bluuebunny/crossref_metadata_2025 huggingface dataset:
The melanocytes in the epidermis of the rhesus monkey (Macaca mulatta)
Authors: Yun Jeung S. , Montagna William
Published: February 2005

The epidermal melanocytes which, except in the ears, face and friction surfaces, are normally nonmelanotic become gradually DOPA positive and melanogenic after exposures to ultraviolet light. Peak melanogenic activity is attained after 23 exposures (over a one‐month period). With continued treatment, however, both DOPA positivity and melanogenic activity decline. After 46 exposures (over a two‐month period) the population of DOPA positive melanocytes is about one‐half of that found after 23 exposures. The population of Langerhans cells, normally high in untreated skin, drops steadily as the melanocytes become melanogenic. When, after 46 exposures, the active melanocyte population drops, that of the Langerhans cells rises. There is, thus, an inverse relation between melanocyte activity and the number of Langerhans cells.
Time and duration of DNA synthesis in rabbit eggs after sperm penetration
Authors: Szollosi Daniel
Published: February 2005

Rabbit eggs 11–18 hours after mating were incubated with tritiated thymidine for 30 minutes, fixed in osmium tetroxide and prepared for autoradiography. DNA synthesis in both pronuclei takes place between 3–6 hours after fertilization. The presynthetic and synthetic periods are short, followed by a long postsynthetic period.
The teratogenic effect of tetanus toxin on the central nervous system of the early chick embryo
Authors: Corliss Clark E. , Fedinec Alexander A. , Robertson G. Gordon
Published: February 2005

Chick embryos, incubated at 38–39°C to stages 8–11 (Hamburger‐Hamilton staging), were injected (under the vitelline membrane) with ten MLD (mice) per 0.05 ml of tetanus toxin or with avian physiological saline solution. Seventeen hours after the injection the embryos were harvested and fixed in Bouin's solution. Selected control and experimental specimens were sectioned for histological study.

Observations of gross specimens show that open neural folds of younger embryos are more susceptible than are the more extensively closed tubes of older embryos. The progressively more caudal restriction of toxin‐susceptible sites with increasing age is a manifestation of this correlation with the degree of closure at injection time.

Study of serial sections establishes the concentration of lesions almost exclusively in neural tissue, especially in the alar region of the neuraxis. Tetanus‐induced lesions include encephaloschisis, myeloschisis and platyneury at various levels of the neural tube. These basic defects are comparable to those reported after treatment with many CNS teratogens.

Suggestions are made concerning the possible effect of tetanus toxin on biochemical interactions that might lead to aberrations from the normal morphogenesis of the central nervous system.
Rapid wax plate modeling
Authors: Sack W. O.
Published: February 2005

An accelerated method for the production of wax plate models from serial sections is described. Serial sections are projected on the back of 1 mm wax plates and the sharp image produced on the front of the plate is cut out directly with a knife. The construction of a simple projection apparatus which permits back‐lighted projection is described and illustrated. The apparatus is built of common‐size lumber and a small sheet of Plexiglas. It consists of a screen for the image and a wooden track on which a light source and microscope can be moved back and forth for different magnifications. Commercially available wax plates can be used. A method and the equipment needed to produce larger plates are described.

The cut‐out images when piled up to form the model are welded together and strengthened by inserting heated straight pins. The exterior of the model is smoothed with an electrically heated glass instrument which provides constant heat of desired temperatures. The construction of the glass instrument is illustrated.
Morphological variability of keratohyalin
Authors: Farbman Albert I.
Published: February 2005

With the aid of the electron microscope, it has been possible to demonstrate that the configuration of keratohyalin in rat tongue epithelium is highly variable. The configurations described by others are seen, i.e., the globular or irregular granules made up of homogeneous electron‐opaque material. In addition to these, there are two other types of granules. One type is constituted heterogeneously of material similar in density to that usually described and another slightly less dense material. In the other type, keratohyalin is arranged as a dense rim around an electron‐translucent, amorphous center. In addition to the cytoplasmic keratohyalin granules, intranuclear dense granules were demonstrated. The morphology of these intranuclear granules is similar in some ways to cytoplasmic keratohyalin.
Response of murine cutaneous nerves to skin painting with methylcholanthrene
Authors: Fitzgerald M. J. T. , Lavelle S. M.
Published: February 2005

A saturated solution of 20‐methylcholanthrene in benzene was applied to the ear and trunk of 59 BALB mice. The effects upon cutaneous innervation were compared with that of 50% turpentine in acetone (13 mice) and of skin abrasion with sandpaper (11 mice). Silver impregnation techniques showed that the carcinogentreated epidermis was invaded by nerve fibers whose number was related to the degree of epidermal hyperplasia, but not to the period of treatment or to the animals' age at the time of first painting. Hair follicles showed changes in the size, number and length of nerve endings. Growth of cutaneous nerves was already evident on the fourth day of exposure to methylcholanthrene. Turpentine elicited only a slight neural reaction after 60 days; and the sandpaper treatment was without effect.
Fertilization and early development after radiocobalt irradiation of rabbit oocytes and sperm in the female tract
Authors: Chang M. C. , Hunt Dorothy M. , Turbyfill C. L.
Published: February 2005

One hundred and seven female rabbits were divided into three groups and irradiated with 400 r from a radiocobalt source. The first group (71 animals) was irradiated before or 4–12 hours after mating and an ovulating injection of H.C.G. The second group (27 animals) were irradiated at about the same time after injection but inseminated after irradiation. The third group (9 animals) were inseminated with spermatozoa which had been irradiated in other females.

The ova were recovered at various times for the determination of fertilization, cleavage, and blastocyst formation. Groups of animals were autopsied 14 or 29 days later for the determination of fetal development. The fertilization rate was not disturbed whether sperm, oocytes, or both were irradiated. The disturbance of nuclear material, the aberration of chromosomes, the retardation of cleavage, the fragmentation of cytoplasm, and the failure of blastocyst formation and embryonic development were observed especially whenever oocytes were irradiated. Irradiation of oocytes before mating and injection appeared to be less harmful but no differential effects were observed when irradiation was at 4, 6, 8, 10 or 12 hours after ovulating injection or when oocytes alone or both the oocytes and sperm were irradiated, probably due to the dosage being too high. Irradiation of sperm in the female tract was less harmful, normal blastocysts and apparently normal fetuses were obtained when nonirradiated ova were fertilized by such spermatozoa.
Prenatal development of the retina in a diurnal primate (Macaca mulatta)
Authors: Keefe J. R. , Ordy J. M. , Samorajski T.
Published: February 2005

Observations were made on the pre‐ and postnatal development of the photoreceptors in the central region of the retina in the diurnal rhesus monkey. Histologic findings on the level of development of the retina at birth revealed a macula with the characteristic adult foveal depression. Observations on the ultrastructural development of the receptor inner and outer segments revealed that the photoreceptors were well differentiated even at birth. An evaluation of the prenatal morphogenesis of the photoreceptors indicated that the initial differentiation may take place as early as 100–125 days after conception. At 100 days after conception, the pigment epithelium consisted of a single layer of cuboidal cells with cytoplasmic content of smooth endoplasmic reticulum, but was only sparsely populated with mitochondria and rough endoplasmic reticulum. The photoreceptor inner segments contained vesiculation in the supranuclear region, while the incipient outer segments consisted of outbudding ciliary processes. By 125 days postconception, the pigment epithelium contained such cytoplasmic specializations as increases in rough endoplasmic reticulum and mitochondria, as well as greater organelle complexity. In the photoreceptor outer segments there were arrays of closed bimembranous discs, with vesiculation at the apical tip in the inner segments. A comparison of the pre‐ and postnatal ultrastructural changes in the choroid and the interstitial zone comprising the photoreceptor outer segments and the cell processes of the pigment epithelium suggested that the changes in these areas represent a critical aspect in the maturation of the retina.
Electron microscopy of erythropoiesis in the avian yolk sac
Authors: Edmonds Richard H.
Published: February 2005

The formation of the first blood cells which develop in the area vasculosa of the chick embryo have been examined to seven days of incubation. Angioblasts have been seen to arise from the mesoderm and to give origin to the first endothelium and intravascular blood islands. This occurs as the intercellular spaces enlarge and coalesce. The angioblasts and blood islands are not syncytial but are held in close relation by attachment areas and cytoplasmic processes. Two cell types arise concurrently from the blood islands, a stem cell and cells which have begun their differentiation into the primitive red cell series. The morphological events associated with this differentiation are similar to those in other hematopoietic organs. The definitive series of red blood cells arises from the stem cells at 4 to 5 days of incubation. The morphological differentiation of the definitive red cell is generally similar to that of the primitive series although the late and mature stages show structural differences. Nuclear structure, relation of interchromatin material to nuclear pores and the presence of marginal bands in the definitive series allow a differentiation between the two series.

Granulocytes arise from extravascular stem cells at about five days of incubation but at seven days are not fully mature or abundant.

Limited observations on the avian thrombocyte are reported.
Cytology of the fetal zone of the adrenal gland of the armadillo
Authors: Enders Allen C. , Schlafke Sandra , Warren Robert
Published: February 2005

The fine structure of the adrenal gland of the fetal armadillo was examined by electron microscopy to determine whether or not there were two cell types in the parenchyma of the fetal zone, as suggested by examination by light microscopy, and whether any of the cells of this zone had the cytological features associated with steroid production.

Two cell types were found. One cell type is composed of large cells situated in clusters and containing a relative paucity of organelles. The other cell type is composed of smaller, eosinophilic, PAS positive cells, situated primarily in a reticular pattern around the blood vessels. This second cell type has numerous spherical mitochondria with tubular cristae and an extensive tubular agranular endoplasmic reticulum. It is concluded that this latter cell type is responsible for the steroid production reported by other authors. Both of the cell types of the fetal zone appear to be derived from the original mesenchymal blastema of the adrenal gland.
Cerebral cell population under hypoxia
Authors: Shivers Richard R. , Roofe Paul Gibbons
Published: February 2005

Three pregnant albino Sprague‐Dawley rats were subjected to simulated high altitudes of 18,000 feet (365 mm Hg) in low pressure chambers during their entire pregnancy. The brains of the newborn rats were removed immediately after birth and placed in 10% formalin. The brains were sectioned, stained, and analyzed for changes in the number of cells in the cerebral cortex of the frontal lobes. An equal volume of control material was similarly prepared and analyzed. A volume of tissue of about one‐fourth cubic millimeter was used in the control and in the experimental tissue. The results indicated a 19.29% increase in the number of cells in the frontal cortex of newborn rats subjected to simulated high altitude anoxia. This increase is believed to be due to a proliferation of glial elements in the areas of the cortex which were studied. The cell hyperplasia seen here may be a response to physiological stresses placed upon the fetus by maternal anoxia.
A modified Golgi‐Cox method with counterstain for the study of synapses
Authors: Ha Hongchien
Published: February 2005

The method described was found especially valuable for the study of synaptic connections and unimpregnated cells. Brains and spinal cords of the young cat, dog and frog were fixed by perfusion with gum acacia saline and formalin. The brains and spinal cords were removed and immersed in 10% formalin in saline for two weeks or more. Tissues were sliced into blocks 3 mm thick, washed and impregnated in a modified Golgi‐Cox solution for from 6 to 8 weeks. Parlodion sections of 80 μ to 100 μ thick were treated with 5% ammonium tetroxide and counterstained with 0.25% cresyl fast violet. The sections were then differentiated in 95% alcohol, dehydrated, cleared and mounted. The method tends to prevent shrinkage, promote staining of axons, terminals and synapses and stains unimpregnated neurons.
Lipoprotein in the normal and regenerating limb tissues of the adult newt, Diemictylus viridescens
Authors: Schmidt Anthony J.
Published: February 2005

Lipids tightly bound to cell and tissue proteins (lipoproteins) were investigated with the acetone‐sudan procedure in cryostat‐cut sections of normal and regenerating limb tissues of the adult newt, Diemictylus viridescens.

Nuclear and cytolplasmic membranes of all tissues stained moderately black; the nucleo‐ and cytoplasm stained less intensely than their membranes. Connective tissue fibers of the dermis, mysial and neural sheaths, and tunics of blood vessels yielded intense responses. In striated muscle of the limb, myofibrils and associated striations responded strongly. Nerve myelin responded weakly.

In the preblastemic regenerate, the fibrous adepidermal basement membrane terminated abruptly at the surface of amputation. A distal fibrocellular residue was evident in continuity with the retrograde degeneration of amputation‐injured muscle: observations suggest a possible contribution to the fibrocellular reticulum from myofibrils. The regeneration blastema appears isolated from proximal limb tissues by the intervening fibrocellular reticulum. The response of the blastema cell is relatively weaker than that of other cells and tissues. Regenerating muscle is recognized by the appearance of prominently stained myofibrils in myoblastic extensions off the limb stump musculature. The matrix and chondrocytes of regenerating cartilage stain for lipoprotein, with the osteoid of osteogenic centers responding strongly.

Polychrome responses were obtained from hyalin‐bodies within interphase nuclei, and from chromosomes in mitosis, suggesting that chromosomal lipid has been stained.

Supporting the lipidic character of the observed responses is the negative reaction following long term lipid extraction in warm chloroform: methanol.
Gross structure of the ear, nasal cavity and Paranasal sinuses of the chimpanzee
Authors: House E. L. , Pansky B. , Jacobs M. S. , Wagner B. M.
Published: February 2005

Gross examination of the chimpanzee skull revealed that: there are three ethmoidal sinuses; the sphenoid sinus is immense and is divided into a superior and inferior part; the huge maxillary sinus contains a distinct bony canal for the nasolacrimal duct; the anterior and middle ethmoidal sinuses drain into the superior meatus; the frontal sinus drains via the middle ethmoid; the posterior ethmoid and sphenoid sinuses open into the sphenoethmoidal recess and also communicate with each other; the maxillary sinus opens into the middle meatus through a large ostium; the nasolacrimal duct drains into the inferior meatus; the mastoid process is small but contains a central cavity which communicates with the middle ear; the broad and smooth planum tympanum serves as the floor of the external auditory canal, the latter forming an angle of 30° with the horizontal; the tympanic membrane makes an angle of 30° with the floor of the canal and is deeply recessed antero‐inferiorly; except for the extreme slope of the tympanic membrane and the malleus, the middle ear is similar to man; the inner ear is likewise similar; the carotid artery and the large carotid plexus lie in a definite osseous tube surrounded by pneumatized bone but attached to the periotic capsule; the chimpanzee is subject to otitis media.
Leucocyte‐like cells of the vagina and uterus, and their modification during the normal estrous cycle and by progestin and estrogen treatment
Authors: Nellor John E. , Brown Joan E.
Published: February 2005

Examinations of genital tract tissues and vaginal smears of normal cycling and progestin and estrogen treated cattle, sheep, and swine suggest that the majority of leucocyte‐like cells appearing in the tissues and smears of non‐infected animals are not of immediate blood origin, but originate from undifferentiated genital tract mesenchymal cells. During the luteal phase of the cycle, or during progestational treatment, plasma cells are produced in great numbers. They penetrate the stroma, epithelium, and lumen of the vagina as intact cells. Shortly after their entry into the vaginal lumen, they appear similar to polymorphonuclear leucocytes, as the result of dissolution of the nuclear membrane and scattering of the wedge‐shaped nuclear masses throughout the cell. The relative paucity of leucocyte‐like cells in the vaginal smear close to the time of ovulation results from interruption of the migration and differentiation of the plasma cells within the genital tissues, by estrogen induced fragmentation of the plasma cells. Eosinophilic polychromatin fragmenting plasma cells account for the majority of eosinophilic leucocytes in healthy genital tract tissues during proestrus and estrus.
Effects of cortisone acetate upon hydration of embryonic palate in two inbred strains of mice
Authors: Jacobs Richard M.
Published: February 2005

An absolute and relative loss of water was recorded in 169 palates derived from the offspring of cortisone treated and control mice. Experimental sample consisted of 38 time‐pregnant females of A/Jax and C57BL inbred strains. Animals were killed on thirteen and one‐third, fifteen and one‐third or eighteen and one‐third day of gestation and the fetuses were removed by laparotomy. Palatine shelves were dissected, weighed, desiccated and weighed again, under standardized conditions. The results tend to confirm the hypothesis that cortisone‐induced mechanical incompetence of embryonic palate may be associated with disturbed water metabolism and diminished cohesion of the tissues. It has been proposed that the observed differences of response of each strain to teratogenic and palatal edema‐inducing action of cortisone may be based upon genetically controlled metabolic polymorphism which determines the pathway of cortisone biotransformation and decay in the tissues.
The fine structure of the thrombocyte in the dogfish (Mustelus canis) with special reference to microtubule orientation
Authors: Shepro David , Belamarich Frank A. , Branson Roger
Published: February 2005

The cytoplasm of the dogfish (Mustelus canis) thrombocyte was found to contain microtubules. The tubules which measured 230 Å in diameter appeared singly and in groups. They were found in all parts of the cytoplasm but usually close to the perinuclear area. Similar arrangements of tubules were observed in eosinophils and hemoblasts, but not in the mature, smaller lymphocytes. The orientations of the perinuclear bundles frequently reflected the shape of the nuclei, appearing in furrows, indentations, and between lobes.
Weight changes of the submandibular glands in the rat resulting from denervation
Authors: Martin William D. , Smith R. Dale
Published: February 2005

In the lingual nerve of the rat, the number of myelinated fibers ranged from 3,215 to 3,744, with diameters ranging from 0.7 to 9.7 μ. The nerves were unimodal with a peak at 2–3 or 3–4 μ. In the chorda tympani, the number of myelinated fibers ranged from 444 to 538, with diameters ranging from 1.1 to 8.7 μ. The nerves were unimodal with a peak at 1–3 μ.

Sixteen days after section of the lingual, chordalingual (the lingual nerve distal to the union with chorda tympani) and chorda tympani nerves as well as intracranial section of the facial nerve, significant weight losses were recorded for the submandibular and retrolingual glands. The greatest weight losses occurred after intracranial section of the facial nerve or section of the chordalingual nerve (retrolingual glands lost 42 and 39%, submandibular glands lost 20 and 28% respectively). Intracranial section of the facial nerve demonstrates that the degree of weight loss is correlated with the number of myelinated fibers (1–3 μ diameter) which degenerate, and that the weight loss is not the result of operative damage to the vascular supply of the glands.
Cytoplasmic microtubules in mammalian erythropoietic cells
Authors: Grasso Joseph A.
Published: February 2005

Electron microscopic examination of rabbit erythroblasts revealed the presence of microtubules, 210–270 Å in diameter, composing a marginal band in the cell periphery. This band was composed of 6–8 microtubules arranged more or less parallel to one another. Transverse sections indicated that 16–18 tubules may comprise the band. The latter appeared to be poorly formed or absent in reticulocytes and erythrocytes. Microtubules were also found in the deeper regions of the cytoplasm as well as composing th emitotic spindle of dividing erythroblasts. With the exception of the procentriole and the asters and chromosomes of dividing cells, microtubules were not continuous with other organelles. The function of the marginal band is interpreted as imparting elasticity and resiliency to the cell, a cytoskeleton responsible for maintenance of cell form. “Coated” micropinocytotic vesicles in erythroblasts, hepatocytes, and reticulo‐endothelial cells are also described. Most of the “coated” vesicles in erythropoietic cells did not contain ferritin. It is suggested that, in the “coated” vesicles, ferritin may be in a highly dilute form or, alternatively, that its relative absence may indicate that iron is obtained predominantly through the plasma transferrin system rather than through incorporation of iron in the form of ferritin.
Derivation of the vascular elements in the fetal cotyledon of the hemochorial placenta: A contribution to the theory of placental morphogenesis
Authors: Reynolds S. R. M.
Published: February 2005

A schematic plan of late developmental organization of the fetal cotyledonary elements of the hemochorial placenta is presented. It involves mechanical shaping by hemodynamics and stretching of the elements involved in the late chorion frondosum stage after the 2nd month of gestation. The result is the fetal cotyledon as described by Wilkin. The components of the fetal cotyledon are derived from differentiated vascular elements in tertiary stem, or anchoring, villi and vascular elements of the blastoderm which are formed by the twenty‐first day after ovulation.
Localization of the neural control of luteinization in the feminine male rat (FALE)
Authors: Gorski Roger A.
Published: February 2005

Castration of the male rat during the first three days of life allows retention of the cyclic pattern of gonadotrophin release with which the male is born. Since the neonatally castrated male shares several endocrine characteristics with the female, the terms feminine male or FALE have been employed to identify these animals. Twenty‐seven of 28 FALES developed corpora lutea (CL) in ovarian transplants provided no other treatment was initiated. In contrast, exposure to constant illumination, suprachiasmatic lesions, or transection of anterior hypothalamic pathways prevented CL formation in 18 of 20 FALES. These findings support the concept that the preoptic‐anterior hypothalamic region is an essential component of the neural mechanism which regulates the cyclic luteinization of ovarian grafts in the FALE. Since the FALE is a male rat in which differentiation has not been permitted to occur, it is suggested that sexual differentiation of the normal male hypothalamus consists of an alteration in function of this preoptic system.
Relation between the size of ovarian isografts and abnormal reproductive cycles in the mouse
Authors: Browning Henry C. , White Wilma D.
Published: February 2005

Groups of 10 to 14 castrated female BALB / c mice received viable uni‐ or bilateral intraocular isografts of one‐eighth or of one‐thirty‐second of an ovary. Ten other animals remained intact. At biopsy five months later, the mammary glands of all animals showed little or no stimulation. Most animals with one or two one‐eighth or two one‐thirty‐second, grafts had shown normal vaginal and ovarian cycles prior to this time, but some had been in continuous metestrus and had acyclic grafts with vesicular follicles. Most animals with one one‐thirty‐second grafts were similarly in metestrus, but some were in diestrus with grafts lacking follicular structures. At autopsy eight months after grafting, almost all mice with one or two one‐eighth grafts had alveolar proliferaiton with secretion in the mammary glands. All were in continuous metestrus with acyclic grafts, and most had uterine cystic hyperplasia and peri‐medullary adrenal degeneration. At the same time, slightly more and slightly less than a half of the mice with one or two one‐thirty‐second grafts, respectively, showed these same abnormalities. Intact mice were devoid of them. The development of this mammary‐uterine‐adrenal syndrome appeared to be directly related to grafted ovarian tissue per se and to the size of the grafts. It may depend upon a pituitary‐ovarian imbalance with a failure of LH release.
Species differences in egg transport in response to exogenous estrogen
Authors: Greenwald Gilbert S.
Published: February 2005

The effect of exogenous estrogen on tubal transport of ova was determined in the guinea pig, hamster, mouse, rabbit and rat. The animals were given a single injection of estradiol cyclopentylpropionate (ECP) shortly after mating. The dose of ECP required to interrupt pregnancy in 80% or more of the animals was as follows: guinea pig (10 μg); hamster (25 μg); mouse (1 μg); rabbit (50 μg); rat (10 μg). Acceleration of egg transport through the oviduct occurred after the following doses of ECP: guinea pig (50–100 μg); hamster (100 μg); mouse (1 μg and above); rabbit (25 μg); rat (10 μg and above). Hence, the amount of estrogen which accelerates egg transport in the guinea pig and hamster is considerably higher than the dose which interrupts pregnancy.

Retentionof ova for longer than the normal period of tubal passage (tube‐locking) resulted from the following doses of ECP: guinea pig (250 μg); hamster (250 μg); mouse (1 μg); rabbit (100 μg); rat (no dose). In the species in which ova were tubelocked, the majority of eggs were located at the ampullary‐isthmic junction rather than the utero‐tubal region of the oviduct.

Tube‐locking of ova was never observed in the rat; ECP always caused premature entry of eggs into the uterus and eventual expulsion per vaginam. For example, eggs passed through the cervix by 12 hours after the administration of 250 μg ECP at day 1 of pregnancy.
An ordered complex of filaments surrounding the lipid droplets in developing adipose cells
Authors: Wood Eunice M.
Published: February 2005

Examination of the lipid‐cytoplasm interface of the weakly osmiophilic fat droplets in developing adipose cells from chick bone marrow reveals that the lipid does not lie free in the cytoplasm, nor is it bounded by a membrane, but instead is encompassed by a highly ordered complex of small, 80 Å thick, filaments.

In oblique sections, superimposition of the images of adjacent filaments results in a more or less continuous line which resembles a membrane. Perhaps this view of the system of filaments, in sections where heavily osmicated fat had retracted slightly from the interface, is responsible for reports that the lipid in adipose cells is enclosed by a membrane.

It is suggested that a similar system of filaments may be visualized in adipose cells of other species after extraction of the strongly osmiophilic fat which obscures details at the surface of the lipid droplets.

Although the true functional significance of the filaments is not yet known, the morphological evidence alone suggests that they may provide support for the lipid inclusions. An interpretation of the geometry of the filaments, consistent with the present evidence, is presented.
The absorptive activity of ameloblasts during the maturation of enamel
Authors: Reith Edward J. , Cotty Val F.
Published: February 2005

The activity of ameloblasts during the maturation of enamel was investigated by means of autoradiography. Young rats were given daily injections of radioactive sulfur. Injections were started when the rats were five days old and continued until some of the rats were 12 days old. Developing teeth were removed at different times and prepared for autoradiography.

In every specimen that was examined, silver grains were found over enamel that was adjacent to tall, secretory ameloblasts. These cells have been identified as being engaged in matrix formation.

At the end of matrix formation, the tall ameloblasts become structurally reorganized, and the reorganized cells now act on the enamel as it matures. Despite the fact that the animals receive daily injection of labeled sulfur, the silver grains over the maturing enamel decrease and silver grains are observed over the cytoplasm of the shortened ameloblasts.

It is concluded therefore that one of the activities of the reorganized (transporting) ameloblasts is to remove sulfur or a sulfated compound from the enamel during its maturation.
Age and the cell cycle of the mouse colonic epithelium
Authors: Thrasher Jack D.
Published: February 2005

The colonic progenitor population has been investigated in four age groups of male Swiss albino mice utilizing tritium thymidine and autoradiography. The duration of the progenitor cell cycle and its component phases as well as the DNA synthetic index were determined for each age group following sequential sacrifice of the experimental animals.

Analysis of the kinetics of metaphase labeling revealed that the mean duration of the cell cycle lengthens with age, whereas S (about 7.8 hours), G2 and M remain relatively constant. Estimates of the cell cycle from the ratio of the S‐phase duration to the DNA synthetic index also demonstrate an increase with age, although the values derived from this method do not agree with those based on metaphase labeling.

Determination of the DNA synthetic index disclosed a decrease in the percentage of labeled cells with increasing age. Thus, the prolongation of the mean duration of the cell cycle apparently results from an increase in the G1‐phase.
The relationship of histochemically reactive histidine to histidase activity in the epidermis of growing rats
Authors: Reaven Eve P. , Cox Alvin J.
Published: February 2005

The histochemical localization of histidine in the epidermis and its relationship to skin histidase activity was described in rats varying in age from 17 days post‐coitum to 240 days post partum. In the fetal rat, the earliest histidase activity developed coincidentally with the first appearance of stainable histidine in the keratohyalin granules. In the neonatal period, histidase activity increased rapidly to several times the normal adult levels, corresponding in time to a period when the epidermal histidine‐containing zone was especially thick. As the thickness of this zone varied in subsequent periods during the life of the rat, parallel changes were observed in epidermal histidase activity suggesting the existence of a close interrelationship of histidine and histidase at the site of epidermal keratinization during the maturation of normal skin.
Studies on the thymus of the mammal XV. Sites of aminopeptidase activity in the thymus of the mouse
Authors: Smith Christianna
Published: February 2005

Sites of aminopeptidase activity in the thymus of the mouse were compared in material incubated in L‐leucyl‐beta‐naphthylamide and in L‐leucyl‐4‐methoxy‐beta‐naphthylamide hydrochlorides as substrates. Sites of activity were most clearly demonstrated in frozen sections, postfixed in cold acetone, incubated in L‐leucyl‐4‐methoxy‐beta‐naphthylamide hydrochloride with Naphthanil Diazo Blue B and mounted in glycerogel.

In thymuses of young mice, septa, medullary arteries and arterial capillaries were most strongly stained. Cortical lymphocytes and most medullary lymphocytes lacked aminopeptidase activity. In older mice, the high reactivity of the medulla contrasted sharply with the mostly unreactive cortex. In the medulla, the walls of the blood vessels, mesenchymal reticular cells and lymphocytes in the region of blood vessels were reactive. In the cortex, capsule, septa, and arterial capillaries were reactive; mesenchymal reticular cells, weakly so, and lymphocytes, unreactive. It would appear that much of the activity demonstrated by biochemical methods applied to thymic homogenates is a measure of reactive blood vessels and medullae. The general reaction of the medulla and the presence there of scattered, highly reactive cells lends added weight to the conclusion that the metabolic activities within the medulla are not the same as in the cortex.
The histological fine structure of perineurium
Authors: Burkel William E.
Published: February 2005

Extraocular muscles of the rat possess numerous nerves suitable for the study of fine structure. In these muscles, small nerves made up of one to ten myelinated and unmyelinated nerve fibers are surrounded by two or three layers of perineurium. The perineurium is arranged in concentric sleeves, each one cell thick. Continuous boundary membranes separate the perineural sleeves from the epineural and endoneural tissue space, but the boundary membranes may be spotty or absent between individual sleeves. The presence of boundary membranes around perineural cells distinguishes them from nearby fibroblasts which lack similar membranous investment. Tight intercellular junctions join the cells comprising each sleeve so that the nerves are completely ensheathed in perineurium. The number of sleeves decreases as the nerve becomes smaller, either by the termination of the innermost sleeve or by the loss of a sleeve as the nerve branches. The last sleeve ends shortly before the termination of the nerve. The perineurium is thus open‐ended peripherally and, at these places, the epineurium and endoneurium are continuous. Continuities between the epineurium and endoneurium also exist at the entrance and exit of blood vessels supplying the nerve and at points where reticular fibers pierce the perineurium. These structural features correlate well with the action of the perineurium as a diffusion barrier and as a pathway in the transmission of infections.
Comparative study of human internal iliac artery based on adachi classification
Authors: Roberts W. H. , Krishingner Gene L.
Published: February 2005

This study is based upon a dissection of 167 pelvic halves of Caucasian bodies. The distribution of the four major types, as based upon the Adachi classification, corresponds closely to that of the Western populations. The composite group has a distribution almost identical with the Japanese population studied by Adachi. No instances of the rare Type V were encountered. One unusual specimen which we have designated as Type VI is described.
Developmental relationship between the appearance of lymphocytes and lymphopoietic activity in the thymus and lymph nodes of the fetal cat
Authors: Ackerman G. Adolph
Published: February 2005

The origin and development of the lymphocyte populations of the thymus and the lymph nodes have been studied in the fetal cat. Fetuses ranging in age from 25 days (16 mm) to 50 days (98 mm) of gestation have been examined following formol‐sublimate‐acetic acid fixation, parlodion‐paraffin embedding and subsequent staining with toluidine blue, hematoxylin‐eosin and periodic acid‐Schiff methods.

These studies have shown an occasional lymphocyte in the primitive lymph nodes as early as the thirtieth day of gestation. A number of small‐ and medium‐sized lymphocytes are scattered randomly in the mesenchymal condensation of the developing lymph nodes by 33 days. Lymphocyte proliferation proceeds relatively slowly, and morphological evidence suggests that lymphocytes appear to develop from the mesenchymal or reticular cells of the developing lymph nodes without the intermediate formation of lymphoblasts. In the thymus, the first lymphocytic cells formed are lymphoblasts. These cells appear initially between 31 and 33 days. Lymphoblastic transformation is not generalized until the thirty‐fifth day; at this time, an occasional medium‐sized lymphocyte is evident and vascularization of the thymus begins. Development proceeds rapidly and the thymus is filled with medium‐sized and small lymphocytes by 40 days. At this time, large clusters of small lymphocytes are evident in the capsular connective tissue, and these cells soon enter lymphatic vessels located in the capsular connective tissue.

These observations indicate that the initial appearance of lymphocytes in lymph nodes precedes the appearance of lymphocytic precursors (lymphoblasts) in the thymus by 1–2 days and the development of lymphocytes in the thymus by approximately five days. Therefore, the early lymphocyte population in the lymph nodes is not dependent upon the dissemination of thymic lymphocytes or their precursors. Thymic lymphocytes, however, may contribute to the lymphocyte population of the lymph nodes at later stages of fetal development, after vascularization of the thymus and after the formation of lymphatic vessels in the capsule.
Prolonged individuality of the accessory contribution to the vagus: A peculiarity of the pig
Authors: Safanie A. H.
Published: February 2005

The bulbar and spinal components of the accessory nerve of the pig are thoroughly integrated in a common trunk at the jugular foramen. The fibers of bulbar origin separate from this trunk to form the internal ramus. The latter is especially demonstrable in the pig, since it is independent over a considerable distance in the upper part of the neck before joining the vagus. As far distally as the origin of the recurrent laryngeal nerve, the efferent fibers contributed to the vagus by the accessory nerve remain histologically separate from the afferent fibers belonging properly to the vagus. Parasympathetic, branchiomotor and afferent fibers can be distinguished in the vagal trunk without the necessity of inducing selective degeneration by supranodose vagotomy.
The skin of the whale (Balaenoptera physalus)
Authors: Giacometti Luigi
Published: February 2005

Skin specimens were obtained from every representative region of the body of an adult Finback whale (Balaenoptera physalus) and examined by means of various histochemical and histological techniques. The following characteristic features were found:

The epidermis is exceedingly thick over the general body surfaces and varies from a maximum of 3.0 mm over the ventral surface to 2.5 mm on the back.

The complex understructure of the epidermis has rete ridges oriented to the craniocaudad body axis.

The papillary layer of the dermis has long and pointed papillae which are wedged into the epidermis.

The sensory cutaneous nerve endings demonstrated by silver impregnation and cholinesterase consist predominantly of small Vater‐Pacini corpuscles situated in the higher level of the dermis.

The intricate blood capillary network, positive for alkaline phosphatase is encased in the dermal papillae.

There are no hair follicles, sebaceous and sweat glands.
Changes in the anteroposterior dimensions of the human male skull during the third and fourth decade of life
Authors: Kendrick George S. , Risinger Hubert L.
Published: February 2005

A cephalometric radiographic appraisal of the anteroposterior skull growth which occurs during a one‐year interval was made on 71 caucasoid males at the Baylor University College of Dentistry, Dallas, Texas. The subjects were from 22–34 years of age. The dimensions assessed were the anterior cranial depth, the posterior cranial depth, upper facial depth, middle facial depth and lower facial depth. A significant increase was shown to occur in all the dimensions over a period of one year except that of the lower facial depth. It was concluded that skull growth does occur in male adults after the age generally accepted as that of maturity.
Fine structure of nerve terminals in the human gut
Authors: Pick Joseph , De Lemos Carmen , Ciannella Arnold
Published: February 2005

An electron microscopical investigation was made of neuronal terminals in operatively removed human duodenum and jejunum. No intraepithelial neuronal elements were found. The lamina propria mucosae, submucosa and muscular layer possessed, in addition to large bundles of unmyelinated nerve fibers, small ones consisting of three or four axons wrapped by infoldings of one Schwann cell. Some of these axons were light; others contained mitochondria and clear vesicles measuring 200–500 Å across. Still other axons had dense‐cored vesicles with a diameter ∼ 700 Å. The plasma membranes of vesiculated axons were not thickened and only in part invested by the Schwann cell, but were covered by a basement membrane. Such profiles were interpreted as nerve terminals, and were separated from fibers of the muscularis mucosae, bases of epithelial cells and submucous capillaries by interspaces measuring 5,000–6,800 Å. The gap between neuronal terminals and smooth muscle in the muscular wall was smaller (900 Å, more often 1,500–3,000 Å). The myenteric plexus contained nerve bundles consisting of the usual axons and of preterminals; some of the latter contained small clear vesicles, others predominantly larger granulated vesicles, and still others a mixture of both types of vesicles. The similarities and differences of neuronal terminals occurring in animals and in man were pointed out. The significance of the findings of this study was discussed in the light of current concepts of the physiology of autonomic nerve transmission.
Annulate lamellae in cat lateral geniculate neurons
Authors: Doolin Paul F. , Barron Kevin D. , Seber Almera
Published: February 2005

Annulate lamellae occur in the perikaryon and dendritic extensions of lateral geniculate body neurons in the adult cat. The perikaryal arrays are 3‐dimensional membranous stacks composed of parallel rows of agranular, flattened cisterns alternating with amorphous jinear parallel densities. Each lamella contains periodic constrictions and annuli spanned by a diaphragm‐like condensation. Tenuous threads interconnect the lamellae at the annular rims with the parallel densities located midway between successive lamellae. Terminal ends of lamellae are sometimes dilated and are coextensive with cytoplasmic granular endoplasmic reticulum. Individual components of dendritic configurations are repeated at shorter intervals than their major somal counterparts, and the midregion densities are absent.

Annulate lamellae occur at a distance of 2 μ or more from the nucleus. Their origin remains undetermined. The lamellar structures are relatively resistant to marked changes displayed by cytoplasmic membranes in neurons undergoing atrophic degeneration.
Electron microscopic observations of dense bodies in parietal cells of the hamster (Mesocricetus auratus)
Authors: Winborn William B. , Bockman Dale E.
Published: February 2005

Parietal cells of the fundic region of the stomach in the golden hamster (Mesocricetus auratus) contain numerous electron‐dense bodies which have different morphologies. Granular dense bodies are the most common, with lamellar and crystalloid forms less frequent; angular dense bodies with bizarre profiles are seen rarely. In random counts on sections of identical thickness, profiles of electron dense bodies averaged five per cell section and as many as 20 to 30 per cell section are found occasionally. These structures bear a striking resemblance to lysosomes described by other workers. Electron microscopic studies were made of frozen sections of the stomach incubated in Gomori's substrate mixture. Results indicated a discrete localization of acid phosphatase reaction products within the dense bodies. Studies on glutaraldehyde fixed material without further fixation in osmium tetroxide demonstrate features not readily discernable with standard osmium fixation.
Development of cortical granules and the cortical reaction in rat and Hamster eggs
Authors: Szollosi Daniel
Published: February 2005

The origin of cortical granules is described in hamster and rat oocytes by electron microscopy. They occur first near vesicular elements of small Golgi complexes. Most of these Golgi complexes lie peripherally, but in the rat, there are a few also near the germinal vesicle. The granules arise at the concave surfaces of the Golgi complexes and apparently migrate to the cell membrane where they become aligned in close association to it. Cortical granules are found in the cytoplasm of the first polar body but not in the second. The cortical reaction, initiated by sperm attachment, consists of a gradual fusion of the membranes surrounding cortical granules with that of the egg plasma membrane and eversion of their contents into the perivitelline space. Occasionally, in the rat several granules fuse laterally to form larger cortical “caverns.” Such caverns have a single opening to the perivitelline space. The origin and extrusion of cortical granules can be compared usefully with the synthesis and merocrine‐type secretion of proteinaceous granules or mucoid droplets.
Orthogonal arrays of Microtubules in flattening cells of the epidermis
Authors: Branson Roger J.
Published: February 2005

Microtubules, 210–230 Å in diameter and many microns in length, with an associated “clear zone” around them, 450–550 Å in diameter, are demonstrated in large numbers in cells of the Stratum Granulosum of newborn rat epidermis. Few microtubules are found in the uppermost portion of the Stratum Granulosum nor are they found above this layer in the Stratum Corneum. Few microtubules are found in the germinal cells of the epidermis. Upon entering the Stratum Granulosum, cells undergo shape changes involving elongation and flattening. Microtubules have elsewhere been implicated in whole cell movement and in the movement of portions of cytoplasm, including specifically cell elongation and the related functions of maintenance of asymmetric cell shapes and projections. Evidence is presented here in support of the hypothesis that microtubules are the basic cytoplasmic structure responsible for this motility. Two cortical arrays of microtubules, parallel and orthogonal in orientation, are demonstrated at different stages of cell flattening in epidermis. If the mode of action of microtubules is undulation and resulting “intracytoplasmic peristalis,” these orthogonal arrays represent a mechanism for the formation of the shape of squamous cells. The similar orientations of microtubule populations in many cells would seem to indicate that microtubule undulation and the resulting interaction between neighboring cells accounts for the transmission of axes of orientation between cells.