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1.
Biofilm development on AISI-1020 carbon steel coupons installed at the outlet of a heat exchanger was evaluated at the thirtieth and the sixtieth days of exposure. Water temperature varied between 41 and 60°C. The most probable number technique (MPN) was applied to quantify mesophilic and thermophilic species of aerobic, anaerobic, and sulphate-reducing bacteria (SRB) in planktonic and sessile phases. The results showed predominance of thermophilic aerobic bacteria in both phases, corresponding to 9.5±0.8×106cells/ml in the planktonic phase. In biofilms, maximal aerobic cell concentration, 7.8±0.6×108cells/cm2, was registered at the sixtieth day. An increase in the number of thermophilic anaerobic and SRB with elapsed time was also observed. The results obtained after 60 days were 5.8±0.4×107 and 8.9±0.9×104cells/cm2 for anaerobic and sulphate-reducing bacteria, respectively. Scanning electron microscopy showed a varied composition of species in the biofilms and corrosion on the carbon steel surfaces after biofilm removal.  相似文献   

2.
1.Phencyclidine (PCP) is an inhibitor of the nicotinic acetylcholine receptor (AChR) with characteristics of an open-channel blocker. The location of PCP binding site on the AChR molecule is unknown.2.PCP inhibits the AChR from electric organ with a higher potency than muscle AChR. To find the molecular basis of this difference, we expressed the two native and six hybrid receptors, and two receptors containing mutated mouse subunits in Xenopus laevis oocytes. The inhibition of ACh-induced current in these receptors by PCP was studied using whole-cell voltage-clamp. All hybrid receptors generated robust ACh-induced currents, while incomplete receptors (-less or -less) did not.3.PCP potency was higher on hybrids containing Torpedo and subunits regardless of the and subunit origin. A mouse subunit containing the asparagine 6 to the serine mutation in the M2 segment conferred a high sensitivity to PCP.4.These results support the conclusion that the amino acid residues at the position 6 of the M2 segments contribute to the PCP potency difference between Torpedo and mouse receptors.5.Another noncompetitive inhibitor of the AChR, the cembranoid eupalmerin acetate (EUAC), also inhibited the electric organ receptor with a somewhat higher potency than muscle AChR. However, the IC50 values for EUAC inhibition of hybrid receptors did not follow the pattern observed for PCP. Therefore, these two inhibitors interact differently with the AChR molecule.  相似文献   

3.
A new method for cytofluorometric analysis of mitochondrial membrane potential has been developed by using TMRM as a cationic, mitochondrial selective probe. The method is based on limited treatment of cultured cells with digitonin which permeabilises the plasma membrane and leaves mitochondria intact. The resulting signal of TMRM-stained cells thus represents only the probe accumulated in mitochondria. Fibroblasts and cybrids were used as a model cell systems and optimal conditions for digitonin treatment and staining by TMRM were described. The TMRM signal collapsed by valinomycin, KCN and antimycin A and FCCP titration was used to gradually lower and characterise the stability of . The method is suitable for sensitive measurement of in different types of cultured cells.  相似文献   

4.
Transgenic mice were produced by microinjection of a DNA construct composed of the bovine -casein (-CN) cDNA under the control of the goat -CN 5 promoter elements and 3 flanking regions into pronuclear-stage embryos. The gene construct targeted the expression of bovine -CN RNA to the mammary gland and secretion of bovine -CN in the milk. In the three lines studied (BC-7, BC-31 and BC-67) the transgene was stably integrated and propagated as a Mendelian locus. Expression of the bovine protein in lactating mice from the three transgenic lines was demonstrated by northern and western blots. In ten different tissues analysed by northern blotting, expression was confined to the mammary gland of lactating transgenic mice from line BC-7, with low-level expression also observed in the salivary gland of lines BC-31 and BC-67. Transgene expression in the mammary gland paralleled normal casein gene expression during lactation and was not observed in virgin females. The level of bovine -CN mRNA expression on day 10 of lactation in hemizygous transgenic females in relation to endogenous mRNA of whey acid protein (WAP) gene expression was 14%, 69% and 127% in lines BC-7, BC-31 and BC-67, respectively. No association between transgene copy number and expression was observed. The bovine -CN concentration in milk on day 10 of lactation ranged from 0.94 to 3.85 mg of protein per ml of milk. The bovine -CN expressed in mouse milk had the same molecular mass and immunoactivity with polyclonal antibodies as did -CN from bovine milk. A high degree of variation in the production of bovine -CN within each of the transgenic lines was observed.  相似文献   

5.
The aims of this study were to characterize specific mRNAs and the expression pattern for isoforms of calcium/calmodulin-dependent protein kinase II (CaMKII) in the human brain. We cloned and sequenced the CaMKII and subunit cDNAs, and used them to study the CaMKII expression in human brain. Four distinct isoforms of CAMKII were isolated. Two of them were characterized as CaMKII and subunits. The other two showed similar nucleotide sequences, but one had a 33-bp insertion relative to the subunit, and the other had a 75-bp deletion relative to the subunit. These alterations are located within the variable regions. These two isoforms were characterized as CaMKII B and e. Northern blot analysis showed that a 4.4-kb messenger RNA for the isoform and a 3.9-kb messenger RNA for the isoform were expressed in both human fetal and adult brain to different degrees. The results indicate that CaMKII expression is developmentally regulated. The CaMKII isoform expression was confirmed in human fetal and adult brain using RT-PCR with specific primers, which flanked the CaMKII variable regions. The CaMKII , B, , and e isoforms were characterized in both human fetal and adult brain.  相似文献   

6.
We investigated aquatic macrophytes, water quality, and phytoplankton biomass and species composition in three shallow lakes with different levels of vegetation cover and nutrient concentration in Kushiro Moor, during August 2000. Trapa japonica can live in a wide range of nutrient levels. This species forms an environment with a steeper extinction of light, higher concentrations of dissolved organic carbon (DOC), lower concentrations of dissolved oxygen (DO) near the bottom, and lower concentrations of nitrate+nitrite and soluble reactive phosphorus (SRP) than other vegetation types. The pH was much higher in a Polygonum amphibium community, and the DO near the bottom did not decrease compared to a T.japonica community in the summer. The relationship between chlorophyll a and the limiting nutrient (total phosphorus (TP) when total nitrogen (TN):TPis 10 and TN/10 when TN:TP is <10) significantly differed between lakes with and without submerged vegetation. The chlorophyll a concentrations at a given nutrient level were significantly lower in water with submerged macrophytes than in water without them. Correspondence analysis showed that the difference in phytoplankton community structure across sites was largely due to the presence or absence of submerged macrophytes, and the ordination of phytoplankton species in the lakes with submerged macrophytes is best explained by environmental gradients of TN, chlorophyll, pH and SRP.  相似文献   

7.
Quantification of the time course and amplitude of endplate currents (EPC) was made with respect to dispersion of quanta secretion and to changes in the exponential decay of miniature endplate currents (mepc). The relationship between RPC amplitude and mepc follows a double-exponential curve with 1= 0.3 ms and 2 = 6 ms. If the amplitude of fully synchronised EPC is taken as 100%, then the loss of EPC amplitude is already 42% with physiological parameters of dispersion (the half-rise and decay constant of distribution of secretion probability = 0.5 ms, mepc =1 ms). This loss is even more substantial if secretion is more dispersed or miniature endplate currents decay faster. Correspondence to: F. Vyskocil  相似文献   

8.
A -carotene oxygenase is described which occurs in the Cyanobacterium Microcystis. It cleaves -carotene and zeaxanthin specifically at the positions 7,8 and 7,8, while echinenone and myxoxanthophyll are not affected. The oxidative cleavage of -carotene leads to the formation of -cyclocitral and crocetindial and that of zeaxanthin to hydroxy--cyclocitral and crocetindial in nearly stoichiometric amounts. Oxidant is dioxygen as has been demonstrated by high incroporation (86%) of 18O2 into -cyclocitral. -Carotene oxygenase is membrane bound, sensitive to sulfhydryl reagents, antioxidants and chelating agents. Iron seems to be an essential part of the enzyme activity. Cofactors necessary for the reaction could not be detected.Abbreviations TLC thin layer-chromatography - PIPES piperazine-N,N-bis-(2-ethanesulfonate) Na - TES 2{[tris-(hydroxymethyl)-methyl]-amino} ethanesulfonic acid Dedicated to Professor G. Drews on occasion of his 60th birthday  相似文献   

9.
Summary A study was made of the effect of genotype and temperature (25 and 17°C) on sex ratio in the hybrids D. virilis Sturt. X D. littoralis Sokolov. A genetic system has been found controlling sex-differential viability. In the F1 of the reciprocal hybrids D. virilis X D. littoralis the sex ratio is normal, though at 17°C females are slightly excessive. The abnormal sex ratio is observed only in the progeny of test crosses.The major gene causing the death of female progeny of the cross [ (, D. virilis x , D. littoralis) x D. virilis] x D. littoralis is located on chromosome 2 of D. virilis. It is expressed as a lethal if chromosome 5 is heterogeneous virilis-littoralis. Chromosome 3 of D. virilis bears a modifier-enhancer and chromosome 5, a suppressor, of this lethal found in chromosome 2. This genetic system has a maternal effect and functions at 25°C, interacting with the X-chromosome of D. littoralis. If the maintainance temperature is lowered to 17°C, the progeny of the cross hybrid FB1 x D. littoralis is predominantly female. Partial death of males is accounted for by a disturbance in the interaction between the genes of X-chromosome in certain combinations with the D. virilis autosomes and the Y-chromosome of the paternal species D. littoralis.Sex-differential mortality in the hybrids D. virilis x D. littoralis is one of the isolating factors between these species which does not appear to act until the second and subsequent F1 generations due to the formation of the recombination load.  相似文献   

10.
SCM2, a novel gene encoding a yeast tryptophan permease, was cloned as a high-copy-number suppressor of cse2-1. The cse2-1 mutation causes cold sensitivity, temperature sensitivity and chromosome missegregation. However, only the cold-sensitive phenotype of cse2-1 cells is suppressed by SCM2 at high copy. SCM2 is located on the left arm of yeast chromosome XV, adjacent to SUP3 and encodes a 65 kDa protein that is highly homologous to known amino acid permeases. Four out of five disrupted scm2 alleles (scm21-4) cause slow growth, whereas one disrupted allele (scm25) is lethal. Cells with both the scm21 and trp1-101 mutations exhibit a synthetic cold-sensitive phenotype and grow much more slowly at the permissive temperature than cells with a single scm21 or trp1-101 mutation. A region of the predicted SCM2 protein is identical to the partial sequence recently reported for the yeast tryptophan permease TAP2, indicating that SCM2 and TAP2 probably encode the same protein.  相似文献   

11.
We investigated the flash-induced electrochromic absorbance change, A 515, of isolated intact chloroplasts in continuous monochromatic background light of different intensities and wavelengths. From the variation of the amplitude of A 515 in background illumination the steady-state turnover time of electron transport was found to be around 100 msec and the slowest process could be assigned to a photosystem 1 driven cycle. The change of pH induced by nigericin, ATP, or ADP did not modify substantially the turnover time.In contrast to earlier observations the slow rise (10 msec) of A 515 in untreated chloroplasts persists also at high-intensity background illumination exciting both photosystems. The proportion of the slow rise of A 515 in nigericin-treated chloroplasts increases in the presence of background light. This result on the slow rise is discussed in terms of two different models existing in the literature.  相似文献   

12.
A soluble -3/4-fucosyltransferase secreted into the growth medium of the human A431 epidermoid carcinoma cell line has been purified 700 000 fold by a series of steps involving chromatography on Phenyl Sepharose 4B, CM-Sephadex C-50 and GDP-hexanolamine Sepharose 4B. The untreated spent culture medium transferred almost ten times more fucose to the subterminalN-acetylglicosamine residue in the Type 1 (Gal 1-3GlcNAc) disaccharide than to the subterminal sugar in the Type 2 (Gal 1-4GlcNAc) disaccharide; the relative activity with these two substrates remained virtually unchanged throughout the purification procedure. At no stage was any -3-fucosyltransferase species acting solely onN-acetylglucosamine residues in Type 2 chains separated from the bulk of the -3/4-fucosyltransferase activity. The purified enzyme preparation showed insignificant activity with glycoprotein substrates having N-linked oligosaccharide chains with terminal Type 2 sequences but transferred fucose to a mucin-type glycoprotein with O-linked oligosaccharide chains with terminal Type 1 structures. Lactose was a poor substrate but the activity of the enzyme was influenced by the presence of substituents on the terminal -galactosyl residue and 2-fucosyllactose was almost as good an acceptor as the Type 1 disaccharide. The properties of the purified enzyme with regard to specificity, divalent cation requirements, pH optimum, andM r, closely resembled those of the Lewis-blood-group gene associated -3/4-fucosyltransferase isolated from human milk.Deceased June 1991.  相似文献   

13.
Sequence comparison of the -subunit of phosphorylase kinase with -tropomyosin revealed 32% identity, and 49% similarity, between the region of -tropomyosin coded by exon 5 and a 39 amino acid segment of the kinase subunit. A subsequence of the -subunit segment and a sequence overlapping the same -subunit region are homologous with: (a) a region of the cytoplasmic domain of EGF receptor (50% identity) and (b) a Ca2+-binding domain of the chain of S-100 protei (50% identity) respectively. Statistical analysis shows that these homologies are significant. The biological implication of the above similarities is discussed.  相似文献   

14.
Phase resetting associated with changes of burst shape   总被引:1,自引:0,他引:1  
Based on our stochastic approach to phase resetting of an ensemble of oscillators, in this article we investigate two stimulation mechanisms which exhibit qualitatively different dynamical behaviour as compared with the stimulation mechanism analysed in a previous study. Both the old as well as one of the new stimulation mechanisms give rise to a characteristic desynchronization behaviour: A stimulus of a given (non-vanishing) intensity administered at a critical initial ensemble phase for a critical duration T crit annihilates the ensemble's synchronized oscillation. When the stimulation duration exceeds T crit a transition from type 1 resetting to type 0 resetting occurs. The second new stimulation mechanism does not cause a desynchronization which is connected with a phase singularity. Correspondingly this mechanism only leads to type 1 resetting. In contrast to the stimulation mechanism analysed in a previous study, both new stimulation mechanisms cause burst splitting. According to our results, in this case peak or onset detection algorithms are not able to reveal a correct estimate of the ensemble phase. Thus, whenever stimulation induced burst splitting occurs, phase-resetting curves determined by means of peak or onset detection may be nothing but artifacts. Therefore it is necessary to understand burst splitting in order to develop reliable phase detection algorithms, which are e.g. based on detecting bursts' centers of mass. Our results are important for experimentalists: Burst splitting is, for instance, well-known from tremor resetting experiments. Thus, it often turned out to be at least rather difficult to derive reliable phase-resetting curves from experimental data.  相似文献   

15.
Summary A previous method of measuring the swelling pressure ( g ) of the cytoplasmic gel of the giant axon ofLoligo vulgaris was refined. The estimates of g made with the improved method were consistent with those made with the earlier method. In these methods the activity of the solvent in the gel is measured by increasing the activity of the solvent in the internal phase of the gel by application of hydrostatic pressure to the gel directly. Comparable values for the activity of the solvent in the gel were obtained also by an alternate method, in which the deswelling of the gel is measured upon decreasing the activity of the solvent in the external phase by addition of a nonpenetrating high mol wt polymer (i.e., Ficoll).Additional support was obtained for the earlier suggestion that g contributes to the swelling and shrinkage pattern of the whole axon. In part, the new evidence involved two consecutivedirect measurements of intraxonal pressure. The first measurement was that of a mixed pressure composed of g and m ( m being the effective osmotic pressure due to the intra-extraxonal gradient in the activity of mobile solutes). The subsequent measurement was that of g alone. The latter measurement was made feasible by destroying the axolemma, thereby eliminating the contribution of m . An estimate of m was obtained by subtracting g from the total pressure measured initially. The m determined by the above method was two orders of magnitude smaller than the theoretical osmotic pressure. This is consistent with the m determined previously, where osmotic intra-extraxonal filtration coefficients were compared to the hydrostatic. The mixed pressure experiments lend credence to the idea that the substantial contribution of g to the water relations of the whole axon is due to g being of the same order of magnitude as m .The degree of free swelling of axoplasmic gels was studied as a function of pH, salt concentration, and hydration radius of the anion of the salt used. The swelling increased with an increase in the reciprocal of the hydration radius, a decrease in salt concentration, and at pH below or above 4.5.The nature of the constraints to the free swelling of axoplasm in axons immersed in seawater was studied. With the seawater employed, these constraints appeared to be due more to the retractive forces of the sheath than to m .  相似文献   

16.
Organogenetic buds were induced from hypocotyl and cotyledon explants of oil crop Perilla frutescens in Murashige and Skoog (MS) medium supplemented with 5.7 M indole-3-acetic acid (IAA) and 8.9 – 13.3 M 6-benzylaminopurine (BA). Shoots were rooted on MS medium with 2.9 M IAA and 1.4 M gibberellic acid (GA3) and the regenerated plants flowered and set seeds normally.  相似文献   

17.
The homology of class I major histocompatibility complex (MHC) antigens, class II MHC antigens, and immunoglobulin molecules has suggested their divergence from a common ancestral gene. We report here a monoclonal antibody (mAb), PAC. M1, which reacts with HLA class I heavy chains, HLA class II and chains, and the light chain of human immunoglobulin by Western blot analysis. PAC.M1 reacted with 44 kd, 33 kd, and 29 kd species when tested on membrane glycoproteins from TRa1, a B-lymphoblastoid cell line (B-LCL). Two-dimensional electrophoresis and Western blotting of TRa1 glycoproteins showed that these species had the appropriate electrophoretic mobilities for class I heavy chain and class II and subunits. The presence of the epitope was verified on class II and subunits by Western blotting of purified -invariant chain complexes, and on class I heavy chains by Western blotting of purified class I antigens. The PAC. M1 mAb also reacted with immunoglobulin light chains when Western blotting was performed with normal human serum and purified IgG and IgM as antigens. While reactivity of the mAb with beta-2 microglobulin ( 2m) was difficult to detect by Western blotting, binding of PAC.M1 to purified 2m was detectable in a solid-phase binding assay. Thus, PAC.Ml reacts with a determinant shared by a number of members of the immunoglobulin superfamily.  相似文献   

18.
Thewm7 haplotype of the major histocompatibility complex (MHC), derived from the Japanese wild mouseMus musculus molossinus, enhances recombination specific to female meiosis in theK/A interval of the MHC. We have mapped crossover points of fifteen independent recombinants from genetic crosses of thewm7 and laboratory haplotypes. Most of them were confined to a short segment of approximately 1 kilobase (kb) of DNA between theA 3 andA 2 genes, indicating the presence of a female-specific recombinational hotspot. Its location overlaps with a sex-independent hotspot previously identified in theMus musculus castaneus CAS3 haplotype. We have cloned and sequenced DNA fragments surrounding the hotspot from thewm7 haplotype and the corresponding regions from the hotspot-negative B10.A and C57BL/10 strains. There is no significant difference between the sequences of these three strains, or between these and the published sequences of the CAS3 and C57BL/6 strains. However, a comparison of this A3/A2 hotspot with a previously characterized hotspot in theE gene revealed that they have a very similar molecular organization. Each hotspot consists of two elements, the consensus sequence of the mouse middle repetitive MT family and the tetrameric repeated sequences, which are separated by 1 kb of DNA.The nucleotide sequence data reported in this paper have been submitted to the DNA Data Bank of Japan nucleotide sequence database and have been assigned the accession numbers d90007-9. Offprint requests to: T. Shiroishi.  相似文献   

19.
Students wearing swim suits were exposed for 30 min to neutral room temperature (TR=28C). During the following 60 min they were subjected to gradual decreases or increases of room temperature reaching 12C or 45C, respectively. Static thermal stimuli were applied to the palms of the right (38C) and left (25C) hands. Hands and feet of all subjects were thermally isolated at 22C ambient temperature. General thermal comfort (GTC), local thermal comfort (LTC), skin blood flow (which is proportional to heat transport index ) several body temperatures, oxygen-consumption , and sweat rate (S), were measured. After moderate intermittent heat exposures (7 times for 1h at TR=42.5C) the experiments started again. From GTC, LTC, or as functions of TR, no new knowledge about thermoregulatory or adaptive mechanisms was available. The high in the cold stimulated left hand, however, and the oscillatory thresholds (OSC) for rhythmic vasomotion indicated the peripheral influence of skin temperature, as well as local, mean skin temperature (¯Ts) and core temperature. When exposed to moderate temperature decreases or increases the body seems to react only with increasing thermal resistance by vasoconstriction or an increase of sweat rate, respectively. Moderate heat adaptation is only able to raise sweat rate, but not the thresholds and gain of the S-function. We assume that functional studies of adaptive modifications in humans must be conducted at temperatures greatly beyond those used in these experiments.  相似文献   

20.
The building up of the two types of reaction centers, PS II and PS II, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS II centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS II centers, which built up more rapidly than PS II centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DGDG digalactosyldiacylglycerol - FAME Tatty acid methyl esters - HEPES acide (N-[2-hydroxyethyl]piperazine-N-[2-ethane sulfonic] - MGDG monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - PG phosphatidylglycerol - PQ plastoquinone - PS I Photosystem I - PS II Photosystem II - QA primary quinone electron acceptor of PS II - QB secondary quinone electron acceptor of PS II - SQDG sulfoquinovosyldiacylglycerol  相似文献   

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