bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitric oxide‐dependent modulation of the delayed rectifier K+ current and the L‐type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea‐pig cardiomyocytes
Authors: Bai Chang‐Xi , Takahashi Kentaro , Masumiya Haruko , Sawanobori Tohru , Furukawa Tetsushi
Published: June 2004

Ginsenoside Re, a major ingredient of Panax ginseng, protects the heart against ischemia–reperfusion injury by shortening action potential duration (APD) and thereby prohibiting influx of excessive Ca2+. Ginsenoside Re enhances the slowly activating component of the delayed rectifier K+ current (IKs) and suppresses the L‐type Ca2+ current (ICa,L), which may account for APD shortening.

We used perforated configuration of patch‐clamp technique to define the mechanism of enhancement of IKs and suppression of ICa,L by ginsenoside Re in guinea‐pig ventricular myocytes.

S‐Methylisothiourea (SMT, 1 μM), an inhibitor of nitric oxide (NO) synthase (NOS), and N‐acetyl‐L‐cystein (LNAC, 1 mM), an NO scavenger, inhibited IKs enhancement. Application of an NO donor, sodium nitroprusside (SNP, 1 mM), enhanced IKs with a magnitude similar to that by a maximum dose (20 μM) of ginseonside Re, and subsequent application of ginsenoside Re failed to enhance IKs. Conversely, after IKs had been enhanced by ginsenoside Re (20 μM), subsequently applied SNP failed to further enhance IKs.

An inhibitor of guanylate cyclase, 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ, 10 μM), barely suppressed IKs enhancement, while a thiol‐alkylating reagent, N‐ethylmaleimide (NEM, 0.5 mM), clearly suppressed it. A reducing reagent, di‐thiothreitol (DTT, 5 mM), reversed both ginsenoside Re‐ and SNP‐induced IKs enhancement.

ICa,L suppression by ginsenoside Re (3 μM) was abolished by SMT (1 μM) or LNAC (1 mM). NEM (0.5 mM) did not suppress ICa,L inhibition and DTT (5 mM) did not reverse ICa,L inhibition, whereas in the presence of ODQ (10 μM), ginsenoside Re (3 μM) failed to suppress ICa,L.

These results indicate that ginsenoside Re‐induced IKs enhancement and ICa,L suppression involve NO actions. Direct S‐nitrosylation of channel protein appears to be the main mechanism for IKs enhancement, while a cGMP‐dependent pathway is responsible for ICa,L inhibition.

British Journal of Pharmacology (2004) 142, 567–575. doi:10.1038/sj.bjp.0705814
Drosophila melanogaster GRD and LCCH3 subunits form heteromultimeric GABA‐gated cation channels
Authors: Gisselmann Günter , Plonka Justina , Pusch Hermann , Hatt Hanns
Published: June 2004

In addition to its action as a fast inhibitory neurotransmitter, γ‐aminobutyric acid (GABA) is thought to mediate excitatory action by activating cation currents in some cell types in invertebrates. However, to date no GABA receptor capable of mediating such action has been identified at the molecular level in insects. Using a systematic expression screening approach, we found that the Drosophila ligand‐gated ion channel subunits GRD and LCCH3 combine to form cation‐selective GABA‐gated ion channels when coexpressed in Xenopus laevis oocytes. The heteromultimeric receptor is activated by GABA (EC50=4.5 μM), muscimol (EC50=4.8 μM) and trans‐4‐aminocrotonic acid (EC50=104.5 μM), and partially by cis‐4‐aminocrotonic acid (EC50=106.3 μM). Picrotoxin effectively blocked the GABA‐gated channel (IC50=0.25 μM), but bicuculline, TPMTA, dieldrin and lindane did not. The benzodiazepines flunitrazepam and diazepam did not potentiate the GABA‐evoked current. Our data suggest that heteromultimeric channels composed of GRD and LCCH3 subunits form GABA‐gated cation channels in insects.

British Journal of Pharmacology (2004) 142, 409–413. doi:10.1038/sj.bjp.0705818
Hypericum perforatum L (St John's wort) preferentially increases extracellular dopamine levels in the rat prefrontal cortex
Authors: Yoshitake Takashi , Iizuka Ryuji , Yoshitake Shimako , Weikop Pia , Müller Walter E , Ögren Sven Ove , Kehr Jan
Published: June 2004

The effects of hydro‐alcoholic extracts of Hypericum perforatum L on extracellular serotonin (5‐HT), noradrenaline (NA) and dopamine (DA) levels and the acidic metabolites (3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5‐hydroxy‐3‐indoleacetic acid (5‐HIAA)) were examined by in vivo microdialysis in the prefrontal cortex of awake rats. Thus, a single dose (60 mg kg−1 i.p. or 300 mg kg−1 p.o.) of H. perforatum increased DA concentrations to 165 and 140% of control values, respectively, and increased locomotor activity in nonhabituated rats. DOPAC and HVA levels were markedly reduced. 5‐HT concentrations were elevated only moderately, while the NA levels were not affected by any treatment. The whole‐tissue analysis revealed that hypericum increased, whereas the monoamine oxidase (MAO) A/B inhibitor phenelzine decreased DA and 5‐HT turnover. The present data indicate that the mechanism of action of hypericum extract in vivo is more complex than the inhibition of monoamine reuptake or metabolism observed in vitro. The finding of preferential enhancement of DA transmission is in agreement with human studies measuring DA‐mediated neuroendocrine responses.

British Journal of Pharmacology (2004) 142, 414–418. doi:10.1038/sj.bjp.0705822
Vasoactive properties of CORM‐3, a novel water‐soluble carbon monoxide‐releasing molecule
Authors: Foresti Roberta , Hammad Jehad , Clark James E , Johnson Tony R , Mann Brian E , Friebe Andreas , Green Colin J , Motterlini Roberto
Published: June 2004

Carbon monoxide (CO), one of the end products of heme catabolism by heme oxygenase, possesses antihypertensive and vasodilatory characteristics. We have recently discovered that certain transition metal carbonyls are capable of releasing CO in biological fluids and modulate physiological functions via the delivery of CO. Because the initial compounds identified were not water soluble, we have synthesized new CO‐releasing molecules that are chemically modified to allow solubility in water. The aim of this study was to assess the vasoactive properties of tricarbonylchloro(glycinato)ruthenium(II) (CORM‐3) in vitro and in vivo.

CORM‐3 produced a concentration‐dependent relaxation in vessels precontracted with phenylephrine, exerting significant vasodilatation starting at concentrations of 25–50 μM. Inactive CORM‐3, which does not release CO, did not affect vascular tone.

Blockers of ATP‐dependent potassium channels (glibenclamide) or guanylate cyclase activity (ODQ) considerably reduced CORM‐3‐dependent relaxation, confirming that potassium channels activation and cGMP partly mediate the vasoactive properties of CO. In fact, increased levels of cGMP were detected in aortas following CORM‐3 stimulation.

The in vitro and in vivo vasorelaxant activities of CORM‐3 were further enhanced in the presence of YC‐1, a benzylindazole derivative which is known to sensitize guanylate cyclase to activation by CO. Interestingly, inhibiting nitric oxide production or removing the endothelium significantly decreased vasodilatation by CORM‐3, suggesting that factors produced by the endothelium influence CORM‐3 vascular activities.

These results, together with our previous findings on the cardioprotective functions of CORM‐3, indicate that this molecule is an excellent prototype of water‐soluble CO carriers for studying the pharmacological and biological features of CO.

British Journal of Pharmacology (2004) 142, 453–460. doi:10.1038/sj.bjp.0705825
Water‐soluble carbon monoxide‐releasing molecules: helping to elucidate the vascular activity of the ‘silent killer’
Authors: Chatterjee Prabal Kumar
Published: June 2004

Carbon monoxide (CO) is formed during the degradation of haeme by haeme oxygenase (HO). As well as being an important signalling molecule and vasodilator, CO also possesses antihypertensive, anti‐inflammatory and antiapoptotic qualities and protects against ischaemic tissue injury. Several approaches have been used to investigate the therapeutic potential of CO, ranging from direct administration of CO gas to the use of prodrugs, which generate CO upon metabolism. A novel approach involves the use of specific CO carriers, which will release measurable, controllable and effective amounts of CO into biological systems. Transitional metal carbonyls based around iron, manganese or ruthenium have recently been developed as CO‐releasing molecules (CO‐RMs) that, under appropriate conditions, will release CO. Such molecules have been shown to provide cardioprotection in both ex vivo and in vivo experiments. To date, CO‐RMs have been largely incompatible with biological systems in that they are only soluble in organic solvents or have to be preactivated either by physical or chemical stimuli. However, the recent development of water‐soluble CO‐RMs has provided new opportunities to investigate the pharmacological and biological features of CO without such confounding influences. CORM‐3, a novel water‐soluble CO‐RM, has recently been used to confirm the cardioprotective actions of CO. In this issue of British Journal of Pharmacology, Foresti and co‐workers report that CORM‐3 delivers CO, produces aortic vasodilation ex vivo and reduces blood pressure in vivo via modulation of the same cGMP and potassium channels utilised by endogenous and exogenous CO. These findings suggest that CORM‐3 has the potential for use as a modulator of vascular function and hypertension. However, the use of water‐soluble CO‐RMs raises several questions of their own which will need to be addressed if CO‐RMs are to be of future use therapeutically.

British Journal of Pharmacology (2004) 142, 391–393. doi:10.1038/sj.bjp.0705826
4‐Chloro‐benzo[F]isoquinoline (CBIQ) activates CFTR chloride channels and KCNN4 potassium channels in Calu‐3 human airway epithelial cells
Authors: Szkotak A J , Murthy M , MacVinish L J , Duszyk M , Cuthbert A W
Published: June 2004

Calu‐3 cells have been used to investigate the actions of 4‐chloro‐benzo[F]isoquinoline (CBIQ) on short‐circuit current (SCC) in monolayers, whole‐cell recording from single cells and by patch clamping.

CBIQ caused a sustained, reversible and repeatable increase in SCC in Calu‐3 monolayers with an EC50 of 4.0 μM. Simultaneous measurements of SCC and isotopic fluxes of 36Cl− showed that CBIQ caused electrogenic chloride secretion.

Apical membrane permeabilisation to allow recording of basolateral membrane conductance in the presence of a K+ gradient suggested that CBIQ activated the intermediate‐conductance calcium‐sensitive K+‐channel (KCNN4). Permeabilisation of the basolateral membranes of epithelial monolayers in the presence of a Cl− gradient suggested that CBIQ activated the Cl−‐channel CFTR in the apical membrane.

Whole‐cell recording in the absence of ATP/GTP of Calu‐3 cells showed that CBIQ generated an inwardly rectifying current sensitive to clotrimazole. In the presence of the nucleotides, a more complex I/V relation was found that was partially sensitive to glibenclamide. The data are consistent with the presence of both KCNN4 and CFTR in Calu‐3.

Isolated inside‐out patches from Calu‐3 cells revealed clotrimazole‐sensitive channels with a conductance of 12 pS at positive potentials after activation with CBIQ and demonstrating inwardly rectifying properties, consistent with the known properties of KCNN4. Cell‐attached patches showed single channel events with a conductance of 7 pS and a linear I/V relation that were further activated by CBIQ by an increase in open state probability, consistent with known properties of CFTR. It is concluded that CBIQ activates CFTR and KCNN4 ion channels in Calu‐3 cells.

British Journal of Pharmacology (2004) 142, 531–542. doi:10.1038/sj.bjp.0705846
Visualizing Roles of Variables in Program Animation
Authors: Sajaniemi Jorma , Kuittinen Marja
Published: June 2004

Visualizations may be used to assist in learning elementary computer programming - a skill that is hard to acquire by many students. This article presents a program animation system, PlanAni, that is based on the concept of the roles of variables. Roles represent schematic uses of variables that occur in programs over and over again, and a set of nine roles covers practically all variables in novice-level programs. PlanAni has been evaluated in a classroom experiment comparing traditional teaching with role-based teaching and animation. The results suggest that the introduction of roles provides students with a new conceptual framework that enables them to mentally process program information in a way similar to that of good code comprehenders. The use of role-based animation seems to assist in the adoption of role knowledge and expert-like programming strategies. A semi-structured interview with the teacher indicates that students like to work with the animator and that the system clarifies many concepts in programming.
When Facial Attractiveness is Only Skin Deep
Authors: Jones Benedict C , Little Anthony C , Burt D Michael , Perrett David I
Published: June 2004

Whilst the relationship between aspects of facial shape and attractiveness has been extensively studied, few studies have investigated which characteristics of the surface of faces positively influence attractiveness judgments. As many researchers have proposed a link between attractiveness and traits that appear healthy, apparent health of facial skin might be a property of the surface of faces that positively influences attractiveness judgments. In experiment 1 we tested for a positive correlation between ratings of the apparent health of small skin patches (extracted from the left and right cheeks of digital face images) and ratings of the attractiveness of male faces. By using computer-graphics faces, in experiment 2 we aimed to establish if apparent health of skin influences male facial attractiveness independently of shape information. Results suggest that apparent health of facial skin is correlated both with ratings of male facial attractiveness (experiment 1) and with being a visual cue for judgments of the attractiveness of male faces (experiment 2). These findings underline the importance of controlling for the influence of visible skin condition in studies of facial attractiveness and are consistent with the proposal that attractive physical traits are those that positively influence others' perceptions of an individual's health.
Bistability and Biasing Effects in the Perception of Ambiguous Point-Light Walkers
Authors: Vanrie Jan , Dekeyser Mathias , Verfaillie Karl
Published: June 2004

The perceptually bistable character of point-light walkers has been examined in three experiments. A point-light figure without explicit depth cues constitutes a perfectly ambiguous stimulus: from all viewpoints, multiple interpretations are possible concerning the depth orientation of the figure. In the first experiment, it is shown that non-lateral views of the walker are indeed interpreted in two orientations, either as facing towards the viewer or as facing away from the viewer, but that the interpretation in which the walker is oriented towards the viewer is reported more frequently. In the second experiment the point-light figure was walking backwards, making the global orientation of the point-light figure opposite to the direction of global motion. The interpretation in which the walker was facing the viewer was again reported more frequently. The robustness of these findings was examined in the final experiment, in which the effects of disambiguating the stimulus by introducing a local depth cue (occlusion) or a more global depth cue (applying perspective projection) were explored.
Is There an Assignment of Top and Bottom during Symmetry Perception?
Authors: Hulleman Johan , Humphreys Glyn W
Published: June 2004

We report data from a discrimination task in which participants had to decide whether a single-item display was either vertically symmetric or asymmetric. This decision was found to be easier when items with a top–bottom polarity were placed in an orientation where the wide end was the base of the stimulus and the narrow end was the top. The difference in reaction times between this orientation and its inversion was about 10 ms. We suggest that top and bottom labels are assigned to stimuli during the detection of bilateral symmetry.
Representational Momentum in Spatial Hearing
Authors: Getzmann Stephan , Lewald Jörg , Guski Rainer
Published: June 2004

The final position of a moving visual object usually appears to be displaced in the direction of motion. We investigated this phenomenon, termed representational momentum, in the auditory modality. In a dark anechoic environment, an acoustic target (continuous noise or noise pulses) moved from left to right or from right to left along the frontal horizontal plane. Listeners judged the final position of the target using a hand pointer. Target velocity was 8° s−1 or 16° s−1. Generally, the final target positions were localised as displaced in the direction of motion. With presentation of continuous noise, target velocity had a strong influence on mean displacement: displacements were stronger with lower velocity. No influence of sound velocity on displacement was found with motion of pulsed noise. Although these findings suggest that the underlying mechanisms may be different in the auditory and visual modality, the occurrence of displacements indicates that representational-momentum-like effects are not restricted to the visual modality, but may reflect a general phenomenon with judgments of dynamic events.
The Modulation of the Flash-Lag Effect by Voluntary Attention
Authors: Namba Janaina , Baldo Marcus Vinícius C
Published: June 2004

In the flash-lag effect (FLE), a flashing object appears to lag behind a moving object when both happen to be physically aligned to each other. According to an earlier account of the FLE (Baldo and Klein 1995 Nature378 565–566), this perceptual phenomenon would result from differential delays in the perceptual processing of moving and flashing stimuli, presumably involving attentional mechanisms. Here, we have attempted to demonstrate in a more convincing way the participation of voluntary attention as a major component of the FLE. In experiment 1 the observer's attentional set was induced by the spatial probability structure of the visual stimulus. A flashing dot (relative to which the location of a moving dot should be judged) was presented, in separate blocks, at fixed, alternating, or randomly chosen locations. The two former conditions, providing a higher spatial predictability, yielded a smaller FLE than the latter condition, which provided a lower spatial predictability of the flashing dot. In experiment 2 we employed a standard cueing procedure, in which a participant was instructed to shift covertly his/her attentional focus according to a symbolic cue. The cue indicated, with a validity of 80%, the visual hemifield at which the flashing dot would be presented. As predicted by our conceptual model, the mean magnitude of the FLE in the valid trials was significantly smaller than that found in the invalid ones. Therefore, both experiments provided strong evidence supporting the participation of voluntary attention in the FLE. Attentional mechanisms should be seen not as the primary cause of the FLE, but rather as an important modulatory component of a broader process whose spatiotemporal dynamics engenders the FLE and possibly other related phenomena. Even though we elected an account based on the influence of attention on perceptual latencies, our empirical findings are compatible with other theoretical models embraced by the current flash-lag controversy and should be accommodated by every attempt to explain this perceptual phenomenon.
Ambiguous Figures: Living versus Nonliving Objects
Authors: Verstijnen Use M , Wagemans Johan
Published: June 2004

Eleven series of figures were studied, each series ranging from one extreme interpretation via five ambiguous intermediates to a second extreme interpretation. Triplets consisting of an ambiguous exemplar in the middle flanked on the left and right by its two extreme interpretations were presented to large groups of subjects. The initial aim was to establish the levels of perceptual ambiguity of each exemplar in a series, and normative data on the ambiguous figures are provided for future reference and use. However, several biases were encountered and these were examined in more detail.

In experiment 1 the subject's task was to compare the middle figure with the flankers and draw an arrow from the middle figure towards the flanking extreme they judged the most similar. Here, an overall preference for the left extreme was found. Therefore the instructions were reversed in experiment 2; flankers had to be compared with the middle figure. The preference for the left extreme remained for figures of living objects, but for nonliving objects the preference switched to the right extreme. To do away with any effect of the arrows, in experiment 3 subjects were divided into two groups each receiving different instructions and were asked to circle one of the extremes. However, the pattern of biases remained the same. The bias found with figures of living objects may be explained on the basis of top–down processes. For nonliving figures, an hypothesis based on bottom–up processes like neural fatigue was considered but rejected.
Distance Estimation in a Dynamic Simulated Environment: A Visual Field Dependence Problem?
Authors: Vianin Pascal , Baumberger Bernard , Flückiger Michelangelo
Published: June 2004

Egocentric distance estimation implies that the subject perceives his own location in the environment. In a simulated environment, subjects have to transpose perceptively their own observation point in order to assume their virtual body position. As only visual information specifies this position, their ability to perceive the camera viewpoint should be linked to the field dependence – independence factor (FDI).

Field-independent subjects underestimated the mid-distance between their own virtual body position and a far-located target; their bisection was located between the projective (2-D) and the simulated (3-D) mid-distance which indicates their difficulty in considering the in-depth simulated spatial references. High correlations between the vertical estimation in the rod-and-frame test and the egocentric-distance-estimation task (with shifted camera) suggest a similar perceptive process in both tasks. This result is confirmed by the better performances of the field-dependent subjects in this condition. In conclusion, we discuss the relationship between FDI and the sense of presence in virtual environments.
The length of test required to measure liveweight change when testing for feed efficiency in cattle
Authors: Kearney G. A. , Knee B. W. , Graham J. F. , Knott S. A.
Published: June 2004

Measuring differences in the efficiency of converting feed to liveweight gains of beef cattle depends on assessments of feed intake and animal growth over a specified period. Previous studies have shown that feed intake can be measured with sufficient precision after 35 days, however, to assess growth rate with acceptable precision, a feeding period of 70 days is required when the cattle are weighed fortnightly. In order to test if more frequent weighing could improve the precision of estimates of liveweight, or reduce the duration of tests, animals were tested in units where an automatic weighing system recorded the liveweight of an animal every time it entered a feeder. Eight groups of beef bulls (171 animals in total) were tested. A random coefficient regression model including a cubic spline for time was used to estimate average daily gain. Evaluation of the residual variance, slope (average daily gain), and its standard error from the models showed that through the use of automated liveweight measurement, the duration of tests could be decreased to 56 days without reducing the precision of estimates of liveweight change. Depending on the precision required, further decreases in testing time could be accommodated.
Manipulating gastrointestinal starch digestion to improve the efficiency of feed utilisation
Authors: Channon A. F. , Rowe J. B.
Published: June 2004

We have reviewed the ways in which the site of starch digestion in the gastrointestinal tract can affect the efficiency of feed utilisation in feedlot cattle. The benefits of starch digestion in the small intestine, as opposed to the rumen, include reduced risk of acidosis and higher energetic efficiency, provided that starch is digested in the small intestine. Undigested starch reaching the colon and caecum is less efficiently used and can lead to fermentative acidosis. There may be an opportunity to use appropriate grain selection and processing to reduce fermentation and ensure efficient digestion of starch in the small intestine. The potential for genetic variation between animals in starch digestion is also discussed. Efficient utilisation of feed grains is likely to involve appropriate choice and treatment of grain, as well as identification and selection of animals capable of efficient digestion of starch in the small intestine.
Genetic improvement of feed efficiency of beef cattle: what lessons can be learnt from other species?
Authors: Pitchford W. S.
Published: June 2004

About half of the feed in beef production systems is used to maintain the breeding herd. Of the remaining 50%, about 20% is used by the breeding cow for pregnancy and lactation and 30% is used by the growing calf. There seems little opportunity to improve efficiency of production (lactation and growth) but reasonable opportunity to increase maintenance efficiency. The mean heritability of net feed efficiency from 35 estimates across 7 species/types was 0.25 ± 0.02. Unfortunately, the genetic correlation between net feed efficiency in young bulls and mature cows is likely to be significantly less than 1, thus responding slowly to selection.While it seems clear that improvements in maintenance efficiency can be made, they may come at a cost. In poultry and mice, increased net feed efficiency has been associated with increased fatness but in pigs and beef cattle there is some evidence of the reverse. While a number of studies have predicted that selection for efficiency may result in lower proportions of crucial, metabolically active visceral organ tissues, there are few studies to support this.Poultry and mouse studies both clearly show that increased net feed efficiency is associated with decreased heat production. This decrease is due to both decreased cost of digestion (heat loss) and decreased activity. In poultry, this decreased heat loss resulted in the more efficient line being more affected by high temperatures. Also, it is possible that at low temperatures, the differences in efficiency may not exist. At this stage it is not clear if the decreased activity is an adaptive advantage or disadvantage. In mice and possibly also pigs and poultry, increased net feed efficiency has been associated with a decreased reproductive rate measured as litter size or egg number. This should definitely be of concern when embarking on selection for improved net feed efficiency in the beef industry. It is recommended that since feed intake is both difficult and expensive to measure, a gene or marker test should be developed, and correlated effects on a range of production traits be carefully evaluated.
Direct response to selection for post-weaning net feed intake in mice and correlated responses in post-weaning growth, intake, gross digestibility and body composition
Authors: Hughes T. E. , Pitchford W. S.
Published: June 2004

Seven generations of divergent selection on a phenotypic index of net feed in mice produced a realised heritability estimate of 0.27 ± 0.07. Despite small negative genetic correlations of net feed intake with daily gain and liveweight, correlated responses in these economically important traits were negligible. Still, more efficient animals tended to be fatter during the early post-weaning phase. Gross digestibility was also affected, which may have implications for the overall energy balance of a biological system.
Genotype differences and their impact on digestive tract function of ruminants: a review
Authors: Hegarty R. S.
Published: June 2004

Physiological factors that cause between-animal variation in digestive function were evaluated as possible selection traits to achieve improved growth and feed-use efficiency by ruminants. Comparative studies of the digestive function of Bos taurus and Bos indicus cattle, as well as selection lines of dairy cows and sheep were reviewed to determine the scope and significance of diversity in rumen function. All investigations indicated differences in digesta retention time between genotypes. Therefore, the digesta retention time, either the total mean retention time (MRT) or the ruminal retention time (RRT), may be suitable selection traits for improving animal productivity.Differences in MRT and RRT may affect animal productivity by changing the number and diversity of rumen microorganisms, the volatile fatty acid (VFA) pattern, the composition and maintenance energy requirement of the microbes, and thus the energetic efficiency of microbial growth. Further effects associated with changed RRT include a possible reduction in methane production and increased long-chain fatty acid (LCFA) synthesis in the rumen, which may consequently affect the energetic efficiency of the ruminant. It is concluded that despite strong evidence of genetic diversity in gut function, the central role of MRT and RRT in digestive metabolism has not been fully appreciated, nor have their contribution to productivity differences among livestock of similar or divergent genotypes been adequately investigated.
How does pregnancy and lactation affect efficiency of female mice divergently selected for post-weaning net feed intake?
Authors: Hughes T. E. , Pitchford W. S.
Published: June 2004

Females from lines of mice divergently selected for post-weaning net feed intake maintained significant line differences in daily feed intake (0.8 g/day difference, 22%) and net feed intake (± 0.35 g/day respectively) both before and during pregnancy. Dam/litter units converged completely for daily feed intake immediately in the postnatal stage, during a period of negative energy balance when feed intake and rate of gain were both maximised. Feed intake net of that required for growth and maintenance of liveweight was effectively zero for both lines during this 2-week period. The lines re-diverged in late-lactation. Variance for all traits increased substantially over the 11�weeks of the experiment.In an extensive production environment, where peak lactation generally coincides with abundant pasture supply, this short convergence would have little impact on overall production efficiency. Consequently, selection for post-weaning net feed intake based on growth/weight components remains a potential means to improve production efficiency.
Metabolic differences in Angus steers divergently selected for residual feed intake
Authors: Richardson E. C. , Herd R. M. , Archer J. A. , Arthur P. F.
Published: June 2004

Residual feed intake measures variation in feed intake independent of liveweight and liveweight gain. First generation steer progeny (n = 33) of parents previously selected for low or high post-weaning residual feed intake were examined to determine metabolic processes contributing to variation in residual feed intake. Blood samples were taken from the steers from weaning through to slaughter. These samples were analysed for key metabolites and hormones. Total urine and total faecal collections were taken from the steers in an animal-house experiment to estimate dry matter digestibility, microbial protein production and protein turnover. At weaning, there were phenotypic correlations between concentrations in plasma of β-hydroxy butyrate (r = 0.55, P<0.001), aspartate aminotransferase (r = 0.34; P<0.001), urea (r = 0.26, P<0.1) and total plasma protein (r = 0.26, P<0.1), and subsequent residual feed intake over the whole experiment (feedlot plus animal-house phases), but no evidence of associations with genetic variation in residual feed intake. At the start of the feedlot residual feed intake test period plasma levels of glucose, creatinine and aspartate aminotransferase were correlated with residual feed intake over the experiment (r = 0.40, –0.45 and 0.43, respectively, P<0.05), providing evidence of phenotypic associations with residual feed intake, and concentrations of urea and triglycerides were correlated with sire estimated breeding values for residual feed intake (b = 1.20 and –0.08, respectively, P<0.05), providing evidence for genetic associations with residual feed intake. At the end of the experiment, concentrations of plasma insulin, cortisol and leptin were correlated with residual feed intake over the experiment (r = 0.43, –0.40 and 0.31, respectively, P<0.05). Plasma concentrations of urea, insulin and cortisol illustrated trends for an association with sire estimated breeding values for RFI (b = –0.35, 0.98 and 12.19, respectively, P<0.1). The ratio of allantoin : creatinine in urine, as a measure of rumen microbial production, tended to be correlated with residual feed intake in the animal house (r�=�0.32, P<0.1) but not with residual feed intake over the entire experiment (r = 0.10, P>0.05). Neither the ratio of 3-methyl histidine : creatinine in urine, as a measure of rate of muscle breakdown, nor the dry matter digestibility measured in the animal house were correlated with residual feed intake in the animal house (r = 0.04, P>0.05), or residual feed intake over the whole experiment (r = –0.22, P>0.05), and neither were associated with genetic variation in residual feed intake.It is hypothesised that high-RFI (low-efficiency) steers have higher tissue energy requirements, are more susceptible to stress and utilise different tissue substrates (partly as a consequence of differences in body composition) to generate energy required in response to exposure to a stressful stimulus.
Biological basis for variation in residual feed intake in beef cattle. 1. Review of potential mechanisms
Authors: Herd R. M. , Oddy V. H. , Richardson E. C.
Published: June 2004

There is a growing body of evidence that there is genetic variation in beef cattle feed intake relative to their liveweight and weight gain. Difference in feed intake, above and below that expected or predicted on the basis of size and growth, is measured as residual feed intake. Variation in residual feed intake must be underpinned by measurable differences in biological processes. This paper summarises some plausible mechanisms by which variation in efficiency of nutrient use may occur and presents several testable hypotheses for such variation. A� companion paper [Richardson and Herd (2004) Aust. J. Exp. Ag. 44, 431–441] presents results from experiments on cattle following divergent selection for residual feed intake. There were at least 5 major processes identified by which variation in efficiency can arise. These are associated with variation in intake of feed, digestion of feed, metabolism (anabolism and catabolism associated with and including variation in body composition), activity and thermoregulation. The percentage contribution of different mechanisms, to variation in residual feed intake, was: 9% for differences in heat increment of feeding; 14% for differences in digestion; 5% for differences in body composition; and 5% for differences in activity. Together, these mechanisms may be responsible for about one-third of the variation in residual feed intake. The remaining two-thirds were likely to be associated with heat loss due to variation in other processes, such as protein turnover and ion transport. There is no shortage of candidate mechanisms that, singularly or in combination, might contribute to genetic variation in energy utilisation in ruminants. Further research in beef cattle, to better define these mechanisms and enable their incorporation into breeding programmes, may lead not only to cattle which eat less for the same performance, but are superior in other traits as well.
Age-structured red blood cell susceptibility and the dynamics of malaria infections
Authors: McQueen Philip G. , McKenzie F. Ellis
Published: June 2004

Malaria parasites and immune responses in an infected human interact on a dynamic landscape, in which a population of replicating parasites depletes a population of replenishing red blood cells (RBCs). These underlying dynamics receive relatively little attention, but they offer unique insights into the processes that control most malaria infections. Here, we focus on the observation that three of the four malaria-parasite species that infect humans are restricted to particular age classes of RBC. We explicitly incorporate this observation in models of infection dynamics to distinguish common from species-specific pressures on host immune responses, and we find that age structuring has profound effects on the course of infection. For all four species conditions exist under which the parasites may persist at low densities, or may clear, even in the absence of an immune response. Catastrophic anemia can occur even with the two species that attack only the youngest RBCs, although only a small fraction of cells are parasitized at any point. Furthermore, with these two, compensatory erythropoetic responses in the host accelerate parasite population growth. A “basic reproduction rate” characterizes these differences in outcomes.
Fluorescence-aided molecule sorting: Analysis of structure and interactions by alternating-laser excitation of single molecules
Authors: Kapanidis Achillefs N. , Lee Nam Ki , Laurence Ted A. , Doose Sören , Margeat Emmanuel , Weiss Shimon
Published: June 2004

We use alternating-laser excitation to achieve fluorescence-aided molecule sorting (FAMS) and enable simultaneous analysis of biomolecular structure and interactions at the level of single molecules. This was performed by labeling biomolecules with fluorophores that serve as donor–acceptor pairs for Förster resonance energy transfer, and by using alternating-laser excitation to excite directly both donors and acceptors present in single diffusing molecules. Emissions were reduced to the distance-dependent ratio
E
, and a distance-independent, stoichiometry-based ratio
S
. Histograms of
E
and
S
sorted species based on the conformation and association status of each species.
S
was sensitive to the stoichiometry and relative brightness of fluorophores in single molecules, observables that can monitor oligomerization and local-environment changes, respectively. FAMS permits equilibrium and kinetic analysis of macromolecule-ligand interactions; this was validated by measuring equilibrium and kinetic dissociation constants for the interaction of
Escherichia coli
catabolite activator protein with DNA. FAMS is a general platform for ratiometric measurements that report on structure, dynamics, stoichiometries, environment, and interactions of diffusing or immobilized molecules, thus enabling detailed mechanistic studies and ultrasensitive diagnostics.
Coevolution of gene expression among interacting proteins
Authors: Fraser Hunter B. , Hirsh Aaron E. , Wall Dennis P. , Eisen Michael B.
Published: June 2004

Physically interacting proteins or parts of proteins are expected to evolve in a coordinated manner that preserves proper interactions. Such coevolution at the amino acid-sequence level is well documented and has been used to predict interacting proteins, domains, and amino acids. Interacting proteins are also often precisely coexpressed with one another, presumably to maintain proper stoichiometry among interacting components. Here, we show that the expression levels of physically interacting proteins coevolve. We estimate average expression levels of genes from four closely related fungi of the genus
Saccharomyces
using the codon adaptation index and show that expression levels of interacting proteins exhibit coordinated changes in these different species. We find that this coevolution of expression is a more powerful predictor of physical interaction than is coevolution of amino acid sequence. These results demonstrate that gene expression levels can coevolve, adding another dimension to the study of the coevolution of interacting proteins and underscoring the importance of maintaining coexpression of interacting proteins over evolutionary time. Our results also suggest that expression coevolution can be used for computational prediction of protein-protein interactions.
Ectopic Expression of the Petunia MADS Box GeneUNSHAVENAccelerates Flowering and Confers Leaf-Like Characteristics to Floral Organs in a Dominant-Negative Manner[W]
Authors: Ferrario Silvia , Busscher Jacqueline , Franken John , Gerats Tom , Vandenbussche Michiel , Angenent Gerco C. , Immink Richard G.H.
Published: June 2004

Several genes belonging to the MADS box transcription factor family have been shown to be involved in the transition from vegetative to reproductive growth. The Petunia hybrida MADS box gene UNSHAVEN (UNS) shares sequence similarity with the Arabidopsis thaliana flowering gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1, is expressed in vegetative tissues, and is downregulated upon floral initiation and the formation of floral meristems. To understand the role of UNS in the flowering process, knockout mutants were identified and UNS was expressed ectopically in petunia and Arabidopsis. No phenotype was observed in petunia plants in which UNS was disrupted by transposon insertion, indicating that its function is redundant. Constitutive expression of UNS leads to an acceleration of flowering and to the unshaven floral phenotype, which is characterized by ectopic trichome formation on floral organs and conversion of petals into organs with leaf-like features. The same floral phenotype, accompanied by a delay in flowering, was obtained when a truncated version of UNS, lacking the MADS box domain, was introduced. We demonstrated that the truncated protein is not translocated to the nucleus. Using the overexpression approach with both the full-length and the nonfunctional truncated UNS protein, we could distinguish between phenotypic alterations because of a dominant-negative action of the protein and because of its native function in promoting floral transition.
Tomato Heat Stress Transcription Factor HsfB1 Represents a Novel Type of General Transcription Coactivator with a Histone-Like Motif Interacting with the Plant CREB Binding Protein Ortholog HAC1[W]
Authors: Bharti Kapil , von Koskull-Döring Pascal , Bharti Sanita , Kumar Pravir , Tintschl-Körbitzer Angelika , Treuter Eckardt , Nover Lutz
Published: June 2004

In contrast with the class A heat stress transcription factors (HSFs) of plants, a considerable number of HSFs assigned to classes B and C have no evident function as transcription activators on their own. However, in the following article, we provide evidence that tomato (Lycopersicon peruvianum) HsfB1 represents a novel type of coactivator cooperating with class A HSFs (e.g., with tomato HsfA1). Provided the appropriate promoter architecture, the two HSFs assemble into an enhanceosome-like complex, resulting in strong synergistic activation of reporter gene expression. Moreover, HsfB1 also cooperates in a similar manner with other activators, for example, with the ASF1/2 enhancer binding proteins of the 35S promoter of Cauliflower mosaic virus or with yet unidentified activators controlling housekeeping gene expression. By these effects, HsfB1 may help to maintain and/or restore expression of certain viral or housekeeping genes during ongoing heat stress. The coactivator function of HsfB1 depends on a histone-like motif in its C-terminal domain with an indispensable Lys residue in the center (GRGKMMK). This motif is required for recruitment of the plant CREB binding protein (CBP) ortholog HAC1. HsfA1, HsfB1, and HAC1/CBP form ternary complexes in vitro and in vivo with markedly enhanced efficiency in promoter recognition and transcription activation in plant and mammalian (COS7) cells. Using small interfering RNA–mediated knock down of HAC1 expression in Arabidopsis thaliana mesophyll protoplasts, the crucial role for the coactivator function of HsfB1 was confirmed.
Silencing of Hydroxycinnamoyl-Coenzyme A Shikimate/Quinate Hydroxycinnamoyltransferase Affects Phenylpropanoid Biosynthesis[W]
Authors: Hoffmann Laurent , Besseau Seébastien , Geoffroy Pierrette , Ritzenthaler Christophe , Meyer Denise , Lapierre Catherine , Pollet Brigitte , Legrand Michel
Published: June 2004

The hydroxyl group in the 3-position of the phenylpropanoid compounds is introduced at the level of coumarate shikimate/quinate esters, whose synthesis implicates an acyltransferase activity. Specific antibodies raised against the recombinant tobacco (Nicotiana tabacum) acyltransferase revealed the accumulation of the enzyme in stem vascular tissues of tobacco, in accordance with a putative role in lignification. For functional analysis, the acyltransferase gene was silenced in Arabidopsis thaliana and N. benthamiana by RNA-mediated posttranscriptional gene silencing. In Arabidopsis, gene silencing resulted in a dwarf phenotype and changes in lignin composition as indicated by histochemical staining. An in-depth study of silenced N. benthamiana plants by immunological, histochemical, and chemical methods revealed the impact of acyltransferase silencing on soluble phenylpropanoids and lignin content and composition. In particular, a decrease in syringyl units and an increase in p-hydroxyphenyl units were recorded. Enzyme immunolocalization by confocal microscopy showed a correlation between enzyme accumulation levels and lignin composition in vascular cells. These results demonstrate the function of the acyltransferase in phenylpropanoid biosynthesis.
The ArabidopsisSKU6/SPIRAL1Gene Encodes a Plus End–Localized Microtubule-Interacting Protein Involved in Directional Cell Expansion[W]
Authors: Sedbrook John C. , Ehrhardt David W. , Fisher Sarah E. , Scheible Wolf-Rüdiger , Somerville Chris R.
Published: June 2004

The sku6-1 mutant of Arabidopsis thaliana exhibits altered patterns of root and organ growth. sku6 roots, etiolated hypocotyls, and leaf petioles exhibit right-handed axial twisting, and root growth on inclined agar media is strongly right skewed. The touch-dependent sku6 root skewing phenotype is suppressed by the antimicrotubule drugs propyzamide and oryzalin, and right skewing is exacerbated by cold treatment. Cloning revealed that sku6-1 is allelic to spiral1-1 (spr1-1). However, modifiers in the Columbia (Col) and Landsberg erecta (Ler) ecotype backgrounds mask noncomplementation in sku6-1 (Col)/spr1-1 (Ler) F1 plants. The SPR1 gene encodes a plant-specific 12-kD protein that is ubiquitously expressed and belongs to a six-member gene family in Arabidopsis. An SPR1:green fluorescent protein (GFP) fusion expressed in transgenic seedlings localized to microtubules within the cortical array, preprophase band, phragmoplast, and mitotic spindle. SPR1:GFP was concentrated at the growing ends of cortical microtubules and was dependent on polymer growth state; the microtubule-related fluorescence dissipated upon polymer shortening. The protein has a repeated motif at both ends, separated by a predicted rod-like domain, suggesting that it may act as an intermolecular linker. These observations suggest that SPR1 is involved in microtubule polymerization dynamics and/or guidance, which in turn influences touch-induced directional cell expansion and axial twisting.