bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of manual and computer‐generated customized blocks for whole brain fields used in the treatment of medulloblastoma
Authors: Liu M. , Carrie C. , Parker W. , Freeman C.R. 
Published: August 2002

AbstractBackgroundBy using CT simulation and three‐dimensional planning, we have developed a simple but accurate method of producing customized blocks for the cranial fields in the treatment of medulloblastoma. We compare here the margins and the volume of normal tissues included in the treatment volume with those obtained using blocks generated manually.ProcedureCustomized blocks for the whole brain field are generated using CT planning and autoblock function. The clinical target volume (CTV) is defined as the whole cerebrospinal fluid pathway, and the whole brain and spinal cord are contoured. A margin of 1.1 cm is generated using the autoblock function to account for set‐up errors (3–5 mm) and penumbra (approximately 7 mm). A separate set of blocks was generated manually without the knowledge of the ones generated by the CT‐simulator. These 2 sets of blocks were compared for a cohort of 7 consecutive patients.ResultsOverall, the manual blocks and the computer‐generated blocks were quite similar. Those generated manually had more variations; they were always tighter (median of 6 mm tighter; range: 3–7 mm) at the level of the cribriform plate and in 5/7 patients were more generous (median of 6 mm more generous, range: 0–6 mm) at the temporal lobes. Dosimetric analysis showed that both methods provide adequate coverage of the CTV, with 100% of the CTV receiving > 95% of the prescribed dose for both.ConclusionsThe customized block method for whole brain fields is simple to use and ensures adequate coverage of the target volume. Med Pediatr Oncol 2002;38:55–57. © 2002 Wiley‐Liss, Inc.
A tutorial comparison of the NMRIT and LAOCOON approaches for analyses of complex solution‐phase nuclear magnetic resonance spectra
Authors: Manatt Stanley L. 
Published: August 2002

AbstractFor spin ½ nuclei the two most frequently used iterative approaches for determinations of NMR chemical shifts (hi) and coupling constants (Ji), NMRIT and LAOCOON, are discussed. When multiple pulse techniques for extraction of these parameters fail or lead to complicated spectra in the cases of very strongly coupled spin systems and systems involving magnetically nonequivalent, chemical shift equivalent nuclei, recourse to these iterative methods is necessary. The former approach employs the energy levels derived from the observed transition frequencies, whereas the latter approach uses the observed transition frequencies. Derivations of the general iterative equations for both approaches are given, along with the specific equations for the ABC spin system. The matrix nature of the derivation of these equations is stressed. Also discussed is the modified NMRIT program, NMRENIT, which has major advantages over the former in cases with symmetry and in cases where not enough lines can be assigned to link all the energy levels. The advantages of the latter program over LAOCOON in certain cases are discussed. Some general advice on the use of both approaches is presented. The Hoffman energy level approach is also discussed and it is shown that it yields the same iterative equations as the LAOCOON approach. Copyright © 2002 John Wiley & Sons, Ltd.
Epikatonic acid from Austroplenckia populnea: structure elucidation by 2D NMR spectroscopy and X‐ray crystallography
Authors: Silva G. D. F. , Duarte L. P. , Vieira Filho S. A. , Doriguetto A. C. , Mascarenhas Y. P. , Ellena J. , Castellano E. E. , Cota A. B. 
Published: August 2002

AbstractFrom the chloroform extract of Austroplenckia populnea, epikatonic acid, friedelin, populnonic acid, abruslactone A, salaspermic acid and 22β‐epi‐maytenfolic acid were isolated. The structure and stereochemistry of epikatonic acid were established by two‐dimensional NMR spectroscopic techniques (HMQC, HMBC and NOESY) and later confirmed by single crystal X‐ray diffraction as 3β‐hydroxy‐olean‐12‐en‐29‐oic acid, which unambiguously established the configuration of the hydroxyl group at C‐3 as 3β‐OH and the carboxyl group at C‐20 as 20α‐COOH. The crystal structure shows two independent molecules in the asymmetric unit. The crystal packing is stabilized by four O–H·O intermolecular hydrogen bonds, which give rise to infinite double chains along the c axis. Copyright © 2002 John Wiley & Sons, Ltd.
A 1H NMR and molecular modelling investigation of diastereotopic methylene hydrogen atoms
Authors: Tormena Cláudio F. , Freitas Matheus P. , Rittner Roberto , Abraham Raymond J. 
Published: August 2002

AbstractThe 1H NMR spectra of methyl 3‐bromo‐2‐methylpropionate (1a) and the corresponding chloro compound (2a) show no long‐range coupling between the methyl and methylene protons. In contrast, in the analogous dihalocompounds, methyl 2,3‐dibromo‐2‐methylpropionate (1b) and methyl 2,3‐dichloro‐2‐methylpropionate (2b), one of the methylene protons exhibits a large 4JHH coupling (0.8 Hz) to the methyl group, but the other proton shows no observable splitting. This can be explained quantitatively by calculations of the conformational preferences in these compounds combined with the known orientation dependence of the 4JHHcouplings. One conformer predominates in the dihalo compounds 1b and 2b, and this is responsible for the 4JHH coupling. In 1a and 2a all three conformers are populated and the 4JHH couplings average to zero. The technique is a potentially general method of unambiguously assigning diastereotopic methylene protons. Copyright © 2002 John Wiley & Sons, Ltd.
Heterogeneity of surface colour centres on alkaline earth metal oxides as revealed through EPR/ENDOR spectroscopy
Authors: Purnell Ian J. , Chiesa Mario , Farley Robert D. , Murphy Damien M. , Rowlands Christopher C. , Cristina Paganini Maria , Giamello Elio 
Published: August 2002

AbstractA variety of surface anion vacancies, or point defects, are created by high‐temperature activation of a series of polycrystalline alkaline earth metal oxides (MgO, CaO and SrO). Subsequent UV irradiation of the activated oxide under a hydrogen atmosphere results in the generation of surface colour centres [FS+(H)], by electron trapping at these anion vacancies. The paramagnetic properties of these colour centres were studied by EPR and ENDOR spectroscopy. 1H ENDOR spectroscopy revealed that a well defined heterogeneity of trapped electron species exists on each oxide surface, as characterized by the different superhyperfine couplings between the trapped electron and the nearby proton of the FS+ (H) centre. On MgO and CaO two dominant FS+ (H) centres were identified (labelled sites I and II) whereas on SrO three FS+ (H) species were found (sites I, II and III). The possible surface sites responsible for electron stabilization are discussed, and include a 3C corner mono‐vacancy, a 4C mono‐vacancy and an anion–cation di‐vacancy. The results indicate that regardless of the oxide used, a common degree of morphological similarities exists on each oxide. Copyright © 2002 John Wiley & Sons, Ltd.
Molecular motion in some radiolabelled dipeptides: a muon spin relaxation study
Authors: Rhodes Christopher J. , Dintinger Timothy C. , Morris Harry , Scott Christopher A. 
Published: August 2002

AbstractActivation parameters were determined for the dynamics of radicals formed by muonium addition to glycylglycine (GlyGly; H3N+CH2CONHCH2CO2−) and the doubly protected alanylalanine derivative [Boc‐AlaAla‐Bz; ButOCONHCH(Me)CONHCH(Me)CO—O—CH2Ph]. GlyGly forms an adduct by muonium addition to the amide carbonyl group which isomerizes by flipping the muon between opposite sides of the molecule, requiring an activation energy of 20.4 kJ mol−1. In Boc‐AlaAla‐Bz, muonium addition to the benzene ring of the benzyl (—CH2Ph) group occurs, exhibiting an activation energy of 9.4 kJ mol−1, believed to be from torsion about the C—Ph bond. Copyright © 2002 John Wiley & Sons, Ltd.
Phosphoryldithioformates: Part V. Unusual linewidth variations in the ESR spectra of some spin adducts of (dimenthoxy)phosphoryl methyl dithioformate
Authors: Alberti Angelo , Benaglia Massimo , Macciantelli Dante , Hudson Andrew , Masson Serge 
Published: August 2002

AbstractUnusual temperature‐dependent linewidth variations were observed in spin adducts of (dimenthoxy)phosphoryl methyl dithioformate with bulky free radicals, possibly involving a combination of restricted rotation of a methyl group and slow molecular tumbling. Copyright © 2002 John Wiley & Sons, Ltd.
Isotope‐induced chemical shifts 2Δ10/11B(29Si) in alkenylsilanes containing three‐ and four‐coordinate boron. A new tool for studying weak intramolecular boron–element bonds
Authors: Wrackmeyer Bernd , Tok Oleg L. 
Published: August 2002

AbstractNumerous alkenylsilanes with silyl and boryl groups in cis ‐positions at the CC bond were studied for the first time by 29Si NMR with regard to isotope‐induced chemical shifts Δ10/11B(29Si). Such effects are transmitted across an Si—X—B bridge (X = H, OR, SR, Cl) most efficiently if the interactions in this bridge are weak. In the absence of an Si—X—B bridge, 3Δ10/11B(29Si) effects were not observed. In such cases, where, depending on the substituents, both weak and strong B—X bonding are possible, the 2Δ10/11B(29Si) effects were readily observed only for weak B—X interactions (except for X = Cl), whereas for strong B—X bonding the effects were small or not detectable. Thus, the 2Δ10/11B(29Si) values provide another tool for probing weak interactions which are not clearly reflected by other NMR data. Copyright © 2002 John Wiley & Sons, Ltd.
Fitting dynamic NMR lineshapes
Authors: Bain Alex D. , Rex Darrell M. , Smith Rashida N. 
Published: August 2002

AbstractThe lineshapes in an NMR spectrum, due to dynamic processes within the sample, provide an excellent way of measuring the rates of these processes. As the process speeds up, lines broaden, coalesce and finally sharpen into an average peak. Mathematical techniques for simulating these lineshapes have long been available, and rates can be extracted by fitting the calculated lineshape to the experiment. This is often done by manual iteration and visual comparison. The principal iterative program, DNMR5, is somewhat clumsy by modern standards. A recent reformulation of the theory of the lineshapes, which describes the spectrum as a sum of transitions, simplifies setting up the iterative process. This approach is described in general, and illustrated with the two‐site equally populated case. Copyright © 2001 John Wiley & Sons, Ltd.
Conformational study of the tricyclic sesquiterpene β‐panasinsene aided by ab initio calculations and simulated 1H NMR parameters†
Authors: Flores‐Sandoval César A. , Cerda‐García‐Rojas Carlos M. , Joseph‐Nathan Pedro 
Published: August 2002

AbstractAb initio calculations of the tricyclic sesquiterpene β‐panasinsene (1) provided theoretical H—C—C—H dihedral angles that allowed us to predict the corresponding 1H–1H vicinal coupling constant values, using a generalized Karplus‐type equation. These values, together with the experimental 1H chemical shifts extracted from an HMQC spectrum, were used as the initial input data for the full spectral simulation of 1, which provided an excellent correlation with the experimental 1H NMR spectrum after a few iterations. The complete assignment of the 1H NMR parameters allowed us to determine the conformation of 1 in solution. The four‐membered ring exists in a more flattened conformation than cyclobutane, with torsion angles of ∼12°. The five‐membered ring possesses a half‐chair conformation with pseudorotational parameters θm = 39.5° and P = 3.8°, while the six‐membered ring exists in a conformation close to the canonical chair, with angular variables θ = 9.2° and P2 = 15.5°, and the total puckering amplitude Q = 54.5°. Application of this procedure to β‐panasinsen‐5α‐ol (2) and β‐panasinsen‐5‐one (3) gave similar results. Copyright © 2001 John Wiley & Sons, Ltd.
Complete 1H and 13C NMR assignments of stigma‐5‐en‐3‐O‐β‐glucoside and its acetyl derivative
Authors: Faizi Shaheen , Ali Muhammad , Saleem Rubeena , Irfanullah  , Bibi Sarah 
Published: August 2002

AbstractUnambiguous and complete assignments of 1H and 13C NMR chemical shifts for stigma‐5‐en‐3‐O‐β‐glucoside, isolated from Brassica rapa sb.sp. campestris and Aloe barbadensis, and its acetyl derivative are presented, based on DEPT, HETCOR, COLOC, HMBC, COSY‐45°, NOESY and J‐resolved experiments. Copyright © 2001 John Wiley & Sons, Ltd.
Dynamic and magnetic susceptibility effects on the MAS NMR linewidth of a tetrapeptide bound to different resins
Authors: Furrer Julien , Elbayed Karim , Bourdonneau Maryse , Raya Jésus , Limal David , Bianco Alberto , Piotto Martial 
Published: August 2002

AbstractUnder magic angle spinning, the NMR spectrum of the tetrapeptide Ala‐Ile‐Gly‐Met bound to a Wang resin, and swollen in DMF, exhibits proton and carbon linewidths that are sharp enough to allow the complete characterization of the peptide using classical liquid‐state NMR methods. The proton linewidths of the bound peptide remain, however, about three times larger than those of the free peptide in solution. The residual NMR linewidth originates essentially from incompletely averaged magnetic susceptibility effects due to the Wang resin. Replacing the aromatic Wang resin with a PEGA or POEPOP resin removes this effect. To investigate the contribution to line broadening of the peptide dynamics, relaxation studies were performed on the peptide bound to Wang and POEPOP resins. Copyright © 2001 John Wiley & Sons, Ltd.
A relationship between the half‐width of 73Ge NMR signals and hypercoordination in some phenylgermanes
Authors: Takeuchi Yoshito , Tanaka Katsumi , Aoyagi Shigenobu , Yamamoto Hiroyuki 
Published: August 2002

Abstract73Ge NMR spectra of some phenylgermanes were determined. The chemical shifts and half‐widths are discussed in terms of structure and in relation to hypercoordination of germanium atoms. It appears that linewidths can be a measure of hypercoordination. Copyright © 2002 John Wiley & Sons, Ltd.
3D Heteronuclear long‐range 1H–13C scalar correlation at natural abundance: application to oligosaccharide analysis
Authors: Hernández Griselda , LeMaster David M. 
Published: August 2002

AbstractA 3D 1H–13C–1H refocused INEPT transfer experiment is proposed in which the initial coherence transfer of 1H longitudinal to 13C transverse magnetization is tuned to the long‐range 1H, 13C couplings while the reverse INEPT component transfers the magnetization to the directly bonded 1H. Integration of a constant time 1H evolution period into the long‐range coherence transfer interval provides absorption mode signals for each dimension. A 13C purge component at the beginning of the sequence selects for 12C‐bound 1H magnetization that is then transferred to a 13C‐bound hydrogen, thus strongly suppressing the diagonal signals. This experiment is expected to be of particular value for situations in which resonance overlap in the 13C dimension renders 2D long‐range heteronuclear correlation data ambiguous. In combination with a diagonal‐suppressed 3D 1H–13C–1H TOCSY‐HSQC experiment, complete assignment of the ring resonances of the Lewis‐b hexasaccharide was obtained on a 4.2 mM sample using a conventional 500 MHz probe (0.1% ethylbenzene signal‐to‐noise ratio of 600), suggesting its applicability to sub‐millimolar samples using cryoprobe technology. Copyright © 2002 John Wiley & Sons, Ltd.
Structural characterization of monomeric and oligomeric arylamides by solution and solid‐state NMR spectroscopy
Authors: Cavallaro Stefano , Cum Giampietro , Gallo Raffaele , Spadaro Agatino , Visalli Giuseppe 
Published: August 2002

AbstractAn extensive study of both liquid‐ and solid‐state NMR spectroscopy was undertaken in order to elucidate the structural features of a phenyleneterephthalamide oligomer (OPTA) and of some related diarylamides. 1D‐ and 2D‐COSY measurements allowed us to assign completely the proton signals of the title compounds in solution, while 1D‐, 2D‐HETCOR and 2D‐COLOC measurements were used to assign 13C resonances. Solid‐state 13C NMR experiments, by conventional cross‐polarization (CP) at different contact times and with the dipolar dephased CP technique, were used to characterize these molecules in the solid state. Such techniques allowed us to differentiate among different carbon atoms; in the resulting spectra it was then possible to observe the selective appearance of signals from protonated and quaternary carbon atoms. It was also ascertained that the limited structural mobility of the insoluble OPTA, existing as a single monophasic species, can be explained in terms of hydrogen‐type bonds present in the solid state. Copyright © 2002 John Wiley & Sons, Ltd.
Aromatase plays a key role during normal and temperature‐induced sex differentiation of tilapia Oreochromis niloticus
Authors: D'cotta Helena , Fostier Alexis , Guiguen Yann , Govoroun Marina , Baroiller Jean‐Francois 
Published: August 2002

AbstractIn the tilapia Oreochromis niloticus, sex is determined genetically (GSD), by temperature (TSD) or by temperature/genotype interactions. Functional masculinization can be achieved by applying high rearing temperatures during a critical period of sex differentiation. Estrogens play an important role in female differentiation of non‐mammalian vertebrates. The involvement of aromatase, was assessed during the natural (genetic all‐females and all‐males at 27°C) and temperature‐induced sex differentiation of tilapia (genetic all‐females at 35°C). Gonads were dissected between 486–702 degree × days. Aromatase gene expression was analyzed by virtual northern and semi‐quantitative RT‐PCR revealing a strong expression during normal ovarian differentiation concomitant with high levels (465 ± 137 fg/g) of oestradiol‐17β (E2‐17ß). This was encountered in gonads after the onset of ovarian differentiation (proliferation of both stromal and germ cells prior to ovarian meiosis). Genetic males exhibited lower levels of aromatase gene expression and E2‐17ß quantities (71 ± 23 fg/ g). Aromatase enzyme activity in fry heads established a sexual dimorphism in the brain, with high activity in females (377.9 pmol/head/hr) and low activity in males (221.53 pmol/head/hr). Temperature induced the masculinization of genetic females to a different degree in each progeny, but in all cases repression of aromatase expression was encountered. Genetic males at 35°C also exhibited a repression of aromatase expression. Aromatase brain activity decreased by nearly three‐fold in the temperature‐masculinized females with also a reduction observed in genetic males at 35°C. This suggests that aromatase repression is required in the gonad (and perhaps in the brain) in order to drive differentiation towards testis development. Mol. Reprod. Dev. 59:265–276, 2001. © 2001 Wiley‐Liss, Inc.
Inhibiting 3‐phosphoglycerate kinase by EDTA stimulates the development of the cleavage stage mouse embryo
Authors: Lane Michelle , Gardner David K. 
Published: August 2002

AbstractAddition of EDTA to the medium significantly enhances mouse embryo development in culture. Embryos cultured in the absence of EDTA exhibit abnormal increases in glycolytic activity that result in reduced development. Culture with EDTA was able to prevent this increase in glycolysis and, therefore, maintain developmental competence. EDTA was shown to inhibit the activity of the glycolytic enzyme, 3‐phosphoglycerate kinase. Additionally, the effect of EDTA on maintaining high rates of embryo development in culture could be mimicked by the addition of Cibacron blue, an inhibitor of 3‐phosphoglycerate kinase. The inhibition of 3‐phosphoglycerate kinase by EDTA could be overcome by the addition of exogenous magnesium, indicating that the effect of EDTA was to reduce the availability of this co‐factor to the glycolytic kinases. Embryos cultured with EDTA had significantly lower levels of intracellular magnesium compared to embryos cultured without EDTA. Therefore, the effect of EDTA appears to be as a chelator of divalent cations such as magnesium, that are required for normal activity of kinases such as 3‐phosphoglycerate kinase. Mol. Reprod. Dev. 60: 233–240, 2001. © 2001 Wiley‐Liss, Inc.
Distinct roles for distal‐less genes Dlx3 and Dlx5 in regulating ectodermal development in Xenopus
Authors: Luo Ting , Matsuo‐Takasaki Mami , Sargent Thomas D. 
Published: August 2002

AbstractIn vertebrates, there are six or more copies of genes related to the Drosophila pattern formation homeodomain gene Distal‐less. Among this family, Dlx3 and Dlx5 share extensive sequence homology and have similar, but distinctive, expression patterns, suggesting that these two factors may have substantially redundant developmental functions. Here we show that at the earliest phases of embryogenesis in Xenopus, there are significant differences between Dlx3 and Dlx5 expression and that this correlates with different functions in the restriction of neural crest and neural plate boundaries, respectively. Mol. Reprod. Dev. 60: 331–337, 2001. © 2001 Wiley‐Liss, Inc.
Spermatogenesis in the golden hamster: The role of c‐kit
Authors: Vigodner M. , Lewin L. M. , Shochat L. , Golan R. 
Published: August 2002

Abstractc‐kit is related to the family of transmembrane tyrosine kinase receptors. Mutations in genes for either c‐kit or its ligand, Steel factor, result in infertility, but the role of c‐kit/SCF system in spermatogenesis is not well understood. In this study Western blot analysis together with confocal microscopy were used to follow c‐kit expression in hamsters during the first spermatogenic wave in mature animals and in old age. Three antibodies raised against different domains of c‐kit were tested on Western Blot. Confocal microscopy was performed after incubation of fixed seminiferous tubules with tested antibodies followed by binding of FITC‐labeled secondary antibody. Longitudinal sections of seminiferous tubule were observed by confocal microscopy to determine in which stages of spermatogenesis and in which cell types c‐kit was found. C‐kit bands of 80,140, and 150 kDa were observed on Western blot, indicating that c‐kit is a name related to several proteins sharing some common domains. Only the band of 150 kDa correlated with positive staining of c‐kit in tubules using confocal microscopy. We term this protein c‐kit150T (150 kDa, testis). We demonstrated that c‐kit150T appeared in differentiating hamster spermatogonia at stages VII–VIII of adult spermatogenesis and at day 13–14 during the first spermatogenic wave. It remained attached to the cell until late pachytene. This suggests that c‐kit may play a role in preparing the germinal cells to enter meiosis. In order to evaluate the effect of aging on the number of germ cells, B2 spermatogonia/Sertoli cell ratio was calculated in the group of young animals (5–7 months) compared to this ratio in older ones (20–26 months). A significant decrease (P < 0.01) in the number of B2 spermatogonia in the group of old hamsters as compared to young ones was seen. The calculated value for the B2 spermatogonia/Sertoli cell ratio was 5.6 ± 0.7 in young animals and 3.8 ± 1.2 in the 20–26 months ones. In addition, decrease in the intensity of staining for c‐kit was detected in the old hamsters. These may be the reasons for subfertility in old age and in other cases of testicular disorders. Mol. Reprod. Dev. 60: 562–568, 2001. © 2001 Wiley‐Liss, Inc.