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1.
An endodeoxyribonuclease, designated CreI, was purified 16,000-fold from zygotes of the eukaryote Chlamydomonas reinhardtii. CreI preferentially attacks the sequence TATA producing double strand breaks with 3'-phosphomonoester and 5'-hydroxyl termini. The endonuclease has an Mr = 27,000 and requires Ca2+ at pH 7.5 for optimal activity. 相似文献
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G Sager 《Gegenbaurs morphologisches Jahrbuch》1987,133(4):563-571
Series of values for body height of adults ranging from 150 to 190 cm and the corresponding body weights for 9 age groups from 15 to 65 a are interrelated by 5 test functions. Results of nonlinear regressions as gained by minimization of the sums of the squares and absolute values of the deviations are summarized in tables for comparison. The last position in the goodness-of-fit is held by the allometric relation W = alpha L beta preceded by the exponential type W = abL. No considerable gain can be realised by taking the expression W = a exp (b Lp). A big step is reached, however, with the change to the form W = W150 + alpha (L-150) beta reducing the linear deviations to about 1/3 or more. Finally the 3-parameter structure W = W A + alpha (L-150) beta yields even closer approximations. Tables with the results for the last 2 relations are given together with a graph for the best approximation. 相似文献
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R. Myles Riner Kathryn Maino Collins Garrett E. Foulke George V. Moorhead Phillip Terry 《The Western journal of medicine》1987,147(5):602-608
In a pilot project sponsored by the California State Emergency Medical Services Authority, validated, verifiable criteria were developed for the vertical categorization of hospital emergency services in 11 different groupings of medical and surgical emergencies. We describe the development of an assessment process and categorization criteria to identify the most appropriate receiving facility for interfacility transfer and, in selected instances, field triage of patients with different levels of severity of illness or injury. We propose that this facility assessment project be used in the critical care planning process for the eventual vertical categorization of hospital emergency services in California and as a template for similar projects in other states. 相似文献
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Deoxyribonucleoside triphosphate imbalance. 5-Fluorodeoxyuridine-induced DNA double strand breaks in mouse FM3A cells and the mechanism of cell death 总被引:10,自引:0,他引:10
A Yoshioka S Tanaka O Hiraoka Y Koyama Y Hirota D Ayusawa T Seno C Garrett Y Wataya 《The Journal of biological chemistry》1987,262(17):8235-8241
The mechanism of cytotoxic action of 5-fluorodeoxyuridine (FdUrd) in mouse FM3A cells was investigated. We observed the FdUrd-induced imbalance of intracellular deoxyribonucleoside triphosphate (dNTP) pools and subsequent double strand breaks in mature DNA, accompanied by cell death. The imbalance of dNTP pools was maximal at 8 h after 1 microM FdUrd treatment; a depletion of dTTP and dGTP pools and an increase in the dATP pool were observed. The addition of FdUrd in culture medium induced strand breaks in DNA, giving rise to a 90 S peak by alkaline sucrose gradient sedimentation. The loss of cell viability and colony-forming ability occurred at about 10 h. DNA double strand breaks as measured by the neutral elution method were also observed in FdUrd-treated cells about 10 h after the addition. These results lead us to propose that DNA double strand breaks play an important role in the mechanism of FdUrd-mediated cell death. A comparison of the ratio of single and double strand breaks induced by FdUrd to that observed following radiation suggested that FdUrd produced double strand breaks exclusively. Cycloheximide inhibited both the production of DNA double strand breaks and the FdUrd-induced cell death. An activity that can induce DNA double strand breaks was detected in the lysate of FdUrd-treated FM3A cells but not in the untreated cells. This suggests that FdUrd induces the cellular DNA double strand breaking activity. The FdUrd-induced DNA strand breaks and cell death appear to occur in the S phase. Our results indicate that imbalance of the dNTP pools is a trigger for double strand DNA break and cell death. 相似文献
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Summary Electron microscopy of cat parotid glands revealed great heterogeneity in the secretory granules of normal unstimulated acinar cells. Electrical stimulation of the parasympathetic nerve to the gland evoked a copious flow of parotid saliva which was accompanied by an extensive depletion of the secretory granules from the acinar cells. Exocytosis was captured as it was occurring by means of perfusion-fixation, and showed that the events occur in a conventional manner. Stimulation of the sympathetic nerve caused only a very small flow of saliva, and no acinar degranulation was detected. It can be concluded that the parasympathetic secretomotor axons provide the main drive for parotid acinar degranulation in the cat. This contrasts with the rat in which sympathetic impulses provide the main stimulus for parotid acinar degranulation. These dissimilarities serve to emphasise how extensively species differences may influence autonomic responses in salivary glands. 相似文献
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Comparison of transfer RNA and ribosomal RNA intron splicing in the extreme thermophile and archaebacterium Desulfurococcus mobilis 总被引:8,自引:0,他引:8
The structure of the exon-intron boundary was compared for an intron within 23S ribosomal RNA of Desulfurococcus mobilis and a newly discovered intron in tRNA(Met) from the same organism. The occurrence of a putative common structural feature suggests that intron excision occurs by the same mechanism. The possible recognition of this structural feature by the cleavage enzyme was investigated for the ribosomal RNA intron using RNA substrates exhibiting various exon and intron deletions. The results support the involvement of the structural features in the cleavage process. The evolutionary implications of these results are considered. 相似文献