bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of the density of spermatogonia in the seminiferous epithelium of the Chinese hamster: I. Undifferentiated spermatogonia
Authors: De Rooij D. G. , Janssen J. M.
Published: February 2005

The topographical arrangement of the clones of Asingle, Apaired, and Aaligned (As, Apr, and Aal) spermatogonia on the basement membrane of seminiferous tubules of the Chinese hamster was studied. It was found that at least some of these clones are not distributed at random as clones of similar cell number were often seen in clusters. Areas were found with few or many As spermatogonia. Also, clusters of Apr spermatogonia were found, indicating that in such an area many As spermatogonia more or less synchronously formed Apr spermatogonia. Since clusters of clones of 16 Aal spermatogonia were observed, it can be concluded that these clusters of Apr spermatogonia may proliferate in at least a roughly synchronous way.

It was found that over large areas the densities of undifferentiated spermatogonia may be very low or high in comparison to the mean density in the animal. Whether the ratio of self‐renewal and differentiation of the stem cells changed locally in response to the high or low density of undifferentiated spermatogonia in particular areas was investigated. No indications for a regulatory mechanism to keep the density of stem cells and/or the density of undifferentiated spermatogonial clones at a certain level could be detected in the normal Chinese hamster. This lack of regulation was at least partly responsible for the widely different numbers of A1 spermatogonia that were formed in the various areas studied in stage IX.
Pathways of lymph flow through superficial inguinal lymph nodes in the pig
Authors: Spalding Hugh , Heath Trevor
Published: February 2005

The pig lymph node has an unusual structure in that tissue containing lymph nodules generally occupies a central position. Our aim was to describe the lymphatic pathways through this node. We studied the structure of these pathways with light and electron microscopy, made casts of lymphatic vessels and sinuses with Microfil, and studied the distribution within the node of subcutaneously injected carbon particles.

Most afferent lymphatics penetrate deeply within the node, where they give off several branches to peritrabecular sinuses that ramify through centrally located nodular tissue. However, where an afferent lymphatic enters the node there is a subcapsular sinus over an area of nodular tissue that occupies a conventional superficial position. Some lymph reaches this sinus from the central peritrabecular sinuses, but there can also be direct communications between this sinus and the afferent lymphatic.

After flowing through sinuses in nodular tissue, lymph enters tissue that is analogous to medullary tissue in other species. This tissue is of two types, one consisting mainly of a diffuse network of reticular cells around spaces up to 10–12 μm across, and one that more closely resembles conventional medullary tissue. Lymph then flows to collecting ducts, which lack valves, and then to efferent lymphatics.

Our findings do not support suggestions that a purely physical obstruction of lymphocytes in the lymph node accounts for the dearth of lymphocytes in efferent lymph of pigs.
Two‐headed, two‐necked conjoined twin calf with partial duplication of thoracoabdominal structures: Role of blastocyst hatching
Authors: McGirr Wendy J. , Partlow Gary D. , Fisher Kenneth R. S.
Published: February 2005

Gross anatomical analysis of a derodidymic monosomic stillborn male calf from an embryo transfer recipient was carried out. Two normal heads were present on two necks which were fused at the shoulders. Although the ribs were abnormal in shape and number, there was one trunk and four legs. The vertebrae were double and partially fused from the thoracic region to the sacrum, which was singular and normal. In the thoracic region there was a single vertebral canal that contained two incompletely fused spinal cords which shared common meninges. In the lumbar region there was a spina bifida. The medial neck musculature was variously fused. Two esophagi entered one enlarged rumen and the liver and gall‐bladder had extra lobes. Two sets of lungs occupied three pleural cavities and also part of the pericardial cavity. Two hearts were joined by a common cavernous venous sinous. The vasculature cranial to the heart reflected the doubling. The vasculature caudally was singular. The calf was uniscrotal and ipsilaterally cryptorchid. Our results are consistent with the hypothesis that atypical “hatching,” that is, emergence of the blastocyst from the zona pellucida, may cause anomalous twinning.
Postnatal development of the duct system in the mouse parotid gland
Authors: Domon Masaharu , Kurabayashi Tohru
Published: February 2005

The morphology of the parotid gland in adult mice is mouse strain‐specific. C57BL/6 and C3H/He strains of mouse are representatives of two types of the morphology identified previously. The postnatal development of such morphologic differences was investigated by sialography of excised glands of these strains of mouse. It was observed that the mouse strain‐dependent morphological characteristics were already present at birth, except for the branching pattern of the peripheral duct system, which became differentiated at 3 weeks of age. These results indicate that the C3H/He mouse‐specific branching pattern of the peripheral ducts reflects the profile of matured secretory units and ducts, and that the C57BL/6 mouse‐specific pattern resembles that of an immature C3H/He mouse.
Ultrastructure of human fetal mammary gland
Authors: Kellokumpu‐Lehtinen P. , Johansson R.‐M. , Pelliniemi L. J.
Published: February 2005

Early cytodifferentiation of human fetal mammary gland was studied at the time of the beginning of the sexual differentiation during the sixth to eleventh developmental weeks. The gland appeared as a solid epithelial ingrowth into the underlying mesenchyme on both sides of the thoracic wall at the age of 5 weeks in both sexes. These ingrowths contained primitive glycogen‐rich cells with large nuclei. The surrounding mesenchymal cells gathered around the basal lamina. These cells differentiated into fibroblasts, and collagen fibers were seen in the mesenchyme near the mammary buds. No lumina appeared within the buds during this study. Differences between the male and female mammary epithelium or mesenchyme were not observed, although androgen synthesis and secretion in the fetal testis had already begun. The close connections and concomitant differentiation of the mammary bud epithelium and mesenchyme during the early embryogenesis in this study suggest that epithelio‐mesenchymal interaction plays an important role in the differentiation of human mammary gland.
Taste bud development in chickens (Gallus gallus domesticus)
Authors: Ganchrow Judith R. , Ganchrow Donald
Published: February 2005

Oral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin‐and‐eosin‐stained sections (10 μm) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16–20 days of incubation (E) and, posthatch days 1 and 50–60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium. Only spherical‐shaped buds were observed on E17 and E18, and these spherical clusters never penetrated to the surface of the stratified epithelial layer. E19 marked a transitional stage when mature bud features began to emerge: the buds assumed a more elongate shape, several kinds of cells comprising the bud were distinguishable and the first taste pores were observed. During the ensuing embryonic days, buds continued to elongate commensurate with the deepening oral epithelium and by hatching virtually all buds opened to the oral cavity. No marked morphological changes in taste bud structure were observed on the day of hatching and at 50–60 days posthatching. Taste bud numbers increased dramatically during E17 and E18, peaked on E19, and remained relatively constant there‐after. It is concluded that the morphological sequence of taste bud development in chickens is similar to that in mammals. The timing of bud ontogeny, though initiated only during the third trimester in ovo, essentially is completed by hatching, thus providing the precocial hatchling with the sensory apparatus essential for gustatory experience.
Position of the larynx in odontoceti (toothed whales)
Authors: Reidenberg Joy S. , Laitman Jeffrey T.
Published: February 2005

This study examines the positional relationships of the odontocete (toothed whale) larynx to further an understanding of their breathing, swallowing, and vocalizing abilities. Seventeen specimens representing nine cetacean genera (Delphinus, Stenella, Tursiops, Grampus, Delphinapterus, Globicephala, Kogia, Mesoplodon, and Phocoena) were studied post mortem. Nine specimens were sectioned in the midsagittal plane and the position of the larynx relative to vertebral levels, skull base, and palatal structures was recorded. In eight specimens that could not be bisected for reasons of large size or condition of preservation, the larynx was removed by a ventral approach for further dissection. The results show that the upper respiratory tract of the odontocetes has evolved away from a basic mammalian pattern. Laryngeal position among terrestrial mammals usually corresponds to the level of cervical vertebrae 1–3. The odontocete larynx, however, lies rostral to the level of the atlas and extends to the presphenoidal synchondrosis. Its extension above the level of the foramen magnum is due to three factors: (1) The larynx is elongated into a tubular extension that projects beyond the soft palate into the nasopharynx; (2) the neck region is shortened owing to the highly compressed cervical vertebrae; and (3) the skull base is oriented in the same direction as the cervical vertebrae because of the horizontal and fusiform alignment of the head and thorax. Whereas the larynx of most terrestrial mammals is separable from the nasopharynx, that of the odontocetes studied may be permanently intranarial, held in place by the palatopharyngeal sphincter. Laryngeal position may affect their vocal abilities, allowing odontocetes to simultaneously swallow and echolocate.
Sensory innervation of pulp and dentin in adult dog teeth as demonstrated by autoradiography
Authors: Byers Margaret R. , Närhi Matti V. , Dong Willie K.
Published: February 2005

In order to study the location of sensory nerve fibers in dog teeth, we injected 3H‐amino acids into the left trigeminal ganglion of 2 anesthetized adult dogs; we then waited 24 hours for axonal transport of labeled protein and prepared the fixed decalcified teeth for autoradiography. Heavily labeled sensory neurons were found in the maxillary and mandibular divisions of each injected ganglion and its peripheral nerves and central root. Numerous labeled axons were found entering dental roots; they arborized mostly in the crown to end in peripheral pulp or inner dentin. Some labeled fibers extended 150–175 μm into dentinal tubules, but most intradentinally labeled fibers were less than 100 μm long. The dentinal innervation was most concentrated in the crown, with autoradiographic label over more than 50% of the tubules at the tip of each pulp horn. Differences in innervation density for coronal, cervical, intercuspal, septal, radicular, and reparative dentin were analyzed. In some regions, labeled endings branched along the pulp‐predentin border but did not enter the dentinal tubules.

Electron microscopic autoradiograms were prepared to confirm specific labeling of nerve fibers and nerve endings, and to describe their ultrastructure and association with odontoblasts. The results show that labeled sensory fibers in dog teeth have an ultrastructure similar to that described previously for rat molars and for monkey and cat teeth. No specific junctions were found between labeled sensory fibers and odontoblasts, in agreement with previous studies of other teeth.
Nonclathrin‐coated vesicles are involved in endocytosis in kidney collecting duct intercalated cells
Authors: Brown Dennis , Weyer Patrick , Orci Lelio
Published: February 2005

Intercalated cells of the kidney collecting duct are able to modify the structure of their apical plasma membrane in response to different physiological conditions. It has been proposed that this process involves the transfer of membrane components (including a proton‐pumping ATPase) to and from the apical membrane by a specialized population of tubulovesicles that are found in the apical cytoplasm of these cells. These vesicles have a prominent cytoplasmic coat of regularly arranged dense studs that we have recently shown to be immunocytochemically and morphologically distinct from clathrin. In this study, we have examined the function of these vesicles by using horseradish peroxidase as a tracer of endocytosis at the light and electron microscopic levels. Following the intravenous injection of rats with the tracer, we found a massive labeling of the tubulovesicle compartment of intercalated cells, providing direct evidence that these nonclathrin‐coated vesicles are involved in endocytotic events in this cell type. This novel membrane coating material could contain the cytoplasmic domains of molecules transported to and from the plasma membrane by these vesicles (e.g., an H+ ATPase) or it could be a molecule that is involved in vesicle function, by analogy with clathrin.
Structure and neural control of the pectoralis in pigeons: Implications for flight mechanics
Authors: Dial Kenneth P. , Kaplan Sandra R. , Goslow G. E. , Jenkins Farish A.
Published: February 2005

The pectoralis muscle in pigeons (Columba livia) is composed of two heads (sternobrachialis, thoracobrachialis) that are separately innervated and have different fiber orientations. High‐speed film and electromyographic studies of free‐flying pigeons reveal that the pectoralis is activated prior to wing depression (the power stroke) and that its two heads are differentially recruited during takeoff, level flight, and landing. The elecrical activity patterns of both heads support an interpretation that intramuscular elasticity provides energy storage. The pectoralis is not only the prime wing depressor but is also capable of adjusting the excursion of the wing during different phases of flight.
Morphogenesis of the truncus arteriosus of the chick embryo heart: Movements of autoradiographic tattoos during septation
Authors: Thompson Robert P. , Abercrombie Vant , Wong Matthew
Published: February 2005

In order to trace tissue movements during septation of the embryonic truncus arteriosus into aortic and pulmonary cardiac outlets, the cephalic margin of the developing tubular heart of chick embryos was tattooed at Hamilton‐Hamburger Stages 20–22 using diffusion micropipettes filled with 0.5% agarose and radioactive macromolecular precursors (tritiated thymidine, uridine, and leucine). Following further incubation for 2, 48, or 96 hours, the locations of such tatoos were determined by autoradiography of sectioned tissue and computer reconstruction of the developing outflow tract.

Two hours after tattooing, radiolabeled cells were clustered at the right distal margin of the myocardial tube, as intended. Two days later, during septation of the outflow tract into the two arterial streams, label was concentrated along the posterior margin of the myocardium, between the developing aortic and pulmonary valve anlagen to the embryo's right and left, respectively. Four days following tattooing, as truncal septation neared completion, remaining label was found primarily to the left of the aortic valve ring posterior to the pulmonary outlet. The movements of thymidine tattoos during septation were demonstrated in a series of 31 embryos, 14 fixed at 2 hours, 12 at 2 days, and 5 at 4 days following tattooing; similar results were seen in uridine and leucine labeled hearts.

The motion of such tattoos in the developing chick heart suggests that the left side of the definitive semilunar valve ring derives from the right distal margin of the primitive tubular heart and that normal morphogenesis of the great arterial streams involves both retraction and rotation of the embryonic truncus arteriosus.
Bone “mass” and the “mechanostat”: A proposal
Authors: Frost H. M.
Published: February 2005

The observed fit of bone mass to a healthy animal's typical mechanical usage indicates some mechanism or mechanisms monitor that usage and control the three longitudinal growth, bone modeling, and BMU‐based remodeling activities that directly determine bone mass. That mechanism could be named a mechanostat. Accumulated evidence suggests it includes the bone itself, plus mechanisms that transform its mechanical usage into appropriate signals, plus other mechanisms that detect those signals and then direct the above three biologic activities. In vivo studies have shown that bone strains in or above the 1500–3000 microstrain range cause bone modelling to increase cortical bone mass, while strains below the 100–300 microstrain range release BMU‐based remodeling which then removes existing cortical‐endosteal and trabecular bone. That arrangement provides a dual system in which bone modeling would adapt bone mass to gross overloading, while BMU‐based remodeling would adapt bone mass to gross underloading, and the above strain ranges would be the approximate “setpoints” of those responses.

The anatomical distribution of those mechanical usage effects are well known. If circulating agents or disease changed the effective setpoints of those responses their bone mass effects should copy the anatomical distribution of the mechanical usage effects. That seems to be the case for many agents and diseases, and several examples are discussed, including postmenopausal osteoporosis, fluoride effects, bone loss in orbit, and osteogenesis imperfecta.

The mechanostat proposal is a seminal idea which fits diverse evidence but it requires critique and experimental study.
Decrease of proteoglycan granule number but increase of their size in articular cartilage of young rabbits after physical exercise and immobilization by splinting
Authors: Paukkonen Kari , Helminen Heikki J.
Published: February 2005

The effects of physical exercise (running) and immobilization by splinting on the number and size of proteoglycan (PG) granules and the diameter of collagen fibers of the articular cartilage were studied with the transmission electron microscope with a stereological method. The lateral tibial condyles of 24 young rabbits were examined. The analysis was carried out in the superficial, middle, and deep zones of uncalcified articular cartilage and also in the pericellular, territorial, and interterritorial regions of each zone. PGs were demonstrated in situ by using en bloc staining with the cationic dye ruthenium red, which binds to negative groups of glycosaminoglycans. Results of the control group showed that there was a large pericellular number of PG granules, and the number of granules tended to increase through cartilage depth. The mean diameter of PG granules was highest in the superficial zone and decreased through cartilago depth. The collagen fibers were thicker in the interterritorial than in the territorial region and their diameters increased from superficial toward the deep zone of uncalcified cartilage. Results of the experimental groups showed that the number of ruthenium‐red‐positive PG granules decreased by 3–46% in all zones and regions after both physical exercise and joint immobilization. On the other hand, the diameter of PG granules increased by 4–42% in all zones and regions in all groups. Collagen fibers in the territorial region of the middle zone were thinner in the exercised and in the splinted knee, while thicker in the contralateral knee to the splinted limb, as compared with the controls. Depending on its degree, mechanical stress or loading of the joint is suggested to have either anabolic or catabolic effects on articular cartilage.
Structural features of the apical and tubulovesicular membranes of rodent small intestinal tuft cells
Authors: Trier Jerry S. , Allan Carol H. , Marcial Manuel A. , Madara James L.
Published: February 2005

Tuft cells are present in most columnar epithelia derived from endoderm including the small intestine. They are characterized by long, wide apical microvilli and an extensively developed cytoplasmic tubulovesicular system. We examined in detail the structural features of the apical plasma membrane of small intestinal tuft cells from adult guinea pigs, rats, and adult and suckling mice with freeze‐fracture and conventional transmission electron microscopy methods and utilized cationized ferritin and horseradish peroxidase as tracers to determine whether tuft cells endocytose macromolecules. The microvillus membrane of intestinal tuft cells has few P‐face intramembrane particles, displays little alkaline phosphatase activity, and is highly enriched in cholesterol. Tuft cell tight junctions resemble those of absorptive cells in strand count and strand‐to‐strand crosslinks but, unlike those of absorptive cells, they display many abluminal free‐ending strands. Tuft cells of adult and suckling mouse intestine show no evidence of internalization of cationized ferritin or, in suckling mice, uptake of horseradish peroxidase. We conclude that the microvillus membrane of small intestinal tuft cells is protein poor but cholesterol‐rich and that small intestinal tuft cells do not endocytose macromolecules in bulk from the intestinal lumen.
Isolation and cytochemical characterization of globule leukocytes from rat tracheal epithelium
Authors: Baert Johan
Published: February 2005

Globule leukocytes, dispersed throughout the respiratory epithelium as single cells, were isolated from rat trachea and were enriched by centrifugation on a discontinuous Percoll gradient. The isolation and enrichment procedure yields a cell fraction containing 75% globule leukocytes. The cell viability, as assessed by trypan blue exclusion, was at least 98%. Cells were maintained in short‐term culture without apparent loss of viability and enzyme activity. The isolated globule leukocytes seem not to express significant levels of cytotoxicity against 51Cr‐labeled YAC‐1 target cells. In fixed cytocentrifuge smears, globule leukocytes appear as more or less rounded to oval cells with a low nucleo‐cytoplasmic ratio and with a mostly eccentrically located nucleus. Characteristic intracytoplasmic granules are stained with toluidine blue, alcian blue, and May‐Grünwald‐Giemsa stains. The applied cytochemical methods demonstrate that tracheal globule leukocytes are stained for alpha naphthyl acetate esterase and naphthol‐AS‐D‐chloroacetate esterase, but not for alpha naphthyl butyrate esterase, N‐acetyl‐DL‐phenylalanine‐B‐naphthyl esterase, and endogenous peroxidase. Isolated rat peritoneal cells were used as positive control cells for the cytochemical reactions. The obtained cytochemical profile of tracheal globule leukocytes is compared to the known cytochemical profile of intestinal globule leukocytes and large granular lymphocytes. The cytochemical dissimilarities between tracheal and intestinal globule leukocytes may suggst that both kinds of globule leukocytes represent a different form of the same cell type or even different cell types.

The cytochemical pattern of tracheal globule leukocytes is closely related to that of large granular lymphocytes, which have been postulated as a possible source for globule leukocytes.
Application of the fiber‐optic perfusion fluorometer to absorption and exsorption studies in hairless mouse skin
Authors: Shackleford John M. , Yielding K. Lemone
Published: February 2005

This study was undertaken to test the fiber‐optic perfusion fluorometer as a direct means of evaluating skin absorption and exsorption in hairless mice. Skin‐barrier compromise was accomplished in the absorption experiments by application of dimethyl sulfoxide to the skin surface or by partial removal of the stratum corneum with sticky tape. Absorbed fluorescein was measured easily in unanesthetized control (skin‐barrier intact) and experimental mice. Unabsorbed chemical did not fluoresce 15 minutes after application, although it was present on the surface of the skin as a dry powder. The time course of fluorescein elimination from the skin was related to a rapid phase (vascular removal) and a slow phase (reservoir entrapment).

In the exsorption experiments the fluorescein was injected intraperitoneally. Back skin on the right side was swabbed with either dimethyl sulfoxide or 1% capsaicin in alcohol prior to the injections, and differences in skin fluorescence on the left (control) and right sides were recorded. One application of dimethyl sulfoxide or capsaicin increased the level of skin exsorption. Three applications of dimethyl sulfoxide almost doubled the amount of exsorbed dye, whereas three applications of the capsaicin inhibited the exsorption process.

It was concluded that the fiber‐optic perfusion fluorometer provides an excellent technique in support of other methods of investigating the skin.
Exposure to formaldehyde in anatomy: An occupational health hazard?
Authors: Pabst Reinhard
Published: February 2005

The adverse effects of formaldehyde have been discussed very emotionally in public. Anatomists, technicians in histology and embalming laboratories, as well as medical students during their dissection course are all exposed to formaldehyde, which in many situations crosses the threshold for irritation of the eyes and upper respiratory tract. There is no doubt about the acute toxic effects and the occurrence of contact dermatitis caused by formaldehyde. Studies in rats and mice using high concentrations over an extremely long period (which would not be tolerated by humans) resulted in squamous carcinoma of the nose. Epidemiologic studies on the mortality of medical personnel exposed to formaldehyde do not provide sufficient evidence of cancerogenicity. A number of recommendations will be given for defining the exact concentration in a dissecting room or laboratory and for ways of reducing formaldehyde concentrations and thus minimizing adverse health hazards. These data could initiate a discussion among anatomists, and with technicians and students, based on a sound scientific background rather than on emotion.
The effects of cholesterol depletion on cellular morphology
Authors: De Pace Dennis M. , Esfahani Mojtaba
Published: February 2005

Cells of the U937 cell line were grown in delipidated calf serum for 24 and 48 hr. These cells are known cholesterol auxotrophs. When grown for 48 hr without an exogenous source of cholesterol, these cells are known to become depleted of their intracellular cholesterol stores by greater than 95%. The result is an aggregation of the cells upon mild agitation of the culture. Examination of the cell aggregate from these cultures revealed cells in various stages of altered morphology. There was a loss of microvilli from the cells. Subsequently, the Golgi complex became dilated, and secondary lysosomes and myelin figures accumulated in the cytoplasm. The cells became swollen, and the rough endoplasmic reticulum became dilated. A small percentage of the cells showed complete disintegration, with release of membrane‐bound fragments and other intercellular debris. These events suggest that the depletion of cholesterol results in the inability of the cell to produce usable membrane. As a consequence, the synthetic apparatus of the cell becomes disrupted.
Microtubules, intermediate filaments, and actin filaments in the odontoblast of rat incisor
Authors: Nishikawa Sumio , Kitamura Hironori
Published: February 2005

Actin filaments, intermediate filaments, and microtubules in the odontoblasts of rat incisors were investigated electron microscopically using heavy meromyosin and taxol. Actin filaments were abundant at the periphery of the odontoblast process in the form of a network or in bundles. In a branch of the odontoblast process, longitudinally oriented actin filament bundles were found. Most actin filaments were associated with the plasma membrane via electron‐dense material which stained with tannic acid. The intermediate filaments had a diameter of 11 to 13 nm. They were distributed throughout the cytoplasm of odontoblasts. They ran lengthwise in the core of the odontoblast process, which showed a different distribution compared with that of actin filaments. Microtubules, which were disrupted after Triton X‐100 but preserved by addition of taxol, tended to be associated with intermediate filaments. Such a relation was also seen in conventional preparations. Coated vesicles, which were abundant at the periphery of the odontoblast process, were often associated with actin filaments. Therefore, it is suggested that actin filaments, in the odontoblast process at least, play a role associated with the coated vesicles at the periphery of the process, and may be involved in coated vesicle transport.
Early stages of development in the caudal neural tube of the golden syrian hamster (Mesocricetus auratus)
Authors: Shedden Peter M. , Wiley Michael J.
Published: February 2005

Secondary neurulation is the morphogenetic process whereby the caudal segments of the neural tube are derived from cells in the embryonic tail bud. Comparative studies have demonstrated similar characteristics in the mechanism of secondary neurulation among tailless species, which are thought to be due to the evolutionary reduction in tail length (Hughes and Freeman, 1974). In order to explore this hypothesis further, light and scanning electron microscopy was used to study early stages of neurulation in the tail buds of hamster embryos. The golden Syrian hamster is a relatively common laboratory rodent with a reduced tail. In this species, secondary neurulation first became apparent in embryos with approximately 17 pairs of somites. This was well before closure of the posterior neuropore which occurred at the 21‐somite stage. The lumen of the neural tube appeared to extend into the tail bud in an even and progressive fashion accompanied by reorientation and rearrangement of tail‐bud cells. The mechanism appeared to be similar to that reported in long‐tailed rodents.
Electron microscopic and autoradiographic characterization of hindlimb muscle regeneration in the mdx mouse
Authors: Anderson J. E. , Ovalle W. K. , Bressler B. H.
Published: February 2005

The pattern of postnatal growth and development of skeletal muscle in mdx mice was studied by light and transmission electron microscopy and by autoradiography and was compared with that in their normal age‐matched controls at 4 and 32 weeks of age. The muscle weights of both the extensor digitorum longus (EDL) and soleus muscles of mdx mice were significantly greater than those in control mice at both ages. Body weights of male and female mdx mice were also increased over controls up to 12 weeks of age. At 4 weeks, both the EDL and soleus muscles exhibited focal areas of degeneration, necrosis; and regeneration of centrally nucleated extrafusal fibers resulting in a wide range of fiber sizes. By 32 weeks, the majority of fibers in both muscles were centrally nucleated, and focal areas of recent regeneration were observed. By electron microscopy, the course of macrophage infiltration into areas of degenerating fibers and the ongoing regeneration of myofibers within redundant cylinders of external lamina were noted. This pattern was frequent in 4‐week‐old mdx muscles and was present to a lesser degree at 32 weeks. A notable lack of both adipose tissue infiltration and fibrotic change in the endomysium were observed in muscles at both ages. Autoradiograms of muscles from 4‐week‐old mdx mice injected with tritiated thymidine showed an increased proportion of labeled sublaminal nuclei at 24 and 48 hours after injection compared to controls. At 32 weeks of age, labeling of nuclei in muscles of mdx mice was also greater than in controls, but was reduced compared to muscle labeling in 4‐week‐old mdx mice. The observed features of mdx muscle tissue suggest that this animal model is more applicable to the study of regeneration dynamics than to Duchenne‐type human muscular dystrophy.
Ultrastructural studies of bovine retinal microvascular basement membranes with the cationic dye ruthenium red
Authors: Schmidley James W.
Published: February 2005

Our recent observation that the basement membranes of brain microvessels do not stain with the cationic dye ruthenium red has raised the question of whether the basement membranes of this and other vascular beds functioning as barriers between blood and neural tissues are deficient in the polyanionic macromolecules, such as glycosaminoglycans, which are responsible for the ruthenium red staining of other vascular basement membranes. We therefore attempted to produce staining in the only barrier‐type microvascular basement membrane known to contain heparan sulfate. Bovine retinas were fixed by immersion in aldehyde fixatives containing ruthenium red, buffered with either 10 mM or 100 mM sodium cacodylate. We found discrete, electron‐dense deposits of ruthenium red in vascular basement membranes, quite similar to those seen in vascular basement membranes of nonneural tissues after exposure to ruthenium red. These deposits were more distinct and more frequent in tissue exposed to ruthenium red–aldehyde solutions buffered with 10 mM cacodylate. They were not seen if ruthenium red was omitted from the fixative. The results demonstrate that anionic macromolecules in basement membranes of barrier‐type microvessels can be stained with cationic dyes, and suggest that the failure of brain microvessels to stain with ruthenium red may be the result of a relative or total lack of polyanion in this basement membrane, or of other unique properties.
Anatomical observation of six calves affected with segmental aplasia of the spinal cord
Authors: Hiraga Takeo , Abe Mitsuo
Published: February 2005

Four male and two female Holstein‐Friesian calves with segmental aplasia of the spinal cord were examined macroscopically and radiographically, and in some cases also histologically. External symptoms included inability to stand, deep depression of the body near the middle of the back but without any blemish in the skin, and slight reduction of the body length. Both hind limbs were almost normal. In every case segmental aplasia of the spinal cord was observed between the caudal thoracic and the cranial lumbar region. Owing to this defect, the vertebrae of that limited area consisted only of the body and the ribs fused on both sides. The sternum showed abnormal ossification at its caudal part. Other defects were observed such as kyphoscoliosis (six cases), polycystic kidney (one case), cryptorchidism (one case), and XX/XY chimerism (one case). From these findings it was apparent that this anomaly was uniquely different from the other two main spinal cord anomalies, spina bifida and perosomus elumbis. One conceivable pathogenesis of this rare anomaly, it was conjectured, is as follows: This anomaly results primarily from a segmental disorder of the neural tube, probably due to vascular problems, whereby a part of the spinal cord fails to develop properly from its normal genesis. Anomalous shapes of the vertebral column and ribs are perhaps secondary defects caused by aplasia of the spinal cord.
Coordinated three‐dimensional reconstruction from serial sections at macroscopic and microscopic levels of resolution: The human heart
Authors: McLean Miriam R. , Prothero John
Published: February 2005

This report describes procedures we have developed for obtaining correlated quantitative structural information at two very different levels of resolution. Accurate reconstructions of entire organs and samples of tissue within organs were produced in correct scalar and topographical relationship using computer‐assisted techniques. A specially designed sectioning apparatus, a macrovibratome, was used to section serially the ventricles of the human heart macroscopically. Photographs were taken of every slice. A tissue block excised from a slice at a specified locus in the left ventricular wall was embedded in plastic; serial‐3 μm sections were cut in each of two orthogonal orientations. Photomicrographs were taken by semi‐automated microscopy. Images of both macroscopic and microscopic sections were projected onto a bitpad and manually digitized. The resulting tables of x‐, y‐, and z‐coordinates were reassembled on a VAX 11/750 computer, then transferred to a high‐performance graphics workstation and displayed as three‐dimensional images. Microscopic images were shown in the correct reference frame with respect to the macroscopic (parent) structure.
EHDP‐induced rachitic syndrome in rats is not reversed by vitamin D metabolites
Authors: Atkin Isaac , Ornoy Asher , Pita Julio C. , Muniz Ofelia E. , Agundez Agueda , Castiglione Greg , Howell David S.
Published: February 2005

To examine whether either of the two known active vitamin D metabolites 1,25(OH)2D3 or 24,25(OH)2D3 could reverse the mineralization defect induced by 1‐hydroxyethylidene‐1,1‐bis phosphonate (EHDP), a model of EHDP‐induced rickets was used. Rats at the age of 31 days were injected for 10 consecutive days with EHDP (10 mg/kg). Other littermates were treated with a combination of EHDP and either 1,25(OH)2D3 or 24,25(OH)2D3 or were treated following 10 days of EHDP, with either of the vitamin D metabolites for an additional 72 hr. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscope studies of growth plate cartilage and bone. EHDP‐treated rats revealed signs of typical rickets, manifested by widened growth plates and impaired bone mineralization. Transmission electron microscope (TEM) examination revealed matrix vesicles distributed throughout the growth plate; however, there appeared to be an arrest of the spread of the crystals at the provisional zone of calcification. Treatment with either 1,25(OH)2D3 or 24,25(OH)2D3 failed to reverse the rachitic condition of the animals. Serum calcium blood levels were elevated in the 1,25(OH)2D3 and EHDP‐treated group. 1,25(OH)2D3 and 24,25(OH)2D3 further increased the already elevated serum alkaline phosphatase levels observed in EHDP rats, although the increase observed with 1,25(OH)2D3 was not statistically significant. In contrast to this, 24,25(OH)2D3 lowered the Cfl levels of alkaline phosphatase to the normal range despite the absence of apparent morpholoogical healing of the EHDP rachitic condition. It therefore appears that in our animal model pharmacological doses of vitamin D metabolites do not reverse the EHDP‐induced mineralization defect.
The ductuli efferentes of the goat: A morphological study
Authors: Goyal Hari O. , Williams Carol S.
Published: February 2005

The morphology of the ductuli efferentes of the goat was compared with that of other animal species, especially with that of the bull. Both in the goat and in the bull, it forms a slightly brownish, bulbous mass of highly convoluted ductules (18–19 in the goat, 13–16 in the bull) that occupies approximately one third of the first limb of the caput epididymidis. The epithelium consists of two major cell types, ciliated and nonciliated, and a few intraepithelial lymphocytes and macrophages. The nonciliated cells can be further divided into three types: type II cells are characterized by specific granules that are dense, mostly homogeneous, eosinophilic, osmiophilic, and positive to periodic acid‐Schiff (PAS) staining; type III cells are characterized by specific vacuoles that appear empty and do not stain with PAS, eosin, or osmium; type I cells lack both granules and vacuoles. These morphological, histochemical, and tinctorial differences observed among nonciliated cell types suggest that they are probably independent cell types rather than functional stages of one cell type. All three cell types are endowed with absorptive features such as microvilli, pinocytotic vesicles, and subapical vacuoles, but a higher differentiation of these features in type III cells suggests their greater role in the absorption of testicular fluid.

Whether granules of type II cells and vaculoes of type III cells are absorptive and/or secretory remains unresolved from the available data. However, some circumstantial evidence, as presented in the discussion, supports the latter possibility.
Ontogeny of immunoreactive calcitonin gene‐related peptide in thyroid C cells from dogs, rabbits, and guinea pigs
Authors: Kameda Yoko
Published: February 2005

Ontogeny of immunoreactive calcitonin gene‐related peptide (CGRP) in thyroid C cells of dogs, rabbits, and guinea pigs from early fetuses to adults was investigated by an immunoperoxidase method, in comparison with the development of immunoreactive calcitonin and somatostatin. The presence of immunoreactive CGRP in mature C cells was different from species to species. Dog and rabbit C cells revealed intense immunoreactivity for CGRP, whereas guinea pig C cells revealed very weak immunoreactivity or none. In dog fetuses, the appearance of immunoreactive CGRP was early. At around 35 days of gestation, when the follicular cells were not yet organized into follicles, immunoreactivities for three peptides—calcitonin, somatostatin, and CGRP—began to appear in C cells. While the highest population of somatostatin‐positive cells was attained when the primordial follicles were vigorously formed throughout whole thyroid parenchyma and their frequency progressively declined thereafter, CGRP‐positive cells as well as calcitonin‐positive cells gradually increased in number and intensity with gestational age. The developmental pattern of immunoreactive CGRP coincided with that of immunoreactive calcitonin in dog C cells. In rabbit fetuses, at 25 days of gestation, when thyroid follicles stored large amounts of colloid and C cells already exhibited intense immunoreactivity for calcitonin, CGRP immunoreactivity as well as somatostatin immunoreactivity began to appear. Subsequently, immunoreactivities for the three peptides gradually increased with age, although calcitonin immunoreactivity was outstandingly intense among them. In guinea pig C cells, intense immunoreactivity for CGRP was not observed in any stages or development. These results indicate that there are developmental profiles of CGRP characteristic for each animal, and the ratio of CGRP and calcitonin produced from calcitonin genes in C cells seems to be fixed for life.
Vascular histodifferentiation in the chick chorioallantoic membrane: A morphometric study
Authors: Shumko John Z. , Defouw David O. , Feinberg Richard N.
Published: February 2005

This study presents a quantitative description of ultrastructural changes associated with focal histodifferentiation of the chick choriollantonic membrane (CAM) microvasculature. Early vessels (4–8 days of a 21‐day incubation period) were lined by a thin, but continuous endothelium which was characterized by punctate appositional contacts, an incomplete or absent basal lamina, and few plasmalemmal vesicles. During this stage, there was little ultrastructural distinction between CAM arterioles, capillaries, and venules. During the intermediate stage (9–13 days), the arteriolar endothelium displayed more extensive junctional apposition. In addition, the interstitial (periendothelial) space contained more collagen fibrils and increased cell volume densities, some of which resembled presumptive smooth muscle cells. In contrast to the arterioles, endothelial appositions of the venules and capillaries remained punctate during the intermediate stage. The interstitial space of the venules displayed an increase in cell and fibril densities but to a lesser extent than that observed in the arterioles. The capillaries did not exhibit any significant changes in their periendothelial spaces. By the late stage (14–18 days), a circular tunic containing several layers of presumptive smooth muscle cells surrounded only the arteriolar endothelium. The endothelium of both the arterioles and venules increased in mean thickness. The arterioles also displayed complex interdigitating endpthelial appositions. All CAM vessels exhibited a progressive increase in the number of endothelial plasmalemmal vesicles and a more complete basal lamina during the developmental stages. These observations served to distinguish differential patters of vessel maturation along the length of the microvascular system.
Response of the intermaxillary suture cartilage to alterations in masticatory function
Authors: Hinton Robert J.
Published: February 2005

Like the condylar cartilage of the mandible, the cartilage at the intermaxillary suture in the rat is secondary in origin and persists well into adulthood. While the condylar cartilage is generally considered to be responsive to changes in its local biomechanical environment, little is known of the response of the intermaxillary suture cartilage to similar stimuli. In order to study the effect of changes in occlusal loads on intermaxillary suture cartilage metabolism, male weanling Sprague‐Dawley rats were divided into four groups: soft diet (to discourage molar mastication), incisor clipped (to discourage incision), incisor clipped/soft diet (both treatments), and control (untreated). At 39 days of age, the intermaxillary suture opposite the first molars was removed and compared to control tissue by using histological, histochemical, and biochemical analyses. Alcian blue—stained coronal sections demonstrated moderate decreases in staining intensity and decreased chondrocyte hypertrophy in the soft diet and incisor‐clipped groups. However, sutures in the incisor‐clipped/soft diet group showed a considerably reduced extent of cartilage and greatly diminished cartilage hypertrophy. [35S]‐sulfate incorportion (dpm/μg DNA) into acid‐insoluble proteoglycans was significantly reduced (P≤.01) in all three experimental groups compared to controls. [35S] incorporation was further reduced in the incisor‐clipped/soft diet group relative to both of the other experimental groups. Staining for alkaline phosphatase activity showed decreased intensity in the experimental groups and was almost absent in the incisor‐clipped/soft diet group. These data demonstrate the plasticity of the intermaxillary suture cartilage and provide circumstantial evidence that the observed changes in cartilage morphology and metabolism may be attributable to alterations in the local biomechanicla environment of the suture.
Lung lamellar body amphiphilic topography: A morphological evaluation using the continuum theory of liquid crystals: I. Closed surfaces: Closed spheres, Concentric tori, and Dupin cyclides
Authors: Stratton C. J. , Zasadzinski J. A. N. , Elkins D.
Published: February 2005

The structure and symmetry of the bilayers of in vivo phospholipid lung lamellar bodies is shown to be analogous to thermotropic smectic‐A liquid crystals and in vitro lyotropic multilamellar liquid crystalline liposomes. This structural similarity has led us to extend biophysical and geometrical principles that have long been used to predict the layer conformations in these in vitro systems to in vivo lung lamellar bodies. These configurations were demonstrated by electron micrographs of thin sections of rodent, monkey, and human lung lamellar bodies prepared by lipid‐retaining embedment procedures. The bilayer configurations in all species were consistent with the two geometries predicted by minimal energy solutions of a continuum theory of liquid crystals subject to the boundary conditions imposed by the amphiphilic nature of lung surfactant lipid: concentric (either closed or partially closed) spheres and Dupin cyclides. These bilayer arrangements in lung lamellar bodies were virtually identical to the bilayer configuration of in vitro multilamellar liposomes. The agreement between the two predicted configurations and our observations shows that multilamellar liquid crystalline bilayer aggregate organization is universal in any aqueous environment.