bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural study of thoracic duct lymphocytes of mice
Authors: Wivel Nelson A. , Mandel Mark A. , Asofsky Richard M.
Published: February 2005

The fine structure of cells in mouse thoracic duct lymph was described, and the changes in cell population during a prolonged drainage of five days were characterized. From 93.9–97.0% of the cells were lymphocytes and 99.9% of them had the greatest axis ranging from 5.0–6.3 μ. Those cells which ranged in greatest dimension from 6.3–9.0 μ constituted 3–6% of the total population and were lymphocytes, developing and mature plasma cells, monocytes, polymorphonuclear leukocytes, and unclassified cells. The developing and mature plasma cells increased from 1.4–5.5% when day 1 of cannulation was compared with day 2. These cells constituted 3.5% of the population of day 3 and 3.9% on days 4 and 5. The numbers of these cells appeared to account for most of the increase in large lymphocytes seen by light microscopy. Approximately 5% of the lymphocytes contained inclusions which had the appearance of lipid. The findings were compared with previous observations in other mammalian systems.
Studies on the tadpole tail I. Structure and organization of the notochord and its covering layers in Rana catesbeiana
Authors: Bruns Romaine R. , Gross Jerome
Published: February 2005

This paper presents a detailed description of the notochord and its covering layers in the tail of the premetamorphic bullfrog (Rana catesbeiana) tadpole.

In general, the notochord is a tapered, rod‐like structure composed of large vacuolated cells. It is covered by a thin basement membrane and by several thicker layers of connective tissue whose organization around the notochord differs along the length of the tail. In the proximal half of the tail the notochord and its basement membrane are followed consecutively by the notochord sheath, the elastica externa and the outer connective tissue sheath. In the distal part, however, the basement membrane is followed by the elastica interna, the notochord sheath and the outer connective tissue sheath. Toward the tip of the tail the connective tissue layers gradually become thinner and finally disappear leaving the tip of the notochord with its basement membrane lying in loose mesenchymal tissue.
Role of spermatogonia in the repair of the seminiferous epithelium following X‐irradiation of the rat testis
Authors: Dym Martin , Clermont Yves
Published: February 2005

In the normal adult rat testis, type A0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A1 spermatogonia.

The behavior of type A0 and A1 spermatogonia was investigated following administration of a single dose of x‐rays (300 r) to the testis. Using whole mounts of seminiferous tubules, the type A0 and A1 cells were counted at various intervals after irradiation. At 8 and 13 days after irradiation, type A1 spermatogonia reached lowest values, i.e., 6% and 3% of non‐irradiated control, while type A0 reached the lowest value, i.e., 62% of control at eight days. Thereafter the numbers of type A0 and A1 progressively increased to return to normal at 39 days. It was thus concluded that the type A0 were comparatively more resistant to x‐irradiation than type A1 spermatogonia.

To verify if the surviving type A0 proliferated in the irradiated testis, animals were injected with 3H‐thymidine three hours before they were sacrificed at various times after x‐irradiation. In irradiated testes the labeling indices of the surviving type A (A0, A1–A4) were the same as in the non‐irradiated testes except in stages V‐VI of the cycle of the seminiferous epithelium. While in the controls only 2% of type A cells were labeled at these two stages of the cycle, after irradiation the labeling index of type A reached a maximum of 31% at 13 days to return to control values by 39 days. Since at 13 days after irradiation type A0 spermatogonia were the predominant component of the spermatogonial population, it was concluded that these cells must have incorporated 3H‐thymidine and thereby contributed to the reconstruction of the spermatogonial population partially destroyed by irradiation.
Electron microscope studies of sperm incorporation into the golden hamster egg
Authors: Yanagimachi R. , Noda Y. D.
Published: February 2005

Hamster eggs freed from the cumulus oophorus and zona pellucida were inseminated in vitro with capacitated spermatozoa. As soon as the spermatozoon reaches the surface of the egg cytoplasm, numerous microvilli of the egg surround the spermatozoon. Those microvilli attached to the acrosomal collar region of the spermatozoon quickly spread over the inner acrosomal membrane of this region, dislodging the outer acrosomal membrane and the overlying sperm plasma membrane. At the same time, microvilli fuse with the plasma membrane of the postnuclear cap region of the spermatozoon, and the egg cytoplasm quickly flows around the nucleus of that region of the spermatozoon. The inner acrosomal membrane persisting on the sperm head never fuses with the egg (microvillar) plasma membrane. This membrane is destined to disintegrate and be absorbed into the egg cytoplasm. Incorporation of the sperm flagellum into the egg cytoplasm takes place by fusion between plasma membranes of the spermatozoon and egg.
Nerve contributions to the pelvic plexus and the umbilical cord
Authors: Pearson Anthony A. , Sauter Ronald W.
Published: February 2005

Serial sections of human embryos and fetuses reveal that the sacral nerves which contribute fibers to the pelvic plexus often have dorsal, ventral, and oblique communicating rami. The ventral rami resemble the white rami of upper thoracic nerves and some of their fibers pass close by or through the chain ganglia and into the pelvic plexus. The sizes of the ventral rami are often in inverse proportion to that of the pelvic splanchnic nerves. That is, when the pelvic splanchnic nerves are poorly developed, the ventral rami are large, and conversely, when the pelvic splanchnic nevers are well developed, these rami are small. The pelvic plexus was found to receive fibers from the sympathetic trunk and its ganglia in addition to those from the hypogastric plexus and the pelvic splanchnic nerves.

Analysis of the observations made in this study together with a review of the literature in light of the present day classification of nerve fibers raises serious doubts concerning the limits set for the outflow of preganglionic nerve fibers from the spinal cord and the distribution of gray and white rami as described in recent textbooks in terms of their histological and physiological significance.

Nerve fibers from the pelvic plexus can be traced along the walls of the bladder and the urachus and along the umbilical arteries into the umbilical cord. In embryos, only a few scattered nerve fibers were found distal to the umbilicus, but in fetuses at term, distinct nerve bundles were identified in the cord. These bundles sent branches to the walls of the umbilical arteries; other branches terminated as “end‐nets” in Wharton's jelly. These nets appeared as fine fibers with nodular swellings at irregular intervals. Innervation of the umbilical arteries was richest within the first few inches of the cord. Beyond this region, the nerves rapidly decreased in number. “End‐nets” were present as far as four inches from the umbilicus. Granular cells resembling Langerhans' cells were found in the cord. Often these cells were closely associated with fine nerve fibers.
Locomotor adaptations in the disc‐winged bat Thyroptera tricolor. I. Functional organization of the adhesive discs
Authors: Wimsatt William A. , Villa‐R Bernardo
Published: February 2005

Locomotor capability on smooth vertical surfaces is rare in mammals. The adhesive discs on thumbs and soles of bats of the family Thyropteridae are uniquely specialized for this purpose, but their functional organization remains virtually unexplored. The face of the discs is concave, has a characteristic dermatoglyphic pattern, and is permanently moist. Each disc is supported by a biconcaval fibrocartilagenous framework; its circular “rim” is divided into 60–80 chambers, each accommodating a sudoriparous gland which discharges on the disc face. Glandular form and cytology are unique, reflecting special functional adaptations. Other significant adaptations involve the epidermis, distribution of adipose tissue, extrinsic muscle insertions, disc relations to digital joints, and distribution of certain sensory endings. The discs have no intrinsic musculature and are manipulated from without. Experiments with living Thyroptera and analysis of the internal organization of the discs verify that their functional mode is suctorial rather than some other adhesive mechanisms; special relationships within the thumb discs suggest that the adhesive force may be to some extent adjustable under normal use.
Fine structural modifications of the rat chromatoid body during spermiogenesis
Authors: Susi F. R. , Clermont Y.
Published: February 2005

The chromatoid body of rat spermatocytes and spermatids was studied with routine electron microscopy and the PA‐silver method for detection of glycoproteins. The chromatoid body consists of a membrane‐free aggregate of electron dense, finely filamentous material, in association with small vesicles. In late pachytene spermatocytes, there may be more than one chromatoid body; its dense component is diffusely reticulated. In young spermatids, there is only one chromatoid body per cell; the dense component is fairly compact, but it encloses less dense areas continuous with the cytoplasm. Within the less dense areas, as well as at the periphery of the dense component, small (400–800 Å) oval or tubular vesicular structures are observed whose contents exhibit a positive reaction for glycoprotein in PA‐silver stained sections. When the spermatid nucleus begins to elongate, the chromatoid body takes the form of an arc around the axial filament proximal to the centriolar apparatus. Soon thereafter, the bulk of the chromatoid body condenses into a sphere of very dense filamentous material surrounded by a corona of enlarged glycoprotein‐containing vesicles. In the later stages of spermiogenesis, the chromatoid body migrates away from the nucleus and disintegrates by fragmentation. It is noted that the chromatoid body undergoes its major morphological changes, possibly indicative of its active phase, while located in the para‐centriolar region, at the time when the nucleus elongates, and the connecting piece and ring of the spermatid are formed.
Histology of the corpus luteum in the ewe: Changes during the estrous cycle and early pregnancy, and in response to some experimental treatments
Authors: Thwaites C. J. , Edey T. N.
Published: February 2005

A technique, developed for the objective histological evaluation of the corpus luteum of the sheep, was applied to normal cyclic and pregnant ewes as well as to ewes subjected to various experimental treatments. Gross histological regression of the corpus luteum progressed rapidly between days 15 and 17 of the estrous cycle. Similar regressive changes did not occur in pregnant ewes; up to day 40, the oldest stage studied, corpora lutea of early pregnancy were similar in appearance to those of mid‐cycle.

Stresses such as high environmental temperature and acute undernutrition, which may lead to embryo mortality, had no significant effect on corpus luteum histology. Exogenous progesterone slightly depressed the size and weight of the corpus luteum but was without significant effect on its histology. Exogenous cortisol, and more particularly corticotropin, were sometimes associated with marked histological regression of the corpus luteum, although in ewes treated with these hormones there was no significant reduction in embryo survival at the time of autopsy.

The observations do not support the suggestion that corpus luteum failure is a frequent cause of embryonic death in the ewe. The technique presented is considered sufficiently sensitive to detect quite small changes in the histological appearance of the corpus luteum, although the relationship of these changes to progesterone secretion is not known. However, the dramatic regression observed between days 15 and 17 of the estrous cycle fits the known pattern of progesterone secretion at this time.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. III. Intermediate, distal, and collecting segments of the ammocoete
Authors: Youson John H. , McMillan Donald B.
Published: February 2005

The presence of microvilli and well‐developed organelles in the cells of the non‐ciliated intermediate segment of the ammocoete nephron suggests that this is not simply a conducting tubule but may be involved in the formation of urine. This region more closely resembles the thin limb of the loop of Henle of mammals than the intermediate segment of lower vertebrates.

The distal segment consists of dark and light cells possessing varying amounts of glycogen, mitochondria, and smooth endoplasmic reticulum. Basal infoldings of the plasma membrane are lacking in the distal cells but wide intercellular spaces are present. Angular prismatic mitochondrial cristae are found within the glycogen‐rich cells of the intermediate and distal segments.

The collecting segment also possesses narrow intercellular spaces as well as an abundance of organelles, particularly smooth endoplasmic reticulum and mitochondria, suggesting that this region may also be involved in urine formation.
Morphological changes in mouse eggs due to aging in the fallopian tube
Authors: Szollosi Daniel
Published: February 2005

Morphological changes in mouse eggs due to aging become evident after the eggs have spent approximately 12 hours in the oviduct. The spindle rotates at first and is radially disposed. Later the entire spindle migrates to the center of the egg. In most eggs the spindle is maintained throughout the first 24 hours after ovulation. In some eggs a nucleus is reconstituted without formation of polar body II. Other eggs break into several cytoplasmic fragments but a nucleus is seen only in the largest fragment. The cortical granules lose their proximity to the cell membrane, migrate centrad and frequently swell. The cumulus cells and the cells of the corona radiata degenerate and/or disperse.
The relationship of the developing inner ear, subarcuate fossa and paraflocculus in the rat
Authors: McClure Theodore D. , Daron Garman H.
Published: February 2005

A study of the development of the subarcuate fossa and its relationships to the semicircular canals and to the paraflocculus was made in the rat. Specimens ranging from 12‐day embryos through 31 days after birth and adults were used for dissection and microscopic studies.

Two distinct steps are identified in the development of the fossa. First preceded by the differentiation of the semicircular canals, a primitive subarcuate fossa, which is completely filled with loose vascularized connective tissue, develops in the periotic capsule. Second, the primitive dura mater of the posterior cranial fossa evaginates into the area of the primitive fossa displacing the loose connective tissue contained therein, to form a laterally projecting cavity from the posterior cranial fossa, the definitive subarcuate fossa. Thus, the primitive subarcuate fossa appears passively as a product of the pattern of development of the periotic capsule.

The paraflocculus of the cerebellum does not appear to influence the development of the definitive subarcuate fossa since it secondarily occupies the area of the fossa. The pedunculated nature of the paraflocculus is associated with, and probably results from, the diameter of the ostium of the fossa being smaller than its greatest width.

A comparison is made of the development of the subarcuate fossa within the periotic capsule in the rat and man. In the adult rat a definitive subarcuate fossa is present, while in adult man only a rudimentary counterpart exists.
Vasculogenesis in the chick embryo. An ultrastructural study
Authors: Gonzalez‐Crussi Frank
Published: February 2005

The morphogenesis of the extra‐embryonic circulatory system of the chick was studied by light and electron microscopy, from precirculatory stages until the beginning of the definitive circulation. Early mesodermal migrations of prospective vasoformative cells and formation of blood islands take place with minimal morphologically expressed cytodifferentiation. The earliest mesodermal clusters are not syncytial. Formation of vascular lumina is not due to lysis of central cells. Undifferentiated mesenchyme possesses the capacity to establish complex junctional devices at points of contact with like cells. The first formed blood islands show intimate relationships with endoderm. The initial capillary network is sinusoidal in type, the endothelium being unsupported by a basement membrane. The major vitelline vessels acquire a more complex anatomy but the capillaries retain this simple pattern throughout the period studied. Several phases in the histogenesis of vitelline vessels are recognized, which could be correlated with the known progression of arterial pressure patterns. Continuing differentiation and mesenchymal investment of vascular walls, after stages 22–23 of Hamburger and Hamilton ('51), in correspondence with the last sustained pressure elevation, leads to completion of the adult vascular structure.
The fine structure of the peripheral nerve root sheath in the subarachnoid space in the rat and other laboratory animals
Authors: Haller Frederick R. , Low Frank N.
Published: February 2005

Spinal nerve roots from several laboratory animals (rat, mouse, dog, chinchilla) were fixed by perfusion with buffered aldehydes and prepared for electron microscopy. The fine structure of the root sheath possesses a common histologic organization wherever found. Its cellular and fibrous coverings are arranged in several lamellae which can be divided into two basic layers. The cytology of the outer layers resembles the characteristics of cells which line the subarachnoid space elsewhere (pia, arachnoid, arachnoid trabeculae, blood vessel adventitia). These cells adjacent to the subarachnoid space are arranged loosely and are in close association with extracellular connective tissues. The junctions between them appear to be intermittent, which would allow communication between the subarachnoid space and the intercellular spaces. The inner layers (adjacent to the endoneurium) are regularly arranged and are close to each other. Facing the endoneurium a boundary (basement) membrane is almost invariably associated with the basal cell layer. The inner cell layers are more nearly comparable to perineurium but, because of structural variations, are not readily classified. However, in its totality, the root sheath does not correspond histologically to pia, arachnoid or perineurium as they are found in their usual locations.
Tooth transplantation in the mouse. I. The use of procion dyes and tritiated proline in a study of syngeneic tooth germ transplantation
Authors: Klein Jan , Secosky Walter R. , Klein Dagmar
Published: February 2005

Tooth germs of first molars from four‐ to six‐day old mice were transplanted heterotopically into the connective tissue under the dorsal skin of adult syngeneic recipients. The rate of the transplants was studied by histologic staining, vital staining with procion dyes, and autoradiography. Together these methods provided the following picture of the development of the transplant. Extraction of the tooth germ severs its vascular connections and disturbs the nutritional environment of the tooth so that many cells undergo necrosis and degeneration. The resulting inflammatory response clears the transplant of necrotic tissue, leaving a fibrous pulp of low cellularity and an extensively disrupted odontoblastic layer; the enamel organ is reduced to only a few epithelial cells. In the second week following transplantation, however, the surviving cells start to proliferate and the tissues of the transplant begin to reorganize. Reorganization starts at the apical foramen and spreads to the rest of the tooth. The central pulp is penetrated by new blood vessels, its cellular content is reestablished, and its morphology returns to normal. Odontoblasts start producing dentin which at first is highly irregular and contains many cells (osteodentin). Later the dentin formation becomes more and more regular and the dentin assumes its normal tubular structure. New enamel is not formed at any time after transplantation. The cells of the enamel organ undergo squamous metaplasia and form epithelial cysts. Abortive root formation is observed but typical roots never develop. Rudiments of periodontal ligament develop rarely. The transplants are enclosed in a capsule of connective tissue.

It is concluded that the heterotopically transplanted tooth germs maintain their capability to recover, develop, and differentiate in syngeneic recipients. Although almost all of the developmental processes continue in the transplant after a period of adjustment, some of them are abortive.
Observations on the caudal end of the spinal cord
Authors: Pearson Anthony A. , Sauter Ronald W.
Published: February 2005

The 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

A 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

The 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

The 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

The 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

Tissue 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

The 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

This 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

Implantation 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

Electron 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

The 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

Several 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

Cyclical 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

Most 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

The 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.
Surface morphology of endocardial thrombus induced by a high‐fat diet
Authors: Maguire K. F. , Doran G. A.
Published: February 2005

Mice and rats fed a diet consisting of 25% by weight of polysaturated animal fat, developed endocardial thrombus after seven weeks. The surface appearance as seen with the scanning electron microscope is described.
The development of smooth‐surfaced endoplasmic reticulum in adrenal cortical cells of fetal guinea pigs
Authors: Black Virginia H.
Published: February 2005

In 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

The 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

Penetration 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.
Distribution of diazo‐positive (argentaffin) cells in the small intestine of rats of various ages
Authors: Josephson R. L. , Altmann G. G.
Published: February 2005

In unit lengths of longitudinally cut histological sections of the rat small intestine, the number of diazo‐positive argentaffin cells was determined along with the number of other epithelial cells. From these results, the frequency of argentaffin cells among the epithelial cells was calculated. The number, as well as the frequency, was maximal in the proximal duodenum and progressively decreased to a minimum in the mid‐intestine. Thereafter, it increased progressively caudally to reach a second maximum in the terminal ileum. The frequency in the terminal ileum was almost as high as in the proximal duodenum. When calculated for the duodenum of various age groups, it decreased from eight to two argentaffin cells per 1000 epithelial cells from newborn to adult ages respectively. It was calculated furthermore that the total number of diazo‐positive argentaffin cells in the rat small intestine should be around six million. Considering that the argentaffin cells are renewed about every four days (Ferreira and Leblond, ′71), about 1.5 million of them should be formed as well as exfoliated daily.

The cells in the villi were stained more intensely than in the crypts, indicating that the argentaffin cells accumulate granules as they migrate from the crypts toward the villus tips, where indeed, intensely stained exfoliating argentaffin cells were occasionally observed. It is suggested that the exfoliation of argentaffin cells full of granules may be a mode of secretion for 5‐hydroxytryptamine into the intestinal lumen.
Fine structural observations on the development of the sperm head in the mouse
Authors: Dooher G. B. , Bennett D.
Published: February 2005

The stages of spermiogenesis in the mouse were investigated with the electron microscope with emphasis on morphogenesis of the sperm head. The nucleus undergoes chromosomal condensation in the concluding stages of spermiogenesis. Chromosomal condensation proceeds centrifugally and in a caudal direction, beginning in the anterior third of the nucleus. It is proposed that chromosomes establish attachments to the nuclear envelope prior to the onset of chromosomal condensation and that this arrangement of the chromosomes is an orderly one which facilitates the condensation process.