Childhood asthma predisposes to spontaneous pneumomediastinum.

Spontaneous pneumomediastinum is a rare condition for which potentially life threatening differential diagnoses must be excluded. A case is presented of a young man with a history of severe childhood asthma, who was successfully treated conservatively.

Thymic carcinoma--analysis of nineteen clinicopathological studies.

BACKGROUND: Primary thymic carcinomas are rare tumours with nonuniform management protocols and poor prognosis due to delayed diagnosis and highly malignant behaviour. This review summarises the major clinicopathological studies to assess more fully the prognostic importance of tumour histology and staging as well as treatment benefit. METHODS: A Medline search from 1966 to date was carried out and relevant references gleaned from these. Nineteen clinicopathological studies form the core of this review. Demographic data and clinical features were examined in all studies. Correlation of outcome with histology was possible in fifteen of the studies and with tumour staging in thirteen. RESULTS: Thymic carcinomas occur most commonly in the fifth to sixth decades of life, usually presenting with symptoms of space occupation or invasion. Paraneoplastic syndromes are rarely associated, except with the well differentiated thymic carcinoma. Of 140 thymic carcinomas, 40 were squamous cell, 19 were spindle cell and 16 were lymphoepithelioma-like. Completely resected stage I and II tumours demonstrated the best survival. CONCLUSIONS: Complete surgical resection is taken to be the desired treatment, but the continued high mortality and relapse rates and the variable benefit of adjuvant therapies challenge this strategy.

Videothoracoscopic drainage of mediastinal abscess: an alternative to thoracotomy.

A late-presenting high esophageal perforation that resulted in a massive mediastinal abscess and bronchopleural fistula in an elderly moribund patient unfit for radical surgery was successfully drained using a videothoracoscopic technique.

Aorto-atrial fistula after operated type A dissection.

The development of a fistula between the aorta and right atrium is a rare complication of ascending aortic dissection and has a high mortality if not diagnosed and surgically treated. Clinical diagnosis is best supported by specialised imaging. In addition it may present technically very challenging problems. We report the first case which follows aortic root replacement for an acute type A dissection. Aorto-right atrial fistula (AoRAF) rarely complicates ascending aortic dissection. We report the first case to follow corrective surgery for aortic dissection.

Relocation of the internal mammary artery graft in a case of coronary-subclavian steal.

Reverse flow in the internal mammary artery coronary graft in the presence of subclavian stenosis is rare. We describe a 67-year-old man who 7 years after coronary artery surgery was admitted with left subclavian artery stenosis and retrograde flow in the pedicled left internal mammary artery graft. Subsequent redo triple coronary artery bypass grafts included regrafting the left internal mammary artery graft to a new vein conduit.

G(i) activator region of alpha(2A)-adrenergic receptors: distinct basic residues mediate G(i) versus G(s) activation.

The structural determinants of G protein coupling versus activation by G protein-coupled receptors are not well understood. We examine the role of two distinct basic regions in the carboxyl terminal portion of the third intracellular loop of the alpha(2A)-adrenergic receptor to dissect these aspects of function. Changing three arginines to alanines by mutagenesis and stable expression in Chinese hamster ovary-K1 cells impaired the alpha(2)-adrenergic receptor G(s)-mediated stimulation of cyclic AMP (cAMP) accumulation, whereas G(i)-mediated inhibition was normal. When two (B2) or three (B3) basic residues closer to transmembrane span 6 were mutated to alanine, normal ligand binding was observed, but G(i)-mediated inhibition of cAMP accumulation showed 20-fold and 50-fold decreases in agonist potency for the B2 and B3 mutants, respectively. Surprisingly, a normal G(s) response was seen for the B2 mutant, and the B3 mutant showed only a 6-fold decrease in agonist potency. Mutation of both the three alanines and B3 residues to alanines showed a 200-fold decrease in agonist potency for G(i)-mediated inhibition of cAMP accumulation, whereas the G(s) response was nearly completely eliminated. The three basic residues (which include the BB of the BBXXF motif) play a role as G(i) activators rather than in receptor-G protein coupling, because high-affinity agonist binding is intact. Thus, we have identified three basic residues required for activation of G(i) but not required for receptor-G protein coupling. Also, distinct basic residues are required for optimal G(i) and G(s) responses, defining a microspecificity determinant within the carboxyl terminal portion of the third intracellular loop of the alpha(2a) adrenergic receptor.

Delayed presentation of foreign body reaction secondary to retained pacing wires.

Temporary pacing wires are often left behind, assumed not to cause problems. We present 2 cases of delayed presentation of anterior mediastinal foreign body reaction secondary to retained pacing wires after coronary operations performed more than 5 years previously.

Two closely related kappa variable region pseudogenes pose an evolutionary paradox.

Two pseudogenes belonging to the Igk-V1 variable region group have been isolated from BALB/c mice. The genes share greater than 96.5% identity of nucleotide sequence in a 1800 base pair (bp) region surrounding the coding region, but deletions of 221 bp and 84 bp have removed essential sequences from the two genes. As the deletions are different in the two pseudogenes, they must have occurred independently in each gene during or subsequent to the duplication event which gave rise to the genes from a common ancestral gene. Polymerase chain reaction analysis was used to identify the pseudogenes in inbred strains of mice. BALB/c (Igkc) and AKR (Igka), prototype strains representative of the predominant kappa haplotypes, possess both pseudogenes but no intact copy. Only one of the pseudogenes was present in SJL (Igka). Strains C58, c.C58 (Igkd) and NZB (Igkb) possessed an intact version of the gene. This distribution of haplotypes is consistent with a close linkage of the pseudogenes with other Igk-V1 genes on chromosome 6. The translated amino acid sequence of the pseudogenes indicates that prior to their acquiring deletions they encoded typical Igk-V1 variable regions except for an unusual FR2 region, in which the conserved proline at position 44 is replaced by leucine and the normally hydrophobic position 36 was occupied by histidine. Possible mechanisms to explain the occurrence of deletions in both of the pseudogenes in the recent evolution of BALB/c are discussed. One explanation would be that the two genes were already nonfunctional at the time of the duplication so that the subsequent deletions represent neutral events which became fixed in the inbred strains by a process of genetic drift. Alternatively, if the genes were functional at the time of duplication, their rapid loss due to deletion events suggests that negative selection may have acted to eliminate the genes from the V-region repertoire.