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1.
Mycotoxin production by various toxigenic fungi, growing on a bread analogue, was investigated at various water activities (aw ) and pH combinations. Citrinin, ochratoxin A and sterigmatocystin could be detected at aw > 0·80, while patulin was only observed at aw = 0·95. These results show that some toxins may be produced at lower water activities than have been reported on synthetic media and suggest that, where possible, natural substrates should be used to investigate factors affect-ing mycotoxin production in foodstuffs. 相似文献
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JOSEPH J. NAPOLITANO MARY E. WALL CAROL S. GANZ 《The Journal of eukaryotic microbiology》1970,17(2):158-161
SYNOPSIS. An amoeboflagellate isolated from common soil is described. The amoeboid stage is typically limax and contains a well differentiated uroid region. The flagellate has 2 flagella, which emerge anteriorly and are equal in length. It has a ventral cytostome near the anterior border. The cyst is helmet-shaped and without opercula. Polar masses are present during nuclear division. 相似文献
4.
Subdivision of equine Tf into H1 and H2 总被引:6,自引:0,他引:6
Subdivision of equine TfH into two variants, designated H1 (faster) and H2 (slower), has been accomplished by high voltage, thin layer polyacrylamide gel electrophoresis at pH 7.9. Transferrin H1 and H2 have been shown to be controlled by codominant alleles and gene frequencies of the Tf alleles have been determined in the Australian Thoroughbred, Standardbred. Quarter Horse and Arabian Horse breeds. 相似文献
5.
Salt Stress Causes Acceleration of Purine Catabolism and Inhibition of Pyrimidine Salvage in Zea mays Root Tips 总被引:1,自引:0,他引:1
PETERSON TODD A.; LOVATT CAROL J.; NIEMAN RICHARD H. 《Journal of experimental botany》1988,39(10):1389-1395
Nucleotide metabolism was studied in apical 5.0 mm root tipsof corn plants (Zea mays L., cv. Pioneer 3906) hydroponicallycultured for 7 d and then salinized for 19 d at a rate calculatedto reduce the osmotic potential (o) of the solutions by O.1MPad1 to a final o = -0.4 MPa. Saline treatments withtwo different molar ratios of Ca2+/Na+ were employed, viz.,003 (2.5 mol m3 CaCl2 + 86.5 mol m3 NaCl)for the NaCl treatment and 0.73 (31.5 mol m3 CaCl2 +43.1 mol m3 NaCl) for the NaCl + CaCl2 treatment. Bothsalt treatments reduced root growth by more than 30%. The capacityof roots to provide purine nucleotides either by de novo synthesisor by re-utilization of existing bases, e.g. salvage of hypoxanthineto adenine nucleotides, was not affected by either salt treatment.However, catabolism of hypoxanthine was accelerated more than3.5-fold by both salt treatments, demonstrating an increasedcapacity for purine catabolism which would shift the normal1: 1 ratio of synthesis: degradation of purine nucleotides observedfor the roots of healthy control plants to less than 0.2 duringsalt stress. The ratio of pyrimidine nucleotide synthesis: degradationwas also reduced. In this case, the unfavourable shift towardnucleotide degradation resulted because both salt treatmentsreduced salvage capacity by more than 25%, but had no compensatingeffect on de novo synthesis or catabolism of pyrimidines. Key words: Salinity, osmotic potential, nucleotide metabolism 相似文献
6.
Cytokinin was found to be a controlling or limiting factor invessel regeneration around a wound in internodes of Coleus blumeiBenth. in which the endogenous cytokinin level was minimized.The cytokinin was applied in aqueous solution to the base ofexcised, mature internodes that had an active vascular cambium.Each internode also received IAA in lanolin at its apical end.Under low (0.1 %, w/w) or high (10%, w/w) auxin concentrations,the control internodes (without exogenous cytokinin) exhibitedsmall amounts of vessel regeneration. At appropriate concentrationszeatin, kinetin and 6-benzylamino-purine (BAP) induced a significantincrease in vessel regeneration around the wound. The threecytokinins also induced novel patterns of supplementary regenerationfurther from the wound surface. Kinetin and BAP showed the strongestpromoting effect at 5 and 10 µg ml1, while zeatinwas most effective at 20 µg ml1. At a low (0.1%) auxin level zeatin was the most effective cytokinin, whereaskinetin was the most effective one at high (1 %) auxin. An inhibitoryeffect on vessel regeneration was observed at the highest kinetinconcentration tested (50 µg ml1). The regenerationof vessels induced by cytokinin was very polar. Many more regeneratedvessel members differentiated below the wound than above it,and the regeneration process proceeded acropetally from thebase of the internode to its upper parts. Our results implya basipetal polar increase in cambium responsiveness along thestem axis from internode 5 to 7. The possible significance ofsuch a basipetal increase in cambium sensitivity in wood formationin trees is discussed. Auxin, Coleus blumei, cytokinin, vascular differentiation, vessel regeneration, wound xylem 相似文献
7.
Summer squash plants {Cucurbita pepo L., cv. Early ProlificStraightneck) hydroponically cultured under optimal boronnutrition (+ B)3 until age 5 d were transferred to hydroponicsolutions supplemented with excess boron (+ + B)3. As boronaccumulated in the leaves with time, leaf conductance to watervapour, 14CO2 fixation, and chlorophyll content of the oldestleaf became significantly less than in the + B-control plantsof the same age; shoot growth essentially ceased. Boron alsoaccumulated in the roots; concomitant inhibition of root elongationand lateral root development resulted. These metabolic changesall occurred prior to the accumulation of sufficient boron tocause the appearance of any symptoms characteristic of borontoxicity. Key words: Boron toxicity, Stomatal conductance, Photosynthesis, Transpiration, Shoot and root growth, Cucurbita pepo 相似文献
8.
MARK A. JAMES SONIA MONTENEGRO-JAMES CAROL FAJFAR-WHETSTONE FEDERICO MONTEALEGRE JAMES ERICKSON MIODRAG RISTIC 《The Journal of eukaryotic microbiology》1987,34(3):328-332
Antigenic similarities between Plasmodium and Babesia parasites of the phylum Apicomplexa have been previously demonstrated primarily by the serological cross reactivity observed in the indirect fluorescent antibody (IFA) test. We have now studied the antigenic relationship between the human malaria parasite, Plasmodium falciparum, and the hemoparasitic agent of cattle, Babesia bovis, using rabbit monospecific antibodies produced against individual culture-derived P. falciparum polypeptides and bovine polyspecific antibodies to B. bovis exoantigens. These respective antibodies were found to be distinctly cross reactive in the IFA test using infected erythrocytes (squirrel monkey—P. falciparum; bovine—B. bovis) as antigen substrates. Immunofluorescence was shown to be highly specific for parasite surfaces. Additionally, the degree of reactivity with soluble exoantigens contained in Plasmodium and Babesia culture supernatants was monitored by a two-site enzyme immunoassay employing the cross-reactive antibodies. Further evidence for antigenic cross reactivity between P. falciparum and B. bovis parasites was shown with the in vitro inhibition assay. Antibodies to P. falciparum and B. bovis were found to be highly inhibitory for the in vitro growth of P. falciparum in human erythrocytes. 相似文献
9.
SUMMARY. Diatoms from surface sediment samples from lakes on both sides of a glacial drift border in eastern Minnesota show that Araphidinate diatom genera like Fragilaria, Asterionella and Synedra are more common in lakes in drift with lower CaCO3 whereas Stephanodiscus and Melosira species are more abundant in those with high CaCo3 . In a lake sediment core from low carbonate drift Fragilaria crotonensis and Asterionella formosa increased when pioneer farmers arrived. These results confirm speculation that high A/C ratios are associated with low-alkalinity eutrophic lakes. 相似文献
10.
Kimball and Wilson1 reported that the arabinose analogue of cytidine (ara-C) inhibited DNA polymerase in a crude extract prepared from Ehrlich ascites cells. Furth and Cohen2 observed cytosine arabinoside triphosphate (ara-CTP) inhibited DNA polymerase in extracts from either calf thymus or bovine lymphosarcoma tissue, although these investigators3 had already found no effect of ara-CTP on DNA polymerase from Escherichia coli. The inhibition in both of these cases could be substantially reversed by dCTP; but incorporation of the arabinose nucleotide (ara-CMP) into DNA could not be unequivocally demonstrated. Graham and Whitmore4 reported the incorporation of ara-C into DNA in vivo and the inhibition of a DNA polymerase from L cells by ara-CTP. They found that ara-CMP was initially incorporated into small DNA strands but subsequently appeared in long strands. Momparler5 has presented evidence that, in vitro, ara-C incorporation was limited to the 3′-hydroxyl end of DNA chains. Such incorporation might be expected to block further chain elongation but this expectation was not supported by the evidence presented by Graham and Whitmore. 相似文献