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Biomedical subjects

P Barker

Publications and source records attributed to P Barker.

At least 19 recordsLinked to original sources
PubMed1992

Visualization of diagnostic heteroduplex DNAs from cystic fibrosis deletion heterozygotes provides an estimate of the kinking of DNA by bulged bases.

Previous studies (Hsieh, C.-H., and Griffith, J. D. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 4833-4837) of DNAs containing extra or bulged bases on one of the two strands of a duplex showed that they exhibit slower electrophoretic mobility than non-bulged DNAs, indicating that bulges create stiff kinks in the DNA. Here we paired a 97-base single-stranded DNA from the intact cystic fibrosis (CF) gene with a complementary 94-base strand containing a central 3-base deletion (delta F508), common to many CF patients. This produced a 94-base pair DNA with a central 3-base bulge. Visualization of these DNAs by electron microscopy showed that twice as many bulge-containing DNAs had a central kink as compared with the non-bulged controls. Examination of the distribution of kinking angles showed that the bulged population contained 5-7-fold more molecules with a central kink of 80 +/- 10 degrees than did the control molecules. When the 3-base bulge was replaced by a 3-base gap, the resulting duplex DNA showed central kinks with a somewhat lower frequency but greater range of kinking angles.

Base Sequence↗
PubMed1992

Movements of the vocal cords on induction of anaesthesia with thiopentone or propofol.

Using a fibreoptic laryngoscope, we have recorded on video tape the movements of the vocal cords after induction of anaesthesia with either propofol or thiopentone. The angle formed by the vocal cords decreased after induction of anaesthesia in both groups. This reduction in angle was significantly greater in the thiopentone group. The vocal cords closed completely in four patients in the thiopentone group and one patient in the propofol group. This difference may be explained by greater depression of laryngeal reflexes by propofol and this may account for the lower incidence of laryngospasm after induction of anaesthesia with propofol in comparison with thiopentone.

Adult↗
PubMed1992

Regurgitation of gastric contents during general anaesthesia using the laryngeal mask airway.

We have investigated the incidence of regurgitation of gastric contents during general anaesthesia administered via a laryngeal mask airway (LMA) or face mask and Guedel airway in 56 patients with no risk factors for regurgitation. Patients swallowed a gelatin capsule containing methylene blue 10 min before induction of anaesthesia. Fibreoptic laryngoscopy in the LMA group or conventional laryngoscopy in the face mask group was performed at the end of surgery. Dye was observed within the laryngeal mask in seven of 28 patients (25%). No patients in the face mask-Guedel airway group regurgitated dye (P = 0.005). There was no evidence of aspiration of dye.

Adult↗
PubMed1992

Effect of the laryngeal mask airway on lower oesophageal sphincter pressure in patients during general anaesthesia.

We have studied the tone of the lower oesophageal sphincter (LOS) in 40 adults undergoing routine body surface surgery and allocated randomly to receive anaesthesia either by face mask and Guedel airway or by laryngeal mask airway. In the laryngeal mask group there was a mean (SEM) decrease in barrier pressure (LOS minus gastric pressure) of 3.6 (1.4) cm H2O, compared with a mean increase of 2.2 (1.2) cm H2O in the face mask group (P < 0.005).

Adult↗
PubMed1992

A comparison of gastric emptying rate after cimetidine and ranitidine measured by applied potential tomography.

Gastric emptying was measured using applied potential tomography (APT) after crossover administration of 800 mg cimetidine and 300 mg ranitidine orally. Ten volunteers were studied, each on two occasions. Two hours after taking ranitidine or cimetidine, the volunteer was given a liquid and gastric emptying was measured over 60 min. There was a small but statistically significant delay in gastric emptying following ranitidine compared with cimetidine (P less than 0.04). The median (range) time to 50% emptying (t50) was 24 (15-60) min after ranitidine compared with 22 (15-46) min after cimetidine.

Administration, Oral↗
PubMed1992

Spatiotemporal increases in epidermal growth factor receptors following peripheral nerve injury.

Non-neuronal cells of peripheral nerve respond to axonal injury with a series of cellular changes that facilitate neuronal regeneration. To characterize the potential role of the epidermal growth factor (EGF) family of proteins in this response, we monitored the expression of EGF receptor mRNA and protein in the injured rat sciatic nerve. EGF receptor mRNA is synthesized in both primary cultured fibroblasts and Schwann cells, and Schwann cells express EGF receptor-like immunoreactivity. In situ hybridization and immunocytochemistry revealed that EGF receptor mRNA and protein are expressed in Schwann cells and fibroblasts of the sciatic nerve in vivo, and that receptor levels increase following nerve injury. Thirty-six hours postlesion, EGF receptors were expressed in gradients along the nerve both proximal and distal to the lesion, with the highest levels localized adjacent to the transection site. By 72 hr, receptor levels were maintained in a gradient in the proximal segment, but were uniformly increased throughout the portions of the distal segment that were analyzed. These changes were similar to those observed for low-affinity NGF receptor mRNA and protein, with transection causing increased expression in both Schwann cells and fibroblasts. Northern blots confirmed that primary cultured fibroblasts express low-affinity NGF receptor mRNA. To determine whether spatiotemporal gradients were a general characteristic of the nerve injury response, we monitored expression of the mRNA encoding the major myelin protein P0. Levels of P0 mRNA decreased initially in cells immediately adjacent to the transection site and, by 72 hr, were uniformly decreased throughout the distal segment. These data suggest that members of the EGF family of proteins may play a role in the peripheral nerve response to injury, and demonstrate a generalized gradient of cellular responses that commence at the transection site and progress distally in the nerve in the absence of intact axons.

Animals↗
PubMed1992

A study of the effect of Picolax on body weight, cardiovascular variables and haemoglobin concentration.

This study compared the effect of Picolax when administered for large bowel preparation in combination with preoperative fasting on body weight, haemoglobin concentration, haematocrit, and cardiovascular variables with matched subjects who were fasted before surgery. Picolax resulted in significantly greater weight loss, increases in haemoglobin concentration combined with cardiovascular changes suggesting hypovolaemia in the Picolax group. Intravenous fluid replacement is recommended in patients receiving Picolax.

Adult↗
PubMed1991

Coagulation screening before epidural analgesia in pre-eclampsia.

A questionnaire survey of current practice at a small cross-section of obstetric units, covering 22% of all United Kingdom deliveries, revealed a marked lack of standard practice regarding requests for coagulation screens on pre-eclamptic patients who require epidural procedures. A retrospective audit was therefore carried out on 434 coagulation screens requested for pre-eclamptic patients in whom epidural analgesia might have been considered. Borderline abnormalities of coagulation were found in only 10 patients (2%). Platelet counts of less than 150 x 10(9)/litre were present in 28% of cases. 'Significant' thrombocytopenia (less than 100 x 10(9)/litre) and all coagulation abnormalities were only encountered in severe pre-eclampsia (diastolic blood pressure of greater than 110 mmHg and proteinuria of + + or greater). Furthermore, coagulation abnormality was always associated with a reduced platelet count (mean, 97 x 10(9)/litre). This study would therefore support anaesthetic practice which restricted any requests for coagulation testing to severe pre-eclamptic patients only. For these patients first line testing could be limited to a platelet count.

Analgesia, Epidural↗
PubMed1991

Computerised axial tomography of the trachea. A useful investigation when a retrosternal goitre causes symptomatic tracheal compression.

Case histories are reported of three patients who had large retrosternal goitres which were responsible for significant abnormalities of the airway. Computerised axial tomography demonstrated the exact anatomy. The site of tracheal compression was shown and accurate measurements of the diameter of the trachea at its narrowest point were made. This information was useful when the management of the patient was planned.

Aged↗
PubMed1991

Effect of prior administration of cold saline on pain during propofol injection. A comparison with cold propofol and propofol with lignocaine.

A single-blind, randomised, controlled study was undertaken to compare the efficacy of three methods of preventing pain during injection of propofol on induction of anaesthesia. Patients were allocated randomly to receive unmodified propofol, propofol with 0.05% lignocaine, propofol at 4 degrees C and unmodified propofol preceded by 10 ml of 0.9% saline at 4 degrees C. Prior injection of cold saline reduced the incidence of pain and discomfort significantly (22%) compared with unmodified propofol (75%; p less than 0.005) and was similar to that after cold propofol (33%) and propofol with lignocaine (44%). There was no significant difference between the treatment groups.

Adult↗
PubMed1991

Relationships between skin temperature and perfusion in the arm and leg.

Relationships between skin temperature (Tsk) and perfusion have been studied to provide a basis for the use of Tsk in the non-invasive assessment of limb circulation in peripheral vascular disease. Raising the ambient temperature (Ta) from 20 to 30 degrees C increased the perfusion of the glabrous skin of the hands and feet without changing that of the skin of the forearm or calf. On a fractional basis the response in the hand and foot was the same. Tsk was higher in the arms than the legs and in the proximal than distal parts of the limbs. A fall in Tsk was often seen when Ta rose from 20 to 25 degrees C and was attributed to counter-current cooling. Subsequently Tsk rose even in regions where there was no increase in skin perfusion. Tsk can only be related to its perfusion in the fingers, palm and toes. Forearm Tsk was related to the perfusion of the digits. This relationship implies a link with the arterial inflow to the limb which determines the size of its thermal core. Heat conduction from the core seemed important for the skin of areas like the forearm and calf where the constant, low perfusion limited the amount of heat which could be transported to it directly by the blood. The importance of conduction was supported by studies, at Ta 20 degrees C, on subjects during calf muscle exercise and on patients with arterio-venous fistulae. Here an increase in the arterial inflow to the limb was associated with a rise in Tsk of the forearm/calf unrelated to the perfusion of its skin.

Adult↗
PubMed1978

Behavior therapy for autistic children: a study of acceptability and outcome.

An inpatient program for autistic children which used behavior modification methods is described, and a follow-up study of the first 15 children discharged from the program is reported. In general, the outcome results appear to be comparable to those of other treatment methods. A second main purpose of the study was to assess the acceptability of this program to parents and to document their impressions regarding their child's period of inpatient care. Overall, a high level of acceptability was found.

Autistic Disorder↗