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Biomedical subjects

D J Sanders

Publications and source records attributed to D J Sanders.

At least 19 recordsLinked to original sources
PubMed1994

Effect of humidification on inhalation induction with isoflurane in children.

A well practised technique is important in achieving quiet induction of anaesthesia in children, but the volatile agent used also influences the process. Isoflurane results in more airway problems than halothane but recent studies have described several ways of improving the acceptability of isoflurane for inhalation induction of anaesthesia. We have studied the effect of humidification of inspired gases on respiratory complications and hypoxic episodes during induction. Forty-one children undergoing inhalation induction of anaesthesia with isoflurane and nitrous oxide in oxygen were allocated randomly to receive either humidified or non-humidified gas. Humidification did not result in a lesser incidence of problems. These findings are contrary to the results in a similar study in a predominantly adult sample which demonstrated a significantly lower incidence of complications using humidified gases.

Anesthesia, Inhalation↗
PubMed1992

Auto- and cross-correlation analysis of subthalamic nucleus neuronal activity in neostriatal- and globus pallidal-lesioned rats.

Statistical analyses (autocorrelation and first-order interstimulus interval) were conducted on the spontaneous activity of over 420 subthalamic neurons recorded in 5 groups (control, large globus pallidus kainic acid lesion, partial globus pallidus kainic acid lesion, partial globus pallidus ibotenic acid lesion and neostriatal lesion) of anesthetized rats. Cross-correlation and peristimulus time histogram (to frontal motor cortex stimulation at 0.7 mA) analyses were conducted on pairs (n = 58) of subthalamic neurons recorded simultaneously on a single microelectrode. Lesion of the globus pallidus increased spontaneous firing rate as compared to controls and shifted the pattern of spontaneous activity from either a regular or irregular pattern to a markedly bursting pattern. Neostriatal lesion reduced firing rate and reduced the likelihood of highly regular firing. In control, neostriatal and partial lesioned animals, approximately 1 in 3 pairs of neurons showed correlated firing. The correlations were joint increased probabilities of firing over intervals of 200-400 ms, suggesting a shared excitatory input. No short-interval (less than 10 ms) correlations were seen. Large globus pallidus lesion increased the likelihood of correlated firing (12 of 16 pairs). In all groups of animals the peristimulus time histograms (PSTHs) to motor cortex stimulation were more similar than would be expected by chance and pairs of neurons showed the same increases in response following globus pallidus lesion. Thus adjacent neurons share common cortical inputs and responsiveness to those inputs. These changes indicate that the globus pallidus influences the spontaneous firing rate and pattern of subthalamic neurons as well as the degree of correlated firing of adjacent neurons.

Action Potentials↗
PubMed1992

Phototoxicity testing in guinea-pigs.

The photoirritant potential of topically applied chemicals was studied using guinea-pigs. Solutions of test chemicals were applied to the skin, and after 30 min the animals were irradiated with near-ultraviolet radiation. Skin reactions were assessed subjectively between 3 and 72 hr after the start of treatment. Acridine and anthracene caused immediate photoirritation, whereas reaction to 8-methoxy-psoralen (8-MOP) was delayed; acridine was weakly active compared with the strong photoirritancy of anthracene and 8-MOP. Ethanol and a mixture of dimethylacetamide-acetone-ethanol (DAE) were satisfactory solvents, and a time interval of 15 to 30 min between application and irradiation was optimal. It is concluded that animal tests should not be recommended if ingredients have negligible absorption of sunlight. The safety hazard of ingredients absorbing near-ultraviolet and visible radiation may be assessed by laboratory animal procedures to satisfy governmental regulations. The use of guinea-pigs allows the study to act as a preliminary test for the selection of non-photoirritant concentrations for photoallergy testing and reduction of animal numbers. The risk to consumers of photoactive products may be properly assessed by human studies.

Acridines↗
PubMed1992

Thoracic electrical bioimpedance measurement of cardiac output and cardiovascular responses to the induction of anaesthesia and to laryngoscopy and intubation.

Noninvasive methods of determining cardiac output (by thoracic electrical bioimpedance) and arterial pressure (by intermittent oscillometry) were used to record minute-by-minute changes in heart rate, mean arterial pressure, stroke volume, cardiac output and systemic vascular resistance following induction of general anaesthesia and laryngoscopy and intubation in 60 healthy female patients who were either unpremedicated, or premedicated with temazepam or papaveretum-hyoscine. Anaesthesia was induced with a sleep dose (3-5 mg.kg-1) of thiopentone and maintained with 70% nitrous oxide in oxygen with 0.5-1% enflurane. Tracheal intubation was facilitated by administration of vecuronium 0.1 mg.kg-1. Mean arterial pressure and cardiac output decreased maximally 5 min after induction in all premedication groups by mean estimates of 21-25% and 14-22% respectively. Heart rate increased initially one minute after induction, but decreased to less than the baseline value 5 min after induction. Systemic vascular resistance was unchanged. The stimulus of laryngoscopy and tracheal intubation was accompanied by a significant pressor response and tachycardia one minute after intubation (with mean increases in mean arterial pressure and heart rate of 29-34% and 22-33% respectively). The increase in mean arterial pressure was secondary to an increase in systemic vascular resistance (36-57%), and was accompanied by a decrease in stroke volume (-25 to -31%). These changes were significant in all three groups. Cardiac output decreased only in unpremedicated patients. There were wide variations in the different haemodynamic indices.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Non-invasive measurement of cardiac output by thoracic electrical bioimpedance: a study of reproducibility and comparison with thermodilution.

The performance and reproducibility of the BoMED NCCOM3 thoracic electrical bioimpedance cardiograph (TEB) has been evaluated in volunteers and patients. In resting supine volunteers, we determined the coefficient of variability over short time periods (30 min) and over several days, and examined the effects of differences in electrode type and electrode placement. The mean (range) intra-subject coefficients of variation (CV) for thoracic fluid index (TFI) and stroke volume (SV) were 1.0% (0.4-1.8%) and 4.7% (2.1-8.5%), respectively over a 30-min period. The corresponding CV were 5.6% (2.3-10.9%) and 10.9% (6.1-14.8%) for measurements made at rest on four separate occasions. Use of different electrode types (RedDot and Medicotest) resulted in differences in TFI (P less than 0.01), but not in mean values for SV or cardiac output (Q); their use in individual subjects revealed differences of up to 20% in SV and Q. Alterations in electrode placement by 5 cm in the horizontal and diagonal planes produced no significant changes in TFI, SV or Q; changes in the longitudinal plane produced a graded change. Increases of 5 cm and 10 cm in thoracic length produced mean increases in TFI of 9.8% and 39.8%, respectively, and mean decreases in Q of 8.4% and 16.7% and SV of 7.5% and 15.8%. TEB measurements of Q and SV were compared with thermodilution (TD) in 16 intensive care patients. Mean (SEM) Q by TEB was 5.63 (1.10) litre min-1 compared with TD 4.38 (0.72) litre min-1 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Dose-response study of ultraviolet radiation for induction of photoallergy to tetrachlorosalicylanilide in guinea pigs.

The dose of ultraviolet light (UV) required to induce photoallergy to tetrachlorosalicylanilide (T4CS) in guinea pigs was studied. A simple induction technique consisting of only one treatment with adjuvant, chemical and UV was used. The concentration of T4CS, which was administered either topically or intradermally, was low to reduce self-screening of UV by the chemical. Doses of UVA from fluorescent blacklamps ranged from 0.4 to 300 kJ/m2. All animals were challenged with topically applied T4CS and 40 kJ/m2 UV. The results showed that incidence of photoallergy increased with increasing dose of UV and reached a plateau between 4.5-45 kJ/m2 following intradermal T4CS and 4-120 kJ/m2 following topical T4CS. The studies demonstrated for the first time decreased response following larger induction doses of UV; photoallergy was not induced by the largest induction dose of 300 kJ/m2. Attenuation of UVB during induction did not affect the decrease. The lack of response may be attributable to further photochemical reactions of a T4CS-protein conjugate with loss of antigenic properties, or to immune suppression initiated by either UVA or an interaction of T4CS and UVA.

Allergens↗
PubMed1986

Practice nurses and antismoking education.

A questionnaire on antismoking activities and education was sent to 369 nurses in general practice. The response rate was 80%. Although most of the nurses sometimes advised patients about smoking, routine antismoking education occurred less frequently. Only a few regularly referred smokers to other agencies for help, recommended aids to stop smoking, or used antismoking literature. Although the nurses thought that they had an important role in helping smokers to give up, they expressed little confidence in their effectiveness, believing that advice from the general practitioner and the smoker's personal determination to give up have more impact. The nurses expressed a need for training in antismoking education. Seventy seven per cent were interested in attending seminars and listed information about smoking, techniques for stopping, and counselling skills as priorities. If practice nurses are to use opportunities in primary care to help smokers there is clearly a need to provide further training and to establish the effectiveness of nurses in their role as smoking educators.

Attitude of Health Personnel↗
PubMed1984

The use of retrograde transport of horseradish peroxidase for studying the dendritic trees and axonal courses of particular groups of tract cells in the spinal cord.

Modifications have been made in Mesulam 's method for labelling neurons by retrograde transport of horseradish peroxidase, with tetramethylbenzidine as chromogen, with the object of increasing the extent of labelling of dendrites and axons. A procedure was devised specifically for studying spinomedullary and medullospinal tract systems, involving implanting easily-made HRP-agar pellets into areas of controlled damage in particular spinal fascicles, and sealing the site of implant with cyanoacrylate glue. Lesions of other fascicles were often made to limit transport to the implanted fascicle. Fourth-order dendrites were regularly labelled over long (30 cm or more) transport distances: axons were also labelled over this whole distance, often allowing exact study of the initial course of particular axons. Controls in both cat and rat showed that the uptake of HRP under these circumstances occurred almost wholly from the region of axonal damage at the site of implant which can be characterized histologically.

Animals↗
PubMed1984

Comparison of effect of peptide length and sulphation on acid secretory potency of gastrin in the cat in vivo and in vitro.

The gastric-acid secretory potency of gastrin peptides was investigated in vivo, in conscious cats prepared with gastric fistula, and in vitro, with kitten isolated gastric mucosae. The influence of peptide length on potency was investigated by comparing synthetic human gastrin heptadecapeptide, non-sulphate (shG17ns) with a synthetic gastrin butyloxycarbonyl hexapeptide (G6ns), and the influence of sulphation by comparison of G6ns with its sister sulphated peptide (G6s). When exogenous doses were compared, shG17ns was the most potent peptide (mean exogenous dose for half-maximal stimulation (EDe50) : 0.33 nmol kg-1 h-1), and was 15.8 times more potent than G6ns (EDe50:5.14 nmol kg-1 h-1). This potency ratio was reduced to 9.4 when circulating immunoreactive concentrations of the two peptides were compared (mean circulating concentration for half-maximal stimulation (EDc50) : shG17ns, 201 pM; G6ns, 1890 pM). The greater potency ratio when exogenous doses were compared was due to the greater metabolic clearance rate (m.c.r.) of the shorter gastrin (m.c.r.: shG17ns, 37 ml kg-1 min-1; G6ns, 121 ml kg-1 min-1). In vitro, shG17ns (mean concentration for half-maximal stimulation (EC50) : 1.99 nM) was 2.8 times more potent than G6ns (EC50: 5.57 nM). Sulphation of the hexapeptide increased its potency 3.6-fold when exogenous doses were compared (EDe50 G6s: 1.42 nmol kg-1 h-1). The greater potency of the sulphated peptide appeared to be due to its lower m.c.r. (20 ml kg-1 min-1), and was eliminated when circulating concentrations were compared; potency ratio G6ns: G6s, 1.1. We conclude that the increased potency of short gastrin peptides observed upon sulphation is likely to be due to increased resistance to metabolic clearance. Part of the increased potency observed with increasing peptide length can also be explained by increased resistance to clearance, but the small potency difference in vitro may reflect greater affinity for gastrin receptors.

Animals↗
PubMed1982

A quantitative analysis of the feeding behavior of suckling rabbits.

Three experiments are reported on the feeding behavior of suckling rabbits ("kittens"). In the 1st the latency with which the kittens attached to the nipple, and then left the nipple, was determined. Attachment was very rapid and wholly reliable: on the 80 tests the nipple was seized in every case in under 9 sec, and on 67 of these in less than 3 sec. The kittens also invariably left the nipple within the next minute. If the kittens were 5 or 10 days old speed of attachment was unaffected by the presence or absence of saliva on the nipple, but 15- and 20-day-old kittens seized the sucked nipples more rapidly than the unsucked nipples. In a 2nd experiment with 12-day-old kittens, washing the nipple with solvents did not affect speed of attachment; nor did saliva. The results show that suckling rabbits, in contrast to rat pups, are not heavily dependent on saliva cues. In the 3rd experiment both attachment latency and milk intake were shown to be affected by an internal stimulus, a gastric load of.9% saline, 5 g/25 g body weight: attachment latency was significantly increased and milk intake reduced by 75%.

Animals↗
PubMed1980

Gastric acid and pepsin-stimulating activity of non-sulphated fragments of gastrin in the cat.

The gastric acid and pepsin-stimulating activities of several C terminal fragments of non-sulphated human gastrin were investigated in the conscious cat prepared with cannulated gastric fistulae with a reproducible, continuous infusion method to construct dose-response curves. The gastric acid-stimulating activities were quantified by reference to the ED50 and were compared with the activity of synthetic non-sulphated human gastrin 17 (SHG17NS) and cat gastrin 17 (SCG17NS). SHG17NS had an ED50 of 0.329 nmol kg-1 h-1. SHG16NS, SHG15NS and SHG13NS all showed similar activities to SHG17NS. SCG17NS tested at low doses had similar activity to SHG17NS. SHG10NS, G5 and G4 and peptavlon showed progressively lower acid-stimulating activities: 26, 12, 9 and 9%, respectively, compared with SHG17NS. The gastric acid-stimulating activities of all the peptides were paralleled by similar pepsin-stimulating activities. The ratios of pepsin secretion:acid secretion were similar for all the peptides (1--2 microgram pepsin/microEq H+). The results are discussed in relation to the biological activity of the circulating gastrin components in the cat compared with other species and it is argued that component IV (corresponding to gastrin tetradecapeptide or minigastrin) is a major, physiologically active, circulating form of the hormone in the cat.

Animals↗