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1.
The continuous control of the maximum position of the dye absorption band (the zero of the derivative dD ()/d of the cell's optical density D ()) in a nematic matrix is demonstrated experimentally, as a result of changing the angle between the optical axis of a planar-oriented sample and the plane of polarization of absorbed light incident normal to the optical axis. The theory proposed describes quantitatively the experimental dependence (). The rotation of the polarizer with given frequency results in the spectral position modulation of the solute band maximum () within (=0°)–(90°)=700 cm–1.  相似文献   

2.
Summary The seasonal progression of phenophases in 21 shrub species of the Chilean matorral was analyzed. Five modules or basic units that are responsible for the aboveground architecture of the plants were characterized. These modules appear to be organized in seven different spatial arrangements. In drought-deciduous species a module type with an absolute short shoot with limited apical growth, leafy or spiny, predominated. In evergreen species long shoot and temporal leafy short shoot module types were more frequent. The spatial arrangement of morphologically different modules and the temporal sequence of their formation allow a dynamic interpretation of the modular architecture of the plants.  相似文献   

3.
Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731ml/ha+FC 435-66 petroleum oil at 46.8l/ha, pyridaben 75WP at 469g/ha, ethion 4EC at 7.01l/ha+FC 435-66 petroleum oil at 46.8l/ha, propargite 6.55 EC at 3.51l/ha, chlorfenapyr 2SC at 1.46l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8l/ha, sulphur 80DF at 16.81kg/ha, dicofol 4EC at 7.01l/ha, fenbutatin oxide 50WP at 2.24kg/ha, benomyl 50WP at 2.24kg/ha, benomyl 50WP at 1.68kg/ha+ferbam 76 GF at 5.60kg/ha, ferbam 76GF at 11.21kg/ha, neem oil 90EC at 46.8l/ha, and copper hydroxide DF (40% metallic copper) at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha, fenbuconazole 2F at 280ml/ha+FC 435-66 petroleum oil at 46.8l/ha, FC 435-66 petroleum oil applied alone at 46.8l/ha or 23.4l/ha, and diflubenzuron 25WP at 1.40kg/ha. Pesticides that were non-toxic included: fenbuconazole 2F at 585ml/ha, malathion 57EC at 5.85l/ha, FC 435-66 petroleum oil at 46.8l/ha, carbaryl 80S at 3.36kg/ha, chlorpyrifos 4EC at 4.68l/ha, and formetanate 92SP at 1.12kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.  相似文献   

4.
Summary A comparative study was made of the photoperiodic and thermoperiodic induction of diapause in the phytoseiid mite Amblyseius potentillae. Sensitivity to thermoperiod was found to be highest during the protonymphal and deutonymphal stages, with some sensitivity still being present in the young adult. Summation of both photoperiodic and thermoperiodic cycles was shown to take place, which demonstrated the presence of a photoperiodic counter as well as a thermoperiodic counter in these mites. Vitamin A appeared to be necessary for some early step in the physiological mechanism of diapause induction and not just for the expression of the diapause response. The light sensitivity threshold for photoperiodic induction of diapause was found to be extremely low, viz. less than 0.02 W/cm2. Moreover, the light sensitivity threshold appeared to be strongly temperature dependent in A. potentillae. Experiments in which the mites experienced various sequences of short-day photoperiods and short-day thermoperiods, applied either concurrently or in succession, showed that the information collected by the photoperiodic counter and the thermoperiodic counter is integrated into one induction sum. These results strongly suggest that photoperiodic and thermoperiodic induction of diapause in these mites is based on the same physiological mechanism.Abbreviations DD continuous darkness - LL continuous light - LD light-dark cycle (e.g. LD 16:8 is a cycle of 16 h of light and 8 h of darkness) - TC thermoperiodic cycle (e.g. TC 16:8 (27°: 15°) is a thermoperiod with a 16 h thermophase of 27 °C and an 18 h cryophase of 15°C)  相似文献   

5.
The occurrence of adenosine 5-triphosphate-3-diphosphate-synthesizing activity was detected in five strains of actinomycetes; Streptomyces morookaensis, Streptomyces aspergilloides, Streptomyces hachijoensis, Actinomyces violascens and Streptoverticillium septatum, out of 825 strains of actinomycetes, bacteria, fungi and imperfecti. Purine nucleotide pyrophosphotransferase were extracellularly excreted associating with the cell growth, and were purified partially or to apparent homogeniety from the culture filtrate. The enzymes are a monomeric protein with a molecular weight of 18000–26000 and synthesize adenosine, guanosine and inosine 5-phosphate (mono, di or tri)-3-diphosphate such as pApp, ppApp, pppApp, pGpp, ppGpp, pppGpp and pppIpp by transferring a pyrophosphoryl group from the 5-position of ATP, dATP and pppApp to the 3-position of purine nucleotides in the presence of a divalent cation and in alkaline state.Abbreviations pppApp adenosine 5-triphosphate 3-diphosphate - ppApp adenosine 5-diphosphate 3-diphosphate - pApp adenosine 5-monophosphate 3-diphosphate - pppGpp guanosine 5-triphosphate 3-diphosphate  相似文献   

6.
Summary Cyclic nucleotide phosphodiesterase in the basal-lateral segment of plasma membranes from proximal tubule cells of the rabbit renal cortex was studied and compared to that in the brush border segment of the plasma membrane. Both adenosine 3,5-monophosphate and guanosine 3,5-monophosphate were hydrolyzed by the basal-lateral membrane, but activity varied differently with the two substrates in a complex concentration-dependent manner. Activity with adenosine 3,5-monophosphate was greater than, equal to, or less than with guanosine 3,5-monophosphate, at concentrations of 1000, 100, and 10 to 1 m, respectively. Basal-lateral membrane phosphodiesterase activities at 1 and 500 m substrate exhibited differential responses to pH, metals, heat, and a heat stable inhibitor. Stimulation by guanosine 3,5-monophosphate and inosine 3,5-monophosphate of adenosine 3,5-monophosphate hydrolysis was found in basal-lateral but not in brush border membranes. This stimulation was potentiated by ethyleneglycol-bis(-aminoethyl ether)N,N-tetraacetic acid and ethylenediaminetetraacetate, inhibited by Triton X-100, and totally blocked by Zn2+. The findings indicate that multiple forms of phosphodiesterase are present in the basal-lateral segment and these differ from the activities in the brush border region of the plasma membrane. The characteristics of (i) allosteric, guanosine 3,5-monophosphate-sensitivity of adensoine 3,5-monophosphate phosphodiesterase, and (ii) relatively high guanosine 3,5-monophosphate phosphodiesterase activity, in basal-lateral membranes, which are also enriched in adenylate and guanylate cyclase, suggest an important physiological role for these phosphodiesterases in the regulation of net production of cyclic nucleotides in the renal cortex.  相似文献   

7.
The coatomer complex is involved in intracellular protein transport and comprises an assembly of seven polypeptide subunits designated , , , , , , and COP. Rooted phylogenetic trees constructed from the full-length cDNA and amino acid sequences of 49 COP entities in different eukaryotes from yeast to man generally revealed striking conservation of each subunit through evolution. Both nucleotide and protein trees displayed close relationships between and subunits, between and subunits, and between and subunits, implying evolution from common ancestors as well as functional similarity. Interestingly, although 6 out of 7 -COP genes appeared to be grouped and related to the -COP genes, 4 out of 7 -COP gene products clustered with other groups of other COP subunit proteins. A 5 coding segment of the murine -COP gene was amplified by RT-PCR and cycle-sequenced. The partial predicted amino acid sequence of this murine homolog was exactly identical to the human and bovine counterparts. Of particular significance was the complete identity of the first 25 and 35 N-terminal residues which constitute the gastrointestinal hormone xenin and its precursor proxenin, thus emphasizing their strict evolutionary conservation and alluding to their physiological importance.  相似文献   

8.
Two potato (Solanum tuberosum L.) cultivars (Astrid and Bodenkraft) differing in their nitrogen acquisition from the soil (Hunnius, 1981) were used in nutrient solutions to study the effect of increasing concentrations of nitrate (0.05; 0.5; 5.0 mol m-3) particularly on root growth and morphology. In each variety increasing nitrogen concentrations stimulated shoot growth more than root growth. At all nitrate concentrations, the variety with higher nitrogen acquisition (Astrid) had a significantly larger root system. The larger root system of Astrid compared to Bodenkraft was particularly evident when surface area and total length of the roots, instead of root dry weight were used as parameters. The results stress the importance of root length and surface area for nitrogen acquisition from soils.  相似文献   

9.
Summary To obtain information on the dynamic and quantitative aspects of displospory in a facultative apomict,Allium tuberosum (2n = 32), we cytologically observed the entire course of female meiosis and embryosac development in cv Tender-Pole by the clearing-staining-squash method. A time-table of its course was constructed in terms of bud length and days pre-anthesis. Chromosome threads were observed in pairs at the earliest stage of meiosis, after which 32 autobivalents developed. Thus, endoreduplication must have occurred during premeiotic interphase or at the onset of female meiosis. Such endoreduplicational meiosis also occurred on the male side, though the frequency (3.9%) was much lower than that on the female side (80%). The degree of diplospory calculated as the percentage of reduplicated embryo-sac mother cells varied to some extent among six cultivars: Huhehaote and Manchuria showed the highest degree of diplospory (98%), and Kaohsiung the lowest (76%).  相似文献   

10.
The production of five chain variants (Hb G-Georgia, Hb St. Luke's, Hb Lloyd, Hb Montgomery, and Hb G-Philadelphia) in heterozygotes was evaluated through hematological observations, hemoglobin quantification, and biosynthetic studies. All heterozygotes for Hb St. Luke's and Hb Lloyd and most heterozygotes with Hb G-Georgia and Hb Montgomery had normal hematology and average / values of about 1.1. They were assigned a normal genotype (G/), although the proportions of Hb St. Luke's and Hb G-Georgia were low (10 to 13%) and those of Hb Lloyd and Hb Montgomery twice as high (20%). Data from short-term incubations confirmed this genotype for some of these heterozygotes. Isolated Hb St. Luke's and Hb G-Georgia gave low G/ values (0.2 and 0.3) indicating that these Hb variants were defective at the level of Hb assembly. Isolated Hb Montgomery and Hb G-Philadelphia, however, gave higher G/ values of 0.6 and 0.8, respectively. A second type of variability existed among Hb G-Georgia (20 vs. 13%), Hb Montgomery (28 vs. 20%), and Hb G-Philadelphia (47 vs. 34%) heterozygotes, in whom the levels of Hb G differed. The occurrence of higher levels of these three chain heterozygosities was associated with hematological or biosynthetic evidence of a mild or moderate chain deficiency due to an -thalassemia-2 heterozygosity (G/0 or 0G/) or a homozygosity (0G/0), respectively.This study was supported in part by USPHS Research Grants HLB-05168 and HLB-15158.  相似文献   

11.
The role of -tocopherol uptake system in human erythrocyte in the uptake of plasma -tocopherol has been suggested. However no information is available on -tocopherol uptake activity of human erythrocytes in the presence of high levels of D-glucose which is known to lead to pathological alterations in different cells including human erythrocytes. Therefore, in order to examine the effect of D-glucose on the binding of -tocopherol to human erythrocytes, the binding characteristics of -tocopherol to these cells were established first. Binding of [3H]-tocopherol to human erythrocytes was both saturable and specific. Scatchard analysis of -tocopherol binding to these cells showed the presence of two independent classes of binding sites with widely different affinities. The high affinity binding sites had a dissociation constant (Kd1) of 90 nM with a binding capacity (n1) of 900 sites per cell, whereas the low affinity binding sites had a dissociation constant (Kd2) of 5.2 M and a binding capacity (n2) of 105,400 sites per cell. Trypsin treatment abolished all the -tocopherol binding activity. Competition for the binding of -tocopherol to human erythrocytes was effective with other homologues of -tocopherol (-tocopherol, -tocopherol and -tocopherol) and their potency was almost equal to -tocopherol itself. The order of preference was -tocopherol > -tocopherol -tocopherol -tocopherol. Incubation of human erythrocytes with various concentrations of D-glucose did not affect -tocopherol uptake activity. Our data demonstrate the presence of an -tocopherol uptake system in human erythrocytes and that the -tocopherol uptake activity is not modulated by the presence of D-glucose.  相似文献   

12.
Poly--hydroxyalkanoate (PHA) from crotonate-grown cultures of Syntrophomonas wolfei contained only the d-isomer of -hydroxybutyrate. The PHA from cultures grown with trans-2-pentenoate or one of several hexenoates as the substrate also contained small amounts (5%) of -hydroxypentanoate or -hydroxyhexanoate, respectively. Thus, some PHA was synthesized without cleavage of the carbon skeleton of the substrate, but the predominant route for PHA synthesis was by the condensation and subsequent reduction of acetyl-coenzyme A (CoA). The ratio of the -hydroxypentanoate to the -hydroxybutyrate in PHA in pentenoate-grown cultures increased immediately after inoculation and then decreased as the amount of the -hydroxybutyrate in PHA increased. The amount of -hydroxypentanoate in the PHA did not markedly change throughout the remainder of growth. These data indicated that the unbroken carbon-chain was used for polymer production only in the early stages of growth and, later, polymer synthesis occurred by the condensation and reduction of acetyl-CoA molecules.  相似文献   

13.
The enhanced expression of the RI subunit of cyclic AMP-dependent protein kinase type 1 (PKA-I) has been correlated with cancer cell growth. We have investigated the effects of sequence-specific inhibition of RI gene expression on the growth of MCF-7 human breast cancer cells. We report that RI antisense treatment results in a reduction in RI expression at both mRNA and protein levels and inhibition of cell growth. The growth inhibition was accompanied by changes in cell morphology, cleavage of poly(ADP-ribose) polymerase (PARP) and appearance of apoptotic nuclei. In addition, bcl-2 protein level was reduced and p53 expression increased in growth arrested cells. Interestingly, RI antisense inhibited cell viability and induced apoptosis in the absence of p53, suggesting that these actions of RI antisense are exerted independent of p53. In contrast, two- and four-base mismatched control oligonucleotides had no effect on either cell growth or morphology. These results demonstrate that the RI antisense, which efficiently depletes the growth stimulatory molecule RI, induces cell differentiation and apoptosis, providing a new approach to combat breast cancer cell growth.  相似文献   

14.
Single-node cuttings of potato cultivars Jemseg, Katahdin, Russet Burbank and Superior were cultured on a multiplication medium containing MS salts and no growth regulators. Cultures were exposed to 8 h (SD) and 16 h (LD) photoperiodic regimes. The subsequent plantlets were excised and single node cuttings from each photoperiodic regime were placed under SD or LD on a second medium containing growth regulators which promoted tuberization. Production of microtubers was strongly influenced by genotype and by photoperiodic treatments. Superior produced stunted plantlets and some microtubers under SD conditions in the multiplication medium. The number of microtubers formed by Jemseg was not influenced by photoperiod. However, Katahdin and Russet Burbank formed fewer microtubers under LD-LD conditions compared to LD-SD, SD-SD and SD-LD regimes. Compared with the other regimes, LD-SD photoperiod generally promoted microtuber formation with larger diameters and significantly (p<0.05) greater fresh weight. The intensity of the tuberization stimulus was affected by daylength, and this was characterized by microtubers with secondary tubers, the growth of more than one axillary microtuber, and microtubers subtended by stolons. The maturity group of the potato cultivars and photoperiodic regime in vitro strongly influenced the production of microtubers. These results can be employed to adapt light regimes for multiplication and tuberization to the specific requirements for cultivars from different maturity groups, and thus increase the efficiency of potato multiplication protocols.  相似文献   

15.
Calcium channel subunits have profound effects on how 1 subunits perform. In this article we summarize our present knowledge of the primary structures of subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with 1 subunits, the effects of subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by subunits, such as long-lasting prepulse facilitation of 1C (absent in 1E) and inhibition by G protein dimer of 1E, absent in 1C. One subunit, a brain 2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of 1 in oocytes requires a subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for 1 alone channels seen in cells with limited subunit expression. In one model, dissociates from the mature 1 after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of would then have subunit composition 1. In the other model, the chaperoning remains associated with the mature channel and 1 alone channels would in fact be 1 channels. Upon co-expression of high levels of the regulated channels would have composition [1].  相似文献   

16.
The relationship between growth and interferon- (IFN-) production in the recombinant cell line CHO 320 was studied by varying the foetal calf serum (FCS) concentration. The specific growth rate varied with the initial FCS concentration in a manner which could be well fitted by the Monod model. TheK s and max values were found to be 0.771% (v/v) serum and 0.031 h–1 respectively. The average specific IFN- production rates during the exponential phase increased with increasing FCS concentration. A good correlation between specific production rate and specific growth rate was found in all phases of the culture except the lag phase and it was clearly demonstrated that IFN- production was growth associated. Specific glucose and glutamine utilisation rates were inversely related to specific growth rates.  相似文献   

17.
Summary Tumor-bearing mice have a greater sensitivity to the acute lethal effects of the administration of high-dose recombinant human tumor necrosis factor (rhTNF-) compared to normal, non-tumor-bearing mice. We studied whether or not the presence of tumor per se was responsible for the enhanced rhTNF- toxicity. Tumor-bearing mice underwent tumor excision or sham operation before the systemic administration of rhTNF at staged times (0.5–24 h) following surgery. There was little survival difference between sham-operated tumor-bearing mice and tumor-bearing mice undergoing tumor excision (at 24 h, treatment with 12 µg rhTNF-, survival:sham-operated tumor bearers = 0/12, excised tumor-bearers = 0/12;P 2 <0.01 compared to non-tumor-bearers). Mice without tumors receiving sham operation, had minimal toxicity (10 of 12 mice surviving). The injection of 3 ml Ringer's lactate i.p. before i.v. rhTNF- therapy increased survival in tumor-bearing animals; following pretreatment with Ringer's lactate 30/42 mice survived 12 µg rhTNF- compared to 6/42 surviving a similar rhTNF- dose without hydration (P 2 <0.001). Since the production of oxygen free-radical metabolites has been postulated to play a role in the acute toxicity of rhTNF-, bismuth subnitrate was used to induce the enzyme metallothionein to act as a natural scavenger for these metabolites. Daily oral bismuth subnitrate treatments improved survival of mice with MCA-106 or MCA-102 sarcoma and of mice without tumors, with higher rhTNF- doses (12–20 µg), without reducing the therapeutic effect of rhTNF- against the weakly immunogenic MCA-106 sarcoma. These studies suggest methods for reducing the toxicity of rhTNF- administration in clinical trials.  相似文献   

18.
Summary The immunogold technique, employing antisera with clear-cut specificities, was used to localise different processing stages of pro-opiomelanocortin (POMC) in rabbit melanotropic cells. While the antiserum against 3-MSH labelled all the secretory granules including intrasaccular condensations in the Golgi apparatus, antisera against -MSH only labelled extra-Golgi secretory vesicles (SV). All extra-Golgi SV were likewise labelled with the three antisera against -MSH used, despite their different specificities for the desacetylated, N-acetylated or C-amidated forms of the peptide. The antibody against -endorphin also labelled the extra-Golgi SV, while only some SV were labelled with the antibody against -endorphin. These results correlate with biochemical data in favour of mainly — if not exclusively — intragranular processing of POMC. Except for 3-MSH, the cleavage of which could coincide with Golgi packaging of secretory material, other post-translational modifications of the precursor seem to occur when SV are discharged outside the Golgi area. The cleavage of -endorphin appears to be a later step in POMC processing, occurring in some mature SV.  相似文献   

19.
Embryogenetic pathways differ markedly among monotremes, marsupials, and placentals, and their analysis provides information of fundamental importance to recognition of mammalian evolutionary directions. The cap of cuboidal cells of the marsupial late unilaminar blastocyst, generally known as the embryonic area, probably is induced to form (prior to origin of Hensen's node) by signals from earliest hypoblastic cells (anterior visceral endoderm). The thickened cap is a medullary plate of sauropsid terminology because it includes epiblastic cells presumptive to neurectoderm (including neural crest), Hensen's node, primitive streak, and gut endoderm. The remainder of the definitive embryo (i.e., parts of epidermal origin, including ectodermal placodes) derives from squamous ectoderm (surrounding the medullary plate) of the blastocyst's ill-named trophoblastic area. Amniotic ectoderm develops farther distally within the trophoblastic area. The autapomorphic inner cell mass (ICM) of placental mammals is homologous to medullary plate of the marsupial blastocyst plus morphologically undefined, proximal parts of surrounding ectoderm (of the trophoblastic area). Considerations of early cell lineages in marsupials are greatly affected by recognition that the boundary between future embryonic and extra-embryonic tissues does not match the margin of the medullary plate (i.e., embryonic area). Marsupials and monotremes largely conform to sauropsid early embryogenesis, but placentals express, at earliest developmental stages, innovations unique within Amniota that are linked to early establishment of the brain. Neonatal marsupials and hatchling monotremes are extremely altricial and closely comparable anatomically/physiologically; they share a temporal pattern in combining early morphogenesis of craniofacial features (related to suckling) with deferral of telencephalic completion into postnatal/posthatching life. Placentals contrast greatly in establishing the central nervous system prior to rudiments of the cranial skeleton and associated musculature, and they complete essentials of forebrain development before birth. Comparative evidence from transitory periderm suggests that primordial eutherians had extremely altricial hatchlings or newborns, whichever was the mode of early development. Details remain unknown about the origin of the unique specialization of ICM plus encapsulating trophoblast from the more generalized blastula of ancestral synapsids.  相似文献   

20.
This paper is about power, medicine andthe identity of the African as a patient of westernmedicine. From a conventional perspective and asencoded in the current quest for wholeness thatcharacterises South African biomedical discourse, theAfrican patient – like any other patient – has alwaysexisted as an authentic and subjectified being, whosetrue attributes and experiences have been denied bythe mechanistic, reductionistic and ethnocentricpractices of clinical medicine. Against this liberalhumanist perspective on the body as ontologicallyindependent of power, this paper offers a Foucaultianreading of the African patient as – like any otherpatient – contingent upon the force relations immanentwithin and relayed through the clinical practices ofbiomedicine. A quintessential form of disciplinarymicro-power, these fabricate the most intimaterecesses of the human body as manageable objects ofmedical knowledge and social consciousness to makepossible the great control strategies of repression,segmentation and liberation that are the usual focusof conventional investigations into the place andfunction of medicine in society. Since the 1930s whenthe African body first emerged as a discrete object ofa secular clinical knowledge, these have repeatedlytransformed the attributes and identity of the Africanpatient, and the paper traces this archaeology ofSouth African clinical perception from then until the1990s to show how its quest for wholeness is not anend point of discovery or liberation, but merelyanother ephemeral crystallization of socio-medicalknowledge in a constantly changing force field ofdisciplinary power.  相似文献   

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