GABA signalling modulates stomatal opening to enhance plant water use efficiency and drought resilience

The non-protein amino acid γ-aminobutyric acid (GABA) has been proposed to be an ancient messenger for cellular communication conserved across biological kingdoms. GABA has well-defined signalling roles in animals; however, whilst GABA accumulates in plants under stress it has not been determined if, how, where and when GABA acts as an endogenous plant signalling molecule. Here, we establish endogenous GABA as a bona fide plant signal, acting via a mechanism not found in animals. Using Arabidopsis thaliana, we show guard cell GABA production is necessary and sufficient to reduce stomatal opening and transpirational water loss, which improves water use efficiency and drought tolerance, via negative regulation of a stomatal guard cell tonoplast-localised anion transporter. We find GABA modulation of stomata occurs in multiple plants, including dicot and monocot crops. This study highlights a role for GABA metabolism in fine tuning physiology and opens alternative avenues for improving plant stress resilience.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

High parasite diversity accelerates host adaptation and diversification

Host-parasite species pairs are known to coevolve, but how multiple parasites coevolve with their host is unclear. By using experimental coevolution of a host bacterium and its viral parasites, we revealed that diverse parasite communities accelerated host evolution and altered coevolutionary dynamics to enhance host resistance and decrease parasite infectivity. Increases in parasite diversity drove shifts in the mode of selection from fluctuating (Red Queen) dynamics to predominately directional (arms race) dynamics. Arms race dynamics were characterized by selective sweeps of generalist resistance mutations in the genes for the host bacterium's cell surface lipopolysaccharide (a bacteriophage receptor), which caused faster molecular evolution within host populations and greater genetic divergence among populations. These results indicate that exposure to multiple parasites influences the rate and type of host-parasite coevolution.

Youth employment, mental health and substance misuse: a challenge to mental health services

Employment is the cornerstone of social inclusion, the means by which individuals play a full and active part in society and has a pivotal role in helping young people to negotiate the transitional period between the child and adulthood. Employment therefore should be seen as a right and given a higher priority by health and social care agencies. There are numerous difficulties preventing some young people from achieving full employment and these are compounded for young people with concurrent mental health and substance misuse problems (dual diagnosis). The coexistence of these two problems is on the increase and they are recognized as significant barriers to employment. Unemployment may lead to social alienation, criminal or other antisocial activity and a higher incidence of suicide. Consequently, there is a danger of young unemployed people slipping into a spiral of self-defeating, antisocial and risky behaviour. There is little evidence of health and social care agencies working in partnership with voluntary sector organizations to tackle the growing problem of dual diagnosis and youth unemployment, although there are obvious linkages between employment, psychological health, social inclusion and substance misuse. It is therefore worth exploring the issues surrounding work, mental health and substance misuse in young people if we are to generate new ways of thinking about and responding to the needs of this target group. This presents a challenge to mental health services, particularly nurses who face the impact of these issues in their day to day practice but often lack the preparation and support to adequately address them.

A review of 47 cases of unerupted maxillary incisors

OBJECTIVES

To study the prevalence of aetiological factors associated with unerupted maxillary incisors and to follow the outcome of treatment in a study of 47 cases.

DESIGN

A retrospective study.

SETTING

The Dental Department, St Luke's Hospital, Malta, the School Dental Clinic of Malta and the private practices of two orthodontists in Malta.

SAMPLE AND METHODS

Forty-seven patients with a total of 53 unerupted maxillary incisors were classified according to the aetiological factors causing non-eruption. The relative prevalence of the various aetiologies were ascertained, and the outcome after treatment was recorded to assess the efficacy of the treatment methods being used.

RESULTS

The most common cause of lack of eruption was the presence of supernumerary teeth (47% of patients). The other 53% of cases were distributed more or less equally between the remaining aetiological factors, which were odontomes (9%), dilacerations (9%), tooth germ malposition (12%), crowding (4%), one case of a calcifying odontogenic cyst (2%) and one case of trauma to the preceding deciduous tooth (2%). The aetiology of 15% of cases could not be ascertained. Once supernumerary teeth were removed, maxillary incisors usually erupted successfully with the help of conventional treatment methods such as surgical exposure and orthodontics. A relatively large number of incisors that failed to erupt due to other aetiological factors had to be extracted.

CONCLUSIONS

Maxillary incisors that fail to erupt due to the presence of supernumerary teeth have a better prognosis than unerupted incisors with less common aetiologies.

Comparison of a high pressure liquid chromatographic analysis and an enzyme immunoassay technique for quantitation of disopyramide in serum or plasma

High pressure liquid chromatographic (HPLC) and enzyme immunoassay (Emit) methods for measuring disopyramide concentrations in plasma and serum were compared. The precision of both methods was satisfactory, with all coefficients of variation in the range 1.3--6.5%. Quantitation was comparable, with a correlation coefficient of 0.991 (n = 96). There was no interference in either method from lignocaine, digoxin, propranolol, procainamide or N-monodealkylated disopyramide. HPLC was superior in terms of lower cost, the ability to quantitate metabolite concentrations, lack of interference by lipaemia or haemolysis and slightly better within-run precision. However, Emit was considered the method of choice for routine therapeutic drug monitoring because of its relative simplicity and speed of performance.