bluuebunny/crossref_metadata_2025 huggingface dataset:
Filamentary rod‐shaped granules in clara cells of rats
Authors: Baert J. , Vandenberghe M. P.
Published: February 2005

The bronchiolar Clara cells of rats contain characteristic rodshaped granules always surrounded by a unit membrane. These granules contain thin filaments about 9 to 10 nm in diameter lying in a pale matrix. Our morphological results suggest that the filamentary rod‐shaped granules originate from the common, round‐to‐oval, electron‐dense Clara cell granules, as we found different intermediate structures between these two kinds of granules. The electron‐dense granules are digested by pepsin, whereas the filamentary rod‐shaped granules are apparently not affected. The biochemical nature and the possible function of the filamentary rod‐shaped granules are also discussed in relation to the secretory activity of the Clara cells.
Interfollicular smooth muscle in the skin of the domesticated pig (Sus scrofa)
Authors: Stromberg M. W. , Hwang Y. C. , Monteiro‐Riviere N. A.
Published: February 2005

An interfollicular smooth muscle that spans the triad of hair follicles has been identified in the skin of the domesticated pig (Sus scrofa). This muscle has been previously noted by other investigators and identified as an arrector pili muscle. However, it cannot be interpreted as such for the following reasons: (1) It lies opposite the arrector pili muscle on the follicle; (2) the orientation of its fibers is perpendicular to those of the arrector pili; (3) the two muscles are not continuous; their attachments are different; and (4) contraction of the interfollicular muscle would have little effect on erection of the hairs. Based on structural evidence, it is postulated that upon contraction the muscle draws the base of the three aligned follicles together into a triangular conformation. In so doing, it may rotate the outer two follicles of the triad. Its specific functional role is unknown.
Regeneration of submandibular salivary gland autografted in the rat tongue
Authors: Sharawy Mohamed , O'Dell Norris L.
Published: February 2005

Autologous SMG fragments were implanted in tongues of male rats which were sacrificed 15–20 min, 24 hr, 72 hr, 1 week, or 8 weeks after implantation. The tongues were excised, fixed, and processed for light and electron microscopy. In addition, some rats were injected with [3H]‐thymidine 1 hr before sacrifice and the labeling indices (L.I.) of the salivary epithelial and interstitial cells were calculated. Twenty‐four hours after implantation, SMG autografts showed massive central necrosis with some acini and ducts surviving at the periphery of the lobules. There was marked infiltration of the autografts with neutrophils and macrophages. Also the basal laminae surrounding the necrotic acini and ducts remained intact. The morphology of the autografts after 72 hr was similar to that after 24 hr except that there was additional necrosis and acini and ducts could no longer be identified in the autografts. By 1 week after implantation, the autografts showed lobular morphogenesis, ductal branching, and revascularization. At this time, the regenerating salivary epithelium appeared undifferentiated with no evidence of secretory granules. The L.I. of interstitial and ductlike structures showed significant increases over control values at 1 week after implantation, and then declined toward control levels by 3 weeks after implantation. By 8 weeks after implantation, there was evidence of acinar and striated ductal cytodifferentiation in two autografts. The results emphasize the potential of SMG autografts to regenerate subsequent to severe tissue necrosis.
Ultrastructural changes in hamster lung four hours to twenty‐four days after exposure to elastase
Authors: Morris Shirley M. , Stone Philip J. , Snider Gordon L. , Albright John T. , Franzblau Carl
Published: February 2005

A single endotracheal instillation of elastase initiates a series of changes in animal lungs that results in a condition resembling human panlobular emphysema. An ultrastructural examination of this series of changes was conducted on the lungs of male golden hamsters exposed to 3H‐methylated pancreatic elastase and sacrificed at intervals between 4 hour and 24 days after exposure to enzyme.

Lung tissue between 4 and 48 hours showed evidence of hemorrhage and progressive degradation of elastic fibers. Very little indication of epithelial cell damage accompanied these changes. Four days after exposure to elastase, synthesis of new elastic fibers began with the appearance of small clumps of microfibrils in close association with interstitial cells, fibroblasts, and smooth muscle cells. There was also evidence of alterations in alveolar type II cells at this time. Small fibrillar elastic fibers continued to be present in the lung through twenty‐four days and may represent a slow repair process or may indicate a structural difference in elastic fibers synthesized after exposure to elastase. Evidence of the continued degradation of elastic fibers could be found up to 16 days after exposure to elastase, revealing that repair processes were occurring in some areas of the lung while destructive processes still predominated in other areas.
Morphological correlates of hormone secretion in the rat adrenal cortex and the role of filopodia
Authors: Pudney J. , Sweet P. R. , Vinson G. P. , Whitehouse B. J.
Published: February 2005

Rat adrenals in different states of stimulation were examined by transmission electron microscopy following perfusion fixation using an in situ isolated‐circulation technique. In unstimulated glands, intracortical capillaries were constricted and the cells of the cortex were pressed closely together with little development of filopodia or intercellular spaces. Glands fixed during the period of operative stress, or following a 1 hr perfusion with Adrenocorticotropic hormone (ACTH) showed that the radially orientated capillaries of the cortex were massively expanded, and the cells of both the glomerulosa and fasciculata exhibited an extensive development of filopodia on their surfaces. These filopodia extended into enlarged intercellular spaces, where they often entered into complex relationships with filopodia from neighboring cells.

The development of filopodia by cells of the adrenal cortex was also observed using scanning electron microscope techniques. In cells either icubated with ACTH in vitro or isolated from adrenals of rats treated with ACTH in vivo, the filopodia were numerous, often branched, and could reach as much as 1 μm in length. In contrast, adrenal cells obtained from animals pretreated with cortisol were smooth surfaced.

Other cell characteristics, including mitochondria, smooth endoplasmic reticulum, dense granules, and coated vesicles did not show such dramatic correlations with the state of stimulation. It is considered that the development of filopodia and intercellular space is related to secretory mechanisms in the rat adrenal cortex.
An electron microscopic radioautographic study of collagen secretion in periodontal ligament fibroblasts of the mouse: II. Colchicine‐treated fibroblasts
Authors: Cho Moon‐Il , Garant Philias R.
Published: February 2005

Colchicine administered intravenously depolymerized microtubules and disrupted the normal organization of the Golgi apparatus in periodontal ligament fibroblasts. Radioautography with 3H‐proline indicated that collagen secretion was completely inhibited during a period of approximately 4 hours following the onset of the colchicine effect. During this period of secretory inhibition, labeled collagen precursors were present within a variety of dense bodies, primarily located in a juxtanuclear location replacing the normal Golgi complex. The time course of 3H‐proline labeling from 2 to 8 hours suggested that small, newly formed dense bodies fused to form larger dense bodies and pleomorphic structures (zebra bodies), within which collagen precursors appeared to undergo partial polymerization. Autophagosomes, many labeled with 3H‐proline, also increased in number after colchicine administration. A gradual decline in 3H‐proline label occurred from 4 to 24 hours, presumably due to exocytosis of dense bodies or by the digestion of labeled collagen precursors within autophagosomes.

These results support the concept that an intact microtubular network is essential for the organized transport of collagen precursors, from the rough endoplasmic reticulum to the Golgi apparatus, and the eventual transport and exocytosis of collagen secretory granules.
Utrastructural observations on melanosome aggregation in genetically defective melanocytes of the mouse
Authors: Koyama Yoh‐Ichi , Takeuchi Takuji
Published: February 2005

Cultivated mouse melanocytes with the genotype of D/‐ and d/d obtained from dorsal skin of infants, and the variant melanoma cells (subline agm) in which melanosomes were aggregated around the nucleus were characterized by means of electron microscopy. In D/‐ melanocytes, dendrites contained a number of microtubules and 10‐nm filaments, mitochondria, endoplasmic reticulum, and peripherally distributed melanosomes. On the other hand, in d/d melanocytes and agm cells, melanosomes were aggregated in the perinuclear region of the cell body. Their fibrous dendrites contained numerous microtubules and 10‐nm filaments, mitochondria, and endoplasmic reticulm. It is suggested that the interactive process of melanosomes with cytoskeletal elements is defective in d/d melanocytes, and that a similar defect is present in agm cells.
A morphologic and morphometric analysis of fetal lung development in the sheep
Authors: Alcorn Daine G. , Adamson T. Michael , Maloney John E. , Robinson Peter M.
Published: February 2005

In the sheep, fetal lung development proceeds to a later stage of maturity than in smaller laboratory animals. Of the four stages in pulmonary development recognizable in this species–embryologic, pseudoglandular, canalicular, and aveolar–the latter three are described in the present study using histologic, morphometric, and ultrastructural techniques. During the pseudoglandular stage, the major airways developed centrifugally. Cartilaginous, glandular, muscular, vascular, and neural elements were present in major airway walls from an early age. During the canalicular stage, volume expansion of the lung was accomplished by rapid growth of large terminal spaces. In the final stage, alveoli were formed following subdivision of the large terminal spaces by alveolar crests. The alveolar lining epithelium differentiated during the latter two stages producing a large increase in alveolar surface area, particularly during the alveolar stage; a large increase in pulmonary capillary surface area also accompanied alveolar development. Thus, just prior to birth, the fetal sheep lung has a well‐developed airway system and alveolar network, in preparation for postnatal gas exchange.
Ultrastructural stereologic analysis of fetal rabbit type II alveolar epithelial cells following maternal pilocarpine treatment or fasting
Authors: Smith Dennis M. , Shelley Sue A. , Balis John U.
Published: February 2005

We have previously reported that subcutaneous administration of 5 mg/kg pilocarpine HC1, a muscarinic agonist, to pregnant white rabbits on days 24 through 27 of gestation results in an acceleration of fetal lung maturation. In the present study the ultrastructural differences observed within alveolar type II cells of 28‐day fetuses from the pilocarpine and control groups were quantified by stereologic analysis. In addition, maturational changes occurring within the lungs of 28‐day fetuses obtained from pregnant rabbits which were fasted for 7 days (days 21–28) were similarly analyzed.

Stereologic analysis revealed that the fetal type II cells in the pilocarpinetreated group possessed a significantly greater volume density of lamellar inclusion bodies and rough endoplasmic reticulum and a significantly smaller volume density of glycogen than did controls. The volume density values for fetal type II cells of the fasted group were, with the exception of the Golgi apparatus, found to be intermediate between those of the control and the pilocarpine‐treated groups. It was also noted that a high percentage of the lamellar inclusion bodies within type II cells of the fasted group appeared morphologically abnormal, being characterized by a highly irregular outline and tightly packed lipid membranes.

The results of this study substantiate and quantify our previously reported observation of accelerated maturation in pilocarpine‐treated fetuses. In addition, they suggest a similar, though not as pronounced, effect of maternal fasting prior to delivery. However, the abnormal morphology of the lamellar inclusion bodies in the fasted group may reflect a qualitative change in the pulmonary surfactant produced by these fetuses.
Skull preparation using the enzyme‐active detergent technique
Authors: Mooney Mark P. , Kraus Eric M. , Bardach Janusz , Snodgass John I.
Published: February 2005

With the increasing use and need for macerated skulls and bony structures in medical research and resident and medical student studies, an economical, easy, and efficient method of obtaining cleaned and bleached specimens has been developed. The process requires short‐term skeletal simmering in a 10% solution of commercially available enzymatic detergent and water. Over 50 skulls have been macerated in our laboratory resulting in substantial saving in research money, time, and effort.
Isolation of human erythrocyte inside‐out vesicles alters their molecular architecture
Authors: Wise Gary E.
Published: February 2005

Inside‐out (I.O.) vesicles isolated from human erythrocyte ghosts induced to endocytose have been used for biochemical studies to determine localization of molecules within the membrane. It was the purpose of this study to examine such vesicles by freeze‐etch electron microscopy to determine the architecture of the peripheral proteins on the protoplasmic surface. Examination of the I.O. vesicles while still in the interior of the ghosts showed that a globular material was randomly distributed on the outer surface (protoplasmic surface of the original plasma membrane) of the I.O. vesicles. The random distribution of the globular material becomes altered, however, if the I.O. vesicles are isolated from the ghosts by shearing and centrifugation. Freeze‐etching of these isolated I.O. vesicles revealed that the globular material was now clustered on the protoplasmic surface (PS), as were the intramembranous particles (IMPs) in the extracellular face. Thus, the lateral mobility of the IMPs is dependent upon the distribution of molecules at the protoplasmic surface of the membrane. Moreover, this change in distribution of the globular material at the surface is not due to a partial loss of major membrane proteins, because SDS‐polyacrylamide gel electrophoresis revealed that equal amounts of the major proteins were present in nonisolated vesicles as compared to isolated vesicles. Although isolated I.O. vesicles have been used extensively to demonstrate that glycoproteins span the membrane, these results suggest that one should cautiously interpret data obtained from such isolated vesicles in view of the fact that there is an alteration of the distribution and perhaps configuration of molecules at the PS following isolation of I.O. vesicles.
Light and electron microscopic immunohistochemical localization of somatostatin in the endocrine and exocrine portions of the pancreas of the chick embryo (gallus domesticus)
Authors: Kalliecharan Rajdeo , Steeves John
Published: February 2005

A discrete population of cells containing immunoreactive somatostatin was shown by the peroxidase antibody bridge technique at both the light and electron microscopic level to be present in the pancreas of chick embryos. Based on the stage of development, somatostatin‐positive cells, at the light microscopic level, were found in the alpha and beta islets, in isolated islets that did not correspond with any known alpha or beta islets, as well as in the acinar tissue. Quantitative determination indicated that, at all ages examined, there were a greater number of somotostatin cells associated with the alpha islets per square millimeter of tissue than with either the beta islets or acinar tissue of the exocrine pancreas.

Ultrastructural observations on day 15 of development confirm and reinforce the light microscopic observations pertaining to the localization of the somatostatin‐positive cells. The results also show that the PAP reaction was localized only on the granules of the somatostatin positive cells. These granules were primarily found in the apical region of these cells adjacent to blood vessels.
A study of motor nerve terminals on cat nuclear bag1 intrafusal muscle fibers using the ChE staining technique
Authors: Kucera Jan
Published: February 2005

Muscle spindles were traced in serial transverse sections of cat tenuissimus muscles. Histochemical staining for “myofibrillar” adenosine 5′‐triphosphatase was employed to identify nuclear bag1 intrafusal muscle fibers. Staining for cholinesterases (ChE) was used to demonstrate the termination sites of motor axons along the fibers. Several types of ChE deposits could be distinguished along the bag1 fibers based on intensity of staining and morphological characteristics. Most ChE deposits could be classified as either the “pale” or the “nonpale” plates. Some ChE active areas fitted neither of these two categories. Among 328 ChE “plates” encountered on 192 bag1 fiber poles, 197 (60%) were of the “pale” and 27(8%) of the “nonpale” type with 104(32%) remaining unclassified.

These histochemical observations are discussed with regard to the current structural and functional concepts of motor innervation of the nuclear bag1 fiber. It is suggested that the histochemical (ChE staining intensity) and morphological (length and form) characteristics of bag1 fiber motor endings are not determined solely by the nature of the corresponding motor axons.
Cell surface specializations and intercellular junctions in human amniotic epithelium: An electron microscopic and freeze‐fracture study
Authors: King Barry F.
Published: February 2005

Cell surface specializations and intercellular junctions of human term amniotic epithelium were examined by conventional thin‐section electron microscopy, after staining with the cationic probes ruthenium red and cationic ferritin, and by freeze‐fracture methods. Desmosomes were the predominant type of intercellular junction and often the most apical of the junctional types. In freeze‐fracture replicas, desmosomes were characterized by roughly circular areas of large, often irregular, P‐face intramembranous particles. Gap junctions were identified in the laterobasal regions between cells. In thin sections they were characterized by a narrow intercellular space, and in freeze‐fracture replicas had a typical plaquelike arrangement of P‐face intramembranous particles and E‐face depressions. Hemidesmosomes at the basal cell surface were characterized by occasional large particles and clusters of particles on both the E and P fracture faces. No evidence of tight junctions was found. The apical cell surface was heavily stained by both ruthenium red and cationic ferritin, indicating the negatively charged nature of this surface. Ruthenium red penetrated between the epithelial cells and bound to anionic materials on the lateral cell surfaces, especially at the location of desmosomes. Below the base of the intercellular cleft, large ruthenium red‐positive granules were present in the extracellular matrix. The possibility that the anionic substances in the intercellular region may contribute to the control of permeability in the amniotic epithelium is discussed.
Morphology, proliferation, and differentiation of undifferentiated spermatogonia in the chinese hamster and the ram
Authors: Lok D. , Weenk D. , de Rooij D. G.
Published: February 2005

The population of undifferentiated spermatogonia was studied in whole mounted seminiferous tubules of the Chinese hamster and the ram. The morphology of the differentiating spermatogonia in the ram is also described.

The nuclear morphology of the undifferentiated spermatogonia was found to vary considerably. 3H‐thymidine labeling studies in the Chinese hamster revealed that this variability is associated with the phases of the cell cycle. In both animals the undifferentiated spermatogonia were found to lie isolated (As), paired (Apr), or in groups of four, eight, or sixteen cells (Aal). We described how the varying morphology can be used to identify the composing clones of a cluster of undifferentiated spermatogonia.

Cell counts performed throughout the whole cycle of the seminiferous epithelium revealed a very similar pattern of proliferation in the Chinese hamster and the ram. The number of As + Apr spermatogonia remained constant throughout the epithelial cycle. However, the occurrence of labeled and mitotic cells showed that As, Apr as well as Aal spermatogonia do proliferate. In both animals the mitotic activity of the undifferentiated spermatogonia is very low during the lifespan of A2 spermatogonia but increases considerably among A3, staying high among Intermediate spermatogonia. Thereafter, mitotic activity subsides to a lower level until the cycle repeats itself. Clones of 16 Aal in the Chinese hamster only exceptionally divide further.

The results in the ram are incompatible with a scheme of stem cell renewal in which the A1 spermatogonia derive from A2 spermatogonia (Hochereau‐de Reviers et al., 1976). It is proposed that in the ram, like in rodents, the As spermatogonia are the spermatogonial stem cells and that the A1 spermatogonia derive quantitatively from the undifferentiated spermatogonia at each epithelial cycle.

It could be calculated from the number of newly formed clones that both in the Chinese hamster and the ram, on the average, each As spermatogonium will have to divide several times during one epithelial cycle.

Unlike in rodents, in the ram differentiation into A1 spermatogonia brings about a distinct morphologic change enabling us to observe that some Apr and rarely As spermatogonia transform into A1 spermatogonia. Thus, all undifferentiated spermatogonia are able to differentiate into A1 but the chance for this to occur increases strongly with the clonal size.
Continuity of intracellular channels with extracellular space in adipose tissue and liver: Demonstrated with tannic acid and lanthanum
Authors: Joan Blanchette‐Mackie E. , Scow Robert O.
Published: February 2005

Tannic acid was used to demonstrate continuity of intracellular channels with extracellular space in white adipose tissue of adult rats, brown adipose tissue of suckling rats, and liver of diabetic rats. Electron‐opaque material resulting from treatment of glutaraldehyde‐fixed tissue with tannic acid was found in extracellular space, invaginations of cell surfaces, vesicles, and intracellular channels. Electron‐opaque material was present in channels that surrounded lipid droplets in both white and brown adipocytes and in hepatocytes. The small distance between the lumen of marked channels and lipid droplets in adipocytes indicates that a monolayered structure, perhaps a leaflet of membrane lining the channel, separates the lipid droplet from the lumen of the channel, suggesting that the lipid droplet may be located between leaflets of the membrane lining the channel. Similar findings were obtained in brown adipose tissue using lanthanum instead of tannic acid to mark intracellular channels continuous with extracellular space. Since endoplasmic reticulum is the primary site of triacylglycerol synthesis in adipocytes, marked channels near lipid droplets may be elements of endoplasmic reticulum. Some of the channels marked with tannic acid in hepatocytes contained lipoprotein particles, whereas others were located, in relation to mitochondria and lipid droplets, in the same sites as endoplasmic reticulum in untreated tissue. This indicates that some of the channels marked with tannic acid in hepatocytes are endoplasmic reticulum. Presence of electron‐opaque material in intracellular channels and vesicles, but not in cytoplasm, of treated tissue indicates the channels and vesicles were open to extracellular space during treatment with tannic acid or lanthanum and, furthermore, that their membranes were continuous with plasma membrane.
Proliferative activity in the rat epididymis during postnatal development
Authors: Sun Eric L. , Flickinger Charles J.
Published: February 2005

The proliferative activity of the rat epididymis during postnatal development was investigated with the use of autoradiography. Animals at 14, 21, 28, 35, and 56 days of age were sacrificed 2 hours following the administration of 3H‐thymidine. Cell types that showed a significant labeling index were columnar cells in 14‐ and 21‐day‐old animals; principal and basal cells in 28,35 and 56 day old rats. During this period of development, the pattern of cellular activity in the initial segment differed from the middle and terminal segments in having a peak of activity on day 28. The middle and terminal segments had similar proliferative patterns.

In two additional experiments, 10‐ and 21‐day‐old rats were given 3H‐thymidine and killed 1 week later on day 16 and 28. Labeled narrow cells were present in day 16 animals, whereas labeled narrow, principal, and basal cells were found in day 28 rats. It was concluded that columnar cells are the precursor to narrow, principal and basal cells.
Development of neuroepithelial bodies in pre‐ and postnatal mouse lungs: Scanning electron microscopic study
Authors: Hung Kuen‐Shan
Published: February 2005

The development of pulmonary neuroepithelial bodies (NEBs) in pre‐ and postnatal mice were studied with scanning electron microscope. In the fetuses, at 17 days' gestation, the NEBs were recognized as slight epithelial elevations covered by developing Clara cells. At 18 days, the small apical surfaces of the specialized cells began to be exposed to the bronchiolar lumen. At 19 days (full term), numerous microvilli‐covered surfaces of the specialized cells were located between the dome‐shaped Clara cells. At this stage, the boundary of the NEBs was well outlined by the developing ciliated cells. In the postnatal animals, the surface structure of the specialized cells remained the same as that of the 19‐day fetuses, but the modified Clara cells gradually became wide and flat. In older mice, some NEBs formed obvious spherical mounds projecting into the bronchiolar lumen. The rapid differentiation of the microvillar projections on the surfaces of the specialized cells shortly before birth should provide the animals ample surface area to make contact with the airway contents.
Osmium vapor fixation of pulmonary surfactant
Authors: Callas Gerald
Published: February 2005

Electron microscopic techniques presently employed to preserve the alveolar lining layer are inadequate, and published reports have failed to demonstrate surfactant as a continuous layer over the alveolar surface. Osmium vapor insufflation into the airway combined with vascular perfusion preserves the alveolar lining layer (surfactant). In all the alveoli studied, the combination of airway and vascular fixation of the surfactant layer offers a visualization of surfactant as a continuous layer over the alveolar surface.
A new plastic for morphometric investigation of blood vessels, especially in large organs such as the human liver
Authors: Hanstede Johan G. , Gerrits Peter O.
Published: February 2005

In this paper a technique is described, using Araldite CY 223 and hardener HY 2967 as injection material, for preparing corrosion casts or histological sections. The plastic has a viscosity (at 39–40°C) similar to that of blood, a gelling time of approximately 17min (at 40°C), and an exothermic transition energy of ΔH = 80.28 ± 3.20 cal/gm. The influence of the plastic on the tissue is discussed. The histological sectioning of fixed tissue containing Araldite‐filled blood vessels after embedding in 2‐hydroxyethyl‐methacrylate (GMA) is described. When using GMA in a modification of the mixtures of Ruddell (1967) and Sims (1974), methylbenzoate is recommended as an intermedium in order to obtain a more uniform infiltration and reproducible section thickness. At the same time methylbenzoate is recommended as a storing fluid. Sections of 2–3 μm afford satisfying morphologic and morphometric results. This method allows various arterial wall dimensions to be measured easily, and provides a suitable means to compare histometric values with SEM data derived from corrosion casts.
Cephalic neurulation in the mouse embryo analyzed by SEM and morphometry
Authors: Jacobson Antone G. , Tam Patrick P. L.
Published: February 2005

A detailed account of mouse neurulation is given based mostly on SEM analysis over 20 hr of development. Many observations and measurements were made on staged living embryos and on embryos prepared for scanning and light microscopy to help deduce what mechanisms may contribute to neural tube formation. Each‐lateral half of the early cephalic neural plate makes a convex bulge, opposite to the way it must fold to form a tube. Underlying mesenchyme and matrix are reported to have a role in forming these bulges. Processes that form the tube must overcome this opposed folding and the forces that produce it. Cranial flexure begins long before tube formation. The flexure commences at the rostral tip of the cephalic neural plate, then the apex of the flexure migrates caudally to the mesencephalic region. Early appearance of this flexure imposes a mechanical impediment to tube closure in forebrain and midbrain regions. Tube closure begins in the cervical region exactly where the neural plate is reflected dorsally by a bend in the embryo. This bend may mechanically assist closure in this region. Cells of the mouse neural plate are reported to contain organized microfilaments and microtubules, and the plate cells appear to change shape (reduce apical area and increase cell height) in the same manner as that suggested in embryos of some other species to contribute to neural tube formation. Measurements show that the lateral edges of the cephalic neural plate elongate craniocaudally more than the midline of the plate through each period. This elongation could contribute to the folding of the plate into a tube. The progress of cranial ventral flexure pauses while tube formation occurs, but edge elongation continues, presumably contributing to tube formation. There is considerable increase in volume of the neural plate during tube closure, and cell proliferation and enlargement of daughter cells seem sufficient to account for this growth. Mitotic spindles are positioned to place the majority of the daughter cells into the long axis of the neural plate, so ordered growth may be the main mechanism of elongation of the plate in the craniocaudal direction, which in turn may assist in tube formation. Mouse cephalic neural plates appear overlying already segmented cranial mesenchyme according to previous reports, and neuromeres develop precociously in the open plates, where their positions correlate exactly with the underlying segmented mesenchyme.
Scanning electron microscopic study of arterial cushions in rats: A novel application of the corrosion‐replication technique
Authors: Casellas D. , Dupont M. , Jover B. , Mimran A.
Published: February 2005

The morphology and organ distribution of arterial cushions were studied in adult rats (body weight ranging from 200 to 500 gm) by scanning electron microscopic (SEM) observation of corrosion casts. Scanning electron microscopic observations of renal vascular casts were correlated with SEM views of the luminal surfaces of similarly fixed vessels; there was a striking similarity in shape, organ distribution, and dimensions between fixed arterial cushions and indentations at the surfaces of casts. Application of this technique to 11 different organs, some of which had never been studied by SEM before, revealed the occurrence of indentations at branching sites similar to those found in kidneys (and hence they were termed “cushions”). Our findings are in generally good agreement with previous light and transmission electron microscopic studies on rats. Our results support the view that arterial cushions are present throughout the vasculatures of the rat. A quantitative morphologic study of replicated branching sites related to “cushions” showed a great variability of the parent‐to‐daughter luminal diameter ratio (range 0.87–16.38) and of branching angles. A fruitful application of this technique to other laboratory animals may be anticipated.
Ultrastructural evidence for steroid‐hormone production in the adrenal of the marsupial, Isoodon macrourus, at birth
Authors: Gemmell R. T. , Singh‐Asa P. , Jenkin G. , Thorburn G. D.
Published: February 2005

To determine whether the adrenal gland of the bandicoot is actively producing steroid hormones at birth, the cellular structure was examined by electron microscopy, and the concentration of cortisol in the gland was determined by radioimmunoassay.

Two distinct cell populations were seen in the adrenal gland. One group of cells possessed dark staining granules, normally observed in catecholamine‐secreting cells, and the second group contained large amounts of smooth endoplasmic reticulum and mitochondria with tubulo‐vesicular cristae. Both features are characteristic of steroid‐secreting cells. A concentration of 0.094 ng of cortisol per adrenal was determined by pooling glands from nine individual newborn bandicoots.

This evidence of cortisol secretion from the bandicoot adrenal at birth indicates that, as in many eutherians, the marsupial adrenal may play an important role in determining the length of gestation.
Clonal proliferation of peritoneal exudate cells from New Zealand black mice: Age‐related changes
Authors: Murray Michael J. , Erickson Kent L. , Gershwin M. Eric
Published: February 2005

Proliferation and differentiation of peritoneal exudate colonyforming cells (PE‐CFC) were examined in BALB/c, C57BL/6, and NZB mice; NZB mice provided an experimental animal model for studies of autoimmunity. At 1 and 12 months of age, the number of PE‐CFC from NZB mice was significantly less than the number of PE‐CFC for other tested strains, whereas the number of clusters formed was reduced only in the older NZB mice. In contrast, 1‐ to 12‐month‐old BALB/c and C57BL/6 mice showed no significant age or strain‐dependent alterations in PE‐CFC. Although the latency period preceding colony growth remained constant for all strains and ages, significant variation in colony size was observed for NZB mice; the largest colonies were noted in the oldest group. We also observed age‐associated variations in colony morphology; therefore, age‐and strain‐dependent differences may exist in the differentiation or functional attributes of PE‐CFC subpopulations. The results specifically indicate that NZB mice have age‐related alterations in PEC proliferative and differentiation capacities.
Morphologic and functional studies of mouse hepatocytes in primary culture
Authors: Klaunig James E. , Goldblatt Peter J. , Hinton David E. , Lipsky Michael M. , Knipe Stephen M. , Trump Benjamin F.
Published: February 2005

Mouse liver cells in primary culture were evaluated by highresolution light microscopy (HRLM) and transmission electron microscopy (TEM). Cells after 2 hours of culture in L‐15 medium supplemented with 10% fetal bovine serum were spherical in shape, and were either individual or in small clusters of up to ten cells. Following 1 day in culture, hepatocytes were flattened and usually found in groups. Bile canaliculus‐like structures were apparent between hepatocytes. Tight junctions and desmosomes were also present along adjacent plasma membranes. Autophagic vacuoles were seen within the cytoplasm. After 2 days in culture, hepatocytes appeared more elongated and flattened than in earlier sampling periods. Both autophagic and clear vacuoles were seen in the cytoplasm. Mitochondria were present in a variety of shapes and sizes. Small bundles of microfilaments were frequently seen in the basal region of cross‐sectioned cells. From the fourth until the eighth day in culture, hepatocytes displayed further progression of the morphologic changes seen after 2 days. Nuclear elongation and the projection of cytoplasmic pseudoinclusions into the nucleus were also evident after 4 days. Cytoplasmic and nuclear changes were eventually observed in all hepatocytes by the eight day of culture. DNA synthesis in the cells during culture was investigated by autoradiography. The percentage of S‐phase labeled cells was 0.1% after 1 day of culture. The labeling index increased to 1.02%, 3.14%, and 5.88% after 2, 4, and 6 days of culture, respectively. Synthesis of albumin by the liver cells was also detectable during the first 8 days of primary culture. A gradual drop in albumin synthesis was noted with increased time in culture. The percentage of hepatocytes that histochemically stained for gamma glutamyl transpeptidase (GGT) progressively increased from 0.01% of the cells after 2 hours culture to 3.14% of the cells after 8 days of culture.
Comparative study of ultrastructures of the lateral‐line organs and the palatal taste organs in the African clawed toad, Xenopus laevis
Authors: Toyoshima Kuniaki , Shimamura Akitatsu
Published: February 2005

The fine structure of the lateral‐line organ and the palatal taste organ in the African clawed toad, Xenopus laevis, was examined by means of electron microscopy.

The lateral‐line organ consisted of hair and accessory cells. The apical surface of a hair cell was studded with one kinocilium and 20 to 40 stereocilia. Synaptic bodies and subsynaptic cisternae were found in the cytoplasm of a hair cell adjacent to the synaptic contacts with the afferent and the efferent nerve endings, respectively. Crystalline bodies were observed in both the nucleoplasm and the cytoplasm of almost all hair cells.

The palatal taste organ consisted of three types of cells: the taste, sustentacular, and the Merkel cells. The taste cells contained numerous dense‐cored vesicles which accumulated in close association with both the afferent synapses and the basal plasma membrane. The possibility was raised from the ultrastructural results that these vesicles had dual functions as both neurotransmitter and hormone. The existence of Merkel cells in the palatal taste organ suggested that this organ might function not only as a chemoreceptor but also as a mechanoreceptor.

In spite of possible chemosensory function of the lateral‐line organ in Xenopus, its ultrastructure was significantly different from that of the typical gustatory organ, the palatal taste organ, in this animal.
Relationship between granule‐containing cells and blood vessels in the rat autonomic ganglia
Authors: Abe Hiroshi , Watanabe Hiroshi , Yamamoto Toshi Yuki
Published: February 2005

Granule‐containing (GC) cells and related blood vessels in the superior cervical ganglion and the pelvic plexus of the rat were examined by light and electron microscopy of serial thin sections. In the superior cervical ganglion, GC cells formed many clusters of more than 20 cells. These clusters were supplied with dense networks of fenestrated capillaries, while the ordinary ganglion cells had continuous capillaries distributed more sparsely. Several continuous capillaries diverged from the networks in the GC cell clusters to join with capillaries around the ganglion cells. In the pelvic plexus, continuous capillaries with well‐developed pericytes were distributed similarly around the GC cells and the ganglion cells. Dense networks of fenestrated capillaries in the clusters were never seen. Based on these observations, the physiological significance of the GC cells was discussed.
The behavior of bursal lymphoid follicle‐associated cells after treatment with testosterone
Authors: Lupetti M. , Dolfi A. , Michelucci S.
Published: February 2005

Administration of androgens produces damage in lymphoid tissue and in the bursa of Fabricius. After IM administration of 5 mg of testosterone propionate (TP) beginning at hatching and continued during the following 4 days, a significant reduction in the bursal weights is observed. Histologically, an increase in the connective tissue is observed and cystic formations are also found. In all cysts examined, there is continuity of the cystic lumen with the free surface. The follicle‐associated epithelial (FAE) cells are on the bottom of the pseudocysts and form a separation between the pseudocystic cavity and the lymphoid tissue which is still further inwards. These cells do not lose their esterase activity, even though they are often flattened. Furthermore, they disappear in the pseudocysts deprived of lymphoid tissue. A new hypothesis is advanced that the FAE cells originate from the mesenchyme with differentiation in the histocytic line.
Ultracytochemical localization of guanylate cyclase in the oviduct of estrogen‐stimulated rat
Authors: Kang Yuan‐Hsu , West William L. , George Mariam
Published: February 2005

Many reports have indicated that estrogens increase uterine guanosine 3′,5′‐cyclic monophosphate (cGMP)levels via increasing the activity of guanylate cyclase. In the present study, guanylate cyclase activity was studied cytochemically in the oviduct of immature rats 24 hours after one or two doses (20 μg/kg, subcutaneously) of diethylstilbestrol (DES), one dose per day. The reaction product indicating guanylate cyclase was localized in the plasma membrane of epithelial cells, endothelial cells, and smooth muscle cells of all DES‐treated animals, but was absent from those of the vehicle control immature rats. The Golgi saccules of secretory cells and the periciliary membrane of ciliated cells were stained for the enzyme 24 hours after the first and second dose of DES, but the activity seemed diminished 24 hours after the second dose. Likewise, reaction product indicating guanylate cyclase was more prominent in the plasma membrane of epithelial cells of animals treated with one dose of DES than those animals treated with two doses of DES. However, in the endothelial and smooth muscle cells, guanylate cyclase activity increased after two doses of the estrogen. Further, pinocytotic vesicles or caeolae in these cells were also strongly stained for the enzyme after one and two doses of DES. These findings confirm the suggestion that guanylate cyclase plays a significant role in the growth, differentiation, and function (secretion and transport) of the oviduct.
Light‐microscopic and microspectrofluorometric characterization of porphyrin‐containing astrocytes in mouse optic nerve
Authors: Terr L. I. , Weiner L. P.
Published: February 2005

Fluorescence spectroscopy has been employed to investigate the emission spectrum of unusual orange‐red fluorescence found in the mouse optic nerve. Comparison of the spectra obtained with those of a number of porphyrins used as standards (protoporphyrin, uroporphyrin, and coproporphyrins) shows that the autofluorescence excited at about 400 nm (Soret band) is due to the presence of a mixture of these or other porphyrins in the nerve. Phase contrast, dark‐field, and light‐microscopy techniques demonstrated that the fluorescence is emitted by dense, coarse inclusions in the cytoplasm of astrocytes. The inclusions also exhibit high activity of endogenous peroxidase, a heme (porphyrin)‐ containing enzyme, characteristic for process of phagocytosis. A possible particiption of these astrocytes in phagocytosis is delineated.
Identification and responsiveness of prolactin‐containing secretory granules in clonal rat mammotrophs
Authors: McGill John R.
Published: February 2005

Clonal pituitary cells (2B8) derived from embryonic Rathke's pouch epithelium of Wister‐Imamichi rats established by Ishikawa et al. (1977) were used in this study. Late‐passage 2B8 cells were found to contain small secretory granules which contained immunoreactive prolactin as demonstrated by electron microscopic immunocytochemistry. When 2B8 cells were incubated in the presence of various agents that are known to stimulate or inhibit prolactin secretion, the volume density of the secretory granules in the cytoplasm was shown to be altered.
Development of the frontal bone and cranial meninges in the embryonic chick: An experimental study of tissue interactions
Authors: Tyler Mary Stott
Published: February 2005

The frontal region of the embryonic chick was studied to determine whether epithelial influences are necessary for frontal bone development. The frontal bone is a membrane bone, of neural crest and head mesodermal origin, which develops within mesenchyme sandwiched between two epithelia, neural ectoderm and epidermis. Rudiments were treated enzymatically to separate epithelial and mesenchymal tissues. Frontal mesenchyme then was grown as chorioallantoic membrane grafts either in the presence or absence of neural ectoderm and/or epidermis. The results indicate that neural ectoderm, though required during early stages of development to induce frontal bone development (Schowing, 1968), is not required during later stages (HH 22–30, the stages tested in this study) for osteogenesis. Epidermis, however, was shown to be required for frontal bone development during the stages tested. Frontal mesenchyme formed bone when epidermis was present on the outer aspect of the mesenchyme, and did not form bone when the epidermis had been removed prior to grafting, whether or not neural ectoderm was present. This dependence upon epidermis continues beyond the onset of meningeal differentiation. Once the outer ectomeninx‐dermis is distinguishable from the inner endomeninx, osteogenic capabilities are confined to the ectomeninx‐dermis layer. Furthermore, the ectomeninx‐dermis layer attached to epidermis is able to form membrane bone in the absence of the endomeninx and neural ectoderm. The endomeninx, though normally nonchondrogenic, was shown to be capable of forming cartilage when the neural ectoderm is removed. Neural ectoderm, therefore, may have an inhibitory effect on chondrogenesis in the endomeninx.
Boar spermatozoa observed by rapid‐freeze and deep‐etch method
Authors: Toyama Yoshiro , Nagano Toshio
Published: February 2005

Boar spermatozoa were observed by a rapid‐freeze, deep‐etch, and rotary shadowing technique. Domains of particles were found on the ES face of the plasma membrane in the proximal part of the postacrosomal region. Particles are 17 nm in diameter, have a central pit, and appear to contain either five or six subunits. The diameter of the subunits is about 7 nm. The particles are arranged hexagonally within the domain. Straight parallel ridges, 15 nm wide, were found on the entire PF face of the plasma membrane in the postacrosomal region. The ridges run almost parallel to the long axis of the spermatozoon. Part of the postacrosomal sheath could be seen through artificial openings in the PF face of the plasma membrane. The postacrosomal sheath seems to be a sheet of closely packed particles 7 nm in diameter and has striations with a periodicity of 15 nm. The ridges on the PF face of the cell membrane appear to be reflected by the striations of the postacrosomal sheath. In the neck and tail regions of the spermatozoa, orderly arranged particles were observed on the ES and PF faces of the plasma membrane.
Giant bistratified bipolar cells in monkey retina
Authors: Mariani Andrew P.
Published: February 2005

A bipolar cell type with a dendritic span in the outer plexiform layer (OPL) larger than any other type of monkey retinal bipolar cell and an axon which terminates in two separate strata (Polyak's 7a and 7d) of the inner plexiform layer (IPL) are described from Golgi‐impregnations of the rhesus monkey retina. These giant bistratified bipolar cells connect with many cones in the OPL, and although the axon has terminals in both the outer and inner parts of the IPL, Golgi‐electron microscopy (EM) demonstrates that the nature of this cell type's dendritic contacts with cones is as wide‐cleft basal junctions.