Statistical moments in pharmacokinetics

Statistical moments are parameters that describe the characteristics of the time courses of plasma concentration (area, mean residence time, and variance of residence time) and of the urinary excretion rate that follow administration of a single dose of a drug. The relationship between the moments of a time-course curve and pharmacokinetic profiles of drug disposition, i.e., absorption, distribution, metabolism, and excretion, is described. The moments are related to the extent and rate of bioavailability, and it is shown that they can be effectively applied to the deconvolution operation.

High speed liquid chromatographic determination of cephalexin in human plasma and urine

A rapid and accurate high speed liquid chromatographic method has been developed for the determination of cephalexin in human plasma and urine. The method involves micropore filtration of urine specimens and methanol extraction of plasma samples followed by HSLC separation on a bonded reverse phase column utilizing a mobile phase of methanol-water containing acetic acid. The quantitativity of UV response at 254 nm covered a wide range of cephalexin concentrations down to 0.5 microgram/ml, and no metabolite peaks were detected. The time courses of plasma level and urinary excretion were determined until 6 hours after oral administration of cephalexin capsules to healthy volunteers. The pharmacokinetic parameters were estimated using a two compartment open model.

A new heat-stable acid phosphatase test for mycobacteria

The heat-stable (70degrees C) acid phosphatase test performed by the method of Kind and King is a simple method for differentiating Mycobacterium kansasii, M. marinum, M. gastri, M. nonchromogenicum, and M. triviale from other slowly growing mycobacteria, and M. fortuitum from other rapidly growing acid-fast bacilli.

A psychophysiological study of determinants for detection of deception

Three studies were conducted to obtain available data on the determinants for detection of deception rates. (a) Psychophysiological measures were evaluated for effectiveness in detecting deception. A relevant-irrelevant method was used with two conditions; neutral stimulus and personal stimulus. Of the physiological variables, skin potential response, skin resistance response, finger pulse volume, and skin blood flow were significant indicators of deception. (b) Three experiments were conducted to study the psychophysiological effects of false and true feedback of skin potential response on the detection rates. It was concluded that the subjects receiving information that they were detectable were easier to detect than the subjects who believed that they were not detected and the subjects who received feedback of actual responses. (c) With the use of skin potential response channel, significant detection rates were obtained for all experiments under the condition that subjects verbally lied by means of "No" responses. On the other hand, the subjects who were motivated to deceive produced differentially augmented responses in the absence of any verbal response and also when the subjects told the truth to critical items and lied to irrelevant ones.

Noncovalent modification of deoxyhemoglobin S solubility and erythrocyte sickling

Ammonium sulfate, as well as potassium phosphate, can be used to measure solubility differences between hemoglobin S and hemoglobin A. In addation, the solubility of deoxyhemoglobin C(Harlem) in 1.96 M phosphate has a markedly different temperature dependence from that of deoxyhemoglobin S. This observation indicates that the solubility measurement is quite sensitive to changes in protein structure. Because of the large degree of comparability between the solubility and the aggregation of deoxyhemoglobin S, solubility was used to measure the effectiveness of organic compounds as noncovalent modifiers of deoxyhemoglobin S aggregation. Organic solvents (ethanol, dimethylsulfoxide, 1,4-dioxane, dimethylformamide) alter the solubility characteristics of deoxyhemoglobin S in 1.96 M phosphate buffer, pH 7.0. The concentrations of solvent necessary to provide a half-maximal effect are remarkably similar (about 0.5 M), although the chemical nature of these compounds is quite different. The effect of these solvents must be to prevent the noncovalent bond formation necessary to produce the insoluble hemoglobin precipitate, perhaps by altering the water structure around the deoxyhemoglobin S molecules. In addition to these organic solvents, guanidine hydrochloride and urea, two well-known protein denaturants, were studied. Guanidine hydrochloride was as effective as the best organic solvent in increasing the solubility of deoxyhemoglobin S; urea was far less effective. Studies in vitro with intact erythrocytes from individuals homozygous for hemoglobin S showed that sickling is decreased up to 50% by treatment with ethanol. This offers further evidence that solubility is monitoring a phenomenon similar to the aggregation of deoxyhemoglobin S inside erythrocytes. While use of these particular compounds in vitro would seem to have no clinical implications, these studies do suggest that the use of chemicals that do not modify hemoglobin S covalently should be explored in efforts to prevent deoxyhemoglobin S aggregation.