bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preimplantation development, fate of the zona pellucida, and observations on the glycogen‐rich oviduct of the little bulldog bat, Noctilio albiventris
Authors: Rasweiler John J. 
Published: February 2005

AbstractThe reproductive biology of Noctilio albiventris was investigated histologically in 112 females collected at the start of their synchronized breeding season during two different sampling years in the Cauca Valley of Colombia. Both ovaries were functional, but the animals were generally observed to be monovular. Embryonic development in the oviduct was found to proceed to blastocyst formation and loss of the zona pellucida. In 22 animals the discarded zona had been left behind in the oviduct upon passage of the embryo into the uterus and was still undissolved at the time of amniogenesis, the latest stage examined. The zonae which had passed into the uterus with the embryos often exhibited signs of dissolution. Most of the early blastocysts were morphologically distinctive, lacking a typical inner cell mass and being instead largely bilaminar. Degenerating ova from previous ovulations were found in the oviducts of two pregnant bats, suggesting that Noctilio may be another species in which the embryo stimulates its own escape from the oviduct. During tubal passage of the embryo the secretory cells of the oviductal ampulla and isthmus exhibited a transient engorgement with glycogen, particularly on the side ipsilateral to the new corpus luteum.
Development of the metatarsophalangeal joint of the chick embryo: Morphological, ultrastructural and histochemical studies
Authors: Mitrovic Dragoslav R. 
Published: February 2005

AbstractThe histogenesis and mechanism of joint clefting of the developing chick embryo up to the fifteenth day of incubation have been studied morphologally, ultrastructurally, and by histochemical methods. Cell degenration was consistently noted 24 hours after differentiation of the joint tissue, and it is postulated that this early cell necrosis might account for the loosening of the medial part of articular mesenchyme (interzone) leading to differentiation of a three‐layered embryonic joint. At the time of joint clefting degenerative cells were also seen in the peripheral parts of the developing articular cavity. In somes cases clefting was immediately preceded and/or accompanied by the appearance of elongated, basophilic and electron‐opaque cells closely arranged along the zone of tissue cleavage. These cells were thought to be implicated in some way in the clefting process and later to constitute a surface cell layer of articular cartilage. In addition to these observations clear morphological and histo‐autoradiographic evidence was found for the presence of an organic component, presumably mucopolysaccharide, in the primitive synovial fluid. Fluid secretion might also account for tissue cleavage at the sites of its accumulation.The data reported here suggest that joint cavity formation results from a combination of both intrinsic, genetically expressed and extrinsic mechanical factors acting synchronously.
The role of movement in the development of a digital flexor tendon
Authors: Beckham Cassandra , Dimond Richard , Greenlee Theodore K. 
Published: February 2005

AbstractD‐tubocurarine was injected into the air sac of 8‐day chick embryos to prevent movement of the digits of the hind limb. The embryos were paralyzed from the tenth to the eighteenth day, when the experiment was terminated. The immobilization of the flexor digitorum profundus tendons in the tarsus resulted in a loss of specialized structures around and on this tendon, as determined by light and electron microscopy. Specialized areas observed in the normal chick (synovial cavity, fibrocartilaginous area, and elastic vinculum) failed to form, as a result of the paralysis of the digit.Several authors have shown previously that movement is a requirement for the molding and maintenance of joint cavities in vivo, in ovo and in vitro (see text for references). We have shown that movement of the tendon is required to produce a functional tendon apparatus in the embryo and predict that movement is also required for regeneration after injury.
Endothelial cell membrane: Differences in the density of intramembranous particles between tissue‐ and blood‐fronts revealed by freeze‐fracture
Authors: Shaklai Matityahu , Tavassoli Mehdi 
Published: February 2005

AbstractSignificantly higher density of intramembranous particles (IMP) was noted in the endothelial plasma membrane facing the blood‐front compared to the tissue‐front. The difference may be related to the function of the vascular endothelium as an active barrier between the blood and the tissue.
An ultrastructural study of developing extracellular matrix in vitelline blood vessels of the early chick embryo
Authors: Murphy Mark E. , Carlson Edward C. 
Published: February 2005

AbstractThis investigation was designed to describe the morphological events in embryonic development of peripheral blood vessels (vasculogenesis) and to relate this process to the appearance of extracellular matrix (ECM) during growth and maturation of these tissues. Extraembryonic vitelline vessels of the early chick embryo were chosen for this study and light, transmission, and scanning electron microscopy were carried out on vessels excised from chick embryos (Hamburger‐Hamilton stages 8 through 23). Our data show that early (stage 10) vessels are composed of two distinct epithelial layers, an inner layer of presumptive endothelium surrounded by a layer of splanchnopleuric mesoderm. During development, the inner layer gives rise to mature vascular endothelium while splanchnopleuric mesoderm differentiates to form primitive vascular smooth muscle. Ultrastructural studies show the presence of collagen and basal lamina in the extracellular space between these two layers during initiation of endothelial and smooth muscle cytodifferentiation. Furthermore, ruthenium red‐positive material is present on basal surfaces of developing vascular endothelium at this time, indicating possible glycosaminoglycans (GAG) or other polyanionic components of the ECM. These data suggest that the sequential production of basal lamina, collagen(s), and/or GAG's by developing peripheral vessel wall epithelia may be critical to their final differentiation.
The effect of cytochalasin B on the neuroepithelial cells of the mouse embryo
Authors: Webster William , Langman Jan 
Published: February 2005

AbstractEleven‐day mouse embryos were cultured in a medium containing cytochalasin B (10 μg/ml) to examine the effect of the drug on the developing CNS. The embryos were exposed to the drug for two hours. After culturing, the embryos were prepared for light and electron microscopy and the neuroepithelium of the cerebral vesicles was examined. The following abnormalities were noted in the cytochalasin B‐treated embryos: (1) mitotic figures were situated in the middle of the neuroepithelial layer instead of on the lumen, indicating that premitotic nuclear migration had been prevented; (2) binucleate cells were found in the neuroepithelial layer, indicating that cytochalasin B does not interfere with mitosis but prevents cytokinesis; (3) the microfilaments usually seen in the apex of the neuroepithelial cells were disrupted and formed an amorphous mass of filamentous material; (4) some neuroepithelial cells were free in the lumen, whereas others protruded into the ventricle but appeared to remain attached to the internal limiting border by their junctional complexes; and (5) in some regions the neuroepithelial cells had broken away from their end‐feet at the basal lamina. These morphological changes were associated with a change in the internal limiting boundary from concave to convex and vacuolation of the external processes of the cells. The relationship between cytochalasin B, microfilaments and these morphological changes is discussed.
Influence of abdominal temperature on epididymal function in the rat and rabbit
Authors: Bedford J. Michael 
Published: February 2005

AbstractThe effects of body temperature on sperm maturation and sperm storage in the epididymis have been studied in rats and rabbits by surgical reflection of the epididymis into the abdomen without disturbing its continuity with a functional scrotal testis. Rats so treated remained fertile during a period of 13 months, as judged by a sequence of normal litters born to their female cage mates, and cryptepididymal rabbits remained fertile for four months or more according to the individual, as evidenced by eggs fertilized and litters born after artificial insemination or natural mating. By contrast, spermatozoa confined by ligatures within an abdominal cauda epididymidis never retain their potential for motility for more than a brief period (5 days in rat; 8–10 days in rabbit), as compared with several weeks in contra‐lateral scrotal controls. It is uncertain whether their early death at abdominal temperatures resulted primarily from a suppressive effect of the temperature on the spermatozoa themselves, or on the caudal epithelium.Because of an increasing presence of apparently immature spermatozoa in the ejaculate of the first cryptepididymal rabbit between 7 and 11 months postoperatively, the rate of sperm transport through the epididymis of seven cryptepididymal rabbits was estimated by labelling with tritiated thymidine. As judged by the time of appearance of labelled spermatozoa in the ejaculate, transposition of the rabbit epididymis to the abdomen ultimately causes a progressive increase in the rate of sperm transport through it from a normal of nine days to two to five days in the cryptepididymal state.Thus, although maturation may eventually be compromised to some degree because of an increased rate of sperm passage, and sperm storage is inhibited, abdominal temperature apparently does not alter the essential biochemical nature of the epididymal milieu required for maturation. These results are reviewed in light of the suggestion (Bedford, '78) that the cauda epididymidis has been the prime mover in scrotal evolution.
Cytodifferentiation of secretory cells in the sublingual gland of the prenatal rat: A histological, histochemical and ultrastructura study
Authors: Redman Robert S. , Ball William D. 
Published: February 2005

AbstractSublingual and submandibular glands were prepared for light and electron microscopy, and for histochemical staining with periodic acid‐Schiff (PAS), Alcian Blue (AB) or both (AB‐PAS). Between 15 and 17 days post‐conception, the sublingual gland undergoes active morphogenesis from a single, solid bud into a branched glandular tree. At 18 days the first overt signs of secretory differentiation appear in the formation of cells with three kinds of secretion granules; that is, electron‐dense serous granules, empty‐looking mucous granules with fine thread‐like substructures, and granules which have the general appearance of mucous granules but also contain an internal, electron‐dense core (“mixed” granules). During the period from 18 to 20 days, all three types of granulated cells increase in number, with mucous cells predominating, and they all border directly on the acinar lumina, in seemingly random combinations in different acini. This diversity is reflected in the histochemical staining, since most acini and cells are both PAS‐ and AB‐positive, but a substantial minority stain only with PAS, indicating that they contain serous granules. By comparison, all secretory cells in the submandibular gland stain with PAS but not with AB after the initial appearance of secretory granules at 18 days. From 20 days to birth (at 22 days), the cells with mixed granules disappear, while the cells with serous granules become fewer in number and displaced to the peripheral outpocketings of the acini. As a result of these changes, the general organization in the newborn is similar to that in the adult, i.e., purely mucous acini with serous demilunes.
The structure and innervation of cat knee menisci, and their relation to a “sensory hypothesis” of meniscal function
Authors: O'Connor Brian L. , McConnaughey J. Scott 
Published: February 2005

AbstractPrevious work on dog knee menisci demonstrated structural differences between the meniscal horns and the meniscal bodies (O'Connor, 1976). Of particular interest was the observation that the meniscal horns possessed an abundant blood and nerve supply, while the meniscal bodies did not. The presence of nerves in the meniscal horns prompted the speculation that menisci might perform a sensory function.The present study was undertaken in order to establish whether or not similar regional differences existed in cat knee menisci, structures previously believed to lack a corpuscular mechanoreceptor system (Freeman and Wyke, 1967).Differences between the meniscal horns and meniscal bodies similar to those reported in the dog were found to characterize cat knee menisci. In particular, the meniscal horns possessed a rich neurovascular supply, while the meniscal bodies did not. Most important, at least two morphologically different mechanoreceptors were identified in the meniscal horns, but none were identified in the meniscal bodies.
Immunocytochemical localization of renin in the submandibular gland of the mouse during postnatal development
Authors: Gresik E. W. , Michelakis A. , Barka T. 
Published: February 2005

AbstractThe localization of renin in the developing mouse submandibular gland was studied immunocytochemically using the unlabelled antibody‐enzyme method of Sternberger (1974). Bouin‐fixed submandibular glands of mice of both sexes were examined at 5‐day‐intervals from birth (day 0) to 50 days of age. At all stages studied, only granular convoluted tubule (GCT) cells stained immunocytochemically for renin; such cells were first seen in glands of 30‐day‐old males and of 30‐day‐old females. The size and number of renin‐containing GCT cells increased rapidly in males, attaining adult status by 50 days of age. In females, differentiation of GCT cells immunoreactive for renin was slower and less regular than in males, and at 50 days of age the GCT segment had not yet reached adult conditions with respect to the distribution of renin. Renin appears in GCT cells at later ages than other GCT cell products (e.g., EGF and amylase), suggesting the existence of independent developmental control for the expression of various biologically active substances in the GCTs.
Demonstration of neurosecretory substance in previosly scanned specimens: Adaptation of the gomori aldehyde‐fuchsin method for correlative SEM/TEM/LM histochemistry
Authors: Coates P. W. , Teh E. C. 
Published: February 2005

AbstractThe Gomori aldehyde‐fuchsin (AF) method for selective staining of neurosecretory substance (NSS) has been adapted to tissue previously prepared for both scanning and transmission electron microscopy (SEM/TEM). The procedure results in precise correlation of light microscopic (LM) histochemistry with SEM/TEM of the same tissue.
Shunting in intracranial microvasculature demonstrated by sem of corrosion‐casts
Authors: Anderson Bettina G. , Anderson Wesley D. 
Published: February 2005

AbstractThe use of methyl methacrylate corrosion‐casts has made it possible to examine the intracranial microvasculature on a three‐dimensional scale with the scanning electron microscope. By this means we have compared regions of four cerebral and cerebellar arteries among three domestic animal species. The results of this study suggest that there are from one to three different levels of interarteriolar anastomosis between branches of the same or adjacent vessels. In the horse and ox anastomoses were demonstrated (1) at the level of the precapillary arterioles, (2) along the arterioles, and (3) between small pial arteries. In the dog only the first‐named anastomoses were evident in this study. These morphological characteristics may explain, in part, the shunting mechanism by which hypoxia may be reduced among intracranial capillary networks.
The effect of lanthanum on the nexus of the anterior byssus retractor muscle of Mytilus edulis L.
Authors: Brink Peter R. , Kensler Robert W. , Dewey Maynard M. 
Published: February 2005

AbstractThe nexus of the anterior byssus retractor muscle (ABRM) of Mytilus has been observed with freeze‐fracture techniques. Pits appear in the EF face and particles in the PF face, designating it as an A‐type nexus. Under control conditions (lanthanum‐free) the center‐to‐center spacing of pits and particles ranged from 14.0 nm to 15.5 nm. When lanthanum chloride (5 mM) was used in incubation media before fixation and glycerination, marked changes in the nexal membrane were observed. These changes involved close packing and long‐range ordering of pits in the EF face, as shown by optical diffraction. In the presence of lanthanum the center‐to‐center spacing of the pits was 11.7 nm, while the particles remained at a spacing of 15.0 nm. From this we conclude that specific agents can alter the array of pits and particles in a nexus (gap junction).
Microfilaments, the smooth endoplasmic reticulum and synaptic ribbon fields in the pinealocytes of the baboon (Papio ursinus)
Authors: Theron J. J. , Biagio R. , Meyer A. C. , Boekkooi S. 
Published: February 2005

AbstractMicrofilaments (MF, 5–8 nm in diameter) are a prominent feature of the pinealocyte cytoplasm of baboons (Papio ursinus) kept under controlled lighting conditions. MF occurred as a filamentous network in these cells during the light phase of the diurnal light‐dark cycle, while a close structural association was noted between MF and the membranes of the smooth endoplasmic reticulum (SER). This association was especially evident during the dark period. Increased numbers of single synaptic ribbons (SR, vesicle‐crowned rodlets), together with large aggregations of SR, i.e., ribbon fields (RF), were seen in the pinealocyte cytoplasm of baboons killed during the dark phase. It is suggested that the vesicles of RF may arise from those of the SER and that MF may play a role in the movement of SER‐vesicles to those areas of the cytoplasm where new RF are being formed.
Retinal development in the lamprey (Petromyzon marinus L.): Premetamorphic ammocoete eye
Authors: Dickson D. Howard , Collard Tom R. 
Published: February 2005

AbstractDevelopment of the retina of the ammocoete begins early in embryogenesis, with the formation of the optic vesicle, but development of the rudimentary eye is suspended and remains arrested during larval life. Prior to the onset of metamorphosis, the retina of the ammocoete is completely undifferentiated, with the exception of a small area (Zone II) surrounding the optic nerve head, where all of the adult retinal layers are found. The photoreceptors in this area have developed to include synaptic contacts as well as inner and outer segments. The pigment epithelium in this area, too, has differentiated to include well‐formed melanin granules, myeloid bodies and endoplasmic reticulum and is closely associated with the receptor cell outer segments. With the approach of metamorphosis, differentiation of the remainder of the retina (Zone I) begins, taking place in a radial fashion from the optic nerve head. Differentiating pigment epithelial cells adjacent to the differentiated retinal zone begin to accumulate melanin granules. In the neural retina, junctional complexes are established in the form of an external limiting membrane, and connecting cilia project into the optic ventricle. Photoreceptor differentiation begins with the formation of a mitochondria‐filled ellipsoid within the inner segment.Development and differentiation of the ammocoete retina is unique to vertebrates in that only a small area of differentiated retina is present during the larval stage. The remainder of the retina differentiates and becomes functional during metamorphosis.
The corpus luteum of the guinea pig. IV. Fine structure of macrophages during pregnancy and postpartum luteolysis, and the phagocytosis of luteal cells
Authors: Paavola Laurie G. 
Published: February 2005

AbstractLittle information is available on the ultrastructure of macrophages in the corpus luteum or their importance in the regression of luteal tissue. In the present study, the fine structure of activated luteal macrophages during pregnancy and the postpartum period was examined by electron microscopy of guinea pig ovaries fixed by vascular perfusion. In these corpora lutea, macrophages can readily be distinguished from luteal cells. Activated macrophages typically display three prominent inclusions in their cytoplasm: (1) heterophagic vacuoles, (2) distinctive large dense inclusions, and (3) large and small electron‐lucent vacuoles. In addition, they contain numerous smaller lysosome‐like dense bodies. Activated macrophages in corpora lutea also characteristically show many surface protrusions, such as processes, folds or pseudopodia, which often occur in close contact with nearby luteal cells. Generally, nuclei of macrophages are irregular in shape and display a dense border of heterochromatin, thus differing from those of luteal cells.Macrophages seem to be most abundant in regressing corpora lutea, where they commonly display heterophagic vacuoles containing recognizable luteal cell fragments, evidence that these phagocytes ingest senescent luteal cells. The digestion of luteal cell components in heterophagic vacuoles presumably gives rise to the distinctive large dense inclusions typically seen in macrophages. The findings of this study indicate that macrophages play a central role in luteolysis by phagocytizing luteal cells or their remnants. They therefore appear to bring about the reduction in volume of the corpus luteum that occurs as this tissue regresses. These results taken together with those previously published (Paavola, 1978) further indicate that breakdown of the corpus luteum during postpartum luteolysis in guinea pigs involves both autophagy and heterophagy.
Functional heterogeneity in a multipinnate muscle
Authors: Herring Susan W. , Grimm Arthur F. , Grimm Betsy R. 
Published: February 2005

AbstractMany mammalian muscles have a complex internal architecture. This type of structure could allow a single muscle to produce a variety of force vectors through selective regional contractions. This hypothesis was tested electromyographically in the multipinnate pig masseter by recording simultaneously from several intramuscular sites. It was found that the activity in different portions of the masseter varied systematically during the various phases of mastication. Anatomical correlates of the differential activity included fasciculus orientation and length, sarcomere length in specific jaw positions, and histochemical fiber type. The usual assumptions made about muscles for biomechanical analysis, such as uniform contraction and constant line of action, are inappropriate for complex muscles such as the pig masseter.