Relative Contributions Of Environment Research Articles

Microbial community coalescence and nitrogen cycling in simulated mortality decomposition hotspots

BackgroundThe pulsed introduction of dead plant and animal material into soils represents one of the primary mechanisms for returning organic carbon (C) and nitrogen (N) compounds to biogeochemical cycles. Decomposition of animal carcasses provides a high C and N resource that stimulates indigenous environmental microbial communities and introduces non-indigenous, carcass-derived microbes to the environment. However, the dynamics of the coalesced microbial communities, and the relative contributions of environment- and carcass-derived microbes to C and N cycling are unknown. To test whether environment-derived, carcass-derived, or the combined microbial communities exhibited a greater influence on C and N cycling, we conducted controlled laboratory experiments that combined carcass decomposition fluids and soils to simulate carcass decomposition hotspots. We selectively sterilized the decomposition fluid and/or soil to remove microbial communities and create different combinations of environment- and carcass-derived communities and incubated the treatments under three temperatures (10, 20, and 30 °C).ResultsCarcass-derived bacteria persisted in soils in our simulated decomposition scenarios, albeit at low abundances. Mixed communities had higher respiration rates at 10 and 30 °C compared to soil or carcass communities alone. Interestingly, at higher temperatures, mixed communities had reduced diversity, but higher respiration, suggesting functional redundancy. Mixed communities treatments also provided evidence that carcass-associated microbes may be contributing to ammonification and denitrification, but that nitrification is still primarily carried out by native soil organisms.ConclusionsOur work yields insight into the dynamics of microbial communities that are coalescing during carcass decomposition, and how they contribute to recycling carcasses in terrestrial ecosystems.

An assessment of ethnic and environmental influences on the phenotypes of hypertension

Abstract Background Hypertension is a growing global concern with developing countries now having the highest prevalence. Environmental factors such as socioeconomic status and diet, together with ethnicity-related factors may influence the development of hypertension and its complications such as left ventricular hypertrophy (LVH). However, the relative contributions of environment and ethnicity to these outcomes remain poorly understood. Purpose To test the hypothesis that black hypertensives living in Nigeria would have a higher prevalence of hypertensive target organ damage (i.e. LVH and dysfunction) compared with black hypertensives living in the UK. Methods We conducted a three-arm comparative study based on self-defined ethnicity and country of residence. We carried out detailed cardiovascular phenotyping in untreated Black hypertensives (n=53) living in Nigeria (BNig), untreated Black (BUK) hypertensives (n=25), and untreated White (WUK) hypertensives (n=59) living in the UK. We measured brachial and central blood pressure and undertook 2D echocardiography in all the participants. In addition, we collected serum and 24-hour urine biochemistry. Results The three groups had similar mean age and BMI (Table 1). The BNig group had significantly higher brachial SBP (P=0.01) and LV mass index (LVMI); P<0.001) compared with the BUK group. Furthermore, both BNig & BUK groups each had significantly higher brachial SBP (BNig: 162mmHg, BUK: 151mmHg) and LVMI (BNig: 100.9g/m2, BUK:86.4 g/m2) compared with the WUK group (Brachial SBP: 144mmHg, LVMI: 82.2g/m2). The prevalence of concentric LVH was similar in the two UK groups (BUK: 10%, WUK: 12%) but higher in the BNig group (41%). Septal early diastolic velocity was significantly lower in BNig group (7.0cm/s) compared to BUK (10.0cm/s) and WUK (10.0 cm/s). After adjusting for 24-hour sodium, brachial SBP (162mmHg) in the BNig group was still significantly higher compared with the other two groups [F(2,109)=13.805, BK (151mmHg, P=0.032), White UK (145mmHg, P<0.001)). However, after controlling for SBP, difference in LVMI persisted only between the BNig (EMM: 98.4 g/m2) versus WUK (EMM: 84.2 g/m2) groups, with no significant difference in BNig vs BUK (86.6g/m2, P=0.156) [F(2,128)=4.245, p=0.016]. Conclusion Our data suggest that higher SBP and salt intake do not explain all of the environmental differences in the prevalence of LVH and LV dysfunction in hypertensive patients drawn from different ethnicities and environments, suggesting that other factors are likely to play an important role. Further work is in a larger group is required to confirm these findings. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Niger Delta Development Commission

The effects of dispersal ability on metacommunity structure of macroinvertebrates in subtropical Chinese high-mountain streams: seasonal shifts in relative contribution of local environment and spatial processes.

It is generally recognized that dispersal mode can affect the relative role of environmental and spatial factors in structuring biotic communities. Disentangling the effects of dispersal mode on metacommunity structuring is essential to understanding the mechanisms of community assembly. Despite high seasonal variation in assemblage structure and phenological features of lotic macroinvertebrates, few studies examined the seasonal changes in the relative contribution of environmental and spatial processes. Here, we used two-season (spring and autumn) investigation data to link dispersal mode with local environmental and spatial factors that regulate macroinvertebrate metacommunity in a Chinese high-mountain stream network. Our aims were (1) to disentangle the relative role of environmental and spatial processes on structuring macroinvertebrate with different dispersal ability (aquatic passive: AqPa, terrestrial passive: TePa, and terrestrial active: TeAc) and (2) to determine seasonal shifts in metacommunity structuring processes. We found that assemblages of TeAc (with highest dispersal capacity) in both seasons were influenced more by environmental filtering than spatial structuring, whereas assemblages of TePa were mainly determined by spatial processes. Unexpectedly, AqPa group showed low spatial control in both seasons, probably due to their underestimated dispersal capacity via animal vector. The relative role of environmental and spatial factors was broadly stable across two seasons for AqPa and TeAc groups, but the TePa showed seasonal differences in the relative role of spatial factors, because of their seasonally changing dispersal capacity. In summary, our study emphasizes the use of dispersal mode for understanding metacommunity structuring mechanisms.

Altered growth patterns of a mountain Ok population of Papua New Guinea over 25 years of change

The Mountain Ok (Mt Ok) people of Telefomin, who live at the interior of Papua New Guinea (PNG), were documented over 25 years ago to be one of the shortest populations on record, with average adult height below the fifth percentile (US). Serum Growth Hormone was detectable, Insulin-like Growth Factor-1 and serum indicators of protein nutritional status fell within the normal range, suggesting that these were not primary factors for their relative short stature. Since the Telefolmin people have experienced recent socioeconomic changes, they were re-evaluated in 2008, to examine height, weight, and body mass index (BMI), for insight into relative contributions of environment and other factors that modulate stature in children and adults. Cross-sectional anthropometric data were collected from 474 individuals at Telefomin in 2008, and compared with anthropometric data from 342 individuals measured in 1983. The height of Telefolmin subjects, below the fifth percentile in 1983, remained below the fifth percentile in 2008. Weight and BMI of peripubertal and adult age groups increased from 1983 to 2008. Male and female heights at peripubertal ages were significantly greater in 2008. Nevertheless, final adult height did not change significantly over the 25 years. Recent socioeconomic changes appear to contribute to increased weight, BMI, and stature at younger ages in the Mt Ok at Telefomin. In contrast, unchanging adult stature may reflect a delay in the impact of socioeconomic changes, or genetic influences that modulate responsiveness to other growth regulators.

Mechanisms of carcinogenesis and individual susceptibility to cancer

The population can be divided into four groups, or "oncodemes," depending on the relative contributions of environment and genetics to their risk of cancer. These oncodemes are: 1) background (random mutations in normal people); 2) environmental (environmental carcinogens acting on normal people); 3) environmental/genetic (environmental carcinogens acting on genetic susceptibility); and 4) genetic, with genetic susceptibility being more important than environmental exposure. Most cancer probably occurs in oncodemes 2 and 3. However, the contribution that genetic susceptibility to cancer makes to the total cancer burden is unknown. Genetic susceptibility may be important in occupational settings, where exposure to carcinogens is presumed to be restricted to concentrations believed to confer "acceptable" risks. This approach takes no account of individual susceptibility. The range over which metabolic polymorphisms exert their effects suggests that differences in pharmacogenetics between individuals may be important in occupational carcinogenesis. If this range were extrapolated to risk of human disease, at a given exposure one person might be 10-200 times more sensitive than another. Several metabolic polymorphisms have been linked to susceptibility to cancer. For some of these polymorphisms, genes have been cloned and genotypic tests based on use of the polymerase chain reaction have been developed. Limited data suggest that the effects of these polymorphisms on human cancer are complex. The genotypic testing of individuals occupationally exposed to carcinogens may provide firmer information on the relative contributions of nature and nurture on chemically induced cancer. The use to which such information is put demands wide debate.

Antipyrine Metabolism in African Villagers

Antipyrine clearance has been measured from serial serum samples in 49 healthy black Africans from a village in Southern Africa. The subjects follow a lifestyle which minimally exposes them to environmental inducing or inhibiting agents. Food is mainly maize cereal with a protein content of only about 8.8%, together with greens. Antipyrine clearance, half-life and apparent volume of distribution (mean +/- SD) were, respectively, 0.538 +/- 0.163 ml min-1, kg-1, 14.81 +/- 6.5 h and 0.626 +/- 0.075 litre/kg. These results do not differ significantly from the mean values found in a group of lactovegetarian Indo-Pakistani immigrants to Britain. This would suggest that the major environmental determinant influencing hepatic mixed-function oxidase activity is the presence or absence of meat in the diet. However, the relative contributions of environment and heredity will be difficult to determine.