bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between nuclear DNA synthesis and centrosome reproduction in sea urchin eggs
Authors: Sluder Greenfield , Lewis Kirsten 
Published: June 2005

AbstractThe importance of nuclear DNA synthesis for the doubling, or reproduction, of centrosomes in cells that are not growth‐limited, such as sea urchin eggs, has not been clearly defined. Studies of enucleated, fertilized eggs show that nuclear activities are not required at each cell cycle for the normal reproduction of the complete centrosome. However, other studies report that the inhibition of nuclear DNA synthesis in intact eggs by the drug aphidicolin prevents centrosome reproduction and entry into mitosis as seen by nuclear envelope breakdown. To resolve this paradox, we systematically characterized the effect of aphidicolin on cell division in eggs from three species of sea urchins. Eggs were continuously treated with 5 or 10 μg/ml aphidicolin starting 5 min after fertilization. This blocked total incorporation of 3H‐thymidine into DNA by at least 90%, as previously reported. We found that the sperm aster always doubles prior to first mitosis. Over a period of several hours, the centrosomes reproduce in the normal 2‐4‐8‐16 fashion, with a period that is longer and more variable than normal. In every culture, a variable percentage of the eggs undergoes nuclear envelope breakdown. Once broken down, the nuclear envelope never visibly reforms even though centrosomes continue to double. Fluorescent labeling of DNA revealed that the chromatin does not condense into discrete chromosomes. Whether or not the nuclear envelope breaks down, the chromatin appears as an amorphous mass of fibers stretched between first two and then four asters. Later, the nuclear envelope/chromatin loses its association with some or all centrosomes. Our results were the same for all eggs at both drug concentrations. Thus, nuclear DNA synthesis is not required for centrosome reproduction in sea urchin eggs.
Photoperiodic control of antler cycles in deer: VII. Role of light vs. dark in suppression of circannual rhythms
Authors: Goss Richard J. 
Published: June 2005

AbstractThe antler replacement cycle in the sika deer (Cervus nippon) is abolished on simulated equatorial photoperiods (12L/12D), the old antlers failing to be regenerated for indefinite durations. Constant but unequal light and dark periods have been shown to permit expression of circannual rhythms, as have constant and equal periods not measuring 12 hr in length. To test whether equinoctial circannual suppression could be attributed to the 12‐hr durations of the light periods or the dark periods, groups of yearling deer were exposed to 12L/9D, 9L/12D, 12L/16D, or 16L/12D, beginning on the autumnal equinox. All such deer cast and regenerated their antlers by spring. Therefore, suppression of the circannual antler cycle on 12L/12D is due neither to the 12‐hr photoperiod, nor to the 12‐hr scotoperiod, but to a combination of both.
Budding, life‐span, regeneration, and colonial regulation in the ascidian, Symplegma reptans
Authors: Sugino Yasuo M. , Nakauchi Mitsuaki 
Published: June 2005

AbstractIn the colonial ascidian, Symplegma reptans, the oozooid from which a particular colony has developed always degenerates about 30 days after metamorphosis, while all other zooids of the same colony are vigorous. Furthermore, an irregular type of regeneration, “blastogenic regeneration” (regeneration with the aid of budding), occurs if the zooids or their fragments are isolated under artificial conditions. Employing this species, we examined how budding and the life‐span of a zooid are affected by the other zooids of the same colony and studied the relationship between the nature of fragments of zooids and the mode of regeneration. To survey the effects of the other buds and zooids of the same colony, all buds from the oozooid were removed. The zooids from which buds were removed made about twice as many buds as the controls, and they lived a little longer than the controls. This result suggests that budding of a zooid is inhibited by the ambient zooids in the same colony. When the fragments of zooids were cultured alone, they regenerated either by epimorphosis or by blastogenic regeneration according to the extent of surgical removal of tissue. In cases in which two or more buds were formed during blastogenic regeneration, only the first bud grew. These results indicate that budding and regeneration are regulated both at the zooidal level and at the colonial level.
Sources of calcium and the involvement of calmodulin during steroidogenesis and oocyte maturation in follicles of Rana pipiens
Authors: Francisco Susan Kleis‐San , Schuetz Allen W. 
Published: June 2005

AbstractIn the amphibian ovarian follicle, progesterone production is thought to induce maturation of the enclosed oocyte. Intracellular mechanisms regulating these events in the somatic and germ cells are incompletely understood. However, calcium appears to play a role in the production and action of progesterone. Experiments using calcium antagonists were carried out to delineate the role of extra‐ and intracellular calcium during in vitro stimulation of follicular steroidogenesis and oocyte maturation. Calcium‐free medium, verapamil, and La3+ were used to block Ca2+ influx and inhibited follicular progesterone accumulation in response to frog pituitary homogenate (FPH) or exogenous cAMP + IBMX. Progesterone accumulation was not impaired under identical conditions when pregnenolone was added to cultured follicles. TMB‐8, an inhibitor of intracellular Ca2+ mobilization, partially inhibited progesterone levels stimulated by FPH at low doses but not higher doses of the inhibitor. However, TMB‐8 inhibited FPH‐induced oocyte germinal vesicle breakdown (GVBD) in a dose‐dependent manner, as well as maturation due to exogenous progesterone or La3+. Calmodulin antagonists, W‐7, R24571, and trifluoperazine, were used to assess the involvement of calmodulin in the responses of these two cell types. All three antagonists inhibited progesterone accumulation induced by FPH with the apparent order of potency being R24571 > W‐7 > TFP. W‐7 inhibited cAMP‐induced progesterone elevation, but had no effect on conversion of pregnenolone to progesterone. Of these three calmodulin antagonists, only R24571 exhibited a dramatic ability to inhibit GVBD induced by exogenous progesterone and was associated with morphologic alterations in the oocytes. These data suggest that Ca2+, acting through calmodulin at some specific step(s) distal to cAMP elevation and prior to pregnenolone formation, is involved in FPH‐induced progesterone accumulation, apparently with the participation of both extracellular and intracellular pools of Ca2+. In the oocyte, mobilization of Ca2+ from intracellular stores appears to be of primary importance to maturation while extracellular Ca2+ is not. These data provide further evidence that Ca2+ mediates the hormonally provoked responses in both cell types in the intact follicle, but that the source of Ca2+ may differ. Using intact follicles it seems apparent that exploiting this difference with selective inhibitors provides a means for differential modulation and functional uncoupling of these cells with regard to steroidogenesis and steroid action.
In vitro study of serum protein synthesis in the livers of larvae and adults of the lamprey, Petromyzon marinus L.
Authors: Ito Misa A. , Filosa Michael F. , Youson John H. 
Published: June 2005

AbstractUsing electrophoretic and immunoelectrophoretic methods we had previously characterized three major serum proteins of the lamprey, Petromyzon marinus: SDS‐I, CB‐III, and AS. SDS‐I is present in highest concentration at the upstream migration period of the life cycle, whereas AS is present in highest concentration at the larval (ammocoete) period. Since the liver has been shown to be the major site of serum protein synthesis in many vertebrates, it may be assumed that the lamprey liver also engages in the same activity. In the present work we present evidence that the three major serum proteins of the lamprey are indeed synthesized by the liver. Liver slices from the larval and upstream migrant period were separately incubated with [35S]‐methionine. After 2 or 3 hours of incubation, Triton X‐100‐soluble material was extracted from the liver slices and examined by crossed immunoelectrophoresis (CIE) and autoradiography. When extracts from the larval liver were run with antiserum made against larval serum, autoradiograms of the CIE patterns showed that AS and CB‐III had been synthesized; the synthesis of AS was confirmed by the use of monospecific antiserum against AS. There was no indication of SDS‐I synthesis during the incubation period. When extracts from the upstream migrant liver were run with antiserum made against whole serum from upstream migrants, autoradiograms of the resulting CIE patterns showed that SDS‐I and CB‐III had been synthesized; when antiserum against AS was used for the CIE, autoradiograms showed that AS had not been synthesized during the incubation period. Thus the differences in concentration of AS and SDS‐I in the different periods of the life cycle may be due to differences in the synthetic capabilities of the liver at these periods.
Characterization of turtle liver nuclear estrogen receptors, seasonal changes, and pituitary dependence of cytosolic and nuclear forms
Authors: Riley Deborah , Callard Ian P. 
Published: June 2005

AbstractA nuclear hepatic estrogen receptor was characterized in the female turtle Chrysemys picta for the first time. The characteristics of this receptor were similar to those previously described in the cytosol, using DNA‐cellulose column chromatography (Riley et al., '87). The development of a different method for measurement of turtle cytosolic estrogen receptors allowed comparison of cytosolic and nuclear estrogen receptor regulation. Cytosolic and nuclear estrogen receptors exhibited high affinity (Kd, nuclear, 2.3 × 10−9M), limited capacity (10 – 170 fmol/g liver), steroid specificity for natural and synthetic estrogen, and target tissue specificity. Sucrose gradient analyses of crude cytosol revealed specific peaks of radioactivity at 4S and 9S, however a single 4S peak was present in nuclear extracts and ammonium sulfate precipitated cytosol. The levels of liver nuclear estrogen receptor changed significantly during the annual reproductive cycle, while cytosolic receptors were maintained at a constant level. Vitellogenic animals had higher levels of nuclear estrogen receptor and a greater percentage of total receptor in the nuclear fraction. In nonreproductive animals with low nuclear and high cytosolic estrogen receptor, short term (20 h) or chronic (1 week) estrogen exposure resulted in an increase in nuclear receptor to levels similar to naturally vitellogenic animals; however, depletion of cytosolic receptor was observed. Hypophysectomy of reproductively inactive animals resulted in loss of nuclear estrogen receptors in both control and estrogen‐injected turtles and restoration was achieved by ovine growth hormone (oGH) replacement. Cytosolic estrogen receptor levels and depletion after estrogen treatment were unaffected by hypophysectomy, however an increase above control occurred in hypophysectomized turtles treated with oGH. These data suggest that both estrogen and a pituitary factor similar to oGH are necessary for the achievement of high levels of nuclear estrogen receptor associated with vitellogenesis.
Cardiovascular effects of prostaglandin I2 and prostaglandin F2α in the unanesthetized bullfrog, Rana catesbeiana
Authors: Robleto Daniel O. , Herman Ceil A. 
Published: June 2005

AbstractThe cardiovascular effects of prostaglandin (PG)I2 and PGF2α were compared in the unanesthetized American bullfrog (Rana catesbeiana). Control mean arterial pressure (MAP) and heart rate (HR) were 25.7 ± 1.1 mm Hg and 35.1 ± 1.1 beats/min, respectively. Intravenous injections of PGI2 decreased MAP and increased HR in a dose‐dependent fashion over the range of concentrations tested (0.03, 0.3, 3, and 10 μg/kg‐body weight [bw]. Neither atropine (1 mg/kg‐bw) nor verapamil (1 mg/kg‐bw) treatment altered the MAP or HR responses to PGI2 (3 μg/kg‐bw). However, propranolol (5 mg/kg‐bw) significantly blunted the hypotensive effects without affecting the increase in HR. Prostaglandin F2α (tested at 0.3, 3, 30, and 100 μg/kg‐bw) increased both MAP and HR. Mean arterial pressure increased with concentrations greater than 0.3 μg/kg‐bw and reached peak effects at 30 μg/kg‐bw. Prostaglandin F2α increased HR at doses greater than 0.3 μg/kg‐bw. Neither the pressor nor positive chronotropic effects of PGF2α (30 μgk/kg‐bw) were affected by atropine or propranolol. However, verapamil significantly attenuated the pressor effects without affecting the increase in HR. These results demonstrate that both prostaglandins have qualitatively similar effects on HR, but opposite effects on MAP. Prostaglandin I2 is a hypotensive prostaglandin, while PGF2α is hypertensive. The pressor effects of PGF2α are partially dependent on calcium influx. The positive chronotropic effects of both prostaglandins are indepdent of the autonomic nervous system, suggesting a different mechanism of action.
Conditions for the appearance of maturation promoting factor following germinal vesicle disruption of prophase‐arrested starfish oocytes
Authors: Guerrier P. , Neant I. , Charbonneau M. , Moreau M. 
Published: June 2005

AbstractIn this paper, we report that so‐called “incompetent” prophase‐arrested oocytes of Marthasterias glacialis and Asterias rubens fail to produce any aster or spindle when their nucleoplasm and cytoplasm are mixed via pressure or microinjection. We also show that the same incompetent oocytes always complete their maturation up to second polar body extrusion and female pronucleus formation following a 30 sec shaking treatment, which results at once in germinal vesicle (GV) disruption and produces the same mixing of their nuclear and cytoplasmic compartments.32P phosphate incorporation into proteins and cell fusion experiments indicates that this mechanical treatment induces an increased protein phosphorylation and triggers the formation of active maturation promoting factor (MPF) molecules which are not produced following a simple nucleoplasm transfer. While bovine serum albumin (BSA) had no effect on this process, the intracellular Ca2+antagonists (2‐[(2‐bist[Carboxymethyl]‐amino‐5‐methylphenoxy)‐methyl]‐6‐methoxy‐8‐bis[carboxy‐methyl]‐aminoquinolinetetrakis‐[acetoxymethyl]ester) (Quin 2‐AM) and 8(N‐N‐diethylamino) octyl‐3,4,5‐trimethoxybenzoate (TMB 8) were found to inhibit both hormone‐induced and shaking‐induced maturations. These results exclude the possibility that shaking might act by releasing arachidonic acid in the external medium. Instead, they suggest that such a mechanical treatment may trigger the same significant changes in Ca2+ concentration or compartmentalization that have been shown to occur following hormone stimulation and that seem to be required for activating resting female centrioles as well as latent MPF precursors and protein kinases.
Formation of flagella during interphase in secondary spermatocytes from Xenopus laevis in vitro
Authors: Abé Shin‐Ichi , Asakura Shoji , Ukeshima Atsumi 
Published: June 2005

AbstractIn cell culture, single motile flagella, 1 μm in length, were observed to grow from secondary spermatocytes of Xenopus laevis within 2–3 hours after telophase I, at 22°C. About 90% of the secondary spermatocytes formed flagella as observed by phase‐contrast microscopy. The flagella grew up to 2–6 μm in length during interphase II, which lasted about 18 hours. The presence of the “9 + 2” microtubular structure of the flagellar axonemes of secondary spermatocytes was confirmed by electron microscopy. When chromosomal condensation began (prophase II), the flagella were resorbed into the cells and, after the second meiotic division, a flagellum was formed again by each of the round spermatids. Thus, there appears to be a close relationship between the meiotic division cycle and the formation of flagella. The possible contribution of Sertoli cells to the formation of flagella in secondary spermatocytes was examined by reducing the number of Sertoli cells to less than ten per culture. Under these conditions, flagella formed in secondary spermatocytes with very high efficiency. It is very likely that secondary spermatocytes form flagella in vivo, since the secondary spermatocytes were observed to have flagella immediately after dissociation of the testes.
Human sperm acrosome reaction‐initiating activity associated with the human cumulus oophorus and mural granulosa cells
Authors: Siiteri Jon E. , Dandekar Pramila , Meizel Stanley 
Published: June 2005

AbstractThis report describes the detection and partial characterization of preovulatory human cumulus oophorus and mural granulosa cell‐associated activity capable of initiating the human sperm acrosome reaction (AR) in vitro. Fragments of preovulatory human cumulus (cells plus extracellular matrix) were washed 3 times, incubated for 24 hr and the spent media and washes assayed for their ability to initiate the human sperm acrosome reaction (AR) in vitro. AR activity was present in the first two washes but not the third wash; however, AR activity was recovered in the spent medium after 3×‐washed fragments were incubated for 24 hr under conditions which maintained the viability of the cumulus cells. The spent media of preovulatory human mural granulosa cells contained AR‐initiating activity after 1–3, 3–6, and 6–9 days of culture. The properties of the AR activity present in spent media of human cumulus fragments included resistance to loss of activity during treatment with pronase; resistance to loss of activity during treatment with chondroitinase ABC or bacterial hyaluronidase; heat stability after overnight incubation; lack of extraction by chloroform‐methanol; an apparent molecular weight (MW) of 50,000, as determined by Sephadex G‐75 column chromatography; conversion to a lower apparent MW activity by incubation with pronase. These properties are also characteristic of a fraction derived by Sephadex G‐75 chromatography of preovulatory human follicular fluid which also has been shown to stimulate the human sperm acrosome reaction in vitro. The AR activity from spent media of human mural granulosa cells is also found in a 50,000 MW Sephadex G‐75 fraction. We propose that the sources of the 50,000 MW human follicular fluid AR activity are the cumulus oophorus and the mural granulosa cells.
Inhibition of RNA synthesis in embryo of Xenopus laevis by protease inhibitor
Authors: Miyata Shohei , Shimazaki Taketo , Okamoto Yoriyuki , Motegi Naoya , Kitagawa Mistuo , Kihara Hirozi K. 
Published: June 2005

AbstractWe have studied the role of proteases during the development of Xenopus laevis embryos with the aid of protease inhibitors. The activity of proteases was found to be only minimal in the unfertilized egg and during the initiation of development, but activity began to increase at the morula stage. When the activity of proteases was inhibited by antipain, an inhibitor of endopeptidase activity, RNA synthesis in the embryo was inhibited. To examine the relationship between the inhibitory effect of antipain on protease activity and its effect on RNA synthesis, antipain was reduced with NaBH4 to inactivate its protease inhibitory activity. The reduced antipain did not inhibit RNA synthesis in the embryo. Antipain effectively inhibited synthesis of both rRNA and poly(A)+RNA but not 4S RNA. We therefore suggest that protease activity plays an important role in the initiation and/or continuation of RNA synthesis.
First successful transfer of cryopreserved feline (Felis catus) embryos resulting in live offspring
Authors: Dresser B. L. , Gelwicks E. J. , Wachs K. B. , Keller G. L. 
Published: June 2005

AbstractSexually mature domestic cats were hormonally stimulated to induce superovulation; embryo recovery was accomplished by laparotomy. Embryos were frozen by conventional embryo freezing methods used in the domestic cattle embryo transfer industry. Thawing was achieved in a 28°C or 37°C waterbath or in ambient air. Overnight culture of the frozen‐thawed embryos in a supplemented Nutrient Mixture F‐10 (Ham's) or Earle's Balanced Salt Solution with 20% heat‐treated newborn calf serum resulted in five successful term litters from recipient queens. Embryo recipients who became pregnant had been treated with a subcutaneous injection of follicle‐stimulating hormone (FSH‐P) once every 24 hr for 6 days in the amount of 0.2 mg/day for the first 5 days and 0.1 mg on the sixth day, followed by two intramuscular 750 IU injections of human chorionic gonadotropin 24 hr apart, beginning on the same day as the sixth injection of FSH‐P.
Treatment of brachial nerves with colchicine inhibits limb regeneration in the newt Notophthalmus viridescens
Authors: Scadding Steven R. 
Published: June 2005

AbstractIn urodele amphibians, limb regeneration is dependent on innervation and is blocked by the administration of colchicine. The objective of this experiment was to determine if colchicine blocks limb regeneration by a direct action on the blastema cells or by an indirect action on the nerves, specifically, if colchicine treatment of the brachial nerves would inhibit limb regeneration in the newt Notophthalmus viridescens. Colchicine was applied to the nerves by implanting a colchicine‐loaded silastin block adjacent to the brachial nerves of an amputated newt limb. With appropriate dose levels of colchicine, limb regeneration was completely inhibited. Contralateral control limbs, carrying unloaded silastin blocks, and control limbs with colchicine‐loaded blocks implanted equidistant from the blastema, but not adjacent to the brachial nerves, regenerated normally. Thus, the results indicate that the colchicine inhibition of limb regeneration is mediated by colchicine effects on the nerves. The possible mechanism of colchicine action on nerves may involve either wallerian degeneration, or inhibition of axoplasmic transport, or both.
Aldehyde dehydrogenase activity in brain and liver of the rainbow trout (Salmo gairdneri Richardson)
Authors: Nilsson Göran E. 
Published: June 2005

AbstractAldehyde dehydrogenase (ALDH) activity was measured in brain and liver of rainbow trout by using 3,4‐dihydroxyphenylacetaldehyde (DOPAL, the biogenic aldehyde derived from dopamine) as the substrate. The amount of the corresponding acid produced was quantified by high‐performance liquid chromatography with electrochemical detection. Both in brain and liver, the ALDH activity showed a high affinity for the substrate with an apparent Km of 3.7 μM in brain and 2.4 μM in liver. The kinetic experiments with brain ALDH also indicated the presence of an isozyme with a low affinity for DOPAL with a Km around 150 μM. The Vmax of the liver ALDH activity varied between 179 and 536 nmol/min·g, i.e., about 25–75 times higher than that of the low‐Km activity in brain. The ALDH activity showed a maximum around pH 8.5, it was stimulated by Mg2+, and disulfiram was found to be a potent inhibitor of the enzyme. The results suggested that the majority of the ALDH activity was located in mitochondria (60–70% with regard to the brain and 70–80% with regard to the liver), while the remaining activity appeared to be cytosolic in both organs. No microsomal ALDH activity could be found.