Prospective evaluation of criteria for microbiological diagnosis of prosthetic-joint infection at revision arthroplasty. The OSIRIS Collaborative Study Group

A prospective study was performed to establish criteria for the microbiological diagnosis of prosthetic joint infection at elective revision arthroplasty. Patients were treated in a multidisciplinary unit dedicated to the management and study of musculoskeletal infection. Standard multiple samples of periprosthetic tissue were obtained at surgery, Gram stained, and cultured by direct and enrichment methods. With reference to histology as the criterion standard, sensitivities, specificities, and likelihood ratios (LRs) were calculated by using different cutoffs for the diagnosis of infection. We performed revisions on 334 patients over a 17-month period, of whom 297 were evaluable. The remaining 37 were excluded because histology results were unavailable or could not be interpreted due to underlying inflammatory joint disease. There were 41 infections, with only 65% of all samples sent from infected patients being culture positive, suggesting low numbers of bacteria in the samples taken. The isolation of an indistinguishable microorganism from three or more independent specimens was highly predictive of infection (sensitivity, 65%; specificity, 99.6%; LR, 168.6), while Gram staining was less useful (sensitivity, 12%; specificity, 98%; LR, 10). A simple mathematical model was developed to predict the performance of the diagnostic test. We recommend that five or six specimens be sent, that the cutoff for a definite diagnosis of infection be three or more operative specimens that yield an indistinguishable organism, and that because of its low level of sensitivity, Gram staining should be abandoned as a diagnostic tool at elective revision arthroplasty.     

Risk factors in heart transplantation. A statistical study of New Zealand cases

The bioactivation of N-nitrosoamines and polycyclic aromatic hydrocarbons (PAH) is mediated by the mixed function oxidase system, which includes dimethylnitrosamine N-demethylase I (DMN-dI), arylhydrocarbon hydroxylase (AHH), cytochrome P-450, cytochrome b5 and NADPH-cytochrome c reductase of liver microsomes. The present study shows the influence of N-nitroso compounds on the activities of the above-mentioned enzymes. Single-dose treatment (20 mg/kg body weight) of male mice with ethylbutylnitrosamine, propylbutylnitrosamine, or dibutylnitrosamine: increased (1) the activity of DMN-dI by 108%, 104%, 51%, respectively; (2) the cytochrome P-450 content by 106%, 72%, 51%, respectively; (3) the activity of AHH by 95%, 106%, 80% respectively; (4) the cytochrome b5 content by 164%, 97%, 94% respectively; and (5) decreased the activity of NADPH-cytochrome c reductase by 55%, 50% and 45%, respectively. Methylpropylnitrosamine decreased the activity of DMN-dI by 44% and the P-450 content by 50%. Diphenylnitrosamine also decreased cytochrome P-450 by 54%, AHH activity by 64% but increased the activity of DMN-dI by 42%, the cytochrome b5 content by 159% and NADPH-cytochrome c reductase activity by 57%. It seems from this study that the activity of AHH is dependent on P-450 content but DMN-dI is not since the compounds that increased or decreased the activity of AHH had parallel effects on P-450 content. Also, the extent to which the altered activities of DMN-dI, P-450, AHH, cytochrome b5 and NADPH-cytochrome c reductase depends on the type of alkyl groups linked to the nitroso group.     

Spectroscopic evidence for a conformational transition in horseradish peroxidase at very low pH

Resonance Raman (RR), electronic absorption, and circular dichroism (CD) spectroscopies of the ferric, ferrous, and ferrous-CO forms of horseradish peroxidase (HRP-C) at pH 3.1 are reported. The CD spectra in the UV region show only a small decrease in the alpha-helical content upon pH lowering, whereas dramatic changes are observed in the Soret region. The final form of ferric HRP-C is 5-coordinate high-spin heme whose histidine ligand is replaced by a water ligand with a polar character. The electronic and CD spectra show the presence of an intermediate form with a 6-coordinate heme. Therefore, the cleavage of the proximal Fe-imidazole bond is preceded by the binding of a distal water molecule. For the ferrous form of HRP-C, the pH-dependence of the absorption spectra revealed only the native form in the range pH 5-7 and an unfolded form with a Soret maximum at 383 nm at pH 3.1. An intermediate state, characterized by a Soret maximum at 424 nm, was observed only in a transient way, within a few milliseconds. A metastable and a final species are observed also for the ferrous-CO complex at pH 3.1, as proved by isosbestic points in the electronic absorption spectra. The two forms show different RR nu(Fe-C) and IR nu(CO) modes. The metastable form corresponds to a heme where histidine is replaced by water. The final form is due to the displacement of the water ligand by the proximal histidine. We propose a kinetic model to account for our results at pH 3.1 for the ferric, ferrous, and ferrous-CO forms.     

The difficulty of obtaining immunologic responses in mucosae. Use of coadjuvants]

The search of immunogenicity represents a real problem to be solved with the new techniques to vaccines design. Despite of numerous initiatives to increase the immune response at mucosal sites, there are few substances available to exert an adequate immunogenicity in mucosal compartments. On this hand the research on mucosal adjuvants has arise interest. Mechanism of both: immunogenicity and adjuvanticity, were reviewed putting emphasis mainly in two mucosal adjuvants, cholera toxin and the protoxin Cry1Ac from Bacillus thuringiensis.     

Diagnosis and staging of pancreatic neoplasms

The relative value of current approaches to the diagnosis and staging of pancreatic cancer is discussed. A rational sequence of testing is recommended based on the clinical presentation of the patient and the local institutional expertise and facilities that are available.     

Novel aspects of the regulation of a cDNA (Arf1) from Chlamydomonas with high sequence identity to animal ADP-ribosylation factor 1

ADP-ribosylation factor (ARF) is a highly conserved, low molecular mass (ca. 21 kDa) GTP-binding protein that has been implicated in vesicle trafficking and signal transduction in yeast and mammalian cells. However, little is known of ARF in plant systems. A putative ARF polypeptide was identified in subcellular fractions of the green alga Chlamydomonas reinhardtii, based on [32P]GTP binding and immunoblot assays. A cDNA clone was isolated from Chlamydomonas (Arf1), which encodes a 20.7 kDa protein with 90% identity to human ARF1. Northern blot analyses showed that levels of Arf1 mRNA are highly regulated during 12 h/12 h light/dark (LD) cycles. A biphasic pattern of expression was observed: a transient peak of Arf1 mRNA occurred at the onset of the light period, which was followed ca. 12 h later by a more prominent peak in the early to mid-dark period. When LD-synchronized cells were shifted to continuous darkness, the dark-specific peak of Arf1 mRNA persisted, indicative of a circadian rhythm. The increase in Arf1 mRNA at the beginning of the light period, however, was shown to be light-dependent, and, moreover, dependent on photosynthesis, since it was prevented by DCMU. We conclude that the biphasic pattern of Arf1 mRNA accumulation during LD cycles is due to regulation by two different factors, light (which requires photosynthesis) and the circadian clock. Thus, these studies identify a novel pattern of expression for a GTP-binding protein gene.     

Fatal Campylobacter jejuni infection in a patient splenectomised for thalassaemia

A 35 year old man with a fatal Campylobacter jejuni infection is described. He had HbE/beta zero thalassaemia and had undergone splenectomy nine months previously for hypersplenism; he also had chronic hepatitis C infection. He presented with high grade fever but no gastrointestinal symptoms and rapidly progressed to septicaemic shock and hepatic encephalopathy despite treatment with penicillin, gentamicin, and, later, chloramphenicol and ceftazidime. Only one case of Campylobacter jejuni septicaemia occurring post-splenectomy has been reported previously, also in an iron overloaded thalassaemia patient. Unusual Gram negative bacilli must be covered by the chosen antibiotic regimen when splenectomised thalassaemic patients present with high grade fever.