Expression of beta-amyloid induced age-dependent presynaptic and axonal changes in Drosophila.

Alzheimer's disease (AD) is attributable to synapse dysfunction and loss, but the nature and progression of the presynaptic structural and functional changes in AD are essentially unknown. We expressed wild-type or arctic form of beta amyloid(1-42) (Abeta) in a small group of neurons in the adult fly and performed extensive time course analysis of the function and structure of both axon and presynaptic terminals at the identified single-neuron level. Abeta accumulated intracellularly and induced a range of age-dependent changes, including depletion of presynaptic mitochondria, slowdown of bi-directional transports of axonal mitochondria, decreased synaptic vesicles, increased large vacuoles, and elevated synaptic fatigue. These structural and functional synaptic changes correlated with age-dependent deficit in motor behavior. All these alterations were accelerated in flies expressing the arctic form of Abeta. The depletion of presynaptic mitochondria was the earliest detected phenotype and was not caused by the change in axonal transport of mitochondria. Moreover, axonal mitochondria exhibited a dramatic reduction in number but a significant increase in size in aged Abeta-expressing flies, indicating a global depletion of mitochondria in the neuron and an impairment of mitochondria fission. These results suggest that Abeta accumulation depletes presynaptic and axonal mitochondria, leading to other presynaptic deficits.

Age-related changes in anxiety are task-specific in the senescence-accelerated prone mouse 8.

In the senescence-accelerated prone mouse 8 (SAMP8), an excellent model of brain aging, aged individuals have impairments in learning and memory. One study has indicated that the anxiety is also reduced in those mice. However, increased anxiety with aging has been observed in other models, such as C57BL mice and rats. Altered emotion is linked to impairments in learning and memory. Thus, we were interested in further characterizing the pattern of age-related changes in anxiety in this strain. In the present study, a battery of tasks (i.e., elevated plus maze, open field, black-white alley, food neophobia and hole-board) was used to determine the age-related alterations in anxiety in the SAMP8 mice. Three age groups (2, 6, and 10 months of age) of SAMP8 mice and their control SAMR1 (senescence-accelerated resistant mouse 1) mice were used. The results showed that the effect of age was significant only in the elevated plus maze and black-white alley tasks. The SAMP8 showed a tendency toward increased anxiety with age as measured by the time spent on the open arms of elevated plus maze. When the sexes were separated for analysis, the increased anxiety was significant in the old (10-month-old) male SAMP8. In the black-white alley task, however, anxiety levels in the old male SAMP8 mice were lower than those of the middle-aged (6-month-old) mice, but similar to those in the young (2-month-old) mice. These results suggested that the age-related anxiety levels of SAMP8 mice are sex- and task-specific.

Pysicochemical properties of Tibetan hull-less barley starch.

Objectives of this study were to (1) determine the starch physicochemical properties of two commercial Tibetan hull-less barley varieties, Beiqing (BQ) and Kangqing (KQ); and (2) understand the relationship between unique properties of the starches, their structures, and impacts of growing conditions. The BQ barleys were grown at a location with lower temperature and less rainfall compared with the KQ barleys. The BQ starches showed significantly lower onset-gelatinization temperature (54.1-54.9 °C), larger gelatinization-temperature range (9.4-10.6 °C), and higher peak-viscosities (138.9-153.9RVU) than the KQ starches (55.1-56.1 °C, 7.4-8.8 °C, and 63.4-64.7RVU, respectively). After a treatment with 2% sodium-dodecyl-sulphate solution, the KQ starches showed substantially greater increases in peak viscosities than the BQ starches. Annealing of starch and enhanced amylose-lipid complex formation, resulting from higher growing temperature during the development of the KQ starches, likely contributed to the differences in thermal and pasting properties between the BQ and KQ starches.

Dosage effects of Waxy gene on the structures and properties of corn starch.

The objective of this study was to understand dosage effects of the Waxy gene on the structures of amylose and amylopectin and on the properties of corn starch. Reciprocal crossing of isogenic normal and waxy corn lines was conducted to develop hybrids with different dosages (0, 1, 2, 3) of Waxy gene in the endosperm. The amylose content of starch and proportions of branch chains of DP 17-30 and extra-long branch chains (DP>100) of amylopectin were positively correlated with the Waxy-gene dosage. Proportions of short (DP<17) and long branch-chains (DP 30-80), however, were negatively correlated with the Waxy-gene dosage. The gelatinization conclusion-temperature and temperature-range of the starch were negatively correlated with the Waxy-gene dosage, indicating that amylose facilitated dissociation of the surrounding crystalline regions. These results helped us understand the function of granule-bound starch synthase I in the biosynthesis of amylose and amylopectin and impacts of Waxy-gene dosages on the properties of corn starch.

Characterization and development mechanism of Apios americana tuber starch.

Apios americana is a wild legume-bearing plant with edible tubers. Domestication of Apios is in progress because of the superior nutritional value and health benefits of the tuber. Objectives of this study were to: (1) characterize physicochemical properties of the Apios tuber starch; and (2) understand differences in starch structures and properties between the mother (seed) and child (progeny) tubers and the mechanism of starch development. Granules of the Apios tuber starch displayed ellipsoidal, rod, or kidney shape with diameter ranges of 1-30µm. The mother tuber starches displayed greater percentage crystallinity, larger gelatinization enthalpy-changes, longer branch-chain lengths of amylopectin, and lower pasting viscosity than their counterpart child tuber starches. The mother tuber starch of Apios 2127 displayed distinct two peaks of gelatinization, which were attributed to starch granules located at different regions of the tuber having different structures and properties. The mother tuber displayed more active starch biosynthesis in the periphery than in the center of the tuber.

Characterization of normal and waxy corn starch for bioethanol production.

Objectives of this study were to compare ethanol production between normal and waxy corn using a cold fermentation process and to understand effects of starch structures and properties on ethanol production. Ethanol yields positively correlated (p < 0.01) with starch contents of kernels of the normal and waxy corn. The average starch-ethanol conversion efficiency of waxy corn (93.0%) was substantially greater than that of normal corn (88.2%). Waxy corn starch consisted of very little amylose and mostly amylopectin that had a shorter average branch chain length than normal corn amylopectin. Regression analyses showed that average amylopectin branch chain lengths and percentage of long branch chains (DP > 37) of waxy corn starch negatively correlated with the starch hydrolysis rate and the ethanol yield. These results indicated that starch structures and properties of the normal and waxy corn had significant effects on the ethanol yield using a cold fermentation process.