bluuebunny/crossref_metadata_2025 huggingface dataset:
Autonomic innervation in rabbit salivary glands
Authors: Freitag Per , Engel Milton B.
Published: February 2005

Autonomic innervation of rabbit salivary glands was demonstrated by modifications of the methods of Falck for catecholamines and Koelle for the localization of cholinesterase activity. To avoid and diminish artifacts, tissues were rapidly frozen, cut in a cryostat, and freeze‐dried under vacuum. Catecholamine fluorescence and cholinesterase activity were found in the serous parotid and the mainly mucous submandibular gland, strongly indicating that both glands are innervated by sympathetic and parasympathetic fibers. In the parotid gland, the sympathetic ground plexus apparently forms a denser network than that seen in the submandibular gland. Catecholamine fluorescence, indicating sympathetic nerves, is found to be closely related to most acini, blood vessels of both glands, and some ducts of the submandibular gland. Cholinesterase activity, signaling the presence of parasympathetic fibers, was observed around many acini, ducts, and some blood vessels of both glands. A theory is presented that the autonomic innervation of salivary glands influences the state of intracellular colloids, water, and electrolytes during secretion.
Age criteria for the prenatal and immature mongoose in Hawaii
Authors: Tomich P. Quentin , Devick William S.
Published: February 2005

Anatomical age markers are established in the small Indian mongoose (Herpestes auropunctatus) for embyronic, fetal, nestling and juvenile stages. Embryos and fetuses excised from living pregnant females and placed on a time scale of 49 days, the known gestation period, indicate that implantation is at approximately eight to ten days after insemination and that the transition from embryo to fetus occurs at about 14 to 28 days. The sequence of stages grossly discernible in prenatal development is highly similar to that in other mammals. Age in laboratory‐reared pups was correlated with a regular sequence of tooth eruption and replacement. The full set of permanent teeth is present at the age of 22 weeks. M3 was found in 2.8% of 142 adult skulls examined. Prominent reductions occur in the slope of the growth curve during early fetal stages, and at birth, weaning and independence from the mother.
The distribution of acetylcholinesterase and catecholamine containing nerves in the rat lung
Authors: El‐bermani Al‐Walid , McNary William F. , Bradley Donna E.
Published: February 2005

The distribution of catecholamine and acetylcholinesterase containing nerve fibers in the rat lung was studied employing specific histochemical techniques. Silver impregnation and methylene blue staining was used to allow comparison with the results of previous workers. Catecholamine containing nerve fibers were found associated with the nerve plexus about bronchial arteries and were carried to the bronchial wall and the pulmonary vessel wall along branches of the artery. Acetylcholinesterase containing fibers followed along the bronchi and bronchioles and were found in the adventitia, mucosa and submucosa, Acetylcholinesterase containing nerves were not found in the perivascular plexi with the exception of a few positive nerve fibers within the larger pulmonary veins.
Morphologic changes in white and brown adipose tissue by insulin, thyroxin and cortisol in organ culture
Authors: Slavin Bernard G. , Elias Joel J.
Published: February 2005

In order to compare the morphologic response of white and brown fat to various hormones in vitro the technique of organ culture was used in this study. Explants of white and brown fat from young mice fasted for 48 hours were exposed to culture media supplemented with insulin, thyroxin or cortisol. Morphologic changes due to these hormones were studied by means of histologic analyses and cell width measurements. Insulin acted to increase the size of cells and intracellular lipid content of brown and white fat explants when compared to similar explants exposed to unsupplemented media. Brown fat explants reacted earlier than white fat in this case. Thyroxin or cortisol alone had no influence on cell width or intracellular lipid content of these tissues. With the combination of insulin and thyroxin only white fat cells showed a greater increase in lipid deposition than that seen with insulin alone. No significant changes were noted when the combination of insulin and cortisol, or when all three hormones were added to the culture medium compared to that seen with insulin alone. The conclusion reached confirms those of other authors that brown and white fat possess enough dissimilarities to be classified as two different types of tissue.
Hormonal control of the deciduomal response of the golden hamster uterus
Authors: Harper M. J. K.
Published: February 2005

When pseudopregnant hamsters were ovariectomized and their uteri traumatized on day 4, deciduomal growth (not significantly different from that seen in intact controls) could be maintained by daily injections of 1, 2 or 4 mg of progesterone either alone or in combination with 1, 2 or 5 μg of estrone. When ovariectomy was performed on day 1 of pseudopregnancy and uterine traumatization on day 4, induction and maintenance of a deciduomal response could be achieved with 1 or 2 mg/day of progesterone alone (or in some cases in combination with 1 μg/day of estrone) from days 1 to 3 followed by 1 or 2 mg/day of progesterone in combination with 1, 2 or 5 μg/day of estrone from days 4 to 7. The best results were obtained with progesterone alone (2 mg/day) before trauma and estrone (2 μg/day) and progesterone (2 mg/day) after trauma.
The cytology of hofbauer cells
Authors: Enders Allen C. , King Barry F.
Published: February 2005

Cytological investigation of Hofbauer cells in various stages of gestation reveals that they are similar to normal macrophages except for unusually large cytoplasmic flanges and included vacuoles. The system of vacuoles is apparently the result of macropinocytotic activity. The individual vacuoles undergo asymmetrical collapse in regions adjacent to small juxtavacuolar tubules thought to be derived from the agranular endoplasmic reticulum. In addition, coated micropinocytotic vesicles are common. Hofbauer cells thus appear to be a type of macrophage with an unusual capacity for fluid ingestion. In younger placentas, Hofbauer cells are usually associated with extracellular compartments within the stroma. These compartments are relatively free of collagen fibrils and demonstrable ground substance and are clearly demarcated from the rest of the stroma by processes of fibroblasts. The abundance of these cells in early placentas, their location in the stroma, and evidence of their pinocytotic activity suggest that these cells may play a role in removal of proteins from interstitial fluid. Hofbauer‐like cells were also studied in the guinea pig and the little brown bat. Of these two species, the Hofbauer‐like cells of the bat more closely resemble human Hofbauer cells in that they show evidence of extensive macropinocytotic activity.
The cell population in pancreatic islets of amphisbaenidae — a light and electron microscopic study
Authors: Rhoten William B.
Published: February 2005

A diversity of cell types have been found in the pancreatic islets of three species of Amphisbaenidae in a light and electron microscopic investigation. The A cells have been characterized as having phosphotungstic acid hematoxylin and orange G positive secretory granules which are electron opaque and 450–500 mμ, in diameter. The B cells possess aldehyde fuchsin reactive granules which are slightly larger than A granules, approximately 550 mμ, and have a variety of profiles in the electron microscope. The D cells are characterized as being fast green positive and argyrophilic in the light microscope, and in the electron microscope have small, 200–300 mμ, secretory granules with a core of moderate electron opacity. In D cells the Golgi apparatus is more highly developed than in A or B cells. Bipes islets contain a presumptive fourth cell type possessing large secretory granules with irregular profiles and focal internal densities. An additional cell type, found in Amphisbaena manni and Bipes, has small, electron opaque granules.
A histochemical and fine structural study of early extracellular connective tissue in the chick embryo
Authors: O'connell James J. , Low Frank N.
Published: February 2005

The histochemistry of developing connective tissues and its relation to early connective tissue fibrils was investigated in the perinotochordal area of the chick embryo. Chick embryos were sacrificed at one, two, three, four, six and ten days of incubation and were prepared for both light and electron microscopy. Five histochemical stains (PAS, alcian blue, Hale colloidal iron, metachromatic toluidine blue, methenamine silver) were used to demonstrate polysaccharides, mucoproteins and mucopolysaccharides. Mature connective tissue elements were demonstrated by Mallory's connective tissue stain and Weigert's resorcin‐fuchsin stain. Routine electron microscopic techniques served to demonstrate extracellular connective tissue fibrils.

The first positive response for all histochemical stains occurs on the third day of incubation. Moderate microfibrillar growth precedes this by one day. Light microscopic staining patterns differ from electron microscopic fibrillar arrangements. In the perinotochordal area microfibrils later contribute to the cartilaginous model of the future vertebral body. By the sixth day, dense microfibrillar concentrations appear in the precartilage area where acid mucopolysaccharides are intensely concentrated. Staining for mature connective tissue fibrils does not occur until the tenth day.
Migration of bone marrow lymphocytes demonstrated by selective bone marrow labeling with thymidine‐H3
Authors: Brahim F. , Osmond D. G.
Published: February 2005

Thymidine‐H3 was injected into the femoral and tibial marrow (labeled marrow) of guinea pigs while the hind limb circulation was arrested temporarily and non‐radioactive thymidine was administered systemically. Blood and lymphoid tissue radioautographs were subsequently examined for the presence of marrow‐derived labeled cells.

Small lymphocytes in the labeled marrow showed a wave of labeling, maximal at two to three days. Concurrently, labeled small lymphocytes appeared in the blood and lymphoid tissues, mainly the spleen and mesenteric lymph node. Their numbers were greatest at four to five days, and declined rapidly thereafter. At first they appeared predominantly in the splenic red pulp and throughout the lymph node cortex, including the subcapsular sinus. By four to five days they were also concentrated in the splenic white pulp, including periarteriolar lymphoid sheaths, and in the lymph node medullary cords. They were detected within medullary sinuses, hilar lymphatics and thoracic duct lymph. Labeled monocytes and large lymphoid cells also appeared in the blood and lymphoid tissues, mainly in the spleen.

It is concluded that bone marrow is a major source of circulating newly‐formed small lymphocytes many of which migrate rapidly into the spleen and mesenteric lymph node.
Phenobarbital‐induced proliferation of smooth endoplasmic reticulum after administration of triparanol
Authors: Loker Edward , Scallen Terence J. , Dietert Scott E.
Published: February 2005

The effect of triparanol, an inhibitor of cholesterol synthesis, on the phenobarbital induced proliferation of the smooth endoplasmic reticulum (SER) is reported. Hepatocytes of hamsters treated with phenobarbital alone display the expected proliferation of the SER. Those given triparanol alone do not show this phenomenon but appear similar to controls with the exception of increased numbers of dense bodies characteristic of this treatment. Hepatocytes of hamsters receiving triparanol followed by phenobarbital display a SER proliferation of approximately the same magnitude as that achieved with phenobarbital alone. The effectiveness of the triparanol blockade is documented by the administration of labeled mevalonic acid and the subsequent quantitation of the amount of labeled cholesterol and labeled desmosterol. Desmosterol is the primary end product after triparanol treatment. Greater than 95% of the labeled sterol appears as desmosterol indicating a high degree of blockade. It is concluded that newly‐synthesized cholesterol is not a prerequisite for the phenobarbital induced proliferation of the SER. Several possible explanations for these results are discussed.
Effects of sex hormones on diet‐induced atrial thrombosis
Authors: Wilson Jack L. , Ashburn Allen D. , Williams W. Lane
Published: February 2005

Male and female Taconic Swiss mice were fed a high‐fat (28%), low‐protein (8%), hypolipotropic diet. Intact mice and gonadectomized mice, with and without injections of estrone or testosterone phenylacetate were studied.

The sex of the animals did not alter the incidence or type of diet‐induced cardiovascular lesions. During the 6–12 weeks of feeding thrombi developed in the atrial lumina of 75%–88% of intact and gonadectomized male and female mice. The only prominent decrease in the incidence of such thrombosis was in gonadectomized animals of both sexes receiving estrone where it was reduced to 6%–16%. In castrated males receiving injections of testosterone phenylacetate (Perandren) the incidence of thrombosis was 65%.
Two unique features of the anterior cerebellum in the higher primates, including man
Authors: Dillon Lawrence S. , Atkins David L.
Published: February 2005

Two morphological traits of the anterior cerebellar lobe unique to the higher anthropoid primates are described, and a search for their possible origins is made among representatives of the major subdivisions of the Anthropoidea. One trait involves the gradual reduction and migration of lobule II until it ultimately becomes located upon and fused with lobule I. Hence, in the higher anthropoids, the lingula actually consists of lobules I and II combined. This reduction and migration of lobule II from its normal position places lobule III adjacent to the lingula in the location occupied by lobule II among other mammals. The second distinctive feature concerns the inclusion of the anterior cerebellar peduncle on each side into the anterior medullary velum, so that they form a continuous morphological unit, separate and distinct from the remaining components on the ventral surface. This modification is found only in the members of the Hominoidea. In addition, several observations upon certain ontogenetic changes in lobular structure are reported.
Association of tendon organs with spindles in muscles of the cat's leg
Authors: Marchand R. , Bridgman C. F. , Shumpert E. , Eldred E.
Published: February 2005

The incidence and patterns of association of tendon organs (TO's) with muscle spindles was studied in serial histological sections of the extensor digitorum brevis (EDB) muscles of an adult cat. Some observations were obtained from the medial gastrocnemius and soleus muscles of a second cat, and the EDB muscle of a two‐toed sloth. An intimate relation of a TO to a nearby spindle, wherein the “spindle tendon” passes alongside the TO to attach to the aponeurosis, was found for 50% of cat EDB TO's, and 20 to 25% of the TO's in the other muscles. In cat EDB samples both TO's and spindles found in “tendon organ‐spindle dyads” had larger cross‐sectional areas at the equator than “solitary” units, and dyad TO's received the attachments of more extrafusal fibers than did solitary TO's. A number of the “solitary” TO's were found to be in line at a greater distance with spindles that lay along the extrafusal fibers inserting onto the TO. The possible developmental and functional significance of these findings is discussed.
Early differentiation of the chick embryo spinal cord in organ culture: Light and electron microscopy
Authors: Lyser Katherine M.
Published: February 2005

Chick embryo spinal cord has been explanted at two‐day stages, when few or no cells have formed axons, and cultured for five to seven days. The effects of various culture methods and the presence or absence of other tissues on differentiation have been studied. Many cells with axons and numerous nerve fibers were seen in silver‐stained sections of completely isolated neural tube cultured in a fold of vitelline membrane, as well as in neural tube explanted with adjacent tissues and in isolated neural tube recombined with somites. Electron micrographs of corresponding cultures showed cell bodies similar to those of fairly early nerve cells in vivo and processes with the structure of axons. Some characteristic differences in cell fine structure and in histological organization among these types of cultures were observed. Isolated neural tube cultured directly on a millipore filter did not survive or differentiate as well. These observations indicate that initial phases of nerve cell differentiation can proceed in organ culture and that there is no specific requirement for interaction with adjacent mesodermal tissues. This system can be used profitably for further investigation of factors controlling various aspects of differentiation in the central nervous system.
The fine structure of monkey and human spermatozoa
Authors: Zamboni L. , Zemjanis R. , Stefanini M.
Published: February 2005

The fine structure of spermatozoa of two species of monkey, Macaca mulatta and Macaca nemestrina, and man was studied following fixation of seminal fluids in buffered picric acid‐formaldehyde (PAF). The various components of the sperm have been studied mostly in light of the behavior of this cell at the time of conjugation with the ovum.

The possible equivalence between acrosome and lysosomes has been discrussed considering the origin, enzymatic activity, and mechanism of action of these two classes of organelles. The fine morphology of the post‐acrosomal cap has been found to be comparable to that of a septate desmosome. We have introduced the hypothesis that the cap plays a role in establishing and maintaining adhesion between the spermatozoon and the ovum at the time of gamete conjugation. The formation of the scrolls of the nuclear membrance in the posterior region of the nucleus has been put into relation with the modifications of volume and shape of the spermatid nucleus. The function of the scrolls could be to increase the surface through which nucleocytoplasmic exchanges take place. The possibility that the presence of a voluminous cytoplasmic droplet in human spermatozoa is a sign of cellular immaturity has also been discussed.
The fine structure of the neck of mammalian spermatozoa
Authors: Zamboni L. , Stefanini M.
Published: February 2005

The study of the fine structural organization of the various components of the neck of mature spermatozoa of rabbit, monkey and man has demonstrated that the striated columns of the connecting piece implant on the proximal centriole, that the distal centriole does not disappear but persists albeit in a modified form and that the central tubules of the axoneme of the flagellum terminate at the lower vault of the proximal centriole. Of the two centrioles, the most plausible candidate for the role of basal body of the flagellum and center of the sperm motility appears to be the proximal centriole. This hypothesis is supported directly by the apparent continuity of this centriole with all the contractile elements of the flagellum, and indirectly by the consideration that the distal centriole cannot be a basal body in that its lumen is traversed throughout by a central pair of tubules. The orientation of the proximal centriole at an angle to the flagellum, a unique situation since basal bodies are normally oriented on the same axes of cilia and flagella, has been tentatively accounted for by the particular type of motility of the spermatozoon.
The epithelium of the vaginal introitus in the rat
Authors: Gitlin Gershon
Published: February 2005

The epithelium in the region of the vaginal introitus in the rat (“introital epithelium”) was examined in sexually mature animals in different stages of the estrous cycle. It was found to be stratified squamous in type and invariably cornified, irrespective of the state of the vaginal epithelium above it. Thus, it failed to undergo the estrous cyclic changes seen in the rest of the vaginal epithelium. The introital epithelium extends for a distance of 1.5 to 5 mm above the vaginal orifice.
Cytoarchitecture of rat liver during compensatory growth
Authors: Iatropoulos Michael J.
Published: February 2005

The possibility of the formation of new lobules in rat liver during the course of compensatory growth has been investigated. Two methods inducing regeneration were used: the method of subtotal hepatectomy and the method of porcelain bead implantation. Observations were made at 28, 42, 56, 68, 84 and 112 days after subtotal hepatectomy, and at 28 and 42 days after implantation of the bead.

The results obtained from subtotal hepatectomy were expressed as the lobular radius (or portal‐central vein distance) measured in micra. The values were 404 μ at the twenty‐eighth day after hepatectomy and 324 μ at the one‐hundred‐twelfth day. The results obtained from bead implantation were 352 μ at the twenty‐eighth day after implantation and 305 μ at the forty‐second day.

It is concluded that regenerating rat liver undergoes structural changes involving new lobule formation between the fifty‐sixth and the one‐hundred‐twelfth day after subtotal hepatectomy, and sometime after the fourth week after bead implantation. The difference in times after which structural changes occur is explained by the difference in intensity of stimulus in the two methods.
The spermatogonial stem cell population in adult rats. I. Their morphology, proliferation and maturation
Authors: Huckins Claire
Published: February 2005

Whole mounted segments of seminiferous tubules from rat testes have been used to investigate the morphology and proliferative activity of the undifferentiated type A spermatogonial population. This has led to the formulation of a new model for spermatogonial stem cell renewal. Three groups of undifferentiated A spermatogonia were classified according to their topographical arrangements as isolated, paired, and aligned spermatogonia. It was proposed that the isolated (as well as a few paired) spermatogonia, which were always present throughout the seminiferous epithelium, are the functional stem cells and should therefore be designated as As. Through sporadic divisions, the As spermatogonia both maintain their own numbers and give rise to pairs of cells which are destined to eventually differentiate. The latter undergo several synchronous divisions in succession, thereby forming increasingly longer chains of aligned spermatogonia. The proliferation of these chains, primarily in stages I–V, leads to a gradual expansion in the size of the undifferentiated type A population. When the population attains its maximal size in stage V, mitotic activity among the aligned cells ceases, and all of these cells morphologically transform without further division into typical A1 spermatogonia. Subsequently, the cohort of A1 cells synchronously divides in stage IX to begin the long process of spermatogonial maturation. The isolated (and a few paired) cells, which do not undergo this transformation and remain quiescent during the stage IX peak of mitosis, form a residual stock of stem cells, that, during the course of another cycle, rebuild the population of aligned A spermatogonia. In this way, a continual supply of type A1 spermatogonia which will cyclically differentiate is insured.
A three‐dimensional reconstruction of the rods in rat maxillary incisor enamel
Authors: Warshawsky H. , Smith C. E.
Published: February 2005

A three‐dimensional reconstruction of the rod profiles seen in inner and outer rat incisor enamel was made from serial 1 μ cross sections of a decalcified upper incisor. The enamel rod was found to be an elongated structure which travelled incisally relative to its origin and ran continuously from the dentino‐enamel junction to the enamel surface. The rod was divisible into an inner and outer enamel portion. The inner enamel portion began at the dentinoenamel junction and travelled incisally for about 20 μ with either a mesial or lateral tilt towards the outer enamel. The outer enamel portion of the rod was straight and ran incisally for about 60 μ as it gradually approached the enamel surface.

Inner enamel portions of rods were arranged in rows parallel to the cross sectional plane of the incisor. All the rods in each row were tilted either mesially or laterally such that individual rods of adjacent rows crossed each other at 90°. Outer enamel portions of rods were not arranged in rows but all passed incisally parallel to one another.
Fine structure of rat pituitary cilia
Authors: Carpenter Esther
Published: February 2005

Pituitary glands of 30 ♀ rats from one to seven and one‐half months old were fixed in glutaraldehyde followed by osmium tetroxide. One five‐month gland was fixed in Karnovsky's paraformaldehyde mixture.

Cilia in the residual cleft at all ages and in the electron lucid vesicles found in the pars distalis during the first two months occur in great numbers per cell and show the 9 + 2 pattern (9 peripheral doublets around 2 central tubules slightly separated from each other) characteristic of kinocilia. The spaces into which these cilia project may contain disintegrating cells as well as colloid‐like material of variable density.

Cilia found in or between parenchymal cells of the pars distalis usually occur one per cell and lack central tubules. One of the doublets is often displaced toward the center. Cilia have been seen in three types of granular as well as in non‐granular cells. A pair of cilia enclosed in the same membrane was found once within and twice between parenchymal cells.

Central tubules appear to develop only in locations (cleft and vesicles) where motility is possible. The single cilia found in parenchymal cells may be considered immature and are presumably non‐functional.
Ultrastructural aspects of the main excretory duct of rat submandibular gland
Authors: Shackleford John M. , Schneyer Leon H.
Published: February 2005

Recent data indicate active transport of Na+ and K+ by the main excretory duct (MED) of the rat submandibular gland. In view of these data submandibular MED's of four adult rats were investigated by transmission electron microscopy. Luminal surfaces of two MED's were examined with the scanning electron microscope. The duct is surrounded by connective tissue, blood vessels and neuron perikarya. Blood supply to the ductal epithelium consists of a plexus of sinusoidal capillaries. Three principal cell types compose the epithelium: light cells, dark cells, and basal cells. The basal cells resemble those of striated ducts except for the presence of numerous hemidesmosomes along basal plasma membranes of MED basal cells. Light cells show basal infoldings, and bulbous enlargements may occur at their distal aspects. Dark cells are narrow, electron dense cells with prominent microvilli at the luminal surface. Intercellular clefts penetrate MED epithelium from the lumen to a depth of one‐third the epithelial thickness. Surfaces of the clefts are lined by dark and light cells. Intercellular tissue spaces are present at lateral boundaries of all cells and extend from the epithelial base to distal cytoplasmic levels.
Histochemical study of estrogenic and antiestrogenic effects of clomiphene citrate on glycogen synthesis by myometrium and luminal epithelium of rat uterus
Authors: Poteat William L. , Bo Walter J.
Published: February 2005

Glycogen localization in the myometrium and luminal epithelium of the rat uterus was studied by the periodic acid‐leucofuchsin technique after ovariectomized rats had been treated with various regimens of 1.0 μg estradiol dipropionate and 50.0 μg clomiphene citrate. Three regimens were used: (a) one or three dosages of clomiphene, alone or in combination with one or three dosages of estradiol; (b) a single dosage of clomiphene before a single dosage of estradiol; (c) a single dosage of clomiphene after a single dosage of estradiol.

The estrogenic effect of clomiphene on the myometrium was less than that of estradiol. Clomiphene suppressed myometrial glycogen accumulation induced by estradiol when administered with estradiol, six hours before the hormone, or as long as 24 hours after estradiol. The luminal epithelium responded differently to estradiol and clomiphene: the number of luminal epithelial cells containing glycogen strikingly increased after clomiphene treatment but not after estradiol treatment. A few scattered cells contained glycogen 24 hours after one dosage of the drug. Forty‐eight hours after a single dosage or after three dosages of the drug administered one per day, every luminal epithelial cell contained glycogen. The effect of clomiphene on the luminal epithelium may be either a unique action of the drug or an abnormal response of the tissue, similar to that reported for high doses of estradiol. This effect of clomiphene on the luminal epithelium may possibly be a factor in the drug's ability to block blastocyst implantation in the rat.
The ultrastructure of the keratinizing epithelia of the incisor and molar gingivae of the albino rat: Similarities and differences
Authors: Martinez I. Ricardo
Published: February 2005

Ultrastructural differences suggest that the keratinizing epithelium of the incisor gingiva (IG) is more rigid and durable than that of the molar gingiva (MG). The more numerous and larger collagen fibrils of the lamina propria, the more dense and homogeneous basal lamina, the more numerous anchor filaments distributed along the basal lamina and the larger and more frequently occurring hemidesmosomes along the base of basal cells all provide the IG epithelium with a firmer base and stronger attachment than the MG. The presence of many and long filaments in the IG and their aggregation into bundles inserted into the attachment plaques of desmosomes also suggest that this epithelium is tougher than the MG. This is further emphasized by the larger size of the desmosomes and their more frequent occurrence along the plasma membrane of cells of the IG. The ultrastructure of membrane‐coating granules and their role in membrane modifications appear to be the same in both the IG and MG. As the irregularly shaped keratohyalin granules of the IG increase in size, the dense amorphous material spreads out over the bundles of tonofilaments. On the other hand, as the spherical keratohyalin granules of the MG grow in size, they maintain their spherical shape and do not appear to be associated with or spread out over the filaments. The flattened horny cells of the IG with smooth contours and joined together by closely spaced desmosomes appear to be more protective and less easily detached by the abrading stress of mastication than those of the MG, which are irregular in shape with convoluted cell membranes and widely spaced desmosomes.
Ultrastructure of hepatic sinusoids in sheep
Authors: Grubb Donald J. , Jones Albert L.
Published: February 2005

The fine structure of the sheep hepatic sinusoid has been examined. Unlike that of most previously studied mammals, the sheep sinusoid has a continuous endothelial lining and a distinct basal lamina. Another unusual feature of the sheep sinusoidal endothelium is the presence of fenestrae closed by thin, single‐layered diaphragms. Between the basal lamina and the hepatic parenchyma, processes of perivascular connective tissue cells are seen in unusual abundance. Particles consistent in size with very low density lipoproteins are found on both sides of the basal lamina, but the mechanism of transport of these particles across the endothelial barrier is unknown.
The connective tissue ground substance in the mouse uterine cervix: An electron microscopic histochemical study
Authors: Leppi T. John , Kinnison Patricia A.
Published: February 2005

Sections of uterine cervix from ovariectomized mice treated with relaxin (R) or estradiol benzoate (EB) alone or EB and R in combination were exposed to dialyzed iron solutions prior to epoxy embedding. Control mice were untreated or received the hormone vehicles. Prior to iron staining, some sections were exposed to: (1) 0.05% testicular hyaluronidase for four hours at 37°C; or (2) acidified methanol for four hours at 60°C. Ultrastructurally, the uterine cervical walls from control mice and those treated with R contained densely packed bundles of collagenous fibrils and cells that resembled fibrocytes with few organelles. Except for spurious intracellular iron deposits, there was no iron staining of extracellular components.

Fibroblasts of cervices from mice treated with EB or EB and R were larger with highly developed endoplasmic reticulum and Golgi components. Small cytoplasmic vesicles were present close to the cell surface and each contained a thin inner rim of material. The stroma was characterized by widely dispersed bundles of collagenous fibrils in a greatly expanded cervical wall where there was extracellular iron staining that was prominent near cell surfaces and between individual fibrils within an amorphous material. Brief digestion with testicular hyaluronidase resulted in a reduction of extracellular iron staining, although deposits remained adjacent to cell surfaces, between fibrils and within cytoplasmic vesicles. Acidic methylation caused severe tissue damage so that an assessment of iron deposition in thin sections was impossible.
A new technique of measuring blood vessel volume in bone applied to the mandible and humerus of the rat
Authors: Brady J. M. , Cutright D. E.
Published: February 2005

This report describes a method developed to measure the blood volume and vascularity of bone. The technique utilized neutron‐activated silicone rubber perfusion material and was applied to normal rats from 1 to 18 months of age. By this means it was determined that blood vessel volume over the 18 month growth period measured increased from 8.41 to 15.45 μliters in the mandible and from 2.71 to 4.68 μliters in the humerus. Vascularity decreased from 2.91 to 1.18 μliters per mg × 10−2 of dry mandible and from 3.30 to 0.81 μliters per mg × 10−2 of dry humerus over the same period. Changes in volume and vascularity were greatest in the early months attaining a plateau at from four to six months of age, from 6 to 18 months of age, blood vessel volume increased gradually in the mandible while remaining constant in the humerus. Vascularity in these tissues paralleled changes in vascular volume.
Ultrastructural studies of the effects of reserpine on mouse abdominal sympathetic paraganglia
Authors: Mascorro Joe A. , Yates Robert D.
Published: February 2005

Male and female A/Jax mice 10–18 days of age were given one, two, or three daily subcutaneous injections of Serpasil (Reserpine USP; 2.5 mg/kg) and sacrificed 24 hours after the last injection. Abdominal extra‐adrenal tissue was processed for electron microscopy to determine the effects of this catecholamine depleting drug on the dense cored cytoplasmic granules of the parenchymal chief cells.

Electron microscopic investigations of sympathetic paraganglia from treated animals revealed a marked decrease in granule opacity as compared to that seen in cells from control animals. The cells with granules reduced in opacity following reserpine treatment could be consistently distinguished from those of non‐treated animals which led us to assume that the drug depleted the amine content from its storage site in the granule without completely destroying the granule structure. These results further substantiate our earlier speculations that the granules in abdominal paraganglion chief cells of the mouse contain catecholamines.
A comparative study of sebaceous gland ultrastructure in subhuman primates. III. Macaques: Ultrastructure of sebaceous glands during fetal development of rhesus monkeys (Macaca mulatta)
Authors: Bell Mary
Published: February 2005

Sebaceous glands from fetal rhesus monkeys have been studied from the onset of their differentiation to complete maturation. Sebaceous differentiation in fetuses closely parallels that in adults with the exception that agranular endoplasmic reticulum is virtually absent from differentiating cells during early ontogeny, whereas it is abundant in their counterparts in adult animals. As the adult pattern of sebaceous differentiation becomes established, the amount of agranular endoplasmic reticulum increases in these cells. Golgi zones are prominent in differentiating cells during early ontogenetic development.
The structure of Tomes' granular layer in dog premolar teeth
Authors: Shackleford John M.
Published: February 2005

Microradiographic, polarized light, phase‐contrast and scanning electron microscopic aspects of Tomes' granular layer were studied in undemineralized and demineralized premolar teeth from four dogs. The microradiographic studies show Tomes' layer to consist of a narrow zone of hypomineralized‐hyperorganic dentinal matrix subjacent to the cementum. The zone appears as a series of focal points in cross sections or as an interrupted line in apico‐coronal cuts through the tooth. Polarized light and phase‐contrast microscopy demonstrate a morphological pattern similar to that of the microradiographs. Scanning electron microscopy suggests one component of Tomes' layer to be fibrillar. Tomes' granular layer of dog teeth may be important in protecting the tooth from sudden insults or large occlusal forces transferred to dentine via the periodontal ligament.
Ultrastructure of the thyroid gland of the cream hamster
Authors: Nève Pierre , Wollman Seymour H.
Published: February 2005

The typical thyroid epithelium of the cream variant of the Syrian hamster differs from that of other common mammalian species. One obvious difference noted by light microscopy is that the cells contain numerous PAS‐positive granules apical to the nucleus. By electron microscopy these granules are dense granules resembling lysosomes. The cells have exceptionally long microvill and numerous junctions and interdigitations of lateral plasma membranes with those of their neighbors. Many organelles in the cells are stratified rather than arranged at random. In addition to the dense granules and centrioles, the Golgi apparatus is usually located at the level of the apical end of the nucleus. The granular reticulum is primarily in the basal half of the cell, although some is apical. Microtubules are especially abundant and are located ainly close to the lateral surfaces and around the nucleus, although some are near apical or basal plasma membranes. The microtubules frequently appear to be in contact with mitochondria and dense granules, but their role in the positioning or stratification of organelles is uncertain.
Frog pineal photoreceptor renewal: Preliminary observations
Authors: Bunt Ann Heffington , Kelly Douglas E.
Published: February 2005

The intracranial epiphysis of the adult frog, Rana pipiens, has been examined by electron microscopic cytochemistry and radioautography. Acid phosphatase is localized within vacuoles of macrophages free in the lumen, in subspherical vesicles of the ellipsoid portions of photoreceptive cell inner segments, and in occasional heterogeneous cytoplasmic inclusions of the supportive cells.

The distribution of radioactivity in the epiphysis at intervals of 1, 3, 5, 9, 14, 25, and 60 days following injection of tritiated leucine, as determined by quantitative radioautography, is consistent with an hypothesized process of continual renewal of photoreceptive cell outer segments. The pattern of radioautographic labeling of the pineal photoreceptors, which resembles more closely that of retinal cones than rods, is correlated with previous morphologic and electrophysiological studies of these cells.

The radioautographic and cytochemical data suggest that macrophages within the epiphyseal lumen are involved in phagocytosis and, ultimately, in digestion of degenerate outer segments. They may perform a function similar to that of pigment epithelial cells of the lateral eye retina.
Effects of unilateral ovariectomy of the pregnant hamster on the remaining ovary
Authors: Chatterjee Amar , Greenwald Gilbert S.
Published: February 2005

Unilateral ovariectomy of hamsters on day 1 of pregnancy resulted in an increase in weight of the remaining ovary by day 4, primarily by increasing the number of antral follicles. The ovulability of these follicles was tested by injecting 20 IU human chorionic gonadotropin (HCG) on day 12 of pregnancy. Following this treatment, the unilaterally ovariectomized animals ovulated 29.4 eggs whereas intact animals ovulated 16.6 eggs per ovary. In both instances, the number of antral follicles ovulated by HCG was between 40% and 50% of the number present. Luteal weight was unaltered by semispaying, indicating that the regulation of corpus luteum growth does not fit a negative feedback system.

The ability of exogenous steroids to prevent ovarian compensation was assessed by injecting either progesterone (2 mg) or estradiol cyclopentylpropionate (1 μg) daily from days 8 to 11 of pregnancy. Either steroid injected into the semispayed hamsters prevented the expected increase in the remaining ovary in weight, follicular development and the ovulatory response to HCG. The same hormonal treatment of intact, pregnant animals slightly increased mean ovarian weight but did not affect follicular development.

These results suggest that unilateral ovariectomy of the pregnant hamster, by decreasing peripheral level of ovarian steroids, partially reduces the inhibition of gonadotropin secretion and therefore leads to ovarian compensation.
Fine structure of ultimobranchial follicles in the thyroid gland of the rat
Authors: Nève Pierre , Wollman Seymour H.
Published: February 2005

The mature ultimobranchial follicle of the rat consists of two or more layers of cells (U cells) surrounding a lumen containing cell debris. The ultrastructure of the outer, or basal, U cell is characterized by the presence of half desmosomes on the basal plasma membrane and pinocytotic vesicles near it, by little granular reticulum but an abundance of free ribosomes, by clusters of fibrils connected to desmosomes and possibly free in the cytoplasm. The cell ages by accumulation of clusters of fibrils and it undergoes differentiation to form more apical U cells which contain fewer ribosomes and have fibrils dispersed in the cytoplasm. The apical U cell is desquamated into the lumen and ultimately becomes a carcass containing a dense matting of fibers and vacuoles containing a reticulated material resembling that in the lumen. U cells are observed associated with typical thyroid epithelium in the thyroid of the newborn rat in relatively large follicles containing colloid and desquamated cells. They also form rods of cells in the very young rat. Mixed follicles containing both U cells and typical thyroid epithelium occur at all ages.
Role of chondrocytes and hydrocortisone in resorption of proximal fragment of Meckel's cartilage: An in vitro and in vivo study
Authors: Melcher A. H.
Published: February 2005

The possibility that chondrocytes of the proximal fragment of Meckel's cartilage may participate in resorption of the extracellular substance of the cartilage and outlive its removal, has been investigated in vitro and in vivo. Mandibles from 18 day in utero mouse foetuses were cultured for 14 days on an an antibiotic‐free chemically defined medium. When tested histochemically for acid phosphatase heavy deposits of reaction product were evident in cells in areas where resorption appeared to be occurring. When maintained on medium containing 1.0 μg/ml hydrocortisone, groups of chondrocytes hypertrophied and were reactive for acid phosphatase, and this was accompanied by loss of intervening extracellular substance. These changes were intensified by increasing the oxygen tension of the environment and by further supplementing the medium with 1.0 μg/ml triiodothyronine. Chondrocytes in the vicinity of sites of resorption could incorporate 3H‐proline and 3H‐thymidine. In vivo, chondrocytes in the vicinity of resorbing areas in two to three day post‐partum animals were highly reactive for acid phosphatase, and could incorporate 3H‐thymidine, 3H‐proline, and 3H‐uridine. These observations have been interpreted to suggest that resorption of the proximal fragment of Meckel's cartilage is not necessarily accompanied by death of the chondrocytes, and that the chondrocytes may participate in removal of the extracellular substance. Furthermore, the response of the chondrocytes of Meckel's cartilage to hydrocortisone in vitro appears to differ from the response that has been reported to occur in a number of other cells in vitro.
Fine structure of sinusoids and portal capillaries in the liver of the adult sheep and the newborn lamb
Authors: Gemmell Robert T. , Heath Trevor
Published: February 2005

In adult sheep, the hepatic sinusoids have an endothelial lining with numerous gaps and fenestrae and are surrounded by a complete basal lamina. In newborn lambs, the sinusoids have a relatively thick endothelium with fewer gaps, and the space of Disse contains a partially formed endothelial basal lamina. In both adult sheep and lambs, perisinusoidal cells appear to form a network around the sinusoid. In portal areas, the endothelium of the smaller capillaries is fenestrated, but the larger capillaries have unfenestrated walls and are enmeshed in processes of pericytes. Projections of endothelial cells partially or completely occlude the lumen of some portal capillaries, and of a large majority of sinusoids scattered throughout the lobule.
A radiographic and histologic study of bone in the active and hibernating bat (Myotis lucifugus)
Authors: Whalen Joseph P. , Krook Lennart , Nunez Eladio A.
Published: February 2005

A radiographic and histologic study of bat bones showed that there is a progressive loss of bone tissue during hibernation and abrupt reversal at arousal. Enhanced osteolysis accounted for the bone loss; osteoclasia was not observed.
Histological and radiographic study of the spheno‐occipital synchondrosis in cynomolgus monkeys, Macaque Irus
Authors: Adams D. , Harkness M.
Published: February 2005

The spheno‐occipital synchondroses of 20 cynomolgus monkeys have been examined histologically and radiographically. The findings by these two methods have been compared and correlated with the dental age of the monkeys. The radiographic examination was carried out on the isolated clivus region while serial sections were used for histological examination. Comparison of the synchondrosis by the two methods resulted in six disagreements when the synchondroses were classified as open, partly closed or closed. It is suggested that this difficulty is due to superimposition of shadows on the radiographs and small degrees of histological union not being recognised radiographically. It is further suggested that care should be taken in determining the age at closure when radiographs alone are used as the criterion. The dental age at initial closure appeared to vary widely in some cases occurring at an early mixed dentition stage and in others as late as the adolescent dentition. The closure of the synchondrosis was not related to the eruption time of any particular tooth. The pattern of closure did not conform to the classical type, i.e., from above downwards nor indeed was any consistent pattern revealed in either the radiographs or histological sections.