首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The origins of capers, their use and cultivation are discussed. Capers seeds and charcoal are often recovered from archaeological sites of the Mediterranean and West Asia. These are referred to as C. Spinosa L. This is mostly a group of cultivars restricted to localities surrounding the Western Mediterranean and some places in the Eastern Mediterranean. Identification of the findings is discussed in terms of seed morphology, present distribution and ancient uses of C. aegyptia Lam., C. sicula Veill., C. cartilaginea Decne, C. orientalis Veill., C. decidua (Forssk.) Edgew. and other species. Citations of Capparis in early Rabbinic, Mesopotamian and Greco-Roman texts are presented. Received June 3, 2002 / Accepted October 8, 2002 Correspondence to: D. Rivera  相似文献   

2.
GABA(A) receptors are the major inhibitory transmitter receptors in the central nervous system. They are chloride ion channels that can be opened by gamma-aminobutyric acid (GABA) and are the targets of action of a variety of pharmacologically and clinically important drugs. GABA(A) receptors are composed of five subunits that can belong to different subunit classes. The existence of 19 different subunits gives rise to the formation of a large variety of distinct GABA(A) receptor subtypes in the brain. The majority of GABA(A) receptors seems to be composed of two alpha, two beta and one gamma subunit and the occurrence of a defined subunit stoichiometry and arrangement in alphabetagamma receptors strongly indicates that assembly of GABA(A) receptors proceeds via defined pathways. Based on the differential ability of subunits to interact with each other, a variety of studies have been performed to identify amino acid sequences or residues important for assembly. Such residues might be involved in direct protein-protein interactions, or in stabilizing direct contact sites in other regions of the subunit. Several homo-oligomeric or hetero-oligomeric assembly intermediates could be the starting point of GABA(A) receptor assembly but so far no unequivocal assembly mechanism has been identified. Possible mechanisms of assembly of GABA(A) receptors are discussed in the light of recent publications.  相似文献   

3.
Exechia and Bibio have retained several plesiomorphic groundplan features of Diptera and Bibionomorpha, including a fully exposed and sclerotized head capsule, the transverse undivided labrum, the absence of movable premandibles, and undivided mandibles without combs. The fusion of the hypostomal bridge with the head capsule and largely reduced antennae are derived features shared by both taxa. The absence of teeth at the anterior hypostomal margin is a potential autapomorphy of Bibionomorpha. A basal position of Anisopodidae is suggested by a number of plesiomorphies retained in this family. Apomorphies of Bibionomorpha excluding Anisopodidae are the reduction of tentorial elements, the partial fusion of the labrum and clypeus, one-segmented antennae, the absence of a separate submental sclerite, the loss of the labial palpus, and the reduction of the pharyngeal filter apparatus. Head structures of Bibio are largely unmodified. The subprognathous orientation is one of few autapomorphic features. In contrast, the mouthparts of Exechia are highly modified in correlation with the specialized food uptake. The rasping counterrotating movements of maxillae and mandibles with teeth oriented in opposite directions are carried out by strongly developed extensors and flexors of the paired mouthparts. The modified labium mechanically supports the “drill head” formed by the mandibles und maxillae. The necessary stability of the head capsule is provided by the hypostomal bridge which also compensates the far-reaching reduction of the tentorium.  相似文献   

4.
The 5-HT(3) and GABA(A) receptors are members of the Cys-loop family of neurotransmitter-gated ion channels that also include receptors for glycine and acetylcholine. The 5-HT(3) and acetylcholine receptors (cationic ion channels) and the GABA(A) and glycine receptors (anionic ion channels) generally depolarize or hyperpolarize, respectively, the neuronal membrane. Within the amino-terminal extracellular region, all members of this family exhibit a similar architecture of ligand binding domains and a number of key residues are completely conserved. The molecular characterization of their ligand binding and gating characteristics has benefited from the existence of a large repertoire of individual subunits that contribute to the pentameric ion channel. Although differences do exist, advances in our knowledge of one member offers valuable insight into the family as a whole. Each member of the Cys-loop receptors (and all other multimeric ion channels) must face the same challenges: How to assemble individual subunits into an ion channel and which subunits to use? How are assembled receptors distinguished from those that are unassembled or misassembled, then exported from the endoplasmic reticulum and delivered to the cell surface? How are they targeted to, and anchored at synaptic and extrasynaptic sites? How and when are they to be removed from these sites to provide long-term regulation of neuronal activity? In this review, we summarize our current knowledge for the 5-HT(3) and GABA(A) receptors that have provided complementary information and helped us build an overall picture of how receptor biogenesis and trafficking occurs.  相似文献   

5.
R M Wartell 《Biopolymers》1972,11(4):745-759
Helix–coil transition curves are calculated for poly (dA) poly(dT) and poly (dA-dT) poly (dA-dT) using the integral equation approach of Goel and Montroll.5 The transitions are described by the loop entropy model with the exponent of the loop entropy factor, k, remaining an arbitrary constant. The theoretical calculations are compared with experimental transition curves of the two polymers. Results indicate that the stacking energies for these two polymers differ by about 1 kcal/mole of base pairs. Also, a fit between theory and experiment was not possible for k > 1.70.  相似文献   

6.
Iron (III) binding proteins are isolated from echidna (Tachyglossus aculeatus multiaculeatus) and platypus (Ornithorhynchus anatinus) milk and blood. On the basis of several criteria it is shown that the milk proteins are not lactoferrins, but are transferrins similar to the corresponding transferrins from the blood. The heterogeneity of the proteins, particularly the echidna milk transferrin, is, at least in part, due to different levels of sialic acid. Their N-terminal sequences (30 residues) are determined and compared with those of other transferrins and lactoferrins. The role of the proteins is discussed.  相似文献   

7.
西藏嵩草属(莎草科)的修订   总被引:5,自引:0,他引:5  
在标本观察和野外调查的基础上,对西藏的嵩草属Kobresia植物进行了分类学修订,共确认了36种和1亚种。更正了6个类群的学名,它们正确的名称是K. esenbeckii,K. fissiglumis,K. gammiei,K. littledalei,K. myosuroides ssp. bistaminata和K. vaginosa。有13个名称,即K. angusta,K. cercostachys var. capillacea,K. clarkeana,K. curticeps var. gyirongensis,K. deasyi,K. glaucifolia,K. hookeri,K. nudicarpa,K. prainii var. elliptica,K. seticulmis,K. stenocarpa,K. stenocarpa var. simplex和K. williamsii处理为异名,其中K. prainii var. elliptica,K. glaucifolia和K. stenocarpa var. simplex为新异名。发现了西藏分布的一个新记录种密穗嵩草K. handel-mazzettii。还收录了最近发表的假钩状嵩草K. pseuduncinoides和阔鳞嵩草K. woodii。此外,重新编制了西藏嵩草属分种和亚种检索表,并较为详细地登记了各类群在西藏的分布地点。  相似文献   

8.
This protocol describes the synthesis of oligo(poly(ethylene glycol) fumarate) (OPF; 1-35 kDa; a polymer useful for tissue engineering applications) by a one-pot reaction of poly(ethylene glycol) (PEG) and fumaryl chloride. The procedure involves three parts: dichloromethane and PEG are first dried; the reaction step follows, in which fumaryl chloride and triethylamine are added dropwise to a solution of PEG in dichloromethane; and finally, the product solution is filtered to remove by-product salt, and the OPF product is twice crystallized, washed and dried under vacuum. The reaction is affected by the molecular weight of PEG and reactant molar ratio. The OPF product is cross-linked by radical polymerization by either a thermally induced or ultraviolet-induced radical initiator, and the physical properties of the OPF oligomer and resulting cross-linked hydrogel are easily tailored by varying PEG molecular weight. OPF hydrogels are injectable, they polymerize in situ and they undergo biodegradation by hydrolysis of ester bonds. The expected time required to complete this protocol is 6 d.  相似文献   

9.
A taxonomic review of Phlebotomus (Idiophlebotomus) (Psychodidae)   总被引:1,自引:0,他引:1  
Five known species (asperulus Quate & Fairchild, erebicolus Quate, pholetor Quate & Fairchild, sejunctus Quate, and stellae Quate) of the caverni-colous subgenus Phlebotomus (Idiophlebotomus) are discussed in relation to newly recognized species from West Malaysia and India. P. frondifer n.sp. and P. tubifer n.sp. are described and a key to the adults of all seven species is given. General features of the subgenus are discussed, with particular reference to the functional relationships between the specialized morphology of the mouthparts and the probable bat hosts of these species.  相似文献   

10.
[Alpha 1(III)]3 collagen was solubilized by pepsin digestion of normal human placental membranes and was purified by differential salt precipitation and carboxymethylcellulose chromatography. This collagen was digested with CNBr, and the resultant nine peptides were isolated and characterized. The chains are cross-linked by cysteinyl residues in the COOH-terminal peptide. Isolation of peptides derived from CNBr digestion of insoluble tissues was used as an assay for the presence of [alpha 1(I)]2alpha 2 and [alpha 1(III)]3 collagens. Both types are present in human skin, intestine, liver, spleen, kidney, lung, aorta, umbilical cord, placental membranes, and myocardium. Bone and tendon contain [alpha 1(I)]2alpha 2 collagen but, unlike the other tissues, lack [alpha 1(III)]3 collagen. Both [alpha 1(I)]2alpha 2 and[alpha 1(III)]3 collagens are present in scars of human skin, myocardium, tendon, and liver and of rabbit skin. The degree of hydroxylation of proline was 4 to 5% lower in the same peptides in skin, bone, and tendon than in the other tissues. The degree of hydroxylation of lysine in the same peptides derived from different tissues varied more widely.  相似文献   

11.
The functional regulation of integrins is a major determinant of cell adhesion, migration and tissue maintenance. The binding of cytoskeletal proteins to various sites of integrin cytoplasmic domains is a key mechanism of this functional regulation. Expression of recombinant integrin alpha(IIb)beta(3) and alpha(M)beta(2) lacking the GFFKR-region in CHO cells results in constitutively activated integrins. In contrast, CHO cells stably expressing either a GFFKR-deleted alpha(V(del))beta(3) or a FF to AA-substituted alpha(V(AA))beta(3) do not reveal a constitutively activated integrin. Adhesion to immobilized fibrinogen is strongly impaired in alpha(V(del))beta(3) or alpha(V(AA))beta(3)-expressing cells, whereas it is not impaired in alpha(IIb)beta(3) and alpha(M)beta(2), both lacking the GFFKR-region. In a parallel plate flow chamber assay, alpha(V)beta(3)-expressing cells adhere firmly to fibrinogen and spread even at shear rates of 15 to 20 dyn/cm(2), whereas alpha(V(del))beta(3) or alpha(V(AA))beta(3) cells are detached at 15 dyn/cm(2). Actin stress fiber formation and focal adhesion plaques containing alpha(V)beta(3) are observed in alpha(V)beta(3) cells but not in alpha(V(del))beta(3) or alpha(V(AA))beta(3)-expressing cells. As an additional manifestation of impaired outside-in signaling, phosphorylation of pp125(FAK) was reduced in these cells. In summary, we report that the GFFKR-region of the alpha(V)-cytoplasmic domain and in particular two phenylalanines are essential for integrin alpha(V)beta(3) function, especially for outside-in signaling. Our results suggest that the two beta(3)-integrins alpha(IIb)beta(3) and alpha(V)beta(3) are differentially regulated via their GFFKR-region.  相似文献   

12.
Tubers, culms, rhizomes, and leaves of Bolboschoenus cf. yagara (Ohwi) YC Yang et M Zhan were reported from the sediments of Zhangcun Formation, Late Pliocene in Shanxi Province, China. The fossil species possesses trigonous culms. And tubers are cordiform, spindle shaped, or round, and are covered by roots in internodes and often connected by rhizomes. This is the first convincing fossil record of Cyperaceae in China.  相似文献   

13.
Recent studies on the IF(1) inhibitor protein of the mitochondrial F(1)F(0)-ATPase from molecular biochemistry to possible pathophysiological roles are reviewed. The apparent mechanism of IF(1) inhibition of F(1)F(0)-ATPase activity and the biophysical conditions that influence IF(1) activity are summarized. The amino acid sequences of human, bovine, rat and murine IF(1) are compared and domains and residues implicated in IF(1) function examined. Defining the minimal inhibitory sequence of IF(1) and the role of conserved histidines and conformational changes using peptides or recombinant IF(1) is reviewed. Luft's disease, a mitochondrial myopathy where IF(1) is absent, is described with respect to IF(1) relevance to mitochondrial bioenergetics and clinical observations. The possible pathophysiological role of IF(1) in conserving ATP under conditions where cells experience oxygen deprivation (tumor growth, myocardial ischemia) is evaluated. Finally, studies attempting to correlate IF(1) activity to ATP conservation in myocardial ischemic preconditioning are compared.  相似文献   

14.
Summary The ultrastructure of the auricles, the ostia, and the ventricle of L. asellus and T. marmorea is described. The heart wall consists of an epicardium, a basement membrane, and an inner loose myocardium. The epicardial cells of the auricle are podocytes. The exposed cell body and the branched processes show pedicles. Ventricular epicardium is flat and simple. The slender, unbranched, mononucleated muscle fibres have a peripheral nucleus located midway along the fibre. Mitochondria are peripherally located, leaving the center to longitudinally running thick and thin myofilaments. Dense bodies and attachment plaques make up the Z-material. Sarcomeres and myofibrils are absent, as are transverse tubules and intercalated disks. The sarcoplasmic reticulum consists of peripheral tubules and subsarcolemmal cisternae, some of which radiate, branch, and run between myofilaments. Couplings are lacking. Ventricular fibres in T. marmorea show nexuses and desmosomes; in L. asellus only nexuses. The muscular ostia are tubular, and muscle fibres resemble those of the ventricle; nexuses are detected in T. marmorea and desmosomes in L. asellus. The only nervous elements observed are some nerve processes, structurally similar to those of other molluscs.Supported by grants from the Norwegian Research Council for Science and Humanities  相似文献   

15.
Copper(II) and nickel(II) complexes are prepared of potentially quadridentate ligands (LH3), N-{2-(2- hydroxyethylamino)ethyl}- (seeH3), N-{3-(2-hydroxy- ethylamino)propyl}- (steH3), and N-{2-(3-hydroxypropylamino)ethyl}-salicylamide (setH3). The nickel complexes Na[Ni(see)] and Na[Ni(set)]·1/2H2O are diamagnetic and square-planar, in which the ligands act as a quadridentate one coordinated through secondary amino-N, and deprotonated phenolic-O, alcoholic-O, and amido-N atoms. The three copper complexes Na [CuL]·H2O (L = see, ste, set) with a normal magnetic moment have a similar square-planar structure. In another type complexes Cu(LH)·H2O (LH = seeH, setH) an alcohol group is not deprotonated. Two isomers are present in Cu(seeH)·H2O: one has a normal and the other a subnormal magnetic moment. The difficulty of complex formation of steH3 may be attributed to an unfavourably fused 6-6-5 membered chelate ring with strain.  相似文献   

16.
Mitochondria are well-characterized intracellular organelles usually concentrated in locations of high energy consumption. Light microscopic and transmission electron microscopic observations of the internal anatomy of the feather mites Diplaegidia columbae and Falculifer rostratus were conducted. In the anterior half of the bodies of the mites, we found several dozen of distinctive mitochondria-rich (MR) cells filled with abundant, large mitochondria. Mitochondria are placed individually or enclosed in small groups within an elaborated lamellar system forming a mitochondria–lamellae complex (MLC). The role of the MLC as well as the MR cells is not clear at present, but their involvement in heat generation is hypothesized and briefly discussed.  相似文献   

17.
The organ of Bellonci (oB) in Boreomysis arctica (Krøyer) is described. The fine structure of the organ is found to agree with that of the oB among other investigated peracarideans. The difficulties met by Chaigneau in 1971 when homologizing the organs in B. arctica and in the Isopoda have been eliminated. Into the cavity of the oB, (probably) sensory neurones protrude. The perikarya of the neurones are found in the wall of the oB. On the dendrites there are subterminal dendritic swellings from which dendritic branches and cilia arise. The branching dendrites are characteristic of the oB in B. arctica. Also the cilia branch, thus increasing the amount of sensory membranes in the organ.  相似文献   

18.
The acid-base and copper (II) complexing properties of the heteropolynucleotide poly(inosinic)-poly(cytidylic) acid were studied by means of potentiometric, spectrophotometric, CD, and molecular fluorescence titrations in a working aqueous medium of 0.15 M ionic strength at 37°C. The study of the acid-base equilibria has proved the existence of four different species in the pH interval 2–11. Two new species are detected in the presence of copper(II) ion, at acidic and neutral pH values. Spectrophotometric, CD, melting, and fluorescence data were treated with a multivariate curve resolution procedure that allowed the determination of the number of species simultaneously present in each system [acid-base equilibria, copper(II) complexation equilibria], and the estimation of their concentration profiles and of the pure spectra for each species. From the concentration profiles an unambiguous assignment of which species are present at any pH conditions can be made. Furthermore, the knowledge of the pure uv-visible, fluorescence, and CD spectra recovered by the proposed resolution method for each species brings important structural information. When this mathematical approach was applied to the thermal denaturation data, the melting profile and the uv pure spectra for all the different species or conformations formed in the melting process, were calculated. © 1997 John Wiley & Sons, Inc. Biopoly 42: 271–283, 1997  相似文献   

19.
The enzymes chlorocatechol-1,2-dioxygenase, chloromuconate cycloisomerase, dienelactone hydrolase, and maleylacetate reductase allow Ralstonia eutropha JMP134(pJP4) to degrade chlorocatechols formed during growth in 2,4-dichlorophenoxyacetate or 3-chlorobenzoate (3-CB). There are two gene modules located in plasmid pJP4, tfdC(I)D(I)E(I)F(I) (module I) and tfdD(II)C(II)E(II)F(II) (module II), putatively encoding these enzymes. To assess the role of both tfd modules in the degradation of chloroaromatics, each module was cloned into the medium-copy-number plasmid vector pBBR1MCS-2 under the control of the tfdR regulatory gene. These constructs were introduced into R. eutropha JMP222 (a JMP134 derivative lacking pJP4) and Pseudomonas putida KT2442, two strains able to transform 3-CB into chlorocatechols. Specific activities in cell extracts of chlorocatechol-1,2-dioxygenase (tfdC), chloromuconate cycloisomerase (tfdD), and dienelactone hydrolase (tfdE) were 2 to 50 times higher for microorganisms containing module I compared to those containing module II. In contrast, a significantly (50-fold) higher activity of maleylacetate reductase (tfdF) was observed in cell extracts of microorganisms containing module II compared to module I. The R. eutropha JMP222 derivative containing tfdR-tfdC(I)D(I)E(I)F(I) grew four times faster in liquid cultures with 3-CB as a sole carbon and energy source than in cultures containing tfdR-tfdD(II)C(II)E(II)F(II). In the case of P. putida KT2442, only the derivative containing module I was able to grow in liquid cultures of 3-CB. These results indicate that efficient degradation of 3-CB by R. eutropha JMP134(pJP4) requires the two tfd modules such that TfdCDE is likely supplied primarily by module I, while TfdF is likely supplied by module II.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号