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At least 19 recordsLinked to original sources
PubMed1977

Denervated skeletal muscle fibers develop discrete patches of high acetylcholine receptor density.

Denervated skeletal muscle fibers of mice develop discrete patches of high acetylcholine receptor density. The patches vary in size from less than 1 micrometer up to 30 micrometers, depending on the muscle and the period of denervation. Within the patches the acetylcholine receptor density is some 20 times greater than elsewhere along the muscle fiber and probably approaches that in the subsynaptic membrane.

Acetylcholine↗
PubMed1977

Temporary contacts formed between developing optic fibers in the chick.

Temporary junctions were observed between developing optic fibers of the chick embryo and were distributed along the entire length of the axons from the cell body to the tip of the growth cone. These junctions were present in all material studied between days E-3 and E-18, the latter being the start of myelin formation of the optic tract. Junctions between adjacent axons were focal in nature and showed a decrease in the size of the intercellular space caused by a close apposition of the plasma membrane. With the experimental techniques used final identification of these junctions could not be made but are thought to be of two types--the gap and occludens junctions. Temporary fasciae adherentes junctions were observed at the end of the axon, between the growth cone and adjacent neural tissue. Speculation was made on the functional role of these temporary junctions.

Animals↗
PubMed1978

Histochemistry and acetylcholine receptor distribution in normal and denervated monkey extraocular muscles.

In monkey extraocular muscles (EOM), a battery of histochemical reactions delineates three muscle fiber types, coarse, fine, and granular. Normal EOM are compared with EOM denervated by intracranial oculomotor nerve section. The experimentally denervated EOM fibers did not show the constellation of histologic responses typical of denervated limb muscle, making a diagnosis of a denervation process in EOM muscle very difficult. Although the denervated fine and granular fibers (but not the coarse fibers) develop diffuse extrajunctional acetylcholine receptors (AChR) following experimental denervation, this is not a reliable criterion of denervation because not all of those fibers developed it and they did not show it beyond a 12-week period following nerve section; moreover, myopathic mechanisms have previously been shown capable of provoking diffuse extrajunctional AChR in limb-muscle fibers.

Acetylcholine↗
PubMed1976

Formation of myoneural and myotendinous junctions in the chick embryo. Role of acetylcholinesterase-rich granules in the developing muscle fibers.

The mode of formation of the myoneural and myotendinous junctions was investigated in the thigh muscles of the chick embryo. Myotendinous junctions first appeared on day 11 of incubation, whereas myoneural junctions developed on day 12. Intracellular AChE activity in the muscles increased by the 12th day of incubation, and decreased rapidly after the formation of the myoneural junctions. Light and electron microscopically, AChE activity was demonstrated in the nuclear envelope, sarcoplasmic reticulum, Golgi complex, and in large granules which appeared to be derived from the Golgi complex. Large granules showing an intense AChE activity accumulated in the sarcoplasm at the poles of the muscle fiber before the formation of myotendinous junctions. After the translocation of this intracellular enzyme onto the sarcolemma, most likely the result of an exocytosis of the granules, the myotendinous junctions were formed. The AChE-rich granules present in the middle of myotubes developed into spindle- or comma-shaped cisternae which were located in the sarcoplasm just below the presumptive motor endplates. The present results suggest that the transport of AChE-rich granules to the sarcolamma is the first step in the formation of myoneural and myotendinous junctions.

Acetylcholinesterase↗
PubMed1978

Sharpey fiber bone development in surgically implanted dog mandible. A scanning electron-microscopic study.

Ticonium metal implant placed surgically in the previously edentulatized adult dog mandible induced the formation of an extensive Sharpey fiber system. Sharpey's fibers extended from the peri-implant area, deep into alveolar bone. The frequency of Sharpey's fibers and the degree of their mineralization varied from scattered location and unmineralized state to heavy clustering and full mineralization. This study suggests that the formation of Sharpey's fibers and the degree of their mineralization are determined by biophysical forces of pressure received at a given site.

Alveolar Process↗
PubMed1975

Acetylcholine receptor turnover in membranes of developing muscle fibers.

[125I mono-iodo-alpha-bungarotoxin is used as a specific marker in a description of acetylcholine receptor metabolism. It is concluded that acetylcholine receptors in the surface membranes of chick and rat myotubes developing in cell cultures have a half-life of 22-24 h. Alpha-bungarotoxin (bound to a receptor which is removed from the membrane) is degraded to monoiodotyrosine which appears in the medium. Several observations are consistent with a model in which receptors or alpha-bungarotoxin-receptor complexes are internalized and then degraded: (a) the rate of appearance of iodotyrosine does not reach its maximal rate until 90 min after alpha-bungarotoxin is bound to the surface receptors; (b) 2,4-dinitrophenol, reduced temperature, and cell disruption all inhibit the degradation process. The degradation of surface receptors is not coupled to the process by which receptors are incorporated into the membrane. Evidence suggest that receptors are incorporated into the surface membrane from a presynthesized set of receptors containing about 10% as many alpha-bungarotoxin binding sites as does the surface. Additionally, a third set of acetylcholine receptors is described containing about 30% as amny binding sites as does the surface. These "hidden" recptors are not precursors yet are not readily accessible for binding of extracellular alpha-bungarotoxin. These findings are discussed in relation to both plasma membrane biosynthesis and control of chemosensitivity in developing and denervated skeletal muscle.

Animals↗
PubMed1975

[Clinical, electron-microscopic, and histochemical investigations of conjunctivitis lignosa (author's transl)].

A case is briefly described in which a typical conjunctivitis lignosa appeared after the eye had suffered lime burns. In order to help clarify the morphological connection between mucopolysaccharide production and fiber development in the tumor tissue which occurred after the burn, samples were examined histologically, histochemically and with the use of the electron microscope. The tumor had a cartilage like consistency. Its structure could be devided into three regions. Region A is the pseudo-membrane. It has root like extensions which anchor it to the underlying tissue, and which morphologically appear partially homogeneous and partially fibrous. Blood cells and cell remnants are included in the tissue of the pseudomembrane. The histochemical examination of the pseudomembrane did not present a uniform picture. Along with small amounts of dermatan-sulfate and chondroitin-sulfate B the membrane probably contained a rather large amount of hyaluronic acid. The pseudomembrane borders on a granular tissue (Region B) which is distinguished by the wide metachromatic sheathes of the blood vessels found in it and the particularly large number of active fibroblasts along its edges. The silver impregnation method and the electron-microscopic examination showed that the vascular sheathes consist of bundles of reticular fibers which constitute a three-dimensional network. A similar sort of sheath was observed around the fibroblasts. Chondroitin-sulfate makes up the largest fraction of the mucopoly-saccharides near the fibers and appears particularly concentrated at the intersections of the fibers, although it is also diffusely distributed as well. Dermatan-sulfate (or heparan-sulfate) is found only in the mucopolysaccharide sheath of the fibers themselves. The deep region of the tumor (Region C) consists almost exclusively of blood vessels, their sprouts and the fibroblasts which, with their wide fibrous sheathes, almost fill the spaces between the blood vessels. The reticular fibers and their mucopolysaccharide sheathes have the same structure as that observed in Region B, The fact that the mucopolysaccharides did not appear in plaques but rather as bound primarily to the fibers is grounds for suggesting that a fiber development disorder, probably stemming from the pericytes and fibroblasts rich in ergastoplasm and fibrilles, could play the principle role in conjunctivitis lignosa. The cartilagen like consistency of the tumor could be a result of the arrangement of the fibers and their mucopolysaccharide sheathes. Brief remarks are included concerning the therapeutic consequences of the study.

Adult↗
PubMed1975

[Demonstration of temporary multi-innervation of the cerebellar Purkinje cells by the ascending fibers during development in the rat].

The one-to-one relationship between cerebellar Purkinje cells and climbing fibres in the adult rats is the result of a regressive process affecting a multi-afferent pathway during the early post-natal period, as shown from the innervation by several independent climbing fibres of more than 50% of the Purkinje cells tested electrophysiologically on days 8 and 9.

Action Potentials↗
PubMed1976

Lateral motion of fluorescently labeled acetylcholine receptors in membranes of developing muscle fibers.

We have made direct, quantitative measurements of the lateral motion and age-dependent distribution of acetylcholine receptors (AChR) on the surface of rat myotubes in primary culture. AChR were fluorescently marked with tetramethylrhodamine-labeled alpha-bungarotoxin and AChR lateral motion was measured by the fluoresence photobleaching recovery technique. We found two coexisting distinct classes of AChR: (i) mobile, uniformly distributed AChR that appear on all myotubes shortly after fusion from myoblasts; and (ii) immobile, dense, highly granular AChR in patches of 10-60 mum size that appear shortly after fusion and disappear after myotubes have become extensively interconnected. In addition, evidence of turnover of AChR labeled with tetramethylrhodamine-alpha-bungarotoxin is seen in the gradual internalization of surface fluorescence within 36 hr after labeling. The relevance of these results to an understanding of the membrane dynamics and localization of muscle AChR is discussed.

Age Factors↗
PubMedDate not supplied

[Development of fiber endoscopes and some aspects of gastrointestinal endoscopy].

Clinical evaluation of the up-to-date fibre endoscope models makes it possible to set apart 3 successive stages in the course of creating gastro-intestinal endoscopy, viz. construction of instruments with side optics, making esophagofibroscopes with end optics and transformation of esophagofibroscopes into panendoscopes. Depending upon the nature of the disease and the diagnostic objectives to be fulfilled various types of fibre endoscopes, both new and old, are recommended for clinical use.

Biomedical Engineering↗
PubMed1976

[A functional-morphologic analysis of reactive changes in nerve fibers during development of collateral circulation in nerves].

After stopping the blood circulation along the femoral artery the collateral blood circulation is developing unevenly in different nerves. It depends on the architectonics of blood vessels of the zone. In time the intravenous anastomosis in the distal part of the ischiatic nerve sharply increases. It is pulsing and compressing the nerve bundles and may have a negative influence on nerve fibres. Reactive morphological changes of the axis cylinder, myelin incisions and Ranvier's constrictions are found in such a nerve. The analysis has shown that the changes noted have a character of local non-specific process accompanying physiological manifestations of parabiosis.

Animals↗
PubMed1976

Postnatal cytochemical development of muscle fibers in segmental tail muscles of the rat.

Postnatal development of extrafusal and intrafusal muscle fibers was examined histochemically in segmental tail muscles of the rat. At birth all fibers show a strong reaction for myosin ATPase, uniformity in diameter, and homogeneity in staining intensity. During the first postnatal week, the muscle fibers undergo gradual hypertrophy and hyperplasia but they all maintain the same intense homogeneous staining pattern for the enzyme. By day 9, further differentiation of the muscle fibers results in the formation of a second intrafusal fiber type while the extrafusal fibers are still relatively homogeneous. Finally, two kinds of extrafusal fiber and a third type of intrafusal fiber can be distinguished by day 21. This histochemical fiber pattern is essentially maintained in the adult. These findings show that fiber type development in rat tail muscles lags behind the usual time course of myogenesis known to occur in more rostral regions of the animal. It also indicates that histochemical differentiation of intrafusal fibers in these muscles does not parallel that which occurs in extrafusal fibers. It is likely that arrival and initial contact of sensory nerve terminals on developing intrafusal fibers at day 7 directly influences their relatively early histochemical heterogeneity.

Adenosine Triphosphatases↗
PubMed1992

[Guiding effect of embryonic fimbria graft on cholinergic fiber growth in hippocampus of adult rats].

In view of the fact that in embryonic and neonatal central nervous system (CNS), the pathway of developing fiber tracts is capable of guiding the axonal growth, it would be interesting to know whether a similar effect exists on the axonal growth in adult CNS. Embryonic fimbria was grafted into the hippocampus of the adult rat. Two weeks later, the grafts were examined for cholinergic fibers with AChE histochemical method. It was found that a lot of cholinergic fibers appeared in the embryonic graft, but none of them in the adult fimbria graft as control. If the fimbria-fornix was transected at the time of grafting, no cholinergic fibers could subsequently be detected in both the embryonic graft and the host hippocampus. If a suspension of embryonic fimbria was used as a graft, only a few of long cholinergic fibers could be found in the grafted area. However, if tissue fragments of embryonic fimbria adhered to a strip of nitrocellulose filter were grafted as previously, numerous cholinergic fibers from the host hippocampus were found to be attracted around the strip and grow along the surface of the filter. The results seem to indicate that grafted embryonic fimbria or its tissue fragments are able to guide cholinergic fiber growth in adult hippocampus. It is possible that embryonic fimbria and other pathways of developing CNS fiber tracts provide a natural substrate for guiding axonal growth in adult CNS.

Acetylcholine↗
PubMed1979

Retinal pigment epithelium. Interrelations of endoplasmic reticulum and melanolysosomes in the black mouse and its beige mutant.

By cytochemistry (acid phosphatase and tyrosinase activities) GERL, a specialized hydrolase-rich region of endoplasmic reticulum (ER), can be visualized in the cells of the mouse retinal pigment epithelium. Previously catalase cytochemistry permitted us to identify microperoxisomes, with numerous continuities to the ER. The present report reveals the extensive continuities of the ER to pigment granules in various stages of maturation. When the pigment granules, which we consider to be "melanolysosomes," first appear they consist of electron-opaque grains within dilated areas of the ER. As the dilations enlarge, fine fibrils appear in the ER cisternae. Thicker fibers develop from the fibrils; these fibers are generally obscured when melanin deposition occurs. At all stages, the melanolysosomes appear to be connected to the ER.

Acid Phosphatase↗