Differences In Relative Activity Research Articles

Does social thermal regulation constrain individual thermal tolerance in an ant species?

In ants, social thermal regulation is the collective maintenance of a nest temperature that is optimal for individual colony members. In the thermophilic ant Aphaenogaster iberica, two key behaviours regulate nest temperature: seasonal nest relocation and variable nest depth. Outside the nest, foragers must adapt their activity to avoid temperatures that exceed their thermal limits. It has been suggested that social thermal regulation constrains physiological and morphological thermal adaptations at the individual level. We tested this hypothesis by examining the foraging rhythms of six populations of A. iberica, which were found at different elevations (from 100 to 2,000m) in the Sierra Nevada mountain range of southern Spain. We tested the thermal resistance of individuals from these populations under controlled conditions. Janzen's climatic variability hypothesis (CVH) states that greater climatic variability should select for organisms with broader temperature tolerances. We found that the A. iberica population at 1,300m experienced the most extreme temperatures and that ants from this population had the highest heat tolerance (LT50=57.55°C). These results support CVH's validity at microclimatic scales, such as the one represented by the elevational gradient in this study. Aphaenogaster iberica maintains colony food intake levels across different elevations and mean daily temperatures by shifting its rhythm of activity. This efficient colony-level thermal regulation and the significant differences in individual heat tolerance that we observed among the populations suggest that behaviourally controlled thermal regulation does not constrain individual physiological adaptations for coping with extreme temperatures.

Point-of-Care Assay of Telomerase Activity at Single-Cell Level via Gas Pressure Readout.

Detection of telomerase activity at the single-cell level is one of the central challenges in cancer diagnostics and therapy. Herein, we describe a facile and reliable point-of-care testing (POCT) strategy for detection of telomerase activity via a portable pressure meter. Telomerase primer (TS) was immobilized onto the surface of magnetic beads (MBs), and then was elongated to a long single-stranded DNA by telomerase. The elongated (TTAGGG)n repeat unit hybridized with several short PtNP-functionalized complementary DNA (PtNPs-cDNA), which specifically enriched PtNPs onto the surfaces of magnetic beads (MBs), which were separated using a magnet. Then, nanoparticle-catalyzed gas-generation reaction converted telomerase activity into significant change in gas pressure. Because of the self-amplification of telomerase and enrichment by magnetic separation, the diluted telomerase equivalent to a single HeLa cell was facilely detected. More importantly, the telomerase in the lysate of 1 HeLa cell can be reliably detected by monitoring change in gas pressure, indicating that it is feasible and possible to study differences between individual cells. The difference in relative activity between different kinds of cancer cells was easily and sensitively studied. Study of inhibition of telomerase activity demonstrated that our method has great potential in screening of telomerase-targeted antitumor drugs as well as in clinical diagnosis.

Functional diversity for biomass deconstruction in family 5 subfamily 5 (GH5_5) of fungal endo-β1,4-glucanases.

Endo-β1,4-glucanases in glycosyl hydrolase family 5 (GH5) are ubiquitous enzymes in the multicellular fungi and are common components of enzyme cocktails for biomass conversion. We recently showed that an endo-glucanase of subfamily 5 of GH5 (GH5_5) from Sporotrichum thermophile (StCel5A) was more effective at releasing glucose from pretreated corn stover, when part of an eight-component synthetic enzyme mixture, compared to its closely related counterpart from Trichoderma reesei, TrCel5A. StCel5A and TrCel5A belong to different clades of GH5_5 (GH5_5_1 and GH5_5_2, respectively). To test whether the superior activity of StCel5A was a general property of all enzymes in the GH5_5_2 clade, StCel5A, TrCel5A, and two additional members of each subfamily were expressed in a common host that had been engineered to suppress its native cellulases (T. reesei Δxyr1) and compared against each other alone on pure substrates, in synthetic mixtures on pure substrates, and against each other in synthetic mixtures on real biomass. The results indicated that superiority is a unique property of StCel5A and not of GH5_5_2 generally. The six Cel5A enzymes had significant differences in relative activities on different substrates, in specific activities, and in sensitivities to mannan inhibition. Importantly, the behavior of the six endo-glucanases on pure cellulose substrates did not predict their behavior in combination with other cellulolytic enzymes on a real lignocellulosic biomass substrate.

Is there a difference in the pattern of muscle activity when performing neck exercises with a guild board versus a pulley?

Guild boards and pulleys are apparatus commonly used to train cervical muscle function for their purported benefit in facilitating activity of the deeper muscle layers, although this effect has not been substantiated. The objective of this study was to compare the activity of the different layers of cervical muscles when performing exercise with these 2 types of apparatus. A total of 19 healthy persons (mean age 28 years, (standard deviation 7 years). Ultrasound measurements of muscle deformation and deformation rate were recorded from the dorsal and ventral neck muscle layers during extension and flexion exercises. Pulley exercises were performed in the upright sitting position against a standardized resistance (men 2 kg, women 1 kg) and guild board exercises at an angle of 45º. The dorsal muscles generally showed greater levels of deformation and deformation rate during exercise with the guild board compared with the pulley system (p < 0.05), but with no significant differences in relative activity between the deep and superficial muscle layers (condition × muscle interaction (p > 0.05)). No differences were observed for the ventral muscles between exercise methods (p > 0.05). While both exercise methods appear to train cervical muscle function, neither appear to be more selective in facilitating deep cervical muscle activity, probably as they involve very similar cervical kinematics.

Selective activation of neuromuscular compartments within the human trapezius muscle

Task-dependent differences in relative activity between “functional” subdivisions within human muscles are well documented. Contrary, independent voluntary control of anatomical subdivisions, termed neuromuscular compartments is not observed in human muscles. Therefore, the main aim of this study was to investigate whether subdivisions within the human trapezius can be independently activated by voluntary command using biofeedback guidance. Bipolar electromyographical electrodes were situated on four subdivisions of the trapezius muscle. The threshold for “active” and “rest” for each subdivision was set to >12% and <1.5% of the maximal electromyographical amplitude recorded during a maximal voluntary contraction. After 1 h with biofeedback from each of the four trapezius subdivisions, 11 of 15 subjects learned selective activation of at least one of the four anatomical subdivisions of the trapezius muscle. All subjects managed to voluntarily activate the lower subdivisions independently from the upper subdivisions. Half of the subjects succeeded to voluntarily activate both upper subdivisions independently from the two lower subdivisions. These findings show that anatomical subdivisions of the human trapezius muscle can be independently activated by voluntary command, indicating neuromuscular compartmentalization of the trapezius muscle. The independent activation of the upper and lower subdivisions of the trapezius is in accordance with the selective innervation by the fine cranial and main branch of the accessory nerve to the upper and lower subdivisions. These findings provide new insight into motor control characteristics, learning possibilities, and function of the clinically relevant human trapezius muscle.

Pd on low-sureace-area α-alumina system: Is metallic Pd active for methane combustion?

Palladium (Pd) supported on alumina with various additives is the catalyst of choice for the catalytic combustion of methane. This catalyst is interesting in that it can change dramatically under reaction conditions and can chemically interact withhigh-surface-area (HSA) y -alumina supports. Much has been made of the observation that the apparent activity of these catalysts decreases in certain regimes as temperature increases, leading to the assertion that Pd metal is not active for methane oxidation, at least under fuel-leam conditons. This phenomenon has been suggested as a means to keep a catalyst from overheating in practical combustor designs. In this paper, we show that for Pd supported on low-surface-area (LSA) α-alumina, the methane oxidation activity increases as PdO is reduced to Pd at a fixed operating temperature, even for fuel-lean gas mixtures. This higher activity is significantly greater than the highest turnover frequencies reported by previous investigators when extrapolated back to 550 K and 2% methane in air. We propose that the differences in relative activity for methane oxidation between catalysts supported on different alminase are likely related to differences in morphology, the state of the Pd phases, differences in catalyst poisoning by water, and interactions between the Pd phases and the support. Most of these parameters were not directly monitored in previous studies.

Phospholipase activity of Mycobacterium leprae harvested from experimentally infected armadillo tissue

Three types of phospholipase activity--phospholipase A1, A2, and lysophospholipase--were detected in Mycobacterium leprae harvested from armadillo tissue at about 25% of the specific activity found in a slowly growing mycobacterium, Mycobacterium microti, which was grown in medium to optimize its phospholipase activity. The highest activity found was lysophospholipase, which released fatty acid from 2-lyso-phosphatidylcholine. Phospholipase activity was detected by using phosphatidylcholine and phosphatidylethanolamine. Differences in relative activities with these three types of substrate distinguished phospholipase activity in M. leprae extracts from armadillo liver extracts. Furthermore, retention of activity in M. leprae after NaOH treatment showed that the activity associated with M. leprae was not host derived. The specific activity of phospholipase was 20 times higher in extracts of M. leprae than in intact M. leprae organisms. Diazotization, a treatment which abolishes activities of surface enzymes exposed to the environment by the formation of covalent azide bonds with exposed amino groups, did not affect M. leprae's phospholipase activity, with one exception: release of arachidonic acid from phosphatidylcholine, which was partially inhibited. Phenolic glycolipid I, the major excreted amphipathic lipid of M. leprae, inhibited phospholipase activity, including release of arachidonic acid, for both M. leprae- and armadillo-derived activity.

Analyzing the oxidation of graphite using a microcomputer

A graphics program, written in BASIC and designed for use on a microcomputer, has been created which analyzes the oxidation of a single layer of a graphite crystallite. With this program, one can see how differences in relative activities of reactive sites can produce differently shaped holes and edges in graphite crystallites. The results then can be compared with experimental observations to test proposed burning mechanisms. Using the program has shown that proposed relative activities of active sites does produce equilateral hexagonal etch pits, as observed experimentally.

Cell cycle dependent activities of DNA polymerases alpha and delta in Chinese hamster ovary cells.

The activities of DNA polymerases alpha and delta, in extracts from Chinese hamster ovary (CHO) cells, were assayed in order to determine whether these polymerases are regulated during the cell cycle. An exponential population of CHO cells was separated into enriched populations of G-1, S, and G-2/M phases of cell cycle by centrifugal elutriation. Total cell homogenates from each population were assayed for DNA polymerase activity by measuring labeled nucleotide incorporation into the exogenous templates oligo(dT).poly(dA) and DNase I activated calf thymus DNA. In these experiments, specific DNA polymerase inhibitors were added to assays of the cellular extracts to allow for the independent measurement of activities of DNA polymerases alpha and delta. Comparisons of total DNA polymerase activity from cellular extracts, sampled from each portion of the cell cycle, demonstrated no significant change with respect to the concentration of total protein. However, results indicate that the activity of DNA polymerase delta increases with respect to that of DNA polymerase alpha in the G-2/M portion of the cell cycle. This difference in relative activities of DNA polymerases alpha and delta suggests a coordinate regulation of a specific species of DNA polymerase during the cell cycle.

Role of submarine canyons in shaping the rise between Lydonia and Oceanographer canyons, Georges Bank

Three large submarine canyons, Oceanographer, Gilbert, and Lydonia, indent the U.S. Atlantic continental shelf and, with four additional canyons, dissect the continental slope in the vicinity of Georges Bank. On the upper rise, these canyons merge at a water depth of approximately 3100 m to form only two valleys. Differences in channel morphology of the canyons on the upper rise imply differences in relative activity, which is inconsistent with observations in the canyon heads. At present, Lydonia Canyon incises the upper rise more deeply than do the other canyons: however, seismic-reflection profiles show buried channels beneath the rise, which suggests that these other six canyons were periodically active during the Neogene. The rise morphology and the thickness of inferred Neogene- and Quaternary-age sediments on the rise are attributed to the presence and activity of the canyons. The erosional and depositional processes and the morphology of these canyons are remarkably similar to those of fluvial systems. Bear Seamount, which has approximately 2000 m of relief on the rise, has acted as a barrier to downslope sediment transport since the Late Cretaceous. Sediment has piled up on the upslope side, whereas much less sediment has accumulated in the “lee shadow” on the downslope side. Seismic-reflection profile data show that Lydonia Canyon has not eroded down to the volcanic rock of Bear Seamount.

The effects of in vitro ageing on the exopeptidases of human diploid fibroblasts

Six exopeptidases present in human diploid fibroblasts were identified by separation on polyacrylamide gel electrophoresis and their activity profiles against 17 dipeptides, two tripeptides and l-leucine -p- nitroanilide determined. No differences in relative activity or in the electrophoretic patterns of any of the six exopeptidases were detected with ageing. Aminoacylarylamidase activity assayed spectrophotometrically showed significantly increased activity in the middle age-group cells as opposed to the enzyme isolated from young and old cells. Heat-inactivation studies using the same substrate suggested the possibility of an increased proportion of heat-labile enzyme in the old cells but interpretation of the data was difficult because of the complex nature of the inactivation curves obtained. Overall, the results tended to refute the hypothesis that age-related changes in the free amino acid pool of human diploid fibroblasts were associated with significant alterations in the activities of cellular exopeptidases.

Combined autoradiography and immunofluorescence for estimation of single cell activity by ammonium‐oxidizing bacteria1,2

Immunofluorescence and 14CO2 autoradiography were used for simultaneously enumerating and assaying the autotrophic activity of ammonium‐oxidizing bacteria in seawater. Relative activity (14CO2 assimilation as measured by autoradiography) and abundance were measured in simulated in situ incubations at seven stations in the primary NO2‒ maximum region of the Northeast Pacific Ocean. More than 104 cells· liter were present; relative activity often showed a peak near the surface and an increase in the NO2‒ max region below the photic zone. The method permits assessment of individual cell activity; most cells at all depths were active in CO2 assimilation, usually at low and quite variable levels. There were no differences in relative activity between samples incubated under simulated in situ conditions and in the dark.Relative activity was positively correlated with the abundance of ammonium‐oxidizing bacteria, temperature, total dark CO2 assimilation (as measured by liquid scintillation counting of replicate samples), and pheopigment concentration, and negatively correlated with oxygen concentration.

Sublethal effects of treated liquid effluent from a petroleum refinery. III. Avoidance and other locomotor responses of rainbow trout

Locomotor behaviour of individual rainbow trout ( Salmo gairdneri) was observed in a chamber with side-by-side flows of clean water and 0, 1, 10, or 30% oil refinery effluent, with a steep gradient between the two flows. None of the concentrations caused statistically significant avoidance or preference as measured by changes in time spent by fish in the four areas of the chamber (upstream or downstream and north or south side). Similarly, the side of entry of the effluent was not related to any differences in relative activity in the four areas, as measured by the numbers of movements fish made within the areas. When 30% effluent was present, the general level of activity in all parts of the chamber appeared to be lower than activities for the other concentrations, but the difference was at the borderline of statistical significance ( P=0.06). Behavioural response to the effluent was less important than direct physiological effects on trout, previously documented with the same effluent. The tested batches of effluent had an overall 3-day LC 50 of about 100% effluent. The effluent exceeded Canadian regulations in average level of ammonia, was somewhat elevated in oil-plus-grease and residue, but was well below regulatory limits for phenols and sulphides.

EXAMINATION OF ALLELIC VARIATION AT THE HEXOKINASE LOCI OF DROSOPHILA PSEUDOOBSCURA AND D. PERSIMILIS BY DIFFERENT METHODS

Recently a number of electrophoretic techniques have been applied to reveal the presence of additional genetic variation among the electrophoretic mobility classes of the highly polymorphic xanthine dehydrogenase (XDH ) and esterase-5 (est-5) loci. We examined the hexokinase loci of Drosophila pseudoobscura and D. persimilis using a variety of techniques to determine whether further allelic variation could be revealed for these much less polymorphic loci and to analyze the nature of the known variation at the hexokinase-1 (hex-1) locus. The following studies were conducted: 135 strains of the two species from six localities were examined with buffer pH ranging from 5.5 to 10.0; 40 strains of D. pseudoobscura and 9 strains of D. persimilis from Mather were studied using starch gel concentrations ranging from 8.5 to 15.5% and were examined for differences in heat stability and reactivity to the thiol reagent pCMSA; strains were also tested for susceptibility to urea denaturation and differences in relative activities. Major findings of the work are: (1) No additional allelic variation could be detected at any of the hexokinase loci by applying these techniques. The finding of abundant hidden genetic variation in XDH and est-5 does not extend to all enzyme loci. (2) Evidence from studies using pCMSA indicates that the hex-1 alleles 0.6, 0.8, 1.0 and 1.2 of the two species form a series of unit charge steps. Since the 0.94 allele of D. persimilis has mobility intermediate between 0.8 and 1.0, it is argued that routine electrophoretic techniques are sensitive to at least some conservative amino acid substitutions. (3) Strong correlations were found at the hex-1 locus between low allelic frequency, reduced relative activity and reduced stability to heat and urea denaturation. Since the three sibling species, D. pseudoobscura, D. persimilis and D. miranda, all appear to share a common high frequency allele (1.0) at that locus, these findings are taken as evidence that the observed allelic frequencies are a result of directional selection and mutation, rather than any form of balancing selection.