Histological assessment of the presence or absence of infection in fracture non-union

BACKGROUND

Infection is a major cause of non-unions. Infection is not always evident clinically, nor on bacteriological analysis. If it is untreated, non-union treatment may fail.

AIM

To establish whether histological analysis is of value as an adjunct to microbiology in establishing the diagnosis of infection.

METHODS

Sixty patients who had both bacteriological and histological analysis of their non-unions were studied. Infection was indicated by an acute inflammatory response. In 45 of the 60 fractures, microbiological and clinical diagnoses were in agreement; in this subset the histology results were compared to the established diagnoses.

RESULTS

The histological diagnosis for the 45 fractures in the group with a definite diagnosis gave four false negatives but no false positives. This represents a sensitivity of 87.1%, (95% CI, 70-96%) and a 100% specificity (95% CI, 77-100%). The overall accuracy was 91.1%. (95% CI, 79-98%) The predictive value of a positive test was 100% and of a negative test was 77.8%. In 25% of the series a definite diagnosis could not be made with purely clinical and microbiological information; with the additional histological information it was possible to determine the infection status of the non-union.

CONCLUSION

Histology is of particular use when the microbiology is negative or equivocal.

Pulmonary embolism: clinical features and management

Pulmonary embolism (PE) often presents diagnostic difficulties, as its presentation is varied and non-specific. This article attempts a logical approach to the management of a patient with suspected PE, starting with how it may occur, the assessment of clinical probability of PE and subsequent investigations and treatment.

Peptides corresponding to the N and C termini of IkappaB-alpha, -beta, and -epsilon as probes of the two catalytic subunits of IkappaB kinase, IKK-1 and IKK-2

The signal-inducible phosphorylation of serines 32 and 36 of IkappaB-alpha is the key step in regulating the subsequent ubiquitination and proteolysis of IkappaB-alpha, which then releases NF-kappaB to promote gene transcription. The multisubunit IkappaB kinase (msIKK) responsible for this phosphorylation contains two catalytic subunits, termed IKK-1 and IKK-2. Using recombinant IKK-2, a kinetic pattern consistent with a random, sequential binding mechanism was observed with the use of a peptide corresponding to amino acids 26-42 of IkappaB-alpha. Values of 313 microM, 15.5 microM, and 1.7 min(-1) were obtained for K(peptide), K(ATP), and k(cat), respectively. The value of alpha, a factor by which binding of one substrate changes the dissociation constant for the other substrate, was determined to be 0.2. Interestingly, the recombinant IKK-1 subunit gave similar values for alpha and K(ATP), but values of 1950 microM and 0.016 min(-1) were calculated for K(peptide) and k(cat), respectively. This suggests that the IKK-2 catalytic subunit provides nearly all of the catalytic activity of the msIKK complex with the IKK-1 subunit providing little contribution to catalysis. Using peptides corresponding to different regions of IkappaB-alpha within amino acids 21-47, it was shown that amino acids 31-37 provide most binding interactions (-4.7 kcal/mol of binding free energy) of the full-length IkappaB-alpha (-7.9 kcal/mol) with the IKK-2. This is consistent with the observation that IKK-2 is able to phosphorylate the IkappaB-beta and IkappaB-epsilon proteins, which have consensus phosphorylation sites nearly identical to that of amino acids 31-37 of IkappaB-alpha. A peptide corresponding to amino acids 279-303 in the C-terminal domain of IkappaB-alpha was unable to activate IKK-2 to phosphorylate an N-terminal peptide, which is in contrast to the results observed with the msIKK. Moreover, the IKK-2 catalyzes the phosphorylation of the full-length IkappaB-alpha and the amino acid 26-42 peptide with nearly equal efficiency, while the msIKK catalyzes the phosphorylation of the full-length IkappaB-alpha 25,000 times more efficiently than the 26-42 peptide. Therefore, the C terminus of IkappaB-alpha is important in activating the msIKK through interactions with subunits other than the IKK-2.

The multisubunit IkappaB kinase complex shows random sequential kinetics and is activated by the C-terminal domain of IkappaB alpha

The multisubunit IkappaB kinase (IKK) catalyzes the signal-inducible phosphorylation of N-terminal serines of IkappaB. This phosphorylation is the key step in regulating the subsequent ubiquitination and proteolysis of IkappaB, which then releases NF-kappaB to promote gene transcription. As measured by 33P incorporation into a GST-IkappaB alpha fusion protein, varying both the concentration of GST-IkappaB alpha and [gamma-33P]ATP resulted in a kinetic pattern consistent with a random, sequential binding mechanism. Values of 55 nM and 7 microM were obtained for the dissociation constants of GST-IkappaB alpha and ATP, respectively. The value of alpha, a factor by which binding of one substrate changes the dissociation constant for the other substrate, was determined to be 0.11. This indicates that the two substrates bind in a cooperative fashion. Peptides corresponding to either amino acids 26-42 (N-terminal peptide) or amino acids 279-303 (C-terminal peptide) of IkappaB alpha inhibited the IKK-catalyzed phosphorylation of GST-IkappaB alpha; the C-terminal peptide, unexpectedly, was more potent. The inhibition by the C-terminal peptide was competitive with respect to GST-IkappaB alpha and mixed with respect to ATP, which verified the sequential binding mechanism. The C-terminal peptide was also a substrate for the enzyme, and a dissociation constant of 2.9-6.2 microM was obtained. Additionally, the N-terminal peptide was a substrate (Km = 140 microM). Competitive inhibition of the IKK-catalyzed phosphorylation of the C-terminal peptide by the N-terminal peptide indicated that the peptides are phosphorylated by the same active site. Surprisingly, the presence of the C-terminal peptide greatly accelerated the rate of phosphorylation of the N-terminal peptide as represented by a 160-fold increase in the apparent second-order rate constant (kcat/Km). These results are consistent with an allosteric site present within IKK that recognizes the C terminus of IkappaB alpha and activates the enzyme. This previously unobserved interaction with the C terminus may represent an important mechanism by which the enzyme recognizes and phosphorylates IkappaB.

Patterns and potential value of cardiac troponin I elevations after pediatric cardiac operations

BACKGROUND

Perioperative myocardial injury is a major determinant of postoperative cardiac dysfunction for congenital heart disease, but its assessment during this period is difficult. The objective of this study was to determine the suitability of using postoperative serum concentrations of cardiac troponin I (cTnI) for this purpose.

METHODS

Cardiac troponin I levels were measured serially in the serum of patients undergoing uncomplicated repairs of atrial septal defect (n = 23), ventricular septal defect (n = 16) or tetralogy of Fallot (n = 16). The concentrations were correlated with intraoperative parameters (cardiopulmonary bypass time, aortic cross-clamp time, and cardiac bypass temperature), and postoperative parameters (magnitude of inotropic support, duration of intubation, and postoperative intensive care and hospital stay).

RESULTS

Postoperative absolute cTnI levels were lesion specific, with a pattern of increase and decrease similar for each lesion. For the total cohort, significant correlations between postoperative cTnI levels at all times (r = 0.43 to 0.83, p < 0.05) until 72 hours were noted for all parameters, except for cardiac bypass temperature. When evaluated as individual procedure groups, no significant relationships were noted in the atrial septal defect group, whereas postoperative cTnI levels were more strongly correlated with all intraoperative and postoperative parameters in the ventricular septal defect group than in the tetralogy of Fallot group.

CONCLUSIONS

This study suggests that cTnI values immediately after operation reflect the extent of myocardial damage from both incisional injury and intraoperative factors. Cardiac tropinin I levels in the first hours after operation for congenital heart disease are a potentially useful prognostic indicator for difficulty of recovery.

Acyanotic cardiac lesions with normal pulmonary blood flow

This article, the second in a series discussing acyanotic cardiac defects, examines acyanotic cardiac defects with normal pulmonary blood flow: pulmonary stenosis, peripheral pulmonary stenosis, coarctation of the aorta, and valvular aortic stenosis. A similar defect, interrupted aortic arch, is also discussed. The hemodynamics, clinical presentation, differential diagnosis, surgical repair, and medical management of each defect are presented. Parental teaching needs are identified and discussed.

Chromosome abnormalities in congenital heart disease

Refinements in cytogenetic techniques have promoted progress in understanding the role that chromosome abnormalities play in the cause of congenital heart disease. To determine if mutations at specific loci cause congenital heart disease, irrespective of the presence of other defects, and to estimate the prevalence of chromosome abnormalities in selected conotruncal cardiac defects, we reviewed retrospectively cytogenetic and clinical databases at St. Louis Children's Hospital. Patients with known 7q11.23 deletion (Williams syndrome), Ullrich-Turner syndrome (UTS), and most autosomal trisomies were excluded from this analysis. Two groups of patients were studied. Over a 6.5-year period, 57 patients with chromosomal abnormalities and congenital heart disease were identified. Of these, 37 had 22q11 deletions; 5 had abnormalities of 8p; and 15 had several other chromosome abnormalities. The prevalence of chromosome abnormalities in selected conotruncal or aortic arch defects was estimated by analysis of a subgroup of patients from a recent 22-month period. Chromosome abnormalities were present in 12% of patients with tetralogy of Fallot, 26% in tetralogy of Fallot/pulmonary atresia, 44% in interrupted aortic arch, 12% in truncus arteriosus, 5% in double outlet right ventricle, and 60% in absent pulmonary valve. We conclude that chromosome analysis should be considered in patients with certain cardiac defects. Specifically, fluorescent in situ hybridization (FISH) analysis of 22q11 is indicated in patients with conotruncal defects or interrupted aortic arch. High resolution analysis should include careful evaluation of the 8p region in patients with either conotruncal or endocardial cushion defects.

Acyanotic lesions with increased pulmonary blood flow

The neonatal nurse is a vital link in the recognition and management of infants born with congenital heart disease. This article examines the acyanotic cardiac defects with increased pulmonary blood flow: patent ductus arteriosus, atrial septal defect, ventricular septal defect, and endocardial cushion defects. The hemodynamics, clinical presentation, differential diagnosis, surgical repair, and medical management of each defect are presented. Parental teaching needs are identified and discussed.

Deletion within chromosome 22 is common in patients with absent pulmonary valve syndrome

Interstitial deletions in chromosome 22 and features associated with CATCH-22 syndrome have been reported in patients with conotruncal congenital heart anomalies. Absent pulmonary valve syndrome is characterized by absent or rudimentary pulmonary valve cusps, absent ductus arteriosus, conoventricular septal defect, and massive dilation of the pulmonary arteries. Because absence of the ductus arteriosus is a key element in the pathogenesis of this syndrome and aortic arch malformations are frequently seen in patients with CATCH-22 syndrome, we hypothesized that patients with absent pulmonary valve syndrome would have a high incidence of deletions in the critical region of chromosome 22. Eight patients with absent pulmonary valve syndrome were studied. Metaphase preparations were examined with fluorescent in situ hybridization of the N25 (D22S75) probe to the critical region of chromosome 22q11.2. Deletions were detected in 6 of 8 patients. The presence of deletions in chromosome 22 in most of the patients we have examined with a diagnosis of absent pulmonary valve syndrome supports a specific genetic and embryologic mechanism involving the interaction of the neural crest and the primitive aortic arches as one cause of congenital absence of the pulmonary valve.

Use of split-skin grafting in the treatment of chronic leg ulcers

Chronic leg ulcers are a common problem for which many different forms of treatment have been used. In this study we reviewed the results of split-skin grafting of ulcers of different aetiologies; 26 patients were reviewed. The mean duration of ulceration was 27.5 months. Of the 28 ulcers, ten were due to venous disease, three arterial disease, six rheumatoid arthritis, seven traumatic, and two diabetic. Healing rates of 85% for traumatic and 67% for rheumatoid ulcers were achieved, whereas rates of only 20% and 33% were achieved for venous and arterial ulcers (P < 0.02 Fisher's exact test). We conclude that in the presence of vascular disease, split-skin grafting is not an effective treatment for chronic leg ulceration. Vascular assessment and treatment should be carried out before attempting skin grafting.

Malignant schwannoma mistakenly diagnosed as carpal tunnel syndrome

A rare nerve sheath tumour masquerading as carpal tunnel syndrome is described. It arose in a digit, with perineural spread proximally along the median nerve.

Unexpected similarities in the crystal structures of the Mcg light-chain dimer and its hybrid with the Weir protein

The covalently linked hybrid of two human lambda-type light chains (Mcg and Weir) crystallizes as trigonal bipyramids in ammonium sulfate [Ely et al., Molec. Immun. 22, 85-92 (1985)]. While markedly different in appearance from the barrel-shaped crystals of the parental Mcg dimer, the bipyramids of the hybrid have the same space group: trigonal P3(1)21. Moreover, the unit cell dimensions are practically identical: a = 72.3 A in both proteins; c = 188.1 A in the hybrid and 185.9 A in the Mcg dimer. These observations imply that the crystal packing and the main features of the three-dimensional structures are closely similar in the Mcg X Weir hybrid and the Mcg dimer. The "constant" domains of the Mcg and Weir proteins belong to the same genetic subclass and were expected to interact in comparable ways in hybrids and parental dimers. However, the overall similarities in the "variable" domain pairs in the hybrid and Mcg dimer were completely unpredicted, since the amino acid sequences of the heterologous variable domains differ by 36 residues. By difference Fourier analysis the Weir light chain has been tentatively identified as monomer 1 (heavy-chain analogue) and the Mcg protein as monomer 2 (light-chain analogue) in the hybrid dimer. Substitutions in key positions in the hypervariable loops explain the differences in binding activity of the Mcg and Weir dimers. In the Mcg dimer bis(dinitrophenyl)lysine spans two relatively spacious subsites (A and B), with primary contacts involving tyrosines 34 and 38 of monomer 2. The Weir dimer, which does not bind dinitrophenyl ligands, has serine and phenylalanine in homologous positions. Moreover, the bilateral replacement of valine 48 and serine 91 in Mcg by leucine and methionine in the Weir dimer should effectively block access to subsite B. In the hybrid binding activity for bis(dinitrophenyl)lysine is restored because the Mcg light chain is present as the monomer 2 subunit.

Three-dimensional structure of the Mcg IgG1 immunoglobulin

The three-dimensional structure of an IgG1(lambda) immunoglobulin from a patient (Mcg) with amyloidosis was determined at 6.5-A resolution with X-ray diffraction techniques. The protein crystallized from water in the space group C2221, with a = 87.8, b = 111.3 and c = 186.3 A; the crystallographic asymmetric unit was a half-molecule consisting of one light and one heavy chain. The structure was solved by the multiple isomorphous replacement method with five heavy-atom derivatives. Electron density maps were interpreted with the aid of a protein modeling system used in conjunction with an Evans and Sutherland Picture System II graphics station. IgG1 molecules were tightly packed in the crystal lattice, with numerous intermolecular contacts. The two-fold axis relating identical halves of each molecule was found to be parallel to the y crystallographic axis. Electron density modules collectively representing one molecule were identified as three lobes representing the two antigen-binding (Fab) arms and the Fc region. An interchain disulfide bond connecting the two CL domains was located on the molecular diad and used as a landmark in the interpretation of the electron density map. A computer graphics method was developed to produce a solid image model of the IgG1 molecule in any prescribed orientation.

A rare cause of ischemic colitis: polyarteritis nodosa

This paper details the first case report of a patient with fulminant, gangrenous, ischemic colitis caused by polyarteritis nodosa which was successfully treated surgically. Ischemic colitis is a rare complication of polyarteritis nodosa. It should be suspected in patients with a past history of polyarteritis nodosa who develop abdominal pain and rectal bleeding. The identification of cutaneous lesions preoperatively and or mesenteric or serosal vascular beading at operation are helpful in establishing this diagnosis. Prognosis is generally determined by the extent of systemic involvement by polyarteritis nodosa, and death is generally associated with renal failure.

Structure of concanavalin A at 4.25-ångström resolution

An electron density map produced by x-ray diffraction analysis of concanavalin A has been calculated to 4.25 A from data of three isomorphous heavy atom derivatives. The crystals are orthorhombic, with unit-cell dimensions of 63.1, 87.0, and 89.2 A for a, b, and c, respectively. The space group is I222, with eight asymmetric units per unit cell. The crystal asymmetric unit contains 27,000 daltons of protein and reflects the chemically unique component (protomer) within the oligomer. Separate chemical studies indicate that the protomer consists of two different polypeptide chains. Four protomers cluster around the intersection of three mutually perpendicular two-fold rotation axes to form a molecule of 108,000 daltons. The molecule can also be subdivided into two-protomer units of 54,000 daltons. Within the two-protomer unit, there are significantly more contacts joining the protomers than there are between adjacent two-protomer units that form the total molecule. These results provide a possible explanation for disagreement in molecular weights obtained in previous ultracentrifugal studies.