Tropical pasture carbon cycling: relationships between C source/sink strength, above-ground biomass and grazing

We measured net ecosystem CO₂ exchange (NEE) in Panamá over C₄ pasture plots that varied in grazing intensity. After adjusting for variation in light, there were noticeable effects of grazing‐related variables on CO₂ exchange that were largely dependent on the developmental stage of the plant canopy. Above‐ground productivity was positively related to grazing intensity (r²=0.30). Two experimentally grazed fields had significantly lower standing crop biomass but no significant difference in CO₂ uptake (24.2 μmol/m²/s) compared with two ungrazed fields (20.3 μmol/m²/s). Grazed fields had significantly lower ecosystem respiration rates (10.3 μmol/m²/s) than did ungrazed fields (17.6 μmol/m²/s). These results suggest that, although these pastures were possible sources of CO₂ during the time intervals sampled, the size of the sources tended to be dampened by cattle grazing through reductions in ecosystem respiration. Thus, it appears that disturbance caused by cattle grazing will not always result in an increase in CO₂ release from tropical pastures to the atmosphere.     

Diagnosis of In Situ Air Sparging Performance Using Transient Groundwater Pressure Changes during Startup and Shutdown

Groundwater pressure measurements during startup and shutdown of in situ air sparging (IAS) systems are used to diagnose air flow behavior below the water table. The magnitude of the pressure response provides insight into the permeability of the zone into which the air is flowing. The duration of elevated pressures during startup and reduced pressures during shutdown indicate the extent to which air is being trapped below the water table by lower-permeability layers. The pressure measurements can be easily and quickly repeated and as a result are useful for both pilot tests and for optimizing operating conditions of existing IAS systems. Whether used alone or in conjunction with other diagnostic tools, pressure measurements are an important tool for assessing IAS performance.     

A novel technique for the identification of CpG islands exhibiting altered methylation patterns (ICEAMP)

Aberrant CpG methylation changes occurring during tumour progression include the loss (hypomethylation) and gain (hypermethylation) of methyl groups. Techniques currently available for examining such changes either require selection of a region, then examination of methylation changes, or utilise methylation-sensitive restriction enzymes to identify an alteration. We describe here a novel method that identifies genomic regions as a consequence of altered methylation during tumourigenesis. A methyl-CpG binding domain column isolates methylated GC-rich sequences from both tumours and surrounding normal tissue. Subsequent subtractive hybridisation removes sequences common to both, leaving only methylated sequences unique to the tumour. Libraries of sequences generated using DNA derived from a breast tumour (histological grade; poorly differentiated) as ‘tester’ and from matched normal tissue as ‘driver’ were examined; 26% of clones had the sequence criteria of a CpG island (CGI). Analysis using the bisulfite technique revealed that a number of these sequences were methylated in tumour DNA relative to the normal control. We have therefore demonstrated the ability of this technique, the identification of CGI exhibiting altered methylation patterns (ICEAMP), to isolate tumour-specific methylated GC-rich sequences. This will allow a comprehensive identification of methylation changes during tumourigenesis and will lead to a better understanding of the processes involved.     

Recurrent Genomic Gains in Preinvasive Lesions as a Biomarker of Risk for Lung Cancer

Lung carcinoma development is accompanied by field changes that may have diagnostic significance. We have previously shown the importance of chromosomal aneusomy in lung cancer progression. Here, we tested whether genomic gains in six specific loci, TP63 on 3q28, EGFR on 7p12, MYC on 8q24, 5p15.2, and centromeric regions for chromosomes 3 (CEP3) and 6 (CEP6), may provide further value in the prediction of lung cancer. Bronchial biopsy specimens were obtained by LIFE bronchoscopy from 70 subjects (27 with prevalent lung cancers and 43 individuals without lung cancer). Twenty six biopsies were read as moderate dysplasia, 21 as severe dysplasia and 23 as carcinoma in situ (CIS). Four-micron paraffin sections were submitted to a 4-target FISH assay (LAVysion, Abbott Molecular) and reprobed for TP63 and CEP 3 sequences. Spot counts were obtained in 30–50 nuclei per specimen for each probe. Increased gene copy number in 4 of the 6 probes was associated with increased risk of being diagnosed with lung cancer both in unadjusted analyses (odds ratio = 11, p<0.05) and adjusted for histology grade (odds ratio = 17, p<0.05). The most informative 4 probes were TP63, MYC, CEP3 and CEP6. The combination of these 4 probes offered a sensitivity of 82% for lung cancer and a specificity of 58%. These results indicate that specific cytogenetic alterations present in preinvasive lung lesions are closely associated with the diagnosis of lung cancer and may therefore have value in assessing lung cancer risk.     

Population regulation and demography in a harvested freshwater crayfish from Madagascar

Despite advances in statistical techniques for investigating population dynamics based on mark–recapture data, the majority of our understanding about demography and regulation comes from relatively few taxa. Most proposed generalisations about the association between demography and variation in population size are based on data from vertebrates, there are few sufficiently detailed invertebrate studies to examine whether these generalisations are widely supported. The population biology of freshwater invertebrates is especially poorly known. We present a large-scale mark–recapture study of an endemic freshwater crayfish from Madagascar ( Astacoides granulimanus ). Variation in density, caused by difference in fishing pressure due to local taboos, allowed us to investigate density-dependent regulation. We found evidence of density dependence in fecundity operating through the proportion of reproductive females by size but no significant evidence of density dependence in growth. Using a prospective analysis based on the elasticities from a size-structured matrix model, we found that both recruitment rates and survival rates of large individuals were strongly associated with deterministic population growth – a result that differs from generalisations drawn from vertebrate studies. A central assumption in mark–recapture studies is that handling does not affect mortality. By treating the number of times an individual was captured as an individual covariate, easily done using the freeware program MARK, we were able to test for, and take account of, handling-induced mortality. Our results show interesting similarities, and important differences, to generalisations based on vertebrate studies and emphasise the importance of population studies on poorly known taxa.     

Further characterization of type 2 and type 3 chain blood group A glycosphingolipids from human erythrocyte membranes

Blood group A glycosphingolipids with slow chromatographic mobilities have been separated systematically with an improved chromatographic procedure, and their structures have been analyzed by application of a panel of monoclonal antibodies defining A determinants carried by type 1, type 2, type 3, and type 4 carbohydrate chains as well as by 1H NMR spectroscopy and methylation analysis. Of several A-active fractions, previously termed Aa, Ab, Ac, and Ad, in decreasing order of thin-layer chromatographic mobility, the third fraction (Ac) was characterized as containing one type 3 chain A component and one type 2 chain A component without branching, which have been termed type 3 chain Ab and nor-Ac, respectively. (Formula: see text). The major component present in the fourth A-active fraction (Ad) was isolated and characterized as a branched type 2 chain glycolipid formerly termed Ac. The major component in the fifth A-active fraction (Ae) was identified as a branched type 2 chain A previously termed Ad. The structures of Ac (n = 1) and Ad (n = 2) are (Formula: see text).     

Pulmonary ventilation, blood gases, and blood pH after training of the arms or the legs.

In two groups of young healthy subjects who performed arm training (N = 5) and leg training (N = 5), respectively, the respiratory adaptation to submaximal exercise with trained and nontrained muscle groups was compared by measurement of the ventilatory equivalent (Ve/Vo2, pH, and blood gases (Pco2, Po2, and So2) in arterial blood and in venous blood from exercising extremities. After training Ve/Vo2 was significantly reduced during exercise with trained muscles, but unchanged during exercise with nontrained muscles. The reduction in Ve/Vo2 was closely related to a less pronounced increase in heart rate and in arterial lactate content, but showed no quantitative correlation to changes in arterial adaptations in trained muscles are mainly responsible for the reduction in Ve/Vo2. After training during exercise with trained as well as nontrained muscles a shift to the right of the blood oxygen dissociation curve occurred as extremities was lower while corresponding Po2 was higher.