bluuebunny/crossref_metadata_2025 huggingface dataset:
Impacts of Brassica break-crops on soil biology and yield of following wheat crops
Authors: Smith Brendan J. , Kirkegaard John A. , Howe Geoff N.
Published: January 2004

Biofumigation refers to the allelopathic effects of brassicas on non-desirable soil organisms in a rotation cropping system. These effects are additional to non-hosting of root diseases, responsible for much of the break-crop effect observed in a following cereal crop. We investigated the biofumigation impacts of canola on take-all disease and rhizosphere microorganisms of following wheat crops. The biofumigation potential of the canola was tested by comparing effects of Brassica and non-Brassica break-crops and by using canola varieties with differing levels of root glucosinolates, the precursors of isothiocyanates, which are thought to be the primary biofumigant molecules released by brassicas. There was no evidence that biofumigation was related to superior growth of wheat following brassicas compared with non-Brassica break-crops, nor among the wheat crops following canola varieties with differing root glucosinolate levels. However, the break-crop effect was evident in agronomic, take-all, and some rhizosphere microbial measurements of the wheat–wheat rotations compared with fallow–wheat or break-crop–wheat rotations. Thus the break-crop effect was the primary advantage conferred by the brassicas. Any additional biofumigation effect on yield or disease was not significant in our study and does not appear to be influenced by root glucosinolate content. For broad-acre cropping with current canola or mustard varieties, and adequate grass weed control, the agronomic characteristics of canola varieties chosen should take precedence over their biofumigation potential.
Puroindoline genes and their effects on grain quality traits in southern Australian wheat cultivars
Authors: Cane Karen , Spackman Merrin , Eagles H. A.
Published: January 2004

Grain hardness is a major determinant of the classification and end-use of wheat. Two genes, Pina-D1 and Pinb-D1, have a major effect on this trait, so for wheat breeding programs it is important to identify the alleles of these genes present in elite germplasm. This study was conducted to identify the alleles present in southern Australian germplasm, and to determine if they affected quality characteristics other than grain hardness.Only 3 genotypes were identified. These were Pina-D1a/Pinb-D1a producing soft grain, Pina-D1a/Pinb-D1b producing moderately hard grain, and Pina-D1b/Pinb-D1a producing very hard grain. WW15 was the probable source of Pina-D1a/Pinb-D1b in most cultivars; however, Halberd represented another source. An important source of Pina-D1b/Pinb-D1a was the CIMMYT line Pavon, with sources from the old Australian cultivars Gabo and Falcon probably still present in modern germplasm.In an analysis of grain quality data from the Victorian Institute for Dryland Agriculture breeding program, the Pina-D1b/Pinb-D1a genotype had a significantly higher water absorption and significantly lower milling yield than the Pina-D1a/Pinb-D1b genotype, which indicates that these genes will impede the development of hard-grained cultivars that combine high water absorption and high milling yield.
Fructosyltransferase activity and fructan accumulation during development in wheat exposed to terminal drought
Authors: Goggin Danica E. , Setter Tim L.
Published: January 2004

Fructans act as storage carbohydrates in wheat (Triticum aestivum L.) stems, and published data indicate that these can account for up to 70% or more of grain dry matter under conditions of drought. The activity of enzymes involved in fructan synthesis (fructosyltransferases) in wheat was measured during development of three high-yielding wheat cultivars (cvv. Kauz, Westonia and Attila A) exposed to rainfed conditions, and one cultivar (cv.�Westonia) exposed to irrigated conditions. Fructan concentration was on average 2.5-fold higher in the stems of rainfed wheat compared with irrigated samples, but average fructosyltransferase activity was similar in both. There was a weak positive correlation (r2=0.35–0.38) between fructan concentration and fructosyltransferase activity across development in the stems of both rainfed and irrigated wheat. Soon after anthesis, 31% of accumulated fructans in rainfed Westonia stems were located in the penultimate internode, although fructosyltransferase activity was five times higher in the bottom two internodes than the penultimate internode.
Stomatal conductance and root-to-shoot signalling in chestnut saplings exposed to Phytophthora cinnamomi or partial soil drying
Authors: Maurel Marion , Robin Cécile , Simonneau Thierry , Loustau Denis , Dreyer Erwin , Desprez-Loustau Marie-Laure
Published: January 2004

The effects of root infection by Phytophthora cinnamomi on stomatal conductance in Castanea sativa L. saplings were investigated to determine the potential role of root-derived chemical signals. A split-root experiment was carried out, in which inoculation of the pathogen or drought was applied to the root systems in either one or both compartments. At the end of the experiment plant sap extracts were collected and their effects on stomatal conductance were determined by leaf bioassay. Inoculation or drought imposed in both compartments resulted in decreases in stomatal conductance (gs), transpiration rate, soil-to-leaf specific hydraulic conductance, leaf water potential, xylem [ABA] and root biomass, but not in the ratio of root-to-leaf mass in inoculated plants. Conversely, only gs and xylem [ABA] were affected in plants inoculated or droughted in one compartment, and no changes were detectable in leaf water potential and soil-to-leaf specific hydraulic conductance. The leaf bioassay showed that gs in chestnut was sensitive to ABA but not to Phytophthora elicitins. Stomatal conductance was reduced by some sap extracts, both from control and inoculated plants. Our results suggest the involvement of different signals, chemical and hydraulic, in regulating stomatal conductance of chestnut at different stages of stress.
An experimental system for analysis of the dynamic sap-flow characteristics in young trees: results of a beech tree
Authors: Steppe Kathy , Lemeur Raoul
Published: January 2004

This paper describes an experimental system designed for analysis of the dynamic water flow through young trees, complemented with test results of a 2-year-old beech tree (Fagus sylvatica L.). The system allows automatic and simultaneous measurements of a complex set of plant physiological processes at leaf, branch, stem and root levels [transpiration (E), sap flow (F) and diameter fluctuations (Δd)], in combination with the micrometeorological variables that control these processes [soil and air temperature (Ts and Ta), vapour pressure deficit of the air (D) and photosynthetically active radiation (PAR)]. A 2-d experimental period was used to study the whole-tree water transport dynamics of the young beech tree. Good correspondence between E of the leaves and F in the supporting branch was found. An increased time lag between the F measurements along the hydraulic pathway down towards the root system was observed, indicating the non-steady-state nature of the water flow. The daytime Δd of stem and branch revealed the depletion and the replenishment of internal water reserves. The daily amount of water withdrawn from internal storage was 5% of the total daily transpiration. A good linear relationship was found between the rate of change in internal water storage and the rate of change in stem diameter, having no time lag. We conclude that the data obtained with this system will allow experimental assessment of hydraulic properties in young trees and facilitate calibration of models for non-steady-state conditions of water flow in young trees.
Cloning and characterisation of the gene encoding HMG-CoA reductase from Taxus media and its functional identification in yeast
Authors: Liao Zhihua , Tan Qiumin , Chai Yourong , Zuo Kaijing , Chen Min , Gong Yifu , PengWang  , Pi Yan , Tan Feng , Sun Xiaofen , Tang Kexuan
Published: January 2004

In plants, the first committed step in the pathway for biosynthesis of isoprenoids is catalysed by 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR, EC: 1.1.1.34). Here we report for the first time the cloning of a full-length cDNA encoding HMGR (Tm–HMGR) from a taxol-producing gymnosperm, Taxus media Rehder. The full-length cDNA of Tm–HMGR (GenBank accession number: AY277740) was 2307 base pairs (bp), with a 1791-bp open reading frame (ORF) encoding a 596-amino-acid polypeptide. Bioinformatic analysis revealed that Tm–HMGR contained two trans-membrane domains and a catalytic domain, and showed high homology to other plant HMGRs. Phylogenetic analysis indicated that Tm–HMGR was more ancient than other plant HMGRs. The structural modelling showed that Tm–HMGR had the typical spatial structure of HMGRs whose catalytic domains could be folded and divided into three spatial domains, L-domain, N-domain and S-domain. Southern blot analysis revealed that Tm–HMGR belonged to a small HMGR gene family. Northern blot analysis showed that Tm–HMGR was expressed in roots, stems and needles, with higher expression in stems and needles than in roots. Functional complementation of Tm–HMGR in a HMGR-deficient mutant yeast demonstrated that Tm–HMGR mediated the biosynthesis of mevalonate and provided the general precursor for taxol biosynthesis.
Chlorophyll fluorescence of submerged and floating leaves of the aquatic resurrection plant Chamaegigas intrepidus
Authors: Woitke Markus , Hartung Wolfram , Gimmler Hartmut , Heilmeier Hermann
Published: January 2004

The role of submerged and floating leaves in plant photosynthetic performance of the aquatic resurrection plant Chamaegigas intrepidus Dinter was investigated by monitoring chlorophyll fluorescence under the fluctuating natural field conditions that characterise the extreme habitat of this species. The performance of the two different leaf types during desiccation–rehydration cycles in the field was examined. PSII quantum efficiency indicates a similar regeneration capacity in both leaf types after water stress. Electron transport rates under controlled light conditions were 3–4 times higher in floating leaves than in submerged leaves. The two leaf types showed specific adaptations to their ambient photosynthetic photon flux densities (PPFD), shade tolerance in the submerged leaves and adaptation to high PPFD in floating leaves. These results imply a significant role of the floating leaves for total plant carbon gain. It is concluded that the combination of high N content of floating leaves and a high availability of CO2 and light at the water surface contributes to the importance of this leaf type for photosynthesis in C. intrepidus.
Differences in the ROS-generating efficacy of various ultraviolet wavelengths in detached spinach leaves
Authors: Barta Csengele , Kálai Tamás , Hideg Kálmán , Vass Imre , Hideg Éva
Published: January 2004

The capacity of ultraviolet (UV) radiation to generate reactive oxygen species (ROS) in spinach leaves was studied with fluorescent sensors. Leaf segments were exposed to short-term (15–30 min), narrow-band UV irradiation of various wavelengths between 290–390 nm corresponding to equal numbers of photons and, depending on the wavelength, 18–36 μmol m–2 s–1 quantum flux. This caused 5–30% loss of photosynthesis measured as loss of variable chlorophyll fluorescence. In accordance with previous results, photosynthesis was less affected by longer than by shorter wavelength UV. UV-irradiated leaves were probed for two major representatives of ROS, namely the superoxide radical anion, a product of electron transfer to oxygen, and singlet oxygen, which is usually formed in photosensitised reactions between oxygen and triplet dyes. Both ROS were detected, but the efficacy of UV in promoting their production was different. Formation of superoxide radicals was positively correlated with loss of photosynthesis; more radicals were observed in leaves exposed to shorter UV wavelengths than in leaves irradiated at 370–390 nm, suggesting a functionally damaged electron transport as a possible site of oxygen reduction. Singlet oxygen was, however, mainly inducible in leaves exposed to longer UV wavelengths and was barely induced by 290–300-nm irradiation. The mechanism of singlet oxygen generation by UV radiation in the leaf, reported for the first time, is not clear, but the process does not appear to be linked to the UV-induced damage of photosynthesis.
Analysis of the asparagus (Asparagus officinalis) asparagine synthetase gene promoter identifies evolutionarily conserved cis-regulatory elements that mediate Suc-repression
Authors: Winichayakul Somrutai , Moyle Richard L. , Coupe Simon A. , Davies Kevin M. , Farnden Kevin J. F.
Published: January 2004

In asparagus (Asparagus officinalis L.), increased levels of asparagine (Asn) and Asn synthetase (AS) transcript are detected during foliar senescence and in harvested spears, possibly triggered by signals from a reduced supply of carbohydrate. To identify cis-elements mediating this regulation, the asparagus AS gene promoter was isolated and analysed by DNA sequencing, followed by expression of AS::GUS (β-glucuronidase) reporter-gene constructs in transgenic tissue, and electrophoretic mobility shift assays (EMSA). The 1958-base pair (bp) region of the AS promoter upstream of the translation initiation ATG (–1958 bp region) was sufficient to confer sucrose (Suc)-regulated expression on the GUS reporter gene in asparagus callus and protoplasts, which were transformed by particle bombardment and electroporation, respectively. Removal of Suc from callus or protoplast media resulted in the induction of GUS activity. Deletion analysis of this 1958-bp fragment identified elements in the –640 to –266�bp region as important for both high GUS levels and mediating the Suc response. This was supported by EMSA results, which showed the formation of three nuclear protein–DNA complexes with the –558 to –284 bp fragment of the promoter. A 20-bp oligonucleotide, designed to match the sequence from –423 to –404 bp, was able to out-compete formation of one of these protein-DNA complexes, suggesting a specific interaction with this sequence. This region of the promoter, overlapping with the 20-bp oligonucleotide sequence, contains a 10-bp stretch identical to a sequence previously shown to mediate low Suc induction of an Oryza sativa (rice) α-amylase gene, and may thus represent a conserved Suc-responsive element.
Can We Improve the Assessment of Discharge Readiness?
Authors: Malviya Shobha , Voepel-Lewis Terri , Ludomirsky Achiau , Marshall Janelle , Tait Alan R.
Published: January 2004

Background

Current recommended discharge criteria might not be rigorous enough to detect residual sedation. This study evaluated the use of the Bispectral Index (BIS monitor), the University of Michigan Sedation Scale (UMSS; i.e., 0-4 observational scale), and a Modified Maintenance of Wakefulness Test (MMWT; visual observation of the time the child is able to stay awake) in assessing return to baseline status.

Methods

Twenty-nine children sedated for echocardiographic examination were studied. Nurses administered sedatives and monitored and discharged children according to institutional guidelines. Children were monitored with the BIS(R) throughout the study. Trained observers assigned UMSS scores every 10-15 min until revised discharge criteria were met (i.e., UMSS score of 0 or 1, MMWT duration >/= 20 min). The MMWT value was recorded at each observation following the procedure. Subsequently, blinded observers recorded average BIS values for the 5 min before each UMSS observation.

Results

There were moderate correlations between the BIS, MMWT, and UMSS scores (r = 0.68-0.78; P < 0.01). Revised criteria correctly identified children who were awake and alert (BIS value >/= 90) in 88% of the cases. Only 55% of the children had returned to baseline BIS values when discharged by the nurse, compared with 92% when revised criteria were met (P < 0.05). It took longer to meet revised criteria compared with standard criteria (75.3 +/- 76.2 min vs. 16.4 +/- 13.1 min; P = 0.001).

Conclusions

The incorporation of specific, objective discharge criteria (i.e., UMSS score of 0 or 1, MMWT duration >/= 20 min) may ensure a status closer to baseline (BIS value >/= 90) compared with nursing judgment using standard criteria. However, such assurance may delay the discharge of sedated children.
Mixed-effects Modeling of the Intrinsic Ventilatory Depressant Potency of Propofol in the Non-steady State
Authors: Bouillon Thomas , Bruhn Joergen , Radu-Radulescu Lucian , Andresen Corina , Cohane Carol , Shafer Steven L.
Published: January 2004

Background

Despite the ubiquitous use of propofol for anesthesia and conscious sedation and numerous publications about its effect, a pharmacodynamic model for propofol-induced ventilatory depression in the non-steady state has not been described. To investigate propofol-induced ventilatory depression in the clinically important range (at and below the metabolic hyperbola while carbon dioxide is accumulating because of drug-induced ventilatory depression), the authors applied indirect effect modeling to Paco2 data at a fraction of inspired carbon dioxide of 0 during and after administration of propofol.

Methods

Ten volunteers underwent determination of their carbon dioxide responsiveness by a rebreathing design. The parameters of a power function were fitted to the end-expiratory carbon dioxide and minute ventilation data. The volunteers then received propofol in a stepwise ascending pattern with use of a target-controlled infusion pump until significant ventilatory depression occurred (end-tidal pressure of carbon dioxide > 65 mmHg and/or imminent apnea). Thereafter, the concentration was reduced to 1 microg/ml. Propofol pharmacokinetics and the Paco2 were determined from frequent arterial blood samples. An indirect response model with Bayesian estimates of the pharmacokinetics and carbon dioxide responsiveness in the absence of drug was used to describe the Paco2 time course. Because propofol reduces oxygen requirements and carbon dioxide production, a correction factor for propofol-induced decreasing of carbon dioxide production was included.

Results

The following pharmacodynamic parameters were found to describe the time course of hypercapnia after administration of propofol (population mean and interindividual variability expressed as coefficients of variation): F (gain of the carbon dioxide response), 4.37 +/- 36.7%; ke0, CO2, 0.95 min-1 +/- 59.8%; baseline Paco2, 40.9 mmHg +/- 12.8%; baseline minute ventilation, 6.45 l/min +/- 36.3%; kel, CO2, 0.11 min-1 +/- 34.2%; C50,propofol, 1.33 microg/ml +/- 49.6%; gamma, 1.68 +/- 21.3%.

Conclusion

Propofol at common clinical concentrations is a potent ventilatory depressant. An indirect response model accurately described the magnitude and time course of propofol-induced ventilatory depression. The indirect response model can be used to optimize propofol administration to reduce the risk of significant ventilatory depression.
Children Undergoing Repeated Exposures for Radiation Therapy Do Not Develop Tolerance to Propofol
Authors: Keidan Ilan , Perel Azriel , Shabtai Esther L. , Pfeffer Raphael M.
Published: January 2004

Background

The purpose of this study was to apply clinical criteria and Bispectral Index monitor data for evaluating the development of tolerance to propofol in children undergoing repeated drug exposure.

Methods

Children undergoing multiple sessions of radiation therapy during anesthesia for various malignancies were given a predetermined dose of propofol at each session. Heart rate, blood pressure, oxygen saturation, respiratory rate, requirement of additional propofol, and time to emergence and discharge were recorded. The Bispectral Index was monitored continuously, and parameters were extracted and averaged for each week of therapy.

Results

Fifteen children (aged 2.5-10 yr) were treated for an average of 5 weeks (24 +/- 6 sessions). There were no significant differences in physiologic parameters or requirements of additional propofol between the weeks of treatment. Bispectral Index data analysis showed that although a nonlinear change with time for each parameter could not be rejected, the differences between the first and last intervals were nonsignificant.

Conclusions

Overall changes with time resulted from random fluctuations without a consistent trend. Combined with clinical data, Bispectral Index parameters showed that tolerance to propofol does not develop in children undergoing repeated exposures to the drug during radiation therapy.
Effects of Two Target-controlled Concentrations (1 and 3 ng/ml) of Remifentanil on MACBARof Sevoflurane
Authors: Albertin Andrea , Casati Andrea , Bergonzi Piercarlo , Fano Greta , Torri Giorgio
Published: January 2004

Background

The aim of this prospective, randomized, double-blind study was to determine the effects of two different target-controlled concentrations of remifentanil (1 and 3 ng/ml) on the sevoflurane requirement for blunting sympathetic responses after surgical incision (MACBAR).

Methods

Seventy-four patients aged 20-50 yr, with American Society of Anesthesiologists physical status I, were anesthetized with propofol, cisatracurium, and sevoflurane with a mixture of 60% nitrous oxide in oxygen. Then, patients were randomly allocated to receive no remifentanil infusion (n = 27) or a target-controlled plasma concentration of 1 ng/ml (n = 27) or 3 ng/ml remifentanil (n = 20). Sympathetic responses to surgical incision (presence or absence of an increase in either heart rate or mean arterial blood pressure of 15% or more above the mean of the values measured during the 2 min before skin incision) were determined after a 20-min period of stable end-tidal sevoflurane and target-controlled remifentanil concentrations. Predetermined end-tidal sevoflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential-allocation technique.

Results

The MACBAR of sevoflurane was higher in the group receiving no remifentanil (2.8% [95% confidence interval: 2.5-3.0%]) as compared with patients of the groups receiving 1 ng/ml (1.1% [0.9-1.3%]; P = 0.012) and 3 ng/ml remifentanil (0.2% [0.1-0.3%]; P = 0.006). When considering a minimum anesthetic concentration (MAC) value in this age population and the contribution of 60% nitrous oxide (0.55 MAC), the combined MACBAR values, expressed as multiples of the MAC, were 1.95 MAC, 1.1 MAC, and 0.68 MAC, in the three groups, respectively.

Conclusion

A target-controlled concentration of 1 ng/ml remifentanil results in a 60% decrease in the MACBAR of sevoflurane combined with 60% nitrous oxide. Increasing the target concentration of remifentanil to 3 ng/ml produces a further 30% decrease in the MACBAR values of sevoflurane.
Antichemical Protective Gear Prolongs Time to Successful Airway Management
Authors: Flaishon Ron , Sotman Alexander , Ben-Abraham Ron , Rudick Valery , Varssano David , Weinbroum Avi A.
Published: January 2004

Background

Airway management is the first step in resuscitation. The extraordinary conditions in mass casualty situations impose special difficulties in airway management, even for experienced caregivers. The authors evaluated whether wearing surgical attire or antichemical protective gear made any difference in anesthetists' success of airway control with either an endotracheal tube or a laryngeal mask airway.

Methods

Fifteen anesthetists with 2-5 yr of residency and wearing either full antichemical protective gear or surgical attire intubated or inserted laryngeal masks in 60 anesthetized patients. The study was performed in a prospective, randomized, crossover manner. The duration of intubation/insertion was measured from the time the device was grasped to the time a normal capnography recording was obtained.

Results

Endotracheal tubes were introduced significantly (P < 0.01) faster when the anesthetist wore surgical attire (31 +/- 7 vs. 54 +/- 24 s for protective gear), but the mean times necessary to successfully insert laryngeal masks were similar (44 +/- 20 s for surgical attire vs. 39 +/- 11 s for protective gear). Neither performance failure nor incidences of hypoxemia were recorded.

Conclusions

This first report in humans shows to what extent anesthetists' wearing of antichemical protective gear slows the time to intubate but not to insert a laryngeal mask airway compared with wearing surgical attire. Laryngeal mask airway insertion is faster than tracheal intubation when wearing protective gear, indicating its advantage for airway management when anesthetists wear antichemical protective gear. If chances for rapid and successful tracheal intubation under such chaotic conditions are poor, laryngeal mask airway insertion is a viable choice for airway management until a proper secured airway is obtainable.
An Investigation to Dissociate the Analgesic and Anesthetic Properties of Ketamine Using Functional Magnetic Resonance Imaging
Authors: Rogers Richard , Wise Richard G. , Painter Deborah J. , Longe Sarah E. , Tracey Irene
Published: January 2004

Background

Anatomic sites within the brain, which activate in response to noxious stimuli, can be identified with the use of functional magnetic resonance imaging. The aim of this study was to determine whether the analgesic effects of ketamine could be imaged.

Methods

Ketamine was administered to eight healthy volunteers with use of a target-controlled infusion to three predicted plasma concentrations: 0 (saline), 50 (subanalgesic), and 200 ng/ml (analgesic, subanesthetic). Volunteers received noxious thermal stimuli and auditory stimuli and performed a motor task within a 3-T human brain imaging magnet. Activation of brain regions in response to noxious and auditory stimuli and during the motor task was compared with behavioral measures.

Results

The analgesic subanesthetic dose of ketamine significantly reduced the pain scores, and this matched a decrease in activity within brain regions that activate in response to noxious stimuli, in particular, the insular cortex and thalamus. A different pattern of activation was observed in response to an auditory task. In comparison, smaller behavioral and imaging changes were found for the motor paradigm. The lower dose of ketamine gave similar but smaller nonsignificant effects.

Conclusion

The analgesic effect can be measured within a more global effect of ketamine as shown by auditory and motor tasks, and the analgesia produced by ketamine occurs with a smaller degree of cortical processing in pain-related regions.
Alterations in Rat Brain Proteins after Desflurane Anesthesia
Authors: Fütterer Carsten D. , Maurer Martin H. , Schmitt Anne , Feldmann Robert E. , Kuschinsky Wolfgang , Waschke Klaus F.
Published: January 2004

Background

Volatile anesthetics disappear from an organism after the end of anesthesia. Whether changes of protein expression persist in the brain for a longer period is not known. This study investigates the question of whether the expression of proteins is altered in the rat brain after the end of desflurane anesthesia.

Methods

Three groups (n = 12 each) of rats were anesthetized with 5.7% desflurane in air for 3 h. Brains were removed directly after anesthesia, 24 h after anesthesia, or 72 h after anesthesia. Two additional groups (n = 12 each) served as naive conscious controls, in which the brains were removed without previous anesthesia 3 or 72 h after the start of the experiment. Cytosolic proteins were isolated. A proteome-wide study was performed, based on two-dimensional gel electrophoresis and mass spectrometry.

Results

Compared with conscious controls, significant (P < 0.05) increase/decrease was found: 3 h of anesthesia, 5/2 proteins; 24 h after anesthesia, 13/1 proteins; 72 h after anesthesia, 6/4 proteins. The overall changes in protein expression as quantified by the induction factor ranged from -1.67 (decrease to 60%) to 1.79 (increase by 79%) compared with the controls (100%). Some of these regulated proteins play a role in vesicle transport and metabolism.

Conclusion

Desflurane anesthesia produces changes in cytosolic protein expression up to 72 h after anesthesia in the rat brain, indicating yet unknown persisting effects.
Long-term Impairment of Acquisition of a Spatial Memory Task following Isoflurane–Nitrous Oxide Anesthesia in Rats
Authors: Culley Deborah J. , Baxter Mark G. , Yukhananov Rustam , Crosby Gregory
Published: January 2004

Background

The authors demonstrated previously that isoflurane-nitrous oxide anesthesia attenuates performance improvement on an already-learned spatial memory task and that the effect persists for weeks. This experiment was designed to test the hypothesis that learning of new information is particularly susceptible to prolonged disruption after general anesthesia.

Methods

Six- (n = 5) and 20- (n = 5) month-old male Fischer 344 rats were anesthetized for 2 h with 1.2% isoflurane, 70% nitrous oxide, and 30% oxygen. Age-matched control rats received 30% oxygen and 70% nitrogen (n = 5 per group). Rats breathed spontaneously, and anesthetic and oxygen concentrations were measured. Spatial learning was assessed daily for 21 days on a 12-arm radial maze (RAM) beginning 48 h after anesthesia. In a post hoc experiment to examine locomotion, swim speed was assessed in a separate group of identically treated rats (n = 3 per group) for 4 days beginning 48 h after anesthesia.

Results

Aged rats were slower to complete the maze, made fewer correct choices before first error, and made more errors at baseline than young rats (P < 0.05). Anesthesia worsened maze performance in both age groups, as evidenced by increased time to complete the maze and a decreased number of correct choices before first error (P < 0.05), but there were no statistically significant differences in total number of errors. Interestingly, there were no age-by-anesthesia interactions. Aged rats swam slower than adult rats (P < 0.001), but there were no differences between the control and anesthesia groups.

Conclusions

Isoflurane-nitrous oxide anesthesia is associated with a persistent deficit in RAM performance that is not explained by impaired locomotion. This impairment occurs in adult and aged rats, indicating that it is not an age-specific phenomenon. Thus, RAM performance is altered after general anesthesia for longer than predicted by the pharmacology of the drugs used, which, by inference, suggests a long-term deficit in learning/memory.
Pharmacokinetics of Intrathecal Oligodeoxynucleotides
Authors: Krupp Jennifer L. , Bernards Christopher M.
Published: January 2004

Background

Intrathecal administration of antisense oligonucleotides is a frequently used technique to alter gene expression for research purposes. However, in the future, antisense oligonucleotides will likely be administered intrathecally to humans for therapeutic purposes. To date, there have been no systematic studies of the pharmacokinetics of intrathecal oligonucleotides. This study was designed to fill that knowledge gap.

Methods

Microdialysis probes were placed intrathecally at the L4, L1, and T11 vertebral levels and epidurally at the L4 vertebral level in pigs. One of the study oligodeoxynucleotides (10-, 18-, or 30-nucleotide-long sequences of the human MDR-1 gene) was injected intrathecally at the L4 level at time 0. Microdialysis samples were obtained for measurement of oligodeoxynucleotide samples at 5-min intervals until 20 min, 10-min intervals until 60 min, and 20-min intervals until 180 min. Noncompartmental pharmacokinetic analysis was performed using PK Solutions software.

Results

Mean residence time and terminal elimination half-life did not differ significantly among the three oligodeoxynucleotides at any sampling site. In contrast, area under the concentration-time curve differed significantly among the oligodeoxynucleotides at all sampling sites and was inversely related to oligodeoxynucleotide length at the L4 and L1 intrathecal sites but not the T11 or epidural sampling sites. Similarly, clearance and volumes of distribution at the L4 level differed significantly among the oligodeoxynucleotides and were directly related to oligodeoxynucleotide length.

Conclusion

The intrathecal pharmacokinetics of oligodeoxynucleotides are largely determined by oligodeoxynucleotide length. This contrasts with smaller drug molecules, such as opioids, for which intrathecal and epidural pharmacokinetics are largely determined by lipid solubility, not size. The potential clinical utility of this information is that oligodeoxynucleotide distribution within the central nervous system may be controllable to some degree by varying oligodeoxynucleotide length.
Hypothermic Preconditioning Increases Survival of Purkinje Neurons in Rat Cerebellar Slices after an In Vitro Simulated Ischemia
Authors: Yuan Hui-Bih , Huang Yueming , Zheng Shuqiu , Zuo Zhiyi
Published: January 2004

Background

A period of hypothermia before ischemia (hypothermic preconditioning) induces a delayed phase of ischemic tolerance in rat brain. However, whether hypothermic preconditioning induces an acute phase (within a few hours after the hypothermia) of ischemic tolerance remains unknown. This study was designed to determine the time window of the hypothermic preconditioning-induced acute phase of neuroprotection, which is useful information for situations during surgery with anticipated ischemic episodes, and its involved mechanisms.

Methods

Survival of Purkinje cells in rat cerebellar slices was evaluated after a 20-min oxygen-glucose deprivation (OGD, in vitro simulated ischemia) followed by a 4-h recovery. Mild hypothermia (33 degrees C) for 20 min was applied at various times before the OGD.

Results

The hypothermia applied immediately to 3 h before the OGD equally effectively reduced OGD-induced Purkinje cell death/injury. Glibenclamide, a selective KATP channel blocker; 8-cyclopentyl-1,3-dipropylxanthine, a selective adenosine A1 receptor antagonist; and farnesyl protein transferase inhibitor III, a selective inhibitor to reduce Ras farnesylation, abolished hypothermic preconditioning-induced neuroprotection when applied during the hypothermia. OGD increased the expression of high-mobility group I(Y) proteins, which are nuclear transcription factors to enhance the expression of putatively damaging proteins such as cyclooxygenase-2, in cerebellar slices. This increase was attenuated by hypothermic preconditioning.

Conclusions

Hypothermic preconditioning induces an acute phase of neuroprotection. This neuroprotection depends on activation of the signaling molecules, adenosine A1 receptors, KATP channels, and Ras. Inhibition of putatively damaging proteins via the effects of hypothermic preconditioning on high-mobility group I(Y) expression may also be involved in hypothermic preconditioning-induced neuroprotection.
Determinants of the Sensitivity of AMPA Receptors to Xenon
Authors: Plested Andrew J. R. , Wildman Scott S. , Lieb William R. , Franks Nicholas P.
Published: January 2004

Background

There is substantial and growing literature on the actions of general anesthetics on a variety of neurotransmitter-gated ion channels, with the greatest attention being focused on inhibitory gamma-amino butyric acid type A receptors. In contrast, glutamate receptors, the most important class of fast excitatory neurotransmitter-gated receptor channels, have received much less attention, and their role in the production of the anesthetic state remains controversial.

Methods

alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors formed from a variety of different subunits were expressed in Xenopus oocytes and HEK-293 cells, and their sensitivities to the inhalational general anesthetics xenon, isoflurane, and halothane were determined using two-electrode voltage clamp and patch clamp techniques. The effects of desensitization on anesthetic sensitivity were investigated using cyclothiazide and site-directed mutagenesis. An ultrarapid application system was also used to mimic rapid high-concentration glutamate release at synapses.

Results

The authors show that xenon can potently inhibit AMPA receptors when assayed using bath application of kainate. However, when the natural neurotransmitter l-glutamate is used under conditions in which the receptor desensitization is blocked and the peak of the glutamate-activated response can be accurately measured, the pattern of inhibition changes markedly. When desensitization is abolished by a single-point mutation (L497Y in GluR1 and the equivalent mutation L505Y in GluR4), the xenon inhibition is eliminated. When AMPA receptors are activated by glutamate using an ultrarapid application system that mimics synaptic conditions, sensitivity to xenon, halothane, and isoflurane is negligible.

Conclusions

AMPA receptors, when assayed in heterologous expression systems, showed a sensitivity to inhalational anesthetics that was minimal when glutamate was applied rapidly at high concentrations. Because these are the conditions that are most relevant to synaptic transmission, the authors conclude that AMPA receptors are unlikely to play a major role in the production of the anesthetic state by inhalational agents.
Paravertebral Analgesia with Levobupivacaine Increases Postoperative Flap Tissue Oxygen Tension after Immediate Latissimus Dorsi Breast Reconstruction Compared with Intravenous Opioid Analgesia
Authors: Buggy Donal J. , Kerin Michael J.
Published: January 2004

Background

Directly measured tissue oxygen tension (Pto2) reflects the adequacy of local tissue oxygenation and influences surgical wound healing. Epidural analgesia increases Pto2 compared with intravenous morphine analgesia after abdominal surgery. The authors tested the hypothesis that paravertebral regional anesthesia and analgesia would increase Pto2 compared with intravenous opioid-based anesthesia and analgesia.

Methods

Twenty patients scheduled to undergo mastectomy with immediate latissimus dorsi breast reconstruction were randomized to receive either general anesthesia with postoperative intravenous morphine analgesia or combined general-paravertebral anesthesia with continuous paravertebral postoperative analgesia using levobupivacaine in this prospective, cohort study. All patients had a local tissue oxygen sensor implanted in the flap muscle. Data were downloaded continuously for 20 h postoperatively.

Results

The mean Pto2 over the 20-h period was significantly higher in patients receiving paravertebral anesthesia (75 +/- 38 vs. 44 +/- 23 mmHg [mean +/- SD]; P = 0.03). Intraoperative blood loss was less in paravertebral patients (1.2 +/- 0.4 vs. 1.7 +/- 0.5 l; P = 0.04). Dynamic visual analog scale pain scores were significantly lower in paravertebral patients. Intraoperative and postoperative fluids administered, hemoglobin, core temperature, intraoperative end-tidal carbon dioxide, and mean arterial pressure were similar in both groups.

Conclusion

The postoperative latissimus dorsi flap Pto2 was higher for 20 h after breast reconstruction with paravertebral analgesia compared with intravenous morphine analgesia.
Quantifying Net Staffing Costs Due to Longer-than-average Surgical Case Durations
Authors: Abouleish Amr E. , Dexter Franklin , Whitten Charles W. , Zavaleta Jeffery R. , Prough Donald S.
Published: January 2004

Background

Anesthesiology departments incur staffing costs that are not covered by revenue because the operating room (OR) time allocation and case scheduling are not done to maximize OR efficiency and because surgical durations are longer than average. The purpose of this article is to demonstrate a method to quantify net anesthesia staffing costs due to longer-than-average surgical durations and evaluate the factors that influence staffing costs.

Methods

Data collected from two anesthesiology departments in academic hospitals for 1 yr included date of surgery, time that patients entered the OR, time that patients exited the OR, surgical service, and the Current Procedural Terminology code for the primary surgical procedure. Anesthesia care performed outside the main surgical suite and services not billed with American Society of Anesthesiologists units were excluded. National average surgical durations were determined from the Current Procedural Terminology code from the Centers for Medicare and Medicaid Services' database. Actual surgical durations were then used to determine staffing solutions to maximize OR efficiency; national average surgical durations were then used to determine a second solution. The difference in staffing costs between these two staffing solutions represented the staffing costs attributable to longer surgical durations. Costs were converted to dollar amounts using compensation values reported in a national compensation survey. The differences in revenue were determined by applying conversion factors to the differences in surgical durations. The annual net cost attributable to longer surgical durations equaled the staffing costs minus the revenue produced by longer durations. Net staffing costs were estimated for two hospitals using median staffing compensation and median payer mix. Net staffing costs were then recalculated by varying the parameters (conversion factors, limits on differences between actual and average surgical duration, levels of compensation, surgical service size of OR allocation).

Results

Using the median compensation of staff and an average conversion factor, the net annual staffing costs attributable to longer surgical durations were $672,100 for the first hospital. However, if staff members were highly compensated and the payer mix was unfavorable, the net staffing costs were $1,688,000. Reducing the difference between actual and average duration resulted in lower staffing costs. Net staffing costs were less in a second hospital studied that had many low-volume surgical services.

Conclusions

Longer-than-average surgical durations can increase net staffing costs for anesthesiology groups. The increase is dependent on factors such as staffing compensation and payer mix.
Symmetrically 4,6-disubstituted 2-aminopyrimidines and 2-amino-5-nitrosopyrimidines: interplay of molecular, molecular–electronic and supramolecular structures
Authors: Quesada Antonio , Marchal Antonio , Melguizo Manuel , Low John N. , Glidewell Christopher
Published: January 2004

The structures of six symmetrically 4,6-disubstituted 2-aminopyrimidines, four of them containing a 5-nitroso substituent, have been determined. The nitroso compounds, in particular, exhibit polarized molecular–electronic structures leading to extensive charge-assisted hydrogen bonding. The intermolecular interactions observed include hard hydrogen bonds of N—H...N and N—H...O types together with O—H...O and O—H...N types in 2-amino-4,6-bis(2-hydroxyethylamino)-5-nitrosopyrimidine; soft hydrogen bonds of the C—H...O type in both 2-amino-4,6-bis(morpholino)-5-nitrosopyrimidine (3) and 2-amino-4,6-bis(benzylamino)-5-nitrosopyrimidine (4), and of the C—H...π(arene) type in both 2-amino-4,6-bis(piperidino)pyrimidine (1) and 2-amino-5-nitroso-4,6-bis(3-pyridylmethoxy)pyrimidine (5); and aromatic π...π stacking interactions in 2-amino-5-nitroso-4,6-bis(3-pyridylmethoxy)pyrimidine. The supramolecular structures formed by the hard hydrogen bonds are finite, zero-dimensional in (1), one-dimensional in 2-amino-4,6-bis(3-pyridylmethoxy)pyrimidine (2), two-dimensional in both (3) and (4), and three-dimensional in both (5) and 2-amino-4,6-bis(2-hydroxyethylamino)-5-nitrosopyrimidine.
Different packing in three polymorphs of 2,4,6-trimethoxy-1,3,5-triazine
Authors: Fridman Natalya , Kapon Moshe , Sheynin Yana , Kaftory Menahem
Published: January 2004

2,4,6-Trimethoxy-1,3,5-triazine was found to exhibit three different polymorphs. The α-polymorph undergoes reversible phase transformation to the β-polymorph at 340 K with an enthalpy of 3.9 kJ mol−1. The heat of fusion of the β-polymorph at 404 K is 18.1 kJ mol−1. The low-tempreature phase (α-polymorph) crystallizes in the orthorhombic space group Pnma. The high-tempreature phase (β-polymorph) can be obtained from the melt and cystallizes in the monoclinic space group P21. The γ-polymorph is obtained by crystallization from a 1:1 mixture of methanol and methylenechloride from hydrolyzed 2,4-dimethoxy-6-oxybenzophenone-1,3,5-triazine. The γ-polymorph melts at 409 K with an enthalpy of 11.4 kJ mol−1. The γ-polymorph crystallizes in the trigonal space group R3c. The molecules occupy a crystallographic threefold axis. Molecules of 2,4,6-trimethoxy-1,3,5-triazine are planar in all three polymorphs. The major difference between the three polymorphs is the mode of packing of the molecules in the crystal.
Jahn–Teller distortions, cation ordering and octahedral tilting in perovskites
Authors: Lufaso Michael W. , Woodward Patrick M.
Published: January 2004

In transition metal oxides, preferential occupation of specific d orbitals on the transition metal ion can lead to the development of a long-range ordered pattern of occupied orbitals. This phenomenon, referred to as orbital ordering, is usually observed indirectly from the cooperative Jahn–Teller distortions (CJTDs) that result as a consequence of the orbital ordering. This paper examines the interplay between orbital ordering, octahedral tilting and cation ordering in perovskites. Both ternary AMX
3 perovskites containing an active Jahn–Teller (J–T) ion on the octahedral site and quaternary A

2

MM′X
6 perovskites containing a J–T ion on one-half of the octahedral sites have been examined. In AMX
3 perovskites, the tendency is for the occupied 3d
3x
2

−r
2
and 3d
3z
2

−r
2
orbitals to order in the ac plane, as exemplified by the crystal structures of LaMnO3 and KCuF3. This arrangement maintains a favorable coordination environment for the anion sites. In AMX
3 perovskites, octahedral tilting tends to enhance the magnitude of the J–T distortions. In A
2
MM′X
6 perovskites, the tendency is for the occupied 3d
3z
2

−r
2
orbitals to align parallel to the c axis. This pattern maintains a favorable coordination environment about the symmetric M′-cation site. The orbital ordering found in rock-salt ordered A
2
MM′X
6 perovskites is compatible with octahedral rotations about the c axis (Glazer tilt system a
0
a
0
c
−) but appears to be incompatible with GdFeO3-type octahedral tilting (tilt system a
−
b
+
a
−).
Quininium (R)-mandelate, a structure with large Z′ described as an incommensurately modulated structure in (3+1)-dimensional superspace
Authors: Schönleber Andreas , Chapuis Gervais
Published: January 2004

Quininium (R)-mandelate, C20H25N2O_2^+·C8H7O_3^-, is an organic salt with an incommensurately modulated structure. The superspace approach is required for a precise description of the structure at room temperature. In addition to the main reflections, the diffraction pattern also exhibits higher-order satellite reflections. The large number of first- and second-order satellite reflections with relatively strong intensities indicates a significant modulation. No average structure solution could be obtained on the basis of the main reflections only and hence the structure solution was performed in two suitable superstructure approximations, including satellite intensities. Positional modulation functions and modulation functions for the anisotropic atomic displacement parameters were introduced. The modulation originates from a competition between intramolecular and intermolecular forces, which is reflected, in the superspace formalism, in the modification of hydrogen bonds along the internal space variable t.
An X-ray powder diffraction study of the spin-crossover transition and structure of bis(2,6-dipyrazol-1-ylpyrazine)iron(II) perchlorate
Authors: Money Victoria A. , Radosavljevic Evans Ivana , Elhaïk Jerome , Halcrow Malcolm A. , Howard Judith A. K.
Published: January 2004

The crystal structure of the iron(II) spin-crossover compound [Fe(C10H8N6)2](ClO4)2 in the high-spin state has been solved from powder X-ray diffraction data using the DASH program and refined using Rietveld refinement. The thermal spin transition has been monitored by following the change in unit-cell parameters with temperature. The title compound has been found to undergo a crystallographic phase change, involving a doubling of the crystallographic a axis, on undergoing the spin transition.