bluuebunny/crossref_metadata_2025_split huggingface dataset:
The estrous cycle in golden hamsters: A circadian pacemaker times preovulatory gonadotropin release
Authors: Stetson Milton H. , Gibson Jeffrey T. 
Published: June 2005

AbstractIn a population of cycling female hamsters entrained to an LD 6:18 light cycle (lights 1000–1600 hours), preovulatory release of luteinizing hormone and follicle‐stimulating hormone occurred in some animals at 1300–1400 hours and in others at 1900 hours. In every case peak release was phase‐locked (2–3‐hour positive phase angle) to the circadian rhythm of locomotor activity. The pattern of entrainment of gonadotropin release on LD 6:18 is fully explicable in terms of the hamster's phase response curve to light. We conclude that periodic gonadotropin release in cycling females is timed by a circadian oscillator (biological clock) that is probably the same oscillator driving the circadian rhythm of locomotor activity.
Two types of hemocytes in localization of clottable protein in Japanese horseshoe crab, Tachypleus tridentatus
Authors: Shishikura F. , Chiba J. , Sekiguchi K. 
Published: June 2005

AbstractLocalization of clottable protein (CP) in hemocytes of the Japanese horseshoe crab, Tachypleus tridentatus, was investigated by a fluorescent antibody technique. The cytoplasmic granules in the minority of hemocytes (15%) were stained strongly and uniformly while those in the majority of hemocytes (85%) were not. In contrast, the cytoplasmic matrix of the majority was stained with various degrees of intensity and that of the minority was not. The two types of hemocytes which showed different intracellular localization of CP might be in different maturational stages or might play different roles in blood coagulation.
Incorrect connections made by a regenerating cockroach motoneuron
Authors: Whitington Paul M. 
Published: June 2005

AbstractAn identified cockroach motoneuron, mesothoracic cell 30, the fast excitatory motoneuron to the coxal depressor muscles, has been found to make connections with inappropriate muscles after regenerating to a leg from which its correct muscles had been excised. Thus the specificity of innervation shown by motoneurons regenerating to a normal, intact leg cannot be due solely to a one‐to‐one matching of motoneurons with muscles.
Synthesis of RNA by male pronuclei of fertilized sea urchin eggs
Authors: Longo Frank J. , Kunkle Mel 
Published: June 2005

AbstractExperiments have been conducted in an effort to determine when the paternally derived genome of sea urchin embryos becomes active in RNA synthesis. Participation of the paternal genome in RNA transcription as early as fertilization has been indicated by the following: (1) polyspermic zygotes consistently demonstrate greater levels of incorporation of labelled precursor (3H‐uridine) into RNA when compared to monospermic eggs. (2) Monospermic and polyspermic eggs treated with actinomycin D show the same levels of incorporation of label into RNA. (3) Analysis of autoradiographs demonstrates the incorporation of 3H‐uridine into male and female pronuclei.
Heart rate response to light in the embryo of the Japanese quail (Coturnix coturnix)
Authors: Ockleford Elizabeth M. , Vince Margaret A. 
Published: June 2005

AbstractThe effects of exposure to light were investigated during and shortly after the period of light stimulation. A particular objective was to evaluate any responses to the type of illumination conditions generally used for observation of avian embryos. Twenty 16‐day Japanese quail embryos were illuminated for 15 minutes each during a total recording period of 55 minutes. Heart rate, respiration rate and an approximate measure of activity were recorded. Mean heart rate was found to be higher during stimulation than before and did not return to the prestimulation level during the recording period after stimulation ceased. The lack of an immediate heart rate response to the onset of stimulation separates the effects of light from those of touch, rotation, odours, tastes and maternal calls. The possibility that light may act to stimulate accelerated development is discussed.
Segregation during cleavage of a factor determining endodermal alkaline phosphatase development in ascidian embryos
Authors: Whittaker J. R. 
Published: June 2005

AbstractLocalized alkaline phosphatase activity (EC 3.1.3.1) develops progressively in endodermal tissues of the presumptive digestive system in Ciona intestinalis embryos. It was first detected histochemically at late gastrulation, and a puromycin sensitivity period coincident with this time suggests that new alkaline phosphatase is synthesized. Embryos in which cell division was blocked with cytochalasin B at early cleavage stages up to the 64‐cell stage, eventually differentiated strong alkaline phosphatase activity in certain cells at each cleavage‐arrested stage. The maximum cell numbers and their positions were identical to those of the previously known endodermal cell lineage. Actinomycin D did not prevent development of endodermal alkaline phosphatase when administered from fertilization onwards, nor did other inhibitors of RNA synthesis (chromomycin A3, cordycepin, and daunomycin). There is probably a preformed maternal mRNA for endodermal alkaline phosphatase present in the unfertilized Ciona egg. Either this RNA itself, or some related translation factor, is localized in the egg cytoplasm and segregated during early cleavages into the endodermal cell lineage of the embryo.
Effects of neurotransmitters upon the discharge of secretory product from the cutaneous glands of the red‐spotted newt
Authors: Hoffman Charles W. , Dent James Norman 
Published: June 2005

AbstractThe effects of sympathetic and parasympathetic agonists and antagonists on discharge of secretory product by the granular and mucous glands were examined in the red‐spotted newt, Notopthalmus viridescens viridescens. Observations were made also on the South African clawed toad, Xenopus laevis, the grass frog, Rana pipiens, and the crested newt, Triturus cristatus.In contrast to the granular glands of the South African clawed toad and the grass frog, which were stimulated by α‐adrenergic agents, those of the red‐spotted newt discharge in response to acetylcholine, either in vitro when added to the Holtfreter's solution in which explants were incubated, or in vivo when injected subcutaneously. Granular glands of the crested newt were also discharged in response to subcutaneous injection of acetylcholine. Stimulation of the granular glands by acetylcholine was blocked by atopine but not by tubocurarie, indicating that the cholinergic receptors are muscarinic rather than nicotinic. The mucous glands of the red‐spotted newt, on the other hand, did not discharge in response to either acetylcholine or to adrenergic agents.
Evidence for multiple cell surface chicken fetal‐leukemic antigens (CFA) in the developing chick and other avian species
Authors: Dietert R. R. , Sanders B. G. 
Published: June 2005

AbstractChicken fetal antigen (CFA), a membrane antigen present on fetal chicken red blood cells is lost with chicken development, and reappears on the red blood cells of leukemic chickens. Seven avian species were found to possess CFA. A species hierarchy comparing the quantitative expression of CFA has been established. The levels of CFA expression with development are compared in the chicken and Japanese quail.Specific adsorptions of R‐anti‐CFA with avian red blood cells revealed the existence of multiple CFAs. Four groups of antigenic determinants (CFA a,b,c,d) have been characterized and defined by their expression among avian species. Multiple CFA determinants are discussed with regard to possible membrane alterations and gene function.
Regulation of cell proliferation in tadpole limb epidermis by thyroxine
Authors: Wright Mary L. 
Published: June 2005

AbstractThe mechanism of thyroxine control of cell proliferation was investigated by studying cell cycle kinetics in limb epidermis of control and thyroxine‐treated Rana pipiens tadpoles using repeated labeling and construction of percent labeled mitoses curves. Changes in labeling index may be attributed primarily to alteration in either the relative length of S in the cell cycle (S/T), or the growth fraction of the cell population. In limb bud epidermis of Stage III tadpoles growth fraction, like labeling index, increased in basal cells but did not change in outer layer after 24 hours of 3, 30 or 300 μg/l thyroxine treatment. Changes in cell cycle parameters, however, were small and similar in both outer and basal layers, and there was no appreciable change in S/T. At Stages IX to XI, changes in labeling index and growth fraction were also parallel. Both parameters increased in intermediate and basal cells but decreased in outer layer after 30 or 300 μg/l thyroxine treatment for 48 hours. In addition, there was a decrease in S/T, due to a lengthening of G1 + ½M and a shortening of S. The cell cycle changes at Stages IX to XI were similar in all layers as at Stage III, regardless of whether labeling index increased or decreased. The results indicate that the specific changes in labeling index observed during thyroxine‐induced growth and differentiation of limb epidermis are linked closely to regulation of size of the proliferative pool, although alterations in cell cycle parameters are of some significance in older tadpoles.
The presence of sperm‐specific surface isoantigens on the egg following fertilization
Authors: O'Rand Michael G. 
Published: June 2005

AbstractSperm surface isoantigens can be detected on the surface of fertilized eggs by using cytotoxic (complement dependent) sperm‐specific isoantisera. These isoantigens cannot be detected on unfertilized eggs. This may indicate their transfer from sperm to egg during fertilization.
Pigment cell differentiation in embryonic mouse skin and isolated epidermis: An in vitro study
Authors: Mayer Thomas C. , Oddis Leroy 
Published: June 2005

AbstractPigment cell differentiation was studied in cell cultures derived from 14‐day embryonic mouse skin, and in cultures of dermal or epidermal skin cells. Cell cultures from dissociated whole skin produced melanocytes in very small numbers, and they were always present in association with groups of epithelial‐like cells. Cell cultures from dissociated dermis produced no melanocytes during the three week culture period.Epidermal cultures established from mechanically produced small aggregates of cells first formed melanocytes after 30 hours in culture, and large numbers of melanocytes were present after two days. Epidermal cells, in contrast to other cells, did not survive in culture beyond 11 days, and consequently surviving populations of pure melanocytes were left remaining on the plate surface. Epidermal cultures prepared from albino embryos resulted in amelanotic melanocyte populations remaining following the epidermal cell death. Epidermal cell cultures from white‐spotting mutant embryos (W/W and S1/S1) left no cells on the plate recognizable as being of the pigment cell lineage. The enhancement of melanoblast differentiation by epidermal cells, and the relationship between melanocytes and epidermal cells revealed in cell culture may be useful in the analysis of early stages of melanoblast differentiation, and in the study of mechanisms of gene action involved in this process.
Photokinesis and behavioral thermoregulation in adult sea lampreys (Petromyzon marinus)
Authors: McCauley Robert W. , Reynolds William W. , Huggins Norman H. 
Published: June 2005

AbstractPhotokinetic responses of adult sea lampreys were used to facilitate study of their thermoregulatory behavior in a laboratory thermal gradient. Lampreys swam about actively when room lights were switched on, but attached themselves to the side walls at temperature‐dependent sites in the gradient when lights were turned off. Attachment sites were significantly correlated with temperature (correlation coefficient = 0.73, p < 0.01). Acete mean preferred temperature of five lampreys, previously acclimated at 10°C, was 14.3 ± 3.0 (S.D.) °C. This is the first experimental demonstration of behavioral thermoregulation in this ancient class of jawless vertebrates (Agnatha).
Are sugar residues involved in the specific cell recognition of mating in Paramecium?
Authors: Kitamura Akio , Hiwatashi Koichi 
Published: June 2005

AbstractTo characterize the chemical nature of the substances responsible for the agglutinative mating reaction in Paramecium caudatum, the effects of a variety of reagents on the mating activity of detached cilia were studied quantitatively. Treatment of mating‐reactive cilia with sodium periodate (NaIO4) markedly decreases mating activity of the cilia. However, the addition of sodium aspartic acid or pre‐treatment with 5% formalin inhibits the NaIO4‐inactivation. This result indicates that the oxidation of some surface components of cilia other than the mating substances is responsible for this inactivation. Five kinds of glycosidases, α‐mannosidase, α‐L‐fucosidase, β‐galactosidase, β‐glucosidase and neuraminidase, have no demonstrable effect on the mating acitivity of the cilia. On the other hand, trypsin destroys the mating activity even in a concentration as low as 0.00001%. These results strongly suggest that no sugar moiety is directly involved in the mating agglutination in P. caudatum.
Inhibition of “spontaneous,” notochord‐induced, and collagen‐induced in vitro somite chondrogenesis by the calcium ionophore, A23187
Authors: Kosher Robert A. 
Published: June 2005

AbstractThe present study represents a first step in investigating the possible involvement of calcium (Ca2+) in the stimulation of somite chondrogenesis elicited by extracellular matrix components produced by the embryonic notochord. The ionophore, A23187, a drug that facilitates Ca2+ uptake leading to elevation of cytoplasmic Ca2+ levels, at concentrations of 0.25–1.0 ug/ml severely impairs “spontaneous” somite chondrogenesis, i.e., inhibits the formation of the small amount of cartilaginous matrix normally formed by embryonic somites in vitro in the absence of inducing tissues. This inhibition is reflected in a considerable reduction in sulfated glycosaminoglycan (GAG) accumulation by A23187‐treated somite explants. Furthermore, A23187 inhibits the striking stimulation of cartilaginous matrix formation and sulfated GAG accumulation normally elicited by the embryonic notochord and collagen substrates. In fact, 1.0 μg/ml of A23187 reduces sulfated GAG accumulation by somites cultured in association with notochord or on collagen to a level even below that accumulated by somites cultured in the absence of these inductive agents. Although these results must be interpreted with caution, they provide incentive for considering a possible regulatory role for Ca2+ in the chondrogenic response of somites to extracellular matrix components produced by the embryonic notochord.
Effects of ecdysterone, inokosterone and eyestalk ablation on limb regeneration in the fiddler crab, Uca pugilator
Authors: Rao K. Ranga 
Published: June 2005

AbstractBilateral ablation of eyestalks or injection of either ecdysterone or inokosterone (two 25‐μg doses or five 10‐μg doses into crabs weighing on an average 1.5 g) caused precocious proecdysis and ecdysis in the fiddler crab, Uca pugilator. On a weight basis ecdysterone was more effective than inokosterone in exerting the effects. Whether the accelerated proecdysis was accompanied by regenerative limb growth depended on the degree of limb bud development at the time of treatment with ecdysones. Ecdysterone and inokosterone blocked the initiation of basal limb growth when administered as two 25‐μg doses into crabs exhibiting scar tissue without any visible limb bud. When injected into crabs with limb buds in various stages of basal limb growth exogenous ecdysones accelerated basal limb growth and led to proecdysial limb growth. The degree of acceleration of limb bud growth noticed within three to six days after injection of ecdysones into crabs with limb buds in early stages of basal limb growth was greater than that resulting from eyestalk ablation. In crabs with limb buds in later stages of basal growth, the degree of acceleration of limb bud growth evoked by exogenous ecdysones was similar to that resulting from eyestalk ablation. The final sizes of the limb buds preceding ecdysis in eyestalkless crabs and crabs injected with ecdysones depended on the proecdysial duration available for regeneration.The rate of proecdysial limb growth has been known to vary with the speed at which the crabs complete the proecdysial stages of the molt cycle. This study shows that the time required for the initiation and completion of the basal limb growth also varies depending on how soon the intact and eyestalkless crabs approach proecdysis and ecdysis.
A correlation between the activity of divalent cation activated adenosine triphosphatase in the cell membrane and low salinity tolerance of the ribbed mussel, Modiolus demissus demissus
Authors: Watts John A. , Pierce Sidney K. 
Published: June 2005

AbstractA comparison was made between the bound divalent cation stimulated adenosine triphosphatase (ATPase) activity of the cell membrane and the regulation of free amino‐acid (FAA) permeability in the myocardium of the bivalve (Modiolus demissus) during isosmotic and hypoosmotic stress. The FAA efflux induced by isosmotic, divalent cation free, artificial sea water (ASW) was reduced by Ca2+, Mg2+, Mn2+ and Co2+ at concentrations non‐lethal to the intact heart. However, the order of effectiveness in reducing the efflux was not the same as the effectiveness of the divalent cations on the stimulation of ATPase activity. In addition, ATPase activity with the concentrations of Ca2+ and Mg2+ in full strength ASW or in 50% ASW was inhibited by Co2+ and stimulated by Mn2+ Under isosmotic conditions, modification of ATPase activity by Co2+ or Mn2+ did not alter FAA permeability. However, during hypoosmotic stress, the recovery of normal FAA permeability correlated with divalent cation activated ATPase activity; increased enzyme activity in the presence of Mn2+ was coincident with a decreased FAA efflux and decreased enzyme activity in the presence of Co2+ accompanied an increased FAA efflux.Therefore, the recovery of normal FAA permeability during a hypoosmotic stress is correlated with divalent ATPase activity. During isosmotic conditions, FAA permeability may be controlled by divalent cation binding.
The role of extra cellular material in chick neurulation. II. Surface morphology of neuroepithelial cells during neural fold fusion
Authors: Lee Hsin‐Yi , Sheffield Joel B. , Nagele Robert G. 
Published: June 2005

AbstractChanges in cell surface morphology of the neuroepithelium during fusion of neural folds in the chick were studied. As the folds were about to meet, a thick extra cellular coat material (ECM) appeared between the two leading edges. Cell membranes forming the fusion area were relatively smooth and heavily coated with ECM. By contrast, the apical surface of most cells lining the wall of the neural tube was folded with much less ECM. During the contact of neural folds, ECM was displaced from the space between the two leading edges, leaving a thin, closely adherent “typical” cell surface coat. Trypsin and concanavalin A inhibited proper alignment and fusion of apposing neural folds by modifying the surface of developing neuroepithelium. Results of this study support a hypothesis that ECM may serve temporarily as an adhesive to bind together the leading edges of neural folds until establishment of more intimate contacts (junctional complexes).
Preconjugant cell‐cell interaction in the ciliate Euplotes crassus: A possible role of the ciliary ampules
Authors: Verni F. , Rosati G. , Luporini P. 
Published: June 2005

AbstractEuplotes crassus, like other species of Euplotes, possesses organelles commonly known as ampules, which are associated with the roots of cilia and organelles composed of cilia. Ampules of E. crassus greatly increase their functional activity during the cellular interaction which takes place after mixing cells of complementary mating type. Material is rapidly stored in the ampules, starting a few minutes after cell mixing, until a maximum of full ampules is reached in congregated cells which are closely approaching each other. Once the interacting cells have entered the agglutinative stages, the ampules show a dramatic decrease in their contents, so that cells just paired carry very few ampules filled by material.We infer that the material contained in the ampules has an important role in making the mixed cells competent to unite in pairs.
Estradiol‐17β interference with meiotic maturation in Rana pipiens ovarian follicles: Evidence for inhibition of 3β‐hydroxysteroid dehydrogenase
Authors: Spiegel Judith , Jones Elizabeth , Snyder B. W. 
Published: June 2005

AbstractIncreasing doses of estradiol‐17β added to in vitro incubations inhibited pregnenolone‐induced germinal vesicle breakdown in Rana pipiens ovarian follicles. The inhibition was reversed with increasing concentrations of pregnenolone added to the medium. Because no evidence of estradiol‐17β inhibition or interaction with progesterone‐induced GVBD was observed, the effect of estradiol‐17β on the conversion of 3H‐pregnenolone to 3H‐progesterone was investigated. Estradiol‐17β in doses as low as 10−7 M significantly inhibited the conversion of 3H‐pregnenolone to 3H‐progesterone in follicles incubated in vitro. It is suggested that estradiol‐17β is a feedback inhibitor of 3β‐hydroxysteroid dehydrogenase‐isomerase, the enzyme complex that converts pregnenolone to progesterone, a necessary step in the initiation of GVBD.
Effect of trypsin inhibitors and Concanavalin A on the fertilization of Bufo arenarum coelomic oocytes
Authors: Cabada Marcelo O. , Mariano Marta I. , Raisman Jorge S. 
Published: June 2005

AbstractThe effect of trypsin inhibitors (obtained from soybean, lima bean and ovomucoid) and Concanavalin A on fertilization in Bufo arenarum was tested. In order to study the effect of these substances at the level of the vitelline envelope of the oocytes, a new bioassay was designed. This bioassay employs coelomic oocytes to which some oviducal factors necessary for their fertility was added.Trypsin inhibitors block both the lytic effect of the acrosomal proteases on the vitelline envelope and fertilization. This indicates that the blockade of fertilization is a consequence of the inhibition of the lytic effect of the acrosomal proteases.Concanavalin A is effective as well in blocking the lytic effect of acrosomal proteases and fertilization. These effects are reversed by some sugar antagonists of the lectin, thus indicating that the effect of Concanavalin A is through its saccharide‐binding capacity. These results suggested the involvement of glucosidic residues of the vitelline envelope in amphibian fertilization (the saccharide residues might be involved in the attack of the vitelline envelope by the acrosomal proteases).The possible mechanism of action of these substances is discussed.