The effect of salinity on respiratory metabolism in selected ontogenetic stages of the freshwater shrimp Macrobrachium olfersii (Decapoda,palaemonidae)

• 1.1. The effect of acute salinity exposure (0, 7, 14, 21, 28 and 35%.S) on the respiratory metabolism of selected ontogenetic stages (zoeae, postlarvae and adults) of the freshwater shrimp Macrobrachium olfersiiwas examined.
• 2.2. Metabolic rates are salinity independent from 14 to 28%. S in zoeae 1–4, but tend to increase with increasing salinity in zoeae 5 and 8. Postlarvae exhibit maximal rates in midrange salinities while in adult shrimps, oxygen consumption rates decrease with salinity increase.
• 3.3. Salinity has little effect on the metabolism-weight relationship, regression analysis indicating that b varies from 0.69 in 0%. S to 0.62 in 35%. S.
• 4.4. Data are discussed as to whether larval responses reflect adaptation to the adult biotope and whether development of the larval neurosecretory system might affect metabolic response to salinity exposure.

     

The respiratory metabolism of honey-bee colonies at low temperatures

Honey-bee colonies exposed to temperatures between 20° C and -39° C produced less CO₂ at 10° C than at higher or lower temperatures.

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Zusammenfassung Honigbienenvölker wurden im Winter aus ihren Stöcken genommen und in galvanisierten Eisenbehältern (Tanks) Temperaturen zwischen 20 und -39° C ausgesetzt. Das Kohlendioxyd der aus den Behältern abgesogenen Luft wurde absorbiert und gewogen. Die CO₂-Produktion sank, wenn die Temperatur von 20 auf 10° erniedrigt wurde und stieg bei niederen Temperaturen wieder an. Diese Veränderungen verliefen in umgekehrter Richtung, wenn die Temperatur erhöht wurde.

     

The effects of neurotensin on selected parameters of lipid metabolism in rats

15 nM/kg b.m. of neurotensin (NT) caused a significant inhibition of LMA within 30 min of administration and this effect persisted up for to the 240 th minute of the experiment. A 15 nM/kgb.m. dose also caused a reduction in SLA which persisted up to the 120 th minute. Sixty minutes after an intraperitoneal administration of NT a decrease in the cholesterol and NEFA levels and an increase in the TG and glycerol levels were observed. These effects were inhibited by the NTR2-blocker (levocabastine) and were not subject to change after an in vivo application of SR 48692.     

Chloragosomes of lumbricidae as specific electron acceptors. In vitro investigations.

Measurements of the redox potential values in buffered salt solutions containing body wall homogenate, body wall homogenate with isolated chloragosomes and in both solutions enriched with NAD have shown that chloragosomes are specific electron acceptors which prevent the rapid decrease of the redox potential under anaerobic conditions. The substances responsible for the electron-acceptor activity are most probably identical with the flavins, carotenes and metalloporphyrins present in chloragosomes as shown by the visible absorption spectra of the extracts. The results support the assumption that chloragosomes may play an important role in the metabolism under hypoxic and anoxic conditions.     

The screening of selected microorganisms for use as models of mammalian drug metabolism

Summary Fifty fungi and two Streptomyces species were screened for their ability to metabolise the probe substrates aminopyrine, diazepam, testosterone, theophylline and warfarin. The metabolism of the ¹⁴C-labelled substrates by whole growing cells was compared with that by rat liver microsomes using TLC-autoradiography. Testosterone, warfarin and diazepam were readily metabolised by most microorganisms, and aminopyrine and theophylline were only metabolised by a few. A relationship between substrate lipophilicity and number of microorganisms able to biotransform the substrate was observed, lipophilic substrates being favoured for metabolism, analogous to mammalian cytochrome P-450. A wide variety of metabolites were produced by the screened cultures, with a significant number co-chromatographing with mammalian metabolites. Most microorganisms appeared to exhibit cytochrome P-450-type oxidative reactions such as hydroxylation and N-demethylation, similar to mammalian hepatic microsomal cytochrome P-450 systems. Offprint requests to: D. A. Griffiths     

In vivo respiratory metabolism of illuminated leaves

Day respiration of illuminated C(3) leaves is not well understood and particularly, the metabolic origin of the day respiratory CO(2) production is poorly known. This issue was addressed in leaves of French bean (Phaseolus vulgaris) using (12)C/(13)C stable isotope techniques on illuminated leaves fed with (13)C-enriched glucose or pyruvate. The (13)CO(2) production in light was measured using the deviation of the photosynthetic carbon isotope discrimination induced by the decarboxylation of the (13)C-enriched compounds. Using different positional (13)C-enrichments, it is shown that the Krebs cycle is reduced by 95% in the light and that the pyruvate dehydrogenase reaction is much less reduced, by 27% or less. Glucose molecules are scarcely metabolized to liberate CO(2) in the light, simply suggesting that they can rarely enter glycolysis. Nuclear magnetic resonance analysis confirmed this view; when leaves are fed with (13)C-glucose, leaf sucrose and glucose represent nearly 90% of the leaf (13)C content, demonstrating that glucose is mainly directed to sucrose synthesis. Taken together, these data indicate that several metabolic down-regulations (glycolysis, Krebs cycle) accompany the light/dark transition and emphasize the decrease of the Krebs cycle decarboxylations as a metabolic basis of the light-dependent inhibition of mitochondrial respiration.     

一种昆虫呼吸代谢测定方法的改进

为了探索精准、简易的昆虫呼吸代谢测定办法,本文基于Sable小动物呼吸测量系统,比较了应用Sable呼吸测量系统配置的8通道气路转换器呼吸室和采用鲁尔接头注射器作为替代呼吸室测试昆虫的呼吸代谢。结果表明:应用测量系统自带呼吸室和应用替代呼吸室检测棉铃虫蛹O_2消耗量(前者为0.2425(±0.0143) mL/g·h,后者为0.2389(±0.0146) mL/g·h)和CO_2释放量(前者为0.1562(±0.0098) mL/g·h,后者为0.1639(±0.0092) mL/g·h),两种测试方法无显著差异。与采用系统配置8通道气路转换器和自带呼吸室每测试7个样本耗时2.30 h相比较,应用替代呼吸室测试21个样本仅耗时2.75 h,明显节省测试时间。应用替代呼吸室,从呼出二氧化碳动态亦可以区分黑纹粉蝶不同虫态或不同发育状态的呼吸代谢差异。通过对两种测试方法的分析,推荐应用鲁尔接头注射器作为替代呼吸室的改进方法进行昆虫呼吸代谢生理的研究。