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1.
Using the normal adult rat hepatocytes, plated on rat tail collagen-coated dishes and fed a chemically defined medium, we demonstrate here that ciprofibrate at 0.1 mM concentration, increases significantly the mRNA levels of fatty acyl-CoA oxidase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional protein, and thiolase (the three enzymes of the β-oxidation system), and causes peroxisome proliferation. Increase in mRNA levels of these genes was evident within 1 h and was maximal 24 h after the addition of ciprofibrate. In hepatocytes cultured in the absence of ciprofibrate, the basal levels of these enzymes were low and further declined with time. Concomitant treatment of hepatocytes with cycloheximide did not inhibit or superinduce the mRNA levels, indicating that this induction may represent a primary (direct) effect of this compound on the expression of these genes and does not apparently involve short-lived repressor protein(s).  相似文献   
2.
A number of nucleotide phosphoramidites are now available that permit the chemical synthesis of RNA, modified RNA and RNA-DNA chimeric oligonucleotides. Since the chemical strategy allows the introduction of a particular modification at any given site in a nucleotide polymer, very subtle and specific questions regarding structure-function relationships in RNA may be addressed.  相似文献   
3.
The characterization of cytokeratin (CK) in adult oral mucosa and developing teeth have been well documented in human. Cytokeratin distribution in developing oral mucosa has not yet been described. The aim of this study was to identify the expression of CK in human fetal tongue (week 10 to week 23) and to correlate the results with morphological maturation. Simple epithelial CK are expressed in all cell layers during the early stages, essentially in peridermal cells. From the 14th week, CK 18 is present only in the taste buds, making this polypeptide a reliable marker for this sensory organ. CK 4 and 13 are expressed from the 10th to the 23rd week by both ventral and dorsal lingual epithelia. Terminal differentiation keratins (CK 1, 2 and 10-11) can only be detected immunohistochemically at the 14th week in some cells on the external surface of some papillae. The number of these papillae and positive cells increase at the 19th and 23rd weeks. The terminal differentiation markers are expressed several weeks earlier than the formation of a well-distinguished keratinized layer.  相似文献   
4.
Phosphoramidite reagents can phosphitylate guanine bases at the O6-position during solid phase synthesis and serious chain cleavage occurs if the base phosphitylation is not eliminated before the iodine/water oxidation step. This can be accomplished by blocking the O6-position with a 2-cyanoethyl protecting group for deoxyribonucleotides or with a p-nitrophenylethyl group for ribonucleotides, regenerating the guanine base with water or acetate ions, or using N-methylanilinium trifluoroacetate (TAMA) as the phosphoramidite activator. The effectiveness of these methods was demonstrated by both 31P NMR studies and by the synthesis of d(Gp)23G, (Gp)14G, and d-(Gp)13rG sequences.  相似文献   
5.
A true hemoglobin (Hb) was shown to be present in the root nodules of Alnus glutinosa L. After purification by gel filtration and ion exchange, the Hb formed a stable complex with oxygen. This oxygen complex could then be converted to carboxyhemoglobin by treatment with CO. Optical absorption spectra typical of Hb were observed. The molecular weight was estimated to be 15 100 by gel filtration, and 18 300 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Hb was largely insoluble when the initial homogenization was done in the absence of a detergent. Under these conditions much of the Hb appears to be associated with clusters of Frankia , the nitrogen-fixing actinomycete that infects plant cells within the nodules. The exact localization of the Hb in vivo is uncertain. The relatively low average concentration of Hb in Alnus nodules suggests that it is either confined to a relatively small fraction of total nodule volume, or has a function other than facilitation of O2 transport.  相似文献   
6.
Preparation and regeneration of mycelial protoplasts from Alternaria eichhorniae were examined. A commercially available muralytic enzyme, Novozym 234, was used for isolation of protoplasts. The mycelial age and the pH of the stabilized buffer affected the formation of protoplasts. The maximum production of protoplasts (3,9 × 108/g fresh weight mycelia) was obtained from 24-h-old mycelia digested with Novozym 234 (20 mg/ml) in a stabilized buffer of pH 6.4 and incubated in the dark at 30°C on a rotary shaker (90 r.p.m.) for 6 h. Morphological characteristics of the protoplasts varied and depended on the age of the mycelia used in protoplast production. Moreover, mycelial age had a highly significant influence (P = 0.0001) on the frequency of protoplast regeneration.  相似文献   
7.
Alternaria infectoria E . G . Simmons was isolated from naturally infected eggs of the fig wax scale insect , Ceroplastes rusci L . (Homoptera: Coccidae) , that were showing different degrees of shriveling . This fungus proved to be pathogenic to eggs , nymphs and adults of this pest . The fungus had significant effects on both the mortality and hatchability of the eggs ( P = 0 . 0001) . Three days after exposure to the fungus , nearly one - third (31 . 5%) of the fungus - treated eggs became discolored and 17% showed moderate shrinking but no mortality . Fifteen days post - application , 91% of the fungus - treated eggs were diseased (74 . 8% of them were dead) due to A. infectoria, while no disease developed on the untreated eggs . Hatching decreased by 39 . 6% over a 15 - day period in the fungus - treated eggs compared to the control . Additionally , crawlers hatching from fungus - treated eggs became infected . The fungus seemed to induce crawlers to enter the settling stage . Seventy - two per cent of the fungus - treated crawlers versus 9% of the untreated controls entered the settling stage 6 days after exposure to the fungal inoculum . The highest level of nymphal mortality attributed to A. infectoria occurred when 30% (wet w:v blended mycelium in water containing 0 . 5% w:v Metamucil) inoculum was applied , and a high relative humidity was maintained for the following 48 h . This is the first record of A. infectoria on the fig wax scale and for the genus Alternaria as an entomopatho genic fungus .  相似文献   
8.
RBC counts, Ht value and Hb content in both species exposed to DDT and endrin concentrations were not significantly different from those of controls. WBC counts in both species exposed to the two pesticides for 96 hr decreased significantly at different concentrations. The variance ratios of cations and anions were consistently more concentrated in the serum of DDT- and endrin-exposed fishes. Serum cholesterol was sharply elevated in all the lots exposed to pesticides. Exposure to sublethal concentrations of DDT and endrin impaired liver function, as evidenced by the transfer of major cations from hepatic tissue to the serum and by elevated serum cholesterol.  相似文献   
9.
The use of deoxyribonucleotide substitution in RNA (mixed RNA/DNA polymers) permits an evaluation of the role of 2'-hydroxyl groups in ribozyme catalysis. Specific deoxyribonucleotide substitution at G9 and A13 of the ribozyme decreases the catalytic activity (kcat) of the ribozyme by factors of 14 and 20, respectively. The reduction of the reaction rate concomitant with the absence of these 2'-OHs or the 2'-OH of the substrate U7 position can be partially compensated by increasing the Mg2+ concentration above 10 mM. The KMg of the all-RNA ribozyme is 5.3 mM, and the lack of either of the three influential 2'-OHs increases this value by a factor of approximately 3. These and other reaction constants for the ribozyme and the deoxy-substituted analogues have been determined by assuming a three-step mechanism. The data presented here provide the basis for the formulation of a molecular model of ribozyme activity.  相似文献   
10.
Abstract

The synthesis of phosphoramidites of 6-modified pyrimidine ribonucleosides and their incorporation into hammerhead ribozymes and influence on nuclease stability and catalytic activity is described.  相似文献   
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