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81.
Block of outward current in cardiac purkinje fibers by injection of quaternary ammonium ions 总被引:6,自引:5,他引:1 下载免费PDF全文
We have studied the effects of iontophoretic injection of the quaternary ammonium compounds tetraethylammonium (TEA) and tetrabutylammonium (TBA) in cardiac purkinje fibers. We find that TBA(+) is a more effective blocker than TEA(+), but injection of either compound reduces the time-dependent outward plateau currents, transient outward current (I(to)), and the delayed rectifier (I(x)). Our findings provide evidence that these outward cardiac currents are carried by channels that in some respects are pharmacologically similar to squid axon potassium channels. We demonstrate that this procedure is a new tool that can be useful in the analysis of membrane currents in the heart. 相似文献
82.
In a 5-L fermentor (NBS-MF 105), Saccharomyces cerevisiae W303-181 (1.0 g dry matter/L) was inoculated into 3.0 L of liquid medium containing glucose (10 or 20 g/L), yeast nitrogen base (YNB, 3.7 or 7.4 g/L), l-histidine (0.02 g/L), l-tryptophan (0.02 g/L), uracil (0.02 g/L), and adenine (0.02 g/L). The culture was carried out batchwise for 12 or 24 h at 30 degrees C, pH 4.6 or 5.7, aeration of 0, 0.8, 1.7 or 2.2 vvm, and agitation of 400 rpm. The highest G6PDH productivity (10.5 U/L.h) and specific activity (320 U/mg of protein) occurred at aeration of 2.2 vvm, pH 5.7, 10 g/L of glucose, and 3.7 g/L of YNB. The G6PDH specific activity attained was comparable with those of commercial preparations, which are between 50 and 600 U/mg of protein. 相似文献
83.
de Menezes JE Machado FE Lemos TL Silveira ER Braz Filho R Pessoa OD 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(1-2):19-22
Two new secondary metabolites, the phenylpropanoid 3-(2',4',5'-trimethoxyphenyl)propanoic acid (1) and the sesquiterpene (+)-1beta,4beta,6alpha-trihydroxyeudesmane (2) were isolated from the heartwood of Cordia trichotoma Vell., along with the known sesquiterpenes (-)-1beta,4beta,7alpha-trihydroxyeudesmane (3) and (+)-1beta,4beta,11-trihydroxyoppositane (4). Their structures were elucidated by means of spectroscopic data interpretation, mainly 1D and 2D NMR and mass spectrometry. 相似文献
84.
IB Masters MM Eastburn PW Francis R Wootton PV Zimmerman RS Ware AB Chang 《Respiratory research》2005,6(1):16
Background
Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.Methods
Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.Results
Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.Conclusion
We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements. 相似文献85.
86.
87.
Laís Alves Antonio Moreira Danilo Gustavo Rodrigues de Oliveira Maria Bernardete Cordeiro de Sousa Daniel Marques Almeida Pessoa 《PloS one》2015,10(6)
New World monkeys have polymorphic color vision, in which all males and some females are dichromats, while most females are trichromats. There is little consensus about which selective pressures fashioned primate color vision, although detection of food, mates and predators has been hypothesized. Behavioral evidence shows that males from different species of Neotropical primates seem to perceive the timing of female conception and gestation, although, no signals fulfilling this function have been identified. Therefore, we used visual models to test the hypothesis that female marmosets show chromatic and/or achromatic cues that may indicate the time of parturition for male and female conspecifics. By recording the reflectance spectra of female marmosets’ (Callithrix jacchus) sexual skin, and running chromatic and achromatic discrimination models, we found that both variables fluctuate during the weeks that precede and succeed parturition, forming “U” and inverted “U” patterns for chromatic and achromatic contrast, respectively. We suggest that variation in skin chroma and luminance might be used by female helpers and dominant females to identify the timing of birth, while achromatic variations may be used as clues by potential fathers to identify pregnancy stage in females and prepare for paternal burdens as well as to detect oestrus in the early post-partum period. 相似文献
88.
Suzana Vieira Rabêlo Fernanda Granja da Silva Oliveira Michele Miriam Calixto de Lira Livia Macedo Dutra Adilson Sartoratto Marta Cristina Teixeira Duarte Maria Claudia dos Santos Luciano Maria Francilene Souza Silva Cláudia do Ó Pessoa Manoel Odorico de Moraes Filho Emmanoel Vilaça Costa Jackson Roberto Guedes da Silva Almeida 《Phyton》2021,90(3):921-931
This study aimed to identify the chemical composition of essential oil from fruits (EOAF) and the hexanic crude
extract from aerial parts (At-Hex) of atemoya (Annona cherimola x Annona squamosa), a hybrid belonging to the
Annonaceae family. Cytotoxic and antimicrobial activity was also evaluated. OEAF was obtained by hydrodistillation using a Clevenger apparatus, and their composition was analyzed by gas chromatography-mass spectrometry
(GC-MS) analyses. Cytotoxicity was tested against human tumor cell lines HCT-116 (colon carcinoma), SF-295
(glioblastoma), OVCAR-8 (ovarian carcinoma) and HL60 (leukemia) using 3-(4,5-dimethyl-2-thiazolyl)-2,5-
diphenyl-2H-tetrazolium bromide (MTT) assay, while antimicrobial activity was conducted by bioauthography
method against eleven microorganisms strains. Twenty-four compounds were identified in the EOAF and
twenty-nine in At-Hex. The monoterpenes linalool (25.70%), α-pinene (10.38%), β-pinene (9.12%), transocimene (7.43%), and the sesquiterpene bicyclogermacrene (12.58%) were the major constituents of EOAF,
whereas the sesquiterpene spathulenol (13.91%) was the main compound of At-Hex. At-Hex showed a high
cytotoxicity against SF-295 (glioblastoma). These findings show an important chemotaxonomic contribution
for the Annonaceae family, mainly for the Annona genus. Atemoya proved to be a promising source of substances
with potential cytotoxic activity. 相似文献
89.
Background
The influence of sperm competition upon sperm size has been a controversial issue during the last 20 years which remains unresolved for mammals. The hypothesis that, when ejaculates compete with rival males, an increase in sperm size would make sperm more competitive because it would increase sperm swimming speed, has generated contradictory results from both theoretical and empirical studies. In addition, the debate has extended to which sperm components should increase in size: the midpiece to accommodate more mitochondria and produce more energy to fuel motility, or the principal piece to generate greater propulsion forces. 相似文献90.
Elthon G. Ferreira Diego V. Wilke Paula C. Jimenez Julieta R. de Oliveira Otília Deusdênia L. Pessoa Edilberto R. Silveira Francisco A. Viana Cláudia Pessoa Manoel Odorico de Moraes Eduardo Hajdu Letícia Veras Costa‐Lotufo 《化学与生物多样性》2011,8(8):1433-1445
Five guanidine alkaloids, mirabilin B ( 1 ), 8bβ‐hydroxyptilocaulin ( 2 ), ptilocaulin ( 3 ), and a mixture of the 8β‐ and 8α‐epimers, 4 and 5 , of 8‐hydroxymirabilin (1,8a;8b,3a‐didehydro‐8‐hydroxyptilocaulin), were isolated from Monanchora arbuscula colonies collected off the northeastern Brazilian coast. All structures were elucidated by spectroscopic analysis, including 1D (1H‐, 13C‐ (BB), and 13C‐DEPT) and 2D (COSY, HSQC, and HMBC) NMR experiments, and comparison with the literature data. The cytotoxicity of the isolated compounds were evaluated against four tumor cell lines, showing that mirabilin B ( 1 ) and the two epimers were inactive, while 8bβ‐hydroxyptilocaulin ( 2 ) and ptilocaulin ( 3 ) presented IC50 values in the range of 7.9 to 61.5 μM , and 5.8 to 40.0 μM , respectively. Further studies on the mechanism of action of ptilocaulin, using HL‐60 leukemia cells, demonstrated that this guanidine compound induced apoptosis of the treated cells. 相似文献