Category-specific deficits for grammatical classes of words: evidence for possible anatomical correlates

The sialic acid content and the cell-surface hydrophobicity index of 40 group B streptococci (GBS) strains were assessed. GBS isolated from invasive infections (virulent strains) presented an increased level of sialic acid content (1.4%) when compared with GBS isolated from asymptomatic patients (0.53%). Treatment of GBS strain 85634 with neuraminidase resulted in a decrease (about 25%) in the net negative surface charge as assessed by cell electrophoresis. This finding suggests that sialic acid residues are important anionogenic groups exposed on GBS cell surface. N-acetylneuraminic acid was the only sialic acid derivative characterized in the strain 85634 as evaluated by gas-liquid chromatography. GBS from different serotypes presented a hydrophobic index mean value of 0.9. Even though the sialic acid contributed effectively to the negative charge on GBS cell surface, no difference was observed in the hydrophobic index when virulent and avirulent strains were compared.     

Influence of sex steroids on the secretory function of the epididymis in castrated rats

Secretory response of the epididymis to exogenously administered testosterone, estrogen and progesterone was investigated using the levels of sialic acid and glycerylphosphorylcholine as indices. Testosterone was found to be most potent in stimulating the (GPC) secretory function of the organ. An enigmatic finding of the present study was that while estrogen showed the ability to stimulate both sialic acid and GPC levels, progesterone exerted its influence only on sialic acid. Studies on the accessory genital organs (weight of seminal vesicles and ventral prostate and fructose level of coagulating gland) also revealed a stimulatory effect of the steroids.     

Evidence for multiple open and inactivated states of the hKv1.5 delayed rectifier

We previously found in human blood a fraction of low-density lipoprotein (LDL) that is characterized by a reduced content of sialic acid. Desialylated LDL also has a low neutral carbohydrate level, decreased content of major lipids, small size, high density, increased electronegative charge and altered tertiary apolipoprotein B structure. Unlike native LDL, this fraction of desialylated (multiple-modified) LDL induces the accumulation of lipids in smooth muscle cells cultured from unaffected human aortic intima, i.e. it exhibits atherogenic properties. In this study, we attempted to elucidate the mechanism of desialylation and other changes in the multiple-modified LDL by investigating the possibility of LDL modification by different cells and the blood plasma. A 24-h incubation at 37 degrees C of lipoprotein with intact endotheliocytes, hepatocytes, macrophages and smooth muscle cells or cell homogenates did not cause alterations either in the physical properties or in the chemical composition of native LDL. On the other hand, a significant fall in the lipoprotein sialic acid level was observed already after a 1-h incubation of native LDL with an autologous plasma-derived serum. While LDL sialic acid level continuously decreased, LDL became capable of inducing the accumulation of total cholesterol in the smooth muscle cells cultured from unaffected human aortic intima after 3 h of incubation. Starting from the sixth hour of LDL incubation with serum, a steady decrease in the lipoprotein lipid content was observed as well as the related reduction of LDL size. Following 36 h of incubation, an increase in the negative charge of lipoprotein particles was also seen. Prolonged incubation of LDL with plasma-derived serum (48 and 72 h) leads to the loss of alpha-tocopherol by the LDL as well as to an increase in LDL susceptibility to copper oxidation and to accumulation of cholesterol covalently bound to apolipoprotein B, a marker of lipoperoxidation. Degradation of apolipoprotein B starts within the same period of time. Hence, desialylation of LDL particles represents one of the first or the primary act of modification which is, apparently, a sufficient prerequisite for the development of atherogenic properties. Subsequent modifications just enhance the atherogenic potential of LDL. The loss of sialic acid by LDL occurred at neutral pH and was not inhibited by the sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. The [3H]sialic acid removed from LDL was not found in free form, but in the plasma fraction precipitated by trichloroacetic acid. These data along with the fact that cytidine-5'-triphosphate inhibited LDL desialylation suggest that enzymes close to sialyltransferases play a role in this process. Thus, this study demonstrated that the LDL modification processes imparting atherogenic properties to this lipoprotein can take place in human blood plasma. Multiple modification of LDL is a cascade of successive changes in the lipoprotein particle: desialylation, loss of lipids, reduction in particle size, increase of its electronegative charge and peroxidation of lipids.     

Influenza A virus lacking the NS1 gene replicates in interferon-deficient systems

Erythrocyte aggregation, which plays an important role in the physiological behavior of blood fluidity, was found to be enhanced in hypertension and hypercholesterolemia. While the role of macromolecule bridging force has been widely described, cellular factors related to membrane sialic acid content, which might contribute to the negative charge of cell surface causing the repulsion of erythrocytes, have been less studied. Cell age-dependent changes in membrane sialic acid content (in micromoles per gram of integral membrane protein) were investigated in 24 normotensive and 24 hypertensive matched subjects, each divided into 2 identical subgroups according to a cutoff of 6.2 mmol/L serum cholesterol. A progressive and significant (P<0.001) decrease in membrane sialic acid content associated with an increase (P<0.001) of disaggregation shear rate threshold (laser reflectometry in the presence of dextran) were observed with increased erythrocyte density (erythrocytes fractionated by density using ultracentrifugation) in both normotensive and hypertensive groups regardless of the cholesterol level. However, disaggregation shear rate threshold was significantly higher and sialic acid content was lower (P<0.001) in both hypertensive and normotensive subjects with hypercholesterolemia compared with either normotensive or hypertensive subjects with low cholesterol, respectively. A high membrane sialic acid content variance, beginning in the younger erythrocytes, was due mainly to triglyceride and LDL cholesterol levels (R2=0.49 for low, R2=0.43 for middle, and R2=0.54 for high densities, ie, young, mean, and senescent erythrocytes, respectively). We conclude that an early decrease in erythrocyte sialic acid content may influence the rheological properties of blood by increasing the adhesive energy of erythrocyte aggregates.     

Studies with an intravas nylon device in rat

Contraceptive efficacy of an intravas device (IVD) was investigated in rat. The IVD used consisted of a nylon suture which did not occlude the lumen of the vas completely and permitted a free passage of spermatozoa. Its presence for periods ranging from 15 to 180 days did not produce any changes in the histology of the testis and epididymis; In the vas deferens the tall columnar ciliated epithelium was replaced by squamous epithelium. A spermatic granuloma developed on the vas at the entry of the IVD and its frequency of occurrence and size increased with the passage of time. The device caused an increase in the vasal protein, sialic acid and phospholipid content, and a decrease in the level of glycogen and alkaline phosphatase activity at 15 days. The level of portein, glycogen and alkaline phosphatase activity returned to normalcy at 90 days but the sialic acid and phospholipid content remained elevated. Notwithstanding these alterations the device failed to affect the spermatozoal number, morphology, motility and their fertilizing ability. The significance of these findings is discussed.     

Studies on comprehensive evaluation of toxic hazard in low-concentration benzene pollution

Early adverse effects of exposure to benzene in a concentration less than 32 mg/m3 on the employees' health were comprehensively evaluated with WHO neurobehavioral core test battery, cytokinesis-block micronucleus assay for peripheral blood lymphocytes, determination of serum level of sialic acid and T-lymphocyte assay with alpha-naphthyl acetate esterase (ANAE) stain. Results revealed emotional irritability could be found in the exposed employees and 24% of them showed an abnormal percentage of micronuclei formation and increased serum level of sialic acid.     

Tandem lesions and other products in X-irradiated DNA oligomers

Serum sialic acid is related to mortality from cardiovascular disease and is increased in patients with diabetic microangiopathies. The purpose of this study was to examine whether serum sialic acid is associated with ischemic disease of the lower extremities, using the ankle versus brachial arterial-pressure ratio. The subjects were NIDDM patients attending diabetic clinics. They received a questionnaire on smoking and duration of diabetes, and physical examinations including measurement of blood pressure of upper and lower extremities. Fasting blood was taken for measurement of sialic acid, total and HDL cholesterol, and HbA1c. Serum sialic acid was significantly correlated with ankle versus brachial arterial-pressure ratio (r = -0.32) and HbA1c (r=0.45). The correlation with ankle versus brachial arterial-pressure ratio was evident in the patients with low ankle versus brachial arterial-pressure ratios (r = -0.66), but was not significant in those with normal ankle versus brachial arterial-pressure ratios (r=0.16). The correlation with HbA1c was significant independently of ankle versus brachial arterial-pressure ratios. Mean serum sialic acid was higher in patients with very low ankle versus brachial arterial-pressure ratios (< 0.9) than in those with normal ankle versus brachial arterial-pressure ratios (> or = 1.0) or slightly low ankle versus brachial arterial-pressure ratios (0.9 approximately 1.0). These results suggest that serum sialic acid reflects the status of blood glucose control and the progression of ischemic disease of the lower extremities in NIDDM patients.     

In vivo bioactivities and clearance patterns of highly purified human luteinizing hormone isoforms

Previous studies have shown that highly purified isoforms of human pituitary LH exhibited a 20-fold range of in vitro bioactivities. The aim of this study was to determine the corresponding plasma half-lives, metabolic clearance rates (MCR), and in vivo bioactivities of these human (h) LH isoforms. Cannulated adult male rats were administered hLH isoforms as a bolus i.v. injection. For the half-life studies, blood was then serially collected over a 6-h period, and serum was assayed for hLH using a specific immunofluorometric assay. All hLH (n = 19) isoforms exhibited biexponential disappearance profiles with an initial fast half-life (t 1/2) for component A of 12.8 +/- 3.7 min, followed by a slow component B with t 1/2 of 58.9 +/- 4.4 min. The prevalence of component B in relation to component A increased significantly (r = 0.81, P < 0.001) over a 3-fold range when correlated with the sialic acid content of the isoform. Similarly, the MCR showed a significant correlation (r = 0.77, P < 0.001) with sialic acid content. The basis for the two t 1/2 components was then investigated. In the first experiment, rat plasma containing primarily component B was collected 90 min after hLH isoform administration and injected into a second animal. Only component B was observed with no evidence of component A, which indicates that the two t 1/2 components are not the product of the redistribution of the hLH isoform between body compartments. In the second experiment, component B was found to be dependent on sialic acid content, as desialylated hLH isoforms showed a rapid disappearance (t 1/2 = 8.6 +/- 3.1) with the component B proportion decreasing to < 10% of that of the nondesialylated control. This data indicates that sialic acid protects component B from rapid clearance. In addition, the proportion of the two components is dependent on sialic acid content, suggesting that the molecular location of the sialic acid on the carbohydrate moieties of hLH has a critical role in the clearance process. To determine the in vivo bioactivity of the hLH isoforms, an acute in vivo bioassay was developed in male rats. The assay was based on the hLH dose-dependent increase in total testosterone release in the same rat model as used in the plasma disappearance studies. Using the second International Standard (IS) hLH (0.3 IU-2.6 IU/kg) as standard, a linear dose-response of 24-h integrated serum testosterone levels was observed, with an index of precision of 0.11. Using this in vivo assay, a 16-fold range in in vivo bioactivities (3,200 to 51,100 IU/mg) was observed for 14 hLH isoforms. These in vivo bioactivities correlated with sialic acid content (r = 0.78, P < 0.001), MCR (r = 0.56, P < 0.05) and LH in vitro bioactivity (r = 0.75, P < 0.001) as determined using mouse Leydig cells in culture. Desialylation lead to over a 100-fold decrease in in vivo bioactivity of hLH. It is concluded that hLH isoforms are cleared in vivo by a two-component clearance mechanism, the proportion of which varies between isoforms and is dependent on sialic acid content of the isoform. These findings suggest that the molecular location of sialic acid on the hLH isoform is critical in defining the plasma disappearance of component B, whereas the mechanism of elimination of component A may well involve the hepatic GalNAc-sulphate receptor. Using an in vivo bioassay, the 16-fold difference in bioactivity between isoforms is attributed primarily to differences in their in vitro activity at the cellular level with a minor influence (< 2-fold) due to differences in in vivo clearance.     

Usefulness of biochemical tumor markers (CEA, Ca 19-9, ferritin and sialic acid) in diagnosis and prognosis of colonic neoplasms

The aim of the study was: to determine the value of CEA, Ca 19-9, ferritin and sialic acid in diagnostics, to assess the prognostic role of serum CEA and Ca 19-9 levels before surgery and to evaluate their usefulness in diagnostics of recurrences. The study included 352 patients with colorectal carcinoma (adenocarcinoma). The preoperative level of CEA was elevated in 286 patients, Ca 19-9 in 108, ferritin in 60 and sialic acid in 58 patients. All of them are poor markers in diagnostics because of the low sensitivity, respectively 47.6%, 37.0%, 16.7% and 55.2%. Preoperative high, CEA and Ca 19-9 values are associated with a significantly poorer prognosis and with frequency of recurrences.     

Sialic acid determinations of serum and urine specimens in calcium-containing urinary stone formers

PURPOSE: The aim of the present study was to compare sialic acid concentrations of serum and urine specimens in both calcium (Ca)-containing urinary stone formers and non-stone formers. Moreover, we studied inhibitory activity of sialic acid upon the calcium oxalate (CaOx) crystal aggregation and growth. MATERIALS AND METHODS: Sialic acid determinations were done on fresh serum and urine samples of 35 Ca-containing urinary stone formers (stone formers group) and 20 non-stone formers (patient controls group). Inhibitory activity of sialic acid upon the CaOx crystal aggregation and growth was studied by using in vitro assay method of seed crystal system. RESULTS: Serum sialic acid concentrations were found to be similar in the two groups. Urinary sialic acid concentrations were significantly lower in the urine specimens of stone formers than in their patient controls. Sialic acid showed a dose dependent inhibitory activity upon the CaOx crystal aggregation and growth into seed crystal method. CONCLUSION: It is suggested that urinary sialic acid may play some role during the phase of stone formation from the results of the present study, because sialic acid shows marked inhibitory activity upon the CaOx crystal aggregation and growth at concentrations higher than 100 mg/dl.     

Optimization of the assay for sialic acid determination in low density lipoprotein

Sialic acid level in blood plasma and circulating glycoproteins is considered to be a marker for a number of pathologic conditions, including atherosclerosis, cancer, etc. The precise measurement of sialic acid level is an important laboratory procedure to allow correct interpretation of results. Colorimetric methods commonly used for the measurement of sialic acid are not highly specific, as interfering substances may alter the results. Among these, malondialdehyde and other aldehydes play the decisive role. In the circulation, aldehydes are commonly produced during lipid peroxidation in the lipid core of lipoprotein particles, especially low density lipoprotein (LDL). To establish the impairment to the sialic acid determination in LDL introduced by interfering substances, the optimized assay based on Warren's traditional method was developed and tested in 606 LDL samples. The optimization implies the comparison of color developed using the standard Warren procedure with that due to contaminating agents, mainly thiobarbituric acid-reactive substances (TBARS). In LDL stored at 4 degreesC, the estimates obtained by the modified procedure were 41.5% or 30.1 nmol/mg lower, on average, compared to the standard procedure (n = 45, P < 0.0001). Even in LDL stored at -70 degreesC, sialic acid estimates obtained by the modified procedure were 6.6% or 3.6 nmol/mg lower, on average, compared to the standard measurement (n = 561, P < 0.005). Thus, the modified procedure avoids significant distortion of the measurement induced by the presence of interfering agents.     

Outcome and changing cause of unilateral vocal cord paralysis

In order to examine the effects of altered protein sialylation on neural cell function, B104 rat neuroblastoma cells were stably transfected with the cDNA coding for alpha2,6(N) sialyltransferase (ST(6)N). Lectin blot analysis of the clones demonstrated an increase in staining of the Sambucus nigra lectin, which detects alpha2,6 linked sialic acid, in parallel with enzyme activity. There was a concomitant decrease in staining by the Maackia amurensis lectin which labels alpha2,3-linked sialic acid, indicating that the individual sialyltransferase enzymes may compete for penultimate galactose acceptor sites. While there was an initial increase in protein-bound sialic acid in parallel with enzyme activity, the sialylation of the cells was demonstrated to be saturable. There was an inverse relationship between cell adhesion to a fibronectin substrate and ST(6)N activity suggesting that the negatively charged sugar acts to modulate cell-substrate interaction. These cells will provide an ideal model system with which to further investigate the effect of altered sialic acid on neural cell function.     

Quantitative analysis of bacterial toxin affinity and specificity for glycolipid receptors by surface plasmon resonance

The primary virulence factors of many pathogenic bacteria are secreted protein toxins which bind to glycolipid receptors on host cell surfaces. The binding specificities of three such toxins for different glycolipids, mainly from the ganglioside series, were determined by surface plasmon resonance (SPR) using a liposome capture method. Unlike microtiter plate and thin layer chromatography overlay assays, the SPR/liposome methodology allows for real time analysis of toxin binding under conditions that mimic the natural cell surface venue of these interactions and without any requirement for labeling of toxin or receptor. Compared to conventional assays, the liposome technique showed more restricted oligosaccharide specificities for toxin binding. Cholera toxin demonstrated an absolute requirement for terminal galactose and internal sialic acid residues (as in GM1) with tolerance for substitution with a second internal sialic acid (as in GD1b). Escherichia coli heat-labile enterotoxin bound to GM1 and tolerated removal or extension of the internal sialic acid residue (as in asialo-GM1 and GD1b, respectively) but not substitution of the terminal galactose of GM1. Tetanus toxin showed a requirement for two internal sialic acid residues as in GD1b. Extension of terminal galactose with a single sialic acid was tolerated to some extent. The SPR analyses also yielded rate and affinity constants which are not attainable by conventional assays. Complex binding profiles were observed in that the association and dissociation rate constants varied with toxin:receptor ratios. The sub-nanomolar affinities of cholera toxin and heat-labile enterotoxin for liposome-anchored gangliosides were attributable largely to very slow dissociation rate constants. The SPR/liposome technology should have general applicability in the study of glycolipid-protein interactions and in the evaluation of reagents designed to interfere with these interactions.     

Participation of sialic acid residue in the fibrinogen-fibrin conversion by thrombin

In order to estimate the effects of sialic acid residues in fibrinogen on the fibrinogen-fibrin conversion by bovine thrombin the Michaelis constant (Km) and maximum velocity (Vmax) were determined. The Km value obtained by the use of intact-fibrinogen was smaller than that of asialo-fibrinogen. This fact suggests that the sialic acid residues affected the formation of the enzyme-substrate complex. It was also found that in comparison with the asialo-fibrinogen, the intact-fibrinogen was significantly influenced in the gel formation time by the ionic strength in the reaction solution.     

Infection of glial cells by the human polyomavirus JC is mediated by an N-linked glycoprotein containing terminal alpha(2-6)-linked sialic acids

The human JC polyomavirus (JCV) is the etiologic agent of the fatal central nervous system (CNS) demyelinating disease progressive multifocal leukoencephalopathy (PML). PML typically occurs in immunosuppressed patients and is the direct result of JCV infection of oligodendrocytes. The initial event in infection of cells by JCV is attachment of the virus to receptors present on the surface of a susceptible cell. Our laboratory has been studying this critical event in the life cycle of JCV, and we have found that JCV binds to a limited number of cell surface receptors on human glial cells that are not shared by the related polyomavirus simian virus 40 (C. K. Liu, A. P. Hope, and W. J. Atwood, J. Neurovirol. 4:49-58, 1998). To further characterize specific JCV receptors on human glial cells, we tested specific neuraminidases, proteases, and phospholipases for the ability to inhibit JCV binding to and infection of glial cells. Several of the enzymes tested were capable of inhibiting virus binding to cells, but only neuraminidase was capable of inhibiting infection. The ability of neuraminidase to inhibit infection correlated with its ability to remove both alpha(2-3)- and alpha(2-6)-linked sialic acids from glial cells. A recombinant neuraminidase that specifically removes the alpha(2-3) linkage of sialic acid had no effect on virus binding or infection. A competition assay between virus and sialic acid-specific lectins that recognize either the alpha(2-3) or the alpha(2-6) linkage revealed that JCV preferentially interacts with alpha(2-6)-linked sialic acids on glial cells. Treatment of glial cells with tunicamycin, but not with benzyl N-acetyl-alpha-D-galactosaminide, inhibited infection by JCV, indicating that the sialylated JCV receptor is an N-linked glycoprotein. As sialic acid containing glycoproteins play a fundamental role in mediating many virus-cell and cell-cell recognition processes, it will be of interest to determine what role these receptors play in the pathogenesis of PML.     

Relationship between serum total sialic acid and C-reactive protein in silicosis

Serum total sialic acid and C-reactive protein (CRP) were studied in 68 patients with silicosis divided into 3 groups according to the evolutive stage of disease. The results were compared with the data obtained in a control group of 35 healthy subjects. The changes in serum total sialic acid levels were in parallel with those of CRP in silicosis. Patients in stage III had the highest mean values of serum total sialic acid (p < 0.01) and of CRP (p < 0.001). Linear regression analysis revealed a close positive correlation between serum total sialic acid and CRP levels in silicosis (r = 0.86, p < 0.01).     

Platelet sialic acid and platelet survival after aggregation by ADP

Some investigators have reported recently that platelet surface sialic acid is decreased during ADP-induced aggregation, whereas others have reported an increase. Since removal of sialic acid from the platelet surface shortens platelet survival, we have determined the survival of platelets that have been aggregatad by ADP. We have also measured the amount of sialic acid in the suspending fluid of platelets after ADP-induced aggregation. ADP-induced aggregation did not cause the loss of sialic acid from rabbit platelets (which do not undergo a release reaction in response to ADP) nor from washed human platelets in a medium containing physiologic concentrations of calcium in which granule contents are not released. In a medium without added calcium, ADP caused the release of 14C-serotonin (42.5% +/- 3%) from human platelets, but less than 4% of the sialic-acid-containing material was released. It seems likely that little of the releasable sialic acid of platelets is in the dense granules or the alpha-granules. Thrombin (5 U/ml) released 90.0% +/- 3.4% of the serotonin from human platelets but only 20.6% +/- 7.4% of the total sialic-acid-containing material. Neuraminidase removed 42.3% of the total sialic acid, presumably from the platelet surface. Rabbit platelets that had been aggregated by ADP and deaggregated survived normally when returned to the circulation. This observation also provides evidence that they had not lost membrane sialic acid during aggregation and deaggregation.     

Purification of the lysosomal sialic acid transporter. Functional characteristics of a monocarboxylate transporter

Sialic acid and glucuronic acid are monocarboxylated monosaccharides, which are normally present in sugar side chains of glycoproteins, glycolipids, and glycosaminoglycans. After degradation of these compounds in lysosomes, the free monosaccharides are released from the lysosome by a specific membrane transport system. This transport system is deficient in the human hereditary lysosomal sialic acid storage diseases (Salla disease and infantile sialic acid storage disease, OMIM 269920). The lysosomal sialic acid transporter from rat liver has now been purified to apparent homogeneity in a reconstitutively active form by a combination of hydroxyapatite, lectin, and ion exchange chromatography. A 57-kDa protein correlated with transport activity. The transporter recognized structurally different types of acidic monosaccharides, like sialic acid, glucuronic acid, and iduronic acid. Transport of glucuronic acid was inhibited by a number of aliphatic monocarboxylates (i.e. lactate, pyruvate, and valproate), substituted monocarboxylates, and several dicarboxylates. cis-Inhibition, trans-stimulation, and competitive inhibition experiments with radiolabeled glucuronic acid as well as radiolabeled L-lactate demonstrated that L-lactate is transported by the lysosomal sialic acid transporter. L-Lactate transport was proton gradient-dependent, saturable with a Km of 0.4 mM, and mediated by a single mechanism. These data show striking biochemical and structural similarities of the lysosomal sialic acid transporter with the known monocarboxylate transporters of the plasma membrane (MCT1, MCT2, MCT3, and Mev).     

Sialic acid in lymphocytes and sera from mothers and their newborns after normal deliveries

Sialic acid was determined in newborn and maternal lymphocytes as well as in newborn and maternal serum immediately after normal deliveries. A significant increase in sialic acid in newborn as compared to maternal lymphocytes was found. Sialic acid concentration seems to be sex-dependent for newborn lymphocytes only, and higher concentrations of sialic acid were observed in male as compared to female newborn lymphocytes. No differences between the sialic acid concentration in maternal and control lymphocytes could be found. In newborn serum, sialic acid was significantly reduced as compared to maternal or control serum. No sex-linked differences were observed. No differences between the concentration of maternal and control serum were detected.     

Plasma sialic acid as a marker of the effect of the treatment on metastatic colorectal cancer

The concentration of total sialic acid (TSA) is increased in the plasma of patients with many types of cancer. The purpose of this study was to assess the usefulness of the TSA marker in predicting the efficacy of the treatment, and to compare TSA with two common markers, carcinoembryonic antigen (CEA) and the carbohydrate antigen 19-9 (CA 19-9). The study was performed on 44 patients treated for advanced colorectal carcinoma by a weekly 8 h continuous infusion of 5-fluorouracil (1300 mg/m2) plus bolus injection of L-folinic acid (100 mg/m2). TSA, CEA and CA 19-9 levels were measured before and after 3 months of treatment and their variations analysed as a function of the response to the treatment. TSA levels of patients with metastatic colorectal carcinoma before treatment (959 +/- 265 mg/l) were significantly higher than those of 32 healthy people (584 +/- 99 mg/l). The percentage of patients with TSA concentration above the cut-off level (782 mg/l) was 73% before treatment and 23% after. All patients who experienced an objective response to the treatment (complete, partial or minor response) (n = 29) had a significant decrease of TSA levels (t = 5.96; P < 0.001). When the disease was considered as stabilised (n = 10), TSA changed slightly, but it increased with progressive disease (4 out of 5 patients). Changes in CEA and CA 19-9 did not correlate as well as TSA to the treatment efficacy. Initial levels of TSA did not permit prediction of the efficacy of the treatment since they were not significantly different between the five response groups. TSA seems to be more likely involved in tumour changes than in tumour volume. Its determination could provide useful information about the spreading and metastatic properties of the tumour. TSA normalisation is an indicator of probable tumour growth arrest and its elevation could be a marker of relapse.