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Biomedical subjects

E A Stringer

Publications and source records attributed to E A Stringer.

28 records · Page 2Linked to original sources
PubMed1980

Rabbit reticulocyte initiation factor 2 contains two polypeptide chains of molecular weights 48,000 and 38,000.

Eukaryotic initiation factor 2 (eIF-20) purified from rabbit reticulocyte lysates consists of equimolar amounts of two polypeptide chains of Mr 48,000 and 38,000. Determination of the molecular weight of the native factor gave a value which is consistent with a Mr of 86,000 indicating that the factor is composed of one Mr 48,000 and one Mr 38,000 polypeptide. The purified factor exhibited all the binding activities characteristic of eIF-2. The factor formed ternary complexes with Met-tRNAfMet and GTP; it bound GDP to form a binary complex; and it also possessed the property of binding a wide variety of RNA species, including reoviral mRNA, phage T3 mRNA, rRNAs, and tRNA. Furthermore, the ternary complex formed by purified eIF-2 interacted with the 40S ribosomal subunit in the presence of AUG codon to form a 40S initiation complex. These results indicate that all binding activities attributed to eIF-2 are contained in the 48,000- and 38,000-dalton polypeptides.

Animals↗
PubMed1980

Bilateral total hip arthroplasty: a single procedure.

A total of 196 patients with bilateral hip disease underwent the simultaneous bilateral total hip arthroplasty procedure (392 hips), compared with 427 patients with unilateral disease and one hip replaced. A multiple regression analysis showed no difference between the 2 groups in regard to age, sex, and preoperative diagnosis. The mean length of operation was 3 hours for the bilateral group and one hour and 15 minutes for the unilateral group, with a mean blood loss of 3 units and 0.5 units respectively (the majority of the patients were given hypotensive anesthesia. Post-operative complications revealed no differences in the phlebitis (1% for each group), clinical pulmonary emboli (1% for each group), dislocation (1% for unilateral and none for the bilateral group), and non-union of the greater trochanter (11% for the unilateral group and 12% for the bilateral group). The unilateral group revealed 25% ectopic ossification vs. 36% for the bilateral group (p < 0.008). The mean hospital stay was 14 days for the unilateral group and 16 days for the bilateral group, at respective costs of $4,137 and $5,780. There were signs of clinical loosening in 1% of both groups. The infection rate was 1% for both. An analysis of covariance revealed no follow-up differences between the 2 groups in regard to pain, abduction status, or functional capabilities, although the range of motion was better in the unilateral group (p < 0.001), as may be expected, with less initial range of motion, there was also more postoperative ectopic ossification. Replacement of both hips under one anesthetic benefits patients in that the postoperative complications are the same as for the procedure for one hip; the length of hospitalization and convalescence are only slightly longer; the postoperative follow-up shows no differences except for a slight restriction in range of motion for the bilateral group; and the cost represents a 30% savings over that of a unilateral hip performed twice.

Adult↗
PubMed1979

Purified eukaryotic initiation factor 2 from calf liver consists of two polypeptide chains of 48,000 and 38,000 daltons.

Eukaryotic initiation factor 2 (eIF-2), which specifically binds Met-tRNAMetf and forms stable ternary complexes with GTP, has been purified from ribosomal salt wash proteins from calf liver. The purified factor exhibits only two polypeptide bands of Mr = 48,000 and 38,000 following electrophoresis in 15% polyacrylamide gels in the presence of sodium dodecyl sulfate. Densitometric tracings show the two polypeptides are present in a molar ratio of 1:1. This suggests a Mr = 86,000 for the native enzyme, a value which agrees with the apparent molecular weight determined by physical methods. Less pure preparations of eIF-2 show additional polypeptide bands, including 50,000- and 46,000-dalton bands, all of which can be removed by further purification without affecting the activity of eIF-2.

Animals↗
PubMed1979

Predictive range of motion after total knee replacement.

Evaluation of 145 consecutive total knee arthroplasties pre- and postoperatively revealed that regardless of the preoperative deformity (varus, valgus, and flexion contracture), normal alignment of the knee with full extension was obtainable. The amount of flexion to be achieved postoperatively may be determined by the amount of flexion the patient had preoperatively, especially if the degree of flexion was less than 75 degrees. The prosthesis design, sex, age and diagnosis of rheumatoid arthritis were found not to correlate with postoperative motion and stability. In the osteoarthric knee, however, statistical analyses at 6 and 12 months generally showed less postoperative than preoperative range of motion.

Adult↗
PubMed1977

Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli.

1. Studies on the function of initiation factor 1 (IF-1) in the formation of 30 S initiation complexes have been carried out. IF-1 appears to prevent the dissociation of initiation factor 2 (IF-2) from the 30 S initiation complex. The factor has no effect on either the initial binding of IF-2 nor does it increase the amount of IF-2 dependent fMet-tRNA and GTP bound to the 30 S subunit. Bound fMet-tRNA remains stable to sucrose gradient centrifugation even in the absence of IF-1. 2. It is postulated that the presence of IF-2 on the 30 S complex is necessary so that at the time of junction with the 50 S subunit to form a 70 S complex, the 70 S-dependent GTPase activity of IF-2 can hydrolyze GTP. This hydrolysis provides a means by which GTP can be removed to facilitate formation of a 70 S initiation complex active in peptidyl transfer. In support of this postulate, it was observed that 30 S initiation complexes formed in the absence of IF-1 could be depleted of their complexes were still able to accept 50 S subunits to form 70 S complexes which could still donate fMet-tRNA into peptide linkages. These results indicate that 30 S complexes lacking GTP do not require IF-2 for formation of active 70 S complexes. 3. IF-1, which is required to prevent dissociation of IF-2 from the 30 S initiation complex, is also required for release of IF-2 from ribosomes following 70 S initiation complex formation. The mechanisms of the release of IF-2 has been studied in greater detail. Evidence is presented which rules out the presence of a stable IF-2 GDP complex on the surface of the 70 S ribosome following GTP hydrolysis and of any exchange reactions between IF-1 and guanine nucleotides necessary for effecting the release of IF-2. IF-2 remains on the 70 S initiation complexes after release of guanine nucleotides and can be liberated solely by addition of IF-1.

Binding Sites↗
PubMed1976

Interaction of bacterial initiation factor 2 with initiator tRNA.

Interaction of bacterial polypeptide chain initiation factor 2 (IF-2) with Escherichia coli formylmethionyl-tRNA in the absence of free Mg2+ renders the fMet-tRNA adsorable to nitrocellulose membrane filters. This reaction does not require GTP and is strongly inhibited by low concentration (1 mM) of Mg2+ in the reaction mixture. The structural requirements of the tRNA for binary complex formation have been studied using modified fMet-tRNAfMet molecules and a series of N-blocked and normal aminoacyl-rRNAs. It has been observed that IF-2 will not blind either to free formylmethionine or to a short fMet-oligonucleotide, but will bind to any xRNA structure covalently attached to an N-blocked methionine group. The E. coli initiator and noninitiator methiionine tRNAs, which have many differences in primary structure, were found to bind identically. In addition, fMet-tRNAfMet molecules containing structural modidifications at 20 different sites had the same affinity for IF-2 as unmodified fMet-tRNAfMet. N-blocked eukaryotic initiator tRNAs were also found to bind strongly to the factor. Binary complex formation was readily reversible, f[14C]Met-tRNAfMet being competed out by addition of an equal amount of unlabeled fMet-tRNAfMet to the preformed complex. In contrast, deacylated tRNAfMet was a poor compeitor, a 30-fold excess being required for 50% inhibition of complex formation in the presence of limiting factor. Although tRNAs having an N-blocked methionine were found to have the greatest affinity for IF-2, specificity for the amino acid in binary complex formation was not absolute. Partial binding was observed with N-substituted tyrosine, valine, and phenylalanine tRNAs, and weak or no binding with N-subsituted lysine, alanine, and leucine tRNAs. In all cases, N-blocked derivatives had a higher affinity for IF-2 than the corresponding unsubstituted aminoacyl-tRNAs. These results indicate that IF-2 alone is not capable of distinguishing the nucleotide sequence of tRNAs and selects the initiator tRNA by recognizing the fMet moiety. The overall data suggest that the role of IF-2 in formation of the ribosomal initiation complex is to stablize the interaction of fMet-tRNAfMet with the ribosome at low Mg2+ concentrations by binding to both the ribosomal particle and the fMet group of the tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1974

Thiostrepton inhibition of initiation factor 1 activity in polypeptide chain initiation in Escherichia coli.

Thiostrepton, a peptide antibiotic, inhibits the GTP-dependent 70S initiation complex formation (as measured by binding of fMet-tRNA to ribosomes and concomitant hydrolysis of GTP) only when initiation factor 1 is present to permit catalytic recycling of initiation factor 2 in the initiation reaction. When initiation factor 1 is absent, the binding of fMet-tRNA and GTP hydrolysis occur stoichiometrically with respect to initiation factor 2, and thiostrepton has no effect on either reaction under these conditions. Detailed analysis of this inhibition process shows that thiostrepton prevents catalytic recycling of initiation factor 2 by blocking the action of initiation factor 1, which is required for the dissociation of initiation factor 2 from the 70S initiation complex. This dissociation is necessary for the catalytic reutilization of initiation factor 2 in the initiation reaction. The antibiotic does not directly inhibit GTP hydrolysis per se in initiation. The inhibition of fMet-tRNA binding to ribosomes by thiostrepton is also dependent on the concentration of GTP; the inhibition is most pronounced at low concentrations of GTP, but at a high molar ratio of GTP to thiostrepton, the inhibition is completely abolished.

Anti-Bacterial Agents↗
PubMedDate not supplied

Intraoperative wound cultures: their value and long-term effect on the patient.

A series of 856 total hip arthroplasties in 681 consecutive patients was reviewed in an attempt to determine what variables are significant in identifying the patient "at risk" for postoperative wound infection. Variables such as sex, age, preoperative diagnosis, laterality, and wound closure had no influence on the results of the intraoperative cultures. No statistical correlation was found between these factors and the patient's outcome. However, in patients who had undergone previous hip surgery long-term results were not as favorable as those in patients with per primam operations (12.0% versus 8.5%, respectively, had long-term postoperative problems). The most significant finding of this study was in the area of intraoperative culture results versus the patient's end-result. Here, it was found that when culture results were subdivided into zero, one, or two (both opening and closing) positive cultures, zero or one positive culture had no effect on patient outcome. However, two positive cultures were indicative of complications (p less than 0.001). One-third of these hips either developed loosening or long-term postoperative pain, of which 75% went on to become infected. The "at risk" patient was thus defined as the patient who had positive intraoperative cultures.

Arthroplasty↗
PubMedDate not supplied

Laminar air-flow versus conventional air operating systems: a seven-year patient follow-up.

A 7-year follow-up was conducted on 183 total hip replacements and evaluated for infection. Eighty-seven operations were done in a horizontal laminar air-flow operating room and 89 were done in a conventional operating room without laminar air-flow. In the laminar air-flow group, there were 2 infections (2.2%) and 6 (6.7%) in the conventional operating room. Excluding those patients who had undergone previous operations, there were 3 infections out of 76 (4%) in the conventional operating room group. One infection out of 68 (1%) occurred in the laminar air-flow group. There were no statistical differences in the infection rates. These data are interpreted to suggest that daily uncontrollable variables which may produce infections are minimized by the use of laminar air-flow operating rooms.

Bacterial Infections↗