Sialic acid concentrations in the urine of men with and without renal stones

Summary It has been suggested that urinary sialidase may play a role in the formation of renal stones. The present study was therefore undertaken to compare spectrophotometrically the different types of sialic acid concentrations and sialidase activities in fresh first morning urine specimens of men (21–65 years) with (13) and without (9) calcium oxalate renal stones. Although the free urinary sialic acid concentrations of the two groups of men were statistically about the same (P=0.0614), the total (P=0.003) and bound (P=0.0012) urinary sialic acid concentrations differed significantly. Both the total and bound sialic acid concentrations were lower in the urine specimens of the stone patients than in their healthy counterparts. This decrease in urinary sialic acid concentrations was firstly thought to be the result of elevated breakdown enzymes of sialic acid, which would favour the production of pyruvate. However, spectrophotometric determinations of the endogenous pyruvate concentrations of the two types of urine specimens did not differ significantly (P=0.0708). Secondly, the decrease in total urinary total sialic acid concentration of stone patients, could be attributed to less sialic acid synthesis or less renal excretion. Therefore, the same experiments were repeated using serum of 13 patients and 9 healthy men. Conversely, the total (P=0.4425) and bound (P=0.2850) serum sialic acid concentrations were found to be similar in the two types of subjects. However, the free serum sialic acid concentration of stone patients was significantly lower than in the healthy subjects (P=0.0062). This phenomenon is also reflected in the average ratio for serum free: bound sialic acid in healthy and stone patients, 1:7.9 and 1:18.7 respectively (P=0.0009). The lower free serum sialic acid concentration may lead to lower renal excretions of sialic acid. This may explain the decrease in total urinary sialic acid concentration in stone patients. The lower bound urinary sialic acid concentrations in patients was also reflected in the urinary free: bound sialic acid ratio for healthy (1:2.3) and stone patients (1:1.3). The difference between these two groups of men was highly significant (P=0.0001). This phenomenon might be explained by the urinary sialidase activities, which was spectrophotometrically determined at 334 nm at 37°C of 11 patients with stones and 17 healthy men. The ages of both groups of men were the same (P=0.326). An increase in urinary sialidase activity was observed with the stone patients (P=0.00001) when compared to specimens of healthy men. This might explain the decrease in urinary bound sialic acid concentration of the stone group. It seems from these results that the urinary concentration of sialic acid and the activity of urinary sialidase, may play a role in the pathogenesis of the multifactorial disease, urolithiasis.     

新城疫病毒pIRHN核酸疫苗构建和表达及对肿瘤细胞的影响

目的：研究NDV HN基因抗肿瘤作用及其可能机制。方法：以 pIRES1neo为表达载体构建了 NDV HN基因的pIRHN核酸疫苗，在体外转染HeLa细胞，用间接免疫荧光和Western blot检测pIRHN在真核细胞中表达状况，用荧光显微镜、DNA琼脂糖电泳及TUNEL染色等方法，检测HN基因导致细胞死亡的类型；用3，5-二羟基甲苯法测定HeLa细胞唾液酸含量的变化。结果：pIRHN 转染HeLa细胞后，能够在真核细胞中表达，能促进肿瘤细胞死亡，其死亡方式主要以诱导细胞凋亡为主，pIRHN使 HeLa细胞唾液酸含量减少。结论：用 NDV HN基因所构建的核酸疫苗能够在真核细胞中高效表达，表达的 HN蛋白主要位于胞膜，胞浆中亦有 HN蛋白表达；pIRHN具有抗肿瘤作用，可能通过其表达产物与肿瘤细胞唾液酸受体的相互作用，发挥其抗肿瘤作用。本实验为迸一步阐明NDV抗肿瘤作用机制提供了理论依据。     

Native and sialic acid masked Lewisa antigen reactivity in medullary thyroid carcinoma

Forty-six medullary thyroid carcinomas (MTC) were subjected to a qualitative and quantitative characterization of native and sialic acid masked Lewis^a (Le^a) antigens. Immunohistochemical investigations included monoclonal antibodies (MABs) directed against alpha(2,3)-sialyl-Le^a, i.e. CA19-9 (MAB 19-9), native Le^a (MAB anti Le^a) and alpha(2,3) sialyl type 1 structure, i.e. CA 50 (MAB C50). To detect sialic acid masked Le^a reactivity, MAB anti-Le^a was also applied to native and enzymatically desialylated tissue sections with and without masking of sialic acid residues by sialic acid and sequence specific lectins. Only 7 MTC (15%) displayed a weak expression of CA19-9, while 16 (33%) showed moderate positive staining for native Le^a. Twenty-seven tumours exhibited a strong staining by the N'ase MAB anti Le^a staining sequence. The latter could most effectively be inhibited by the simultaneous masking of alpha(2,3)-and alpha-(2,6)-linked sialic acid residues due to the comptetitive binding of sialic acid and sequence specific lectins: Maackia amurensis agglutinin (specific alpha(2,3)-linked sialic acid) and Sambucus nigra agglutinin (specific alpha(2,6)-linked sialic acid). Thus, in MTC the major portion of sialic acid masked Le^a antigen reactivity is different from that detected by the MAB 19-9. The antigen reactivity is probably due to Le^a structures containing both alpha(2,3) and alpha(2,6)-linked sialic acid residues. A highly significant correlation between the expression of CA50 and that detected by the N'ase MAB anti-Le^a staining sequence indicates that the alpha(2,3)-sialyl type 1 chain represents a common intermediate structure within the pathway of the biosynthesis of sialylated Le^a antigens, excluding the formation of CA19-9 via the formation of the disialyl type 1 structure. This is subsequently fucosylated to the corresponding sialic acid masked Le^a. Preliminary clinicopathological studies indicate that the sialic acid masked Le^a antigens detected by the N'ase MAB anti-Le^a staining sequence are related to biologically aggressive MTC.     

地砷病患者部分生化指标的测定

对病区地砷病、非地砷病患者及对照组居民体内的部分生化指标进行了检测。结果表明,地砷病患者血清中的ＧＰＴ活性、ＵＮ和ＳＡ含量明显高于对照组,ＬＤＨ及ＧＳＨＰｘ活性明显降低;病区非地砷病患者ＬＤＨ活性、ＳＡ含量明显升高,ＧＳＨＰｘ活性明显降低,其它各组及各指标与对照组相比无显著差异。相关分析显示,病区病人组及非病人组血中ＳＡ含量与各自尿砷水平呈正相关（ｒ＝０５０,ｒ＝０４６）,ＧＳＨＰｘ与尿砷呈负相关（ｒ＝－０５１,ｒ＝－０４８）。提示,ＳＡ和ＧＳＨＰｘ可作为砷中毒的早期诊断指标。砷可能对接砷居民肝功、肾功产生一定影响。     

2型糖尿病患者血清肿瘤坏死因子和唾液酸联合检测的临床意义

目的　探讨血清 TNF和 SA含量在 2型糖尿病患者发生和发展中作用。方法　分别应用放免法和化学法测定 88例 2型糖尿病患者血清 TNF和 SA含量 ,并与 35名正常人作对照。结果　 2型糖尿病患者血清TNF、SA含量则显著地高于正常人组 (P<0 .0 1) ,且与胰岛素水平呈明显的正相关 (r=0 .6 82 5 ,0 .6 2 6 3,P<0 .0 1)。结论　测定 2型糖尿病患者血清中 TNF、SA含量的变化对其观察病情的变化具有重要的临床价值     

食管癌患者手术切除前后SA、CEA和SCP检测的临床意义

目的　探讨食管癌患者手术切除前后血清 SA、CEA、SCP水平的变化。方法　应用放免法测定 4 3例食管癌患者血清 CEA含量 ,化学法测定 SA和 SCP含量 ,并以 35名正常健康人作对照。结果　食管癌患者在手术切除前血清 SA、CEA、SCP水平非常显著地高于正常人组 (P<0 .0 1) ,手术切除后 6个月转移者血清 SA、CEA、SCP水平持续异常 ,未转移者血清 SA、CEA、SCP在正常水平。结论　血清 SA、CEA、SCP含量测定的变化与食管癌患者的病情和预后密切相关 ,有一定的临床应用价值     

Role of sialoglycan structures for the function of the epidermal growth factor receptor and the in vitro proliferation of head and neck cancer

Squamous cell carcinomas of the head and neck have been found to show a high expression of the receptor for epidermal growth factor (EGF). This overexpression of the receptor has been associated with malignant transformation of cells, although there is still debate as to what extent this receptor takes part in the proliferation of malignant cells and which function it fulfills. The factors which determine receptor-ligand interaction are also not clearly defined. That the extracellular domain of the EGF receptor carries carbohydrate or sialoglycan structures might be important for function of the receptor. Since tumor specific enzymes can possibly alter such structures, it was the aim of our study to investigate the role of these structures on the EGF receptor during the proliferation of head and neck carcinomas. We used the human laryngeal squamous carcinoma cell line HLaC 79 and altered, for the first time, specific glycan structures with sialidase α-2,3 and α-2,6, causing desialylation. Changes were also produced by endo-β-galactosidase and sialyltransferase. Findings were monitored by labeling with bromo-deoxyuridine. To determine receptor affinity, ¹²⁵I-labeled EGF was employed. Results showed that both cell proliferation and receptor affinity depended on the level of sialylation of the receptor carbohydrate side chains. Desialylation led to a statistically significant reduction of tumor cell proliferation to 65 ± 33% (P < 0.01), while receptor affinity decreased to 70 ± 26% (P < 0.01).The importance of EGF receptor for the proliferation of malignant cells seems to depend on the level of sialylation of glycan structures on receptor protein. A release of enzymes by tumor cells may then produce auto-control of tumor proliferation on its own. Received: 5 November 1997 / Accepted: 21 April 1998     

GNE myopathy associated with congenital thrombocytopenia: A report of two siblings

GNE myopathy is an autosomal recessive muscular disorder caused by mutations in the gene encoding the key enzyme in sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK). Here, we report two siblings with myopathy with rimmed vacuoles and congenital thrombocytopenia who harbored two compound heterozygous GNE mutations, p.V603L and p.G739S. Thrombocytopenia, which is characterized by shortened platelet lifetime rather than ineffective thrombopoiesis, has been observed since infancy. We performed exome sequencing and array CGH to identify the underlying genetic etiology of thrombocytopenia. No pathogenic variants were detected among the known causative genes of recessively inherited thrombocytopenia; yet, candidate variants in two genes that followed an autosomal recessive mode of inheritance, including previously identified GNE mutations, were detected. Alternatively, it is possible that the decreased activity of GNE/MNK itself, which would lead to decreased sialic content in platelets, is associated with thrombocytopenia in these patients. Further investigations are required to clarify the association between GNE myopathy and the pathogenesis of thrombocytopenia.