Melting temperature analysis as quantitative method for detection of point mutations

Different methods have been devised to detect point mutations. Some are very sensitive, detecting mutations even in a background of normal tissue, but none provide information about the percentage of cells with mutant DNA. Here we describe an easy, fast and reliable method, melting temperature analysis, which not only detects point mutations but also provides quantitative information on the percentage of cells with mutant DNA. By this method we detected a G-A transition in codon 12 of the K-ras gene in DNA of subjects with colorectal cancer. The K-ras mutation was found in 9/10 bowel cancers and 8/10 normal adjacent samples. It was also detected in 4/7 stool samples from the same patients. In colorectal cancers, the proportion of K-ras mutant cells was variable: in two the mutant/wild-type DNA ratio was 30/70, in three 50/50, and in four 70/30. Melting temperature analysis was sensitive for the detection of point mutations in bowel cancer and also in apparently normal tissue, providing quantitative information about the percentage of cells with mutant DNA.

Purine nucleotide catabolism in rat liver: labelling of uric acid and allantoin after treatment with oxonic acid and allopurinol

In our previous experiments on rat liver we found that 15' after intraperitoneal administration of 14C-formate the specific radioactivity of allantoin was always higher than that of uric acid. The present experiments have been carried out to interpret this unexpected result, which was only observed in liver and we studied: a) the incorporation of 14C-glycine into uric acid and allantoin; b) the effects of two competitive inhibitors of xanthine oxidase and uricase, oxonic acid and allopurinol respectively, on levels of uric acid and allantoin in liver and on their specific radioactivity after administration of labelled precursor. The results suggested: a) that under normal conditions, the formation of allantoin is so fast that it exceedes export from liver to serum, and thus the radioactivity of labelled precursors accumulates in allantoin; b) that when allopurinol or oxonic acid are administered, the rate of export exceeds that of allantoin formation and the incorporation of radioactivity into allantoin is lower; c) that not all the data, however, could be interpreted on this basis, but seems to require the existence of different pools of uric acid, which are transformed separately into allantoin.

Comparative determination of purine compounds in carotid plaque by capillary zone electrophoresis and high-performance liquid chromatography

Allantoin, uric acid (UA), hypoxanthine (Hx) and xanthine (X) were determined on carotid plaque by capillary zone electrophoresis (CZE) and high-performance liquid chromatography (HPLC). Comparison of the results showed that capillary zone electrophoresis may have similar or even superior analytical performance to HPLC, especially for the determination of allantoin in biological samples.

Determination of p185 and adenylosuccinate lyase (ASL) activity in preneoplastic colon lesions and intestinal mucosa of human subjects

OBJECTIVES

The HER2 gene has been found amplified in a number of human adenocarcinoma leading to elevated levels of expression of its encoded product, p185 protein. Because little information is available on the tissue and tumor specificity of this gene product, we studied the expression of p185 protein in preneoplastic colon lesions. Adenylosuccinate lyase (ASL, EC 4.3.2.2) is known to increase in malignancies such as colorectal, breast, and prostate cancer. In order to evaluate the potential of ASL as a tumor marker, its activity was determined and compared with the expression of p185.

DESIGN AND METHODS

p185 was determined by an immunohistochemical procedure in patients with the preneoplastic lesions. ASL activity was evaluated in intestinal mucosa adjacent to colorectal cancers (patient group A) and in preneoplastic colorectal lesions (group B). The enzyme activity was evaluated in dialyzed supernatants, following the disappearance of substrate (adenylosuccinate AMP-S) and the formation of product (adenosine 5'-monophosphate-AMP), separated by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Increased expression of p185 and elevated ASL activity were observed in tubular and tubulo-villous adenoma and may, therefore, be associated with the early stages of colorectal cancer.

Behaviour of human lymphocytic isoenzymes of 5'-nucleotidase

The behaviour of 5'-nucleotidase isoenzymes (ecto-5'-nucleotidase, e-Ns and c-N-II soluble 5'-nucleotidases) was studied in lymphocytes from patients with B-cell chronic lymphocytic leukemia. A strong reduction in ecto- and soluble activities was observed, although the pattern of the three 5'-nucleotidases did not always strictly overlap. A significant decrease (p<0.05) in ecto-5'-nucleotidase, e-Ns and c-N-II was found in B and T populations (B lymphocytes: 1.13, 0.88 and 1.26 nmol/h/10(6) cells versus 95.96, 9.64 and 13.73 nmol/h/10(6) cells in controls; T lymphocytes: 1.31, 0.23 and 0.06 nmol/h/10(6) cells versus 9.25, 1.31 and 2.10 nmol/h/10(6) cells in healthy subjects). The percentage of ecto-5'-nucleotidase-positive cells (CD73+) was reduced in leukemia patients, indicating a lower number of active molecules on the cell surface. The results of RT-PCR analysis showed that the ecto-5'-nucleotidase mRNA of leukemia patients was not defective.

Fast-atom bombardment mass spectrometry for mapping of endogenous methylated purine bases in urine extracts

Fast-atom bombardment (FAB) mass spectrometry, linked with tandem mass spectrometry (MS/MS), was employed for the identification of methylated purine bases in four urinary extracts of healthy subjects and fourteen urinary extracts of patients bearing colorectal tumors. In order to obtain an easy structural identification of the species present in urinary extracts, the MS/MS spectra of MH+ species of twenty nine diagnostically relevant purine bases were studied. Even if definitive quantitative data cannot be obtained by this approach, FAB mass spectra of urine extracts lead to a readily reproducible mapping of endogenous purine bases, allowing a distinction between healthy and sick subjects. Bases such as 9-ethyladenine, N6-2-isopentenyladenine and N6-benzyladenine were detected only in urine samples of colorectal tumor bearing patients. The detection in urine of compounds such as 7-methylguanine and 1-methylguanine, and their increase in the urine of colorectal tumor bearing patients, has been justified either by a more rapid turnover of nucleic acids in tumor tissue or by an increase in the extent of their methylation. The obtained results indicate that the method can be employed for diagnostic purposes.

Serum erythropoietin and blood lead concentrations

The aim of the study was to test the hypothesis that high blood lead levels are associated with depressed serum erythropoietin concentrations in workers occupationally exposed to lead. The results in exposed workers and in a control group of unexposed subjects were compared. Blood lead values were < or = 20 micrograms/dl in unexposed subjects and > or = 30 micrograms/dl in exposed subjects. The two groups of exposed workers and the control population were matched for sex and age. Hemoglobin levels were not affected by blood lead values and did not differ significantly between the three groups. The two-tailed, nonparametric Mann-Whitney U-test was used to compare unpaired groups. The Spearman rank correlation test was used to evaluate the dose-effect relationship between Pb and EPO. The analysis of the data indicate that erythropoietin values are significantly lower in exposed subjects than a controls. However no correlation was demonstrated between blood lead concentrations and erythropoietin in any group.

Levels of folic acid in plasma and in red blood cells of colorectal cancer patients

The levels of folic acid have been determined by radioimmunological method in the plasma and in the red blood cells of normal subjects and colorectal cancer patients. A decrease was evident both in the plasma and erythrocytes of cancer patients. The possible reasons and applications of this observation are discussed.

Patient education: renal osteodystrophy and adequacy of dialysis

At The Kidney Center of Delaware County in Southeastern Pennsylvania, tools were developed that address adequacy of dialysis and renal osteodystrophy. Team members use the tools to provide quality care and education of patients. In this article, the tools, their use, and their benefits, are discussed.

Different mass spectrometric approaches in the identification of endogenous methylated purine bases in urine extracts

A preliminary identification of endogenous and exogenous methylated purine bases in urinary extracts of healthy and tumor-bearing subjects has been performed using high performance liquid chromatography, and tandem mass spectrometry (MS/MS). MS/MS gave particularly fast and sensitive analyses, allowing the simultaneous and rapid determination of 26 different urinary methylated purines. Both sets of data confirm that tumor-bearing patients show changed levels of methylated purine bases.

Pattern of vitamin B12 and folic acid during pregnancy

The aim of this study was to evaluate folate and vitamin B12 serum concentrations and their reciprocal relationships during pregnancy in relation to gestational age and levels of hemoglobin. Serum levels of vitamin B12 (B12) and folic acid (FA) were assessed by RIA in 213 women between the 6th and 43rd week of pregnancy. For 195 of these subjects, hemoglobin and hematocrit values were available. The logarithm (log) of B12 levels was found to be inversely correlated with weeks of pregnancy (R = -0.261; p < 0.001). A decrease in B12 levels occurred before the 27th week and was significant only in the subgroup of patients having hemoglobin levels above 11 g/dl. The log FA concentrations did not show any significant correlation with weeks of pregnancy irrespective of Hb levels. There was also a highly significant correlation between log B12 and log FA after 27 weeks and in the subgroups divided according to Hb levels (< or = and > 11 g/dl). It is therefore concluded that: (1) the demand for vitamin B12 is high in the first 27 weeks of pregnancy due to increasing maternal and embryo-fetal erythropoiesis and in order to sustain normal maternal Hb levels in the last weeks of pregnancy; (2) vitamin B12 might favor the absorption and utilization of FA after 27 weeks of pregnancy.

Nitrogen metabolism during liver regeneration

Nitrogen metabolism was investigated in regenerating liver-bearing rats through the following parameters: (1) liver aminoacid content, (2) plasma and urinary urea and creatinine, (3) plasma and urinary oxypurines, uric acid and allantoin. Two groups of aminoacids were considered: (1) the essential aminoacids (phenylalanine, tyrosine, isoleucine, lysine, leucine, valine, arginine, histidine and methionine); (2) the non-essential aminoacids (aspartic acid, asparagine, glutamic acid, glutamine, alanine, glycine, serine, threonine and proline). Some of the first group tended to decrease, and those of the second group to increase, immediately after partial hepatectomy. Few ketogenic aminoacids are probably oxidized to provide energy. The flux of aminoacids for gluconeogenesis is minutely controlled, therefore, those of the second group being spared at first and set aside for protein synthesis, which increases on the second and third days after partial hepatectomy. Plasma and urinary urea, oxypurines, uric acid and allantoin did not show any significant variations after partial hepatectomy. The conclusion emerging from the present research is that, although variations in aminoacid composition and metabolism and in purine nucleotide metabolism have been demonstrated to occur in the regenerating liver, the overall nitrogen catabolism, as reflected by the principal end products, does not undergo substantial variations. The remaining liver is able to fulfil this function.

Erythropoietin and transferrin concentrations during pregnancy in relation to hemoglobin levels

Serum levels of erythropoietin (EPO) were assayed by ELISA at the same time as red blood cells (RBC), hemoglobin (Hb), hematocrit (Hct), serum iron and transferrin in 136 pregnant women, divided on the basis of hemoglobin values (> or < or = 10.5 g/dl) and weeks of pregnancy (< or > or = 27th week). In the overall population, a parallel increase with weeks of pregnancy was shown by serum concentrations of EPO expressed as a logarithm (multiple R = 0.367, P < 0.0001), and transferrin levels (multiple R = 0.529, P < 0.0001). It was found that EPO levels did not differ significantly between anemic and non-anemic patients before the 27th week, but the difference became highly significant (P < 0.01) after the 27th week in favour of anemic patients. Before the 27th week, the correlations between log EPO and RBC, Hct, Hb and iron were not significant, whereas the correlation between log EPO and transferrin was significant (P < 0.01); after the 27th week, the correlations and significance of the regression found were: log EPO vs Hb (Pearson coefficient = -0.384; P < 0.001), vs Hct (Pearson coefficient = -0.370; P < 0.01), vs transferrin (Pearson coefficient = 0.392; P < 0.0001), vs iron (Pearson coefficient = -0.274, P < 0.05). In the population divided according to Hb levels, the correlation was positive and significant in both groups between log EPO and transferrin (Hb > 10.5 g/dl: Pearson coefficient = 0.524, P < 0.0001; Hb < or = 10.5: Pearson coefficient = 0.614, P < 0.0001), but was inverse and significant only in the group with Hb < or = 10.5 g/dl between log EPO and serum iron (Pearson coefficient = -0.481, P < 0.01). The variations in EPO were related to Hb levels after the 27th week of pregnancy and were closely correlated with transferrin over the whole period. The physiological mechanism of these changes is discussed.

Effects of testosterone on cholesterol levels and fatty acid composition in the rat

The effects of testosterone treatment on cholesterol levels and its fatty acid components were studied in adult rats. Cholesterol levels increased both in the liver and in the serum of castrated rats. Androgen administration restored the normal values only in the serum. A general decrease in unsaturated and essential fatty acids in cholesterol esters was evident after testosterone administration. In the liver, only the C16:O/C16:1 ratio clearly increased after testosterone administration, which inhibited the delta 9 unsaturation of palmitic acid, but not of stearic acid. In the serum the C16:O/C16:1, C18:O/C18:1, and C18:2/C2O:4 ratios decreased after castration and were restored by testosterone. The results indicate a clear inhibition of delta 9 unsaturation of palmitic and stearic acids, of delta 5 unsaturation and elongation in organs other than the liver. No effect was evident on delta 6 unsaturation. This suggests that fatty acid unsaturations are regulated differently by testosterone in different tissues. For delta 9 unsaturation in the liver, the effect also seems to be substrate-dependent.

Levels and variability of purine nucleotides in normal human lymphocytes

Anion-exchange, high performance liquid chromatography was used to determine purine nucleotides in lymphocytes of healthy males and females of various ages. We observed a considerable dispersion of values which were unrelated to age or sex, possibly linked to various states of activation of circulating lymphocytes and to other unknown factors.

[Enzymes of the inosinic crossing point in human lymphocytes]

At the "inosinic branch point", inosinic acid (IMP) can be channelled either to guanylic acid (GMP) or to adenylic acid (AMP). The 4 enzymes involved in these processes are IMP-dehydrogenase (IMP-DH) and GMP synthetase for the formation of GMP and adenylosuccinate (AMP-S) synthetase and lyase for the formation of AMP. The Authors study the behavior of these enzymes in peripheral blood lymphocytes from normal and leukemic patients. The cells were isolated as previously reported. GMP synthetase was assayed with radiochemical method, IMP-DH and AMP-S synthetase with a radiochemical method coupled to HPLC, while AMP-S lyase was determined following the formation of AMP separated by AMP-S by HPLC, without using labelled precursors. Except for GMP synthetase, which was very low, no activity was detectable in normal lymphocytes; while AMP-S was absent also in leukemic cells, the remaining three activities were well evident. The results open the possibility of using the inosinic branch point enzymes as tumor markers.

[Behavior of the enzymes of the salvage pathway of purine bases in leukemia lymphocytes]

The Authors present a procedure for the determination of adenine phosphoribosyltransferase (APRT) and hypoxanthine phosphoribosyltransferase (HPRT) in lymphocytes which exhibits high sensitivity and requires low quantities of lymphocytes. 5 normal subjects and 4 patients affected by chronic lymphocytic leukemia (CLL) were considered. Human lymphocytes were prepared and treated as previously reported. To the incubation mixtures buffered with 50 mM TRIS-HCl pH 7.4 either 14C-adenine or 14C-hypoxanthine was added: after deproteinization and neutralization we followed the formation of either 14C-adenylic acid (AMP) or 14C-inosinic acid (IMP) by HPLC. A Supelcosil C18 5 microns (250 X 4.5 mm) column was used: IMP was eluted with 20 mM KH2PO4 pH 5.5 while AMP with a linear gradient to 40% B in 20 min., where A was 20 mM KH2PO4 pH 5.5 and B methanol/water 60:40. Evaluation of AMP and IMP formed was carried out by determination of the radioactivity of the collected peaks. The values of APRT in leukemic patients were enhanced when referred to the proteins and those of HGPRT decreased: the Authors propose to complete the study evaluating the intracellular content of adenine and hypoxanthine.

Plasma oxypurines in gastric and colorectal cancer

Reverse phase high performance liquid chromatography has been used for the determination of plasma hypoxanthine, xanthine, and uric acid in normal subjects and in patients with gastric and colorectal cancer. Plasma oxypurines are significantly elevated in either type of cancer, while uric acid concentration is only higher in gastric cancer. The variations are related to the stage of the tumors, and the physiopathology of their occurrence is discussed.

[Analysis of uric acid and oxypurines in normal subjects and in gout patients]

The behavior of plasma and urine oxypurines (hypoxanthine and xanthine) and of uric acid has been studied in normal subjects and in gout patients. Oxypurines and uric acid were increased in the plasma of gout patients but only the urinary excretion of hypoxanthine was higher in this group. The interpretation of the observed variations is discussed.

[Clearance of oxypurines in normal subjects and in gout patients subjected to a purine-free diet. Effects of allopurinol]

The clearance of uric acid, hypoxanthine and xanthine has been examined in gout patients and in normal subjects compared to creatinine, after a purine-free diet. The treatment decreased the clearance in normal subjects, but showed an opposite effect in gout patients. The clearances both of uric acid, hypoxanthine and xanthine were enhanced by allopurinol. The interpretation of the observed variations is discussed.

[Clearance of oxypurines and uric acid in patients with gout]

The clearance of uric acid, hypoxanthine and xanthine has been examined in gouty patients and in normal subjects comparatively to the creatinine clearance. The clearance of the three purine compounds was lower in the gouty patients, while the creatinine clearance showed a normal behavior. These results indicate that either the tubular excretion or the carriers of the considered metabolites probably undergo specific alterations in the gout.

[Behavior of plasma and urine purines, after a purine-free diet, in normal subjects and patients with gout]

Plasma and urine oxypurines (hypoxanthine and xanthine) and uric acid, were evaluated in normal subjects and in gouty patients before and after a purine free diet. After a 7-days period, plasma oxypurines were remarkably higher in normal subjects, while they did not undergo variations in gouty patients, which showed higher in basal conditions. No significant changes in urinary excretion were observed in both cases. The interpretation of the observed variations is discussed.

[Purine metabolism in human tumors]

Levels of oxypurines (hypoxanthine and xanthine) and uric acid were measured in plasma and urine of tumor bearing patients (gastric and colon rectal tumors), and of subjects affected by non specific diseases. In both groups, an increase in plasma purine bases and a decrease of their excretion was observed as compared to healthy controls; no substantial variations concerning uric acid were found. Possible mechanisms inducing alterations of purine metabolism in so different conditions are discussed.

The excretion of oxypurines in normal subjects

Reverse phase high performance liquid chromatography was used for the determination of urinary hypoxanthine and xanthine in normal subjects. The values observed in normal subjects agree with those reported by other authors. Excretion of hypoxanthine and xanthine was not related to sex. Urinary oxypurines were related to age, and, when corrected for body surface area (1.73 m2), they were significantly higher in normal children under 15 years of age than in adults.