Vibrio Cholerae neuraminidase susceptible N-acetyl neuraminic acid (sialic acid) levels in human leukaemia.
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Granulocytes↗
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Anti-inflammatory effect of sialic acid.
Sialic acid was shown to possess anti-inflammatory properties as measured by carrageenan-induced rat paw oedema and pleurisy tests. As the number of leukocytes mobilized was significantly reduced it was concluded that the inhibitory effect of sialic acid on leukocyte accumulation is responsible for the inhibition of exudate/oedema formation.
Animals↗
Cytidine-5'-monophosphate-N-acetylneuraminic acid. Asialoglycoprotein sialic acid transferase activity in liver and serum of patients with juvenile hepatic cirrhosis and alpha-1-antitrypsin deficiency.
The molecular basis for the accumulation of a substance which displays the immunological reactivity of alpha-1-antitrypsin within vesicles of liver parenchymal cells of individuals with hepatic cirrhosis and serum alpha-1-antitrypsin deficiency remains unclear. We recently reported that serum from a patient with alpha-1-antitrypsin deficiency and hepatic cirrhosis was substantially deficient in sialyltransferease (EC 2.4.99.1) an enzyme which transfers sialic acid from cytidine 5'-monophosphate-N-acetylneuraminic acid to a variety of asialoglycoprotein acceptors. In the present report we have extended these studies to include serum from five additional patients with alpha-1-antitrypsin deficiency and juvenile hepatic cirrhosis as well as a liver specimen obtained at autopsy of one of these patients. We find the sialytransferase activity in serum from six patients with alpha-1-antitrypsin deficiency and hepatic cirrhosis to be 50% of healthy pediatric control values and 30% of pediatric patients with liver disease. However, serum from family members homozygous for alpha-1-antitrypsin deficiency but without hepatic cirrhosis, and serum from patients with a variety of other kinds of liver disease, failed to exhibit the marked sialytransferase deficiency. Similar assays carried out on a homogenate of a liver sample from one patient with alpha-1-antitrypsin deficiency and hepatic cirrhosis indicated that the deficiency of sialyltransferase activity was not demonstrable in liver. Furthermore, a comparative kinetic analysis of serum and liver sialytransferase in normal and afflicted individuals failed to detect differences in substrate affinities which might account for a decrease in functional sialyltransferase capacity in individuals with alpha-1-antitrypsin deficiency and hepatic cirrhosis. These observations suggest that the serum sialyltransferase deficiency in such patients probably arises after chronic and extensive liver disease involving hepatic accumulation of alpha-1-antitrypsin rather than the enzyme deficiency being the primary cause of the hepatic cirrhosis and alpha-1-antitrypsin deficiency.
Adolescent↗
Serum sialic acid levels in lung cancer patients.
The levels of N-acetyl neuraminic acid (sialic acid) in normal men and pre-and post-menopausal women were determined. Smoking post-menopausal estrogen therapy, oral contraceptives, and refreezing had no effects on sialic acid levels. Pre-treatment values from patients with lung carcinoma showed markedly elevated levels of sialic acid (0.697 +/- 0.149 muM/ml) as compared to those from normal controls (0.432 +/- 0.067 muM/ml). The potential usefulness of sialic acid as a biological marker is discussed.
Adenocarcinoma↗
Inhibition by N-acetyl neuraminic (sialic) acid of platelet aggregation induced by different stimuli.
Addition of N-acetyl neuraminic acid (sialic acid, NANA) to citrated rat platelet-rich plasma significantly inhibited aggregation induced by near-threshold concentration of ADP, collagen or thrombin. In heparinized rat platelet-rich plasma aggregation of platelets induced by endotoxin or tumour cells of various origins was also inhibited by sialic acid. It is suggested that exogenous or endogenous sialic acid may act against various aggregating stimuli on the platelet membrane by masking a common factor through which various aggregating agents exert their effect.
Adenosine Diphosphate↗
Sialic acid in thyroglobulin. II. Influence of sialic acid on ionization of tyrosine residues.
During electrophoresis in polyacrylamide gel at pH 9-5, it was noticed that sialic acid-poor thyroglobulin contains fewer low molecular weight fragments than sialic acid-rich thyroglobulin. Splitting off of sialic acid diminishes thenumber of phenolic groups of tyrosine, MIT, DIT and T4, which dissociate below pH 12-5. This phenomenon was interpreted as a result of lowered hydrophilia of these regions of the thyroglobulin molecule which contains tyrosine and its iodinated derivatives.
Animals↗
[Sialic acids in plants. Note III. Sialic acid content of pollens].
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Pollen↗
Influence of phospholids on liver damage. I. Carbontetrachloride poisoning and alterations in amino acid uptake, peroxidation, sialic acid content, and lysosomal enzymes.
Changes in peroxidation, amino acid uptake [alpha-amino isobutyrate (AIB)], sialic acid content and lysosomal enzymes were followed in rats after carbon-tetrachloride enzymes were followed in rats after carbontetrachloride poisoning and treatment with phospholipids (EPL). Uptake and retention of AIB by liver and brain increased after CCI4 poisoning. EPL had no effect on these changes. EPL diminished markedly, however, the excessive peroxidation caused by CC14.
Aminoisobutyric Acids↗
Glucose suppression of deoxyribose interference in the thiobarbituric acid determination of sialic acid.
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Animals↗
Inhibition of alkaline phosphatase by sialic acid.
The interaction of human organ alkaline phosphatases (orthophosphoric-monoester phosphohydrolases (alkaline optimum), EC 3.1.3.1) with sugars was studied. Hexosamines, N-acetylneuraminic acid (NANA or sialic acid), N-acetylmuramic acid and N-acetylglycolylneuraminic acid inhibited human organ alkaline phosphatase activities. Of these, sialic acid was the most effective inhibitor. The pH profiles for the enzymes in the absence and presence of sialic acid were similar. The sialic acid - enzyme complex was more heat stable than the free enzyme between 20 and 45 degrees C. Lineweaver-Burk plots of 1/v versus 1/S at various concentrations of sialic acid showed intersecting straight lines indicating that the mechanism of inhibition was a mixed type. The Ki value obtained from the plots of 1/v versus the square of sialic acid concentration was 0.07 mM for the hepatic, sialidase-treated hepatic, and intestinal alkaline phosphatases. The respective Hill coefficients varied somewhat with the alkaline phosphatase isoenzyme. Hyperbolic curves were obtained when the percentage of remaining activity was plotted against the substrate concentration at different concentrations of sialic acid. The Hill coefficient was lowered in the presence of sialic acid. The sialidase-treated hepatic enzymes used gave the most effective conversion. Partial denaturation of the enzyme with urea, or pronase digestion had a little if any effect on the sialic acid inhibition with constant time.
Alkaline Phosphatase↗
Stable thiobarbituric acid chromophore with dimethyl sulphoxide. Application to sialic acid assay in analytical de-O-acetylation.
With dimethyl sulphoxide instead of butanol in the thiobarbituric acid assay for sialic acid, a non-fading chromophore with lambdamax. = 549 nm was produced in a homogeneous solution, allowing dilution of the test mixture in case of high colour yield. This test adapted well to studies on alkaline de-O-acetylation. Bovine and rat submaxillary mucins, and rabbit Tamm-Horsfall urinary sialoproteins contain O-acetyl isomers of neuramine acid that are resistant to the thiobarbituric acid assay. Alkaline de-O-acetylation converted resistant O-acetylneuraminic acid into thiobarbituric acid-reactive sialic acid, and such conversion paralleled de-O-acetylation as measured by the ferric hydroxamate method. The colour increment was similar when the alkaline treatment of bovine submaxillary mucin either preceded or followed the acid hydrolysis. Only alkaline preptreatment was effective with rat submaxillary mucin. By selecting optimal conditions for alkaline de-O-acetylation, O-acetyl isomers can be accurately assessed by the thiobarbituric acid assay.
Acetylation↗
Sialic acid in human semen.
Sialic acid of seminal fluid of eighty two human subjects has been studied in relation to infertility. Normozoospermic group had highest sialic acid content (94 mgm/100 ml of the fluid) and was significantly different from other groups. The lowest sialic acid level was observed in necrozoospermic group (54 mgm/100 ml of the fluid). Azoospermic (62 mgm/100 ml) and vasectomised group (73 mgm/100 ml) had 33 and 22 percent less sialic acid level respectively than normozoospermic group. For the pooled observation sialic acid was found to be correlated (r = 0.282, significant at 5 percent level) with the total sperm count.
Fertility↗
Independence of sialic acid levels in normal and malignant growth.
Sialic acid content in breast or tumor tissue and serum of mouse strains that are either susceptible or resistant to breast cancer was measured at various age periods. Sialic acid content was also studied in normal lung tissue and in lung adenoma and hepatoma. Sialic acid levels during nonmalignant growth of a tissue were measured in breast tissue during pregnancy and lactation, and in regenerating liver, as well as in newborn and postnatal liver. The sialic acid content, when expressed per mg of protein, increased in mammary tumor, lung adenoma, and hepatoma. It also increased in nonmalignant growth of breast tissue during pregnancy and lactation and of regenerating liver and postnatal liver. Increase in sialic acid per mg DNA was observed only in lung tumors, regenerating liver, and postnatal liver. It appears that the changes in sialic acid level are independent of the normal or malignant growth of a tissue and that these changes might be the function of the parameter used to express the sialic acid values, i.e., either the DNA content or protein content of a given tissue.
Adenoma↗
Sialic acid uptake by fibroblasts.
The existence of surface sialytransferases that use cytidine monophosphate (CMP)-sialic acid as substrate has been postulated in previous studies. This is based on the assumption that if whole, viable cells can catalyze the transfer of sialic acid from CMP-sialic acid to endogenous acceptors, then the transferases carrying out the reaction must be on the cell surface, provided that (1) CMP-sialic acid does not enter the cells, and (2) CMP-sialic acid does not break down outside the cells, yielding free sialic acid which then may enter the cells, in amounts large enough to explain the incorporation. We now report evidence showing that after incubation of intact NIL, BHK, and 3T3 fibroblasts with CMP-sialic acid, at least 78% of the sialic acid incorporated by these cells is the result of free sialic acid uptake. When cells growing in a monolayer were incubated with a mixture of CMP-[14C]sialic acid and [3H]CMP-sialic acid with a ratio of 3H/14C=0.60, this ratio was found to be markedly increased in whole cells. Chemical analyses of the radioactive species in the incubation medium showed that a considerable portion of the radiolabeled sugar nucleotide had broken down to cytidine, phosphoric acid, and sialic acid. Upon incubation of cells with doubly labeled sugar nucleotide in the presence of a large excess of both nonradiolabeled cytidine and sialic acid, the cells incorporated less than 6% of both isotopes. Incubation of cells with a mixture of CMP-[14C]sialic acid and [3H]sialic acid resulted in only 20-40% of the radioactivity within the cells being membrane bound, and 70-90% of this incorporation could be inhibited by the addition of 10 mM azide to the incubation medium. The possibility that a small fraction of the total incorporation of sialic acid by these cells is due to surface sialytransferases cannot be completely ruled out. The uptake of free sialic acid by these fibroblasts is concentration dependent and a portion of it is incorporated into glycoproteins and glycolipids. Considerable loss of cell integrity was observed when fibroblasts grown on plates were removed by (ethylenedinitrilo)-tetraacetic acid or trypsin and subsequently incubated in buffer, indicating that these preparations are not suitable for intact cell studies.
Azides↗
Role of sialic acid in erythrocyte survival.
The role of membrane sialic acid in erythrocyte survival is unclear, although there is evidence for a reduction in sialic acid and surface charge in older erythrocytes. We reduced the surface charge of human, rat, and rabbit erythrocytes by removing sialic acid with neuraminidase. Reduction in sialic acid correlated with decreases in electrophoretic mobility and loss of PAS staining of membrane glycoproteins on polyacrylamide gels. No changes in ATP levels or deformability were found. 51Cr erythrocyte survivals in rats and rabbits showed rapid clearance of desialylated erythrocytes with sequestration by the liver. These results suggest that reduction in erythrocyte sialic acid is a mechanism of erythrocyte destruction and may be important in erythrocyte senescence.
Animals↗
Serum sialic acid elevations in malignant melanoma patients.
Elevated membrane sialic acid (n-acetyl neuraminic acid) concentration may be a general phenomenon associated with malignant or transformed cells. In this study, sera from 30 normal persons and 25 melanoma patients were examined to determine first, if serum sialic acid elevations were associated with malignant melanoma, and second, if there was a relationship between tumor burden and serum sialic acid level. Significantly elevated sialic acid concentrations were found in the melanoma patients (p less than 0.005), and levels tended to be greater in those with a large tumor burden (p less than 0.05). Thus, increased serum sialic acid could prove to be a valuable clinical monitor of change in tumor burden as a result of therapy or change due to recurrence of disease following treatment.
Adolescent↗
Isolation of sialic acid from casein and reclamation of residual casein.
Crystalline sialic acid was isolated in 50 to 60% yields from a commercial grade of dry isoelectric casein by Warren's hydrolysis procedure. One part of casein was heated at 80 C/60 min in ten parts of .18 N sulfuric acid (pH 1.5). A crude sialic acid preparation (7.8%) was obtained from the hydrolysate after addition of calcium hydroxide to remove protein at pH 4.6 and sulfate as calcium sulfate at pH 7.0 followed by concentration and lyophilization of the soluble material. Highly purified sialic acid (95%) was obtained by chromatography on Dowex-1 X 8 with a gradient of 0 to 2 M sodium acetate. The sialic acid positive fraction was passed through Duolite C20H followed by lyophilization. Slow evaporation of a concentrated solution of this material produced typical crystals of N-acetylneuraminic acid. The study also included an examination of the properties of the residual sialic acid-free casein. Electrophoretic patterns, solubility properties, rennet sensitivity, and viscous character revealed that the residual casein was remarkably similar to intact casein. However, the calcium sensitivity of this modified protein was increased in the presence of .1 M calcium chloride.
Calcium↗
Effects on platelet function of removal of platelet sialic acid by neuraminidase.
A number of investigators have implicated sialic acid on the surface of platelets in platelet function. In this study we have quantitated the amount of sialic acid removed by purified neuraminidase from the surface of washed platelets of man, rabbit, or pig and examined the effects of this removal. Purified neuraminidase did not induce the release of platelet granule contents. Platelets were pre-labeled with 14C-serotonin for measurement of the release reaction or with 51Cr for determination of adherence to a collagen-coated surface or damaged aortic surface, and for in vivo platelet survival studies. Washed, neuraminidase-treated platelets were resuspended in Tyrode's solution containing 0.35 per cent albumin or in citrated platelet-free plasma from the same species. Both resuspending fluids contained apyrase. Aggregating agents tested were ADP, acid-soluble collagen, thrombin, ristocetin (with human platelets), polylysine, and serotonin (with rabbit platelets). With all of these agents except polylysine, aggregation of neuraminidase-treated human or rabbit platelets was slightly enhanced compared with control platelets; aggregation of pig platelets was unchanged. When release-inducing agents were used, neuraminidase-treated platelets released more of their 14C-serotonin than control platelets. The extent to which rabbit platelets adhered to a collagen-coated surface or to the damaged surface of everted rabbit aorta was unchanged by pretreatment of platelets with neuraminidase. Therefore it seems unlikely that sialic acid is involved in platelet adherence to collagen. When more than 15 per cent of total sialic acid had been removed from rabbit platelets, they were completely cleared from the circulation within 1 hour of their injection into rabbits. When 8 to 10 per cent of total sialic acid had been removed, the platelets were not cleared immediately from the circulation but were cleared more quickly than control platelets. Thus, although removal of up to 65 per cent of platelet sialic acid has only a slightly enhancing effect on platelet aggregation and release in vitro, removal of as little as 8 to 10 per cent results in the recognition of platelets as "foreign" in vivo.
Adenosine Diphosphate↗