Structural insights on pathogenic effects of novel mutations causing pyruvate carboxylase deficiency

Pyruvate carboxylase (PC), a key enzyme for gluconeogenesis and anaplerotic pathways, consists of four domains, namely, biotin carboxylase (BC), carboxyltransferase (CT), pyruvate carboxylase tetramerization (PT), and biotin carboxyl carrier protein (BCCP). PC deficiency is a rare metabolic disorder inherited in an autosomal recessive way. The most severe form (form B) is characterized by neonatal lethal lactic acidosis, whereas patients with form A suffer chronic lactic acidosis with psychomotor retardation. Diagnosis of PC deficiency relies on enzymatic assay and identification of the PC gene mutations. To date, six mutations of the PC gene have been identified. We report nine novel mutations of the PC gene, in five unrelated patients: three being affected with form B, and the others with form A. Three of them were frameshift mutations predicted to introduce a premature termination codon, the remaining ones being five nucleotide substitutions and one in frame deletion. Impact of these mutations on mRNA was assessed by RT‐PCR. Evidence for a deleterious effect of the missense mutations was achieved using protein alignments and three‐dimensional structural prediction, thanks to our modeling of the human PC structure. Altogether, our data and those previously reported indicate that form B is consistently associated with at least one truncating mutation, mostly lying in CT (C‐terminal part) or BCCP domains, whereas form A always results from association of two missense mutations located in BC or CT (N‐terminal part) domains. Finally, although most PC mutations are suggested to interfere with biotin metabolism, none of the PC‐deficient patients was biotin‐responsive. Hum Mutat 0:1–7, 2009. © 2009 Wiley‐Liss, Inc.     

非荧光法与荧光法芯片检测细菌感染的研究

目的 研制一种用于快速检测急症常见感染细菌的芯片反应系统。方法 应用生物信息学技术，设计检测细菌的探针和聚合酶链反应扩增引物，探针点制成寡核苷酸芯片，待测样本经扩增并标记生物素或CY5荧光素后与芯片杂交，再经链酶亲和素-碱性磷酸酶显色反应后，获得肉眼可见的杂交信号，或通过荧光检测仪读出样本的检测结果。结果 建立了针对临床急症患者标本的非荧光法与荧光法芯片检测系统，芯片的检测灵敏度(大肠埃希菌)为10～100CFU／反应体系。结论 两种方法不仅能快速、灵敏地检测靶细菌感染，且重复性好、信号强及不易出现非特异信号。生物素酶联显色芯片法由于更为经济、简便而有重要的临床价值。     

Diagnosis of persistent ovarian carcinoma with three-step immunoscintigraphy

The diagnosis of recurrent ovarian carcinoma is usually determined at surgical re-exploration since the main non-invasive diagnostic tests have low accuracy. It would be desirable to have a high accuracy non-invasive diagnostic procedure. With this aim, we have assessed the utility of three-step immunoscintigraphy. Thirty patients were intravenously injected with biotinylated monoclonal antibodies MOv18 and B72.3, followed by avidin-streptavidin injection and finally by 111In-biotin. Tumour recurrences were imaged 2 h post radioactivity injection. All patients underwent surgical re-exploration 3-4 days after immunoscintigraphy; the presence of tumour in the area of immunoscintigraphic uptake was evaluated in the biopsied material. Twenty-one patients studied were true-positive, five were true-negative, four were false-positive and none was false-negative. The diagnostic accuracy, positive predictive value and negative predictive value were 87%, 84% and 100% respectively. If these findings are confirmed in a larger number of patients, we expect immunoscintigraphy to be introduced as a cost-effective procedure in the follow-up of patients who have received surgery for ovarian carcinoma, since it promises to reliably identify patients who do not require surgical re-exploration, and guide biopsies when they are indicated.     

Detection of cytomegalovirus by DNA-DNA hybridization employing probes labelled with 32-phosphorus or biotin

Various factors influencing the detection of human cytomegalovirus (HCMV) in infected cells by DNA-DNA hybridization have been investigated. Employing the Hind III O fragment of HCMV AD169 labelled with 32P, we found that detection sensitivity was highly influenced by the method employed for extraction of DNA from infected cells. Excision of the Hind III O fragment from the vector by restriction endonuclease digestion prior to 32P-labelling further improved the detection capability of the probe. Similarly, cytomegalovirus (CMV) DNA detection employing biotin-labelled probes and streptavidin/alkaline phosphatase in the hybridot assay was also highly dependent on the method of DNA extraction prior to hybridization. Finally, we describe an in situ assay employing a biotin-labelled probe and fluorescein-conjugated avidin to detect CMV DNA in cultured cells.     

Morules with optically clear nuclei in ovarian borderline endometrioid tumor

Optically clear nuclei (OCN) have been observed in morules of some neoplasms and in some conditions unrelated to the development of the morules. We first report a case of ovarian borderline endometrioid tumor (BET) showing the morules associated with OCN. The patient was a 47-year-old premenopausal woman with a left ovarian cystic tumor, atypical endometrial hyperplasia, and elevated serum levels of FSH, LH, estradiol, and CA 125. The resected ovarian tumor measured 6 cm in diameter, and showed a papillary growth. Histologically, the ovarian tumor was consistent with BET, and the morules with OCN were scattered. Immunohistochemically, OCN were proven to be rich in biotin. An aberrant nuclear expression of beta-catenin was observed in both the tumor cells and the morular cells. Our case may suggest the possibility that the appearance of OCN with or without morules in ovarian tumors is related to endometrioid differentiation of the tumor cells, and should be recognized as a diagnostic clue of ovarian endometrioid tumors. Although female sex hormones have been reported to play a role in the occurrence of OCN, the participation of beta-catenin mutation has also been suggested.     

Targeting the sodium-dependent multivitamin transporter (SMVT) for improving the oral absorption properties of a retro-inverso Tat nonapeptide

Purpose. To investigate the potential for delivering large peptides orally by altering their absorptive transport pathways and improving intestinal permeability. The absorptive transport of retro-inverso (R.I.-) K-Tat9 and R.I.-K(biotin)-Tat9, novel peptidic inhibitors of the Tat protein of HIV-1, and their interactions with human SMVT (hSMVT), a high affinity, low capacity transporter, were investigated using Caco-2 and transfected CHO cells. Methods. Following synthesis on a PAL resin using Fmoc chemistry, the transport of R.I.-K-Tat9 (0.01-25 M) and R.I.-K(biotin)-Tat9 (0.1-25 M) was evaluated across Caco-2 cells. The transport and kinetics of biotin, biocytin and desthiobiotin (positive controls for SMVT) were also determined. Uptake of R.I.-K-Tat9 and R.I.-K(biotin)-Tat9 (both 0.1-10 M) was determined in CHO/hSMVT and CHO/pSPORT (control) cells. Results. The absorptive transport of R.I.-K-Tat9 was passive, low (P_m1 × 10^–6 cm/sec) and not concentration dependent. R.I.-K(biotin)-Tat9 permeability was 3.2-fold higher than R.I.-K-Tat9 demonstrating active (E_a = 9.1 kcal/mole), concentration dependent and saturable transport (K_m = 3.3 M). R.I.-K(biotin)-Tat9 uptake in CHO/hSMVT cells (K_m = 1.0 M) was 500-fold greater than R.I.-K-Tat9 (at 10 M). R.I.-K(biotin)-Tat9 transport in Caco-2 and CHO/hSMVT cells was significantly inhibited by known substrates of SMVT including biotin, biocytin, and desthiobiotin. Passive uptake of R.I.-K(biotin)-Tat9 was significantly greater than R.I.-K-Tat9 uptake in CHO/pSPORT cells. Conclusions. These results demonstrate that the structural modification of R.I.-K-Tat9 to R.I.-K(biotin)-Tat9 altered its intestinal transport pathway resulting in a significant improvement in its absorptive permeability by enhancing nonspecific passive and carrier-mediated uptake by means of SMVT. The specific interactions between R.I.-K(biotin)-Tat9 and SMVT suggest that targeting approaches utilizing transporters such as SMVT may substantially improve the oral delivery of large peptides.     

Cerebrospinal fluid levels of biotin in various neurological disorders

OBJECTIVES: To analyse biotin concentrations in human cerebrospinal fluid (CSF) and serum from controls without evidence of nutritional or neurological disorders and patients with common neurological disorders. PATIENTS AND METHODS: Cerebrospinal fluid was obtained from patients by lumbar puncture, serum was prepared from freshly drawn whole blood and biotinidase in samples was inhibited before being analysed for biotin by radioligand assay. RESULTS: Assay characteristics were within an acceptable range (intra-and interassay coefficient of variations were 8.8 and 12.0 respectively, recovery: 91-114% and sensitive, lowest standard concentration 15 ng/l). Significantly lower values for biotin were found in patients with multiple sclerosis (both CSF and serum) in comparison to the controls. Significantly reduced values for cerebrospinal fluid biotin were found in epileptics compared to controls, whereas, in serum the difference was approaching significance. No significant differences were observed in other groups of patients. CONCLUSION: There is a significant reduction in cerebrospinal fluid biotin in epileptics and patients with multiple sclerosis compared to controls. In epileptics this may be related to competition between biotin and anticonvulsants bearing carbamide ring for absorption. Reduction of biotin levels in patients with multiple sclerosis could be attributed to intestinal malabsorption caused by the underlying disease or a biotin-binding immunoglobulin which may be involved in multiple sclerosis pathogenesis.     

用cDNA:RNA斑点杂交法检测肠道病毒RNA的实验研究

用Biotin标记的Coxsackie B3病毒cDNA为探针,以25种肠道病毒标准毒株为检测病毒,建立了检测肠道病毒基因RNA的斑点杂交方法。该方法的检测敏感性为50～80TCID_(50)斑点,操作较简便,试剂稳定安全、可长期保存。所使用的pCB Ⅲ/35.51对肠道病毒有很广的杂交谱;pCBⅢ/29在严格条件下,仅与Coxsackie B3病毒RNA反应。因此,这些探针所具有的杂交特性很适合作为临床标本中肠道病毒的检测探针。     

用BA-ELISA法测定载脂蛋白A-I

介绍一种高灵敏度的裁脂蛋白A-I(Apo A-I)的测定方法——生物素-亲和素酶联免疫吸附测定法(BA-ELISA)。本法的工作范围为0.25～4ng Apo A-I,灵敏度约0.1ngAp0 A-I,较已报道的放射免疫法(RIA)和ELISA高3～5倍以上。热处理或加入变性剂均不影响人血清Apo A-I的免疫测定结果。组内和组间变异系数分别为4.55和8.04。经本法测定77名正常成年人血清Apo A-I为1.34±0.23g/L((?)±SD),而且正常成年人血清ApoA-I浓度与高密度脂蛋白-胆固醇(HDL-C)的浓度呈高度相关(r=0.83,p<0.001)。     

Free light chains in the CSF in multiple sclerosis

Summary The presence of free light chains (FLC) was investigated in 32 patients with clinically definite or laboratory supported definite multiple sclerosis (MS), 2 patients with neurosyphilis and 10 normal controls. The detection of FLC in unconcentrated cerebrospinal fluid (CSF) was performed by means of agarose isoelectric focusing, followed by transfer of proteins to nitrocellulose membranes, double immunofixation, avidin-biotin amplification and peroxidase staining. Bands due to FLC were clearly demonstrated in the CSF of 28 MS patients; 3 of them showed only kappa FLC, 10 only lambda FLC, while 15 had both kappa and lambda FLC. The CSF of 4 MS patients was FLC negative. In both cases of neurosyphilis FLC bands were observed. FLC were never found in normal CSF. Among the indexes of intrathecal immunological activity (IgG oligoclonal bands, FLC, IgG index, intra-blood-brain barrier IgG synthesis rate, pleocytosis) the FLC proved to be the second most frequent abnormality in MS CSF, the presence of IgG oligoclonal bands being the first. In one MS case an FLC band was found, while all the other indexes of intrathecal IgG production were negative. A high correlation was found between an elevated number of FLC and pleocytosis. The presence of FLC in MS CSF seems to indicate a recent immunological stimulation leading to increased synthesis of FLC within the CNS.