Several scales of biodiversity affect ecosystem multifunctionality

Society values landscapes that reliably provide many ecosystem functions. As the study of ecosystem functioning expands to include more locations, time spans, and functions, the functional importance of individual species is becoming more apparent. However, the functional importance of individual species does not necessarily translate to the functional importance of biodiversity measured in whole communities of interacting species. Furthermore, ecological diversity at scales larger than neighborhood species richness could also influence the provision of multiple functions over extended time scales. We created experimental landscapes based on whole communities from the world’s longest running biodiversity-functioning field experiment to investigate how local species richness (α diversity), distinctness among communities (β diversity), and larger scale species richness (γ diversity) affected eight ecosystem functions over 10 y. Using both threshold-based and unique multifunctionality metrics, we found that α diversity had strong positive effects on most individual functions and multifunctionality, and that positive effects of β and γ diversity emerged only when multiple functions were considered simultaneously. Higher β diversity also reduced the variability in multifunctionality. Thus, in addition to conserving important species, maintaining ecosystem multifunctionality will require diverse landscape mosaics of diverse communities.     

Effects of spontaneous breathing during airway pressure release ventilation on renal perfusion and function in patients with acute lung injury

OBJECTIVE: Controlled mechanical ventilation can impair systemic and renal blood flow and function, which may be aggravated by respiratory acidosis. We hypothesized that partial ventilatory support using airway pressure release ventilation (APRV) with spontaneous breathing provides better cardiopulmonary and renal function than full ventilatory support using APRV without spontaneous breathing. DESIGN: Prospective randomized study. SETTING: Intensive care unit of a university hospital. PATIENTS: Twelve patients with acute lung injury (ALI). INTERVENTIONS: Airway pressure release ventilation with and without spontaneous breathing, maintaining either the same minute ventilation (V(E)) or the same airway pressure (Paw) limits. MEASUREMENTS: Systemic hemodynamics were estimated by double-indicator dilution, effective renal blood flow (ERBF) by para-aminohippurate, and glomerular filtration rate (GFR) by inulin clearance. RESULTS: Compared to APRV with spontaneous breathing, cardiac index (CI) was decreased when the upper Paw limit was increased to provide the same V(E) (4.26+/-1.21 l min(-1) m(-2)vs 3.72+/-0.99 l min(-1) m(-2); p<0.05) while CI was increased when Paw limits were held constant (4.91+/-1.41 l min(-1) m(-2); p<0.05). Effective renal blood flow and GFR were higher during APRV with spontaneous breathing (858+/-388 ml min(-1) m(-2) and 94+/-47 ml min(-1) m(-2)) than during APRV without spontaneous breathing and the same V(E) (714+/-236 ml min(-1) m(-2)and 82+/-35 ml min(-1) m(-2)) or the same Paw (675+/-287 ml min(-1) m(-2) and 80+/-41 ml min(-1) m(-2); p<0.05). Urine volume did not change. CONCLUSIONS: Spontaneous breathing during APRV was associated with better renal perfusion and function than APRV without spontaneous breathing applying either the same V(E) or the same Paw limits. Maintaining spontaneous breathing during ventilatory support may, therefore, be advantageous in preventing deterioration of renal function in patients with ALI.     

General approach to reversing ketol-acid reductoisomerase cofactor dependence from NADPH to NADH

To date, efforts to switch the cofactor specificity of oxidoreductases from nicotinamide adenine dinucleotide phosphate (NADPH) to nicotinamide adenine dinucleotide (NADH) have been made on a case-by-case basis with varying degrees of success. Here we present a straightforward recipe for altering the cofactor specificity of a class of NADPH-dependent oxidoreductases, the ketol-acid reductoisomerases (KARIs). Combining previous results for an engineered NADH-dependent variant of Escherichia coli KARI with available KARI crystal structures and a comprehensive KARI-sequence alignment, we identified key cofactor specificity determinants and used this information to construct five KARIs with reversed cofactor preference. Additional directed evolution generated two enzymes having NADH-dependent catalytic efficiencies that are greater than the wild-type enzymes with NADPH. High-resolution structures of a wild-type/variant pair reveal the molecular basis of the cofactor switch.     

Nutrient enrichment,biodiversity loss,and consequent declines in ecosystem productivity

Anthropogenic drivers of environmental change often have multiple effects, including changes in biodiversity, species composition, and ecosystem functioning. It remains unknown whether such shifts in biodiversity and species composition may, themselves, be major contributors to the total, long-term impacts of anthropogenic drivers on ecosystem functioning. Moreover, although numerous experiments have shown that random losses of species impact the functioning of ecosystems, human-caused losses of biodiversity are rarely random. Here we use results from long-term grassland field experiments to test for direct effects of chronic nutrient enrichment on ecosystem productivity, and for indirect effects of enrichment on productivity mediated by resultant species losses. We found that ecosystem productivity decreased through time most in plots that lost the most species. Chronic nitrogen addition also led to the nonrandom loss of initially dominant native perennial C₄ grasses. This loss of dominant plant species was associated with twice as great a loss of productivity per lost species than occurred with random species loss in a nearby biodiversity experiment. Thus, although chronic nitrogen enrichment initially increased productivity, it also led to loss of plant species, including initially dominant species, which then caused substantial diminishing returns from nitrogen fertilization. In contrast, elevated CO₂ did not decrease grassland plant diversity, and it consistently promoted productivity over time. Our results support the hypothesis that the long-term impacts of anthropogenic drivers of environmental change on ecosystem functioning can strongly depend on how such drivers gradually decrease biodiversity and restructure communities.     

From the Cover: Predicting overfishing and extinction threats in multispecies fisheries

Threats to species from commercial fishing are rarely identified until species have suffered large population declines, by which time remedial actions can have severe economic consequences, such as closure of fisheries. Many of the species most threatened by fishing are caught in multispecies fisheries, which can remain profitable even as populations of some species collapse. Here we show for multispecies fisheries that the biological and socioeconomic conditions that would eventually cause species to be severely depleted or even driven extinct can be identified decades before those species experience high harvest rates or marked population declines. Because fishing effort imposes a common source of mortality on all species in a fishery, the long-term impact of a fishery on a species is predicted by measuring its loss rate relative to that of species that influence the fishery’s maximal effort. We tested our approach on eight Pacific tuna and billfish populations, four of which have been identified recently as in decline and threatened with overfishing. The severe depletion of all four populations could have been predicted in the 1950s, using our approach. Our results demonstrate that species threatened by human harvesting can be identified much earlier, providing time for adjustments in harvesting practices before consequences become severe and fishery closures or other socioeconomically disruptive interventions are required to protect species.Marine fisheries are an important global source of food and livelihoods (1–4), but there are concerns that current fishing practices threaten some marine species with severe depletion or eventual extinction (2–5). Many of the largest commercial fishing methods, such as trawling, longlining, and seining, unavoidably catch multiple species simultaneously (6–9). Multispecies fisheries pose a particular threat of extinction or severe depletion because fishing can remain profitable as long as some valuable species remain abundant, even while others collapse (6–11). In contrast, in a single-species fishery profits tend to fall as the target population declines, thereby removing the incentive to fish before extinction occurs (10). Multispecies fisheries pose a threat to two types of species or stocks (populations): (i) commercially valued species, called “weak stocks”, which are more vulnerable to overharvesting than are other commercially valuable species (6), and (ii) by-catch species, which are caught accidentally and create little economic incentive to cease fishing as their populations collapse because they have little or no commercial value (7–9).Failure to prevent collapse of weak stocks and by-catch species can impose substantial long-term environmental and economic costs. Slow-growing populations are most likely to collapse, but can take several decades to recover (5). Recovery often requires long-term fishery closures or reductions in effort, having substantial economic and social consequences (3, 5). Moreover, population declines caused by one fishery can diminish yields and profits in other commercial or artisanal fisheries that depend on the same species (e.g., ref. 12).Despite these costs, species threatened by fishing have rarely been identified until after their populations have declined substantially (2–5, 7, 8). Assessments of fishery impacts on species mostly focus on estimating current exploitation rates or past population trends (13–15), which identifies already declining species rather than predicting future declines. Data limitations have made empirical prediction of future threats from fishing challenging, particularly for weak stocks and by-catch species. Oceans are difficult to sample extensively, and few economic incentives exist to gather data on species other than the most commercially valued species (7, 8). Some predictive models (e.g., ref. 16) have been developed to forecast the impacts of some fisheries, but these are often data intensive. Some of the characteristics that make a population susceptible to overfishing are well known—for example, low population growth rates (3–11, 17, 18), high value and/or low fishing costs (10, 11, 17–19), and schooling behavior (18). Recently, some correlative approaches based on these characteristics have been developed for assessing likely relative threats to data-poor species (4, 20–22). However, predicting the severity of future threats in absolute terms with this type of approach can be challenging.Here, we present a mechanistic approach that uses readily available data to predict the potential of current fishing practices, if maintained, to eventually cause a population to be driven extinct or “overfished”, here defined as depletion below its maximum sustainable yield (MSY) abundance (N_MSY) (3). Our approach identifies combinations of biological and socioeconomic conditions that are likely to eventually lead to high mortality rates and population declines. As we show, these conditions can be identified long before either occurs.We test the predictive power of our approach on eight tuna and billfish populations of the Western and Central Pacific Ocean fisheries. High-seas tuna and billfish have elicited recent conservation concern due to significant population declines and range contractions found in many species (17, 23, 24). Three of the populations in our study, bigeye tuna (Thunnus obesus) and both the northern and the southern striped marlin (Tetrapturus audax) populations, have been recently identified as experiencing overfishing—meaning their exploitation rates have exceeded the MSY exploitation rate (F_MSY) (24–27). A fourth, blue marlin (Makaira nigricans), whose overfishing status has been subject to considerable uncertainty (28), has undergone a significant population decline and range contraction (13, 23, 28). We determine whether our approach could have predicted threats to these four populations, using data from as early as the 1950s, and assess the threats predicted by the latest available data to all populations.     

Inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) expression in fulminant hepatic failure

BACKGROUND/AIMS: Inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) have important functions in inflammation and vasoregulation but their role in fulminant hepatic failure (FHF) is not well understood. METHODS: Intrahepatic in situ staining and semi-quantification of iNOS and eNOS by immunohistochemistry in 25 patients with FHF, in 40 patients with chronic liver diseases (CLD) and in ten normal controls (NC). RESULTS: Expression patterns of iNOS and eNOS differed. While in NC only faint iNOS expression was found in some Kupffer cells/macrophages and hepatocytes, eNOS was expressed constitutively in sinusoidal and vascular endothelial cells. In CLD, iNOS expression was induced in Kupffer cells/macrophages and hepatocytes, representing the main iNOS expressing cell types. Additionally, bile ducts, vascular endothelial cells and lymphocytes also expressed iNOS (P = 0.001). In contrast, no differences were found between eNOS expression in CLD and NC (P = 0.64). The same cell types expressed eNOS and iNOS in FHF but numbers of both were significantly enhanced, exceeding the levels seen in CLD (P < 0.001, P = 0.017). CONCLUSIONS: Our data demonstrate that iNOS and eNOS are differently regulated in physiologic conditions and in liver disease. While eNOS seems to be involved in the physiological regulation of hepatic perfusion, strong upregulation of iNOS might contribute to inflammatory processes in FHF.     

Congenital central hypoventilation syndrome associated with Hirschsprung's disease and neuroblastoma: Case of multiple neurocristopathies

We report on a male infant with the rare combined occurrence of congenital central hypoventilation syndrome (CCHS or Ondine's curse), Hirschsprung's disease (HD), and neuroblastoma. Current therapeutical options leave no doubt that children with isolated forms of CCHS, HD, or neuroblastoma must be treated, but management decisions and the ethical dilemma become more difficult with the presence of multiple neurocristopathies. Our patient was dependent on mechanical ventilation and total parenteral nutrition, when a neuroblastoma was diagnosed at age 5 months. We initiated an attempt at curative chemotherapy. The tumor failed to respond to recommended chemotherapeutic regimens, and the patient died at 11 months of age. We emphasize the importance of screening CCHS patients for associated illnesses such as neuroblastoma and ganglioneuroblastoma at time of diagnosis. Pediatr Pulmonol. 2002; 33:71–76. © 2002 Wiley‐Liss, Inc.     

Use of out-of-hospital variables to predict severity of injury in pediatric patients involved in motor vehicle crashes

STUDY OBJECTIVE: We sought to create a clinical decision rule, on the basis of variables available to out-of-hospital personnel, that could be used to accurately predict severe injury in pediatric patients involved in motor vehicle crashes as occupants. METHODS: We analyzed the National Automotive Sampling System database, a national probability sample, using pediatric patients up to 15 years old (occupants only) involved in motor vehicle crashes from January 1993 to December 1999. The National Automotive Sampling System database includes patients from regions throughout the country, weighted to represent a nationwide sample. Twelve out-of-hospital variables were used in classification and regression tree analysis to create a decision rule separating children with severe injuries (Injury Severity Score [ISS] > or =16) from those with minor injuries (ISS < 16). Misclassification costs and complexity parameters were selected to yield a decision tree with appropriate sensitivity and specificity for the identification of severely injured patients, while also being simple and practical for out-of-hospital use. Probability weights were used throughout the analysis to account for the sampling design and sampling weights. RESULTS: Using a sample size of 8,392 children, we constructed a decision rule using 3 out-of-hospital variables (Glasgow Coma Scale score, passenger space intrusion > or =6 in [> or =15 cm], and restraint use) to predict those patients with an ISS of 16 or more. Internal cross-validation was used to determine the sensitivity and specificity, yielding values of 92% and 73%, respectively, for the prediction of patients with an ISS of 16 or more. CONCLUSION: Out-of-hospital variables available to field personnel could be used to effectively triage pediatric motor vehicle crash patients using the decision rule developed here. Prospective trials would be needed to test this decision rule in actual use.     

Oxidative stress, aging and the proteasomal system

Oxygen free radicals and other oxidants are causingpotential danger for intracellular proteins during thelifetime of cells and organisms. Therefore, proteinoxidation is one of the natural consequences ofaerobic life. The degradation of non-functional,oxidized proteins is an essential part of theantioxidant defenses of cells. The major proteolyticsystem responsible for the removal of oxidizedcytosolic proteins is the proteasomal system. Thissystem consists of the 20S 'core' proteasome and amultitude of various regulators. It is known thatcertain components of this system are regulated duringoxidative stress and aging.One of the highlights of age-related changes ofcellular metabolism is the accumulation of oxidizedproteins. The question whether the accumulation ofoxidized proteins during aging is due to a malfunctionof the intracellular proteolytic machinery of the cellremains still unsolved. The information availableabout an age-related decline of the proteasomal systemis very contradictory. The current literature aboutthe proteasomal system, the regulation of this systemduring oxidative stress and the age-related changesare in the focus of this review.     

Acute hepatitis C: high rate of both spontaneous and treatment-induced viral clearance

BACKGROUND & AIMS: Acute hepatitis C virus infection accounts for approximately 20% of cases of acute hepatitis today. The aim of this study was to define the natural course of the disease and to contribute to the development of treatment strategies for acute hepatitis C virus. METHODS: The diagnosis of acute hepatitis C virus in 60 patients was based on seroconversion to anti-hepatitis C virus antibodies or clinical and biochemical criteria and on the presence of hepatitis C virus RNA in the first serum sample. RESULTS: Fifty-one of 60 (85%) patients presented with symptomatic acute hepatitis C virus. In the natural (untreated) course of acute symptomatic hepatitis C (n = 46), spontaneous clearance was observed in 24 patients (52%), usually within 12 weeks after the onset of symptoms, whereas all asymptomatic patients (n = 9) developed chronic hepatitis C. The start of antiviral therapy (interferon-alpha with or without ribavirin) beyond 3 months after the onset of acute hepatitis induced sustained viral clearance in 80% of treated patients. CONCLUSIONS: The management of acute hepatitis C has to take into account the high rate of spontaneous viral clearance within 12 weeks after the onset of symptomatic disease. Treatment of only those patients who remain hepatitis C virus RNA positive for more than 3 months after the onset of disease led to an overall viral clearance (self-limited and treatment induced) in 91% of patients, and unnecessary treatment was avoided in those with spontaneous viral clearance. Patients with asymptomatic acute hepatitis C virus infection are unlikely to clear the infection spontaneously and should be treated as early as possible.