Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region

Marmosets (genus Callithrix) are a diverse group of platyrrhine primates with 13-15 purported taxa, many of them considered endangered. Morphological analyses constitute most of the basis for recognition of these forms as distinct taxa. The purpose of this study was to provide a molecular view, based on mitochondrial control region sequences, of the evolutionary history of the marmosets, concomitant with a molecular phylogenetic perspective on species diversity within the group. An additional purpose was to provide the first comparative examination of a complete New World monkey control region sequence with those of other mammals. The phylogenetic analyses provide convincing support for a split between the Atlantic forest and Amazonian marmosets, with the inclusion of the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade. The earliest branch of the Atlantic forest group was C. aurita. In the Amazonian group, the analyses do not support the recognition of C. humeralifer and the recently described C mauesi as distinct taxa. They do, however, support a clear distinction between C. argentata and a strongly supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic forest group, the phylogenetic tree suggests mixing between C. penicillata, C. kuhli, and possibly C. jacchus. Most of the sequence features characteristic of other mammal control regions were also evident in marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3 were not clearly identifiable. Tandem repeat units often associated with heteroplasmy in a variety of other mammals were not evident in the marmoset sequences.      

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Changes in soil carbon with stand age – an evaluation of a modelling method with empirical data

Forest soils store a substantial amount of carbon, often more than the forest vegetation does. Estimates of the amount of soil carbon, and in particular estimates of changes in these amounts are still inaccurate. Measuring soil carbon is laborious, and measurements taken at a few statistically unrepresentative sites are difficult to scale to larger areas. We combined a simple dynamic model of soil carbon with litter production estimated on the basis of stand parameters, models of tree allometry and biomass turnover rates of different biomass components. This integrated method was used to simulate soil carbon as forest stands develop. The results were compared with measurements of soil carbon from 64 forest sites in southern Finland. Measured carbon stocks in the organic soil layer increased by an average of 4.7±1.4 g m^?2 a^?1 with increasing stand age and no significant changes were measured in the amount of carbon in mineral soil. Our integrated method indicated that soil carbon stocks declined to a minimum 20 years after clear‐cutting and the subsequent increase in the soil carbon stock (F/H ? 1 m) was 5.8±1.0 g m^?2 a^?1 averaged over the period to next harvesting (～125 years). Simulated soil carbon accumulation slowed down considerably in stands older than 50 years. The carbon stock measured (F/H ? 1 m) for the study area averaged 6.8±2.5 kg m^?2. The simulated carbon stock in soil was 7.0±0.6 kg m^?2 on average. These tests of the validity of the integrated model suggest that this method is suitable for estimating the amount of carbon in soil and its changes on regional scales.     

Developments in craniomaxillofacial surgery: use of self-reinforced bioabsorbable osteofixation devices.

Because of the problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, absorbable devices present an appealing alternative. Devices made of the polymers polylactide, polyglycolide, and their copolymers (PLGA and P[L/DL]LA) are currently the most commonly used. Ultrahigh-strength implants can be manufactured from these polymers with the self-reinforcing technique. Over the authors' almost two decades of study, both in experimental and clinical settings, self-reinforced devices have proved to be biocompatible, easy to handle, and mechanically strong, even for the fixation of femoral neck fractures. In craniomaxillofacial surgery, the authors have used self-reinforced devices for over 8 years without complications. Because of the more favored degradation characteristics, currently the copolymeric self-reinforced devices (P[L/DL]LA, Biosorb FX and PLGA, Biosorb PDX; Elite Performance Technologies, Solana Beach, Calif.) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. The authors' share their experience and their studies of self-reinforced devices, which possess the highest strength and ductility of all bioabsorbable products.     

Ground wētā in vines of the Awatere Valley,Marlborough: biology,density and distribution

The endemic New Zealand ground wētā (Hemiandrus sp. ‘promontorius’) has a Naturally Uncommon conservation status. This is because of the paucity of information on its density and distribution. Here, the biology, density and distribution of a population of this wētā found in and around vineyards in the Awatere Valley, Marlborough was studied. Wētā density was assessed in vineyards, paddocks and shrublands in this valley. Soil moisture, penetration resistance, pH and organic matter were recorded at locations with and without wētā. Wētā density in vineyards was significantly higher than in either paddocks or shrub habitats. In vineyards, the density of this insect was significantly higher under-vines than in the inter-rows. Higher numbers of this wētā were found in moist soils that required lower force to burrow. Females laid an average of 55 eggs between March and April, which hatched in September. These findings highlight the intersection between agriculture and conservation.     

Insulin‐ and Exercise‐Stimulated Skeletal Muscle Blood Flow and Glucose Uptake in Obese Men

Objective: Insulin resistance in obese subjects results in the impaired use of glucose by insulin‐sensitive tissues, e.g., skeletal muscle. In the present study, we determined whether insulin resistance in obesity is associated with an impaired ability of exercise to stimulate muscle blood flow, oxygen delivery, or glucose uptake. Research Methods and Procedures: Nine obese (body mass index = 36 ± 2 kg/m²) and 11 age‐matched nonobese men (body mass index = 22 ± 1 kg/m²) performed one‐legged isometric exercise during hyperinsulinemia. Rates of femoral muscle blood flow, oxygen consumption, and glucose uptake were measured simultaneously in both legs using [¹⁵O]H₂O, [¹⁵O]O₂, [¹⁸F]fluoro‐deoxy‐glucose, and positron emission tomography. Results: The obese subjects exhibited resistance to insulin stimulation of glucose uptake in resting muscle, regardless of whether glucose uptake was expressed per kilogram of femoral muscle mass (p = 0.001) or per the total mass of quadriceps femoris muscle. At similar workloads, oxygen consumption, blood flow, and glucose uptake were lower in the obese than the nonobese subjects when expressed per kilogram of muscle, but similar when expressed per quadriceps femoris muscle mass. Discussion: We conclude that obesity is characterized by insulin resistance of glucose uptake in resting skeletal muscle regardless of how glucose uptake is expressed. When compared with nonobese individuals at similar absolute workloads and under identical hyperinsulinemic conditions, the ability of exercise to increase muscle oxygen uptake, blood flow, and glucose uptake per muscle mass is blunted in obese insulin‐resistant subjects. However, these defects are compensated for by an increase in muscle mass.     

Insights into deglutathionylation reactions. Different intermediates in the glutaredoxin and protein disulfide isomerase catalyzed reactions are defined by the gamma-linkage present in glutathione

Glutaredoxins are small proteins with a conserved active site (-CXX(C/S)-) and thioredoxin fold. These thiol disulfide oxidoreductases catalyze disulfide reductions, preferring GSH-mixed disulfides as substrates. We have developed a new real-time fluorescence-based method for measuring the deglutathionylation activity of glutaredoxins using a glutathionylated peptide as a substrate. Mass spectrometric analysis showed that the only intermediate in the reaction is the glutaredoxin-GSH mixed disulfide. This specificity was solely dependent on the unusual gamma-linkage present in glutathione. The deglutathionylation activity of both wild-type Escherichia coli glutaredoxin and the C14S mutant was competitively inhibited by oxidized glutathione, with K(i) values similar to the K(m) values for the glutathionylated peptide substrate, implying that glutaredoxin primarily recognizes the substrate via the glutathione moiety. In addition, wild-type glutaredoxin showed a sigmoidal dependence on GSH concentrations, the activity being significantly decreased at low GSH concentrations. Thus, under oxidative stress conditions, where the ratio of GSH/GSSG is decreased, the activity of glutaredoxin is dramatically reduced, and it will only have significant deglutathionylation activity once the oxidative stress has been removed. Different members of the protein disulfide isomerases (PDI) family showed lower activity levels when compared with glutaredoxins; however, their deglutathionylation activities were comparable with their oxidase activities. Furthermore, in contrast to the glutaredoxin-GSH mixed disulfide intermediate, the only intermediate in the PDI-catalyzed reaction was PDI peptide mixed disulfide.