Root Growth, Secondary Root Formation and Root Gravitropism in Carotenoid-deficient Seedlings of Zea mays L.

The effect of ABA on root growth, secondary-root formation androot gravitropism in seedlings of Zea mays was investigatedby using Fluridone-treated seedlings and a viviparous mutant,both of which lack carotenoids and ABA. Primary roots of seedlingsgrown in the presence of Fluridone grew significantly slowerthan those of control (i.e. untreated) roots. Elongation ofFluridone-treated roots was inhibited significantly by the exogenousapplication of 1 mM ABA. Exogenous application of 1 µMand 1 nM ABA had either no effect or only a slight stimulatoryeffect on root elongation, depending on the method of application.The absence of ABA in Fluridone-treated plants was not an importantfactor in secondary-root formation in seedlings less than 9–10d old. However, ABA may suppress secondary-root formation inolder seedlings, since 11-d-old control seedlings had significantlyfewer secondary roots than Fluridone-treated seedlings. Rootsof Fluridone-treated and control seedlings were graviresponsive.Similar data were obtained for vp-9 mutants of Z. mays, whichare phenotypically identical to Fluridone-treated seedlings.These results indicate that ABA is necessary for neither secondary-rootformation nor for positive gravitropism by primary roots. Zea mays, gravitropism, carotenoid-deficient, Fluridone, root growth, vp-9 mutant     

The Effects of pH and Carbon Dioxide on Ion Uptake by Excised Barley Roots

The effects of carbon dioxide concentrations up to 8 per centin air on uptake of potassium and chloride at two pH levels,nominally pH 6 and 8, werestudied. In all experiments, enhanced uptake of potassium occurred atthe higher pH level with carbon dioxidefree air, but chlorideuptake was generally unaffected. At nominal pH 6, 1 per cent carbon dioxide reduced and 6 percent increased potassium uptake. There was no effect on chlorideuptake except with 1 per cent carbon dioxide where a markedenhancement was recorded. At nominal pH 8, l and 2 per cent carbon dioxide increased potassiumuptake whereas 6 and 8 per cent were inhibitory. Chloride uptakewas favoured by 1 and 8 per cent concentrations of the gas.     

THE TOXIC EFFECTS OF TRIALKYLTIN COMPOUNDS ON NERVE AND MUSCLE

The toxicity of trimethyltin chloride and triethyltin sulphate on animal tissues was assessed by their effects on isolated phrenic nerve-diaphragm preparations. Studies by electron microscopy show that the inhibitory effects of these compounds on the muscular contractility of this tissue are associated with (a) the disruption of mitochondria and disorganisation of muscle fibres and (b) the depletion of neuromicrotubules in the axons of nerves innervating the muscle. The neurotoxie effect of triethyltin sulphate on neuromicrotubules is further substantiated by its inhibition (in a concentration-dependent manner) of the specific colchicine-binding activity of the crude and purified tubulin preparations derived from brain tissue. In addition, both triethyltin sulphate and trimethyltin chloride at a concentration greater than 100 μM completely prevent the normal in vitro assembly of microtubules from tubulin.     

CpG联合铝佐剂对HCV免疫原体液免疫作用的影响

目的:探讨胞苷酸鸟苷寡脱氧核苷酸(CpG ODN)联合铝佐剂对丙型肝炎病毒(HCV)重组免疫原的体液免疫作用。方法:采用高交叉HCV-HVR1和E1重组蛋白与CpG ODN、铝佐剂组合,免疫BALB/c小鼠后以ELISA、酶联免疫斑点测定、流式细胞术、免疫沉淀等方法检测相关体液免疫指标和免疫血清多抗的交叉反应性。结果:CpG联合铝佐剂激发了最高的特异性抗体滴度;佐剂通过提高抗体分泌细胞数量、增加脾脏中记忆B细胞数量、增加脾淋巴细胞IL-6、IL-10分泌浓度实现体液免疫增效;CpG则能提高免疫效率,联合铝佐剂时显著提高浆细胞数量;12份HCV阳性血清中有10份可与多抗HVR1 IgG发生免疫沉淀。结论:CpG和铝佐剂联合应用具有协同作用,多抗HVR1 IgG具有较好的交叉反应性。     

17-DMAG diminishes hemorrhage-induced small intestine injury by elevating Bcl-2 protein and inhibiting iNOS pathway, TNF-α increase, and caspase-3 activation

Background

Hemorrhage increases inducible nitric oxide synthase (iNOS) and depletes ATP levels in various tissues. Previous studies have shown that geldanamycin, an inducer of heat shock protein 70kDa (HSP-70) and inhibitor of iNOS, limits both processes. Reduction in NO production limits lipid peroxidation, apoptosome formation, and caspase-3 activation, thereby increasing cellular survival and reducing the sequelae of hemorrhage. The poor solubility of geldanamycin in aqueous solutions, however, limits its effectiveness as a drug. 17-DMAG is a water-soluble analog of geldanamycin that might have greater therapeutic utility. This study investigated the effectiveness of 17-DMAG at reducing hemorrhagic injury in mouse small intestine.

Results

In mice, the hemorrhage-induced iNOS increase correlated with increases in Kruppel-like factor 6 (KLF6) and NF-kB and a decrease in KLF4. As a result, increases in NO production and lipid peroxidation occurred. Moreover, hemorrhage also resulted in decreased Bcl-2 and increased TNF-α, IL-6, and IL-10 concentrations, p53 protein, caspase-3 activation, and cellular ATP depletion. A shortening and widening of villi in the small intestine was also observed. Treatment with 17-DMAG significantly reduced the hemorrhage-induced increases in iNOS protein, jejunal alteration, and TNF-α and IL-10 concentrations, but 17-DMAG did not affect the hemorrhage-induced increases in p53 and IL-6 concentration. 17-DMAG treatment by itself upregulated HSP-70, Bcl-2, and p53.

Conclusion

Since 17-DMAG is water soluble, bioactive, and not toxic, 17-DMAG may prove useful as a prophylactic drug for hemorrhage.     

Forecasting the effects of global change scenarios on bioaccumulation patterns in great lakes species

Climate change will have substantial impacts on biodiversity, particularly for aquatic species. Warming temperatures and changing weather patterns will also remobilize and modify chemical partitioning. Holding millions of cubic yards of sediments contaminated with persistent legacy chemicals such as polychlorinated biphenyls (PCBs) and dioxins, the Laurentian Great Lakes are a laboratory for observing interactions between biological and chemical responses to climate change. They provide a wide range of habitat to a variety of species, from littoral forage fish to deep‐water predators. In this paper, we couple bioenergetic and bioaccumulation models to investigate the biological and chemical effects of climate change in the Great Lakes. We consider three species: round goby, a warm‐water invasive forage fish; mottled sculpin, a cool‐water native forage fish; and lake trout, a cold‐water native predator. Using our coupled models, we calculate the accumulation of a representative persistent chemical, PCB‐77, under four climate scenarios for Lake Erie and Lake Superior. Predator–prey (lake trout–round goby) interactions and food availability (high–low) are incorporated into our simulations. For cool‐ to cold‐water species (sculpin, lake trout) we find that warm temperatures limit growth. For warm‐water species (round goby) cold temperatures limit growth. The impact of climate warming on growth depends on the winter lows as well as the summer highs of the scenario, in combination with the species' critical upper and lower thermal limits. We find conditions for high growth and consumption rates generally lead to high bioaccumulation. However, this can be confounded by predator–prey dynamics, as mismatches in the temperature preferences of predator and prey can lead to mismatches in relative growth and uptake rates. As predator–prey dynamics are expected to undergo substantial shifts with changing climate, these relative thermal sensitivities will be key in determining the implications of climate change for bioaccumulation, particularly in top predator species.     

The Role of Anaerobic Respiration in Germinating Muskmelon Seeds: I. IN RELATION TO SEED LOT QUALITY

Five muskmelon (Cucumis melo L.) cultivar seedlots from a commercialsource and freshly produced seeds of two cultivars, when artificiallyaged, were found to differ in their viability and vigour asdetermined by germination tests. Furthermore, the various commercialseedlots without ageing also exhibit a range of deteriorationlevels. Low vigour seeds had higher respiratory quotient valuesthan the high vigour seeds as a result of a higher level ofCO₂ production. This high level of CO₂ evolution in low vigourseeds may have been due to anaerobic respiration. Levels of acetaldehyde and ethanol produced by imbibing seedswere negatively associated with seed viability and vigour. After6 h of imbibition low vigour seeds produced significantly moreethanol and acetaldehyde than high vigour seeds. After 24 hof imbibition, ethanol continued to accumulate in the commercialseedlots up to 10-fold the amount produced after 6 h of imbibition,whereas, acetaldehyde levels increased less. However, in thefreshly produced, artificially aged seeds (except the most extremeageing), ethanol levels were reduced and no acetaldehyde productioncould be detected, indicating re-utilization of ethanol. It is suggested that ethanol production in the first hours ofimbibition can be used as a reliable index to predict germinationin muskmelon seedlots. Key words: Germination, Cucumis melo L., Seeds, Anaerobic respiration     

Persistence of Oral Structures in the Sexual Process of Amicronucleate Paramecium tetraurelia

ABSTRACT In the sexual process, amicronucleate Paramecium tetraurelia , unlike micronucleates, fail to produce an oral apparatus, but resorb the pre-existing one. Exceptions were found in some amicronucleate cell lines in which about 1% of the cells possessed oral structures, including pieces of oral membranelles, sometimes complete with buccal cavity, after autogamy or conjugation. By following oral development in the sexual process in some detail, the present study supports the view that these oral structures are derived from the pre-existing oral apparatus and not newly developed from the oral primordium. The possible involvement of the micronucleus and the pre-existing oral apparatus in oral resorption is discussed. The possession of a functional oral apparatus after the sexual process may open up a new evolutionary avenue to the amicronucleates.     

Sperm surface galactosyltransferase activities during in vitro capacitation

Studies using genetic and biochemical probes have suggested that mouse sperm surface galactosyltransferases may participate during fertilization by binding N- acetylglucosamine (GlcNAc) residues in the egg zona pellucida. In light of these results, we examined sperm surface galactosyltransferase activity during in vitro capacitation to determine whether changes in enzymatic activity correlated with fertilizing ability. Results show that surface galactosyltransferases on uncapacitated sperm was preferentially loaded with poly N-acetyllactosamine substrates. As a consequence of capacitation in Ca(++)-containing medium, these polylactosaminyl substrates are spontaneously released from the sperm surface, thereby exposing the sperm galactosyltransferase for binding to the zona pellucida. Sperm capacitation can be mimicked, in the absence of Ca(++), either by washing sperm in Ca(++)-free medium, or by pretreating sperm with antiserum that reacts with the galactosyltransferase substrate. In both instances, sperm galgactosylation of endogenous polylactosaminyl substrates is reduced, coincident with increased galactosylation of exogenous GlcNAc, and increased binding to the zona pellucida. Binding of capacitated sperm to the egg can be inhibited by pronase-digested high molecular weight polyactosaminyl glycoside extracted from epidymal fluids or from undifferentiated F9 embryonal carninoma cells. Thus, these glycosides function as “decapacitation factors” when added back to in vitro fertilization assays. These glycoside “decapacitation factors” inhibit sperm-egg binding by competeing for the sperm surface galactosyltransferase, since (a) they are galactosylated by sperm in the presence of UDP[(3)H]galactose, and (b) enzymatic removal of terminal GlcNAc residues reduces “decapacitation factio” competition. On the other hand “conventional” low molecular weight glycosides, isolated from either epididymal fluid or differentiated F9 cells, fail to inhibit capacitated sperm binding to the zona pellucida. These results define a molecular mechanism for one aspect of sperm capacitation, and help explain why removal of “decapacitation factos” is a necessary prerequisite for sperm binding to the zona pellucida.     

Spectral properties of a long-wavelength absorbing form of protochlorophyll in seeds of Cyclanthera explodens

The in vivo absorbance spectrum of the inner seed coat of Cyclanthera explodens Naud. showed a main peak in the red region at 671 nm and a weak shoulder at about 640 nm. The pigments were extracted with acetone. separated by paper chromatography and analysed spectrophotometrically. The only detectable pigment was protochlorophyll. The in vivo fluorsecence emission spectra had two main peaks, one at 632 and one at 691 nm. The relation between the two peaks was changed when the exvcitation wavelength was altered from 440 to 460 nm. Excitation at 420 nm gave an additional fluorescence emission peak at 595 nm. These data indicate the presence of at least three forms of protochlorophyll in the Cyclantera seed coat. The spectrum of circular dichroism had a very intence and characteristic signal in the red region with a negative asymmetrical Cotton effect (664 (+), 669 (0) and 687 (?) nm). This indicates that at least one of the protochlorophyll forms is present in a more or less crystalline form.