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A Olin

Publications and source records attributed to A Olin.

34 records · Page 2Linked to original sources
PubMed1992

Purification and initial characterization of peptidyl-tRNA hydrolase from rabbit reticulocytes.

We have identified an activity in rabbit reticulocyte lysate as peptidyl-tRNA hydrolase, based upon its ability to hydrolyze native reticulocyte peptidyl-tRNA, isolated from polyribosomes, and N-acylaminoacyl-tRNA, and its inability to hydrolyze aminoacyl-tRNA, precisely the same substrate specificity previously reported for peptidyl-tRNA hydrolase from bacteria or yeast. The physiological role of the reticulocyte enzyme may be to hydrolyze and recycle peptidyl-tRNA that has dissociated prematurely from elongating ribosomes, as suggested for the bacterial and yeast enzymes, since reticulocyte peptidyl-tRNA hydrolase is completely incapable of hydrolyzing peptidyl-tRNA that is still bound to polyribosomes. We have purified reticulocyte peptidyl-tRNA hydrolase over 5,000-fold from the postribosomal supernatant with a yield of 14%. The purified product shows a 72-kDa band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis that has co-purified with enzyme activity and comprises about 90% of the total stained protein, strongly suggesting that the 72-kDa protein is the enzyme. Sucrose density gradient analysis indicates an apparent molecular mass for the native enzyme of 65 kDa, implying that it is a single polypeptide chain. The enzyme is almost completely inactive in the absence of a divalent cation: Mg2+ (1-2 mM) promotes activity best, Mn2+ is partly effective, and Ca2+ and spermidine are ineffective. The hydrolase shows a Km of 0.60 microM and Vmax of 7.1 nmol/min/mg with reticulocyte peptidyl-tRNA, a Km of 60 nM and Vmax of 14 nmol/min/mg with Escherichia coli fMet-tRNA(fMet), and a Km of 100 nM and Vmax of 2.2 nmol/min/mg with yeast N-acetyl-Phe-tRNA(Phe). The enzyme has a pH optimum of 7.0-7.25, it is inactivated by heat (60 degrees C for 5 min), and its activity is almost completely inhibited by pretreatment with N-ethylmaleimide or incubation with 20 mM phosphate. The fact that the enzyme hydrolyzes E. coli but not yeast or reticulocyte fMet-tRNA(fMet) may be explained, at least in part, by structural similarities between prokaryotic tRNA(fMet) and eukaryotic elongator tRNA that are not shared by eukaryotic tRNA(fMet).

Animals↗
PubMed1989

Determination of selenium in fish flesh by hydride generation atomic absorption spectrometry.

Selenium was determined in freeze-dried fish flesh from perch, pike-perch and the fish flesh reference materials MA-A-2 No. 1174 and MA-B-3 No. 151 (both from the International Atomic Energy Agency) by hydride generation atomic absorption spectrometry. Four different decomposition procedures were tested. They yielded consistent results for the four specimens, but the certified concentration level of selenium in the reference material MA-A-2 was not reached. This indicated losses or the presence of very stable selenium-containing compounds in this fish flesh. Neutron activation analysis of the reference material, however, was in agreement with those results obtained.

Animals↗
PubMed1989

Atomic absorption spectrometric determination of selenium in human blood components.

We separated blood from five healthy blood donors into plasma, erythrocytes, platelets, and leukocytes; counted the number of cells in each fraction; and determined the selenium content of each component by hydride generation atomic absorption spectrometry. The mean (+/- SD) selenium concentrations and amounts measured were as follows: whole blood 102.3 +/- 16.1 micrograms/L, plasma 76.9 +/- 10.6 micrograms/L, erythrocytes 13.7 +/- 2.8 ag per cell, platelets 4.8 +/- 1.1 ag per cell, and leukocytes 99 +/- 26 ag per cell.

Blood Platelets↗
PubMed1988

Fluorimetry of selenium in body fluids after digestion with nitric acid, magnesium nitrate hexahydrate, and hydrochloric acid.

A digestion procedure involving nitric acid, magnesium nitrate hexahydrate, and hydrochloric acid suffices for selenium determinations in whole blood, serum, and urine by molecular fluorescence spectrometry. To test the accuracy of the method we compared the results with those from hydride-generation atomic absorption spectrometry, and we also analyzed reference materials.

Humans↗
PubMed1984

Free physeal transplantation in the rabbit. An experimental approach to focal lesions.

UNLABELLED: We have developed a procedure to transplant free autogenous iliac-crest physeal grafts into defects created in the lateral aspect of the distal femoral physis of rabbits. Excision of a portion of the lateral part of the physis led consistently to formation of a bone bridge, growth arrest, and valgus deformity. There was no evidence of increased activity by the persisting physis to fill the defect or of differentiation of mesenchymal cells into a functioning physeal layer. We carried out preliminary studies to define the optimum conditions for obtaining and transplanting a free autogenous iliac-crest physeal graft into the femoral physeal defect. The iliac apophysis is composed of a fibrocartilaginous layer, cartilage similar to epiphyseal cartilage, and a physis. The graft included the physis and some overlying epiphyseal cartilage but the outermost fibrocartilaginous layer and the surrounding perichondrium were removed, as these two tissues were believed to inhibit diffusion. The graft was separated gently from the metaphysis. Histological studies showed that the separation occurred at the lower hypertrophic-chondrocyte zone. After optimum techniques had been developed for transplantation and the feasibility of the procedure had been established in twenty-one rabbits, the capacity of the physeal transplants to prevent bone-bridge formation, growth arrest, and valgus deformity was evaluated in thirty-nine rabbits, three to four months old, using the standardized transplantation procedure. The results were assessed in terms of the gross and radiographic appearance of the femur, measurements of length, and histological characteristics. The transplanted physis retained its normal morphology, united with the residual part of the original femoral physis, and participated in endochondral bone formation. Bone-bridge formation between the femoral epiphysis and metaphysis, growth arrest, and valgus deformity were prevented or minimized in most animals, and the physeal transplants yielded good or excellent results in 60 per cent of the procedures using stringent criteria. The results of this study show that free physeal transplants into focal defects can remain viable and function satisfactorily if they are fashioned properly and inserted gently. CLINICAL RELEVANCE: This study demonstrated that transplantation of an iliac-crest physis into a defect of the lateral aspect of the distal femoral physis can prevent bone-bridge formation, growth arrest, and the development of valgus deformity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Epidemiological aspects of fecal colonization with P-fimbriated Escherichia coli in neonates.

Fecal colonization with P-fimbriated Escherichia coli has caused epidemic outbreaks of extraintestinal E. coli infections in the neonatal unit of Danderyd Hospital. The aerobic fecal flora was therefore studied in 1,955 newborn children born at Danderyd Hospital during a period of 2.5 years. E. coli was found in 58% of the maternity ward children and in 57% of the neonatal unit children. A P-fimbriated strain was found in 12% and 17% of the children, respectively (p less than 0.01). There was a significant increase in the frequency of children colonized with E. coli, and especially P-fimbriated E. coli, with length of stay in the neonatal unit. There was a statistical correlation between bed occupancy and colonization with P-fimbriated E. coli (r = 0.46, p less than 0.01) during this study period. We found an incidence of P-fimbriated E. coli of 10 to 20% among the E. coli strains isolated from the fecal specimens which we regard as the baseline incidence.

Bacteriological Techniques↗