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C D Lu

Publications and source records attributed to C D Lu.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Effect of inhibition of expression PCNA with ribozyme on the proliferation of HeLa cells].

The Proliferating Cell Nuclear Antigen (PCNA), which is an auxiliary protein for DNA polymerase delta, is found to be essential for cellular DNA replication. A designed hammerhead ribozyme, with high efficiency to cleave the PCNA mRNA site-specificly in vitro, was constructed into a self-trimming expression plasmid, and then was introduced into HeLa cells by lipofectin reagent. Small molecular RNAs, isolated from total cellular RNA with the same length as active ribozyme, can cleave the target RNA in vitro, which suggested that this expression plasmid can yield active ribozyme molecules in cells. In comparison with the vector control, the entrance of S phase of the HeLa cells transfected by the ribozyme expression plasmid was delayed 8 hours after serum stimulation. Mean-while, those cells transfected by mutant inactive ribozyme as antisense RNA control was delayed only 3 hours. These results demonstrated that this ribozyme can inhibit the DNA replication in HeLa cells effectively and could be used as a potential tool to study the function of PCNA in cellular DNA replication and cell cycle progression.

Cell Cycle↗
PubMed1995

Participation of the purine repressor in control of the carbamoylphosphate synthetase operon in Salmonella typhimurium.

Previous work has shown that the carAB operon of Salmonella typhimurium is transcribed from tandem promoters, P1 and P2, that are negatively controlled by pyrimidines and arginine, respectively. The results reported here show that purines also negatively control expression of carAB and that this effect is absent in a purR::Tn10 derivative. Primer-extension experiments established that the purine effect is exerted at P1, thus redefining this promoter as sensitive to both purines and pyrimidines. The results of gel-retardation experiments as well as DNase I and premethylation footprintings indicate that the purine repressor interacts with a PUR box 85 bp upstream of P1. Modification of this PUR box by site-directed mutagenesis abolishes the repression by purines in a carA::lacZ fusion, confirming that this box functions in vivo in purine control of carAB expression.

Amino Acid Sequence↗
PubMed1995

Response to dietary fat and cholesterol in young adult boars genetically selected for high or low plasma cholesterol.

Twenty-eight young adult boars (age 7 to 8 mo) genetically selected for four generations for high (HG) or low (LG) plasma cholesterol were studied to assess dietary and genetic effects and their interactions on cholesterol metabolism. Boars within a genetic group were paired according to their plasma cholesterol concentration at 8 wk of age and were fed for 15 wk (2.7 kg/d) one of two diets (16.5% fat and 1,156 mg of cholesterol/kg diet, HD; or 3.1% fat and 0 cholesterol diet, LD) in a 2 x 2 factorial arrangement. Plasma total cholesterol (P < .01) and HDL-cholesterol (P < .01) concentrations were higher in boars fed HS (P < .01) and in HG boars (P < .01). There was a trend toward a diet x genotype interaction for plasma HDL-cholesterol (P < .06). Plasma insulin concentration tended to be lower in boars fed HD (P < .09) or HG boars (P < .10). There was a diet x genotype interaction for plasma glucagon (P < .04) concentration and a trend toward an interaction for insulin (P < .07). After 15 wk, all boars were killed by electrocution and exsanguination and measurements were taken. Backfat thickness was greater (P < .01) and carcass length (P < .01) and weights of the four lean cuts (P < .02) were lower in LG than in HG boars. No microscopic atherosclerotic plaques were observed in aorta or coronary arteries. Cholesterol concentration in subcutaneous fat was lower (P < .04) in LG boars, suggesting that cholesterol content of depot fat can be reduced by genetic selection in swine.

Adipose Tissue↗
PubMed1994

Structure and regulation of the carAB operon in Pseudomonas aeruginosa and Pseudomonas stutzeri: no untranslated region exists.

The carAB operons from Pseudomonas aeruginosa PAO1 and Pseudomonas stutzeri JM300 were characterized by Southern and DNA sequence analyses. The results show that the previously reported sequence for carA (S. C. Wong and A. T. Abdelal, J. Bacteriol. 172:630-642, 1990) is derived from P. stutzeri and not P. aeruginosa, as originally reported. Therefore, the amino-terminal sequence of the purified carA product is identical to that derived from the nucleotide sequence in both organisms, P. stutzeri having four additional amino acids. The results also show that while carA and carB are contiguous in P. stutzeri, as is the case in other bacteria, they are surprisingly separated by an open reading frame (ORF) of 216 amino acids in P. aeruginosa. S1 nuclease mapping experiments with RNA extracted under a variety of growth conditions, as well as experiments using different lacZ fusions, indicate that the carA-ORF-carB operon of P. aeruginosa is transcribed from a single promoter. Moreover, these experiments demonstrate that expression of this single transcript is controlled by both arginine and pyrimidines and that variation in arginine levels specifically modulates transcriptional initiation, while pyrimidine regulation is exerted subsequent to transcriptional initiation. Modification of a rho-independent terminator-like structure, which is present upstream of carA in P. aeruginosa, removed all transcriptional sensitivity of a carA::lacZ fusion to pyrimidines. This result, when coupled with the finding that translation of an 18-amino-acid leader polypeptide (associated with this putative rho-independent terminator), is inversely proportional to pyrimidine concentration in the cell, strongly suggests that regulation of carA by pyrimidines is mediated through an attenuation-type mechanism in P. aeruginosa.

Amino Acid Sequence↗
PubMed1994

Lipiodolization with or without gelatin sponge in hepatic arterial chemoembolization for hepatocellular carcinoma.

Fifty-two patients with unresectable hepatocellular carcinoma were divided into 2 groups. Group A (n = 24) received lipiodolization with gelatin sponge and group B (n = 28) lipiodolization alone. Angiography after hepatic arterial chemoembolization revealed a satisfactory accumulation of lipiodol and obliteration of the microvasculature in the tumors in both groups. However, prolonged obliteration of proximal hepatic arteries was noted in 70%-80% of patients in group A, in contrast to the patency of the arteries in group B. Collateral circulation was found more frequently in group A than in group B, in which recanalization of tumor vessels and phenomenon of iodized oil "wash-out" were seen. There were no significant differences in therapeutic effects in patients with low risk. In those with high risk, the response rates were 28.6% and 64.2%. The half-year survival rates were 28.5% and 62.8%, 1-year survival rates 7.1% and 27.5%, and 2-year survival rates 0% and 13.7% in group A and B respectively. The differences were significant (P < 0.05). Serious complications occurred more frequently in group A than in group B. The therapeutic effects of lipiodolization without gelatin sponge for patients with high risk were significantly superior to those of lipiodolization with gelatin sponge. We conclude that the modality of hepatic arterial chemoembolization should be chosen according to the patient's clinical conditions.

Adult↗
PubMed1993

In vitro cleavage of HPV16 E6 and E7 RNA fragments by synthetic ribozymes and transcribed ribozymes from RNA-trimming plasmids.

A RNA-trimming plasmid pRG523 is constructed, in which three Rz genes, GR5(5'-cis-Rz gene), HR2G(trans-Rz gene) and GR3(3'-cis-Rz gene), are arranged in the order from 5' to 3' downstream from the T7 promoter. In vitro transcription of this plasmid shows that the trans-Rz can be trimmed to definite lengths by the cis-Rz on both sides of the trans-Rz. In vitro cleavage of HPV16 E6 and E7 RNA fragments of different lengths by synthetic Rz and that of E7 RNA with a length of 171 nt by synthetic Rz and transcribed Rzs with different lengths of flanking sequences is studied. The results show that the non-base-pairing flanking sequences on both Rz and target RNA can affect the cleavage reaction.

Base Sequence↗
PubMed1993

Complete sequence of the Salmonella typhimurium gene encoding malate dehydrogenase.

The nucleotide (nt) sequence of mdh (encoding malate dehydrogenase) in Salmonella typhimurium is presented. The relative positions of argR (encoding arginine repressor) and mdh on the chromosome of S. typhimurium were determined from analysis of the nt sequence. The homology of the 3'-terminal end with only one of two published mdh sequences in Escherichia coli identifies the correct sequence in this organism.

Amino Acid Sequence↗
PubMed1993

Sulfate supplementation of growing goats: effects on performance, acid-base balance, and nutrient digestibilities.

Castrated male goat kids (20 Alpine, 12 Angora) were individually fed isonitrogenous and isoenergetic diets containing 2.28% N and S (added as CaSO4) at either .11 (basal), .20, .28, or .38% of dietary DM. Sulfate supplementation during the 8-wk growth trial quadratically increased ADG (P < .05) and tended to increase quadratically the DMI (P < .07) of goats, with a peak value for the .20% S diet. Even when analyzed using DMI as a covariate, ADG was quadratically increased (P < .05) by added S. Sulfate supplementation linearly increased (P < .001) S intake, fecal S output, and S retention. Sulfate supplementation tended to increase quadratically (P < .06) the blood plasma concentration of L-lactate. However, sulfate supplementation did not significantly affect (P > .10) plasma sulfate, plasma cystine, ruminal ammonia N concentrations, or purine N content of isolated ruminal bacteria. Sulfate supplementation quadratically increased (P < .05) fractional N retention. Urinary output of uric acid increased quadratically (P < .01) with S supplementation, presumably reflecting ruminal bacterial protein synthesis. Calculated by regression, the optimal dietary S content for maximum ADG was .22% S (N:S = 10.4:1), for maximum DMI it was .24% S (N:S = 9.5: 1), for maximum N retention it was .23% (N:S = 9.9: 1), and for maximum absorbed N retained it was .22% (N:S = 10.4:1). These results support the current estimate of the S requirement of goats for growth (N:S = 10:1).

Acid-Base Equilibrium↗
PubMed1992

PCNA-dependent DNA polymerase delta from rabbit bone marrow.

Proliferating cell nuclear antigen (PCNA) and PCNA-dependent DNA polymerase delta were partially purified and characterized from rabbit bone marrow. Rabbit DNA polymerase delta sediments at 8.2 S upon glycerol density gradient centrifugation. Similar to calf thymus PCNA-dependent DNA polymerase delta, a 125-123-kDa doublet and 48-kDa polypeptides correlate with DNA polymerase activity. Western blotting of rabbit DNA polymerase delta with polyclonal antibody to calf thymus PCNA-dependent DNA polymerase delta gives the same results as calf thymus delta; the 125-123-kDa doublet is recognized. PCNA-dependent DNA polymerase delta is resistant to inhibition by dideoxynucleotides and is relatively insensitive to inhibition by N2-[p-(n-butyl)phenyl]dGTP. A 3'-->5' exonuclease copurifies with the DNA polymerase. The processivity of DNA polymerase delta alone is very low but greatly increases with the addition of PCNA from rabbit bone marrow or calf thymus. Comparative studies of the original DNA polymerase delta from rabbit bone marrow demonstrate a lack of recognition by antibodies to calf thymus delta and a high degree of processivity in the absence of PCNA. Additionally, the originally described DNA polymerase delta is a single polypeptide of 122 kDa. These features would recategorize the original delta to the epsilon category by recently proposed convention. PCNA-dependent DNA polymerase delta is a relatively minor component of rabbit bone marrow compared to DNA polymerase alpha and PCNA-independent DNA polymerase delta (epsilon), the relative proportions being alpha, 60%; delta, 7%; and epsilon, 30%.

Animals↗
PubMed1992

Characterization of the arginine repressor from Salmonella typhimurium and its interactions with the carAB operator.

Primer extension experiments showed that the argR gene, encoding the arginine repressor in Salmonella typhimurium, is transcribed from a single promoter that is negatively regulated by arginine. A repressor overproducing strain was constructed and the repressor was purified to homogeneity. Gel filtration, sedimentation and cross-linking studies established that the native repressor is a hexamer of identical 17,000 Mr subunits. Gel retardation experiments indicate that the apparent dissociation constant for repressor/carAB operator is 6 x 10(-12) M. These experiments showed that arginine is essential for binding of the repressor to the DNA and that pyrimidine nucleotides have no significant effect on this binding. These results indicate that the effect of pyrimidines on expression of the arginine sensitive "downstream" carAB promoter is not directly mediated by the arginine repressor. These experiments also suggest that a single hexamer binds to the carAB operator, which carries two previously defined "ARG box" sequences that characterize operators for arg genes. Gel retardation experiments with DNA fragments carrying the individual ARG boxes showed that both boxes are required for effective binding of the hexameric repressor to the operator, indicating that the ARG boxes comprise a single binding site for the repressor. Analysis of the potential secondary structure of the arginine repressor does not reveal any of the recognizable structural motifs common to a number of DNA-binding proteins. A combination of DNase I, premethylation interference, depurination and hydroxyl radical footprinting techniques were employed to characterize the interactions of the repressor with the carAB operator, with the results suggesting that the repressor predominantly interacts with A.T residues in this region. Comparative DNA sequence analysis of the known arginine operators of enteric bacteria further indicates that the specificity of interaction may be based more on the precise distance between two defined A.T-rich regions rather than on the specific nucleotide sequence.

Amino Acid Sequence↗
PubMed1992

Sulfate supplementation of alpine goats: effects on milk yield and composition, metabolites, nutrient digestibilities, and acid-base balance.

Effects of sulfate supplementation on milk yield and composition, ruminal and blood metabolites, acid-base status, and nutrient digestibilities were determined using 30 multiparous, lactating Alpine does. Goats were fed isonitrogenous diets containing .16 (basal), .26, or .36% S (DM basis) during a 13-wk lactation trial that coincided with wk 3 to 15 of lactation. During wk 16 to 17, four does from each treatment were placed in a metabolism crate to measure nutrient digestibility and balance. Feed intake, yield of 4% fat-corrected milk, and milk S content were not affected by added S, but the goats fed the .26% S diet had a trend of higher persistency of lactation (P < .20). During wk 10 and 15 of lactation, milk solids-not-fat percentage was higher (P < .10) for does fed the .26% S diet. Sulfur supplementation resulted in quadratic decreases in ruminal ammonia N (P < .05) in wk 15 and in plasma urea N in wk 10 and 15 (P < .05) but in linear increases (P < .05) in ruminal protein S concentrations throughout the experiment. Added S had little effect on blood acid-base status. Apparent digestibilities of DM, OM, ash, ADF, and GE were increased linearly (P < .10) by added S. The milk N:S ratio remained constant. Increasing S from .16 to .26% of diet DM was beneficial to lactating Alpine goats during early lactation.

Acid-Base Equilibrium↗
PubMed1992

Dietary protein level and ruminal degradability for mohair production in Angora goats.

Twenty-eight Angora goat doelings (average BW 22.1 kg) were used in a 150-d study to examine the effects of dietary CP level and degradability on mohair fiber production. A 2 x 2 factorial arrangement was instituted using conventional, solvent-extracted soybean meal (high degradability) or expelled, heat-treated soybean meal (low degradability) incorporated into low- (12%) or high- (19%) CP diets. Grease and clean mohair weights were greater (P less than .05) in goats fed the diets containing 19% CP. Mohair fiber diameter was not affected (P greater than .10) by dietary CP level. Clean mohair weight tended (P less than .08) to be higher in the goats fed diets containing expelled, heat-treated soybean meal. Body weight gains were not affected (P greater than .10) by CP level or degradability, whereas DMI increased (P less than .01) with increasing CP level. Ruminal fluid pH and total VFA concentrations were not affected (P greater than .10) by diet. Ruminal ammonia N concentration increased (P less than .05) as CP level in the diet increased, and postprandial changes in concentrations were less noticeable in the group fed expelled, heat-treated soybean meal. Plasma urea N (P less than .001) and total protein (P less than .01) concentration increased as dietary CP level increased. Plasma glucose was elevated (P less than .001) 2 h after feeding in the goats fed conventional, solvent-extracted soybean meal, whereas glucagon concentrations were greater at 0 and 4 h in the group fed expelled, heat-treated soybean meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1992

Sulfate supplementation of Angora goats: metabolic and mohair responses.

Eight castrated male Angora goats were used in a repeated, simultaneous 4 x 4 Latin square designed experiment to evaluate metabolic and mohair responses of Angora goats to sulfate supplementation. Goats had ad libitum access to isonitrogenous diets containing a .16 (basal), .23, .29, or .34% S (DM basis), which yielded N:S ratios of 12.7, 8.3, 6.8, or 5.5:1. Feed intakes were not affected (P greater than .20) by dietary S level. Quadratic increases (P less than .05) to S supplementation were observed in grease and clean mohair production, grease and clean staple strength, and staple length. Mohair diameter, med fiber, kemp fiber, S, and cysteine contents were not affected (P greater than .05) by supplemental S. Averaged across the prefeeding, 2, 4, and 6 h postprandial sampling times, ruminal pH, ammonia N, total S, organic S, protein S, and plasma urea N and organic S concentrations were quadratically increased (P less than .05) by supplemental S. Ruminal sulfate S, total sulfide S, and plasma sulfate S were linearly increased (P less than .05) by supplemental S. Retention of N and mohair S yield exhibited quadratic increases (P less than .05), but S retention exhibited a linear increase (P less than .001) with increased S intake. Calculated by regression, the optimum dietary S concentration for maximum clean mohair production was .267% of dietary DM for a N:S ratio of 7.2:1, suggesting that the National Research Council N:S ratio of 10:1 is inadequate for Angora goats. The optimum level of digestible S was calculated to be .18% of the diet DM.

Animal Feed↗
PubMed1992

Dietary fiber and milk yield, mastication, digestion, and the rate of passage in goats fed alfalfa hay.

Two experiments were conducted to study the effect of intake of fiber on productive performance of high producing dairy goats during early to midlactation. Four dietary treatments were isonitrogenous and consisted of combinations of chopped alfalfa hay and concentrate, yielding 14, 18, 22, and 26% ADF. In Experiment 1, 40 multiparous Alpine does were used in a completely randomized block design. Milk fat content and total chewing time increased, and milk yield tended to decrease, as dietary ADF intake increased. Chewing efficiency [min/(g x kg BW.75)] for DM decreased, whereas that for ADF increased as ADF intake increased. Prediction equations were the following: milk fat yield, g/d = 115.78 - .128 x ADF intake, g/d + .00021 X (ADF intake)2 (r = .55); total chewing time, min/d = 345.33 + .32 x ADF intake, g/d (r = .60). In Experiment 2, 20 does were used in a completely randomized design. Apparent digestibilities of DM and energy decreased as dietary ADF intake increased. Rumen turnover rate and transit time of liquid were affected by ADF intake. Transit time of hay decreased as ADF intake increased. Intake of ADF affected pH and ammonia, acetate, and butyrate concentrations in the rumen. Acetate to propionate ration increased with ADF intake. No apparent trends were observed in whole blood beta-hydroxybutyrate or in plasma NEFA concentrations related to ADF intake. It appeared that DMI and milk fat yield leveled at 22% ADF or 43% NDF. For lactating dairy goats producing more than 3.5 kg/d of milk, calculated fat output reached a plateau when they consumed 587 g/d of ADF and spent 512 min/d chewing.

3-Hydroxybutyric Acid↗
PubMed1991

Conformation of DNA-DNA polymerase I complex observed by scanning tunneling microscopy.

The conformation of a complex of a 41 mer/31 mer DNA fragment and the Klenow fragment of DNA polymerase I of Escherichia coli was studied by scanning tunnelling microscopy (STM). The results shows that near two turns of double helix of this DNA fragment was outside of enzyme while another part containing more than one turn of helix and 10 nucleotides single strand was combined with enzyme. The dimension and shape of DNA polymerase I (KF) in complex were different from that of free enzyme. The conformation of DNA-DNA polymerase I (KF) complex and the application of STM in studying structure of complex of DNA polymerase with DNA were discussed.

Base Sequence↗
PubMed1990

Influence of alfalfa maturity on feed intake and site of nutrient digestion in sheep.

Four wethers fitted with ruminal, duodenal and ileal cannulas were used to study effects of maturity of alfalfa hay on intake, digestion and rate of passage of nutrients in various sites of the digestive tract. Pre-, early-, and mid-bloom hays were harvested from the same field; full-bloom hay was acquired from elsewhere due to wether conditions. Dry matter intake decreased (P less than .05) as intakes of NDF and ADF increased. This was attributed to decreased digestibility and increased retention time of undigested residues. Digestion of OM in the stomach (% of intake) was 44.2, 47.4, 38.8 and 35.1 for pre-, early-, mid- and full-bloom hay, respectively. Digestion of ADF in the stomach was lower for mid-bloom than for pre-and early-bloom hay (P less than .05). Degradation of alfalfa protein in the rumen was 94, 88, 81 and 78% for pre-, early-, mid- and full-bloom hay, respectively. Concentration of ruminal NH3 N, flow of N at the duodenum, fecal N and urinary N decreased of the hay and to N intake. Digestion of N in the small intestine (g/d) decreased as maturity advanced (P less than .05). Duodenal flow of total amino acids was greater (P less than .05) when animals consumed pre-bloom hay than when they consumed more mature hays. Relative feed value calculated from the detergent fiber analysis correlated with actual value determined biologically (r = +.81). Intake and site of nutrient digestion of alfalfa hay were influenced by the stage of maturity at harvest.

Amino Acids↗