bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the surface morphologies of the cells in the bursa cloacalis (bursa of Fabricius) and thymus during ontogeny of the chick embryo
Authors: Schoenwolf Gary C. , Singh Upendra
Published: February 2005

Slices or sections through the bursa cloacalis and thymus of chick embryos at 7–21 days of incubation were observed by light and electron microscopy to determine whether major differences existed in the surface morphologies of lymphoid cells in these organs, and whether the surface morphologies of these cells changed during ontogeny. These organs were fixed concurrently and identically at each stage.

The thymus was packed at all stages with spherical cells having fine structures characteristic of those of lymphoid cells. Many irregularly shaped, epithelial cell processes were present between lymphoid cells.

The bursa contained many irregularly shaped stromal cells as well as spherical cells. The latter were few in number during early development, but became the predominant type of cell near the end of incubation. Spherical cells in the bursa consisted of three types based on fine structure: lymphoid cells, granulocytic cells, and cells which were probably precursors of granulocytic cells. Spherical cells in the bursa could not be classified into these three types by their surface morphologies, however, because the latter at any one stage of development were similar. At 7–8 days of incubation, spherical cells in the bursa could not be differentiated consistently from neighboring stromal cells by scanning electron microscopy alone, but by 9 days, spherical cells could be identified routinely by this method.

At 9–10 days of incubation, only minor differences existed in the surface morphologies of the spherical cells in the bursa and thymus: Bursal cells displayed long, ridgelike processes, whereas thymic cells exhibited fine surface undulations and large blebs. At 11 days, the surfaces of the spherical cells in the bursa were covered by numerous short microvilli, but the surfaces of thymic cells were unchanged. Bursal cells retained their microvilli through 14 days of incubation, but between 15 and 21 days progressively lost their microvilli, becoming essentially bald near the end of this period. Likewise, thymic cells gradually lost their surface wrinkles and blebs. Near the time of hatching, both types of cells were smoothsurfaced and tightly packed, with individual cells assuming polyhedral configurations.
Satellite cell distribution within the soleus muscle of the adult mouse
Authors: Snow Mikel H.
Published: February 2005

The frequency of satellite cells was quantitated by electron microscopy in five proximal to distal regions of the soleus muscle of adult mice. In all, 236 satellite cell nuclei and 4,475 myonuclei were counted on 51 transverse thin sections. The mean percentage of satellite cells, as a ratio of satellite cells to myonuclei, per region was found to be 5.4%, 5.3%, 5.0%, 5.2% and 4.9% for the most proximal to distal areas, respectively. Analysis of variance revealed no significant differences between either the regions or the animals studied. The number of satellite cell nuclei per cross‐sectional area of muscle was also calculated for each of the five regions, and these values did not vary significantly from the proximal to distal ends of the muscle. Despite the fact that satellite cells were frequently noted in close association with cross‐sectional profiles of myoneural junctions, this study establishes that the number of such perisynaptic satellite cells was not large enough to affect significantly the mean percentages of all satellite cells counted within the motor endplate regions (areas 3 and 4) of the soleus muscle. It is concluded from this study that satellite cells are uniformly distributed throughout the whole muscle.
The structure of bursae ovaricae surrounding the ovaries of the golden hamster
Authors: Martin Gary G. , Sack Marty , Talbot Prudence
Published: February 2005

The ovaries of many mammals lie within membranous sacs called bursae ovaricae. In this study, we have examined the morphology of the bursa surrounding the hamster ovary using light and electron microscopy. The bursa is composed of three layers: (1) an inner, discontinuous bursal epithelium that faces the ovary; (2) a middle layer of connective tissue that contains fibroblasts, bundles of smooth muscle cells, and blood vessels; and (3) an outer, continuous epithelium that faces the peritoneal cavity. One side of the bursa has a thin layer of connective tissue, and because the ovary may be seen through it, we refer to this region of the bursa as the “window”. Elsewhere a thick layer of fat joins the connective tissue and blocks visualization of the ovary. Tracers (Evans blue and lanthanum) applied to the peritoneal surface do not penetrate beyond the peritoneal epithelium. Tracers injected into the bursal cavity penetrate all layers of the bursa, but do not pass through the peritoneal epithelium. Therefore, the bursa prevents tracer exchange between the bursal and peritoneal cavities, but exchange does take place between the bursal cavity and blood vessels within the bursa. We suggest that bundles of smooth muscle cells within the bursa may serve to regulate fluid volume and pressure within the bursal cavity. Possible functions of the complete bursa in the hamster are discussed.
The effects of castration on size and appearance of Sharpey's fibers of rat femurs: A scanning electron microscopic and microradiographic study
Authors: Wink Carole S.
Published: February 2005

Areas of Sharpey fiber bone from the proximal posterior diaphyseal surfaces of anorganic control and castrate osteopenic rat femurs were examined with the scanning electron microscope (SEM). The diameter of Sharpey fiber bundle insertion sites from castrate bone was significantly greater (P ≤0.001) than that from control bone. The fiber bundle insertions appeared as small pits and projections in control bone and as large pits in castrate bones. Microradiographs of cross sections of the Sharpey fiber bone revealed a greater (P ≤ 0.05) area of outer, lamellated periosteal bone in the castrates than in the controls, suggesting an accelerated bone apposition rate along castrate osteopenic femoral periosteal surfaces.
The histology and fine structure of glands in the rat respiratory tract
Authors: Spicer S. S. , Setser M. E. , Mochizuki I. , Simson J. A. V.
Published: February 2005

The structure of rat respiratory glands has been investigated by light and electron microscopy. The glands exhibited a tubulo‐acinar organization. Individual secretory units were composed of serous tubules or serous demilunes and mucous tubules with narrow lumens at the blind end (proximally), and of mucous ducts with wide lumens which opened to the tracheal lumen distally. Near the junction of the duct with the trachea, mitochondria‐rich cells and a few ciliated cells were interspersed with mucous cells. It was found that the histology as well as the ultrastructure of the secretory product of these gland cells varied depending upon the location of the glands in the airway. For this reason, the glands of the epiglottis, larynx and trachea have been described separately. Epiglottal glands consisted of many mucous tubules, a few serous elements and an occasional mucous duct. Laryngeal glands contained many serous and mucous tubules and a few mucous ducts. Tracheal glands were composed of serous tubules, a few mucous tubules and prominent mucous ducts. Serous tubule cell granules formed a uniform population within a cell profile but varied in cells of the epiglottis, compared with those of the larynx and trachea. Granules in mucous tubule cells differed from those of serous cells. Mucous cell granules also appeared uniform within a single cell but differed from cell to cell and at different levels of the respiratory tract. A particular granule type was predominant at each level. Cells of mucous ducts differed somewhat from those of mucous tubules and comprised two general secretory cell populations. Proximal mucous duct cells contained abundant granules that generally resembled those of mucous tubule cells but were localized in two areas of the cytoplasm. Dilated cisternae of rough endoplasmic reticulum with a bizonal content similar in density to zones seen in mature granules further characterized proximal mucous duct cells. The distal mucous duct cell generally contained sparse apical granules and lacked dilated rough endoplasmic reticulum.
A freeze‐fracture study of the guinea pig yolk sac epithelium
Authors: King Barry F.
Published: February 2005

The yolk sac epithelium functions in endocytic absorption of macromolecules from the uterine lumen and in maintaining permeability barriers between the maternal (uterine) compartment and underlying fetal compartments. In this study, cell membranes and intercellular junctions of the guinea pig yolk sac were examined using the freeze‐fracture technique. Intramembranous particle (IMP) distribution and size were examined in microvilli, intermicrovillous membrane, and endocytic pits. IMPs on the P‐fracture face were not evenly distributed within these membrane domains and the IMPs were of several sizes. In addition, short filamentous strands sometimes bridged between the cytoplasm and the E‐face of endocytic pit membranes. These results indicated that the regions of yolk sac cell membrane involved in endocytosis did not have unusual numbers or distributions of IMPs compared to other membrane regions. The intercellular junctions between endoderm cells consisted of zonulae occludentes, gap junctions, and desmosomes. The zonula occludens usually consisted of four or five interconnected strands or ridges, and were elaborately developed where three cells abutted one another. Gap junctions were infrequent, small, and often associated with the zonula occludens. Desmosomes were observed both as typical macular structures and as more extensive, elongated structures. These results confirm previous thinsection studies of yolk sac indicating the presence of tight junctions. However, the extent of development of tight junctions does not correlate with the reported absence of a potential difference across yolk sac epithelium. The presence of gap junctions does not confirm results of previous freeze‐fracture studie sof other yolk sacs.
Morphology and distribution of microtubules in the presecretory and secretory ameloblasts of the rat incisor
Authors: Nishikawa Sumio , Kitamura Hironori
Published: February 2005

The morphology and distribution of microtubules in the ameloblast of the rat incisor were examined. Two types of microtubules distribution were observed: isolated single tubules and multiple tubules. The latter formed bundles of tubules and filaments or sheets of filaments. The thickness of the filament or sheet was almost the same as that of the wall of the microtubule. The filament or sheet as well as the microtubule were negatively stained when treated with tannic acid. The microtubules of the single type were small in number at the undifferentiated stage of the cell. They increased in number in the distal portion of the cell during differentiation, and their number reached a peak in the proximal portion of Tomes' process at the secretory stage of the cell. On the other hand, the multiple microtubules showed a different distribution in the secretory stage of the cell, i.e., they were mostly distributed between the Golgi region and the distal terminal web.
The distribution of satellite cells and their relationship to specific fiber types in soleus and extensor digitorum longus muscles
Authors: Gibson Marcia C. , Schultz Edward
Published: February 2005

Fiber type classification of p‐phenylene‐diamine‐stained transverse sections of rat skeletal muscle correlated with electron microscopic observations demonstrate that satellite cells are not equally distributed among the various fiber types in either the EDL or soleus at 1 and 12 months of age. Of the three fiber types in the EDL, satellite cells are observed most frequently on Type IIA fibers, and at approximately equal frequencies on Type IIB and Type I fibers. Satellite cells in the soleus, in contrast to the EDL, are not often encountered on Type IIA fibers, but are preferentially associated with Type I fibers in that muscle. The frequency with which satellite cells are found on specific fiber types is distinct for the soleus and EDL and appears to correspond with their growth characteristics. The distribution of satellite cells according to fiber type does not provide an explanation for the differences in the percentage of satellite cell nuclei between the EDL and soleus.
Preovulatory changes in cumulus‐oocyte complex of the hamster
Authors: Leibfried M. Lorraine , First Neal L.
Published: February 2005

An orderly series of associations was found between the cumulus and the stages of nuclear development in the hamster oocyte as the oocytecumulus complex underwent preovulatory maturation. Ten hours prior to ovulation meiotic resumption was first seen in the oocyte. The onset of cumulus dissociation with corresponding morphological changes in cumulus cells was observed eight hours prior to ovulation. Completion of the first meiotic division in the oocyte and full cumulus dissociation occurred 2 hours prior to ovulation. Cumulus dissociation was found to occur only in vesicular follicles destined to ovulate and not in follicles undergoing atresia. Cells with large vacuolar inclusions with distorted, hyperchromatic nuclei were found in the maturing cumulus.
Development of harderian gland during metamorphosis in anurans
Authors: Shirama Kazuhiko , Kikuyama Sakae , Takeo Yuji , Shimizu Kiyoshi , Maekawa Kyutaro
Published: February 2005

Development of Harderian gland of larvae of Rana japonica, Bufo bufo japonicus, and Xenopus laevis was studied. In the adult animals, welldeveloped Harderian glands were invariably present in the orbit. In Rana and Bufo, the gland first appeared at late prometamorphic stage and in Xenopus it appeared around climax stage.

In thyroidectomized tadpoles of Bufo and Rana, the Harderian gland was induced by thyrozine. In hypophysectomized tadpoles of Bufo the gland developed when they were treated with thyrozine or TSH.
Development of ultrastructural heterogeneity among hepatocytes in the mouse
Authors: Asada‐Kubota Mari , Kanai Kazuo , Kanamura Shinsuke
Published: February 2005

Ultrastructural stereological analyses of periportal and centrilobular hepatocytes of newborn, 5‐ and 10‐day‐old, and adult male ddY mice were carried out to study the postnatal development of the morphologic heterogeneity among hepatocytes. In newborn animals, the periportal and centrilobular cells did not differ in the volume densities of the smooth and rough endoplasmic reticulum; in the volume and numerical densities of the mitochondria, lysosomes, peroxisomes, and lipid droplets; or in the shape (the axial ratio) of the mitochondria. In 5‐day‐old animals, the volume densities of the mitochondria and rough endoplasmic reticulum were greater in periportal cells than centrilobular cells, and the volume density of the smooth endoplasmic reticulum was greater in centrilobular cells than periportal cells. In 10‐day‐old animals, a further difference was seen in the numerical density of the mitochondria, which was greater in centribular cells than periportal cells. Adult hepatocytes showed also a difference in the axial ratio of the mitochondria, which was greater in centrilobular than periportal cells; there was no difference in the volume density of the rough endoplasmic reticulum. When the data were expressed as volume and number per hepatocyte, the patterns of sublobular distributions of these organelles differed from the patterns seen in the volume and numerical density data, mainly in adult animals. This difference was caused by the marked increase in hepatocyte volume between 10 days of age and adulthood, especially in centrilobular cells.

The results show that, in general, the ultrastructural heterogeneity among hepatocytes, evident in adult animals, is not present in newborn animals but arises during postnatal development, and suggest the occurrence of a lobular gradient in postnatal development of hepatocyte functions.
Cellular kinetics of the bone remodeling sequence in the rat
Authors: Van Phuc Tran , Vignery Agnes , Baron Roland
Published: February 2005

The kinetics of the bone remodeling sequence in the rat has been studied using a system in which well‐synchronized remodeling units were induced along the periosteum of rat mandibles. Remodeling of the periosteal surface of the mandibles was induced according to Tran Van (1979) by extraction of the opposing row of teeth; namely, the right maxillary molars were extracted under light ether anesthesia, therefore allowing the right mandibular molars to egress; this, in turn, induced a wave of remodeling activity on the buccal side of the periosteal surface of the alveolar bone. The quantification of the different cellular activities involved in bone remodeling has been performed up to 16 days after induction. This allowed us to demonstrate the sequential activity of the different cell types involved in bone remodeling, to study the cellular kinetics of this sequence of events, and to directly measure the duration of each phase of the bone remodeling sequence. A single wave of osteoclasts appeared 3 days after induction, reached a peak at 4–5 days, and then decreased sharply. This was followed by a single wave of mononuclear cells (Baron et al., 1980) within remodeling sites during the reversal phase; they appeared 4 days after induction, reached a peak by day 7, and then decreased sharply. This reversal activity was then followed by osteoblasts forming new bone on top of a reversal cement line in the remodeling sites, starting 6 days after induction and increasing until the end of the experiment. In addition, the synchronization of the system used in this study allowed direct measurement of the duration of the successive steps of the remodeling sequence. The directly measured values have then been compared to previous data calculated from other systems.
Formation of the outer dense fibers during spermiogenesis in the rat
Authors: Irons Margaret J. , Clermont Yves
Published: February 2005

The morphogenesis of the outer dense fibers (ODF) in rat spermatids has been studied by electron microscopy, and the synthesis and incorporation of proteins into the ODF during this process have been followed by radioautography using 3H‐proline and 3H‐cystine as precursors for ODF proteins. In the first phase (steps 8–14), nine very fine fibers termed anlagen of the ODF develop in association with the microtubule doublets. These first appear along the most proximal portion of the axoneme in step 8 of spermiogenesis; during steps 9–14 they gradually increase in length in a proximal‐to‐distal direction, being first observable along the forming midpiece and later along the principal piece as well. In the second phase (steps 15–16), the rudimentary fibers suddenly increase in diameter, with the most dramatic growth occurring in step 16, and assume a close resemblance to the mature ODF. This striking transformation, which appears to result from simultaneous deposition of electron‐dense material along the length of anlagen of the ODF, coincides with a period of rapid incorporation of 3H‐proline and 3H‐cystine‐containing proteins, which become permanent structural components of the ODF. These proteins, which comprise the bulk of the ODF, are synthesized in the cytoplasm of spermatids during the acrosome and early maturation phases. In the final phase (steps 17–19) the fibers continue to enlarge very slowly, assuming their definitive form in step 19 of spermiogenesis. Thus formation of the ODF in the rat is a lengthy multistep procedure, requiring from step 8–19 of spermiogenesis and utilizing proteins synthesized throughout most of this period.
Ultrastructure of turkey hepatocytes
Authors: Bhatnagar M. K. , Singh A.
Published: February 2005

Hepatocytes of normal male and female turkey livers perfused in situ with a fixative containing 4% glutaraldehyde in 0.05 M phosphate buffer (pH 7.4) were examined by electron microscopy. The hepatocytes, arranged in two‐cell‐layered plates, were polygonal and had three spatially different surfaces. The vascular surface was formed by microvilli, which at times projected into the sinusoids past the space of Disse. The interhepatocytic surfaces were closely applied and contained an occasional gap junction. The biliary surface participated in bile canaliculus formation and had short, regular microvilli. Tight junctions and adherens junctions were close to the canalicular lumen. The hepatocyte nucleus was located towards the vascular pole. The cytoplasm of hepatocytes of the females had many lipid droplets. The pleomorphic mitochondria, with relatively electron dense matrices were surrounded by one or, rarely, two profiles of flattened rER. Golgi complex was often observed in the vicinity of the nucleus, whereas the centrioles were located in the pericanalicular area of the biliary pole, which was rich in microtubules. These microtubules were extremely long, at times covering a substantial distance between the Golgi complex and bile canaliculi; microtubules occasionally formed bundles near the biliary pole. Small vesicles in close proximity of the microtubules were frequently observed. The spatial relationship between Golgi complex, microtubules, vesicles, and centrioles at the biliary pole of the hepatocyte appears to support the concept that the bile secretory mechanism in avian hepatocytes may involve a centrioles‐microtubules‐vesicles‐Golgi complex system.
Early myelin formation and glial cell development in the human spinal cord
Authors: Okado Nobuo
Published: February 2005

In order to identify the onset of myelination as well as to clarify the development of glial cells in human cervical spinal cord 21 embryos and fetuses ranging from 5 weeks of ovulation age (16 mm in crown‐rump length) to 13 weeks (110 mm) were examined with the light and electron microscope. The first appearance of definite myelinated fibers occurred in the lateral portion of the ventral marginal layer of a 66‐mm (10‐week) fetus. These nascent myelinated axons were always of larger diameter than unmyelinated axons. Although they occurred infrequently, there were, nevertheless, degenerative changes observed in some of these first myelinated axons in the 66‐mm fetus. By this time glial cells in the marginal layer rapidly increased in number and substantial differentiation had occurred. Young oligodendrocytes are considered as the only myelin‐forming cells in the human spinal cord.
DNA content, mitotic activity, and incorporation of tritiated thymidine in the developing inner ear of the rat
Authors: Khan Khalid M. , Marovitz William. F.
Published: February 2005

The rat inner ear is ectodermally derived from a region adjacent to the developing hindbrain. Beginning on day 8 of a 22‐day gestational period, this zone of ectoderm first forms the otic placode, then the otocyst, and ultimately the definitive membranous labyrinth. This report provides an estimation of total DNA content of the developing inner ear, and hence an estimation of the total number of cells that comprise the inner ear at each developmental stage. The incorporation of 3H‐thymidine indicates that most cells of the inner ear undergo DNA synthetic activity during gestational days 13 to 15. Radioautographic observations indicate a zone of DNA synthetic activity at the base of the outpocketing cochlear duct during early development. At the later stages of development, DNA synthesis is restricted to the cristae ampullares of the semicircular canals and the maculae of the utricle and the saccule. In contradistinction to the findings of other investigators, the statoacoustic ganglion complex undergoes terminal mitosis during gestational days 17 and 18. The gestational period between days 13 and 15 may prove to be a critical stage in normal otic development. The normal values of total DNA content and the number of cells that comprise the inner ear during development, established by these methods, can be compared with pathologic inner ears to provide quantitative means of assessing the damage in malformed inner ears. These values also form the baseline for future experimental studies of inner ear development.
Development of the glycogen body through the whole length of the chick spinal cord
Authors: Uehara Masato , Ueshima Toshihiko
Published: February 2005

The development of the glycogen body was studied throughout the entire length of the chick spinal cord. The glycogen body cells first appeared at stage 31 on each side of the ependymal septum from the 26th to 28th segments of the spinal cord. By stage 34 the paired primordia of the glycogen body extended from the 25th to 29th segments. In the middle of the structure described classically as the glycogen body (i.e., the portion restricted to the level of the spinal nerves 26–29), these primordia were fused dorsally at stage 34 and had fused completely by stage 37. The paired primordia extended from the cervical enlargement to the lumbosacral portion of the spinal cord by stage 36 and extended to the upper cervical segments by stage 38. They were totally fused throughout the entire length of the spinal cord by stage 42. The glycogen containing cells, in the classical glycogen body level, appeared ventrolateral to the central canal at stage 35. Thereafter they increased in number and glycogen content, and extended rostrad and caudad from the classical glycogen body level. They fused to each other and then fused with the glycogen body. Therefore, the bilateral clusters of the glycogen‐containing cells are considered as the ventral paired primordia of the glycogen body. The development of the glycogen body is essentially the same pattern as in the classical glycogen body throughout the entire length of the spinal cord.
Aspects of renal vascular organization and early vascular tubular relations of the marsupial Isoodon obesulus
Authors: Burger C. H. , Cross R. B.
Published: February 2005

Renal vascular tubular relationships were studied in the marsupial Isoodon obesulus (the common brown bandicoot). The microcirculation was filled with colored silicone rubber by intra‐arterial injection of the intact kidney. Nephrons were defined by the injection of silicone rubber of a contrasting color into the space of Bowman's capsule in thick, cleared slices of renal tissue. The details of the vascular tubular relationship in this marsupial are strikingly similar to relationships previously described in true mammalian kidneys. An unusual feature is a wide (600μ) glomerulus‐free zone at the outer cortex. This zone contains the proximal and distal convoluted tubules of the most superficial cortical nephrons and is perfused by efferent vessels from glomeruli in superficial strata of the cortex.
Circadian ultrastructural changes in rat gastric parietal cells under altered feeding regimens: A morphometric study
Authors: Jacobs Danielle M. , Sturtevant Ruthann P.
Published: February 2005

The ultrastructure of rat gastric parietal cells was studied at six timepoints of the 24‐hour day. The rats, maintained on a 12 hour: 12 hour light‐dark regimen, had been subjected to either a 40‐hour fast or to a 4‐hour mid‐light restricted feeding period. At each time point, the volume density (Vv) of secretory canaliculi, surface density (Sv) of microvesicles and RER, and the numerical density (Nv) of multivesicular bodies were determined in cells of the neck and base of glands. Circadian variation of the four variables was suggested in both experiments. Canalicular and microvesicular measurements suggested that a rhythm in gastric acid secretion may persist during fasting; a peak and trough, respectively, occurred in the late dark phase, as in our previous report on ad libitum‐fed rats. Restriction of feeding to that which is normally the rat's resting phase caused an apparent 180 degree phase‐shift in the rhythm. The data suggested, however, that additional factors may have influenced the cellular activity pattern. At all timepoints in both experiments, cells of the neck of glands had higher RER and canalicular values than did cells of the base of glands. This suggests that parietal cells in glandular necks may be more active than those farther removed from the stomach lumen. There was no correlation between the Nv of multivesicular bodies and glandular location of the cells.
A cellular investment of bone marrow
Authors: Menton D. N. , Simmons D. J. , Orr B. Y. , Plurad S. B.
Published: February 2005

We describe a method for cleanly separating; the cell layers at the bone‐marrow interface, which reveals that the myeloid tissue is invested by an epithelial‐like layer of specialized squamous cells we call the marrow sac. The scanning electron microscope showed that the sac was fenestrated and that some of its cells pass as perivascular elements with the marrow capillaries that penetrate the bony cortex. The transmission electron microscope (TEM) showed that the cells comprising the marrow sac are less than 0.1 μm thick, overlap at their margins without specialized cell junctions, and are more electron dense than the reticular or fibroblastic cells of the marrow stroma. The fenestrations in the sac were intercellular and were usually occupied by cells having an ultrastructure compatible with an osteoprogenitor cell (OPC) lineage. The observation of a close proximity between the cells of the marrow sac and the osteogenic cells that line the endosteal surfaces of bone suggest that the sac cells, along with the OPCs of the superficial marrow stroma, should be included in any morphological or functional definition of an endosteum.
Tanycytes in long‐term ovariectomized ewes treated with estrogen exhibit ultrastructural features associated with increased cellular activity
Authors: Coates Penelope W. , Davis Steven L.
Published: February 2005

Ependymal tanycytes on the floor of the third ventricle of longterm ovariectomized (OVX) female sheep (ewes) and OVX ewes treated with 17β‐estradiol (E2β) were investigated with scanning and transmission electron microscopy (SEM and TEM) for evidence of differences in ultrastructure. Plasma concentrations of luteinizing hormone (LH) in the same ewes that were analyzed ultrastructurally were 45.1 ± 28.7 ng/ml in the nontreated OVX group, and 2.2 ± 1.3 ng/ml in the OVX + E2β group, confirming the widely reported negative feedback effect of estrogen on LH. With SEM, the most prominent difference between groups was that tanycytes on the floor of the third ventricle in OVX ewes had very few surface membrane modifications, particularly microvilli, and appeared relatively bare‐surfaced compared to those from the estrogen‐treated group. Tissues from estrogen‐treated OVX ewes were, for the most part, covered with a fuzzy nap of delicate microvilli. Transmission electron microscopy confirmed and extended this impression. With TEM, tanycytes in E2β‐treated ewes exhibited not only a more luxurious display of microvilli but also a much richer complement of welldeveloped organelles including rough endoplasmic reticulum, ribosomes, Golgi complexes, microtubules, and filaments than tanycytes in OVX alone ewes. Collectively, the fine structural data indicates a positive correlation between tanycytes displaying well‐developed features associated with heightened cellular activity – synthesis, secretion and/or absorption – and the presence of estrogen.
Evolution of sertoli cell processes invading the cytoplasm of rat spermatids
Authors: Morales C. , Clermont Y.
Published: February 2005

Sertoli cell processes invaginating the cytoplasm of rat spermatids were investigated in thin or thick sections stained respectively with ferrocyanide‐reduced osmium (Karnovsky, 1971) and the Ur‐Pb‐Cu metallic impregnation method (Thiéry and Rambourg, 1976). Two types of Sertoli cell processes were observed: Some, seen in steps, 11–15 of spermiogenesis, were associated with a tight network of ER cisternae located within the spermatid cytoplasm subjacent to the plasma membrane facing the Sertoli cell process; others, seen from step 11 until the end of spermiogenesis, were not associated with such a spermatid subsurface ER network. Following their formation, the ER‐associated Sertoli cell processes were cleaved into double‐walled vesicles. Concomitantly, the enclosed Sertoli cell cytoplasm underwent autolysis followed by the dissolution of the Sertoli cell plasma membrane leaving within the spermatid cytoplasm many empty‐looking vacuoles delimited only by the plasma membrane of the spermatid. Thereafter, i.e., in steps 15 and 16 of spermiogenesis, these vacuoles clustered, and with the collapse of the vacuoles they gave rise to a single compact mass of interlaced ER cisternae and small vacuoles. With the dissolution of ER cisternae, in step 18, this mass was finally dispersed. These observations suggested that the ER‐associated Sertoli cell processes may constitute a pathway for the delivery of material from the Sertoli cells into spermatids. In contrast, the Sertoli cell processes not associated with a network of ER cisternae did not show cleavage or autolysis and appear to be involved mainly in holding the cytoplasm of the spermatid in place.
The cytoskeleton of human polymorphonuclear leukocytes: Phagocytosis and degranulation
Authors: Ryder Mark I. , Niederman Richard , Taggart Edward J.
Published: February 2005

Current evidence indicates that polymorphonuclear leukocyte (PMN) chemotaxis and phagocytosis are effected by an actin–myosin contractile system. However, the structural relationship of the contractile cytoskeleton to cell motility is still in question. In addition, while evidence suggests that microtubules are responsible for orientation during chemotaxis, the role of microtubules in degranulation is unresolved. To determine the organizational relationship between these cytoskeletal elements and phagocytosis, we examined whole‐mount preparations of PMNs engulfing bacteria. These preparations were examined in the transmission electron microscope (EM) and photographed as stereo pairs. Two important observations were made. First, there was an increased density of cytoskeletal elements in the pseudopod surrounding bacteria. Second, microtubule elements were intimately associated with lysosomal granules, vesicles, and phagosomes. Lysosomal granules and vesicles aligned along microtubules and clustered around phagosomes. This suggests that the microtubules may provide a tracking mechanism whereby lysosomes are specifically parceled out to phagocytic vacuoles. These results also suggest that phagocytosis and degranulation may involve different effector mechanisms.
Substructure of granules from serous cells of porcine tracheal submucosal glands
Authors: Turek John J. , Sheares Bradley T. , Carlson Don M.
Published: February 2005

The ultrastructure of serous cells from porcine tracheal submucosal glands was studied by conventional transmission electron microscopy (TEM), and by cytochemical methods to stain for complex carbohydrates. In tissue fixed and processed for TEM, and stained with uranyl acetate and lead citrate, the condensing granules of serous cells occasionally possessed a hexagonal and sometimes a lamellar substructure. Tissue fixed in paraformaldehyde‐glutaraldehyde and stained with periodic acid‐thiocarbohydrazide‐silver proteinate (PTS) or with phosphotungstic acid (PTA) showed secretory granules stained for complex carbohydrates and revealed a substructure similar to that noted in the condensing granules. The dark staining substructure revealed by either the PTS or the PTA technique appeared to correspond to electron‐lucent areas observed in the condensing granules by conventional TEM. The PTS staining probably demonstrated the presence of neutral glycoprotein, since the serous‐cell granules did not react with a dialyzed iron stain for acidic glycoproteins. Treatment of periodic acid oxidized thin sections with pronase or pepsin prior to thiocarbohydrazide and silver proteinate treatment decreased the intensity of the PTS staining, but did not digest away any components of the granules. The substructure revealed by the carbohydrate stains may be a reflection of the mechanism of packaging or the macromolecular structure of the glycoproteins in the serous‐cell granules.
Calcium‐containing lysosomes in the outer mantle epithelial cells of Amblema, a fresh‐water mollusc
Authors: Jones Ruth Gwendolyn , Davis Walter L.
Published: February 2005

The cells of the outer mantle epithelium contain numerous large pleomorphic electron dense bodies. In their fine structure they resemble lysosomes. Positive acid phosphatase histochemistry confirms that these supranuclear and subnuclear structures are lysosomes. A major portion of the intralysosomal material is resistant to high‐temperature microincineration, indicative of an inorganic component. Subsequent microprobe analyses identified considerable calcium within these organelles. Such entities are similar in structure and ionic content to the lysosomes of avian intestinal absorbing cells, another calcium‐transporting epithelium. These mantle lysosomes may function in transcellular calcium transport during shell formation, growth, and repair, especially since the mantle is the shell‐forming organ in molluscs.
Localization of enkephalin‐like immunoreactivity in the cat carotid and aortic body chemoreceptors
Authors: Hansen John T. , Brokaw James , Christie Douglas , Karasek Michal
Published: February 2005

The purpose of this study was to determine if enkephalin‐like immunoreactivity was present in the glomus cells of the carotid and aortic body peripheral arterial chemoreceptors. Cat carotid and aortic bodies were reacted with antisera to met‐ and leu‐enkephalin using the indirect peroxidase‐antiperoxidase immunocytochemical method of Sternberger (1979). Both the carotid and aortic bodies demonstrated clusters of immunoreactive cells for both met‐ and leuenkephalin. Additionally, met‐enkephalin‐like immunoreactivity was observed in many of the dense‐core vesicles of the glomus cells of the carotid body. The glomus cells of these chemoreceptors are known to contain catecholamines which may modulate chemoreceptor activity. The presence of opioid peptide‐like substances co‐existing with the glomus cell catecholamines, perhaps in the same vesicles, may have important implications for a trophic influence of these peptides on glomus cell chemoreceptor modulation.
A reexamination of rat ductuli efferentes
Authors: Iwan Lewis‐Jones D. , Harrison Ronald G. , Machillan Evan W.
Published: February 2005

In 33 testes from a random selection of rats a 10% suspension of India ink in normal saline was introduced through the rete testis into the emergent ductuli efferentes. Low‐Power microsocopy and microradiography confirmed the individually independent origin of each ductule.

Five ductules were isolated in each of 17 testes, 4 ductules in 6, 6 ductules in 8, and in 2 testes, 7 and 9 ductules, respectively. In six animals minor variations existed as between the right and left testes ± 1 in 4 and ±2 in 2.

It is necessary to exercise great caution in the interpretation of results of experimental work on alteration of the ductuli, because of variability between colonies and within strains of rats.
Cell flux through S phase in the mouse duodenal epithelium determined by cell sorting and radioautography
Authors: Bjerknes Matthew , Cheng Hazel
Published: February 2005

An accumulation of cells in early S phase was observed in normal mouse duodenal epithelium studied with flow cytometry (Cheng and Bjerknes, 1982). To determine if this accumulation of cells was the result of a lower rate of DNA synthesis, animals were given a single injection of 3H‐thymidine and the epithelium collected one hour later. The epithelium was processed for flow cytometry. Seven sort windows were established in different portions of the DNA histogram. Cells from each window were sorted onto glass slides that were then processed for radioautography. The number of silver grains over the nuclei of each sorted population was counted. It was found that cells in early S phase had significantly fewer grains over their nuclei than did mid‐ or late‐S phase cells. We conclude that the accumulation of cells in early S phase is due, at least in part, to a lower rate of DNA synthesis in early than in mid or late S phase.
Heterogeneity in the distal nephron of the salamander (Ambystoma tigrinum): A correlated structure function study of isolated tubule segments
Authors: Hinton David E. , Stoner Larry C. , Burg Maurice , Trump Benjamin F.
Published: February 2005

Studies on isolated perfused tubules of the tiger salamander (Ambystoma tigrinum) have shown that the distal nephron is heterogeneous with respect to function (Stoner, 1977). In this study, the initial portion of the distal tubule (diluting segment) exhibited a voltage, positive in the lumen, and a net absorption of chloride. Since the chloride was transported against an electrochemical gradient, its transport was active. More distad, the junctional segment exhibited a lumen‐negative voltage and sodium, rather than chloride, was transported actively. More recently Delaney and Stoner (1981) have demonstrated in vitro that the collecting duct of this species also has a lumen‐negative voltage which is probably associated with active sodium reabsorption.

The primary objective of the present paper was to correlate the morphology of the diluting and junctional segments of the Ambystoma distal tubules with the physiologic data from the same isolated perfused tubules. The results indicate that the morphological heterogeneity previously demonstrated in distal tubules of Necturus exists with respect to both structure and function in Ambystoma. The cell types found in the amphibian distal nephron appear to be homologous to those seen in the mammalian nephron.
A radiographic study of the growth in width of the human fetal vertebral column
Authors: Bagnall K. M. , Harris P. F. , Jones P. R. M.
Published: February 2005

Only a few studies have concerned themselves with the development of the fetal vertebral column, and this paper attempts to extend the literature. Standards are presented for the growth in width of the human vertebral column between 10 and 26 weeks of conceptual age. The growth patterns show that cervical and lumbar enlargements are not present at 8 weeks but develop slowly and become clearly present at 26 weeks. The growth equations also show that groups of vertebrae have their own growth patterns, indicating that the vertebral column could be separated into five groups: C1–C5, C6–C7, T1–T12, L1–S1, and S2–S5. Furthermore, comparisons with growth patterns available for growth in length from other studies reveal that some vertebrae appear to develop in one dimension independently of another.
A further case of hyperrotation of the colon
Authors: Pellatt A. , Evans A.
Published: February 2005

The anomalies resulting from abnormal rotation of the midgut loop are briefly reviewed. A case of hyperrotation with cecal ascent is described—only the second such case reported, so far as the authors are aware. The liver in this subject was larger than average, and the suggestion is made that the presence of a large liver combined with exuberant growth of the ascending colon may explain the hyperrotation. Although this anomaly is clearly very rare and not in itself pathological, the highly unusual position of the cecum and much of the ascending colon in these cases may cause problems in the diagnosis of appendicitis or during laporatomy.
The morphology of the starling (Sturnus vulgaris) bursa of Fabricius: A scanning and light microscope study
Authors: Glick Bruce , Oláh Imre
Published: February 2005

Two starlings, a male and female, were sampled from the nest in 1980 and 1981. Scanning electron microscopy and light microscopy revealed the bursa of Fabricius to be similar in these two nestlings. In the center of the elongated bursa is a wide central canal from which blind secondary canals branch. The luminal surface of the central canal is smooth and lacks the plicae characteristically observed in the chicken's bursa. The central and secondary canals contain a mixture of epithelial cells: mucin‐producing goblet cells and epithelial cells with deeply stained granules. The former cells are present in the chicken's bursa while the latter cells are not. These epithelial cells lack the florid microvilli observed in the chicken7apos;s interfollicular epithelium. The secondary canals are lined by bursal follicles which are divided into a cortex and medulla by epithelial cells. The epithelial cells of the corticomedullary border form an arch which partly encloses lymphocytes. A row of lymphoblasts commonly line the archlike epithelial cells. Follicle‐associated epithelium (FAE) appears at the apex of the bursal follicle. Unlike the chicken, one may observe tingible‐body macrophages associating with the FAE. A prominent terminal web is located beneath the apical surface of the FAE.
Active locomotion of human primordial germ cells in vitro
Authors: Kuwana Takashi , Fujimoto Toyoaki
Published: February 2005

The locomotion of human primordial germ cells (PGCs) in vitro was observed using 16‐mm time‐lapse microcinematography. PCGs dissociated from 5‐ to 6‐week human embryos were cultured in vitro using L‐15 medium and human cord serum, and their movement on three artificial and two natural substrates was compared. Three‐dimensional collagenous fiber nets reconstructed in the culure dish were found to be appropriate for PGC movement, although the cells did not migrate actively on any of the other substrates. The PGCs moved actively in an amoeboid fashion, extending pseudopodlike cytoplasmic processes toward the direction of movement. The direction of PGC locomotion was random. One PGC showed the most active motility; the velocity of the cell locomotion averaged 25 μm/h and it became extremely elongated, measuring 92 μm in its longer axis, whereas in the stationary state the PGC was rounded and measured 20 μm in diameter. Thus, the present study offers evidence that human PGCs can migrate actively.
Simultaneous ultrastructural visualization of acetylcholinesterase activity and tritiated norepinephrine uptake in renal nerves
Authors: Barajas Luciano , Wang Patricia
Published: February 2005

In this investigation we have combined the methods of ultrastructural demonstration of acetylcholinesterase activity with electron microscopic autoradiography for the demonstration of norepinephrine uptake. The results show electron‐dense deposits indicative of acetylcholinesterase activity associated with perivascular axons overlaid by concentrations of silver grains representing exogenous tritiated norepinephrine. Forty‐five percent of the intervaricose regions and 19% of the varicosities overlaid by autoradiographic grains showed “moderate” amounts of cholinesterase staining. A greater proportion of autoradiographic grains was observed on the varicosities than in the intervaricose regions; however, the amount of acetylcholinesterase activity was greater in the intervaricose regions than in the varicosities. This investigation provides evidence for the presence of periaxonal acetylcholinesterase staining in adrenergic axons in the rat kidney.