Contrasting effects of thiol-modulating agents on endothelial NO bioactivity

The bioactivity of endothelium-derived nitric oxide(NO) is an important component of vascular homeostasis that issensitive to intracellular redox status. Because glutathione (GSH) is a major determinant of intracellular redox state, we sought to define itsrole in modulating endothelial NO bioactivity. In porcine aorticendothelial cells (PAECs), we depleted intracellular GSH (>70%) using1) buthionine-(S,R)-sulfoximine (BSO), whichinhibits GSH synthesis; 2) diamide, which oxidizes thiols;or 3) 1-chloro-2,4-dinitrobenzene (CDNB), which putativelydepletes GSH through glutathione S-transferase activity.Cellular GSH depletion with BSO had no effect on endothelial NObioactivity measured as A-23187-induced cGMP accumulation. In contrast,oxidation of intracellular thiols with diamide inhibited bothA-23187-induced cGMP accumulation and the cGMP response to exogenousNO. Diamide treatment of either PAECs, PAEC membrane fractions, orpurified endothelial nitric oxide synthase (eNOS) resulted insignificant inhibition (~75%) of eNOS catalytic activity measured asL-[³H]arginine-to-L-[³H]citrullineconversion. This effect appeared related to oxidation of eNOS thiols asit was completely reversed by dithiothreitol. Glutathione depletionwith CDNB inhibited A-23187-stimulated cGMP accumulation but not thecGMP response to exogenous NO. Rather, CDNB treatment impaired eNOScatalytic activity in intact PAECs, and this effect was reversed byexcess NADPH in isolated purified eNOS assays. Consistent with theseresults, we found spectral evidence that CDNB reacts with NADPH andrenders it inactive as a cofactor for either eNOS or glutathionereductase. Thus thiol-modulating agents exert pleiotropic effects onendothelial NO bioactivity, and these data may help to resolve a numberof conflicting previous studies linking GSH status with endothelialcell NO bioactivity.

     

Candidate diagnostic biomarkers for neurodevelopmental disorders in children and adolescents: a systematic review

Neurodevelopmental disorders – including attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, communication disorders, intellectual disability, motor disorders, specific learning disorders, and tic disorders – manifest themselves early in development. Valid, reliable and broadly usable biomarkers supporting a timely diagnosis of these disorders would be highly relevant from a clinical and public health standpoint. We conducted the first systematic review of studies on candidate diagnostic biomarkers for these disorders in children and adolescents. We searched Medline and Embase + Embase Classic with terms relating to biomarkers until April 6, 2022, and conducted additional targeted searches for genome-wide association studies (GWAS) and neuroimaging or neurophysiological studies carried out by international consortia. We considered a candidate biomarker as promising if it was reported in at least two independent studies providing evidence of sensitivity and specificity of at least 80%. After screening 10,625 references, we retained 780 studies (374 biochemical, 203 neuroimaging, 133 neurophysiological and 65 neuropsychological studies, and five GWAS), including a total of approximately 120,000 cases and 176,000 controls. While the majority of the studies focused simply on associations, we could not find any biomarker for which there was evidence – from two or more studies from independent research groups, with results going into the same direction – of specificity and sensitivity of at least 80%. Other important metrics to assess the validity of a candidate biomarker, such as positive predictive value and negative predictive value, were infrequently reported. Limitations of the currently available studies include mostly small sample size, heterogeneous approaches and candidate biomarker targets, undue focus on single instead of joint biomarker signatures, and incomplete accounting for potential confounding factors. Future multivariable and multi-level approaches may be best suited to find valid candidate biomarkers, which will then need to be validated in external, independent samples and then, importantly, tested in terms of feasibility and cost-effectiveness, before they can be implemented in daily clinical practice.     

Purification of human cytidine deaminase: molecular and enzymatic characterization and inhibition by synthetic pyrimidine analogs

Cytidine deaminase has been purified to homogeneity from human placenta by a rapid and efficient procedure consisting of affinity chromatography followed by hydrophobic interaction chromatography. The final enzyme preparation showed a specific activity of 64.1 units/mg, corresponding to about 46,000-fold purification with respect to the crude extract. The enzyme is a 52-kDa oligomeric protein composed of four apparently identical subunits. The acidic isoelectric point is 4.5. The enzyme's stability is strictly dependent on the presence of reducing agents. Amino acid analysis reveals the presence of five thiol groups per monomer which cannot be titrated by Ellman's reagent in the native enzyme. However, the presence of sulfhydryl groups involved in the catalytic activity was evidenced by the inhibition exerted by p-chloromercuribenzoate and heavy metal ions. In addition, the protection effected by the substrate against the p-chloromercuribenzoate inhibition and the competitive inhibition exerted by 5-(chloromercuri)cytidine suggest the presence of a thiol group(s) in the catalytic site of the enzyme. pH studies have shown that the rapid decline of activity occurring at pH 4.5 might result from the protonation of the pyrimidine ring at the N-3 position. The enzyme catalyzes the deamination of cytidine, deoxycytidine, and several analogs, including antineoplastic agents, thus abolishing their pharmacological activity. Therefore, several pyrimidine nucleoside analogs have been tested as potential inhibitors of the enzyme. The competitive inhibition exerted by cytidine analogs having the ribose moiety replaced by aliphatic chains is interesting.     

A one-step procedure for the isolation of fructose 1,6-bisphosphatase and fructose 1,6-bisphosphate aldolase from rabbit liver

Human ceruloplasmin, which is usually cleaved by limited proteolysis into three major fragments during preparation ($\text{M}{}_{\mathrm{<mtext>r</mtext>}}\text{? 18,650}$, 50,000, and 70,000) was isolated in good yield as an undegraded single-chain protein ($\text{M}{}_{\mathrm{<mtext>r</mtext>}}\text{? 135,00}$). The cryosupernatant from fresh frozen plasma (100 liters) was fractionated with polyethylene glycol (PEG 4000) at + 5°C yielding a ceruloplasmin-enriched fraction in the 20% PEG supernatant. Three steps of chromatography on DEAE-Sephacel, hydroxyapatite, and Sephadex G-200 produced a homogeneous protein with maximal enzymatic activity and the $\text{A}{}_{610}\text{A}{}_{280}$ ratio of 0.046 corresponding to 98–100% purity. Two forms of ceruloplasmin having this absorbance ratio were obtained; Form I was predominant and was studied further. The procedure separated both forms from apoceruloplasmin and degraded ceruloplasmin. The single-chain ceruloplasmin (Form I) had an NH₂-terminal sequence of Lys-Glu-Lys-His-Tyr-Tyr-Ile-, the same as for the 70,000 fragment, and is suitable for structural study by sequence analysis and physicochemical methods.     

Structural features of neutral protease from Bacillus subtilis deduced from model-building and limited proteolysis experiments

The overall folding of neutral protease from Bacillus subtilis has been predicted by computer-aided modelling, taking as a basis the known three-dimensional structure of thermolysin. As expected from the 50% similarity of sequence between the two proteins, the structure of B. subtilis protease is similar to that of thermolysin, including the two-domain topology and location of elements of regular secondary structure (helices and strands), whereas specific differences were predicted in loop regions. A protruding and loose loop predicted in B. subtilis has been detected also experimentally by a limited proteolysis approach. Incubation of B. subtilis protease at pH 9.0 for 24 h at room temperature with trypsin at 20:1 ratio (by mass) leads to a specific and almost quantitative fission of the Arg214-Asn215 peptide bond located in a highly exposed, and thus probably flexible, loop of the protease. On the other hand, thermolysin was completely resistant to tryptic hydrolysis when reacted under identical conditions. The 'nicked' B. subtilis protease can be isolated by gel filtration chromatography at neutral pH, whereas the two constituting fragments 1-214 and 215-300 are separated under protein-denaturing conditions. Overall, these results indicate that the limited proteolysis approach can pinpoint a peculiar difference in surface structure between the two similar protein molecules of B. subtilis neutral protease and thermolysin and emphasize the potential use of proteolytic enzymes as structural probes of globular proteins.     

Studies on the biology,histology and cytogenetics of two sublines of a murine ovarian reticular cell sarcoma

Two sublines of the ovarian reticular cell sarcoma M5 in C57BL mice respond differently to cyclophosphamide and other alkylating agents. The subline R16, which is resistant to cyclophosphamide, was obtained by treating M5 mice repeatedly with this compound and subsequently transplanting the regrowing tumor for 16 passages. The R16 subline shows biological characteristics perfectly superimposable to those of the parent line and histologically resembles an undifferentiated mesenchymal neoplasia with numerous atypical nuclei and karyokinetic figures with large necrotic areas. The cytogenetic examination of the distribution in the chromosomal number of R16 indicates that this subline may be considered a clone of the parent line with a modal class of 35 chromosomes (34–37) versus a class of 34 (31–37) in the M5 tumor line. The presence of metacentric chromosomes characterizes the modal class of the two lines, 23 in the R16, and 25 in the M5 tumor lines.Abbreviations M5 murine ovarian reticular cell sarcoma - M5-CTX-16R(R16) subline of M5 made resistant to cyclophosphamide - CTX cyclophosphamide     

Allocation pattern,ion partitioning,and chlorophyll a fluorescence in Arundo donax L. in responses to salinity stress

Biometric and physiological analyses of salt stress responses were performed in two time-course experiments on giant reed (Arundo donax L). Experiment I evaluated biomass production in plants exposed to 128, 256, 512 mM NaCl for 84 days. For Experiment II, plants grown under 256 mM NaCl were further assessed for chlorophyll a fluorescence, ionic partitioning, and proline content at 14 and 49 days after treatment (DAT). Biomass allocation was affected with all the concentrations of NaCl used from 28 DAT onward. Proline biosynthesis in leaves was more stimulated than that in roots after salt stress. Photosynthetic efficiency of photosystem II (PSII) was not affected by salt stress up to 42 DAT, while 49 DAT plants exhibited a significant reduction of both potential (Φ_PSII) and maximal (F_v/F_m) PSII quantum yield. A. donax resulted a moderately sensitive species in response to 256 and 512 mM NaCl, concentrations that are however higher than that commonly found in most marginal lands (such as 128 mM or lower), where the biomass yield is appreciable, especially in short-term cultivation (56 DAT here). Altogether, this study indicates that A. donax can be considered as a promising and valuable energy crop for exploiting the Mediterranean marginal land.     

Effect of ascorbic acid treatment on conduit vessel endothelial dysfunction in patients with hypertension

Hypertension is associated with low plasma ascorbic acid levels and impaired endothelial function. Recent evidence suggests that increased vascular oxidative stress contributes to the pathophysiology of endothelial dysfunction and hypertension. We recently showed that chronic oral ascorbic acid therapy lowers blood pressure in hypertensive patients. We hypothesized that it would also improve endothelial vasomotor function. In a randomized, double-blind, placebo-controlled study, we examined the effect of acute (2 g po) and chronic (500 mg/day for 1 mo) ascorbic acid treatment on brachial artery flow-mediated dilation in 39 patients with hypertension. Compared with 82 age- and gender-matched normotensive controls, these patients had impaired endothelium-dependent, flow-mediated dilation of the brachial artery [8.9 +/- 6.1 vs. 11.2 +/- 5.7% (SD), P < 0.04]. After therapy, plasma ascorbic acid concentrations increased acutely from 50 +/- 12 to 149 +/- 51 micromol/l and were maintained at 99 +/- 33 micromol/l with chronic treatment (both P < 0.001). As previously reported, chronic ascorbic acid therapy reduced systolic and mean blood pressure in these patients. However, acute or chronic ascorbic acid treatment had no effect on brachial artery endothelium-dependent, flow-mediated dilation or on endothelium-independent, nitroglycerin-mediated dilation. These results demonstrate that conduit vessel endothelial dysfunction secondary to hypertension is not reversed by acute or chronic treatment with oral ascorbic acid. The effects of this treatment on resistance vessel vasomotor function warrant further investigation.     

Linkage Disequilibrium and Genome-Wide Association Mapping in Tetraploid Wheat (Triticum turgidum L.)

Association mapping is a powerful tool for the identification of quantitative trait loci through the exploitation of the differential decay of linkage disequilibrium (LD) between marker loci and genes of interest in natural and domesticated populations. Using a sample of 230 tetraploid wheat lines (Triticum turgidum ssp), which included naked and hulled accessions, we analysed the pattern of LD considering 26 simple sequence repeats and 970 mostly mapped diversity array technology loci. In addition, to validate the potential for association mapping in durum wheat, we evaluated the same genotypes for plant height, heading date, protein content, and thousand-kernel weight. Molecular and phenotypic data were used to: (i) investigate the genetic and phenotypic diversity; (ii) study the dynamics of LD across the durum wheat genome, by investigating the patterns of LD decay; and (iii) test the potential of our panel to identify marker–trait associations through the analysis of four quantitative traits of major agronomic importance. Moreover, we compared and validated the association mapping results with outlier detection analysis based on population divergence. Overall, in tetraploid wheat, the pattern of LD is extremely population dependent and is related to the domestication and breeding history of durum wheat. Comparing our data with several other studies in wheat, we confirm the position of many major genes and quantitative trait loci for the traits considered. Finally, the analysis of the selection signature represents a very useful complement to validate marker–trait associations.