Silicon: its manifold roles in plants Epstein, E
Annals of applied biology,
October 2009, Letnik:
155, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
The title of this essay declares that silicon does have roles in plants and all participants in this conference know that that is so. This knowledge, however, is not shared by the general community ...of plant biologists, who largely ignore the element. This baffling contrast is based on two sets of experience. First, higher plants can grow to maturity in nutrient solutions formulated without silicon. That has led to the conventional wisdom that silicon is not an essential element, or nutrient, and thus can be disregarded. Second, the world's plants do not grow in the benign environment of solution culture in plant biological research establishments. They grow in the field, under conditions that are often anything but benign. It is there, in the real world with its manifold stressful features, that the silicon status of plants can make a huge difference in their performance. The stresses that silicon alleviates range all the way from biotic, including diseases and pests, to abiotic such as gravity and metal toxicities. Silicon performs its functions in two ways: by the polymerization of silicic acid leading to the formation of solid amorphous, hydrated silica, and by being instrumental in the formation of organic defence compounds through alteration of gene expression. The silicon nutrition of plants is not only scientifically intriguing but also important in a world where more food will have to be wrung from a finite area of land, for that will put crops under stress.
Background:
There are multiple complications reported for anterior cervical diskectomy and fusion (ACDF), one of the most common cervical spine operations performed in the US (e.g. estimated at ...137,000 ACDF/year).
Methods:
Multiple studies analyzed the risks and complications rates attributed to ACDF.
Results:
In multiple studies, overall morbidity rates for ACDF varied from 13.2% to 19.3%. These included in descending order; dysphagia (1.7%-9.5%), postoperative hematoma (0.4%-5.6% (surgery required in 2.4% of 5.6%), with epidural hematoma 0.9%), exacerbation of myelopathy (0.2%-3.3%), symptomatic recurrent laryngeal nerve palsy (0.9%-3.1%), cerebrospinal fluid (CSF) leak (0.5%-1.7%), wound infection (0.1-0.9%-1.6%), increased radiculopathy (1.3%), Horner’s syndrome (0.06%-1.1%), respiratory insufficiency (1.1%), esophageal perforation (0.3%-0.9%, with a mortality rate of 0.1%), and instrument failure (0.1%-0.9%). There were just single case reports of an internal jugular veing occlusion and a phrenic nerve injury. Pseudarthrosis occurred in ACDF and was dependant on the number of levels fused; 0-4.3% (1-level), 24% (2-level), 42% (3 level) to 56% (4 levels). The reoperation rate for symptomatic pseudarthrosis was 11.1%. Readmission rates for ACDF ranged from 5.1% (30 days) to 7.7% (90 days postoperatively).
Conclusions:
Complications attributed to ACDF included; dysphagia, hematoma, worsening myelopathy, recurrent laryngeal nerve palsy, CSF leaks, wound infection, radiculopathy, Horner’s Syndrome, respiratory insufficiency, esophageal perforation, and instrument failure. There were just single case reports of an internal jugular vein thrombosis, and a phrenic nerve injury. As anticipated, pseudarthrosis rates increased with the number of ACDF levels, ranging from 0-4.3% for 1 level up to 56% for 4 level fusions.
Circumpolar expansion of tall shrubs and trees into Arctic tundra is widely thought to be occurring as a result of recent climate warming, but little quantitative evidence exists for northern ...Siberia, which encompasses the world's largest forest‐tundra ecotonal belt. We quantified changes in tall shrub and tree canopy cover in 11, widely distributed Siberian ecotonal landscapes by comparing very high‐resolution photography from the Cold War‐era ‘Gambit’ and ‘Corona’ satellite surveillance systems (1965–1969) with modern imagery. We also analyzed within‐landscape patterns of vegetation change to evaluate the susceptibility of different landscape components to tall shrub and tree increase. The total cover of tall shrubs and trees increased in nine of 11 ecotones. In northwest Siberia, alder (Alnus) shrubland cover increased 5.3–25.9% in five ecotones. In Taymyr and Yakutia, larch (Larix) cover increased 3.0–6.7% within three ecotones, but declined 16.8% at a fourth ecotone due to thaw of ice‐rich permafrost. In Chukotka, the total cover of alder and dwarf pine (Pinus) increased 6.1% within one ecotone and was little changed at a second ecotone. Within most landscapes, shrub and tree increase was linked to specific geomorphic settings, especially those with active disturbance regimes such as permafrost patterned‐ground, floodplains, and colluvial hillslopes. Mean summer temperatures increased at most ecotones since the mid‐1960s, but rates of shrub and tree canopy cover expansion were not strongly correlated with temperature trends and were better correlated with mean annual precipitation. We conclude that shrub and tree cover is increasing in tundra ecotones across most of northern Siberia, but rates of increase vary widely regionally and at the landscape scale. Our results indicate that extensive changes can occur within decades in moist, shrub‐dominated ecotones, as in northwest Siberia, while changes are likely to occur much more slowly in the highly continental, larch‐dominated ecotones of central and eastern Siberia.
Frequent right ventricular (RV) pacing can lead to a decline in left ventricular ejection fraction (LVEF).
This study aimed to identify incidence and predictors of RV pacing-induced cardiomyopathy ...(PICM).
We retrospectively studied 1750 consecutive patients undergoing pacemaker implantation between 2003 and 2012. Patients were included if baseline LVEF was normal, single-chamber ventricular or dual-chamber pacemaker (but not implantable cardioverter-defibrillator or biventricular pacemaker) was implanted, frequent (≥20%) RV pacing was present, and repeat echocardiogram was available ≥1 year after implantation. PICM was defined as ≥10% decrease in LVEF, resulting in LVEF <50%. Patients with alternative causes of cardiomyopathy were excluded. Predictors of the development of PICM were identified using multivariate Cox proportional hazards modeling.
Of 257 patients meeting study criteria, 50 (19.5%) developed PICM, with a decrease in mean LVEF from 62.1% to 36.2% over a mean follow-up period of 3.3 years. Those who developed PICM were more likely to be men, with lower baseline LVEF and wider native QRS duration (bundle branch blocks excluded; P = .005, P = .03, and P = .001, respectively). In multivariate analysis, male gender (hazard ratio 2.15; 95% confidence interval 1.17-3.94; P = .01) and wider native QRS duration (hazard ratio 1.03 per 1 ms increase; 95% confidence interval 1.01-1.05; P < .001) were independently associated with the development of PICM. Native QRS duration >115 ms was 90% specific for the development of PICM.
PICM may be more common than previously reported, and risk for its occurrence begins below the commonly accepted threshold of 40% pacing burden. Men with wider native QRS duration (particularly >115 ms) are at increased risk. These patients warrant closer follow-up with a lower threshold for biventricular pacing.
Soils in Arctic and boreal ecosystems store twice as much carbon as the atmosphere, a portion of which may be released as high-latitude soils warm. Some of the uncertainty in the timing and magnitude ...of the permafrost–climate feedback stems from complex interactions between ecosystem properties and soil thermal dynamics. Terrestrial ecosystems fundamentally regulate the response of permafrost to climate change by influencing surface energy partitioning and the thermal properties of soil itself. Here we review how Arctic and boreal ecosystem processes influence thermal dynamics in permafrost soil and how these linkages may evolve in response to climate change. While many of the ecosystem characteristics and processes affecting soil thermal dynamics have been examined individually (e.g., vegetation, soil moisture, and soil structure), interactions among these processes are less understood. Changes in ecosystem type and vegetation characteristics will alter spatial patterns of interactions between climate and permafrost. In addition to shrub expansion, other vegetation responses to changes in climate and rapidly changing disturbance regimes will affect ecosystem surface energy partitioning in ways that are important for permafrost. Lastly, changes in vegetation and ecosystem distribution will lead to regional and global biophysical and biogeochemical climate feedbacks that may compound or offset local impacts on permafrost soils. Consequently, accurate prediction of the permafrost carbon climate feedback will require detailed understanding of changes in terrestrial ecosystem distribution and function, which depend on the net effects of multiple feedback processes operating across scales in space and time.
Abstract Treatment of acute myocardial infarction (AMI) has improved significantly in recent years, but many patients have adverse left ventricular (LV) remodeling, a maladaptive change associated ...with progressive heart failure. Although this change is usually associated with large infarcts, some patients with relatively small infarcts have adverse remodeling, whereas other patients with larger infarcts (who survive the first several days after AMI) do not. This paper reviews the relevant data supporting the hypothesis that individual differences in the intensity of the post-AMI inflammatory response, involving 1 or more inflammatory-modulating pathways, may contribute to adverse LV remodeling. It concludes by outlining how individual variations in the inflammatory response could provide important novel therapeutic targets and strategies.
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