The Protozoan Tetrahymena: Cellular Model for Biological Studies

Biological research, including clinical trials, mainly uses animals as model organisms. Currently, animal experimentation remains controversial for several reasons, namely the implementation of animal protection and ethics panels, the high costs and the long duration of experiments. These constraints encourage researchers to use alternative methods in order to overcome these barriers. The ciliate Tetrahymena is a unicellular eukaryotic organism that has contributed significantly to the acquisition of knowledge in the field of fundamental biology. Characterised by a well-ordered structure and a short life cycle, the protozoan Tetrahymena is very commonly used in the laboratory due to the ease involved in handling it. Therefore, this organism has allowed researchers to elucidate a number of mechanisms in higher organisms including mammals. This bibliographic review describes the favourable biological characteristics of the protozoan Tetrahymena as well as various physiological and molecular studies that have been carried out on this organism. Studies have shown that Tetrahymena is one of the alternatives to animal experimentation and a major contributor to the development of biological and life sciences.

Studies on coccidian oocysts (Apicomplexa: Eucoccidiorida) / Estudos sobre oocistos de coccídios (Apicomplexa: Eucoccidiorida)

The oocysts of the coccidia are robust structures, frequently isolated from the feces or urine of their hosts, which provide resistance to mechanical damage and allow the parasites to survive and remain infective for prolonged periods. The diagnosis of coccidiosis, species description and systematics, are all dependent upon characterization of the oocyst. Therefore, this review aimed to the provide a critical overview of the methodologies, advantages and limitations of the currently available morphological, morphometrical and molecular biology based approaches that may be utilized for characterization of these important structures. It has become apparent that no single methodology is sufficient to fully characterize these structures and the majority of researchers favor the use of combinational or polyphasic approaches.

Os oocistos de coccídios são estruturas robustas, frequentemente isoladas das fezes ou urina de seus hospedeiros, os quais oferecem resistência a danos mecânicos e permitem que os parasitas sobrevivam e permaneçam infecciosos por períodos prolongados. O diagnóstico da coccidiose, descrição das espécies e sistemática são dependentes da caracterização do oocisto. Portanto, esta revisão teve como objetivo fornecer uma visão crítica das metodologias, vantagens e limitações dos métodos morfológicos, morfométricos e moleculares que podem ser utilizados para a caracterização destas estruturas importantes. Tornou-se evidente que nenhuma metodologia única é suficiente para caracterizar completamente essas estruturas e que a maioria das pesquisas favorecem o uso de metodologias combinadas ou polifásicas.

Molecular studies in growth hormone gene deletions in patients with isolated growth hormone deficiency.

Human GH deficiency (GHD) occurs in 1 in 4,000-10,000, and up to 30 percent of cases have an affected first degree relative suggesting many cases may be familial. To determine the GHD cases cased by GH gene defects we analyzed the GH genes of 90 consecutive cases. Genomic DNAs were used for PCR amplification of 2.7 kb fragments containing subjects’ GH gene; these PCR products were subjects to determine GH gene deletions. PCR products of 1900 and 1919 bp were obtained. By using the combination of restriction enzymes BglI, HaeII and SmaI to digest these PCR products, the various sizes of GH gene deletion can be detected. None of the possible deletions was found in these patients by either PCR or Southern blot analysis.