bluuebunny/crossref_metadata_2025_split huggingface dataset:
Myogenic cell formation in regenerating rat skeletal muscle injured by mincing II. An autoradiographic study
Authors: Snow Mikel H. 
Published: February 2005

AbstractMyonuclei and satellite cell nuclei were differentially labelled with 3H‐thymidine in uninjured skeletal muscle of young rats and then traced autoradiographically at intervals after mincing the radioactive hindlimb muscles to determine the source of regenerating presumptive myoblasts. Labelled nuclei were detected by light microscopic examination of 1‐m̈ thick autoradiographs and identified by electron microscopic examination of an adjacent section. Repeated injections of 3H‐thymidine during fetal and neonatal development, followed by a 4‐ to 5‐week maturation period, resulted in labelling of 20% of the myonuclei. Satellite cells were not observed to be labelled in this series. Eight to sixteen hours after mincing, 20% of the pyknotic myonuclei were labelled, whereas none of the regenerating presumptive myoblasts appeared labelled. A single injection of 3H‐thymidine administered to 18‐day‐old rats, followed by sacrifice within ten hours, resulted in labelling of 23% of the satellite cell nuclei. Myonuclei were not observed to be labelled in this series. Eight to sixteen hours after mincing, silver grains were detected over both pyknotic and regenerating cell nuclei. These experiments indicate that many satellite cells survive muscle injury and transplantation to become regenerating myogenic cells at a time when most, if not all, myonuclei are undergoing pyknosis.
Neurohistochemical evidence supporting an absence of adrenergic and cholinergic innervation in the human placenta and umbilical cord
Authors: Reilly Frank D. , Russell Paul T. 
Published: February 2005

AbstractNeurohistochemical techniques were used to determine the distribution of adrenergic and cholinergic nerves in the human placenta and the umbilical cord adjacent to the chorion. These morphologic studies demonstrate the absence of neural elements in these sites. The significance of these findings to the placental innervation controversy is discussed.
The origin, migration and fine morphology of human primordial germ cells
Authors: Fujimoto Toyoaki , Miyayama Yukihiko , Fuyuta Masatoshi 
Published: February 2005

AbstractHuman primordial germ cells (PGCs) were observed ultrastructurally in stages from their endodermal to gonadal locations. Primitive PGCs in the hind‐gut epithelium of the 4‐week embryo, were recognized as well demarcated cells from the neighboring cells. At the time of separation, the basal lamina of the epithelium was broken, then, through the gap so opened, the PGCs started to escape into the outer mesenchyme. In embryos at five weeks, PGCs were in the migration stage, and were found in the dorsal mesentery, at the coelomic angle and in the forming germinal ridge. In embryos at six weeks or later, almost all PGCs were accumulated in the gonad. The PGC was characterized by its large size and the large and round nucleus with conspicuous nucleolus, and by the presence of abundant glycogen particles and a considerable number of lipid droplets in the cytoplasm. Alkaline phosphatase activity was demonstrated selectively on the plasma membrane of the PGC. The shape of PGC was irregular, often had pseudopodia in PGCs in the separation and migration stages, suggesting their amoeboid movement in vivo, but was generally round or elliptic in PGCs in the settlement stage. The PGC was usually surrounded by and in close association with adjacent somatic cells.
Immunological and morphological effects of vasectomy in the rabbit
Authors: Alexander Nancy J. , Tung Kenneth S. K. 
Published: February 2005

AbstractHalf of the rabbits developed antisperm antibodies (measured by either indirect immunofluorescence or sperm immobilization tests) after either a unilateral or bilateral vasectomy. The raised antibody levels, particularly six months or longer after vasectomy, often accompanied patchy orchitis. Seminiferous tubules from such animals exhibited sloughed, multinucleated, and immature germinal cells which were engulfed by phagocytic cells. Mononuclear infiltrates were occasionally present. The basal lamina infolded and thickened by means of supernumerary layers and appeared to be endocytosed by cells of the seminiferous tubules. Four months after vasectomy, numerous phagocytic cells were seen to migrate through the intact epithelium of zone 1 in the caput epididymidis, and were particularly prevalent in animals that exhibited testicular damage. These macrophages may serve to present sperm antigens to lymphocytes.
The carotid and orbital retia of the pronghorn, deer and elk
Authors: Carlton Candy , McKean Tom 
Published: February 2005

AbstractSelective cooling of the brain during heat stress has been shown by others to be a method of temperature regulation for mammals having carotid retia. This study describes the macroscopic anatomy of the cranial circulation of elk, deer and pronghorn as it might pertain to the functioning of carotid retia and orbital retia as heat exchangers. Emphasis has been placed on describing the source of venous blood bathing these retia, for blood flow from these sources to the ophthalmic plexus and cavernous sinus will establish a temperature difference between arterial and venous blood, and influence the magnitude of this gradient. The pronghorn possesses a carotid rete with greater density and smaller calibre vessels overall and a more highly vascular orbital rete compared to the elk and the deer. These anatomical differences may indicate differences in efficiency of heat exchange in the retia. It is suggested that the orbital rete is anatomically in a position to moderate extremes of temperature by cooling arterial blood flowing to neural tissue of the eye and olfactory bulbs.
The number of nuclei in adult rat muscles with special reference to satellite cells
Authors: Schmalbruch H. , Hellhammer U. 
Published: February 2005

AbstractThe number and the size of different populations of nuclei were studied in skeletal muscles and in the diaphragm of male Wistar rats of 200‐250 g weight. Nuclei on cross‐sections were counted and classified by electron microscopy, their incidence was corrected for their different lengths, and the number of nuclei per mm3 of muscle was determined by light microscopy. The total number of nuclei per mm3 was 5 · 104 in the superficial part of the anterior tibial muscle, it was 10 · 104 in the soleus, and it was 15 · 104 in the diaphragm. Half of the nuclei were localized inside muscle fibres. The incidence of satellite cell nuclei on cross sections was 4% of muscle nuclei in the anterior tibial muscle, and 8% in soleus and diaphragm. The number of satellite cells per mm3 muscle were 900, 4,900, and 5,300 in these muscles.More than half of the satellite cells were closely associated with a capillary. In the anterior tibial muscle, and in 1‐μm sections no satellite cells could be identified by light microscopy. In the soleus muscle and in the diaphragm, satellite cells were more rich in cytoplasm and many were visible in the light microscope.
Membrane alterations during cornification of mammalian squamous epithelia: A freeze‐fracture, tracer, and thin‐section study
Authors: Elias Peter M. , McNutt N. Scott , Friend Daniel S. 
Published: February 2005

AbstractTight junctions (zonulae occludentes) create a pericellular barrier to the diffusion of large molecules in non‐keratinizing mammalian epithelia. However, in cornifying epithelia such as the epidermis, the importance of tight‐junctional elements versus secreted intercellular lipid for barrier function is uncertain. In an attempt to resolve this question, we compared membrane structure in the stratum granulosum and stratum corneum of epidermis, esophagus, and vagina of newborn and adult humans and mice under both normal and various experimental conditions. We incubated pieces of epidermis in organ culture and infused tissues with lanthanum or horseradish peroxidase in vivo and in vitro. All were processed for electron microscopy of freeze‐fracture replicas or thin sections. Lanthanum seeped outward to the stratum granulosum in all tissues examined‐further apical migration was halted by lamellar‐body contents in skin. A similar pattern of intercellular lamellar lipid deposition and membrane structure occurred in all epithelia studied. Freeze‐fracture replicas of these obstructive regions revealed occasional, incomplete junctional strands (particularly in moist epithelia) and abundant lamellar material, but complete zonulae occludentes were never encountered. A possible relationship between moisture and tight junction formation was further suggested by organ culture experiments during which brief incubations stimulated an increase in the number of junctional strands and diminished numbers of lamellar bodies. We conclude that, in the epithelia studied, the deposition of secreted lamellar body contents forms the barrier to water‐soluble tracer loss: tight‐junctional elements are either absent or too fragmentary to constitute an effective barrier.
Closure of the neural tube in the cephalic region of the mouse embryo
Authors: Geelen Jan A. G. , Langman Jan 
Published: February 2005

AbstractIn mouse embryos varying in age from 9 to 20 somites the first closure of the neural groove was found to occur in the cervical region. The fusion process gradually proceedéd in rhombencephalic direction until it reached a level just caudal to the otic pits. Shortly afterwards the prosencephalic walls fused together independent of the rhombencephalic closure. This prosencephalic fusion process proceeded caudally in the direction of the mesencephalon until it reached the rostral portion of the rhombencephalon. In this region the two independent fusion processes met each other. In addition the prosencephalic fusion proceeded in rostral direction toward the anterior neuropore, which was the last part of the brain vesicles to close. Hence, the closure of the brain vesicles is not a zipper‐like process proceeding from the rhombencephalon to the anterior neuropore, but occurs at several places at the same time and proceeds in a rostral as well as in a caudal direction.At the cellular level considerable differences in the fusion process were found to exist between the various brain vesicles. In the rhombencephalon the first bridge between the two opposing walls was formed by surface ectoderm and neural crest cells. In the mesencephalon single squamous ectoderm and a few neuroepithelial cells established the first contact, whereas in the prosencephalon the apical ends of several neuroepithelial cells fused together to overbridge the gap between the opposing walls. The surface ectoderm cells subsequently covered the neuroepithelial bridge. In the region of the anterior neuropore the fusion was similar to that between the prosencephalic walls, the only difference being that in the anterior neuropore area many more darkly stained particles indicating cell degeneration, were present than in the prosencephalon. It is thus concluded that considerable differences exist in the fusion of the neural walls between the various brain vesicles.
Lipids and cholesterol clefts in the lacunar cells of snake skin
Authors: Jackson Morris K. , Sharawy Mohamed 
Published: February 2005

AbstractThe lacunar cell layer in rat snake epidermis contains many characteristic intracellular vacuoles. The lipid nature of these large round vacuoles was demonstrated by histochemical and ultrastructural investigations. Rhomboid‐shaped clefts, similar to cholesterol ester clefts, were observed in proximity to the vacuoles.
Ultrastructural characterization of nuage in spermatocytes of the rat testis
Authors: Russell Lonnie , Frank Beryn 
Published: February 2005

AbstractAt least six different types of nuage, as judged by morphological appearance, were found in spermatocytes of the adult rat testis. These were characterized by form, distribution, and association with other organelles. The appearance (with time) and the dissociation of some nuage types were recorded in conjunction with other events of the spermatogenic cycle. The data indicate that all types of nuage behave in a dynamic way. Especially interesting were the findings concerning the chromatoid body. This structure was first observed in mid‐pachytene spermatocytes. By late diplotene and during the first meiotic division, it had lost its prominence such that its eventual fate could not be determined. Large dense (0.5 μm) bodies appeared de novo in the cytoplasm of newly formed secondary spermatocytes. They were seen scattered throughout the cell and in association with mitochondria. With time these bodies appeared to coalesce to form the large definitive chromatoid of a type similar to that known to be present throughout most of the remainder of spermiogenesis.
Acetylcholinesterase activity of primary sensory neurons and dorsal root fibers in the cat
Authors: McNeill M. Evelyn , Norvell John E. 
Published: February 2005

AbstractDorsal roots and spinal ganglion cells of adult cats were studied for acetylcholinesterase (AChE) content. An inverse correlation exists between cell size and AChE activity; large neurons are AChE‐negative whereas small ones are intensely AChE‐positive. A few AChE‐positive fibers were demonstrated in the dorsal roots. A possible correlation between AChE activity and substance P content of primary sensory neurons is discussed.
Distribution of surface coat material on fusing neural folds of mouse embryos during neurulation
Authors: Sadler T. W. 
Published: February 2005

AbstractFusing and non‐fusing regions of neural folds from mouse embryos were examined during neurulation for the distribution of extracellular macromolecules (surface coats) prior to and at the time of closure. Ruthenium red staining of 10th day ICR/DUB mouse embryos was used to detect the distribution of surface coat material. Light microscopic examination of fusing and non‐fusing regions in the midbrain, hindbrain, and spinal cord showed a consistent increase in ruthenium red positive material immediately prior to closure. Heavy deposits of positive staining material were present along apical neural fold borders and overlying ectoderm cells. This staining pattern was consistent in the three regions examined, but the pattern of initial contact between opposing neural folds differed. In mid‐ and hindbrain areas contact was initiated by overlying ectoderm, whereas in spinal cord regions contact was first established by neuroepithelial cells. Once contact between opposing neural folds was initiated a decrease in stainable material was observed.
Satellite cells of rat muscles as studied by freeze‐fracturing
Authors: Schmalbruch Henning 
Published: February 2005

AbstractSatellite cells in rat muscles were studied by freeze‐fracturing. They were found not to be fusiform but to have several narrow projections embedded in grooves of the muscle fibre membrane. Short projections of the muscle fibre covering the outer face of the satellite cells were observed as well. In the P‐face of the cell membrane of satellite cells, membrane particles and caveolae were less frequently seen than in the P‐face of the muscle membrane. Thus the surface of the satellite cells looked more smooth than that of the muscle fibres. Junctions between muscle fibre and satellite cell were not found. The presence of cytoplasmic extensions of satellite cells may suggest that these cells are motile.
Effects of complete tail bud extirpation on early development of the posterior region of the chick embryo
Authors: Schoenwolf Gary C. 
Published: February 2005

AbstractThe tail bud was completely extirpated down to the yolk from 65 embryos at stages 13‐17 to determine whether the posterior part of the noto‐chord originates from the tail bud or from a more anterior region (i.e., prospective notochordal region). About 40% of the 44 surviving embryos developed near‐normal tails, con̈taining a localized defective region beginning near the base of the tail and extending a short distance posteriorly, about 15% developed truncated, cone‐shaped tails, containing a defective region beginning near the base of the tail and extending towards the tip, and about 45% developed short, ventral tail remnants, containing a localized defective region beginning near the base of the tail and extending a short distance posteriorly. The tail was absent in only one embryo. These differences were probably due primarily to variation in the amount of healing and regeneration that occurred, and were independent of the stage at which the operation took place. The tail region has a tremendous capacity for regeneration since a near‐normal tail frequently developed. The location of the beginning of the defective region near the base of the tail suggests that the tail bud primarily gives rise to tail structures. All embryos had neural tube defects, about 30% developed large, midline somites within the defective region, and about 25% developed an ourenteric outgrowth. The notochord was always normal within the defective region. These results are consistent with the view that the tail bud contributes cells to the posterior part of the neural tube, but not to the notochord.
The site of collagen resorption in the periodontal ligament of the rodent molar
Authors: Beertsen Wouter , Brekelmans Margot , Everts Vincent 
Published: February 2005

AbstractIn an attempt to determine the pattern of collagen phagocy‐tosis by fibroblasts in the periodontal ligament, a stereologic investigation of the mesial root of the maxillary first molar of the rat was undertaken. The distribution of fibroblasts containing intracellular collagen fibrils was studied at the electron microscope level in the periodontal ligament along resorbing and non‐resorbing surfaces of the alveolar wall. It appeared that fibroblasts with collagen‐containing vacuoles were more or less randomly distributed across the width of the periodontal ligament. No major differences were observed among the alveolar, cemental and intermediate zones of the ligament. However, local variations in the occurrence of cells containing intracellular collagen fibrils may occur. A relatively high concentration of ingested collagen fibrils was seen in fibroblasts located in the direct vicinity of osteoclasts, but not in the vicinity of osteoblasts. These observations suggest that remodelling of collagen is even‐ly distributed throughout the ligament, but may be influenced by local circumstances, such as the occurrence of bone resorption.
Attrition of the human leydig cell population with advancing age
Authors: Kaler Lawrence W. , Neaves William B. 
Published: February 2005

AbstractExisting evidence suggests that the aging human male experiences a gradual decline in testosterone production, a phenomenon that should be reflected in the Leydig cell population of the testis. It has been pro‐posed that Leydig cells diminish in number with increasing age, but conflicting claims characterize reports on this topic. We have reinvestigated this possibility by histometric analysis of perfused testes from 25 men ranging from 18 to 87 years of age. Average single Leydig cell volume (2,943 ± 623 μm3, X S. D.) did not change significantly with increasing age (r = 0.24, P > 0.2), suggesting that surviving cells remain active. Total testis weight (43.5 ± 13.9 g) also did not change with age (r = 0.04, P > 0.5). However, both total Leydig cell volume and the absolute number of Leydig cells per individual decreased significantly as functions of age (r = −0.71, P < 0.002, and r = −0.61, P < 0.005, respectively). Analysis of the relationship between these two parameters indicates that the total volume of Leydig cell cytoplasm contained within the human testis is determined by the number of cells present. Our results show that a pair of young adult testes endowed with more than 700 million Leydig cells at 20 years of age may be expected to undergo an attrition rate of approximately 80 million cells per subsequent decade of life. Thus, Leydig cell attrition is an important correlate of declining androgen status in aging men.
Morphological and quantitative analysis of spermatogonia in mouse testes using whole mounted seminiferous tubules. I. The normal testes
Authors: Huckins C. , Oakberg E. F. 
Published: February 2005

AbstractThe spermatogonial populations in ten normal adult mice were analyzed using whole mounted seminiferous tubules. The undifferentiated A spermatogonia as well as the six generations of differentiating spermatogonia were clearly identifiable on whole mounts. Description plus quantitation of these cell types revealed that they behaved in essentially the same manner as their counterparts in the rat. Single undifferentiated A cells were classified as type A stem cell spermatogonia. They were distributed throughout the seminiferous epithelium, and by periodic mitoses, maintained their stock and furnished cells which would eventually differentiate. Although initially resembling the As spermatogonia, the progeny which were destined to differentiate were classified as type Aalv spermatogonia because they were linked by cytoplas‐mic bridges, and because they usually underwent one or more synchronous mitotic divisions to form short chains of aligned cells. Ultimately, division of Aal cells were no longer seen, and the cells appeared to gradually acquire the typical morphological characteristics of A1 spermatogonia; these continued to differentiate according to the well‐established pattern. It was concluded that the cyclic production of cohorts of A1 cells in this manner would ensure a continual supply of spermatogonia for differentiation.
Characterization of Sertoli cell‐germ cell junctional specializations in dissociated testicular cells
Authors: Romrell Lynn J. , Ross Michael H. 
Published: February 2005

AbstractTo further characterize Sertoli cell‐germ cell junctional specializations seminiferous tubules from sexually mature Sprague‐Dawley rats were dissociated by enzymatic and mechanical methods. Ultrastructural analysis of cell suspensions prepared by incubation in collagenase alone or by mechanical methods revealed that spermatids remained attached to Sertoli cells or Sertoli cell fragments. Such cellular associations were found only between Sertoli cell fragments and spermatids in which the developing acrosome had made contact with the plasma membrane (step 8 and subsequent steps of spermiogenesis). Furthermore, the fragments were confined to that region of the plasma membrane over the acrosome. The Sertoli cell half of this adhesive site displayed the typical elements of Sertoli cell junctions, filamentous bundles and associated cisterna of endoplasmic reticulum, in apposition to the spermatids. The spermatids demonstrated no surface specializations at the attachment sites. In contrast, in cell suspensions prepared with trypsin, spermatids were free of attachments to Sertoli cells or their fragments. These results demonstrate that: (1) the junctions act to bind cells together, (2) adhesive type contact is established between Sertoli cells and spermatids at step 8 and subsequent steps of spermiogenesis, (3) contact is restricted to the spermatid plasma membrane over the acrosome, and (4) spermatids can be freed from the junctional specializations by treatment with trypsin.
A fine structural analysis of the myelin sheath in rat spinal roots
Authors: Coggeshall Richard E. 
Published: February 2005

AbstractThe present study is concerned with the fine structure of the myelin sheath in rat and monkey spinal roots. Pictures are obtained that show that the intraperiod gap of the myelin sheath is continuous and opens into both the internal and external mesaxons, which in turn open into the periaxonal and endoneurial extracellular spaces. These results are compatible with the idea that the intraperiod gap is a cleft that traverses the thickness of the myelin sheath and links the periaxonal and endoneurial extracellular spaces.