Simplified photometric copper-soap method for rapid assay of serum lipase activity.
(33/534)
We modified the method of Yang and Biggs [Clin. Chem. 17, 512 (1971)] for greater speed and simplicity. Serum is incubated with an emulsified olive oil substrate, the fatty acids extracted, the copper soap formed, and phases separated, all in a single tube. An aliquot of the organic phase is removed for color development. One analysis can be completed in 35 min, 20 in less than 2 h. The method is accurate and precise. Results correlate well with the unmodified colorimetric method, and with the classical titrimetric lipase procedure. The reference interval (normal range) is 20 to 180 U/liter. (+info)
Evaluation of a nephelometric assay for haptoglobin and its clinical usefulness.
(34/534)
Serum haptoglobin has been advocated as an indicator of intravascular hemolysis. We have evaluated a nephelometric determination of serum haptoglobin. The assay is sensitive and exhibits within-run precision in the range of 2.5-7.4% coefficient of variation (CV) and between-run precision of 7.0% (CV). In addition, when haptoglobin values determined with the nephelometric assay were compared with hemoglobin-binding capacity determined by electrophoresis, the correlation coefficient was 0.968. The assay is essentially independent of phenotype and free of significant interference by hemolysis. The clinical correlation of haptoglobin values obtained for 100 selected patients with the nephelometric technique correlated well, if less than 250 mg/L, with the presence of hemolytic disease. (+info)
Measurement of effects of antibiotics in bioluminescent Staphylococcus aureus RN4220.
(35/534)
The spread of antibiotic resistance among pathogenic bacteria is a serious threat to humans and animals. Therefore, unnecessary use should be minimized, and new antimicrobial agents with novel mechanisms of action are needed. We have developed an efficient method for measuring the action of antibiotics which is applied to a gram-positive strain, Staphylococcus aureus RN4220. The method utilizes the firefly luciferase reporter gene coupled to the metal-inducible cadA promoter in a plasmid, pTOO24. Correctly timed induction by micromolar concentrations of antimonite rapidly triggers the luciferase gene transcription and translation. This sensitizes the detection system to the action of antibiotics, and especially for transcriptional and translational inhibitors. We show the results for 11 model antibiotics with the present approach and compare them to an analytical setup with a strain where luciferase expression is under the regulation of a constitutive promoter giving only a report of metabolic inhibition. The measurement of light emission from intact living cells is shown to correlate extremely well (r = 0.99) with the conventional overnight growth inhibition measurement. Four of the antibiotics were within a 20% concentration range and four were within a 60% concentration range of the drugs tested. This approach shortens the assay time needed, and it can be performed in 1 to 4 h, depending on the sensitivity needed. Furthermore, the assay can be automatized for high-throughput screening by the pharmaceutical industry. (+info)
Comparison of two spatially resolved near-infrared photometers in the detection of tissue oxygen saturation: poor reliability at very low oxygen saturation.
(36/534)
Two spatially resolved oximeters, NIRO-300 and OM-200, were compared with regard to the measurement of oxygen saturation values in two forearm muscle groups at rest and during arterial occlusion in nine healthy volunteers. There was a significant correlation between the muscle oxygen saturation values obtained at rest using the two oximeters (n=33, r(2)=0.43, P<0.0001), whereas these values were significantly different during arterial occlusion. Thus, although there was good agreement between muscle oxygen saturation values measured using the two oximeters, the operating range of the tissue oximeters should be recognized and indicated. (+info)
Cimetidine administration and tubular creatinine secretion in patients with compensated cirrhosis.
(37/534)
Cimetidine inhibits the tubular secretion of creatinine, without altering the glomerular filtration rate (GFR). During cimetidine administration the creatinine/inulin clearance ratio approaches unity in patients with renal failure. We determined the clearance of lithium (an index of fluid delivery to the distal nephron), inulin (a measure of the actual GFR) and creatinine during cimetidine administration to investigate the occurrence of tubular creatinine secretion in patients with compensated cirrhosis. A total of 12 patients with Child-Pugh A cirrhosis were studied initially. The subjects consumed a stable diet containing 100 mmol of sodium. On successive days, 9 h creatinine clearances were measured, first without and then with the oral administration of cimetidine (400 mg as a priming dose, followed by 200 mg every 3 h). During the first study day, 4 h renal lithium clearance was also calculated. A further group of five patients with fully compensated cirrhosis underwent the measurement (on successive days) of plasma inulin clearance, first without and then with the oral administration of cimetidine (same schedule of drug administration). Cimetidine administration unmasked a marked overestimation of GFR when calculated as creatinine clearance (baseline, 138+/-20 ml/min; +cimetidine, 89+/-13 ml/min; P<0.01). Consequently, during cimetidine administration the calculated lithium fractional excretion (a measure of the fraction of filtered sodium load that is delivered to the loop of Henle) rose from 21.4+/-13.2% to 32.3+/-18.9% (P<0.05), and the ratio between absolute distal tubular sodium reabsorption and filtered sodium load rose from 20.6+/-13.1% to 31.6+/-19.3% (P<0.01). Cimetidine caused no significant decrease in the actual GFR (i.e. inulin clearance) when administered to the second group of patients with compensated cirrhosis. Our data demonstrate significant tubular secretion of creatinine in patients with compensated cirrhosis and, consequently, a marked overestimation of GFR and filtered sodium load and an underestimation of the fractional distal tubular sodium reabsorption when these parameters are calculated by means of the traditional creatinine and lithium clearance computation. The true GFR (measured as inulin clearance) is unaffected by cimetidine administration. (+info)
Comprehensive-trace level determination of methyltin compounds in aqueous samples by cryogenic purge-and-trap gas chromatography with flame photometric detection.
(38/534)
A comprehensive method was developed for the sensitive and fast determination of trace levels of methyltin compounds in aqueous samples. Tin compounds in aqueous solution at pH 5 were converted to the corresponding volatile hydrides: CH3SnH3, (CH3)2SnH2, and (CH3)3SnH, by reaction with potassium borohydride. A CP-4010 purge and trap injector (PTI) was used to purge analyte species from water directly. The volatile derivatives were base-line separated on a capillary column in an Angilent-6890 gas chromatograph by a suitable temperature program and were detected by a flame photometric detector (FPD). The detection limits were 18 ng L-1 for monomethyltin, 12 ng L-1 for dimethyltin, and 3 ng L-1 for trimethyltin, respectively. This method was successfully applied to the determination of methyltin compounds in different aqueous samples. (+info)
A comparative study of stimulus-specific pupil responses in the domestic fowl (Gallus gallus domesticus) and the human.
(39/534)
Pupil responses triggered by specific stimulus attributes such as spatial structure, colour and light flux changes were measured in eight domestic fowl. Comparative experiments were also carried out in human subjects. The results were unexpected in that large increments in light flux caused only small constrictions of the pupil. A red stimulus, on the other hand, caused a relatively large pupil response, but a green stimulus was less effective. This finding suggests that the size of the pupil, apart from being controlled by well-described pretectal pathways that mediate luminance responses, is also subject to other inputs. The pupil response in the domestic fowl may therefore make an effective quantitative indicator of things of significance to the animal. In some ways these observations are similar to other findings in primates in that the processing of stimulus attributes such as colour and structure that are not normally associated with the light reflex pathway can cause a pupil response. The fowl pupil does however respond very fast when large light flux changes or red stimuli are involved. Results obtained with sinusoidally modulated light flux changes reveal a short response latency of 105 ms (SD=8.3). In contrast, human responses measured for similar stimulus conditions reveal a latency of 434 ms (SD=36). The speed of pupil response in the fowl is significantly higher than in humans, but the response amplitude is usually small. Another interesting observation is the lack of sustained response to changes in ambient illumination. These findings suggest that the input to the pupilloconstrictor neurones in the fowl consists largely of transient neurones with little sustained component. (+info)
In vivo assessment of retinal carotenoids: macular pigment detection techniques and their impact on monitoring pigment status.
(40/534)
Of the many carotenoids found within human tissue, only the carotenoids within the human retina can be assessed noninvasively at present. Such assessment should eventually provide a more complete understanding of the functional role of retinal lutein (L) and zeaxanthin (Z) (termed macular pigment, MP) in human vision. The emerging data allow for some initial observations. For example, there appears to be wide variation (>factor of 10) in the concentration of MP. Although MP levels have been recorded from nondetectable to 1.20 OD (optical density), the "average" levels, relative to what is possible, appear low. This may be due in part to the low average dietary intake of L and Z in the typical U.S. diet. Nonetheless, individual differences in MP may also be influenced by nondietary factors such as genetics, demographics and lifestyle characteristics. Some evidence indicates that the MP carotenoids may protect the retina and lens, and could improve vision through some optical mechanisms. Consequently, efforts to determine typical MP levels and the factors that influence individual differences in MP density should be continued. (+info)