Bridging structural and cell biology with cryo-electron microscopy.

Most life scientists would agree that understanding how cellular processes work requires structural knowledge about the macromolecules involved. For example, deciphering the double-helical nature of DNA revealed essential aspects of how genetic information is stored, copied and repaired. Yet, being reductionist in nature, structural biology requires the purification of large amounts of macromolecules, often trimmed off larger functional units. The advent of cryogenic electron microscopy (cryo-EM) greatly facilitated the study of large, functional complexes and generally of samples that are hard to express, purify and/or crystallize. Nevertheless, cryo-EM still requires purification and thus visualization outside of the natural context in which macromolecules operate and coexist. Conversely, cell biologists have been imaging cells using a number of fast-evolving techniques that keep expanding their spatial and temporal reach, but always far from the resolution at which chemistry can be understood. Thus, structural and cell biology provide complementary, yet unconnected visions of the inner workings of cells. Here we discuss how the interplay between cryo-EM and cryo-electron tomography, as a connecting bridge to visualize macromolecules in situ, holds great promise to create comprehensive structural depictions of macromolecules as they interact in complex mixtures or, ultimately, inside the cell itself.

Características citomorfológicas de las alteraciones plaquetarias cuantitativas y su relación con otras alteraciones celulares / Cytomorphological characteristics of quantitative platelet alterations and its association with other cell alterations

Introducción: Las alteraciones cuantitativas de plaquetas son producidas por el incremento o disminución de los conteos globales de plaquetas. El incremento o trombocitosis se produce por redistribución o aumento de la producción medular; la disminución puede ser el resultado de una reducción de la producción, redistribución o acortamiento de la sobrevida de las plaquetas en circulación. Objetivo: Describir los hallazgos citomorfológicos más importantes en las alteraciones cuantitativas de plaquetas. Métodos: Se realizó una revisión de la literatura, en inglés y español, en la base de datos PubMed y el motor de búsqueda Google Académico de artículos publicados en los últimos 10 años. Se hizo un análisis y resumen de la bibliografía revisada. Análisis y síntesis de la información: Las alteraciones cuantitativas de plaquetas se caracterizan por variaciones en el número y morfología de estas células. Estas se asocian a causas congénitas o adquiridas, en la que la detallada anamnesis de los pacientes es un elemento importante en el diagnóstico. En la trombocitosis se debe diferenciar una trombocitosis reactiva de una enfermedad medular primaria; mientras que en la trombocitopenia se debe considerar el origen étnico de los pacientes y la morfología de los leucocitos. Son numerosas las causas hereditarias de trombocitopenia con anomalías morfológicas de plaquetas y granulocitos. Conclusiones: Las alteraciones cuantitativas de plaquetas son un amplio número de entidades con semejanzas y diferencias en cuanto a presentación y manifestaciones clínicas. Los exámenes de laboratorio constituyen una herramienta importante en el diagnóstico, pronóstico y el seguimiento de los pacientes afectados(AU)

Introduction: Quantitative platelet alterations are produced by the increase or decrease in global platelet counts. Platelet count increase or thrombocytosis is produced by redistribution or increased marrow production. Platelet decrease may result from production, redistribution, or shortened survival of circulating platelets. Objective: To describe the most significant cytomorphological findings in quantitative platelet alterations. Methods: A literature review was carried out, in English and in Spanish, in the database PubMed and with the search engine of Google Scholar, of articles published in the last ten years. An analysis and summary of the revised bibliography was made. Information analysis and synthesis: Quantitative platelet alterations are characterized by variations in the number and morphology of these cells. These are associated with congenital or acquired causes, in which detailed anamnesis of patients is an important element in the diagnosis. In thrombocytosis, reactive thrombocytosis must be differentiated from primary marrow disease; while in thrombocytopenia, the ethnic origin of the patients and the morphology of the leukocytes must be considered. Hereditary causes of thrombocytopenia with morphological abnormalities of platelets and granulocytes are numerous. Conclusions: Quantitative platelet alterations are a large number of entities with similarities and differences in terms of presentation and clinical manifestations. Laboratory tests are an important tool for diagnosis, prognosis, and follow-up of affected patients(AU)

Citología en base líquida: parámetros de eficacia / Liquid based cytology: efficacy parameters

OBJETIVO: Comparar la eficacia de la citología con la utilización de medio líquido en relación con la convencional, en pacientes que acudieron al Servicio de Ginecología de la Maternidad “Concepción Palacios”. MÉTODOS: Se llevó a cabo un estudio prospectivo y comparativo, que incluyó a 177 pacientes a las cuales se les realizó ambas citologías (convencional y líquida). RESULTADOS: Se obtuvieron 114 muestras con células metaplásicas y de la unión escamo- cilíndrica con la citología convencional y 60 con citología en base líquida (P=0,001). Con la citología en base líquida se encontraron menos casos sin exudado inflamatorio, más con exudado moderado, y se diagnosticaron más casos de infección por virus de papiloma humano. Con la técnica convencional se observaron más casos de vaginosis bacteriana. Los resultados citológicos, en relación con las células epiteliales, fueron similares con ambas técnicas: 171 y 157 negativos, 2 y 8 atipias de células escamosas de significado incierto y 4 y 12 lesiones intraepiteliales de bajo grado, para citología convencional y en base líquida, respectivamente. Hubo 23 falsos negativos y 1 falso positivo con la citología convencional mientras que con la citología en base líquida hubo 18 falsos negativos y 10 falsos positivos. CONCLUSIONES: La sensibilidad, el valor de predicción positivo y el valor de predicción negativo, de la citología procesada según ambas técnicas, fueron similares, la especificidad de la citología convencional fue más alta.

OBJECTIVE: To compare the efficacy of cytology with the use of liquid medium in relation to the conventional, in patients who attended the gynecology service in Maternidad “Concepción Palacios”. METHODS: Carried out a comparative and prospective study that included 177 patients which underwent both PAP (conventional and liquid). RESULTS: 114 samples with metaplastic cells and from the union escamo-cylindrical were obtained with conventional cytology and 60 with liquid-based cytology (P = 0.001). With liquid-based cytology found fewer cases without inflammatory exudate, most with moderate exudate, and more cases of infection were diagnosed by human papillomavirus. With the conventional technique, there were more cases of bacterial vaginosis. The cytologic findings, in relation to the epithelial cells, were similar with both techniques: 171 and 157 negatives, 2 and 8 atypia of squamous cells of uncertain significance and 4 and 12 intraepithelial lesions of low grade, for conventional smear and liquid-based, respectively. There were 23 false negative and false positive 1 with conventional cytology while with liquid-based cytology had 18 false negative and false positive 10. CONCLUSIONS: The sensitivity, the positive predictive value and the negative predictive value of Cytology processed according to both techniques were similar, the specificity of conventional cytology was higher.

Células glandulares atípicas em esfregaços cervicovaginais: significância e aspectos atuais / Atypical glandular cells in cervical smears: significance and current aspects

Células glandulares atípicas (AGC) em esfregaços cervicovaginais são achados citológicos raros, porém de significado representativo. Sua incidência varia, na literatura, de 0,08 por cento a 0,81 por cento. O sistema Bethesda de 2001 classifica estas lesões glandulares como AGCs sem outras especificações, AGCs provavelmente neoplásicas, adenocarcinoma cervical in situ (AIS) e adenocarcinoma invasivo. Das mulheres portadoras de AGC, grande parte não apresentará qualquer tipo de alteração histológica em avaliação subseqüente. Entretanto, em 17,4 por cento a 62,2 por cento dos casos serão encontradas lesões histológicas significativas, como neoplasias intra-epiteliais cervicais, AIS, neoplasias escamosas e glandulares, cervicais e endometriais, bem como neoplasias de outras localizações. O risco de doença significativa está relacionado à subdivisão de AGC encontrada. Em virtude da elevada probabilidade de anormalidades histológicas significativas em casos de AGC, a simples repetição citológica é insuficiente para o seguimento dessa condição. Esta atualização descreve a epidemiologia, a avaliação e a conduta das pacientes portadoras dessa anormalidade citológica.

Atypical glandular cells (AGC) on cervical smears are unusual but important cytologic diagnosis. The incidence of AGC ranges from 0.08 percent to 0.81 percent of all cervical smears tests. The 2001 Bethesda System nomenclature classifies these glandular lesions as AGC not otherwise specified, AGC favor neoplasia, endocervical adenocarcinoma in situ (AIS) and invasive adenocarcinoma. Of women with AGC smears, a great number will have no histologic abnormalities on further evaluation. However, 17.4 percent to 62.2 percent are found to have significant histologic lesions such as cervical intraepithelial neoplasia, AIS, squamous and glandular cancers from sites farther the cervix and endometrium. The risk of significant disease is related to the AGC subclassification that was found. Because of the high likelihood that AGC is associated with significant histological disease, simply repeating the cytological smear is not sufficient for the management of this condition. This review describes the epidemiology, evaluation and management of patients with these citologic readings.

Death by fine tunning

Since the first evidence that physiological cell death is a normal feature of cell life, there has been considerable effort in trying to define the mechanisms, regulation and morphology of cell death events. In nearly four decades of investigation, several types of cell death have been described in a wide range of organisms and cells, and this has led to great deal of confusion regarding the morphology and regulation of these processes. Historically, cell death has been characterized as physiological or accidental (necrosis). However, in the past fi ve years, several attempts have been made to define the types of cell death based on mechanistic and morphological criteria. Currently, at least three types of cell death apoptosis, autophagy and necrosis are recognized and share some mechanisms in common. Thus, cell death is more than simply being a caspase-mediated phenomenon. The aim of this review is to discuss recent findings on how cells choose to die in different biological contexts, and to consider the morphological changes associated with each cell type of cell death.

Bacteria-induced apoptosis: an approach to bacterial pathogenesis

Several pathogenic or opportunistic bacteria can induce or inhibit host cell apoptosis. The modulation of cellular pathways that results in the induction or delay of host cell apoptosis is an important mechanism of bacterial virulence. These processes can be mediated by various host cell signaling pathways that are subverted by the bacteria. Pathogens can activate apoptotic proteins such as caspases, inactivate anti-apoptotic proteins such as NFêB and mitogen-activated protein kinases, or up-regulate the endogenous receptor/ligand system that induces apoptosis, generally when the bacteria are bound to the host cell surface. Bacteria-induced apoptotic or anti-apoptotic processes are often related to the ability of the bacteria to reach the host tissues. However, since apoptosis is also involved in host defense mechanisms against infectious agents, this phenomenon apparently plays a central role in host-pathogen interactions.

Aspectos morfológicos de células da série eritrocítica de Caiman crocodilus yacare (Daudin, 1802; Reptilia, crocodilia) / Morphologic caracteristics of cells on the erytrocytic series of the Caiman crocodilus yacare (Daudin, 1802; Reptilia, crocodilia)

Com o objetivo de estudar o sistema hematopoético do réptil Caiman crocodilus yacare, foram utilizados cinco exemplares hígidos e jovens (aproximadamente um ano de idade), provenientes de São Paulo e de Mato Grosso do Sul. Amostras de sangue periférico foram colhidas em EDTA, através da punção do seio venoso cervical, e da medula óssea por punção aspirativa do osso femural. Estudo histológico da medula óssea femural foi realizado através da coloração por HE, Giemsa e técnica de Gomori para fibras reticulínicas. Os esfregaços de sangue e de medula foram processados para coloração panótica (Leishman ou Rosenfeld). A presença de sítios hematopoéticos ativos foi demonstrada histologicamente nos cortes transversais do fêmur, principalmente no terço distal. As células da linhagem eritrocítica foram encontradas dentro dos vasos capilares sinusóides medulares, na região central do osso. As células precursoras desta linhagem estavam aderidas à parede do vaso, e suas sucessoras distribuídas em direção ao centro do sinusóide à medida que amadureciam. Nos esfregaços de medula, as células imaturas da linhagem eritrocítica mostraram-se arredondadas e com núcleo predominantemente frouxo, em contraposição às células maduras, de núcleo condensado e forma em geral elíptica. Foram vistos pró-eritroblastos, eritroblastos basofílicos, policromáticos e ortocromáticos, e finalmente eritrócitos.