Efficacy and safety of rituximab as second-line therapy in immune thrombocytopenic purpura based on ethnicity: A descriptive study among the Arabic population.

BACKGROUND: Rituximab is used as second-line therapy in patients with immune thrombocytopenic purpura (ITP) who do not respond to first-line management. The response rate for Rituximab is variable in different populations ranging from 30% to 90%. The adverse effects of rituximab in patients with ITP range from infusion site reactions to the reactivation of hepatitis B virus and progressive multifocal leukoencephalopathy and interpopulation variation. METHODS: We conducted a single-center, retrospective study in Qatar's National Center for Cancer Care & Research. The study included patients with chronic refractory ITP who received rituximab as second-line therapy. Descriptive and summary statistics were used to describe the sociodemographic parameters of the study cohort. RESULTS: Of the 41 patients with chronic ITP, 26 were Arabs, 12 were Asians, and 3 were of other ethnicities. Rituximab was associated with an overall response rate of 80.4%. Arabic patients had the highest clinical response (84.6%) among the ethnicities with the lowest adverse effects (11.5%). Asians had a response rate of 66.6%, and adverse effects were seen in 16.7% of the patients. CONCLUSIONS: In chronic refractory ITP, rituximab appears to have a better clinical response in the Arabic population with minimal toxicity than in other ethnicities.

Clinical features and prognostic factors of intensive and non-intensive 1014 COVID-19 patients: an experience cohort from Alahsa, Saudi Arabia.

BACKGROUND: COVID-19 is a worldwide pandemic and has placed significant demand for acute and critical care services on hospitals in many countries. OBJECTIVES: To determine the predictors of severe COVID-19 disease requiring admission to an ICU by comparing patients who were ICU admitted to non-ICU groups. METHODS: A cohort study was conducted for the laboratory-confirmed COVID-19 patients who were admitted to six Saudi Ministry of Health's hospitals in Alahsa, between March 1, 2020, and July 30, 2020, by reviewing patient's medical records retrospectively. RESULTS: This cohort included 1014 patients with an overall mean age of 47.2 ± 19.3 years and 582 (57%) were males. A total of 205 (20%) of the hospitalized patients were admitted to the ICU. Hypertension, diabetes and obesity were the most common comorbidities in all study patients (27.2, 19.9, and 9%, respectively). The most prevalent symptoms were cough (47.7%), shortness of breath (35.7%) and fever (34.3%). Compared with non-ICU group, ICU patients had older age (p ≤ 0.0005) and comprised a higher proportion of the current smokers and had higher respiratory rates (p ≤ 0.0005), and more percentage of body temperatures in the range of 37.3-38.0 °C (p ≥ 0.0005); and had more comorbidities including diabetes (p ≤ 0.0005), hypertension (p ≥ 0.0005), obesity (p = 0.048), and sickle cell disease (p = 0.039). There were significant differences between the non-ICU and ICU groups for fever, shortness of breath, cough, fatigue, vomiting, dizziness; elevated white blood cells, neutrophils, alanine aminotransferase and alkaline aminotransferase, lactate dehydrogenase, and ferritin, and decreased hemoglobin; and proportion of abnormal bilateral chest CT images (p < 0.05). Significant differences were also found for multiple treatments (p < 0.05). ICU patients group had a much higher mortality rate than those with non-ICU admission (p ≤ 0.0005). CONCLUSION: Identifying key clinical characteristics of COVID-19 that predict ICU admission and high mortality can be useful for frontline healthcare providers in making the right clinical decision under time-sensitive and resource-constricted environment.

Haemorrhoidectomy under local anaesthesia versus spinal anaesthesia: a systematic review and meta-analysis.

AIMS: To evaluate comparative outcomes of local anaesthesia (LA) and spinal anaesthesia (SA) in patients undergoing haemorrhoidectomy. METHODS: A systematic online search was conducted using the following databases: PubMed, Scopus, Cochrane Database, The Virtual Health Library, Clinical trials.gov , and Science Direct. Only randomised controlled trials (RCTs) comparing excisional haemorrhoidectomy under LA and SA were included. Post-operative pain score, need for rescue analgesia, urinary retention, headache, rectal bleeding, and operative time were the evaluated outcome parameters. RESULTS: Seven RCTs reporting a total number of 440 patients of whom 222 patients underwent haemorrhoidectomy under LA and 218 patients had the procedure under SA were included. LA was associated with significantly lower post-operative pain at 6 h (mean difference (MD) - 2.25, P = 0.0001) and at 24 h (MD - 0.87, P = 0.0002), need for a rescue analgesia (risk ratio (RR) 0.18, P = 0.002), urinary retention (RR 0.17, P = 0.0001), and headache (RR 0.09, P = 0.0003) compared with SA. However, there was no significant difference in rectal bleeding (RR 0.89, P = 0.70) and operative time (MD 1.15, P = 0.19) between LA and SA. CONCLUSION: Compared with SA, LA may be associated with significantly lower post-operative pain, need for rescue analgesia, urinary retention, and headache making it an attractive choice of anaesthesia in day-case surgery for those who are not either fit for GA or refuse such anaesthetic modality.

Crystal structure and stereochemical studies of KD(P)G aldolase from Thermoproteus tenax.

Carbon-carbon bond forming enzymes offer great potential for organic biosynthesis. Hence there is an ongoing effort to improve their biocatalytic properties, regarding availability, activity, stability, and substrate specificity and selectivity. Aldolases belong to the class of C-C bond forming enzymes and play important roles in numerous cellular processes. In several hyperthermophilic Archaea the 2-keto-3-deoxy-(6-phospho)-gluconate (KD(P)G) aldolase was identified as a key player in the metabolic pathway. The carbohydrate metabolism of the hyperthermophilic Crenarchaeote Thermoproteus tenax, for example, has been found to employ a combination of a variant of the Embden-Meyerhof-Parnas pathway and an unusual branched Entner-Doudoroff pathway that harbors a nonphosphorylative and a semiphosphorylative branch. The KD(P)G aldolase catalyzes the reversible cleavage of 2-keto-3-deoxy-6-phosphogluconate (KDPG) and 2-keto-3-deoxygluconate (KDG) forming pyruvate and glyceraldehyde 3-phosphate or glyceraldehyde, respectively. In T. tenax initial studies revealed that the pathway is specific for glucose, whereas in the thermoacidophilic Crenarchaeote Sulfolobus solfataricus the pathway was shown to be promiscuous for glucose and galactose degradation. The KD(P)G aldolase of S. solfataricus lacks stereo control and displays additional activity with 2-keto-3-deoxy-6-phosphogalactonate (KDPGal) and 2-keto-3-deoxygalactonate (KDGal), similar to the KD(P)G aldolase of Sulfolobus acidocaldarius. To address the stereo control of the T. tenax enzyme the formation of the two C4 epimers KDG and KDGal was analyzed via gas chromatography combined with mass spectroscopy. Furthermore, the crystal structure of the apoprotein was determined to a resolution of 2.0 A, and the crystal structure of the protein covalently linked to a pathway intermediate, namely pyruvate, was determined to 2.2 A. Interestingly, although the pathway seems to be specific for glucose in T. tenax the enzyme apparently also lacks stereo control, suggesting that the enzyme is a trade-off between required catabolic flexibility needed for the conversion of phosphorylated and nonphosphorylated substrates and required stereo control of cellular/physiological enzymatic reactions.

The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) of Sulfolobus solfataricus: a key-enzyme of the semi-phosphorylative branch of the Entner-Doudoroff pathway.

Archaea utilize a branched modification of the classical Entner-Doudoroff (ED) pathway for sugar degradation. The semi-phosphorylative branch merges at the level of glyceraldehyde 3-phosphate (GAP) with the lower common shunt of the Emden-Meyerhof-Parnas pathway. In Sulfolobus solfataricus two different GAP converting enzymes-classical phosphorylating GAP dehydrogenase (GAPDH) and the non-phosphorylating GAPDH (GAPN)-were identified. In Sulfolobales the GAPN encoding gene is found adjacent to the ED gene cluster suggesting a function in the regulation of the semi-phosphorylative ED branch. The biochemical characterization of the recombinant GAPN of S. solfataricus revealed that-like the well-characterized GAPN from Thermoproteus tenax-the enzyme of S. solfataricus exhibits allosteric properties. However, both enzymes show some unexpected differences in co-substrate specificity as well as regulatory fine-tuning, which seem to reflect an adaptation to the different lifestyles of both organisms. Phylogenetic analyses and database searches in Archaea indicated a preferred distribution of GAPN (and/or GAP oxidoreductase) in hyperthermophilic Archaea supporting the previously suggested role of GAPN in metabolic thermoadaptation. This work suggests an important role of GAPN in the regulation of carbon degradation via modifications of the EMP and the branched ED pathway in hyperthermophilic Archaea.

Glycerate kinase of the hyperthermophilic archaeon Thermoproteus tenax: new insights into the phylogenetic distribution and physiological role of members of the three different glycerate kinase classes.

BACKGROUND: The presence of the branched Entner-Doudoroff (ED) pathway in two hyperthermophilic Crenarchaea, the anaerobe Thermoproteus tenax and the aerobe Sulfolobus solfataricus, was suggested. However, so far no enzymatic information of the non-phosphorylative ED branch and especially its key enzyme - glycerate kinase - was available. In the T. tenax genome, a gene homolog with similarity to putative hydroxypyruvate reductase/glycerate dehydrogenase and glycerate kinase was identified. RESULTS: The encoding gene was expressed in E. coli in a recombinant form, the gene product purified and the glycerate kinase activity was confirmed by enzymatic studies. The enzyme was active as a monomer and catalyzed the ATP-dependent phosphorylation of D-glycerate forming exclusively 2-phosphoglycerate. The enzyme was specific for glycerate and highest activity was observed with ATP as phosphoryl donor and Mg2+ as divalent cation. ATP could be partially replaced by GTP, CTP, TTP and UTP. The enzyme showed high affinity for D-glycerate (Km 0.02 +/- 0.01 mM, Vmax of 5.05 +/- 0.52 U/mg protein) as well as ATP (Km of 0.03 +/- 0.01 mM, Vmax of 4.41 +/- 0.04 U/mg protein), although at higher glycerate concentrations, substrate inhibition was observed. Furthermore, the enzyme was inhibited by its product ADP via competitive inhibition. Data bank searches revealed that archaeal glycerate kinases are members of the MOFRL (multi-organism fragment with rich leucine) family, and homologs are found in all three domains of life. CONCLUSION: A re-evaluation of available genome sequence information as well as biochemical and phylogenetic studies revealed the presence of the branched ED pathway as common route for sugar degradation in Archaea that utilize the ED pathway. Detailed analyses including phylogenetic studies demonstrate the presence of three distinct glycerate kinase classes in extant organisms that share no common origin. The affiliation of characterized glycerate kinases with the different enzyme classes as well as their physiological/cellular function reveals no association with particular pathways but a separate phylogenetic distribution. This work highlights the diversity and complexity of the central carbohydrate metabolism. The data also support a key function of the conversion of glycerate to 2- or 3-phosphoglycerate via glycerate kinase in funneling various substrates into the common EMP pathway for catabolic and anabolic purposes.

The semi-phosphorylative Entner-Doudoroff pathway in hyperthermophilic archaea: a re-evaluation.

Biochemical studies have suggested that, in hyperthermophilic archaea, the metabolic conversion of glucose via the ED (Entner-Doudoroff) pathway generally proceeds via a non-phosphorylative variant. A key enzyme of the non-phosphorylating ED pathway of Sulfolobus solfataricus, KDG (2-keto-3-deoxygluconate) aldolase, has been cloned and characterized previously. In the present study, a comparative genomics analysis is described that reveals conserved ED gene clusters in both Thermoproteus tenax and S. solfataricus. The corresponding ED proteins from both archaea have been expressed in Escherichia coli and their specificity has been identified, revealing: (i) a novel type of gluconate dehydratase (gad gene), (ii) a bifunctional 2-keto-3-deoxy-(6-phospho)-gluconate aldolase (kdgA gene), (iii) a 2-keto-3-deoxygluconate kinase (kdgK gene) and, in S. solfataricus, (iv) a GAPN (non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase; gapN gene). Extensive in vivo and in vitro enzymatic analyses indicate the operation of both the semi-phosphorylative and the non-phosphorylative ED pathway in T. tenax and S. solfataricus. The existence of this branched ED pathway is yet another example of the versatility and flexibility of the central carbohydrate metabolic pathways in the archaeal domain.

Structural Basis of allosteric regulation and substrate specificity of the non-phosphorylating glyceraldehyde 3-Phosphate dehydrogenase from Thermoproteus tenax.

The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) of the hyperthermophilic Archaeum Thermoproteus tenax is a member of the superfamily of aldehyde dehydrogenases (ALDH). GAPN catalyses the irreversible oxidation of glyceraldehyde 3-phosphate (GAP) to 3-phosphoglycerate in the modified glycolytic pathway of this organism. In contrast to other members of the ALDH superfamily, GAPN from T.tenax (Tt-GAPN) is regulated by a number of intermediates and metabolites. In the NAD-dependent oxidation of GAP, glucose 1-phosphate, fructose 6-phosphate, AMP and ADP increase the affinity for the cosubstrate, whereas ATP, NADP, NADPH and NADH decrease it leaving, however, the catalytic rate virtually unaltered. As we show here, the enzyme also uses NADP as a cosubstrate, displaying, however, unusual discontinuous saturation kinetics indicating different cosubstrate affinities and/or reactivities of the four active sites of the protein tetramer caused by cooperative effects. Furthermore, in the NADP-dependent reaction the presence of activators decreases the overall S0.5 and increases Vmax by a factor of 3. To explore the structural basis for the different effects of both pyridine nucleotides we solved the crystal structure of Tt-GAPN in complex with NAD at 2.2 A resolution and compared it to the binary Tt-GAPN-NADPH structure. Although both pyridine nucleotides show a similar binding mode, NADPH appears to be more tightly bound to the protein via the 2' phosphate moiety. Moreover, we present four co-crystal structures with the activating molecules glucose 1-phosphate, fructose 6-phosphate, AMP and ADP determined at resolutions ranging from 2.3 A to 2.6 A. These crystal structures reveal a common regulatory site able to accommodate the different activators. A phosphate-binding pocket serves as an anchor point ensuring similar binding geometry. The observed conformational changes upon activator binding are discussed in terms of allosteric regulation. Furthermore, we present a crystal structure of Tt-GAPN in complex with the substrate D-GAP at 2.3 A resolution, which allows us to analyse the structural basis for substrate binding, the mechanism of catalysis as well as the stereoselectivity of the enzymatic reaction.

Reconstruction of the central carbohydrate metabolism of Thermoproteus tenax by use of genomic and biochemical data.

The hyperthermophilic, facultatively heterotrophic crenarchaeum Thermoproteus tenax was analyzed using a low-coverage shotgun-sequencing approach. A total of 1.81 Mbp (representing 98.5% of the total genome), with an average gap size of 100 bp and 5.3-fold coverage, are reported, giving insights into the genome of T. tenax. Genome analysis and biochemical studies enabled us to reconstruct its central carbohydrate metabolism. T. tenax uses a variant of the reversible Embden-Meyerhof-Parnas (EMP) pathway and two different variants of the Entner-Doudoroff (ED) pathway (a nonphosphorylative variant and a semiphosphorylative variant) for carbohydrate catabolism. For the EMP pathway some new, unexpected enzymes were identified. The semiphosphorylative ED pathway, hitherto supposed to be active only in halophiles, is found in T. tenax. No evidence for a functional pentose phosphate pathway, which is essential for the generation of pentoses and NADPH for anabolic purposes in bacteria and eucarya, is found in T. tenax. Most genes involved in the reversible citric acid cycle were identified, suggesting the presence of a functional oxidative cycle under heterotrophic growth conditions and a reductive cycle for CO2 fixation under autotrophic growth conditions. Almost all genes necessary for glycogen and trehalose metabolism were identified in the T. tenax genome.