bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytoskeletal organization of rat oocytes during metaphase II arrest and following abortive activation: A study by confocal laser scanning microscopy
Authors: Zernicka‐Goetz Magdalena , Kubiak Jacek Z. , Antony Claude , Maro Bernard 
Published: February 2005

AbstractIn metaphase II arrested rat oocytes (M il), microtubles were found in the taper‐shaped meiotic spindle and in the cytoplasm as asters and free microtubules. Whereas spindle microtubules were acetylated, those located in the cytoplasm were not. Cytoplasmic microtubules were also labile as assessed by mild cooling. In contast to mouse oocytes, rat microtubule organizing centers (MTOCs) did not react with MPM‐2 antibody by immunofluorescence despite the fact that this antibody reacts with several proteins as shown by immunoblot. However, cytoplasmic MTOCs in M II‐arrested rat oocytes could be detected by their nucleating capacity in the presence of taxol, a drug that induced the formation of numerous cytoplasmic asters. In addition, taxol caused a change in the spindle shape and the formation of astral microtubules at the spindle poles. Meiotic spindles (as well as chromosomes devoid of microtubules after nocodazoletreatment) were overlaid by an actin‐rich domain. Spontaneous abortive activation led to the extrusion of the second polar body followed by another metaphase arrest— metaphase III; however, normal spindles did not form and dispersed chromosomes surrounded by microtubles were observed. Electron microscopic studies confirmed these observations and revealed that the kinetochores are located deep within the chromosomes in contrast to mouse kinetochores, and this might be responsible for the absence of a metaphase III spindle in the rat oocyte. Induced activation caused transition to interphase with the formation of a characteristic microtubule network. This study shows that there are several significant differences in the cytoskeletal organization of rat and mouse oocytes. © 1993 Wiley‐Liss, Inc.
Binding characteristics and immunolocalization of porcine seminal protein, PSP‐I
Authors: Kwok Simon C. M. , Soares Michael J. , McMurtry John P. , Yurewicz Edward C. 
Published: February 2005

AbstractPSP‐l, a 13 kDa protein purified from boar seminal plasma, was found to have about 50% amino acid sequence homology with a family of zona pellucida‐binding proteins known as spermadhesins. These proteins are produced by the accessory gland(s) of the male reproductive tract and coat the spermatozoa during ejaculation. In this study, we have investigated the possible biological functions of PSP‐I using a solid‐phase protein binding assay and its site of synthesis using both Western blot and immunocytochemical analyses. PSP‐I was found to bind a number of proteins including endo‐β‐galactosidase digested ZP3, soybean trypsin inhibitor, lgA, lgG and α‐casein, indicating that it may have multiple functions. The protein or carbohydrate structures were not critical in the binding, since polyvinyl sulfate could effectively inhibit the binding of PSP‐l to these proteins. Western blot analysis using specific antiserum to PSP‐l showed that the protein was present in the seminal vesicle but not in the testes, epididymis or prostate. The protein was revealed by immunocytochemical analysis in the epithelium of seminal vesicles but not in the testes or the epididymis. It is concluded that PSP‐I is synthesized by the epithelium of the seminal vesicles, secreted into the semen during ejaculation, and may be involved in various reproductive functions, such as preventing premature acrosome reaction and immunosuppression. © 1993 Wiley‐Liss, Inc.
Changes in ovarian follicles and in vitro sex hormone release in the lizard Podarcis sicula sicula
Authors: Ciarcia Gaetano , Paolucci Marina , Di Fiore Maria Maddalena 
Published: February 2005

AbstractAn in vitro superfusion method was used to test sex hormone release from different kinds of ovarian follicle (growing follicles, postovulatory follicles, and atretic follicles) in the lizard Podarcis sicula sicula. Sex hormone output changes with the stage of follicle evolution and sexual cycle. Previtellogenetic follicles prevail in early‐spring quiescent ovaries and secrete mainly progesterone, which is probably utilized at that phase to delay ovarian resumption. In the active ovary, progesterone output from previtellogenetic follicles decreases, whereas vitellogenetic follicles produce a significant amount of 17β‐estradiol, which is necessary for sustaining vitellogenin synthesis by the liver and oviduct growth. As follicles become ripe, progesterone production is resumed, and it increases in young postovulatory follicles. This is in line with the functions assigned to the hormone at that phase of the sexual cycle, i.e., the induction of oocyte maturation and the regulation of egg retention in the oviduct. Postovulatory follicles can also synthetize 17β‐estradiol. After oviposition, this hormone, which is secreted by the old postovulatory follicles, can reinitiate vitellogenin synthesis, allowing the development of a new oocyte set. Our data confirm that active, although ephemeral, corpora lutea are also formed in oviparous species. A limited contribution to ovarian sex steroid production derives also from atretic follicles, at least at the early stages of the breeding cycle. © 1993 Wiley‐Liss, Inc.
Lysophosphatidylcholine disrupts the acrosome of tammar wallaby (macropus eugenii) spermatozoa
Authors: Sistina Yulia , Lin Minjie , Rodger John C. 
Published: February 2005

AbstractThe acrosomal status of wallaby spermatozoa was evaluated by light and electron microscopy after incubation in 1–100 μM lysophosphatidylcholine (LPC) for up to 120 min. Treatment with 1 and 10 μM LPC for 120 min did not lead to acrosomal loss, or detectable alteration to the acrosome, as detected by Bryan's staining and light microscopy. Incubation with 25 μM LPC had little effect on acrosomal loss, however statistically significant changes (P < 0.05) in the acrosomal matrix (altered) were detected after 10‐min incubation by light microscopy. Around 50% of acrosomes were altered after 20‐min incubation in 50 μM LPC (P < 0.001), and 40% of spermatozoa had lost their acrosome after 60‐min incubation (P < 0.001). Treatment with 75 and 100 μM LPC led to rapid acrosomal loss from around 50% of spermatozoa within 10 min (P < 0.001), and by 60 min acrosomal loss was 70–80%. LPC, like the diacylglycerol DiC8 (1,2‐di‐octanoyl‐sn‐glycerol), is thus an effective agent to induce loss of the relatively stable wallaby sperm acrosome, and it also induces changes within the acrosomal matrix.Ultrastructure of the LPC‐treated spermatozoa revealed that the plasma membrane and the acrosomal membranes were disrupted in a manner similar to that seen after detergent treatment (Triton X‐100). There was no evidence of point fusion between the plasma membrane overlying the acrosome and the outer acrosomal membrane. The plasma membrane was the first structure to disappear from the spermatozoa. The acrosomal membranes and matrix showed increasing disruption with time and LPC concentration. Wallaby spermatozoa incubated with LPC at concentrations that induced significant acrosomal loss also underwent a rapid decline in motility that suggested that acrosomal loss may be due to cell damage, rather than a physiological AR. This study concluded that LPC‐induced acrosomal loss from tammar wallaby spermatozoa is due to its action as a natural detergent and not as a phosphoinositide pathway intermediate. The study further demonstrates the unusual stability of the marsupial acrosomal membranes. © 1993 Wiley‐Liss, Inc.
Biochemical characterization and epididymal localization of the maturation‐dependent ram sperm surface antigen ESA152
Authors: Weaver Frances E. , Dino Judith E. , Germain Bonnie J. , Wolf David E. , Fairbanks Grant 
Published: February 2005

AbstractWe examine here the biochemical properties and epididymal localization of a maturation dependent ram sperm surface antigen. A monoclonal antibody, ESA152, identifies an antigen that is present on the surface of ejaculated sperm, but is absent from testicular sperm. Crosslinking of the ESA152 antigen with bivalent antibodies induces the acrosome reaction, redistributing the antigen into the anterior region of the sperm head where it associates with the fusion product of the plasma membrane and the outer acrosomal membrane. The ESA152 antigen appears as a polypeptide of 18 kDa on immunoblots of SDS‐polyacrylamide gels. The ESA152 epitope includes the sialic acid termini of N‐linked oligosaccharides, as shown by its sensitivity to neuraminidase and endoglycosidase F. The ESA152 antigen is a highly hydrophobic integral membrane protein that resists aqueous extraction, partitions into the detergent phase of Triton‐X‐114, and solubilizes in chloroform‐methanol mixtures. The anchoring of ESA152 is unaffected by phosphtidylinositol specific phospholipase C. The antigen is absent from extracts of caput and corpus epididymidis but appears abruptly in the first segment of the cauda. Immunofluorescence reveals that the ESA152 epitope first appears in clusters of cells in the luminal epithelium of the proximal cauda, prior to or concurrent with its appearance on sperm. © 1993 Wiley‐Liss, Inc.
Molecular dynamics of insulin/IGF‐I receptor transmembrane signaling
Authors: Pessin Jeffrey E. , Frattali Anne L. 
Published: February 2005

AbstractTo examine the molecular basis of ligand‐stimulated intramolecular β‐subunit autophosphorylation, hybrid receptors composed of wild‐type and mutantinsulin and insulin‐like growth factor‐1 (lGF‐l) half‐receptor precursors were characterized. Previous studies have demonstrated that assembly of the IGF‐I wild‐type half‐receptor (αβWT) with a kinase‐defective half‐receptor (αβA/K) produced a substrate kinase‐inactive holoreceptor in vitro [Treadway et al. (1991): Proc Natl Acad Sci USA 88:214–218]. To extend these studies, the vaccinia virus/ bacteriophage T7 expression system was used to generate various hybrid receptor complexes in cultured cells. As was observed for hybrid receptors assembled in vitro, the wild‐type/mutant hybrid receptors formed in situ were also incapable of phosphorylating several peptide substrates. However, ligand‐stimulated β‐subunit autophosphorylation was still observed. To determine the molecular basis for this discrepancy, hybrid receptors were assembled from a truncated β‐subunit insulin half‐receptor (αβδ43). and a kinase‐defective half‐receptor (αβA/K). Under these conditions, insulin‐stimulated autophosphorylation primarily oc‐curred on the full‐length kinase‐inactive β‐subunit (αβA/K) without significant labeling of the kinase‐active truncated β‐subunit (αβδ43). A similar IGF‐I hybrid receptor species was characterized, and the same pattern of autophosphorylation was observed in response to IGF‐I. These data demonstrate that both insulin and IGF‐I stimulate an intramolecular trans‐autophosphorylation reaction between two adjacent β‐subunits within the holoreceptors. Furthermore, our data suggest that trans‐phosphorylation between two functional β‐subunits is required for substrate kinase activation of the insulin and IGF‐I holoreceptors. These results suggest a molecular basis for the dominant‐negative phenotype observed in heterozygous, insulin‐resistant patients possessing one kinase‐defective insulin receptor allele. © 1993 Wiley‐Liss, Inc.
IGF binding proteins and their functions
Authors: Clemmons David R. 
Published: February 2005

AbstractThe insulin‐like growth factor (IGF) binding proteins (IGFBPs) have several functions, including transporting the IGFs in the circulation, mediating IGF transport out of the vascular compartment, localizing the IGFs to specific cell types, and modulating both IGF binding to receptors and growth‐promoting actions. The functions of IGFBPs appear to be altered by posttranslational modifications. IGFBP‐3, ‐4, ‐5, and ‐6 have been shown to be glycosylated. Likewise all the IGFBPs have a complex disulfide bond structure that is required for maintenance of normal IGF binding. IGFBP‐2, ‐3, ‐4, and ‐5 are proteolytically cleaved, and specific proteases have been characterized for IGFBP‐3, ‐4, and ‐5. Interestingly, attachment of IGF‐I or II to IGFBP‐4 results in enhancement of proteolysis, whereas attachment of either growth factor to IGFBP‐5 results in inhibition of proteolytic cleavage. Cleavage of IGFBP‐3 results in the appearance of a 31 kDa fragment that is 50‐fold reduced in its affinity for the IGF‐I or IGF‐II. In spite of the reduction in its affinity, this fragment is capable of potentiating the effect of IGF‐I on cell growth responses; therefore, proteolysis may be a specific mechanism that alters IGFBP modulation of IGF actions. Other processes that result in a reduction in IGF binding protein affinity are associated with potentiation of cellular responses to IGF‐I and ‐II. Specifically, the binding of IGFBP‐3 to cell surfaces is associated with its ability to enhance IGF action and with a ten‐ to 12‐fold reduction in its affinity for IGF‐I and IGF‐II. Likewise, binding of IGFBP‐5 to extracellular matrix (ECM) results in an eightfold reduction in its affinity and a 60% increase in cell growth in response to IGF‐I. Another post‐translational modification that modifies IGFBP activity is phosphorylation. IGFBP‐1, ‐2, ‐3, and ‐5 have been shown to be phosphorylated. Phosphorylation of IGFBP‐1 results in a sixfold enhancement in its affinity for IGF‐I and ‐II. Following this enhancement of IGFBP‐1 affinity, this binding protein loses its capacity to potentiate IGF‐I growth‐promoting activity. Future studies using site‐directed mutagenesis to modify these proteins should enable us to determine the effect of these posttranslational modifications on the ability of IGFBPs to modulate IGF biologic activity. © 1993 Wiley‐Liss, Inc.
Fertilization and early embryonic development in the blue fox (Alopex lagopus)
Authors: Farstad W. , Hyttel P. , Grøndahl C. , Mondain‐Monval M. , Smith A. J. 
Published: February 2005

AbstractA total of 15 blue fox vixens aged 1–6 years were mated, 12 once on the first day of estrus and three a second time 48 hr after the first mating, and were killed 4 hr to 8 days following mating. Ova were collected from the oviducts, evaluated by stereomicroscopy, and studied by transmission (TEM; N = 49, 12 vixens) or scanning (SEM, N = 11, three vixens) electron microscopy. At 0–3 days after ovulation, the ova had not cleaved and were at different stages of meiotic maturation. In about one‐half of these ova, representing all stages of meiotic maturation, a decondensing sperm head without nuclear envelope or a small pronucleus with partial nuclear envelope was observed. No clear relationship was found between maternal meiotic stage and the stage of paternal pronucleus formation. Sperm tails were never identified in the ooplasm. Cortical granules were released after sperm penetration at early stages of meiotic maturation. Thus the block against polyspermic penetration was activated during maturation of the oocyte. The first two‐cell stage appeared 4 days after ovulation (3 days after mating), the first four‐cell stage the following day (day 5), and the first eight‐cell stage 6 days after ovulation (5 days after mating). In a single vixen mated late (7 days postovulation) two‐ to four‐cell stages appeared the following day (day 8). This indicates that the time required for the first cleavage division decreases with increasing interval from ovulation to mating. The development of a functional nucleolus with fibrillar centers and fibrillar and granular components at the eight‐cell stage indicates activation of embryonic RNA synthesis in fox embryos at the six‐ to eight‐cell stage, suggesting that the embryonic genome is activated at this stage. © 1993 Wiley‐Liss, Inc.
Derivation and characterization of putative pluripotential embryonic stem cells from preimplantation rabbit embryos
Authors: Graves Kathy H. , Moreadith Randall W. 
Published: February 2005

AbstractWe have derived putative embryonic stem (ES) cell lines from preimplantation rabbit embryos and report here their initial characterization. Two principal cell types emerged following serial passage of explanted embryos, and each has subsequently given rise to immortalized cell lines. One cell type has morphology identical to primary outgrowths of trophectoderm, is strictly feeder‐cell dependent, and spontaneously forms trophectodermal vesicles at high cell density. The second type appears to represent pluripotent ES cells derived from the inner cell mass as evidenced by (1) ability to grow in an undifferentiated state on feeder layers, (2) maintenance of a predominantly normal karyotype through serial passage (over 1 year), and (3) ability to form embryoid bodies, which form terminally differentiated cell types representative of ectoderm, mesoderm, and endoderm. These ES cells may ultimately be suitable for introduction of germline mutations (via homologous recombination). The rabbit's size, reproductive capability, and well‐characterized physiology make it suitable for a wide range of investigations, particularly for development of large animal models of human disease. © 1993 Wiley‐Liss, Inc.
Identification of receptor tyrosine kinases in the rat testis
Authors: Loveland Kate Lakoski , Hedger Mark P. , Risbridger Gail , Herszfeld Daniella , De Kretser David M. 
Published: February 2005

AbstractEvidence of receptor/ligand interactions that regulate testis cell function was sought in order to broaden the current understanding of the molecular basis of testis cell function. Using reverse transcription and the polymerase chain reaction, we have obtained novel evidence for the expression of three mRNAs encoding receptor tyrosine kinases in the adult rat testis: the platelet‐derived growth factor type A receptor (PDGF‐RA), the basic fibroblast growth factor receptor (flg), and fetal liver kinase 1 (Flk‐1). A 6.8 kb transcript encoding the PDGF‐RA was observed in RNA prepared from testes of rats aged day 5 through adult, with a decline in relative abundance with increasing age after day 17. Analysis of mRNA from isolated cell preparations (day 21 Sertoli cells, adult Leydig cells, round spermatids, and primary spermatocytes) and testes depleted of specific cell types [ethane dimethane sulfonate (EDS)‐treated and cryptorchid] indicated that the Leydig cell was the predominant source of this mRNA in the adult testis. The addition of PDGF‐BB to cultures of highly purified adult rat Leydig cell preparations resulted in a 40% increase in LH‐stimulated testosterone production, confirming a role for this growth factor in regulation of Leydig cell function. These data indicate that the Leydig cell is a principal site of action of PDGF in the testis. © 1993 Wiley‐Liss, Inc.
cis‐Acting DNA elements involved in oocyte‐specific expression of mouse sperm receptor gene mZP3 are located close to the gene's transcription start site
Authors: Lira Sergio A. , Schickler Michael , Wassarman Paul M. 
Published: February 2005

AbstractWe report that cis‐acting DNA elements involved in oocyte‐specific expression of the mouse sperm receptor gene (mZP3) are located close to the gene's transcription start site. Mice bearing a transgene that consists of only 153 nt of mZP3 5′‐flanking region fused to the firefly luciferase gene (153‐ZP3/LUC) expressed the reporter gene in ovary not in a wide variety of tissues; although two of three lines carrying 153‐ZP3/LUC also expressed the transgene in forebrain and hypothalamus. Within the ovaries of transgenic mice, luciferase activity was restricted to growing oocytes. However, levels of luciferase activity in these oocytes were lower than those in oocytes from mice bearing transgenes that contain a larger segment of mZP3 5′‐flanking region (470–6,500 nt) fused to the firefly luciferase gene. Mice bearing a trans‐gene that consists of 470 nt of mZP3 5′‐flanking region and mZP3 intragenic sequences (ZDT) were also analyzed. The presence of mZP3 intragenic sequences did not result in significantly increased levels of firefly luciferase activity in oocytes of mice carrying the ZDT transgene. Overall, these results suggest that as little as 153 nt of mZP3 5′‐flanking region is sufficient to target expression of the firefly luciferase gene to mouse oocytes and that the mZP3 intragenic sequences probably do not contain enhancer elements. Rather, enhancer elements are probably present between — 153 and — 470 nt of the mZP3 5′‐flanking region. © 1993 Wiley‐Liss, Inc.
Evidence for a cannabinoid receptor in sea urchin sperm and its role in blockade of the acrosome reaction
Authors: Chang Michael C. , Berkery Diana , Schuel Regina , Laychock Suzanne G. , Zimmerman Arthur M. , Zimmerman Selma , Schuel Herbert 
Published: February 2005

AbstractDelta‐9‐tetrahydrocannabinol ((−)δ9 THC), the primary psychoactive cannabinoid in marihuana, reduces the fertilizing capacity of sea urchin sperm by blocking the acrosome reaction that normally is stimulated by a specific ligand in the egg's jelly coat. The bicyclic synthetic cannabinoid [ H]CP‐55,940 has been used as a ligand to demonstrate the presence of a cannabinoid receptor in mammalian brain. We now report that [ H]CP‐55,940 binds to live sea urchin (Strongylocentrotus purpuratus) sperm in a concentration, sperm density, and time‐dependent manner. Specific binding of [ H]CP‐55,940 to sperm, defined as total binding displaced by (−)δ9 THC, was saturable: KD 5.16 ± 1.02 nM; Hill coefficient 0.98 ± 0.004. This suggests a single class of receptor sites and the absence of significant cooperative interactions. Sea urchin sperm contain 712 ± 122 cannabinoid receptors per cell. Binding of [ H]CP‐55,940 to sperm was reduced in a dose‐dependent manner by increasing concentrations of CP‐55,940, (−)δ9 THC, and (+)δ9 THC. The rank order of potency to inhibit binding of [ H]CP‐55,940 to sperm and to block the egg jelly stimulated acrosome reaction was: CP‐55,940 > (−)δ9THC > (+)δ9THC. These findings show that sea urchin sperm contain a stereospecific cannabinoid receptor that may play a role in inhibition of the acrosome reaction. The radioligand binding data obtained with live sea urchin sperm are remarkably similar to those previously published by other investigators using [ H]CP‐55,940 on mammalian brain and nonneural tissues. The cannabinoid binding properties of this receptor appear to have been highly conserved during evolution. We postulate that the cannabinoid receptor may modulate cellular responses to stimulation. © 1993 Wiley‐Liss, Inc.