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1.
As a short-lived radical that diffuses across membranes, rather than interacting with membrane-bound receptors, nitric oxide (NO) represents a significant departure from synthetically derived radiosensitizers. An endogenous compound, NO may equal or surpass its molecular cousin, oxygen, as a hypoxic radiosensitizer, through pleiotropic phenotypic effects on tumor perfusion, cell signaling, mitochondrial respiration, the fixation of radiation-induced damage, and the radioprotection of normal tissue. However, unlike oxygen, in the context of radiosensitization, the clinical role and utility of NO are poorly understood, with often contradictory and controversial reported effects: whether NO functions as a radiosensitizer may ultimately be contextual to the tumor microenvironment. This may make NO manipulation an ideal candidate for a personalized radiosensitization approach tailored to specific patient and tumor types/microenvironmental characteristics. Effective delivery of NO both systemically and directly to the tumor may be critical to the success of this approach. Compounds that release NO or NO precursors have the potential to drive innovation and result in a new fertile branch of the radiosensitizer tree.  相似文献   

2.
Brown bears are recorded from Ireland during both the Late Pleistocene and early–mid Holocene. Although most of the Irish landmass was covered by an ice sheet during the Last Glacial Maximum (LGM), Irish brown bears are known to have hybridized with polar bears during the Late Pleistocene, and it is suggested that the Irish brown bear population did not become extinct but instead persisted in situ through the LGM in a southwestern ice-free refugium. We use historical population modelling to demonstrate that brown bears are highly unlikely to have survived through the LGM in Ireland under any combination of life-history parameters shown by living bear populations, but instead would have rapidly become extinct following advance of the British–Irish ice sheet, and probably recolonized Ireland during the end-Pleistocene Woodgrange Interstadial from a closely related nearby source population. The time available for brown bear–polar bear hybridization was therefore restricted to narrow periods at the beginning or end of the LGM. Brown bears would have been extremely vulnerable to extinction in Quaternary habitat refugia and required areas substantially larger than southwestern Ireland to survive adverse glacial conditions.  相似文献   

3.
Larvae of Hysterothylacium use various invertebrates as intermediate hosts. Definite hosts include fish, birds, reptiles or marine mammals. This study describes the occurrence of Hysterothylacium (Nematoda, Anisakidae) larvae parasitizing the pericardic cavity of Diplodon suavidicus (Unioniformes, Hyriidae) specimens collected in the Amazon basin, Brazil. This is the first record of this nematode parasitizing freshwater bivalves in South America. The high prevalence, medium intensity and medium abundance suggest that D. suavidicus acts as intermediate host for Hysterothylacium species in that environment.  相似文献   

4.
The land planarian species Microplana terrestris (Müller, 1774), shows a wide distribution in the north of the Iberian Peninsula, where mature humid forests can be found. Since most terrestrial planarians require the presence and good condition of wet forests to survive, a parallel evolution of the taxon and its habitat might be expected. Performing molecular analyses (mitochondrial cytochrome oxidase I and nuclear ITS-1 genes) we estimated the demography and biogeographic history of the species in that region. Our results show the species to present levels of genetic diversity likely originating before the Pleistocene. However, it presents a genetic structure that presumably resulted from its survival in various refugees during the Pleistocene glacial cycles. The two main genetic groups, present on the Iberian Peninsula, seem to have different origins: the western one being of Iberian origin, while the eastern group may have been the result of a re-colonization from the north. In both cases, their biogeographical history mirrors their habitat range movements, reinforcing the phylogeographical hypothesis put forward for its preferred habitat, i.e. humid forests.  相似文献   

5.
Last lynxes in Portugal? Molecular approaches in a pre-extinction scenario   总被引:1,自引:1,他引:0  
The Iberian lynx is the most threatened felidin the world and has suffered a declinethroughout its range. Effective monitoring ofthe species' presence is essential. Fieldwork inpreviously identified areas of lynx occurrencein Portugal has resulted in the collection of104 possible lynx scats. Recently, there hasbeen little or no evidence of lynx presence andscats could be confused with others from moreabundant carnivores such as wildcat, fox anddog. In order to confirm or not exclude thepresence of the species, identification ofscats was performed through the amplificationof lynx-specific mitochondrial DNA sequences.Two samples collected in Malcata NaturalReserve in 1997 were identified as lynx. Thisis the most recent and reliable proof of lynxpresence in Portugal*. Given the territorialbehavior of lynx, stable resident populationswould have produced a higher proportion ofpositively identified scats. Local extinctionsmight have taken place, and this genetic datasupports a suspected national pre-extinctionscenario for the species. Genetic analysisusing a non-invasive approach has proved to bean informative part of the lynx monitoringprogram. Technical problems faced and overcomeare also presented.  相似文献   

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Ituarte S  Papeschi AG 《Genetica》2004,122(2):199-206
Male karyotype and meiosis of Tenagobia fuscata (Corixoidea, Micronectidae) are studied. The species possesses a male diploid chromosome number 2n = 28 + XY, holokinetic chromosomes, absence of m chromosomes and an achiasmatic male meiosis. Autosomes divide pre-reductionally while the sex chromosomes do so post-reductionally. Banding techniques (C, DAPI and CMA) show that large heterochromatic AT-GC rich bands are generally terminally located, although some interstitial bands are also detected. Many bivalents are heteromorphic for heterochromatin amount and location. This is the first report of a species with achiasmatic male meiosis within the Nepomorpha. These cytogenetic features markedly differ from all previous reports for 26 species of the superfamily Corixoidea. T. fuscata occurs in permanent shallow water bodies, and most known individuals are brachypterous. Their dispersion depends on occasional floodings of the water bodies they occupy. Since achiasmatic meiosis maintains groups of co-adapted genes, this feature could be an adaptive strategy of the species to the particular type of habitat and ecological niche it occupies.  相似文献   

9.
The last instar larva and pupa of Melipotis cellaris (Guenée) are described and illustrated, based on specimens collected in northern Chile, associated with Acacia macracantha (Fabaceae).  相似文献   

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Immunocytochemical demonstration of protein kinase C (PKC) subspecies (, , ) was carried out in Pacinian corpuscles of rat hind feet using monoclonal or polyclonal antibodies against each of these subspecies. The inner core cells and lamellae and the Schwann cell cytoplasm of the nerve fiber innervating the corpuscle were strongly positive for PKC -immunoreactivity (IR). In contrast, the axon terminal and the outer core did not display any positive -IR. Very weak PKC -IR was detected in the ultraterminal region of the axon terminal, while the trunk region showed no immunoreactivity. Very faint PKC -IR was found also in the lamellar cells located at the periphery of the inner core and the endoneurial fibroblasts in the intermediate layer. PKC -IR was not detected in any part of the corpuscle. The strong PKC -IR in the inner core and the presence of absence of PKC -, -, and -IR in the axon terminal are discussed from the point of view of the functional aspects of each part.  相似文献   

12.
Argyrotaenia sphaleropa (Meyrick) is associated with various fruit species in South America. This tortricid was first detected in citrus, Citrus sinensis (L.) Osbeck, in Brazil, in commercial groves in northern Paraná, during the 1994/95-crop season. The aim of this work was to study the biology of this lepidopteran under laboratory conditions (28 +/- 2 degrees C, 70 +/-10% UR, 14h photofase) using the citrus cultivar Pêra. Larvae obtained from egg masses collected in a commercial citrus grove in Rolandia, PR, were individually placed on citrus terminal leaves inside glass shell vials (8.5 x 2.5 cm) until adulthood. A male and a female moth were then transferred to acrylic cages (13 x 10 cm) containing inside a bouquet made with new citrus flush to serve as oviposition substrate. Adults were fed daily with a 10% honey solution. The biological parameters evaluated were duration of development of egg, larval and pupal stages; pupae weight; duration of pre-oviposition and oviposition periods, fecundity and longevity. The length of the egg to adult stage was around 36 days. The pre-oviposition period was almost two days, the oviposition period approximately ten days and the embryonary period around six days. Adult longevity was almost 15 days for females and nine days for males, and the lifetime fecundity was slightly over 180 eggs.  相似文献   

13.
The seasonal distribution of Acanthocephalus tumescens (Acanthocephala : Echinorhynchidae) among Galaxias maculatus (Pisces : Galaxiidae) in Lake Gutiérrez was studied from March 1994 to June 1996. Acanthocephalus tumescens always occurs in the intestine, has an overdispersed frequency distribution, a similar proportion of sexes, and females are larger than males. Mean intensity and prevalence are low and increase with host length. The pattern of the infection shows seasonality, with recruitment in winter and a reproductive period during spring-summer.  相似文献   

14.
Life-history theory predicts that parasitized hosts should alter their investment in reproduction in ways that maximize host reproductive success. I examined the timing of asexual reproduction (fragmentation and regeneration) in the polychaete annelid Pygospio elegans experimentally exposed to cercariae of the trematode Lepocreadium setiferoides. Consistent with adaptive host response, polychaetes that became infected by metacercariae of trematodes fragmented sooner than unexposed controls. Parasites were not directly associated with fission in that exposed polychaetes that did not become infected also fragmented earlier than controls. For specimens of P. elegans that were not exposed to trematodes, new fragments that contained original heads were larger than those that contained original tails, whereas original head and tail fragments did not differ in size for infected polychaetes. In infected specimens, metacercariae were equally represented in original head and tail fragments and were more likely to be found in whichever fragment was larger. Despite early reproduction, parasitism was still costly because populations of P. elegans exposed to parasites were smaller than controls when measured 8 weeks later and because exposure to cercariae reduced survivorship of newly divided polychaetes. Taken together, my results suggest that early fragmentation is a host response to minimize costs associated with parasitism.  相似文献   

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A Loni  RS Hart  A Lucchi 《ZooKeys》2012,(219):87-91
The finding of Zombrus bicolor (Enderlein) (Hymenoptera: Braconidae: Doryctinae) in a Tuscan vineyard of the Siena province (Italy) represents the first record of this species in western Europe. A female was captured in summer 2009 with a malaise trap located in an organic vineyard. Until this finding, the species was recorded only in the Oriental regions of continental China, Taiwan, Korea and Japan and, very recently, in the eastern and southern parts of the Palaearctic region.  相似文献   

17.
We describe a multivariate metric comparison of three sandfly species showing strong differences in size, which questions the geographical distribution of one of them. Two species are represented by a single population (L. robusta and L. guilvardae) and one by two populations (L. serrana). All of them belong to the series serrana (Diptera, Psychodidae, Phlebotominae). The morphometric data confirm that L. guilvardae is a distinct species. However, they suggest that L. robusta and L. serrana in Ecuador are the same taxon, and that it is distinguishable from the population of L. serrana in Bolivia. A multilocus enzyme electrophoresis analysis comparing L. serrana in Bolivia and L. robusta in Ecuador adds further evidence that these two populations are distinct species. Thus, our data seem to indicate that, in Ecuador, the population previously identified as L. serrana is actually the same species as the allopatric population previously identified as L. robusta. Accepting L. serrana in Ecuador as small-sized L. robusta, the resulting geographic distribution of this latter becomes in closer agreement with ecology and epidemiology.  相似文献   

18.
During monthly sampling from Lake Alada (Bolu, Turkey) between April 2003 and June 2004, nine ostracod taxa (Candona candida, Cypridopsis vidua, Darwinula stevensoni, Eucypris virens, Eucypris sp., Heterocypris sp., Limnocythere inopinata, Physocypria kraepelini, and Tonnacypris lutaria) were recorded from seven stations. Physocypria kraepelini was commonly found in the lake while the others were recorded in particular months. UPGMA analyses clustered three groups based on their occurrence. Accordingly, the occurrence of species (C. candida, E. virens, and T. lutaria) was positive and significantly related to each other. Two species, P. kraepelini and D. stevensoni, showed a significant positive relationship with electrical conductivity. A significant negative correlation was found between the occurrence of P. kraepelini and dissolved oxygen, while there was a significant positive correlation between the occurrence of P. kraepelini and turbidity. About 76% of the relationship between species and environmental factors was explained by the first two axes of canonical correspondence analyses (CCA). Temperature and dissolved oxygen were the two most important influences on the species assemblages. All species showed different but high optima and tolerance ranges, corresponding with their cosmopolitan characteristics. These responses may be related to unstable ecological characteristics of Lake Alada, which is often subjected to human activity.  相似文献   

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Six late Rupelian populations of Nephrolepidina praemarginata (Douvillé, 1908) have been isolated from a succession of the Caltavuturo Formation (Madonie Mts, Sicily). A total of 25 embryonal parameters were obtained from oriented equatorial sections of megalospheric specimens; 8 indexes were derived from selected parameters and 9 indexes were considered for the neanic apparatus, out of which 2 are introduced here: N05 (number of annuli in a radius of 0.5 mm) and r5 (distance occupied by the first five annuli). The data show marked deviations from the expected trend of traditional biometric measures; this is interpreted as dependent on environmental factors. Previous studies on the succession evidenced an increase in basin depth; this can be inferred also from the biometric analysis of the inner characters of the allochthonous Nephrolepidina tests. Here, we explore the paleobiological potential of parameters linked to embryo size and wall thickness, and discuss how depth-dependent parameters may affect the interpretation of evolutionary trends and biostratigraphy in radial foraminifers.  相似文献   

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