Heavy metals in the volcanic and peri-urban terrain watershed of the River Yautepec, Mexico.

Thirty-four water samples were collected all along the course of River Yautepec, Morelos State, Central Mexico, in three different zones based on the physical and anthropogenic setting. In situ measurements of physical characteristics (temperature, pH, conductivity, and turbidity) were also performed at each sampling station. Likewise, total/dissolved metal concentrations (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Cd, As, and Pb) were determined using an atomic absorption spectrophotometer. Located in a peri-urban and volcanic zone of Central Mexico, the river system presented impacts of both natural and anthropogenic activities. Results revealed differences in pH values (6.7-8.23) in all the three zones probably due to the influences of volcanic ash and local geological formations, whereas conductivity levels (635-1098 µs/cm) were high indicating the effect of agricultural and industrial activities. The relative order of the concentrations of metals in both the total and dissolved fractions was observed to be in the following order: zone I, Fe > Zn > Mn > Cu > Pb > Ni > Cr > As > Cd > Hg; zone II, Fe > Zn > Pb > Ni > Mn > Cu > Cr > Cd > As > Hg; zone III, Fe > Pb > Zn > Mn > Ni > Cu > As > Cd > Cr > Hg. Calculated heavy metal evaluation index (HEI) values indicated less contamination. However, concentrations of Fe and Pb were observed to be higher than the permissible limits set forth by the Mexican government for human consumption. Henceforth, the prerequisite for maintaining and improving the health of a river system depends on continuous long-term monitoring of the dynamic ecosystem for sustainable management.

Low pH formulation of whole IgG antivenom: impact on quality, safety, neutralizing potency and viral inactivation.

Low pH treatment improves the tolerance to intravenous infusion, the stability, and the viral safety of various therapeutic immunoglobulins G preparations, but has never been evaluated for horse plasma-derived antivenoms. We have studied the impact of low pH formulation on the quality, safety, stability, potency and viral inactivation of a whole IgG antivenom used to treat viperid snake bite envenoming. Horse plasma-derived whole immunoglobulins purified by caprylic acid were incubated for 24 h at low pH in the presence of 4% sorbitol, then sterile-filtered and stored liquid at 2-8°C. Appearance, aggregates, purity, safety tests in mice, venom antibody titre, and neutralization potency tests were controlled. Low pH treatment did not affect the physico-chemical characteristics, safety and potency of antivenom for at least 6 months of storage, but a major increase in aggregates was observed. In vitro antibody titre and in vivo neutralizing potency were maintained. There were ≥ 5.5 log inactivation of Herpes Simplex Virus-1, an enveloped virus, but no significant inactivation of the non-enveloped Poliovirus type 3. Low pH treatment appears feasible to improve the viral safety of antivenoms without affecting the neutralization potency. The possibility to formulate antivenoms at low pH requires further investigations to avoid formation of aggregates.

Influence of age on molecular characteristics and rheological behavior of nopal mucilage.

Nopal mucilages are of interest due to a variety of potential applications, which include their use as thickeners and rheological modifiers. In this work, changes in molecular characteristics of nopal mucilages with their age and its influence on the rheological behavior of their solutions were analyzed by light scattering, high performance liquid chromatography, a colorimetric method, and linear viscoelastic rheometrical measurements. For this, mucilages obtained from cladodes from Opuntia ficus-indica with different ages, namely 20, 80, and 600 days, respectively, were extracted using water as solvent and then subjected to freeze-drying. The weight-average molecular weight (M w) of the mucilages was found to increase along with the age; meanwhile, the concentration of uronic acids increased and the galactose, rhamnose, and xylose contents decreased. Increasing M w with age resulted in enhanced viscoelastic behavior of solutions, namely, higher viscosity and elasticity at lower mucilage concentrations. Also, along with increasing M w, decrease in neutral sugar contents and increase of pectic compounds (uronic acids) and Ca+ cations in mucilages with age promoted formation of weak gels. Overall, the molecular weights and rheological behaviors reported in this work for nopal mucilages are comparable to those of widely used thickeners such as xanthan and guar gums, which suggest their use in similar applications regarding its age.

Experimental comparison of excision and swabbing microbiological sampling methods for carcasses.

Bovine sides, ovine carcasses, and porcine carcasses were individually inoculated by dipping in various suspensions of a marker organism (Escherichia coli K-12 or Pseudomonas fluorescens), alone or in combination with two meat-derived bacterial strains, and were sampled by two standard methods: cotton wet-dry swabbing and excision. The samples were examined for bacterial counts on plate count agar (PCA plate counts) and on violet red brilliant green agar (VRBGA plate counts) by standard International Organization for Standardization methods. Average bacterial recoveries by swabbing, expressed as a percentage of the appropriate recoveries achieved by excision, varied widely (2 to 100%). Several factors that potentially contributed to relatively low and highly variable bacterial recoveries obtained by swabbing were investigated in separate experiments. Neither the difference in size of the swabbed area (10, 50, or 100 cm2 on beef carcasses) nor the difference in time of swabbing (20 or 60 min after inoculation of pig carcasses) had a significant effect on the swabbing recoveries of the marker organism used. In an experiment with swabs preinoculated with the marker organism and then used for carcass swabbing, on average, 12% of total bacterial load was transferred inversely (i.e., from the swab to the carcass during the standard swabbing procedure). In another experiment, on average, 14% of total bacterial load was not released from the swab into the diluent during standard swab homogenization. Use of custom-made swabs with abrasive butts, around which metal pieces of pan scourers were wound, markedly increased PCA plate count recoveries from noninoculated lamb carcasses at commercial abattoirs compared with cotton swabs. In spite of the observed inferiority of the cotton wet-dry swabbing method compared with the excision method for bacterial recovery, the former is clearly preferred by the meat industry because it does not damage the carcass. Therefore, further large-scale evaluation of the two carcass sampling methods has been undertaken under commercial conditions and reported separately.

El papel del médico en la elección de un método anticonceptivo / Medical role selecting contraceptive method

La anticoncepción es el derecho de una pareja de decidir el número de hijos, el momento de tenerlos y su adecuado espaciamiento, así como evitar embarazos contraindicados por razones médicas. Se distinguen métodos naturales (coito interrumpido, coito reservado, lavado vaginal, lactancia y abstinencia periodica), y métodos artificiales (de barrera, hormonales, dispositivos ultrauterinos y esterilización). En esta parte del trabajo se brindará información sobre cada uno de los métodos. En la segunda parte que se publicará próximamente se analizarán los aspectos médico-legales derivados de la indicación incorrecta por parte del médico. Palabras claves: anticoncepción, anticonceptivos.

El papel del médico en la elección de un método anticonceptivo / The role of a physician in selecting a contraceptive

La mala práctica en Medicina y Farmacia es revisada. Los médicos pueden incurrir en mala práctica si no obtienen el consentimiento informado previo de la paciente o si no le advierten sobre los efectos secundarios.