bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of enzymes on extracellular connective tissue components in the developing chick aorta
Authors: Newman Timothy L. , Low Frank N.
Published: February 2005

The fine structure of developing connective tissue components of the chick embryo aorta of eight and nine days incubation ages was studied after treatment with one of seven enzymes (α‐amylase, α‐chymotrypsin, collagenase, elastase, β‐glucuronidase, hyaluronidase, and trypsin). Both tissue pieces and thin sections of aldehyde‐fixed aorta and great vessels were utilized. All preparations were mounted on stainless steel grids and stained with silver metalloporphyrin, uranyl acetate, and lead citrate.

The homogeneous component of elastic fibers (elastin) responded only to elastase, indicating that it was well characterized early in its development. Eight‐day elastin was less susceptible to digestion than nine‐day elastin. Microfibrils were only slightly responsive to the actions of α‐amylase and trypsin, while α‐chymotrypsin completely eliminated them. Of the three connective tissue components, unit collagenous fibrils showed the greatest response. Complete or nearly complete digestions were effected by α‐amylase, α‐chymotrypsin, collagenase, and trypsin. Less extensive effects were produced by β‐glucuronidase and hyaluronidase.
Supraependymal cells in recesses of the monkey third ventricle
Authors: Coates Penelope W.
Published: February 2005

Scanning electron microscopy reveals unique supraependymal cells in preoptic and infundibular recesses of 3‐ to 21 ‐week‐old monkeys. Most supraependymal cells are located on nonciliated areas, and characteristically have round bodies from which multiple branched processes extend. Surface spherules occur on cell bodies and processes. Processes exhibit local enlargements, interweave with processes from other cells, and penetrate underlying ependyma.
Long‐term effects of ionizing radiation on the rat spinal cord: Intramedullary connective tissue formation
Authors: Gilmore Shirley Ann
Published: February 2005

The purpose of this study was to evaluate by light microscopy the effects of ionizing radiation on spinal cords of rats irradiated when three days of age and killed at intervals up to 28 months after irradiation. The amounts of x‐rays administered (2,000 R; 1,000 R; 500 R) were those which had been demonstrated by short‐term studies in this laboratory to cause either no histopathologic changes or only transient, reparable alterations. The most significant and previously unreported finding was the development, usually restricted to the gray matter, of elongated, spindle‐shaped cells that produce prodigious amounts of fibers clearly demonstrated by the Wilder's reticular stain. In cases where extensive cellular development had occurred, these cells were oriented around the perikarya of the large ventral motor neurons and formed a well‐developed capsule of reticular fibers. This phenomenon occurred more frequently in rats receiving the greater amounts of radiation and killed 12 months or more after exposure. The other observation of interest was the development of lesser amounts of connective tissue‐producing cells in the dorsal gray matter, where these cells were seen initially in the substantia gelatinosa. The significance of these changes is discussed in relation to previously reported long‐term effects of ionizing radiation on the central nervous system.
Innervation of the rat lung. Acetylcholinesterase‐containing nerves of the bronchial tree
Authors: El‐Bermani Al‐Walid I.
Published: February 2005

The innervation to the bronchial tree of the rqt was studied using silver impregnation and methylene blue staining in conjunction with histochemical demonstration of acetylcholinesterase and one‐micron sections of osmium‐bed, plastic‐embedded material. Innervation to the bronchial structures enters the lung along two pathways: (1) in bundles of nerves along the bronchi (peribronchial bundles), and (2) as nerve bundles associated with bronchial arteries (periarterial bundles) to innervate bronchial arteries and respiratory passageways. Fibers within the peribronchial bundles and associated nerve cells contain acetylcholinesterase. Varicose nerve plexuses associated with bronchial muscle (intermuscular nerves) are acetylcholinesterase‐positive, as are the submucosal nerves. Submucosal nerves are of two types. One type originates directly from the peribronchial bundles after passing through the muscularis without innervating it. These nerves extend circumferentially and longitudinally with respect to the bronchiole. The second submucosal nerve type originates from the intermuscular nerve plexus. These nerves have a radial orientation within the bronchial submucosa and reach the mucosa. It is concluded that the intermuscular nerves are postganglionic parasympathetics. The two types of submucosal nerves are thought to perform different functions.
Postnatal development of the mouse dentate gyrus in organotypic cultures of the hippocampal formation
Authors: LaVail Jennifer H. , Wolf Merrill K.
Published: February 2005

The hippocampal formation of newborn mice was explanted and maintained in Maximow culture assemblies for up to 35 days. At the time of explantation, only the suprapyramidal limb of the dentate gyrus was cytoarchitectonically distinct, and electron microscopy of newborn hippocampus revealed no definitive synapses. Histogenesis, as indicated by the development of the infrapyramidal limb of the dentate gyrus, and synaptogenesis, as indicated by the in vitro formation of mossy fiber synapses on the dendrites of hippocampal pyramidal neurons were studied by light and electron microscopy. At 12 days and thereafter in culture, mossy fiber terminals were found in synapsis with dendritic spines probably belonging to pyramidal cells of the hippocampal zone CA4. Near dentate granule cell somata a few axosomatic and many axospinous and axodendritic synapses were found. The data indicate that granule cells of the developing dentate gyrus are capable of differentiation in vitro into a structure essentially equivalent to that developed in vivo. The granule cells may become arranged into a recognizable granule cell layer, and develop dendritic processes which receive synapses virtually identical to those found in the intact organ. The differentiation of these features proceeds in the absence of the extrinsic afferents from the septum or from the contralateral hippocampal formation.
Structure and cytochemistry of the acinar cell in the rat maxillary gland
Authors: Vidić Branislav
Published: February 2005

The ultrastructural and cytochemical properties of the maxillary gland were investigated in 24 adult Sprague‐Dawley rats of both sexes. The relationship between the interstitial cell and/or excitatory cholinergic terminals with the secretory cell was discussed. The secretory material containing primarily neutral lipids, proteins, carbohydrates and mucosubstances appeared electron‐opaque following staining with uranyl acetate and lead citrate. Ruthenium red precipitated strongly on zymogenic granules which showed an increasing affinity for phosphotungstic acid, paralleling a rise in pH towards 7.7. The process of fusion of the plasma membrane with the membrane of secretory granules was observed, although some membrane‐bound granules were identified in the acinar and ductal lumina. Intracellular membranous structures were best revealed with phosphotungstic acid at pH 1.0–1.5, whereas ruthenium red reacted primarily with lipid inclusions and tonofilaments. Acid phosphatase activity was predominantly limited to secondary lysosomes and, to a lesser degree, to primary lysosomes and Golgi saccules. The morphological and chemical properties of secondary lysosomes in the secretory cell suggested a pronounced hydrolytic activity related to lipid inclusions and endocytotic vesicles.
The fine morphology of mouse primordial germ cells in extragonadal locations
Authors: Zamboni L. , Merchant H.
Published: February 2005

The localization and morphologic characteristics of mouse primordial germ cells at stages of embryonal development preceding formation of the undifferentiated gonads have been studied by means of high resolution light microscopy and electron microscopy. At day 9 of intrauterine life, the germ cells are found in the wall of the hind‐gut, at days 10 and 11 in the dorsal mesentery, and at day 12 they are mostly in the genital ridges or adjacent areas. Our observations confirm the hypothesis that germ cells attain their definitive location by ameboid movements. On the basis of morphologic characteristics displayed during migration, germ cells appear to be highly undifferentiated elements; for their energy requirements, they may depend on close association with somatic cells and on availability of exogenous substances of metabolic importance. Upon arrival at the genital ridges, the cells lose their ameboid features and assume a structural organization which is much simpler than that of precedinng stages. This indicates that migration is followed by a period of relative quiescence; mitosis is now the only evident activity. Interphase cells may occasionally be connected by intercellular bridges; it would seem that the first mitotic divisions with incomplete cytokinesis, a feature known to characterize oogonia and spermatogonia in sexually differentiated gonads, occur shortly after arrival of the germ cells in the genital ridges.
Studies on the progestational endometrium of the rabbit. I. Light microscopy, day 0 to day 13 of gonadotrophin‐induced pseudopregnancy
Authors: Davies J. , Hoffman L. H.
Published: February 2005

A study of the progestational evolution of the endometrium of the rabbit in pseudopregnancy suggests a division into the following phases: (1) priming phase (0–24 hours), in which no significant changes were observed except for leucocytic invasion of the epithelium, (2) proliferative phase (1–4 days), in which mitosis is active and the epithelium becomes pseudostratified and the glands proliferate, (3) phase of epithelial relayering and folding (4–6 days), in which the epithelium is single‐layered and there is evidence of secretory activity, (4) phase of cell fusion (6–8 days), in which the columnar cells fuse into multinucleated masses, and (5) maximally progestational phase (8–13 days), in which almost all the epithelial cells are multinucleated except for occasional ciliated cells, and, in some animals with evidence of the effects of high systemic levels of estrogen, extensive ciliation, especially antimesometrially. A final phase (6), not studied in detail, is a declining phase marked by degeneration and sloughing of the multinucleated epithelium and replacement with predominantly ciliated cells. Reconstruction of the minor mucosal folds, as distinct from the six or so major folds present in the non‐pregnant animal, shows that these are true elevations of the mucosa above the level of the mouths of the glands. The current concept of progestational changes in the endometrium of the rabbit as predominantly due to glandular proliferation is incorrect; this has important implications for analysis of the implantation process.
The effect of injected cycloheximide on early amphibian development
Authors: Manner Harold W. , Lau Peggy O.
Published: February 2005

Cycloheximide is a known inhibitor of cytoribosomal translation. Previously published results indicated that embryos cultured in cyclo‐heximide developed only to the midblastula stage. The current study involved injecting one μg of cycloheximide into each developing embryo of Rana pipiens. The three stages selected for the injection were the two‐cell, late four‐cell, and morula. The embryos stopped developing at the four‐cell, sixteen‐cell and midblastula stages, respectively. Control embryos injected at the same stages with Holtfreter's solution developed normally. The results would indicate that de novo protein synthesis is necessary, not just at the midblastula stage, but throughout the entire cleavage period. The results are discussed in light of previous investigations.
The ependymal surface of the lateral ventricle of the dog as revealed by scanning electron microscopy
Authors: Allen Delmas J. , Low Frank N.
Published: February 2005

Young dogs were perfused with buffered aldehydes at fluid pressures approaching normal physiological values. Surface tissue from the temporal horns of the lateral ventricles were prepared for scanning electron microscopy, using postosmication, critical point drying and gold‐palladium coating.

The ependymal surfaces are mostly ciliated but nonciliated areas occur along the medial walls. The latter areas are characterized by depressions, pores, fenestrations and a unique population of supraependymal cells. These polymorphic cells probably represent both conductive (neuronal) and supportive (neuroglial) elements. Adjacent to cilia‐free areas, transitional zones are observed. Here, a net‐like surface pattern consisting of smooth hexagonal cells is outlined by microvilli of varying lengths and isolated tufts of cilia are present.
Fine structure of the venom gland epithelium of the south american rattlesnake and radioautographic studies of protein formation by the secretory cells
Authors: Warshawsky H. , Haddad A. , P. Gonçalves R. , Valeri V. , L. De Lucca F.
Published: February 2005

The South American rattlesnake venom gland is made up of secretory tubules lined by a simple columnar epithelium containing horizontal cells, mitochondria‐rich cells, and the principal cell type, the columnar secretory cells. This cell has a round basal nucleus and abundant rough endoplasmic reticulum, the cisternae of which are variably distended with flocculent material containing many dense intracisternal granules. The supranuclear Golgi apparatus is spherical, with stacks of flattened saccules at the periphery and large vacuoles containing masses of dense material, and other dense granules in the center. Similar but smaller granules are present at the apex where they fuse with the microvillus‐covered apical membrane and release their content into the lumen. Protein synthesis was studied in snakes injected with 3H‐tyrosine and sacrificed at several times after injection. Radioautographs showed reactions at one half and one hour over the ribosomes and membranes of the rough endoplasmic reticulum. At two hours the immature face of the Golgi apparatus was labeled. At four hours Golgi saccules and vacuoles with dense masses (secretory granules) were labeled, and at eight hours the dense masses within the secretory granules were heavily labeled both in the Golgi region and in the apex near the lumen. Labeled material was found in the lumen at two days. Intracisternal granules were first labeled at eight hours, and by two days reactions remained only over the flocculent content and intracisternal granules of the rough endoplasmic reticulum. Thus, venom protein was synthesized on the rough endoplasmic reticulum, migrated through the Golgi apparatus and accumulated in the dense masses of the secretory granules, which moved to the apex and were extruded. The labeling of intracisternal granules at eight hours and two days after injection indicated a storage nature for these granules.
Mucopolysaccharide in the glomerular basement membrane of a hibernator (1)
Authors: L. Zimny Marilyn
Published: February 2005

The glomerular basement membrane in the kidney of a hibernating 13‐lined ground squirrel, when compared with that of a non‐hibernating animal, stains positively with ruthenium red indicating the presence of acid mucopolysaccharide. This increased quantity of anionic material accompanying hibernation may be responsible for maintaining water and electrolyte balance by acting as a resin for the exchange of cations between the capillary and urinary spaces, attracting water and concentrating protein.
Ciliary activity in the human and Macaca nemestrina oviduct
Authors: Gaddum‐Rosse P. , Blandau R. J. , Thiersch J. B.
Published: February 2005

The direction of ciliary beat has been examined in vitro in human and pig‐tailed macaque (M. nemestrina) oviducts. Ducts removed under anesthesia were slit open longitudinally while submerged in Hanks solution at 37° C, and particulate matter was applied to the mucosal surface. Contrary to previous observations in pig and rabbit oviducts, transport of particles was consistently in a downward direction, toward the proximal (uterine) end, in the two species examined in this study.
The atrioventricular valves of the guinea‐pig. II. An ultrastructural study
Authors: Hibbs Richard G. , Ellison Jeffrey P.
Published: February 2005

Each atrioventricular valve of the guinea‐pig consists of a core of connective tissue and muscle covered by endothelial cells. The muscle forms an annulus at the attached margin of the valve adjacent to the fibrous annulus. Some fibers from the lower part of the muscular annulus turn sharply toward the free margin of the valve and form a complex meshwork. These fibers resemble atrial muscle, but are noteworthy in that each contains myofibrils that are oriented in different directions. Some muscle fibers have features similar to those of conducting fibers, i.e., glycogen rich cytoplasm containing few myofibrils. Unmyelinated nerve fibers are numerous in both the mitral and tricuspid valves, but myelinated fibers were found only in the mitral valve. Typical adrenergic terminals were found adjacent to some cholinergic endings. Mitochondria‐filled terminals (sensory?) and a third type of motor terminal were present also. Bundles of collagenous fibers extend from the chordae tendineae into the valve cusps where they fan out into small bundles. The other formed elements of the stroma are microfibrils and a flocculent material. There are a few elastic fibers beneath the endothelium. Interstitial cells, many of which possess solitary flagella are scattered throughout the matrix.
Histochemical changes in developing mouse liver after administration of phenobarbital
Authors: Richards Thomas C.
Published: February 2005

The effects of phenobarbital on development of some microsomal enzymes and neutral lipid were studied in mouse liver during a period of rapid cell differentiation. Specific alterations attributable to phenobarbital were identified in developing liver and used as markers for the onset of certain aspects of cell maturation. This investigation was designed to determine (1) the earliest developmental age at which fetal liver can react to phenobarbital and (2) the nature of the alterations in developing and adult liver.

Intraperitoneal injections of phenobarbital were given for three days to 14, 17 and 19 day pregnant mice. Histochemical techniques were used to localize neutral lipid and the activities of NADPH diaphorase, glucose‐6‐phosphatase, and glucose‐6‐phosphate dehydrogenase. Total cell lipid was measured in livers from 17‐ and 19‐day pregnant mice and livers from their fetuses.

The density of reaction product for NADPH diaphorase and glucose‐6‐phosphate dehydrogenase increased while glucose‐6‐phosphatase decreased in adult liver. Similar changes were seen in livers from day‐19 fetal animals but not in fetuses of younger ages. Neutral lipid droplets increased in size and number after phenobarbital in fetal mice of day 19 of gestation but not in mice of day 17 of gestation.

It was concluded that liver from day‐19 fetal mice had gained the competence, lacking in earlier ages, to respond to phenobarbital by increased production of some enzymes and neutral lipid.
The corticotroph of the rat adenohypophysis: A comparative study
Authors: Bowie E. Phyllis , Williams Glenn , Shiino Masataka , Rennels Edward G.
Published: February 2005

The immunological and cytological specificity of antiserum to adrenocorticotrophic hormone was established and the corticotroph defined at the light microscopic level by immunocytochemistry. Our observations substantiated recent reports by several investigators. By comparing thin methacrylate sections with adjacent 1 μ‐methacrylate sections immunochemically stained with anti‐ACTH, the ACTH cell was identified at the ultrastructural level and its morphology studied. Using the criteria established at light and electron microscopic levels, the corticotroph was readily found in tissue which had been fixed in paraformaldehyde‐osmium mixture and embedded in epoxy resin. Ultrastructural changes in this cell in response to experimentally designed alterations in the pituitary ACTH levels confirmed this identification. The ACTH cell was likewise identified in glutaraldehyde‐fixed material. Thyrotrophs were tentatively defined. Several ultrastructural studies responsible for conflicting reports in the literature were investigated. It was concluded that the corticotroph is a unique cell type and that granule size and morphology remain important criteria for adenohypophyseal cell identification regardless of the fixation used. The need for a definitive immunocytochemical study of thyrotrophs at the ultrastructural level was recognized.
Enzymatic digestion of presynaptic structures in electroreceptors of elasmobranchs
Authors: Szamier R. Bruce
Published: February 2005

Sites of synaptic transmission between receptor cells and afferent nerves in electroreceptors of elasmobranchs are distinguished by a dense presynaptic ribbon surrounded by synaptic vesicles. Digestion by pronase or protease of thin sections of Epon embedded tissue selectively removes the presynaptic ribbon without affecting other synaptic structures. Presynaptic ribbons are composed in part of protein which differs significantly from other components of the synaptic complex.
The fine structure of monkey sertoli cells in the transitional zone at the junction of the seminiferous tubules with the tubuli recti
Authors: Dym Martin
Published: February 2005

The monkey testis contains an axial rete in a highly vascular central core of loose connective tissue. Seminiferous tubules join the rete along its entire length. The short terminal segments of the tubules are lined mainly by Sertoli cells. There is then a transition from Sertoli cell epithelium to the simple cuboidal epithelium of tubuli recti, which connect the seminiferous tubules to the rete testis.

Electron microscopic observations of the Sertoli cell in the terminal regions of the seminiferous tubules reveal a highly lobulated nucleus, a unique nucleolus and a columnar cell body with an irregular free surface bearing processes of varied form projecting into the tubule lumen. The cytoplasm is characterized by a well developed rough endoplasmic reticulum, large numbers of lipid droplets, and an extraordinary abundance of 70 Å filaments. Occasionally these latter are so densely packed that other organelles are excluded from large areas of the cytoplasm. Profiles of smooth endoplasmic reticulum are few in marked contrast to the usual condition of Sertoli cells elsewhere in the seminiferous tubules.

Many of the Sertoli cells in the terminal regions of the seminiferous tubules contain spermatozoa in various stages of degradation. Small lymphocytes, never observed in normal seminiferous tubules, are distributed in small numbers among the Sertoli cells of the transitional zone. No desmosomes or other junctional specializations are observed at the interface of lymphocytes with the surrounding Sertoli cells. The cytology of the terminal region of the seminiferous tubules is discussed in relationship to exit of sperm from the tubules, the blood‐testis barrier, and the pathogenesis of immune orchitis.
“Caveolated cells” characterized by deep surface invaginations and abundant filaments in mouse gastro‐intestinal epithelia
Authors: Nabeyama A. , Leblond C. P.
Published: February 2005

Light and electron microscope examination of gastro‐intestinal epithelia in the adult mouse revealed the widespread presence of a cell type characterized by deep surface invaginations or “caveolae” and, accordingly, called “caveolated cell.”

The caveolated cells are scattered within the epithelia of stomach, small and large intestine; they have a narrow apex bordering the lumen and a wide base in contact with the basement membrane. In the light microscope, they display microvilli longer than in nearby cells; the cytoplasm is usually pale and contains an apical group of parallel fibrils, next to which are minute light spaces which may correspond to the caveolae. In the electron microscope, each fibril is found to be composed of a bundle of straight filaments, extending from the core of a microvillus down into the deeper portion of the supranuclear region; microtubules are often associated with these filaments. Filaments of a different type are arranged in bundles which go from desmosome to desmosome around the apical region of the cell. The caveolae are long and tortuous channels opening at the cell surface between the microvilli and extending deep into the cytoplasm. From the walls of caveolae, polyp‐like structures project into the lumen. The heads of the polyps are believed to be released into this lumen where they appear as small spheres. These in turn may come out of the caveolae to appear between and next to the microvilli.

Caveolated cells are not numerous, e.g., they make up less than 1% of the epithelial cells in the crypts of descending colon. They may be found in the intestinal crypts among poorly differentiated cells, and at the surface of stomach and intestine among fully differentiated cells. They appear to undergo renewal, but since they have not been seen in mitosis, they probably arise from the differentiation of some other epithelial cells.
Changes in the mucosa of the small intestine following methotrexate administration or abdominal X‐irradiation
Authors: Altmann G. G.
Published: February 2005

Adult male rats received 5 mg methotrexate daily and were sacrificed 1, 1.5, 2, 2.5 and 3 days after the beginning of the treatment. Other groups received 9,000 rads of abdominal x‐radiation and were sacrificed 1, 2 and 3 days later. Histological samples were taken from five regions of the small intestine and processed for light microscopic examination. Average area occupied by the crypts and the villi respectively, was measured per unit length of histological section. A few animals received 3H‐thymidine an hour before the methotrexate treatment or irradiation; the histological samples were processed for radioautography.

Significant mitotic activity was absent throughout the experiments. During the first 1.5 days, mainly the crypts diminished. Radioautography revealed that migration of crypt cells to the villi continued during this time. During the second and third days, the villi also showed marked diminution, and cell migration became irregular. In general, the histometric data were similar after methotrexate and irradiation. Epithelial denudation started in terminal ileum on the third day after methotrexate. The epithelium was much reduced but not yet denuding at this time in the irradiated animals.

Methotrexate inhibition of DNA and RNA synthesis was assumed to be associated, respectively, with mitotic inhibition and with a decline of protein synthesis which manifested itself in villus diminution. Survival of epithelial cells varied presumably according to the amount of RNA pool and was longest in cells being in the S‐phase at the onset of the treatment. The similarity of the data after irradiation implied a similar sequence of events.
Hepatic glycogen patterns in fasted and fed rats
Authors: Babcock Muriel B. , Cardell Robert R.
Published: February 2005

Hepatic glycogen patterns are described for rats adapted to a precisely controlled feeding schedule and ad libitum fed rats. Liver samples were processed for biochemical and histochemical glycogen analysis at precise intervals following a 22 hour fast and a 2 hour meal. Histochemical determination of glycogen (PAS) after freeze substitution showed lobular patterns of hepatic glycogen which correlate with chemically determined glycogen levels and nutritional states of the rats. After 22 hour fasting, hepatocytes from rats with low glycogen levels (< 0.09%) exhibited no significant staining. In control fed rats, feeding caused glycogen deposition throughout the lobule but in greatest concentration centrilobularly throughout the early phases of glycogen accumulation. As glycogen deposition continued, periportal lobular patterns were observed in rats with high glycogen levels (> 5%). Glycogen depletion reduced glycogen staining in cells throughout the lobule, but centrilobular patterns prevailed until late in depletion when periportal patterns appeared. Ad libitum‐fed rats showed similar glycogen patterns except maximum deposition was characterized by centrilobular or even lobular distribution of glycogen, and periportal patterns of glycogen were seen only rarely in extreme fasted rats. Differences in lobular patterns between ad libitum and control fed rats is apparently related to lower maximum hepatic glycogen levels reached by ad libitum‐fed animals.
Studies on the response of the adult newt kidney to partial nephrectomy
Authors: Scadding Steven R. , Liversage Richard A.
Published: February 2005

The response of the kidneys of 237 adult newts [Notophthalmus (Diemictylus) viridescens] to partial nephrectomy (15 to 30% of right kidney removed) and sub‐total nephrectomy (70 to 90%) was studied histologically and autoradiographically to determine their regenerative potential. The response involved both hypertrophy and hyperplasia as indicated by increases in 3H‐thymidine labelled nuclei and also 3H‐leucine incorporation by the remaining cells of the kidney. Leucine incorporation increased within 24 hours and continued to increase until 5 days after partial nephrectomy (17% increase over control level) or 15 days after sub‐total nephrectomy (36% increase). The number of thymidine labelled nuclei, however, did not increase for the first 5 days and then continued to increase up to 10 days after partial nephrectomy (to 3X control level) and 20 days after sub‐total nephrectomy (to 5X control level).

An accumulation of cells appeared on the cut surface of the kidney by 15 to 20 days after nephrectomy. It consisted of modified epithelial cells from the tubules and was characterized by marked basophilia. The number of 3H‐thymidine labelled nuclei in the accumulation increased about 10 to 20 times over control levels at its peak on days 12 to 15; 3H‐leucine incorporation doubled at its peak on days 10 to 15. Nevertheless, after day 20 the cell accumulation decreased in size due to cell resorption or sloughing or both; it had disappeared by day 50 with no new tissue resulting. The newt kidney does not appear to exhibit any regenerative potential and, therefore, it is similar to mammalian kidneys in this respect.
The fetal membranes and unusual giant cell placenta of the jerboa (Jaculus) and jumping mouse (Zapus)
Authors: King Barry F. , Mossman Harland W.
Published: February 2005

The development of the fetal membranes of the North African jerboa (Jaculus) and the North American jumping mouse (Zapus) were examined by light microscopy, and the interhemal membrane of Zapus was studied by electron microscopy. Early stages of Jaculus show implantation to be antimesometrial with the embryonic disc oriented mesometrially. Amniogenesis is by folding and there is a distinct epamnionic cavity. Yolk sac inversion is complete, but the disappearance of the parietal segment occurs relatively late, during the early fetal period. Those early stages of Zapus which were available indicated a close similarity to Jaculus. Both Jaculus and Zapus are unusual in the manner of development and composition of the chorio‐allantoic placenta. Development of cytotrophoblast and syncytiotrophoblast is arrested early and these layers eventually disappear. Trophoblastic giant cells migrate into the allantoic mesenchyme to form the maternal blood channels of the labyrinth. In Jaculus, a complex interdigitation exists between yolk sac villi and arterial channels bringing maternal blood to the labyrinth. This relationship is much less intimate and extensive in Zapus. Electron microscopic examination of the interhemal membrane of Zapus shows it to be hemomonochorial, its only trophoblastic element being the giant cell cytoplasm. Thus, the Zapus placenta is to date one of very few hemochorial placentas known to lack trophoblastic syncytium in its interhemal membrane. Comparison of the total development and structure of the fetal membranes in these two genera with that of other rodents indicates that the membranes of the Dipodoidea, like the Geomyoidea, are intermediate in type between those of the Sciuromorpha and Myomorpha.
Autoradiographic localization of 3H‐testosterone or its metabolites in the neonatal rat brain
Authors: Sheridan Peter J. , Sar Madhabananda , Stumpf Walter E.
Published: February 2005

The distribution of neurons which concentrate testosterone or its metabolites in the brain of 2‐day old female rats was determined using autoradiography. A specific topographic pattern of neurons which concentrate testosterone or its metabolites was obtained similar, but not identical, to the one found in adult male rats. The demonstrated sites of nuclear uptake and retention of testosterone or its metabolites by specific neurons in the neonatal brain probably provide the anatomical substrate for sexual differentiation of the brain.
A cytochemical and radioautographic analysis of erythropoiesis at the ultrastructural level
Authors: Rosse Cornelius , Trotter John A.
Published: February 2005

The morphogenetic events of erythroid differentiation in guinea pig bone marrow were studied by electron microscopy. The diaminobenzidine (DAB) reaction and radioautographic detection of Fe55 incorporation permitted a more objective identification of erythroid cells than was possible in previous studies. With the combined use of these two methods morphological events of cell maturation could be correlated reliably with cytoplasmic hemoglobin content, thus providing a basis for the description of various maturation stages.

The oxidation of DAB by hemoglobin coupled with OsO4 treatment results in a generalized increase in cytoplasmic electron opacity proportional to the amount of hemoglobin present. Measurements of cytoplasmic density were carried out on electron microscopic negatives of DAB‐reacted specimens that were not stained otherwise. Only those cells were regarded as erythroblasts in which the cytoplasm was at least twice as dense as in recognizable, differentiated, non‐erythroid cells, using reticular cell cytoplasm in each specimen as the base line for the comparisons.

In bone marrow cells, iron incorporation occurred overwhelmingly for hemoglobin synthesis. In normal marrow, blast cells which incorporated iron but did not contain hemoglobin in detectable amounts were defined as Stage I erythroid cells. They were morphologically of the same type as erythroblasts with the minimum amount of detectable hemoglobin (Stage II). Cells in maturation stages of progressively increasing hemoglobin content were assigned to Stages III to V. Stage III erythroblasts correspond morphologically to proerythroblasts of light microscopic preparations. The DAB reaction in them was obvious without densitometric measurements but remained mottled.

The morphological characteristics of each of the maturation stages are described with particular emphasis on the earliest erythroid cells, since the methods employed permit their identification with greater degrees of discrimination and objectivity than is possible with the light microscope or with conventional methods of electron microscopy.

The DAB reaction was positive in the heterochromatin in Stages III and IV but it was negative in the pyknotic chromatin of erythroblasts in Stage V of maturation. The predominantly extended chromatin and also the large and complex nucleoli of earlier cells began to condense during Stage IV. Silver grains due to Fe55 disintegration were observed over the nuclei of erythroblasts in all maturational stages.

The perinuclear cisterna was DAB‐negative and it became wider as maturation progressed. It was bridged in places by DAB‐negative material connecting the cytoplasm to euchromatic areas of the nucleus. DAB‐positive substance was not seen in nuclear pores at any stage of maturation. At the time of extrusion, nuclei did not contain DAB‐positive material but were occasionally labeled with Fe55.
Constant occurrence of adrenocortical tissue in the juvenile rabbit ovary
Authors: Mori Hiroshi , Matsumoto Keishi
Published: February 2005

Adrenocortex‐like cells were consistently found in the mesovarium or in the hilus of the ovary of rabbits less than three months old. The adrenocortex‐like cells occurred usually in the form of nodules among or near the mesonephric tubules. But they sometimes appeared within the rete ovarii either in direct contact with the epithelial cells or scattered in the stroma. Similar cells were newly formed in the ovarian medulla of one‐month‐old rabbits following injection of ACTH (adrenocorticotropic hormone).

Electron micrographs showed that the adrenocortex‐like cells characteristically had a well developed agranular endoplasmic reticulum and mitochondria containing tubular cristae which were arranged in villiform fashion. In addition, most endothelial cells of the capillaries among the adrenocortex‐like cells had fenestrations. The enzyme activity of 3β‐hydroxysteroid dehydrogenase was histochemically demonstrated only in the identical cells of one‐month‐old rabbits. It was concluded, therefore, that the adrenocortex‐like cells in the rabbit ovary were actually adrenocortical cells.

This morphological conclusion was confirmed by the biochemical demonstration of 11β‐hydroxylase, an enzyme specifically found in the adrenal cortex. The ovarian tissue, including the mesovarium from one‐month‐old rabbits, was capable of converting progesterone to corticosterone.
Light and electron microscopic studies of retzius lines in human cervical enamel
Authors: Weber Dennis F. , Eisenmann Dale R. , Glick Paul L.
Published: February 2005

Unaltered mature enamel and partially demineralized mature enamel from the cervical third of human permanent teeth were examined by means of transmission electron microscopy, microradiography, phase contrast and Nomarski differential interference microscopy. The Retzius lines in the outer third of the cervical enamel had a staircase configuration. The steps in the stair‐case pattern formed the bases of triangular regions which were radiolucent and ultrastructurally contained fewer crystallites than the adjacent enamel. In the outer prismless layer, the Retzius lines had a curvilinear configuration and were also crystallite deficient. The structure of the Retzius lines in the inner portion of the cervical enamel was not nearly as well defined.
Cell types in cutaneous type I mechanoreceptors (Haarscheiben) and their alterations with injury
Authors: English Kathleen B.
Published: February 2005

Type I mechanoreceptors (also called Haarscheiben or “domes”) are small elevations on the cat's skin, each being supplied by a myelinated sensory fiber. The fiber terminates in apposition to specialized receptor cells (Merkel cells) lying at the base of the epithelium investing the structure. When a group of domes was injured some of the neighboring domes became structurally altered as determined by light and electron microscopy. The changes observed resembled those which accompany denervation and involved the loss of Merkel cells and their apposed sensory nerve terminals from the dome. Since this trauma was produced indirectly it has been called secondary injury. Cells showing some of the morphological features of both keratin‐producing epithelial cells and Merkel cells were observed in secondarily injured domes and in non‐injured domes. The presence of such transitional cells suggests that Merkel cells may be derived from keratinocytes.
The permeability to carbon of the sinusoidal lining cells of the embryonic rat liver and rat bone marrow
Authors: Bankston Patrick W. , De Bruyn Peter P. H.
Published: February 2005

This study is concerned with the passage of carbon particles through the sinusoidal lining cells of bone marrow and embryonic liver of the rat. A carbon suspension (Pelikan C11/1431A, Günther Wagner, Hanover) diluted 1:1 with double strength Tyrode solution, was administered through the aorta for the bone marrow studies and through the umbilical vein for observations on the embryonic liver. The carbon particles have a diameter ranging from 220 to 380 Å with a mean diameter of 280 Å. Within three minutes after the injection, the particulate was present in the extravascular spaces. Neither the sinusoidal walls of the bone marrow nor of the embryonic rat liver prior to 16 days gestation have preformed apertures. In both cases, the carbon particles enter the extravascular space through fenestrae with diaphragms. No carbon particles occur in the junctional spaces between the lining cells. The temporary pores caused by diapedetic blood cells maintain a tight seal and no particulate was observed leaving the vascular space at these sites. At 17 days of gestation, open gaps develop in the endothelial lining of the embryonic rat liver and particulate material leaves the vascular lumen through these openings. The presence of bristle‐coated vesicles containing particulate material at the abluminal side of the lining cells is interpreted as a retrograde uptake by these phagocytic cells rather than as evidence for vesicular transmural transport.
The mode of origin of pulmonary acini and respiratory bronchioles in the fetal lung
Authors: Boyden Edward A.
Published: February 2005

Between the 50th day of embryonic life

Stage 20 (O'Rahilly and Boyden, '73; Wells and Boyden, '54).

and the 30th week of gestation no reconstructions of the developing parenchyma of the human lung seem to have been attempted. To bridge this long gap, only two techniques have been utilized hitherto: counting the generations of branches in the growing segments of the lung and analyzing the changing cytology with the aid of the electron microscope. At least two important objectives remain: a knowledge of when the respiratory units known as pulmonary acini appear and the order in which capillary invasion of its component parts takes place.

At the 16th week of gestation, peripheral units have not attained their full complement of branches and their boundaries are not delimited. At 17 weeks, acini of varying sizes can be recognized as discrete terminal units at the periphery of the segmental trees, having attained their full, though underdeveloped, complement of fetal branches, as gauged by later counts of generations made at 30 weeks of age (Boyden, '69). The 17th is also the week in which capillaries first invade the peripheral branches of the acinus. Although significantly later stages have not yet been obtained, the evidence available (including that from unpublished work on monkey fetuses) strongly suggests that canalization (before birth), like alveolization (after birth)

Boyden and Tompsett, '65; Boyden, '67.

proceeds mainly in a centripetal direction.
Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine I. Columnar cell
Authors: Cheng Hazel , Leblond C. P.
Published: February 2005

The columnar cells, i.e., the cells which contain neither mucous globules, nor entero‐endocrine granules, nor Paneth type secretion, were investigated independently of other cells in duodenum, jejunum and ileum using light and electron microscopy as well as radioautography in mice sacrificed at various times after single injection or continuous infusion of 3H‐thymidine.

The columnar cells exhibit local differences allowing their classification into four sub‐groups: (a) The crypt‐base columnar cells are immature proliferative cells occupying the nine lowest cell positions of the crypt on the average. (b) The mid‐crypt columnar cells occupy the next positions up to 19 in ileum and 27 elsewhere; they proliferate and show features gradually changing from undifferentiated ones near the base to partially differentiated ones higher up. (c) The crypt‐top columnar cells occupy the rest of the crypt; they do not divide but they continue to differentiate. (d) Finally, the villus columnar cells are fully differentiated absorptive cells.

Cryp‐base and mid‐crypt columnar cells take up 3H‐thymidine label prior to division. With time after a 3H‐thymidine injection, the intensity of their labeling decreases, while heavily labeled columnar cells appear in crypt‐top by six hours and on the villus by 12 and more hours. Hence, columnar cells migrate. The migration is associated with gradual differentiation from the immature crypt‐base columnar cells to the mature villus columnar cells. The latter eventually reach the villus tips where they drop into the lumen.

The columnar cells constitute a large majority of the epithelial cells (95, 94 and 89% in duodenum, jejunum and ileum, respectively). Hence, they are likely to play a key role in the renewal of the epithelium in the three regions of the small intestine. The turnover time of columnar cells estimated from results of continuous 3H‐thymidine infusion is 3.3 days in duodenum and 3.4 days in jejunum.

Evidence from turnover time data indicates that the mitoses of columnar cells produce more cells than required for their own renewal. Presumably some of the mitoses give rise to cells of a type other than columnar.
Microappendages on the ventral surface of the primitive streak chick embryo
Authors: Harri James E. , Low Frank N.
Published: February 2005

Fresh pullet eggs (White Leghorn Strain) were incubated to obtain the primitive streak stage of development. Blastoderms were fixed in situ with isotonic aldehyde fixatives and prepared for scanning electron microscopy by means of postosmication, critical point drying and gold‐palladium coating.

The ventral surface of the chick blastoderm exhibits extreme pleomorphism. There is variation among microappendages (microvilli, blebs, ruffles) which tend to define cellular outlines. In recessed areas adjacent to the ventrolateral aspect of the primitive streak microappendages are present in great profusion. Here clusters of them possess intricate physical relationships. Microvilli may arise from either blebs or ruffles. Other microvilli may terminate in blebs. Extensive connecting structures are present. The primitive streak chick embryo is discussed as a model for the study of microappendages of the plasmalemma.
Intrapulmonary airway morphology in three species of monkeys: A correlated scanning and transmission electron microscopic study
Authors: Castleman W. L. , Dungworth D. L. , Tyler W. S.
Published: February 2005

Intrapulmonary airways were studied in rhesus (Macaca mulatta), stumptail (Macaca arctoides), and bonnet (Macaca radiata) monkeys by correlated scanning and transmission electron microscopy. Lobar, segmental, and subsegmental bronchi in all three macaques were lined by pseudostratified columnar epithelium composed primarily of ciliated cells, mucous cells, and basal cells. Neuronal processes and cells containing dense‐core vesicles were also observed. Terminal bronchioles in rhesus and stumptail monkeys were short and only developed to a single generation. Terminal bronchioles were moderately longer in bonnet monkeys and were occasionally developed to two generations. Terminal bronchioles in bonnet and stumptail monkeys were lined by ciliated pseudostratified columnar epithelium which included nonciliated bronchiolar epithelial (Clara) cells. The arrangement of epithelium in terminal bronchioles differed slightly in rhesus monkeys. All three species had long respiratory bronchioles. They were lined by simple, nonciliated cuboidal and squamous epithelium which usually did not contain secretory droplets. Capillaries were often observed immediately below the luminal epithelium. Cuboidal cells containing dense‐core vesicles were a rare component of the epithelium of respiratory bronchioles in stumptail monkeys. Alveolar ducts were lined by an epithelium composed of type I and type II cells. The results of this study indicate that there is general similarity in the mucosal structure of bronchi and respiratory bronchioles between macaques and man but that there are differences in the number of generations and epithelial lining of terminal bronchioles.