End-to-end distance distribution in fluorescent derivatives of bradykinin in interaction with lipid vesicles.

Cellular membranes have relevant roles in processes related to proteases like human kallikreins and cathepsins. As enzyme and substrate may interact with cell membranes and associated co-factors, it is important to take into account the behavior of peptide substrates in the lipid environment. In this paper we report an study based on energy transfer in two bradykinin derived peptides labeled with the donor-acceptor pair Abz/Eddnp (ortho-aminobenzoic acid/N-[2,4-dinitrophenyl]-ethylenediamine). Time-resolved fluorescence experiments were performed in phosphate buffer and in the presence of large unilamelar vesicles of phospholipids, and of micelles of sodium dodecyl sulphate (SDS). The decay kinetics were analyzed using the program CONTIN to obtain end-to-end distance distribution functions f(r). Despite of the large difference in the number of residues the end-to-end distance of the longer peptide (9 amino acid residues) is only 20 % larger than the values obtained for the shorter peptide (5 amino acid residues). The proline residue, in position 4 of the bradykinin sequence promotes a turn in the longer peptide chain, shortening its end-to-end distance. The surfactant SDS has a strong disorganizing effect, substantially broadening the distance distributions, while temperature increase has mild effects in the flexibility of the chains, causing small increase in the distribution width. The interaction with phospholipid vesicles stabilizes more compact conformations, decreasing end-to-end distances in the peptides. Anisotropy experiments showed that rotational diffusion was not severely affected by the interaction with the vesicles, suggesting a location for the peptides in the surface region of the bilayer, a result consistent with small effect of lipid phase transition on the peptides conformations.

[Acute urinary retention in a child with acute disseminated encephalomyelitis]. / Encefalomielite acuta disseminata. Descrizione di un caso clinico pediatrico con ritenzione urinaria acuta.

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory demyelinating encephalomyelitis with often monosymptomatic abrupt onset, followed by multifocal neurologic symptomatology depending on lesion-site. Diagnosis is made on the basis of characteristic magnetic resonance imaging (MRI) signal alterations. ADEM is sensitive to steroid therapy, immunoglobulins and plasmapheresis, presents usually a monophasic course and disappears completely after 2 or 3 weeks. Resolution of MRI lesions appears usually within 6 months of presentation. We report on a 14-year-old male, admitted to our Emergency Unit because of fever and acute urinary retention with a normal neurological examination. Urinary tract ultrasonography and mictional cystography were normal; electrophysiology showed a mild involvement of the peripheral nervous system and brain and spine MRI revealed disseminated areas of increased signal on T2-weighted sequences suggestive of ADEM. Steroid therapy brought about clinical recovery in a few days. Resolution of lesions on MRI after 4 months and absence of relapses during four-year clinical follow-up confirmed definitive diagnosis. Our case is interesting because, to our knowledge, this is the first literature report with acute urinary retention as predominant symptom in monosymptomatic forms. Another peculiar feature is the absence of associated neurologic symptomatology despite MRI evidence of important brain and spine alterations.

Metabolic and genetic risk factors for migraine in children.

Migraine can induce ischaemic stroke, and is considered an independent risk factor for stroke in the young. To date, the nature of the link between migraine and stroke is essentially unknown. Forty-five children were studied. Homocysteine levels (fasting and post methionine load), vitamin B12 and plasma folate levels, factor V Leiden, factor II G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C mutations were examined. Compared with controls, patients with migraine had higher levels of post-methionine load homocysteine values (19.5 +/- 4.9 vs. 16.9 +/- 1.9; P = 0.025) and significantly lower folate levels (5.8 +/- 2.6 vs. 7.5 +/- 2.1; P = 0.002). We found a trend toward an increased risk of migraine in subjects carrying a homozygous mutant genotype for MTHFR C677T and MTHFR A1298C polymorphisms. Genetic prothrombotic conditions do not seem to be related to migraine in the young, whereas the biochemical differences between migrainous patients and controls are an appealing topic for further investigation.