Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes.

Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6 kg m(-2)) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3 months and 14 months after char addition. N(2)O, CH(4) and CO(2) fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3 months, but after 14 months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N(2)O fluxes were from 26% to 79% lower than N(2)O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N(2)O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH(4) fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14 months after biochar incorporation.

An improved polymerase chain reaction (PCR) protocol for unambigous detection of growth hormone gene deletions.

hGH-1 gene deletions are detected by simultaneous PCR amplification along the two homologous DNA sequences flanking the hGH-1 gene on both sides and are differentiated by SmaI restriction enzyme digestion. We have observed that among the SmaI digested PCR products from normal homozygous subjects, from those heterozygous for the 7.6 kb deletion and from those heterozygous for a 6.7 kb deletion, along with the expected fragments there is an unexpected 1470 bp fragment. This fragment arises from the co-amplification of a third homologous sequence located downstream from the hGH-1 gene and it confuses differentiation between normal homozygous and heterozygous for 7.6 kb subjects from the 6.7 kb heterozygous subjects. To overcome this problem we have improved PCR conditions using a different reverse primer. These changes avoid the interaction of the primers with the third homologous sequence located downstream from the hGH-1 gene and prevent the appearance of this additional band that complicates the interpretation of the results. We conclude that the new reverse primer sequence avoids the amplification of the downstream hGH-1 gene sequence and the production of the 1474 bp band after SmaI endonuclease enzyme digestion and makes it possible to differentiate homozygous normal subjects and those who are heterozygous for a 7.6 kb deletion from those who are heterozygous for a 6.7 kb deletion.

Plasma sex hormones are significantly associated with plasma leptin concentration in healthy subjects.

OBJECTIVE: In humans a sexual dimorphism of plasma leptin concentration has been demonstrated but its significance remains to be established. Sex hormones may have a role. PATIENTS: Eighty healthy, non-obese subjects (41M/39F) were studied. MEASUREMENTS: In the whole group of subjects plasma sex hormones, leptin and insulin concentrations were determined, body fat content assessed by bioimpedance analysis, body fat distribution evaluated and insulin-mediated glucose uptake measured by euglycemic hyperinsulinemic glucose. RESULTS: After adjustment for age, gender, amount of body fat, waist/hip ratio (WHR) and fasting plasma insulin concentration, fasting plasma leptin was still significantly correlated with plasma DHEAS (r = -0.30, P < 0.006), oestradiol (r = 0.53, P < 0.001) and testosterone (r = -0.43, P < 0.001) in all subjects (n = 80). Independently of age, amount of body fat and WHR, fasting plasma leptin concentration correlated with plasma oestradiol (r = 0.38, P < 0.01) and total testosterone (r = -0.58, P < 0.001) in males (n = 41) and with fasting plasma oestradiol (r = 0.48, P < 0.002) in females (n = 39). To investigate the independent contribution of anthropometric and hormonal variables to fasting plasma leptin concentration, a multivariate stepwise regression analysis with fasting plasma leptin concentration as dependent variable was made. In the entire group (n = 80), the whole model explained 43% of fasting plasma leptin concentration with fasting plasma insulin, total testosterone and oestradiol concentrations significantly and independently associated with plasma leptin concentration. In this model, fasting plasma DHEAS, testosterone and oestradiol explained 25% of the variability in plasma leptin concentration. CONCLUSION: Our study demonstrates that plasma sex hormone concentrations are associated with plasma leptin concentration.

Serum levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in healthy centenarians: relationship with plasma leptin and lipid concentrations, insulin action, and cognitive function.

It has been demonstrated that healthy centenarians have more favorable anthropometric characteristics and insulin-mediated glucose uptake than aged subjects. The plasma insulin-like-growth factor I (IGF-I) concentration may account for such differences. Three groups of subjects were studied: 1) adults (< 50 yr; n = 30), 2) aged subjects (75-99 yr; n = 30), 3) centenarians (> 100 yr; n = 19). In all subjects, fasting plasma IGF-I, IGF-binding protein-3 (IGFBP-3), leptin, and lipid concentrations were determined; body composition was assessed by bioimpedance analysis; and insulin-mediated glucose up-take was evaluated by euglycemic hyperinsulinemic glucose clamp. IGF-I declined with advancing age, but no differences between aged subjects and centenarians were found. IGFBP-3 showed a trend similar to IGF-I, but lower values were present in centenarians than in aged subjects. Nevertheless, centenarians had a plasma IGF-I/IGFBP-3 molar ratio greater than that in aged subjects. Centenarians had also a whole body glucose disposal (WBGD) greater than that in aged subjects, but similar to that in adults. Mini Mental State Examination (27 +/- 2.1 vs. 18.3 +/- 3.1; P < 0.02) and Instrumental Activities Daily Living (26 +/- 2.6 vs. 8.4 +/- 4.1; P < 0.001) scores were significantly different in aged subjects and centenarians, respectively. In centenarians, the plasma IGF-I/IGFBP-3 molar ratio correlated with the body mass index (r = -0.55; P < 0.009); the amount of body fat (r = -0.62; P < 0.003); fat-free mass (r = 0.56; P < 0.008); fasting plasma leptin (r = -0.63; P < 0.004), triglycerides (r = -0.58; P < 0.01), free fatty acid (r = -0.64; P < 0.005), and low density lipoprotein cholesterol (r = -0.59; P < 0.009) concentrations; Mini Mental State Examination (r = 0.53; P < 0.0.03); and WBGD (r = 0.64; P < 0.005). All correlations were independent of daily fat and carbohydrate intake and WBGD (P < 0.05 for all). No significant correlations between the plasma IGF-I/IGFBP-3 molar ratio and plasma total (r = 0.31; P = NS) and high density lipoprotein cholesterol (r = 0.34; P = NS) concentrations were present. The correlation between the plasma IGF-I/IGFBP-3 molar ratio and WBGD persisted after adjustment for body fat, fasting plasma insulin concentration, daily carbohydrate and fat intake, and daily physical activity (r = 0.55; P < 0.009), but not after further adjustment for plasma free fatty acid concentration (r = 0.30; P = 0.17). In conclusion, healthy centenarians have plasma IGF-I/IGFBP-3 molar ratio greater than aged subjects. A more elevated plasma IGF-I/IGFBP-3 molar ratio might improve insulin action and plasma lipid concentration in centenarians.