Long-term future risk of severe exacerbations: Distinct 5-year trajectories of problematic asthma.

BACKGROUND: Assessing future risk of exacerbations is an important component of asthma management. Existing studies have investigated short- but not long-term risk. Problematic asthma patients with unfavorable long-term disease trajectory and persistently frequent severe exacerbations need to be identified early to guide treatment. AIM: To identify distinct trajectories of severe exacerbation rates among "problematic asthma" patients and develop a risk score to predict the most unfavorable trajectory. METHODS: Severe exacerbation rates over five years for 177 "problematic asthma" patients presenting to a specialist asthma clinic were tracked. Distinct trajectories of severe exacerbation rates were identified using group-based trajectory modeling. Baseline predictors of trajectory were identified and used to develop a clinical risk score for predicting the most unfavorable trajectory. RESULTS: Three distinct trajectories were found: 58.5% had rare intermittent severe exacerbations ("infrequent"), 32.0% had frequent severe exacerbations at baseline but improved subsequently ("nonpersistently frequent"), and 9.5% exhibited persistently frequent severe exacerbations, with the highest incidence of near-fatal asthma ("persistently frequent"). A clinical risk score composed of ≥2 severe exacerbations in the past year (+2 points), history of near-fatal asthma (+1 point), body mass index ≥25kg/m2 (+1 point), obstructive sleep apnea (+1 point), gastroesophageal reflux (+1 point), and depression (+1 point) was predictive of the "persistently frequent" trajectory (area under the receiver operating characteristic curve: 0.84, sensitivity 72.2%, specificity 81.1% using cutoff ≥3 points). The trajectories and clinical risk score had excellent performance in an independent validation cohort. CONCLUSIONS: Patients with problematic asthma follow distinct illness trajectories over a period of five years. We have derived and validated a clinical risk score that accurately identifies patients who will have persistently frequent severe exacerbations in the future.

Nitric oxide synthase expression and activity in the tight-skin mouse model of fibrosis.

OBJECTIVES: Nitric oxide (*NO) is an important physiological signalling molecule and a potent vasodilator. We have previously demonstrated abnormal *NO metabolism in the plasma of patients with systemic sclerosis (SSc; scleroderma), a disease that features vascular dysfunction as well as collagen overproduction and fibrosis. The aim of the present study was to examine nitric oxide synthase (NOS) expression and activity and assess the potential role of antioxidants in the scleroderma-like syndrome of the tight-skin 1 (TSK-1/+) mouse, an experimental animal model for fibrosis. METHODS: Skin, lung or plasma was taken from TSK-1/+ (n = 15) and wild-type (WT; n = 12) littermate mice. Type 1 collagen, endothelial NOS (eNOS), haemoxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) protein and gene expression were determined by western blot and reverse transcriptase-polymerase chain reaction. eNOS expression was further determined by immunohistochemistry. NOS activity was evaluated by conversion of [14C] L-arginine to [14C] L-citrulline. Levels of circulating plasma nitrite/nitrate (NO(x)) were also measured. Total antioxidant activity was evaluated by ABTS+ production (ABTS = 2,2'-azino-bis-[3-ethylbenz-thiazoline-6-sulphonic acid). RESULTS: In the skin, eNOS was present in the epidermal layer, hair follicles and also in the endothelial cells lining the blood vessels. Expression of both the eNOS protein and gene was significantly reduced in TSK-1/+ skin tissue, while type 1 collagen protein was elevated compared with WT. Furthermore, there was decreased NOS activity in TSK-1/+ skin tissue; however, there was no measurable difference in plasma NO(x). Correspondingly, the protective antioxidant enzyme HO-1 and the associated transcription factor Nrf2 showed reduced protein and gene expression levels in TSK-1/+ skin, while there was also less total antioxidant activity. In TSK-1/+ lung tissue, however, we observed no difference in collagen protein expression, *NO metabolism or HO-1 expression and total antioxidant activity compared with WT. CONCLUSIONS: The findings suggest that there is also abnormal *NO metabolism in the TSK-1/+ mouse model of fibrosis, particularly in the skin, while expression and activity of protective antioxidants are reduced. The TSK-1/+ mouse may also be useful for testing treatments that target vascular endothelial cell function in patients with SSc.

A role for membrane transport in modulation of intramuscular free glutamine turnover in streptozotocin diabetic rats.

We wished to examine the effects of diabetes on muscle glutamine kinetics. Accordingly, female Wistar rats (200 g) were made diabetic by a single injection of streptozotocin (85 mg/kg) and studied 4 days later; control rats received saline. In diabetic rats, glutamine concentration of gastrocnemius muscle was 33% less than in control rats: 2.60 +/- 0.06 mumol/g vs. 3.84 +/- 0.13 mumol/g (P < 0.001). In gastrocnemius muscle, glutamine synthetase activity (Vmax) was unaltered by diabetes (approx. 235 nmol/min per g) but glutaminase Vmax increased from 146 +/- 29 to 401 +/- 94 nmol/min per g; substrate Km values of neither enzyme were affected by diabetes. Net glutamine efflux (A-V concentration difference x blood flow) from hindlimbs of diabetic rats in vivo was greater than control values (-30.0 +/- 3.2 vs. -1.9 +/- 2.6 nmol/min per g (P < 0.001)) and hindlimb NH3 uptake was concomitantly greater (about 27 nmol/min per g). The glutamine transport capacity (Vmax) of the Na-dependent System Nm in perfused hindlimb muscle was 29% lower in diabetic rats than in controls (820 +/- 50 vs. 1160 +/- 80 nmol/min per g (P < 0.01)), but transporter Km was the same in both groups (9.2 +/- 0.5 mM). The difference between inward and net glutamine fluxes indicated that glutamine efflux in perfused hindlimbs was stimulated in diabetes at physiological perfusate glutamine (0.5 mM); ammonia (1 mM in perfusate) had little effect on net glutamine flux in control and diabetic muscles. Intramuscular Na+ was 26% greater in diabetic (13.2 mumol/g) than control muscle, but muscle K+ (100 mumol/g) was similar. The accelerated rate of glutamine release from skeletal muscle and the lower muscle free glutamine concentration observed in diabetes may result from a combination of: (i), a diminished Na+ electrochemical gradient (i.e., the net driving force for glutamine accrual in muscle falls); (ii), a faster turnover of glutamine in muscle and (iii), an increased Vmax/Km for sarcolemmal glutamine efflux.

Involvement of integrins and the cytoskeleton in modulation of skeletal muscle glycogen synthesis by changes in cell volume.

Muscle glycogen synthesis is modulated by physiologically relevant changes in cell volume. We have investigated the possible involvement of integrin-extracellular matrix interactions in this process using primary cultures of rat skeletal muscle subject to hypo- or hyper-osmotic exposure with integrin binding peptide GRGDTP to disrupt integrin actions and the inactive analogue GRGESP as control. Osmotically induced increases (77%) and decreases (34%) in glycogen synthesis (D-[14C]glucose incorporation into glycogen) were prevented by GRGDTP (but not GRGESP) without affecting glucose transport. Cytoskeletal disruption with cytochalasin D or colchicine had similar effects to GRGDTP. Osmotically induced modulation of muscle glycogen synthesis involves integrin-extracellular matrix interactions and cytoskeletal elements, possibly as components of a cell-volume 'sensing' mechanism.

The nitration of platelet cytosolic proteins during agonist-induced activation of platelets.

The nitration of protein tyrosine residues by peroxynitrous acid has been associated with pathological conditions. Here it is shown, using a sensitive competitive enzyme-linked immunosorbent assay and immunoblotting for nitrotyrosine, that spontaneous nitration of specific proteins occurs during a physiological process, the activation of platelets by collagen. One of the main proteins nitrated is vasodilator-stimulated phosphoprotein. Endogenous synthesis of nitric oxide and activity of cyclo-oxygenase were required for the nitration of tyrosine. The nitration was mimicked by addition of peroxynitrite to unstimulated platelets, although the level of nitrotyrosine formation was greater and its distribution among the proteins was less specific.

Characterization of glucose transport and glucose transporters in the human choriocarcinoma cell line, BeWo.

In this study we have characterized 2-deoxyglucose (2DG) transport and hexose transporter expression in the human choriocarcinoma cell line, BeWo. 2DG uptake in BeWo cells displayed saturable kinetics (V(max), 29+/-1.5 nmol/min/mg protein;K(m), 1.5+/-0.02 m m) and was significantly inhibited in the presence of 2-deoxyglucose, mannose and 3- O -methyl glucose (all at a competing concentration of 30 m m) by up to 97 per cent, but not by galactose or fructose. Glucose uptake was not Na(+)-dependent, but was inhibited by cytochalasin B (by approx 85 per cent) indicating that hexose uptake was mediated via a facilitative glucose transport mechanism. Northern and immunoblot analyses revealed that BeWo cells expressed GLUT1 and GLUT5, but not GLUT2 or GLUT3. On immunoblots, GLUT1 migrated as a broad protein band on SDS-gels (average M(r)of 55 kDa) and treatment with N -glycanase resulted in a significant shift in its electrophoretic mobility; the core protein migrating as a 40 kDa band indicating that the carrier was heavily glycosylated. GLUT5 was detected as a discrete 60 kDa band and like GLUT1, the observed immunoreactive signal was lost when using antiserum that had been pre-adsorbed with the antigenic peptide. Our findings indicate that BeWo cells express a facilitative glucose transport system with characteristics broadly similar to those reported in isolated human placental membrane vesicles and that they are likely to serve as a useful experimental system for studying the regulation of placental glucose transport and transporter expression.

Simple aspiration versus chest-tube insertion in the management of primary spontaneous pneumothorax: a systematic review.

BACKGROUND: The initial treatment of a primary spontaneous pneumothorax (PSP) is controversial. Guidelines of the British Thoracic Society recommend simple aspiration for all PSP requiring intervention. The placement of chest tubes is only advocated for patients who fail simple aspiration. However, the American College of Chest Physicians Delphi Consensus Statement found simple aspiration to be rarely appropriate in the management of PSP. AIMS: To compare simple aspiration with chest-tube drainage in the initial management of PSP. METHODS: Meta-analysis of randomized controlled trials (RCTs). OUTCOME MEASURES: Reductions in duration of hospital stay, recurrence rate and pain or dyspnoea score were classified as benefits, whereas reductions in successful events were classified as risks. DATA COLLECTION AND ANALYSIS: For dichotomous data, the relative risk (RR) and 95% confidence intervals were calculated. For continuous data, weighted mean differences (WMD) were used. RESULTS: Three RCTs were identified with a combined total of 194 patients. Simple aspiration was associated with shorter hospitalization (WMD -1.30 days [-2.20 to -0.39]). The results for success rate could not be combined because of differences in outcome definitions. However, a pooled result for "success at 1 week or more" showed no significant difference between either intervention (RR 0.86 [0.67, 1.11]). Results of recurrence at 1 year were also not significantly different (RR 0.73 [0.39-1.38]). Different reporting systems for pain scores meant that data could not be pooled. Only one trial reported dyspnoea scores. CONCLUSION: RCT evidence in this field is limited, and the total sample size is too small to make any firm conclusion. On the basis of current available evidence, simple aspiration is advantageous in the initial management of PSP because of shorter hospitalization. There is no significant difference in recurrence at 1 year using either modality, and the efficacy data are inconclusive.

Primary endotracheal neurogenic tumors.

Benign tumors in the tracheobronchial tree are rare. We report two cases of primary endotracheal neurogenic tumors in patients who presented insidiously. Both patients did not manifest other clinical features of neurofibromatosis (Von Recklinghausen's disease). A single procedure using rigid bronchoscopy and neodymium: yttrium-aluminum-garnet laser resection resulted in excellent resolution of airway patency with good follow-up results in both cases.

Amino acid transport during muscle contraction and its relevance to exercise.

The functional significance of amino acid transport in skeletal muscle has been explored by the use of a variety of techniques including work in isolated perfused organs, isolated incubated organs and tissue culture of muscle cells. The results suggest that although there is a wide variety of amino acid transport systems of different characteristics and with different responses to ionic, hormonal and nervous modulation, the amino acid glutamine (transported by system Nm) demonstrates some unusual properties not observed with amino acids transported by other systems. Glutamine is transported at very high rates in skeletal muscle and heart and both the glutamate and glutamine transporter appear to be adaptively regulated by the availability of glutamine. Glutamine appears to be involved in the regulation of a number of important metabolic processes in heart and skeletal muscle (e.g., regulation of the glutathione reduced/oxidised ratio and regulation of protein and glycogen synthesis). Furthermore, glutamine transport appears to interact with systems for regulation of volume control and many of the metabolic features attributable to changes in glutamine concentration appear to be modulated via alteration in cytoskeletal status.

All that wheezes is not asthma--broncholithiasis, a forgotten disease.

INTRODUCTION: Asthma is a common condition seen by medical practitioners. However, 'all that wheezes is not asthma', is an important adage not to be forgotten. We report a case of broncholithiasis which was initially misdiagnosed as asthma. CLINICAL PICTURE: An 81-year-old female presented with cough and intermittent wheezing associated with one episode of haemoptysis. Chest radiograph and CT thorax were suggestive of broncholithiasis. This was confirmed by flexible bronchoscopy. TREATMENT: The broncholith was successfully extracted using flexible bronchoscopy. OUTCOME: The patient had complete resolution of symptoms post procedure. CONCLUSIONS: Physicians should always entertain other differential diagnoses which may mimic asthma.

Management of ruptured intracranial aneurysms in the post-ISAT era: outcome of surgical clipping versus endovascular coiling in a Singapore tertiary institution.

INTRODUCTION: The results of the International Subarachnoid Aneurysm Trial (ISAT) in 2002 have significantly influenced the management of ruptured intracranial aneurysms. There is now an established shift worldwide toward endovascular coiling as the initial treatment of choice. We assessed the outcomes of patients admitted to our institution for aneurysmal subarachnoid haemorrhage (SAH), comparing the outcomes of patients (World Federation of Neurosurgical Societies [WFNS] grades 1-3) who underwent surgical clipping versus those who underwent endovascular coiling. METHODS: We retrospectively reviewed patients admitted to the National University Hospital for SAH secondary to ruptured intracranial aneurysm in 2005-2009. Patients were divided into two groups - clipping and coiling. Data on individual demographics, comorbidities, Fisher grading and Glasgow Outcome Scale scores were collected for the two groups and subjected to relevant statistical analyses. RESULTS: Of the 133 patients admitted for nontraumatic SAH, 89 had ruptured aneurysms. Among the 56 patients classified as WFNS grades 1-3, 23 underwent coiling while the remaining 33 underwent clipping. A significant association was found between Fisher grade and the likelihood of developing hydrocephalus in these patients. CONCLUSION: Although we acknowledge the presence of management bias in our institution, our findings were similar to those of the ISAT trial. Upon correlation between our results and current evidence-based findings, our findings show that clipping provides similar long-term outcomes as endovascular coiling. In the event that an aneurysm is deemed unsuitable for coiling, clipping remains an effective option.

Severe adenovirus pneumonia requiring extracorporeal membrane oxygenation support--Serotype 7 revisited.

INTRODUCTION: Adenovirus causing severe fatal pneumonia has been well described in infants, children, and patients with immunocompromised function, but reports in previously healthy adults are rare. We report 3 cases of severe adenovirus pneumonia in whom conventional mechanical ventilation failed and required extracorporeal membrane oxygenation support. METHODS: Retrospective case records review of 3 patients admitted to the medical intensive care unit, Singapore General Hospital, a tertiary care university-affiliated hospital, with severe adenovirus pneumonia requiring extracorporeal membrane oxygenation support from February to March 2013. RESULTS: All 3 patients were previously healthy immunocompetent adults from the community with negative HIV serology. Duration prior to development of respiratory failure requiring intubation and invasive mechanical ventilation was 2, 8 and 3 days. Veno-venous extracorporeal membrane oxygenation (ECMO) support as rescue ventilation was instituted in all 3 patients after 2, 16, and 5 days of conventional mechanical ventilator support. Duration on ECMO support was 16, 22, and 9 days and mechanical ventilation was 18, 62, and 19 days respectively. Length of stay in intensive care unit was 18, 68, and 21 days, and length of stay in hospital was 20, 70, and 31 days respectively. Two of the 3 patients died. CONCLUSION: The mainstay of treatment for patients with severe adenovirus pneumonia is still supportive, with the use of antivirals not apparently effective. Whilst ECMO support for rescue ventilation may be considered, the outcomes do not appear as promising as other viral pneumonias, mirroring that previously described in the paediatric population.

Human immunodeficiency virus testing in patients with newly-diagnosed tuberculosis in Singapore.

INTRODUCTION: Infection with human immunodeficiency virus (HIV) is the most well-known risk factor for the development of tuberculosis (TB). The joint statement by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America recommends that all patients with TB undergo testing for HIV infection after counselling. We looked at physician compliance with this recommendation in Singapore. METHODS: A retrospective review of the case records of all patients diagnosed with microbiologically-proven TB between September 2005 and December 2006 (inclusive) at the Singapore General Hospital was conducted. RESULTS: Between September 2005 and December 2006, 493 patients were diagnosed with tuberculosis at our institution. HIV testing was performed in 184 patients (37.3 percent), of whom 15 (8.2 percent) was seropositive. Univariate analysis showed that an age equal to or younger than 60 years, male gender, non-pulmonary tuberculosis, inpatient location at diagnosis, and having an infectious diseases physician as the attending doctor were all significantly associated with HIV testing (p-value is less than 0.05). CONCLUSION: Compliance with HIV testing in all newly-diagnosed tuberculosis patients is poor, with less than 40 percent of patients being tested at our institution. We need to address the factors associated with failure to test, and reinforce to our physicians the importance of HIV testing in these patients.

Langerhans cell histiocytosis with hypogonadotrophic hypogonadism.

Langerhans cell histiocytosis (LCH) is a rare disease characterised by monoclonal proliferation and infiltration of organs by large mononuclear cells. Organs commonly involved include the lungs and pituitary gland. However, the disease association with hypogonadotrophic hypogonadism has not been reported in the literature, to our knowledge. We report a 26-year-old Chinese man with LCH, recurrent pneumothoraces, diabetes insipidus and hypogonadotrophic hypogonadism. The clinical features and management of the disease are reviewed.

An unusual complication of dengue infection.

We present an unusual complication of dengue infection resulting in postviral phrenic neuropathy and diaphragmatic paralysis in a 34-year-old man. There is a paucity of literature on this condition, with postviral neuropathies previously reported to be associated commonly with herpes zoster, poliovirus, and rarely, West Nile virus and human immunodeficiency virus infections. To our knowledge, this is the first reported case of flavivirus causing isolated postviral phrenic neuropathy and diaphragmatic paralysis.

Integrin and cytoskeletal involvement in signalling cell volume changes to glutamine transport in rat skeletal muscle.

1. Muscle glutamine transport is modulated in response to changes in cell volume by a mechanism dependent on active phosphatidylinositol 3-kinase. We investigated the possibility that this mechanism requires interactions between the extracellular matrix (ECM), integrins and the cytoskeleton as components of a mechanochemical transduction system. 2. Using skeletal muscle cells, we studied effects of (a) inactivating integrin-substratum interactions by using integrin-binding peptide GRGDTP with inactive peptide GRGESP as control, and (b) disrupting the cytoskeleton using colchicine or cytochalasin D, on glutamine transport after brief exposure to hypo-osmotic, isosmotic or hyperosmotic medium (170, 300 and 430 mosmol kg-1, respectively). 3. Neither GRGDTP nor GRGESP significantly affected basal glutamine uptake (0.05 mM; 338 +/- 58 pmol min-1 (mg protein)-1) but GRGDTP specifically prevented the increase (71%) and decrease (39%) in glutamine uptake in response to hypo- and hyperosmotic exposure, respectively. 4. Colchicine and cytochalasin D prevented the increase and decrease in glutamine uptake in response to changes in external osmolality. They also increased basal glutamine uptake by 59 +/- 19 and 85 +/- 16%, respectively, in a wortmannin-sensitive manner. 5. These results indicate involvement of ECM-integrin-mediated cell adhesion and the cytoskeleton in mechanochemical transduction of cell volume changes to chemical signals modulating glutamine transport in skeletal muscle. Phosphatidylinositol 3-kinase may function to maintain the mechanotransducer in an active state.

Sodium-dependent glutamate transport in cultured rat myotubes increases after glutamine deprivation.

Glutamine produced and stored in skeletal muscle is an important source of nitrogen and energy for the whole body in health and disease and, unsurprisingly, glutamine turnover in muscle is subject to substantial metabolic control. L-Glutamate, a necessary substrate for glutamine synthetase, is transported into muscle cells by Na(+)-dependent and -independent transport systems. In primary cultures of rat skeletal muscle myotubes (a useful model system for studies of muscle metabolism and membrane transport), Na(+)-dependent glutamate transport (Km approximately 0.7 mM glutamate) shows adaptive upregulation (65% increase in transport Vmax from 2.7 to 4.4 nmol.min-1 x mg protein-1) in cells within 24 h of glutamine depletion (t1/2 for increase of approximately 4 h), whereas Na(+)-independent glutamate uptake remains unaltered. Up-regulation of transport is suppressed by inhibitors of gene transcription (actinomycin-D) and translation (cycloheximide) and is reversed by glutamine supplementation. Increased glutamate transport capacity should provide extra substrate for glutamine synthesis in muscle cells. Thus, in concert with previously discovered increases in cell glutamine transport capacity and glutamine synthetase activity, it may represent part of a co-ordinated response to decreased glutamine availability (e.g., under circumstances of increased glutamine utilization by other tissues in vivo.

Interventional bronchoscopy for tuberculous tracheobronchial stenosis.

This study investigated the use of interventional bronchoscopic techniques in the management of patients with symptomatic tracheobronchial stenosis from tuberculosis. The current authors evaluated their experience with interventional bronchoscopic techniques in 21 consecutive patients at the Singapore General Hospital, Singapore, from November 1994 to March 2001. All patients underwent rigid bronchocopy using the Dumon rigid ventilating bronchosope under general anaesthesia. A combination of techniques was used (mechanical or balloon dilatation, Nd-YAG laser and stenting using the Dumon stent). The mean+/-SD increase in luminal diameter of the tracheal lesions was from 4.5+/-2.5 mm pre-procedure to 11.9+/-1.7 mm post-procedure, whereas that for the mainstem bronchi stenosis was from 2.6+/-1.0 mm to 8.3+/-2.4 mm. All patients had immediate relief of symptoms post-intervention. Two patients who presented with acute respiratory failure could be weaned off mechanical ventilation immediately post-procedure. At the end of the study period, 52% (11 out of 21) remained asymptomatic. Bronchoscopic intervention provided immediate symptomatic relief in all of the studied patients. However, repeated sessions may be required to maintain this improvement. It is concluded that interventional bronchoscopic techniques are useful in the management of patients with tracheobronchial stenosis from tuberculosis.

Responses of glutamine transport in cultured rat skeletal muscle to osmotically induced changes in cell volume.

1. In order to investigate the relationship between cellular hydration state and the rate of glutamine transport, tracer glutamine uptake into primary rat myotubes was studied at external osmolalities of 170, 320 or 430 mosmol kg-1. 2. Incubation of myotubes with glutamine (2 mM; 30 min) at 320 mosmol kg-1 increased cell volume and glutamine transport (by 35 and 36%, respectively); insulin (66 nM; 30 min) also increased cell volume and glutamine transport (by 22 and 40%, respectively) and the effects of insulin and glutamine combined were additive. The increase in glutamine uptake following glutamine pre-incubation represented an increase in Vmax of Na(+)-dependent glutamine transport. 3. There was an inverse relationship between myotube glutamine transport and external osmolality after 30 min exposure. 4. During hyposmotic (170 mosmol kg-1) exposure there were large, rapid increases of cell volume and glutamine transport; the latter increased transiently (during the cell swelling phase) by a maximum of approximately 80% at 2 min, (due to an increased Vmax for Na(+)-dependent glutamine transport) then decayed to a new elevated steady state after 30 min exposure. 5. During hyperosmotic (430 mosmol kg-1) exposure there were rapid decreases in glutamine transport and myotube cell volume (both by approximately 30%) to values which were maintained for at least 15 min. 6. The volume-sensitive glutamine transport process features characteristics of the insulin-sensitive system Nm transporter. 7. Modulation of Na(+)-dependent glutamine transport by insulin and cell volume changes may contribute towards regulation of muscle metabolism.