bluuebunny/crossref_metadata_2025_split huggingface dataset:
Juvenoid hormone methyl farnesoate is a sex determinant in the crustacean Daphnia magna
Authors: Olmstead Allen W. , Leblanc Gerald A. 
Published: October 2002

AbstractDaphnids (Daphnia magna) utilize cyclic parthenogenesis as a reproductive strategy. During periods of abundant resources, these organisms reproduce asexually. In response to environmental cues that signal the onset of environmental adversity, daphnids produce males and reproduce sexually. The environmental cues that stimulate the sexual reproductive phase are well known; however, the endocrine signals that transduce these environmental cues remain unknown. The present study was undertaken to test the hypothesis that the crustacean juvenoid hormone, methyl farnesoate, is a male sex determinant in this species. Continuous exposure to aqueous concentrations of methyl farnesoate greater than approximately 30 nM stimulated a concentration‐dependent production of male‐containing broods of organisms. Short‐term exposures to methyl farnesoate during periods of egg and embryo maturation revealed that male sex determination occurred during a specific 12‐hour period of ovarian egg development. Exposure of eggs to 400 nM methyl farnesoate during this sensitive developmental period resulted in the production of all‐male broods of offspring, while exposure to concentrations as low as 52 nM produced mixed broods of males and females. This active concentration range of methyl farnesoate is consistent with levels measured in the hemolymph of some decapod crustaceans. These results demonstrate that methyl farnesoate is capable of programming daphnid embryos to develop into males and is likely the endocrine factor responsible for initiating the sexual reproductive phase in these organisms. J. Exp. Zool. 736–739, 2002. © 2002 Wiley‐Liss, Inc.
Specific binding of the endocytosis tracer horseradish peroxidase to intestinal fatty acid‐binding protein (I‐FABP) in apical membranes of carp enterocytes
Authors: Concha Margarita I. , Santander Cristián , Villanueva Julieta , Amthauer Rodolfo 
Published: October 2002

AbstractIn a previous study we had demonstrated that a 15‐kDa protein present in carp intestinal brush‐border membrane vesicles (BBMV) was able to bind the endocytosis tracer horseradish peroxidase (HRP) with high specificity. Here we show that this protein corresponds to a peripheral membrane protein, identified by partial amino acid sequence analysis as the intestinal fatty acid‐binding protein (I‐FABP), a member of the small cytosolic fatty acid binding protein family (FABPs). The presence of I‐FABP and its HRP‐binding activity was demonstrated both in the cytosolic and membrane‐associated fractions of intestinal mucosa by Western and ligand blot analyses, respectively. Also, both fractions displayed significant capacity to bind [3H]palmitic acid, a known ligand for I‐FABP. Immunohistochemical analysis showed that I‐FABP localizes both in the cytosol and in the brush‐border membranes of epithelial cells. Taken together the unusual extra‐cellular localization of I‐FABP as well as its ability to interact with HRP suggests a novel function for this protein in the intestinal mucosa. J. Exp. Zool. 293:541–550, 2002. © 2002 Wiley‐Liss, Inc.
Dynamics of vitellogenin mRNA expression and changes in hemolymph vitellogenin levels during ovarian maturation in the giant freshwater prawn Macrobrachium rosenbergii
Authors: Jayasankar Vidya , Tsutsui Naoaki , Jasmani Safiah , Saido‐Sakanaka Hisako , Yang Wei‐Jun , Okuno Atsuro , Hien Tran Thi Thanh , Aida Katsumi , Wilder Marcy N. 
Published: October 2002

AbstractThe dynamics of vitellogenin mRNA expression during ovarian maturation in Macrobrachium rosenbergii were examined by measuring hemolymph vitellogenin (Vg) levels and Vg mRNA expression in the hepatopancreas and ovary at differing reproductive stages in both intact and eyestalk ablated animals. Vg mRNA was quantified using real‐time RT‐PCR and hemolymph Vg was measured by enzyme immunoassay. In intact animals, Vg mRNA levels in the hepatopancreas and hemolymph Vg levels showed a gradual increase during the molt cycle concomitant with increasing gonadosomatic index (GSI), with Vg levels decreasing prior to ecdysis although GSI continued to increase. Eyestalk ablation was seen to accelerate Vg synthesis as well as ovarian maturation, although it did not alter the overall pattern of Vg expression. Vg mRNA expression was negligible in the ovary of both intact and eyestalk ablated animals, confirming that the hepatopancreas is the principal site of Vg synthesis in M. rosenbergii with the ovary being only a minor contributor. This study has shown that Vg synthesis is correlated to ovarian maturation and the molt cycle in M. rosenbergii. J. Exp. Zool. 293:675–682, 2002. © 2002 Wiley‐Liss, Inc.
Effects of altered photoperiod and temperature, serotonin‐affecting drugs, and melatonin on brain tyrosine hydroxylase activity in female catfish, Heteropneustes fossilis: A study correlating ovarian activity changes
Authors: Chaube R. , Joy K.P. 
Published: October 2002

AbstractExposure of female catfish, Heteropneustes fossilis to 30‐day regimes of long photoperiod (16L), elevated temperature (28 ± 2°C), or a combination of both stimulated brain tyrosine hydroxylase (TH) activity significantly over that of control fish held in natural conditions in gonad resting (10.5L:13.5D, 10 ± 2°C) and preparatory (12.5L:11.5D,18 ± 2°C) phases. The response was high in the combination group in both phases. The increase in TH activity was higher in forebrain regions (telencephalon and hypothalamus) than medulla oblongata. Exposure of the fish to short photoperiod (8L:16D) and total darkness decreased the enzyme activity significantly in both resting and preparatory phases regardless of the temperature. The inhibition was high in fish held under total darkness. Gonadosomatic index (GSI) was significantly elevated in long photoperiod and high temperature groups, alone or in combination, and decreased significantly in short photoperiod (only in preparatory phase) and total darkness groups. Administration of the serotonin precursor 5‐hydroxytryptophan (5‐HTP; 5mg/100g body weight [BW], three daily intraperitoneal [i.p.] injections prior to sacrificing) stimulated TH activity in fish held under long and normal photoperiods in both phases. Three daily injections of the serotonin blocker parachlorophenylalanine (p‐CPA; 10mg/100g BW) and melatonin (75 µg/100g BW) prior to sacrificing inhibited brain TH activity significantly in both phases. GSI was significantly stimulated by 5‐HTP, and inhibited by both p‐CPA and melatonin injections. Changes in TH activity and GSI can be correlated and explained on the basis of previous reports on changes in catecholamine activity that modulates gonadotropin secretion in the catfish. Further, the photoperiod and temperature‐induced changes in TH activity may be modulated by alterations in serotonergic activity. J. Exp. Zool. 293:585–593, 2002. © 2002 Wiley‐Liss, Inc.
Radiosynthesis of [123I]N‐(3‐iodoprop‐(2E)‐enyl)‐2α‐(imino‐methyl)‐3β‐(3′,4′‐dichlorophenyl) nortropane as a potential SPET tracer for dopamine transporter
Authors: Yu Meixiang , Airaksinen Anu J. , Gee Antony D. , Lötjönen Simo , Kuikka Jyrki T. , Vepsäläinen Jouko J. , Hiltunen Jukka , Bergström Kim A. 
Published: October 2002

AbstractThe radiosynthesis of a novel tropane derivative [123I]KUC‐25019, [[123I];N‐(3‐iodoprop‐(2E)‐enyl)‐2α‐(imino‐methyl)‐3β‐(3′,4′‐dichlorophenyl)nortropane], a potential inhibitor of the dopamine transporter is reported. The synthetic routes include the preparation of standard reference, the stannyl precursor and the 123I‐labeling synthesis. The no‐carrier‐added 123I‐labeling has about 20% yield, the specific activity of [123I]KUC‐25019 is > 107 GBq/µmol and the radiochemical purity of [123I] KUC‐25019 is >95%. Copyright © 2002 John Wiley & Sons, Ltd.
New preparation of [123I]PE2I: investigation of the oxidation and purification steps
Authors: Berthommier E. , Loc'h C. , Chalon S. , Olivier C. , Emond P. , Dao Boulanger H. , Lelait M.A. , Mauclaire L. 
Published: October 2002

AbstractIn order to simplify preparation of [123I]PE2I, iodogen and hydrogen peroxide were examined as oxidants for the preparation of radioiodinated PE2I, e.g. (E)‐N‐(3‐iodoprop‐2‐enyl)‐2β‐carbomethoxy‐3β‐(4′‐tolyl) nortropane). Among the oxidizing compounds assayed, iodogen appears to afford the best results for this purpose (high radiochemical yield, high chemical purity and a reasonable reaction time). A simplified and efficient method is described here for the preparation of [123I]PE2I based on the exchange of a 123I tributyl tin analogue in oxidative conditions followed by purification by solid phase extraction (SPE). Using this method, [123I]PE2I was obtained with a radio‐pharmaceutical yield over 60%, with chemical and radiochemical purities higher than 95% without the addition of a carrier (Na127I) (2G Bq/nmol) or with a specific activity adjusted to 85–90 MBq/nmol in the presence of the carrier. Copyright © 2002 John Wiley & Sons, Ltd.
Nerve growth factor and enhancement of proliferation, invasion, and tumorigenicity of pancreatic cancer cells
Authors: Zhu Zhaowen , Kleeff Jörg , Kayed Hany , Wang Li , Korc Murray , Büchler Markus W. , Friess Helmut 
Published: October 2002

AbstractNerve growth factor (NGF) exerts both stimulatory and inhibitory effects on neuronal and certain non‐neuronal tumors. In pancreatic cancer NGF is overexpressed, and this overexpression is associated with increased perineural invasion. NGF has the potential to stimulate the growth of some pancreatic cancer cell lines, and this effect is mediated by the phosphorylation of tyrosine kinase receptor A and mitogen‐activated protein kinase activation; it is dependent on the expression levels of tyrosine kinase receptor A and p75 receptors. To determine whether cancer cell–derived NGF can participate in the regulation of pancreatic cancer cell proliferation, PANC‐1 human pancreatic cancer cells were stably transfected with a full‐length human β‐NGF expression vector. In vitro and in vivo growth characteristics were analyzed by proliferation assays and invasion assays and in a nude mouse tumor model. Stable transfection of NGF in PANC‐1 cells resulted in enhanced anchorage‐dependent growth, with a decrease in doubling times of up to 50%, and in an approximately twofold increase in anchorage‐independent cell growth and cell invasion. Furthermore, stably transfected PANC‐1 cells showed enhanced tumorigenicity in nude mice. These results suggest that NGF has the capacity to act in a paracrine and/or an autocrine manner in pancreatic cancer and that it enhances cancer cell growth and invasion in vivo, thereby contributing to the aggressiveness and poor prognosis of this disease. © 2002 Wiley‐Liss, Inc.
Contributions of mitogen‐activated protein kinase and nuclear factor kappa B to N‐(4‐hydroxyphenyl)retinamide–induced apoptosis in prostate cancer cells
Authors: Shimada Keiji , Nakamura Mitsutoshi , Ishida Eiwa , Kishi Munehiro , Yonehara Shin , Konishi Noboru 
Published: October 2002

AbstractThe synthetic retinoid N‐(4‐hydroxyphenyl)retinamide (4‐HPR) has been shown to induce apoptosis in various types of tumors, including prostate cancer. We sought to examine the key mechanisms affecting the resistance to 4‐HPR–induced apoptosis in three human prostate cancer cell lines, PC‐3, DU145, and LNCaP. Concentrations of more than 40 μM 4‐HPR produced apoptosis to almost the same extent in all cell lines; however, only the LNCaP line remained highly sensitive to concentrations less than 10 μM. These differing sensitivities at low concentrations correlated well with the level of constitutive activation of nuclear factor kappa B (NFκB) in the individual cell lines. We found that NFκB activation inhibited c‐jun NH2‐terminal kinase and caspase 3 activation induced by 4‐HPR and that NFκB inhibition by the I kappa B alpha phosphorylation inhibitor compound Bay 117082 resulted in increasing sensitization of both PC‐3 and DU145 lines to apoptosis induced by 4‐HPR at low concentrations. Furthermore, we found that inhibition of extracellular signal–regulated kinase (ERK) enhanced the suppression of NFκB by 4‐HPR and also resulted in sensitization to apoptosis in the DU145 cell line, in which ERK is activated constitutively. It thus appears that mitogen‐activated protein kinase associated with the activity of NFκB plays an important role in the degree of resistance to 4‐HPR‐induced apoptosis in human prostate cancer cells. © 2002 Wiley‐Liss, Inc.
Analgesic use for postoperative pain: differences arise when comparing departments of surgery
Authors: Soler‐Company Enrique , Baños Josep‐E. , Faus‐Soler Teresa , Morales‐Olivas Francisco , Montaner‐Abasolo Carmen 
Published: October 2002

AbstractPurposeThe goal of the study is to analyse whether the analgesic therapy of postoperative pain during the first 2 days after surgery differs among the different surgical departments.MethodsPatients were randomly chosen from among all those who underwent elective surgery. Characteristics of analgesic treatment (drug, dosage, schedule) and pain intensity were determined at the postoperative anaesthetic care unit and in the first and second postoperative days on the ward. All comparisons were carried out by surgical departments.ResultsSix hundred and twenty‐three patients from six surgical departments were studied. Analgesic treatment orders varied greatly among the different departments, and these differences were statistically significant regarding number of drugs, type of drugs, analgesic schedule, and completeness of medical orders. Some differences were also observed regarding drug dosage. Patients from gynaecology and obstetrics, traumatology and orthopaedics and general surgery reported the most severe pain.ConclusionsThe treatment of postoperative pain differs among the surgical departments, especially regarding analgesic schedules and completeness of analgesic orders. Analgesic therapy may often be based more on customary habits than on the patients' pain intensity. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis and properties of biodegradable chitin‐graft‐poly(L‐lactide) copolymers
Authors: Kim Ji Young , Ha Chang Sik , Jo Nam Ju 
Published: October 2002

AbstractIn this study, novel biodegradable polymers were synthesized by ring opening polymerization (ROP) of L‐lactide on chitin in an N,N‐dimethyl acetamide (DMAc)/lithium chloride (LiCl) solvent system, and chitin was used as macroinitiator to afford new materials. Lithium chloride (LiCl) was used as catalyst. The synthesized copolymers [chitin‐graft‐poly(L‐lactide) (PLLA)] were characterized by Fourier transform infrared (FTIR) spectroscopy to confirm the newly formed ester bond. From the FTIR spectra, the peak intensity of ester bond in the chitin‐graft‐PLLA copolymers increased in comparison to that of L‐lactide monomer. Therefore, it was confirmed that PLLA was successfully grafted on to chitin. Also, cross polarization–magic angle spinning (CP‐MAS), 13C solid state NMR spectroscopy and differential scanning calorimetry were used to characterize novel chitin‐graft‐PLLA copolymers.© 2002 Society of Chemical Industry
Supramolecular polymer chemistry—scope and perspectives
Authors: Lehn Jean‐Marie 
Published: October 2002

AbstractThe connection of molecular monomers through non‐covalent intermolecular interactions leads to the formation of polymolecular entities defining a supramolecular polymer chemistry. The basic features of this field are presented and illustrated by some selected results. Thus, the molecular recognition directed association between monomers bearing complementary hydrogen bonding groups leads to linear supramolecular polymers and liquid crystals. Also, rigid rod, two‐dimensional, metal coordination‐based, side‐chain and cross‐linked supramolecular polymeric entities may be envisaged and several types have been generated. Like supramolecular materials in general, supramolecular polymers are reversible, constitutionally dynamic materials, capable of modifying their constitution by exchanging, recombining, incorporating components. They may present a variety of novel properties and behave as adaptive materials.© 2002 Society of Chemical Industry
Morphology and enzymatic degradation of poly(ϵ‐caprolactone) single crystals: does a polymer single crystal consist of micro‐crystals?
Authors: Iwata Tadahisa , Doi Yoshiharu 
Published: October 2002

AbstractSolution‐grown lamellar single crystals of poly(ϵ‐caprolactone) (PCL) were prepared from a dilute solution of n‐hexanol by the isothermal crystallization condition or the self‐seeding method. Hexagonal‐shaped lamellar crystals with and without spiral growth were obtained, and the crystals produced well‐resolved electron diffraction diagrams. The chain‐packing structure and morphological complexity in lamellar crystals were investigated by bright‐field and dark‐field diffraction contrast methods of transmission electron microscopy. Based on both diffraction contrast images, it was revealed that both tightly and loosely chain‐packing regions exist in one lamellar crystal. Thus, it was emphasized that PCL solution‐grown lamellar single crystals consist of micro‐crystals with nano‐order size for the crystalline core region. Lipase type XIII from Pseudomonas sp was used for the enzymatic degradation of the PCL lamellar crystals. Enzymatic degradation progressed perpendicularly from the crystal lateral sides, without decrease of the molecular weight and lamellar thickness, yielding notched‐shaped morphologies to the crystals. These results further indicate that PCL lamellar crystals consist of nano‐order micro‐crystals, and that enzyme hydrolyzes the loosely chain‐packing regions between the tightly chain‐packing regions (micro‐crystal regions).© 2002 Society of Chemical Industry
Effect of photo‐initiators on melt degradation of polypropylene and starch‐filled polymer
Authors: Bagheri Rouhallah , Naimian Faranak 
Published: October 2002

AbstractSix series of the processed polypropylene (pp) samples containing 0.25–1 wt% photo‐initiators (PIs, four aromatic carbonyl, two ferric compounds) and also a series of 6 wt% corn‐starch‐filled pp containing 0.5 wt% of each PI, were prepared using a mixer in a closed system at 180 °C for 5 min. The melt flow index (MFI) and apparent viscosity measurments of the processed pp–PI samples showed a large increase in MFI/or decrease in apparent viscosity at 0.25 wt% of the PIs. Further increase in the amounts of PIs led these properties to reach a constant value at 0.5 wt% of the PIs. The presence of corn starch in the samples corresponded to a much lower increase in the MFI or decrease in the apparent viscosity. Ferric stearate and Irgacure 184 amoung the PIs showed the highest and lowest melt degradation effects, respectively. Carbonyl measurments of all the film samples showed good correlations between chemical changes in the pp structure and variations in the flow properties during processing. UV absorption of the films also evidenced the presence of the aromatic carbonyl PIs in the pp matrix after melt processing.© 2002 Society of Chemical Industry
Ethylene polymerization by iron complexes with symmetrical and unsymmetrical ligands
Authors: Ma Zhi , Sun Wen‐Hua , Li Zi‐Long , Shao Chang‐Xing , Hu You‐Liang , Li Xiu‐Hua 
Published: October 2002

AbstractA series of penta‐coordinated iron complexes with 2,6‐bis(imino)pyridine ligands were prepared and used in ethylene polymerization or oligomerization with methylaluminoxane as (MAO) co‐catalyst. The activity of the complexes depends strongly on the steric and electronic effects of the ligands, in which the electronic conjugated system plays an important role. N,N′‐Bis(α,α‐diphenyl) methyl 2,6‐bis(imino)pyridine iron complex (1) could not activate ethylene, N,N′‐difluorenyl‐2,6‐bis(imino)pyridine iron complex (2) exhibited high activity for ethylene oligomerization, whilst N,N′‐diaryl 2,6‐bis(imino)pyridine iron complexes (3–6) performed ethylene polymerization. The results are collected and briefly discussed.© 2002 Society of Chemical Industry
Tissue engineering matrixes by emulsion templating
Authors: Busby Wendy , Cameron Neil R , Jahoda Colin A B 
Published: October 2002

AbstractFoams containing poly(lactic acid) (PLA) have been prepared from the corresponding macromonomers using high internal phase emulsions (HIPEs) as templates to create the porous structure. The resulting PolyHIPE foams have been investigated by scanning electron microscopy and the influence of diluent type, either reactive (styrene or methyl methacrylate (MMA)) or unreactive (toluene), on foam morphology has been determined. The morphology was found to depend on the type of diluent: styrene resulted in cellular materials at low PLA levels but tended to give structures characteristic of phase separation at higher PLA content; MMA yielded porous cellular materials at all levels of PLA; toluene tended to give soft materials that collapsed on drying. The swelling of the foam materials in toluene, isopropyl alcohol (IPA) and water was also investigated. It was found that most of the foams swelled to a relatively low extent in all solvents, apart from that of low PLA content made with toluene. This was ascribed to a low crosslinking level and high porosity of this material. Cell and tissue growth studies on the resulting foams, as well as analogues prepared from poly(ε‐caprolactone) (PCL) macromonomers, using whole chicken embryo explants, rat skin explants or individual human skin cells, indicated excellent biocompatibility of all foams over the length of each experiment (maximum length 6 days). Comparative studies indicated that cells adhered to PCL‐based materials more rapidly than their PLA‐containing counterparts.© 2002 Society of Chemical Industry
From prebiotic macromolecules to synthetic polypeptides: a new, efficient synthesis of α‐amino acid N‐carboxyanhydrides (NCAs)
Authors: Boiteau Laurent , Collet Hélène , Lagrille Olivier , Taillades Jacques , Vayaboury Willy , Giani Olivia , Schué François , Commeyras Auguste 
Published: October 2002

AbstractWhile polypeptide materials present important application potentialities, the expense of amino acid N‐carboxyanhydride (NCA) monomers strongly limits their applications. We present here a new, promising synthetic route to NCA through N‐carbamoylamino acid nitrosation by gaseous NOx(1 < x < 2) in the solid–gas phase. This very efficient reaction (which was originally developed in a prebiotic context) works in the absence of solvent and with minimum waste, and presents interesting economic features. Some mechanistic investigations aimed at the optimisation and scale‐up of this reaction in the solid‐gas phase are presented.© 2002 Society of Chemical Industry
ω‐OH polystyrene and ω‐OH poly(n‐butyl acrylate) as reactive stabilizers for the preparation of uniform polyurethane particles in a dispersed medium
Authors: Cloutet Eric , Radhakrishnan Bindushree , Cramail Henri 
Published: October 2002

Abstractω‐OH polystyrene (PS‐OH) and ω‐OH poly(n‐butyl acrylate) (PnBA‐OH) have been designed to act as both stabilizers and reactants in the synthesis of polyurethanes (PURs) in a dispersed medium. Uniform PUR particles with a size ranging from 0.2 µm to 5 µm could be prepared by step‐growth polymerization of ethylene glycol (EG) and tolylene‐2,4‐diisocyanate (TDI) at 60 °C in cyclohexane, in the presence of dibutyl tin dilaurate (DBTDL) as the catalyst and either hydroxy‐terminated polystyrene (PS‐OH) or hydroxy‐terminated poly(n‐butyl acrylate) (PnBA‐OH) as the reactive stabilizer. Parameters such as the manner of addition of the reactants, the concentration and length of the stabilizer, were varied to tune the polyurethane particle size. While the molar mass of ω‐OH PnBA was allowed to increase from 6000 to 15 000 g mol−1, the particle size was found to decrease from 2 µm to 200 nm.© 2002 Society of Chemical Industry