bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of taurine in regulation of intracellular calcium level and neuroprotective function in cultured neurons
Authors: Chen W.Q. , Jin H. , Nguyen M. , Carr J. , Lee Y.J. , Hsu C.C. , Faiman M.D. , Schloss J.V. , Wu J.Y.
Published: August 2002

Glutamate‐induced excitotoxicity has been implicated as an important mechanism underlying a variety of brain injuries and neurodegenerative diseases. Previously we have shown that taurine has protective effects against glutamate‐induced neuronal injury in cultured neurons. Here we propose that the primary underlying mechanism of the neuroprotective function of taurine is due to its action in preventing or reducing glutamate‐induced elevation of intracellular free calcium, [Ca2+]i. This hypothesis is supported by the following findings. First, taurine transport inhibitors, e.g., guanidinoethyl sulfonate and β‐alanine, have no effect on taurine's neuroprotective function, suggesting that taurine protects against glutamate‐induced neuronal damage through its action on the extracellular membranes. Second, glutamate‐induced elevation of [Ca2+]i is reduced to the basal level upon addition of taurine. Third, pretreatment of cultured neurons with taurine prevents or greatly suppresses the elevation of [Ca2+]i induced by glutamate. Furthermore, taurine was found to inhibit the influx but not the efflux of 45Ca2+ in cultured neurons. Taurine has little effect on the binding of [3H]glutamate to the agonist binding site and of [3H]MDL 105,519 to the glycine binding site of the N‐methyl‐D‐aspartic acid receptors, suggesting that taurine inhibits 45Ca2+ influx through other mechanisms, including its inhibitory effect on the reverse mode of the Na+/Ca2+ exchangers (Wu et al. [2000] In: Taurine 4: taurine and excitable tissues. New York: Kluwer Academic/Plenum Publishers. p 35–44) rather than serving as an antagonist to the N‐methyl‐D‐aspartic acid receptors. J. Neurosci. Res. 66:612–619, 2001. © 2001 Wiley‐Liss, Inc.
Lactate reduces glutamate‐induced neurotoxicity in rat cortex
Authors: Ros Jacqueline , Pecinska Nadja , Alessandri Beat , Landolt Hans , Fillenz Marianne
Published: August 2002

Experiments were carried out to test the hypothesis that lactate reduces the neurotoxicity of glutamate in vivo. MAP2 immunohistochemistry was used to measure lesion size, and microdialysis to measure the changes in glucose and lactate in the extracellular compartment. After implantation of a microdialysis probe 100 mM glutamate with or without 6 mM lactate was added to the perfusion medium and infused into the cortex of unanesthetized rats. Infusion of 100 mM glutamate for a period of 30 min produced a lesion of 6.05 ± 0.64 mm3, an increase in lactate of 124 ± 19% above basal and a 21 ± 9% reduction of glucose below basal level. When 6mM L‐lactate was perfused together with 100 mM glutamate there was a significant reduction in the size of the lesion and there was no reduction in dialysate glucose. When L‐lactate was replaced with D‐lactate the lesion size and the increase in dialysate lactate were greater than after glutamate alone. The neuroprotective role of L‐lactate is attributed to its ability to meet the increased energy demands of neurones exposed to high concentrations of glutamate. © 2001 Wiley‐Liss, Inc.
Quantitative imaging of glutathione in hippocampal neurons and glia in culture using monochlorobimane
Authors: Keelan Julie , Allen Nicola J. , Antcliffe David , Pal Shoubik , Duchen Michael R.
Published: August 2002

Glutathione (GSH) is a major antioxidant system in the mammalian central nervous system (CNS). Abnormalities of GSH metabolism have been associated with many disorders of the CNS, including Parkinson's, Alzheimer's, and Huntingdon's diseases and ischaemic/reperfusion injury. Investigation of GSH levels in the CNS generally relies on biochemical assays from cultures enriched for different cell types. Because glia influence neuronal metabolism, we have studied cultures in which neurons and glia are cocultured. This approach demands fluorescence imaging to differentiate between the different cell types in the culture, permitted by the use of monochlorobimane (MCB), which reacts with GSH to produce a fluorescent product. We have defined the conditions required to ensure steady‐state MCB loading and show the specificity of MCB for GSH through a reaction catalysed by glutathione‐S‐transferase (GST). [GSH] was consistently higher in glia than in neurons, and [GSH] in both cell types decreased with time in culture. Inhibition of GSH synthesis by buthionine sulfoximine (BSO) caused a greater proportional depletion of GSH in glia than in neurons. The depletion of GSH induced by BSO was significantly greater in cells cultured for >10 days. Furthermore, release of GSH from glia and its breakdown by the ectoenzyme γ‐glutamyltranspeptidase (γGT) maintains [GSH] in neurons. In older cultures, inhibition of γGT by acivicin caused significant depletion of neuronal GSH. After inhibition of GSH synthesis by BSO, inhibition of the glia‐neuron trafficking pathway by acivicin caused widespread neuronal death. Such neurotoxicity was independent of the endogenous glutamate and nitric oxide synthase, suggesting that it is not due to secondary excitotoxicity. © 2001 Wiley‐Liss, Inc.
Proliferation of Schwann cells and regulation of cyclin D1 expression in an animal model of Charcot‐Marie‐Tooth disease type 1A
Authors: Atanasoski Suzana , Scherer Steven S. , Nave Klaus‐Armin , Suter Ueli
Published: August 2002

Overexpression of PMP22 is responsible for the most common form of inherited neuropathy, Charcot‐Marie‐Tooth disease (CMT) type 1A. The PMP22‐transgenic rat (CMT rat) is an animal model of CMT1A, and its peripheral nerves show the characteristic features of ongoing demyelination and remyelination that is also seen in CMT1A patients. Since Schwann cell proliferation is a prominent feature of peripheral nerves in inherited peripheral neuropathies, we examined proliferation and the expression of cyclin D1 in CMT rats. D‐type cyclins are required for the initial steps in cell division and nuclear import is crucial for the function of cyclin D1 in promoting cell proliferation. Like normal myelinating Schwann cells in wild‐type rats, remyelinating Schwann cells in CMT rats show perinuclear cyclin D1 expression. Schwann cells with nuclear cyclin D1 expression, as well as proliferating Schwann cells, were both associated with demyelinated axonal segments. Supernumerary onion bulb Schwann cells, however, do not express cyclin D1 and were not proliferating. Thus, cyclin D1 expression and its subcellular localization correlate directly with distinct physiological states of Schwann cells in this animal model of CMT1A. © 2002 Wiley‐Liss, Inc.
Role of CB1 and CB2 receptors in the inhibitory effects of cannabinoids on lipopolysaccharide‐induced nitric oxide release in astrocyte cultures
Authors: Molina‐Holgado Francisco , Molina‐Holgado Eduardo , Guaza Carmen , Rothwell Nancy J.
Published: August 2002

The purpose of this study was to investigate the role of the central cannabinoid receptor (CB1) in mediating the actions of the endogenous cannabinoid agonist anandamide and the synthetic cannabinoid CP‐55940. Activation of primary mouse astrocyte cultures by exposure to bacterial lipopolysaccharide (LPS) caused a marked (approximately tenfold) increase in nitric oxide (NO) release. Coincubation with the cannabinoid agonists anandamide or CP‐55940 markedly inhibited release of NO (–12% to –55%). This effect was abolished by SR‐141716A (1 μM), a CB1 receptor antagonist. SR‐141716A alone also significantly increased NO release in response to LPS, suggesting that endogenous cannabinoids modify inflammatory responses. In contrast, coincubation with the CB2 receptor antagonist SR‐144528 (1 μM) abolished the inhibitory effects of the endogenous cannabinoid anandamide on LPS‐induced NO release, although this may reflect nonspecific effects of this ligand or cannabinoid actions through atypical receptors of anandamide. We also showed that endogenous or synthetic cannabinoids inhibit LPS‐induced inducible NO synthase expression (mRNA and protein) in astrocyte cultures. These results indicate that CB1 receptors may promote antiinflammatory responses in astrocytes. © 2002 Wiley‐Liss, Inc.
Myelin protein zero exists as dimers and tetramers in native membranes of Xenopus laevis peripheral nerve
Authors: Thompson Amanda J. , Cronin Maureen S. , Kirschner Daniel A.
Published: August 2002

Protein zero (P0) glycoprotein is the major integral membrane protein of the peripheral nervous system myelin in higher vertebrates. Previous findings indicate the formation of tetrameric assemblies from studies on isolated P0. To determine whether in intact myelin the P0 exists as oligomers, we isolated myelin from sciatic nerve of Xenopus laevis and analyzed it using sodium dodecyl sulfate and urea gel electrophoresis. P0 oligomerization was confirmed using Western blotting, which showed monomeric P0 at ∼30 kDa and oligomeric P0 at ∼60 kDa and ∼120 kDa. A variety of denaturing conditions failed to convert any appreciable amount of oligomer to monomer. Instead, the addition of these denaturants further increased the amount of dimer and tetramer while decreasing the amount of monomer. Native gels showed dimeric P0 without the appearance of monomer or tetramer, suggesting that dimeric P0, the most prominent form of the protein, is the most stable and likely occurs in the native myelin membrane array. © 2002 Wiley‐Liss, Inc.
Suppression of BDNF‐induced expression of neuropeptide Y (NPY) in cortical cultures by oxygen‐glucose deprivation: A model system to study ischemic mechanisms in the perinatal brain
Authors: Barnea Ayalla , Roberts Jodie
Published: August 2002

The aim of this study was to establish a culture system that can serve as a model to study hypoxic‐ischemic mechanisms regulating the functional expression of NPY neurons in the perinatal brain. Using an aggregate culture system derived from the rat fetal cortex, we defined the effects of oxygen and glucose deprivation on NPY expression, using BDNF‐induced production of NPY as a functional criterion. NPY neurons exhibited a differential susceptibility to oxygen and glucose deprivation. Although the neurons could withstand oxygen deprivation for 16 hr, they were dramatically damaged by 8 hr of glucose deprivation and by 1–4 hr of deprivation of both oxygen and glucose (N+Glu−). One‐hour exposure to N+Glu− led to a transient inhibition (≈50%) of NPY production manifesting within 24 hr and recovering by 5 days thereafter, a 2‐hr exposure to N+Glu− led to a sustained inhibition (50–75%) manifesting 1–5 days thereafter, and a 4‐hr exposure to N+Glu− led to a total irreversible suppression of BDNF‐induced production of NPY manifesting within 24 hr and lasting 8 days after re‐supply of oxygen and glucose. Moreover, 1‐hr exposure to N+Glu− led to a substantial and 4‐hr exposure led to a total disappearance of immunostaining for MAP‐2 and NPY but not for GFAP; indicating that neurons are the primary cell‐type damaged by oxygen‐glucose deprivation. Analysis of cell viability (LDH, MTT) indicated that progressive changes in cell integrity take place during the 4‐hr exposure to N+Glu− followed by massive cell death 24 hr thereafter. Thus, we defined a culture system that can serve as a model to study mechanisms by which ischemic insult leads to suppression and eventually death of NPY neurons. Importantly, changes in NPY neurons can be integrated into the overall scheme of ischemic injury in the perinatal brain. © 2002 Wiley‐Liss, Inc.
β‐Amyloid peptide induces ultrastructural changes in synaptosomes and potentiates mitochondrial dysfunction in the presence of ryanodine
Authors: Mungarro‐Menchaca Xavier , Ferrera Patricia , Morán Julio , Arias Clorinda
Published: August 2002

In Alzheimer's disease (AD), loss of synapses exceeds neuronal loss and some evidence suggests a role of β‐amyloid protein (Aβ) in synaptic degeneration through a mechanism which may involve intraneuronal Ca2+ dyshomeostasis. Emerging evidence points to the participation of the internal Ca2+ stores in the pathophysiology of neurodegeneration in AD. To test the involvement of intrasynaptic Ca2+ mobilization in Aβ toxicity, we explored the role of ryanodine receptor activation in rat cortical synaptosomes taken as a model system for the central presynapses. Evaluation of synaptosomal mitochondrial redox capacity was assessed by the MTT reduction technique, and ultrastructural changes of synaptosomes after exposure to Aβ and ryanodine were evaluated by electron microscopy. Our results show that Aβ potentiates mitochondrial dysfunction in the presence of ryanodine and induces morphological changes consisting of mitochondrial swelling and intense small synaptic vesicles depletion. These changes were accompanied by a reduction in the content of synaptophysin and actin proteins. The reduction of actin immunoreactivity was reversed in the presence of a wide range caspase inhibitors, suggesting the activation of synaptic apoptotic mechanisms. © 2002 Wiley‐Liss, Inc.
Tenascin‐R is expressed by Schwann cells in the peripheral nervous system
Authors: Probstmeier Rainer , Nellen Jörg , Gloor Sergio , Wernig Anton , Pesheva Penka
Published: August 2002

The extracellular matrix glycoprotein tenascin‐R (TN‐R) has been implicated in a variety of cell‐matrix interactions involved in the molecular control of axon guidance and neural cell migration during development and regeneration of the central nervous system (CNS). Whereas TN‐R is amply expressed in the early postnatal and adult mammalian CNS, the protein has so far not been detected in different compartments of the peripheral nervous system (PNS). Here we provide first evidence that TN‐R (predominantly TN‐R 160 isoform) is transiently expressed in the sciatic nerve of late embryonic (E14–18) and neonatal mice, while at later developmental stages, both protein and mRNA are downregulated. In vitro, TN‐R protein was found to be expressed by both undifferentiated and neuronally differentiated PC12 cells and by L1‐positive Schwann cells (SC), but not by other neural and non‐neural cell types in cell cultures derived from embryonic (E17/18) hindlimbs and neonatal sciatic nerves. In the developing PNS, TN‐R expression correlated with axon growth and SC migration during the period of skeletal muscle innervation. Based on different in vitro approaches, we found that the substrate‐bound glycoprotein selectively inhibits the fibronectin‐dependent: (1) neurite outgrowth from dorsal root ganglion neurons (strongly expressing α5β1 integrin and the disialoganglioside GD3) by a ganglioside‐sensitive signaling mechanism; and (2) migration of primary myoblasts and other non‐neuronal cells in a ganglioside‐independent manner. Our findings suggest the functional role of TN‐R in PNS pattern formation during distinct stages of axon pathfinding and skeletal muscle innervation. J. Neurosci. Res. 64:70–78, 2001. © 2001 Wiley‐Liss, Inc.
Nongenomic antiapoptotic signal transduction by estrogen in cultured cortical neurons
Authors: Honda Kazuhiro , Shimohama Shun , Sawada Hideyuki , Kihara Takeshi , Nakamizo Tomoki , Shibasaki Hiroshi , Akaike Akinori
Published: August 2002

Estrogen replacement therapy in menopausal women has been suggested to be beneficial in preventing the progression of cognitive impairment in Alzheimer disease. We demonstrated previously that the phosphatidylinositol 3‐kinase (PI3‐K)/Akt signal transduction pathway plays a pivotal role on the neuroprotection provided by 17β‐estradiol against acute glutamate toxicity. In the present study, we investigated the mechanism of neuroprotection against apoptosis because acute glutamate toxicity predominantly induced necrosis. 17β‐estradiol provided neuroprotection against apoptosis induced by staurosporine. This neuroprotection was inhibited by pretreatment with a PI3‐K inhibitor, LY294002. An estrogen receptor specific antagonist, ICI182780, also suppressed the neuroprotection provided by 17β‐estradiol. Western blotting analysis demonstrated that treatment with 17β‐estradiol induced the phosphorylation of Akt within 5 min, which was suppressed by pretreatment with LY294002 and ICI182780. Furthermore, 17β‐estradiol induced phosphorylation of the cAMP response element binding protein (CREB) at Ser133 within 15 min and then upregulated Bcl‐2 in a PI3‐K/Akt‐dependent manner. Because CREB is known to be a transcription factor for Bcl‐2, these results suggest that 17β‐estradiol exerts its antiapoptotic effects by CREB phosphorylation and Bcl‐2 upregulation via nongenomic activation of the PI3‐K/Akt pathway in cultured cortical neurons. J. Neurosci. Res. 64:466–475, 2001. © 2001 Wiley‐Liss, Inc.
Lipopolysaccharide‐induced switch between retinoid receptor (RXR) α and glucocorticoid attenuated response gene (GARG)‐16 messenger RNAs in cultured rat microglia
Authors: Kitamura Yoshihisa , Spleiss Olivia , Li Hongwei , Taniguchi Takashi , Kimura Hiroshi , Nomura Yasuyuki , Gebicke‐Haerter Peter J.
Published: August 2002

Glucocorticoid‐attenuated response genes (GARG) belong to a recently described family of genes responsive to the action of dexamethasone. Full‐length cDNA of one member of this family, GARG16, has been cloned from rat microglia and regulation of its mRNA expression has been studied. Moreover, regulation of retinoid/retinoic acid activated transcription factor (RXR/RAR) mRNAs in mixed astrocyte and in purified microglia cultures has been investigated. RARβ mRNA was undetectable in microglia by RT‐PCR, whereas clearly present in the mixed cultures. RXRα, RARγ, and GARG16 mRNAs were found in both culture systems. RXRα mRNA was strongly expressed in control microglia but rapidly declined upon treatment with LPS. Conversely, GARG16 mRNA was almost untraceable in control microglia but rapidly increased by LPS. Time‐course studies revealed an oscillating behavior of expression of both mRNAs during the first 6 hr, which receded to control levels (RXRα high, GARG16 low) at 72 hr of LPS‐treatment. Additionally, p38 MAPK and SEK phosphorylations peaked at 1 hr followed by steady declines, whereas MEK and c‐Jun showed double peaks at 1+4 hr and 1+6 hr, respectively, before subsiding to control levels. This behavior was not observed in comparative studies with TNF‐α, interleukin‐10 (IL‐10), or interferon‐γ inducible protein 10 (IP‐10). Finally, inhibitors of p38 MAPK, p42/p44 ERK, and PKCα as well as the use of dexamethasone revealed major influences of the p38 MAPK‐c‐Jun‐AP‐1 signaling pathway on RXRα and GARG16 mRNA expressions. The counter regulatory control of GARG16 and RXRα mRNA expression is believed to be an example of a fine‐tuned cellular mechanism to react to inflammatory stimuli. J. Neurosci. Res. 64:553–563, 2001. © 2001 Wiley‐Liss, Inc.
Estrogen attenuates cell death induced by carboxy‐terminal fragment of amyloid precursor protein in PC12 through a receptor‐dependent pathway
Authors: Chae Hee‐Sun , Bach Jae‐Hyung , Lee Myoung‐Woo , Kim Hye‐Sun , Kim Yong‐Sik , Kim Kyung Yong , Choo Kwan Young , Choi Se Hoon , Park Cheol‐Hyoung , Lee Sang Hyung , Suh Yoo‐Hun , Kim Sung Su , Lee Won Bok
Published: August 2002

In the present study, we investigated effects of estrogen on cell death induced by carboxy‐terminal fragment of amyloid precursor protein (CT), a candidate causative substance in the pathogenesis of Alzheimer's disease. 17β‐Estradiol attenuated CT‐induced cell death in PC12 cells, whereas 17α‐estradiol, nonestrogenic stereoisomer, did not exert any significant protective effect on CT‐induced cell death. These results suggest that protective effects of estrogen may be mediated by estrogen receptor (ER) in PC12 cells. To confirm the results, we determined the effects of tamoxifen, an estrogen receptor antagonist. Tamoxifen blocked the protective effects of 17β‐estradiol, although it did not affect those of 17α‐estradiol. Overall, it might be thought that the protective effect of estradiol on CT‐induced cell death is achieved by hormonal properties mediated through the estrogen receptor rather than the structural properties as a reducing agent. J. Neurosci. Res. 65:403–407, 2001. © 2001 Wiley‐Liss, Inc.
Differential regulation of p75 and trkB mRNA expression after depolarizing stimuli or BDNF treatment in basal forebrain neuron cultures
Authors: Elliott Robert C. , Black Ira B. , Dreyfus Cheryl F.
Published: August 2002

Extensive evidence suggests that BDNF regulates neural function and architecture after depolarization. Expression of BDNF is increased after depolarization, and the ability of BDNF to modulate synaptic function is well documented. To further investigate BDNF signaling after activity, we analyzed the effects of depolarization or BDNF treatment on receptor mRNA expression in cultured basal forebrain neurons. Levels of mRNA coding for the cognate BDNF receptor, trkB, as well as the common neurotrophin receptor, p75, were quantitated simultaneously using a sensitive solution hybridization technique. Depolarization or BDNF treatment increased p75 mRNA expression 94% and 195%, respectively. In contrast, trkB message decreased 23% after depolarization but was unchanged by BDNF treatment. Together, these changes resulted in significant increases in the p75/trkB ratio after depolarization or BDNF treatment that could alter BDNF binding or signal transduction. J. Neurosci. Res. 66:83–88, 2001. © 2001 Wiley‐Liss, Inc.
Expression of arginase isozymes in mouse brain
Authors: Yu Hong , Iyer Ramaswamy K. , Kern Rita M. , Rodriguez Williams I. , Grody Wayne W. , Cederbaum Stephen D.
Published: August 2002

The two forms of arginase (AI and AII) in man, identical in enzymatic function, are encoded in separate genes and are expressed differentially in various tissues. AI is expressed predominantly in the liver cytosol and is thought to function primarily to detoxify ammonia as part of the urea cycle. AII, in contrast, is predominantly mitochondrial, is more widely expressed, and is thought to function primarily to produce ornithine. Ornithine is a precursor in the synthesis of proline, glutamate, and polyamines. This study was undertaken to explore the cellular and regional distribution of AI and AII expression in brain using in situ hybridization and immunohistochemistry. AI and AII were detected only in neurons and not in glial cells. AI presented stronger expression than AII, but AII was generally coexpressed with AI in most cells studied. Expression was particularly high in the cerebral cortex, cerebellum, pons, medulla, and spinal cord neurons. Glutamic acid decarboxylase 65 and glutamic acid decarboxylase 67, postulated to be related to the risk of glutamate excitotoxic and/or γ‐aminobutyric acid inhibitoxic injury, were similarly ubiquitous in their expression and generally paralleled arginase expression patterns, especially in cerebral cortex, hippocampus, cerebellum, pons, medulla, and spinal cord. This study showed that AI is expressed in the mouse brain, and more strongly than AII, and sheds light on the anatomic basis for the arginine→ornithine→glutamate→GABA pathway. J. Neurosci. Res. 66:406–422, 2001. © 2001 Wiley‐Liss, Inc.
A theory‐based measure of conflict management strategies in the workplace
Authors: De Dreu Carsten K. W. , Evers Arne , Beersma Bianca , Kluwer Esther S. , Nauta Aukje
Published: August 2002

Conflict management influences individual wellbeing, group performance and organizational effectiveness. This research examined the psychometric qualities of two versions of the newly developed test for conflict handling. The lean version (Study 1 and 2) included problem solving, forcing, yielding and avoiding as distinct conflict management strategies, and the expanded version (Study 3) also included compromising. A negotiation study (Study 1) showed substantial convergence between self‐reports, opponent‐reports and observer rated behavior for problem solving, forcing and yielding, but not for avoiding. In Study 2 and Study 3 the psychometric properties were examined of the lean and the expanded version, respectively. Confirmatory factor analyses revealed good to excellent psychometric qualities of both versions of the scale. We conclude that the scale is a parsimonious, flexible and valid instrument to assess conflict management strategies at work. Copyright © 2001 John Wiley & Sons, Ltd.
Possible influence of QBO on teleconnections relating Indian summer monsoon rainfall and sea‐surface temperature anomalies across the equatorial pacific
Authors: Chattopadhyay J. , Bhatla R.
Published: August 2002

The relationship between the all‐India monsoon rainfall and sea‐surface temperature (SST) anomalies over different Niño regions of the equatorial Pacific Ocean have been examined from 1949 to 1995 using the full time series, as well as by grouping the seasonal rainfall and SST data according to phases of the Quasi‐Biennial Oscillation (QBO) at the 50‐hPa level. The results suggest that Indian monsoon rainfall shows the strongest inverse correlation with the SST anomalies over the Niño 3 region for all the seasons from the concurrent summer to the following winter. When the seasonal rainfall and SST data are stratified according to the phases of QBO, the concurrent correlations are highly enhanced during the east years of QBO over the Niño 3 region and highly reduced during the west years of QBO. This interesting result may explain the different behaviour of the Indian monsoon in different El Niño‐Southern Oscillation (ENSO) years. The ENSO events continuing during the monsoon season which are associated with easterly phases of QBO are likely to cause drought, while events which are associated with westerly phases of QBO are likely to result in a normal monsoon. Copyright © 2002 Royal Meteorological Society
Low frequency and quasi‐biennial oscillations in the Malaysian precipitation anomaly
Authors: Tangang Fredolin T.
Published: August 2002

The spatial and temporal variability of the precipitation anomaly in Malaysia in the quasi‐biennial (1.5–2.5 years) and the low‐frequency (3–7 years) bands were investigated. The oscillations in both bands contributed a significant proportion of the variance in the precipitation anomaly. The most dominant modes for both bands had large impacts on the stations in Sabah, Sarawak and on the east coast of the Malaysian peninsula. These dominant modes had a similar manifestation, i.e. the stations experienced enhanced rainfall during periods of large negative anomaly of sea surface temperature (SST) in the central‐eastern Pacific Ocean and suppressed rainfall during periods of large positive SST anomaly. Hence, these areas may face severe drought during an El Niño event and flood during La Niña. Both bands appeared to have large‐scale coherence with SST, sea level pressure and zonal wind over the tropical Pacific and Indian Oceans and South China Sea. However, the two signals differed with respect to timing and propagation. Copyright © 2001 Royal Meteorological Society
Molecular orbitals and electronic spectra of benzo-fused and related porphyrin analogues
Authors: KOBAYASHI NAGAO , KONAMI HIDEO
Published: August 2002

Molecular orbital (MO) calculations of more than 60 porphyrinic π conjugated structures have been performed within the framework of the Pariser–Parr–Pople approximation. The results of a series of compounds are introduced and summarized in order to show how they vary depending on the systematic change in molecular structure. These are shown schematically or itemized. Our results are compared with the spectra of the corresponding known compounds and with the MO results reported by previous workers, if available. In addition, the results have continually been compared, where possible, with those of tetraazaporphyrin or phthalocyanine systems. In naphthalene- or anthracene-fused compounds, these molecule-centered orbitals often appear, and these are indicated using either triangles or circles in figures if they appear between HOMO – 3 and LUMO + 3 orbitals.
Synthesis and characterization of new metal-free and metal phthalocyanines with peripheral N'-2-(cyanoethyl)-aminoethylsulfanyl substituents
Authors: AǦIRTAŞ M. S. , BEKAROǦLU Ö.
Published: August 2002

The synthesis of new metal-free and zinc(II), cobalt(II) phthalocyanines substituted with four 4-(2-N'-cyanoethyl)aminoethylsulfanyl groups is described. The new compounds have been characterized by elemental analysis and IR, 1 H NMR and UV-vis spectroscopy.
Atlantic ocean heat piracy and the bipolar climate see‐saw during Heinrich and Dansgaard–Oeschger events
Authors: Seidov Dan , Maslin Mark
Published: August 2002

The millennial‐scale asynchrony of Antarctic and Greenland climate records during the last glacial period implies that the global climate system acts as a bipolar see‐saw driven by either high‐latitudinal and/or near‐equatorial sea‐surface perturbations. Based on the results of recent modelling of generic Heinrich and Dansgaard–Oeschger scenarios, we discuss the possibility that oscillations of the deep‐ocean conveyor may have been sufficient to cause this bipolar see‐saw. The bipolar climate asynchrony in our scenarios is caused by the toggle between North Atlantic heat piracy and South Atlantic counter heat piracy. Ocean circulation has an enhanced sensitivity to the northern deep‐water source as the North Atlantic Deep Water (NADW) cannot enter the Southern Ocean at depths shallower than the bottom of the Drake Passage. Any shoaling of the NADW can, therefore, increase the northward incursion of Antarctic Bottom Water (AABW), and trigger an interhemispheric climate oscillation. As hundreds of years are required to warm the respective high latitudes, the observed climate lead and lags between the two hemispheres can be explained entirely by the variability of the meridional overturning and by the corresponding change in the oceanic heat transport. Accordingly, it is entirely feasible for the global climate to work like a pendulum, which theoretically could be controlled by pushing at either of the deep‐water sources. Our model scenarios suggest that it is entirely feasible for the bipolar climate see‐saw to be controlled solely by variations in NADW formation. Copyright © 2001 John Wiley & Sons, Ltd.
Prospects of international initiatives in agri‐food biotechnology
Authors: Tzotzos George T
Published: August 2002

Although advances in ag‐biotech are primarily determined by commercial considerations, the role of government policies and financial institutions (eg venture capital institutions and other financial brokers) is significant in guiding the innovation through funding of research, regulation, technology transfer legislation and appropriate patenting policies. In the developing world, market failure coupled with the absence of risk capital and ineffective regulatory government policies (biosafety, intellectual property, etc) constitute significant impediments to private investment for innovation in ag‐biotech. The role of international agencies in overcoming some of the barriers for the transfer of ag‐biotech to the developing world cannot be overemphasised. Programmes of international agencies concentrate on actions that strengthen the capacity of national and international research systems and facilitate the introduction of policy and institutional reforms that are conducive to investment and technology transfer. The paper focuses on trends that are emerging from such programmes and draws conclusions on their effectiveness to meet manifest needs in developing countries.

© 2001 Society of Chemical Industry
Cranberry proanthocyanidins associate with low‐density lipoprotein and inhibit in vitro Cu2+‐induced oxidation
Authors: Porter Mandy L , Krueger Christian G , Wiebe Donald A , Cunningham David G , Reed Jess D
Published: August 2002

Antioxidant activity of six fractions of cranberry phenolic compounds was determined by inhibition of Cu2+‐induced low‐density lipoprotein (LDL) oxidation. The phenolic composition of each fraction was determined by high‐performance liquid chromatography. The phenolic fractions were mixed with aliquots of modified human serum prior to LDL isolation. The serum was modified to remove very‐low‐density lipoprotein and chylomicrons that may bind phenolic compounds. Only fractions 5 and 6 that contained proanthocyanidins (PAs) significantly increased the lag time of LDL oxidation, and the lag time for fraction 6 was significantly higher than for fraction 5. The mass distribution of PAs in these fractions was obtained by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry, a technique that allows rapid characterisation of the molecular weight distribution in mixtures of oligomeric compounds. Fraction 5 contained trimers through heptamers, whereas fraction 6 contained pentamers through nonamers. In addition, fraction 6 contained PA oligomers with more doubly linked, A‐type interflavan bonds. Results indicate that PAs specifically associate with LDL in modified serum and increase the lag time of Cu2+‐induced oxidation. Differences between fractions 5 and 6 in PA structure and effects on LDL oxidation suggest that the degree of polymerisation and the nature of the interflavan bond influence antioxidant properties.

© 2001 Society of Chemical Industry
CD44 expression in human gliomas
Authors: Ranuncolo Stella Maris , Ladeda Virginia , Specterman Sergio , Varela Mirta , Lastiri José , Morandi Ana , Matos Elena , De Kier Joffe Elisa Bal , Puricelli Lydia , Pallotta María Guadalupe
Published: August 2002

Background and Objectives

Glioma invasiveness involves the attachment of tumor cells to the brain extracellular matrix, rich in hyaluronic acid (HA). CD44, the principal receptor for HA is found as a standard molecule (CD44s) or as variants (CD44v). We undertook a retrospective study to evaluate the expression pattern of CD44s, the isoforms CD44v3, v4/5 and v6 and to correlate their expression with clinical‐anatomopathological parameters and survival rate.

Methods

The expression of these molecules was evaluated immunohistochemically in 84 gliomas.

Results

No expression of CD44v was detected in any tumors. CD44s staining of tumor cells was found in 70 of 84 (83.3%) of the gliomas. In 23 of 39 (59.0%) of the GBM more than the 70% of the cells were stained, while only 2 of 21 (9.5%) of LGA showed high expression. The association between CD44 and histological grade remained when the prognostic variables were considered in a multivariate analysis. Higher expression of CD44 was associated with worse overall survival rate; however, the Cox analysis indicated that survival was not associated with CD44.

Conclusions

Our results suggest that overexpression of CD44s could be relevant in determining the highly invasive behaviour of gliomas, though it does not behave as an independent prognostic factor for survival. J. Surg. Oncol. 2002;79:30–36. © 2002 Wiley‐Liss, Inc.
Desmoid tumors: A novel approach for local control
Authors: Baliski Christopher R. , Temple Walley J. , Arthur Keith , Schachar Norman S.
Published: August 2002

Background and Objectives

After resection, desmoid tumors are associated with a recurrence rate that is typically 25–50%. Although this is an unusual problem, we instituted a prospective cohort study with neoadjuvant chemotherapy and radiation, followed by surgical resection, in an effort to improve local control.

Methods

Between 1985 and 1999, 13 patients with potentially resectable disease were managed with a treatment protocol of preoperative doxorubicin (30 mg continuous infusion daily for 3 days) and radiotherapy (10 × 300 cGy). Resection was performed 4–6 weeks later. All lesions were resected with an intended margin of 1 cm, but clear adventitial margins were accepted in order to preserve critical structures.

Results

The median follow‐up was 71 months (range, 22–109). Six patients (46%) presented after failure of a previous surgery. Clear microscopic margins were obtained in 11 patients, and 2 patients had positive margins. There were two local recurrences (15% local recurrence). Both recurrences followed resection of large thigh lesions, which appeared at 30 and 49 months of follow‐up. In one patient with a chest wall tumor, two new primary desmoid tumors developed outside the treatment area, in the ipsilateral arm and forearm. Eleven patients have been disease free for a median of 71 months (range, 22–109).

Conclusions

For potentially resectable lesions, this protocol provides excellent local control, even in those with recurrent disease. Neoadjuvant treatment with doxorubicin and radiotherapy appears to be a better option than surgery alone, or surgery and adjuvant radiotherapy. These results need to be confirmed in larger, prospective randomized trials. J. Surg. Oncol. 2002;80:96–99. © 2002 Wiley‐Liss, Inc.
Pelvic neoplasms in children
Authors: Groff Diller B.
Published: August 2002

The pelvis of the infant and child has different anatomic relationships than the adolescent or adult pelvis, and the knowledge of congenital anomalies of the rectum and bladder can assist in treating the primary neoplasms of the pelvis. The most common neoplasms are rhabdomyosarcomas of the bladder, prostate, and vagina; sacrococcygeal teratoma; and the germ cell tumors, including teratomas, endodermal sinus tumors, and the choriocarcinomas. Rapidly improving chemotherapy for all of these lesions has resulted in a changed role for the surgeon. Less radical resection of these tumors is being performed whereas it is necessary to have more precise histologic and genetic identification of the tumor and the specific anatomic location and extent of the tumor in the pelvis. Survival for all types of childhood pelvic neoplasms has improved dramatically under the influence of the combined children's cancer study groups, which have been functioning for the last 20 years. Because of the complexities of diagnosis and treatment of these pelvic neoplasms in childhood and because the survival rates have dramatically improved with the most current therapy, these children should be cared for in a children's center that is part of the major children's cancer study groups. J. Surg. Oncol. 2001; 77:65–71. © 2001 Wiley‐Liss, Inc.
Fair trade in tourism to protected areas­— A micro case study of wildlife tourism to South Luangwa National Park, Zambia
Authors: Mvula Cheryl D.
Published: August 2002

Wildlife tourism to protected areas is one of the fastest growing sectors of the tourism industry. However, although tourism development brings rewards, its benefits are seldom distributed equitably. Host communities, particularly in the developing world, are increasingly counting the costs of development that has failed to put their rights and interests on a par with those of their visitors. This paper reports on the impacts of wildlife tourism to South Luangwa National Park, Zambia on the rural local communities that reside there. It assesses local people's attitude towards tourism in the area and solicits their views on how the benefits to the community could be increased. The findings of the research show that experience has so far encouraged the community to want more involvement with tourism and tourists. It indicates, however, that the benefits of tourism currently reach few local people and that in certain instances inequality and discrimination is evident in the employment practice of the local tourism industry. It goes on to highlight the range of factors that inhibit or constrain greater local involvement in tourism, and points to community tourism based on cultural heritage as a potential way of maximising the benefits of tourism to communities, while minimising the impacts. Copyright © 2001 John Wiley & Sons, Ltd.
UK tour operator strategies: causes and consequences
Authors: Klemm Mary , Parkinson Lynn
Published: August 2002

This paper is an investigation of the competitive strategies of British tour operators and their impact on the image and quality of tourist destinations. The strategies considered are the vertical integration of tour operators with travel retailers and airlines, pricing and contracting systems in the resort, and developments in market segmentation. The authors also consider the rationale, development and impact of tour operator branding, a strategy that has accelerated the trend towards standardised holiday products. The study concludes by outlining policies to counteract the negative effects of tour operator strategies and work towards a more fruitful partnership between mass market tour operators and tourist destinations. Copyright © 2001 John Wiley & Sons, Ltd.
OH concentration time histories in n‐alkane oxidation
Authors: Davidson D. F. , Herbon J. T. , Horning D. C. , Hanson R. K.
Published: August 2002

OH radical concentration time histories were measured behind reflected shocks in the oxidation of four n‐alkanes: propane, n‐butane, n‐heptane, and n‐decane. Initial reflected shock conditions of these measurements were 1357–1784 K, 2.02–3.80 atm, with fuel concentrations of 300–2000 ppm, and equivalence ratios from 0.8 to 1.2. OH concentrations were measured using narrow‐linewidth ring‐dye laser absorption of the R1(5) line of the A–X (0,0) transition at 306.5 nm. These concentration time‐history measurements were compared to the modeled predictions of eight large n‐alkane oxidation mechanisms currently available in the literature and the kinetic implications of these measurements are discussed. These data, in conjunction with recent measurements of n‐alkane ignition times and ethylene yields in n‐alkane pyrolysis experiments, also performed in this laboratory, provide a unique database of species concentration time histories for n‐alkane mechanism validation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 775–783, 2001
Substituent effects on the disproportionation—combination rate constant ratios for gas‐phase halocarbon radicals, Part 5: Reactions of CF3 + CF3CH2CHCH3 and CF3CH2CHCH3 + CF3CH2CHCH3
Authors: Ferguson John D. , Holmes Bert E.
Published: August 2002

Rate constant ratios, kd/kc for the disproportionation/combination reaction have been measured as 0.07 ± 0.02 when an H is removed from the CH2 position of the CF3CH2CHCH3 radical and as 0.24 ± 0.03 when the H is removed from the CH3 position in the reaction with the CF3 radical. For the self‐reaction between two CF3CH2CHCH3 radicals, kd/kc has been measured as 0.27 ± 0.03 when the H is removed from the CH2 position and as 0.47 ± 0.04 when the H is removed from the CH3 position. The branching fraction, corrected for the number of hydrogens at each site, is 0.70 favoring the methyl position when the acceptor radical is CF3 and 0.54 when CF3CH2CHCH3 is the acceptor radical. Branching fraction results show that the CF3 substituent on the CF3CH2CHCH3 radical hinders disproportionation when CF3 is the acceptor radical. When the accepting radical is CF3CH2CHCH3 the CF3 substituent may slightly impede the disproportionation reaction, but the branching ratio is nearly statistical. The effect of substituents on the donor radical, CF3CH2CHX, will be discussed for the series X = H, CF3, Cl, and CH3 when the acceptor radical is CF3. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 549–557, 2001
Is sustainable development based on agriculture attainable in Kenya? A multidisciplinary case study of Murang'a district
Authors: Ekbom A. , Knutsson P. , Ovuka M.
Published: August 2002

Kenya's development seems trapped in a vicious circle caused by soil erosion, declining soil fertility, land fragmentation, fluctuating agricultural production, widespread poverty, corruption, ethnic tension, rapid population, urban growth and a declining economy. The development challenge is to reverse the negative effects of these processes and promote sustainable development. This paper, based on multidisciplinary work discusses whether sustainable development based on agriculture is attainable in Murang'a district in Kenya's Central Highlands. Firstly, it investigates some biophysical aspects of sustainable agriculture such as land use across time, soil nutrient status and yield, cultivated crops and soil productivity by analysing aerial photographs and soil samples and conducting interviews. It suggests that the area has gone through major biophysical changes. Second, it relates the farmers' attitude to promotion of sustainable development as carried out by the National Soil and Water Conservation Programme. It suggests that farmers carry ideas of corruption, often following ethnic lines that hampers efficient implementation of the extension advise. Finally, it identifies links behind rural‐urban migration by estimating households' probability of generating incomes outside the farm, typically in urban areas. Opportunistic farming, manifested by temporary reduction of farming on own land to satisfy immediate income needs, is very common among farmers.

More needs to be done to promote agro‐based, small‐scale rural industries, improve agricultural management practices, facilitate appropriate credits, enhance marketing opportunities, ensure timely crop payments, and increase participation in decision making. It is important to realize that for farmers to embrace policies which promote agriculturely‐based sustainable development the policies ought to biophysically possible, socio‐politically acceptable and economically feasible. Copyright © 2001 John Wiley & Sons, Ltd.
Fallow cultivation system and farmers' resource management in Niger, West Africa
Authors: Wezel A. , Haigis J.
Published: August 2002

A survey was carried out in 136 farm‐households from seven villages in 1995 and 1996 to analyse the traditional fallow cultivation system in Niger. Farmers were asked to give information about land use on their fields, focusing on cropping and fallow periods as well as on cultivation changes compared to the past. In addition, they were interviewed about their management strategies to maintain or improve soil fertility.

Millet‐based systems clearly dominate at all sites, either in pure form or intercropped with cowpea, groundnut, sorghum or roselle. At present, almost half of all farmers cultivate their fields on average up to 5 years until it is left fallow. About one‐third use their fields permanently. Most farmers use short fallow periods of 1 to 5 years. Moreover, there was a decrease in the cropping area left fallow, and the fallow period also decreased steadily in the past years. In the mid‐1970s the average fallow period was about 8 years, decreasing to 2.5 years in 1996. The actual fallow periods are too short to allow sufficient positive effects on soil fertility and farmers are aware of this problem. Consequently, farmers employ different fertilization techniques which aim at maintaining or restoring the soil nutrient pool of the fields while providing physical protection against wind and water erosion. Most farmers use animal manure to improve soil fertility and apply mulch from different sources, millet stalks and branches, for soil regeneration. Few farmers employ other strategies such as mineral fertilizer or planting pits.

The farmers try to optimize the use of internal and external resources resulting in a mixture of different fertilization and soil protection methods. Internal resources play by far the most important role. Due to the generally limited resource availability farmers concentrate their management efforts on certain areas within each field or on selected fields only. This means a decreased crop production for the individual household and a higher risk of soil degradation because of soil mining or increased erosion risk on the field area where soil fertility management cannot be practised. Copyright © 2002 John Wiley & Sons, Ltd.