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Biomedical subjects

W Lin

Publications and source records attributed to W Lin.

At least 235 records · Page 13Linked to original sources
PubMed1993

R56865, a Na(+)- and Ca(2+)-overload inhibitor, reduces myocardial ischemia-reperfusion injury in blood-perfused rabbit hearts.

The cardioprotective effects of R56865 were studied in isolated rabbit hearts, blood-perfused with a support rabbit system. The effect on ischemic injury was evaluated by comparing myocardial contracture and contents of ATP catabolites and of lactate during 60 min of normothermic ischemia in untreated hearts (group I) and in hearts treated with 0.63 mg/kg of R56865 starting 20 min before ischemia (group II; n = 5 in each group). R56865 delayed the onset, and decreased the extent of ischemic contracture, but had no effect on the myocardial content of ATP, of its catabolites of lactate. The effect on reperfusion injury was studied by monitoring left ventricular function during 80-min reperfusion after the 60-min ischemia in three groups (n = 6 in each): an untreated group (group I) and two groups treated with R56865 given either before (group II) or after ischemia (group III). Ultrastructural changes and cellular calcium distribution after reperfusion were also studied. R56865 improved the recovery of function and prevented contracture during reperfusion. Left ventricular end-diastolic pressure was 13.2 +/- 2.8 mmHg in group II and 31.3 +/- 8.1 mmHg in group III vs 45.0 +/- 2.6 mmHg in group I (P < 0.0001 for II vs I; P > 0.05 for III vs I). Left ventricular developed pressure, maximum dP/dt and minimum dP/dt recovered to 71.0 +/- 5.4%, 98.9 +/- 6.1%, 85.3 +/- 4.8% of baseline values, respectively, in group II, to 64.5 +/- 3.0% (P > 0.05), 76.8 +/- 3.0%, 70.2 +/- 4.0% in group III, vs 52.0 +/- 6.5%, 58.9 +/- 6.9% and 53.6 +/- 5.8% in untreated hearts (P < 0.05 for II or III vs I). Coronary flow was 24.5 +/- 2.2 ml/min and 19.8 +/- 1.8 ml/min in groups II and III vs 14.8 +/- 0.7 ml/min (P < 0.05) in the untreated group. On histology the myocardium in hearts treated either before or after ischemia was well protected and calcium distribution was almost normal after reperfusion, while in untreated hearts, most of the myocardium displayed irreversible damage accompanied by massive intracellular calcium accumulation. We conclude that R56865 could attenuate Ca(2+)-overload, thereby reducing myocardial ischemia-reperfusion injury after an extended period of ischemia.

Animals↗
PubMed1993

Intracranial MR angiography: application of magnetization transfer contrast and fat saturation to short gradient-echo, velocity-compensated sequences.

To circumvent artifacts related to saturation, turbulence, and data processing in three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography, the authors used a high-resolution (256 x 512), short, asymmetric velocity-compensated gradient-echo sequence, magnetization transfer contrast (MTC) between all excitation pulses to suppress brain parenchyma signal, and frequency-offset fat saturation (FS) to suppress fat signal. Signal intensity and blood-background contrast was measured in several regions of interest on conventional 3D TOF MR images, MTC images, and those with MTC and FS in seven volunteers. One patient each with an arteriovenous malformation, an aneurysm, and stenosis in the intracranial vascular system underwent the protocols with an echo time (TE) of 5 msec and then a TE of 8 msec. Use of the 5-msec-TE sequence with MTC and FS led to reduced problems associated with signal void in areas of fast flow in patients. In volunteers and patients, vascular visualization was superior to that of current 3D TOF techniques.

Artifacts↗
PubMed1993

Preparation of sub-100 nm human serum albumin nanospheres using a pH-coacervation method.

Human serum albumin (HSA) nanospheres of about 100 nm diameter were prepared using a pH-coacervation method whereby acetone was added to an HSA solution (pH 9.0). The particles obtained were cross-linked by glutaraldehyde. Increasing the pH of the HSA solution resulted in a gradual rise in the particle size of the resultant nanospheres. A higher cross-linking efficiency was obtained with increased glutaraldehyde concentration and cross-linking time. No significant differences in surface properties, as determined by zeta potential measurements, were recorded between particles prepared from HSA solutions with different pH. The nanospheres were quite stable over 4 days in both phosphate buffer saline (PBS) solution (pH 7.4) and rat serum, but degraded rapidly over 6 hours when incubated in PBS solution containing trypsin.

Animals↗
PubMed1992

[Adsorption in stratum corneum and percutaneous penetration of propranolol hydrochloride].

The sorption and rate of permeation of propranolol hydrochloride were measured as a function of drug concentration in the solution bathing rat skin in vitro. The sorption isotherm was nonlinear, and can be expressed in Langmuir form. The lag time and apparent permeability coefficient through intact skin decreased as the concentration of donor compartment increased, and those through stripped skin were not varied. These results indicate that an adsorption process existed when propranolol hydrochloride penetrated through the stratum corneum. Based on the adsorption--diffusion theory, a mathematical formula was developed for expressing the relationship between the concentration of drug and permeability coefficient through the skin quantitatively.

Animals↗
PubMed1992

[The effect of molecular volume and partition coefficient on percutaneous absorption].

A series of 8 p-aminobenzoate esters were selected as model drugs to study the effect of molecular volume and partition coefficient on percutaneous absorption. The octanol/water partition coefficient and solubility of these compounds were determined and their penetration rate through rat skin in vitro was measured using a Keshany-Chien diffusion cell. The results showed that when the molecular volume was increased the permeation coefficient was decreased. However, when the partition coefficient was increased, the permeation coefficient was increased at first and then reached a plateau. The mathematical formula has been derived from a bi-layer diffusion model to show how the molecular volume and the partition coefficient influence the permeation coefficient. The formula could be used to estimate the permeation coefficient of drug through skin.

4-Aminobenzoic Acid↗
PubMed1992

Overexpression of alpha 2-adrenergic receptors in fetal rat heart: receptors in search of a function.

alpha 2-Adrenergic receptors are transiently overexpressed by many types of developing cells. In the current study, the developmental profile and cellular function of these receptors were examined in the fetal and neonatal rat heart. alpha 2-Receptors, assessed with [3H]rauwolscine binding, were extremely high in fetal hearts on gestational day 19, 30-fold higher than values seen in adults. Receptor binding decreased by two-thirds by gestational day 21 and dropped by half again by postnatal day 3. To assess potential cellular functions controlled by the alpha 2-receptors, the capability of an alpha 2-agonist (clonidine) to inhibit membrane-associated adenylate cyclase activity was measured in three different settings: basal enzyme activity, the enzymatic response to isoproterenol (dependent upon beta-receptor linkages to the regulatory protein, Gs), and the response to forskolin (independent of receptor-Gs interactions). Despite the high number of alpha 2-receptors in fetal hearts, clonidine failed to alter any of the adenylate cyclase activity measures. In light of the postulated role of alpha 2-receptors in the maintenance of fetal/neonatal atrioventricular conduction, the excess alpha 2-receptors are probably linked to other cellular events, such as movement of calcium into the cell.

Adenylyl Cyclases↗
PubMed1992

[Pharmacokinetic analysis of enterohepatic circulation of piroxicam in rabbits].

The concentration (c)-time (t) curves of piroxicam showed double peaks following iv 10 mg dose to 4 rabbits. A new mathematical model of enterohepatic circulation was proposed to explain this double-peak phenomenon and showed good agreement with data. This model provides not only the common pharmacokinetic parameters: T1/2 = 1.12 +/- 0.32 h, V1 = 0.64 +/- 0.12 L, AUC = 34.7 +/- 7.8 micrograms.h-1.ml-1, but also the parameters of enterohepatic circulation of piroxicam: the cycling amount of drug Db = 3.9 +/- 1.4 mg, reabsorption fraction Fb = 0.50 +/- 0.04, reabsorption rate constant Ka = 2.55 +/- 0.50 h-1. It is indicated in this study that enterohepatic circulation results in a 20% average increase of the effective amount of piroxicam.

Animals↗
PubMed1991

Interpersonal relations and helping norms among university students of Japan, Taiwan, and Korea.

This study investigated the effects of interpersonal relations on some aspects of moral judgment among 68 Japanese, 70 Chinese, and 92 Korean university students. The subjects were asked to judge agents' acts in stories about varied helping situations which formed a factorial design: familiarity and kinship between subjects and the agent, those between the agent and the victim, and actions. Analysis showed that the two relationships between the agent and the victim significantly affected judgments in three cultures. The magnitudes of the effects of kinship between agent and victim varied across the cultures.

Adult↗
PubMed1991

[The effect of inorganic fillers on the properties of light-curing composites].

Light curing composite resins became the preferred material in treating carious or traumatic lesions of anterior teeth. Attempts to improve the properties of these materials lead to the development of hybrid composites with an amount of anorganic fillers of more than 80 weight %. It was the purpose of this study to investigate whether composites with higher amounts of anorganic filler show better properties than those with lower amounts of filler. Eight commercial and two experimental composites have been tested for their resistance to abrasion by simulated toothbrushing, polymerization shrinkage, water sorption, porosity, and surface quality. The results showed no correlation between the amount of anorganic filler on the one hand and tested properties on the other. The amount of anorganic filler is no quality criterium per se, the properties of a composite are rather influenced by composition and quality of the organic matrix, even if the amount of anorganic fillers increases to more than 80 weight %.

Composite Resins↗
PubMed1991

Activities of a cancellous bone-cell-stimulating substance.

A bone-cell-stimulating substance (BCSS) that initiates appositional bone formation in intact rats was examined for its effects on DNA and collagen synthesis in tibial and calvarial organ cultures of 17-day-old embryonic chicks. BCSS stimulated collagen synthesis in both types of bone. BCSS stimulated DNA synthesis in tibiae but inhibited synthesis in calvaria from the same chicks. Insulinlike growth factor, transforming growth factor-beta, platelet-derived growth factor, and fetal bovine serum also affected DNA synthesis differently in calvaria and tibiae. BCSS was able to modify some of the effects of these growth factors on DNA.

Animals↗
PubMed1991

Technologic advances in magnetic resonance angiography.

Magnetic resonance angiography continues to develop both in technical capabilities and in clinical applications. Head and neck MR angiography is now in common use and is being compared to digital subtraction angiography (DSA) on a daily basis. New approaches to MR angiography in the abdomen and thorax and peripheral areas are making progress. Even coronary angiography is likely to fall prey to MR angiography and the prowess of those designing new techniques. The role of contrast agents in MR angiography is becoming more evident; contrast agents are likely to play an important role in the future. Furthermore, quantitative flow velocity measurements of major vessels are also possible and are of interest to clinicians for blood flow information. This review covers these and other recent developments in MR angiography, including both technical and clinical developments.

Blood Flow Velocity↗
PubMed1991

Velocity quantification in magnetic resonance imaging.

A variety of methods has been developed for quantitating flow in vivo. These are usually based on the principles of velocity-phase or TOF information. The former allows a point-by-point 2D image of velocity, but also has other manifestations involving real-time 1D projections or 1D projections with 1D velocity information (flow zeugmatography). The TOF methods use the in-flow of unsaturated spins into a saturated region (for example) to estimate flow. The concepts, features, and clinical applications of these and other techniques are reviewed in this article.

Blood Flow Velocity↗
PubMed1990

Observations on the treatment of allergic rhinitis with the method of invigorating vital energy and strengthening the body surface resistance.

From clinical practice, the authors concluded that the principal pathogenic factor in allergic rhinitis is deficient resistance of the body surface, and the patient is exposed to invasion of wind-evil. 495 cases of the allergic rhinitis have been treated with the method of invigorating vital energy and strengthening the body surface resistance (Bu Qi Gu Biao); the total effective rate was 84%, and the recurrence rate was 13.2% in a follow-up of 2 years. The changes in plasma cyclic nucleotides of the patients, and the ultrastructure of nasal mucosa of patients and animal models were also observed before and after treatment. The results showed that the TCM therapy tended to normalize the plasma cyclic nucleotide level, to improve the morphology and function of cells and organelles, to restore the function of mucosal cilia, to reduce the infiltration of eosinophils and their degranulation, to reduce tissue edema, and to eliminate the deposit of immune complexes.

Adolescent↗
PubMed1990

[Color stability of light curing composites].

Eight commercial and two experimental light cured composite have been tested for color stability after experimental aging. Color differences were measured by computer-controlled spectrophotometry and expressed in terms of L*A*B* color coordinates (CIELAB). Although three composites with a high content of anorganic filler showed the best color stability and the material with the lowest anorganic filler content showed the greatest discoloration, there was no strong correlation between the amount of anorganic filler on the one hand and color stability after experimental aging on the other.

Color↗