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Biomedical subjects

P Fu

Publications and source records attributed to P Fu.

89 records · Page 5Linked to original sources
PubMed1991

System identification of electrically coupled smooth muscle cells: the passive electrical properties.

A system model approach based on a network model is used to investigate the passive electrical properties of coupled smooth muscle cells. This approach makes use of a gradient method of optimization to estimate the passive electrical parameters directly from the magnitude of the input impedance or voltage transfer function of the network model. The need for subjective measurements of parameters and many intermediate steps involved in the analysis using the conventional signal model approach are eliminated. The coupling resistance and capacitance are estimated with sound theoretical and mathematical grounds directly from experimental data. From the simulated results using SPICE, it is evident that the system model approach is accurate, flexible, and reproducible. These properties grant the new approach excellent potential for future studies of drug actions on smooth muscle cells and their associated electrical coupling. Also, sensitivities of the network model with respect to its parameters can readily be obtained. This may provide new insight into the coupling mechanisms of smooth muscle cells.

Electric Conductivity↗
PubMed1990

Changes in red blood cell choline and choline-bound lipids with oral lithium.

The influence of oral lithium on the concentration of red blood cell choline (Ch), lecithin, glycerophosphorylcholine (GPCh) and phosphorylcholine (PCh) was studied. The concentration of RBC Ch was significantly elevated and the concentration of lecithin, GPCh and PCh significantly depressed in 16 patients on oral lithium compared to 9 age-matched controls. We conclude that lithium markedly depletes the red blood cell of choline containing compounds including lecithin. These changes may be responsible for both the therapeutic efficacy and the toxicity of lithium.

Administration, Oral↗
PubMed1989

Computation of the passive electrical parameters of neurons using a system model.

Time-domain analysis of voltage responses to current pulse stimulation has been used to estimate the electrotonic parameters of neurons using the signal model. Errors are likely to accumulate from various steps of the analysis due to noise and electrode artifacts. A system model, which has inherent noise immunity and filtering properties, is presented here. This model employs frequency-domain analysis of the input impedance of a neuronal model (an RC cable). The resistances and capacitances of the system model are estimated from the cell-input impedance using an optimization strategy. Using the expression for the input impedance, any specified number of equalizing time constants can be computed exactly. The accessibility to these equalizing time constants 1) provides greater insight into the charge equalization along the length and circumference of the cable, and 2) improves the estimation of all other passive parameters including the electrotonic length. Thus, the system model approach allows information to be extracted more directly and accurately than the signal model approach.

Animals↗
PubMed1989

A longitudinal assessment of haloperidol doses and serum concentrations in Asian and Caucasian schizophrenic patients.

Over 3 months, 13 Caucasian and 16 Asian schizophrenic patients were sequentially treated with weight-adjusted fixed doses and clinically determined, variable doses of haloperidol. During the fixed-dose phase, Asians had a slightly higher mean serum haloperidol concentration and a significantly higher rating for extrapyramidal symptoms. During the variable-dose phase, the Asian patients' mean required dose was significantly lower, resulting in lower serum haloperidol concentrations at the first emergence of extrapyramidal symptoms and for optimal clinical response. These results indicate pharmacodynamic differences in therapeutic response but no significant difference in steady-state serum concentration between the two groups.

Adult↗
PubMed1986

Effect of dietary selenium levels on methylbenzylnitrosamine-induced esophageal cancer in rats.

Male Sprague-Dawley rats fed selenium deficient diets received either 0 ppm, 0.15 ppm or 4.0 ppm selenium in the drinking water. Animals were treated with methylbenzylnitrosamine (MBN). Dietary selenium deficiency had no effect on MBN-induced esophageal carcinogenesis. Animals treated with 4 ppm selenium in the drinking water during the initiation and post-initiation period had the same number of tumors as the group which received 0.15 ppm selenium for the entire experimental period. The incidence and frequency of carcinomas was lowest in the group which was supplemented with extra selenium (4.0 ppm) during the period of carcinogen administration and highest in the group which received 4.0 ppm selenium during the post-initiation period.

Animals↗
PubMed1984

Fetal lung liquid regulation by neuropeptides.

The fetal lung, filled with fluid during intrauterine life, is recognized as a site of fluid production, significantly contributing to amniotic fluid volume. To assess possible hormonal control of lung liquid production, we studied the effect of intravenous vasopressin or vasotocin on lung liquid production in chronically catheterized fetal sheep. Both vasopressin and vasotocin infusion resulted in a significant decrease in lung fluid production (38% and 40%, respectively) when compared to that in control animals receiving saline infusion. There was no significant change in lung fluid osmolality, sodium, or potassium. These findings suggest that lung liquid production in utero may be regulated by the fetus and that vasopressin or vasotocin may be of physiologic importance in lung fluid dynamics during the third trimester of ovine pregnancy and perhaps during parturition.

Animals↗
PubMed1976

The effects of large volume intravenous fluid infusion on neonatal renal function.

Twenty healthy infants weighing less than 2,000 gm were studied at low (3.6 ml/kg/hr) or high (10.3 ml/kg/hr) rates of intravenous infusion. Inulin clearance determined by the constant infusion method was greater at the high rate of infusion (p = less than 0.05). Inulin clearance in two groups of infants over 2,000 gm studies at the same low or high rates of infusion did not increase at the higher rate of infusion. Since the GFR in infants less than 2,000 gm depends partially on the rate of intravenous infusion, small, healthy preterm infants may benefit from a rate of fluid administration greater than the low rate. When studies at low and high rates of infusion were compared in the 20 infants less than 2,000 gm, the fractional urinary sodium excretion increased with the increased fluid load. Delivery of fluid from the proximal tubule (CH2O =Na per dl GFR) increased (p less than 0.005). Free-water clearance and the absolute volume of urine increased at the high rate of infusion. These data indicate that the healthy preterm infant less than 2,000 gm, like the adult, compensates by increasing free-water clearance and urine volume when challenged with a large fluid load. Although fluid changes of short duration are appropriately handled, the effect of continuous rapid infusion on water and sodium balance in infants of this size remains to be determined.

Body Fluids↗
PubMedDate not supplied

Chemical analysis of a 30-year-old bottle of lyophilized plasma.

The biochemical constituents of a 30-year-old sealed bottle of lyophilized plasma were analyzed. The results in this communication show that the process of lyophilization and storage has not seemed to cause any great changes in plasma components, including hormones, enzymes, and proteins.

Blood Preservation↗