bluuebunny/crossref_metadata_2025 huggingface dataset:
Somatic tissue–male germ cell barrier in three hermaphrodite invertebrates: Dugesia biblica (Platyhelminthes), Placobdella costata (Annelida), and Levantina hierosolyma (Mollusca)
Authors: O'Donovan P. , Abraham M.
Published: February 2005

The gonads from three hermaphrodite species of different invertebrate phyla were studied at the ultastructure level. In the flatworm Dugesia biblica, male germ cells in different stages of development lay in the lumen of testicular follicles surrounded by overlapping parietal cells. The intercellular space formed by cytoplasmic extensions running parallel to the testis wall is occluded by septate junctions and by an electron‐dense material. In the leech Placobdella costata, the testis is lined by a unicellular layer of parietal cells surrounded by densely packed connective tissue fibers. No specialized occluding junctions were found between the parietal cells; however, plasmalemma thickenings and electron‐dense material in the intercellular space near to the testis lumen were observed. In the lumen, germ cells develop connected to cytoplasmic masses, the cytophore. In the land snail Levantina hierosolyma, male and female germ cells are found together in the same acini; each acinus is surrounded by a thick basement membrane. At the periphery of the acinus is the ovarian layer; centrally to it is the testicular layer. Intercalated between them is a double cellular layer of follicular cells and of Sertoli cells. The inter‐Sertoli space is characterized by elaborate septate junctions. In the three species studied male germ cells develop within the lumina of compartments isolated from the somatic tissue. This separation is brought about by specialized septate junctions, and/or by electron‐dense material between the cells that form the testis walls, and also by densely packed connective tissue fibers. Our observations strengthen the view that a male germ cell‐somatic tissue barrier as described in the literature of the testes of vertebrates and of invertebrates from various phyla is of general occurrence in the animal kingdom.
Submandibular duct salivary bladder of the rat
Authors: Mercurio Anthony R. , Mitchell Ormond G.
Published: February 2005

This investigation is a light and electron microscopic description of the submandibular duct salivary bladder of the rat, a dilation of the distal end of the main excretory duct. The wall of the bladder consists of (1) a mucosa with pseudostratified epithelium, (2) a submucosal layer of connective tissue, and (3) an underlying layer of striated muscle. The pseudostratified columnar epithelium lining the bladder is composed of three cell types: (1) light cells, (2) dark cells, and (3) basal cells. The lamina propria contains bundles of collagen, attenuated fibrocytes, capillaries with fenestrated endothelia, and nerve fibers which enter the epithelial layer. The capillaries of the submucosa are not fenestrated. The morphology of the wall of this structure provides evidence that the primary fluid of the submandibular gland is modified in the bladder by transepithelial fluid and ion transport.
Evocation of venation pattern in the wing of a moth, Manduca sexta
Authors: Nardi James B. , Norby Shong Wan
Published: February 2005

The insect wing is formed from an epithelial sheet that folds during development to establish a saclike tissue with an upper and a lower epithelial monolayer. The adult cuticle formed by the upper and lower monolayers has a distinctive pattern of thickened regions called veins. The venation pattern on the lower surface matches that on the upper surface. As demonstrated by transposition of grafts from the upper monolayer, determination of venation pattern occurs prior to pupation in both wing monolayers. However, the pattern is not expressed until later in adult development. Expression of this determined pattern occurs autonomously in most circumstances. One circumstance in which the pattern fails to be expressed is in pieces of the upper monolayer that are isolated from the lower monolayer before adult cuticle deposition and expression of venation pattern. The only evident interaction between the two monolayers of the wing occurs during a 3‐day period, 6–8 days after pupation. During this time, the basal laminae segregating upper monolayer from lower monolayer disappear, and the basal ends of cells form desmosomal junctions at the interface between upper and lower monolayer. Transposition as well as isolation of tissue fragments from the upper monolayer suggest that this interaction between the basal surfaces of the two monolayers is a prerequisite for evocation of venation pattern.
Fine structure of the gene's organ in the camel tick Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae)
Authors: El Shoura Samir M.
Published: February 2005

Gene's organ of the camel tick Hyalomma (Hyalomma) dromedarii is located in the anterodorsal region of the body cavity ventrad to the scutum. It consists of a short stalk, dividing posteriorly into 2 pairs of horns and then into tubular glands. In unfed ticks, the eipithelial layer of both the stalk and horns is lined internally by 2 cuticular layers; an inner, thin, greatly folded, dense layer surrounds the organ main lumen, and an outer, thick, slightly folded, less dense layer abuts the cell apices. Only the inner cuticular layer extends into the horn posterior region and appears perforated with numerous pore canals and covered with fine, cuticular projections. The horn and tubular glands epithelium is structurally consistent with a secretory function that apparently increases as feeding progresses. During oviposition, the inner cuticular layer unfolds and inflates into a pair of balloonlike structures that evert through the organ external aperture to receive and manipulate each egg as it is laid, coating it with a waxy layer that prevents desiccation. The fine cuticular projections may have a function in gripping the eggs as they leave the vagina. This organ appears to be everted by hydrostatic pressure from the hemolymph and is retracted by muscles.
Ovary of the pipefish, Syngnathus scovelli
Authors: Begovac Paul C. , Wallace Robin A.
Published: February 2005

Gross dissection, light microscopy, and transmission electron microscopy were used to generate a detailed understanding of the ovarian anatomy of the pipefish, Syngnathus scovelli. The ovary is a cylindrical tube bounded by an outer layer consisting of a smooth muscle wall and an inner layer of luminal epithelium, with follicles sandwiched between the two layers. A remarkable feature of this ovary is a sequential pattern of follicle development. This pattern begins at the germinal ridge with a gradient of follicles of increasing developmental age extending to the mature edge. The germinal ridge is an outpocketed region of the luminal epithelium containing early germinal cells and somatic prefollicular cells. Therefore, the germinal ridge and luminal epithelium share the same ovarian compartment and follicle formation occurs within this compartment. The mature edge is defined as the site of oocyte maturation and ovulation. The outer ovarian wall contains unmyelinated nerve fibers throughout. Longitudinally oriented unmyelinated nerves are also observed near the smooth muscle bundles associated with the mature edge. Oocytes near the mature edge are polarized such that the germinal vesicle (nucleus) is generally oriented toward the luminal epithelium. The sandwichlike organization of the ovary results in follicles that have a shared theca. An extensive lymphatic network is also interspersed among the follicles. Thus, the exceptional features of the pipefish ovary make it particularly well suited for the examination of early events in oogenesis. Specifically, we characterize pipefish folliculogenesis in detail.
Hemocytes of Leiobunum limbatum and two other species of harvestmen (Arachnida, Opiliones): Morphological classification and functional aspects
Authors: Dannhorn D. R. , Seitz K. A.
Published: February 2005

The hemocytes of Leiobunum limbatum, Mitopus morio, and Opilio ravennae number from about 8,000 (juveniles) to 41,000 (pregnant females) per microliter of hemolymph. Five different types of hemocytes occur in all three species and both sexes. According to their ultrastructural appearance and their similarities to other arthropod hemocytes these five types are designated as prohemocyte, plasmatocyte, granulocyte, coagulocyte, and spherulocyte. From the ultrastructural point of view the prohemocytes are interpreted as stem cells for plasmatocytes which on their part differentiate into granulocytes. Transitional stages which would indicate the origin of coagulocytes and spherulocytes could not be found.

Granulocytes and spherulocytes are interpreted as being storage cells; coagulocytes burst when hemolymph is transferred to a microscopic slide. Plasmatocytes are involved in the removal of dead cells or cell fragments. Plasmatocytes are demonstrated as being able to phagocytize and digest bacteria.
Fertilization and aqueous development of the puerto rican terrestrial‐breeding frog, Eleutherodactylus coqui
Authors: Elinson Richard P.
Published: February 2005

The Puerto Rican tree frog, Eleutherodactylus coqui, has internal fertilization and direct development on land. In light of these reproductive adaptations, the events of fertilization and early development were studied. Cytological examination of just‐fertilized eggs showed that sperm entry is restricted to about 10% of the surface of these large, yolky eggs, and all nuclear events of the first cell cycle occur near the animal pole. Although the oocytes have cortical granules, a number of polyspermic fertilizations were found. One clutch consisted of eggs with a high frequency of polyspermy and of normal development. This raises the possibility that normal development can occur despite multiple sperm entry, a situation not found in other anuran amphibians. With respect to saline requirements, the sperm and the embryo are similar to those in amphibians with external fertilization and aqueous development. Sperm motility was high in low‐tonicity conditions, and the normally terrestrial embryo could develop completely from a fertilized egg to a froglet in a low‐tonicity aqueous solution.
Viviparous development in Botrylloides (Compound Ascidians)
Authors: Mukai Hideo , Saito Yasunori , Watanabe Hiroshi
Published: February 2005

The mode of sexual reproduction and embryogenesis was compared in 3 species of Botrylloides: B. simodensis, B. lenis, and B. violaceus. In all species, a testis and an egg (occasionally 2 eggs), the former being anterior to the latter, mature in the mantle on either side of a zooid. The egg is surrounded by 2 follicular layers and is attached by a vesicular follicle stalk (oviduct) to the atrial brood pouch. The egg is ovulated into the brood pouch, where it is fertilized and undergoes embryogenesis. The egg of B. simodensis is heavily yolked and measures about 180 μm in diameter. The course of embryogenesis in this species is that typical of ascidians. A mature tadpole larva is produced and shed in about 5 days; then, the mother zooid degenerates. The larva is smallest of the three species and has 8 ampullae. The metamorphosed oozooid bears a single bud on the right side only. Extraembryonic nutrition seems to be very limited.

Both Botrylloides lenis and B. violaceus are species which display extreme examples of viviparity. Their eggs are devoid of yolk granules, measuring about 90 μm in diameter in the former species and 60 μm in the latter. The course of embryogenesis is similar in these 2 species. The neurula stage is characterized by a spherical vesicular shape owing to precocious differentiation of the embryonic pharynx, whose ectoderm becomes vacuolated. At the posterior end of the neurula, the mesodermal cells are located in a mass, from which the tail is extended later. In B. lenis, embryogenesis takes about 20 days. At the neurula stage of the embryo, the mother zooid becomes a mantle sac as a result of visceral disintegration. During further embryogenesis, the growth of buds of successive generations in the colony is characteristically arrested. A swimming larva of this species is somewhat larger than that of B. simodensis. It has 14–24 ampullae, and the oozooid carries a single bud on its right side. In B. violaceus, the gestation period lasts for more than a month. At the early gastrula stage of the embryo, the body of the mother zooid fully disintegrates. Only the brood pouch bearing the embryo survives and remains connected with the colonial vascular system. In this species, sexual reproduction does not affect the growth of buds in the colony. The swimming larva is gigantic, being furnished with 24–34 ampullae, and the oozooid always bears 3 buds, 2 on the right side and one on the left side.
Cleavage and membrane formation in the blastoderm of the dipteran Ceratitis capitata wied
Authors: Callaini Giuliano
Published: February 2005

In the Ceratitis capitata embryo, furrow formation follows the last mitosis divisions and leads to cellular blastoderm formation. This process displays several interesting features and requires the participation of bundles of microfilaments which are located at the furrow base at the onset of cytokinesis and contract synchronously, determining furrow growth. The new membranes for furrow growth seem to be largely provided by the fusion of many vesicles. Surface projections do not appear to contribute significantly to this phenomenon. At the end of cytokinesis the microfilaments are sandwiched between the plasma membrane and cisternae of endoplasmic reticulum. Subsequently the microfilaments disappear from the cytoplasmic side of the membrane but remain beneath the membranes of the connections and at the periphery of the yolk sack until gastrulation. On the basis of these observations some ultrastructural aspects of furrow formation and the role that the microfilaments may play during this process are discussed.
Specializations within the lumbosacral spinal cord of the pigeon
Authors: Schroeder D. M. , Murray R. G.
Published: February 2005

The prominent accessory lobes of Lachi in birds are considered to be marginal nuclei; similar nuclei have been implicated in mechanoreceptive functions in snakes and lampreys. Reptile studies emphasized the involvement of the denticulate ligament with this mechanoreceptive function. This investigation examines the fine structure of the accessory lobes of Lachi in pigeons and their interaction with ligaments for features which might support such a mechanoreceptive function. In the lumbosacral area of the spinal cord, the lateral longitudinal ligaments and the ventral longitudinal ligament are hypertrophied. The ventral transverse ligaments are present only within the lumbosacral segments of the spinal cord and they interconnect with the lateral and ventral longitudinal ligaments. The lateral longitudinal ligament makes intimate contact with the spinal cord, and many glial processes from the spinal cord mingle with and are firmly attached to collagenous fibers of the ligament. The lobes lie dorsal to the lateral longitudinal ligament in the exact area where it interconnects with the transverse ligament. The lobe's multipolar neurons have a number of synaptic contacts but no unusual specializations were noted. Most of each lobe is composed of interdigitating saccular structures filled to varying degrees with flocculent material. The sacs are extensions of the cytoplasm of neuroglial cells, which also give rise to membranes surrounding neuronal processes and the sacs themselves. A possible functional relationship of the lobes and the ligaments of the lumbosacral spinal segments within the vertebral column is described.
Anterior dorsal ventricular ridge in the lizard: Embryonic development
Authors: Yanes C. , Batista M. A. Perez , Trujillo J. M. Martin , Monzon M. , Marrero A.
Published: February 2005

In lacertids the telencephalic vesicle starts its development at stage E = 30, at which time it is lined by a homogeneous nucleated zone in which particular ventricular zone territories or sulci cannot be distinguished. At stage E = 32 coinciding with the initial development of the anterior dorsal ventricular ridge (ADVR), one may distinguish the ventricular zone b in the dorsolateral wall of the ventricle adjacent to the sulcus lateralis. The ADVR continues growing by incorporation of cells produced in two proliferative zones (zone b and wall of the sulcus lateralis) and appears fully developed in postnatal lizards. Ultrastructural characteristics of young ADVR neurons between stages E‐32 and E‐33 are typical of those in immature cells. Beginning at stage E‐34, some of these neurons appear to be degenerating (pycnotic). Thereafter, neurons of the ADVR develop abundant cytoplasmic organelles and the neuropile grows quickly. Myelination starts in the ADVR between stages E‐38 and E‐40, but is not observed in other striatal masses in the same period. Vascularization begins and is well developed at E‐40. The first synaptic contacts were observed in embryos of stage E=38; they are chiefly axo‐dendritic, although some are axo‐somatic. Degenerating neurons were found in the ADVR up to hatching. From stage E‐40 onward, the ADVR shows a greater and more rapid differentiation than all other striatal nuclei, including the ventral and amygdaloid complex.
Structural heterogeneity in the basal regions of the teeth of the red‐backed salamander, Plethodon cinereus (Amphibia, Plethodontidae)
Authors: Moury J. David , Curtis Sherill K. , Pav Denise I.
Published: February 2005

Ultrastructural and histochemical features of marginal (monostichous) teeth associated with the jawbones are compared with those of palatal (polystichous) teeth that compose two patches in the roof of the mouth. The apices and uncalcified regions are similar in both kinds of teeth, but the basal regions display distinctive differences. While bases (pedestals) of marginal teeth are essentially hollow cylinders that attach to the jawbones by their labial faces, bases of teeth in palatal patches are fused to form two horizontal plates which lack direct attachment to underlying bone. The plates are separated from each other by a pulp‐filled space containing fibroblasts, blood vessels, and vertically oriented elements resembling bony spicules. Cylindrical pedestals like those of marginal teeth project from the ventral plate. While the identity of the material composing the basal regions remains controversial, the following evidence suggests that it is similar to “bone of attachment” (Tomes, '23): most of it, unlike dentin, does not develop in direct association with an enamel organ; alcian blue stains the bases of developing teeth but stains dentin, developing dentin, enamel, or mature bone very weakly (if at all); bases of teeth in palatal patches develop in isolation from the parasphenoid bone and thus cannot be considered extensions of it; and marginal teeth attach directly to the jawbones, but the material composing their bases does not blend with the bone. Structural heterogeneity of the basal regions appears to be linked to functional differences exhibited by these two types of teeth.
Fine structure of the pyloric region and of the hindgut in the proturan Neocondeellum dolichotarsum (insecta, protura)
Authors: Dallai Romano , Yin Wen‐Ying , Xue Luzhen , Fanciulli Pietro Paolo
Published: February 2005

The fine structure of the midgut, pyloric region, Malpighian papillae, and hindgut in the proturan, Neocondeellum, was studied.

Midgut cells, rich in rough endoplasmic reticulum and mitochondria, are linked to each other by smooth septate junctions. No peritrophic membrane is visible over the microvilli.

The posterior cells of the midgut carry short microvilli and are surrounded by a muscular pyloric sphincter. Behind such sphincter is a wide pyloric chamber that has cells with very long microvilli pointing anteriorly toward the midgut. These cells with their microvilli form a kind of stopper that controls the passage of the intestinal content into the hindgut. The Malpighian papillae have an apical globular secretory region producing proteinaceous material, which is then collected in a microvillate cistern at the proximal end of the cell. A peduncle formed by flattened squamous cells joins each papilla to the hindgut epithelium. The hindgut shows two differently organized regions, both engaged in fluid reabsorption. The principal cells of the anterior region show a system of apical subcuticular cavities into which thin microvilli extend. In the cytoplasm of these cells, there are numerous mitochondria associated with infoldings of the plasma membrane.

The principal cells of the posterior hindgut region have bundles of long microvilli beneath the cuticle. Also, these cells exhibit at their base an abundant system of infoldings of the plasma membrane and mitochondria.

The results are considered in relation to the phylogenetic relationship between Neocondeellum and other proturan genera.
Morphogenesis of the prehensile autopodium in the common chameleon (Chamaeleo Chamaeleo)
Authors: Hurle J. M. , Garcia‐Martinez V. , Ganan Y. , Climent V. , Blasco M.
Published: February 2005

This report documents the development of the autopodium of the common chameleon (Chamaeleo chamaeleo) using light microscopy, scanning electron microscopy, and transmission electron microscopy. Three main periods were distinguished during the morphogenesis of this structure. In the first period (stages 33‐35 of chameleon development) the autopodium is paddle‐shaped with a prominent apical ectodermal ridge (AER) along the distal margin. During this period the AER has structural features similar to other reptilian and avian vertebrates except for the scarcity or absence of gap junctions. The second period of autopodium morphogenesis (stage 36 of chameleon development) is characterized by the formation of a central cleft which divides this structure into two digital segments. In the forelimb the autopodial cleft occupies the space between digits 3 and 4. In the hindlimb the cleft occupies the space between digits 2 and 3. Mesenchymal cell death constitutes a constant feature during cleft formation. In addition to cell death during this process, we have observed that the AER flattens out in the zone of cleft formation while in the digital portions of the autopodium it takes on a polystratified appearance. In the last period of autopodial morphogenesis (stage 37 of chameleon development) digits become free by means of interdigital mesenchymal cell death.
Development of the glycogen body of the Japanese quail, Coturnix Japonica. I. Light microscopy of early development
Authors: De Gennaro Louis D. , Benzo Camillo A.
Published: February 2005

The glycogen body is a functionally enigmatic structure located in lumbosacral region of the spinal cord in birds. This tissue is unique to birds, and, although it is believed to be present in all species, studies on the glycogen body to date have been confined largely to the domestic chicken. The present study is the first to describe the glycogen body of the Japanese quail (Coturnix japonica) during incubation and at hatching. Light microscopy and histochemistry were used to identify the glycogen body in the spinal cord of the developing quail beginning at 7 days of incubation and to ascertain the presence of nerve fibers in that tissue at hatching.
A golgi study of the dorsal cortex in the lizard Psammodromus algirus
Authors: Guirado Salvador , Davila J. C. , De La Calle A. , Giron F. Marin
Published: February 2005

The dorsal cortex of Psammodromus algirus is three‐layered. From the pia to the ependyma, it consists of a superficial plexiform layer, a cellular layer, and a deep plexiform layer. Five neuronal types have been classified in the dorsal cortex. Pyramidal neurons represent 18.75% of neurons and differ morphologically depending on their position in the pars medialis or lateralis of dorsal cortex. Pyramidal neurons in the pars medialis are smaller and their apical dendritic fields are less extensive than those of pyramidal neurons in the pars lateralis. Bitufted neurons represent 22.5% of dorsal cortical neurons and are only found in the cellular layer of the pars lateralis. Multipolar neurons are distributed in the pars medialis and lateralis, in the cellular layer and the deep plexiform layer; they represent 46.25% of the total impregnated cells. Bipolar neurons are found mainly in the deep plexiform layer and form 11.25% of neurons. Two subtypes may be distinguished: horizontal and vertical bipolar cells. Juxtaependymal neurons represnt 1.25% and are located just above the ependyma. All the neurons in the cellular layer are projection cells.
Metamorphosis of the excretory system of Paragonimus ohirai (Trematoda), with special reference to its functional significance
Authors: Orido Yasuhide
Published: February 2005

The fine structure of the excretory system was studied in metacercariae and juveniles of Paragonimus ohirai. The former were in vitro excysted, and the latter were collected from the abdominal cavity of a rat 24 hours postinfection. The terminal organs of the excretory system were composed of a flame cell and the first cell of a tubule. In the excysted metacercaria, there was no space between these cells to allow the passage of fluid. This suggests that the terminal organs of P. ohirai may be inactive in this stage. The excretory bladder was formed of epithelial cells which contained numerous lipid droplets and a large amount of glycogen in the cytoplasm. The bladder of the metacercaria seems to function as a storage area for nutrients and other materials. These characteristics of the metacercaria are considered to be related to the enclosed conditions created by encystment. Excretory organs had undergone cytomorphosis in the juveniles and appear to possess active excretory function. The periflagellar space in the terminal organs was formed, and lipids and concretions were excreted from a thin layer of the excretory epithelia into the lumen.
Peripheral neurosecretory cells on the thoracic median nerves of the locust, Schistocerca gregaria
Authors: Myers Camilla M. , Evans Peter D.
Published: February 2005

The distribution of neutral red staining peripheral cell bodies along the nerve trunks of the thoracic median nervous system of the locust, Schistocerca gregaria, is described. Backfilling of the cells with cobalt chloride solution reveals that they are neurones with characteristic axonal processes that terminate in the neurohaemal areas of the median nerve. The neurones react with the dye acridine orange, indicating their neurosecretory nature. This is confirmed by their ultrastructural appearance at the electron microscope level. The distribution and staining properties of the cells are compared with those of peripheral neurones from other insects and the nature of their neurosecretory product is discussed.
Ergatoid reproductives in Nasutitermes columbicus (Isoptera, Termitidae)
Authors: Noirot Charles , Thorne Barbara L.
Published: February 2005

Numerous functional ergatoid replacement reproductives were found in one colony of Nasutitermes columbicus in Panama. Their morphology was mainly workerlike, although several imaginal characters such as the compound eyes and variable wing buds were more or less developed. The sex organs were fully mature and the fat body of the females, not of the males, was of the “royal” type. The development of the eyes was not accompanied by the differentiation of the optic lobes of the brain, nor was the presence of wing buds correlated with a development of the wing muscles.
Ultrastructure of the gametolytic gland and seminal receptacle in Hypselodoris messinensis (Gastropoda, Opisthobranchia)
Authors: Medina A. , Griffond B. , Garcia‐Gomez J. C. , Garcia F. J.
Published: February 2005

The gametolytic gland of Hypselodoris messinensis is a voluminous globular structure that encloses a large mass of degenerative gametes, especially waste exogenous sperm. The epithelial cells of this organ show some features characteristic of secretory cells and probably release hydrolytic enzymes into the lumen. The amorphous material accumulated in the gametolytic gland does not appear to be reabsorbed by the lining epithelium.

The seminal receptacle stores exogenous sperm received during copulation. The spermatozoa are oriented radially: their heads are embedded in the epithelium and their tails are directed toward the center of the lumen. The epithelial cells of the seminal receptacle may synthesize certain substances that induce sperm activation and maintain them in adequate physiological conditions. However, they apparently do not perform an important function of sperm nourishment.

The nuclear chromatin of spermatozoa stored in the seminal receptacle is not homogeneously condensed, but forms longitudinal filaments. The significance of this phenomenon, which also occurs in other nudibranchs, remains to be understod.
A quantitative analysis of mitochondria during fetal mouse oogenesis
Authors: Nogawa Takayoshi , Sung Weng Kong , Jagiello Georgiana M. , Bowne Wilbur
Published: February 2005

A quantitative analysis of mitochondrial populations during the meiotic prophase of mouse oogenesis was carried out. The mean absolute area occupied by mitochondria and the mean number of mitochondria per cell increases in a linear fashion from pachytene through dictyate. The mean area occupied by mitochondria increases at pachytene and thereafter. Both small and large aggregations of mitochondria are seen, particularly during the later stages of prophase. Vacuolated mitochondria are present from preleptotene through pachytene. Mitochondria show major dynamic changes throughout fetal mouse oogenesis, which may suggest significant functional activities yet to be elucidated.
Ocular changes accompanying eye loss in the spider family uloboridae
Authors: Opell Brent D.
Published: February 2005

In uloborid spiders, eye loss is accompanied by increased visual angles, optical material investment, and potential visual acuity of the retained eyes. Relative to carapace volume, the six‐eyed Hyptiotes cavatus and two four‐eyed Miagrammopes species have greater retinal hemisphere areas and lens volumes than do the eight‐eyed uloborids Waitkera waitkerensis, Uloborus glomosus, and Octonoba sinensis. In Waitkera, in which the eyes have little visual overlap, and in Miagrammopes, in which eye loss simplifies the spiders' patterns of visual overlap, increased retinal cell density enhances potential visual acuity. However, this occurs at the expense of potential retinal cell sensitivity.
Morphology of the kidney of adult bowfin, Amia calva, with emphasis on “renal chloride cells” in the tubule
Authors: Youson John H. , Butler David G.
Published: February 2005

The nephron of adult bowfin, Amia calva, was described using light and electron microscopic techniques. The kidney of the bowfin possesses an abundant supply of renal corpuscles with each consisting of a glomerulus and a Bowman's capsule of visceral (podocyte) and parietal layers. No juxtaglomerular apparatus is present. The epithelium of the tubule is continuous with the parietal epithelium and is divisible in descending order into neck, first proximal, second proximal, first distal, second distal, and collecting segments. The tubules drain into a complex system of collecting ducts that ultimately unite with the main excretory duct, the archinephric duct. Mucous cells are the dominant cell throughout the entire ductular system. Nephrostomes are dispersed along the kidney capsule.

The neck segment has a ciliated epithelium, and while both proximal segments possess a prominent brush border, the fine structure of the first implies involvement in protein absorption and the second in the transport and reabsorption of solutes. The cells of the first distal segment are characterized by deep infolding of the plasma membrane and a rich supply of mitochrondria suggesting the presence of a mechanism for ion transport. The second distal segment is composed of cells resembling the chloride cells of fishes and these cells are present in progressively decreasing numbers in the collecting segment and duct system so that only a few are present in the epithelium of the archinephric duct. The “renal chloride cells” possess an abundant network of smooth tubules and numerous mitochondria with a rich supply of cristae. Glycogen is also a conspicuous component of these cells. The presence of “renal chloride cells” in this freshwater holostean, in other relatively primitive freshwater teleosts, and in larval and adult lampreys is discussed with reference to both phylogeny and the need for a special mechanism for renal ion conservation through absorption.
Cellular organization and peritrophic membrane formation in the cardia (Proventriculus) of Drosophila melanogaster
Authors: King David G.
Published: February 2005

The peritrophic membrane of Drosophila melanogaster consists of four layers, each associated with a specific region of the folded epithelial lining of the cardia. The epithelium is adapted to produce this multilaminar peritrophic membrane by bringing together several regions of foregut and midgut, each characterized by a distinctively differentiated cell type. The very thin, electron‐dense inner layer of the peritrophic membrane originates adjacent to the cuticular surface of the stomadeal valve and so appears to require some contribution by the underlying foregut cells. These foregut cells are characterized by dense concentrations of glycogen, extensive arrays of smooth endoplasmic reticulum, and pleated apical plasma membranes. The second and thickest layer of the peritrophic membrane coalesces from amorphous, periodic acid‐Schiff‐positive material between the microvilli of midgut cells in the neck of the valve. The third layer of the peritrophic membrane is composed of fine electron‐dense granules associated with the tall midgut cells of the outer cardia wall. These columnar cells are characterized by cytoplasm filled with extensive rough endoplasmic reticulum and numerous Golgi bodies and by an apical projection filled with secretory vesicles and covered by microvilli. The fourth, outer layer of the peritrophic membrane originates over the brush border of the cuboidal midgut cells, which connect the cardia with the ventriculus.
Studies on the subcommissural organ of Salmo gairdneri
Authors: Schäfer Heike , Blüm Volker
Published: February 2005

The light microscopic analysis of serial sections of the subcommissural organ (SCO) of the rainbow trout (Salmo gairdneri) shows that the form of the groove‐like (in cross section) organ varies over its total length. Its rostral origin is a tunnel‐like structure anterior to the orifice of the hollow pineal stalk. The SCO forms the dorsal wall of the brain. Caudally the SCO is increasingly displaced from the surface of the brain by the fibers of the posterior commissure; the organ ends in a tabular area beyond the latter. The orifice of the pineal stalk is surrounded by the ependyma of the SCO that invaginates like a funnel and joins with the ependyma of the pineal stalk after a considerable narrowing. The rudimentary parapineal organ is located on the left side of the brain and is connected with the left habenular ganglion through the parapineal tract. It contacts the third ventricle with a short channel within the ependyma of the SCO. The histological organization of the ependymal and hypendymal cells of the SCO is typical of teleosts. Secretory material is located basally and apically in relation to the nucleus, but there is no indication of a basal secretory release. Basal ependymal processes terminate with broadened endings at the membrana limitans externa. The apical product is discharged into the third ventricle, where it aggregates into the thread‐like structure of Reissner's fibre. The SCO cells have no direct contact with cerebral or meningeal blood vessels.
Morphology of defense glands of the opilionids (daddy longlegs) Leiobunum vittatum and L. flavum (Arachnida: Opiliones: Palpatores: Phalangiidae)
Authors: Clawson Robert C.
Published: February 2005

Opilionid defense glands consist of 0.5 × 0.9‐mm sacs attached to the underside of low tubercles located on the dorsal side of the cephalothorax, posterior to the first pair of legs. Each gland opens via an elongated slit, located in the posterior floor of a crater that is situated at the summit of the tubercle. The center of the sac, called the reservoir, is lined by a cuticle consisting of epicuticle and endocuticle which is continuous through the slit with the exoskeleton. The layers of cuticle vary in thickness with different locations in the gland. A hemocoelomic (basement) membrane, 0.5–1, μ thick, forms the boundary between glandular cells and hemocoel. The gland has a nonsecretory portion consisting only of cuticle‐supporting cells and a secretory portion consisting of secretory and cuticle‐supporting cells. The cuticle lining the reservoir in the secretory area is broached by many cuticle‐lined ductules, each of which drains an isolated intercellular space called the intercalated cistern. This in turn drains microvilli‐lined canaliculi located between and extending into secretory cells. The cisterns are devoid of microvilli. Secretory cell cytoplasm contains a Golgi apparatus, many free ribosomes, rough endoplasmic reticulum (RER), two types of granules (speckled and dense), and mitochondria. Speckled granules are partially filled with fairly large particles and are found in association with the Golgi apparatus. They also surround canaliculi into which they empty. Dense granules are packed with very small particles, have a gray homogeneous appearance, and are scattered throughout the cytoplasm. Mitochondria containing matrix granules tend to scatter throughout the cytoplasm but are concentrated around canaliculi.
Aspects of shell formation in eggs of the tuatara, Sphenodon punctatus
Authors: Packard Mary J. , Thompson Michael B. , Goldie Kenneth N. , Vos Marta
Published: February 2005

The flexible shell from eggs of the tuatara (Sphenodon punctatus) is comprised of both calcareous and fibrous components. The calcareous material is organized into columns that extend deep into the fibrous shell membrane. Many of the fibers of the membrane are enclosed within the crystalline matrix of the columns. Columns widen and flatten slightly at the outer surface of the eggshell to form cap‐like structures composed of a compact crystalline matrix containing no fibers. The outer surface of eggs laid prior to completion of shell formation consists of a series of nodes obscured by a densely fibrous matrix. Similar nodes also are found at the inner surface of partially shelled eggs. The nodes represent the outer and inner aspects of columns that had not completed formation prior to oviposition. Our interpretation is that a layer (or layers) of the shell membrane forms first, with nucleation of columns occurring shortly thereafter. Columns grow into the membrane a short distance and enclose fibers of the membrane, but the primary direction of column growth is toward what will become the outer aspect of the shell. Calcareous columns and the shell membrane form more or less in concert until crystal growth outstrips that of the membrane and a cap‐like apex of compact crystalline material is formed. The end result is an eggshell in which the shell membrane and calcareous material form a single unit for much of the thickness of the shell.
Some histological aspects of the hip joint capsule in the vervet monkey
Authors: Walji A. H.
Published: February 2005

Microscopic studies show that the capsule of the hip joint in the vervet monkey (Cercopithecus aethiops pygerythrus) is preponderantly collagenous. Among the collagen fiber bundles are varying quantities of elastic fibers that demonstrate a definite, differential regional distribution. The highest concentration of elastic tissue is found in the posterior, postero‐inferior, and inferior aspects of the hip joint capsule, whereas the anterior and superior aspects of the capsule are preponderantly collagenous. It is postulated that this regional distribution of elastic tissue is related to the differential functional requirements of the posterior, postero‐inferior, and inferior aspects of the capsule for flexibility and stretchability. These requirements appear to be a consequence of the habitual postures and locomotory positions assumed at the hip joint by these primarily quadrupedal primates. Collagen, on the other hand, being much more resistant to deformation and relatively noncompliant, is the predominant tissue in the anterior and superior aspects of the joint.
On the nervous system of Velella (hydrozoa: Chondrophora)
Authors: Mackie G. O. , Singla C. L. , Arkett S. A.
Published: February 2005

Silver impregnations, immunofluorescence microscopy, and electron microscopy of the nervous system of Velella confirm previous reports that there are two nerve nets, one composed of small and the other of “giant” neurites. Only one of these systems, the small‐fibered open one, shows FMRFamide‐like immunoreactivity. It appears to be primarily a sensory network. Despite presence of a neuropeptide in these neurons, they did not contain dense‐cored vesicles. The “giant” nerve net (closed system) shows many connections that appear syncytial in the silver preparations. While it is confirmed that gap junctions are present between some neurites in the closed system, it is likely that fusion of neurites also occurs and that the system is a partial syncytium. Membrane complexes with gap junctions are abundant in the cytoplasm. It is suggested that fusion occurs by the engulfment of small neurons by large, resulting in an excess of cell membrane, which is internalized with gap junctions still intact. These internalized membranes appear to break up into vesicles eventually. A similar process may occur in the “giant” swimming motor neuron net of the medusa Polyorchis.
Adrenergic innervation of the large arteries and veins of the semiarboreal rat snake Elaphe obsoleta
Authors: Donald John A. , Lillywhite Harvey B.
Published: February 2005

Fluorescence histochemsitry was used to study the adrenergic innervation of the large arteries and veins at six points along the body of the semiarboreal rat snake Elaphe obsoleta. Apart from the vessels adjacent to the heart, there was a marked contrast in the density of adrenergic innervation of anterior and posterior systemic arteries and veins. The anterior arteries and veins have little adrenergic innervation in contrast to the extremely dense innervation of the arteries and veins posterior to the heart. The innervation pattern is consistent with known physiological adjustments to gravity and suggests a mechanism for regulating dependent blood flow via sympathetic nerves. In comparison to the posterior systemic arteries, parallel segments of pulmonary artery taken from the same body position of Elaphe contained a much sparser innervation by adrenergic nerves. The sparser innervation can be correlated with less gravitational disturbance in the pulmonary artery, which is relatively short in this and in other arboreal snakes.
Afferent projections of the trigeminal nerve in the goldfish, Carassius auratus
Authors: Puzdrowski R. L.
Published: February 2005

The horseradish peroxidase (HRP) histochemical technique was used to examine the peripheral distribution and afferent projections of the trigeminal nerve in the goldfish, Carassius auratus. Sensory fibers of the trigeminal nerve distribute over the head via four branches. The ophthalmic branch distributes fibers to the region above the eye and naris. The maxillary and mandibular branches innervate the regions of the upper and lower lip, respectively. A fourth branch of the trigeminal nerve was demonstrated to be present in the hyomandibular trunk.

Upon entering the medulla the trigeminal afferent fibers divide into a rostromedially directed bundle and a caudally directed bundle. The rostromedially directed bundle terminates in the sensory trigeminal nucleus (STN) located within the rostral medulla. The majority of fibers turn caudally, forming the descending trigeminal tract. Fibers of the descending trigeminal tract terminate within three medullary nuclei: the nucleus of the descending trigeminal tract (NDTV), the spinal trigeminal nucleus (Spv), and the medial funicular nucleus (MFn). All projections, except for those to the MFn, are ipsilateral. Contralateral projections were observed at the level of the MFn following the labeling of the ophthalmic and maxillomandibular branches. All branches of the trigeminal nerve project to all four of the trigeminal medullary nuclei. Projections to the STN and MFn were found to be topographically organized such that the afferents of the ophthalmic branch project onto the ventral portion of these nuclei, while the afferents of the maxillo‐ and hyomandibular branches project to the dorsal portion of these nuclei.

Cells of the mesencephalic trigeminal nucleus were retrogradely labeled following HRP application to the ophthalmic, maxillary, and mandibular branches of the trigeminal nerve. In addition to demonstrating the ascending mesencephalic trigeminal root fibers, HRP application to the above‐mentioned branches also revealed descending mesencephalic trigeminal fibers. The descending mesencephalic trigeminal fibers course caudally medial to the branchiomeric motor column and terminate in the ventromedial portion of the MFn.
Role of actin filaments in shape formation of mesenteric mesothelial cells of the bullfrog
Authors: Sugimoto Keiji , Fujii Sachiko , Ichikawa Yasuaki , Nakamura Itsuo
Published: February 2005

The role of actin filaments in the development of cellular shape in the mesenteric mesothelium of the bullfrog was studied by using a simple, new technique for making en face preparations of mesothelial sheets. By using these mesothelial cell preparations, the distribution of actin was determined by means of fluorescence microscopy with 7‐nitrobenz‐2‐oxa‐1,3‐diazole (NBD)‐phallacidin and that of myosin by means of immunofluorescence microscopy. Although fluorescence produced by both NBD‐phallacidin and antimyosin staining was found exclusively along the margins of the cells, its intensity was altered in correspondence with changes in cell shape. For instance, tadpole‐type mesothelial cells with either and irregular or very slender cell shape showed very weak fluorescence. On the other hand, frog‐type mesothelial cells with a polygonal shape showed intense fluorescence at their margins and had circumferential bundles of acting filaments at their apices. Furthermore, intercellular junctions between the mesothelial cells developed as the cell shape became polygonal during metamorphosis. The present study showed that development of circumferential bundles of acting filaments and intercellular junctions may serve to establish and maintain the definitive polygonal cellular pattern in the mesenteric mesothelium of the bullfrog.