bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships between picophytoplankton and environmental variables in lakes along a gradient of water colour and nutrient content
Authors: Drakare Stina , Blomqvist Peter , BergstrÖm Ann‐Kristin , Jansson Mats 
Published: July 2003

SUMMARY 1. Biomass and production of picophytoplankton, phytoplankton and heterotrophic bacterioplankton were measured in seven lakes, exhibiting a broad range in water colour because of humic substances. The aim of the study was to identify environmental variables explaining the absolute and relative importance of picophytoplankton. In addition, two dystrophic lakes were fertilised with inorganic phosphorus and nitrogen, to test eventual nutrient limitation of picophytoplankton in these systems.2. Picophytoplankton biomass and production were highest in lakes with low concentrations of dissolved organic carbon (DOC), and DOC proved the factor explaining most variation in picophytoplankton biomass and production. The relationship between picophytoplankton and lake trophy was negative, most likely because much P was bound in humic complexes. Picophytoplankton biomass decreased after the additions of P and N.3. Compared with heterotrophic bacterioplankton, picophytoplankton were most successful at the clearwater end of the lake water colour gradient. Phytoplankton dominated over heterotrophic bacteria in the clearwater systems possibly because heterotrophic bacteria in such lakes are dependent on organic carbon produced by phytoplankton.4. Compared with other phytoplankton, picophytoplankton did best at intermediate DOC concentrations; flagellates dominated in the humic lakes and large autotrophic phytoplankton in the clearwater lakes.5. Picophytoplankton were not better competitors than large phytoplankton in situations when heterotrophic bacteria had access to a non‐algal carbon source. Neither did their small size lead to picophytoplankton dominance over large phytoplankton in the clearwater lakes. Possible reasons include the ability of larger phytoplankton to float or swim to reduce sedimentation losses and to acquire nutrients by phagotrophy.
Assessment of the relative contribution of COX‐1 and COX‐2 isoforms to ischemia‐induced oxidative damage and neurodegeneration following transient global cerebral ischemia
Authors: Candelario‐Jalil Eduardo , González‐Falcón Armando , García‐Cabrera Michel , Álvarez Dalia , Al‐Dalain Said , Martínez Gregorio , León Olga Sonia , Springer Joe E. 
Published: July 2003

AbstractWe investigated the relative contribution of COX‐1 and/or COX‐2 to oxidative damage, prostaglandin E2 (PGE2) production and hippocampal CA1 neuronal loss in a model of 5 min transient global cerebral ischemia in gerbils. Our results revealed a biphasic and significant increase in PGE2 levels after 2 and 24–48 h of reperfusion. The late increase in PGE2 levels (24 h) was more potently reduced by the highly selective COX‐2 inhibitor rofecoxib (20 mg/kg) relative to the COX‐1 inhibitor valeryl salicylate (20 mg/kg). The delayed rise in COX catalytic activity preceded the onset of histopathological changes in the CA1 subfield of the hippocampus. Post‐ischemia treatment with rofecoxib (starting 6 h after restoration of blood flow) significantly reduced measures of oxidative damage (glutathione depletion and lipid peroxidation) seen at 48 h after the initial ischemic episode, indicating that the late increase in COX‐2 activity is involved in the delayed occurrence of oxidative damage in the hippocampus after global ischemia. Interestingly, either selective inhibition of COX‐2 with rofecoxib or inhibition of COX‐1 with valeryl salicylate significantly increased the number of healthy neurons in the hippocampal CA1 sector even when the treatment began 6 h after ischemia. These results provide the first evidence that both COX isoforms are involved in the progression of neuronal damage following global cerebral ischemia, and have important implications for the potential therapeutic use of COX inhibitors in cerebral ischemia.
Obliteration of α‐melanocyte‐stimulating hormone derived from POMC in pituitary and brains of PC2‐deficient mice
Authors: Miller Ruthellen , Aaron Wade , Toneff Thomas , Vishnuvardhan Daesety , Beinfeld Margery C. , Hook Vivian Y. H. 
Published: July 2003

AbstractAlpha‐melanocyte‐stimulating hormone (α‐MSH) is a neuropeptide expressed in pituitary and brain that is known to regulate energy balance, appetite control, and neuroimmune functions. The biosynthesis of α‐MSH requires proteolytic processing of the proopiomelanocortin (POMC) precursor. Therefore, this study investigated the in vivo role of the prohormone convertase 2 (PC2) processing enzyme for production of α‐MSH in PC2‐deficient mice. Specific detection of α‐MSH utilized radioimmunoassay (RIA) that does not crossreact with the POMC precursor, and which does not crossreact with other adrenocorticotropin hormone (ACTH) and β‐endorphin peptide products derived from POMC. α‐MSH in PC2‐deficient mice was essentially obliterated in pituitary, hypothalamus, cortex, and other brain regions (collectively), compared to wild‐type controls. These results demonstrate the critical requirement of PC2 for the production of α‐MSH. The absence of α‐MSH was accompanied by accumulation of ACTH, ACTH‐containing imtermediates, and POMC precursor. ACTH was increased in pituitary and hypothalamus of PC2‐deficient mice, evaluated by RIA and reversed‐phase high pressure liquid chromatography (RP‐HPLC). Accumulation of ACTH demonstrates its role as a PC2 substrate that can be converted for α‐MSH production. Further analyses of POMC‐derived intermediates in pituitary, conducted by denaturing western blot conditions, showed accumulation of ACTH‐containing intermediates in pituitaries of PC2‐deficient mice, which implicate participation of such intermediates as PC2 substrates. Moreover, accumulation of POMC was observed in PC2‐deficient mice by western blots with anti‐ACTH and anti‐β‐endorphin. In addition, increased β‐endorphin1−31 was observed in pituitary and hypothalamus of PC2‐deficient mice, suggesting β‐endorphin1−31 as a substrate for PC2 in these tissues. Overall, these studies demonstrated that the PC2 processing enzyme is critical for the in vivo production of α‐MSH in pituitary and brain.
Cytochrome c, released from cerebellar granule cells undergoing apoptosis or excytotoxic death, can generate protonmotive force and drive ATP synthesis in isolated mitochondria
Authors: Atlante Anna , De Bari Lidia , Bobba Antonella , Marra Ersilia , Calissano Pietro , Passarella Salvatore 
Published: July 2003

AbstractIn rat cerebellar granule cells, cytochrome c release takes place during glutamate toxicity and apoptosis due to deprivation of depolarising levels of potassium. We show that, as in necrosis, the released cytochrome c present in the cytosolic fraction obtained from cerebellar granule cells undergoing apoptosis can operate as a reactive oxygen species (ROS) scavenger and as a respiratory substrate. The capability of the cytosolic fraction containing cytochrome c, obtained from cerebellar granule cells undergoing either necrosis or apoptosis, to energise coupled mitochondria isolated by the same cells is also investigated. We show that, in both cases, the cytosolic fraction containing cytochrome c, added to mitochondria, can cause proton ejection, and membrane potential generation and can drive ATP synthesis and export in the extramitochondrial phase, as photometrically measured via the ATP detecting system.Cytochrome c, separated immunologically from the cytosolic fraction of apoptotic cells when added to mitochondria, is found to cause proton ejection to generate membrane potential and to drive ATP synthesis and export in a manner not sensitive to the further addition of the cytosolic fraction depleted of cytochrome c, which failed to do this. In the light of these findings we propose that in apoptosis the released cytochrome c can contribute to provide ATP required for the cell programmed death to occur.
Repeated variable prenatal stress alters pre‐ and postsynaptic gene expression in the rat frontal pole
Authors: Kinnunen Anu K. , Koenig James I. , Bilbe Graeme 
Published: July 2003

AbstractExposure of pregnant women to stress during a critical period of fetal brain development is an environmental risk factor for developing schizophrenia in the adult offspring. We have applied a repeated variable stress paradigm to pregnant Sprague–Dawley rats during the last week of gestation coinciding with the second trimester in human brain development. Here we report our findings from a microarray analysis of the frontal pole of the prenatally stressed adult offspring and non‐stressed adult controls complemented with measurement of plasma corticosterone levels following exposure to an acute stress. The direction of change of selected genes was confirmed by real time quantitative fluorescence PCR andin situhybridization. The analysis revealed significant changes in genes associated with the NMDA receptor/postsynaptic density complex and the vesicle exocytosis machinery including NMDA receptor NR1 and NR2A subunits, densin‐180, brain enriched guanylate kinase‐associated protein, synaptosome‐associated protein of 25 kDa, synaphin/complexin and vesicle‐associated membrane protein 2/synaptobrevin 2. Interestingly, some of the changes in this animal preparation are analogous to changes observed in schizophrenic and bipolar patients. Our results suggest that application of a repeated variable prenatal stress paradigm during a critical period of fetal brain development reprograms the response of the hypothalamo–pituitary–adrenal axis to acute stress and results in gene expression changes that may have enduring effects on synaptic function in the offspring during adulthood.
NT‐4 protein is localized in neuronal cells in the brain stem as well as the dorsal root ganglion of embryonic and adult rats
Authors: Katoh‐Semba Ritsuko , Ichisaka Satoshi , Hata Yoshio , Tsumoto Tadaharu , Eguchi Kazuyo , Miyazaki Noriko , Matsuda Motoko , Takeuchi Ikuo K. , Kato Kanefusa 
Published: July 2003

AbstractWe have newly established a sensitive, two‐site enzyme immunoassay system for neurotrophin‐4 (NT‐4) and investigated its tissue distribution in the rat nervous system. The minimal limit of detection of the assay is 0.3 pg/0.2 mL of assay mixture. Concentrations of NT‐4 were found to be extremely low in all brain regions, irrespective of the animal age, the highest level being found in the brain stem of 40‐day‐old rats, at 0.12 ng/g wet weight. NT‐4 levels in young adult rats were significantly lower in the thalamus and higher in the olfactory bulb, neocortex, hypothalamus and brain stem than respective levels in 1‐week‐old rats. NT‐4 immunoreactivity was strong in large neurons of the red nucleus and pontine reticular nucleus as well as the locus coeruleus, and moderate in cells in the mesencephalic trigeminal nucleus and interstitial nucleus of the medial longitudinal fasciculus. In the rat embryo, stong staining of NT‐4 was detected in cells of regions corresponding to the midbrain/pons from E11.5 through E15.5. The intensity was decreased after E13.5 when the cytoplasm of cells in the medulla oblongata, fibers of the cerebellar primordium, and both cells and fibers of the dorsal root ganglion were also stained. Concentrations of NT‐4 were detected in regions including the hindbrain and the dorsal root ganglion. Immunoblotting of NT‐4‐immunoreactive proteins extracted from these two regions revealed a band corresponding to mature NT‐4 with a molecular mass of ∼14 kDa. Kainic acid and another glutamte agonist, (+/–)‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid did not affect NT‐4 levels in the hippocampus. The present results show NT‐4 to be localized in very limited brain cells and fibers from the embyonic period through to the young adult, suggesting specific roles in brain functions.
A palmitoylated RING finger ubiquitin ligase and its homologue in the brain membranes
Authors: Araki Kazuaki , Kawamura Meiko , Suzuki Toshiaki , Matsuda Noriyuki , Kanbe Daiji , Ishii Kyoko , Ichikawa Tomio , Kumanishi Toshiro , Chiba Tomoki , Tanaka Keiji , Nawa Hiroyuki 
Published: July 2003

AbstractUbiquitin (Ub) ligation is implicated in active protein metabolism and subcellular trafficking and its impairment is involved in various neurologic diseases. In rat brain, we identified two novel Ub ligases, Momo and Sakura, carrying double zinc finger motif and RING finger domain. Momo expression is enriched in the brain gray matter and testis, and Sakura expression is more widely detected in the brain white matter as well as in many peripheral organs. Both proteins associate with the cell membranes of neuronal and/or glial cells. We examined their Ub ligase activity in vivo and in vitro using viral expression vectors carrying myc‐tagged Momo and Sakura. Overexpression of either Momo or Sakura in mixed cortical cultures increased total polyubiquitination levels. In vitro ubiquitination assay revealed that the combination of Momo and UbcH4 and H5c, or of Sakura and UbcH4, H5c and H6 is required for the reaction. Deletion mutagenesis suggested that the E3 Ub ligase activity of Momo and Sakura depended on their C‐terminal domains containing RING finger structure, while their N‐terminal domains influenced their membrane association. In agreement, Sakura associating with the membrane was specifically palmitoylated. Although the molecular targets of their Ub ligation remain to be identified, these findings imply a novel function of the palmitoylated E3 Ub ligase(s).
Cellular prion protein function in copper homeostasis and redox signalling at the synapse
Authors: Vassallo Neville , Herms Jochen 
Published: July 2003

AbstractThe fundamental physiological function of native cellular prion (PrPC) remains unknown. Herein, the most salient observations as regards prion physiology are critically evaluated. These include: (i) the role of PrPC in copper homeostasis, particularly at the pre‐synaptic membrane; (ii) involvement of PrPC in neuronal calcium disturbances; and (iii) the neuroprotective properties of PrPC in response to copper and oxidative stress. Ultimately, a tentative hypothesis of basic prion function is derived, namely that PrPC acts as a sensor for copper and/or free radical stimuli, thereby triggering intracellular calcium signals that finally translate into modulation of synaptic transmission and maintenance of neuronal integrity.
Localization of the RNA‐binding proteins Staufen1 and Staufen2 at the mammalian neuromuscular junction
Authors: Bélanger Guy , Stocksley Mark A. , Vandromme Marie , Schaeffer Laurent , Furic Luc , DesGroseillers Luc , Jasmin Bernard J. 
Published: July 2003

AbstractStaufen is an RNA‐binding protein, first identified for its role in oogenesis and CNS development in Drosophila. Two mammalian homologs of Staufen have been identified and shown to bind double‐stranded RNA and tubulin, and to function in the somatodendritic transport of mRNA in neurons. Here, we examined whether Staufen proteins are expressed in skeletal muscle in relation to the neuromuscular junction. Immunofluorescence experiments revealed that Staufen1 (Stau1) and Staufen2 (Stau2) accumulate preferentially within the postsynaptic sarcoplasm of muscle fibers as well as at newly formed ectopic synapses. Western blot analyses showed that the levels of Stau1 and Stau2 are greater in slow muscles than in fast‐twitch muscles. Muscle denervation induced a significant increase in the expression of Stau1 and Stau2 in the extrasynaptic compartment of both fast and slow muscles. Consistent with these observations, we also demonstrated that expression of Stau1 and Stau2 is increased during myogenic differentiation and that treatment of myotubes with agrin and neuregulin induces a further increase in the expression of both Staufen proteins. We propose that Stau1 and Stau2 are key components of the postsynaptic apparatus in muscle, and that they contribute to the maturation and plasticity of the neuromuscular junction.
Rottlerin, an inhibitor of protein kinase Cδ (PKCδ), inhibits astrocytic glutamate transport activity and reduces GLAST immunoreactivity by a mechanism that appears to be PKCδ‐independent
Authors: Susarla Bala T. S. , Robinson Michael B. 
Published: July 2003

AbstractProtein kinase C (PKC) regulates the activity and/or cell surface expression of several different neurotransmitter transporters, including subtypes of glutamate transporters. In the present study, the effects of pharmacological inhibitors of PKC were studied in primary astrocyte cultures that express the glutamate aspartate transporter (GLAST) subtype of glutamate transporter. We found that general inhibitors of PKC, bisindolylmaleimide I (Bis I), bisindolylmaleimide II (Bis II), staurosporine and an inhibitor of classical PKCs, Gö6976, had no effect on Na+‐dependent glutamate transport activity. However, rottlerin, a putative specific inhibitor of PKCδ, decreased transport activity with an IC50value (less than 10 µm) that is comparable to that reported for inhibition of PKCδ. The effect of rottlerin was very rapid (maximal effect within 5 min) and was due to a decrease in the capacity (Vmax) for transport. Rottlerin also caused a drastic loss of GLAST immunoreactivity within 5 min, suggesting that rottlerin accelerates GLAST degradation/proteolysis. Rottlerin had no effect on cell surface or total expression of the transferrin receptor, providing evidence that the effect on GLAST cannot be attributed to a non‐specific internalization/degradation of plasma membrane proteins. Down‐regulation of PKCδ with chronic phorbol ester treatment did not block rottlerin‐mediated inhibition of transport activity. These results suggest a novel mechanism for regulation of the GLAST subtype of glutamate transporter and indicate that there is a rottlerin target that is capable of controlling the levels of GLAST by controlling the rate of degradation or limited proteolysis. It appears that the target for rottlerin may not be PKCδ.
Evaluation of blood–brain barrier thiamine efflux using the in situ rat brain perfusion method
Authors: Lockman P. R. , Mumper R. J. , Allen D. D. 
Published: July 2003

AbstractThiamine is an essential, positively charged (under physiologic conditions), water‐soluble vitamin requiring transport into brain. Brain thiamine deficiency has been linked to neurodegenerative disease by subsequent impairment of thiamine‐dependent enzymes used in brain glucose/energy metabolism. In this report, we evaluate brain uptake and efflux of [3H]thiamine using the in situ rat brain perfusion technique. To confirm brain distribution was not related to blood–brain barrier endothelial cell uptake, we compared parenchymal and cell distribution of [3H]thiamine using capillary depletion. Our work supports previous literature findings suggesting blood–brain barrier thiamine uptake is via a carrier‐mediated transport mechanism, yet extends the literature by redefining the kinetics with more sensitive methodology. Significantly, [3H]thiamine brain accumulation was influenced by a considerable efflux rate. Evaluation of the efflux mechanism demonstrated increased stimulation by the presence of increased vascular thiamine. The influx transport mechanism and efflux rate were each comparable throughout brain regions despite documented differences in glucose and thiamine metabolism. The observation that [3H]thiamine blood–brain barrier influx and efflux is regionally homogenous may have significant relevance to neurodegenerative disease linked to thiamine deficiency.
Na+ stimulates binding of dopamine to the dopamine transporter in cells but not in cell‐free preparations
Authors: Chen Nianhang , Rickey Judy , Reith Maarten E. A. 
Published: July 2003

AbstractAlthough Na+ is crucial for the function of the dopamine (DA) transporter (DAT), its role in the substrate binding step has been questioned. To address this issue, we investigated the effect of Na+ on DA binding by measuring the potency of DA in inhibiting the binding of the cocaine analogue [3H]2β‐carbomethoxy‐3β‐(4‐fluorophenyl)tropane (CFT) in intact cells expressing DAT in their plasma membranes and in membranes isolated from these cells. In cells, Na+ substantially enhanced the potency of DA in inhibiting CFT binding. This effect of Na+ was independent of buffer compositions and substitutes (sucrose vs. NMDG), more pronounced at 4°C than 25°C, and correlated with its stimulatory effect on DA uptake Km. Removing extracellular Na+ had little effect on intracellular concentrations of Na+ and K+, or on membrane potential. These data suggest that extracellular Na+ most likely acts at the transporter level to enhance the binding of external DA during the transport cycle. In contrast, in cell‐free membrane preparations the Na+ stimulation was abolished without impairment of the potency of DA in inhibiting CFT binding, regardless of whether sucrose was used to maintain the buffer osmolarity. The difference in Na+ dependence for DA to inhibit CFT binding between plasma membranes of intact cells and isolated membranes raises the possibility that intracellular ion environment, alone or in combination with other cellular factors, plays a critical role in determining DA–DAT interaction and the integration of Na+ modulation in this interaction.
Regulation of noradrenergic function by inflammatory cytokines and depolarization
Authors: Li Wei , Knowlton David , Woodward William R. , Habecker Beth A. 
Published: July 2003

AbstractAlthough the sympathetic neurons innervating the heart are exposed to the inflammatory cytokines cardiotrophin‐1 (CT‐1), interleukin‐6 (IL‐6) and tumor necrosis factor alpha (TNFα) after myocardial infarction, the effects of these cytokines on noradrenergic function are not well understood. We used cultured sympathetic neurons to investigate the effects of these cytokines on catecholamine content, the tyrosine hydroxylase co‐factor, tetrahydrobiopterin (BH4), and norepinephrine (NE) uptake. CT‐1, but not IL‐6 or TNFα, suppressed NE uptake and catecholamines in these neurons, whereas CT‐1 and, to a lesser extent, IL‐6 decreased BH4 content. CT‐1 exerted these effects by decreasing tyrosine hydroxylase, GTP cyclohydrolase (GCH) and NE transporter mRNAs, while IL‐6 lowered only GCH mRNA. The neurons innervating the heart are also activated by the central nervous system after myocardial infarction. We examined the combined effect of depolarization and cytokines on noradrenergic function. In CT‐1‐treated cells, depolarization caused a small increase in BH4 and NE uptake, and a large increase in catecholamines. These changes were accompanied by increased TH, GCH and NE transporter mRNAs. CT‐1 and depolarization regulate expression of noradrenergic properties in an opposing manner, and the combined treatment results in elevated cellular catecholamines and decreased NE uptake relative to control cells.