bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of DNA inhibitors upon DNA synthesis and development of Drosophila embryos
Authors: Parente Anthony , Arking Robert , Kalata Karen 
Published: June 2005

AbstractStaged wildtype embryos Drosophila melanogaster were permeabilized and then subjected to a short pulse of either methyl‐3H‐thymidine, one of four different inhibitors of DNA synthesis (mitomycin C, 5‐fluorouracil, nalidixic acid, or 1‐β‐D‐arabino‐furanosylcytosine‐5′‐monophosphate), or a combination of both. The incorporation of methyl‐3H‐thymidine into acid insoluble material was at a maximum during the first half‐hour of embryogenesis, after which the incorporation dropped to half the initial value and remained constant throughout the remainder of development. There was no correlation between the rate of incorporation of methyl‐3H‐thymidine into DNA and the known periods of high mitotic activity. The time course of the estimated specific activity of the DNA newly synthesized in vivo closely paralleled the known changes in the DNA polymerase activity determined in vitro. The known periods of high mitotic activity in the embryo (0–3 hours, 5–12 hours) agree with the periods of maximal sensitivity of the embryo to the inhibitors of DNA synthesis. All four DNA inhibitors affected the incorporation of methyl‐3H‐thymidine into DNA, although they did not affect it in any simplistic manner. Inhibitor treatment during early cleavage resulted in arrested development, and treatment during late cleavage and blastoderm stages resulted in abnormal development, and treatment during late blastoderm and early gastrula resulted in normal development. The major phenotypic abnormality caused by the inhibitors is an abnormal distribution of blastoderm cells. As judged by the ID50 values, the embryos remained very sensitive to the effects of the inhibitors until the stages of head and body segmentation, when they then very rapidly became insensitive.
Relationships between the release of acid, the cortical reaction, and the increase of protein synthesis in sea urchin eggs
Authors: Nishioka David , McGwin Natalie F. 
Published: June 2005

AbstractCortical granule discharge has been separated from Na+‐‐dependent acid release and the increase of protein synthesis in sea urchin eggs. When 2% egg suspensions are inseminated or treated with the ionophore A23187 in normal sea water, cortical granule discharge is induced and the pH of the suspensions decrease approximately 0.35 pH units. When a similar suspension is treated with A23187 in Na+‐free sea water, cortical granule discharge is induced, but the pH of the suspension decreases only 0.05 pH units, and the rate of protein synthesis remains at the level of the unfertilized egg. When 0.05 M NaCl is added to this suspension, the pH decreases the remaining 0.30 pH units, and the rate of protein synthesis increases to the level of the fertilized egg. Thus, there appear to be two components of acid release from sea urchin eggs at fertilization: (1) a Na+‐independent component which correlates with cortical granule discharge; and (2) a Na+‐dependent component which correlates with the increase of protein synthesis.
Autonomous development of reciprocally exchanged regeneration blastemas of normal forelimbs and symmetrical hindlimbs
Authors: Stocum David L. 
Published: June 2005

AbstractNormal upper arm blastemas and blastemas derived from double posterior or double anterior thighs of A. mexicanum were reciprocally exchanged either by autografting or homografting between dark and white animals. Those grafted blastemas which survived always regenerated a morphology and pigmentation characteristics of the donor limb. Thus, upper arm blastemas on double anterior or posterior thigh stumps regenerated normal forelimbs. Double anterior blastemas on normal upper arm stumps failed to regenerate, and double posterior blastemas on normal upper arm stumps regenerated posterior half hindlimbs. These results show that the morphogenetic field of the regenerate is reflected in the composition of the limb stump, and that its pattern is expressed autonomously.Supernumerary limbs formed where posterior and anterior tissues of graft and host were opposed in 35–43% of cases where normal upper arm blastemas were grafted to symmetrical thighs. The morphology and pigmentation of the supernumeraries suggests that they are probably derived from both graft and stump, although a singular origin from either graft or stump is not ruled out in some cases.
A study of hetero‐specific sperm‐egg interactions in the rat, mouse, and deer mouse using in vitro fertilization and sperm injection
Authors: Thadani Vijay M. 
Published: June 2005

AbstractHetero‐Specific fertilization of zona‐free eggs is used in these experiments as a tool to analyze the barriers to hybridization and to gain insight into the mechanisms of normal fertilization. When the zonae of rat eggs, which are a barrier to hetero‐specific fertilization, are removed with pronase, the eggs can be fertilized by mouse sperm and the zygotes start to develop normally. A rat egg fertilized with mouse sperm completes meiosis and forms both male and female pronuclei. Chromosomes from both parents are found on the spindle at the metaphase stage of the first cleavage division. Under present culture conditions, embryos develop only to the two‐cell stage, but this initial development of the hybrid is apparently normal.The question of whether sperm and egg membrane fusion is requisite for normal development is addressed by injecting sperm directly into the cytoplasm of unfertilized eggs. The injection of mouse sperm into rat eggs frequently leads to activation and formation of male and female pronuclei. The first cleavage division is indistinguishable from that following hetero‐specific fetilization. Capacitated and uncapacitated sperm react alike when injected into eggs. Egg activation, however, is necessary for male pronucleus formation. Sperm from the deer mouse Peromyscus maniculatus bairdii, which are incapable of fertilizing even zona‐free rat eggs, respond like mouse sperm when injected into rat eggs. These data indicate that sperm interactions with the egg cytoplasm are less species‐specific than interactions at the egg surface. Furthermore, the normal surface interactions of sperm and eggs are not essential for the start of development.
Electrophysiological responses of the central nervous system in the presence of homospecific and heterospecific sex pheromones in nereids (Annelida polychaeta)
Authors: Boilly‐Marer Yolande , Lassalle Bernard 
Published: June 2005

AbstractThe influence of sex pheromones on the electrical activity in the brain and the nerve cord was studied in mature and immature nereids. The pheromone of the opposite sex induces an intense electrical activity in the brain and the nerve cord only when the nereid is mature and possesses transformed parapodial cirri (swollen cirri in this work). The integrity of the connections between brain and nerve cord is also required for the stimulation of the electrical activity of the brain but not for the nerve cord. The electrical activity of the brain and the nerve cord is also stimulated by heterospecific pheromones of the opposite sex in the same way as with homospecific sex pheromones. Thus, homospecific and heterospecific sex pheromones are both perceived by mature (epitokous) nereids. The stimulation is received by the transformed parapodial cirri and is transmitted to the brain through the nerve cord.
Histone synthesis in preimplantation rabbit embryos
Authors: Matheson R. Clair , Schultz Gilbert A. 
Published: June 2005

AbstractIntracellular specific radioactivities of lysine and arginine were measured in preimplantation rabbit embryos. In conjunction with measurements of radioactivity incorporated into total protein and histones and amino acid composition data, absolute rates of synthesis were calculated. Total protein is synthesized at a rate of 0.78 ng/hr/embryo or 0.049 ng/hr/cell for the 2‐day (16‐cell) cleavage embryo and 2,828 ng/hr/embryo or 0.036 ng/hr/cell for the 6‐day (80,000‐cell) blastocyst. Calculated rates of accumulation for histone proteins were 40 pg/hr/embryo for the 2‐day cleavage embryo (5.12% of total protein accumulation) and 96,600 pg/hr/embryo (3.42% of total protein accumulation) for the 6‐day blastocyst. These amounts of histone synthesis are only slightly in excess of that required to package newly synthesized DNA into nucleosomes during the cycle of replication, suggesting that histone and DNA synthesis are quantitatively coordinated. Further, when cytosine arabinoside was used to inhibit DNA synthesis by 97% in cleavage embryos, amino acid incorporation into histone was inhibited by 82%, while total incorporation was reduced by about 20%, indicating that histone and DNA synthesis are also temporally coordinated.
Anaerobic metabolism, gas exchange, and acid‐base balance during hypoxic exposure in the channel catfish, Ictalurus punctatus
Authors: Burggren Warren W. , Cameron James N. 
Published: June 2005

AbstractGill ventilation, blood gas and acid‐base values, ṀO2, ṀCO2 and the gas exchange ratio have been measured before, during, and after exposure to hypoxia in the channel catfish, Ictalurus punctatus.I. punctatus maintains ṀO2 at control levels to a PIO2 as low as 60 mm Hg, through a profound branchial hyperventilation. Concomitantly, however, a lactic acidosis usually develops, indicating a significant anaerobic glycolysis. Both a metabolic acidosis and respiratory alkalosis occur in Ictalurus during hypoxic exposure, with the former usually predominating. ṀCO2 doubles and the gas exchange ratio (RE) increases from 0.8 at control levels to 2.0 at hypoxic levels, indicating that, in addition to anaerobic glycolysis, nonglycolytic pathways producing CO2 also operate during hypoxic exposure.Analysis reveals that at least half of the increased ṀCO2 during hypoxic exposure is due strictly to lactate acidfication of the tissue HCO3− pool, rather than from metabolic production of molecular CO2. Thus, the actual respiratory quotient (RQ) only rises to 1.5 during hypoxic exposure.Within one hour of a return to air saturated water, a large lactate “flush” and severe plasma acidosis occur, and control levels for these and other values are not reachieved for 2–6 hours after hypoxic exposure.Complete analysis of O2 and CO2 exchange in the catfish exposed to short‐term hypoxia thus must consider both the time course of acid‐base disturbance and the evolution of CO2 from the acidified tissue bicarbonate pool.
Segmental innervation of rotated and supernumerary axolotl hindlimbs
Authors: Bennett M. R. , McGrath P. A. 
Published: June 2005

AbstractThe segmental nerve supply to axolotl limbs was misrouted by severing the limbs at the level of the femur, rotating them 180° around their long axis, and then suturing them to the intact proximal stump. Following return of the blood supply to the rotated limb by the cross‐anastomosing of blood vessels, a blastema often formed to the side of the rotation site giving rise to a supernumerary limb. The muscles of both rotated and supernumerary limbs were innervated by the segmental nerves. The percentage of cells innervated by segmental nerves 16 and 17 in each muscle was determined with intracellular electrodes at 14 weeks after the operation. Despite histological evidence that nerves had been misrouted in the rotated limb, the percentage innervation of each muscle by nerves 16 and 17 was similar to that in the unoperated contralateral controls. The same results were obtained for the supernumerary limbs. In some muscles a few synaptic sites were found innervated by segmental nerves which did not innervate that muscle in the contralateral controls. These had synaptic potentials with very low quantal contents if immediately adjacent sites were innervated by the segmental nerve, which did innervate that muscle in the contralateral controls. The results suggest that the selective properties of synaptic sites are alone sufficient to determine the entire segmental innervation pattern of the muscles in a limb.
Respiratory properties of whole blood and hemoglobin from the burrowing reptile, Amphisbaena alba
Authors: Johansen K. , Abe A. S. , Weber R. E. 
Published: June 2005

AbstractRespiratory properties of whole blood and hemoglobin solutions have been studied in the burrowing reptile, Amphisbaena alba.Whole blood is distinguished from that of other squamate reptiles by an extraordinary high O2 affinity (P50 = 12 mmHg at pH 7.60 and 25°C). The Bohr factor,ϕ, was large at −0.85 and the n‐value was 1.80. O2 capacity averaged 12.0 vol%. The molar concentration of erythrocyte ATP was high and twice that of hemoglobin.Stripped Amphisbaena hemoglobin shows an extremely high O2 affinity and reduced pH sensitivity compared to whole blood (P50 = 1 mmHg at pH 7.60 and 25°C, ϕ = −0.35, n‐value = 2.0). The hemoglobin O2 affinity was much more sensitive to ATP than for other poikilotherm vertebrates.Isoelectric focusing revealed a multicomponent hemoglobin with the major components showing similar O2 affinities and Bohr shifts.The data obtained are discussed in relation to the burrowing habits of Amphisbaena and found to be adaptive to a fossorial mode of life.
Changes in RNA and protein synthesis in the neural retina during lens regeneration in newts
Authors: Gulati Adarsh K. 
Published: June 2005

AbstractSince neural retina stimulates regeneration of a lens from the dorsal iris in newts, RNA and protein synthesis in the neural retina was investigated during this process. Incorporation of 3H‐leucine using liquid scintillation counting was employed to compare RNA and protein synthesis in the neural retina from sham‐operated control eyes with that in eyes during lens regeneration. An initial increase in 3H‐uridine uptake was seen one to three days after lentectomy. This was followed by greater incorporation of 3H‐leucine, indicating increased protein synthesis between 5 to 15 days after lens removal. A decrease in 3H‐uridine uptake was also seen at 5 to 12 days after lentectomy. After 20 days both the RNA and protein synthesis returned to the normal level. Since the increase in protein synthesis is preceded by an increase in RNA synthesis, the two processes might be related. The results indicate significant changes in the synthesis of macromolecules by the neural retina following lentectomy. These may be indirectly related to the production of the neural retinal factor with stimulates lens differentiation.
Transport of nitrite across fish gills
Authors: Bath R. N. , Eddy F. B. 
Published: June 2005

AbstractThe results show that rainbow trout (Salmo gairdneri) are able to concentrate NO ions in the blood plasma. After 24 hr in water containing 0.7 mM/l NO, the blood plasma contained about 5mM/l NO suggesting that the gills have the ability to transport NO2 against a concentration gradient.
Histochemical, enzymatic, and contractile properties of skeletal muscle fibers in the lizard Dipsosaurus dorsalis
Authors: Gleeson Todd T. , Putnam Robert W. , Bennett Albert F. 
Published: June 2005

AbstractLizard skeletal muscle fiber types were investigated inthe iliofibularis (IF) muscle of the desert iguana (Dipsosaurus dorsalis). Three fiber types were identified based on histochemical staining for myosin ATPase (mATPase), succinic dehydrogenase (SDH), and αglycerophosphate dehydrogenase (αGPDH) activity. The pale region of the IF contains exclusively fast‐twitch‐glycolytic (FG) fibers, which stain dark for mATPase and αGPDH, light for SDH. The red region of the IF contains fast‐twitch‐oxidative‐glycolytic (FOG) fibers, which stain dark for all three enzymes, and tonic fibers, which stain light for mATPase, dark for SDH, and moderate for αGPDH confirm these histochemical interpretations. Lizard FG and FOG fibers possess twitch contraction times and resistance to fatigue comparable to analogous fibers in mammals, but are one‐half as oxidative and several times as glycolytic as analogous fibers in rats. Lizard tonic fibers demonstrate the acetylcholine sensitivity common to other vertebrate tonic fibers.
Localization of smooth‐muscle myosin in branchial pillar cells of snapper (Chrysophys auratus) by immunofluorescence histochemistry
Authors: Smith D. G. , Chamley‐Campbell J. 
Published: June 2005

AbstractSmooth muscle myosin was localized in pillar cells by immunofluorescence histochemistry of gills from snapper (Chrysophys auratus). The amount of myosin present is comparable to that seen in mammalian vascular smooth muscle. No differences in the distribution of myosin‐containing pillar cells, either within or between different secondary lamellae, were noted. The possibility that contractile proteins in pillar cells could function as autoregulators of blood flow, by responding with changes in active tension to alterations in the rate of change of pressure with each cardiac cycle, is discussed.
Tetrodotoxin‐Sensitive action potentials from the brain of the polyclad flatworm, Notoplana acticola
Authors: Keenan Larry , Koopowitz Harold 
Published: June 2005

AbstractAction potentials recorded intracellularly from the brain of the polyclad flatworm, Notoplana acticola, show reductions in amplitude in the presence of 3.2 × 10−5 M tetrodotoxin. Vibration responder cells and spontaneously active cells were sensitive to tetrodotoxin. One cell was found that did not respond to the toxin. Most brain cells filled with Lucifer Yellow dye were found to be heteropolar multipolar neurones quite unlike those commonly found in other invertebrate ganglia.
Metabolic consequences of the extent and disposition of the aqueous intracellular environment
Authors: Clegg James S. 
Published: June 2005

AbstractAttention is focused on the aqueous compartments of eucaryotic cells (nucleoplasm, cytosol, and interior compartments of cytoplasmic membrane‐bound organelles). Previous work on the relationship between cell water content, the physical properties of cell water, and metabolic activity in cysts of the brine shrimp, Artemia is summarized and discussed in that context. A previously proposed general model of the organization of metabolic activity in the aqueous compartments will be summarized.
Verification of an in vitro bioassay for limb bud polarizing activity
Authors: Maccabe Jeffrey A. , Knouse Eunice R. , Richardson Kathryn E. Y. 
Published: June 2005

AbstractAn in vitro bioassay for limb bud polarizing activity in the chick embryo has been verified by two procedures, demonstrating that the culture procedure mimics occurrences in vivo. First, no activity can be detected with the in vitro assay 24 hours after removal of the posterior region of the limb. In addition, after a positive assay for activity, the responding tissue develops into polarized limb structures when transplanted to a host embryo. After a negative assay, the transplanted responding tissue fails to develop into recognizable limb structures. Since polarizing activity is defined by its ability to induce polarized limb structures in vivo we conclude that the in vitro system provides a valid assay for limb polarizing activity.
Aspirin‐induced teratogenesis: A unique pattern of cell death and subsequent polydactyly in the rat
Authors: Klein Kenneth L. , Scott William J. , Wilson James G. 
Published: June 2005

AbstractOffspring of pregnant rats treated with a high dose of aspirin on day 11 of gestation frequently had predominantly right‐sided polydactyly of the hindlimbs at term. Aspirin‐treated embryos removed on day 12 exhibited a unique pattern of preaxial mesodermal cell death in the hindlimb buds. In addition, these embryos had a delay of the normal episode of cell death in the preaxial apical ectodermal ridge and an absence of cell death in a zone of physiological necrosis in the preaxial mesoderm thought to be instrumental in controlling preaxial digit formation. The role of cell death in the pathogenesis of polydactyly is discussed.
Regeneration of antennae and its control of molting in the terrestrial isopod, Armadillidium vulgare
Authors: Madhavan Kornath , Madhavan Mekkara Mandaravally 
Published: June 2005

AbstractThe interactions of regeneration and pregnancy controls on the duration of different stages of molting in the pillbug Armadillidium vulgare were determined by removing the antennae during different stages of the molt cycle of the nonovigerous and ovigerous animals. Removal of one or two antennae from the males during the beginning of stage C (intermolt period) of their molting cycle resulted in regeneration and shortening of stage C and thereby in acceleration of ecdysis. Further, removal of both antennae induced the animals to ecdyse within 1–4 days of each other, thus providing a convenient method of synchronizing the molt cycle. Amputation of both antennae from males in late stage C also resulted in regeneration; however, the duration of stage C was lengthened, resulting in a delay in ecdysis. Amputation of both antennae from males and nonovigerous females in the middle of preecdysis (stage D) resulted in molting without regeneration and on schedule like the control animals. However, the antennaless animals regenerated their antennae, shortened their intermolt period (stage C), and ecdysed precociously. From these results, we conclude that amputation, before the critical period in the molt cycle of the pillbugs (during stage C), prevents the release of ecdysteroids and, consequently, generalized apolysis until regeneration is completed, whereupon this block is removed and generalized apolysis and further events of molting occur. Once ecdysteroid release has been initiated to cause generalized apolysis, as in stage D, amputation does not prevent the further events of molting. Amputation of both antennae during the beginning of the intermolt period in the ovigerous females, although permitting regeneration, did not immediately stimulate ecdysis as in the nonovigerous animals; instead, it occurred only after release of the larvae from the brood pouch. When compared to the control ovigerous animals, the overall length of stage C was shortened. The results obtained from the antennal amputations during different physiological stages of the pillbug show that of all the stages of the molt cycle, stage C is labile, and its duration is affected by regeneration and pregnancy.
Morphology of neurons containing monoamines within leech segmental ganglia
Authors: Lent Charles M. 
Published: June 2005

AbstractThe monoamine‐containing neurons within leech segmental ganglia are vitally and selectively stained by Neutral Red dye—a procedure facilitating the investigation of their morphology by means of intracellular injections of the tracer enzyme, horseradish peroxidase. The colossal Retzius cells are peripheral effector neurons which project large axons into the lateral roots and smaller axons into the anterior and posterior longitudinal connectives. All classes of the smaller ganglionic neurons which also contain serotonin (VL, DL, M, and E), as well as the catecholamine soma in the anterior root (AR), have extensive arborizations within the neuropile and project their axons only into the longitudinal connectives. Each of the five classes of small amine cell has a highly specific morphology and appears to be an interneuron.
The effect of prolactin on the rate of forelimb regeneration in newts exposed to photoperiod extremes
Authors: Maier C. Eberhardt , Singer Marcus 
Published: June 2005

AbstractFour groups of bilaterally amputated newts were exposed to (1) continuous light, LL; (2) continuous light with daily prolactin injections, LL‐PRL; (3) total darkness, DD; or (4) total darkness with daily prolactin injections, DDPRL. The results confirmed that LL animals regenerate their limbs more rapidly than DD. The results also showed that LL‐PRL animals do not respond to the exogenous prolactin but that DD‐PRL animals do respond and in fact regenerate at a rate which exceeds not only DD but also LL and LL‐PRL. The possible synergism between prolactin and photoperiod is discussed.