bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological evidence for a probable secretory site of the male sex pheromones of Nauphoeta cinerea (blattaria, blaberidae). 2. electron microscope studies
Authors: Menon Maya
Published: February 2005

Light and electron microscopy of the glandular epithelium of intersegmental membranes between sternites three and seven and tergites two and eight of various age groups of Nauphoeta cinerea male adults and one age group of female adults discloses differences in the epithelia of the intersternite and intertergite. The intersternal epithelium appears thicker, more glandular, and stratified. Altogether, seven cell types are recognizable, six in the male and two in the female. They are designated as types 1, 2a, 2b, 2c, 3, 4, and 5. Of these, types 1, 2a, 3, and 4 are recognizable on the sternum; types 1, 2b, and 5 on the tergum of the mature male integuments. Types 1 and 2c are found on the sternum of mature female. The cell types undergo morphological differentiation after adult emergence and show different stages of secretory activity. Type 1 are squamous cuticle‐secreting cells; type 2a, 2b, and 2c are columnar‐glandular and contain electron‐transparent secretory vesicles of various sizes, which increase greatly in number and size in the 5‐day‐old adult males when the glands are most active. The vesicular size and number also differ between types 2a, 2b, and 2c cells of the same age group. The vesicles are assumed to be derived from smooth endoplasmic reticulum. The type 2 gland cells are also provided with a secretory end apparatus lined by cuticle and bordered by microvilli through which the secretion is believed to be released by exocytosis. The end apparatus leads into a cuticular ductule that opens to the surface of the cuticle as a cup‐shaped receptacle, which is more conspicuous in the male intersternite. In the active gland cells, the mitochondria near the end apparatus are swollen and vacuolated. Type 3 cells are seen only on the intersternum and are believed to secrete the cuticular ductule that proceeds from the end apparatus. Type 4 cells are also recognizable only on the male intersternum and contain closely packed, electron‐dense bodies, which are most numerous in mature (5‐day‐old) males. Type 5 cells with their dense cytoplasm are located basally in the intertergal epithelium. The functional significance of type 4 and 5 cells in the males and type 2c cells in the female is not clear. On the basis of differences in morphology, pheromone activity, and sexual behavior, it is suggested that the pheromones secreted by the intersternal and intertergal glands in the male are different, the former secreting a seducin that attracts the female to the male and the latter an “aphrodisiac” acting as a contact pheromone important in accomplishing mating.
The effects of sex steroid treatments on sexual differentiation in a unisexual lizard, Cnemidophorus uniparens (Teiidae)
Authors: Billy Allen J. , Crews David
Published: February 2005

Cnemidophorus uniparens is a parthenogenetic unisexual species of lizard in which each individual develops as a female, making it a unique animal model for the study of sexual differentiation. In one study, administration of exogenous testosterone before and/or after hatching influenced the development of the gonads, the accessory reproductive ducts, the renal sex segment of the mesonephric kidney, and the femoral glands, a secondary sex character. Testosterone treatment also affected the cross‐sectional area of the gonad and the proportions of cortical and medullary tissues present in the developing gonad. The oviducts and femoral glands of testosterone‐treated individuals were hypertrophied; the collecting tubules of the kidney of these animals contained granules, an androgen‐dependent, sexually dimorphic character in squamate reptiles. In another study, testosterone, dihydrotestosterone, or estradiol were administered to C. uniparens embryos. No treatment effects on gonadal development were detected on the day of hatching. However, estradiol, but not testosterone and dihydrotestosterone, stimulated development of the oviducts. Taken together these studies suggest that androgen aromatization may play a role in sexual differentiation in lizards.
Proportions of mammalian‐type and reptilian‐type nephrons in the kidneys of two passerine birds
Authors: Goldstein David L. , Braun Eldon J.
Published: February 2005

We compared the proportions of mammalian‐type and reptilian‐type nephrons in the kidneys of two species of passerine birds. The desert house sparrow (Passer domesticus) is relatively well adapted for water conservation, whereas the white‐crowned sparrow (Zonotrichia leucophrys) is more mesic adapted. The two species do not differ in body mass, but the kidneys of P. domesticus are significantly smaller than those of Z. leucophrys. Associated with its smaller size, the house sparrow kidney has significantly fewer glomeruli (35,700 per kidney) than does the white‐crowned sparrow kidney (53,000 per kidney). The medullary cones, which contain the loops of Henle of the mammalian‐type nephrons, are significantly longer in house sparrows than in white‐crowned sparrows (2.2 vs. 1.9 mm). The number of medullary cones, the number of nephrons per medullary cone, and, hence, the number of mammalian‐type nephrons do not differ between the two species. The smaller number of nephrons in the kidney of the house sparrow therefore represents a smaller number of reptilian‐type nephrons. Desert house sparrows have 18% mammalian‐type nephrons, whereas white‐crowned sparrows have 10% mammaliantype nephrons. The relative reduction of reptilian‐type nephrons in P. domesticus may reduce the flow of dilute urine through the collecting ducts, thereby permitting a greater concentration gradient to be established along the length of the medullary cones.
Comparative features of the surface morphology of the basilar papilla in five families of salamanders (amphibia; caudata)
Authors: White James S.
Published: February 2005

The surface morphology of the basilar recess and papilla was examined in 14 species of newts and salamanders selected from the five families of urodeles (Ambystomatidae, Salamandridae, Hynobiidae, Cryptobranchidae, and Amphiumidae) known to have this end‐organ. In this sampling, the general organization of basilar structures is essentially similar across species investigated. The recess forms a tubular diverticulum of the proximal part of the lagena. One wall of the recess is associated with a diverticulum of the intracapsular periotic sac, and an adjacent wall is occupied by the basilar papilla. The papilla contained from as few as five hair cells in specimens of Taricha torosa to over 200 hair cells in Cryptobranchus allegheniensis. In most species, the papilla showed a morphological continuum between tall centrally or distally placed ciliary bundles and short ciliary bundles near the papillar margins. In certain species examined, tall bundles had kinocilia with swellings near their tips. Most forms showed a tendency to have groups of ciliary bundles morphologically polarized either toward or away from the saccule. In Cryptobranchus and Dicamptodon, many bundles had a random orientation. The gross and fine structural features of the basilar complex are compared in urodeles and anurans, and “generalized” features for the amphibian basilar complex are suggested. The basilar complex of Cryptobranchus is interpreted as being most generalized, representing a structural form from which most features of the basilar complex in other urodeles and anurans can be derived.
Functional morphology of the M. Gastrocnemius medialis of the rat during growth
Authors: Woittiez R. D. , Heerkens Y. F. , Huijing P. A. , Rijnsburger W. H. , Rozendal R. H.
Published: February 2005

Length‐force relations, both active and passive, and twitch contraction characteristics were quantified for left medial gastrocnemius muscles of four young, four adult, and four old male Wistar rats. Muscle and bundle optimum length and muscle weight were also determined and subsequently used for calculation of a number of morphological characteristics of the muscles. Fiber optimum length was derived from muscle bundle optimum length. Generally, physiological characteristics remained constant during growth. There was no change either in active tension at muscle optimum length or in active working range relative to fiber optimum length, relative passive fiber stiffness, active force relative to passive force at optimum length, twitch contraction time and twitch half relaxation time at optimum length. A number of morphological changes, however, did take place in the medial gastrocnemius muscle during growth. Fiber optimum length increased but only by about 2 mm from youth to old age, whereas muscle optimum length increased by approximately 14 mm, presumably owing to extensive hypertrophy of the muscle fibers during growth. The priority for force of the medial gastrocnemius muscle (defined as the quotient of physiological cross‐sectional area of a muscle and the cubed root of its volume, a measure independent of architecture and dimensions of muscles) increased during growth. This increase indicates that during growth the muscle shifts relatively more towards force generation than towards excursion generation. These findings are discussed in view of existing scaling theories.
Zymogen granule size in pancreas of nursing rats
Authors: Ermak Thomas H. , Rothman S. S.
Published: February 2005

Dramatic depression in granule volume density and size was measured in acinar cells of postnatal rat pancreas following the initiation of feeding. Volume density decreased about threefold from 45% at birth to 16% 2 days thereafter. Mean granule diameter decreased from 1.50 μm to 0.80 μm, an 85% decrease in corresponding granule volume. At the same time, numerical density approximately doubled. At 2 days after birth, cells with smaller granules had lower volume densities, and differences in mean granule volume between cells accounted for most of the differences in volume density. Although the distribution of granule diameter in newborns was lognormal, the distribution at 2 days was heavily skewed to larger sizes. This was the result of skewed distributions within individual cells and not an artifact of sampling. The results corroborate the central role of granule volume in determining changes in the volume density of zymogen granules in the pancreas and suggest that zymogen granules can act as capacitors that can change size as a function of the enzyme contained within.
Differential localization of vasopressin‐ and oxytocin‐immunoreactive cells and conventional neurosecretory cells in the ganglia of the earthworm Pheretima hilgendorfi
Authors: Kinoshita Kiyoshi , Kawashima Seiichiro
Published: February 2005

Cells containing arginine vasopressin (AVP)‐ and oxytocin (OXT)‐like substances were immunohistochemically visualized in the cerebral, subesophageal, and ventral nerve cord ganglia of the earthworm Pheretima hilgendorfi. Whether these anti‐AVP– and anti‐OXT–reactive cells are identical with classical aldehyde fuchsin (AF)‐positive neurosecretory cells was tested in serial sections. In all ganglia, groups of scattered neuronal cell bodies and axons strongly reactive to AVP and OXT antisera were observed, but AF‐positive cells consisting of type a (dark blue) and type b (purple) cells were predominantly present in the cerebral and subesophageal ganglia. In the cerebral and subesophageal ganglia anti‐AVP– and anti‐OXT–reactive cells were generally larger than AF‐positive cells. Some AF‐positive cells were reactive either to anti‐AVP or anti‐OXT serum, but some failed to react to either serum. Anti‐AVP– and anti‐OXT–reactive cells were not immunoreactive to OXT and AVP antisera, respectively. Electron microscopic observations showed that the granules of type a cells were larger and less electron dense than those of type b cells and anti‐AVP–reactive cells. The present cytological observations clearly showed that AVP‐ and OXT‐like substances were widely present in the ganglionic cells of the earthworm
Evidence of a microtrabecular cytoskeletal lattice in glandular cells of hydrozoan planulae
Authors: Walch E. Timothy , Martin Vicki J. , Archer William E.
Published: February 2005

Hydrozoan planulae of Pennaria tiarella and Podocoryne carnea were processed for transmission electron microscopy using diethylene glycol distearate (DGD). The DGD functions as a removable embedding medium to produce embedment‐free sections of intact planulae. Images of glandular cells obtained using embedment‐free sections were compared with those from conventional Spurr‐embedded sections. In unembedded sections a large number of thin anastomosing fibers were observed throughout the cytoplasm of the glandular cell. The fibers appeared to coalesce in certain areas to form thick bundles of fibers that partitioned the glandular cytoplasm into spherical compartments. The meshwork of fibers is three‐dimensional and resembles a microtrabecular lattice. Mitochondria are suspended within and attached to the network of fibers, thus suggesting a cytoskeletal role of the fibers. This study documents the presence of a cytoplasmic fiber system within cells of intact invertebrate larvae.
Ultrastructure of duvernoy's gland from the wandering garter snake, Thamnophis elegans vagrans (Serpentes, Colubridae)
Authors: Kardong Kenneth V. , Luchtel Daniel L.
Published: February 2005

In addition to the supralabial glands (strips of glandular tissue lying along the maxilla), most snakes of the family Colubridae possess an enlarged oral gland lying behind the eye and emptying near the rear maxillary teeth, the Duvernoy's gland. Duvernoy's gland is most probably homologous to the venom gland of viperid and elapid snakes, and occasionally has been implicated in cases of human envenomation. Although of possible medical concern, there is reason to believe that secretion from this gland serves a biological role different from that of the venom gland, namely a role primarily in digestion rather then largely in rapid prey immobilization. The parenchyma of the Duvernoy's gland comprise two cell types, a serous cell containing numerous, electron‐dense secretory granules, and myoepithelial cells. There are no mucous cells in the parenchyma; instead cells of this type are located exclusively in the lining epithelium of the main duct. Numerous unmyelinated nerves pass between secretory acini. Observations of the supralabial gland reveal that this gland, in addition to serous cells, also contains mucous cells and a putative third cell type we designate as an intermediate cell.

In cellular morphology, Duvernoy's gland is closest to the venom gland of elapids, and least like the venom gland of viperids. Compared to the venom glands in both families of venomous snakes, Duvernoy's gland lacks a large luminal secretory reservoir. Emptying of Duvernoy's gland is thought to involve release of secretion granules into the lumen, and movement of the secretory product from there may be supplemented by mechanical pressure exerted externally by nearby contracting striated mucles. These differences in structure and mechanism of secretion release are taken as evidence that although they are homologous, the two types of glands, Duvernoy's and venom glands, are functionally distinct.
The vacuolar cells of Oscarella lobularis (Porifera, Demospongiae): Ulatrastructural organization, origin, and function
Authors: Gaino Elda , Burlando Bruno , Buffa Paola
Published: February 2005

This work is concerned with the ultrastructural organization and some histochemical features of the vacuolar cells of the demosponge Oscarella lobularis. Vacuolar cells are characterized by large clear vacuoles containing an aqueous fluid. They are commonly found in the mesohyl of this sponge and tend to constitute a sort of parenchyma in the choanosome. Mobile cells of the mesohyl appear to differetiate into vacuolar cells through the progressive formation of wide cytoplasmic lacunae. We have identified four types of cells showing progressive transformation toward the vacuolar cell type. Precursors (types 1–4) of the vacuolar cells probably derive from endopinacocytes, since they share several histochemical and ultrastructural characteristics with them. Our data support the notion that vacuolar cells are involved in the synthesis of collagen, act as a mechanical support of the sponge body, and are eventually extruded from the sponge through the canals of the aquiferous system.
Comparative studies on the histology of the ovotestis in Hypselodoris tricolor and Godiva banyulensis (Gastropoda, Opisthobranchia), with special reference to yolk formation
Authors: Medina A. , Garcia J. C. , Moreno F. J. , Lopez‐Campos J. L.
Published: February 2005

The histology of the ovotestis was studied by light and electron microscopy in two nudibranch gastropod species. While in Hypselodoris tricolor the ovotestis is intimately associated with the digestive gland tissue, the large gonadal mass of Godiva banyulensis is placed freely in the haemocoele. This fact results in great histological differences between both species.

As is common among Mollusca, the immature yolk granule in Hypselodoris and Godiva presumably originates from membrane‐rich cytoplasmic inclusions, which we have termed dense multivesicular bodies. Such inclusions consist of an outer membrane enclosing membrane remnants and a granular, electron‐dense material. These elements are accumulated and mixed in the center of the dense multivesicular body and could be actually transformed into the paracrystalline core of the immature yolk granule, the cortex of which is made up of part of the central accumulation materials that have not spread into the crystal. During vitellogenesis, some mitochondria are subjected to a process of transformation affecting mainly their inner membrane (including mitochondrial cristae) and matrix. However, the conversion of modified mitochondria into yolk precursors, as reported for other gastropod species, could not be determined with absolute certainty on the basis of our observations on static material.

The mature yolk granule consists of a central paracrystalline core, similar in structure to that of the immature yolk granule, and a peripheral membranous cortex, which seems to spread centripetally, thus permitting the crystal to grow. The cortical material consumed in synthesizing the central core appears to be restored by addition of degenerative mitochondria to the yolk granule surface.
The rete mirabile cranica in the genus Mobula: A comparative study
Authors: Schweitzer Jeff , Notarbartolo‐Di‐Sciara Giuseppe
Published: February 2005

Devil rays (Mobulidae) have large brains that rest in a voluminous chondrocranium almost completely filled by a rete mirabile cranica (RMC). The RMC is a massive arterial network grossly divisible into a “caudal RMC” supplying blood to the brain, and an expanded, more complex “precerebral RMC” nested within the large cranial cavity rostral to the telencephalon.

Both the caudal and precerebral retia originate from the posterior portion of the profundae cerebri arteries, which lie ventral to the brain and form the sides of a vascular triangle, the base of which is anterior and formed by the joining of the internal carotids; the vertex is posterior and median, corresponding to the anterior extreme of the spinalis impar artery. Vessels of the caudal RMC branch posteriorly from the profundae cerebri and course over and into the brain. Vessels branching more anteriorly course rostrally to form the precerebral RMC, which takes the shape of the cranial cavity and completely envelops the olfactory peduncles. Large retial arteries (1‐mm diameter) branch and taper to about 50–150 μm, forming a system of small arteries or arterioles. Many give rise to a mesh of tertiary vessels (precapillary arterioles or capillaries, ca. 20–50 μm in diameter), which, along with arterioles, are embedded in the adventitia of these arteries, with which they communicate by numerous anastomoses. Although the function of the RMC remains enigmatic, its complexity and fine structure are suggestive, and hypotheses of its role are discussed.
The ultrastructure of the morula cells of Eupentacta quinquesemita (Echinodermata: Holothuroidea) and their role in the maintenance of the extracellular matrix
Authors: Byrne Maria
Published: February 2005

The ultrastructure of the morula cells of Eupentacta quinquesemita and the distribution of these cells in the dermal connective tissue are described. Morula cells are abundant in the dermis and appear to function in the maintenance of the extracellular matrix (ECM) as a source of ground substance material. The synthetic activity of these cells is described in detail. Morula cells are filled with large secretory vesicles containing three electrondense materials which are derived from rough endoplasmic reticulum and Golgi activity. The synthetic product of these cells contains glycosaminoglycans and is secreted into the ECM by degranulation. The ultrastructural and histochemical similarity of the degranulation product to the ECM ground substance suggests that they are comprised of the same material. Morula cells appear to function primarily in connective tissues where ground substance predominates. The cells often contain secretory vesicles at various stages of formation, all of which eventually mature and degranulate. The synthetic pathway of the morula cells appears to result ultimately in the complete disruption and death of the cells. The function of morula cells in the holothuroid ECM is discussed, and the synthetic activity of the cells is compared with that of other secretory cells.
Fine structure of the photosensitive iris of the toad, Bufo marinus
Authors: Rubin L. , Eller P. , Nolte J.
Published: February 2005

The iris of the toad Bufo marinus is directly photosensitive and will constrict in response to light striking only the iris. This is true even when the iris is isolated from the rest of the eye, and therefore from reflex neuronal influences initiated in the retina. This autonomous response is probably mediated by the sphincter pupillae muscle, since no specialized photoreceptors are present in the iris, nor does the sphincter exhibit any specializations likely to subserve a purely photoreceptive function. The photosensitive sphincter appears typical of smooth muscle and, like mammalian sphincters, possesses many intercellular junctions. The iris possesses a well‐developed neuronal plexus with fibers projecting into the sphincter muscle layer. Nerve terminals contain small, agranular (30–70nm) and large, dense‐cored (80–120nm) vesicles. No consistent postsynaptic specializations are seen on any cells of the iris, including the cells of the sphincter muscle. The anterior pigment epithelial cells of the iris appear specialized and resemble the myoepithelial dilator muscle described by Kelly and Arnold ('72) for the iris of rats.
Morphometric estimates of the surface areas of the tracheal and cuticular systems in Peripatus acacioi marcus and marcus (Onychophora)
Authors: Bicudo José Eduardo Pereira Wilken
Published: February 2005

The surface areas of the tracheal and cuticular systems of Peripatus acacioi individuals of different body weights were determined by morphometric analysis. The results demonstrate that both surfaces increase with body weight, although the observed increase in the surface area of the tracheal system appears to be at a greater rate. The slopes of the two regression lines obtained are statistically different. It is therefore suggested that the preferential route for water loss in P. acacioi is related to the size of the animals, i.e., smaller onychophorans would lose water mainly through the cuticle, while larger ones would lose water through the respiratory surfaces.
Embryonic development of Bithynia tentaculata L. (Prosobranchia, Gastropoda). I. Cleavage
Authors: Van Dam W. I.
Published: February 2005

The cell‐lineage of Bithynia tentaculata L. has been studied through the formation of the fourth quartet of micromeres, i.e., the 81‐cell stage. Up to the 28‐cell stage, the cleavage pattern is radially symmetrical, and the divisions take place synchronously in the quadrants. Bilateral symmetry is established by the formation of the mesentoblast 4d at the future dorsal side. A resting stage preceding the formation of 4d is lacking. The mesentoblast 4d is formed earlier than the other fourth quartet cells, and it divides twice before 4a‐4c are formed. Bilateral symmetry in the molluscan cross becomes apparent by different divisions of the tipcell and the basal cell in the dorsal arm. Dorsoventrality is progressively corroborated by the divisions in the second and third quartets of micromeres, which take a different course in the A and B quadrants on the one side and in the C and D quadrants on the other side.
Pigment epithelial ensheathment and phagocytosis of rod tips in the retina of Rana catesbeiana
Authors: Tsukamoto Yoshihiko
Published: February 2005

Two modes of shedding of rod disc membranes were observed by electron microscopy in bullfrog retinas illuminated for various periods from 10 min to 2 hr. One mode is “autonomous shedding” whereby rods shed disc packets directly into the subretinal space. Most of the discarded disc packets are subsequently brought into contact with villous apical processes of pigment epithelial (PE) cells and are ultimately engulfed by these cells. When some of the shed disc membranes remain in the subretinal space, it appears that these remanants may be phagocytized by ameboid phagocytes. The other mode is “cooperative shedding” whereby rods shed disc packets with the participation of pigment epithelial ensheathment. Shedding of a disc packet from a rod tip, and enclosing of the rod tip by a broad, sleeve‐like apical process of a PE cell, take place simultaneously. The separated disc packets may be immediately engulfed by the PE cells without risk of failure. Both villous and sleeve‐like types of apical processes of PE cells in the bullfrog lack pigment granules, in contrast to the finger‐like apical processes that do contain pigment granules. Villous and sleeve‐like apical processes that do contain pigment granules. Villous and sleeve‐like processes therefore probably belong to the same category as the leaf‐like apical processes of PE cells in mammalian retinas.
Vascularization of a lobster muscle
Authors: Govind C. K. , Guchardi John
Published: February 2005

The vascularization of the distal accessory flexor muscle (DAFM) in the walking legs of the lobster, Homarus americanus, was examined with dye injection and electron microscopy. Vascularization of this flat, thin DAFM is via two vessels, one supplying the tendinal region of the muscle and the other the exoskeletal region. The vessels that originate from the single major limb vessel, subdivide extensively over the DAFM and form a profuse network that has hitherto gone unnoticed. The degree of vascularization of individual fibers was determined by periodic sampling along its length with thin‐section electron microscopy. At each and every sampling station, individual fibers had several (seven to eight), small‐diameter (4 μm) blood vessels in their cross‐sectional profile. In contrast, nerve terminals of the excitor and inhibitor axon were rarely encountered. This high degree of vascularization was found amongst fibers that are from different regions of the DAFM and differ in the performance of their excitatory synapse but are similar in their structural and contractile properties.
Development of extracellular matrix in chick paravertebral sympathetic ganglia
Authors: Luckenbill‐Edds Louise
Published: February 2005

Alcian blue staining coupled with enzyme digestion or critical electrolyte staining revealed differences in the development of extracellular matrix (ECM) within sympathetic ganglia compared with the surrounding capsule. On day 5 of chick development (Hamburger‐Hamilton stage 26) only hyaluronic acid (HA) could be detected in the ECM surrounding condensing primary ganglia. By day 7 (st 30) the ganglionic capsule contained HA, as well as sulfated glycosaminoglycans (GAGs), and this pattern continued into the adult stage. During the later stages of embryonic life (st 41–45) satellite cells appear, showing fine structural characteristics that point to their role in the secretion of intraganglionic ECM. Only during these stages could ECM be detected histochemically within ganglia, the same stages (days 15–19) when routine electron microscopic methods reveal collagen fibrils embedded in a granular ground substance. Thus, the intranganglionic environment appears as a separate compartment free of detectable amounts of GAG until late embryonic stages when ECM is secreted around satellite cells. This developmental pattern could represent a role of ECM in the histological stabilization of ganglia during the late stages of differentiation, since the appearance of intraganglionic ECM is correlated with the appearance of small dense‐cored vesicles characteristic of adult neurons. The developmental pattern of ECM in differentiating sympathetic ganglia is compared with that of other tissues that undergo condensation and morphogenesis.
Fine structure of spermatophores of some Oribatid mites (Acari, Arachnida)
Authors: Kümmel Georg , Dobner Christa
Published: February 2005

The ultrastructure of spermatophores was studied in seven species of Oribatei. Each spermatophore is composed of a head and a stalk which is attached to the substratum. The spherical head consists of two distinct portions: (1) the sperm package; and (2) the head matrix. Position and structure of the sperm package are described in the different species, as well as the various structures in the head matrix. The sperm package contains sperm embedded in secretory products. The most characteristic feature of the sperm is an electron‐dense chromatin body. Mitochondria lie adjacent to it or are partly or completely incorporated into the chromatin body. The cytoplasmic surface of the plasma membrane regularly bears an electron‐dense layer; the plasma membrane is covered by a secretory sheath. The spermatophores of the Oribatei are structurally complicated and not uniform. The possible role of the spermatophore's structural elements is discussed and an attempt is made to evaluate characteristic features taxonomically.
Ultrastructure and function of the circulatory organs of Leiobunum limbatum and two other species of harvestmen (arachnida: Opiliones)
Authors: Dannhorn D. R. , Seitz K. A.
Published: February 2005

The ultrastructure of the circulatory organs of Leiobunum limbatum, Mitopus morio, and Rilaena triangularis (Arachnida: Opiliones) has been investigated. We studied the organization of the heart, the myocardial contractile elements, its tubular system, organelles, and cell‐junctions. The epicardium exhibits a large number of longitudinally arranged microtubules and is attached to the myocardium by special membrane complexes. Because of these structures, the epicardium is interpreted as the elastic antagonist to the heart muscle. At both ends of the heart the epicardium continues into a nonbranching aorta. Consequently the ultrastructure of the aortal wall, containing numerous microtubules, is similar to the ultrastructure of the epicardium. At the posterior end of the heart is a muscular slit‐valve, while at the anterior end is a lobe‐valve that lacks contractile elements. The heart is innervated by a dorsal ganglion. It covers the entire length of the heart and contains neural and glial cells. Two different types of neurosecretory granules and both electron‐dense and electron‐lucent synaptic vesicles are described.
Native variant limb skeletal patterns in the red‐backed salamander, Plethodon cinereus, are not regenerated
Authors: Dinsmore Charles E. , Hanken James
Published: February 2005

Species of the salamander genus Plethodon have a characteristically uniform morphology. Morphological conservatism at the level of interspecific comparisons, however, is not always reflected within species. Perhaps the most extreme example of intraspecific variation is the recent description of extensive variability in limb‐skeletal patterning both within and between populations of the widespread species P. cinereus. We utilized limb regeneration following experimental amputation as a tool (1) to examine whether naturally occurring variant skeletal patterns result from limb loss and regeneration in nature, and (2) to assay the intrinsic (i.e., genetic) component of between‐individual variation in mesopodial patterning. We observed the following. First, regenerate patterns are strikingly different from native patterns: interelement fusions in regenerates are typically between proximodistally adjacent cartilages, whereas interelement fusions in native variant limbs occur exclusively between laterally adjacent cartilages. Fusions also are over ten times more frequent in regenerates than in native limbs. Second, there is no strong correlation between native limb pattern (typical vs. variant) and the regenerate pattern. We conclude that variability in field‐collected P. cinereus reflects extensive intrapopulation variation in limb‐skeletal patterning during original limb development, rather than regeneration in nature, and that limb regeneration analysis provides no evidence of a strong genetic component to between‐individual variation. Finally, unusual mesopodial patterns produced during limb regeneration may be related to the mechanical factors impinging on the regenerating limb in this terrestrial species.
The fine structure of the dorsal column nucleus and the nucleus of bischoff of the python (Python reticulatus)
Authors: Tan C. K. , Gopalakrishnakone P.
Published: February 2005

Three types of neuronal perikaryal profiles were identified in the dorsal column nucleus and the nucleus of Bischoff of the python (Python reticulatus). Type I neuronal profiles are large (diameters 12–20 μm) with a deeply indented uncleus. The cisterns of rough endoplasmic reticulum (rER) are mostly randomly dispersed. Axosomatic synapses are few. Type II neuronal profiles (9–11 μm) have a smooth, round, or slightly oval nucleus. Several small stacks of rER are present. Type III neuronal profiles (8–10 μm) have little cytoplasm. The nuclear margin is irregular but not deeply infolded. The rER usually consists of a single long perinuclear ribosome‐studded cistern. Two types of astrocytic profiles have been identified. Both types contain abundant filaments. Type I astrocytes are large cells, and the nucleus is very irregular in shape. Type II astrocytes are smaller and are found among the myelinated axons in the dorsal funiculus. Two classes of axon terminals have been identified. One class contains round synaptic vesicles (R profiles) and the other flattened vesicles (F profiles). Some R profiles are small (SR profiles), others are large (LR profiles). Some R profiles also contain a few large, dense‐cored vesicles. The R and F profiles establish axodendritic and axoaxonal synapses, some of which are located in the synaptic glomeruli and others in the extraglomerular neuropil. In most of the axoaxonal synapses, the presynaptic element is an F profile and the post synaptic element an LR profile. Occasionally, LR profiles are presynaptic to F profiles.

The findings in the python are compared with those of the dorsal column nuclei of the rat, cat, and monkey.
Study of atresia in the ovary during the annual reproductive cycle and nesting cycle of the pied myna
Authors: Gupta S. K. , Maiti B. R.
Published: February 2005

Atretic follicles of the ovary of the Indian pied myna (Sturnus contra contra) were studied in birds collected each month throughout the year. Histological examination included histochemical techniques for 3β‐hydroxy‐steroid dehydrogenase (3β‐HSDH) and for lipids. Atretic follicles were mainly of two types: nonbursting (lipoidal and cystic) and bursting (Types I–VI). Nonbursting atresia was observed in the smaller follicles (< 500 μm in diameter), whereas larger follicles (> 500 μm in diameter, viz., small developing, large developing, and yolky follicles) showed exclusively a bursting type of atresia. Sudanophilic lipid was found in both types (lipoidal and cystic) of nonbursting atresia, but was present only in early stages of bursting atresia. Activity of 3β‐HSDH was absent in nonbursting atresia, but present in early stage of bursting atresia. Nonbursting atresia was common throughout the year and higher in frequency than the bursting type. Bursting atresia was common during March through May and attained its peak level during the nesting cycle.
Evolution of the female cuticular organ in the asellota (crustacea, isopoda)
Authors: Wilson George D. F.
Published: February 2005

In an effort to understand the variation and probable origin of a female copulatory organ found in isopods of the asellote superfamily Janiroidea, the morphology of female reproductive structures among the Asellota was surveyed. Examples of four asellote superfamilies were studied using whole mount staining after potassium‐hydroxide maceration or clearing with lactic acid. In contradiction to previous conclusions, the cuticular organ is shown to occur in the more primitive Asellota, although the position of its opening varies considerably. In the genera Asellus, and Stenetrium, Munna, and Santia, the cuticular organ originates adjacent to the oopore, and in the remaining janiroidean isopods, it is placed dorsally and usually anteriorly. This information permits a simple hypothesis explaining the origin of the cuticular organ: it was present in the proximate ancestor of the Asellota and evolved to the janiroidean condition by anterodorsal migration.
Morphological studies of the spinal cord in tetraodontiformes fishes
Authors: Uehara Masato , Ueshima Toshihiko
Published: February 2005

The spinal cord of two tetraodontiform fishes, the Japanese file fish (Navodon modestus) and the panther puffer (Takifugu pardalis), are unusual among vertebrates in having a markedly abbreviated spinal cord with a long and flattened filum terminale. Only the rostral short part of the cord of both species is cylindrical; the greater part of the cord is markedly flat. The majority of the spinal nerve roots leave the short cylindrical part. The flattened part of the cord contains the central canal, myelinated nerve fibers, and a few motoneurons surrounding the cauda equina, and it is histologically similar to the filum terminale of amphibians and mammals. The spinal cords of other teleosts, the sun‐fish and angler, also are abbreviated and possess a filum terminale and cauda equina. These orders possess an enormous head and short trunk. However, the correlation between this body form and an abbreviated cord is not causal, since the tetraodontiform species described here show ordinary body proportions. The spinal cord may be abbreviated in tetraodontiform fishes in general.
Contraction properties and motor nucleus morphology of the two heads of the cat flexor carpi ulnaris muscle
Authors: Glenn Loyd L. , Whitney Jeffrey F.
Published: February 2005

Previous studies have examined the isometric contraction properties of the two heads of the cat flexor carpi ulnaris acting as a single unit. In this study, the contraction properties and fiber architecture of each head of the flexor carpi ulnaris were determined separately and related to previous reports on the histochemical characteristics of this muscle. The morphology of retrograde‐labeled motor nuclei for the two heads of the muscle was also examined. The humeral head had a significantly longer contraction time (48 msec) than the ulnar head (36 msec) as well as a significantly lower tetanic fusion frequency (28 Hz vs. 35 Hz). The maximum tetanic tension per gram of muscle tissue was 71% greater in the ulnar head. Motoneurons of the flexor carpi ulnaris formed a column 12 mm long and 0.5 mm wide in the center of the ventral grey in spinal segments C8 and T1. The ulnar head had α‐motoneurons with greater soma diameters than those in the humeral head. The smaller soma diameter, slower contraction time, and weaker contraction in the humeral head correlate with the preponderance of oxidative‐metabolic muscle fiber types found in the humeral head by other workers. These correlations suggest that the humeral head plays a major role in maintaining a sustained antigravity tension that prevents the wrist from buckling during standing.
Morphology, distribution, and density of sensory receptors in the glabrous skin of the cat rhinarium
Authors: Abrahams V. C. , Hodgins M. , Downey D.
Published: February 2005

The sensory organization of the cat rhinarium has been investigated. Individual rete pegs were found to contain a triad of receptors comprising (a) free nerve endings ascending in the peg to terminate in close proximity to the skin surface, (b) a basally situated layer of Merkel corpuscles, and (c) an abundance of encapsulated receptors lying at the base and to one side of the rete peg. Neither the Merkel corpuscles nor the encapsulated receptors were evenly distributed. Merkel corpuscles were more abundant dorsally; ventrally they were fewer and asymmetrically arranged within individual rete pegs. The encapsulated corpuscles were more evenly distributed, but dorsally they were consistently present as encapsulated clusters of up to nine corpuscles.
An anatomical and functional analysis of cat biceps femoris and semitendinosus muscles
Authors: English Arthur W. M. , Weeks Ophelia I.
Published: February 2005

The anatomy, architecture, and innervation patterns of the hamstring muscles, biceps femoris, and semitendinosus were examined in adult cats using microdissection and glycogen‐depletion techniques. The biceps femoris muscle consists of two heads. The anterior head, which attaches mainly to the femur, is divided into two parts by the extramuscular branches of its nerve. The posterior head is innervated by a single nerve. Semitendinosus is composed of two heads, one proximal and one distal to a tendonous inscription, each of which is separately innervated. The extramuscular branches of the nerves to these hamstring muscles thus partition them into innervation subvolumes termed parts. The available evidence suggests that each of the parts of these muscles so innervated is not equivalent to the collections of single motor units that have been described for ankle extensors as neuromuscular compartments. It is quite likely that each of the parts of the hamstring muscles may contain more than one neuromuscular compartment. Using chronically implanted EMG electrodes, the activation patterns of different parts of the hamstring muscles were analyzed during locomotion. The anterior and middle parts of biceps femoris are active during the early stance phase, probably producing hip extensor torque. The posterior part of biceps femoris and semitendinosus act most consistently as flexors, during the early swing phase, but also may function in synergy with hip, knee, and ankle joint extensors near the time of foot placement. Greater variability is found in the activity patterns of posterior biceps femoris and semitendinosus with respect to the kinematics of the step cycle than is observed for anterior and middle biceps femoris. It is suggested that this variation may reflect a larger role of sensory feedback in shaping the timing of activity in posterior biceps femoris and semitendinosus than in ‘monarticular’ muscles.
Nerve terminals and synapses in the cardiac ganglion of the adult lobster Homarus americanus
Authors: Morganelli Peter M. , Sherman R. G.
Published: February 2005

The cardiac ganglion in the lobster Homarus americanus was examined with a transmission electron microscope. Nerve terminals often existed in large aggregations surrounded by glial and connective tissue elements. Axo‐axonic and axo‐dendritic synapses were present. Six ultrastructurally different types of nerve terminal, each containing an abundance of vesicles, were distinguished: three formed discrete chemical synapses as indicated by typical release site morphology; three did not. The latter appear to be neurosecretory axon terminals of extrinsic neurons. More than one morphologically distinct type of synaptic vesicle occurred commonly in a given terminal, suggesting the presence of coexisting neurotransmitters and/or neuroregulatory factors. Symmetrical chemical synapses and electrotonic junctions between axons were present.
The cytoarchitecture of the torus semicircularis in the teleost Barbus meridionalis
Authors: Cuadrado M. I.
Published: February 2005

The torus semicircularis of Barbus meridionalis is composed of two nuclei, the nucleus centralis and nucleus lateralis. Its cytoarchitecture was studied in sections stained by Nissl and Golgi‐Colonnier techniques. In the nucleus lateralis two portions were identified: the ‘pars lateralis’ and the ‘pars medialis.’ Cytoarchitecturally, both portions are identical. They exhibit a layered structure in which there is an alternation of cell‐poor and cell‐rich laminae designated as: (1) the subependymal layer; (2) the layer of small cells; (3) the fibrillar layer; and (4) the layer of disperse cells. The subependymal layer consists of fine fibers and some small rounded‐ovoid cells whose dendritic prolongations course horizontally or ventrally. The second layer has small, densely‐packed cells with rounded‐ovoid and triangular somata and a main dendritic trunk that courses ventrally. The third layer contains dendritic fields of the cells of layer two and of cells from layer four. The fourth layer is composed of fusiform neurons with two dendritic trunks of equal thickness, rounded‐ovoid neurons with one or two main dendritic trunks and multipolar triangular stellate neurons with equal dendritic trunks.

The nucleus centralis comprises a fibrillar cortex with a structure identical to that of the subependymal layer. There is also a cellular region with the same cell types as those found in the nucleus lateralis. These two nuclei thus compose the torus semicircularis of the barbel. They exhibit the same cytological characteristics and both are differentiated by their cytoarchitectural and functional orders.
Morphology of chemosensory organs required for feeding in the leechhirudo medicinalis
Authors: Elliott Ellen J.
Published: February 2005

Sensilla that line the upper edge of the lip in the leechHirudo medicinalisand that contain chemoreceptors required for feeding were examined in the scanning and transmission electron microscopes. The sensilla include two size‐classes of ciliated button‐like mounds—one about 35 μm in diameter and another about 10 μm in diameter. The larger sensilla are at the center of unpigmented patches of skin which are visible in the light microscope, while the smaller sensilla have not been previously described as distinct structures. Electron microscopy, though not light microscopy, shows that the lip sensilla differ markedly from the segmental sensilla of the leech, which have been shown to mediate mechanoreception and photoreception. In particular, the chemosensory lip sensilla contain multiciliated cells with cilia of a uniform length, whereas the segmental sensilla contain uniciliated cells with long, whip‐like cilia, as well as multiciliated cells with short, stiff cilia. Thus, the two types of sensilla differ morphologically as well as functionally. In addition to the ciliated sensilla along the upper lip, structures consisting of a short, club‐like process surrounded by granular material were observed inside the mouth. These structures may also be chemosensory organs.