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Biomedical subjects

W Giles

Publications and source records attributed to W Giles.

67 records · Page 4Linked to original sources
PubMed1977

Dipylidiasis in a 57-year-old woman.

An interesting case of tapeworm infection in a human caused by Dipylidium caninum was recently diagnosed in the Illawarra area of N.S.W. Since it involved and adult (a 57-year-old woman) and recorded human infections are rare in the Australian literature, it was decided to describe this case of dipylidiasis.

Cestoda↗
PubMed1977

Membrane currents underlying activity in frog sinus venosus.

1. The spontaneous electrical activity of small strips of muscle from the sinus venosus region of the heart of Rana catesbeiana was investigated using the double sucrose gap technique. The voltage clamp was used to record the ionic currents underlying the pace-maker depolarization and the action potential.2. The records of spontaneous electrical activity are very similar to those obtained from the sinus venosus using micro-electrodes. Moreover, the pace-maker activity is almost completely insensitive to tetrodotoxin (TTX) at 2.0 x 10(-6) g/ml., which suggests that the pace-maker responses can be classified as primary, as opposed to follower pacing.3. In response to short rectangular depolarizing voltage clamp pulses, only one inward current is activated. This current is almost completely insensitive to TTX but can be blocked by manganese ions. It appears, therefore, to be equivalent to the slow inward (Ca(2+)/Na(+)) current, I(si), of other cardiac tissues. The threshold for I(si) is near to the maximum diastolic potential, indicating that it must be activated during the pace-maker depolarization.4. Interruption of the normal pace-maker depolarization by rapid activation of the voltage clamp circuit reveals the time-dependent decay of outward current. This current reverses between -75 and -90 mV and, therefore, is probably carried mainly by potassium ions.5. Outward current decay is not a simple exponential, and Hodgkin-Huxley analysis suggests that two distinct components of outward current may be present. One of these is activated in the potential range of the pace-maker depolarization and the other at more positive potentials. Both outward currents reach full, steady-state activation at about zero mV, i.e. within the ;plateau' range of the sinus action potential.6. These results are compared with other recently published voltage clamp data from the rabbit sino-atrial node.7. A hypothesis for the generation of pace-maker activity is presented which involves (i) decay of outward current and (ii) activation of the slow inward current, I(si).

Action Potentials↗
PubMed1976

Cellular basis for the T wave of the electrocardiogram.

Differences in action potential duration in different regions of the mammalian ventricle are not systematically present when quiescent tissue is first stimulated, but develop rapidly during repetitive activity. The effects of ouabain and temperature suggest the involvement of the Na+-K+ exchange pump.

Action Potentials↗
PubMed1976

Changes in membrane currents in bullfrog atrium produced by acetylcholine.

1. A double sucrose-gap voltage-clamp technique has been used to study the effects of acetylcholine on the membrane currents in atrial trabeculae of the bullfrog, Rana catesbeiana. 2. The second, or slow inward (Ca2+/Na+) current, was found to be markedly reduced by concentrations of acetylcholine greater than approximately 2-0 X 10(-8)M. The resulting decrease in net calcium entry provides a straightforward explanation for the negative inotropic action of acetylcholine in atrial muscle. 3. Measurements of membrane resistance near the resting potential showed that relatively high doses of acetylcholine (approximately 10(-7) M) decrease membrane resistance by about twofold. This effect is shown to be the result of an increase in a time-independent background current which appears to be carried mainly by potassium ions. 4. Using appropriate pharmacological techniques, it has been possible to demonstrate: (i) that the peak slow inward current is reduced to about half its initial value before any significant increase in background current occurs; (ii) that even when a sufficient dose of acetylcholine to produce an increase in background current is used, the background current shows inward-going rectification and cannot account for the observed reduction in the slow inward current. 5. No consistent change was observed in the degree of activation of the time-dependent outward membrane currents after application of concentrations of acetylcholine which produced large decreases in the peak slow inward current. 6. These results are discussed in relation to previous electro-physiological and radioisotope studies of the mechanism of the negative inotropic effect of acetylcholine in cardiac muscle.

Acetylcholine↗
PubMed1975

Effect of hypoxia on immediate ventilatory load response in dogs.

The effective elastance of the respiratory system (which has been previously shown to provide an index of the ability of the respiratory musculature to compensate rapidly for transient mechanical ventilatory loads) was measured in six hypoxic dogs to determine whether hypoxia hindered immediate load-compensatory mechanisms. The effective elastance value was computed from measurements of control tidal volume and the pressure developed at the airway opening during the first inspiratory effort following airway occlusion at FRC. The mean effective elastance was 197 cmH2O/l while the animals were breathing room air and did not change significantly when the animals were rendered hypoxic by reducing the inspired oxygen concentration, in five dogs, or by controlled hemorrhage, in two dogs. It was concluded that inasmuch as effective elastance measurements remain constant during hypoxia, the stability of ventilation is not significantly impaired in this situation.

Animals↗
PubMedDate not supplied

Clinical use of Doppler ultrasound in pregnancy: information from six randomised trials.

The objective of this report was to undertake an overview of the clinical utility of umbilical Doppler ultrasound in the management of high-risk pregnancies. The study is designed as a formal meta-analysis of 6 randomised trial reports selected by predetermined criteria and was performed at the Division of Reproductive Medicine, Newcastle University, Australia. A total of 6 randomised controlled trials amounted to 2,102 patients in the experimental (Doppler) group and 2,133 patients in the control group. All patients had high-risk pregnancies. The management of pregnancies with Doppler was compared to those with standard obstetric management (i.e. excluding Doppler). Main outcome measures were perinatal mortality in the form of intrauterine deaths as well as obstetric performance indicators including caesarean section, elective delivery, fetal distress in labour, antenatal admissions and admissions to Neonatal Intensive Care Unit. The meta-analysis shows a significant reduction in perinatal mortality in the groups in which Doppler was used. Typical odds ratio was 0.5 [95% confidence intervals (CI) 0.34, 0.73]. The specific reduction in perinatal mortality occurred in intrauterine deaths in otherwise normally formed fetuses. The typical odds ratio was 0.54 with 95% CI 0.32, 0.89. This meta-analysis shows a significant reduction in overall perinatal mortality, specifically in the form of intrauterine deaths in otherwise normally formed babies.

Cesarean Section↗