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Biomedical subjects

C H Cheng

Publications and source records attributed to C H Cheng.

At least 127 records · Page 7Linked to original sources
PubMed1993

Clinical experience and model analysis on beta-2-microglobulin kinetics in high-flux hemodialysis.

Beta-2-microglobulin (beta 2M) is associated with amyloidosis. The study of beta 2M kinetics can provide information on the elimination of this uremic toxin. A beta 2M kinetic model modified from Gotch, considering the volume changes between intracellular, interstitial, and intravascular compartments and the generation stimulation and inhibition during hemodialysis is proposed. The clinical experiments on 8 stable hemodialysis patients treated with polysulfone (F80) and polymethyl methacrylate (PMMA, BK2.1p) 3 times a week were conducted. There was an 18% decrease of beta 2M clearance in the period from 30 to 180 min with a time-averaged beta 2M clearance of 48 ml/min using polysulfone dialyzers (F80). In PMMA dialyzers, there was a 64% decrease of beta 2M clearance from 30 to 180 min with a time-averaged clearance of 56.3 ml/min. During hemodialysis, the generation rate was 0.379 mg/min in polysulfone and 0.828 mg/min in PMMA dialyzers. There was a stimulation generation of 0.309 mg/min in polysulfone and 0.749 mg/min in PMMA during hemodialysis. In conclusion, we provide a beta 2M kinetic model including volume changes, polymerization, generation stimulation, and inhibition that is similar to the human physiological condition. This model can be used for further clinical study.

Blood Flow Velocity↗
PubMed1993

Two years experience with the Palmaz-Schatz coronary stent in a heterogeneous patient population.

Between January 1991 and December 1992, 136 Palmaz-Schatz coronary stents were implanted in 113 native coronary arteries in 106 patients. Forty-seven patients presented with stable angina, 50 with unstable angina, 7 with congestive cardiac failure and unstable angina and 2 were asymptomatic. Stenting was carried out in 15 patients for restenosis after coronary angioplasty (PTCA), 32 for significant dissection during PTCA (with 19 acute and 13 threatened closure), 10 for suboptimal PTCA results and 56 for de novo lesions, 52 (92.9%) of which were either ACC/AHA type B or C. Successful delivery was achieved in 97.2% (103/106) of patients or 97.3% (110/113) of vessels. Percent diameter stenosis was reduced from 78 +/- 13% to 4 +/- 11%. There were two subacute stent thromboses (1.9%), resulting in Q-Wave myocardial infarction. Three deaths (2.9%) occurred, all from the group with congestive cardiac failure and unstable angina. Major bleeding/vascular complications occurred in 4 patients (3.9%). All patients were followed up for a mean of 18 months (6 months to 30 months). Eighty-five patients were asymptomatic. Three patients were angina-free but continued to have, albeit improved, congestive cardiac failure. Ten patients had recurrence of angina, all within 6 months of the stenting procedure. Four were treated medically and 4 had PTCA of whom one eventually had coronary bypass surgery. Two patients had new lesions, successfully treated by PTCA or stenting. In conclusion, a high rate of successful delivery of the Palmaz-Schatz coronary stent can be achieved in a wide spectrum of patients with few complications which are mostly related to anticoagulation. It offers very effective bailout for acute closure during PTCA. Despite the presence of unfavorable pre-procedure patient and lesion characteristics, the acute and long term clinical results are encouraging.

Adult↗
PubMed1993

Presence of growth hormone receptors in carp liver and intestine.

Membranes were prepared from tissues of the carp Ctenopharynogodon idellus including liver, kidney, intestine, adipose tissue, ovary, gill, heart, muscle and spleen. The carp liver and intestine membranes bound 125I-labeled bovine growth hormone and the binding could be displaced by cold bovine growth hormone. No changes in the ability to bind 125I-labeled bovine growth hormone occurred after treatment of the carp liver membrane with DNase, RNase, alpha-amylase and beta-glucosidase, suggesting that neither nucleic acids nor carbohydrates played an important part in the hepatic binding of growth hormone. Treatment of carp liver membranes with either chymotrypsin or trypsin produced a decrease in the growth hormone binding activity, indicating that the growth hormone receptor on carp liver membrane is a protein. Treatment of carp liver membranes with p-chloromercuribenzoate brought about a reduction in 125I-bGH binding. The inhibition could be reversed by dithioerythritol, suggesting the involvement of essential sulfhydryl group in bGH binding.

Animals↗
PubMed1992

Profiles of interaction of R(+)/S(-)-zacopride and anxiolytic agents in a mouse model.

The mouse black and white test box was used to measure changes in behaviour in an aversive situation where the administration of R(+)-zacopride (but not S(-)-zacopride) alone decreased aversive responding to the white area. A similar anxiolytic profile of action was observed using parachlorophenylalanine (PCPA), whose effects were antagonised by a co-treatment with R(+)-zacopride and reversed by S(-)-zacopride to an exacerbation of the aversive response. An anxiolytic profile of action was also observed using ondansetron, granisetron, chlordiazepoxide, diazepam, ritanserin, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), E4424 (2-[4-[4-(4-chloro-l-pyrazoyl)butyl]-l-piperazinyl]-pyrimidine), umepsirone, DuP753 (2-n-butyl-4-chloro-5-hydroxy-methyl-1-[2(1H-tetrazol-5-yl) biphenyl-4-yl)methyl)]-imidazole), SQ29,852 ((S)-1-[6-amino-2[hydroxy)(4-phenyl-butyl)phosphinyl]-oxy)-1- nexy]-2-proline), devazepide and guanfacine, and this was retained following co-treatment with PCPA. The anxiolytic profile of action of PCPA was also retained following co-treatment with renzapride which when administered alone failed to modify behaviour. However, the ability of chlordiazepoxide, diazepam, ondansetron and E4424 (but not devazepide, DuP753 or SQ29,852) to reduce aversive responding was inhibited by co-treatment with R(+) and/or S(-)-zacopride. It is concluded that the reduction in aversive responding caused by pharmacological manipulation at the benzodiazepine, 5-HT receptor subtypes 5-HT1A, 5-HT1C/5-HT2 and 5-HT3 (but not at the cholecystokin CCKA or angiotensin receptors or inhibition of angiotensin converting enzyme) can be inhibited by R(+) and S(-)-zacopride. The data is discussed in terms of zacopride having an agonist or partial agonist effect at the 5-HT3 receptor.

Animals↗
PubMed1992

Growth hormone binding sites in tilapia (Oreochromis mossambicus) liver.

125I-labeled bovine and tilapia growth hormones were used to assess the presence of growth hormone receptors in membranes prepared from tissues of the tilapia Oreochromis mossambicus. The highest level of specific binding was detected in liver membranes from animals of both sexes and the binding was protein-dependent. Tilapia growth hormone, bovine growth hormone, and ovine prolactin, but not tilapia prolactin, potently inhibited the hepatic binding of 125I-labeled bovine growth hormone. Scatchard analysis of the 125I-labeled bovine growth hormone binding data revealed a Bmax (maximum binding) value of 180 fmol/mg protein and a Kd (dissociation constant) value of 13 nM. Tilapia growth hormone potently inhibited hepatic binding of 125I-labeled tilapia growth hormone. Scatchard analysis revealed a single class of binding sites with Bmax and Kd values of 390 fmol/mg protein and 2.5 nM, respectively. Bovine growth hormone and ovine prolactin were less potent while tilapia prolactin was inactive in inhibiting hepatic 125I-labeled tilapia growth hormone binding.

Animals↗
PubMed1992

Toxic effects of solstitialin A 13-acetate and cynaropicrin from Centaurea solstitialis L. (Asteraceae) in cell cultures of foetal rat brain.

Extracts of the aerial parts of the yellow star thistle (Centaurea solstitialis L.) were prepared using petroleum ether, chloroform and methanol and toxicity assessed in primary cell cultures of striatum, frontal cortex and mesencephalon, containing the substantia nigra or raphe nucleus from the brain of the foetal rat. Chloroform extracts significantly reduced the percentage of live cells whereas the petroleum ether extract was inactive. The ability of the methanol extract to reduce the percentage of live cells could not be distinguished from the effects of the vehicle controls for methanol. Subsequently, the plant material was extracted with dichloromethane and 10 fractions were obtained by column chromatography. Fractions 5, 6, 7 and 8 caused concentration-dependent cell death in the culture of substantia nigra, the other fractions were not toxic at the concentrations used. In further studies, solstitialin A was isolated from fraction 9, solstitialin A 13-acetate from fraction 6 and solstitialin A-3 acetate and cynaropicrin from fraction 7. Solstitialin A 13-acetate and cynaropicrin were toxic to cultures of substantia nigra cells. It is concluded that, of the compounds identified, solstitialin A 13-acetate and cynaropicrin have toxic potential in cell cultures, containing cells from the substantia nigra of the rat, the specificity of action to cells of the substantia nigra remains to be shown, and that a toxic action in the midbrain may contribute to the nigro-pallidal encephalomalacia, caused by the ingestion of the yellow star thistle by horses.

Animals↗
PubMed1992

Differential modulation of extracellular levels of 5-hydroxytryptamine in the rat frontal cortex by (R)- and (S)-zacopride.

1. The ability of various anxiolytic and potential anxiolytic agents to modify 5-hydroxytryptamine (5-HT) release in the frontal cortex of the rat was assessed by the microdialysis technique. 2. The benzodiazepine receptor agonist, diazepam (2.5 mg kg-1, i.p.), the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.32 mg kg-1, s.c.) and the 5-HT1A receptor partial agonist buspirone (4.0 mg kg-1, i.p.) maximally reduced extracellular levels of 5-HT in the rat frontal cortex by approximately 50-60%, 70-80% and 30-40%, respectively. 3. (R)-zacopride (1.0-100 micrograms kg-1, i.p.) dose-dependently reduced extracellular levels of 5-HT in the rat frontal cortex (approximately 80% maximal reduction) whereas the other 5-HT3 receptor antagonists ondansetron (10 micrograms kg-1, i.p.) and (S)-zacopride (10-100 micrograms kg-1, i.p.) were ineffective. 4. In contrast to (S)-zacopride (100 nM; administered via the microdialysis probe), (R)-zacopride (1.0-100 nM; administered via the microdialysis probe) induced a concentration-dependent reduction in extracellular levels of 5-HT in the rat frontal cortex (approximately 70% maximal reduction). 5. In contrast to ondansetron (100 micrograms kg-1, i.p.), (S)-zacopride (10-100 micrograms kg-1, i.p.) dose-dependently reversed the (R)-zacopride (10 micrograms kg-1, i.p.) induced reduction in extracellular levels of 5-HT in the rat frontal cortex. The highest dose of (S)-zacopride (100 micrograms kg-1, i.p.) completely prevented the (R)-zacopride response.In addition, (S)-zacopride (100 nM; administered via the microdialysis probe) attenuated the inhibitory action of (R)-zacopride (10 nM; administered via the microdialysis probe) on extracellular levels of 5-HT in the rat frontal cortex.6. In conclusion, the present study provides further evidence of the ability of diazepam, 8-OH-DPAT and buspirone to reduce the activity of the central 5-hydroxytryptaminergic system in vivo. Furthermore,the results indicate that the ability of (R)-zacopride to reduce the in vivo release of 5-HT in the rat frontal cortex does not correlate with its 5-HT3 receptor antagonism. However, the differential affinity of (R)- and (S)-zacopride for a (S)-zacopride-insensitive (R)-zacopride site in rat cerebral cortex mirrors the relative activity of the two zacopride stereoisomers to modify the in vivo release of 5-HT in the frontal cortex of the rat and their ability to release suppressed behaviour in animal models of anxiety.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Hypocalcemia and myocardial function in uremia.

To investigate whether hypocalcemia affects cardiac performance in uremic patients, we studied the hemodynamic changes with short- and long-term correction of hypocalcemia in 4 uremic patients on dialysis using continuous wave Doppler study. At rest, 1 h of intravenous calcium infusion increased calcium level from 1.74 +/- 0.17 to 1.92 +/- 0.16 mmol/l (p less than 0.05). Cardiac output represented by minute distance increased from 10.5 +/- 2.0 to 12.1 +/- 2.5 m (p less than 0.05), but heart rate and blood pressure were unchanged. The peak velocity and acceleration of ascending aortic blood flow increased during calcium infusion. With long-term replacement, calcium level increased from 1.74 +/- 0.17 to 1.94 +/- 0.15 mmol/l (p less than 0.05), but resting hemodynamics were unchanged. On exercise testing, exercise duration increased from 10.6 +/- 1.6 min to 12.9 +/- 1.5 min (p less than 0.01), but hemodynamic parameters at peak exercise were similar. We conclude that acute calcium replacement enhanced cardiac contractility in uremic patients, but cardiac performance at rest and peak exercise was not improved with long-term therapy. This reflects different cardiac responses to acute versus chronic calcium replacement.

Adult↗
PubMed1992

Pentazocine addict nephropathy: a case report.

Medical complications associated with narcotic addiction include bacterial endocarditis, pneumonia, pulmonary embolism and renal disease. Renal disorders associated with pentazocine abuse are rarely reported. They vary with method of administration, dosage, and duration of abuse. We describe a 33-year-old male addict, using intravenous pentazocine for 6 years. He has nephrotic syndrome with a rapid deterioration of renal function to a uremic stage within 3 weeks. The laboratory data includes: IgG 1270 mg/dl, IgA 369mg/dl, IgM 326mg/dl, C'3 65.2 mg/dl, C'4 16.3 mg/dl, and serum soluble interleukin-2 receptor level (sIL-2R) greater than 6000U/ml. A renal biopsy revealed membranoproliferative glomerulonephritis (MPGN) type I with tubulointerstitial nephritis. Immunofluorescent (IF) study revealed granular deposition of C'3 and IgM in mesangium and the glomerular capillary wall. The pathogenesis of glomerular disease in drug addicts is discussed, and the literature reviewed.

Adult↗
PubMed1992

Clinical application of ejection fraction by gated MRI.

To evaluate the clinical desired accuracy of the left ventricular ejection fractions (EFs) calculated by magnetic resonance imaging (MRI). Within one to three days post coronary angiography and left ventriculogram, twenty-five adults were studied by MR imaging. They had nuclear medicine studies for left ventricular ejection fractions as well. EKG-gated spin-echo 30-msec echo-delay images were obtained in end systole and end diastole in a plane parallel to the ventricular septum. Analysis of ventricular volumes and ejection fractions were performed using the area-length method. The EFs calculation by gated MRI were compared with that obtained by angiocardiography and nuclear medicine studies. The linear regression line obtained for ejection fraction was y = 0.858x +6.813, r = 0.753, p = 0.009; y' = 1.567x'-24.692, r' = 0.783, p' = 0.002. The above figure indicate a reasonable correlation among these three methods.

Humans↗
PubMed1992

The sea bream liver contains receptors for growth hormone and prolactin.

Different tissues of the black sea bream Mylio macrocephalus including the liver, gills, intestine, muscle, gonad, swim bladder, spleen, heart and kidney were examined for the presence of prolactin and growth hormone receptors. Membranes were prepared from the tissues and 125I-labeled ovine prolactin and bovine growth hormone were used as ligands. It was found that the liver contained the highest level of specific 125I-labeled ovine prolactin and bovine growth hormone binding, suggesting the existence of hepatic prolactin and growth hormone receptors. The protein nature of the hepatic growth hormone receptor was revealed by the reduction of specific 125I-labeled growth hormone binding after treatment of hepatic membranes with trypsin and chymotrypsin.

Animals↗
PubMed1991

Angiotensin converting enzyme density is increased in temporal cortex from patients with Alzheimer's disease.

The present study assesses the binding density of the selective angiotensin converting enzyme (ACE) radioligand [3H]ceranapril in brain tissue homogenates derived from patients with Alzheimer's disease and those from age-, sex- and post-mortem delay-matched neurologically normal patients. Saturation studies with [3H]ceranapril identified that the specific binding (defined by captopril, 10 microM) was homogenous and of high affinity. ACE inhibitor recognition site density was higher by some 70% in the temporal cortex (Brodmann area 22) from Alzheimer's patients whereas densities were similar in frontal cortex and cerebellum when compared to control tissue. It is unknown whether this apparently selective alteration in ACE density is directly related to, or a compensatory effect of the disease, but it provides additional support for the development of compounds which interact with the central angiotensin system as novel therapies for cognitive dysfunction.

Aged↗
PubMed1991

Improvement of exercise capacity after nifedipine in patients with Eisenmenger syndrome complicating ventricular septal defect.

We investigated the potential benefit of a preferential pulmonary vasodilatory effect of nifedipine in 4 patients with Eisenmenger syndrome complicating ventricular septal defect. First-pass radionuclide scan was performed at rest to measure intracardiac shunting before and after nifedipine. Two hours after 20 mg sublingual nifedipine, right-to-left shunt increased from 16.3 +/- 1.4 to 20.4 +/- 1.5% (p less than 0.05), but systemic arterial oxygen saturation (SAO2) remained steady. With 4 weeks of maintenance nifedipine therapy, resting intracardiac shunting and SAO2 were unchanged from baseline. Symptom-limited cycle ergometry was performed before and after maintenance nifedipine with placebo control. Exercise duration was prolonged (8.7 +/- 0.6 vs. 6.8 +/- 0.9 min; p less than 0.02) and SAO2 at each stage of exercise was consistently increased in all patients after nifedipine. Cardiac output and the SAO2 at peak exercise were similar. Thus, chronic nifedipine therapy increases SAO2 on exercise and improves maximal exercise capacity in patients with Eisenmenger syndrome, which is not predicted by study of resting intracardiac shunting after acute therapy.

Administration, Oral↗
PubMed1991

Presence of prolactin receptors in eel liver and carp kidney and growth hormone receptor in eel liver.

1. 125I-labelled ovine prolactin and bovine growth hormone were used to test for the presence of prolactin and growth hormone receptors in membrane prepared from tissues of the white eel Anguilla japonica, the carp Ctenopharynogodon idellus and the ricefield eel Monopterus albus. 2. High levels of specific 125I-labelled ovine prolactin binding were found in white eel liver membranes and carp kidney membranes. 3. High levels of specific 125I-labelled bovine growth hormone binding were detected in white eel liver membranes. 4. Tissues of the ricefield eel did not bind 125I-labelled ovine prolactin or bovine growth hormone. 5. The results suggest the presence of prolactin receptors in white eel liver and carp kidney membranes and growth hormone receptors in white eel liver membranes.

Animals↗
PubMed1991

Grade changes in peer influence on adolescent cigarette smoking: a comparison of two measures.

The effects of peer influence on adolescent cigarette smoking were investigated in longitudinal study of 309 white, middle-class subjects in the 8th and 11th grades. Subjects provided data on their smoking behavior, the proportion of their friends who smoked, and the identity of their best friend. Data from the person named as best friend was used to measure peer smoking, rather than the adolescent's perceptions of the friend's smoking. Peer influence was defined as the difference between the subject's smoking behavior and that of their best friend. This definition (PI1) minimized the confounding of peer influence with selective association. The effects of peer influence on change in smoking behavior were found to be stronger for 8th than 11th graders and for boys than girls. When the proportion of friends who smoke (PI2) was used as the measure of peer influence, the effects of peer influence were stronger for 11th than 8th graders. The relative merits of the two measures are discussed, and the argument is made that the difference between friend and adolescent smoking is a more appropriate measure of peer influence than the proportion of friends who smoke.

Adolescent↗
PubMed1991

Prediction of magnetically induced electric fields in biological tissue.

There are many potential medical applications in which it is desirable to noninvasively induce electric fields. One such application that serves as the backdrop of this work is that of stimulating neurons in the brain. The magnetic fields necessary must be quite high in magnitude, and fluctuate rapidly in time to induce the internal electric fields necessary for stimulation. Attention is focused on the calculation of the induced electric fields commensurate with rapidly changing magnetic fields in biological tissue. The problem is not a true eddy current problem in that the magnetic fields induced do not influence the source fields. Two techniques are introduced for numerically predicting the fields, each employing a different gauge for the potentials used to represent the electric field. The first method employs a current vector potential (analogous to A in classical magnetic field theory where DEL x A = B) and is best suited to two-dimensional (2-D) models. The second represents the electric field as the sum of a vector plus the gradient of a scalar field; because the vector can be determined quickly using Biot Savart (which for circular coils degenerates to an efficient evaluation employing elliptic integrals), the numerical model is a scalar problem even in the most complicated three dimensional geometry. These two models are solved for the case of a circular current carrying coil near a conducting body with sharp corners.

Brain↗