[Laryngeal masks. Possibilities and limits]. / Larynxmaske. Möglichkeiten und Grenzen.

Introduction of the laryngeal mask airway (LMA) has been a revolutionary development in airway management over the last decades. It was first used clinically in 1981 by A. Brain and has been widely used in Germany since 1990. Originally intended as a substitute for conventional mask respiration for short periods of general anaesthesia, the laryngeal mask is in the meantime used in many areas as an alternative to elective endotracheal intubation as well as an option for controlling difficult airways. This contribution provides an overview of the basics as well as practical aspects of LMA use, and discusses the possibilities and limitations of the laryngeal mask in daily practice.

Effects of climate-driven temperature changes on the diversity of freshwater macroinvertebrates.

Increasing temperatures due to climate change were found to influence abundance and timing of species in numerous ways. Whereas many studies have investigated climate-induced effects on the phenology and abundance of single species, less is known about climate-driven shifts in the diversity and composition of entire communities. Analyses of long-term data sets provide the potential to reveal such relationships. We analysed time series of entire communities of macrozoobenthos in lakes and streams in Northern Europe. There were no direct linear effects of temperature and climate indices (North Atlantic Oscillation index) on species composition and diversity, but using multivariate statistics we were able to show that trends in average temperature have already had profound impacts on species composition in lakes. These significant temperature signals on species composition were evident even though we analysed comparatively short time periods of 10-15 years. Future climate shifts may thus induce strong variance in community composition.

[Persistent left superior vena cava with right-left shunt into the left atrium]. / Persistierende linke Vena cava superior mit Rechts-Links-Shunt zum linken Atrium.

UNLABELLED: Persistent left superior vena cava with right-left shunt into the left atrium. HISTORY AND CLINICAL FINDINGS: A 72-year-old patient was admitted to the hospital following bleeding into the basal ganglia secondary to a hypertensive crisis. INVESTIGATIONS: The patient was found to suffer from marked hypoxaemia (pO2 49 mmHg) and erythrocytosis (Hb 18,5 g/dl). Subsequent investigations raised suspicion of a right-left shunt. This was verified by a contrast echocardiogram which was performed transthoracically by injection of echo-contrast material from the left. To improve imaging of the shunt a transoesophageal contrast-echocardiogram was carried out. This showed that the persistent left superior vena cava did not, as previously expected, lead directly into the left atrium, but had a connection to the left superior pulmonary vein. This anatomical variant, which so far to our knowledge has not been reported in the literature, could be confirmed by spiral computed tomography. Apart from an atrial septal aneurysm no other cardiac anomaly could be identified. TREATMENT AND COURSE: Ligation of the left superior vena cava could have been a therapeutic option, but the patient declined operative intervention. CONCLUSION: In cases of profound hypoxemia and erythrocytosis the differential diagnosis must include a persistent left superior vena cava with anomalous connection to the left atrium. Trans-thoracic and transoesophageal contrast-echocardiography is a simple and reliable method to diagnose persistent left superior vena cava as well as concomitant cardiac anomalies.

Enzymatic characterization of the recombinant Arabidopsis thaliana nitrilase subfamily encoded by the NIT2/NIT1/NIT3-gene cluster.

Three of the nitrilase isoenzymes of Arabidopsis thaliana (L.) Heynh. are located on chromosome III in tandem and these genes (NIT2/NIT1/NIT3 in the 5'-->3' direction) encode highly similar polypeptides. Copy DNAs encompassing the entire coding sequences for all three nitrilases were expressed in Escherichia coli as fusion proteins containing a C-terminal hexahistidine extension. All three nitrilases were obtained as enzymatically active proteins, and their characteristics were determined, including a detailed comparative analysis of their substrate preferences. All three nitrilases converted indole-3-acetonitrile (IAN) to indole-3-acetic acid (IAA), albeit, compared to the most effective substrates found, phenylpropionitrile (PPN), allylcyanide, (phenylthio)acetonitrile and (methylthio)acetonitrile, with low affinity and velocity. The preferred substrates are either naturally occurring substrates, which may originate from glucosinolate breakdown, or they are close relatives of these. Thus, a major function of NIT1, NIT2 and NIT3 is assigned to be the conversion to carboxylic acids of nitriles from glucosinolate turnover or degradation. While all nitrilases exhibit a similar pH optimum around neutral, and NIT1 and NIT3 exhibit a similar temperature optimum around 30 degrees C independent of the substrate analyzed (IAN, PPN), NIT2 showed a remarkably different temperature optimum for IAN (15 degrees C) and PPN (35-40 degrees C). A potential role for NIT2 in breaking seed dormancy in A. thaliana by low temperatures (stratification), however, was ruled out, although NIT2 was the predominantly expressed nitrilase isoform in developing embryos and in germinating seeds, as judged from an analysis of beta-glucuronidase reporter gene expression under the control of the promoters of the four isogenes. It is possible that NIT2 is involved in supplying IAA during seed development rather than during stratification.

Plant concepts for mineral acquisition and allocation.

Plant biotechnology is expected to make a major contribution to the steady increase of crop production in the near future. The improvement of mineral assimilation has to meet the challenges of reducing fertilizer application in developed countries, preserving the environment, enabling sustainable agriculture management and generating low-input crops with increased performance in areas where soil infertility limits productivity. Natural genetic resources and engineered plants will help to achieve the implementation of traits for improved mineral assimilation.

Indole-3-acetic acid is synthesized from L-tryptophan in roots of Arabidopsis thaliana.

The promoter of the nit1 gene, encoding the predominantly expressed isoform of the Arabidopsis thaliana (L.) Heynh. nitrilase isoenzyme family, fused to the beta-glucuronidase gene (uidA) drives beta-glucuronidase expression in the root system of transgenic A. thaliana and tobacco plants. This expression pattern was shown to be controlled developmentally, suggesting that the early differentiation zone of root tips and the tissue surrounding the zone of lateral root primordia formation may constitute sites of auxin biosynthesis in plants. The root system of A. thaliana was shown to express functional nitrilase enzyme. When sterile roots were fed [2H]5-L-tryptophan, they converted this precursor to [2H]5-indole-3-acetonitrile and [2H]5-indole-3-acetic acid. This latter metabolite was further metabolized into base-labile conjugates which were the predominant form of [2H]5-indole-3-acetic acid extracted from roots. When [1-13C]-indole-3-acetonitrile was fed to sterile roots, it was converted to [1-13C]-indole-3-acetic acid which was further converted to conjugates. The results prove that the A. thaliana root system is an autonomous site of indole-3-acetic acid biosynthesis from L-tryptophan.

Structural analysis of the nit2/nit1/nit3 gene cluster encoding nitrilases, enzymes catalyzing the terminal activation step in indole-acetic acid biosynthesis in Arabidopsis thaliana.

A 13.8 kb DNA sequence containing the promoters and the structural genes of the Arabidopsis thaliana nit2/nit1/nit3 gene cluster has been isolated and characterized. The coding regions of nit2, nit1 and nit3 spanned 1.9, 1.8 and 2.1 kb, respectively. The architecture of the three genes is highly conserved. Each isoform consists of five exons separated by four introns. The introns are very similar with respect to size and position, but differ considerably in sequence composition. In contrast to the coding sequences the three promoters are very different in sequence, size and in their repertoire of cis elements, suggesting differential regulation of the three nitrilase isoenzymes by the developmental program of the plant and by diverse environmental factors. The nit1 promoter was subjected to analysis in planta. Translational fusions placing the nit1 full-length promoter and a series of 5'-deletion fragments in front of the uidA gene encoding beta-glucuronidase (GUS) were used for Agrobacterium tumefaciens-mediated transformation of Nicotiana tabacum. GUS expression was highest in fully expanded leaves and in the shoot apex as well as in the apices of developing lateral buds, whereas the GUS activity displayed by developing younger leaflets was restricted to the tips of the expanding leaves. Within the root tissue GUS expression was restricted to the root tips and the tips of newly forming lateral roots. Structural features of the nitrilase gene family and nitrilase gene expression patterns are discussed in context with current knowledge of auxin biosynthesis and auxin effects on different tissues.

Structure of the gene encoding nitrilase 1 from Arabidopsis thaliana.

The nitrilases of Arabidopsis thaliana (At) catalyze the conversion of indole-3-acetonitrile (IAN) to indole-3-acetic acid (IAA), thus controlling the last step of auxin biosynthesis. A full-length genomic clone encoding the complete cluster of the At nitrilases 1 to 3 (NIT1-3), including the respective promoter regions, has been isolated and the NIT1 isoform has been sequenced. The coding region (nit1) spans about 2.3 kb and is composed of five exons separated by four introns. The exon-intron splice junctions agree with the consensus sequences typical for plant genes. In agreement with the known cDNA sequence, the exons encode a protein of 346 amino acids (aa) with a deduced molecular mass of 38.2 kDa. The transcription start point (tsp) of nit1 was determined by primer extension experiments. This tsp defines a 5' untranslated region of 36 bp and is located 32 bp downstream from a TATA box. The promoter region of nit1 is located within the approx. 1.5-kb intergenic part that separates the nit2 and nit1 coding sections.