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Biomedical subjects

S Y Lin

Publications and source records attributed to S Y Lin.

At least 307 records · Page 17Linked to original sources
PubMed1989

Effects of endothelin on porcine coronary arterial strips.

Endothelin, a novel endothelium derived 21-residue vasoconstrictor peptide synthesized by Peninsula Laboratories, provoked a concentration-dependent contraction of porcine coronary arterial strips. EC50 value for endothelin was 14 +/- SD 4 nmol/L (n = 6), and significantly lower than the values for 5-hydroxytryptamine (5-HT, 0.28 +/- 0.07 mumol/L, n = 6) and 15-methyl-prostaglandin F2 alpha (15-methyl-PGF2 alpha, 4 +/- 3 mumol/L, n = 7). The maximal increase in tension caused by endothelin was 5.4 +/- 1.1 g, being much greater than that induced by 5-HT (3.7 +/- 0.8 g, P less than 0.05) and 15-methyl-PGF2 alpha (3.7 +/- 0.6 g, P less than 0.01). The changes in tension provoked by endothelin (2-20 nmol/L) were attenuated significantly after pretreated with tetrodotoxin (TTX, 30 mumol/L, P less than 0.05 or 0.01). The results suggest that endothelin is one of the most potent vasoconstrictive agents, and its action is partially related to voltage-sensitive Na+ channel in the cell membrane.

Amino Acid Sequence↗
PubMed1989

Hemodynamic response to ketamine and diazepam in dogs with acute cardiac tamponade.

Induction of anesthesia may produce a significant hazard to patients with critical cardiovascular status. Ketamine has been advocated as the drug of choice for maintaining cardiovascular performance during induction of anesthesia in high-risk surgical patients. There is no detailed information on the use of ketamine in patients with acute cardiac tamponade. The purpose of this study was to assess the safety of ketamine in acute cardiac tamponade in dogs. Sixteen dogs were studied and a Swan-Ganz catheter was inserted through the right external jugular vein to measure hemodynamic parameters. Data obtained before tamponade was used as the control, then, tamponade was accomplished by infusing a mixture of saline and blood from the same dog through a catheter into the pericardial sac. Ketamine, 2 mg/kg intravenously resulted in an improvement of cardiac output from 1.2 +/- 0.5 L/min to 2.2 +/- 0.3 L/min (p less than 0.05). The addition of diazepam 0.3-0.5 mg/kg blunted the ketamine-induced cardiostimulation and resulted in a fall in cardiac output from 2.2 +/- 0.3 L/min to 1.7 +/- 0.2 L/min (p less than 0.05). Five dogs with intrapericardial pressure above 10 mmHg did not respond to ketamine. Diazepam did not blunt any more to these decompensated dogs. This study demonstrated that ketamine plays a beneficial role in acute cardiac tamponade as a safe induction agent. Limitation still existed when using ketamine in dogs with high intrapericardial pressure because they showed only negative inotropic effect during decompensation. Diazepam inhibited the cardiostimulant effects of ketamine in dogs with tamponade, but could not elicit a negative inotropic effect during decompensation. The practical application of ketamine and diazepam in patients with acute cardiac tamponade could be determined by evaluation of intrapericardial pressure through a needle-transducer kit.

Acute Disease↗
PubMed1989

The optimal dose of atropine via the endotracheal route.

Fifty ASA class I or II patients, undergoing general or gynecological surgery under general anesthesia with endotracheal intubation, were randomly divided into five groups. Group I received 10 ug/kg atropine intravenously, group II to V received 10 ug/kg, 20 ug/kg, 30 ug/kg, 40 ug/kg, respectively via endotracheal route through an epidural catheter. All were given five manual deep breaths after the injection of atropine. The maximum increase in heart rate (MIHR) and the time to maximum heart rate (TMHR) were evaluated. There was no marked MIHR in group II. Group III had a MIHR similar to that of group I (17.5/min vs 20/min, p greater than 0.05), but had a longer TMHR than group I (120 sec vs 82.5 sec, p less than 0.005). Groups IV and V had greater MIHR than group I (28.7 and 29.5 vs 20/min, p less than 0.005), and a TMHR similar to that of group I (85 and 90.2 vs 82.5 sec, p greater than 0.05). For emergency procedures, if atropine must be given without an intravenous catheter, 30 ug/kg or more given endotracheally can achieve an effect comparable to that of 10 ug/kg given intravenously.

Adult↗
PubMed1989

In-vitro dissolution behavior of some sustained-release theophylline dosage forms.

In-vitro dissolution of theophylline from six commercially sustained-release (SR) preparations (Euphyllin retard, Euphyllin retard mite, Theovent L.A. 125 mg, Theovent L.A. 250 mg, Phyllocontin and Uniphyllin) was determined by using rotating basket and rotating bottle apparatus. The effect of pH and rotating speed on the dissolution rate of these SR products was also studied. Scanning electron microscope was used to observe the change of surface topograph and inner texture of these products before, during and after dissolution. The results indicates that the dissolution behavior was pH-dependent which corresponding to the types of SR products. The rotating bottle method was only suitable for the evaluation of release rate of spansule-type SR products and was not suitable for matrix-type SR tablets due to the sticking occurred on the bottle surface leading to faster dissolution and larger variation. The release mechanism of these six SR products can be deduced into three models. Fickian transport (Phyllocontin), non-Fickian transport (Euphyllin, Theovent L.A. 250 mg and Uniphyllin) and zero order transport (Theovent L.A. 125 mg).

Delayed-Action Preparations↗
PubMed1989

The effect of low dose intravenous lidocaine in tracheal intubation with atracurium.

This study investigated the effect of low dose intravenous lidocaine during tracheal intubation with atracurium. Forty patients were studied in double blind, randomized groups. Intravenous lidocaine, 1 mg/kg, or saline was given to the patients three minutes before induction. This result showed there is no difference about the intubation condition between these groups. The changes in mean arterial blood pressure and heart rate after laryngoscopy and intubation were similar in both groups. However, the lidocaine group had a shorter time to have 75% twitch depression (when the first twitch of train of four equals 25% of the original height) than the control group (p less than 0.05). The addition of intravenous lidocaine 1 mg/kg during induction has no significant advantage although it can shorten the intubation time.

Adult↗
PubMed1989

[An observation of the 24-hour variations of the F-V curve and FEV1 in asthmatics].

This paper reported 24 hours dynamic observation of the ventilatory functions of 200 asthmatics by using flow-volume curves. The results are as follows: 1. In most instances there were marked rhythmic variations of the ventilatory function. The highest value of them was recorded mostly at noon, while lowest value in early morning. 2. When the obstruction of the airway was worse, the rhythmic variation of the ventilatory function became more serious. 3. The diurnal ventilatory functions were closely related to the lower ventilatory function at night. 4.24 hrs variation of the resistance of the small airway were greater than those of the large airway. 5. Abnormal variation of the small airway resistance was observed in convalescent cases and one fourth of them had abnormal fluctuation of the large airway resistance.

Adult↗
PubMed1988

Effect of excipients on tablet properties and dissolution behavior of theophylline-tableted microcapsules under different compression forces.

Theophylline ethylcellulose microcapsules were tableted by compression with or without excipients [lactose or hydroxypropyl cellulose (HPC-H)]. Tablets without excipients had a crushing strength that was independent of the applied compression force and the particle size of the microcapsules used, but tablet thickness decreased with an increase in the particle size of the microcapsules. The dissolution characteristics of theophylline from tableted microcapsules without excipients were almost independent of the applied compression force, but showed a sustained-release behavior. However, the thickness, crushing strength, and dissolution properties of tablets containing excipients were found to be affected by the type of excipient. Tableted microcapsules containing lactose showed an increase in tablet crushing strength that correlated with an increase in the applied compression pressure, but the tablet thickness did not change. In contrast, tableted microcapsules containing HPC-H showed a decrease in tablet thickness with an increase in the applied compression pressure, but the tablet crushing strength was initially reduced and then increased with an increase in the compression force. There was a rapid release rate for theophylline from tableted microcapsules containing lactose; a zero-order release rate for theophylline was found in tableted microcapsules containing HPC-H. The insoluble compacted matrix formation, disintegration of tablet, rupture of microcapsules, and gel matrix formation may be responsible for the release behavior of theophylline-tableted microcapsules with or without excipients. The reduced surface area and porosity resulted in a prolongation of the release from tableted microcapsules compared with untableted microcapsules.

Capsules↗
PubMed1988

Cytotoxicity, sister-chromatid exchange, chromosome aberration and transformation induced by 2,2-dichlorovinyl-O,O-dimethyl phosphate.

2,2-Dichlorovinyl-O,O-dimethyl phosphate (DDVP), an extensively used household insecticide, was assayed for its genotoxicity in primary rat tracheal epithelial (RTE) cells. Cytotoxicity of DDVP to RTE cells was dose-dependent, killing about 50% of the cell population at a dose of 80 micrograms/ml. Sister-chromatid exchange (SCE) and chromosomal aberrations induced by this insecticide were positive in RTE cells although the doses needed for significant inductions were much higher than those by a known genotoxic agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The level of transformation induced by DDVP in RTE cells was about 1/5 that induced by MNNG at a dose of similar cytotoxicity. The slope of the regression line for induced transformation is 1.27. DDVP probably induces the genotoxic effect in RTE cells by a one-hit mechanism.

Animals↗
PubMed1988

Renal ornithine decarboxylase activity, polyamines, and compensatory renal hypertrophy in the rat.

We determined the role of ornithine decarboxylase (ODC) in compensatory renal hypertrophy (CRH) by relating renal ODC activity and polyamine content to kidney size, expressed as a percent of body weight, 1 wk after unilateral nephrectomy (UN). In normal rats, renal ODC activity increased from 11.0 +/- 7.4 (SD) to 36.7 +/- 15.4 pmol 14CO2.min-1.g wet wt-1 3 h after UN (P less than 0.002); 1 wk later the remaining kidney weight had increased from 0.38 to 0.46% body weight (P less than 0.001). Renal concentration of putrescine, the product of ODC's decarboxylation of ornithine, was increased 3, 8, and 48 h after UN, but concentrations of polyamines synthesized later in the pathway, spermidine and spermine, were not appreciably affected. Pretreatment with difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, as a 1% drinking water solution inhibited both base-line renal ODC activity and putrescine concentration as well as increases stimulated by UN, although concentrations of spermidine and spermine were not decreased. In these rats, CRH still occurred, since kidney weight increased from 0.36 to 0.46% (P less than 0.001). A 2% DFMO solution caused depletion of all three polyamines, but CRH took place nevertheless. In hypophysectomized rats, both increased renal ODC activity and CRH occurred as well, indicating that these two consequences of UN do not require intact pituitary function. Although increased renal ODC activity and CRH after UN are correlated in normal and hypophysectomized rats, CRH takes place in rats treated with DFMO despite inhibition of ODC activity and depletion of polyamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Controlled release of adriamycin HCl from polymeric needle devices.

Two types of polymeric needle devices (reservoir type and matrix type) were prepared. The release behavior and mechanism of adriamycin HCl from these needle devices were investigated and deduced. Adriamycin HCl released from reservoir type needle devices exhibited a zero order release kinetic, but a Higuchi membrane-diffusion controlled model was shown in matrix type needle devices. A lag time and burst effect were obtained in reservoir type and matrix needle devices, respectively. The release of adriamycin HCl from these needle devices was controlled and can be monitored by adding a hydrophilic or hydrophobic additive.

Biocompatible Materials↗
PubMed1988

Insulin controlled-release microcapsules to prolong the hypoglycemic effect in diabetic rats.

A solvent evaporation process was employed for preparing insulin microcapsules by using biodegradable polymers [polylactic acid (PLA), HP-55] and non-biodegradable polymers [ethylcellulose (EC), ethylenevinyl acetate (EVA)]. The release behavior of insulin microcapsules in pH 7.4 phosphate buffer solution was undertaken by a continuous flow column method. Seven types of insulin microcapsules were respectively injected into the flanks of fasting-diabetic SD rats induced by streptozotocin. The glucose levels and insulin concentrations in the blood were periodically sampled from the tail and assayed by a glucose analyzer and RIA method. Body weights were measured twice per week. The release rate was controllably dependent on the polymer used. The PLA microcapsules could maintain normoglycemia only for five days, whereas the (PLA + 1%EVA) microcapsules exhibited two times the hypoglycemic effect of PLA microcapsules, but (PLA + 1%EVA) microcapsules treated with 4% wax extended the duration of hypoglycemic effects for two weeks. There was no significant effect for insulin-HP-55 microcapsules. The EC microcapsules prolonged the hypoglycemic effect for 15 days, however, the (EC + 1%EVA) microcapsules could maintain the same effect for up to three weeks. The slower the release rate of insulin microcapsules in vitro the longer the hypoglycemic effect of insulin microcapsules in vivo. A close relationship between in vitro release behavior and in vivo hypoglycemic efficacy of insulin microcapsules was obtained.

Animals↗
PubMed1987

Bioavailability studies of theophylline ethylcellulose microcapsules prepared by using ethylene-vinyl acetate copolymer as a coacervation-inducing agent.

The bioavailability of theophylline microcapsules prepared by using ethylene-vinyl acetate (EVA) copolymer as a coacervation-inducing agent was studied in rats. The dissolution rate of the microcapsules was determined by the rotating-basket and rotating-bottle methods. The higher the concentration of EVA copolymer used, the more sustained was the release of theophylline from the microcapsules. The mean maximum serum levels (Cmax) and time to maximum serum levels (tmax) were not significantly different for theophylline microcapsules prepared by a lower concentration of EVA copolymer (0 and 0.83%, respectively), compared with those for theophylline powder; whereas a significant difference was found when the higher concentration of EVA copolymer was used (greater than 1.7%). With regards to the area-under-the-curve (AUC) value, there was no significant difference between the theophylline powder and theophylline microcapsules. The elimination kinetics and the corresponding half-life (t1/2) were significantly different when the concentration of EVA copolymer was greater than 3.3%. From the above results, it is evident that theophylline microcapsules prepared by using 3.3 and 5.0% EVA copolymer as the coacervation-inducing agent may act as sustained-release dosage forms. The correlation between the dissolution rate in vitro and the bioavailability in rats for theophylline microcapsules was investigated. The mean Cmax and tmax correlated well with the time taken to release 75% of the drug in vitro (t 75%); however, the mean AUC showed no valid correlation with t 75%. This implies that the dissolution rate correlated better with the rate of absorption (Cmax, tmax) than with the extent of absorption (AUC).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Induction of sister-chromatid exchanges by pesticides in primary rat tracheal epithelial cells and Chinese hamster ovary cells.

Possible induction of sister-chromatid exchanges by butachlor, paraquat, phorate and monocrotophos was examined in primary rat tracheal epithelial (RTE) and Chinese hamster ovary (CHO) cells. At dose levels that killed less than 50% of the cell population, monocrotophos induced SCEs positively in CHO and RTE cells, while paraquat was positive only in RTE cells. In two trials of the same experiment, paraquat and butachlor in CHO cells, and phorate in either RTE or CHO cells failed to induce a significant number of SCEs at any dose level within the ranges assayed. On the other hand, in RTE cells, butachlor induced a significant number of SCEs at a dose level of 5 micrograms/ml in one trial, but was insignificant in another. The inductions in these assays were, however, dose-dependent. The addition of S9 mixture did not alter the results of SCE induction by these 4 pesticides in CHO cells. RTE cells were more vulnerable to paraquat in cytotoxicity and SCE assays than CHO cells. Cytotoxicities were ranked as butachlor greater than phorate greater than paraquat greater than monocrotophos to CHO cells and paraquat greater than butachlor greater than phorate greater than monocrotophos to RTE cells. Significant cell cycle delays were only found in the treatments with the highest dose levels of butachlor, paraquat and phorate in CHO cells. In addition, this is the first report on SCE induction in RTE cells.

Animals↗
PubMed1987

Drug release from tablets containing cellulose acetate phthalate as an additive or enteric-coating material.

A formulation containing cellulose acetate phthalate for preparing enteric-coated granules was developed with the use of granulation and microencapsulation techniques. Drug release from tablets or tableted microcapsules was measured in a disintegration apparatus and an in vitro variable-pH release simulator of the flow type. The release mechanism for the tablets or tableted microcapsules was determined with the Higuchi matrix model, a first-order kinetic model, and the Weibull distribution function. Adding acetone directly to the mixture of sulfamethoxazole and cellulose acetate phthalate resulted in enteric-coated granules with more prolonged release than other granulation methods. Microencapsulation of the granules significantly delayed the drug release and enhanced the effectiveness of the enteric coating. Microencapsulated granules show release patterns that are sustained and can be simulated with three different release models, i.e., with square-root time plotting, diffusional first-order plotting, and Weibull distribution plotting. The enteric-coating behavior of the tablets was more clearly demonstrated with the variable-pH release stimulator than with a fixed-pH dissolution method.

Capsules↗