bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological variations of pigment granules in eyes of the rhesus monkey
Authors: Hu Funan , Endo Hidehiko , Alexander N. J.
Published: February 2005

Melanin granules of rhesus monkey eyes develop in four stages. Early in stage I, they are small, spherical or elongated, membrane‐limited vesicles containing parallel arrays of membranes oriented along the long axis and having regular periodicity. Melanization of these membranes, which is indicated by increased thickness and electron opacity, leads to the formation of stages II and III granules. In stage IV, their internal structure is completely obliterated by electron‐dense melanin. During this process of development, melanosomes are transformed from thin, long vesicles into large ovoid bodies.

By 60 days of gestation, melanosomes have developed in the pigmented epithelium of the iris, ciliary body, and retina, those in the retina being more mature and fully pigmented than the others.

Stromal pigment cells of the uveal tract develop later than those of the pigmented epithelium. Pigment first appears in the iris at 140 days, then in the ciliary body, and lastly (150 days) in the choroid, where only well‐developed melanosomes are found.

Melanosomes of the stromal pigment cells as well as those of the pigmented epithelium may have their origin in the iris. Early melanosomes (stage II) are present almost exclusively in the iridial cells whereas mature forms are found in the ciliary and retinal cells.
Cinemicrography of mouse oocyte maturation utilizing nomarski differential‐interference microscopy
Authors: Sorensen Ralph A.
Published: February 2005

The analysis of in vitro mouse oocyte maturation using Nomarski differential‐interference optics and time‐lapse cinemicrography provides information on the morphological events of oocyte maturation and their duration with greater precision than previously available. Furthermore, some previously unreported morphological events are described. The breakdown of the germinal vesicle was preceded for 41 minutes by extreme activity of the germinal vesicle membrane. The perivitelline space formed precociously by expansion of the zona pellucida rather than by shrinkage of the oocyte. Condensation of the bivalents, centromeric repulsion, formation of the metaphase I plate, and growth of the spindle apparatus were observed. Metaphase I, defined as the period from formation of the metaphase plate to the beginning of anaphase, lasted four hours and twenty‐seven minutes. Anaphase chromosome separation began 11 hours and 15 minutes after disintegration of the nucleolus, and was complete within ten minutes. Polar body formation began before the completion of anaphase. The mid‐body formed between the separating anaphase dyads, and moved with the telophase spindle to the newly formed oocyte‐polar body boundary.
Canaliculi and tubulovesicles of rat parietal cells
Authors: Leeson Thomas S.
Published: February 2005

Mucosa of the rat stomach was (fast) frozen rapidly by immersion in liquid nitrogen or Freon 22 before chemical fixation in glutaraldehyde and/or osmium tetroxide. In parietal cells, continuity between membranes of the canalicular system and tubulovesicles was seen. This confirms the hypothesis that membrane flow between the two elements occurs in the secretory cycle. Such continuity is difficult to demonstrate in material fixed directly and presumably, therefore, the rapid freezing was effective in preventing changes in membranes and membrane flow during the period of fixation.
Localization of thiamine pyrophosphatase in synaptic vesicles
Authors: Griffith D. L. , Bondareff W.
Published: February 2005

In the perikarya of pontine reticular formation neurons thiamine pyrophosphatase activity was localized within the innermost lamellae of the Golgi complex and, to a lesser extent, within cisternae of the rough endoplasmic reticulum. In axons, thiamine pyrophosphatase activity was localized within tubular profiles, presumed to be endoplasmic reticulum, and in axonal terminals it was found within presynaptic vesicles. This selective localization of pyrophosphatase activity suggests the derivation of synaptic vesicles from membranes of the Golgi complex.
Intramural distribution of adrenergic and cholinergic nerve fibers innervating arterioles of the hamster cheek pouch
Authors: Ausprunk Dianna H. , Berman Herbert J. , McNary William F.
Published: February 2005

Electron microscopic, autoradiographic and histochemical techniques were used to determine the distribution of adrenergic and cholinergic nerve fibers within the walls of arterioles having a width of 35 to 60 μ in the hamster cheek pouch. Nerves were confined to the adventitia and their varicose regions were distributed so that 86% were located within 1 μ of the media. Arterioles exposed to 3H‐norepinephrine and examined by light microscopic autoradiography exhibited several sites of silver grain accumulation, as a result of the uptake of 3H‐norepinephrine by adrenergic nerve fibers. In electron autoradiographs, approximately 70% of all adventitial nerve fibers exhibited silver grains and are therefore considered to be noradrenergic. The majority of all nerve‐associated silver grains were located near the adventitial‐medial junction. Smooth muscle cells sometimes possessed concentrations of silver grains above background levels, perhaps reflecting the capacity of these cells to take up norepinephrine. Acetylcholinesterase activity was demonstrated in 16 to 44% of the adventitial nerve fibers and they are presumed to be cholinergic. Acetylcholinesterase‐stained fibers were distributed throughout the adventitia with 43% being located closer than 1 μ to the media. The morphological identification of a dual adrenergic and cholinergic innervation of arterioles of the hamster cheek pouch indicates the probable presence of an active as opposed to a passive vasodilatory mechanism.
Palatal closure in the mouse as demonstrated in frozen sections
Authors: Greene R. M. , Kochhar D. M.
Published: February 2005

During development of the secondary palate, mouth‐opening reflexes and swallowing movements have been observed previously. They have been assumed to be necessary in order to allow the descent of the tongue, thus enabling movement of the palatine shelves from a vertical position lateral to the tongue, to a horizontal position superior to the tongue. Interpretation of fixed, paraffin‐embedded sections, showing large spaces in the oral cavity, has added to the concept that the tongue descends into a space.

Hexane‐quenched, cryostat‐cut, frozen sections of fetal mice heads show that no oral space exists at any time during elevation of the palatine shelves. Interpretation of static micrographs indicates that prior to shelf elevation the tongue is in contact with the nasal septum above and the vertical palatine shelves laterally. When the shelves elevate they seem to “flow” dorsally and interpose themselves between the tongue inferiorly and the nasal septum superiorly.
The independent functions of the two heads of the lateral pterygoid muscle
Authors: McNamara James A.
Published: February 2005

Investigations on the role of the lateral pterygoid muscle in mandibular movements have been limited due to difficulties in obtaining consistent neuromuscular recordings in human subjects. The rhesus monkey was used as a substitute experimental animal. Thirty‐three Macaca mulatta were monitored in 113 electromyographic recording sessions. Two distinct functional patterns were identified from the region of the lateral pterygoid muscle, depending upon the location of the electrodes within this muscle. Through anatomical dissection of areas of electrode placement in 12 animals, the two patterns of activity were related to the inferior and superior heads of the lateral pterygoid muscle. The inferior head acted synergistically with the suprahyoid muscle group in opening movements of the mandible. No activity was noted in closing movements, or in swallowing. In contrast, the superior head was not active during opening movements. Electromyographic activity of the superior head, antagonistic to the suprahyoid muscles, was observed during such closing movements as chewing and clenching of the teeth and during deglutition. The superior head presumably positioned or stabilized the condylar head and disc against the articular eminence during closing movements of the mandible, while the inferior head assisted in the translation of the condylar head downward, anteriorly, and contralaterally during opening movements. Thus, the two heads of the lateral pterygoid can be considered as two functionally distinct muscles.
Fine structure of olfactory epithelium in the mud puppy, Necturus maculosus
Authors: Farbman Albert I. , Gesteland Robert C.
Published: February 2005

The olfactory epithelium of Necturus is approximately 300 μ thick, or two to three times the thickness seen in most other vertebrates. The epithelium contains three cell types, olfactory receptor cells, supporting cells and basal cells. The receptor cell population is made up of both non‐ciliated and ciliated cells in a ratio varying from 1:1 to 2:1. The ciliated cell morphology is essentially similar to that of other vertebrates. The non‐ciliated cells contain groups of centrioles located at various levels in the supranuclear cytoplasm and a fibrogranular complex similar to that seen in cells engaged in ciliogenesis. This variable morphology suggests a continuous turnover of olfactory cell population, or, at least, a continuous turnover of the dendritic portion of the cell. Alternatively it may indicate that there are two different receptor cell populations with different functions. The supporting cells in the olfactory epithelium contain a variable number of secretory granules. In the anterior part of the nasal sac there are relatively more cells with many granules whereas in the posterior region the supporting cell cytoplasm contains mostly smooth endoplasmic reticulum. Olfactory receptor axons are ensheathed in groups by basal cell cytoplasm before they leave the epithelium.
The coronary vessels in the heart of a marsupial, Trichosurus vulpecula
Authors: Dowd David A.
Published: February 2005

The coronary arteries and veins are described in the phalanger (Trichosurus vulpecula), an Australian marsupial, after study of 16 hearts. Several hearts were prepared by injection of the vessels with either latex or vinyl plastic.

The distributing branches of both coronary arteries are within the myocardium and are not visible on the surface of the heart. The right coronary artery arises in typical fashion and supplies the non‐septal wall of the right ventricle almost entirely, the dorsal half of the interventricular septum, the dorsal part of the non‐septal wall of the left ventricle and part of the right artium and its ventral auricle. The left coronary artery also arises typically and supplies the greater part of the non‐septal wall of the left ventricle, the ventral part of the interventricular septum, part of the infundibulum, the left atrium and part of the right atrium. At its origin it is larger than the right coronary artery. The ventral and dorsal septal arteries have an unusual course lying in the subendocardial tissue of the right ventricle. It is believed that arteries in this position have not been described previously.

The great cardiac vein opens directly into the right atrium. A typical coronary sinus is present but formed only from veins draining the dorsal aspect of the heart.

It is concluded that the coronary circulation in T. vulpecula closely resembles that of the avian heart and is unlike both the monotreme and placental mammalian patterns.
Prenatal size–age relationships and external morphology in the mongolian gerbil (Meriones unguiculatus)
Authors: Bagwell J. N. , Leavitt W. W.
Published: February 2005

Embryos from timed matings were studied at days 12–24 of gestation with respect to crown‐rump length and external appearance. A linear increase in length was observed from the twelfth (2.5 mm) to the twenty‐fourth (27.7 mm) day with the largest increases occurring between days 20 and 21 (3.8 mm) and days 22 and 23 (4.2 mm). The smallest daily increases were observed between days 15 and 16 (1.01 mm) and days 21 and 22 (1.03 mm), while the average daily increment for the remaining days was between 1.5 mm and 2.5 mm. Major changes in external appearance occurred on days 13, 14, 17 and 20 of gestation. Those features which could be observed externally were described for each of the days during the period studied. Late prenatal development in the gerbil resembles that of other myomorph rodents but proceeds at a slower rate than in other species such as the mouse or hamster. This slower rate of development may be of value when precise timing of drug administration and recovery of embryos is necessary.
Preliminary ultrastructural demonstration of hyaluronic acid‐proteoglycan interaction in cartilage matrix
Authors: Quintarelli G. , Vocaturo A. , Bellocci M. , Rodén L. , Ippolito E. , Baker J. R.
Published: February 2005

Recent chemical studies have indicated that the chondroitin sulfate proteoglycan of cartilage interacts with hyaluronic acid to form high molecular weight aggregates. In the present study, morphological evidence has been obtained that this interaction represents a physiologically occurring phenomenon, as indicated by the finding that the proteoglycan particles disappear from tissue sections on digestion with a hyaluronidase from Streptomyces hyalurolyticus, which is specific for hyaluronic acid.
Electron microscopic immunohistochemical localization of growth hormone‐release inhibiting hormone (somatostatin) in the rat median eminence
Authors: Pelletier Georges , Labrie Fernand , Arimura Akira , Schally Andrew V.
Published: February 2005

Using an immunohistochemical technique at the electron microscopic level, we have observed that growth hormone‐release inhibiting hormone (somatostatin), the hormone which inhibits the release of growth hormone, is contained in the secretory granules of many nerve endings mainly located in the external zone of the median eminence.
Identification of two populations of lymphocytes in rats and mice by routine transmission electron microscopy
Authors: Pereira Gerard
Published: February 2005

Staining en bloc in aqueous uranyl acetate following double fixation in glutaraldehyde and osmium tetroxide reveals two types of lymphocytes (dark and light) in most rat and mouse lymphatic tissues studied by transmission electron microscopy. While only dark lymphocytes populate the thymus, both dark and light lymphocytes congregate within the bone marrow and the thymus‐independent areas or the spleen and lymph nodes. Two similar types of plasma cells coexist in the spleen and lymph nodes.
Alterations in hepatocytes after manipulation of the diet: Copper, zinc and cadmium interactions
Authors: Miller M. L. , Murthy L. , Basom C. R. , Petering H. G.
Published: February 2005

Morphometric analyses of liver parenchymal cells were performed on male albino rats fed a semipurified diet supplemented with two levels of copper and zinc. These metals were administered in demineralized drinking water to four groups of animals at two levels. (1) 0.25 μgm Cu/ml, 2.5 μgm Zn/ml, and (2) 1.0 μgm Cu/ml, 10 μgm Zn/ml. Cadmium, also administered in the drinking water daily to rats at 17.2 μgm cadmium/ml, was given to one group of animals on each of the two semipurified diets. Two groups of rats were given laboratory chow plus 17.2 μgm Cd/ml for 71 days and for 280 days.

Volume densities of all organelles diminished significantly when levels of copper and zinc were lowest. Surface densities of rough and smooth endoplasmic reticulum were significantly decreased.

Higher levels of copper and zinc produced morphologic and morphometric parameters which fell just below those obtained for rats fed chow. Glycogen accumulation was highest when the levels of metal were low. Lipid inclusions were more frequent with semipurified diets than with chow.

Hepatocytes from rats fed the semipurified diet with low copper and zinc plus cadmium demonstrated a significant increase in smooth endoplasmic reticulum compared to animals fed the semipurified diet alone. The smooth endoplasmic reticulum changed little when cadmium was given to rats receiving adequate copper and zinc. Smooth endoplasmic reticulum increased when diets included chow and cadmium whereas rough endoplasmic reticulum decreased.

Cup‐shaped and elongated mitochondria with longitudinal cristae appeared in hepatocytes from animals fed chow with cadmium. These were not seen with semipurified diets and cadmium.
Studies on the NZB mouse thymus. I. Thymus weight relationships to age and body weight from birth to old age
Authors: Simpson L. O.
Published: February 2005

The relationship of age and body weight to thymus weight in mature NZB mice is reported. Multivariate analysis of data obtained from nearly 1000 mice shows that the decrease in the weight of the thymus, which occurs during thymic involution, may be represented by a smooth curve which flattens out about the twentieth lunar month of age. NZB mouse thymus weight does not appear to be influenced by Coombs test positivity and involution patterns are similar to those of non‐autoimmune mouse strains.
Neuromuscular spindles and depressor masticatory muscles of monkey
Authors: Dmytruk Rostyslaw J.
Published: February 2005

The purpose of this study was to obtain anatomical information concerning the presence of neuromuscular spindles in depressor muscles of the mandible of the monkey. The lateral pterygoid and anterior belly of digastric muscles were examined with serial paraffin sections of heads of seven fetal pig‐tailed monkeys and of muscles dissected out of five adolescent rhesus monkeys. No neuromuscular spindles were evident in these muscles, nor in the mylohyoid and posterior belly of digastric muscles. The fetal muscles contained a concentration of muscle spindles in the horizontal portion of the temporal muscle and in the deep portion of the masseter muscle, in the region anterior to the temporomandibular joint. These last two muscles insert into the anterosuperior portion of the articular disc.
In vivo and electron microscopic observations on Schwann cells in developing tadpole nerve fibers
Authors: Billings‐Gagliardi Susan , De Webster Henry F. , O'Connell Maureen F.
Published: February 2005

The migration of Schwann cells and their early association with axons were studied in transparent tadpole tail fins. Nomarksi optics revealed that in vivo these cells are pleomorphic, changing their shape by extending and withdrawing long, blunt pseudopods. Daily observations of the same fiber fascicles for a month or more combined with intensive short‐term studies of other tadpoles showed that migrating Schwann cells move sporadically at rates of up to 114 μm/day. They are usually, although not always, in contact with one or more axons. In the electron microscope, these migrating cells are similar in cytoplasmic structure to others that have settled down and begun to spread along axons; however, they possess no basal lamina. Later, Schwann cells become more spindle‐shaped and acquire a basal lamina. Schwann cell surface characteristics and the changes imposed by the presence of the basal lamina may be important in the establishment of permanent axon‐Schwann cell relationships. In our living material we were unable to visualize the intricate, rapidly changing associations between Schwann cells and small axonal fascicles that precede myelination. However, they are probably more complex than Speidel's studies would indicate.
Localization of granules stained artifactually with the Fink‐Heimer technique in certain brain stem nuclei of the pigeon
Authors: Russell Lonnie D. , Hard Walter L.
Published: February 2005

Sections of normal pigeon brain treated with the Fink‐Heimer technique frequently show granular deposits, suggestive of degenerating synaptic terminals, in relation to the soma of cells in the nucleus ruber and formatio reticularis. Electron microscopic examination of such reactive cells shows the argyrophilic granules to be intracellular inclusions which have the appearance of catecholamines.
Ultrastructure of the sinus wall of murine bone marrow in myelogenous leukemia
Authors: Campbell Ferrell
Published: February 2005

The ultrastructure of bone marrow of RF mice having an acute myelogenous leukemia induced by inoculation with leukemic cells was investigated. In several respects sinuses of leukemic marrow are similar to normal marrow. Sinuses are present in numbers approximating that of the normal; the lining cells of the sinus wall have organelles similar in distribution and number to those of normal lining cells; the sinus wall is continuous, having openings only in conjunction with blood cells that are migrating through it (migration pores); migration pores occur within and not between lining cells. Abnormalities observed in leukemic marrow are the occurrence of virus‐like particles in leukemic cells, the presence of numerous particles 300 to 500 Å in diameter in the extracellular space, reduction in the number of adventitial cells of the sinus wall and an increase in the thickness and distribution of extracellular material located near the basal surface of lining cells.
Cyclic AMP induces ultrastructural differentiation of normal adult human adrenocortical cells cultured in vitro
Authors: Armato Ubaldo , Nussdorfer Gastone G. , Mazzocchi Giuseppina , Andreis Paola G. , Draghi Enrica
Published: February 2005

Electron microscopic studies have revealed that cyclic AMP, like ACTH, induces structural differentiation of adult human adrenocortical cells cultured in vitro. These findings support the hypothesis that cyclic AMP can function as an intracellular mediator of the action of ACTH on the human adrenal gland.
A fine structural study of the development of the chick flexor digital tendon: A model for Synovial sheathed tendon healing
Authors: Greenlee Theodore K. , Beckham Cassandra , Pike Diana
Published: February 2005

The development of the synovial sheathed flexor digital tendon in the chick was studied by light and electron microscopy in 12‐day embryos to 22‐day post‐hatched chickens. Areas of specialized connective tissue differentiation were identified in this complex structure consisting of a lubricated synovial sheath, elastic vincula and fibrocartilaginous adaptations on the surface of the tendon. The presence of some of these specialized adaptations may be related to tendon. The presence of some of these specialized adaptions may be related to the specific types of mechanical forces and stresses applied to the developing connective tissue system. This model system appears to be appropriate for the experimental study of tendon injuries related to thehuman hand.
Light dependence of osmium reactivity in mouse photoreceptor cells
Authors: Pourcho Roberta G. , Bernstein Maurice H.
Published: February 2005

Mouse photoreceptor cells exhibit local accumulations of osmium deposits after prolonged osmic staining at slightly elevated temperatures. Deposits were evident along the membranes of outer segment lamellae, Golgi cisternae and vesicles, nuclear envelopes, and synaptic vesicles. Other membranes within the photoreceptor cells were unreactive. No osmium reactivity was seen in other cells of the retina except for osmiophilic outer segment material which had been phagocytized by the pigment epithelium. In the outer segments, inner segments, and synaptic regions of the photoreceptor cells, the amount of osmium reactivity was increased by light stimulation and decreased following extended dark adaptation. The possible significance of the localized osmium reactivity is discussed.
Midbodies and beaded threads
Authors: Bellairs Ruth , Bancroft Mary
Published: February 2005

When the dorsal surface of the young chick embryo is examined by SEM, long threads are visible, each of which appears to connect pairs of cells; these cells may be separated from each other by several intervening cells. Many of the threads possess a bead‐like structure about half way along their length. When sections of the beads are examined by TEM they are found to resemble midbodies. Furthermore, the threads possess longitudinally arranged structures within them, which are probably the remnants of the microtubules which were part of a mitotic spindle. It is concluded that each bead is a midbody and that each beaded thread is the remains of a telophase bridge connecting two daughter cells which were incompletely separated after mitosis had taken place. The possible function of the beaded threads is considered.
The hypothalamic magnocellular neurosecretory system of the guinea pig. I. Immunohistochemical localization of neurophysin in the adult
Authors: Silverman A. J.
Published: February 2005

With the use of the unlabeled antibody enzyme technique and antiserum against bovine neurophysin I, neurophysin was localized in the hypothalamic magnocellular neurosecretory system of the adult guinea pig. Immunoreactive deposits were found in the perikarya of the supraoptic and paraventricular nuclei, their fiber projections and terminals in the posterior pituitary. No parvicellular neurophysin‐positive components were observed. In the median eminence neurophysin was seen in the zona interna where axons of the supraoptico‐hypophysial tract pass on their way to the neural lobe. The peptide was also present in axons projecting into zona externa which terminate on the primary portal plexus.
The fine structure of the chinchilla placenta
Authors: King Barry F. , Tibbitts F. Donald
Published: February 2005

The structure of the placental labyrinth, interlobular or “coarse” syncytium, visceral (splanchnopleuric) yolk sac, giant cells and subplacenta of the chinchilla was studied with the electron microscope. The fine structure of the interhemal membrane of the placental labyrinth was found to be hemomonochorial, consisting of a single layer of syncytial trophoblast. In this respect, the placental labyrinth was similar to that of another caviomorph rodent, the guinea pig. The labyrinthine trophoblast had pinocytotic vesicles as well as larger vacuoles and multivesicular bodies. The interlobular syncytium contained granular endoplasmic reticulum, and in one case from early in gestation there were intracisternal granules in the ER. The visceral endodermal cells of the inverted yolk sac placenta had a well‐developed system of apical vesicles and tubules as well as larger cytoplasmic vacuoles. Their appearance was similar to that of endodermal cells found in other rodents which are known to absorb proteins and other substances from the uterine lumen. Towards term the giant cells were often vacuolated and contained large deposits of glycogen as well as lipid droplets. The syncytial trophoblast of the subplacenta contained numerous moderately electron‐dense granules which may be secretory in function; cytotrophoblastic cells lacked these granules. The subplacental syncytium often surrounded spaces or lacunae which contained an electron‐dense granular material.
Differentiation of normal human mammary epithelial cells in culture: An ultrastructural study
Authors: Russo Jose , Furmanski Philip , Bradley Ronald , Wells Peter , Rich Marvin A.
Published: February 2005

An ultrastructural and cytochemical study of normal human mammary epithelial cells cultured from post‐weaning breast fluids is described. Cells were examined at the time of plating and at intervals up to 28 days in culture. Three different stages in the morphological differentiation of these cells in vitro were observed: (1) the first stage was the formation of a monolayer of single cells, which occurred between days 1 and 10 in culture. The cells in this stage were not interconnected by junctional complexes and lacked Mg++‐ dependent ATPase activity in the plasma membranes, but did contain a large quantity of lipid and exhibited some secretory characteristics. (2) The second stage, occurring at 10 to 16 days in culture, was characterized by the formation of junctional complexes, the appearance of Mg++‐dependent ATPase in the plasma membrane and a decrease in the number of dense bodies with peroxidase activity. (3) The third stage, occurring at 16 to 28 days in culture, was characterized by the formation of stratified layers of epithelial cells, which were inter‐connected by a large number of desmosomes with numerous pleomorphic microfilaments. The Mg++‐dependent ATPase activity in the plasma membrane was retained and the dense bodies with peroxidase activity were rarely observed at this stage. During the last seven days in culture, secondary lysosomes, autophagosomes and residual bodies were prominent in the cells of the stratified layer. After 28 days in culture, the cells began to round up and slough off the culture plate.
An electron microscopic study of the closure of the optic fissure in the golden hamster
Authors: Geeraets Ragnit
Published: February 2005

During early development of the mammalian eye, invagination and differential growth result in the formation of a cleft, the optic fissure, through which the hyaloid artery reaches the interior of the optic cup. Closure of this fissure was studied by electron microscopy in hamster embryos from days 10 through 12 of gestation. Closure occurred only when and where the basal lamina, which invests the entire wall of the optic cup, had disappeared. No morphological evidence was found that indicated a mechanism for the breakdown of the basal lamina lining the fissure, the fusion of surface cells of opposing sides and restoration of the basal lamina along inner and outer margins of the wall after closure. While in previous light microscopic investigations of the developing human eye eversion of the inner layer into the fissure has been reported, an inversion of the outer layer was found in this study. During inversion cells of the outer layer temporarily changed their orientation. While most of these cells remained within the layer when it returned to its normal position, some cells became separated and degenerated. Inversion of the outer layer, breakdown of the basal lamina and degeneration of superfluous cells appear to be necessary events for a normal closure to occur.
An electron microscopic study on the type I pneumocyte in the cat: Differentiation
Authors: Mercurio Anthony R. , Rhodin Johannes A. G.
Published: February 2005

This investigation describes the differentiation of the type I pneumocyte from undifferentiated pulmonary epithelium. Cells lining subpleural alveolar septa were photographed from serial sections with the electron microscope and a three dimensional representation of each cell was obtained by transferring the contours of the cell membranes from micrographs to transparent plastic sheets which were then spaced to scale and stacked. The results of this study indicate that: (1) the only reliable criterion for differentiating between type I and type II cells is the commencement of attenuation of the type I cell; (2) differentiation of the type I cell occurs via the formation of one or more cytoplasmic attenuations that eventually fuse peripherally, thereby surrounding the unattenuated cell soma; (3) with respect to individual cells, blood‐air barriers tend to form in distal areas of the attenuating cytoplasm before proximal areas; (4) both type I and type II pneumocytes retain certain characteristics that reveal their common origin.
Osteopetrosis in the ia rat cured by spleen cells from a normal littermate
Authors: Marks Sandy C.
Published: February 2005

Osteopetrosis in ia rats has been cured by combining whole‐body irradiation with infusion of spleen cells from a normal littermate. The cure, first seen radiographically and histologically as areas of resorption below the epiphyseal plates of long bones, progressed to produce marrow cavities of normal proportions. Treatment of ia rats with either radiation or normal spleen cells alone was not successful. Furthermore, osteopetrosis was induced in normal littermates when radiation was combined with infusion of mutant (ia) spleen cells. These results show that spleen cells contribute to the resorbing capacity of the skeleton and suggest that osteoclasts might have a hematogenous origin.
Osteoligamentous guidance of the movements of the human thumb
Authors: Bojsen‐Møller Finn
Published: February 2005

On examination of the thumbs of 20 dissected preparations of ligaments and joints, of ten dry skeletons and of a number of living hands, apoposition (from apo = away from) was distinguished as a position in which the first carpometacarpal joint is fully abducted and laterally rotated and in which one or both distal joints of the thumb are flexed. Apoposition is commonly used in writing and it has a specific osteoligamentous basis for its stability: (1) a Y‐shaped intermetacarpal ligament is attached by two crura to the base of the second metacarpal bone and by a common stem to the first metacarpal. Together with the palmar and dorsal oblique ligaments it becomes taut at abduction and establishes thereby a fixed center for the circumduction. Stability is enhanced as the circumduction takes place in the radial flat part of the joint away from the center; (2) of the two palmar prominences of the head of the first metacarpal bone the radial is the larger. At 25–30° flexion in the metacarpophalangeal joint the prominence fits into an excavation on the base of the proximal phalanx in a manner which together with the ulnar collateral ligament locks the joint against mutual abduction and lateral rotation, and (3) the radial part of the trochlea of the interphalangeal joint is larger than the ulnar and secures, together with the ulnar collateral ligament, the joint against a radial luxation. Apoposition does not require activity of the thumb muscles; it is brought about by applying an external force to the ulnar side of the thumb and it is checked by ligaments and the shape of the joints.
Loss of cortical granules in mouse ova activated in vivo by electric shock
Authors: Zamboni Luciano , Patterson Harlan , Jones Marilyn
Published: February 2005

This report documents for the first time the occurrence of a cortical reaction in parthenogenetic mouse ova activated by electric shock in vivo.
Presumptive relationships between ventricular proliferation and development of the lateral motor columns in the spinal cord of Rana pipiens larvae
Authors: Pollack Emanuel D.
Published: February 2005

The extent of mitotic activity in the proliferative ventricular zone of the developing frog (Rana pipiens) spinal cord is a function of both the longitudinal cord level and the developmental stage. Counts of mitotic cells in the ventricular zone demonstrated higher levels of proliferation in the dorsal than ventral halves of the spinal cord with decreasing total proliferative activity from the early to late larval (tadpole) stages. Mitoses were virtually absent from the ventricular zone by the conclusion of metamorphosis.

Changes in mitotic counts at different levels of the spinal cord can be correlated with the presence or absence of the brachial or lumbosacral pairs of lateral motor columns. A parallel also exists between the caudo‐cephalic direction of motor column development and a similar progression of mitotic activity in the ventricular zone, a portion of which gives rise to the spinal motor neurons.

It is suggested that proliferation in the ventricular zone during the larval frog stages contributes to the presumptive motor neuron population that migrates into the lateral motor columns during their later maturation.
Organization of desmosomes in Bowman's gland duct cells in a marsupial
Authors: Kratzing Jean E.
Published: February 2005

Non‐secretory cells lining the ducts of Bowman's gland in the olfactory epithelium of the bandicoot (Isoodon macrourus) are united below the duct lumen by an unusually well‐organized series of desmosomes linked by conspicuous fibrillar bundles with long mitochondria aligned close to the bundles. It is suggested that these junctional specializations may help to maintain an intact duct lumen in a part of the epithelium with considerable intercellular space.
Fine structure of the secretory and nonsecretory ameloblasts in the frog. I. Fine structure of the secretory ameloblasts
Authors: Zaki A. E. , MacRae Edith K.
Published: February 2005

Amelogenesis in the tooth germs of the frog Rana pipiens was examined by electron microscopy at different stages of tooth development. Cellular changes in secretory ameloblasts during this process showed many basic similarities to those in mammalian amelogenesis.

Amelogenesis can be divided into three stages based on histological criteria such as thickness of enamel and the relative position of the tooth germ within the continuous succession of teeth. These stages are early, transitional and late. The fine structure of the enamel‐secreting cells reflects the functional role of these ameloblasts as primarily secretory in the early stage, possibly transporting in the late stage and reorganizing between the two functions in the transitional stage. In early amelogenesis the cell exhibits well‐developed granular endoplasmic reticulum, Golgi complex, microtubules, dense granules, smooth and coated vesicles, lysosome‐like bodies in supranuclear and distal portions of the cell and mitochondria initially concentrated in the basal part of the cell. Numerous autophagic vacuoles are observed concomitant with the loss of some cell organelles at the transitional stage. During late amelogenesis the ameloblasts exhibit numerous vesicles, granules, convoluted cell membranes, junctional complexes and widely distributed mitochondria. Toward the end of amelogenesis, cells become oriented parallel to the enamel surface and the number of organelles is reduced.

Amelogenesis in the frog is an extracellular process and mineralization seems to occur simultaneously with matrix formation.
Formation and turnover of plasma membrane glycoproteins in kidney tubules of young rats and adult mice, as shown by radioautography after an injection of 3H‐fucose
Authors: Haddad A. , Bennett Gary , Leblond C. P.
Published: February 2005

The formation and turnover of the glycoproteins of the plasma membrane have been investigated by quantitative radioautography in the kidney tubules of young rats and adult mice killed at various time intervals after an intravenous injection of 3H‐fucose.

In young (40 g) rats killed five to ten minutes after the injection, radioautographs of distal tubule cells show that the Golgi apparatus contained about 85% of the cell label. By 30 hours, only 8% of the label remained in this organelle, whereas 67% was in the plasma membrane, indicating that most of the label had migrated from Golgi apparatus to this membrane. Similarly, in proximal tubule cells, about 82% of the label was initially in the Golgi apparatus, but less than 2% remained at 30 hours, at which time 78% was in the plasma membrane. In the latter cells, the apical tubules and vacuoles became heavily labeled before the apical microvilli did and, therefore, may be involved in the transit of label from the Golgi apparatus to the microvillous membrane.

The results are interpreted to mean that, in kidney tubule cells, the Golgi apparatus is the site of a continuous incorporation of fucose into glycoproteins and that these migrate to the plasma membrane. In fully formed cells, such a conclusion would imply a continuous turnover of plasma membrane glycoproteins. However, in the rapidly growing kidney of young rats many new cells are added daily, the growth of which might involve net addition as well as turnover of glycoproteins. Accordingly, the experiment has been repeated in adult mice, in which the cells are assumed to be fully formed. Furthermore, since turnover implies eventual decrease of incorporated label, some of the animals have been killed at longer intervals, up to 27 days after injection. In these adult mice, as in young rats, prompt Golgi uptake and subsequent migration of label to the plasma membrane were observed in distal and proximal tubule cells. With time the label content of the plasma membrane decreased gradually, and by 27 days had virtually disappeared. From grain counts, it is concluded that the mean half‐life of glycoproteins in the apical membrane of distal tubule cells is about two days, whereas in both the apical and basal membranes of proximal tubule cells, it is slightly over three days.
Histochemistry of interafusal muscle fibers outside the spindle capsule
Authors: Kucera Jan
Published: February 2005

Regional differences in histochemical properties along the length of rat intrafusal muscle fibers were examined. Outside the muscle spindle capsule the nuclear bag fibers lose their hitherto characteristic ATPase activity and stain in a manner similar to that of extrafusal type I muscle fibers, perhaps in relationship to spindle skeletofusimotor innervation.
Observations on destruction of spermatozoa in the cauda epididymidis and proximal vas deferens of non‐seasonal male mammals
Authors: Cooper T. G. , Hamilton D. W.
Published: February 2005

The electron microscope has been used to examine luminal spermatozoa from the cauda epididymidis and proximal vas deferens of rats, mice, hamsters and guinea pigs. Free in the lumen of all species are accumulations of a dense material within which are vesicles, granules and dense bodies, as well as spermatozoa. The spermatozoa are undergoing a process of degeneration as judged by a loss of plasma membrane from both heads and tails and further disruption of acrosomal membranes, mitochondrial sheaths and outer dense fibers. Disruption of spermatozoa also occurs outside these obvious dense masses when the luminal protein precipitated by the fixation procedure has contact with the spermatozoon. Intact spermatozoa are separated from luminal material by a clear “halo”.
Fine structure of spermatozoa of the Asiatic musk shrew, Suncus murinus
Authors: Koehler James K.
Published: February 2005

The fine structure of spermatozoa of the Asian musk shrew, Suncus murinus, has been investigated using air‐dried and critical‐point‐dried replicas in addition to freeze‐fractured specimens. Asymmetry in the structure of the head, notably the acrosome, can be recognized in critical‐point‐dried replicas as a slight dorsoventral convexity not apparent in air‐dried specimens. Freezeetching reveals a dense accumulation of intramembranous particles just anterior to the posterior ring, but relatively few other characteristic membrane conformations associated with the head. Gelatin smears visualized with the light microscope show a vigorous lytic response, but preliminary efforts to remove the acrosome by physiological or enzymatic incubation have thus far not been successful.
Cytological differentiation of human fetal skeletal muscle
Authors: Tomanek Robert J. , Colling‐Saltin Ann‐Sofi
Published: February 2005

The ultrastructural differentiation of several different muscles was investigated in human fetuses ranging in age from 13 weeks to neonatal.

At approximately 16 weeks of gestation cell clusters containing both myotubes and satellite cells lie enclosed by a newly formed basal lamina and show evidence of fusion. The development of organelles is evident in myoblasts, proceeds as the cells transform into myofibers, and continues in the neonate. Filament synthesis occurs primarily in the cell periphery where thin filaments appear to align themselves in relations to parallel arrays of ribosome‐studded thick filaments; Z line formation follows the appearance of thin filaments. Intermediate filaments, approximately 10‐12 nm thick, were also consistently observed in perinuclear regions and distal to filament assembly.

Although sarcoplasmic reticulum (SR) development is closely related to fibril formation, connections between Z lines and SR are not consistent, thus supporting the conclusion that SR does not evoke the formation of the Z line. Bristlecoated vesicles appear to be the precursors of elements of the SR, possibly the lateral sacs. Development of the transverse tubules, as invaginations of the sarcolemma, is closely associated with the formation of lateral sacs since the latter occur along the sarcolemma as soon as transverse tubules appear.

Cytological differentiation is similar, though not identical, in several different muscles. During the last trimester muscle fibers show some evidence of diversity, mainly of variation in Z line width. In general the results suggest that the sequence and stages of human myogenesis are similar to those of other species.
Cell body locations and axonal pathways of neurons innervating muscles of mastication in the rat
Authors: Limwongse Visaka , Desantis Mark
Published: February 2005

In the rat the size distributions of cell bodies in the trigeminal motor nucleus and of myelinated fibers in the portio minor were bimodal. The size distribution of mesencephalic nuclear somata was unimodal. The number of fibers in the portio minor was approximated by the number of somata in the motor and mesencephalic nuclei. Within the motor nucleus large and small cells were chromatolytic after destruction of the portio minor. Injections of horseradish peroxidase (HRP) into the masseter and temporalis muscles labeled both the large and small neurons in the dorsolateral part of the nucleus. Similar injections into the anterior belly of the digastric and mylohyoid muscles labeled neurons in the ventrolateral part of the nucleus, but these neurons were not among the smallest in the nucleus. Within the mesencephalic nucleus chromatolytic somata occurred only ipsilaterally after unilateral lesions of the portio minor, and in lesser numbers after destroying the portio major. Unilateral injections of HRP into the masseter and temporalis muscles labeled cells in the ipsilateral mesencephalic nucleus and trigeminal ganglion. Labeling of mesencephalic neurons was abolished by lesions of the portio minor. Similar injections into the anterior belly of the digastric and mylohoid muscles labeled cells in the ipsilateral trigeminal ganglion, but not in the mesencephalic nucleus. These results are discussed in light of previous work on the trigeminal system.
The effect of 5‐bromodeoxyuridine on the postnatal development of the rat cerebellum: Morphologic and radioautographic studies
Authors: Yu Wan‐Hua A.
Published: February 2005

Effects of a thymidine analog, 5‐bromodeoxyridine (BrdU), on the development of rat cerebella were studied. BrdU, when 15 milligram per 100 gram body weight was injected twice daily into 2‐day‐old rats for three consecutive days, caused a transient inhibition of cell formation and destruction of stem cells in the external granular layer. This was followed by a prolonged period of regeneration with delayed dissolution of the external granular layer; however, the restitution in cell number was incomplete and resulted in a miniature cerebellum with significantly reduced myelination at 35 days of age. The regeneration of the external granular layer appeared to alter the synchronized morphogenetic processes of the cerebellar cortex. The “desynchronization” of morphogenetic events appears to account for the peculiar cytoarchitectonic organization of the cerebellar cortex in the BrdU‐injected animals, i.e., irregular stacking of Purkinje cells, formation of granule cell ectopia, and sagittal alignment of parallel fibers in the molecular layer. It is postulated that the misalignment of parallel fibers is the consequence of BrdU substitution in place of thymine in the nuclear DNA of granule cell precursors. The present schedule of BrdU injections also appeared to reveal an additional, early period of oligodendroglial proliferative activity which did not coincide with the onset of myelination.