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Biomedical subjects

R L Alston

Publications and source records attributed to R L Alston.

8 recordsLinked to original sources
PubMed1989

Initiation complex formation on Euglena chloroplast 30S subunits in the presence of natural mRNAs.

An in vitro system has been developed that allows the formation of translation initiation complexes with Euglena chloroplast 30S ribosomal subunits and natural mRNAs. For these experiments two regions of the Euglena chloroplast genome have been cloned behind the T7 transcriptional promoter and the corresponding RNAs synthesized in vitro. These mRNAs are capable of forming initiation complexes with chloroplast 30S subunits in the presence of fMet-tRNA and E. coli initiation factors. Deletion of the normal translation start site results in a message that is no longer recognized by the chloroplast subunits suggesting that the correct AUG initiation codon on the mRNA is being selected by the small ribosomal subunit. Initiation complex formation with the chloroplast 30S subunits is specific for chloroplast mRNAs and mRNA from the phage MS2 is not active in this system.

Animals↗
PubMed1981

A batch staining method for brain slices allowing volume measurements of grey and white matter using an image analyzing computer (Quantimet 720).

Normal formalin-fixed gelatin-embedded cerebral hemispheres were serially sliced and the 25 to 30 slices form each hemisphere were batch stained by a modification of Mulligan's method. following washing in water the slices were immersed in Mulligan's acid/copper sulfate/phenol solution for 20 minutes at room temperature, treated with a xylene/Polyclens mixture for 20 seconds and immediately transferred to a 2% sodium hydroxide solution for 10 seconds. Final staining was by immersion in 2% potassium ferrocyanide which was followed by washing in tap water. The grey matter was stained a brick red color while the whiteness of the white matter was accentuated. Following staining the slices were stored between sheets of black paper in 2% aqueous formalin prior to measurement of the respective areas of grey and white matter using a Quantimet 720 image analyzing computer. The method is rapid and color stable, and reduces the risk of exposure to toxic fumes by eliminating the need for hot phenol solutions. This technique is also suitable for the macroscopic demonstration and quantitation of demyelinating conditions in the brain.

Brain↗
PubMedDate not supplied

Variation with age in the volumes of grey and white matter in the cerebral hemispheres of man: measurements with an image analyser.

The total volumes and relative quantities of grey and white matter have been measured in sixty-five normal male and sixty-five normal female cerebral hemispheres. Fixed hemisphere volume was found to fall linearly at 3.5% per decade for men from 641 ml at the age of 20 to 463 ml at the age of 100. For women the decrease was 1.9% per decade from 531 ml at 20 years to 462 ml at 100 years. After correction for the effects of fixation and for the secular increase in brain size, it was concluded that mean hemisphere volume remained roughly constant between the ages of 20 and 50 years (558 ml for men, 474 ml for women). After the age of 50 the mean volume in both sexes fell at about 2% per decade. The ratio of the volumes of grey to white matter was the same for the two sexes at all ages. Its mean value was 1.3 at the age of 20, falling to 1.1 at the age of 50, then rising steadily to over 1.5 at 100 years. It is impossible in practice to correct these measurements for the effects of fixation or secular change. Fourteen hemispheres from thirteen elderly female dements were also measured. The total volume was 18% lower than for an age-matched group of normals, but the ratio of grey to white matter was identical.

Adult↗
PubMedDate not supplied

Automated differential cell counting on a sector of the normal human hippocampus: the influence of age.

The neurons and the glia of the human hippocampus are notoriously vulnerable in various pathological conditions including those linked to ageing. There may even be differences between the young and the old in the absence of manifest disease. Using an image analyser, systematic measurements of cell numbers in the region of the Sommer (Hl) sector of the human hippocampus have been made on post-mortem tissue from thirty-seven female and forty-nine male subjects aged between 15 and 96 years. In fifteen male and fifteen female subjects both hemispheres were available for analysis so that measurements were made on a total of 116 hemispheres. For each specimen the fresh volume of the hemisphere was measured and corrections subsequently made for changes in size which occurred during fixation, processing, mounting and staining. After all the correction factors had been applied the number of nucleolated neurons was found to fall by about 3.6% per decade (P less than 0.0001). There was no significant age-related change in the number of glia. Marked individual variations were found.

Adolescent↗