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Biomedical subjects

R A Jones

Publications and source records attributed to R A Jones.

At least 19 recordsLinked to original sources
PubMed1992

Thermodynamics and structure of a DNA tetraplex: a spectroscopic and calorimetric study of the tetramolecular complexes of d(TG3T) and d(TG3T2G3T).

We report a combined thermodynamic and structural characterization of a DNA tetraplex. Using spectroscopic and calorimetric techniques, we demonstrate that d(TG3T) and d(TG3T2G3T), in the presence of K+, form stable tetramolecular complexes. From differential scanning calorimetry measurements, we obtain the following thermodynamic profiles for formation of each tetraplex at 25 degrees C: delta G degrees = -6.9 kcal/mol of tetraplex (or -2.3 kcal/mol of tetrad; 1 cal = 4.184 J), delta H degrees = -62.6 kcal/mol of tetraplex (or -20.9 kcal/mol of tetrad), and delta S degrees = -186.9 cal.K-1.mol-1 of tetraplex (or -62.3 cal.K-1.mol-1 of tetrad) for the d(TG3T) tetraplex; and delta G degrees = -20.2 kcal/mol of tetraplex (or -3.4 kcal/mol of tetrad), delta H degrees = -123.2 kcal/mol of tetraplex (or -20.5 kcal/mol of tetrad), and delta S degrees = -346.0 cal.K-1.mol-1 of tetraplex (or -57.7 cal.K-1.mol-1 of tetrad) for the d(TG3T2G3T) tetraplex. These data demonstrate that at 25 degrees C a G-tetrad can exhibit considerable stability, comparable to or even exceeding that of most Watson-Crick nearest-neighbor interactions, with this stability resulting from a very favorable enthalpy of formation. Temperature-dependent CD measurements reveal that the melting temperatures of both tetraplexes exhibit unusually low salt dependences. This unexpected behavior may reflect a diminished charge density due to bound K+ ions. For each complex, the Na+ and K+ forms exhibit drastically different isothermal and temperature-dependent CD profiles, with the K+ forms of each tetraplex melting more sharply and at a higher temperature than the Na+ forms. Using one- and two-dimensional NMR techniques, we show that the strands in the tetramolecular complex of d(TG3T), K+ are all parallel and that the guanine glycosidic conformations are all anti.

Base Sequence↗
PubMed1992

An integrated ELF magnetic-field generator and incubator for long-term in vitro studies.

Long-term studies of the effects of low-frequency magnetic fields on cells in culture require an incubator that is free of contaminating magnetic fields and that provides automatic control of exposure duration, uniform applied fields, a uniform and well-controlled environmental temperature, and high reliability of the total system. We describe a dual-incubator system in which the enclosed solenoid of either unit can provide a sham exposure while the other generates a magnetic induction of up to 500 microT. Each solenoid-incubator unit contains an enclosed rack that can hold as many as 140 petri dishes for culturing cells; each unit is heated radiantly by circulating warm water. Field-exposure conditions and temperatures are continuously monitored and controlled by a microcomputer.

Cells, Cultured↗
PubMed1992

Measured energy expenditure and plasma substrate and hormonal changes after severe head injury.

The influence of head trauma on the pattern of response to injury has been studied. Metabolic and hormonal data from brain injured patients over 20 days following injury were compared with an existing data base from non-head-injured patients and control subjects. The results demonstrated elevated concentrations of plasma glucose, lactate, non-esterified fatty acids (NEFA), cortisol, glucagon and insulin above that of control values in both groups after injury. Head injury as a separate factor did not affect the concentrations of any of these plasma substrates and hormones independently of its contribution to the Injury Severity Score (ISS). However, plasma catecholamine concentrations were higher in the head injured initially and at 7 days after injury. All head-injured patients showed an increase in metabolic rate (above predicted values) at some stage after injury. It should be noted, however, that there were some features of head injury (and its treatment) such as paralysis, ventilation and fasting which were not matched in the non-head-injured group. It was concluded that the metabolic changes occurring after head injury are similar to those occurring after extracranial injury and that therapeutic intervention has a major effect on the level of energy expenditure seen in these patients.

Adolescent↗
PubMed1992

Resistance to phloem transport of potato leafroll virus in potato plants.

A 'double-graft sandwich' technique in which sections of potato stem from different potato cultivars were grafted between a susceptible healthy stock plant and a potato leafroll virus (PLRV)-infected scion was used to study the rate of phloem transport of PLRV in cultivars differing in resistance to PLRV infection (IR) and accumulation (AR). Resistance to phloem transport (i.e. delayed PLRV systemic movement) was found in Bismark cultivar (IR A(S)). This was independent of IR and AR as the rate of movement in Bismark cultivar was markedly slower than that in Omega and Spunta (IR AR), Delaware (I(S) AR), and Desiree and Renova (I(S) A(S)) cultivars. It operated in Bismark cultivar stems of two different ages, but did not operate against potato virus X (PVX) and was not influenced by previous infection with this virus. Aphid vector (Myzus persicae) feeding preferences and colonization rates differed between cultivars, but the cultivar characteristics responsible were unrelated to IR, AR or resistance to phloem transport. Delayed systemic movement of PLRV out of leaves inoculated with viruliferous aphids was independent of AR and resistance to phloem transport, and remained unaffected by previous infection with PVX. It was also independent of cultivar factors causing different aphid feeding preferences and colonization rates, but may be linked to IR.

Biological Transport↗
PubMed1992

Obesity stigma reduction in medical students.

The purpose of this study was to develop and evaluate an educational intervention designed to modify the stigma held by first-year medical students towards obese patients. The intervention, composed of video, audio and written components, was based on Petty and Cacioppo's elaboration likelihood model. Prior to the course, the medical students held largely accurate beliefs about the causes of obesity, but they still maintained negative stereotypes of the obese as lazy and lacking in self-control. Analysis of students' attitudes toward obese patients five weeks and one year after the course indicates that the intervention was effective. At the five-week assessment, students in the intervention group differed from students in the control group on six of eight measures of attitudes toward the obese. One year after the course, the intervention group was significantly more likely to rate genetic factors as important in obesity and less likely to blame the obese for their condition.

Adult↗
PubMed1992

Self-perceived information needs and concerns of elderly persons.

The research was intended to identify the dimensions underlying self-perceived information needs and concerns of an elderly population. The spontaneously mentioned needs and concerns expressed in 271 letters from a sample of the population were extracted and a multidimensional scaling procedure was used to represent the 58 most frequently mentioned items in configurations of varying dimensionality. To interpret the multidimensional spaces, another sample of 176 elderly subjects was asked to rate the 58 concerns on eight properties. These ratings were then regressed onto the multidimensional configurations. The results indicate that the most frequently mentioned information needs and concerns of elderly persons can be parsimoniously understood in terms of three underlying dimensions: (1) Improving the Quality of Life vs Securing the Necessities of Life, (2) Health-related vs Not Health-related, and (3) Individual vs Societal Responsibility.

Activities of Daily Living↗
PubMed1979

Infants of very low birthweight. A 15-year analysis.

357 babies weighing 501--1500 g were born alive at Hammersmith Hospital in 1961--75. 58.5% died in the neonatal period and 1.4% at 4--25 months of age. 1.4% of the total are untraced, 5.3% have major handicap, 5.6% have minor handicap, and 27.8% are apparently normal. There was no significant improvement in neonatal mortality in three 5-year periods, 1961--65, 1966--70, and 1971--75, except that more small-for-gestational-age babies survived in the last period than in the first. More of these babies survived than did babies whose birthweight was appropriate for gestational age. There was no significant improvement in the proportion of handicapped children among the very-low-weight liveborn babies throughout the 15-year period, despite increasing complexity of care.

Adolescent↗
PubMed1979

Postoperative hypophosphataemia.

The possible mechanisms of postoperative hypophosphataemia were studied in women undergoing uncomplicated cholecystectomy. Six patients were allocated to each of three groups. Group I received no intravenous fluids, group II received dextrose/saline solution alone and group III received dextrose/saline solution with phosphorus supplementation. The serum concentration of inorganic phosphorus fell in all three groups, the greatest fall being in the group receiving dextrose/saline solution. However, the lowest level reached (0.82 mmol/l) was within the normal range for our laboratory. Concentrations of red blood cell adenosine triphosphate and 2,3-diphosphoglycerate showed similar changes. The operations were not associated with a large catabolic response nor with an increase in urinary phosphorus excretion. The postoperative reduction in serum concentration of inorganic phosphorus appeared to be due mainly to haemodilution. There is no indication for routine phosphorus supplementation following uncomplicated elective surgery.

Cholecystectomy↗
PubMed1979

Dosage schedule for intravenous aminophylline in apnoea of prematurity, based on pharmacokinetic studies.

15 preterm infants were treated for recurrent apnoea with theophylline. 5 were given oral choline theophyllinate, but this was erratically absorbed. 14 were given IV aminophylline on 23 occasions. Apparent volume of distribution of theophylline in 12 infants was 0.71 +/- 0.18 1/kg (mean +/- SD). Plasma clearance rate measured in 11 infants at steady state was 18.6 +/- 4.8 ml/kg per hour. Calculations show that a loading dose of 6.2 mg/kg aminophylline intravenously and maintenance of 4.4 mg/kg per day would produce serum levels of between 6 and 12 mg/l in all but one of the infants studied, with no infant having toxic levels.

Aminophylline↗
PubMed1979

Potential clinical applications of a new method for quantitation of plasma levels of 5-fluorouracil and 5-fluorodeoxyuridine.

A new high-pressure liquid chromatographic method for the clinical assay of 5-fluorouracil and 5-fluoroudexyuridine has been developed. The sensitivity and specificity of the method equals that of gas chromatography/mass spectrometric methods. The practical value of the method has been demonstrated by its application in several preliminary clinical studies of 5-fluorouracil in which plasma levels of 10(-8)-10(-6)M were readily monitored.

Chromatography, High Pressure Liquid↗
PubMed1979

Infant feeding.

Explore the source record for details and available documents.

Animals↗
PubMed1978

Common mistakes in infant feeding: survey from London borough.

A survey of infant-feeding practices among 265 mothers of 12-week-old infants in a London borough showed that only 18 gave breast milk alone, 236 giving bottle feeds, and 197 solids. Serious mistakes in feed preparation were common, and only 51 mothers followed manufacturers' instructions exactly. Most mothers (239) had attended a well-baby clinic, but clinic staff gave conflicting advice on infant feeding. Health workers must pay greater attention to educating mothers on the details of infant feeding if the risks of hypernatraemia and obesity are to be reduced.

Animals↗
PubMed1978

High-pressure liquid chromatography in polynucleotide synthesis.

Reverse phase high-pressure liquid chromatography (HPLC) using columns containing microparticulate materials with bonded octadecyl groups has been developed as a rapid and efficient method for the separation of nucleosides, nucleotides, and, in particular, of protected oligonucleotides which are standard intermediates in the stepwise synthesis of deoxyribopolynucleotides. Reported are extensive studies of the influence of the different purine and pyrimidine bases, of protecting groups, of the phosphate groups, and of the chain lengths of oligonucleotides on their retention on such columns. Further, the application of HPLC in the stepwise synthesis of an oligonucleotide, d(G-G-A-A-G-C-T-T-A-A-C), has been described. The methods, which are herein described, lend themselves to separations on a preparative scale and effect a marked reduction (up to 50%) in the time required for the synthesis of oligonucleotides.

Chromatography, High Pressure Liquid↗