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D T Peterson

Publications and source records attributed to D T Peterson.

16 recordsLinked to original sources
PubMed1979

Role of eukaryotic initiation factor 5 in the formation of 80 S initiation complexes.

The function of eukaryotic initiation factor 5 (eIF-5) from rabbit reticulocyte lysate has been studied by sucrose gradient preparation of 40 S and 80 S initiation complexes. eIF-5 is required for transfer of initiator tRNA from 40 S preinitiation complexes to puromycin-reactive 80 S complexes. The transfer is dependent upon GTP hydrolysis and is associated with release of eIF-2 and eIF-3 from the 40 S subunit. The GTP-dependent loss of eIF-2 and eIF-3 is catalyzed by eIF-5 in the absence of 60 S subunits or when subunit joining is prevented by edeine, but not when GTP is replaced by GuoPP(NH)P. Unstable 40 S subunit . Met-tRNAf complexes generated by eIF-5 can form puromycin-reactive 80 S complexes when 60 S subunits are added in the absence of added GTP. In addition, kinetic evidence is presented that indicates GTP hydrolysis occurs prior to 80 S complex formation.

Animals↗
PubMed1979

Binding and release of radiolabeled eukaryotic initiation factors 2 and 3 during 80 S initiation complex formation.

The AUG-dependent formation of an 80 S ribosomal initiation complex was studied using purified rabbit reticulocyte initiation factors radiolabeled by reductive methylation. The radiolabeled initiation factors were as biologically active as untreated factors. Reaction mixtures containing a variety of components (AUG, GTP, Met-tRNAf, initiation factors, and 40 S and 60 S ribosomal subunits) were incubated at 30 degrees C and then analyzed on linear sucrose gradients for the formation of ribosomal complexes. The results show that both eukaryotic initiation factor (eIF)-3 and the ternary complex (eIF-2.GTP.Met-tRNAf) bind independently to the 40 S subunit and each of these components enhances the binding of the other. All of the polypeptides of eIF-2 and eIF-3 participate in this binding. Formation of an 80 S ribosomal complex requires eIF-5 and 60 S subunits in a reaction that is stimulated by eIF-4C. Both eIF-2 and eIF-3 are released from the 40 S preinitiation complex during formation of the 80 S initiation complex. Release of eIF-2 and eIF-3 does not occur and 80 S ribosomal complexes are not formed if GTP is replaced by a nonhydrolyzable analog such as guanosine 5'-O3-(1,2-mu-imido)triphosphate. Despite a variety of attempts, it has not yet been possible to demonstrate binding of eIF-4C, eIF-4D, or eIF-5 to either 40 S or 80 S ribosomal complexes.

Animals↗
PubMed1975

Pericardial cyst ten years after acute pericarditis.

A case of pericardial cyst development in the years after an episode of acute pericarditis is reported. The method of diagnosis allowed confirmation of the condition without thoracotomy. These aspects of the case are relevant to the genesis of pericardial cysts in general and establish ultrasound and subsequent contrast roentgenography are advocated as adequate means of diagnosis in this condition.

Aged↗
PubMed1973

The effect of experimental diabetes mellitus and insulin replacement on hepatic ultrastructure and protein synthesis.

The following study was conducted in order to define the specific alterations in hepatic ultrastructure responsible for the decrease in hepatic protein synthesis associated with experimental diabetes. Rats received intravenous alloxan (70 mg/kg) and 48 h later were either sacrificed or given insulin for 1, 2, 4, 6, or 24 h. Specimens for electron microscopic evaluation and morphometric analysis were taken from the same livers used to isolate ribosomes for measurement of in vitro protein synthesis. Our results show that hepatocytes from animals with untreated alloxan diabetes show varying degrees of disorganization and loss of rough endoplasmic reticulum (RER) which is directly related to the severity of the alloxan diabetes. A significant correlation existed between the severity of ultrastructural changes as judged by the loss of both membrane and polysome components of the RER and degree of inhibition of protein synthesis (P < 0.001). Abnormalities of hepatic ultrastructure and protein synthesis were reversed within 24 h of insulin administration. The data are consistent with the view that it is the relative decrease in hepatic polysomes that results from the loss of RER in alloxan diabetes that is responsible for the decrease in hepatic protein synthesis.

Animals↗
PubMed1973

Characteristics of membrane-bound and free hepatic ribosomes from insulin-deficient rats. I. Acute experimental diabetes mellitus.

Membrane-bound and free ribosomes were prepared by discontinuous density gradient centrifugation from livers of rats 2-3 days after receiving alloxan (75 mg/kg) or streptozotocin (100 mg/kg). Hepatocytes from these animals were also examined by electron microscopy and subjected to quantitative morphometric analysis. The results indicated that the two populations of hepatic ribosomes respond differently to acute insulin deficiency. There was an overall reduction (P < 0.001) in total number of bound ribosomes per volume cytoplasm: the remaining bound ribosomes underwent a shift to smaller-sized ribosomal messenger RNA (mRNA) aggregates (P < 0.02); and the proteinsynthetic activity of these bound ribosomes was less than normal (P < 0.02) when protein synthesis was directed by endogenous mRNA. However, there was no difference between bound ribosomes from livers of normal and diabetic rats when protein synthesis was directed by polyuridylic acid. In contrast, free ribosomes were unchanged in number and degree of ribosomal mRNA aggregation, but displayed a significantly increased rate of in vitro protein synthesis (P < 0.01) as compared to normal controls. This increased protein-synthetic activity occurred when amino acid incorporation was directed by endogenous mRNA or polyuridylic acid. These changes in structure and function of bound and free hepatic ribosomes were prevented by the concomitant administration of insulin. The decrease in protein-synthetic activity of bound hepatic ribosomes from acutely diabetic rats seems to be secondary to marked disruption and disaggregation of the rough endoplasmic reticulum (RER) with production of smaller ribosomal mRNA aggregates which incorporate less amino acids into protein. Increased protein synthetic activity of free ribosome appears to be related to the ability of these ribosomes to copy mRNA more efficiently.

Amino Acids↗