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Biomedical subjects

W Craelius

Publications and source records attributed to W Craelius.

6 recordsLinked to original sources
PubMed1992

Heart rate variability as an index of autonomic imbalance in patients with recent myocardial infarction.

Autonomic nervous activities are estimated in three groups of patients: Group A consists of patients who had experienced myocardial infarction (MI) within 2-6 weeks before the tests; Group B consists of patients who had MI more than one year previously; Group C consists of matched controls, free of cardiac disease. Autonomic activity is estimated using postural effects on heart rate variability (HRV): a sympathetic activity index is defined as HRV power within a low frequency band (0.04-0.12 Hz) in the tilt position and a parasympathetic activity index is defined as HRV power in a high frequency band (0.18-0.28 Hz) in the supine position. Results show that, relative to controls, Group A patients have reduced parasympathetic activity index (5 + 3 against 13 + 8, normalised units; p < 0.05) and an increased ratio of sympathetic to parasympathetic activity (17 + 17 against 4 + 2; p < 0.05). Group B is not significantly different from Group A or C. The period of 2-6 weeks post-MI thus appears to be characterised by depressed parasympathetic nervous activity which can be measured using HRV analysis.

Aged↗
PubMed1991

Acute thyroid hormone promotes slow inactivation of sodium current in neonatal cardiac myocytes.

Sodium current (INa) inactivation kinetics in neonatal cardiac myocytes were analyzed using whole cell voltage clamp before and after acute treatments with thyroid hormone (3,5,3'-triiodo-L-thyronine, T3). In untreated neonatal myocytes, INa inactivation was predominantly mono-exponential, with 93 +/- 3% (S.D.; n = 9) of the peak amplitude decaying with a time constant, tau h1, of 1.8 +/- 0.5 ms at -30 mV. The remaining 7% of control INa decayed more slowly, with a time constant, tau h2, of 9.3 +/- 3.0 ms at -30 mV. The contribution of slowly-inactivating channels to peak current was increased from 7% to 43 +/- 27% within 5 min of exposure to 5-20 nM T3 (nine cells; P less than 0.005). The time constants for both the fast- and slow-inactivating components of peak current (tau h1 and tau h2) were not significantly changed by acute T3 treatment, nor was steady-state INa inactivation (h infinity) affected. Thyroid hormone action on sodium inactivation was partially reversible by lidocaine. These findings indicate that T3 acts at the neonatal cardiac cell membrane to promote slow inactivation kinetics in sodium channels.

Animals↗
PubMed1990

Electrophysiological basis of ventricular late potentials.

The presence of late potentials on the body surface recording was correlated with ventricular activation maps of reentrant circuits in the postinfarction canine model of reentrant excitation. Late potentials were found to correlate with delayed myocardial activation. However, during a reentrant rhythm complete diastolic activity on the body surface could not be detected if the mass of electrically active cells was too small and/or if very slow conduction in part of the reentrant circuit generated low amplitude extracellular potentials. Myocardial zones responsible for late potentials during a basic rhythm (e.g., sinus rhythm) may not necessarily be part of the critical zone of slow conduction during reentrant activation. Dynamic changes in late potentials are not amenable to temporal signal averaging techniques but could be detected by a high resolution beat-to-beat recording. A thorough understanding of the electrophysiological limitations of late potentials in the signal-averaged ECG could result in better utilization of the technique in clinical practice as well as in the development of new approaches for the detection of the arrhythmogenic substrate.

Action Potentials↗
PubMed1978

Comparative epidemiology of multiple sclerosis and dental caries.

The geographical distribution and other epidemiological characteristics of multiple sclerosis (MS) are compared with those of dental caries. The rates of death due to MS in Australian states are linearly related to the numbers of decayed, missing, and filled (DMF) teeth found in individuals from those states (r=0.97, P less than 0.002). In the United States of America, a strong positive correlation (r=0.55, P less than 0.001) also exists between MS death rates and dental caries indices. The prevalence of MS in 45 countries or areas correlates well with the frequencies of DMF teeth among children of school age in those locations (r=0.78, P less than 0.001). The prevalence of MS also correlates well with the percentage of edentulous individuals in certain countries (r=0.99, P less than 0.001). A review of the literature shows that the risk for dental caries is lower among the following groups: the lower socioeconomic classes in the United States of America; Chinese immigrants to England compared with natives; blacks compared with whites; and males compared with females. The dental caries risk is higher during pregnancy and lactation. All these trends have been described for MS as well. It is suggested that dental caries may be a more accurate epidemiological model for MS than poliomyelitis. It is also suggested that MS and dental caries may share certain aetiological factors, two of which may be dietary excess of certain fats, and vitamin D deficiency.

Australia↗
PubMed1976

The distribution of GABA sensitivity on crayfish muscle receptor organs.

1. The effectiveness of inhibition of gamma-aminobutyric acid (GABA) at various points on crayfish abdominal muscle receptor organs (MROs) was investigated by iontophoretic methods that have a spatial resolution of 8 mum. 2. The MROs in the rostral abdominal segments, which receive inhibitory innervation, were always strongly inhibited by focal iontophoretic application of GABA; MROs in the 6th abdominal segment, which do not receive inhibitory innervation, were usually not strongly inhibited. 3. In the rostral MROs, the magnitude of GABA current necessary to abolish stretch induced impulses was least for dendritic points; it increased as a function of distance from the dendrites, over an area extending from the receptor muscle to a point on the axon 200 mum from the cell body. 4. Outward currrents from NaCl-filled micropipettes had no effect on impulse production when applied to the dendritic region of rostral MROs, but could produce transient inhibition of impulses when applied to the axon. 5. It is suggested that a high degree of GABA sensitivity is localized to the rostral MRO dendrites, where inhibitory synapses are most numerous.

Aminobutyrates↗