The ENT emergency clinic: a prospective audit to improve effectiveness of an established service.

BACKGROUND: Ear, nose and throat emergency clinic services vary greatly between trusts. Their common aim is to enable acute conditions to be seen quickly and effectively within an optimum environment. There is however no 'gold standard' for service. OBJECTIVES: To identify an efficient model of service, and to determine whether introduction of a referral and appointment based system improves patient waiting times and appropriateness of referrals. METHODS: A prospective audit, comprising: an initial survey to appraise the existing service; telephone surveys of eight trusts in the West Midlands to determine variability of ENT emergency clinic services and to identify components of an effective service; and re-audit following implementation of a verbal referral and appointment based service. RESULTS: The new service significantly reduced patient waiting times, from 70 minutes to 35 minutes (t = 6.776; p < 0.01), with an associated reduction in the variability of waiting times. Inappropriate referrals were reduced from 7 to 2 per cent. These results were achieved when a 72 per cent referrer compliance with the service was observed. CONCLUSIONS: A verbal referral and appointment based system improves patient waiting times and appropriateness of referrals. Maintenance of high referrer compliance with such a system should be considered, and a tool for monitoring referring practitioners is suggested. This clinic construct model is offered as an example in order to aid delivery of an effective ENT emergency service in departments with similar patient demand and staff resources.

Spontaneous cervical surgical emphysema following childbirth.

OBJECTIVE: We report a case of post-partum surgical cervical emphysema, which is a rare but well recognised complication of labour. By reporting the first case in the ENT literature, we aim to raise awareness of this complication, particularly amongst trainees, to ensure that patients are managed most appropriately. CASE REPORT: A 36-year-old, primigravida woman developed neck swelling and odynophagia post-partum. Surgical cervical emphysema was palpated, with further examination excluding pneumomediastinum and pneumothorax. The patient was managed conservatively, with complete resolution of symptoms within a week. CONCLUSIONS: Surgical cervical emphysema, pneumothorax and pneumomediastinum are all well recognised post-partum complications. The vast majority of cases do not present with respiratory or cardiac compromise and can be appropriately managed conservatively, with expectation of resolution in a fortnight. There is no evidence that such patients are at increased risk during subsequent pregnancies.

Endoscopic palliation of malignant dysphagia: a challenging task in inoperable oesophageal cancer.

BACKGROUND: The main goal when managing patients with inoperable oesophageal cancer is to restore and maintain their oral nutrition. The aim of the present study was to assess the value of endoscopic palliation of dysphagia in patients with oesophageal cancer, who either due to advanced stage of the disease or co-morbidity are not suitable for surgery. PATIENTS AND METHODS: All the endoscopic palliative procedures performed over a 5-year period in our unit were retrospectively reviewed. Dilatation and insertion of self-expandable metal stents (SEMS) were mainly used for tight circumferential strictures whilst ablation with Nd-YAG laser was used for exophytic lesions. All procedures were performed under sedation. RESULTS: Overall 249 palliative procedures were performed in 59 men and 40 women, with a median age of 73 years (range 35-93). The median number of sessions per patient was 2 (range 1-13 sessions). Palliation involved laser ablation alone in 24%, stent insertion alone in 22% and dilatation alone in 13% of the patients. In 41% of the patients, a combination of the above palliative techniques was applied. A total of 45 SEMS were inserted. One third of the patients did not receive any other palliative treatment, whilst the rest received chemotherapy, radiotherapy or chemoradiotherapy. Swallowing was maintained in all patients up to death. Four oesophageal perforations were encountered; two were fatal whilst the other two were successfully treated with covered stent insertion and conservative treatment. The median survival from diagnosis was 10.5 months (range 0.5-83 months) and the median survival from 1st palliation was 5 months (range 0.5-68.5 months). CONCLUSION: Endoscopic interventions are effective and relatively safe palliative modalities for patients with oesophageal cancer. It is possible to adequately palliate almost all cases of malignant dysphagia. This is achieved by expertise in combination treatment.

Transcription analysis of two disparate rRNA operons in the halophilic archaeon Haloarcula marismortui.

The genome of the halophilic archaeon Haloarcula marismortui contains two rRNA operons designated rrnA and rrnB. Genomic clones of the two operons and their flanking regions have been sequenced, and primary transcripts and processing intermediates derived from each operon have been characterized. The 16S, 23S, and 5S genes from the two operons were found to differ at 74 of 1,472 positions, 39 of 2,922 positions, and 2 of 122 positions, respectively. This degree of sequence divergence for multicopy (paralogous) rRNA genes was 10- to 50-fold or more higher than anticipated. The two operons exhibit other profound differences that include (i) the presence in rrnA and the absence in rrnB of tRNAAla and tRNACys genes in the intergenic and distal regions, respectively, (ii) divergent 5' flanking sequences, and (iii) distinct pathways for processing and maturation of 16S rRNA. Processing and maturation of 16S and 23S rRNA from rrnA operon transcripts and of 23S rRNA from rrnB operon transcripts follow the canonical halophilic pathway, whereas maturation of 16S rRNA from rrnB operon transcripts follows an unusual and different pathway that is apparently devoid of any 5' processing intermediate.

Structural basis for the binding of an anti-cytochrome c antibody to its antigen: crystal structures of FabE8-cytochrome c complex to 1.8 A resolution and FabE8 to 2.26 A resolution.

A complete understanding of antibody-antigen association and specificity requires the stereochemical description of both antigen and antibody before and upon complex formation. The structural mechanism involved in the binding of the IgG1 monoclonal antibody E8 to its highly charged protein antigen horse cytochrome c (cyt c) is revealed by crystallographic structures of the antigen-binding fragment (Fab) of E8 bound to cyt c (FabE8-cytc), determined to 1.8 A resolution, and of uncomplexed Fab E8 (FabE8), determined to 2.26 A resolution. E8 antibody binds to three major discontiguous segments (33 to 39; 56 to 66; 96 to 104), and two minor sites on cyt c opposite to the exposed haem edge. Crystallographic definition of the E8 epitope complements and extends biochemical mapping and two-dimensional nuclear magnetic resonance with hydrogen-deuterium exchange studies. These combined results demonstrate that antibody-induced stabilization of secondary structural elements within the antigen can propagate locally to adjacent residues outside the epitope. Pre-existing shape complementarity at the FabE8-cytc interface is enhanced by 48 bound water molecules, and by local movements of up to 4.2 A for E8 antibody and 8.9 A for cyt c. Glu62, Asn103 and the C-terminal Glu104 of cyt c adjust to fit the pre-formed VL "hill" and VH "valley" shape of the grooved E8 paratope. All six E8 complementarity determining regions (CDRs) contact the antigen, with CDR L1 forming 46% of the total atomic contacts, and CDRs L1 (29%) and H3 (20%) contributing the highest percentage of the total surface area of E8 buried by cyt c (550 A2). The E8 antibody covers 534 A2 of the cyt c surface. The formation of five ion pairs between E8 and flexible cyt c residues Lys60, Glu62 and Glu104 suggests the importance of mobile regions and electrostatic interactions in providing the exquisite specificity needed for recognition of this extremely conserved protein antigen. The highly homologous VL domains of E8 and anti-lysozyme antibody D1. 3 achieve their distinct antigen-binding specificities by expanding the impact of their limited sequence differences through the recruitment of different sets of conserved residues and distinctly different CDR L3 conformations.

Structural basis for the root effect in haemoglobin.

The remarkable ability of root effect haemoglobins to pump oxygen against high O2 gradients results from extreme, acid-induced reductions in O2 affinity and cooperativity. The long-sought mechanism for the root effect, revealed by the 2 angstrom crystal structure of the ligand-bound haemoglobin from Leiostomus xanthurus at pH 7.5, unexpectedly involves modulation of the R-state. Key residues strategically assemble positive-charge clusters across the allosteric beta1 beta2-interface in the R-state. At low pH, protonation of the beta N terminus and His 147(HC3)beta within these clusters is postulated to destabilize the R-state and promote the acid-triggered, allosteric R-->T switch with concomitant O2 release. Surprisingly, a set of residues specific to root effect haemoglobins recruit additional residues, conserved among most haemoglobins, to produce the root effect.

The structure of avian eye lens delta-crystallin reveals a new fold for a superfamily of oligomeric enzymes.

The crystal structure of turkey delta-crystallin, a principal soluble components of the avian lens, has been determined to a resolution of 2.5 A. It is a tetramer, of 200,000 M(r), with 222 symmetry. The subunit has a new fold composed of three mainly alpha-helical domains. One domain is a bundle of five long helices which forms a 20-helix bundle at the core of the tetramer. delta-crystallin shares approximately 90% sequence identity with the enzyme argininosuccinate lyase (EC 4.3.2.1), indicating that it is an example of a 'hijacked' enzyme. It is also distantly related to the class II fumarases, aspartases, adenylosuccinases and 3-carboxy-cis,cis-muconate lactonising enzyme. The structure reveals a putative active-site cleft which is located on the boundary between three subunits of the tetramer. This is the first three-dimensional structure of a representative of this superfamily of enzymes.

Sequence heterogeneity between the two genes encoding 16S rRNA from the halophilic archaebacterium Haloarcula marismortui.

The halophilic archaebacterium, Haloarcula marismortui, contains two nonadjacent ribosomal RNA operons, designated rrnA and rrnB, in its genome. The 16S rRNA genes within these operons are 1472 nucleotides in length and differ by nucleotide substitutions at 74 positions. The substitutions are not uniformly distributed but rather are localized within three domains of 16S rRNA; more than two-thirds of the differences occur within the domain bounded by nucleotides 508 and 823. This domain is known to be important for P site binding of aminoacylated tRNA and for 30-50S subunit association. Using S1 nuclease protection, it has been shown that the 16S rRNAs transcribed from both operons are equally represented in the functional 70S ribosome population. Comparison of these two H. marismortui sequences to the 16S gene sequences from related halophilic genera suggests that (i) in diverging genera, mutational differences in 16S gene sequences are not clustered but rather are more generally distributed throughout the length of the 16S sequence, and (ii) the rrnB sequence, particularly within the 508-823 domain, is more different from the out group sequences than is the rrnA sequence. Several possible explanations for the evolutionary origin and maintenance of this sequence heterogeneity within 16S rRNA of H. marismortui are discussed.

Biochemical implications from the variable gene sequences of an anti-cytochrome c antibody and crystallographic characterization of its antigen-binding fragment in free and antigen-complexed forms.

To study the nature of antibody-antigen interactions, we have determined the variable gene sequences of the anti-cytochrome c immunoglobulin G1 (IgG1) monoclonal antibody E8, and obtained diffraction-quality crystals of the E8 antigen-binding fragment (Fab), both free and bound to its antigen, horse cytochrome c. The FabE8 crystals belong to space group P21 with unit cell dimensions of a = 45.0 A, b = 85.1 A, c = 63.3 A and beta = 105.5 degrees, have one FabE8 molecule per asymmetric unit and diffract to at least 2.1 A resolution. Crystals of the FabE8-cytochrome c complex belong to space group P212121 with unit cell dimensions of a = 84.3 A, b = 73.3 A and c = 94.9 A, accommodate one complex per asymmetric unit and diffract to 2.4 A resolution. In the nucleotide-derived amino acid sequences, the light-chain variable domain (VL) but not the heavy-chain variable domain (VH) of E8 is nearly identical to that of the anti-lysozyme antibody D1.3, differing by only five amino acid residues. Only one of these interacts with lysozyme in the D1.3-lysozyme crystal structure. Six negative and four positive charges in the VH complementarity determining regions of E8 complement four positive and three negative charges in the E8 epitope on cytochrome c. These data suggest that only a subset of the residues in an antibody-protein interface may be critical for binding and that the VH may play a dominant role in antigenic recognition.

Surface interactions of gamma-crystallins in the crystal medium in relation to their association in the eye lens.

A comparative study of intermolecular interactions in crystals of two homologous low molecular weight proteins, gamma-II and gamma-IIIb crystallins, from calf eye lens was carried out. Crystal packings for these proteins are very different: intermolecular contact areas compose about 33% of the total accessible surface area of gamma-II as compared with 13% in gamma-III. Two key residues seem to be mainly responsible for the differences in protein association in the crystal medium. These are Ser 103 and Leu 155 in gamma-II, which are replaced by Met 103 and His 155 in gamma-IIb. A similar substitution of these residues is observed in different gene products of gamma-crystallins from a number of vertebrates. This is consistent with the existence of a genetically controlled mechanism for determining intermolecular association of gamma-crystallins in the native medium of the lens.