bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology of rabbit collecting duct
Authors: LeFurgey Ann , Tisher C. Craig
Published: February 2005

Recently the assumed structural and functional homogeneity of the collecting duct (CD) has been questioned. The objective of this study was to determine if heterogeneity occurs in luminal surface membrane structure or in cytoplasmic configuration of cells in the collecting duct or both. Straight segments of cortical and medullary CD were examined in perfusion‐fixed rabbit kidneys with scanning electron microscopy (SEM), light (LM) and transmission electron microscopy (TEM). Principal cells were the most abundant cells in all CD regions; intercalated cells comprised 37% of the cell population in the cortex, 18% in the outer medulla, and < 1% in the inner medulla. SEM revealed two surface patterns among the ciliated principal cells: 1, located in the cortex and outer medulla, with few surface microvilli, and 2, located in the inner medulla, with abundant microvilli. Intercalated cells exhibited four distinctive luminal surface configurations: I, numerous short microvilli; II, both short and elongate microvilli; III, microplicae alone; and IV, both microvilli and microplicae. Intercalated cells with patterns I and II were predominant in the cortex, while cells with patterns III and IV were most common at the corticomedullary junction. TEM confirmed that marked variation existed in cytoplasmic structures of both principal and intercalated cells. These findings may either indicate the presence of several specific types of principal and intercalated cells or reflect different functional states of the principal and intercalated cells. Regardless of their significance, their presence must be considered in studies seeking to establish precise structural‐functional relationships in this region of the rabbit renal tubule.
Reduced cell proliferation in fetal lung after maternal administration of pilocarpine. A scintillation autoradiographic study
Authors: Smith Dennis M. , Shelley Sue A. , Balis John U.
Published: February 2005

Fetuses were obtained on the 28th gestational day from pregnant New Zealand white rabbits treated daily, on the 24th through the 27th gestational day, with pilocarpine HCl, 5 mg/kg in saline, or saline alone. Lung fragments from these fetuses were incubated for two hours in medium containing 3H‐thymidine. Scintillation autoradiography of 1‐μm‐thick sections of these fetal lungs revealed that the lung tissue from pilocarpine‐treated fetuses had significantly lower labelled cell indices for both alveolar epithelial cells and interstitial cells. These results indicate that pilocarpine treatment promotes differentiation of immature cells in the fetal lung at the expense of cell proliferation.
Structure of the endodermal epithelium of the chick yolk sac during early stages of development
Authors: Mobbs Ian G. , McMillan Donald B.
Published: February 2005

The structure of the areas pellucida and vasculosa of the early chick embryo (stages 11–29) was examined by light, transmission and scanning electron microscopy. The most striking feature of the endodermal cells of these areas is the presence of large intracellular yolk drops which are characteristic of the regions in which they are found: lipid‐like homogeneous drops in the area pellucida, heterogeneously composed pleomorphic drops in the mid‐region of the area vasculosa and granular drops at the periphery of the area vasculosa in the region of the sinus terminalis. On morphological criteria it is postulated that granular drops may arise by direct engulfment of extracellular yolk, but this does not appear to be true for pleomorphic or homogeneous drops. Since the apical junctions between endodermal cells across the yolk sac are tight, they seal off the extraembryonic compartment from the vitelline circulation and presumably prevent intercellular passage of the yolk constituents. Thus the endodermal epithelium must mediate the transport of nutrients from the yolk mass to the developing embryo. Endodermal cells exhibit a variation across the yolk sac in the presence and number of structures associated with uptake of extracellular materials. The mid‐region of the area vasculosa appears to be the most endocytotically active region with an abundance of microvilli, bristle‐coated pits and vesicles and apical canaliculi and vacuoles. There is a close association between the endoderm and vitelline blood vessels and this association is maintained, as the yolk sac develops, by the formation of small vessels juxtaposed between the vascular surface of the endoderm and the walls of the large vitelline vessels.
Maturation of rabbit auricular chondrocytes grown in vitro in monolayer culture
Authors: Moskalewski S. , Adamiec I. , Gołaszewska A.
Published: February 2005

Chondrocytes isolated from auricular cartilage of 7‐day‐old rabbits were grown in vitro until the onset of phase III, occurring after 10‐14 population doublings (PD). The size of cells and their dry mass were measured at various PD levels. These data were compared with results of analogous measurements of chondrocytes freshly isolated from 28‐day‐old rabbits.

Both in vivo, during cartilage growth, and in vitro, some of the chondrocytes increased considerably in size and acquired two nuclei.

Chondrocytes cultured in vitro for 4 population doublings were still capable of depositing elastic fibers in culture and forming cartilage after intramuscular transplantation. After longer periods of cultivation the ability of cells to produce a cartilage matrix declined.

It is suggested that the auricular chondrocytes may represent a convenient model for comparative studies of cell aging in culture and in vivo, owing to the simplicity of matching senescent cells arising in both these situations.
Ultrastructural organization of the hamster renal pelvis
Authors: Lacy Eric R. , Schmidt‐Nielsen Bodil
Published: February 2005

The renal pelvis of the hamster has been studied by light microscopy (epoxy resin sections), transmission electron microscopy, and morphometric analysis of electron micrographs. Three morphologically distinct epithelia line the pelvis, and each covers a different zone of the kidney. A thin epithelium covering the outer medulla (OM) consists of two cell types: (1) granular cells are most numerous and have apically positioned granules which stain intensely with toluidine blue, are membrane‐bound, and contain a fine particulate matter that stains light grey to black in electron micrographs. (2) Basal cells do not have granules, are confined to the basal lamina region, and do not reach the mucosal epithelial surface. The inner medulla (IM) is covered by a pelvic epithelium morphologically similar to collecting duct epithelium of IM. Some cells in this portion of the pelvic epithelium (IM) stain intensely dark with toluidine blue, osmium tetroxide, lead, and uranyl acetate. Transitional epithelium, which separates cortex (C) from pelvic urine, has an asymmetric luminal plasma membrane and discoid vesicles, each of which is similar to those previously observed in mammalian ureter and urinary bladder epithelia. Based on morphological comparisons with other epithelia, the IM and OM pelvic epithelia would appear permeable to solutes and/or water, while the transitional epithelium covering the C appears relatively impermeable. It would also appear that the exchange of solutes and water between pelvic urine and OM would involve capillaries, primarily, since morphometric analysis showed that both fenestrated and continuous capillaries of the OM were extremely abundant ( > 60% of OM pelvic surface area) just under the thin pelvic epithelium.
Neuronal‐vascular relationships in the raphe nuclei, locus coeruleus, and substantia nigra in primates
Authors: Felten David L. , Crutcher Keith A.
Published: February 2005

A fluorescence histochemical and electron microscopic study of the monoaminergic cell groups in the squirrel monkey and Rhesus monkey brains has revealed the direct apposition of blood vessels to perikarya and dendrites of monoaminergic neurons. Capillaries and small arterioles or venules, ranging from 8–50 μm in diameter, showed perikarya and dendrites abutting the basement membrane without evidence of glial interposition. This neuronal‐vascular relationship was present in 20% to 30% of the small vessels in the serotonergic nuclei raphe dorsalis and centralis superior and in the nor‐adrenergic locus coeruleus. Such contacts were clearly present but observed less frequently in the dopaminergic substantia nigra pars compacta and in the serotonergic nuclei raphe obscurus, pallidus, magnus, and pontis. We postulate that monoamine‐containing neurons apposed to blood vessels in certain regions of the brain may be influenced directly by hormones or other substances in blood.
Complex carbohydrates of rat tracheobronchial surface epithelium visualized ultrastructurally
Authors: Spicer S. S. , Mochizuki I. , Setser M. E. , Martinez J. R.
Published: February 2005

Application of cytochemical methods for complex carbohydrates at the light and electron microscopic levels served further to differentiate secretory cells of the rat tracheobronchial surface epithelium into serous and mucous categories, and permitted subclassification of serous cells into four types and of mucous cells into three types. The granules in different serous cells and Clara cells varied in staining with the periodic acid‐thiocarbohydrazide‐silver proteinate (PA‐TCH‐SP) method, but generally lacked dialyzed iron (DI) affinity and apparently contained neutral glycoprotein. However, in some focal areas, serous and Clara cell granules showed a pattern of DI staining similar to the PA‐TCH‐SP reactivity. The PA‐TCH‐SP and DI methods stained granule glycoconjugate comparably in the three mucous cell types. The lack of high iron diamine (HID) affinity in these sites testified to carboxylated, periodate‐reactive mucosubstance, presumably sialylated glycoprotein. The luminal surface of the apical plasmalemma of all surface epithelial cells stained with DI but lacked HID affinity. The PA‐TCH‐SP technique stained the surface of the apical plasmalemma of mucous cells, serous cells, and Clara cells in decreasing order of intensity. Microvilli of ciliated cells were PA‐TCH‐SP‐positive, but cilia were unreactive and apparently contained a glycosaminoglycan rather than the presumed sialylated glycoprotein of the other surfaces. DI and PA‐TCH‐SP reactivity of the apical far exceeded that of the basolateral plasmalemma in all surface epithelial cells. Two strata, presumed to be the lamina lucida and the lamina diffusa of the basement membrane under all the surface epithelial cells, stained with the DI but not the PA‐TCH‐SP method and apparently contained glycosaminoglycan. Intraepithelial cells, interpreted as globule leukocytes, appeared to represent mast cells infiltrating the epithelium and carrying out endocytic activity.
Ultrastructural studies on migrating epidermal cells during the wound healing stage of regeneration in the adult newt, Notophthalmus viridescens
Authors: Repesh Lillian A. , Oberpriller Jean C.
Published: February 2005

The ultrastructure of the epidermal cells which migrate over the wound surface of the amputated limb of the adult newt, Notophthalmus viridescens, was observed with transmission (TEM) and scanning (SEM) electron microscopy. In order to aid in the visualization of polyanionic surface materials on the wound epithelium and wound surface with TEM, the basic dye, ruthenium red, was introduced into the fixatives and buffer. Control limbs were processed without ruthenium red. Shortly after amputation, basal cells at the wound margin possessed elongated, flattened profiles with long pseudopodial projections (lamellipodia and filopodia) that appeared to make contact with the fibrin exudate covering the stump tissues. Epidermal cells proximal to the site of amputation were also in a state of mobilization. Large intercellular spaces and a reduction in the number of desmosomes were observed in the migrating cells. Epidermal cell nuclei became characteristically euchromatic with well‐developed nucleoli. Microfilaments were seen within the cytoplasm, extending toward the plasma membrane of cellular processes. Phagocytosed material was also present in the migrating cells. By approximately 9 hours post‐amputation, wound closure was complete, and the wound epithelium consisted of three to four cell layers of a non‐cornified epidermis. Generally, the amount of extracellular material present on the surface and in the enlarged intercellular spaces of migrating epidermal cells remained the same throughout the period of wound closure. A layer of polyanionic material was observed consistently over the fibrin meshwork covering the wound surface with TEM.
The stem‐cell zone of the small intestinal epithelium. V. Evidence for controls over orientation of boundaries between the stem‐cell zone, proliferative zone, and the maturation zone
Authors: Bjerknes Matthew , Cheng Hazel
Published: February 2005

We studied, in mouse jejunum, the possibility that coordinate systems related to crypt axis or muscularis mucosae have an influence over the orientation of the boundaries between three crypt compartments: the stem‐cell, the proliferative, and the maturation zones. Segments of jejunum, from male Swiss albino mice injected with 3H‐thymidine 1 hour before death, were collected, embedded in Epon, and 1‐μm‐thick serial sections were prepared and radioautographed. Similar material was also obtained from an experimental preparation in which the anti‐mesenteric border of a short segment of jejunum was involuted surgically, thus creating a fold similar to the plicae circulares in the human intestine. The crypts lining the sides and top of the folds were greatly tilted, relative to the muscularis mucosae 2 weeks after surgery. The angle formed between the crypt axis and the plane of the muscularis mucosae (Θ) was measured. This was related to the angle formed between the crypt axis and the 3H‐thymidine‐labeled leading edge (β), and that between the crypt axis and the upper boundary of the Paneth‐cell distribution (α). The angle α indicates the orientation of the boundary between the stem‐cell and proliferative zones, while β indicates the orientation of the boundary between the proliferative and maturation zones. We found that β remained perpendicular to the crypt axis for all degrees of crypt tilt (Θ). In contrast, α did not remain perpendicular to the crypt axis over all degrees of crypt tilt. When crypts were tilted by more than 30°, α reoriented and was found to be parallel to the plane of the muscularis mucosae. However, in crypts tilted less than 30°, α remained perpendicular to the crypt axis. We concluded that there are probably two coordinate systems that provide information to the crypt epithelium. The first is a coordinate system related to crypt axis that influences the orientation of the boundary between the proliferative and maturation zones and the second is related to muscularis mucosae an influences the orientation of the boundary between the stem‐cell and proliferative zones. The latter has a threshold of about 30°, which probably represents the range of peristalsis‐induced crypt tilt.
Development of the outflow tract and closure of the interventricular septum in the normal human heart
Authors: McBride Robert E. , Moore G. William , Hutchins Grover M.
Published: February 2005

The majority of congenital heart malformations in humans involve defects in the atrioventricular valves, the crest of the interventricular septum, and/or the outflow tract, but the position and timing of these structures during cardiac development is controversial. We examined all 622 staged, serially sectioned normal human embryos and fetuses in the Carnegie Embryological Collection, and obtained a statistical tabulation of the appearance of the endocardial cushion components and surrounding structures for 382 embryos in good condition between stages 9 and 23 inclusive, when the heart normally develops. Accurately scaled drawings of ventral and lateral views of the hearts of seven embryos from stage 13 through 22 were prepared from graphic reconstructions in order to visualize the relationships of the structures under consideration. We found that development of the outflow tract septum follows the apparent functional separation of both the left and right ventricles and the blood streams leaving them. Elevations of the endocardial cushion material are continuous throughout the outflow tract and develop as a consequence of the elliptical configuration imposed on the circular cross section of the outflow tract. The membranous interventricular septum is formed of cushion material in the space bounded by the outflow tract septum, interventricular septum, and the fused AV cushion and right outflow tract cushion. The results of this study are consistent with the assertion that functional separation of the aortic and pulmonary outflow tracts precedes anatomic septation, and that anatomic septation is brought about by mechanical modeling of developing myocardium and endocardial cushion material.
Adipocyte development in the rat hypodermis
Authors: Hausman G. J. , Campion D. R. , Richardson R. L. , Martin R. J.
Published: February 2005

The relationship between hair‐follicle development and adipocyte formation in the rat hypodermis was studied. Skin samples from rats of various body weights were prepared for histological, histochemical, and electron microscopic analysis. Adipocyte formation in the rat hypodermis was linked spatially and temporally with hair‐follicle growth and development. Cells trapped along the invading edge of hair follicles developed into adipocytes after the descent of the follicles through the dermis. Histochemical characteristics of the outermost cells of hair follicles indicated hypoxic conditions. These conditions may have directed a vascularization process that resulted in a network of adipocytes and capillaries around these follicles. Thus, under normal conditions, adipocyte formation is an integral phase of hair‐follicle development in the rat.
Periarterial macrophage sheaths (Ellipsoids) in cat spleen—an electron microscope study
Authors: Blue Julia , Weiss Leon
Published: February 2005

Periarterial macrophage sheaths (PAMS), a term we introduce to replace “ellipsoids,” surround arterial capillaries in the red pulp of the spleen and are major sites for clearance of blood‐borne particles. PAMS and their arterial capillaries in cat spleens in various states of congestion and contraction were studied by transmission electron microscopy. Thorotrast, a colloidal suspension of thorium dioxide, was injected to label macrophages.

A PAMS consisted of a fine meshwork of reticular cells and reticular fibers which held macrophages and formed a cylindrical sheath around an arterial capillary lying in its longitudinal axis. Some PAMS were spongy due to loosening of cell associations by plasma infiltration; others were tightly compressed. Blood cells were both free in the interstices of the PAMS and attached to macrophages.

Reticular cells formed a closely applied but incomplete layer adventitial to the arterial capillary and extended branches which contributed to the meshwork. Small villous processes on the major branches of reticular cells approached each other, sometimes forming intercellular junctions, and fit into complementary indentations in the surfaces of macrophages and endothelial cells. Thin filaments within reticular cells filled the villous processes and formed a border beneath the plasmalemma; intermediate filaments ran through the centers of the branches. Reticular fibers lay between reticular cells. Basement membrane fabricated of the same material as reticular fibers lay between the endothelium and reticular cells. Macrophages contained Thorotrast and abundant debris of phagocytized cells and were joined by extensive interdigitation of micropseudopodia. Endothelial cells were long rods which lay parallel and were joined along their bases by interdigitating lateral processes. Intercellular junctions were present at some points, but at others lateral processes were everted to form open interendothelial slits through which blood cells could pass. Endothelial cells possessed great numbers of randomly oriented intermediate filaments and small patches of thin filaments scattered along the basal plasmalemma and in lateral processes. Thin filaments may function to attach cells to one another and to the basement membrane and may assist in closing interendothelial slits. We believe that the endothelium responds to changes in arterial blood pressure and blood flow. It stretches to allow dilatation and recoils, probably due to the intermediate filaments, squeezing blood cells through interendothelial slits.
Scanning electron microscope studies of the auditory papillae of some iguanid lizards
Authors: Miller Malcolm R.
Published: February 2005

The papillae basilares of 16 species (10 genera) of iguanid lizards were studied by scanning electron microscopy. Variations in the surface structures of the auditory papillae showed the following major differences: (1) papillae with localization of the unidirectional hair cells at the apical end of the papilla (Anolis carolinensis); (2) papillae with absence or loss of a portion of the apical bidirectional hair‐cell segment (Basiliscus basiliscus); (3) papillae with a central, short‐ciliated, unidirectional hair‐cell segment, and 3–6 irregular rows of long‐ciliated bidirectional hair cells located in the apical and basal regions (Iguana iguana, Crotaphytus collaris, C. wislizeni, Dipsosaurus dorsalis, Sauromalus obesus); (4) papillae in which the apical and basal bidirectional hair‐cell segments are reduced to two rows of hair cells (Sceloporus occidentalis, S. clarki, S. orcutti, S. jarrovi, S. undulatus, S. magister, Callisaurus draconoides, Uta stansburiana).

The above differences in auditory papilla structure agree closely with other anatomical differences that delineate iguanid assemblages. Thus the species in the four groups above fall respectively into the following iguanid groups: (1) anolines, (2) basiliscines, (3) iguanines, and (4) sceloporines.
Morphodynamics of outgrowths of mouse trophoblast in the presence and absence of a monolayer of uterine epithelium
Authors: Van Blerkom Jonathan , Chavez Daniel J.
Published: February 2005

Mouse blastocysts were cultured in the presence and absence of a confluent uterine, luminal, epithelial monolayer in order to assess (1) comparative developmental abilities and (2) the existence and nature of embryo‐uterine intercellular contacts. Embryonic development and mural trophoblast outgrowth were examined by light, transmission and scanning electron microscopy, and by time‐lapse cinematography. The results demonstrate that cultured mouse blastocysts are capable of development that is essentially equivalent to the early egg cylinder stage in the presence and absence of a uterine epithelial substratum. Penetration of the endometrium and displacement of uterine luminal epithelial cells in vivo is paralleled in vitro by the displacement of uterine cells from the advancing edge of outgrowing mural trophoblast. The ability of mural trophoblast to continue to outgrow and displace uterine cells persists for a finite period of time. The findings are discussed with respect to (1) the nature of embryo‐uterine contact in vivo and (2) mechanisms proposed to explain trophoblastic displacement of uterine luminal epithelial cells during normal implantation.
Structure of the human respiratory acinus
Authors: Schreider Jay P. , Raabe Otto G.
Published: February 2005

Silicone rubber corrosion casts of the human lung in a state of end inspiration were used to study several specimens of the human pulmonary acinus. Four of the acini were measured in detail with respect to duct length and diameter, the number of alveoli per duct, and the branching pattern of the ducts. The acini were found to have irregular branching patterns, including dichotomous, trichotomous, and side branches. There were, on the average, eight to 12 duct generations and about 7.1 × 103 alveoli per acinus. The polygonal alveoli had an average diameter of 250 μm. The lengths and diameters of the ducts varied considerably; however, the dimensions tended to decrease in the more proximal portions of the acini. The number of alveoli per duct also varied, with an average of ten alveoli per duct. On the basis of the measurements, two models, a “surrogate path” model and an “average path” model, were used to summarize the data, with the surrogate path model being more useful for calculations such as particle desposition in the airways, and the average path model being most illustrative of the anatomical structures.
Development and phylogenetic significance of the fetal membranes and placenta of the African hystricognathous rodents Bathyergus and Hystrix
Authors: Luckett W. Patrick , Mossman Harland W.
Published: February 2005

Morphogenesis of fetal membranes in African and American hystricognathous rodents is essentially the same, even in the possession of such uniquely derived features as a subplacenta and a capillary ring on the inverted yolk sac, features that are unknown in any other rodent group. This is good evidence that the African and American hystricognaths comprise a monophyletic group. Certain interesting features of the decidua, decidual giant cells, periplacental bilaminar omphalopleure, and epamnion are described in Bathyergus and Hystrix. Of special interest in Bathyergus is the widespread decidualization of the uterine connective tissue, even that of the myometrium and perimetrium; and the presence of numerous, usually binucleate, decidual giant cells.
Regeneration of mouse digital corpuscles
Authors: Idé Chizuka
Published: February 2005

Changes in morphology and nonspecific cholinesterase (ChE) activity during the reinnervation of digital corpuscles of mouse toe pads after transection of the sciatic nerve were examined by light and electron microscopy. Reinnervation occurred about 30 days after nerve section. A small‐diameter axon was present near the shrunken atrophic lamellae of the previously denervated corpuscle. From 40 to 60 days after nerve transection, the ingrowing axons branched; and the enlarged tip of each branch contained numerous mitochondria. Lamellar cells and cytoplasmic lamellae at this stage were still smaller than normal. Lamellar cells had normal structure by 4 months after nerve section. Following reinnervation, evidence of ChE activity in the interlamellar spaces at first remained unchanged in intensity and distribution from that of the denervated corpuscle. About 10 days after reinnervation, enzyme activity increased in the perineural spaces and was evident, as in the normal corpuscle, in the cisternae of the rough endoplasmic reticulum and nuclear envelope of the lamellar cell body. By 4 months after nerve division, the intensity and distribution of the ChE activity were almost the same as in the normal corpuscle. From the above findings the following conclusions could be drawn: (1) The shrunken atrophic lamellar cells remaining after denervation are utilized by the ingrowing axons to regenerate normal digital corpuscles. (2) The lamellar cell is dependent on the well‐developed axon terminals to maintain its normal morphology and to synthesize ChE.
The testis and its excurrent ducts in American caenolestid and didelphid marsupials
Authors: Rodger J. C.
Published: February 2005

The present study examines and compares the structure of the testis and its excurrent ducts in a caenolestid and four didelphid marsupials. Of particular interest was the site of sperm pairing in the epididymis and whether this feature, shared by both American marsupial families but not by any Australian marsupial, was associated with changes in the morphology of the duct.

In contrast to the testes of most Australian marsupials, except the peramelids (bandicoots), the intertubular space in the American marsupials was filled by Leydig cells (around 20% of testis volume). The opossum testes were unusual compared with those of eutherian mammals in that histological sections of individual seminiferous tubules contained only a single cellular association irrespective of the length of the tubule sectioned. The rete testis, as in the Australian dasyurids (devil, quoll, etc.), was a simple branching duct system that arose deep within the testis and emerged as a single duct at the testicular hilus. This arrangement is completely different from that in kangaroos and Australian possums, indicating a diversity of rete form in the marsupials similar to that seen in eutherian mammals. The rete emptied into a single, essentially straight, efferent duct that became convoluted towards the epididymis, where it formed a distinct structure adjacent to the caput epididymidis. The efferent ducts were highly variable in diameter and epithelial height, suggesting that the duct was not of uniform character along its length, or that the initial single duct had divided to form ducts of different characters. Sperm pairs were first seen in the proximal cauda epididymidis, and their appearance was correlated with changes in the character of the duct and its epithelium. The distal ductus deferens of Caenolestes, in contrast to those of the didelphids and indeed all other marsupials, was a convoluted ampulla‐like structure adjacent to the prostate gland. In the other marsupials the only accessory sex glands are a segmented prostate and bulbourethral glands.
Microvasculature of the mouse testis and excurrent duct system
Authors: Suzuki Fumie
Published: February 2005

The microvascular architecture of the mouse testis and excurrent duct system was examined by a casting method with the aid of scanning electron microscopy and by sectioning techniques for light and transmission electron microscopy. Two fundamental types of peritubular capillary arrangements were noted in relation to the tubules. The first type most typically appeared in the testis. In this type, peritubular capillaries interconnected intertubular blood vessels to form a rope‐ladder‐like structure. The length of the individual peritubular capillaries was short, and a number of the capillaries encircled eachtubule. Adjacent tubules shared a single layer of capilaries. The vascular organization of the ductuli efferentes and of the middle segment of the epididymis was also of this type, but the number of peritubular capillaries was much fewer compared with that of the testis. In the second type, the peritubular capillaries formed a network encircling each tubule in its subepithelial layer. The capillary organization in the initial and terminal segments of the epididymis and the ductus deferens belonged to the second type. In the distal part of the ductus deferens, a prominent venous plexus was formed in the most peripheral subepithelial layer.
A fine‐structural study of interstitial cell changes in the testes of Necturus maculosus during a portion of the annual cycle, and possible evidence for local feedback control by seminiferous epithelium
Authors: Ucci Angelo A.
Published: February 2005

The developmental stages of the interstitial cells of Leydig in Necturus maculosus were studied in testes of animals obtained in November and December. As a consequence of the caudal to cranial progression of the wave of spermatogenesis, samples obtained from cranial, central, and caudal portions of these testes exhibit regional differences in the morphology of their Leydig cells. In these samples, fibroblast‐like stromal cells with large, dense, elongated nuclei and thin sheets of cytoplasm surround the cranial seminiferous lobules that usually contain spermatozoa. Such stromal cells possess a small juxtanuclear Golgi apparatus, profiles of smooth and rough endoplasmic reticulum, and mitochondria with tubular and shelf‐like cristae.

In the central area of the testis, interstitial cells with oval nuclear profiles and a finer chromatin pattern surround degenerating seminiferous lobules. The abundant cytoplasm of these cells contains predominantly smooth endoplasmic reticulum interspersed with a few lipid droplets. These cells contain mitochondria that are packed with tubular cristae.

In the caudal part of the testis, the Leydig cells have a round nucleus with finely dispersed chromatin. Numerous lipid droplets accumulate in the ample cytoplasm, which is filled with smooth endoplasmic reticulum. The juxtanuclear Golgi apparatus becomes enlarged; associated with it are vesicles with an electron‐dense content. The cristae of the mitochondria are more numerous and have tubules of 50‐nm diameter mixed with arrays of small tubules 25–30 nm in diameter.

The appearance of morphologically mature interstitial cells of Leydig only adjacent to degenerated seminiferous lobules in the caudal portion of the testis suggests the possibility of local feedback control of Leydig‐cell development.
Corneal splitting in the developing lamprey Petromyzon marinus L. eye
Authors: Dickson D. Howard , Graves Debra A. , Moyles Michael R.
Published: February 2005

The cornea of the adult lamprey has both dermal (spectacle) and scleral components. These are separated by a thin mucoid layer that allows free movement of the globe.

This study has shown that during the larval (ammocoete) stage, the lamprey cornea develops in a manner similar to that of other lower vertebrates. Just prior to the period of transformation to the adult parasite, the outer dermal portion of the ammocoete cornea (spectacle) consists of an anterior stratified columnar epithelium with goblet cells at the surface. The stroma of the dermal cornea consists of a thick outer layer of orthogonally oriented collagen with branching fibroblasts and a thin, loosely organized inner layer with slender elongated fibroblasts. The scleral cornea is lined internally by a flattened monolayer of mesodermal cells, the corneal endothelium. Its narrow stroma is composed entirely of thin, orthogonally aranged, collagen‐fiber lamellae, and is bounded externally by a thin continuous mesothelial layer of cells that abuts directly onto the loose stromal component of the dermal cornea.

During the early stages of transformation, the anterior epithelium of the dermal cornea becomes stratified squamous in type. Later, the inner loose stroma of the dermal cornea (spectacle) begins to separate from the scleral cornea components, and a third complete mesothelial layer forms a distinct inner border for the dermal cornea. A mucoid layer is formed between the dermal (spectacle) and scleral corneas and remains throughout the adult life.
The formation of the primitive choanae and the junction of the primary and secondary palates in the mouse
Authors: Tamarin Arnold
Published: February 2005

This study has followed the development of the primary choanae in the mouse and has shown that they originate at the developmentally strategic position of junction between the primordia of the primary and secondary palates and that this basic anatomic relationship is maintained throughout further development. Involution of the oronasal membrane begins late in the 11th day (stage 19) with the formation of interstitial gaps. The gaps enlarge and coalesce so that a completely patent opening between nasal passage and stomodeum is established by 13 days (stage 21). The membrane consists of two layers of simple squamous epithelium which become separated as involution progresses. The form of the choanal antrum changes from a simple funnel‐shaped ellipse early in the 13th day to a complex slitlike opening within the following 24 hours. This coincides with the completion of a definitive primary palate and the enlargement and elevation of the shelves of the secondary palate. The maturation of the incisive papilla and interchoanal columella is related to the final stages of choanal morphogenesis. Thus, by stage 22 (14 days) the shape of the primary choanae and their anatomic relationship to the primary and secondary palates are established, and they remain essentially unchanged in later stages.
Splenic white pulp and associated vascular channels in chicken spleen
Authors: Oláh Imre , Glick Bruce
Published: February 2005

We have studied the chicken spleen by light and transmission electron microscopy. Germinal centers are located at the beginning of the central artery which is surrounded by the periarterial lymphatic sheath (PALS). The central artery has no branch crossing the PALS, and there is no histologically identifiable marginal zone in the chicken spleen. The central artery continues as penicilliform capillaries.

The mid‐portion of the penicilliform capillary is surrounded by the ellipsoid or Schweigger‐Seidel sheath. The endothelial lining of this part of the pencilliform capillary contains small channels, formed between neighboring endothelial cells, which enter the ellipsoid. These channels allow circulating substances to accumulate in the ellipsoid.

The cells of the ellipsoid are reticular cells, round or ovoid in shape, exhibiting a limited number of cell junctions. At the surface of the ellipsoid are ellipsoid‐associated cells (EAC) which have an affinity for toluidine blue. After perfusion fixation, the majority of the cells in the ellipsoid are lost; this suggests weak cellular connections between the ellipsoid cells. The ellipsoid‐associated cells remain in loco. On the basis of their shape and cytological features, two stages of EACs can be distinguished. The round or ovoid EACs elaborate active Golgi zones surrounded by numerous small vesicles containing an electron‐dense substance. Occasionally, mitotic figures can be seen among them which may suggest that they are immature forms. In the second or more mature stage, the EACs assume an elongated spindle shape. The spindle‐shaped EACs reveal inactive Golgi cis‐ternae and fewer but larger granules than the round or immature EACs. Unmyelinated nerve fibers and nerve ending were observed in the ellipsoid.

Perfusion fixation reveals that the distal portions of the penicilliform capillaries extend into the red pulp and become the sinuses. Therefore, the circulation of the chicken spleen is anatomically closed except for the channels in the mid‐portion of the penicilliform capillary.

The periellipsoid white pulp (PWP) possesses a few small lymphocytes, macrophages, and plasma cells with the majority of cells being young blastlike cells which may replenish the EACs and ellipsoidal cells.

Carbon, injected intravenously, appears on the EAC membrane by 30 minutes, while Brucella abortus is completely phagocytized at this time. Binding the carbon triggers the EAC to detach from the ellipsoid and migrate to the periellipsoidal white pulp (PWP). The EACs phagocytize carbon by 2 hours, and by 5 and 8 days are present in the red pulp and surround the germinal centers at the border of the periarterial lymphatic sheath, respectively. Secretory cells which have been identified in germinal centers might originate from EACs.
Ultrastructural configuration of sarcomeres in passive and contracted frog sartorius muscle
Authors: Bergman Ronald A.
Published: February 2005

The structural configuration of passive and contracted sarcomeres from frog sartorius muscle was determined for sarcomere lengths between 1.4 and 3.07 μm. Sarcomeres fixed with glutaraldehyde, without detectable contractile activity, were invariably rectangular in shape in longitudinal section regardless of sarcomere length. The structure of sarcomeres excited by osmium tetroxide and contracted depended upon sarcomere length. For lengths greater than 1.6 μm, longitudinally sectioned sarcomeres were convexoconvex (or barrel‐shaped). At 1.6 μm, contracted sarcomeres were invariably rectangular in shape. Below 1.6 μm, sarcomeres were compressed and appeared concavoconcave. The results of this study provide models for isovolumetrically contracted sarcomeres which differ significantly from those previously reported.
The gill in the spiny dogfish, Squalus acanthias: Respiratory and nonrespiratory function
Authors: De Vries R. , De Jager S.
Published: February 2005

Aspects of functional anatomy with respect to water and blood flow through the gills of Squalus acanthias and one specimen of Mustelus mustelus are described. A reconstruction of an entire filament has been made. (1) The cavernous body in the proximal segment of the filament is relatively small, contains a small amount of elastic tissue, and has no connections with the underlying afferent filament artery, except at its junction to the middle segment. In the middle segment of the filament, the wall and columns of the cavernous body are well supplied with elastic tissue. The size of the cavernous body increases gradually distally. The underlying afferent filament artery opens into it with numerous pores and eventually becomes incorporated in the cavernous body. The distal segment of the filament is characterized by the rapid increase in size of the cavernous body. Toward the free edge of the filament it almost reaches the efferent filament artery; toward the diaphragm it forms an anastomosing bridge with the neighboring filaments. Wall and columns in the distal segment of the cavernous body are richly supplied with elastic tissue. The afferent filament artery is no longer discernible. (2) In living specimens the tips of opposite filaments are in close apposition during the whole respiratory cycle. Application of artificial ventral aortic pressure to freshly killed specimens evoked the same reaction in the filament tips. The cavernous bodies provide the hydrostatic skeleton, necessary to keep the gill sieve closed. Lamellae are equipped with finger‐like appendages to facilitate adherence to the opposite filament tips. Lamellar appendages also reduce the dead space between lamellae of neighboring filaments. (3) The whole of cavernous bodies may also serve as an elastic blood reservoir with a function similar to that of the bulbus arteriosus in teleost fish. (4) Of all suitable places, only the lamellar streambed was clear and convincing in its response to perfusion with adrenalin or acetylcholine. (5) Structural details of the nonrespiratory circulation within the gills are described.
Ultrastructural characterization of the nasal respiratory epithelium in the rat
Authors: Monteiro‐Riviere Nancy A. , Popp James A.
Published: February 2005

This ultrastructural study of the respiratory epithelium of the rat nasal mucosa revealed six morphologically distinct cell types: goblet cells, basal cells, ciliated cells, nonciliated columnar cells, cuboidal cells, and brush cells. The latter three have not been previously characterized in the rat nasal mucosa by transmission electron microscopy. Cuboidal cells observed on the conchae

The term “conchae” has now been accepted by NOMINA ANATOMICA VETERINARIA (1983) to replace the word “turbinate”. Therefore, dorsal nasal conchae = nasoturbinates and ventral nasal conchae = maxilloturbinates.

and lateral wall had short apical microvilli which were less dense than the microvilli of the nonciliated columnar cells. Nonciliated columnar cells also identified on the conchae and lateral wall had short microvilli and an extensive network of smooth endoplasmic reticulum in the apical region. The brush cell had distinct ultrastructural features; it was pear‐shaped, with the broad base adjacent to the basement membrane and large microvilli on the surface. Microfilaments, microtubules, vesicles, and paired cisternae were found in the apical cytoplasm. Brush cells occurred singly on the conchae and lateral wall but were not identified in the respiratory epithelium of the nasal septum. These findings indicate the complexity of cell types composing the rat nasal respiratory epithelium.
Role of binucleate cells in fetomaternal cell fusion at implantation in the sheep
Authors: Wooding F. B. P.
Published: February 2005

In the sheep conceptus, individual intraepithelial binucleate cells first appear at 14 days post‐coitum (d.p.c.); and by 16 d.p.c. they form 15‐20% of the trophectoderm where it is apposed to the caruncular sites of initial attachment to the uterine epithelium. These binucleate cells and their derivatives can be recognized in the placenta by electron microscopy after selective staining of their Golgi body and its products, the numerous characteristic granules. Between 16 and 24 d.p.c. the uterine epithelium transforms to syncytial plaques. Evidence from ultrastructure and serial semithin sections indicates that this transformation is initiated by migration of fetal binucleate cells up to the microvillar junction and their fusion with individual uterine epithelial cells, producing trinucleate fetomaternal hybrid cells. These cells then appear to release their granules to the endometrium. It is suggested that continued binucleate‐cell migration and fusion with the trinucleate cells, together with displacement and/or death of the remaining uterine epithelial cells, produces the plaques of syncytium that cover the entire caruncle by 20‐24 d.p.c. This caruncular syncytium, in which no nuclear division has been found, expands enormously in area during the formation and maintenance of the cotyledons, deriving its nuclei from binucleate migration.
The early changes of parietal cell structure in the course of secretory activity in the rat
Authors: Vial Juan D. , Garrido Jorge , González Alfonso
Published: February 2005

The fine structure of the rat parietal cell was studied, both at rest and after stimulation by refeeding or insulin administration. Experiments on fixation procedures showed that whenever the fixative contained sucrose at a concentration higher than 0.2 M, the system of cytoplasmic membranes was clearly tubular in arrangement, whereas the omission of sucrose in the fixative usually resulted in a vesicular structure. The study with the high‐voltage electron microscope of thick sections prepared by conventional techniques or by impregnation with zinc iodide‐osmium (ZIO) revealed that the tubules are grouped into fascicles, and that these form a feltwork that is especially thick toward the cell apex. The development of the secretory canaliculus after stimulation appears to take place by an in situ remodeling of the cytoplasmic domain occupied by the tubular system. Cells examined after short periods of stimulation (5–15 min) showed images of the tubular system and of the canalicular structure which differed both from the nonstimulated and from the fully active (30–45 min of stimulation) cell. These features include the formation of wide cisternae and of pericanalicular cytoplasmic trabeculae or laminae, whose fine structure bears close resemblance to that of the intracanalicular processes in the same cells. These images can be ordered into a hypothetical sequence which is proposed as a model to explain the transformation of the tubular system and intervening cytoplasmic matrix into secretory canaliculus.
Unmyelinated fibers in the cervical and lumbar ventral roots of the cat
Authors: Wee Beth E. F. , Emery Dennis G. , Blanchard Janet L.
Published: February 2005

Ventral spinal roots at all spinal levels in humans contain many unmyelinated axons, as do all spinal roots of the cat which have been examined. Rats, however, have fewer unmyelinated fibers in cervical and certain lumbar ventral roots. To determine if unmyelinated fibers are distributed uniformly in ventral roots of the cat, cervical and lumbar ventral roots were examined by light and electron microscopy, and axons were counted. Lesions were made to determine the origin of unmyelinated fibers in ventral root L6. From 5 to 15% of the axons in cervical ventral roots are unmyelinated. This distribution of unmyelinated fibers in the cat is similar to the distribution in humans, although the cervical ventral roots of the cat contain relatively fewer unmyelinated fibers than the cervical ventral roots of humans. Approximately 24% of the axons in ventral root L6 are unmyelinated. More than 90% of these axons degenerate proximal to, but not distal to, a ventral rhizotomy and ipsilateral to a dorsal root ganglionectomy. Thus, most unmyelinated axons in ventral root L6 appear to arise from dorsal root ganglion cells. Much variation in the number and percent of unmyelinated axons in ventral roots at the same spinal level exists between individual cats and between opposite sides of the same cat.