bluuebunny/crossref_metadata_2025 huggingface dataset:
Searching for evidence of DFNB2
Authors: Astuto Lisa M. , Kelley Philip M. , Askew James W. , Weston Michael D. , Smith Richard J.H. , Alswaid Abdulrahman F. , Al‐Rakaf Mona , Kimberling William J.
Published: August 2002

Deafness is the most common form of sensory impairment in humans, affecting about 1 in 1,000 births in the United States. Of those cases with genetic etiology, approximately 80% are nonsyndromic and recessively inherited. Mutations in several unconventional myosins, members of a large superfamily of actin‐associated molecular motors, have been found to cause hearing loss in both humans and mice. Mutations in the human unconventional Myosin VIIa (MYO7A), located at 11q13.5, are reported to be responsible for both syndromic and nonsyndromic deafness. MYO7A mutations are responsible for Usher syndrome type Ib, the most common genetic subtype of Usher I. Usher I is clinically characterized by congenital profound deafness, progressive retinal degeneration called retinitis pigmentosa (RP), and vestibular areflexia. Although a wide spectrum of MYO7A mutations have been identified in Usher Ib patients, four mutations have been reported to cause DFNB2, a recessive deafness without retinal degeneration, and one mutation has been implicated in a single case of dominant nonsyndromic hearing loss (DFNA11). Our study attempts to ascertain additional DFNB2 families to investigate the disparate nonsyndromic phenotype and alleged causative mutations. Data from both linkage and heterogeneity analyses on 36 selected autosomal recessive nonsyndromic deafness (RNSD) families, all previously excluded by mutational analysis from GJB2 (Cx26), the leading cause of nonsyndromic deafness, showed no evidence of DFNB2 within the sample. These negative results and the isolated reports of DFNB2 bring into question whether certain MYO7A mutations produce nonsyndromic recessive hearing loss. © 2002 Wiley‐Liss, Inc.
Novel and previously reported single‐nucleotide polymorphisms in the human 5‐HT1B receptor gene: No association with cocaine or alcohol abuse or dependence
Authors: Cigler Tessa , LaForge K. Steven , McHugh Pauline F. , Kapadia Sagar U. , Leal Suzanne M. , Kreek Mary Jeanne
Published: August 2002

Evidence from animal self‐administration and human genetics studies suggests that the serotonin1B (5‐HT1B) receptor may be involved in modulating responses to cocaine or alcohol. We hypothesize that polymorphisms, including single‐nucleotide polymorphisms (SNPs), in the human 5‐HT1B receptor gene, may be associated with individual differences in vulnerability to cocaine or alcohol abuse or dependence. A total of 210 subjects were studied, including individuals with a primary diagnosis (DSM‐IV criteria) of cocaine abuse or dependence, alcohol abuse or dependence, and controls with no history of previous or current illicit drug or alcohol abuse or dependence. Genomic DNA samples were isolated from each individual. For 157 of the subjects, polymerase chain reaction (PCR) was used to amplify the entire coding region of the 5‐HT1B receptor gene as well as parts of the 5′ and 3′ untranslated regions. PCR products were sequenced in forward and reverse directions on an automated sequencer. Amplified DNA from an additional 53 subjects was sequenced in the 5′ untranslated region to gain additional data on the frequency of one identified SNP. Seven polymorphisms were identified: one novel SNP in the 5′ untranslated region (UTR) of the gene (A‐161T); one SNP not reported in any published scientific communication (but found to be recorded in GenBank) in the 3′ UTR (A1180G); two novel dinucleotide deletions at positions − 184/− 183 and − 182/− 181; and three previously identified SNPs (T‐261G, C129T, G861C). Data were stratified by ethnicity and pooled Relative Risk was calculated for combined alcohol abuse and dependence cases and controls, and also for combined cocaine abuse and dependence cases and controls. No significant differences between cases and controls were found. © 2001 Wiley‐Liss, Inc.
Immigration and hybridization patterns of yellow and anubis baboons in and around Amboseli, Kenya
Authors: Alberts Susan C. , Altmann Jeanne
Published: August 2002

In 1986, Samuels and Altmann reported evidence for a hybrid zone between Papio anubis and Papio cynocephalus in Amboseli, Kenya, in a baboon population that has been the subject of long‐term study since 1971 [Samuels & Altmann, International Journal of Primatology 7:131–138, 1986]. In the current report we document ongoing patterns of hybridization in Amboseli between anubis and yellow baboons. In July 2000, we exhaustively scored living members of study groups for their degree of hybridity, using seven phenotypic characteristics (five in juveniles). We also scored all former members of study groups on the basis of photographic records, field notes, and observer recollections. A total of five anubis males and 11 males with hybrid phenotypes have immigrated into study groups over the course of the long‐term study, and immigrations by hybrid males have increased in frequency over time. Further, the increasing frequency of hybrid phenotypes among animals born into study groups indicates that anubis and hybrid males have successfully reproduced in study groups. However, hybrid phenotypes and anubis immigrations were limited to groups in the southwestern portion of the Amboseli basin, with no hybrids occurring in the six eastern groups. Finally, we present evidence that anubis and hybrid males in Amboseli exhibit patterns of natal dispersal that are different from those of yellow males in Amboseli: males with anubis or hybrid phenotypes were significantly more likely to immigrate as juveniles or young subadults than were yellow males. Am. J. Primatol. 53:139–154, 2001. © 2001 Wiley‐Liss, Inc.
Reproductive behavioral changes during the ovarian cycle of lesser bushbabies (Galago moholi) in captivity
Authors: Lipschitz David L. , Galpin Jacqueline S. , Meyer Denny
Published: August 2002

Behavioral patterns were quantified in seven heterosexual lesser bushbaby (Galago moholi) pairs during the estrous cycle to determine the relative significance of behavioral and nonbehavioral components of female sexuality in mate attraction. Increases in the occurrence of several male behaviors indicating female attractiveness were initiated during vaginal swelling when the female was sexually nonreceptive. Female behavioral estrus, as indicated by intromission, was confined to a portion of vaginal opening coinciding with proestrous and vaginal estrous smears. Female attractiveness was maintained for much of the period of vaginal opening, whereas female receptivity ended a day or two earlier than attractiveness. Female receptive and proceptive behaviors were not well defined or extensive, and few female behaviors exhibited significant changes during the cycle. Scent‐marking behaviors, such as urine washes, and male grooms, were generally elevated outside the behavioral estrous period. In G. moholi, male sexual arousal appears to be elicited primarily by female attractiveness, while behavioral components of female sexuality appear to be less important in influencing mate attraction. Am. J. Primatol. 55:101–115, 2001. © 2001 Wiley‐Liss, Inc.
Ancient mitochondrial DNA evidence for prehistoric population movement: The numic expansion
Authors: Kaestle Frederika A. , Smith David Glenn
Published: August 2002

The mitochondrial DNA of modern Native Americans has been shown to fall into one of at least five haplogroups (A, B, C, D, or X) whose frequencies differ among tribal groups. The frequencies of these five haplogroups in a collection of ancient individuals from Western Nevada dating to between approximately 350–9,200 years BP were determined. These data were used to test the hypothesis, supported by archaeological and linguistic data, that the current inhabitants of the Great Basin, the Numic speakers, are recent immigrants into the area who replaced the previous non‐Numic inhabitants. The frequency distributions of haplogroups in the ancient and modern Native Americans differed significantly, suggesting that there is a genetic discontinuity between the ancient inhabitants and the modern Numic speakers, providing further support for the Recent Numic Expansion hypothesis. The distribution of mitochondrial haplogroups of the ancient inhabitants of the Great Basin is most similar to those of some of the modern Native American inhabitants of California. Am J Phys Anthropol 115:1–12, 2001. © 2001 Wiley‐Liss, Inc.
Founding Amerindian mitochondrial DNA lineages in ancient Maya from Xcaret, Quintana Roo
Authors: González‐Oliver Angélica , Márquez‐Morfín Lourdes , Jiménez José C. , Torre‐Blanco Alfonso
Published: August 2002

Ancient DNA from the bone remains of 25 out of 28 pre‐Columbian individuals from the Late Classic‐Postclassic Maya site of Xcaret, Quintana Roo, was recovered, and mitochondrial DNA (mtDNA) was amplified by using the polymerase chain reaction. The presence of the four founding Amerindian mtDNA lineages was investigated by restriction analysis and by direct sequencing in selected individuals. The mtDNA lineages A, B, and C were found in this population. Eighty‐four percent of the individuals were lineage A, whereas lineages B and C were present at low frequencies, 4% and 8%, respectively. Lineage D was absent from our sample. One individual did not possess any of the four lineages. Six skeletons out of 7 dated from the Late Classic period were haplotype A, whereas 11 skeletons out of 16 dated from the Postclassic period were also haplotype A.

The distribution of mtDNA lineages in the Xcaret population contrasts sharply with that found in ancient Maya from Copán, which lack lineages A and B. On the other hand, our results resemble more closely the frequencies of mtDNA lineages found in contemporary Maya from the Yucatán Peninsula and in other Native American contemporary populations of Mesoamerican origin. Am J Phys Anthropol 116:230–235, 2001. © 2001 Wiley‐Liss, Inc.
Major histocompatibility complex class II polymorphisms in Macaca mulatta: factors influencing comprehensive genotyping of Macaca mulatta (Mamu)‐DQA1 alleles by PCR‐RFLP in archival samples
Authors: Rolfs Becky K. , Wu Ching Ching , Lerche Nicholas W. , Smith David G.
Published: August 2002

In the last 5 years, HLA class II genotyping methods have been adapted for genotyping of class II loci in rhesus macaques. Since previously published typing protocols were used on samples that were collected and stored under ideal conditions, it was of interest to determine if these methods were adequate for genotyping a large collection of archival samples from which DNA had been isolated and stored under various conditions. Established macaque DQA1 typing protocols were modified to optimize the typing procedure and enhance the ability to successfully genotype DNA from samples that were of poor quality and/or quantity. Long‐term storage of whole‐blood buffy coats or stored DNA extracted from whole‐blood buffy coats did not affect typing success; however, amplification and typing of DNA extracted from archival samples of plasma were difficult and resulted in a low success rate. This suggests that amplification and DQA1‐genotyping of archival samples is possible with a modified protocol, but is influenced by the age and source of the sample, and to a lesser extent, the method used to extract DNA from sample substrates. Am J Phys Anthropol 116:296–301, 2001. © 2001 Wiley‐Liss, Inc.
Cigarette smoking and the incidence of Parkinson's disease in two prospective studies
Authors: Hernán Miguel A. , Zhang Shumin M. , Rueda‐DeCastro Ana M. , Colditz Graham A. , Speizer Frank E. , Ascherio Alberto
Published: August 2002

An inverse association between cigarette smoking and idiopathic Parkinson's disease has been reported in several retrospective studies, but prospective evidence is available only for men. We assessed the association between the incidence of Parkinson's disease and smoking in two large prospective cohort studies comprising men and women. New cases of Parkinson's disease were identified in the Nurses' Health Study for 1976–1996, and in the Health Professionals Follow‐up Study for 1986–1996. Smoking history was assessed at baseline and updated on subsequent biennial questionnaires. In women, the age‐adjusted rate ratios (95% confidence intervals) for Parkinson's disease relative to never‐smokers were 0.7 (0.5, 1.0) for past smokers, and 0.4 (0.2, 0.7) for current smokers. In men, the age‐adjusted rate ratios for Parkinson's disease relative to never‐smokers were 0.5 (0.4, 0.7) for past smokers, and 0.3 (0.1, 0.8) for current smokers. In both cohorts, the strength of the association decreased with time since quitting (among past smokers), increased with number of cigarettes per day (among current smokers), and increased with pack‐years of smoking. These prospective findings confirm that an inverse association between smoking and the incidence of Parkinson's disease exists in both men and women.
Diffusion‐ and perfusion‐weighted MRI response to thrombolysis in stroke
Authors: Parsons Mark W. , Barber P. Alan , Chalk Jonathon , Darby David G. , Rose Stephen , Desmond Patricia M. , Gerraty Richard P. , Tress Brian M. , Wright Peter M. , Donnan Geoffrey A. , Davis Stephen M.
Published: August 2002

Diffusion‐ and perfusion‐weighted magnetic resonance imaging provides important pathophysiological information in acute brain ischemia. We performed a prospective study in 19 sub‐6‐hour stroke patients using serial diffusion‐ and perfusion‐weighted imaging before intravenous thrombolysis, with repeat studies, both subacutely and at outcome. For comparison of ischemic lesion evolution and clinical outcome, we used a historical control group of 21 sub‐6‐hour ischemic stroke patients studied serially with diffusion‐ and perfusion‐weighted imaging. The two groups were well matched for the baseline National Institutes of Health Stroke Scale and magnetic resonance parameters. Perfusion‐weighted imaging–diffusion‐weighted imaging mismatch was present in 16 of 19 patients treated with tissue plasminogen activator, and 16 of 21 controls. Perfusion‐weighted imaging–diffusion‐weighted imaging mismatch patients treated with tissue plaminogen activator had higher recanalization rates and enhanced reperfusion at day 3 (81% vs 47% in controls), and a greater proportion of severely hypoperfused acute mismatch tissue not progressing to infarction (82% vs −25% in controls). Despite similar baseline diffusion‐weighted imaging lesions, infarct expansion was less in the recombinant tissue plaminogen activator group (14cm3 vs 56cm3 in controls). The positive effect of thrombolysis on lesion growth in mismatch patients translated into a greater improvement in baseline to outcome National Institutes of Health Stroke Scale in the group treated with recombinant tissue plaminogen activator, and a significantly larger proportion of patients treated with recombinant tissue plaminogen activator having a clinically meaningful improvement in National Institutes of Health Stroke Scale of ≥7 points. The natural evolution of acute perfusion‐weighted imaging–diffusion‐weighted imaging mismatch tissue may be altered by thrombolysis, with improved stroke outcome. This has implications for the use of diffusion‐ and perfusion‐weighted imaging in selecting and monitoring patients for thrombolytic therapy.
Dopaminergic modulation of cortical function in patients with Parkinson's disease
Authors: Mattay Venkata S. , Tessitore Alessandro , Callicott Joseph H. , Bertolino Alessandro , Goldberg Terry E. , Chase Thomas N. , Hyde Thomas M. , Weinberger Daniel R.
Published: August 2002

Patients with idiopathic Parkinson's disease suffer not only from classic motor symptoms, but from deficits in cognitive function, primarily those subserved by the prefrontal cortex as well. The aim of the current study was to investigate the modulatory effects of dopaminergic therapy on neural systems subserving working memory and motor function in patients with Parkinson's disease. Ten patients with stage I and II Parkinson's disease were studied with functional magnetic resonance imaging, during a relatively hypodopaminergic state (ie, 12 hours after a last dose of dopamimetic treatment), and again during a dopamine‐replete state. Functional magnetic resonance imaging was performed under three conditions: a working memory task, a cued sensorimotor task and rest. Consistent with prior data, the cortical motor regions activated during the motor task showed greater activation during the dopamine‐replete state; however, the cortical regions subserving working memory displayed greater activation during the hypodopaminergic state. Interestingly, the increase in cortical activation during the working memory task in the hypodopaminergic state positively correlated with errors in task performance, and the increased activation in the cortical motor regions during the dopamine‐replete state was positively correlated with improvement in motor function. These results support evidence from basic research that dopamine modulates cortical networks subserving working memory and motor function via two distinct mechanisms: nigrostriatal projections facilitate motor function indirectly via thalamic projections to motor cortices, whereas the mesocortical dopaminergic system facilitates working memory function via direct inputs to prefrontal cortex. The results are also consistent with evidence that the hypodopaminergic state is associated with decreased efficiency of prefrontal cortical information processing and that dopaminergic therapy improves the physiological efficiency of this region.
A functional polymorphism in the prodynorphin gene promotor is associated with temporal lobe epilepsy
Authors: Stögmann Elisabeth , Zimprich Alexander , Baumgartner Christoph , Aull‐Watschinger Susanne , Höllt Volker , Zimprich Fritz
Published: August 2002

The prodynorphin gene (PDYN) encoding the anticonvulsant peptide dynorphin is a strong candidate for a seizure suppressor gene and thus a possible modulator of susceptibility to temporal lobe epilepsy. We performed a case control association study in 155 patients with nonlesional temporal lobe epilepsy and 202 controls and found that PDYN promotor low‐expression L‐alleles confer an increased risk for temporal lobe epilepsy in patients with a family history for seizures. Irrespective of the familial background, L‐homozygotes display a higher risk for secondarily generalized seizures and status epilepticus.
Human brain mapping in dystonia reveals both endophenotypic traits and adaptive reorganization
Authors: Meunier Sabine , Garnero Line , Ducorps Antoine , Mazières Leonor , Lehéricy Stéphane , Tézenas Du Montcel Sophie , Renault Bernard , Vidailhet Marie
Published: August 2002

Dystonia has a wide clinical spectrum from early‐onset generalized to late‐onset sporadic, task‐specific forms. The genetic origin of the former has been clearly established. A critical role of repetitive skilled motor tasks has been put forward for the latter, while underlying vulnerability traits are still being searched for. Using magnetoencephalography, we looked for structural abnormalities reflecting a preexisting dysfunction. We studied finger representations of both hands in the primary sensory cortex, as compared in 23 patients with unilateral task‐specific dystonia and 20 control subjects. A dramatic disorganization of the nondystonic hand representation was found in all patients, and its amount paralleled the severity of the dystonic limb motor impairment. Abnormalities were also observed in the cortex coding the dystonic limb representation, but they were important only in the most severely affected patients. The abnormal cortical finger representations from the nondystonic limb appear to be endophenotypic traits of dystonia. That finger representations from the dystonic limb were almost normal for the less severely affected patients may be due to intrinsic beneficial remapping in reaction against the primary disorder.
Disease mechanisms revealed by transcription profiling in SOD1‐G93A transgenic mouse spinal cord
Authors: Olsen Mary K. , Roberds Steven L. , Ellerbrock Brenda R. , Fleck Timothy J. , McKinley Denise K. , Gurney Mark E.
Published: August 2002

Mutations of copper,zinc‐superoxide dismutase (cu,zn SOD) are found in patients with a familial form of amyotrophic lateral sclerosis. When expressed in transgenic mice, mutant human cu,zn SOD causes progressive loss of motor neurons with consequent paralysis and death. Expression profiling of gene expression in SOD1‐G93A transgenic mouse spinal cords indicates extensive glial activation coincident with the onset of paralysis at 3 months of age. This is followed by activation of genes involved in metal ion regulation (metallothionein‐I, metallothionein‐III, ferritin‐H, and ferritin‐L) at 4 months of age just prior to end‐stage disease, perhaps as an adaptive response to the mitochondrial destruction caused by the mutant protein. Induction of ferritin–H and –L gene expression may also limit iron catalyzed hydroxyl radical formation and consequent oxidative damage to lipids, proteins, and nucleic acids. Thus, glial activation and adaptive responses to metal ion dysregulation are features of disease in this transgenic model of familial amyotrophic lateral sclerosis.
Depletion of corticotrophin‐releasing factor neurons in the pontine micturition area in multiple system atrophy
Authors: Benarroch Eduardo E. , Schmeichel Ann M.
Published: August 2002

We sought to determine whether the putative pontine micturition center in the human dorsal pons contains corticotrophin‐releasing factor (CRF) neurons, and whether these neurons are depleted in patients with multiple system atrophy and bladder dysfunction. Brains were obtained at autopsy from 4 control subjects and 4 patients with clinical diagnosis of multiple system atrophy, confirmed neuropathologically. Serial 50μm cryostat sections were obtained throughout the rostral half of the pons, and every eighth section was processed for CRF immunocytochemistry (rabbit polyclonal antibody). Consecutive sections were stained for nicotinamide adenine dinucleotide phosphate diaphorase (NADPH‐d) to identify neurons of the laterodorsal tegmental nucleus or for both CRF and NADPH. Locus ceruleus neurons were identified by their neuromelanin content. Abundant CRF immunoreactive neurons were identified in the dorsal pontine tegmentum just ventral to the locus ceruleus. CRF neurons were intermingled with, but distinct from, the NADPH‐d‐reactive neurons of the laterodorsal tegmental nucleus. In all multiple system atrophy cases, there was a severe depletion of these CRF‐immunoreactive neurons (26.6 ± 3 neurons/section in patients; 73.7 ± 4 neurons/section in controls). Our results suggest that depletion of CRF neurons in the putative pontine micturition center may contribute to the severe bladder dysfunction that characterizes multiple system atrophy.
A disorder similar to Huntington's disease is associated with a novel CAG repeat expansion
Authors: Margolis Russell L. , O'Hearn Elizabeth , Rosenblatt Adam , Willour Virginia , Holmes Susan E. , Franz Mary L. , Callahan Colleen , Hwang Hyon S. , Troncoso Juan C. , Ross Christopher A.
Published: August 2002

Huntington's disease (HD) is an autosomal dominant disorder characterized by abnormalities of movement, cognition, and emotion and selective atrophy of the striatum and cerebral cortex. While the etiology of HD is known to be a CAG trinucleotide repeat expansion, the pathways by which this mutation causes HD pathology remain unclear. We now report a large pedigree with an autosomal dominant disorder that is clinically similar to HD and that arises from a different CAG expansion mutation. The disorder is characterized by onset in the fourth decade, involuntary movements and abnormalities of voluntary movement, psychiatric symptoms, weight loss, dementia, and a relentless course with death about 20 years after disease onset. Brain magnetic resonance imaging scans and an autopsy revealed marked striatal atrophy and moderate cortical atrophy, with striatal neurodegeneration in a dorsal to ventral gradient and occasional intranuclear inclusions. All tested affected individuals, and no tested unaffecteds, have a CAG trinucleotide repeat expansion of 50 to 60 triplets, as determined by the repeat expansion detection assay. Tests for the HD expansion, for all other known CAG expansion mutations, and for linkage to chromosomes 20p and 4p were negative, indicating that this mutation is novel. Cloning the causative CAG expansion mutation for this new disease, which we have termed Huntington's disease‐like 2 (HDL2), may yield valuable insight into the pathogenesis of HD and related disorders.
Cytotoxic evaluation of arsenic compounds in alveolar macrophages in hamsters
Authors: Okada Mitsushi , Inoue Yoko , Karube Hitomi , Niitsuya Masato , Tohnori Hideki , Aizawa Yoshiharu , Okayasu Isao , Kotani Makoto
Published: August 2002

Gallium arsenide (GaAs) causes various toxic effects in animals, including pulmonary diseases. Although their toxicity is not completely investigated, GaAs is used in workplaces in various semiconductor products. The present report was designed to clarify the toxicity of GaAs suspension and arsenic chloride (AsCl3) solution as additives to the alveolar macrophages in hamsters using magnetometry, enzyme release assays and morphological examinations. Alveolar macrophages obtained from hamsters by tracheobronchial lavage and adhered to disks in the bottom of wells were exposed to ferrosoferric oxide and additives. Ferrosoferric oxide particles were magnetized externally and the remanent magnetic field was measured. Relaxation, a fast decline of remanent magnetic fields radiated from alveolar macrophages, was delayed and decay constants decreased dose‐dependently due to exposure to GaAs suspensions. Relaxation was much delayed and decay constants decreased considerably due to exposure to AsCl3 solutions. Because the relaxation is thought to be associated with the cytoskeleton, exposure to GaAs impairs their motor function. Enzyme release assay and morphological findings indicated damage to macrophages. Thus the cytotoxicity caused cytostructural changes and cell death. According to DNA electrophoresis and TUNEL methods, necrotic changes occur more frequently than apoptotic changes. In conclusion, exposure to GaAs suspension and AsCl3 solution induced cytotoxicity of alveolar macrophages. Copyright © 2001 John Wiley & Sons, Ltd.
Toward new biosilicones: hydrosilylation of fish oil unsaturated fatty acid esters
Authors: Delpech Fabien , Asgatay Saadia , Castel Annie , Rivière Pierre , Rivière‐Baudet Monique , Amin‐Alami Amal , Manriquez Juan
Published: August 2002

Hydrosilylation of fatty acid methyl esters (FAMEs) were efficiently catalyzed by Speier's and Wilkinson's catalysts in the case of vinylic acid esters, but less efficiently in the case of ­non‐vinylic ones, which gave non‐regiospecific additions. In the latter case, initiation by radicals led to regiospecific reactions for oleic esters (C10‐silylation). This regiospecificity can be attributed to the higher stability of the C10‐silylated adduct and of the corresponding radical intermediate. Only regioselective addition was observed for linoleic esters (C13‐silylation ≈ 70%, C10 ≈ 20%, C9 ≈ 10%). Molecular modeling was used to examine the stability of the isomeric products and radicals. The new concept of radical initiation sequence has been successfully applied to FAMEs and then was extended to crude fish oil. Copyright © 2001 John Wiley & Sons, Ltd.
Organotin mefenamic complexes—preparations, spectroscopic studies and crystal structure of a triphenyltin ester of mefenamic acid: novel anti‐tuberculosis agents
Authors: Kovala‐Demertzi Dimitra , Dokorou Vaso , Ciunik Zbigniew , Kourkoumelis Nikolaos , Demertzis Mavroudis A.
Published: August 2002

The triphenyltin adduct of mefenamic acid, [SnPh3L] (1), the monophenyltin complex [PhSnOL]
n (2), and the dibutyltin complex [SnBu2L2] (3), where HL is 2‐[bis(2,3‐dimethylphenyl)amino]benzoic acid (mefenamic acid), have been prepared and structurally characterized by means of vibrational, 1H and 13C NMR spectroscopies. The crystal structure of 1 has been determined by X‐ray crystallography. X‐ray analysis revealed a pseudo‐pentacoordinated structure containing Ph3Sn coordinated to the carboxylato group. The structural distortion is a displacement from the tetrahedron toward the trigonal bipyramid. Significant CH–π interactions and intramolecular hydrogen bonds stabilize the structure 1. The polar imino hydrogen atom participates in intramolecular hydrogen bonds. Complex 1 is self‐assembled via CH–π and stacking interactions. Vibrational and NMR data are discussed in terms of the crystal structure and the proposed structures for 1–3. Compounds 1 and 3 were tested for antimycobacterial activity against Mycobacterium tuberculosis H37Rv. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of electrical conductivity models for conductive polymer composites
Authors: Clingerman Matthew L. , King Julia A. , Schulz Kirk H. , Meyers Jeffrey D.
Published: August 2002

The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers, such as carbon fibers and graphite. The resulting composites could be used in applications such as interference shielding and electrostatic dissipation. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials in order to achieve more efficient material design that could reduce costly experimental work. The electrical conductivity of carbon‐filled polymers was studied by adding four single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project include chopped and milled forms of polyacrylonitrile (PAN) carbon fiber, ThermocarbTM Specialty Graphite, and Ni‐coated PAN carbon fiber. Material was extruded and injection‐molded into test specimens, and then the electrical conductivity was measured. Data analysis included a comparison of the results to existing conductivity models. The results show that the model proposed by Mamunya, which takes into account the filler aspect ratio and the surface energy of the filler and polymer, most closely matched the conductivity data. This information will then be used in the development of improved conductivity models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1341–1356, 2002
New conducting thermoplastic elastomers. I. Synthesis and chemical characterization
Authors: Carone E. , D'Ilario L. , Martinelli A.
Published: August 2002

In the last 20 years, much interest has been focused on conducting polymers to find new materials to transfer from research to industry. However, in many cases, as for elastomers for which intrinsically conducting materials are unavailable, it is necessary to use conducting particles that are physically mixed with the polymeric matrix to give loaded rubbers. In this work we report the synthesis and the chemical characterization of an intrinsically conducting material with good mechanical and electrical conduction properties. To achieve such a global goal, we covalently linked, by an amidation reaction, the terminal NH2 of Emeraldine (EB) and sulfonated Emeraldine (SPAN) to a free carboxylic group belonging to the repetitive unit of a functionalized segmented polyurethane. The reaction was carried out by activating such a carboxylic group with N,N′‐dicyclohexylcarbodiimide and N‐hydroxysuccinimide. The reaction yields and the chemical properties of the polymers were studied by proton and carbon‐13 nuclear magnetic resonance, ultraviolet, and Fourier transform infrared spectroscopy. The average numbers of EB or SPAN aromatic rings per polyether urethane acid (PEUA) repetitive unit, which cannot be assumed to be amidation degree because at this moment the molecular weights of the inserted EB and SPAN chains are unavailable, were 6 in case of the polymer obtained from the pristine Emeraldine and 1 for that obtained from the sulfonated Emeraldine. This result could be because SPAN was used in the acidic form, which depresses the nucleophilicity of the NH2 group because of the presence of the sulfonic protons. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 857–867, 2002
UV exposure and temperature effects on curing mechanisms in thin linseed oil films: Spectroscopic and chromatographic studies
Authors: Boyatzis S. , Ioakimoglou E. , Argitis P.
Published: August 2002

The influence of thermal and photochemical treatment in the curing mechanisms of thin linseed oil films is studied. The role of copper acetate pigments is also investigated under the above conditions. UV and FTIR absorption spectroscopy and chromatographic product analysis are used as the main analytical techniques, which allowed the identification of significant changes in the curing mechanism in each case. Yellowing, crosslinking, and fragmentation inside the film material proceed to a different extent according to the conditions. Peroxide destruction is induced by UV exposure at early curing stages and affects the course of the yellowing process. Yellow product formation is also favored by curing at elevated temperatures, which is accompanied in this case by decreased crosslinking in the cured film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 936–949, 2002; DOI 10.1002/app.10117
pH/temperature‐responsive semi‐IPN hydrogels composed of alginate and poly(N‐isopropylacrylamide)
Authors: Ju Hee Kyung , Kim So Yeon , Kim Seon Jeong , Lee Young Moo
Published: August 2002

Amino semitelechelic poly(N‐isopropylacrylamide) (PNIPAAm) was prepared by radical polymerization with aminoethanethiol hydrochloride as a chain‐transfer agent. Semi‐interpenetrating polymer network (semi‐IPN) hydrogels, composed of alginate and amine‐terminated PNIPAAm, were prepared by crosslinking with calcium chloride. From the swelling behaviors of semi‐IPNs at various pH's and Fourier transform infrared spectra at high temperatures, the formation of a polyelectrolyte complex was confirmed from the reaction between carboxyl groups in alginate and amino groups in modified PNIPAAm. Semi‐IPN hydrogels reached an equilibrium swelling state within 24 h. The water state in hydrogels, investigated by differential scanning calorimetry, showed that sample CAN55 [alginate/PNIPAAm (w/w) = 50/50] exhibited the lowest equilibrium water content and free water content among the hydrogels tested, which was attributed to its more compact structure compared to other samples and the high content of interchain bonding within the hydrogels. Alginate/PNIPAAm semi‐IPN hydrogels exhibited a reasonable sensitivity to the temperature, pH, and ionic strength of swelling medium. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1128–1139, 2002
Sequencing of N‐vinyl‐2‐pyrrolidone/glycidyl methacrylate copolymers by one‐dimensional and two‐dimensional nuclear magnetic resonance spectroscopy
Authors: Brar A. S. , Kumar Rajeev
Published: August 2002

Copolymers of N‐vinyl‐2‐pyrrolidone (V) and glycidyl methacrylate (G) monomers of different compositions were prepared by free‐radical solution polymerization. The copolymer composition of these copolymers was determined with 1H‐NMR spectra. The reactivity ratios calculated from the Kelen–Tudos and nonlinear least‐square error‐in‐variable methods were rV = 0.03 ± 0.01 and rG = 5.05 ± 0.84 and rV = 0.02 and rG = 4.72, respectively. The triad sequence distribution in terms of V and G centered triads was determined from 13C{1H}‐NMR spectroscopy. The complete spectral assignment of 13C{1H}‐ and 1H‐NMR spectra was performed with the help of distortionless enhancement by polarization transfer and two‐dimensional 13C–1H heteronuclear single quantum coherence. The 1H–1H couplings were explained with total correlation spectroscopy and nuclear Overhauser enhancement spectroscopy spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 50–60, 2002; DOI 10.1002/app.10186
Synthesis and characterization of nylon 1012/clay nanocomposite
Authors: Wu Zenggang , Zhou Chixing , Qi Rongrong , Zhang Hongbin
Published: August 2002

A nylon 1012/clay nanocomposite was prepared by melt polycondensation polymerization of diamine and diacid in the presence of organoclay. The nylon 1012 and nanocomposite were characterized by Fourier transform IR spectroscopy with attenuated total reflection, and a shift of the SiOSi band toward a lower wavenumber was found as the result of the strong interaction of nylon 1012 with the organoclay. The X‐ray diffraction analysis and transmission electron microscopy observation showed that the clay minerals were exfoliated. Clay platelets increased the crystallization rate but decreased the crystallinity. Differential scanning calorimetry and dynamic mechanical thermal analysis measurements showed that the glass‐transition temperature of the nylon 1012/clay nanocomposite decreased to some degree as compared to nylon 1012 because of the combined effect of confinement and the reduction of the physical crosslink density. The mechanical properties of the nanocomposite such as the tensile strength and tensile modulus are higher than those of nylon 1012, and the water absorption is reduced because of the improvement in the barrier property of the nanocomposite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2403–2410, 2002
Blend of high‐density polyethylene and a linear low‐density polyethylene with compositional‐invariant mechanical properties
Authors: Rana S. K.
Published: August 2002

This article presents the tensile properties and morphological characteristics of binary blends of the high‐density polyethylene (HDPE) and a linear low‐density polyethylene (LLDPE). Two constituents were melt blended in a single‐screw extruder. Injection‐molded specimens were evaluated for their mechanical properties by employing a Universal tensile tester and the morphological characteristics evaluated by using a differential scanning calorimeter and X‐ray diffractometer. It is interesting to observe that the mechanical properties remained invariant in the 10–90% LLDPE content. More specifically, the yield and breaking stresses of these blends are around 80% of the corresponding values of HDPE. The yield elongation and elongation‐at‐break are around 65% to corresponding values of HDPE and the modulus is 50% away. Furthermore, the melting endotherms and the crystallization exotherms of these blends are singlet in nature. They cluster around the corresponding thermal traces of HDPE. This singlet characteristic in thermal traces entails cocrystallization between these two constituting components. The clustering of thermal traces of blends near HDPE meant HDPE‐type of crystallites were formed. Being nearly similar crystallites of blends to that of HDPE indicates nearness in mechanical properties are observed. The X‐ray diffraction data also corroborate these observations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2604–2608, 2002
Swelling and dissolution behavior of poly(methyl methacrylate) films in methyl ethyl ketone/methyl alcohol mixtures studied by optical techniques
Authors: Stamatialis D. F. , Sanopoulou M. , Raptis I.
Published: August 2002

Swelling and dissolution behavior of poly(methyl methacrylate) (PMMA) films during unidimensional penetration of methyl ethyl ketone/methyl alcohol (MEK/MA) liquid mixtures at 22°C is presented. Optical microscopy and two‐beam interferometry were applied to clamped PMMA films to obtain information on penetration kinetics and penetrant concentration profiles. Dissolution by pure MEK was initially controlled by Case II penetration kinetics and at later stages of the process, by stress cracking in the absence of a surface layer. Introduction of increasing amounts of MA in the liquid solvent resulted in moderation of the fragmentation process, enhanced penetration rates at the early stages of the process, deviations from Case II kinetics at the later stages, and the existence of a surface layer. These results indicate that penetration of MEK/MA mixtures and dissolution of PMMA are characterized by lower diffusion Deborah, and higher dissolution, numbers compared to those of pure MEK. Swelling by pure MA, as well as by nonsolvent MEK/MA mixtures, was characterized by Case II penetration kinetics. A pronounced minimum in the penetration rate versus liquid mixture composition plot was observed at 30 : 70 v/v MEK/MA composition. Laser interferometry was applied to very thin PMMA films, supported on a silicon substrate, to study selected cases. The results obtained were very similar to those obtained by optical microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2823–2834, 2002; DOI 10.1002/app.10258
Study on the volumetric expansion of benzoxazine curing with different catalysts
Authors: Liu Xin , Gu Yi
Published: August 2002

A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1107–1113, 2002; DOI 10.1002/app.10267
Plasma polymerization of random polyaniline–polypyrrole– iodine copolymers
Authors: Morales J. , Olayo M. G. , Cruz G. J. , Olayo R.
Published: August 2002

This work presents the synthesis by plasma and the characterization of polypyrrole–polyaniline–iodine copolymer thin films. The objective was to study the conditions to randomly copolymerize different and noncombinable monomers to create new copolymers with enhanced selective properties. The study was focused on the influence of the monomer mass ratio r on the structure of the copolymers. The monomer ratio r is important since it represents the contribution of each monomer to the structure and to the properties of the copolymer. The mainstream techniques used to characterize the plasma polymers were infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The electric conductivity was studied as a function of the relative humidity. The results indicated that the copolymers with iodine have better conductive properties at lower relative humidity and that the copolymers without iodine are more stable at moderately high temperatures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 263–270, 2002
Effect of resin impregnation methods at the early stage of densification on the impregnation efficiency, microstructure, and thermal stability of carbon–carbon composites
Authors: Cho Donghwan , Ahn Young Seok , Lee Jin Yong
Published: August 2002

The effect of impregnation methods and heat‐treatment temperature at the early stage of densification on the impregnation efficiency, microstructure, and thermal stability of carbon–carbon composites prepared from carbon–phenolic green composites was studied. The results suggest that simultaneous application of pressure and heat provides better impregnation performance during densification at the early stage of carbon–carbon composite fabrication than ultrasonic impregnation and vacuum infiltration impregnation. Also, optical microscopic examination strongly supports the result of the impregnation efficiency obtained using three different resin impregnation methods. An additional heat‐treatment at 2000 °C after carbonization results in better thermal stability and a denser microstructure of the fiber and matrix of the composite. For the carbonized composites, including a fully cured furfuryl alcohol resin impregnant, the weight loss measured by a thermogravimetric method quantitatively agrees with the weight loss occurred in a carbonization furnace at the corresponding temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 183–192, 2002
Effect of isotacticity distribution on the crystallization and melting behavior of polypropylene
Authors: Lu Hongbin , Qiao Jinliang , Xu Yibin , Yang Yuliang
Published: August 2002

The crystallization and melting behavior are closely related not only to the external conditions such as undercooling and cooling rate, but also to the chain structure characteristics such as isotacticity distribution. The isotacticity distribution of three commercial isotactic polypropylenes (iPP) used in this work was characterized using Temperature‐Rising Elution Fractionation (TREF) combining with Size‐Exclusion Chromatography (SEC). Their crystallization and melting behavior were observed by Differential Scanning Calorimetry (DSC) and Polarized Light Microscopy (PLM). The results indicated that for iPP with similar molecular weight and isotacticity, the difference in isotacticity distribution not only led to the variation in nucleation and growth rates of crystal, but also changed the perfection of crystals formed under the same condition, even causing the formation of different crystalline modification and the change in the equilibrium melting temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 333–341, 2002
Reactions of trithiocyanuric acid with oxiranes. III. Reactions with epichlorohydrin
Authors: Kucharski Mieczysław , Chmiel‐Szukiewicz Elżbieta
Published: August 2002

Reactions of trithiocyanuric acid with an excess of epichlorohydrin were investigated. Trifunctional polyetherols containing the s‐triazine ring were prepared. The structure of the products was verified using elemental analysis, 1H‐NMR, and IR techniques. Some of the physical properties and the thermal stability of polyetherols were analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1154–1160, 2002
Development of polyimide membranes for the separation of water vapor from organic compounds
Authors: Huang Jingui , Cranford Richard J. , Matsuura Takeshi , Roy Christian
Published: August 2002

Attempts were made to develop solvent‐resistant polyimide capillary membranes with integrally skinned asymmetric structure to be used for the treatment of wood dryer emissions or vacuum pyrolysis aqueous effluents. Model mixtures of 1‐propanol (1‐PrOH)/H2O and acetic acid (AA)/ H2O, with concentrations of 10–90 wt % of organic components, were used as vaporous feeds. Solvent‐resistant membranes with good mechanical and excellent vapor separation properties were prepared from polyimides based on PMDA and BPDA by the dry/wet phase‐inversion technique. Molecular structure largely influences membrane properties. For the asymmetric polyimide membranes studied, a tendency similar to that of homogeneous dense membrane was found. Membranes prepared from polyimides with diamine and dianhydride moieties, both containing rigid backbone and aromatic rings, displayed higher permeability and selectivity. Test conditions exhibited influences on membrane separation performance. Membranes prepared from copolyimide BPDA–50DDS/50ODA and PMDA–50DDS/50ODA exhibited the best mechanical and chemical properties as well as water vapor separation properties, which are considered to be of practical usefulness for applications of these membranes in the removal of water from water/organic mixtures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 139–152, 2002