bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural changes in sperm from the fiddler crab, Uca tangeri (crustacea, brachyura), during the acrosome reaction
Authors: Medina Antonio , Rodriguez Antonio 
Published: February 2005

AbstractThe acrosome reaction (AR) was induced in sperm from the brachyuran crustacean Uca tangeri either by mixing male and female gametes in filtered seawater or by treating the spermatozoa with the divalent cation ionophore A23187. This latter method provided a sufficient number of reacted spermatozoa to allow a detailed ultrastructural study of the AR. The process consists of two separate phases: (a) initial release of the acrosomal vesicle contents, and (b) further elongation of the acrosomal filament, which causes reversal of the rigid capsule limiting the acrosomal vesicle contents. The elongate acrosomal filament consists of an apical perforatorium and a basal columnar structure called here the proximal piece. The former derives from the perforatorium of the uninduced sperm stage with only small ultrastructural changes. The proximal piece forms from myelin‐like membrane layers which are initially distributed all around the subacrosomal region and then accumulate in a column at the perforatorial base, thus promoting a sudden forward projection of the perforatorium. The AR in brachyurans is thought to be a passive mechanism that utilizes the negative pressure exerted on the nucleus—caused by emptying of the acrosomal vesicle—for an organized accumulation of membrane‐rich material immediately behind the perforatorium, with the final result of the raising of a 3 μm long acrosomal filament. © 1992 Wiley‐Liss, Inc.
Analysis of the expression of a large number of novel genes isolated from mouse prepubertal testis
Authors: Starborg Maria , Brundell Eva , Höög Christer 
Published: February 2005

AbstractThe analysis of genes expressed in a restricted temporal and spatial manner during spermatogenesis has given insights into different gene‐regulatory mechanisms active in germ cells. However, very few genes have so far been described that are predominantly active in spermatogonia and the early meiotic cell types of testis. To isolate a battery of such genes, more than 100 different mRNA molecules were isolated from a mouse prepubertal testicular cDNA library, and their expression patterns in different tissues analyzed. Thirty mRNAs, 26 of them previously not described in the literature, were found to be predominantly expressed in mouse testis. A detailed analysis of their expression patterns identified a number of mRNA molecules differentially expressed in testicular cell types, including both germ cells and somatic cell types. Characterization of these mRNAs also revealed five distinct temporal phases of gene expression during prepubertal germ cell development. Three different genes, mainly active in the spermatogonial and the early meiotic cell types of testis, were isolated and will be used to characterize further stage‐specific gene expression during germ cell differentiation. © 1992 Wiley‐Liss, Inc.
Identification of a mouse B‐type cyclin which exhibits developmentally regulated expression in the germ line
Authors: Chapman Deborah L. , Wolgemuth Debra J. 
Published: February 2005

AbstractTo begin to examine the function of cyclins in mammalian germ cells, we have screened an adult mouse testis cDNA library for the presence of B‐type cyclins. We have isolated cDNAs that encode a murine B‐type cyclin, which has been designated cycB1. cycB1 was shown to be expressed in several adult tissues and in the midgestation mouse embryo. In the adult tissues, the highest levels of cycB1 transcripts were seen in the testis and ovary, which contain germ cells at various stages of differentiation. The major transcripts corresponding to cycB1 are 1.7 and 2.5 kb, with the 1.7 kb species being the predominant testicular transcript and the 2.5 kb species more abundant in the ovary. Examination of cDNAs corresponding to the 2.5 kb and 1.7 kb mRNAs revealed that these transcripts encode identical proteins, differing only in the polyadenylation signal used and therefore in the length of their 3′ untranslated regions. Northern blot and in situ hybridization analyses revealed that the predominant sites of cycB1 expression in the testis and ovary were in the germinal compartment, particularly in early round spermatids in the testis and growing oocytes in the ovary. Thus cycB1 is expressed in both meiotic and postmeiotic cells. This pattern of cycB1 expression further suggests that cycB1 may have different functions in the two cell types, only one of which correlates with progression of the cell cycle. © 1992 Wiley‐Liss, Inc.
Mediation of the actions of insulin and insulin‐like growth factor‐1 on preimplantation mouse embryos in vitro
Authors: Harvey Mark B. , Kaye Peter L. 
Published: February 2005

AbstractPrevious studies showed that both insulin and insulin‐like growth factor‐1 (IGF‐1) stimulate metabolism and growth of preimplantation embryos. Because the effects of insulin occur with very low doses, it was suggested that its effects were mediated by its own receptors. However, the effects of IGF‐1 occurred at higher doses, suggestive of cross reaction with the insulin receptor but still in the range for mediation via its own receptor. The aim of this study was to investigate the mediation of the metabolic and growth effects of insulin and IGF‐1 using a specific insulin receptor antagonist. The antagonistic B‐10 Fab fragment (B‐10f) completely blocked stimulation of protein synthesis by both insulin and IGF‐1, indicating that the insulin receptor mediates this action of both hormones. Alternately, only insulin's stimulation of inner cell mass mitogenesis and morphological development was inhibited by the B‐10 Fab fragment. This showed that growth stimulation by insulin and IGF‐1 was mediated via different receptors, insulin through its own receptor and IGF‐1 through some other receptor. However, mediation via the IGF‐2 receptor is not excluded since IGF‐1 stimulates compaction when there is evidence for only the presence of the IGF‐2 receptor. In summary, insulin or IGF‐1 at physiological concentrations stimulates preimplantation mouse embryos, suggesting an important role for both these growth factors in early development. © 1992 Wiley‐Liss, Inc.
Phosphatidylcholine and phosphatidylinositol‐specific phospholipases C of bull and rabbit spermatozoa
Authors: Hinkovska‐Galchev Vania , Srivastava Prakash N. 
Published: February 2005

AbstractAcrosomal reaction is an essential prerequisite to fertilization. The changes in lipid composition of sperm membranes cause fusion of the plasma and outer acrosomal membranes that results in the exocytosis of acrosomal contents. We report that both bull and rabbit spermatozoa contain a phosphatidylcholine‐specific phospholipase C (PC‐PLC) that hydrolyzes L‐α‐dipalmitoyl‐(choline‐methyl‐14C‐153.0 Ci/mmol and a phosphatidyl‐inositol‐specific phospholipase C (Pl‐PLC)) that hydrolyzes L‐α‐(Myo)‐lnositol‐2‐3H (N)‐5.2 Ci mmol. Pl‐PLC from bull sperm acrosome has been purified 568 × fold with a specific activity 6.25 ± 0.6 nmol/min/mg protein, km 0.004 mM, and Vmax 12 nmol/min/mg protein. Both enzymes had optimum at pH 7.5. The activity of PC‐PLC remained unaffected by varying concentrations of Ca2+, whereas Pl‐PLC activity was significantly increased. The bulk of Pl‐PLC was found to be associated with inner acrosomal membrane of bull and rabbit sperm, while PC‐PLC was found in the outer acrosomal membranes in the bull sperm and the plasma membrane of the rabbit sperm. Both enzymes are compartmentalized in sperm cell. © 1992 Wiley‐Liss, Inc.
Biosynthesis of prostaglandins by human spermatozoa in vitro and their role in acrosome reaction and fertilization
Authors: Roy Ashim C. , Ratnam Shan S. 
Published: February 2005

AbstractFive homogenates of human sperm cells were separately incubated with [14C]arachidonic acid in the presence of reduced glutathione, L‐tryptophan, and haematin as cofactors. The cyclooxygenase products of archidonic acid metabolism were extracted, separated, and measuréd for their radioactivity. The rate of formation of prostaglandin (PG)D2, PGE2, PGF2α, 6‐keto PGF1α, and thromboxane (TX)B2 were 18.0 ± 1.11, 10.9 ± 0.68, 5.8 ± 0.21, 3.9 ± 0.13 and 6.6 ± 0.52 pmol/106 cells/min, respectively. These results are discussed in relation to the hypothesis that cyclooxygenase metabolites of certain polyunsaturated fatty acids play an important part in the sperm acrosome reaction and fertilization. © 1992 Wiley‐Liss, Inc.
In vitro decondensation of mammalian sperm and subsequent formation of pronuclei‐like structures for micromanipulation
Authors: Montag Markus , Tok Veronica , Liow Swee‐Lian , Bongso Ariff , Ng Soon‐Chye 
Published: February 2005

AbstractIn this study, we describe an efficient protocol for the formation of in vitro developed pronuclei for micromanipulation techniques. Our approach involved incubation of demembranated or permeabilized mammalian sperm in a phosphate buffer supplemented with heparin and β‐mercaptoethanol. Under the prevailing conditions, we achieved a uniform and reliable synchronous decondensation of sperm nuclear DNA. This initial decondensation facilitated the removal of mammalian protamines upon subsequent incubation in an amphibian egg extract. The interchange of protamines for histones to stabilize the DNA structure is recognized as a prerequisite for pronuclear formation. Furthermore, immunocytochemical studies have revealed that pronuclear development is accompanied by the formation of a nuclear lamina with corresponding DNA synthesis. The method described gave a high yield of nuclei during pronuclear formation. Ultimately, our aim is to transfer the in vitro‐developed pronuclei into mammalian oocytes by micromanipulation. This novel procedure may prove useful in alleviating severe male factor problems especially in oligozoospermic cases in our in vitro fertilization center. (c) 1992 Wiley‐Liss, Inc.
Expression of estrogen receptor gene in mouse oocyte and during embryogenesis
Authors: Wu Tsung‐Chieh J. , Wang Lai , Wan Yu‐Jui Y. 
Published: February 2005

AbstractEstrogen is required for oocyte maturation and embryonic development in vivo; however, the mechanism involved is not clear. Since the effect of estrogen is mediated through the estrogen receptor (ER), we examined the ontogeny and expression of the ER gene in mouse oocytes and embryos of various gestational stages using the highly sensitive reverse transcriptase‐polymerase chain reaction (RT‐PCR) technique. Total RNA, extracted from 40 ovulated oocytes, 2‐cell embryos, morulae, and blastocysts, was reverse transcribed into cDNA. A pair of primers flanking the 453‐bp region encoding the hormone‐binding domain of ER was used for 30 cycles of PCR. The identity of the amplified product was confirmed by sizing and Southern blot hybridization. The results indicated that ER gene is expressed in unfertilized oocytes and cumulus–oocyte complexes. The amount of ER mRNA decreases in 2‐cell embryos, coincident with degradation of maternal mRNA. No ER transcript can be detected in the morulae or blastocyst stage when the embryonic genome has been activated. Postimplantation embryos do not contain detectable ER mRNA until gestation day 8. The levels of ER mRNA increase from day 10 to day 18 of gestation. These data suggest that estrogen, secreted by granulosa cells, may directly influence oocyte growth and maturation in vivo. Since estrogen is known to stimulate the production of growth factors in mouse uteri, the absence of ER mRNA in periimplantation embryos suggests that the effects of estrogen on early embryogenesis may be indirect, i.e., through estrogen‐regulated growth‐promoting factors produced by the reproductive tract. In mid‐ and late‐post‐implantation embryos which contain ER mRNA, estrogen may affect embryonic development through the receptor‐mediated mechanisms. © 1992 Wiley‐Liss, Inc.
Human sperm proteins from testicular and epididymal origin that participate in fertilization: Modulation of sperm binding to zona‐free hamster oocytes, using monoclonal antibodies
Authors: Boue Franck , Lassalle Bruno , Duquenne Clotilde , Villaroya Svetlozara , Testart Jacques , Lefevre Anick , Finaz Catherine 
Published: February 2005

AbstractIn order to identify human sperm surface proteins involved in the gamete recognition process, mouse monoclonal antibodies were directed against human spermatozoa and screened with live spermatozoa by enzyme‐linked immunosorbent assay (ELISA). Immunoperoxydase staining of human testis showed the early presence of four corresponding proteins on germinal cells, while six were detected primarily in testis fluid. The presence of 17 proteins was evidenced in the epididymis. Eight were detected with a decreasing gradient from the begining to the end of the organ, including vasa efferentia for three of them. The other nine were observed in only one defined segment, usually the caput epididymis, which was found to be the most active region. Comparison of spermatozoa patterns from testis, vasa efferentia, and the three regions of epididymis pointed out a progressive coating. By contrast, three antibodies displayed a migration of spermatozoa surface domains in the course of epididymal transit. Six antibodies were found to inhibit human spermatozoa adherence to zona‐free hamster oocytes, while nine promoted it. Molecular weights of antigens corresponding to nine of the antibodies ranged from 11 to 215 kDa. No correlation could be established with previously described human proteins. These observations emphasize the role of epididymis in human sperm maturation. © 1992 Wiley‐Liss, Inc.
The cell biology of blastocyst development
Authors: Watson Andrew J. 
Published: February 2005

AbstractPreimplantation development encompasses the “free”‐living period of mammalian embryo‐genesis, which culminates in the formation of a fluid‐filled structure, the blastocyst. Cavitation (blastocyst formation) is accompanied by the expression of a novel set of gene products that contribute directly to the attainment of cell polarity with the trophectoderm, which is both the first epithelium of development and the outer cell layer encircling the inner cell mass of the blastocyst. Several of these gene products have been identified and include the tight junction (ZO‐1), Na/K‐ATPase (α and β subunits), uvomorulin, gap junction (connexin43), and growth factors such as transforming growth factor‐α (TGF‐α) and epidermal growth factor (EGF). This review will examine the role(s) of each of these gene products during the onset and progression of blastocyst formation. The trophectodermal tight junctional permeability seal regulates the leakage of blastocoel fluid and also assists in the maintenance of a polarized Na/K‐ATPase distribution to the basolateral plasma membrane domain of the mural trophectoderm. The polarized distribution of the Na/K‐ATPase plays an integral role in the establishment of a trans‐trophectoderm Na+ gradient, which drives the osmotic accumulation of water across the epithelium into the nascent blastocoelic cavity. The cell adhesion provided by uvomorulin is necessary for the establishment of the tight junctional seal, as well as the maintenance of the polarized Na/K‐ATPase distribution. Growth factors such as TGF‐α and EGF stimulate an increase in the rate of blastocoel expansion, which could, in part, be mediated by secondary messengers that result in an increase in Na/K‐ATPase activity. Insight into the mechanism of cavitation has, therefore, directly linked blastocyst formation to trophectoderm cell differentiation, which arises through fundamental cell biological processes that are directly involved in the attainment of epithelial cell polarity. © 1992 Wiley‐Liss, Inc.
A major mRNA of the human epididymal principal cells, HE5, encodes the leucocyte differentiation CDw52 antigen peptide backbone
Authors: Kirchhoff Christiane , Krull Nora , Pera Ilka , Ivell Richard 
Published: February 2005

AbstractHE5, a very abundant human epididymal gene product, was cloned by a differential screening procedure which employed testis as the primary negative control tissue. Sequencing of the HE5 cDNA showed it to be identical to that encoding the peptide backbone of the human leucocyte differentiation antigen CDw52. Since human genomic DNA contained only one cross‐hybridizing fragment, this implies that both products were transcribed from the same gene. Northern blot analysis and in situ transcript hybridization revealed a highly tissue‐ and cell‐type‐specific expression pattern for HE5, showing the gene product to originate from epithelial cells of the epididymal and deferent duct. The possible identity of the HE5 product with the CDw52 antigen suggests a link between the immune and reproductive systems. © 1993 Wiley‐Liss, Inc.
Region‐specific variation of gene expression in the human epididymis as revealed by in situ hybridization with tissue‐specific cDNAs
Authors: Krull Nora , Ivell Richard , Osterhoff Caroline , Kirchhoff Christiane 
Published: February 2005

AbstractThree tissue‐specific gene probes that had been isolated by differential screening from a human epididymal cDNA library—HE1, HE2, and HE5—were employed to investigate regional specializations in the human epididymis. All 3 cDNAs were derived from major transcripts of the epithelial cells lining the epididymal duct. Each mRNA species, however, exhibited a discrete longitudinal pattern of hybridization with maxima in different regions of this organ, suggesting regional specializations of gene expression. The HE5 mRNA, which was recently shown to encode the peptide backbone of the human leukocyte differentiation antigen CDw52, showed maximum levels in the distal corpus epididymidis and in the vas deferens, whereas the HE2 mRNA was found predominantly in the caput and proximal corpus sections of the epididymis. HE1 mRNA was found in high amounts in all parts of the epididymis, displaying a 2‐peak expression pattern with maxima in the distal caput and distal corpus of the epididymal duct. © 1993 Wiley‐Liss, Inc.
Chromatin and microtubule organization in the first cell cycle in rabbit parthenotes and nuclear transplant embryos
Authors: Pinto‐Correia Clara , Collas Philippe , De Leon F. Able Ponce , Robl James M. 
Published: February 2005

AbstractArtificial activation and nuclear transfer in rabbit oocytes have been used in past years in an attempt to develop viable techniques for cloning in cattle. The procedures established in our laboratory, using the rabbit as a model, consistently lead to high rates of development to the blastocyst stage. However, the rate of embryos developing to term is considerably lower. In the present study, we undertook a detailed immunocytochemical study of the patterns of both microtubules and chromatin during the first cell cycle of electrical pulse‐activated oocytes and of nuclear transfer embryos. Our goal was to investigate the responses of the cell to the different stimuli applied and to establish the sequence of events leading to first cleavage in the absence of normal fertilization. Our results show that, in both electrically activated oocytes and nuclear transfer embryos, although the initial development patterns are rather unusual, embryos become synchronized at the time of the formation of a pronuclear‐like structure, and then organize metaphase spindles and cleave. These spindles consistently present small defects, suggesting that problems in the formation of the mitotic apparatus during the first cell cycle may have a long‐term effect leading to embryo mortality. © 1993 Wiley‐Liss, Inc.
Development of androgenetic mouse embryos produced by in vitro fertilization of enucleated oocytes
Authors: Kono Tomohiro , Sotomaru Yusuke , Sato Yasuhiro , Nakahara Tatsuo 
Published: February 2005

AbstractEnucleated mouse oocytes were successfully fertilized in vitro, and the resultant androgenetic eggs developed to the blastocyst stage. The proportion of enucleated oocytes fertilized in vitro was high (87–99%) at sperm concentrations ranging from 10–100 × 104/ml. At high sperm concentrations (100–1,000 × 104), 35–45% of the fertilized eggs resulted in heterozygous bispermic androgenones. The proportion of hemizygous haploid and heterozygous diploid androgenones developing to blastocysts was 11% and 43%, respectively. Hemizygous diploidization, however, showed no positive effect on development. These results clearly show that the procedure reported here is efficient and reliable for the production of androgenetic eggs. © 1993 Wiley‐Liss, Inc.
Forskolin and the meiosis inducing substance synergistically initiate meiosis in fetal male germ cells
Authors: Byskov Anne Grete , Fenger Mogens , Westergaard Lars , Andersen Claus Yding 
Published: February 2005

AbstractWe have shown that Meiosis Inducing Substance (MIS) and forskolin synergistically and dose dependently induce meiosis in germ cells of cultured fetal mouse testes. We used a bioassay which consists of fetal mouse testes and ovaries cultured for 6 days. In this study MIS media are spent culture media from 24 hour cultures of minced adult mouse testes. In the bioassay one gonad of each fetus is cultured either in MIS medium, in control medium with forskolin, or in MIS medium with forskolin. The other gonad serves as the control and is cultured in control medium. After culture the gonads are fixed, squashed, and DNA‐stained. In these preparations germ cells and somatic cells can be distinguished, and the number of germ cells in the different stages of meiosis is counted as is the number of somatic cells in mitosis. MIS activity is defined to be present in a medium when meiosis is induced in male germ cells during culture. We found that MIS media as well as forskolin induced meiosis in fetal male germ cells in a dose‐dependent manner. In addition, MIS media and forskolin acted synergistically by inducing meiosis. Female germ cells seem to be unaffected by the various culture media. These findings indicate that receptors for stimuli of meiotic initiation may exist in germ cells or neighbouring somatic cells. In addition to induction of meiosis, MIS media and forskolin also dose dependently increase the number of male germ cells compared to controls. This increase is correlated with induction of advanced stages of meiosis: Male germ cells seem to survive better if they are triggered to enter meiosis. Neither MIS media nor forskolin affected the growth of somatic cells. We therefore propose that MIS media has a growth factor activity with a specific effect on meiotic initiation. © 1993 Wiley‐Liss, Inc.