Identification of a novel mutation in ZAP70 and prenatal diagnosis in a Turkish family with severe combined immunodeficiency disorder

Protein tyrosine kinases (PTKs) play an important role in T cell development and activation. In vitro and in vivo defects, resulting in variable deficiencies in thymic development and in T cell antigen receptor (TCR) signal transduction, in PTKs have been shown. ZAP70, one of those PTKs, is a 70-kDa tyrosine phosphoprotein and associates with the ζ chain and undergoes tyrosine phosphorylation following TCR stimulation. It is expressed in T and natural killer (NK) cells. Several mutations were shown to lead to an autosomal recessive form of severe combined immunodeficiency disease (SCID).     

Selection Shapes the Robustness of Ligand-Binding Amino Acids

The phenotypes of biological systems are to some extent robust to genotypic changes. Such robustness exists on multiple levels of biological organization. We analyzed this robustness for two categories of amino acids in proteins. Specifically, we studied the codons of amino acids that bind or do not bind small molecular ligands. We asked to what extent codon changes caused by mutation or mistranslation may affect physicochemical amino acid properties or protein folding. We found that the codons of ligand-binding amino acids are on average more robust than those of non-binding amino acids. Because mistranslation is usually more frequent than mutation, we speculate that selection for error mitigation at the translational level stands behind this phenomenon. Our observations suggest that natural selection can affect the robustness of very small units of biological organization.     

A New Type of Anatolian Propolis: Evaluation of Its Chemical Composition,Activity Profile and Botanical Origin

This study was undertaken to analyze the phenolic profiles of 19 propolis samples from Turkey by using a high‐performance thin‐layer chromatographic (HPTLC) method in order to identify their plant origins. Furthermore, their antioxidant and antimicrobial activity profiles were comparatively evaluated. For the appraisal of antioxidant potential, total phenolic (TPC) and total flavonoid contents (TFC) of propolis samples were firstly determined and then their effects on free radicals were evaluated by FRAP, ABTS^.+, CUPRAC, DPPH^. and HPTLC‐DPPH^. methods. Antimicrobial activity of propolis samples against Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 11229) and Candida albicans ATCC 10231 were determined by disc diffusion and broth dilution methods. HPTLC fingerprinting analyses revealed that O‐type (botanical origin from Populus nigra L.) was the primarily available propolis type in Turkey. Moreover, 3‐O‐methylquercetin (3MQ) rich propolis was identified as a new propolis type for the first time. Principal component analysis (PCA) indicated that 3MQ‐type propolis differs from the O‐type. Antioxidant activity studies showed that O‐type of propolis possesses higher antioxidant effect than the other tested propolis types. Quercetin, caffeic acid, caffeic acid phenethyl ester (CAPE) and galangin were determined to contribute significantly to the antioxidant potential of O‐type propolis among others. Propolis extracts exerted moderate antimicrobial activity against the tested microorganisms with MIC values between the ranges of 128–512 μg/mL.     

Synergistic effects of hormone therapy drugs and usnic acid on hormone receptor‐positive breast and prostate cancer cells

The aim of this study was to investigate the combined effects of usnic acid (UA) and Tamoxifen (Tam) or Enzalutamide (Enz) on hormone receptor‐positive breast and prostate cancer (BC and PC), respectively. The antiproliferative and apoptotic effects of Tam or Enz alone and in combination with UA on MCF7 and LNCaP cancer cells were detected. The results of the WST‐1 assay indicated that UA was a promising anticancer compound that significantly enhanced the effectiveness of hormone therapy drugs compared with each drug alone (combination index < 1). In addition, the combination of UA with Tam or Enz remarkably induced more cell cycle arrest at the G0/G1 phase and apoptosis than only drug‐treated cells (P < 0.01). Consequently, our findings suggest that the combination of UA with Tam or Enz may be a potential therapeutic approach for the treatment of BC and PC and further studies are required to exploit the potential mechanisms of synergistic effects.     

Germline mutations in the extracellular domains of the 55 kDa TNF receptor, TNFR1, define a family of dominantly inherited autoinflammatory syndromes

Autosomal dominant periodic fever syndromes are characterized by unexplained episodes of fever and severe localized inflammation. In seven affected families, we found six different missense mutations of the 55 kDa tumor necrosis factor receptor (TNFR1), five of which disrupt conserved extracellular disulfide bonds. Soluble plasma TNFR1 levels in patients were approximately half normal. Leukocytes bearing a C52F mutation showed increased membrane TNFR1 and reduced receptor cleavage following stimulation. We propose that the autoinflammatory phenotype results from impaired downregulation of membrane TNFR1 and diminished shedding of potentially antagonistic soluble receptor. TNFR1-associated periodic syndromes (TRAPS) establish an important class of mutations in TNF receptors. Detailed analysis of one such mutation suggests impaired cytokine receptor clearance as a novel mechanism of disease.     

Role of Cysteine Residues in Human Plasma Phospholipid Transfer Protein

Phospholipid transfer protein (PLTP) belongs to a family of human plasma lipid transfer proteins that bind to small amphophilic molecules. PLTP contains cysteines at residues 5, 129, 168, and 318. Bactericidal/permeability-increasing protein, which is a member of the same gene family, contains an essential disulfide bond between Cys₁₃₅ and Cys₁₇₅; these residues, which correspond to Cys₁₂₉ and Cys₁₆₈ in PLTP, are conserved among all known members of the gene family. To identify the importance of these and the remaining cysteine residues to PLTP secretion and activity, each was replaced by a glycine by site-directed mutagenesis. The mutant as well as wild-type PLTP cDNAs were cloned into the mammalian expression vector pSV·SPORT1, and the PLTP cDNAs were transfected to COS-6 cells for expression. PLTP Cys₁₂₉ Gly and PLTP Cys₁₆₈ Gly were secretion incompetent. Neither PLTP mass nor activity was detectable in cell lysates and culture medium. Relative to wild-type PLTP, PLTP Cys₅ Gly and PLTP Cys₃₁₈ Gly exhibited similar specific activities but partially impaired PLTP synthesis and secretion. Intracellular PLTP appeared as two bands of 75 and 51 kDa corresponding to reported molecular masses for the glycosylated and nonglycosylated forms. The specific activities of PLTP Cys₅ Gly and PLTP Cys₃₁₈ Gly were similar in the cell lysates and medium, suggesting that glycosylation does not affect transfer activity.     

Application of isotopic ratio mass spectrometry for the in vitro determination of demethylation activity in human liver microsomes using N-methyl-13C-labeled substrates

The reaction of demethylation mediated by cytochrome P450 (CYP) leads to the equimolar production of demethylated metabolite and formaldehyde. From a 13C-substrate labeled on a carbon of the methyl moiety, [13C]formaldehyde (H13CHO) is liberated. A highly sensitive and specific assay involving the oxidation of H13CHO to 13CO(2) by a double-enzymatic-step reaction is reported. The 13CO(2) was quantified by the method of reverse isotopic dilution based on gas chromatography-isotope ratio mass spectrometry analysis. The method first involves the limiting step of the CYP-dependent reaction, which is stopped with a mixture of zinc sulfate 5 mM and trichloroacetic acid 100 mM. Then, the transformation of H13CHO to 13CO(2) is performed with the formaldehyde (0.2 unit) and the formate (0.2 unit) dehydrogenase NAD-dependent enzymes. The recovery of 13CO(2) from the incubation mixture was equal to 91.4 +/- 3.0%. The accuracy and the precision of the present method were within 12 and 10%, respectively. The limit of quantification was set to 25 pmol. The performance of the assay was validated on human liver microsomes with five probes: [13C]erythromycin, [1-13C]caffeine, [3-13C]caffeine, [7-13C]caffeine, and [13C(2)]aminopyrine. This method is useful for the rapid determination of N-demethylase activity of human liver microsomes from methyl-13C-substrates.     

Effects of Environmental Lead Pollution, Smoking, and Smokeless Tobacco (Maras Powder) Use on Blood Lead Level

One hundred sixty-four adult male volunteers (29 controls [Group 1] and 135 combi drivers) enrolled in the study. The combi drivers were divided into three groups as nonusers of either Maras powder or cigarette (Group 2), smokers (Group 3), and users of Maras powder (Group 4). Blood lead levels (BLLs) were analyzed by atomic absorption spectrophotometer. BLL was detected as 2.8 ± 2.3 μg/dL in Group 1 (n = 29); however, it was 3.5 ± 1.6 μg/dL in Group 2 (n = 33), 3.8 ± 2.4 μg/dL in Group 3 (n = 62), and 3.9 ± 2.4 μg/dL in Group 4 (n = 40). BLL in Group 1 was found significantly lower than other groups (p < 0.05). The use of cigarette or Maras powder by the drivers did not give rise to a marked difference on the BLLs (p > 0.05). BLL of (combi) drivers was detected to be significantly higher than nondrivers; however, it was still under the hazardous level of 10 μg/dL announced by WHO. Although there are publications reporting that usage of tobacco increases the level of lead in blood, both smoking and use of Maras powder did not affect BLL markedly in our study. Poster presented (the abstract section published in Congress Book) at the 7th Congress of Turkish Family Physicians, 23–26 May 2006, Cesme-IZMIR, Turkey.     

Evaluation of the natural killer cytotoxicity and the levels of cytokines in rats with type I diabetes mellitus

Type I diabetes mellitus (insulin-dependent DM = IDDM) is a chronic disease characterized by specific destruction of pancreatic beta cells, resulting in an absolute lack of insulin. Immune mechanisms, genetic susceptibility, and environmental factors are all implicated in the pathogenesis of Type 1 diabetes. This study was aimed at determining the efficiency of cytokines, natural killer (NK) cells in the pathophysiology of IDDM. Therefore, we evaluated the plasma levels of cytokines by specific enzyme-linked immunosorbent assay (ELISA) and the cytotoxicity activity of NK cells by anti-candididal index in rats with type I diabetes. We found that the cytotoxicity activity of NK cells in IDDM groups significantly decreased compared to the control groups. The levels of interferon-gamma (IFN-gamma) in IDDM groups were slightly higher than in healthy controls. These results indicate that the changes of T H1 type cytokines such as IFN-gamma and NK cell activity can play a role in the etiology of IDDM. The data may provide new strategies for the treatment of IDDM.