bluuebunny/crossref_metadata_2025 huggingface dataset:
The sodium and chloride dependence of chloride secretion by the opercular epithelium
Authors: Degnan Kevin J.
Published: June 2005

The effects of ion substitutions on the Cl− secretion rate and tissue conductance of isolated short‐circuited opercular epithelia from sea‐water‐adapted Fundulus heteroclitus were investigated. Serosal Na+ substitution had the same effect on the Cl− secretion rate that serosal Cl− substitution had on the active component of the Cl− efflux. This similarity indicated a 1:1 Na‐Cl requirement for active Cl− secretion across this epithelium, which supports the proposal of a coupled NaCl uptake mechanism at the serosal membrane of Cl− secretory epithelia. Mucosal Na+ and Cl− substitutions appeared to inhibit completely the active Cl− secretory flux. The reductions in the tissue conductance with mucosal ion substitutions suggested that this effect can be attributed to a blocking of the apical membrane Cl− conductance. These mucosal ion effects suggested a possible direct regulatory influence of the external salinity on the Cl− secretion rate and tissue conductance, which provide alternative explanations for observations with the teleost gill epithelium.
Nucleoside triphosphate changes during the peripheral life‐span of erythrocytes of adult rainbow trout (Salmo gairdneri)
Authors: Lane Hugo C.
Published: June 2005

Determinations of nucleoside triphosphates (NTP) were made on rainbow trout erythrocytes segregated into age classes following velocity sedimentation at unit gravity. The NTP content of young cells was lower than that of mature cells, whereas it was significantly higher in the oldest cell population. Thin‐layer chromatography of erythrocyte cell extracts showed that both ATP and GTP were present and that the former dominated in all age groups. Potassium cyanide was significantly more effective than iodoacetate in lowering NTP levels in the cells of the young age class whereas in the oldest cells the reverse was true.
Histone acetylation and deacetylation of nuclei from sea urchin Hemicentrotus pulcherrimus embryos during early stages of development
Authors: Horiuchi Kentaro , Fujimoto Daisaburo , Uto Norihiko
Published: June 2005

Nuclei were isolated from sea urchin (Hemicentrotus pulcherrimus) embryos during early stages of development, and the rates of histone acetylation and deacetylation were examined. Histone acetylation was measured in the presence of 6 mM sodium n‐butyrate, a potent inhibitor of deacetylase, and in the absence of the inhibitor. The deacetylation activity was estimated from the difference between the rates with and without the inhibitor. The activities of the acetylation and the deacetylation, and the ratio of deacetylation to acetylation were unchanged during the stages between early blastula and gastrula. Autoradiographic analysis of acetylated histones showed that all of the internal histones of the nucleosomes were acetylated and that no apparent difference was found in the pattern of the acetylated fractions during the stages compared.
Mechanisms of flagellar motility deduced from backward‐swimming bull sperm
Authors: Phillips David M. , Kalay Dan
Published: June 2005

Under certain conditions of cryopreservation, bull spermatozoa undergo an interesting structural alteration. The sperm tail becomes bent back on itself to form a hairpin shape. The bend in the tail occurs at a very precise point, 11 μm behind the neck, and it causes the tail to become kinked. Flagellar microtubules and dense fibers become broken and the ninefold symmetry of the flagellum is greatly distored. Although the portion of the flagellum between the kink and the sperm head does not propagate a wave, the distal portion of the flagellum propagates a base‐to‐tip wave, causing the spermatozoan to progress backward. These observations suggest that the mammalian spermatozoon does not need basal structures to propagate a flagellar wave.
ATP‐γ‐S (adenosine 5′‐0(3‐thiotriphosphate)) blocks progesterone‐induced maturation of the Xenopus oocyte
Authors: Bellé R. , Boyer Jeanne , Ozon R.
Published: June 2005

ATP‐γ‐S microinjection into Xenopus oocyte prevents progesterone induced maturation. Inhibition is time and dose dependent; 50% inhibition occurs when 50 nl of 0.5 mM ATP‐γ‐S solution are microinjected/oocyte 1 hr prior to the hormonal trigger. ATP‐γ‐S inhibited oocytes can be induced to mature (100%) following microinjection of extracts containing maturation promoting factor (MPF). Our results suggest that the maturation protein(s) has been stabilized in ovo by ATP‐γ‐S microinjection, in its phosphorylated inhibitory form.
Partial characterization of the cytosolic and mitochondrial aspartate aminotransferase from ribbed mussel gill tissue
Authors: Paynter Kennedy T. , Hoffmann Richard J. , Ellis Lehman L. , Bishop Stephen H.
Published: June 2005

The cytosolic (cAAT) and mitochondrial (mAAT) aspartate aminotransferases were partially purified from gill tissue of the ribbed mussel, Modiolus demissus, and individually characterized with respect to heat stability, electrophoretic mobility, pH optimum, Km for substrates, rates in the forward vs. the reverse direction, and reactivity with aminooxyacetic acid (AOA). Isozyme analysis for this population of ribbed mussels indicated three alleles for the cAAT and a single all ele for the mAAT. The mAAT was a single isozymic form with a broad pH optimum and relatively low Kms for aspartate, oxaloacetate, and 2‐oxoglutarate and high Km for glutamate substrates. The cAAT used for the kinetic studies was a single (homozygous) isozymic form, showed great variation in Km and Vmax with pH, and had high Kms for the amino acid substrates and low Kms for the ketoacid substrates. Both enzymes were inhibited to the same degree by AOA. It is hypothesized that the cAAT is involved more with aspartate synthesis and the mAAT with aspartate catabolism.
Influence of osmolytes, thin filaments, and solubility state on elasmobranch phosphofructokinase in vitro
Authors: Hand Steven C. , Somero George N.
Published: June 2005

Skeletal muscle phosphofructokinase (PFK) purified from the thornback ray is rapidly inactivated by urea concentrations as low as 50 mM at pH values below 7.0. Urea‐induced loss of PFK activity is not offset by trimethylamine‐N‐oxide. Protection against urea‐inactivation in vivo, where urea concentration may approach 0.5 M, may be due to two effects. Filamentous (F) actin and muscle thin filaments moderately reduce the urea‐induced loss of PFK activity. The binding of PFK to F‐actin and to thin filaments is shown by ultracentrifugation experiments. PFK activity in vivo also may be stabilized in this species by the formation of a particulate enzyme form which is totally resistant to inactivation by physiological concentrations of urea.
Corticotropin‐releasing factor (CRF) stimulates locomotor activity in intact and hypophysectomized newts (amphibia)
Authors: Moore Frank L. , Roberts John , Bevers Jeb
Published: June 2005

Locomotor activity of rough‐skinned newts (Taricha granulosa) was significantly higher in intact and hypophysectomized males injected intracranially with 100 ng CRF (ovine corticotropin‐releasing factor) than in those injected with 10 ng CRF or saline. In addition, an injection of corticosterone or dexamethasone failed to stimulate newt locomotor activity. These results provide evidence that CRF can act independently of pituitary hormones to stimulate locomotor activity in a nonmammalian vertebrate.
Pinocytosis in fertilized sea urchin (Arbacia punctulata) eggs
Authors: Carron Christopher P. , Longo Frank J.
Published: June 2005

Fertilized and unfertilized Arbacia eggs were incubated with extracellular tracers in an effort to: (1) correlate the onset of pinocytosis with egg activation and its possible role in restructuring the zygote's surface and (2) determine the fate of internalized vesicles and their contents. Zygotes incubated with horseradish peroxidase (HRP), native ferritin, or cationized ferritin incorporated tracers within coated vesicles by 4–7 minutes postinsemination. In contrast, endocytosis by unfertilized eggs was not observed. Zygotes taken at intervals up to cleavage (60 minutes postinsemination) exhibited all three tracers within coated and uncoated vesicles and lysosomes. HRP reaction product was identified within Golgi cisternae in only a few zygotes; native and cationized ferritin were never observed within Golgi elements. The sequential appearance of tracers in pinocytotic vesicles and lysosomes of fertilized eggs suggests that surface‐related components are interiorized and then modified or degraded. Because the zygote surface undergoes a reduction in area, temporally correlated with the onset of pinocytosis, it is possible that endocytosis may be instrumental in the accommodation of the plasmalemma. The interiorization of surface membrane in fertilized eggs may represent a mechanism for the alteration of developmentally related cell surface components.
Regulation of the permeability of the medaka fish embryo chorion by exogeneous sodium and calcium ions
Authors: Cameron Ivan L. , Hunter Keithley E.
Published: June 2005

We questioned if the optically transparent noncellular chorion, or egg envelope, which encapsulates the entire medaka fish (Oryzias latipes) embryo might in some way constitute a permeability barrier to high concentrations of the diuretic called amiloride. More specifically, we questioned if removal of cations from the exogenous environment of the medaka embryo might make the chorion more permeable to amiloride and thereby make the fish embryos more sensitive to the inhibitory and lethal effects of this drug. To test this question, chorion‐encapsulated medaka embryos were exposed to: deionized‐distilled water, to Yamamoto‐Ringer's (Y‐R) solution, to Yamamoto‐Ringer's containing choline chloride as a substitute for NaCl, and to isotonic NaCl solution in the presence of and in the absence of amiloride. Briefly, the prediction that the medaka embryos would be most sensitive to amiloride's inhibitory effects in distilled water was confirmed. Further studies showed that the presence of Na+ or of Ca2+ alone in the culture solution gave partial protection against the lethal effects of the amiloride. Electron probe X‐ray microanalysis studies indicated that addition of Ca2+ and other cations to the culture solution caused the concentrations of cations to increase in the chorion, and that increase was correlated to a visible decrease in the permeability of the chorion to the amiloride. This decreased permeability of the chorion apparently protected the embryo from the amiloride. The decreased permeability of the chorion to amiloride, which occurred in the presence of the cations present in Y‐R solution, was found to be reversible once the cations were washed from the chorion.
Caudal movement of tissues ventral to the cervical somites and the development of the shoulder in the chick embryo
Authors: Searls Robert L. , Brown Joyce
Published: June 2005

It has been suggested that formation of the shoulder in the embryonic chick is caused by caudal movement of the pleural coelom (Yander and Searls, '80a,b; Searls, '83). The cells of the somatopleure over the pleural coelom move into the base of the wing causing a thickening at the cranial base of the wing (the shoulder). In the previous work cited what caused the pleural coelom to move in a caudal direction could not be determined.

It has now been observed that part of this movement is due to increase in the cranial‐caudal width of the hyoid arch. The mandibular arch does not move relative to the base of the wing or the somites. The caudal margin of the hyoid arch on the surface of the neck moves caudally at a rate of four to six somites per day, overgrowing the cervical sinus in the process. The aortic arches move in the same direction at a rate of 2 to 3 somites per day. It is suggested that the more medial elements of the hyoid arch are increasing in size, displacing the cervical sinus in a caudal direction. Part of the caudal movement of the cranial margin of the pleural coelom is also due to increase in length of the trachea. The trachea branches from the larynx ventral to about the eighth somite from 4 to 7 days of development. The distance from the cranial end of the trachea to the bifurcation that produces the left and right bronchi increases so that the bronchi become medial to the shoulder at 5.5 days, and the distance from the cranial end of the trachea to the pleural coelom increases so that the pleural coelom becomes medial to the shoulder at 4.5 days.
Closure of the squid cornea: A muscular basis for embryonic tissue movement
Authors: Arnold John M.
Published: June 2005

The squid cornea is derived from epithelial tissue behind the eyeball. The future cornea is pulled over the developing eyeball by contraction of muscle cells which develop just behind the leading edge. Treatment with cytochalasin B or colchicine does not stop this embryonic tissue movement, suggesting that the muscle is the main motive force in corneal closure.
Limb regeneration in anuran tadpoles following repeated amputations
Authors: Kollros Jerry J.
Published: June 2005

Limbs were amputated through the thigh in stages from V onward in Rana pipiens, R. sylvatica, and Pseudacris nigrita tadpoles to establish regenerative capacity. Normal regenerates were produced through stages XII, XI, and XIII, respectively, for the three species. However, hypomorphic forms with reduced toe numbers or a single spikelike spur, or nonregeneration, could appear as early as stages VII or VIII, and increased in frequency thereafter. Pseudacris produced the largest fraction of hypomorphs and R. sylvatica the smallest. Regenerated limbs of various stages were reamputated just distad of the initial transection level and produced regenerates with almost the same frequency as did the initial amputees. In R. pipiens reamputation and regeneration was followed for up to six sequences, with but little change in frequency or quality of regeneration, even when the contralateral control limbs were in stages XIV–XVII, well beyond the possibility of regeneration after transection through the thigh. Clearly, the hormonal milieu did not limit regeneration, though rate of regeneration accelerated as metamorphic climax was approached. Foot sizes were measured in R. pipiens, and were seen in control animals to be correlated to both stage and to tadpole length. Regenerated feet tended to be slightly larger than control feet of the same stage, showed comparable relationships between length and width, but correlated more poorly with tadpole length.
Uniform cartilage differentiation in micromass cultures prepared from a relatively homogeneous population of chondrogenic progenitor cells of the chick limb bud: Effect of prostaglandins
Authors: Gay Steven W. , Kosher Robert A.
Published: June 2005

Even at very early stages of development (i.e., stages 22–24), the embryonic chick limb bud consists of a heterogeneous mixture of chondrogenic, myogenic, and fibrogenic progenitor cells in various stages of differentiation. In contrast, the distal subridge region of a stage 25 wing bud appears to be a relatively homogeneous population of undifferentiated chondrogenic progenitor cells. In the present study, we confirm the results of a number of investigators that when the heterogeneous cells of whole stage 23/24 limb buds are subjected to high density cell culture (micromass culture) the cells in various discrete regions of the culture aggregate with one another and differentiate into cartilage nodules. The cartilage nodules in such cultures, however, are separated from one another by a considerable amount of nonchondrogenic tissue. In fact, nonchondrogenic tissue constitutes a relatively high proportion of the micromass cultures of whole stage 23/24 limb bud cells. In contrast, when stage 25 subridge mesenchymal cells are subjected to micromass culture, a virtually uniform sheet of cartilage is formed throughout the culture, and little, if any, nonchondrogenic tissue is detectable. The micromass culture of stage 25 subridge mesenchymal cells thus provides an excellent system in which a relatively homogeneous group of chondrogenic progenitor cells progressively and uniformly undergo chondrogenesis in a readily manipulable culture situation. Such a system is ideally suited for studies on the molecular regulation of cartilage differentiation.

In the present study, we have also demonstrated that exogenous prostaglandin E2 (PGE2) elicits a dose‐dependent stimulation of chondrogenesis in micromass cultures of both stage 25 subridge mesenchymal cells and the cells of whole stage 23/24 limb buds. The stimulatory effect of PGE2 is greatly potentiated by the phosphodiesterase inhibitor theophylline, suggesting that its influence on chondrogenesis is mediated by its ability to increase cAMP levels. PGE1 is just as effective as PGE2 in stimulating chondrogenesis, whereas PGF1α, 6‐keto PGF1α and thromboxane B2 have no effect. On the basis of these observations and previous studies, the possibility that endogenous prostaglandins might regulate limb cartilage differentiation by acting as local mediators of cAMP accumulation is discussed.
Immunofluorescent localization of extracellular matrix components during muscle morphogenesis. I. In normal chick embryos
Authors: Kieny M. , Mauger A.
Published: June 2005

Type I collagen is the major collagenous component of embryonic and early postnatal musculature. It is found in tendons, muscle envelopes around individual myofibers (endomysium), around muscle bundles (perimysium), and around muscle bulks (epimysium), as well as in loose connective tissue of intermuscular spaces and perimuscular tunica.

Type III collagen deposition follows with some delay that of type I collagen in all mentioned locations. This type of collagen, however, is not a permanent component of tendons, from which it disappears during the second half of the incubation.

Fibronectin, at first ubiquitously present around connective tissue cells and myogenic cells, becomes progressively restricted to the basal lamina zone, so as to delineate each myofiber.

Laminin at first surrounds groups of muscle cells as long as the latter have not reached the stage of myofiber. At that time, laminin becomes restricted to the immediate surrounding of each myofiber.
Immunofluorescent localization of extracellular matrix components during muscle morphogenesis. II. In chick embryos with hereditary muscular dysgenesis (cn/cn)
Authors: Mauger A. , Kieny M. , Goetinck P. F.
Published: June 2005

The immunofluorescent distribution of types I and III collagen, fibronectin, and laminin during muscle morphogenesis of the crooked neck dwarf mutant chick embryo differs from that of the normal chick. The drastic difference is related to the inability of the mutant embryo to maintain a harmonious muscle pattern. The first sign of the defect is the disaggregation of type I collagen fibers of the tendons and the disorganization of the intermuscular spaces. The organization of the connective tissue never proceeds beyond the appearance of an epimysial envelope, rich in types I and III collagen, which becomes disorganized shortly after. No perimysial envelopes displaying types I and III collagen fibers and fibronectin, nor endomysial sheaths develop. Only large spaces filled with types I and III collagen fibers subdivide groups of muscle cells irregularly. On the whole, type III collagen is less abundant than type I collagen. Fibronectin disappears from the periphery of the muscle cell. Laminin is more thickly deposited in the basal lamina around irregularly sized muscle cells than around the normal muscle cell. The results are discussed in terms of morphogenetic interactions between connective tissue cells and muscle cells, and in terms of fibrosis, which characterizes some muscle diseases.
Histogenesis in 11‐day mouse embryo limb buds explanted in organ culture
Authors: Milaire J. , Mulnard J.
Published: June 2005

Fore‐ and hindlimb buds from 11‐day mouse embryos with 40 to 52 somites (including the four occipital pairs) were explanted in organ culture and submitted to systematic histological analysis. Chondrogenesis occurs normally in culture in all preskeletal rudiments which were already represented by condensed blastemas before explantation. In the proximal territories, the progress of cartilage differentiation occurs according to the normal pattern and can be revealed histologically much earlier than in bulk preparations. In all explanted hindlimbs as well as in forelimbs from embryos with less than 50 somites, a primary coalescence occurs between the IId and IIId digital rays, leading to various fusions from soft tissue syndactyly to oligosyn‐dactyly. This is the result of two combined unfavorable effects of the culture conditions: the lack of simultaneous volumetric growth of the foot‐ or handplate, which normally would provide the necessary space for the laying down of a pentadactylous pattern, and a loss of cells resulting from abnormal cell death affecting selective mesodermal sites in the zeugopod and in the marginal subridge area, the latter being more severely affected in hindlimb buds. Several observations suggest that the preferential sensitivity of the marginal mesoderm might be related to early changes in the apical ectoderm, which itself becomes excessively necrotic and rapidly looses its pseudostratified configuration. The forelimb buds from embryos with 50 somites and more usually develop a pentadactylous pattern with a better individuation of digital structures. In all explants, the prospective mesoderm of digit I exhibits stronger regulatory tendencies.
Uptake and distribution of exogenous serum proteins in the cultured rat embryo
Authors: Rhinehardt Ann E. , Carey Sean W. , Young Marian F. , Klein Norman W.
Published: June 2005

Head fold stage rat embryos were cultured on a medium consisting of adult rat serum for 48 hr. During the final 10 or 20 hr of culture [35S]‐methionine was added to the medium. Sera from visceral yolk sac blood vessels, exocoelomic cavity fluid, and amniotic sac fluid were analyzed by SDS‐polyacrylamide gel electrophoresis followed by Amido Black staining and fluorography. Amido Black staining showed bands in all three embryonic fluid compartments which migrated at rates comparable to transferrin, alpha‐feto‐protein, albumin, IgG, and hemoglobin. Fluorography, however, showed that radioactivity was restricted to alpha‐fetoprotein, IgG, and hemoglobin. This suggested that at least some transferrin and albumin were transferred intact from the exogenous medium to the embryonic fluid compartments.
Isolation and structural characterization of chicken hypothalamic luteinizing hormone releasing hormone
Authors: King J. A. , Millar R. P.
Published: June 2005

Studies on partially purified chicken hypothalamic luteinizing hormone releasing hormone (LHRH) utilizing chromatography, radioimmunoassay with region‐specific antisera, enzymic inactivation, and chemical modification established that the peptide is structurally different from mammalian hypothalamic LHRH. These studies demonstrated that arginine in position 8 is substituted by a neutral amino acid. On the basis of conformational criteria and evolutionary probability of amino acid interchange for arginine, the most likely substitution was glutamine. We therefore synthesized [Gln8]‐LHRH and established that it had identical chromatographic, immunologic, and biological properties to the natural chicken peptide. In concurrent studies, purification of 17 μg of an LHRH from 249,000 chicken hypothalami was achieved using acetic acid extraction, immuno‐affinity chromatography, and cation exchange and reverse phase high performance liquid chromatography. Amino acid composition and sequence analyses confirmed the structure of this form of chicken LHRH as pGlu‐His‐Trp‐Ser‐Tyr‐Gly‐Leu‐Gln‐Pro‐Gly‐NH2.
Avian gonadotropin receptors: A comparative view
Authors: Ishii Susumu , Kubokawa Kaoru
Published: June 2005

Avian testicular receptors for gonadotropins show a species‐specificity similar to mammalian receptors for the binding affinity to gonadotropins of various origins. In the affinity‐capacity relationships, avian FSH receptors are classified in the same group with chelonians, that is, they exhibit relatively low affinity and high capacity. FSH receptors of the Japanese quail resemble the rat receptor with respect to the temperature‐dependence of affinity in the low‐temperature range, but also resemble reptilian or amphibian receptors with respect to binding affinities in the middle‐ to high‐temperature range. We conclude that avian gonadotropin receptors have some characteristics of homeothermic vertebrates, but still retain characteristics of poikilothermic groups.
Hormonal mediation of reproductive behavior
Authors: Ottinger M. A. , Adkins‐Regan E. , Buntin J. , Cheng M.‐F. , Devoogd T. , Harding C. , Opel H.
Published: June 2005

Reproductive capability requires synchronization of both endocrine and behavioral components of reproduction. The classic view of reproductive behavior was that there was simply direct stimulation of a behavioral response by the appropriate gonadal steroid. However, it has become clear with recent developments in the field of behavioral endocrinology that the relationship of hormonal and behavioral processes is complex. In addition to the complexity of the mechanisms involved, other factors, both social and environmental, influence both the endocrine and behavioral responses. This paper provides an overview of selected issues within the field of behavioral endocrinology which deal with mechanisms of hormonal induction of behavior at various stages of the life cycle and with factors that interact with these processes.
Endocrine control of the nasal salt glands in birds
Authors: Butler David G.
Published: June 2005

In birds, adrenocortical hormones probably sustain nasal salt gland (NSG) function, indirectly, through their influence on renal and cardiovascular function. Adrenalectomy blocks the response by duck NSG to hypertonic saline only if the ducks are maintained on freshwater. However, if adrenalectomized ducks are fed 0.9% NaCl ad libitum the NSG secrete fluid and osmolytes at the normal rate. Adrenalectomy did not prevent the significant functional hypertrophy of the NSG that always follows adaptation to saline. Mean arterial blood pressure was lower than normal two days after adrenalectomy. Stroke volume decreased by about 50% but there was a commensurate increase in cardiac frequency, so cardiac output was unchanged. There was no measurable change in total peripheral vascular resistance. There was at least a twentyfold increase in blood flow rate to the NSG when they were actively secreting fluid, but this increase was totally blocked after adrenalectomy. An inadequate supply of blood and not a corticosteriod deficiency in the secretory cells was the primary reason for NSG failure. Single intravenous injections of as little as 28 pm/kg bw of (Asp1, Val5)‐angiotensin II (AII) had no measurable effect on mean arterial blood pressure in conscious ducks but did shut off the NSG for about 4 min; then the NSG switched on again. NSG blood flow decreased after AII.
Lethal factors and enzymes in the secretion from Duvernoy's gland of three colubrid snakes
Authors: Rosenberg Herbert I. , Bdolah Avner , Kochva Elazar
Published: June 2005

Secretion from Duvernoy's gland of the colubrid snakes Malpolon, Spalerosophis, and Thamnophis was obtained by pilocarpine stimulation and tested for lethality and selected enzymatic activities. Pools of secretion from Malpolon and Spalerosophis were fractionated by gel filtration, and several major active fractions were examined. The secretion from Malpolon had an LD50 of 6.5 μg/gm in mice; two lethal fractions with LD50's of 2.75 μg/gm and 4.5 μg/gm were isolated. One of these fractions appears to be a basic phospholipase A with a molecular weight of about 17,000. Spalerosophis had a secretion with an LD50 of 2.75 μg/gm in mice; one main lethal fraction with an LD50 of 2.5 μg/gm was isolated. Secretion from Thamnophis had an LD50 of 33.3 μg/gm; it was not fractionated owing to a paucity of material.

At least two of the snake species examined have toxic secretions that may be important during feeding by killing or weakening and helping to subdue the struggling prey.
Redox regulation of caffeine contractures
Authors: Gábriel M. , Puppi A. , Szabó I. T. , Dely M.
Published: June 2005

The amplitude of caffeine contractures, tissue redox‐state potential, and electrical activity were simultaneously measured in the sartorius muscle of the frog, Rana esculenta following oxidant (methylene blue) and reductant (ascorbate, hydroquinone) treatments.

Pretreatment with oxidant, in parallel with the increment of redox‐state potential, increased, while pretreatment with reductant, in parallel with the decrement of redox‐state potential, decreased significantly the amplitudes of caffeine contractures. The electrical activity, registered simultaneously, was not changed significantly.

The mechanism of action of caffeine contractures is related to the increase of cytoplasmic Ca2+, and the results indicate that the actual redox‐state potential level, as one of the determinants of the internal milieu, is also a regulatory factor in relation to the excitation‐contraction coupling.
Effects of changes in hydrostatic pressure on Na transport in gammarid amphipods from Lake Baikal
Authors: Roer R. D. , Bekman M. Y. , Shelton M. G. , Brauer R. W. , Shvetzov S. G.
Published: June 2005

A 60–140‐atm change in the hydrostatic pressure causes fresh water gammarid amphipods from Lake Baikal to lose Na+ to the medium. This effect occurs whether the change is an increase in pressure for shallow species or a decrease in pressure for deep species. The pressure effect is predominantly upon unidirectional influx. A pressure‐induced change in the dynamic fluidity of the membrane is suggested as a possible mode of action.
Nerve growth factor induces neural differentiation in undifferentiated cells of early chick embryos
Authors: Lee Hsin‐Yi , Nagele Robert G. , Roisen Fred J.
Published: June 2005

Nerve growth factor (NGF) induced differentiation in postnodal pieces (PNPs) of stage 4 chick embryos. This induction was highly selective for neural tissue; no other structures developed in the NGF‐treated PNPs. Furthermore, the number of PNPs showing neural differentiation was dependent on the concentration of NGF, but there was no correlation between the concentration of NGF (5–100 ng/ml) and extent of neuralization. The neural inducing capacity of NGF could be abolished by anti‐NGF antibody. NGF‐induced neural differentation was accompanied by elevated intracellular levels of cyclic AMP. Exogenous cyclic AMP (175 μg/ml) was able to stimulate neural differentiation but, unlike NGF, induced other structures (e.g., notochord and pulsatile tissue). Overall results suggest that (1) cells from chick embryos at developmental stages much earlier than previously thought are responsive to NGF and (2) NGF or a closely related substance may serve as a neural inducer in the chick embryo.
Differentiation of mouse ectopic germinal cells in intra‐ and perigonadal locations
Authors: Francavilla Sandro , Zamboni Luciano
Published: June 2005

Four hundred and thirteen ectopic germinal cells in the testicular and extratesticular stroma and in the rete testis of mouse fetuses from day 13 of uterine development to term were studied together with 161 ectopic germinal cells in the rete ovarii and periovarian stroma of female fetuses at days 17 and 18 of intrauterine life. The morphology and the differentiation of these ectopic germinal cells were compared to those of germinal cells within seminiferous and ovigerous cords. While the ectopic germinal cells in the testis and in the rete testis followed patterns of differentiation identical with those in the seminiferous cords throughout the period included in the study, those in the extratesticular stroma behaved like entopic germinal cells only through day 17, since at days 18 and 19 many of them entered meiotic prophase just like XX germinal cells in the ovigerous cords. No differences were noted between ectopic and entopic ovarian germinal cells. The results of this study show that the factors responsible for the male differentiation of XY germinal cells are not limited to the seminiferous cords but operate throughout the testicular territory, and confirm that outside the testis, XY germinal cells differentiate as female; our study also corroborates the thesis that the differentiation of XX germinal cells is an autonomous and ubiquitous process.
Divergence in vascular actions of prostacyclin during vertebrate evolution
Authors: Piomelli D. , Pinto A. , Tota B.
Published: June 2005

Prostacyclin (PGI2) generation by teleost and elasmobranch fish vascular wall was detected, as 6‐keto‐PGF1α‐like immunoreactivity, in the incubation medium of ventral aorta rings from Anguilla anguilla, Conger conger and Scyliorhinus stellaris. The average yields after 15 min incubation were the following (ng of 6‐keto‐PGF1α‐like/g of wet tissue): A. anguilla =116.8 ±30; C. conger = 7.50; S. stellaris = 58.0 ± 10.

Accordingly, the vascular responses to synthetic PGI2 were examined on the isolated and saline‐perfused head of four teleost (A. anguilla, C. conger, S corpaena porcus and Solea solea) and two elasmobranch (S. stellaris and Torpedo marmorata) species. In teleosts, PGI2 gave a dose‐related increase in overall gill vascular resistance, unaffected by indomethacin, phenoxybenzamine and phentolamine pretreatment or by previous decerebration of the animal. Conversely, in elasmobranchs PGI2 elicited a diphasic response, characterized by a transient, not dose‐related constriction, followed by a longer lasting and dosedependent dilation.

The effects of PGI2 on isolated branchial arch (in A. anguilla, C. conger and S. stellaris) and ventral aorta strips (in C. conger and S. stellaris) were also examined. Both preparations shared the same responsivity of the head in toto, confirming the divergence observed in this respect between teleosts and elasmobranchs. The reactivity of teleost branchial vessels to this autacoid appears to be unique among the other vertebrates examined thus far.
Blocks to polyspermy in Chaetopterus
Authors: Eckberg William R. , Anderson Winston A.
Published: June 2005

Blocks to polyspermy may act either at the level of the egg plasma membrane to prevent gamete fusion or at the level of egg surface coats to prevent gamete attachment. The present study was undertaken to determine what type(s) of block(s) to polyspermy exist in Chaetopterus. The results showed the existence of both types. A rapid block acts at the plasma membrane level based on independence from detectable changes in the vitelline layer and is dependent on external sodium ions. A vitelline layer block had been predicted on morphological evidence and is supported here by demonstrating an increase in polyspermy following chemical disruption of the vitelline layer. However, the vitelline layer of the fertilized egg retained its ability to initiate the acrosome reaction in sperm and attach sperm which had undergone the acrosome reaction. The vitelline layer block resulted from the retraction of egg microvilli from the vitelline layer, and not from elevation of the vitelline layer per se. Thus the vitelline layer of the fertilized egg could be involved in preventing sperm penetration into the egg without being altered structurally or functionally.
Fat bodies and reproduction in female Anolis carolinensis
Authors: Greenberg Dorianne S. , Gist Daniel H.
Published: June 2005

The role of the fat body in supporting ovarian growth was studied in the lizard Anolis carolinensis. Environmental and social stimulation of ovarian growth in well‐fed animals was not accompanied by reductions in fat body weight or by increases in serum nonesterified fatty acid (NEFA) levels. Adiposectomy had no effect on serum NEFA, but did reduce hepatic glycogen compared to sham‐operated controls. Adiposectomized lizards receiving injections (either hormone or carrier) also had lower hepatic glycogen levels when compared to uninjected controls. Administration of estradiol to ovariectomized lizards was effective in increasing serum levels of NEFAs, but had little effect on fat body weights. Follicle‐stimulating hormone (FSH) administration increased serum free fatty acid levels in sham‐operated lizards but was without effect in adiposectomized animals. It is concluded that the lipids contained in the lizard fat body are not preferentially utilized for reproduction and may not be used for that purpose if adequate energy is supplied from other sources.
Amino acid metabolism in euryhaline bivalves: Regulation of glycine accumulation in ribbed mussel gills
Authors: Ellis Lehman L. , Burcham James M. , Paynter Kennedy T. , Bishop Stephen H.
Published: June 2005

Glycine levels in isolated ribbed mussel (Modiolus demissus) gill tissue increased slightly and decreased markedly when incubated at high and low salinities, respectively. Low levels of the enzymes involved in the biosynthesis of serine from triose phosphate intermediates, the serine hydroxy‐methyltransferase, and serine dehydrase were detected in gill tissue homogenates. Experiments using gill tissue incubated with (U‐14C)‐glycine and (U‐14C)‐serine indicated interconversion between serine and glycine and transfer of label to alanine, asparate, glutamate, CO2, organic acids, and protein. Glyoxylate was metabolized more slowly than glycine and was probably converted to glycine for catabolism. Studies using (1‐14C)‐glycine and (2‐14C)‐glycine with isolated gill tissue and mitochondria indicated that the mitochondrial glycine cleavage enzyme was the major route of glycine catabolism. Metabolic controls activating or inhibiting the glycine cleavage enzyme regulate tissue glycine accumulation and catabolism during hypersalinity or hyposalinity stress.
Repair of fractured lower jaws in the spotted salamander: Do amphibians form secondary cartilage?
Authors: Hall Brian K. , Hanken James
Published: June 2005

Secondary cartilage forms on avian and mammalian dermal bones, both during normal ontogeny and during repair of fractures, but it has not been observed in any other vertebrate class. We fractured the left lower jaws of adult spotted salamanders, Ambystoma maculatum, to see whether secondary cartilage would form during fracture repair. It did not. Instead, periosteal hyperplasia produced a callus from which new dermal bone formed to bridge the fracture. Meckel's cartilage underwent superficial dissolution but showed a minimal chondrogenic response. A large callus cartilage did form, but it appeared to arise by metaplasia from connective tissue adjacent to the bone. Thus, the environment within the fracture is conducive to chondrogenesis but the periostea of the dermal bones either are not able to respond to that environment or are unable to synthesize cartilage‐specific products. Among recent vertebrates, the ability to form secondary cartilage is limited to birds and mammals and is not a primitive property of the periostea of dermal bones shared by “lower” vertebrate classes.
Effects of temperature upon capacitation of guinea pig spermatozoa
Authors: Fleming Alan D. , Kuehl Thomas J.
Published: June 2005

Spermatogenesis in many mammalian species requires a temperature a few degrees below body core temperature. Upon ascent through the male tract and deposition in the female tract, the temperature of spermatozoa is increased to body core temperature. This report investigates the effects of temperatures above or below normal body core temperature, which is also the usual temperature of in vitro gamete incubations and fertilization, upon sperm acrosome reacting ability and fertility. Epididymal guinea pig spermatozoa were preincubated in a Ca2+‐free medium at temperatures of 15°C, 25°C, 37°C, or 44°C for increasing periods of time. At 15°C or 25°C, no or very few spermatozoa acquired the ability to acrosome react upon exposure to Ca2+ even after 18 hr of culture or warming up to 37°C. A known stimulator of acrosome‐reacting ability, lysophosphatidylcholine, was ineffective in promoting acrosome‐reacting ability in spermatozoa incubated at 15°C or 25°C. At 37°C the percentage of acrosome reaction increased steadily over time, reaching about 65% after 18 hr. At 44°C the time course of acquisition of acrosome‐reacting ability was greatly accelerated with a percentage at 2 hr comparable to that achieved at 37°C only after 18 hr of preincubation. This effect of incubation at 44°C could be reversed by cooling the spermatozoa to 37°C before they were exposed to Ca2+. Spermatozoa induced to undergo the acrosome reaction after preincubation at 44°C were fully capable of fertilizing intact guinea pig eggs. These results are discussed in relation to possible temperature‐dependent or ‐sensitive mechanisms that may be components of the capacitation process.
Occurrence and metabolism of D‐aspartate in the gutless bivalve Solemya reidi
Authors: Felbeck Horst
Published: June 2005

High concentrations of free D‐aspartate were measured in foot tissue and symbiotic bacteria containing gill tissue of Solemya reidi. The enzyme D‐aspartate racemase could be shown to be present in the tissues but not D‐aspartate oxidase or glutamate oxaloacetate transaminase (D‐aspartate as substrate). Externally administered radiolabeled D‐aspartate is rapidly taken up and metabolized by the tissues of the animal. The possible role of D‐aspartate in the metabolism of S. reidi is discussed.
Repeated furrow formation from a single mitotic apparatus in cylindrical sand dollar eggs
Authors: Rappaport R.
Published: June 2005

The methods used previously to demonstrate the ability of a single mitotic apparatus to elicit multiple furrows involved considerable cell distortion and did not permit the investigator to control the positioning of the parts or to observe satisfactorily the early stages of furrow development. In this investigation, Echinarachnius parma eggs were confined in 82 μm i.d. transparent, silicone rubber‐walled capillaries, and the mitotic apparatus was moved by pushing the poles inward with 55‐μm‐diameter glass balls. When the mitotic apparatus was shifted immediately after the furrow first appeared, a new furrow appeared in the normal relation to the new position in 1–2 minutes. The same mitotic apparatus could elicit up to 13 furrows as it was shifted back and forth by alternately pushing in the poles. The previous furrow regressed as the new furrow developed. The operations protracted the furrow establishment period to as long as 24.5 minutes after establishment of the first furrow. The characteristics of furrow regression were related to the distance the mitotic apparatus was moved. It is unlikely that regression was caused either by stress imposed on the surface or the removal of the mitotic apparatus from the vicinity of the furrow.
Electrophysiology of identified neurosecretory and non‐neurosecretory cells in the cockroach pars intercerebralis
Authors: Krauthamer Victor
Published: June 2005

Two cell types can be distinguished with intracellular recording from the pars intercerebralis of the American cockroach (Periplaneta americana). The first type, which corresponds morphologically to the medial neurosecretory cell, always had spontaneously occurring, overshooting action potentials. These action potentials are probably endogenously produced. Tetrodotoxin experiments revealed that sodium is the dominant ion of the action potential. The action potentials are followed by a relatively long after‐hyperpolarization. The input resistance of these cells ranged from 120 to 390 MΩ. A mathematical model, based on cellular morphology and response to current pulses, revealed a membrane time constant of about 100 msec and an exonal:somatic conductance ratio of approximately 13. Area‐specific membrane resistance was estimated at 33 kΩ cm2. These cells also often had reversible and spontaneous inhibitory postsynaptic potentials. The second cell type, which is non‐neurosecretory, never produced spontaneous action potentials and rarely had synaptic potentials. Action potentials could be evoked by current injection into the cell body or by extracellular stimulation of their axons in the posteroventral portion of the the protocerebrum. These action potentials also depend on sodium ions. Their input resistance ranged from 16 to 35 MΩ. They had a membrane time constant of approximately 15 msec and an axonal:somatic conductance ratio of about 9. Their area specific membrane resistance was estimated at 14 kΩ cm2.
Morphology of identified neurosecretory and non‐neurosecretory cells in the cockroach pars intercerebralis
Authors: Krauthamer Victor
Published: June 2005

Electrophysiologically identified cells of the cockroach pars intercerebralis (Periplaneta americana) were injected with the dye Lucifer Yellow for morphological examination and with horseradish peroxidase for ultrastructural marking. In addition to this, uninjected cells were also studied to elaborate the findings from the injected material. The two electrophysiologically distinct classes of cells (type I and type II) correspond to two distinct morphological and ultrastructural classes. Type I cells are the medial neurosecretory cells of the pars interecrebralis, which project their axons to the retrocerebral neuro‐hemal complex. Their cell bodies have a mean diameter of 17 μm, and they contain neurosecretory granules 200 nm in diameter. Arborizations emanate from the axon in the anterior part of the protocerebral neuropil. The type II cell bodies are larger (38 μm in diameter). Their axons project into the contralateral circumesophageal connective. These cells were usually multipolar, having somatic arborizations in the anterior portocerebral neuropil. The cell bodies contain vesicles 40 nm in diameter, numerous trophospongia, and a multi‐layered glial envelope.
Notochordal development as influenced by the insecticide dicrotophos (Bidrin)
Authors: Garrison James C. , Wyttenbach Charles R.
Published: June 2005

White Leghorn chicken embryos were treated at different ages with the insecticide dicrotophos to determine the time period of maximum effect upon notochordal development. Doses of insecticide ranging from 250 μg to 2.0 mg were injected into eggs at 8, 16, 24, 32, 40, 48, 72, or 96 hr of incubation and the eggs allowed to incubate for an additional 48 hr. Dicrotophos treatment caused dorsoventral and lateral folding of the notochord, with the cervical region being most severely affected. Although there was no apparent difference in dose responsiveness at any one age, there was an obvious age relationship. Notochordal responsiveness, expressed as both the number and severity of folds, was low among the 8‐ and 16‐hr treated embryos, increased to a maximum in the 48‐hr treatment group, and then declined among the older embryos. The time of maximum effect correlates closely with the time of sheath deposition and vacuolization of the notochord, but not to initial formation of the notochord from the mesoblast or later extracellular matrix production by sclerotome cells. It is proposed that dicrotophos interferes with some aspect of sheath formation. The pressure exerted by the vacuolization upon a structurally weakened sheath is thought to cause the observed folding.
Is there a limit on in situ, genomic replication in Drosophila?
Authors: Butterworth F. M. , Rasch E. M. , Johnson M. B.
Published: June 2005

The number of genomic replications of four separate tissues was determined in Drosophila melanogaster by summing the total number of nuclei and the maximum amount of DNA per nucleus in each tissue. It was found that for a given tissue the total number of nuclei was generally inversely proportional to the maximum amount of DNA per nucleus. In addition the sum of the number of divisions giving rise to the nuclei and the number of DNA replications occurring in the nucleus in each tissue never exceeded 20.