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Eight flavonoids, four 6-oxygenated flavones, two methyl ethers of luteolin, apigenin 6,8-C-diglucoside and quercetin 3-O-glucoside,
were isolated fromNama lobbii andN. rothrockii, sole members of sects.Arachnoidea andCinerascentia, respectively. Both taxa diverge markedly from other namas in morphology and chromosome number and their placement inNama has been questioned. The occurrence of 6-oxygenated flavones in these taxa adds to their already distinctive nature. Flavonoid
evidence argues that both are more closely allied toEriodictyon than either is toNama. 相似文献
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The injection of as little as 0.5 microgram phosphorylcholine-(PC) conjugated mouse immunoglobulin into BALB/c neonates within 48 hr of birth results in complete unresponsiveness to PC for 3 to 4 wk. Thereafter, anti-PC responses can be detected in tolerized animals, but these responses differ significantly from those of normal BALB/c mice. First, the magnitude of responsiveness does not approach normal levels even 9 mo after birth. Second, although the initial responses as tolerance is broken can be T15+, idiotypic dominance is not established; instead, a heterogeneous T15- population eventually emerges, which includes clones with higher and with lower avidity than T15. Unirradiated unresponsive mice will help transplanted normal B cells to produce T15+ responses to thymus-dependent PC antigens. The responses of animals recovered from tolerance are stable upon adoptive transfer. We have, moreover, found no evidence of either loss of idiotype-specific T cell help or generation of suppression. Therefore, neonatal exposure to PC tolerogen can effect profound, permanent changes in the antigen-specific B cell compartment independent of any influence on conventional T cell regulatory mechanisms. 相似文献
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Pasco David Smith Stuart Quan Albert Richards James Nandi Satyabrata 《Cell and tissue research》1983,234(1):57-70
The avidin-biotin-peroxidase complex immunoperoxidase technique was employed to determine the intercellular distribution of thioesterase II in rat mammary glands. This enzyme is responsible for shifting the product specificity of the fatty-acid synthetase enzyme complex from long to medium chain fatty acids. Thioesterase II was found exclusively in the cells lining the lumen of the ductal and alveolar structures in glands from mature virgin (150 days old) and pregnant rats. The ductal cell staining intensity was considerably less than that of the alveolar cells in the mature virgin rat glands. No immunoreactive thioesterase II was found in the stromal, adipose, vascular, or myoepithelial components of the gland in the developmental stages examined. In the glands from immature virgin rats (40-45 days old) thioesterase II was again found only in the epithelial cells lining the lumen of the ductal and end-bud structures although this layer was usually more than one cell thick. Quantitative determination of thioesterase II activity in cytosol preparations revealed similar levels in mammary fragments from enzymatically-dissociated glands obtained from mature virgins and in end buds derived from immature virgins, but somewhat higher levels in mammary structures derived from late-pregnant animals. These immunohistological and biochemical results demonstrate thioesterase II's usefulness as a mammary epithelial cell-specific marker. 相似文献
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A c-type cytochrome from Hydrogenomonas eutropha was purified 150-fold by butanol extraction, ammonium sulfate precipitation, and column chromatography. Three distinct c-type cytochromes were recovered which did not bind with either carbon monoxide or cyanide and hence did not appear to be denatured. Polyacrylamide gel electrophoresis indicated that one protein was acidic and the other two were basic. The acidic cytochrome c had a sedimentation coefficient of 3.46. Its amino acid composition was not markedly different from other bacterial cytochromes, but relative to mammalian cytochromes c it was low in lysine, threonine, and isoleucine and high in alanine and valine. 相似文献
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<正> 胎盘型碱性磷酸酶(P-ALP)是碱性磷酸酶(EC3.1.3.1.ALP)的一种同工酶。P-ALP除出现于妊娠妇女血清外,一些学者还从恶性肿瘤患者血清中发现此酶,并证明它是一种特异性较强的肿瘤标志物。据此,建立P-ALP的简易纯化方法,制备纯度较高的酶制品是建立P-ALP灵敏的微量检测法的先决条件。本文报道以L-苯丙氨酸(L-phe)为配基,用氯代环氧丙烷活化Sepharose 4B的亲和层析法,从人胎盘纯化P-ALP,并对其部分性质进行了研究。 相似文献