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551.
Zinnia grandiflora afforded a new elemanolide with a δ-lactone ring. 相似文献
552.
Abstract: Species composition and impact of larval parasitoids during an endemic density phase of a pine forest pest, the common pine sawfly Diprion pini (L.), were investigated by exposure of laboratory-reared larvae of the sawfly to parasitoid attack in natural habitats. Colony-associated host larvae of different instars were exposed continuously from early June until end of September of the years 1994 and 1995 in two pine stands with a different history of pine sawfly outbreaks. Host larvae were exchanged after a defined time interval and those collected up were examined in the laboratory for parasitism. Parasitoid assemblages were shown to be very species poor at both pine stands. The dominant species were the ichneumonid Olesicampe macellator and the tachinid Drino gilva , which reached attack rates on the collected host larvae of 60 and 94%, respectively, during peak activity. The patterns of temporal attack, of multiparasitism, and of superparasitism of these dominant species were studied. In an additional experiment, the response of these species to different host-patch sizes (number of host larvae per colony) were investigated. No aggregative response to higher host-patch densities could be detected. The role and function of these larval parasitoids in the population dynamics of D. pini are discussed. 相似文献
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Myenteric plexus-longitudinal muscle strips prepared from tolerant/dependent guinea-pigs and continuously exposed to normorphine, display a contracture upon naloxone challenge. This phenomenon represents a sign of abstinence. Removal of the opiate by extensive washing resulted in the failure of naloxone to induce the abstinence sign, while the plexus still displayed considerable, although reduced, tolerance to morphine. Reexposure of withdrawn preparations to normorphine reinduced the ability to display the abstinence sign. Highly tolerant preparations exhibited a 30 fold increase in sensitivity to serotonin and prostaglandin E1 when tested a few minutes after naloxone-precipitated withdrawal. Supersensitivity rapidly declined when normorphine was washed off the preparation, while reincubation of withdrawn tissues with the opiate resulted in reinduction of supersensitivity. The data confirms a close relationship between a state of tolerance and dependence (including display of the abstinence sign) and supersensitivity to putative neurotransmitters or neuromodulators, becoming evident following administration of naloxone. 相似文献
557.
F Herz 《Archives of biochemistry and biophysics》1973,158(1):225-235
KB cells, derived from a human nasopharyngeal carcinoma, have high alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) activity. Specific activity is 150 times higher than in HeLa S3 cells. Alkaline phosphatase activity in KB cells exhibits heterogeneity consisting of a large heat-labile and a small heat-stable component. Enzyme activity is modulated by the osmolality of the culture medium. Increasing the osmolality by the addition of NaCl results in reduction of activity. A similar effect is noted when KB cells are grown with prednisolone (Δ′-hydrocortisone). The activities of acid phosphatase, β-galactosidase and N-acetyl-β-glucosaminidase are not affected by hyperosmolality and/or prednisolone. The reduction in alkaline phosphatase activity is accompanied by an increase in the proportion of the heat-stable and a decrease of the heat-labile enzyme components. The alterations in specific activity and thermostability are independent of the basal culture medium employed. Enzyme stability at 56 °C is inversely related to the buffer concentration, but the differences in stability between the alkaline phosphatases of control cultures and of KB cells grown in hyperosmolar medium or with prednisolone can be recognized with various buffering mixtures. 相似文献
558.
Isolation and structure determination of goyazensolide, a new heliangolide responsible for the schistosomicidal properties of Eremanthus goyazensis Sch.-Bip., is reported. 相似文献
559.
Ashok Kumar Singhal Ram Prakash Sharma Jogendra Nath Baruah Serengolam V. Govindan Werner Herz 《Phytochemistry》1982,21(4):949-951
Roots of Millettia pachycarpa furnished retenone, cis-12a-hydroxyrotenone, rot-2′-enonic acid and cis-12a-hydroxyrot-2′-enonic acid. 相似文献
560.
Protein expression in relation to the cell cycle of exponentially growing human prostatic epithelial cells 总被引:1,自引:0,他引:1
F. Herz B. Czerniak D. Deitch R. P. Wersto D. A. Simmons L. G. Koss 《Cell proliferation》1991,24(3):321-330
This report concerns the study of the relationship between protein expression and the cell cycle in exponentially proliferating benign and malignant human prostate epithelial cells in short-term cultures. Multiparameter flow cytometric measurements were performed to correlate the expression of prostate-specific acid phosphatase, epithelial membrane antigen and epitectin with cell cycle progression. The expression of the three proteins was heterogeneous in G1 cells. The early post-mitotic cells exhibited the lowest levels when compared with late G1 cells, wherein the expression was many times greater. There was no further increase as the cells progressed through S and G2 + M. These findings, corroborating prior observations in other systems, suggest the possibility that the levels of the proteins studied increase during the G1 phase of the cell cycle and drop during or immediately after cytokinesis. As an alternate explanation, the heterogeneity of protein expression characteristic of G1 cells may be due, at least in part, to an asymmetric apportionment of cell constituents at mitosis. 相似文献