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981.
1. The biosynthesis of cholesterol was studied, by using various precursors, in rats subjected to several dietary regimes. 2. The use of 3H2O as a substrate to demonstrate differences in cholesterogenesis under various conditions was validated by using rats fed on cholesterol or cholestyramine. Cholesterol feeding resulted in decreased cholesterogenesis, whereas cholestyramine caused an increase. 3. With acetate as precursor, the biosynthesis of both digitonin-precipitable sterol and fatty acids was increased in vitro in response to a meal. 4. In rats fed ad libitum, hepatic cholesterogenesis was increased at midnight relative to mid-morning as measured by using acetate precursor in vitro. However, no such difference was found by using 3H2O in vivo. 5. The lipogenic response was measured in meal-fed rats by using 3H2O or octanoate in vivo. In contrast with findings with acetate in vitro, no postprandial stimulation of cholesterogenesis was seen with either 3H2O or octanoate as precursor, whereas fatty acid biosynthesis from either substrate was increased. 6. These findings are discussed with respect to current theories about the circadian rhythm of cholesterogenesis. Such theories are based on experiments using isolated enzyme measurements or non-physiological precursors such as acetate. 7. It is considered that results obtained with 3H2O give an accurate representation of cholesterogenesis under various conditions, and it is therefore suggested that hepatic cholesterogenesis in rats is not subjected to the same degree of diurnal rhythm as has previously been believed. 相似文献
982.
983.
JT Willerson RW Parkey EM Stokely FJ Bonte S Lewis RA Harris G Blomqvist LR Poliner LM Buja 《Canadian Metallurgical Quarterly》1977,11(4):291-298
The dynamics of changes in serum lipids (free fatty acids, free glycerol, triglycerides, total cholesterol, and phospholipids) were studied in male Wistar rats irradiated in an open experimental field with a daily dose of 15.48 mC.kg.--1 (60 R) up to a total exposure of 774.0 mC. kg.--1 (3,000 R). The resulting changes occurred in several periods. Initial period of 0--7 days included a drop in triglyceride level and a rise in free glycerol, total cholesterol, and phospholipids in both control and irradiated rats. The period of 14--25 days marked the appearance of serum hyperlipaemia. Between 25--50 days, the levels of the different fractions oscillated and existing changes became more pronounced. The general level of serum lipids during continuous gamma-irradiation exceeded that found in controls. Changes in control animals from experimental field reflected the influence of a changed environment. The modifying factor affecting both irradiated and control rats was night fasting prior to sacrificing the animals and, probably, also the presence of an infradian rhythm in some serum lipid fractions. 相似文献
984.
A high-pressure liquid chromatographic procedure for the selective determination of adenosine in the presence of other nucleic acid components is reported. Reversed-phase microparticle columns and an isocratic elution mode of dilute potassium dihydrophosphate and anhydrous methanol were used. The analysis is specific for adenosine and is achieved in less than 10 min. An example of the use of this analysis in a biomedical study is reported. 相似文献
985.
RA Silva G Morales E Eulert A Montenegro R Yba?ez 《Canadian Metallurgical Quarterly》1998,76(1-2):153-157
Some new commercial methods for the extraction of viral RNA have been introduced recently. In addition to the study published previously (Verhofstede, C., Reniers, S., Van Wanzeele. F., Plum J., 1996. AIDS 8, 1421-1427), seven different methods (four newly developed and three reference methods) for extraction of HIV-1 RNA from plasma have been evaluated. The RNA preparation method that gave the best results (acceptable reproducibility, highest sensitivity, reasonable price, fast and easy to perform), was the QIAamp Viral RNA kit from QIAgen. The High Pure Viral RNA Kit (Boehringer Mannheim) as well as the non-commercialised extraction kits were also very sensitive. The non-commercial tests seem less suitable for routine use and for the processing of large number of samples. Two methods, RNA Insta-Pure LS (Eurogentec) and PANext RNA extraction kit 1 (NTL, PANsystems GmbH) are not adapted for HIV plasma extraction. The single step methods using glass fibre or silica column are rapid (from 60 to 75 min depending on the number of wash steps) and although the price is high they are cheaper than the Boom extraction methods: High Pure Viral RNA Kit (Boehringer Mannheim) ($3.3/sample), QIAamp Viral RNA Kit (Qiagen) ($3.6/sample), Boom extraction ($5/sample). The Qiagen kit is the only kit that combines sensitivity with reproducibility, it is commercialised, rapid and affordable in price and can be automated. For most of the methods evaluated the inter-test variability was acceptable (mean variation coefficient between duplicate extractions varied between 26.4 and 48.6%). 相似文献
986.
KS Warren RA Swan RP Hobbs Heriyanto EM Kuhn JL Heeney 《Canadian Metallurgical Quarterly》1998,34(3):644-646
The liver fluke Platynosomum fastosum was identified upon necropsy of three ex-captive orangutans (Pongo pygmaeus) which had been part of a rehabilitation program for reintroduction to the wild. This trematode has not been reported in orangutans previously and is commonly found in cats in Southeast Asia. Cross infection from cats via intermediate hosts, to orangutans kept in captivity as pets, could explain their presence in the latter. Although P. fastosum caused intrahepatic and bile duct damage, death of the hosts could not be attributed solely to the presence of the liver fluke infection. 相似文献
987.
Arf proteins are ubiquitous, eukaryotic regulators of virtually every step of vesicular membrane traffic. ADP-ribosylation factors are essential in yeast and the lethality resulting from either overexpression or underexpression (deletion) of Arf genes has previously been ascribed to dysregulation of the secretory process. We have identified a family of four genes (Suppressors of Arf ts, SAT) as high copy suppressors of a loss of function allele of ARF1 (arf1-3). Those proteins with SAT activity were found to contain a minimal consensus motif, including a C2C2H2 cluster with a novel and specific spacing. Genetic interactions between members of this family and with ARF1 are consistent with each sharing a common cellular pathway. Included in this family is Gcs1, a protein previously described (Poon, P. P., Wang, X., Rotman, M., Huber, I., Cukierman, E., Cassel, D., Singer, R. A., and Johnston, G. C. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 10074-10077) to possess Arf GTPase-activating protein (GAP) activity, demonstrating a direct interaction between Arf and at least one of these suppressors. The suppression of the loss of Arf function by overexpression of Gcs1 and demonstration of direct, preferential binding of Gcs1 to the activated form of Arf (Arf.GTP) lead us to conclude that the biological role of Gcs1 is as an effector of the essential function of Arf in mitotic growth, rather than a down-regulator as implied by the biochemical (Arf GAP) activity. Suppression of the growth defect of arf1(-3) cells was observed under conditions that did not alter the secretory defect associated with arf1(-) mutation, indicating that the essential role of Arf in eukaryotes can be distinguished from role(s) in the secretory pathway and appear to employ distinct pathways and effectors. 相似文献
988.
Z Zhang O Sibbesen RA Johnson PR Ortiz de Montellano 《Canadian Metallurgical Quarterly》1998,6(9):1501-1508
The catalytic turnover of xenobiotics by cytochrome P450cam results in both the formation of organic metabolites and the uncoupled production of H2O2, and H2O. Previous studies have shown that a receptor-constrained three-dimensional screening program (DOCK) can be used to identify potential ligands (ergo substrates) for the enzyme (De Voss, J. J.; Sibbesen, O.; Zhang, Z.; Ortiz de Montellano, P. R. J. Am. Chem. Soc. 1997, 119, 5489). A new set of 10 compounds has now been examined to further test the substrate specificity of P450cam and the ability of DOCK to identify substrates for this enzyme. The results expand the known specificity of P450cam and define limitations in the use of DOCK to predict its substrate specificity. 相似文献
989.
IR Weber R Neidlein W von der Saal F Grams H Leinert K Strein RA Engh R Kucznierz 《Canadian Metallurgical Quarterly》1998,8(13):1613-1618
Based on the structures of aminopyridine thrombin inhibitors (1), a series of aminoalkyl- and guanidinoalkyl-substituted diarylsulfonamides were prepared. The most potent derivative, N-[3-(4-guanidinobutoxy)-5-methyl-phenyl]-benzenesulfonamide (6c) had Ki = 0.18 microM for thrombin and did not inhibit trypsin, plasmin, or factor Xa. Comparison of the X-ray structures of the thrombin/1b and the thrombin/6c complexes revealed important aspects which govern the binding of such diarylsulfonamides to thrombin. 相似文献
990.
BG Taal CA Hoefnagel RA Valdes Olmos H Boot JH Beijnen 《Canadian Metallurgical Quarterly》1996,14(6):1829-1838
PURPOSE: To evaluate the therapeutic effect of iodine-131-labeled metaiodobenzylguanidine (131I-MIBG) and unlabeled MIBG in patients with carcinoid tumor. MATERIALS AND METHODS: A therapeutic dose of 7.4 GBq (200 mCi) 131I-MIBG infused over 4 hours was administered to 30 patients with either carcinoid syndrome (n = 20) or tumor symptoms such as pain and fever due to carcinoid tumor (n = 10). In general, two courses were given, 6 weeks apart. Due to radioactivity, patients had to be isolated for 5 to 7 days. Subsequently, we studied the effect of unlabeled MIBG based on the possible pharmaceutic activity of MIBG and to avoid the isolation procedure. A doseescalation study of 8.5, 17, and 34 mg/m2 MIBG infused over 4 hours at 4-week intervals was performed in 20 patients with carcinoid syndrome who were not suitable for treatment with the radioactive compound. RESULTS: Following 131I-MIBG treatment, symptomatic responses were observed in 60% of patients (median duration, 8 months; maximum, 2 years). Side effects were mild and rapidly reversible in 16 patients, and were related to the isolation procedure in seven of these patients. Unlabeled MIBG resulted in symptomatic improvement in 60% of patients (median duration, 4.5 months). Side effects, which included changes in blood pressure, were mild and transient. Symptomatic responses were not accompanied by biochemical responses. CONCLUSION: Both MIBG treatment regimens were equally effective in the palliation of symptoms, but duration of response tended to be much longer with the radioactive compound. However, the unlabeled compound provided a simpler treatment, eg, in elderly patients and those in poor condition, without the need for isolation. 相似文献