bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconstitution of the external granular layer of the cerebellar cortex in infant rats after low‐level X‐irradiation
Authors: Altman Joseph , Anderson William J. , Wright Kenneth A.
Published: February 2005

The heads of three‐day old rats were irradiated with a single dose of 200 r x‐ray and the animals were killed afterwards at intervals ranging from ten minutes to five days. Necrosis in the external granular layer of the cerebellum was evident by the fourth hour and the pyknotic cells increased in number up to 12 hours after irradiation. Between 24 to 48 hours all the pyknotic cells disappeared and the width of the layer was drastically reduced. By the third day after irradiation the external granular layer began to increase in width, and by the fourth day it was indistinguishable from normal. In adults of this group the cerebellum appeared structurally normal. In another experiment the cerebellum of rats was exposed from birth onward to 200 r on five successive days. In the animals killed immediately or one day after the last radiation session the external granular layer was totally or subtotally eradicated. In the animals surviving for four days the external granular layer reappeared over many regions of the cerebellum, and by the sixth day after irradiation it was present over its entire surface. In the latter group in animals that survived to 30 and 90 days of age the cerebellum contained a large, though subnormal, population of granule cells, indicating that the reconstituted cells were able to differentiate. These results suggested that the proliferative matrix of the postnatally developing cerebellum may be endowed with regenerative capacity.
The ultrastructure of the placental labyrinth in the kangaroo rat, Dipodomys
Authors: King Barry F. , Tibbitts F. Donald
Published: February 2005

Representative pieces of labyrinth of near‐term chorioallantoic placentas from three species of Dipodomys and one species of Microdipodops were fixed in glutaraldehyde and osmium tetroxide and examined with the electron microscope. The barrier separating the fetal and maternal blood streams in the labyrinth was found to consist of (1) the fetal endothelium and its associated basal lamina (basement membrane), (2) a single layer of trophoblast which is cellular rather than syncytial, and (3) the maternal endothelium and its associated basal lamina. Thus the chorioallantoic placenta appears to be of the endotheliochorial type in these rodents rather than hemochorial or hemoendothelial as previously suggested.
The testicular interstitial cells of a lion and a three‐toed sloth
Authors: Sinha Akhouri A. , Seal Ulysses S.
Published: February 2005

The fine structure of testicular interstitial cells of lion and three‐toed sloth showed an abundance of agranular endoplasmic reticulum, mitochondria and lipid droplets. Mitochondria were usually small and rod to rounded in shape, but large bizarre forms, such as triangular, oval and rounded with tubular and lamellar cristae were also observed. Mitochondria with lamellar cristae occurred in lion, but not in three‐toed sloth. These cristae were highly developed and appeared unique for the testicular interstitial cells. Both small and large mitochondria closely adhered to lipid droplets which were found singly or in clusters. The stored lipid droplets probably serve as a major source of substrate in androgen biosynthesis. The possible role of agranular endoplasmic reticulum in androgen biosynthesis is suggested.
Eruption pathway formation in the presence of experimental tooth impaction in puppies
Authors: Cahill Donald R.
Published: February 2005

Eruption 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

A 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

The 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

An 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

The 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

This 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

Cerebellar 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

In 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

The 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

The 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

Concentrations 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

The 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

Light 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

Nuclear 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

Mature 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

Taste 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

Forelimbs 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

In 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.
The effect of temperature differentials upon the differentiation of Mauthner's cell in Ambystoma
Authors: Piatt Jean
Published: February 2005

Eggs of Ambystoma maculatum were separated into three groups and maintained at 5°, 8° and 14°C, respectively, until stage 27. At this stage the otic vesicle was extirpated from the right side, thus eliminating the VIIIth cranial ganglion and root. The number of cases in which Mauthner's cell (MC) failed to differentiate in the absence of VIIIth roots was compared among the three temperature groups.

In a total of 713 animals, MC was absent on the side of operation in 200 cases (28.05%). Comparison of the three temperature groups with respect to the absence of MC is as follows: 14°, 39 of 212 cases (18%); 8°, 83 of 266 cases (31%); 5°, 78 of 235 cases (33%). Statistical analysis of these data demonstrates a significant difference between either one of the colder groups and the 14° group with regard to suppression of MC. When the two colder groups are tallied as a single sample, the difference is even more significant. There is no significant difference between the 5° and 8° groups. These results indicate that the differentiation of MC is more dependent upon the ingrowth of VIIIth root fibers when morphological development has been delayed by prolonged hypothermia.
Extracellular lining of bronchioles after perfusion‐fixation of rat lungs for electron microscopy
Authors: Gil Joan , Weibel Ewald R.
Published: February 2005

Rat lungs were fixed by perfusion of fixatives through pulmonary vessels which resulted in good fixation of bronchioles. This technique allows the preservation of a hitherto not described extracellular lining of the bronchiolar surface, which by conventional fixation (immersion or instillation of the fixatives into the airways) is washed out. The cilia appear to be embedded in an extra‐cellular, amorphous material. This material is often lined at its surface by a strongly osmiophilic layer. Tubular myelin figures can also be identified. Comparison with recent physiological and biochemical work, which establishes the presence of surface‐active material in the airways, strengthens the conclusion that this layer is related to bronchiolar “surfactant” fixed in situ. A mixed origin of this material from the Clara cells and from the alveolar surface lining layer is suggested.
An electromyographic study of the mylohyoid muscle
Authors: Lehr Robert P. , Blanton Patricia L. , Biggs Norman L.
Published: February 2005

An electromyographic investigation of the mylohyoid muscle was undertaken to determine its activity relative to isolated movements of the tongue and mandible and during various functions involving multiple parts of the oral apparatus. Data was obtained from 20 subjects. Using bipolar fine‐wire electrodes, the anterior fibers were found to be more active than the posterolateral fibers in a majority of activities performed. Tongue movements produced slightly more activity in the postero‐lateral fibers; the anterior fibers were more active during mandible movements. During mastication, deglutition, sucking and blowing, both the anterior and postero‐lateral fibers were markedly active.
Ultrastructural changes in the cell cycle of cultured melanoma cells
Authors: Hu Funan
Published: February 2005

The fine structure of the synchronized cultures of B16 melanoma cells at different days of incubation was studied.

Our observations demonstrate that the endoplasmic reticulum first develops in the dividing cells as simple flattened smooth cisternae, which become paired or multilamellated during nuclear reconstruction and form annulate lamellae as well as typical endoplasmic reticulum with ribosome‐studded membranes in the postmitotic and interphase cells.

The presence of both premelanosomes and melanosomes in dividing cells is unequivocal evidence that functionally mature melanocytes are capable of proliferation.
Osmium‐zinc iodide reactivity in human blood and bone marrow cells
Authors: Clark Michael A. , Ackerman G. Adolph
Published: February 2005

Buffy coats from blood and bone marrow were fixed in phosphate‐buffered glutaraldehyde, exposed to the osmium‐zinc iodide (OZI) reagent for 24 hours, dehydrated and embedded in Epon 812. OZI reactivity of blood and bone marrow cells was selectively confined to the cisternae of the rough endoplasmic reticulum (RER), Golgi complex, nuclear envelope and to the mito‐chondrial matrices; membranes and other organelles were non‐reactive. Some variation in intensity and distribution of OZI reactivity was evident within individual cells and organelles. Continuities between the cisternae of the nuclear envelope and RER as well as between these cisternae and those of the Golgi complex were more conspicuous in OZI preparations than in specimens prepared for routine electron microscopy.

The amount and distribution of the cisternal elements and mitochondria within the developing leukocytes and erythrocytes of the bone marrow were evaluated using the OZI technique. All leukocyte granules and their precursor forms fail to stain with the OZI reagent; portions of the Golgi complex most closely associated with the packaging of the cytoplasmic granules also are non‐reactive following exposure to the OZI reagent. Reactivity is absent in mature erythrocytes while mitochondria and cisternal components of immature erythroid cells yield positive OZI reactions. Heat, methanol and cyanide inhibit OZI reactivity while a dimorphism of OZI staining is induced between mitochondria and cisternal components by N‐ethylmaleimide.
Mineralized spherules in the cells and matrix of calcifying cartilage from developing bone
Authors: Kashiwa Herbert K. , Komorous James
Published: February 2005

Fresh tibias and occipital bones from newborn mice and rats, as well as from 18‐day‐old mouse and chick embryos, were stained with 10% GBHA and 5% AgNO3solutions to localize calcium and phosphate or carbonates in sphenules within the cytoplasm of chondrocytes and in the matrix of the calcifying cartilages. The mineralized spherules in the matrix adjacent to the hypertrophied chondrocytes were approximately 0.5 to 1 μ in diameter. This was comparable in size to the spherules found within the cytoplasm of the chondrocytes. The spherules within the core of the spicules distal to the hypertrophied chondrocytes were about 2–3 μ in diameter. The larger spherules were shown to contain an organic core which stained metachromatically with toluidine blue and was also stained with aldehyde fuchsin. The spherules were not visible after PAS reactions due to the intense staining. The labile GBHA and silver acetate positive spherules localized in the chondrocytes may be the source of the extracellular mineralized spherules.
The fine structure of the mouse adrenal cortex and the ultrastructural changes in the zona glomerulosa with low and high sodium diets
Authors: Shelton James H. , Jones Albert L.
Published: February 2005

The ultrastructure of the normal mouse adrenal cortex and the zona glomerulosa as stimulated by sodium restriction and repressed by high salt intake is reported. The mitochondria are zone specific, the endoplasmic reticulum tubular and the endothelium fenestrated. An intimate relationship between elements of reticulum, mitochondria and lipid droplets is seen in all animals. The rough reticulum is poorly developed in all but the glomerulosa of salt‐restricted animals. The Golgi apparatus, associated vesicles and surface microvilli are relatively more developed in the inner cortical zones and in the glomerulosa cells of stimulated animals, whereas surface coated pits and vesicles do not vary. Lysosome‐like granules are more prominant in the control reticularis and in the glomerulosa of animals on high salt intake.

In stimulated glomerulosa cells, there is an early depletion of lipid droplets and a transient increase in rough reticulum followed by a progressive increase in smooth reticulum and Golgi apparatus. At three weeks, the lipid droplets are restored. In repressed glomerulosal cells, there is atrophy of the cytoplasmic organelles while lipid droplets are increased in number and osmiophilia. An accompanying feature is the appearance of cytoplasmic β‐glycogen. These observations are discussed as to their relation to adrenocortical steroidogenesis and secretion.
Alkaline phosphatase in rodent secondary palate development. A histochemical and biochemical study
Authors: Sweney L. R. , Shapiro B. L.
Published: February 2005

Alkaline phosphatase (AlPase) has been examined histochemically and biochemically in Swiss White (SW) mouse and Sprague‐Dawley (SD) rat embryos during comparable stages of secondary palatal development. In the rats, AlPase was not detectable histochemically until after shelf transposition. Enzyme activity by biochemical assay was low in stages before shelf elevation. The mice, in contrast, showed AlPase in posterior areas of the developing shelves soon after shelf formation by histochemical techniques. With biochemical assays AlPase was higher in mouse than in rat shelves in early stages. After shelf transposition AlPase activity in the rat approached AlPase activity in the mouse by biochemical assays, but was demonstrable only in the posterior areas of the secondary palate by histochemical techniques.
Quantitative studies of the greater petrosal nerve of the mouse with the electron microscope
Authors: Shimozawa Atsumi
Published: February 2005

Quantitative counts of the greater petrosal nerve fibers of the mouse with the electron microscope have shown that, on an average, 70.8% and 28.7% of the total nerve fibers (1,111) were unmyelinated and myelinated fibers respectively. Unexpected high incidence of unmyelinated fibers in the greater petrosal nerve may indicate that it contains a fair amount of sympathetic post‐ganglionic fibers. The unmyelinated fibers in the nerve may well represent parasympathetic preganglionic fibers.
Satellite cells as the source of nuclei in muscles of growing rats
Authors: Moss F. P. , Leblond C. P.
Published: February 2005

The source of the new nuclei appearing during the growth of muscle fibers was examined in the tibialis anterior muscle of young Sherman rats (14–17 days of age) using radioautography at various intervals after a single injection of a small, non‐toxic dose of 3H‐thymidine (2 μCi/g body weight). Two techniques were employed: (1) labeled nuclei were detected in 1 μ thick radioautographs examined in the light microscope, and identified by simultaneous electron microscope examination of an adjacent section. The nuclei were then classified either as “true” muscle nuclei (within the plasmalemma of the fibers) or as belonging to “satellite cells” (which are mononucleated cells with scanty cytoplasm wedged between plasmalemma and basement membrane). (2) Muscle fibers freed by collagenase digestion were radioautographed one hour after 3H‐thymidine injection in order to determine the total number of labeled nuclei (true muscle nuclei plus those of satellite cells) per unit length of fiber.

Certain nuclei within the basement membrane of muscle fibers are labeled one hour after 3H‐thymidine and, therefore, synthesize DNA. The electron microscope demonstrates that these nuclei invariably belong to satellite cells, never to true muscle nuclei. Furthermore, the total number of labeled nuclei per unit length of fiber doubles between 1 and 24 hours; and, therefore, the labeled satellite cell nuclei undergo mitosis.

Following mitosis, half of the daughters of satellite cells are incorporated into the fibers to become true muscle nuclei. The remaining half divides again later; and half of their daughter cells are incorporated. Thus, satellite cells in young rats divide repeatedly and function as a source of true muscle nuclei.
Ultrastructural changes in mouse yolk sac associated with the initiation of vitelline circulation
Authors: Haar Jack L. , Ackerman G. Adolph
Published: February 2005

The endodermal cells of the visceral yolk sac have been studied from the seventh to eleventh day of gestation. The absorptive capacity of the cells is established by the seventh day as indicated by the presence of microvilli, coated invaginations and vacuoles, the apical canalicular system and abundance of absorptive droplets and vacuoles in these cells. Changes in cellular structure during the next three to four days include the development of the cisternal system of the rough endoplasmic reticulum, an increase in mitochondrial number and their localization near absorptive droplets and the formation of multiple Golgi complexes. Intercellular spaces form between the endodermal cells by eight to eight and one‐half days and coincide with the disappearance of the basal lamina separating the endoderm and mesoderm (angioblastic cords); these changes correlate with the formation of the vitelline vessels. As the vitelline circulation becomes functional, the visceral basal lamina is re‐established, the intercellular clefts decrease in prominence and the absorptive storage droplets and vacuoles decrease in size and number.

The apical junctional complex of the endodermal cells forms a continuous barrier for the direct passage of material from the yolk sac cavity to the developing vitelline vessels as established by the use of ruthenium red. The absorption and intracellular storage of macromolecules in the visceral endodermal cells was traced through the intermicrovillous apical coated invaginations, coated vesicles, apical canaliculi and storage vacuoles using ferritin.

Immunofluorescent studies indicate the presence of immunoglobulin (anti‐mouse gamma globulin) in the cytoplasm of the visceral endodermal cells as early as 9 to 11 days. Several blast‐like cells which also were observed in the vitelline vessels at 11 days exhibited positive fluorescence for immunoglobulin.
An electron microscopic study of mouse eggs matured in vivo and in vitro
Authors: Merchant Horacio , Chang M. C.
Published: February 2005

Mouse oocytes obtained at various times after administration of HCG or after culture were studied with the electron microscope. Gradual changes were observed in the perivitelline space, plasma membrane and cortical cytoplasm. Disappearance of the regular microvilli, the formation of lamellae‐like processes and vesicular bodies were observed. A progressive increase in the number of cortical granules and multivesicular complexes was observed simultaneously with the disappearance of the rough endoplasmic reticulum. In general, eggs which were matured either in vivo or in vitro showed similar patterns of morphological differentiation. Degenerative changes were seen in most eggs cultured for 17 hours, but not for nine hours or less. In aged tubal eggs recovered at 26 and 36 hours after injection of HCG, the number of cortical granules was decreased relative to previous stages and their extrusion from the egg was apparent. The fertilizability of the eggs matured in vitro and the role of the cortical granules are discussed in terms of the reaction of the zona pellucida.
Dendrite bundles in Lamina IX of cat spinal cord: A possible source for electrical interaction between motoneurons?
Authors: Matthews Murray A. , Willis William D. , Williams Vick
Published: February 2005

Longitudinally‐oriented bundles of closely‐aligned motoneuron dendrites in Lamina IX of cat spinal cord were examined. These dendrites were interrelated in one of several ways: (1) They were separated by a space of several microns containing small myelinated and unmyelinated fibers, synaptic boutons, and glial processes; (2) Some dendrites were separated by a gap of 0.2–0.5 μ which contained only an attenuated astrocyte process; (3) The plasma membranes of the adjacent dendrites were occasionally found in direct apposition and in most of these instances there was no detectable specialization of the opposing membranes; (4) There were definite modifications along the appositional membranes. These zones were characterized by a gap of ∼ 180 Å, and symmetrical, non‐polarized aggregations of electron‐opaque material were found along the cytoplasmic surfaces of the membranes.

It is suggested that the spatial arrangement and appositional relations of these dendrites represent a morphological substrate for the weak electrical facilitation known to occur between motoneurons in the cat spinal cord.
Structure of mammalian portal vein: Postnatal establishment of two mutually perpendicular medial muscle zones in the rat
Authors: Ts'ao Chung‐Hsin , Glagov Seymour , Kelsey Billy F.
Published: February 2005

In all mammalian species examined thus far, the media of the adult mammalian portal vein consists of two mutually perpendicular smooth muscle zones separated by a fibrous layer. The cells of the muscle zone nearest the intima are arranged circumferentially and resemble smooth muscle of other vessels; the muscle cells of the thicker, vascularized outer zone are longitudinal and contain mitochondria and pinocytotic vesicles in great abundance, suggesting relatively high metabolic activity. The adult configuration is not present at birth and only develops during the first three postnatal weeks in the rat. Partitioning of the media commences at about three days and contrasting orientation and composition of the cells of the two muscle zones is not established until seven to ten days after birth. Vasa vasorum appear in the outer muscle layer at about two weeks and nerve fibers appear even later. Post‐natal establishment of a special, double layered neuromuscular structure may be related to the adaptation of the portal circulation to the effective closure of the ductus venosus.
Adjustment of the myelin sheath to changes in axon caliber
Authors: Friede Reinhard L. , Miyagishi Tsutomu , Johnstone Millicent
Published: February 2005

“Chronic” axon swellings were produced by applying a snug ligature around the sciatic nerve of rats by the fourteenth postnatal day, allowing the nerve to compress itself by its subsequent growth. The technique results in swelling of the entire myelinated fiber population proximal to the constriction, and in hypoplasia or arrested growth distal to it. “Chronic” axon swellings differed strikingly from the “reactive” axon swellings in the stumps of transected nerves in having normal or slightly below normal concentrations of axoplasmic organelles, including mitochondria and smooth endoplasmic reticulum.

Swelling of the axons was associated with attenuation of their sheaths having normal interperiod width but fewer turns of myelin lamellae than found in normal fibers of comparable calibers. Release of the compression resulted in rapid restitution of axon swellings; the excess axoplasm was drained from the fibers and the sheaths rapidly acquired normal thickness. The magnitude of all observed changes in the sheaths of swollen and of restituted fibers was consistent with a rearrangement of the existing turns of myelin lamellae without change in the total amount of myelin. The myelin sheath appears capable of adjusting to both increases or decreases in axon size by slippage of its lamellae.
The anterior buccal gland of the Rat: A mucous salivary gland which develops as a branch of stensen's duct
Authors: Redman Robert S.
Published: February 2005

Examination of serial histologic sections of the head and neck regions of rats at selected age intervals from 14 days in utero to 100 days postnatally revealed that at 16 days in utero, a second salivary gland arises from the rudimentary parotid (Stensen's) duct. This gland develops more rapidly than the parotid gland; its acini are essentially mature prior to weaning, preceding parotid acini in this respect by several days. All cells of the secretory units of the mature gland stain positively with both alcian blue and periodic acid‐Schiff, indicating that the gland is of pure mucous type. The body of the gland occupies a space lateral and mostly superior to the maxillary buccal sulcus, nestled beneath the anterior bulge of the masseter muscle, near the point where the buccal and mandibular marginal branches of the facial nerve cross paths. It is the only salivary gland in the buccal wall anterior to the third molar; hence, the proposed name of anterior buccal gland. These observations suggest: (1) Samples of rat parotid saliva collected proximally and distally to the junction of the ducts of the parotid and anterior buccal glands are likely to differ significantly in the quality and quantity of mucosubstances which they contain. (2) The divergent differentiation of two branches of the same glandular primordium in this instance implies differences in the inductive qualities of their respective mesenchymal beds.