Association of MBL2 gene exon 1 variants with autoimmune thyroid disease in Brazilian patients

We investigated the association between MBL2 gene exon 1 functional polymorphisms and autoimmune thyroid disease (AITD) in 163 Brazilian patients (87 with Hashimoto thyroiditis, HT; 76 with Graves' disease) and 214 healthy controls. Individuals carrying MBL2 O allele are at higher risk of developing AITD (OR = 1.58, 95% CI: 1.11-2.26; P-value = 0.009) and HT (OR = 1.67, 95% CI: 1.09-2.55; P-value = 0.013) as suggesting a possible role for mannose-binding lectin in influencing disease susceptibility.

Phase I-II study on isolation antiblastic fotemustine perfusion after dacarbazine chemosensitization for advanced melanoma of the extremities

Isolation limb perfusion (ILP) is the treatment of choice for locally advanced limb melanoma. With melphalan, the referral drug, complete response (CR) is achieved in about 50% of patients, but significant local toxicity occurs in up to 30%. The aim of the present phase I-II study was to challenge fotemustine (F) in ILP after systemic chemosensitization with dacarbazine (DTIC), given its lower toxicity and greater efficacy, as reported in a previous pilot study. Eleven patients with locally advanced limb melanoma were subdivided into triplets, and given F ILP at escalating doses (starting from 25 mg/l) after intravenous administration of 500 mg/m2 DTIC. Acute and chronic locoregional and systemic toxicity, tumour response and clinical outcome were evaluated. Two patients in the first triplet had G3-G4 local toxicity, so that the scheduled F dosage was halved. At drug levels of 12.5, 15.6 and 18.2 mg/l, local toxicity decreased, but only one of eight patients showed CR. The trial was then interrupted due to the low tolerability and poor efficacy of this perfusion regimen. At present, F ILP after DTIC chemosensitization should not be recommended for the treatment of locally advanced limb melanoma.

Pressure-induced formation of inactive triple-shelled rotavirus particles is associated with changes in the spike protein Vp4

Rotaviruses are non-enveloped, triple-shelled particles that cause enteritis in animals and humans. The interactions among the different viral proteins located in the three concentric layers make the rotavirus particle an excellent model for physico-chemical and biological studies of viral assemblage. SA11-4S rotaviruses subjected to high pressure were inactivated by more than five log units. After pressure treatment, the particles were recovered with slight structural changes when compared to the control. Electron microscopy suggested subtle changes in the viral outer layer in some pressurised particles. Fluorescence spectroscopy showed that much more dramatic changes were produced by urea denaturation than by pressure. Based on the fluorescence spectrum, the genome resistance to ribonuclease, and the absence of changes in hydrodynamic properties, there was little or no disruption of the capsid under pressure. On the other hand, hemagglutination assays indicated that the main component affected by pressure was the spike protein VP4, thus accounting for changes in interaction with host cells and greatly reduced infectivity. The changes leading to inactivation did not cause removal of VP4 from the outer capsid, as verified by size-exclusion chromatography. Antibodies raised against pressurised material were as effective as antibodies raised against the intact virus, based on their neutralisation titre in plaque reduction assays, enzyme-linked immunosorbent assays and direct interaction with the particle, as measured by gel-filtration chromatography. Therefore, the new conformation of the pressurised particle did not result in loss of immunogenicity. We propose that pressure alters the receptor-binding protein VP4 by triggering changes similar to those produced when the virus interacts with target cells. As the changes in VP4 conformation caused by pressure occur prior to virus exposure to target cells, it leads to non-infectious particles and may lead to the exposure of previously occult epitopes, important for vaccine development.

Allelic distribution of four tetranucleotide repeat loci (D3S1358, D18S51, D19S253, and FGA) in a population from Porto (North Portugal)

Allele frequencies for four short tandem repeat loci were determined in a population sample from Porto (North Portugal), using the polymerase chain reaction (PCR), in order to investigate possible genetic differences between populations from the center and north of Portugal. After denaturing PAGE electrophoresis, nine alleles were identified for D3S1358 (n = 256), 13 alleles for D18S51 (n = 235), 10 alleles for D19S253 (n = 238), and 15 alleles for FGA (n = 181). No deviations from Hardy-Weinberg equilibrium were found. The allele frequencies observed are similar to those of the Portuguese population compared except for the D3S1358 system.

Isolated limb perfusion with fotemustine after chemosensitization with dacarbazine in melanoma

Isolated limb perfusion (ILP) has been reported as the most effective treatment for localized recurrent melanoma of the limbs. In terms of local and regional control with melphalan, complete remission is achieved in about 40% of patients, with frequent toxicity causing significant short-term disability in many and long-term incapacity in a few. Since 1989, several studies have reported success using a combination of fotemustine and dacarbazine (DTIC) in the systemic treatment of disseminated melanoma and brain metastasis. In May 1995, we began a pilot study with systemic DTIC 400 mg/m2 given intravenously about 4 h before ILP using fotemustine in an intra-arterial bolus of 100-150 mg/m2 as the perfusion agent. By July 1996, 10 patients had been included in the study. The results were evaluated in terms of the response rate (five complete responses and one partial response in the six patients who could be evaluated), local toxicity (nine patients with level I and one with level II, measured on the Wieberdink scale) and systemic toxicity (nine patients with level 0 and one with level 1, measured on the World Health Organization scale). Treatment was effective, with a similar response rate to that obtained with melphalan but with much lower toxicity, so this protocol may represent an innovation in loco-regional therapy and should be further investigated in a large trial.

Population study of the HUMTH01, HUMVWA31A, HUMF13A1, and HUMFES/FPS STR polymorphisms in the north of Portugal

Allele and genotype frequencies of four short tandem-repeat loci were determined in a population sample from the North of Portugal using the polymerase chain reaction (PCR). After denaturing PAGE, 6 alleles were identified for HUMTH01 (n = 419), 9 alleles for HUMVWA31A (n = 376), 12 alleles for HUMF13A1 (n = 232), and 5 alleles for HUMFES/FPS (n = 409). No deviation from Hardy-Weinberg equilibrium was found. The allele frequencies observed are similar to those of the European populations compared. The combined power of discrimination is 0.999.

Replicon rescue: a novel strategy to clone the genomic DNA flanking insertions of integrating shuttle vector DNA

A novel cloning strategy, replicon rescue, was developed for cloning genes disrupted by plasmid insertions. After ligation to a tetracycline resistance cassette, fragments containing a bacterial origin of replication from the insertion are recovered in Escherichia coli because they replicate autonomously. Restriction enzymes for cloning are so chosen that the only legitimate two fragment ligation yielding TetR clones involves a fragment spanning the boundary of the insertion. Replicon rescue was used successfully firstly in a test system to clone the chromosomal orl from a Klebsiella aerogenes strain, and secondly to recover a disrupted gene from a phototaxis-deficient mutant of Dictyostelium.

Efficient circularization in Escherichia coli of linear plasmid multimers from Dictyostelium discoideum genomic DNA

Transformation of Escherichia coli with Dictyostelium discoideum genomic DNA containing integrated shuttle vectors in multicopy, tandemly duplicated format resulted in the establishment of the linear plasmid molecules as circular monomeric replicons. The transformation efficiencies were comparable to those obtained with circular plasmid DNA and the recovered plasmids were free of deletions and rearrangements. Digestion of the genomic DNA prior to the transformation using restriction enzymes that cut within the inserted plasmids reduced the transformation efficiency dramatically and a high proportion of the recovered plasmids carried deletions. Our results provide evidence that the linear plasmid multimers cyclize in E. coli by homologous recombination in order to be established as autonomously replicated plasmids. The efficiency of recircularization was found to be independent of the recA gene product but dramatically reduced in the absence of recB recC or sbcB gene products. However, the paradoxically high efficiency of transformation with plasmid multimers of a recB recC sbcB mutant indicated the presence of an additional pathway for recombinational recircularization independent of these gene products. Unlike previous studies using as a DNA source linearized plasmid monomers and dimers that were created in vitro, the use of linear plasmid multimers integrated into the D. discoideum genome ensured that none of the E. coli transformants we obtained could be attributed to low levels of uncut circular plasmid molecules. The efficient recovery of the plasmid monomers faithfully reflects the structure of the insertion and thus provides a useful tool in the characterization of such plasmid insertions in the genome of D. discoideum.

Dissociation of a native dimer to a molten globule monomer. Effects of pressure and dilution on the association equilibrium of arc repressor

The monomer-dimer association reaction of Arc repressor was studied by pressure-induced dissociation and by dilution. The dissociation was measured by the decrease (red shift) in the average energy of emission of the tryptophan fluorescence. Pressure dissociation also promoted a decrease in the excited-state lifetime of the single tryptophanyl residue, Trp14. These observations suggest that Trp14 becomes exposed to an aqueous environment following dissociation. The pressure-dissociation curves were concentration dependent, with p1/2 (half-dissociation pressure) shifting to higher pressures as the concentration increased. The dissociation constant (KdO) obtained by extrapolating the pressure-dissociation curves to atmospheric pressure was similar to that determined from the dilution curve (KdO = 30 nM). An anomalous steepness of dissociation in response to dilution was observed, suggesting that conformational changes occur as a result of dissociation of Arc repressor. Binding of bis(8-anilinonaphthalene-1-sulfonate) to Arc repressor was not significantly affected by pressure dissociation, whereas thermal or urea denaturation was accompanied by a dramatic decrease in binding. These results suggest that the conformational changes that follow dissociation induced by pressure are more limited than those following denaturation. The tryptophan anisotropy decreased by about one-half, suggesting the dissociation of a globular dimer to a compact monomer. On the other hand, denaturation by urea promoted an increase in anisotropy, as expected for a random-coil conformation. Dissociated Arc has the hydrodynamic properties of a folded monomer. On the other hand, dissociated Arc has a high degree of exposure of hydrophobic side-chains, and the distribution of conformations is much broader than that in the folded dimer. These features suggest that the dissociated subunit is a molten globule. The subunit interaction was substantially increased by a single amino acid substitution (Pro8----Leu), and the free energy of stabilization amounted to -2.9 kcal/mol. This increased stability suggests that residue 8 is located in the dimer interface and that part of the tertiary and most of the quaternary structure constraints result from the interaction between the intersubunit beta-strands.