Experimental Ecosystem Eutrophication Causes Offsetting Effects on Emissions of CO2, CH4, and N2O from Agricultural Reservoirs

Despite decades of research and management efforts, eutrophication remains a persistent threat to inland waters. As nutrient pollution intensifies in the coming decades, the implications for aquatic greenhouse gas (GHG) emissions are poorly defined, particularly the responses of individual GHGs: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The biogeochemical controls of each gas can differ, making it difficult to predict the overall effect of nutrient pollution on the net radiative forcing of aquatic ecosystems. Here, we induced eutrophication of small nitrogen (N)-limited agricultural reservoirs and measured changes in diffusive GHG emissions within a before-after-control-impact (BACI) study design during June to September 2021. Each gas exhibited a unique response to 300% increases in primary production, with a shift from an overall CO2 source to a sink, a modest increase in N2O flux, and, unexpectedly, no significant change in CH4 emissions. The lack of net directional change in CO2-equivalent GHG emissions in fertilized reservoirs during the summer contrasts findings from empirical studies of eutrophic lakes. Our findings illustrate the difficulty in extrapolating among different sized ecosystems and suggest that forecast 2-fold increases in agricultural N fertilization by 2050 may not result in consistently elevated GHG emissions during summer, at least from small reservoirs in continental grassland regions.

Salinity causes widespread restriction of methane emissions from small inland waters

Inland waters are one of the largest natural sources of methane (CH4), a potent greenhouse gas, but emissions models and estimates were developed for solute-poor ecosystems and may not apply to salt-rich inland waters. Here we combine field surveys and eddy covariance measurements to show that salinity constrains microbial CH4 cycling through complex mechanisms, restricting aquatic emissions from one of the largest global hardwater regions (the Canadian Prairies). Existing models overestimated CH4 emissions from ponds and wetlands by up to several orders of magnitude, with discrepancies linked to salinity. While not significant for rivers and larger lakes, salinity interacted with organic matter availability to shape CH4 patterns in small lentic habitats. We estimate that excluding salinity leads to overestimation of emissions from small Canadian Prairie waterbodies by at least 81% ( ~ 1 Tg yr-1 CO2 equivalent), a quantity comparable to other major national emissions sources. Our findings are consistent with patterns in other hardwater landscapes, likely leading to an overestimation of global lentic CH4 emissions. Widespread salinization of inland waters may impact CH4 cycling and should be considered in future projections of aquatic emissions.

CO2 dynamics in a small and old subtropical reservoir in East Asia: Environmental controls driving seasonal and spatial variability

Inland waters have been increasingly viewed as hotspots for greenhouse gas (GHG) emissions owing to their strong capability to intercept and mineralize carbon from the terrestrial environment. Although small waterbodies in humid subtropical climates have the potential to emit considerable amounts of GHG, their emission patterns have remained understudied. This study involved intensive measurements of carbon dioxide (CO₂) emissions from a small reservoir and its upstream and downstream reaches located in subtropical Hong Kong. Our results revealed that a variety of metabolic, hydrological, and hydrochemical processes play a critical role in regulating its CO₂ dynamics. The reservoir was an overall source of CO₂ to the atmosphere with an average areal flux of 24.6 mmol m^-2 d^-1, and it occasionally functioned as a sink for atmospheric CO₂ under intense solar radiation when primary productivity was high. This flux is on the low side relative to that of global (sub)tropical reservoirs, which was likely attributable to the prolonged history of the reservoir (>150 years) and the occasional undersaturation of CO₂ in the water column. We also noticed pronounced differences in the underlying controls of CO₂ dynamics between the reservoir and its upstream and downstream reaches, emphasizing the importance of taking into account the distinct characteristics of both lentic and lotic waters when evaluating catchment-scale CO₂ fluxes.

Percutaneous transluminal coronary angioplasty in Singapore General Hospital in 1995: a medical audit

BACKGROUND

There are few reports which describe the outcomes of unselected groups of patients undergoing percutaneous transluminal coronary angioplasty (PTCA) locally. This study has undertaken to audit the outcome of patients undergoing elective PTCA at Singapore General Hospital.

METHODS

Procedural data and acute outcomes were recorded prospectively in all patients undergoing PTCA over a 12 month period. A retrospective casenotes review of all patients were carried by independent observers to determine out-of-lab complications.

RESULTS

Seven hundred and eight-two patients underwent PTCA in 1995. Acute angiographic success rate was 90.9% and early clinical success rate was 89% ie excluding death, coronary bypass surgery and non fatal myocardial infarction. There were only two deaths in the series (0.26%).

CONCLUSION

The audit confirms the importance of a high volume PTCA cases to achieve excellent results. The data serve as a useful background for future comparison of outcomes.

Prosthetic valve thrombosis: a case report and review of the literature

An elderly man with a St Jude mitral prosthesis presented to our institution in cardiogenic shock. Acute thrombosis of the valve was diagnosed by fluoroscopy and transoesophageal echocardiography. Successful lysis of the thrombus was achieved with intravenous streptokinase therapy and the patient recovered without any adverse sequelae. Prosthetic valve thrombosis is a life-threatening condition that requires prompt detection and surgical intervention. Thrombolytic therapy is a promising alternative to surgery especially in critically ill patients.

Percutaneous transluminal coronary angioplasty of an anomalous right coronary artery arising from a separate ostium in the left sinus of Valsalva. A case report

The authors describe a case of angioplasty in an anomalous right coronary artery arising from an aberrant ostium in the left sinus of Valsalva anterior and slightly superior to the ostium of the left main coronary artery. The patient also had associated bicuspid aortic valve. To the best of their knowledge, this is the first case of angioplasty in an aberrant right coronary artery originating from an ectopic ostium. The choice of guiding catheter and balloon angioplasty catheter is discussed.

Single coronary artery: a case report and review of current literature

We present a case of a single coronary artery where the right coronary artery (RCA) arose from its proximal part. This rare anomaly was detected during elective coronary angiography in a patient with suspected coronary artery disease. The single coronary artery originated from the left sinus of valsalva, giving rise to RCA proximally and distally dividing into left anterior descending (LAD), ramus intermedius and left circumflex (LCX) arteries. The anginal symptoms in this patient was attributed to a significant stenosis at the proximal LAD which was subsequently dilated by coronary angioplasty. To the best of our knowledge, this is the first reported case of angioplasty of LAD in an anomalous single coronary artery.

Intracoronary stenting in the treatment of acute or threatened closure in angiographically small coronary arteries (< 3.0 mm) complicating percutaneous transluminal coronary angioplasty

The effect of the Flex-Stent on immediate and long-term angiographic and clinical results for acute and threatened closure was evaluated in 42 consecutive patients with coronary arterial segments < 3.0 mm in diameter after percutaneous transluminal coronary angioplasty (PTCA). Forty-two consecutive patients were treated with Flex-Stent (2.0 or 2.5 mm) for acute or threatened closure complicating PTCA. Ten patients (24%) had acute closure and 32 (76%) had threatened closure with a residual luminal stenosis of > 50%. Successful stent deployment was achieved in 40 patients (95%) with a primary clinical success rate of 90% (freedom from myocardial infarction, coronary artery surgery, and death). In-hospital complications occurred in 5 patients (some patients fell into more than one category): 3 (7.1%) had coronary bypass surgery, 1 (2.4%) had acute stent thrombosis, 1 (2.4%) had subacute stent thrombosis, 2 (4.8%) had myocardial infarction, and 1 (2.4%) had dextran allergy. There was no hospital death. Clinical follow-up was complete at a mean of 14.8 +/- 7.6 months, and recurrence of angina was noted in 20 of 38 eligible patients (53%). Angiographic restenosis was found in 19 of 29 patients (66%) (76.3% of eligible patients) on follow-up angiography (mean 5.9 +/- 4.6 months). Fourteen patients (74%) underwent successful repeat PTCA at the stented site, 4 of 38 patients (11%) had bypass surgery. Intracoronary stenting in the treatment of acute or threatened closure in arteries < 3.0 mm is effective in improving the acute clinical outcome and is a viable nonsurgical alternative for this subset of patients.

A lesion marker to facilitate placement of the Simpson's atherocath device during directional atherectomy of left anterior descending coronary artery stenoses

Placement of the directional coronary atherectomy cutter requires frequent angiographic contrast injections to aid in the precise location of the device in relation to the target stenosis. A method is described to enable rapid positioning of this device across stenotic lesions occurring in the left anterior descending coronary artery, with the use of a simple lesion marker. Two short lines demarcating the limits of the stenotic lesion are drawn onto a transparent one-sided adhesive plastic sheet that has been pasted beforehand onto the active monitor screen. Using this reference marker, the atherectomy device can be reliably positioned across the stenotic lesion.

Results of percutaneous transseptal mitral commissurotomy in patients 40 years and above with those under 40 years of age: immediate and 5-year follow-up results

Patients with mitral stenosis in Western countries are relatively old. It is anticipated that percutaneous transseptal mitral commissurotomy (PTMC) may have more complications and may not be as effective in this group of patient as in younger patients due to more calcification and fibrosis of the mitral valve. We analysed the clinical, hemodynamic, echocardiographic data in 296 consecutive patients divided prospectively into two groups; group 1 consisted of 184 patients > or = 40 years and group 2 of 112 patients < 40 years coming mostly from developing countries. The immediate gain in valve area was 2.18 +/- 0.61 cm2 in group 1 vs. 2.31 +/- 0.65 cm2 in group 2 (P = ns). The incidence of acute regurgitation requiring surgical intervention was similar in both groups. Follow-up data up to 5 years after PTMC was available in 170 patients (92.4%) in group 1 (mean 20 +/- 13 months) and 83 patients (74.1%) in group 2 (mean 29 +/- 17 months). Restenosis by Doppler method (valve area less than 1.5 cm2 with loss of at least 50% initial gain in valve area) was found in 33 patients in group 1 (29.2%) vs. 11 (14.9%) in group 2 (P < 0.05). Events free from death, need for mitral valve replacement or repeat PTMC at 5 year follow-up was 76% in group 1 vs. 87% in group 2 (P < 0.05). We conclude that the immediate effectiveness and acute complications of PTMC in patients 40 years and above are comparable to younger patients. Restenosis is clearly higher and there is a trend towards need for mitral valve replacement in patients 40 years and above at follow-up. However, the continuing benefit for the majority of the patients 40 years and above (76% free from adverse events) would suggest that PTMC is an appropriate treatment modality even in the older patients.

Percutaneous balloon aortic valvotomy

We report our first case of percutaneous balloon aortic valvotomy in a 72-year-old Chinese female with critical aortic stenosis and carcinoma of the stomach. The presence of critical aortic stenosis (mean aortic pressure gradient of 65 mmHg and an aortic valve area of 0.5 cm2) placed her at a high risk for gastrectomy. After balloon valvotomy of the aortic valve, the mean pressure gradient fell to 21 mmHg and the aortic valvular area increased to 1.0 cm2. She improved clinically and subsequently underwent surgery with no haemodynamic complication. Overseas experience has shown that percutaneous balloon valvotomy can be done with little technical difficulty and excellent patient tolerance, resulting in good haemodynamic and clinical improvement and a low acute complication rate. Present follow-up data however suggest significant mortality and restenosis rates at the end of one year. Percutaneous balloon aortic valvotomy (PBAV) has a significant though narrowly defined role in the management of patients with severe calcific aortic stenosis.

Percutaneous transseptal balloon mitral valvotomy: initial experience in Singapore

Between June 1990 and August 1991, 28 percutaneous transseptal balloon mitral valvotomy procedures were attempted in 27 patients (23 women and 4 men; mean age 39.8 +/- 9.3 years) with severe mitral stenosis. Successful mitral valvotomy was achieved in 25 patients (primary success rate of 92%). Mitral valve area increased from 0.82 +/- 0.17 cm2 to 1.53 +/- 0.48 cm2 (p < 0.001) and the mean mitral valve gradient decreased from 13.4 +/- 7.4 to 6.0 +/- 5.4 mmHg (p < 0.05). There were no deaths, one patient had cardiac tamponade after transseptal puncture and required emergency pericardiocentesis with successful percutaneous balloon valvotomy 6 months later. One patient had an unsuccessful valvotomy because the mitral valve could not be crossed and another patient had an inadequate dilatation. Our initial experience in percutaneous transseptal mitral valvotomy confirms the safety and efficacy of this new technique for the treatment of rheumatic mitral stenosis.

An unusual case of systemic lupus erythematosus with isolated hypoglossal nerve palsy, fulminant acute pneumonitis, and pulmonary amyloidosis

A 53 year old Chinese man with systemic lupus erythematosus (SLE) had an isolated 12th nerve palsy and acute pneumonitis. He died of respiratory failure despite intensive treatment. A limited necropsy was performed, and amyloid deposits were identified in both lung and kidney tissue. This case is highly unusual because (a) to our knowledge an isolated hypoglossal nerve palsy associated with active SLE has never been reported; (b) only one of nine reported cases of amyloidosis in patients with SLE had amyloid deposits in the lung.

Relapse of idiopathic pulmonary haemorrhage and glomerulonephritis associated with cytomegalovirus (CMV) infection

A 49 year old man who developed idiopathic pulmonary haemorrhage and glomerulonephritis responded initially to immunosuppressive treatment and plasmapheresis. However, he died later from massive pulmonary haemorrhage and necropsy showed cytomegalovirus infection of the lungs. We propose that relapse of pulmonary haemorrhage may be associated with cytomegalovirus infection and that preventive measures against acquiring the virus through blood products should be considered for elective transfusions in view of the relatively good long term prognosis of this syndrome.