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Biomedical subjects

C F Chen

Publications and source records attributed to C F Chen.

At least 271 records · Page 15Linked to original sources
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↗
PubMed1991

Effects on renal excretion in rats after injection of bile extracts from some fresh-water fish.

Bile acid extracts were prepared from grass carp, bighead, common carp, milk fish and tilapia. Injection of the fish bile extracts (3.6 mg/kg, i.v.) into rats increased renal excretion of water, sodium and potassium; decreased blood pressure; and hemolyzed RBCs. The diuretic, natriuretic, hypotensive and hemolytic actions of the bile extracts were stronger in grass carp, bighead and common carp, moderate in milk fish, and weakest in tilapia.

Animals↗
PubMed1991

Cytotoxic activities of tanshinones against human carcinoma cell lines.

Fifteen tanshinone analogues isolated from the chloroform extract of Danshen roots (Salviae Miltiorrhizae Radix) by chromatographic procedures were tested for their cytotoxic activities against KB, Hela, Colo-205 and Hep-2 carcinoma cell lines. Several of them were effective at concentrations below 1 micrograms/ml concentrations. Tanshinone analogues with either hydroxy substitutions or olefinic feature in ring A demonstrated higher biologic activities. Analysis of structure-activity relationship indicate that the basic requirement for activity is the presence of a furano-o-naphthoquinone in the molecule. Compounds which lack an intact furan ring were found to be inactive. It is suggested that the planar phenanthrene ring of the tanshinones may be essential for interaction with DNA molecule whereas the furano-o-quinone moiety could be responsible for the production of reactive free radicals in the close vicinity of the bases to cause DNA damage.

Abietanes↗
PubMed1991

Effects of atrial natriuretic factor in chronic hypoxic spontaneously hypertensive rats.

The present study was designed first to investigate the pulmonary hypertensive effects of chronic hypoxia in spontaneously hypertensive rats and second to compare the cardiovascular effects of atrial natriuretic factor on rats exposed to hypoxia and on control rats kept at sea level. Catheters were placed in the femoral and pulmonary arteries for measurement of mean systemic arterial pressure and mean pulmonary arterial pressure. The cardiac output was measured by thermodilution method. It was found that 4 weeks of simulated 18,000-foot hypoxia led to polycythemia, right ventricular hypertrophy, and pulmonary hypertension, which resulted from an increased pulmonary vascular resistance. However, systemic arterial pressure was not significantly different between the two groups of rats. Atrial natriuretic factor administration decreased systemic arterial pressure and pulmonary arterial pressure to a lesser extent in the hypoxic group compared with the sea level control group. It is concluded that these animals showed an impaired response to atrial natriuretic factor after long-term exposure to hypoxia.

Animals↗
PubMed1991

Natural radiation background in metropolitan Taipei.

A high-pressure ionization chamber was used to measure the natural background radiation in metropolitan Taipei, Taiwan, R.O.C. during a period in 1987-1988. The average exposure rate was 27.55 x 10(-10) C kg-1 h-1 including cosmic radiation, but the radon contribution was excluded. Scintillation survey meter, gamma-ray spectroscopy for soil samples, in-situ measurement with a NaI(Tl) detector coupled to a portable multichannel analyzer, instrumental neutron activation analysis of rock samples, and even thermoluminescent dosimeters were used as complementary measuring devices. Areas of higher radiation background were detected. They are the radium-bearing Peitou stones, an unusual occurrence of uraniferous zone at Sanhsia, and uranium precipitation in the glassy olivine basalt in a tea field at Tachi. All these areas are located in suburban sites of Taipei. Three types of building in Taipei City were selected for radon detection. No significantly elevated level of radon was detected, since Taipei is located in a semitropical area where ventilation of buildings is not a problem.

Background Radiation↗
PubMed1991

Effects of atrial natriuretic factor on renal function in chronic hypoxic rats.

The renal effects of atrial natriuretic factor (ANF) were studied in chronic hypoxic (HA) and sea level (SL) rats. It was found that after 4 weeks of exposure to simulated 18,000 ft hypoxia, all HA rats were in apparently good health, and base line renal function was not significantly different from SL rats. Both doses (0.1 and 0.3 microgram/minutes/kg) of ANF administered produced a marked increase in urinary flow, sodium and potassium excretion in the SL rats. In the HA rats, the increase in water and salt excretion were comparatively mild, and the only statistically significant response was to the higher dose of ANF. ANF did not cause significant changes in the glomerular filtration rate in either group of rats. It is concluded that these animals showed an impaired response to ANF after exposure to chronic hypoxia.

Altitude Sickness↗
PubMed1991

The role of interscapular brown adipose tissue in cold acclimation in the rat.

The role of the interscapular brown adipose tissue (IBAT) in the defense against cold exposure and subsequent acclimation to it was studied in the rat, a homeotherm. When placed at 4 degrees C, the rat was able to maintain a constant core temperature even though skin and even more so tail temperature dropped drastically. Metabolic rate became significantly higher than control animals kept at 23 degrees C after 24 hrs and continued to rise throughout the 6 weeks exposure period. Starting at week 1, there was hypertrophy of the IBAT with concomitant proliferation of mitochondria. Bilateral surgical removal of IBAT led to significant reduction in metabolic rate only in the fully cold-acclimated rat. However, the survival rate was not affected. It is thus concluded that IBAT played an important but not absolutely essential role in cold acclimation.

Acclimatization↗
PubMed1991

Serotonin (5-HT1c) receptors in pig choroid plexus.

It is very important to find suitable reaction conditions to attain a high specific binding (specific/total binding) in the receptor binding study. Membrane homogenates of pig choroid plexus are known to have exclusively serotonin (5-hydroxytryptamine, 5-HT) receptor of the subtype 5-HT1c. In this study, we used the membrane preparation of pig choroid plexus tissue and the specific binding of [3H]5-HT was 72-84% to serotonin receptor subtype 5-HT1c, as defined by the inhibition of 1 uM 5-HT, when a radioligand concentration of 0.5 nM of [3H]5-HT was used in the assay. Analysis of the properties of specific [3H]5-HT binding in pig choroid plexus tissue membrane preparation revealed linear Scatchard plots. In Tris-HCl buffer without CaCl2, pargyline or ascorbic acid, high average of affinity dissociation constant (Kd) of 1.3 +/- 0.2 nM (SEM, n = 4) and also a high average of receptor density (Bmax) of 284 +/- 12 fmol/mg of protein were found. Pig choroid plexus proves to be a good material for 5-HT1c receptor binding study.

Animals↗
PubMed1991

[Clinical application of Chinese forearm flap: 5-year review].

Twenty-nine patients treated with the Chinese forearm flap from 1985 to 1989 were reviewed. This flap was used for soft tissue defect reconstruction in 19 cases, and phallus reconstruction in 10 patients. There were two cases of total flap failure and two cases of partial failure. Twenty cases used sensory flaps. Donor site complications included partial loss of the skin graft with tendon exposure in one patient (3.4%), limitation of range of movement of the wrist joint in one case (3.4%), and paresthesia over the radial site of the hand in 12 patients. On functional evaluation, 20 patients demonstrated no significant loss of strength in the donor extremity.

Adult↗
PubMed1990

The hypotensive and negative chronotropic effects of dehydroevodiamine.

The cardiovascular effects of dehydroevodiamine, an alkaloid isolated from Evodia rutaecarpa Jussieu, were studied in both in vivo and in vitro experiments. The in vivo experiments revealed that i.v. administration of dehydroevodiamine elicited a slight but significant reduction in blood pressure and a marked decrease in heart rate which was confirmed by an increased cycle length of the electrocardiogram. However, a hemodynamic experiment with microspheres showed that the total peripheral resistance was not altered by dehydroevodiamine. The blood flows of various organs were not significantly changed except those of kidney and skin, in which blood flow was decreased. In vitro, the spontaneously beating atria were significantly suppressed by dehydroevodiamine in a dose-dependent manner. These findings suggested an important effect of dehydroevodiamine in suppressing the heart, which may largely contribute to the hypotensive effect of this alkaloid. However, its vasodilator effect on hindquarter muscles cannot be neglected.

Alkaloids↗
PubMed1990

Evaluation of the clinical pharmacology of nilvadipine in patients with mild to moderate essential hypertension.

Eighty-four patients with diastolic blood pressure ranging from 100-115 mm Hg were randomized into a multicenter, parallel, double-blind, placebo-controlled, dose response study with nilvadipine (6 mg, 8 mg, 10 mg tid for 28 days). The hypotensive response pattern to nilvadipine was similar with all three doses although duration of response was dose dependent. Maximal decreases in diastolic blood pressure occurred at 1 hour when assessed on days 1 and 15 (16.0, 17.4, and 15.8 mm Hg, vs 17.2, 18.7, and 17.5 mm Hg, respectively). The hypotensive effect remained significant compared to placebo for at least 4 hours after dosing. The increase in heart rate associated with the maximal hypotensive response was minimal and not clinically significant (day 1: 7.6, 5.2, and 4.0 beats/min with 6, 8, and 10 mg; day 15: 4.0, 5.1, 2.6 beats/min with 6, 8, 9, and 10 mg, respectively). Finally, a correlation between plasma drug concentrations and nilvadipine-induced hypotensive response was observed (r = 0.48). Black and white hypertensive patients had similar hypotensive responses. Plasma nilvadipine concentrations on day 15 were similar to those on day 1 suggesting no accumulation of drug with a tid regimen. The most common drug related side effect was headache; less frequently seen were dizziness, edema, palpitations, and abdominal pain. Nilvadipine was well tolerated (only three patients were discontinued due to side effects). The efficacy, lack of tachycardia, and side effect profile observed in this study suggest that nilvadipine may be an important addition to the treatment of hypertension.

Blood Pressure↗
PubMed1990

A study on the vascular supply of the supraspinatus tendon.

The vascular supply of the rotator cuff in 22 adult shoulders was studied by way of mixture infusion of gelatin and India ink and vascular cast, in combination with Scanning Electronic Microscopy of the vascular pattern in the supraspinatus tendon. It was found that the vessels of the supraspinatus tendon mainly derive from the anterior circumflex humeral and suprascapular arteries. Macroscopically, an avascular zone or critical zone could be seen on the surface of supraspinatus, and the mean distance of the external edge from the osteo-tendinous attachment was 7.8 mm. The area of the avascular zone increased with age.

Arteries↗
PubMed1990

Effects of endothelin and vasopressin on portal pressure of rats.

Endothelin is a vasoconstrictor peptide which has recently been isolated and sequenced from the vascular endothelial cells. It was reported to increase blood pressure in vivo and produce a prolonged contraction with a slow onset in vitro. The purpose of this study was to investigate whether endothelin can lower the portal pressure as another endogenous vasoconstriction peptidevasopressin (AVP) can. Heart rate, systemic blood pressure, portal pressure, and portal vein blood flow were measured. Effects of endothelin on these parameters were compared with those of AVP. Endothelin 10(-10) mol/Kg significantly decreased all of the parameters mentioned. At the higher dose (5 x 10(-10) mol/Kg), however, the portal pressure and blood pressure were increased and portal vein blood flow was unchanged. On the other hand, AVP decreased the portal pressure and portal vein blood flow but elevated the systemic blood pressure. In vitro experiments revealed that endothelin contracted both tail artery and portal vein of rat and vasopressin contracted only tail artery. We concluded that although both are endogenous vasoconstricting peptides, endothelin and AVP affect differently on arterial and venous vascular beds as well as on portal pressure.

Animals↗
PubMed1990

Characterization of two new cell lines derived from oral cavity human squamous cell carcinomas--OC1 and OC2.

Two continuous cell lines, OC1 and OC2, have been established. Each one was derived from a surgical specimen of buccal mucosa squamous carcinoma from a Chinese man. Both cell lines grew as adherent monolayers and had an epithelioid morphology. The cell lines have now been grown in vitro for more than 200 passages over a 2-year period. Both cell lines were tumorigenic in nude mice. Histologic examination of the mice tumors showed a positive identification with those from the original human squamous cell carcinoma. Electron microscopic examination convincingly demonstrated their epithelial origin. Chromosomal numbers of the OC1 cell ranged from 58 to 78 and of the OC2 cells ranged from 62 to 82. Analysis of cytokeratin showed that all cell lines were positive. The carcinoembryonic antigen (CEA) tested negative in these two cell lines. The OC2 cell line showed the presence of HPV16, but the OC1 cell line did not. These cell lines should be useful for investigation of anticancer treatment and for their possible relationship to human papilloma virus (HPV).

Carcinoma, Squamous Cell↗
PubMed1990

Plasma electrolyte changes after ingestion of bile extract of the grass carp (Ctenopharyngodon idellus) in rats.

Some Chinese people believe that eating the gallbladder of the grass carp (Ctenopharyngodon idellus) may improve their visual acuity. However, ingestion of grass-carp bile, in severe cases, may kill human beings and experimental animals. The cause of death after eating grass-carp bile was studied in rats. The bile acid fraction was prepared from the n-hexane-insoluble and alcohol-soluble parts of grass-carp and hog bile. The bile extract (6 ml/kg, 15%) was administrated by gastric intubation to conscious female Long-Evans rats. Ingestion of grass-carp bile extract killed all the experimental rats in 2-8 h and was associated with a decrease in blood pressure and an increase in plasma potassium, hydrogen ions, blood urea nitrogen and hematocrit. However, rats that ingested hog bile or saline showed no significant changes in the measured parameters. If the rats were fed cholestyramine-treated grass-carp bile extract, they survived without significant change in the measured parameters. This report demonstrates that a drastic increase in plasma potassium and hydrogen ions probably caused the death of the rats, and also shows that bile acid (alcohol) in grass-carp bile is related to the toxicity.

Animals↗
PubMed1990

Respiratory function in patients with spinal cord injuries: effects of posture.

The purpose of this study was to evaluate the respiratory function of spinal cord injuries (SCI) during different postures. Measurements were performed with a Fukuda PM 80 spirometer on 31 chronic stable SCI and 22 normal controls. Among the SCI patients, there were 12 quadriplegics and 19 paraplegics. The respiratory parameters, including forced vital capacity (FVC) and forced expiratory volume during first second (FEV1.0) were collected in each subject during supine, sitting and standing postures. The results revealed that SCI patient had impaired FVCs (p less than 0.05), the degree of impairment depending upon the level of cord injury (r = 0.81). The FEV1.0/FVC ratio of SCI was normal. For quadriplegics, the FVC during sitting and standing fell on 30 to 50% of normal values. The FVCs of paraplegics during all postures were around 80% of the predicted values. The FVC in the control group was reduced by 5 to 7% when changing postures from erect to supine. This study concludes that respiratory impairment does occur in SCI. The results obtained display a typical pattern of restrictive pulmonary impairment. The severity of the impairment is affected by the level of cord damage and is posturally dependent.

Adult↗
PubMed1990

Mechanism of gating of T-type calcium channels.

We have analyzed the gating kinetics of T-type Ca channels in 3T3 fibroblasts. Our results show that channel closing, inactivation, and recovery from inactivation each include a voltage-independent step which becomes rate limiting at extreme potentials. The data require a cyclic model with a minimum of two closed, one open, and two inactivated states. Such a model can produce good fits to our data even if the transitions between closed states are the only voltage-dependent steps in the activating pathway leading from closed to inactivated states. Our analysis suggests that the channel inactivation step, as well as the direct opening and closing transitions, are not intrinsically voltage sensitive. Single-channel recordings are consistent with this scheme. As expected, each channel produces a single burst per opening and then inactivates. Comparison of the kinetics of T-type Ca current in fibroblasts and neuronal cells reveals significant differences which suggest that different subtypes of T-type Ca channels are expressed differentially in a tissue specific manner.

Animals↗