共查询到20条相似文献,搜索用时 15 毫秒
1.
Wenbing Li Longjiang Yu Pengpeng Zhou Min Zhu 《World journal of microbiology & biotechnology》2007,23(10):1489-1492
Summary A helical shaped bacterium capable of producing magnetosomes, designated WM-1, was isolated from freshwater sediment through
an improved isolated method that combined magnetic separation and the “race track” method. The strain WM-1 was Gram-negative,
0.2–0.4 μm in diameter and 3–4 μm in length. The strain WM-1 was identified as genus Magnetospirillum in the α-Proteobacteria according to the sequence analysis of the 16S rDNA, the morphology and physiological characteristics.
The shape of the magnetosomes in WM-1was cuboidal by electron microscopy. Statistical analysis of WM-1 magnetosome crystals
showed that the average number of magnetosomes in a WM-1 bacterium was 8 ± 3.4, and the average length was 54 ± 12.3 nm, and
the average width was 43 ± 10.9 nm. 相似文献
2.
Atsushi Arakaki Ayana Yamagishi Ayumi Fukuyo Masayoshi Tanaka Tadashi Matsunaga 《Molecular microbiology》2014,93(3):554-567
Magnetotactic bacteria synthesize magnetosomes comprised of membrane‐enveloped single crystalline magnetite (Fe3O4). The size and morphology of the nano‐sized magnetite crystals (< 100 nm) are highly regulated and bacterial species dependent. However, the control mechanisms of magnetite crystal morphology remain largely unknown. The group of proteins, called Mms (Mms5, Mms6, Mms7, and Mms13), was previously isolated from the surface of cubo‐octahedral magnetite crystals in Magnetospirillum magneticum strain AMB‐1. Analysis of an mms6 gene deletion mutant suggested that the Mms6 protein plays a major role in the regulation of magnetite crystal size and morphology. In this study, we constructed various mms gene deletion mutants and characterized the magnetite crystals formed by the mutant strains. Comparative analysis showed that all mms genes were involved in the promotion of crystal growth in different manners. The phenotypic characterization of magnetites also suggested that these proteins are involved in controlling the geometries of the crystal surface structures. Thus, the co‐ordinated functions of Mms proteins regulate the morphology of the cubo‐octahedral magnetite crystals in magnetotactic bacteria. 相似文献
3.
J. Eleazar Barboza-Corona Tomás Ortiz-Rodríguez Norma de la Fuente-Salcido Dennis K. Bideshi Jorge E. Ibarra Rubén Salcedo-Hernández 《Antonie van Leeuwenhoek》2009,96(1):31-42
Bacillus thuringiensis HD-73 was transformed with the endochitinase gene chiA74 under the control of a strong promoter (pcytA) and a 5′ mRNA stabilizing (STAB-SD) sequence (HD-73-pEBchiA74). Expression levels were compared with those observed from
the wild type strain (HD-73) and the recombinant HD-73 strain expressing chiA74 under the control of its native promoter (HD-73-pEHchiA74). The chitinolytic activity of HD-73-pEBchiA74 was markedly elevated,
being ~58- and 362-fold higher than, respectively, HD-73-pEHchiA74 and parental HD-73, representing the highest levels of
chitinase expression in recombinant B. thuringiensis reported to date. Parasporal crystals measured under transmission electron microscopy showed that HD-73 produced crystals
of 1.235 (±0.214) and 1.356 (±0.247) μm in length when the bacterium was grown in respectively, NBS and NBS with glucose.
Otherwise, HD-73-pEBchiA74 synthesized crystals of 1.250 (±0.222) and 1.139 (±0.202) μm in length when cultivated in NBS and
NBS with glucose, respectively, values that showed a diminution of ~10 and 20% compared with crystals produced by HD-73-pEHchiA74
grown under the same conditions. Comparison of viable spore counts per ml showed that HD-73-pEBchiA74 produced fewest viable
spores (1.5 × 109, 1.3 × 109), compared to HD-73-pEHchiA74 (4.9 × 109, 5.3 × 109) and HD-73 (6.8 × 109, 8.8 × 109) when grown in NBS and NBS supplemented with glucose, respectively. No change in cellular protease activity was observed
despite the overproduction of the chitinase. 相似文献
4.
Magnetotactic bacteria produce either magnetite (Fe3 O4 ) or greigite (Fe3 S4 ) crystals in cytoplasmic organelles called magnetosomes. Whereas greigite magnetosomes can contain up to 10 atom% copper, magnetite produced by magnetotactic bacteria was considered chemically pure for a long time and this characteristic was used to distinguish between biogenic and abiogenic crystals. Recently, it was shown that magnetosomes containing cobalt could be produced by three strains of Magnetospirillum . Here we show that magnetite crystals produced by uncultured magnetotactic bacteria can incorporate manganese up to 2.8 atom% of the total metal content (Fe+Mn) when manganese chloride is added to microcosms. Thus, chemical purity can no longer be taken as a strict prerequisite to consider magnetite crystals to be of biogenic origin. 相似文献
5.
Weidong Pan Chuanfang Chen Xiaoke Wang Qiufeng Ma Wei Jiang Jing Lv Long‐Fei Wu Tao Song 《Bioelectromagnetics》2010,31(3):246-251
Magnetotactic bacteria are a diverse group of microorganisms which possess one or more chains of magnetosomes and are endowed with the ability to use geomagnetic fields for direction sensing, thus providing a simple and excellent model for the study of magnetite‐based magnetoreception. In this study, a 50 Hz, 2 mT pulsed magnetic field (PMF) was applied to study the effects on the formation of magnetosomes in Magnetospirillum sp. strain AMB‐1. The results showed that the cellular magnetism (Rmag) of AMB‐1 culture significantly increased while the growth of cells remained unaffected after exposure. The number of magnetic particles per cell was enhanced by about 15% and slightly increased ratios of magnetic particles of superparamagnetic property (size <20 nm) and mature magnetosomes (size >50 nm) were observed after exposure to PMF. In addition, the intracellular iron accumulation slightly increased after PMF exposure. Therefore, it was concluded that 50 Hz, 2 mT PMF enhances the formation of magnetosomes in Magnetospirillum sp. strain AMB‐1. Our results suggested that lower strength of PMF has no significant effects on the bacterial cell morphologies but could affect crystallization process of magnetosomes to some extent. Bioelectromagnetics 31:246–251, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
6.
Ji-Won Moon Claudia J. Rawn Adam J. Rondinone Lonnie J. Love Yul Roh S. Michelle Everett Robert J. Lauf Tommy J. Phelps 《Journal of industrial microbiology & biotechnology》2010,37(10):1023-1031
Production of both nano-sized particles of crystalline pure phase magnetite and magnetite substituted with Co, Ni, Cr, Mn,
Zn or the rare earths for some of the Fe has been demonstrated using microbial processes. This microbial production of magnetic
nanoparticles can be achieved in large quantities and at low cost. In these experiments, over 1 kg (wet weight) of Zn-substituted
magnetite (nominal composition of Zn0.6Fe2.4O4) was recovered from 30 l fermentations. Transmission electron microscopy (TEM) was used to confirm that the extracellular
magnetites exhibited good mono-dispersity. TEM results also showed a highly reproducible particle size and corroborated average
crystallite size (ACS) of 13.1 ± 0.8 nm determined through X-ray diffraction (N = 7) at a 99% confidence level. Based on scale-up experiments performed using a 35-l reactor, the increase in ACS reproducibility
may be attributed to a combination of factors including an increase of electron donor input, availability of divalent substitution
metal ions and fewer ferrous ions in the case of substituted magnetite, and increased reactor volume overcoming differences
in each batch. Commercial nanometer sized magnetite (25–50 nm) may cost $500/kg. However, microbial processes are potentially
capable of producing 5–90 nm pure or substituted magnetites at a fraction of the cost of traditional chemical synthesis. While
there are numerous approaches for the synthesis of nanoparticles, bacterial fermentation of magnetite or metal-substituted
magnetite may represent an advantageous manufacturing technology with respect to yield, reproducibility and scalable synthesis
with low costs at low energy input. 相似文献
7.
The chlorellavorus bacterium (Bdellovibrio chlorellavorus Gromov and Mamkaeva 1972) attaches to (but does not enter) cells of the unicellular green alga,Chlorella, which is killed and the cell contents of which are digested. The bacterium is pleomorphic (vibrios 0.3 μm wide; cocci 0.6
μm wide), and it has a Gram-negative cell wall structure pili, and a single, unsheathed, polar flagellum. Division may occur
only in bacterial cells attached to algal cells, an attachment mediated by a pad (245×36 nm) of unknown composition. Bacterial
growth occurs only in the presence of liveChlorella cells, and not on various bacteriological culture media, killedChlorella cells, 4 strains ofPrototheca, or 24 strains of Gram-negative bacteria. The chlorellavorus bacterium may not require algal protein synthesis, since the
bacterium grows on algae in the presence of cycloheximide (30 μg/ml). Although the DNA base composition of the chlorellavorus
bacterium (50 mol % G+C) is in the same range asBdellovibrio bacteriovorus, its ultrastructure, developmental cycle, host range, and format of its intermicrobial association all distinguish the chlorellavorus
bacterium from members of the genusBdellovibrio. 相似文献
8.
Isolation of obligately alkaliphilic magnetotactic bacteria from extremely alkaline environments 总被引:1,自引:0,他引:1
Lefèvre CT Frankel RB Pósfai M Prozorov T Bazylinski DA 《Environmental microbiology》2011,13(8):2342-2350
Large numbers of magnetotactic bacteria were discovered in mud and water samples collected from a number of highly alkaline aquatic environments with pH values of ≈ 9.5. These bacteria were helical in morphology and biomineralized chains of bullet-shaped crystals of magnetite and were present in all the highly alkaline sites sampled. Three strains from different sites were isolated and cultured and grew optimally at pH 9.0-9.5 but not at 8.0 and below, demonstrating that these organisms truly require highly alkaline conditions and are not simply surviving/growing in neutral pH micro-niches in their natural habitats. All strains grew anaerobically through the reduction of sulfate as a terminal electron acceptor and phylogenetic analysis, based on 16S rRNA gene sequences, as well as some physiological features, showed that they could represent strains of Desulfonatronum thiodismutans, a known alkaliphilic bacterium that does not biomineralize magnetosomes. Our results show that some magnetotactic bacteria can be considered extremophilic and greatly extend the known ecology of magnetotactic bacteria and the conditions under which they can biomineralize magnetite. Moreover, our results show that this type of magnetotactic bacterium is common in highly alkaline environments. Our findings also greatly influence the interpretation of the presence of nanometer-sized magnetite crystals, so-called magnetofossils, in highly alkaline environments. 相似文献
9.
Montero-Astúa M Chacón-Díaz C Aguilar E Rodríguez CM Garita L Villalobos W Moreira L Hartung JS Rivera C 《Journal of microbiology (Seoul, Korea)》2008,46(5):482-490
Coffee plants exhibiting a range of symptoms including mild to severe curling of leaf margins, chlorosis and deformation of
leaves, stunting of plants, shortening of internodes, and dieback of branches have been reported since 1995 in several regions
of Costa Rica’s Central Valley. The symptoms are referred to by coffee producers in Costa Rica as “crespera” disease and have
been associated with the presence of the bacterium Xylella fastidiosa. Coffee plants determined to be infected by the bacterium by enzyme linked immunosorbent assay (ELISA), were used for both
transmission electron microscopy (TEM) and for isolation of the bacterium in PW broth or agar. Petioles examined by TEM contained
rod-shaped bacteria inside the xylem vessels. The bacteria measured 0.3 to 0.5 μm in width and 1.5 to 3.0 μm in length, and
had rippled cell walls 10 to 40 nm in thickness, typical of X. fastidiosa. Small, circular, dome-shaped colonies were observed 7 to 26 days after plating of plant extracts on PW agar. The colonies
were comprised of Gram-negative rods of variable length and a characteristic slight longitudinal bending. TEM of the isolated
bacteria showed characteristic rippled cell walls, similar to those observed in plant tissue. ELISA and PCR with specific
primer pairs 272-l-int/272-2-int and RST31/RST33 confirmed the identity of the isolated bacteria as X. fastidiosa. RFLP analysis of the amplification products revealed diversity within X. fastidiosa strains from Costa Rica and suggest closer genetic proximity to strains from the United States of America than to other coffee
or citrus strains from Brazil. 相似文献
10.
A thermostable DNA polymerase I from a mesophilic Bacillus sphaericus strain C3-41 was characterized in this study. The polI was cloned, sequenced and over-expressed in Escherichia coli. The expressed 110 kDa fusion protein of PolI was stable at 70°C for 1 h. Compared with DNA polymerase I of E. coli (TaKaRa), the relative polymerase activity of this PolI was 3.33 ± 0.1 RFU μl−1 at 37°C using fluorescent quantitative analysis. It showed higher polymerase activity than E. coli PolI at higher temperature, with a relative activity of 3.75 ± 0.1 RFU μl−1 at 70°C. The polI sequence analysis and the protein structure prediction indicated that this protein had a high similarly to other PolI from thermophilic micro-organisms. This information is of importance for future study for evolution of the house-keeping gene polI in entomopathogenic bacterium B. sphaericus. 相似文献
11.
Magnetotactic bacteria synthesize intracellular magnetosomes that are comprised of membrane‐enveloped magnetic crystals. In this study, to identify the early stages of magnetosome formation, we isolated magnetosomes containing small magnetite crystals and those containing regular‐sized magnetite crystals from Magnetospirillum magneticum AMB‐1. This was achieved by using a novel size fractionation technique, resulting in the identification of a characteristic protein (Amb1018/MamY) from the small magnetite crystal fraction. The gene encoding MamY was located in the magnetosome island. Like the previously reported membrane deformation proteins, such as bin/amphiphysin/Rvs (BAR) and the dynamin family proteins, recombinant MamY protein bound directly to the liposomes, causing them to form long tubules. We established a mamY gene deletion mutant (ΔmamY) and analysed MamY protein localization in it for functional characterization of the protein in vivo. The ΔmamY mutant was found to have expanded magnetosome vesicles and a greater number of small magnetite crystals relative to the wild‐type strain, suggesting that the function of the MamY protein is to constrict the magnetosome membrane during magnetosome vesicle formation, following which, the magnetite crystals grow to maturity within them. 相似文献
12.
MS Muntyan DA Morozov SS Klishin NV Khitrin GY Kolomijtseva 《Biochemistry. Biokhimii?a》2012,77(8):917-924
The electrical potential on the membrane was measured in cells of strains AL2 and ALJ15 of the extremely alkaliphilic bacterium Thioalkalivibrio versutus using the penetrating cation tetraphenylphosphonium (TPP+) and a TPP+-selective electrode. The potentials were -228 ± 5 and -224 ± 5 mV, respectively, i.e. higher than in most alkaliphilic bacteria. Membrane potential in the cells was estimated by measuring the inner cell volume by two independent methods: (1) estimation of total cell volume by light microscopy and (2) estimation of the inner aqueous volume of the cells with allowance for the distribution difference of tritium labeled water penetrating through the membranes and a nonpenetrating colored protein. The inner cell volume was 2.4 ± 0.2 and 2.2 ± 0.1 μl/mg of cell protein by the two methods, respectively. Computer computation was used as an alternative to manual calculation to count the number of cells for estimation of total cell volume. 相似文献
13.
Preliminary characterization of a tentatively novel rumen bacterial species from the genus Treponema
A new spirochetal strain was isolated from the rumen of a black-and-white Holstein cow and preliminarily characterized. The
sugar fermentation tests and morphological observations indicated this organism to be a member of a novel, as yet undescribed
spirochetal rumen species. The small subunit ribosomal RNA genes were amplified and the PCR products were cut with the restriction
endonucleasesTaql,Ddel,Hhal andSau3Al. The comparison of the observed RFLP with the hypothetical fragment lengths of the computer analyzed 16S rRNA sequences
from the type strains of the ruminal spirochetesTreponema bryantii andT. saccharophilum confirmed the tentative novel identification. Transmission electron microscopy showed that the bacterium has the typical
spirochetal structures,i.e. the outer sheath, the protoplasmic cylinder and the axial filament (it is not yet clear how many flagella compose the filament).
An additional extracellular structure was observed which appeared as an exocytoplasmic polar flagellum, approximately 2 μm
long and protruding from one tip of the cell. The average size of the cells was 0.5×10–15 μm and the wavelengths and the amplitudes
of the primary coils were 2.9 and 1.3 μm, respectively. 相似文献
14.
The present research work was aimed to formulate clotrimazole encapsulated Cavamax W7 composite ethosomes by injection method
for improved delivery across epidermis. 32 factorial design was used to design nine formulations (F1-F9) and compared with ethosomal formulations (F10-F12). F9 with
vesicle size of 202.8 ± 4.8 nm, highest zeta potential (−83.6 ± 0.96 mV) and %EE of 98.42 ± 0.15 was selected as optimized
composite ethosome and F12 as reference ethosomal formulation. As revealed by transmission electron microscopy F9 vesicles
were more condensed, uniformly spherical in shape than F12 vesicles. Vesicular stability studies indicated F9 to be more stable
as compared to F12. Both F9 and F12 were incorporated in carbopol 934 gel base to get G1–G8 gel formulations and evaluated
for in vitro skin permeability. Cavamax W7 composite ethosomal optimized gel (G5) showed higher in vitro percent cumulative drug permeation (88.53 ± 2.10%) in 8 h and steady state flux (J
ss) of 3.39 ± 1.45 μg/cm2/min against the J
ss of 1.57 ± 0.23 μg/cm2/min for ethosomal gel (G1) and 1.13 ± 0.06 μg/cm2/min for marketed formulation. The J
ss flux of G5 was independent of amount of drug applied/unit area of skin. In vivo confocal laser scanning microscopic study of G5 depicted uniform and deeper penetration of rhodamine B (marker) in epidermis
from Cavamax W7 composite ethosomal gel in comparison to G1. Finally, G5 demonstrated better (p < 0.05) antifungal activity against Candida albicans and Aspergillus niger than G1 thus, signifying that Cavamax W7 composite ethosomes present a superior stable and efficacious vesicular system than
ethosomal formulation for topical delivery of clotrimazole. 相似文献
15.
Veena Agrawal Pratima Rani Sardar 《In vitro cellular & developmental biology. Plant》2007,43(6):585-592
In vitro regeneration through somatic embryogenesis as well as organogenesis using cotyledon of a woody medicinal legume, Cassia angustifolia is reported. The cotyledons dissected from semi-mature seeds, if inoculated on Murashige and Skoog’s medium (MS) supplemented
with auxin alone or in combination with cytokinin, produced direct and indirect somatic embryos. A maximum of 14.36 ± 2.26
somatic embryos per 20 mg of explants including callus were produced in 70% cultures on MS medium with 2.5 μM benzyladenine
(BA) + 10 μM 2,4-dichlorophenoxyacetic acid (2,4-D). Although the percentage of embryogenic cultures was higher (83.33%) at
10 μM 2,4-D + 1 μM BA, the average number of somatic embryos was much less (7.6 ± 0.85) at this level, whereas at 2.5 μM BA
and 5 μM 2,4-D, there was a simultaneous formation of both somatic embryos and shoots. The somatic embryos, although started
germinating on the same medium, developed into full plantlets only if transferred to MS basal with 2% sucrose. Cytokinins
alone did not induce somatic embryogenesis, but formed multiple shoots. Five micromolar BA proved optimum for recurrently
inducing shoots in the competent callus with a maximum average of 12.04 ± 2.10 shoots and shoot length of 2.26 ± 0.03 cm.
Nearly 91.6% shoots (2–2.5 cm in size) organized an average of 5.12 ± 0.58 roots on half strength MS + 10 μM indole-3-butyric
acid. All the plantlets have been transferred successfully to soil. Types of auxin and its interaction with cytokinin significantly
influenced somatic embryogenesis. 相似文献
16.
The genus Dierama comprises plants with a potential to be developed as ornamentals. D. erectum seeds were decontaminated and germinated on 1/10th strength Murashige and Skoog (Physiol Plant 15:473–497, 1962) (MS) media
without plant growth regulators or sucrose. In an experiment investigating the effects of 6-benzyladenine (BA), meta-Topolin (mT), kinetin (KIN) and zeatin (Z) with or without α-naphthaleneacetic acid (NAA), the highest shoot number per hypocotyl (4.20 ± 0.51)
was obtained from MS medium supplemented with 1.0 μM Z after 8 weeks. This was followed by a combination of 2.0 μM KIN and
2.0 μM NAA with 3.67 ± 0.81 shoots per explant. BA treatments produced 3.20 ± 0.22 shoots per hypocotyl explant when 2.0 μM
was combined with 1.0 μM NAA, while mT gave 3.09 ± 0.99 shoots per explant when 2.0 μM mT was combined with 2.0 μM NAA. Adventitious shoot regeneration was optimised when shoots were grown under a 16-h photoperiod
at 100 μmol m−2 s−1 on MS medium supplemented with 1.0 μM BA. This resulted in an average of 12.73 ± 1.03 shoots per hypocotyl explant. Various
concentrations of ancymidol, activated charcoal and sucrose did not promote in vitro corm formation of this species. Plants
rooted successfully after 8 weeks on MS medium supplemented with 1.0 μM indole-3-butyric acid (IBA) and had an average root
number of 2.73 ± 0.40. After 2 months of acclimatisation, plants had formed corms. The largest corms (of diameter 0.45 ± 0.03 cm)
were produced in plants pre-treated with 0.5 μM IBA. The highest plant survival percentage of 73% was also associated with
this treatment. 相似文献
17.
Al-Hussain Bani Hani SM El-Dwairi QA Bataineh ZM Al-Haidari MS Al-Alami J 《Cellular and molecular neurobiology》2008,28(3):411-416
The morphological and quantitative features of neurons in the adult human ventral anterior thalamic nucleus were studied in
Golgi preparations. Two neuronal types were found and their quantitative features were studied. Golgi-type I neurons were
medium to large cells with dense dendritic trees and dendritic protrusions and short hair-like appendages. They have somatic
mean diameter of 30.8 μm (±9.4, n = 85). They have an average 100.3 dendritic branches, 48.97 dendritic branching points, and 58.85 dendritic tips. The mean
diameters of their primary, secondary, and tertiary dendrites were 3.1 μm (±1, n = 80), 1.85 μm (±0.8, n = 145), and 1.5 μm (±0.4, n = 160), respectively. Golgi-type II neurons were small to medium cells with few sparsely branching dendrites and dendritic
stalked appendages with or without terminal swellings. They have somatic mean diameters of 22.2 μm (±5.8, n = 120). They have an average 33.76 dendritic branches, 16.49 dendritic branching points, and 21.97 dendritic tips. The mean
diameters of their primary, secondary, and tertiary dendrites were 1.6 μm (±0.86, n = 70), 1.15 μm (±0.55, n = 118), and 1 μm (±0.70, n = 95), respectively. These quantitative data may form the basis for further quantitative studies involving aging or some
degenerative diseases that may affect cell bodies and/or dendritic trees of the Golgi-type I and/or Golgi-type II thalamic
neurons. 相似文献
18.
Patrizia Bonora Ilaria Principi Alejandro Hochkoeppler Roberto Borghese D. Zannoni 《Archives of microbiology》1998,170(6):435-441
The halophilic purple nonsulfur bacterium Rhodospirillum sodomense has been previously described as an obligate phototroph that requires yeast extract and a limited number of organic compounds
for photoheterotrophic growth. In this work, we report on chemoheterotrophic growth of R. sodomense in media containing either acetate or succinate supplemented with 0.3–0.5% yeast extract. Plasma membranes isolated from
cells grown aerobically in the dark contained three b-type and three c-type membrane-bound cytochromes with E
m,7 of +171 ± 10, +62 ± 10 and –45 ± 13 mV (561–575 nm), and +268 ± 6, +137 ± 10 and –43 ± 12 mV (551–540 nm). A small amount
of a soluble c-type cytochrome with a mol. mass of 15 kDa (E
m,7≥ +150 mV) was identified. Spectroscopic and immunological methods excluded the presence of cytochrome of the c
2
class and high-potential iron-sulfur proteins. Inhibitory studies indicated that only 60–70% of the respiratory activity
was blocked by low concentrations of cyanide, antimycin A, and myxothiazol (10, 0.1, and 0.2 μM, respectively). These results
were interpreted to show that the oxidative electron transport chain of R. sodomense is branched, leads to a quinol oxidase that is fully blocked by 1 mM cyanide and that is involved in light-dependent oxygen
reduction, and leads to a cytochrome c oxidase that is inhibited by 10 μM cyanide. These features taken together suggest that R. sodomense differs from the closely related species Rhodospirillum salinarum and from other species of the genus Rhodospirillum in that it contains multiple membrane-bound cytochromes c.
Received: 8 June 1998 / Accepted: 25 August 1998 相似文献
19.
A. A. Bukinich 《Journal of Evolutionary Biochemistry and Physiology》2010,46(1):61-68
By using the patch-clamp method in the whole cell configuration, modulating effect of dopamine on GABA-activated currents
has been studied on isolated multipolar spinal cord neurons of the ammocaete (larva of the lamprey Lampetra planeri). At application of dopamine (5 μM), there was observed in some cases a decrease of the GABA-activated current, on average,
by 33.3 ± 8.7% (n = 8, p < 0.01), in other cases—an increase of the amplitude, on average, by 37.3 ± 11.8% (n = 5, p < 0.01). Concentration of GABA amounted to 2 mM. Study of action of agonists of D1- and D2-receptors on amplitude of chemocontrolled
currents has shown that agonist of D1-receptors (+)-SKF-38393 (5 μM) decreases the GABA-activated current amplitude, on average,
by 63.1 ± 11.7% (n = 8, p s< 0.01); the agonist of D2-receptors (−)-quinpirole (5 μM) produces in various cells the dopamine-like effects: an increase
of the GABA-activated current amplitude, on average, by 61.0 ± 13.8% (n = 8, p < 0.01) and a decrease of amplitude, on average, by 55.7 ± 2.0% (n = 6, p < 0.01). It has been shown that antagonist of D2-receptors sulpiride (5 μM) does not block effects produced by dopamine.
The dopamine effects were partially blocked by antagonist of D1-receptors (+)-SCH-23390 (5 μM): a decrease of the GABA-activated
amplitude current amounted, on average, to 11.7 ± 1.8% (n = 7, p < 0.01), while an increase of amplitude—8.3 ± 2.0% (n = 5, p < 0.01). At the same time, effects of agonist of D1-receptors quinpirole (5 μM) were partially blocked by antagonist of D1-receptors
(+)-SCH-23390: a decrease of the GABA-activated current amplitude amounted, on average, to 9.2 ± 3.4% (n = 6, p < 0.01) and an increase of amplitude—6.3 ± 1.8% (n = 10, p < 0.01). The obtained data indicate differences of mechanisms of the receptor-mediated effect of agonists of dopamine receptors
on GABA-activated and potential-activated currents of multipolar neurons of the ammocaete spinal cord. 相似文献
20.
Variation of chromophoric dissolved organic matter and possible attenuation depth of ultraviolet radiation in Yunnan Plateau lakes 总被引:2,自引:0,他引:2
The increase of ultraviolet radiation (UVR, 280–400 nm) caused by stratospheric ozone depletion has profound effects on aquatic
ecosystems. High-altitude lakes in the Yunnan Plateau are exposed to high intensities of UVR and contain low concentrations
of chromophoric dissolved organic matter (CDOM). Thirty-eight lakes in the Yunnan Plateau with elevations from 1291 to 3809
m above sea level were investigated to study CDOM concentrations and possible effects of UVR on the lake ecosystem. The attenuation
of UVR in the Yunnan Plateau lakes was calculated from the absorption coefficient of CDOM based on an empirical relationship
from lakes in the Alps and Pyrenees mountains. Absorption coefficients [α(λ)] at 320 nm [α(320)] ranged from 0.52 to 14.05 m−1 (mean ± standard deviation, 4.40 ± 3.85 m−1) and at 380 nm [α(380)] from 0.05 to 4.51 m−1 (1.40 ± 1.30 m−1). The exponential slope coefficient for the relationship of wavelength to α(λ) ranged from 16.2 to 41.4 μm−1 (21.74 ± 4.93 μm−1) over the 280–400 nm interval. Normalized fluorescence emission (NFLU) at 450 nm from an excitation wavelength of 355 nm,
F
n(355), averaged 7.93 ± 3.22 NFLU. A significant positive relationship was found between α(355) and F
n(355). The estimated diffuse attenuation coefficients of UV-B (320 nm) and UV-A (380 nm) ranged from 0.55 to 15.77 m−1 and from 0.24 to 6.73 m−1; the corresponding 1% attenuation depths ranged from 0.29 to 8.44 m and from 0.68 to 19.12 m. Twenty-five of 38 lakes had
1% UV-B attenuation depths of 1.5 m or more. The median 1% attenuation depth was 28.8% of the sampling depth for UV-B radiation
and 60% for UV-A. In addition to CDOM, chlorophyll α (Chla) and total suspended matter (TSM) also may contribute to attenuation of UVR. 相似文献