Synthesis and characterization of leiurotoxin I analogs lacking one disulfide bridge: evidence that disulfide pairing 3-21 is not required for full toxin activity

Leiurotoxin I (Lei-NH2), a toxin isolated from the venom of the scorpion Leiurus quinquestriatus hebraeus, is a blocker of the apamin-sensitive Ca(2+)-activated K+ channels. It is a 31-residue polypeptide cross-linked by three disulfide bridges which are presumably between Cys3-Cys21, Cys8-Cys26, and Cys12-Cys28. To investigate the role of these disulfides, analogs of Lei-NH2 lacking one disulfide bridge (i.e., [Abu3,21]Lei-NH2, [Abu8,26]Lei-NH2, and [Abu12,28]Lei-NH2) were chemically synthesized by selective replacement of each pair of half-cystines forming a bridge by two alpha-aminobutyrate (Abu) residues. The two disulfide pairings of the main folded form of the synthetic analogs were established by enzymatic proteolysis. They were as expected between Cys8-Cys26 and Cys12-Cys28 for [Abu3,21]Lei-NH2 but were unexpectedly between Cys3-Cys12 and Cys21-Cys28 for [Abu8,26]Lei-NH2 and between Cys3-Cys8 and Cys21-Cys26 for [Abu12,28]Lei-NH2. The synthetic peptides were tested in vitro for their capacity to compete with the binding of [125I]apamin to rat brain synaptosomes and in vivo for their neurotoxicity in mice. In both assays, [Abu3,21]Lei-NH2 exhibited full Lei-NH2-like activity whereas [Abu8,26]Lei-NH2 and [Abu12,28]-Lei-NH2 possessed only residual activities (< 2% native toxin activity). This suggests that disulfide bridge Cys3-Cys21 is not essential per se for high toxin activity. Circular dichroism (CD) spectroscopy of the three analogs showed that only [Abu3,21]Lei-NH2 exhibited a CD spectrum similar to that of Lei-NH2, suggesting they both adopt closely related conformations, in agreement with the pharmacological data. Structural models of the analogs were constructed on the basis of the disulfide pairing assignment and compared with that of Lei-NH2.     

Clinical value of studying hematuria using phase-contrast microscopy

To evaluate the examination of urine erythrocytes with a contrast phase microscope for the etiological diagnosis of haematuria (erythrocytes > 10/mm3 of non centrifuged urine) the charts of 84 patients with haematuria were reviewed. A nephrological origin had been established with certainty in 56 cases with a renal biopsy and an urological origin was also established with certainty in 28 cases thanks to appropriate radiological, endoscopical and pathological examinations. The morphological criteria of the erythrocytes deformation were those of Birch and Fairley but the quantitative criteria of these authors (either 80 or 100%) were found to be of no value. By successive approaches the threshold of 20% of deformed erythrocytes was selected and found to be the best criterion for diagnosing glomerular hematuria: the sensitivity of the test is then 73% and its specificity 60%. As these results were relatively modest, conditions which decrease the percentage of deformed erythrocytes were excluded to improve the sensitivity, such as macroscopic haematuria and also examinations made during the 6 hours following furosemide administration whereas conditions which increase the percentage of deformed erythrocytes and which are easily diagnosed such as urinary infections, lithiasis and renal insufficiency associated with an uropathy were excluded in order to improve the specificity. Then the examination has a sensitivity and a specificity of 90% which makes it clinically relevant, authorizing a wait and see attitude in case there is an isolated microscopic haematuria of glomerular type.     

Direct cost of antibiotic therapy prescribed for nosocomial bacteremia. Prospective study during 6 months at a CHU (University Hospital Center)

A six-month prospective study of costs associated with antimicrobial therapy in nosocomial bacteremia was conducted from November 1, 1995 to April 30, 1996 in a 1837-bed teaching hospital, with the help of the hospital pharmacists and hospital hygiene unit. Only the costs due to the antimicrobials themselves were taken into account. A total of 238 cases of nosocomial bacteremia occurred during the study period. The total direct cost of antimicrobial therapy was 444,931 French francs (FF), i.e., 6.8% of total expenditures for antimicrobials. Mean cost per case was 1869 FF, and was 2.6-fold higher in the 21 patients with bacteremia due to more than one organism (P = 0.03). CAses with an identifiable portal of entry contributed 75% of the total cost. Portals of entry associated with the highest cost included central venous lines (103,928 FF) and urinary tract infections (50,810 FF). Although 20% of nosocomial bacteremias due to coagulase-negative staphylococci did not lead to antimicrobial therapy, the remaining 80% contributed 40.8% of the total cost, followed by nosocomial bacteremias due to Escherichia coli with 19.7% of the total cost. Thirty-seven patients (15.5%) did not receive specific antimicrobial therapy, for the following reasons: death before treatment initiation, transfer to another hospital, antimicrobial therapy initiated earlier for another infection elsewhere in the body due to a different organism, or other form of treatment. The results of this study highlight the need for prevention.     

Measurement of nonlinear coefficient and phase matchingcharacteristics of AgGaS2

The nonlinear optical characteristics of AgGaS₂ were investigated by measuring visible parametric fluorescence with a pump wavelength of 600 nm. A value of d₃₆ [AgGaS₂ ]=31±5×10^-12 m/V for the nonlinear coefficient was determined. The temperature dependence of phase matching up to 100°C was studied. A significant temperature effect, although much smaller than for LiNbO₃, was found and results in a change in the infrared difference frequency generated of ~0.6 cm^-1 -°C^-1     

Structure Formation in Tailor-Made Buriti Oil Emulsion During Simulated Digestion (Adv. Funct. Mater. 49/2023)

Functional food emulsions enriched in health-promoting nutrients can help to maintain and improve health and lifestyle. The oil extracted from the Amazonian buriti fruit is renowned for its high levels of carotenoid, vitamin E, and unsaturated fatty acids, which have been linked to improvements in cardiometabolic health. Here, buriti oil in water emulsions are developed and their colloidal transformations are investigated in an advanced digestion model with oral, gastric, and intestinal parts with in situ synchrotron small-angle X-ray scattering, cryogenic electron microscopy, and dynamic light scattering under simulated “healthy” and “compromised” digestive conditions. The interior oil phase of whey-stabilized buriti oil-in-water emulsion transforms into highly ordered lyotropic liquid crystalline structures during simulated intestinal digestion at compromised bile conditions. Simulated gastric digestion influences intestinal digestion by slowing it down, resulting in less ordered structures. The digestion-triggered structure formation is pH- and bile salt-dependent and can be modulated by adding vitamin E to the oil. This tailoring of structures during digestion offers a new pathway to steer digestion kinetics and nutrient bioavailability.