bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and physical properties of telechelic monodispersed diols 4. Monoaddition of 10‐undecenol to novel dithiols
Authors: Améduri Bruno , Berrada Khalid , Boutevin Bernard , Mélas Michel , Bowden Roy D. 
Published: April 2003

AbstractThe synthesis of novel telechelic monodispersed diols produced from the radical monoaddition of an excess of 10‐undecenol with novel α, ω‐dithiols, initiated by peroxides, is presented. The telechelic dithiols employed were prepared from nonconjugated dienes and a commercially available dithiol, or by esterification of adipic acid with 2‐mercaptoethanol. From these dithiols, the diols were selectively obtained in high yields. Such α, ω‐dihydroxylated compounds were characterized by both 1H and 13C NMR spectroscopy. The diol which exhibits the ester functions shows excellent solubility in common organic solvents contrarily to the other ones. The physical properties (Tg, Tm and decomposition temperatures) of these diols were compared and it is noted that the thermostability of these monodispersed telechelic diols is much better than those of the polydispersed commercially available ones such as poly(ethylene glycol)s or poly(tetramethylene glycol)s.
New poly(amide‐imide)s syntheses, 6. Preparation and properties of poly(amide‐imide)s derived from 2,7‐bis(4‐aminophenoxy)naphthalene, trimellitic anhydride and various aromatic diamines
Authors: Yang Chin…Ping , Chen Wen‐Tung 
Published: April 2003

AbstractAn imide ring‐containing dicarboxylic acid, 2,7‐bis[4‐(N‐trimellitoyl)phenoxy]naphthalene (1,1′,3,3′‐tetraoxo‐2,2′‐[2,7‐naphthylenedioxybis(1,4‐phenylene)]di‐1H, 3H‐isoindole‐5‐carboxylic acid (3)), was prepared by condensation of 2,7‐bis(4‐aminophenoxy)naphthalene (4,4′‐(2,7‐naphthylenedioxy)dianiline) and trimellitic anhydride (1,2,4‐benzenetricarboxylic acid 1,2‐anhydride). A series of new aromatic poly(amide‐imide)s 5 containing bis(phenoxy)naphthalene moieties having inherent viscosities of 0,8–1,57 dL/g were prepared by direct polycondensation of this diimide‐diacid 3 with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents in 1‐methyl‐2‐pyrrolidone (NMP) in the presence of calcium dichloride. Polymers 5 show excellent solubility in polar solvents such as NMP, and most of them could be cast into transparent and tough films. Measurements of wide‐angle X‐ray diffraction revealed that those polymer containing p‐phenylene or oxyphenylene groups are partially crystalline. Amorphous members exhibit glass transition temperature in the range of 250–311°C. Thermal analyses indicated that these polymers are fairly stable, and the 10% weight loss temperature were recorded in the ranges of 526–575°C in nitrogen and 481–556°C in air.
A propos de quelques anomalies de la polymérisation radicalaire du vinyl‐1‐imidazole
Authors: Chapiro Adolphe , Randriamahefa Solo , Schmitt Nicole 
Published: April 2003

AbstractThe polymerization of 1‐vinylimidazole (VI) was initiated with benzoyl peroxide (POB) in bulk and in methanol solutions while gamma‐ray initiation was used for the reaction in a ternary mixture with methanol and hexane. These conditions were chosen in order to understand better some anomalies observed in the grafting of VI on radiation‐peroxidized polyethylene. It was found that POB induces an addition reaction onto VI giving rise to a polymer of low molecular weight. This reaction occurs at low temperature and could involve ionic species. VI not being miscible with hexane, its gamma‐ray initiated polymerization was investigated in a ternary mixture with methanol at 60°C. Under such conditions the reaction proceeds “normally”, except in the vicinity of a demixing point where a strong auto‐acceleration occurs. This effect presumably results from a phase separation into micro‐droplets in which the reaction proceeds similarly to an emulsion polymerization. It is concluded that the abnormal behaviour of VI in the grafting reaction onto peroxidized polyethylene observed earlier follows from the initiation process by peroxides and not from the hydrocarbon nature of polyethylene.
Phase transition of liquid‐crystalline polyesters with biphenyl mesogen under high pressures
Authors: Maeda Yoji , Toriumi Hirokazu 
Published: April 2003

AbstractThe structural and thermal behavior of liquid‐crystalline polyesters at hydrostatic pressure was investigated by using a high‐pressure DTA and a wide‐angle X‐ray scattering apparatus equipped with a high‐pressure sample vessel. The thermotropic polyesters (two homopolymers and the corresponding copolymer) are based upon 4,4′‐biphenyldiol as the mesogen and aliphatic dibasic acids containing 7 and 8 methylene groups as flexible spacer, which are labeled as PB‐7, PB‐8, and PB‐7,8 (30/70 mol‐%), respectively. The phase diagrams of the PB‐7, PB‐8 and PB‐7,8 samples were constructed for pressures up to 300 MPa. At room temperature both the PB‐7 and the PB‐8 crystals are compressed hydrostatically in the molecular chain and lateral packing directions. The d spacing of the low‐angle reflection of the PB‐8 crystal, corresponding to the layer spacing, decreases by about 2,6 ± 0,2 Å at the crystal (K)‐smectic H(SH) transition under all pressures, while the crystal reflections of PB‐7 disappear at the K‐nematic (N) transition. The d spacings of the wide‐angle reflections of both crystals, corresponding to the lateral packing in the crystals, expand gradually with increasing temperature up to the K‐mesophase transition. The increase in lateral spacing of the PB‐8 crystal at the K‐SH transition changes slightly from ca. 0,29 Å at 0,1 MPa to 0,22 Å at 300 MPa. It is concluded that the transition mechanisms of the K‐SH transition of PB‐8 and the K‐N transition of PB‐7 are maintained at pressures up to 300 MPa.
Chain transfer reaction to terminal olefins in the polymerization of 1‐phenyl‐1‐propyne with Nb and Ta catalysts
Authors: Kouzai Hiroaki , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractEffects of various olefins as chain transfer agents were studied in the polymerization of 1‐phenyl‐1‐propyne catalyzed by NbCl5—Bu4Sn (1:2) (Bu: butyl) and TaCl5—Bu4Sn (1:2). In the Nb‐catalyzed polymerizations, Si‐containing terminal olefins, especially butyldimethylvinylsilane and dimethylphenylvinylsilane, proved to greatly lower the polymer molecular weight; e.g., the number‐average molecular weight (M̄n) of the polymer formed without an olefin was 2,0 · 105, whereas it decreased to 7 · 103 − 1 · 104, i.e., below 1/20 in the presence of the Si‐containing olefins (1/5 equivalent to the monomer). In the Ta‐catalyzed polymerization, in contrast, hydrocarbon terminal olefins like 1‐octene were effective; e.g., while the M̄n of the polymer reached 4,0 · 105 without an olefin, the M̄n was no more than 9 · 103 − 2 · 104, i.e., smaller than 1/25 in the presence of olefins. Poly(1‐phenyl‐1‐propyne) obtained using the Nb catalyst in the presence of butyldimethylvinylsilane possesses the terminal butyldimethylsilyl group derived from the added olefin. Thus, suitable olefins are useful to control the molecular weight of poly(1‐phenyl‐1‐propyne) by chain transfer, which verifies the metal‐carbene mechanism for the polymerization of 1‐phenyl‐1‐propyne by group 5 transition metal catalysts.
Immobilization of bioactive substances on poly(alkylene phosphate)s, 1. Immobilization of 2‐phenylethylamine
Authors: Tzevi Raina , Todorova Galina , Kossev Krassimir , Troev Koljo , Georgiev Emil M. , Roundhill D. Max 
Published: April 2003

AbstractPoly(alkylene phosphate)s of low molecular weight were synthesized by polytransesterification of dialkyl phosphonates with poly(ethylene glycol)s (PEG). These poly(alkylene phosphonate)s were then converted into poly(alkylene phosphate)s by using the Atherton‐Todd reaction in methanol as a solvent. The compound 2‐phenylethylamine was immobilized on these polymers via ionic bonds. These immobilizations were achieved by both alkylation and dealkylation reactions. The final products from these reactions are the polyanions. The structures of these products were determined by a combination of 1H, 31P and 31C NMR spectroscopy.
Yolk proteolysis in rainbow trout oocytes after serum‐free culture: Evidence for a novel biochemical mechanism of atresia in oviparous vertebrates
Authors: Wood Antony W. , Kraak Glen Van Der 
Published: April 2003

AbstractOur recent studies show little evidence for increased granulosa cell apoptosis during atresia in teleost follicles, in direct contrast to the mammalian model. Histological evidence suggests that atresia in many oviparous vertebrates involves proteolytic degradation of the energy‐rich yolk storage proteins within the oocyte. This study tests the hypothesis that physiological conditions that promote atresia (hormone withdrawal) lead to increased lysosomal protease activity in rainbow trout oocytes. We subjected rainbow trout ovarian follicles to conditions that promote atresia (serum‐free culture) for up to 72 hr, and measured the activity of lysosomal proteases using routine enzymatic assays. Furthermore, we used high performance liquid chromatography to quantify the increase in free amino acids resulting from proteolysis of yolk proteins. Concomitantly, we evaluated the extent of follicular apoptosis during prolonged serum‐free culture, using caspase‐3‐like activity and DNA fragmentation as indicators of apoptosis. Our results show a significant, time‐dependent increase in cathepsin L‐like, but not cathepsin D‐like, activity levels during culture in serum‐free medium; increased cathepsin L‐like activity is confirmed by a significant increase in oocyte free amino acid content after 72 hr culture. In contrast, we detected only a transient increase in apoptosis during prolonged serum‐free culture, as revealed through both radioactive 3′end‐labeling of oligonucleosomal DNA fragments, and caspase‐3‐like activity. The results of this study provide the first evidence for a novel mechanism of follicular atresia in teleosts involving cathepsin‐mediated yolk proteolysis. Mol. Reprod. Dev. 65: 219–227, 2003. © 2003 Wiley‐Liss, Inc.
Calcitonin acts as a first messenger to regulate adenylyl cyclase/cAMP and mammalian sperm function
Authors: Adeoya‐Osiguwa S.A. , Fraser L.R. 
Published: April 2003

AbstractCalcitonin stimulates capacitation in uncapacitated mouse spermatozoa and then inhibits spontaneous acrosome loss in capacitated cells, responses similar to those elicited by fertilization promoting peptide (FPP), a peptide known to regulate the adenylyl cyclase/cAMP pathway. This study investigated the hypothesis that calcitonin also modulates this pathway. Calcitonin significantly stimulated cAMP production in uncapacitated spermatozoa and then inhibited it in capacitated cells; the magnitude of both stimulatory and inhibitory changes was similar to that obtained with FPP but the inhibitory responses to FPP preceded those of calcitonin. This possibly reflects the involvement of two different adenosine receptors in response to FPP compared with one calcitonin receptor. Calcitonin receptors were located on the acrosomal cap and the flagellum, the midpiece having a greater abundance than the principal piece. Although both calcitonin and adenosine receptors are found in the head and flagellum, there was no evidence for cross‐talk between them. Chlortetracycline investigations to determine the minimum extracellular Ca2+ requirement for responses to calcitonin revealed that calcitonin significantly stimulated capacitation in Ca2+‐deficient medium but FPP did not. Calcitonin also significantly stimulated cAMP production under these conditions, and similarly preincubated suspensions, when diluted into +Ca2+ medium, were significantly more fertile in vitro than untreated controls. These results indicate that calcitonin, like FPP, acts as a first messenger to regulate the production of cAMP and mammalian sperm function, but the differences in Ca2+ requirements suggest that calcitonin and FPP may regulate different isoforms of adenylyl cyclase. Mol. Reprod. Dev. 65: 228–236, 2003. © 2003 Wiley‐Liss, Inc.
Genomic structure and promoter activity of the testis haploid germ cell‐specific intronless genes, Tact1 and Tact2
Authors: Hisano Mizue , Yamada Shuichi , Tanaka Hiromitsu , Nishimune Yoshitake , Nozaki Masami 
Published: April 2003

AbstractThe Tact1 and Tact2 genes, each of which encodes an actin‐like protein, are exclusively expressed and translated in haploid germ cells in testis. To characterize the haploid germ cell‐specific gene structure, a mouse genomic library was screened with a Tact1 cDNA as a probe, and four independent phage clones containing the Tact1 gene were isolated. Southern hybridization and sequencing analyses revealed that Tact1 and Tact2 were single copy genes contained on a common fragment in a head‐to‐head orientation, and that the distance between these genes was less than 2 kb. Comparison of the nucleotide sequences of genomic DNA and cDNA demonstrated that Tact1 and Tact2 lack introns, although all known actin or actin‐related genes in mammals contain introns. Human Tact orthologues also lack introns and are located within 6.4 kb in a head‐to‐head orientation. These findings indicate that Tact1 and Tact2 or one of these genes arose by retroposition of a spliced mRNA transcribed from an actin progenitor gene prior to the divergence of rodents and primates. The Tact1 and Tact2 genes are unusual retroposons in that they have retained an open reading frame and are expressed in testicular germ cells, because almost all retroposons become pseudogenes. It was revealed that a 2kb sequence between the two genes bidirectionally controls haploid germ‐cell specific expression by analyzing transgenic mice. Comparison of the murine Tact genes with their human orthologues showed a high level of identity between the two species in the 5′‐upstream and non‐coding sequences as well as in the coding region, indicating that conserved elements in these regions may be involved in the regulation of haploid germ cell‐specific expression. The promoter region contains no TATA‐, CCAAT‐ or GC‐boxes, although there are potential cAMP response element (CRE)‐like motifs in the 5′‐upstream region and the 5′‐untranslated region in Tact1 and Tact2, respectively. Transient promoter analyses indicate that CREMτ may activate Tact1 and Tact2 expression in germ cells. Mol. Reprod. Dev. 65: 148–156, 2003. © 2003 Wiley‐Liss, Inc.
Hyperglycemia‐induced apoptosis affects sex ratio of bovine and murine preimplantation embryos
Authors: Jiménez Adela , Madrid‐Bury Ninoska , Fernández Raúl , Pérez‐Garnelo Sonia , Moreira Pedro , Pintado Belén , de la Fuente Julio , Gutiérrez‐Adán Alfonso 
Published: April 2003

AbstractThe effect of glucose in the medium used during in vitro culture on both cell death by apoptosis and the sex ratio of bovine blastocysts derived from in vitro‐matured and in vitro‐fertilized oocytes was evaluated. Oocytes were matured, inseminated, and cultured in vitro in mSOF medium with 10% FCS with or without glucose supplementation. Exposure to high concentrations of glucose (10, 20, and 30 mM) during bovine embryo development in vitro from zygote to blastocyst resulted in a decrease in the number of cells per embryo and an increase in the frequency of apoptotic cells. A significantly higher proportion of females was found among those embryos that developed under hyperglycemic conditions in vitro. Moreover, both murine and bovine blastocysts incubated for 6 hr in 20 mM glucose had a significantly higher number of apoptotic cells in comparison to control. In this study, we also determined whether blastocyst production of the X‐linked inhibitor of apoptosis protein (XIAP) differs between the sexes. Our results show that female bovine blastocysts produce significantly higher amounts of XIAP mRNA than males and this could be crucial in explaining the higher proportion of female blastocysts observed following in vitro culture under hyperglycemic conditions which induce apoptosis. Moreover, a higher proportion of female murine blastocysts cultured under hyperglycemic conditions were implanted in the uterus (65.3 of implantations from embryos cultured with 20 mM of glucose are females vs. 49% in control). This mechanism provides an explanation for the significant reduction of male children born to diabetic mothers. Mol. Reprod. Dev. 65: 180–187, 2003. © 2003 Wiley‐Liss, Inc.
Cloning and expression of a novel cDNA encoding shell coat protein, cp4, from the brushtail possum (Trichosurus vulpecula)
Authors: Cui Shuliang , Selwood Lynne 
Published: April 2003

AbstractThe marsupial conceptus is enclosed by several egg coats of evolutionary significance and unknown composition, of which the shell coat in mammals occurs only in marsupials and monotremes. Intact coats are vital to marsupial embryonic development. Towards a better understanding of the marsupial coat proteins, a cDNA sequence (cp4) encoding a shell coat protein was cloned from the brushtail possum. A cDNA library of a zygote stage uterus was screened using a deduced oligonucleotide sequence based on a partial amino acid sequence of the coat protein. This study has confirmed a single copy cp4 gene encoding a unique protein of 306 amino acids, although its N‐terminus shares high sequence identity with the C‐terminal half of the enzyme α‐enolase. Using Northern blots, the expression of cp4 in adult tissues showed that cp4 transcript is restricted predominantly to the uterus with two stages of expression occurring in the gravid uterus at early cleavage and bilaminar stages, suggesting an important developmental role for CP4. Using RT‐PCR, cp4‐specific expression as represented by the 3′‐end 400 bp was present in heart, liver, oviduct, and uterus. Uterine expression reflected the increase found with Northern blot except that expression was low at unilaminar and bilaminar stages. Mol. Reprod. Dev. 65: 141–147, 2003. © 2003 Wiley‐Liss, Inc.
Antisense oligodeoxynucleotide inhibits expression of recombinant porcine follicle‐stimulating hormone receptor
Authors: Zhu Changhong , Wang Yifang , Nixon Mark D. , La Barbera Andrew R. 
Published: April 2003

AbstractFollicle‐stimulating hormone (FSH) regulates folliculogenesis in the ovary and spermatogenesis in the testis via specific, high affinity membrane‐bound receptors (FSHR). To assess the role of FSHR gene expression in regulating expression of FSHR protein in the plasma membrane, the effects of a porcine FSHR cDNA antisense oligodeoxynucleotide (ODN) on FSHR mRNA levels and 125I‐FSH binding were determined in Chinese hamster ovary cells stably expressing recombinant porcine FSHR (pFSHR‐CHO cells). An 18‐mer phosphorothioated antisense ODN corresponding to the region surrounding the translation initiation codon of the porcine FSHR cDNA was synthesized. An 18‐mer phosphorothioated nonsense sequence of identical nucleotide composition was synthesized for use as a control. pFSHR‐CHO cells were cultured in the absence or presence of 1–20 μM antisense or nonsense ODN for 24 hr and then assayed for porcine FSHR mRNA, using quantitative reverse transcription and competitive polymerase chain reaction, and for 125I‐FSH binding activity. Treatment with 10 μM antisense ODN caused a paradoxical increase in porcine FSHR mRNA. Nonsense ODN had no effect on porcine FSHR mRNA. Antisense, but not nonsense, ODN (10 μM) inhibited membrane binding of 125I‐FSH by 13.6 ± 0.8% (mean ± SEM, n = 3, P < 0.05) in 24 hr. Treatment of cells with antisense ODN (10 μM) for 48 hr resulted in a 76 ± 1.5% (P < 0.05) inhibition of 125I‐FSH binding. These results indicate that an FSHR antisense ODN effectively inhibits porcine FSHR synthesis and inhibition of receptor synthesis causes a decrease in functional membrane‐bound FSHR. Mol. Reprod. Dev. 65: 188–193, 2003. © 2003 Wiley‐Liss, Inc.
Differences in the BOLD fMRI response to direct and indirect cortical stimulation in the rat
Authors: Austin V.C. , Blamire A.M. , Grieve S.M. , O'Neill M.J. , Styles P. , Matthews P.M. , Sibson N.R. 
Published: April 2003

AbstractFunctional MRI (fMRI) exploits a relationship between neuronal activity, metabolism, and cerebral blood flow to functionally map the brain. We have developed a model of direct cortical stimulation in the rat that can be combined with fMRI and used to compare the hemodynamic responses to direct and indirect cortical stimulation. Unilateral electrical stimulation of the rat hindpaw motor cortex, via stereotaxically positioned carbon‐fiber electrodes, yielded blood oxygenation level‐dependent (BOLD) fMRI signal changes in both the stimulated and homotypic contralateral motor cortices. The maximal signal intensity change in both cortices was similar (stimulated = 3.7 ± 1.7%; contralateral = 3.2 ± 1.0%), although the response duration in the directly stimulated cortex was significantly longer (48.1 ± 5.7 sec vs. 19.0 ± 5.3 sec). Activation of the contralateral cortex is likely to occur via stimulation of corticocortical pathways, as distinct from direct electrical stimulation, and the response profile is similar to that observed in remote (e.g., forepaw) stimulation fMRI studies. Differences in the neuronal pool activated, or neurovascular mediators released, may account for the more prolonged BOLD response observed in the directly stimulated cortex. This work demonstrates the combination of direct cortical stimulation in the rat with fMRI and thus extends the scope of rodent fMRI into brain regions inaccessible to peripheral stimulation techniques. Magn Reson Med 49:838–847, 2003. © 2003 Wiley‐Liss, Inc.
Assessment of myocardial blood volume and water exchange: Theoretical considerations and in vivo results
Authors: Bjørnerud Atle , Bjerner Tomas , Johansson Lars O. , Ahlström Håkan K. 
Published: April 2003

AbstractThe measured signal response in contrast‐enhanced myocardial perfusion imaging has been shown to be affected by the rate of water exchange between the intravascular and extravascular compartments, the effect being particularly significant when intravascular contrast agents are used. In the present study, the T1 relaxation rates were measured in eight pigs in blood and myocardium using a Look‐Locker sequence after repeated injections of the intravascular contrast agent NC100150. The selection of myocardial region of interest was automated based on a minimum chi‐square method. The intra‐ and extravascular water exchange rates and the myocardial blood volume were calculated from the measured relaxation rates by applying a two‐compartment water exchange limited model that accounts for biexponential longitudinal relaxation. The following (mean ± SD) values were obtained for the exchange frequency (f), the extravascular residence time (τe), the intravascular residence time (τi) and blood volume (BV), respectively: f = 1.39 ± 0.52 s‐1, τe = 708 ± 264 ms, τi = 107 ± 63 ms, and BV = 11.2 ± 2.1 mL/100 g. The mean value of f was found to be about 15% higher if biexponential relaxation was not accounted for, supporting the hypothesis that significant biexponential relaxation in tissues with large blood volume can lead to an overestimation of water exchange rates unless corrected for. Magn Reson Med 49:828–837, 2003. © 2003 Wiley‐Liss, Inc.