Two-year-olds will name artifacts by their functions

Do young children take functional information into account in naming artifacts? In three studies of lexical categorization, 112 children 2 years of age learned new names for novel artifacts with novel functions and then extended the names to new objects. The objects were designed to have functions that were causally related in simple and compelling ways to perceptible aspects of their physical structure. Despite only minimal opportunity to familiarize themselves with the objects, children generalized the names in accordance with the objects' functions. This result obtained even when children had to discover the functions of the named objects on their own (Experiment 2) and when all the test objects had some discernible function (Experiment 3). Two-year-olds name by function when they can make sense of the relation between the appearances and the functions of artifacts.

Cocaine and kindling alter the sensitivity of group II and III metabotropic glutamate receptors in the central amygdala

G-protein-coupled metabotropic glutamate receptors (mGluRs) are being implicated in various forms of neuroplasticity and CNS disorders. This study examined whether the sensitivities of mGluR agonists are modulated in a distinct fashion in different models of synaptic plasticity, specifically, kindling and chronic cocaine treatment. The influence of kindling and chronic cocaine exposure in vivo was examined in vitro on the modulation of synaptic transmission by group II and III metabotropic glutamate receptors using whole cell voltage-clamp recordings of central amygdala (CeA) neurons. Synaptic transmission was evoked by electrical stimulation of the basolateral amygdala (BLA) and ventral amygdaloid pathway (VAP) afferents in brain slices from control rats and from rats treated with cocaine or exposed to three to five stage-five kindled seizures. This study shows that after chemical stimulation with chronic cocaine exposure or after electrical stimulation with kindling the receptor sensitivities for mGluR agonists are altered in opposite ways. In slices from control rats, group II agonists, (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (LCCG1) and (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740), depressed neurotransmission more potently at the BLA-CeA than at the VAP-CeA synapse while group III agonist, L(+)-2-amino-4-phosphonobutyrate (LAP4), depressed neurotransmission more potently at the VAP-CeA synapse than at the BLA-CeA. These agonist actions were not seen (were absent) in amygdala neurons from chronic cocaine-treated animals. In contrast, after kindling, concentration response relationships for LCCG1 and LAP4 were shifted to the left, suggesting that sensitivity to these agonists is increased. Except at high concentrations, LCCG1, LY354740, and LAP4 neither induced membrane currents nor changed current-voltage relationships. Loss of mGluR inhibition with chronic cocaine treatment may contribute to counter-adaptive changes including anxiety and depression in cocaine withdrawal. Drugs that restore the inhibitory effects of group II and III mGluRs may be novel tools in the treatment of cocaine dependence. The enhanced sensitivity to group II and III mGluR agonists in kindling is similar to that recorded at the lateral to BLA synapse in the amygdala where they reduce epileptiform bursting. These findings suggest that drugs modifying mGluRs may prove useful in the treatment of cocaine withdrawal or epilepsy.

Transposition of the great vessels: a series of three cases with a review of the literature

Improvements in surgical techniques have led to increased survival in transposition of the great vessels. We present three women who required anaesthetic management for labour analgesia, instrumental delivery and evacuation of retained products; the literature is reviewed with regard to anaesthetic techniques and maternal outcome, and recommendations made for the management of this increasingly common condition.

A single-molecule study of RNA catalysis and folding

Using fluorescence microscopy, we studied the catalysis by and folding of individual Tetrahymena thermophila ribozyme molecules. The dye-labeled and surface-immobilized ribozymes used were shown to be functionally indistinguishable from the unmodified free ribozyme in solution. A reversible local folding step in which a duplex docks and undocks from the ribozyme core was observed directly in single-molecule time trajectories, allowing the determination of the rate constants and characterization of the transition state. A rarely populated docked state, not measurable by ensemble methods, was observed. In the overall folding process, intermediate folding states and multiple folding pathways were observed. In addition to observing previously established folding pathways, a pathway with an observed folding rate constant of 1 per second was discovered. These results establish single-molecule fluorescence as a powerful tool for examining RNA folding.

Video teleconferencing with realistic simulation for medical education

This report describes how realistic patient simulation can be used with video teleconferencing to conduct long-distance clinical case discussions with realistic re-enactments of critical events. By observing what appears to be a real procedure unfolding in real time, it is intended that audience members will better learn and appreciate the lessons from conferences. A commercially available mannequin simulator and video teleconferencing technology were used in nine sessions between a free-standing simulation center and different conference sites throughout the U.S. Transmission was via high-speed telephone lines. In each conference, a clinical scenario was simulated on a screen. Audience members asked questions of a live simulated "patient" and family and later advised the care team on routine treatments and management of urgent clinical problems that arose during management of the mannequin simulator in a highly realistic clinical setting. Ninety-eight percent of respondents from one audience of 150 (response rate 60%) judged the quality of the presentation as "very good or excellent." In response to the statement that "the educational value of the presentation was much greater than that of a standard case conference," 95% scored 4 or 5 on a five-point Likert scale (where 5 is highest agreement). While all conferences were conducted successfully, there were instances of technical challenge in using teleconferencing technology. Technical information about the teleconferencing system and scenario preparation, contingency planning for failures, and other details of using this new teaching modality are described. Although audiences were enthusiastic in their response to this approach to clinical case conferences, further study is needed to assess the added value of interactive simulation for education compared to standard conference formats.

Attenuation of and protection induced by a leucine auxotroph of Mycobacterium tuberculosis

Attenuated mutants of Mycobacterium tuberculosis represent potential vaccine candidates for the prevention of tuberculosis. It is known that auxotrophs of a variety of bacteria are attenuated in vivo and yet provide protection against challenge with wild-type organisms. A leucine auxotroph of M. tuberculosis was created by allelic exchange, replacing wild-type leuD (Rv2987c), encoding isopropyl malate isomerase, with a mutant copy of the gene in which 359 bp had been deleted, creating a strain requiring exogenous leucine supplementation for growth in vitro. The frequency of reversion to prototrophy was <10(-11). In contrast to wild-type M. tuberculosis, the DeltaleuD mutant was unable to replicate in macrophages in vitro. Its attenuation in vivo and safety as a vaccine were established by the fact that it caused no deaths in immunodeficient SCID mice. Complementation of the mutant with wild-type leuD abolished the requirement for leucine supplementation and restored the ability of the strain to grow both in macrophages and in SCID mice, thus confirming that the attenuated phenotype was due to the DeltaleuD mutation. As a test of the vaccine potential of the leucine auxotroph, immunocompetent BALB/c mice, susceptible to fatal infection with wild-type M. tuberculosis, were immunized with the DeltaleuD mutant and subsequently challenged with virulent M. tuberculosis by both the intravenous and aerosol routes. A comparison group of mice was immunized with conventional Mycobacterium bovis BCG vaccine. Whereas all unvaccinated mice succumbed to intravenous infection within 15 weeks, mice immunized with either BCG or the DeltaleuD mutant of M. tuberculosis exhibited enhanced and statistically equivalent survival curves. However, the leuD auxotroph was less effective than live BCG in reducing organ burdens and tissue pathology of mice challenged by either route. We conclude that attenuation and protection against M. tuberculosis challenge can be achieved with a leucine auxotroph and suggest that to induce optimal protection, attenuated strains of M. tuberculosis should persist long enough and be sufficiently metabolically active to synthesize relevant antigens for an extended period of time.

Small angle X-ray scattering reveals a compact intermediate in RNA folding

We have used small angle X-ray scattering (SAXS) to monitor changes in the overall size and shape of the Tetrahymena ribozyme as it folds. The native ribozyme, formed in the presence of Mg2+, is much more compact and globular than the ensemble of unfolded conformations. Time-resolved measurements show that most of the compaction occurs at least 20-fold faster than the overall folding to the native state, suggesting that a compact intermediate or family of intermediates is formed early and then rearranges in the slow steps that limit the overall folding rate. These results lead to a kinetic folding model in which an initial 'electrostatic collapse' of the RNA is followed by slower rearrangements of elements that are initially mispositioned.

Awake fibreoptic intubation skills in obstetric patients: a survey of anaesthetists in the Oxford region

A survey of anaesthetists in the Oxford region was conducted to determine their skills and practice in performing awake fibreoptic intubation. Forty-two consultant obstetric anaesthetists (group O), 21 consultant anaesthetists with an interest in difficult airway management (group D) and 20 anaesthetic specialist registrars in their final training year (group S) were sent a questionnaire on management of a patient with a known difficult airway for elective caesarean section. All but one responded. If regional anaesthesia was unsuccessful or contraindicated, 75/82 respondents (91.5%) would choose to secure the airway by awake intubation. Of the remaining seven, six would use general anaesthesia and spontaneous respiration, five (6.1%) with the laryngeal mask airway and one (1.2%) with mask and airway and one (1.2%) local infiltration by the surgeon. Although awake fibreoptic intubation was the technique chosen by 98.7%, only six (8.1%) had experience of its performance in an obstetric patient. Of the 68 anaesthetists without such experience, only 12/31 (38.7%) group O compared to 13/18 (72.2%) group D and 12/19 (63.2%) group S would be confident to perform awake fibreoptic intubation in an obstetric patient. Only one anaesthetist in the survey practised awake fibreoptic intubation in non-obstetric patients regularly (>3/month). However, 69/82 respondents replied that all consultant obstetric anaesthetists should be experienced in performing awake fibreoptic intubation. We conclude that despite the value of awake fibreoptic intubation, consultant obstetric anaesthetists are less confident in performing it than those with an interest in difficult airway management and final year specialist registrars.

Awake fibreoptic intubation following failed regional anaesthesia for caesarean section in a parturient with Still's disease

The anaesthetic management of a 25-year-old parturient with juvenile rheumatoid arthritis (Still's disease) and a difficult airway presenting for elective Caesarean section is described. Inadequate block after epidural anaesthesia necessitated general anaesthesia. This was safely accomplished by securing the airway with awake oral fibreoptic intubation before general anaesthesia was induced. The problems of performing an awake fibreoptic intubation in a pregnant patient are discussed and a simple method for performing the technique is described.

Failed intubation in a parturient with spina bifida

We describe a case of unexpected difficult intubation and ventilation during induction of general anaesthesia for caesarean section. This case was particularly challenging as the parturient suffered with particularly severe cord tethering following surgery for spina bifida as a child. The observed change in anticipated intubation difficulty during pregnancy, and the use of the laryngeal mask airway as a life-saving device in obstetrics are described. Consideration of the difficulties of anaesthetising the patient with spina bifida for caesarean section in general, and the issues relevant in deciding whether to continue with surgery or to wake the patient up in particular are discussed. Suggestions are made for the management of this emergency situation in those not skilled in fibreoptic intubation.

Multidisciplinary team interventions for delirium in patients with chronic cognitive impairment

BACKGROUND

Delirium is common in hospitalized elderly people. In the frail elderly, delirium may occur in 60% of those hospitalized. In the cognitively impaired, 45% have been shown to develop delirium and these patients have longer lengths of stay and a higher rate of complications which, amongst other things, together contribute to an increase in cost of care. The combination of being elderly and chronically cognitively impaired leads to a high risk of delirium with the associated increased risk of prolonged hospital stay, complications, and poor outcomes. The management of delirium has commonly been multifaceted - the primary emphasis has always been on the diagnosis and therapy of the precipitating factors, but as this may not be immediately resolved, symptomatic and supportive care may become of major importance.

OBJECTIVES

The objective of this review is to assess the available evidence for the effectiveness, if any, of multidisciplinary team interventions in the coordinated care of patients with delirium superimposed on an underlying chronic cognitive impairment compared with the usual care of older cognitively impaired patients.

SEARCH STRATEGY

The Cochrane Controlled Trials Register (Cochrane Library, up to and including Issue 1, 1998) was searched using the terms 'delirium, controlled trial, cognitive'. MEDLINE, EMBASE and Psychlit (Ovid via Winspirs up to Feb 1998) were also searched with the same terms. Other sources including personal communications, ongoing trials, conference proceedings, handsearching and reference lists of published papers and books were all searched for relevant randomized controlled trials. The total yield from searching was 157 from which 8 (eight) were retained for consideration in the review.

SELECTION CRITERIA

From the initial search yields, all randomised controlled trials involving the management of elderly patients with delirium were identified. A single reviewer (AMB) discarded irrelevant publications based on the title of the publication and its abstract. In the event that the article could possibly be relevant, it was retrieved for further assessment. All references were compiled in a list with a commentary on type of article, eg review, prospective study etc and this was independently considered by the second reviewer (RR) who agreed to review all randomised controlled studies reported on patients with delirium. Selection for possible inclusion in this review was then made on the basis of the participants reported as having chronic cognitive impairment, who then developed incident delirium and were randomly assigned to either coordinated multidisciplinary care or usual care. The outcomes of interest were length of stay in hospital, morbidity (including complications), patient distress & impact on care environment, mortality, discharge arrangements and follow-up including assessment of cognitive function at 6 months. Studies in which patients with chronic cognitive impairment or dementia, managed for incident delirium, according to ICD 9 criteria (see note) were considered eligible for inclusion in the review. Studies of risk factors and non-randomized studies were excluded. Note: this classification has been widely utilised throughout the English speaking medical literature over the past 20 years: ICD 10 is still being incorporated into clinical coding systems and has not been utilised in studies published in 1996. (ABSTRACT TRUNCATED)

Oxford positioning technique improves haemodynamic stability and predictability of block height of spinal anaesthesia for elective caesarean section

A novel positioning technique was tested to see whether the unpredictability of block height and haemodynamic instability during spinal anaesthesia for caesarean section could be reduced. In this 'Oxford' position, the woman is placed left lateral with an inflated bag under the shoulder and pillows supporting the head. Following spinal injection the woman is turned to an identical right lateral position. This is maintained until just before incision to minimise aorto-caval compression, when she is placed in the wedged supine position. Sixty women undergoing elective caesarean section were randomised to receive spinal anaesthesia using hyperbaric bupivacaine in either the Oxford (group O), or the sitting position followed immediately by the wedged supine position (group S). Ephedrine 6 mg was given every minute that systolic blood pressure was less than 80% of baseline. In group S, 9/30 women lost pinprick sensation up to T4 at 5 minutes compared with 2/30 in group O (chi2 test, P = 0.04). Block height was more variable in group S than in group O (f test, P = 0.001). Blood pressure decreased by a greater amount initially: group S women required more ephedrine (15.5 +/- 12.9 versus 9.2 +/- 7.7 mg, t test, P = 0.03). Block height with spinal anaesthesia for caesarean section is more predictable and haemodynamically stable if the Oxford position is used whilst anaesthesia develops.

Intra and inter-specific microsatellite variation in the Leishmania subgenus Viannia

Leishmania species of the subgenus Viannia are responsible for a large proportion of New World leishmaniasis. Here we report the development of a set of microsatellite markers which are able to discriminate between all species within the subgenus Viannia, including the closely related species pairs: Leishmania (V.) braziliensis and Leishmania (V.) peruviana; Leishmania (V.) panamensis and Leishmania (V.) guyanensis. Potential species hybrids were uncovered in the analysis. These markers are sufficiently polymorphic such that within-species epidemiological, population and genetic studies are theoretically possible for all species analyzed.

New pathways in folding of the Tetrahymena group I RNA enzyme

Previous studies have shown that the earliest detectable step in folding of the Tetrahymena ribozyme is tertiary structure formation of the peripheral element P5abc. This, along with other results, has suggested that P5abc may serve as a scaffold upon which additional tertiary structure is built. Herein we use the onset of oligonucleotide cleavage activity as a readout for native state formation and investigate the effect of P5abc on the rate of folding to the native structure. Despite the early folding of P5abc, its removal to give the E delta P5abc variant decreases the rate of attainment of an active structure less than fivefold (20-100 mM Mg2+, 15-50 degrees C). Furthermore, P5abc added in trans is able to bind the folded E delta P5abc ribozyme and promote oligonucleotide cleavage at least tenfold more rapidly than folding of the wild-type ribozyme, indicating that E delta P5abc does not have to first unfold before productively binding P5abc to form the true native state. This suggests that a state with the overall tertiary structure formed but with P5abc unfolded represents a viable on-pathway intermediate for the wild-type ribozyme. These results provide strong evidence for the existence of two pathways to the native state: in one pathway P5abc forms tertiary structure first, and in another it forms late. The pathway in which P5abc forms first is favored because P5abc can fold quickly and because its tertiary structure is stable in the absence of additional structured elements, not because P5abc formation is required for subsequent folding steps. In the course of these experiments, we also found that most of the ribozyme population does not reach the native state directly under standard conditions in vitro, but instead forms an inactive structure that is stable for hours. Finally, the fraction that does fold to the native state folds with a single rate constant of 1 min-1, suggesting that there are no significantly populated "fast-track" pathways that reach the native state directly by avoiding slow folding steps.

DnaJ dramatically stimulates ATP hydrolysis by DnaK: insight into targeting of Hsp70 proteins to polypeptide substrates

Most, if not all, of the cellular functions of Hsp70 proteins require the assistance of a DnaJ homologue, which accelerates the weak intrinsic ATPase activity of Hsp70 and serves as a specificity factor by binding and targeting specific polypeptide substrates for Hsp70 action. We have used pre-steady-state kinetics to investigate the interaction of the Escherichia coli DnaJ and DnaK proteins, and the effects of DnaJ on the ATPase reaction of DnaK. DnaJ accelerates hydrolysis of ATP by DnaK to such an extent that ATP binding by DnaK becomes rate-limiting for hydrolysis. At high concentrations of DnaK under single-turnover conditions, the rate-limiting step is a first-order process, apparently a change of DnaK conformation, that accompanies ATP binding and proceeds at 12-15 min-1 at 25 degrees C and 1-1.5 min-1 at 5 degrees C. By prebinding ATP to DnaK and subsequently adding DnaJ, the effects of this slow step may be bypassed, and the maximal rate-enhancement of DnaJ on the hydrolysis step is approximately 15 000-fold at 5 degrees C. The interaction of DnaJ with DnaK.ATP is likely a rapid equilibrium relative to ATP hydrolysis, and is relatively weak, with a KD of approximately 20 microM at 5 degrees C, and weaker still at 25 degrees C. In the presence of saturating DnaJ, the maximal rate of ATP hydrolysis by DnaK is similar to previously reported rates for peptide release from DnaK.ATP. This suggests that when DnaK encounters a DnaJ-bound polypeptide or protein complex, a significant fraction of such events result in ATP hydrolysis by DnaK and concomitant capture of the polypeptide substrate in a tight complex with DnaK.ADP. Furthermore, a broadly applicable kinetic mechanism for DnaJ-mediated specificity of Hsp70 action arises from these observations, in which the specificity arises largely from the acceleration of the hydrolysis step itself, rather than by DnaJ-dependent modulation of the affinity of Hsp70 for substrate polypeptides.

Specificity from steric restrictions in the guanosine binding pocket of a group I ribozyme

The 3' splice site of group I introns is defined, in part, by base pairs between the intron core and residues just upstream of the splice site, referred to as P9.0. We have studied the specificity imparted by P9.0 using the well-characterized L-21 Scal ribozyme from Tetrahymena by adding residues to the 5' end of the guanosine (G) that functions as a nucleophile in the oligonucleotide cleavage reaction: CCCUCUA5 (S) + NNG <--> CCCUCU + NNGA5. UCG, predicted to form two base pairs in P9.0, reacts with a (kcat/KM) value approximately 10-fold greater than G, consistent with previous results. Altering the bases that form P9.0 in both the trinucleotide G analog and the ribozyme affects the specificity in the manner predicted for base-pairing. Strikingly, oligonucleotides incapable of forming P9.0 react approximately 10-fold more slowly than G, for which the mispaired residues are simply absent. The observed specificity is consistent with a model in which the P9.0 site is sterically restricted such that an energetic penalty, not present for G, must be overcome by G analogs with 5' extensions. Shortening S to include only one residue 3' of the cleavage site (CCCUCUA) eliminates this penalty and uniformly enhances the reactions of matched and mismatched oligonucleotides relative to guanosine. These results suggest that the 3' portion of S occupies the P9.0 site, sterically interfering with binding of G analogs with 5' extensions. Similar steric effects may more generally allow structured RNAs to avoid formation of incorrect contacts, thereby helping to avoid kinetic traps during folding and enhancing cooperative formation of the correct structure.