从能量角度粗谈人体的几个定量问题

本文构思源于线粒体的功能研究,从能量角度,分析了静息状态下裸露的人体散热及功耗,其中辐射散热占1／2以上,对流散热约1／3,排泄散热约1／8;进而讨论了人体所需食物、氧和水;同时探讨人体生理温度的维持,粗略计算了人体理想最低功耗及负熵量,提供了满足个体需求的简便算法,为越来越流行的节食减肥或节食长寿留下可供参考的红线。     

Inhibition of Sporulation of Genus Bacillus by Various Microbial Protease Inhibitors

Several analogs modifying the 6-methoxy-2-methoxymethyl-3-(3,4-methyienedioxyphenyl)-1,4-benzodioxan-7-yl group of haedoxans were synthesized and their insecticidal activity was examined. 2-(2,6-Dimethoxyphenoxy)-1-hydroxy-6-(2-methoxy-5-methoxyethoxyphenyl)-3,7-dioxabicyclo-[3.3.0]octane, which lacked the 3-(3,4-methylenedioxybenzyloxy) moiety of the benzodioxanyl group, was not insecticidal, but caused prolonged paralysis of the housefly. A compound replacing the 6-(2-methoxy-5-methoxyethoxyphenyl) by 6-(5-butoxy-2-methoxyphenyl) exhibited insecticidal activity comparable to one thirty-thousandth of that of haedosan A. It became evident that the 1,4-benzodioxane framework charging the 3-(3,4-methylenedioxy)phenyl group is important for the insecticidal activity of haedoxans.     

Comparison of Mineral Balances in Germfree and Conventional Mice When Sodium Phytate is Added to Purified Diet

A strain of Alcaligenes isolated from soil was a good producer of β-glucuronidase, and the enzyme was purified from the cell-free extract by sequential column chromatography on DEAE-Toyopearl, Toyopearl HW-55F, and Phenyl-Sepharose CL-4B. By these procedures, two β-glucuronidases designated as β-glucuronidases I and II were purified 240- and 508-fold, respectively. β-Glucuronidase I, with a molecular weight of 75,000, had an optimum pH at 7.5 and the enzyme II, with a molecular weight of 300,000, had maximum activity at pH 6.0. Both enzymes were strongly inhibited by saccharo-1,4-lactone, glucaro-δ-lactam, p-chloromercuribenzoate, Hg²⁺, and N-bromosuccinimide. β-Glucuronidase I was active toward estrogen-3-β-glucuronides and inert toward β-glucuronide conjugates of menthol, estrogen-17β-, estrogen-16α-, androsterone-3α-, testosterone-17β-, cortisol-17α-. β-Glucuronidase II hydrolyzed all of these substrates. β-Glucuronidase I was inhibited by phenolphthalein and its glucuronide.     

Some New Aryl-5′-fluoro-2′-meth-oxyphenyl Ketones and Their Thiosemicarbazones as Possible Fungicides

Feeding studies on rice genetically modified with soybean glycinin were performed on rats for four weeks. The rats were divided into three groups, each being fed on (I) only a commercial diet, (II) this diet plus control rice and (III) this diet plus rice genetically modified with glycinin. The rats were fed with 10 g/kg-weight of rice every day by oral administration. During the test period, the rats in every group grew well without marked differences in appearance, food intake, body weight, or cumulative body weight gain. There were also no significant differences in the blood count, blood composition or internal organ weights among the rats. Necropsy at the end of the experiment indicated neither pathological symptoms nor histopathological abnormalities in the liver and kidney. Judging from these results, the rice genetically modified with glycinin is considered to have been essentially the same in nutritional and biochemical characteristics as the control rice.     

Isolation of Intact Chloroplasts from Spinach Leaf by Centrifugation in Gradients of the Modified Silica “Percoll”

The isolation of the photosynthetically competent chloroplast preparations was undertaken by means of the density gradient centrifugation on the modified silica sol “Percoll.” A clear separation of the intact chloroplast sustaining the high photosynthetic activities (light dependent CO₂ fixation ca. 130μmol/mg Chl·hr) was established. The contamination of mitochondria and peroxisomes was estimated to be less than 3% by measuring the activities of their marker enzymes. The chloroplasts were proved to be free from endoplasmic reticulum and cytosol. The photosynthetic CO₂ fixation of the isolated chloroplast preparations was saturated by illumination of the light intensity of 20,000 Lux (12 mW/cm², 400~750 nm).     

Fusarium langsethiae – a HT‐2 and T‐2 Toxins Producer that Needs More Attention

Fusarium langsethiae is a toxigenic fungus that was formally described as a new species in 2004. This fungus was first detailed in the 1990s but was initially referred to as ‘powdery Fusarium poae’ having a spore morphology similar to F. poae but a mycotoxin profile like that of Fusarium sporotrichioides. The species has been isolated from infected oat, wheat and barley grains but has been reported as more problematic in the former crop rather than the latter two. Whilst the epidemiology of F. langsethiae remains unclear, the fungus has been shown to produce high levels of type‐A trichothecenes HT‐2 and T‐2 toxins in small‐grain cereals. HT‐2 and T‐2 toxins are two of the most potent trichothecenes capable of inhibiting protein synthesis in eukaryotes. In this regard, mycotoxin contamination caused by F. langsethiae is clearly a food and feed safety hazard. With the European Commission considering legislation of HT‐2 and T‐2 toxins, more information is required not only on the producer and conditions favouring mycotoxin production, but also on reliable methods of pathogen detection and reduction of cereal contamination. This review describes recent research concerning the known epidemiology of F. langsethiae and suggestions of what needs to be known about the fungus in order to be able to understand and employ measures for preventing its infection and contamination of cereals with HT‐2 and T‐2 toxins.     

Effects of predation environment and food availability on somatic growth in the Livebearing Fish Brachyrhaphis rhabdophora (Pisces: Poeciliidae)

Variation in somatic growth rates is of great interest to biologists because of the relationship between growth and other fitness‐determining traits, and it results from both genetic and environmentally induced variation (i.e. plasticity). Theoretical predictions suggest that mean somatic growth rates and the shape of the reaction norm for growth can be influenced by variation in predator‐induced mortality rates. Few studies have focused on variation in reaction norms for growth in response to resource availability between high‐predation and low‐predation environments. We used juvenile Brachyrhaphis rhabdophora from high‐predation and low‐predation environments to test for variation in mean growth rates and for variation in reaction norms for growth at two levels of food availability in a common‐environment experiment. To test for variation in growth rates in the field, we compared somatic growth rates in juveniles in high‐predation and low‐predation environments. In the common‐environment experiment, mean growth rates did not differ between fish from differing predation environments, but the interaction between predation environment and food level took the form of a crossing reaction norm for both growth in length and mass. Fish from low‐predation environments exhibited no significant difference in growth rate between high and low food treatments. In contrast, fish from high‐predation environments exhibited variation in growth rates between high and low food treatments, with higher food availability resulting in higher growth rates. In the field, individuals in the high‐predation environment grow at a faster rate than those in low‐predation environments at the smallest sizes (comparable to sizes in the common‐environment experiment). These data provide no evidence for evolved differences in mean growth rates between predation environments. However, fish from high‐predation environments exhibited greater plasticity in growth rates in response to resource availability suggesting that predation environments may exhibit increased variation in food availability for prey fish and consequent selection for plasticity.     

Nonconsumptive effects in a multiple predator system reduce the foraging efficiency of a keystone predator

Many studies have demonstrated that the nonconsumptive effect (NCE) of predators on prey traits can alter prey demographics in ways that are just as strong as the consumptive effect (CE) of predators. Less well studied, however, is how the CE and NCE of multiple predator species can interact to influence the combined effect of multiple predators on prey mortality. We examined the extent to which the NCE of one predator altered the CE of another predator on a shared prey and evaluated whether we can better predict the combined impact of multiple predators on prey when accounting for this influence. We conducted a set of experiments with larval dragonflies, adult newts (a known keystone predator), and their tadpole prey. We quantified the CE and NCE of each predator, the extent to which NCEs from one predator alters the CE of the second predator, and the combined effect of both predators on prey mortality. We then compared the combined effect of both predators on prey mortality to four predictive models. Dragonflies caused more tadpoles to hide under leaf litter (a NCE), where newts spend less time foraging, which reduced the foraging success (CE) of newts. Newts altered tadpole behavior but not in a way that altered the foraging success of dragonflies. Our study suggests that we can better predict the combined effect of multiple predators on prey when we incorporate the influence of interactions between the CE and NCE of multiple predators into a predictive model. In our case, the threat of predation to prey by one predator reduced the foraging efficiency of a keystone predator. Consequently, the ability of a predator to fill a keystone role could be compromised by the presence of other predators.     

Parasite infection alters host stable‐isotope composition under controlled feeding

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