The distribution pattern of species of the genus Dactylopius Costa in Mexico was analyzed in relation to the distribution of their host plants (subfamily Opuntioideae) to evaluate the specificity of the insect-host association. The distribution of Dactylopius currently recognized is narrower than that of its hosts and probably is not representative. Therefore, a broader distribution of the Dactylopius species in correspondence with those of their hosts was hypothesized. Insects and their hosts were collected and georeferenced in 14 states of Mexico from 2005 to 2007. The distribution areas, maps, and habitat characteristics of Dactylopius, Opuntia sensu stricto, Nopalea and Cylindropuntia were determined on the basis of field collections and examination of museum collections. This information was complemented with information from the exhaustive examination of microscope slides from a local insect collection, plants from local herbaria, and literature reviews. The current distribution of the genus Dactylopius and its hosts included 22 and 25 states of Mexico, respectively, and Dactylopius had a continuous distribution according to its hosts, broader than recognized hitherto. The new georeferenced records of the five Mexican Dactylopius species are reported. Insects with morphological characteristics of D. confusus combined with those of D. salmianus were identified, as well as insects with characteristics of D. opuntiae combined with those of D. salmianus. These records suggest that the number of local Dactylopius species could be higher than previously thought or that possible new processes of hybridization between native and introduced species may be occurring.

The rheological properties of hydrophilic pharmaceutical polymers used for oral solid dosage forms could have an effect on the kinetics of drug release when they come in contact with gastrointestinal fluids. Hydroxypropylmethylcellulose (HPMC) and sodium carboxymethylcellulose (CMCNa) are common ingredients of pharmaceutical drug tablets. Therefore, the viscoelastic behavior of solutions and hydrated tablets of the individual polymers and their mixtures was studied at different pHs. The viscoelastic behavior of solutions and tablets was different, but it was pH dependent. At pH 1.3 the largest differences were observed. Gelation was not observed in any of the examined samples.

Las propiedades reológicas de los polímeros hidrofílicos con los cuales se elaboran medicamentos orales sólidos, podrían afectar la cinética de liberación del fármaco una vez que se encuentren en contacto con los fluidos gastrointestinales. La hidroxipropilmetilcelulosa (HPMC) y la carboximetilcelulosa sódica (CMCNa) son ampliamente utilizadas en la elaboración de tabletas, por lo cual se estudiaron sus propiedades viscoelásticas a diferentes pH's, a partir de disoluciones y tabletas hidratadas de los polímeros individuales y de sus mezclas. Se observaron diferencias en el comportamiento viscoelástico entre las disoluciones y las tabletas, el cual fue dependiente del pH y de la proporción de los componentes. A pH 1.3 se observaron las mayores diferencias. En ningún caso se detectó la formación de geles verdaderos.