bluuebunny/crossref_metadata_2025 huggingface dataset:
The Equivalence of Learning Paths in Early Science Instruction
Authors: Klahr David , Nigam Milena
Published: September 2004

In a study with 112 third- and fourth-grade children, we measured the relative effectiveness of discovery learning and direct instruction at two points in the learning process: (a) during the initial acquisition of the basic cognitive objective (a procedure for designing and interpreting simple, unconfounded experiments) and (b) during the subsequent transfer and application of this basic skill to more diffuse and authentic reasoning associated with the evaluation of science-fair posters. We found not only that many more children learned from direct instruction than from discovery learning, but also that when asked to make broader, richer scientific judgments, the many children who learned about experimental design from direct instruction performed as well as those few children who discovered the method on their own. These results challenge predictions derived from the presumed superiority of discovery approaches in teaching young children basic procedures for early scientific investigations.
The Influence of Afrocentric Facial Features in Criminal Sentencing
Authors: Blair Irene V. , Judd Charles M. , Chapleau Kristine M.
Published: September 2004

Prior research has shown that within a racial category, people with more Afrocentric facial features are presumed more likely to have traits that are stereotypic of Black Americans compared with people with less Afrocentric features. The present study investigated whether this form of feature-based stereotyping might be observed in criminal-sentencing decisions. Analysis of a random sample of inmate records showed that Black and White inmates, given equivalent criminal histories, received roughly equivalent sentences. However, within each race, inmates with more Afrocentric features received harsher sentences than those with less Afrocentric features. These results are consistent with laboratory findings, and they suggest that although racial stereotyping as a function of racial category has been successfully removed from sentencing decisions, racial stereotyping based on the facial features of the offender is a form of bias that is largely overlooked.
Linguistic Markers of Psychological Change Surrounding September 11, 2001
Authors: Cohn Michael A. , Mehl Matthias R. , Pennebaker James W.
Published: September 2004

The diaries of 1,084 U.S. users of an on-line journaling service were downloaded for a period of 4 months spanning the 2 months prior to and after the September 11 attacks. Linguistic analyses of the journal entries revealed pronounced psychological changes in response to the attacks. In the short term, participants expressed more negative emotions, were more cognitively and socially engaged, and wrote with greater psychological distance. After 2 weeks, their moods and social referencing returned to baseline, and their use of cognitive-analytic words dropped below baseline. Over the next 6 weeks, social referencing decreased, and psychological distancing remained elevated relative to baseline. Although the effects were generally stronger for individuals highly preoccupied with September 11, even participants who hardly wrote about the events showed comparable language changes. This study bypasses many of the methodological obstacles of trauma research and provides a finegrained analysis of the time line of human coping with upheaval.
Effect of magnetic attachment with stress breaker on lateral stress to abutment tooth under overdenture*
Authors: Gonda T. , Ikebe K. , Ono T. , Nokubi T.
Published: September 2004

summary  Recently, a newly developed magnetic attachment with stress breaker was used in retentive components in overdentures. Excessive lateral stress has a more harmful effect on natural teeth than axial stress, and the magnetic attachment with stress breaker is expected to reduce lateral forces on abutment teeth and protect it teeth from excessive stress. However, the properties of this retainer have not yet been determined experimentally. This study compares the lateral forces on abutment teeth for three retainers under loading on the denture base in a model study. A mandibular simulation model is constructed to measure lateral stress. Three types of retentive devices are attached to the canine root. These devices include the conventional root coping, the conventional magnetic attachment and the new magnetic attachment with stress breaker. For each retentive device, load is generated on the occlusal table of the model overdenture, and the lateral stress on the canine root and the displacement of the overdenture measured. The magnetic attachment with stress breaker does not displace the denture and exhibits lower lateral stress in the canine root than conventional root coping and magnetic attachments.
A comparative study of two fissure sealants: a 2‐year clinical follow‐up
Authors: Yildiz E. , Dörter C. , Efes B. , Koray F.
Published: September 2004

summary  The aim of the study was to compare the fluoride‐containing fissure sealants (Helioseal F) with the conventional (Concise Light Cure White Sealant) fissure sealants in their retention and caries‐prevention capabilities in young population. Sealant materials were applied by three dentists on 122 fissures of first and second molars in 59 adults, 18–20 years of age. One hundred and twenty‐two non‐carious and unsealed molar teeth were selected as controls. The teeth were assessed using the following criteria: 1 – fully retained (FR), 2 – partially lost (PL), 3 – totally lost (TL) and 4 – decayed (D). All teeth were clinically assessed at 3, 6, 12 and 24 months by two examiners who were blinded to the sealant materials. Data were statistically analysed with chi‐square tests. After 3 months 72·1% of sealants were fully retained, at 24 months this had dropped to 46·7%. The partial loss of sealants was at 3 months (15·6%), 6 months (26·2%), 12 months (27·9%) and 24 months (27%). The total loss of Helioseal F (16·4, 19·7, 18, 23% at 3rd, 6th, 12th and 24th months, respectively) was more than the total loss of Concise Light Cure White Sealant (8·2, 9·8, 11·5, 18%, respectively); meaning that the retention rate of Helioseal F was lower than for Concise Light Cure White Sealant. No caries was detected at 3rd and 6th months in all sealant‐treated teeth. The incidence of caries in Helioseal F treated teeth at 12 and 24 months was 11·5% and 0% in Concise Light Cure White Sealant treated teeth. The incidence of caries in all fissure‐sealant‐treated‐teeth after 24 months was 5·7 and 25·4% in control group. The results underline that the application of fissure sealants to young people in this sample is an effective method for the prevention of fissure caries.
Corrosion‐fatigue of laser‐repaired commercially pure titanium and Ti‐6Al‐4V alloy under different test environments
Authors: Zavanelli R. A. , Guilherme A. S. , Pessanha‐Henriques G. E. , Antônio de Arruda Nóbilo M. , Mesquita M. F.
Published: September 2004

summary  This study evaluated the corrosion‐fatigue life of laser‐repaired specimens fabricated from commercially pure titanium (CP Ti) and Ti‐6Al‐4V alloy, tested under different storage conditions. For each metal, 30 dumbbell rods with a central 2·3 mm diameter were prepared by lost‐wax casting with the Rematitan System. Simulating the failure after service, corrosion‐fatigue life in different media at room temperature (air, synthetic saliva and fluoride synthetic saliva) was determined at a testing frequency of 10 Hz for intact specimens and after laser repairing, using a square waveform with equal maximum tensile and compressive stress that was 30% lower than the 0·2% offset yield strength. For laser welding, the fractured specimens were rejoined using a jig to align the sections invested in type‐IV dental stone. The adjacent areas of the gap was air‐abraded with 100 μm aluminum oxide, laser welded and retested under the same conditions as the initial intact specimens. The number of cycles at failure was recorded, and the fracture surface was examined with a scanning electron microscope (SEM). The number of cycles for failure of the welded and intact specimens was compared by anova and the Tukey test at a 5% probability level. Within the limitations of this study, the number of cycles required for fracture decreased in wet environments and the laser repairing process adversely affected the life of both metals under the corrosion‐fatigue conditions.
Regulation of carotenoid biosynthesis in plants: evidence for a key role of hydroxymethylbutenyl diphosphate reductase in controlling the supply of plastidial isoprenoid precursors
Authors: Botella‐Pavía Patricia , Besumbes Óscar , Phillips Michael A. , Carretero‐Paulet Lorenzo , Boronat Albert , Rodríguez‐Concepción Manuel
Published: September 2004

Carotenoids are isoprenoid pigments that function as photoprotectors, precursors of the hormone abscisic acid (ABA), colorants and nutraceuticals. A major problem for the metabolic engineering of high carotenoid levels in plants is the limited supply of their isoprenoid precursor geranylgeranyl diphosphate (GGPP), formed by condensation of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) units usually synthesized by the methylerythritol phosphate (MEP) pathway in plastids. Our earlier work with three of the seven MEP pathway enzymes suggested that the first reaction of the pathway catalyzed by deoxyxylulose 5‐phosphate synthase (DXS) is limiting for carotenoid biosynthesis during tomato (Lycopersicon esculentum) fruit ripening. Here we investigate the contribution of the enzyme hydroxymethylbutenyl diphoshate reductase (HDR), which simultaneously synthesizes IPP and DMAPP in the last step of the pathway. A strong upregulation of HDR gene expression was observed in correlation with carotenoid production during both tomato fruit ripening and Arabidopsis thaliana seedling deetiolation. Constitutive overexpression of the tomato cDNA encoding HDR in Arabidopsis did not increase carotenoid levels in etioplasts. By contrast, light‐grown transgenic plants showed higher carotenoid levels and an enhanced seed dormancy phenotype suggestive of increased ABA levels. The analysis of double transgenic Arabidopsis plants overproducing both the enzyme taxadiene synthase (which catalyzes the production of the non‐native isoprenoid taxadiene from GGPP) and either HDR or DXS showed a twofold stronger effect of HDR in increasing taxadiene levels. Together, the data support a major role for HDR in controlling the production of MEP‐derived precursors for plastid isoprenoid biosynthesis.
Cambial meristem dormancy in trees involves extensive remodelling of the transcriptome
Authors: Schrader Jarmo , Moyle Richard , Bhalerao Rupali , Hertzberg Magnus , Lundeberg Joakim , Nilsson Peter , Bhalerao Rishikesh P.
Published: September 2004

The establishment of the dormant state in meristems involves considerable physiological and metabolic alterations necessary for surviving unfavourable growth conditions. However, a global molecular analysis of dormancy in meristems has been hampered by the difficulty in isolating meristem cells. We used cryosectioning to isolate purified cambial meristem cells from the woody plant Populus tremula during active growth and dormancy. These samples were used to generate meristem‐specific cDNA libraries and for cDNA microarray experiments to define the global transcriptional changes underlying cambial dormancy. The results indicate a significant reduction in the complexity of the cambial transcriptome in the dormant state. Although cell division is terminated in the dormant cambium, the cell cycle machinery appears to be maintained in a skeletal state as suggested by the continued presence of transcripts for several cell cycle regulators. The downregulation of PttPIN1 and PttPIN2 transcripts explains the reduced basipetal polar auxin transport during dormancy. The induction of a member of the SINA family of ubiquitin ligases implicated in auxin signalling indicates a potential mechanism for modulation of auxin sensitivity during cambial dormancy. The metabolic alterations during dormancy are mirrored in the induction of genes involved in starch breakdown and the glyoxysomal cycle. Interestingly, the induction of RGA1 like gene suggests modification of gibberellin signalling in cambial dormancy. The induction of genes such as poplar orthologues of FIE and HAP2 indicates a potential role for these global regulators of transcription in orchestrating extensive changes in gene expression during dormancy.
Plastid transformation reveals that moss tRNAArg‐CCG is not essential for plastid function
Authors: Sugiura Chika , Sugita Mamoru
Published: September 2004

Three distinct arginine tRNA genes, trnR‐CCG, trnR‐ACG, and trnR‐UCU, are present in the plastid genome of bryophytes, whereas only the latter two trnR genes are present in the major vascular plants, except for black pine. trnR‐CCG is located between rbcL and accD in the moss Physcomitrella patens and it was previously believed to be functional in plastids. However, no trnR‐CCG transcript has been detected by Northern hybridization, and the codon usage of CGG is quite low in plastid protein‐coding sequences. This raises the possibility that trnR‐CCG is non‐functional. To investigate this possibility, we integrated a foreign gene into the trnR‐CCG coding region via homologous recombination, and constructed stable plastid trnR‐CCG knock‐out moss transformants. The trnR‐CCG knock‐out transformants grew normally, indicating that the P. patenstrnR‐CCG gene is not essential for plastid function.
Overexpression of the plasma membrane‐localized NDR1 protein results in enhanced bacterial disease resistance in Arabidopsis thaliana
Authors: Peter Coppinger  , Repetti Peter P. , Day Brad , Dahlbeck Douglas , Mehlert Angela , Staskawicz Brian J.
Published: September 2004

Previous studies have established that mutations in the NDR1 gene in Arabidopsis thaliana suppress the resistance response of three resistance proteins, RPS2, RPM1, and RPS5, to Pseudomonas syringae pv. tomato (Pst) strain DC3000 containing the cognate effector genes, avrRpt2, avrRpm1, and avrpPhB, respectively. NDR1 is a plasma membrane (PM)‐localized protein, and undergoes several post‐translational modifications including carboxy‐terminal processing and N‐linked glycosylation. Expression of NDR1 under the NDR1 native promoter complements the ndr1‐1 mutation, while overexpression of NDR1 results in enhanced resistance to virulent Pst. Sequence analysis and mass spectrometry suggest that NDR1 is localized to the PM via a C‐terminal glycosylphosphatidyl‐inositol (GPI) anchor. GPI modification would potentially place NDR1 on the outer surface of the PM, perhaps allowing NDR1 to act as a transducer of pathogen signals and/or interact directly with the pathogen.
Phosphoinositide‐specific phospholipase C is involved in cytokinin and gravity responses in the moss Physcomitrella patens
Authors: Repp Alexander , Mikami Koji , Mittmann Franz , Hartmann Elmar
Published: September 2004

The phosphoinositide signalling pathway is important in plant responses to extracellular and intracellular signals. To elucidate the physiological functions of phosphoinositide‐specific phopspholipase C, PI‐PLC, targeted knockout mutants of PpPLC1, a gene encoding a PI‐PLC from the moss Physcomitrella patens, were generated via homologous recombination. Protonemal filaments of the plc1 lines show a dramatic reduction in gametophore formation relative to wild type: this was accompanied by a loss of sensitivity to cytokinin. Moreover, plc1 appeared paler than the wild type, the result of an altered differentiation of chloroplasts and reduced chlorophyll levels compared with wild type filaments. In addition, the protonemal filaments of plc1 have a strongly reduced ability to grow negatively gravitropically in the dark. These effects imply a significant role for PpPLC1 in cytokinin signalling and gravitropism.
Increased susceptibility to photoinhibition in pre‐existing needles experiencing low temperature at spring budbreak in Sakhalin spruce (Picea glehnii) seedlings
Authors: Kitao Mitsutoshi , Qu Laiye , Koike Takayoshi , Tobita Hiroyuki , Maruyama Yutaka
Published: September 2004

The seasonal changes in photosynthetic properties in 1‐year‐old needles of Sakhalin spruce (Picea glehnii) were measured using the chlorophyll fluorescence technique at various temperatures (5, 10, 20, 25 and 30°C). In the course of seasonal change, a temporary decrease in the quantum yield of PSII electron transport (ΦPSII) was observed just before budbreak. A decline in photochemical quenching (qP) was observed at the same time as that of ΦPSII but only at the two lowest temperatures (5 and 10°C). Photochemical efficiency of open PSII (Fv′/Fm′) also declined just before budbreak at 25 and 30°C. An increase in thermal energy dissipation as indicated by a decrease in Fv′/Fm′ before budbreak was not significant at lower temperatures (5 and 10°C) in spite of the declines in qP. This implies that thermal energy dissipation necessitated by the decline in ΦPSII might not be sufficiently strong to prevent a decline in qP at lower temperatures. On the other hand, at higher temperatures no decline was observed in qP because ΦPSII decreased to a relatively small extent, therefore thermal energy dissipation is sufficient in coping with the excessive energy accumulation in PSII. Seedlings of Sakhalin spruce exposed to ambient air temperature below 10°C before budbreak exhibited photoinhibition indicated by a decrease in the maximal photochemical efficiency of PSII (Fv/Fm) after an overnight dark adaptation. The present study suggests that 1‐year‐old shoots of Sakhalin spruce have an increased susceptibility to photoinhibition at low temperature just before budbreak.
Gene expression during recovery from phosphate starvation in roots and shoots of Arabidopsis thaliana
Authors: Müller Renate , Nilsson Lena , Krintel Christian , Hamborg Nielsen Tom
Published: September 2004

Expression of phosphate starvation inducible genes was studied during recovery from phosphate starvation of Arabidopsis thaliana. Genes analysed were ACP5 (encoding an acid phosphatase), RNS1 (encoding an RNase), At4 and IPS1 (both of unknown function), Pht1;7 and Pht2;1 (encoding phosphate transporters). Plants grown at limiting phosphate exhibited reduced growth rate and accumulated anthocyanins, soluble sugars, and starch. Re‐supply of phosphate resulted in dramatic uptake of phosphate, increased growth rate and decreased levels of anthocyanins, soluble sugars, and starch in leaf tissue. In both shoots and roots re‐supplied with Pi, transcript levels decreased rapidly, and first changes were observed within 30 min. These alterations in gene expression occurred before the content of carbohydrates decreased, indicating that transcriptional regulation was due to phosphate sensing, and not a secondary effect of carbon accumulation. The data reveal different response rates for individual genes and demonstrate that roots and shoots can differ with respect to both timing and genes responding. In general, the changes in transcriptional activity in roots preceded the changes in shoots. Furthermore, transcriptional regulation was observed in isolated roots and shoots. This implies that roots do not strictly require a signal from the shoot, and vice versa, in order to respond to phosphate starvation.
Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activity
Authors: Jiao Shunxing , Hilaire Emmanuel , Paulsen Avelina Q. , Guikema James A.
Published: September 2004

The photosynthetic apparatus contains several protein complexes, many of which are regulated by environmental conditions. In this study, the influences of microgravity on PSI and PSII in Brassica rapa plants grown aboard the space shuttle were examined. We found that Brassica plants grown in space had a normal level of growth relative to controls under similar conditions on Earth. Upon return to Earth, cotyledons were harvested and thylakoid membranes were isolated. Analysis of chlorophyll contents showed that the Chl a/b ratio (3.5) in flight cotyledons was much higher than a ratio of 2.42 in the ground controls. The flight samples also had a reduction of PSI complexes and a corresponding 30% decrease of PSI photochemical activity. Immunoblotting showed that the reaction centre polypeptides of PSI were more apparently decreased (e.g. by 24–33% for PsaA and PsaB, and 57% for PsaC) than the light‐harvesting complexes. In comparison, the accumulation of PSII complex was less affected in microgravity, thus only a slight reduction in D1, D2 and LHCII was observed in protein blots. However, there was a 32% decrease of OEC1 in the flight samples, indicating a defective OEC subcomplex. In addition, an average 54% increase of the 54 kDa CF1‐β isoform was found in the flight samples, suggesting that space‐grown plants suffered from certain stresses, consistent with implications of the increased Chl a/b ratio. Taken together, the results demonstrated that Brassica plants can adapt to spaceflight microgravity, but with significant alterations in chloroplast structures and photosynthetic complexes, and especially reduction of PSI and its activity.
Growth, nutrient utilization and parameters of mineral metabolism in Nile tilapia Oreochromis niloticus (Linnaeus, 1758) fed plant‐based diets with graded levels of microbial phytase
Authors: Portz L. , Liebert F.
Published: September 2004

Diets with graded levels of the experimental microbial phytase SP1002 (0, 500, 1000, 2000 and 4000 FTU/kg) were fed to juvenile Nile tilapia (average BW = 68.8 g) for 60 days (n = 4). A digestibility trial ran parallel to the growth trial using 0.3 g TiO2/100 g as an indigestible marker. The efficiency of phytase supplementation was evaluated by parameters of growth response, crude protein and mineral utilization (using body composition data), apparent nutrient digestibility, mineral content in scale and vertebra and inorganic phosphorus in blood plasma. Data were submitted to anova and Tukey‐test using SAS‐program. Significant improvements (p < 0.01) were found for growth, FCR and SGR, mainly for diets with 1000 and 2000 FTU/kg phytase supplementation. Protein utilization was significantly increased and maximized between 1000 and 2000 FTU/kg. Phosphorus utilization increased significantly up to 4000 FTU/kg. Digestibility of protein and phosphorus was also significantly improved. Phosphorus concentration in the blood, vertebra and scale increased significantly after phytase addition. Similarly, calcium and magnesium concentration in vertebra and scale were increased. Generally, phytase supplementation between 1000 and 2000 FTU/kg resulted in growth rates and mineralization parameters similar to a control diet with inorganic phosphorus.
Macronutrient digestibility, nitrogen balance, plasma indicators of protein metabolism and mineral absorption in horses fed a ration rich in sugar beet pulp
Authors: Olsman A. F. S. , Huurdeman C. M. , Jansen W. L. , Haaksma J. , van Oldruitenborgh‐Oosterbaan M. M. Sloet , Beynen A. C.
Published: September 2004

In a cross‐over study with six mature horses, the effect of iso‐energetic replacement of dietary glucose by beet pulp on macronutrient digestibility, nitrogen metabolism and mineral absorption was studied. The test ration contained 25% beet pulp in the total dietary dry matter. Beet pulp feeding significantly lowered crude fat and non‐structural carbohydrate digestibility, but had no significant effect on digestibility of other macronutrients, faecal and urinary nitrogen excretion and the faecal to urinary nitrogen excretion quotient. However, on the beet pulp diet, plasma ammonia and creatinin concentrations were significantly lower than on the glucose diet. No diet effect on magnesium absorption was observed. It is suggested that dietary beet pulp stimulates the conversion of ammonia into urea.
Additional dietary zinc for weaning piglets is associated with elevated concentrations of serum IGF‐I
Authors: Carlson D. , Poulsen H. D. , Vestergaard M.
Published: September 2004

Two experiments were performed in order to study how weaning and post‐weaning dietary zinc level affect serum IGF‐I. Further, whether the growth‐enhancing effect of 2500 ppm of dietary zinc (Zn2500) and/or 175 ppm of dietary copper (Cu175) in post‐weaning diets is associated with elevated serum IGF‐I levels in piglets was studied. Experiment 1 included 54 piglets (six litters of nine piglets). One piglet from every litter was assigned to a control group (blood sampled 1 day before weaning). At weaning the remaining eight piglets from every litter were allocated randomly to four dietary treatments with increasing zinc inclusions (Zn100, Zn250, Zn1000, Zn2500). In exp. 2, 48 piglets (six litters of eight piglets) were allocated to four dietary treatments (Zn100, Zn100Cu175, Zn2500, Zn2500Cu175). All piglets in exp. 1 were blood sampled at −1, 1–2, 5–6 or 14–15 days after weaning and in exp. 2 blood samples were taken from all pigs 5–7 days after weaning. Feed intake was recorded per pen (two piglets) and weight gain was recorded for every piglet. Just after weaning feed intake was very low, piglets lost weight and serum IGF‐I decreased in exp. 1. However, the piglets fed 2500 ppm of zinc reached pre‐weaning levels of serum IGF‐I at 14–15 days post‐weaning, whereas piglets receiving lower zinc levels showed no changes in serum IGF‐I. In exp. 2, additional dietary zinc in weaning diets for piglets was found to be associated with increased feed intake, improved growth rate and increased serum IGF‐I. High levels of dietary copper did not affect any of these measurements. Zinc‐induced rise in serum IGF‐I was partly due to increased feed intake. After correcting for differences in feed intake, zinc significantly increased serum IGF‐I. However, to completely separate effects of feed intake from effects of zinc status, pair‐feeding should be considered in future studies.
The selenium requirement of the puppy
Authors: Wedekind K. J. , Yu S. , Combs G. F.
Published: September 2004

Current selenium (Se) recommendations for the puppy are based on extrapolation from other species (0.11 mg Se/kg diet). The purpose of this study was to experimentally determine the Se requirement in puppies. Thirty beagle puppies (average = 8.8 weeks old) were utilized in a randomized complete block design with age, litter and gender used as blocking criteria. Puppies were fed a low Se (0.04 mg Se/kg diet) torula yeast‐based diet for 14 days (pre‐test period) after which this same diet was supplemented with five levels of Na2SeO3for 21 days (experimental period) to construct a response curve (0, 0.13, 0.26, 0.39 or 0.52 mg Se/kg diet). Response variables included Se concentrations and Se‐dependent glutathione peroxidase activities (GSHpx) in serum as well as serum total triiodothyronine (TT3), serum total thyroxine (TT4) and serum free T4(FT4). No significant changes in food intake and body weight gain occurred, and no clinical signs of Se deficiency were observed. A breakpoint for serum GSHpx could not be determined in our study due to analytical difficulties. A broken‐line, two‐slope response in serum Se occurred with a breakpoint at 0.17 mg Se/kg diet. When Se from the basal diet was added to this estimate, the breakpoint for serum Se equated to 0.21 mg Se/kg diet. TT3increased linearly with increasing Se intake, whereas TT4was unchanged. However, the ratio of TT4 : TT3decreased linearly in response to supplemental Se. In summary, although we estimated the selenium requirement for the puppy based on serum Se, our 0.21 mg Se/kg diet estimate is higher than that seen for adult dogs, kittens, rats or poultry (0.13, 0.15, 0.15 and 0.15 mg Se/kg diet respectively). This difference may be due to the fact that GSHpx was used as the biomarker of Se status.
12‐Lipoxygenase plays a key role in cell death caused by glutathione depletion and arachidonic acid in rat oligodendrocytes
Authors: Wang Hong , Li Jianrong , Follett Pamela L. , Zhang Yumin , Cotanche Douglas A. , Jensen Frances E. , Volpe Joseph J. , Rosenberg Paul A.
Published: September 2004

Oxidative injury to premyelinating oligodendrocytes (preOLs) in developing white matter has been implicated in the pathogenesis of periventricular leukomalacia, the lesion underlying most cases of cerebral palsy in premature infants. In this study, we investigated the pathways of OL death induced by intracellular glutathione (GSH) depletion. We found that the lipoxygenase (LOX) inhibitors AA‐861 and BMD‐122 (N‐benzyl‐N‐hydroxy‐5‐phenylpentamide; BHPP), but not the cyclooxygenase (COX) inhibitor indomethacin, fully protected the cells from GSH depletion caused by cystine deprivation. Arachidonic acid (AA), the substrate for 12‐LOX, potentiated the toxicity of mild cystine deprivation and at higher concentration was itself toxic. This toxicity was also blocked by 12‐LOX inhibitors. Consistent with a role for 12‐LOX in the cell death pathway, 12‐LOX activity increased following cystine deprivation in OLs. Blocking 12‐LOX with AA‐861 effectively inhibited the accumulation of reactive oxygen species (ROS) induced by cystine deprivation. These data suggest that, in OLs, intracellular GSH depletion leads to activation of 12‐LOX, ROS accumulation and cell death. Mature OLs were more resistant than preOLs to cystine deprivation. The difference in sensitivity was not due to a difference in 12‐LOX activity but rather appeared to be related to the presence of stronger antioxidant defense mechanisms in mature OLs. These results suggest that 12‐LOX activation plays a key role in oxidative stress‐induced OL death.
Haemorrhage‐evoked decompensation and recompensation mediated by distinct projections from rostral and caudal midline medulla in the rat
Authors: Heslop David J. , Bandler Richard , Keay Kevin A.
Published: September 2004

The haemodynamic response to blood loss consists of three phases: (i) an initial compensatory phase during which resting arterial pressure is maintained; (ii) a decompensatory phase characterized by a sudden, life‐threatening hypotension and bradycardia; and (iii) if blood loss ceases, a recompensatory phase during which arterial pressure returns to normal. Previous research indicates that topographically distinct, rostral and caudal parts of the caudal midline medulla (CMM) contain neurons that differentially regulate the timing and magnitude of each of the three phases. Specifically, decompensation depends critically on the integrity of the rostral CMM; whereas compensation and recompensation depend upon the integrity of the caudal CMM. This study aimed to determine, using retrograde and anterograde tracing techniques, if the rostral and caudal CMM gave rise to different sets of projections to the major cardiovascular region of the ventrolateral medulla (VLM) and spinal cord. It was found that rostral and caudal CMM each have projections of varying density to the region containing bulbospinal (presympathetic) motor neurons in the rostral VLM and preganglionic sympathetic motor neurons in the intermediolateral cell column of the spinal cord. Via these projections vasomotor tone and hence arterial pressure can be regulated. More strikingly: (i) consistent with a role in mediating bradycardia during decompensation, the rostral CMM projects uniquely to VLM regions containing vagal cardiac motor neurons; and (ii) consistent with its role in mediating recompensation, the caudal CMM projects uniquely onto tyrosine hydroxylase‐containing, caudal VLM (A1) neurons whose activity mediates vasopressin release, on which recompensation depends.
Tyrosine hydroxylase‐positive neurons intrinsic to the human striatum express the transcription factorNurr1
Authors: Cossette Martine , Parent André , Lévesque Daniel
Published: September 2004

The putative dopaminergic (DA) neurons intrinsic to human striatum were studied to determine their similarity with DA neurons of the substantia nigra pars compacta (SNpc). The comparison was based on morphological features and on the presence or absence ofNurr1, an orphan receptor of the nuclear receptor family that is essential for the expression of DA phenotype by developing SNpc neurons. Immunohistochemistry for the neuronal nuclear protein (NeuN; a neuronal marker) andin situhybridization for tyrosine hydroxylase (TH) and/orNurr1were applied topost‐mortemtissue obtained from seven normal individuals. On one hand, the TH‐positive multipolar neurons in the human striatum, which were subdivided into three groups according to their size and pattern of dendritic arborization, were found to be morphologically similar to TH‐positive neurons of the SNpc. The distribution frequency of striatal TH‐positive neurons, according to their diameter, closely matches the frequency observed for multipolar TH‐positive cells in the SNpc. On the other hand, the proportion of neurons expressingNurr1and TH mRNA transcripts on single striatal section was similar to the proportion of TH‐immunoreactive neurons observed on adjacent sections. More importantly, in each striatum analysed, virtually all cells that stained for TH also expressed NeuN andNurr1. This study provides novel data that confirm the existence of DA neurons intrinsic to the human striatum. It also provides the first evidence for the existence of striking morphological and chemical similarities between the DA neurons present at striatal level and those that populate the SNpc.
Locomotor and oculomotor impairment associated with cerebellar dysgenesis in Zic3‐deficient (Bent tail) mutant mice
Authors: Aruga Jun , Ogura Hiroo , Shutoh Fumihiro , Ogawa Miyuki , Franke Barbara , Nagao Soichi , Mikoshiba Katsuhiko
Published: September 2004

We examined the adult neural phenotypes of the Bent tail mutant mouse. The Bent tail mutant mouse was recently shown to lack a submicroscopic part of the X chromosome containing the Zic3 gene, which encodes a zinc‐finger protein controlling vertebrate neural development. While nearly one‐fourth of hemizygous Bent tail (Bn/Y, Zic3‐deficient) mice developed neural tube defects in their midbrain and hindbrain region, the other Bn/Y mice showed apparently normal behaviour in a C57BL/6 genetic background. A battery of behavioural and eye movement tests revealed impaired spontaneous locomotor activity, reduction of muscle tone and impairments of vestibuloocular and optokinetic eye movements in these mice. Morphological examination of the mutant brain showed a significant reduction in the cell numbers in the cerebellar anterior lobe and paraflocculus–flocculus complex. Our results indicate that the cerebellar dysgenesis characterized by subregional hypoplasia affects the locomotor activity, muscle tone and eye movement control of the mice. These findings may have some clinical implications in relation to disorders characterized by cerebellar dysgenesis, such as Joubert syndrome.
Single‐pulse transcranial magnetic stimulation over the frontal eye field can facilitate and inhibit saccade triggering
Authors: Nyffeler Thomas , Bucher Oliver , Pflugshaupt Tobias , Von Wartburg Roman , Wurtz Pascal , Hess Christian W. , Müri René M.
Published: September 2004

The aim of this study was to investigate the effect of single‐pulse transcranial magnetic stimulation on the triggering of saccades. The right frontal eye field was stimulated during modified gap and overlap paradigms with flashed presentation of the lateral visual target of 80 ms. In order to examine possible facilitating or inhibitory effects on saccade triggering, three different time intervals of stimulation were chosen, i.e. simultaneously with onset of the target, during the presentation and after target end. Stimulation applied simultaneously with target onset significantly decreased the latency of contralateral saccades in the gap but not in the overlap paradigm. Stimulation after target end significantly increased saccade latency for both sides in the gap paradigm and for the contralateral side in the overlap paradigm. Stimulation during presentation had no effect in either paradigm. The results show that, depending on the time interval and the paradigm tested, a facilitation or inhibition of saccade triggering can be achieved. The results are discussed in a context of two probable transcranial magnetic stimulation effects, a direct interference with the frontal eye field on the one hand and a remote interference with the superior colliculus on the other hand.
Presynaptic muscarinic acetylcholine receptors suppress GABAergic synaptic transmission in the intermediate grey layer of mouse superior colliculus
Authors: Li Fengxia , Endo Toshiaki , Isa Tadashi
Published: September 2004

The intermediate grey layer (the stratum griseum intermediale; SGI) of the superior colliculus (SC) receives cholinergic inputs from the parabrachial region of the brainstem. It has been shown that cholinergic inputs activate nicotinic acetylcholine (nACh) receptors on projection neurons in the SGI. Therefore, it has been suggested that they facilitate the initiation of orienting behaviours. In this study, we investigated the effect of muscarinic acetylcholine (mACh) receptor activation on GABAergic synaptic transmission to SGI neurons using the whole‐cell patch‐clamp recording technique in slice preparations from mice. The GABAA receptor‐mediated inhibitory postsynaptic currents (IPSCs) evoked in SGI neurons by focal electrical stimulation were suppressed by bath application of 10 µm muscarine chloride. During muscarine application, both the paired‐pulse facilitation index and the coefficient of variation of IPSCs increased; however, the current responses induced by a transient pressure application of 1 mm GABA were not affected by muscarine. Muscarine reduced frequencies of miniature IPSCs (mIPSCs) while the amplitudes of mIPSCs remained unchanged. These results suggestd that mAChR‐mediated inhibition of IPSCs was of presynaptic origin. The suppressant effect of muscarine was antagonized by an M1 receptor antagonist, pirenzepine dihydrochloride (1 µm), and a relatively specific M3 receptor antagonist, 4‐DAMP methiodide (50 nm). By contrast, an M2 receptor antagonist, methoctramine tetrahydrochloride (10 µm), was ineffective. These results suggest that the cholinergic inputs suppress GABAergic synaptic transmission to the SGI neurons at the presynaptic site via activation of M1 and, possibly, M3 receptors. This may be an additional mechanism by which cholinergic inputs can facilitate tectofugal command generation.
Cascades of response vectors of olfactory receptor neurons in Xenopus laevis tadpoles
Authors: Schild Detlev , Manzini Ivan
Published: September 2004

Olfactory receptor neurons (ORNs) of Xenopus laevis tadpoles respond to water‐born stimuli such as amino acids. Their sensitivity spectra with respect to amino acids have recently been shown to become more selective over ontogenetic stages [Manzini & Schild (2004) J. Gen. Physiol., 123, 99–107]. In this paper, we undertake a theoretical analysis of this data set and determine the correlational relationships among odorant responses represented as binary response vectors. We first show that, on the one hand, the number of 204 ORN classes (out of 283 recorded ORNs) cannot be explained by a random expression pattern of olfactory receptors (ORs). On the other hand, this number does not appear to be reconcilable with the idea that individual ORNs express one type of OR each. The covariance matrix of stimulus responses shows that the responses to some stimuli are correlated to those of others. Furthermore, the response vectors show positive as well as negative correlations among each other. While the positive correlations can partly be explained by the differing response frequencies to the odorants used, the negative ones cannot. Finally, we analyse the similarity among responses using the Hamming distance as a distance measure, the result being that most response vectors differ from others by small Hamming distances. Such vectors are shown to form pattern cascades, possibly reflecting a decreasing number of ORs being expressed over ontogenetic stages.
A disaccharide derived from chondroitin sulphate proteoglycan promotes central nervous system repair in rats and mice†
Authors: Rolls Asya , Avidan Hila , Cahalon Liora , Schori Hadas , Bakalash Sharon , Litvak Vladimir , Lev Sima , Lider Ofer , Schwartz Michal
Published: September 2004

Chondroitin sulphate proteoglycan (CSPG) inhibits axonal regeneration in the central nervous system (CNS) and its local degradation promotes repair. We postulated that the enzymatic degradation of CSPG generates reparative products. Here we show that an enzymatic degradation product of CSPG, a specific disaccharide (CSPG‐DS), promoted CNS recovery by modulating both neuronal and microglial behaviour. In neurons, acting via a mechanism that involves the PKCα and PYK2 intracellular signalling pathways, CSPG‐DS induced neurite outgrowth and protected against neuronal toxicity and axonal collapse in vitro. In microglia, via a mechanism that involves ERK1/2 and PYK2, CSPG‐DS evoked a response that allowed these cells to manifest a neuroprotective phenotype ex vivo. In vivo, systemically or locally injected CSPG‐DS protected neurons in mice subjected to glutamate or aggregated β‐amyloid intoxication. Our results suggest that treatment with CSPG‐DS might provide a way to promote post‐traumatic recovery, via multiple cellular targets.
Unilateral cochlear ablation produces greater loss of inhibition in the contralateral inferior colliculus
Authors: Vale Carmen , Juíz José M. , Moore David R. , Sanes Dan H.
Published: September 2004

Bilateral cochlear ablation leads to a profound weakening of synaptic inhibition within the inferior colliculus (IC) of gerbils [Vale & Sanes (2000) J. Neurosci., 20, 1912–1921]. To examine whether unilateral deafening leads to similar functional alterations, we studied the effect of unilateral cochlear ablation on inhibitory synaptic properties both ipsilateral and contralateral to the deafened ear. Lateral lemniscal and commissure of the IC‐evoked inhibitory postsynaptic currents (IPSCs) were recorded in an IC brain slice preparation using whole‐cell and gramicidin perforated‐patch electrodes in the presence of kynurenic acid. Unilateral cochlear ablation led to a 23 mV depolarizing shift in the IPSC equilibrium potential for IC neurons contralateral to the deafened ear, but only a 10 mV depolarization in the ipsilateral IC. Lateral lemniscal‐evoked inhibitory synaptic conductance declined significantly in the ipsilateral and contralateral IC, whereas commissural‐evoked inhibitory synaptic conductance declined only contralateral to the ablated cochlea. An analysis of paired‐pulse facilitation showed that inhibitory transmitter release was more affected ipsilateral to the ablated cochlea. Thus, unilateral cochlear ablation modifies inhibitory synapses in the inferior colliculus, but these changes appear to be dominated by postsynaptic alterations in the contralateral IC, and by presynaptic changes in the ipsilateral IC.
The β‐amyloid precursor protein controls a store‐operated Ca2+ entry in cortical neurons
Authors: Bouron Alexandre , Mbebi Corinne , Loeffler Jean‐Philippe , De Waard Michel
Published: September 2004

A polyclonal antibody (APP‐Ab) raised against the extracellular domain of the beta‐amyloid precursor protein (APP) triggers a marked neuronal cell death preceded by activation of Ca2+‐dependent enzymes, neurite degeneration, oxidative stress and nuclear condensation [Mbebi et al. (2002) J. Biol. Chem., 277, 20979–20990]. We have investigated whether activation of APP by this antibody could promote cell death through cellular Ca2+ homeostasis alteration. We carried out time‐lapse recordings of intracellular Ca2+ signals in cultured mice cortical neurons by means of a scanning confocal microscope. When applied in the presence of 2 mm external Ca2+, APP‐Ab elicited a long‐lasting elevation of the intracellular concentration of Ca2+ ([Ca2+]i). Experiments performed in the absence of external Ca2+ showed that APP‐Ab triggers the release of Ca2+ from intracellular stores. The re‐admission of external Ca2+ provides an additional rise of Ca2+ most likely through store‐operated channels. A pretreatment of the cells with pertussis toxin, to inhibit the activity of Gi/Go proteins, or with the phospholipase C inhibitor, 3‐nitrocoumarin, prevented both the APP‐dependent elevation of Ca2+ as well as the APP‐Ab‐mediated cell death. Similarly, the store‐operated channel inhibitors, 2‐APB or SKF‐96365 block both the APP‐Ab‐dependent Ca2+ entry and the APP‐Ab‐mediated cell death. Altogether, our data provide functional evidence that APP can perturb intracellular Ca2+ homeostasis by emptying intracellular Ca2+ stores and triggering Ca2+ entry through store‐operated channels. In response to APP activation, the long‐lasting elevation of [Ca2+]i due to an entry of Ca2+ via store‐operated channels appears as a major event that leads to neuronal cell death.
Bone morphogenetic proteins regulate ionotropic glutamate receptors in human retina
Authors: Shen Wen , Finnegan Sarah , Lein Pamela , Sullivan Susan , Slaughter Malcolm , Higgins Dennis
Published: September 2004

Bone morphogenetic proteins (BMPs) are required for the development of retina, but their role in the mature eye is unknown. We therefore examined the expression of BMP‐7 in adult human retina and assessed its effects on horizontal cells cultured from adult human retina. BMP‐7 expression was detected in all retinal layers, with high levels of expression being present in the inner and outer nuclear layers. Human horizontal cells, found in the inner nuclear layer, possess both AMPA and kainate receptors, and glutamatergic agonists that activate these receptors induce prominent inward currents. Exposure to BMP‐7 suppresses the kainate receptor current but enhances the AMPA receptor current. BMP‐6, activin, and cartilage‐derived morphogenic protein‐2 (CDMP‐2) have similar effects to BMP‐7 and act just as rapidly (< 1 s). In contrast BMP‐2 and transforming growth factor‐β2 are inactive. The actions of BMP‐7 on both AMPA and kainate receptors were blocked by the nonselective kinase inhibitor, staurosporine. In contrast, the serine/threonine kinase inhibitors blocked only the effects of BMP‐7 on the AMPA current. Thus, BMPs rapidly and differentially regulate two ionotropic glutamate receptors through distinct pathways, neither of which involves nuclear regulatory activity. These observations suggest that BMPs might modify synaptic function in the mature nervous system.
Multiple GABAA receptor subtypes regulate hippocampal ripple oscillations
Authors: Ponomarenko A. A. , Korotkova T. M. , Sergeeva O. A. , Haas H. L.
Published: September 2004

High‐frequency oscillations (140–200 Hz) were recorded in behaving rats from the CA1 area of the hippocampus. As generation of these synchronous patterns is assumed to depend on coordinated interneuronal inhibition, we studied the interference of benzodiazepines with the fine structure and occurrence of ripple oscillations. The nonselective GABAA receptor α‐subunit agonist, diazepam, lowered the frequency of ripple oscillations and reduced their occurrence, amplitude and duration. Zolpidem, an α1‐subunit selective benzodiazepine elevated ripple duration but acted similar to diazepam in other respects. The nonselective α‐subunit benzodiazepine antagonist, flumazenil, reduced ripple numbers, amplitude and duration. Wavelet based analysis of the dynamics of intraripple frequency revealed a dramatic decay within a ripple. Only diazepam (1 mg/kg) accelerated this intraripple frequency accommodation. The effects were not due to increased behavioural activity and alertness as evident from vigilance state control. The results suggest a differential role of GABAA receptor subtype specific inhibitory mechanisms in the mediation and fine‐tuning of the network synchronization during ≈200 Hz hippocampal oscillations.