bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural changes of the head components of the rat spermatid during late spermiogenesis
Authors: Lalli Michael , Clermont Y.
Published: February 2005

The transformation of the nucleus, acrosomic system, and perinuclear theca (perforatorium and post‐acrosomal dense lamina) was analyzed during the maturation phase, i.e., steps 14 to 19 of spermiogenesis. Following partial condensation of chromatin from steps 11–14, the nucleus continues to condense during the following steps until the end of spermiogenesis. The redundant nuclear envelope which forms along the apical and ventral aspects of the nucleus and around the implantation fossa regresses during steps 17–19. The acrosomic system splits into two portions early in step 15 to give rise to: (a) the main portion with its crest‐like acrosome running along the dorsal aspect of the nucleus and head cap extending over the lateral surfaces of the nucleus; and (b) a smaller head‐cap segment which is seen in steps 15 and 16 along one side of the nucleus at its apical extremity. This separated head‐cap segment reaches the apical‐ventral aspect of the head during step 17 and condenses in synchrony with the rest of the acrosomic system in step 19 of spermiogensis. The large crescentic acrosome, which in step 15 forms a large fin at the caudal extremity of the acrosomic apparatus, moves anteriorly during steps 16 and 17, while the whole acrosomic system extends farther apically beyond the tip of the nucleus. The perforatorium and post‐acrosomal dense lamina form a rigid capsule (perinuclear theca) that covers tightly the sickle‐shaped nucleus and binds the inner acrosomal membrane and the post‐acrosomal membranes. The post‐acrosomal dense lamina, which includes the ventral spur, appears early in step 15 as a dense cytoplasmic layer applied to the nucler envelope at the caudal extremity of the nucleus except over the perifossal zone. The perforatorium forms during step 19 of spermiogenesis as a result of the condensation of a wispy cytoplasmic material which has accumulated in the subacrosomal space during steps 14–18. Thus the spermatid's head is deeply modified during the maturation phase and takes its definitive shape only at the last step of spermiogenesis.
Fetal and neonatal rat intestinal capillaries: A TEM study of changes in the mural structure
Authors: Milici Anthony J. , Bankston Patrick W.
Published: February 2005

The development of intestinal mucosal capillaries was studied in Wistar rats from the fourteenth day of gestation through the second postnatal day with the transmission electron microscope. The microvessels develop first as continuous capillaries without a basal lamina and become fenestrated during later stages of gestation. In the thickened areas of the cytoplasm of endothelial cells at early stages, there is a paucity of pinocytotic vesicles; but some vesicles are observed which are larger than those in the adult. Later in gestation these larger vesicles can still be seen, but the frequency of their occurrence decreases with the maturation of the vessels. The intercellular junctions vary in length and shape, and the space between the outer leaflets of the apposed cell membranes is usually 20 nm. Surrounding the abluminal surface of the endothelium, the incipient basal lamina appears attenuated and incomplete until at least the second day of neonatal life.
The hematogenous origin of osteoclasts: Experimental evidence from osteopetrotic (microphthalmic) mice treated with spleen cells from beige mouse donors
Authors: Marks Sandy C. , Walker Donald G.
Published: February 2005

The excessive skeletal mass and reduced bone resorption characteristic of osteopetrosis in microphthalmic (mi) mice can be corrected by irradiation and transfer of spleen cells from a normal littermate. Osteoclasts in beige (bg) mice, a mutation without osteopetrosis, have giant lysosomal granules. These two facts were exploited to trace osteoclast lineage.

Microphthalmic mice treated with whole‐body irradiation and spleen cells from a beige donor resorbed the excessive skeletal mass and recovered from osteopetrosis. Furthermore, osteoclasts in treated mi mice had giant lysosomal granules and resembled those found in bg donors when examined by light and transmission electron microscopy.

These data provide direct evidence for a hematogenous origin of osteoclasts in mammals.
Pallidal projections to the mesencephalic locomotor region (MLR) in the cat
Authors: Garcia‐Rill E. , Skinner R. D. , Gilmore S. A.
Published: February 2005

The entopeduncular nucleus (EN) in the cat, the homologue of the primate internal globus pallidus and main output of the basal ganglia, is known to project to the mesencephalic tegmentum. We have been able to elicit antidromic responses in single EN neurons from a site in the posterior mesencephalon, then transect the brainstem (precollicular‐postmamillary) and elicit locomotion and rhythmic movements of the limbs by stimulation of the same site in the same animal. These studies demostrate the existence of a direct projection from the EN to the mesencephalic locomotor region (MLR). However, this is not a particularly large pathway since fewer than 5% of the EN cells appear to project to the MLR.

In a parallel series of anatomical experiments, injections of fluorescent dyes into the area of the MLR induced retrograde labeling of cell bodies in the EN and motor cortex. Injections of tritiated amino acids into the motor cortex resulted in labeling in the area anterior to the MLR. We assume that these connections may be involved, in part, in the sequencing and ordering of series of voluntary movements in which locomotion is involved.
Osteoclast cell‐surface specializations and nuclear kinetics during egg‐laying in Japanese quail
Authors: Miller Scott C.
Published: February 2005

Medullary bone deposits serve as a reservoir of labile calcium for egg‐shell calcification in birds. Quantitative transmission‐electron‐microscope methods and light‐microscope autoradiographic cell‐population‐kinetic analyses were used to determine changes in cell‐surface specializations and population dynamics of medullary bone osteoclasts during egg‐laying in Japanese quail. Prior to egg‐shell formation, from 0 to about 8 hours after the previous oviposition, very few osteoclast profiles had ruffled borders. The appearance of ruffled borders coincided with the beginning of egg‐shell calcification, about 9‐10 hours after the previous oviposition. During egg‐shell calcification, from about 10‐21 hours after the previous oviposition, most osteoclast profiles had ruffled borders. Ruffled borders disappeared at the completion of egg‐shell calcification and commencement of egg‐shell pigmentation. Thus, functional activities of medullary bone osteoclasts appear to be closely synchronized with egg‐shell calcification during egg‐laying.

From 1 to 48 hours after a single injection of 3H‐thymidine (3H‐TdR), very few labeled osteoclast nuclei were seen during egg‐laying. Following multiple injections of 3H‐TdR, the percentage of labeled nuclei reached a peak at about 170 hours after the first injection. At this peak‐labeling time, relatively few of the osteoclast profiles that had labeled nuclei had two or more; although the average number of nuclei per osteoclast profile was about 3.6. These kinetic data suggest that the medullary bone osteoclast population has a prolonged rate of turnover compared to rapid changes in cell activities associated with each 24‐hour egg‐laying cycle; and collectively they would suggest that rapid changes in osteoclast functions occur independently of changes in cell‐population dynamics.
Cochlear nuclear complex of mice
Authors: Webster Douglas B. , Trune Dennis R.
Published: February 2005

Using serial sections stained with luxol fast blue‐cresyl violet, the cochlear nuclei of CBA/J mice were parcellated into the same cytoarchitectonic areas and layers that Osen (1969) used in cats. Within the spherical cell areas, the distribution of Nissl substance is more reliable than soma shape in identifying the spherical cells. The area of large spherical cells is extremely small in CBA/J mice but does contain significantly larger neurons than the small spherical cell area. In Golgi preparations, bushy cells are found in all areas of the ventral cochlear nucleus except in the octopus cell area and granule cell layer. They are more numerous anteriorly than posteriorly and details of their morphology are quite variable. Stellate cells are found throughout the ventral cochlear nuclei but are present in greatest numbers in the multipolar cell area; they are rare in the large spherical cell area and octopus cell area. Because size, soma morphology, and dendritic arborization vary on a continuum rather than in discrete steps, we have not subcategorized these neurons. Octopus cells are restricted to the posterior, dorsomedial area of the ventral cochlear nucleus. In the central region of the dorsal cochlear nucleus, stellate cells abound and are categorized as vertical, elongate, or radiate cells. In the granule layer of the dorsal cochlear nucleus there are both fusiform and Purkinje‐like neurons, so named because of their resemblance to cerebellar Purkinje cells. These Purkinje‐like cells differ from fusiform cells in having (1) a smaller cell body, spherical in shape, (2) no basal dendrites, (3) a sagittal dendritic orientation, (4) elaborate dendritic branching, and (5) abundant dendritic spines.
An immunocytochemical study of the cytogenesis of pancreatic endocrine cells in the lizard, Anolis carolinensis
Authors: Rhoten William B. , Hall Carl E.
Published: February 2005

The differentiation of the pancreatic endocrine cells in the lizard Anolis carolinensis following oviposition was examined. Immediately postoviposition (PO) there was no apparent differentiation of epithelioid cells into endocrine or exocrine components. Individual subpopulations of the endocrine‐like cells, which could not be identified during the early PO period on the basis of either their tinctorial properties at the light‐microscopic level or their granule morphologies at the electron‐microscopic level, exhibited specific hormonal localization by peroxidase‐antiperoxidase complex immunocytochemistry. All four hormones searched for, insulin, glucagon, somatostatin, and pancreatic polypeptide (PP), were present in epithelioid cells shortly after oviposition. However, the immunostained secretory granules in the early PO period were smaller than those of the adult. Secretory granule morphologies that are typical of the adult were acquired at different times during development. Delta granules were observed first and were followed by alpha granules, and beta granules which appeared shortly before birth. The secretory granules of the PP‐containing F cells could not be readily placed within this maturation sequence. Mosaic cells (containing more than one hormone) were not seen. Levels of immunoreactive insulin and glucagon in the pancreas increased several fold from day 10 to day 28 PO, but the attainment of adult beta‐granule morphologies did not appear to be directly related to insulin itself. The results show that cytodifferentiation of the anolian endocrine pancreas occurs postoviposition and that immunocytochemical methods can be used to follow an organelle sequence during development. These findings suggest that subcellular organelles undergo structural remodeling during maturation which, at least in the case of secretory granules, may have functional significance.
A cytochemical study of the Golgi apparatus of the spermatid during spermiogenesis in the rat
Authors: Tang X. M. , Lalli M. F. , Clermont Y.
Published: February 2005

The reactivity of the various components of the Golgi apparatus of rat spermatids for three phosphatase activities (nicotinamide adenine dinucleotide phosphatase, NADPase; thiamine pyrophosphatase, TPPase; cytidine monophosphatase, CMPase) and the incorporation of 3H‐fucose by the spermatids was analyzed at the 19 steps of spermiogenesis, i.e., during and after this organelle elaborated the glycoprotein‐rich acrosomic system. During steps 1–3, the Golgi apparatus produced, in addition to the proacrosomic granules, multivesicular bodies that became associated with the chromatoid body. NADPase was located within the four or five intermediate saccules of Golgi stacks, and TPPase was found in the last one or two saccules on the trans aspect of the stacks from steps 1 to 17 of spermiogenesis. CMPase was located within the thick saccular GERL elements found in the trans region of the Golgi apparatus from steps 1 to 7 of spermiogenesis, but the CMPase‐positive GERL disappeared from the Golgi apparatus after its detachment from the acrosomic system at step 8. The acrosomic system itself was reactive for CMPase and TPPase but was negative for NADPase, while the multivesicular bodies were CMPase and NADPase positive but unreactive for TPPase. Tritiated‐fucose was readily incorporated within the Golgi apparatus of steps 1–17 spermatids; in steps 1–7 it was subsequently incorporated within the acrosomic system and multivesicular bodies. These various data indicated (1) that the Golgi apparatus of spermatids, although it loses its CMPase‐positive GERL element in step 8, retains evidence of functional capacity until it degenerates in step 17; (2) that in early spermatids the various saccular components of the Golgi are specialized with respect to enzymatic activities; and (3) that each Golgi region may contribute in a coordinated fashion to the formation of the acrosomic system and multivesicular bodies.
Morphologic changes in the lung during the lifespan of Fischer 344 rats
Authors: Pinkerton Kent E. , Barry Brenda E. , O'Neil John J. , Raub James A. , Pratt Philip C. , Crapo James D.
Published: February 2005

Pulmonary structure and function were quantitatively investigated over the lifespan of the Fischer 344 rat by morphometric and physiologic techniques. Male animals 1 week, 6 weeks, 5 months, 14 months, and 26 months of age and female animals 5 months, 14 months, and 26 months of age were studied. All alveolar tissue compartments demonstrated significant increases in volume, surface area, and cell number during the first 5 months of life. From 5 to 26 months of age, remodelling in the epithelial and interstitial compartments continued to take place while the endothelial compartment remained relatively unchanged. In the epithelial compartment the ratio of type II cells to type I cells lining the alveolar surface decreased as age increased. In the interstitial compartment the volume of the noncellular components of the interstitium increased by 39% in males and by 89% in females from 5 to 26 months of age. Physiologic measurements of lung volumes in males at 6 weeks, 14 months, and 26 months demonstrated progressive increases in vital capacity (VC) and total lung capacity (TLC). Morphometric pulmonary‐diffusion capacity (DLO2) increased in males from 1 week to 5 months of age and remained relatively unchanged from 5 to 26 months of age in both sexes.
Overall architecture and pattern of lymph flow in the rat lymph node
Authors: Sainte‐Marie G. , Peng F.‐S. , Bélisle C.
Published: February 2005

The immunogenic content of the afferent lymph stimulates structures in the lymph node. Thus, a better knowledge of the processes of lymph flow and filtration in the organ should help us better understand various aspects of the node's function. To gain this understanding, we analyzed the distribution of flow in rat node draining areas locally injected with a small dose of China ink. Because the lymph‐flow pattern is likely related to the overall architecture of the node, we simultaneously studied its morphology. Indeed, while the different structures of the node are known, some aspects of its overall architecture need to be resolved. The present work aimed to accomplish this by an analysis of semiserial sections of nodes from various anatomical locations in normal rats; the sections were stained by the Dominici technique or silver‐impregnated.

With respect to their architecture, the nodes could be distinguished into those with either a discontinuous or a continuous subcapsular sinus and peripheral cortex. These are referred to here, respectively, as segmented and nonsegmented nodes. In the segmented nodes, the subcapsular sinus with the peripheral cortex is separated by “gaps,” in which medullary sinuses reached the capsule. Further, a node appears to be divided into one or more “physiological compartments,” each one representing a nodal area related to an opening of an afferent lymphatic.

The findings on China‐ink distribution indicate that the lymph‐flow pattern varies in different nodes and is determined by the particular architecture of a node, i.e., the lymph flow in a given node aligns itself along the pattern of segmentation of the organ. The findings suggest that the lymph content is first held by the endothelium lining the inner wall of a restricted area of the subcapsular sinus in a concentration which decreases with the distance from the related afferent lymphatic opening. Part of the content, possibly its nonimmunogenic fraction, would later be released to flow further along the sinus. It would then be phagocytosed by the macrophage accumulation located in the portions of medullary sinuses into which the lymph enters from the subcapsular sinus. The lymph thus filtered then flows along the medullary sinuses and leaves the organ. The latter findings also indicate that a node is divided into physiological compartments, each one being stimulated by the lymph from a given afferent lymphatic opening. As the immunogenic content of the lymph can differ from one lymphatic to another, this explains the frequent variations in similar structures located in different areas of a given node. Hence, the pattern of distribution of the openings of the afferent lymphatics of a node can account for the particularities of its overall architecture and its division into physiological compartments.
Immunocytochemical localization of corticotropin‐releasing factor (CRF) in the rat brain
Authors: Merchenthaler I. , Vigh S. , Petrusz P. , Schally A. V.
Published: February 2005

The immunocytochemical localization of neurons containing the 41 amino acid peptide corticotropin‐releasing factor (CRF) in the rat brain is described. The detection of CRF‐like immunoreactivity in neurons was facilitated by colchicine pretreatment of the rats and by silver intensification of the diaminobenzidine end‐product. The presence of immunoreactive CRF in perikarya, neuronal processes, and terminals in all major subdivisions of the rat brain is demonstrated. Aggregates of CRF‐immunoreactive perikarya are found in the paraventricular, supraoptic, medial and periventricular preoptic, and premammillary nuclei of the hypothalamus, the bed nuclei of the stria terminalis and of the anterior commissure, the medial septal nucleus, the nucleus accumbens, the central amygdaloid nucleus, the olfactory bulb, the locus ceruleus, the parabrachial nucleus, the superior and inferior colliculus, and the medial vestibular nucleus. A few scattered perikarya with CRF‐like immunoreactivity are present along the paraventriculo‐infundibular pathway, in the anterior hypothalamus, the cerebral cortex, the hippocampus, and the periaqueductal gray of the mesencephalon and pons. Processes with CRF‐like immunoreactivity are present in all of the above areas as well as in the cerebellum. The densest accumulation of CRF‐immunoreactive terminals is seen in the external zone of the median eminence, with some immunoreactive CRF also present in the internal zone. The widespread but selective distribution of neurons containing CRF‐like immunoreactivity supports the neuroendocrine role of this peptide and suggests that CRF, similarly to other neuropeptides, may also function as a neuromodulator throughout the brain.
Development of the connective tissue network in the neonatal hamster heart
Authors: Borg Thomas K.
Published: February 2005

The formation of the connective tissue network, composed principally of collagen, in the left ventricle of the neonatal hamster heart developed primarily during the first 20 days postpartum. The weave network of the endomysium, which was absent at birth, was visible by 4 days and was similar to that of the adult by 15 days postpartum. Myocyte‐myocyte and myocyte‐capillary struts formed gradually as the heart underwent physiological hypertrophy. These data were similar to the development of the connective tissue network in the rat except that the myocyte‐myocyte struts were more numerous in the hamster. Presumably this is because the hamster has a higher heart rate, which would require more mechanical coupling of the myocytes. Formation of the struts appears to take place at precise areas on the sarcolemma through the interaction of collagenous and noncollagenous components of the extracellular matrix.
Implantation in the rhesus monkey: Initial penetration of endometrium
Authors: Enders Allen C. , Hendrickx Andrew G. , Schlafke Sandra
Published: February 2005

A series of peri‐implantation stages of the rhesus monkey has been collected; these range from preimplantation blastocysts through initial implantation to early villus formation. The three earliest postimplantation specimens encompass the stages of penetration into and through the uterine luminal epithelium and into endometrial blood vessels. The day of pregnancy was established by radioimmunoassay of estrogen (E) levels to determine the prevulatory E peak, and in each instance the embryo was examined to determine the extent of development. The conceptus collected on day 9.5 of pregnancy was the earliest implantation stage; it ballooned above a depression in the endometrium to which it was firmly attached. A column of syncytial trophoblast penetrated into the uterine epithelium to the basal lamina of the latter. The syncytial trophoblast shared junctional complexes with the uterine epithelial cells to which it was apposed at the margin of the site of epithelial penetration. Basal to the apical junction complexes, processes of syncytium indented uterine epithelial cells. Several epithelial cells had been partially isolated and surrounded by flanges of syncytial trophoblast. In the next specimen, at 10.0 days after ovulation, the uterine epithelium had initiated the epithelial plaque reaction. The trophoblast had extended along the residual basal lamina of the uterine epithelium and into the neck of an adjacent uterine gland. Cytotrophoblast was abundant in the central region of the implantation site, and was intermixed with syncytium which formed the majority of the peripheral trophoblast. In several places clefts had formed in the syncytial trophoblast; these clefts were lined with microvilli, had intermicrovillous caveolae, and consequently more closely resemble the trophoblast that eventually lines the intervillous spaces than the trophoblast involved in initial invasion. In the day‐10.5 specimen, in addition to prelacunar clefts, lacunae containing maternal blood were present for the first time. The basal lamina was penetrated in many places, and syncytial trophoblast was interposed between maternal endothelial cells of the underlying vessels.

It was concluded that syncytial trophoblast is the first tissue to penetrate the uterine luminal epithelium; that the basal lamina of the uterine luminal epithelium, but not the basal lamina of endothelium, constitutes a temporary barrier to trophoblast penetration; that invasion is accomplished with less destruction of maternal tissue than previously suggested; and that the rapid superficial growth of the placenta is made possible by the early tapping of the endometrial vessels.
The early development of the AV node and bundle in the ferret heart
Authors: Marino Thomas A. , Severdia Joseph
Published: February 2005

The development of the atrioventricular (AV) junctional tissues in the ferret embryonic heart was studied on days 16, 18, and 21 of gestation. This important region of the heart was examined with PAS and toluidine‐blue staining at the light microscope level and with transmission electron microscopy at the ultrastructural level. By day 16 of gestation the ferret heart was in the initial stages of convolution. The heart was at the primitive four‐chamber stage by 18 days postcoitum. On day 21 of gestation the heart was in the process of being septated. The AV nodal primordia were first observed as two clusters of cells in the dorsal wall of the common atrium of the 16 day ferret embryo heart. These nodal primordial cells were morphologically different from working myocardial cells or cells of the AV canal. The AV canal cells were particularly numerous in the dorsal wall of the canal and eventually gave rise to the AV bundle in this region. On day 18 of gestation the morphological differences between the AV nodal, AV canal, and myocardial cells were readily apparent. By 21 days postcoitum, the AV node with its two regions had reached its definitive anatomic position. The AV bundle was also present in its normal adult location. The AV nodal cells were distinctly different when compared to the ventricular or atrial myocytes at this stage in development. In addition, the AV bundle cells were morphologically different from the AV nodal cells and working myocardial cells. A discussion of these findings relates this information to current descriptions of how the AV node and bundle develop.
A morphometric analysis of craniofacial growth and changes in spatial relations during secondary palatal development in human embryos and fetuses
Authors: Diewert Virginia M.
Published: February 2005

Staged human embryos and fetuses in the Carnegie Embryological Collection were morphometrically analyzed to show craniofacial dimensions and changes in spatial relations, and to identify patterns that would reflect normal developmental events during palatal formation. Normal embryos aged 7–8 weeks postconception (Streeter‐O'Rahilly stages 19–23) and fetuses aged 9–10 weeks postconception, in eight groups with mean crownrump (CR) lengths of 18–49 mm, were studied with cephalometric methods developed for histologic sections. In the 4‐week period studied, facial dimensions increased predominantly in the sagittal plane with extensive changes in length (depth) and height, but limited changes in width. Growth of the mandible was more rapid than the nasomaxillary complex, and the length of Meckel's cartilage exceeded the length of the oronasal cavity at the time of horizontal movement of the shelves during stage 23. Simultaneously with shelf elevation, the upper craniofacial complex lifted, and the tongue and Meckel's cartilage extended forward beneath the primary palate. Analysis of spatial relations in the oronasal cavity showed that the palatomaxillary processes became separated from the tongue‐mandibular complex as the head extended, and the tongue became positioned forward with growth of Meckel's cartilage. As the head position extended by 35°, the cranial base angulation was unchanged and the primary palate maintained a 90° position to the posterior cranial base. However, the sagittal position of the maxilla relative to the anterior cranial base increased by 20° between stages 19 and 23. In the late embryonic and early fetal periods, the mean cranial 128° and the mean maxillary position angulation of approximately 34° were similar to the angulations previously shown to be present later prenatally and postnatally. The results suggest that human patterns of cranial base angulation and maxillary position to the cranial base develop during the late embryonic period when the chondrocranium and Meckel's cartilage form the primary skeleton.
Effects of pinealectomy on reproduction in the Syrian hamster mutant anophthalmic white (Wh)
Authors: Hagen Susan C. , Asher James H.
Published: February 2005

The gene Wh, causing anophthalmia in the Syrian hamster, Mesocricetus auratus, is a pleiotropic gene affecting eye development, pigmentation, hearing, and reproduction. Male hamsters homozygous for this gene are usually sterile. Since both Wh and the pineal organ are known to suppress reproductive function, the objective of this study was twofold: (1) to determine whether Wh, by itself, influences testicular differentiation; and (2) to determine whether removal of the pineal gland will restore fertility to both experimentally blinded (B), genetically normal [wh/wh(B)] hamsters and mutant, eyeless (Wh/Wh) hamsters. Accordingly, one testis from each of ten wh/wh(B) and ten Wh/Wh hamsters at approximately 60 days of age was removed, and these testes were compared at the gross and light microscopic level. Since all testes were identical at 60 days of age and contained normal differentiating germ cells, the gene Wh does not appear to affect initial testicular differentiation. Testicular tissues from at least ten wh/wh, wh/wh(B), heterozygous (Wh/wh), and Wh/Wh(B) hamsters, at 135 days of age, were also compared. Testes from all wh/wh(B), and 70% of the Wh/Wh hamsters were hypoplasic and aspermic. Approximately 30% of the testes from Wh/Wh hamsters contained some seminiferous tubules with normal sperm present. Pinealectomy fully restored adult testicular size and morphology in all wh/wh(B) and Wh/Wh hamsters. Thus, it was demonstrated that the atrophy of testes from Wh/Wh individuals is a pineal‐mediated phenomenon due to failure of eye development and the subsequent lack of a functional visual pathway. Testes from Wh/Wh hamsters appear to be completely competent to respond to the normal, antigonadotrophic effects of the pineal.
Characterization of putative secretory sites on ameloblasts of the rat incisor
Authors: Nanci A. , Warshawsky H.
Published: February 2005

The distribution and structure of the putative sites where enamel matrix is secreted from the ameloblast were studied by correlating the external topography with the distribution of organelles in Tomes' process cut in various planes of section. Both the interrod and rod secretion sites are associated with deep membrane infoldings. It was found that the interrod secretion site completely surrounds each ameloblast, and the marked interdigitation of adjacent cells results in a cooperative growth front for interrod enamel. In contrast, the rod secretion site is present on only one surface of the interdigitating portion of Tomes' process. Numerous granules were observed adjacent to the membrane infoldings associated with both sites, and granules were seen fused to membrane infoldings suggesting that the matrix of enamel is a merocrine secretion product.
Seasonal variations in the fine structure of the Necturus maculosus urinary bladder epithelium: Low transporters and high transporters
Authors: Karnaky Karl J. , Lau Kim R. , Garretson Leon T. , Schultz Stanley G.
Published: February 2005

Although the urinary bladder of Necturus maculosus provides an important model system for studying the mechanisms of active Na absorption, little critical attention has been paid to the fine structure of its epithelium. Moreover, two distinct groups of urinary bladders, low and high Na transporters, have been described based on short‐circuit current or transepithelial potential difference. In the present study, over an 11‐month period, stable electrical parameters (short‐circuit current, transepithelial potential difference, and resistance) were recorded from 63 chamber‐mounted bladders. Analysis of these parameters revealed a highly significant difference between two groups (low transporters and high transporters) occurring at different times of the year. Consistent with these data, in urine collected from the bladders, the Na concentration in low transporters was significantly higher than that in high transporters. A subpopulation of these bladders was subsequently fixed and examined at the light and/or electron microscopic level. Low‐transporting bladders were characterized unequivocally by a thin, stratified squamous epithelium only 6–15 μm thick. High‐transporting bladders were composed predominantly of columnar‐shaped granular cells up to 70 μm in height, with ciliated, mitochondria‐rich, and basal cells present in small numbers. There is thus a correlation between transport activity, as measured by electrophysiological techniques and urine sodium analysis, and the structure of the tissue. Moreover, these parameters exhibit significant seasonal variation, the underlying mechanisms of which remain obscure.
Maturation of spermatozoa in the epididymis of the Chinese hamster
Authors: Yanagimachi R. , Kamiguchi Y. , Mikamo K. , Suzuki F. , Yanagimachi H.
Published: February 2005

Chinese hamster spermatozoa gain their ability to move when they descend from the testis to the distal part of the caput epididymis, but it is not until they enter the corpus epididymis that they become capable of fertilizing eggs. The maturation of the spermatozoa proceeds as they further descend the tract and perhaps continues even in the vas deferens. During transit between the distal caput and proximal cauda epididymides, small membrane‐limited vesicles (and tubules) appear on the plasma membrane over the acro somes of the spermatozoa. The number of vesicles appearing on the sperm brane reaches a maximum when the spermatozoa are in the proximal cauda epididymis. It declines sharply in the distal cauda epididymis. Spermatozoa in the vas deferens are free of the vesicles. The origin, chemical nature, and functional role of the vesicles that appear on the sperm surface during epididymal transit must be the subject of further investigation.
Photoreceptor fine structure in the archerfish (Toxotes jaculatrix)
Authors: Braekevelt Charlie R.
Published: February 2005

The fine structure and arrangement of the photoreceptor cells of the archerfish (Toxotes jaculatrix) have been studied by electron microscopy. Rods, twin cones, and single cones are present. In the light‐adapted state, the rods are very tall cells reaching almost to the base of the retinal epithelial cells. The outer segment is composed of membraneous discs of uniform diameter displaying a single incisure. The rod inner segment displays a distal small ellipsoid and an extremely thin myoid region. The nuclei of rods are electron‐dense, and the synaptic spherule displays two or three invaginated sites. The single cone is similar to the individual members of a twin cone and displays a tapering outer segment and accompanying accessory outer segment. The wider cone inner segment contains a large, centrally loated ellipsoid and a peripheral region rich in endoplasmic reticulum, polysomes, and microfilaments. Twin cones display subsurface cisternae along their entire contiguous surfaces. The cone nuclei are large and vesicular and located vitread to the external limiting membrane. The synaptic pedicle of cones is lager and moe electron‐lucent and contains more invaginated “ribbon” synaptic sites (ten to 12) than do rods. In addition, small “coated” invagination and larger synaptic vesicle‐filled processes are also seen within cone pedicles. In the light‐adapted state the cone photoreceptors are arranged in a repeating square mosaic pattern with one single cone surrounded by four twin cones.
Usage pattern of the complex masticatory muscles in the shingleback lizard,Trachydosaurus rugosus: A model for muscle placement
Authors: Gans Carl , Carrier David , De Vree Frits
Published: February 2005

This wide‐ranging, omnivorous lizard of Australia has a very complex adductor muscle mass, with fibers differing in length by a factor of three and in insertion angle by 90°. Stimulated muscles produce maximal moment with the mouth nearly fully open. The opening mechanism appears to involve only simple rotation and no translation of the mandible. EMGs indicate that the entire mass is activated equivalently in crushing and there are no temporal subdivisions, for instance, matching activity to angle of opening. During crushing of hard objects, the chin is brought into contact with the ground so that the subvertebral muscles may aid buccal closure. The lizards also activate the muscles in a pulsatile staircase effect leading to an unfused tetanus that generates forces several times the twitch level. Application in parallel of a maximum number of sarcomeres to the crushing bite appears to be the major design characteristic. Hence, this species offers an ideal case for analysis of the effects of different sarcomere placements on the simple movement generated. For the primary adductor muscles, the angles of fiber insertion relative to the lines connecting each insertion with the jaw joint are equivalent; this relation persists as the mouth opens. Also, fiber lenghts are proportional to the distance between jaw joint and site of insertion so that each sarcomere contributes equally to the movement generated. Complex tendons provide additional space for muscle placement. Some of these also extend beyond the bony attachment sites, producing tendinous “coronoid processes.” The fibers of laterally and ventrally placed muscles are short relative to the length of the entire muscle, insert at relatively short moment arms, and undergo short excursion during opening; however, there are many such fibers. Also, muscles with a low incident angle are crossed; they apparently protect the jaw joint from horizontal (disarticulating) forces.
Effects of short‐day photoperiods and of castration on the structural integrity of the ventral and dorsal prostates of the Syrian hamster (Mesocricetus auratus)
Authors: Buzzell Gerald R. , Toma Jean G. , O'Brien M. Gail , Haskins Julie
Published: February 2005

Short‐day photoperiods and castration both cause reductions in the weights of male accessory sex glands. In the Syrian hamster, we have found that the ventral prostate loses less weight following these treatments than does the dorsal prostate. In this paper, we report on the effects of the pineal and of castration on the structural integrity of these glands, as assessed by stereological techniques. Short days result in little alteration to the ventral prostate or its acinar composition. The typical acinus is narrower following 10 weeks in short days. The ventral prostate also responds to castration with a narrower acinus, and, in addition, it shows a decrease in the epithelial volume fraction and increases in those of the lumen and muscular stroma. In neither case is there a change in the proportion of the gland consisting of acinar or interacinar components. Short‐day photoperiods and castration generally show similar effects in the dorsal prostate. In both cases, there are increases in the proportion of the gland made up of interacinar tissue. Within the acini, there are decreases in the volume fractions of lumen and large increases in those of lamina propria and muscular stroma. Following both treatments, typical acini are narrower and show reduction in the thickness of the epithelium and increases in the thickness of the lamina propria and muscular stroma.

Thus, in the ventral prostate, both short days and castration lead to subtle changes which are different with each treatment and which differ from those that occur in the dorsal prostate. In the dorsal prostate, there are relative increases in the proportions of nonepithelial elements following both of these treatments. These results are discussed in relation to the mode of action of the pineal in causing accessory sex gland regression.
Anionic surface properties of aortic and mitral valve endothelium from New Zealand white rabbits
Authors: Sarphie T. G.
Published: February 2005

The luminal surfaces of the endothelium lining the two surfaces of the aortic arterial (AAR) and ventricular (AVT), and mitral ventricular (MVT) and atrial (MAT), valve cusps were studied with cationic ferritin (CF) and ferritin (Fer)‐conjugated lectins (WGA, RCA, SBA). The arterial (AAR) and ventricular (MVT) surfaces of the aortic and mitral cusps, which are exposed to more turbulent fluid mechanical forces and lower wall shear stresses, had the greatest density of CF labeling. The endothelia of the four surfaces displayed a gradient of decreasing density from the nuclear region to the periphery. Neuraminidase, chondroitinase ABC and AC, heparinase, heparitinase, hyaluronidase (testicular), and pronase E digestions suggested that a significant number of the anionic sites labeled by CF are associated with sialoglycoproteins and glycosaminoglycans such as chondroitin 4/6 sulfates, dermatan sulfates, and heparan sulfates. The localization of WGA receptors on the endothelium of AAR and MVT demonstrated a greater density of sialyl moieties than on the AVT and MAT. There was no binding of Fer‐RCA with specificity for D‐galactopyranosides or Fer‐SBA with affinity for N‐acetylglucosamine and D‐galactose to the endothelium unless it was first treated with neuraminidase. Hence, sialic acids are shown to be among the more superficial components of this glycocalyx and to be largely responsible for the greater densities over the endothelium of AAR and MVT.
Avian sebokeratocytes and marine mammal lipokeratinocytes: Structural, lipid biochemical, and functional considerations
Authors: Elias Peter M. , Menon Gopinathan K. , Grayson Stephen , Brown Barbara E. , Rehfeld S. Jerry
Published: February 2005

In terrestrial mammals, stratum corneum lipids derive from two sources: deposition of lamellar body lipids in stratum corneum interstices and excretion of sebaceous lipids onto the skin surface, resulting: in a two‐compartment (bricks and mortar) system of lipid‐depleted cells surrounded by lipid‐enriched intercellular spaces. In contrast, intracellular lipid droplets, normally not present in the epidermis of terrestrial mammals, are prominent in avian and marine mammal epidermis (cetaceans, manatees). We compared the transepidermal water loss, ultrastructure, and lipid biochemistry of the viable epidermis and tratum corneum of pigeon apterium, fledgling (featherless) zebra finches, painted storks, cetaceans, and manatees to those of humans and mice. Marine mammals possess an even more extensive lamellar‐body secretory system than do terrestrial mammals; and lamellar‐body contents, as in terrestrials, are secreted into the stratum corneum interstices. In cetaceans, however, glycolipicls, but not ceramides, persist into the stratum corneum; whereas in manatees, glycolipids are replaced by ceramides, as in terrestrial mammals. Acylglucosylceramides, thought to be critical for lamellarbody deposition and barrier function in terrestrial mammals, are present in manatees but virtually absent in cetaceans, a finding that indicates that they are not obligate constituents of lamellar‐body‐derived membrane structures. Moreover, cetaceans do not elaborate the very long‐chain, saturated N‐acyl fatty acids that abound in terrestrial mammalian acylglucosylceramides. Furthermore, cold‐water marine mammals generate large, intracellular neutral lipid droplets not found in terrestrial and warm‐water marine mammals; these lipid droplets persist into the stratum corneum, suggesting thermogenesis, flotation, and/or cryoprotectant functions. Avians generate distinctive multigranular bodies that may be secreted into the intercellular spaces under xerotic conditions, as in zebra fledglings; ordinarily, however, the internal lamellae and limiting membranes deteriorate, generating intracellular neutral lipid droplets. The sphingolipid composition of avian stratum corneum is intermediate between terrestrials and cetaceans (= 50% glycolipids), with triglycerides present in abundance. In the midstratum corneum of avians, neutral lipid droplets are released into the interstices, forming a large extracellular, lipid‐enriched compartment, surrounding wafer‐thin corneocytes, with a paucity of both iipid and keratin (“platesand‐platesand‐mortar” rather than the “bricks‐and‐mortar” of mammals). These studies demonstrate remarkable structural and biochemical heterogeneity of epidermal lipids in various homeotherms and provide new insights into the functions of specific lipid‐enriched organelles in these organisms.
Teratogenic antibody internalization by rat visceral yolk‐sac endoderm in vitro: An ultrastructural colloidal gold tracer study
Authors: Leung Christopher C. K. , Yan Cai‐Lou , Cheewatrakoolpong Boonlert
Published: February 2005

Previous work from our laboratory has demonstrated that specific rabbit immunoglobulins G (IgG) against a glycoprotein antigen of rat kidney proximal tubule or a cross‐reacting visceral yolk‐sac endodermal cell antigen will induce abnormal embryonic development when they are injected into pregnant rats during the period of organogenesis. It has been proposed that these antibodies may induce embryopathy by interfering with functions of the visceral yolksac placenta, an important organ providing nutrients to the embryo at this stage of development. In order to gain some insight into the underlying pathogenic mechanism(s) in which specific teratogenic IgG may interfere with visceral yolk‐sac functions, we examined the uptake of these teratogenic IgG by the visceral yolk‐sac endodermal cells at the electron microscopic level microscopic level.

The results demonstrated that teratogenic rabbit IgG specifically localized on the fuzzy coat of the external apical cell membrane of the visceral yolk‐sac endoderm at the intermicrovillous region. Within 5 min, the IgG were rapidly internalized via coated pits and micropinocytic vesicles. Within 30 min, an increasing proportion of gold particles appeared within uncoated vesicles or vacuoles of various sizes; most of the gold particles were in close proximity to the inner membranous lining of the vesicles. Similar findings were observed after 1‐or 2‐hr incubation. After 24‐ to 48‐hr culture, however, the gold particles appeared to have dissociated from the inner surface of the vesicle membrane. For all the time points studied, gold particles were not observed in close association with the basal or lateral plasmalemma of the endodermal cells or in the connective tissue spaces and blood vessels of the visceral yolk‐sac placenta. We interpret the results as follows: (1) the teratogenic rabbit IgGs interacted with their antigen on the apical plasma membrane of the visceral yolk‐sac endodermal cells; (2) the teratogenic IgGs (coupled to their antigen) were internalized by endocytosis via coated pits; (3) the IgGs were later either hydralyzed or dissociated from their antigen in uncoated vesicles or vacuoles: and (4) there was little or no evidence to indicate that the IgGs were transported between or across the endodermal cells to reach the embryo.

It is postulated that the responsible antigen may be receptor which plays an important role in transporting nutrient(s) to the embryo. Specific polyclonal teratogenic IgGs may either interfere with receptor‐ligand interaction or inhibit recycling of such a receptor, thereby causing abnormal embryonic development.
Normal stages of cardiac organogenesis in the mouse: II. Development of the internal relief of the heart
Authors: Vuillemin Mauricette , Pexieder Tomas
Published: February 2005

Normal stages of intracardiac development of the mouse heart are illustrated by a collection and analysis of two complementary SEM views, the septal and parietal halves of the right ventricle and conotruncus. These views are particularly suitable for understanding the septation of the outflow tract of the heart. They represent references for the studies of the pathogenesis of conotruncal malformations. The analysis is based on 90 hearts between 11ed and 15ed at intervals of 8 hours with an additional stage at 16ed. They were prepared by perfusion fixation, microdissection, and critical point drying and were examined in SEM. The following main features of the intracardiac morphogenesis were observed: (1) the presence of two spirally positioned conotruncal ridges, their disto‐proximal fusion, and the formation of the semilunar valves at their distal part; (2) the trabecular transformation of the conotruncal wall; and (3) the presence of two different interventricular foramina (FIV II and FIV III), with the final closure of FIV III at 14edl6h‐15ed.

As a result of these observations, our description of the outflow tract septation and its interpretation are different from other conceptions based on mechanisms such as bulbar shift, bulbar absorption, torsions, or transfer of the aorta into the left ventricle.