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1.
Abstract A pap + Escherichia coli isolate from a turkey with colisepticemia expressed P fimbriae with a major subunit of an apparent molecular mass of 18 kDa which reacted with anti-F11 serum. This fimbriae was purified and polyclonal antiserum was produced in rabbits. The N-terminal amino acid sequence of the major fimbrial subunit of the avian P fimbriae was identical to that of F11. On immunoblotting, the antiserum against the avian P fimbriae strongly reacted with the major subunit of the homologous fimbriae, with F11, and with F1651 fimbriae. Some antigenic determinants on the major subunits of F13, F71, and F72 fimbriae, with a stronger reaction against F13 fimbriae, were also recognized. The F11 antiserum reacted similarly to the antiserum against avian P fimbriae although cross-reactions against F13, F71, and F72 fimbriae were equivalent. In a competitive enzyme-linked immunosorbent assay, serological differences were observed between the purified avian P fimbriae and F11. Thus, the avian P fimbriae is closely related but not identical to F11 fimbriae which are associated with E. coli isolated from human urinary tract infection.  相似文献   

2.
Abstract The gene cluster coding for expression of F71 fimbriae of the uropathogenic Escherichia coli strain AD110 has been cloned by a cosmid-cloning procedure. A positive clone was further subcloned to a plasmid of 17.5 kilobases (kb), pPIL110-75. Analysis of pPIL110-75 showed that at least six genes are present encoding proteins with apparent M rs of 75 000, 36 000, 23 000, 20 000, 17 000 and 14 000. The 20-kDa protein, encoding the F71 fimbrial subunit is dispensable for expression of the MRHA phenotype. Complementation experiments of mutants in the F72 gene cluster by gene products of the F71 gene cluster show that the two gene clusters are related.  相似文献   

3.
The influence of genetic manipulation of the structural genes coding for major P-fimbrial subunits on the formation of fimbriae in Escherichia coli was studied. Deletion of two regions that code for hypervariable parts of the P fimbrillin resulted in strong reduction or total absence of fimbria production. Replacement of deleted amino acids by other amino acid residues restored the formation of fimbriae. The hypervariable regions may be important for biogenesis of fimbriae by imposing correct spacing between conserved regions of the protein. The potential for substituting amino acids in the P-fimbrial subunit opens interesting possibilities for use of fimbriae as carriers of foreign antigenic determinants. An antigenic determinant of foot-and-mouth disease virus (FMDV) was incorporated in the F11 fimbrial subunit. Hybrid fimbriae, recognized by an FMDV-specific neutralizing monoclonal antibody directed against FMDV, were formed.  相似文献   

4.
Five strains of filamentous fungi belonging to the genera Mortierella and Cunninghamella were examined for the content of dihomo-γ-linolenic, arachidonic, eicosapentaenoic acids and prostaglandins (type E2 and F ). Prostaglandins were detected using an ELISA method in mycelia of all tested strains (range 50–4800 ng g−1 of PGE2 and 6–30 ng g−1 of PG F ). Several micro-organisms also produced prostaglandins in the culture medium (2·2–137·6 μg l−1 for PGE2 and 0·4–7·8 μg l−1 for PG F ).  相似文献   

5.
Within the Astigmata, setal homologies with the general chaetotaxic systems developed for acariform mites by F. Grandjean have never been convincingly established. This study deals with all body regions, exclusive of legs and gnathosoma, mostly utilizing as models astigmatid species from three different families. Six hypotheses which attempt to explain the ontogeny of segments, setae and cupules in the caudal bend region are compared using three-dimensional views obtained by scanning electron microscopy. The hypotheses are evaluated by in-group comparisons testing their consistency with presumed segmental boundaries, and by out-group comparisons with oribatid mites. The strongest, most parsimonious hypothesis suggests that larval astigmatid mites possess segment F, but not its setae, and the two pairs posterior to segment F are h l and h 2, whilst the five setae added in the protonymph are h 3, f 2 and ps 1–3. Six pairs of structures on the deutonymphal anal plate are identified as modified setae, and evidence supporting their homologies with setae of other instars is discussed for the first time. A comparison of the principal chaetotaxic systems used for the dorsal and anal regions of the Astigmata is presented. Application of Grandjean's setal signatures to these regions, as well as to the coxisternal and genital regions, is discussed and illustrated by examples.  相似文献   

6.
A new chemical indicator for monitoring steam sterilization processes has been calibrated in F 0 units. The effective temperature range for F 0 measurements using this device has been shown to lay between 115 and 123°C. The effective F 0 range of the device has been shown to be 4–23 F 0 units. Using the device, measurements can be made within 0.5 units of conventionally calculated F 0 values.  相似文献   

7.
Four additional cattle blood group antigenic factors, provisionally termed Fl, F6, F10 and F15, were shown to belong to the C system. Factor Fl appears to be a linear subtype of C"(initially designated F2, or P1B1). It is suggested that future international nomenclature should adopt C", and C"2 in place of Fl and C . No phenogroup was found to include C" together with C2 or C1, but a few phenogroups lack the three factors. Thus C1, C2 and C"do not form a closed system within the C system as concluded by Duniec et al. (1973). The effectiveness of the additional factors to uncover the genetic variability of the C system, and to translate phenotypes into genotypes is exemplified in the Charolais breed.  相似文献   

8.
Kinetic fluorescence imaging was used to set a new detection limit for plant exposure to low levels of destruxins – phytotoxins of Alternaria brassicae . A general experimental algorithm is presented that can be used to identify the combination of fluorescence parameters providing the highest contrast between the affected and unaffected plants or plant segments. Leaves of canola ( Brassica napus ) and white mustard ( Sinapis alba ) were exposed to various concentrations of destruxins and images of key fluorescence signals ( F 0, F M, F P, and of F S) were captured in a single kinetic experiment. Contrast was quantified within these images between the leaf areas exposed to destruxins and the untreated areas. The highest contrast was found in the image constructed by pixel-to-pixel division of images F 0 by F P and F 0 by F M. Using the F 0/ F M ratio image, we were able to detect exposure to destruxin concentration as low as approximately 0.05 mg l−1 applied to canola leaf and approximately 10 mg l−1 when applied to mustard. The detection limits were significantly lower than those obtained by optical microscopy indicating that kinetic chlorophyll fluorescence imaging can be used as a diagnostic tool in screening for varieties with an enhanced resistance to destruxins of Alternaria brassicae .  相似文献   

9.
Zolpidem is a positive allosteric modulator of GABAA receptors with sensitivity to subunit composition. While it acts with high affinity and efficacy at GABAA receptors containing the α1 subunit, it has a lower affinity to GABAA receptors containing α2, α3, or α5 subunits and has a very weak efficacy at receptors containing the α5 subunit. Here, we show that replacing histidine in position 105 in the α5 subunit by cysteine strongly stimulates the effect of zolpidem in receptors containing the α5 subunit. The side chain volume of the amino acid residue in this position does not correlate with the modulation by zolpidem. Interestingly, serine is not able to promote the potentiation by zolpidem. The homologous residues to α5H105 in α1, α2, and α3 are well-known determinants of the action of classical benzodiazepines. Other studies have shown that replacement of these histidines α1H101, α2H101, and α3H126 by arginine, as naturally present in α4 and α6, leads to benzodiazepine insensitivity of these receptors. Thus, the nature of the amino acid residue in this position is not only crucial for the action of classical benzodiazepines but in α5 containing receptors also for the action of zolpidem.  相似文献   

10.
11.
Speciation, the evolution of reproductive isolation between populations, serves as the driving force for generating biodiversity. Postzygotic barriers to gene flow, such as F 1 hybrid sterility and inviability, play important roles in the establishment and maintenance of biological species. F 1 hybrid incompatibilities in taxa that obey Haldane's rule, the observation that the heterogametic sex suffers greater hybrid fitness problems than the homogametic sex, are thought to often result from interactions between recessive-acting X-linked loci and dominant-acting autosomal loci. Because they play such prominent roles in producing hybrid incompatibilities, we examine the dominance and nature of epistasis between alleles derived from Drosophila persimilis that confer hybrid male sterility in the genetic background of its sister species, D. pseudoobscura bogotana . We show that epistasis elevates the apparent dominance of individually recessive-acting QTL such that they can contribute to F 1 hybrid sterility. These results have important implications for assumptions underlying theoretical models of hybrid incompatibilities and may offer a possible explanation for why, to date, identification of dominant-acting autosomal "speciation genes" has been challenging.  相似文献   

12.
Abstract: The pentameric subunit composition of a large population (36%) of the cerebellar granule cell GABAA receptors that show diazepam (or clonazepam)-insensitive [3H]Ro 15-4513 binding has been determined by immunoprecipitation with subunit-specific antibodies. These receptors have α6, α1, γ2S, γ2L, and β2 or β3 subunits colocalizing in the same receptor complex.  相似文献   

13.
The visual pigments in the retinal rods of elvers ( Anguilla anguilla L.) were examined by microspectrophotometry and high performance liquid chromatography. The glass elver stage had a mixture of rhodopsin P5011 and porphyropsin P5232 with the former predominating (P5011:P5232= c. 60:40). More mature pigmented elvers had a predominance of the porphyropsin P5232 (P5011:P5232= c. 10:90). The shift between the proportions of each pigment was monitored over a 7-month period and was shown to occur in individual retinal rods. This shift is a reverse of the pigment shift that occurs in adult eels during their downstream migration.  相似文献   

14.
Abstract The role of cytochrome b 562, a fragile constituent of the respiratory terminal oxidase supercomplex of the thermoacidophilic archaeon, Sulfolobus sp. strain 7, was investigated spectroscopically in the membrane-bound state. Cytochrome b 562 did not react with CO or cyanide in the membrane-bound state, while it was irreversibly modified to a CO-reactive form ( b 562) upon solubilization in the presence of cholate and LiCl. Cyanide titration analyses with the succinate-reduced membrane suggested that cytochrome b 562 was upstream of both the ' g y= 1.89' Rieske FeS cluster and the a -type cytochromes. These results show that the b -type cytochrome functions as an intermediate electron transmitter in the terminal oxidase supercomplex.  相似文献   

15.
Calcium/calmodulin-dependent kinase II (CaMKII) facilitates L-type calcium channel (LTCC) activity physiologically, but may exacerbate LTCC-dependent pathophysiology. We previously showed that CaMKII forms stable complexes with voltage-gated calcium channel (VGCC) β1b or β2a subunits, but not with the β3 or β4 subunits ( Grueter et al. 2008 ). CaMKII-dependent facilitation of CaV1.2 LTCCs requires Thr498 phosphorylation in the β2a subunit ( Grueter et al. 2006 ), but the relationship of this modulation to CaMKII interactions with LTCC subunits is unknown. Here we show that CaMKII co-immunoprecipitates with forebrain LTCCs that contain CaV1.2α1 and β1 or β2 subunits, but is not detected in LTCC complexes containing β4 subunits. CaMKIIα can be specifically tethered to the I/II linker of CaV1.2 α1 subunits in vitro by the β1b or β2a subunits. Efficient targeting of CaMKIIα to the full-length CaV1.2α1 subunit in transfected HEK293 cells requires CaMKII binding to the β2a subunit. Moreover, disruption of CaMKII binding substantially reduced phosphorylation of β2a at Thr498 within the LTCC complex, without altering overall phosphorylation of CaV1.2α1 and β subunits. These findings demonstrate a biochemical mechanism underlying LTCC facilitation by CaMKII.  相似文献   

16.
Studies of postcopulatory sexual selection typically estimate a male's fertilization success from his paternity success ( P 2) calculated at hatching or birth. However, P 2 may be affected by differential embryo viability, thereby confounding estimations of true fertilization success ( F 2). This study examines the effects of variation in the ability of males to influence embryo viability upon the inequality between P 2 and F 2. It also investigates the consequences of this inequality for testing the hypothesis that polyandrous females accrue viability benefits for their offspring through facilitation of sperm competition (good-sperm model). Simulations of competitive mating trials show that although relative measures of male reproductive success tend to underestimate the strength of underlying good-sperm processes, good-sperm processes can be seriously overestimated using P 2 values if males influence the viability of the embryos they sire. This study cautions the interpretation of P 2 values as a proxy for fertilization success or sperm competitiveness in studies of postcopulatory sexual selection, and highlights that the good-sperm hypothesis needs empirical support from studies able to identify and separate unequivocally the males' ability to win fertilizations from their ability to influence the development of embryos.  相似文献   

17.
Rainbow trout body mucus dialysed with acidified distilled water at pH 7,5 and 3 experienced ion depletion which was greatest at pH 3 and minimal between pH 7 and 5. Mucus Na+ loss is exacerbated in the presence of 1 mg I−1 aluminium as A12(SO4), at pH 5 and 7. Al2(SO4), causes greater depletion of Na+ from mucus than A1C13. A lethal level of zinc (2 mg 1−1) does not deplete mucus Na or K+, unlike a lethal level of aluminium (1 mg 1−1) at pH 7. The results are discussed in terms of the ionoregulatory role of mucus in heavy metal and acid toxicity.  相似文献   

18.
Abstract: We have investigated the isozymes of a phosphoinositide-specific phospholipase C (PLC) in bovine retina using several monoclonal antisera to PLCβ1, γ1, and δ1. Immunoblot analysis showed that all three isozymes were present in the retina. Immunocytochemical localization in frozen bovine retina sections showed that PLCγ1 was present in the photoreceptor cell layer, outer plexiform cell layer, inner plexiform cell layer, and ganglion cell layer. Immunoreaction within the photoreceptor cell layer was dependent on dark/light adaptation state of retinas. Immunoblot analysis of rod outer segments (ROS) with monoclonal or polyclonal antibodies to PLCγ1 showed the presence of an immunoreactive band of 140 kDa. ROS prepared from retinas light-adapted in vitro had more PLCγ1 on immunoblots than ROS from dark-adapted retinas. PLC enzyme activity in ROS from light-adapted retinas was 69 and 46% higher than ROS from dark-adapted retinas, when assayed in the presence and absence of ATP, respectively. This increase in enzyme activity was observed at [Ca2+]free between 0.32 and 100 µ M . These results demonstrate the presence of PLCγ1 in bovine ROS and show that ROS prepared from light-adapted retinas are enriched in this isozyme, suggesting that light may promote the binding of this isozyme to bleached ROS membranes.  相似文献   

19.
20.
Stomatal response to humidity: implications for transpiration   总被引:1,自引:1,他引:0  
Abstract. Transpiration rates from apple leaves are analysed in terms of the ratio of latent heat flux (λ E ) to leaf net radiation ( Q 1) and the climatological resistance ( ri ). Increases in stomatal resistance with increasing leaf to air vapour pressure gradient ( D ), described by an empirical model, are incorporated in the analysis. This humidity effect causes the proportion of energy dissipated as latent heat to fall as Q 1 increases, so that leaf transpiration rates in high energy environments are likely to be similar to those in lower energy environments. Boundary layer resistance ( r a) exerts an increasingly important effect on transpiration rates as Q 1 increases. At constant Q 1 stomatal closure in response to increasing D results in very small changes in leaf temperature ( T 1) across a wide range of ambient vapour pressure deficits (δ e ); r a is then the major factor determining T 1. The implications of these results are discussed.  相似文献   

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