Characterization of Small-size Egg-bearing Thai ss-strain Rotifers Brachionus rotundiformis and Their First Offspring     

Agus  Somamihardja Amrit  Bart 《Journal of the World Aquaculture Society》2008,39(4):528-534

This study selected small (100–120 μm) egg-bearing females from a local Thai ss population and characterized their first offspring's life history in an attempt to produce small-size rotifers. Mean lorica length of selected small adult females was 120 ± 6 μm at the time of collection, and this mean length did not increase over their lifetime. While their first offspring life span was only 5.11 ± 0.35 d, the reference population longevity was higher, 9.65 ± 0.4 d. The length of reproductive period of offspring from the small-size egg-bearing female was 2.58 ± 0.38 d, shorter than that of reference population 6.83 ± 0.58 d. Although the rate of egg production was not different between small egg-bearing female and reference population, the total number of eggs produced by the small egg-bearing female's first offspring was lower (4.78 ± 0.60) compared to the reference population (11.83 ± 1.26). The small egg-bearing female's first offspring had a higher egg to lorica length ratio (76.1 ± 1.64%) than the reference population (56.6 ± 1.3%), indicating a relatively high investment in reproduction. The small egg-bearing female's first offspring reached only 125 ± 6 μm in 36 h, and further culture of their offspring over 35 d resulted in a mean offspring size, 163 ± 11 μm, similar to the reference population (159 ± 16 μm). This shows that population mean size reduction is not likely to result from selecting small egg-bearing females within a single generation. The unique reproductive characteristics of small egg-bearing female place it in its own category.  相似文献   

Studies on some quantitative relations between the metabolism of nitrates and nitrites in domestic animals. Normal values of nitrates and methemoglobins in the blood of poultry and geese. Formation and production of methemoglobin in poultry blood     

M Bartík  A Bundza  K Fried  J Mezencev 《Archiv fuer experimentelle veterinaermedizin》1965,19(2):555-558

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Characterization of the Microbial Community Involved in the Suppression of Pythium aphanidermatum in Cucumber Grown on Rockwool     

Postma J  Geraats BP  Pastoor R  van Elsas JD 《Phytopathology》2005,95(7):808-818

ABSTRACT The root pathogen Pythium aphanidermatum induced lower levels of disease in cucumber (Cucumis sativus) plants on unsterilized, re-used rockwool slabs than on heat-sterilized, re-used rockwool. Several recolonization treatments of the sterilized rockwool enhanced the suppressiveness of the rockwool. Microbial community structures in the different rockwool treatments were investigated by plate counts on selective media. Disease suppressiveness in the different rockwool treatments showed the highest correlation with the culturable number of filamentous actinomycetes in both experiments (r = 0.79 and 0.94), whereas the numbers of Trichoderma spp. correlated with suppression only in the first experiment (0.86). The numbers of total culturable bacteria, fluorescent pseudomonads, Bacillus spores, and fungi all showed lower correlations with disease suppressiveness. The filamentous actinomycetes enumerated with the plate counts were mainly Streptomyces spp., of which 10% were antagonistic toward P. aphanidermatum in dual culture. The composition of the bacterial and actinomycete populations was studied with polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Multivariate analyses of these patterns with canonical correspondence analysis showed significant correlations between the microbial composition and the disease suppressiveness. However, none of the bands in PCR-DGGE patterns occurred exclusively in the treatments that had enhanced disease suppressiveness. Bands extracted from the actinomycete-specific DGGE gels showed closest similarity with members of several actinomycete genera, i.e., Streptomyces, Mycobacterium, Microbacterium, Rhodococcus, Curtobacterium, and Tsukamurella. The possible mechanism of disease suppressiveness in used rockwool slabs, based on the results obtained with culture-dependent and culture-independent detection methods, is discussed.  相似文献   

Perfrin,a novel bacteriocin associated with netB positive Clostridium perfringens strains from broilers with necrotic enteritis     

Leen Timbermont  Lina De Smet  Filip Van Nieuwerburgh  Valeria R Parreira  Gonzalez Van Driessche  Freddy Haesebrouck  Richard Ducatelle  John Prescott  Dieter Deforce  Bart Devreese  Filip Van Immerseel 《Veterinary research》2014,45(1):40

Necrotic enteritis in broiler chickens is associated with netB positive Clostridium perfringens type A strains. It is known that C. perfringens strains isolated from outbreaks of necrotic enteritis are more capable of secreting factors inhibiting growth of other C. perfringens strains than strains isolated from the gut of healthy chickens. This characteristic could lead to extensive and selective presence of a strain that contains the genetic make-up enabling to secrete toxins that cause gut lesions. This report describes the discovery, purification, characterization and recombinant expression of a novel bacteriocin, referred to as perfrin, produced by a necrotic enteritis-associated netB-positive C. perfringens strain. Perfrin is a 11.5 kDa C-terminal fragment of a 22.9 kDa protein and showed no sequence homology to any currently known bacteriocin. The 11.5 kDa fragment can be cloned into Escherichia coli, and expression yielded an active peptide. PCR detection of the gene showed its presence in 10 netB-positive C. perfringens strains of broiler origin, and not in other C. perfringens strains tested (isolated from broilers, cattle, sheep, pigs, and humans). Perfrin and NetB are not located on the same genetic element since NetB is plasmid-encoded and perfrin is not. The bacteriocin has bactericidal activity over a wide pH-range but is thermolabile and sensitive to proteolytic digestion (trypsin, proteinase K). C. perfringens bacteriocins, such as perfrin, can be considered as an additional factor involved in the pathogenesis of necrotic enteritis in broilers.  相似文献   

An entomopathogenic fungus for control of adult African malaria mosquitoes     

Scholte EJ  Ng'habi K  Kihonda J  Takken W  Paaijmans K  Abdulla S  Killeen GF  Knols BG 《Science (New York, N.Y.)》2005,308(5728):1641-1642

Biological control of malaria mosquitoes in Africa has rarely been used in vector control programs. Recent developments in this field show that certain fungi are virulent to adult Anopheles mosquitoes. Practical delivery of an entomopathogenic fungus that infected and killed adult Anopheles gambiae, Africa's main malaria vector, was achieved in rural African village houses. An entomological inoculation rate model suggests that implementation of this vector control method, even at the observed moderate coverage during a field study in Tanzania, would significantly reduce malaria transmission intensity.  相似文献   

Molecular biology. miRNAs in neurodegeneration     

Hébert SS  De Strooper B 《Science (New York, N.Y.)》2007,317(5842):1179-1180

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A comprehensive survey of the Plasmodium life cycle by genomic, transcriptomic, and proteomic analyses     

Hall N  Karras M  Raine JD  Carlton JM  Kooij TW  Berriman M  Florens L  Janssen CS  Pain A  Christophides GK  James K  Rutherford K  Harris B  Harris D  Churcher C  Quail MA  Ormond D  Doggett J  Trueman HE  Mendoza J  Bidwell SL  Rajandream MA  Carucci DJ  Yates JR  Kafatos FC  Janse CJ  Barrell B  Turner CM  Waters AP  Sinden RE 《Science (New York, N.Y.)》2005,307(5706):82-86

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Noncanonical TGFβ signaling contributes to aortic aneurysm progression in Marfan syndrome mice     

Holm TM  Habashi JP  Doyle JJ  Bedja D  Chen Y  van Erp C  Lindsay ME  Kim D  Schoenhoff F  Cohn RD  Loeys BL  Thomas CJ  Patnaik S  Marugan JJ  Judge DP  Dietz HC 《Science (New York, N.Y.)》2011,332(6027):358-361

Transforming growth factor-β (TGFβ) signaling drives aneurysm progression in multiple disorders, including Marfan syndrome (MFS), and therapies that inhibit this signaling cascade are in clinical trials. TGFβ can stimulate multiple intracellular signaling pathways, but it is unclear which of these pathways drives aortic disease and, when inhibited, which result in disease amelioration. Here we show that extracellular signal-regulated kinase (ERK) 1 and 2 and Smad2 are activated in a mouse model of MFS, and both are inhibited by therapies directed against TGFβ. Whereas selective inhibition of ERK1/2 activation ameliorated aortic growth, Smad4 deficiency exacerbated aortic disease and caused premature death in MFS mice. Smad4-deficient MFS mice uniquely showed activation of Jun N-terminal kinase-1 (JNK1), and a JNK antagonist ameliorated aortic growth in MFS mice that lacked or retained full Smad4 expression. Thus, noncanonical (Smad-independent) TGFβ signaling is a prominent driver of aortic disease in MFS mice, and inhibition of the ERK1/2 or JNK1 pathways is a potential therapeutic strategy for the disease.  相似文献   

Furfuryl ethyl ether: important aging flavor and a new marker for the storage conditions of beer   总被引：1，自引：0，他引：1  

Vanderhaegen B  Neven H  Daenen L  Verstrepen KJ  Verachtert H  Derdelinckx G 《Journal of agricultural and food chemistry》2004,52(6):1661-1668

Recently, it was reported that furfuryl ethyl ether is an important flavor compound indicative of beer storage and aging conditions. A study of the reaction mechanism indicates that furfuryl ethyl ether is most likely formed by protonation of furfuryl alcohol or furfuryl acetate followed by S(N)2-substitution of the leaving group by the nucleophilic ethanol. For the reaction in beer, a pseudo-first-order reaction kinetics was derived. A close correlation was found between the values predicted by the kinetic model and the actual furfuryl ethyl ether concentration evolution during storage of beer. Furthermore, 10 commercial beers of different types, aged during 4 years in natural conditions, were analyzed, and it was found that the furfuryl ethyl ether flavor threshold was largely exceeded in each type of beer. In these natural aging conditions, lower pH, darker color, and higher alcohol content were factors that enhanced furfuryl ethyl ether formation. On the other hand, sulfite clearly reduced furfuryl ethyl ether formation. All results show that the furfuryl ethyl ether concentration is an excellent time-temperature integrator for beer storage.  相似文献   

Ascorbic acid concentration in Cv. conference pears during fruit development and postharvest storage     

Franck C  Baetens M  Lammertyn J  Verboven P  Davey MW  Nicolaï BM 《Journal of agricultural and food chemistry》2003,51(16):4757-4763

L-ascorbic acid (L-AA) concentration changes during the development of cv. Conference pears and the influence of postharvest handlings (gas condition, cooling rate, cooling duration) on L-AA breakdown were studied. L-AA concentration fluctuates in young fruits, remains stable during fruit maturation, and starts to decline 1 week before commercial harvest. The most rapid decrease in L-AA concentration was found during immediate controlled atmosphere. During short-term storage, only the gas condition was found to influence L-AA breakdown; no significant difference between gradually or immediately cooled pears was determined. Under air conditions, both cooling strategies did not differ from the L-AA breakdown in pears allowed to ripen on the tree up until 3 weeks after the optimal harvest date. During long-term storage, the cooling duration (1-3 weeks) had no effect whereas both O2 and CO2 had a significant effect on L-AA retention. After 7 months of storage, no difference was found in dehydroascorbic acid concentration; the L-AA and total L-AA concentrations, in contrast, were significantly lower in the 5% CO2 conditions.  相似文献