Phrenic palsy and analgesic quality of continuous supraclavicular vs. interscalene plexus blocks after shoulder surgery.

BACKGROUND: Hemidiaphragmatic palsy is a common consequence of the interscalene brachial plexus block. It occurs less commonly with the supraclavicular approach. Register data suggest that the analgesic quality of a supraclavicular blockade is sufficient for arthroscopic shoulder surgery, although data on the post-operative analgesic effect are lacking. METHODS: After approval by the ethics committee, patients having arthroscopic shoulder surgery under general anaesthesia were randomized to receive a continuous interscalene or supraclavicular blockade. Phrenic nerve function was evaluated through ultrasound examination of the diaphragm in combination with spirometry. Pain scores at rest and activity etc. were determined before catheter insertion, during observation in the post- anaesthesia care unit (PACU) and on post-operative day 1 (POD1). The initial application of 10 ml of ropivacaine 0.2% was followed by continuous application of 4 ml of ropivacaine 0.2%, plus a patient controlled analgesia (PCA) bolus of 4 ml/h. RESULTS: One hundred and twenty patients were randomized, of which 114 data sets were analysed. Complete hemidiaphragmatic paresis occurred in 43% of the interscalene group vs. 24% in the supraclavicular group during PACU stay. Rates of dyspnoea and hoarseness were similar. Horner's syndrome occurred in 21% of the interscalene but only 3% of the supraclavicular group on POD1. Pain scores were comparable for pain at rest and during stress at each time point. CONCLUSIONS: This trial showed a significantly greater incidence of phrenic nerve palsy of the interscalene group in PACU, but not on POD1. Post-operative analgesic quality was similar in both groups. Continuous supraclavicular blockade is a suitable alternative to the continuous interscalene technique.

TRIPTYCHON and CAPRICE mediate lateral inhibition during trichome and root hair patterning in Arabidopsis.

Trichome patterning in Arabidopsis is a model for the generation of a spacing pattern from initially equivalent cells. We show that the TRIPTYCHON gene that functions in lateral inhibition encodes a single-repeat MYB-related transcription factor that lacks a recognizable activation domain. It has high sequence similarity to the root hair patterning gene CAPRICE. Both genes are expressed in trichomes and act together during lateral inhibition. We further show that TRIPTYCHON and CAPRICE act redundantly in the position-dependent cell fate determination in the root epidermis. Thus, the same lateral inhibition mechanism seems to be involved in both de novo patterning and position-dependent cell determination. We propose a model explaining trichome and root hair patterning by a common mechanism.

The Short antennae gene of Tribolium is required for limb development and encodes the orthologue of the Drosophila Distal-less protein.

Insects bear a stereotyped set of limbs, or ventral body appendages. In the highly derived dipteran Drosophila melanogaster, the homeodomain transcription factor encoded by the Distal-less (Dll) gene plays a major role in establishing distal limb structures. We have isolated the Dll orthologue (TcDll) from the beetle Tribolium castaneum, which, unlike Drosophila, develops well-formed limbs during embryogenesis. TcDll is initially expressed at the sites of limb primordia formation in the young embryo and subsequently in the distal region of developing legs, antennae and mouthparts except the mandibles. Mutations in the Short antennae (Sa) gene of Tribolium delete distal limb structures, closely resembling the Dll phenotype in Drosophila. TcDll expression is severely reduced or absent in strong Sa alleles. Genetic mapping and molecular analysis of Sa alleles also support the conclusion that TcDll corresponds to the Sa gene. Our data indicate functional conservation of the Dll gene in evolutionarily distant insect species. Implications for evolutionary changes in limb development are discussed.

Differential regulation of target genes by different alleles of the segmentation gene hunchback in Drosophila.

hunchback (hb) is a key regulatory gene in the early segmentation gene hierarchy of Drosophila. It codes for a transcription factor of the Cys2-His2 zinc finger type and shows two separate zinc finger domains in its coding region. hb forms a morphogenetic gradient in the middle of the embryo that is required for setting the spatial boundaries of several target genes. We have analyzed the molecular lesions found in the different hb alleles and have studied the differential effects of these alleles on a number of such target genes. We find that in mutants in which the HB protein lacks a functional second finger domain, the regulation of the target genes Krüppel (Kr) and knirps (kni) is differentially affected. While this domain is required for the correct regulation of Kr, it is not necessary for the repression of kni. Furthermore, mutations affecting this domain lead to a decreased protein stability. The integration of the expression pattern of target genes was found to be distorted in a second class of mutants between the two finger domains which lead to gain of function or neomorphic phenotypes. The effects of these mutations were studied in detail and it was found that they fall into two classes, the first one interfering with the function of the maternal hb product, the second leading to a delayed segmentation. The function of the latter class appears to be linked to the secondary expression of hb in the parasegment 4 (PS4) stripe at blastoderm stage.

Chromophore-assisted laser inactivation of patched protein switches cell fate in the larval visual system of Drosophila.

The Drosophila segment-polarity gene patched (ptc) is an integral component of the segmentation gene cascade acting in the early embryo. At later stages of embryogenesis, ptc is expressed in the primordia of epithelial placodes of a specific portion of the brain, the optic lobes. Mutant analysis shows that the lack of ptc activity alters the fate of optic-lobe primordia precursors. In ptc mutants they give rise to supernumerary neurons in the larval light-sensory system, termed Bolwig organ, which is derived from precursor cells next to the optic-lobe anlagen. We specifically eliminated ptc protein by chromophore-assisted laser inactivation (CALI) in late wild-type embryos. Such embryos show a normal segment pattern, but they develop phenocopies equivalent to the phenotype of ptc mutant Bolwig organs. Our results demonstrate that the CALI technique can be applied to separate genetic functions at different developmental stages of a living organism and that the segment-polarity gene ptc is redeployed to functionally discriminate between distinct developmental pathways in adjacent pools of precursor cells.