刺激家兔中脑导水管周围灰质抑制束旁核伤害性放电的脊髓上机制

本工作比较了家兔脊髓背侧1/2进行横切前后刺激中脑中央灰质对束旁核伤害性放电的抑制率的改变。实验表明中央灰质既可通过公认的脊髓下行纤维抑制脊髓水平的痛传递,减弱束旁核单位的痛敏放电,也可通过某种脊髓上机制实现对束旁核的抑制。我们对这两种机制的相对重要性作了分析。用直11个束旁核痛敏单位所作的计算表明,在脊髓切割前,刺激中央灰质可使束旁核痛敏放电抑制67.5%,脊髓背侧1/2横切后,同样的中脑刺激只能使痛敏放电抑制42.9%。如以切割前的抑制率作为直100%,则切割可使抑制减弱36.5%,这一部分抑制应当是由被切断的脊髓下行纤维实现的,其余63.5%则可能主要通过脊髓上机制来实现。考虑到脊髓背半部横切不可能全部切断下行纤维,故实际上脊髓上机制的重要性不会有上述数值表示的那么大。     

Effects of Monensin and Veratridine on Acetylcholine Release and Cytosolic Free Ca2+ Levels in Cerebrocortical Synaptosomes of Rats

High-affinity specific receptors of endothelin (ET-1) were identified on primary cultures of mouse embryo striatal astrocytes by binding experiments performed with 125I-ET-1. Stimulation of production of inositol phosphates, a biphasic increase of the intracellular calcium concentration, and inhibition of cyclic AMP accumulation were observed in the same cells under ET-1 stimulation. Pretreatment of these cells with Bordetella pertussis toxin affected these effects to different extends, an observation suggesting that they are mediated by multiple transduction pathways, possibly involving several guanine nucleotide-binding proteins.     

Biogeochemical pathways of cadmium through an artificially contaminated intertidal mud flat system — a medium-scale enclosure experiment

Summary Two Bremerhaven caissons were used to investigate the interactions of cadmium (Cd) with sea water, particulate matter, sediments, suspended particular matter (SPM), and organisms in enclosed sea water-sediment systems, on the tidal mud flats of Jade Bay (FRG). One caisson was artificially contaminated by continuously injecting cadmium (as a chloride) so as to maintain a Cd concentration of 100 g/l in the inflowing water of each tidal cycle for 22 days. The other caisson was used as a control system. About 30% of the total Cd introduced into the caisson was transferred from the aqueous phase to the other phases during each tidal cycle. Cadmium appears to accumulate in elements of the system in the order SPM, organisms, sediments, water. SPM, initially low in Cd entering the system, rapidly accumulated Cd from solution after the first tidal cycle and the concentration continued to increase during the experiment. Particulate Cd transferred to the sediments results in the development of a Cd-rich layer that attained a depth of 4 cm over the course of the experiment. Among the biota, the blue mussel (Mytilus edulis) progressively accumulated the highest concentrations of Cd whereas other taxa, like polychaetes, accumulated less of the metal. Differnces in Cd accumulation appear to be due to the habitats of the different species and their ability to assimilate Cd from the dissolved and particulate phases. Together, the data indicate that in the contamination of tidal mud flats with aqueous cadmium most of the metal would remain available to the organisms in the aqueous phases and weakly bound to particulate matter. This would present the greatest environmental danger to filter feeders but not to animals living in the sediments.     

The contribution of symbiotic yeast to toxin resistance of the cigarette beetle (Lasioderma serricorne)

Representative plant allelochemicals were tested for toxicity to larvae of the cigarette beetle Lasioderma serricorne (F.) that were either untreated, treated with fungicides, or treated to render them free of symbiotic yeast (aposymbiotic) through surface sterilization of eggs. Insects rendered symbiont-free had higher mortality and/or developmental rates than controls when fed diets containing flavone, resorcinol or tannic acid. Fungicides reduced symbiont populations and/or caused morphological abnormalities. Two hydrolytic enzymes, which made up a significant protion of mycetome hydrolytic activity, were absent when symbionts were not present, as indicated by gel electrophoresis. This information indicates symbionts do contribute to the survival of their host by detoxifying toxins.

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Résumé La toxicité relative de substances allélochimiques végétales typiques a été examinée sur des larves de L. serricorne F. traitées aux fongicides et rendues aposymbiotiques par stérilisation superficielle des ufs. La toxicité de la nicotine est relativement inaffectée chez les larves aposymbiotiques; cependant les toxicités des resorcinol, flavone et acide tannique sont significativement augmentées chez les insectes ayant reçu un traitement pour éliminer leurs symbiontes. L'électrophorèse sur gel a montré que quelques enzymes responsables de l'hydrolyse du 1-naphthyl acétate, réaction enzymatique de la détoxification enzymatique, sont absentes chez les insectes aposymbiotiques. L'acide sorbique a réduit significativement l'effectif de symbiontes, tandis que le bénomyl a réduit leur gamme provoquant la multiplication anormale d'autres espèces. Ces résultats montrent que les symbiontes contribuent aux possibilités de détoxification de l'insecte. L'élimination des symbiontes peut être une technique efficace pour lutter contre les insectes qui en contiennent, puisqu'elle les priverait de leur contribution à l'alimentation et à la détoxification. Cette stratégie est vraisemblablement compatible avec des programmes de lutte intégrée, puisque les prédateurs et parasites ne contiennent pas de symbiontes.

     

Biosynthèse de la sticticine chez le lichen Lobaria laetevirens

Biosynthesis of sticticin in the lichen Lobaria laetevirens (Lightf.) Zahlbr .
Sticticin is the most important soluble nitrogenous compound in the thallus of L. laetevirens from which it was isolated for the first time. As its concentration can exceed 1 M when thallus water content reaches 10–12%, it might play an efficient role in osmoregulation. Its biosynthesis was investigated by supplying the lichen with L-[U-14C]tyrosine, DL-3,4-dihydroxyphenyl [3-¹⁴C]alanine and L-[methyl-¹⁴C]me-thionine. The main pathway involves, first, N-methylations of tyrosine, then a hydroxylation of the ring and finally an esterification of the acid function.     

The Effect of Temperature on the Fatty Acid Composition of Tetrahymena pyriformis WH-14

SYNOPSIS. A reduction in the growth temperature of Tetrahymena pyriformis strain WH-14 from 35 C to 15 C resulted in distinct alterations in the fatty acid composition of the glycerophospholipids. The proportion of normal saturated acids declined from 26 to 19%; palmitoleic acid increased by 6%, and the composition of the polyunsaturated fatty acids increased in 18:2 Δ^6,11(n) and decreased in 18:2 Δ^9,12(n) and 18:3 Δ^6,9,12(n). The unsaturation index (the average number of double bonds/100 molecules) did not change with a shift in temperature.
Two biosynthetic pathways exist in Tetrahymena for the formation of unsaturated fatty acids. The observed changes in fatty acid composition that accompany a lowering of the environmental temperature can be accounted for by a reduction in the accumulation of products of the fatty acid pathway leading to the formation of γ-linolenic acid [16:0(n) → 18:0(n) → 18:1 Δ⁹(n) → 18:2 Δ^9,12(n) → 18:3 Δ^6,9,12(n)] and an increase in the components of the pathway leading to the formation of 18:2 Δ^6,11(n) [16:0(n) → 16:1 Δ⁹(n) → 18:1 Δ¹¹(n) → 18:2 Δ^6,11(n)]. The data suggest that the regulatory mechanism in Tetrahymena differs from that found in some bacteria where a simple substitution of unsaturated fatty acids for saturated fatty acids occurs at low culture temperatures.     

真菌芳香聚酮化合物的合成生物学研究进展*

真菌芳香聚酮化合物是由真菌非还原聚酮合酶(NR-PKSs)催化形成的具有广泛生物活性的一类天然产物。大部分内源真菌菌株存在难培养、致病性或产率低等问题,从根本上限制了真菌芳香聚酮化合物的开发和应用。随着合成生物学和代谢工程的发展,很多具有生物活性的聚酮产物实现了在工业微生物(如酿酒酵母、构巢曲霉等)中的异源生产,相关研究逐渐成为热点。从合成途径解析与挖掘、底盘细胞的构建与改造等方面综述了近年来真菌芳香聚酮化合物的合成生物学研究进展,为未来真菌芳香聚酮化合物人工代谢途径的高效构建和实现工业化生产奠定基础。     

Does phenotypic plasticity initiate developmental bias?

The generation of variation is paramount for the action of natural selection. Although biologists are now moving beyond the idea that random mutation provides the sole source of variation for adaptive evolution, we still assume that variation occurs randomly. In this review, we discuss an alternative view for how phenotypic plasticity, which has become well accepted as a source of phenotypic variation within evolutionary biology, can generate nonrandom variation. Although phenotypic plasticity is often defined as a property of a genotype, we argue that it needs to be considered more explicitly as a property of developmental systems involving more than the genotype. We provide examples of where plasticity could be initiating developmental bias, either through direct active responses to similar stimuli across populations or as the result of programmed variation within developmental systems. Such biased variation can echo past adaptations that reflect the evolutionary history of a lineage but can also serve to initiate evolution when environments change. Such adaptive programs can remain latent for millions of years and allow development to harbor an array of complex adaptations that can initiate new bouts of evolution. Specifically, we address how ideas such as the flexible stem hypothesis and cryptic genetic variation overlap, how modularity among traits can direct the outcomes of plasticity, and how the structure of developmental signaling pathways is limited to a few outcomes. We highlight key questions throughout and conclude by providing suggestions for future research that can address how plasticity initiates and harbors developmental bias.     

Interplay between the RNA binding‐protein Musashi and developmental signaling pathways

Musashi comprises an evolutionarily conserved family of RNA‐binding proteins (RBP) that regulate cell fate decisions during embryonic development and play key roles in the maintenance of self‐renewal and differentiation of stem cells and adult tissues. More recently, several studies have shown that any dysregulation of MSI1 and MSI2 can lead to cellular dysfunctions promoting tissue instability and tumorigenesis. Moreover, several reports have characterized many molecular interactions between members of the Musashi family with ligands and receptors of the signaling pathways responsible for controlling normal embryonic development: Notch, Transforming Growth Factor Beta (TGF‐β), Wingless (Wnt) and Hedgehog Signaling (Hh); all of which, when altered, are strongly associated with cancer onset and progression, especially in pediatric tumors. In this context, the present review aims to compile possible cross‐talks between Musashi proteins and members of the above cited molecular pathways for which dysregulation plays important roles during carcinogenesis and may be modulated by these RBP.     

Circular RNA ciRS‐7 promotes tube formation in microvascular endothelial cells through downregulation of miR‐26a‐5p

Atherosclerosis is one of the most common and crucial heart diseases involving the heart and brain. At present, atherosclerosis and its major complications comprise the leading causes of death worldwide. Our purpose was to identify the role of ciRS‐7 in atherosclerosis. Tubulogenesis of HMEC‐1 cell was evaluated utilizing tube formation assay. Cell Counting Kit‐8 assay and flow cytometry were utilized to test viability and apoptosis. Migration assay was utilized to determine the migration capacity of experimental cells. Western blot was applied to examine apoptosis and tube formation‐associated protein expression. In addition, the above experiments were repeated when silencing ciRS‐7, overexpressing ciRS‐7, and upregulating miR‐26a‐5p. HMEC‐1 cells formed tube‐like structures over time. Silencing ciRS‐7 suppressed viability, migration, and tube formation but promoted apoptosis. Oppositely, overexpressing ciRS‐7 reversed the effect in HMEC‐1 cells. miR‐26a‐5p expression was elevated by silencing ciRS‐7 and reduced by overexpressing ciRS‐7. Moreover, overexpressing ciRS‐7 facilitated viability, migration, and tube formation via upregulating miR‐26a‐5p. Conclusively, overexpressing ciRS‐7 mobilized phosphoinositide 3‐kinase/protein kinase B (PI3K/AKT) pathway and suppressed c‐Jun N‐terminal kinase (JNK)/p38 pathway. ciRS‐7 exerted influence on apoptosis, viability, migration, and tube formation through mediating PI3K/AKT and JNK/p38 pathways by miR‐26a‐5p downregulation in HMEC‐1 cells.