bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface coats of the mouse blastocyst and uterus during the preimplantation period
Authors: Enders Allen C. , Schlafke Sandra
Published: February 2005

A glycoprotein coat is demonstrable on the free surface of both the blastocyst and uterine luminal epithelium of the mouse on day 4 and day 5 of normal pregnancy, and on day 7 of delayed implantation, using concanavalin A‐peroxidase and ruthenium red. The coats are apparently negatively charged, as shown by their binding with colloidal thorium dioxide. The cell coat on uterine epithelium is appreciably thicker than that on the blastocyst. The information currently available is sufficient to suggest that simplistic mechanisms such as change in charge or total thickness cannot be the sole basis of initial adhesion, but that some localized reduction of the uterine surface coat accompanies adhesion. However, considerably more information is necessary concerning the nature of the surface coats before a more comprehensive understanding of the role of adhesion in implantation can be achieved.
The postnatal growth of the rat lung III. Morphology
Authors: Burri Peter H.
Published: February 2005

In order to investigate the postnatal growth of the gas exchange apparatus, the lungs of rats aged 1, 4, 7, 10, 13, and 21 days were fixed by intra‐tracheal instillation of glutaraldehyde. The analysis and interpretation of the morphological changes observed by light and electron microscopy were based on the results of previous morphometric and autoradiographic studies performed on the same material.

The newborn rat has no alveoli, but breathes with smooth walled air channels and saccules, which correspond to the prospective alveolar ducts and alveolar sacs, respectively. The bulk of alveoli are formed between days 4 and 13 by a rapid outgrowth of secondary septa from the primary septa present at birth. The arrangement of elastic fibers during this period suggests that these may play a role in septal outgrowth. Based on ultrastructural observations a model is described for the capillarisation of the secondary septa. Some evidence is given that alveoli may also be formed by outpouchings in the walls of terminal bronchioles.

Primary and secondary septa have initially an immature appearance. They both show an apparently double capillary network, whereas the mature interalveolar septum is just wide enough to accommodate a single capillary. Possible mechanisms for this structural transformation which occurs within three weeks after birth are discussed.
Ultrastructural development of the chorioallantoic placental barrier in the bat Macrotus waterhousii
Authors: Bodley H. Daniel
Published: February 2005

The phyllostomid bat, Macrotus waterhousii, undergoes delayed development. Implantation occurs early in the nine‐month gestation, but the blastocyst remains relatively dormant until the sixth month when a chorioallantoic, hemodichorial placenta forms and a two and one‐half to three‐month growth pattern occurs leading to parturition.

The barrier in the chorioallantoic placenta at first includes maternal capillary endothelium, but during the early part of the rapid growth phase the endothelium is replaced by blocks of syncytial trophoblast which penetrate the basal lamina. The basal lamina then apparently thickens and remains as the intrasyncytial lamina. Thus, the definitive barrier for maternal nutrients consists in order of passage of syncytial blocks, intrasyncytial lamina, syncytiotrophoblast, cytotrophoblast, fetal basal lamina and capillary endothelium.
A quantitative study of the satellite cell population in postnatal mouse lumbrical muscle
Authors: Schultz Edward
Published: February 2005

The satellite cell population in mouse lumbrical muscle is quantitated at ages 7, 14, 21 and 30 days. Satellite cell nuclei comprise nearly 30% of the nuclei within the fiber basal lamina in the youngest animals studied. Growth is accompanied by a rapid decrease in the percentage of satellite cell nuclei. This is not accounted for by the increase in myonuclei, but rather there is an absolute decrease in the number of satellite cells. This loss in satellite cells occurs in spite of their high rate of division and is explained by a high percentage incorporation of the daughter cells of satellite divisions. It is further suggested that the percent incorporation of available cells decreases with age.
Hormonal influences on the morphogenesis of the preputial gland of embryonic mice
Authors: Cunha Gerald R.
Published: February 2005

Fetal preputial glands from 14‐ to 17‐day old mouse embryos undergo comparable growth, branching, and display similar degrees of cytodifferentiation when cultured in vitro on medium lacking hormones, on this medium in the presence of either of the fetal gonads, and on medium supplemented with testosterone dipropionate. Conversely, morphogenesis of these anlagen is markedly suppressed by estrogen and an anti‐androgen, Cyproterone acetate. These observations demonstrate that acquisition of androgen‐sensitivity is a late event in the morphogenesis of the preputial gland and correlate with the developmental properties of preputial mesenchyme as demonstrated in earlier studies on the epithelio‐mesenchymal interaction.
Ultrastructure of the cilia of thymic cysts in “nude” mice
Authors: Cordier Andre C.
Published: February 2005

The ciliary ultrastructure is studied in the ciliated cells of the thymic cysts of the “nude” mouse. The cilium is made up of two segments: the intracellular basal body and the extracellular cilium shaft.

The basal body extends in a rootlet and demonstrates three annexes: basal foot, anchoring system and tonofibrillar web. The rootlet, composed of one central and nine peripheral chambers, is closely and constantly associated with smooth endoplasmic reticulum. The classical periodicity of the basal foot can be explained by its internal structure. The anchoring system binds the upper part of the basal body to the cell membrane. The cilium shaft is divided into four segments: implantation base, proximal segment, intermediate segment and tip. The details of particular structures in the implantation base and in the proximal segment are given on transverse and longitudinal sections. In the intermediate part, a peculiar desmosome‐like structure, binds some doublets with the ciliary membrane. At the tip level, A tubules end up in an opaque plate and membranes are covered with several intricated cristae.
Vein size in intact and hysterectomized mice during the estrous cycle and pregnancy
Authors: Forbes Thomas R. , Taku Elaine
Published: February 2005

The diameters of the ovarian, uterine, and femoral veins and the inferior vena cava were measured during stages of the estrous cycle in intact and hysterectomized mice and at intervals during pregnancy in mice with embryos in both uterine horns or in only the left horn. At metestrus I vein sizes were the least and were not significantly different in intact and hysterectomized mice. Ovarian and uterine veins showed the same or increased diameters at other stages of the cycle; veins enlarged progressively during pregnancy in intact mice. Non‐gravid uterine horns showed little size increase as compared to gravid horns. Increases in vein diameter appeared to be correlated with local production of reproductive hormones.

Evidence for transuterine migration of embryos was observed in 21 of 53 mice in which one uterine tube had been ligated or one ovary had been removed.
Electron microscopy of the intestine of the african lungfish, Protopterus aethiopicus
Authors: Purkerson M. L. , Jarvis J. U. M. , Luse S. A. , Dempsey E. W.
Published: February 2005

Electron microscopic observations are reported on the intestine of the African lungfish, Protopterus aethiopicus. The lungfish has a spiral valve rather than a true stomach. Segments of mucosa from this area reveal, by transmission microscopy, that most cells have distinct striated borders with parallel microvilli. Fibrils within the core of the microvilli extend deeply into the cytoplasm. Microvilli on the surface of goblet cells are less regularly arranged than those of absorptive cells. Interspersed among the cells with striated borders are cells, similar in cytologic appearance except that they are covered with tufts of kinetocilia. By transmission electron microscopy, abnormal cilia having one complete complement of microtubules plus incomplete sets from other cilia which share some of the peripheral doublets of the complete cilium are enclosed by a single membrane. Cilia are usual in the intestine of many lower forms but ordinarily absent in higher vertebrates. Their functional significance in this primitive fish is unknown.
The implantation chamber, blastocyst and blastocyst imprint of the rat: A scanning electron microscope study
Authors: Enders Allen C.
Published: February 2005

Splitting the uterus longitudinally through implantation sites makes it possible to obtain access to blastocysts and implantation chambers during stages of implantation of the blastocyst in the rat. On the afternoon of day 5 of pregnancy, blastocysts lie in a shallow antimesometrial depression and tend to fall free of the uterus when the chamber is opened. On day 6, blastocysts are oriented in a mesometrial‐antimesometrial plane, occupy a distinct implantation chamber, and tend to adhere to one side or the other of the uterus, leaving an imprint on the contralateral side. After about noon of day 6, some of the blastocysts split in half laterally, and by day 7 all blastocysts which are exposed are split. In addition to demonstrating increased adhesion of blastocyst to uterine epithelium, the procedure clearly shows the progressive elongation of the implantation chamber. The embryonic cell mass is specifically oriented on day 6, and is clasped but not distorted, whereas the abembryonic trophoblast is slightly compressed and indented by the uterine epithelium. The microvilli of the uterine epithelium within the imprint become progressively flattened when compared to the microvilli of the implantation chamber outside of the imprint. The method provides a means of gaining direct access to the surface of uterine epithelium precisely where it has been in association with the blastocyst not only for scanning electron microscopy but also for studies of the properties of the surface constituents.
The systemic arterial pattern of the guinea pig: The abdomen
Authors: Shively Michael J. , Stump John E.
Published: February 2005

The systemic arterial pattern of the guinea pig was studied to determine the arrangement of the major arterial trunks and their branches. Fiftynine specimens were examined by dissection, angiography or corrosion casting. The arterial arrangement was found to resemble a typical mammalian pattern, although some exceptions were noted. For example, the guinea pig usually has a single vessel, the celiacomesenteric trunk, instead of separate celiac and cranial mesenteric arteries. The celiac components of this vascular axis were found to originate in four different patterns. Also, the renal arteries were found to be single or double on either side with double origins more frequent.
Rapid freezing of deep cerebral structures for electron microscopy
Authors: van Harreveld A. , Fifkova Eva
Published: February 2005

A method is described for the investigation of deep cerebral structures by freeze‐substitution. The head of a mouse is sectioned in a guillotinelike apparatus. The exposed surface is subjected to freeze‐substitution. Electron micrographs prepared from this material exhibit under a layer of sheared tissue, a layer of tissue comparable with that observed previously in micrographs of the cerebral and cerebellar cortices subjected to freeze‐substitution of their natural surfaces. By varying the plane in which the head is sectioned any structure in the brain can be made accessible to freeze‐substitution.
Development of beaks of Rana pipiens larvae
Authors: Kaung Hue‐Lee Cheng
Published: February 2005

Rana pipiens larval beaks consist of column cells, sheath cells and basal cells which supply cells to column and sheath. Each column consists of disk‐like precone cells, cone cells and keratinized cone cells; they are cells in different stages of the process of keratinization.

Beaks first appear externally at embryonic stage 24. Epidermal cells align at the tip of the jaw at stage 21. They increase in number and change in shape. Keratinization starts at stage 23. By stage 24, the apical column cells are keratinized and the histological organization is set for the whole larval period.

During the larval period, the numbers of column cells increase until stages VIII or IX, stay relatively constant during mid‐larval stages, and decrease at late larval stages. The beak is completely shed at stage XX. The widening of the beaks goes on during the entire larval period. Along the cutting edge of the jaw the booth spikes increase in number and in individual width as the animal grows older and larger.

Thyroid hormone causes a premature reduction of the column cell number and a precocious beak loss. The loss of beak at metamorphic climax is a thyroid dependent event.
Development of the tibial tuberosity
Authors: Ogden John A. , Hempton Robert F. , Southwick Wayne O.
Published: February 2005

The tibial tuberosity develops by a concomitant, and juxtaposed, outgrowth of hyaline cartilage and ingrowth of fibrovascular tissue. During the fetal period this hyaline cartilage outgrowth is progressively distally displaced to become situated adjacent to the anterior portion of the tibial metaphysis. About four to six months post‐natally a growth plate develops under the tibial tuberosity. This growth plate shows structural adaptations that permit accommodation of large tensile stresses. The growth plate of the tibial tuberosity has three distinct regions — (a) a zone of endochondral bone formation, (b) a zone of intramembranous bone formation through fibrocartilage, and (c) a zone of intramembranous bone formation through fibrous tissue.
Skeletal effects of magnesium deficiency in normal, ovariectomized, and estrogen‐treated rats
Authors: Bogoroch Rita , Belanger Leonard F.
Published: February 2005

The effects of magnesium deficiency in ovariectomized and estrogen‐treated rats were examined in histological sections of bones and various soft tissues. The changes observed in the femora of intact rats deprived of magnesium for three weeks were: 1. a general increase in diaphyseal thickness, 2. the presence of localized fibrous or bony‐like masses in subperiosteal and metaphyseal sites, and 3. the occurrence, although rare, of endosteal hyperplasia. In ovariectomized, magnesium‐deprived animals, the incidence and location of fibrous masses were similar to that in the femora of magnesium‐deficient intact rats; however, no increase in diaphyseal thickness was noted. Daily injections of 25 μg estradiol caused a reduction of the frequency of skeletal hyperplasia from 80% to 20%, as well as a reduction in femoral diaphyseal thickness. Estradiol hormone administration also brought about a marked alleviation of the dermal and neural manifestations of magnesium deficiency, but, at the same time, caused an exacerbation of renal calcinosis.
Post‐natal development of the median eminence of the guinea pig
Authors: Silverman Ann‐Judith , Desnoyers Patricia
Published: February 2005

The ultrastructure of the median eminence of neonatal (newborn, 1‐, 3‐, 5‐, and 10‐day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non‐fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neurosecretory granules (1,500‐1,700 Å) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68‐72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is not yet complete.
The normal human thymic vasculature: An ultrastructural study
Authors: Bearman Robert M. , Bensch Klaus G. , Levine Gerald D.
Published: February 2005

Electron microscopy of the normal human thymus demonstrates a characteristic vascular‐parenchymal relationship. The vascular lumen is always separated from the thymic parenchyma by: the endothelial cell cytoplasm, a muscular coat in arterioles and veins, the vascular basal lamina, a perivascular space containing collagen fiber and cells, the epithelial‐reticular cell basal lamina and the epithelial‐reticular cell cytoplasm. The width of this perivascular space is proportional to the size of the vessel it surrounds; it is wide around the vessels in the septa and at the cortical‐medullary junction, but narrow around capillaries. While many cells are present in this space around the larger vessels, only collagen is observed around the capillaries. Lymphocytes are the predominant cell type in the space; however, plasma cells, eosinophils, histiocytes, polymorphonuclear leukocytes, mast cells and unidentified granulated cells are also seen.

The vascular complex described above may function as a blood‐thymus barrier, as the initial site of exposure of the lymphocytes to circulating antigen and as the route of emigration of lymphocytes from the thymus.
Smooth muscle in lymph node capsule and trabeculae
Authors: Folse Dean S. , Beathard Gerald A , Granholm Norman A.
Published: February 2005

This study focuses on the confusion in existing literature concerning the presence of smooth muscle in the capsule and trabeculae of lymphnodes. Human and bovine nodes from several anatomical areas and several individuals of each species were examined by conventional light, electron and fluorescence microscopy. Smooth muscle cells, independent of blood vessels, were demonstrated in the trabeculae and capsules of lymph nodes of both species examined by all three techniques. The need for further study on the function of these cells is indicated.
The fine structure of the interhemal membrane of the rat chorioallantoic placenta during prolonged pregnancy
Authors: Jollie William P.
Published: February 2005

In placentas from viable rat fetuses which surgically had been retained beyond term in lactating animals for as long as four days, the fine structue of much of the interhemal membrane was quite like that of full‐term placentas. Moreover, contrary to what has been reported previously (Jollie, 1964a), in retained placentas which were autopsied at term there were few changes in the four cytoplasmic layers of the membrane which could be interpreted as degenerative. With prolongation of the placenta beyond normal delivery the number of pericytes which were associated with the allantoic endothelium increased; the basal lamina separating the endothelium from trophoblast III progressively became more focally split; and the apposed plasma membranes between this latter layer and trophoblast II appeared to dissociate. Trophoblast II became regionally divided in its cytoplasmic organization, its more superficial zone becoming highly infolded and/or vacuolar. As a consequence, the intertrophoblastic space between layers I and II became more extensive and complex. Within this space, a flocculent material appeared; and there was ultrastructural evidence of massive pinocytosis from the space by trophoblast II. With increased prolongation of gestation, a variety of lysosome‐like inclusions appeared within this layer of the membrane.
Ultrastructure of baboon parotid gland
Authors: Tandler Bernard , Erlandson Robert A.
Published: February 2005

The parotid gland of the olive baboon, Papio anubis, was examined by electron microscopy. The acini are all serous in nature, and consist of pyramidal cells with abundant secretory granules of varying size. These granules consist of a dense matrix in which a denser spherule or lenticular body is present. Granules linked by a short isthmus are observed in the apical cytoplasm, and granules in the process of discharging their contents to the acinar lumen may be connected to the luminal plasma membrane by a neck‐like protrusion. Intercalated duct cells contain granules reminiscent of those found in the rat submandibular acinar cells. The striated ducts consist of tall cells interloked in a complex fashion near their bases, with numerous vertically‐oriented mitochondria lodged in their basal crenulations. Small vesicles whose contents vary in density are present in the apical cytoplasm as are large deposits of lipofuscin. The striated duct cells display a proclivity for ballooning into the duct lumen. Excretory ducts consist of simple to pseudostratified columnar epithelium, and lack basal striations or apical blebs.
Growth of the second metacarpal according to chronological age and skeletal maturation
Authors: Kimura Kunihiko
Published: February 2005

In relation to chronological age and skeletal maturation, the growth of the second metacarpal is discussed based on radiographs of the right hand and wrist in 499 male and 424 female Japanese aged 1 to 18 years. When plotted against age, bone length and width present the general growth pattern of Scammon, the adolescent spurt occurring at about 13 years in the males and 11 years in the females, and the mean values are significantly larger in the males than in the females at age 15 years for length, and age 13 years for width, and later. The growth curves of both sexes are almost parallel to each other for bone length plotted against skeletal maturation. Bone width progresses in parallel in males and females until about adolescence, whereafter there is a more rapid increase in growth in the males than in the females. The mean values for length and width are almost always significantly greater in the males than in the females. The width/length index decreases rapidly until a certain period, the minimum value being at about ten years or a maturity corresponding to that age, and then increase slightly again to reach an equilibrium state on the basis of both age and skeletal maturation. At any given age, the mean values are always greater in the males than in the females. However, according to skeletal maturation, the sex differences are steadily significant at and after the skeletal maturity corresponding to about 12 years in the males and 10 years in the females.
A macroscopic study of the brain of Bison bison bison, the American Plains Buffalo
Authors: Harper Jon W. , Maser Jack D.
Published: February 2005

The macroscopic anatomy of the brain of the American Plains Buffalo (Bison bison bison) is detailed herein for the first time. Many features vary significantly from most previously described ungulate species including its large size, fissural pattern of the cerebral hemispheres and well developed insular cortex. The midbrain, particularly the tectum, is outstanding: the superior colliculi appear to be the largest reported for any mammal and occupy most of the dorsal midbrain by surface area and volume estimates. The cerebellum is small relative to the total brain volume, a peculiarity reported elsewhere for other ungulates. Morphometric criteria further indicate the brain of bison is highly specialized. Drawing from various lines of evidence, it is suggested that the anatomical uniqueness of the present day bison brain may represent a vestige of the past, remaining largely unchanged over a broad expanse of geologic time.
Quantitation of ultrastructural changes in the mouse pineal in response to continuous illumination
Authors: Upson Rosalyn H. , Benson Bryant , Satterfield Virginia
Published: February 2005

Adult male mice were exposed to either alternating illumination or constant illumination for 70 days. Light and dark pinealocytes were compared as to distribution within the gland and ultrastructure. Quantitative studies with the electron microscope revealed a significant reduction in pinealocyte size and Golgi complex size in constant light treatment, as well as a marked but non‐significant reduction in the concentration of lipid droplets and irregular vacuoles. Under constant light treatment the cross‐sectional area of pinealocyte pericapillary terminals and the number of granulated vesicles per terminal decreased significantly. A greater number of mitochondria appeared swollen, with rarified matrix and reduced numbers of cristae, with constant light treatment.

These results provide ultrastructural correlation with the known reduction of pineal weight, protein synthesis and antigonadotrophic activity that is seen with constant light treatment. The marked decrease in concentration of pinealocyte granulated vesicles in constant light treatment gives morphological support to the theory that these vesicles contain antigonadotrophic secretory material.
Alterations in the fine structure of the prostate and seminal vesicle of rats treated with cyproterone acetate
Authors: Loving Charles K. , Flickinger C. J.
Published: February 2005

Young adult male rats were treated with daily injections of 10 mg of cyproterone acetate for periods up to 16 weeks. Samples of the ventral prostate and the seminal vesicle were studied with the light and electron microscopes. Alterations visible with the light microscope included decreases in cell size, cytoplasmic basophila, the size of the nucleolus, and the amount of luminal secretory material. Ultrastructural changes in the epithelium of both glands involved mainly the organelles that participate in the formation of secretions. Large declines were observed in the abundance of rough endoplasmic reticulum, size of the Golgi apparatus, and number of secretory vacuoles. Lipid droplets accumulated in the seminal vesicle epithelium, and lysosomes were numerous in both glands. Changes were first observed microscopically in the seminal vesicle after one week and in the prostate after two or three weeks. Maximal development of the alterations occurred after treatment for approximately eight weeks.
Cell associations and surface features in cultures of juvenile rat seminiferous tubules
Authors: Eddy E. M. , Kahri A. I.
Published: February 2005

Short pieces of seminiferous tubules from juvenile rats were grown in tissue culture and studied by phase contrast light microscopy while living and by transmission and scanning electron microscopy after fixation and appropriate processing. The pieces of tubules remodeled in vitro, with the original explant becoming surrounded closely by a sheet of epithelioid cells and more peripherally by elongate cells. The epithelioid cells were identifiable as Sertoli cells because of the presence of characteristic Sertoli‐Sertoli cell junctions near their upper surface. The elongate cells were derived from peritubular tissues, but could not be specifically identified as to cell type. Clusters of stellate cells and of round cells were present on the upper surface of the Sertoli cell sheets, but not on the elongate cells or the bare floor of the culture dish. The stellate cells were spermatogonia and the round cells were spermatocytes, as identified by fine structural features. Intercellular bridges were maintained between germ cells in culture without being surrounded by processes of Sertoli cells. Rudimentary junctions were present between germ cells and Sertoli cells in culture. The shape of germ cells in vitro was the same as the shape in situ, indicating that shape is an inherent feature of germ cells and is not determined by surrounding Sertoli cells.
The development of the lung in the pig‐tail monkey (Macaca nemestrina,L.)
Authors: Boyden Edward A.
Published: February 2005

This study covers the period from the fortieth day after ovulation to the thirty‐eighth day after birth. In addition, lungs of two mature monkeys have been analyzed. Birth occurs about the one hundred sixty‐eighth day (24 weeks after ovulation). By the fortieth day the patterns of the bronchopulmonary segments are well established. These are the tools of the investigator. The curve of growth for the first 60 days parallels that of the rhesus monkey but is steeper than the human curve. At 63 days (9 weeks) pairs of rosette‐like clusters of epithelial buds (future alveolar ducts) have appeared on peripheral branches of the segmental bronchi and continue to grow in size until the twelfth week. Then they resemble the paired rosettes of human acini of the seventeenth postovulatory week (Boyden, ′74) and probably represent the primitive unit from which the human was derived. In both man and monkey, canalization of the rosettes starts at about the same relative time (the 17th and 12th week, respectively) and spreads centralwards from the rosettes along the bronchioles of each segmental bronchus. In man, canalization forms acini (alveolar ducts and respiratory bronchioles). In the monkey, due to the monopodial pattern of branching, it produces racemes of alveolar ducts, each raceme ending basally in a pseudorespiratory bronchiole (127th day). By the one hundred fortieth day, enough surfactant has been secreted to support a premature infant. At one hundred fifty days, 11 generations of bronchi, followed by 16 of pseudorespiratory bronchioles, are present in the medial basal segment, followed in turn by 19 generations of prealveolar ducts (the latter provided with delicate spiral muscles) each giving off alternate branches of alveolar ducts. After one hundred fifty days of gestation, generations of bronchi, pseudorespiratory bronchioles, prealveolar ducts and cartilages (15) remain virtually constant for at least 38 days after birth. By the adult stage the number of generations of pseudorespiratory bronchioles has been reduced to three and the prealveolar ducts increased (at the former's expense) to 27. This study is concluded with a comparison of the lungs of the newborn monkey with those of the human/neonate and puppy.
The Sertoli cell junctional specialization during spermiogenesis and at spermiation
Authors: Ross Michael H.
Published: February 2005

The relationship between developing spermatids and Sertoli cell junctional specializations was studied with the electron microscope during spermiogenesis and at spermiation. At stage I of the seminiferous cycle, the newly formed spermatids are found in apposition to junctional specializations at the lateral surfaces of the Sertoli cell. Visualization of the junctional site of this early stage appears to be dependent on orientation and plane of section. As differentiation proceeds, the spermatids elongate and come to lie within deep recesses of the Sertoli cell. At this time the junctional specialization is limited to the acrosomal portion of the spermatid. During the maturation phase, the spermatids, while maintaining the same relationship to the junctional specialization, approach the lumen. When stage VIII of the cycle is reached, the stage in which spermiation occurs, the spermatids are at the luminal surface. The relationship of the spermatid head to the junctional specializations is quite variable during this stage. Some spermatids are observed still attached to the Sertoli cell at the junctional site, while others are found completely or partially surrounded by Sertoli cytoplasm, but with no evidence of the normally interposed junctional specialization. Yet, in other instances, the spermatids are observed in a position slightly removed from the junctional site. Also evident are profiles of junctional specializations at a free surface of the Sertoli cell, there being no attached spermatid. In some instances the junctional specializations appeared in apposition to a residual body. In the case of the free surface profiles, the junctional specialization at times lined an empty cleft or crypt‐like recess, giving the impression that the spermatid head had just been dislodged from the junctional contact site. The findings indicate that the spermatid is in contact with a junctional specialization from its initial appearance and remains so until spermiation is initiated. It is postulated that spermiation is initiated through a physiological change in the junctional specialization resulting in loss of adhesion and consequent release of the sperm head from its attachment site. A similar mechanism is proposed in relation to the inter‐Sertoli junctional complex to account for the means by which the spermatocytes cross this barrier to reach the adluminal compartment of the seminiferous epithelium.
The ligaments of the human wrist and their functional significance
Authors: Mayfield J. K. , Johnson R. P. , Kilcoyne R. F.
Published: February 2005

The ligamentous anatomy of the wrist was analyzed by studying (1) 28 dissected human wrists, (2) and by examination of 19 wrist injuries created mechanically. Six volar intracapsular ligaments are described, two stabilizing the distal carpal row, three stabilizing the proximal carpal row and one stabilizing the proximal scaphoid pole. More specific terminology for these ligaments is proposed. An explanation of how these ligaments participate in the mechanical functioning of the carpus is advanced. Mechanically created wrist injuries had ruptures of specific ligaments as described augmenting a need for a more specific terminology. Suspected mechanisms of injury in perilunate and lunate dislocations are mentioned based upon the functional understanding of the intracapsular ligaments.
The subdural neurothelium of the cranial meninges in man
Authors: Rascol Madeleine M. , Izard Jacques Y.
Published: February 2005

The neurothelium obtained from human biopsy specimens is a very thin cellular layer located between the dura mater and the arachnoidea. It is a pluri‐stratified squamous layer which has some epithelial features (desmosomes and tonofilaments), and lacks connective tissue fibers in the extracellular spaces. Usually there is increased nuclear and cytoplasmic density and enlarged extracellular spaces from the deepest to the most superficial layer.

Since neurothelium is fragile and easily torn apart, it probably occupies the position considered to be the subdural space.
The accessory optic fiber system of the golden hamster with special reference to retinohypothalamic projection
Authors: Lin Homin , Alexander Mary , Giolli Roland A.
Published: February 2005

The hamster accessory optic fiber system has been investigated with the use of de Olmos‐Ingram and Fink‐Heimer silver methods following the production of unilateral ocular enucleation. It was found that this fiber system consists of both crossed and uncrossed inferior and superior fasciculi. The fibers of the inferior fasciculus (anterior accessory optic tract) run along the medial edge of the cerebral peduncle and terminate within the medial terminal nucleus of the accessory optic system. The fibers of the superior fasciculus (posterior accessory optic tract) leave the main optic tract, pass superficially over the medial geniculate nucleus and the cerebral peduncle; they synapse within the dorsal, the lateral and the medial terminal accessory optic nuclei. The presence of a retinohypothalamic tract could not be confirmed.
The nuclear fibrous lamina in human cells: Studies on its appearance and distribution
Authors: Cohen Arthur H. , Sundeen James R.
Published: February 2005

The nuclear fibrous lamina, a structure of unknown function, is situated at the nuclear periphery directly apposed to the inner nuclear membrane. Although it has been well described in invertebrate and many non‐human vertebrate cells, its occurrence in human tissue has not been emphasized. This survey of a large variety of human cells has documented the lamina to be present, although of varying thickness, in a large number of cell types. It is consistently thickest in mesenchymal or mesenchymally derived cells and its apperance and thickness is not correlated with pathologic alterations.
The mammalian rete testis — a morphological examination
Authors: Dym Martin
Published: February 2005

The fine structure of the rete testis was examined in several primates, domestic animals and rodents. The rete testis consists of a series of interconnected wide channels lined with a simple cuboidal to columnar epithelium, resting on a thick basal lamina. Beneath the basal lamina dense bundles of collagen fibrils and a few blood vessels, lymphatics or nerve tissue are found. The epithelial cells are characterized by large, deeply indented nuclei, spherical or short rod‐shaped mitochondria, supranuclear Golgi profiles, some cisterns of rough endoplasmic reticulum, free ribosomes and numerous micropinocytotic vesicles in the ectoplasmic regions. Smooth endoplasmic reticulum, secretory granules, lysosomes or other types of dense bodies are rarely seen. The apical surface of the cells bears numerous microvilli and a single very long flagellum which is presumed to be motile. Adjoining lateral cell membranes exhibit a juxtaluminal tight junction, elaborate interdigitations and desmosomes. The basal plasma membrane is highly irregular greatly increasing its surface area of contact with the underlying interstitium. The nuclei of the rete epithelial cells contain pale‐staining, spherical structures, 2 m̈ in diameter, composed of circularly oriented fine filaments. The significance of the nuclear structures remains unknown. Thorotrast was injected into the lumen of the hamster and rat rete testis and 30 minutes later the proximal portion of the excurrent duct system of the testis was prepared for electron microscopy. Whereas the ductuli efferentes and first part of the epididymis possessed numerous apical vesicles filled with the thorotrast, this electron opaque substance was rarely found in the epithelium of the rete testis. Thus, incorporation of particulate matter into the lining cells of the rete from its lumen is apparently less active than in the epithelium of the ductuli and epididymis. Vascularly introduced intercellular tracer compounds such as lanthanum nitrate or horseradish peroxidase did not enter the lumen of the rete testis from the interstitium. These tracer molecules appeared to be blocked by the juxtaluminal tight junction separating adjacent epithelial cells. This latter observation suggests that a blood‐testis barrier exists at the level of the rete testis epithelium. Although physiological studies have indicated that the composition of fluid secreted in the seminiferous epithelium is considerably modified in the rete testis, the present morphological study does not provide additional evidence to support a secretory or absorptive function for this region of the excurrent duct system of the testis.
Ultrastructural distinction between reticular and collagenous fibers with an ammoniacal silver stain
Authors: Snodgrass Michael J.
Published: February 2005

Reticular and collagenous fibers stain differently when subjected to ammoniacal silver reduction. A variety of tissues were subjected to such a “reticulin” technique and the association of reaction product with intercellular connective tissue elements was studied with the electron microscope. The reaction with reticular fibers was primarily associated with the interfibrillar matrix, and was globular in form having a wide variety of particle sizes. Conversely, in dermal collagen the unit fibrils were stained rather than the interfibrillar matrix. The precipitate was punctate in form and was associated with the cross striations of unit collagen fibrils. Large microfibrils also reacted positively with the stain, imparting a faint periodicity. Basement membranes were stained uniquely. The underlying plasmalemma and the lamina densa were heavily stained with silver while the lamina lucida was relatively unstained. The unit fibrils of the lamina reticularis stained in the same manner as dermal unit collagen while the ground substance remained unstained. This represents a clear distinction between the argentophilic characteristics of collagenous fibers, reticular fibers, and basement membranes.
Degeneration of germ cells in normal, hypophysectomized and hormone treated hypophysectomized rats
Authors: Russell Lonnie D. , Clermont Yves
Published: February 2005

In normal adult rats some germ cells degenerate at several vulnerable steps of spermatogenesis. These are the type A spermatogonia, midpachytene spermatocytes, primary and secondary spermatocytes which degenerate during their respective maturation divisions and step 7 and 19 spermatids. In the present study, these degenerating cells were examined under the electron microscope, and their frequency was determined in toluidine blue stained semithin sections of testes from normal, hypophysectomized (at 5.5 days after operation) and hypophysectomized rats injected with FSH and LH separately or in combination. With the exception of the step 19 spermatids, the degenerating germ cells underwent necrosis in vacuolated spaces delimited by Sertoli cells. In the case of the affected step 19 spermatids, an apical cytoplasmic process of the Sertoli cell initially ensheathed a long segment of their flagellum, and then each degenerating cell was drawn deep in the seminiferous epithelium where it was phagocytozed by the Sertoli cell. Soon after hypophysectomy the incidence of degenerating mid‐pachytene spermatocytes, step 7 and 19 spermatids which are present in stages VII or VIII of the cycle of the seminiferous epithelium, increased significantly. In contrast the number of degenerating primary or secondary spermatocytes during the meiotic divisions seen in stage XIV of the cycle or of any other germinal cell was not significantly modified. While the injection of FSH alone had no influence on the number of degenerating cells in hypophysectomized rats, injections of LH at the two doses administered (0.7 μg or 20 μg) reduced significantly the number of degenerating cells seen in stages VII‐VIII of the cycle; combined injections of FSH and LH (20 μg) reduced the number of these degenerating cells to the normal low values. Thus it appeared that the mid‐pachytene spermatocytes and the step 7 and 19 spermatids, all present in the adluminal compartment of the seminiferous epithelium in stages VII or VIII of the cycle, were more sensitive to the presence of absence of gonadotropic hormones than the other germ cells present in the seminiferous epithelium.
Electron microscopic studies on the myotomes of larval lamprey, Lampetra japonica
Authors: Nakao Taisuke
Published: February 2005

Myotomes of the caudal one‐third of the body of 26‐day‐old larval lampreys, Lampetra japonica, were studied by electron microscopy. Each myotome consists of horizontally stacked muscle lamellae. The myotomes are covered laterally by a single layer of flattened cells called here “lateral cells,” and the other aspect is covered by an external lamina. The myotomes are mid‐segmentally innervated.

Each muscle lamella usually contains two single cortical layers of myofibrils along the dorsal and ventral sarcolemma with a nucleus and mitochondria interposed between two layers. Numerous peripheral couplings are observed with relatively less developed triads. There are no membrane specializations to connect adjacent muscle lamellae within a myotome. Intermyotomal junctions are, however, noted between tips of cytoplasmic processes of muscle lamellae of adjoining myotomes. They resemble tight or gap junctions. No myofibrils are present in these cytoplasmic processes. Myotendinous junctions, with “terminal couplings” (Nakao, 1975), are seen under development at the myoseptal ends of muscle lamellae.

Lateral cells contain only ordinary organelles and no special structures such as myofibrils are found in the cytoplasm. They are connected to each other and to muscle lamellae by primitive desmosomes. They generally have no external lamina investment.
Development of meissner corpuscle of mouse toe pad
Authors: Idé Chizuka
Published: February 2005

The cytologic development of Meissner corpuscles of the mouse toe pad has been studied using light and electron microscopy, and correlated with silver impregnations of frozen sections. By 18 days of gestation, neurites are seen near the epidermis, but intraepidermal neurites are few. One day after birth, the number of intraepidermal neurites increases, and some accompanying Schwann cells extend their cytoplasmic processes penetrating the basal lamina of the epidermis. Four days after birth, Schwann cells invade the epidermis further, extending many cytoplasmic processes which are intimately associated with basal cells of epidermis. These specialized Schwann cells which contact the epidermis proper also begin to develop cytoplasmic lamellae and thus denote the onset of lamellar cell development. By eight days after birth, the developing lamellar cells become more elaborated, and their cytoplasmic processes contain caveolae and filaments, characteristic features of lamellar cells. This developmental sequence supports the concept that lamellar cells are derived from Schwann cells. Through all stages of development, neurites and Schwann cells interact closely with epidermal cells. Epidermal cells may be essential for corpuscle formation. By 20 to 25 days after birth, mouse toe pad Meissner corpuscles are cytologically mature.
Location of progenitor cells in periodontal ligament of mouse molar stimulated by wounding
Authors: Gould T. R. L. , Melcher A. H. , Brunette D. M.
Published: February 2005

Wounds were made in the alveolar process overlying the mesial root of the mandibular first molar of 35‐g mice to expose periodontal ligament. Dividing cells were arrested in metaphase by injection of vinblastine sulphate three hours before death three, five and seven days after wounding. Serial 1‐m̈m plastic sections of the wound were stained with hematoxylin and eosin. The distance between the mitotic figures and the nearest blood vessel, bone and cementum was measured in every fourth section. No mitotic figure was measured twice. The distances of at least 500 interphase cells from the closest blood vessel were measured in each wound. At all time periods the distribution of mitotic cells was significantly closer to blood vessels than that of interphase cells (p < 0.01). From three days to seven days after wounding there was a significant shift of mitotic activity away from the bone side of the ligament, but not away from blood vessels (p < 0.05). Approximately 10% of all mitotic cells lay close to cementum, but not close to blood vessels. The majority of the dividing cells were confirmed to be paravascular, and appeared to belong to two populations, one adjacent to bone, the other in the body of the ligament. A third population, not paravascular, lay adjacent to cementum.