PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Transfer”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed1977

Stringent regulation of the synthesis of a transfer ribonucleic acid biosynthetic enzyme: transfer ribonucleic acid(m5U)methyltransferase from Escherichia coli.

This paper describes the regulation of a transfer ribonucleic acid (tRNA) biosynthetic enzyme, the tRNA(m5U)methyltransferase (EC 2.1.1.35). This enzyme catalyzes the formation of 5-methyluridine (m5U, ribothymidine) in all tRNA chains of Escherichia coli. Partial deprivation of charged tRNAVal can be imposed by shifting strains carrying a temperature-sensitive valyl-tRNA ligase from a permissive to a semipermissive temperature. By using two such strains differing only in the allelic state of the relA gene, it was possible to show the tRNA(m5U)methyltransferase to be stringently regulated. Upon partial deprivation of charged tRNAVal, the differential rate of tRNA(m5U)methyltransferase synthesis was found to decrease in a strain with stringent RNA control (relA+), whereas it increased in the strain carrying the relA allele. This increase of accumulation of tRNA(m5U)methyltransferase activity required protein synthesis. Thus, when tRNA is partially uncharged in the cell, the relA gene product influences the expression of tRNA(m5U)methyltransferase gene.

Bacterial Proteins↗
PubMed1977

In vivo aminoacylation of transfer ribonucleic acid in Bacillus subtilis and evidence for differential utilization of lysine-isoaccepting transfer ribonucleic acid species.

The presence or absence of certain amino acids has different effects on the ability of Bacillus subtilis to sporulate, and the intracellular pool size of amino acids has been reported to vary during sporulation. The idea that these variations might exert a regulatory effect through aminoacylation of transfer ribonucleic acid (tRNA) was investigated by studying the levels of aminoacylation in vivo in the logarithmic or stationary phase of growth. Both the periodate oxidation method and the amino acid analyzer were used to evaluate in vivo aminoacylation. The results indicated that in general the level of aminoacylation of tRNA's remained constant through stage III of sporulation, although there were detectable variations for specific amino acid groups. Our studies also showed that periodate oxidation damaged certain tRNA's; therefore, the results obtained by such a method should be interpreted with caution. Because the damage can affect certain isoaccepting species specifically, the periodate oxidation method cannot be used to establish which isoaccepting species are acylated in vivo. We also investigated the possibility of preferential use of particular tRNA species by polyribosomes. These results demonstrated a preferential use of lysyl-tRNA's at different growth stages. Control mechanisms operating during the early stages of sporulation, therefore, do not affect the overall level of aminoacylation. However, there is an effect on the levels of aminoacylation of specific amino acids and on which isoaccepting species are utilized by the polyribosome system.

Acylation↗
PubMed1980

Assembly of the mitochondrial membrane system: isolation of mitochondrial transfer ribonucleic acid mutants and characterization of transfer ribonucleic acid genes of Saccharomyces cerevisiae.

A method is described for isolating cytoplasmic mutants of Saccharomyces cerevisiae with lesions in mitochondrial transfer ribonucleic acids (tRNA's). The mutants were selected for slow growth on glycerol and for restoration of wild-type growth by cytoplasmic "petite" testers that contain regions of mitochondrial deoxyribonucleic acid (DNA) with tRNA genes. The aminoacylated mitochondrial tRNA's of several presumptive tRNA mutants were analyzed by reverse-phase chromatography on RPC-5. Two mutant strains, G76-26 and G76-35, were determined to carry mutations in the cysteine and histidine tRNA genes, respectively. The cysteine tRNA mutant was used to isolate cytoplasmic petite mutants whose retained segments of mitochondrial DNA contain the cysteine tRNA gene. The segment of one such mutant (DS504) was sequenced and shown to have the cysteine, histidine, and threonine tRNA genes. The structures of the three mitochondrial tRNA's were deduced from the DNA sequence.

Base Sequence↗
PubMed1985

Partial purification and characterization of glutaryl-coenzyme A dehydrogenase, electron transfer flavoprotein, and electron transfer flavoprotein-Q oxidoreductase from Paracoccus denitrificans.

Glutaryl-coenzyme A (CoA) dehydrogenase and the electron transfer flavoprotein (ETF) of Paracoccus denitrificans were purified to homogeneity from cells grown with glutaric acid as the carbon source. Glutaryl-CoA dehydrogenase had a molecular weight of 180,000 and was made up of four identical subunits with molecular weights of about 43,000 each of which contained one flavin adenine dinucleotide molecule. The enzyme catalyzed an oxidative decarboxylation of glutaryl-CoA to crotonyl-CoA, was maximally stable at pH 5.0, and lost activity readily at pH values above 7.0. The enzyme had a pH optimum in the range of 8.0 to 8.5, a catalytic center activity of about 960 min-1, and apparent Michaelis constants for glutaryl-CoA and pig liver ETF of about 1.2 and 2.5 microM, respectively. P. denitrificans ETF had a visible spectrum identical to that of pig liver ETF and was made up of two subunits, only one of which contained a flavin adenine dinucleotide molecule. The isoelectric point of P. denitrificans ETF was 4.45 compared with 6.8 for pig liver ETF. P. denitrificans ETF accepted electrons not only from P. denitrificans glutaryl-CoA dehydrogenase, but also from the pig liver butyryl-CoA and octanoyl-CoA dehydrogenases. The apparent Vmax was of similar magnitude with either pig liver or P. denitrificans ETF as an electron acceptor for these dehydrogenases. P. denitrificans glutaryl-CoA dehydrogenase and ETF were used to assay for the reduction of ubiquinone 1 by ETF-Q oxidoreductase in cholate extracts of P. denitrificans membranes. The ETF-Q oxidoreductase from P. denitrificans could accept electrons from either the bacterial or the pig liver ETF. In either case, the apparent Km for ETF was infinitely high. P. denitrificans ETF-Q oxidoreductase was purified from contaminating paramagnets, and the resultant preparation had electron paramagnetic resonance signals at 2.081, 1.938, and 1.879 G, similar to those of the mitochondrial enzyme.

Amino Acids↗
PubMed1986

Electron transfer flavoprotein from Methylophilus methylotrophus: properties, comparison with other electron transfer flavoproteins, and regulation of expression by carbon source.

When grown on methylated amines as a carbon source, Methylophilus methylotrophus synthesizes an electron transfer flavoprotein (ETF) which is the natural electron acceptor of trimethylamine dehydrogenase. It is composed of two dissimilar subunits of 38,000 and 42,000 daltons and 1 mol of flavin adenine dinucleotide. It was reduced by trimethylamine dehydrogenase to a stable anionic semiquinone form, which could not be converted, either enzymatically or chemically, to the fully reduced dihydroquinone. This ETF exhibited spectral properties which were nearly identical to ETFs from bacterium W3A1, Paracoccus denitrificans, and pig liver mitochondria. M. methylotrophus ETF cross-reacted immunologically and enzymatically with the ETF of bacterium W3A1 but not with the other two ETFs. In M. methylotrophus and bacterium W3A1, ETF and trimethylamine dehydrogenase were each expressed during growth on trimethylamine and were each absent during growth on methanol.

Animals↗
PubMed1983

Efficient procedure for transferring specific human genes into Chinese hamster cell mutants: interspecific transfer of the human genes encoding leucyl- and asparaginyl-tRNA synthetases.

We have developed a simple and efficient procedure for transferring specific human genes into mutant Chinese hamster ovary cell recipients that does not rely on using calcium phosphate-precipitated high-molecular-weight DNA. Interspecific cell hybrids between human leukocytes and temperature-sensitive Chinese hamster cell mutants with either a thermolabile leucyl-tRNA synthetase or a thermolabile asparaginyl-tRNA synthetase were used as the starting material in these experiments. These hybrids contain only one or a few human chromosomes and require expression of the appropriate human aminoacyl-tRNA synthetase gene to grow at 39 degrees C. Hybrids were exposed to very high doses of gamma-irradiation to extensively fragment the chromosomes and re-fused immediately to the original temperature-sensitive Chinese hamster mutant, and secondary hybrids were isolated at 39 degrees C. Secondary hybrids, which had retained small fragments of the human genome containing the selected gene, were subjected to another round of irradiation, refusion, and selection at 39 degrees C to reduce the amount of human DNA even further. Using this procedure, we have constructed Chinese hamster cell lines that express the human genes encoding either asparaginyl- or leucyl-tRNA synthetase, yet less than 0.1% of their DNA is derived from the human genome, as quantitated by a sensitive dot-blot nucleic acid hybridization procedure. Analysis of these cell lines with Southern blots confirmed the presence of a small number of restriction endonuclease fragments containing human DNA specifically. These cell lines represent a convenient and simple means to clone the human genomic sequences of interest.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Transfer RNA and aminoacyl transfer RNA in developing rats.

The total transfer RNA (tRNA) level in the liver, kidney, skeletal muscle and heart muscle of developing rats was determined by purification using (3H)tRNA as an internal standard. Liver and kidney contained almost twice as much tRNA per gram tissue as heart and skeletal muscle. There were no apparent differences between the sexes. The aminoacylation capacities of six tRNA species (alanyl, aspartyl, leucyl, methionyl, phenylalanyl, and tryptophanyl) from rat liver were not different during 3 developmental stages (suckling, weaning and young adult), and there were also no differences noted between males females. The in vivo percent aminoacylation of 4 tRNAs (aspartyl, leucyl, methionyl, and phenylalanyl) was lower during the newborn and suckling periods than in weaning and young adult rat livers. The tRNA of young adults was almost completely aminoacylated in vivo with the exception of alanyl-tRNA.

Acylation↗
PubMed2006

Macrophage phospholipid transfer protein contributes significantly to total plasma phospholipid transfer activity and its deficiency leads to diminished atherosclerotic lesion development.

OBJECTIVE: Systemic phospholipid transfer protein (PLTP) deficiency in mice is associated with a decreased susceptibility to atherosclerosis, whereas overexpression of human PLTP in mice increases atherosclerotic lesion development. PLTP is also expressed by macrophage-derived foam cells in human atherosclerotic lesions, but the exact role of macrophage PLTP in atherosclerosis is unknown. METHODS AND RESULTS: To clarify the role of macrophage PLTP in atherogenesis, PLTP was selectively disrupted in hematopoietic cells, including macrophages, by transplantation of bone marrow from PLTP knockout (PLTP(-/-)) mice into irradiated low-density lipoprotein receptor knockout mice. Selective deficiency of macrophage PLTP (PLTP(-M/-M)) resulted in a 29% (P<0.01 for difference in lesion area) reduction in aortic root lesion area as compared with mice possessing functional macrophage PLTP (384+/-36*10(3) microm2 in the PLTP(-M/-M) group (n=10), as compared with 539+/-35*10(3) microm2 in the PLTP(+M/+M) group (n=14)) after 9 weeks of Western-type diet feeding. The decreased lesion size in the PLTP(-M/-M) group coincided with significantly lower serum total cholesterol, free cholesterol, and triglyceride levels in these mice. Furthermore, plasma PLTP activity in the PLTP(-M/-M) group was 2-fold (P<0.001) lower than that in the PLTP(+M/+M) group. CONCLUSION: Macrophage PLTP is a significant contributor to plasma PLTP activity and deficiency of PLTP in macrophages leads to lowered atherosclerotic lesion development in low-density lipoprotein receptor knockout mice on Western-type diet.

Animals↗
PubMedDate not supplied

Molecular cloning, sequence, and expression of cynomolgus monkey cholesteryl ester transfer protein. Inverse correlation between hepatic cholesteryl ester transfer protein mRNA levels and plasma high density lipoprotein levels.

A cDNA clone containing the coding region for cynomolgus monkey cholesteryl ester transfer protein (CETP) was isolated by the polymerase chain reaction with primers based on the human CETP cDNA sequence and cDNA synthesized from liver poly (A+) RNA. Analysis of that cDNA indicated that the nucleotide and amino acid sequences of cynomolgus monkey CETP were greater than 95% homologous with the human sequences. A fragment of the cDNA was used to develop an internal-standard/RNAse protection assay that allowed precise quantification of CETP mRNA levels. Analysis of total RNA from various tissues with this assay revealed that the liver and thoracic aorta expressed high levels of CETP mRNA; the mesenteric fat, adrenal gland, spleen, and abdominal aorta had low but detectable levels of the mRNA; and the brain, kidney, intestine, and skeletal muscle had undetectable levels of that mRNA. When the monkeys were made hypercholesterolemic by a high-fat, high-cholesterol (HFHC) diet, hepatic levels of CETP mRNA increased from 1.6 +/- 0.4 pg/micrograms total RNA (mean +/- SEM) to 4.1 +/- 0.8 pg/micrograms (p less than 0.005); mesenteric fat CETP mRNA increased from 0.4 +/- 0.1 pg/micrograms total RNA to 5.3 +/- 2.2 pg/micrograms (p less than 0.05); and plasma CET activity increased approximately fourfold. The CETP mRNA levels in the thoracic and abdominal aortas were not significantly increased in monkeys fed the HFHC diet, even though those animals had gross atherosclerosis. The apoprotein E mRNA levels, however, were markedly increased in the aortas of monkeys with atherosclerosis, with the largest increase occurring in the abdominal aorta. Taken together, these data suggest that lipid deposition in the artery was not accompanied by increased expression of the CETP gene in that tissue. Statistical analysis showed that a strong, negative correlation existed between hepatic CETP mRNA levels and both high density lipoprotein cholesterol (r = -0.85, p less than 0.001) and apoprotein A-I (r = -0.84, p less than 0.001). These data suggest that HFHC diet-induced changes in high density lipoprotein metabolism may be linked to altered expression of a function CETP gene.

Animals↗
PubMed1997

Adenoviral gene transfer of phospholamban in isolated rat cardiomyocytes. Rescue effects by concomitant gene transfer of sarcoplasmic reticulum Ca(2+)-ATPase.

Phospholamban forms an integral part of the cardiac sarcoplasmic reticulum (SR) and regulates the activity of SR Ca(2+)-ATPase (SERCA2a). A number of studies have suggested a decrease in SERCA2a relative to phospholamban in heart failure. To test the hypothesis that changes in the relative abundance of phospholamban to SERCA2a could account for the pathophysiological abnormalities in Ca2+ handling observed in failing myocardium, we created a recombinant adenovirus designed to overexpress phospholamban (Ad.RSV.PL). In neonatal rat cardiomyocytes, Ad.RSV.PL increased the expression of phospholamban in a concentration-dependent fashion, reaching 280 +/- 43% at a multiplicity of infection (MOI) of 10.0 plaque forming units (pfu)/cell at 48 hours. The relationship between Ca(2+)-ATPase activity and [Ca2+] was shifted rightward in membrane preparations from cardiomyocytes infected with Ad.RSV.PL. Intracellular Ca2+ transients measured in the neonatal cells infected with Ad.RSV.PL (MOI, 10 pfu/cell) were characterized by (1) a significant prolongation of the relaxation phase (344 +/- 26 versus 710 +/- 56 milliseconds, P < .01), (2) a decrease in peak [Ca2+]i (967 +/- 43 versus 630 +/- 33 nmol/L, P < .01), and (3) an elevation in resting [Ca2+]i (143 +/- 14 versus 213 +/- 17 nmol/L, P < .05). Similarly, the time course of shortening was prolonged in myocytes infected with Ad.RSV.PL. These effects were partially restored by simultaneous transduction with an adenovirus carrying SERCA2a. Cardiomyocytes infected with Ad.RSV.PL had an abnormal frequency response: a decrease in peak [Ca2+]i and an increase in resting [Ca2+]i with increasing frequency. These findings indicate that adenovirus-mediated gene transfer of phospholamban modifies intracellular Ca2+ handling and the frequency response in cardiomyocytes. Our results suggest that alterations in the ratio of phospholamban to SERCA2a could account for the abnormalities in Ca2+ handling observed in heart failure and that overexpression of SERCA2a can largely correct these abnormalities.

Adenoviridae↗
PubMed1975

A novel function of Escherichia coli transfer RNA nucleotidyltransferase. Biosynthesis of the C-C-A sequence in a phage T4 transfer RNA precursor.

The biosynthesis of the phage T4-coded proline and serine transfer RNA species proceeds through a precursor RNA containing both tRNA sequences. Neither tRNA sequence in the precursor RNA contains the 3'-terminal C-C-A common to all mature tRNAs. Seidman and McClain ((1975) Proc. Natl. Acad. Sci. U. S. A. 72, 1491-1495) have proposed that the C-C-A sequence is added to serine tRNA while it is still part of the large precursor RNA. In the present work, I show that, in vitro, a purified preparation of Escherichia coli tRNA nucleotidyltransferase (EC 2.7.7.25) accurately synthesized 3'-terminal C-C-A in the serine tRNA portion of the precursor RNA. This result establishes a role of tRNA nucleotidyltransferase in the biosynthesis of the phage T4 serine tRNA. The finding that tRNA nucleotidyltransferase utilizes the large precursor RNA as a substrate represents a novel function of the enzyme.

Adenine Nucleotides↗
PubMed2004

[Study of GE7-transferring system mediated beta-galactosidase gene transfer in a rat model of ovarian tumor by intraarterial route].

OBJECTIVE: To investigate the efficiency and targeting of the GE7 system mediated gene transfer in the chemically induced ovarian tumor by intraarterial route. METHODS: Animal models were chemically induced by 7,12-dimethylbenz[a]anthracene (DMBA). GE7-polylysine/beta-galactosidase (beta-gal)/polylysine-HA20 complexes were constructed. Fifteen rats with induced ovarian tumor were divided into three groups, the complexes were injected through ovarian artery and tail vein, respectively. The tumor, heart, liver, spleen, lung and kidney were obtained at 72 h. X-gal staining was used to check expression of beta-gal. RESULTS: beta-gal was expressed strongly and well-distributed in tumor in the first group, and stained blue in the liver, spleen, lung and kidney, but much weaker than that of tumor. In the second group, beta-gal was expressed in the tumor, and weakly expressed in the liver, none was detected in the other organs. In the third group beta-gal was detected in the lung slightly, none was detected in the tumor and other organs. CONCLUSIONS: When GE7 complexes were administrated through ovarian artery, the introduced gene expressed preferentially in ovary. This result was the basis of intraarterial administration of therapeutic gene to treat ovarian cancer.

Animals↗
PubMed1975

Interaction of normal and tumor transfer RNA methyltransferases with ethionine-induced methyl-deficient rat liver transfer RNA.

The tRNA methyltransferases from normal rat liver and Novikoff hepatoma have been compared with respect to their base specificity, capacity to methylate, and reaction kinetics, using mixed Escherichia coli B transfer RNA (tRNA) and ethionine-induced partially methyl-deficient rat liver tRNA. The pattern of base methylation of the two substrates is different with the use of enzymes from either source. In particular, N1-methylguanine methylation is much greater in the methyl-deficient rat liver tRNA. The enzymes from the two sources also show differences in specificity of base methylation in either substrate, particularly in the percentage of N2-methylguanine synthesized. The Novikoff hepatoma enzymes have a greater capacity for methylation with either type of tRNA than do rat liver enzymes. The methyl-deficient rat liver tRNA is a poorer substrate for the enzymes from both sources than is E. coli B tRNA in terms of rate of methylation as well as total acceptance of methyl groups. The affinity constants are somewhat higher for the methyl-deficient rat liver tRNA than for E. coli B tRNA. The Novikoff hepatoma enzymes, in general, have larger affinity constants than the rat liver enzymes. Maximal velocities for the various base-specific enzymes are lower with the methyl-deficient rat liver tRNA, with the exception of the 1-methylguanine specific enzymes. These enzymes from either rat liver or Novikoff hepatoma exhibit approximately a 2.5-fold greater maximal velocity with methyl-deficient rat liver tRNA.

Animals↗
PubMed1992

Mock embryo transfer in early luteal phase, the cycle before in vitro fertilization and embryo transfer: a descriptive study.

OBJECTIVE: To investigate visually the uterine retention or sequestration of boluses of radiopaque dye, mimicking embryo transfer (ET). DESIGN: During the cycle before in vitro fertilization (IVF) and ET, patients underwent a mock ET of 40 microL of radiopaque dye into the uterine cavity. The patient was positioned supine for retroverted or axial and knee chest for anteverted uteri. The position of the dye at injection, during and after catheter removal, and during patient roll over and standing was monitored. SETTING: Treatment of infertility in a private practice. PATIENTS: Thirty-four IVF patients. INTERVENTIONS: During the cycle before IVF/ET, patients underwent a mock ET using a bolus of 40 microL of radiopaque dye. MAIN OUTCOME MEASURES: Planned before visual observation began. RESULTS: The dye remained primarily in the uterine cavity in only 68% (optimum ET position is knee chest for anteverted and supine for retroverted or axial uterus) and 48% (nonoptimum position is supine for anteverted uterus) at mock ET; in those groups, a 33% clinical pregnancy rate (PR) per retrieval resulted. Dye motility into the fallopian tube(s), cervix, and/or vagina is 38.2%, 8.8%, and 11.8%, respectively. CONCLUSIONS: If the mock ET had been the actual ET, 32% (optimum ET position) and 52% (nonoptimum ET position) of all patients would have lost their opportunity for pregnancy as a result of the ET procedure. Our 33% PR per retrieval among those patients who retained the dye in utero is more consistent with our expectations, given the advanced technologies of IVF/ET today.

Embryo Transfer↗
PubMed1980

Transfer with dialysable transfer factor of T-lymphocyte cytolytic response to tick-bone encephalitis virus antigen in naive mice.

Transfer factor activity was demonstrated in the dialysable extract from lymphocytes from outbred donor mice, in which immunization with live attenuated Langat (E5 "14") virus induced a stage of high resistance against challenge with virulent tick-borne encephalitis virus. Administered to naive inbred recipient mice, the extract conveyed in them specific cytolytic activity, exerted by their T lymphocytes, as demonstrated by the 51Cr release assay on tick-borne encephalitis virus-infected syngeneic L-929 cells.

Animals↗
PubMed1982

Euglena gracilis chloroplast transfer RNA transcription units. I. Physical map of the transfer RNA gene loci.

The locations of transfer RNA genes with respect to the restriction endonuclease cleavage map of Euglena gracilis Klebs, strain Z Pringsheim chloroplast DNA have been determined. Purified chloroplast tRNAs were treated with snake venom phosphodiesterase to remove the 3'-CCA terminus, and radioactively labeled by the action of Escherichia coli tRNA nucleotidyltransferase in the presence of [alpha-32P]CTP. Chloroplast DNA was treated individually and with combinations of the enzymes Bal I, Bam HI, Eco RI, Pst I, Pvu II, Sal I, and Xho I. The location of tRNA genes with respect to the cleavage sites for these enzymes was determined by hybridization of the 32P-labeled tRNAs to membrane filter blots of the chloroplast DNA restriction nuclease fragments following gel electrophoresis. The 145-kilobase pair genome was resolved into nine areas of strong tRNA hybridization, separated by areas of weak or no tRNA hybridization. The loci of tRNA genes are within the Eco RI fragments Eco A, B, G, H, I, J', P, Q, and V.

Base Sequence↗
PubMed1977

Specificity of transfer factor. In vitro lymphoblast transformation of peripheral lymphocytes to Leishmania major antigen in the presence of transfer factor.

The in vivo and in vitro demonstration of specificity of transfer factor (TF) has so far been hampered by lack of a suitable antigen. The host partiality of Leishmania suggested that in the case of leishmania antigen it should be possible to obtain lymphocytes of both donors and recipients of TF which were either sensitized or truly virgin. Lymphoblast transformation of normal donor lymphocytes to leishmania major antigen (LMA) was therefore measured in the presence of TF prepared from donors with a history of cutaneous leishmania infection (LSTFd) and normal donors (NSTFd). A clear augmentation of the lymphoblast transformation equal to that usually seen when lymphocytes from sensitized individuals are exposed to LMA was observed with LSTFd. An insignificant increase in lymphoblast transformation, however, occurred when NSTFd was used together with LMA and when LSTFd or NSTFd was used alone. The results, although limited by the number of TF preparations, tested, clearly substantiate the in vitro specificity of TF.

Antigens↗