bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the caudal end of the spinal cord
Authors: Pearson Anthony A. , Sauter Ronald W. 
Published: February 2005

AbstractThe development of the structural pattern of the lower sacral and coccygeal segments of the spinal cord in human, rabbit and monkey embryos and fetuses has been studied. The changes observed in serial sections from above downward are outlined, beginning with typical sections through the lower sacral cord. Among the changes, other than diminution in size of the spinal cord and reduction in size of the lower spinal nerves, there is a gradual disappearance of the posterior funiculus. As this occurs the gray matter appears to spread dorsally and the central canal widens. The gray matter becomes reduced in size and the lateral funiculus extends farther dorsally. A little lower down, the gray matter of the alar plate is reduced further in size and there is corresponding enlargement of the central canal. This enlargement constitutes the terminal ventricle. The spinal cord rapidly becomes smaller as both the fibers and the gray matter are diminished. In some specimens, fibers decussate dorsal to the lower end of the terminal ventricle. Little remains of the lower end of the spinal cord except the ependymal wall of the central canal and the surrounding fiber bundles. The shape and size of the lower end of the central canal is subject to variations.In the lower part of the spinal cord a longitudinal bundle on each side is formed by fiber contributions from the anterior horn cells in the basal plates. This bundle contributes fibers to the fifth sacral and the first and second coccygeal nerves. It is designated the sacrococcygeal fasciculus.
The nerves of the umbilical cord in man and the rat
Authors: Ellison Jeffrey P. 
Published: February 2005

AbstractA thiocholine technique was used to visualize nerves in human and rat umbilical cords. The allantoic part of the rat umbilical cord was found to be separate from the vitelline part of the cord and its vessels were not innervated. However, acetylcholinesterase‐positive nerves formed a plexus around the vessels of the vitelline part of the 21‐day rat umbilical cord. These nerves displayed fusiform swellings and terminated as simple endings close to the yolk sac wall. The findings suggest that the vitelline circulation in the rat may function under neural control.An investigation of full‐term human umbilical cords revealed extrafetal acetylcholinesterase‐positive nerves. Nerve bundles passed from the fetus into the cord and split into a plexus. Beaded nerve terminals were found about 15–20 cm from the fetus. Some of these endings touched the media of the vein; others ended freely in the cord substance between the arteries and the vein. There were no periarterial terminals and no nerves were found in the maternal half of the cord.The free nerve endings in the human cord may have been sensory, since they made no terminal effector contact. However, it should be noted that similar terminals touched the media of the umbilical vein. The endings described could be sensory receptors for the sphincter of the ductus venosus that controls venous return from the fetus.
Penetration of the uterine epithelium during implantation in the rabbit
Authors: Enders Allen C. , Schlafke Sandra 
Published: February 2005

AbstractThe structure of interacting trophoblast and uterine epithelium was studied in 16 rabbits from seven days zero hours to seven days 20 hours post coitus. The most common type of penetration of the uterus by the trophoblast consisted of a peg from a trophoblastic knob that extended to the basal lamina of the uterine luminal epithelium and was bordered by uterine epithelial cells with which it shared junctional complexes. In early implantation sites there was direct evidence of fusion of the syncytial trophoblast with apical ends of individual uterine epithelial cells. Since no evidence of epithelial dissociation or mechanical intrusion of trophoblast between epithelial cells was found, it is suggested that fusion is the normal method of epithelial penetration by the trophoblast in the rabbit. The cytoplasm of the fused uterine cells was apparently converted into syneytium of the trophoblastic knob. Subsequent to formation of the trophoblastic peg, penetration of the basal lamina and of maternal blood vessels occurred, and the attached trophoblastic knobs increased in width. At later stages when symplasma formation by the uterine epithelium was extensive, fusion included trophoblast between knobs. Since the penetration peg is formed by fusion of trophoblast with uterine epithelium, the cell membrane first associated with the maternal connective tissue is of maternal origin. However, new membrane formed after fusion would be expected to have histocompatibility factors from both the trophoblast and the fused maternal epithelial cells.
Electromyography of deep back muscles in man
Authors: Donisch Eric W. , Basmajian John V. 
Published: February 2005

AbstractThe deep layers of the transversospinal back muscles were studied in 25 healthy human subjects. Bipolar fine wire electrodes were inserted bilaterally at the level of the sixth thoracic and the third lumbar spinous processes. Activity was registered simultaneously in sitting and standing, and during movements while in these positions. It was shown that the same muscle group displayed different patterns of activity in the thoracic compared to the lumbar level. Variations in the pattern of activity during forward flexion, extension and axial rotation suggest that the transversospinal muscles adjust the motion between individual vertebrae. The experimental evidence confirms the anatomical hypothesis that the multifidi are stabilizers rather than prime movers of the whole vertebral column.
Wallerian degeneration: A reevaluation based on transected and colchicine‐poisoned nerves in the amphibian, Triturus
Authors: Singer Marcus , Steinberg Marta C. 
Published: February 2005

AbstractThe sequence of degeneration in colchicine‐poisoned or in transected peripheral nerve fibers is reported. The results lead us to conclude that the Schwann cell is the predominant agent of axon and myelin destruction. The Schwann cytoplasm burgeons, swells the Schmidt‐Lanterman clefts and the adaxonal layer of cytoplasm, and invades the electron‐dense bands of myelin. The axolemma and adaxonal membranes are eroded and Schwann organelles invade the axoplasm commingling with those of the axon to form a peripheral “reactive zone.” The reactive zone of organelles surrounds a core of compacted neurofilaments which may persist for days. Eventually the entire contents, commingled organelles and neurofilaments, are destroyed. The myelin sheath is destroyed without being separated from its Schwann cell of origin.
The fine structure of cellular layers and connective tissue space at spinal nerve root attachments in the rat
Authors: Haller Frederick R. , Haller Ann C. , Low Frank N. 
Published: February 2005

AbstractTissue containing the attachment of nerve roots to the spinal cord was dissected from seven rats perfused with buffered aldehydes. Both dorsal and ventral roots were obtained from all cord levels. All tissues were prepared routinely for electron microscopy.The outer layers of the root sheath are homologous with the outer layers of the pia mater and are essentially continuous with it. The inner layers of the root sheath, which are a structurally modified and centrally directed continuation of the perineurium across the subarachnoid space, terminate as an open‐ended tube near the junction of the peripheral and central nervous systems. Here there is direct continuity between the endoneurial connective tissue space and the pial connective tissue space. The latter, in turn, communicates directly with the subarachnoid space through fenestrations between pial cells. The relationship of this to certain clinical manifestations is briefly discussed.
The postnatal development of the retina in the normal and rodless CBA mouse: A light and electron microscopic study
Authors: Caley David W. , Johnson Clement , Liebelt Robert A. 
Published: February 2005

AbstractThe postnatal development of the retina in control (CBA/S) and rodless (CBA/Ki) mice was studied by light and electron microscopy. In the control mice, the major increase in retinal thickness occurs between birth and seven days. The inner and outer segments begin to grow into the optic ventricle between seven and ten days with their most rapid growth occurring between 12 to 15 days; by 35 days the retina appears mature. During development, the nuclear layers become thinner while the optic ventricle (layer of rods) and the plexiform layers become thicker. At birth, the mutant or rodless retina is indistinguishable from the control; however, the inner and outer segments fail to develop beyond the primitive seven‐ to ten‐day stage. At 15 days the outer nuclear layer becomes reduced to only a few nuclei in thickness. Many degenerating elements are found in the cavity of the optic ventricle and in the outer nuclear and plexiform layers. By 35 days the mutant retina lacks photoreceptors and is reduced in thickness to less than that at birth. The pigment epithelium is heightened in regions where degeneration is incomplete but becomes highly attenuated in regions where visual cell degeneration is complete. The optic ventricle contains the villous processes of the pigment epithelium and the fringe processes of the Müller cells. The outer limiting membrane is contiguous with remnants of the outer plexiform layer. Between the outer plexiform layer and the inner limiting membrane, the mutant retina is normal in appearance and dimension. The delayed appearance of the smooth endoplasmic reticulum of the pigment epithelium is implicated in the failure of outer segment maturation. The role of both Müller and pigment epithelial cells in removal of the products of retinal degeneration is discussed.
The ureteral lumen during peristalsis
Authors: Woodburne Russell T. , Lapides Jack 
Published: February 2005

AbstractThis study concerns the size and shape of the ureteral lumen and an assessment of its enlargement during peristalsis. To stop the action of the living dog ureter, it was flooded with isopentane close to its freezing point (− 160° C). The ureter remained frozen until completion of all technical procedures. Photographs of the cut end of active ureters also provided evidence of its luminal characteristics and a movie was achieved of its continuous action. The totally collapsed lumen is stellate in form, epithelial surfaces being in virtual contact. As the lumen opens the points of the stars are last to go, but a square shape and finally a circle result. In a typical experiment, the collapsed lumen had a cross sectional area of 0.12 mm2, enlarging to 2 mm2 in diuresis. This × 17 enlargement occurred over a 3 cm length of the peristaltic wave. Enlargement of the lumen is largely accommodated by thinning of the muscle coats and attenuation of the mucous membrane, there being relatively little gross enlargement of the total segment.Direct photography of the cut end of the proximal segment of the ureter completely confirms the section studies.
Implantation in the ferret: Epithelial penetration
Authors: Enders Allen C. , Schlafke Sandra 
Published: February 2005

AbstractImplantation in the ferret occurs during the 24 hours between 12 and 13 days post coitus. The thinned zona pellucida is disrupted irregularly along the lateral aspects of implantation chambers. Some of the trophoblastic cells enlarge and develop into plaques of syncytium. Protoplasmic projections from these syncytial plaques intrude between adjacent uterine luminal epithelial cells to which the syncytium is adhering. Interesting ectoplasmic pads from the syncytial trophoblast indent the uterine epithelial cells prior to adhesion, and there are ectoplasmic regions where trophoblast cell membrane is closely applied to uterine cell membranes at all sites of epithelial penetration. Intrusion of trophoblast between uterine luminal epithelial cells is apparently the major mechanism of epithelial penetration in the ferret.
Hepatic ultrastructure in two species of normal, fasted and gravid teleost fishes
Authors: Weis Peddrick 
Published: February 2005

AbstractElectron microscopic examination of the livers of two teleost fishes, the zebrafish (Brachydanio rerio) and the mosquito fish (Gambusia affinis), indicates that they are morphologically similar to each other in most aspects but different in several ways from other teleosts which have been described. The perisinusoidal space of Disse is greatly reduced in relation to other vertebrates, and is represented by plasmalemmal folds in the hepatocytes apposed to the sinusoidal endothelium. There are desmosomal connections between hepatocytes and those mesothelial cells adjacent to the pancreas. Other characteristics include lack of basement laminae throughout and accumulations of fine filaments within the hepatocytes parallel to the extracellular canaliculi. Intracellular canaliculi are incompletely surrounded by such filaments.In fish which have been starved, or in gravid females, an expected loss of glycogen is accompanied by a concentration of rough endoplasmic reticulum and elongation of mitochondria, which in starved fish may be pleomorphic. In either condition, the liver undergoes severe atrophy.
Electromyography of the oral stage of swallowing in man
Authors: Hrycyshyn Alan W. , Basmajian John V. 
Published: February 2005

AbstractThe geniohyoid, anterior belly of digastric, mylohyoid, and genioglossus muscles of 20 human subjects were studied electromyographically to determine the temporal relationships of their activities during the act of swallowing. Although the firing order of the four muscles varied within the same subject, the best estimate of the “true” firing sequence was established for each of the 18 subjects who provided statistically significant data. However, no definite universal pattern could be established for the four muscles because there was great inter‐subject variability in both the duration and the sequence of activity. Therefore, at least with respect to these four muscles, each individual has his own swallowing pattern, but different people may swallow quite differently.The type of bolus (saliva vs water) may influence the duration of the muscles' activity. On the other hand, posture (semi‐reclined vs sitting) did not seem to have any influence. There was no evidence to indicate that posture and/or the type of bolus are correlated with the sequence of muscular activity.The anterior belly of the digastric muscle was not active in one‐quarter of the swallows studied. When active during deglutition, all muscles had a general electromyographic pattern of one to many summations of activity separated by relatively quiet periods before and after each swallow.
Autoradiographic studies of t12/t12 mouse embryos
Authors: Hillman Nina 
Published: February 2005

AbstractSeveral studies have indicated that morula‐staged t12/t12 mouse embryos are deficient in nucleolar RNA synthesis and that this deficiency may be a causal factor of death. The present investigation was undertaken to see if decreased RNA synthesis in t12/t12 embryos occurs prior or subsequent to developmental arrest. In this study, embryos obtained from +/t12 inter se matings were labeled with 3H‐5‐uridine at specific cleavage stages and then subjected to high resolution autoradiographic study. These staged embryos were either examined immediately following labeling or were reincubated in nonradioactive medium and then studied. Comparisons between autoradiographs of the phenotypically mutant embryos and their phenotypically wild‐type littermates revealed no significant difference between these two groups in either the amount or distribution of the incorporated RNA precursor at any cleavage stage. Late morula t12/t12 embryos, prior to the appearance of advanced degenerate changes following developmental arrest, did not differ significantly in their labeling patterns from the labeling patterns of phenotypically wild‐type late morula. These findings indicate that the initial effect of the t12/t12 genome is not on rRNA synthesis. The incorporation of the labeled precursor into the intranuclear fibrillo‐granular bodies which characterize t12 homozygotes, was also studied.
An ultrastructural study of the natural secretory cycle of the parathyroid gland of the bat
Authors: Nunez Eladio A. , Whalen Joseph P. , Krook Lennart 
Published: February 2005

AbstractCyclical ultrastructural changes in chief cells of the bat parathyroid during hibernation are described. The morphology indicates that the cells increase in activity at the start of hibernation and decrease in activity at the end. During early hibernation, the main alterations are an increase in granular endoplasmic reticulum, an increase in the number of prosecretory granules associated with the Golgi apparatus, an increase in the number of mature secretory granules, and the appearance of numerous, large cytoplasmic lipid droplets. An unusual finding is that the lipid droplets are preferentially associated with mitochondria and glycogen deposits. At this time there is also an increase in the size of intercellular spaces and the concentration of secretory granules near the plasma membrane. By late hibernation, however, there is a marked reduction in the amount of granular endoplasmic reticulum, fewer mitochondria, inconspicuous Golgi apparatuses, and a reduction in the size of intercellular spaces. In addition, lipid droplets are absent. These observations are discussed in relation to the cyclic secretory changes which occur in bat parafollicular cells and in bone during hibernation.
The structure of the sarcotubular system in avian muscle
Authors: Hikida Robert S. 
Published: February 2005

AbstractMost avian skeletal muscles have their triads at the A‐I junction, and there is a complex sarcoplasmic reticulum in the Z‐line region because of the architectural arrangement of two triads in one sarcomere. The sarcotubular system in the pigeon serratus superficialis metapatagialis muscle was examined with the electron microscope. In these muscles the t‐tubules open to the extra‐cellular space, and there is an indication that mitochondria may connect to the sarcotubular system. The elements of the sarcoplasmic reticulum between two triads of a single sarcomere is similar to that in the frog, and consists of the triads, intermediate cisternae, longitudinal tubules, and fenestrated collar. In the portion of the sarcoplasmic reticulum between triads of adjacent sarcomeres, the triads are coupled. This is brought about by triads extending from one sarcomere to the next and by the connection of the reticulum between triads of adjacent sarcomeres. Some of the tubules making up the Z‐line reticulum have a fenestrated appearance, similar to the fenestrated collar.
Desmosome‐like junctions in the spiral ganglia of cats
Authors: Adamo Norma J. , Daigneault Ernest A. 
Published: February 2005

AbstractThe spiral ganglia of adult cats contain desmosome‐like junctions between lamellae of perikaryal or axonal myelin, between Schwann cell and neuronal plasmalemma, and between the perikaryon of myelinated neurons and cellular structures not identified as to cellular origin. The possibility exists that the unidentified cellular structures observed may be part of another neuron, thus forming a means by which neurons in a spiral ganglion can communicate.
The development of smooth‐surfaced endoplasmic reticulum in adrenal cortical cells of fetal guinea pigs
Authors: Black Virginia H. 
Published: February 2005

AbstractIn most steroid‐secreting cells smooth‐surfaced endoplasmic reticulum is prominent. This organelle is a site of major enzymes involved in steroid biosynthesis. In fetal guinea pig adrenal cortical cells the development of tubular smooth‐surfaced reticulum precedes all other apparent morphological changes at the cellular level, serving as the earliest indicator of structural differentiation. Its appearance coincides with the earliest evidence of steroid production by the adrenals (Ortiz et al., 1966). Further development and differentiation of this organelle in inner cortical cells gives rise to complex paracrystalline arrays. Subsequent segregation of cells containing these arrays to the deeper cortical regions, the deep zona fasiculata and zona reticularis, heralds the histological zonation of the cortex into three definitive regions. In the outer cortical cells of the developing zona glomerulosa, cisternal reticulum becomes prominent and in late fetal life large areas of the cisternal membranes become smooth‐surfaced. Combined with information from bioassay experiments of Price and coworkers (Ortiz et al., 1966) the early appearance of the smooth reticulum supports the thesis that the adrenal is capable of steroid biosynthesis early in fetal development, before zonation of the cortex occurs.As the endoplasmic reticulum develops, polyribosomes become widely spaced on its surface. They may be involved in the synthesis and maintenance of the expanding smooth‐surfaced reticulum and its associated steroidogenic enzymes, analogous to the development of smooth endoplasmic reticulum and associated enzymes in rat hepatocytes (Dallner et al., 1966a,b).The gradual confinement of cells containing paracrystalline arrays of smooth reticulum to the deep cortical zones implies functional significance for this compartmentalized form of endoplasmic reticulum.
The distribution of negative surface charges on mammalian spermatozoa
Authors: Yanagimachi R. , Noda Y. D. , Fujimoto M. , Nicolson G. L. 
Published: February 2005

AbstractThe relative density and distribution of acidic negative residues on the plasma membranes of spermatozoa of seven mammalian species were studied using a colloidal iron hydroxide (CIH) labeling technique. The surface distribution of negative residues is discontinuous on mature spermatozoa from the cauda epididymidis or on ejaculated spermatozoa of the rabbit, mongoose, rat, guinea pig and hamster. Tail regions are generally more densely labeled with CIH than head regions, indicating that sperm tails have more acidic negative charges than heads. In these species, the density of the negative surface charge is rather uniform within a particular segment of the spermatozoa and abruptly changes at the junctions to morphologically distinct segments, suggesting that the biochemical properties of the plasma membrane also change at these junctions. In bull (cauda epididymal) and human (ejaculated) spermatozoa, the entire surfaces of spermatozoa are densely labeled with CIH. Comparison of testicular, caput and cauda epididymal spermatozoa of rabbit, bull and hamster suggests that the negative surface charges of spermatozoa increase with epididymal maturation of spermatozoa. A possible chemical nature of the residue(s) has been suggested from neuraminidase digestion and methylation experiments.
Penetration of peroxidase into peripheral nerve fibers
Authors: Krishnan N. , Singer Marcus 
Published: February 2005

AbstractPenetration of macromolecules into living peripheral nerve was studied in vivo and in vitro using horse‐radish peroxidase. Peroxidase penetrates the epi‐ and perineurium and is sequestered in the Schwann cell body. It then is apparent in the incisures (clefts) of Schmidt‐Lanterman and the paranodal loops. After prolonged incubation the marker appears in the adaxonal Schwann cytoplasm and periaxonal space. It then is visualized inside the axon within vesicles and agranular endoplasmic reticulum both at the node and internodal regions. More rapid penetration occurs at the node of Ranvier than at the internodal region.