bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Conductances and Viscosities of Tetrabutylammonium Thiocyanate in Acetonitrile in the Temperature Range 25–45 °C
Authors: Chakraborty Jayanti Moitra , Das Bijan
Published: February 2004

The electrical conductances and viscosities of the solutions of tetrabutylammonium thiocyanate (Bu4NCNS) in acetonitrile have been reported at 25, 30, 35, 40 and 45 °C. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance (Λ0), the association constant (K
Λ) and the association diameter (R). The viscosity data have been analyzed by the Jones–Dole equation for the associated electrolytes to evaluate the viscosity B-coefficients of the electrolyte. These data have also been analyzed by the transition-state treatment to obtain the contribution of the solutes to the free energy of activation for viscous flow of the solution. The ionic contributions to the limiting molar conductance (Λ0), the viscosity B-coefficient and the free energy of activation for viscous flow have been estimated using the “reference electrolyte” tetrabutylammonium tetraphenylborate (Bu4NBPh4). Slight ionic association was always found for this salt in this solvent medium. The tetrabutylammonium ion is found to be unsolvated whereas the thiocyanate ion undergoes solvation in acetonitrile in the temperature range investigated here.
New Method to Analyse IR-Studies of Monomer-Dimer Self-Association: 2,2-Dimethyl-3-Ethyl-3-Pentanol in Carbon Disulfide as an Example
Authors: Chen Jenn-Shing , Kao Dah-Yu
Published: February 2004

Two new equations have been derived to treat the IR data from the monomer-dimer self-association. Equation (9), in the text, is to regress the integrated absorbances of the monomer bands to determine the molar absorptivity of the monomer band, ε
m, and the dimerization constant, K. Equation (13), in the text, is to regress those of dimer band to obtain the molar absorptivity of the dimer band, ε
d, and dimerization constant K. The self-association in the dilute solution of 2,2-dimethyl-3-ethyl-3-pentanol in carbon disulfide at different temperatures has been used as an example to demonstrate the usage of these two equations. The discrepancy between the values of K at the same temperature determined either from the monomer band or from the dimer band can be used as a criterion for the goodness of determination. The standard enthalpy and entropy of dimerization have also been obtained via a van’t Hoff plot from the data of K at different temperatures. The advantages of this new approach have also been discussed.
Jäntti’s Method for the Fast Measurement of Adsorption Combined with Diffusion
Authors: Poulis Johannes A. , Massen Carel H. , Robens Erich , Reichenauer Gudrun
Published: February 2004

On the basis of a molecular model for adsorption kinetics Jäntti introduced a method to calculate equilibria immediately after a change of the pressure of the sorptive gas. In the present paper we show the usefulness of the Jäntti-approach to multilayer adsorption combined with diffusion of the adsorbate into the solid.
Ionic Liquids: Promising Solvents for Electrochemistry
Authors: Endres Frank
Published: February 2004

Ionic liquids are solvents that are solely composed of ions. By definition their melting points are below 100 °C. Typical cations are substituted imidazolium ions, like 1-butyl-3-methylimidazolium, or tetraalkylammonium ions, like e.g. trioctyl-methyl-ammonium. Some important anions are hexafluorophosphate, trifluoromethylsulfonate, bis(trifluoromethylsulfonyl)imide. Many ionic liquids have negligible vapour pressures even at temperatures of 300 °C and more, they can have viscosities similar to water, ionic conductivities of up to 0.1 (Ω cm)−1, and, which makes them interesting for electrochemistry, wide electrochemical windows of more than 6 Volt. In this review article recent results of the author are summarized. It is shown that with the scanning tunneling microscope the processes during phase formation can be probed in situ with high quality. An important result is that semiconductors, shown at the example of germanium, can be made electrochemically on the nanoscale and that the electronic properties (band gap) can be measured in situ with current/voltage tunneling spectroscopy. Ionic liquids will gain a rising interest in electrochemistry as elements and compounds can be made electrochemically which are not accessible by conventional aqueous or organic electrochemistry.
Localization of CD9 in pig oocytes and its effects on sperm–egg interaction
Authors: Li Yong-Hai , Hou Yi , Ma Wei , Yuan Jin-Xiang , Zhang Dong , Sun Qing-Yuan , Wang Wei-Hua
Published: February 2004

CD9 is a cell surface protein that participates in many cellular processes, such as cell adhesion. Fertilization involves sperm and oocyte interactions including sperm binding to oocytes and sperm–oocyte fusion. Thus CD9 may play an essential role during fertilization in mammals. The present study was conducted to examine whether CD9 is present in porcine gametes and whether it participates in the regulation of sperm–oocyte interactions. The presence of CD9 in ovarian tissues, oocytes and spermatozoa was examined by immunohistochemistry, immunofluorescence and immunoblotting. Sperm binding and penetration of oocytes treated with CD9 antibody were examined byin vitrofertilization. The results showed that CD9 was present on the plasma membrane of oocytes at different developmental stages. A 24 kDa protein was found in oocytes duringin vitromaturation by immunoblotting and its quantity was significantly (P< 0.001) increased as oocytes underwent maturation and reached the highest level after the oocytes had been cultured for 44 h. No positive CD9 staining was found in the spermatozoa. Both sperm binding to ooplasma and sperm penetration into oocytes were significantly (P< 0.01) reduced in anti-CD9 antibody-treated oocytes (1.2 ± 0.2 per oocyte and 16.6% respectively) as compared with oocytes in the controls (2.5 ± 0.4 per oocyte and 70.3% respectively). These results indicated that CD9 is expressed in pig oocytes during early growth and meiotic maturation and that it participates in sperm–oocyte interactions during fertilization.
Epidermal growth factor activates cytosolic [Ca2+] elevations and subsequent membrane permeabilization in mouse cumulus–oocyte complexes
Authors: O'Donnell John B , Hill Julia L , Gross David J
Published: February 2004

The role of epidermal growth factor (EGF) in the maturation of mammalian oocytes is well known but not well characterized. It is known that EGF enhances oocyte maturationin vitroand that EGF stimulation of cumulus–oocyte complexes (COCs) induces pulsatile Ca2+efflux from the cell complex. By use of quantitative Fura-2 imaging, EGF-stimulated changes in intracellular [Ca2+] in germinal vesicle stage murine COCs are shown to occur in a subpopulation of cumulus cells that interact cooperatively within individual COCs. Oocytes fail to respond to EGF stimulus. In many of the cumulus cells responding with a rise in intracellular [Ca2+], a concomitant permeabilization of the plasma membrane is found. Neither cumulus cells of control COCs nor those that show a rise in intracellular [Ca2+] in response to calcium ionophore treatment display a similar membrane permeabilization, although those cells responding with a prolonged [Ca2+] increase in response to thimerosal or thapsigargin do display plasma membrane permeabilization. Thus, EGF stimulation of mammalian COCs activates release of Ca2+from intracellular stores of cumulus cells, the depletion of which activates permeabilization of the plasma membrane. This membrane permeabilization leads to loss of cell contents and presumptive cumulus cell death. This catastrophic EGF-induced plasma membrane permeabilization of individual cumulus cells within a COC leads to pulsatile Ca2+efflux as previously seen, and may lead to improved cumulus cell expansion during COC maturation.
Involvement of glucocorticoids in testicular involution after active immunization of boars against GnRH
Authors: Wagner A , Claus R
Published: February 2004

Active GnRH immunization of boars inhibits LH and testicular steroids but the consequences for spermatogenesis are unknown. Six boars were immunized three times against GnRH at 20, 24 and 28 weeks. Another six boars served as controls. Plasma LH and FSH were determined at 28 and 31 weeks. Testosterone and cortisol were determined before killing the pigs at 32 weeks. Tissue samples were taken for histology and fluid from the seminiferous tubuli for steroid determination. Individual germ cells were counted in histological sections. The glucocorticoid receptor (GCR), mitosis of spermatogonia and apoptosis were characterized by immunocytochemistry. Immunization reduced LH and testosterone to base levels whereas FSH was not changed. Testis weight was reduced by 64% due to a loss of Leydig cell cytoplasm (90.3%) and a decrease of tubule diameters (60.6%). Except for A-spermatogonia, all other spermatogenic cells were reduced by about 60%. Mitosis was reduced in immunized boars. Expression of GCRs was limited to spermatogonia and differed between immunized boars (8% of spermatogonia) and controls (2%). In the controls, androgen concentrations in tubular fluid were tenfold higher compared with immunized boars. Cortisol concentrations were of the order of 40 nmol/l both in the tubular fluid and blood plasma. These concentrations did not differ between groups. Apoptosis occurred only in spermatogonia and pachytene spermatocytes and was twofold higher in immunized boars compared with controls. Thus the availability of glucocorticoids in the tubuli and the expression of GCRs initiate apoptosis, which in turn reduces sperm yield. Testosterone is known to be an inhibitor of GCR expression, thus increasing the efficiency of spermatogenesis.
Effect of medium on the kinematics of frozen–thawed ram spermatozoa
Authors: Mortimer Sharon T , Maxwell W M Chis
Published: February 2004

Cervically inseminated cryopreserved ram spermatozoa have reduced fertility due to poor mucus-penetrating ability. This effect is ameliorated by the addition of 20% (v/v) seminal plasma (SP) to the phosphate-buffered saline (PBS) thawing medium. The aims of this study were to determine whether the impaired mucus penetration was due to alterations in the sperm motility and, if so, whether these alterations were due to the SP or its viscosity, or to the medium components. To this end, artificial SP medium (ASP), a medium which supports motility but not capacitation, was compared with PBS and SP. Thawed, pooled semen from seven mature rams was layered under 1 ml each of PBS, SP and ASP and motile spermatozoa allowed to swim up (37 °C, 30 min). Upper regions of the overlays were harvested, and the capacitation status of the spermatozoa in each suspension determined by chlortetracycline (CTC) analysis. Sperm movement was videotaped in 300 μm chambers for both computer-aided sperm analysis assessment and manual flagellar curvature analysis. There was no effect of the culture medium on the concentration of spermatozoa recovered by swim up, nor on the proportion of motile spermatozoa. However, the spermatozoa resuspended in PBS did show changes associated with capacitation in both the CTC-binding patterns and in their movement patterns. These changes were significantly greater than those observed in spermatozoa resuspended in SP or ASP. These results indicated that the differences in sperm movement and function observed in SP medium were not due to changes in viscosity, but rather to components of the medium.
Impact of feline zona pellucida glycoprotein B-derived synthetic peptides on in vitro fertilization of cat oocytes
Authors: Ringleb Jennifer , Rohleder Marlies , Jewgenow Katarina
Published: February 2004

Although immunocontraception based on porcine zona pellucida (ZP) proteins is widely applied in many species, it is not suitable for cat contraception due to the lack of cross-reactivity. Since the first ZP gene expressed during oocyte growth in domestic cats is ZPB, we assumed that immunization with feline ZPB (fZPB)-derived synthetic peptides may cause irreversible infertility, which would be preferable in stray cats. Thus, the present study evaluated the immunogenicity and the contraceptive potential of synthetic fZPB peptides. Antigenic epitope sequences were detected via epitope mapping using specific rabbit anti-fZP antibodies. Six peptides representing the recognized epitopes were synthesized subsequently. Two out of six peptides (ZPB amino acid residue 130–149 = P3 and 175–193 = P6) cross-reacted with anti-fZP antiserum in dot blot analysis and ELISA. Coupled to BSA, both peptides were utilized to produce specific antibodies in rats. Despite several booster injections the antibody titers monitored by ELISA did not exceed 1:5000. Both rat antisera were tested for contraceptive potential in cat in vitro maturation/in vitro fertilization (IVF). Antiserum against peptide P3 significantly inhibited sperm binding and fertilization of cat oocytes in vitro (57.3% of sperm binding; 41.5% of fertilization), whereas the inhibition by anti-P6 was not significant. Pre-incubation of sperm cells with both peptides before IVF failed to affect either sperm binding or fertilization (22.3 ± 3.7 sperm/egg vs 25.5 ± 5.8 for P3 and 20.7 ± 4.0 for P6, respectively). In conclusion, antibodies directed against one of the two identified antigenic determinants of fZPB inhibited sperm binding and IVF and therefore showed promising results as a contraceptive. However, the specific immune response and anti-fertile properties of this synthetic vaccine have to be examined in vivo to verify the suitability of its components.
Expression patterns of cytokines, p53 and nitric oxide synthase isoenzymes in corpora lutea of pseudopregnant rabbits during spontaneous luteolysis
Authors: Boiti Cristiano , Guelfi Gabriella , Zerani Massimo , Zampini Danilo , Brecchia Gabriele , Gobbetti Anna
Published: February 2004

The gene expressions for macrophage chemoattractant protein-1 (MCP-1), interleukin (IL)-1β, IL-2 and p53 were examined by semi-quantitative RT-PCR in corpora lutea (CL) of rabbits during spontaneous luteolysis at days 13, 15, 18 and 22 of pseudopregnancy. In the same luteal tissue, total activity of nitric oxide (NO) synthase (NOS) and genes for both endothelial (eNOS) and inducible (iNOS) isoforms were also analysed. From day 13 to 15, MCP-1 and IL-1βmRNA levels rose (P≤ 0.01) almost 2-fold, and the transcript for p53 almost 8-fold, but then all dropped (P≤ 0.05) from day 18 onward. IL-2 mRNA abundance was higher (P≤ 0.01) on day 13 and then gradually declined. During luteolysis, eNOS mRNA decreased 40% (P≤ 0.05) by day 15, but thereafter remained unchanged, while iNOS mRNA was barely detectable and did not show any clear age-related pattern throughout the late luteal stages. Total NOS activity progressively increased (P≤ 0.01) from day 13 to 18 of pseudopregnancy and then dropped to the lowest (P≤ 0.01) levels on day 22. Luteal progesterone content also declined during CL regression from 411 to 17 pg/mg found on days 13 and 22 respectively, in parallel with the decrease in blood progesterone concentrations. These data further support a physiological role of NO as modulator of luteal demise in rabbits. Locally, luteal cytokines may be involved in the up-regulation of NOS activity, while downstream NO may inhibit steroroidogenesis and induce expression of p53 gene after removal of the protective action of progesterone.
Effects of follicle size and electrolytes and glucose in maturation medium on nuclear maturation and developmental competence of bovine oocytes
Authors: Iwata Hisataka , Hashimoto Shu , Ohota Mayuko , Kimura Koji , Shibano Kenichi , Miyake Masashi
Published: February 2004

The concentrations of electrolytes (Na, K, Cl, Mg and Ca) and glucose in small follicle (SF) follicular fluid (SFF) and large follicle (LF) follicular fluid (LFF) from slaughterhouse-derived ovaries were studied. Oocytes were matured in medium based on synthetic oviductal fluid. The effects of various concentrations of electrolytes (Na, K, Ca and Mg) and glucose in the maturation medium on the progression of nuclear maturation and subsequent development were also studied. K in SFF was significantly greater than that in LFF. The Mg concentration in follicular fluid (FF) is 2.0–2.3 mM, which is greater than the concentration present in medium generally used for culture. The glucose concentration in FF is about 3.5–3.9 mM and rapidly decreases during the preservation of ovaries. LF oocytes resumed nuclear maturation and progressed to the M2 stage significantly faster than those collected from SF oocytes. In addition, more LF oocytes developed to blastocysts than did SF oocytes. Changing the Na/K ratio in the maturation medium from 16 to 24 did not affect either the progression of nuclear maturation or the rate of development. A low concentration of Mg (0.5 mM) combined with a low Ca concentration (0.5 mM) inhibited the rate of development, but did not affect the progression of nuclear maturation. On the other hand, increasing the Mg concentration to 2.0 mM from 0.5 mM hastened the progression of nuclear maturation and improved the rate of blastulation, irrespective of the Ca concentration. The progression of nuclear maturation was faster and the rate of development was greater with 5.56 mM glucose than with 1.5 mM glucose. The difference in time needed to progress to M2 among the experiment was about 2–3 h. Therefore, prolonging the maturation periods from 21 to 24 h did not change the rate of development. Our results show that the concentrations of Mg and glucose in the maturation medium and the follicle size enveloping the oocyte affect the progression of nuclear maturation and subsequent development. The time requirement for oocytes to reach M2 is strongly related to the developmental competence of the oocytes.
Ligands and receptors mediating signal transduction in sea urchin spermatozoa
Authors: Neill Anna T , Vacquier Victor D
Published: February 2004

Sea urchins have long been a model system for the study of fertilization. Much has been learned about how sea urchin sperm locate and fertilize the egg. Sperm and eggs are spawned simultaneously into the surrounding seawater. Sperm signaling pathways lead to downstream events that ensure fertilization. Upon spawning, sperm must acquire motility and then they must swim towards or respond to the egg in some way. Finally, they must undergo a terminal exocytotic event known as the acrosome reaction that allows the sperm to bind to the vitelline layer of the egg and then to fuse with the egg plasma membrane. Motility is stimulated by exposure to seawater, while later events are orchestrated by factors from the egg. The sperm signaling pathways are exquisitely tuned to bring the sperm to the egg, bind, and fuse the two cells as quickly as possible.
Quality of porcine blastocysts produced in vitro in the presence or absence of GH
Authors: Kidson A , Rubio-Pomar F J , Van Knegsel A , Van Tol H T A , Hazeleger W , Ducro-Steverink D W B , Colenbrander B , Dieleman S J , Bevers M M
Published: February 2004

GH receptor (GHR) mRNA is expressed in bovinein vitroproduced embryos up to the blastocyst stage and GH improves the quality of bovine embryos by increasing blastocyst cell numbers and reducing the incidence of apoptosis as evaluated by DNA strand-break labelling. Porcinein vitroproduced blastocysts have lower cell numbers thanin vivoblastocysts and exhibit higher incidences of apoptosis. Therefore we investigated the effects of 100 ng GH/ml NCSU23 medium duringin vitroculture of presumptivein vitrofertilized sow zygotes on embryo development and blastocyst quality (defined by diameter, cell number, apoptosis and survival after non-surgical transfer).In vivoproduced blastocysts were analysed concurrently as a reference value. GHR was expressed in embryos from the 2-cell to blastocyst stages. GH had no effect on blastocyst development or cell numbers, but increased the mean blastocyst diameter. The incidence of apoptosis, detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL), was decreased by GH, but when non-TUNEL-labelled apoptotic fragmented nuclei were included, no difference was seen. GH appeared to slow down the progression of apoptosis though.In vivoproduced blastocysts presented no apoptotic nuclei, and contained higher cell numbers and larger diameters. Pregnancy rates on day 11 were similar for all groups, but survival was poorer forin vitrothanin vivoproduced blastocysts. In this study GH appeared to be beneficial only from the blastocyst stage, but the presence of GHR from early cleavage stages nevertheless indicates a role for GH throughout porcine embryo development and deserves further investigation.
Factors affecting developmental competence of equine oocytes after intracytoplasmic sperm injection
Authors: Choi Y H , Love L B , Varner D D , Hinrichs K
Published: February 2004

This study was conducted to evaluate the effect of initial cumulus morphology (expanded or compact) and duration of in vitro maturation (24, 30 or 42 h) on the developmental competence of equine oocytes after intracytoplasmic sperm injection (ICSI). The effect of manipulation temperature (room temperature vs 37 °C) at the time of ICSI and concentration of glucose (0.55 vs 5.5 mM) during embryo culture was also investigated. The nuclear maturation rates of expanded (Ex) oocytes were significantly (P < 0.001) higher than those of compact (Cp) oocytes at all maturation times (61–72 vs 23–25% respectively). Forty-eight hours after ICSI of mature Ex oocytes, the rate of cleavage with normal nuclei was significantly (P < 0.05) higher for oocytes matured for 24 h than for those matured for 30 or 42 h (73 vs 57–59% respectively). For Cp oocytes, the morphologic cleavage rates for oocytes matured for 30 h were significantly higher (P < 0.05) than for those matured for 24 or 42 h (86 vs 55–61% respectively). The overall proportion of embryos having more than four normal nuclei at 48 h culture was significantly higher (P < 0.05) for Cp than for Ex oocytes. Manipulation temperature did not affect development of embryos from Ex or Cp oocytes at 96 h after ICSI. Culture in high-glucose medium significantly increased morphologic cleavage of Cp, but not Ex, oocytes (P < 0.05). Embryos from Cp oocytes had a significantly higher average nucleus number after 96-h culture than did embryos from Ex oocytes. These data indicate that developmental competence differs between Ex and Cp equine oocytes, and is differentially affected by the duration of maturation and by composition of embryo culture media.
Quantitative analysis of mitochondrial DNAs in macaque embryos reprogrammed by rabbit oocytes
Authors: Yang Cai-Xia , Kou Zhao-Hui , Wang Kai , Jiang Yan , Mao Wen-Wei , Sun Qing-Yuan , Sheng Hui-Zhen , Chen Da-Yuan
Published: February 2004

In cloned animals where somatic cell nuclei and oocytes are from the same or closely related species, the mitochondrial DNA (mtDNA) of the oocyte is dominantly inherited. However, in nuclear transfer (NT) embryos where nuclear donor and oocyte are from two distantly related species, the distribution of the mtDNA species is not known. Here we determined the levels of macaque and rabbit mtDNAs in macaque embryos reprogrammed by rabbit oocytes. Quantification using a real-time PCR method showed that both macaque and rabbit mtDNAs coexist in NT embryos at all preimplantation stages, with maternal mtDNA being dominant. Single NT embryos at the 1-cell stage immediately after fusion contained 2.6 × 104copies of macaque mtDNA and 1.3 × 106copies of rabbit mtDNA. Copy numbers of both mtDNA species did not change significantly from the 1-cell to the morula stages. In the single blastocyst, however, the number of rabbit mtDNA increased dramatically while macaque mtDNA decreased. The ratio of nuclear donor mtDNA to oocyte mtDNA dropped sharply from 2% at the 1-cell stage to 0.011% at the blastocyst stage. These results suggest that maternal mtDNA replicates after the morula stage.
Conditioned medium increases the polyploid cell composition of bovine somatic cell nuclear-transferred blastocysts
Authors: Li G-P , White K L , Aston K I , Meerdo L N , Bunch T D
Published: February 2004

The effects of bovine cumulus cell-conditioned medium on cloned bovine embryonic development and subsequent chromosome complement were examined using an air-dry procedure. Conditioned media were prepared using CR1aa supplemented with either fetal bovine serum (FBS) or bovine serum albumin (BSA). Nuclear-transferred embryos were reconstructed with nuclei from cumulus cells. Similar cleavage, morula, and blastocyst development was observed in conditioned media groups compared with the co-culture group. No differences (P > 0.05) were observed in the composition of blastocyst chromosomes after co-culture in different media, either with or without starvation of donor cells. The overall diploid blastocyst rate ranged from 75% to 84%. Chromosomal complement of blastocysts, however, was very different between conditioned medium and co-culture treatments. Overall incidence of chromosomal anomalies was 40% in conditioned medium, which was significantly higher (P < 0.001) than the co-culture group (20%). Moreover, a higher incidence (P < 0.05) of chromosomally abnormal blastocysts (41.5%) was observed after culture with FBS-containing conditioned medium than those cultured in BSA-containing conditioned medium (31.4%). No diploid improvement was observed after exchange of the culture system from conditioned medium to co-culture, or from co-culture to conditioned medium after the first 72 h of culture. The results of this study also indicated that the overall cell number was much lower (P < 0.01) in blastocysts with chromosomal abnormalities than those with a normal diploid state. We have concluded that medium conditioned with bovine cumulus cells increases the incidence of chromosomal anomalies in nuclear reconstructed embryos.
Bone morphogenetic protein (BMP) ligands and receptors in bovine ovarian follicle cells: actions of BMP-4, -6 and -7 on granulosa cells and differential modulation of Smad-1 phosphorylation by follistatin
Authors: Glister Claire , Kemp C Fred , Knight Philip G
Published: February 2004

Given the paucity of information on the potential roles of bone morphogenetic proteins (BMPs) in the ruminant ovary we conducted immunolocalization and functional studies on cells isolated from bovine antral follicles. Immunocytochemistry revealed expression of BMP-4 and -7 in isolated theca cells whereas granulosa cells and oocytes selectively expressed BMP-6. All three cell types expressed a range of BMP-responsive type-I (BMPRIB, ActRI) and type-II (BMPRII, ActRII, ActRIIB) receptors supporting autocrine/paracrine roles within the follicle. This was reinforced by functional experiments on granulosa cells which showed that BMP-4, -6 and -7 promoted cellular accumulation of phosphorylated Smad-1 but not Smad-2 and enhanced ‘basal’ and IGF-stimulated secretion of oestradiol (E2), inhibin-A, activin-A and follistatin (FS). Concomitantly, each BMP suppressed ‘basal’ and IGF-stimulated progesterone secretion, consistent with an action to prevent or delay atresia and/or luteinization. BMPs also increased viable cell number under ‘basal’ (BMP-4 and -7) and IGF-stimulated (BMP-4, -6 and -7) conditions. Since FS, a product of bovine granulosa cells, has been shown to bind several BMPs, we used the Biacore technique to compare its binding affinities for activin-A (prototype FS ligand) and BMP-4, -6 and -7. Compared with activin-A (Kd0.28 ± 0.02 nM; 100%), the relative affinities of FS for BMP-4, -6 and -7 were 10, 5 and 1% respectively. Moreover, studies on granulosa cells showed that preincubation of ligand with excess FS abolished activin-A-induced phosphorylation of Smad-2 and BMP-4-induced phosphorylation of Smad-1. However, FS only partially reversed BMP-6-induced Smad-1 phosphorylation and had no inhibitory effect on BMP-7-induced Smad-1 phosphorylation. These findings support functional roles for BMP-4, -6 and -7 as paracrine/autocrine modulators of granulosa cell steroidogenesis, peptide secretion and proliferation in bovine antral follicles. The finding that FS can differentially modulate BMP-induced receptor activation and that this correlates with the relative binding affinity of FS for each BMP type implicates FS as a potential modulator of BMP action in the ovary.
Effect of steroid hormones on tissue remodelling and progesterone receptors in the uterus of seasonally anoestrous brushtail possums (Trichosurus vulpecula)
Authors: Sizemore R J , Hurst P R , McLeod B J
Published: February 2004

This study describes progesterone receptor (PR) location within uterine cells and associated morphological changes to the uterine luminal and glandular epithelium in seasonally anoestrous brushtail possums treated with oestradiol and/or progesterone.

Twenty-four adult female possums (n= 6/group) were treated with oestradiol, progesterone, oestradiol followed by progesterone or with the oil vehicle alone for 6-day periods. Uterine tissue was recovered, weighed and processed for light and transmission electron microscopy and for immunohistochemistry for PRs. Stereological techniques were used to quantify epithelial cell and constituent volumes for both luminal and glandular tissues. Plasma concentrations of oestradiol and progesterone were determined by radioimmunoassay.

Mean uterine wet weights were significantly heavier (P< 0.001) following oestradiol/progesterone treatment and maximum gland dilation, cellular and stromal growth, maximum cell height, and cell and constituent volumes were recorded after this treatment regimen. Cell nuclei and debris were commonly observed in gland lumina, and nuclear PRs were found predominantly in stromal cells following oestradiol-only treatment. Sequential treatment with oestradiol and then progesterone caused a decline in the number of positively stained cells. Epithelial cells contained extensive secretory organelles and degenerating cells were common within the glands.

Oestradiol treatment induced cell and cell constituent growth and promoted PR formation in anoestrous possum uterine tissue. Subsequent exposure to progesterone stimulated uterine tissues to reach maximum wet weights and led to the cellular maturation necessary to remodel the uterus in preparation for pregnancy.
Distribution of mitochondria in reconstructed mouse oocytes
Authors: Fulka Helena
Published: February 2004

It has been suggested that nucleus replacement (transfer) may be used as an efficient oocyte therapy in order to prevent transmission of mutated mitochondrial DNA from mother to offspring in humans. The essential and not yet answered question is how mitochondria surrounding the karyoplast will be distributed in the newly reconstructed oocytes. In our model experiments, we have evaluated the distribution of mitochondria in reconstructed immature mouse oocytes when germinal vesicle karyoplasts, with labeled mitochondria, were fused to unlabeled cytoplasts. The penetration of mitochondria from karyoplasts into cytoplasts can be detected almost immediately after the beginning of fusion. In immature reconstructed oocytes, mitochondria are first located in the oocyte center but they are homogenously distributed within the whole cytoplasm before the completion of maturation. Fusion of oocytes at different stages of maturation suggests that the speed of mitochondria distribution is cell cycle dependent.
Effect of deslorelin implants on follicular development, parturition and post-partum oestrus in the tammar wallaby (Macropus eugenii)
Authors: Herbert C A , Trigg T E , Cooper D W
Published: February 2004

The effect of treatment with slow release implants containing the GnRH agonist, deslorelin, was investigated in female tammar wallabies. Pouch young were removed from 16 wallabies presumed to be carrying quiescent blastocysts. Eight received a 5 mg deslorelin implant and eight received a placebo implant. Animals were caught daily from day 25 to day 30 and their pouches inspected for newborn young and their urogenital sinus checked for a copulatory plug. Treatment with deslorelin did not affect reactivation of a dormant blastocyst and subsequent birth in 4/8 animals, but post-partum mating was inhibited in these animals. Five control and five treated animals were killed within 0–48 h post partum and their reproductive tracts analysed. At autopsy, all five control animals had large preovulatory follicles but only one deslorelin-treated animal showed signs of follicular development. These differences were also reflected in the weights of the lateral vaginae, with treated animals showing no evidence of oestrogenic stimulation. The remaining three control and three treated animals were monitored for approximately 2 years. The long-term contraceptive effects of a single 5 mg deslorelin implant lasted for just under one year. These results indicate that slow release deslorelin implants inhibit follicular development in the female tammar wallaby for extended periods of time and may have potential application in reproductive management of captive marsupials in the kangaroo family.
Hot Isostatic Pressing (HIP) of Elemental Powder Mixtures and Prealloyed Powder for NiTi Shape Memory Parts
Authors: Schüller E. , Hamed O.A. , Bram M. , Sebold D. , Buchkremer H.P. , Stöver D.
Published: February 2004

For NiTi shape memory alloys, powder metallurgical (PM) processes are pioneering production routes. One promising route for the PM fabrication of NiTi compacts is Hot Isostatic Pressing (HIP). For the present investigation, cost‐effective elemental powder mixtures as well as high‐purity prealloyed NiTi powders were used. To evaluate HIP as an alternative to melting processes, reproducibility of sufficient shape memory and mechanical properties were verified.
Role of Manganes in the Soldering Reaction in Magnesium High Pressure Die Casting
Authors: Tang C. , Jahedi M. , Brandt M.
Published: February 2004

The significance of soldering in high pressure die casting (HPDC) of magnesium alloys could have a major economic impact on die casters and a study of the soldering phenomenon during HPDC of magnesium alloys has been undertaken. In this paper results of dip tests are presented involving the immersion of samples made from H13 tool steel into molten magnesium alloys with different aluminium and manganese contents.
General Corrosion and Galvanic Corrosion Properties of Differently PVD Treated Magnesium Die Cast Alloy AZ91
Authors: Hoche H. , Blawert C. , Broszeit E. , Berger C.
Published: February 2004

Developing PVD coating systems with better corrosion resistance leads to a duplex process, consisting of a plasma anodisation and an Al2O3 top coating which can both be performed in a modified commercial PVD unit. The tested specimens were investigated by means of optical microscopy, SEM and EDX. Furthermore a novel immersion technique to determine the time dependent corrosion behavior of coated magnesium alloys is introduced.
Creep Resistant Magnesium Alloys for Powertrain Applications
Authors: Pekguleryuz M.O. , Kaya A.A.
Published: February 2004

Creep resistant magnesium alloys are candidate materials for automotive powertrain applications. Since the 90's, a number of new creep‐resistant magnesium alloy systems have been investigated and developed. These are for the most part based on rare‐earth, alkaline earth, and silicon additions. This paper gives an overview of creep resistance in magnesium and a review of creep resistant magnesium alloys for power‐train applications.
Influence of Rolling Conditions on the Microstructure and Mechanical Properties of Magnesium Sheet AZ31
Authors: Kaiser F. , Bohlen J. , Letzig D. , Kainer K.U. , Styczynski A. , Hartig C.
Published: February 2004

Two aspects of the deformation behavior of magnesium sheets are the subject of this paper. First it will give a mechanical characterization of a commercial magnesium with a focus on the anisotropy and the possible microstructural causes of this behavior. The rolling process will be part of the second aspect. The aim is to show the influence of the parameters on the microstructure and texture and how this could affect the anisotropy in the rolled sheets.
Microfabrication of Three‐Dimensional, Free‐Standing Ceramic MEMS Components by Soft Moulding
Authors: Zhang D. , Su B. , Button T.W.
Published: February 2004

This paper describes a soft moulding technique for the near net‐shape fabrication of three‐dimensional (3D) free‐standing ceramic structures with dimensions in the micrometer range for application in the micro‐electromechanical systems (MEMS). Highly concentrated alumina suspensions have been patterned on thin photoresist layers coated on alumina substrates by the use of soft polymer moulds.
Design of Nanoporous Superalloy Membranes for Functional Applications
Authors: Rösler J. , Mukherji D.
Published: February 2004

Materials exhibiting gas permeable porosity are of particular interest for a number of functional applications. Here, the authors show a new nanoporous superalloy membrane, far surpassing existing gas permeable porous metals in fineness and regularity of the porosity. This may not only open the path for new medical applications it may also help realizing the vision of miniaturized fuel cells powering laptops and cellular phones.
Fatigue Simulation of Light Weight Components of Magnesium
Authors: May U. , Berg‐Pollack A.
Published: February 2004

More and more, magnesium alloys are being used as materials for safety components. Therefore, an assessment of the structural durability is very important with regard to the product liability requirements. Within the scope of the Fraunhofer WISA‐project “Leichtbau mit Magnesium” (lightweight construction with magnesium), the use of different magnesium alloys as materials for safety components is investigated. In this communication, some of the steps in assessing the structural durability of a cast vehicle component of the magnesium alloy AS21X are presented.
Understanding Magnesium Corrosion—A Framework for Improved Alloy Performance
Authors: Song G. , Atrens A.
Published: February 2004

The purpose of this paper is to provide a succinct but nevertheless complete mechanistic overview of the various types of magnesium corrosion. The understanding of the corrosion processes of magnesium alloys builds upon our understanding of the corrosion of pure magnesium. This provides an understanding of the types of corrosion exhibited by magnesium alloys, and also of the environmental factors of most importance. This deep understanding is required as a foundation if we are to produce magnesium alloys much more resistant to corrosion than the present alloys. Much has already been achieved, but there is vast scope for improvement. This present analysis can provide a foundation and a theoretical framework for further, much needed research. There is still vast scope both for better fundamental understanding of corrosion processes, engineering usage of magnesium, and also on the corrosion protection of magnesium alloys in service.
Die Casting for High Performance—Focus on Alloy Development
Authors: Bakke P. , Westengen H.
Published: February 2004

Development of magnesium die casting alloys is the art of combining a thorough understanding of thermodynamic aspects of alloy composition and phase formation with the solidification kinetics as experienced in the die casting process. The microstructures obtained will determine The Alloy Property profile, which must be in line with the targeted application requirements. Successful development of an industrial alloy means that also The Diecasting Performance profile as well as the Alloy Production and Recycling profile must be fulfilled. In the present paper, a summary of current alloy development efforts will be given. Results from alloy development work by Hydro Magnesium will be presented, focusing mainly on creep resistant alloys. Specifically, alloys within the Mg‐Al‐RE system are highlighted.
Properties of Graphite‐Strengthened Magnesium
Authors: Ferkel H.
Published: February 2004

Mg was dispersion‐strengthened with graphite by powder metallurgy. The material was produced by ball milling Mg micropowder (median particle diameter 40 μm) with 3 vol.‐% graphite powder (median particle diameter 1–2 μm). After 8 h ball milling the product was consolidated by hot extrusion. Structural analysis revealed that a submicrocrystalline structure developed during ball milling. Tensile tests showed that the material was brittle even up to 300 °C and, therefore, most mechanical tests were carried out under compression. Under those conditions the reinforced material showed yield stresses of 270 MPa at ambient temperature, 170 MPa at 150 °C, and 125 MPa at 300 °C. Mg processed under the same conditions, but without graphite addition, had significantly lower yield stresses. The dispersion‐strengthened Mg showed a marked increase in creep resistance: at 200 °C and a stress, σc, of 100 MPa, the secondary creep rate, ϵs, was in the lower 10–9 s–1 range and at 300 °C and σc of 80 MPa, ϵs values of up to 1 × 10–8 s–1 were measured. The results are discussed.
Comparative Dimerization of 1‐Butene with a Variety of Metal Catalysts, and the Investigation of a New Catalyst for CH Bond Activation
Authors: Small Brooke L. , Schmidt Roland
Published: February 2004

Catalytic dimerization of 1‐butene by a variety of catalysts is carried out, and the products are analyzed by gas chromatography and mass spectrometry. Catalysts based on cobalt and iron can produce highly linear dimers, with the cobalt‐based dimers exceeding 97 % linearity. Catalysts based on vanadium and aluminum prefer to make branched dimers, which are most often methyl‐heptenes in the case of vanadium and almost exclusively 2‐ethyl‐1‐butene in the case of aluminum. The vanadium catalyst also produces substantial amounts of dienes and alkanes, suggesting a competing hydrogenation/dehydrogenation pathway that appears to involve vinyl CH bond activation. Nickel catalysts are generally less selective than those based on iron or cobalt for making linear dimers, but they can make dimers with 60 % linearity. The major by‐products for the nickel systems are trisubstituted internal olefins. An important side reaction that must be considered for dimerization reactions is 1‐butene isomerization to 2‐butene, which makes recycling the butene difficult for a linear dimerization process. Aluminum, iron, and vanadium systems promote very little isomerization, but nickel and cobalt systems tend to isomerize the undimerized substrate heavily.
Discrete Triangle, Square and Hexametallic Alkynyl Cyano‐Bridged Compounds Based on [cis‐Pt(CCR)2(CN)2]2− Building Blocks
Authors: Forniés Juan , Gómez Julio , Lalinde Elena , Moreno M. Teresa
Published: February 2004

Novel mixed bis(alkynyl)bis(cyano)platinate(II) species [cis‐Pt(CCR)2(CN)2]2− (1 a: R = tBu, 1 b: R = Ph) have been prepared and their potential as building blocks in the generation of self‐organized systems with a variable molecular architecture has been studied. The reaction of 1 with the ditopic acceptor species [{cis‐Pt(C6F5)2S}2(dppa)] (dppa=diphenylphosphinoacetylene) gave the dianionic cyanide/dppa bridged molecular platinotriangles (NBu4)2[(C6F5)2Pt(μ‐dppa){(μ‐CN)2Pt(CCR)2}Pt(C6F5)2] (2). X‐ray analysis of 2 a confirmed that the “Pt2(C6F5)4(μ‐dppa)” binuclear moiety is connected to the dianionic “Pt(CCR)2(CN)2” unit by two bridging cyanide ligands. Moreover, treatment of 1 with the solvent cationic species [M(cod)(acetone)2]+ afforded heterometallic molecular squares Pt2M2 (M=Rh, Ir) containing cyanide bridges and terminal alkynyl ligands, (NBu4)2[cyclo{[cis‐Pt(CCR)2(μ‐CN)2][M(cod)]}2] (3: M=Rh, 4: M = Ir). The solid‐state structures of phenyl derivatives have been determined by X‐ray crystallography. The terminal alkynyl ligands in these cyanide‐bridged molecular squares 3 and 4 have been used in the assembly of higher multimetallic complexes. Thus, very unusual bis(double‐alkynide)‐cyanide‐bridged hexametallic compounds (NBu4)2[{(C6F5)2Pt(μ‐CCPh)2(μ‐CN)2}2{M(cod)}2] (5 b: M=Rh, 6 b: M = Ir) were easily formed by simple reactions of 3 b and 4 b with two equivalents of [cis‐Pt(C6F5)2(thf)2]. An X‐ray diffraction study on complex 5 b indicated that the derivative was formed by a simultaneous migration of one σ‐alkynyl group from each “Pt(CCPh)2(μ‐CN)2” corner of the square to both “Pt(C6F5)2” units, resulting in bent σ,π‐double‐alkynyl bridging systems. Finally, the novel supramolecular anionic assemblies (NBu4)4[cyclo{[cis‐Pt(CCR)2(μ‐CN)2][SnPh3]}4] 7 have been obtained by self‐assembly of 1 and [SnPh3(acetone)2]+.
Prompt Chemoenzymatic Synthesis of Diverse Complex‐Type Oligosaccharides and Its Application to the Solid‐Phase Synthesis of a Glycopeptide with Asn‐Linked Sialyl‐undeca‐ and Asialo‐nonasaccharides
Authors: Kajihara Yasuhiro , Suzuki Yasuhiro , Yamamoto Naoki , Sasaki Ken , Sakakibara Tohru , Juneja Lekh Raj
Published: February 2004

We describe herein the preparation of 24 pure asparagine‐linked oligosaccharides (Asn‐oligosaccharides) from asparagine‐linked biantennary complex‐type sialylundecasaccharide [(NeuAc‐α‐2,6‐Gal‐β‐1,4‐GlcNAc‐β‐1,2‐Man‐α‐1,6/1,3‐)2‐Man‐β‐1,4‐GlcNAc‐β‐1,4‐GlcNAc‐β‐1‐asparagine, 2] obtained from egg yolk. Our synthetic strategy aimed at adapting branch specific exo‐glycosidases digestion (β‐D‐galactosidase, N‐acetyl‐β‐D‐glucosaminidase and α‐D‐mannosidase) of the individual asialo‐branch after preparation of monosialyloligosaccharides obtained from 2 by acid hydrolysis of NeuAc. In order to perform branch specific exo‐glycosidase digestion, isolation of pure monosialyloligosaccharides obtained was essential. However, isolation of two kinds of monosialyloligosaccharides are difficult by HPLC due to their highly hydrophilic nature. Therefore, we examined chemical protection with hydrophobic protecting (Fmoc and benzyl) groups. These chemical protection enabled us to separate the monosialyloligosaccharides by use of a HPLC column (ODS) on synthetic scales. Using these pure monosialiloligosaccharides enable us to obtain 24 Asn‐linked oligosaccharides (100 mg scale) within a few weeks by branch specific exo‐glycosidase digestions (α‐D‐neuraminidase, β‐D‐galactosidase, N‐acetyl‐β‐D‐glucosaminidase and α‐D‐mannosidase). In addition, solid‐phase synthesis of glycopeptide having Asn‐linked sialyl‐undeca‐ and asialo‐nonasaccharides thus obtained, was also performed on an acid labile HMPA‐PEGA resin.
Efficient Synthesis of S‐Linked Glycopeptides in Aqueous Solution by a Convergent Strategy
Authors: Zhu Xiangming , Schmidt Richard R.
Published: February 2004

In naturally occurring glycopeptides and glycoproteins the glycan residues generally possess N‐ and O‐linkages to the peptide backbone. Here we report the synthesis of the corresponding S‐linked glycopeptides by a convergent strategy to provide compounds which should be quite stable to glycosidases. To this end, peptides that contain β‐bromoalanine and γ‐bromohomoalanine were generated either directly by bromination of serine and homoserine residues, respectively, or by standard ligation of the corresponding amino acids. 1‐Thiosugars of O‐acetyl protected GalNAc, GlcNAc, and lactose were prepared by known procedures. Reaction of the thiosugars with these peptides in an ethyl acetate/water two‐phase system, which contained TBAHS and NaHCO3, or in a one‐phase system that consists of DMF/water and which contains NaHCO3, led to the desired S‐linked glycopeptides cleanly and in almost quantitative yield. This reaction also worked well for O‐unprotected 1‐thiosugars.