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Biomedical subjects

R Garrett

Publications and source records attributed to R Garrett.

47 records · Page 3Linked to original sources
PubMed1977

Alloxan diabetic neuropathy: electron microscopic studies.

Peripheral nerves of diabetic rats were studied 2 years after alloxan injection. We observed demyelination and remyelination, axonal degeneration and regeneration, reduplication of basal laminae around vessels and Schwann's cells, as well as onion bulb formation by proliferated Schwann's cells. Crystalline deposits composed of aggregates of fibrillary electron dense material often occurred in vessel walls and endoneurium of diabetic animals but rarely were seen in nerves from age-matched control animals. Glycogen accumulated in myelinated and unmyelinated axons within mitochondria. Axoplasmic inclusions resembling Lafora's bodies and the inclusions of glycogenosis type IV were frequent and often were accompanied by deposits of particulate glycogen. The findings suggest that the neuropathy in alloxan diabetes is caused by metabolic impairment of anxons, Schwann's cells, and vessels, leading to segmental demyelination and axonal degeneration.

Animals↗
PubMed1976

The binding site of protein L1 on 23-S ribosomal RNA of Escherichia coli. 1. Isolation and characterization.

Ribonucleoproteins were prepared by ribonuclease digestion of a reconstitued complex of ribosomal protein L 1 and 23-S RNA from Escherichia coli. Three main ribonucleoproteins were identified. The largest was only obtained in an impure state at low ribonuclease concentration, whereas the two smaller ones, which were difficult to separate from one another electrophoretically, were stable over a range of enzyme concentrations. The two smaller ribonucleoproteins yielded a total of 13 RNA subfragments that were judged to be homogeneous electrophoretically. The latter were characterized for molecular weight and the subfragment composition of each of these ribonucleoproteins was established. Furthermore, the subfragments were shown to be maintained together in each ribonucleoprotein by RNA-RNA interactions. The primary and specific binding site of protein L1 was localized on one continuous RNA subfragment of about 110 nucleotides in length by two newly developed binding methods.

Binding Sites↗
PubMed1975

Small-angle x-ray studies on the structure of 16-S ribosomal RNA and of a complex of ribosomal protein S4 and 16-S ribosomal RNA from Escherichia coli.

16-S ribosomal RNA and a complex of ribosomal protein S4 and 16-S rRNA were studied in solution by small-angle X-ray scattering. Concentration series of the 16-S rRNA and the S4 - 16-S-rRNA complex were measured in 37.5 mM Tris-HCl buffer pH 7.4 at 5 degrees C. The following data were determined. The radii of gyration for the 16-S rRNA and S4 - 16-S-rRNA complex were R = 17.6 +/- 0.6 nm, respectively. The two respective values of the radii of gyration of the cross-section were Rq,1 = 8.42 +/- 0.1 nm and 8.33 +/- 0.3 nm, and Rq,2 = 0.988 +/- 0.03 nm and 0.996 +/- 0.03 nm. The largest diameters of the 16-S RNA and S4 - 16-S-RNA complex were L = 61.8 +/- 1 nm and 60.0 +/- 1 nm, respectively. Volumes of V = 1570 +/- 60 nm3 were found for both particles. In the Tris buffer used, no significant differences were found between the scattering curves of 16-S rRNA and the complex is a flat elliptical cylinder with the following dimensions: large axis 61.7 nm, small axis 35.4 nm and height 2 nm. The theoretical scattering curve fits the experimental one as long as the shape of the measured curve is due only to the overall shape of the particle. A model equivalent over the whole measured angular range is one built up from a large number of spheres that simulate the known substructure of the RNA. The outer dimensions of this model correspond to those of the flat elliptical cylinder.

Bacterial Proteins↗
PubMed1975

An investigation of the 16-S RNA binding sites of ribosomal proteins S4, S8, S15, and S20 FROM Escherichia coli.

The RNA binding sites of four 30-S ribosomal subunit proteins from Escherichia coli, namely S4, S8, S15, and S20 were prepared from reconstituted single protein - 16-S-RNA complexes by mild enzymic digestion of non-protected RNA regions. Oligonucleotide fingerprints of the protected RNA regions were obtained and their positions were located within the 16-S-RNA sequence. They were not completely contiguous regions of RNA; oligonucleotides had been excised from each of them. The binding sites of S4 and S20, and those of S8 and S15 showed overlapping. The specificity of the RNA binding sites was confirmed by a reconstitution method.

Bacterial Proteins↗
PubMed1975

Evidence for tertiary structural RNA-RNA interactions within the protein S4 binding site at the 5'-end of 16S ribosomal RNA of Escherichia coli.+.

Evidence is presented for tertiary structural interaction(s) (interactions(s) between two regions of an RNA molecule that are widely separated in the RNA sequence) within the 5'-one third of the 16S ribosomal RNA of Escherichia coli that constitutes the binding site of protein S4. The two main interacting RNA regions were separated by about 120 nucleotides (sections Q to M) of the 16S RNA sequence. A second, smaller gap, of 13 nucleotides, occurred within section C". The two main interacting regions contain about 150 nucleotides (sections H" to Q) and 160 nucleotides (sections M to C"). They are folded back on one another and, especially in the presence of protein S4, are strongly protected against ribonuclease digestion. The intermediate region (sections Q to M), however, is relatively accessible to ribonucleases in the S4-RNP. By partial removal of subfragments from the RNA complex it was possible to localise the two main interacting sites within sections H" - H and sections I" - C". Three main criteria for the specificity of the RNA-RNA interactions were invoked and satisfied. The possibility of other tertiary structural RNA-RNA interactions occurring in other regions of the 16S RNA is discussed. Finally, all the structural information on the S4-RNP is summarised and a tentative model is proposed.

Base Sequence↗
PubMedDate not supplied

Calibration of a prototype in vivo total body composition analyser using 14 MeV neutron activation and the associated particle technique.

A prototype in vivo total body composition analyser has been constructed for determining the total body contents of nitrogen (TBN), carbon (TBC) and oxygen (TBO) in young experimental animals such as sheep or pigs by 14 MeV neutron activation using a commercially available associated particle sealed tube neutron generator (APSTNG). The instrument was calibrated by scanning phantoms of different sizes in the mass range 10-36 kg, filled with a mixture of elements as found in a normal human body. Good agreement was found between the measured and expected values of N, O and C when two phantoms of similar dimensions but of different composition were scanned. With four 15 cm x 15 cm cross section and 45 cm long NaI(T1) gamma detectors and a radiation dose of approximately 20 microSv due to neutrons, the expected precisions for a 28 kg animal, CV% (based on counting statistics) are N: 9.3, C: 2.3 and O: 1.4.

Animals↗
PubMedDate not supplied

A feasibility study of in vivo 14-MeV neutron activation analysis using the associated particle technique.

The feasibility of using the time correlated associated particle technique for in vivo 14-MeV neutron activation analysis has been investigated. Gamma rays following neutron inelastic scattering with nitrogen, carbon, and oxygen have been measured with a 12.5 x 10-cm NaI (T1) detector. The results have been scaled to a proposed facility comprising four such detectors past which the subject would be scanned. Based on counting statistics, the precision of estimation of these elements has been determined to be 2.1%, 1.0%, and 1.1%, respectively, for experimental measurements on a sample containing physiological concentrations of the major body elements. The average body dose level would be restricted to 0.3 mSv.

Alpha Particles↗