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Biomedical subjects

K C Huang

Publications and source records attributed to K C Huang.

At least 55 records · Page 3Linked to original sources
PubMed1985

Screening test for urinary glycosaminoglycans and differentiation of various mucopolysaccharidoses.

The Ames MPS paper spot test and the cetylpyridinium chloride (CPC)-citrate turbidity test were used to detect urinary glycosaminoglycans (GAGs) as screening tests for the diagnosis of mucopolysaccharidoses (MPSs). The simplicity and reliability of these two methods were evaluated. The MPS paper spot test correlated more closely with the carbazole test than did the CPC-citrate turbidity test. The monodimensional electrophoresis of Cappelletti et al was also used to screen the subtypes of MPSs using differences in electrophoretic patterns. MPS VII cannot be distinguished from normal by its electrophoretic pattern, but can be detected by the MPS paper spot test. Therefore, the MPS paper spot test combined with monodimensional electrophoresis can detect these subtypes of MPSs (MPS I-II, III, IV, VI, VII). Since only 20 ml of random urine is needed and the result can be obtained with complete reliability in only 7 hours, this screening test appears to be useful for the early diagnosis of MPSs.

Adolescent↗
PubMed1984

Effect of penicillin on the renal tubular secretion of methotrexate in the monkey.

The effect of penicillin on the renal tubular secretion of methotrexate (MTX) in rhesus and cynomolgus monkeys was studied in vivo and in vitro. In stop-flow experiments in ketamine-anesthetized monkeys, the ratios of urine/plasma MTX concentration to urine/plasma inulin concentration of proximal tubular samples were about 2-fold greater than the base-line free-flow values of 3.3 to 4.8, indicating net proximal tubular secretion. MTX secretion was inhibited by penicillin, which lowered the base-line U/PMTX/U/Pinulin ratios to 0.8 to 1.3; the effect persisted over a 30-min period after discontinuation of penicillin administration. Penicillin also slowed the disappearance of MTX from plasma over a 2-hr period after i.v. bolus administration of MTX. In experiments with renal cortical slices, MTX uptake at 25 degrees was linear over the initial 30 min. The uptake Km and Vmax were 0.09 mM and 0.11 mumol/g of tissue/30 min, respectively. Penicillin competitively inhibited MTX uptake; the Ki was 0.83 mM. MTX efflux from preloaded slices (incubated with 0.5 mM MTX for 45 min) was a first-order process with an initial t1/2 of 7.1 min, which decreased to 2.0 min in the presence of 1.36 mM penicillin. It was concluded that MTX and penicillin share a common secretory system in the kidney and that penicillin blocks MTX secretion by inhibiting cellular uptake and stimulating efflux.

Animals↗
PubMed1983

Transport of methotrexate in cortical slices of monkey kidney: effect of organic anions and vincristine.

Thin cortical slices of cynamolgus and rhesus monkey kidney were used to study the renal transport of methotrexate (MTX). In experiments with renal cortical slices, MTX uptake at 25 degrees C was linear over the initial 30 min and was temperature-dependent. The Km was 0.094 mM for MTX uptake at 25 degrees C and Vmax was 0.098 mumol/g of tissue/30 min. In the presence of either 1 mM 2,4-dinitrophenol, p-aminohippurate or acetylsalicylate, MTX uptake was competitively inhibited. 2,4-Dinitrophenol had the greatest and acetylsalicylate had the least inhibitory effect. Folinic acid, folic acid and ouabain produced little or no effect on MTX uptake. MTX efflux from preloaded slices (preincubated with 0.5 mM MTX for 45 min) was a first-order process with T 1/2 of 7.13 +/- 0.86 min. In the presence of vincristine or p-aminohippurate the half-lives for MTX were 15.25 +/- 0.91 and 4.59 +/- 0.47 min, respectively. Thus vincristine, an organic base, was found to augment MTX uptake, due to a reduction in the rate of efflux of MTX from the cortical tissues, whereas p-aminohippurate, an organic acid, was found to decrease MTX intracellular concentration by blocking influx and stimulating efflux. It was concluded that the renal transport of MTX in monkey kidney is mediated predominantly by an organic anion secretory process and that there is probably little or no reabsorptive transport.

2,4-Dinitrophenol↗
PubMed1983

Video stethoscope--a simple method for assuring continuous bilateral lung ventilation during anesthesia.

Complications of endotracheal intubation and mechanical ventilation are infrequent but important causes of intraoperative morbidity and mortality. We have developed a simple method of monitoring the ventilation of both lungs during general anesthesia and have evaluated this technique in 25 patients undergoing surgery under general anesthesia. A small plastic electrocardiographic electrode casing fitted with a microphone was affixed to the skin overlying each hemithorax in a location where preliminary auscultation showed that breath sounds could be heard. The sounds from each microphone were amplified and displayed on an oscilloscope screen in an X-Y format. The patterns seen on the screen allowed easy identification of right mainstem intubation, esophageal intubation, or proper endotracheal tube placement. This preliminary study suggests that our technique is feasible and provides more information about the position of the endotracheal tube than presently used methods.

Anesthesiology↗
PubMed1982

Renal tubular transport of folic acid and methotrexate in the monkey.

The renal excretion of folic acid and methotrexate (MTX) was investigated in pentobarbital-anesthetized cynomolgus, rhesus, and AFrican green monkeys by standard clearance and stop-flow techniques. The renal clearance of folic acid was below inulin clearance at all plasma concentrations studied; the (U/P)folic/(U/P)In ratio increased from 0.26 at a concentration of 0.03 mM to a plateau value of 0.9 at concentrations above 0.2 mM, indicating net reabsorption by a saturable system. In stop-flow experiments, base-line (U/P)folic/(U/P)In ratios during free-flow periods were below 1.0, but increased by twofold in stop-flow samples derived from the proximal tubule, indicating net secretion during stopped flow. The stop-flow pattern of MTX excretion was similar, except the base-line flow pattern of MTX excretion was similar, except the base-line (U/P)MTX/(U/P)In ratio exceeded 1.0, indicating net secretion during both free-flow and stopped-flow periods. Secretion of both compounds was inhibited by p-aminohippuric acid and other organic acids but not by L-glutamic acid. It is concluded that folic acid is transported bidirectionally, while evidence was obtained only for secretion of MTX.

Animals↗
PubMed1981

Structural specificity in the renal tubular transport of tyrosine.

The structural requirements for aromatic amino acid reabsorption and secretion in the dog were investigated using a series of tyrosine analogs. In clearance experiments, l-tyrosine and l-phenylalanine underwent net reabsorption at rates 5 to 6 times greater than those of the corresponding d-enantiomers and about 1.5 time those of o- and m-dl-tyrosine. 3-(p-hydroxyphenyl)Propionic acid underwent net secretion under conditions of polyuria and high urinary pH and net reabsorption under conditions of oliguria and low pH. In stop-flow experiments, (U/Pl-amino acid)/(U/Pln) ratios, where U/P = concentration in urine and plasma and In = inulin, of proximal tubular samples were 1.5 to 5-fold greater than the control (free-flow) values of 0.1 to 0.3, indicating tubular secretion. Secretion was inhibited, and net reabsorption enhanced, by probenecid, p-aminohippuric acid and 2,4-dinitrophenol. (U/Pd-amino acid)/(U/PIN) ratios of proximal tubular samples were below the control values of 0.6 to 0.8, indicating tubular reabsorption. Probenecid had no effect on the overall pattern but caused a slight decrease in the relative clearance values. The stop-flow pattern of 3-(p-hydroxyphenyl)propionic acid excretion was similar to that of the I-amino acids. It was concluded that the I-amino acids undergo bidirectional transport and that the I-configuration and amino group are required for optimal active reabsorption, whereas ring hydroxylation has little effect on reabsorption transport. No absolute structural requirements for active secretion were elucidated.

Absorption↗
PubMed1980

Effect of glucagon on ion transport in mouse intestine.

Effects of glucagon (GN) on short-circuited mouse intestine were studied. GN (30 microgram . ml-1), added to the serosa of intestine mounted in an Ussing chamber and bathed in glucose-free Ringer, induced significant increases of 43% in serosal-to-mucosal Cl- flux (Js leads to m Cl), 315% in net Cl- secretion (Jnet Cl), 85% in net residual flux (J net R), 61% in short-circuit current (Isc), and 44% in open-circuit potential difference (PD). The mucosal-to-serosal Cl- flux and both unidirectional Na+ fluxes (Jm leads to s Na and Js leads to m Na) were unchanged. In a glucose Ringer bathing medium, GN exhibited no significant effects on ion fluxes and electrical parameters. To eliminate the possibility that observed GN-induced changes in PD and Isc were partially due to changes in membrane surface charge, the effects of GN in Cl- -free Ringer were studied. Under these conditions, GN had no effect on electrical parameters. Furthermore, GN elicited no effect on cAMP levels in either the presence or absence of glucose. These findings suggest that 1) the effect of GN on Jnet Cl is masked in the presence of glucose, 2) GN-induced increases in Isc and PD are a reflection of the increase in Jnet Cl and are neither due to changes in membrane surface charge nor to an increase in net Na+ flux, and 3) GN-induced secretory diarrhea is in part due to changes in electrolyte transport.

Animals↗
PubMed1979

Renal tubular transport of methotrexate in the rhesus monkey and dog.

The mechanism and localization of renal transport of methotrexate (MTX) were studied in the rhesus monkey and the dog. It was found that in both animals MTX was bound with plasma protein in a range of 50 to 68% varying with the MTX plasma concentration. Paper chromatographic analysis showed that a negligible amount of MTX was metabolized. The excretion of MTX in rhesus monkey was mainly by tubular secretion which was blocked by probenecid, but in the dog a bidirectional transport mechanism for MTX was indicated. Tubular secretion was localized in the proximal tubules, and a tubular reabsorptive process was in the distal section. Simultaneous administration of folic acid blocked the tubular reabsorption of MTX, resulting in an increase of renal excretion. Maximum tubular excretory capacity determination showed that a maximum tubular excretory capacity value of approximately 5 mumol/100 ml of glomerular filtrate was observed in the rhesus monkey at a plasma concentration of 0.07 mM and a value of 2 mumol/100 ml of glomerular filtrate for the dog. Studies with renal cortical slice technique also indicated that the monkey kidney can accumulate greater amounts of MTX than can the dog kidney.

Animals↗
PubMed1978

Short circuit current in tight and leaky epithelia.

The effect of short circuit current on the unidirectional fluxes of ions transported across tight and leaky epithelia was investigated. It was found that short circuiting of the frog gastric mucosa (classified as a tight epithelium) caused a decease of the passive JClms and a significant increase of the net Cl- secretion. However, no significant change of H+ secretory rate was observed. On the other hand, short circuiting of the mouse intestine (a known leaky membrane) caused a simultaneous increase of both Jms and Jsm fluxes of Na+ while the net fluxes of Na+ and Cl- remained unchanged. Also, short circuiting did not change the water permeability of the mouse intestine. To explain some of these results a theoretical model is presented to demonstrate that while short circuiting can block the passive ionic movement, it will cause an increase in the energy consumption of the system and introduce certain important changes in the ionic barriers and e.m.fs. The simultaneous increase in the unidirectional fluxes of Na+ under short circuit conditions can best be explained by a decrease in the polarized nature of the transepithelial shunt, thereby increasing the diffusion coefficient of the ion(s). Such an increase is specially favorable to the Na+ rather than an anion.

Animals↗
PubMed1977

Effect of nicotine on gastric acid secretion: evidence of electrogenic pump theory.

In vitro studies on H+ secretion, potential difference (PD), short-circuit current (Isc), and resistance across stripped mucosa of frog stomach in Cl-medium have shown that addition of nicotine in the serum bathing fluid caused a marked inhibition of the H+ secretory rate and an increase of PD and Isc without change of the transmucosal resistance. A dose-response correlation was indicated. During the first 8 min, the changes in the measured parameters, namely, PD versus Ih and Isc versus Ih, were linear. After 8 min, a deviation from linearity was observed. From the slope of the regression lines, the resistance of the electrogenic Cl- pump on the mucosal membrane (Rcl) was calculated to be 127 omega cm2 and the resistance of the chloride pathway on the serosal side (Rcl) was 407 omega cm2. The resistance of the H+ pump on the mucosal membrane (Rh) in Cl- medium was estimated to be 385 omega cm2. The sum of the emf's of the Cl+ pump on the mucosal membrane and of the Cl- gradient across the serosal membrane, namely Ecl + Ecl, was found to be 35 mV. The presence of such linear relationships between measured versus the H+ rate and Isc versus Ih lends support to the electrogenic theory of HCl secretion.

Animals↗
PubMed1976

Effect of diuretics on intestinal transport of electrolytes, glucose, and amino acid.

The jejunal mucosal membrane of albino mice was used to study the electrical properties and ion transport. The membrane was bathed in Krebs-Ringer solution with or without glucose. When ethacrynic acid (EA), furosemide, or amiloride was added to the bathing fluid of both sides, a transient increase followed by a decrease of both potential difference (PD) and short circuit current (Isc) were observed. In glucose-containing bathing medium, EA inhibited both net Na and Cl flux and residual flux; however, EA had little effect on both Na and Cl flux in glucose-free bathing medium. Studies using everted intestinal sac technique showed that EA inhibited both glucose and L-tyrosine across the mucosal membrane against concentration gradients. Furosemide and amiloride were less potent than EA in inhibiting the Na and Cl flux when the bathing solution contained glucose. But these two compounds had no effect on glucose and L-tyrosine transport across the intestinal mucosa. Furthermore, they did inhibit Cl flux even in the condition of glucose-free bathing medium. It is postulated that all three diuretics act on the brush-border membrane of the intestine. EA probably inhibits the Na-glucose cotransporting system; furosemide and amiloride inhibit the simple diffusion process of Na entry of Cl exit by decreasing the conductance of the membrane.

Amiloride↗