bluuebunny/crossref_metadata_2025_split huggingface dataset:
Follicular placenta and embryonic growth of the viviparous four‐eyed fish (Anableps)
Authors: Knight Frank M. , Lombardi Julian , Wourms John P. , Burns John R. 
Published: February 2005

AbstractIn the four‐eyed fish, Anableps (Atheriniformes, Anablepidae), eggs are fertilized and embryos develop to term within the ovarian follicles. Development is highly matrotrophic. During gestation, the largest term embryo of A. anableps examined had grown to a total length of 51 mm and attained a dry weight of 149 mg. The postfertilization weight increase is 298,000%. The largest term embryo of A. dowi examined had grown to a total length of 77 mm and attained a dry weight of 910 mg. The postfertilization weight increase is 843,000%. Embryonic weight increases result from nutrient transfer across the follicular placenta. This structure is formed by apposition of the maternal follicular epithelium to absorptive surface cells of the embryo's pericardial trophoderm. The latter, a ventral ramification of the pericardial somatopleure, replaces the yolk sac during early gestation. The external surface of the pericardial trophoderm develops hemispherical projections, termed vascular bulbs. Within each bulb, the vascular plexus of the trophoderm expands to form a blood sinus. Cells of the external surface of the bulbs possess microplicae. Microvilli are absent. During middle to late gestation, the juxtaembryonic follicular epithelium differentiates into two regions. One region consists of shallow, pitlike depressions within which vascular bulbs interdigitate in a “ball and socket” arrangement. Follicular pits are formed by the curvilinear distortion of the apical surfaces of follicle cells. The second region in contact with the dorsal and lateral surfaces of the embryo, is comprised of villous extensions of the hypertrophied follicular epithelium. In both regions, follicle cells appear to constitute a transporting rather than a secretory epithlium. In terms of percentage of weight increase, the follicular placenta of Anableps appears to be the most efficient adaptation for maternal‐embryonic nutrient transfer in teleost fishes and closely approaches the efficiency (1.2 × 106%) of oophagy and embryonic cannibalism in lamnoid sharks.
A cineradiographic and electromyographic study of mastication in Tenrec ecaudatus
Authors: Oron Uri , Crompton A. W. 
Published: February 2005

AbstractRegular chewing was studied in the specialized Malagasy insectivore Tenrec ecaudatus with the aid of precisely correlated electromyography of the main adductors, digastrics, and two hyoid muscles and cineradiography for which metallic markers were placed in the mandibles, tongue, and hyoid bone. During the power stroke the body of the mandible moves dorsally and medially. The medially directed component of movement at this time is greatly increased by simultaneous rotation of the mandible about its longitudinal axis. The highly mobile symphysis, spherical dentary condyle, loss of superficial masseter muscle and zygoma, and the simplified zalamnodont molars all appear to be related to the large amount of mandibular rotation that occurs during occlusion. The balancing side lateral pterygoid muscle (inferior head) apparently shifts the working side mandible laterally during the last part of opening and the first part of closing. The working side temporalis and the superficial masseter muscle are both responsible for the shift back to the midline. The temporalis is usually active to the same extent on the working and balancing sides during the power stroke. The level of activity (amplitude) of the temporalis and duration of the power stroke increase with harder foods. Whenever soft foods are chewed, the superficial masseter is only active on the working side; whenever foods of increasing hardness are chewed, its level of activity on the balancing side increases to approach that of the working side. Mandibular rotation is greatly reduced when hard foods are chewed.
Body mass and natural diet as determinants of the number and volume of adipocytes in eutherian mammals
Authors: Pond Caroline M. , Mattacks Christine A. 
Published: February 2005

AbstractTotal dissection of a randomly collected sample of 202 adult and subadult eutherian mammals, combined with site‐specific adipocyte volume determination, shows that the number of adipocytes in the body is proportional to (Body Mass)0.74 for predominantly carnivorous species and to (Body Mass)0.78 for mainly herbivorous, nonruminant mammals. Adipocyte expansion or shrinkage, not proliferation or depletion of adipocyte number, is the principal mechanism of adipose tissue enlargement and reduction. Therefore, the adipocytes of large mammals are larger than those of smaller specimens of similar dietary habits and fatness. We suggest that the presence of more numerous, smaller adipocytes in smaller mammals is related to their higher mass‐specific metabolic rate. The adipose tissue of mammals with a predominantly carnivorous diet contains 4.6 times as many adipocytes as that of herbivorous nonruminants of similar body mass; but nonruminant herbivores are not necessarily fatter because the adipocytes of carnivorous mammals are proportionately smaller than those of nonruminant herbivores. We suggest that a carbohydrate‐based energy metabolism is associated with fewer, relatively larger adipocytes and that when lipids and proteins form the major dietary energy source, adipose tissue consists of a greater number of smaller adipocytes.
Ultrastructure of the spermatozoon and spermiogenesis in the interstitial annelid Potamodrilus fluviatilis
Authors: Bunke Dieter 
Published: February 2005

AbstractThe ultrastructure of spermatozoa and its genesis (spermiogenesis) have been investigated in the interstitial annelid Potamodrilus fluviatilis. The mature spermatozoa are threadlike cells which are bent at the base of the flagellum, giving the cell a hairpinlike appearance. The acrosome consists of an unusual, long, flasklike vesicle with a granum in its basal part. The cylindrical nuclear region is characterized by a monolayer of vesicles enwrapping the posterior half of the nucleus. This region is endowed with a number of altered rodlike mitochondria. No middlepiece is present. The basal body of the flagellum is obliquely arranged with respect to the long axis, giving rise to a curved flagellum, which, along most of its length, exhibits a thick layer of vacuolized cytoplasm around the axoneme. During spermiogenesis, which occurs in the body fluid, spermatids develop at the surface of syncytial masses which have been formed during meiotic divisions. The acrosome protrudes in the distal part of the cell, while the basal body of the flagellum is shifted toward the proximal region, which connects the cell with the cytophore. These are unusual features in annelid spermiogenesis. As indicated in Discussion, the phylogenetic implications of these findings include the assumption that Potamodrilus is not related to any oligochaete or even any other clitellate group or species and, hence, has to be excluded from these taxa.
The musculature of squid arms and tentacles: Ultrastructural evidence for functional differences
Authors: Kier William M. 
Published: February 2005

AbstractThe transverse muscle mass of the arm and the transverse and circular muscle masses of the tentacle of squid (Loligo pealei and Illex illecebrosus) were examined by transmission electron microscopy. Previous work had indicated that although similar in gross arrangement, the transverse muscle mass of the tentacle creates rapid elongation during prey capture while the transverse muscle mass of the arm is involved in creating bending movements. The difference in function between the transverse muscle masses of the arms and tentacles is reflected in differences in ultrastructure. The transverse muscle mass of the arm is made up of regular, obliquely striated muscle fibers 1–6 μm in diameter. The transverse and associated circular muscle masses of the tentacle are made up of cross‐striated muscle fibers 1–3 μm in diameter. The cross‐striated muscle fibers have A bands approximately 0.5 μm (I. illecebrosus) and 0.9 μm (L. pealei) in length and a resting sarcomere length of 0.9 μm (I. illecebrosus) and 1.6 μm (L. pealei), suggesting a relatively high shortening speed for this muscle type. The cross‐striated cells are not divided up into myofibrils, and the sarcoplasmic reticulum is located beneath the sarcolemma. Vernier displacements of the sarcomeres were observed. The myofilaments of the obliquely striated muscle fibers of the arm surround a central core containing mitochondria and the cell nucleus. The sarcoplasmic reticulum of the obliquely striated cells is located beneath the sarcolemma, in the plane of the Z elements, and surrounding the mitochondrial core.
Gross and fine structure of the antennal circulatory organ in cockroaches (Blattodea, Insecta)
Authors: Pass Günther 
Published: February 2005

AbstractThe antennal circulatory organ ofPeriplaneta americanaandBlaberus craniiferwas investigated by light and electron microscopy. This organ consists of two pulsatile ampullae located near the antennal base which are interconnected by a large transverse muscle and associated blood vessels which run into the antennae. Diastole is caused simultaneously in both ampullae by the transverse muscle. Systole is produced passively by the elasticity of the wall of the ampullae and minute accessory tendons. Both elastic structures contain fine unbanded extracellular filaments.The antennal vessels possess two distinct regions: a proximal convoluted region lying within the hemocoel of the head and a narrower distal region running through the antenna and opening near the antennal apex. The length of the proximal portion increases markedly during ontogeny in correlation with the growing antenna. Its wall consists of a high‐prismatic epithelium ensheathed by a thick layer of collagen fibrils. The structure of the wall cells is comparable to that found in some salt transporting epithelia: it shows a polar organization with basal infoldings, a large number of mitochondria, and typical arrangement of the junctions or mitochondrial‐scalariform junctional complexes. The possible physiological function of this epithelium in ionic or osmoregulation of the hemolymph entering the antenna is discussed. The wall of the distal vessel region consists of a flat single‐layered epithelium and seems to be specialized only for delivery of hemolymph to antennae. The structure and function of the antennal heart in cockroaches is compared to that found in other insects.
Autolysis and heterolysis of the epidermal cells in anuran tadpole tail regression
Authors: Kinoshita Tsutomu , Sasaki Fumie , Watanabe Kyozo 
Published: February 2005

AbstractAutolysis and heterolysis of the degenerating epidermis of the tail fin of Rana japonica tadpoles during spontaneous metamorphosis were observed by transmission and scanning electron microscopy. In the early climactic stages of metamorphosis (st. 19–20), the outermost epidermal cells developed vacuoles that were acid phosphatase positive and showed apparent breakdown of the cell membrane. The cells shrunk, perhaps due to the rupture of the cell membrane, and sloughed off without typical cornification. As tail resorption proceeded, autolysis of the epidermal cells spread towards the inner layers, in which some epidermal cells lost desmosomal junctions. They also displayed atrophic figures with condensed cytoplasm, breakdown of the cell membrane, and pycnotic nuclei. Lymphocytes, neutrophils and macrophages were already present in the basal layers of the premetamorphic epidermis (st. 10). Based on ultrastructural observation, blood cells could be distinguished from autolysing epidermal cells. Only a few blood cells were found in the early climactic stages of metamorphosis (st. 19–20), but the number of the blood cells, especially macrophages, greatly increased during the final stages of metamorphosis (st. 23–24). During the final stages, many macrophages were observed to phagocytose the autolysing epidermal cells by projecting slender pseudopodia into the inner epidermis. Macrophages also were observed to pass through the degraded basal lamella. These results suggest that not only autophagy but also heterophagy of the epidermal cells by the macrophages is a major process in the regression of the tail fin epidermis.
Salivary gland ultrastructure of the unfed adult and feeding female ofHaemaphysalis (Rhipistoma) leachi(Ixodoidea: Ixodidae)
Authors: El Shoura Samir M. 
Published: February 2005

AbstractThe paired salivary glands of unfed adultHaemaphysalis (Rhipistoma) leachicontain one type of agranular and three types of granular alveoli connected to a salivary duct system. Type I agranular alveoli consist of one large, central cell surrounded by peripheral cells with numerous basal membrane infoldings indicative of epithelia involved in fluid transport. Glycogen particles, lipid‐like droplets, and the parallel pattern of infolded membranes disappeared from the peripheral cells during feeding. Types II, III, and IV granular alveoli contain some agranular interstitial epithelial cells, cap cells, and fundus cells, but are predominantly composed of structurally different granular cell types a, b, c, d, e, and f. Agranular cells develop during the early stages of feeding. Granular a, c, e, and f cells release their granules directly after attachment to the host and possibly are involved in cement secretion required for firm attachment to it. The b cell granules are replaced by b1filamentous granules during feeding. Golgi bodies and rough endoplasmic reticulum (RER) participate in the formation of most types of granules. The d cells contain lamella‐like structures and condensing vacuoles, probably responsible for lysosome formation. The main salivary duct and all types of alveoli are innervated by neurosecretory axons.
Ultrastructure of salivary glands ofOrnithodoros (Ornithodoros) moubata(Ixodoidea: Argasidae)
Authors: El Shoura Samir M. 
Published: February 2005

AbstractThe paired salivary glands of unfed adultOrnithodoros (Ornithodoros) moubataare composed of type I (agranular) and type II (granular) alveoli. Type I alveoli consis of one large central cell surrounded by peripheral cells having the morphology of fluid‐transporting epithelia. Type II alveoli contain granular and agranular cells; the former are comprised of morphologically distinct types of cells (a, b, and c) containing granules of different structures and chemical composition with respect to polysaccharide and protein. The agranular cells are the interstitial and cap cells. Golgi bodies and rough endoplasmic reticulum (RER) are found in all granular cells and apparently are involved in granule formation. No appreciable structural changes were observed in type I alveoli during or after feeding. Type c cell granules are released before granules from types a and b cells and may contain anticoagulant substances that promote the blood flow of the host during the tick feeding. Although the cap cells are not structurally affected by feeding, interstitial cells are developed into transporting epithelia.
Developmental events of the pectoral muscle in rainbow trout larvae (Salmo gairdneri)
Authors: Henderson Vernon 
Published: February 2005

AbstractSkeletal muscles of developing pectoral fins in rainbow trout larvae (Salmo gairdneri) were analyzed by electron microscopy. Large, branched mitochondria were dominant structures in developing myotubes. Mitochondria were associated with the tubular system (T and SR). New mitochondria arose from old ones when the latter extruded whorls of paired membranes surrounding a nonmembranous core. The core was comprised in part of a dense material, presumably, DNA. The developing muscles were characterized by two sets of caveolae which provided the major contributions to the tubular system. Large caveolae gave rise to elements traditionally designated as SR tubules but which later lost their exterior connections. Small caveolae gave rise to small diameter tubules that appear to be analogous to T tubules, which maintained connections with the exterior. Both tubular elements abutted mitochondria. The two elements ran parallel to each other and intersected with each other to form junctions. Each set of elements possessed intratubular junctions.
Architecture of a lamellicorn flagellum (Phyllopertha horticola, scarabaeidae, coleoptera, insecta)
Authors: Ågren Lennart 
Published: February 2005

AbstractThe distal three of the seven flagellar segments of the scarabaeid beetle Phyllopertha horticola are lamelliform, gathered into a club, and possess five sensillar fields that are packed with sensilla placodea. The most proximal surface of the club bears only hair‐shaped sensilla. On the inner four sensillar fields a narrow central elongated zone houses pit organs and cavities with sunken sensilla placodea and other sensilla. The most distal, fifth sensillar field is smooth. The sensilla placodea seem to be of several types. The only distinct difference between the sexes is the shorter and more rounded lamellae of the female. The total count of sensilla placodea in males outnumbers that of the females by about 60%.
The fine structure of the spermatozoa of Siphonaria algesirae (Gastropoda, Pulmonata)
Authors: Azevedo Carlos , Corral Laura 
Published: February 2005

AbstractThe sperm of Siphonaria algesirae (Gastropoda, Pulmonata), a species with internal fertilization, was studied by light and electron microscopy. The spermatozoon is a very long, uniflagellate cell composed of a conical head with an apical acrosome, a midpiece with a helically coiled external sheath containing a complex mitochondrial derivative with a wavelength of ∼ 5.5 μm, and an endpiece. There are no axonemal microtubules. Instead, nine homogeneous coarse fibers with transverse striations in the apical zone project toward the anterior section of the midpiece. In the posterior zone of the midpiece the coarse fibers are differentiated in a common microtubular axoneme. The complex mitochondrial derivative of the midpiece shows an organized group of 100 Å diameter spherical particles. Externally the midpiece is surrounded along its length by a cylinder formed by two membranes. A complex structure separates the transitional zone between the midpiece and the endpiece.
Ovarian cycle in the frog Rana cyanophlyctis: A quantitative study of follicular kinetics in relation to body mass, oviduct, and fat body cycles
Authors: Pancharatna M. , Saidapur S. K. 
Published: February 2005

AbstractIn Rana cyanophlyctis, all stages of oocyte development are present throughout the year owing to continuous and asynchronous gametogenetic activity, but quantitative differences occur in the frequency distribution of the first growth phase (FGP) and second growth phase (SGP) oocytes. The number of SGP oocytes influences ovarian weight; therefore, seasonal changes in the number of SGP oocytes and ovarian mass are correlated. Mean ovarian weight and gonadosomatic index follow comparable changes during the annual cycle. The body mass of the frog undergoes only minor seasonal variations. Also, the body mass does not influence the number of oocytes in the frog.Small FGP oocytes always formed the dominant type in the ovary. Only 20–0% of FGP oocytes were recruited to SGP stage during the prebreeding months (March–April). The breeding season extends over 2– months (July–September) and an adult R. cyanophlyctis spawns 3,000–,500 eggs of 1,300–1,350 μm diameter in size. The breeding is not followed by any resting period, and therefore oogonial proliferation and recruitment of FGP oocytes start soon after the breeding months (October‐December). Atretic oocytes are present in all months but their number is greatest during prebreeding and breeding months. The frequency distribution of oocytes in the right and the left ovaries is identical. The oviducts undergo seasonal changes that are correlated with ovarian weight, whereas the fat body cycle is inversely related to ovarian weight.
Fine structure of the statocyst sensilla of the mysid shrimp Neomysis integer (Leach, 1814) (Crustacea, Mysidacea)
Authors: Espeel Marc 
Published: February 2005

AbstractThe fine structure of the statocyst sensilla of Neomysis integer was investigated. The statocyst contains about 35 sensilla, which are composed of two bipolar sensory cells, nine enveloping cells, and a seta.The sensory cells consist of an axon, a perikaryon, and a dendrite. The dendrite contains a proximal segment with a ciliary rootlet and at least one basal body, and a distal segment with a ciliary axoneme (9 × 2 + 0) at its base. The distal segment extends along the peripheral wall of the seta and is in close contact with the wall of the hair shaft.The enveloping cells surround the proximal and distal segments of the dendrite. The innermost enveloping cell contains a scolopale rod. It surrounds the receptor lymph cavity and secretes flocculent material into this cavity. From the tip of the cell a dendritic sheath, which encloses the distal segment of the dendrite, emerges. A peculiar feature of the second enveloping cell is the presence of a scolopale‐like rod, which is more slender and less pronounced than in the first enveloping cell.The seta consists of three parts: a socket, a tubular midpart, and a gutter‐like apical part, the tip of which penetrates into the statolith. The seta shows over its full length a bilaterally symmetrical axis that is coplanar with the plane in which the seta is bent toward the statolith.The structure of the seta and the position of the distal segments provide morphological evidence for directional sensitivity of the sensilla and for the magnitude of shear on the setal wall being an adequate stimulus.
The role of a sertoli cell actin‐myosin system in sperm bundle formation in the ratfish, Hydrolagus colliei (Chondrichthyes, Holocephali)
Authors: Stanley Hugh P. , Lambert Charles C. 
Published: February 2005

AbstractSertoli cells in the ratfish entirely surround a clone of spermatids to form a spermatocyst. As spermiogenesis proceeds within the cyst cavity, the acrosome areas become apposed to the Sertoli cell plasma membrane lining the spermatocyst. The spermatids elongate and are gathered into an increasingly compact bundle oriented with acrosomal tips directed toward the Sertoli cell base. As all acrosome areas move closer together, Sertoli cell microfilaments oriented parallel to the long spermatid axis appear and increase in concentration. Actin and myosin were demonstrated in the microfilament area with fluorescent antibodies and NBD‐Phallacidin. Simultaneously, endocytosis of Sertoli cell membrane between spermatid attachment sites removes the intervening membrane and allows the latter sites to approach each other. Sertoli cell endocytosis is spatially and temporally related to a unique projection at the basal rim of each acrosome. During midspermiogenesis, structured intercellular material appears between the Sertoli cell and the acrosomal region of each spermatid. Its periodicity is closely related to periodic arrangement of Sertoli cell actin and material within the spermatids. These attachment sites move together upon endocytosis, gathering a clone of spermatids into a closely packed bundle.