Zinc-histidine as nucleation centers for growth of ZnS nanocrystals.

Histidine is a chelator of zinc, most notably in zinc-finger proteins (zinc coordinated by cysteine and histidine) and in hyperaccumulator plants. Sulfide incorporation into molecules containing metal-cysteinyl complexes has been shown to occur in vivo in certain yeasts, leading to enhanced metal tolerance. Demonstrated here for the first time is incorporation of sulfide into zinc-histidine, resulting in histidine-ZnS nanocrystals (NCs) having unique optical properties. Sulfide complexation occurred optimally at alkaline pH into zinc-(histidine)2 species, and UV/Vis absorption maxima were red-shifted as increasing sulfide addition occurred. Intermediate sulfide concentrations led to multiple, thermodynamically preferred NC species within a sample. Fluorescence of histidine-ZnS NCs was greater than ZnS prepared previously with cysteinyl peptides. Transmission electron microscopy and selected-area electron diffraction indicated hexagonal ZnS crystals having an average size of 4.2 nm. A photocatalytic application of histidine-ZnS NCs was shown by efficient degradation of p-nitrophenol and paraquat in the presence of UV irradiation.

Nitrite and nitrosyl compounds in food preservation.

Nitrite is consumed in the diet, through vegetables and drinking water. It is also added to meat products as a preservative. The potential risks of this practice are balanced against the unique protective effect against toxin-forming bacteria such as Clostridium botulinum. The chemistry of nitrite, and compounds derived from it, in food systems and bacterial cells are complex. It is known that the bactericidal species is not nitrite itself, but a compound or compounds derived from it during food preparation. Of a range of nitrosyl compounds tested, the anion of Roussin's black salt [Fe4S3(NO)7]- was the most inhibitory to C. sporogenes. This compound is active against both anaerobic and aerobic food-spoilage bacteria, while some other compounds are selective, indicating multiple sites of action. There are numerous possible targets for inhibition in the bacterial cells, including respiratory chains, iron-sulfur proteins and other metalloproteins, membranes and the genetic apparatus.

Characterization of the bactericidal effects of sodium nitroprusside and other pentacyanonitrosyl complexes on the food spoilage bacterium Clostridium sporogenes.

The potent bactericidal activity of sodium nitroprusside (SNP; Na2[Fe(CN)5(NO)]) towards Clostridium sporogenes has been investigated. SNP inhibited cell growth in the concentration range of 10 to 40 microM. Concentrations above 80 microM caused irreversible loss of cell viability and cell lysis. Inhibition of cell growth was similar in complex and in defined media. SNP was found to be unreactive towards individual components of the defined medium, with the exception of cysteine. The chemical characteristics responsible for the potency of SNP were investigated by synthesizing analogs of SNP in which the Fe was replaced by different metals. The inhibitory potency of the pentacyanonitrosyl complexes decreased in the order Fe > Cr > V, which correlates with N-O stretching frequency (vNO). In contrast, the Ru complex which had a vNO comparable to that of Fe was a poor inhibitor. Electron paramagnetic resonance spectroscopy showed that SNP was rapidly reduced to the paramagnetic Fe(I) compound [Fe(CN)4(NO)](2-) on contact with cells. Analysis of fractions from SNP-treated cells showed 90% oxidation of thiols in the cell walls compared with those in control cells. The toxicity of SNP involves S-nitrosation and reduction, the lack of toxicity of the Ru analog being consistent with the fact that it has poor reactivity towards thiols. When C. sporogenes cells were exposed to sublethal concentrations of SNP and viewed under the electron microscope, they showed blisters on the surface. These results point to the cell wall surface as a primary point of attack of the nitrosyl complex.

[Psychopharmaceuticals in primary care: prescription quality]. / Psicofármacos en atención primaria: calidad de la prescripción.

OBJECTIVE: Using criteria based on the bibliography, to assess drugs prescription in a Health Centre, in order to put forward corrective measures in line with the defects identified. DESIGN: Descriptive and retrospective study. SETTING: Santa Maria de Benquerancia Health Centre (Toledo). PARTICIPANTS: A sample of 40% of the clinical records of patients over 14 produced records of patients treated with drugs for psychic disorders between October 1990 and October 1991. MEASUREMENTS AND MAIN RESULTS: 248 prescriptions for these drugs were found. The most common diagnoses were: neurotic depression (33.1%), anxiety (25.8%) and insomnia (10.1%). Benzodiazepines made up 78.2% of the prescriptions. Of 8 quality criteria assessed, the compliance level was acceptable by WHO standards except in the recording in the notes of the diagnosis or problem for which the drug was prescribed (74.2% non-compliance); Alprazolam and Triazolam were not considered first-choice benzodiazepines (31.3% non-compliance); and there was 44.5% non-compliance by Primary Care physicians with the non-prescription of anti-psychotic or stimulant MAO inhibitor antidepressants. CONCLUSIONS: Quality-control studies, such as this one, in order to identify problems, to take corrective measures and subsequently assess them, are useful in improving care procedures.

Streptococcus associated toxic shock.

In the past few years, there appears to have been a change in the spectrum of disease caused by group A beta-haemolytic streptococcus (GABHS), and a toxic shock-like syndrome caused by this organism has recently been described in adults. We report four children with an acute illness characterised by rapid progression of shock, erythematous rash, multisystem organ involvement, electrolyte derangements, and desquamation who fulfil the previously established diagnostic criteria for toxic shock syndrome. Three of the children had extensive cutaneous and soft tissue infection and the fourth had peritonitis. All four developed bacteraemia. Treatment included aggressive cardiovascular resuscitation and antibiotic therapy. Although no patient died, they suffered multiple and severe complications requiring prolonged treatment and hospitalisation. Streptococcal toxic shock syndrome is a separate and clearly defined entity occurring in previously healthy children.