Biomedical subjects

C F Chen

Publications and source records attributed to C F Chen.

At least 19 recordsLinked to original sources

PubMed1992

Increase of plasma neuropeptide Y-like immunoreactivity following chronic hypoxia in the rat.

In an attempt to understand the changes of circulating neuropeptide Y (NPY) during hypoxia, the plasma level of NPY was investigated by radioimmunoassay. Exposure of rats to hypobaric hypoxia at an altitude of 18,000 ft for 4 weeks causes an increase of pulmonary pressure and an elevation of plasma NPY-like immunoreactivity (NPY-LI). However, the systemic blood pressure was not elevated by this chronic hypoxia. Also, plasma noradrenaline (NA) estimated by chromatographic analysis (HPLC-ECD) was not markedly raised. Failure of bretylium and guanethidine, sympathetic neuron blockers, in reducing the plasma NPY-LI level of these rats ruled out the participation of adrenergic nervous terminals. Adrenal medulla seems responsible for this elevation of plasma NPY-LI because this magnitude disappeared in adrenalectomized rats. These data suggest that chronic hypoxia induced an elevation of circulating NPY from the adrenal gland of rats.

Adrenal Glands↗

PubMed1992

The vasorelaxant effect of evodiamine in rat isolated mesenteric arteries: mode of action.

The roles of the endothelium, Ca2+ and K+ fluxes in the evodiamine-induced attenuation of vascular contractile responses to vasoactive agents were examined. The results showed that: (1) in rat mesenteric artery rings, evodiamine elicited a concentration-dependent attenuation in the contractile response generated by phenylephrine. The inhibitory potency was greater for intact than for endothelium-denuded preparations. Thus, the vasodilator action of evodiamine appeared to be partially endothelium-interactive (dependent). (2) Evodiamine pretreatment had a greater inhibitory effect on the phenylephrine-induced tonic contraction (via Ca2+ influx) than on the phasic contraction (via Ca2+ release). In addition, evodiamine was more potent to inhibit the restoration by CaCl2 of contractile responses to phenylephrine than a potassium depolarizing solution in media that had been kept calcium-free. These results suggest that block of the Ca2+ influx through receptor-mediated Ca2+ channels may be the major mechanism underlying the vasodilator effect of evodiamine. (3) A K+ channel blocker, tetraethylammonium, almost completely abolished the vasodilatation induced by minoxidil (a known K+ channel opener) but not evodiamine. The possible involvement of K+ channel activation of the vasodilator effect produced by evodiamine was therefore excluded.

Animals↗

PubMed1992

Relationship of age at menarche and subsequent fertility.

We investigated retrospectively the relationship between the age at menarche and reproductive ability in 2278 married women. Those who had a pregnancy experienced menarche at a mean age (+/- SEM) of 13.7 +/- 0.1 years, and those who were infertile had menarche at a mean age of 14.0 +/- 0.2 years, difference in the times of onset of menarche being significant (P less than 0.05). Moreover, a group in whom menstruation started after the age of 18 years had a significantly higher rate of infertility (15.7%) than the others (5.0%). Irregular menstruations during the first few years after menarche was also related to decreased reproductive ability. These findings indicate the importance of menarche before the age of 18 for normal reproductive functioning.

Adolescent↗

PubMed1992

Determination of glycyrrhizin in rabbit plasma by high-performance liquid chromatography with photodiode-array ultraviolet detection and its pharmacokinetics application.

A simple and sensitive high-performance liquid chromatographic method for the determination of glycyrrhizin in rabbit plasma has been developed. Up to 0.1 ml of plasma containing glycyrrhizin was deproteinized by acetonitrile, which contained an internal standard (indomethacin). The supernatant was injected onto a LiChrospher RP-18 column using a methanol-water-ammonia solution (80:20:0.1, v/v, pH 3.0-3.2, adjusted with perchloric acid) as the mobile phase and ultraviolet detection at 254 nm, followed by ultraviolet spectrum identification (between 200 and 380 nm) with a photodiode-array detector. The method is rapid, easily reproduced, selective and sensitive. It was applied to pharmacokinetic studies of glycyrrhizin in rabbit, after a 2 mg/kg intravenous administration. A biphasic phenomenon with a rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve. Compartmental analysis yielded a two-compartment model.

Animals↗

PubMed1992

Pharmacokinetics of glycyrrhizin after intravenous administration to rats.

A simple high-performance liquid chromatographic method was developed to study the pharmacokinetics of glycyrrhizin in the rat after bolus intravenous administration at a dose of 20, 50, or 100 mg/kg. The decline in the concentration of glycyrrhizin in plasma was generally biexponential at each dose, but the terminal disposition became much slower as the dose was increased. A greater-than-proportional increase in the glycyrrhizin concentration in plasma was observed with an increase in the dose, a result suggesting a dose-dependent glycyrrhizin disposition. The disposition of drug in plasma at each dose fitted well to a two-compartment pharmacokinetic model. The apparent total body clearance decreased significantly with increases in the dose. On the other hand, the apparent distribution volume after intravenous administration was unaffected by the dose. The results indicate that the pharmacokinetics of glycyrrhizin is nonlinear.

Animals↗

PubMed1992

Use of polyvalent phage for reduction of streptomycetes on soil dilution plates.

An isolation method was developed in which prior to inoculation soil suspensions were exposed to suspensions of polyvalent phage isolated to Streptomyces spp. The phage susceptibility of streptomycetes provided a selective means of reducing streptomycetes on isolation plates subsequent to inoculation, and this reduction was persistent after long incubation periods. The efficiency and applicability of the method developed were checked with different samples from a range of sources. The increased chances of development of other genera after the reduction of streptomycetes on soil dilution plates were assessed.

Actinomycetales↗

PubMed1992

Direct renal effects of endothelin in chronic hypoxic spontaneously hypertensive rats.

1. The direct renal effects of endothelin (ET) were studied in eight chronic hypoxic rats (HA) and eight sea level (SL) spontaneously hypertensive rats (SHR). 2. After 4 weeks of exposure to simulated 5486 m (18,000 ft) hypoxia, all HA rats were in apparently good health, and baseline renal function, except effective renal blood flow, was not significantly different from SL rats. 3. Intrarenal arterial administration of ET (600 ng/kg per h) reduced ipsilateral renal excretion of water, sodium and potassium, glomerular filtration rate and effective renal plasma flow in both SL and HA rats to almost the same extent. 4. Administration of ET antiserum, however, increased the renal excretion of water in HA rats. 5. It is concluded that ET may play a role in the renal regulation of chronic hypoxic SHR.

Animals↗

PubMed1992

Disposition of asarone after intravenous administration to rabbits assessed using HPLC.

A simple and sensitive high-performance liquid chromatography (HPLC) method for the determination of asarone in rabbit plasma has been developed. Up to 0.1 mL of plasma containing asarone was deproteinated by acetonitrile, which contained an internal standard (indomethacin). The supernatant was injected into a Nucleosil 7C18 column using acetonitrile-water-triethylamine (55:45:0.1 v/v, pH 5.4-5.5, adjusted with orthophosphoric acid) as the mobile phase and UV detection at 257 nm, followed by UV spectrum identification (between 200 and 380 nm) with a photodiode array detector. The method is rapid, easily reproduced, selective and sensitive. It was applied to pharmacokinetic studies of asarone in rabbit, after 5, 10, or 20 mg kg-1 intravenous administration. Rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve. The plasma disposition at each dose fitted well to a two-compartment open model and the terminal disposition became much slower as the dose was increased, suggesting a nonlinear dose-dependent plasma asarone disposition.

Allylbenzene Derivatives↗

PubMed1992

Rapid immunostaining of live nerve for identification of sensory and motor fasciculi.

Six New Zealand white rabbits were anesthetized with pentobarbital, and sciatic nerves were exposed and cut at the mid thigh. Both proximal and distal ends were incubated directly with Blue-SAb in a micropipe of 5 mm diameter covering the nerve trunk ends for 30 minutes at room temperature. After removal of the micropipe, the nerve ends were washed with physiological saline. Blue-stained fasciculi, i.e., sensory fasciculi were seen among unstained ones under the operating microscope. This method requires no histological sections. Neural cells of the spinal cord and ganglion were cultured in RPM11640 medium containing Bright Blue. The growth and metabolism of the neural cells were tested by MTT assay and their morphology was observed. Statistical difference between the experiment and control groups was determined, indicating that Bright Blue had no effect on the neural cells and their repairing power. This rapid immunostaining technique offers a good approach for the identification and accurate coaptation of sensory fasciculi in peripheral nerve repair.

Animals↗

PubMed1992

Toxic effect of bile acid ingestion in rats.

Ingestion of raw bile from some grass carp fish has been reported to be associated with impairment of renal function in some Chinese people. 5 alpha-cyprinol, the main bile alcohol in these fish, has been suggested as the toxic compound causing electrolyte imbalance. In this study, we attempted to determine whether oral administration of pure bile acids also affects the electrolyte balance in rats. Twenty-four female Long-Evans rats weighing 200-250 g were used. Conscious cannulated animals were prepared and studied with gastric intubation of 15%, 4.8 mL/kg of sodium cholate (SC), sodium deoxycholate (SD), and water; there were three groups of eight rats in each. A drastic drop in blood pressure, elevation of the ST segment of the EKG, increases in plasma potassium, hydrogen, blood urea nitrogen, and oxygen partial pressure were found. All rats treated with bile acids died within 24 hours. Six SD rats and three SC rats died within eight hours after oral administration of bile acid. It is concluded that the effects of feeding rats bile acids are very similar to the toxic action seen after ingestion of grass carp bile.

Animals↗

PubMed1992

Microencapsulated pancreatic islets: a pathologic study.

Dog pancreatic islets isolated by an enzymatic digestion method were encapsulated in an alginate-poly L-lysine-alginate membrane. These microencapsulated pancreatic islets were cultured in vitro to study their ability of insulin secretion. Portions of these in vitro-cultured microencapsulated pancreatic islets were taken out for a viability dye exclusion study as well as for pathologic studies to correlate them with insulin secretion ability. We found that there was a strong correlation between them. Good insulin-secreting microcapsules showed well-preserved cell membranes and beta-cell granules. An in vitro culture for one to two days in RPMI-1640 made the islets more stable, the cellular surface became smoother and the beta-granules were in better shape. The microencapsulated pancreatic islets were also injected into the peritoneum of streptozotocin-induced diabetic CDF1 mice. Blood glucose levels dropped and stayed low for up to 60 days. But, when non-encapsulated dog pancreatic islets were used, the blood glucose levels remained low for only about 14 days. A small portion of the injected microcapsules were washed out at specific times for pathologic study. Up to 28 days after injection, only a few of the injected microcapsules showed pericapsular cellular infiltrate. However, after 56 days, most of the microcapsules showed dense pericapsular cellular infiltrate. Immunohistochemical analysis of these infiltrates showed that the majority of cells were fibroblasts and macrophages. Most of the cells located in the inner portion of the infiltrate were fibroblasts, while the macrophages were located mainly on the outer portion. Both scanning and transmission electron microscopy showed that the surface of the microcapsule outer wall was much smoother than the inner wall. The size of the microcapsules was approximately 0.6-0.8 mm and the thickness of the wall measured around 10 nm. The smaller the microcapsule is, the less chance there is of rupture with release of the xenographic islets. Once the wall of the transplanted microcapsules was ruptured, the inner surface showed more increased inflammatory cell and fibroblast infiltration than the outer surface.

Animals↗

PubMed1992

Cardiovascular effects of endothelin in chronic hypoxic rats.

This study was undertaken to investigate the effects of endothelin (ET) on cardiovascular function in chronic hypoxic rats (HA) and sea level controls (SL). Catheters were placed in femoral and pulmonary arteries for measurements of mean systemic arterial pressure (Psa) and mean pulmonary arterial pressure (Ppa). The cardiac output was measured by thermodilution method. It is very interesting to find that intravenous injection of ET (0.2 and 1 nmol/kg) caused a decrease in pulmonary arterial pressure (from 44 +/- 2.6 to 36 +/- 1.9 mmHg, p < 0.05) which sustained for about 10 min while the systemic arterial pressure rise (1 nmol/kg) or no significant change (0.2 nmol/kg) in the HA rats. The depressor action of ET is mainly resulted from the drop of cardiac output in HA rats, since the pulmonary vascular resistance resisted to the action of ET in those chronic hypoxic rats could be due to a simple loss of reaction to ET or the release of vascular dilators which balance the ET vasoconstrictive action. This report also found indomethacin and saralasin did not involve the action of ET on pulmonary arterial depression.

Animals↗

PubMed1992

Experimental podophyllotoxin (bajiaolian) poisoning: I. Effects on the nervous system.

Bajiaolian, one of the species in the Mayapple family (Podophyllum pelatum), has been widely used as a traditional Chinese herbal medicine for the remedies of snake bites, general weakness, poisons, condyloma accuminata, lymphadenopathy, and certain tumors in China. In Western medicine, Podophyllum was first used medically as a laxative in the early 19th century. Since 1940, the resin of podophyllum has also been used topically for various skin lesions, such as warts and condyloma. Human poisonings have been reported. An animal model was established to investigate the neurotoxic effects of Bajiaolian. Podophyllotoxin, the major active ingredient in Podophyllum, was injected (ip) to young adult male rats at doses of 0, 5, 10, or 15 mg.kg-1 b.w.. The animals were sacrificed 72 h after injection. Neuronal changes were readily observable in animals treated with 10 or 15 mg.kg-1 of the toxin. Edematous changes of the anterior horn motoneurons were observed in the spinal cord. No neuronal necrosis was found. The type of neuronal swelling is believed to be only a transient change and would probably subside with time if no further assaults occur. More serious and perhaps longer term of changes were found in the dorsal ganglion neurons and the nerve fibers (axons) in the central and peripheral nervous system. Severe depletion of the Nissl substance (RNA/polyribosomes) was observed in the dorsal root ganglion neurons. Alterations in these sensory neurons would give rise to and correlate with the sensory disturbances experienced by the patients. Bodian staining also revealed a dose-related increase in the coarseness (thickness) of the nerve fibers (axons) in the cerebellum, cerebral cortex, brainstem, and spinal cord. This is the first scientific study showing the neurotoxicity of Bajiaolian, a commonly used Chinese herbal medicine. Toxicities on other organ systems by this drug certainly exist. Caution should be exercised in the dispensing and usage of this medicine.

Animals↗

PubMed1992

Experimental podophyllotoxin (bajiaolian) poisoning: II. Effects on the liver, intestine, kidney, pancreas and testis.

Young male rats were orally intubated with podophyllotoxin: Group I, control animals, orally fed with vehicle only; Group II, fed with an initial dose of 5 mg.kg-1 b.w., followed by a daily dose of 1.67 mg.kg-1 b.w. for 7d. Group III, fed with an initial dose of 15 mg.kg-1 b.w., followed by a daily dose of 5 mg.kg-1 b.w. for 7d. All animals were sacrificed 72 h after the last dosing. Histopathological examination revealed dose-related fatty change of the liver, atrophy and degenerative changes of the intestinal epithelial linings and testicular seminiferous tubules. Depletion of the pancreatic acinar cell granules was also apparent in the Group III animals. No pathology, however, was observed in the kidneys. The present study demonstrated for the first time degenerative changes in the liver, intestine, testis, and pancreas of animals ingested podophyllotoxin. These pathological changes correlate well with the clinical signs/symptoms of abnormal liver function, abdominal pain and diarrhea, and reduced serum amylase in humans poisoned by podophyllum. Inhibition of protein synthesis and mitosis (disruption of microtubules) are believed to be the underlying mechanisms of these changes observed in the animals intoxicated by podophyllotoxin.

Animals↗

PubMed1992

A new method for clitoroplasty in male-to-female sex reassignment surgery.

Sex reassignment surgery has proved to be the best resolution for primary transsexuals. In 1980, Dr. Rubin stated that preservation of the glans to reconstruct the clitoris in male-to-female sex reassignment surgery gave good cosmetic and functional results. In his series, Rubin used the corpus spongiosum as the vascular pedicle of the neoclitoris, but urine leakage is a complication. From 1988 to the present, the dorsal portion of the glans penis with the dorsal neurovascular pedicle has been used here for clitoroplasty in nine male-to-female primary transsexuals. All neoclitorides survived well, with good preservation of light touch and sexual sensation. No urine leakage has occurred. Six patients who were followed reported sexual satisfaction.

Adult↗

PubMed1991

Mechanism of vasodilatory effect of berberine in rat mesenteric artery.

The aim of this experiment was to study the mechanism by which berberine inhibits phenylephrine-induced contractions in isolated mesenteric arteries. The results show that berberine (10(-7)-3 x 10(-5) M) induced a dose-dependent vasodilation, and that the vasorelaxant effect of berberine was attenuated by the removal of the endothelium. Two known inhibitors of endothelium-derived relaxing factor (EDRF), L-NG-nitro arginine (L-NOARG) (a specific inhibitor of nitric oxide formation from L-arginine) and methylene blue (an inhibitor of soluble guanylyl cyclase), significantly attenuated the vasodilator response to berberine. In addition, berberine, like other vasodilators, differently affected the phasic and tonic contractile response elicited by either phenylephrine or high potassium. Berberine (3 x 10(-7) M) significantly inhibited the phasic contraction induced by phenylephrine but, in contrast to verapamil, had no effect on the high potassium-induced contraction. Moreover, berberine abolished the caffeine-induced contraction in Ca(2+)-free/EGTA medium. In conclusion, berberine vasodilates the rat mesenteric artery in part by indirectly releasing EDRF but mainly by directly blocking the release of Ca2+ from internal stores.

Animals↗

PubMed1991

High-performance liquid chromatographic determination of 18 alpha-glycyrrhetinic acid and 18 beta-glycyrrhetinic acid in rat plasma: application to pharmacokinetic study.

A high-performance liquid chromatographic method for the separation and determination of 18 alpha-glycyrrhetinic acid and 18 beta-glycyrrhetinic acid has been developed. Indomethacin was used as an internal standard. The drugs were separated on a reversed-phase column and detected by UV detection at a wavelength of 254 nm. Methanol-water-perchloric acid-ammonia (80:20:0.4:0.4, v/v) was used as the mobile phase at pH of 7.0-7.5. The detection limit of both compounds was 0.1 microgram/ml in rat plasma. The method was applied to pharmacokinetic studies of glycyrrhetinic acids in rats. The results suggest that the pharmacokinetics appeared to be non-linear in nature.

Ammonia↗

PubMed1991

Pulse-echo ultrasound speed measurements: progress and prospects.

The data on the relationship of sound speed to tissue condition, and the development of methods for measurement of sound speed in vivo, are outlined. The methods developed by the authors are discussed. These include methods which use the spatial shift in images of targets viewed from different directions, time-of-flight measurements along incrementally tracked beams and echo tracking during transaxial compression of tissue. The reported sound-speed values are discussed, discrepancies noted and suggestions made on the potential clinical applications of in vivo sound-speed estimation.

Humans↗