bluuebunny/crossref_metadata_2025_split huggingface dataset:
Needle dark respiration in relation to within‐crown position in Scots pine trees grown in long‐term elevation of CO2 concentration and temperature
Authors: Zha Tianshan , Wang Kai‐Yun , Ryyppö Aija , Kellomäki Seppo 
Published: March 2003

Summary

The spatial distribution of leaf respiration in relation to specific needle area (SLA) and nitrogen concentration was studied in Scots pines ( Pinus sylvestris
) grown in environment‐controlled chambers for 4 yr under ambient conditions (CON), elevated CO
2 concentration (ambient + 350 µmol; EC), elevated temperature (ambient + 2–3°C; ET) or a combination of EC and ET (EC + ET).
Dark respiration rates within the crown were measured on attached needles using a portable photosynthesis analyzer.
Respiration rates decreased with increasing within‐crown depth and were linearly related to within‐crown positions, regardless of the treatments. The needles in the different depths in the crown had relatively similar responses of respiration to EC, ET and EC + ET. Respiration rates were reduced by EC relative to CON at any given within‐crown position, but were increased by ET and EC + ET. Respiration positively correlated with N concentration and negatively with SLA on an area basis.
It is assumed that respiratory acclimation to a change in light environment can occur irrespective of treatment. We suggested that SLA is a key determinant of respiration.
Horizontal gene transfer in the phytosphere
Authors: Van Elsas Jan Dirk , Turner Sarah , Bailey Mark J. 
Published: March 2003

SummaryHere, the ecological aspects of gene transfer processes between bacteria in the phytosphere are examined in the context of emerging evidence for the dominant role that horizontal gene transfer (HGT) has played in the evolutionary shaping of bacterial communities. Moreover, the impact of the putative capture of genetic material by bacteria from plants is discussed. Examples are provided that illustrate how mobile genetic elements (MGEs) influence the behaviour of bacteria in their natural habitat, especially in structured communities such as biofilms on plant surfaces. This community behaviour is used as a framework to pose questions on the evolutionary role and significance of gene transfer processes in plant‐associated habitats. Selection within the highly structured phytosphere is likely to represent a dominant force shaping the genetic make‐up of plant‐associated bacterial communities. Current understanding of the triggering and impact of horizontal gene transfer, however, remains limited by our lack of understanding of the nature of the selective forces that act on bacteria in situ. The individual, colony, population and community level selection benefits imposed by the ability to use specific carbon sources or survive selective compounds are clear, but it is not always possible to assess what drives gene transfer and persistence. The role of HGT in the adaptation of host bacteria to their environmental niche is still not fully understood.
Determination of cholesterol in dairy products by infrared techniques: 2. FT‐NIR method
Authors: Paradkar Manish M , Irudayaraj Joseph 
Published: March 2003

A Fourier transformed near‐infrared (FT‐NIR) method for rapid determination of cholesterol in dairy products was demonstrated. FT‐NIR spectrum of pure cholesterol was characterized and the region between 3550 and 3650 cm−1 was found to be the most significant in cholesterol content determination. The FT‐NIR method was found to accurately predict the cholesterol content in a variety of dairy products with r2 value greater than 0.98 and SEP estimates of less than 1.70. The FT‐NIR procedure with suitable multivariate statistical model was further validated by recovery studies and compared with a conventional method. Results indicate that FT‐NIR has the potential for rapid estimation of cholesterol.
Comparison of different bacterial culture systems for the production of reduced‐fat Cheddar cheese
Authors: Fenelon M A , Beresford T P , Guinee T P 
Published: March 2003

Six different culture systems, two controls (A and B) containing mesophilic starter lactococci and four experimental systems (C, D, E and F) containing mesophilic lactococci plus adjunct cultures (all of which contained
Lactobacillus helveticus
), were compared for their effects on the quality of reduced‐fat Cheddar cheese (175 g/kg fat). Adjunct cultures (i.e. C, D and F) resulted in cheeses having significantly higher concentrations of low molecular mass peptides (i.e. < 0.5 kDa) and free amino acids than the control cheeses. The adjunct cultures D and F resulted in cheeses that received higher flavour scores and were more acceptable than the control cheeses at 90 and 180 days.
Protein kinase C‐mediated functional regulation of dopamine transporter is not achieved by direct phosphorylation of the dopamine transporter protein
Authors: Chang Mi‐Yoon , Lee Sang‐Hun , Kim Jin‐Hyuk , Lee Ki‐Hwan , Kim Young‐Sik , Son Hyeon , Lee Yong‐Sung 
Published: March 2003

Dopaminergic neurotransmission is terminated by the action of the presynaptic dopamine transporter (DAT). It mediates Na+/Cl− ‐dependent re‐uptake of extracellular dopamine (DA) into the cell, and is regarded as a major regulatory mechanism for synaptic transmission. Previous works have documented that protein kinase C (PKC) activator or inhibitor alters DA uptake by DAT, suggesting that PKC phosphorylation plays an important regulatory mechanism in DAT function. Based on the existence of consensus amino acid sequences for PKC phosphorylation, it has been postulated that PKC regulation of DAT is mediated by the direct phosphorylation of DAT protein. In this study, we try to discover whether the functional regulation of DAT by PKC is due to direct phosphorylation of DAT. The PKC null mutant hDAT, where all putative PKC phosphorylation sites are eliminated, has been constructed by the replacement of serine/threonine residues with glycines. The mutation itself showed no effect on the functional activities of DAT. The DA uptake activity of PKC null mutant was equivalent to those of wild‐type hDAT (80–110% of wild‐type). Phorbol ester activation of PKC inhibited DA uptake of wild‐type hDAT by 35%, and staurosphorine blocked the effect of phorbol ester on DA uptake. The same phenomena was observed in PKC null mutant DAT, although no significant phosphorylation was observed by PKC activation. Confocal microscopic analysis using EGFP‐fused DAT revealed that the activation of PKC by phorbol ester elicited fluorescent DAT to be internalized into the intracellular space both in wild‐type and PKC null mutant DAT in a similar way. These results suggest that PKC‐mediated regulation of DAT function is achieved in an indirect manner, such as phosphorylation of a mediator protein or activation of a clathrin‐mediated pathway.
Identification of a novel member of the T1R family of putative taste receptors
Authors: Sainz Eduardo , Korley Julius N. , Battey James F. , Sullivan Susan L. 
Published: March 2003

In the gustatory system, the recognition of sugars, amino acids and bitter‐tasting compounds is the function of specialized G protein‐coupled receptors. Recently, two members of novel subfamily of G protein‐coupled receptors were proposed to function as taste receptors based on their specific expression in taste receptor cells. Here, we report the identification of a third member, T1R3, of this family of receptors. T1R3 maps near the telomere of mouse chromosome 4 rendering it a candidate for the Sac locus, a primary determinant of sweet preference in mice. Consistent with its candidacy for the Sac locus, T1R3 displays taste receptor cell‐specific expression. In addition, taster and non‐taster strains of mouse harbor different alleles of T1R3.
The pituitary adenylate cyclase‐activating polypeptide modulates glutamatergic calcium signalling: investigations on rat suprachiasmatic nucleus neurons
Authors: Kopp Michael D. A. , Meissl Hilmar , Dehghani Faramarz , Korf Horst‐Werner 
Published: March 2003

Circadian rhythms generated by the hypothalamic suprachiasmatic nucleus (SCN) are synchronized with the external light/dark cycle by photic information transmitted directly from the retina via the retinohypothalamic tract (RHT). The RHT contains the neurotransmitters glutamate and pituitary adenylate cyclase‐activating polypeptide (PACAP), which code chemically for ‘light’ or ‘darkness’ information, respectively. We investigated interactions of PACAP and glutamate by analysing effects on the second messenger calcium in individual SCN neurons using the Fura‐2 technique. PACAP did not affect NMDA‐mediated calcium increases, but influenced signalling cascades of non‐NMDA glutamate receptors, which in turn can regulate NMDA receptors. On the one hand, PACAP amplified/induced glutamate‐dependent calcium increases by interacting with α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA)/kainate signalling. This was not related to direct PACAPergic effects on the second messengers cAMP and calcium. On the other hand, PACAP reduced/inhibited calcium increases elicited by glutamate acting on metabotropic receptors. cAMP analogues mimicked this inhibition. Most neurons displaying PACAPergic neuromodulation were immunoreactive for vasoactive intestinal polypeptide, which is a marker for retinorecipient SCN neurons. The observed PACAPergic effects provide a broad range of interactions that allow a fine‐tuning of the endogenous clock by the integration of ‘light’ and ‘darkness’ information on the level of single SCN neurons.
The γ‐aminobutyric acid receptor B, but not the metabotropic glutamate receptor type‐1, associates with lipid rafts in the rat cerebellum
Authors: Becher Anja , White Julia H. , McIlhinney R. A. Jeffrey 
Published: March 2003

Recent evidence suggests that specialized microdomains, called lipid rafts, exist within plasma membranes. These domains are enriched in cholesterol and sphingolipids and are resistant to non‐ionic detergent‐extraction at 4°C. They contain specific populations of membrane proteins, and can change their size and composition in response to cellular signals, resulting in activation of signalling cascades. Here, we demonstrate that both the metabotropic γ‐aminobutyric acid receptor B (GABAB receptor) and the metabotropic glutamate receptor‐1 from rat cerebellum are insoluble in the non‐ionic detergent Triton X‐100. However, only the GABAB receptor associates with raft fractions isolated from rat brain by sucrose gradient centrifugation. Moreover, increasing the stringency of isolation by decreasing the protein : detergent ratio caused an enrichment of the GABAB receptor in raft fractions. In contrast, depletion of cholesterol from cerebellar membranes by either saponin or methyl‐β‐cyclodextrin treatment, which solubilize known raft markers, also increased the solubility of the GABAB receptor. These properties are all consistent with an association of the GABAB receptor with lipid raft microdomains.
Modulation of microglial superoxide production by α‐tocopherol in vitro: attenuation of p67phox translocation by a protein phosphatase‐dependent pathway
Authors: Egger Tamara , Hammer Astrid , Wintersperger Andrea , Goti Daniel , Malle Ernst , Sattler Wolfgang 
Published: March 2003

As in other phagocytic cells, the NADPH‐oxidase system in microglia is thought to be primarily responsible for the production of superoxide anion radicals (O2−·), a potentially cytotoxic reactive oxygen species. The assembly of a functional NADPH‐oxidase complex at the plasma membrane depends on the phosphorylation and subsequent translocation of several cytosolic subunits. Immunocytochemical and subcellular fractionation experiments performed during the present study revealed that the NADPH‐oxidase subunit p67phox translocates from the cytosol to the plasma membrane upon stimulation. Pre‐incubation of microglia in α‐tocopherol (αTocH) containing medium decreased O2−· production in a time‐ and concentration‐dependent manner, findings attributed to attenuated p67phox translocation to the plasma membrane. Moreover, αTocH‐supplementation of the culture medium resulted in decreased microglial protein kinase C (PKC) activities, an effect that could be partially or completely reversed by the addition of protein phosphatase inhibitors (okadaic acid and calyculin A). The addition of the PKC‐inhibitor staurosporine inhibited the microglial respiratory burst in a manner comparable to αTocH. The addition of okadaic acid or calyculin A completely restored O2−· production in αTocH‐supplemented cells. The present findings suggest that αTocH inactivates PKC via a PP1 or PP2A‐mediated pathway and, as a consequence, blocks the phosphorylation‐dependent translocation of p67phox to the plasma membrane. As a result, O2−· production by the microglial NADPH‐oxidase system is substantially inhibited.
Identification and characterization of a novel Nogo‐interacting mitochondrial protein (NIMP)
Authors: Hu Wen‐Hui , Hausmann Oliver N. , Yan Ming‐Shan , Walters Winston M. , Wong Paul K. Y. , Bethea John R. 
Published: March 2003

AbstractNogo is a potent inhibitor of regeneration following spinal cord injury. To develop a better understanding of the mechanisms responsible for regenerative failure we used a yeast two‐ hybrid approach to try and identify proteins that interact with Nogo. We identified a novel mitochondrial protein designated Nogo‐interacting mitochondrial protein (NIMP) in a screen of an adult human brain cDNA library. This interaction was confirmed by co‐immunoprecipitation in both brain tissue (endogenous) and transfected HEK293T cells (overexpressed). In support of these studies we demonstrate that Nogo interacts with the UQCRC1 and UQCRC2 components of complex III, within the mitochondrial respiratory chain. The mitochondrial localization of NIMP was evidenced by confocal image analysis and western blot analysis of isolated mitochondria. NIMP is highly conserved and ubiquitously expressed in mitochondria‐enriched tissues. Within the CNS, NIMP‐like immunoreactivity is present in neurons and astrocytes. These data suggest that NIMP is a novel mitochondrial protein that interacts with Nogo. The interaction of Nogo with mitochondrial proteins may provide insight into the mechanisms for Nogo‐induced inhibition of neurite growth.
The cytotoxicity of dopamine may be an artefact of cell culture
Authors: Clement Marie‐Véronique , Long Lee Hua , Ramalingam Jeyakumar , Halliwell Barry 
Published: March 2003

AbstractAdministration of l‐DOPA is commonly used to treat Parkinson's disease, yet controversy continues as to whether the dopamine arising from it aggravates neuronal loss. Several authors have reported cytotoxic effects of l‐DOPA and dopamine on cultured cells, but others have not. In this report using the rat pheochromocytoma cell line PC12 and the M14 human melanoma cell line we show that dopamine‐mediated cell death is not specific for neuronal cells. Moreover, our data show that both l‐DOPA and dopamine interact with commonly used cell culture media, undergoing oxidation to generate hydrogen peroxide and dopamine semiquinones/quinones. Catalase and reduced glutathione could protect against cytotoxicity. These results suggest that caution needs to be employed when using cell culture studies to predict effects of l‐DOPA and/or dopamine in vivo because of the extracellular generation of reactive species in the culture media.
Sepsis inhibits reduction of dehydroascorbic acid and accumulation of ascorbate in astroglial cultures: intracellular ascorbate depletion increases nitric oxide synthase induction and glutamate uptake inhibition
Authors: Korcok Jasminka , Wu Feng , Tyml Karel , Hammond Robert R. , Wilson John X. 
Published: March 2003

AbstractSepsis is associated with oxidative stress and impaired glutamatergic transmission in brain. We investigated whether sepsis impairs accumulation of the antioxidant, ascorbate, and uptake of glutamate by astrocytes. Bacterial endotoxin (Escherichia colilipopolysaccharide, LPS) and the inflammatory cytokine, interferon‐γ (IFNγ), were applied to primary astrocyte cultures to model sepsis. In the absence of ascorbate, the combination of LPS and IFNγ (LPS + IFNγ) up‐regulated inducible nitric oxide synthase (iNOS) and decreased the initial rate of glutamate uptake by 50% within 24 h. Cell viability and facilitated glucose transport activity were not affected at 24 h. Pre‐treatment with ascorbate‐2‐O‐phosphate increased intracellular ascorbate concentration and attenuated the induction of iNOS and inhibition of glutamate uptake caused by LPS + IFNγ. Subsequent experiments examined the mechanisms by which cells accumulate ascorbate. LPS + IFNγ decreased slightly the initial rate of uptake of ascorbate and inhibited markedly the rate with which intracellular dehydroascorbic acid (DHAA) was reduced to ascorbate. We conclude that septic insult impairs astrocytic clearance of DHAA from the extracellular fluid and decreases intracellular ascorbate concentration. Furthermore, sepsis induces iNOS and inhibits glutamate uptake by astrocytes through mechanisms that can be modulated by intracellular ascorbate. These results indicate treatments that increase intracellular ascorbate concentration may be beneficial for patients at risk for neurologic complication in sepsis.
Pharmacological characterization of cloned chicken neuropeptide Y receptors Y1 and Y5
Authors: Holmberg Sara K. S. , Mikko Sofia , Boswell Timothy , Zoorob Rima , Larhammar Dan 
Published: March 2003

AbstractThe neuropeptide Y (NPY) receptor subtypes Y1 and Y5 are involved in the regulation of feeding and several other physiological functions in mammals. To increase our understanding of the origin and mechanisms of the complex NPY system, we report here the cloning and pharmacological characterization of receptors Y1 and Y5 in the first non‐mammal, chicken (Gallus gallus). The receptors display 80–83% and 64–72% amino acid sequence identity, respectively, with their mammalian orthologues. The three endogenous ligands NPY, peptide YY (PYY) and pancreatic polypeptide (PP) have similar affinities as in mammals, i.e. NPY and PYY have subnanomolar affinity for both receptors whereas chicken PP bound with nanomolar affinity to Y5 but not to Y1. A notable difference to mammalian receptor subtypes is that the Y1 antagonist SR120819A does not bind chicken Y1, whereas BIBP3226 does. The Y5 antagonist CGP71863A binds to the chicken Y5 receptor. Anatomically, both Y1 and Y5 have high mRNA expression levels in the infundibular nucleus which is the homologous structure of the hypothalamic arcuate nucleus in mammals. These results suggest that some of the selective Y1 and Y5 antagonists developed in mammals can be used to study appetite regulation in chicken.
Intracellular Ca2+ signals evoked by stimulation of nicotinic acetylcholine receptors in SH‐SY5Y cells: contribution of voltage‐operated Ca2+ channels and Ca2+ stores
Authors: Dajas‐Bailador Federico A. , Mogg Adrian J. , Wonnacott Susan 
Published: March 2003

AbstractNeuronal nicotinic acetylcholine receptors (nAChR) can regulate several neuronal processes through Ca2+‐dependent mechanisms. The versatility of nAChR‐mediated responses presumably reflects the spatial and temporal characteristics of local changes in intracellular Ca2+ arising from a variety of sources. The aim of this study was to analyse the components of nicotine‐evoked Ca2+ signals in SH‐SY5Y cells, by monitoring fluorescence changes in cells loaded with fluo‐3 AM. Nicotine (30 µm) generated a rapid elevation in cytoplasmic Ca2+ that was partially and additively inhibited (40%) by α7 and α3β2* nAChR subtype selective antagonists; α3β4* nAChR probably account for the remaining response (60%). A substantial blockade (80%) by CdCl2 (100 µm) indicates that voltage‐operated Ca2+ channels (VOCC) mediate most of the nicotine‐evoked response, although the α7 selective antagonist α‐bungarotoxin (40 nm) further decreased the CdCl2‐	resistant component. The elevation of intracellular Ca2+ levels provoked by nicotine was sustained for at least 10 min and required the persistent activation of nAChR throughout the response. Intracellular Ca2+ stores were implicated in both the initial and sustained nicotine‐evoked Ca2+ responses, by the blockade observed after ryanodine (30 µm) and the inositoltriphosphate (IP3)‐receptor antagonist, xestospongin‐c (10 µm). Thus, nAChR subtypes are differentially coupled to specific sources of Ca2+: activation of nAChR induces a sustained elevation of intracellular Ca2+ levels which is highly dependent on the activation of VOCC, and also involves Ca2+ release from ryanodine and IP3‐dependent intracellular stores. Moreover, the α7, but not α3β2* nAChR, are responsible for	a fraction of the VOCC‐independent nicotine‐evoked Ca2+ increase that appears to be functionally coupled to ryanodine sensitive Ca2+ stores.
Modulation of synaptic signalling complexes by Homer proteins
Authors: Thomas Ulrich 
Published: March 2003

AbstractThe number of neurotransmitter receptors in the postsynaptic membrane and their functional coupling to intracellular signalling cascades are important determinants of synaptic strength – and hence potential targets for plasticity related modulation. In this context, Homer/Vesl proteins have gained particular interest for three main reasons: (i) they constitute part of the molecular scaffold at postsynaptic densities of excitatory synapses in the mammalian brain; (ii) they physically link type‐I metabotropic glutamate receptors to the postsynaptic density and to inositol 1,4,5‐triphosphate receptors in the subsynaptic endoplasmic reticulum; and (iii) Homer‐1a, which has been categorized as an immediate early gene isoform, exerts dominant‐negative activity, suggesting that it is involved in activity dependent rearrangements at synaptic junctions. Although these fundamental aspects have been reviewed previously by Xiao et al., this review will address primarily more recent studies on the regulation of Homer 1a expression and on the role of Homer/Vesl proteins in spine morphogenesis and receptor targeting and signalling.