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Biomedical subjects

A Prescott

Publications and source records attributed to A Prescott.

25 records · Page 2Linked to original sources
PubMed1991

Control of anthocyanin biosynthesis in flowers of Antirrhinum majus.

The intensity and pattern of anthocyanin biosynthesis in Antirrhinum flowers is controlled by several genes. We have isolated six cDNA clones encoding enzymes in the pathway committed to flavonoid biosynthesis and used these to assay how the regulatory genes that modify colour pattern affect the expression of biosynthetic genes. The biosynthetic genes of the later part of the pathway appear to be co-ordinately regulated by two genes, Delila (Del), and Eluta (El), while the early steps (which also lead to flavone synthesis) are controlled differently. This division of control is not the same as control of anthocyanin biosynthesis by the regulatory genes R (S) and C1 in maize aleurone, and may result from the adaptive significance of different flavonoids in flowers and seeds, reflecting their attractiveness to insects and mammals respectively. El and del are probably involved in transcriptional control and both genes appear to be able to repress expression of some biosynthetic genes and activate expression of others.

Anthocyanins↗
PubMed1991

Outcome and cost analysis of scheduled versus emergency scleral buckling surgery.

Conventional wisdom holds that a retinal detachment of recent onset should be regarded as a surgical emergency. A delay in surgery may result in an extension of detachment for patients with an attached macula and a worse visual outcome for patients with a detached macula. However, the potential disadvantages of performing surgery on an emergency basis must be weighed against the risks of delaying surgery; disadvantages include a greater frequency of operative complications resulting from fatigue factors among the operating personnel, an increased anesthetic risk due to inadequate time to assess and stabilize coexisting medical problems, and higher hospital costs. In this retrospective study covering 4 1/2 years, we compared the risks, benefits, length of hospitalization, and costs of scleral buckling surgery for retinal detachments performed as an emergency procedure or on the day following admission. After a 15% random selection from 884 consecutive operations, 48 emergency procedures were compared with 89 scheduled procedures. Patients selected for emergency surgery had better visual prognoses than scheduled patients. The potential for risk of systemic complications was not a reason for postponing surgery. None of the 18 patients with an attached macula experienced macular involvement while awaiting scheduled surgery. There were no differences between emergency and scheduled patients in ocular or systemic complications, rate of reattachment, rate of decreased visual acuity following surgery, visual outcome adjusted for prognosis, or, since 1985, length of hospital stay. Cost was greater for patients having emergency surgery, because of a difference in pay scales for support personnel.

Cost-Benefit Analysis↗
PubMed1989

Activity of the transposon Tam3 in Antirrhinum and tobacco: possible role of DNA methylation.

The transposon Tam3 from Antirrhinum majus can transpose in a heterologous host (Nicotiana tabacum); thus the element is autonomous, probably encoding the specific information required for its own transposition. In transgenic tobacco Tam3 rapidly becomes methylated at its ends whilst adjacent flanking sequences remain hypomethylated. This methylation may account for our failure to detect Tam3 transposition in the progeny of transgenic tobacco. Treatment with the inhibitor of cytosine methylation, 5 aza-cytosine appeared to induce transposon related activity at a low level. In Antirrhinum methylation also appears to be associated with inactivation of Tam3 copies.

DNA↗
PubMed1989

Chemical reactivity of aluminium-based pharmaceutical compounds used as phosphate-binders.

Several aluminium-containing substances, including antacids used as phosphate-binders in treating renal failure, have been analysed in-vitro under different pH conditions for the release of Al3+ ions and for binding of phosphate. Control experiments on different forms of pure aluminium hydroxide validated the methods. At pH 2 it was the most amorphous forms which released Al3+ most rapidly. These aluminium ions, available for absorption by the patient, were released from all antacids tested, but no firm phosphate-binding was detected while the pH remained at 2. Phosphate was bound at pH 8, by adsorption onto the surface of aluminium hydroxide. No significant amounts of free Al3+ exist in solution at pH 8, since at that pH aluminium hydroxide is precipitated. The most amorphous forms of this solid were the most efficient phosphate-binders. Alumino-silicate salts require prior exposure to acid to produce free Al3+ before they can act as phosphate-binders, whereas amorphous aluminium hydroxide acts as an efficient phosphate-binder without prior exposure to acid. Chemical principles are employed to show why aluminium release and phosphate-binding are separate and independent processes. Methods are proposed for maximizing the activity of phosphate- binders in-vivo, while minimising aluminium release.

Aluminum↗
PubMed1989

Urinary excretion of 3-methylhistidine, creatinine and total nitrogen by Kenyan children during acute measles and after recovery.

The urinary excretion of 3-methylhistidine (3MH), creatinine and total nitrogen was measured during the course of energy balance studies on 20 black Kenyan children. Studies were carried out over 24 h during an acute attack of measles with a second (control) study after recovery, and complete urinary collections were obtained on 14 ill and 18 recovered children. The nutritional status was assessed by anthropometry, and energy intake was determined by duplicate diet analysis. Twelve out of 13 acutely ill and 6 out of 17 recovered children were in negative energy balance. No effect on the rate of excretion of 3MH or of creatinine attributable to differences in nutritional status, of energy intake or to infection was observed. The linear relationship between the excretion rate of all three metabolites and body weight which was observed in recovered children was absent during acute infection. Nitrogen excretion was correlated (P less than 0.05) with the level of energy intake. The linear relationship between the rate of excretion of 3MH and creatinine and of 3MH and nitrogen was significantly closer in recovered than in ill children. The simultaneous effects of infection, underfeeding (and oliguria) on the rate of excretion of protein metabolites may be complex and contradictory. Our results suggest that the excretion of 3MH, creatinine and nitrogen is sustained during infection accompanied by negative energy balance. Disruption during infection of the relationship between the excretion of all three metabolites and body weight, and between 3MH and the other two metabolites suggests perturbation in protein metabolism at this time.

Child, Preschool↗