Noise in the transduction of chemotactic stimuli to the flagellar motor of E. coli will affect the random run-and-tumble motion of the cell and the ability to perform chemotaxis. Here we use numerical simulations to show that an intermediate level of noise in the slow methylation dynamics enhances drift while not compromising localization near concentration peaks. A minimal model shows how such an optimal noise level arises from the interplay of noise and the dependence of the motor response on the network output. Our results suggest that cells can exploit noise to improve chemotactic performance.

-A paraganglioma is a rare tumor, composed of chromaffin cells, groups of cells associated to the autonomous system. When the tumor occurs in the adrenal gland, it is called pheochromocitoma. The malignant paraganglioma is a very rare presentation; it is diagnosed by local recurrence after total resection of the primary mass, or findings of distant metastases. We present a case report of a 29-year-old woman with cervico-brachial pain. In 1995 she underwent a carotid body tumor resection. Magnetic resonance imaging (MRI), plain X-rays and computerized tomography scan revealed multiple lesions in C5, T5 and T12. She underwent a surgical procedure to correct the cervical lesion. The histological and immunohistochemical assays revealed a malignant paraganglioma. She received adjuvant radiotherapy, showing clinical improvement after treatment, presenting no symptoms after one year. The therapeutic approach is based on the total resection of the tumor. The treatment of distant metastases can be made with adjuvant measures such as conventional radiotherapy, I¹³¹-MIBG, or chemotherapy, especially in malignant pheochromocitomas.KEY WORDS: paraganglioma, vertebral metastasis, spinal tumor P P P P Paraganglioma maligno com metástase vertebral: relato de caso araganglioma maligno com metástase vertebral: relato de caso araganglioma maligno com metástase vertebral: relato de caso araganglioma maligno com metástase vertebral: relato de caso araganglioma maligno com metástase vertebral: relato de caso RESUMO -O paraganglioma é tumor raro, composto de células cromafins, associado ao sistema nervoso autônomo. Quando localizado na glândula supra-renal, o tumor é chamado feocromocitoma. Descreve-se um caso de paciente do sexo feminino, 29 anos, que se apresentou com cervicobraquialgia e que havia sido operada em 1995 para exérese de tumor glômico da carótida cervical. RM, RX e TC revelaram múltiplas lesões acometendo o corpo vertebral de C5, T5 e T12. Foi submetida à ressecção cirúrgica radical da lesão cervical, com substituição do corpo vertebral por prótese de titânio. A histopatologia e o estudo imunohistoquímico da lesão confirmaram o diagnóstico de paraganglioma maligno. As outras lesões foram tratadas com radioterapia. Um ano após os procedimentos, a paciente apresenta-se assintomática. O tratamento destas lesões consiste na associação da ressecção cirúrgica radical do tumor e medidas complementares como radioterapia convencional, aplicação de I 131 -MIBG, ou quimioterapia, principalmente nos paragangliomas malignos. PALAVRAS-CHAVE: paraganglioma maligno, metástase vertebral, tumor vertebral

-The surgical management of cerebrospinal fluid (CSF) rhinorrhea has changed after the introduction of functional endoscopic sinus surgery.The following three cases illustrate the repair of CSF leaks with the use of rigid endoscope. Two patients had the diagnosis and the site confirmed after intrathecal fluoresceine saline injection. The obliteration of the CSF was achieved with fat free, mucoperichondrial or mucoperiostal free grafts taken from middle or inferior turbinate and kept in place by fibrin glue. Primary closure was achieved in all patients. The repair of the CSF rhinorrhea by endonasal endoscopic surgery is safe, effective and is a valid alternative to the cranial approach.KEY WORDS: cerebrospinal fluid rhinorrhea, endoscopic surgery, fluoresceine. Oclusão das fístulas liquóricas nasais sob visão endoscópicaRESUMO -Descrevemos a técnica de oclusão endoscópica por via endonasal de fístula liquórica proveniente do andar anterior em três pacientes. Dois pacientes tiveram o diagnóstico e os orifícios da fístula localizados após injeção intratecal de fluoresceína sódica. A oclusão foi obtida com enxerto de gordura livre, fragmentos de mucopericôndrio septal ou mucoperiósteal retirado do corneto médio ou inferior e selados com o auxílio de cola de fibrina. A cirurgia endoscópica endonasal é técnica segura e eficaz no tratamento da fístula esfeno-etmoidal, constituindo alternativa à abordagem craniana.

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A myloidoma of soft tissue is rare and there have been no previously published reports of limb involvement. We describe a case in which the tumour was present in the popliteal fossa. There was no evidence of systemic amyloid disease or of malignant neoplasm one year after the diagnosis.