bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of decidualization in the pseudopregnant rat
Authors: O'shea Jeremy D. , Kleinfeld Ruth G. , Morrow Henry A.
Published: February 2005

The ultrastructure of the endometrial stroma in rats bearing deciduomata was examined in detail on day 9 (day of vaginal cornification = day 0) of pseudopregnancy, together with the development of deciduomata from day 4 to day 8. Five major regions were recognizable on day 9. (1) In the basal zone, which contributes to endometrial regeneration following decidualization, stromal cells remained fibrocyte‐like and were separated by wide bands of collagen fibrils. Capillaries were fenestrated and large. (2) The capsule surrounding the antimesometrial (region of the) deciduoma was composed of flattened cells, showing mitosis, which appeared to provide a source of appositional growth of the deciduoma. (3) The large, tightly packed, polyploid cells of the antimesometrial deciduoma showed morphological evidence of protein synthetic activity, an absence of smooth endoplasmic reticulum, and surface specializations suggestive of adhesion (adherens junctions), communication (gap junctions), and maintenance of an extensive surface area (lamellar processes). These cells came into very close apposition with capillary endothelial cells, which were seldom fenestrated, lacked any continuous basal lamina, and showed evidence of high metabolic activity. (4) The loosely packed mesometrial deciduoma contained a structurally supportive, “fixed” population of spiny cells and a “free” population of granulated cells and their putative precursors, together with a meshwork of large, sinusoidal capillaries whose endothelium was generally supported by a basal lamina. (5) The peripheral parts of the glycogenic area, which was structurally similar to the mesometrial deciduoma, contained many grossly enlarged intercellular spaces of undetermined function. The stromal cells at day 4, which give rise to all non‐vascular elements except the granulated cells mentioned above, were structurally simple and fibrocyte‐like. Only two distinct regions, subepithelial and deep, were recognizable. Capillaries at day 4 generally possessed a continuous endothelium, with a complete basal lamina and many pericytes. Between days 5 and 8, the stromal cells showed divergent forms of differentiation according to their position in the endometrium. Ultrastructural differentiation of the vasculature also showed divergence according to position, leading to the various types of capillaries seen at day 9. Regional variation, and high levels of structural organization, characterize the “programed” decidual response in the pseudopregnant rat.
Morphology of taste buds on the gill arches of the mullet Mugil cephalus, and the killifish Fundulus heteroclitus
Authors: Hossler Fred E. , Merchant Lynn Harris
Published: February 2005

The morphology of taste buds on the gill arches of two euryhaline teleosts, the mullet Mugil cephalus, and the killifish Fundulus heteroclitus, were investigated using light microscopic and scanning and transmission electron microscopic techniques. On the mullet gill arches, taste buds were limited to the pharyngeal surfaces of the smooth‐surfaced gill rakers. On the killifish gill arches, taste buds were located on the pharyngeal surfaces of all gill rakers and on the gill arch itself at the bases of the gill rakers. Despite dramatic differences in gill‐raker structure between these two species, the taste buds themselves were similar ultrastructurally and closely resembled those described in other fishes. Cells within the taste buds included spindle‐shaped dark and light cells and basal cells. Ultrastructural features of both the light and dark cells could support either receptor or transport functions. Tufts of microvilli, including one thick microvillus per light cell and numerous thin microvilli per dark cell, protruded at the apex of each taste bud between the ridged surface epithelial cells. Light cells contained numerous tubular membrane elements some of which appeared to open onto the apical surface of the taste bud. Dark cells contained numerous microtubules and apical, electron‐lucent vesicles possibly involved in transport.
The afferent connections of the inferior olivary complex in rats: A study using the retrograde transport of horseradish peroxidase
Authors: Swenson Rand S. , Castro Anthony J.
Published: February 2005

Retrograde transport of horseradish peroxidase (HRP) was used to define the origin of afferents to the inferior olivary complex (IOC) in rats. Using both ventral and dorsal surgical approaches to the brainstem, HRP was injected into the IOC through a micropipette affixed to the tip of a 1‐μl Hamilton syringe. After a 2‐day postoperative survival, animals were sacrificed by transcardiac perfusion with a 1% paraformaldehyde‐1.25% gluteraldehyde solution, and brains were processed according to the DeOlmos protocol (1977), using o‐dianisidine as the chromogen.

Labeled cells were found at many levels of the nervous system extending from lumbar spinal cord to cerebral cortex. This wide‐ranging input from numerous regions clearly underscores the complexity of the IOC and its apparent involvement in several functions.

Within the spinal cord, labeled neurons were identified from cervical to lumbar but not at sacral levels. These neurons were found contralaterally in the neck region of the dorsal horn and in the medial portions of the intermediate gray.

In the caudal brainstem, reactive cells in the dorsal column nuclei, the spinal trigeminal nucleus, and the subnucleus y of the vestibular complex were observed primarily contralateral to the injection sites. Labeling within the gigantocellular, magnocellular, ventral, and lateral reticular nuclei and the nucleus prepositus hypoglossi was primarily ipsilateral. Reactive neurons in the medial and inferior vestibular nuclei were predominantly ipsilateral or contralateral to HRP injections into the caudal or rostral IOC, respectively.

The dentate and interposed nuclei of the cerebellum contained small, lightly labeled neurons primarily contralateral to the injection site, while the fastigial nuclei contained a few relatively large, heavily labeled cells bilateral to caudal olivary injections.

Ipsilaterally labeled mesencephalic regions included the periaqueductal gray, interstitial nucleus of Cajal, rostromedial red nucleus, ventral tegmental area, medial terminal nucleus of the accessory optic tract, nucleus of the optic tract, and the lateral deep mesencephalic nucleus. The caudal part of the pretectum and small cells of the stratum profundum of the superior colliculus were labeled predominantly contralateral to the injection.

In the caudal diencephalon labeled neurons were most numerous within the nucleus of Darkschewitsch and the subparafascicular nucleus, primarily ipsilateral to olivary injections. Scattered reactive neurons were also found within the ipsilateral zone incerta. With the exception of the zona incerta, all labeled mesencephalic and diencephalic nuclei had some bilateral representation of labeled cells.

No labeled neurons were identified within the basal ganglia, while numerous reactive cells were found bilaterally within layer V of the frontal and parietal cerebral cortex.
Studies on the organization and regeneration of bone marrow: Origin, growth, and differentiation of endocloned hematopoietic colonies
Authors: Lambertsen Richard H. , Weiss Leon
Published: February 2005

Hematopoietic colonies were studied by light microscopy in the marrow of alternate fraction x‐irradiated mice (C576J/B1) to investigate the microenvironmental organization of marrow and identify early hematopoietic cellstromal cell interactions. Undifferentiated colonies (UC) were detected at 3 days postirradiation, showed a marked predilection for bone surfaces, and disappeared as differentiated colonies developed. Some UC occurred along marrow arteries. Neutrophilic granulocyte colonies (GC) occurred in all areas at 3 days but grew rapidly only subosteally. Few eosinophilic colonies (GCe) occurred. Erythrocytic colonies (EC) appeared at 4 days as dispersed populations of motile cells within a localized area of marrow; these tended to proliferate initially in intermediate and central marrow zones. Macrophage colonies (MϕC) of two “subtypes” were detected, peaking in relative frequency at 4 days. These appeared active in stromal repair and monocytopoiesis. Megakaryocyte colonies (MC) originated along bone and differentiated away from bone. From 3–5 days, the frequency of GC > UC > MϕC ≫ MC ≅ GCe. All colony types except UC, MϕC, and central GC increased in size and became mixed in differentiation by 12–14 days. For several weeks, however, erythropoiesis concentrated toward central areas, whereas granulopoiesis and thrombopoiesis concentrated along bone. Some mixed colonies showed an abrupt transition from erythrocytic, centrally, to granulocytic, subosteally. These results were interpreted as evidence that in x‐irradiated marrow: (1) hematopoietic microenvironments (HMs) for stem‐cell proliferation and commitment to differentiation, with the possible exception of HMs determining erythroid differentiation, occur in endosteal and periarterial regions; (2) a proliferative and/or chemotactic stimulus to erythroid progenitors exists in intermediate and central marrow regions; and (3) some subosteal regions may exclude erythropoiesis, or preferentially support nonerythroid differentiation. Elaborate associations occurred between macrophages and early UC, GC, and EC, but not MC hematopoietic cells. UC and GC often associated with osteoclasts. Reticular and other fibroblastic cells associated with the cells of all colony types.
The equine spleen: An electron microscopic analysis
Authors: Tablin Fern , Weiss Leon
Published: February 2005

The capacity of the equine spleen to store and rapidly release as much as half the circulating blood volume after adrenergic stimulation depends upon the size of the spleen, its muscular capsule, and the distinctive structure of its red pulp. The unit, or lobule, of red pulp is a cylinder of pulp spaces organized in a reticular meshwork, supplied by a peripheral ring of arterial capillaries, and drained by a central venule. Reticular cells, which make up the meshwork of the pulp, contain an extraordinarily large complement of microfilaments and intermediate filaments and are richly innervated by nerves containing both dense and lucent core vesicles typical of adrenergic nerves. The wall of the pulp venule contains large apertures. The capacious red pulp would thus appear capable both of large‐scale blood storage and, by the contractile adrenergic innervated reticulum and open venous vasculature, of rapid expression of stored blood into the circulation.

Antigen‐presenting cells are present not only in B and T cell zones in white pulp but in the periarterial macrophage sheath of red pulp as well. The periarterial macrophage sheath is one of the first sites of antigen capture, and the presence of these cells confers on it an immunological role.
The distribution of cathepsin D in rat tissues determined by immunocytochemistry
Authors: Whitaker John N. , Rhodes Roy H.
Published: February 2005

The distribution of cathepsin D (CD) was surveyed in rat tissues by light microscopic immunocytochemistry. Although immunoreactive CD was detected in all tissues examined, there was a marked difference in the amount in the cytoplasm of different cell types of the same organ. In the retina large amounts of CD were present in the pigment epithelium, ganglion cells, and Müller cells. Moderate to large amounts of CD were also found in neuronal perikarya of the gastrointestinal tract and adrenal medulla; in macrophages in the lung, liver, and spleen; in some secretory cells of the submandibular and lacrimal glands; in parts of renal distal convoluted and collecting tubules; and in the surface transitional epithelium of the calyx, ureter, and urinary bladder. Other cells adjacent to cells containing large amounts of the enzyme had little or no detectable CD themselves. These included hopatocytes, the proximal tubular cells of the kidney, selected cells of the submandibular gland, cells of the zona glomerulosa of the adrenal cortex, and lymphocytes in lymphoid organs. The localization of CD indicates that its degradative effect is exerted preferentially in certain cell types and suggests that physiological influences on CD may have a variety of effects in different organs.
Preantral follicle development during the menstrual cycle in the Macaca mulatta ovary
Authors: Koering Marilyn J.
Published: February 2005

Ovaries obtained from 18 adult, regularly cycling rhesus monkeys were evaluated to determine the status of preantral follicle development at various stages throughout the menstrual cycle. The ovaries were serially sectioned, and all preantral follicles on every 20th section were classified as developing or atretic, counted and/or measured, and grouped according to size.

Results from this study revealed (1) that a significant increase (P < 0.05) occurred in the mean percentage of developing preantral follicles >100 μm in diameter during the periovulatory period, suggesting that follicles in this size range had developed a sensitivity to the unique hormonal milieu present during that stage of the cycle; (2) that similar numbers of primordial and developing preantral follicles were present in the right and left ovaries of a pair, showing that neither ovary had a predominance over the other; (3) that the mean number of developing preantral follicles varied directly with the size of the primordial follicle pool; (4) that atresia was minimal with no significant differences between the various stages of the cycle in any size group; and (5) that polyovular follicles were abundant in certain pairs of ovaries, but could not be related to age or stage of cycle.
Contributions of placodal and neural crest cells to avian cranial peripheral ganglia
Authors: D'amico‐Martel Adele , Noden Drew M.
Published: February 2005

The method of embryonic tissue transplantation was used to confirm the dual origin of avian cranial sensory ganglia, to map precise locations of the anlagen of these sensory neurons, and to identify placodal and neural crest‐derived neurons within ganglia. Segments of neural crest or strips of presumptive placodal ectoderm were excised from chick embryos and replaced with homologous tissues from quail embryos, whose cells contain a heterochromatin marker. Placode‐derived neurons associated with cranial nerves V, VII, IX, and X are located distal to crest‐derived neurons. The generally larger, embryonic placodal neurons are found in the distal portions of both lobes of the trigeminal ganglion, and in the geniculate, petrosal and nodose ganglia. Crest‐derived neurons are found in the proximal trigeminal ganglion and in the combined proximal ganglion of cranial nerves IX and X. Neurons in the vestibular and acoustic ganglia of cranial nerve VIII derive from placodal ectoderm with the exception of a few neural crest‐derived neurons localized to regions within the vestibular ganglion. Schwann sheath cells and satellite cells associated with all these ganglia originate from neural crest. The ganglionic anlagen are arranged in cranial to caudal sequence from the level of the mesencephalon through the third somite. Presumptive placodal ectoderm for the VIIIth, the Vth, and the VIIth, IXth, and Xth ganglia are located in a medial to lateral fashion during early stages of development reflecting, respectively, the dorsolateral, intermediate, and epibranchial positions of these neurogenic placodes.
Follicular growth and kinetics during the estrous cycle, pregnancy and postpartum in the Indian mole rat (Bandicota bengalensis)
Authors: Kaur P. , Guraya S. S.
Published: February 2005

Follicular growth and kinetics were studied in detail in the ovaries of the Indian mole rat (Bandicota bengalensis) during various stages of the estrous cycle; days 7, 12, 15, 19, and 21 of pregnancy; and day 2 postpartum. The sizes of follicles, oocytes, nuclei, and nucleoli were measured. In all rats, regression coefficients, a, and intercepts, b, were calculated in oocyte/follicle, oocyte nucleus/follicle and oocyte nucleus/oocyte regressions. The oocyte reached its maximum size when the average follicle diameter was 117 μm in nonpregnant rats and 131 μm in pregnant rats. The oocyte nucleus attained maximum size when the follicle diameter was 110 μm during the estrous cycle and 111 μm during pregnancy and postpartum. Maximum values of the diameter of the largest antral follicle and average diameter of the four largest antral follicles were observed during proestrus (473 and 442 μm, respectively) and on day 21 of pregnancy (611 and 538 μm, respectively). X2 analysis showed that distribution of various types of follicles was not independent of the stage of the estrous cycle and pregnancy. In estrus and metestrus most of the follicles were between stages I and V. However, by diestrus and proestrus, follicles of all size groups developed. The numbers of stage I and II follicles did not differ as pregnancy advanced. More stage V follicles were present on day 12 than on day 7 of pregnancy; however, their numbers decreased by day 15. Afterwards, progressive increase of stage V and (VI + VII) follicles was observed until day 21. This was accompanied by the shift of follicles from stage (III + IV) on days 19 and 21 of pregnancy and even of stage II on day 2 postpartum. Wherever possible, the results have been compared with previous observations in various rodent species.
CSF‐contacting pinealocytes in the pineal recess of the Mongolian gerbil: A correlative scanning and transmission electron microscope study
Authors: Welsh Marcia G.
Published: February 2005

The pineal recess of the Mongolian gerbil was studied using correlative scanning and transmission electron microscopy. The surface of the pineal recess can be subdivided into three distinct zones: (1) central, (2) transitional, and (3) peripheral. In the gerbil, the deep pineal gland is located deep to the central and transitional zones. The ependyma of the peripheral zone is densely ciliated and resembles that of the main ventricular lining. Ependymal cells of the transitional zone are sparsely ciliated but possess numerous microvilli on their apical surfaces. Supraependymal neurons were identified in the transitional zones. These cells appear to make a synaptic‐like contact with the underlying ependymal cells. Of the three zones, the central zone demonstrated the greatest amount of morphological variability. Although a number of supraependymal structures could be identified in the central zone, the most remarkable feature was the presence of protruding cells that possessed no significant surface features Employing correlative transmission electron microscopy, the protruding cells were shown to be CSF‐contacting pinealocytes. The number of CSF‐contacting pinealocytes present in the central zone varied from one cell to large clusters that covered the entire zone. The results of this investigation demonstrate the presence of a direct contact and the potential for interaction between the deep pineal gland and the CSF of the pineal recess in the gerbil.
Comparative study of the arterial and lacunary systems of the ventricular myocardium of elasmobranch and teleost fishes
Authors: Tota B. , Cimini V. , Salvatore G. , Zummo G.
Published: February 2005

The typical fish heart has a spongy trabeculated ventricular myocardium (spongiosa) supplied by the venous blood of the intertrabecular spaces (lacunae); hence it is called a “venous heart.” However, in some fishes a more complex ventricular muscle is found (mixed type), in which the spongiosa is covered by an outer layer of densely arranged myocardial bundles (compacta). The compacta receives oxygenated blood from the coronary vessels. The objective of this study was to investigate relations between myoarchitecture and blood supply with an emphasis on the hitherto unexplored, putative vascular connections between the arterial and the lacunary circuits. Using histological methods combined with vascular cast techniques and India ink injections, it was possible to define four different types of ventricular myocardium and its microvsculature. In some of them an intramural network arises from the subepicardial arterial system supplying the compacta and also is distributed to the spongiosa. Extensive arterio‐luminal vessels connect this coronary bed with the lacunary circuit of the spongiosa, so realizing the first evolutionary step of the Thebesian system. The highest development of these connections is found in some very active pelagic fishes. The functional morphology of these vascuar patterns is discussed in relation to the phylogenetic and functional context of the fish heart. It appears that the concept of the piscine heart as a typical “venous” type is an oversimplified generalization, at least on morphological grounds.
Morphological observations on mucus‐secreting nongoblet cells in the deep crypts of the rat ascending colon
Authors: Altmann G. G.
Published: February 2005

In the ascending colon of adult male rats, large accumulations of differentiated, mucous‐type cells were observed which formed the deep one‐half to one‐third of the crypts almost exclusively. Mitotic activity was localized to the midcrypt, to columnar‐type cells. The mucous‐type cells were designated as “deep crypt secretory” (DCS), and their histological study was initiated. In the light microscope, the apical cytoplasm was distended with mucous vacuoles which stained differently from goblet cells after using periodic acid‐Schiff (PAS), alcian blue, or a Masson stain. In electron‐micrographs, a well‐developed Golgi complex and rough edoplasmic reticulum in addition to a large number of electron‐opaque vacuoles indicated active production of a glycoprotein. The mdcrypt mitotic activity was further demonstrated by using the colchicine technique and 3H‐thymidine radioautography. A gradual increse of mucus content and a decrease of nuclear and nucleolar size in the DCS cells from midcrypt to crypt base indicated that these cells originate in midcrypt and mature as they progress toward the crypt base. Cell counts showed that the number of cells constituting the crypts was about the same all along the colon, but the percentage of DCS cells varied: 33% in ascending and 21% in transverse colon. Only 5% and 8% deep‐crypt mucous‐type cells were found in descending colon and cecum, respectively; but these cells differed in appearance from the mature DCS cells. In conclusion, the presence of a large number of nonmitotic end cells with intense secretory activity has been ascertained for the deep crypts of the ascending colon. The exact relation of these cells to the vacuolated or other epithelial cell types remains for further study.
Three‐dimensional reconstruction of a rat stage V Sertoli cell: I. Methods, basic configuration, and dimensions
Authors: Wong Vivien , Russell Lonnie D.
Published: February 2005

A model of a rat stage V Sertoli cell was reconstructed from semiserial sections. Seventy‐five montages were made from 96 grids that supported the 223 sections needed to traverse the reconstructed cell. Section thickness (184.6 nm) and spacing of sections were calculated based on the diameter of spherical germ cell nuclei included within the sections. The outline of the cell border was traced on acetate sheets and from there traced on Plexiglas; then the Plexiglas was cut with a hot wire. The model, enlarged to a magnification of 7,800 times, was made from five parts that may be disassembled. The cell dimensions, as determined from the model, were 89.8 μm in the centripetal axis, 41.2 μm in the longitudinal axis, and 29.5 μm in the circumferential axis. The cell was irregularly columnar in shape with a base resting on the basal lamina and lateral surfaces in contact with adjacent Sertoli cells and round germ cells. Lateral processes were of three types: (1) conical processes extending from the lateral surface near its base; (2) cup‐shaped, sheet‐like processes partially encompassing round germ cells; and (3) flattened, sheet‐like processes extending between round germ cells. Elongate spermatids occupied deep, irregularly shaped cylindrical recesses oriented in the centripetal axis of the Sertoli cell. The walls of the Sertoli cell forming these cylinders were thick basally and sheet‐like and very thin near the lumen where they anastomosed and also composed the lateral walls of the cell. The tapered luminal extensions of the sheet‐like, cylindrical processes were termed apical processes. The volume of the reconstructed cell was calculated to be 6,012 μm3. This study has provided the first unencumbered view of the external profile of a Sertoli cell. The model represents one of two major configurations that the Sertoli cell assumes during the spermatogenic cycle.
Three‐dimensional reconstruction of a rat stage V Sertoli cell: II. Morphometry of Sertoli–Sertoli and Sertoli–germ‐cell relationships
Authors: Weber James E. , Russell Lonnie D. , Wong Vivien , Peterson R. N.
Published: February 2005

Sertoli–Sertoli and Sertoli–germ‐cell configurational relationships were studied using morphometric techniques and direct measurements as obtained from micrographs used to reconstruct a model of a rat stage V Sertoli cell. Regional areas of the Sertoli cell surface, which faced germ cells, other Sertoli cells, or noncellular structures, were expressed as relative surface area percentages; and the absolute surface areas for these regional areas were calculated. The surface area of the reconstructed cell, in its unmagnified state, was found to be 12,163 μm2. Cell processes were enumerated and studied using morphometric techniques. The surface area of the reconstructed Sertoli cell facing germ cells and Sertoli cells was also determined. Five Sertoli cells showed extensive contact with the reconstructed cell at the level of the Sertoli‐Sertoli junctional contact region. This contact region averaged 3.51 μm in width. The relative and absolute surface area of subsurface ectoplasmic specialization of the Sertoli cell that faced germ cells and other Sertoli cells was calculated, and the extent of penetration of step 17 spermatids into the Sertoli crypts was determined. Surface relationships of the reconstructed cell to cellular and noncellular elements were depicted on outline drawings of the Sertoli cell.
Some observations on the structure of Suncus liver with special reference to the vitamin A‐storing cell
Authors: Matsumoto Emiko , Hirosawa Kazushige
Published: February 2005

The structure of the liver of the thick‐tailed shrew (Suncus murinus) was studied with special reference to the vitamin A‐storing cell. The macroscopic arrangement of hepatic lobes was the same as those of rodents. Connective tissues of Glisson's sheath were not prominent. There were gradual differences in the size and the cytoplasmic contents of hepatocytes among perihepatic, intermediate, and periportal regions. These correspond to the acinar zones 3, 2, and 1 of Rappaport, respectively. The ultrastructural features of the hepatocyte were numerous microvilli, a large mass of glycogen particles (α‐particles), and well‐developed Golgi complexes and lysosomes in the peribiliary region. Cellular elements of the sinusoid were the same as those of rodents.

Vitamin A‐storing cells were demonstrated by autoradiography of tritiated retinyl acetate administered orally. They were distributed in the perihepatic and intermediate regions. The number of vitamin A‐storing cells was much smaller than that in the mouse liver and did not increase after excess vitamin A was given to the animal. Cytological features of the vitamin A‐storing cells in Suncus liver were similar to those for other mammalian livers. The scarceness of vitamin A‐storing cells and the low amount of vitamin A esters suggest that Suncus does not store much vitamin A in the liver.
Synaptic changes in the hypothalamus of the prepuberal female rat administered estrogen
Authors: Clough Richard W. , Rodriguez‐Sierra Jorge F.
Published: February 2005

Subcutaneous administration of estradiol benzoate (EB) to prepuberal female rats can advance vaginal opening, phasic pituitary gland luteinizing hormone (LH) secretion, and ovulation, presumably through a neural mechanism. This study investigated whether these effects are associated with changes in synaptic profiles in the arcuate nucleus of the hypothalamus (ARC) and the preoptic area (POA). Twenty‐five‐day‐old female rats were adminstered EB, EB followed by progesterone on day 27, or oil vehicle alone; or they received no treatment. Blood was collected by jugular venipuncture at 1600 hr, on day 27, and plasma was assayed for LH by radioimmunoassay. Rat brains were immediately perfused for electron microscopy, and the ARC and POA were dissected out. Tissue blocks from these areas were processed with phosphotungstic acid for selective staining of neural synapses. Serum LH was markedly elevated in the EB‐treated rats compared with controls. In the treated groups, LH values in serum were above 1,000 ng/ml, whereas the control values were less than 50. This acute rise of serum LH was accompanied by an acute increase of synaptic volume percent, area density, and numerical density in the ARC of EB‐treated rats. The numerical density of the control groups was approximately 800 million observed synapses per cubic millimeter, whereas in the EB‐treated groups, there were approximately 1.8 billion synapses per cubic millimeter. We found no differences in synaptic profiles of the POA in EB‐treated animals as compared to the controls. We conclude from this study that estrogens act through neural mechanisms to accelerate maturation of neuroendocrine processes that govern phasic pituitary gland LH release and that this maturation process entails synaptogenesis in the ARC.
Pattern regulation in the anterior half of the embryonically produced symmetrical forelimb of the axolotl, Ambystoma mexicanum
Authors: Tank Patrick W.
Published: February 2005

Symmetrical forelimbs were created in the axoltl by performing surgery on embryos at stages 32–34. The technique of J. M. W. Slack (J. Embryol. Exp. Morphol., 39:151–168, 1977) was utilized. Several experiments were then performed to test the ability of thesesymmetrical forelimbs to participate in pattern formation. When symmetrical limbs were amputated without previous surgery, 58% failed to regenerate. When symmetrical limbs were wounded in the plane of symmetry and permitted to heal for 30 days prior to amputation, 75% failed to regenerate. When the anterior half of the symmetrical limb was exchanged with the posterior half of the contralateral forelimb followed by amputation 30 days later, both limbs failed to regenerate. When the anterior half of the symmetrical limb was exchanged with the anterior half of an asymmetrical limb followed by amputation 30 days later, the previously symmetrical limbs regenerated asymmetrical hands, and previously asymmetrical limbs failed to regenerate. These results indicate that wounding increases the occurrence of regenerative failure in embryonically produced symmetrical forelimbs. The anterior half of the embryonically produced symmetrical forelimb behaves unpredictably and in a manner not easily described with any of the current models of pattern regulation. The posterior half of the embryonically produced symmetrical forelimb behaves predictably during pattern formation.
Retrograde hrp identification of neurons in the rhombencephalon and spinal cord of the rat that project to the dorsal mesencephalon
Authors: Morrell J. I. , Pfaff D. W.
Published: February 2005

Neurons in the rhombencephalon and spinal cord of the rat that project to the dorsal midbrain were identified using the HRP retrograde neuroanatomical tracing method. Retrogradely labeled neurons were most numerous in the reticular formation, specifically in nucleus pontis oralis, caudalis, and gigantocellularis and in the sensory trigeminal complex. Neurons that project were also found in certain raphe nuclei, the parabrachial nuclei, the deep cerebellar nuclei, the vestibular cochlear complex, and the spinal cord.

The diverse distribution of neurons that project to the midbrain is understandable in the context of the known diverse functions of the region, which include a role in sexual and other behaviors, nociception, and various autonomic functions.
Changes in uterine mast cells during the estrous cycle in the Syrian hamster
Authors: Brandon Janet M. , Evans Janet E.
Published: February 2005

Adult virgin female Syrian hamsters were killed at known stages of the estrous cycle, and mast cells were counted in the myometrium, endometrium, and mesometrial‐triangle region of the uterus and in the pinna. Tissues were fixed in Helly's solution, and mast cells were stained using 0.06% toluidine blue in 0.12 M Michaelis' veronal acetate‐hydrochloric acid buffer, pH 4.5. The number of mast cells in the myometrium and endometrium was found to vary with the estrous cycle, whereas the number in the mesometrial‐triangle region and the pinna showed no such variation. The number of mast cells in the myometrium and endometrium was lowest on day 4 of the cycle (the day before the night during which ovulation would occur) and increased approximately twofold to maximal levels found on days 1 and 2. Intermediate levels were seen on day 3. The origin of the increase in mast cell numbers from day 4 to day 1 was investigated using a combined alcian blue–safranin stain to differentiate between immature and mature mast‐cell granules. The results obtained did not support the hypothesis that the increase was due to de novo differentiation of mast cells from precursors, but, equally, no evidence was obtained to refute this hypothesis.
Bone formation by isolated calvarial osteoblasts in syngeneic and allogeneic transplants: Light microscopic observations
Authors: Moskalewski Stanislaw , Boonekamp Piet M. , Scherft Johannes P.
Published: February 2005

Taking advantage of recently developed methods for osteoblast isolation, we used these cells to study bone morphogenesis in syngeneic and allogeneic intramuscular transplants.

Syngeneic osteoblasts from fetal rat calvaria produced small islands of bone by the third day after transplantation. These islands increased in size and began to fuse after about 14 days. At the surface of the woven bone laid down first, lamellar bone developed. The amount of this bone increased, and in 56‐day‐old transplants solid blocks of bone were present. Osteoclasts were scarce, and the woven bone remained unresorbed. Bone marrow was absent. The structure of bone in transplants differed from that of mature calvarial bones in which only remnants of woven bone remained and bone marrow was well developed. The scarcity of osteoclasts in transplants could be caused by their relative paucity among the injected cells, since these cells responded strongly to added parathyroid hormone by increased production of cyclic adenosine monophosphate (cAMP) but only weakly to calcitonin.

Osteoblasts isolated from the surface of calvarial lamellar bone of 28‐day‐old rats formed woven bone similar to the bone formed by fetal cells. This suggests that the type of bone produced does not depend on the intrinsic properties of the osteoblasts.

Bone formed in an allogeneic system was surrounded by infiltrations containing lymphocytes, macrophages, and osteoclastlike cells in 14‐day‐old transplants. Osteoblasts at the bone periphery were destroyed and bone matrix was resorbed by infiltrating cells. Numerous bone lacunae were enlarged, suggesting the occurrence of osteocytic osteolysis.

Isolated osteoblasts cultured for three population doublings or longer did not form bone after transplantation, although they retained some reactivity toward parathyroid hormone.
Structure, cytochemistry, endocytic activity, and immunoglobulin (Fc) receptors of rat testicular interstitial‐tissue macrophages
Authors: Miller Scott C. , Bowman Beth M. , Rowland Heidi G.
Published: February 2005

Macrophages are common in rat testicular interstitial tissues. Interstitial‐tissue macrophages were characterized using ultrastructural, cytochemical, immunologic, and autoradiographic methods. Testicular interstitial‐tissue macrophages have a single indented nucleus, paranuclear Golgi complex, rough endoplasmic reticulum, coated vesicles, and numerous heterogeneous lysosomal vacuoles. Long filopodia and lamellopodia extend from the macrophage cell body into the lymphatic space. Macrophages are usually found adjacent to Leydig cells, and numerous Leydig cell processes are inserted into coated membrane invaginations on the macrophage surface. Secondary lysosomal vacuoles in the macrophage are cytochemically reactive for acid phosphatase (trimetaphosphatase) and aryl sulfatase. Testicular interstitial macrophages are endocytically active, avidly incorporating exogenously administered trypan blue dye and monomeric plutonium‐citrate. Macrophages were isolated from the testes by allowing them to adhere to glass. The isolated macrophages were found to have receptors for the Fc portion of immunoglobulin G on their surface. The association of macrophages with Leydig cells and their endocytic and immunologic activity suggests that these cells may play an important role(s) in testicular functions. In addition, the ability of these cells to incorporate exogenous materials indicates that they could have a role in gonadal toxicity reactions.
Difference in muscle spindle structure between pigeon muscles used in aerial and terrestrial locomotion
Authors: Maier Alfred
Published: February 2005

Muscle spindle density (number of spindes per gram of muscle) of all 29 muscles of the forearm and leg of the domestic pigeon was evaluated by counting receptors in van Gieson‐stained serial cross sections. Extra‐ and intrafusal fiber‐type profiles were determined from histochemical preparations. Muscles of the leg had on the average significantly more avian slow‐twitch oxidative extrafusal fibers (22.5 vs. 0.8%) and slower contraction times than muscles of the forearm, but fiber‐type profiles and gross actions of muscles showed no consistent relation to the relative abundance of receptors. Differences in intrafusal fibertype composition among spindles were sought because of their potential effect on the quality of the afferent discharge. The number of intrafusal fibers per spindle was on the average significantly less (4.57 vs. 5.99) in the muscles of the leg than in those of the forearm; and of spindles with the same number of intrafusal fibers, those in the leg had smaller periaxial spaces. Distribution of intrafusal fiber types identified with the myofibrillar adenosine triphosphatase reaction differed among spindles of varying sizes. An acid‐ and alkali‐labile type occurred most frequently (P = 0.05) in spindles with one to three intrafusal fibers, and an acid‐labile and alkali‐stable type was most often seen (P = 0.05) in spindles with 4 to 7 intrafusal fibers. The smaller receptors were more abundant in the leg, while the larger ones were about equally distributed between the two extremities. Muscle fibers with dimensions that sometimes approached small extrafusal fibers were present in about 3% of the axial bundles examined, most of them in the forearm. The selective morphological variation of avian muscle spindles may represent the structural basis for qualitatively different afferent discharges that relate to the characteristic types of locomotion served by the two extremities.
Iron loading in the liver of parasitic adult lampreys, Petromyzon marinus L
Authors: Youson J. H. , Sargent P. A. , Sidon E. W.
Published: February 2005

Electron microscopic and histochemical procedures were used to describe iron loading in the normal liver of parasitic adult sea lampreys, Petromyzon marinus L. Ferric iron is present in large quantities as ferritin in the cytoplasmic matrix, in hemosiderin granules, and in large vacuoles of hepatocytes. Ferritin is also found in the lateral intercellular space, in the perivascular space, and in the sinusoidal lumen. Large crystals in the cytoplasmic and nuclear matrices of some hepatocytes likely represent excessive aggregations of ferritin molecules. Ferrous iron is localized at the lateral cell membrane and vacuolar membranes of hepatocytes. Iron accumulation is less significant in Kupffer cells which are present in small numbers. The relationship of iron loading in the adult lamprey liver to the sanguivorous diet, the rate of erythrophagocytosis, the absence of bile ducts and canaliculi, and the nature of iron‐binding proteins in the plasma are considered. Emphasis is placed on the similarity of the above morphological findings to those resulting from experimentally induced and pathological states of iron loading in other vertebrates, and on the potential use of the lamprey as a model for studying iron loading in the vertebrate liver.
Morphometric analysis of the corpus luteum of 16‐day pregnant rats: The effect of preparative procedures on volume of luteal cell, interstitial, and vascular compartments
Authors: Dharmarajan A. M. , Meyer G. T. , Bruce N. W.
Published: February 2005

The volumes of the major tissue compartments, vascular space, interstitial space, and luteal cells, in the corpus luteum (CL) of 16‐day pregnant rats were determined morphometrically after different fixation procedures. Ovaries were fixed by perfusion at physiologic pressures (PF), by immersion directly in fixative (IF), by immersion after clamping blood vessels to prevent escape of blood (IFC), or by immersion after administration of heparin to prevent blood clotting (IFH). Three CL in each of eight ovaries were examined for each fixation method. Total volumes were significantly larger in CL fixed by PF and IFC, and approximated physiologic volumes as assessed from frozen ovaries. Perfusion‐fixed CL had significantly larger vascular and interstitial spaces and smaller cell volumes than immersion‐fixed CL. Capillary surface area varied significantly between the four groups in accordance with absolute volume of vascular space. Estimated numbers of endothelial cells and amounts of connective tissue differed significantly, presumably due to difficulties in identifying these components in immersion‐fixed CL with collapsed vessels. The fixation methods used caused substantial fluid shifts between the three major compartments. A theoretical approach for considering these shifts and the likely physiologic situation was developed.
“Synaptic” ribbons and spherules of the guinea pig pineal gland: Inverse day/night differences in number
Authors: Vollrath L. , Schultz R. L. , McMillan P. J.
Published: February 2005

The present study deals with the functionally enigmatic “synaptic” ribbons and spherules of guinea pig pinealocytes. Whereas the ribbons have been shown to exhibit a 24‐hr rhythmicity with low numbers during the day and high numbers at night, very little of a definitive nature is known about the spherules. Sixteen male guinea pigs of the Hartley strain were perfusion fixed, 8 between 0900–1100 hr, and 8 between 2100–2300 hr. The ribbons and spherules were counted in the pineal parenchyma of the proximal, intermediate, and distal regions. In confirmation of earlier studies, it was found that “synaptic” ribbons are equally abundant in the proximal, intermediate, and distal regions of the gland, during both the day and the night, and that they increase significantly in number at night when compared with daytime values. The spherules, by contrast, are more abundant proximally and are present in greater numbers during the day than at night. As ribbons and spherules are usually not found in one and the same pinealocytic profile, and based on previous electrophysiological studies, it is proposed that the ribbons are morphological markers of nocturnally active pinealocytes, whereas spherules characterize diurnally active pinealocytes.
Sertoli cells of the golden‐mantled ground squirrel (Spermophilus lateralis): A model system for the study of shape change
Authors: Vogl A. W. , Lin Y. C. , Dym M. , Fawcett D. W.
Published: February 2005

Sertoli cells of the ground squirrel (Spermophilus lateralis), a seasonal breeder, were examined by light and electron microscopy and their structure, particularly the organization of the cytoskeleton, was related to events that occur in the seminiferous epithelium during spermatogenesis. Among the events considered and described are the apical movement of elongate spermatids, withdrawal of residual cytoplasm from germ cells, transport of smooth endoplasmic reticulum (SER) between the base and apex of the Sertoli cells, and sperm release. These events are dramatically evident in this species because the seminiferous epithelium is thin, i.e., there are few germ cells, and both the germ cells and Sertoli cells are large.

Sertoli cells of the ground squirrel have a remarkably well developed cytoskeleton. Microfilaments occur throughout the cell but are most evident in ectoplasmic specializations associated with junctions. Intermediate filaments occur around the nucleus, as a layer at the base of the cell, and adjacent to desmosome‐like junctions with germ cells. Intermediate filaments, together with microtubules, are also abundant in regions of the cell involved with the transport of SER, in cytoplasm associated with elongate spermatids, and in processes that extend into the residual cytoplasm of germ cells. Our observations of ultrastructure are consistent with the hypothesis that Sertoli cell microtubules are involved with the movement of germ cells within the seminiferous epithelium, and further implicate these structures as possibly playing a role in the retraction of residual cytoplasm from germ cells and the intracellular transport of SER. The abundance and organization of intermediate filaments suggest that these cytoskeletal elements may also be involved with events that occur during spermatogenesis.
Colchicine‐induced changes in the cytoskeleton of the golden‐mantled ground squirrel (Spermophilus lateralis) sertoli cells
Authors: Vogl A. W. , Linck R. W. , Dym M.
Published: February 2005

Study of Sertoli cells of the ground squirrel provides a unique opportunity to examine cell structure and function. The cells are large, have an elaborate cytoskeleton, and undergo dramatic changes in organization during spermatogenesis. Microtubules (MTs) are prominent elements of the cytoskelton and appear to be associated structurally with many of the events that occur during sperm production. To investigate the function of MTs, animals were injected subcutaneously with colchicine, and their seminiferous epithelia examined by light and electron microscopy. Some animals were injected with 30–80 mg of the drug per kg body weight and sacrificed 3 to 5 hr later. Others were given 0.3 mg/kg/day for 6 days and processed on day 7. Virtually no MTs were seen in Sertoli cells after short‐term treatments, and their numbers were greatly reduced after the long‐term injections. Intermediate filaments were very evident throughout the cytoplasm of treated cells, particularly in the short‐term studies. Moreover, a close association of some of these filaments with centrioles was observed. In all cases, elongate spermatids which normally move apically did not do so. Indeed, some spermatids appear to have been pulled to a basal position after having moved apically prior to treatment. Also, smooth endoplasmic reticulum (SER) accumulated basally in the Sertoli cell, unlike controls, and the acrosomes of late spermatids developed abnormally or did not complete their shape changes. Cell junctions appeared normal and sperm release was observed. In conclusion, our data suggest that Sertoli cell MTs are necessary for the normal development and translocation of spermatids in the seminiferous epithelium and are involved with positional changes in Sertoli cell SER. They do not appear essential for the maintenance of cell junctions.