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171.
We tested the hypothesis that hyperoxia does not cause adequate constriction of choroidal vessels of the newborn (1 to 5 days old) pig, resulting in increased O2 delivery to the retina, possibly due to excess production and/or effects of vasodilators such as nitric oxide (NO). Hyperoxia (100% O2, 45 minutes) led to a decrease in retinal blood flow (RBF) of both newborn and juvenile (5 to 6 weeks old) pigs and also reduced choroidal blood flow (ChBF) in juvenile but not in newborn pigs; the absence of hyperoxia-induced ChBF response in the newborn was associated with a rise in choroidal O2 delivery. Ibuprofen (prostaglandin G/H synthase inhibitor) and 1,3-dimethyl-2-thiourea (a free radical scavenger) did not modify the choroidal hemodynamic responses to hyperoxia in newborn pigs. However, in newborn animals treated with the NO synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME), hyperoxia caused a decrease in blood flow and O2 delivery to the choroid. Consistent with these effects of L-NAME, hyperoxia induced an increase in choroidal cGMP in newborn pigs ventilated with 100% O2 and stimulated nitrite production in isolated choroids exposed to hyperoxia from newborn but not juvenile pigs; these effects were inhibited by NOS blockers. Also, both constitutive and inducible NOS activities were higher in choroidal tissues from newborn than from juvenile animals. In addition, the vasorelaxant effect of the NO donor sodium nitroprusside in vitro was also greater on choroids from newborn than from juvenile pigs. Finally, L-NAME prevented the hyperoxia-induced increase in peroxidation products in the choroid of newborns. It is concluded that hyperoxia does not lead to a decrease in blood flow and O2 delivery to the choroid of the newborn because of increased NO synthesis and effects; since the choroid is the main source of O2 supply to the retina, the present data contribute in providing an explanation for the increased susceptibility of the immature neonate to hyperoxia-induced retinopathy. 相似文献
172.
Al-Buriahi M. S. Kavaz E. Perişanoğlu U. Alalawi A. Çakıcı T. Alomairy S. Rammah Y. S. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(12):4546-4562
Journal of Inorganic and Organometallic Polymers and Materials - In the current study, 10PbO-xSrO-(90-x)B2O3 (x is between 20 and 45 mol% with a step of 5 mol%) glasses with SrO... 相似文献
173.
Contact kairomones from adult southern green stink bugs, Nezara viridula (L.) (Heteroptera: Pentatomidae) that elicit foraging behavior of the egg parasitoid Trissolcus basalis (Wollaston) were investigated in laboratory experiments. Chemical residues from tarsi and scutella of N. viridula induced foraging by gravid female T. basalis. Residues from body parts of female N. viridula elicited stronger responses than those from the corresponding body parts of males. Deproteinized tarsi still elicited searching
responses from wasps, indicating that the kairomone was not proteinaceous. Hexane extracts of host cuticular lipids induced
searching responses from T. basalis, with a strong preference for extracts from female hosts. Extracts consisted primarily of linear alkanes from nC19 to nC34, with quantitative and qualitative differences between the sexes. Extracts of female N. viridula contained more nC23, nC24, and nC25 than the corresponding extracts from males, whereas nC19 was detected only in extracts from males. Direct-contact solid phase microextraction (DC-SPME) of N. viridula cuticle and of residues left by adult bugs walking on a glass plate confirmed gender-specific differences in nC19. Trissolcus basalis females responded weakly to a reconstructed blend of the straight-chain hydrocarbons, suggesting that minor components other
than linear alkanes must be part of the kairomone. Addition of nC19 to hexane extracts of female N. viridula significantly reduced the wasps’ arrestment responses, similar to wasps’ responses to hexane extracts of male hosts. Overall,
our results suggest that a contact kairomone that elicits foraging by T. basalis females is present in the cuticular lipids of N. viridula, and that the presence or absence of nC19 allows T. basalis females to distinguish between residues left by male or female hosts. The ecological significance of these results in the
host location behavior of scelionid egg parasitoids is discussed. 相似文献
174.
175.
Toxicity of the contact insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and cypermethrin to granary weevil Sitophilus granarius (L.) adults from five populations previously selected with deltamethrin and pirimiphos-methyl, and two populations that had no contact with pesticides over an interval of 12 generations, was investigated in the laboratory by application to filter paper. The populations originated from storage facilities situated in different parts of the former Yugoslavia.A population originating from Apatin and one from Belgrade Port were selected three times each at the LD50 level with deltamethrin and pirimiphos-methyl, respectively. In separate experiments, weevils from Belgrade Port were selected once at the pirimiphos-methyl LD70 level and Bijeljina and Kikinda populations both once at the deltamethrin LD70 level. All selection doses were at a level obtained from determining weevil mortality after 24 h of exposure to treated filter paper.Compared with the toxicity to laboratory weevils, the weevils from Apatin after the third selection were found to be 32.1 and 51.9 times less susceptible to deltamethrin at the LD50 and LD95 levels, respectively, while those from Belgrade Port were 2.7 and 3.2 times less susceptible to pirimiphos-methyl. Selection of Belgrade Port weevils at the pirimiphos-methyl LD70 did not significantly affect their susceptibility to that insecticide but it caused a significant decrease in deltamethrin toxicity, which is indicative of a cross-resistance between the two compounds. Selection of Bijeljina weevils caused an increased resistance to deltamethrin, while selection of Kikinda weevils had little effect on their susceptibility to dichlorvos, but it caused a significant decrease in malathion and cypermethrin toxicity, and resistance to deltamethrin markedly increased (RR=238.8 at LD50 and 660.8 at LD95 levels, compared with laboratory weevils). Chlorpyrifos-methyl was the most toxic insecticide to all populations, while cypermethrin was the least toxic compound. 相似文献