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1.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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2.
Morgan JA DeJong RJ Lwambo NJ Mungai BN Mkoji GM Loker ES 《The Journal of parasitology》2003,89(2):416-418
Experimental crosses between Schistosoma mansoni and S. rodhaini have shown that hybrid offspring are viable, yet, until now, no naturally occurring hybrid has been identified. A collection of freshwater snails from Nyamlebi-Ngoma, Ukerewe Island, Lake Victoria, Tanzania, yielded a mixed infection within a single Biomphalaria sudanica of S. mansoni females and S. mansoni-S. rodhaini hybrid males. The hybrids were identified using deoxyribonucleic acid (DNA) sequences. Mitochondrial DNA 16S and 12S sequences of the hybrids match those of S. mansoni, whereas their nuclear ribosomal DNA ITS1 and ITS2 sequences match those of S. rodhaini. The identification of hybrids in Tanzania highlights the possibility that the genetic identity of either parasite species might be modified by introgression. 相似文献
3.
A wide-ranging examination of plastid (pt)DNA sequence homologies within
higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion
with methylation-sensitive restriction enzymes and Southern analysis was
used to distinguish plastid and nuclear DNA in order to assess the extent
of variability of promiscuous sequences within and between plant species.
Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum
(tobacco), and Chenopodium quinoa, showed homogenity of these sequences,
while intraspecific sequence variation was observed among different
cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum
aestivum (wheat). Hypervariability of plastid sequence homologies was
identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta
vulgaris (beet), in which individual plants were shown to possess a unique
spectrum of nuclear sequences with ptDNA homology. This hypervariability
apparently extended to somatic variation in B. vulgaris. No sequences with
ptDNA homology were identified by this method in the nuclear genome of
Arabidopsis thaliana.
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4.
Nitric oxide during ischemia attenuates oxidant stress and cell death during ischemia and reperfusion in cardiomyocytes 总被引:4,自引:1,他引:3
Iwase H Robin E Guzy RD Mungai PT Vanden Hoek TL Chandel NS Levraut J Schumacker PT 《Free radical biology & medicine》2007,43(4):590-599
Nitric oxide (NO) has been implicated as a cardioprotective agent during ischemia/reperfusion (I/R), but the mechanism of protection is unknown. Oxidant stress contributes to cell death in I/R, so we tested whether NO protects by attenuating oxidant stress. Cardiomyocytes and murine embryonic fibroblasts were administered NO (10-1200 nM) during simulated ischemia, and cell death was assessed during reperfusion without NO. In each case, NO abrogated cell death during reperfusion. Cells overexpressing endothelial NO synthase (NOS) exhibited a similar protection, which was abolished by the NOS inhibitor N(omega)-nitro-l-arginine methyl ester. Protection was not mediated by guanylate cyclase or the mitochondrial K(ATP) channel, as inhibitors of these systems failed to abolish protection. NO did not prevent decreases in mitochondrial potential, but cells protected with NO demonstrated recovery of potential at reperfusion. Measurements using C11-BODIPY reveal that NO attenuates lipid peroxidation during ischemia and reperfusion. Measurements of oxidant stress using the ratiometric redox sensor HSP-FRET demonstrate that NO attenuates protein oxidation during ischemia. These findings reveal that physiological levels of NO during ischemia can attenuate oxidant stress both during ischemia and during reperfusion. This response is associated with a remarkable attenuation of cell death, suggesting that ischemic cell death may be a regulated event. 相似文献
5.
6.
Dent A Malhotra I Mungai P Muchiri E Crabb BS Kazura JW King CL 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(10):7139-7145
African infants are often born of mothers infected with malaria during pregnancy. This can result in fetal exposure to malaria-infected erythrocytes or their soluble products with subsequent fetal immune priming or tolerance in utero. We performed a cohort study of 30 newborns from a malaria holoendemic area of Kenya to determine whether T cell sensitization to Plasmodium falciparum merozoite surface protein-1 (MSP-1) at birth correlates with infant development of anti-MSP-1 Abs acquired as a consequence of natural malaria infection. Abs to the 42- and 19-kDa C-terminal processed fragments of MSP-1 were determined by serology and by a functional assay that quantifies invasion inhibition Abs against the MSP-1(19) merozoite ligand (MSP-1(19) IIA). Infants had detectable IgG and IgM Abs to MSP-1(42) and MSP-1(19) at 6 mo of age with no significant change by age 24-30 mo. In contrast, MSP-1(19) IIA levels increased from 6 to 24-30 mo of age (16-29%, p < 0.01). Infants with evidence of prenatal exposure to malaria (defined by P. falciparum detection in maternal, placental, and/or cord blood compartments) and T cell sensitization at birth (defined by cord blood lymphocyte cytokine responses to MSP-1) showed the greatest age-related increase in MSP-1(19) IIA compared with infants with prenatal exposure to malaria but who lacked detectable T cell MSP-1 sensitization. These data suggest that fetal sensitization or tolerance to MSP-1, associated with maternal malaria infection during pregnancy, affects the development of functional Ab responses to MSP-1 during infancy. 相似文献
7.
Steinauer ML Hanelt B Mwangi IN Maina GM Agola LE Kinuthia JM Mutuku MW Mungai BN Wilson WD Mkoji GM Loker ES 《Molecular ecology》2008,17(23):5062-5074
Hybridization and introgression can have important consequences for the evolution, ecology and epidemiology of pathogenic organisms. We examined the dynamics of hybridization between a trematode parasite of humans, Schistosoma mansoni, and its sister species, S. rodhaini, a rodent parasite, in a natural hybrid zone in western Kenya. Using microsatellite markers, rDNA and mtDNA, we showed that hybrids between the two species occur in nature, are fertile and produce viable offspring through backcrosses with S. mansoni. Averaged across collection sites, individuals of hybrid ancestry comprised 7.2% of all schistosomes collected, which is a large proportion given that one of the parental species, S. rodhaini, comprised only 9.1% of the specimens. No F1 individuals were collected and all hybrids represented backcrosses with S. mansoni that were of the first or successive generations. The direction of introgression appears highly asymmetric, causing unidirectional gene flow from the rodent parasite, S. rodhaini, to the human parasite, S. mansoni. Hybrid occurrence was seasonal and most hybrids were collected during the month of September over a 2-year period, a time when S. rodhaini was also abundant. We also examined the sex ratios and phenotypic differences between the hybrids and parental species, including the number of infective stages produced in the snail host and the time of day the infective stages emerge. No statistical differences were found in any of these characteristics, and most of the hybrids showed an emergence pattern similar to that of S. mansoni. One individual, however, showed a bimodal emergence pattern that was characteristic of both parental species. In conclusion, these species maintain their identity despite hybridization, although introgression may cause important alterations of the biology and epidemiology of schistosomiasis in this region. 相似文献
8.
Mackroth MS Malhotra I Mungai P Koech D Muchiri E King CL 《Journal of immunology (Baltimore, Md. : 1950)》2011,186(5):2780-2791
In malaria endemic regions, a fetus is often exposed in utero to Plasmodium falciparum blood-stage Ags. In some newborns, this can result in the induction of immune suppression. We have previously shown these modulated immune responses to persist postnatally, with a subsequent increase in a child's susceptibility to infection. To test the hypothesis that this immune suppression is partially mediated by malaria-specific regulatory T cells (T(regs)) in utero, cord blood mononuclear cells (CBMC) were obtained from 44 Kenyan newborns of women with and without malaria at delivery. CD4(+)CD25(lo) T cells and CD4(+)CD25(hi) FOXP3(+) cells (T(regs)) were enriched from CBMC. T(reg) frequency and HLA-DR expression on T(regs) were significantly greater for Kenyan as compared with North American CBMC (p < 0.01). CBMC/CD4(+) T cells cultured with P. falciparum blood-stage Ags induced production of IFN-γ, IL-13, IL-10, and/or IL-5 in 50% of samples. Partial depletion of CD25(hi) cells augmented the Ag-driven IFN-γ production in 69% of subjects with malaria-specific responses and revealed additional Ag-reactive lymphocytes in previously unresponsive individuals (n = 3). Addition of T(regs) to CD4(+)CD25(lo) cells suppressed spontaneous and malaria Ag-driven production of IFN-γ in a dose-dependent fashion, until production was completely inhibited in most subjects. In contrast, T(regs) only partially suppressed malaria-induced Th2 cytokines. IL-10 or TGF-β did not mediate this suppression. Thus, prenatal exposure to malaria blood-stage Ags induces T(regs) that primarily suppress Th1-type recall responses to P. falciparum blood-stage Ags. Persistence of these T(regs) postnatally could modify a child's susceptibility to malaria infection and disease. 相似文献
9.
A. Desiree LaBeaud Tamara Banda Julie Brichard Eric M. Muchiri Peter L. Mungai Francis M. Mutuku Erin Borland Ginny Gildengorin Sarah Pfeil Crystal Y. Teng Kristin Long Mark Heise Ann M. Powers Uriel Kitron Charles H. King 《PLoS neglected tropical diseases》2015,9(2)
BackgroundChikungunya virus (CHIKV) and o’nyong nyong virus (ONNV) are mosquito-borne alphaviruses endemic in East Africa that cause acute febrile illness and arthritis. The objectives of this study were to measure the seroprevalence of CHIKV and ONNV in coastal Kenya and link it to demographics and other risk factors.MethodologyDemographic and exposure questionnaires were administered to 1,848 participants recruited from two village clusters (Milalani-Nganja and Vuga) in 2009. Sera were tested for alphavirus exposure using standardized CHIKV IgG ELISA protocols and confirmed with plaque reduction neutralization tests (PRNT). Logistic regression models were used to determine the variables associated with seropositivity. Weighted K test for global clustering of houses with alphavirus positive participants was performed for distance ranges of 50–1,000 meters, and G* statistic and kernel density mapping were used to identify locations of higher seroprevalence.Conclusions/SignificanceAlphavirus exposure, particularly ONNV exposure, is common in coastal Kenya with ongoing interepidemic transmission of both ONNV and CHIKV. Women and adults were more likely to be seropositive. Household location may be a defining factor for the ecology of alphaviral transmission in this region. 相似文献
10.
JN Matthiessen 《Australian Journal of Entomology》1999,38(4):348-353
In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival. 相似文献