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Biomedical subjects

R P Jones

Publications and source records attributed to R P Jones.

15 recordsLinked to original sources
PubMed1992

Voltage fields surrounding needles used in regional anaesthesia.

Using a bench model, we have studied the voltage fields surrounding both insulated and uninsulated needles used in regional anaesthesia. The findings were compared with earlier computer predictions which suggested that the fields would be markedly different for the two types of needle. The results confirm that the fields differ markedly and suggest that the use of insulated needles may not necessarily improve the accuracy of nerve location and that uninsulated needles may be more appropriate.

Anesthesia, Conduction↗
PubMed1991

Variable apparatus deadspace.

A variable apparatus deadspace was used to maintain normocapnia during artificial ventilation of the lungs in anaesthetised adults. End-tidal carbon dioxide tension could be varied, if the need arose, within the range 4.0-5.2 kPa in both open and circle breathing systems when a fixed tidal volume of 12 ml.kg-1 and minute volume ventilation of 120 ml.kg-1.min-1 were employed.

Abdomen↗
PubMed1988

Absence status epilepticus resulting from metrizamide and omnipaque myelography.

Two cases of absence status are described, one case following metrizamide myelography and the other from omnipaque myelography. Metrizamide has been well known to cause convulsive seizures even in patients without epilepsy. The exact mechanism is not known but appears to be direct neuronal toxic effects possibly due to competitive inhibition of hexokinase activity. The acute confusional state following myelography from water soluble agents is reviewed. In view of the difficulty in clinical diagnosis and the excellent response to anticonvulsant therapy, the possibility of this clinical entity should be specifically excluded by EEG in any person suffering from prolonged confusion following myelography with water soluble agents.

Aged↗
PubMed1987

Ethanol and the fluidity of the yeast plasma membrane.

Evidence is presented for an exponential increase in yeast plasma membrane fluidity (as measured by passive permeability to acetic acid) with ethanol concentration. The role of adaptation of yeast cells to ethanol can be seen in the existence of a threshold concentration before the onset of an observed fluidizing effect. The physiological state of the yeast cells is also demonstrated to influence the sensitivity of the membrane to fluidization by ethanol. On the basis of these results, the concept that increased fluidity is an adaptive response conferring ethanol tolerance is disputed. An alternative hypothesis, namely that the observed increase in fluidity is the net result of a number of more fundamental changes, is presented to explain the observed effects.

Cell Membrane↗
PubMed1987

Factors influencing deactivation of yeast cells exposed to ethanol.

The lyotropic series discovered in 1888 by Hofmeister describes the effect of solutes on the structure and physical chemistry of the aqueous phase. Chaotropic members of the lyotropic series destructure the aqueous phase while antichaotropic solutes act to enhance the structuredness of the aqueous phase. This alteration of the aqueous phase affects the physical structure or physicochemical state of any other phase exposed to the aqueous phase, such as the plasma membrane of any cell. Solute lyotropy is therefore, via its ability to alter the physicochemical state of the plasma membrane, able to modify the processes of yeast cell deactivation (i.e. the processes leading to loss of ability to replicate and to eventual cell death) in the presence of toxic solutes such as ethanol. In this study the effect of a variety of salts and non-ionic solutes upon cell deactivation in the presence of 16% w/v ethanol is explained in terms of the lyotropic series. Chaotropic salts protect against ethanol-induced deactivation and antichaotropic salts enhance the rate of this process. It is proposed that the mechanism by which chaotropic solutes exert their protective effect involves a reduction in the activity coefficient of the ethanol, thereby reducing the concentration of ethanol within the plasma membrane.

Cell Membrane↗
PubMed1985

The logical status of brain death criteria.

This article is an attempt to clarify a confusion in the brain death literature between logical sufficiency/necessity and natural sufficiency/necessity. We focus on arguments that draw conclusions regarding empirical matters of fact from conceptual or ontological definitions. Specifically, we critically analyze arguments by Tom Tomlinson and Michael B. Green and Daniel Wikler, which, respectively, confuse logical and natural sufficiency and logical and natural necessity. Our own conclusion is that it is especially important in discussing the brain death issue to observe the distinction between logical and natural sufficiency/necessity in a strict fashion.

Brain Death↗
PubMed1979

Acute bilateral anterior dislocation of the shoulders.

In 3 cases of simultaneous bilateral anterior dislocation of the shoulders, considering the forces which predispose to anterior dislocations, it is postulated that in each case forced abduction and external rotation or abduction with hyperextension causes these injuries to occur.

Adult↗