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1.
Mitochondrial DNA evolution in the genus Equus 总被引:7,自引:0,他引:7
Employing mitochondrial DNA (mtDNA) restriction-endonuclease maps as the
basis of comparison, we have investigated the evolutionary affinities of
the seven species generally recognized as the genus Equus. Individual
species' cleavage maps contained an average of 60 cleavage sites for 16
enzymes, of which 29 were invariant for all species. Based on an average
divergence rate of 2%/Myr, the variation between species supports a
divergence of extant lineages from a common ancestor approximately 3.9 Myr
before the present. Comparisons of cleavage maps between Equus przewalskii
(Mongolian wild horse) and E. caballus (domestic horse) yielded estimates
of nucleotide sequence divergence ranging from 0.27% to 0.41%. This range
was due to intraspecific variation, which was noted only for E. caballus.
For pairwise comparisons within this family, estimates of sequence
divergence ranged from 0% (E. hemionus onager vs. E. h. kulan) to 7.8% (E.
przewalskii vs. E. h. onager). Trees constructed according to the parsimony
principle, on the basis of 31 phylogenetically informative restriction
sites, indicate that the three extant zebra species represent a
monophyletic group with E. grevyi and E. burchelli antiquorum diverging
most recently. The phylogenetic relationships of E. africanus and E.
hemionus remain enigmatic on the basis of the mtDNA analysis, although a
recent divergence is unsupported.
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2.
The consequence of harvesting young leaves of cassava as vegetable on the vulnerability of the crop to cassava mosaic disease (CMD) and on storage root yield was investigated using 30 cassava genotypes planted in IITA fields located in the humid forest (Port Harcourt?:?Onne), forest-savannah transition (Ibadan), southern guinea savannah (Mokwa) and northern guinea savannah (Zaria) agroecologies in Nigeria. Tender apical leaves and shoots of the cassava genotypes were removed from forty plants per cassava genotype with the same number of plants considered as control. Whitefly infestation, disease incidence (DI) and symptom severity (ISS) of the disease were assessed at monthly interval for six months and also at the ninth month after planting (MAP). Yield reduction due to this treatment was calculated as percentage harvest index (HI). Whitefly population fluctuated throughout the period of observation at all locations with higher population obtained generally for treated plants compared to control plants. Sprouting leaves of some treated genotypes were observed with severe mosaic symptoms, while corresponding control showed no mosaic symptoms. Contrarily, no remarkable difference was observed in Zaria between the mean ISS of treated and control cassava genotypes. There was a highly significant difference (P?<?0.01) in DI and ISS among cassava genotypes across all locations. Also, there was a highly significant interaction (P?<?0.01) in symptom severity between location (loc) and genotype, genotype and treatment (trt), loc and trt. Interaction between loc, genotypes and trt with regard to DI was highly significant at 2, 3 and 4 MAP, while with ISS, the interaction was highly significant all through the counting period. There was a positive relationship between DI and ISS on plants of genotypes 96/1039 and ISU. The percentage HI (27.4) of treated plants of genotype 95/0166 in Ibadan was remarkably lower than the value obtained for corresponding control (41.9) plants. Also, sharp distinction in% HI of treated (39.5) and control (43.8) ISU was observed in Onne with their respective ISS values as 3.7 and 3.2. Therefore, harvesting tender apical leaves and shoots of cassava as vegetables should be discouraged as it increases the severity of CMD infection in the regenerating shoots of cassava with attendant storage root yield reduction. 相似文献
3.
TO Sogbanmu AO Osibona OA Oguntunde AA Otitoloju 《African Journal of Aquatic Science》2018,43(3):281-292
Physiological, biochemical and histological indices in Clarias gariepinus broodstock, and teratogenic indices in embryos exposed to sublethal concentrations of naphthalene, phenanthrene and pyrene were investigated in 2014 using a static-renewal bioassay protocol. Phenanthrene (1.41 mg l?1) was the most toxic, followed by pyrene (1.53 mg l?1) and naphthalene (7.21 mg l?1), based on 96 h LC50 values. Hepatosomatic indices were significantly higher in naphthalene- and pyrene-treated males compared with solvent controls, whereas fecundity in females was significantly lower by factors of 2.4 (naphthalene), 2.8 (phenanthrene) and 2.4 (pyrene), compared with controls. Catalase levels were lower in female phenanthrene-treated fish compared with controls. Histological alterations observed in PAH-treated fish include oedema, inflammatory cells, epithelial lifting and hyperplasia in the gills, vacuolation, haemosiderin pigments and sinusoidal congestion in the liver, and degenerated zona radiata in the ovary. Teratogenic effects were not observed, as evidenced by the lack of histological alterations in embryos spawned from pre-exposed broodstock. Sex-specific responses and the utility of biomarkers at cellular and individual levels of organisation are therefore demonstrated for holistic evaluations of polycyclic aromatic hydrocarbons in ecotoxicological studies. 相似文献
4.
Liubashina OA Itsev DE 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2006,92(8):957-966
In neurophysiological and histochemical experiments on rats, amygdalo-fugal modulation of cells within NO-producing areas of the hypothalamus was studied. Electrical stimulation of the medial area of the central nucleus caused obvious excitatory neuronal reactions within the medial part of the paraventricular nucleus and rostral portion of the lateral hypothalamic area. The observed amygdala-induced neuronal responses were enhanced after i.v. N-nitro-1-arginine methyl ester (L-NAME, 10 mg/kg). The nistochemical study revealed that the central nucleus stimulation caused an increase in number and optical density of the NADPH-d-positive cells within the parvicellular zone of the paraventricular nucleus and in the medial part of the lateral hypothalamic area. The NO-producing cells within the ventrolateral part of the lateral hypothalamic area were inhibited. The described phenomenon may underlie the amygdalo-fugae modulation of autonomic outflow. 相似文献
5.
Robles-Hernández L J Hernández-Huerta AC González-Franco OA Hernández-Rodríguez A Núñez-Barrios R Pérez-Leal 《Phyton》2015,84(2):253-261
Chili pepper is one of the main crops of economic importance in Mexico, and Fusarium wilting is a disease that limits its production. In addition, the inappropriate use of agrochemicals in farming activities generate environmental and health problems. Therefore, in this study the effectiveness of Streptomyces sp PRIO41 was evaluated as a (1) biocontrol agent of Fusarium spp and (2) plant growth promoter bacteria. Assays of pathogenicity and virulence of Fusarium spp. in jalapeño pepper seeds, and interactions of these pathogens with Streptomyces PRIO41 were evaluated under two nutritional conditions. In the greenhouse, the effectiveness of Streptomyces sp. PRIO41 was determined as a (1) biocontrol of Fusarium, and (2) plant growth promoter of wilt of pepper plants. The results showed that all fungal isolates caused symptoms in pepper seeds and seedlings with different degrees of virulence. Interactions in vitro showed that Streptomyces showed the most effective range of virulence against Fusarium isolates in the poor medium (37.6%-100%), with fungicidal effects in some cases. In the greenhouse, Streptomyces PRIO41 reduced Fusarium wilting up to a 40%, and positively affected all vegetative growth parameters, particularly plant height, leaf area, root length, and leaf and root dry biomasses. This study showed the potential of Streptomyces PRIO41 as a biocontrol agent of Fusarium spp., and as a biofertilizer of pepper plants. 相似文献
6.
Pantellev SS Martseva AA Liubashina OA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2011,97(12):1336-1345
In experiments on anaesthetized rats, the neuronal mechanisms underlying processing of the nociceptive information from the colon within the nucleus of the solitary tract were studied. In addition, the role of nitric oxide in these processes was estimated. Analysis of changes in c-fos expression revealed that nociceptive colorectal distension (CRD) resulted in activation of neurons mainly in the medial, commissural, parvicellular and dorsomedial subnuclei of the solitary tract nucleus. Non-noxious CRD evoked in these subdivisions weak phasic excitatory neuronal responses. Under noxious CRD, neurons with phasic (58%) and tonic (42%) responses were revealed. The phasic neuron responses were significantly enhanced in comparison with non-noxious CRD. Inhibition of the neuronal NO-syntheses resulted in significant decrease of neuron responses to noxious CRD and the number of cells with tonic reactions. Therefore, neurons with tonic responses may be directly related to NO-depended processing ofnociceptive information from colon. 相似文献
7.
The orthocladiine Chironomidae genus Stictocladius Edwards was described originally from South America. Although recognised subsequently as present also in Australia and New Zealand, the true diversity in the Neotropics has remained unclear. After more than a decade of collections of both isolated adults and aquatic immature stages, we can recognise several new taxa and associate some immature stages. Thus, we describe Stictocladius prati n. sp. as male, female, pupa and larva; Stictocladius acutus n. sp. and Stictocladius acrilobus n. sp. as male, female and pupa; Stictocladius fimbriatus n. sp. as male and female; Stictocladius fovigus n. sp. and Stictocladius nudiventer n. sp. as male and pupa; and Stictocladius privicalcar n. sp. and Stictocladius prostatus n. sp. each as male imago alone. The male and female of Stictocladius pulchripennis Edwards is redescribed and the pupa described. The male and female of Stictocladius flavozonatus Edwards and the male of Stictocladius calonotum Edwards are described. Five pupal types are described: Stictocladius sp. A (near S. acrilobus), Stictocladius sp. B (possibly S. calonotum), Stictocladius sp. C (near S. calonotum), Stictocladius sp. D (possibly S. flavozonatus) and Stictocladius sp. E with uncertain affinity. A larva from Chile of the Stictocladius ??sofour type?? (Stictocladius sp. F) and an unreared larva from North America (Stictocladius sp. G) possibly belonging to S. acutus are described. Keys to named Neotropical male and female imagines of Stictocladius and to all pupal forms of Neotropical Stictocladius are provided. Some data concerning fourth instars of Stictocladius are presented. Means of differentiation from putative sister taxon Lopescladius are discussed. 相似文献
8.
Liubashina OA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2002,88(10):1343-1355
Mechanisms of the amygdala central nucleus (CNA) influence on gastric motor reflex activity were studied in electrophysiological and neuroanatomical experiments in Wistar rats. In the anaesthetized animals, electrical stimulation of the CNA affected spontaneous gastric motility and caused inhibitory as well as excitatory changes of vagus-induced gastric relaxation. The most significant and mainly inhibitory effects were observed under the stimulation of the medial CNA. Microinjection of the anterograde tracer Phaseolus vulgaris-leucoagglutimn (PHA-L) into the different divisions of the CNA revealed direct projections from its dorso-medial portion to the gastric related area of the dorsal vagal complex. Electrical stimulation of this amygdaloid area was found to change activity of the bulbar gastric related neurons. Inhibitory and excitatory changes of their vagus-induced responses under the amigdala stimulation were manifested as a general modulation of all phases of the reaction or a selective modulation of some of them. These mechanisms may underlie the amygdalo-fugal modulation of gastric motor reflex activity. 相似文献
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10.
A Bell OA Rodríguez LA de Castro e Paula MB Padua J Hernández-Cerón CG Gutiérrez A De Vries PJ Hansen 《BMC veterinary research》2008,4(1):22