bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen excretion is enhanced during urine recycling in two species of terrestrial crab
Authors: Wolcott Donna L. 
Published: June 2005

AbstractTerrestrial crabs confront the problems of salt and water balance and nitrogen excretion in a terrestrial environment with organ systems evolved to function while immersed in an aquatic environment. Their antennal glands produce urine that is essentially isosmotic to the blood, and contains very little nitrogenous waste, yet terrestrial crabs are excellent iono‐ and osmoregulators in nature. Because voided urine is passed to the branchial chamber for reclamation of ions, the gills, the major organ for ion regulation in aquatic crabs, are still able to perform their ion‐regulating role even in air‐exposed individuals. The present study demonstrates that, during urine recycling, the gills retain their function as the major avenue for nitrogen excretion as well. In two species of terrestrial crab, Gecarcinus lateralis and Cardisoma guanhumi, the concentration of ammonia increases more than 10‐fold in urine during recycling at the gill, greatly enhancing the amount of nitrogen that can be excreted for a given volume of water lost in the urine. Additional results show that without the ability to reclaim ions from the urine by recycling it at the gills, G. lateralis would be unable to remain in osmotic equilibrium.
Labeling of developing vascular endothelium after injections of rhodamine‐dextran into blastomeres of Xenopus laevis
Authors: Rovainen Carl M. 
Published: June 2005

AbstractThe goal of this work has been to label endothelial cells with flurescent marker and to record their behavior during angiogenesis in vivo. Single blastomeres in 16–128‐cell‐stage embryos of pigment‐deficient Xenopus laevis were injected intracelluarly with 5% tetramethylrhodamine dextran. Subsequently, the embryos and tadpoles were examined with an epifluorescence microscope, a silicon‐intensified target (SIT) camera, and video recordings. Clones that would include endothelium could be selected as early as stages 33–36 on the basis of heavy labeling in the ventral mesodermal core of the tail. Strands of fluorescent cells and early vessels appeared in the tail at stages 39–41. Subsequently, groups of endothelial cells were followed in case histories in the tail and in the aortic arches and gills of tadpoles.Two main results were that the patterns of fluorescent endothelial cells were stable in established arteries, veins, and capillaries for at least 2–12 days, and that labeled endothelial cells migrated distally in elongating sprouts.In addition, it was inferred that endothelium was derived from multiple blastomeres, probably in the ventral vegetal regions. Only small fractions of total endothelium were labeled from any single blastomere. None of the early blastomeres produced exclusive clones of vascular endothelium; other labeled cell types in various clones included muscle fibers, lymphatics, mesodermal stellate cells, blood cells, gut, proctodeum, and some epidermis, in addition to endothelial cells.The method of intracellular marking of blastomeres is recognized as a direct approach for charting lineage and fate tables in embryos of Xenopus and other species. The present study extends the period of observation in vivo for up to 2 weeks in the growing tadpole and focuses on endothelial cells during angiogenesis. Even though fluorescent dextran was apparently packaged in vesicles and metabolized, individual cells and small groups could be identified and followed with time. This method provides excellent opportunities for addressing problems in vascular development in the living animal.
Transverse ionic passages through the cuticular ductules from the haemocoel to the glandular cavities and the lumen of the spermathecal duct in female crickets (Gryllus bimaculatus)
Authors: Yasuyama Kouji , Kimura Tetsuya , Yamaguchi Tsuneo 
Published: June 2005

AbstractIn the spermathecal duct of the female cricket Gryllus bimaculatus, the glandular cells, each of which has a central cavity, and the cuticular ductules, extending from the cuticular intima of the spermathecal duct, are widely distributed along the duct's length, except in the proximal and distal regions. The cuticular ductules approach the glandular cavities along a tortuous course and enter them, or run down towards them to terminate in the region of the basement membrane. When an isolated spermathecal duct was incubated in an ionic lanthanum solution, deposits of lanthanum were found in the lumina of the cuticular ductules, the secretory cavities of the glandular cells, and in the openings of the cuticular ductules to the lumen of the spermathecal duct, but also in the intercellular space, and the surface of muscle fibers surrounding the spermathecal duct. This finding suggests that each cuticular ductule is a tripartite passage between the haemocoel, the glandular cavity, and the lumen of the spermathecal duct.
Effect of temperature on the splenic mechanism of respiratory compensation in the newt
Authors: Frangioni Giuliano , Borgioli Gianfranco 
Published: June 2005

AbstractThe spleen of the newt Triturus cristatus carnifex (Laurenti), an urodele amphibian, hoards erythrocytes when the animal is well‐oxygenated and releases them into the bloodstream when the animal is in a hypoxic condition. Between the extremes of congestion and decongestion the weight of the spleen varies up to a ratio of 6:1. However, the degree of the phenomenon depends on the temperature, which, in ectotherms, regulates metabolic rate and thus oxygen demand. In order to assay the degree of hypertrophy reached by congested spleens in standard respiratory conditions, groups of eight animals—previously anesthetized by immersion for 20 minutes in a 0.2% solution of chlorbutol in tap water at 18°C—were exposed to 100% humid air in a thermostatic chamber set at a temperature of 6, 12, 18, 24, 27, 30, or 33°C. Each animal remained at the set temperature until surpassing the minimum time necessary for maximum hypertrophy to be reached, equal to the time necessary for 4,000 heartbeats. At 33°C the spleens are almost completely bloodless, while at the other temperatures their hypertrophy from congestion increases linearly as the temperature diminishes, reaching maximum values at 6°C. Though the progressive congestion of the spleen as the temperature descends is due mainly to blood cells and only very slightly to plasma, erythrocyte concentration in the blood remains constant at all the lower temperatures up to that of anesthesia (18°C); this phenomenon implies variability of blood volume in the newt. Instead, above 18°C, the values of the hematic parameters increase as the temperature rises, reaching a maximum increment of about 30% by 27°C.
Subdivisions of the terminal nerve in Xenopus laevis
Authors: Hofmann Michael H. , Meyer Dietrich L. 
Published: June 2005

AbstractThe majority of recent studies on the terminal nerve (nt) in various vertebrates either involved tracer injections into the nasal cavity or made use of the LHRH‐/FMRFamide‐like immunoreactivity (ir) of a portion of its fibers. The present investigation was designed to determine the extent of overlap between data rendered by the two methods in Xenopus. The findings reveal no overlap of nt projections visualized by the two experimental techniques. This result sheds doubt on the validity of current definitions of the nt system.
Sex differences in hepatic monooxygenases in winter flounder (Pseudopleuronectes americanus) and scup (Stenotomus chrysops) and regulation of P450 forms by estradiol
Authors: Gray Elisabeth Snowberger , Woodin Bruce R. , Stegeman John J. 
Published: June 2005

AbstractDetails concerning the endogenous regulation of hepatic cytochrome P450 mono‐oxygenases in teleosts, and the features of this regulation common among fish species, are poorly known. Gonadally mature female winter flounder (Pseudopleuronectes americanus) have been reported to have severalfold lower levels of microsomal cytochromes P450 and b5 and NADPH cytochrome c reductase than do males (Stegeman and Woodin ('84) Mar. Environ. Res., 14:422–425). These strong sex differences prompted more detailed study of P450 regulation in winter flounder liver, and a comparison with sex differences in another marine teleost, scup (Stenotomus chrysops). Ethoxyresorufin O‐deethylase (EROD) activity/nmol P450 was less in gonadally mature females than in males of both species. Immunoblot analysis with MAb 1‐12‐3 to P450E (the EROD catalyst) showed that the content of P450E counterpart was also much less in females of both species. Aminopyrine N‐demethylase (APND) and testosterone 6β‐hydroxylase (6β‐OHase) activities per nmol P450 were higher in gonadally mature female than in mature male flounder, differences not seen in scup. Polyclonal antibodies to scup P450A were shown to detect proteins in a number of teleosts. The levels of anti‐P450A cross‐reacting protein were greater in mature female than in male flounder, but as with 6β‐OHase activity, the content of this protein was not sexually differentiated in scup. Estradiol treatment of winter flounder depressed the rates of EROD, APND, 6β‐OHase, and estradiol 2‐OHase activities per mg protein, but APND and 6β‐OHase activities per nmol P450 were unchanged. Thus, E2 promotes general decreases in some hepatic P450‐catalyzed activities, but in achieving sex differences there is also specific regulation of the P450E counterpart, and possibly of the 6β‐OHase (P450A?). Other factors, temporal or hormonal, can modify the effect of E2 treatment, and may contribute to the specific regulation of P450 forms in naturally maturing fish, and to species differences in this regulation.
Resumption of meiosis in pig oocytes cultured with cumulus and parietal granulosa cells: The effect of protein synthesis inhibition
Authors: Motlik Jan , Nagai Taku , Kikuchi Kazuhiro 
Published: June 2005

AbstractIn denuded and cumulus‐enclosed pig oocytes, puromycin at concentrations 5, 10, and 25 μg/ml did not lower the rate of germinal vesicle breakdown (GVBD) after 24 h of culture. GVBD was prevented in 50, 75, and 100 μg/ml of puromycin. After 40 h of culture, 5 and 10 μg puromycin/ml impaired significantly incidence of metaphase II (42 and 30%), respectively. Concetrations of 25 and 50 μg puromycin/ml absolutely prevented the first polar body (I PB) expulsion. The results indicated that GVBD in pig oocytes is far less sensitive to puromycin than I PB expulsion.Culture of cumulus‐enclosed pig oocytes isolated with a piece of membrana granulosa (C+P oocytes) did not allow GVBD after 24 and 32 h in control medium. After 24 h of culture, GVBD occurred in 43 and 56% of C + P oocytes in the medium supplemented with 17 and 25 μg puromycin/ml. GV was broken down in 80 and 68% of C + P oocytes cultured in 17 and 25 μg puromycin/ml for 32 h. It is concluded that inhibition of protein synthesis by puromycin released pig oocytes from the block exerted by granulosa cells.
Subzero temperature adaptations in arthropods from the summit of Mauna Kea, Hawaii
Authors: Duman John G. , Montgomery Steven L. 
Published: June 2005

AbstractA preliminary study of subzero temperature adaptations was made of arthropods from the summit (4,200 m) of Mauna Kea, Hawaii. This barren, alpine stone desert aeolian habitat commonly experiences snow and nightly subzero temperatures in spite of its subtropical location. In mid‐December, collections were made of a wolf spider (Lycosa sp.). the lygaeid bug (Nysius wekiuicola), and a noctuid caterpillar (Agrotis sp.). The Agrotis caterpillars were freeze tolerant. They had quite high supercooling points (SCP = −4.8°C) and survived a 24 hr frozen exposure at −6.2°C. The site of nucleation is apparently not the hemolymph, as the hemolymph SCP was −15.1°C. The spiders and wekiu bugs were not freeze tolerant. The SCPs of the spiders (X = −5.8°C) were not particularly low, but these highly mobile arthropods may be able to seek thermally buffered microhabitats when the need arises. The wekiu bugs showed greater supercooling abilities, with some individuals supercooling to −18°C, although the SCPs were quite variable. The subzero temperature adaptations of the arthropods from such an isolated subtropical site are remarkable adaptive capabilities.
Hepatic ulstrastructure changes associated with the parr‐smolt transformation of Atlantic salmon (Salmo salar)
Authors: Robertson John C. , Bradley Terence M. 
Published: June 2005

AbstractLiver samples of two groups of juvenile Atlantic salmon (Salmo salar) were collected fall through spring and examined by light and transmission electron microscopy. One group of fish was maintained under simulated natural photoperiod (SNP), the other under an 8 month advanced, phase‐shifted photoperiod (8MA). As indicated by changes in branchial Na+/K+ATPase activity, salinity tolerance, and morphological characteristics, fish in the SNP group underwent parr‐smolt transformation in the spring. Smoltification‐associated changes in ultrastructure were observed in liver parenchymal cells only. Hepatocytes of SNP smolts were smaller with markedly decreased glycogen content as compared to cells of SNP parr. An increase in mitochondrial size and a decrease in numbers of mitochondria per hepatocyte were also seen during smoltification. In smolt hepatocytes, the nucleus and mitochondria occupied a greater percent of the cell volume than in parr liver parenchymal cells. Rough and smooth endoplasmic reticulum, dense bodies, and Golgi profiles also appeared to occupy more of the cell volume of smaller hepatocytes seen during smoltification. No smoltification‐associated changes were seen in hepatocyte nuclear size, chromatin state, or nucleolar frequency. During the fall, Atlantic salmon in the 8MA group underwent some morphological and osmoregulatory changes associated with smoltification. Hepatic fine structure of these fish in the fall resembled that seen in SNP smolts. In spring, 8MA fish exhibited no indications of smoltification, and hepatocyte ultrastructure of these fish was similar to that of SNP parr. Biological implications of observations are discussed, particularly in light of other investigations concerning the liver and smoltification.
Axon composition of the proprioceptive PD nerve during growth and regeneration of lobster claws
Authors: Cooper R. L. , Govind C. K. 
Published: June 2005

AbstractA prominent chordotonal organ spanning the propus and dactyl (PD) joint in the chelipeds of the lobster Homarus americanus has the somata of its sensory cells embedded in an elastic strand while their axons collectively travel in a nerve to the ganglion. Electron microscopic examination of the PD nerve revealed several large and many small axon profiles denoting few movement‐sensitive and many position‐sensitive cells. This axon composition typified the nerve in the normally occurring, paired asymmetric crusher and cutter claws, as well as in the experimentally induced, paired symmetric cutter claws. In the asymmetric condition, the crusher nerve had many more axons than the cutter while in the symmetric condition, the numbers were equivalent between the paired cutter claws. In a size‐graded series of lobsters with paired asymmetric claws there was an increase in the number and size of axons in keeping with an increase in claw size. In a newly regenerated claw, the PD nerve was a miniature version of its pristine counterpart with smaller and fewer axons. Moreover, in newly regenerated paired asymmetric claws, the crusher nerve did not have a larger number of axons than the cutter, suggesting that PD nerve has not fully differentiated. The distribution of axons according to size was, however, similar to the pristine nerve in that there were few large axons and many small ones, suggesting that the ratio of large, movement‐sensitive cells to small, position‐sensitive ones in the PD organ is rigidly specified during regeneration and growth.
Lens formation from the cornea following implantation into hindlimbs of larval Xenopus laevis: The influence of limb innervation and extent of differentiation
Authors: Filoni Sergio , Albanesi Cristina , Bernardini Sergio , Cannata Stefano M. 
Published: June 2005

AbstractCorneal fragments of larval Xenopus laevis at stage 48 (according to Nieuwkoop and Faber, ′56), were implanted into sham denervated unamputated hindlimbs, denervated unamputated hindlimbs, amputated and sham denervated hindlimbs, and amputated and denervated hindlimbs of larvae at stages 52 and 57.The results show that unamputated limbs at stage 52, either innervated or denervated, manifest a weak capacity to promote the first lens‐forming transformations of the outer cornea. This capacity is absent in both limb types at stage 57. After amputation, limbs of both early and late stages form a regenerative blastema and support lens formation from the outer cornea. Denervation of early stage limbs has no appreciable effect on blastema formation and lens‐forming transformation of corneal implants. However, denervation of late stage limbs inhibits both processes.These results indicate that the limb tissues of the early stage limbs contain non‐neural inductive factors at a low level and that after limb amputation and blastema formation the level of these factors becomes high enough to promote lens formation from implanted cornea, even after denervation. In contrast, the limb tissues of late stage limbs do not contain a suitable level of non‐neural inductive factors.
Developmental expression and hormonal regulation of the nuclear 29 kDa juvenile hormone‐binding protein in Manduca sexta larval epidermis
Authors: Palli Subba Reddy , McClelland Scott , Hiruma Kiyoshi , Latli Bachir , Riddiford Lynn M. 
Published: June 2005

AbstractWe have utilized a high specific activity photoaffinity analog of methoprene, [3H]‐methoprene diazoketone (MDK), to study the developmental expression and hormonal regulation of the 29 kDa juvenile hormone (JH)‐binding protein. The 29 kDa MDK‐binding protein was detected in the epidermis of the feeding 4th and 5th instar larvae but decreased in abundance during the molts to the 5th instar and the pupa. This protein was also detected in day 1 pupal epidermis. Culturing of day 2 5th instar larval integument in the presence of 2 × 10−6 M 20‐hydroxyecdysone (20HE) caused a threefold decrease in the 29 kDa MDK‐binding protein. Presence of 3 × 10−6 M JH I prevented this loss. Allatectomy of molting 4th instar larvae after the critical period for JH for a larval molt resulted in the absence of the 29 kDa MDK‐binding protein in epidermis isolated 25 hr later or from either day 1 5th instar larvae or day 1 pupae. Application of 5 μ of JH I or methoprene at the time of allatectomy and every 12 hr thereafter until dissection was necessary for the presence of this protein in day 1 5th instar larval epidermis. Application of 5 μg of JH I on the day of wandering and the next day caused the appearance of the 29 kDa MDK‐binding protein in the epidermis of day 1 pupae formed by allatectomized larvae.
The behavior and cytoskeletal system of chick gastrula mesodermal cells on substrata coated with lines of fibronectin
Authors: Toyoizumi Ryuji , Shiokawa Koichiro , Takeuchi Shigeo 
Published: June 2005

AbstractIn order to investigate the mechanism of the formation of the mesodermal layer during chick gastrulation, we observed the behavior of fragments of mesodermal cells explanted and cultured on substrata coated with parallel lines of fibronectin (FN). We also examined the distribution of F‐actin, α‐actinin, and vinculin in explanted fragments by immunocytochemical methods noting particularly their distribution with respect to FN lines.Explants of mesodermal cells flattened on FN‐coated substrata and then became elliptical with the major axis of the ellipse oriented along the FN lines and migrated along them. The peripheral cells of explants extended filopodia and lamellipodia which attached preferentially to FN lines and then contracted, pulling other mesodermal cells in explants along passively. Vinculin and α‐actinin in peripheral anchoring filopodia and lamellipodia co‐localized with the terminations of F‐actin bundles and with FN lines, suggesting that the peripheral cells were the moving force for explant translocation.We propose based on these results that in vivo, peripheral cells of invaginated cell mass are guided by the known FN‐rich fibrous extracellular matrix on the basal surface of epiblast to move outwards; the rest linked to the peripheral cells are pulled away from the primitive streak to spread in tandem to form the mesodermal layer.
Regulation of ovarian steroidogenesis in vitro in the viviparous shark, Squalus acanthias
Authors: Tsang Paul C. W. , Callard Ian P. 
Published: June 2005

AbstractWe investigated the steroid biosynthetic capabilities of ovarian granulosa and thecal elements of the viviparous dogfish, Squalus acanthias. In this report we present evidence that granulosa cells secrete quantitatively important amounts of progesterone (P), testosterone (T) and estradiol‐17β (E), while theca has a more limited capacity to synthesize T and E. Ovarian granulosa cells were obtained from animals at each stage of gestation. After collagenase dispersion, an aliquot of 250,000 cells was incubated at 18°C in basal medium, containing Eagle's salts, glutamine, penicillin, streptomycin and adjusted with 136 mM sodium chloride and 350 mM urea. After a 4 hour incubation, the content of P, T, and E in medium was determined by radioimmunoassay. P was not detectable at any time, while E was present throughout the cycle, being maximal when gestation is three quarters complete (Stage C). T gradually increased from Stage B toward late pregnancy. In Stage C granulosa cells, E production increased in the presence of graded doses of T substrate. Also, a homologous pituitary extract (1/25 equivalents) and the calcium ionophore A23187 stimulated production of all 3 steroids. Using radioisotopes, granulosa cells showed a wide range of synthetic capacities. In Stage C thecal tissue, E production also increased in the presence of graded doses of T substrate, while pituitary extract only increased T. When granulosa and theca were recombined, in the presence of pituitary extract, P levels decreased with a corresponding increase in T, when compared to granulosa alone. These data suggest a possible interaction between granulosa and theca for steroid biosynthesis. They further indicate that granulosa cells alone have the capacity to synthesize P, T, and E, without any input from theca.
Short‐term effects of triiodothyronine on the bowfin, Amia calva (holostei), and the lake char, Salvelinus namaycush (teleostei)
Authors: Ballantyne J. S. , John T. M. , Singer T. D. , Oommen O. V. 
Published: June 2005

AbstractTo assess the role of triiodothyronine (T3) in mediating short‐term changes in metabolism, such as those occurring in circadian patterns, we examined the effects of intraperitoneal injection of T3 on the oxidation of substrates by isolated mitochondria from liver of the bowfin, Amia calva, and red muscle and liver of the lake char, Salvelinus namaycush. Selected enzymes were measured in red muscle and liver of the lake char. Three hours after intraperitoneal injection of T3, oxidation of some substrates by mitochondria isolated from the liver of the bowfin was reduced. Similar treatment had no effect on substrate oxidation in liver mitochondria isolated from lake char. Oxidation of substrates by lake char red muscle mitochondria was stimulated by T3 injection. Citrate synthase levels were increased in red muscle suggesting that changes in enzyme activity may be in part responsible for the short‐term mitochondrial responses to T3 injection.