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52.
《Bioorganic & medicinal chemistry letters》2014,24(18):4538-4541
Inhibition of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway by PI3K/mTOR dual inhibitors provides a promising new approach to the treatment of cancers. In this Letter, we identified structurally novel and potent PI3K/mTOR dual inhibitors from a series of 2-amino-4-methylpyrido[2,3-d]pyrimidine derivatives. Their synthesis and structure–activity relationships are reported. 相似文献
53.
The capsular polysaccharide (CPS) of Staphylococcus aureus strain Smith was labelled by growth of bacteria in the presence of radioactive N-acetylglucosamine and was separated from labelled cell wall components by affinity chromatography on wheat germ agglutinin following dissolution of the cells by lysostaphin. The products were partially characterised chemically and immunochemically. Similar labelled components were found in the culture fluid during growth. In a pulse-chase experiment, cell-bound CPS was released continuously into the culture fluid at the same rate as cell wall turnover and there was no evidence of direct excretion of CPS. 相似文献
54.
N. D. De With 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(5):337-343
InLymnaea stagnalis, oral uptake of ambient medium was studied using51Cr-ethylenediaminetetra-acetic acid. In normal snails Cr-ethylenediaminetetra-acetic acid uptake showed two components: a
high uptake rate within the first hour followed by moderate uptake proportional with time. The tracer accumulated mainly in
the digestive system. All animals showed initial, transient uptake. Moderate uptake proportional with time did not occur in
snails in which the buccal ganglia had been extirpated, in which both the buccal ganglia had been extirpated and the oesophagus
was sectioned, or in snails provided with an oesophageal fistula. These snails did not accumulate tracer in the intestinal
system. This type of tracer accumulation clearly represented oral ingestion of surrounding water. The oral water ingestion
rate ranged from 8 to 12 μl·h−1·g−1. Assuming complete absorption, this accounts for 20–30% of the urine production rate. At low external concentrations the
contribution of oral water ingestion to Na+ balance is negligible. However, its importance will grow with increasing external concentrations and becomes a major factor
at higher concentrations. The ingestion rate increased almost sixfold when starving snails were allowed to feed. It is suggested
that oral water ingestion is a consequence of making bite cycles and swallowing. 相似文献
55.
Yukihiko Toquenaga 《Population Ecology》1993,35(1):57-68
Competition between contest and scramble strategists was examined using two strains of Callosobruchus maculatus, the contest strain (iQ) and the scramble strain (tQ). The direct larval interference experiment within each strain showed that the contest strain performed strong direct interference throughout its larval stage against the conspecific opponent(s). The scramble strain also performed its interference, but only during the 3rd and the 4th larval stages. The inter-strain larval competition experiments inside a large and small mung bean (Vigna radiata) showed that the contest strain was, in general, superior to the scramble strain in competition, but the competition results were density- and frequency-dependent. In the large beans, the proportion of adult emergence of the contest strain increased with the increase of its own initial density but decreased as the initial density of the scramble strain increased. The shape of the proportion of adult emergence became nonlinear in the small beans. The cause of the complexity of inter-strain competition results was discussed in the light of the difference in larval interference ability between the two strains. 相似文献
56.
Phytochrome A is readily cleavable by proteolytic agents to yield an amino-terminal fragment of 66 kilodalton (kDa), which
consists of residues 1 to approximately 600, and a dimer of the carboxy-terminal 55-kDa fragment, from residue 600 or so to
the carboxyl terminus. The former domain, carrying the tetrapyrrole chromophore, has been studied extensively because of its
photoactivity, while less attention has been paid to the non-chromophoric portion until quite recently. However, the evidence
gathered to date suggests that this domain is also of great improtance. We present here a review of the structure and the
biochemical and physiological functions of the two domains, of parts of these domains, and of the cooperation between them. 相似文献
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60.
Activity of salivary glands in secreting honey‐elaborating enzymes in two subspecies of honeybee (Apis mellifera L) 下载免费PDF全文
Aliaa A. Al‐Sherif Adel M. Mazeed Mohamed A. Ewis Emad A. Nafea El‐Seid E. Hagag Ahmed A. Kamel 《Physiological Entomology》2017,42(4):397-403
The activity of invertase, glucose oxidase and amylase in the cephalic (post‐cerebral) and thoracic salivary glands is determined in Egyptian and Carniolan honeybees (Apis mellifera L). For this purpose, three ages of worker bees are selected for enzyme assays. The results show that the three target enzymes are detected in the two glands during the three worker ages, except invertase, which cannot be detected in the cephalic gland of newly emerged bees of both subspecies. In both glands, the secretion of invertase is highest, followed by amylase and then glucose oxidase. In Carniolan bees, invertase secretion of the cephalic and thoracic glands increases gradually with age. In Egyptian bees, invertase increases with age only in the cephalic gland, whereas, in the thoracic gland, the highest secretion activity is detected in 10–15‐day‐old bees. The highest amounts of glucose oxidase and amylase in the cephalic gland are detected in newly emerged individuals of both Egyptian and Carniolan bees. In the thoracic gland, however, the highest activity of both enzymes is recorded only in newly emerged Egyptian bees. The results are discussed in the light of bee management and biological aspects of the two subspecies. 相似文献