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Biomedical subjects

M Crawford

Publications and source records attributed to M Crawford.

At least 19 recordsLinked to original sources
PubMed1992

Assessment of corticospinal and somatosensory conduction simultaneously during scoliosis surgery.

The function of descending motor pathways and that of ascending sensory pathways in the spinal cord were monitored at the same time in 120 patients undergoing surgery for scoliosis. Transcranial electrical stimulation of the motor cortex was performed simultaneously with stimulation of the tibial nerves in the popliteal fossae, and the descending and ascending volleys were recorded from the spinal cord at two levels using epidural electrodes. Stable recordings of both volleys have been obtained in all neurologically normal patients and in many with pre-existing neurological deficits. The experimental conditions which resulted in reliable recordings were explored in select patients and include: a vertex-anode/lateral cathode montage for transcranial stimulation, epidural recording of evoked corticospinal and somatosensory volleys at two spinal levels, a high-pass filter of 500 Hz, and stable anaesthesia. The epidural recording allows full muscle relaxation and the use of volatile anaesthetics; recording at two levels allows a deterioration in function to be identified quickly and distinguished from an artifactual change.

Anesthetics↗
PubMed1992

ECMO in newborn infants: the New South Wales experience.

Extracorporeal membrane oxygenation (ECMO) has been used at the Prince of Wales Children's Hospital, Sydney for the treatment of newborn infants with life-threatening respiratory or cardiac failure since August 1989. The main indications are that the disease is reversible, the surviving infant is likely to be normal and there is an 80% likelihood of death without ECMO. Eighteen of 19 newborn infants have survived at least 2 months after ECMO. The 15 infants receiving ECMO (nine with meconium aspiration, six with persisting pulmonary hypertension) who did not have a congenital diaphragmatic hernia were normal survivors. One death occurred at 5 months of age from chronic lung disease. Three of four infants with congenital diaphragmatic hernia were discharged following ECMO and appeared normal at 6, 9 and 18 months of age. These results are similar to results from other centres internationally. It appears that ECMO is a useful therapy for near-term newborn infants with otherwise fatal cardiorespiratory failure.

Extracorporeal Membrane Oxygenation↗
PubMed1992

Gender-linked differences in everyday memory performance.

Recent research has demonstrated that people hold beliefs about how well others perform everyday memory tasks according to another's sex. For example, meta-memory ratings indicate that other men and other women are believed to differ in their success at performing certain memory tasks (Crawford, Herrmann, Holdsworth, Randall & Robbins, 1989). In the present study, two experiments investigated whether gender stereotypes concerning everyday memory have any validity. Experiment 1 presented female and male subjects with two tasks that the aforementioned meta-memory ratings had shown are implicitly gender marked: learning a shopping list (a sterotypically feminine task) and learning directions to go to a particular place (a stereotypically masculine task). The results were consistent with the gender stereotypes, i.e. women recalled more of the shopping list than men whereas men recalled more of the directions than women. The second experiment investigated whether memory performance would be influenced by mere changes in the label of materials in memory tasks to be biased toward male or female gender background: labelling a shopping list as pertaining to 'groceries' or to 'hardware store'; and a set of directions to 'make a shirt' or to 'make a workbench'. The results also indicated that memory performance varied in ways consistent with gender stereotypes.

Adolescent↗
PubMed1992

Corticospinal volleys evoked by electrical stimulation of human motor cortex after withdrawal of volatile anaesthetics.

1. In twenty-two neurologically normal patients undergoing surgery for scoliosis, corticospinal volleys to transcranial electrical stimulation of the motor cortex were recorded from the spinal cord using epidural electrodes. While anaesthesia was maintained by nitrous oxide and narcotics, volatile anaesthetics were withdrawn to determine whether such agents had a depressant effect on the evoked corticospinal volley. 2. Profound changes were documented in liminal D waves, there being an increase in amplitude averaging 392% following withdrawal of the volatile anaesthetic. There was a proportionately smaller increase (averaging 26%) in supraliminal D waves; these had a complex bifid or trifid shape indicating that some corticofugal axons were being activated deep to cortex. In general the effect on the D wave of withdrawing the anaesthetic agent was similar to that of increasing stimulus intensity. 3. Withdrawal of isoflurane dramatically increased the number of I waves and their mean amplitude. In the absence of isoflurane, I3 (mean latency 3.5 ms after the D wave) became the dominant I wave. The amplitude of I2 (mean latency 2.2 ms) became slightly smaller. The change in I waves could not be likened to an increase in stimulus intensity, because I waves invariably increase in, or remain of the same, amplitude as stimulus intensity is increased. 4. These findings indicate that changes in motor cortex excitability can result in major changes in the corticospinal volley produced by transcranial electrical stimulation, affecting both the D wave and I waves. They caution against identifying a cortical action solely on the basis of a change in the responses to magnetic stimulation of motor cortex but no such change to electrical stimulation.

Adolescent↗
PubMed1991

A comparison of postoperative analgesia provided by wound infiltration or caudal analgesia.

A prospective randomised study was performed to compare postoperative analgesia produced by caudal block with that of local wound infiltration in 54 children following unilateral inguinal herniotomy. There was no statistically significant difference in the analgesia produced by these two methods. The requirement for additional postoperative analgesia and the incidence of side-effects was similar in the two groups.

Analgesia, Epidural↗
PubMed1991

Central nervous system effects of acetate: contribution to the central effects of ethanol.

Acetate, resulting from ethanol metabolism in the liver, is released into the circulation and is utilized in a number of tissues, including the brain. In its metabolism, acetate leads to the production of adenosine, a powerful physiological mediator. We have investigated the effect of acetate on central nervous system (CNS) function in rodents. Sodium acetate in doses resulting in blood concentrations comparable to those attained after the administration of 1 to 2 g/kg ethanol, had significant CNS effects. Both ethanol and acetate produced a dose-dependent impairment of motor coordination. This effect of acetate was fully blocked by the adenosine receptor blocker 8-phenyltheophylline (8PT), whereas the dose-response relationship for ethanol was shifted to the right by about 30%. The inspired concentration of sevoflurane to achieve anesthesia was significantly reduced by both these agents. General anesthesia was potentiated in a dose-dependent fashion by ethanol and by acetate. The effect of acetate on anesthetic requirements was fully blocked by 8PT. The effect of ethanol on sevoflurane anesthetic requirements was inhibited by 22 to 35% by 8PT. Locomotor activity in mice was reduced by acetate in a dose-dependent fashion, an effect that was also fully blocked by 8PT. On the other hand, ethanol at a dose of 1 to 2 g/kg increased locomotor activity. This likely results from a direct stimulatory effect of ethanol, opposed by an inhibitor effect of acetate. The administration of 8PT enhanced the stimulation of locomotor activity induced by ethanol. In conclusion, acetate, a product of ethanol metabolism has significant CNS effects that can either potentiate or antagonize the effects of the ethanol molecule per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1991

Metastatic vaginal carcinoma to the temporal bone.

Metastatic carcinoma of the temporal bone is being reported with increasing frequency. A literature review reveals 16 new cases reported in the past 2 years. In this article we present the first case of vaginal squamous cell carcinoma metastatic to the temporal bone reported in the literature. The pathophysiology, clinical presentation, and diagnostic difficulties of metastatic carcinoma to the temporal bone are discussed.

Aged↗
PubMed1990

Erythrocyte fatty acids, plasma lipids, and cardiovascular disease in rural China.

Cardiovascular disease (CVD) mortality (coronary heart disease, hypertensive heart disease, and stroke), plasma lipids, and red blood cell fatty acid composition were examined in an ecologic study in 65 rural counties in the People's Republic of China. Means of plasma total cholesterol, triglyceride, low-density-lipoprotein (LDL) cholesterol, and high-density-lipoprotein (HDL) cholesterol concentrations were substantially lower and the ratio of HDL cholesterol to total cholesterol was higher in this Chinese population than in Western populations. Mortality rates for CVD in China were well below Western values. Within China neither plasma total cholesterol nor LDL cholesterol was associated with CVD. A strong inverse correlation between red blood cell oleate concentrations and CVD was observed. However, red blood cell oleate concentrations were not associated with plasma cholesterol but were strongly negatively associated with arachidonate concentrations, suggesting potential diminution of CVD by oleate through reduced platelet aggregability. The results indicate that geographical differences in CVD mortality within China are caused primarily by factors other than dietary or plasma cholesterol.

Adult↗
PubMed1990

Effects of duration of fasting on gastric fluid pH and volume in healthy children.

To determine the effects of duration of fasting before elective surgery on gastric fluid pH and volume in children, a prospective, randomized, blinded study of 100 unpremedicated children, aged 1-14 yr, was undertaken. Each child was given 2 mL/kg of water orally and then fasted 2, 4, or 6 h preoperatively. After induction of anesthesia and tracheal intubation, gastric fluid was aspirated through a large-bore, multiorifice orogastric tube. Gastric fluid pH was measured using a calibrated PHM62 radiometer. Gastric fluid volume was the total volume of fluid aspirated from the stomach. The duration of fasting was between 2.0 and 8.5 h. We found that neither gastric fluid pH nor gastric fluid volume correlated with the duration of fasting. The mean (+/- SD) gastric fluid pH was 1.80 +/- 0.79 and the mean (+/- SD) gastric fluid volume was 0.56 +/- 0.39 mL/kg. Gastric fluid pH was less than 2.5 and volume greater than 0.4 mL/kg in 53% of children. We conclude that healthy children may receive 2 mL/kg of water up to 2 h before elective surgery without decreasing gastric fluid pH or increasing gastric fluid volume beyond values obtained after fasting for 6 h.

Adolescent↗
PubMed1989

Identification of Gly-Pro-Glu (GPE), the aminoterminal tripeptide of insulin-like growth factor 1 which is truncated in brain, as a novel neuroactive peptide.

A truncated form of IGF-1 which lacks the aminoterminal tripeptide Gly-Pro-Glu (GPE) is found in human brain. It was proposed that GPE may result from neural specific processing and also have a function within the CNS. GPE was synthesized and shown to inhibit glutamate binding to the N-methyl-D-aspartate (NMDA) receptor. Whilst the carboxyterminal glutamate was necessary for NMDA receptor binding, the aminoterminal glycine potentiated receptor crossreaction. Furthermore, GPE had a potent stimulatory effect on the potassium induced release of acetylcholine from rat cortical slices. A less potent stimulation of dopamine release from striatum was also observed. The specific competitive NMDA receptor antagonist, (+/-)2-amino-7-phosphonoheptanoate (AP7), inhibited the action of GPE on dopamine but not on acetylcholine release. These studies have identified GPE as a novel neuroactive peptide with a potent action on acetylcholine release and support the general concept that the proteolytic products of the IGF-1 precursor play a role in the regulation of brain function.

Acetylcholine↗