bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of cell movement in early organ primordia of the chick embryo
Authors: Robert Hilfer S. , Marrero Leslie , Sheffield Joel B.
Published: February 2005

Purse‐string constriction of the cytoskeleton at cell poles is generally accepted as the causal mechanism for invagination during early stages of organ formation. However, it is known that other cell movements, including intercalation, play a role in the organotypic shape changes that occur during gastrulation and neurulation. Such cell movements have not been investigated in pouching and branching epithelial primordia. There is reason to suspect that cells within these organ primordia might exchange their neighbors for others, that is, intercalate or translocate, at sites of sharp folding such as borders with the surrounding epithelial sheet or where a bend occurs within the primordium. The greatest difficulty in identifying these movements has been the need to use intact embryos so that the processes are not distorted. This study explores the possibility of using time‐lapse video recording to identify cell movement at these locations. Three organ primordia were tested: otic and thyroid placodes, which had not been tested previously, and neural plate as a control, where movements of this sort have been documented. Embryos or parts containing the primordia were immobilized and cell apices visualized with Hoffman modulation contrast optics. Recordings to an optical memory disc recorder were transferred to a microcomputer for image analysis. The viewing procedure allows reasonably clear visualization of cell apices, and image analysis permits tracking of a number of adjacent cell apices over an extended time period. Several types of movement were found to occur within cell sheets, and the relative abundance of each type depends on the specific primordium. In the neural plate, some cells move many cell diameters from their neighbors. In the other two primordia, most cells show limited shifts in position relative to their neighbors except at regions where folds are formed. In other regions, adjacent cells move as a unit. Knowledge of the movements which occur in any particular primordium is essential to an understanding of the mechanisms controlling its formation.
Glycoconjugate expression of cells of human anagen hair follicles during keratinization
Authors: Ohno Jun , Fukuyama Kimie , Epstein William L.
Published: February 2005

Changes in the expression of glycoconjugates in cells of the inner root sheath (IRS) and outer root sheath (ORS) of human anagen hair follicles were investigated by lectin histochemistry. Concanavalin A (Con A) and Ricinus communis (RCA‐I) stained hair follicle cells regardless of their differentiation stages. In IRS, Ulex europeaus‐I (UEA‐I) bound to the surface of the cells as soon as they were morphologically defined, and Glycine max (SBA) stained as their differentiation progressed. Innermost (IM) cells of ORS layers were reactive with UEA‐I at the stage where Henle's cells were keratinized, while the reactivity of UEA‐I was lost at the site of the completion of IRS keratinization where SBA reaction was detected. Staining of both UEA‐I and SBA was prominent in other ORS cells at the levels where SBA binding in IM cells became strong. The staining intensity increased up to the position of the follicular isthmus. In addition, a sugar residue recognized by Dolichos biflorus (DBA) was detected in differentiaed cells of ORS. In contrast, the DBA reaction was not found at all in cells of IRS, infundibulum, and epidermis. These findings identified a complexity of carbohydrate metabolism in the cells of different layers at various stages of keratinization. IM cells differentiate independently from other ORS cells but seem responsive to the degree of IRS keratinization. All ORS cells possess a unique sugar moiety not found in other keratinocytes either in the hair or epidermis.
Immunofluorescent studies for α‐actinin in cultured cardiomyopathic hamster heart cells
Authors: Li Jian , Lemanski Larry F.
Published: February 2005

Primary cultures of cardiac myocytes from normal and genetically cardiomyopathic (CM) newborn hamsters (strain UM X7.1) were analyzed by indirect immunofluorescent microscopy after 3, 5, 7, and 9 days in culture. The cultures were fixed in cold acetone and immunostained by an indirect method using FITC‐labelled anti‐α‐actinin to label the myofibrillar Z bands. Most normal and CM myocytes appeared round in shape after 3 days in culture. Normal cardiac myocytes began to exhibit cytoplasmic projections after 5 days in culture and their myofibrils usually showed parallel arrangements with respect to each other. The cardiac cells from CM hearts showed an obvious myofibril disarray. Moreover, projections formed later than normal. As the size of the cells increased, more and more projections formed in normal hamster myocytes during development. By contrast, most of the cardiomyopathic myocytes showed few projections even as late as 9 days in culture. Hence, the number of projections per cell was much less in cardiomyopathic myocytes than in normal, especially after 7 and 9 days in culture. These results suggest that cardiomyopathic cells have abnormal shapes in culture and, in particular, fail to form projections as in normal cells. Whether this unusual behavior is related to an abnormality of the membranes or cytoskeletal system in cardiomyopathic heart cells or to some other factor requires further study.
Whole population cell kinetics of jejunal and colonic epithelium in lactating dams
Authors: Cheng Hazel , Bjerknes Matthew
Published: February 2005

Previous studies make it likely that the response of the intestinal epithelium as a whole to lactation is different from that observed in the crypt population alone. We confirm this difference by whole population cell kinetics measurements of jejunal and colonic epithelium in mice that have been suckling pups for various lengths of time. We found that the fraction of cells in S phase in jejunal epithelium was significantly increased after only 1 week of lactation, maintained this elevated level after 2 weeks of lactation, but returned to normal during the third week of lactation. The cell number density in jejunum was also significantly higher after 2 and 3 weeks of lactation before returning to normal by 4 weeks. In the colonic epithelium no changes were found in the distribution of cells in G1, S, and G2 + M phases. However, a significant increase in cell number density was observed after 2 weeks of lactation, followed by a sharp decrease to a level significantly below that of normal mice after 3 and 4 weeks of lactation.

We conclude that the observed significant increase in the fraction of S phase in jejunal epithelium of lactating mice is probably due to a smaller relative expansion of the villus population when compared with the expansion of the crypt population. Our data also indicate that a number of cell kinetic parameters in the intestinal epithelium of lactating mice are changing throughout the period of lactation. Thus the intestinal epithelium is probably not in a steady state during lactation.
High‐resolution scanning electron microscopic studies on the three‐dimensional structure of the transverse‐axial tubular system, sarcoplasmic reticulum and intercalated disc of the rat myocardium
Authors: Ogata Takuro , Yamasaki Yuichi
Published: February 2005

The three‐dimensional structure of the transverse‐axial tubular system, sarcoplasmic reticulum (SR), and intercalated disc of the rat left ventricle was examined by high‐resolution scanning electron microscopy after removal of the cytoplasmic matrices by the osmium‐DMSO‐osmium procedure. In the intermyofibrillar space, the transverse tubules (T‐tubules) are accompanied by longitudinally oriented axial tubules and together form a transverse‐axial system. The junctional SR is usually small but occasionally medium or large in size and couples with the T‐ or with the axial tubules. On the surface of the junctional SR facing the T‐ or the axial tubule, tiny junctional processes are seen. One or two sarcotubules, the so‐called Z‐tubules, frequently run parallel to the T‐tubule. The sarcotubules derived from the junctional SR or from the Z‐tubule run longitudinally or obliquely and form polygonal meshes around the myofibrils. On the surface of the SR at the H‐band level, small fenestrations of 12–40 nm in diameter, and tiny hollows 8–20 nm in diameter are seen. Bulbous swellings of the SR, the corbular SR, are preferentially seen near the Z‐band. The large and flat SR, known as the cisternal SR, intercalates among the SR meshes. In the subsarcolemmal space, the sarcotubules form a multilayered network (peripheral SR). The cisternal SR is frequently intercalated in these meshes and closely associated with the inner surface of the sarcolemma. The intercalated disc appears as a prominently undulated membrane demarcating the border between two adjacent heart muscle cells, and occasionally small projections 60–90 nm in diameter and 200–600 nm in length display on its surface.
Distribution pattern of acetylcholinesterase in early embryonic chicken hearts
Authors: Lamers Wouter H. , Geerts Willie J. C. , Moorman Antoon F. M.
Published: February 2005

To study the developmental appearance of acetylcholinesterase in early embryonic hearts, an enzyme‐histochemical study was carried out in chicken embryos ranging from cardiogenic plate to late tubular stages. Initially acetylcholinesterase is present in all cells of the (future) myocardium. When 13–14 pairs of somites have developed, i.e., shortly before blood propulsion starts, acetylcholinesterase selectively disappears from the ventral and lateral wall of the developing ventricle. Slightly later, when 18–19 pairs of somites have developed, acetylcholinesterase also disappears from the dorsal and anterior wall of the atrium. High concentrations of acetylcholinesterase remain present in the outflow tract and lower concentrations in a continuous tract along the lesser curvature of the heart, the atrial side of the atrioventricular canal, and the left wall of the atrium. In late tubular stages of heart development, acetylcholinesterase is reexpressed in the inner myocardial layer of the ventricle, i.e., in the developing trabeculae and the ventricular side of the atrioventricular canal, where it is continuous with the acetylcholinesterase‐expressing cells of the atrial side of the atrioventricular canal. The expression pattern of acetylcholinesterase in early embryonic chick hearts coincides with that of areas that control the conduction of the impulse and may reveal a cholinergic signal transduction system that is responsible for a coordinated contraction pattern of the myocardium prior to the development of the definitive conductive system.
Morphometry and frequency of afferent synaptic terminals in the rabbit dorsal–lateral geniculate nucleus
Authors: Carmona Ramón , Calvente Ruth , Abadía‐Molina Francisco , Abadía‐Fenoll Francisco
Published: February 2005

Morphological and morphometric features of the retinal synaptic terminals (RLP) and cortical synaptic terminals (RSD) were analyzed in the αE sector of the rabbit dorsal–lateral geniculate nucleus (dLGN). A methodological approach was selected which allowed us to determine volume of the neuropil and elsewhere record variations in the size and distribution of the two types of terminals found in the three zones (superior, middle, and inferior) from up to down into which the αE sector of the dLGN was divided. After obtaining an isotropic, uniform, and pseudorandom (IUR) sample, the terminals were examined on the basis of a set of morphometric parameters. An analysis of these data showed the retinal terminals (RLP) to be more numerous and to occupy a greater total area of the neuropil in the dorsal (superior) zone of the nucleus, whereas the number and total area occupied by cortical terminals (RSD) did not vary in the superior, middle, and inferior zones. Upon comparing the two types of terminals, the RLP were larger and more widely distributed, the greatest differences between the two appearing in the dorsal (superior) zone of the dLGN.
Ultrastructure of substance P immunoreactive elements in the periaqueductal gray matter of the rat
Authors: Gioia M. , Bianchi R.
Published: February 2005

Substance P (SP) is a non‐opioid peptide that generates a potent, analgesia when injected into the periaqueductal gray matter (PAG)The aim of this study was to investigate the fine neuronal structures and synaptic circuits involved in SP action in rats by means of electron microscopy, using immunocytochemical (ICC) pre‐embedding methods. A conventional ultrastructural study, carried out to interpret the ICC data correctly, shows small sized nerve cell bodies with a high nucleus–cytoplasmic ratio; absence of an extensive granular endoplasmic reticulum; and few axo‐somatic contacts having symmetrical and asymmetrical junctions in equal proportions. The large neuropil is characterized by numerous thin unmyelinated axons and axodendritic synapses mainly showing pleomorphic vesicles and asymmetrical junctions.

The ICC analysis showed moderately labeled nerve cell bodies with the same structural, synaptic, and dimensional features as the negative cells. In the neuropil SP immunoreactivity is shown by dendrites, synapses, and thin elements which are unidentifiable structurally. No SP terminals synapsing on SP nerve cell bodies were found and only occasional SP light labeled terminals synapsing on negative perikarya were seen. The SP boutons generally have pleomorphic vesicles and asymmetrical junctions.

On the basis of these data a possible excitatory activity of PAG SP synapses could be hypothesized. This activity would take place on postsynaptic neurons generally at a dendritic level. Our ultrastructural findings give support to an excitatory role carried out by SP neurons of the PAG, as suggested by the role of PAG circuitry on spinal nociception.
Organization and development of the mineral phase during early ontogenesis of the bony fin rays of the trout Oncorhynchus mykiss
Authors: Landis William J. , Géraudie Jacqueline
Published: February 2005

Characterization of mineral deposition has been studied by electron optical methods during early ontogenesis of lepidotrichia, the bony fin rays, of the trout Oncorhynchus mykiss (the former Salmo gairdneri). The fin rays consist of an extracellular granular ground substance containing in part a network of collagen fibrils within the basal lamella of the fin dermoepidermal interface. Growth of individual rays proceeds in a proximodistal direction. The mineral phase appears as electron‐dense needle or plate‐like particles and is associated with the collagenous matrix. On analysis of progressively maturing tissue, the mineral was characterized as a poorly crystalline hydroxyapatite with Ca/P molar ratios in the range of 1.0–1.4, corresponding to distal and proximal areas, respectively. With selected‐area electron diffraction and dark field imaging of lepidotrichia, the mineral particles were found to be about 3–10 nm thick and 12–20 nm in length (along their crystallographic c‐axes), possibly aggregated into larger crystals 35–40 nm long observed with bright field microscopy. No definitive relation was found between either the c‐ or a,b‐axes images of the crystals and the periodic structure of collagen, which forms the framework for mineral deposition in this and in other vertebrate calcifying tissues.
Mandibular and molar vascularization in guinea pigs. Scanning electron microscopic study of corrosion casts
Authors: Aharinejad S. , Franz P. , Firbas W. , Fakhari M.
Published: February 2005

The vascularization of the mandible, molar teeth, and periodontal ligament of adult male and female albino guinea pigs (Cavia porcellus) was studied by scanning electron microscopy of vascular corrosion casts. Main routes of mandibular blood supply and drainage are shown, and the intrinsic vascular patterns of the mandible, the molars, and the periodontal ligament are described. Results are compared to findings in man and in other mammals.
Ontogenic appearance of three fatty acid binding proteins in the rat stomach
Authors: Iseki Shoichi , Kanda Tatsuo , Hitomi Masahiro , Ono Teruo
Published: February 2005

With the use of specific antibodies against three structurally different fatty acid binding proteins (FABPs), viz, liver FABP (L‐FABP), heart FABP (H‐FABP), and intestinal FABP (I‐FABP), the localization and relative amount of the immunoreactive proteins were determined by immunoblotting and immunocytochemistry in the gastric epithelium of rats during prenatal and postnatal development. H‐FABP immunoreactivity was first detected at embryonic day 20 (E20), with predominant localization in the parietal cells, whereas I‐FABP immunoreactivity was detected at the day of birth in the surface mucous cells. Both immunoreactivities were continuously localized in the same cell types with increasing intensity into adulthood. In contrast, the immunoreactivity for L‐FABP showed remarkable changes in intensity and localization during development of the rat stomach. It was first detected in the surface mucous cells of E19. In the first 2 weeks of postnatal life, i.e., the suckling period, L‐FABP immunoreactivity reached a peak in intensity and was localized not only in the surface mucous cells, but also in some of the parietal cells, brush cells, and endocrine D cells. In the following few weeks of weaning, the reactivity of surface mucous cells and parietal cells disappeared, leaving only a small amount of total L‐FABP immunoreactivity in the adult stomach, which was localized exclusively in the brush cells and D cells. These results revealed that the appearance of the three types of FABPs in the rat stomach is specific to cell types and developmental stages.
The ischiourethralis muscle of the rat: Anatomy, innervation, and function
Authors: Dail William G. , Sachs Benjamin D.
Published: February 2005

The ischiourethralis (IU), a striated perineal muscle presumed to be involved in sexual reflexes, was studied in the rat. The paired muscle arises from the penile crus and the penile bulb and unites in a raphe over the deep dorsal vein of the penis. Retrograde tracing studies show that the muscle is innervated by neurons in the dorsolateral nucleus of the lumbar spinal cord, a pudendal nerve motor nucleus which also innervates the ischiocavernosus muscle. Excision of the IU muscle did not interfere with the ability of males to display normal copulatory behavior, nor did it affect significantly the number and intensity of reflexive erections. It nevertheless remains possible that the IU may contribute to intense glans erection by compressing the deep dorsal vein.
Ultrastructure of the submandibular gland in the African multimammate rodent, Praomys natalensis
Authors: Toyoshima Kuniaki , Tandler Bernard
Published: February 2005

Praomys natalensis, an African rodent that is phenotypically and cytogenetically intermediate to rats and mice, possesses a submandibular gland that is histologically similar to that in both of these near relatives, but is ultra‐structurally unique. Acinar cells, which are seromucous in nature, contain secretory granules that often contain a perfect “bull's eye” inclusion (or some variant of this configuration) suspended in a dense matrix. The Golgi apparatus in these cells has an unusual structure, with the Golgi saccules often being doubled over, so that the outermost saccule also is the innermost. This peculiar architecture apparently arises fairly late in the secretory process, i.e., a Golgi apparatus of conventional structure gives rise to a nascent granule (condensing vacuole), then its saccules secondarily fold over. Intercalated ducts are preceded by a ring of specialized cells that have a number of serous‐type granules, the duct cells themselves being devoid of such granules. Granular convoluted tubules (GCT) contain large dense granules that appear to be spontaneously involved in chain exocytosis. These GCT granules probably are the repositories of nerve growth factor, which is particularly abundant in Praomys. Striated ducts for the most part are typical in appearance, but they and, to a lesser extent, GCTs contain prominent, membrane‐bound crystalloids with a periodicity of about 15 nm.
Rat small intestinal mucins: A quantitative analysis
Authors: Kemper Abbie C. , Specian Robert D.
Published: February 2005

Although much is known about the qualitative distribution of mucin‐secreting goblet cells in the small intestine, the quantitative distribution of stored mucins remains undefined. The purpose of this study was to determine the distribution of neutral stored mucin in the rat small intestine by using morpho‐metric techniques and once established, to verify that this methodology could detect secretion in animals exposed to a known mucin secretagogue. Twelve male Wistar rats (five baseline, five pilocarpine‐treated, and two vehicle controls) were fixed by vascular perfusion. After a brief fixation the intestine was removed, cut into 10 equal segments, sliced, and fixed overnight. Methacrylate sections from each segment were stained with periodic acid‐Schiff and toluidine blue. For mor‐phometry, the volume of epithelium per surface area of epithelial basal lamina was calculated with a Merz grid. The volume density of stored mucin per epithelium was determined by point‐counting on a square lattice grid. Volumes were related to either surface area of epithelial basal lamina or mucosal surface area. Due mostly to contributions by villus stored mucin, the total amount of product was found to increase proximally to distally in the small bowel, with the most dramatic increases occurring in the first three segments. When subjected to pilocarpine, a massive secretory response was evoked, resulting in a near total depletion of crypt stored mucin at all levels of the small bowel. Secretion of villus stored mucin also occurred throughout the small intestine, however reaching levels of significance at only a few points. This study describes the distribution of stored mucin in the small intestine under baseline and accelerated secretory conditions.
Regeneration of skeletal muscle in streptozotocin‐induced diabetic rats
Authors: Gulati Adarsh K. , Swamy M. S.
Published: February 2005

The present study analyzes the regeneration of skeletal muscle in diabetic rats. Intravenous injection of streptozotocin (STZ) was used to induce diabetes. Six weeks later the extensor digitorum longus (EDL) muscles from diabetic rats were either transplanted into diabetic or normal hosts to initiate regeneration. Normal EDL muscle transplants in normal and diabetic hosts were also performed for comparison. One, 2, 4, and 12 weeks after transplantation, the EDL regenerates were morphologically analyzed. Regeneration and formation of neuromuscular junctions were observed in all transplants, including diabetic regenerates in diabetic hosts. The overall mass and myofiber size of the diabetic EDL regenerate in the diabetic host was significantly reduced in spite of complete regeneration. Recovery of the diabetic muscle mass and the myofiber size was observed after transplantation into normal hosts. A reduction in mass and myofiber size was observed in normal EDL muscles transplanted into diabetic hosts. It is concluded that poor recovery of diabetic muscle is related to metabolic and structural alterations in the diabetic host, rather than to innate capacity of the muscle to per se undergo regeneration and reinnervation. The observed enhancement in recovery of diabetic muscle after transplantation in a normal host and deterioration of normal muscle after transplantation in a diabetic host shows that the host environment determines the success of muscle regeneration.
Two‐phase in vitro culture of explanted chick embryos
Authors: Flamme Ingo , Albach Karin , Müller Stefan , Christ Bodo , Jacob Heinz Jürgen
Published: February 2005

The present study describes a method of culturing chick embryos together with their surrounding area vasculosa on two different culture media in succession. Embryos in the 2nd day of incubation (stages 13, 14, 15 according to Hamburger and Hamilton, 1951) were explanted from the yolk with the aid of a ring of filter paper and transferred dorsal side up to a silicone culture dish containing the first culture medium (89.5 % L‐15, 10 % fetal calf serum, 0.5 % Antibiotics). The paper ring was clamped onto the wall of the culture dish by a steel ring so that the embryo was fixed for the culture period. After 4 ± 1, 8 ± 1, 12 ± 1 hrs, the embryos were taken from the culture dishes and transferred to others containing a yolk‐albumen mixture as culture medium; 81.2 % of embryos survived the first phase of culture. On the second medium 50.3 % of explanted embryos were still alive at stage 20 (HH), and 7.9% of them reached the 5th day of development (St 25 HH).

The average length of survival in vitro was found to be influenced by both the length of the first culture phase and the stage at which embryos were explanted.

This culture method may be useful for teratological tests, since in the first phase of culture, concentrations of test substances and the time of exposure can be exactly adjusted, and in the second phase, the embryo is allowed to develop quite normally, under conditions similar to those in ovo.
Ultrastructure of the sublingual gland in the African multimammate rodent
Authors: Toyoshima Kuniaki , Tandler Bernard
Published: February 2005

The sublingual gland of Praomys natalensis, an African rodent that is phenotypically and cytogenetically intermediate to mice and rats, is a mixed gland, consisting of mucous acini that are capped by serous demilunes, of intercalated ducts, and of some short striated ducts that quickly become excretory ducts. The mucous cells are typical in appearance, with lucent granules that contain an assortment of scattered vermiform or particulate densities. The serous cells display an array of secretory granules with a highly unusual substructure. Rather than a pattern based on the manner in which light and dark regions are disposed in their matrix, these granules contain packets—some furled, some flat—of membranes that exhibit a pronounced axial periodicity of ∼5 nm. Intercalated ducts are simple in structure, with no obvious morphological specializations. Striated ducts resemble those in the salivary glands of less exotic rodents, but they and the excretory ducts often have clusters of cytoplasmic crystalloids consisting of linear densities that intersect at right angles and that have a periodicity in both directions of ∼ 12 nm.
Three‐dimensional structure of dense bodies in rabbit renal artery smooth muscle
Authors: McGuffee Linda J. , Mercure Juanita , Little Sally A.
Published: February 2005

In this report, we present a three‐dimensional computer assisted reconstruction study from serial thin sections through a rabbit renal artery smooth muscle cell. In a series of 32 consecutive thin (100‐nm) sections, one longitudinally oriented cell was followed and photographed in alternating sections. The profiles of the cell surface and dense bodies were reconstructed from these 16 planes and the distribution, size, shape, and spatial relationships among these components was examined. The reconstructed images showed that the cell decreases in diameter from its widest region in the center to the two ends in a step‐wise taper. Within the cell, dense bodies are numerous. Relative to the cell axes, a membrane associated dense body (MDB) can be ≤3.5 μm long, 0.25 μm wide, and may extend up to 2 μm in depth. While the MDB profile in one section may be aligned with the long axis of the cell, in an adjacent section the same dense body may appear almost circular or wedge shaped. The same is true of cytoplasmic dense bodies (CDBs). Compared with MDBs, CDBs are smaller in all dimensions. Some, but not all, CDBs line up in strings oriented with the long axis of the cell. The continuity of dense bodies over considerable cell depth and their change in shape may have important implications for integration of contractile activity and for transmitting passive tension to the extracellular matrix.
Kinetics of the tingible body macrophage response in mouse germinal center development and its depression with age
Authors: Smith J. P. , Lister A. M. , Tew J. G. , Szakal A. K.
Published: February 2005

Although tingible body macrophages (TBM) have been recognized in germinal centers for over 100 years, their role in the germinal center response is not clear. In this study, the kinetics of the TBM response was quantitatively assessed and correlated with the kinetics of germinal center development in young mice. The TBM response in old mice (which have an age‐related depression of germinal center development; Szakal et al., 1990) was analyzed for comparison. Young and old immune mice were challenged with human serum albumin and 0, 1, 3, 5, 7, 10, and 14 days later the popliteal and axillary lymph nodes were evaluated. Germinal centers were localized histochemically in alternate serial sections using horseradish peroxidase conjugated peanut agglutinin. TBM numbers were determined per germinal center on adjacent sections by the presence of tingible bodies or histochemically by using the monoclonal antibody Mac‐2. Analysis of lymph nodes from young mice showed that TBM numbers decreased with the dissociation of preexisting germinal centers. TBM reappeared 5 days after challenge and the TBM kinetics paralleled the increase in size of de novo germinal centers. In fact, a constant ratio of one TBM to every 350–450 B cells was maintained from day 5 to day 10. In old lymph nodes, TBM were generally absent throughout germinal center development. The lack of TBM prior to germinal center development and their absence in aged mice are inconsistent with the concept that TBM are required for the induction of the germinal center reaction. However, the data are consistent with a role for TBM in regulating the magnitude of the germinal center reaction.
Implementing Boissonnat's method for generating surface models of craniofacial cartilages
Authors: Lozanoff Scott , Deptuch John J.
Published: February 2005

Surface modeling of embryonic craniofacial morphology typically is accomplished using data derived from planar contours. Methods currently available for reconstructing embryonic craniofacial anatomy from contour data rely on shortest‐path algorithms in order to interpolate surfaces. However, these techniques either fail or require a considerable amount of user interaction when complex surfaces are modeled since foramina and structural divisions cannot be interpolated properly. Recently, a new approach has been described by Boissonnat that constructs a polyhedral volume between sets of planar contours. Surfaces are interpolated by identifying the planes formed when the contours intersect the polyhedron. The purpose of this study is to determine whether craniofacial cartilages from embryonic mice can be reconstructed in an accurate and reliable fashion using this method. Embryonic mice were collected and processed for routine histological sectioning. Serial sections of the anterior cranial base and nasal capsule were obtained, subjected to videomicroscopy, and modeled. Reconstructions of the anterior cranial base and nasal capsule from embryonic mice were compared to the same structures in age‐matched specimens that were processed with whole‐mount staining procedures. The models compared well with the whole‐mount preparations. In addition, the reconstruction technique accurately rendered complex surface features of the embryonic anterior cranial base and nasal capsule including foramina and structural branches.
The subdural space interpreted as a cellular layer of meninges
Authors: Frederickson Richard G.
Published: February 2005

The subdural region within the cranial meninges is examined in guinea pigs by electron microscopy. The fine structures of the arachnoid membrane and dura are described separately in specimens that have been isolated from each other during removal from the cranial cavity. In addition, the fine structure of the intact dura‐arachnoid is described, where the subdural space would be present in an undisrupted state. Lastly, the inner surface of the dura and the outer surface of the arachnoid membrane are examined at the point of separation between the two specimens where the dura is reflected from the arachnoid by experimental dissection. From these observations morphologic criteria are established for identifying the constituents and boundaries of the subdural space and for explaining mechanisms in the histogenetic process of “opening” or enlarging this space.

The morphologic identity of the classic subdural space is reinterpreted in light of the findings. The subdural space, traditionally described as a fluid‐filled potential cavity existing in an extracellular compartment, is not apparent in the guinea pig. Instead, fragile cells designated as light cells occupy the compartment between the dura and arachnoid, with very little extracellular space available. Experimental opening of the subdural space occurs, significantly, along pathways extending by fracture through the cytoplasm and intercellular separation of these light cells rather than by enlargement of a preexisting mesothelial‐lined intercellular space between these cells and the true arachnoid cells. Cytoplasmic fine structure of light cells suggests a close kinship with cells in the meningeal layer of the dura. The functional significance of the light cells and their possible role in subdural hematomas is discussed.
Distribution and morphological characteristics of axons in the periodontal ligament of cat canine teeth and the changes observed after reinnervation
Authors: Loescher A. R. , Holland G. R.
Published: February 2005

The distribution and morphological characteristics of myelinated and non‐myelinated axons innervating the lower canine periodontal ligament (PDL) in adult cats have been analysed. After perfusion fixation and decalcification, the teeth were slit transversely, divided into segments, and embedded in plastic. Ultrathin sections of each segment were examined in the electron microscope and used to reconstruct the whole PDL at 1, 4, 7, and 9 mm from the tooth apex. One millimeter from the tooth apex there were a mean of 920 myelinated axons and 1,415 non‐myelinated axons. The numbers of axons declined toward the tooth crown. Bundles of myelinated and small non‐myelinated axons lay adjacent to the blood vessels midway between the bone and cementum. Isolated myelinated axons appeared to have split away from these main nerve bundles and entered the avascular zone of the ligament, where they lost their myelin sheaths to become large non‐myelinated axons rich in mitochondria. These non‐myelinated axons sometimes appeared to be linked to collagen fibres and were thought to be the mechanoreceptor terminals.

Twelve weeks after sectioning and inferior alveolar nerve, the total number of axons innervating the periodontal ligament was 50% of that found in the contralateral controls. The large non‐myelinated axons had smaller mean diameters and contained fewer mitochondria, a change which may be consistent with a reduction in mechanoreceptor excitability.
Parasympathetic postganglionic cells in the glossopharyngeal nerve trunk and their relationship to unmyelinated nerve fibers in the fungiform papillae of the frog
Authors: Inoue Katsuhiro , Kitada Yasuyuki
Published: February 2005

The glossopharyngeal nerve of the frog is made up of afferent nerve fibers and efferent, parasympathetic and sympathetic nerve fibers. The precise origin and course of the parasympathetic efferent nerve fibers in the fungiform papillae of the frog's tongue were investigated. We found the ganglionic cells in the lingual branch of the frog glossopharyngeal nerve. The surface of the ganglionic cell bodies was partly covered by synaptic endings that impinged upon it. Synaptic endings contained clear synaptic vesicles and large dense‐cored vesicles. After cutting of the glossopharyngeal nerve proximal to the jugular ganglion, synaptic endings were found to show definite signs of degeneration. These findings led us to the conclusion that the ganglionic cells in the lingual branch of the glossopharyngeal nerve are the parasympathetic postganglionic cells. After cutting of the glossopharyngeal nerve distal to the jugular ganglion, some unmyelinated nerve fibers in the fungiform papillae and postganglionic cells in the lingual branch remained intact. These results strongly suggest that the origin of some of the unmyelinated nerve fibers is the parasympathetic postganglionic cell in the lingual branch.
Potentiation of cochlear hair cell loss by acoustic stimulus and gentamicin in the guinea pig
Authors: Bhattacharyya Tapan K. , Dayal Vijay S.
Published: February 2005

We explored the possibility of synergism between a pure‐tone stimulus and gentamicin in causing cochlear injury by analyzing hair cell loss. Guinea pigs receiving daily injections of gentamicin (200 mg/kg body wt.) for 1 week were exposed to a 2 kHz tone (95 dB SPL, 2 hours daily). Surface preparations of the spiral organ were studied by phase contrast microscopy, and the extent of hair cell loss in the entire organ of Corti was recorded in cytocochleograms.

Gentamicin by itself was slightly ototoxic, damaging the innermost row of outer hair cells, whereas exposure to sound alone caused no hair cell loss. Combined antibiotic and acoustic exposure produced extensive cochlear damage. A few animals showed massive hair cell degeneration and collapse of the organ of Corti, except in the apical turn. The site of damage was possibly determined by the frequency of the sound stimulus. Thus, an intermittent tonal stimulus such as that used in the present experiment can be harmless by itself, but causes injury to cochlear hair cells in guinea pigs when administered in combination with gentamicin.
Changes in actin distribution during sperm development in the opossum, Monodelphis domestica
Authors: Olson Gary E. , Winfrey Virginia P.
Published: February 2005

The distribution of actin in spermatogenic cells and epididymal spermatozoa of the opossum, Monodelphis domestica, was examined by immuno‐fluorescence microscopy to identify its potential function in the major structural events of sperm development. In spermatogenic cells actin was located at the site of initial interaction between the nucleus and acrosome and remained present through subsequent acrosome morphogenesis. Actin was also associated both with the posterior pole of the nucleus, at the site of flagellar attachment, and with the manchette. Thus actin may play a role in establishing the specific associations of spermatid organelles and in the streamlining of the cells' architecture. In epididymal spermatozoa two sites of actin localization are present. The first site is surrounding the connecting piece where it may participate in the characteristic 90° rotation of the head. The second site was a ring of actin surrounding the lateral boundary of the acrosome where it may play a role in the sperm pairing process which also occurs in the epididymis.
Cytoplasmic distribution of poly(A)‐containing RNA in developing Necturus maculosus oocytes with reference to annulate lamellae
Authors: Ganion L. R.
Published: February 2005

The cytoplasmic distribution of poly(A)+ mRNA and its relationship to annulate lamellae were examined in developing Necturus maculosus oocytes by in situ hybridization with [3H]poly(U). The specificity of [3H]poly(U) binding was tested by incubating control ovarian sections with either KOH or RNase A before in situ hybridization. In both experiments, the silver grain densities were markedly reduced. Poly(A)+ RNA is uniformly distributed in the cytoplasm until the mid‐growth phase and then later in vitellogenesis becomes localized in the subcortical ooplasm. The silver grain density in the cytoplasm varied during oogenesis and was greatest in previtellogenic oocytes. Annulate lamellae commonly are observed with the light microscope in oocytes prior to vitellogenesis. In such oocytes, the labeled mRNA probe is observed over cytoplasmic regions of annulate lamellae. The results suggests that a differential localization of messenger RNA occurs during oogenesis in Necturus maculosus. Furthermore, poly(A)+ RNA is present in cytoplasmic regions of annulate lamellae.
Prenatal and postnatal development of the large intestine in the insectivore Suncus murinus, the laboratory shrew
Authors: Kiso Yasuo , Oku Kazuomi , Matsuda Hiroshi , Yamauchi Shoji
Published: February 2005

Development of the large intestine in the insectivore Suncus murinus (the laboratory shrew) was investigated from day 21 to 30 of gestation and from birth to 20 days of age. Two days before birth, the stratified epithelium in the large intestine changed into a single layer. Although neither villi nor villus‐like structures were ever present, fissures, corresponding to openings of the crypts, appeared on the mucosal surface before birth. These increased in number as well as in width and depth, connected with each other, and gave the mucosal surface a ridge‐like appearance by 20 days of age. An elevation containing submucosae appeared shortly after birth and formed a large circular fold during the neonatal period. Goblet cells were the predominant epithelial cell type. Individual epithelial cells were mature‐looking a few days before birth; goblet cells contained numerous mucous globules and absorptive cells possessed well‐developed organelles. However, although goblet cells increased in number and exhibited active mucous‐releasing forms after birth, absorptive cells never showed morphologic evidence of active endocytosis, such as apical endocytotic complexes and large supranuclear vacuoles. Each epithelial cell was similar in ultrastructure to that of the adult shortly after birth.
Effects of maternal bilateral ureteral ligation on the differentiation of glomerular anionic sites in fetal rat kidney
Authors: Okada Toshiya , Morikawa Yoshio
Published: February 2005

Effects of maternal bilateral ureteral ligation on the differentiation of glomerular anionic sites in fetal kidney were studied with the colloidal iron method. The ligation was performed on days 17, 19, and 21 of pregnancy, and the animal were euthanized 1 day after each ligation. On fetal day 20, in the fetuses from ligated mothers, colloidal iron was concentrated in laminae rarae interna and externa of the glomerular basement membrane. In the fetuses from sham‐ligated mothers, however, a different pattern of iron distribution was noted. In most areas of the glomerular basement membrane, colloidal iron was randomly distributed as in both fetuses of fetal day 18. In the remaining areas, the same pattern of colloidal iron distribution as was noted in the fetuses from ligated mothers of fetal day 20 was observed. On fetal day 22, colloidal iron was densely accumulated in laminae rarae interna and externa of the glomerular basement membrane in both groups. However, the iron‐free zone was slightly thicker in the fetuses from the ligated mothers. These findings suggest that maternal bilateral ureteral ligation accelerates the differentiation of glomerular anionic sites in the kidney of fetal rats.
A method for preparing skeletal muscle fiber basal laminae
Authors: Carlson Edward C. , Carlson Bruce M.
Published: February 2005

Previous attempts to prepare skeletal muscle basal laminae (BL) for ultrastructural analyses have been hampered by difficulties in successfully removing skeletal muscle proteins and cellular debris from BL tubes. In the present study we describe a two phase method which results in an acellular muscle preparation, the BL of which are examined by light, transmission electron, and scanning electron microscopy. In the first phase, excised rat extensor digitorum longus muscles are subjected to x‐radiation and then soaked in Marcaine to inhibit muscle regeneration and to destroy peripheral muscle fibers. The muscles are then grafted back into their original sites and allowed to remain in place 7–14 days to allow for maximal removal of degenerating muscle tissue with minimal scar tissue formation. In the second phase, the muscle grafts are subjected sequentially to EDTA, triton X‐100, DNAase, and sodium deoxycholate to remove phagocytizing cells and associated degenerating muscle tissue. These procedures result in translucent, acellular muscle grafts which show numerous empty tubes of BL backed by endomysial collagenous fibers. These preparations should be useful for morphological analyses of isolated muscle BL and for possible in vitro studies by which the biological activity of muscle BL can be examined.
Extracellular matrix of the developing heart in normal and cardiac lethal mutant axolotls, Ambystoma mexicanum
Authors: Fransen Margaret E. , Lemanski Larry F.
Published: February 2005

As part of an ongoing study of heart development in normal and cardiac lethal mutant axolotls ( Mexican salamanders) we examined the extracellular matrix (ECM) by microscopical methods. With scanning electron microscopy we are unable to detect ECM on the apical surface of cells of the early cardiogenic mesoderm. During the period of lateral plate migration, which coincides with the period of cardiogenic induction of mesoderm by anterior endoderm, there is little ECM, aside from some microfibrils, on the basal surface of the endoderm or mesoderm of the pharyngeal region. Later, a basal lamina (BL) is found on the endoderm and along portions of the developing endocardial and myocardial tubes. By the time of heartbeat initiation the BLs are complete and invested with striated collagen‐like fibrils that are sparsely distributed in the “cardiac jelly” of normal and mutant hearts. Striated fibril deposition, which increases with time, is generally random in orientation, with the exception of some regions where there is a preferred directionality. During the post‐hatching period striated fibrils appear in the subepicardial space. In addition, branching fibers that are probably elastin appear in the bulbus arteriosus. In these later stages the density of fibrils in the cardiac lethal mutant heart is much less than normal. Indirect immunofluorescent microscopy reveals laminin and fibronectin in the basal; aminae of the endocardial and myocardial tubes of both normal and cardiac llethal mutant hearts. In addition, punctate and fibrillar staining for fibronectin, and punctate staining for laminin are found in the cardiac jelly. These matrix proteins are not abundant at the apical (exterior) surface of the myocardium until the epicardium appears. These results are similar to reports on ECM in other developing vertebrate hearts.