[Parameatal cyst: presentation of two cases and a review of the literature]. / Quiste parameatal: presentación de dos casos y revisión de la literatura.

OBJECTIVE: To describe two additional cases of parameatal urethral cyst. The literature is reviewed and the etiology and treatment of this disease are discussed. METHODS: Two patients aged 20 and 24 years with parameatal urethral cyst are described. The patients were seen at the Gea González Hospital (México) during the period 1987-1988. The first case was asymptomatic and the cyst had been present since birth and in the other case, the cyst appeared at age 24 and caused irregular stream. Laboratory tests, surgical excision and pathological analysis of the cyst were performed. RESULTS: The laboratory tests were normal, no problems were encountered during surgical excision, the symptoms disappeared and there were no postoperative complications or recurrence. Pathological analysis demonstrated columnar epithelium in both cases. CONCLUSIONS: Parameatal urethral cyst is a rare benign condition that is asymptomatic in most of the cases. It may be present since birth or appear later and is prevalent in young males. Its etiology remains unclear and treatment is by complete surgical excision to avoid complications and recurrence.

Entamoeba histolytica and E. invadens: sulfhydryl-dependent proteolytic activity.

Sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (2-ME) activated proteolytic enzymes present in extracts of Entamoeba histolytica and E. invadens; SDS (0.5%) and 2-ME (1.4 and 715 mM) doubled the enzymatic activity when assayed on a stained insoluble substrate. Urea (4 M) did not reduce this activity, suggesting that amebic proteases are stable in the above denaturant conditions. Specific reagents for sulfhydryl (-SH) groups completely inhibited proteolytic activity regardless of pH. Inhibition with alkylating agents, such as N-ethylmaleimide and iodoacetamide, was reversed with 715 mM 2-ME as was also observed with papain. We conclude from these results that the main proteolytic enzymes contained in extracts of E. histolytica and E. invadens are dependent on free thiol groups.