bluuebunny/crossref_metadata_2025_split huggingface dataset:
ENU‐induced allele of brachyury (Tkt1) exhibits a developmental lethal phenotype similar to the original brachyury (T) mutation
Authors: Justice Monica J. , Bode Vernon C. 
Published: June 2005

AbstractNew alleles of brachyury (Tkt1, Tkt4) were induced in the mouse complete tw5 haplotype by ethylnitrosourea (ENU). Like the original brachury (T) mutation, the new alleles cause a short‐tailed phenotype in heterozygotes, and interact with the t complex tail interaction factor (tct) in trans to cause phenotypically tailless mice. Because ENU is mainly a point mutagen, it is important to determine that the new alleles are homozygous embryonic lethal mutations like the original T allele, and to characterize their embryonic lethal phenotype. Moreover, the Tkt1 mutation maps to an inverted position relative to quaking (qk) in t haplotypes as compared with its position on normal chromosome 17. The Tkt1 allele was separated from the resident tw5 lethal gene, tclw5, by recombination, allowing embryology studies to be performed. Embryological analyses show that the Tkt1 allele is nearly identical to the classic T allele. At 9 and 10 days of development, homozygous Tkt1/Tkt1 embryos are grossly abnormal with properties including 1) irregular, disorganized somite pairs, 2) a shortened posterior end of the embryo, 3) an irregular neural tube, and 4) an abnormal notochord. In addition, 10 day‐old abnormal embryos have anterior limb buds that point dorsally rather than ventrally, and are smaller than normal littermates. We conclude that the Tkt1 mutation is a valuable allele for both mapping and molecular characterization of the brachyury locus.
Induction of acrosomal filament formation in the sperm of Sicyonia ingentis
Authors: Griffin Fred J. , Clark Wallis H. 
Published: June 2005

AbstractThe acrosome reaction (AR) in the sperm of Sicyonia ingentis, which consists of the exocytosis of an acrosomal vesicle followed by the formation of an acrosomal filament, can be induced in vitro when sperm are incubated in egg water (Griffin et al., '87). Egg water (EW) was determined to possess a protein/carbohydrate ratio of approximately 4:1 and contain trypsin‐like proteolytic activity (based on the hydrolysis of synthetic peptidyl‐MCA substrates and the results of protease activity SDS‐PAGE). Results of this study demonstrate that the two phases of the AR are elicited by separate inducers or inducing activities within EW and suggest a role for an EW trypsin‐like proteolytic activity in filament formation. The protein concentration of EW (within the range of 20–80 μg/ml) correlated with acrosomal filament formation in sperm but not with acrosomal exocytosis. EW‐induced filament formation was inhibited in the presence of soybean trypsin inhibitor and p‐aminobenzamidine, although acrosomal exocytosis was not. Bovine trypsin, chymotrypsin, and Pronase induced filament formation in the small number of sperm that had spontaneously undergone acrosomal exocytosis in sea water (not incubated in EW), but did not induce additional sperm to undergo exocytosis.
In vitro fertilization of Siberian hamster oocytes
Authors: Parkening T. A. 
Published: June 2005

AbstractSiberian hamsters were superovulated and various media were tested in an effort to fertilize the recovered oocytes in vitro. The highest percentage of fertilized ova was achieved by using a modified Tyrode's medium, designated MT (Bavister, J. Reprod. Fertil., 18:544–545, '69), previously formulated to fertilize Syrian hamster ova in vitro. Spermatozoa incubated in this medium in a concentrated state overnight (14 hr) and then diluted (1 hr) fertilized 39% of the ova. Similar results (40%) were obtained with this medium by adding 20% human follicular fluid to fresh concentrated sperm for 30 min and then diluting the sperm for 2–3 hr prior to the addition of ova. Ova fertilized in vitro cleaved to the two‐cell stage but failed to develop any further in culture. Two‐cell embryos recovered from mated hamsters and cultured did not undergo additional cleavage. Four‐cell embryos collected from mated females and cultured cleaved to the six‐ to eight‐cell stage and stopped. Techniques and media used for fertilizing large numbers of Syrian and Chinese hamster ova in vitro will have to be modified to achieve the same degree of success in the Siberian hamster.
Changes in density and viscosity of chicken egg albumen and yolk during incubation
Authors: Meuer Hans‐Jürgen , Egbers Christoph 
Published: June 2005

AbstractIn early stages of avian development, respiratory gas exchange takes place mainly through the blood vessels of the yolk sac membrane. Therefore, a short distance between the yolk sac membrane and the eggshell is required to ensure a sufficient oxygen supply of the embryo. In freshly laid eggs the yolk sphere is located approximately in the center of the egg, but soon after the beginning of incubation it moves to the upper pole right beneath the eggshell. The cause for this displacement is not known. To quantify the forces acting on the yolk sphere of chicken eggs during incubation, we measured the densities of albumen, yolk and subembryonic fluid and the viscosity of the liquid albumen. We found that between day 0 and day 4 of incubation the calculated buoyancy due to density differences between the egg components increases only threefold. This is probably too small to overcome the yield stress of the gel‐like thick albumen that forms a capsule around the yolk sphere. A different process responsible for the yolk displacement is proposed. Under reduced gravity, the movements of the yolk are influenced substantially by the fluid properties of the thin albumen, especially yield stress. Furthermore, acceleration peaks present in a space laboratory will probably displace the yolk sphere away from the eggshell. This is strong evidence that an early chick embryo will not be able to survive in a space laboratory in ovo.
Lampbrush and mitotic chromosomes of the hemiclonally reproducing hybrid Rana esculenta and its parental species
Authors: Bucci Stefania , Ragghianti Matilde , Mancino Giorgio , Berger Leszek , Hotz Hansjürg , Uzzell Thomas 
Published: June 2005

AbstractMitotic chromosomes of the European water frogs Rana ridibunda and Rana lessonae, the parental species of Rana esculenta, differ significantly in their centromeric regions: when C‐banded or when made fluorescent, the centromeres of R. ridibunda (and of the ridibunda chromosomes in R. esculenta) are visible as a conspicuous dark granule or as a conspicuous fluorescent spot; the centromeres of R. lessonae (and of the lessonae chromosomes in R. esculenta) are inconspicuous or not fluorescent. Lampbrush chromosomes of these three taxa are described in detail for the first time; those of R. ridibunda and R. lessonae differ significantly in morphostructural characters such as conspicuousness of centromeres and number, form, and location of giant loops as well as in chiasma frequency. Chromosomes of the two parental species can thus be distinguished when present in lampbrush complements of hybrids. Reproduction in both sexes of natural R. esculenta lineages is hemiclonal: only the unrecombined genome of one parental species, usually R. ridibunda, is transmitted to haploid gametes (hybridogenesis). In 18 hybrids from natural populations of Poland, somatic tissues had allodiploid complements with chromosomes from each parental species. In contrast, spermatocytes I of five males and oocytes I of seven of eight females (221 of 222 oocytes) were autodiploid and contained only R. ridibunda chromosomes that formed n bivalents. These 12 hybrids thus were hybridogenetic. A single female hybrid had oocytes I (33 of 34) with genomes of both parental species; they showed various disturbances including tetraploidy, reduced number of chiasmata, and incomplete synapsis resulting in univalents. This individual thus was not hybridogenetic. The irregular lampbrush patterns indicate that such hybrids will have severely reduced fertility and most of their successful gametes will result in allotriploid progeny.
Improved developmental potential of rabbit oocytes fertilized by sperm microinjection into the perivitelline space enlarged by hypertonic media
Authors: Yang Xiangzhong , Chen Jingbo , Chen Yu Qi , Foote Robert H. 
Published: June 2005

AbstractThe objectives of the present study were: 1) to develop a simple and more efficient technique for sperm microinjection than is currently available, using the rabbit as a model, and 2) to evaluate the development of rabbit oocytes fertilized by single or multiple sperm microinjection. Hyperosmotic sucrose in phosphate‐buffered saline (SPBS) was employed to dehydrate oocytes to increase the perivitelline space for sperm microinjection and prevent possible injury to the vitellus. In the first experiment, 58% (n = 29) oocytes treated with 0.5 M SPBS developed to morulae following multiple sperm microinjection compared, respectively, to 47% (n = 34) and 60% (n = 15) for control IVF with or without sucrose exposure (P > 0.05). Blastocyst development from microinjected oocytes, however, was much lower (P < 0.05) than that of controls (14% vs. 42% and 40%, respectively). Sham operation by puncturing the zona pellucida of the sucrose‐treated oocytes with the microinjection pipette did not increase parthenogenesis (P > 0.05). In Experiment 2 a smallersize injection pipette and shorter sucrose exposure time after sperm microinjection resulted in 41% (n = 42) of the oocytes developing into blastocysts for the microinjection group, whereas only 21% (n = 24) developed to blastocysts in the control IVF group (P < 0.05). When relatively older oocytes (17 hr post ovulation injection) were used to test if microinjection could reduce the time to fertilization and cleavage (Expt. 3), an average of 27% (n = 63) blastocysts resulted from microinjection vs. 0% (n = 28) for the control IVF group.
Low temperature tolerance of the gemmules of Eunapius fragilis
Authors: Boutselis Nicholas J. , Fell Paul E. , Loomis Stephen H. 
Published: June 2005

AbstractThis present study has shown that hydrated gemmules of Eunapius fragilis (Leidy) are able to survive brief exposure to temperatures as low as −100°C. However, the rates at which the gemmules are cooled and warmed have a marked effect on their survival. Hydrated gemmules exhibited good survival when cooled to −30°C at 0.1°C/min or 0.5°C/min. On the other hand, gemmules cooled at 1.0°C/min or 10.0°C/min did not survive. The effect of warming rate on the survival of gemmules exposed to −30°C was less pronounced than that of the cooling rate. However, gemmules which were warmed very slowly (0.1°C/min) showed a low level of germination. Hydrated gemmules also survived exposure to −72°C for at least 30 days. It appears that the time of exposure to low temperature is far less important in determining survival than the rates at which the gemmules are cooled to such low temperatures and then subsequently warmed.
Two types of striated muscle suggest two‐geared swimming in the pteropod mollusc Clione limacina
Authors: Satterlie Richard A. , Goslow G. E. , Reyes Arjun 
Published: June 2005

AbstractForward locomotion in the pteropod mollusc Clione limacina occurs in two distinct speeds, slow and fast. Fast swimming can include an initial ballistic escape phase following proper stimulation. Escape swimming is always followed by a period of fast swimming (both are forms of fast swimming), but changes from slow to fast swimming can occur without activation of the escape phase. Light and electron microscopical examination of the swim musculature reveals two types of striated muscles, suggesting that the neuromuscular system is designed to operate with two distinct “gears”. Histochemical staining for myosin ATPase (alkaline preincubation) and NADH diaphorase suggests that swim musculature includes slow‐twitch, fatigue‐resistant fibers and fast‐twitch fatigable fibers. Combined electrophysiological and force transducer recordings support the twitch speed dichotomy, as fast‐twitch motor units were found to have twitch times of 20 ms (time to peak tension) while slow‐twitch motor unit twitch times were found to be more than three times as long. Fatigue tests were used to simulate both slow and fast swimming. Fatigue rates during simulated fast swimming suggest that the change from escape swimming to fast swimming may be partly explained by fatigue in the fast‐twitch motor units, but other factors, possibly including peripheral modulation of muscle activity, must also contribute to the change.
Apolipoprotein A‐I synthesis during the acclimatization of the carp (Cyprinus carpio)
Authors: Inostroza Juan , Vera Maria Ines , Goicoechea Oscar , Amthauer Rodolfo , Krauskopf Manuel 
Published: June 2005

AbstractTotal protein and apo A‐I synthesis were studied in suspensions of isolated hepatocytes from winter‐ and summer‐acclimatized carp. The overall protein synthesis in liver is significantly higher in summer‐adapted fish. Although apo A‐I synthesis accounts for the same fraction of the total protein synthesis when assayed at the seasonal environmental temperature in both adaptive states, winter‐acclimatized fish synthesize apo A‐I at 10°C at a higher rate than the summer fish. Thus, reprogramming of apo A‐I synthesis accompanies the adaptative compensatory response.Differences were found in the apo A‐I content in liver of carp acclimatized to the cold and warm seasons. The low apo A‐I content found in the liver of winter‐acclimatized carp reverses upon treatment of the fish with insulin. This apo A‐I enhancement leads to hepatocytes resembling those of the summer‐acclimatized state.
Calcium‐dependent proteolysis in crustacean claw closer muscle maintained in vitro
Authors: Mykles Donald L. 
Published: June 2005

AbstractAn organ culture system was developed to determine the role of calciumdependent proteinases (CDPs) and lysosomes in the degradation of proteins in the claw closer muscle of the land crab, Gecarcinus lateralis. Elevating intracellular calcium concentrations with caffeine, dibucaine, or ionophore A23187 stimulated proteolysis, as measured by the release of primary amines and tyrosine to the culture medium, 69 to 192%; A23187 also stimulated the degradation of actin and myosin heavy chain in the intact tissue. Cysteine proteinase inhibitors (leupeptin; L‐trans‐epoxysuccinyl‐leucylamido‐(3‐methyl)butane or Ep‐475; ethyl(+)‐(2S,3S)‐3‐[(S)‐methyl‐1‐(3‐methylbutylcarbamoyl)‐butylcarbamoyl]‐2‐oxiranecarboxylate or EST) suppressed proteolysis 24 to 53% while pepstatin A, an inhibitor of aspartic proteinases, and lysosomal inhibitors (chloroquine, 3‐methyladenine, monensin) had no effect. EST also suppressed, by 30 to 35%, A23187‐stimulated release while chloroquine did not; A23187‐stimulated hydrolysis of myosin heavy chain was inhibited 26% by EST and Ep‐475. The myosin heavy chain fragment pattern in supernatant fractions resembled that produced when CDPs were incubated with myofibrils in vitro; both lacked a 145‐kDa fragment produced in reaction mixtures containing purified myosin. This suggests that CDPs degrade in situ myosin polymerized into thick myofilaments rather than myosin monomers. Ultrastructural studies showed that A23187 also induced a preferential removal of the Z‐line. These results are consistent with the hypothesis that CDPs, but not lysosomes, are involved in the turnover of myofibrillar and non‐myofibrillar proteins in crustacean striated muscle.
Analysis of the inhibitory effect of inorganic phosphate on development of four‐cell hamster embryos in vitro
Authors: Monis Helena , Bavister Barry D. 
Published: June 2005

AbstractHamster 4‐cell stage embryos were cultured in a protein‐free, glucose‐free medium to study the nature of developmental inhibition by inorganic phosphate (Pi). In the absence of Pi, between 40 and 55% of embryos were able to develop to the blastocyst stage but addition of Pi to the medium reduced this proportion to 5–20%. The inhibition did not appear to be due to contamination of the Pi salt with heavy metals because EDTA did not relieve the effect. Inhibition by Pi showed no dose‐response relationship over the range tested (1–350 μM). In contrast, another divalent anion (sulphate) produced no inhibition of 4‐cell embryo development at concentrations as high as 5.6 mM. Embryos were less sensitive to inhibition by Pi after the third cleavage division had occurred, and development of mid or late 8‐cell embryos was unaffected by Pi. After exposure to Pi for 1 h, embryos could recover and continue development but longer exposure was detrimental to subsequent development. These results indicate that the inhibitory effect is specific to phosphate ions, is not due to contaminants in the Pi salt, is evoked by very low concentrations of Pi, is stage‐specific, and is reversible following brief exposure of embryos to Pi. These effects may be artifacts of the culture milieu, or they may reflect some unknown characteristic of the early cleavage stage hamster embryo.
Fatty acid synthesis and accumulation rates in daphniids
Authors: Goulden Clyde E. , Place Allen R. 
Published: June 2005

AbstractFatty acid accumulation and synthesis rates were measured in two species of daphniid Cladocera, Daphnia magna and D. pulex, to determine what fraction of deposited fatty acids accumulated by these zooplankton species are dietary and what fraction are synthesized de novo. Fatty acid accumulation rates were measured as the increment in lipid weight during the adult third instar. Lipids were extracted, separated on chromarods, and quantified by flame‐ionization detection. Fatty acid synthesis rates were measured by exposing adult third‐instar females to [3H]2O and [U‐14C]‐acetate. Synthetic rate estimates using [U‐14C]‐acetate were consistently less than estimates obtained by using [3H]2O. Lipid content (percent of dry weight) from D. magna cultures supplied with high algal food (100,000 cells/ml) increased from 16.6% at the beginning of the third instar (eggs removed from brood pouch) to 22% at the beginning of the fourth instar (with eggs). The increase in lipid of D. pulex under identical conditions ranged from 19.8% to 30.6% total lipid and under low food conditions (4,000 cells/ml) ranged from 37% to 40% lipid. Accumulated fatty acids were associated largely with triacylglycerol (60–80% of accumulated lipid) or phospholipid (10–20% of accumulated lipid). Fatty acid accumulation for high‐food animals was 1,043 ng/hr/individual and 364 ng/hr/individual for D. magna and D. pulex, respectively. The corresponding fatty acid synthesis rates were 17 ng/hr/individual and 6 ng/hr/individual, respectively. Low‐food adults of D. pulex accumulated fatty acids at a rate of 192 ng/hr/individual and only synthesized fatty acids at a rate of 0.3 ng/hr/individual. Incorporated label was present in a slow turnover pool of complex polar lipids. Fatty acid synthesis contributes less than 2% of the accumulated total fatty acids in these daphniids.
Differentiation in vitro of sea urchin micromeres on extracellular matrix in the absence of serum
Authors: Benson Steve , Chuppa Sandy 
Published: June 2005

AbstractPrevious investigations have demonstrated that differentiation in vitro of micromeres from sea urchin embryos requires the presence of serum. In this report we demonstrate that differentiation of micromeres, as judged by their ability to form spicules, will occur in the absence of serum if the cells are cultured on a reconstituted extracellular matrix prepared from Engelbreth‐Holm‐Swarm (EHS) tumors. These results suggest that a permissive environment provided by the EHS matrix is sufficient to induce micromere differentiation and may allow the isolation and characterization of the active component.
Behavior of rabbit dental tissues in heterospecific association with embryonic quail ectoderm
Authors: Fuenzalida Marcela , Lemus Roxana , Romero Sergio , Fernandez‐Valencia Rafael , Lemus David 
Published: June 2005

AbstractThe behavior of dental tissues from the rabbit, Oryctolagus cuniculus, in association with epithelium from the quail, Coturnix coturnix japonica, has been examined. Adult and embryo rabbits were employed in this study. Dental papillae from teeth at the cap stage from rabbit embryos and dental pulp from adult rabbits were isolated surgically and recombined with skin ectoderm from 72‐hour‐old quail embryos. The recombined tissues were cultured for 48 hours on semi‐solid medium and subsequently removed and placed on chorio‐allantoic membranes of 7‐day‐old chick embryos. Control cultures (dental pulp, dental papillae, and quail ectoderm) showed regression, atrophy, or differentiation according to the phenotype of the tissue. After 8 days in explant culture, heterologous recombinants composed of dental papillae and flank skin ectoderm from quail embryos developed differentiated chimeric tooth structures. It was unclear whether or not enamel was being secreted. The fact that the interactions between the enamel epithelium and the dental papillae are reciprocal is well known. The differentiation of odontoblasts can only occur in the presence of an enamel organ. Thus, the quail epithelium must have been induced to become an enamel organ, the lack of enamel proteins notwithstanding. Apical pulp and root pulp from adult rabbits plus quail ectoderm showed a high degree of regression and atrophy. At around 15 days of gestation, the rabbit dental papillae at the cap stage have already acquired odontogenic potential. By contrast, under the same experimental conditions, the dental pulp from continuous‐growth teeth from adult rabbits did not show odontogenic potential. It may be that, under less stringent experimental conditions (for example, in combinations of rabbit embryonic epithelium or first‐arch epithelium from quail embryos with pulp from adult rabbits), other results might be obtained.
β‐keratin expression in avian tongue cell aggregates
Authors: Carver W. E. , Knapp L. W. , Sawyer R. H. 
Published: June 2005

AbstractRotation‐mediated aggregation was used to test the capacity of early embryonic tongue cells from different regions of the tongue to reorganize histotypically and terminally differentiate in vitro. Cells dissociated from the anterior ventral (AV) or posterior ventral (PV) surface of the 12 day embryonic tongue were cultured 6 days, fixed, and embedded in paraffin. Indirect immunofluorescence microscopy was used to demonstrate the occurrence and distribution of β‐keratins, the presence of which represented regional and differentiation specific markers of late tongue development. Aggregates of AV cells were organized into a β‐keratin‐producing stratified epithelium. Similar PV aggregates formed only an α‐keratin‐producing stratified epithelium. The epithelial cells of these tongue tissue constructs expressed α‐ and β‐keratins in a manner consistent with the temporal and histotypical expression of keratins observed in vivo.