Management of vagus nerve stimulation therapy in the peri-operative period: Guidelines from the Association of Anaesthetists: Guidelines from the Association of Anaesthetists.

Vagus nerve stimulation is a well-established treatment option for patients with drug-resistant epilepsy and has an expanding range of other clinical indications. Side effects of vagus nerve stimulation therapy include: cough; voice changes; vocal cord adduction; rarely, obstructive sleep apnoea; and arrhythmia. Patients with implanted vagus nerve stimulation devices may present for unrelated surgery and critical care to clinicians who are unfamiliar with their function and safe management. These guidelines have been formulated by multidisciplinary consensus based on case reports, case series and expert opinion to support clinicians in the management of patients with these devices. The aim is to provide specific guidance on the management of vagus nerve stimulation devices in the following scenarios: the peri-operative period; peripartum period; during critical illness; and in the MRI suite. Patients should be aware of the importance of carrying their personal vagus nerve stimulation device magnet with them at all times to facilitate urgent device deactivation if necessary. We advise that it is generally safer to formally deactivate vagus nerve stimulation devices before general and spinal anaesthesia. During periods of critical illness associated with haemodynamic instability, we also advise cessation of vagus nerve stimulation and early consultation with neurology services.

Calcium-mediated changes in gap junction structure: evidence from the low angle X-ray pattern.

Rat liver gap junctions were isolated in Ca2+-free media and analyzed in controlled environments by x-ray diffraction of partially oriented pellets. Different treatments of the same preparations were compared. The ordered hexagonal lattices gave rise to detail that was sensitive to low Ca2+ concentrations (0.05 mM), but not to Mg2+ (up to 0.16 mM) or pH (between 6.0 and 8.0). The major Ca2+-mediated responses were reductions in the intensity of the (1, 0) peak and in the off-equatorial contributions to the (2, 1) peak, and changes of scale equivalent to a decrease (approximately 2%) in lattice dimension, but an increase (approximately 4%) in the dimension perpendicular to the lattice. A simple structural interpretation of these findings is that Ca2+ induces the subunits of the channel-forming assembly, the connexon, to align more nearly parallel to the channel, thereby causing the connexon to become slightly longer and more radially compact. The rearrangement is of the same nature as one found under less physiological circumstances by electron microscopy (Unwin, P. N. T., and G. Zampighi, 1980, Nature (Lond.)., 283:545-549), and may be part of a coordinated mechanism by which the channel closes.

Fine-needle aspiration of non-Hodgkin's lymphoma. Southern blot analysis for antigen receptor, bcl-2, and c-myc gene rearrangements.

To determine the utility of Southern blot analysis for fine-needle aspiration samples, the authors prospectively analyzed immunoglobulin, T-cell receptor, c-myc, and bcl-2 gene rearrangements in 27 cases of known or suspected lymphoma. Adequate DNA for analysis was obtained from 20 of 27 cases (74%), including 18 of 22 (82%) with non-Hodgkin's lymphoma (NHL). Patients whose tumors showed sclerosis, cellular degeneration, or necrosis yielded inadequate DNA. Of the 18 NHLs with successful Southern blot studies, 17 tumors had a B-cell lineage and one was an adult T-cell leukemia/lymphoma; clonal integration of the human T-cell leukemia virus I (HTLV-I) genome was present in the latter case. Four cases had bcl-2 rearrangements and two had c-myc rearrangements. One patient with follicular small cleaved cell NHL that evolved to a small noncleaved cell NHL had coexisting bcl-2 and c-myc rearrangement in the aspiration specimen of the high-grade NHL, suggesting sequential bcl-2 and c-myc activation during the tumor's progression. Southern blot analysis is a useful technique for establishing tumor cell lineage, clonality, and the presence of oncogene rearrangements in fine-needle aspiration specimens of NHL.

Experimentally induced foot rot in feedlot cattle fed rations containing organic iodine (ethylenediamine dihydriodide) and urea.

Foot rot was experimentally induced in feedlot cattle with a mixed inoculum of Fusobacterium necrophorum (Sphaerophorus necrophus) and Bacteroides melaninogenicus. Both bacteria were isolated from the lesions. Isolates of F necrophorum from 2 of the lesions were serologically compared, using a passive hemagglutination test with the strain used to induce the lesions. These isolates were serologically similar but not identical, indicating antigenic change had occurred during animal passage. The addition of ethylenediamine dihydriodide or urea to the rations did not affect the frequency of experimentally induced foot rot.

Two configurations of a channel-forming membrane protein.

The protein oligomer forming the gap junction channel has been analysed in two Ca2+-sensitive states by electron microscopy of membranes in frozen aqueous solutions. Switching between states occurs by a small cooperative rearrangement involving tilting of the subunits, which may be responsible for the effect of Ca2+ on channel permeability in vivo.

Habituation of fright and arousal responses in the teleosts Carassius auratus and Rutilus rutilus.

The habituation of fright and arousal responses of goldfish (Carassius auratus) and roach (Rutilus rutilus) to the repeated operation of a plunger in the water was studied. The early response was of fright, which habituated, and the response characteristic of arousal appeared, which then habituated as well. Longer intervals between stimuli required more presentations of the stimulus for habituation to occur in goldfish. Roach required more presentations of the stimulus than goldfish for the responses to habituate, and telencephalic ablation severely impaired habituation of arousal, though not fright responses, in this species. The results are discussed in relation to recent work on arousal, habituation, and telencephalic function in fish.

The primary structure of HLA-A32 suggests a region involved in formation of the Bw4/Bw6 epitopes.

All HLA-B locus molecules have either the Bw4 or Bw6 epitopes. In addition, the Bw4 epitope is found on HLA-Aw23, Aw24, and A32, and Bw6 is also found on HLA-Cw3. The structural basis for these determinants and the evolution of their distribution among products of the HLA-B locus has been a long standing puzzle. To identify residues that may be involved in these determinants, we have cloned a gene for A32 and sequenced the protein encoding exons. Comparison of the predicted protein sequence with other HLA-A,B,C sequences identified residues 79 through 83 of the alpha 1 domain as having a pattern of polymorphic substitution that correlates with the presence and absence of the Bw4 and Bw6 epitopes.

Molecular cloning of bovine class I MHC cDNA.

Two cDNA cloned from a Hereford cow B cell line (BL-3) have allowed the determination of the complete coding region for two class I molecules encoded by the bovine MHC (BoLA). The predicted protein sequences have all the features expected of expressed class I molecules that present peptide Ag to cytotoxic T cells. Comparison with class I molecules from other species strongly suggests these cDNA are derived from different genes and provides evidence for the existence of a second expressed class I BoLA locus. The BoLA proteins show greater similarity to HLA than to H-2 molecules, correlating with the cross-reactions of W6/32 and other murine anti-HLA-A,B,C mAb with BoLA molecules. The basis for the W6/32 epitope and the preferential association of H-2 class I H chains with bovine beta 2-m is examined.

Comparison of the structure of HLA-Bw47 to HLA-B13 and its relationship to 21-hydroxylase deficiency.

Adrenal 21-hydroxylase deficiency is strongly associated with HLA-Bw47. This rare HLA allele and the HLA-B13 allele are both found in positive genetic linkage disequilibrium with HLA-A3, -Cw6, -DR7 and also display serological cross-reactivity. To investigate the relationship between these two alleles at the structural level, the nucleotide sequences of the HLA-B13 and HLA-Bw47 genes have been determined. They differ by 28 nucleotides, resulting in 14 amino acid substitutions: 5 in the alpha 1 domain, 8 in the alpha 2 domain, and 1 in the transmembrane region. Comparison of HLA-Bw47 nucleotide sequence with other HLA-B sequences shows a segment of 228 bp identical with B44 in the alpha 1 domain and a segment of 218 bp identical with B27 in the alpha 2 domain, but only a 91 bp segment of identity with B13 in the alpha 1 domain. The complex pattern of substitutions and their degree of divergence indicate that HLA-B13 and HLA-Bw47 alleles are not related by a simple mutational event.

Role of cytotoxic T lymphocytes in murine cytomegalovirus infection.

Cell-mediated immunity is important in host control of CMV infection. A chromium release microcytoxicity assay was used to evaluate the role of cytotoxic T lymphocytes (CTL) in murine CMV infection. Within a few days after intranasal inoculation virus was detected in cultures of buffy-coat, spleens, anterior cervical lymph nodes and salivary glands. CTL were first detected on day 5 post-infection in spleen and peripheral blood, and on day 6 in anterior cervical nodes. The course of the CTL response approximated to that of virus titres during the acute phase of infection in the spleen and blood. The findings indicate that CTL are distributed to infected tissues and appear to be important during the acute, viraemic phase of infection.

HLA-A and B polymorphisms predate the divergence of humans and chimpanzees.

Major histocompatibility complex (MHC) glycoproteins bind processed fragments of proteins and present them to the receptors of T lymphocytes. The extraordinary polymorphism of class I MHC molecules in man (HLA-A, B and C) and mouse (H-2 K, D and L) poses many questions concerning their diversification and evolution. Comparison of allelic sequences within a species suggests diversity is generated by the assortment of point mutations into varied combinations by mechanisms of recombination and gene conversion. We have now compared class I MHC alleles in two closely related species: humans (Homo sapiens) and chimpanzees (Pan troglodytes). Chimpanzee homologues of HLA-A, HLA-B and a non-classical gene have been identified. No features distinguishing human and chimpanzee alleles could be found. Individual HLA-A or B alleles are more closely related to individual chimpanzee alleles than to other HLA-A or B alleles. These results show that a considerable proportion of contemporary HLA-A and B polymorphism existed before divergence of the chimpanzee and human lines. The stability of the polymorphism indicates that hyper-mutational mechanisms are not necessary to account for HLA-A, B and C diversity.

Gene conversion in the evolution of the human and chimpanzee MHC class I loci.

Sixty-five DNA sequences from human and chimpanzee major histocompatibility complex class I loci were searched for statistical evidence of past gene conversion. Twenty-four potential conversions were detected; they were distributed across both variable and conserved portions of the gene, and involved both classical and non-classical loci. The majority spanned less than 100 bp, comparable in length to the conversions observed in spontaneous mutations in mice. Both within-locus and between-locus conversions were observed. Certain areas of the antigen recognition site appear to have been the target for multiple conversion events. The implications of these findings for the evolution of the class I multigene family are discussed.

Diversity and diversification of HLA-A,B,C alleles.

The nucleotide sequences encoding 14 HLA-A,B,C and 5 ChLA-A,B,C molecules have been determined. Combining these sequences with published data has enabled the polymorphism in 40 HLA-A,B,C and 9 ChLA-A,B,C alleles to be analyzed. Diversity is generated through assortment of point mutations by recombinational mechanisms including gene and allelic conversions. The distribution and frequency of silent and replacement substitutions indicate that there has been positive selection for allelic diversity in the 5' part of the gene (exons 1 to 3) and for allelic homogenization and locus specificity in the 3' part of the gene (exons 4 to 8). These differences may correlate with the lengths of converted sequences in the two parts of the gene and frequency of the CpG dinucleotide. Locus-specific divergence of HLA-A,B, and C demonstrates that recombinational events involving alleles of a locus have been more important than conversion between loci. This contrasts with the predominance of gene conversion events in the evolution of mutants of the H-2Kb gene. However, a striking example of gene conversion involving HLA-B and C alleles of an oriental haplotype has been found. Comparison of human and chimpanzee alleles reveals extensive sharing of polymorphisms, confirming that diversification is a slow process, and that much of contemporary polymorphism originated in ancestral primate species before the emergence of Homo sapiens. There is less polymorphism at the HLA-A locus compared to HLA-B, with greater similarity also being seen between HLA-A and ChLA-A alleles than between HLA-B and ChLA-B alleles. Although greater diversity is seen in the 5' "variable" exons of HLA-B compared to HLA-A, there is increased heterogeneity in the 3' "conserved" exons of HLA-A compared to HLA-B.

Rapid cloning of HLA-A,B cDNA by using the polymerase chain reaction: frequency and nature of errors produced in amplification.

A method for cloning full-length HLA-A,B cDNA (1.1 kilobases) by using the polymerase chain reaction (PCR) is described. Six HLA-A,B alleles (HLA-A2, -A25, -B7, -B37, -B51, and -B57) were cloned, and their structures were determined. Multiple PCR clones for each allele were sequenced to obtain both an accurate consensus sequence and an "authentic" clone having that sequence. Sequences from 50 clones encoding five different alleles permit assessment of the frequency and nature of PCR-produced errors. These include recombinations, deletions, and insertions in addition to point substitutions. Authentic clones were obtained at a frequency of between 30% and 70%, and analysis of three or four clones generally should be sufficient for characterization of an allele.

Multiple genetic mechanisms have contributed to the generation of the HLA-A2/A28 family of class I MHC molecules.

The genetic events that produce diversity in class I MHC genes and proteins has been investigated by using a family of closely related HLA-A alleles. Five genes coding for HLA-A2.2Y, HLA-A2.3, and HLA-Aw68.2 have been isolated. Exon sequences are compared with the known sequences for HLA-A2.1, HLA-A2.2F, HLA-A2.4, HLA-Aw68.1, and HLA-Aw69. Pairwise comparison of the eight unique sequences shows that point mutation, reciprocal recombination, and gene conversion have all contributed significantly to the diversification of this family of alleles. These results are compared with those of other studies that have emphasized the role of gene conversion. A predominance of coding substitutions in the alpha 1 and alpha 2 domains is found, consistent with positive selection for polymorphism being a major factor in the fixation of these alleles. In the three cases examined, genes for phenotypically identical proteins gave identical nucleotide sequences, indicating that most, if not all, of the class I polymorphism is detectable by immunological methods. The apparent stability of the sequences suggests that the events generating some of the alleles occurred before the origin of modern Homo sapiens.

HLA-B51 and HLA-Bw52 differ by only two amino acids which are in the helical region of the alpha 1 domain.

Genes encoding the serologically cross-reactive HLA-B51 and HLA-Bw52 molecules were isolated and the exons sequenced. HLA-B51 genes obtained from Caucasian and Oriental individuals were identical. HLA-Bw52 differs from HLA-B51 by four nucleotide substitutions in exon 2 encoding the alpha 1 domain. These comprise one isolated silent substitution in codon 23 and a cluster of three coding substitutions in codons 63 and 67. Amino acid substitutions of N----E at position 63 and F----S at position 67 are the only differences between HLA-B51 and HLA-Bw52 and these residues are postulated to form HLA-B51 specific epitopes. HLA-B51 could have been formed from HLA-Bw52 by the combination of a genetic exchange with HLA-B8 and a point mutation. Similarity of HLA-B51 and HLA-Bw52 with HLA-Bw58 suggest they also share a common ancestor.

Nature of polymorphism in HLA-A, -B, and -C molecules.

Diversity in 39 HLA-A, -B, and -C molecules is derived from 20 amino acid positions of high variability and 71 positions of low variability. Variation in the structurally homologous alpha 1 and alpha 2 domains is distinct and may correlate with partial segregation of peptide and T-cell receptor binding functions. Comparison of 15 HLA-A with 20 HLA-B molecules reveals considerable locus-specific character, due primarily to differences at polymorphic residues. The results indicate that genetic exchange between alleles of the same locus has been a more important mechanism in the generation of HLA-A, -B, and -C diversity than genetic exchange events between alleles of different loci.