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排序方式: 共有169条查询结果,搜索用时 15 毫秒
1.
To further investigate the role of opioid peptides and specific opiate receptor subtypes in central cardiovascular regulation by hindbrain nuclei, mu (D-Ala2,MePhe4,Gly-ol5 enkephalin, DAGO), delta (D-Ala2,D-Leu5 enkephalin, DADL) or kappa (MRZ 2549) agonists were microinjected into hindbrain nuclei of spontaneously or artificially respired, pentobarbital-anesthetized rats. In the nucleus tractus solitarius (NTS), DAGO and DADL (0.3 nmol) elicited pressor responses and tachycardia. MRZ (3.0–16 nmol) depressed blood pressure in spontaneously breathing rats, but accelerated heart rate in artificially ventilated animals. Blood pressure and heart rate of spontaneously breathing animals were not altered following nucleus ambiguus (NA) injection of DAGO or DADL (0.3 nmol), but were elevated in artificially respired animals; MRZ (3.0–10 nmol) injected into the NA depressed blood pressure in both groups. These data suggest that in the absence of respiratory depression, NTS and NA mu receptors mediate pressor responses and tachycardia; kappa receptors in the NA mediate a decrease in blood pressure but cardioacceleration in the NTS. 相似文献
2.
Microbial characterization during composting of municipal solid waste 总被引:29,自引:0,他引:29
Hassen A Belguith K Jedidi N Cherif A Cherif M Boudabous A 《Bioresource technology》2001,80(3):217-225
This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60–55°C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2×107 to 3.1×103 and 107 to 1.5×103 cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5×106 to 2.6×103 cells/g WDW and mesophilic bacteria were reduced from 5.8×109 to 1.8×107 bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60°C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost. 相似文献
3.
Salma Kloula Ben Ghorbal Abdelwaheb Chatti Mohamed Marwan Sethom Lobna Maalej Mouadh Mihoub Sana Kefacha Moncef Feki Ahmed Landoulsi Abdennaceur Hassen 《Current microbiology》2013,67(1):112-117
The changes in lipid composition enable the micro-organisms to maintain membrane functions in the face of environmental fluctuations. The relationship between membrane fatty acid composition and UV-C stress was determined for mid-exponential phase and stationary phase Pseudomonas aeruginosa. The total lipids were obtained by dichloromethane/methanol (3:1) and were quantified by GC. The TLC analysis of phospholipids showed the presence of three major fractions phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. Significant modifications, as manifested by an increase of UFA, were obtained. Interestingly, this microorganism showed a remarkable capacity for recovery from the stressful effects of UV-C. 相似文献
4.
Induction of micronuclei by Zearalenone in Vero monkey kidney cells and in bone marrow cells of mice: protective effect of Vitamin E 总被引:7,自引:0,他引:7
Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin mainly produced by Fusarium graminaerum, found as a world-wide contaminant mainly of corn and wheat. Previous studies have demonstrated that among several other effects on animals and humans, ZEN also displays hepatotoxicity, immunotoxicity and nephrotoxicity. ZEN is mainly known as a hormonal disrupter due to its estrogenic activities and consequent toxicity for reproduction. Furthermore, mutagenic and genotoxic proprieties of ZEN were disclosed recently, the molecular mechanisms of which are not yet well understood. In the present study, the genotoxic potential of ZEN was evaluated using genotoxicity tests: the 'cytokinesis block micronucleus assay' in Vero monkey kidney cells and the 'in vivo mouse bone marrow micronucleus assay'. In cultured cells treated with 5, 10 and 20 microM ZEN, the frequency of binucleated micronucleated cells (BNMN) was assessed in 1000 binucleated cells and in mice given oral doses of 10, 20 and 40 mg/kg bw, the frequency of polychromatic erythrocytes micronucleated (PCEMN) in bone marrow cells was assessed in 2000 polychromatic erythrocytes (PCE). The potential prevention of ZEN-induced effects by 25 microM Vitamin E (Vit E) was also evaluated.In vivo, doses of 10, 20 and 40 mg/kg bw ZEN representing, respectively 2, 4 and 8% of the LD50 (LD50 of ZEN in mice is 500 mg/kg bw), were administered to animals either with or without pre-treatment with Vit E (216.6 mg/kg bw) in order to evaluate its preventive potential.ZEN was found to induce micronuclei (MN) in a dose-dependent manner in cultured Vero cells as well as in mouse bone marrow cells. The present data emphasise the likely clastogenic pathway among the molecular mechanisms that underlay the ZEN-induced genotoxicity. Vit E was found to prevent partially-from 30 to 50%-these toxic effects, most likely acting either as a structural analogue of ZEN or as an antioxidant. 相似文献
5.
The aim of this study was to characterize the impact of heavy metals on phenotypical markers of Pseudomonas aeruginosa. Twenty-two isolates of P. aeruginosa, either clinical (20) or secondary treated wasterwater (2), were used to inoculate micro-ecosystems of sterile distilled water or secondary waste effluent in the presence of subminimal inhibitory concentrations of a variety of heavy metals commonly encountered in the aquatic naturally habitat (Ca2+, Co2+, Cr3+, Cu2+, Hg2+, Ni2+, Zn2+). Micro-ecosystems were exposed to visible light at laboratory temperature and individual strains were reisolated after a 1-, 3-, or 6-month period. The re-isolates (129) were characterized using hierarchical classification analysis in order to define affinities among variants of P. aeruginosa. Subsequently, discriminant analysis was used to detect eventual relationships among the different phenotypical markers studied. Results of the hierarchical classification, based on qualitative or quantitative approaches, showed clearly that incubation of P. aeruginosa in the presence of heavy metals altered the studied phenotypical markers, namely serotype, phage type, MIC of metals, and pyocin type. Discriminant analysis showed that the studied phenotypical markers could be classified into four clusters: C1 (L1 and L2 phage types, Hg tolerance and/or resistance, S2 serotype), C2 (P2 pyocin type, Cd tolerance and/or resistance, S1 serotype), C3 (Co and Cr tolerance and/or resistance) and C4 (P1 pyocin type, Ni, Zn, and Cu tolerance and/or resistance). 相似文献
6.
Chaabani H 《Annales de génétique》2002,45(4):197-206
Present human populations show a complex network of genetic relationships, which reflects mainly their unique origin and their migration and isolation history since the recent creation of modern man. The scrutiny of their genetic characteristics, according to GM polymorphism, shows that the continuity of the genetic variation between populations from neighbouring continents, assured by intermediate world part populations, is against any attempt to divide present human populations into major groups. GM polymorphism analysis also shows three remarkable levels of genetic differentiation, which would have appeared, respectively, within populations of sub-Saharan Africa, Europe and East Asia. The first small groups of people that split from the common ancestral population gave the sub-Saharan Africans. On the other hand, Asians diverged mainly from Europeans and Near East populations during a later period. The confrontation between the phylogeny and the frequency distribution of GM haplotypes shows that the ancestral population of actual South-Arabia people could be a candidate for a common ancestral population. The first major expansions of modern humans were proposed in a hypothetical scenario, which will open a new track in the research of our geographic origin. 相似文献
7.
8.
Imed Hassen Yassine M'Rabet Chaouki Belgacem Ons Kesraoui Hervé Casabianca Karim Hosni 《化学与生物多样性》2015,12(4):637-651
The chemical composition of the volatile oils obtained from the roots, leaves, flowers, and stems of Thapsia garganica of Tunisian origin was investigated by GC‐FID and GC/MS analyses. Sesquiterpene hydrocarbons and oxygenated monoterpenes were predominant in the oils of all plant parts. Bicyclogermacrene (21.59–35.09%) was the main component in the former compound class, whereas geranial (3.31–14.84%) and linalool (0.81–10.9%) were the most prominent ones in the latter compound class. Principal‐component (PCA) and hierarchical‐cluster (HCA) analyses revealed some common constituents, but also significant variability amongst the oils of the different plant parts. This organ‐specific oil composition was discussed in relation to their biological and ecological functions. For the evaluation of the intraspecific chemical variability in T. garganica, the composition of the flower volatile oils from four wild populations was investigated. Bicyclogermacrene, linalool, and geranial were predominant in the oils of three populations, whereas epicubenol, β‐sesquiphellandrene, and cadina‐1,4‐diene were the most prominent components of the oil of one population. PCA and HCA allowed the separation of the flower oils into three distinct groups, however, no relationship was found between the volatile‐oil composition and the geographical distribution and pedoclimatic conditions of the studied populations. 相似文献
9.
Anis Raddaoui Alexandra S. Sim?es Rekaya Baaboura Sofia Félix Wafa Achour Tarek Ben Othman Mohamed Béjaoui Raquel Sá-Le?o Assia Ben Hassen 《PloS one》2015,10(10)
BackgroundPneumococcal disease, a major cause of morbidity and mortality globally, has higher incidence among young children, the elderly and the immunocompromised of all ages. In Tunisia, pneumococcal conjugate vaccines (PCVs) are not included in the national immunization program. Also, few studies have described the epidemiology of S. pneumoniae in this country and, in particular, no molecular typing studies have been performed. The aim of this study was to evaluate serotype distribution, antimicrobial resistance and clonality of Streptococcus pneumoniae isolated from neutropenic patients in Tunisia.MethodsFifty-nine S. pneumoniae were isolated from infection (n = 31) and colonization (n = 28) sites of patients (children and adults) attending the National Centre of Bone Marrow Transplantation in Tunis between 2005–2011. All isolates were characterized by serotype, antimicrobial resistance pattern and multilocus sequence typing (MLST).ResultsThe majority (66.1%) of the isolates belonged to five serotypes all included in PCVs: 6B, 9V, 14, 19F and 23F. The potential coverage of the 10-valent and 13-valent PCV was of 71.2% and 76.3% respectively. Resistance rates were very high and 69.5% of the isolates were multidrug resistant: non-susceptibility rates to penicillin, amoxicillin and cefotaxime were 66.1%, 40.7% and 27.1%, respectively; resistance rates to erythromycin, clindamycin, tetracycline, chloramphenicol and trimethoprim-sulfamethoxazole, were 69.5%, 61.0%, 37.3%, 22.0% and 67.8%, respectively. The most frequent serotypes had STs characteristic of multidrug resistant international clones known to be highly successful and important causes of pneumococcal infection: Spain 23F-ST81, France 9V/14-ST156, Spain 6B-ST90, 19F-ST320, and Portugal 19F-ST177.ConclusionsThe majority of S. pneumoniae strains recovered from immunocompromised patients in Tunisia are representatives of multidrug resistant pandemic clones that express serotypes targeted by PCVs. To contain the burden of pneumococcal disease and improve treatment choices among Tunisian immunocompromised patients PCVs should be offered to all of them. 相似文献
10.
Fatma Bensassi Ali Rhouma Mohamed Ghrab Hassen Bacha Mohamed Rabeh Hajlaoui 《Mycotoxin Research》2010,26(3):199-203
Aflatoxins (AFs) are potent sources of health risks to both humans and animals. Among them, AFB1 is the most hazardously toxic
and the most frequent in various food commodities, including pistachio nuts. In this survey, the effect of the storage period
on AFB1 accumulation on pistachio nuts was investigated. A total of 49 samples collected during the crop year of 2005 from
the most cultivated pistachio cultivars in Tunisia were rapidly screened by enzyme-linked immunosorbent assay (ELISA) combined
with an immunoaffinity step. The obtained results showed that the contamination of pistachio nuts has occurred clearly after
two years of storage for all the tested cultivars except the case of Mateur variety and Thyna ecotypes. In this study, the
cultivar Mateur was found to be the most susceptible cultivar to contamination by AFB1. After 4 years of storage, the average
contamination levels in nut samples ranged from 2.7 ± 0.3 to 12.7 ± 2.2 μg/kg for AFB1, according to the cultivar. These levels
exceeded the maximum permitted limit of 2 μg/kg set by the European Commission in nuts. 相似文献