Induction of heme oxygenase-1 expression inhibits platelet-dependent thrombosis

Heme oxygenase-1 (HO-1) plays a key role in protecting tissue from oxidative stress. Although some studies implicate HO-1 in modulating thrombosis after vascular injury, the impact of HO-1 on the rate of clot formation in vivo is poorly defined. This study examined the potential function of HO-1 in regulating platelet-dependent arterial thrombosis. Platelet-rich thrombi were induced in C57BL/6J mice by applying 10% ferric chloride to the exposed carotid artery. Mean occlusion time of wild-type mice (n = 10) was 14.6 +/- 1.0 min versus 12.9 +/- 0.6 min for HO-1-/- mice (n = 11, p = 0.17). However, after challenge with hemin, mean occlusion time was significantly longer in wild-type mice (16.3 +/- 1.2 min, n = 15) than HO-1-/- mice (12.0 +/- 1.0 min, n = 9; p = 0.021). Hemin administration induced an approximately twofold increase in oxidative stress, measured as plasma thiobarbituric acid reactive substances. Immunohistochemical analysis revealed that hemin induced a robust increase in HO-1 expression within the carotid arterial wall. Ex vivo blood clotting within a collagen-coated perfusion chamber was studied to determine whether the accelerated thrombosis observed in HO-1-/- mice was contributed to by effects on the blood itself. Under basal conditions, mean clot formation during perfusion of blood over collagen did not differ between wild-type mice and HO-1-/- mice. However, after hemin challenge, mean clot formation was significantly increased in HO-1-/- mice compared with wild-type controls. These results suggest that, under basal conditions, HO-1 does not exert a significant effect on platelet-dependent clot formation in vivo. However, under conditions that stimulate HO-1 production, platelet-dependent thrombus formation is inhibited by HO-1. Enhanced HO-1 expression in response to oxidative stress may represent an adaptive response mechanism to down-regulate platelet activation under prothrombotic conditions.     

Heme oxygenase-1 promotes neovascularization in ischemic heart by coinduction of VEGF and SDF-1

Heme oxygenase-1 (HO-1) is a stress-inducible enzyme with multiple protective functions in cardiovascular systems. Studies have shown that the timely cardiac HO-1 overexpression at acute phase of ischemic infarction (MI) provides protection via its anti-apoptotic and anti-inflammatory effects. Here we demonstrate that a delayed HO-1 transduction mediated by a recombinant adeno-associated virus in ischemic hearts of mice with permanent coronary artery ligation significantly attenuated left ventricular fibrosis and cardiac dysfunctions examined at 4 weeks post MI. HO-1-mediated protection was correlated with enhanced vascularization in the ischemic myocardium. HO-1 gene transfer resulted in a notable increase in the number of c-kit⁺- stem cells recruited to the infarcted area at 10 days after ligation. HO-1-mediated stem cell recruitment was also demonstrated in the heart of non-ischemic mice receiving intravenous infusion of green fluorescent protein-bearing bone marrow stem cells. Additional experiments revealed that vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) were highly induced in HO-1 transduced myocardium. Mononuclear cell infiltration was evident and colocalized with angiogenic factors in the same region. Flow cytometry analysis of the mononuclear cells isolated from HO-1-transduced left ventricles revealed that over 50% of cells expressed CD34, a marker of hematopoietic stem cells and endothelial progenitor cells. VEGF and SDF-1 blockade by neutralizing antibodies significantly attenuated HO-1-mediated neovascularization and protection in infarcted mice. These data suggest that cardiac HO-1 gene transfer post MI provides protection at least in part by promoting neovascularization through inducing angiogenic factors and the recruitment of circulating progenitor/stem cells.     

70%肝切除对大鼠胎肝细胞脾内移植后增殖能力的影响

研究70％肝切除对大鼠胎肝细胞脾内移植后增殖影响。分离孕3周SD大鼠胚胎肝细胞，将其移植入70％肝切除大鼠脾内，分别于移植后7天和30天应用流式细胞仪分析肝切除大鼠残肝细胞的细胞周期，用图像分析法检测脾内移植肝细胞面积密度。与对照组比较，胎肝细胞移植后7天，肝切除鼠残细胞S期细胞比例明显增加（P＜0．05），Gz/M期细胞比例明显减少（P＜0．01）。而其牌内移植 胎肝细胞面积密度则显著升高（P＜0．05）；30天后，残 细胞再生状态与移植胎肝细胞的面积密度与对照组比较均无显著性差异。研究表明，70％肝切除的肝再生有利于大鼠肝细胞脾内移植后的增殖。     

Relapsed and late-onset Nipah encephalitis

An outbreak of infection with the Nipah virus, a novel paramyxovirus, occurred among pig farmers between September 1998 and June 1999 in Malaysia, involving 265 patients with 105 fatalities. This is a follow-up study 24 months after the outbreak. Twelve survivors (7.5%) of acute encephalitis had recurrent neurological disease (relapsed encephalitis). Of those who initially had acute nonencephalitic or asymptomatic infection, 10 patients (3.4%) had late-onset encephalitis. The mean interval between the first neurological episode and the time of initial infection was 8.4 months. Three patients had a second neurological episode. The onset of the relapsed or late-onset encephalitis was usually acute. Common clinical features were fever, headache, seizures, and focal neurological signs. Four of the 22 relapsed and late-onset encephalitis patients (18%) died. Magnetic resonance imaging typically showed patchy areas of confluent cortical lesions. Serial single-photon emission computed tomography showed the evolution of focal hyperperfusion to hypoperfusion in the corresponding areas. Necropsy of 2 patients showed changes of focal encephalitis with positive immunolocalization for Nipah virus antigens but no evidence of perivenous demyelination. We concluded that a unique relapsing and remitting encephalitis or late-onset encephalitis may result as a complication of persistent Nipah virus infection in the central nervous system.     

Synthesis of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands for use in palladium-catalyzed cross-coupling reactions

3-Aryl-2-phosphinoimidazo[1,2-a]pyridine ligands were synthesized from 2-aminopyridine via two complementary routes. The first synthetic route involves the copper-catalyzed iodine-mediated cyclizations of 2-aminopyridine with arylacetylenes followed by palladium-catalyzed cross-coupling reactions with phosphines. The second synthetic route requires the preparation of 2,3-diiodoimidazo[1,2-a]pyridine or 2-iodo-3-bromoimidazo[1,2-a]pyridine from 2-aminopyridine followed by palladium-catalyzed Suzuki/phosphination or a phosphination/Suzuki cross-coupling reactions sequence, respectively. Preliminary model studies on the Suzuki synthesis of sterically-hindered biaryl and Buchwald–Hartwig amination compounds are presented with these ligands.

3-Aryl-2-phosphoimidazo[1,2-a]pyridine ligands were prepared via two complimentary synthetic routes and were evaluated in the Suzuki–Miyaura and Buchwald–Hartwig amination cross-coupling reactions.

Palladium-catalyzed cross-coupling reactions have revolutionized the formation of C–C and C–X bond formation in the academic and industrial synthetic organic chemistry sectors.^1,2 Applications such as synthesis of natural products,³ active pharmaceutical ingredients (API),⁴ agrochemicals,⁵ and materials for electronic applications⁶ are showcased. Snieckus described in his 2010 Nobel Prize review that privileged ligand scaffolds represented the “third wave” in the cross-coupling reactions where the “first wave” was the investigation of the metal catalyst-the rise of palladium and the “second wave” was the exploration of the organometallic coupling partner.¹ In the last twenty years, it was recognized that the choice of ligand facilitated the oxidative addition and reductive-elimination steps of the catalytic cycle of transition metal-catalyzed cross-coupling reactions, increasing the overall rate of the reaction. For example, bulky trialkylphosphines facilitated the oxidative addition processes of electron-rich, unactivated substrates such as aryl chlorides.^7,8 Sterically demanding ligands also provided enhanced rates of reductive elimination from [(L)_nPd(aryl)(R), R = aryl, amido, phenoxo, etc.] species by alleviation of steric congestion.⁹ Privileged ligands such as Buchwald''s biarylphosphines,^10,11 Fu''s trialkylphosphines,^7,8,12 Nolan–Hermann''s N-heterocyclic carbenes (NHC),^13–15 Hartwig''s ferrocenes,^16,17 Beller''s bis(adamantyl)phosphines^18,19 and N-aryl(benz)imidazolyl or N-pyrrolylphosphines,^20,21 Zhang''s ClickPhos ligands,^22,23 and Stradiotto''s biaryl P–N phosphines,^24,25 to mention a few, have found wide-spread use in Suzuki–Miyaura, Corriu–Kumada, Heck, Negishi, Sonogashira, C–X (X = S, O, P) cross-coupling and Buchwald–Hartwig amination reactions (Fig. 1). Preformed catalysts with these ligands attached to the palladium metal center are also recognized as well-defined entities in cross-coupling reactions.²⁶Open in a separate windowFig. 1Privileged ligands for palladium-catalyzed cross-coupling reactions.The term privileged structure was first coined by Evans et al. in 1988 and was defined as “a single molecular framework able to provide ligands for diverse receptors”.²⁷ In the last three decades, it is clear that privileged structures are exploited as opportunities in drug discovery programs.^28–31 For example, imidazo[1,2-a]pyridines are privileged structures in medicinal chemistry programs (Fig. 2).³² Imidazo[1,2-a]pyridines are a represented motif in several drugs on the market such as zolpidem, marketed as Ambien™ for the treatment of insomnia,³³ minodronic acid, marketed as Bonoteo™ for oral treatment of osteoporosis,³⁴ and olprinone, sold as Coretec™ as a cardiotonic agent.³⁵Open in a separate windowFig. 2Imidazo[1,2-a]pyridines as privileged structures in medicinal chemistry and in our cross-coupling reactions approach.Our group is interested in a long-term research program directed at the use of key privileged structures that are employed in drug discovery programs as potential phosphorus ligands for cross-coupling reactions. In our entry into the use of privileged structures from the medicinal chemistry literature for our investigation into new phosphorus ligands, we have developed two complementary synthetic routes for the preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands from 2-aminopyridine as our initial substrate.Our first synthetic route for the preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands 3a–3l required the copper(ii) acetate iodine-mediated double oxidative C–H amination of 2-aminopyridine (1) with arylacetylenes under an oxygen atmosphere to give 3-aryl-2-iodoimidazo[1,2-a]pyridines 2a–2d (Scheme 1).^36,37Open in a separate windowScheme 1Preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands 3a–3l from 2-aminopyridine via copper-catalyzed arylacetylene cyclizations/palladium-catalyzed phosphination reactions sequences.Phenylacetylene and 2-/3-/4-methoxyphenylacetylenes were commercially available reagents. With intermediates 2a–d in hand, we explored several cross-coupling phosphination reactions and we found that palladium-catalyzed phosphination with DIPPF ligand in the presence of cesium carbonate as the base in 1,4-dioxane under reflux provided twelve new ligands 3a–3l as shown in 38 Moderate to good yields were obtained under these cross-coupling conditions. There are few commercially available dimethoxyphenylacetylenes, and most are prohibitively expensive, and so an alternative synthetic strategy was explored.Palladium-catalyzed phosphination of 3-aryl-2-iodoimidazo[1,2-a]pyridines 2a–2d^a

Evolving Pattern of Laparoscopic Gastric Band Access Port Complications

Laparoscopic gastric banding (LGB) is the commonest bariatric procedure in Australia. The commonest complication of LGB is access port or tubing (AP/T) problems, requiring revisional surgery. The aim of this study was to document the evolving pattern of AP/T complications. All patients whose LGB procedure (Allergan(TM) Bands) and AP/T revision (Allergan(TM) port revision sets) were performed by one surgeon (1999 to 2008) were included, giving 167 AP/T revisions in 124 patients out of a total 1,928 LGB patients. All patient follow-up details were prospectively recorded and retrospectively analysed. Incidence of LGB AP/T problems was 8.7%. Mean time to first AP/T revision was 2 years. Over the last 4 years of the series, the number of LGB insertions was constant, but the number of AP/T revisions progressively increased. Twenty-seven percent of AP/T revision patients required two or more AP/T revisions. Sixty-two percent of the AP/T complications were leaks. Half the AP complications were flipping of the AP. There was no correlation of AP/T problems with any changes to port design to date. Infection rate for LGB insertion was 0.67%. The incidence of LGB AP/T complications progressively increases with duration after LGB insertion. Occurrence of one AP/T problem appears to select a subgroup more likely to experience further AP/T problems. To date, revisions of port design do not appear to have solved AP/T problems. Recent introduction of a significantly redesigned port may reduce AP/T failures.     

Current applications of human pluripotent stem cells: possibilities and challenges

Stem cells are self-renewable cells with the differentiation capacity to develop into somatic cells with biological functions. This ability to sustain a renewable source of multi- and/or pluripotential differentiation has brought new hope to the field of regenerative medicine in terms of cell therapy and tissue engineering. Moreover, stem cells are invaluable tools as in vitro models for studying diverse fields, from basic scientific questions such as developmental processes and lineage commitment, to practical application including drug screening and testing. The stem cells with widest differentiation potential are pluripotent stem cells (PSCs), which are rare cells with the ability to generate somatic cells from all three germ layers. PSCs are considered the most optimal choice for therapeutic potential of stem cells, bringing new impetus to the field of regenerative medicine. In this article, we discuss the therapeutic potential of human PSCs (hPSCs) including human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), reviewing the current preclinical and clinical data using these stem cells. We describe the classification of different sources of hPSCs, ongoing research, and currently encountered clinical obstacles of these novel and versatile human stem cells.     

SingHealth Radiology Archives pictorial essay Part 2: gastroenterology,musculoskeletal, and obstetrics and gynaecology cases

The Singapore Health Services cluster (SingHealth) radiology film archives are a valuable repository of local radiological cases dating back to the 1950s. Some of the cases in the archives are of historical medical interest, i.e. cerebral angiography in the workup of patients with hemiplegia. Other cases are of historical social interest, being conditions seen during earlier stages of Singapore’s development, i.e. bound feet. The archives form a unique portal into the development of local radiology as well as the national development of Singapore. A selection from the archives is published in commemoration of the International Day of Radiology in 2020, as well as the 200th anniversary of the Singapore General Hospital in 2021. This pictorial essay comprises gastroenterology, musculoskeletal and obstetrics and gynaecology cases from the archives.     

肝门部冷冻对肝脏血流动力学影响的实验研究

目的：探讨第一肝门深低温冷冻对肝脏血流动力学的影响。方法：选健康小猪１５只,实验组８只,阻断肝门,用冷冻头深低温冷冻第一肝门。对照组７只,仅阻断肝门。以彩色多普勒观察肝动脉及门静脉血流动力学变化,同时做肝功能及肝脏病理检查。结果：实验组动物术后肝动脉阻力指数、搏动指数增加,肝动脉、门静脉血流减慢、血流量减少,肝动脉、门静脉结构无明显改变;胆管系统不可逆损伤;肝功能进行性损害。结论：深低温冷冻第一肝门会严重影响肝动脉、门静脉血流动力学