bluuebunny/crossref_metadata_2025 huggingface dataset:
The fine structure of early tooth formation in an lguanid lizard, Anolis carolinensis
Authors: Piesco Nicholas P. , Kallenbach Ernst
Published: February 2005

Cytodifferentiation and hard tissue formation were studied in Anolis to collect information regarding the phylogenetic history of enamel and the functional significance of the events seen in the mammalian tooth during differentiation. The differentiation of the ameloblasts of Anolis, like that of mammals, shows two phases: In the early phase, the cells are short and rich in free ribosomes, in the late phase the cells elongate, develop an extensive rough endoplasmic reticulum, and the Golgi apparatus moves into that part of the cell next to the basal lamina (the cell apex). The early epithelial‐mesenchymal interface resembles that of mammals, suggesting that early mechanisms of induction and epithelial‐mesenchymal interaction are similar in Anolis and in mammals.

Preameloblast processes and preameloblast‐preodontoblast contacts in Anolis are rudimentary compared to those of mammals. While in mammals the preameloblast processes shape the future DEJ (dentin‐enamel junction), their involvement in establishing the shape of the DEJ of Anolis is questionable. We suggest that the great development of preameloblast‐preodontoblast contacts in mammals may simply increase the efficiency of inductive interactions between these cell types.
The cardiovascular chromaffin cell system of the southern hemisphere lamprey, Geotria australis gray
Authors: Epple A. , Hilliard R. W. , Potter I. C.
Published: February 2005

This study demonstrates that the silver technique of Grimelius (Acta Soc. Med. Ups. 73:243–270, 68) is ideally suited for the study of cardiovascular chromaffin cells in lampreys. This method showed that in the Southern Hemisphere lamprey, Geotria australis, the distribution of chromaffin cells differs from that described for holarctic species. In G. australis, the chromaffin cells are found mainly in the sinus venosus, atrium, and nearby regions of the cardinal and jugular veins, and they are absent from the ventricle and conus arteriosus. The location and discreteness of the large accumulation of chromaffin cells in the lateral wall of the right posterior cardinal vein of adults resemble those of the precardiac axillary bodies of elasmobranchs. Chromaffin cells become more abundant during metamorphosis. The possible phylogenetic and functional significance of lamprey chromaffin cells is briefly discussed.
Aquatic prey capture in ambystomatid salamanders: Patterns of variation in muscle activity
Authors: Shaffer H. Bradley , Lauder G. V.
Published: February 2005

Functional morphologists commonly study feeding behavior in vertebrates by recording electrical activity from head muscles during unrestrained prey capture. Rarely are experiments designed to permit a partitioning of variation in muscle electrical activity patterns. Analysis of muscle activity during aquatic prey capture in two morphologivally distinct species of salamanders, Ambystoma dumerilii and A. mexicanum, is conducted to assess variation at four levels: between species, among individuals within species, among experiments conducted on different days, and among feedings. The results show that (1) mean correlations among the 11 electromyographic variables measured for each feeding are low and vary considerably among individuals, (2) many of the variables show significant differences among experimental days, (3) only one variable, the difference in timing between the depressor mandibulae and sternohyoideus muscles, showed significant variation between species, and (4) seven of the 11 variables showed significant variation among individuals within species. Overall, the variation between feedings (trials) was high, and there was some variation between days on which the experiments were conducted. Neither electrode position within the muscle nor satiation contributed to the high trial variance. The results suggest that functional analyses of feeding behavior should include an assessment of variation due to individuals, days, and trials, because the amount of variation at these levels may render differences between species nonsignificant.
Use of the term “Trophoblast” for tissues in therian mammals
Authors: Lillegraven Jason A.
Published: February 2005

Use of the term “trophoblast” in descriptions of therian (marsupial and eutherian) mammals has caused confusion because of misinterpretations of blastular homologies and because of imprecise application in functional versus ontogenetic‐phylogenetic senses. Marsupials follow the plan of early development characteristic of noneutheian amniotes. Eutherians, in contrast, are unique in the early determination of presumptive embryonic versus extraembryonic cells through formation of inner cell mass versus trophoblastic (or trophectodermal) tissues, respectively. No cellular unit of the eutherian blastula is recognizable unequivocally as the homologue of a specific part of the protodermal marsupial blastula; progressive deletion of innovative but phylogenetically older ontogenetic steps probably figured importantly in the evolution of eutherian early embryogenesis. Because of marked differences in mode of formation and in cellular fates, homology of the blastocoel between marsupials and eutherians is questioned. It is suggested that use of the term “trophoblast” (1) be restricted to eutherians in discussions of ontogenesis or phylogenesis, and (2) be deemphasized in the functional sense (i.e., fetal‐maternal exchanges) for marsupials, in favor of the more appropriate tissue terms of “choriovitelline” and “chorioallantoic” membranes. Integral to the origin of the eutherian style of embryogenesis was the evolution during Cretaceous time of neomorphic, extraembryonic tissues (i.e., trophoblast) having physiological properties that allowed the unique combination of (1) intimate apposition of fetal and maternal tissues and circulatory systems, along with (2) sustained, active morphogenesis. Marsupials have not achieved such a combination.
Structure and function of the antennae of Euphydryas editha (Lepidoptera: Nymphalidae)
Authors: Odendaal F. J. , Ehrlich P. R. , Thomas F. C.
Published: February 2005

Males of Euphydryas editha (Lepidoptera: Nymphalidae) need their antennae to mate successfully, but females do not. Antennal structure was investigated in the hope of explaining this functional dimorphism, which is opposite to that in other butterflies (e.g., Myers, '68; Grula and Taylor, '80). No external differences between the sexes were observed with electron microscopy. There are four types of antennal sensilla: the spine, which acts mainly as a mechanoreceptor, shallow dish hairs and hidden hairs, which are chemoreceptors, and a whiplike sensillum of uncertain function. The internal morphology of male and female antennae differs in several respects which may relate to functional differences. The mating systems of butterflies are discussed briefly to explain our results and those of others.
Innervation of the early pelvic fin bud of the trout embryo, Salmo gairdneri
Authors: Géraudie Jacqueline
Published: February 2005

Innervation of the early pelvic fin bud in the trout embryo involves four nerves. Electron microscopy discloses axons in the mesodermal mesenchyme and in the epidermis of the bud as early as stage I of the development of the pelvic fins. Sensory axons alone penetrate the epidermis. Unmyelinated axons invade the pelvic fin territory before the bud is obvious on the abdomen. Schwann cells occur in the vicinity of the ventral edge of the myotomes and later in the core of the bud and in subepidermal regions. Consequently, the nerve fibers are present early in the development of the pelvic fin bud of the trout embryo. Although the role of these axons is unknown, it is speculated that they play a role in development. Our results are discussed in the light of data available in the literature dealing with the development of tetrapod appendages.
Structural variability of collagen fibers in the calcareous axial rod of a sea pen
Authors: Franc S. , Ledger P. W. , Garrone R.
Published: February 2005

Previous studies revealed that the organic matrix of the skeletal rod of the sea pen, Veretillum cynomorium, contained about 50% collagenous protein. The present ultrastructural study, based upon conventional staining methods, shows the existence of an abundant, longitudinally arranged nonbanded and fibrillar material separated by a reticular matrix. After incubation with 3H‐proline, labeling is specifically localized on the fibrillar material. Some fibers occasionally display a transverse striation with a period of 11 to 14 nm which can be associated with a chevron striation. Infrequently, some other fibers display a more distinct banding of 55 to 70 nm or even yield a checkerboard pattern. However, a majority of fibers remain without a regular structure comparable to the periodic striations observed in the collagen of other animals. After treatment with 1% PTA in 70% ethanol, all the fibers show a clear banding of 14 nm and some of them possess two types of striations. The same result is obtained on fibers mechanically dissociated and negatively stained. As these methods show a periodic banding pattern on all the fibers, it is likely that all the fibers (striated or not) observed after routine electron microscopy correspond to collagen material. This collagen appears to be both polymorphic and completely new in comparison to that which is characteristic of the mesoglea. The polymorphic aspect is compared to that obtained from vertebrate collagens.
The seminal receptacle and sperm storage in Cochlostoma montanum (Issel) (Gastropoda: Prosobranchia)
Authors: Giusti Folco , Selmi Maria Gloria
Published: February 2005

Females of Cochlostoma montanum (Prosobranchia, Cochlostomatidae) have a seminal receptacle which is not a separate diverticulum of the oviduct. The seminal receptacle derives from a differentiated portion of the renal oviduct which has an inner wall composed of only one layer of cells. These cells are of two different types, both actively involved in secretory activity. One type is represented by goblet cells filled with large vesicles containing an electron‐dense, homogeneous, and partially paracrystalline material. This material is expelled into the lumen through macro‐apocrine or holocrine types of secretion. The other type is represented by ciliated cells rich in small vesicles containing granular material. Probably neither kind of secretion has a nutritive function; rather they serve as matrix for spermatozoa that immobilize them and prevent their expulsion from the receptacular portion of the oviduct. Spermatozoa are inserted in invaginations of the apex of both these epithelial cells. The sperm plasma membrane covering the acrosome forms long digitations which expand toward the corresponding invaginations of the receptaculum cells. This type of adhesion is a novelty for Mollusca and resembles that in seminal receptacles of some Annelida.
Histochemical and biochemical studies of the hepatopancreas peroxidase of the freshwater crayfish, Cambarus robustus
Authors: Merrill D. P. , Reife R. A. , Tiersch T. R. , Austin R. S.
Published: February 2005

Crayfish are among the few invertebrate species reported to possess endogenous peroxidase activity. The enzyme is found within the hepatopancreas, the principal digestive and absorptive organ of the crustacean body. Cambarus robustus, a species found in abundance in the streams of western New York, was used in this study. Homogenates of 18 hepatopancreases were assayed for peroxidase activity using guaiacol as the substrate. Although present in all organs, peroxidase activity displayed a greater than 50‐fold difference between the two extremes (0.05–;2.72 units/mg protein). Histochemical examination using diaminobenzidine revealed peroxidase activity within a line of cells extending along the distal two‐thirds of the lengths of all hepatopancreatic tubules. The cells function to synthesize the enzyme, sequester it within vacuoles of increasing size, and eventually secrete it into the tubule lumen. Since the tubule is constantly renewed by distal mitotic activity and concomitant proximal exfoliation, this histochemical technique permits not only the examination of the ontogeny of this peroxidase‐positive cell line, but also offers additional insight into the mechanism of hepatopancreatic tubule renewal.
Ameloblastic secretion and calcification of the enamel layer in shark teeth
Authors: Kemp Norman E.
Published: February 2005

Tooth primordia at early stages of mineralization in the sharks Negaprion brevirostris and Triaenodon obesus were examined electron microscopically for evidence of ameloblastic secretion and its relation to calcification of the enamel (enameloid) layer. Ameloblasts are polarized with most of the mitochondria and all of the Golgi dictyosomes localized in the infranuclear end of the cell toward the squamous outer cells of the enamel organ. Endoplasmic reticular membranes and ribosomes are also abundant in this region. Ameloblastic vesicles bud from the Golgi membranes and evidently move through perinuclear and supranuclear zones to accumulate at the apical end of the cell. The vesicles secrete their contents through the apical cell membrane in merocrine fashion and appear to contribute precursor material both for the basal lamina and the enameline matrix. The enamel layer consists of four zones: a juxta‐laminar zone containing newly polymerized mineralizing fibrils (tubules); a pre‐enamel zone of assembly of matrix constituents; palisadal zones of mineralizing fibrils (tubules); and interpalisadal zones containing granular amorphous matrix, fine unit fibrils, and giant cross‐banded fibers with a periodicity of 17.9 nm. It seems probable that amorphous, non‐mineralizing fibrillar and mineralizing fibrillar constituents of the matrix are all products of ameloblastic secretion. Odontoblastic processes are tightly embedded in the matrix of the palisadal zones and do not appear to be secretory at the stages investigated. The shark tooth enamel layer is considered homologous with that of other vertebrates with respect to origin of its mineralizing fibrils from the inner dental epithelium. The term enameloid is appropriate to connote the histological distinction that the enamel layer contains odontoblastic processes but should not signify that shark tooth enamel is a modified type of dentine. How amelogenins and/or enamelins secreted by ameloblasts in the shark and other vertebrates are related to nucleation and growth of enamel crystallites is still not known.
The trophotaenial placenta of a viviparous goodeid fish. II. Ultrastructure of trophotaeniae, the embryonic component
Authors: Lombardi Julian , Wourms John P.
Published: February 2005

Embryos of the viviparous goodeid fish Ameca spendens develop within the ovarian lumen, where they establish a placental association with the maternal organism and undergo a 15,000% increase in embryonic dry weight. The placenta consists of an embryonic component, the trophotaeniae, and a maternal component, the internal ovarian epithelium. Examination with light microscopy and with transmission and scanning electron microscopy reveals that trophotaeniae of A. splendens are extraembryonic membranes consisting of five ribbon‐like processes originating from a tube‐like mass of tissue that extends outward from the perianal region of developing embryos. There are two sets of lateral processes and a longer single median process. Trophotaeniae possess an outer epithelium that surrounds a highly vascularized core of loose connective tissue. Epithelial cells possess apical microvilli and a pronounced endocytotic apparatus. Cells of the trophotaenial epithelium are either tightly apposed along their lateral margins or separated by enlarged intercellular spaces. Regions of the trophotaenial epithelium possessing enlarged intercellular spaces are distributed in patches. The trophotaenial epithelium is continuous with the embryonic hindgut epithelium and is considered to be derived from it. Comparison of trophotaenial morphology in A. splendens with that reported in Xenotoca eiseni reveals differences in histological organization. The former possess unsheathed trophotaeniae, whereas the latter are sheathed. We postulate that the apposition of trophotaenial epithelium to the internal ovarian epithelium constitutes a placental association equivalent to a noninvasive, epithelioform of an inverted yolk sac placenta. Structural relationships of embryonic and maternal tissues of the trophotaenial placenta are discussed in relation to maternal‐embryonic nutrient transfer processes.
Functional organization of battery cell complexes in tentacles of Hydra attenuata
Authors: Hufnagel L. A. , Kass‐Simon G. , Lyon M. K.
Published: February 2005

Ultrastructural and light microscopic observations on the organization of thick and thin regions of hydra's tentacles, made on serial sections and on whole fixed, plastic‐embedded tentacles, reveal the existence of two levels of anatomical order in the tentacle ectoderm: (1) The battery‐cell complex (BCC), composed of a single epitheliomuscular cell (EMC) and its content of enclosed nematocytes and neurons; and (2) the battery cell complex ring (BCC ring), an arrangement of 4 or more BCCs into larger units organized as rings around the circumference of the tentacle. All EMCs of the distal tentacle appear to contain batteries of nematocytes, and are, therefore, called “battery cells.” Apart from battery cell complexes and migrating nematocytes, there are no other cell types in the tentacle ectoderm. Battery cells are composed of three distinct regions: the cell body, peripheral attenuated extensions and myonemes. Thick tentacle bands are composed of cell bodies, whereas thin bands are made up of attenuated extensions. Myonemes contribute to both thick and thin regions. It was confirmed that each battery cell has several myonemes, which appear to interdigitate with myonemes of other more proximal and distal battery cells, but not with battery cells of the same BCC ring. Nematocytes have several basal processes. Some processes insert between myonemes and contact the mesoglea; other processes insert into cuplike extensions of myonemes, and are connected to myonemal cups by desmosomal junctions. These observations are discussed in relation to mechanical and electrical aspects of tentacular contraction and bending.
Mineral content of the organ of Bellonci in the marine amphipod Gammarus setosus
Authors: Steele V. J. , Oshel P. E.
Published: February 2005

Calcium is demonstrated by energy and wavelength dispersive X‐ray microanalysis to be the major component of the granules that fill the fuselli of the organ of Bellonci in Gammarus setosus. The presence of calcium was confirmed by chelation with EDTA and by other cytochemical techniques. X‐ray microanalysis indicated the simultaneous presence of iron in the region of the fuselli occupied by the calcium granules, but this could not be confirmed by cytochemical means in resin‐embedded tissue by light or transmission electron microscopy.
Muscle system organization in the echinoderms: III. Fine structure of the contractile apparatus of the arm flexor muscles of the comatulids (Antedon mediterranea)
Authors: Carnevali M. Daniela Candia , Saita Abele
Published: February 2005

The crinoid arm muscles consist of obliquely striated fibers with striking differences in function and in ultrastructural features. These fibers can be distinguished mainly on the basis of different myofilament arrangements (A‐ and B‐type patterns) and are variously combined at different levels (proximal, intermediate, and distal portions) of the arm. Some rare smooth fibers (C‐type) are irregularly distributed in the periphery and in the core of the bundle. The characteristic features of the A‐ and B‐type obliquely striated fibers are (1) a continuous and homogeneous structure of the Z line and (2) a very heterogeneous arrangement of myosin filaments which vary widely in size, number, and distribution from section to section. The significance of such an atypical, obliquely striated muscle may be related to the double skeletal system combination (endoskeleton and hydroskeleton) of the crinoid arms.
Secretory cells in the clitellar epithelium of Eisenia foetida (Annelida, Oligochaeta): A histochemical and ultrastructural study
Authors: Morris G. M.
Published: February 2005

Eight secretory cell types are identified in the clitellar epithelium of Eisenia foetida, of which five have been described in detail previously (i.e., the large granular, fine granular, metachromatic, orthochromatic, and small granular proteinacecus cells).

The remaining three secretory cell types are mucus‐producing cells specific to the clitellar epithelium (type 3), cells associated with the chaetal follicles (type 4), and cells that occur exclusively in the tubercula pubertatis (type 5). Type 3 cells secrete a mucus containing neutral and acid mucosubstances. Ultrastructurally, type 3 cells are characterized by membrane‐bound globules 0.4 to 3.7 μm in diameter. The contents of the globules have a finely reticulate appearance. The secretion of type 4 cells contains a collagenlike protein and neutral and sulfated acid mucosubstances. Type 4 cell secretory granules are membrane bound and range in diameter from 0.8 to 1.6 μm. They contain large, electron‐dense, spheroid cores which are surrounded by parallel orientated microfibrils 14 nm in diameter. Type 5 cells give variable responses to the histochemical techniques used in the present study. An elastinlike protein is detected in about half of the type 5 cells and acid and neutral mucosubstances in the remainder. At the ultrastructural level the secretory granules vary in shape from spheroid to polygonal. Their finely, electron‐dense contents exhibit progressive swelling which results in the eventual rupture of the limiting membranes of the granules. The necks of types 3, 4, and 5 cells contain a peripheral ring of microtubles (20 ± 1 nm in diameter).
Placentation in the lizard Gerrhonotus coeruleus with a comparison to the extraembryonic membranes of the oviparous Gerrhonotus multicarinatus (Sauria, Anguidae)
Authors: Stewart James R.
Published: February 2005

Paraffin sections of an ontogenetic series of embryos of the viviparous lizard Gerrhonotus coeruleus and the oviparous congener G. multicarinatus reveal that although general features of the development of the chorioallantoic and yolk sac membranes are similar, differences are evident in the distribution of the chorioallantoic membrane in late stage embryos. An acellular shell membrane surrounds the egg throughout gestation in both species although the thickness of this structure is much reduced in G. coeruleus over that of G. multicarinatus. The initial vascular membrane to contact the shell membrane in both species is a trilaminar omphalopleure (choriovitelline membrane) composed of ectoderm, mesoderm of the area vasculosa, and endoderm. This transitory membrane is replaced by the vascularized chorioallantois as the allantois expands to contact the inner surface of the chorion. Prior to the establishment of the chorioallantois at the embryonic pole, a membrane begins to form within the yolk ventral to the sinus terminalis. This membrane, which becomes vascularized, extends across the entire width of the abembryonic region and isolates a mass of yolk ventral to the yolk mass proper. The outer membrane of the yolk pole is a nonvascular bilaminar omphalopleure (chorionic ectoderm and yolk endoderm). In G. multicarinatus the bilaminar omphalopleure is supported internally by the vascularized allantoic membrane, whereas in G. coeruleus the allantois does not extend beyond the margin of the isolated yolk mass and the bilaminar omphalopleure is supported by the vascularized intravitelline membrane. Both the chorioallantoic placenta (uterine epithelium, chorionic ectoderm and mesoderm, and allantoic mesoderm and endoderm) and the yolk sac placenta at the abembryonic pole (uterine epithelium, chorionic ectoderm, and yolk sac endoderm) persist to the end of gestation in G. coeruleus.
Cellular structure of adipose tissue in birds
Authors: Pond Caroline M. , Mattacks Christine A.
Published: February 2005

In a randomly collected sample of 91 wild and captive birds, in which there is no significant correlation between fatness and body mass, the total number of adipocytes is proportional to (Body Mass)0.68. The adipose tissue of larger birds consists of proportionately fewer adipocytes; therefore, the adipocytes of larger birds are larger, in relation to the fatness of the specimens, than those of the smaller species. The cellularity of the adipose tissue of predominantly carnivorous birds does not differ from that of mainly herbivorous species. The adipocytes in the abdominal cavity and around the thigh are on average 29% larger than those in the superficial and clavicular depots; however, these site‐specific differences were variable and were statistically insignificant in many of the specimens. The size of the adipocyte complement is highly variable even among specimens of a single species and similar body mass, suggesting that in birds the number as well as the volume of adipocytes might increase or decrease as the adipose tissue expands or shrinks.
Scanning electron microscopic study of the male genital tract during its highest and lowest activities in the seasonal reproductive cycle of the soft‐shelled turtle
Authors: Kumar De Tapas , Maiti B. R.
Published: February 2005

The objective of the present investigation was to study by scanning electron microscopy the epithelial surface structures of different segments of the male genital tract (ductuli efferentes, proximal and distal epididymes, and vas deferens) during highest (July) and lowest (January) activity in the annual reproductive cycle of the soft‐shelled turtle. The study has revealed that there are distinct regional differences in the male genital tract. The ductuli efferentes have three types of cells, long‐ciliated, short‐ciliated, and microvilli‐bordered cells. The proximal epididymis has two types of cells, microvilli‐bordered cells and smooth‐surfaced cells; the distal epididymis has only tall, smooth‐surfaced cells. The vas deferens contains both smooth‐surfaced and microvilli‐bordered cells. Cells of the genital tract in July show several differences from comparable cells in January: Ciliated cells of the ductuli efferentes have longer cilia, cells of the proximal epididymis have microvilli distended by secretory materials, and cell apices in the distal epididymis are surmounted by an abundance of huge secretory blebs. There is no discernible change in the vas deferens. The findings suggest that all segments of the male genital tract, except the vas deferens, become active in July and have regressed by January in the annual sexual cycle.
Fine structure and classification of shrimp hemocytes
Authors: Martin Gary G. , Graves Brenda L.
Published: February 2005

The structure of hemocytes from two species of penaeid shrimp was examined by light and electron (TEM) microscopy. Hemocytes from the two species are indistinguishable and are classified as either agranular, small‐granule, or large‐granule hemocytes. Agranular hemocytes are the smallest of the hemocytes, lack granules, compose only 5–10% of the circulating hemocytes, and are nonrefractile when examined by light microscopy. Small‐granule hemocytes are the most abundant type of hemocyte (75% of all hemocytes), appear nonrefractile, and contain a variable number (1–40) of granules (0.4 μm diameter). Large‐granule hemocytes compose 10–20% of the hemocytes. They are filled with granules (0.8 μm in diameter) that are highly refractile when examined by light microscopy and are electron‐dense when examined by TEM. Our classification scheme is based solely on the absence or presence and relative size of granules. Features used by other researchers, such as cell size, shape, and staining properties, were not used because these features are subtle and/or subjective. The proposed classification is compared with schemes developed for other decapods, and its usefulness and limitations are discussed. This scheme will serve as a basis for further studies on the maturation and physiological function(s) or crustacean hemocytes.
Structure of dactyl sensilla in the kelp crab, Pugettia producta
Authors: Hamilton K. A. , Linberg K. A. , Case J. F.
Published: February 2005

In the kelp crab, Pugettia producta, flat plate setae cover all but the ventral surfaces of the walking leg dactyls. Dendrites enter the setal shaft located inside the plate superstructure, and extend to a region of the setal tip that contains a system of minute pores resembling the pore systems found in chemosensory sensilla of insects. Presumably, much of the chemosensitivity of the dactyls in the kelp crab is mediated by the plate setae.

In the interior of the dactyl, supporting cells and the neurons innervating plate setae, other types of setae, and other presumptive sensilla form scolopidia. Large scolopidia, containing as many as 12 dendrites, appear to innervate some of the plate setae and also large ventral rodlike setae that might be chemosensory. Two of the dendrites of large scolopidia usually have more densely packed microtubules, longer ciliary axonemes, slightly larger rootlets, and dark A fibers with arms, characteristics indicative of mechanosensory function. Some dactyl setae, therefore, could be both mechanosensory and chemosensory. Small scolopidia containing two or three dendrites that exhibit mechanosensory characteristics appear to innervate small, rodlike setae, which presumably are strictly mechanosensory. The two types of structures located on the epicuticular cap, elliptical structures resembling campaniform sensilla and small cones in pits resembling CAP organs, appear to be dually innervated and presumably are mechanosensory, although other functions are possible.

The internal positions of the scolopidia, together with the support afforded by an extracellular dendritic sheath, by the scolopale, and by desmosomelike and septate junctions, may serve to protect internal portions of setal dendrites, some of which appear to remain functional in nonmolting adults that have abraded setae.
Ultrastructure of the colon of Locusta migratoria
Authors: Peacock A. J.
Published: February 2005

The ultrastructure of the colon of Locusta migratoria is described. The colon is lined by a thick cuticle that, for the most part, adheres to the underlying epithelium. The cuboid epithelial cells are characterized by moderate invaginations of the apical and, to a lesser extent, basal plasma membranes; the lateral plasma membranes are relatively flat. The bulk of the mitochondria are located in the apical region of the cell and are not particularly associated with any of the plasma membranes. The basal region of the cells contains much rough endoplasmic reticulum, glycogenlike granules, and a predominance of spherical, electron‐dense bodies of various sizes. Where muscle fibers make contact with the epithelium, the cells are much reduced; the cytoplasm is usually less electron‐dense, and, typically, the nucleus has a thick layer of granular material associated with the inner nuclear membrane. The apical and basal plasma membranes of the reduced epithelial cells contain numerous hemidesmosomes. The apical hemidesmosomes occur in pairs around an extracellular space that contains electron‐opaque material. The latter forms tonofibrillae that extend into the endocuticle. Bundles of microtubules are associated with the hemidesmosomes. The tubules traverse the cell from the apical to the basal region. The possible significance of these findings is discussed.
Patterns of cells and extracellular material of the sea urchin Lytechinus variegatus (Echinodermata; Echinoidea) embryo, from hatched blastula to late gastrula
Authors: Galileo Deni S. , Morrill John B.
Published: February 2005

Scanning electron microscopy of six stages of Lytechinus variegatus embryos from hatching through gastrulation reveals changes in the shapes of the ectodermal cells and morphological changes in the extracellular material (ECM) in relation to the locations and migratory activities of mesenchyme cells. The classical optical patterns in the blastular wall (Okazaki patterns) are due to differential orientations of the cells, which bend and extend sheet‐like lamellipodia over adjoining cells toward the eventual location of the primary mesenchymal ring. The blastocoelic surfaces of the blastomeres become covered with a thin basal lamina (BL) composed of fibers and nonfibrous material. During primary mesenchyme cell (PMC) ingression, a web‐like ECM is located in the blastocoel overlying the amassed PMCs. This ECM becomes sparse in migratory mesenchyme blastulae, and is confined to the animal hemisphere. Localized regions of intertwining basal cell processes in the blastular wall are also present during PMC migration. While a distinct BL is present during early and midgastrulation, blastocoelic ECM is absent. Late gastrulae, on the other hand, have an abundance of blastocoelic ECM concentrated near secondary mesenchyme cell protrusive activity. ECM appearing at both the early mesenchyme and late gastrula stages are probably remnants of degraded BL and intercellular matrix preserved by fixation for SEM. Thus, early mesenchyme ECM is formed of BL material whose degradation is necessary for entry of PMCs into the blastocoel. Late gastrula ECM is apparently a degradation product of BL and intercellular material whose destruction is required for fusion of the gut with oral ectoderm in formation of the mouth.
Structure of the radially asymmetrical uncalcified region 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

The teeth of the adult plethodontid salamander, Plethodon cinereus, were examined by light and electron microscopy with emphasis on the ringlike zone of uncalcified dentin that divides the calcified portion of each tooth into a proximal pedestal and a distal apex. The uncalcified region displays radial asymmetry, forming an integral part of the posterior wall of the tooth but bulging into the pulp cavity anteriorly, thus forming a hingelike structure. All portions of the dentin, including the uncalcified region, are composed predominantly of collagenous fibers but lack elastin. In scanning electron micrographs of teeth from which the oral mucosa has been removed, the location of the anterior uncalcified hinge is marked externally by a notch‐like articulation of the apex and pedestal. Sites of transition between calcified and uncalcified areas of the dentin show no special modifications in transmission electron micrographs, but collagenous fibers in calcified portions are associated with more electron‐dense amorphous material than are those in the uncalcified region. Odontoblasts associated with the uncalcified region possess ultrastructural features closely resembling those of odontoblasts found in calcified areas. The uncalcified region seems to afford the teeth a certain degree of flexibility, and the asymmetry of the region appears to allow the teeth to flex only in a posterior direction, thus facilitating the entry of living prey but hindering its escape. The uncalcified region also seems to permit the apex of a tooth to break away from its pedestal without damage to underlying bone.
Microcirculation in rat spleen (sinusal), studied by means of corrosion casts, with particular reference to the intermediate pathways
Authors: Schmidt E. E. , MacDonald I. C. , Groom A. C.
Published: February 2005

Blood vessels and their connections in rat spleen were traced over considerable distances by scanning electron microscopy of microcorrosion casts prepared by injection of minimal amounts of casting material. The periarterial lymphatic sheath and lymphatic nodules are highly developed, containing an abundance of capillaries which terminate in the marginal sinus (MS) and marginal zone (MZ). The MS, which consists of a series of discontinuous flattened vascular spaces interconnected by short capillaries, shows circumferential filling followed by flow radially outward into the MZ. Contrary to the generally accepted view, many venous sinuses begin as open‐ended tubes at the MS or MZ, allowing free entry of blood into the venous system, thereby bypassing the reticular meshwork of the red pulp. The majority of arterial capillaries terminate in the reticular meshwork (“open” circulation), but evidence for direct connections between capillaries and venous sinuses (“closed” circulation) was also obtained. Casts of the subcapsular region reveal an elaborate system of venous sinuses in fan‐shaped arrays, superimposed on an extensive network of capillaries draining into flattened reticular spaces; such casts provide a three‐dimensional map useful in interpreting light microscopic observations of red cell flow in vivo. Sphincter‐like constrictions in venous sinuses, at points of connection with larger sinuses, indicate that these are possible sites for control of intrasplenic flow distribution.
The development and homology of the chelonian carpus and tarsus
Authors: Burke Ann C. , Alberch Pere
Published: February 2005

The long‐standing controversies involving the number and homologies of the elements of the carpus and tarsus of turtles are reviewed from a developmental perspective. The analysis is based on a detailed description of the chondrogenesis of the carpus and tarsus in the species Chelydra serpentina and Chrysemys picta. The first stage described is the differentiation of a Y‐shaped chondrogenetic condensation involving the humerus (femur)‐radius/ ulna (tibia/fibula). This stage is followed by the early formation of a series of connected condensations off the distal end of the postaxial element (ulna or fibula). This linear array, which we refer to as the primary axis, comprises the ulnare‐distal carpal 4‐metacarpal 4 in the carpus and the fibulare‐distal tarsal 4‐metatarsal 4 in the tarsus. There are two precondensations that branch off the primary axis. The proximal one will soon form the intermedium while the distal one will generate a digital arch that will give rise sequentially to digits 3‐2‐1, in this order. Digit 5 is not part of the digital arch and forms as an independent condensation.

We emphasize that chondrogenetic foci often form as “branches” off existing condensations. This well‐defined pattern of connectivity is used to establish unambiguous homologies and allows comparisons with other vertebrates. We conclude that preaxial elements such as the radiale and tibiale are absent in the turtles examined and probably in all turtles. The observed proximal elements that form in the anterior region of the limb and that are often homologized as radiale or tibiale have clear connections to the postaxial elements. For this reason we argue that these elements should be homologized as centralia. Therefore, we find two chondrogenetic condensations in the tarsus and three in the carpus, which we consider centralia. They subsequently fuse with neighboring elements in a complex pattern. We also describe the variable presence of a late‐developing element in the tarsus of Chelydra, which, to our knowledge, has never been described. We propose this element to be an atavistic pretarsale.

Comparison of the chondrogenetic pattern in turtles with those described in the literature for other vertebrates indicates that there are two invariant patterns in all tetrapods with the exception of the urodeles. These are (1) the primary axis and (2) the digital arch.
The anatomy and functional morphology of the large hermaphroditic duct of three species of Aplysia, with special reference to the atrial gland
Authors: Painter Sherry D. , Kalman Vivian K. , Nagle Gregg T. , Zuckerman Robin A. , Blankenship James E.
Published: February 2005

The anatomy and functional morphology of the large hermaphroditic duct of three species of gastropod mollusc (Aplysia californica, A. dactylomela, and A. brasiliana) were examined. Each duct is composed of two parallel compartments, the red hemiduct (RHD) and the white hemiduct (WHD), which are distinguishable from the outside of the duct. Four secretory regions, all exocrine in morphology, are recognizable: the RHD secretory epithelium, the atrial gland (or atrial gland‐like epithelium), the WHD secretory epithelium, and the accessory gland of the copulatory duct (AGCD). Of these regions, only the atrial gland (or atrial gland‐like epithelium) contains egg‐laying activity and only the atrial gland (or atrial gland‐like epithelium) is immunocytochemically labeled by serum antibodies generated against low molecular weight. A. californica atrial gland peptides. The RHD is the functional oviduct: the egg cordon passes through a channel lined by the RHD secretory epithelium and bordered by the atrial gland (or atrial gland‐like epithelium); the eggs are separated from both the WHD secretory epithelium and the AGCD by internal folds of the duct. The WHD is the functional copulatory duct: the penis, exogenous sperm, and endogeneous sperm pass directly by the AGCD and in close proximity to the WHD secretory epithelium; they are separated from both the RHD secretory epithelium and the atrial gland (or atrial gland‐like epithelium) by internal folds. The atrial gland (or atrial gland‐like epithelium) is thus not likely to have a prostatic function or to be directly stimulated by the penis during copulation; it may play a role in oviductal function.
Tooth replacement and growth in the young green iguana, Iguana iguana
Authors: Kline L. W. , Cullum D. R.
Published: February 2005

A study using eight rapidly growing young green iguanas (Iguana iguana; initial mean weight 68.0 ± 3.8 gm) examined the changes in the wave replacement of teeth, the increased size of the teeth, and the posterior migration of tooth positions over a period of 16 weeks. The teeth increase in width as the lizards grow. The tooth positions shifted posteriorly, providing adequate space for the larger replacement teeth. These observations suggest that the wave replacement of teeth allows for growth of the dentition in length and height adequate to maintain tooth size in proportion to the overall size of the individual.
Relationship of symbiotic microorganisms to metanephridium: Phagoctic activity in the metanephridial epithelium of two species of oligochaeta
Authors: Villaro A. C. , Sesma P. , Alegría D. , Váazquez J. J. , López J.
Published: February 2005

It is known that a number of species in the annelid family Lumbricidae harbor symbiotic microorganisms in the lumen of their nephridia. The purpose of the present paper is the study of the relationship between microbes and epithelial cells lining the metanephridium of two species of Oligochaeta, which show two different patterns of microbial colonization. A new interesting feature, the phagocytosis and intracellular destruction of microorganisms by the nephridial epithelial cells, has been observed in our laboratory for the first time. In Scheroteca savignyi minor, the phagocytic activity takes place in the bladder, the most distal region of the nephridium, next to the nephridiopore, which may prevent the microorganisms from entering the more proximal regions. In Octolasion cyaneum the microbes reach the striated duct, where they live in symbiosis, adhere to the cell's surface, and are engulfed and destroyed by the cells of the middle tubule—the more proximal, neighboring region. The phagocytosis and intracellular degradation of microorganisms probably lead to the massive formation of lamellar bodies, which are observed in these cells and in the neighboring ones.
A microscopic examination of the male turkey proctodeal gland
Authors: Bakst Murray R. , Cecil Helene C.
Published: February 2005

The morphology of the dorsal proctodeal gland of the mature male turkey closely resembles that of the proctodeal gland of the mature female Japanese quail. This exocrine gland is a collection of compound, coiled, tubular units. Diffuse lymphoid tissue and germinal centers are distributed throughout the lamina propria and are closely associated with the surface and glandular epithelia. The morphology and histochemistry of the proctodeal gland mucosa suggest that it may secrete muco‐substance(s) and may have immunogenic capabilities.
Morphogenesis during molting of the setae in the statocyst sensilla of the mysid shrimp Neomysis integer (Leach, 1814) (crustacea, mysidacea)
Authors: Espeel Marc
Published: February 2005

The morphogenesis of the setae in the statocyst sensilla of Neomysis integer was studied. Immediately before ecdysis, a new seta lies inverted between the enveloping cells. All of the nine enveloping cells, except the first one, secrete a well defined part of the new seta. The second, third, fourth, and fifth have a trichogen function; the sixth has a trichogen‐tormogen function; and the seventh, eighth, and ninth enveloping cells have a tormogen function. It could not be established whether the dendritic sheath is replaced at molt. In the second and third enveloping cells, there is a differential secretion of cuticular material forming the wall of the distal part of the seta. As a consequence, this wall is not homogeneous. The possible role of this heterogeneity in the formation of the gutter‐like apical part of the seta is discussed. A mechanism is proposed by which the pore develops at the transition between the midpart and the apical gutter‐like part. Before ecdysis, the distal segments of the sensory cells are still connected with the wall of the old seta in the same way as during intermolt. No degeneration is apparent in the distal segments during preparation for the molt. These morphological findings suggest that sensitivity of the sensilla must be maintained until the moment of the ecdysis.