bluuebunny/crossref_metadata_2025 huggingface dataset:
An ultrastructural analysis of mitosis and cytokinesis in the zygote of the sea urchin, Arbacia punctulata
Authors: Longo Frank J.
Published: February 2005

Post‐fertilization events leading to the cleavage of the zygote of the sea‐urchin, Arbacia punctulata were examined with the light and electron microscopes. Prior to prophase of the first cleavage division, endoplasmic reticulum and annulate lamellae become organized around the zygotic nucleus to produce a crescent‐shaped structure which is defined as the streak (Harvey, '56). With the advent of prophase the streak undergoes morphogenic events which lead to the formation of the mitotic asters. During this transition there is a loss of annulate lamellae and a concomitant increase in endoplasmic reticulum. Annulate lamellae are not found as a part of the mitotic apparatus and are not again observed within the embryo until the two cell stage. During telophase, karyomeres are formed which consist of chromosomes delimited by a porous bilaminar envelope. Blastomere nuclei are produced following the fusion of the outer laminae, and subsequently by the fusion of the inner laminae of the envelopes encompassing the karyomeres.
An electron microscopic study of the tympanal organ 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. The following study examines the fine structure of the tympanal organ in the foreleg tibia of the cricket, Gryllus assimilis. This investigation provides the first fine structure analysis of this structure and shows that the tibial tympanal organ is not a scolopophorus organ. It consists of highly modified epithelium, associated with the anterior tympanic membrane, and receives innervation from the anterior ganglion.
The fine structure of a cephalic sensory receptor in the copepod Doropygus seclusus Illg (Crustacea: Copepoda: Notodelphyidae)
Authors: Dudley Patricia L.
Published: February 2005

A cephalic organ of presumed sensory function is described in nauplii and copepodids of the ascidicolous copepod Doropygus seclusus Illg. The receptor, located bilaterally in the anterodorsal head region, is composed of dendrites of extra optic protocerebral origin which have ciliary protrusions with basal bodies, no rootlets, and a basal infrastructure of the 9 + 0 type. The cilia do not branch and their distal terminations contain only one to four microtubules. In nauplii and free‐living copepodids, a large epidermal supporting cell encapsulates the end of one dendrite and its cilia in a sac. Other dendrites and their cilia pass through the supporting cell and, terminally, the cilia escape to form a whorled fascicle which contacts the anterolateral cephalic cuticle. The latter end organ reaches its greatest development in the second copepodid stage — the stage which infects the ascidian. All of the symbiotic stages of the copepod have only a proportionately smaller end organ of the saccular type and apparently lack the end organ consisting of whorls of ciliary ends. The function of the receptor is unknown, but it is suggested that the end organ which disappears in the symbiotic stages functions in second copepodids in host recognition.
Distribution of monoamine‐containing neurons in the brain stem of the frog, Rana temporaria
Authors: Parent A.
Published: February 2005

The distribution of monoamine (catecholamine and 5‐hydroxytryptamine)‐containing nerve cell bodies in the brain stem and hypothalmus of the frog (Rana temporaria) was investigated with the help of the histofluorescence technique of Falck and Hillarp ('62). At the level of the hypothalmus of this amphibian brain, catecholamine‐containing nerve cell bodies are found mainly within three areas of the periventricular gray substance, namely the peroptic recess organ, the paraventricular organ and the lateral recess region. On the other hand, most of the 5‐hydroxytryptamine (serotonin)‐containing nerve cell bodies of the brain stem of Rana temporaria appear to be concentrated within the midbrain tegmentum. This huge mesencephalic nerve cell collection can be subdivided into medial and lateral groups. More caudally, at the level of the isthmic tegmentum, another group of 5‐hydroxytryptamine‐containing perikarya located close to the midline, within the so‐called raphae region, is clearly outlined. The latter group of neurons extends caudally as far as the level of the medulla oblongata. In addition, a small group of catecholamine‐containing nerve cell bodies is also found in the ventromedial portion of the rostral midbrain tegmentum, whereas a few other catecholamine type neurons are scattered throughout the lower brain stem of the frog and more especially near the ependymal wall of the fourth ventricle. As a whole, the 5‐hydroxytryptamine‐containing neuronal systems of the brain stem of Rana temporaria are much more elaborated than the catecholamine neuronal systems of the same structure.
Electron microscopy of the esophageal ganglion complex of the gastropod pulmonate Triodopsis divesta. I. Ultrastructure of the epineurium
Authors: Dyer Robert F. , Cowden Ronald R.
Published: February 2005

The epineurium of the esophageal complex of the gastropod pulmonate Triodopsis divesta was examined by electron microscopy. The epineurium consists of two main regions: an inner dense fibrous region adjacent to the avascular neural tissue of the ganglion and an outer cellular region comprised of a variety of cell types embedded in a connective tissue matrix. The dense fibrous region contains smooth muscle cells and associated nerve processes and is invested on the neural side by thin processes of glial cells. The outer highly cellular region contains smooth muscle cells, nerve processes, wandering cells (amebocytes), globular cells, and myoepithelial cells comprising the walls of the vascular system. In addition, a cell type not previously identified in other gastropod epineuria is present. These cells resemble neurosecretory cells. The morphology and structural interrelationships of these various constituents are presented and the possible functions of individual cell types and the epineurium in general are discussed in relation to information available on other molluscs.
Sense organs on the antennal flagellum of two species of embioptera (Insecta)
Authors: Slifer Eleanor H. , Sekhon Sant S.
Published: February 2005

Five different kinds of sense organs have been identified on the antennal flagellum of males of Ptilocerembia sp: (1) tactile hairs, (2) thick‐walled chemoreceptors, (3) chemoreceptors with thick walls and many pores, (4) thin‐walled chemoreceptors and (5) campaniform sense organs. The third type has not been reported previously for other species of insects and combines the characteristics of typical thick‐walled and thin‐walled chemoreceptors. The campaniform sense organs are situated in sets of three, 120° apart, on the periphery of the distal end of nearly every subsegment. They lie at the transition zone where the thicker cuticle of the subsegment changes to the thin membrane between subsegments.
Histogenesis of atretic ovarian follicles in a seasonally breeding bird
Authors: Erpino Michael J.
Published: February 2005

Histologic examination of ovaries from a non‐migratory population of scrub jays (Aphelocoma coerulescens) disclosed a marked annual cycle in the incidence of atresia. Atretic follicles became more common as the nesting season progressed and were most abundant immediately after the cessation of breeding. Atresia involved a dissociation of granulosa cells and movement of these cells into the follicle. Subsequently, granulosa cells showed steatogenesis and ultimately disappeared simultaneously with the invasion of the follicle by ex‐thecal gland cells. The data suggest that the diverse histology of avian atretic follicles reflects different stages in the process of atresia rather than multiple origins. Ovarian stromal glands apparently arise both from ex‐thecal gland cells of atretic follicles and stromal connective tissue. A possible secretory role of atretic follicles is considered.
Heart Development in the Mexican Salamander, Ambystoma mexicanum. I. Gross anatomy, histology and histochemistry
Authors: Lemanski Larry F.
Published: February 2005

Gross anatomical, histological and histochemical studies of heart development in Mexican salamanders, Ambystoma mexicanum, are reported. Gross observation suggests that heart development in this urodele species is similar to other amphibians. Histological studies in early embryos show the ventromedially migrating sheets of precardiac mesoderm to be composed of two layers of cells. The right and left dorsal layers fuse and give rise to the myocardium, while the ventral layers form the pericardium. The endocardium arises from cells released by the leading edges of the migrating mesoderm mantles. In early myocardial cells, most of the proteins and carbohydrates are contained in yolk platelets; subsequently, these substances become distributed throughout the cytoplasmic matrixes. In early heart cells free lipid droplets are abundant but decline in size and number as development progresses. Concomitantly, there is an increase in bound lipids. Reticular fibers are detected in the endocardial‐myocardial spaces simultaneously with trabeculae formation. Collagen appears somewhat later in development.
Palatogenesis in hamster. II. Ultrastructural observations on the closure of palate
Authors: Chaudhry A. P. , Shah R. M.
Published: February 2005

Formation of secondary palate in hamster was studied with electron microscopy. Prior to assuming horizontal position, the palatal shelves were covered by a two to three cell layer thick epithelium which was separated from the underlying mesenchyme by an intact basal lamina. Epithelial cells were attached to each other by desmosomes. Early hemidesmosomes could be identified as thickenings of the cytoplasmic membrane opposing the basal lamina. Epithelial cells, like other embryonic cells, contained only few organelles but were rich in polyribosomes. As the horizontal shelves approached each other towards the midline, lysosomes and tonofilaments appeared in the superficial and basal cells of the epithelia. Superficial cells showed degeneration and eventual lysis. Fusion of the opposing epithelia occurred between the deeper cells by means of newly formed desmosomes. The epithelial seam resulting from fusion of the epithelia was limited on each side by a continuous basal lamina. Its subsequent thining and eventual fragmentation resulted from the loss of cells by autophagy. There was no evidence of mesenchymal invasion of the epithelial seam. Mesenchymal macrophages appeared in the later stage of palatogenesis and were responsible for phagocytosis of cellular debris.

Formation of the soft palate was basically similar to that of the secondary hard palate and occurred by fusion of the opposing shelves. Similarly, anterior closure of the palate occurred by fusion of the lower end of the nasal septum to the primary and secondary palates. Hyperplasia of the opposing epithelia, prior to their fusion, was often seen.

It is suggested that formation of the palate occurs in predictable and coordinated fashion and that timely appearance of lysosomes causing lysis of intervening epithelia is of great significance in normal palatogenesis.
Scanning electron microscopy of scales from different body regions of three lizard species
Authors: Stewart Glenn R. , Daniel Ronald S.
Published: February 2005

The Oberhautchen of scales from the dorsal, parietal, and ventral regions of Sceloporus occidentalis (Iguanidae), Gerrhonotus multicarinatus (Anguinidae), and Anniella pulchra (Anniellidae) were examined with a scanning electron microscope. At low magnification, all scales of S. occidentalis exhibit well‐defined outlines of cells belonging to the Oberhautchen layer and the previously overlying clear layer. The dorsal and parietal cells of this species exhibit a minutely dentate Oberhautchen that forms tooth‐like spinules 0.2 to 0.5 μ long and arranged in irregular rows. Minute pits 0.1 to 0.3 μ in diameter characterize the Oberhautchen of a ventral scale.

Cell outlines are not evident on the scales of G. multicarinatus. The Oberhautchen of dorsal and parietal scales of this species is prominently laminated. Laminae are less prominent on scales of the lateral fold, and no intrinsic surface structure is evident on a ventral scale. In contrast, the fossorial anguinomorph Anniella pulchra exhibits Oberhautchen surfaces with practically no intrinsic microornamentation. However, what appear to be outlines of Oberhautchen cells are visible on the dorsal and ventral scales.

These observations suggest that modifications of Oberhautchen microornamentation may have evolved to reduce friction with the substrate or other scales. The lack of pronounced microornamentation of the Oberhautchen on some body scales may indicate that a complex interdigitation between clear layer and Oberhautchen cells is not essential to the sloughing process.
The blood system of the flabelligerid polychaete Flabelliderma commensalis (Moore)
Authors: Spies Robert B.
Published: February 2005

The blood system of the flabelligerid polychaete, Flabelliderma commensalis has been explored by dissection, light and electron microscopy and absorption spectrophotometry. The main longitudinal vessels are the dorsal, ventral, perineural, sub‐oesophageal, supra‐oesophageal and heart. Each segment has a segmental vessel which communicates with the dorsal vessel in thoracic setigers and the gut sinus in abdominal setigers. Branches of the segmental vessels in setigers 2–9 supply the gonads. A blood sinus envelopes most of the gut. Circulation is maintained by the pumping of the heart which immediately supplies blood to the supra‐oesophageal ganglion, the branchiae and the palps. These are paralleled by a system of collecting vessels. The sinus of the supra‐oesophageal ganglion receives a number of different axonal endings, some of which may be neurosecretory. The retroperitoneal vessels in their most developed form are composed of an intima, longitudinal and circular muscles and a peritoneum. The heart vessel contains a cardiac body whose cells appear to contain vacuoles of blood pigment. The blood pigment exhibits the absorption characteristics of a chlorocruorin with maxima at 438, 558 and 606 nm.
Microtubules and muscle attachment in the integument of the balanidae
Authors: Koulish Sasha
Published: February 2005

Attachment of muscle of the integument was studied in two species of Balanidae, Balanus balanoides and B. improvisus with electron microscopy. Specilalized epithelial cells (tendon cells) intervene between the muscle and overlying cuticle. An extensive desmosome‐like junction exists between these two tissues. The tendon cell contains huge amounts of microtubules aligned parallel to the long axis of the inserting muscle. Tension exerted by contracting muscles is conveyed to the chitinous exoskeleton via the specially organized tendon cells and the extensive myo‐tendinal cell junctions.
Preliminary investigation of variations in tooth replacement in adult Necturus maculosus
Authors: Miller William A. , Rowe Dorothy J.
Published: February 2005

Although there are a number of studies on tooth replacement patterns in lower vertebrates, most do not indicate whether this process is continuous throughout the year or is affected by either breeding or seasonal cycles. We have surveyed the replacement patterns found in living and specifically killed Necturus maculosus (Amphibia: Proteidae) to determine the nature of their variation throughout the year prior to investigating possible controlling mechanisms of the formation and eruption of amphibian teeth. Some animals (34), kept in a large outside tank, were killed at monthly intervals and their tooth‐bearing bones radiographed using a modification of the technique previously described (Miller and Radnor, '70). Other animals (9), kept at 4°C, were anesthetized with tricaine methanesulphonate (M.S. 222), and wax impressions taken with beading (carding) wax of the functioning teeth at regular intervals. Animals examined in the late spring and summer (25) showed no signs of active tooth replacement. Small replacement teeth visible beneath each functioning tooth enlarged only slightly throughout the summer. In early and late fall some functioning teeth were lost and replacement teeth grew and erupted to replace them. Replacement patterns were very irregular and classical alternate form rarely seen. In a number of animals the replacement series was formed from every third tooth. Animals kept constantly at 4°C showed no replacement phenomena. Patterns varied between the different bones of the jaws and did not support the Zahnreihe concept of Edmund ('60).
Structure and function of the olfactory apparatus in the fresh‐water carp, Labeo rohita ham. buch.
Authors: Ojha P. P. , Kapoor A. S.
Published: February 2005

The oval olfactory rosette of the carp Labeo rohita belongs to Burne's ('09) rosette column one or to Bateson's (1889) rosette type three. The total olfactory area of the fish is greater than its total retinal area; however, it has been classified with Teichmann's ('54) group of eye‐nose fishes. Each olfactory chamber communicates with an anterior, ventral accessory sac; in spite of Burne's ('09) observation that accessory sacs are absent in carps. Movements of the jaw bones dilate and compress the accessory sac. Water is drawn in through the posterior opening (and not through the anterior as suggested by Liermann, '33, and Johnson and Brown, '62) and also expelled through it when the mouth opens and closes for normal respiratory function. Hence, the accessory sac does not draw water across the olfactory rosette through the anterior opening. At intervals, the fish opens its mouth full and wide and draws water into the chamber through the anterior opening as well.
Stereotaxic map of the muscle fibers in the indirect flight muscles of Drosophila melanogaster
Authors: Levine Jon D. , Hughes Malcolm
Published: February 2005

It is possible to monitor the electrical activity of the motor neurons of Drosophila by recording the electrical activity of the muscle fibers. We have found that it is possible to specify the location of the subcuticular terminations and to describe the orientation within the thorax for the individual muscle fibers, because of the large size of the fibers and because the surface anatomy of Drosophila is known in detail. A map has been made to indicate the location of the muscle fibers with respect to superficial landmarks. The importance of the stereotaxic map for physiological studies is discussed.
The role of cell death during morphogenesis of the mammalian eye
Authors: Silver J. , Hughes A. F. W.
Published: February 2005

Serial sections of embryonic rat eyes were stained with hematoxylin and eosin, quantified (by counting pycnotic and viable nuclei), reproduced by camera lucida on wax plates, and moulded into reconstructions in order to study the normal progression of cellular death during morphogenesis. At least nine distinct necrotic loci (A through I) can be distinguished. Immediately following contact between the retina and surface ectoderm (day 11) degenerating cells were observed in (A) the ventral extent of the optic vesicle, beginning in the mid‐retinal primordium and continuing ventrally in the optic stalk, (B) in the rostral optic stalk base, and (C) in the surface ectoderm encircling the early lens placode. No degeneration was observed in the dorsal half of the presumptive retina, in the entire pigment epithelium, or in the lens placode proper. During day 11.5 the lens placode thickens and forms a degenerating locus (D) in its ventral portion opposite the underlying pycnotic zone in the retina (A). During day 12 the ventral pycnotic zone (A) divides into two subunits (A1 and A2). Invagination of the lens displaces its marginal and ventral components (C and D) so that they come to occupy the lens pore area and presumptive corneal epithelium. Simultaneous invagination of the retinal rudiment juxtaposes the pigment epithelium which concurrently forms a necrotic area (E) adjacent ventrally to that in the retina (A1). Degeneration appears in the caudal optic stalk (I). The density of viable cells decreases adjacent to pycnotic areas in the retina and pigment epithelium and increases within these death centers. During day 13 the optic fissure forms within the subunits of the ventral pycnotic zone (A1 and A2). Degenerations are seen in the dorsal optic stalk (F) and in the walls of the optic fissure (G and H). Throughout these stages necrosis appears only in those portions of the eye rudiment where invagination is either retarded or completely absent.

In part, these observations suggest that cell death serves (1) to retard or inhibit invagination within death centers, (2) to integrate the series of invaginations which mould the dorsal optic cup and optic fissure, (3) to assist formation of the pigment epithelium monolayer, and (4) to orient the lens vesicle within the eye cup. The spatio‐temporal relationship between necrotic loci suggests that pycnotic cells in the retina may influence their production in the lens and pigment epithelium. Preliminary observations on the mouse, pig, and human substantiate those on the rat.
Some structural and cytochemical observations on the axial filament complex of lung‐fluke spermatozoa
Authors: Burton Paul R.
Published: February 2005

As seen in transverse section, doublet elements of the axial unit of spermatozoa of Haematolocchus medioplexus, a frog lung‐fluke, possess walls made up of protofibrillar subunits 50–60 Å in diameter. The partition between A and B members of a doublet element often show extra protofibrils which may partially occlude the “lumen” of the A tubule. Each A tubule possesses outer and inner lateral arms which repeat at longitudinal intervals of about 215 Å and which appear to be structurally dissimilar; the outer arm is expanded at its free end and the inner arm often connects to the B tubule of the adjacent doublet element. Regularly‐spaced radial links connect the central sheath of an inner core complex to the A tubules of the peripheral doublet elements. Tests for magnesium‐activated ATPase activity provide evidence that the enzyme is associated with the surfaces of doublet elements and the surface of the central sheath. Finally, study of an axial unit which developed in an abnormal manner suggests that normal differentiation of an axial unit may depend on the elaboration of a core complex and radial links.
Ultrastructural features of cardiac muscle cells in a tarantula spider
Authors: Sherman R. G.
Published: February 2005

The ultrastructural features of cardiac muscle cells and their innervation were examined in the tarantula spider Eurypelma marxi Simon. The cells are transversely striated and have an A band length of about three microns. H zones are indistinct and M lines are absent. Thick and thin myofilament diameters are approximately 200 and 70 Å respectively. Eight to 12 thin filaments usually surround each thick one. Accumulations of thick and thin myofilaments occur perpendicular to the bulk of the myofilaments in some cells. The Z line is discontinuous and thick filaments may pass through the spaces in the Z line. Extensive systems of sarcoplasmic reticulum and transverse tubules are present; these form numerous dyadic junctions in both A and I band regions. Sarcolemmal invaginations form Z line tubules; lateral extensions of the plasma membrane portion of these invaginations form dyads. Nerve branches of the cardiac ganglion make multiple neuromuscular synapses with at least some of the cardiac muscle cells. Both large granular and small agranular vesicles are present in the presynaptic terminals. Intercalated discs similar to those present in other arthropod hearts occur between the ends of adjacent cardiac muscle cells.
Cytophysiological basis of disruptive pigmentary patterns in the leopard frog Rana pipiens. I chromatophore densities and cytophysiology
Authors: Smith‐Gill Sandra J.
Published: February 2005

Statistical analyses of chromatophore densities and morphological states in wild type, burnsi, and kandiyohi: adult Rana pipiens integument yielded the conclusion that disruptive pigmentary pattern is permanently defined by regional chromatophore densities. Spatial chromatophore patterning is enhanced and rendered more visible by the morphological and physiological differences among chromatophores within the various pattern regions. Specifically, (1) chromatophores were differentialy distributed among pattern regions, (2) greater complexity of gross disruptive patterning had greater underlying melanophores densities, (3) there were significant density differences among non‐sib individual animals, among fertilization, and among shipment batches, but not among full‐sibs, and (4)kandiyohi individuals had more while burnsi individuals had fewer total melanophores than wild type. A stellate morphology was significantly correlated with high melanophore density, although the relationship of melanophore density to melanophore morphology differed among pattern regions and among genotypes. The functional interrelationships of density and morphology, and their role in disruptive patterning and coloration, are discussed.
Ultrastructural analysis of the functional copulatory organ of the male rotifer, Asplanchna brightwelli
Authors: Aloia Roland C. , Moretti Richard L.
Published: February 2005

The male rotifer copulatory organ is composed of a urethral canal extending from the tip of the copulatory organ internally to a layer of microvilli. The microvilli project from two different cell types, referred to as the internal and peripheral microvillar cells according to their location. At this microvillar junction a second canal, the vas deferens, continues posteriorly and enters the sperm duct region of the testis. The channel of the vas deferens is formed from the inner wall of three separate cells; the cap, intermediate and basal cells. Peripheral to these cells and parallel to them for their entire length, cross sections of seven prostate gland cells can be observed. Anteriorly, these gland cells are connected to the basal end of the microvillar layer via a short neck region, through which glandular secretion occurs only during copulation. The mechanism of secretion appears to be a form of exocytosis whereby the secretory granule membrane fuses with the cell plasmalemma so that rupturing at the point of fusion will release the granule content into the neck region.

The prostate gland cells contain an abundance of autophagic vacuoles while most of the other cells of the copulatory organ contain primary lysosomes and cytolosomes. These organelles may be associated with the aging process in rotifers, or, as in the case of the prostate gland‐autophagic vacuoles, with a fast organelle turnover during secretion.
Tooth replacement in the bowfin (Amia calva — Holostei)
Authors: Miller William A. , Radnor Carolyn J. P.
Published: February 2005

The dissected tooth bearing bones of 20 specimens of Amia calva (Pisces:Holostei) ranging from the third to tenth season have been examined radiographically and in alizarin red S stained and cleared specimens. Although forms of alternate (1:1) tooth series replacement (sensu Edmund, '60) were frequently observed, even in the youngest, immature specimens, many examples of irregular replacement were recorded. In several bones, the maxillae in particular, series with every third (2:1) or fourth (3:1) tooth replacing were seen and possible patterns of 2:2, were recorded. It is concluded that these data are not consistent with the Zahnreihen concept but support a morphogenic field concept of tooth development.
Superficial venous arrangement of the face and neck of the tufted capuchin, Cebus apella linnaeus, 1758
Authors: Madeira Miguel C. , Watanabe Ii‐Sei
Published: February 2005

The description of the superficial veins of the face and neck was based upon the dissection of 28 male and female adult tufted or brown capuchin monkeys (Cebus apella), captured in southern Goiás, Brazil.

Although the venous arrangement of these areas is basically the same in all primates, some characteristic differences were noted: 1. the anterior jugular and common facial veins were absent; 2. most specimens had a venous hyoid arch, and a connecting vessel between the external jugular and subclavian veins; 3. the inferior petrosal sinus drains into the external jugular v. through the postglenoid foramen; 4. the facial, lingual and cephalic veins open into the external jugular vein; 5. both the internal and external jugular veins have about the same diameter; 6. the vascular pattern appears to be quite stable; anatomical variations appear to be few and unimportant.
Development of electric organs of Gymnarchus niloticus (Fam. Gymnarchidae). II. Formation of spindle
Authors: Srivastava C. B. L. , Szabo T.
Published: February 2005

The development of electric organ spindles of Gymnarchus niloticus has been investigated with respect to the exact time and place of origin and the process of formation of the adult plan. The results are compared with those of Dahlgren ('14). A common primordium for all the electroplates of of a spindle as held by Dahlgren ('14) is not supported by the present work.
The chicken trigeminal ganglion II. Fine structure of the neurons during development,
Authors: Gaik Geraldine C. , Farbman Albert I.
Published: February 2005

A morphological study of the developing chick trigeminal ganglion was done. For descriptive convenience, four stages of development have been defined: Phase I (2 to 4 days of incubation) — Both the neural crest and epidermal placode contribute to the forming trigeminal ganglion, which is comprised of clusters of undifferentiated cells and primitive neuroblasts. Toward the end of this phase, satellite cells and unmyelinated nerve fibers are seen. Phase II (5 to 10 days of incubation) — In the lateral portion of the ganglion, large differentiating neuroblasts and young bipolar and pseudounipolar neurons were present. The latter were characterized by a large, eccentrically located nucleus at one pole, a long axonal process at the opposite pole, and a clear centrosphere region between the two. In the medial region of the ganglion, most of the neurons were smaller and more closely packed together. Phase III (11 to 17 days of incubation) — The ganglion was constituted of bipolar and pseudounipolar cells with an apparently random distribution of small and large neurons. Nissl bodies appeared in developing neurons. Phase IV (18 days of incubation to 3 weeks post‐hatching) — Light and dark neurons first made their appearance. Dark neurons were characterized by (1) clear perinuclear cytoplasm containing a Golgi apparatus, vesicles and mitochondria and (2) a peripheral cytoplasm of densely packed stacks of Nissl substance. Light neurons contained individual clumps of Nissl substance distributed in a pale cytoplasmic matrix.
Morphological and physiological studies of the silkmoth ovary I. The general histology and some histochemical properties of the ovary of Samia Cynthia (Drury)
Authors: White Joan F. , Larsen Joseph R.
Published: February 2005

Ovaries of the giant silkmoth Samia cynthia Drury have been studied histologically and histochemically during diapause, adult development, and after injury to the diapause animal. In addition to cellular changes involved in follicular growth and vitellogenesis, changes in the intermediate layer cells are very striking, showing a distinct pattern during ovarian development and after injury. Two types of granules, one periodic acid‐Schiff (PAS) positive, the other paraldehyde‐fuchsin (PF) positive, change in their number and distribution in the intermediate cells during development and after injury. The PAS‐positive granules appear during the first one‐third of development, increase in number and size until the tenth day, then gradually dwindle in number and size, and disappear in the adult cells. The PF‐positive granules, present in moderate numbers in the diapause animal, decrease in number until the tenth day of adult development, then reappear, and are present again in adult intermediate cells. After injury to a diapause pupa, intermediate cells show a greatly increased number of PF‐positive granules, but none that are PAS‐positive.

The PAS‐positive granules are a neutral or mildly acidic mucosubstance, and may correspond to lysosomal activity, while the PF‐positive granules may be a neurosecretory‐like substance or the product of hormone‐dependent protein synthesis, since the patterns of granule distribution in the intermediate cells seem to reflect both general metabolic and hormone‐related events.
Gross and microscopic morphology of the Glandula proctodealis (foam gland) of Coturnix c. japonica (Aves)
Authors: Klemm Robert D. , Knight Carl E. , Stein Sherryl
Published: February 2005

The dorsal proctodeal wall of the Coturnix contains a gland which is especially well‐developed in the sexually active male and which secretes a foamy exudate. This gland has not been recorded in any other genus of birds and appears to be unique to members of the genus Coturnix. On the basis of its location in the adult we have named this gland the proctodeal gland (glandula proctodealis). Structure of the gland does not conform to any curently defined category of glands because it is an aggregate of individual glandular units each of which opens independently into the proctodeal cavity but with the entire structure enclosed by a connective tissue capsule. We have thus characterized it as an aggregate gland. Observations on the arrangement and composition of the fibrous capsule and its intimate relationship to the perimysium of M. sphincter cloacae indicate that release of the secretion probably results from contraction of the cloacal musculature. Preliminary data suggest that development of glandular tissue in the female may be a function of age rather than of androgen sensitivity which characterizes the male gland. It is concluded that the chemical nature of the glandular secretion and its function in the sexually active bird, as based on presently available information, remains unknown.
Cutaneous wound healing in the sea cucumber, Thyone briareus
Authors: Menton David N. , Eisen Arthur Z.
Published: February 2005

Wound healing in the integument of the sea cucumber, Thyone briareus, was studied for up to 50 days after inflicting wide excisional wounds and for 14 days after producing incisional wounds. Rapid re‐epithelialization of the wound was effected by the migration of epidermal cells and pigment cells from the periphery of the wound margin. This occurred without apparent evidence of concomitant mitotic activity. Dermal wound healing was completed by the fourteenth day in the incision wounds but occurred very slowly in the broad excision wounds. Morula cells seem to be involved in both epidermal and dermal wound healing, although their precise role is unknown. In excisional wounds the integument was never completely restored to its normal appearance during 50 days of observation.
Ultrastructural characteristics and innervation of the pineal organ of the antarctic seal Leptonychotes weddelli
Authors: Cuello Augusto Claudio
Published: February 2005

The electron microscopy of the epiphysis cerebri of the antarctic seal Leptonychotes weddelli revealed a highly organized organ. The general cytological characteristics of the pinealocytes and the glial cells are described. The capillary blood vessels are the nonfenestrated type. The organ is richly innervated by mainly unmyelinated nerve fibers. Most of the axons end in the inner part of the organ, around vessels, some of them in relation with pinealocytes. The significance of the findings is discussed.
Early development of the kelp fly, Coelopa frigida (Diptera). II. Morphology of cleavage and blastoderm formation
Authors: Schwalm Fritz E. , Bender Harvey A.
Published: February 2005

Cleavage and blastoderm formation in Coelopa frigida are extremely rapid developmental processes. In short (6–7 minutes) successive cell cycles, nuclei multiply and spread out through the egg. The movement seems to be aided by endoplasmic vesicles and cisternae which are in direct contact with the nuclear membrane. The first cells to separate from the egg plasmodium in early superficial cleavage stages are the pole cells.

Precursor material from multivesicular bodies forms the pole cell membranes. The primary nuclei from the posterior pole region are removed from the blastoderm by the pole cell segregation. Blastoderm nuclei from the regions adjacent to the posterior pole migrate into the residual periplasm after pole cell segregation has been completed and constitute the blastoderm nuclei in that region of the egg. Nucleoli are not revealed during internal cleavage. They appear in pole cells shortly after their segregation. The generation time of the blastoderm nuclei increases after the twelfth cleavage. Concurrently, nucleoli form in the blastoderm nuclei and permanent cell membranes separate individual blastoderm cells. After blastoderm cells have been separated from each other, they remain in contact with the interior yolk sac by means of cytoplasmic canals. This contact is maintained at least during the early phases of blastokinesis. Observations on nuclear migration and rapid membrane formation are discussed as examples of protein assembly from subunits as an alternative to de novo protein synthesis in early stages of development.
Scanning and transmission electron microscopic studies of jejunal microvilli of the rat, hamster and dog, ,
Authors: Anderson James H. , Taylor A. B.
Published: February 2005

Scanning and transmission electron microscopy were used to investigate the surface area and number per unit area of microvilli from jejunal villus epithelial cells in the rat, hamster and dog.

The calculated mean microvillus surface area was 0.419 μ2, 0.573 μ2, 0.751 μ2 for the rat, hamster and dog respectively.

The largest number of microvilli per square micron freeze dried villus surface was measured in the rat with a mean value of 65. Hamster and dog freeze dried specimens had lower mean values of 54 and 34 microvilli respectively.

The total microvilli surface area in square micron per square micron villus surface was more closely related for the three species with values of 27.23 for the rat, 30.94 for the hamster and 25.53 for the dog.

These data indicate an inverse relationship between the mean microvillus surface area and population density in the species studied. However, the total microvilli surface area per unit villus surface is relatively similar for the three species.

The observed number of microvilli per unit villus surface was shown to vary depending upon the dehydration technique employed for preparation of scanning electron microscopic specimens. This variation probably reflects shrinkage artifact and should be considered in soft tissue studies involving the scanning electron microscope.
Developmental aspects of sirenomelia in the mouse
Authors: Schreiner Ceinwen A. , Hoornbeek Frank K.
Published: February 2005

The mutant gene srn produces sireniform abnormalities in the mouse. The effects of this gene on normal prenatal development were examined histologically by retrograde analysis from day 10 through day 18 of gestation.

The sireniformphenotype is characterized by the fusion of the hindlimbs and accompanying defects of the posterior appendicular skeleton. Visceral defects involve the urogenital system and the lower intestinal tract. A single umbilical artery arises from the dorsal aorta and controls the fetal circulatory pathway normally mediated by the lateral umbilical arteries. This artery is believed to have resulted from the fusion of the paired primitive umbilical arteries.

It is suggested that the srn mutation causes a narrowing of the posterior amnion early in development. The resulting abnormal pressure causes a dorsal displacement of the hindgut, allowing fusion of the hindlimb buds. Abnormal structural relationships and pressure in the narrowed posteriior region disrupt normal urogenital and intestinal development and increase the proximity of the primitive umbilical arteries.
Histological and histochemical studies on the formation of statoblasts of a fresh‐water bryozoan, Pectinatella gelatinosa
Authors: Mukai Hideo
Published: February 2005

The course of the statoblast formation in Pectinatella gelatinosa was divided into four stages and studied histologically and histochemically. The bottom of the cystigenous cup is a center of cystigenous cell differentiation and the peripheral zone of the inner cystigenous layer turns to the outer cystigenous layer as the cystigenous cup grows. The annulus is formed by migration and transformation of the outer cystigenous cells.

During early stages, the yolk cells have an intensely pyroninophilic or RNA‐rich cytoplasm. The cytoplasmic pyroninophilia then diminishes as the amount of yolk granules increases.

Several kinds of yolk substances occur in the mature statoblast. During statoblast formation glycogen appears first, then glycoprotein and finally neutral unsaturated lipid.

Acid phosphatase activity is associated with granular structures in the cytoplasm. In the cystigenous vesicle, acid phosphatase activity is low and confined to the apical extremity of the cell. Histochemically detectable alkaline phosphatase activity is not involved in the formation of the statoblast.
Histological development of the cement gland in Xenopus laevis: A light microscopic study
Authors: Lyerla Timothy A. , Pelizzari John J.
Published: February 2005

The differentiation and degeneration of the cement gland in Xenopus laevis is described. The gland is first observed histologically at stage 19 (neural tube stage) as a packed group of apical ectoderm cells heavily laden with oocyte pigment granules, lying ventral to the cranial neural fold. By tailbud stage 35/36, the gland cells have increased in height and are approximately ten times taller than nonglandular apical ectoderm cells. The nuclei divide the gland cells into an apical region that is eosinophilic and contains oocyte pigment granules, and a basal region that contains clear droplets. The cells are decreasing in height by stage 40 (early tadpole) and begin to lose their pigment granules. Between stages 45 and 48, the pigment is extruded and the clear basal droplets diminish in number. From stage 48 to 49 the cells become vacuolated and the histotypic characteristics of the functional gland are lost. The gland is not vascularized, nor do phagocytic cells appear in its vicinity during any stage of its development. It remains bordered at its base by subjacent basal ectoderm during its entire life cycle of 10 to 12 days at room temperature.
Innervation of abdominal paraganglia: An ultrastructural study
Authors: Mascorro Joe A. , Yates Robert D.
Published: February 2005

Abdominal extra‐adrenal chromaffin tissue, or paraganglia, was examined at the ultrastructural level to elucidate the innervation of this adrenal medullary homologue. Paraganglia display unmyelinated nerve fibers surrounded by Schwann cell cytoplasm. These nerves are separated from the paraganglion Type I (granule‐containing) cells by cytoplasmic projections of paraganglion Type II (satellite) cells. However, serial sections show that the nerves eventually make synaptic contact with the Type I cell. At the axon‐chromaffin cell junction, only the outer aspect of the nerve is covered by the satellite cell. The presynaptic endings contain numerous synaptic vesicles, mitochondria and glycogen particles. The vesicles are predominantly of the clear‐cored variety, but a few possess centers which are elecron opaque. The pre‐ and postsynaptic membranes are separated bya subsynaptic space and occasionally exhibit the membranal densities usually associated with synaptic areas. These ultrastructural studies establish definite evidence that abdominal paraganglion cells are innervated.
Diversity in patterns of coital contact of mosquitoes: A scanning electron microscopic study
Authors: Spielman Andrew , Waterman Robert E. , Meller Samuel M.
Published: February 2005

Specimens, representative of each of the major taxa of mosquitoes, were fixed in copula and the external genitalia examined by scanning electron microscopy. The periphery of the basin‐like everted aedeagus of Aedus aegypti precisely matches that of the everted atrial membrane of the female. These structures are appressed during coitus and sealed by pressure of the paraprocts, aedeagal pouch and proctiger. When everted, the aedeagus of male Culex pipiens reveals a ridged dome that surrounds the genital opening. This dome seals itself laterally into a gutter formed by pad‐like extensions of the female's genital lips and is sealed dorsally by pressure of the aedeagal apodeme. The aedeagus of another culicine species, Wyeomyia smithii, bears the gonopore at the apex of a spined tube. This tube is inserted between the female's genital lips and is sealed within the genital atrium. The aedeagus of the toxorhynchitine species Toxorhynchitis brevipalpus is immobile and is inserted deep within the genital atrium of the female where it is sealed by pressure of the atrial walls. Males of each of these mosquitoes deliver a mixture of semen and sperm to the copulatory bursa of the female. After withdrawal of the aedeagus, sperm is transferred to the spermathecae.

In contrast, sperm of Anopheles quadrimaculatus are delivered directly to the spermathecal duct. The tube‐like aedeagus is positioned by its leaflets during sperm transfer and is driven deep into the atrium, where a mixture of semen and sperm is ejaculated.

The significance of mechanical barriers to mating between species is discussed.
Cytological definition of the poriferan stylocyte: A cell type characterized by an intranuclear crystal
Authors: Harrison Frederick W. , Dunkelberger Dana , Watabe Norimitsu
Published: February 2005

The stylocyte (Gr. stylos; pillar) of Corvomeyenia carolinensis Harrison (Spongillidae), a previously undescribed proiferan cell type, was examined using phase contrast microscopy, histochemistry and electron microscopy. The stylocyte, an anucleolate amoebocyte, is characterized by a rhomboidal intranuclear crystal. The crystal, lacking an investing membrane, is embedded directly into the nucleoplasm. It is homogenous with no demonstrable crystalline subunits. Histochemical studies suggest that the crystal is proteinaceous, containing no DNA or RNA. Cytoplasmically, the stylocyte contains promienent homogenous smooth membrane‐bound inclusions which contain high levels of neutral (PAS‐positive) and polycarboxylated mucopolysaccharides but low levels of glycogen and no significant phosphatase activity. The granular endoplasmic reticulum is poorly developed. Correspondingly, with various histochemical methods, little or no cytoplasmic RNA is demonstrated. Because electron microscopic studies of C. carolinensis indicate the probable absence of viral inclusions in the sponge and because the crystal contains no histochemically demonstrable nucleic acid, the evidence appears to suggest that the crystal neither represents an assemblage of mature virus units nor a virus‐induced structure. The stylocyte cell type may play a role in nutrient cycling in C. carolinensis with the crystal acting either as a site of protein storage or as an excretory product.