二化螟为害水稻产量损失预测模型研究

1989年在重庆巴县白市驿设置了三种不同肥力水平180个一代二化螟自然为害及18个控制螟害的隔离小区,4月30日至6月29日每隔5天系统调查了苗数、枯鞘株数和枯心株数的发生情况,收获时考种,建立了不同生育期苗数、枯鞘、枯心数对产量损失的二次回归模型。详细讨论了苗数、枯鞘和枯心数的消长规律及对产量的影响。     

Relationship between Mycobacterium avium subspecies paratuberculosis, IL-1alpha, and TRAF1 in primary bovine monocyte-derived macrophages

Mycobacterium avium subspecies paratuberculosis (MAP) is a facultative intracellular pathogen that resides in host macrophage cells. Presently, little is known about how MAP is able to subvert the normal bacteriocidal functions of infected macrophages. Previously, we reported that ileal tissues from MAP infected cattle contained high levels of interleukin-1 alpha (IL-1alpha) and tumor necrosis factor receptor-associated factor 1 (TRAF1), relative to ileal tissues from uninfected cattle. High-level expression of these two proteins could have profound effects on macrophage function, intracellular signaling, and apoptosis. We now demonstrate that high levels of TRAF1 protein are located primarily within macrophages infiltrating areas of MAP infection. We have also utilized cultured bovine monocyte-derived macrophage cells (MDM) either infected with live MAP or stimulated with recombinant IL-1alpha (rIL-1alpha) to determine if there is a relationship between IL-1alpha and TRAF1 expression. These studies have identified a dose dependent increase in TRAF1 protein levels in bovine MDM in response to infection with live MAP or following treatment with rIL-1alpha. Sustained TRAF1 protein expression was dependent upon interaction of rIL-1alpha with it's receptor and rIL-1beta was also able to enhance TRAF1 gene expression. Our results suggest that MAP may use the IL-1-TRAF1 system to enhance TRAF1 protein expression in infected bovine MDM. These novel results provide evidence for a new avenue of research on the effect of MAP and other intracellular pathogens on macrophage signaling and apoptosis.     

Phase-matched generation of coherent soft X-rays

Phase-matched harmonic conversion of visible laser light into soft x-rays was demonstrated. The recently developed technique of guided-wave frequency conversion was used to upshift light from 800 nanometers to the range from 17 to 32 nanometers. This process increased the coherent x-ray output by factors of 10(2) to 10(3) compared to the non-phase-matched case. This source uses a small-scale (sub-millijoule) high repetition-rate laser and will enable a wide variety of new experimental investigations in linear and nonlinear x-ray science.     

Characterization of a chitosanase isolated from a commercial ficin preparation

A chitosanolytic enzyme was purified from a commercial ficin preparation by affinity chromatographic removal of cysteine protease on pHMB-Sepharose 4B and cystatin-Sepharose 4B and gel filtration on Superdex 75 HR. The purified enzyme exhibited both chitinase and chitosanase activities, as determined by SDS-PAGE and gel activity staining. The optimal pH for chitosan hydrolysis was 4.5, whereas the optimal temperature was 65 degrees C. The enzyme was thermostable, as it retained almost all of its activity after incubation at 70 degrees C for 30 min. A protein oxidizing agent, N-bromosuccinimide (0.25 mM), significantly inhibited the enzyme's activity. The molecular mass of the enzyme was 16.6 kDa, as estimated by gel filtration. The enzyme showed activity toward chitosan polymers exhibiting various degrees of deacetylation (22-94%), most effectively hydrolyzing chitosan polymers that were 52-70% deacetylated. The end products of the hydrolysis catalyzed by this enzyme were low molecular weight chitosan polymers and oligomers (11.2-0.7 kDa).     

Hibiscus sabdariffa extract inhibits the development of atherosclerosis in cholesterol-fed rabbits

Hibiscus sabdariffa L., a local soft drink material and medicinal herb, is usually used effectively in native medicines against hypertension, pyrexia, and liver disorders. Here, we report an extract, HSE (H. sabdariffa extract), which is designed to exhibit hypolipidemia and antiatherosclerotic effects in rabbits with experimental atherosclerosis. New Zealand White rabbits were fed with a normal diet, high cholesterol (1.3%), lard oil (3%) diet (HCD) with or without 0.5 or 1% HSE for 10 weeks. The levels of triglyceride, cholesterol, and low-density lipoprotein cholesterol (LDL-C) were lower in the serum of rabbits fed HCD plus HSE than in the serum of rabbits fed HCD. Feeding HSE (0.5 and 1% in the diet) to rabbits significantly reduced severe atherosclerosis in the aorta. Histopathological examination showed that HSE reduced foam cell formation and inhibited smooth muscle cell migration and calcification in the blood vessel of rabbits. These results suggest that HSE inhibits serum lipids and shows an antiatherosclerotic activity.     

Technical efficiency analysis of milkfish (Chanos chanos) production in Taiwan—an application of the stochastic frontier production function

Milkfish has been farmed in Taiwan for over 300 years. Faced with limited land resources, a labor shortage, decreasing demand, and growth of imported fisheries products, the industry is looking at the problem of how to maintain a sustainable and efficient production. This study specifies a stochastic production frontier function to estimate potential milkfish farm output and efficiency by using 1997–1999 data from a survey of 433 aquaculture milkfish farms. Both Translog and Cobb–Douglas frontier production models are estimated using the maximum likelihood estimation method. Empirical results show that the Translog stochastic production function model fits the data better and that milkfish farming in Taiwan exhibits diminishing returns to scale. We also compare estimated maximum potential milkfish production per hectare under various pond conditions to provide managers with information about how to boost efficiency. In addition, this study estimates substitution elasticities and complementarity of input factors for milkfish farms to provide helpful information for milkfish farmers on how to reallocate input resources and help raise milkfish productivity through improvements in technical efficiency.     

Chitosan Oligosaccharide Alleviates Abnormal Glucose Metabolism without Inhibition of Hepatic Lipid Accumulation in a High-Fat Diet/Streptozotocin-Induced Diabetic Rat Model

This study investigated the effects of chitosan oligosaccharide (COS) on glucose metabolism and hepatic steatosis in a high-fat (HF) diet/streptozotocin-induced diabetic rat model. Male Wistar rats were divided into: (1) normal control (NC group), (2) HF diet (HF group), (3) streptozotocin (STZ)-induced diabetes with HF diet (DF group), and DF group supplemented with (4) 0.5% COS (D0.5F group), (5) 1% COS (D1F group), and (6) 5% COS (D5F group) for 4 weeks. COS supplementation significantly decreased the plasma glucose, BUN, creatinine, uric acid, triglyceride (TG), and total cholesterol (TC) levels, and hepatic glucose-6-phosphatase activity, and significantly increased hepatic hexokinase activity and glycogen content in diabetic rats; but the increased hepatic TG and TC levels could not be significantly decreased by COS supplementation. Supplementation of COS increased superoxide dismutase activity and decreased lipid peroxidation products in the diabetic rat livers. COS supplementation significantly increased phosphorylated AMP-activated protein kinase (AMPK) protein expression, and attenuated protein expression of hepatic phosphoenolpyruvate carboxykinase (PEPCK) and phosphorylated p38 and renal sodium-glucose cotransporter-2 (SGLT2) in diabetic rats. These results suggest that COS may possess a potential for alleviating abnormal glucose metabolism in diabetic rats through the inhibition of hepatic gluconeogenesis and lipid peroxidation and renal SGLT2 expression.