Biomedical subjects

G C Webster

Publications and source records attributed to G C Webster.

18 recordsLinked to original sources

PubMed1991

Evaluation of a "do not resuscitate" policy in intensive care.

The decision to withhold cardiopulmonary resuscitation from a patient within an intensive care unit (ICU) may be a difficult but appropriate one for which there are few guidelines. We describe the formulation of a Do Not Resuscitate (DNR) policy in our multidisciplinary ICU. To evaluate the effect of implementation of the DNR policy on physician practice and on communication among physicians, nurses, patients and their families, we interviewed physicians and nurses caring for patients designated DNR before (n = 8) and after (n = 17) implementation of the DNR policy. We found that DNR orders in the ICU were not infrequent (2-3 per week). All patients designated DNR were either irreversibly ill or not responsive to maximal therapy, and 22 of 25 were not competent. The DNR order was not accompanied by withdrawal of other therapy in 50% of cases and one patient recovered and was discharged from hospital. The implementation of the DNR policy encouraged greater physician consultation with other physicians, patients and their families. Although there were differences in perception of communication between physicians and nurses, we believe that the DNR policy influenced physician practice and enhanced overall communication in the ICU.

Age Factors↗

PubMed1984

Effect of age on peptide chain initiation and elongation in preparations from brain, liver, kidney and skeletal muscle of the C57B1/6J mouse.

The effects of age on the initiation and elongation stages of protein synthesis were measured in cell-free preparations from brain, liver, kidney and skeletal muscle of young (3-5 months) and senescent (23-27 months) female C57B1/6J mice. The ability to form initiation complexes from isolated 40 S and 60 S ribosomal subunits decreased only slightly with age. In contrast, the rate of peptide chain elongation decreased by 67% in brain preparations, 80% in liver, 81% in kidney and 85% in skeletal muscle of the senescent mice when compared with the young mice.

Aging↗

PubMed1984

Lowered rates of protein synthesis by mitochondria isolated from organisms of increasing age.

The rate of protein synthesis was measured in isolated mitochondria from Drosophila melanogaster and from the livers and kidneys of C57BL/6J mice of increasing ages. Over the life-span of the organisms, the synthesis of mitochondrial proteins decreased to a level which was less than half the original rate. Concomitant with this decrease, the amount of mitochondria which could be isolated from the organisms declined by about 30%. Thus, the separate translational system of mitochondria exhibited an age-related decrease in activity which was in addition to the decrease already observed in the cytoplasmic ribosomal system.

Aging↗

PubMed1984

Specific disappearance of translatable messenger RNA for elongation factor one in aging Drosophila melanogaster.

The molecular basis was sought for the previously observed drop in the synthesis of elongation factor one (EF-1) and subsequent decline in overall protein synthesis in aging Drosophila melanogaster. It has been found that translatable poly(A+)RNA for EF-1 disappears at about the same time that EF-1 synthesis decreases. This disappearance is specific for EF-1, since overall poly(A+)RNA levels and their translation to cellular proteins remain constant over the life-span of the organism. The disappearance of translatable RNA is not the result of a specific loss of the polyadenylate segment of poly(A+)RNA, since poly(A-)RNA exhibits a similar specific loss of translation ability for EF-1.

Aging↗

PubMed1983

Decline in synthesis of elongation factor one (EF-1) precedes the decreased synthesis of total protein in aging Drosophila melanogaster.

The decrease in the rate of protein synthesis in aging adult Drosophila melanogaster was found previously to be due, to a great extent, to a drop in the rate of peptide chain elongation, and principally to lowered activity of elongation factor one (EF-1). This decrease does not appear to be caused by appearance of an inhibitor of peptide chain elongation. Instead, the synthesis of EF-1 declines markedly early in adult life. This decrease is followed by lowered activity of EF-1 and by a drop in the synthesis of most of the cellular proteins.

Aging↗

PubMed1982

Effects of age on the post-initiation stages of protein synthesis.

The peptide chain elongation stage of protein synthesis in Drosophila melanogaster was found to decrease markedly with age. The decrease paralleled the age-related decrease in overall protein synthesis. In contrast, the termination stage showed little decrease until the organisms were very old. Of the three reactions that comprise peptide chain elongation, the binding of aminoacyl-tRNA to ribosomes decreased greatly with age, and the decrease paralleled that of peptide chain elongation and of overall protein synthesis. The peptidyl transfer reaction decreased moderately, and the translocation reaction exhibited no measurable decrease with age. Thus, decreased binding of aminoacyl-tRNA to ribosomes appeared to be a major contributor to the age-related decreases in peptide chain elongation and overall protein synthesis.

Aging↗

PubMed1982

Progressive reduction in protein synthesis during involution and aging of the mouse thymus.

Total proteolytic activity and protein synthesis were measured in cell-free extracts of the thymus during its involution in 1-30-week-old C57Bl/6J mice, and in 10-, 12-, 14-, and 24-month-old adult mice of the same strain. The mean specific activity of the proteolytic enzymes exhibited no significant change during involution or throughout the mean life-span of the animals. In contrast, the rate of protein synthesis decreased rapidly during involution, and continued to decrease at a slower rate during aging of the mice.

Acid Phosphatase↗

PubMed1982

Age-related DNA fragmentation in two varieties of Drosophila melanogaster, Phaseolus (cotyledons), and three tissues of the mouse.

Agarose gel electrophoresis showed that no age-related DNA fragmentation occurred in wild-type or vestigial wing Drosophila, or in DNA from mouse brain and heart. DNA from mouse liver possessed a large fragment, estimated at 24 megadaltons, in all ages tested. Phaseolus cotyledon DNA possessed a fragment of approximately 3.5 megadaltons in both imbibed seeds and 12-day-old cotyledons. Thus, there appeared to be no age-related increase in the break-down of DNA into large fragments.

Aging↗

PubMed1981

Changes in the levels and the rate of synthesis of transfer RNA in tissues of mice of different ages.

Levels of transfer RNA (tRNA) were determined in liver, kidney, skeletal muscle, heart, and brain of young (35-day), adult (12-month) and old (24-month) female C57BL/6J mice. Kidney and liver showed little change in tRNA levels between young and adult mice, but the levels decreased in old mice. Skeletal muscle tRNA decreased steadily from young to old mice. Heart tRNA increased during maturation to adult organisms and then decreased in old individuals. Brain levels of tRNA increased steadily. No age-related change in the rate of transport of orotic acid into cells was observed. However, all tissues exhibited a decrease in uridine pools between adult and old mice. Most importantly, all tissues of aging mice showed a decrease in the rate of tRNA synthesis.

Aging↗

PubMed1981

The effect of age on the initiation of protein synthesis in Drosophila melanogaster.

Polyribosome levels exhibited a marked, age-related decrease in adult Drosophila melanogaster. Since decreased polyribosome levels can be due to decreased initiation of translation, initiation was measured by determination of methionyl-tRNA binding to the 40 S and 80 S initiation complexes. Compared with 1-day-old adults, 48-day-old adults exhibited no more than a 12% decrease in methionyl-tRNA binding to 40 S subunits and a 20% decrease in binding to 80 S particles. Increased age, therefore, had relatively little effect on initiation, and the decreased polyribosomal content was probably due to the deterioration of some other component of the translation system.

Aging↗

PubMed1981