The meiofauna asssociated whith Sargassum cymosum at Lázaro Beach, Ubatuba, São Paulo

In this study, the meiofauna associated with Sargassum cymosum was qualitatively and quantitatively analyzed between December 1990 and July 1991. Sampling was carried out on a moderately exposed shore at Lázaro Beach, Ubatuba (32°S - 45°W). Each alga was washed in a formaldehyde solution and the fauna in suspension was washed through a series of 500, 250, 120 and 60 µm mesh sieves. The biomass of each taxonomic group was estimated as ash-free dry weight (AFDW) according to size categories. Algae volume and dry weight were determined, incIuding epiphytes. Densities of epifauna ranged from 502.9 to 2706.6 ind.20 ml-1 as algae volume. The biomass values (326.6 to 1214.4 µg.20 ml-1 AFDW) represented a low standing stock. Harpacticoid copepods and their nauplii were the dominant group and also showed the highest biomass values, being represented by larger individuaIs (250 to 120 µm). Higher values were observed between the end of the summer and the beginning of the fali (March and April), decreasing until winter (July). This variation may be explained by habitat complexity changes, or reproduction of some taxa, as higher meiofaunal densities were found on the 60 µm mesh sieve, incIuding high percentages of nauplii.Este trabalho avalia qualitativa e quantitativamente a meiofauna associada a Sargassum cymosum estimando-se a densidade e biomassa da fauna, assim como uma possível variação temporal. As coletas foram realizadas à nordeste da Praia do Lázaro, Ubatuba (23°S - 45°W), de dez/90 a jul/91. As frondes foram mergulhadas em solução de água e formaldeído, e os organismos em suspensão retidos em uma série de malhas (500,250, 120 e 60 µm). Para cada grupo taxonômico foi estimada a biomassa em µg de peso seco livre de cinzas. Como medida de substrato foi determinado o volume e a biomassa em peso seco de alga, incluindo-se as algas epífitas. Os valores de densidade da meiofauna variaram entre 502,9 a 2706,6 ind.20 mrl de alga. A biomassa estimada por sua vez apresentou valores baixos, entre 326,6 a 1214,41-µg.20 ml-1 peso seco livre de cinzas. Copepoda Harpacticoida e seus náuplios foram dominantes numericamente e em relação à biomassa. Os valores de densidade e biomassa da meiofauna foram altos no final do verão (março) e início do outono (abril), e diminuíram gradativamente até o início do inverno (julho). Esta variação pode ser explicada por mudanças na complexidade do habitat ou, ainda, devido ao período reprodutivo de alguns táxons, já que a maior quantidade de meiofauna ocorreu na malha de 60 µm (náuplios)

Variação espacial entre verão e inverno da meiofauna do Canal de São Sebastião - SP

Spatial and seasonal variation of the density and biomass of meiofauna at higher taxonomic group levels were studied and related to sediment characteristics and water masses in São Sebastião Channel. The sampling was done at ten stations in the channel in February (summer) and August (winter) 1994. In the summer, the mean density was 605 ± 442 individuals per 4.9 cm², and in the winter, the mean density decreased to 213 ± 181 individuals per 4.9 cm². Total mean biomass ranged from 184.7 ± 156.8 ¼g x 4.9 cm-2 to 66.6 ± 48.9 ¼g x 4.9 cm-2, showing similar pattern as the density. Nematoda was the main group at most stations followed by Copepoda, as function of sediment type. Meiofauna characteristics at São Sebastião Channel reflected both the heterogeneous spatial distribution of the sediment along the channel and its seasonal variation, as well.A variação espacial e temporal da densidade e biomassa da meiofauna, em nível de grupos taxonômicos superiores, foi analisada e relacionada com as características do sedimento e as massas de água no Canal de São Sebastião. As coletas foram realizadas em dez estações, em fevereiro (verão) e agosto (inverno) de 1994. No verão, a densidade média foi de 605 ± 442 ind x 4,9 cm-2 e no inverno, 213 ± 181 ind x 4,9 cm-2. A biomassa média total variou de 184,7 ± 156,8 ¼g x 4,9 cm-2, no verão, diminuindo para 66,6 ± 48,9 ¼g x 4,9 cm-2, no inverno, mostrando padrão semelhante ao da densidade. Nematoda foi o grupo dominante em quase todas as estações, seguido de copepoda, em função do sedimento predominante. As características gerais da meiofauna na Canal de São Sebastião refletiram tanto a heterogeneidade espacial da distribuição dos sedimentos ao longo do canal, como também a sua variação temporal

Effect of oxygen on the expression of renin-angiotensin system components in a human trophoblast cell line

During the first trimester, normal placental development occurs in a low oxygen environment that is known to stimulate angiogenesis via upregulation of vascular endothelial growth factor (VEGF). Expression of the placental renin-angiotensin system (RAS) is highest in early pregnancy. While the RAS and oxygen both stimulate angiogenesis, how they interact within the placenta is unknown. We postulated that low oxygen increases expression of the proangiogenic RAS pathway and that this is associated with increased VEGF in a first trimester human trophoblast cell line (HTR-8/SVneo). HTR-8/SVneo cells were cultured in one of three oxygen tensions (1%, 5% and 20%). RAS and VEGF mRNA expression were determined by qPCR. Prorenin, angiotensin converting enzyme (ACE) and VEGF protein levels in the supernatant, as well as prorenin and ACE in cell lysates, were measured using ELISAs. Low oxygen significantly increased the expression of both angiotensin II type 1 receptor (AGTR1) and VEGF (both P < 0.05). There was a positive correlation between AGTR1 and VEGF expression at low oxygen (r = 0.64, P < 0.005). Corresponding increases in VEGF protein were observed with low oxygen (P < 0.05). Despite no change in ACE1 mRNA expression, ACE levels in the supernatant increased with low oxygen (1% and 5%, P < 0.05). Expression of other RAS components did not change. Low oxygen increased AGTR1 and VEGF expression, as well as ACE and VEGF protein levels, suggesting that the proangiogenic RAS pathway is activated. This highlights a potential role for the placental RAS in mediating the proangiogenic effects of low oxygen in placental development

Alternative Oxidase Dependent Respiration Leads to an Increased Mitochondrial Content in Two Long-Lived Mutants of the Ageing Model Podospora anserina

The retrograde response constitutes an important signalling pathway from mitochondria to the nucleus which induces several genes to allow compensation of mitochondrial impairments. In the filamentous ascomycete Podospora anserina, an example for such a response is the induction of a nuclear-encoded and iron-dependent alternative oxidase (AOX) occurring when cytochrome-c oxidase (COX) dependent respiration is affected. Several long-lived mutants are known which predominantly or exclusively respire via AOX. Here we show that two AOX-utilising mutants, grisea and PaCox17::ble, are able to compensate partially for lowered OXPHOS efficiency resulting from AOX-dependent respiration by increasing mitochondrial content. At the physiological level this is demonstrated by an elevated oxygen consumption and increased heat production. However, in the two mutants, ATP levels do not reach WT levels. Interestingly, mutant PaCox17::ble is characterized by a highly increased release of the reactive oxygen species (ROS) hydrogen peroxide. Both grisea and PaCox17::ble contain elevated levels of mitochondrial proteins involved in quality control, i. e. LON protease and the molecular chaperone HSP60. Taken together, our work demonstrates that AOX-dependent respiration in two mutants of the ageing model P. anserina is linked to a novel mechanism involved in the retrograde response pathway, mitochondrial biogenesis, which might also play an important role for cellular maintenance in other organisms

Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

δ13C of nematode communities in 27 sites was analyzed, spanning a large depth range (from 130 to 2,021 m) in five Antarctic regions, and compared to isotopic signatures of sediment organic matter. Sediment organic matter δ13C ranged from −24.4 to −21.9‰ without significant differences between regions, substrate types or depths. Nematode δ13C showed a larger range, from −34.6 to −19.3‰, and was more depleted than sediment organic matter typically by 1‰ and by up to 3‰ in silty substrata. These, and the isotopically heavy meiofauna at some stations, suggest substantial selectivity of some meiofauna for specific components of the sedimenting plankton. However, 13C-depletion in lipids and a potential contribution of chemoautotrophic carbon in the diet of the abundant genus Sabatieria may confound this interpretation. Carbon sources for Antarctic nematodes were also explored by means of an experiment in which the fate of a fresh pulse of labile carbon to the benthos was followed. This organic carbon was remineralized at a rate (11–20 mg C m−2 day−1) comparable to mineralization rates in continental slope sediments. There was no lag between sedimentation and mineralization; uptake by nematodes, however, did show such a lag. Nematodes contributed negligibly to benthic carbon mineralization