bluuebunny/crossref_metadata_2025 huggingface dataset:
Hair growth in skin grafts placed on hairless mice
Authors: Argyris Thomas S. , Argyris Bertie F.
Published: February 2005

The purpose of this study is to investigate the possibility that hair growth is triggered by the loss of a specific hair follicle inhibitor.

If the loss of an inhibitor is a sufficient cue for the triggering of hair growth, then hair follicles in skin grafts placed on hairless mice should remain in the growth phase of the hair growth cycle, and never enter the resting phase. This would be expected because hairless skin has no hair follicles, and therefore presumably produces no hair follicle inhibitor itself. Thus, no build‐up of a hair follicle inhibitor within the graft should occur.

Female hairless mice (HRS/J) approximately 60 days of age received skin grafts from haired female litteremates. These skin grafts took well and remained healthy throughout the period of investigation, which ranged from 240–380 days.

The hair follicles of the grafts undergo cycles of growth and rest. They may remain in the resting phase for as long as two to three months. Therefore, hair follicles of grafts placed on the backs of the hairless mice do not remain permanently in the growth phase of the hair cycle.

Additional experiments help rule out the possibility that (1) the lack of continuous hair growth of the hair follicles in the grafts is due to the scar preventing the diffusion of inhibitors from the graft into the host skin, and (2) that the hair follicle remnants in the host hairless skin produce a hair follicle inhibitor in sufficient concentration so that the hair follicles of the graft enter the resting phase.
The fine structure of secretory granules in submandibular glands of the rat during early postnatal development
Authors: Kim S. K. , Han S. S. , Nasjleti C. E.
Published: February 2005

The secretory end‐pieces of the submandibular gland of rats during the first week of postnatal development are studied with regard to the fine structure of the secretion granules in these end‐pieces. The terminal ends of the secretory ducts during this period consist of two types of cells; one cell is an acinar‐type and the other is a duct‐type found in the gland of adult rats. The secretion granules of the acinar‐type cells are similar in appearance to those of the acinar cells in the gland of adult rats, and the structure of these granules remains the same throughout the week. However, granules widely different in appearance are present in the duct‐type cells, and their structure varies in different cells as well as within a single cell at different stages of development. These granules contain unusual substructures which are not found in the secretion granules of adult rats, suggesting that the granules are transitory. Granules containing short tubular profiles are predominant in the gland of one day‐old rats. A large number of granules in three day‐old rats contain elongated tubules. More granules of widely different substructures are present in the gland of seven day‐old rats than in the gland of younger rats. The matrix of the granules in seven day‐old rats is of higher density than that of the granules in younger rats. In the dense matrix of these granules, less dense tubules form fingerprint‐like or somewhat more irregular patterns.
The connections of the intra‐osseous segment of the facial nerve in baboon (Papio sp.)
Authors: Vidić Branislav
Published: February 2005

To supply some additional data about the intra‐osseous connections of the seventh nerve in a potentially available experimental animal, the baboon, 16 neuromuscular complexes (otic ganglion, nerve which results from the junction between the lesser petrosal nerve and the and the communicating branch, lesser petrosal nerve, communicating branch, initial part of the greater petrosal nerve, all three intra‐osseous parts of the facial nerve, stapedius muscle, auricular branch of the vagus) were macroscopically evaluated with the aid of a microdissecting scope, and removed in toto. Two dissections were achieved only partially. Each neuromuscular complex was fixed in 5% formalin, dehydrated, embedded in paraffin, sectioned serially at 10 to 15 μ, and either stained with Luxol Fast Blue or impregnated by Bodian's silver technique. In all specimens considered, the auricular branch of the vagus, before it joined the descending intra‐osseous part of the facial nerve, gave off an ascending bundle. This bundle sent a few ramifications to the stapedius muscle and finally mixed with axones in the intra‐osseous segment of the seventh nerve close to the second facial genu. The fibers in the ascending bundle were predominately myelinated with a diameter varying from 1.7 μ to 9.9 μ. The communicating branch proper separated from the fibers of the second intra‐osseous part of the facial nerve, and continued anteriorly through the sheath toward the geniculate ganglion. From there, the branch as an isolated bundle extended further anteriorly to reach the otic ganglion, after it joined the lesser petrosal nerve. The number of fibers in the communicating branch ranged from 50 to 580, and the diameter of myelinated fibers varied between 1.7 and 4.4 μ. Numerous ganglion cells, presumably of the autonomic type, found in the communicating branch, in the lesser petrosal nerve, and occasionally in the second intra‐osseous part of the facial nerve resembled by their form and diameter the ganglion cells in the otic ganglion.
The non‐fibrous nature of the von Korff fibres in developing dentine. A light and electron microscope study
Authors: Cate A. R. Ten , Melcher A. H. , Pudy G. , Wagner D.
Published: February 2005

First molar tooth germs were dissected from one‐ and seven‐day‐old mice, fixed in gluteraldehyde and impregnated in bulk using silver nitrate for the demonstration of reticulin. After impregnation the tooth germs were embdded in Epon, and thin sections cut for examination with both the light and electron microscope. Control tooth germs were prepared similarly, but were not impregnated with silver. Light microscopic examination showed the classical picture of von Korff fibres. These were associated with the formation of mantle dentine. von Korff fibres were not found associated with forming circumpulpal dentine. Examination of successive sections with the electron microscope showed silver particles between the widely separated, newly differentiated, odontoblasts. In forming circumpulpal dentine, the odontoblasts were closely aligned and no silver particles were found in the now narrowed extracellular spaces. Examination of control sections revealed that the extracellular compartment between the newly differentiated odontoblasts consisted of ground substance and a few sparse collagen fibrils which were too small to be resolved with the light microscope. It is considered that the “von Korff fibres” seen with the light microscope represent silver impregnation of the extracellular material, which is mainly ground substance, in the continuum between the widely separated odontoblasts.
Intracristal helices in salivary gland mitochondria
Authors: Hand Arthur R.
Published: February 2005

Helical filaments have been found within dilated intracristal spaces of normal rat salivary gland mitochondria. Filament diameter measured 35–45 Å, and the helix diameter and pitch were 140–155 Å. They were found in as many as 25% of the mitochondria of acinar and intercalated duct cells. Helices were not found in mitochondria of the striated duct cells.
Tissue cholesterol preservation: Solubility of cholesterol digitonide in ethanol
Authors: Sterzing Peter R. , Scaletti Joseph V. , Napolitano Leonard M.
Published: February 2005

The solubility of purified cholesterol digitonide in absolute and aqueous ethanols was investigated. The results indicate that preservation of cholesterol (or other 3‐B‐hydroxysterols) in tissues prepared for electron and light microscopy by digitonin‐containing fixatives may not be quantitative when ethanol and, in particular, absolute ethanol, is used for dehydration.
The histophysiology of rat plantar sweat glands
Authors: Munger Bryce L. , Brusilow Saul W.
Published: February 2005

The plantar sweat glands of the rat have been studied by light and electron microscopy. These glands differ from conventional eccrine sweat glands of man, other primates, and cats in that the secretory segment contains only one type of secretory cell. This cell is characterized by a relatively nondescript cytoplasm containing numerous vesicles, extensive interdigitations of adjacent plasma membranes and small microvilli projecting into the lumen. In the resting gland, two types of cells can be distinguished on the basis of mitochondrial morphology. Some cells contain mitochondria in condensed configurations, and others contain mitochondria in the more orthodox configuration. Following stimulation, these differences are not pronounced; and the condensed mitochondria have evidently changed into more orthodox mitochondria in appearance. No distinct cytologic pathway for secretion could be defined, correlated with the most unusual ionic composition of the sweat in this animal (very high levels of potassium). The sweat glands of the rat foot pad then are unique as compared with other cutaneous glands both in their cytologic appearance and in the chemical composition of the sweat they elaborate.
Ultrastructural differentiation of the endodermal cells of the yolk sac of the bat, Tadarida brasiliensis cynocephala
Authors: Stephens R. J. , Easterbrook N.
Published: February 2005

In Tadarida, the endodermal cells that form the yolk sac originally delaminate from the inner cell mass and proliferate to form a complete lining of the trophoblastic vesicle, creating a bilaminar omphalopleure. These cells remain squamous until the splanchnic mesoderm migrates in between the two layers of the omphalopleure, at which time they begin to hypertrophy. The current study is an analysis of the cytological changes that accompany this hypertrophy as well as additional changes that occur throughout the remainder of the gestation period. Among the early changes are: (1) the formation of numerous microvilli along the apical surface of the cells, (2) the appearance of coated vesicles, also along the apical plasma membrane, (3) the establishment of a system of absorption tubules in the apical cytoplasm, (4) an increase in mitochondria, and (5) the appearance of glycogen within the channels of the membranous organelle.

A wave of hematopoietic activity follows the migration of splanchnic mesoderm around the trophoblastic vesicle, and at this time the erythroblasts and embryonic erythrocytes can be seen in a close relationship with the endodermal cells.

Subsequent changes include the enlargement of the membranous organelle and the appearance of a paracrystalline membranous structure. In addition, the endodermal cells store large quantities of lipid and glycogen that are substantially depleted just before birth.
The common cardinal veins in the chick embryo: Their origin and development as studied by radioautographic mapping
Authors: Rosenquist Glenn C.
Published: February 2005

The origin of the common cardinal veins (CCVs) in the chick embryo was traced by radioautographic mapping of the movements of tritiated thymidine‐labeled grafts excised from head process to three somite stage embryos and transplanted to the endoderm‐mesoderm layer of similarly staged recipient embryos.

At the head process stage the CCV cells are migrating anteriorly and laterally from the streak in the lateral plate, posterolateral to the cells which will form the pulmonary veins and aortic arches, posterior to the cells destined for the ventricular septum, and dorsal to the liver mesoderm cells. At the 15–17 somite stage, the CCV cells are in the somatic mesoderm of the lateral mesocardium, where an anastomosis between the CCVs and heart establishes channels needed for the efficient return of blood from the various embryonic venous tributaries. This investigation suggests that during the stages studied, the cells which will form the anterior portion of each CCV are positioned anterior to the cells which will form the posterior portion of each CCV.
Arterial supply of the cervical spinal cord (with special reference to the radicular arteries)
Authors: Chakravorty Binoy G.
Published: February 2005

Arterial supply of the cervical spinal cord has been discussed with special reference to the radicular arteries. Thirty‐one human spinal cords have been studied with postmortem positive pressure injection techniques using coloured, and radio‐opaque media. Observations concluded that radicular arteries were main sources of supply to spinal cord except at the highest segments (C1C2C3), where intracranial vertebral branches contribute. Average number of significant radicular arteries is two or three, in two‐thirds of the specimens only one was present. These feeding radicular arteries usually enter into the spinal canal through the intervertebral foramina accompanying C4C5C6 nerve roots to join the anterior and posterior spinal arteries. Anterior, and posterior spinal arteries are probably of segmental origin, and there is only a sparse anastomosis between them. The common radicular artery divides into an anterior, and a posterior branch of which one predominates in size. Cervical radicular arteries may originate from subclavian branches other than vertebral, of these ascending cervical branch of thyrocervical trunk is most important. A terminal zone probably exists at highest thoracic segments where craniocervical, and thoracic radicular flows meet. The filling of the anterior spinal trunk in the cervical region depends on the availability of at least one major anterior radicular artery. Interruption of radicular supply may be precipitated by trauma, spondylosis and other lesions resulting into ischaemia, and myelopathy; the risk is greater if there is only one radicular artery which is involved.
The development of the periodontium. A transplantation and autoradiographic study
Authors: Cate A. R. Ten , Mills C. , Solomon G.
Published: February 2005

First molar tooth germs were dissected from one‐day‐old mice; placed for one hour in McCoy's medium containing 10 μc tritiated thymidine and transplanted subcutaneously into young adult animals of the same strain. Seven, 14, 21 and 28 days after implantation the host animals were sacrificed and the transplants harvested. The transplants were then serially sectioned and autoradiographs prepared. Control sections were prepared of first molar tooth germs in situ, after dissection from the jaws and after labelling with tritiated thymidine. Forty‐nine of the 115 transplanted tooth germs continued development with the formation of enamel, dentine, cement, periodontal ligament and bone. In some instances the transplanted tooth germs “erupted” through the skin with the establishment of an epithelial attachment. Examination of control sections showed that the transplants consisted of dental organ, dental papilla and a layer of ectomesenchymal cells continuous with the dental papilla and investing the dental organ. Examination of autoradiographs of the transplants showed labelling of cementoblasts and periodontal ligament fibroblasts, thereby establishing their origin from the ectomesenchymal cells investing the tooth germ.
Transport and barrier function in the chorioallantoic placenta of the bat, Myotis lucifugus
Authors: Enders Allen C. , Wimsatt William A.
Published: February 2005

The chorioallantoic placenta of the bat (Myotis lucifugus) is hemodichorial and has an ectoplasmic layer and an intrasyncytial lamina interposed between the maternal blood space and the underlying endoplasmic portion of the syncytial trophoblast. The barrier and/or transport function of the trophoblast of this species was investigated. When Thorotrast was injected into the maternal vascular system, only small amounts appeared in the trophoblast, and it could not be demonstrated deep to the syncytial trophoblast.

Injected peroxidase and ferritin were both rapidly taken up by the trophoblast, these tracers being found in coated vesicles and tubules, in multivesicular bodies, and in dense bodies. Peroxidase was transported across the trophoblast and could be found in macrophages in the fetal connective tissue and in vesicles in the fetal endothelium. Since ferritin is present in the cytotrophoblast, macrophages and fetal endothelium in uninjected as well as injected animals, the exogenous material could not be followed beyond the syncytium. In addition to demonstrating the cytological pathway by which absorbed proteins cross the trophoblast of the chorioallantoic placenta of the bat, the results of this study suggest that the labyrinth in this species should be considered a possible route for passage of endogenous proteins to the fetus.
Neuroglial population in the spinal white matter of neonatal and early postnatal rats: An autoradiographic study of numbers of neuroglia and changes in their proliferative activity
Authors: Gilmore Shirley Ann
Published: February 2005

The temporal pattern of increase in number of neuroglia in spinal cord white matter and the amount of multiplication in situ of these cells were studied in rats ranging from less than 12 hours following birth to 30 days of age. Autoradiographs of sections from animals killed four hours after injection of tritiated thymidine were studied; counts of the total neuroglial population and of the number of labeled neuroglia were made in the white matter of each half of the cord (hemisection). During the first two weeks following birth, the number of neuroglia per hemisection increased six times; thereafter, the population appeared to be stable. The increases in number of labeled neuroglia appeared to parallel the rise in total population, particularly during the period of greatest population increase, i.e., days 7 through 12. After 12 days, when the total population stabilized, there was a marked and rapid decrease in the number of labeled cells. The walls of the central canal were examined in view of the role this area plays in the initial development of the nervous system. In rats killed during the first 14 days postnatally, the dorsal and ventral walls were incomplete; however, numerous, unidentified cells adjacent to these walls were oriented as if entering the dorsal median septum and the ventral median sulcus. By 22 days the central canal area had more of its adult appearance.
The structure of developing bone marrow sinuses in extramedullary autotransplant of the marrow in rats
Authors: Tavassoli Mehdi , Weiss Leon
Published: February 2005

The structure of the developing sinuses of the bone marrow was studied in extramedullary autotransplants of the marrow in rats just before the onset of hemopoiesis. Sinuses are highly branching channels with walls consisting of a single layer of endothelium. The wall thickness varies considerably but larger sinuses generally have a thinner wall. Endothelial cells may overlap and interdigitate displaying junctional densities. Abrupt thinning of endothelium was observed in some areas but no apertures were noted. The endothelium is sometimes surrounded by collagen, but no basement membrane is present. Twenty‐four percent of the endothelial surface is covered by pericytes and often rarified cytoplasmic spurs extend into perisinus areas. Microfilaments were seen under the cell membrane of pericytes. Medium‐sized lymphocytes are frequently seen in the sinal lumen and intersinal tissue and they may constitute hemopoietic stem cells.
Morphological studies of the altered pulps of the New Zealand white rabbit after resection of the inferior alveolar nerve and/or the superior cervical ganglion
Authors: Avery J. K. , Strachan D. S. , Corpron R. E. , Cox C. F.
Published: February 2005

This study was carried out to determine the effects of denervation of the pulp organs of teeth, particularly on the odontoblasts and their processes. Therefore, resection of the inferior alveolar, cervical sympathetic, or a combination of both types of nerves supplying the mandibular incisor teeth of New Zealand white rabbits was performed and the results compared to adjacent, unaltered teeth. Neural stains were used to evaluate the presence or absence of nerve elements, while histochemical and titrametric methods were employed to determine the presence, location and concentration of cholinesterase enzymes in these teeth. Dilation of blood vessels was noted after cervical sympathetic resection and larger nerve trunks as well as peripherally located fine fibers were absent in the pulps following inferior alveolar nerve resection. Further, irregular dentin formation and associated small openings in the tips of the teeth were observed after nerve resection. Titrametric analysis indicated a significant decrease in the concentration of cholinesterase in the pulp organ of incisors 15–19 days after resection of either the inferior alveolar nerve or both inferior alveolar and cervical sympathetic nerves. Only a slight decrease in the concentration of cholinesterase was noted after removal of the cervical sympathetic nerve alone. Histochemical results confirmed a decrease in cholinesterase after resection of the inferior alveolar, cervical sympathetic or both nerves. The concentration of the oxidative enzyme, succinic dehydrogenase, however, increased after all three types of nerve resection. This increase was apparent particularly in the odontoblastic cells underlying the predentin.
The origin of osteoclasts in estrogen‐stimulated bone resorption of the pubic symphysis of the mouse
Authors: Corwin James A. , Morehead James R.
Published: February 2005

Four‐week‐old female mice were injected with estradiol, and the following day received intraperitoneally one μC/gm body weight of thymidine‐methyl 3H. At various intervals following the injection of thymidine‐3H, pairs of mice were sacrificed, the pubic symphyses excised and prepared for radioautographs of transverse sections. Examination of the radioautographs revealed that the highest percentage of labeled cells was to be found in the osteoprogenitor cell population at all time intervals examined. The number of osteoclasts and the percentage of labeled osteoclasts rose progressively. The percentage of labeled osteoblasts rose and then fell, but was at all times much less than that of the osteoprogenitor cell population.

Since the osteoprogenitor cell population was the only one in which the percentage of labeled cells was high enough to account for the rise in the percentage of labeled osteoclasts, the conclusion was drawn that the labeled osteoclasts arose from the labeled osteoprogenitor cells.

In support of the above conclusion, and in keeping with the theory that the osteoprogenitor cell undergoes “differential” mitosis, one daughter cell going on to become an osteoclast or an osteoblast and one daughter cell remaining in the osteoprogenitor cell population, the number of silver grains over the labeled osteoclast nuclei was observed to be roughly one‐half that over the labeled osteoprogenitor cell nuclei.
Prismatic and other unusual arrays of mitochondrial cristae in astrocytes of cats and hamsters
Authors: Morales Ricardo , Duncan Donald
Published: February 2005

Further work with mitochondria containing prismatic cristae has revealed that this type occurs as a constant feature and in some abundance in the dorsolateral region of the spinal cord of the cat at cervical, thoracic and lumbar levels. All such mitochondria occur in astrocytes. The most common forms are long rods with an abundance of matrix and very few cristae. The matrix in the majority of such mitochondria is of moderate density and without discernible organization. In others the matrix consists of closely packed rodlets with or without occasional prismatic cristae. A frequent pattern is a core of longitudinal rodlets surrounded by a rim of circumferential ones. In the circumferential zone a single row of triangular cristae is present. The unusual mitochondria vary greatly in size, from 0.2–5.0μ Mitochondria containing ordered arrays of cristae that are triangular in cross section are for the most part much smaller than those with very few cristae and smaller than similar mitochondria described in the Syrian hamster. It is concluded that close packing in the matrix (obviously hexagonal in many instances) is the cause of the prismatic shape of the cristae.
Ultrastructural comparisons of paired cisternae in leukemic and mesenchymal cells during mitosis
Authors: Kelley Robert O.
Published: February 2005

Paired membranous lamellae were observed in tumor cells from chloroleukemic rats and human embryonic mesenchyme during mitosis. These structures are morphologically identical. Their role during karyokinesis and their relationship to the nuclear envelope is discussed. In addition, it is suggested that at least two mechanisms for breakdown and restoration of nuclear envelope exist during mitosis: (1) vesiculation and (2) lamellation (the formation of membranous lamellae).
Fine structure of a fifth type of epithelial cell in the thyroid gland of the C3H mouse
Authors: Nève Pierre , Wollman Seymour H.
Published: February 2005

A new cell with relatively little cytoplasm has been identified in the second kind of follicle in the C3H mouse thyroid gland. It has as ultrastructural characteristics the presence of clusters of fiber in the cytoplasm, vesicles near the basal plasma membrane, and half desmosomes in the basal plasma membrane. It resembles the U cell found in the ultimobranchial follicle of the Fischer rat thyroid, but has a somewhat larger amount of granular reticulum. It is found in the follicle wall between other epithelial cells and the basement membrane, but occasionally is in contact with the lumen. It also occurs as a double layer in the follicle wall. Cell debris in the lumen of the follicle contains fibrils and may be the result of desquamation of this fibril‐containing cell.
Deep splenic lymphatics in the marmot: An electron microscopic study
Authors: Janout Váçlav , Weiss Leon
Published: February 2005

Deep splenic lymphatics, studied in five marmots, entwine major arteries of white pulp. Lymphatics vary in prominence from spleen to spleen and within a spleen.

These lymphatics constitute efferent channels likely draining splenic fluid flowing within the spleen counter‐current to blood.

The endothelium is irregular, thin and imperforate, beset with vacuoles and containing filaments. Its hyaloplasm is light or dark. Flap‐like inter‐endothelial cell junctions without membranous specializations are typical. Endothelial cells richly interdigitate with one another resulting in extensive, closely‐spaced intercellular junctions. Long endothelial processes extend into subjacent connective tissue.

The lymphatics lie in an extracellular ground substance, continuous with that surrounding arteries and with the fibrous reticulum of white pulp. Filaments, about 100 Å in width, lie in the ground substance close upon the basal endothelial surface. The filaments appear to attach to the endothelium and run out into surrounding collagenous fibers. The collagen is abundant, occurring in thick layers around lymphatics and extending, with the ground substance, into the white pulp.

Macrophages, replete with phagosomes, surround lymphatic vessels and extend processes toward them, penetrating the peri‐lymphatic connective tissue. Erythrocytes lie outside these vessels and within their lumen. Sheets of plasma cells may surround the lymphatics. Lymphocytes, in large number, are present around the lymphatics, cross their wall between endothelial cells, and lie in their lumen.
The diffuse labyrinthine endotheliodichorial placenta of the free‐tail Bat: A light and electron microscopic study
Authors: Stephens R. J. , Cabral L. J.
Published: February 2005

In Tadarida, the diffuse endotheliodichorial placenta is established over the parietal area of the uterus and is prominent, for an extended period of time during midgestation, both prior to and during the development of the definitive discoidal structure. A transitory yolk sac placenta precedes the establishment of the diffuse placenta. The tissues of the yolk sac are displaced from the trophoblast through collapse, and by the advance of the allantoic mesoderm. Allantoic vessels infiltrate the cords of cellular trophoblast that extend into the syncytium that, in turn, has penetrated deeply into the maternal endometrium. The syncytium progressively phagocytizes the maternal tissues, leaving the superficial maternal blood vessels and attendant pericytes intact, but destroys many of the deeper maternal vessels. Several morphological changes occur in the pericytes during the period that the superficial maternal capillaries retain their integrity, suggesting that they play an important role in maintaining these vessels which are eventually destroyed also.

The cytotrophoblast is the most undifferentiated cell type throughout gestation. The syncytium, on the other hand, contains a large array of organelles that vary in concentration from one area to another within this tissue. Particular attention was paid to cytoplasmic structures potentially related to transport phenomena. Among those described are (1) coated vesicles and tubules in the syncytium at its interface with the cellular trophoblast, (2) microvilli extending from the cytotrophoblast into the syncytium some of which contained lines of pinocytotic vesicles, (3) coated vesicles along the plasma membrane of the syncytium toward the maternal tissues, and (4) pinocytotic vesicles associated with the endothelium of both the allantoic and maternal blood vessels.
The shearing properties of single osteons
Authors: Ascenzi Antonio , Bonucci Ermanno
Published: February 2005

The shearing strength of single human osteons has been investigated using a microtesting machine equipped with a microwave micrometer. The results Were related to the degree of calcification and the orientation of collagen fiber bundles in successive lamellae of the osteons. The following conclusions were made: (1) Osteons having a marked longitudinal spiral course of fiber bundles in successive lamellae are least able to support shearing stress. This suggests that in the other types of osteon the compactness of bone is strengthened by the lamellae having marked transversal spiral course of the fiber bundles. (2)Ultimate shearing strength and modulus of elasticity of osteons increase as calcification proceeds. (3) The shearing strength of single osteons is markedly lower than the tensile and compressive strength for samples of the same type. (4) In osteons loaded along their axis the range of elastic deformation is barely more than 1% of the length of the sample. (5) With the technical procedure used in this investigation the shearing of osteons appears to be preferentially related to the lamellar structure. In osteons loaded excentrically the portions which have slipped out have a rather irregular shape and in many cases one or two fractures occur. (6) The resistance to shearing of the cementing substance at the boundaries of the osteon may be greater than the resistance of the osteon itself.
Inclusion bodies of the epithelium of the urinary bladder in the rhesus monkey
Authors: Lucas John A. , Moser James H. , Schardein James L.
Published: February 2005

Inclusion bodies observed by light microscopy in the superficial epithelial cells of the urinary bladder of the rhesus monkey have been examined by electron microscopy. The inclusions varied from focal aggregates of fibrils in their least differentiated form to mature, paranuclear inclusion bodies 3 × 5 μ in size composed of orderly arranged fibrillar structures. The fibrils comprising the inclusions were indistinguishable from cytoplasmic tonofilaments. The significance of the inclusions remains obscure in the absence of known physiologic alteration.
Follicular histology and physiological correlates in the preovulatory hamster
Authors: Norman Reid L. , Greenwald Gilbert S.
Published: February 2005

The surge in plasma luteinizing hormone (LH) in the proestrous hamster begins at 1430 (Turgeon and Greenwald, '72) and this is followed by a sharp increase in follicular and interstitially derived progesterone at 1500 (Norman and Greenwald, '71). The purpose of the present study was to relate various histologic events in the ovary of the preovulatory hamster to these physiological changes, dating from the LH increase between 1430 and 1500. The earliest maturational changes in the oocyte occurred at 1600 as the nuclear membrane began to disappear, correlating with an increase in the number of pycnotic nuclei in the surrounding cumulus cells and an abrupt reduction in mitotic activity in the membrana granulosa. It is possible that the latter event is related to increased progesterone secretion by the follicle at 1500. The most rapid increase in follicular diameter occurred between 2000 and 2200 ‐ five to seven hours after the LH surge and was accompanied by a pronounced stromal edema especially of the medullary portion of the ovary. During this same time period, meiosis proceeded to the metaphase stage and the cumulus cells began to disperse to form the corona radiata. Of the eight hours required for the first meiotic division, four to six hours are spent in metaphase. The majority of animals (75%) ovulated by 0100 and all animals ovulated by 0200. Therefore, ovulation occurred 10 to 11 hours after the LH surge at 1500.
Endocrine‐like cells in human fetal lungs: An electron microscopic study
Authors: Cutz Ernest , Conen Patrick E.
Published: February 2005

This study of primitive bronchial epithelium in human fetuses revealed cells of distinctive ultrastructural appearance. These cells contained cytoplasmic granules similar to neurosecretory‐type granules and are termed fetal Kultschitzky‐type cells (K‐type cells) of lung. The fetal K‐type cells appear similar to certain cells in mature lungs and in other tissues that have an endocrine function. The advanced cytoplasmic differentiation and large numbers of K‐type cells in early stages of fetal development suggests that these cells might also have an important, probably endocrine function.
Adrenergic and cholinergic nerve terminals in the rat parotid gland. Electron microscopic observations on permanganate‐fixed glands
Authors: Hand Arthur R.
Published: February 2005

The innervation of the acinar cells of the rat parotid gland was studied using potassium permanganate fixation. Adrenergic terminals, characterized by the presence of small granular vesicles, and cholinergic terminals, containing small agranular vesicles, made close contact with the acinar cells. Both adrenergic and cholinergic terminals were observed in contact with the same cell, and subsurface cisterns of endoplasmic reticulum were found in relation to the contact areas of both types of endings. In addition, both adrenergic and cholinergic axons were found within the same Schwann cell sheath in the connective tissue spaces.
Support of normal salivary gland morphogenesis by mesenchyme derived from accessory sexual glands of embryonic mice
Authors: Cunha Gerald R.
Published: February 2005

The mesenchymal specificity of epithelium from the submandibular salivary gland of embryonic mice was re‐investigated employing standard epithelio‐mesenchymal separation and recombination techniques. For this purpose, tissue recombinants were constructed with epithelium and mesenchyme of the submandibular salivary gland and the seminal vesicle, preputial gland, and urogenital sinus. Salivary glands were dissected from 13‐day and the accessory sexual glands from 13– to 19–day old embryos. Tissue recombinants were grown for two to three weeks in the anterior chamber of the eye of adult male hosts.

Mesenchyme from accessory sexual glands supported the growth, branching, and differentiation of epithelium from the salivary gland. After three weeks of intraocular growth, most of these heterotypic recombinants were indistinguishable from intraocular grafts of this gland. However, recombinants constructed with mesenchyme from the urogenital sinus or preputial gland exhibited an age dependent developmental response. Mesenchyme from 15‐ to 16‐day old embryos supported normal morphogenesis of the salivary gland, whereas atypical epithelial differentiation occurred when 13‐ or 14‐day old mesenchyme was employed. On the other hand, the reciprocal recombinants composed of mesenchyme from the salivary gland and epithelium derived from accessory sexual glands resulted in abortive epithelial differentiation regardless of the age of the tissues. These results suggest that the mesenchymal specificity of epithelium from the salivary gland may be related to the morphogenetic sensitivity of the heterotypic mesenchyme to androgens.
A fluorescence study on the ability of the notochord to synthesize and store catecholamines in early chick embryos
Authors: Kiray Margaret L. , Gilmoae Shirley Ann
Published: February 2005

The role that catecholamines play in presympathetic embryogenesis is relatively unknown. All catecholamine‐producing cells develop both the enzymes needed for catecholamine synthesis and an amine pump for the uptake of extraneous catecholamines. This investigation was undertaken to define areas which are able to produce and store catecholamines in the presympathetic chick embryo. Embryonic chicks between two and four days of incubation (stages 11 to 23) were incubated in a medium containing norepinephrine, dopa or dopa with cocaine, and treated for fluorescence according to the method of Falck and Owman. Norepinephrine uptake was considered to be evidence of the presence of an amine pump. The conversion of dopa, a nonfluorescent precursor of dopamine, to dopamine which is fluorescent was considered to be an indication that the enzyme dopa decarboxylase was present. Cocaine, an amine pump inhibitor, applied simultaneously with dopa would prevent dopamine synthesized in one site from entering other cells. It was found that the notochord was intensely fluorescent in the presence of norepinephrine. No other sites of norepinephrine uptake were seen. The notochord could also convert dopa to dopamine indicating the presence of dopa decarboxylase in notochordal cells. Similar results were obtained when cocaine was added to the incubation medium. It is concluded that the notochord is a possible site of catecholamine synthesis and storage in presympathetic chick embryos.
Juxtaglomerular granular cells and nephron autoregulation
Authors: Dunihae F. W. , Whortan E. B.
Published: February 2005

Histological study of serially sectioned glomeruli in rat and mouse kidneys possessing different aggregates of juxtaglomerular granular cells has revealed that between 15 and 29% of glomeruli in control animals are not associated with these granular cells and that almost universal association occurs only when the granular cells are greatly increased. Thus, a significant number of nephrons in control rats are not continuously autoregulated through a local renin‐angiotensin mechanism, assuming that a lack of granules is associated with a lack of synthesis and release of renin. This association between granular cells and glomeruli is usually greater in the outer half than in the inner half of the cortex regardless of the content of granular cells; although the difference is not as great as prior reports indicate. Stimuli which either increase or decrease granularity of juxtaglomerular cells produce a similar and parallel response in both cortical regions, suggesting that control or regulation of granular cells is the same in both areas. It further suggests that the reported difference in filtration rates between superficial and deep glomeruli following sodium loading and sodium deprivation is not mediated through a differential alteration of juxta‐glomerular cell granularity. A linear regression equation was developed by which the per cent of all glomeruli associated with granular cells may be estimated from given mean juxtaglomerular granular cell indices (GCI).
Tissue cholesterol preservation: Factors associated with retention of cholesterol in rat sciatic nerve fixed for electron microscopy
Authors: Sterziag P. R. , Napolitano L. M.
Published: February 2005

The retention of cholesterol in rat sciatic nerve fixed in glutaraldehyde‐digitonin was investigated. Maximal retention ( >85% ) was achieved after fixation at room temperature, post‐fixation in OsO4, and dehydration in an ethanol series, 60, 80, 95, 100% (2 changes), five minutes per change. Fixing in the cold, increasing the dehydration time, changing from ethanol to acetone, or reducing the concentration of digitonin from 0.2% to 0.02%, resulted in a decrease in cholesterol retained. The greatest loss of cholesterol was found in the two changes of absolute ethanol, and therefore we recommend dehydration through 95% ethanol, followed by infiltration and embedding according to the procedure of Idelman ('64).
Effects of vitamin A deficiency on ultimobranchial tissue in the rat thyroid
Authors: Krupp Patricia
Published: February 2005

Ultimobranchial follicles in the thyroid glands of young Wistar rats, 4 to 12 weeks old, are lined by non‐keratinized stratified squamous epithe‐lium and contain desquamated cellular material. Mitoses are observed in the epithelium of these follicles which are variable in size, shape and frequency. Thyroid glands of young vitamin A deficient rats also contain ultimobranchial follicles. These follicles differ from those found in animals on a stock diet in that the stratified squamous epithelium produces keratinized concentric whorls of non‐nucleated luminal debris. After placing vitamin A deficient rats on a stock diet desquamated cellular material is no longer keratinized and resembles that seen in the control animals. Vitamin A deficient diet apparently keratinizes the stratified squamous epithelium of pre‐existing ultimobranchial follicles rather than solely having a metaplastic effect on thyroid‐like follicles of ultimobranchial tissue origin.
A three dimensional representation of the odontogenic epithelium of the rat incisor
Authors: Michaeli Y. , Greulich R. C.
Published: February 2005

A three dimensional reconstruction of the basal end of the rat incisor, together with analytical data attesting to the reproducibility of the method is presented. The size and shape of the tooth varies little from animal to animal, while the sizes of the functional compartments are much less uniform.

The odontogenic sheath is divided into three zones: Proliferation, differentiation and apposition. The proliferative zone is subdivided into two segments: The basal segment which gives rise to ameloblasts shows the highest cell production; an anterior segment located around the pulp opening which will give rise to the part of the tooth covered by cementum and has a much lower cell production.

Total cell production can be obtained only in transverse sections, while mid‐sagittal sections can serve only for comparative purposes.
A scanning electron microscopic study of the ependymal surface of the third ventricle of the rabbit, rat, mouse and human brain
Authors: Bruni J. E. , Montemurro D. G. , Clattenburg R. E. , Singh R. P.
Published: February 2005

In all species studied, the upper two‐thirds of the third ventricle is lined by ependymal cells with a profusion of long cilia that extend into the lumen. In the rabbit, rat, and mouse, an abrupt transition to a sparsely ciliated ependymal surface occurs along the lower one‐third of the ventricular wall, at the level of the underlying ventromedial (VM) nucleus. Unique to the rat transition zone however, is a predominance of microvilli. In the human, a subtle transition to a sparsely ciliated ependymal surface occurs somewhat higher at about the level of the underlying dorsomedial (DM) nucleus. Along the upper expanse of the rabbit infundibular recess (IR) ciliary bundles are infrequent, although occasional solitary cilia are seen. The characteristic features of this region, however, are the non‐ciliated ependymal cells with their many irregular bleb or microvilli‐like surface protrusions. In contrast to the rabbit, the same region in the rat and mouse is distinguished by an irregular ependymal surface with stout bleb‐like protrusions and many single cilia. Similarly in the human, cilia become progressively fewer toward the IR. Although the non‐ciliated epen‐dymal surface in this region resembles that of the rabbit, the surface blebs and microvilli‐like protrusions are fewer in number and less prominent. The lateral walls of the third ventricle display a consistent regional variation in the morphology of the luminal ependymal surface in all species studied. Although it is not possible to establish unequivocally the nature or significance of these regional differences, the structural modifications of the ependymal surface in the region of the IR are entirely consistent with the secretory or absorptive function attributed to ependyma in this area.
The effects of hyperthyroidism on the fine structure of the zona fasciculata of the rat adrenal cortex
Authors: Moore N. A. , Callas Gerald
Published: February 2005

Chronic hyperthyroidism was induced in radiothyroidectomized and surgically thyroidectomized adult male rats by feeding a diet of 0.3–0.4% desiccated thyroid for four to ten week periods. Short term hyperthyroidism was induced in intact rats by the intraperitoneal injection of 250 μg/day of sodium levothyroxine for ten days. Adrenal glands were fixed by perfusion with 3% phosphate buffered glutaraldehyde and post‐fixed in 1% osmium tetroxide. The zona fasciculata of the adrenal glands from experimental and control animals was examined in the electron microscope. Drastic mitochondrial alterations characterized the zona fasciculata of hyperthyroid rats. Initially, mitochondria became more nearly round and contained increased numbers of paracrystalline tubular inclusions of the type described by Kjaerheim ('67) and Wheatley ('68). In more altered states many mitochondria were filled with clusters of parallel tubular cristae of varying complexity which at times enveloped islands of mitochondrial matrix and fingers of cytoplasm which projected into the mitochondrion. Aggregations of numerous mitochondria occupied much of the cytoplasm of highly altered cells. Modifications of this nature have not been described following ACTH stimulation of the adrenal cortex. This raises the distinct possibility that thyroid effects on the adrenal cortex are not entirely ACTH mediated.
Electron microscopic studies on fate of erythroblast ribosomes
Authors: Campbell Ferrell R.
Published: February 2005

Electron microscopic observations are reported which demonstrate that ribosomes are extruded during the final stages of maturation in erythroid cells of rats and guinea pigs. Concentration of ribosomes in the cytoplasm, formation of a membrane bounded vesicle containing these ribosomes and extrusion of the vesicle are described and discussed.