bluuebunny/crossref_metadata_2025_split huggingface dataset:
Renewal of normal and degenerating photoreceptor outer segments in the Ozark cave salamander
Authors: Besharse Joseph C. , Hollyfield Joe G. 
Published: June 2005

AbstractTo determine whether photogoreceptor degeneration in the Ozark cave salamander is associated with cessation or changes in the kinetics of outer segment (OS) renewal, an autoradiographic study of 3H‐leucine incorporation in photoreceptors was carried out. Six days after isotope injection rods and cones showed labeling in both inner and outer segments. Cone OS were diffusely labeled whereas rods contained a band of radioactivity at the base of the OS. At 13 and 21 days the radioactive band in rods was located progressively nearer the distal tip of the OS. The rate of rod OS renewal ranged from 0.30 to 0.38 μ of OS length per day at 18°C. L‐thyroxin induced metamorphosis and light increased the renewal rate compared to larvae in darkness, and adults with photoreceptors in an early stage of degeneration had a slightly higher renewal rate than larvae. Light and electron microscope autoradiographs of degenerate photoreceptors revealed that even in the final stages of degeneration when OS are reduced to small, irregular whorls of membrane, 3H‐leucine labeling was present in inner segments and OS membranes. These observations demonstrate that OS renewal occurs in both larvae and adults, and suggest that photoreceptor degeneration may be due to disruption of some aspect of the OS disposal process.
Protein synthesis and germ plasm in cleavage embryos of Xenopus laevis
Authors: Hogarth K. , Dixon K. E. 
Published: June 2005

Abstract(3H) Leucine was injected into unfertilized eggs, fertilized eggs, and Stage 2–12 embryos of X. laevis. Incorporation of the leucine into protein by blastomeres containing germ plasm was studied autoradiographically. Eggs, both fertilized and unfertilized, actively synthesized protein, as did embryos from Stage 2 onwards. Probably all blastomers containing germ plasm were labelled. In embryos from Stages 4–12, the germ plasm itself was also labelled, and this result suggests that the germ plasm is metabolically active during cleavage.
Developmental effects of exposing Drosophila embryos to ether vapour
Authors: Bownes Mary , Seiler Maxine 
Published: June 2005

AbstractDrosophila embryos at precise developmental stages were exposed to ether vapour. The defects in the resulting embryos and adults were observed. Ether disrupted embryogenesis in specific ways, causing defects primarily at the anterior of the embryo and disorganizing the arrangement of the segments. Adults showed deficiencies and duplications of many imaginal disc and histoblast derivatives. Phenocopies of the bithorax mutation which transforms metathorax to mesothorax were observed. They were first induced at the syncytial blastoderm stage, had their peak of production at the cellular blastoderm, and were no longer observed after the anterior and posterior midgut were partially invaginated. It was observed that not only are the haltere/wing transformations confined to the anterior compartment, but also leg 3 to leg 2 transformations only occurred in the anterior leg compartment.
The activities of some lysosomal hydrolases in the development of the cement gland in Xenopus laevis
Authors: Hsu Teresa Wei , Lyerla Timothy A. 
Published: June 2005

AbstractThe hydrolases B‐glucuronidase, B‐galactosidase and N‐acetyl‐B‐D‐glucosaminidase were examined in Xenopus laevis for their pH optima, sedimentability by differential centrifugation and optimal incubation temperatures for their assays. Enzyme activities were enriched in the 20,000 × g fraction of tissue homogenates, and all three of the enzymes exhibited acid pH optima, supporting the assumption that these are lysosomal enzymes in X. laevis. Total and specific activities of B‐glucuronidase and N‐acetyl‐B‐D‐glucosaminidase were significantly higher in homogenates from regressing cement glands compared with those from preregressing glands. Cement gland regression, then is, apparently accompanied by lysosomal activation.
Oxygen‐binding properties of hemoglobins from estivating and active African lungfish
Authors: Weber Roy E. , Johansen Kjell , Lykkeboe Gunnar , Maloiy Geoffrey M. O. 
Published: June 2005

AbstractThe oxygen‐binding characteristics and the multiplicity of the stripped hemoglobin from active lungfish Protopterus amphibius, are the same as in specimens that have been estivating for about 30 months, showing that alteration in the hemoglobin molecules is not involved in the earlier reported increase in oxygen affinity of whole blood during estivation (Johansen et al., '76). At pH 7.0 and 26°C the hemolysates show a high oxygen affinity (P50 = 3.1 Torr), a Bohr factor (Δ log P50/Δ pH) of −0.33, and a cooperativity coefficient (n) of 1.7. Between 15 and 26°C, the apparent heat of oxygenation (ΔH) is −8.6 Kcal·mole−1 at pH 7.0, corre‐sponding with data for other fish. A low sensitivity of oxygen affinity to urea appears to be adaptive to the high urea concentrations in estivating lungfish. The salt sensitivity is, however, similar to human hemoglobin.The hemoglobin consists of two major (electrophoretically anodal) components, which differ slightly in oxygen affinity but are both sensitive to pH and nucleoside triphosphates (NTP). Guanosine triphosphate (GTP), the major erythrocytic organic phosphate, however, depresses the oxygen affinity of the composite and separated hemoglobins more effectively than ATP suggesting that GTP is the primary modulator of oxygen affinity.Comparative measurements reveal only one major hemoglobin component in P. annectens which has a markedly lower oxygen affinity and phosphate sensitivity than P. amphibius hemoglobins and thus seems less pliable to phosphate‐mediated variation in oxygen affinity.The data are discussed in relation to the hemoglobin systems of other fish.
Thymus‐dependent lymphoid regions in the spleen of the lizard, Calotes versicolor
Authors: Pitchappan R. M. , Muthukkaruppan V. R. 
Published: June 2005

AbstractThis paper describes the distribution of thymus‐derived lymphocytes in the spleen of the lizard, Calotes versicolor. Our studies reveal the existence of red and white pulp in the spleen. The red pulp consists of collagenous fibrous septae containing lymphocytes, erythrocytes and sinuses. The white pulp is an area enclosed by fibrous septae, containing lymphocytes, reticular cells and arterioles. The region around the arteriole in the white pulp was depleted of lymphocytes either one month after adult thymectomy or after anti‐thymocyte serum treatment. The repopulation of this region was observed in sham‐thymectomized controls, but not in thymectomized lizards. Therefore, this peri‐arteriolar region may be designated as a thymus‐dependent area, as described previously in higher vertebrates. The significance of these findings is discussed in relation to the phylogeny of the immune system.
The nature and development of sex attractant specificity in cockroaches of the genus periplaneta. IV. Electrophysiological study of attractant specificity and its determination by juvenile hormone
Authors: Schafer Rollie 
Published: June 2005

AbstractThe antennae of male Periplaneta americana acquire a large number of olfactory receptors at the adult stage. Electrophysiological methods (single unit and electroantennogram recording) show that a portion of the receptors added at the adult ecdysis are sex attractant receptors. Sex attractant receptors are not present in large numbers on larval and adult female antennae. The differentiation of pheromone receptors is inhibited during normal larval development by juvenile hormone. Topical application of juvenile hormone‐mimic to male antennae during the terminal larval instar inhibits their development. Comparative electrophysiological studies indicate a high degree of cross‐reactivity of the P. americana sex attractant among four other species within the genus Periplaneta.
Ureotelism in the slug, Limax flavus linné
Authors: Horne Francis R. 
Published: June 2005

AbstractThe slug, Limax flavus, excretes both urea and purines.
Urea and purines account for up to 59 and 41% of the excretory nitrogen, respectively.
Of the purines excreted uric acid predominates (64%) with quanine (22%) and xanthine (14%) usually being voided in lesser amounts. Neither adenine or hypoxanthine was detected.
Urea was excreted in urine while the purines were deposited irregularly, as semi‐solid, yellowish nubs.
Neurotrophic stimulation of DNA synthesis in the regenerating forelimb of the newt, Triturus
Authors: Jabaily Joseph A. , Singer Marcus 
Published: June 2005

AbstractThe effect of infusions of soluble newt brain extracts on deoxyribonucleic acid (DNA) synthesis in the denervated, regenerating newt blastema has been studied. When moderate early to early regenerates are denervated for 48 hours, DNA synthesis normally drops to about 40% of that found in contralateral, innervated blastemas. Infusion of brain extract halfway through the denervation period (at 24 hours) approximately doubles the rate of DNA synthesis in denervated regenerates.
The effect of 5‐bromodeoxyuridine on the postnatal development of the rat testis
Authors: Barasch Jonathan M. , Bressler Robert S. 
Published: June 2005

AbstractThe effects of 5‐bromodeoxyuridine (BrdU) on postnatal testicular development were studied in rats treated on the second, third and fourth days of life. Testes were removed for study at 5, 15 and 35 days of age. Body weights and diameters of seminiferous cords and tubules were significantly less in the treated than control animals. At 15 days of age fewer pachytene spermatocytes were present in treated animals. At 35 days of age the testes of treated animals contained fewer canalized cords. Spermatids exhibited an altered distribution of chromatin material, contained less agranular endoplasmic reticulum and fewer mitochondria, and had not yet developed tails. Sertoli cells and Leydig cells of treated animals contained less agranular endoplasmic reticulum and more lipid droplets than the normal.
Temporal coordination and spatial autonomy in regulation of ciliary pattern in double forms of a hypotrich ciliate Paraurostyla weissei
Authors: Jerka‐Dziadosz Maria 
Published: June 2005

AbstractRegulation of cortical pattern was analyzed in homopolar back‐to‐back doublets of Paraurostyla weissei. After surgical removal of the anterior quarter of one component, both components form primordia of the ciliature, each one positioning the primordia according to its own boundaries. Both regenerated components were measured several hours after the operation, and the number of cortical elements was counted in each component. On the average, the operated component is smaller by about 17% and possesses about 25% fewer AZM membranelles and about 14% fewer left marginal cirri than the unoperated component. The analysis shows that in spite of the endoplasmic and membrane continuity and the morphogenetic signals passing from one component to the other, the two halves of a doublet show remarkable autonomy both in positioning of the primordia and in regulation of the number of cortical elements, which remain proportionate to the size of each component of the double form.
Changes in the levels of chloride cells and (Na+ + K+)‐dependent ATPase in the gills of yellow and silver eels adapting to seawater
Authors: Thomson A. J. , Sargent J. R. 
Published: June 2005

AbstractChanges were measured in the numbers of chloride cells and the levels of (Na+ + K+)‐dependent ATPase in the gills of immature, yellow eels and mature, silver eels during adaptation from freshwater to seawater. The percentage of chloride cells in yellow eels more than doubled after six days in seawater; at this time the specific activity and concentration of (Na+ + K+)‐dependent ATPase in gills start to increase in parallel to reach maxima after two weeks that are 2.5 times the starting values. It is concluded that adaptation of yellow eels to seawater involves an increase in the numbers of chloride cells in gills as well as an increased amount of (Na+ + K+)‐dependent ATPase per chloride cell. Mature silver eels in freshwater had essentially the same numbers of chloride cells and the same specific activity of the enzyme in the gills as yellow eels fully adapted to seawater. Transferring silver eels to seawater did not alter the percentage of chloride cells in gills although the level of (Na+ + K+)‐dependent ATPase and its specific activity increased slightly. Thus, although the silver eel is better prepared for life in seawater than the yellow eel, it still has to attain an increased level of (Na+ + K+)‐dependent ATPase in its chloride cells to be fully adapted to seawater.
Physiological adjustments to dilution of the external medium in the lip‐shark Hemiscyllium plagiosum (bennett). I. Size of body compartments and osmolyte composition
Authors: Chan D. K. O. , Wong T. M. 
Published: June 2005

AbstractThe lip‐shark Hemiscyllium plagiosum can survive gradual dilution of the external medium to a salinity of about 12% sea water.Throughout the range in salinity from undiluted sea water to 25% sea water a plasma osmolarity greater than that of the medium is maintained. In undiluted sea water the concentrations of the plasma electrolytes Na+, K+, Ca++, Mg++ and Cl− are much lower than those of the medium. The high plasma osmolarity is due largely to urea.In dilute media, lip‐sharks gain considerable amounts of water. There is a marked expansion of the blood volume and intramuscular fluid space. Although the massive influx of water causes a significant decline in electrolyte concentrations in plasma and intramuscular space, the total electrolyte content is maintained. Urea content, on the other hand, declines significantly following adaptation to dilute media.Near the lowest salinity in which survival can occur there is a rapid decline in concentration of Ca++ in the plasma and intramuscular fluid. The concentration gradient of K+ and Cl− between the extracellular and intracellular compartments of the parietal muscle also declines so that the calculated diffusion potential across the myolemma for both ions decreases significantly. These changes may be related to the inactivation of muscle and respiratory failure prior to death.
Progesterone‐induced DNA polymerase activity in full‐grown oocytes of xenopus laevis
Authors: Grippo P. , Locorotondo G. , Taddei C. 
Published: June 2005

AbstractDNA polymerase activity increases in full‐grown oocytes of Xenopus laevis during in vitro progesterone‐induced maturation. This increase in inhibited by cycloheximide. The presence of the oocyte's nucleus (germinal vesicle) seems essential for the induction of this increase: in previously enucleated oocytes, the level of DNA polymerase activity does not change during progesterone treatment.Furthermore, a new form of DNA polymerase is detectable by DEAE chromatography in in vitro matured oocytes.
Relationship between net 45calcium influx across a perfused isolated eel gill and the development of post‐stanniectomy hypercalcemia
Authors: So Ying‐Peng , Fenwick James C. 
Published: June 2005

AbstractThe net 45calcium influx was measured in perfused isolated individual hemibranchs taken from Anguilla rostrata L. at various intervals following the surgical removal of the Corpuscles of Stannius. Total plasma calcium concentrations were record at the same time.A relationship between the development of post‐stanniectomy hypercalcemia and the net rate of 45calcium uptake in the isolated gills is suggested. The net influx of 45calcium increased rapidly during the first week, peaked at two weeks and dropped back to control levels at three weeks. Plasma calcium levels followed the same trend over the first two weeks but continued to rise through the third week before dropping slightly during the fourth week.We conclude that the corpuscles of Stannius play some role in controlling the branchial uptake of calcium and that the gills are of primary importance in the appearance of post‐stanniectomy hypercalcemia.
Ultrastructural analysis of gene interaction and melanosome differentiation in the retinal pigment cells of the albino goldfish
Authors: Kajishima Takao , Takeuchi Ikuo K. 
Published: June 2005

AbstractThe genotype of albino goldfish is represented by pp,cc, and the non‐albino fish is PP,CC. The P gene begins to control the melanosome formation of retinal pigment cells at St‐21; and the C, which is epistatic to P and p, governs melanosome formation in the dermal melanophores and in retinal pigment cells after St‐22. Then in the pp,CC fish, between St‐21 and St‐22, melanosomes of the pigmented retina are albino in type, but after St‐22 they become non‐albino in type. From ultrastructural observations on the melanosomes of these late‐melanizing fish, it is apparent that the incompletely melanized albino pigment granules can differentiate into normal melansomes under the control of the C gene. The processes of melanosome maturation in the late‐melanizing goldfish are evident from these observations.
Studies of the developmental potential of 4‐ and 8‐cell stage mouse blastomeres
Authors: Kelly Susan J. 
Published: June 2005

AbstractThe object of this study was to assess the full developmental potential of all the blastomeres in 4‐cell and 8‐cell stage mouse embryos. Isolated blastomeres at these stages have limited developmental powers, and in order to follow their development into the postimplantation period a method of combining each blastomere into a chimaeric composite was devised. Preliminary experiments indicated the most favourable genetic combinations and blastomere arrangements. For the 4‐cell stage embryos each individual donor blastomere was combined with genetically distinct blastomeres at the same stage to make a “Quarted” of composite embryos. The occurrence of the donor cell characters in these composites when they were recovered at the tenth day of pregnancy and at term, indicates that each 4‐cell stage blastomere is totipotent and may contribute extensively to a mouse and also to the yolk sac and trophoblast. Eight‐cell stage blastomeres were obtained in pairs, each pair being derived from a particular 4‐cell stage blastomere. The development of the pairs were followed in chimaeric composites. Each blastomere of a pair was found to have the same range of developmental potential. This indicates a lack of segregation of morphogenetic factors and implies totipotency of the 8‐cell stage blastomeres. The relevance of these results to the current theories of blastocyst differentiation is discussed.
Exceptional tolerance to low pH of some tropical blackwater fish
Authors: Dunson William A. , Swarts Fred , Silvestri Mark 
Published: June 2005

AbstractCardinal, neon, and emperor tetras (Cheirodon axelrodi, Hyphessobrycon innesi, Nematobrycon palmeri), small South American characin fish often found in acidic blackwater rivers, have an unusual tolerance to sulfuric acid solutions of low pH. Most cardinal tetras withstand immediate transfer to water at pH 3.5 for an indefinite period. With gradual adjustment to further stepwise lowering of the pH, one individual survived at a pH of 3.1 for five weeks. This is by far the most acidic solution known to be tolerated for extended periods by any fish. The lower incipient lethal level (for 50% survival) is estimated to be about 3.35 for neon and cardinal tetras. On the other hand, common guppies (Poecilia reticulata), a species generally considered to be highly resistant to environmental change, all died after 11 days at pH 4.75. Both guppies and tetras lose large amounts of body sodium on exposure to lethal pH's.
Nucleic acid synthesis in preimplantation rabbit embryos. III. A “dark period” immediately following fertilization, and the early predominance low molecular weight RNA synthesis
Authors: Manes Cole 
Published: June 2005

AbstractThis report stems from efforts to characterize the products of trancription during the initial stages of cleavage in the rabbit embryo, since previous studies have suggested that RNA synthesis is required during this period for the continuation of normal development. Early cleaving embryos were exposed to radiolabeled precursors of nucleic acids in vitro and RNA extracted and analyzed by polyacrylamide gel electrophoresis and BD‐cellulose chromatography. No unequivocal evidence of RNA synthesis could be obtained during the first three cleavage divisions; all apparent “embryonic” RNA synthesis could be ascribed to contaminating follicle cells. After the fourth cleavage, however, there is readily detectable incorporation of radioisotope into RNA by embryos which have been denuded of follicle cells. Two‐thirds of the cytoplasmic RNA labeled during a 4‐hour period is 25–30 × 103 daltons in size, and some of this low molecular weight RNA can be aminoacylated and shown to be transfer RNA. A low level of ribosomal RNA synthesis is detectable at this stage. The contribution, if any, of the rabbit embryonic genome to development prior to the 16‐cell stage remains to be defined.
An analysis of water‐content regulation in osmoconforming limpets (Mollusca: Patellacea)
Authors: Tarr Kathleen J. 
Published: June 2005

AbstractThe capacity to regulate body volume is important in the ability of soft‐bodied osmoconforming marine animals to withstand osmotic stress. In the present study two intertidal limpets, Collisella digitalis and Notoacmea scutum, which differ in their tolerance of osmotic stress, are compared in their ability to regulate water content. Two direct measurements and two mathematical approaches developed by Oglesby ('75) and Machin ('75), respectively, have been used. Both species are osmoconformers over the range 500–1,500 mOs/1 but showed a slight tendency to hyporegulate Cl− and Na+ in the hemolymph. In weight and tissue hydration changes following a change in osmotic pressure of the medium, C. digitalis did not vary as widely as did N. scutum and so appears to have better control of body volume. This correlates well with the previous finding that C. digitalis tolerates a wider range of salinity than does N. scutum.
The phylogenetic distribution of red cell 2,3 diphosphoglycerate and its interaction with mammalian hemoglobins
Authors: Scott A. F. , Bunn H. F. , Brush A. H. 
Published: June 2005

AbstractIn order to better understand the extent to which 2,3 diphosphoglycerate (DPG) contributes to red cell function in the mammals, we assayed DPG levels in blood from a taxonomically diverse set of 71 species representing 14 orders. In addition, for 66 species and 4 hemoglobin phenotypes of the sheep, the effect of DPG on oxygen affinity was measured by determining P50 values for hemoglobin in the absence of DPG and at 0.2 mM and 1.0 mM concentrations. Most mammals had high levels of red cell DPG and phosphate‐free hemoglobins with a relatively high oxygen affinity. In contrast, two taxonomically unrelated groups had both very low intra‐erythrocytic DPG concentrations as well as hemoglobins of native low oxygen affinity that interacted weakly with DPG. This latter group includes the Feloidea (order Carnivora) and the Bovoidea (order Artiodactyla). The relationship between DPG concentration, hemoglobin oxygen affinity and the interaction of DPG with hemoglobin is treated quantitatively to provide a model of mammalian red cell function. This derived expression is compared with descriptive allometric equations for whole blood P50 and is shown to provide statistically reasonable predictions.