Carbohydrate—Fat Interactions and Obesity Examined by a Two‐Compartment Computer Model

Objective: A systems dynamics computer model was developed to examine how the interactions between carbohydrate and fat metabolism influence body weight regulation. It reflects the operation of a two reservoir‐system: one representing the body's limited glycogen, and the other, its large fat reserves. The outflows from the reservoirs correspond to the oxidation of glucose and fat, whose relative contributions are affected by the size of the prevailing glycogen and fat reserves. Together, they meet the body's energy expenditure. Replenishments occur three times per day, in portions restoring total glycogen content to specific levels. A parameter mimicking the action of insulin is necessary to create realistic responses. Research Methods and Procedures: The model was run for 125‐day periods to establish the degree of adiposity for which rates of fat oxidation become commensurate with fat intake and the influence thereon of various dietary, environmental, lifestyle, and inherited variables. Results: Equivalent degrees of adiposity can be sustained under a variety of conditions. For instance, the impact on steady‐state body fat contents of a 10% increase or decrease in the energy provided by dietary fat is offset by a 26‐gram decrease or increase in mean glycogen levels. Discussion: Environmental factors such as food diversity, palatability, and availability can be expected to raise the range within which glycogen levels are habitually maintained. This restrains fat oxidation, until expansion of the fat mass is sufficient to promote fat oxidation to a rate commensurate with dietary fat intake. This metabolic leverage can explain why increased food offerings tend to raise the prevalence of obesity.     

Beyond genomics

The added value obtained by combining genomic analysis with proteomic analysis and supplementary information on mechanisms of interaction has been well illustrated in a recent paper by Ideker et al. This gives a far more meaningful interpretation of metabolic responses to a mutation or change in environment than could be obtained from correlation of expression profiles alone, and it provides evidence that addition of metabolomics data would give even further gains. The results also hint at competition between mRNA molecules for translation, so that responses at the protein level are attenuated relative to changes in gene expression.     

Mammals of south-east Asian islands and their Late Pleistocene environments

Aim The environments that existed in south‐east Asian islands during the last glacial are poorly known, limiting our understanding of mammalian biogeography in the region. The objective of this research is to investigate the ecological characteristics of mammal faunas on small islands, and to see whether the habitat requirements of the species in those faunas can be used to deduct the vegetation types that existed on islands before becoming isolated by rising sea levels. Location The maps presented here cover the small islands of tropical south‐east Asia, including the Burmese, Thai and Cambodian islands in the north, the islands off the coast of west Sumatra in the west, the islands around Java in the south, and the islands off the east coast of Borneo in the east, including the Philippine islands of Palawan and those in the Sulu Archipelago. Methods The presence records of mammal species on 215 small islands in the region were compiled, and the habitat requirements for each of these species was assessed (species that had probably been introduced by humans were excluded from the analysis). For each island location (longitude and latitude), maximum altitude of the island, total area, depth to nearest land, distance to nearest island, and distance to nearest mainland were assessed. Geographical and statistical analyses were used to investigate patterns of mammalian habitat requirements. Results The geographical analysis showed that forest‐dependent species, i.e. species that are only found in primary forest (lowland and mountainous), appear to be concentrated on islands off west Sumatra, in the Lingga and Riau Archipelagos, around Palawan, and around Bunguran Island; they are absent mostly from the islands of the Java Sea, those off the east coast of eastern Borneo, from most islands in the Sunda Strait, several islands in the northern South China Sea, and from all islands off the west coast of the Malay/Thai Peninsula and in the Gulf of Thailand. Species that generally occur outside primary forest, that is those in secondary forest, gardens, plantations and open areas mostly occurred on islands where the forest‐dependent species were absent. The statistical analysis showed that latitude and size of islands were important factors that determined the absence and presence of forest‐dependent species on small islands. Main conclusions The data suggest that during the last glacial there were several areas in the Sundaic region that remained forest covered: west of Sumatra, north‐west of Borneo, the Malacca Straits and around Palawan. Other areas may have been covered by more open vegetation types like tree savanna, or open deciduous forest: on and to the east of the Malay/Thai Peninsula, the Java Sea area, including the Sunda Strait, and eastern Borneo.     

E.tenella感染雏鸡特异性抗体的动态变化和母源免疫的研究

本实验用斑点酶联免疫试验 (Dot ELISA)检测了E .tenella感染雏鸡特异性抗体、免疫母鸡卵黄和后代血清中特异性母源抗体的动态变化及不同日龄雏鸡的抗球虫水平。结果表明 :(1)雏鸡感染E .tenella后第 6d即可在循环血液中检测到特异性IgG ,于第 18天达到峰值 ,第 30天降至感染后第 7天时的水平。 (2 )母鸡二次免疫后第 5天卵黄中即有高水平的母源抗体 ,免疫母鸡后代 1日龄时母源抗体滴度高达 9.83,与未免疫对照组差异极显著 (P <0 .0 1) ,二者都随着日龄增长降低 ,但免疫组下降幅度很小 ,2 9日龄时仍和对照组 18日龄水平相当。 (3)免疫母鸡后代对再感染的抵抗力显著增强 ,卵囊减少率高达 93%,抗球虫指数和相对增重率都与对照组差异极显著 (P <0 .0 1) ,雏鸡的抗球虫水平随着日龄增长逐渐降低 ;母源抗体、抗球虫指数和相对增重率三者之间两两呈现明显的正相关 ,而这三者又都与卵囊产量呈明显的负相关。     

Effect of visible light on superoxide dismutase (SOD) activity in the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

Superoxide dismutase (SOD) was studied in the agarophyte Gracilariopsis tenuifrons. Similar SOD activity (130 ± 9U mg^-1) was observed in material from different regions of SouthAmerica, from different phases of the life cycle (gametophytes andtetrasporophytes), and from apical and basal sections of the thallus.In alga grown under a light-dark cycle, SOD activity in samples takenat different times exhibited a diurnal rhythm. The activity measured duringthe day phase was twice as much as during the night phase. This rhythm didnot persist under constant light, indicating light regulation of SOD activity.SOD activity was tested in algae submitted to different light intensities anddifferent wavelengths. It increased with the light intensity. The blue lightwavelength exerted a greater induction of SOD activity than other specificwavelengths.     

ROLE OF RICE VOLATILES IN THE FORAGING BEHAVIOUR OF CYRTORHINUS LIVIDIPENNIS REUTER

Abstract Experiments were conducted in laboratory to study the impacts of rice genotypes and nitrogen levels on the preference of the egg predator, Cyrtorhinus lividipennis , for eggs of brown planthopper(BPH), Nilaparvata lugens (Stal), and their relation to the rice volatiles. In two-choice tests, the female predators showed different preference for BPH eggs on different rice genotypes, but not for BPH eggs on rice plants treated with different levels of nitrogen. The olfactory response test revealed that more predator oriented to the odour from healthy rice plants compared with the plain air (control); the predator preferred BPH nymph-damaged plants to healthy plants, and BPH female adult-damaged plants to BPH nymph-damaged plants. The comparative studies between rice genotypes and nitrogen levels indicated that there were obvious differences in attractiveness to the predator between rice genotypes, while there was no significant difference between rice plants treated with different levels of nitrogen. The results showed that rice volatiles played an important role in mediating the foraging behaviour of C. lividipennis . Implications for augmenting the effectiveness of natural enemies by adjusting rice attributes and cultural practices are discussed.     

Predominance of terrestrial organic matter in sediments from a cyanobacteria- blooming hypereutrophic lake

Although an understanding of the quantity and quality of sedimentary organic matter (SOM) pools is necessary to design sound environmental management strategies for lacustrine systems, the characterization of organic matter sources and the assessment of their relative contributions to eutrophic and inland lake sediments remain insufficient. In this study, the contribution of potential organic matter sources to sediments in shallow and hypereutrophic lake Taihu, China was assessed on the molecular level using source-specific fatty acid biomarkers. The results indicated that SOM was composed mainly of terrestrial plants with a maximal contribution of 45.3 ± 2.4% to the total organic carbon, which accounted for approximately 66% among the determined organic matter sources. Evidence suggests the terrestrial plants remained in a fresh state in surface sediments: the correlation (R² = 0.62, p < 0.05) between bacterial and terrestrial plant carbon was strong. On the other hand, aquatic plant and bacterial carbon contributed 5–15% to the total organic carbon, which was followed by the faint contribution (<5% of total organic carbon) of algae-derived organic carbon including cyanobacteria, diatoms, and dinoflagellates. The results provided details of the contributions of SOM sources, illustrating the usefulness of fatty acid biomarkers in discriminating organic matter sources within lake environments. Although organic matter sources of sediments varied in spatial and temporal patterns, the strong correlation between terrestrial plant and total organic carbon (R² = 0.60, p < 0.05) indicates that terrestrial plants were the dominant source in lake sediments.     

Characterization of cDNA clones for differentially expressed genes in embryos of dormant and nondormant Avena fatua L. caryopses

The molecular regulation of seed dormancy was investigated using differential display to visualize and isolate cDNAs representing differentially expressed genes during early imbibition of dormant and nondormant Avena fatua L. embryos. Of about 3000 cDNA bands examined, 5 cDNAs hybridized with mRNAs exhibiting dormancy-associated expression patterns during the first 48 h of imbibition, while many more nondormancy-associated cDNAs were observed. Dormancy-associated clone AFD1 hybridized with a 1.5 kb mRNA barely detectable in dry dormant and nondormant embryos that became more abundant in dormant embryos after 24 h of imbibition. Clone AFD2 hybridized with two mRNAs, a 1.3 kb message constitutively expressed in dormant and nondormant embryos and a 0.9 kb message present at higher levels in dormant embryos after 3 h of imbibition. Nondormancy-associated clones AFN1, AFN2 and AFN3 hybridized with 1.5 kb, 1.7 kb and 1.1 kb mRNAs, respectively, that were more abundant in nondormant embryos during imbibition. Expression patterns of some mRNAs in dormant embryos induced to germinate by GA₃ treatment were different than water controls, but were not identical to those observed in nondormant embryos. DNA sequence analysis revealed 76% sequence identity between clone AFN3 and a Citrus sinensis glutathione peroxidase-like cDNA, while significant sequence similarities with known genes were not found for other clones. Southern hybridization analyses showed that all clones represent low (1 to 4) copy number genes.