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Biomedical subjects

R J Ellis

Publications and source records attributed to R J Ellis.

178 records · Page 10Linked to original sources
PubMed1970

Specificity of cycloheximide in higher plant systems.

Although cycloheximide is extremely inhibitory to protein synthesis in vivo in higher plants, the reported insensitivity of some plant ribosomes suggests that it may not invariably act at the ribosomal level. This suggestion is reinforced by results obtained with red beet storage tissue disks, the respiration of which is stimulated by cycloheximide at 1 microgram per milliliter. Inorganic ion uptake by these disks is inhibited by cycloheximide at 1 microgram per milliliter while the uptake of organic compounds, by comparison, is unaffected. Ion uptake by all nongreen tissues tested is inhibited by cycloheximide, but leaf tissue is unaffected, indicating that the ion absorption mechanism in the leaf may differ fundamentally from that in the root. It is concluded that cycloheximide can affect cellular metabolism other than by inhibiting protein synthesis and that the inhibition of ion uptake may be due to disruption of the energy supply.

Journal Article↗
PubMed1969

[Chloroplast ribosomes: stereospecificity of inhibition by chloramphenicol].

Chloroplast ribosomes from tobacco leaves show the same stereospecificity of inhibition by chloramphenicol as bacterial ribosomes do. Cytoplasmic ribosomes from the same leaves are unaffected by chloramphenicol. These results remove doubts raised by nonstereospecific effects of chloramphenicol on higher plant cells and support the concept that chloroplasts have evolved from prokaryotes.

Carbon Isotopes↗
PubMed1967

Activation of protein synthesis by microsomes from aging beet disks.

Microsomal fractions isolated from sterile, aged disks of red beetroot incorporate leucine into protein when supplemented with the supernatant fraction, ATP, GTP, and KCl; the incorporation is sensitive to RNase and is not due to bacteria. The microsomal activity is inhibited by puromycin and cycloheximide but is virtually insensitive to both d-threo and l-threo-chloramphenicol, as predicted from physiological studies.Microsomes isolated from fresh disks have much lower incorporating ability than those from disks aged for 1 or 2 days; maximal activity occurs when the rate of protein synthesis by the intact disks is highest. The low activity of fractions from fresh disks is attributable to a deficiency in the microsomal fraction and not to the supernatant fraction; it is not due to a dissociable inhibitor. The RNA content of the microsomal fraction increases with aging and so the increase in incorporating ability may be due to a synthesis of messenger RNA induced by slicing, rather than to an activation of pre-existing messenger. These results support the view that the aging phenomenon involves a derepression of gene activity.

Journal Article↗
PubMedDate not supplied

Optimal use of photomultipliers for chemiluminescence and bioluminescence applications.

Photomultipliers are the preferred detectors for quantifying weak or short-lived light emissions. The quality of signal recovery has an upper limit imposed by the statistical nature of light detection. It is shown that the photon counting method can provide performance close to ideal, whereas performance in the current measuring method is degraded by noise in the multiplier gain process and by the nature of the dark current. Performance variations because of changes in temperature, shock, vibration and magnetic field effects are significantly reduced when using the photon counting method. The effects of dead-time can be corrected making photon counting superior to current measuring with regard to dynamic range. The benefits of using photon counting packages are presented.

Light↗