bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eruption pathway formation in the presence of experimental tooth impaction in puppies
Authors: Cahill Donald R. 
Published: February 2005

AbstractEruption of permanent premolars in puppies was studied by implanting stainless steel wires through the mandible to stop eruptive movement well before the teeth were to appear in the oral cavity. Histologic and radiologic comparisons of operated with normal (unoperated) sides disclosed that the eruptive pathway forms for the impacted teeth although their eruptive movements were effectively prevented. This clearly shows that the mechanism of eruption pathway formation is not dependent upon direct and continual pressure on the bone from the erupting teeth. The genesis of pathway formation appeared to be the same for the impacted teeth as for the controls i.e., through continued ostetoclasis in the margin of the stalk of the dental follicle.
The clefts of schmidt‐lantermann: A quantitative electron microscopic study of their structure in developing and adult sciatic nerves of the rat
Authors: Friede Reinhard L. , Samorajski T. 
Published: February 2005

AbstractA quantitative electron microscopic study of the clefts of Schmidt‐Lantermann in fibers of the sciatic nerves of young and adult rats showed that the clefts are formed by two conical “male” and “female” portions of the sheath. The circumference of the female cone is approximately 15% larger than the male cone. The surfaces of the cleft transect the sheath at angle of approximately 9°. The present data indicate, also, that both the configuration of the conical portions of the sheath and their position relative to each other may change prior to fixation. Calculations indicate that each cleft permits a change in axoplasmic volume by 22%, and a change in fiber length by 9% of the fiber diameter.Clefts were not observed in nerves of rats before the twelfth day of age nor in sheaths of fibers composed of less than 20 lamellae. Newly formed clefts were wider than adult clefts. Transitional forms suggest that clefts may develop from fibers with redundant loops of myelin sheath. Radioautographic data on the incorporation of H3−leucine in nerve fibers did not indicate transport of significant amounts of this isotope into the clefts.
Development of the amphibian pineal organ; cell proliferation and migration
Authors: Hendrickson Anita E. , Kelly Douglas E. 
Published: February 2005

AbstractThe development of the pineal organ in the newt Taricha torosa has been studied utilizing cell counts and radioautography following single injections of tritiated thymidine. Embryos injected two weeks before hatching (series I) demonstrated a grain distribution pattern in the pineal organ and its underlying proliferation zone characteristic of continuous availability of isotope. Larvae injected at hatching (series II) or two weeks after hatching (series III) displayed the expected pulse label pattern for these same regions. With the possible exception of some mitosis insituin the youngest organs, pineal cells originate from a mitotically active cell population which comprises the pineal proliferation zone. After cell division some daughter cells migrate into the pineal organ, moving into the posterior part of the organ during the prehatching period, while from hatching onward the predominant migration is into the anterior part of the organ. Both the pineal photoreceptors and supportive cells arise in this manner with labeled cells of both types found in all three series, but in decreasing numbers from the youngest to the oldest series.Cell counts disclose an approximate ten‐fold increase in the number of cells within the pineal organ from embryonic to adult stages, but the rate of cell addition slows with increasing age. Both photoreceptors and supportive cells show this increase in number with the photoreceptor population being maintained at a constant 14%‐18% of the total pineal population over this entire five‐year period.
Electromyography of genioglossus and geniohyoid muscles during deglutition
Authors: Cunningham Donald P. , Basmajian John V. 
Published: February 2005

AbstractAn electromyographic investigation of the activity of the paired genioglossus and geniohyoid muscles of twenty‐six human subjects during deglutition revealed a general pattern of muscular activity involving an initial build‐up, gradual summation, and tapering of electrical potentials during swallowing of both saliva and water. There is an observable difference in the pattern of swallowing of individuals within a group and among the individual swallows of a single subject. There are longer periods of electrical activity during a saliva swallow than during a water swallow. The type of bolus also seems to affect the pattern of activity in the individual muscles as well as the length of time that they are working. The geniohyoid muscles do not appear to begin their activity with the genioglossus muscles but rather lag behind and they do not appear to be active for as long. Both pairs of muscles appear to remain active during and after the time that the bolus has passed the area of the laryngopharynx. A period of electrical silence occurs prior to the characteristic burst of activity associated with a swallow. This appears to be the result of an active inhibition.
Histology of the oviduct of the leopard frog, Rana pipiens
Authors: Lee Peter A. 
Published: February 2005

AbstractThe first one to three mm of each of the paired female oviducts in Rana pipiensconsists of a folded mucosa lacking tubular glands and enclosed by a serosa. Most of the remainder of the oviduct is lined by a folded mucosa richly endowed with simple tubular, jelly‐secreting glands. The final one to two cm of the uterine portion of the oviduct, however, has a smooth mucosal lining which lacks tubular glands. Jelly‐secreting glands penetrate to the base of the mucosa and open to the lumen between ridges capped with ciliated or mucous secreting epithelial cells. As cells of the jelly‐secreting glands grow and differentiate during the summer, they accumulate a granular secretory product which exhibits basohpilia in hematoxylinstained specimens. This is the essential change in the histological structure of the gland throughout the growing season.The adult male oviduct is a solid cord of cells for about one‐third of its length. The inferior two‐thirds, however, is like the female oviduct at an intermediate stage of seasonal growth with gland cells containing secretory granules which exhibit basophilia.
Actinomycin D and amphibian cells in vitro: Effects on monolayers, postmitotic nucleolar reconstruction and nucleolar emptying at different temperatures
Authors: Robert Burns E. 
Published: February 2005

AbstractThis study was designed to investigate (1) the effects of actinomycin D on monolayers of cells grown from explants of lung from frogs (R. pipiens) and newts (T. viridescens), (2) the effect of actinomycin D on postmitotic nucleolar reconstruction and (3) the possible protective effect that low temperature may have on the cytotoxic action of actinomycin D. Time‐lapse cinematographic studies as well as sequential phase photomicrographic analyses resulted in several conclusions. 10.0 μg/cm3actinomycin D caused a slow emptying of nucleoli followed by cytoplasmic shrinkage and eventual cell death. This cytotoxic effect proceeded from the periphery of the monolayer toward the explant. 100.0 μg/cm3actinomycin D consistently emptied nucleoli in three hours at 25–27°C. Precooled monolayers treated with 100.0 μg/cm3cold actinomycin D for three hours at 4°C showed no nucleolar emptying. Normal cells reconstructed definitive nucleoli 60 minutes after the first early anaphase movements of the chromosomes were noticed. 1.0 μg/cm3actinomycin D delayed, but did not prevent postmitotic nucleolar reconstruction. 10.0 μg/cm3actinomycin D did, however, prevent postmitotic nucleolar reconstruction during the time period studied (190 minutes after early anaphase movement of the chromosomes).
Extracellular space in frozen and ethanol substituted central nervous tissue
Authors: Van Harreveld A. , Steiner Jana 
Published: February 2005

AbstractCerebellar and cerebral cortices were frozen under various conditions; within 30 seconds of circulatory arrest, after eight minutes of asphyxiation, after ten minutes of perfusion with glutaraldehyde and after perfusion with this fixative and osmium tetroxide postfixation. Ethanol was used as the solvent in freeze substitution of these tissues. The resulting EMs closely resembled those of similar material freeze substituted in acetone. There were no differences in extracellular space even though differences have been reported between the space in EMs of conventionally fixed material dehydrated with ethanol or acetone.
The regeneration of a limb muscle in the axolotl from minced fragments
Authors: Carlson Bruce M. 
Published: February 2005

AbstractIn over 50 cases the pubo‐ischio‐tibialis muscle in mature axolotls was removed, minced and the minced fragments replaced into the site from which the muscle was removed. In 13 control animals the same muscle was removed but nothing was replaced. Regenerates were studied at post‐operational intervals of up to 150 days. Both grossly and histologically the regeneration of muscles from minced fragments in the axolotl follows a course very similar to that observed in frogs and rats. There is an initial period of destruction of the sarcoplasm of the minced muscle fragments. This is characterized by intense phagocytic activity. Following this, a population of myoblasts is established and the differentiation of mature muscle fibers ensues. The regeneration of muscles from minced fragments is compared with the formation of muscles in regenerating limbs. Following mincing, new muscle fibers develop rapidly and without the mediation of a blastema. Following limb amputation, a blastema is established before any differentiation of muscle occurs in the regenerate. This occurs more slowly than the differentiation of muscle fibers following mincing. The implications of these differences are discussed.
An ultrastructural study of smooth muscle‐like cells in the theca externa of ovarian follicles in the rat
Authors: O'Shea J. D. 
Published: February 2005

AbstractThe cells of the theca externa of large, antral ovarian follicles in the rat were studied by electron microscopy. Many resembled fibroblasts, while others possessed cytoplasmic filaments and dense bodies characteristic of smooth muscle cells. Filament‐containing cells of intermediate structure appeared to represent transitional forms between the two previous types.Small numbers of smooth muscle‐like cells were found also around small antral follicles, and many corpora lutea possessed locally well‐defined coats of smooth muscle.These observations indicate that cells with a probable contractile function are present in the theca externa of ovarian follicles in the rat. These cells may play a role in the process of ovulation.
The fine structure of the terminal branches of the hepatic arterial system of the rat
Authors: Burkel William E. 
Published: February 2005

AbstractThe fine structure of the smallest branches of the hepatic arterial system of the rat was studied with the light and electron microscope by means of alternate thick and thin serial sections.The terminal arborizations of the hepatic artery closely follow the pattern of the portal vein and give rise to a dense network of capillaries in the periportal connective tissue which closely surrounds the bile ducts. These periductal capillaries end by joining (a) interlobular veins, (b) terminal distributing veins, (c) sinusoids directly or, (d) sinusoids in common with branches of the portal vein. The capillaries arising from larger arterioles have well developed precapillary sphincters at their origins, while those arising from terminal arterioles have less prominent smooth muscle cuffs. There are no smooth muscle sphincters at the terminal ends of the capillaries where they join branches of the portal vein or sinusoids. Large endothelial cells usually guard these junctions and frequently their nuclei bulge into the lumens of the vessels and may close them off. Occasionally unmyelinated nerves with vesicles about 500 Å in diameter, some of which are granulated, are in close proximity to the endothelial cells of the capillaries. Endothelial cells also guard the beginnings of sinusoids originating from the portal vein. The sinusoids arising from periductal capillaries are identical in structure to those directly off from the portal vein. Initially the sinusoids from both types of vessels are like capillaries, with a continuous basement membrane around them and an unfenestrated endothelium. A short distance into the parenchyma they lose their basement membrane, become fenestrated and are typical sinusoids.
Hypophyseal LH and FSH release and uterine nucleic acid changes during the mouse estrous cycle
Authors: Desjardins Claude , Chapman V. M. , Bronson F. H. 
Published: February 2005

AbstractConcentrations of hypophyseal and plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured along with the total amount of uterine DNA and RNA during four stages of the mouse estrous cycle: proestrus, estrus, metestrus, and diestrus. Female mice were exposed to male olfactory stimuli to induce repeatable 4–5 day estrous cycles. The mean concentration of hypophyseal LH dropped from 2.9 μg/mg at diestrus to 0.3 μg/mg at proestrus. During this same time period the concentration of plasma LH increased from 3.3 μg/100 ml to 10.6 μg/100 ml. In contrast to the fluctuations in LH, the concentration of FSH in the hypophyses and plasma remained relatively constant throughout the estrous cycle. Uterine weight and total uterine DNA, RNA, and the ratio of RNA:DNA were all significantly greater (P < 0.05) at proestrus than at metestrus suggesting significant fluctuations in cell numbers and protein synthetic activity of the uterus during the estrous cycle. The fluctuations in LH and FSH release and in uterine nucleic acids noted during the mouse estrous cycle generally agree with observations in laboratory rats. However, the pattern of LH and perhaps FSH release preceding ovulation in mice may be different than that suggested for rats. These differences may be attributed to the greater dependence of mice on male olfactory stimuli.
The prenatal phase of the morphosis of the rat parotid gland
Authors: Redman Robert S. , Sreebny Leo M. 
Published: February 2005

AbstractThe progress of salivary gland morphosis was followed by microscopic examination of serial histologic sections of the heads and necks of rats at age intervals from 13 days in utero to two days postnatally. The anlagen of the submandibular and sublingual glands appear late in the thirteenth or early in the fourteenth day in utero, with the submandibular anlage appearing first. The parotid anlage appears last, later in the fourteenth day in utero, and is located in the buccal wall near the angle of the mouth. The cells of the anlage proliferate to form a narrow cord (the future Stensen's duct) with a cluster of cells at its distal terminus. By 16 days in utero, the terminal cluster has migrated to the vicinity of the developing mandibular ramus, at which point it begins to ramify. Ductal lumena begin to form at 17 days in utero, but the ductal system is not patent until 20 days in utero. These findings indicate that secretions of the parotid gland cannot enter the oral cavity until about two days before birth. The ductal systems of the submandibular and sublingual glands are patent at 17 days in utero, and morphologically both glands appear to be at a more advanced developmental stage than the parotid at the time of birth.
Follicular arrangements in hamster adrenomedullary cells: Light and electron microscopic study
Authors: Al‐Lami Fadhil 
Published: February 2005

AbstractLight and electron microscopic studies of the adrenal medulla of golden hamsters (Mesocricetus auratus) indicates that the chromaffin cells are arranged in hitherto undescribed irregular follicles surrounded by thin‐walled blood vessels. Each follicle is generally one cell thick with a lumen of variable size and shape, which contains finely granulated materials, nerve endings and chromaffin cell processes. Chromaffin cells are polarized; basal regions, containing the nuclei, about on the follicular cavity, and the apical areas are in close proximity to blood vessels. In the central portion of the organ, follicles contain only adrenaline cells while at the periphery “mixed follicles” occur which have both adrenaline and noradrenaline cell types. Occasional follicles with only noradrenaline cells are found in this area also. These findings have been compared with previous observations. The possible function of the follicular cavities has been discussed briefly.
Nuclear bodies in normal and chromatolytic sympathetic neurons
Authors: Dixon J. S. 
Published: February 2005

AbstractNuclear bodies, similar to those described in various types of cells, are frequently observed in the sympathetic neurons of the rabbit superior cervical ganglia both before and after postganglionic section. The bodies are 0.3 to 1.5 μ in diameter and either consist of spheres of finely granular material or else possess a dense outer cortex surrounding a less dense central zone which may contain small dense masses similar to chromatin and/or large (500 Å) or small (200 Å) dense granules. Many bodies of the latter type are unusual in that their central regions are filled with dense parallel filaments (50 and 100 Å in diameter). The thicker filaments are often arranged in an hexagonal array.The function of nuclear bodies is unknown although they have been implicated in protein synthesis. Counts of nuclear bodies were made in a large number of normal nerve cell nuclei and compared with those present in a similar number of neurons at various times after axon section. However no statistically significant difference in the numbers of nuclear bodies could be detected between normal and chromatolytic neurons. Thus the increased protein synthesis following axon section does not affect the number or structure of neuronal nuclear bodies.
Fine structure of scale development in the teleost, Brachydanio rerio
Authors: Waterman Robert Earle 
Published: February 2005

AbstractMature and embryonic scales of the zebrafish, Brachydanio rerio, were examined by light and electron microscopy. Each scale consists of a mineralized “osseous layer” superficially and a deeper, non‐mineralized, “fibrillary plate.” The mineralizing matrix contains randomly oriented filaments in decalcified sections, whereas the fibrillary plate is composed of orthogonally arranged lamellae of banded collagen fibrils embedded in electron dense material.Scale papillae and small scales first appear in the midbody region of fry between 0.95 and 1.14 cm long. The matrix of the osseous layer is produced prior to the fibrils of the fibrillary plate. Foci of mineral deposition appear in this matrix soon after its production, and increase gradually in number and extent. Cells surrounding the periphery of the scale are continuous with two layers of cells beneath the inner surface and with two layers extending a variable distance over the superficial surface. These “scale‐associated” cells are separated from the dermal collagen by other investing cell processes. The probable roles of these cells in scale formation are discussed and the need for further investigation of the fish scale as a mineralizing system is stressed.
Fine structure of degeneration and regeneration in denervated rabbit vallate taste buds
Authors: Fujimoto Sunao , Murray Raymond G. 
Published: February 2005

AbstractTaste buds of rabbit circumvallate papillae were studied with the electron microscope at intervals from six hours to 11 weeks after section of the glossopharyngeal nerve distal to the petrosal ganglion. Nerve endings were first affected, showing degeneration as early as 12 hours and disappearing by 48 hours. Rapid loss of cells and of all buds by ten days followed. Numerous inclusion bodies within type I and type II cells were interpreted as autophagic activity in type II cells and both phagocytic and autophagic activity in type I cells. Type III cells were lost primarily by pyknosis, and phagocytized by type I cells. No clear evidence of dedifferentiation, or extrusion of dead cells, was observed.Regenerated nerves appeared beneath the epithelium at 21 days but new buds first appeared at 25 days, after nerves had penetrated the basement membrane. Intimate contact of nerves with epithelial cells appears to be a precondition for taste bud renewal. Early appearance of cells resembling basal cells (type IV) followed by relatively simultaneous appearance of type I, II and III suggest independent origins for these three types. The data support a humoral hypothesis of trophic action but do not rule out a role for impulse transmission.
The effects of infused materials upon the regeneration of newt limbs. III. Blastemal extracts and alkaline phosphatase in irradiated limb stumps
Authors: Deck James David , Dent James Norman 
Published: February 2005

AbstractForelimbs of adult eastern spotted newts were irradiated with 2000 or 3000 r of x‐rays, and were amputated through the elbow region. Limbs treated in this way or infused by means of a Singer microinfusion apparatus with amphibian Ringer's solution were observed as controls. Experimental limbs were infused at various times with (1) amphibian Ringer's solution containing material extracted from two‐week‐old blastemata from unirradiated limb stumps or (2) one of four concentrations of alkaline phosphatase dissolved in Ringer's solution.Small polyps or blastema‐like conical structures were the only regenerative responses that followed the various infusion procedures. Blastemal extract and Ringer's solution alone seemed to be equally effective in inducting these regenerative growths, but no such growths followed mere irradiation and amputation. Alkaline phosphatase was more effective than either the blastemal extract or Ringer's solution in inducing the growth of conical structures. These initial growths in a number of cases persisted as very short cones composed mostly of amorphous cartilage and connective tissue or as pseudoblastematous aggregations of cells. However, extensive regression of tissues and shortening of the limb was seen rather frequently in limbs treated with alkaline phosphatase.Ringer's solution and blastemal extracts did little to reverse the regeneration‐inhibiting effects of irradiation on amputated limbs. It appears that alkaline phosphatase caused a more frequent, if still limited, reversal of these effects, and it is suggested that a part of these inhibitory effects may result from damage done to the production of alkaline phosphatase.
Experimental studies on the innervation of the diaphragm in cats
Authors: Wilson Andrew S. 
Published: February 2005

AbstractIn 12 cats unilateral transection of the phrenic nerve was followed, after survival periods of 1–30 days, by histological examination of the nerve trunk peripheral to the level of the lesion. In osmium preparations from all of the transected nerves the myelinated fibres showed incomplete degeneration while in three nerve portions impregnated with silver, some persisting axis cylinders were observed. Concurrent studies on the diaphragmatic plexus in six animals showed persistence of some nerve fibres in the crural and posterolateral zone on the side of transection while a comparable number of degenerated fibres were present in the contralateral crural zone. Bilateral phrenectomy in one animal showed persistence of fibres in the crural and posterolateral zones of the left and right sides. Following mobilization of the peripheral third of the phrenic nerve from its interserosal position degeneration was observed in one fasciculus of the diaphragmatic plexus on the side of the lesion.This evidence supports the possibility that accessory fibres join the phrenic nerve in the peripheral third of its course.