The effects of humic substances within the Ah horizon of a Calcic Luvisol on morphological changes related to invertase and peroxidase activities in wheat roots

The chemical and biological characteristics of humus within the Ah horizon (Calcic-Luvisol) have been studied. Attention was paid to variation in the NMR spectra of humic fractions and ¹³C values and to how these changes are related to different biological humic fraction activities.The chemical changes in particular involve the decrease of the aromatic component and the increase of the non-aromatic component within the horizon and the different ¹³C value not only within the horizon but also among the humic fractions distinctive of different molecular sizes.An attempt has been made to explain the vertical chemical changes in terms of processes affecting the biological characteristics of the high and low molecular size humic fractions. The main conclusions are that the low molecular size humic fractions, in the upper part of the horizon, are of greater importance with respect to the other humic fractions in influencing the enzyme activities linked to growth metabolism. The biological role of the high molecular size humic fractions characterised by a relevant content of peptidic- and carbohydratic-C is also presented.     

The carbohydrate-binding module of Fragaria × ananassa expansin 2 (CBM-FaExp2) binds to cell wall polysaccharides and decreases cell wall enzyme activities “in vitro”

A putative carbohydrate binding module (CBM) from strawberry (Fragaria × ananassa Duch.) expansin 2 (CBM-FaExp2) was cloned and the encoding protein was over-expressed in Escherichia coli and purified in order to evaluate its capacity to bind different cell wall polysaccharides “in vitro”. The protein CBM-FaExp2 bound to microcrystalline cellulose, xylan and pectin with different affinities (K_ad = 33.6 ± 0.44 mL g^?1, K_ad = 11.37 ± 0.87 mL g^?1, K_ad = 10.4 ± 0.19 mL g^?1, respectively). According to “in vitro” enzyme assays, this CBM is able to decrease the activity of cell wall degrading enzymes such as polygalacturonase, endo-glucanase, pectinase and xylanase, probably because the binding of CBM-FaExp2 to the different substrates interferes with enzyme activity. The results suggest that expansins would bind not only cellulose but also a wide range of cell wall polymers.     

Personal Networks and Mortality Risk in Older Adults: A Twenty-Year Longitudinal Study

Background

Research on aging has consistently demonstrated an increased chance of survival for older adults who are integrated into rich networks of social relationships. Theoretical explanations state that personal networks offer indirect psychosocial and direct physiological pathways. We investigate whether effects on and pathways to mortality risk differ between functional and structural characteristics of the personal network. The objective is to inquire which personal network characteristics are the best predictors of mortality risk after adjustment for mental, cognitive and physical health.

Methods and Findings

Empirical tests were carried out by combining official register information on mortality with data from the Longitudinal Aging Study Amsterdam (LASA). The sample included 2,911 Dutch respondents aged 54 to 85 at baseline in 1992 and six follow-ups covering a time span of twenty years. Four functional characteristics (emotional and social loneliness, emotional and instrumental support) and four structural characteristics (living arrangement, contact frequency, number of contacts, number of social roles) of the personal network as well as mental, cognitive and physical health were assessed at all LASA follow-ups. Statistical analyses comprised of Cox proportional hazard regression models. Findings suggest differential effects of personal network characteristics on survival, with only small gender differences. Mortality risk was initially reduced by functional characteristics, but disappeared after full adjustment for the various health variables. Mortality risk was lowest for older adults embedded in large (HR = 0.986, 95% CI 0.979—0.994) and diverse networks (HR = 0.948, 95% CI 0.917—0.981), and this effect continued to show in the fully adjusted models.

Conclusions

Functional characteristics (i.e. emotional and social loneliness) are indirectly associated with a reduction in mortality risk, while structural characteristics (i.e. number of contacts and number of social roles) have direct protective effects. More research is needed to understand the causal mechanisms underlying these relations.     

Platelet fragmentation requires a specific structural conformation of human monoclonal antibody against beta3 integrin

We have described an autoantibody against beta3 (GPIIIa49-66), a region of platelet integrin alphaIIbbeta3 that is unique. It induces platelet fragmentation in the absence of complement via antibody activation of platelet NADPH oxidase and 12-lipoxygenase to release reactive oxygen species, which destroy platelets. To study the mechanism of anti-GPIIIa antibody-induced platelet fragmentation, we screened a human single chain Fv antibody library with the GPIIIa49-66 peptide. Nine monoclonal antibodies were identified that were capable of binding to GPIIIa49-66. Surprisingly, binding avidity for GPIIIa49-66 did not correlate with activity of induction of platelet fragmentation. We therefore investigated the requirements for platelet fragmentation. Mutations were introduced into the heavy chain complementary-determining region-3 of clones 11, 43, and 54 by site-directed mutagenesis. The capability of these clones to induce platelet fragmentation or bind to GPIIIa49-66 subsequently changed. Molecular modeling of these clones with their mutants revealed that the ability to induce platelet fragmentation is affected by the side chain orientation of positively charged amino acids in the heavy chain of residues 99-102. Thus, a structural change in the conformation of anti-GPIIIa49-66 antibody contributes to its binding to the beta3 integrin and subsequent antibody-induced platelet fragmentation and aggregate dissolution.     

Casein Utilization by Streptococcus thermophilus Results in a Diauxic Growth in Milk

In milk, Streptococcus thermophilus displays two distinct exponential growth phases, separated by a nonexponential one, during which proteinase synthesis was initiated. During the second exponential phase, utilization of caseins as the source of amino acids resulted in a decrease in growth rate, presumably caused by a limiting peptide transport activity.