Chemically Recyclable, High Molar Mass Polyoxazolidinones via Ring-Opening Metathesis Polymerization

The development of robust methods for the synthesis of chemically recyclable polymers with tunable properties is necessary for the design of next-generation materials. Polyoxazolidinones (POxa), polymers with five-membered urethanes in their backbones, are an attractive target because they are strongly polar and have high thermal stability, but existing step-growth syntheses limit molar masses and methods to chemically recycle POxa to monomer are rare. Herein, we report the synthesis of high molar mass POxa via ring-opening metathesis polymerization of oxazolidinone-fused cyclooctenes. These novel polymers show <5% mass loss up to 382-411 °C and have tunable glass transition temperatures (14-48 °C) controlled by the side chain structure. We demonstrate facile chemical recycling to monomer and repolymerization despite moderately high monomer ring-strain energies, which we hypothesize are facilitated by the conformational restriction introduced by the fused oxazolidinone ring. This method represents the first chain growth synthesis of POxa and provides a versatile platform for the study and application of this emerging subclass of polyurethanes.

Targeted curation of the gut microbial gene content modulating human cardiovascular disease

IMPORTANCE

One of the most-cited examples of the gut microbiome modulating human disease is the microbial metabolism of quaternary amines from protein-rich foods. By-products of this microbial processing promote atherosclerotic heart disease, a leading cause of human mortality globally. Our research addresses current knowledge gaps in our understanding of this microbial metabolism by holistically inventorying the microorganisms and expressed genes catalyzing critical atherosclerosis-promoting and -ameliorating reactions in the human gut. This led to the creation of an open-access resource, the Methylated Amine Gene Inventory of Catabolism database, the first systematic inventory of gut methylated amine metabolism. More importantly, using this resource we deliver here, we show for the first time that these gut microbial genes can predict human disease, paving the way for microbiota-inspired diagnostics and interventions.

Left aorto-ventricular tunnel: A differential diagnosis to aortic regurgitation

Left aorto-ventricular tunnel is a rare congenital heart disorder. A then 19-year-old young lady was referred to our clinic for chronic rheumatic heart disease with aortic regurgitation. However, because of an almost continuous murmur, and an unusual transthoracic echo, she underwent various investigations, finally revealing a rare type 2 left aorto-ventricular tunnel. She had been variously diagnosed as chronic rheumatic heart disease with aortic regurgitation, bicuspid aortic valve with aortic regurgitation, and then possibly coronary arterial (cameral) fistula (based on 2D transthoracic echo) and finally left aorto-ventricular tunnel. This is the first case described in South East Asia who is asymptomatic, apart from a murmur, and her long journey to this final diagnosis illustrates the need to "chase shadows" on echoes, to come to a proper conclusion for the patient.

Concentration-Dependent Solvation Structure and Dynamics of Aqueous Sulfuric Acid Using Multinuclear NMR and DFT

Sulfuric acid is a ubiquitous compound for industrial processes, and aqueous sulfate solutions also play a critical role as electrolytes for many prominent battery chemistries. While the thermodynamic literature on it is quite well-developed, comprehensive studies of the solvation structure, particularly molecular-scale dynamical and transport properties, are less available. This study applies a multinuclear nuclear magnetic resonance (NMR) approach to the elucidation of the solvation structure and dynamics over wide temperature (-10 to 50 °C) and concentration (0-18 M) ranges, combining the ¹⁷O shift, line width, and T₁ relaxation measurements, ³³S shift and line width measurements, and ¹H pulsed-field gradient NMR measurements of proton self-diffusivity. In conjunction, these results indicate a crossover between two regimes of solvation structure and dynamics, occurring above the concentration associated with the deep eutectic point (∼4.5 M), with the high-concentration regime dominated by a strong water-sulfate correlation. This description was borne out in detail by the activation energy trends with increasing concentration derived from the relaxation of both the H₂O/H₃O⁺ and H₂SO₄/HSO₄^-/SO₄^{2- 17}O resonances and the ¹H self-diffusivity. However, the ¹⁷O chemical shift difference between the H₂O/H₃O⁺ and H₂SO₄/HSO₄^-/SO₄^2- resonances across the entire temperature range is nevertheless strikingly linear. A computational approach coupling molecular dynamics simulations and density functional theory NMR shift calculations to reproduce this trend is presented, which will be the subject of further development. This combination of multinuclear, dynamical NMR, and computational methods, and the results furnished by this study, will provide a platform for future studies on battery electrolytes where aqueous sulfate chemistry plays a central role in the solution structure.

Effects of ingested nanocellulose on intestinal microbiota and homeostasis in Wistar Han rats

Micron scale cellulose materials are "generally regarded as safe" (GRAS) as binders and thickeners in food products. However, nanocellulose materials, which have unique properties that can improve food quality and safety, have not received US-Food and Drug Administration (FDA) approval as food ingredients. In vitro and in vivo toxicological studies of ingested nanocellulose revealed minimal cytotoxicity, and no subacute in vivo toxicity. However, ingested materials may modulate gut microbial populations, or alter aspects of intestinal function not elucidated by toxicity testing, which could have important health implications. Here, we report the results of studies conducted in a rat gavage model to assess the effects of ingested cellulose nanofibrils (CNF) on the fecal microbiome and metabolome, intestinal epithelial expression of cell junction genes, and ileal cytokine production. Feces, plasma, and ilea were collected from Wistar Han rats before and after five weeks of biweekly gavages with water or cream, with or without 1% CNF. CNF altered microbial diversity, and diminished specific species that produce short chain fatty acids, and that are associated with increased serum insulin and IgA production. CNF had few effects on the fecal metabolome, with significant changes in only ten metabolites of 366 measured. Exposure to CNF also altered expression of epithelial cell junction genes, and increased production of cytokines that modulate proliferation of CD8 T cells. These perturbations likely represent initiation of an adaptive immune response, however, no associated pathology was seen within the duration of the study. Additional studies are needed to better understand the health implications of these changes in long term.

Clinical and genetic analysis of long QT syndrome in two Malay children

Long QT syndrome (LQTS) is predominantly a genetic cardiac arrhythmia disorder. We report here our study on long QT syndrome from two children from Kelantan, Malaysia. Clinical and genetic findings of these two unrelated Malay children with LQTS is discussed. We found a Long QT, type 1 causal mutation, p.Ile567Thr in the KCNQ1 gene in the first child. A pathogenic mutation could not be detected in the second child, explaining the heterogeneity of this disease.

Arterial stiffness during acute and recovery phases of children with rheumatic fever

Acute rheumatic fever (ARF) is associated with systemic inflammation and arterial stiffness during the acute stage. It has not been reported if arterial stiffness remains after recovery. The aim of this study was to determine the arterial stiffness during acute stage and 6 months after recovery from ARF. Arterial stiffness was assessed by carotid femoral pulse wave velocity (PWV) in 23 ARF patients during the acute stage of ARF and 6 months later. Simultaneously, erythrocyte sedimentation rate (ESR) and other anthropometric measurements were taken during both stages. There was a significant reduction in PWV; 6.5 (6.0, 7.45) m/s to 5.9 (5.38, 6.48) m/s, p=0.003 6 months after the acute stage of ARF. Similarly, ESR was also significantly reduced from 92.0 (37.5, 110.50) mm/hr to 7.0 (5.0, 16.0) mm/hr, p=0.001. In conclusion, arterial stiffness improved 6 months after the acute stage with routine aspirin treatment; this correlates well with the reduction in systemic inflammation.

Older Age Group in Pregnancy is Associated with Increased Arterial Stiffness

Arterial stiffness is an index of vascular health; normal pregnancy is associated with reduced arterial stiffness. This cross sectional study compared arterial stiffness in older (≥35 years) and the younger (≤34 years) age groups of pregnant women. Arterial stiffness was assessed noninvasively in 66 pregnant women between 23 - 32 weeks gestation (41 women ≤ 34 years, 25 women ≥ 35 years) using the parameters pulse wave analysis and pulse wave velocity. Blood pressure (BP), body mass index (BMI), serum total cholesterol (TC) and fasting blood glucose (FBS) were also recorded. Mean ages of the younger and older age groups were 27.6±0.62 and 39.3±0.58 years; no significant difference was seen between the groups in their BMI, TC, FBS, SBP, DBP and gestational age. The older age group of women have increased arterial stiffness (augmentation index 19.4±1.9% vs 13.2±1.6%, p=0.015) and aortic stiffness (pulse wave velocity 8.7±0.3 vs 7.7±0.2 m/s, p=0.004) compared to the younger women. Linear regression analysis showed a positive significant correlation between age and augmentation index (R=0.278, p=0.026), and pulse wave velocity (R=0.350, p=0.004). We conclude that older pregnant women has increased arterial stiffness compared to a younger age group of pregnant women suggesting that vascular changes due to ageing occurs in pregnancy despite cardiovascular adaptations occurring in pregnancy.

"Fishing for lines": removal of endovascular catheters from the cardiovascular system

We present two infants whose endovascular lines were accidentally cut or fractured, and had to be retrieved via transcatheter means in the cardiac catheterisation laboratory. The first case was a two-month-old infant with transposition of the great arteries, requiring an emergency balloon atrial septostomy. An indwelling vascular catheter that was placed in the right femoral vein was accidentally cut and had migrated into the inferior vena cava, before being retrieved. The second case was a one-week-old neonate who presented with pneumonia at birth, and had a long intravenous catheter placed in the left saphenous vein, which became fractured, and subsequently migrated into the heart. This case presented as a pulmonary embolus with haemodynamic instability, as the catheter had partially obstructed the right ventricular outflow tract. This was later retrieved via transcatheter means.

Pulmonary haemosiderosis with juvenile idiopathic arthritis in a Malaysian child

A rare case of childhood pulmonary haemosiderosis with juvenile idiopathic arthritis is discussed, with particular reference to treatment with hydroxychloroquine and sildenafil for pulmonary hypertension which occurs secondary to this disease.

Method optimisation to assess endothelial function in females - Duration of GTN effect

Pulse-wave analysis (PWA) combined with pharmacological challenges has recently been used as a method to measure endothelial function. This involved administration of glyceryl trinitrate (GTN), followed by salbutamol as endothelium-independent and -dependent vasodilators, respectively. The duration of GTN effect needs to be established before the administration of salbutamol. Baseline augmentation index (AIx) and pulse-wave velocity (PWV) measurements were taken in 11 healthy female subjects (mean age 23.27 +/- 3.66 years). Sublingual GTN 0.5 mg was administered for 3 min, followed by AIx and PWV measurements every 5 min till 20 min and then every 10 min until 40 min post-GTN. Maximum change in AIx post-GTN was at 3 min with a mean change from the baseline of -17.86% +/- 4.40% (p < 0.001). There were no significant changes noted after 30 and 40 min with mean change being -0.82% +/- 2.61% and 0.14% +/- 3.20%, respectively (p > 0.05). Significant changes in PWV were noted at 5 and 10 min with the mean change of -0.33 +/- 0.36 m/s and -0.33 +/- 0.35 m/s, respectively (p = 0.01). There were no further changes noted at 15 min and thereafter (p > 0.05). A duration of at least 30 min after GTN is required for AIx and PWV values to reach their baseline. Thus, the administration of salbutamol should be given only after 30 min of sublingual GTN for the assessment of endothelial function.

Anomalous right pulmonary artery from the aorta

Anomalous origin of the right pulmonary artery is a rare form of congenital heart disease. It usually presents in early infancy with heart failure and rapid development of pulmonary hypertension. There are about 131 cases reported in the literature and we report one such case.

Percutaneous closure of atrial septal defect type ostium secundum using the new Intrasept occluder: Initial experience

We report the first experience obtained with the new Intrasept device. We attempted to treat 35 patients with a mean age of 43 +/- 21 years. The mean size of the defect was 17/15 mm. It was successfully closed in 31 patients. In the remaining four the device could not be stabilized because of excessive defect size. A small residual shunt was present immediately following implantation in three patients. No complications occurred during the procedure and at 6 months, 31 patients had an uneventful outcome. Only one patient had a small residual shunt. No thrombus, embolization, or device fracture was documented during a mean follow-up of 17 +/- 11 months. Percutaneous closure of ASD ostium secundum is feasible with the Intrasept device with a high success rate and very good medium-term outcome. Our initial experience and results were excellent with small to medium size defects, however, large defects (>20 mm) remain challenging.

Hydroxyzine-induced supraventricular tachycardia in a nine-year-old child

Hydroxyzine is a first generation antihistamine widely used in the paediatric population for a variety of conditions. A nine-year-old girl presented with supraventricular tachycardia while on clinical doses of hydroxyzine for pruritus. On arrival at the hospital, she was diaphoretic, with cool peripheries, poor peripheral pulses and a heart rate of 250/minute. There was a history of three palpitation episodes with chest tightness during the five months she was taking hydroxyzine. The supraventricular tachycardia eventually reverted to sinus rhythm with intravenous verapamil. Relevant cardiac examination and investigations had not shown any cardiac abnormalities. After discontinuing hydroxyzine, she had no further episodes of supraventricular tachycardia. To our knowledge, this is the first report of hydroxyzine induced-supraventricular tachycardia in the medical literature.

Hansenula anomala infection in a neonate

We present an unusual neonatal fungal infection, Hansenula anomala in a very low birthweight infant who underwent abdominal surgery for an omphalocele. Despite treatment with adequate doses of amphotericin B, the yeast continued to grow from the blood culture, and was only eradicated with the use of oral ketoconazole.