bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitosis in the intact and regenerating planarian Dugesia mediterranea n.sp. II. Mitotic studies during regeneration, and a possible mechanism of blastema formation
Authors: Baguñà Jaume 
Published: June 2005

AbstractIn planarian regeneration mitosis occurs in both anterior and posterior blastemas. The mitotic increase is visible as early as one hour after amputation, reaches a rapid first maximum at 5–12 hours, a relative minimum at 24–30 hours, and a higher and longer second maximum at two to four days depending on body size, level of amputation, and on whether blastema is anterior or posterior. The spatial dynamics of mitosis show a rapid and high mitotic increase in the distal regions but not in the proximal regions. Later, the proliferative zone shifts in sucessive mitotic waves to more proximal regions, paralleling the formation of the head ganglia and nerve cords.These results do not agree with theories of blastema formation through neoblast migration or through cell dedifferentiation, in as much as the local proliferation of neoblasts encountered is sufficiently high and early to account for the number of blastema cells found during period of regeneration. Therefore, we suggest that blastema formation during planarian regeneration occurs mainly through local neoblast proliferation.These results and the data obtained on regeneration rates enable us to suggest that nervous tissue may be one of the factors responsible for the differing mitotic increases found. Since neoblasts are the only planarian cells capable of mitosis, we suggest that neoblast proliferation could be under nervous tissue control through some stimulatory substance (s) released from the nerve terminals. The implications of this hypothesis for the maintenance of axial polarity are also discussed.
Studies on immunoglobulins of Xenopus borealis, Xenopus clivii and Xenopus muelleri
Authors: Hadji‐Azimi Irandokht , Brandt Daniel , Bossus André , Michea‐Hamzehpour Mehrbanou 
Published: June 2005

AbstractFollowing immunization with human IgG three species of anuran amphibians, Xenopus borealis, Xenopus clivii and Xenopus muelleri, were found to synthesize two molecular populations of antibodies associated with 19S and 7S fractions of the sera. These antibodies, designated high (HMW) and low (LMW) molecular weight immunoglobulins, were isolated and their constituent heavy (H) and light (L) polypeptide chains separated following extensive reduction and alkylation in a relative yield of about 70% and 30% respectively. The molecular weights of H and L chains of the three species were determined by SDS‐acrylamide gel electrophoresis. The L chains from both molecules in the three species had a molecular weight of about 26,000. The H chains of the HMW and LMW immunoglobulins had a molecular weigh of about 73,000 and 63,000 respectively. The two populations of immuno globulins were analysed in immunodiffusion plates using rabbit antisera to LMW immunoglobulins. The HMW immunoglobulins were found to be antigenically deficient with respect to LMW immunoglobulins. From these results it was judged that the two populations in each species belonged to distinct classes. The antigenicities of the LMW and HMW immunoglobulins of different species within the genus Xenopus were compared.
Evidence for the role of a trypsin‐like enzyme in the hamster sperm acrosome reaction
Authors: Meizel Stanley , Lui Chung W. 
Published: June 2005

AbstractAcrosome reactions occurring in vitro in hamster sperm capacitated by bovine follicular fluid were severely inhibited by four synthetic trypsin inhibitors and by Zn2 +. Three polypeptide trypsin inhibitors and a synthetic chymotrypsin inhibitor did not inhibit the acrosome reaction, and Ca2 + overcame the inhibition by Zn2. These results suggest that a trypsin‐like enzyme (possibly acrosin) plays a role in the acrosome reaction.
Octopamine: Presence in firefly lantern suggests a transmitter role
Authors: Robertson Harold A. , Carlson Albert D. 
Published: June 2005

AbstractThe lantern of the adult firefly is innervated by a nerve supply with endings similar to other known monoaminergic nerves. However, catecholamines could not be detected in the nerve endings and noradrenaline and adrenaline were relatively weak agonists in eliciting a flash of light when applied to the lantern in vitro. Firefly lanterns were assayed for octopamine using a sensitive, specific enzymatic assay in which octopamine is enzymatically converted to 3H‐synephrine and quantitated by liquid scintillation counting. The presence of substantial amounts (125 ng/g tissue) of octopamine was demonstrated and confirmed by thin layer chromatography. On the basis of this and earlier work, it is suggested that the nerves to the firefly lantern are octopaminergic.
Locomotion of bluefish
Authors: DuBois Arthur B. , Cavagna Giovanni A. , Fox Richard S. 
Published: June 2005

Abstract

Pressures previously measured on the body surface of swimming bluefish were resolved into their backward vectorial components to allow calculation of profile drag. It was 0.18 kg at a speed of 1.8 m/sec. Tangential drag was calculated as if for a thin plate of an area equal to that of the fish. It was 0.08 kg at 1.8 m/sec. Net drag, 0.26 kg, was the sum of profile and tangential drag.
Thrust and drag also were calculated from the changes of acceleration measured during steady swimming, assuming that thrust took place only during the acceleration phase, whereas drag occurred during both acceleration and deceleration. This drag was 0.08 kg at a speed of 1.1 m/sec. It is compatible with the drag of 0.26 at 1.8 m/sec calculated from profile and tangential drag provided drag varies as the square of velocity.
The force required to produce maximal acceleration was measured during a scare. It was calculated to be 6.9 kg at a peak acceleration of 3 g.
The compression strength of the vertebrae was found to be approximately 20 kg per cm2, or roughly three times the force encountered during maximal acceleration. This safety factor of 3 would be reduced when the back was curved, or if opposing groups of muscles were under tension.
The finding that a bluefish can accelerate at 3 g and that the vertebral column is strong enough to withstand this force indicates that the muscles and body structure of a bluefish would be able to withstand the force of gravity if the fish were otherwise equipped for terrestrial life. This fish may have evolved these strengths simultaneously with land animals. It is speculated that other fish may have evolved some degree of strength to overcome inertia and drag during aquatic locomotion, and this evolution may have been a prelude to terrestrial locomotion.
Furrowing in altered cell surfaces
Authors: Rappaport R. 
Published: June 2005

AbstractUnderstanding the process which establishes the cell division mechanism requires analysis of the role of the responding surface as well as that of stimulatory subsurface structures. Cell surface was altered by the expansion which occurs during exovate formation. Exovates appear on the surface of fertilized Arbacia lixula, Paracentrotus lividus and Echinarachnius parma eggs in response to extreme flattening. They result from cytoplasmic outflow initiated in a very restricted portion of the egg surface. Observations of the formation process in pigmented A. lixula eggs revealed that the original surface may be expanded about 100‐fold as the exovate swells. When exovates formed 15–30 minutes after fertilization contain the mitotic apparatus, they divide synchronously with flattened controls. If nucleated exovates are established after the beginning of first cleavage, furrows appear in ten minutes. Exovates established after the beginning of second cleavage develop furrows four minutes after the entrance of the mitotic apparatus. Cytoplasm beneath damaged exovate surfaces sometimes develops partial constrictions independently of the surface in the plane the furrow would have occupied. These results suggest that normal surface structure is unnecessary for furrow establishment and function.
Effect of temperature on spermatogenesis, on the production and action of androgens and on the ultrastructure of gonadotropic cells in the lizard Anolis carolinensis
Authors: Pearson Anita K. , Tsui Hing Wo , Licht Paul 
Published: June 2005

AbstractAdult male lizards (Anolis carolinensis) were kept at either 31° or 20°C for 11 weeks starting December 4, and the activity of the pituitary‐gonadal axis was monitored by examination of pituitaries, testes, androgen target organs and plasma testosterone levels.The gonadotropic cells of both thermal groups were stimulated to secrete for approximately seven weeks. Thereafter, the cells of 31°C animals indicated reduced secretion and increased granule storage, while those at 20°C became hyperactive. Testes enlarged at both temperatures: testicular enlargement at 31°C was due to active spermatogenesis and sperm production, whereas at 20°C, gametogenesis was largely blocked at the spermatocyte level, and enlargement was due to accumulation of cells, growth, and hydration. Leydig cells were larger and more numerous at 31° Epididymal and kidney tubules (androgen target organs) increased in diameter and epithelial height at both temperatures, but responses were markedly greater at 31° Also, male‐male aggressive behavior occurred only at the higher temperature; dominant lizards had slightly higher testosterone levels than subordinates. In contrast, plasma testosterone levels were consistently higher (> 2‐fold) at 20°.Thus the production of gonadotropins in Anolis is stimulated at 20° in late winter, and these hormones promote androgen production but not spermatogenesis. The high androgen level at 20°C evokes only a limited response in epididymis and renal sex tubules, and it neither inhibits the gonadotropic cells of the pituitary nor produces aggressive behavior. These results demonstrate that constituent processes in the pituitary‐gonadal system have different sensitivities to temperature and that thermal effects may be misinterpreted by standard histological or histometric analysis of gonads and accessory sexual structure.
Adenosine 3′, 5′ ‐monophosphate, morphogenetic movements and embryonic neural differentiation in Pleurodeles waltlii
Authors: Wahn Harvey , Lightbody Laurace Townsend , Tchen T. T. , Taylor John D. 
Published: June 2005

AbstractEvidence is presented for the following hypothesis dealing with dibutyryl‐c‐AMP induction of neural differentiation in Pleurodeles waltlii embryos: (1) Dibutyryl‐c‐AMP induces the determination for neural differentiation. (2) Additional dibutyryl‐c‐AMP is not needed for cytodifferentiation. (3) Cytodifferentiation of induced cells can only take place after morphogenetic movements (in vivo) or extensive cell migrations (in vitro). It is suggested that cell migrations, both in vivo and in vitro, lead to the separation of the induced cells from one another or from unidentified inhibitory cells.
Effect of dithiothreitol on meiotic maturation of mouse oocytes in vitro: Dependence of the effect on N6,O2′‐dibutyryl adenosine 3′,5′‐cyclic monophosphate
Authors: Wassarman Paul M. , Turner Pamela E. 
Published: June 2005

AbstractThe inhibitory effect of dithiothreitol on meiotic maturation of mouse oocytes in vitro is a function of the intracellular dibutyryl cyclic AMP concentration. Inhibition of nuclear (germinal vesicle) breakdown by dibutyryl cyclic AMP is reversed upon transfer of oocytes to plain culture medium, where‐as, transfer to medium containing dithiothreitol results in continued inhibition. Dithiothreitol significantly enhances the effectiveness of dibutyryl cyclic AMP as an inhibitor of meiotic maturation. These results suggest that the reported effect of sulfhydryl reducing agents on membrane dissolution and reconstitution, in both meiotic and mitotic cells, may be attributed to their influence on intracellular levels of cyclic AMP.
An analysis of MP gene affected morphogenesis in Tetrahymena pyriformis, syngen 1, (Species 1) ciliates
Authors: Kaczanowski Andrzej 
Published: June 2005

AbstractThe recessive mp gene in syngen 1 (Species 1) of Tetrahymena pyriformis results in a characteristic set of abnormalities of the adoral membranelles, commonly including some extra membranellar segments (Kaczanowski, '75). The abnormal pattern is produced in about 10% of dividing cells, compared to 80% of cells undergoing oral replacement. Thus the percentage of abnormal cells increases during prolonged stationary phase. Abnormal oral replacement arises primarily from a separation of two kinetosomal fields: the field of kinety no. 1 (the K‐1 field), and the anterior field originating from the displaced undulating membrane. Both sites of proliferation appear also during wild type morphogenesis, but they fuse early to form one integrated field (Frankel, ′69). The prolonged separation of the subfields in mp/mp cells results in a separate assembly of adoral membranelles; however, the independently developing membranelles of the two subfields are united later to produce a single oral apparatus. A single gene‐dependent factor apparently alters some property of the cortical layer, which in turn is responsible for a reduced integrity of the oral replacement primordium.
Role of gill Na+ + K+ ‐dependent ATPase in acclimation of blue crabs (Callinectes sapidus) to low salinity
Authors: Towle David W. , Palmer Gloria E. , Harris John L. 
Published: June 2005

AbstractMale blue crabs (Callinectes sapidus Rathbun) were acclimated to salinities of 5 and 34 o/oo. Microsomal preparations of gills from these animals possessed Na+ + K+‐dependent ATPase specific activities of 2.33 ± 0.11 and 1.29 ± 0.11 μmoles Pi min per mg protein respectively, implicating the Na+ + K+‐dependent ATPase in the previously recognized ability of the blue crab to maintain high hemolymph sodium levels in low salinity environments. The specific ATPase activity of gill microsomes increased significantly within two and one‐half hours after transfer of crabs from high to low salinity, prior to stabilization of hemolymph sodium levels. The ATPase isolated from crabs acclimated to the two different salinities were both highly sensitive to ouabain, and required either K+ or NH4+ as well as Na+. Sodium‐dependent phosphorylation of both enzymes was blocked by K+ or NH4+. Polyacrylamide gel electrophoresis of the sodium dodecyl sulfate‐solubilized ATPases revealed one band of radioactivity in each case, with an apparent molecular weight of 104,000. The ability of NH4+ to serve as an effective counterion supports the hypothesis that, in blue crabs acclimated to low salinity, Na+ uptake may be coupled to NH4+ excretion.
Abnormal morphogenesis of feather structure and pattern in the chick embryo integument. I. Macroscopic description
Authors: Brotman Harris F. 
Published: June 2005

AbstractThe development of feathers in embryos from a profusely feathered line derived from a homozygous scaleless mutant stock was compared with that of embryos from a standard White Leghorn stock. The time of appearance of feather primordia, their structure and their arrangement all were altered in mutant embryos. Unit structures ranging in size from hillocks of 300 μ diameter (the size of normal primordia) to ridges 8 mm long were found in varying numbers in the different tracts of the mutant embryos. The hexagonal pattern characterizing feather primordia in normal embryos was disrupted in scaleless high line embryos. Differential growth and morphogenetic sculpting, as evidenced by the appearance of clefts, generate the form of and subdivide the variably shaped unit structures of the mutant as they elongate.Selection for high feather number was successful in dramatically increasing the total amount of feathering but the absence of coordinate controls of pattern and feather structure development led to the aberrant arrangement of tracts and of structures within the tracts. The basic pattern thus appears to have been destroyed by the scaleless mutation, and the alteration of the phenotype accomplished by selection has not apparently restored its control.
Natural hybridization between parthenogenetic and bisexual lizards: Detection of uniparental source by skin grafting
Authors: Cuellar Orlando , McKinney Charles O. 
Published: June 2005

AbstractSkin grafting evidence is used to directly identify the unisexual parent of natural hybrids produced between the bisexual species Cnemidophorus inornatus and the unisexual Cnemidophorus neomexicanus.Reciprocal grafts transplanted among three suspected hybrids between Cnemidophorus inornatus and Cnemidophorus neomexicanus are rejected as well as grafts from the hybrids to C. neomexicanus, indicating that the hybrids are each genetically different from each other and that C. neomexicanus has the ability to reject foreign grafts.Allografts among C. neomexicanus and xenografts from C. neomexicanus to the hybrids are not rejected, indicating that C. neomexicanus is genetically homogeneous and that the hybrids possess genomes genetically identical to C. neomexicanus.Electrophoretic analysis of the hybrids and their probable parents supports the evidence obtained from skin grafting that C. neomexicanus is one of the parents, and suggests that C. inornatus, rather than C. tigris, is the bisexual parent.Chromosome spreads obtained from the hybrids reveal a triploid number of 69, a number consistent with their presumed origin from unreduced diploid ova (2N =46) from C. neomexicanus and haploid sperm (N = 23) from C. inornatus.Preliminary evidence is presented of the first hybrids known between Cnemidophorus inornatus and Cnemidophorus uniparens. Histological examination of the testes suggests that these hybrids are sterile.Included is a list summarizing all known hybrids between bisexual and unisexual species of the genus Cnemidophorus.
Ionophore A23187 induces acrosome reactions in sea urchin and guinea pig spermatozoa
Authors: Summers R. G. , Talbot P. , Keough E. M. , Hylander B. L. , Franklin L. E. 
Published: June 2005

AbstractIonophore A23187, in the presence of extraceullular Ca+2, induces a morphologically normal acrosome reaction in sperm of the sea urchin and precocious acrosome reaction and activation of guinea pig sperm. Increased membrane permeability to Ca+2 is responsible for initiating the acrosome reaction in both sea urchin and guinea pig sperm. In sea urchin sperm, the permeability changes is brought about by egg jelly, whereas in the guinea pig sperm it accompanies capacitation.
The oral apparatus ofTetrahymena pyriformis, strain WH‐6. III. The binding of3H‐cytochalasin B by the isolated oral apparatus
Authors: Gavin R. H. 
Published: June 2005

AbstractThe binding of tritium‐labelled cytochalasin B by the isolated oral apparatus ofTetrahymena pyriformis, strain WH‐6, syngen 1, was investigated. Equilibrium binding studies revealed approximately 1.4 × 105cytochalasin B binding sites per oral apparatus. A Scatchard plot indicates a single class of binding affinities with an association constant of 105liters/mole. Rapid release of oral apparatus‐bound cytochalasin B occurred when oral apparatuses were washed and resuspended in 1 mM TRIS without cytochalasin B. Because cytochalasin B binding to oral apparatus microtubular protein was not detected, microtubules are probably not the cytochalasin B binding site. The probable nature of the cytochalasin B binding site within oral apparatus is discussed.
Biochemical changes in temperature‐activated statoblasts of an ectoproct bryozoan
Authors: Black Robert E. , Proud Virginia K. 
Published: June 2005

AbstractDormant Statoblasts germinate after prolonged treatment at 4° C, followed by incubation at 25° C. At 25° C, the activation period preceding germination is about 3 days; the polypide develops and buds once during the 3 days following germination. During the activation period, respiration increases 4‐fold and no significant changes in DNA, RNA or protein occur. Polysomes and ribosomes in the 8,000‐g supernatant increase. A dramatic 4‐fold increase in respiration occurs between 2 and 6 hours after germination, and little subsequent increase occurs. DNA and RNA increase steadily after germination, but protein remains constant. Actinomyc in D blocks post‐germination development but does not prevent germination. No germination inhibitor is released by statoblasts.
Response of the ovary in the catfish, Heteropneustes fossilis (Bloch), to various combinations of photoperiod and temperature
Authors: Vasal Sudhir , Sundararaj Bangalore I. 
Published: June 2005

AbstractResponses of the ovary of the catfish, Heteropneustes fossilis, to various regimes of photoperiod and temperature, were studied during the different periods of the annual ovarian cycle. During the preparatory and postspawning periods moderate temperatures of 25°C and above, regardless of photoperiod, were more favorable for the formation of yolky (stage III) oocytes than cooler temperature (below 23°C). Even under conditions of continuous dark or light, ovarian development occurred as a function of warm temperatures.Gravid ovaries were maintained beyond the spawning period only with a temperature of 30°C, photoperiod notwithstanding. Nevertheless, moderate or cool temperatures did not prevent the ovarian regression that occurred by the first week of October in the post‐spawning period. Regulation of ovarian activity at least in part by an endogenous circannual rhythm appears possible.
Mating‐type‐specific soluble factors (gamones) in cell interaction of conjugation in the ciliate Oxytricha bifaria
Authors: Esposito Fulvio , Ricci Nicola , Nobili Renzo 
Published: June 2005

AbstractSexual reproduction in Ciliates occurs through pair formation (conjugation) between cells of complementary mating types. In many species, after complementary cells are brought together, a waiting period ensues, which lasts up to the initial visible ciliary interaction leading to cell pairing. An exchange of information, mediated by soluble factors (gamones) takes place during the waiting period of Oxytricha bifaria. This hypotrich ciliate possesses a multiple mating type breeding system, and conjugation may thus occur between cells belonging to any two mating types. The excreted gamones being mating type specific, differ from each other. Any cell pretreated with any one of the complementary gamones starts pairing immediately after mixing. Thus cell interaction does not require heterologous cell to cell contact during the waiting period. A simple readily made apparatus to detect the exchange of information through soluble factors, is described.
The role of sodium and calcium lons in osmoregulation in Hydra littoralis
Authors: Koblick Daniel C. , Rufus Charles D. 
Published: June 2005

Abstract
The frequency of column contractions in Hydra littoralis (taken as a measure of the rate of water elimination) is maximal at about 5 × 10−4M Na+, and falls off markedly at higher and lower concentrations, even though total medium osmotic pressure is kept constant by replacement with K+.
Reduction in Ca++ concentration causes a reduction in the frequency of column contractions. This reduction is half‐maximal at about 4.8 × 10−4 M Ca++.
The significance of these findings in the light of the osmoregulatory mechanism in Hydra is discussed, and it is suggested that Na+ plays a regulatory role in the mechanism of extrusion of water and salts from the cells to the gastrovascular cavity.