An extremely simple and fast microlitre method for the determination of total carbon dioxide in biological samples.

For those clinical laboratories equipped with a microprocessor-controlled gas analyser, an extremely simple method is described for the determination of the total carbon dioxide content in various biological fluids. Since this method needs only 20 microL of blood plasma or is less dependent on the original total carbon dioxide content, it is especially suited for paediatric purposes. With our procedure the time necessary for one determination equals the time for one capillary blood gas analysis.

The diagnostic value of the urine to blood carbon dioxide tension gradient for the assessment of distal tubular hydrogen secretion in pediatric patients with renal tubular disorders.

The urine to blood carbon dioxide tension gradient (U-B PCO2) following alkalinization of the urine (pH = 7.8) has been widely used to assess distal tubular hydrogen secretion. The magnitude of the U-B PCO2 is influenced not only by the rate of hydrogen secretion but also by bicarbonate concentration and water abstraction. Simultaneous administration of sodium bicarbonate and dDAVP improve the reliability of the test in healthy children. Children with distal renal tubular acidosis were not able to increase urinary PCO2, while a normal increase was found in patients with proximal renal tubular acidosis and the Fanconi Syndrome. Four out of nine patients with urolithiasis failed to increase urinary PCO2 following NaHCO3 and dDAVP-administration, despite a normal ability to acidify the urine following NH4Cl administration. To assess the effect of acute alterations in urinary concentration on urinary PCO2, the test was carried out in children with central diabetes insipidus. Despite sharp increase in urinary bicarbonate concentration these patients failed to increase urinary PCO2.

A case of transient renal tubular acidosis type 1,4 hybrid RTA: a study of the pathophysiologic characteristics of the acidification defect.

The diagnosis of transient renal tubular acidosis was made in a 16 months old boy. Bicarbonate titration studies revealed that the acidification defect consisted of an association of proximal and distal tubular acidosis. The effect of experimentally induced potassium depletion revealed that hyperkalemia contributed to the acidification defect. After correction of the acidification disorder a defect in urinary concentration was still present.

A new automated method for the determination of true creatinine in serum by means of the centrifichem centrifugal analyzer, based on Slot's principle; with special reference to low substrate concentrations.

A new automated method is proposed for the accurate determination of the true creatinine concentration in 20 microliter serum, based on the measurement of the initial rate of the decomposition reaction of the creatinine picrate complex caused by decreasing the pH. The results of this method, performed with a Centrifichem centrifugal analyzer system (type 300 F), are compared with the results obtained by two other methods: a manual method based upon the adsorption on Fuller's earth, and the Auto Analyzer method. In these comparative studies special attention is paid to the analysis of sera containing low (normal) substrate concentrations. Calculation of the orthogonal regression between the results obtained by the adsorption method (x) and the proposed method (y) gave: y=0.97x +/- 5 mumol/l (x=91.3 mumol/l, y-93.5 mumol/l), while for the correlation coefficient (r) 0.9721 was found. All sera (n=113) had creatinine concentrations between 40 and 180 mumol/l.

A simple micromethod for the direct determination of the total carbon dioxide content in biological fluids.

A simple method is presented for the determination of the total carbon dioxide content applicable to all biological fluids. This method makes use of a PCO2-electrode, placed in a perspex reaction/measuring chamber, connected with a IL blood gas analyzer, type 413 equiped with an electronic data-ready indicator system. The advantages of the proposed method are: 1. Depending upon the accuracy required for sera, the sample volume can be reduced to 20 or 10 micron1.2. A high degree of accuracy is obtained depending upon the sample volume used; for sera we calculated variation coefficients of 2%, 1% and 0.8% using sample volumes of 10, 20 and 30 micron 1, respectively. 3. The proposed method is simple and requires only two minutes for one determination. 4. In a comparative study an almost perfect relationship was found between the proposed method and the indirect method by calculation with a constant pK1g value.

Mammalian acetoacetate decarboxylase activity. Its distribution in subfractions of human albumin and occurrence in various tissues of the rat.

In this article further information is presented about the characteristics of the mammalian enzyme acetoacetate decarboxylase (acetoacetate carboxylase, EC 4.1.1.4). The Michaelis-Menten plot shows a sigmoidal relationship between the enzyme activity (v) and the substrate concentration (s) indicating an allosteric hindrance. Because of this, the KM value can only be predicted to be equal to or less than 1 X 10(-1) M. Cysteine and glutathione, although activating the spontaneous decarboxylation, have no effect upon the enzyme activity. From experiments with human albumin by means of gel filtration with Sephadex G-200, it can be concluded that the acetoacetate decarboxylase activity does not depend upon the degree of polymerisation of albumin. From experiments performed by means of ion exchange chromatography the enzyme activity may be localized in the non-mercaptalbumin fraction. Investigation of enzyme activity in homogenates of various rat tissues, as well as in their respective subfractions, reveals that: (1) the specific activity of brain tissue exceeds those of liver and kidney and (2) most of the activity in liver tissue is localized in the 20 000 X g supernatant, containing the endoplasmatic reticulum, the ribosomes and the soluble part of the cytoplasm, while in brain tissue a high activity is found in the nuclei fraction.

Sodium chloride restriction and extracellular fluid volume contraction in hyperphosphatiuric vitamin D resistant rickets in the Lowe syndrome.

A patient with a Lowe syndrome was observed from birth. Progressive hyperchloraemic renal tubular acidosis, hypophosphataemia, hyperphosphaturia and generalized hyperaminoaciduria had developed in infancy. Supplementary vitamin D, alkali and a high intake of dietary phosphate were unsuccessful in controlling the severe phosphate diabetes and rickets. Contraction of the extracellular fluid volume by dietary sodium restriction resulted in correction of the acidosis, hypophosphataemia, hyperaminoaciduria, and hyperphosphaturia, and healing of the rickets.

The syndrome of renal tubular acidosis with nerve deafness.

Two brothers with renal tubular acidosis and nerve deafness are described. Studies of the physiopathological characteristics of the renal acidification defect show that the defect is limited to the distal tubule. Renal tubular acidosis with nerve deafness is a distinct nosologic entity that is determined by an autosomal recessive trait.

Copper analysis of nail clippings. An attempt to differentiate between normal children and patients suffering from cystic fibrosis.

From 39 normal children and 36 patients, suffering from cystic fibrosis (C/F), the copper content of finger nail clippings and toe nail clippings were determined. From this study it can be concluded that, although the patients with cystic fibrosis (C/F) have a higher copper content, the determination of copper in nail samples cannot be used in order to differentiate between normal children and patients. Also higher mean copper concentrations were found in finger nail clippings in comparison with toe nails. This difference was significant for patients with cystic fibrosis.