bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and contractile properties of lobster leg‐muscle Fibers
Authors: Jahromi S. S. , Atwood H. L. 
Published: June 2005

AbstractThree leg muscles of the American lobster, namely, the extensor muscle of the carpopodite in the walking legs, the closer muscle of the “cutter” claw, and the closer muscle of the “crusher” claw, were examined to see what types of muscle fiber they contain. In all three muscles, slow and fast fibers, as well as intermediate types, were present. Contraction rates of both types increased with the amplitude of the applied depolarization; slow fibers showed more lability in this respect, but they did not contract as rapidly as the fast fibers even when strongly stimulated. Membrane potential threshold for contraction was positively correlated with resting membrane potential in both types of fiber. Slow fibers differed from fast fibers structurally in having longer sarcomeres and A‐bands, smaller numbers of diads per unit length of muscle fiber, larger thin:thick filament ratios, and more connective tissue and sarcolemmal elements. The two claw closer muscles differed markedly in their proportions of slow and fast fibers, the “cutter” claw having a preponderance of short‐sarcomere, fast fibers. This finding helps to explain the difference in contraction speed of these two claw muscles.
Studies on the transition to ureotelism in the earthworm Lumbricus terrestris L.
Authors: Tillinghast Edward K. , Janson Colette H. 
Published: June 2005

AbstractThe hypothesis that anatomically distinct endocrine centers control the production of urea and ammonia in the earthworm has been examined.This hypothesis is not supported by the present data.Ammonia output is markedly increased by a high protein diet, while the urea output is reduced by digestible carbohydrates.
Transneuronal effects on amphibian limb regeneration
Authors: Tweedle Charles 
Published: June 2005

AbstractThis investigation has demonstrated that in both the newt and axolotl the simultaneous removal of a second limb brings about a significantly slower linear regeneration rate, but only if the second limb removed is directly contralateral to the first one removed. Both morphologic and autoradiographic data point to a more prolonged chromatolysis in the brachial neurons following contralateral forelimb removal. This is thought to bring about the slower regeneration rate seen. Further evidence for this contention is the fact that just the severance of the brachial nerves of one forelimb of an animal will bring about a significantly slower regeneration rate of the contralateral forelimb. In salamanders without intervening nervous connections or CNS tissue between the limbs, i. e., the aneurogenic larvae, no effect on regeneration rate is seen following contralateral double limb removal. Autoradiographs using 3H thymidine as a precursor point to an early effect on growth as being the means that contralateral denervation or limb removal brings about a slower regeneration rate. This is thought to be due to a decrease in the trophic ability of the brachial innervation following the more profound disruption of the brachial neurons that accompanies double limb removal.
DNA content, ribosomal gene multiplicity, and cell size in fish
Authors: Pedersen Roger A. 
Published: June 2005

AbstractThe diploid nuclear DNA contents in eight species of fish have been found to differ over a 178‐fold range. Among these, lungfish have the highest values, and teleosts have the lowest. Shark and coelacanth have intermediate values, which are close to the highest teleost values. Such great variation in DNA contents among vertebrates indicates that fundamental differences in chromosome structure and DNA function have arisen during evolution.In order to gain insight into the organization of genes in organisms with different DNA contents, the relative proportion of the genome coding for ribosomal RNA was determined for five species, winter flounder, goldfish, rainbow trout, dogfish shark, and Australian lungfish. The proportion of ribosomal DNA (r‐DNA) was found to vary over a six‐fold range from flounder to lungfish. In general, species with higher DNA contents have lower proportions of r‐DNA. The r‐DNA proportion of trout is consistent with the view that salmonids are recent tetraploids. If the goldfish is also considered a tetraploid, then its r‐DNA proportion indicates a loss of ribosomal genes subsequent to polyploidization. Measurement of the ribosomal genes in fish DNA's was based on hybridization with yeast ribosomal RNA, which was assumed to be equally homologous with the r‐DNA of all species studied.The activity of multiple copies of genes was studied by measuring the volumes of blood cells in five species. It was found that erythrocyte volume correlated both with ribosomal gene multiplicity and with total DNA content. The size of goldfish and trout erythrocytes suggests that cell volume in these tetraploids has declined to the ancestral diploid level.It is concluded that the multiplicity of specific repetitive genes varies out of proportion with the DNA content, contrary to expectation based on simple polyteny. This variation in the proportions of specific genes and the large variations in total DNA content among fish are thought to be due to a combination of tetraploidy and extensive linear replication of specific chromosomal regions during evolution.
Control of mitotic activity in Wolffian lens regeneration
Authors: Yamada Tuneo , Roesel Marion 
Published: June 2005

AbstractThe total numbers of mitotic cells in the iris epithelium, ciliary epithelium, and ora serrata were counted at various time intervals after lentectomy of adult newts, Notophthalmus (Triturus) viridescens, in bleached serial sections. In some cases colchicine was injected for the purpose of accumulating mitotic figures.In the iris epithelium, which normally shows no mitotic cells, a wave of mitoses is induced by lentectomy. The wave starts on day 4 and has its peak period during days 7 to 15, when a portion of the iris epithelial cells depigment and form the lens vesicle. In the iris epithelium the wave subsides after formation of the regenerated lens and is gone by day 30. On the other hand, in the regenerated lens the mitotic activity is retained in the lens epithelium. The colchicine treatment has revealed an extremely small number of iris epithelial cells going into mitoses within one day after lentectomy. However, the same treatment failed to demonstrate any mitotic cells on days 0, 2, and 3.Mitotic activity is also induced in the ciliary epithelium, which does not take part in formation of the lens regenerate. This induction is much lower in intensity than that in the iris epithelium.The ora serrata area has a low level of mitotic activity in the normal condition, which is elevated to a high level after day 20. Significance of these observations for the mechanism of lens regeneration is discussed.Estimation of the total cell number of iris and ciliary epithelia during the first 15 days after lentectomy indicated an increase in the iris epithelium, which can be accounted for by the number of mitoses counted during the corresponding period in the same tissue.Some data on mitosis in the normal and regenerated lenses are also presented.
Hormonal influences on the glycogen content of normal and delayed implanting mouse blastocysts
Authors: Ozias C. Blake , Weitlauf Harry M. 
Published: June 2005

AbstractThe proportion of delayed implanting mouse blastocysts capable of normal development following transfer to pseudopregnant recipients is influenced by the length of the delay period. Thus, approximately one‐third develop normally when transferred on days 5, 9 or 15 (day 1, day of vaginal plug), while only 3% do so when transferred on day 30 (Weitlauf and Greenwald, '68a). In the present experiments, the amount of glycogen in normal and delayed implanting mouse blastocysts was estimated enzymatically to determine whether it plays a limiting role in embryonic survival.Normal blastocysts and delayed implanting blastocysts (i. e., in mice ovariectomized on day 4) contained a similar amount of glycogen on day 5. However, by day 10 the amount of glycogen in the delayed implanting blastocysts dropped to about half that found on day 5 but showed no further decrease between day 10 and day 30. Therefore, the amount of glycogen in delayed implanting mouse blastocysts does not appear to be the limiting factor in embryonic survival.It was further shown that ovarian hormones influenced the amount of glycogen in the blastocysts. Administration of estrogen to ovariectomized mice caused an increase, while progesterone reduced the levels of glycogen.
Physico‐chemical properties of an agent that induces parthenogenesis in Rana pipiens eggs
Authors: Fraser Lynn R. 
Published: June 2005

AbstractAll previous work on artificial parthenogenesis in frog eggs, where parthenogenesis is identified by cleavage and subsequent embryonic development, has involved the introduction of some cellular element. Earlier workers have shown that the cleavage initiating agent (CIA) is found primarily in the particulate fractions of various tissues, whereas this investigation indicates that the active molecules sediment only in the 10,000 g precipitable fraction. Since dialysis against EDTA does not remove activity, non‐specific adsorption to particles would appear to be excluded although the failure of distilled water treatment to remove activity may indicate that the CIA is associated with membranes. The CIA is trypsin‐sensitive, but DNase and RNase resistant, indicating that the molecules are protein in nature. Activity is also removed by incubation with a number of depolymerizing agents, including KI, KCl, and Sarkosyl, indicating that the CIA may be a polymer which must be polymerized to retain activity. The mechanism of action of this protein polymer appears to be that of a trigger since a wide range of concentrations will initiate cleavage. Colchicine gradually removes activity from a preparation while D2O increases activity. Both of these molecules are known to act on the polymerized form of microtubule protein with colchicine decreasing and D2O increasing polymerization. Electrophoresis of protein from five CIA‐containing frog tissues reveals a component common to all of them which migrates with an Rf similar to that of microtubule protein. The 10,000 g pellet from frog brain has significant 3H‐colchicine‐binding activity, and to date only microtubule protein has been shown to bind colchicine. Electron micrographs of 10,000 g pellet material from frog brain show the presence of pieces of microtubules enclosed in membranous vesicles. It is therefore possible that the CIA is microtubular in nature, with short pieces of microtubules perhaps acting as a “seed” for further polymerization. The unfertilized frog egg contains much unpolymerized microtubule protein but apparently lacks the proper template or catalyst to trigger the necessary centriole replication and spindle formation for cleavage; the CIA may fill this role.
Growth and differentiation of the testes in the large milkweed bug, Oncopeltus fasciatus (Dallas)
Authors: Economopoulos A. P. , Gordon H. T. 
Published: June 2005

AbstractDuring the fourth instar there is a five‐fold increase in testis volume, caused by mitotic proliferation of spermatogonia that leads to accumulation of many layers of cysts of resting spermatocytes. At the beginning of the fifth instar the basal cysts undergo meiotic division, and a wave of meiosis followed by spermateleosis progreses apically. There is little or no spermatogonial multiplication; the three‐fold increase in testis size involves primarily spermatocyte differentiation. The wave of differentiation continues at a slower rate in the young adult; most of the spermatocyte cysts are transformed into about 250,000 spermatozoa by the twelfth day. Multinucleate apical cells that stain deeply with Feulgen reagent are present in the early fourth instar, enlarge in the fifth, and persist in the adult testis.Spermatocyte differentiation is not affected by treatment of nymphs with a synthetic juvenile hormone to analog during the fourth or fifth instar, although the treatment causes moderate to high juvenilization at the metamorphic molt. Since late fourth‐instar testes transplanted into mature male or female adults also undergo extensive transformation of spermatocytes into spermatozoa, molting is not required for differentiation. Treatment of late fourth or early fifth instar nymphs with the chemosterilant tretamine causes high mortality at the metamorphic molt, but the wave of spermatocyte differentiation during the fifth instar proceeds normally, although there is evidence of severe chromosome damage.Comparisons with development in the female of Oncopeltus and in other insect species suggest that there is a profound change in the biochemical milieu at the molt from fourth to fifth instar, many processes preceding this molt tending to be larval in character and to diminish or disappear afterward while processes normally occurring after the molt tend to be adultoid.
Sucrase activity in the intestine of the chick: Normal development and influence of hydrocortisone, actinomycin D, cycloheximide, and puromycin
Authors: Brown Kathren Mortenson 
Published: June 2005

AbstractSucrase activity in the intestine of the chick embryo increases to a pre‐hatching maximum at 19 days. A significant decrease in activity occurs by 20 days, followed by rapid increases in the jejunum and the ileum after hatching, while duodenal activity continues to decrease. The injection of hydrocortisone resulted in significant increases in sucrase activity. The decrease in activity that normally occurred after 19 days was delayed until after 20 days. The hydrocortisone‐induced increases were completely abolished when cycloheximide was administered two or three days after the hormone injection.When actinomycin D was administered at 16 days, there were significant increases in sucrase activity at 18 days, and the maximum activity was produced at 19 days. High activities were obtained when actinomycin D was injected at 17 days. The administration of cycloheximide at 14 or 16 days did not change the sucrase activity through 19 days, but the 20‐day decrease was prevented. Large increases in activity were observed at 20 days when the antibiotic was injected at 17 days. Histological preparations revealed that these two antibiotics did not produce abnormalities in the epithelial cells of the tissues. Puromycin injection inhibited the normal decrease at 20 days. Actinomycin D and cycloheximide were injected simultaneously at 16 days. Cycloheximide did not prevent the elevation of sucrase activity caused by actinomycin D. It is suggested that the development of sucrase activity in the chick intestine may consist of a phase of activation followed by a phase of inhibition. In the first phase, de novo synthesis can apparently be evoked by hydrocortisone.
The effects of complete darkness and vitamin C supplement on the killifish, Fundulus heteroclitus, adapted to sea water. I. Calcium metabolism and gonadal maturation
Authors: Pang Peter K. T. 
Published: June 2005

AbstractAdaptation to complete darkness for eight months had no effect on calcium metabolism in adult male Fundulus heteroclitus in sea water. However, scoliosis and hypocalcemia were evident in juvenile killifish kept in complete darkness for six and a half months. Hypocalcemia was also seen in juveniles after three and a half months in complete darkness but this fall in serum calcium level was prevented by vitamin C supplement in the diet. Complete darkness also induced a delay in testicular maturation in both adults and juveniles but this defect was not corrected by vitamin C supplement.
3,5,3′‐triiodo‐L‐thyronine uptake and development of metamorphic competence by Xenopus laevis embryonic tissues
Authors: Knutson Thomas L. , Prahlad Kadaba V. 
Published: June 2005

AbstractThe purpose of this investigation was to determine whether or not larval tissues of Xenopus laevis are capable of responding to a very short exposure of 3,5,3′‐triiodo‐L‐thyronine (T3), very early in their ontogeny. Ten dejellied embryos were immersed in 15 ml of aged tap water containing 30 μg of T3 per ml of medium. Exactly at the end of 24 hours all of the embryos were removed, rinsed thoroughly in fresh tap water and placed in aged tap water in a larger container. Both gross morphological and histological observations were carried out on embryos and larvae at an interval of 12 hours beginning at the termination of hormone treatment to the end of about 11 days.The following changes were clearly observed in experimental animals (numbers in parenthesis indicate days after fertilization): (a) degenerative changes in adhesive gland (3.5); (b) more extensive development of nasal sac (5.0); (c) a visible and ventrally protruding hyoid arch (6.5); (d) a larger hind limb bud (5.0). In addition to the above, other obvious changes which were seen in experimental animals were a protruding lower jaw due to an extensive and well developed Meckel's cartilage, and a less extensive gut. The head was cone shaped in T3 treated animals. There was no change in tail to body length ratios.The facts mentioned above appear to indicate a differential ontogenetic competence of embryonic and larval tissues of Xenopus in their response to T3.
Daily variations in the fattening response to prolactin in Fundulus grandis held on different photoperiods
Authors: Joseph M. M. , Meier Albert H. 
Published: June 2005

AbstractGulf killifish were placed on three different photoperiods (8L:16D; 12L:12D; 16L:8D) and injected daily for six days with prolactin at one of several times during the day. Gains in fat stores resulted from prolactin injections given eight hours after the onset of light regardless of the length of the photoperiod. Prolactin injections at other times of the day did not stimulate fattening. These results suggest that the endogenous system controlling the daily fattening response to prolactin is phased by the onset of light.
Thyrocalcitonin and its role in calcium regulation in mammals
Authors: Hirsch Philip F. 
Published: June 2005

AbstractThe discovery of thyrocalcitonin, the hypocalcemic, hypophosphatemic hormone secreted by the mammalian thyroid gland, and its current status with respect to cell of origin, chemistry, site and mode of action, and control of its secretion are reviewed. The physiological function of thyrocalcitonin has yet to be established with certainty.Evidence that secretion of thyrocalcitonin prevents postprandial hypercalcemia is presented. Small amounts of calcium administered orally caused hypercalcemia in acutely thyroidectomized but not in intact rats. In the pig, a direct relationship has been established between thyrocalcitonin secretion and levels of blood calcium during hypercalcemia. However, in other studies in which calcium was given orally, thyrocalcitonin secretion rose even without a detectable increase in the concentration of blood calcium. These observations in rats and pigs raised questions regarding the stimulus to the thyroid gland for thyrocalcitonin secretion. Is a small and undetectable rise in the blood calcium after oral calcium a sufficient signal to the thyroid gland or are other factors involved? The recent finding that pentagastrin administered i.v. at low doses increased thyrocalcitonin secretion in pigs suggests that release of gastrin or a related gastrointestinal hormone after oral calcium may thereby aid in regulation of calcium metabolism.The possibility also remains that the principal physiological function of thyrocalcitonin may be unrelated to calcium homeostasis. Attention has been focused on calcium partly because of the nature of the experiments leading to the discovery of thyrocalcitonin. Perhaps the correct pathway to elucidate the true role of this hormone in the body economy has not yet been followed.
Thyroxine induced metamorphosis in Aurelia
Authors: Spangenberg Dorothy Breslin 
Published: June 2005

AbstractThe functional activity of thyroxine in strobilation initiation in Aurelia is explored. Low temperature preconditioned jellyfish polyps are consistently induced to metamorphose by administration of triiodothyronine, diiodotyrosine, monoiodotyrosine, and thyroglobulin, as well as by previously reported iodide and thyroxine (Spangenberg, ′67). Jellyfish synthesize three protein‐bound iodocompounds during strobilation and excrete one protein‐bound compound into the medium. The culture medium containing the iodocompound induced strobilation in the absence of iodide. The protein‐bound compound found in the culture medium and in the polyps is tentatively identified as thyroxine since it consistently was co‐chromatographed with thyroxine in five different solvent systems.No localized site of intense concentration of 131NaI or of 125I‐T4 was found in the polyps during initiation of strobilation. Both substances were present in greater amounts at the distal, differentiating end of the organisms than at the base, particularly during the early pre‐segmentation strobilation period. Distribution of these two substances between the tissue layers during strobilation indicates that thyroxine may be ingested orally and iodide taken up across the epidermis.The strobilation system of Aurelia represents the simplest system in which thyroxine is functional and is probably synthesized. This system, therefore, offers new opportunities for the study of the action of thyroid hormone under less complicated developmental conditions than are found in higher organisms.
A study of the effects of ethidium bromide on the ultrastructure of sea urchin embryos
Authors: Geuskens M. 
Published: June 2005

AbstractThis study describes the ultrastructural changes which result from treatment of sea urchin embryos (Paracentrotus lividus) with ethidium bromide, particularly in: the chromatin (formation of a network of materials of various densities or clumping), the nucleoli (no typical granular region), the mitochondria (swelling, reduction in the number of cristae, appearance of numerous dense granules or a dense mass in the matrix) and the heavy bodies (enlargement and prolonged existence).The experimental conditions were as follows:

Treatment with different doses from ten minutes before fertilization continued for 90 minutes afterwards.
Treatment with a high dose (100 μg/ml) for three hours at the young blastula stage.
Treatment with a low dose (15 μg/ml) for 48 hours from fertilization onwards.
Active nucleo‐cytoplasmic exchange visibly occurs across the nuclear membrane of control embryos throughout development: emission of multivesicular ergastoplasmic sacs into the cytoplasm up to the blastula stage and formation of ergastoplasmic diverticulae by its outer leaflet from the gastrula stage onwards. These signs of nuclear membrane activity are also observed in embryos treated with ethidium bromide.
Studies on the sterility phenotype of the pleiotropic mutant fused of Drosophila melanogaster
Authors: Fausto‐Sterling Anne 
Published: June 2005

AbstractA further description of the sterility phenotype for three different alleles of the female‐sterile mutant fused of Drosophila melanogaster is reported. It was found that:

No more than 35% of the eggs laid by females homozygous for fu, fu57a, and fu59 when mated to Oregon R males are capable of hatching into larvae. This percentage is unaffected by the presence of a Y chromosome in the mother. The data indicate that the mechanism of control in the activation of the wild type allele of fused in an embryo from a homozygous fused mother is imprecise.
Homozygous fu, fu57a, and fu59 females show apparently allelic differences in the number of eggs they are capable of laying.
Heterozygous fu59 females have a somewhat reduced egg laying capacity when compared to Oregon R females if they are the daughters of either homozygous or heterozygous fu59 mothers but show no such difference if they are the daughters of Oregon R mothers. These data are consistent with the idea that fused is hypomorphic.