bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of temperature sensitive stages for sexual differentiation of the gonads in embryos of the turtle, Emys orbicularis
Authors: Pieau Claude , Dorizzi Mireille 
Published: February 2005

AbstractIn order to determine the temperature sensitive stages for sexual differentiation of the gonads in Emys orbicularis, eggs of this turtle were shifted at different stages of embryonic development from the male‐producing temperature of 25°C to the female‐producing temperature of 30°C and reciprocally. Based on the series of developmental stages described by Yntema (′68) for Chelydra serpentina, temperature begins to influence sexual differentiation of Emys orbicularis at stage 16, a stage in which the gonads are still histologically undifferentiated. Its action lasts over the first steps of histological differentiation of the gonads. The minimal exposure at 25°C required for male differentiation of all individuals extends from stage 16 to somewhat before stage 21. For 100% female differentiation, incubation at 30°C must be longer, from stage 16 to somewhat before stage 22. Shorter exposures at 25°C or 30°C during these periods result in different percentages of males, females, and intersexes. Our results show that there is a critical stage (stage 16) which is the same for both male and female differentiation of the gonads. The thermosensensitive periods are rather long, corresponding to 11–12 days at 25°C and 30°C.
An ultrastructural analysis of isolated basement membranes in the acellular renal cortex: A comparative study of human and laboratory animals
Authors: Carlson Edward C. , Kenney M. Cristina 
Published: February 2005

AbstractFreshly harvested kidneys from New Zealand white rabbits, Sprague‐Dawley white rats, rhesus monkeys, and transplant‐quality human kidneys were used in this study. Minced renal cortical tissue blocks (<2 mm3) were treated with 1 mM EDTA, 3% Triton X‐100, 0.025% DNAse, and 4% sodium deoxycholate in an effort to remove all cellular elements and leave the extracellular matrix (ECM) intact. These preparations showed remarkable structural preservation and all components of the ECM, including basement membranes (BMs), maintained their in vivo histoarchitectural relationships. By light microscopy, at least four major BM types were recognizable, including Bowman's capsular BM (BCBM), tubular BM (TBM), glomerular BM (GBM), and peritubular capillary BM (PTCBM). Scanning electron microscopy demonstrated that, despite the lack of supporting interstitium, GBMs in human, monkey, and rat (and rabbit to a lesser degree) exhibit intrinsic structural rigidity such that their convoluted spheroidal shapes are maintained following cell removal. Transmission electron microscopy showed that major BM types are morphologically heterogeneous and vary markedly within and between species. Randomized measurements showed that isolated BM thicknesses (lamina densa only) compared favorably with those reported in cellular preparations. Mean thicknesses of GBMs were within normal ranges in all species with or without power transformations to reduce right‐sided skew of distribution curves. In all species, thickness of BCBM > TBM > GGBM > PTCBM. The striking morphologic heterogeneity of major BM types demonstrated in the acellular renal cortex is not surprising in view of recent biochemical analyses that show that BMs derived from different sources are compositionally disparate. We conclude that BMs should be evaluated and characterized individually and that morphologic definition of isolated BMs is necessary prior to further analysis.
Active supercontraction in rolling‐up muscles of Glomeris marginata (myriapoda, diplopoda)
Authors: Carnevali Maria Daniela Candia , Valvassori Roberto 
Published: February 2005

AbstractThe lateroventral muscles of Glomeris marginata keep the animal rolled up and are able to develop and maintain great tension. Their fibers are not equipped with a particularly strong contractile apparatus but can super‐contract. The sarcomere shortens its resting length by up 60% and in a typical supercontraction the thick filaments pass through the Z‐line into adjacent sarcomeres. The Z‐line structure changes according to the contraction state: It passes from a homogeneous, dense zig‐zag line in decontracted fibers to a rarified, vaguely outlined Z‐band in supercontracted fibers, in which it is possible to see actin and myosin filaments. The Z‐line is thus involved in an active expanding process and is functionally very different from the fragmented and discontinuous Z‐line of “classical” supercontracting muscles. The different meaning of the two cases of supercontraction is discussed.
Cytodifferentiation in the accessory glands of Tenebrio molitor. X. Ultrastructure of the tubular gland in the male pupa
Authors: Happ George M. , Happ Christine M. 
Published: February 2005

AbstractThe tubular accessory gland consists of a simple secretory epithelium surrounded by a muscular coat. Over the pupal instar, the gland increases ten‐fold in volume and 15‐fold in length. Pupal development is divisible into a phase of mitosis and one of cell growth. During the mitotic phase, cytoplasmic membranes are sparse and nuclei move toward the luminal face of the epithelium to undergo division. In the cell growth phase, the cells become more columnar, a few stacks of rough endoplasmic reticulum are formed, and small dense secretory vesicles appear near the apical surface. The hormonal control of the developmental sequence is discussed.
The bursa cloacae (Fabricii) of struthioniforms in comparison with the bursa of other birds
Authors: Von Rautenfeld D. Berens , Budras K.‐D. 
Published: February 2005

AbstractThe late embryonic and postembryonic genesis of the bursa cloacae (Fabricii) of struthioniforms and other birds is described and discussed. The bursa of ostrich and emu is a wall organ of the caudal cloacal chamber. The bursa of rhea is, like the bursa of Gallus, a cranial appendix of the proctodeum. Lobuli bursales of struthioniforms are composed of a peripheral pars lymphoepithelialis (PLE) and a central pars lymphoreticularis (PLR). By contrast, lobuli bursales of Gallus are composed of a peripheral PLR and a central PLE. The fine structure of the bursa of struthioniforms is described. Other than in Gallus, the apical cell association of the PLE of struthioniforms shows secretory granules. This study thus far does not answer in detail the question of how the imprinting mechanism of the B‐lymphocytes operates. It is assumed that they are imprinted in the PLE. Postcapillary venules in the PLR are responsible for the transport of B‐lymphocytes. Hormonal bursectomies have been made to get information about the involution of the bursa of struthioniforms. In these species, involution means a gradual metaplasia while in Gallus it means a complete degeneration of the bursa.
Localization of 3H‐estradiol in the reproductive organs of male and female baboons
Authors: Weaker Frank J. , Sheridan Peter J. 
Published: February 2005

AbstractThe uptake and retention of radiolabeled estradiol by both the male and female reproductive organs were examined in the baboon. Two male and two female baboons were injected intracardially with 1 μg/kg body weight of 3H‐estradiol and two animals, one male and one female, were injected with both labeled and 100 μg/kg body weight of unlabeled estradiol. One and a half hours after the injections, the animals were sacrificed and the uterus, cervix, vagina, oviduct, seminal vesicles, and prostate gland were removed and processed for autoradiography. The stratified squamous epithelia of the cervix and vagina demonstrated a light uptake of the label in the germinative, but not in the superficial cell layers. The columnar cells lining the oviduct and uterine glands were labeled, whereas the luminal epithelium of the uterus and the glandular epithelia of the seminal vesicles and prostate gland did not sequester the tritiated steroid. The interstitial cells of all the organs studied demonstrated a moderate to heavy uptake of the radioactivity, whereas the smooth muscle cells were lightly labeled except in the vagina, in which these cells displayed a moderate number of silver grains.
The conjugation junction of Tetrahymena: Its structure and development
Authors: Wolfe Jason 
Published: February 2005

AbstractThe conjugation junction of Tetrahymena has been examined by thin sections, freeze fracture preparations, and by scanning electron microscopy. The junction is formed where the anterior tips of the pairing cells attach to one another. The structure is essentially a large disk composed of two face‐to‐face plasma membranes separated by a gap of extracellular space measuring about 50 nm. Rows of intramembrane particles are present at the boundary between the junction and ordinary cell cortex. These particles form a ring around the junction. Subjacent to each membrane is a thick mottled layer of material. Pores form in the junction at sites of membrane fusion. Though wider than long, these structures are actually bridges of cytoplasm that connect the conjugating cells. Pores fall into certain size and shape classes, indicating that membrane fusion is highly controlled in this system. At the level of the cytoplasmic bridge the submembrane material is compact and electron‐dense. Changes in the structure of the epiplasmic layer have been monitored as the normal cortex is modified during tip transformation and through formation of the mature conjugation junction. Evidence is provided that the submembrane layer plays a significant role in the regulation of pore formation. This cytoskeletal structure may also limit the extent of membrane fusion, thus controlling the size of the cytoplasmic channels.
A structural analysis of the freshly extruded spermatophore from the lobster, Homarus americanus
Authors: Kooda‐Cisco Marcia J. , Talbot Prudence 
Published: February 2005

AbstractFreshly extruded spermatophores from the lobster, Homarus americanus, were examined using light microscopy and scanning and transmission electron microscopy. The tubular spermatophore is trifoil in shape with two lobes tapered laterally from a third lobe situated ventrally. It is comprised of sperm surrounded by three acellular investments: (1) a primary spermatophore layer, (2) an intermediate layer, and (3) an outer bounding layer. The sperm are packed into a continuous tube contained largely within the ventral lobe and are embedded in a matrix of moderate electron density. The primary spermatophore layer is uniformly thick around the sperm mass and contains at its peripheral margins both ring structures and crystals in an amorphous matrix. The intermediate layer is thicker dorsally than ventrally. Dense granules dominate the ventral half of the intermediate layer while inclusions populate the dorsal half; both react positively to the periodic acid‐Schiff (PAS) technique. The innermost portion of the outer bounding layer is composed of parallel fibrils; a flocculent material is present peripherally. This flocculent substance is presumed to impart stickiness to freshly extruded spermatophores. These observations provide a basis for the future understanding of the mechanisms involved in long‐term storage of sperm in spermatophores.
Ultrastructural study of midgut embryonic cytodifferentiation in the phasmid Clitumnus extradentatus Br.
Authors: Kadiri Zineb , Louvet Jean‐Pierre 
Published: February 2005

AbstractThe embryonic cytodifferentiation of Clitumnus midgut occurs very late when compared to that of other tissues in the embryo. It proceeds from hemolymph towards the yolk, first at the level of the muscular–connective tissue sheath, by the appearance of myofilaments in external–then internal–muscle fibers. In the gut epithelium, cytodifferentiation begins with the appearance of infoldings of the basal membranes of the cells. Then, microvilli and continuous junctions form at the apices of the cells. Microvilli appear in crypts, which seem to represent localized dilatations of intercellular spaces. At the level of these crypts, continuous junctions are formed somewhat later than are microvilli. This midgut differentiation coincides with deposition of the third embryonic (first larval) cuticle, and with a high titer of ecdysteroids.
Mechanisms of rapid morphogenetic movements in the metamorphosis of the bryozoan Bugula neritina (cheilostomata, cellularioidea). I. Attachment to the substratum
Authors: Reed Christopher G. , Woollacott Robert M. 
Published: February 2005

AbstractThe larval morphology, settlement behavior, and the rapid morphogenetic movements that occur during the first 60 sec of metamorphosis of the cellularioid cheilostome bryozoan Bugula neritina have been examined and analyzed by light and electron microscopy. The larva attaches to the substratum at the onset of metamorphosis by the eversion of the internal sac. At the same time, the coronal cilia reverse their direction of beat, spreading an adhesive secreted by the neck region of the everting sac over the metamorphosing larva. During attachment, the larva goes through several configurations that coincide with the sequential contraction and relaxation of certain larval muscles. Histological and ultrastructural evidence indicates that the neck and wall regions of the internal sac are everted by the contraction of the muscles in the equatorial plane of the larva at the same time that the roof region in pulled toward the larval equator by the contraction of the axial muscles. The subsequent relaxation of the axial muscles allows the roof region to be everted by the antagonistic force generated by the sustained contraction of the equatorial musculature. After the roof region attaches to the substratum, the apical disc is temporarily retracted by a second contraction of the axial muscles. The apical disc subsequently reextends as the axial muscles relax just before coronal involution. A comparison of the ontogenetic sequence of rapid morphogenetic movements in the metamorphoses of cheilostome and ctenostome bryozoans indicates that cellularioid cheilostomes have undergone peramorphosis in the aspect of development.
An ultrastructural study of the development of the dermal iridophores and structural pigmentation in Poecilia reticulata (peters)
Authors: Gundersen R. E. , Rivera E. R. 
Published: February 2005

AbstractThree general stages of iridophore development were found in Poecilia reticulata that correspond to the development of structural pigmentation. The first stage was prevalent in fish embryos about to hatch to young fish 4 months old. Dermal cells containing elements of endoplasmic reticulum and a Golgi apparatus developed into iridophores. The endoplasmic reticulum early in iridophore development became a few sparse cisternae, and the Golgi apparatus elaborated long rectangular vacuoles with two membranes. From 5 to 15 vacuoles were arranged in parallel stacks in each developing iridophore. Crystals of guanine were deposited within the inner compartment of each vacuole. At this stage of development, the young fish had only a few dermal iridophores next to the lateral muscle. Fish 4 to 6 months old had a more advanced type of iridophore development including several layers of iridophore cells in the dermis. The innermost iridophores near the muscle had many mature crystal‐containing vacuoles (iridosomes). Each cell had upt to three stacks of 10–20 iridosomes with their long axis oriented at a slight oblique angle to the surface of the fish. The outer layers of iridophores resembled the immature developing cells found in very young fish. The third developmental stage was found in sexually functional adults. All dermal iridophores contained 2–3 groups of 10–20 mature iridosomes. In mature iridophores, the Golgi apparatus was not found in the cytoplasm. The thickness of the guanine crystals (70 nm) and cytoplasmic intervals (90 nm) results in a constructive interference reflection of 496 nm (blue‐green). This iridescence increased concomitantly with the increase in iridophore cells in the dermis and the maturation of their iridosomes.
Ultrastructure of the pineal gland of the eastern chipmunk (Tamias striatus)
Authors: Karasek Michal , King Thomas S. , Hansen John T. , Reiter Russel J. 
Published: February 2005

AbstractThe ultrastructure of the pineal gland of the wild‐captured eastern chipmunk (Tamias striatus) was examined. A homogenous population of pinealocytes was the characteristic cellular element of the chipmunk pineal gland. Often, pinealocytes showed a folliclelike arrangement. Mitochondria, Golgi apparatus, granular endoplasmic reticulum, lysosomes, centrioles, dense‐core vesicles, clear vesicles, glycogen particles, and microtubules were consistent components of the pinealocyte cytoplasm. The extraordinary ultrastructural feature of the chipmunk pinealocyte was the presence of extremely large numbers of “synaptic” ribbons. The number of “synaptic” ribbons in this species exceeded by a factor of five to 30 times that found in any species previously reported. In addition to pinealocytes, the pineal parenchyma contained glial cells (oligodendrocytes and fibrous astrocytes). Capillaries of the pineal gland of the chipmunk consisted of a fenestrated endothelium. Adrenergic nerve terminals were relatively sparse.
The photoreceptors of the west indian manatee
Authors: Cohen Joel L. , Tucker Gail S. , Odell Daniel K. 
Published: February 2005

AbstractUsing light and electron microscopy we found that the manatee retina has both rodlike and conelike photoreceptors in accord with its diurnal behavior pattern. Outer segment disks in both cell types appear to be enclosed along most of their length within the plasma membrane. The synaptic terminals are simple, with small, superficial postsynaptic contacts. The cones have long inner segments, short, conical outer segments and terminals with numerous synaptic ribbons and deeply embedded postsynaptic elements. There are two cone subclasses that may subserve color vision. Morphometry shows that there are more ganglion cells of small size ventrally, and that the thickness of the nerve fiber layer there is reduced, suggesting the presence of a specialized visual area in the retina. However, there were no pronounced differences in cone cell density in any of the regions examined.
Development of the musculus levator externus IV and the musculus obliquus posterior in Haplochromis elegans trewavas, 1933 (teleostei:Cichlidae): A discussion on the shift hypothesis
Authors: Aerts Peter 
Published: February 2005

AbstractAn ontogenetic study of several postembryonic stages of Haplochromis elegans shows that the muscle referred to as “musculus levator externus IV” by previous authors in the adult stage of cichlid fishes is a compound muscle composed of the M. levator externus IV and the central portion of the M. obliquus posterior. Thus the supposed shift of the insertion area of the fourth external levator muscle from the fourth epibranchial to the fifth ceratobranchial, as deduced from adult morphology only, did not occur. Although this ontogenetic discovery does not change the functional specializations ascribed to the muscle by previous authors, it could have very important implications for the phylogenetic placement of the Cichlidae relative to such major taxa as Labroidei and Embiotocidae.
The cellular basis of the aggressive acrorhagial response of sea anemones
Authors: Bigger Charles H. 
Published: February 2005

AbstractSome sea anemones possess structures called acrorhagi at the base of the tentacles. The acrorhagi are utilized solely for aggression. Acrorhagial aggression involves very exquisite intra‐ and interspecific recognition. This study examined acrorhagi and putative acrorhagial analogues or homologues in four species of sea anemone. The morphology and ultrastructure of tentacles, pseudoacrorhagi, column vesicles, and verrucae (adhesive column vesicles) differed from that of acrorhagi. Coral capitate tentacles and acrorhagi have different surface morphology, nematocysts, and functions. Besed on morphology, acrorhagi seem more likely to be homologous to tentacles than to verrucae.Acrorhagial nematocyst discharge and ectodermal peeling, the culmination of the response, were shown to require prior acrorhagial expansion in Anthopleura krebsi and Bunodosoma cavernata. A mechanical mechanism is suggested where‐ by distention of the acrorhagus opens a ciliary pit on the nematocyte surface and exposes the pit wall and microvilli, which may contain the chemoreceptors for the peeling process, including nematocyst discharge. A similar system may also be responsible for changing the threshold of nematocyst discharge in sea anemone tentacles. A case of possible neurosecretion in an anthozoan was also shown in this study.
The architecture of the spleen of the red‐eared slider, Chrysemys scripta elegans (reptilia, testudines)
Authors: Kroese F. G. M. , Van Rooijen N. 
Published: February 2005

AbstractThe morphology of the spleen of the Red‐eared Slider, Chrysemys scripta elegans, has been described. The outer surface of the spleen is covered by a thin fibromuscular capsule, from which a number of trabeculae extend into the parenchyma. The parenchyma of the spleen shows a definite demarcation into a red and white pulp. The white pulp is composed of two lymphoid compartments: lymphoid tissue surrounds both central arterioles and ellipsoids, forming the periarteriolar and periellipsoidal lymphocyte sheath (PALS and PELS, respectively). The ellipsoids consist of a thick layer of reticular tissue, enclosing a capillary with cuboidal endothelium. In contrast with the PALS, reticular fibers are rarely found in the PELS. Even after severe stimulation with paratyphoid vaccine, germinal centers are not found in the spleen of C.s. elegans. The red pulp of the spleen is composed of a system of venous sinuses and cords.