bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of hormones on the inhibitory activity of oocyte maturation present in conditioned media of porcine granulosa cells
Authors: Anderson Larry D. , Stone Sarah Lipford , Channing Cornelia P. 
Published: February 2005

AbstractThis study examines the influence of follicular maturation as well as the role of various hormones upon the secretion of an oocyte maturation inhibitor (OMI) from porcine granulosa cells incubated in vitro. The results demonstrate that the OMI substance, secreted into the media by granulosa cells, is present in a low molecular‐weight fraction (< 10,000 daltons) similar to that found in follicular fluid of porcine antral follicles. Also, as follicular development progresses, the granulosa cells lose their ability to secrete OMI. More importantly, hormones appear to regulate OMI secretion: FSH stimulates OMI secretion and androgens inhibit OMI secretion. These data provide evidence for the proposal of the following hypothesis concerning hormonal regulation of oocyte, meiosis by OMI in the porcine follicle: Whether the oocyte resumes meiosis, either during atresia or ovulation, is dependent upon the proper milieu of gonadotropins, cyclic‐AMP, and steroids within the microenvironment of the follicular compartment. The cellular interactions of these hormones, particularly FSH and androgens, control the amount of OMI (and possibly other intrafollicular factors) secreted in the follicle, which may be involved in either maintaining the immature state or permitting meiotic maturation.
Development of membrane sensitivity to the parthenogenetic agent calcium ionophore A23187 during meiotic maturation in the hamster oocyte
Authors: Eusebi Fabrizio , Salustri Antonietta 
Published: February 2005

AbstractThe response to the parthenogenetic agent Ca‐ionophore A23187 was studied in hamster oocytes undergoing meiotic maturation, by using electrophysiological techniques. Following germinal vesicle breakdown, the activating agent induces a long‐lasting hyperpolarization accompanied by an increased membrane conductance. The duration of the response progressively shortens during the long metaphase I stage. Terminal metaphase I oocytes respond to A23187 by a hyperpolarization that is very similar to that seen in metaphase II oocytes. The ionic mechanism of the change in the membrane sensitivity to A23187 during meiotic maturation is discussed.
Intracellular localization and surface expression of a stage‐specific embryonic glycoprotein
Authors: Polak‐Charcon Sylvie , Calarco‐Gillam Patricia , Johnson Lincoln V. 
Published: February 2005

AbstractThe intracellular and cell surface localization of an embryonic glycoprotein antigen (BL) has been investigated in preimplantation mouse embryos using ultrastructural immunocytochemistry. Several interesting points have emerged: (1) BL antigens are exclusively localized subjacent to the plasma membrane in the cortical region of cells, whereas antigens detected by a control antibody against mouse L cells are distributed throughout the embryo. (2) The distribution of BL antigens is polarized beginning with the first cleavage, with expression confined to the cortex underlying the free or apical portions of cells. No antigen is present underlying regions of cell contact. (3) Although embryonic synthesis of BL antigens does not begin until the two‐cell stage, BL antigens are observed in unfertilized eggs, a fact verified by immunoblotting.
Transmission electron microscopy of impaired spermatogenesis in an avian hybrid
Authors: Swan M. A. 
Published: February 2005

AbstractThe mechanisms involved in the impaired spermatogenesis of male goldfinch x canary hybrids were investigated by transmission electron microscopy and compared with spermatogenesis in the testes of the parent species.In the parent species the testes were of normal structure, with the only unusual observation being that the Sertoli cells were variable in cytoplasmic electron density. In hybrid birds the Sertoli cells were either electron dense or electron lucent with respect to both nucleus and cytoplasm.In the hybrids examined in this study, no spermatozoa were produced. Spermatogenic stages were arrested without formation of synaptonemal complexes. Centrioles were abnormally arranged in both somatic and germ cells. When they moved away from the basement lamina the germ cells degenerated and were phagocytosed. No focal tight junctions were present between Sertoli cells overlying what would normally have been the basal compartment of the tubule. The basement lamina was unusually thickened, peritubular cells were abnormal in structure, and numerous plasma cells were present in the interstitial tissue.The observations reported here suggest that there was an immunological basis for degeneration of germ cells in the hybrid testis.
Characterization of paracrystalline inclusions in chinese hamster oocytes and early embryos
Authors: Parkening T. A. , Payer A. F. , Given R. L. 
Published: February 2005

AbstractParacrystalline inclusions, readily visible with light microscopy, were found to be present in ovarian oocytes (beginning with unilaminar follicles), ovulated ova, and preimplantation embryos of the Chinese hamster. These inclusions appeared to be aggregates of finer filamentous structures visible only with electron microscopy. The use of various histochemical techniques suggested that the paracrystals were composed of protein with little or no lipid associated with them. Autoradiographic studies using 3H‐uridine and enzymatic studies did not support the hypothesis that the paracrystalline inclusions were composed of RNA masked by a crystalline protein lattice.
The involvement of methyl transfer reactions and S‐adenosylhomocysteine in the regulation of bovine sperm motility
Authors: Goh Pauline , Hoskins Dale D. 
Published: February 2005

AbstractThe methylation of proteins and phospholipids has been demonstrated in mammalian sperm. The role of these methylation reactions in the regulation of sperm motility is, however, unclear. A combination of agents [adenosine, L‐homocysteine and erythro‐9‐(2‐hydroxyl‐3‐nonyl) adenine (EHNA)] known to increase the level of S‐adenosylhomocysteine (AdoHcy), a competitive inhibitor of S‐adenosylmethionine (AdoMet)‐mediated methylations, has been shown to inhibit rabbit sperm motility. The level of AdoHcy in response to these agents has, however, not been measured. Therefore, enzymatic protein carboxylmethylation (PCM) and the consequences of its inhibition by elevated intrasperm AdoHcy levels on motility were studied using bovine sperm. Incubation of bovine cauda epididymal sperm with L‐[methyl‐3H]methionine resulted in a linear increase in PCM for up to 2 h. Treatment of sperm with adenosine (0.5 mM), L‐homocysteine (0.5 mM), and EHNA (0.25 mM) produced a dramatic increase in AdoHcy levels after 15 min and a 97% inhibition of PCM after 0.5 h, followed by an inhibition of sperm motility (58% and 97%) after 1 and 2 h. Similar but less marked results were obtained with L‐homocysteine (0.5 mM) alone. Individually, cycloleucine (20 mM), an inhibitor of AdoMet synthetase, and adenosine (0.5 mM) also inhibited PCM (87% and 70%, respectively) after 2 h but had no effect on sperm motility or AdoHcy levels. These studies show for the first time that agents that elevate AdoHcy levels inhibit sperm motility. This, however, leaves open the question of whether protein carboxylmethylation or other methyl transfer reactions, eg, involving phospholipid, might be critical to motility inhibition by AdoHcy. Thus, the mechanism by which AdoHcy inhibits sperm motility remains unclear.
A rat oocyte differentiation antigen (OA‐1) detected by a monoclonal antibody
Authors: Banka Carole L. , Unger Michael W. , Dulbecco Renato , Erickson Gregory F. 
Published: February 2005

AbstractCell surface antigenic changes associated with differentiation of the rat oocyte and early embryo have been demonstrated with a monoclonal antibody (anti‐OA‐1). Antigen is first detectable coincident with initiation of oocyte growth, is a constant feature of all growing oocytes and displays a redistribution during meiotic maturation. Following fertilization, antigen is detectable on the surface of the embryo through the four‐cell stage. This first monospecific marker for the rat oocyte and embryo should prove useful in probing structure/function relationships in oocyte growth, meiotic maturation fertilization, and/or early embryonic development.
Initiation of cleavage in starfish eggs by the injection of triton‐treated spermatozoa
Authors: Yamada Hisafumi , Hirai Setsuro 
Published: February 2005

AbstractTriton X‐100‐treated spermatozoa were injected into immature (fully grown, germinal vesicle stage) or mature (pronuclear stage) oocytes of the starfish, Asterina pectinifera, to study relation between initiation of cleavage and cortical reaction. Immature oocytes into which Triton X‐100‐treated spermatozoa were injected were treated with 1‐methyladenine. Such immature oocytes initiated cleavage after completion of meiosis without formation of the fertilization membrane. The same results were obtained when Triton X‐100‐treated spermatozoa were injected into mature oocytes. Control oocytes into which only calcium‐free sea water was injected did not cleave. These results indicate that the initiation of cleavage is independent of the cortical reaction but dependent on the existence of spermatozoa (spermatozoon) in the egg cytoplasm.
An improved method for isolation of fertile zona‐free mouse eggs
Authors: Boldt Jeffrey , Wolf Don P. 
Published: February 2005

AbstractStudies of sperm‐egg fusion using zona‐free mouse eggs are impaired by the procedures used for removal of the zona pellucida. Methods involving proteolytic digestion or mechanical aspiration through micropipettes are limited in that proteases can adversely affect fertility and mechanical removal often results in low egg yields. An efficient procedure for preparation of zona‐free mouse eggs was developed using a combined enzymatic (chymotrypsin) mechanical approach (CT‐M procedure). Zona‐intact eggs, obtained after hyaluronidase treatment, were exposed to 0.001% α‐chymotrypsin in medium containing 0.5% bovine serum albumin (BSA). Brief (2 minute) exposure to chymotrypsin under these conditions caused pronounced zona distention in a majority (80‐90%) of the eggs, facilitating mechanical removal and resulting in a high yield of zona‐free eggs. Eggs prepared by the CT‐M method displayed identical penetration levels relative to mechanically denuded eggs. CT‐M prepared eggs also showed sperm concentration dependent penetration levels and demonstrated a plasma membrane block to polyspermy, qualities previously observed in mechanically prepared eggs [Wolf DP, 1978, Dev Biol 64:1–10]. Eggs could be exposed to 0.001% CT for zona distention over a 2‐10‐minute time period with no detrimental effects on fertility. The effect of chymotrypsin was also studied by treating zona‐free eggs for 30 minutes over a 1‐1,000–μg/ml range of enzyme, and a concentration‐dependent reduction in penetration levels was observed. These results indicate that the CT‐M method is a useful procedure for the isolation of large numbers of zona‐free mouse eggs.
Cytoplasmic deletion processes during spermatogenesis in mosses
Authors: Miller C. C. J. , Duckett J. G. 
Published: February 2005

AbstractComparative ultrastructural observations reveal that cytoplasmic deletion during spermatogenesis inSphagnumand other mosses (Bryopsida) has two distinct phases. In young spermatids, Golgi‐derived vesicles produce the mucopolysaccharide sheaths in which the gametes are liberated. Golgi bodies, however, play no part in removal of cytoplasm during gamete maturation. Rounding off of the cells during this process results in a 50% reduction in volume.Mid‐spermatid stages inSphagnumare characterised by the sequential loss of Golgi bodies and endoplasmic reticulum (ER) but no further diminution of the cytoplasm. The final stages of nuclear metamorphosis and chromatin condensation, in late spermatids, are marked by the sudden appearance, in the otherwise featureless central cytoplasm, of a membrane vesicle complex (MVC) comprising cisternae, tubules, and smooth and coated vesicles. Following repositioning of the MVC beneath the plasma membrane, rapid shrinkage of the cytoplasm is associated with the presence of vesicle fusion profiles at the cell surface. The MVC is considered to be intimately involved in cytoplasmic breakdown and loss. Acid phosphatase activity can be detected throughout spermatogenesis. Spermatogenous cells and young spermatids possess relatively low levels of the enzyme, restricted to the ER and perinuclear space, but particularly high levels occur in the MVC region of late spermatids ofSphagnum.The deletion process in Bryopsida is much more gradual than that ofSphagnum. Mid‐spermatids contain sheets of ER, Golgi with small vesicles, and irregular cisternae associated with coated vesicles. Vacuoles derived either from dilation of the ER or the coated vesicle complexes gradually increase in size and number at the expense of the cytoplasm. During the early stages of chromatin condensation, a large central vacuole opens onto the anterior face of the gametes. Further discharge of vesicles continues throughout gamete maturation.A comparative survey of spermatogenesis in land plants indicates that cytoplasmic deletion is achieved in different ways in different groups. We speculate that the spermatozoids of the common ancestor of archegoniate plants probably possessed large amounts of cytoplasm. The deletion mechanisms may have originated from a contractile vacuole apparatus.
Effect of Ca2+ channel antagonists on the acrosome reaction of guinea pig and golden hamster spermatozoa
Authors: Roldan E. R. S. , Shibata S. , Yanagimachi R. 
Published: February 2005

AbstractThe effects of Ca2+ channel antagonists on the motility and acrosome reaction of guinea pig spermatozoa were examined by incubating the spermatozoa continuously in Ca2+‐containing capacitating media with 10−6 M to 10−4 M antagonist. Antagonists tested were four voltage‐gated Ca2+ channel antagonists (verapamil, nifedipine, nimodipine, and FR–34235) and two ligand‐gated channel antagonists (NaNO2 and Na‐nitroprusside). None of these antagonists could block the acrosome reaction. Instead, three antagonists (verapamil, nimodipine, and FR‐34235, each at 10−4 M) accelerated the onset of the acrosome reaction with a subsequent decrease in sperm motility. Nifedipine and Na‐nitroprusside at the same concentration caused a complete loss of sperm motility by 4 hr of incubation with no substantial effect on the rate of acrosome reaction. The detrimental effect of antagonists on the motility of spermatozoa appears to be due to a direct, Ca2+‐independent, membrane‐perturbing action of the reagents.The acrosome reaction was not inhibited when guinea pig spermatozoa were precapacitated in Ca2+‐free medium (with a low concentration of lysolecithin) in the continuous presence of antagonists. An acceleration of the onset of the acrosome reaction by verapamil (10−4 M) was also demonstrated in the golden hamster.These results may be interpreted as indicating that the entry of extracellular Ca2+ into spermatozoa, which triggers the acrosome reaction of guinea pig and hamster spermatozoa, is not mediated by Ca2+ channels. This is in marked contrast with the case reported in invertebrate spermatozoa. Possible mechanisms by which some of the antagonists stimulate the acrosome reaction and affect the motility of mammalian spermatozoa are discussed.
Movement and dissolution of the nucleus (germinal vesicle) during Rana oocyte meiosis: Effect of demecolcine (Colcemid) and centrifugation
Authors: Lessman Charles A. , Marshall William S. , Habibi Hamid R. 
Published: February 2005

AbstractDemecolcine (Colcemid; DE), a colchicine derivative, augmented meiosis reinitiation by progesterone in the follicle‐enclosed oocyte of the frog, Rana pipiens. Whereas DE treatment alone had a minor stimulatory effect on germinal vesicle dissolution (GVD), this treatment elicited significant germinal vesicle movement (GVM) as evidenced by translocation of the GV to the oocyte surface. The effects of DE on GVM and progesterone‐induced GVD were also elicited in oocytes lacking follicle cells or other follicle wall components (type IV follicles), indicating that DE has a direct action on the oocyte itself. DE alone did not alter oocyte membrane voltage (Vm), resistance (Rm), or current (Im) and did not interfere with the changes in these parameters usually elicited by progesterone. After 5 hr incubation of follicle‐enclosed oocytes with either DE or progesterone, or combinations of both, the GV could be moved to the animal pole surface with less centrifugal force compared to control follicles. This result suggests that a decrease in ooplasmic viscoelasticity is induced by progesterone, which is mimicked by DE before GVM or GVD normally begins. The results presented here support the idea that DE‐sensitive oocyte components such as microtubules are involved in the process of steroid‐induced meiosis. These findings provide a physiological basis for future studies of cytoskeletal involvement in the events of meiosis.
Osmotic swelling of maturing rat spermatozoa and Lysis of caput spermatozoa by acylcarnitines and acylcholines
Authors: Cooper T. G. 
Published: February 2005

AbstractThe form that rat spermatozoa assume when swelling in hyposmotic media depends on the position of the cytoplasmic droplet, previous exposure to hypertonic media, and the stiffness of the flagellum. Bending at the end of the midpiece occurs when the swelling droplet is situated at this site; this occurs in midcaput cells, but sperm from more proximal sites do not bend in this fashion. Stiffening of caput sperm stored in vitro reduces the incidence of such midpiece bending but looping at the tip of the tail still occurs, and previous exposure of caput spermatozoa to hypertonic media also prevents hairpin bend formation. Mature sperm from the cauda are too stiff to form hairpin loops when placed in hypotonic media unless first treated with a penetrating disulphydryl‐reducing agent, after which swollen spherical vesicles can result from very flexible flagella confined within an intact membrane. Long‐chain acylcarnitines are more potent lytic agents than acylcholines, but, for both, chain lengths of 16 carbon atoms is optimal for preventing the swelling of rat caput sperm.
Nucleolar fine structure and RNA synthesis in bovine oocytes from antral follicles
Authors: Crozet Nicole , Kanka J. , Motlik J. , Fulka J. 
Published: February 2005

AbstractNucleolar ultrastructural changes occurring in vivo in bovine oocytes during follicular growth were analyzed by electron microscopy. The rates of in vitro incorporation of 3H‐uridine by oocytes of the same size class were evaluated by autoradiography.One to two large fibrillogranular, vacuolated nucleoli were present in oocytes from small to medium antral follicles 0.5–3 mm in diameter. These oocytes showed intense hnRNA and rRNA synthesis. The homogeneous, agranular nucleoli in oocytes from follicles 3–4 mm in diameter were composed of a compact fibrillar material. This morphological change was accompanied by an impairment of nucleolar transcriptional activity as well as by a decrease in hnRNA synthesis.
Induction of the acrosome reaction in human spermatozoa by a fraction of human follicular fluid
Authors: Suarez Susan S. , Wolf Don P. , Meizel Stanley 
Published: February 2005

AbstractHuman ejaculated spermatozoa were washed through a Percoll gradient, preincubated for 10 hr in a defined medium containing serum albumin, and then induced to undergo rapid acrosome reactions by addition of human follicular fluid or a Sephadex G‐75 column fraction of the fluid. Induction by follicular fluid did not occur when the spermatozoa were preincubated for only 0 or 5 hr. The reactions were detected by indirect immunofluorescence using a monoclonal antibody directed against the human sperm acrosomal region. The percentage of acrosomal loss counted by transmission electron microscopy agreed with that counted by immunofluorescence. The apparent molecular weight of the Sephadex G‐75 fraction containing the peak of acrosome reaction‐inducing activity was 45,000 ± 4,200 (SD). The occurrence of physiological acrosome reactions was supported by: assessing motility (no significant loss of motility occurred during the treatment period when sperm were preincubated with bovine serum albumin), transmission electron microscopy (the ultrastructural criteria for the acrosome reaction were met), and zona‐free hamster oocyte binding and penetration (spermatozoa pretreated with the active fraction of follicular fluid, then washed and incubated with oocytes, showed significantly greater binding to and penetration of oocytes). The stimulation of the acrosome reaction by follicular fluid is apparently not due to blood serum contamination; treatment of preincubated spermatozoa with sera from the follicular fluid donors had no effect on the spermatozoa. The nature of the active component(s) in that fraction is currently being investigated.
Induction of the acrosome reaction in guinea pig spermatozoa by calmodulin antagonist W‐7
Authors: Nagae T. , Srivastava P. N. 
Published: February 2005

AbstractThe effect of the calmodulin antagonist W‐7 on the capacitation and the acrosome reaction of guinea pig spermatozoa was examined. The characteristic features of the acrosome reaction induced by W‐7 were the dependence on the composition and pH of the medium and on the presence of sodium bicarbonate. The most effective concentration of W‐7 for inducing the acrosome reaction was approximately 5 μM, which is far less than the Kd for calmodulin. Moreover, W‐7 enhanced the ability of spermatozoa to acquire capacitation in a Ca2+‐free medium. The spermatozoa induced to undergo the acrosome reaction by W‐7 were capable of penetrating the zona‐free hamster eggs. W‐5, which has a lower affinity for calmodulin than W‐7, also induced the acrosome reaction in the same manner as W‐7. These results suggest that the naphthalenesulfonamide derivatives W‐7 and W‐5 can induce the acrosome reaction in guinea pig spermatozoa via capacitation in a pH‐dependent, Ca2+‐calmodulin‐independent manner.
Difference of fertilizing capacity between testicular sperm and vas deferens sperm in Cynops pyrrhogaster
Authors: Matsuda Motoko 
Published: February 2005

AbstractThe fertilizing capacity was compared between testicular and vas deferens sperm in Cynops pyrrhogaster. The testicular sperm was not capable of fertilizing jelly eggs. In contrast, the vas deferens sperm was already capable of fertilizing the newt jelly eggs. There was no inhibitory factor for fertilizing jelly eggs in the testis. These results suggest that the testicular sperm is immature as to the fertilizing capacity. The testicular sperm gained the fertilizing capacity for the jelly eggs by treatment with Holtfreter's solution or 1/20 strength Holtfreter's solution. The treatment may promote the step of maturation to achieve the fertilizing capacity. The treated testicular sperm did not fertilize dejellied eggs, although vas deferens sperm fertilized dejellied eggs. Therefore, the maturation state of the treated testicular sperm is different from that of vas deferens sperm. Newt sperm may be matured within the vas deferens, as the newt does not have an organ like the mammalian epididymis.
The kinetics of the first wave of spermatogenesis in the newborn male mouse
Authors: Sung Weng Kong , Komatsu Masanobu , Jagiello Georgiana M. 
Published: February 2005

AbstractA combination of autoradiography and air‐dried techniques was used to calculate the duration of the major meiotic stages in the first wave of spermatogenesis in the newborn mouse. The data indicated that the entry into meiosis occurred asynchronously over 2 days, and the time required for each stage and the total cycle was constant. These time intervals were nearly identical with those estimated for adult animals in the present study and by other authors.