bluuebunny/crossref_metadata_2025 huggingface dataset:
Hysterectomy in the rat: Surgical disruption of the vascular channels reduces number of ova shed
Authors: Peppler Richard D.
Published: February 2005

Cycling rats were hysterectomized and/or unilaterally ovariectomized (ULO) on day 2 (metestrus). Collateral blood supply to the remaining ovary via the uterine artery was left intact or disrupted. Animals were killed in metestrus after one complete estrous cycle. Control rats were also killed at this time.

Counts of tubal ova revealed that intact rats ovulated an average of 4.4 ± 0.4 eggs per ovary (N = 8). Following ULO, rats (N = 8) ovulated 9.6 ± 0.2 eggs. Ligation of the uterine artery decreased the number of eggs ovulated in ULO rats (N = 8) to 5.4 ± 1.1. Hysterectomized rats (N = 8) ovulated 4.8 ± 0.5 eggs per ovary. If the blood supply was disrupted, a reduction to 2.7 ± 0.2 eggs per ovary occurred (N = 8). Hysterectomized and ULO rats (N = 8) ovulated 10.3 ± 0.4 eggs from the remaining ovary but only 5.0 ± 1.0 eggs if the collateral blood supply of the uterine artery was not intact (N = 10).

The results demonstrate that disruption of the vascular channels during the surgical procedures of hysterectomy and/or ULO results in a reduction of the expected ovulation number.
Fine structure of differentiating ameloblasts in the kitten
Authors: Kallenbach Ernst
Published: February 2005

The fine structure of differentiating ameloblasts was studied in the lower second molar of 1‐week‐old kittens after perfusion fixation with and without subsequent decalcification.

The differentiation zone was divided into three phases. In Differentiation 1, ameloblasts are about 27 μm long and face an uninterrupted basal lamina. The predentin adjacent to the basal lamina contains a few collagen fibrils oriented mainly at right angles to the ameloblast surface. This specialized predentin forms a well‐defined layer, up to 1.5 μm thick, referred to as the junctional layer. In Differentiation 2, ameloblast processes extend through the basal lamina and the thickness of the junctional layer. The processes consist of cytoplasmic sheets forming a honeycomb‐like network. Dentin starts to calcify after process‐formation is underway. Two distinct types of odontoblast processes, having different shapes and contents, come in contact with the ameloblasts and push into the ameloblastic layer. In Differentiation 3, stippled material appears in the extracellular spaces between ameloblasts. Later, stippled material‐like substances appear in the predentin close to the ameloblast apex and close to odontoblast processes within the dentin. Ameloblasts now are up to 40 μm high. Enamel secretion starts in small circumscribed areas which gradually enlarge, leading to the disappearance of the ameloblast processes. These findings are compared with results obtained in other species, including man, and their possible functional significance is discussed.
Renal vasculature of the trout demonstrated by scanning electron microscopy, compared with canine glomerular vessels
Authors: Anderson Bettina G. , Anderson Wesley D.
Published: February 2005

In order to gain additional information regarding renal circulatory patterns, we have used both ink and resin injections to study the arterial supply to the mesonephric kidney of trout. Arterial injections through the dorsal aorta with ink were made for histological preparations in which the length, termination and relationship of glomerular vessels were examined. Similar injections with methyl methacrylate were made in preparation of corrosion casts to provide us with gross replicas of the aortic branches to the kidney as well as casts of glomerular structure for scanning electron microscopy.

The sequence of vessels through which arterial blood passed to the renal corpuscle and ultimately to the uriniferous tubules was traced. Each afferent arteriole was found to terminate in three to six brancehs which formed anastomosing circuits of capillaries; these vessels reunited at the hilum to form a single efferent arteriole. The efferent arterioles in turn traveled a short distance to peritubular capillary beds and sinusoids.

Morphological evidence was found for preglomerular sphincter‐like action only. The glomerular vessels were found to be similar to, although less complex than, those of the outer and mid‐cortical regions of the dog kidney.
Morphogenesis of fetal rat duodenal villi
Authors: Mathan Minnie , Moxey Pamela C. , Trier Jerry S.
Published: February 2005

To study the structural features of fetal rat duodenal mucosa associated with histogenesis of villi, duodena from 15‐ to 19‐day fetuses were examined by light and electron microscopy. The duodenal epithelium of 15‐to 18‐day fetuses was stratified. Distinctive junctional complexes associated with membrane‐bounded vesicles and cilia‐like structures were seen in the deeper epithelial layers at 15 and 16 days. Small lumina, designated “secondary lumina,” lined with a variable number of microvilli developed between epithelial cells at these junctional complexes during the sixteenth through eighteenth days. Degenerative changes and exfoliation of superficial epithelial cells were obvious in 17‐ and 18‐day fetuses. In 18‐day fetuses, aggregates of mesenchyme had invaginated the basal aspect of the stratified epithelium. Concomitantly, the number of epithelial layers overlying these mesenchymal projections was decreased. In 19‐day fetuses, well formed, short duodenal villi lined by a simple columnar epithelium which included goblet and endocrine cells were evident. Injection of ferritin into the main duodenal lumen of 17‐day fetuses failed to reveal continuity between the main lumen and the secondary lumina. However, continuity between many secondary lumina and the main lumen was demonstrated in 18‐day fetuses. Thus, major morphological features associated with villus formation in fetal rat duodenum include: (1) formation of many secondary lumina in primitive stratified epithelium, (2) eventual fusion of these lumina with the main duodenal lumen, by their continued growth coupled with exfoliation of degenerating superficial layers and (3) upward growth of mesenchyme towards the lumen as cell exfoliation and expansion of secondary lumina take place.
Fetal and neonatal rat pancreas in organ culture age‐related effects of corticosterone on the acinar cell component
Authors: McEvoy Robert C. , Hegre Orion D. , Lazarow Arnold
Published: February 2005

Fetal rat pancreas (ages 16 to 22 days postcoitum) and neonatal pancreas (4 days postnatal) were grown in organ culture for four days. The medium consisted of chick embryo extract and rooster serum either with or without the addition of corticosterone (3 × 10−5 M). Acinar cell differentiation was assessed using quantitative light microscopic linear scanning of tissue sections and enzymatic analysis of amylase in the culture media and in the explants. In the younger fetal tissue of 16 and 18 days postcoitum exocrine differentiation continued in vitro. The effect of corticosterone was an enhancement of the degree of in vitro differentiation. Even with corticosterone, however, the degree of differentiation in vitro was less than that observed during a similar period in vivo. In differentiated pancreas (20‐ and 22‐day fetal and 4‐day neonatal) the acinar pancreas degenerated under control conditions and a selective growth of the endocrine pancreas was observed. The addition of corticosterone to the media resulted in a maintenance of the differentiated state of the acini except in 22‐day fetal tissue in which the acini were not preserved. The differences between these results and the work of other investigators and the possible in vivo role of adreno corticosteroids in exocrine pancreatic differentiation is discussed.
Genetic spina bifida occulta in the mouse
Authors: Hollander W. F.
Published: February 2005

Spina bifida occulta is one of the major effects of the recessive mutant “snubnose” (symbol sno). Linkage tests have located this mutant in chromosome 4. Defective spinal arch formation typically includes the lumbar and often the posterior thoracic and sacral vertebrae. There is great variation in detail, from nearly normal closure to a trough‐like spinal column. Causes of the variation are not understood. Severely affected specimens may also have defective anterior thoracic vertebrae and reduced size of the sacral vertebrae, with kyphosis. The tail is essentially normal. No external lesion or myelomeningocele has been found, but there have been some instances of paralysis of the hind limbs, possibly from injury. The spinal cord seems normal as a rule, and pigmentation is normal. Embryological study has not been attempted, but the condition seems to be primarily osteogenic in origin.
Type II pulmonary epithelial cells of the newborn opossum lung
Authors: Krause William J. , Cutts J. Harry , Leeson C. Roland
Published: February 2005

The air chambers of the newborn opossum are lined by a respiratory epithelium which appears similar to that lining alveoli of other species. The type II pulmonary epithelial cell is cuboidal in shape, shows apical microvilli, several Golgi complexes, lipid droplets, and numerous cytosomes. The cytosomes contain osmiophilic lamellae and are similar in appearance to whorls of osmiophilic material lying free within the alveolar lumina and on the surface of the respiratory lining epithelium. In the newborn opossum lung, examination of the air chambers with the scanning electron microscope permits the observation of several type II pulmonary epithelial cells in a single field. The potential use of the air chamber of the newborn opossum as an experimental model is suggested.
Cations in the rat pars distalis ultrastructural localization
Authors: Schechter Joel E.
Published: February 2005

Pituitary glands of female Sprague Dawley rats were fixed using the potassium pyroantimonate‐osmium tetroxide technique by immersion or vascular perfusion. Both fixation procedures resulted in similar patterns of cation localization visualized as electron‐dense precipitate within cells of the pars distalis. Nuclei were prominent sites of localization. Cytoplasmic precipitate occurred in association with the endoplasmic reticulum, typically within the cisternal spaces, and also was localized within the mitochondrial matrix and cristae, as well as Golgi membranes, small Golgi‐associated vesicles, and multivesicular bodies. Immature secretory granules often contained precipitate between the core material of the granule and the enclosing smooth membrane. Frequently small antimonate‐containing vesicles bordered the immature secretory granules. Precipitate was variable in secretory granules of more mature appearance although precipitate was apparent occasionally just within a granule's enclosing membrane. Granules closest to the plasma membrane often contained increased amounts of precipitate and small vesicles containing precipitate were observed fusing with them. Instances of granule release by emiocytosis often revealed a clustering of precipitate behind the core material away from the emiocytotic stoma, as well as at the stoma and frequently an increased electron density of filamentous material radiating from the granules' enclosing membranes or from the adjacent plasma membrane. Exposure of section material to the chelating agents EGTA and EDTA indicate that calcium is the primary cation localized within the cytoplasm of these secretory cells. These findings are consistent with a role for calcium as a facilitator in the processes of transport and release of secretory granules.
Elastic fiber formation in monolayer and organ cultures of chondrocytes isolated from auricular cartilage
Authors: Moskalewski Stanislaw
Published: February 2005

Chondrocytes were isolated from auricular cartilage of immature rabbits and maintained in monolayer or organ culture for 14 days. In both types of culture the chondrocytes formed conspicuous elastic fibers. In monolayer culture the fibers could be identified by orcein staining in the culture dish. Electron microscopy of organ cultures revealed the presence of two basic components of elastic fibers, i. e. microfibrils and elastin.
Fine structure of satellite cells in growing skeletal muscle
Authors: Schultz Edward
Published: February 2005

The morphology of satellite cells was investigated in skeletal muscle from mice of various ages between 7 days and 50 weeks. Satellite cells of very young muscle had abundant cytoplasm which was rich in organelles. Free ribosomes were abundant and usually arranged into polysomes of 5–6 units. Cisternae of rough endoplasmic reticulum were heavily studded with ribosomes and occupied the polar regions of the cytoplasm. Marked dilations of the cisternae, filled with an amorphous electron‐lucent material, were a frequent and characteristic feature of satellite cells of very young muscle. The cytoplasm of young cells also contained a well developed Golgi apparatus as well as numerous mitochondria, microfilaments and microtubules. With increasing age there was a rapid reduction in organelles both qualitatively and quantitatively. For example, as the number of ribosomes decreased, their organization into polysomes was lost. The rough endoplasmic reticulum was present in cells of older muscle merely as small isolated rofiles that lacked dilations. These and other features demonstrated during this study are consistent with the concept that satellite cells are metabolically very activie in young muscle but rapidly become quiescent as the animal grows older.
Relationship between the adrenal cortex and thymic involution in “lethargic” mutant mice
Authors: Dung H. C.
Published: February 2005

To determine if the adrenal gland plays a role in the thymic involution which occurs spontaneously in “lethargic” mutant mice, three different studies were made. Morphological studies were made first to determine if there was an indication of histological changes in the adrenal glands. Next, serum levels of corticosterone were measured by radioimmunoassay. Finally, mice were unilaterally adrenalectomized to see if such treatment would improve various symptoms of “lethargic” mutants. Results of the studies showed that lipid granules in the cortical cells of “lethargic” mutants were greatly reduced in number during the time of spontaneous thymic involution, and the mutant mice had a significantly higher level of serum corticosterone than the normal controls. Mutant mice unilaterally adrenalectomized at 15 days of age showed a marked improvement in their condition and their mortality rate decreased. It is concluded that spontaneous thymic involution of “lethargic” mutants is probably associated with adrenocortical hypersecretion.
Surface morphology in the olfactory epithelium of normal male and female rhesus monkeys
Authors: Saini K. D. , Breipohl W.
Published: February 2005

Olfactory epithelium of male and female rhesus monkeys has been studied by transmission electron microscopy. It is shown that the epithelial surface differs greatly between male and female monkeys. Differences are most prominent between male and preovulatory females. During the ovulatory phase of the ovarian cycle remarkable histological alterations occur especially in the sustentacular cells. These alterations are correlated with physiological and behavioral phenomena demonstrating a possible structural basis for the changes in olfactory threshold in relation to sex hormones.
Dependence of Sertoli cell maturation on the pituitary gland in the mouse
Authors: Bressler Robert S.
Published: February 2005

Postnatal development of the Sertoli cell population was studied in testes taken from newborn mice and implanted into the testes of normal, hypophysectomized and testosterone‐treated hypophysectomized adult mice for 13, 15–17 and 17–19 days, respectively. Maturation of the Sertoli cell complement of each specimen was judged by two criteria: (1) the proportion of Sertoli cells exhibiting a nucleolonema; (2) the prevalence of specialized inter‐Sertoli cell junctions. In these respects implants recovered from normal hosts did not differ from sibling controls of the same age. Sertoli cells in implants recovered from hypophysectomized hosts retained the features observed in newborn controls, indicating that maturation of the Sertoli cells is dependent on normal pituitary function. Implants recovered from testosterone‐treated hypophysectomized hosts exhibited a degree of Sertoli cell development intermediate between those recovered from the other two host categories.
3H‐fucose incorporation into glycoproteins of toad bladder epithelial cells
Authors: Strum Judy M. , Ekblad E. B. Margareta
Published: February 2005

Electron microscope autoradiography was used to detect the incorporation of 3H‐fucose into glycoproteins of toad bladder epithelial cells. After short exposure to 3H‐fucose, without a chase period, the Golgi regions of all four cell types were labeled. When exposure to 3H‐fucose was followed by chase periods (1, 3, 4 and 6 hours) the apical and basal‐lateral plasma membranes of granular cells were heavily labeled. Apical granules and the cytoplasm of granular cells were also labeled, suggesting that they both provide the means for glycoprotein transfer from the Golgi to the plasma membranes. The heaviest labeling in mitochondria‐rich cells, after the 1‐ and 3‐hour chase periods, was over the apical tubules, although the apical and basal‐lateral plasma membranes were also heavily labeled. After the 4‐ and 6‐hour chases, the labeling of the apical tubules decreased, whereas the labeling of the plasma membranes increased, strongly suggesting that in these cells apical tubules play a major role in the transfer of glycoproteins from Golgi to the plasma membrane. Our results demonstrate that the route of 3H‐fucose incorporation into plasma membrane glycoproteins and the rate of glycoprotein synthesis and breakdown are not the same in the two major epithelial cell types in toad bladder.
An immunocytochemical study of human pituitary mammotropes from fetal life to old age
Authors: Baker Burton L. , Yu Ya‐Yen
Published: February 2005

The objectives were to (a) describe the cytology and distribution of mammotropes in the human pituitary gland, (b) determine whether the mammotrope is a distinctive secretory cell type and (c) ascertain when it first appears in the fetal hypophysis. Identification of mammotropes was based primarily on the Sternberger peroxidase‐antiperoxidase immunocytochemical method used with an antiserum to human prolactin. Hypophyses from 25 male and 6 female adults, and 21 fetuses ranging in gestational age from 6 to 23 weeks were studied.

In the adult two morphological forms of mammotropes were observed. Mammotrope I possessed a small perikaryon that commonly was located centrally in parenchymal cell cords. From the perikaryon long cytoplasmic processes extended toward neighboring capillaries. Mammotrope I reached its highest incidence in the posterolateral zones of the pars distalis. Mammotrope II possessed a larger perikaryon with short processes; cells of this form were fewer and occurred chiefly in the anteromedian zone. Mammotropes with intermediate morphological features that prevented classification into categories I or II were common in some hypophyses.

Both forms of mammotropes were present prepuberally (one 6‐week and one 9‐year‐old male) and in adult males and females. Mammotropes were only slightly more prominent in females than males. Regression of mammotropes was evident in old age. Mammotropes were distinctly different from somatotropes, corticotropes, gonadotropes and thyrotropes. In the fetal hypophysis mammotropes appeared first at 14 weeks of gestational age and remained few through 16.5 weeks. Their number increased greatly at 23 weeks.
Morphological aspects of type II alveolar pneumocytes following treatment with puromycin in vivo
Authors: Collet A. J. , Chevalier G.
Published: February 2005

Ultrastructural modifications of type II pneumocytes (PNM‐II) in mice were analysed 125 and 155 minutes after puromycin treatment (12 mg/100 gm at 0, 30, 60 and 90 minutes). A quantitative evaluation of the cell compartments was carried out and the inhibition of protein synthesis in PNM‐II was monitored by light microscopic radioautography, following 3H‐leucine injection.

In electron micrographs, following a 125‐minute puromycin treatment, the number and size of lamellar bodies, the precursors of lung surfactant material, appeared markedly reduced. The multivesicular bodies (MVB), which are normally very frequent in PNM‐II, had almost completely disappeared, as had composite bodies. Golgi saccules were dilated, while the area occupied by Golgi vesicles was enlarged. Observations following the 155‐minute puromycin treatment showed a strong enhancement of these modifications. Smooth and coated vesicles of the Golgi area, as well as peroxisomes, did not appear modified by puromycin. Elongated zones of autophagy were more prevalent after 125‐minute treatment than after the 155‐minute one.

Small bodies were frequently observed in the cytoplasm, near the Golgi zone. They were bounded by a smooth membrane and contained tiny vesicles and/or electron‐dense lamellae similar to those present within the lamellar bodies. Parallel membranes formed folds, some of them in continuity with lamellar bodies, thus encircling portions of cytoplasm. These structures, which were few in number in controls, were very frequently observed in treated cells, mainly after the 125‐minute treatment.

These extensive alterations of PNM‐II morphology appeared to be related to a disturbed production of pulmonary surfactant.
Spatial distribution of DNA‐synthesizing cells in colonic crypts of the guinea pig
Authors: Sawicki Wojciech , Blaton Olena , Pindor Maciej
Published: February 2005

The ascending colon of a guinea pig injected with tritiated thymidine was cut serially, autoradiographed and stained with periodic‐acid‐Schiff‐hematoxylin. Maps of transversely sectioned crypts were prepared with the use of a microscope eye‐piece projector. The number and angular positions of pulselabelled (DNA‐synthesizing) cells around the circumference of transverse sections of the crypt were recorded. A method of “statistics of the circumference” was applied in order to find the variances of angular distances between labelled cells and thereby to find the type of arrangement of DNA‐synthesizinbg cells in the crypt.

The spatial distribution of DNA‐synthesizing cells, both around the crypt circumference and along the crypt, was found to be non‐random. While the pattern of nonrandomness around the crypt circumference is such that the DNA‐synthesizing cells tend to occupy positions in the crypt circumference at maximal distances from each other, DNA‐synthesizing cells along the crypt tend to occupy positions at minimal distances from each other. DNA‐synthesizing cells are arranged in the crypt in rows, each consisting of several cells and each parallel to the long axis of the crypt. Apparently the dividing cell of the crypt produces either two proliferating or two differentiating cells. No evidence of differential mitosis could be found.
Fine structure of secretory ameloblasts in the kitten
Authors: Kallenbach Ernst
Published: February 2005

Secretory ameloblasts in lower second molars of 1‐week‐old kittens were studied with the elctron microscope after perfusion‐fixation with and without decalcification.

Ameloblast height varied from 40–65 μm. Tomes' process presented a stepped profile with two type‐1 faces (presumably enamel secreting) and one type‐2 face (thought to be non‐secreting). The type‐1 face was associated with extensive membrane infoldings. The enamel facing the type‐1 face was lined by a dense border, and stippled material was present between cell membrane and enamel. The type‐2 face was characterized by minute membrane invaginations and, sometimes, stippled material between enamel and cell membrane. In cross section, the distal part of Tomes' process showed bilateral symmetry, with one dorsal, one ventral and two lateral aspects. It was suggested that enamel formation occurs in three stages. First, interrod enamel on the lateral aspects of Tomes' processes is formed by two adjacent amelblasts. Next, the interrod enamel on the dorso‐ventral aspects of Tomes' processes is formed mainly by the dorsal extension of one Tomes' process. Finally, the enamel rod is formed by one ameloblast.

Stippled material was consistently present in the extracellular spaces between Tomes' processes and in irregularly shaped vesicles in the ameloblast apex, and occasionally in large masses between the ameloblast cell bodies. Spherical vesicles within the ameloblast, thought to be lysosomes, also could contain material resembling stippled material. The possibility was considered that stippled material is partly derived from enamel, and finally phagocytosed by ameloblasts. There was no clear morphologic evidence for merocrine secretion playing a role in the formation of either enamel, stippled material or the rod sheath.
The transmural migration and release of blood cells in acute myelogenous leukemia
Authors: De Bruyn Peter P. H. , Becker Robert P. , Michelson Sonia
Published: February 2005

The transmural passage of malignant blood cells from the extravascular parenchyma into the sinusoidal lumen has been studied in the bone marrow of rats with myelogenous leukemia. The Shay myelogenous leukemia was chosen as a model system because an increased bone marrow cellularity is, in this leukemia, usually accompanied by an increase in circulating myeloid cells. By means of light microscopy, transmission electron microscopy (TEM) and scanning electron micrroscopy (SEM) it was found that the sinusoidal endothelial lining of the bone marrow remains intact and continuous even in advanced stages of the disease. SEM shows that the malignant myeloblast‐like cell enters the sinusoidal lumen by means of a temporary migration pore, which appears only during the transmural passage of the cell.

Certain nondegenerative changes in the sinusoidal blood vessels are associated with the myelogenous leukemia. The normal radial alignment of sinusoids about the central sinusoid is changed into a tortuous pattern, and intraluminal cytoplasmic bridges which impede the blood flow are formed by the endothelial cells.
Catecholamine accumulation in neural crest cells and the primary sympathetic chain
Authors: Allan I. J. , Newgreen D. F.
Published: February 2005

Catecholamine accumulation in chick embryos of stages 16 to 24 was investigated using formaldehyde‐induced fluorescence. Fluorescence first appeared at stage 21 in the anterior sympathetic chain. After L‐DOPA treatment, this fluorescence appeared at stage 18. Noradrenaline could not advance the onset of fluorescence or reconstitute fluorescence after its depletion by reserpine at stages 22 to 24. Under no conditions could fluorescence be identified in neural crest cells prior to their aggregation to form the primary sympathetic chain. Noradrenaline induced fluorescence in the neural tube, notochord, myotome, sclerotome, gut mesenchyme and suprarenal cortical cells. In addition to these structures, the dorsal pancreas and some blood cells were fluorescent after 1‐DOPA treatment.

The implication of the results for the neural crest origin of APUD (Amine Precursor Uptake Decaboxylase) cells is considered.
High‐voltage electron microscopy of extracellular fibrillogenesis
Authors: Frederickson Richard G. , Morse Dennis E. , Low Frank N.
Published: February 2005

High‐voltage electron microscopy was employed to observe developing extracellular connective tissue elements in the cervical perinotochordal and perivertebral regions in the chick embryo from 2 through 15 days' incubation. During days 2 and 3, small (10 nm) and large (18–20 nm) microfibrils surrounded the notochord, becoming evident around fibroblast‐like cells in day 4. Amorphous material, globular granules and microfibrillar bundles were present at this time. Microfibrillar length increased as did the total population of microfibrils. At four days microfibrils 3–5 nm in diameter arose in all directions from globular granules. During day 9 and thereafter to day 15, microfibrillar diameters increased. This growth formed unit collagenous fibrils 30 nm in diameter or greater. Axial periodicity became evident at day 14.

Small microfibrils appear to be composed largely of glycoproteins and do not contain a significant amount of collagen. The globular granules and associated filaments are probably proteoglycans. The amorphous material is believed to provide molecular collagen to developing fibrils. Large microfibrils and unit collagenous fibrils contain significant amounts of molecular collagen.
Electron microscopic immunohistochemical localization of α‐MSH in the rat brain
Authors: Pelletier Georges , Dube Donald
Published: February 2005

Using an immunohistochemical technique at the electron microscopic level, it has been shown that α‐MSH is localized within the small vesicles of a few cell bodies found in the arcuate nucleus and numerous nerve fibers widely distributed throughout the brain. These findings suggest that α‐MSH could possibly be considered as a neurotransmitter.
Effects of a tumor‐promoting agent on chondrogenesis
Authors: Pacifici M. , Holtzer H.
Published: February 2005

Chondroblasts exposed to the phorbol ester, PMA, rapidly lose their polygonal morphology, and rapidly cease to synthesize or accumulate the chondroblast‐specific Type IV sulfated proteoglycan. This striking effect is reversible if the cells are kept in PMA for up to 72 hours.

A longer exposure induces irreversible effects and results in a population of cells, the vast majority of which lack the phenotypic properties of terminal chondroblasts.
The morphogenetic relationship of the temporal muscle to the coronoid process in human embryos and fetuses
Authors: Spyropoulos Meropi N.
Published: February 2005

The purpose of this investigation was: (a) to study the developmental relationships of the temporal muscle and the coronoid process during the critical initial stages of morphogenesis and (b) to correlate the developmental stages of the muscle and the bone with data describing the functioning of the muscles of mastication in utero.

The heads of 41 human embryos and fetuses, 6 to 11 weeks, estimated fertilization age, were sectioned and examined under light microscopy. The findings are described in terms of six successive stages, each characterized by a major developmental change occurring during that stage.

The data indicate that the temporal and masseter muscle anlagen begin to develop prior to the skeleton to which they ultimately become attached. The coronoid process differentiates subsequently as a discrete entity within the mass of the temporal muscle anlage at an estimated fertilization age of 7 to 7.5 weeks (23–24 mm CRL). At approximately eight weeks of age, the coronoid process unites with the main portion of the mandibular ramus. The findings here presented do not support the conclusion that the coronoid process is self‐differentiating as Washburn (′47) contended. Instead, the development of this feature of the human mandible represents a response that follows the differentiation of the temporal muscle. This conclusion is consistent with the observations drawn from a number of investigations concerning structural and functional development of the face.
Fusion of nasal swellings in the mouse embryo: Surface coat and initial contact
Authors: Gaare John D. , Langman Jan
Published: February 2005

The nasal region of 12‐day‐old mouse embryos was examined with the electron microscope to determine whether a surface coat and membrane specializations are involved in epithelial fusion between the medial and lateral nasal swellings. Ruthenium red was used to examine the distribution of the surface coat.

Prior to contact, a surface coat is always present over the epithelial linings of the nasal swellings in the region of presumptive fusion, and it is often heavier in the fusing than in the non‐fusing regions. At the point of initial contact, the coat is present as a thin film between touching superficial cells, suggesting that it may mediate epithelial contact.

The initial contact between the cells of the medial and lateral nasal swellings is made by short projections from one superficial cell to the surface of an opposing superficial cell. These points of contact then broaden into larger areas until the entire free membranes of opposing superficial cells meet. The contacting membranes, which are separated by a distance of approximately 6–10 nm and show an increased electron‐density, probably provide a firm adhesion between the nasal swellings.
Morphology and hormonal responsiveness of renal cortical tubules in vitro
Authors: Biddulph David M. , Wrenn Robert W.
Published: February 2005

Isolated renal cortical tubules from male hamsters were prepared for studies in vitro in which the effects of parathyroid hormone (PTH) on cyclic nucleotide metabolism and efflux of intracellular calcium were investigated. Morphological studies were also conducted to evaluate the effects of the isolation procedure on the structural characteristics of the in‐vitro preparation of tubules. Tubules, consisting of proximal, distal and collecting duct segments, were observed by electron microscopy to retain specific cellular membrane specializations which characterize these segments in situ (microvilli; basal infoldings and junctional complexes). Organelles were generally normal in their appearance; however, some swelling of mitochondria and endoplasmic reticulum were occasionally observed. Enzyme activity, associated with either luminal membranes (alkaline phosphatase) or lysosome‐like organelles (acid phosphatase) was also retained following the isolation procedure. Preservation of the PTH‐dependent, adenylate cyclase system in isolated tubules was demonstrated, indicating that membrane receptors for PTH were intact. Effects of PTH on cyclic GMP concentrations as well as efflux of 45Ca were also demonstrated. These results indicate that the use of isolated renal tubules in vitro offers an excellent model system for further investigations concerned with mechanisms of hormonal action and regulation of cyclic nucleotide metabolism. The results also suggest a relationship in renal cortical tubules between PTH‐mediated production of cyclic AMP, metabolism of cyclic GMP and transport of calcium.
The corpus luteum of the guinea pig. Fine structure at the time of maximum progesterone secretion and during regression
Authors: Paavola Laurie G.
Published: February 2005

This report describes the fine structure of guinea pig luteal cells during the period of maximum progesterone secretion and throughout involution, in ovaries that have been fixed by perfusion, a technique that provides optimal preservation of steroid‐secreting tissues. Smooth endoplasmic reticulum (smooth ER), a prominent organelle in these cells, is particularly well preserved by this method of fixation. During the time of maximal progesterone secretion, luteal cells contain abundant tubules and cisternae of smooth ER, many mitochondria, a well‐developed Golgi complex and some lipid droplets. This fine structural picture is consistent with active steroidogenesis.

Autophagy plays an important role in the regression of luteal cells in the corpus luteum. The onset of luteolysis is marked by the appearance of structurally complex autophagic vacuoles, one of which has not been described previously in luteal cells. This autophagic vacuole seems to originate from GERL (Golgi‐endoplasmic reticulum‐lysosomes) as a cup‐shaped structure, which subsequently increases in size and complexity. Regressing luteal cells also contain increased numbers of both dense bodies (lysosomes) and lipid droplets, and exhibit changes in nuclear and mitochondrial morphology. In contrast to previous reports in the literature, changes in the morphology of smooth ER were not observed as a characteristic feature of involution in corpora lutea of guinea pigs in the present study. Advanced regression of luteal cells is characterized by multiple fusion of lipid droplets and a decrease in the amount of smooth ER.

Another mechanism active in the breakdown of the corpus luteum is the phagocytosis of luteal cells by macrophages. Although present at all stages, macrophages are most abundant in older corpora lutea, where they often surround dead or dying luteal cells.
Evidence of a specific nidation site in ruminants
Authors: Lee Sue Y. , Mossman Harland W. , Mossman Archie S. , Pino Guido Del
Published: February 2005

The site of umbilical cord attachment in ruminants indicates the limited segment of the uterus where blastocyst attachment occurs and could have potential significance for locating presumptive nidation sites. Measurements of the site of cord attachment were made on impala (Aepyceros melampus) and common duiker (Sylvicapra grimmia) at several stages of gestation. Both implant only in the right uterine horn although they ovulate from either ovary. Relative to uterine length, cord attachment in impala is somewhat closer to the cervix than it is in common duiker. As pregnancy advances in common duiker, the relative position of cord attachment becomes closer to the tubal end. This relationship was not seen in impala and may perhaps be attributed to inadequate data. Upon extrapolation of the data from common duiker, a presumptive attachment area is suggested for this species. This region is located at about 41% of the distance from the internal cervical os to the uterotubal junction. Similar cord attachment data could be used in any ruminant species to indicate the existence and location of a specific nidation site.
The fine structure of the melanocytes of the adult mouse hair follicle during their amelanotic phase (telogen and early anagen)
Authors: Silver Alene F. , Fleischmann Robert D. , Chase Herman B.
Published: February 2005

Melanocyte‐precursor cells have been described previously in telogen and early anagen hair germs by observation of Epon sections using light microscopy. The existence of these precursor cells has not been generally accepted due to lack of ultrastructural evidence. It is our purpose to describe these cells using transmission electron microscopy. We studied hair germs of the dorsal skin of adult mice in the appropriate stages of the hair cycle prior to melanogenesis.

Telogen melanocytes are distinguishable from adjacent keratocytes by their lack of desmosomes, lack of coarse clumps of microfilaments, sparsity of ribosomes, unusually few nuclear pores and presence of dendrites. Melanocytes in early anagen show extensive growth with abundant polysomes, elaborate RER and Golgi zones. They still differ from keratocytes in their lack of desmosomes and clumps of microfilament, and also in the occasional presence of premelanosomes.
Immunocytochemical localization of epidermal growth factor during the postnatal development of the submandibular gland of the mouse
Authors: Gresik Edward W. , Barka Tibor
Published: February 2005

The time of appearance and the pattern of localization of epidermal growth factor (EGF) in submandibular glands of mice was studied during postnatal development immunocytochemically. EGF was first detectable in the granular convoluted tubule (GCT) cells in the glands of males at 20 days of age and of females at 30 days of age. Development of GCT cells containing EGF was rapid in males, approaching adult conditions by 45 days of age. In females EGF‐containing GCTs developed more slowly and irregularly, and did not reach adult status by 45 days of age. It is concluded that EGF is restricted during postnatal development to the GCT cells, and that these cells and the distribution of EGF are represented dimorphically from their first appearance in the submandibular glands of both sexes.
A scanning electron microscopic study of the Sertoli cell and spermiation in the syrian hamster
Authors: Gravis Curtis J.
Published: February 2005

The scanning electron microscope was used to examine the Sertoli cells in normal and germ‐cell‐depleted testes. The Sertoli cells appear to attain characteristic configurations in the various stages of the cycle of the seminiferous epithelium. In tubules containing maturation‐phase spermatids, Stages I‐IV, the Sertoli cells exhibit column‐like bases which give rise to lamellae measuring 25–30 μm in width which ensheath the spermatids and residual cytoplasmic bodies. In the Stages VIII‐IX long flat sheets of Sertoli cytoplasm rest atop the step‐8 and ‐9 spermatids. These sheets are oriented parallel to the basement membrane of the tubule with their long axis parallel to the long axis of the tubule. In Stages V‐VI the head and proximal portion of the tail of the maturation‐phase spermatids are ensheathed in sleeve‐like Sertoli cell processes. Cuff‐like terminations demarcate the terminus of these sleeves that surround maturing spermatids up to spermiation. In tubules undergoing spermiation, the sleeves retract so that only the tip of the spermatid head remains in the sleeve. Appendicular processes extend from the dorsum of the Sertoli cell sleeves in the tubules undergoing spermiation. After spermiation the appendix elongates while the sleeve evaginates until the everted sleeve is a finger‐like process that extends into the tubular lumen. In tubules in which the seminiferous epithelium has been depleted with epinephrine injections the Sertoli cells attain two configurations. The first is characterized by having long attenuated lamellar processes that orient perpendicular to the basement membrane, with numerous ramifying processes arising from the lamellae. In the second configuration the Sertoli cells' lamellae orient parallel to the basement membrane of the tubule and lack the elaborate ramifications seen in the first configuration.
The annular hematoma of the shrew yolk‐sac placenta
Authors: King Barry F. , Enders Allen C. , Wimsatt William A.
Published: February 2005

The annular hematoma of the shrew, Blarina brevicauda, is a specialized portion of the yolk‐sac wall. In this study, we have examined the fine structure of the different cellular components of the annular hematoma. Small pieces of the gestation sacs from seven pregnant shrews were fixed in glutaraldehyde and osmium tetroxide and processed for transmission electron microscopy. In the area of the trophoblastic curtain, the maternal capillary endothelial cells were hypertrophied and syncytial trophoblast surrounded the capillaries. Cellular trophoblast covered part of the luminal surface of the curtain region, whereas masses of apparently degenerating syncytium were present on other areas of the surface. Maternal erythrocytes, released into the uterine lumen from the curtain region, were phagocytized and degraded by the columnar cells of the trophoblastic annulus. No evidence of iron or pigment accumulation was evident in the parietal endodermal cells underlying the annular trophoblast. Parietal endodermal cells were characterized by cuboidal shape, widely dilated intercellular spaces, and cytoplasm containing granular endoplasmic reticulum. Endodermal cells of the visceral yolk‐sac accumulated large numbers of electron‐dense granules as well as glycogen in their cytoplasm. Hemopoietic areas and vitelline capillaries were found subjacent to the visceral endoderm. The various portions of the yolk‐sac wall of Blarina appear to perform complementary functions which are probably important in maternal‐fetal iron transfer.
The ovoimplantation of Microcebus murinus miller (primates, lemuroidea, strepsirhini)
Authors: Strauss F.
Published: February 2005

The process of nidation of Microcebus murinus may be subdivided into several stages (preadhesion, apposition, attachment and invasion), as is indicated for protracted phases of preimplantation. Not until the apposition stage does the inner cell mass orient itself orthomesometrially, while concurrently a nidation plaque develops in the abembryonal trophoblast that overlies and resorbs the coalescent glands. During the subsequent adhesion stage, the paraembryonal, bilaminar omphalochorion becomes attached to the uterine epithelium, with focal resorption of the latter. In addition, chorionic vesicles begin to develop. In the meantime, the embryonic disc has lost its trophoblastic cover as a preliminary to the formation of the pleuramnion.

The formation of a nidation plaque, together with the subsequent central implantation of Microcebus, suggests a close relationship to Loris tardigradus, characterizing the mode of implantation of Strepsirhini. The nidation plaque and its invasive capacity, giving rise to a syndesmochorial placental nucleus, provide a placentological link to Galago demidovii.
Immunocytochemical localization of thyroglobulin in the endostyle of the anadromous sea lamprey, Petromyzon marinus L.
Authors: Wright Glenda M. , Filosa M. F. , Youson J. H.
Published: February 2005

Thyroglobulin (TG) was localized in the endostyle of the anadromous sea lamprey, Petromyzon marinus L. by means of the unlabeled antibody peroxidase‐antiperoxidase immunocytochemical method. TG was found localized on the apical surface and within the cytoplasm of type 2c and 3 cells and in some type 5 cells. By identifying the cells of the endostyle immunocytochemically it may be possible to study more readily the events of endostylar transformation during metamorphosis.
The ultrastructure of the neonatal pig colon
Authors: Wooding F. B. P. , Smith M. W. , Craig H.
Published: February 2005

The neonatal pig colon has several unique structural and developmental features. At birth it has a variable population of epithelial cells which in their arrangement on villus‐like protrusions and in their capability for protein uptake into large preformed supranuclear vacuoles closely resemble neonatal ileal cells. Such villus‐like protrusions and vacuolated cells are not present in the 2‐day‐old piglet. On the first day after birth absorptive epithelial cells which lack supranuclear vacuoles transiently accumulate a large number of lipid droplets, each separated from the cytoplasm only by a proteolipid interface. None of the much smaller lipid droplets bounded by a unit membrane of the smooth endoplasmic reticulum and characteristic of normal small intestinal fat uptake were ever seen in these cells. Very few of the large lipid drops remain on the second day after birth.

This initial capacity of the colon for protein and lipid uptake never reappears.

The pattern of colonic amino acid transport also changes markedly in the first four days of independent life and this may be correlated with the observation that the absorptive cells at birth have microvilli which are twice the length of those on similar cells at and after two days old. These morphological results are discussed in terms of implied functional changes in the neonatal period.
Electron microscopic observations of vaginal development in untreated and neonatally estrogenized balb/c Crgl mice
Authors: Cunha Gerald R. , Lee Andrew K. , Lung Ben
Published: February 2005

Light and electron microscopic examinations of developing Mullerian vaginae were performed on untreated and neonatally estrogenized mice 1 to 12 days old. Vaginae of 1‐day‐old mice have an undifferentiated, pseudostratified columnar epithelium which slowly differentiates in untreated mice into an apparently mucus‐secreting epithelium. By day 12 the rough endoplasmic reticulum (RER), Golgi, and secretion granules are poorly developed features of the apical epithelial cells. In contrast, the stromal cells develop prominent RER and Golgi zones which in part are involved in the synthesis and secretion of collagen, which accumulates in the intercellular spaces.

The effect of estradiol on developing vaginal epithelium is observed after 24 hours of exposure as an increase in RER and the Golgi. Estradiol (E) accelerates the differentiation of mucus‐secreting apical epithelial cells, whose apices become filled with secretory granules, and also promotes the formation of a cornifying epithelium from the underlying basal cells. This latter process is associated with an increase in cellular proliferation, an increase in the occurrence of desmosomes and associated tonofilaments, and the development of extensive interdigitation of plasma membranes.

In untreated and E‐treated mice, the vaginal epithelium is separated from the stroma by a continuous, intact basal lamina. Transport of basal laminar material appears to occur via the processes of endo‐ and/or exocytosis in adjacent epithelial and stromal cells.