bluuebunny/crossref_metadata_2025_split huggingface dataset:
1H,117 Sn J‐HMBC spectroscopy as a tool for the determination of long‐range nJ (1H,117Sn) coupling constants in the investigation of intramolecular donor–acceptor interaction in [2‐(N,N‐dimethylaminomethyl)phenyl]stannanes
Authors: Biesemans M. , Martins J. C. , Willem R. , Lyčka A. , Růžička A. , Holeček J. 
Published: August 2002

Abstract1H, 117Sn J‐HMBC spectroscopy was implemented as a tool for the determination of long range nJ(1H, 117Sn) coupling constants of [2‐(N,N‐dimethylaminomethyl)phenyl]stannanes, ArR1R2R3Sn or Ar2R1R2Sn, where R1, R2 and R3 are Ph or n‐Bu, and/or Cl or Br. It is demonstrated that coupling constants which are too small to be measured from multiplet splittings in the 1H or 117Sn spectra can be measured from the development of the sine modulation of the intensity of the 1H, 117Sn HMBC correlation peaks as a function of the incremented preparation time of the 1H,117Sn HMBC pulse sequence. It is examined whether such couplings can be used as straightforward indicators for the existence of intramolecular nitrogen–tin interactions. While some coupling constants are shown to depend on the strength of the above‐mentioned interaction, it is also demonstrated that 6J(1H,117Sn) coupling constants between the N‐methyl groups and the tin nucleus can be observed even in structures where no nitrogen–tin interactions are possible. Copyright © 2001 John Wiley & Sons, Ltd.
Complexation of selenium to (R)‐Rh2(MTPA)4: thermodynamics and stoichiometry
Authors: Duddeck Helmut , Malik Shahid , Gáti Tamás , Tóth Gábor , Choudhary Muhammad Iqbal 
Published: August 2002

AbstractVariable‐temperature 1H and 77Se NMR data for 3‐phenylselenenyl‐1‐phenyl‐1‐propene (1) in the presence of Rh2(MTPA)4 (Rh*) prove that the equilibria are strongly shifted towards the adduct Rh*···1; free selenide molecules cannot be detected as long as uncomplexed rhodium atoms are available. In the case of excess Rh*, both 1 : 2 and 1 : 1 adducts (Rh* vs 1) are formed, and the latter is slightly favoured. With excess selenide, the system strongly favours the complexation of two selenide molecules (1 : 2 adduct), i.e. one at each rhodium atom. In this situation, intermolecular selenide exchange can be monitored by variable‐temperature 1H NMR spectroscopy and the energy barrier is estimated to be 54–55 kJ mol−1. Copyright © 2001 John Wiley & Sons, Ltd.
Developmentally‐regulated changes of Xist RNA levels in single preimplantation mouse embryos, as revealed by quantitative real‐time PCR
Authors: Hartshorn Cristina , Rice John E. , Wangh Lawrence J. 
Published: August 2002

AbstractXist RNA localizes to the inactive X chromosome in cells of late cleavage stage female mouse embryos (Sheardown et al., 1997: Cell 91:99–107). Fluorescence in situ hybridization (FISH), however, does not quantify the number of Xist transcripts per nucleus. We have used real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) to measure Xist RNA levels in single preimplantation embryos and to establish developmental profiles in both female and male samples. The gender of each embryo was readily established based on Xist RNA levels, by counting Xist gene copies per cell, and by independent detection of the presence/absence of Sry, a Y chromosome‐specific gene. Xist expression in males was found to be very low at all stages, as suggested by FISH. In contrast, female embryos contained measurable levels of Xist mRNA starting at the late 2‐cell stage and rapidly accumulated Xist transcripts until morula stage. Xist RNA accumulation per embryo then reached a plateau, while cell division continued. We propose that during early cleavage high enough levels of Xist mRNA are transcribed to generate a pool of unbound molecules. This pool would serve to temporarily maintain X chromosome inactivation without additional transcription while the trophectoderm and inner cell mass (ICM) differentiate. The ICM would then loose the paternally imprinted pattern of X inactivation originally present in all embryonic cells. Mol. Reprod. Dev. 61:425–436, 2002. © 2002 Wiley‐Liss, Inc.
Expression of the vascular endothelial growth factor and its receptors and effects of VEGF during in vitro maturation of bovine cumulus‐oocyte complexes (COC)
Authors: Einspanier Ralf , Schönfelder Martin , Müller Karin , Stojkovic Miodrag , Kosmann Michaela , Wolf Eckhard , Schams Dieter 
Published: August 2002

AbstractA complete VEGF system consisting of the ligand and two of its receptors has been detected for the first time in the bovine cumulus‐oocyte‐complex (COC). In the course of a 24 hr in vitro maturation procedure (IVM), expression of the smaller VEGF transcripts and their specific receptors flt and flk changed remarkably in a time‐dependent manner as observed by RT‐PCR. The transcript concentrations of VEGF declined within 24 hr of culture, whereas both receptor mRNAs were found enriched between 6 and 12 hr of IVM. In the follicular fluid of growing ovarian follicles, immunoreactive VEGF, measured by RIA, increased significantly, reaching highest concentrations immediately before ovulation of the oocyte. The immunohistochemical localization of VEGF in bovine COCs revealed strong signals within the cumulus cell complex clearly extending beyond the oocyte cytoplasm at the beginning of in vitro maturation. After 24 hr, IVM immunoreactive VEGF disappeared remarkably from cumulus cells and the oocyte cytoplasm. An exogenous application of VEGF at the beginning of a 24 hr IVM significantly improved cleavage rates of zygotes and their development into bovine embryos showing obvious synergistic effects in combination with FSH, when compared with untreated control embryos. In addition, the number of blastomeres in deriving blastocysts increased after VEGF supplementation. These results indicate a functional VEGF system controlling important events beside the known angiogenetic effect during in vivo and in vitro maturation of the bovine COC, possibly affecting the early embryonic viability. Mol. Reprod. Dev. 62: 29‐36, 2002. © 2002 Wiley‐Liss, Inc.
Synaptic pattern of sex complements and sperm head malformation in X‐autosome translocation carrier bulls
Authors: Basrur P.K. , Koykul W. , Baguma‐Nibasheka M. , King W.A. , Ambady S. , de León F.A. Ponce 
Published: August 2002

AbstractTesticular activity and semen characteristics of bulls carrying an X‐autosome translocation t(Xp +;23q −) revealed all stages of spermatogenesis although their semen consisted of few and, exclusively, of malformed spermatozoa. Chromosome painting on metaphase spreads of their mother and synaptonemal complex analysis on these and normal bulls were carried out to test whether the location and meiotic pairing behaviour of the rearranged segments could have contributed to the sperm head malformation and oligospermia in our X‐autosome translocation (X‐AT) carrier bulls. Spermatocytes of X‐AT carriers displayed the rearranged chromosomes in a univalent‐trivalent association, with 23q − always remaining as a univalent and Xp + in synapsis with normal chromosome 23 and the Y chromosome. Chromosome painting studies to test whether the total absence of meiocytes showing a quadrivalent is due to the non‐reciprocal nature of this translocation, identified Xp sequence homology with the distal end of 23q − confirming its relocation to the terminal segment of 23q −. Our synaptonemal complex analyses also confirmed that the bovine pseudo‐autosomal region (PAR) is at the distal ends of Xq and Yp and further revealed that over 85% of spermatocytes of X‐AT carriers (and up to 13% of spermatocytes of normal bulls) sustain a Y‐axis break adjacent to the PAR. Although the exact cause of a Y‐axis break in bovine spermatocytes is not known at present, we believe that the break and possible loss of Yq in such high proportions of spermatocytes of X‐AT carriers could have contributed to the sperm head malformation and oligospermia in our X‐AT carrier bulls. Mol. Reprod. Dev. 59:67–77, 2001. © 2001 Wiley‐Liss, Inc.
Relationship between adenylate cyclase sensitivity to follitropin and FSH receptor mRNA expression in the ovary of the lizard Podarcis sicula
Authors: Borrelli Lucia , De Stasio Roberta , Parisi Elio , Filosa Silvana 
Published: August 2002

AbstractIn mammals, gonadal functions are regulated by two pituitary gonadotropins, follicle‐stimulating hormone (FSH) and luteinizing hormone (LH), that interact with gonadal membrane receptors to activate adenylate cyclase. In comparison to mammalian systems, in squamate reptiles a reduced amount of information exists on gonadotropins and their related receptors. This study is aimed at clarifying if, in the lizard Podarcis sicula, the ovarian sensitivity to FSH is correlated to the reproductive cycle and to the expression of membrane receptors involved in the hormone recognition. The results demonstrate that the ovarian adenylate cyclase responsiveness to FSH parallels ovarian functions, being maximal during the ovulatory period. The ovarian sensitivity to FSH is also related to oocyte growth and vitellogenesis. Northern blot analyses reveal that the FSH receptor mRNA is maximally expressed in vitellogenic oocytes during the reproductive period. These results suggest that, in lizard ovary, hormone activation of adenylate cyclase is mediated by de novo synthesis of receptors specifically involved in FSH recognition. In lizards treated in vivo with FSH during the pre‐ovulatory period, adenylate cyclase becomes refractory to further FSH stimulation 2 hr after treatment, but sensitivity to the hormone is restored after 2 weeks. Nevertheless, while the restored level of activity never exceeds that observed during the nonreproductive period, the expression level of FSH receptor mRNAs is significantly enhanced in these animals. These results suggest that in lizard the processes that regulate ovarian growth, vitellogenesis, and ovulation are controlled by a complex network of signals including gonadotropin, FSH receptor expression, and adenylate cyclase. Mol. Reprod. Dev. 62: 210–215, 2002. © 2002 Wiley‐Liss, Inc.
Maintenance of meiotic arrest in bovine oocytes in vitro using butyrolactone I: Effects on oocyte ultrastructure and nucleolus function
Authors: Fair Trudee , Hyttel Poul , Motlik Jan , Boland Maurice , Lonergan Patrick 
Published: August 2002

AbstractIn this study, we have shown that butyrolactone I (BL‐I), a potent inhibitor of cyclin‐dependent kinases, affects oocyte cytoplasmic morphology and nuclear function in terms of nucleolar ultrastructure and immunocytochemistry. Bovine oocytes were recovered from three classes of follicle size: 1.5–2, 2–3, and 3–6 mm. The oocytes were incubated for 40 hr with BL‐I, and subsequently processed for transmission electron microscopy or immunocytochemistry. A control group of oocytes were processed immediately upon recovery (0 hr). In general, incubation with BL‐I for 40 hr disrupted contact between cells of the cumulus oophorous and the oocyte, caused degeneration of the cortical granules and the peripheral migration of all cytoplasmic organelles. At the level of the nucleus, it induced convolution of the nuclear membrane and caused acceleration of nucleolar compaction in oocytes from follicles < 3 mm and fragmentation of nucleoli, particularly evidenced by immunocytochemistry, in oocytes from follicles > 3 mm. Furthermore, the effects appear to be more profound in fully‐grown oocytes. Mol. Reprod. Dev. 62: 375–386, 2002. © 2002 Wiley‐Liss, Inc.
Remodeling of donor nuclei, DNA‐synthesis, and ploidy of bovine cumulus cell nuclear transfer embryos: Effect of activation protocol
Authors: Alberio Ramiro , Brero Alessandro , Motlík Jan , Cremer Thomas , Wolf Eckhard , Zakhartchenko Valeri 
Published: August 2002

AbstractThe purpose of this study was to investigate the effects of two activation protocols on nuclear remodeling, DNA synthesis during the first cell cycle, chromosome segregation after first mitosis and development to blastocyst of embryos produced by somatic nuclear transfer. Pronuclear formation was significantly higher when activation lasted 5 hr compared to 3 hr for both ethanol–cycloheximide and ionomycin–bohemine treatment. However, the presence of a single nucleus was significantly higher in embryos activated for 3 hr in bohemine. Initiation of DNA synthesis was delayed in ethanol–cycloheximide group, however, after 12 hr labeling 100% of embryos synthesized DNA in both groups. Embryos activated with ethanol–cycloheximide developed to blastocysts at a significantly higher rate than those activated with ionomycin–bohemine. Analysis of 2‐cell embryos with DNA probes for chromosome 6, 7, and 15 by fluorescence in situ hybridization showed that at least 50% of NT embryos were of normal ploidy independent of the activation stimulus. The results presented in this study show differences between the protocols compared on the nuclear events during the first cell cycle and on the development to blastocyst. Mol. Reprod. Dev. 59: 371–379, 2001. © 2001 Wiley‐Liss, Inc.
Nuclear fragmentation characterises paraspermiogenesis in Tubifex tubifex (Annelida, Oligochaeta)
Authors: Boi S. , Fascio U. , Ferraguti M. 
Published: August 2002

AbstractIt is known that tubificine oligochaetes produce two types of spermatozoa: eusperm, fertilizing sperm with regular haploid DNA content; and parasperm, with a much lower DNA content, protecting and carrying the eusperm. Whereas mature spermatozoa and spermatids of the two lines are easily recognized by their morphology and DNA content, little is known about the first steps of differentiation of the two lines. This subject is addressed here in two ways: we have measured DNA content by a new method based on confocal laser microscopy and found that the total DNA content of parasperm cysts is extremely variable and equal or lower than total DNA content of eusperm cysts. Then we focused on the spermatocytes, and we found that the cells which will form paraspermatids undergo a peculiar kind of nuclear fragmentation which differ greatly from a regular cell division. During fragmentation DNA is distributed unevenly among the spermatids and this gives rise to a great and variable number of parasperm with variable DNA content. Immunocytochemical assays revealed that a proper meiotic spindle is never formed during fragmentation and that actin may play an important role in the chromatin division. Electron micrographs showed that the centrioles undergo a phenomenon of mass reproduction similar to that found in ciliated epithelia which supplies each of the numerous paraspermatids of its basal body. Mol. Reprod. Dev. 59: 442–450, 2001. © 2001 Wiley‐Liss, Inc.
Alterations of gene expression in endoderm differentiation of F9 teratocarcinoma cells
Authors: Shimada Naoka , Yamada Kazuya , Tanaka Takashi , Kawata Hiroko , Mizutani Tetsuya , Miyamoto Kaoru , Matsuzawa Tetsuro 
Published: August 2002

AbstractDuring the endoderm differentiation of F9 mouse embryonal carcinoma cells, as induced by sodium butyrate (NaBu) or retinoic acid (RA), gene expressions of alkaline phosphatase (ALPase), pyruvate kinase (PKase) and 5′ ribonucleotide phosphohydrolase (5′‐Nase) were examined. The specific activity of ALPase was found to increase by 3.5‐fold after 48 hr treatment with NaBu. In contrast, specific activity of PKase were decreased by 63%. Northern blot analysis revealed that the elevation of ALPase activity resulted from an increase in the level of liver/bone/kidney (L/B/K)‐type ALPase mRNA and that the decrease of PKase activity was dependent on a reduction in the level of M2‐PKase mRNA. Interestingly, when NaBu was removed from the culture medium, the levels of these mRNAs reverted to their original levels after 16 h. During these processes, the specific activity of 5′‐Nase and the level of its mRNA remained unchanged. In contrast, when F9 cells were treated with RA, only the level of L/B/K‐type ALPase mRNA increased. Lastly, we examined the issue of whether an increase in the level of ALPase mRNA is dependent on the transcriptional activation of the mouse L/B/K‐type ALPase gene. Transient transfection assays using luciferase reporter constructs showed that the promoter activity increased as the result of treatment with RA but not with NaBu. Mol. Reprod. Dev. 60: 165–171, 2001. © 2001 Wiley‐Liss, Inc.
New DAPI and fish findings on egg maturation processes in related hybridogenetic and parthenogenetic Bacillus hybrids (insecta, phasmatodea)
Authors: Marescalchi Ombretta , Scali Valerio 
Published: August 2002

AbstractBacillus stick insects have proved adequate for studying a wide array of reproductive modes: sexual, parthenogenetic, hybridogenetic, androgenetic. Hybridogenetic strains (B. rossius‐grandii) were thought to discard the paternal “grandii” haploset during first meiotic division and keep the “rossius” hemiclone, whereas the clonal B. whitei (=rossius/grandii) would maintain its hybrid structure by fusing back two nonsister nuclei—each derived from previously segregated heterospecific complements—by the end of the 2nd meiotic division. New investigations on laid eggs and ovariole squashes, either DAPI stained or FISH labeled, revealed that in hybridogens the “grandii” set is excluded from the germ line prior to meiosis and that a DNA extra‐synthesis should occur to produce hemiclonal eggs after two cytologically normal meiotic divisions. On the other hand, in B. whitei eggs no genome segregation appears to occur and an intrameiotic DNA extra‐synthesis must take place to produce 2n tetrachromatidic oocytes I; these divide twice and give unreduced clonal eggs. The new findings bring hybridogenetic oogenesis of Bacillus to be coincident with that of the known hemiclonal organisms and point to an independent onset of B. whitei from hemiclonal strains. In addition, B. whitei gains a closer resemblance to B. lynceorum owing to the sharing of a cytologically identical egg maturation mechanism, of the same maternal ancestor and of peculiar chromosomal features. It is here suggested that B. lynceorum originated from the incorporation of an “atticus” genome into a B. whitei egg, according to a pathway of repeated hybridization often occurred with other polyploid hybrids. Mol. Reprod. Dev. 60: 270–276, 2001. © 2001 Wiley‐Liss, Inc.
Cysteine protease inhibitor is specifically expressed in pre‐ and early‐vitellogenic oocytes from the brook trout periovulatory ovary*
Authors: Bobe Julien , Goetz Frederick William 
Published: August 2002

AbstractA cDNA fragment hybridizing with a transcript abundant in the periovulatory ovary was obtained while performing subtractive cloning on brook trout ovulatory and postovulatory ovarian tissue. Using this fragment as a probe, a 478 bp full‐length cDNA was obtained by screening an ovulatory ovarian cDNA library. This cDNA presumably codes for an 88 amino acid protein that is structurally related to a new family of cysteine protease inhibitors characterized by the presence of a type I thyroglobulin motif in the amino acid sequence. Therefore, the protein was tentatively named an oocyte cysteine protease inhibitor (OCPI). On Northern blots, the OCPI cDNA hybridizes with a 0.5 kb transcript present in the ovary during the periovulatory period. The OCPI transcript and protein were localized to the cytoplasm of pre‐ and early‐vitellogenic oocytes. On Northern blots of RNA from other tissues, the OCPI transcript was detected only in the ovary. On Western blots, OCPI was detected in the ovarian tissue at all periovulatory stages tested. The specific localization of both OCPI transcript and protein to pre‐ and early‐vitellogenic oocytes and the structural similarity to protease inhibitors, suggest that OCPI might be involved in the protection of oocytes during the periovulatory period or in the regulation of yolk formation and degradation. Mol. Reprod. Dev. 60: 312–318, 2001. © 2001 Wiley‐Liss, Inc.
On the parameters affecting the sensitivity of MR measures of pressure with microbubbles
Authors: Dharmakumar Rohan , Plewes Donald B. , Wright Graham A. 
Published: August 2002

AbstractRecently, it has been suggested that gas encapsulated distensible microbubbles may serve as pressure probes in the MR field through the relationship between bubble size and 1/T2 or 1/T. Currently, in vivo application of this technique is hindered by the ability of T2 or T to detect pressure changes that are clinically relevant. This work identifies and characterizes, through numerical simulations, the set of parameters which optimize the ability of this technique to detect small pressure changes. Results show that when the bubbles do not interact magnetically, the T2‐ and T‐based measurements of pressure are strongly influenced by the bubble size at atmospheric pressure, static magnetic field strength, magnitude of the susceptibility difference between the encapsulated gas and plasma, bubble volume fraction, and the refocusing interval. In particular, to detect clinically relevant pressure changes, microbubbles need to be approximately 2–3 μm in radius, distributed at a volume fraction of 0.15%, and have a volumetric magnetic susceptibility difference of at least 34 ppm. Magn Reson Med 47:264–273, 2002. © 2002 Wiley‐Liss, Inc.
Monitoring blood oxygen state in muscle microcirculation with transverse relaxation
Authors: Stainsby J.A. , Wright G.A. 
Published: August 2002

AbstractOxygen uptake from the microcirculation is a direct measure of tissue function. Magnetic resonance is capable of detecting differences between oxygenated and deoxygenated blood due to the paramagnetic properties of deoxyhemoglobin. At the level of the microcirculation, however, imaging methods cannot directly visualize the vessels. Instead, bulk MR parameters are investigated for their ability to monitor blood oxygen saturation (%O2) changes in the microcirculation of tissue, specifically skeletal muscle. Experiments in an in vitro model verified the feasibility of detecting changes in exponential decay signals, and also verified the prediction of only two distinct decay components. Experiments in a rabbit model demonstrate that T2′ and monoexponential T2 decay are not sensitive to blood oxygen changes, but that the long‐T2 component in a biexponential fit is correlated to the blood oxygen state. Assuming a two‐pool model for water protons in muscle, and with knowledge of the T2‐%O2 relation, estimates of the microcirculation blood oxygen state can be made with some reasonable assumptions. Magn Reson Med 45:662–672, 2001. © 2001 Wiley‐Liss, Inc.
Utilizing the diffusion‐to‐noise ratio to optimize magnetic resonance diffusion tensor acquisition strategies for improving measurements of diffusion anisotropy
Authors: Armitage P.A. , Bastin M.E. 
Published: August 2002

AbstractIt is well known that quantitative anisotropy measurements derived from the diffusion tensor are extremely sensitive to noise contamination. The level of noise in the diffusion tensor imaging (DTI) experiment is usually measured from some estimate of the signal‐to‐noise ratio (SNR) in the component diffusion‐weighted (DW) images. This measure is, however, highly dependent on experimental parameters, such as the diffusion attenuation b‐value and the diffusion coefficient of the subject. Conversely, the diffusion‐to‐noise ratio (DNR), defined as the SNR of the calculated diffusion tensor trace map, provides a reliable estimate of noise contamination, which is largely independent of such parameters. In this work it is demonstrated how reliable anisotropy measurements can be obtained using an image acquisition strategy that optimizes the DNR of the DTI experiment. This acquisition scheme is shown to provide noise‐independent measurements of typical diffusion anisotropy values found in the human brain. Magn Reson Med 45:1056–1065, 2001. © 2001 Wiley‐Liss, Inc.