bluuebunny/crossref_metadata_2025_split huggingface dataset:
An electromyographic study of reciprocal activity of muscles
Authors: Patton N. J. , Mortensen Otto A. 
Published: February 2005

AbstractAn electromyographic study of elbow flexors and extensors was conducted using 20 adult human subjects to determine if cocontraction occurred during voluntary movement. The interplay of proprioceptive reflex influences arising in the primary and secondary endings of the muscle spindle and in the Golgi tendon organ provide the neurophysiological basis for cocontraction. Whether or not cocontraction occurs during a movement is dependent on the degree to which one proprioceptive influence predominates over the others. This in turn appears to be dependent on factors such as those described below.Incidence and degree of cocontraction was greater during extension than during flexion movements. This may be attributed to the influence of muscle spindle secondary endings.Cocontraction increased with increasing load. Proprioceptive reflexes arising in tendon organs may be involved in this phenomenon.No evidence was found to indicate that the incidence of cocontraction increased with increasing precision of movement. In general, cocontraction was less in skilled and strong subjects than in average subjects during all types of movements.Under the special circumstances of voluntarily attempted cocontraction, evidence of reciprocal inhibition of the antagonist appeared. Proprioceptive reflex activity from tendon organs and from muscle spindle secondary endings are implicated as primarily responsible for this inhibition.
Freeze‐etch observations of rat lung
Authors: Belton John C. , Branton Daniel , Thomas Heriberto V. , Mueller Peter K. 
Published: February 2005

AbstractThe freeze‐etch technique was used to study the fine structure of the terminal respiratory membranes of rat lung. Special emphasis was given to the ultrastructure of the type II alveolar cell and its role in formation of the surface active material. Our morphological evidence supports the theory that membrane‐bound multivesicular bodies in the cytoplasm of type II cells accumulate phospholipid material to form lamellar structures which are extruded onto the alveolar surface as one of the components of the surface active material. Subsequent loss of the lamellar configuration in the surface active layer is discussed. Electron micrographs demonstrate numerous microindentations that extend into the base of alveolar cells and help establish a close relation with the basal lamella.
Inhibition by cycloheximide of ACTH‐induced internal differentiation of mitochondria in cortical cells in tissue cultures of fetal rat adrenals
Authors: Kahri Arvi I. 
Published: February 2005

AbstractTissue cultures of fetal rat adrenals were used to study effects of cycloheximide on the ACTH‐induced synthesis of mitochondrial inner membranes in the cortical cells. Cycloheximide alone added to the culture medium in concentrations of 100‐0.25 μg/ml killed the cortical cells during six days of treatment. At the dosage level of 0.15 μg/ml/6 days, it induced a decrease in the size of mitochondria and an increase in the pleomorphism of mitochondria. Cycloheximide at a concentration of 0.015 μg/ml/6 days induced no change in the ultrastructure of cortical cells. When cycloheximide in concentrations of 0.15 μg/ml/6 days was added to the culture medium together with 100 mU/ml/6 days of ACTH, the ACTH‐induced changes of mitochondrial inner membranes (formation of 600 Å vesicles) was completely inhibited. It also suppressed the ACTH‐induced development of smooth surfaced endoplasmic reticulum, hypertrophy of Golgi apparatus, development of microvilli and accumulation of lipids. However, it had no effects on the ACTH‐induced increase in the number of polysomes 01 the increase of heterochromatin in the nucleus. Cycloheximide (0.08 μg/ml/6 days) given together with 100 mU/ml/6 days of ACTH had incomplete inhibitory effects on the ACTH‐induced differentiation of the cortical cells. Cycloheximide (0.015 μg/ml/6 days) given together with ACTH resulted in only slight inhibition of ACTH‐induced ultrastructural differentiation of adrenal cortical cells in vitro.The present observations suggest that (1) the stimulatory effect of ACTH on mitochondrial protein synthesis is dependent upon nuclear control of protein synthesis; (2) a specific cytoplasmic mitochondrial protein synthesis stimulating factor in the cytoplasm of cortical cells is dependent on ribosomal protein synthesis and is a mediator of ACTH action on the mitochondrion; (3) despite their apparent autonomy, the mitochondria in cortical cells are kept under nuclear control; (4) the only direct locus for the trophic effect of ACTH is in the nucleus.
Postnatal development and properties of ultimobranchial follicles in the rat thyroid
Authors: Wollman Seymour H. , Nève Pierre 
Published: February 2005

AbstractMature ultimobranchial follicles in the Fischer rat thyroid are characterized by being lined by two or more layers of cells (U cells) and by having an abundance of desquamated cells in the lumen. Such follicles, of variable size and shape, were found in almost every lobe in rats at least 30 days old. They were usually in the interior of the lobe in contact with perivascular connective tissue. Ultimobranchial follicles with multiple layers of cells were not observed in the two‐day‐old rat indicating that these follicles are an example of postnatal development. The most common precursor in the rat was a follicle, relatively large compared with the usual thyroid follicle, containing some cells or debris. Other precursor structures included narrow tubes, sheets or spheroids of cells characteristically having little cytoplasm. Intermedlate forms between these precursors and mature ultimobranchial follicles were recognized. Cells were desquamated while nucleated, and, later, the nuclei disappeared. Thus, in some follicles non‐nucleated debris accumulated. Many follicles were composed of mixed populations of cells, both typical thyroid epithelium and U cells. The relative abundance of the two cell types varied markedly as did the proportions of colloid and cell debris.
Stimulation of DNA synthesis in mammalian cell cultures by receptor‐destroying enzyme and neuraminidase
Authors: Caso Louis V. 
Published: February 2005

AbstractReceptor‐destroying enzyme (RDE) and purified neuraminidase (V. cholerae) were added in varying concentrations to cultures of L929 fibro‐blasts, HeLa cells and FL amnion cells. After 96 hours incubation at 36oC, RDE was found to enhance the growth of L929 fibroblasts and FL amnion cells, as measured spectrophotometrically by total DNA synthesis. Neuraminidase was found to stimulate growth in the three cell lines, using the same method of DNA determination. Neuraminidase, moreover, significantly increased the mitotic indices of the three cell lines after 72 hours incubation.
Studies of human adipose tissue in culture I. Incorporation of glucose and release of glycerol
Authors: Smith Ulf 
Published: February 2005

AbstractExplants of human adipose tissue were incubated in Parker's medium 199 and the rates of glucose incorporation into the lipids and release of glycerol determined. Both of these parameters increased in a linear fashion for about seven to eight days. After this period of time there was a decrease in the metabolic rates of explants with a mean cell size larger than about 90‐95 μm. The incorporation of glucose into the lipids was mainly recovered in the glycerol moiety of the triglycerides. Cellular enlargement was associated with an increase in glucose incorporation as well as glycerol release, i.e., an increased turnover of the glyceride‐glycerol. Addition of insulin increased the incorporation of label into the lipids. The stimulatory effect of a single dose of insulin was pronounced for two days and was only slightly discernible after 14 days. Addition of the enzyme inhibitor iodoacetate at a concentration of 10−4 M reduced the incorporation of glucose to about 5% of the controls. The method of tissue culture used in the present investigation may be a useful tool for metabolic as well as morphologic studies of human adipose tissue in vitro.
Immobilization and cartilage transformation into bone in the embryonic chick
Authors: Haal B. K. 
Published: February 2005

AbstractThe fate of the secondary cartilage present on the membrane bones of the embryonic chick has been studied after immobilization. Immobilization was achieved by the in vivo injection of paralysing drugs (tubocurare or decamethonium), by grafting membrane bones onto the chorioallantoic membrane, or by organ‐culturing membrane bones in vitro. In all three situations the cartilage was transformed into a bone‐like tissue, the matrix losing its acid muco‐polysaccharide, accumulating collagen and undergoing calcification. The chondrocytes shrank in size, came to resemble osteoblasts (osteocytes) and acquired alkaline phosphatase activity.In normal development this cartilage is not transformed into bone but is partly replaced by bone and partly converted into a fibrocartilage which forms the definitive articular cartilage. Immobilization prevented this normal sequence.Past studies on the transformation of cartilage to bone are reviewed and are seen to be adaptations of a highly labile tissue to functional demands.
Anatomical observations on the arterial supply to the lumbosacral spinal cord of the cat
Authors: Chambers Gail , Eldred Earl , Eggett Chris 
Published: February 2005

AbstractThe pattern of arterial supply to the cat's lumbosacral spinal cord was examined in a dozen latex‐injected specimens with a view to determining what precautions might be taken in the procedure of rhizotomy to minimize embarrassment of the cord's circulation. The single ventral spinal artery was found to receive on an average 4.1 significant radicular contributions, of which one or two arteries at the fourth or third lumbar levels on the left were invariably of especially large size. Equal numbers, about six to eight, of contributions to the two dorsolateral arterial trunks were present. Anastomotic channels greater than 50 m̈ in diameter were rather poorly developed between dorsolateral and ventral arterial channels, especially across the middorsum. The dorsal radicular artery in 82 of 97 roots examined was seen to pierce the ventral root in order to reach a position along the ventral aspect of the dorsal root. In most cases this penetration occurred central to the ganglion. The bearing of this feature on reported differences in behavioral effects from rhizotomy by intradural section and by ganglionectomy is discussed, as well as other aspects of the effect of rhizotomy on cord criculation.
Identification and enzyme quantitation of the stages of the seminiferous epithelial wave in the rat
Authors: Ant Martti Parvinen , Vanha‐Perttula Tapani 
Published: February 2005

AbstractBased on differences in light absorption the stages of the rat seminiferous epithelial wave were identified by a transillumination technique. The most marked difference was encountered in the boundary between stages VIII and IX where the mature spermatozoa are released into the tubular lumen. Other characteristic transitions were observed between stages VI and VII as well as stages XII and XIII. All stages could be divided into four major, easily recognizable zones. Within the zones the stages could be identified with an accuracy of ± 1 stage. The characteristic changes take place in the tubular center and are due to the development of the acrosome in the spermatid. The acrosome appears to contain material with a strong light absorption capacity.Based on these observations a method was developed to isolate identified fragments of the rat seminiferous tubule in native condition. These fragments were used to quantify the activity of three previously described enzymes: specific tubular acid phosphatase III and IV as well as aminopeptidase III.The tubular acid phosphatase IV showed a high activity in stages corresponding to the final maturation process of the spermatid, whereas acid phosphatase III was evenly active in the different stages. Also aminopeptidase III showed a peak of activity during stages V‐VII coincident with that of acid phosphatase IV, The possible role of these enzymes in the morphological maturation of spermatid and the destruction of the residual body is discussed.
A comparison of a systematic sampling method with complete random sampling for estimating total numbers of nerve fibers
Authors: Tang Douglas B. , Ebbesson Sven O. E. 
Published: February 2005

AbstractThis paper considers the sampling precision of a systematic sampling method for estimating total number of nerve fibers exposed on cross section of a nerve trunk. The mean square error (MSE) associated with systematically selecting every Kth grid square (traversing the section in a serpentine pattern) was determined in each of nine nerve fiber populations and compared to the MSE obtained using a completely random selection of grid squares.For both sampling methods sampling errors of approximately 10% could be achieved by counting in 10% (K = 10) of the available grid squares. To reduce the MSE to 5% or less necessitated, for both methods, counting approximately 50% (K = 2) of the cross sectional area.Although the results of this investigation are based on the study of but one class of nerve fiber population (cervical sympathetic nerve trunks), the authors believe that certain of the results will have practical application in similar quantitative studies. More important, it is hoped that this study will motivate further investigations into the precision of sampling methods currently employed (and others which may be proposed) in the quantitative study of the nervous system.
The role of androgens in the epithelio‐mesenchymal interactions involved in prostatic morphogenesis in embryonic mice
Authors: Cunha Gerald R. 
Published: February 2005

AbstractStandard tissue culture and epithelio‐mesenchymal separation and recombination techniques were applied to the question of sex determination of the male urogenital sinus of embryonic mice. Explants of urogenital sinuses from 12‐ to 17‐day old embryos were cultured in an androgen‐free environment to a gestational age equivalency of 18 to 20 days. The developmental response of these explants led to the following conclusions: (1) Androgens are necessary for initiation of prostatic bud outgrowth; (2) The effect of androgens can be demonstrated at the stage when the fetal testis begins to secrete androgens; and (3) Prior to the appearance of prostatic buds, the urogenital sinus has the capacity to pursue that developmental end‐point independently of further androgen stimulation. In addition, the developmental response of recombinants composed of androgen‐treated and untreated epithelium and mesenchyme from the urogenital sinus has shown that it is the epithelium which is primarily determined by androgens during prostatic morphogenesis.
The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat epididymis
Authors: Hoffer Anita P. , Hamilton David W. , Fawcett Don W. 
Published: February 2005

AbstractThe ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat caput epididymidis was examined with the electron microscope. Specializations of the principal cells associated with absorption include numerous endocytic invaginations of the cell surface, numerous coated vesicles and multivesicular bodies in the apical cytoplasm. It was demonstrated that particulate tracers are taken into the cells and sequestered in secondary lysosomes and multivesicular bodies. Morphological features consistent with secretory activity are also found in the principal cells and include numerous cisternae of rough endoplasmic reticulum with a flocculent grey content and an extremely well‐developed Golgi apparatus. The speculation that the principal cells are actively secretory despite the absence of secretory granules formed in the Golgi and of a visible mechanism for release of the product at the cell surface is discussed.The “halo cells” in the epididymal epithelium were also examined and it is shown that many of these cells are not typical migratory lymphocytes. Chief among the differences are their granule‐containing multivesicular bodies and more abundant endoplasmic reticulum. Nonetheless, it is conceivable that the halo cells are lymphocytes and that the conditions they encounter as they leave the circulation and enter the epididymal epithelium may stimulate morphological changes. The possible immunological significance of these observations is discussed.
A study of endocardial endothelium using freeze‐drying and scanning electron microscopy
Authors: Wheeler E. E. , Gavin J. B. , Herdson P. B. 
Published: February 2005

AbstractThe ventricular endocardium of 20 rats and five dogs was examined with a scanning electron microscope after careful washing with phosphate‐buffer, glutaraldehyde fixation and freeze‐drying. Endothelial cells formed a continuous sheet lining the ventricle in both species. Individual cells were identifiable by a central bulge corresponding to the nucleus and were separated by a polyhedral pattern of intercellular lines. The intimal surfaces of these cells were relatively smooth, although sometimes transverse ridges, small pseudopod‐like projections or indentations suggestive of macropinocytosis were present. Endothelial cells were relatively easily lost in preparation and shrinkage artefacts were also observed. These observations are compared with other scanning electron microscopic studies of endothelium and are discussed with particular reference to the effects of preparative procedures.
Intranuclear annulate lamellae in giant cells of the mouse chorioallantoic placenta
Authors: Pope Robert S. , Ollerich Dwayne A. 
Published: February 2005

AbstractIntranuclear annulate lamellae were initially observed on day 9 of gestation. They increased in frequency until day 12, after which a decline in frequency was noted. Numerous IAL were in close association with nucleoli on days 11 and 12 and numerous large dilatations of the intermembranous space were present. IAL were also associated with cytoplasmic invaginations and inclusions of the nucleus. The frequency of invaginations and inclusions also increased from day 9 to 12 and brought increased amounts of cytoplasm into contact with the nucleus. Continuity of the intermembranous space of the IAL with the perinuclear space and the latter with the cisterns of rough endoplasmic reticulum suggested a possible route for nuclear‐cytoplasmic exchange in either direction.
Tubular myelin assembly in type II alveolar cells: Freeze‐fracture studies
Authors: Smith Una , Smith D. S. , Ryan J. W. 
Published: February 2005

AbstractWe have undertaken a study to coordinate examination of thin sections with that of freeze‐etched material. Results suggest that (1) lamellar bodies have a much more regular structure than hitherto believed. (2) The leaflets of some lamellar bodies reveal a unique substructure of ribs and intramembranous particles displayed in form and spacing (400‐500 Å) like those of tubular myelin as seen in the airspace. (3) As in other membranes of high metabolic activity the fracture face is covered with particles 80‐100 Å in diameter. Our freeze‐etch findings of the previously undetected organization and suborganization of lamellar bodies suggest an entirely new set of morphological criteria for evaluating the maturation of lamellar bodies and their role in the intracellular assembly of the reticular components of the airspace lining.
Axon diameter and myelin thickness—unusual relationships in dorsal root ganglia
Authors: Spencer Peter S. , Raine Cedric S. , WiśNiewski Henryk 
Published: February 2005

AbstractPeripheral nerve fibers close to the sensory neurons of dorsal root ganglia displayed unusually thin myelin sheaths in relation to their axon diameter. Myelinated internodes along each fiber showed large differences in the numbers of myelin lamellae. These fibers are thought to represent spatial progression in degree of myelination as the axon egresses from the nonmyelinated glomerulus to the position of axonal bifurcation. This region is termed the initial complex of dorsal root ganglion cells. While the usual relationship between axon diameter and myelin sheath thickness is seen in the majority of dorsal root ganglion fibers, the fiber comprising each initial complex shows an atypical relationship in that the myelin sheath is unusually thin. Since the pattern of myelination in this small area is incongruous with previous reports attributing the control of myelin sheath thickness solely to axon diameter, the present findings indicate that other, unknown factors are operative in the control of myelination.
Innervation of the vibrissae of the California sea lion, Zalophus californianus
Authors: Stephens R. J. , Beebe I. J. , Poulter T. C. 
Published: February 2005

AbstractThe vibrissae of the California sea lion are richly innervated with myelinated fibers that terminate in three distinctly different endings. Large nerve bundles enter the base of the follicle and immediately branch into smaller bundles that traverse the connective tissue trabeculae below the large ring sinus. Some neurons terminate in a lamellated corpuscle in close relationship to the venous sinuses of the proximal cavernous tissues. The remainder of the nerves continue distally parallel to the glassy membrane terminating in two specific types of endings arranged in a ring about the shaft of the vibrissae at the level of the upper portion of the ring sinus. One type of ending is on the outer surface of the glassy membrane where the myelin sheath terminates abruptly and the sensory ending is flattened into a thick, lancet‐shaped structure. An extension of cytoplasm from a specialized supportive cell covers this terminal segment of the nerve on two sides, while numerous finger‐like extensions protrude into the connective tissue from the narrow, uncovered sides. The second type of ending penetrates the glassy membrane, branches, and terminates in close apposition to the Merkel cells in the outer root sheath. Amyelinated nerves of various sizes are frequently observed in the same bundles as the larger myelinated fibers, but to date, the position of their termination has not been established.
A comparative ultrastructural study of the choroid plexuses of the immature pig
Authors: Davis Donald A. , Lloyd Bolivar J. , Milhorat Thomas H. 
Published: February 2005

AbstractThe fine structure of the choroid plexus of the immature pig consists of an epithelial layer of cells contiguous with a subepithelial region containing fibrillar elements. The apical surface is extended as numerous digitiform microvilli. At irregular intervals, apical tufts of cilia occur that contain 10–14 cilia with a typical 9+2 subfibrillar arrangement. The cytoplasm is composed of randomly distributed smooth tubular endoplasmic reticulum, apically concentrated cisternae of rough endoplasmic reticulum, Golgi areas, glycogen and numerous mitochondria. Lateral cell membranes are typically tortuous, interdigitating and possess an apical tight junction. Various vesicles are found including pinocytotic vesicles, lipoid inclusions and lysosomes. A comparative ultrastructural study of the choroid plexuses from the lateral, third and fourth ventricles failed to demonstrate significant differences between these structures of different embryological origin.
Pathogenesis of abnormal remodeling of bones: Effects of yellow phosphorus in the growing rat
Authors: Whalen Joseph P. , O'Donohue Neil , Krook Lennart , Nunez Eladio A. 
Published: February 2005

AbstractHistologic examination of metaphyseal bone of rats intoxicated with elemental phosphorus showed that inhibition of osteocytic osteolysis and chondrolysis account for widening of trabeculae and retention of the chondroid core. These changes are reflected in increased radiographic density and abnormal remodeling.