苹果双变气调贮藏

苹果双变气调贮藏(TDCA)是在产地简易气调贮藏基础上,总结发展形成的一项新的理论与技术。与传统气调不同,TDCA贮藏初期采用较高温度(10℃或更高),高CO_2(10％以上),并在贮藏期间变动,由高到低。对比试验证明,TDCA贮藏效果优于冷藏,与气调相近。其生理机制在于显著抑制呼吸作用;抑制乙烯的生成和催熟作用,减弱叶绿素和原果胶分解;保持果实色泽和硬度,抑制虎皮病的发生。初步确定的双变模式在生产上应用获得良好效益。同时还讨论了贮藏期间温度和气体成分变动之间相互依赖的辨证关系以及环境因子变动的合理性。     

硅橡胶窗气调帐贮藏苹果的研究

在塑料薄膜帐上镶嵌国产硅橡胶膜的透气窗,作成硅橡胶窗气调帐,贮藏苹果。由于硅橡胶对O_2及CO_2有高的透气性及选择性,选用适当面积的气体交换窗能有效地自动调节帐内的O_2及CO_2浓度,获得气调需要的气体组合,达到长期贮藏保鲜的效果。这种方法经济、简便、易行,在生产上具有实用价值,很有发展前途。     

几种简易的贮藏方法对稻谷（米）品质的影响（简报）

几种稻谷与稻米的简易气调贮藏方法中,以40％ CO_2处理为最好,贮藏14个月的稻米蛋白质含量比对照高,品质不下降,且受高温高湿的影响小。     

双相变动气调——苹果贮藏保鲜的新理论与技术

双相变动气调是一项崭新的苹果气调贮藏理论与技术。它是在总结了中科院上海植物生理研究所自70年代以来,有关苹果采后高CO_2控制成熟衰老、塑料薄膜小包装贮藏和运输技术、硅窗帐贮藏方法,以及辽宁、山东苹果产地贮藏技术和经验,特别是山西省农科院十多年来土窑洞加简易气调贮藏苹果技术和经验的基础上,经过多年多点严格对比试验,证明这项理论和技术贮藏苹果效果明显之后,于1988年由中科院上海植生所刘愚副研究员首次提出“双相变动气调贮藏”新概念。     

贮藏温度和气体组成对苹果乙烯生物合成的影响

苹果果实贮藏在高变温条件下(10℃开始,以后降至0℃)的空气中,随着乙烯形成酶(EFE)和ACC合成酶活性的增高,果实内乙烯浓度迅速上升,ACC和MACC积累。低温(0℃)抑制乙烯生成,ACC和MACC也有积累,但保持较高的EFE,促进ACC合成酶不断上升。低温气调(CA)(3％CO_2,3％O_2)显著抑制乙烯生成和相应的酶活性。高变温情况下,先提高CO_2浓度至12％,然后,随温度变化CO_2降至6％,形成双变气调。双变气调对乙烯生物合成的抑制作用与CA相同。     

羊奶果采后贮藏保鲜初步研究

本文探讨了羊奶果果实成熟度、包装方法、带枝叶与否、气调、温度以及保鲜剂处理对其贮藏效果的影响。试验结果表明,带枝叶的黄色果用3％硫脲等保鲜剂浸果10分钟,晾干后装入干燥器(5％CO_2气调)或塑料框外套2层0.03mm厚的聚乙烯薄膜塑料袋包装,贮藏于室温(15～20℃)下可保鲜38～42天,好果率在97.3％以上;于较适温度6～12℃下,可保鲜75～90天,好果率在90.0％以上。     

应用硅橡胶气体交换窗贮藏几种蔬菜的初步试验

由于硅橡胶薄膜的透气性比聚乙烯薄膜和聚氯乙烯薄膜高,CO_2、O_2和N_2的透性比为12:2:1,透过乙烯的能力也较强。因此,根据一定的贮量和温度条件,在塑料薄膜贮藏密封系统上镶嵌一定面积的硅橡胶薄膜(简称硅膜),形成硅膜气体交换窗(简称硅窗),使系统中的O_2和CO_2维持在一定范围内,从而免去气调贮藏的许多昂贵设备和烦杂     

人工脱涩处理对广西野生柿种质果实贮藏性的影响

为研究广西野生柿种质资源果实采后软化机制,该研究以广西特有的野生柿种质‘油柿''(YS)、‘农家栽培柿''(ZP)和主栽品种‘恭城月柿''为材料,分析了人工脱涩乙烯利处理的果实采后贮藏中可滴定酸含量、可溶性糖含量、硬度、乙烯生物合成量、色差、可溶性单宁含量、果胶及细胞壁降解酶活性的变化。结果表明:(1)与‘恭城月柿''相比,‘油柿''可滴定酸含量高,可溶性糖含量低,转色缓慢,果实易软化。其中,YS-4最不耐贮藏,乙烯利处理后,贮藏第4天硬度降至1.620 N,第6天可溶性单宁含量下降至2.398 mg·g^-1,整个贮藏期原果胶含量下降最慢,末期可溶性果胶值最低,为0.832%; YS-2最耐贮藏,乙烯利处理第8天硬度为YS-4的3.6倍,贮藏末期硬度在所有‘油柿''中最高。(2)‘农家栽培柿''中乙烯利处理贮藏末期ZP-2可滴定酸含量最高,可溶性糖含量低,转色最缓慢,原果胶降幅最小,可溶性果胶含量最高; 相反ZP-3果实转色快且易软化,可滴定酸含量最低,可溶性糖含量低,原果胶降幅最大,可溶性果胶含量低。(3)‘恭城月柿''PG酶活性和Cx酶活性远远高于‘油柿'',各‘油柿''种质的果实软化程度与细胞壁降解酶活性的相关性不同,β-D-Gal酶和Cx酶在‘农家栽培柿''贮藏前期起作用,PG酶在贮藏前期和后期对果实软化起作用,说明不同柿种质品种在软化过程中起主导作用的酶不同。综上认为,与‘恭城月柿''相比,‘油柿''耐贮性差,其中YS-4极不耐贮藏,而‘农家栽培柿''ZP-2极耐贮藏,这为研究柿果实软化机制提供了基础的种质材料。     

氧和二氧化碳对番茄后熟的影响

贮藏番茄的气体中,氧分压低于1%时,产生生理损伤。在13—27℃的温度下,7%的氧分压是不能抑制番茄后熟的临界值。在12—14℃的温度下,2—4%的氧分压是长期贮藏番茄的最适条件,可以推迟呼吸高峰的到来。氧分压高到40—50%有一定的催熟作用。乙烯利在27℃和氧分压为0—1%的条件下,没有催熟作用。当氧分压高于2%时,有催熟作用,并可诱导呼吸高峰的提前出现。适当浓度的 CO_2对番茄的后熟有抑制作用,浓度过大则产生毒害作用。CO_2抑制后熟的作用和对番茄的毒害作用与 O_2分压有拮抗。在一定浓度的 CO_2条件下,提高氧分压可减弱CO_2对后熟的抑制和减轻 CO_2对番茄的生理毒害。     

龙眼果实防腐保鲜技术研究

近几年来,我们探讨了不同的贮藏温度、化学防腐剂、气体组分、包装容器及包装方法对不同品种龙眼果实的防腐保鲜效果。结果表明:龙眼品种间的耐贮性有很大差异,按耐贮性排列:泉州本>乌龙岭>普明庵>福眼>赤壳>水涨;最佳的保鲜贮藏温度为3～4℃;仲丁胺、仲丁胺+赤霉素、多菌灵、甲基托布津、苯甲酸、特克多、FISB-1和FISB-2等不同化学防腐剂对泉州本的防腐效果,以FISB-1和FISB-2防腐效果最佳,贮藏40天,好果率分别为95.0％和95.2％,其他防腐剂处理的好果率为80.7％～86.5％;气调贮藏,CO_2为4％～6％,O_2为6％～8％的气体组分可延长贮藏寿命,降低龙眼果实自身损耗;包装容器以塑料周转箱套薄膜袋气调贮藏效果最佳。     

Race and Racism in America and in Anthropology

Race in North America: Origin and Evolution of a Worldview . Audrey Smedley
Anthropology and Race . Eugenia Shanklin     

Degradation and conversion of somatostatin in normal and diabetic rats in vivo and in vitro

Plasma somatostatin-like immunoreactivity in the portal and jugular veins of streptozotocin diabetic rats was compared with that in normal control rats. In the diabetic group, somatostatin levels in the portal (p less than 0.05) and jugular (p less than 0.01) veins were both elevated compared with those in the control group. Moreover, the degree of elevation was greater in the jugular vein than in the portal vein. To further investigate the role of the liver in the clearance of somatostatin-28 in vivo, 2 micrograms of somatostatin-28 was administered as a bolus into the external jugular vein of intact and functionally hepatectomized rats. The mean half-time of somatostatin-28 was significantly longer in intact diabetic rats than in controls (p less than 0.05). The functional hepatectomy did not cause a significant difference in the half-time in diabetic rats but made it longer in control rats. These results suggest that the longer half-time of somatostatin-28 in diabetic rats in vivo is due to its slower hepatic clearance. The hepatic clearance of somatostatin-28 and somatostatin-14 was further studied in vitro using a recirculating liver perfusion method. The hepatic clearance of 1.2 nM of either somatostatin-28 or somatostatin-14 was significantly lower in diabetic rats than in controls (p less than 0.01). This indicates that elevated plasma somatostatin levels in diabetic rats are caused at least in part by decreased hepatic clearance of somatostatin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trajectories and Constraints in Brain Evolution in Primates and Cetaceans

A negative allometric relationship between body mass (BM) and brain size (BS) can be observed for many vertebrate groups. In the past decades, researchers have proposed several hypotheses to explain this finding, but none is definitive and some are possibly not mutually exclusive. Certain species diverge markedly (positively or negatively) from the mean of the ratio BM/BS expected for a particular taxonomic group. It is possible to define encephalization quotient (EQ) as the ratio between the actual BS and the expected brain size. Several cetacean species show higher EQs compared to all primates, except modern humans. The process that led to big brains in primates and cetaceans produced different trajectories, as shown by the organizational differences observed in every encephalic district (e.g., the cortex). However, these two groups both convergently developed complex cognitive abilities. The comparative study on the trajectories through which the encephalization process has independently evolved in primates and cetaceans allows a critical appraisal of the causes, the time and the mode of quantitative and qualitative development of the brain in our species and in the hominid evolutionary lineage.     

Variation in infectivity and aggressiveness in space and time in wild host-pathogen systems: causes and consequences

Variation in host resistance and in the ability of pathogens to infect and grow (i.e. pathogenicity) is important as it provides the raw material for antagonistic (co)evolution and therefore underlies risks of disease spread, disease evolution and host shifts. Moreover, the distribution of this variation in space and time may inform us about the mode of coevolutionary selection (arms race vs. fluctuating selection dynamics) and the relative roles of G × G interactions, gene flow, selection and genetic drift in shaping coevolutionary processes. Although variation in host resistance has recently been reviewed, little is known about overall patterns in the frequency and scale of variation in pathogenicity, particularly in natural systems. Using 48 studies from 30 distinct host–pathogen systems, this review demonstrates that variation in pathogenicity is ubiquitous across multiple spatial and temporal scales. Quantitative analysis of a subset of extensively studied plant–pathogen systems shows that the magnitude of within‐population variation in pathogenicity is large relative to among‐population variation and that the distribution of pathogenicity partly mirrors the distribution of host resistance. At least part of the variation in pathogenicity found at a given spatial scale is adaptive, as evidenced by studies that have examined local adaptation at scales ranging from single hosts through metapopulations to entire continents and – to a lesser extent – by comparisons of pathogenicity with neutral genetic variation. Together, these results support coevolutionary selection through fluctuating selection dynamics. We end by outlining several promising directions for future research.     

Aminoacylation in Sulfolobus acidocaldarius and in methanogenic and halophilic archaebacteria

Abstract Phenylalanyl-tRNA synthetase (PRS) from the sulphur-metabolizing thermoacidophilic archaebacterium Sulfolobus acidocaldarius has been purified 150-fold using different chromatographic steps. The enzyme has a M _r of 270 000 and exhibits considerable thermostability in a temperature range up to 90°C with optimal activity at 70°C. Conservation of antigenic determinants could not be detected by antibodies against various PRS of all primary kingdoms. As a further means to detect traits of phylogenetic relationship, the cross-species reactivity between PRS and tRNAs of organisms from the three branches of archaebacteria and from all primary kingdoms reveals the group character of all 3 branches of the archaebacterial domain, the sulphur-metabolizing, methanogenic and halophilic archaebacteria.     

Deoxynivalenol and nivalenol in wheat and by-products in Argentina

The deoxynivalenol and nivalenol contamination in wheat and by-products obtained through milling was analized by Trucksess method slightly modified in the proportion of acetonitrile—water (3:1). Only one sample of wheat showed deoxynivalenol contamination, 1,200μg/kg. No samples obtained in different stages of the milling were contaminated with deoxynivalenol or nivalenol. In the commercial wheat flours the levels found ranged between 400 and 800μg/kg, as follows: 400μ/kg, 5 samples; 800jug/kg, 1 sample.     

Obestatin and ghrelin in obese and in pregnant women

We identified, through qPCR, receptor mRNA for a number of gut peptides in female human omental fat: the incretins, GIP and GLP-1, the orexigenic peptides PYY-Y1 and -Y2 and ghrelin, and the anorexigenic peptide obestatin. Four cohorts of women were examined: lean controls (BMI<23), obese (BMI>41), obese diabetic and term pregnant women. Human fat expressed receptor mRNAs for all six peptides. Pregnant women expressed roughly three times as much orphan GPR-39 receptor, a proposed obestatin receptor, than other women and less than half as much of the ghrelin receptor (GHSR-1a). An immunoblot probed with a GPR-39 selective antibody yielded a single band corresponding to the correct molecular weight (52 kDa) for the proposed obestatin receptor. Fluorescent immunohistochemistry of human fat employing the same antibody indicated the receptor protein was localized to the adipocyte cell membrane. The concentration of obestatin circulating in blood was measured in the same cohort of women and was significantly lower in obese and obese diabetic women compared to control.