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Most Gram-negative bacteria are susceptible to polymyxin B (PxB), and development of resistance to this cationic lipopeptide is very rare. PxB mechanism of action involves interaction with both the outer membrane (OM) and the inner membrane (IM) of bacteria. For the design of new antibiotics based on the structure of PxB and with improved therapeutic indexes, it is essential to establish the key features of PxB that are important for activity. We have used an approach based on mimicking the outer layers of the OM and the IM of Gram-negative bacteria using monolayers of lipopolysaccharide (LPS) or anionic 1-palmitoyl-2-oleoylglycero-sn-3-phosphoglycerol (POPG), respectively, and using a combination of penetration assay, analysis of pressure/area curves, and Brewster angle microscopy to monitor surface morphology changes. Synthetic analogue sp-B maintains the basic structural characteristics of the natural compound and interacts with the OM and the IM in a similar way. Analogue sp-C, with a mutation of the sequence d-Phe6-Leu7into d-Phe6-Dab7, shows that this hydrophobic domain is involved in LPS binding. The significant role of the positive charges is demonstrated with sp-Dap analogue, where l-,-diaminobutyric acid residues Dab1and Dab8are replaced by l-,-diaminopropionic acid (Dap), resulting in lower degrees of insertion in both LPS and PG monolayers. The importance of the N-terminal acyl chain is demonstrated with polymyxin B nonapeptide (PxB-np). PxB-np shows lower affinity for LPS compared to PxB, sp-B, or sp-C, but it does not insert into PG monolayers, although it binds superficially to the anionic film. Since PxB microbial killing appears to be mediated by osmotic instability due to OM−IM phospholipid exchange, the ability of the different peptides to induce membrane−membrane lipid exchange has been studied by use of phospholipid unilamellar vesicles. Results indicate that cationic amphipathicity determines peptide activity. [ABSTRACT FROM AUTHOR]

E1(145−162), a peptide corresponding to the structural protein E1 of the GB virus C, has been shown earlier to bind at pH 7.4 to vesicles containing 1,2-dimyiristoyl-sn-glycero-3-phospho-rac-(1-glycerol)] (DMPG) and 1,2-dimyiristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipids. To deepen the understanding of the interaction of E1(145−162) with the lipid membrane, in this paper, we report a detailed study of the surface properties of peptide, miscibility properties, and behavior of mixed monomolecular films of it and three phospholipids DMPG, DMPC, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPG). These studies were performed using the Langmuir balance by means of surface adsorption studies, surface pressure−mean molecular area compression isotherms, and penetration kinetics. The Brewster angle microscopy (BAM) was used to study the morphological properties of pure peptide and the mixed monolayers. The results show us that the peptide showed surface activity concentration dependent when injected beneath a buffered solution (HEPES/NaCl, pH 7.4). This tendency to accumulate into the air/water interface confirms its potential capacity to interact with membranes; the higher penetration of peptide into phospholipids is attained when the monolayers are in the liquid expanded state and the lipids are charged negatively maybe due to its negative electric charge that interacts with the positive global charge of the peptide sequence. The area per molecule values obtained suggested that the main arrangement structure for E1(145−162) peptide is the α-helical at the air−water interface that agreed with computational prediction calculations. Miscibility studies indicated that mixtures become thermodynamically favored at low peptide molar fraction. [ABSTRACT FROM AUTHOR]

Fragile X syndrome is the most common form of hereditary mental retardation. The molecular basis of this syndrome is mainly a CGG expansion in the 5 untranslated region of the FMR1gene. Expansions with more than 200 CGG repeats abolish gene expression causing the classical fragile X phenotype. Premutation carriers (55200 CGG) have normal cognitive function with increased risk of developing premature ovarian failure and fragile X-associated tremorataxia syndrome (FXTAS). Some clinical features associated with FXTAS, such as tremor, gait ataxia, cognitive decline, and generalized brain atrophy, are also seen in other movement disorders. Ninety-five patients referred for HD, who tested negative for the expansion in the IT15gene, were screened for FMR1CGG-repeat expansion. One FMR1premutation male carrier was detected, giving an FXTAS frequency of 1.6. Our results highlight that FXTAS is still not well diagnosed; therefore, we recommend FMR1premutation screenings in all patients with late-onset tremor, ataxia, and cognitive dysfunction. [ABSTRACT FROM AUTHOR]

Abstract: Objective:: The aim of this study was to evaluate the annhypertensive efficacy and tolerability of the angiotensin-converting enzyme inhibitor imidapril and the angiotensin II type 1 receptor antagonist candesartan in mild to moderate essential hypertension. Methods:: The trial was conducted at 8 centers across Portugal and Spain (the Iberian Multicenter Imidapril Study on Hypertension [IMISH] Study Group). Patients aged between 30 and 70 years with essential hypertension were eligible. Following a 2- to 4-week, single-blind, placebo run-in period, patients were randomly assigned to receive imidapril at doses of up to 20 mg/d, or candesartan at doses up to 16 mg/d, once daily in a double-blind, parallel-group design with a 12-week active-treatment period. To achieve the target systolic/diastolic blood pressure (SBP/DBP) of <140/<90 mm Hg, imidapril was titrated from 5 to 20 mg/d and candesartan was titrated from 4 to 16 mg/d. The main end point was the change from baseline in sitting blood pressure (BP) at trough. Secondary end points were response rate, evaluation of SBP and DBP throughout the study, and change of SBP and DBP in subgroup of patients with moderate hypertension, as well as incidence and severity of adverse events related to treatment reported throughout the study. Results:: The intent-to-treat analysis consisted of 122 patients (imidapril group, 60 patients; 32 men, 28 women; mean [SD] age, 54.7 [9.2] years; white race, 59 [99.2%], Hispanic race, 1 [0.8%]; mean [SD] weight, 80.1 [12.8] kg; candesartan group, 62 patients; 36 men, 26 women; mean [SD] age, 53.9 [9.9] years; white race, 62 [100%]; mean [SD] weight, 77.6 [14.1] kg). In the imidapril group, the mean (SD) SBP and DBP were, respectively, 155.7 (10.2) and 96.7 (4.7) mm Hg at baseline and 139.4 (11.9) and 86.9 (7.6) mm Hg at the end of the 12-week treatment period (visit 5); SBP had decreased significantly from baseline, by 10.5% (mean [SD] Δ, −16.3 [12.3] mm Hg [95% CI, −19.5 to −13.1; P < 0.001]) and DBP had decreased significantly, by 10.1% (mean [SD] A, -9.8 [7.8] mm Hg [95% CI, −11.8 to −7.8; P < 0.001]). In the candesartan group, the mean (SD) SBP and DBP values were, respectively, 158.4 [11.2] and 98.3 [4.1] mm Hg at baseline and 139.8 [12.5] and 87.6 7.5] mm Hg at 12 weeks, corresponding to decreases of 11.7% in SBP (mean [SD] A, −18.6 [12.8] mm Hg [95% CI, −21.9 to −15.4; P < 0.001]) and 10.9% in DBP (mean [SD] A, −10.7 [7.3] mm Hg [95% CI, −12.5 to −8.8; P < 0.001]). Response rates were 78.3% (47/60) with imidapril and 69.4% (43/62) with candesartan, and BP normalization (<140/<90 mm Hg) was achieved in 55.0% (33/60) of patients with imidapril and 45.2% (28/62) of patients with candesartan. The incidences of adverse events were similar between groups. Most (73.9%) adverse events were mild in intensity. A serious adverse event (severe anxiety) was reported in the candesartan group and led to study discontinuation. No cases of dry cough or hypotension were reported. Conclusions:: The results of this study suggest that imidapril once daily at doses up to 20 mg and candesartan once daily at doses up to 16 mg were effective in this population of mildly to moderately hypertensive patients. Both treatments were well tolerated. [Copyright &y& Elsevier]