Dissecting the sugarcane expressed sequence tag (SUCEST) database: unraveling flower-specific genes

Existem quase 260.000 clones independentes, seqüenciados a partir da extremidade 5', no banco de dados do SUCEST (Sugarcane Expressed Sequence Tag), os quais foram obtidos a partir de 37 bibliotecas de cDNA preparadas de diferentes tecidos. Este grande número de etiquetas de seqüências expressas (ESTs) fornece uma oportunidade, sem precedentes em plantas, de realizar um 'digital differential screening' em bibliotecas de cDNA selecionadas. Geralmente, a freqüência de um determinado EST está correlacionada ao acúmulo de transcritos nos tecidos dos quais as bibliotecas de cDNA foram construídas, e desta forma, é possível comparar o transcriptoma completo de diferentes tecidos, usando uma análise computacional de um banco de dados de ESTs. Em nossa pesquisa, analisamos os ESTs de cana-de-açúcar de acordo com sua expressäo tecidual e identificamos mais de 1.000 putativos genes específicos de flor. O fato de que usando esta técnica fomos capazes de identificar homólogos em cana-de-açúcar, de vários genes previamente descritos como específicos de pólen, sustenta este método de estimar especificidade tecidual. Além disto, ESTs com similaridade a genes específicos de órgäos reprodutivos foram revelados, como por exemplo, o gene que codifica uma proteína meiótica essencial para a montagem do complexo sinaptonêmico e sinapse normal. Esta abordagem também permitiu a identificaçäo de muitas seqüências anônimas, específicas de flor, que säo boas candidatas para novos genes envolvidos com a reproduçäo de plantas. Este trabalho descreve a análise dos níveis de expressäo gênica de 24 clusters de ESTs, durante o desenvolvimento floral, usando um 'northern blot digital' construído a partir da contagem direta dos ESTs das bibliotecas näo-normalizadas de cDNAs de cana-de-açúcar.

Peri- and postnatal developmental toxicity of beta-myrcene in the rat.

beta-Myrcene (MYR) and essential oils containing this monoterpene have been widely used as scenting agents in cosmetics, detergents, soaps, and as flavouring additives in food and beverages. Recently, MYR was reported to be an analgesic substance and the active principle of lemongrass tea. Despite the importance of human exposure to MYR, its toxicological profile has not been comprehensively studied. The aim of this study was to provide data on the peri- and postnatal developmental toxicity of this terpene. MYR (0.25, 0.5, 1.0 and 1.5 g/kg) in corn oil was given by gavage to female Wistar rats from day 15 of pregnancy, parturition and throughout the period of lactation up to weaning (postnatal day 21). The progeny were examined at birth and subsequently to weaning. Mortality, weight gain and physical signs of postnatal development (ear unfolding, incisor eruption, fur development and eye opening) were evaluated. When the exposed offspring reached maturity (120 days) their reproductive capacity was assessed. No adverse effects on the offspring were seen with the lowest dose tested, but 0.5 g/kg and higher doses decreased birth weight, increased perinatal mortality and delayed the day of appearance of landmarks of postnatal development. Moreover, fertility was impaired in female offspring exposed to the two highest doses of MYR. From the data presented in this paper the no-observed-adverse-effect level for peri- and postnatal developmental toxicity could be set at 0.25 g beta-myrcene/kg body weight.

Study on embryo-foetotoxicity of beta-myrcene in the rat.

beta-Myrcene is a constituent of many essential oils that have been used extensively in cosmetic fragrances and as flavouring additives in the food industry. Recently, this monoterpene was reported to be an analgesic substance. Notwithstanding the widespread use of myrcene and essential oils containing myrcene in perfume and in food additives, experimental studies on the toxicity of this substance are still scarce. This study aimed to provide data on the embryo-foetotoxic potential of beta-myrcene in the rat. beta-Myrcene (0.25, 0.5 and 1.2 g/kg) in corn oil was given orally to Wistar rats from day 6 to 15 of pregnancy. Caesarean sections were performed on day 20 of pregnancy, and the number of resorptions and implantation sites were recorded. Foetuses were weighed, examined for external malformations, and fixed for visceral examination, or cleared and stained with Alizarin Red S for skeleton evaluation. No adverse effects were seen with the two lowest doses tested. Decreased weight gain during the first days of treatment and the death of one of 29 treated dams indicated that the highest dose tested (1.2 g/kg) induced maternal toxicity. A higher incidence of signs of retardation and of anomalies in the foetal skeleton indicated that 1.2 g/kg was also toxic to the rat embryo. From the data presented in this paper the no-observed-adverse-effect level for embryo-foetotoxicity could be set at 0.5 g beta-myrcene/kg body weight.

Neurobehavioral development of rats exposed to toluene through maternal milk.

Organic solvents have been detected in the milk of workers in the rubber industry exposed during gestation to a mixture of solvents at average concentrations lower than the currently accepted occupational limit of exposure (100 ppm). The objective of the present study was to determine if exposure of rat offspring to toluene during lactation, through maternal milk, would affect the developing brain. Three month old, lactating Wistar rats were injected with toluene (1.2 g/kg, sc, N = 10) daily from lactation day 2 (day of delivery = day 1) to day 21. Controls (N = 9) were injected with the vehicle (corn oil). Offspring (7 pups per liter) were evaluated for neurosomatic development and exploratory behavior before weaning and behavior in the open field. A second group of toluene-treated rats (N = 6) and controls (N = 6) was used to evaluate behavior of the offspring in the open-field on day 35 and performance in a shuttle box in adulthood. Toluene levels in blood and milk after a single 1.2 g/kg sc injection were studied in a third group of rats on lactation day 10. Toluene levels in milk 4 h after a single injection (10.3 +/- 6.2) were 5 times higher than in blood (2.1 +/- 0.8). No effects of treatment on offspring development or on any of the behavioral tests were observed. Sex differences were observed in open-field behavior and performance in the shuttle box. The present results suggest that exposure of pups to high concentrations of toluene through maternal milk does not result in blood levels high enough to affect growth or development.

Neurobehavioral development of rats exposed to toluene through maternal milk

Organic solvents have been detected in the milk of workers in the rubber industry exposed during gestation to a mixture of solvents at average concentrations lower than the currently accepted occupational limit of exposure (100ppm). The objective of the present study was to determine if exposure of rat offspring to toluene during laction, through maternal milk, would affect the developing brain. There month old, lactating Wistar rats were injedted with toluene (1.2 g/Kg, sc, N = 10) daily from laction day 2(day of delivery - day 1) to day 21. Controls (N=9) were injected with the vehicle (c0rn oil). Offspring (7 pups per litter) were evaluated form neurosomatic development and exploratory behavior before weaning and behavior in the open field. A second group of toluene treated ratas (N=6) and controls (N=6) was used to evaluate behavior of the offspring in the open-field on day 35 and performance in a shuttle box in adulthood. Toluene levels in blood and milk after a single 1.2 g/Kg sc injection were studied in a third group of rats on laction day 10. Toluene levels in milk 4 h after a single injection (10.3ñ6.2) were 5 times higher than in blood (2.1ñ0.8). No effects of treatment on offspring development or on any of the behavioral tests were observed. Sex differences were observed in open-field behavior and performance in the shuttle box. The present results suggest that exposure of pups to high concentrations of toluene through maternal milk does not result in blood levels high enough to affect growth or development