RESUMEN
Three-dimensional electron microscopy tools have revolutionized our understanding of cell structure and molecular complexes in biology. Here, we describe methods for studying flagellar ultrastructure and biogenesis in two unicellular parasites-Trypanosoma brucei and Leishmania mexicana. We describe methods for the preparation of these parasites for scanning electron microscopy cellular electron tomography, and serial block face scanning electron microscopy (SBFSEM). These parasites have a highly ordered cell shape and form, with a defined positioning of internal cytoskeletal structures and organelles. We show how knowledge of these can be used to dissect cell cycles in both parasites and identify the old flagellum from the new in T. brucei. Finally, we demonstrate the use of SBFSEM three-dimensional models for analysis of individual whole cells, demonstrating the excellent potential this technique has for future studies of mutant cell lines.
Asunto(s)
Movimiento Celular/fisiología , Flagelos/ultraestructura , Leishmania mexicana/fisiología , Trypanosoma brucei brucei/fisiología , Animales , Ciclo Celular/genética , ADN Protozoario/genética , Tomografía con Microscopio Electrónico/métodos , Flagelos/fisiología , Imagenología Tridimensional/métodos , Leishmania mexicana/genética , Leishmania mexicana/crecimiento & desarrollo , Microscopía Electrónica de Rastreo/métodos , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/crecimiento & desarrollo , Moscas Tse-Tse/parasitologíaRESUMEN
At seed maturity, quinoa (Chenopodium quinoa Willd.) perisperm consists of uniform, non-living, thin-walled cells full of starch grains. The objective of the present study was to study quinoa perisperm development and describe the programme of cell death that affects the entire tissue. A number of parameters typically measured during programmed cell death (PCD), such as cellular morphological changes in nuclei and cytoplasm, endoreduplication, DNA fragmentation, and the participation of nucleases and caspase-like proteases in nucleus dismantling, were evaluated; morphological changes in cytoplasm included subcellular aspects related to starch accumulation. This study proved that, following fertilization, the perisperm of quinoa simultaneously accumulates storage reserves and degenerates, both processes mediated by a programme of developmentally controlled cell death. The novel findings regarding perisperm development provide a starting point for further research in the Amaranthaceae genera, such as comparing seeds with and without perisperm, and specifying phylogeny and evolution within this taxon. Wherever possible and appropriate, differences between quinoa perisperm and grass starchy endosperm--a morphologically and functionally similar, although genetically different tissue--were highlighted and discussed.
Asunto(s)
Chenopodium quinoa/citología , Chenopodium quinoa/metabolismo , Semillas/citología , Semillas/metabolismo , Apoptosis/genética , Apoptosis/fisiología , Chenopodium quinoa/genética , Fragmentación del ADN , Péptido Hidrolasas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Semillas/genéticaRESUMEN
A study of the knowledge, perceptions, and behavioral intentions of physicians regarding periodic abstinence (PA) methods was undertaken in Mauritius, Peru, the Philippines, and Sri Lanka. Most respondents considered PA to be useful, although even the PA providers prescribed mainly non-PA methods. Detailed knowledge of PA methods was not evident, but most physicians were willing to initiate general discussion about PA with patients. Physicians favored methods perceived as "scientific" and "modern," which primarily prevent pregnancy and secondarily avoid other health risks. When carefully presented as "scientific" and "modern," methods presented to medical audiences may find acceptance and be more likely to result in referral.
PIP: This study attempts to assess the level of knowledge about periodic abstinence methods and willingness to communicate that knowledge to patients among a sample of 375 physicians from 4 developing countries: Mauritius, Peru, the Philippines, and Sri Lanka. For purposes of this study, periodic abstinence includes the calendar method (rhythm), the Billings method (ovulation method), the temperature method (basal body temperature), and the sympto-thermal method (temperature and cervical mucus observation). 54% of the doctors interviewed did not provide periodic abstinence services. 67% were male, 60% were over 40, 92% were not strongly Catholic, and 42% were general practitioners. Older doctors, female doctors, and strongly Catholic doctors were most likely to provide periodic abstinence services. 54% of providers were general practitioners, 46% were gynecologists, and 36% were clinicians. Both providers and nonproviders were most likely to recommend the pill or the IUD as a contraceptive method. The calendar method was the most commonly provided abstinence method. Providers, in general, had more knowledge about abstinence methods than did nonproviders, but even providers were deficient in knowledge about methods that they did not supply. Of the 3 main abstinence methods, the calendar method was perceived as most traditional, the Billings method as most modern. The sympto-thermal method was perceived as modern but also as "artificial." On a scale of 1 to 7 from bad/nonscientific to good/scientific, the pill scored highest (6.4), while the temperature, Billings, and calendar methods scored 5.2 or 5.1. 47% of all the physicians surveyed said that they would not recommend periodic abstinence to their patients. The majority said that they would respond to inquiries about these methods but would not initiate discussions about them. Among nonproviders, 12% said they would seek future training, but 17% said they had no future plans for either training or service.
Asunto(s)
Actitud del Personal de Salud , Métodos Naturales de Planificación Familiar , Médicos , Adulto , Temperatura Corporal , Catolicismo , Moco del Cuello Uterino , Anticoncepción/métodos , Comparación Transcultural , Femenino , Humanos , Masculino , Mauricio , Perú , Filipinas , Sri LankaRESUMEN
Results of a comparative study of the ovulation method (OM) and symptothermal method (STM) of natural family planning in Colombia are presented. Recruitment of volunteer couples began in August, 1976, and continued through December, 1978, during which time 566 couples were randomly assigned to one or the other of the two methods. The study included 3 to 5 months of training in the method assigned, after which the couples entered the follow-up phase of the study. They remained in follow-up until (1) they dropped out or (2) the study closed in June, 1979. Total dropout rates were high for both methods of natural family planning. One year after entry into the follow-up phase of the study, net pregnancy rates were 24.2% for OM users and 19.8% for STM users. Gross pregnancy rates were 29.2% for OM and 26.1% for STM. Differences in pregnancy rates between the two methods were not statistically significant.
PIP: A comparative study of the use-effectiveness of the OM (ovulation method) and the STM (symptothermal method) of natural family planning was conducted in Bogota and Palmira, Colombia. The pregnancy rates obtained in the study were high for both methods and no significant difference was observed in the pregnancy rates for couples using the OM and for couples using the STM. The study was initiated by the government and the Javeriana University, sponsored by the World Health Organization, and designed and analyzed by the Department of Biostatistics of the University of North Carolina. The planned study was widely publicized and couples were urged to volunteer as study participants. 544 couples, who meet specified requirements, were recruited and randomly assigned to receive training in either the OM or the STM. Training lasted from 3-5 months. 57% of the participants dropped out during the training phase. The remaining 241 couples were then included in the formal follow-up phase of the study and were followed-up monthly for 1 year. Pregnancy rates were computed using both the life table method and the Pearl method. The net cumulative drop-out rate after 1 year of follow up for the 241 couples was 60.1% for OM users and 53.0% for STM users. Net cumulative rate of voluntary withdrawal was 30.3% for OM users and 26.0% for STM users, and the net cumulative pregnancy rate was 24.2% for OM users and 19.8% for STM users. The Pearl pregnancy rate was 33.8/100 users for the OM and 26.0/100 users for the STM users. There were no significant differences in the characteristics of OM and STM participants who took part in the follow-up phase nor between OM and STM drop-outs. The high drop-out and pregnancy rates observed in this study suggested that natural family planning was probably not an effective form of contraception for a large proportion of the Colombian population.
Asunto(s)
Anticoncepción/métodos , Métodos Naturales de Planificación Familiar , Adolescente , Adulto , Temperatura Corporal , Colombia , Femenino , Humanos , Masculino , Pacientes Desistentes del Tratamiento , Educación del Paciente como Asunto , Embarazo , Distribución AleatoriaRESUMEN
PIP: The goal of the Chilean Associacion for the protection of the family (APROFA) is to fight all causes of family disruption, such as alcohol, drugs, pornography, premarital or extramarital sex, and to emphasize sex as a manifestation of love. APROFA believes in the regulation of family size through natural methods, leaving artificial ones for use in specific instances only. Of all the natural methods the calendar one of Ogino-Knaus has been put aside after new discoveries in the field of female genital physiology. The temperature method, on the other hand, has been proven to work effectively, and requires abstinence from sex for only a few days during the cycle.^ieng