bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between thermal conductivity and water content of soils using numerical modelling
Authors: Cosenza P. , Guérin R. , Tabbagh A. 
Published: August 2003

SummaryThere is no simple and general relationship between the thermal conductivity of a soil, λ, and its volumetric water content, θ, because the porosity, n, and the thermal conductivity of the solid fraction, λs, play a major part. Experimental data including measurements of all the variables are scarce. Using a numerical modelling approach, we have shown that the microscopic arrangement of water influences the relation between λ and θ. Simulated values for n ranging from 0.4 to 0.6, λs ranging from 2 to 5 W m−1 K−1 and θ from 0.1 to 0.4 can be fitted by a simple linear formula that takes into account n, λs and θ. The results given by this formula and by the quadratic parallel (QP) model widely used in physical property studies are in satisfactory agreement with published data both for saturated rocks and for unsaturated soils. Consequently, the linear formula and the QP model can be used as practical and efficient tools to investigate the effects of water content and porosity on the thermal conductivity of the soil and hence to optimize the design of thermal in situ techniques for monitoring water content.
Isotope methods for assessing plant available phosphorus in acid tropical soils
Authors: Bühler S. , Oberson A. , Sinaj S. , Friesen D. K. , Frossard E. 
Published: August 2003

SummaryUse of isotope methods to measure the availability of phosphorus (P) in soils that are well supplied with P is well established. We have evaluated such methods for acid tropical soils with very small P contents, which are less well studied. The isotopically exchangeable P in soil suspensions (E value) and that in plant growth experiments (L value) were measured in soils that had received varying amounts of P fertilizer in two field experiments in Colombia. We determined the E values over 4–5 weeks of equilibration allowing for the kinetics of isotope exchange. The decrease in radioactivity in the soil solution at a particular time, t, divided by that at the start (rt/R) was described by three parameters (r1/R, r∞/R, and a coefficient n) derived from the time course of isotopic exchange over 100 minutes. Values of Et were calculated either from measured values of rt/R or those extrapolated until 12 weeks. Agrostis capillaris was grown on the same soils labelled with carrier‐free 33P‐orthophosphate ions to obtain L values. Agreement between E values derived from measured and extrapolated values of rt/R was satisfactory, but errors in n and r∞/R limited the precision with which we could estimate E values. For most soils, the P concentrations in the soil solution were greater than the detection limit of the malachite green method (0.9 µg l−1) but smaller than its quantification limit (3.6 µg l−1). In the soils with the least available P, the P content of the seed limited the determination of the L value. The E values were strongly correlated, but not identical, with the L values measured for the same time of isotopic exchange. We conclude that these approaches are not precise enough to detect in these soils the ability of a plant to access slowly exchangeable forms of P or to quantify the mineralization of organic P. However, these isotope techniques can be used to estimate the total fraction of added fertilizer P that remains available to the plants.
Uncoupling of the ATPase activity from the branch migration activity of RuvAB protein complexes containing both wild‐type and ATPase‐defective RuvB proteins
Authors: Hishida Takashi , Iwasaki Hiroshi , Han Yong‐Woon , Ohnishi Takayuki , Shinagawa Hideo 
Published: August 2003

AbstractBackground:  Escherichia coli RuvAB promotes branch migration of Holliday junctions during recombination repair and homologous recombination. RuvB forms a hexameric ring through which duplex DNA passes and is translocated in an ATP‐dependent manner. ATPase‐deficient RuvB mutant K68A has a mutation in the Walker A motif and exerts a dominant‐negative effect on in vivo repair of UV‐induced DNA damage. In this study, we examined RuvAB‐dependent branch migration in the presence of a mutant RuvB, K68A.Results:  Mixing K68A with wild‐type RuvB resulted in the formation of heterohexamers that showed unique properties of DNA binding, ATPase, and branch migration activities different from those of either wild‐type or mutant homohexamers. RuvB heterohexamers inhibited branch migration and caused Holliday junctions to accumulate during RecA‐mediated strand exchange. In the presence of RuvA, RuvB heterohexamers had Holliday junction‐dependent ATPase activity, but did not promote branch migration.Conclusions:  These results suggest that functional cooperation among the subunits in the hexamers is required for branch migration, but inclusion of inactive subunits is tolerated for ATP hydrolysis. Therefore, we propose that an essential ATP hydrolysis‐dependent functional cooperation is induced in RuvB hexamer subunits during RuvAB‐mediated branch migration.
Glycophorin A requirement for expression of O‐linked antigens on the erythrocyte membrane
Authors: Arimitsu Nagisa , Akimitsu Nobuyoshi , Kotani Norihiro , Takasaki Seiichi , Kina Tatsuo , Hamamoto Hiroshi , Kamura Koushirou , Sekimizu Kazuhisa 
Published: August 2003

AbstractBackground:  Glycophorin A (GPA) has a large number of sialic acid‐containing oligosaccharide chains. GPA is highly conserved among vertebrates, mice with a GPA deletion have not been reported and GPA's physiologic role remains uncertain.Results:  GPA−/− homozygotes were obtained by intercrossing GPA+/− heterozygotes based on Mendelian genetics. The amount of O‐linked oligosaccharide chains in the erythrocyte membrane of GPA−/− mice decreased to 60% compared to that of the wild‐type mice.Flow cytometry and Western blot analysis revealed that the TER antigen that is associated with GPA on the erythrocyte membrane was totally abrogated from the cell surface in GPA−/− mice. Several glycoproteins that were detected with peanut agglutinin (PNA), a lectin that recognizes O‐linked oligosaccharide chains, were absent from the GPA−/− erythrocyte membrane. Erythrocytes lacking GPA were more sensitive to hypo‐osmotic stress than wild‐type erythrocyte.Conclusions:  GPA−/− mice show apparently normal phenotypes at least during the early generations. The disappearance of many glycoproteins recognized by PNA lectin on the GPA−/− erythrocyte membrane proteins suggests that GPA has an essential role in the expression of O‐linked antigens on the erythrocyte membrane protein. These interactions of GPA and other glycoproteins may contribute to maintaining the physical strength of the erythrocyte membrane.
Daytime activity and risk factors for late‐life insomnia
Authors: Morgan Kevin 
Published: August 2003

SummaryLaboratory evidence linking exercise with improved sleep quality raises the possibility that the lower levels of physical activity characteristic of older age groups may contribute to late‐life insomnia. While support for this hypothesis appears to come from epidemiological surveys, few such studies have distinguished satisfactorily between social and physical activities which differ widely in terms of energy cost and theoretical significance. The present analyses were, therefore, designed to assess the independent influence of physical and social activity levels on the prevalence and natural history of late‐life insomnia. Survivors from a nationally representative UK sample (n = 1042) of elderly people originally interviewed in 1985 were reassessed in 1989 (n = 690) and 1993 (n = 410). Detailed assessments of physical and social activities, mental and physical health status, and sleep quality were made at each survey wave. Logistic regression models, adjusted for age, sex and health status, were used to assess relationships between activity levels and the prevalence, remission/persistence, and incidence of late‐life insomnia. Lower physical health, depressed mood and lower physical (but not social) activity levels consistently emerged as significant risk factors for prevalent, persistent and incident insomnia. Age was unrelated to insomnia variables in all the cross‐sectional models, but did emerge as a significant risk for cumulative 4–8‐year insomnia incidence. These findings suggest that, independent of those activities more closely associated with social engagement, higher levels of customary physical activity per se appear to be protective against incident and chronic late‐life insomnia.
Event‐related potentials during forced awakening: a tool for the study of acute sleep inertia
Authors: Bastuji Hélène , Perrin Fabien , Garcia‐Larrea Luis 
Published: August 2003

SummarySleep propensity and sleep inertia were assessed in 43 patients with excessive daytime sleepiness (EDS) and 21 sleep‐deprived controls, using a forced awakening test under continuous electroencephalographic (EEG) recording. Event‐related potentials (ERPs) were first obtained in waking, while participants performed a target detection auditory task. Subjects were then allowed to take a nap with lights off and sleep latency was calculated. After 3 min of continuous sleep, frequent and rare tones were suddenly presented again (and ERPs recorded) in a forced awakening condition, which was repeated a second time if patients fell asleep. ERPs in pre‐nap wakefulness did not differ in patients and controls. On forced awakening, almost half (48%) of EDS patients retained morphologically normal ERPs, but showed a significant delay of P300 relative to waking. In the other half of the patients (and none of the controls), the N200/P300 complex to targets was replaced on forced awakening by high‐amplitude negative waves (‘sleep negativities’). Single subject analysis showed that 65% of patients had abnormal responses during forced awakening (significant P3 delay or sleep negativities), while only three of them (7%) had abnormal ERPs on wakefulness. The presence of sleep negativities was associated with shorter sleep latencies and increased target detection errors on forced awakening. Sleep negativities were more prevalent in narcolepsy and idiopathic hypersomnia than in EDS associated to psychiatric disorders. By combining sleep latency and ERP measures, the forced awakening test provided a robust and relatively rapid tool (45–60 min) to evaluate both sleep propensity and sleep inertia within a single recording session. The test allows each subject to act as his/her own control, thus increasing sensitivity. In the present series, it proved to be much more discriminative than waking ERPs alone to demonstrate specific abnormalities in patients complaining of excessive daytime sleepiness.
The influence of sleep onset on the diurnal variation in cardiac activity and cardiac control
Authors: Carrington Melinda , Walsh Michelle , Stambas Thalia , Kleiman Jan , Trinder John 
Published: August 2003

SummaryHeart rate (HR), blood pressure (BP) and autonomic nervous system (ANS) activity vary diurnally, with a reduction in HR and BP, and a shift to vagal dominance during the dark phase. However, the cause of these changes, particularly the relative influence of sleep and circadian mechanisms, remains uncertain. The present study assessed the effect of sleep onset on HR, BP, high frequency (HF) component of heart rate variability (HRV), low frequency/high frequency (LF/HF) ratio and pre‐ejection period (PEP). Sleep onset was dissociated from circadian influences by having subjects go to sleep at two different circadian phases, their normal time of sleep onset (normal sleep onset, NSO), and after a delay of 3 h (delayed sleep onset, DSO). The assumption was that changes caused by sleep onset would occur in association with sleep onset, irrespective of its timing, while circadian effects would have a consistent circadian phase and be independent of when sleep onset occurred. Thirteen and 17 subjects were run in the NSO and DSO conditions, respectively. Following a 1‐h adaptation period, data collection began 2 h before subjects’ normal time of sleep onset and continued until morning awakening. The lights were turned out after 2 h in the NSO condition and 5 h in the DSO condition. Subjects were required to maintain a supine position throughout the experimental sessions. The night‐time decrease in HR was found to be due to both sleep onset and a circadian influence, with the circadian component being more prominent. In contrast, the fall in BP was largely due to a sleep onset effect. Increased vagal activity, as reflected in the HF component and a shift to vagal dominance in the LF/HF ratio, appeared to be primarily a function of the sleep system, while sympathetic activity, as assessed by PEP, reflected a circadian influence.
Recognition of sialylated meningococcal lipopolysaccharide by siglecs expressed on myeloid cells leads to enhanced bacterial uptake
Authors: Jones Claire , Virji Mumtaz , Crocker Paul R. 
Published: August 2003

SummarySialic acid‐binding immunoglobulin‐like lectins (siglecs) are expressed predominantly in the haemopoietic and immune systems and exhibit specificities for both the linkage and the nature of sialic acids in N‐glycans, O‐glycans and glycolipids. Several siglecs, including sialoadhesin (Sn, siglec‐1) and siglec‐5, bind to NeuAcα2,3Gal, a terminal capping structure that can also be displayed on the lipopolysaccharide (LPS) of Neisseria meningitidis (Nm). In the present study, we examined the potential of siglecs expressed on cells of the immune system to function as receptors for sialylated Nm. We used sialylated and non‐sialylated LPS derivatives of two serogroups (A and B) of Nm in this study. Using recombinant chimeric soluble receptors, siglec‐transfected cell lines and macrophages from wild‐type and Sn‐deficient mice, we observed that sialylated but not non‐sialylated variants of either genetic background were specifically recognized by Sn and siglec‐5, whereas other siglecs examined were ineffective. In addition, macrophages expressing Sn, as well as transfectants expressing Sn or siglec‐5, bound and phagocytosed sialylated bacteria in a siglec‐ and sialic acid‐dependent manner. This study demonstrates that Nm LPS sialylation can lead to increased bacterial susceptibility to phagocytic uptake, a phenomenon in direct contrast to previously reported protective effects of LPS sialylation.
The link between 20S proteasome activity and post‐replication DNA repair in Saccharomyces cerevisiae
Authors: Podlaska Agnieszka , McIntyre Justyna , Skoneczna Adrianna , Sledziewska‐Gojska Ewa 
Published: August 2003

SummaryWe have shown previously that deletion of the Saccharomyces cerevisiae UMP1 gene encoding the 20S proteasome maturase causes sensitivity to UV radiation. In the current report, we have extended this finding to show that mutations specifically compromising chymotrypsin‐like or trypsin‐like activity of 20S proteasome peptidases also result in increased UV sensitivity. We have also established that mutations affecting proteasome activity, namely ump1Δ, pre2‐K108R and pup1‐T20A, result in spontaneous and UV‐induced mutator phenotypes. To elucidate the origin of these DNA repair phenotypes of the proteasomal mutants, we performed epistasis analysis, with respect to UV sensitivity, using yeast strains with the UMP1 deletion in different DNA repair backgrounds. We show that UMP1 is not epistatic to RAD23 and RAD2, which are involved in the nucleotide excision repair (NER) pathway. Instead, our results indicate that UMP1 as well as PUP1 and PRE2 (encoding catalytic subunits of 20S proteasome) belong to an epistatic group of genes functioning in post‐replication DNA repair (PRR) and are hypostatic to RAD18, which, in complex with RAD6, plays a central role in PRR. We also show that UMP1 is epistatic to REV3 and RAD30, although the relationship of UMP1 with these genes is different.
Chromosomal replicases as asymmetric dimers: studies of subunit arrangement and functional consequences
Authors: McHenry Charles S. 
Published: August 2003

SummaryStudies of the DNA polymerase III holoenzyme of Escherichia coli support a model in which both the leading and lagging strand polymerases are held together in a complex with the replicative helicase and priming activities, allowing two identical α catalytic subunits to assume different functions on the two strands of the replication fork. Creation of distinct functions for each of the two polymerases within the holoenzyme depends on the asymmetric character of the entire complex. The asymmetry of the holoenzyme is created by the DnaX complex, a heptamer that includes τ and γ products of the dnaX gene. τ and γ perform unique functions in the DnaX complex, and the interaction between α and τ appears to dictate the catalytic subunit's role in the replicative reaction. This review considers the properties of the DnaX complex including both τ and γ, with the goal of understanding the properties of the replicase and its function in vivo. Recent studies in eukaryotic and other prokaryotic systems suggest that an asymmetric dimeric replicase may be universal. The leading and lagging strand polymerases may be distinct in some systems. For example, Pol e and Pol δ may function as distinct leading and lagging strand polymerases in eukaryotes, and PolC and DnaE may function as distinct leading and lagging strand polymerases in low GC content Gram‐positive bacteria.
Pseudomonas syringae pv. tomato DC3000 HopPtoM (CEL ORF3) is important for lesion formation but not growth in tomato and is secreted and translocated by the Hrp type III secretion system in a chaperone‐dependent manner
Authors: Badel Jorge L. , Nomura Kinya , Bandyopadhyay Sruti , Shimizu Rena , Collmer Alan , He Sheng Yang 
Published: August 2003

Summary Pseudomonas syringae pv. tomato DC3000 is a pathogen of tomato and Arabidopsis that injects virulence effector proteins into host cells via a type III secretion system (TTSS). TTSS‐deficient mutants have a Hrp– phenotype, that is, they cannot elicit the hypersensitive response (HR) in non‐host plants or pathogenesis in host plants. Mutations in effector genes typically have weak virulence phenotypes (apparently due to redundancy), but deletion of six open reading frames (ORF) in the DC3000 conserved effector locus (CEL) reduces parasitic growth and abolishes disease symptoms without affecting function of the TTSS. The inability of the ΔCEL mutant to cause disease symptoms in tomato was restored by a clone expressing two of the six ORF that had been deleted: CEL ORF3 (HopPtoM) and ORF4 (ShcM). A ΔhopPtoM::nptII mutant was constructed and found to grow like the wild type in tomato but to be strongly reduced in its production of necrotic lesion symptoms. HopPtoM expression in DC3000 was activated by the HrpL alternative sigma factor, and the protein was secreted by the Hrp TTSS in culture and translocated into Arabidopsis cells by the Hrp TTSS during infection. Secretion and translocation were dependent on ShcM, which was neither secreted nor translocated but, like typical TTSS chaperones, could be shown to interact with HopPtoM, its cognate effector, in yeast two‐hybrid experiments. Thus, HopPtoM is a type III effector that, among known plant pathogen effectors, is unusual in making a major contribution to the elicitation of lesion symptoms but not growth in host tomato leaves.
In Bacillus subtilis W23, the duet σXσM, two sigma factors of the extracytoplasmic function subfamily, are required for septum and wall synthesis under batch culture conditions
Authors: Minnig Kathrin , Barblan Jean‐Luc , Kehl Sandrine , Möller Siham Beggah , Mauël Catherine 
Published: August 2003

SummaryThe synthesis of poly(RboP), the main Bacillus subtilis W23 teichoic acid, is encoded by tarDF–tarABIJKL operons, the latter being controlled by two promoters designated PtarA‐int and PtarA‐ext. Analysis by lacZ fusions reveals that PtarA‐int activity exhibits sharp increases at the beginning and end of the transition between exponential and stationary growth phase. As confirmed by mRNA quantification, these increases are mediated by ECF sigma factors σX and σM respectively. In liquid media, strain W23 sigX sigM double mutants experience serious difficulties in the transition and stationary growth phases. Inactivation of σX‐ and σM‐controlled regulons, which precludes transcription from PtarA‐int, leads to (i) delays in chromosome segregation and septation and (ii) a transient loss of up to 30% of the culture OD or lysis. However, specific inactivation of PtarA‐int, leading mainly to a shortage of poly(RboP), does not affect growth while, nevertheless, interfering with normal septation, as revealed by electron microscopy. The different sigM transcription in strains W23 and 168 is discussed. In W23, expression of tarA and sigM, which is shown to control divIC, is inversely correlated with growth rate, suggesting that the sigM regulon is involved in the control of cell division.
The immune response of regional lymph nodes during the early stages of Fasciola hepatica infection in cattle
Authors: Hoyle D. V. , Taylor D. W. 
Published: August 2003

SUMMARY In this study we examined regional immune responses to Fasciola hepatica infection in the natural ruminant host. Naïve cattle and those pre‐exposed to a drug‐abbreviated infection were subsequently challenged and lymph nodes extracted at slaughter. In vitro proliferation and cytokine production by mononuclear cells isolated from hepatic and mesenteric lymph nodes were measured after culture with whole fluke antigen (WFA). Hepatic lymph node cells had a significantly greater response to parasite antigen than mesenteric lymph node cells (P < 0·02), although there was no difference in the magnitude of the proliferative response between naïve and pre‐exposed challenged cattle. Mononuclear cells from hepatic lymph nodes produced interferon gamma, interleukin 2 and interleukin 4 after culture with parasite antigen, indicative of a mixed, T helper type 0, response. Comparison of the hepatic node response to a variety of F. hepatica antigens showed that proliferation was lower after culture with cathepsin‐L, than with a high molecular weight fraction, WFA or excretory–secretory antigen. Cell culture supernatant fluid from unstimulated hepatic lymph node cells showed an IgG1 response to antigens of 48, 52–70, 82, 96 and 120–190 kDa on Western blot in pre‐exposed, but not naïve, challenged animals.
On what basis should the effectiveness of decision aids be judged?
Authors: Kennedy Andrew D. M. 
Published: August 2003

AbstractObjective Attempts to synthesize the evidence on the effects of decision aids have been hampered by the lack of consensus regarding how such effectiveness should be measured. This paper seeks to describe and critically assess the range of measures of effectiveness used in randomized controlled trials of decision aids.Search strategy The published systematic reviews of the field were used to identify primary studies evaluating the effects of decision aids.Inclusion criteria Non‐randomized trials were excluded from this review. As were abstracts and theses of subsequently published studies, methodological papers and reports of subgroups of a study's main publication.Main results A wide range of measures were used to evaluate the effectiveness of decision aids. The most commonly used measures sought to assess treatment decisions, patient's knowledge and the decision‐making process. This pattern was repeated when primary measures of effectiveness were examined. No study attempted to measure the extent to which decisions made were consistent with patient's values.Conclusions Within the current literature there is little consensus on what the aims of decision aids should be. If we can agree that the aim of a decision aid is to help patients make specific personal treatment choices, then evaluations of decision aids should measure the primary effectiveness of their interventions in terms of the extent to which they enable patient's to undergo treatments that agree with their values.