bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal variations in the fine structure of the Necturus maculosus urinary bladder epithelium: Low transporters and high transporters
Authors: Karnaky Karl J. , Lau Kim R. , Garretson Leon T. , Schultz Stanley G. 
Published: February 2005

AbstractAlthough the urinary bladder of Necturus maculosus provides an important model system for studying the mechanisms of active Na absorption, little critical attention has been paid to the fine structure of its epithelium. Moreover, two distinct groups of urinary bladders, low and high Na transporters, have been described based on short‐circuit current or transepithelial potential difference. In the present study, over an 11‐month period, stable electrical parameters (short‐circuit current, transepithelial potential difference, and resistance) were recorded from 63 chamber‐mounted bladders. Analysis of these parameters revealed a highly significant difference between two groups (low transporters and high transporters) occurring at different times of the year. Consistent with these data, in urine collected from the bladders, the Na concentration in low transporters was significantly higher than that in high transporters. A subpopulation of these bladders was subsequently fixed and examined at the light and/or electron microscopic level. Low‐transporting bladders were characterized unequivocally by a thin, stratified squamous epithelium only 6–15 μm thick. High‐transporting bladders were composed predominantly of columnar‐shaped granular cells up to 70 μm in height, with ciliated, mitochondria‐rich, and basal cells present in small numbers. There is thus a correlation between transport activity, as measured by electrophysiological techniques and urine sodium analysis, and the structure of the tissue. Moreover, these parameters exhibit significant seasonal variation, the underlying mechanisms of which remain obscure.
Maturation of spermatozoa in the epididymis of the Chinese hamster
Authors: Yanagimachi R. , Kamiguchi Y. , Mikamo K. , Suzuki F. , Yanagimachi H. 
Published: February 2005

AbstractChinese hamster spermatozoa gain their ability to move when they descend from the testis to the distal part of the caput epididymis, but it is not until they enter the corpus epididymis that they become capable of fertilizing eggs. The maturation of the spermatozoa proceeds as they further descend the tract and perhaps continues even in the vas deferens. During transit between the distal caput and proximal cauda epididymides, small membrane‐limited vesicles (and tubules) appear on the plasma membrane over the acro somes of the spermatozoa. The number of vesicles appearing on the sperm brane reaches a maximum when the spermatozoa are in the proximal cauda epididymis. It declines sharply in the distal cauda epididymis. Spermatozoa in the vas deferens are free of the vesicles. The origin, chemical nature, and functional role of the vesicles that appear on the sperm surface during epididymal transit must be the subject of further investigation.
Photoreceptor fine structure in the archerfish (Toxotes jaculatrix)
Authors: Braekevelt Charlie R. 
Published: February 2005

AbstractThe fine structure and arrangement of the photoreceptor cells of the archerfish (Toxotes jaculatrix) have been studied by electron microscopy. Rods, twin cones, and single cones are present. In the light‐adapted state, the rods are very tall cells reaching almost to the base of the retinal epithelial cells. The outer segment is composed of membraneous discs of uniform diameter displaying a single incisure. The rod inner segment displays a distal small ellipsoid and an extremely thin myoid region. The nuclei of rods are electron‐dense, and the synaptic spherule displays two or three invaginated sites. The single cone is similar to the individual members of a twin cone and displays a tapering outer segment and accompanying accessory outer segment. The wider cone inner segment contains a large, centrally loated ellipsoid and a peripheral region rich in endoplasmic reticulum, polysomes, and microfilaments. Twin cones display subsurface cisternae along their entire contiguous surfaces. The cone nuclei are large and vesicular and located vitread to the external limiting membrane. The synaptic pedicle of cones is lager and moe electron‐lucent and contains more invaginated “ribbon” synaptic sites (ten to 12) than do rods. In addition, small “coated” invagination and larger synaptic vesicle‐filled processes are also seen within cone pedicles. In the light‐adapted state the cone photoreceptors are arranged in a repeating square mosaic pattern with one single cone surrounded by four twin cones.
Usage pattern of the complex masticatory muscles in the shingleback lizard,Trachydosaurus rugosus: A model for muscle placement
Authors: Gans Carl , Carrier David , De Vree Frits 
Published: February 2005

AbstractThis wide‐ranging, omnivorous lizard of Australia has a very complex adductor muscle mass, with fibers differing in length by a factor of three and in insertion angle by 90°. Stimulated muscles produce maximal moment with the mouth nearly fully open. The opening mechanism appears to involve only simple rotation and no translation of the mandible. EMGs indicate that the entire mass is activated equivalently in crushing and there are no temporal subdivisions, for instance, matching activity to angle of opening. During crushing of hard objects, the chin is brought into contact with the ground so that the subvertebral muscles may aid buccal closure. The lizards also activate the muscles in a pulsatile staircase effect leading to an unfused tetanus that generates forces several times the twitch level. Application in parallel of a maximum number of sarcomeres to the crushing bite appears to be the major design characteristic. Hence, this species offers an ideal case for analysis of the effects of different sarcomere placements on the simple movement generated. For the primary adductor muscles, the angles of fiber insertion relative to the lines connecting each insertion with the jaw joint are equivalent; this relation persists as the mouth opens. Also, fiber lenghts are proportional to the distance between jaw joint and site of insertion so that each sarcomere contributes equally to the movement generated. Complex tendons provide additional space for muscle placement. Some of these also extend beyond the bony attachment sites, producing tendinous “coronoid processes.” The fibers of laterally and ventrally placed muscles are short relative to the length of the entire muscle, insert at relatively short moment arms, and undergo short excursion during opening; however, there are many such fibers. Also, muscles with a low incident angle are crossed; they apparently protect the jaw joint from horizontal (disarticulating) forces.
Effects of short‐day photoperiods and of castration on the structural integrity of the ventral and dorsal prostates of the Syrian hamster (Mesocricetus auratus)
Authors: Buzzell Gerald R. , Toma Jean G. , O'Brien M. Gail , Haskins Julie 
Published: February 2005

AbstractShort‐day photoperiods and castration both cause reductions in the weights of male accessory sex glands. In the Syrian hamster, we have found that the ventral prostate loses less weight following these treatments than does the dorsal prostate. In this paper, we report on the effects of the pineal and of castration on the structural integrity of these glands, as assessed by stereological techniques. Short days result in little alteration to the ventral prostate or its acinar composition. The typical acinus is narrower following 10 weeks in short days. The ventral prostate also responds to castration with a narrower acinus, and, in addition, it shows a decrease in the epithelial volume fraction and increases in those of the lumen and muscular stroma. In neither case is there a change in the proportion of the gland consisting of acinar or interacinar components. Short‐day photoperiods and castration generally show similar effects in the dorsal prostate. In both cases, there are increases in the proportion of the gland made up of interacinar tissue. Within the acini, there are decreases in the volume fractions of lumen and large increases in those of lamina propria and muscular stroma. Following both treatments, typical acini are narrower and show reduction in the thickness of the epithelium and increases in the thickness of the lamina propria and muscular stroma.Thus, in the ventral prostate, both short days and castration lead to subtle changes which are different with each treatment and which differ from those that occur in the dorsal prostate. In the dorsal prostate, there are relative increases in the proportions of nonepithelial elements following both of these treatments. These results are discussed in relation to the mode of action of the pineal in causing accessory sex gland regression.
Anionic surface properties of aortic and mitral valve endothelium from New Zealand white rabbits
Authors: Sarphie T. G. 
Published: February 2005

AbstractThe luminal surfaces of the endothelium lining the two surfaces of the aortic arterial (AAR) and ventricular (AVT), and mitral ventricular (MVT) and atrial (MAT), valve cusps were studied with cationic ferritin (CF) and ferritin (Fer)‐conjugated lectins (WGA, RCA, SBA). The arterial (AAR) and ventricular (MVT) surfaces of the aortic and mitral cusps, which are exposed to more turbulent fluid mechanical forces and lower wall shear stresses, had the greatest density of CF labeling. The endothelia of the four surfaces displayed a gradient of decreasing density from the nuclear region to the periphery. Neuraminidase, chondroitinase ABC and AC, heparinase, heparitinase, hyaluronidase (testicular), and pronase E digestions suggested that a significant number of the anionic sites labeled by CF are associated with sialoglycoproteins and glycosaminoglycans such as chondroitin 4/6 sulfates, dermatan sulfates, and heparan sulfates. The localization of WGA receptors on the endothelium of AAR and MVT demonstrated a greater density of sialyl moieties than on the AVT and MAT. There was no binding of Fer‐RCA with specificity for D‐galactopyranosides or Fer‐SBA with affinity for N‐acetylglucosamine and D‐galactose to the endothelium unless it was first treated with neuraminidase. Hence, sialic acids are shown to be among the more superficial components of this glycocalyx and to be largely responsible for the greater densities over the endothelium of AAR and MVT.
Avian sebokeratocytes and marine mammal lipokeratinocytes: Structural, lipid biochemical, and functional considerations
Authors: Elias Peter M. , Menon Gopinathan K. , Grayson Stephen , Brown Barbara E. , Rehfeld S. Jerry 
Published: February 2005

AbstractIn terrestrial mammals, stratum corneum lipids derive from two sources: deposition of lamellar body lipids in stratum corneum interstices and excretion of sebaceous lipids onto the skin surface, resulting: in a two‐compartment (bricks and mortar) system of lipid‐depleted cells surrounded by lipid‐enriched intercellular spaces. In contrast, intracellular lipid droplets, normally not present in the epidermis of terrestrial mammals, are prominent in avian and marine mammal epidermis (cetaceans, manatees). We compared the transepidermal water loss, ultrastructure, and lipid biochemistry of the viable epidermis and tratum corneum of pigeon apterium, fledgling (featherless) zebra finches, painted storks, cetaceans, and manatees to those of humans and mice. Marine mammals possess an even more extensive lamellar‐body secretory system than do terrestrial mammals; and lamellar‐body contents, as in terrestrials, are secreted into the stratum corneum interstices. In cetaceans, however, glycolipicls, but not ceramides, persist into the stratum corneum; whereas in manatees, glycolipids are replaced by ceramides, as in terrestrial mammals. Acylglucosylceramides, thought to be critical for lamellarbody deposition and barrier function in terrestrial mammals, are present in manatees but virtually absent in cetaceans, a finding that indicates that they are not obligate constituents of lamellar‐body‐derived membrane structures. Moreover, cetaceans do not elaborate the very long‐chain, saturated N‐acyl fatty acids that abound in terrestrial mammalian acylglucosylceramides. Furthermore, cold‐water marine mammals generate large, intracellular neutral lipid droplets not found in terrestrial and warm‐water marine mammals; these lipid droplets persist into the stratum corneum, suggesting thermogenesis, flotation, and/or cryoprotectant functions. Avians generate distinctive multigranular bodies that may be secreted into the intercellular spaces under xerotic conditions, as in zebra fledglings; ordinarily, however, the internal lamellae and limiting membranes deteriorate, generating intracellular neutral lipid droplets. The sphingolipid composition of avian stratum corneum is intermediate between terrestrials and cetaceans (= 50% glycolipids), with triglycerides present in abundance. In the midstratum corneum of avians, neutral lipid droplets are released into the interstices, forming a large extracellular, lipid‐enriched compartment, surrounding wafer‐thin corneocytes, with a paucity of both iipid and keratin (“platesand‐platesand‐mortar” rather than the “bricks‐and‐mortar” of mammals). These studies demonstrate remarkable structural and biochemical heterogeneity of epidermal lipids in various homeotherms and provide new insights into the functions of specific lipid‐enriched organelles in these organisms.
Teratogenic antibody internalization by rat visceral yolk‐sac endoderm in vitro: An ultrastructural colloidal gold tracer study
Authors: Leung Christopher C. K. , Yan Cai‐Lou , Cheewatrakoolpong Boonlert 
Published: February 2005

AbstractPrevious work from our laboratory has demonstrated that specific rabbit immunoglobulins G (IgG) against a glycoprotein antigen of rat kidney proximal tubule or a cross‐reacting visceral yolk‐sac endodermal cell antigen will induce abnormal embryonic development when they are injected into pregnant rats during the period of organogenesis. It has been proposed that these antibodies may induce embryopathy by interfering with functions of the visceral yolksac placenta, an important organ providing nutrients to the embryo at this stage of development. In order to gain some insight into the underlying pathogenic mechanism(s) in which specific teratogenic IgG may interfere with visceral yolk‐sac functions, we examined the uptake of these teratogenic IgG by the visceral yolk‐sac endodermal cells at the electron microscopic level microscopic level.The results demonstrated that teratogenic rabbit IgG specifically localized on the fuzzy coat of the external apical cell membrane of the visceral yolk‐sac endoderm at the intermicrovillous region. Within 5 min, the IgG were rapidly internalized via coated pits and micropinocytic vesicles. Within 30 min, an increasing proportion of gold particles appeared within uncoated vesicles or vacuoles of various sizes; most of the gold particles were in close proximity to the inner membranous lining of the vesicles. Similar findings were observed after 1‐or 2‐hr incubation. After 24‐ to 48‐hr culture, however, the gold particles appeared to have dissociated from the inner surface of the vesicle membrane. For all the time points studied, gold particles were not observed in close association with the basal or lateral plasmalemma of the endodermal cells or in the connective tissue spaces and blood vessels of the visceral yolk‐sac placenta. We interpret the results as follows: (1) the teratogenic rabbit IgGs interacted with their antigen on the apical plasma membrane of the visceral yolk‐sac endodermal cells; (2) the teratogenic IgGs (coupled to their antigen) were internalized by endocytosis via coated pits; (3) the IgGs were later either hydralyzed or dissociated from their antigen in uncoated vesicles or vacuoles: and (4) there was little or no evidence to indicate that the IgGs were transported between or across the endodermal cells to reach the embryo.It is postulated that the responsible antigen may be receptor which plays an important role in transporting nutrient(s) to the embryo. Specific polyclonal teratogenic IgGs may either interfere with receptor‐ligand interaction or inhibit recycling of such a receptor, thereby causing abnormal embryonic development.
Normal stages of cardiac organogenesis in the mouse: II. Development of the internal relief of the heart
Authors: Vuillemin Mauricette , Pexieder Tomas 
Published: February 2005

AbstractNormal stages of intracardiac development of the mouse heart are illustrated by a collection and analysis of two complementary SEM views, the septal and parietal halves of the right ventricle and conotruncus. These views are particularly suitable for understanding the septation of the outflow tract of the heart. They represent references for the studies of the pathogenesis of conotruncal malformations. The analysis is based on 90 hearts between 11ed and 15ed at intervals of 8 hours with an additional stage at 16ed. They were prepared by perfusion fixation, microdissection, and critical point drying and were examined in SEM. The following main features of the intracardiac morphogenesis were observed: (1) the presence of two spirally positioned conotruncal ridges, their disto‐proximal fusion, and the formation of the semilunar valves at their distal part; (2) the trabecular transformation of the conotruncal wall; and (3) the presence of two different interventricular foramina (FIV II and FIV III), with the final closure of FIV III at 14edl6h‐15ed.As a result of these observations, our description of the outflow tract septation and its interpretation are different from other conceptions based on mechanisms such as bulbar shift, bulbar absorption, torsions, or transfer of the aorta into the left ventricle.
Lymphocyte subpopulations in high endothelial venules and lymphatic capillaries of bronchus‐associated lymphoid tissue (BALT) in the rat
Authors: Otsuki Yoshinori , Ito Yuko , Magari Sumiko 
Published: February 2005

AbstractThe subpopulations of lymphocytes and non‐lymphoid cells in high endothelial venules (HEV) and in lymphatic capillaries surrounding lymphoid follicles in bronchus‐associated lymphoid tissue (BALT) were examined by electron microscopy after preembedding the tissue and staining with an immunoperoxidase technique. The results were compared with those obtained in gut‐associated lymphoid tissue (GALT) reported previously. Monoclonal mouse‐anti‐rat T cell, IgG, IgM, IgA, and Ia antisera were used. Plasma cells that were reactive to anti‐IgG, anti‐IgM, and anti‐IgA were detected as cells in which the 3′, 3′ ‐diaminobenzidine tetrahydroxychloride reaction product was localized in rough endoplasmic reticulum and perinuclear spaces but not on plasma membranes. These plasma cells did not occur in either lymphatic capillaries or HEV in BALT as they did in GALT. Cells with surface Ig (sIg cells), T‐cell antigen (T cells), and Ia antigen (Ia cells) were present in BALT. T cells were located predominantly in the follicular area opposite the bronchial epithelium; IgM‐ and IgG‐reactive cells were found in the follicular area adjacent to the bronchial epithelium; and IgA‐positive cells were found in the lateral part of the area where the T cells were localized (T‐cell area). Ia cells were abundant throughout BALT and in moderate numbers in the epithelium. A striking observation was the presence of “nurse‐cell”‐like structures in the periphery of BALT. The percentages of T, sIgG, sIgM, and sIgA cells in the HEV were 54.7%, 2.4%, 28.9%, and 27.3%, respectively, and in the lymphatic capillaries, 41.2%, 3.8%, 38.2%, and 21.2%, respectively. Non‐lymphoid cells with Ia antigen, presumably interdigitating cells (IDC), were often seen in the two types of vessels. The percentage was 4. 3% in the HEV and 5.6% in the lymphatic capillaries. The results indicate that the largest common lymphocyte subpopulation in the two types of vessels surrounding follicles in BALT is T cells, followed by sIgM or sIgA cells as seen in GALT; IDC may be one of the main migrating cells within BALT.
Morphogenesis of endoplasmic reticulum in Xenopus oocytes after microinjection of rat liver smooth microsomes
Authors: Paiement Jacques , Dominguez J. M. , McLeese J. , Bernier J. , Roy L. , Bergeron M. 
Published: February 2005

AbstractWe have determined the kinetics of endoplasmic reticulum (ER) reconstitution following insertion of rat‐liver smooth microsomes (SM) into Xenopus oocyte cytoplasm using electron microscopy as well as cytochemistry and thick‐section 3‐dimensional reconstruction. Oocytes were fixed 0, 10, 20, 40, 80, and 120 min after microinjection with SM and processed for thin‐ and thick‐section electron microscopy. At 0 min postinjection, rat liver SM were observed as small vesicles and were loosely dispersed amongst oocyte organelles. At 10 min, tubules were discerned among many elongate vesicles; and these structures comprised large cytoplasmic regions delimited by mitochondria and yolk platelets. By 20 min, segregation of transplanted organelles yielded yolk‐platelet‐free regions composed of few vesicles but increasingly numerous, long and anastomosing tubules. By 40 min, a network with numerous tubular branches and fenestrations was observed among the few remaining vesicles. By 80 min, transformation of rat liver SM into a complex network of branching and anastomosing tubules was complete. Three‐dimensional reconstruction revealed the network to be composed of interconnecting elements consisting of anastomosing tubules. The reconstituted network of anastomosing tubules in Xenopus oocytes was compared to the network of anastomosing tubules in rat liver hepatocytes and was found to be essentially identical. Network formation occurred in oocytes pretreated with either vinblastine (40 μM) or nocodazole (0.166 μM), and network organization was maintained in oocytes treated with the same drugs after microinjection and reconstitution. We conclude that SM retain sufficient molecular information for rapid self‐assembly into structures resembling those in the cells from which they were derived. Both the assembly and maintenance of ER structure in oocyte cytoplasm are microtubule‐independent. The formation of such structures following microinjection of SM into living cells provides a unique assay for this type of membrane subfraction.