial cells, Purkinje-like cells, either broad or slender transitional cells and P cells, all previously described) were present in both locations. A sixth cell, pleomorphic and dark in appearance, with a special intertwined relation to P cells, is newly designated as an ameboid cell. It was found solely in the Eustachian ridge. In the same area a rare direct contact between a nerve and a myocardial cell was observed. The importance of these different kinds of cells, their respective cell connections, and their topographic locations inside the internodal pathways are discussed relative to certain functions such as rapid conduction and subsidiary pacemaking. The possible influence of these factors on clinical electrocardiographic changes is considered.
-
Ultrastructure of neurons in the auditory cortex of ageing rats: a morphometric study.
The cell bodies of pyramidal cells in layers II and V of rat auditory cortex were quantitatively examined in groups of rats 3, 6, 15, 23, 27 and 34-36 months of age. The mean diameters of cell bodies of both layer II and layer V neurons, as measured in 1 micron plastic sections, increased between 3 and 15 months of age, then decreased to a diameter that was less in the 36-month-old than in the 3-month-old rats. Morphometry of the nuclei of the cells was done by measuring nuclear area and nuclear envelope length directly on electron micrographs. In the layer II cells, neither parameter changed with advancing age. In the layer V cells, the mean nuclear area decreased significantly in the old animals and the mean envelope length increased. Point-counting techniques were applied to electron micrographs of cell bodies to determine the relative volume of selected organelles, inclusions and ground substance in the perikaryal cytoplasm. In this part of the study the chronological pattern of change in layer II and layer V pyramidal cells was similar. The relative volume of dense bodies increased linearly with advancing age, with a slightly more accelerated rate in layer II cells. The relative volume of ground substance remained essentially constant through 27 months, and then at 34-36 months decreased to 83% and 89% of the three-month level in layer V and layer II, respectively. The relative volume of the rough endoplasmic reticulum (RER) did not change significantly until after 15 months, at which time it began to occupy increasingly a larger fraction of the perikaryal cytoplasm. Finally, the relative volumes of mitochondria, multivesicular bodies and Golgi apparatus did not show clear trends of change during the 33-month period.
-
[Light and electron microscopic studies of the structure and innervation of the ciliary muscle in the human and monkey (Cercopithecus aethiops)].
-
[Component architectonics of the median eminence of the rat neurohypophysis].
-
Neuronal and synaptic organization of the lateral geniculate nucleus of the tree shrew, Tupaia glis.
The ultrastructural study of the lateral geniculate nucleus (LGN) of the tree shrew (Tupaia glis) revealed two types of neurons: (1) a large thalamocortical relay cell (TCR), which may bear cilia, and (2) a small Golgi type-II interneuron (IN) with an invaginated nucleus. The narrow rim of pale cytoplasm of the IN contains fewer lysosomes and fewer Nissl bodies than the cytoplasm of the TCR. The IN perikarya, which in some cases establish somatosomatic contacts, frequently contain flattened or pleomorphic synaptic vesicles. The ratio of TCR to IN is 3:1. Three types of axon terminals were observed in the LGN. Two of them contain round synaptic vesicles but differ in size. The large RL boutons undergo dark degeneration after enucleation; they are the terminals of retino-geniculate fibers. The smaller RS boutons show dark degeneration after ablation of the visual cortex; they are the terminals of the cortico-geniculate fibers. The third type of bouton (F1) does not degenerate after either intervention. The boutons of this type are filled with flattened vesicles and are believed to be intrageniculate terminals. F2-profiles were interpreted as presynaptic dendrites of the IN. The characteristic synaptic glomeruli found in the LGN contain in their center an optic terminal. These optic terminals establish synaptic contacts with dendrites or spine-like dendritic protrusions of TCRs as well as with presynaptic dendrites. Synaptic triads were also seen. The distribution of the individual types of synaptic contacts in layers 3 and 4 were determined. Layer 4 contains only one third of the retino-geniculate synapses and of the synaptic contacts of F1-terminals.
-
Characterization of Na+-independent GABA and flunitrazepam binding sites in preparations of synaptic membranes and postsynaptic densities isolated from canine cerebral cortex and cerebellum.
The binding of [3H]GABA and [3H]flunitrazepam was performed with synaptic membranes and post-synaptic densities (PSDs) isolated from canine cerebral cortex and cerebellum. Two GABA binding sites were found with cerebral cortex membranes but only one with cerebellar membranes. PSDs isolated from these showed only single binding sites, with cerebellar PSDs exhibiting lower KD values and a larger concentration of sites than did cerebral cortex PSDs. In the case of flunitrazepam, only one binding site was found for all four preparations, with cerebellar PSDs having twice the concentration of sites of cerebral PSDs. Photoaffinity labeling of the flunitrazepam receptor in PSDs resulted in the binding to a 51,000 Mr protein in both cases, with cerebellar PSDs again showing an increased concentration over that found in cerebral cortex PSDs. Based on this work, and on earlier work of ourselves and of others, we conclude that both populations of isolated PSDs contain inhibitory sites, but that the intact PSDs in both preparations are derived from Gray type I, probably excitatory, synapses, and that the inhibitory sites are found in the broken-up material in the PSD fractions which are derived from Gray type II, probably inhibitory, synapses.
-
Lectin-labeled membrane is transferred to the Golgi complex in mouse pituitary cells in vivo.
Labeling of the Golgi complex with the lectin conjugate wheat germ agglutinin-horseradish peroxidase (WGA-HRP), which binds to cell surface membrane and enters cells by adsorptive endocytosis, was analyzed in secretory cells of the anterior, intermediate, and posterior lobes of mouse pituitary gland in vivo. WGA-HRP was administered intravenously or by ventriculo-cisternal perfusion to control and salt-stressed mice; post-injection survival times were 30 min-24 hr. Peroxidase reaction product was identified within the extracellular clefts of anterior and posterior pituitary lobes through 24 hr but was absent in intermediate lobe. Endocytic vesicles, spherical endosomes, tubules, dense and multivesicular bodies, the trans-most saccule of the Golgi complex, and dense-core secretory granules attached or unattached to the trans Golgi saccule were peroxidase-positive in the different types of anterior pituitary cells and in perikarya of supraoptico-neurohypophyseal neurons; endoplasmic reticulum and the cis and intermediate Golgi saccules in the same cell types were consistently devoid of peroxidase reaction product. Dense-core secretory granules derived from cis and intermediate Golgi saccules in salt-stressed supraoptic perikarya likewise failed to exhibit peroxidase reaction product. The results suggest that in secretory cells of anterior and posterior pituitary lobes, WGA-HRP, initially internalized with cell surface membrane, is eventually conveyed to the trans-most Golgi saccule, in which the lectin conjugate and associated membrane are packaged in dense-core secretory granules for export and potential exocytosis of the tracer. Endoplasmic reticulum and the cis and intermediate Golgi saccules appear not to be involved in the endocytic/exocytic pathways of pituitary cells exposed to WGA-HRP.
-
Retinal degeneration in the pcd cerebellar mutant mouse. II. Electron microscopic analysis.
The cerebellar ataxia in Purkinje cell degeneration (pcd) mutant mice results from the rapid loss of Purkinje cells between 3 and 5 weeks after birth. The loss of photoreceptors in these mutants begins about the same time but proceeds slowly, with most photoreceptors being lost by 1 year of age. In this study the retinas of pcd/pcd mice and their littermate controls from the age of 10 postnatal days to 15 months were analyzed by electron microscopy. The first signs of photoreceptor cell degeneration are apparent in the region of photoreceptor inner segments as early as postnatal day 13, and more prominently at day 18. During this time, the degeneration is characterized by a large number of vesicles, ranging in diameter from 150 to 350 nm, which are located in the extracellular space adjacent to the photoreceptor inner segments. Analysis of serial sections shows that most of these membrane-bound degeneration profiles are tubular in shape and some are continuous with the cell membrane of the inner segment. Therefore, these "profiles" are thought to arise from tubular outpocketings of the inner segments which cleave off to form isolated membrane-bound profiles. This represents a new and unusual form of photoreceptor degeneration. While the most obvious abnormality in the retina is degeneration of photoreceptor cells, Müller cells also appear to be affected, with swollen apical processes often seen coursing through the outer nuclear layer.
-
Recent advances in the understanding of the muscle spindle.
-
Ultrastructure and functional aspects of the nucleus infundibularis ventralis in the green frog, Rana esculenta.