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Biomedical subjects

B Y Wong

Publications and source records attributed to B Y Wong.

At least 19 recordsLinked to original sources
PubMed1992

Chinese medicinal herbs modulate mutagenesis, DNA binding and metabolism of aflatoxin B1.

Oldenlandia diffusa (OD) and Scutellaria barbata (SB) have been used in traditional Chinese medicine for treating liver, lung and rectal tumors while Astragalus membranaceus (AM) and Ligustrum lucidum (LL) are often used as an adjunct in cancer therapy. In this study, we determined the effects of aqueous extracts of these four herbs on aflatoxin B1 (AFB1)-induced mutagenesis using Salmonella typhimurium TA100 as the bacterial tester strain and rat liver 9000 x g supernatant as the activation system. The effects of these herbs on [3H]AFB1 binding to calf-thymus DNA were assessed. Organosoluble and water-soluble metabolites of AFB1 were extracted and analyzed by high-performance liquid chromatography (HPLC). Mutagenesis assays revealed that all of these herbs produced a concentration-dependent inhibition of histidine-independent revertant (His+) colonies induced by AFB1. At a concentration of 1.5 mg/plate, SB and OD in combination exhibited an additive effect. The trend of inhibition of these four herbs on AFB1-induced mutagenesis was: SB greater than LL greater than AM. LL, OD and SB significantly inhibited AFB1 binding to DNA, reduced AFB1-DNA adduct formation, and also significantly decreased the formation of organosoluble metabolites of AFB1. Our data suggest that these Chinese medicinal herbs possess cancer chemopreventive properties.

Aflatoxin B1↗
PubMed1992

Chinese medicinal herbs modulate mutagenesis, DNA binding and metabolism of benzo[a]pyrene 7,8-dihydrodiol and benzo[a]pyrene 7,8-dihydrodiol-9,10-epoxide.

Oldenlandia diffusa(OD) and Scutellaria barbata (SB) have been used in traditional Chinese medicine for treating liver, lung and rectal tumors. In this study, the effects of aqueous extracts of these two herbs on benzo[a]pyrene 7,8-dihydrodiol. (BaP 7,8-DHD) and benzo[a]pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE)-induced mutagenesis using Salmonella typhimurium TA100 as the bacterial tester strain and rat liver 9000 x g supernatant (S9) as the metabolic activation system were assessed. We also determined the effects of these two herbs on BaP 7,8-DHD and BPDE binding to calf thymus DNA. Organosoluble metabolites of BaP 7,8-DHD and water-soluble conjugates of BaP 7,8-DHD and BPDE were analyzed by high-performance liquid chromatography (HPLC) and alumina column liquid chromatography. Mutagenesis assays revealed that these two herbs produced a significant concentration-dependent inhibition of histidine-independent (His+) revertants induced by BaP 7,8-DHD and BPDE. OD and SB also inhibited BPDE-induced mutagenesis in a concentration-dependent manner in the absence of S9. SB had a greater inhibitory effect than OD. SB significantly inhibited BaP 7,8-DHD and BPDE binding to DNA while OD significantly enhanced DNA binding of both compounds. OD and SB inhibited the formation of organosoluble metabolites of BaP 7,8-DHD and decreased the formation of water-soluble conjugates of BaP 7,8-DHD and BPDE. However, the fraction of the total radioactivity in the water-soluble conjugates present as sulfate and glutathione was increased by OD and SB. Glucuronide fraction was decreased. The results of this study affirm our previous work suggesting that these two Chinese medicinal herbs possess antimutagenic properties and further suggest that they act as blocking agents through a scavenging mechanism.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1989

Magnetic resonance imaging of vascular compression in trigeminal neuralgia. Case report.

A case of trigeminal neuralgia is reported in which preoperative high-resolution magnetic resonance imaging demonstrated vascular compression of the trigeminal nerve. Surgery confirmed compression and indentation of the fifth nerve by a large branch of the superior cerebellar artery. Following microvascular decompression, the patient experienced no further pain. Magnetic resonance imaging may be useful in the evaluation of trigeminal neuralgia to identify a subgroup of patients who could benefit most from decompression.

Blood Vessels↗
PubMed1988

Dextrorphan and dextromethorphan, common antitussives, are antiepileptic and antagonize N-methyl-D-aspartate in brain slices.

The antitussive, dextromethorphan (DM), and its metabolite, dextrorphan (DX), were evaluated for antiepileptic properties in vitro. Interictal bursts and prolonged ictal epileptiform afterdischarges, induced by perfusion of guinea pig neocortical brain slices with Mg2+-free solution, were blocked by DX (1-250 microM) or DM (100 microM). Intracellular records showed that these agents blocked N-methyl-D-aspartate (NMDA)-induced depolarizations without altering intrinsic membrane properties. DX blocked NMDA but not quisqualate-evoked multi-unit excitatory responses. DM is a widely available, orally effective drug with low toxicity in antitussive doses, which has antiepileptic and NMDA-antagonist properties in vitro. Its toxicity and effectiveness as an anticonvulsant should be expeditiously examined in clinical trials.

2-Amino-5-phosphonovalerate↗
PubMed1987

Nigral infusions of muscimol or bicuculline facilitate seizures in developing rats.

The substantia nigra (SN) appears to be a crucial site involved in the modification of seizures. The aim of this study was to elucidate the role of the GABA nigral system in the expression of seizures by comparing the effects of multiple doses of a GABA agonist (muscimol) and a GABA antagonist (bicuculline methobromide) on the development of flurothyl seizures in 16-day-old rat pups. The drugs were infused bilaterally either in the SN or dorsal to the SN. An additional group of pups were infused with bicuculline in the corpus striatum. Results indicate that both drugs facilitated the development of seizures in a dose-related manner when infused into the SN. Infusions of muscimol dorsal to the SN had no effect on seizure latencies while infusions of bicuculline dorsal to SN or corpus striatum still increased the susceptibility of rat pups to seizures. The data suggest that only the effects of muscimol on seizures are specific for the SN and that early in life muscimol may exert its proconvulsant effects via a different receptor site or mechanism than bicuculline.

Animals↗
PubMed1987

Mutual interactions between repeated flurothyl convulsions and electrical kindling.

The interactions between repeated flurothyl seizures and electrical kindling induced from the neocortex or the amygdala were investigated. Three consecutive flurothyl-induced convulsions enhanced the rate of development of subsequent electrical kindling from the neocortex. Similarly multiple (more than 15) generalized kindled seizures, induced from either the neocortex or the amygdala, reduced the latency of onset of flurothyl seizures with repeated exposures producing a 'kindling-like' effect for flurothyl. These results indicate that eventually seizures will beget seizures independently of the site of origination of the seizures.

Amygdala↗
PubMed1986

Age-related substantia nigra-mediated seizure facilitation.

We investigated the role of the GABAergic system of the substantia nigra in seizures of rat pups. Rat pups had bilateral cannulae implanted chronically either in the substantia nigra or 1.5 mm dorsal to it. At age 16 to 17 days, seizures were induced in the cannulated rats and naive (intact) controls by exposure to flurothyl following pretreatment with the GABA agonist, muscimol, or vehicle. Naive rats were the most resistant to flurothyl seizures. Bilateral nigral infusions of muscimol markedly facilitated the development of flurothyl seizures in a dose-response manner and differed significantly from the vehicle controls or rats infused with muscimol dorsally to the substantia nigra. In contrast, bilateral nigral muscimol infusions protected adult rats against the development of flurothyl seizures. Our data indicate that the effects of nigral GABA agonist infusions on seizures are age-dependent; the altered responsivity of the GABAergic nigral system in immature rats may be responsible in part for the increased seizure susceptibility of the developing central nervous system.

Animals↗
PubMed1986

Evaluation of a ventricular septal defect in an orangutan: a case report.

A 15-year-old male Sumatran orangutan (Pongo pymaeus abeli) with a history of an interventricular septal defect was evaluated with cardiac catheterization and two-dimensional echocardiography. Results demonstrated that by Homo sapiens standards the right heart pressures were normal. The oxygen saturations were consistent with a small ventricular septal defect. Echocardiography demonstrated a slight enlargement of the right ventricle.

Animal Diseases↗
PubMed1985

Issues in cognitive-behavioral interventions in academic skill areas.

In this paper, conceptual and methodological issues within three phases of CBM interventions in academic skills are analyzed: Acquisition, evaluation, and generalization. The goal of such analysis is threefold: To enhance understanding of observed problems, clarify specific conceptual issues, and highlight areas that need more conceptual clarification and more research.

Adolescent↗
PubMed1985

Simple method for maintaining serum lidocaine levels in the therapeutic range.

Lidocaine hydrochloride is commonly infused intravenously to prevent ventricular arrhythmias. In some patients, elevations in serum lidocaine levels can cause serious toxic effects. In a group of 19 patients given a constant infusion of lidocaine, we confirmed the observation that serum lidocaine levels rose significantly between four and 24 hours after initiation of therapy. One of these patients manifested a toxic reaction to lidocaine. The lidocaine infusion rate was modified in a second group of 32 patients on the basis of the four-hour serum level. In these patients, after dosage adjustment, the mean lidocaine level did not rise, and all levels remained within the 2- to 4-mg/L therapeutic range at 24 hours. Without dosage adjustment, half of these levels would have fallen outside the desired range. A simple formula can be used to adjust prophylactic lidocaine infusion rates to attain levels that remain therapeutic, yet nontoxic.

Adult↗
PubMed1985

The day-care centre in the management of psoriasis.

In 1980, 118 patients with psoriasis were admitted to the inpatient service of MRH resulting in 3048 patient days of hospitalisation. The day care centre for psoriasis can provide an efficient therapeutic environment thus reducing hospital admissions. The outpatient dithranol-ultraviolet B combination therapy gave a 80% success in clearing 95% of the skin of psoriasis. PUVA therapy gave a clearance of 77% requiring an average of 25 treatment sessions; taking an average of 42 days and total UVA dose of 346 J/cm2. Combination therapy of retinoids and PUVA (REPUVA) gave a success rate of 96% clearance with an average of 18 treatment sessions and average total UVA dose of 142 J/cm2.

Ambulatory Care↗
PubMed1979

Treatment of heart block due to sarcoid heart disease.

The role of glucocorticosteroid therapy for myocardial sarcoidosis is not well defined. This report shows the effect of prednisone therapy on atrioventricular (AV) conduction in a patient with myocardial sarcoidosis and AV block. On three separate occasions AV block was documented prior to prednisone therapy. On the first two occasions the patient had first and second degree AV block which by His bundle electrogram initially was shown to be in the AV node. On the third occasion the patient developed complete heart block. On each occasion treatment with prednisone resulted in improved AV conduction. The results indicate that prednisone therapy can be beneficial in the treatment of AV block due to myocardial sarcoidosis.

Adult↗
PubMed1979

Progression of aortic stenosis.

We assessed progressive stenosis of the aortic valve in 11 adult patients (mean age of 48 years) with aortic stenosis who had undergone two cardiac catheterizations without intervening aortic valve surgery. The mean time between cardiac catheterization was 59 months (range 20 to 133). No patients had mitral valve disease. Two patients had coronary artery disease. The results showed that progressive stenosis of the aortic valve occurred in 10 of 11 patients with a significant decrease in the calculated mean aortic valve area from 1.2 +/- 0.2 sq cm to 0.7 +/- 0.1 sq cm (P less than 0.005); a significant increase in mean left ventricular peak systolic pressure from 149 +/- 8 mm Hg to 199 +/- 3 mm Hg (P less than 0.01), and a significant increase in mean left ventricular aortic pressure gradient from 31 +/- 4 mm Hg to 75 +/- 13 mm Hg (P less than 0.005). On an individual basis, the change in left ventricular pressure and the left ventricular-aortic gradient did not always reflect the decrease in aortic valve area because of variations in cardiac output. The shortest period of time in which progression of aortic stenosis occurred was 27 to 29 months. Thus, progressive stenosis of the aortic valve occurs in adults with isolated aortic valvular stenosis. Significant decrease in the aortic valve area can develop in as short a period as 27 to 29 months.

Adult↗
PubMed1978

Echocardiographic features of an aneurysm of the left sinus of Valsalva.

The echocardiographic features of an aneurysm of the left sinus of Valsalva are described and correlated with angiographic findings. The echocardiogram showed the presence of a thin line of echoes occurring proximal to the anterior leaflet of the mitral valve and moving in and out of apposition with the posterior aortic wall. During systole, this line of echoes moved away from the aorta into the left atrium, and during diastole, the line moved into the aorta. Recognition of these features provides a potential noninvasive way to diagnose aneurysms of the left sinus of Valsalva prior to rupture.

Adult↗