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121.
A simple medium for the study of hepatocyte growth in culture under defined conditions 总被引:3,自引:0,他引:3
Tor-Erik Sand Thoralf Christoffersen 《In vitro cellular & developmental biology. Plant》1988,24(10):981-984
Summary The combination (1∶1) of Dulbecco's modified Eagle's medium and Waymouth's medium MAB 87/3 was found to provide favorable
conditions for serum-free culture and growth of adult rat hepatocytes. In this simple medium, a majority of hepatocytes stimulated
by epidermal growth factor plus insulin entered S phase and divided, with a normal (13 h) interval between DNA synthesis and
cell division. The proliferative response did not require extra substratum or the presence of serum, even during cell isolation
and plating.
This work was supported by the Norwegian Cancer Society. 相似文献
122.
123.
In cultured rat pituitary tumour cells (GH3 cells) the absence of extracellular Ca++ or addition of NaEGTA reduced spontaneous prolactin (PRL) release and abolished the stimulatory effect of thyroliberin (TRH). Readdition of CaCl2, but not of equimolar concentrations of MgCl2 increased spontaneous hormone release, and restored the effect of TRH. The calcium ionophore, A-23187, induced PRL release during normal calcium conditions, but not when an excess NaEGTA was present. TRH increased cyclic AMP accumulation in the presence and the absence of extracellular calcium. The effect of TRH on PRL release and cyclic AMP formation occured concomitantly with an increased efflux of 45Ca2+. Intracellular electrophysiological recordings from the same single cells before and after TRH activation showed increased frequency and duration of the Ca2+ dependent action potentials. We conclude that TRH elevates the Ca2+ influx which depends on the depolarizing action current, and this effect is probably linked to formation of cyclic AMP and PRL release. 相似文献
124.
125.
126.
Isolation and Molecular Characterization of Acanthamoeba Strains from Dental Units in Costa Rica 下载免费PDF全文
Lissette Retana‐Moreira Elizabeth Abrahams‐Sandí Esteban Castro‐Artavia Ana Fernández‐Sánchez Alfredo Castro‐Castillo María Reyes‐Batlle Jacob Lorenzo‐Morales 《The Journal of eukaryotic microbiology》2015,62(6):733-736
Free‐living amoebae are protozoa widely distributed in nature, which can be found in a variety of environments. Four genera are recognized as causal agents of infections in humans and animals: Acanthamoeba, Naegleria, Balamuthia, and Sappinia. In this study, the presence of Acanthamoeba in dental units was determined and the isolates obtained were molecularly characterized; osmotolerance and thermotolerance assays were also performed to evaluate multiplication under these conditions, frequently associated with pathogenicity. The morphological analysis and partial sequencing of the 18S rDNA gene revealed the presence of Acanthamoeba genotype T4 in 14% of the units sampled. Osmotolerance and thermotolerance tests were positive for more than 80% of the isolates. Up to date, this is the first study that reports the detection, identification, and genotyping of Acanthamoeba isolated from dental units in Costa Rica and even in Latin‐America. Further assays to determine the potential pathogenicity of these Acanthamoeba isolates are underway. 相似文献
127.
Gervasi V Nilsen EB Sand H Panzacchi M Rauset GR Pedersen HC Kindberg J Wabakken P Zimmermann B Odden J Liberg O Swenson JE Linnell JD 《The Journal of animal ecology》2012,81(2):443-454
1. Understanding the role of predation in shaping the dynamics of animal communities is a fundamental issue in ecological research. Nevertheless, the complex nature of predator-prey interactions often prevents researchers from modelling them explicitly. 2. By using periodic Leslie-Usher matrices and a simulation approach together with parameters obtained from long-term field projects, we reconstructed the underlying mechanisms of predator-prey demographic interactions and compared the dynamics of the roe deer-red fox-Eurasian lynx-human harvest system with those of the moose-brown bear-gray wolf-human harvest system in the boreal forest ecosystem of the southern Scandinavian Peninsula. 3. The functional relationship of both roe deer and moose λ to changes in predation rates from the four predators was remarkably different. Lynx had the strongest impact among the four predators, whereas predation rates by wolves, red foxes, or brown bears generated minor variations in prey population λ. Elasticity values of lynx, wolf, fox and bear predation rates were -0·157, -0·056, -0·031 and -0·006, respectively, but varied with both predator and prey densities. 4. Differences in predation impact were only partially related to differences in kill or predation rates, but were rather a result of different distribution of predation events among prey age classes. Therefore, the age composition of killed individuals emerged as the main underlying factor determining the overall per capita impact of predation. 5. Our results confirm the complex nature of predator-prey interactions in large terrestrial mammals, by showing that different carnivores preying on the same prey species can exert a dramatically different demographic impact, even in the same ecological context, as a direct consequence of their predation patterns. Similar applications of this analytical framework in other geographical and ecological contexts are needed, but a more general evaluation of the subject is also required, aimed to assess, on a broader systematic and ecological range, what specific traits of a carnivore are most related to its potential impact on prey species. 相似文献
128.
Huber RC Remuge L Carlisle A Lillico S Sandøe P Sørensen DB Whitelaw CB Olsson IA 《Transgenic research》2012,21(4):773-784
Since large animal transgenesis has been successfully attempted for the first time about 25 years ago, the technology has been applied in various lines of transgenic pigs. Nevertheless one of the concerns with the technology--animal welfare--has not been approached through systematic assessment and statements regarding the welfare of transgenic pigs have been based on anecdotal observations during early stages of transgenic programs. The main aim of the present study was therefore to perform an extensive welfare assessment comparing heterozygous transgenic animals expressing GFP with wildtype animals along various stages of post natal development. The protocol used covered reproductory performance and behaviour in GFP and wildtype sows and general health and development, social behaviour, exploratory behaviour and emotionality in GFP and wildtype littermates from birth until an age of roughly 4 months. The absence of significant differences between GFP and wildtype animals in the parameters observed suggests that the transgenic animals in question are unlikely to suffer from deleterious effects of transgene expression on their welfare and thus support existing anecdotal observations of pigs expressing GFP as healthy. Although the results are not surprising in the light of previous experience, they give a more solid fundament to the evaluation of GFP expression as being relatively non-invasive in pigs. The present study may furthermore serve as starting point for researchers aiming at a systematic characterization of welfare relevant effects in the line of transgenic pigs they are working with. 相似文献
129.
Zoe Inman Helen Martin SA Paul Chubb 《The Clinical biochemist. Reviews / Australian Association of Clinical Biochemists》2009,30(3):141-151
Background
The lack of guidelines on reporting standards for protein electrophoresis may have led to significant differences in reports from different laboratories.Objective
To determine the extent of variation in reporting of protein electrophoresis results in Australia and New Zealand.Method
Questionnaires were distributed to laboratories throughout Australia and New Zealand asking about protein electrophoresis practices and reporting.Results
Extensive variation was found in the following reporting practices: (a) units for urine Bence Jones protein (BJP); (b) reporting absence of a paraprotein rather than a normal pattern; (c) numerical reporting of all protein fractions or only the paraprotein; (d) warning of possible inaccuracy in the serum immunoglobulin result of the paraprotein type; (e) co-migration of a paraprotein with a normal serum protein; (f) use of a confirmatory test when a known paraprotein is no longer detectable.Conclusions
A working party should be established to make recommendations on the reporting of protein electrophoresis. Implementation of such recommendations should reduce both report variation between laboratories and the risk of misinterpretation of reports. 相似文献130.
Goutam Sahana Dirk Jan de Koning Bernt Guldbrandtsen Peter S?rensen Mogens Sand? Lund 《遗传、选种与进化》2006,38(2):167-182
This simulation study was designed to study the power and type I error rate in QTL mapping using cofactor analysis in half-sib designs. A number of scenarios were simulated with different power to identify QTL by varying family size, heritability, QTL effect and map density, and three threshold levels for cofactor were considered. Generally cofactor analysis did not increase the power of QTL mapping in a half-sib design, but increased the type I error rate. The exception was with small family size where the number of correctly identified QTL increased by 13% when heritability was high and 21% when heritability was low. However, in the same scenarios the number of false positives increased by 49% and 45% respectively. With a liberal threshold level of 10% for cofactor combined with a low heritability, the number of correctly identified QTL increased by 14% but there was a 41% increase in the number of false positives. Also, the power of QTL mapping did not increase with cofactor analysis in scenarios with unequal QTL effect, sparse marker density and large QTL effect (25% of the genetic variance), but the type I error rate tended to increase. A priori, cofactor analysis was expected to have higher power than individual chromosome analysis especially in experiments with lower power to detect QTL. Our study shows that cofactor analysis increased the number of false positives in all scenarios with low heritability and the increase was up to 50% in low power experiments and with lower thresholds for cofactors. 相似文献