Litter production and nutrient deposition from native woody species in the Brazilian semi-arid region

Agroforestry Systems - The use of native trees in agroecosystems is a promising way to increase litter deposition and nutrient cycling and foster the recovery of degraded areas, especially in...     

Genetic diversity of seeds from four German Douglas fir (Pseudotsuga menziesii) seed orchards

European Journal of Forest Research - In Germany, Douglas fir (Pseudotsuga menziesii Franco) is seen as a valuable species for future cultivation in times of climate change. Local seed production...     

Effects of Feeding Frequency and Handling on Growth and Mortality of Cultured Walking Catfish Clarias fuscus

Two experiments were conducted to study the effects of feeding frequency on growth, and of handling stress on growth and mortality, in intensive tank culture of the walking catfish Clarias fuscus . In the first experiment, fish were grown from an initial weight of 37 g for 34 d. A fixed ration of 3.0% body weight per day was divided into either 1, 2, or 3 feedings per day, and fish were either handled weekly or left unhandled for the entire experiment. Fish given 3 feedings per day experienced 19% faster growth ( P < 0.05) than fish given the same ration in a single feeding per day. These differences in growth reflect differences in assimilation efficiency, assuming all other metabolic costs were constant among treatments. Handling of individuals caused decreased growth; however, there was no effect on mortality.
In the second experiment, fish were grown from an initial weight of 78 g for 29 d. Fish were fed either 1 or 2 satiation feedings per day and were either handled weekly or left unhandled for the entire experiment. Fish fed 2 satiation feedings per day experienced 47% faster growth ( P < 0.05) than fish fed 1 satiation feeding per day, which was assumed to reflect a higher level of food consumption. No effect of handling on either growth or mortality was observed for fish in experiment 2. Multiple meals per day also reduced depensatory growth among individuals in both experiments.     

Morphological studies of peripheral blood cells of the Chinese sturgeon, <Emphasis Type="Italic">Acipenser sinensis</Emphasis>

The peripheral blood cells of one-year-old Chinese sturgeon (Acipenser sinensis) have been studied by light microscopy and transmission electron microscopy. The erythrocyte count was 84.86 × 10⁴ cell mm⁻³ in the peripheral blood of the fish and that of leukocytes was 2.24 × 10⁴ cell mm⁻³. The erythrocytes and four main types of leucocyte—thrombocytes, lymphocytes, granulocytes (including neutrophils and eosinophils), and monocytes, were identified in the peripheral blood. In addition to normal erythrocytes, reticulocytes and division of erythrocytes were observed. Thrombocytes were the most numerous among the leukocytes, and the number of neutrophils with lobated nuclei was larger than for other fish. The structures of the erythrocytes, lymphocytes, monocytes, granulocytes, and thrombocytes of the fish were studied. The erythrocytes were almost completely devoid of organelles, except for some mitochondria and granules. A large number of vacuoles and a few organelles were observed in cytoplasm of the monocytes. There were many microvilli on the membrane and pseudopodia-like cytoplasm bulge in the lymphocytes. The neutrophils were round or oval in shape with bilobed, trilobed, or multilobed nuclei whereas the eosinophils had big special granules, dark stained. There were many vesicles in some thrombocytes, which were related to its phagocytosis; some thrombocytes had almost no cytoplasm or organelles.     

Contents,vol. 8, nos. 1–6, 1990

Contents, vol. 8, nos. 1–6, 1990     

Insights into Insulin and Glucagon Responses in Fish

The focus of this review is the response of insulin and glucagon to various experimental and physiological conditions in fish. Circulating levels of insulin and glucagon have been analyzed in several fish species, principally salmonids. It is generally accepted that, in fish, the insulin secretion in response to amino acids is stronger than to glucose, although this information has been obtained mainly from carnivorous species. Studies of other species demonstrate that the alimentary pattern affect hormonal secretion and should be taken into account when the effects of secretagogues are analyzed. There are few studies of glucagon secretion, even in salmonids, although it is known that amino acids also stimulate its release. The level of this response and its relationship to insulin secretion depends upon the species of fish. We will discuss the significance of these observations, while also considering other important factors, including the influence of neuropeptides and interactions with other pancreatic and gastro-intestinal hormones. Finally, seasonal, temperature and reproductive stage effects will be discussed, all of which should be taken into account when attempting to understand the role of pancreatic hormones in fish. This short review will not cover the action of these hormones on their target tissues.     

Development of a standard test for dough-making properties of oat cultivars

Bread is consumed all over the world. However, so far, production of large volume bread is only possible with wheat. Alternatives, such as oats, are less suitable but this is partly due to the lack of knowledge about their functionality for other purposes than porridge, which is their most common use. Existing standard tests for the dough making characteristics of wheat flour are not suitable for oat flour, hampering research to optimize oats for bread-making purposes. We therefore set out to develop a test to evaluate oat in relation to mixing and dough making properties using wheat as a model. It was possible to reproduce the profile of various qualities of wheat flour using mixtures of oat flour and gluten in different proportions. Our standard test was based on a dough system composed of 87.2% oat flour and 12.8% gluten and it presented similar properties to a wheat flour with regard to resistance to extension. This dough system was sensitive and reliable (coefficient of variation lower than 10%) for detecting differences among oat cultivars, and it can be used to screen oat varieties and individual oat components in relation to relevant properties for bread-making purposes.     

Antiplatelet and Anticoagulant Effects of Diterpenes Isolated from the Marine Alga,Dictyota menstrualis

Cardiovascular diseases represent a major cause of disability and death worldwide. Therapeutics are available, but they often have unsatisfactory results and may produce side effects. Alternative treatments based on the use of natural products have been extensively investigated, because of their low toxicity and side effects. Marine organisms are prime candidates for such products, as they are sources of numerous and complex substances with ecological and pharmacological effects. In this work, we investigated, through in vitro experiments, the effects of three diterpenes (pachydictyol A, isopachydictyol A and dichotomanol) from the Brazilian marine alga, Dictyota menstrualis, on platelet aggregation and plasma coagulation. Results showed that dichotomanol inhibited ADP- or collagen-induced aggregation of platelet-rich plasma (PRP), but failed to inhibit washed platelets (WP). In contrast, pachydictyol A and isopachydictyol A failed to inhibit the aggregation of PRP, but inhibited WP aggregation induced by collagen or thrombin. These diterpenes also inhibited coagulation analyzed by the prothrombin time and activated partial thromboplastin time and on commercial fibrinogen. Moreover, diterpenes inhibited the catalytic activity of thrombin. Theoretical studies using the Osiris Property Explorer software showed that diterpenes have low theoretical toxicity profiles and a drug-score similar to commercial anticoagulant drugs. In conclusion, these diterpenes are promising candidates for use in anticoagulant therapy, and this study also highlights the biotechnological potential of oceans and the importance of bioprospecting to develop medicines.     

Plot-scale manipulations of organic matter inputs to soils correlate with shifts in microbial community composition in a lowland tropical rain forest

Little is known about the organisms responsible for decomposition in terrestrial ecosystems, or how variations in their relative abundance may influence soil carbon (C) cycling. Here, we altered organic matter in situ by manipulating both litter and throughfall inputs to tropical rain forest soils, and then used qPCR and error-corrected bar-coded pyrosequencing to investigate how the resulting changes in soil chemical properties affected microbial community structure. The plot-scale manipulations drove significant changes in microbial community composition: Acidobacteria were present in greater relative abundance in litter removal plots than in double-litter plots, while Alphaproteobacteria were found in higher relative abundance in double-litter and throughfall reduction plots than in control or litter removal plots. In addition, the bacterial:archaeal ratio was higher in double-litter than no-litter plots. The relative abundances of Actinobacteria, Alphaproteobacteria and Gammaproteobacteria were positively correlated with microbial biomass C and nitrogen (N), and soil N and C pools, while acidobacterial relative abundance was negatively correlated with these same factors. Bacterial:archaeal ratios were positively correlated with soil moisture, total soil C and N, extractable ammonium pools, and soil C:N ratios. Additionally, bacterial:archaeal ratios were positively related to the relative abundance of Actinobacteria, Gammaproteobacteria, and Actinobacteria, and negatively correlated to the relative abundance of Nitrospira and Acidobacteria. Together, our results support the copiotrophic/oligotrophic model of soil heterotrophic microbes suggested by Fierer et al. (2007).