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Biomedical subjects

C W Ross

Publications and source records attributed to C W Ross.

61 records · Page 4Linked to original sources
PubMed1976

Attempts to detect cyclic adenosine 3':5'-monophosphate in higher plants by three assay methods.

Endogenous levels of cyclic adenosine-3':5'-monophosphate in coleoptile first leaf segments of oat (Avena sativa L.), potato (Solanum tuberosum L.) tubers, tobacco (Nicotiana tabacum L.) callus, and germinating seeds of lettuce (Lactuca sativa L.) were measured with a modified Gilman binding assay and a protein kinase activation assay. The incorporation of adenosine-8-(14)C into compounds with properties similar to those of cyclic AMP was also measured in studies with germinating lettuce seeds. The binding assay proved reliable for mouse and rat liver analyses, but was nonspecific for plant tissues. It responded to various components from lettuce and potato tissues chromatographically similar to but not identical with cyclic AMP. The protein kinase activation assay was much more specific, but it also exhibited positive responses in the presence of compounds not chromatographically identical to cyclic AMP. The concentrations of cyclic AMP in the plant tissues tested were at the lower limits of detection and characterization obtainable with these assays. The estimates of maximal levels were much lower than reported in many previous studies.

Journal Article↗
PubMed1975

Studies on the presence of adenosine cyclic 3':5'-monophosphate in oat coleoptiles.

The incorporation of adenosine-8-(14)C into adenosine cyclic 3':5'-monophosphate in coleoptile-first leaf segments of Avena sativa L. was investigated. Homogenates of segments incubated in adenosine-8-(14)C for either 4 or 10 hours were partially purified by thin layer chromatography followed by paper electrophoresis. A radioactive fraction, less than 0.06% of the (14)C present in the original homogenate, migrated as adenosine cyclic 3':5'-monophosphate during electrophoresis. Upon treatment with cyclic nucleotide phosphodiesterase, however, less than 10% of this radioactive fraction appeared as 5'-AMP. Deamination with NaNO(2) as well as further chromatographical purification also suggested that only a small fraction of the (14)C in the partially purified samples could be in adenosine cyclic 3':5'-monophosphate. The data suggest that levels of this nucleotide can probably be no greater than 7 to 11 picomoles per gram of fresh weight in oat coleoptiles. Treatment of such coleoptiles with physiologically active concentrations of indoleacetic acid, furthermore, had no significant effect on the (14)C radioactivity in marker adenosine cyclic 3':5'-monophosphate-containing fractions at any stage of purification during several experiments.In a single experiment, no labeled guanosine cyclic 3':5'-monophosphate could be detected in oat coleoptile-first leaf segments incubated in guanosine-8-(14)C either with or without indoleacetic acid. These results do not support the hypothesis that a cyclic nucleotide mediates the action of indoleacetic acid on oat coleoptile extension.

Journal Article↗
PubMed1975

Promotion of radish cotyledon enlargement and reducing sugar content by zeatin and red light.

Effects of zeatin on amino acid and sugar contents of detached radish (Raphanus sativus L.) cotyledons were investigated to determine if accumulation of these solutes contributes to cytokinin-enhanced growth. Protein and amino acid levels were not significantly affected, but in cotyledons incubated in light the hormone caused greater accumulations of reducing sugars than occurred in light controls. Continuous fluorescent light or a few minutes of red light increased both the growth rate and the reducing sugar levels compared to dark controls. A far red treatment following red light overcame the promoting effect of the latter. Amounts of reducing sugars were closely associated with growth under the above conditions. Activity of an unidentified amylase was elevated by continuous light or a red light treatment (nullifiable by far red), suggesting that reducing sugars were derived from starch. Zeatin-treated cotyledons exhibited less amylase activity than did light controls, perhaps implicating cytokinin-stimulated conversion of fats to sugars in light. In darkness zeatin promoted cotyledon growth but did not increase sugar levels nor amylase activity, suggesting that enhanced ion accumulation also contributes to the more rapid water uptake leading to growth.

Journal Article↗
PubMed1974

Activation of 80S Maize Ribosomes by Red Light Treatment of Dark-grown Seedlings.

The in vitro protein synthetic activity of 80S ribosomes from leaves of dark-grown corn seedlings was enhanced (at low Mg(2+) levels) by a 5-minute red light treatment applied 2 hours prior to tissue harvest. The effect was completely reversed by an immediate brief far red treatment, suggesting that ribosome activation is controlled by the phytochrome system. Experiments in which the interval between light treatment and tissue harvest was shortened indicate that the response was quite rapid. The initial increase in activity was detected within 30 minutes, followed by a rapid increase during the next 1.5 hours. No further increase occurred after 2 to 3 hours.The change in ribosome activity relates, at least in part, to an increase in the level of peptidyl-tRNA associated with ribosomes. Removal of peptidyl-tRNA from light-treated ribosomes also completely reversed the red light effect. Activation of ribosomes by 2 to 3 hours continuous white light (as previously reported) differs from red light activation in that reversal of this response requires salt washing of the ribosomes in addition to removal of peptidyl-tRNA.

Journal Article↗
PubMedDate not supplied

Nurses' personal death concerns and responses to dying-patient statements.

This study investigated the concept that a professional's awareness of concerns about her own death is helpful in the treatment of dying patients by using a fantasy of the subject's own life and death in relationship to her response to dying-patient statements. Data produced by this study supported this concept. The study also examined various defensive strategies to fear of death and their relationship to interactions with terminal patients. The defensive strategies were not found to contribute to the differential changes measured by this investigation.

Adult↗