RESUMEN
Carcinoma of the female urethra is uncommon. The review of literature and our own experience indicates that early distal urethral cancers (squamous and adenocarcinoma) can be treated either with surgery (70-80% 5-year survival) or with radiotherapy (brachytherapy) with excellent results (75% 5-year survival). Early proximal or entire urethral cancers (squamous and adenocarcinoma), if treated surgically, will require exenterative procedures. Alternatively, these cancers can be treated with a combination of external beam and brachytherapy with or without chemotherapy with good results and preservation of organs. Surgery can be used for failures or persistent tumors. Advanced cancers require a multimodality approach, and a combination of radiation and chemotherapy appears to be the optimal way to treat these patients-with surgery to be used for biopsy-proven persistent tumors or recurrences.
Asunto(s)
Adenocarcinoma/radioterapia , Braquiterapia/métodos , Carcinoma de Células Escamosas/radioterapia , Neoplasias Uretrales/radioterapia , Adenocarcinoma/diagnóstico , Adenocarcinoma/mortalidad , Antineoplásicos/uso terapéutico , Carcinoma de Células Escamosas/diagnóstico , Carcinoma de Células Escamosas/mortalidad , Ensayos Clínicos como Asunto , Terapia Combinada , Femenino , Humanos , Pronóstico , Dosis de Radiación , Tasa de Supervivencia , Neoplasias Uretrales/diagnóstico , Neoplasias Uretrales/mortalidadRESUMEN
A new nitrogenase from Azotobacter vinelandii has been isolated and characterized. It consists of two proteins, one of which is almost identical with the Fe protein (component 2) of the conventional enzyme. The second protein (Av1'), however, has now been isolated and shown to differ completely from conventional component 1, i.e., the MoFe protein. This new protein consists of two polypeptides with a total molecular weight of around 200,000. In place of Mo and Fe it contains V and Fe with a V:Fe ratio of 1:13 +/- 3. The ESR spectrum of Av1' also differs from conventional component 1 in that lacks the g = 3.6 resonance that arises from the FeMo cofactor but contains an axial signal with gav less than 2 as well as inflections in the g = 4-6 region possibly arising from an S = 3/2 state. This new enzyme can reduce dinitrogen, protons, and acetylene but is only able to utilize 10-15% of its electrons for the reduction of acetylene.