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Biomedical subjects

M J Chow

Publications and source records attributed to M J Chow.

10 recordsLinked to original sources
PubMed1990

Hyperviscosity syndrome in a hypercholesterolemic patient with primary biliary cirrhosis.

A 45-yr-old woman with primary biliary cirrhosis, xanthomatosis, and marked hypercholesterolemia developed symptoms of the hyperviscosity syndrome on three separate occasions. On presentation, she had a plasma total cholesterol concentration of 53.40 mM (2065 mg/dl) and a relative serum viscosity of 2.9. Following three courses of plasma exchange in a 5-day period, the total cholesterol level decreased to 6.75 mM (261 mg/dl) and the viscosity to 1.3. The cutaneous xanthomata were markedly diminished 1 wk following plasma exchange. Despite therapy with colestipol (30 g/d), the hyperviscosity syndrome developed 147 days later. This cycle recurred again 137 days after colestipol was discontinued. Serum viscosity and total cholesterol concentration were highly correlated during the postexchange or accumulation phases (R = 0.95, 95% CI: 0.85, 0.98) and during the exchange or interventional phases (R = 0.95, 95% CI: 0.84, 0.99). Serum viscosity was less significantly correlated with total serum protein (R = 0.84; 95% CI: 0.55, 0.95) or with plasma triglyceride (R = 0.63; 95% CI: 0.26, 0.81). There were no significant correlations of red cell mass, plasma fibrinogen levels, or serum bile salts with viscosity. Subfractionation of plasma into lipoprotein classes showed 45% of total cholesterol in the lipoprotein X fraction and a presumptive slow alpha-lipoprotein species. It is postulated that both the hyperviscosity syndrome and rapid resolution of xanthomata in the patient may be attributable to the physiology of her abnormal lipoprotein particles.

Blood Viscosity↗
PubMed1988

Postjunctional alpha 2-adrenoceptors in blood vessels of human nasal mucosa.

Human nasal mucosa has various types of blood vessels and is a good tissue for demonstrating receptors for many vasoactive substances, including alpha-adrenoceptors. In contrast to the large contractile response induced by alpha 1-agonists, our studies have shown that alpha 2-agonists produce a small maximal contraction. This alpha 2-induced response was easily blocked by alpha 1-antagonists, indicating that it is evoked, at least partially, by the stimulation of alpha 1-adrenoceptors. Noradrenaline (NA)-induced contractions could not be abolished by either alpha 1- or alpha 2-antagonists alone, but were almost completely blocked by the combination of both antagonists. This suggests the presence of postjunctional alpha 2-adrenoceptors. The low-maximal responsiveness to alpha 2-agonists and calcium independency of NA-induced contractions were distinct from our former results obtained on canine nasal specimens.

Adrenergic alpha-Agonists↗
PubMed1988

Nerve excitability test using fine needle electrodes.

The NET using needle electrodes is a simple and useful test. Children readily tolerate the procedure. For prognosticative purposes it is more effective than the conventional NET using surface electrodes. When positive responses to NET using needle electrodes are recorded after 3 days from onset of palsy, irrespective of the absolute threshold value, prognosis is good. In Bell's palsy, NET is positive for 90%, and for 73% in Hunt's syndrome. Apart from one case our patients showed complete recovery by EMG evaluation.

Acupuncture Therapy↗
PubMed1986

Theophylline pharmacokinetics in pregnancy.

Theophylline pharmacokinetics were studied serially in five women during and after pregnancy. Theophylline protein binding was reduced to 11.1% +/- 4.7% (P less than 0.01) and 13.0% +/- 5.9% (P less than 0.01) during the second and third trimesters of pregnancy, respectively, compared with 28.1% +/- 2.8% when the patients were more than 6 months postpartum. Similar comparisons indicate that theophylline distribution volume and elimination t1/2 were increased from 30.7 +/- 4.4 L and 262 +/- 57 minutes to 36.8 +/- 4.2 L (P less than 0.05) and 389 +/- 73 minutes (P less than 0.01) in the third trimester of pregnancy. In the second and third trimesters, intrinsic nonrenal clearance was reduced to 0.82 +/- 0.25 ml/min X kg (P less than 0.05) and 0.67 +/- 0.18 ml/min X kg (P less than 0.01) compared with a remote postpartum value of 1.25 +/- 0.37 ml/min X kg. However, these reductions were offset by increases in theophylline intrinsic renal clearance so that apparent reductions in the overall unbound clearance of this drug did not reach statistical significance either during pregnancy or in the early postpartum period.

Asthma↗
PubMed1986

Comparison of prednisolone kinetics in patients receiving daily or alternate-day prednisone for asthma.

Prednisolone pharmacokinetics were compared in seven patients with asthma managed by alternate-day prednisone therapy and in seven patients with asthma requiring daily doses of prednisone. Steroid requirements of these patients were carefully characterized and had been stable for at least 12 months. Prednisolone volume of distribution, elimination clearance, and elimination t1/2 averaged 0.606 +/- 0.061 and 0.553 +/- 0.162 L/kg, 2.28 +/- 0.43 and 1.93 +/- 0.54 ml/min/kg, and 204 +/- 44 and 214 +/- 19 minutes in patients receiving alternate-day or daily prednisone therapy, respectively. These results indicate that differences in these pharmacokinetic parameters do not account for the well-established clinical observation that some patients require daily prednisone doses and that their disease cannot be managed with alternate-day steroid therapy.

Adult↗
PubMed1985

Kinetics of cocaine distribution, elimination, and chronotropic effects.

The pharmacokinetics of cocaine were studied in five subjects with histories of drug abuse who were otherwise healthy. A two-compartment system was used to model the distribution kinetics of the drug. The steady-state volume of distribution averaged 131.8 L or 1.96 L/kg, elimination clearance was 2.10 L/min, and the t 1/2 was 48 minutes. Cocaine concentrations in a hypothetic biophase were estimated to correlate the chronotropic effects of this drug with its pharmacokinetics. The experimentally determined kinetic parameters indicate that the peak chronotropic effect would occur 7.3 minutes after intravenous bolus injection of cocaine, and that biophase cocaine concentrations would initially accelerate the heart rate by 0.3 bpm for each 1 ng/ml. The kinetic analysis also demonstrated that the chronotropic effects of cocaine decline more rapidly than either plasma levels or biophase concentrations. This progressive attenuation in intensity of the chronotropic effect of a given biophase cocaine concentration could be modeled as a first-order process and is compatible with either the intervention of homeostatic reflex mechanisms or the phenomenon of acute tolerance.

Adult↗
PubMed1985

Reduction in slow intercompartmental clearance of urea during dialysis.

The kinetics of urea and inulin were analyzed in five anesthetized dogs during sequential 2-hour periods before, during, and after hemodialysis. The distribution of both compounds after simultaneous intravenous injection was characterized by three-compartment models, and the total volumes of urea (0.66 +/- 0.05 L/kg) and inulin (0.19 +/- 0.01 L/kg) distribution were similar to expected values for total body water and extravascular space, respectively. Intercompartmental clearances calculated before dialysis were used to estimate blood flows to the fast and slow equilibrating compartments. In agreement with previous results, the sum of these flows was similar to cardiac output, averaging 101% of cardiac output measured before dialysis (range 72% to 135%). Dialysis was accompanied by reductions in the slow intercompartmental clearances of urea (81%) and inulin (47%), which reflected a 90% attenuation in blood flow supplying the slow equilibrating compartments. This was estimated to result in a 10% average reduction in the efficiency with which urea was removed by dialysis (range 2.0% to 16.4%). Mean arterial pressure fell by less than 5% during dialysis, but total peripheral resistance increased by 47% and cardiac output fell by 35%. In the postdialysis period, total peripheral resistance and cardiac output returned toward predialysis values, but blood flow to the slow equilibrating peripheral compartment was still reduced by 80%. These changes parallel activation of the renin-angiotensin system, but further studies are required to establish causality.

Animals↗
PubMed1984

Torsade de pointes induced by N-acetylprocainamide.

N-Acetylprocainamide (NAPA), a class III antiarrhythmic drug, caused torsade de pointes in a 72 year old woman who had this arrhythmia on two previous occasions while being treated with quinidine and disopyramide. Initial evaluation with an intravenous infusion of NAPA indicated a favorable antiarrhythmic response. The QTC interval was prolonged, but the 2.4 ms/microgram per ml incremental QTC interval lengthening caused by NAPA was not greater than usual. During subsequent oral therapy with NAPA, torsade de pointes developed at plasma levels of this drug that appeared to be well tolerated during the initial evaluation.

Acecainide↗
PubMedDate not supplied

The role of 18F-fluorodeoxyglucose positron emission tomography in cancer screening - a preliminary report.

Positron emission tomography (PET) with 18F-fluoro-2 deoxy-D-glucose (FDG) is a non-invasive method for surveying the whole body and detecting various malignancy. A total of 299 subjects underwent whole-body FDG PET studies in our PET center over an 18-month period. FDG PET accurately detected malignant tumors in 7 (2.34%) subjects. False positive FDG PET studies in 3 (1%) subjects and false negative FDG PET studies in 2 (0.6%) subjects were found. Because of the high cost of FDG PET examination, it might not be suitable as a cancer screening test for the general population. However, it is a valuable supplemented tool for routine check-up, particularly for those at high-risk of developing cancer.

Adult↗