bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structure of the chemoreceptor sensillum in Limulus
Authors: Hayes Wilbur F.
Published: February 2005

Each chemoreceptor sensillum of Limulus polyphemus consists of 6–15 bipolar neurosensory cells with distal processes confined within a single cuticular tubule as they extend to the outside environment. The cuticular tubule, which is enveloped by the cuticulo‐tubal cell, opens proximally into a fluid‐filled extracellular space through which the dendrite passes before entering the cuticular tubule. Between the neurosensory cells are one to three microvillar cells also exposed to the extracellular space. This space is enclosed by a sheath cell extending proximally from the inner opening of the cuticular tubule and enveloping the proximal portions of the dendrites, the distal portions of the microvillar cells, as well as the distal portion of some neurosensory cell bodies. Most of the remaining portions of the neurosensory cells and microvillar cells are enveloped by neuroglia. Tight junctions occur between the distal portions of the dendrites in or near the cuticular tubule. Each dendrite has a cilium‐like segment located where it traverses the extracellular space with a 9 + 0 pattern of fibers. Septuplelayered junctions occur among the proximal portions of some dendrites and some neurosensory cell bodies of the same sensillum. The subjacent processes of the sensillum frequently course proximally as isolated axons before joining nerve bundles. In the chilarial and gnathobasal chemoreceptors these nerve bundles course proximally to neuropile clumps of a peripheral nerve plexus. The presence of numerous synaptic vesicles in the neuropiles suggests that chemical transmission may occur among “en passant” synapses formed by the axons. Proximally the neuropiles are joined to the central nervous system by relatively long nerves.
Quantitative histology of changes with age in rat bone cortex
Authors: Singh I. J. , Gunberg D. L.
Published: February 2005

Changes with age in bone cortex of the rat were investigated by establishing histological parameters which could be quantitated to estimate age at death. Decalcified cross sections of mandible, femur and tibia were prepared from rats two to 120 days old, and measurements were made of: (1) number of osteons, (2) average number of lamellae per osteon, (3) average Haversian canal diameter, and (4) number of non‐Haversian (primary) canals. Multiple regression techniques were used to estimate age at death from several combinations of these variables.

With age, the number of osteons per unit area of bone and the number of lamellae per osteon increased, but Haversian canal diameter and the number of primary canals decreased. Multiple regression analyses indicated that age at death could be estimated to ± 3 days of the true value in 95% of the cases. Nomographs based on histological measurements of each bone were prepared which can provide accurate estimates of age between two and 120 days in the Sprague‐Dawley female rat. It was concluded that microstructure of bone cortex can not only be quantitated to provide accurate estimates of age but it may also constitute a sensitive measure of the metabolic state of the organism. The techniques utilized should prove useful in anthropology as well in studies of bone aging.
A re‐examination of the cloacal sacs and gland of the blind snake, Leptotyphlops dulcis (Reptilia: Leptotyphlopidae)
Authors: Kroll James C. , Reno Harley W.
Published: February 2005

The cloacal sacs of Leptotyphlops dulcis are nonglandular, posterior evaginations of the cloaca. The median cloacal gland is tubuloalveolar. Similar unpaired cloacal glands as well as paired sacs are noted in certain colubrid snakes. Terminology applied to these cloacal derivatives is discussed, and a standardization of names is provided.
Organogenesis in normal and lobeless embryos of the marine prosobranch gastropod Ilyanassa obsoleta
Authors: Atkinson James W.
Published: February 2005

The histogenetic and organogenetic capabilities of normal and lobeless embryos of Ilyanassa obsoleta are analyzed. Larvae developed from eggs in which the polar lobe was removed at the trefoil stage of first cleavage were studied in wholemount and section. None showed any evidence of eyes, statocysts, operculum, external shell, heart, or intestine. Sixty per cent of the wholemount larvae observed under polarized light exhibited internal masses of birefringent material resembling shell material. Of eight‐ to nine‐day lobeless larvae studied as stained, sectioned material 100% possessed muscle tissue; 97.5% possessed velar tissue, digestive gland tissue, and style sac tissue; 52.5% possessed two or more style sac areas; 71% exhibited esophagus; 63% possessed stomach tissue; 37% exhibited stomodeal‐like invaginations of the ectoderm; 31% exhibited a lightly staining ciliated area at the tip of the prevelar ectoderm; and 21% possessed glandular ectoderm resembling pedal or mantle gland tissue.

The evidence presented suggests that the material of the polar lobe has an important role not only in cellular differentiation but also in the organization of tissue types into organs or organ primordia.
A light and electron microscopic study of the heart of a crayfish, Procambarus clarkii (Giraud). II. Fine structure
Authors: Howse Harold D. , Ferrans Victor J. , Hibbs Richard G.
Published: February 2005

The adventitia of the crayfish heart is composed of cells that are separated from each other by an intercellular space about 280 Å wide. Desmosomes are present on apposing surfaces of adjacent cells. A basal lamina underlies the adventitia and consists of a dense, amorphous substance that contains numerous fine filaments.

The myocardial cells are striated and an external lamina 0.1 μ thick is present on the surface of the plasma membrane. The nuclei and most of the cytoplasm, glycogen and mitochondria are located at the cell periphery. The myofibrils are composed of thick and thin filaments and confined to the core of the cell. A T system and a well‐developed SR are present. Elements of these organelles form dyads at levels that correspond to the H bands, and triads at levels that correspond to the Z bands of the peripheral myofibrils. The relationship of the T tubules to the myofibrils is discussed.

Locus cells exhibit a unique pattern of intracellular myofibrillar branching. They branch from a region which has a structure similar to the Z band material. The myofibrils radiate outwardly in various directions and form numerous cellular branches which form intercalated discs with adjacent myocardial cells. These discs are more complex than those observed in poikilothermic vertebrates but are simpler than those in mammals.

An endocardium is lacking in the crayfish heart but interstitial cells are present in close association with the myocardial cells and neural elements. Terminal nerve processes deeply embedded in the myocardial cells are described.
Histogenesis of the lymphomyeloid complex in the larval leopard frog, Rana pipiens
Authors: Horton John D.
Published: February 2005

A histological study was undertaken of the differentiation of the lymphomyeloid complex of larvae of the common leopard frog, Rana pipiens, reared at 18–21 °C. Immature lymphocytes are first recognised in the thymus and pronephros at stage I of Taylor and Kollros ('46). By the end of stage II, small lymphocytes are regularly found among the predominant larger lymphoid cells in the thymus, in which corticomedullary differentiation has begun. At this time, a few small lymphocytes are also apparent in the ventral cavity bodies, lymph gland, pronephros, mesonephros and intestine, but rarely occur in the spleen. During stages III and IV extensive development of these components of the lymphomyeloid complex occurs. The organs now contain large numbers of mature lymphocytes and have attained states of differentiation that remain essentially similar in subsequent larval stages. By stage V, small epithelium‐associated lymphoid accumulations are abundant throughout the length of the gastrointestinal tract. The anlagen of the procoracoid body and bone marrow appear just prior to metamorphosis.

The kidneys are the main sites of blood formation in the larva. Masses of granulocytes are also usually found in the abundant ventral cavity bodies. A consideration of the roles of each of the organs provides insight into the ontogeny of the immune system of the Anura in general.
Antennal sense organs of the cockroach, Leucophaea maderae
Authors: Schafer Rollie
Published: February 2005

Adult and nymphal antennae of the cockroach, Leucophaea maderae, contain nine or more different morphological types of sense organs. There is no outwardly apparent sexual dimorphism in adult antennae. Nymphs are dificient in gross numbers of sensilla. Sense organs are classified morphologically by their similarity to known types of sensila and are assigned functions on this basis and preliminary electrophysiological data: Sensilla chaetica (A), thick‐walled mechanoreceptive hairs in groups on the antennal base; S. chaetica (B), thick‐walled setae which are tactile and probably chemoreceptive, occurring in the antennal base and flagellum; S. trichodea (A), thin‐walled chemoreceptive hairs of the flagellum; S. trichodea (B), minute hairs on the scape and pedicel; S. basiconica, thin‐walled chemoreceptive pegs, and S. coeloconica („pit‐pegs”︁) of the flagellum; S. campaniformia and scolopidia, mechanoreceptors in the base and flagellum; plus Johnston's organ and/or connective chrodotonal organs in the pedicel. Calculations based on absolute counts of sensilla and their known innervation yield an estimate of about 3.3 × 104 sensilla and 105 cells per antenna.
The histology of the first batch of eggs and their associated tissues in the ovariole of Dysdercus fasciatus signoret (heteroptera: Pyrrhocoridae) as seen with the light microscope
Authors: Brunt Angela M.
Published: February 2005

In the telotrophic ovarioles of Dysdercus fasciatus, mononucleate, binucleate and multinucleate trophocytes are seen in the germarium. Cellular breakdown of the multinucleate cells is seen in the posterior part of this tissue. The nutritive cords, which are continuous with the trophic core at the one end and the oocytes of the vitellarium at the other, contain material of fibrous appearance which continues into the trophic core. The ovariole is enclosed in two sheaths throughout its length. Prefollicular tissue in the germarium appears to give rise to the follicle cells. Mitosis is common in this zone. Oocytes are at first surrounded by a multilayered epithelium. This is later reduced progressively to one layer. This one layered follicular epithelium is at first columnar but then changes to cuboidal mononucleate, cuboidal binucleate and finally to a squamous binucleate condition This epithelium thus seems to accommodate the increased volume of the oocyte by growth and a change of shape. The oocyte grows fastest at those times when it is surrounded by cuboidal and squamous epithelial cells.
Attachment and metamorphosis of the cheilo‐ctenostome bryozoan bugula neritina (linné)
Authors: Woollacott Robert M. , Zimmer Russel L.
Published: February 2005

The structure, attachment and subsequent metamorphosis of larvae of the marine bryozoan Bugula neritina were studied by light and electron microscopy.

Two points of larval anatomy are of special significance to proper interpretation of the metamorphosis:

Two cytologically similar blastemal tissues, each laden with free ribosomes, occur as parts of the apical organ complex. The upper blastema directly contacts the larval surface, forming the non‐ciliated rows of the apical organ. The lower blastema is internal and is oral to and contiguous with the upper blastema.

The epidermal tissues of the larva are joined in the following sequence, beginning at the aboral pole: a. apical organ complex; b. apical‐connecting cell; c. infolded pallial sinus epithelium; d. vesicular‐connecting cell; e. aboral vesicular epithelium; f. corona; g. oral vesicular epithelium; and i., j., and k. internal sac neck, wall and roof regions.

The initial stages of metamorphosis involve a complex sequence of morphogenetic movements, including:

eversion of the internal sac, permanently attaching the larva to the substrate;

inrolling of the aboral vesicular epithelium, corona, oral vesicular and ciliated epithelia, and neck region of the internal sac into the larval interior; concomitantly the pallial sinus epithelium evaginates;

loss of connection between the invaginated tissues and the surface;

fusion of the pallial sinus epithelium with the wall region of the internal sac, maintaining the integrity of the body surface;

retraction of the apical organ complex and invagination of the pallial sinus epithelium with the simultaneous elevation of the internal sac wall region to the aboral pole.

At the conclusion of these events the preancestrular surface is covered by the wall and roof regions of the internal sac. Cells of the wall region form the epidermis of the body wall except for the attachment disc and secrete a cuticular exoskeleton that is secondarily calcified; the attachment disc is formed by the roof region of the internal sac.

Internally, the ectodermal upper blastema differentiates into the lophophore and digestive tract of the ancestrular polypide, while the lower blastema forms the lining of the lophophoral coelom and the splanchnic (but not the somatic) lining of the visceral coelom. The visceral somatic peritoneum is formed from cells that may originate from the mesodermally derived pigmented cells of the larva to which they are similar in pigmentation and cytology. Such a composite derivation of a coelomic lining has not been described previously.
The fine structural morphology of adrenal cortices of normal and stressed squirrel monkeys
Authors: Penney David P. , Brown Gregory M.
Published: February 2005

The fine structural morphology of the male squirrel monkey adrenal cortex has been examined. When compared to other laboratory animals, the squirrel monkey adrenal cortex secretes large amounts of cortisol and maintains extraordinarily high plasma cortisol levels for prolonged periods of time. The normal cortical cells have numerous mitochondria with either a tubulo‐vesicular or lamellar internal membrane arrangement, a well‐developed agranular endoplasmic reticulum which is arranged in juxtaposition to mitochondria and lipid droplets, several lysosomes, and numerous thin‐walled blood vessels of large caliber, suggestive of a rich blood flow through the gland. These characteristics have heretofore been associated with hypersecretion. Their presence in the squirrel monkey cortex, known to have high secretory activity, lends credence to the correlation of hyperdevelopment of the agranular reticulum with increased rates of secretion of corticoids.

During chair restraint, the plasma cortisol levels rise two to three fold. Adrenocortical cells thus stressed exhibit a depletion and disorientation of membranes both of the agranular endoplasmic reticulum and mitochondria and a loss of ribosomes, lysosomes and, to some degree, intracellular lipid. The animal appears to be responding maximally to the stress of chair restraint. These fine structural characteristics are interpreted as an example of an adrenal cortex in the process of becoming functionally exhausted, since these animals sometimes do not survive the stress of chair restraint.
Cytochemical observations of hemolymph cells during coagulation in the crayfish, orconectes virilis
Authors: Wood Pauline J. , Podlewski John , Shenk Thomas E.
Published: February 2005

Smears of Orconectes virilis hemolymph were prepared by fixation in 10% formalin immediately upon withdrawal, and after an interval of 1, 5, or 15 minutes. These smears were then stained by a variety of histochemical means designed to identify a material which is released from both hyaline and granular cells during the coagulation process. Based upon reactions to various carbohydrate, lipid and protein tests, this material appears to consist of a glycoor muco‐protein, and its localization and activity coincide with the „fibrin ferment”︁ described by Hardy (1892). Its release is probably initiated from the hyaline cells, followed shortly thereafter by a similar activity of the granulocytes. While it cannot be ascertained by the methods used in this study whether or not this material participates actively in clotting, its release is nevertheless coincidental with coagulation.
A histological and histochemical study of the male reproductive system of artemia (Crustacea, Branchiopoda)
Authors: Wolfe Allan F.
Published: February 2005

The male reproductive system of Artemia was studied by routine histological and histochemical techniques to demonstrate the general histology and distribution of proteins, carbohydrates, lipids, and alkaline and acid phosphatases.

The System Consists Of Paired Testes, Vasa Deferentia, Accessory Glands, And Penes. The Testes Contain Germ Cells And Supporting Cells Throughout Their Entire Length. The Former Cells Are Located In Clusters And Undergo A Spermatogenic Maturation Which Is Similar To That Described For OtherAnimals. The Supporting Cells Seem Implicated In The Nourishment Of The Germ Cells. The Vas Deferens, Which Consists Of Secretory Epithelium Surrounded By Circular And Longitudinal Muscles, Secretes The Seminal Fluid, Containing A Neutral Mucopolysaccharide Or Mucoprotein, And Stores The Mature Sperm. The Accessory Gland Consists Of Approximately 20 Pairs Of Gland Cells, Each Pair Drained By A Neck Cell And Duct Cell Into The Collecting Duct. The Glandular Secretion, Mainly A Neutral Mucopolysaccharide Or Mucoprotein, Might Function As A Lubricant, A Copulatory Plug, Or An “Activator Substance” For The Sperm Or For Fertilization. Each Penis Consists Of A Non‐Eversible Part And An Eversible Part Which Is A Tortuous Muscular Tube That Connects The Vas Deferens To The Outside.
Studies on hydroid differentiation VII. The hydrozoan stolon
Authors: Braverman Max
Published: February 2005

The stolon of the colonial marine hydroid Podocoryne carnea differentiates sequentially as a function of age, forming four distinguishable regions characterized by epidermal cell differentiation: The Tip, New Stolon, Cnidogenic Masses, Old Stolon. Radioautographs of sections of colonies exposed to tritiated thymidine show that although cells of the epidermis and gastrodermis of the stolon incorporate the nucleoside into acid stable polynucleotide, cells of the stolon tips do not. Stolon extension is not, therefore, the result of a localized meristem‐like growth zone.

Stolon branching and new polyp formation are, similarly, not signaled by increased thymidine incorporation. The initial event heralding these morphogenetic activities appears to be the reorientation of epidermal cells along a new axis, and the acquisition of perisarc dissolving ability. This evidence is contraindicative of direct dependence of colony form on colony growth.

The larger part of stolon epidermal cells are organized into cnidogenic masses where cnidocytes and possibly other amoebocytic cells are produced.

Although no mitotic figures have been observed in gastroderm cells of the stolon, thymidine incorporation in this tissue occurs with the same frequency as it does in epidermis. Considerable numbers of gastroderm cells can be found in the gastric cavity. Frequently these and gastroderm cells in the stolon and polyps contain more than one nucleus.
A fine structural analysis of the epidermis and cuticle of the oligochaete aeolosoma Bengalense stephenson
Authors: Potswald Herbert E.
Published: February 2005

The fine structure of the epidermis and cuticle has been described for the oligochaete Aeolosoma bengalense. The epidermis is a pseudostratified epithelium and consists of the following cell types: ciliated and nonciliated supportive cells, pigment cells and associated satellite cells, mucous cells, basal cells, and ciliated non‐supportive columnar cells. Overlying and restricted to the supportive cells is a delicate cuticle composed of: (a) a discontinuous layer of membrane‐bounded surface particles; (b) a thin filamentous layer of moderate electron density just under the surface particles; (c) a thicker inner filamentous layer of low electron density. Digestion with pronase effectively removes the cuticle. This, together with the fact that it stains with alcian blue and ruthenium red, indicates that the cuticle contains an acid mucopolysaccharide. Regeneration of the cuticle, following pronase treatment, is marked by the elaboration of numerous microvilli by the supportive cells. Most of the microvilli are transitory and evidence supports a microvillar origin for the cuticular surface particles. The presence of cuticular surface particles may be a characteristic shared in common by all oligochaetes and, perhaps, some polychaetes.
Giant nuclei formation in the yolk sac syncytium of the muskellunge, a bony fish (salmoniformes: esocidae: Esox masquinongy)
Authors: Bachop William , Price John W.
Published: February 2005

In muskellunge blastulae the yolk sac syncytium originally contains nuclei comparable in size to the blastomere nuclei from which the syncytial nuclei arose. By mitosis the originally diploid syncytial nuclei become numerous and crowded together. Continued synchronous mitosis of neighboring syncytial nuclei and the resultant crowding together of their spindles culminates in overlapping spindles, multipolar spindles, disorganized spindles, and the crowding together of large numbers of condensed chromosomes from contigous spindles. When such an aggregation of condensed chromosomes becomes enclosed within one nuclear membrane, a giant nucleus appears in the following interphase. It soon becomes postmitotic.
The parapodial and segmental musculature of Harmothoë imbricata (L.)
Authors: Lawry James V.
Published: February 2005

The segmental anatomy of Harmothoë imbricata deviates from the plan of a typical errant polychaete only slightly. The body is partitioned into 37 nonmetameric segments and is covered by 15 pairs of elytra. The segmental musculature consists of paired dorsal and ventral longitudinal muscles, pairs of dorso‐ventral muscles, and in places the external surface of the worm is covered by a sheet of circularly coursing muscle fibers subjacent to the cuticle. The dorsal tubercles, elytrophores, cirratophores and ventral cirri are moved by muscles derived from segmental and intrinsic parapodial muscles. From the anatomy it is surmised that the lateral bending of the worm during swimming is due to cycles of activity involving the longitudinal muscles (S‐waves). During a cycle of parapodial stepping, parapodial levators and promotors raise a parapodium from the substrate and direct it forward (the recovery stroke), at which time the muscles of the aciculum and setal sacs withdraw the neuropodial setae. During the power stroke parapodial depressors and remotors bring the tip of the parapodium against the substrate, applying a forward thrust and the neuropodial setae are extended. At the conclusion of the power stroke, the recovery stroke begins anew.
Nasal anatomy of trionychid turtles
Authors: Parsons Thomas S.
Published: February 2005

Two trionychid turtles, Trionyx ferox and Lissemys punctata, have similar and distinctive nasal cavities. Most of the parts of the nasal cavities are similar to those in other turtles, but the intermediate regions have many more small ridges and shallow sulci than do those of other turtles; these form a highly complex and distinctive pattern that varies in minor details. In turtles generally, a relatively large intermediate region appears to be correlated with strongly aquatic habits, which supports the interpretation that the vomeronasal epithelium of that region functions in olfaction in an aquatic environment.
Ultrastructure of the peg and hair sensilla on the antenna of larval Aedes aegypti (L.)
Authors: Zacharuk R. Y. , Blue Sharon G.
Published: February 2005

The antenna of fourth instar larvae of Aedes aegypti has one peg organ of a basiconic type innervated by four neurons. The dendrites are ensheathed to near their terminations at the peg tip by an electron‐dense dendritic sheath and by a cuticular sheath. They have easy communication by diffusion with the external environment only at the tip through a peripheral ensheathing membrane and six slit‐channels. One of the dendrites resembles a tubular body proximally and may be mechanoreceptive. The peg generally appears to be a contact chemoreceptor. There are three antennal hairs of a typical sensillum trichodeum type innervated at the base by one neuron each. An intricate terminal mechanism at the insertion of the dendrite in the hair is described. These are believed to be tactile hairs. There are also three antennal hairs each innervated by two neurons. The dendrite from one terminates at the base similar to that of a tactile hair, and is believed to function in a similar mechanoreceptive manner. The dendrite from the second neuron extends naked along the length of the hair lumen. It is believed to be primarily chemoreceptive, in a slow‐acting general sensory function. In all the sensilla there appear to be secretions produced in the junction body regions of the dendrites, and there is evidence for accumulation of secretory materials in the dendritic tips in some of the sensilla.
Oogenesis in Xenopus laevis (Daudin). I. Stages of oocyte development in laboratory maintained animals
Authors: Dumont James N.
Published: February 2005

Oogenesis in the anuran Xenopus laevis can be divided into six stages based on the anatomy of the developing oocyte. Stage I consists of small (50 to 100 μ) colorless oocytes whose cytoplasm is transparent. Their large nuclei and mitochondrial masses are clearly visible in the intact oocyte. Stage II oocytes range up to 450 μ in diameter, and appear white and opaque. Stage I and II are both previtellogenic. Pigment synthesis and yolk accumulation (vitellogenesis) begins during Stage III. Vitellogenesis continues through Stage IV (600 to 1000 μ), the oocytes grow rapidly, and the animal and vegetal hemispheres become differentiated. By Stage V (1000 to 1200 μ) the oocytes have nearly reached their maximum size and yolk accumulation gradually ceases. Stage VI oocytes are characterized by the appearance of an essentially unpigmented equatorial band. They range in size from 1200 to 1300 μ, are postivtellogenic and ready for ovulation. These stages of oocyte development have been correlated with physiological and biochemical data related to oogenesis in Xenopus.
The spermatozoon of Branchiostoma lanceolatum L
Authors: Baccetti Baccio , Burrini Anna G. , Dallai Romano
Published: February 2005

Under the electron microscope, the spermatozoon of Branchiostoma lanceolatum shows a spherical nucleus deeply grooved along its caudal third, a bistratified acrosome enriched by plentiful subacrosomal material, two centrioles, mitochondria fused into a single mass surrounding the centriolar region which is highly asymmetrical, a 9 + 2 flagellum tilted with respect to the longitudinal symmetry axis of the nucleus. The sperm of Branchiostoma shares the overall features of that of the Tunicata and fits in perfectly with the phylogenetic position of the Leptocardia.
Ultrastructural studies of differentiation in the oocyte of the polyclad turbellarian, Prostheceraeus floridanus
Authors: Boyer Barbara Conta
Published: February 2005

Oocyte differentiation in the polyclad turbellarian Prostheceraeus floridanus has been examined to determine the nature of oogenesis in a primitive spiralian. The process has been divided into five stages. (1) The early oocyte: This stage is characterized by a large germinal vesicle surrounded by dense granular material associated with the nuclear pores and with mitochondria. (2) The vesicle stage: The endoplasmic reticulum is organized into sheets which often contain dense particles. Vesicles are found in clusters in the cytoplasm, some of which are revealed to be lysosomes by treatment with the Gomori acid phosphatase medium. (3) Cortical granule formation: Cortical granules are formed by the fusion of filled Golgi vasuoles which have been released from the Golgi saccules. The association between the endoplasmic reticulum and Golgi suggests that protein is synthesized in the ER and transferred to the Golgi where polysaccharides are added to form nascent cortical granules. (4) Yolk synthesis: After a large number of cortical granules are synthesized, yolk bodies appear. They originate as small membrane‐bound vesicles containing flocculent material which subsequently increase in size and become more compact. Connections between the forming yolk bodies and the endoplasmic reticulum indicate that yolk synthesis occurs in the ER. (5) Mature egg: In the final stage, the cortical granules move to the periphery and yolk platelets and glycogen fill the egg. At no time is there any evidence of uptake of macromolecules at the oocyte surface. Except for occasional desmosomes between early oocytes, no membrane specialization or cell associations are seen throughout oogenesis. Each oocyte develops as an independent entity, a conclusion supported by the lack of an organized ovary.
The structure and prenatal morphogenesis of the nasal septum in the rat
Authors: Vidić Branislav , Greditzer Harry G. , Litchy William J.
Published: February 2005

One hundred fetuses of the Sprague‐Dawley rat were used: ten for each prenatal day, beginning with the twelfth day of gestation. Pregnant animals were sacrificed, fetuses removed and subsequently fixed in buffered formalin solution. Fetal heads were dehydrated, embedded in paraffin, and sectioned serially in the rostrocaudal direction at 10 to 15 μ. Serial sections from fetuses representing each day of gestation were stained with either H and E, Mallory's trichrome procedure, Gomori's reaction for alkaline phosphatase, or Steedman's alcian blue reaction. At the twelfth day, the primary nasal cavities were first observed. One day later, the nasobuccal membrane was established, and the vomeronasal organ invaginated into the nasal septum. Following the rupture of the membrane, at the fourteenth day, the nasal and buccal cavities remained in communication until the palatal shelves fused with the septum, at the seventeenth day. Prior to the thirteenth day, the septal skeleton is mesenchymal. The ossification in the vomer started at the sixteenth day and expanded progressively throughout prenatal life. First glandular primordia, one on each side of the septum, were observed during the sixteenth day, the number increased to five at term. The ducts ended in single blind sacs, before the eighteenth day, afterwards, the ducts presented an increasing number of collateral and terminal branches. There was no evidence of mucigen secretion from the septal glands during prenatal life. The initial stratified olfactory epithelium differentiated morphologically into a vestibular, respiratory, and an olfactory epithelium prior to the sixteenth prenatal day.
A light and electron microscopical study of spermatogenesis in Hydra cauliculata
Authors: Moore G. P. M. , Dixon K. E.
Published: February 2005

Morphological changes in the interstitial cells were studied during their differentiation into spermatozoa. Development of the spermatogonium involves an increase in nuclear and nucleolar size, and the formation of a dense mass of cytoplasmic ribosomes. The mature spermatozoon has a relatively simple structure. The head consists of a bullet shaped, homogeneous nucleus, which lacks an acrosome but bears distal membrane specializations. The middle piece is composed of four large spherical mitochondria at the base of nucleus. A single flagellum projects from one of the two centrioles lodged between the mitochondria. The flagellum appears early during development in the primary spermatocyte. During spermiogenesis microtubules associated with the basal body flagellum complex appear to define the axis of chromatin condensation.
A cytological study of the ovary of Rhodnius prolixus. III. Cytoarchitecture and development of the trophic chamber
Authors: Huebner Erwin , Anderson Everett
Published: February 2005

The tropharium of the telotrophic ovarioles of Rhodnius is syncytial with the nurse cell nuclei located in tortuous finger‐like projections arborizing from a common cytoplasmic area, the trophic core. The nurse cell nuclei exhibit prominent nucleoli. Located adjacent to the nuclear envelope are masses of granular material both within the nucleus and adjoining cytoplasm. The cytoplasm consists primarily of ribosomes and mitochondria. The trophic core and the trophic cords that connect the core to individual oocytes characteristically possess parallel arrays of microtubules with ribosomes and mitochondria interspersed between. Surrounding the nurse tissue (germarium) is a thin layer of squamous cells comprising the inner sheath. The inner sheath is encompassed by the non‐cellular tunica propria superficial to which are two external cellular sheaths.

The syncytial nature of the tropharium appears to arise as a result of the fusion of many entangled nurse cell‐oocyte complexes during the late fifth instar. The structural similarities, and possible homologies with the polytrophic type of ovariole is discussed.
A light and electron microscopic study of sensory organs and associated structures in the foreleg tibia of the cricket, Gryllus assimilis
Authors: Friedman Morton H.
Published: February 2005

Early descriptions of insect sensory organs included three presumed mechanotransducers in the tibia of Orthoptera, namely the subgenual organ, the intermediate organ, and the tympanal organ. This investigation re‐evaluates the light microscopic appearances of these organs in the foreleg tibia of the cricket, Gryllus assimilis, initially described by Herbig in 1902.

The study also examines the fine structure of the subgenual and intermediate organs and provides the first fine structure analysis of these structures.

The subgenual and intermediate organs are typical scolopophorus organs suspended perpendicular to each other within the dorsal hemolymph canal. Each is innervated by dendrites from the anterior ganglion. Neither the subgenual, intermediate, nor tympanal organ is structurally related to the larger posterior tympanic membrane.

The study shows that the tibial tympanal organ in the cricket is not a scolopophorus organ, but consists of highly modified epithelium, associated with the anterior tympanic membrane, and receiving innervation from the anterior ganglion.
Observations on the integument of the water mite Arrenurus major (Acari: Parasitengona)
Authors: Redmond B. L.
Published: February 2005

A study of the integument of the aquatic mite Arrenurus major Marshall is presented. When the cuticle is examined with the unaided eye and the light microscope, it appears to possess numerous tiny pits. However, scanning electron micrographs of the cuticle reveal that it is a solid surface with topographical sculpturing of the epicuticle, indicating that the “pits” are an internal phenomenon. In cuticle which has been sectioned, areas devoid of cuticular material beneath the thin exocuticle are revealed. These areas are the pits which are goblet‐shaped.

The integument consists of five major strata. These are from the outside to the inside: (1) a superficial layer with a maximum observed thickness of 725 Å, (2) an epicuticle with a thickness of about 900 Å and composed of at least four sublayers, (3) an exocuticle with a thickness of about 1.5 Å. Fibers of the exocuticle are arranged in a Bouligand pattern and exhibit a regularly occurring discontinuity with a spacing of 200 Å. (4) An endocuticle ranging from 15 to 20 μ in thickness. The endocuticle is characterized by bandings which superficially resemble the lamellae of insects but are not homologous, microfibers which exhibit a preferred orientation, and the presence of the pits; and (5) an epidermis lying beneath the endocuticle and extending into the pits.

Pore canals are present only in the exocuticle and have their origin at the apices of the pits. The pore canals contain a central filament, and a plug is present just beneath the epicuticle.
Suppression of the allograft response by implants of mature lymphoid tissues in larval Xenopus laevis
Authors: Ruben Laurens N. , Stevens Jean M. , Kidder Gerald M.
Published: February 2005

One hundred and twenty‐two larvae of Xenopus laevis, the South African clawed toad, at developmental stages 48, 50, 52 and 54, were implanted in the tail with two allografts from adult tissues. In each case, one allograft was from kidney, while the other was either from kidney, thymus, spleen, or liver. In any particular host the two implants were always from the same donor and the implants were all visually matched in size. The experimental period was a maximum of nine days, so as to minimize the large numbers of changes normally accompanying larval progress from stage to stage. We are concerned with the timing of allograft response initiation under the implant conditions of each experimental group at a particular point in development. An allograft response was defined as an infiltration and accumulation of small lymphocytes in the “test” kidney allograft. Larvae of all stages developed allograft responses within one week post‐implantation when the variable implant was from kidney, but implants from spleen and thymus suppressed both the timing of initiation and the subsequent intensity of the response. Spleen was more effective in this regard than thymus and both were more effective in the earlier larval stages. Liver proved to be toxic to the larvae. The relationship between the maturation of the lymphomyeloid tissues and external morphological staging is also discussed.
Fine structure of the midgut epithelium in the developing brown shrimp, Penaeus aztecus
Authors: Talbot Prudence , Clark Wallis H. , Lawrence Addison L.
Published: February 2005

The midgut epithelium of larval and early postlarval brown shrimp has been studied with light and electron microscopy. Ultrastructurally the features of the midgut do not change during these stages of development. On the basis of electron density, two epithelial cell types can be distinguished, and these are referred to as light and dark cells. The dark cells contain more rough endoplasmic reticulum and more free ribosomes than the light cells. Mitochondria in the dark cells have a matrix which is less electron dense than the mitochondrial matrix of the light cells. Both cell types have a microvillous border with a surface coat. The microvilli lack microfilaments within their core, and a terminal web is not differentiated in the stages examined. Tubular smooth endoplasmic reticulum is abundant in the basal portions of the cells. Electron dense, membrane bound vesicles are consistently seen in association with the Golgi apparatus, apical cell surface, and gut lumen and therefore are believed to be secretory granules. Cells in the anterior portion of the midgut often contain very large lipid droplets in the cytoplasm.
Fine structure of fast‐twitch and slow‐twitch guinea pig muscle fibers
Authors: Tomanek Robert J. , Asmundson Craig R. , Cooper Reginald R. , Barnard R. James
Published: February 2005

The guinea pig soleus muscle is a convenient model for the study of slow‐twitch intermediate (STI) fiber ultrastructure because it is composed entirely of fibers of this class. Such fibers were compared with fast‐twitch red (FTR) and fast‐twitch white (FTW) fibers from the vastus lateralis muscle.

FTW fibers are characterized by small, sparse mitochondria, a narrow Z line and, an extensive sarcoplasmic reticulum arranged primarily in longitudinal profiles at the A band and with numerous expansions at the I band. Abundant mitochondria with a dense matrix and subsarcolemmal and perinuclear aggregations are typical of FTR fibers. These fibers contain a plexus of sarcoplasmic reticulum at the A band and a less extensive network at the I band. The Z lines are wider (890 ± 74 Å) than those of FTW fibers (582 ± 62 Å). STI intermediate fibers are distinguished from other types by wide Z lines (1205 ± 58 Å), a faint M band, and a less extensive sarcoplasmic reticulum. Compared to FTR fibers, STI fiber mitochondria are usually smaller with less notable subsarcolemmal accumulations.

FTW fibers have a more limited capillary supply, rarely contain lipid inclusions, and thus may be restricted to phasic activity. Extensive capillarity, mitochondrial and lipid context, and fast contraction times indicate possible phasic and tonic roles for FTR fibers. STI fibers, characterized by numerous lipid inclusions, extensive capillarity, relatively numerous mitochondria, but slow contraction‐relaxation cycles, are morphologically suited for tonic muscle activity.
The structure of the hemocytes of Galleria mellonella (Lepidoptera)
Authors: Neuwirth Maria
Published: February 2005

Four hemocyte types have been identified in the late last larval instar of Galleria mellonella. Plasmatocytoids are round to spindle shaped cells, 10–20 μ long and 5–10 μ wide. The cytoplasm contains no distinguishing inclusions. Golgi complexes, rough endoplasmic reticulum and free ribosomes are abundant. Granular hemocytes are oval shaped cells, 10–20 μ long and 5–10 μ wide. The granules, their most characteristic feature, have a diameter of 0.2 μ, a microtubular sub‐structure, and are made up of acidic mucosubstances. Lipid droplets may be present in these cells at some stage of development. These cells appear to be phagocytic. Spherule cells are oval shaped, 15–20 μ long and 5–10 μ wide. The spherules, approximately 2 μ in diameter, have a highly ordered substructure and are made up of acidic mucosubstances. Oenocytoids are the largest cells, 20 by 40 μ. The cytoplasm contains mostly free ribosomes and microtubules.
Morphological stages of regeneration in the planarian Dugesia tigrina: A light and electron microscopic study
Authors: Spiegelman M. , Dudley Patricia L.
Published: February 2005

A precise sequence of four morphological stages of head regeneration in the planarian Dugesia tigrina has been determined by light and electron microscopy. Each stage is identified by a particular morphogenetic process: I, wound healing; II, blastema development; III, growth; IV, differentiation. A wound epidermis consisting of a thin, sheet‐like layer of cells, rapidly forms from undamaged epidermal cells at the wound margin. The early blastema is comprised of neoblasts which mature into regeneration cells. The maturational changes include the appearance of a nucleolus, nuclear pores, and perinuclear dense aggregates of granulofibrillar material in these cells. These elements are not evident in the neoblasts of the younger blastema. No mitotic cells are encountered in the blastema or wound epidermis. Cytoplasmic expansion of the regeneration cells is correlated with the formation of numerous microtubules radiating from a juxtanuclear centrosphere. During differentiation of muscle cells, distended, granule‐studded cisternae, having moderately fibrillar contents, are regularly disposed adjacent to small patches of myofilaments. Presumptive epidermal cells are recognized by prominent “islands” of finely fibrillar cytoplasm. These cytoplasmic zones persist for a time during definitive differentiation when Golgi bodies, vacuoles, mucous droplets, and rhabdites become evident. The newly formed epidermal cells become inserted among the cells of the wound epidermis. Thus, cells of both the blastema and of the wound epidermis contribute to the reconstituted epidermis.
The circulatory system of Amphioxus (Branchiostoma floridae) I. Morphology of the major vessels of the pharyngeal area
Authors: Moller Peter C. , Philpott Charles W.
Published: February 2005

In order to clarify the morphology of the circulatory system of amphioxus the blood vessels were investigated using modern techniques of light and electron microscopy.

The pattern of circulation in amphioxus is forward ventrally and backwards dorsally. In addition, circulating corpuscles, usually associated with the blood of higher chordates, are absent.

The circulatory system of amphioxus consists of well defined contractile vessels and vascular spaces or sinuses within a connective tissue matrix. The contractile vessels have a discontinuous endothelial lining resting on a basal lamina and are enclosed by a simple layer of contractile myoepithelial cells. Discontinuous endothelial linings occur throughout the vascular tree, including major and minor afferent and efferent vessels and blood sinuses. This is in contrast to higher animals where the endothelium forms a more or less continuous lining along the inner surface of the boundary layer.

It is suggested that the endothelial cells of amphioxus, like the endothelial cells in capillaries of higher chordates, most likely play a role in the physiology of the circulatory system by removing residues of filtration from the basal lamina, thereby facilitating an exchange of materials to and from the surrounding tissues.
Comparative morphology, functions, and homologies of the coxal glands in oribatid mites (Arachnida: Acari)
Authors: Woodring J. P.
Published: February 2005

1. Forty‐eight species of oribatids in 37 families representing most of the superfamilies were collected from various environments (littoral, salt marsh, litter, sod, and freshwater) and sectioned.

2. The coxal gland is composed of a sacculus and a labyrinth in all stages of all oribatid species. Muscles, originating on the body wall, insert at several points on the thin‐walled sacculus which opens into the labyrinth. The labyrinth has an internal, chitinous supporting skeleton. The type A labyrinth has 3–180° bends, producing four parallel regions, and occurs in all inferior oribatids. The type B labyrinth has 1–180° bend, producing two parallel regions, and occurs in all superior oribatids. The coxal gland duct and the lateral gland duct join, penetrate the body wall, and empty into the posterior end of the podocephalic canal. All oribatids have lateral accessory glands, but only inferior oribatids have rostral and medial glands. Three ductless coxendral bodies are always present.

3. The labyrinth length in oribatids is correlated with body size and the environment of the species. Oribatids from sod, leaflitter, or moss show a simple correlation of labyrinth length (X) to total body length (Y) where Y = 4.64X. Freshwater species have a labyrinth length greater than that of comparably sized terrestrial species and salt water (littoral) species have a labyrinth length less than that of comparably sized terrestrial species. There is a greater reduction in labyrinth length in species restricted to salt marshes than in species not restricted to salt marshes.

4. The probable function of oribatid coxal glands is osmoregulation. Hemolymph filtration would occur across the sacculus by positive hemolymph pressure and contraction of the sacculus muscles. Resorption of ions would occur in the labyrinth, which is noncollapsible due to the internal skeleton. The hypothesis is that in freshwater species the rate of filtration is high and resorption of ions would have to be very efficient, therefore they have an elongated labyrinth; but in salt water species water loss must be minimized and preservation of ions would be a disadvantage, therefore they have a shortened labyrinth. Excre ion may also be a function of the coxal glands. The lateral gland may possibly function as an endocrine gland involved with production of a molting hormone. The rostral glands in inferior oribatids may have a salivary function.

5. The coxal glands ofPeripatus, some millipedes, apterygote insects, decapod crustaceans, and all arachnid orders are homologous. The Tetrastigmata, Notostigmata, Cryptostigmata, and soft ticks have typical arachnid coxal glands. The coxal glands of higher Prostigmata may be modified into salivary, silk, or venom glands. The coxal glands in Mesostigmata, Astigmata, and hard ticks are lacking or highly modified.