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Biomedical subjects

D Hatfield

Publications and source records attributed to D Hatfield.

At least 37 records · Page 2Linked to original sources
PubMed1987

Unique pathway of expression of an opal suppressor phosphoserine tRNA.

An opal suppressor phosphoserine tRNA gene is present in single copy in the genomes of higher vertebrates. We have shown that the product of this gene functions as a suppressor in an in vitro assay, and we have proposed that it may donate a modified amino acid directly to protein in response to specific UGA codons. In this report, we show through in vitro and in vivo studies that the human and Xenopus opal suppressor phosphoserine tRNAs are synthesized by a pathway that is, to the best of our knowledge, unlike that of any known eukaryotic tRNA. The primary transcript of this gene does not contain a 5'-leader sequence; and, therefore, transcription of this suppressor is initiated at the first nucleotide within the coding sequence. The 5'-terminal triphosphate, present on the primary transcript, remains intact through 3'-terminal maturation and through subsequent transport of the tRNA to the cytoplasm. The unique biosynthetic pathway of this opal suppressor may underlie its distinctive role in eukaryotic cells.

Biological Transport↗
PubMed1986

Aminoacyl-tRNA(anticodon): codon adaptation in human and rabbit reticulocytes.

A highly significant correlation was observed between the relative abundances of isoacceptor aminoacyl-tRNAs in human and rabbit reticulocytes and the frequency of their cognate codons in alpha and beta globin mRNAs from the respective tissue. The correlation coefficient (r value) for human reticulocytes was 0.78 and for rabbit reticulocytes was 0.88. These results provide strong evidence that the amounts of most isoacceptors in human and rabbit reticulocytes are adapted to requirements for translating their cognate codons in globin mRNA, i.e., there is an aa-tRNA(anticodon): codon adaptation in these tissues.

Animals↗
PubMed1985

Conserved sequences in both coding and 5' flanking regions of mammalian opal suppressor tRNA genes.

The rabbit genome encodes an opal suppressor tRNA gene. The coding region is strictly conserved between the rabbit gene and the corresponding gene in the human genome. The rabbit opal suppressor gene contains the consensus sequence in the 3' internal control region but like the human and chicken genes, the rabbit 5' internal control region contains two additional nucleotides. The 5' flanking sequences of the rabbit and the human opal suppressor genes contain extensive regions of homology. A subset of these homologies is also present 5' to the chicken opal suppressor gene. Both the rabbit and the human genomes also encode a pseudogene. That of the rabbit lacks the 3' half of the coding region. Neither pseudogene has homologous regions to the 5' flanking regions of the genes. The presence of 5' homologies flanking only the transcribed genes and not the pseudogenes suggests that these regions may be regulatory control elements specifically involved in the expression of the eukaryotic opal suppressor gene. Moreover the strict conservation of coding sequences indicates functional importance for the opal suppressor tRNA genes.

Animals↗
PubMed1984

Selected bibliography and glossary on DRG's prospective pricing.

In 1982, the Tax Equity and Fiscal Responsibility Act modified the Section 223 Medicare Hospital reimbursement limits to include a case mix adjustment based on DRG's. In 1983, Congress amended the Social Security Act to include a national DRG-based hospital prospective payment system for all Medicare patients. In the view of many physicians and administrators the current formulation of DRG's constitute a workable and clinically coherent set of classifications that relate a hospital's case mix to the resources used and costs incurred by the hospital. DRG's are delineated based on principal diagnosis, secondary diagnosis, surgical procedures, age and the discharge status of the patients treated. Through DRG's, hospitals are able to gain an understanding of the patients they treat, the costs incurred and within reason, can anticipate the services required for specific illness. The classification of DRG's is a constantly evolving process. As coding procedures change, as more comprehensive data is collected, and as medical technology and treatment practices change, DRG's will need to be re-examined and revised. The following bibliography and glossary of terms highlights several key words and phases which are relevant to the overall discussion of DRG's.

Bibliographies as Topic↗
PubMed1982

The aminoacyl-tRNA population of human reticulocytes.

The aminoacyl-tRNA population of human reticulocytes has been examined. These studies include: 1) determination of the levels of amino acid acceptance for 20 aminoacyl-tRNAs; 2) comparison of 20 aminoacyl-tRNAs from human reticulocytes to those of rabbit reticulocytes by reverse phase chromatography; 3) comparison of the levels of Ile- and Leu-tRNAs in fetal and adult reticulocytes; and 4) determination of the codon recognition properties of human Ala-, Asn-, His-, Leu-, Thr-, and Val-tRNAs. These studies provide evidence that the aminoacyl-tRNA population of human reticulocytes is adapted to the requirements of protein synthesis.

Adult↗
PubMed1982

Opal suppressor serine tRNAs from bovine liver form phosphoseryl-tRNA.

An unusual minor species of bovine liver serine tRNA has previously been isolated, sequenced, and found to suppress the UGA termination codon in protein synthesis in vitro [Diamond, A., Dudock, B. & Hatfield, D. (1981) Cell 25, 497-506]. We have now found that this tRNA can be a substrate in a specific phosphorylation reaction in which phosphoseryl-tRNA is formed. Moreover, bovine liver contains a second UGA suppressor serine tRNA (tRNASerNCA; N is a modified nucleoside) which also forms phosphoseryl-tRNA. The nucleotide sequence and coding properties of tRNASerNCA are presented.

Animals↗
PubMed1982

Aminoacyl-tRNAs from Physarum polycephalum: patterns of codon recognition.

Isoacceptors of Physarum polycephalum Ala-, Arg-, Glu-, Gln-, Gly-, Ile-, Leu-, Lys-, Ser-, Thr-, and Val-tRNAs were resolved by reverse-phase chromatography and isolated, and their codon recognition properties were determined in a ribosomal binding assay. Codon assignments were made to most isoacceptors, and they are summarized along with those determined in other studies from Escherichia coli, yeasts, wheat germ, hymenoptera, Xenopus, and mammals. The patterns of codon recognition by isoacceptors from P. polycephalum are more similar to those of animals than to those of plants or lower fungi.

Animals↗
PubMed1982

Plasma volume, electrolyte, and endocrine changes during onset of laminitis hypertension in horses.

Acute laminitis-hypertension was produced by carbohydrate overloading of the gastrointestinal tract in 12 adult horses. Obel grade 3 (OG3) lameness developed 40 hours (+/- 3.5, SEM) after overfeeding. At OG3 lameness, mean plasma volume was significantly decreased (P less than 0.005) when compared with base-line values. Before OG3 lameness, transient decreases in serum phosphorus and calcium were recorded. Mild hyponatremia also developed before OG3 lameness and persisted. After establishment of OG3 lameness, persistent hypokalemia and increased plasma aldosterone concentration occurred coincidently. Transient increase in plasma hydrocortisone (cortisol) and renin activity and transient hypochloremia were also recorded during the syndromal phase. Changes in plasma volume and serum electrolytes are discussed and related to the pathogenesis of acute equine laminitis. The alterations in plasma renin activity and aldosterone concentration were interpreted as homeostatic adjustments to fluid and electrolyte imbalances. Differences between the horse and pony during onset of experimental alimentary laminitis are also discussed.

Acute Disease↗
PubMed1981

Structure and properties of a bovine liver UGA suppressor serine tRNA with a tryptophan anticodon.

A bovine liver serine tRNA with a variety of unusual features has been sequenced and characterized. This tRNA is aminoacylated with serine, although it has a tryptophan anticodon CmCA. In ribosome binding assays, this tRNA (tRNASERCmCA) binds to the termination codon UGA and shows little or no binding in response to a variety of other codons including those for tryptophan and serine. The unusual codon recognition properties of this molecule were confirmed in an in vitro assay where this tRNA suppressed UGA termination. This is the first naturally occurring eucaryotic suppressor tRNA to be so characterized. Other unusual features, possibly related to the ability of this tRNA to read UGA, are the presence of two extra nucleotides, compared to all other tRNAs, between the universal residues U at position 8 and A at position 14 and the presence of an extra unpaired nucleotide within the double-stranded loop IV stem. This tRNA is also the largest eucaryotic tRNA sequenced to date (90 nucleotides). Despite its size, however, it contains only six modified residues, tRNASerCmCA shows extremely low homology to other mammalian serine (47-52% homology) or tryptophan (49% homology) tRNAs.

Animals↗
PubMed1979

Aminoacyl-transfer RNA populations in mammalian cells chromatographic profiles and patterns of codon recognition.

The chromatographic profiles of 20 aminoacyl-tRNAs from rabbit liver were compared to those of rabbit reticulocytes by reverse phase chromatography and the chromatographic profiles of 20-aminoacyl-tRNAs from bovine liver were compared to those of bovine brain. The two rabbit tissues showed significant differences in the elution profiles of most aminoacyl-tRNAs, while the elution profiles of the aminoacyl-tRNAs from the bovine tissues showed fewer differences. The patterns of codon recognition of several aminoacyl-tRNAs fractionated from rabbit reticulocytes have also been compared to those fractionated from rabbit liver.

Amino Acyl-tRNA Synthetases↗
PubMed1978

Patterns of codon recognition by isoacceptor aminoacyl-tRNAs from wheat germ.

Isoacceptors of Ala-, Arg-, Glu-, Gln-, Ile-, Leu-, Lys-, Ser-, Thr- and Val-tRNAs from wheat germ have been resolved by reverse phast chromatography. Codon recognition properties have been determined on isolated fractions of each of these aa-tRNAs and codon assignments have been made to a number of isoacceptors. Evolutionary changes which have occurred in patterns of codon recognition by isoacceptor aa-tRNAs in wheat germ and other organisms are discussed.

Biological Evolution↗
PubMed1974

malB region in Escherichia coli K-12: characterization of new mutations.

Phenotypic characterization and mapping of more than 50 Mal(-) mutations located in the malB region lead one to divide the site for Mal(-)lambdas mutations (formerly called gene malB) in that region, into two adjacent genetic segments malJ and malK. malJ and malK are both involved in maltose permeation. It is suggested that (i) malK and lamB, the only known gene specifically involved in phage lambda adsorption (20), constitute an operon of polarity malK lamB. (ii) malJ and malK correspond to two different genes, and (iii) a promoter for the malK lamB operon is located between malJ and malK. Since lambda receptors and maltose permease are inducible by maltose and absent in malT mutants, it is likely that the expression of the malK lamB operon is controlled by the product of gene malT, the positive regulatory gene of the maltose system.

Adsorption↗
PubMed1972

Recognition of nonsense codons in mammalian cells.

The tritiated trinucleotide UGA was used in a binding assay to detect transfer RNAs that recognize this nonsense codon from calf-liver cells. Acylation of transfer RNA with labeled amino acids and determination of codon responses of aminoacyl-tRNAs demonstrate that a species of seryl-tRNA and a species of arginyl-tRNA recognize the codon UGA. Slight responses of cysteinyl-tRNA and of trytophanyl-tRNA to the codon UGA were also observed.

Acylation↗