bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between muscle size and motoneurone survival in temporarily paralyzed embryos
Authors: McLennan Ian S. 
Published: June 2005

AbstractNeuronal cell death has been postulated to occur as a consequence of there being a limited availability of target. This hypothesis was examined by delaying the onset of motoneurone cell death, by temporary paralysis of chick embryos, until the size of the target had increased. Despite the availability of this enlarged periphery, the extent of cell death was unaltered, although the rate of cell death was retarded. It is argued that the extent of cell death is not simply related to target size and may instead be governed by differences in the capacity of particular motoneurones to compete successfully for target cells.
Influence of ethanol on chromosome segregation during the first and second meiotic divisions in the mouse egg
Authors: Kaufman M. H. , Bain I. M. 
Published: June 2005

AbstractThis study was carried out to investigate the influence of ethanol on chromosome segregation during the first and second meiotic divisions. Female mice were given a single intragastric injection of a dilute solution of ethanol either just before or at various times after the HCG injection for inducing superovulation. The mice were mated, and the chromosome constitution of fertilized eggs was determined at the first cleavage mitosis. The technique employed allowed the male‐ and female‐derived pronuclear sets to remain as two discrete groups. Exposure from 1.5 h before to 17 h after the HCG injection induced a high incidence of aneuploidy (15–25%) involving in over 90% of cases only one chromosome, so that either 19 or 21 instead of the normal complement of 20 chromosomes were present in one of the two sets (a previous study using a “marker” chromosome has demonstrated that the nondisjunction induced here invariably involves the female set). We suggest these findings draw attention to the susceptibility of chromosome segregation in female germ cells to interference by ethanol and that the mode of action is likely to be via interference with the normal functioning of the spindle apparatus. It is possible that interference with meiotic chromosome segregation by spindle‐acting agents such as ethanol might account for a proportion of human spontaneous abortions with similar chromosomal defects where no other obvious cause is apparent.
Environmental salinity and the thyroidal response to thyrotropin in juvenile coho salmon (Oncorhynchus kisutch)
Authors: Specker Jennifer L. , Richman N. Harold 
Published: June 2005

AbstractThe effect of environmental salinity on the thyroidal response, measured by plasma concentrations of thyroxine (T4), to exogenous bovine thyrotropin (bTSH) was assessed early and late in the smoltification of coho salmon (Oncorhynchus kisutch). A single injection of 100 mlU bTSH significantly increased plasma T4 concentrations in fish in both fresh water and seawater, and both early (March 19) and late (May 24) in smoltification. In fish transferred to seawater, the increase in T4 titers was somewhat earlier and its duration shorter, suggesting an environmentally induced change in the kinetics of T4 entry and exit from the blood stream. The overall response to TSH was greater near the beginning (March 19) of the smoltification‐associated T4 increase than near the end (May 24), suggesting a development‐related change in thyroid function.
Electrophoretic analysis of pancreatic proteases and zymogen‐activating factors in the mouse
Authors: Isobe Masaharu , Ogita Zen‐Ichi 
Published: June 2005

AbstractMouse pancreatic proteases were analyzed by one‐ and two‐dimensional electrophoresis. Active proteases that existed in the luminal fluid were separated into at least eight bands in 8% polyacrylamide gel. Pancreatic proteases activated by intestinal extract were separated into at least seven bands. The mobilities of these bands were exactly the same as those of proteases in the luminal fluid except for those of the most cathodal band. Two kinds of trypsin (Try‐I group and Try‐II) and one kind of chymotrypsin (Chy‐I) were determined by specific and nonspecific protease staining. Try‐I group and Try‐II were derived from different trypsinogens (Try G‐I group and Try G‐II), whereas Chy‐I was derived from a single chymotrypsinogen (Chy G). Although Try G‐II was activated by both intestinal extract and by bovine trypsin, Try G‐I group activated only by intestinal extract. Intestinal‐activating factors were analyzed by two‐dimensional electrophoresis. Mouse enterokinase (enteropeptidase, EC 3.4.4.8), which can activate bovine trypsinogen, had a slow mobility. In the intestine of the mouse there are several activating factors in addition to enterokinase. Although it is unclear what intestinal‐activating factors can activate Chy G, there is a factor that can convert chymotrypsinogen into chymotrypsin directly. These data suggest that intestinal‐activating factors play an important role in the activating mechanisms of mouse pancreatic zymogens.
Bipartite axiation follows incomplete epiboly in zebrafish embryos treated with chemical teratogens
Authors: Baumann Martin , Sander Klaus 
Published: June 2005

AbstractMedial clefts in the axis of the trunk region are malformations known from many chordates and are mostly referred to as rachischisis anterior. In teleosts, rachischisis was previously ascribed either to secondary rifting of a single uniform axial rudiment, or to the establishment of two (half) axes and body halves physically separate from the very beginning. In order to decide between these conflicting interpretations, we treated zebrafish embryos during blastodisc stages and epiboly with several chemical teratogens causing rachischisis anterior. Treatment with ethanol, Colcemid®, hydroxyurea, or cyclohex‐imide was found to delay the proliferation and movements of the deep cells more strongly than the timing of cell differentiation, so that the deep cells embark on organogenesis before having reached their destinations in the uniform germ shield. Treatment with α‐amanitin, on the other hand, seems primarily to affect the periblast and enveloping layer; the incomplete epiboly observed in these layers appears to restrain deep cell epiboly physically and thus to cause rachischisis. In both instances, the split condition of the embryo's trunk region is clearly due to the ectopic formation of physically separate body halves right from the beginning, a mode we call bipartite axiation. We also describe secondary anomalies specific for individual teratogens, and briefly discuss the possible origins of rachischisis anterior among other chordates including man.
Lysosomes fuse with one half of alga‐bearing phagosomes during the reestablishment of the European green hydra symbiosis
Authors: McNeil P. L. , McAuley P. J. 
Published: June 2005

AbstractSorting of native Chlorella algae during the reestablishment of the European green hydra symbiosis occurs after phagocytosis by host digestive cells, when approximately half the algae subsequently disappear, either by exocytosis or by digestion. Using electron microscopical and cytochemical techniques we have assessed the morphological integrity of algae after phagocytosis and characterized fusion between alga‐bearing phagosomes and host‐digestive cell lysosomes.Five hours after initiation of phagocytosis of algae, approximately 45% were associated with lead reaction product of the lysosomal enzyme acid phosphatase. Some individual alga‐bearing phagosomes had fused, forming large phagolysosomes which contained numbers of algae at various stages of digestive degradation. Thus, sorting may result from the failure of about half of the algae phagocytosed by European digestive cells to prevent lysosome fusion with their phagosomes, and hence their digestion by lysosomal enzymes. Acid phosphatase reaction product was not associated with vacuoles containing established algal or bacterial symbionts.Pretreatment of algae with cationic agents increased the number of algae sorted for digestion, and it also perturbed algal release of photosynthate. It is suggested that algae prevent lysosomal fusion through release of photosynthate, and that sorting is a result either of a rate competition between lysosomal fusion and its inhibition by algae, or of only a proportion of algae releasing photosynthate above the threshold level needed to prevent lysosomal fusion.
Regulation of melanization of tobacco hornworm larval cuticle in vitro
Authors: Hiruma Kiyoshi , Riddiford Lynn M. 
Published: June 2005

AbstractWhen tobacco hornworm larvae (Manduca sexta) are allatectomized 5–6 hr before head capsule slippage in the molt to the fifth (final) larval instar, the new cuticle melanizes 3 hr before ecdysis. After explantation between 7 and 3 hr before the onset of melanization, the new cuticle was found to melanize in vitro in Grace's medium only if β‐alanine was removed. When explanted at the onset of melanization, the presence of β‐alanine had no effect on melanization. The addition of either dopa or dopamine was found to be necessary for complete melanization of pieces explanted before the onset of melanization with 0.3 mM of either dopa or dopamine being optimal. Both of these compounds were incorporated into the cuticular melanin. In this optimal medium, melanization occurred over about a 9‐hr period after a 5‐ to 6‐hr lag period presumably required for adjustment to the medium. Fifty ng/ml 20hydroxyecdysone was found to inhibit melanization of pieces explanted 7 hr but not 3 hr before melanization. The hormone neither inhibited uptake of dopa into the epidermis nor prevented melanization in the cuticle once the prophenoloxidase in the premelanin granules was activated. Therefore, 20hydroxyecdysone may inhibit the activation of the phenoloxidase in the premelanin granules, or may inhibit the incorporation of dopa into the granules.
Neural tube occlusion precedes rapid brain enlargement
Authors: Schoenwolf Gary C. , Desmond Mary E. 
Published: June 2005

AbstractHistological examination of early vertebrate embryos during rapid brain enlargement (an event partially driven by fluid pressure) reveals that the spinal cord lumen is occluded. Occlusion (if it is not merely a fixation artifact) may confine neural tube fluid to brain regions and seal off the ventricles before posterior neuropore closure. We injected neural tubes of living chick embryos with dyes, asking: (1) is occlusion real; and (2) does occlusion precede brain enlargement? Both questions were answered affirmatively. Experimental analyses of occlusion and brain enlargement are in progress.
The thiol‐disulfide balance during maturation of Xenopus laevis oocytes
Authors: Heidemann Steven R. , Hamborg Marlyn A. 
Published: June 2005

AbstractWe measured several of the components involved in the thioldisulfide balance of immature and mature oocytes of Xenopus laevis: total soluble native sulfhydryl, reduced and oxidized glutathione, native sulfhydryl content of soluble protein, and disulfide content of soluble protein. None of these values changed during maturation. Both the immature and mature oocyte were characterized by a relatively high disulfide to sulfhydryl ratio. We also measured native sulfhydryl content of germinal vesicle proteins and enucleated oocyte proteins in immature oocytes. Contrary to early cytochemical findings, our measurements suggest that the germinal vesicle has a lower concentration of protein sulfhydryl than does the cytoplasm.
Regulation of glycolysis in the mouse blastocyst during delayed implantation
Authors: Nieder Gary L. , Weitlauf Harry M. 
Published: June 2005

AbstractThe rate of oxidation of glucose is reduced in mouse embryos in the prolonged free living phase associated with delayed implantation and increases when the embryos are reactivated by estrogen. To determine how these changes in metabolism are regulated, several aspects of glucose metabolism were evaluated in dormant and reactivated blastocysts: 1) Embryos were exposed to 14C‐pyruvate in vitro and evolved 14CO2 was measured. It was found that the rate of production of CO2 was equal in the two types of blastocysts, suggesting that aerobic pathways are fully functional during delayed implantation. 2) Production of lactate in the presence of O2 was measured and a decrease of 30% was found in delayed implanting embryos, suggesting that the overall regulatory mechanism for glucose metabolism resides in the glycolytic portion of the pathway. 3) Capacity for uptake and phosphorylation of glucose was evaluated using 3H‐2‐deoxyglucose and was found to be equal in the two types of embryos. 4) Total amounts of the rate‐controlling enzymes for glycolysis (i.e., hexokinase and phosphofructokinase) in lysates of delayed and reactivated embryos were found to be equal, indicating that amounts of these enzymes are not limiting in delayed implantation. 5) Lactate production, measured under anaerobic conditions, was found to be equal, demonstrating that it is not the capacity for glycolysis but a difference in the degree of allosteric inhibition that is responsible for reduced glucose oxidation in delayed implantation. 6) Levels of ATP, ADP, and hexose‐6‐phosphates were found to be consistent with allosteric inhibition of the glycolytic pathway at phosphofructokinase during delay and a release of this inhibition with reactivation. In addition, finding a high ATP/ADP ratio in delayed implanting blastocysts indicates that the associated depression of macromolecular synthesis is not due to limited energy supply. Rather it suggests that the reduction in glucose metabolism is probably due to a decrease in energy demand.
Evidence for specific binding of uncapacitated boar spermatozoa to porcine zonae pellucidae in vitro
Authors: Peterson R. N. , Russell L. D. , Hunt W. P. 
Published: June 2005

AbstractWashed ejaculated boar sperm and sperm from the cauda epididymis bind to the zona pellucida of fixed porcine eggs in large numbers. Sperm incubated in the presence of dextran sulfate (8 K daltons or 500 K daltons) or fucoidan and then washed no longer bind to eggs. Other acid carbohydrates (heparin, chondroitin sulfates, inositol hexasulfate, carboxymethylcellulose) fail to block sperm‐egg binding even when added directly to sperm‐egg suspensions. Seminal plasma and the seminal vesicle secretion contain basic proteins which bind tightly to sperm and bind reversibly to eggs preventing sperm from binding to eggs. When dextran sulfate or fucoidan are mixed with the vesicular secretion, from which seminal plasma basic proteins originate (Hunt et al., '83), the secretion loses the capacity to prevent sperm from binding to eggs; this suggests that seminal vesicle proteins can bind to the same site on zonae as do sperm and thus seminal plasma may modify sperm‐egg interactions.Corpus and cauda epididymal sperm also bind in large numbers to the zona pellucida of isolated eggs but high concentrations of caput sperm, which exhibit high motility in the presence of caffeine, bind only in few numbers. Thus a component that enhances sperm‐zona binding is apparently formed on the plasma membranes of uncapacitated sperm during passage through the epididymis. This finding, and an earlier observation that antibodies raised against uncapacitated sperm plasma membranes block sperm‐egg binding in vivo (Peterson et al., '83) suggest that this component may be involved in sperm zona interaction in vivo.
Histochemical and biochemical localization of mannitol oxidase in the snail Helix aspersa
Authors: Vorhaben Jean E. , Smith Darwin D. , Campbell James W. 
Published: June 2005

AbstractThe tissue distribution of mannitol oxidase in the snail Helix aspersa has been determined by histochemical and biochemical techniques. Highest activity was found within the alimentary canal and digestive gland where the enzyme presumably acts on ingested naturally occurring polyols, especially mannitol.
The in vitro uptake and distribution of 3H‐fucose and 3H‐mannose in the crayfish retina: A light and electron microscope autoradiographic study
Authors: Hafner G. S. 
Published: June 2005

AbstractThe in vitro uptake and distribution of 3H‐fucose and 3H‐mannose in the crayfish retina was studied using light and electron microscope autoradiography. Animals maintained on a 12:12 light‐dark (L‐D) cycle were incubated for 8 hr in the light beginning at their normal light‐onset time. Both sugars were incorporated into components of the rhabdom microvillous membrane, as indicated by the progressive increase in labeling of this structure during the incubation period. Fucose was initially concentrated in the Golgi apparatus of the receptor cells, where distinct grain clusters were seen after 15‐min incubation in the light. A similar concentration of fucose was also seen in the accessory reflecting pigment cells, as well as neurons and glia of the lamina ganglionaris. After 1 hr and longer, the eighth cell rhabdomere and the distal portion of the main rhabdom appeared more heavily labeled than the proximal region of the rhabdom. With mannose, a more diffuse cytoplasmic label was observed, and there was no evidence of heavy Golgi labeling. The diffuse label in the cytoplasm with mannose was followed by a general increase in labeling over the rhabdom, which was more uniform in comparison with fucose. The pattern of labeling seen in the crayfish photoreceptor with these two sugars is similar to that reported in the vertebrate photoreceptor. The progressive labeling of the rhabdom during the time when membrane loss is also taking place suggests that both aspects of the renewal process in the crayfish occur simultaneously during the period of the light cycle examined. It is proposed that the labeling pattern represents the incorporation of these sugars into glycoproteins present in the microvillous membrane and that one or both of these sugars may be components of the photopigment in these membranes.
Stump currents in regenerating salamanders and newts
Authors: Borgens R. B. , McGinnis M. E. , Vanable J. W. , Miles E. S. 
Published: June 2005

AbstractWe report here that a variety of salamanders and newts from differing habitats all drive a steady ionic electric current out of the forelimb stump tip after forelimb amputation. Several hours after amputation the density of this stump current ranges from about 10 to 100 μA/cm2 in most species, and declines with time.In most cases, the magnitude of the stump current is dependent on the concentration of Na+ in the external medium (an artificial pondwater), suggesting that the well‐known Na+‐dependent transcutaneous voltage described in amphibia (particularly frogs) is the EMF for this stump current. These measurements add to those previously reported for the North American red spotted newt (Notophthalmus viridescens), and suggest that electrical changes following amputation of urodele limbs are widespread among members of this group.
Effects of photoperiods and melatonin on planarian asexual reproduction
Authors: Morita Michio , Best Jay Boyd 
Published: June 2005

AbstractAsexual planarians of the species Dugesia dorotocephala exhibit a distinct day‐night rhythm of fissioning under the influence of normal photoperiod; fissioning occurs only at night. This rhythm is broken by continuous illumination, continuous darkness, or by decapitation. The fissioning rate increases when planarians are exposed to light for less than 1 hr/day or when they are decapitated. These results suggest that the planarian head, probably brain, releases a substance that inhibits fissioning, and that the synthesis and release of this substance are closely related to the environmental photoperiod. Furthermore, fissioning of decapitated planarians is suppressed by continuous treatment with melatonin in their culture water. Fissioning resumes when these are returned to normal culture water. Interestingly, fissioning occurs at night when decapitates are treated with melatonin in the daytime, while it is observed in the daytime with night‐time melatonin treatment. These results are consistent with the hypothesis that melatonin release from brain mediates the influence of environmental photoperiods on fissioning.
Cardiac output and tissue blood flow in the abalone, Haliotis cracherodii (Mollusca, Gastropoda)
Authors: Jorgensen D. D. , Ware S. K. , Redmond J. R. 
Published: June 2005

AbstractLittle is known about the characteristics of hemolymph (blood) flow in animals with open circulatory systems. We measured cardiac output and blood flow to specific tissues in the black abalone, Haliotis cracherodii, a gastropod mollusk. The use of thermodilution allowed us to make repeated measurements of cardiac output and cardiac stroke volume over relatively short time intervals (5–10 heart beats) in resting, unrestrained abalone while disturbing the animals minimally. Anatomical studies of the abalone circulation showed that the arterial system terminated in small diameter (approaching 10–20 μm in some cases) lacunar tissue spaces. Because of this, we used radioactive microspheres (which must be trapped in the tissue vasculature) to measure blood flow rates to selected tissues. The major findings of our study were that 1) cardiac output in the black abalone ranged from about 100 to 150 ml · kg−1 · min−1, and was highly correlated with body size; 2) weight‐specific cardiac stroke volume was about 5 ml · kg−1, considerably larger than that of a mammal; 3) tissue blood flow rates ranged from 10 ml · 100 g−1 · min−1 (foot muscle) to 80 ml · 100 g−1 · min−1 (nephridial tissue), similar to typical tissue blood flow rates in mammals. Our data suggest that the blood in the abalone is directed to the tissues not in proportion to percent total body weight the tissues represent (as might be expected in an open vascular system), but apparently in proportion to tissue metabolic rate.
Photoaffinity labeling of the ouabain binding site in Na, K‐ATPase in developing brine shrimp
Authors: Churchill Lynn , Hall Clifford C. , Peterson Gary L. , Ruoho Arnold E. , Hokin Lowell E. 
Published: June 2005

AbstractAnalysis of purified Na,K‐ATPase from brine shrimp nauplii by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis reveals two large (α) subunits [G.L. Peterson, R.D. Ewing, S.R. Hootman, and F.P. Conte (1978) J. Biol. Chem. 253:4762]. The band with lower mobility in a neutral or alkaline gel is designated α1 and the band with higher mobility α2. Ouabain prevents dephosphorylation of both α1 and α2 as documented by gel analysis, but a higher concentration of ouabain is required to prevent dephosphorylation of α2. The photoaffinity label, [3H]4′(2‐ethyldiazomalonyl) digitoxigenin monodi‐gitoxiside, specifically labels α in a ouabain‐protectable manner without labeling other contaminating proteins in the preparation. Greater than 93% of the total ouabain‐protectable labeling of the α subunits is associated with α1. The photoaffinity label, [3H]4‴ (2‐ethyldiazomalonyl) digitoxin, specifically labels α1 and β in a ouabain‐protectable manner without labeling other contaminating proteins. These data show that in the brine shrimp the third digitoxose residue of digitoxin binds in a region in which the α1 and β chains are in close proximity. Less than 5% of the specific ouabain‐protectable labeling of total α is associated with α2. These studies indicate that cardioactive steriods have higher affinity for the α1 subunit.
A reversal in relative mobility of the two large subunits of brine shrimp (Na+ + K+)‐adenosinetriphosphatase
Authors: Churchill Lynn 
Published: June 2005

AbstractThe two large subunits of brine shrimp Na,K‐ATPase can be resolved by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis at neutral pH and at acidic pH. These subunits appear to reverse their positions on the gel relative to each other when resolved at acidic pH relative to neutral pH. The migration of both subunits is apparently affected by charge, even in the presence of 2.5% sodium dodecyl sulfate.