Giuliano Barbaresi

Determination of copper, zinc, and selenium in human plasma and urine samples by potentiometric stripping analysis and constant current stripping analysis

Potentiometric stripping analysis and constant current stripping analysis are proposed as routine methods for analysis of copper, zinc and selenium in plasma and urine samples. The analytical performance of these methods is comparable with that reported for atomic absorption spectrometry. However the low cost, greater simplicity of the apparatus, and the facility of execution make this methodology a valid candidate for routine application in Clinical Chemistry laboratories.

Effect of pH and CO2 concentration changes on lipids and fatty acids of Saccharomyces cerevisiae

SummaryThe lipid composition of S. cerevisiae cells was studied in different conditions of pH and of HCO3- and CO2 concentration.Increasing the concentration of CO2 in the broth determines an increase of total lipids, of total fatty acids, and of the relative amount of unsaturated fatty acids.Changing the concentration of bicarbonates at constant pCO2 does not affect the lipid composition of the cells. Also pH changes do not have significant effects.

Influence of serum proteins on fructosamine concentration in multiple myeloma

Serum fructosamine levels in 36 subjects with various types of multiple myeloma and in 64 normal controls were evaluated by means of a Nitroblue tetrazolium colorimetric assay. Only the IgA myeloma group showed significantly raised serum fructosamine values (P less than 0.001). In the IgG myeloma group, which showed a higher mean serum protein concentration, serum fructosamine levels were not significantly different from controls. The study shows that elevated IgA levels do influence serum fructosamine and this effect should be taken into due consideration in order to avoid possible misinterpretations in evaluating this widely used index of glucose metabolism.

Effect of phospholipids from Saccharomyces cerevisiae at different stages of development on restoration of succinooxidase activity in lipid-depleted mitochondria

Phospholipids extracted fromSaccharomyces cerevisiae at different stages of development after glucose repression contain three major fatty acids: palmitic, palmitoleic and oleic. The ratio palmitic: palmitoleic strongly decreases beginning at the 6th hour of growth.To test the effect of fatty acid composition and in particular of unsaturation on succinoxidase activity, all these phospholipids, phospholipids from commercial yeast, and Asolectin were incubated with lipid-depleted yeast mitochondria. The amount of P bound was not much different for the various phospholipids; succinoxidase activity was restored best by Asolectin; the least effective reactivation was given by phospholipids from yeast at the middle stages of growth. There are not great differences between the various phospholipids and there is no correlation with unsaturation. If we compare the pattern of appearance of respiration during morphogenesis of yeast mitochondria with the pattern of the capability of the phospholipids from cells at different stages of mitochondrial morphogenesis to restore activity of lipid-depleted yeast mitochondria, we find no correlation. The results of this investigation are consistent with the idea that changes in phospholipids and changes in enzyme activities are not linked by a causal relation.

Automation in urinalysis: sample and data management, and quality control

Reagents: Urine reagent strips Uriflet 7A DIC, Check Sample Set (used for calibration control of Aution analyser) and Rifra-Chek Solutions for calibration and control of Urinometer lot 040 (all by Kyoto, Daiichi, Kagaku Co. Ltd, distributed in Italy by Menarini of Firenze). Urine Controls: Kova Trol 1, Kova Trol 2, and Kova Trol 3: Human Urine (dried) manufactured by ICL Scientific, 18349 Euclid, Fountain Valley, California 92708, USA (distributed in Italy by Boehringer Biochemia Robin Diagnostic Division, Milano).

Use of N-(l-naphthyl)-ethylendiamine-dihydrochloride (NEDD) as secondary calibrator for conjugated bilirubin on the DuPont aca.

N-( 1-naphthyl)-ethylendiamine-dihydrochloride (NEDD) and its derivatives have been used as secondary calibrators for continuous-flow analytical instruments (for example Technicon’s SMAC) [1]. These molecules are known to react with the diazonium salts, yielding azoderivatives which have spectral qualities similar to those of azobilirubin. NEDD has also successfully been employed in the authors’ laboratory as secondary calibrator for conjugated bilirubin on a discrete clinical analyser: the Hitachi 706 [2].

A computer program for intra-laboratory quality control.

Intra-laboratory quality-control (intra-lab QC) is the best way of checking the performance of single components of analytical systems (methods, instruments, technicians) [1]. However, the time-consuming and tedious statistical methods necessary, if manually performed, provide late information that reduces the validity of intra-lab QC. In order to make this type of quality control more useful, a minicomputer program, which automates mathematical and graphical procedures, has been developed. The program assures rapid, unique and unequivocal interpretation ofresults by using a reliability index (RI) I-2 and 3-1. cumulative sum of RIs. Its value progressively increases if there is no variation in the RI sign; it begins again from zero if a sign variation appears. The statistical parameters are calculated monthly to allow retrospective quality-control. Monthly means and standard deviations on untruncated, truncated, and the cumulated results of two control materials are calculated. Truncated data means and related standard deviations are obtained after an iterative truncation deletes outliers (+ 3 SD). The truncated data are summed with those from the previous months and are used to calculate cumulative means and standard deviations. Control charts [7], and two sample plots [8] are printed by means ofthe P6060’s printer.

Sample and data random management in a medical laboratory equipped with automatic analysers.

Recent advances in the performance ofautomatic analysers and in computer technology, although both share the aim of increasing speed, ease and operational capacity, have paradoxically led to a stalemate in many clinical laboratories. The new autoanalysers equipped with computers are capable of coping with a large analytical load, but often they can only partly cope with the data management process and so they increase laboratory tasks. Further, many hospital data processing centres (DPCs), copying their old manual procedures are limited to clerical work, which is a great pity considering their enormous computing powers [-1]. Laboratories often find that their advanced instrument analytical capability is conditioned by two bottlenecks: manual input of test requests and memorization of clinical results [2-1. Since a central data-bank is necessary for the complete clinical and statistical use of laboratory data in a large university hospital [-3-], a computerized system has been developed in the authors’ clinical chemistry laboratory which is connected to the DPC by means of floppy disc information transfer. The system allows positive sample identification by an automatic optical reader and, together with on-line analytical result acquisition, it is possible to process patient specimens at random as they arrive in the laboratory. This feature means that the delays and difficulties encountered with an exclusively centralized management are avoided.