bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of temperature adaptation on the composition of the neutral lipid fraction of rainbow trout (Salmo gairdneri) liver
Authors: Hazel Jeffrey R. 
Published: June 2005

AbstractRainbow trout (Salmo gairdneri) acclimated to 20°C possessed significantly greater quantities of total neutral lipid, triglyceride, and free fatty acids, and smaller quantities of hydrocarbons in their livers than 5°C‐acclimated animals. Regardless of acclimation temperature the relative abundance of the various neutral lipid classes was triglyceride > cholesterol ester > free cholesterol > diglyceride > free fatty acid > wax ester and hydrocarbon. Two patterns of compositional change were observed in response to alterations in environmental temperature. Depot lipids (triglyceride and wax ester) became more unsaturated at lower ambient temperatures due primarily to moderate increases in the content of monoenes, and larger increases in the content of both dienes and polyunsaturates. Increased unsaturation of the triglyceride fraction was mediated primarily by an accumulation of unsaturates belonging to the linoleic and linolenic acid families, whereas oleate‐ and linoleate‐derived fatty acids accumulated in the wax ester fraction. The remaining neutral lipid fractions (free fatty acids, diglycerides, and cholesterol esters) all experienced a decline in the content of unsaturated fatty acids at reduced temperatures due primarily to a loss of monoenes from each fraction and a loss of dienes from the diglyceride and cholesterol ester fractions; unsaturated fatty acids belonging to the oleate family were preferentially lost from these neutral lipids upon cold acclimation. These results suggest that in response to a reduction in environmental temperature, a reorganization of lipid metabolism occurs which in volves a selective uptake of predominantly linolenate‐derived unsaturated fatty acids into phospholipids and linoleate‐derived unsaturated fatty acids into depot lipids, resulting in a free fatty acid fraction enriched in saturated fatty acids.
Dissociation and separation of Xenopus laevis spermatogenic cells
Authors: Risley Michael S. , Eckhardt Ronald A. 
Published: June 2005

AbstractMethods have been developed for the dissociation and fractionation of spermatogenic cells of the South African clawed frog, Xenopus laevis. Testis cells were dissociated with collagenase to obtain cell suspensions (1.2 × 10 8 cells/testis) highly enriched for spermatogenic cells (99.5%). The only testicular somatic cells present in the suspensions in significant numbers were Sertoli cells with mature spermatids embedded in their cytoplasm. Spermatogenic cells prepared by this method exhibited consistently high viabilities (98.7%) as measured by their ability to exclude Trypan blue dye. Subsequent to the dissociation procedure, spermatogenic cells were separated into fractions, each of which was highly enriched for a specific developmental stage, by unit gravity sedimentation and isopycnic centrifugation in Metrizamide gradients. The entire dissociation and fractionation procedure required approximately nine hours to complete and was used to separate as many as 5 × 109 cells with no apparent cytotoxic effects.
Macrocyst formation in the cellular slime mold Dictyostelium mucoroides: Involvement of light and volatile morphogenetic substance(s)
Authors: Filosa Michael F. 
Published: June 2005

AbstractIn the dark, cultures of Dictyostelium mucoroides produce macrocysts while in the light fruiting bodies are formed. However, dark cultures will form fruiting bodies if grown over activated charcoal indicating that some gas or volatile substance is involved. Light cultures will form macrocysts when grown over CO2 absorbents (eg. KOH). If light cultures are grown over both KOH and activated charcoal only fruiting bodies are formed. A light‐mediated reaction involving CO2 assimilation may prevent the synthesis or utilization of the volatile substance needed for macrocyst formation.
HCO3‐stimulated CL efflux in the Gulf toadfish acclimated to sea water
Authors: Kormanik Gregg A. , Evans David H. 
Published: June 2005

AbstractUnidirectional efflux of Cl was examined in the Gulf toadfish, Opsanus beta, in artificial seawater solutions with modified concentrations of Cl and HCO3. Removal of Cl and HCO3 reduced Cl efflux. Addition of HCO3 at typical seawater concentrations stimulated Cl efflux, independent of changes in the transepithelial potential. This active, HCO3‐stimulated Cl efflux is saturable, with a Km of 2.4 mM, typical of the concentration of HCO3 found in sea water, and independent of external pH. Active extrusion of Cl offsets the net diffusional and oral gain of Cl faced by O. beta in sea water.
Regenerative responses in larval axolotl limbs with skin grafts over the amputation surface
Authors: Tassava Roy A. , Garling David J. 
Published: June 2005

AbstractComplete flaps of whole skin over the amputation surface of larval axolotl limbs did not prevent dedifferentiation, DNA synthesis, and mitosis. However, even by two weeks, insufficient cell division had occurred for blastema formation. In about 50% of the cases, small areas of wound epidermis formed over the amputated tip of the radius or ulna. At two weeks after amputation, mitotic figures and dedifferentiated cells which incorporated H3‐thymidine were predominantly located in the vicinity of the small area of wound epidermis. Although delayed in relation to controls, these limbs regenerated.The results are consistent with the view that the wound epidermis is necessary to maintain dedifferentiated cells in the cell cycle.
Solute compatibility with enzyme function and structure: Rationales for the selection of osmotic agents and end‐products of anaerobic metabolism in marine invertebrates
Authors: Bowlus R. David , Somero George N. 
Published: June 2005

AbstractThe major nitrogenous osmolytes present in the cells of marine invertebrates, notably the free amino acids glycine, alanine and proline, and trimethylamine oxide and betaine, are highly compatible with proper enzyme function and structure. These nitrogenous osmolytes display either nonperturbing or, in some cases, favorable effects on enzyme‐substrate and enzymecofactor complex formation, catalytic velocity and protein structural stability. In contrast, inorganic salts (KCl and NaCl) and certain of the free amino acids which play only a minor osmotic role, e.g., arginine and lysine, have galy perturbing effects on one more of these enzymic parameters. The compatible nitrogenous solutes therefore are suitable for use at high (several tenth molar) contcetrations and at widely varying consentrations in osmo conferming species.Certain nitrogenous solutes, especially trimethyline oxide, betaine and glutamate, offset some of the perturbing effects of inorganic ions on enzyme fuction. The selective accumulatin of osmolytes thus unvolves not only the concentration of non‐perturbing solutes, but also a balanced accumulation of solutes with opposing effects on enzumes.The selection of end‐products of anaerobic metabolism also appears to be based, in part, on considerations of solute compatibility with enzyme fuction. Octopine is a non‐perturbing solute, whereas arginine, which is condensed with pyruvate to form octopine, is very strongly perturbing. Succinate has marked stabilizing effects on protein structure.We conclude that the composition of the intracellular fluids of marine invertebrates reflects selection for osmolytes and end‐products whose net effects create a cellular microen vironment which is conducive to otimal enzyme fuction and structure. The accumulation of compatible solutes may preclude the necessity for widespread changes in protein structure in adapting to concentrated or highly variable osmotic environments.
Intermediate filaments connect Z‐discs in adult chicken muscle
Authors: Price Maureen , Sanger Joseph W. 
Published: June 2005

AbstractWhen adult chicken skeletal myofibrils are treated with a myosin‐extracting solution, the Z‐discs with attached actin filaments retain their linear connections with one another in the extracted myofibril. The sarcomere length increases in the extracted myofibrils from a control length of 2.5 μm up to 6 μm. In a sarcomer, eight to fifty 10 nm filaments can be seen in parallel array in the H‐zone. The 10nm‐wide filaments do not bind heavy meromyosin and are two to four μm in length. These intermediate filaments are postulated to be an integral part of the sarcomere, connecting Z‐bands along the length of the myofibril.
Periodic breathing in the crocodile, Crocodylus niloticus: Consequences for the gas exchange ratio and control of breathing
Authors: Glass M. L. , Johansen K. 
Published: June 2005

AbstractThe ventilatory pattern in the Nile crocodile consists of episodes of breathing, interrupted by periods of breath‐holdin, the latter occupying 80% of total time during normal breathing at 25°C.End‐tidal gas composition varied with the periodic breathing but Po2 was always high (Po2<110 torr) and Pco2 low (Pco2<25 torr). The alveolar gas exchange ratio, RE, was very low during the non‐ventilatory periods (RE ≃ 0.5), but increased markedly during ventilation.Breathing of hypoxic and hypercapnic gases caused a pronounced decrease in the duration of breath‐holds. Hypercapnia decreased breathing frequency during ventilatory periods, but increased tidal volume.The results are discussed in relation to the practice of prolonged breath‐holding associated with diving in crocodiles.
DNA reassociation kinetics in diploid and phylogenetically tetraploid cyprinidae
Authors: Mauro Maria Luisa , Micheli Gioacchino 
Published: June 2005

AbstractFour diploid and three phylogenetically tetraploid Cyprinidae (Ostariophysi) have been characterized as for nuclear DNA content, modal chromosome number and DNA reassociation kinetics (hydroxyapatite chromatography).Among the diploid species nuclear DNA content (10−12 g DNA/2C) was 1.62 for Tinca tinca, 1.87 for Scardinius erythrophthalmus, 2.53 for Leuciscus cephalus and 2.75 for Alburnus alburnus, while the phylogenetically tetraploid species Carassius auratus, Barbus barbus and Cyprinus carpio attained 3.40,3.66 and 3.80 respectively. Modal chromosome number was 2n = 48–50 for diploid individuals and 2n = 100–104 for phylogenetically tetraploid ones. In all the species 5–8% of the genome is represented by highly repetitive and foldback DNA. In DNA reassociation kinetics of phylogenetically tetraploid Cyprinidae a distinct plateau separates an intermediate reassociating sequence fraction (about 22% of the genome; with average repetition frequencies between 1,000 and 1,400) from a slow reassociating one (unique DNA; about 72% of the genome). These two genome fractions are not clearly distinguishable from each other in Cot curves of the diploid Cyprinidae, where a similar plateau is not evident.Since simple ploidy changes are not expected to affect DNA reassociation kinetics we suggest a different evolution in the genome organization of the two ploidy groups. Some possible hypotheses are discussed.
Dependence of oral development and cleavage on cell size in the ciliate Stentor
Authors: de Terra Noël 
Published: June 2005

AbstractIn Stentor, the two main cytoplasmic events of cell division are development of the oral primordium that gives rise to the oral apparatus of the posterior daughter cell and cleavage. The present work examines directly the dependence of these two events on the size of the cell body. Cell body size was reduced by various amounts with a microneedle during early stages of cell division and the effects on oral development and cleavage observed. The oral primordium was always resorbed and cleavage never occurred when the cell body was reduced to one quarter of its original size at Stage 3 of cell division; appropriate controls showed that this result was not caused by operation injury. Progressively smaller reductions in cell size yielded correspondingly lower percentages of inhibited cells. These data suggest that the mechanisms underlying the dependence of oral development and cleavage on cell size do not involve accumulation of regulator substances up to a critical concentration during interphase. The fact that oral development can be reversed by reducing cell body size supports the hypothesis that oral development and cell division are initiated when the oral apparatus becomes disproportionately small in relation to cell body size as a result of interphase growth. The size‐dependence of cleavage is probably best understood as a mechanism for regulating cell size in Stentor.
Effect of seasonal variation on immune system of the lizard, Scincus scincus
Authors: Hussein M. F. , Badir N. , El Ridi R. , El Deeb S. 
Published: June 2005

AbstractIn winter, the lizard, Scincus scincus, fails to form humoral antibodies to parenterally introduced rat erythrocytes. The response is slow and feeble in spring whereas, it is quick and vigorous in summer and autumn. In winter, the thymus of Scincus is involuted, white pulp of spleen highly depleted while, gut‐associated lymphoid tissue is rather developed. By the beginning of spring, lymphoid organs start to regenerate. By the end of spring through midfall, the thymus presents a rich lymphoepithelial organization; splenic lymphoid aggregates are so developed that they become confluent and gut aggregates increase in number and size. The data suggest that, the kinetics and magnitude of the lizard's humoral response to foreign erythrocytes, correlate with the state of lymphoid tissue development which, in turn, is affected by seasonal variations.
Fatty acid and sterol synthesis by hepatocytes of thermally acclimated rainbow trout (Salmo gairdneri)
Authors: Hazel Jeffrey R. , Sellner Peggy A. 
Published: June 2005

AbstractIncorporation of tritium from tritiated water into lipid fractions was measured in isolated hepatocytes from rainbow trout (Salmo gairdneri) acclimated to 5°C and 20°C. Hepatocytes from cold‐acclimated trout exhibited significantly higher rates of tritium incorporation into both fatty acid and sterol fractions at assay temperatures of 15°C and 20°C than did hepatocytes from warm‐acclimated trout. Tritium incorporation into the fatty acid fraction was nearly temperature independent in hepatocytes from warm‐acclimated trout (Q10 = 1.39) but markedly temperature dependent (Q10 = 2.63) in hepatocytes from cold‐acclimated trout; in contrast, rates of sterol synthesis were more temperature dependent in warm‐acclimated trout. At 5°C, fatty acid lipogenesis comprised a significantly greater percentage of the total tritium incorporation in hepatocytes from warm‐acclimated trout and the percentage of total lipogenesis attributable to fatty acids decreased significantly in warm‐acclimated trout as the assay temperature increased; the opposite trends were observed in cold‐acclimated trout.
Effect of activity of lateral cilia on transport of amino acids in gills of Mytilus californianus
Authors: Wright Stephen H. 
Published: June 2005

AbstractThe effect of 5‐hydroxytryptamine (5‐HT) on influx of 14C‐glycine in isolated gills of Mytilus was studied. 5‐HT was observed to induce metachronal activity of lateral cilia in in vitro preparations of gills of M. californianus and M. edulis. Active lateral cilia were capable of increasing perfusion of isolated gills of M. californianus, as demonstrated by a significant reduction in the t1/2 for washout of 14C‐inulin from gills treated with 5‐HT. Application of 5‐HT at a concentration of 10−5 M increased influx of 1 μM 14C‐glycine in isolated gills of M. californianus from control values of less than 0.1 μmoles/(g‐hr) to 0.5 μmoles/(g‐hr). Influx of 1μM glycine in gills from M. edulis treated with 5‐HT was more than 700% of control values. 5‐HT had no effect on uptake of glycine in intact, actively pumping M. californianus, indicating that 5‐HT's effect on transport in isolated gills is a result of activating lateral cilia rather than a direct effect on the transport process. The Michaelis constant for influx of glycine was reduced from a control value of 44 μM to 20 μM by treatment of gills from M. californianus with 5‐HT. These observations are consistent with the hypothesis that in vitro preparations of mussel gill have unstirred layers that introduce a significant bias into determinations of transport kinetics. Extrapolation of results obtained with isolated gills to intact animals is dubious.
Germinal vesicle configurations and patterns of polypeptide synthesis of porcine oocytes from antral follicles of different size, as related to their competency for spontaneous maturation
Authors: McGaughey Robert W. , Montgomery Deborah H. , Richter Joel D. 
Published: June 2005

AbstractThe cytogenetic configurations of germinal vesicle (gv) chromatin were analyzed for pools of porcine oocytes harvested from small (1.0–2.0 mm), medium (3.0–5.0 mm), and large (6.0–10.0 mm) antral follicles. Groups of oocytes from these follicular classes also were examined by high‐resolution, two‐dimensional, polyacrylamide gel electrophoresis to compare their patterns of polypeptide synthesis. The results show a high incidence of gross and cytogenetic degeneration among oocytes from small antral follicles as compared with those from medium or large follicles. Pools of oocytes could be separated, on the basis of gross morphology and integrity of adherent granulosa cells, into two classes: “Type A” which appeared normal, and “type B” which appeared to be atretic. Among selected “type A” oocytes a particular chromatin configuration, termed “fibrous” characterizes the gv of oocytes from small follicles; whereas a different configuration, termed “diffuse,” characterizes the gv of oocytes from large follicles. The patterns of polypeptide synthesis were markedly different for samples of “type A” oocytes of the three follicular classes; and the patterns for oocytes from medium and large follicles were more similar to each other than to patterns for oocytes from small follicles. The incidences of maturational development beyond the gv stage in vitro were similar for “type A” oocytes from the three follicular classes (i.e., 66% to 82% maturation); although “type B” oocytes underwent maturation beyond the gv at a significantly reduced incidence (i.e., 20% to 29% maturation). “Type A” oocytes from large follicles completed maturation in vitro (i.e., underwent the first meiotic division) at a significantly higher incidence (55%) than did oocytes from small (11% to 20%) or medium (16%) follicles. Our findings are consistent with the hypotheses that a high proportion of oocytes from small antral follicles are atretic, and that a developmental program controls the molecular and cytogenetic changes occurring in porcine oocytes during follicular growth. These changes appear to be highly correlated with the acquisition of competency to complete maturation in vitro, and possibly also are required for normal fertilization and embryogenesis.
Creatine kinase gene expression during the development of Brachydanio
Authors: Pontier Paul J. , Hart Nathan H. 
Published: June 2005

AbstractThe ontogeny of creatine kinase (CK) in Brachydanio rerio, B. albolineatus and hybrids formed by their reciprocal crosses was investigated using electrophoretic and spectrophotometric methods. Creatine kinase existed in three homodimeric isozymes in tissues of both species: an eye‐brain predominant CK‐B2 form, a skeletal muscle predominant CK‐A2 form, and a stomach specific CK‐C2 form. Zebra and pearl danio embryos exhibited identical progressions of CK isozymes through four days postfertilization. The CK‐B2 isozyme was continuously expressed and was the only CK form present from Stage 1 (fertilization) through Stage 20 (optic cup). The CK‐A2 isozyme initially appeared at Stage 21. Its expression correlated temporally with slow, irregular contractions of the trunk and early differentiation of the trunk somites into myoblasts. Spectrophotometric analysis of total CK showed a sharp decline in activity during the first 10 hours of development (i.e., until the end of gastrulation). Total CK activity remained low until the appearance of the CK‐A2 isozyme.Embryos of reciprocal crosses between B. rerio and B. albolineatus displayed similar patterns of expression of both CK‐B2 and CK‐A2 isozymes. The paternal Ck‐B locus was first expressed in hybrid embryos at 48 hours postfertilization in the form of the CK‐BABR heterodimer. The paternal CK‐B2 homodimer was detected in embryos at 55 hours postfertilization. The parental alleles of the Ck‐B locus were synchronously expressed. The pattern of CK‐A2 expression in hybrids followed a pattern similar to that in intraspecific crosses.Experiments with actinomycin D and cycloheximide supported our previous studies which indicate that nuclear genes of multilocus isozyme systems in Brachydanio are activated during gastrulation. Results of exposing B. rerio embryos to actinomycin D showed that transcription of template RNA coding for the CK‐A2 isozyme occurred during an 8‐hour interval beginning at mid‐gastrulation or about 12 to 20 hours prior to Stage 21. The initial translation of the CK‐A2 template RNA began 15 hours following transcription or five hours prior to the detection of the first enzyme molecules.
Interspecific heterokaryons between oocytes and blastomeres of the mouse and the bank vole
Authors: Bałakier H. 
Published: June 2005

AbstractInterspecific hybrid cells were produced using Sendai‐virus‐mediated fusion of interphase blastomeres from 2‐cell embryos with ovulated oocytes of the mouse and bank vole. Under the influence of the cytoplasm of' oocytes (arrested in metaphase II) premature chromosome condensation occurs in the nuclei of blastomeres, thus implying that the cytoplasmic factor which induces chromosome condensation is not species specific, at least not between these two species.
A comparison between oocyte growth in coculture with granulosa cells and oocytes with granulosa cell‐oocyte junctional contact maintained in vitro
Authors: Eppig John J. 
Published: June 2005

AbstractEvidence is presented that strongly supports the hypothesis that the junctional association between oocytes and granulosa cells must be maintained to promote oocyte growth and development in vitro and that the coculture of oocytes with granulosa cells is not a sufficient condition for oocyte development. Furthermore, it is shown that incorporation of uridine and leucine by oocytes into TCA‐insoluble material is significantly greater in granulosa cell‐enclosed oocytes than in cocultured oocytes.
Pigment synthesis in the Himalayan mouse
Authors: Kidson Susan , Fabian Barry 
Published: June 2005

AbstractThe effect of temperature on pigment synthesis in adult and juvenile Himalayan mice was investigated. Since pigment synthesis only occurs in actively growing hair, adult mice were plucked to induce hair growth. The extent of darkening of the hair was recorded by photography against a reference scale. The presence of pigment granules in hair follicles was investigated histologically. Housing adult and juvenile mice at 15° C results in the synthesis of pigment in growing hair follicles whereas housing at 30° C results in the absence of pigment granules in the growing hair follicles.
Acclimation to successive short term salinity changes by the bivalve Modiolus demissus. I. Changes in hemolymph osmotic concentration, hemolymph ion concentration and tissue water content
Authors: Strange Kevin B. , Crowe John H. 
Published: June 2005

AbstractThe response of Modiolus demissus to successive short term osmotic stress, such as may be experienced on a daily basis during normal tidal fluctuations, was investigated. Results indicate that if M. demissus uses valve closure as a means of avoiding temporary salinity change, the period of time during which it does so must be very short. Animals were found to be essentially in osmotic equilibrium with their environments within three hours of exposure to new salinity regimes.