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Intensive FSH stimulation is a key tool of assisted reproduction technology but can cause severe complications through the development of an excessive number of small ovarian follicles. We tested the hypothesis that, in the late stages of ovulation induction, LH activity in the form of low-dose human CG (hCG) can stimulate and selectively modulate ovarian follicle function and growth, independently of FSH administration. Four groups of GnRH agonist-suppressed normoovulatory women (10 each group) received recombinant human FSH (r-hFSH) (150 IU/d) for 7 d followed by: group A, r-hFSH 150 IU/d alone; group B, r-hFSH 50 IU/d and hCG 50 IU/d; group C, r-hFSH 25 IU/d and hCG 100 IU/d; group D, hCG 200 IU/d alone. Despite several days of lowered or absent r-hFSH administration, 70% of hCG-treated patients successfully completed treatment. In these subjects, preovulatory E2 levels and large (>14 mm diameter) ovarian follicle development were not reduced; conversely, the number of small (<10 mm diameter) ovarian follicles was significantly decreased in groups B-D vs. group A. Low-dose hCG administration did not cause follicle luteinization. We conclude that, following FSH priming, LH activity administration can: 1) stimulate folliculogenesis for several days, in spite of rapidly declining FSH levels; and 2) hasten small follicle demise. Therefore, LH activity administration could be used to design radically novel ovulation induction regimens that, by partly or completely replacing mid-/late follicular phase FSH administration, may reduce costs and improve safety of assisted reproduction technology.

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Gonadotrophin-releasing hormone (GnRH) agonists have become irreplaceable addition to gonadotrophins in ovulation induction for assisted reproduction. Of the several schemes currently employed, long regimens appear to be maximally effective to optimize patient scheduling and to improve clinical results.

Pulsatile gonadotropin secretion is a critical endocrine component of the regulation of the normal menstrual cycle. Pulsatile luteinizing hormone (LH) secretion changes dynamically across the menstrual cycle. Derangements of pulsatile LH secretion are found in virtually every menstrual disorder. This article summarizes the key features of pulsatile LH secretion in the normal menstrual cycle and in ovulatory disorders.

O objetivo deste trabalho foi realizar o mapeamento das áreas suscetíveis a ocorrência de incêndios na Estação Ecológica do Taim, Rio Grande do Sul. Para a obtenção das variáveis estáticas e dinâmicas, foram utilizadas imagens do satélite Landsat 8 e imagens de Radar para a determinação da topografia da área de estudo. Como variáveis dinâmicas utilizou-se a precipitação, temperatura e uso e cobertura da terra, enquanto que variáveis estáticas foram a hipsometria, declividade e distância das estradas. Cada variável foi estratificada e posteriormente ponderada numericamente quanto a sua suscetibilidade a ocorrência a incêndio. As variáveis dinâmicas e estáticas geradas foram integradas utilizando uma equação ponderada resultando no risco de incêndios para a área de estudo. A região central da Estação Ecológica do Taim apresentou maior suscetibilidade a incêndios, englobando a classe de alto risco, totalizando 4.219,56 ha (41,61%), enquanto as regiões periféricas apresentaram risco muito baixo a ocorrência de incêndios, abrangendo 5.419,35 ha (53,44%). As variáveis de maior contribuição à ocorrência de incêndios corresponderam ao uso e cobertura da terra e a temperatura, sendo as áreas de maior risco localizadas na parte central e próximo às estradas, nas quais estão ocupadas por campo nativo. Assim, esses locais devem ter maior atenção e recursos para combate de possíveis incêndios.Palavras-chave: Landsat 8; variáveis dinâmicas e estáticas; geoprocessamento. FIRE RISK AT THE ECOLOGIAL STATION OF TAIM, RIO GRANDE DO SUL ABSTRACT: The objective of this work was to map the areas susceptible to the occurrence of fires at the Taim Ecological Station, Rio Grande do Sul. In order to obtain the static and dynamic variables, Landsat 8 satellite images and Radar images were used to determine the topography of the study area. As dynamic variables were used the precipitation, temperature and land use and coverage, while static variables were hypsometry, slope and distance of roads. Each variable was stratified and numerically weighted as to its susceptibility to fire occurrence. The dynamic and static variables generated were integrated using a weighted equation resulting in fire risk for the study area. The central region of the Taim Ecological Station presented higher susceptibility to fires, encompassing the high risk class, totaling 4,219.56 ha (41.61%), while the peripheral regions had a very low risk of occurrence of fires, covering 5,419.35 ha (53.44%). The variables of greatest contribution to the occurrence of fires corresponded to the land use and land cover and the temperature, being the areas of greater risk in the central region and near the roads, in which they are occupied by the native field. Thus, these sites should have greater attention and resources to combat possible fires.Keywords: Landsat 8; dynamic and static variables; geoprocessing.

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