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Biomedical subjects

C R Lee

Publications and source records attributed to C R Lee.

At least 19 recordsLinked to original sources
PubMed1992

Vasodilator effect of scoparone (6,7-dimethoxycoumarin) from a Chinese herb.

A possible mechanism of the vasodilator effect of scoparone was investigated. Scoparone (10(-6)-3 x 10(-5) M) dilated rat aortic rings precontracted with phenylephrine in a dose-dependent manner. The presence of endothelium facilitated the vasodilator effect. Scoparone depressed the contractile responses to phenylephrine and serotonin, but not that to potassium chloride. Both the vasoconstriction and O2- production induced by alloxan, a diabetogenic compound, were depressed by scoparone. It appears that scoparone exhibited a free radical scavenger-like effect. The dilatation elicited by acetylcholine was potentiated by scoparone. The dilator activity of scoparone was markedly inhibited by methylene blue and hemoglobin, guanylate cyclase inhibitors. Furthermore, the basal guanosine 3',5'-cyclic monophosphate (cGMP) level was elevated in the presence of scoparone. The dilator activity of scoparone was also inhibited by quinacrine (inhibitor of phospholipase A2) and indomethacin (inhibitor of cyclooxygenase). Our results showed further that the output of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, was enhanced by scoparone. It is suggested that the vasodilator effect of scoparone in rat aorta may be mediated through the enhancement of prostacyclin release, protecting against EDRF inactivation, and activating guanylate cyclase.

Animals↗
PubMed1992

Effects of higher-order harmonics on phase determination in an ultrasonic interferometer.

The effect of higher-order harmonic components on phase determination were analyzed to improve the accuracy of transient time measurement in an ultrasonic interferometer with a quadrature detector system. Under ideal conditions the locus of output signals of the phase sensitive detector forms a circle on the phase plane as the frequency changes and any nonideal factor would distort the circle, leading to erratic phase determination. This analysis has shown that the nth-order contribution to the phase is mostly determined by the product of the amplitudes of corresponding components of the reference and echo signals fed to the phase detector. The distortion parameters were obtained by least-squares fitting of the data to the distorted circle in the phase plane, and compared with those roughly estimated from the frequency components of the reference and echo signals. The exemplary numerical phase corrections for the third-order harmonics were carried out, so as to illustrate the improvement in the accuracy of the ultrasonic interferometer.

Acoustics↗
PubMed1992

Patterns of alpha-1-adrenergic receptor expression in regenerating and neoplastic hepatic tissue.

As norepinephrine is a potent hepatocyte comitogen through binding to the alpha 1-adrenergic receptor, we have examined mRNA levels of the alpha 1a- and alpha 1b-adrenergic receptor subtypes in normal and regenerating rat hepatocytes as well as in several different rat hepatoma cell lines. All rat hepatomas examined lacked both alpha 1a- and alpha 1b-receptor message and receptor binding in radioligand binding experiments, suggesting that the growth of dedifferentiated neoplastic rat hepatocytes is not regulated by the alpha 1-adrenergic receptor. Interestingly, unlike the rat hepatomas analyzed, the human hepatocellular carcinoma cell line, HepG2, was positive for both alpha 1a and alpha 1b message at 4.5 kb, yet this cell line lacked receptor binding in radioligand binding assays. While normal and regenerating liver is negative for alpha 1a-receptor expression, it is positive for alpha 1b expression and is characterized by the presence of two bands at approximately 4.0 and 3.2 kb which peaked between 20 and 48 h after partial hepatectomy. A dramatic decrease in message level of the lower band and the continued presence of the upper band between 6 and 12 h after partial hepatectomy, and before the peak in DNA synthesis in regenerating rat liver, may correspond with observed differences in alpha 1-receptor function during liver regeneration.

Animals↗
PubMed1992

Patient compliance with oral chemotherapy as assessed by a novel electronic technique.

PURPOSE: Previous reports have suggested low rates of compliance with the oral component of cancer chemotherapy, which, if confirmed, would have serious implications on treatment. Because of the uncertainties in the methodology used in previous studies, we have assessed compliance with a novel technique. PATIENTS AND METHODS: An "intelligent" tablet bottle was used, which, unknown to the patient, electronically records the times of opening over a period of weeks. The records were scored for overall compliance (total number of bottle openings as a percentage of the prescribed number) and for daily and hourly irregularity indices. Twenty-one patients undergoing treatment for Hodgkin's or non-Hodgkin's lymphoma were monitored for a total of 65 treatment periods, each of up to 2 weeks (852 days in total). Eight measures of side effects and quality of life were self-assessed daily by the patients using a diary card. RESULTS: The overall compliance was 100.6% +/- 20.6% (mean +/- SD). Overall compliance was lower (mean reduction, 10%) in treatment periods with drugs prescribed to be taken three times a day. It was not possible to demonstrate convincingly any relationship between compliance and any of the following: drug type, monitoring period sequence, the diary card scores of side effects and quality of life, number of relapses, and time since initial diagnosis. CONCLUSION: These results are reassuring, but further work is in progress to measure compliance in other treatment regimens in which the side effects are more severe and the prognosis is worse.

Administration, Oral↗
PubMed1991

Vasorelaxant effect of emodin, an anthraquinone from a Chinese herb.

The possible mechanism underlying the vasorelaxant effect of emodin isolated from a Chinese herb, was investigated in this study. Emodin dose dependently relaxed isolated vascular rings of human internal mammary artery and saphenous vein, rabbit thoracic aorta, abdominal aorta and mesenteric artery, and rat thoracic aorta. There were no differences in the sensitivity (IC50) and maximal relaxation between intact and endothelium-denuded preparations of rat aorta. In the presence of emodin (10 microM), the contractile responses of rat aorta to phenylephrine, serotonin and potassium chloride were depressed. The relaxation response to acetylcholine was attenuated by emodin, whereas that to isoproterenol was unaffected. The relaxation response to emodin was inhibited by free radical scavengers, superoxide dismutase, catalase and mannitol, and guanylate cyclase inhibitors, methylene blue and hemoglobin. Catalase was the most effective scavenger. Quinacrine (phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor) and nordihydroguaiaretic acid (NDGA, lipoxygenase inhibitor) potentiated the relaxation induced by emodin. NDGA was the most effective potentiator. Exposure of aortic rings to emodin (10 microM) increased the basal level of guanosine 3',5'-cyclic monophosphate (cGMP). It is suggested that the vasorelaxant effect of emodin may be mainly due to cGMP accumulation as a result of guanylate cyclase activation by free radicals and/or hydrogen peroxide generated from semiquinone.

Animals↗
PubMed1991

Pegademase bovine: replacement therapy for severe combined immunodeficiency disease.

Severe combined immunodeficiency (SCID) represents a syndrome characterized by abnormal function of cellular and humoral immunity. Of the various types of SCID, approximately one-fourth are associated with adenosine deaminase (ADA) deficiency. Treatment consists of bone marrow transplantation, red blood cell transfusions, enzyme replacement, and, more recently, gene therapy. Pegademase bovine is the sole agent available for enzyme replacement therapy of SCID associated with ADA deficiency. The drug is administered intramuscularly to infants from birth and to children of any age at time of diagnosis. At present, few adverse effects or drug interactions have been documented. Although it is expensive (approximately $60,000 annually), pegademase bovine offers an alternative to standard means of therapy.

Adenosine Deaminase↗
PubMed1991

Imidazoles for vaginitis.

Vaginal candidiasis is a common infection in women for which several effective therapeutic agents are currently available. Clotrimazole and miconazole were introduced in 1975, and both recently became available over the counter. These imidazole agents have largely replaced nystatin as primary therapy because of greater antifungal activity and shorter treatment regimens, thereby enhancing patient compliance. The cost for these OTC regimens ranges from $12.00 to $24.00 for the patient.

Female↗
PubMed1990

Total and direct-reacting bilirubin values by automated methods compared with liquid chromatography and with manual methods for determining delta bilirubin.

This study compares total and direct-reacting bilirubin values in 40 serum samples from patients with various diagnoses, as measured by automated methods (Beckman Synchron CX-5, Beckman Astra 8, Kodak Ektachem 700) and HPLC and by a manual method for delta bilirubin. For total bilirubin, within-run CVs were less than 6%. The Ektachem 700 method underestimated bilirubin with serum samples from patients with Crigler-Najjar syndrome and from newborns in whom unconjugated bilirubin concentrations were increased but conjugated bilirubins were not present or were present only in small amounts. The Astra 8 and Synchron CX-5 methods were inaccurate with cholestatic serum samples, in which conjugated bilirubin concentrations were increased and other compounds such as bile acids could be expected to interfere. We conclude that each automated method examined provides reasonable estimates for total and direct-reacting bilirubin values for routine clinical use. The need for each laboratory to select the appropriate bilirubin method for its particular situation is obvious.

Autoanalysis↗
PubMed1988

Day-night rhythm of 5-methoxytryptamine biosynthesis in the pineal gland of the golden hamster (Mesocricetus auratus).

5-Methoxytryptamine is a potent agonist of presynaptic 5-hydroxytryptamine autoreceptors modulating serotonin release in the central nervous system. This methoxyindole can be synthesized in the pineal gland, but its presence in vivo is still controversial, probably because of rapid catabolism by monoamine oxidase. An improved high-pressure liquid chromatography method, with coulometric detection, has been developed for the simultaneous measurement of melatonin, 5-methoxytryptamine, 5-methoxytryptophol and 5-methoxyindolacetic acid. We have demonstrated a day-night rhythmicity in the amount of 5-methoxytryptamine in the pineal gland of golden hamsters (Mesocricetus auratus) maintained under a long photoperiod (14 h light: 10 h darkness) and pretreated with the monoamine oxidase inhibitor pargyline. Levels of 5-methoxytryptamine were highest at 16.30 h and lowest at 00.30 h. The rhythm for 5-methoxytryptamine appears to be the same as for serotonin (opposite in phase to that of melatonin). The identification of 5-methoxytryptamine has been confirmed by analysis with gas chromatography-mass spectrometry.

5-Methoxytryptamine↗
PubMed1979

Inexpensive analog equipment for processing gas chromatography mass spectrometry data.

Using relatively simple analog circuitry, and an inexpensive analog frequency modulated tape recorder (or a modified audio recorder) for data storage, repetitively scanned spectra may be examined on an oscilloscope, and reconstructed mass chromatograms produced. The same equipment may be used for peak matching, and for selective ion detection over the full mass range of a sector instrument.

Chromatography, Gas↗
PubMed1979

Urinary dicarboxylic acids in patients receiving lithium or rubidium salts.

Lithium salts administered in therapeutic doses to four subjects who were kept on controlled diets increased up to fivefold the urinary output of some dicarboxylic acids. Some of the acids affected are intermediates in the tricarboxylic acid cycle, others are chemically similar but not directly related in metabolic terms. This is probably a direct effect on renal transport. Rubidium salts increased urinary 2-oxoglutarate output and blood 2-oxoglutarate levels, probably by some action on intermediary metabolism.

Bipolar Disorder↗
PubMed1978

Effects of rubidium chloride on the course of manic-depressive illness.

Clinical studies of the effects of rubidium ions on the course of manic-depressive illness are reported. It seems that rubidium tends to increase the length of manic phases and possibly reduces the extremes of mood. Rubidium did not seem to produce any severe side effects in the dose administered, but it has a long biological half-life and caution is still required. Some details of the CSF, RBC, saliva and plasma and urine kinetics are also reported.

Adult↗
PubMed1977

Lithium.

Explore the source record for details and available documents.

Erythrocytes↗
PubMed1976

Determination of urinary monohydric and dihydric phenols by gas chromatography of the acetate and TMS derivatives. 4-Dimethylaminopyridine as a catalyst for acetylation reactions.

A procedure is described for the quantitative extraction of phenols from human urine. The compounds were chromatographed as the trimethylsilyl derivatives on wall-coated glass capillary columns. A more specific method of extraction involving the formation of acetate derivatives is also described. The acetates were prepared by treating dilute solutions of phenols at room temperature with acetic anhydride in the presence of 4-dimethylaminopyridine, which is a far more powerful catalyst than pyridine. Under these conditions N-acylamino acids are converted to azlactones.

4-Aminopyridine↗