Identification of functionally important acidic residues in transducin by group-specific labeling

Transducin (T), a GTP-binding protein involved in phototransduction of rod photoreceptor cells, is a heterotrimer arranged as two units, the alpha-subunit (T alpha) and the beta gamma-complex (T beta gamma). The role of the carboxyl groups in T was evaluated by labeling with N,N'-dicyclohexylcarbodiimide (DCCD) and 1-ethyl 3-(3-dimethylaminopropyl) carbodiimide (EDC). Only a minor effect on the binding of beta, gamma-imido guanosine 5'-triphosphate (GMPpNp) to T was observed in the presence of the hydrophobic carbodiimide, DCCD. Similarly, the GMPpNp binding activity of the reconstituted holoenzyme was not significantly affected when T alpha was combined with DCCD-treated T beta gamma. However, the binding of guanine nucleotides to the reconstituted T was approximately 50 per cent inhibited when DCCD-labeled T alpha was incubated with T beta gamma. In contrast, treatment of T with the hydrophilic carbodiimide, EDC, completely impaired its GMPpNp-binding ability. EDC-modified T was incapable of interacting with illuminated rhodopsin, as determined by sedimentation experiments. However, rhodopsin only partially protected against the inactivation of T. Additionally, analyses of trypsin digestion patterns showed that fluoroaluminate was not capable of activating the EDC-labeled T sample. The function of the reconstituted holoenzyme was also disrupted when EDC-modified T alpha was combined with T beta gamma, and when EDC-treated T beta gamma was incubated with T alpha.

Sarcoma de Kaposi diseminado con compromiso pleuropulmonar en un paciente con SIDA / Diseminated Kaposi's sarcoma with pleuropulmonar commitment in a patient with AIDS

Se presenta un paciente con diagnóstico de enfermedad HIV/SIDA en etapa avanzada y sarcoma de Kaposi (SK) diseminado con compromiso cutaneo-mucoso extenso. Ingresa por cuadro de fiebre, dolor toracico derecho y disnea progresiva. La Rx de tórax evidenció derrame pleural derecho, cuya punción y aspiración con biopsia puso de manifiesto un líquido serohemático. El estudio histopatológico arrojó diagnóstico de compromiso pleural por SK. Se le inició tratamiento con terapia antirretroviral en base a AZT mas ddC y ciclos de bleomicina más vincristina a dosis habituales cada 15 días. Se obtuvo mejoría parcial desde el punto de vista clínico y radiológico. Concluimos afirmando que en un paciente con diagnóstico de SK diseminado la aparición de un derrame pleural con líquido serohemático debe hacer sospechar la misma etiologia