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81.
82.
Adriana M. Alippi Graciela N. Albo Jorge Marcangeli Daniel Leniz Alicia Noriega 《Experimental & applied acarology》1995,19(10):607-613
The present study was conducted to determine whether Varroa jacobsoni can transmit American foulbrood (AFB), caused by the bacterium Paenibacillus larvae to healthy colonies by the surface transport of spores. Five two-storey Langstroth colonies of Apis mellifera ligustica were infested by placing a sealed brood comb, with 10% Varroa prevalence, between the central brood combs of each colony. Two months later the colonies were inoculated with P. larvae by adding brood comb pieces with clinical signs of AFB (45±5 scales per colony). After 60 days the brood area was completely uncapped by means of dissecting needles and tweezers, separating the Varroa mites from the larvae and the collected mites were introduced at a rate of 51 per colony into four recipient hives placed in an isolated apiary. Twenty female Varroa specimens were separated at random and observed by SEM. Paenibacillus larvae spores were found on the dorsal shield surface and on idiosomal setae. All colonies died after 4–5 months due to a high incidence of varroosis. No clinical AFB symptoms or P. larvae spores were observed in microscopic preparations. It is concluded that Varroa jacobsoni does not transmit AFB from infected to healthy colonies; it does, however transport P. larvae spores on its surface. 相似文献
83.
Michael J. Soares Belinda M. Chapman Takayuki Kamei Toshiya Yamamoto 《Development, growth & differentiation》1995,37(4):355-364
Trophoblast cell differentiation is crucial to the morphogenesis of the placenta and thus the establishment of pregnancy and the growth and development of the embryo/fetus. In the present review, we discuss current evidence for the existence of regulatory genes crucial to trophoblast cell differentiation and placental morphogenesis. The elucidation of regulatory pathways controlling normal differentiation of trophoblast cells will facilitate the identification of sensitive junctures in the regulatory pathways leading to various developmental disorders, including those associated with the initiation of pregnancy, fetal growth retardation and gestational trophoblast disease. 相似文献
84.
The invasion-associated type III system of Salmonella typhimurium directs the translocation of Sip proteins into the host cell 总被引:8,自引:4,他引:4
The ability of Salmonella typhimurium to interact with host cells is largely dependent on the function of a type III protein-secretion system encoded at centisome 63 of its chromosome. We have shown here that two targets of this protein-secretion system, SipB and SipC, are translocated into cultured intestinal Henle-407 cells. Translocation required the function of the type III secretion apparatus, as an S. typhimurium strain carrying a mutation in invA , which encodes an essential component of this system, failed to translocate the Sip proteins. Null mutations in the genes encoding SipB, SipC or SipD, prevented protein translocation, indicating that these proteins are involved in the translocation process. In contrast, mutations in sipA and sptP , which also encode secreted proteins, did not interfere with the translocation of SipC, indicating that only a subset of targets of the type III secretion system act as translocases. Externally or internally localized bacteria could direct protein translocation into Henle-407 cells as this process occurred in the presence of cytochalasin D at a concentration that prevented bacterial entry, or in the presence of gentamicin added shortly after bacterial internalization at a concentration that killed extracellular Salmonella . These results indicate that protein translocation into host cells may be a universal function of all type III secretion systems. 相似文献
85.
S. Pinto O. Gallo G. Polli S. Boccuzzi R. Paniccia T. Brunelli R. Abbate 《Prostaglandins, leukotrienes, and essential fatty acids》1997,57(6):533-537
A role of prostaglandins (PGs) and leukotrienes (LTs) in the pathogenesis of nasal polyps has been recently suggested. Cyclooxygenase (CO) products (thromboxane B2, PGE2 and 6-keto PGF1 alpha) and lipoxygenase (LO) products (LTB4 and LTC4) were investigated by radioimmunoassay in polyps, hypertrophic turbinates and nasal mucosa from 14 patients with non-allergic (n = 6), allergic chronic rhinitis (n = 6) and aspirin-sensitive asthma (ASA) (n = 2), who underwent polypectomy. In all tissues CO metabolite levels were found higher than LO products (P < 0.01). Nasal polyps showed a significantly lower (P < 0.05) arachidonic acid (AA) metabolism in comparison to nasal mucosa. In polyps of allergic patients significantly higher LTB4 levels (P < 0.001) and a tendency to produce higher amounts of CO products in comparison to non-allergic subjects were observed, whereas in turbinates of non-allergic patients LT levels were significantly higher in comparison to those of allergic ones (P < 0.01). In ASA patients a decreased ratio was found supporting the hypothesis of an imbalance of AA metabolism in this syndrome. These findings seem to indicate that the occurrence of nasal polyps may represent the result of different chronic inflammatory stimuli, regulated in part by AA metabolites. 相似文献
86.
Marcelo J. Yanovsky Jorge J. Casal Juan P. Luppi 《The Plant journal : for cell and molecular biology》1997,12(3):659-667
Phytochromes play a key role in the perception of light signals by plants. In this study, the three classical phytochrome action modes, i.e. very-low-fluence responses (VLFR), low-fluence responses (LFR) and high-irradiance responses (HIR), were genetically dissected using phyA and phyB mutants of Arabidopsis thaliana (respectively lacking phytochrome A or phytochrome B) and a polymorphism between ecotypes Landsberg erecta and Columbia. Seed germination and potentiation of greening, hypocotyl growth inhibition and cotyledon unfolding in etiolated seedlings of the ecotype Landsberg erecta showed biphasic responses to the calculated proportion of active phytochrome established by one light pulse or repeated light pulses. The first phase, i.e. the VLFR, was absent in the phyA mutant, normal in the phyB mutant (both in the Landsberg erecta background) and severely deficient in Columbia. The second phase, i.e. the LFR, was present in the phyA mutant, deficient in the phyB mutant and normal in Columbia. Under continuous far-red light, HIR of etiolated seedlings were absent in phyA and normal in phyB and Columbia. The segregation of VLFR in recombinant inbred lines derived from a cross between Landsberg erecta and Columbia was analysed by MAPMAKER/QTL. Two quantitative trait loci, one on chromosome 2 ( VLF1 ) and another on chromosome 5 ( VLF2 ), were identified as responsible for the polymorphism. Phytochrome A is proposed to initiate two transduction pathways, VLFR and HIR, involving different cells and/or different molecular steps. This is the first application of the analysis of quantitative trait loci polymorphic between ecotypes to dissect transduction chains of environmental signals. 相似文献
87.
Spinalona anophtalma n. gen. n. sp. is describedon parthenogenetic and ephippial females andmales from material collected in a temporary lagoonlocated in the Neovolcanic Province from Mexico at analtitude of 2507 m above sea level. It ischaracterized by a strong armature of the antenna,postabdomen and postabdominal claw, no compound eyeor ocellus, the exopod of thoracic limb IIIwith only four setae and that of P5 with only three setae.This new taxon has no relationwith blind Alona from hypogean habitats. 相似文献
88.
Timothy S. McClintock Fuqiang Xu Jorge Quintero Anne M. Gress Teresa M. Landers 《Journal of neurochemistry》1997,68(6):2248-2254
Abstract: We have isolated from an American lobster ( Homarus americanus ) olfactory organ cDNA library a clone, hGαq , with >80% identity to mammalian and arthropod Gαq sequences. In brain and olfactory organ, hGαq mRNA was expressed predominantly in neurons, including virtually all the neuronal cell body clusters of the brain. Gαq protein was also expressed broadly, appearing on western blots as a single band of 46 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory organ, and aesthetasc hairs. These results suggest that hGαq plays a role in a wide variety of signal transduction events. Its presence in the olfactory aesthetasc hairs, which are almost pure preparations of the outer dendrites of the olfactory receptor neurons, the expression of a single hGαq mRNA species (6 kb) in the olfactory organ, and the localization of hGαq mRNA predominantly in the olfactory receptor neurons of the olfactory organ strongly suggest that one function of hGαq is to mediate olfactory transduction. 相似文献
89.
Enrique A. Gonzlez Froiln Vzquez Jos Ignacio Garabal Jorge Blanco 《Microbiology and immunology》1995,39(12):937-942
Fimbriae isolation by means of thermal shock was applied to fifteen K88-positive (three K88ab, nine K88ac and three K88ad) Escherichia coli reference strains belonging to serotypes O8:K87, O32, O45, O138:K81, O141:K85, O147:K89, O149:K91, and O157, as well as to ten K88-positive enterotoxigenic strains isolated from porcine diarrhea in Spain, all of them belonging to the O149 serogroup. Fimbriae were removed from the bacterial cells by thermal shock at 60 C and then precipitated using ammonium sulfate. The final amount of K88 antigen and the purification degree were not related to the serogroup of the bacteria or to the antigen variant but were related to the buffer used for isolation. Phosphate buffer containing urea was shown to be more effective than Tris-HCl for isolation of K88 antigen. The molecular weights by SDS-PAGE for K88ab, K88ac, and K88ad were 28.5, 29.2, and 31.0 kDa, respectively. All enterotoxigenic E. coli strains isolated in Spain showed the K88ac variant. 相似文献
90.
The present study was conducted on 13 patients with Fanconi anemia, 25 parents and 12 siblings. The chromosomal instability characteristic of this congenital breakage syndrome was associated with the presence of transferable clastogenic material in the plasma, as also reported previously for ataxia telangiectasia and Bloom's syndrome. While all plasma ultrafiltrates from homozygotes had chromosome damaging properties, the clastogenic material had to be concentrated in most heterozygotes to reach detectable levels. The clastogenic effect was exerted via the intermediacy of superoxide radicals, since it was regularly inhibited by superoxide dismutase (SOD). This adds further evidence for a prooxidant state in this hereditary disease. The autosustained clastogenic activity possibly plays a role in the progressive impairment of blood cell-producing bone marrow and may predispose patients to develop cancer and leukemia. Prophylactic use of antioxidants may be recommended, using clastogenic plasma activity as a guide. 相似文献