Microbial responses to P addition in six South African forest soils

Forests growing on highly weathered soils are often phosphorus (P) limited and competition between geochemical and biological sinks affects their soil P dynamics. In an attempt to elucidate the factors controlling the relative importance of these two sinks, we investigated the relationship of between soil microbial growth kinetics and soil chemical properties following amendments with C, N and P in six South African forest soils. Microbial growth kinetics were determined from respiration curves derived from measurements of CO₂ effluxes from soil samples in laboratory incubations. We found that microbial growth rates after C + N additions were positively related to NaOH-extractable P and decreased with soil depth, whereas the lag time (the time between substrate addition and exponential growth) was negatively related to extractable P. However, the growth rate and lag time were unrelated to the soil’s sorption properties or Al and Fe contents. Our results indicate that at least some of the NaOH-extractable inorganic P may be biologically available within a relatively short time (days to weeks) and might be more labile than previously thought. Our results also show that microbial utilization of C + N only seemed to be constrained by P in the deeper part of the soil profiles.     

Tumor necrosis factor and norepinephrine lower the levels of human neutrophil peptides 1-3 secretion by mixed synovial tissue cultures in osteoarthritis and rheumatoid arthritis

Introduction  

Neutrophils and monocytes play an important role in overt inflammation in chronic inflammatory joint diseases such as rheumatoid arthritis (RA). The sympathetic nervous system (SNS) inhibits many neutrophil/monocyte functions and macrophage tumor necrosis factor (TNF), but because of the loss of sympathetic nerve fibers in inflamed tissue, sympathetic control is attenuated. In this study, we focused on noradrenergic and TNF regulation of human neutrophil peptides 1-3 (HNP1-3), which are proinflammatory bactericidal α-defensins.     

Bushman rock shelter,Origstad, Eastern Transvaal,South Africa

Absolute dating of several stratigraphic levels position an infant's mandible relatively to about 29,500 years ago. This mandible may represent the infant stage of an early Negroid from of Homo sapiens afer and was probably associated with cultural material belonging to the transition of the Middle Stone Age to the Late Stone Age.     

Heterosis

Heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of development, and fertility than both parents. Various models have been posited to explain heterosis, including dominance, overdominance, and pseudo-overdominance. In this Perspective, we consider that it might be useful to the field to abandon these terms that by their nature constrain data interpretation and instead attempt a progression to a quantitative genetic framework involving interactions in hierarchical networks. While we do not provide a comprehensive model to explain the phenomenology of heterosis, we provide the details of what needs to be explained and a direction of pursuit that we feel should be fruitful.     

The variant inv(2)(p11.2q13) is a genuinely recurrent rearrangement but displays some breakpoint heterogeneity

Human chromosome 2 contains large blocks of segmental duplications (SDs), both within and between proximal 2p and proximal 2q, and these may contribute to the frequency of the common variant inversion inv(2)(p11.2q13). Despite their being cytogenetically homogeneous, we have identified four different breakpoint combinations by fluorescence in situ hybridization mapping of 40 cases of inv(2)(p11.2q13) of European origin. For the vast majority of inversions (35/40), the breakpoints fell within the same spanning BACs, which hybridized to both 2p11.2 and 2q13 on the normal and inverted homologues. Sequence analysis revealed that these BACs contain a significant proportion of intrachromosomal SDs with sequence homology to the reciprocal breakpoint region. In contrast, BACs spanning the rare breakpoint combinations contain fewer SDs and with sequence homology only to the same chromosome arm. Using haplotype analysis, we identified a number of related family subgroups with identical or very closely related haplotypes. However, the majority of cases were not related, demonstrating for the first time that the inv(2)(p11.2q13) is a truly recurrent rearrangement. Therefore, there are three explanations to account for the frequent observation of the inv(2)(p11.2q13): the majority have arisen independently in different ancestors, while a minority either have been transmitted from a common founder or have different breakpoints at the molecular cytogenetic level.     

Admixture mapping of an allele affecting interleukin 6 soluble receptor and interleukin 6 levels

Circulating levels of inflammatory markers can predict cardiovascular disease risk. To identify genes influencing the levels of these markers, we genotyped 1,343 single-nucleotide polymorphisms (SNPs) in 1,184 African Americans from the Health, Aging and Body Composition (Health ABC) Study. Using admixture mapping, we found a significant association of interleukin 6 soluble receptor (IL-6 SR) with European ancestry on chromosome 1 (LOD 4.59), in a region that includes the gene for this receptor (IL-6R). Genotyping 19 SNPs showed that the effect is largely explained by an allele at 4% frequency in West Africans and at 35% frequency in European Americans, first described as associated with IL-6 SR in a Japanese cohort. We replicate this association (P<1.0x10-12) and also demonstrate a new association with circulating levels of a different molecule, IL-6 (P<3.4x10-5). After replication in 1,674 European Americans from Health ABC, the combined result is even more significant: P<1.0x10-12 for IL-6 SR, and P<2.0x10-9 for IL-6. These results also serve as an important proof of principle, showing that admixture mapping can not only coarsely localize but can also fine map a phenotypically important variant.     

Abnormal systolic blood pressure during treadmill test and brachial artery flow-mediated vasodilatation impairment

The aim of the study was to assess the relationship between systolic blood pressure during maximal treadmill test (SBP9mtt)) and flow-mediated vasodilation (FMD). Abnormal rise of SBP(mtt) is the phenomenon more frequent in hypertensive persons but it could be found in normotensive subjects too. 199 subjects referred to treadmill test were enrolled in the study. Four groups were formed: hypertensives with abnormal SBP(mtt) (group A), hypertensives with normal SBP(mtt) (group B), normotensives with abnormal SBP(mtt) (group C) and normotensives with normal SBP(mtt) (group D). Rise of SBP(mtt) above 200 mmHg was considered abnormal reaction. Simple linear regression analysis showed significant inverse relationship between SBP(mtt) and FMD (F = 20.2036, p < 0.001, R2 = 0.0956). Mean FMD index was worst in hypertensive subjects with abnormal SBP(mtt) (group A), followed by normotensives with abnormal SBP(mtt) (group C), hypertensives with normal SBP(mtt) (group B) and the best was in normotensives with normal SBP(mtt) (3.56 +/- 5.17, 4.19 +/- 5.14, 6.81 +/- 8.43 and 10.92 +/- 7.48%, respectively). In multivariate regression analysis FMD showed significant association with abnormal SBP(mtt) (p < 0.001) along with brachial artery diameter (p < 0.001), male gender (p < 0.001), but not with hypertension (p = 0.073), BMI (p = 0.137) and total cholesterol (p = 0.23) (coefficients: -0.26, -0.40, -0.27, -0.13, -0.11 and -0.07, respectively). There was a significant inverse relationship between SBP(mtt) and FMD. An impairment of FMD exists in normotensive subjects with abnormal SBP(mtt). In hypertensives with abnormal SBP(mtt) an additional impairment of FMD exists when compared to hypertensives with normal SBP(mtt). Abnormal SBP(mtt) should be taken into account in global cardiovascular risk assessment.     

Deletion polymorphism of the angiotensin I-converting enzyme gene in elderly patients with coronary heart disease

Controversy exists as to whether the deletion/deletion (DD) genotype of angiotensin l-converting enzyme (ACE) gene polymorphism is associated with coronary heart disease (CHD). There are only a few studies dealing with this issue in the elderly, also with controversial results. The aim of this study was the assessment of correlation between genetic markers and the risk of CHD in the elderly. The results indicated DD genotype importance for CHD in the elderly as proven by discriminant analysis (chi2 = 25.77; df = 16; p = 0.0620). However, the use of univariate method demonstrated no correlation between DD genotype of ACE gene polymorphism and coronary artery disease. D allele of ACE gene was associated with higher activities of ACE plasma. A weak, but increased risk of MI is associated with high frequency of DD genotype in the elderly. Strong correlation between ACE polymorphism and ACE plasma activities was demonstrated.