bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the nutritional state on repeated head regeneration, growth, and fission in the planarian, Dugesia dorotocephala
Authors: Nentwig M. Ruth , Schauble Muriel K. 
Published: June 2005

AbstractStarved and fed animals were repeatedly decapitated to determine the influence of nutritional state on regeneration rate and capacity, growth in length, fission, and formation of abnormal heads in Dugesia dorotocephala. Animals fed at the end of each regenerative period were able to regenerate a maximum of 40 times, with no significant change in regeneration rate compared to controls decapitated once. Growth in length of the whole animal continued throughout the study and fissioning capacity was maintained. Abnormal head formation was minimal. However, starved animals showed a marked reduction in regenerative capacity and were unable to regenerate more than 16 times. There was also a retardation of regeneration rate, decline in growth rate, loss of fissioning capacity, and a 13‐fold increase in formation of abnormal heads compared to fed animals. Fissioning cyclicity was an interesting and unexpected finding in intact fed controls and fed and starved regenerating animals. An apparently inherent four‐week frequency pattern in fission cyclicity was observed in intact fed controls, while regenerating animals exhibited an initial three‐week cycling pattern, but an alteration occurred after eight or nine regenerations and fed animals changed to a two‐week cycle, while starved animals ceased fissioning entirely. The act of decapitation and subsequent regeneration appeared to alter fissioning cyclicity. Comparative analysis of fission, growth, and abnormal head formation in regenerating animals showed different relationships in both groups. In fed animals fission and growth were inversely related the first eight decapitations, then growth leveled off while fissioning frequency changed. After 13 decapitations fission and growth were directly related and cyclic. Starved animals showed initial fissioning cyclicity, but growth steadily declined and leveled off. Head abnormalities began to increase greatly after the ninth decapitation.
Duration of life and mortality rates in male and female phenotypes in three sex chromosomal genotypes (XX,XY,YY) in the killifish, Oryzias latipes
Authors: Fineman Robert , Hamilton James , Siler William 
Published: June 2005

AbstractMales were shown to be shorter‐lived than females in most species for which data have been avaiable. The present study, utilizing phenotypic sex‐reversal in various genotypes (XX,XY,YY) of the killifish Oryzias latipes, suggests that males outlive females. The stress of producing many large eggs over the major part of the female's life was probably associated with their significantly shorter lifespan.
Maturation of mouse sperm in vitro
Authors: Hoppe P. C. , Whitten W. K. 
Published: June 2005

AbstractPreincubation of sperm in medium for three hours before mixing with ova increased the number of ova fertilized after one hour, thus indicating that sperm maturation occurs in vitro. The presence of cumulus cells increased the proportion of ova fertilized as observed at two and at three hours after the addition of sperm. However, no difference in the proportion of ova fertilized after one hour of incubation was observed using fresh epididymal sperm and ova with or without cumulus cells. No additive effect of cumulus cells and sperm preincubation on fertilization was observed. Sperm preincubation for three hours in the presence of ova either with or without cumulus cells resulted in fertilization similar to that achieved by sperm preincubated in medium alone.
Subcellular localization of the first three enzymes of the ommochrome synthetic pathway in Drosophila melanogaster
Authors: Sullivan David T. , Grillo Santo L. , Kitos Robert J. 
Published: June 2005

AbstractThe subcellular distribution of the first three enzymes in the ommochrome eye pigment pathway were studied by means of differential centrifugation. Tryptophan pyrrolase and kynurenine formamidase are found in the soluble fraction of the homogenate. A relatively small amount of tryptophan pyrrolase, 10 to 15% of the total, is sedimentable. The head region of pupae contains approximately 15% of the total activity of the animal. The subcellular distribution of the activity of the head is not appreciably different from the distribution of activity in the rest of the animal. Therefore no evidence suggests that the enzyme exists in a particulate form specifically in the head. Kynurenine hydroxylase is judged to be a mitochondrial enzyme on the basis of its co‐sedimentation with particles containing cytochrome oxidase and by the demonstration of mitochondria in the sedimented fractions containing kynurenine hydroxylase activity. Kynurenine hydroxylase was judged not to be present in pigment granules since developmental and genetic changes in pigment granule morphology do not affect the sedimentation of kynurenine hydroxylase containing particles. These results on the three enzymes lead us to conclude that they are not organized into a single multi‐enzyme complex as has been previously suggested. A consideration of the six ommochrome deficient mutants indicates that four of these can be explained by existing data. A hypothesis which does not involve enzyme complexes is presented to account for the remaining two.
Functional units in the labellar chemosensory hairs of the mosquito Culiseta inornata (Williston)
Authors: Owen William B. , Larsen Joseph R. , Pappas Larry G. 
Published: June 2005

AbstractElectron micrographs of the labellar chemosensory hairs of the mosquito show that these sensilla have either three or four dendrites extending the length of the shaft. At the tip of each hair is a circular pore. The dendrites are enclosed within a scolopoid structure. At the distal end of the dendrites the microtubules are arranged in a random manner, but, in the proximal area, they are grouped into nine pairs. Near the base the pairs assume a spiral pattern giving rise to a three‐compartmented structure which forms the root proper.Action potentials were recorded from the hairs, using NaCl at concentrations of 0.002 M to 1.0 M. Four different spikes were recognized — water and three salt. The salt spikes were labeled Types a, b, and c. None of these is identical with the L spike from the blowfly. All four spikes were recorded from some hairs which were certainly those with four dendrites.Behavioral studies demonstrated that the rejection threshold of NaCl for labellar hairs was 0.28 M. This coincides with a rapid increase in the electrical activity of the Type c salt cell. From behavioral and electrophysiological evidence it was concluded that acceptance by Culiseta of NaCl in aqueous solution is the result of activity of the water receptor plus input from the salt receptors Types a and b, and that rejection results from activity of the Type c salt cell.
Non‐visual light responsiveness in the pigeon: Developmental and comparative considerations
Authors: Heaton Marieta Barrow , Harth Marshall Stephen 
Published: June 2005

AbstractNon‐visual responsiveness to photic stimulation was investigated in pigeon embryos (days 11½–17½ of incubation) and neonates (6–24 hours posthatch). At all ages observed, these animals exhibited a marked overt response to light onset, a response which occurred even when the entire head was occluded from light, but which could be blocked (in hatchlings) by covering all of the body except the head. It was therefore concluded that retinal or direct brain mediation did not underlie the response, but rather, some form of dermal sensitivity would best account for it. Chicken embryos (day 19 of incubation) and Ring dove hatchlings (12–24 hours posthatch) were similarly investigated. Although there was evidence in both of these species for light‐contingent motility, their responsiveness was seemingly mediated by either visual or direct brain stimulation, since occlusion of the head eliminated the effect. Thus, of the three species tested, only the pigeon appeared to possess the non‐visual dermal light sensitivity. Possible significance of this responsiveness for this species was discussed.
Development of lethal yellow (Ay/Ay) mouse embryos in vitro
Authors: Pedersen Roger A. 
Published: June 2005

AbstractPreimplantation embryos from matings between mice heterozygous for the yellow allele (Ay) of the agouti locus were cultured in vitro and their development was compared with embryos from control matings (Ay/a × a/a). No morphological abnormalities were consistently observed at the eightcell stage, but after 24 hours of culture there were abnormalities in 16.8% of embryos from Ay/a × Ay/a matings. The abnormalities, which consisted primarily of arrest of several blastomeres and their exclusion from the embryo, were also present in 23.9% of embryos removed from the uterus as morulae and blastocysts. Those embryos that became abnormal during preimplantation stages were presumed to be the Ay/Ay homozygotes because their frequency approximated the Mendelian expectation of 25% in Ay/a × Ay/a matings but not in control matings. The morphological abnormalities indicated an effect of the Ay allele as early as the fourth cleavage division.Presumed Ay/Ay early blastocysts collapsed and died without hatching when cultured for five days under conditions that allowed normal embryos to hatch and grow out on the substrate. If the zona pellucida was removed from these blastocysts before culture, limited trophoblastic outgrowth occurred, but the outgrown cells were few and small and the inner cell mass disintegrated entirely.The Ay allele in the homozygous condition thus appears to be a cell lethal that allows growth up to the early blastocyst stage but prevents the normal postblastocyst growth and differentiation of either trophoblast or inner cell mass.
A quantitative study of the peripheral nerve supply in the tadpole tail
Authors: Simpson S. B. , Skirnyk Jarema 
Published: June 2005

AbstractThe anuran tadpole tail is capable of regenerating in the absence of the spinal cord. This is in contrast to urodeles and lizards that require the spinal cord for normal tail regeneration. Quantitation of peripheral nerves in the Rana clamitans tadpole tail reveals an average of 6.9 nerve fibers per unit area of soft tissue. This value falls short of the threshold nerve requirement established for regeneration of the Triturus limb. However, when nerve fiber size is taken into consideration, we find that the axoplasm area per unit area of soft tissue exceeds the threshold requirement for limb regeneration in Triturus. When judged against this standard, regeneration of the tadpole tail in the absence of the spinal cord can be explained on the basis of a sufficient neurotrophic contribution made by the peripheral nerves alone.
Influence of hypophysectomy and starvation on blood glucose levels in the newt, notophthalmus viridescens
Authors: Connelly Thomas G. , Goldstein Aida M. , Yamada Tuneo 
Published: June 2005

AbstractBlood glucose and liver glycogen levels were determined in hypophysectomized, sham‐operated and unoperated control animals all of which had been starved for 10–15 days. The results show that starvation causes a significant decrease in newt blood glucose and that this decrease is not enhanced by hypophysectomy or sham‐operation during a 15‐day period. These data indicate that effects of short periods of hypophysectomy on regenerating tissues are probably not due to a drop in available carbohydrate. However, the data do not indicate what the possible effects of long‐term hypophysectomy on blood glucose would be.
Glycogen synthetase and phosphorylase in developing chick glycogen body
Authors: Benzo Camillo A. , De Gennaro Louis D. 
Published: June 2005

AbstractGlycogen synthetase and phosphorylase activities were quantitatively determined for the first time in glycogen body tissue from late embryonic and neonatal chicks. For comparative purposes, these enzyme activities were examined also in skeletal muscle and liver from pre‐ and post‐hatched chicks. The present data show that the forms of glycogen synthetase which exist in the chick glycogen body are similar to those found in both liver and muscle, while glycogen body phosphorylases more closely resemble those forms characteristic of skeletal muscle.
The effect of ergocornine on melanophores of Ambystoma tigrinum: Evidence for suppression of pituitary MSH release
Authors: Platt James E. , Norris David O. 
Published: June 2005

AbstractInjection of ergocornine into larval tiger salamanders (Ambystoma tigrinum) placed on a black background prevented the increase in melanophore index observed in saline‐injected controls. Larvae pre‐adapted to a black background showed a significant drop in their melanophores indices which persisted for up to 11 days following a single injection of 25 μg ergocornine (2.5 μg/g body weight). Dark‐adapted, ergocornine‐treated larvae with melanin concentrated in the melanophores responded to a single injection of 20 μg mammalian ACTH with rapid and complete dispersion of melanin within the melanophores. The same larvae did not respond similarly to a single injection of 25 μg ovine prolactin. These results support the hypothesis that ergocornine blocked the secretion of pituitary MSH in Ambystoma tigrinum.
Crayfish CNS: Minimal degenerative‐regenerative changes after lesioning
Authors: Bittner George D. , Ballinger M. L. , Larimer J. L. 
Published: June 2005

AbstractRemoval of an abdominal ganglion or a segment of a connective of the ventral nerve cord in crayfish (Procambarus simulans) resulted in little regenerative outgrowth from cut ends of CNS axons and no replacement of ablated cell bodies, even after 9–12 months. A few small‐diameter interneurons, but no giant axons, showed physiological and/or morphological evidence for regeneration across the lesion site. No behavioral, physiological or morphological evidence for degeneration of severed axonal segments of any interneuron (except for a few damaged segments of the septate lateral giant axons) was seen 2–3 weeks after lesioning and survival of isolated segments of medial giant axons was associated with hypertrophy of their glial‐connective tissue sheaths. Very little morphological degeneration of severed CNS interneurons was seen even 9–12 months after lesioning, except for isolated distal stumps of medial giant axons.Physiological evidence for degenerative changes was obtained after 9–12 months for CNS synapses posterior to the lesion site in that these synapses rapidly fatigued with repeated stimulation whereas synapses anteror to the lesion continued to function normally. This difference in synaptic efficacy might be explained by an interruption of a rostral‐caudal transport of axoplasmic proteins in these ventral nerve cords (Fernandez et al., '70, '71). A rostral‐caudal flow of trophic substances might also account for the 9–12 month survival of some anterior segments of lateral giant axons which were disconnected from their original cell bodies but which remained in contact with rostral cell bodies via septate junctions.
Origin of the dental lamina in the regenerating salamander jaw
Authors: Graver Heber T. 
Published: June 2005

AbstractThe origin of the dental lamina (DL) in the regenerating lower jaws of seven species of larval and adult urodeles was examined by various transverse amputation procedures.Collectively the results indicate that jaw and DL regeneration following experimental amputation is a widespread phenomenon in urodeles. In 1/4 and 1/2 amputated jaws of larvae (DL present in the stump), the dental epithelium was replaced from both the anterior and posterior ends of the regenerate area, while in adults it was replaced from the posterior stump tissues only. In 1/4 and 1/2 jaw removals (no DL present in the stump), larval forms exhibited a posterior regrowth of the DL, while in adults DL accumulated at the edge of the regenerate area, resulting in 1/4 and 1/2 edentulous jaws. Removal of all DL in both stumps in larval and adult forms resulted in completely edentulous jaws.The DL does not arise de novo during regeneration, nor is it a direct outgrowth of the DL in the stump. Serial sections made in various planes of the area of the regenerating tip of the DL indicated that DL formation in the regenerate is an epithelio‐mesenchymal interaction caused by the inductive influence of remnant DL in the stump on the adjacent regenerating oral epithelium, resulting in a chain of proliferating and invading cells developing serially and sequentially through time. The mechanism involved in the inductive event remains undetermined.
Fluid reabsorption in the crayfish kidney labyrinth
Authors: Peterson Darryl R. , Loizzi Robert F. 
Published: June 2005

AbstractIn the crayfish, eyestalk extirpation produced noticeable blood dilution within three to four hours when maintained in tap water. Microscopic examination of kidney labyrinth cells following this treatment revealed an increase in the width and number of intercellular spaces and a decreased cell volume. Conversely, exposure of the intact animal to 50% sea water for the same interval concentrated the blood, and intercellular spaces and cell volumes did not change. Finally, with both treatments together (i.e., eyestalk extirpation and immersion in 50% sea water), blood became concentrated, but intercellular spaces increased in width and cells shrunk, as occurred with eyestalk extirpation alone. Effects of these whole‐animal treatments on mitochondria, intracellular compartments and basal invaginations among labyrinth cells are also noted. The findings suggest two conclusions. First, it is proposed that the dilation of intercellular spaces is due to an efflux of fluid from the cells into the lateral compartments. Such movements may be part of a mechanism effecting isotonic transepithelial fluid flow from lumen to blood as demonstrated in other systems. Second, since eyestalk extirpation is known to induce hormonal conditions simulating ecdysis, and since the morphological changes in the labyrinth following extirpation occur whether the blood has become diluted or concentrated, it is suggested that solute reabsorption by the crayfish kidney is under direct hormonal control. Such a mechanism could be especially useful during molt‐induced water uptake to enhance reabsorption of solutes and prevent loss of fluid.
Human chondrogenesis: Glycosaminoglycan content of embryonic human cartilage
Authors: Lash James W. , Saxén Lauri , Kosher Robert A. 
Published: June 2005

AbstractTransitions in glycosaminoglycan content occur during early cartilage development in 5–8 week human embryos. With increasing embryonic age, there is an increase in chondroitin 6‐sulfate relative to chondroitin 4‐sulfate, and a large decrease in heparan sulfate. Keratan sulfate is detectable after 8 weeks. Mesonephros and limb buds show distinct differences from all other tissues.
Deafferentation studies on motor activity in the chick. I. Activity pattern of hindlimbs
Authors: Narayanan C. H. , Malloy R. B. 
Published: June 2005

AbstractNeural crest precursors of dorsal root ganglia at lumbosacral levels of the spinal cord of chick embryos were destroyed by superficial cauterization at very early stages (52–64 hours) in order to study the influence of afferent input from the periphery on activity patterns of the hindlimbs during embryonic, hatching and post‐hatching periods. Neither total nor local activity of the hindlimbs in deafferented chick embryos showed any significant difference quantitatively from those of control embryos between 9 and 17 days of incubation. These embryos exhibited typical prehatching and hatching behavior except the final climax stage of hatching in which the embryo normally cracks the shell around the air space and emerges. The experimental embryos were unable to hatch by themselves. In hatched chicks, legs were incapable of making alternate stepping movements. These observations, discussed in the light of other experimental evidences, suggest that afferent input from the periphery is probably involved in the patterning of coordinated activity of the legs in the chick.
The effect of nerve growth factor on hindlimb regeneration in Xenopus laevis froglets
Authors: Robinson Helen , Allenby Kent 
Published: June 2005

AbstractThe effect of nerve growth factor (NGF) on hindlimb regeneration in postmetamorphic Xenopus laevis froglets was investigated. Two different dosage levels of NGF were tested on froglets whose hindlimbs had been amputated either above or below the knee joint. The course of regeneration in the NGF‐treated froglets was followed for 100 days post‐amputation.Treatment with NGF at a level of 2,500 Biological Units per froglet increases the extent of hindlimb regeneration attained compared with the controls, regardless of the level of amputation. On the other hand, a higher dose of NGF, 5,000 Units per froglet, does not alter the extent of hindlimb regeneration significantly. Treatment with NGF at either dosage does not appear to affect the shape or histological constitution of the regenerated limb segment. The general shape of the regenerate correlates with the level at which the limb was amputated. All regenerates obtained in this study conform to a common pattern in terms of histological constitution. They are composed of a central core of cartilage with a perichondrial membrane surrounded by a thin layer of connective tissue and covered by fully differentiated epidermis. No differentiated bone, muscle or nervous tissue was detected in any of the regenerates, but evidence of cartilage calcification was observed in limbs amputated below the knee. Possible implications of these results are discussed.
Independence of ovarian masculinization and hypothyroidism in frog tadpoles after methimazole treatment
Authors: Hsü Chin‐yün , Huang Hsü‐Cheng , Chang Chieng‐Hsün , Liang Hsü‐Mu 
Published: June 2005

AbstractThis work aims to clarify whether methimazole‐induced sex transformation in tadpole ovaries is due to the goitrogenic property of the drug as some authors have suggested. Intact, thyroidectomized, and hypophysectomized female tadpoles of Rana catesbeiana were reared in 0.005% methimazole solution as experimentals; three parallel groups in tap water served as controls. After four months of goitrogen treatment, all six groups of tadpoles were sacrificed and their gonads sexed histologically. The results showed that intact, thyroidectomized, and hypophysectomized tadpoles in tap water had normal ovaries, while ovaries of intact, thyroidectomized, and hypophysectomized animals in methimazole solution were all transformed at least partially, and in some cases, almost completely to testes. Histologically, the process of sex transformation resulting from methimazole treatment was not different from that observed in heat‐treated tadpoles or in spontaneous sex reversals. These findings demonstrate that the hypophysis and thyroid were not involved in goitrogen‐induced sex transformation. This provides additional evidence in support of our belief that various factors, such as heat, sex hormones, gene action, and goitrogens though diametrically different per se, all deliver a direct and detrimental effect on the ovary, triggering a common pathway from destruction of oocytes to induction of rete cells which results ultimately in sex transformation.