bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mouse embryonic stem cells express receptors of the insulin family of growth factors
Authors: Shi C. Z. , Dhir R. N. , Kesavan P. , Zhang S. L. , Matschinsky F. M. , Heyner S. 
Published: February 2005

AbstractInsulin and insulin‐like growth factors (IGF‐I and ‐II) are members of a family of growth factors which are known to be developmentally regulated during preimplantation mouse embryogenesis. The physiological actions of the insulin family of growth factors are mediated by interactions with specific cell surface receptors that are detectable on the cells of preimplantation mouse embryos. Mouse embryonic stem (ES) cells are totipotent cells derived directly from the inner cell mass of the blastocyst. ES cells have the ability to differentiate into all three germ layers and have unlimited growth potential under certain culture conditions. The great advantage of ES cells is the ability to obtain large amounts of tissue for biochemical studies as compared with preimplantation embryos. To examine in greater detail the biological actions of the insulin family of growth factors, the expression of their cognate receptors on ES cells was examined. ES cells were cultured in DMEM medium supplemented with leukemia inhibitory factor (LIF) to maintain the undifferentiated state. Receptor expression was evaluated at the mRNA level using the reverse transcription polymerase chain reaction (RT‐PCR), and at the protein level by radioactive labeled ligand‐receptor binding assay. Using RT‐PCR, mRNAs of all three growth factor receptors were detected in ES cells. Messenger RNA from ES cells was reverse transcribed into cDNA by AMV reverse transcriptase at 42°C for 1 hr. The reverse transcription reaction was amplified with Taq polymerase and specific primers for insulin, IGF‐I, or IGF‐II receptors by PCR. RT‐PCR and the control plasmid cDNA PCR products were resolved electrophoretically on 3% agarose gels. Each amplified PCR product showed the predicted correct size. The target sequence of RT‐PCR amplified fragments were further verified by restriction enzyme digestion. The expression of receptors at the protein level was confirmed by Scatchard analysis, which showed specific binding of the radiolabeled ligands. This study shows that ES cells may provide a useful model to study the biological actions of the insulin family growth factors. © 1995 wiley‐Liss, Inc.
Xenopus lipovitellin 1 is a Zn2+‐ and Cd2+‐binding protein
Authors: Sunderman F. William , Antonijczuk Katarzyna , Antonijczuk Adam , Grbac‐Ivankovic Svetlana , Varghese Alison H. , Korza George , Ozols Juris 
Published: February 2005

AbstractThis report discusses the identification of a Zn2+‐ and Cd2+‐binding protein of Xenopus laevis that is abundant in vitellogenic oocytes and in embryos from fertilization to stage 46. Oocyte or embryo homogenates were fractionated by SDS‐PAGE, blotted onto nitrocellulose, and probed with 65Zn2+ or 109Cd2+. The resulting autoradiograms showed binding of both radio‐nuclides to a protein, designated pCdZn. Freon extraction of oocyte and embryo homogenates showed pCdZn to be a yolk protein. When pCdZn was isolated from oocyte homogenates by ammonium sulfate precipitation, delipidation, and chromatography, it co‐purified with lipovitellin 1. The amino acid composition of pCdZn closely resembled the reported composition of lipovitellin 1 and the molecular weight of purified pCdZn (∼115 kD) corresponded to reported values for lipovitellin 1 (111–121 kD). Amino acid sequence analyses of five peptides derived from pCdZn yielded 94% identity to the reported sequence of lipovitellin 1, deduced from the DNA sequence of the Xenopus vitellogenin A2 precursor gene. Based on these findings, pCdZn was identified as lipovitellin 1. This study suggests that lipovitellin 1 is the major storage protein for zinc in mature oocytes and developing embryos of Xenopus laevis. © 1995 wiley‐Liss, Inc.
Carbendazim (MBC) disrupts oocyte spindle function and induces aneuploidy in hamsters exposed during fertilization (meiosis II)
Authors: Zuelke Kurt A. , Perreault Sally D. 
Published: February 2005

AbstractPeri‐fertilization exposure to Carbendazim (MBC; a microtubule poison) induces infertility and early pregnancy loss in hamsters. Presently, both in vivo and in vitro techniques were employed to characterize the effects of MBC on cellular aspects of fertilization in hamsters. Exposure to MBC during either in vivo or in vitro fertilization (IVF) induced identical morphological abnormalities in the maternal chromatin of zygotes and embryos. These abnormalities included either multiple second polar bodies (PB2), and/or multiple small female pronuclei (PN), or meiotic arrest. Multiple PB2, multiple female PN, multiple PB2 with multiple female PN, or meiotic arrest were exhibited by approximately 31%, 15%, 12%, and 2% of the in vivo zygotes; and 3%, 16%, 36%, and 20% of IVF zygotes, respectively. The effects of MBC persisted to day 2 of pregnancy as indicated by decreased (P ≤ 0.05) embryo development to the two‐cell stage and the presence of micronuclei in 6% of two‐cell embryos from MBC‐treated females. Immunofluorescence analysis of microtubules (MTs) confirmed that MBC disrupted spindle MTs during IVF. Numerical chromosome analysis revealed that a single dose of MBC administered during in vivo fertilization induced aneuploidy in the resulting pronuclear‐stage zygotes. The present data point to two mechanisms by which peri‐fertilization MBC exposure may induce early pregnancy loss: 1) arrested meiosis with no zygotic cleavage; or 2) induction of zygotic aneuploidy with subsequent developmental arrest. © 1995 wiley‐Liss, Inc.
Analysis of the motility parameters of in vitro hyperactivated hamster spermatozoa
Authors: Shivaji S. , Peedicayil J. , Devi L. Girija 
Published: February 2005

AbstractGolden hamster cauda epididymal spermatozoa under in vitro capacitating conditions exhibited time‐dependent transformation of motility pattern, and the frequency of occurrence of a particular motility type was found to be dependent on the depth of the motility chamber used. The nonhyperactivated spermatozoa with planar motility were the most predominant at 0 hr irrespective of the depth of the motility chamber. But spermatozoa with the helical motility pattern were not detectable up to 6 hr when the Makler chamber was used, whereas in both the slide chamber and cannula, by 2 hr such spermatozoa constituted 90% of the total spermatozoa. However, by 6 hr the hyperactivated circular moving spermatozoa were the predominant type in all the chambers. Sperm motility chamber depths were also found to effect the motility parameter values of hamster spermatozoa, but this effect was also found to be dependent on the type of motility. Increase in chamber depth did not alter any of the motility parameter values of spermatozoa with hatchet type of motility and only increased the amplitude of lateral head displacement (ALH) in planar type. But in spermatozoa with the helical type of motility, an increase in chamber depth increased the progressive velocity (VSL), path velocity (VAP), curvilinear velocity (VCL), straightness (STR), linearity (LIN), and ALH. In spermatozoa with the circular type of motility, an increase in VSL, VAP, VCL, and ALH was also observed, but STR and LIN decreased. The hyperactivated spermatozoa could be distinguished from the nonhyperactivated spermatozoa because the former were swimming in circles, had low progressive velocity, decreased straightness and linearity of path, and also exhibited an increase in the amplitude of lateral head displacement compared to the nonhyperactivated spermatozoa. Further, the spermatozoa with helical motility could be differentiated from the nonhyperactivated, circular, and hatchet spermatozoa in that they had the highest VSL, VAP, VCL, and ALH. Spermatozoa with hatchet movement were slow and exhibited very low STR and LIN. Thus the motility parameters could be used to distinguish the nonhyperactivated and hyperactivated distal cauda epididymal spermatozoa. © 1995 wiley‐Liss, Inc.
Bovine cumulus cell expansion does not depend on the presence of an oocyte secreted factor
Authors: Ralph J. H. , Telfer E. E. , Wilmut I. 
Published: February 2005

AbstractCommunication between the oocyte and its somatic cells has been shown to be important in oocyte development. Here we examined how the oocyte may be involved in bovine cumulus cell expansion. Intact bovine cumulus oocyte complexes (COC) were obtained by puncturing antral follicles. From the intact COC, oocytectomised complexes (OOX) were produced by micro surgical removal of the oocyte. Clumps of cumulus cells (CC) were obtained by micro‐dissection. Intact or OOX complexes or CC were matured in the presence of fetal calf serum and hFSH (6 mlU/ml) for 24 hr and the degree of expansion measured. The presence of the oocyte is not essential to allow bovine cumulus expansion to occur as expansion occurred in all groups. Murine OOX complexes from eCG primed 35–40‐day‐old C57BL6/CBA F1 hybrids (known to require the presence of an oocyte secreted factor for cumulus expansion) were cultured with or without denuded bovine oocytes (1 oocyte/μl). Murine OOX complexes expanded only in the presence of denuded bovine oocytes. Thus some factor produced by bovine oocytes enabled expansion of murine OOX complexes. To determine whether the factor is secreted by bovine oocytes, murine OOX were cultured with or without media conditioned by bovine oocytes (1 oocyte/μl for 4 hr). Significant expansion of murine OOX occurred in media conditioned by bovine oocytes. This shows that the cumulus expansion enabling effect of bovine oocytes is released into the surrounding media. Media conditioned by bovine oocytes and then frozen for up to 1 month showed that the activity by the factor can withstand freezing. © 1995 wiley‐Liss, Inc.
Intracellular calcium reaches different levels of elevation in hyperactivated and acrosome‐reacted hamster sperm
Authors: Suarez Susan S. , Dai Xiaobing 
Published: February 2005

AbstractCalcium plays a role in sperm motility hyperactivation and the acrosome reaction, but the relationship between cytoplasmic calcium (Ca2+ in) levels in the two states was heretofore unknown. The Ca2+ indicator indo‐1 was used to detect Ca2+in in moving hamster sperm in two sets of experiments. In the first experiment, activated, hyperactivated, and zona pellucida‐induced acrosome‐reacted/hyperactivated sperm were analyzed at the time of peak of activity for each state. In the second experiment, sperm in all states were analyzed at one time point. In both sets, mean Ca2+in in the acrosomal region, postacrosomal region, and flagellar midpiece was greater in hyperactivated sperm than in activated sperm, and in acrosome‐reacted/hyperactivated sperm than in unreacted/hyperactivated sperm (P ≤ 0.001). Ca2+in had increased to a greater extent in the midpiece than in the head in hyperactivated sperm, while the reverse was true for acrosome‐reacted sperm. Oscillations at the frequency of the flagellar beat cycle were detected chiefly in the proximal flagellar midpiece of acrosome‐reacted sperm, as they had been previously reported to occur in activated and hyperactivated sperm. Thus, Ca2+in may be maintained at two different elevated levels in sperm, and continues to oscillate after the acrosome reaction. © 1995 wiley‐Liss, Inc.
Differential incorporation of fatty acids into and peroxidative loss of fatty acids from phospholipids of human spermatozoa
Authors: Alvarez Juan G. , Storey Bayard T. 
Published: February 2005

AbstractIntact human sperm incorporated radiolabelled fatty acids into membrane phospholipids when incubated in medium containing bovine serum albumin as a fatty acid carrier. The polyunsturated fatty acids were preferentially incorporated into the plasmalogen fraction of phospholipid. Uptake was linear with time over 2 hr; at this time sufficient label was available to determine the loss of fatty acids under conditions of spontaneous lipid peroxidation. Loss of the various phospholipid types, the loss of the various fatty acids from these phospholipids, and the overall loss of fatty acids were all first order. The loss of saturated fatty acids was slow with first order rate constant k1 = 0.003 hr−1; for the polyunsaturated fatty acids, arachidonic and docosahexaenoic acids, k1 = 0.145 and 0.162 hr−1, respectively. The rate of loss of fatty acids from the various phospholipid types was dependent on the type, with loss from phosphatidylethanolamine being the most rapid. Among the phospholipid types, phosphatidylethanolamine was lost at the greatest rate. Analysis of fatty acid loss through oxidation products was determined for radiolabelled arachidonic acid. Under conditions of spontaneous lipid peroxidation at 37°C under air in the absence of albumin, free arachidonic acid was found in the medium, along with minor amounts of hydroxylated derivative. All the hydroperoxy fatty acid remained in the cells. In the presence of albumin, all the hydroperoxy fatty acid was found in the supernatant bound to albumin; none could be detected in the cells. Albumin is known as a very potent inhibitor of lipid peroxidation in sperm; its action may be explained, based on these results, as binding the damaging hydroperoxy fatty acids. These results also indicate that a phospholipase A2 may act in peroxidative defense by excising a hydroperoxy acyl group from phospholipid and providing the hydroperoxy fatty acid product as substrate to glutathione peroxidase. This formulation targets hydroperoxy fatty acid as a key intermediate in peroxidative degradation. © 1995 wiley‐Liss, Inc.
Identification of a circulatory and oocytic avian apolipoprotein D
Authors: Vieira Amandio V. , Lindstedt Ken , Schneider Wolfgang J. , Vieira Päivi M. 
Published: February 2005

AbstractApolipoprotein D (apo D) is an unusual apolipoprotein with respect to structure and sites of synthesis. It has been identified in the circulatory system of certain mammals, but its physiological role remains poorly understood. In this report, it is shown that apo D is not exclusively a mammalian apolipoprotein, and evidence is presented which suggests a novel function for this protein during oogenesis in the chicken. The avian apo D which we identify has the same molecular mass (29 kDa) as the human protein and also associates preferentially with the plasma lipoprotein fraction. In addition to the 29 kDa avian apo D species, an immunoreactive 24 kDa protein is observed in chicken serum. The chicken apo D (along with the 24 kDa species) is also demonstrated to be present in the yolk of the rapidly growing chicken oocyte, a cell with high endocytic activity. Clathrin‐coated vesicles from chicken oocytes, which we have previously shown to contain specific lipoproteins along with their oocytic receptors (Bujo et al., 1994: EMBO J 13:5165–5175), also contain chicken apo D. Thus, apo D represents a novel candidate for plasma‐to‐oocyte transport of lipids and/or their mobilization during embryogenesis in oviparous species. © 1995 wiley‐Liss, Inc.
Transcriptional regulation by MAP kinases
Authors: Davis Roger J. 
Published: February 2005

AbstractTyrosine kinase growth factor receptors activate MAP kinase by a complex mechanism involving the SH2/3 protein Grb2, the exchange protein Sos, and Ras. The GTP‐bound Ras protein binds to the Raf kinase and initiates a protein kinase cascade that leads to MAP kinase activation. Three MAP kinase kinase kinases have been described‐c‐Raf, c‐Mos, and Mekk—that phosphorylate and activate Mek, the MAP kinase kinase. Activated Mek phosphorylates and activates MAP kinase. Subsequently, the activated MAP kinase translocates into the nucleus where many of the physiological targets of the MAP kinase signal transduction pathway are located. These substrates include transcription factors that are regulated by MAP kinase phosphorylation (e.g., Elk‐1, c‐Myc, c‐Jun, c‐Fos, and C/EBPβ). Thus the MAP kinase pathway represents a significant mechanism of signal transduction by growth factor receptors from the cell surface to the nucleus that results in the regulation of gene expression.Three MAP kinase homologs have been identified in the rat: Erk1, Erk2, and Erk3. Human MAP kinases that are similar to the rat Erk kinases have also been identified by molecular cloning. The human Erk1 protein kinase has been shown to be widely expressed as a 44‐kDa protein in many tissues. The human Erk2 protein kinase is a 41‐kDa protein that is expressed ubiquitously. In contrast, a human Erk3‐related protein kinase has been found to be expressed at a high level only in heart muscle and brain. The loci of these MAP kinase genes are widely distributed within the human genome: erk2 at 22q11.2; erk1 at 16p11.2; and ek3‐related at 18q12‐21.In the yeast Saccharomyces cerevisiae, five MAP kinase gene homologs have been described: smk1, mpk1, hog1, fus3, and kss1. Together, these kinases are a more diverse group than the human erks that have been identified. Thus the erks are likely to represent only one subgroup of a larger human MAP kinase gene family. A candidate for this extended family of MAP kinases is the c‐Jun NH2‐terminal kinase (Jnk), which binds to and phosphorylates the transcription factor c‐Jun at the activating sites Ser‐63 and Ser‐73. Evidence is presented here to demonstrate that Jnk is a distant relative of the MAP kinase group that is activated by dual phosphorylation at Tyr and Thr. © 1995 wiley‐Liss, Inc.
Interactions between Ras and Raf: Key regulatory proteins in cellular transformation
Authors: Marshall Mark 
Published: February 2005

AbstractRas proteins function during cell growth and development as essential, plasma membrane‐bound signaling proteins. Current evidence suggests that Ras is part of a signal transduction chain extending from extracellular signals to transcriptional regulation in the nucleus. Growth factor and cytokine activation of many tyrosine kinase and kinase‐linked receptors recruits many proteins to the plasma membrane including Ras‐specific guanine nucleotide releasing proteins (GNRP). Under the influence of a GNRP, Ras proteins bind GTP, resulting in activation of the Ras signal. The GTP‐bound form of Ras is capable of interacting directly with RasGAP, neurofibromin, and the Raf kinases. Although believed to be endowed with some signaling capacity, RasGAP and neurofibromin act primarily to negatively regulate Ras. Based upon genetic and biochemical studies in a variety of diverse organisms, the Raf kinases are considered the primary targets of Ras signaling. Activation of the Raf kinases is the first step in a cascade of multiple protein kinases, including Mek, Erk1, and Erk2.We are attempting to understand structurally how activated Ras proteins interact specifically with Raf kinases to induce the downstream signals necessary for cell division. Using mutagenesis, peptide epitope scanning, and in vitro reconstitution of protein interactions, we have identified specific sites of association between the Ras‐GTP and c‐Raf‐1 proteins. The interaction between these contact points is essential for the plasma membrane localization of Raf, which ultimately leads to kinase activation. The formation of this protein complex is negatively regulated by protein kinase A (PKA) through phosphorylation of the c‐Raf‐1 N‐terminus. Phosphorylation of c‐Raf‐1 serine 43 is believed to cause an N‐terminal cap structure to cover the Ras docking site. © 1995 wiley‐Liss, Inc.
Dissection of the Torso signal transduction pathway in Drosophila
Authors: Perrimon Norbert , Lu Xiangyi , Hou Xianyu Steven , Hsu Jui‐Chou , Melnick Michael B. , Chou Tze Bin , Perkins Lizabeth A. 
Published: February 2005

AbstractCell fate choice at the anterior and posterior embryonic termini of the Drosophila embryo requires the activation of a signal transduction pathway regulated by the receptor tyrosine kinase Torso. When Torso, which is uniformly distributed in the egg cell membrane, becomes activated locally at the termini, it triggers a phosphorylation cascade that culminates with localized expression of the transcription factors, tailless and huckebein. Expression of tailless and huckebein in turn determines terminal cell fates. Several genes have been characterized which encode proteins that are involved in Torso signaling: the adaptor protein Drk, the GTP‐binding protein Ras1, the guanine nucleotide exchange factor Son of sevenless, and the kinases D‐Raf and D‐Mek. Genetic and molecular evidence supports a model in which these proteins lie in the same biochemical pathway. When activated by its ligand the membrane‐bound receptor tyrosine kinase Torso initiates a signal transduction pathway mediated by Drk, Sos, and Ras1, which in turn activates a phosphorylation cascade mediated by the kinases D‐Raf and D‐Mek, which ultimately control the localized expression of the transcription factors tailless and huckebein. Recently, we found that D‐Raf can be partially activated by Torso in the absence of Ras1, a finding supported by the phenotype of embryos lacking either Drk or Sos activity, as well as by the phenotype of a D‐raf mutation that abolishes binding of Ras1 to D‐Raf. These findings indicate that full D‐Raf activation requires input not only from Ras1 but also from an as yet uncharacterized Ras1‐independent pathway. In addition to these molecules we have characterized the putative protein tyrosine phosphatase Corkscrew as a positive transducer downstream of Torso. © 1995 wiley‐Liss, Inc.
Influence of grain type on the insecticidal efficacy of two diatomaceous earth formulations against Rhyzopertha dominica (F) (Coleoptera: Bostrychidae)
Authors: Kavallieratos Nickolas G , Athanassiou Christos G , Pashalidou Foteini G , Andris Nickolas S , Tomanović Željko 
Published: February 2005

AbstractLaboratory bioassays were carried out in order to evaluate the effectiveness of two diatomaceous earth (DE) formulations, Insecto and SilicoSec, against adults of Rhyzopertha dominica (F) in eight different grain commodities. The adherence of the two DEs to each grain was also measured. The eight grains tested were wheat, whole barley, peeled barley, oats, rye, triticale, rice and maize. These commodities were treated with the DEs at three rates, 0.75, 1.0 and 1.5 g DE kg−1 grain. The mortality of R dominica adults was measured after 24 h, 48 h, 7 days and 14 days of exposure in the treated grains at 26 °C and 55% RH. After the 14‐day mortality count, all adults were removed and the treated grains retained under the same conditions for a further 60 days. The treated grains were subsequently examined for F1 progeny. Significant differences were recorded among the eight grain types as well as between the DE formulations tested. After 14 days of exposure, even at the lowest DE rate for both formulations, adult mortality was high (>90%) in wheat and triticale. In contrast, adult mortality was significantly lower in peeled barley. Increasing the rate improved the efficacy of the DEs significantly in only some of the grains tested. Reproductive capacity in all the treated grains was significantly suppressed when compared with untreated grains. Generally, more F1 individuals of R dominica were noted in the treated peeled barley than in the other commodities. Significant differences in the percentage of DE retention were noted among the eight grains. The highest retention level was noted in rice (>87%) and the lowest in maize (<6%). However, the degree of DE adherence to a given grain was not always indicative of the effectiveness of DE against R dominica. Copyright © 2005 Society of Chemical Industry