The effect of methyl palmoxirate on incorporation of [U-14C]palmitate into rat brain

We examined the dose response, time course and reversibility of the effect of methyl 2-tetradecylglycidate (McN-3716, methyl palmoxirate or MEP), an inhibitor of -oxidation of fatty acids, on incorporation of radiolabeled palmitic acid ([U-¹⁴C]PA) from plasma into brain lipids of awake rats. MEP (0.1, 1 and 10 mg/kg) or vehicle was administered intravenously from 10 min to 72 hr prior to infusion of [U-¹⁴C]PA. Two hr pretreatment with MEP (0.1 to 10 mg/kg) increased brain organic radioactivity 1.2 to 1.8 fold and decreased brain aqueous radioactivity by 1.2 to 3.0 fold when compared to control values. At 10 mg/kg, MEP significantly increased brain organic fraction from 40% in controls to 85%, 30 min to 6 hr pretreatment, and resulted in a redistribution of the radiolabeled fatty acid toward triacylglycerol. MEP changed the lipid/aqueous brain ratio of incorporated [U-¹⁴C]PA from 0.67 to 5.7. The incorporation rate coefficient, k^*, was significantly increased by MEP (10 mg/kg) at 2 hr (31%), 4 hr (59%) and 6 hr (34%). All effects were reversed by 72 hr, consistent with a half-life of 2 days for carnitine palmitoyl transferase I. These results indicate that intravenous MEP may be used with [1-¹¹C]palmitic acid for studying brain lipid metabolism in vivo by positron emission tomography, as it significantly reduces the large unincorporated aqueous fraction that would result in high background radioactivity.     

Design of a bubble-swawm bioreactor for animal cell culture

A stationary bubble-swarm has been used to aerate a mammalian cell culture bioreactor with an extremely low gas flow rate. Prolonging the residence time of the gas bubbles within the medium improved the efficiency of the gas transfer into the liquid phase and suppressed foam formation. An appropriate field of speed gradients prevented the bubbles from rising to the surface. This aeration method achieves an almost 90% transfer of oxygen supplied by the bubbles. Consequently, it is able to supply cells with oxygen even at high cell densities, while sparging with a gas flow of only 0.22·10^–3–1.45·10^–3 vvm (30–200 ml/h).The reactor design, the oxygen transfer rates and the high efficiency of the system are presented. Two repeated batch cultures of a rat-mouse hybridoma cell line are compared with a surface-aerated spinner culture. The used cell culture medium was serum-free, either with or without BSA and did not contain surfactants or other cell protecting agents. One batch is discussed in detail for oxygen supply, amino acid consumption and specific antibody production.     

几种环境因素对玉米叶切块光诱导的影响

利用液相氧电极研究了暗处理、光强、ＣＯ２水平、缺钾和干旱对玉米叶切块光诱导的影响。发现长时间的暗处理、高光强、低ＣＯ２浓度、缺钾和干旱均使光合诱导期拉长。影响光合诱导期的外界逆境如低ＣＯ２浓度、缺钾和干旱也使玉米叶片的净光合速率下降,并对这些结果产生的原因作了分析。     

Role of other plant organs in gibberellic acid-induced delay of leaf senescence in alstroemeria cut flowers

Chlorophyll loss in leaves of cut flowers of alstroemeria (Alstroemeria pelegrina L. cv. Westland) was rapid in darkness and counteracted by irradiation and treatment of the flowers with gibberellic acid (GA₃). The mechanism of the effect of GA₃ under dark conditions was investigated. The content of various carbohydrates in the leaves under dark conditions rapidly decreased; this was not influenced by treatment with GA_3. indicating that the loss of carbohydrates in the leaves did not induce the loss of chlorophyll. Placing the cut flowers in various solutions of organic and inorganic nutrients exhibited no significant effect on the retention of chlorophyll in leaves of dark-senescing flowers. The total nitrogen content in leaves of dark-senescing cut flowers decreased with time. Leaves of GA₃-treated flowers retained more nitrogen. In contrast, the buds of GA₃-treated flowers retained less nitrogen during senescence in the dark than control buds. To investigate whether GA₃ affects export of assimilates from the leaf to various parts of control and GA₃-treated flowers, we labelled one leaf with radioactive carbon dioxide. ¹⁴C-assimilates accumulated preferentially in the flowers, in which the relative specific activity of the youngest floral buds was highest. No significant differences were observed in the distribution of ¹⁴C-labelled compounds between the buds of control and GA₃-treated flowers. To establish the importance of source-sink relations for the loss of leaf chlorophyll we removed the flower buds (i. e. the strongest sink) from the cut flowers. This removal only slightly delayed chlorophyll loss as compared to the large delay caused by GA₃-treatment. In addition, detached leaf tips exhibited chlorophyll loss in the dark, which was delayed by GA₃-treatment in a fashion comparable with that in flowers. Together these data demonstrate that interactions of the leaves with other plant organs are not essential for chlorophyll loss during senescence in the dark. Additionally, we have found no evidence that GA₃ delays the loss of chlorophyll by affecting the transport of nutrients within the cut flowers.     

Transport and metabolism of [3H]iso-pentenyladenine following application to the tips of intact and decapitated tap roots of Pinus pinea

[³H]iso-Pentenyladenine ([³H]iP) was fed for 24 h to the tips of intact and root tip-decapitated Pinus pinea seedlings. Twelve and 24 h after application to the roots of intact plants most of the applied radioactivity (±60%) was transported to the shoot. Root tip removal increased transport of the applied radioactivity to the shoot, but the overall pattern of distribution of radioactivity in the seedling did not change. Large amounts of radioactivity were recovered from the elongation zone of the root. Some radioactivity also accumulated in the older part of the root with well-developed lateral roots. When [³H]iP was applied one day after decapitation, no significant changes in the pattern of radioactivity distribution were found between the intact and decapitated root systems. However, when applied 7 days after decapitation there was a significant increase of radioactivity in the region of the root where lateral roots were emerging. HPLC separation of extracts from the different root sections showed that [³H]iP was extensively metabolized in the root. Six peaks of radioactivity, which co-chromatographed with authentic cytokinin standards, were detected.Abbreviations ABA abscisic acid - ADE adenine - IAA indole-acetic acid - iP iso-pentenyladenine - HPLC high performance liquid chromatography - [OG]DHZ O-glycosyldihydrozeatin - [9R-MP]DHZ ribosyldihydrozeatin monophosphate - [9G]iP iso-pentenyladenine-9-glucoside - [9R]Z ribosylzeatin - [9R]iP iso-pentenyladenosine - TLC thin layer chromatography     

Glucose metabolism by brown trout peripheral blood lymphocytes

Glucose metabolism in peripheral blood lymphocytes from the brown trout Salmo trutta has been studied. Glucose is taken up by means of a sodium-independent saturable process (K _m=10.8 mmol·l^-1), as well as by simple diffusion. Once within the cell, most of glucose is directed to lactate production through either the Embden-Meyerhof pathway or the hexose-monophosphate shunt. Rates of lactate formation are higher than rates of CO₂ formation. Glutamine does not exert an effect on either glucose uptake or glucose metabolism. The present study provides information regarding the nature of energy sources for different cell types in salmonids.Abbreviations 3-OMG 3-O-methyl glucose - EM Embden-Meyerhoff pathway - G6D glucose-6-phosphate dehydrogenase - HK hexokinase - HMS hexose monophosphate shunt - ICDH isocitrate dehydrogenase - K _m apparent Michaelis constant - LDH lactate dehydrogenase - MCB modified Cortland buffer - PBL peripheral blood lymphocytes - PFK fructose-6-phosphate kinase - PK pyruvate kinase - RBC red blood cells - V _max maximal rate of uptake     

Enhanced ethylene production by primary roots of Zea mays L. in response to sub-ambient partial pressures of oxygen

Ethylene production by primary roots of 72–h-old intact seedlings of Zea mays L. cv. LG11 was studied under ambient and sub-ambient oxygen partial pressures (pO₂) using a gas flow-through system linked to a photoacoustic laser detector. Despite precautions to minimize physical perturbation to seedlings while setting-up, ethylene production in air was faster during the first 6h than later, in association with a small temporary swelling of the roots. When roots were switched from air (20–8kPa O₂) to 3 or 5kPa O₂ after 6h, ethylene production increased within 2—3 h. When, the roots were returned to air 16 h later, ethylene production decreased within 2—3 h. The presence of 10kPa CO₂ did not interfere with the effect of 3kPa O₂. Transferring roots from air to 12–5kPa did not change ethylene production, while a reduction to 1 kPa O₂ induced a small increase. The extra ethylene formed in 3 and 5 kPa O₂ was associated with plagiotropism, swelling, root hair production, and after 72 h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension was also slowed down, but the pattern of response to oxygen shortage did not always match that of ethylene production. On return to air, subsequent growth patterns became normal within a few hours. In the complete absence of oxygen, no ethylene production was detected, even when anaerobic roots were returned to air after 16 h.     

Discrete steps in dioxygen activation—The cytochrome oxidase/O2 reaction

The kinetic constraints that are imposed on cytochrome oxidase in its dual function as the terminal oxidant in the respiratory process and as a redox-linked proton pump provide a unique opportunity to investigate the molecular details of biological O₂ activation. By using flow/flash techniques, it is possible to visualize individual steps in the O₂-binding and reduction process, and results from a number of spectroscopic investigations on the oxidation of reduced cytochrome oxidase by O₂ are now available. In this article, we use these results to synthesize a reaction mechanism for O₂ activation in the enzyme and to simulate time-concentration profiles for a number of intemediates that have been observed experimentally. Kinetic manifestation of the consequences of coupling exergonic electron transfer to endergonic proton translocation emerge from this analysis. Energetic efficiency in this process apparently requires that potentially toxic intermediate oxidation states of dioxygen accumulate to substantial concentration during the reduction reaction.     

The Response to Exercise with Constant Energy Intake in Identical Twins

Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above the estimated energy cost of body weight maintenance reached 244 ± 9.8 MJ (Mean ± SEM). Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. Mean body weight loss was 5.0 kg (SEM = 0.6) (p <0.001) and it was entirely accounted for by the loss of fat mass (p <0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p <0.001) which represented about 78% of the estimated energy deficit. Subcutaneous fat loss was slightly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomography (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm² (SEM = 5) to 52 cm² (SEM = 6) (p <0.001). At the same submaximal power output level, subjects oxidized more lipids than carbohydrates after the program as indicated by the changes in the respiratory exchange ratio (p <0.05). Intrapair resemblance was observed for the changes in body weight (p <0.05), fat mass (P <0.01), percent fat (p <0.01), body energy content (p <0.01), sum of 10 skinfolds (p <0.01), abdominal visceral fat (p <0.01), fasting plasma triglycerides (p <0.05) and cholesterol (p <0.05), maximal oxygen uptake (p <0.05), and respiratory exchange ratio during submaximal work (p <0.01). We conclude that even though there were large individual differences in response to the negative energy balance and exercise protocol, subjects with the same genotype were more alike in responses than subjects with different genotypes particularly for body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during sub-maximal exercise were also seen despite the fact that all subjects had experienced the same exercise and nutritional conditions for about three months.     

急性脑出血综合治疗的几个问题探讨：附死亡80例分析

通过对８０例急性脑出血死亡组分析,发现死于脑疝的占６２．５％,脑疝与一种或二种以上合并症同存者占７７．５％,显著高于存活组（Ｐ＜０．０１）．它们互为因果,加速死亡。因此,应重视早期或超早期采用简易定向锥颅脑内血肿碎吸术吸除血肿,同时注意维持生命体征稳定,加强脱水降颅压,预防、控制合并症等综合治疗。且要全面分析,相互兼顾,正确处置。这是帮助机体渡过调控障碍难关,挽救生命的有效治疗措施。