bluuebunny/crossref_metadata_2025 huggingface dataset:
The systemic arterial pattern of the guinea pig: The head, thorax, and thoracic limb
Authors: Shively Michael J. , Stump John E.
Published: February 2005

The systemic arterial pattern of the guinea pig was studied to determine the arrangement of the major arterial trunks and their branches. Fifty‐nine specimens were examined by dissection, angiography, and corrosion casting. The arterial arrangement was found to resemble a typical mammalian pattern, although some exceptions were noted. For example, the internal carotid arteries were small and of questionable significance in the cerebral blood supply. Instead, a major portion of the blood supply to the brain appeared to be provided by the internal ophthalmic arteries. In the thoracic region, large dorsal scapular arteries originated and were distributed in part to the large fat pad in the dorsal cervical region. Also, each vertebral artery arose as two separate rami that anastomosed a few millimeters from their origin. The arterial pattern of the thoracic limb presented no unusual features.
The tectorial membrane of the rat
Authors: Ross Muriel D.
Published: February 2005

Histochemical, x‐ray analytical and scanning and transmission electron microscopical procedures have been utilized to determine the chemical nature, physical appearance and attachments of the tectorial membrane in normal rats and to correlate these results with biochemical data on protein‐carbohydrate complexes. Additionally, pertinent histochemical and ultrastructural findings in chemically sympathectomized rats are considered. The results indicate that the tectorial membrane is a viscous, complex, colloid of glycoprotein(s) possessing some oriented molecules and an ionic composition different from either endolymph or perilymph. It is attached to the reticular laminar surface of the organ of Corti and to the tips of the outer hair cells; it is attached to and enclose the hairs of the inner hair cells. A fluid compartment may exist within the limbs of the “W” formed by the hairs on each outer hair cell surface. Present biochemical concepts of viscous glycoproteins suggest that they are polyelectrolytes interacting physically to form complex networks. They possess characteristics making them important in fluid and ion transport. Furthermore, the macromolecular configuration assumed by such polyelectrolytes is unstable and subject to change from stress or shifts in pH or ions. Thus, the attachments of the tectorial membrane to the hair cells may play an important role in the transduction process at the molecular level.
Scanning and transmission electron microscopy of the rat kidney
Authors: Bulger Ruth Ellen , Siegel Frances Lea , Pendergrass Robert
Published: February 2005

This study utilized scanning and transmission electron microscopy of renal tissue to provide new information on the gross and microscopic structure of the kidney. The luminal surface of the proximal convoluted tubule was characterized not only by the border of microvilli, but also by crater‐like depressions, and circumferential folds. In tissue processed for scanning electron microscopy the proximal tubular cells separated along their lateral surfaces clearly exposing the topography of the lateral cell projections of cytoplasm which have been generally unavailable for viewing because of their interdigitation with adjacent cells. The various segments of the nephron were identified on the basis of position in the kidney, general morphology, and the distribution and form of apical microvilli, cilia, or flaps. The external surface of the papillary tip had several parallel furrows into which the collecting ducts opened. Large plaquelike depressions lined the papillary surface. The opposed surface of the renal pelvis had small plaque‐like depressions separated by narrow ridges. Transmission electron microscopy of plastic‐embedded tissue specimens which had been previously dehydrated by the critical point drying method demonstrated that little damage occurred from this procedure.
Ultrastructure of encapsulated nerve endings in rat gingiva
Authors: Marrtinez I. Richardo , Pekarthy James M.
Published: February 2005

The ultrastructure of a specialized encapsulated nerve ending located in the papillary layer of rat gingiva is described. The axon in the corpuscular ending possesses microvesicles and microtubules, and is surrounded by laminar cells (with basement membrane) and capsular cells (modified fibroblasts, no basement membrane).
The fine structure of developing unit collagenous fibrils in the chick
Authors: Morse Dennis E. , Low Frank N.
Published: February 2005

Perivertebral cervical connective tissue was taken from chick embryos of incubation ages from 72 hours through hatching and from 4, 8, 12, and 16 week old chicks. Preparations for electron microscopy were routine except for en bloc staining with 5% aqueous uranyl acetate. Collagenase digestions of thin sections confirmed the presence of tropocollagen in banded extracellular fibrils.

Banding becomes demonstrable in fibrils at about seven days but repeating units cannot be measured. Close to connective tissue cells the banded material is present in wide sheets. Partially banded fibrils (250 Å wide) physically related to microfibrils are present in acellular regions. Growth in fibril diameter is slow through the second week (up to 300 Å) but increases nearly 200 Å on days 14 and 15. Fibrils larger than 500 Å resist uranium and lead staining following the period of accelerated growth. Smaller fibrils (< 500 Å) continue to stain well. A basic banding pattern of measurable periodicity is established by the eighth day. This consists of a major doublet, two minor doublets, and two singlets. The intraperiod distance does not change significantly with growth (510 Å average). Additional bands near the first minor doublet and singlets of the basic pattern are first clearly demonstrable at 14 and 15 days. Ambiguities in banding and period length are believed to be due to plane of section, interference with detail by other fibrils and flaky amorphous material or possibly to differential shrinkage along the length of a single fibril.
Cortical granules in artificially activated (parthenogenetic) rabbit eggs
Authors: Gulyas Bela J.
Published: February 2005

The fate of cortical granules was ascertained in cold‐shock activated rabbit eggs. Unfertilized oocytes were obtained 14 hours after intravenous injection of Human Chorionic Gonadotropin. Experimental oocytes were stored at 6 to 10°C for 24 hours in F10 medium containing 10% rabbit serum. Control oocytes, and the experimental ones subsequent to cold‐shock treatment, were incubated for 24 hours. Formation of ‘pronuclei’ occurred in 6% of the cold‐shock treated oocytes. None of the control oocytes were activated. Electron microscopic observations show that activation occurred without the dehiscence of cortical granule content into the perivitelline space. Cortical granules were dispersed in the cytoplasm or clumped together at the periphery. Occasionally, cortical granules were found discharged into the perivitelline space with the limiting membrane intact.
The postnatal development of the human temporomandibular joint
Authors: Wright Donald M. , Moffett Benjamin C.
Published: February 2005

Fifty‐one temporomandibular joints (24 male, 27 female) obtained at autopsy were used in the study. Forty‐four specimens were younger than ten years while others ranged to 21 years. These joints were radiographed, sectioned sagittally or frontally, and slide‐mounted as decalcified and undecalcified sections using conventional histologic techniques. The slides were examined microscopically in whole, polarized, and ultraviolet light. Two of the specimens surveyed exhibited fluorescent labeling as a consequence of therapeutic tetra cycline application.

Throughout the postnatal developmental period the articular tissue and disc consist of fibrous connective tissue. Cartilage cells were not observed in these structures at any time during the twenty‐one year age‐span studied. At birth the disc is flat and develops an accentuated S‐shaped profile as the articular tubercle develops.

The articular tubercle is only a small elevation at birth and is formed by a combination of endochondral, immature, and ordinary intramembranous bone formation. The characteristic profile of the temporal portion of the joint is achieved during the first two or three years of life, after which gradual enlargement and compaction of bony structures occur.

While the mandibular condyle grows in a constant posterior, superior, and lateral direction, it does not attain its mature contour until the late mixed dentition age. Condylar growth cartilage is approximately 1.5 mm thick at birth but it thins down in a short time to about 0.5 mm. During the first two years of life the growth cartilage is penetrated by vascularized connective tissue septa whose function appears to be nourishment of the cartilage. The growth cartilage does not show the columnar arrangement of chondrocytes seen in epiphyses, nor are isogenous groups observed. At 16 to 17 years, the growth cartilage becomes thinner and a closing plate of bone is beginning to coalesce below it.
An analysis of the human femur
Authors: Lavelle Christopher L. B.
Published: February 2005

Nineteen linear and three angular dimensions were measured for 590 left femurs derived from Bronze‐Age to present‐day population samples. Univariate analysis showed varying patterns of contrast between the populations, depending upon which femoral dimension was compared. Similarly, multivariate analysis also provided varying patterns of contrast between the populations, depending upon which group of dimensions was included in the analysis. Following standardization of the femoral linear dimensions against the maximum femoral length, in contrast, repeat multivariate analyses showed a progression from the Bronze‐Age to the present‐day samples, although there was only limited discrimination between the samples.
Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine III. Entero‐endocrine cells
Authors: Cheng Hazel , Leblond C. P.
Published: February 2005

The origin, differentiation and renewal of entero‐endocrine cells was examined in the duodenum, jejunum and ileum of the mouse using light and electron microscopic radioautography after a single injection or continuous infusion of 3H‐thymidine. When s‐collidine buffered glutaraldehyde was used for fixation prior to electron microscopic study, all granules in all entero‐endocrine cells were spheroidal and, therefore, their shape could not be used to classify the cells into subgroups, as done after fixation in phosphate buffered aldehyde. Thus, the cells were all considered as belonging in a single family.

In the light microscope, mitosis is not observed in the entero‐endocrine cells identified by iron hematoxylin staining. However, under the electron microscope, a few cells that contain a small number of characteristic granules, some filament bundles and many free ribosomes are in division or are labeled one hour after an injection of 3H‐thymidine. These cells are interpreted as young entero‐endocrine cells. They are located in the crypt base. They resemble crypt‐base columnar cells and are, therefore, suspected of arising from them.

Differentiation may be examined by following the fate of the young enteroendocrine cells which are labeled by 3H‐thymidine. Within the crypts, these cells acquire a gradually increasing number of granules while losing the ability to divide. The few granules initially present usually have a particulate content and may include a small dense core; but, as differentiation proceeds and granules accumulate, their content is mostly dense and homogeneous. The differentiation of precursor cells into mature entero‐endocrine cells takes about two days.

Meanwhile, in the same manner as columnar and mucous cells, enteroendocrine cells migrate up the crypt, reach the villus and are lost at the extrusion zone.

The turnover time of entero‐endocrine cells is estimated to be 3.9 days in duodenum and 4.0 days in jejunum.
A degeneration study of some habenular efferents to the midbrain in a wallaby
Authors: Way John S.
Published: February 2005

In this study, specimens of both sexes of a Western Australian wallaby (Setonix brachyurus) had surgical or electrolytic lesions made in the habenular complex unilaterally. Thirty‐five‐micron sections, cut coronally and parasagitally, were stained by the Nauta‐Gygax ('54) or the Fink‐Heimer ('67) technique to demonstrate degenerating fibers. Degeneration was seen in the habenular commissure and bilaterally in the habenula and fasciculus retroflexus, but was most extensive ipsilaterally. Habenular fibers destined for the tegmentum and central gray passed caudally into the midbrain in a continuous fan‐like array which extended from the central gray dorsally to the interpeduncular nucleus ventrally. In their posterior course some fibers crossed the midline with the decussating cerebellar fibers. The majority of fibers, with those in the fasciculus retroflexus which passed ventral to the decussation of the superior cerebellar peduncle, turned dorsally. They passed mostly just lateral to the midline nuclei and into the central gray where degeneration was seen throughout the entire extent. Terminal degeneration was seen in the interpeduncular nucleus primarily in the dorsal and posterior parts, in the ventral tegmental nucleus and throughout the central gray, but was more densely clustered in the region of the dorsal tegmental nucleus.
Development of the endometrium during the estrous cycle in the bitch
Authors: Barrau Marny D. , Abel John H. , Verhage Harold G. , Tietz W. J.
Published: February 2005

The endometrium of 40 cycling bitches was studied using cytological, cytochemical, and morphometric techniques. Two principal phases of growth and differentiation can be discerned. Phase one begins at the end of anestrus as serum estrogen levels begin to rise and is completed just prior to estrus. It is characterized by growth of the crypts and differentiation of the glandular epithelial cells into well‐developed, mucus‐secreting cells. Growth, initially rapid, gradually slows. The second growth phase does not begin until the middle of estrus as serum progestin levels rise and lasts nearly a week. Both hypertrophy and hyperplasia of the glandular epithelium and growth of the basal glands characterize this stage. The gland cells develop many well‐defined characteristics of absorptive and secretory cells. Another phase of growth occurs in pregnant animals at the onset of implantation. During the third week of metestrus in non‐pregnant bitches, the uterus begins to involute. Acid phosphatase and the number of lysosomes increase dramatically in the epithelial cells particularly in the basal glands. Cells lining the lumen and crypts accumulate numerous large lipid droplets.

The data are discussed in relation to the clear separation of two distinct uterine functions: (1) sperm transport and maintenance and (2) production and secretion of nutritive uterine milk. Extended periods of follicular development, breeding, and preimplantation in the bitch probably impose this separation.
Ultrastructural study of mouse olfactory epithelium following destruction by ZnSO4 and its subsequent regeneration
Authors: Matulionis Daniel H.
Published: February 2005

Regeneration of olfactory epithelium was studied at the ultrastructural level in two different strains of mice (C57B1/6J and SWR/J) following destructive changes induced by nasal irrigation with a 1% aqueous solution of zinc sulfate (ZnSO4).

Three epithelial conditions were seen during the first four to 14 days following treatment: a “surface alteration” state characterized by changes at the apical ends of olfactory and columnar supporting cells, a “squamous‐metaplastic” state, and a “simple‐squamous” state. In the latter two conditions, thought to represent regenerative states, cells contained inclusions similar to secretion granules in Bowman's glands. This observation supports earlier suggestions that new epithelial cells originate from these glands. Later regenerative changes consist of differentiation of new sensory cells and columnar supporting cells in an initially disorganized epithelium. This epithelium then changes to a normal, pseudostratified organization.

Regeneration of the epithelium begins earlier and proceeds more rapidly in the SWR/J strain than in C57B1/6J mice. Possibly, a genetle difference exists between strains. After 72 days the epithelium in both strains had regenerated.
Studies on the progestational endometrium of the rabbit. II. Electron microscopy, day 0 to day 13 of gonadotrophininduced pseudopregnancy
Authors: Davies J. , Hoffman L. H.
Published: February 2005

The fine structure of the endometrial epithelium of the pseudopregnant rabbit from the day of induced ovulation (day 0) to the 13th day is here correlated with previously defined light microscopic phases. In Phase 1 (0–1 day), in which there is a presumed “priming” of the endometrium by ovarian steroidal hormones, no changes were observed. In Phase 2 (1–3 days), in addition to mitotic activity, the epithelium showed a disappearance of the mucification and lymphocytic migration typical of Phase 1 and also of the nonpregnant or “estrous” phase, and showed other nuclear and cytoplasmic changes which probably reflect endogenous growth and protein synthesis. In Phase 3 (4–6 days), two distinct populations of reacting cells were present: (1) surface and cryptal cells investing the now folded mucosal surface, and (2) glandular cells. The first group showed characteristic dome‐like protrusions of the cytoplasm into the lumen, and also showed distinct cytoplasmic and nuclear changes which appear to be a prelude to the succeeding phase of fusion but are not necessarily secretory in type. The glandular cells, in contrast, showed cytoplasmic changes which appear to reflect active secretory activity (hypertrophy of the Golgi area, cytoplasmic vacuoles containing electron‐opaque material, etc.). This phase coincides with the maximal secretion of uterine‐specific proteins, and electron‐opaque material is abundant within the endometrial lumen. In Phase 4 (6–8 days), the surface and cryptal epithelium undergoes a transformation into multinucleated cells, the result of a process of lysis of intervening plasma membranes, the precise mechanism of which (i.e., with or without initial membrane fusion) was not determined. Cell fusion proceeded earlier and more actively mesometrially than antimesometrially. The glandular cells showed evidence of reduced secretory activity, but did not at any stage undergo multinucleate‐cell transformation. In Phase 5 (8–13 days) there was progressive fusion, and the number of nuclei per cytoplasmic sac appeared increased, presumably due to the continued action of progesterone which is maximal during this phase. Glandular cells showed further reduced secretory activity but remained columnar. Ciliation of the epithelium was sporadic in the pre‐secretory phases and rare or absent in the secretory and fusion phases; it became widespread during the phase of decline after day 14, a period which will not be included in this study. The fine structure of the ciliated cells was the same at all stages; there was no evidence for their origin from a reserve population; it is possible that they arise by modification of the multinucleated cells. Cytoplasmic crystals and intramitochondrial densities or lamellae were observed during the secretory and fusion stages, the former only in the glands, the latter in the surface and cryptal epithelium. They appear to be associated with rising or maximal progesterone secretion.
Anti‐horseradish peroxidase associated with the Golgi complex of antibody‐forming cells
Authors: Tomonaga Susumu , Schoefl Gutta I.
Published: February 2005

Observations are reported on the localization of anti‐horseradish peroxidase in antibody‐forming cells in popliteal lymph nodes following a single injection of antigen. Reaction product, marking the site of antibody, was observed not only in the ergastoplasm and cisternae of the Golgi complex, but also in globules associated with the Golgi complex.
Renal morphology of freshwater trout
Authors: Anderson Bettina G. , Loewen Richard D.
Published: February 2005

The nephron of the euryhaline freshwater salmonids is composed of the renal corpuscle and the renal tubules. Throughout much of the renal corpuscle, only the lamina densa separates the fenestrated processes of the endothelial cells from the foot processes of the visceral epithelium. The renal tubule consists of five distinct segments. The neck segment is short and intermittently ciliated; it lacks the mucous cells which appear in the neck segment of some teleosts. The proximal segment bears a dense brush border and is both structurally and functionally divisible into a first and a second segment. The first portion is typified by the presence of short apical tubules, variously sized apical vacuoles, and numerous lysosomes. The second proximal segment is distinguished by the abundance and distribution of mitochondria throughout the cytoplasm. Infoldings of the basilar plasmalemma are especially prominent in this region. A ciliated intermediate segment intervenes briefly between the proximal and distal portions of the tubule. The distal segment consists of cuboidal cells which bear scattered, short microvilli, small vesicles and multivesicular bodies.

Renal tissue from several species of trout was examined in order to establish the basis for a common pattern of histological and ultrastructural characteristics within the family Salmonidae. In all species examined, renal structure was very similar and could readily be compared with that previously described in other freshwater and marine species.
A complex junctional system in endothelial and connective tissue cells of the choroid plexus
Authors: Dermietzel Rolf , Schünke Dorothee
Published: February 2005

Endothelial and connective tissue cells of the choroid plexus have been studied by the freeze‐etching technique. The endothelial cells of pre‐ and postcapillary segments are coupled by a complex junctional system consisting of a combination of tight and gap junctions. Connective tissue cells revealed the same intercellular contacts. Furthermore two different types of gap junctions occurring in membranes of the connective tissue cells are described.
Ultrastructural observations of pineal gland capillaries in four rodent species
Authors: Matsushima Shoji , Reiter Russel J.
Published: February 2005

The fine structure of the capillaries of the pineal glands of the rat, mouse, chinchilla and ground squirrel were investigated. The pineal endothelial cells in the rat, mouse and ground squirrel were often composed of attenuated cytoplasmic portions which contained numerous fenestrations, in contrast to pineal capillaries in the chinchilla which were lined by thick non‐fenestrated endothelial cells. Marked morphological differences were also apparent in terms of the types of vesicles within the cytoplasm and abutting on the cell surface of pineal endothelial cells from the various specius investigated. The interendo‐thelial junctions exhibited remarkable species differences with the chinchilla pineal possessing typical tight endothelial junctions while those in the rat, mouse and ground squirrel lacked such endothelial cell associations. Generally, capillary lining cells in the chinchilla pineal resembled similar cells within the brain, while endothelial cells in pineal glands of rat, mouse and ground squirrel were more typical of those found in other endocrine organs. Species differences in the structure of the pineal capillaries may represent physiological differences as well.
Ultrastructural observations on the maturation of the placental labyrinth of the golden hamster (days 10 to 16 of gestation)
Authors: Carpenter Stanley J.
Published: February 2005

Morphogenesis of the labyrinthine part of the chorioallantoic placenta of the golden hamster between day 10 of gestation and term (day 16) was studied by light and electron microscopy. During this period the labyrinth increases greatly in both size and complexity. Trabeculae of the labyrinth, thin partitions composed of trophoblastic tissue and fetal capillaries which delimit the maternal blood spaces, apparently proliferate both by appositional and interstitial growth. From the time of its formation (day 9 of gestation) until term the labyrinth is hemotrichorial in organization (i.e. three layers of trophoblast separate maternal blood from fetal capillaries). Both the inner and intermediate layers of trophoblast (layers III and II, respectively) are syncytial. The outer trophoblastic layer (III), which is in direct contact with maternal blood, remains cellular, although many of its component cells grow to giant cell dimensions (“labyrinthine giant cells”). Between the tenth and fourteenth days of gestation the anatomical barrier to diffusion between maternal and fetal blood is progressively reduced. This is accomplished both by gradual attenuation of the trophoblastic layers and fetal capillary endothelium and by the formation of discontinuities (gaps) in layer I, and diaphragmed fenestrae in fetal capillary endothelium. The labyrinthine placental barrier is fully developed and probably attains maximal functional efficiency by the fourteenth day of gestation. Late in the fifteenth day of gestation, a few hours before parturition, distinct degenerative changes are apparent in the trophoblastic layers and fetal capillaries of the trabeculae. The factors responsible for initiating these degenerative changes and the onset of parturition are still controversial.
Cell population dynamics of periodontal ligament stimulated with parathyroid extract
Authors: Roberts W. Eugene
Published: February 2005

Young adult rats were injected with parathyroid extract (PTE). Periodontal ligament (PDL) adjacent to a previously resorbing alveolar bone surface was divided into four zones numbered I to IV, from bone to cementum. Zones I and IV were within 25 mμ of the bone and cementum surfaces, respectively, while a line bisecting the center of the PDL separated Zones II and III. A net increase of about 16 total nuclei in all zones was observed during the first five hours after PTE administration. Since local mitosis accounted for no more than two nuclei, approximately 14 cells apparently migrated into the area. Over the first five hours Zones I and II combined showed a 21‐cell increase, being apparently the scle recipients of cells migrating into the field (14) plus approximately seven more from Zone III, which lost cells during the time period. The concurrent histological observation in Zone II, of increased intravascular monocytes and perivascular macrophages during the first five hours, suggests cells are migrating into Zone II via vascular channels. The data suggest two sources for increased PDL cellularity associated with stimulated osteoclast histogenesis: (1) local PDL cellular proliferation and (2) influx of migrating cells (probably through vascular channels) during first five hours after PTE.
Ultrastructure of the early ovary and testis in pig embryos
Authors: Pelliniemi Lauri J.
Published: February 2005

Pig embryos aged 26–27 days were used for an ultrastructural study of the early ovary and testis. Sex was identified by both chromosomal analysis and gonadal histology, with consistent results.

The gonads occupied their original site in the medial coelomic angles in both sexes. The female gonad was composed of three tissues: the surface epithelium, the gonadal blastema and the mesenchyme. The gonadal structure was similar to that seen earlier at the age of 24 days. At 26 days the testis had distinctly differentiated into four tissues. The new components were the testicular cords and the interstitium, both derived from the gonadal blastema. The testicular cords resembled anastomosing sheets more than cords.

The ultrastructure of the tissues and their cell types are described and compared to the previous indifferent stage at the age of 24 days. The cells of the surface epithelium, of the primitive cords, of the mesenchyme, and the primordial germ cells had an ultrastructure that was similar in both sexes. The sustentacular cells of the testicular cords resembled the primitive cord cells and the spermatogonia were similar to the primordial germ cells. No Leydig cells were present yet.

The process of testicular differentiation is described on the basis of the present and a previous study, and a new hypothesis, based on the vascular organization, is presented.
Cortical cytoplasm and configurational changes of RGC‐6 cells exposed to cytochalasin B
Authors: Bondareff William , Tuttle Richard L.
Published: February 2005

RGC‐6 cells, grown to confluency in monolayer cultures, are typically fusiform. In sections of these cells, fixed in situ and examined in the electron microscope, a discontinuous zone of cortical cytoplasm (5–7 nm wide), was found subjacent to the plasma membrane of the free surface. It was composed largely of 5–7 nm microfilaments distributed in an apparently irregular nework and appeared to comprise a discrete zone separating the plasma membrane from the underlying endoplasm.

Following incubation with cytochalasin B (5 μg/ml), the configuration of the cells changed markedly. The perikaryal cytoplasm appeared to swell, while the cellular processes became attenuated and often terminated in flower‐like tips. Although more discontinuous and somewhat less dense, the fine structure of the cortical cytoplasm appeared little affected by incubation with cytochalasin B for one hour. By 48 hours no zone of cortical cytoplasm was found. Subplasmalemmal microfilaments were no longer identifiable and endoplasmic organelles were found in direct contact with the plasma membrane of the free surface, which appeared to have collapsed onto the underlying endoplasm.

The change in cell configuration resulting from exposure to cytochalasin B occurred at 37°C but not at 4°C, suggesting a dependency on metabolic activity. It did not, however, appeared related directly to protein synthesis. Whereas incorporation of 3H‐leucine was decreased to 46.9% and 62.9% of control values after one hour or two hours exposure to cytochalasin B, respectively, no change was found after 24 or 48 hours. It is suggested that the effect of cytochalasin B on cell form, which appeared not to be a direct effect on either protein synthesis or subplasmalemmal microfilaments, may represent a primary response of the cortical cytoplasmic matrix.
Structural modification of Schwann cells in the pancreatic islets of the dog
Authors: Smith Phillip H.
Published: February 2005

In dog pancreatic islets, Schwann cells not only ensheath autonomic nerves but also have cytoplasmic processes that are contiguous with large expanses of the islet surface. These processes are interposed between the islet basal lamina and the endocrine parenchyma. This structrual modification of Schwann cells may play a role in the neural control of islet function.
Light and electron microscopic study of the degeneration and early regeneration of olfactory epithelium in the mouse
Authors: Matulionis Daniel H.
Published: February 2005

Degeneration and early regeneration of olfactory epithelium from two strains of mice was studied at the light and electron microscopic levels from 12 hours to 3 days following nasal irrigation with 1% aqueous solution of zinc sulfate (ZnSO4) (a compound known to selectively damage olfactory epithelium). Distinct patterns of degeneration and stages of regeneration were evident following treatment. During the first 24 hours after treatment three progressive manifestations of the degenerative process were seen: (1) a relatively mild condition which was characterized by surface irregularities produced by cell protrusions, highly vacuolated cytoplasm, presence of large lysosome‐like bodies and prominent intercellular spaces, (2) a more severe condition in which large areas of the epithelium were detached from the basement membrane and cellular debris was present in the nasal chamber, and (3) a condition of total or near‐total denudation of the epithelium of olfactory mucosa. The basal lamina was continuous and intact in most regions and the integrity of the subjacent connective tissue was mostly well‐preserved. Nerve bundles of the fila olfactoria were noted in varying degrees of degeneration during the course of the experiment. The most advanced neural degeneration was seen 24 to 72 hours after treatment. Onset of regeneration was suggested by the appearance of a simple squamous layer of cells above the basement membrane 48 to 72 hours after treatment. In addition to the simple epithelium a stratified epithelium consisting of two to four cell layers was also observed at this time. Glandular cells, containing secretory granules identical to those in Bowman's glandular cells, were noted in an apparent process of migration from the lamina propria into the stratified epithelial layer. The last mentioned observation supports the proposition that new supportive epithelial cells originate from cells of Bowman's gland.
Scanning electron microscopic study of the effects of pressure on the luminal surface of the rabbit aorta
Authors: Swinehart Paul A. , Bentley David L. , Kardong Kenneth V.
Published: February 2005

The effects of pressure on the luminal surface of the rabbit aorta were investigated using the scanning electron microscope. The method followed was perfusion under hydrostatic pressure of a section of thoracic aorta, in vitro. The characteristic ridged pattern seen in sections fixed at zero hydrostatic pressure was to a large extent eliminated when fixation occurred at pressures equivalent to those experienced by the aorta at systole or diastole. This study suggests that the spiral ridged pattern is dependent upon the fixation pressure and may not be present in a normally functioning artery. Any attempts to characterize or interpret the appearance of the luminal arterial wall must take into account the effects of pressure.
The transmural passage of blood cells into myeloid sinusoids and the entry of platelets into the sinusoidal circulation; a scanning electron microscopic investigation
Authors: Becker Robert P. , De Bruyn Peter P. H.
Published: February 2005

Scanning electron microscopic observations of rat bone marrow reveal that the sinusoidal wall is continuous and has no permanent patent apertures allowing free communication between the extravascular and intravascular myeloid compartments. Blood cells migrate into the sinusoids by perforating the endothelial cell body.

Platelets are derived from long intrasinusoidal “proplatelet” processes which originate from the cell body of extravascularly located megakaryocytes. Proplatelet processes frequently occur in clusters, with the probability that all processes in a cluster arise from a single megakaryocyte. The release of platelets into the circulation may be initiated by local constriction along these processes, at which places either individual platelets or larger segments of proplatelet cytoplasm are pinched off. The larger segments may subsequently undergo further fragmentation into individual platelets.
The hypothalamic magnocellular neurosecretory system of the guinea pig. III. Ultrastructure of the fetal neural lobe
Authors: Silverman A. J. , Desnoyers P.
Published: February 2005

The ultrastructure of the fetal guinea pig neural lobe was studied from day 40 to day 60 of gestation. Pituitaries were taken every five days and at least four glands from each gestational period were examined.

Bundles of nerve fibers had invaded the periphery of the gland on day 40. By day 50 axon profiles were distributed throughout the entire posterior pituitary though pituicyte processes continued to act as a barrier between axons and the perivascular space of capillaries. Neural processes established contact with the capillaries between days 55 and 60.

Neurosecretory granules (NSG) were present within a few axons on day 40. The number of axons with NSG and the total quantity of granules increased gradually throughout fetal development. Electron‐lucent granules (microvesicles) were observed infrequently until the day of birth. A population of dense‐cored vesicles, 70–80 mμ in diameter, was present from day 50 onward; a second population with larger diameters was also present throughout the developmental sequence and these increased from 90–130 mμ in diameter to 170–220 mμ in diameter between days 40 and 60.

The presence of neurosecretory granules is discussed in relation to the onset of synthesis and storage of neurohypophysial hormones.
The development of the elastic cartilage of the mouse pinna
Authors: Sanzone Charles F. , Reith Edward J.
Published: February 2005

The development of the elastic cartilage in the mouse pinna was studied with the electron microscope. For descriptive purposes, the developmental process was divided into five stages. These begin with the onset of cartilage matrix production by chondroblasts. The second stage is the major mitotic stage although the cells now resemble chondrocytes and cartilage matrix production evidently continues. This is followed by a period during which cartilage matrix production appears to be the major activity of the chondrocytes. In Stage IV, the cells continue to produce cartilage matrix but at the same time they also produce lipid which comes to occupy most of the cell as a large lipid droplet. In the adult, Stage V, matrix production appears to be at an end and each cell contains a lipid droplet which is so large that the cells bear some resemblance to white fat cells and might be designated as lipochondrocytes.

The adult cartilage matrix contains elastic plates in a three‐dimensional honeycomb pattern. Between the elastic plates and the cells, the matrix contains elements similar to those seen in hyaline cartilage but it does not contain matrix vesicles such as those which have been associated with the calcification of cartilage.

Two types of filaments differing in appearance, size, and location are seen within the chondrocytes. They have been designated cytofilaments and cortical filaments. Cytofilaments are dispersed throughout the cell and also contact the substance of the lipid droplet, cortical filaments (sub‐plasmalemmal microfilaments) are located directly under the plasma membrane. They are thought to be involved in movement of the plasma membrane as a concomitant to extracellular fibrogenesis.
Topographical changes along the neural fold associated with neurulation in the hamster and mouse
Authors: Waterman Robert Earle
Published: February 2005

The topography of the ectoderm was examined by scanning electron microscopy during neurulation in hamster and mouse embryos. Stages from the appearance of the neural folds to closure of the posterior neuropore were studied. Progressive development of a zone of altered cellular morphology was observed along the crests of the neural folds. This zone evolved from and abrupt transition between surface and neural regions of the ectoderm to a narrow band of flattened cells which exhibited numerous membranous “ruffles” in the mouse, or blebs and presumably degenerating cells in the hamster, immediately prior to contact between the folds. These alterations were more prominent along the anterior than the posterior portions of the folds. Contact of the folds occurred first between the flattened cells with subsequent union of the surface cells. Stages of neural crest cell formation were observed subjacent to the zone of alterations in histological sections. It is suggested that the observed surface alterations may reflect changes in the membrane properties of the altered cells which are correlated with both neural crest formation and initial adhesion between the folds.
Scanning microscopy of pituitary vascular casts
Authors: Page Robert B. , Munger Bryce L. , Bergland Richard M.
Published: February 2005

Vascular casts of the pituitary‐median eminence complex from seventeen adult female rabbits were examined with the scanning electron microscope. The results of this study confirm the presence of a single capillary bed common to the entire neurohypophysis. Arterial supply to the rabbit pituitary is only to the neurohypophysis. A direct supply to adenohypophysis was not found.

Within the median eminence there are an external and internal capillary plexus. The internal capillary plexus is directed toward the infundibular recess of the third ventricle. It does not receive a direct arterial supply but derives its blood supply from the external plexus before draining to the adenohypophysis.

Vessels of the posterior median eminence are confluent with vessels of the infundibular stem.

On the basis of these studies, it is proposed that the entire neurohypophysis, not simply the median eminence, serves as the final common pathway to the glandular pituitary. It is also proposed that in the median eminence, vessels are organized to deliver blood containing hypothalamic releasing and inhibiting hormones as well as posterior lobe neural hormones (antidiuretic hormone and oxytocin) to the ventricular surface for subsequent transport to cerebrospinal fluid and distribution to the brain.
Age‐related changes in the intact and sympathetically denervated gerbil pineal gland
Authors: Reiter Russel J. , Welsh Marcia G. , Vaughan Mary K.
Published: February 2005

The pineal gland of four‐month‐old gerbils contains numerous calcareous deposits (corpora arenacea or concretions). Also, the tissue appears vacuolated due to the presence of a number of large rounded spaces. The deposits are usually associated with or lying within these “vacuoles”. By eight months of age, the number of both the corpora arenacea and the “vacuoles” are increased over those present in the pineals of four‐month‐old gerbils. Bilateral superior cervical ganglionectomy at one month of age prevents the formation of both the concretions and “vacuoles”. The cells in the sympathetically denervated pineal glands are smaller than those in pineal glands of animals that possess intact superior cervical ganglia.
Functional anatomy of the hands of fur seals and sea lions
Authors: English Arthur Wm.
Published: February 2005

Dissections and manipulations of the hands of 14 specimens of four genera of fur seals and sea lions and of generalized fissiped carnivores were used to identify the structural modifications involved in formation of the expanded forelimb paddles characteristic of these pinnipeds. These morphological peculiarities were then correlated with differences in locomotor function, both on land and in the water, on the basis of previously published data, for the purpose of identifying modifications of structure and function which have adaptive value. Structural differences found in the manus of fur seals and sea lions include: (1) reduction in size of the ulnar side of the carpus and a radial shift in the length‐order of the digits, (2) development of musculature in the antebrachial fascia which attaches to the caudal margin of the flipper, (3) orientation of the radial side of the manus dorsal and radial to the rest of the hand, (4) increased range of possible midcarpal movement and in deviational mobility at the first and fifth digits, (5) attachment of forearm musculature onto radial digits and (6) well‐developed hypothenar muscles and absence of thenar muscles. Modifications in hand structure are viewed as providing a morphological basis for employment of the hand to advantage during aquatic locomotion while maintaining thrust‐producing and potentially energy‐conserving capacities during movement on land. As such these differences in structure and function are viewed as adaptations to locomotion in the water and on land which are extensions of locomotor adaptations attributed to modifications of forelimb structure and function associated with the generation of massive aquatic locomotor thrust. The adaptive value of such modifications is interpreted as allowing fur seals and sea lions to swim with speed and thereby capture elusive fast‐swimming prey while maintaining a level of terrestrial locomotor ability compatible with their amphibious mode of life.
The effects of 5‐bromodeoxyuridine and isoproterenol on the postnatal differentiation of rat submandibular gland
Authors: Fukushima Masahiro , Barka Tibor
Published: February 2005

The effects of 5‐bromodeoxyuridine (BrdU) on the postnatal differentiation of rat submandibular gland and on the isoproterenol‐induced changes of differentiation were studied. The rats were injected with BrdU for three consecutive days, beginning at two days of age. The total dose of BrdU was 0.9 mg/g body weight. BrdU caused a severe retardation of growth up to 15 days of age. A rapid growth of the animals between 15 and 22 days indicated a recovery from the effect of BrdU. The growth of the submandibular gland was retarded similarly with a corresponding decrease in DNA, RNA and protein content. Incorporation of tritiated thymidine into the submandibular gland was not altered in the BrdU‐treated animals at one and three days after the last injection of the analog. At days 15 and 22 the rate of thymidine incorporation was greater in the submandibular gland of BrdU‐treated rats as compared to littermate controls. Isoproterenol stimulated thymidine incorporation into the submandibular glands of two‐week‐old rats. This stimulation was not observed in rats which received BrdU at age 7–9 days, prior to the administration of isoproterenol.

Electron microscopic observations, including a quantitative analysis of the frequency distribution of the various cell types in the terminal tubules and developing acini, indicated a retardation of acinar cell differentiation in the glands of BrdU‐treated rats. In addition, there was an increase in the number and size of the secretory granules in the terminal tubule cells. BrdU treatment, however, caused no obvious pathologic alterations in the submandibular gland. Administration of isoproterenol for five days, beginning at five days of age, caused an apparent acceleration of the differentiation of acinar cells. In the glands of isoproterenol‐treated rats the acinar cells were enlarged and were filled with homogenous secretory granules. Pretreatment with BrdU partially inhibited the effects of isoproterenol on differentiation and hypertrophy of the submandibular gland. With the given dose of BrdU, approximately 5% of thymine was replaced by bromouracil in the DNA of the submandibular gland. Such a replacement would be consistent with a direct effect of BrdU on the cytodifferentiation in the submandibular gland. However, because of the severe retardation of growth of the BrdU‐treated rats, indirect effects can not be excluded.
Secretion by parafollicular cells beginning at birth: Ultrastructural evidence from developing canine thyroid
Authors: Nunez Eladio A. , Gershon Michael D.
Published: February 2005

The ultrastructure of developing canine parafollicular cells has been examined. The hypothesis that secretion is relatively inactive prior to birth but very active at and following birth was tested. Parafollicular cells develop and accumulate characteristic secretory granules prior to birth. However, there is little or no evidence of exocytosis at this time. At birth and during the neonatal period, but not in adult thyroids, sings of exocytosis of granular contents by parafollicular cells are abdundant. Just prior to the expected date of birth and before evidence of exocytosis appears, parafollicular cells accumulate intracisternal granules within rough endoplasmic reticulum. These observations are consistent with the view that parafollicular cells first become actively secretory around the time of birth and are more active at this time than in early fetal or later adult life.