bluuebunny/crossref_metadata_2025_split huggingface dataset:
F‐actin is involved in control of bovine cumulus expansion
Authors: Šutovský Peter , Fléchon Jacques E. , Pavlok Antonín 
Published: February 2005

AbstractPreviously, we showed that the gonadotropin‐induced expansion of bovine cumulus oophorus occurs concomitantly with the rearrangement of micro‐filaments (MFs) inside cumulus cell cytoplasm (Šutovský et al., 1993: Biol Reprod 49:1277–1287; Šutovský et al., 1994: Reprod Nutr Dev 34:415–425) and that cumulus expansion in cattle is accompanied by the increased expression of extracellular matrix (ECM) glycoproteins laminin and type IV collagen as well as of their actin‐linked membrane receptors, integrin subunits α‐6 and β‐1 (Šutovský and Motlik: 1994). The present study was undertaken to determine the spatial and temporal relationship between cytoskeletal rearrangement and ECM synthesis during cumulus expansion. Using electron microscopy and confocal (LSCM) and conventional fluorescence microscopy, we compared the expression of the above integrins and ECM proteins and the rearrangement of cytoskeleton in the gonadotropin‐stimulated bovine oocyte cumulus complexes (OCCs) with those exposed to gonadotropin stimulation and to ECM synthesis inhibitor 6‐diazo‐5‐oxo‐L‐norleucin (DON), or MF‐disorganizing drug cytochalasin B (CB). In control OCCs, the 24‐hr culture in the presence of follicle stimulating hormone/luteinizing hormone (FSH/LH) caused the expansion of cumuli oophori and an extensive rearrangement of MFs in the cytoplasm of cumulus cells. Concomitantly, we observed an increased deposition of laminin and type IV collagen in the intercellular spaces among cumulus cells. The redistribution of microtubules (MTs), intermediate filaments (IFs), and integrin chains α‐6 and p‐1 also occurred at this time. The addition of 20 μg/ml of CB prevented cumulus expansion and accumulation of laminin and type IV collagen in the OCCs. Moreover, cytochalasin treatment blocked the redistribution of MTs and IFs, and caused the disorganization of MFs and dispersion of integrins in cumulus cells. In contrast, the distribution of integrins and cytoskeletal elements was not affected when we blocked cumulus expansion and ECM protein accumulation by DON. These data suggest that F‐actin acts upstream of ECM synthesis in the cascade of events leading to the expansion of bovine cumulus ooophorus. © 1995 Wiley‐Liss, Inc.
Molecular cloning, tissue distribution, and hormonal control in the ovary of Cx41 mRNA, a novel Xenopus connexin gene transcript
Authors: Yoshizaki Goro , Patiño Reynaldo 
Published: February 2005

AbstractGap junctions (GJ) are aggregates of intercellular channels, composed of connexin (Cx) protein, between adjacent cells. The vertebrate ovarian follicle contains homocellular (granulosa cell‐granulosa cell) and heterocellular (granulosa cell‐oocyte) GJ. However, the function of GJ during final oocyte differentiation (maturation) is controversial. The objectives of this study are to reexamine the number and identity of Cx genes that are expressed in the Xenopus ovary, and to examine the potential role of GJ in oocyte maturation by determining the temporal association between changes in ovarian Cx mRNA content and the process of maturation. We used reverse transcriptase‐polymerase chain reaction to amplify ovarian cDNA fragments using degenerate Cx primers. We amplified three Cx‐like fragments: one was novel and two corresponded to known Cx of Xenopus ovaries (Cx38 and 43). The novel fragment was used to screen an ovarian cDNA library. One positive clone was identified and its nucleotide sequence determined. Its deduced amino acid sequence showed that it corresponded to a novel Cx, Cx41, belonging to the Group II class of Cx. Xenopus Cx41 showed the highest homology to rat Cx37 (65% identity, 80% similarity). Also, the last 10 C‐terminal amino acids of Cx41 were identical to those of rat, mouse, and human Cx37. Cx41 transcripts were detected by riboprobe mapping in ovarian somatic cells, heart, leg muscle, liver and eye, but not in brain or in oocytes of any developmental stage. Full‐grown follicles incubated in vitro with human chorionic gonadotropin became committed to mature within 1–4 hr, and physical signs of maturation (germinal vesicle breakdown) were seen at 4–5 hr. Significant reductions in the levels of Cx41 and 43, but not 38 transcripts were seen at 4 hr, after oocytes had committed to mature. Thus, if availability of Cx mRNA determines availability of Cx protein and GJ, our results would suggest that irreversible commitment to maturation occurred prior to major declines in follicular GJ during the periovulatory period. The present study is the first to report the presence of at least two hormone‐responsive Cx gene transcripts (Cx41 and 43 in Xenopus) in ovaries of a single animal species. © 1995 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
Differential gene expression during early murine yolk sac development
Authors: Palis James , Kingsley Paul D. 
Published: February 2005

AbstractThe visceral yolk sac (VYS), composed of extraembryonic mesoderm and visceral endoderm, is the initial site of blood cell development and serves important nutritive and absorptive functions. In the mouse, the visceral endoderm becomes a morphologically distinct tissue at the time of implantation (E4.5), while the extraembryonic mesoderm arises during gastrulation (E6.5–8.5). To isolate genes differentially expressed in the developing yolk sac, polymerase chain reaction (PCR) methods were used to construct cDNA from late primitive streak to neural plate stage (E7.5) murine VYS mesoderm and VYS endoderm tissues. Differential screening led to the identification of six VYS mesoderm‐enriched clones: ribosomal protein L13a, the heat shock proteins hsc 70 and hsp 86, guanine‐nucleotide binding protein‐related gene, cellular nucleic acid binding protein, and ã‐enolase. One VYS endoderm‐specific cDNA was identified as apolipoprotein C2. In situ hybridization studies confirmed the differential expression of these genes in E7.5 yolk sac tissues. These results indicate that representative cDNA populations can be obtained from small numbers of cells and that PCR methodologies permit the study of gene expression during early mammalian postimplantation development. While all of the mesoderm‐enriched genes were ubiquitously expressed in the embryo proper, apolipoprotein C2 expression was confined to the visceral endoderm. These results are consistent with the hypothesis that at E7.5, the yolk sac endoderm provides differentiated liver‐like functions, while the newly developing extraembryonic mesoderm is still a largely undifferentiated tissue. © 1995 wiley‐Liss, Inc.
Transcription and localization of growth factor mRNA in the bovine oviduct
Authors: Viuff D. , Hyttel P. , Greve T. , Eriksen T. , Alexandersen S. 
Published: February 2005

AbstractIt has become evident that certain growth factors are involved in the regulation of the initial bovine embryogenesis. In the present study, we examined by means of Northern blot and in situ hybridization, the expression and localization in the bovine oviduct of mRNAs encoding for platelet‐derived growth factor (PDGF‐B), basic fibroblast growth factor (bFGF), and insulin‐like growth factor (IGF‐I).Northern blot analysis on oviduct tissue demonstrated transcripts for PDGF‐B and bFGF, but not IGF‐I mRNAs. Two bands with estimated sizes of 5.0 and 1.5 kb were detected for PDGF‐B and two bands with sizes of 7.5 and 4.9 kb for bFGF. In situ hybridization analysis demonstrated localization of PDGF‐B mRNA in the lamina epithelialis and tunica muscularis of the oviduct whereas bFGF mRNA was detected in the lamina propria. It is concluded that the lamina epithelialis and lamina propria of the oviduct represent sites of synthesis of PDGF‐B and bFGF mRNA, respectively. © 1995 wiley‐Liss, Inc.
Ultrastructure of the spermatozoa and eggs of the ocean pout (Macrozoarces americanus L.), an internally fertilizing marine fish
Authors: Yao Z. , Emerson C. J. , Crim L. W. 
Published: February 2005

AbstractUltrastructure of sperm and eggs of the ocean pout (Macrozoarces americanus L.), an internally fertilizing marine teleost, was examined by scanning and transmission electron microscopy. The results showed that the sperm do not have an acrosome but have a very long mid‐piece (one to two times the sperm head length) containing numerous well‐developed elongated mitochondria. The sperm also have two tails (is biflagellate) each consisting of nine peripheral and one central pair (9 ± 2) of microtubules. This long mid‐piece and the biflagellate nature of the sperm appear to be associated with the long life‐span of the sperm and with sperm dispersal in the ovary to fertilize the eggs internally. The ocean pout eggs are enveloped by a porous chorionic membrane similar to that found in other teleosts but have two micropyles, a condition likely related to a mechanism of egg fertilization which increases the egg fertlity in the presence of low sperm numbers. Following insemination, some biochemically undefined excretions appeared on the surface of fertilized eggs and led to the acquisition of adherent capability of the eggs which formed a tightly associated egg mass in sea water. © 1995 wiley‐Liss, Inc.
Intra‐acrosomal 155,000 dalton protein increases the antigenicity during mouse sperm maturation in the epididymis: A study using a monoclonal antibody MC101
Authors: Toshimori K. , Tanii I. , Araki S. 
Published: February 2005

AbstractWe found an intra‐acrosomal antigen of about 155,000 daltons (155 kDa) in a survey using the monoclonal antibody MC101 raised against mouse cauda epididymal spermatozoa. Morphological studies by means of indirect immunofluorescence and immunogold electron microscopy localized the antigen to the cortex region of the anterior acrosome. Avidin biotin complex immunocytochemistry initially demonstrated a faint signal at the anterior acrosome in the testis spermatozoa that increased in intensity as the sperm moved toward the distal epididymis. This incremental immunoreactivity was also confirmed by immunoblotting following one‐dimensional SDS‐PAGE. The 155 kDa protein band was immunostained, and it was much more intense in the cauda epididymal than in the caput and corpus epididymal spermatozoa. Only a trace or no immunostain was evident in the caput or testis spermatozoa. The antigen localization did not change during passage through the epididymis, being confined at the cortex region of the anterior acrosome. The epididymal epithelial cells were not immunostained. These findings suggested that the 155 kDa protein is biochemically modified, further implying that the biochemical alteration of intra‐acrosomal material is involved in sperm maturation in the epididymis. © 1995 wiley‐Liss, Inc.
Structural and endocrine aspects of equine oocyte maturation in vivo
Authors: Grøndahl Christian , Hyttel Poul , Grøndahl Marie Louise , Eriksen Thomas , Gotfredsen Per , Greve Torben 
Published: February 2005

AbstractThe objectives were to describe the ultrastructure of equine oocytes aspirated from small and preovulatory follicles, and to relate the ultrastructural features to follicle size and follicular fluid steroid concentrations.Mares were examined every second day by transrectal ultrasonography, and follicles measuring ≤30 mm were aspirated (in vivo) using a 20‐cm‐long 12‐gauge needle through the flank. Following slaughter, both large and small follicles were aspirated (in vitro) from six mares. The oocytes were isolated under a stereomicroscope and processed for transmission electron microscopy, and the follicular fluid was assayed for progesterone (P4) amd estradiol‐17β (E2). A total of 29 oocytes (32% recovery rate) were aspirated in vivo, and 15 oocytes were recovered in vitro. According to the stage of nuclear maturation, the oocytes could be divided into the following six categories: 1) the central oocyte nucleus (CON) stage, 2) the peripheral spherical oocyte nucleus (PON‐I) stage, 3) the peripheral flattened oocyte nucleus (PON‐II) stage, 4) the oocyte nucleus breakdown (ONBD) stage, 5) the metaphase I (M‐I) stage, and 6) the metaphase II (M‐II) stage. The maturation of the preovulatory follicle was reflected by alterations in the follicular fluid concentrations of steroid hormones. E2 was high in all preovulatory follicles, whereas P4 concentration exhibited a 10‐fold increase during follicle maturation, particularly associated with the progression from M‐I‐to M‐II‐stage oocytes.The nuclear oocyte maturation included flattening of the spherical oocyte nucleus, followed by increasing undulation of the nuclear envelope, formation of the metaphase plate of the first meiotic division, and, finally, the extrusion of the first polar body and the subsequent formation of the metaphase plate of the second meiotic division.The cytoplasmic oocyte maturation changes comprised breakdown of the intermediate junctions between the cumulus cell projections and the oolemma, enlargement of the perivitelline space, the formation and arrangement of a large number of cortical granules immediately beneath the oolemma, the rearrangement of mitochondria from a predominantly peripheral distribution to a more central or semilunar domain, and the rearrangement of membrane‐bound vesicles and lipid droplets from an even distribution to an often semilunar domain, giving the ooplasm a polarized appearance. It is concluded that the final equine oocyte maturation includes a series of well‐defined nuclear and cytoplasmic changes that are paralleled by an increase in P4 concentration in the follicular fluid, whereas E2 concentration remains constantly high. © 1995 wiley‐Liss, Inc.
Formation of the sea urchin male pronucleus in vitro: Membrane‐independent chromatin decondensation and nuclear envelope‐dependent nuclear swelling
Authors: Collas Philippe , Poccia Dominic L. 
Published: February 2005

AbstractWe demonstrate that complete sea urchin male pronuclear development in vitro is a two‐step process involving membrane‐independent chromatin decondensation and nuclear envelope‐dependent pronuclear swelling. In the absence of cytoplasmic membrane vesicles (MVs), permeabilized sperm chromatin decondenses into a spherical nucleus of ≈4 μm in diameter. Pronuclear swelling to ≈7 μm requires an intact nuclear envelope, and the degree of swelling is limited by the amount of MVs assembled on the chromatin. Furthermore, after a nuclear envelope is formed, swelling can occur in the absence of additional cytoplasmic MVs. Nuclear swelling also requires ATP hydrolysis, Ca2+ and cytosolic factors, some of which are sensitive to heat and to the sulfhy‐dryl alkylating agent, N‐ethylmaleimide. The requirement for a nuclear envelope and the rate of pronuclear swelling are consistent with previous in vivo observations. © 1995 wiley‐Liss, Inc.
Low temperature and fertilization‐induced Ca2+ changes in rat eggs
Authors: Ben‐Yosef Dalit , Oron Yoram , Shalgi Ruth 
Published: February 2005

AbstractIn mammalian eggs, activation by sperm that leads to resumption of meiosis is characterized by an explosive transient increase in intracellular calcium ion concentration ([Ca2+]i), followed by [Ca2+]i oscillations. In addition to the spermatozoon, various treatments can induce parthenogenetic activation, accompanied by an elevation of [Ca2+]i. It has been reported that cooling can induce egg activation, yet the mechanism of this phenomenon has not been elucidated. In the present study we followed changes in egg [Ca2+]i (measured by Fura‐2 fluorescence ratio imaging) during activation by cooling, using conditions that ensure a low rate of spontaneous activation.Our present findings demonstrate that cooling induces egg activation as manifested by [Ca2+]i transient(s) and second polar body extrusion. Seventy‐eight of 104 eggs responded to cooling with increased [Ca2+]i. Thirty‐five percent of the responding eggs displayed a single [Ca2+]i transient, while 65% exhibited at least two [Ca2+]i transients within the time window of the experiment (30–40 min). Twenty‐two percent of these eggs displayed high‐frequency oscillations (intervals of 3.5–5.9 min). In these eggs, the overall pattern of calcium dynamics was similar to that observed in eggs activated by sperm, as judged by the transient's intervals, duration, and a gradual increase in the amplitude of successive transients. The amplitudes of [Ca2+]i transients, however, were 2–3 times lower. We propose that cooling affects [Ca2+]i homeostasis to produce fertilization‐like changes in [Ca2+]i, possibly associated with parthenogenetic activation. Moreover, great care should be exercised to prevent temperature changes during egg handling. © 1995 wiley‐Liss, Inc.
Expression of prostatic secretory protein (PSP)‐like protein in porcine corpus luteum: Isolation and characterization of a new gene encoding PSP94‐like protein
Authors: Tanaka Toshiaki , Itahana Koji , Andoh Naoki , Takeya Tatsuo , Sato Eimei 
Published: February 2005

AbstractcDNA clones encoding stage‐and/or space‐specific genes in porcine ovarian follicles have been investigated by differential screening of cDNA libraries of granulosa cells and corpus luteum. A clone corresponding to mRNA preferentially expressed in the functional stage of corpus luteum was found to encode a protein similar to the human prostatic secretory protein, PSP94, which had been originally identified in male genital organs. The expression was detected widely in the functional corpora lutea by in situ hybridization histochemistry, but the signal was most prominent in the luteal cells surrounding blood vessels. In contrast, despite the structural similarity in their products, the expression of this newly identified gene was not detected in procine prostate, suggesting that these structurally related proteins play different roles in mammalian genital organs. © 1995 wiley‐Liss, Inc.
Increased accessibility of the N‐terminus of testis‐specific histone TH2B to antibodies in elongating spermatids
Authors: Unni Emmanual , Mayerhofer Artur , Zhang Yun , Bhatnagar Yogendra M. , Russell Lonnie D. , Meistrich Marvin L. 
Published: February 2005

AbstractChanges in chromatin structure during spermatogenesis were investigated using a monoclonal antibody that immunoreacts with the N‐terminus of the testis‐specific histone TH2B. This monoclonal antibody, which had been raised against rat tyrosine hydroxylase (TH), cross‐reacted with TH2B because of sequence homology at the N‐termini of TH and TH2B. The epitope was localized to the N‐terminus of TH2B as trypsin‐digested chromatin which lacked the N‐terminal tail did not react with anti‐TH and preincubating anti‐TH with a synthetic peptide made from the homologous sequence between TH2B and TH inhibited its binding to TH and TH2B. In histological sections of rat testis, the primary spermatocytes and round spermatids immunoreacted weakly, whereas elongating spermatids at steps 10–12 immunoreacted intensely with anti‐TH. Increased staining of elongating spermatids was also observed in mouse and hamster by immunohistochemistry. However, immunoblotting proteins extracted from separated rat testis cells showed no increase in the TH2B content of these late steps of spermatids. The apparent increase in the immunohistochemical staining corresponds to increased accessibility of the epitope in the elongating spermatids. This indicated that the N‐terminus of TH2B is less tightly bound to DNA or to other proteins at this time in preparation for the removal of TH2B and other histones. © 1995 wiley‐Liss, Inc.
Rabbit whey acidic protein gene upstream region controls high‐level expression of bovine growth hormone in the mammary gland of transgenic mice
Authors: Thépot Dominique , Devinoy Eve , Fontaine Marie‐Louise , Stinnakre Marie‐Georges , Massoud Micheline , Kann Guy , Houdebine Louis‐Marie 
Published: February 2005

AbstractTransgenic mice were produced which secreted high levels of bGH into milk. The 6.3‐kb upstream region of the rabbit whey acidic protein (rWAP) gene was linked to the structural part of the bovine growth hormone (bGH) gene, and the chimeric gene was introduced into mouse oocytes. bGH was detected by radioimmunoassay in the milk of all resulting transgenic mice. bGH concentrations in milk varied from line to line, from 1.0–16 mg/ml. This expression was not correlated to the number of transgene copies. In all lines studied, the mammary gland was the major organ expressing bGH mRNA during lactation. bGH mRNA concentrations were barely detectable in the mammary gland of cyclic females; they increased during pregnancy. These results show that the upstream region of the rWAP gene harbors powerful regulatory elements which target high levels of bGH transgene expression to the mammary gland of lactating transgenic mice. © 1995 wiley‐Liss, Inc.
Kit ligand mediates survival of type a spermatogonia and dividing spermatocytes in postnatal mouse testes
Authors: Packer A. I. , Besmer P. , Bachvarova R. F. 
Published: February 2005

AbstractIn the mouse testis, spontaneous death of spermatogonia has a large impact on the output of differentiating spermatids. The tyrosine kinase receptor c‐kit is expressed in type A, intermediate, and B spermatogonia, and kit‐ligand (KL) is expressed in Sertoli cells. Previous work indicated a depletion of type A spermatogonia after in vivo exposure to an antibody that blocks c‐kit function. The present work was undertaken to determine whether blocking c‐kit function results in apoptosis of spermatogonia or in an inability of spermatogonia to proliferate. Testes sections were stained by a method that detects apoptotic cells in situ. In testes of 8‐day postnatal (P8) males, type A spermatogonia are the predominant germ cell type present. Stained sections from P8 males injected with the c‐kit antagonistic antibody ACK2 showed a fivefold higher rate of cell death than uninjected controls. At least a twofold increase was observed in P12 and P30 injected males and in P30 SId + males as compared to uninjected controls. Determination of the stage of germ cell development that was affected in P30 males indicated that the frequency of gonial cell death was increased fourfold, but the frequency of death in spermatocytes around the time of the meiotic division was increased 15‐fold. It is concluded that KL acts to prevent apoptosis in the testis in vivo, that the membrane bound form of KL may be more effective, and that survival of late meiotic and dividing spermatocytes is regulated by KL through an indirect mechanism probably mediated by Sertoli cells. Thus, KL is an important regulator of spermatid output. © 1995 wiley‐Liss, Inc.