Effects of sodium sulfate on the freshwater microalga Chlamydomonas moewusii: implications for the optimization of algal culture media

The study of the microalgal growth kinetics is an indispensable tool in all fields of phycology. Knowing the optimal nutrient concentration is an important issue that will help to develop efficient growth systems for these microorganisms. Although nitrogen and phosphorus are well studied for this purpose, sulfur seems to be less investigated. Sulfate is a primary sulfur source used by microalgae; moreover, the concentration of this compound is increasing in freshwater systems due to pollution. The aim of this study was to investigate the effects of different sodium sulfate concentrations in the culture medium on growth and growth kinetics of the freshwater microalga Chlamydomonas moewusii. Production of biomass, chl content, kinetic equations, and a mathematical model that describe the microalgal growth in relation with the concentration of sodium sulfate were obtained. The lowest concentration of sodium sulfate allowing optimal growth was 0.1 mM. Concentrations higher than 3 mM generated a toxic effect. This work demonstrates that this toxic effect was not directly due to the excess of sulfate ion but by the elevation of the ionic strength. An inhibition model was successfully used to simulate the relationship between specific growth rate and sodium sulfate in this microalga.     

Salivary and serum procalcitonin and C-reactive protein as biomarkers of periodontitis in United States veterans with osteoarthritis or rheumatoid arthritis

Serum procalcitonin (ProCT) is elevated in response to bacterial infections, whereas high sensitivity C-reactive protein (hsCRP) is a nonspecific inflammatory marker that is increased by excess adipose tissue. We examined the efficacy of ProCT and hsCRP as biomarkers of periodontitis in the saliva and serum of patients with arthritis, which is characterized by variable levels of systemic inflammation that potentially can confound the interpretation of inflammatory biomarkers. Blood and unstimulated whole saliva were collected from 33 patients with rheumatoid arthritis (RA) and 50 with osteoarthritis (OA). Periodontal status was assessed by full mouth examination and patients were categorized as having no/mild, moderate or severe periodontitis by standard parameters. Salivary and serum ProCT and hsCRP concentrations were compared. BMI, diabetes, anti-inflammatory medications and smoking status were ascertained from the patient records. Differences between OA and RA in proportionate numbers of patients were compared for race, gender, diabetes, adiposity and smoking status. Serum ProCT was significantly higher in arthritis patients with moderate to severe and severe periodontitis compared with no/mild periodontitis patients. There were no significant differences in salivary ProCT or salivary or serum hsCRP in RA patients related to periodontitis category. Most of the OA and RA patients were middle aged or older, 28.9% were diabetic, 78.3% were overweight or obese, and slightly more than half were either current or past smokers. The OA and RA groups differed by race, but not gender; blacks and males were predominant in both groups. The OA and RA groups did not differ in terms of controlled or uncontrolled diabetes, smoking status or BMI. The RA patients had been prescribed more anti-inflammatory medication than the OA patients. Our results demonstrate that circulating ProCT is a more discriminative biomarker for periodontitis than serum hsCRP in patients with underlying arthritis. Any elevation in salivary and serum hsCRP due to periodontitis apparently was overshadowed by differences among these patients in factors that influence CRP, such as the extent of inflammation between RA and OA, the extent of adipose tissue, the use of anti- inflammatory medications and smoking status. Although our study showed no differences in salivary ProCT related to severity of periodontitis, this biomarker also may be useful with further refinement.     

Suction feeding mechanics, performance, and diversity in fishes

Despite almost 50 years of research on the functional morphologyand biomechanics of suction feeding, no consensus has emergedon how to characterize suction-feeding performance, or its morphologicalbasis. We argue that this lack of unity in the literature isdue to an unusually indirect and complex linkage between themuscle contractions that power suction feeding, the skeletalmovements that underlie buccal expansion, the sharp drop inbuccal suction pressure that occurs during expansion, the flowof water that enters the mouth to eliminate the pressure gradient,and the forces that are ultimately exerted on the prey by thisflow. This complexity has led various researchers to focus individuallyon suction pressure, flow velocity, or the distance the preymoves as metrics of suction-feeding performance. We attemptto integrate a mechanistic view of the ability of fish to performthese components of suction feeding. We first discuss a modelthat successfully relates aspects of cranial morphology to thecapacity to generate suction pressure in the buccal cavity.This model is a particularly valuable tool for studying theevolution of the feeding mechanism. Second, we illustrate themultidimensional nature of suction-feeding performance in acomparison of bluegill, Lepomis macrochirus, and largemouthbass, Micropterus salmoides, two species that represent oppositeends of the spectrum of performance in suction feeding. As anticipated,bluegills had greater accuracy, lower peak flux into the mouth,and higher flow velocity and acceleration of flow than did bass.While the differences between species in accuracy of strikeand peak water flux were substantial, peak suction velocityand acceleration were only about 50% higher in bluegill, a relativelymodest difference. However, a hydrodynamic model of the forcesthat suction feeders exert on their prey shows that this differencein velocity is amplified by a positive effect of the smallermouth aperture of bluegill on force exerted on the prey. Ourmodel indicates that the pressure gradient in front of a fishthat is feeding by suction, associated with the gradient inwater velocity, results in a force on the prey that is largerthan drag or acceleration reaction. A smaller mouth apertureresults in a steeper pressure gradient that exerts a greaterforce on the prey, even when other features of the suction floware held constant. Our work shows that some aspects of suction-feedingperformance can be determined from morphology, but that thecomplexity of the behavior requires a diversity of perspectivesto be used in order to adequately characterize performance.     

HERITABILITY OF NESTLING BEGGING INTENSITY IN THE HOUSE SPARROW (PASSER DOMESTICUS)

Evolutionary theory of parent–offspring conflict assumes that offspring food solicitation behavior, known as begging, and parental response to begging are subjected to selection and coevolution. This assumption implies that begging intensity should be heritable, at least to some degree. Although some studies have suggested that begging is heritable, the evidence for this is rare and mostly indirect. To assess the heritability of begging we used artificial selection, sibling analysis, and the monitoring of begging intensity in four generations of cross-fostered captive house sparrow nestlings. We also contrasted the heritability of begging with that of morphological traits, known to be heritable in this species. Our results show that adult wing length and body mass were heritable as expected. The heritability estimates of the visual and vocal components of nestling begging (standardized for food deprivation and body mass) were low to moderate, as expected for behavioral traits in general, and lower than previously reported for passerine birds. Our sibling analysis shows that common environment had much greater effect on begging than genetic origin, suggesting that begging evolution may be strongly influenced by gene–environment interaction, probably through the mechanisms that adjust begging response to environmental and social conditions.     

Variation of sesquiterpene lactones in Lactuca aculeata natural populations from Israel,Jordan and Turkey

A comparative phytochemical study of seven sesquiterpene lactones in natural populations of the wild lettuce Lactuca aculeata Boiss. (Asteraceae) was performed, based on 23 accessions derived from eight, two, and single localities from Israel, Jordan, and Turkey, respectively. The compounds were profiled and quantified in leaves and roots of the plants, grown from achenes (cypselas) in a greenhouse under controlled conditions, using reverse phase HPLC with on-line photodiode array detector. In the present study, L. aculeata was confirmed as a taxon strongly characterized by four dominant sesquiterpene lactones: 8-deoxylactucin, jacquinelin, crepidiaside B and lactuside A. An analysis of quantitative results of these four constituents led to the following conclusions: (i) the sesquiterpene lactone contents varied significantly, mainly within the populations; however, for two variables (crepidiaside B and lactuside A in root samples) the contents varied mostly between populations, (ii) these differences are likely to be genetically controlled since all accessions were grown under standardized glasshouse conditions. Accessions containing high levels of some sesquiterpene lactones were found in several populations. These traits should be conserved in situ and ex situ and utilized in further research and lettuce improvement.     

Conserved sequence motifs, alignment, and secondary structure for the third domain of animal 12S rRNA

Secondary structure models are an important step for aligning sequences, understanding probabilities of nucleotide substitutions, and evaluating the reliability of phylogenetic reconstructions. A set of conserved sequence motifs is derived from comparative sequence analysis of 184 invertebrate and vertebrate taxa (including many taxa from the same genera, families, and orders) with reference to a secondary structure model for domain III of animal mitochondrial small subunit (12S) ribosomal RNA. A template is presented to assist with secondary structure drawing. Our model is similar to previous models but is more specific to mitochondrial DNA, fitting both invertebrate and vertebrate groups, including taxa with markedly different nucleotide compositions. The second half of the domain III sequence can be difficult to align precisely, even when secondary structure information is considered. This is especially true for comparisons of anciently diverged taxa, but well-conserved motifs assist in determining biologically meaningful alignments. Patterns of conservation and variability in both paired and unpaired regions make differential phylogenetic weighting in terms of "stems" and "loops" unsatisfactory. We emphasize looking carefully at the sequence data before and during analyses, and advocate the use of conserved motifs and other secondary structure information for assessing sequencing fidelity.      

Bioconversion of Aflatoxin G1 to Aflatoxin B3 by selected fungi

Aflatoxin G₁ (AFG₁) was transformed into aflatoxin B₃ (AFB₃) by the fungiRhodotorula sp,Sporobolomyces sp,Rhizopus oryzae NRRL395,Pythium ultimum, Aspergillus terreus, A clavatus and Penicillium frequentans grown in a medium containing AFG₁, Difco potato dextrose broth, yeast extract, and peptone both in liquid shaken cultures and in solid static cultures at 25°C in the dark. A maximum rate of transformation of 10 % was obtained after 2 to 3 weeks of incubation. The transformation was correlated with an increase in the pH of the media from 5.7 –5.9 to 8.3 – 8.8.Saccharomyces cerevisiae also transformed AFG₁ into AFB₃, but at a slower rate; the pH of the media did not reach above 8.0 until 5 weeks after incubation. No transformation was observed whenA niger andP chrysogenum were tested; in both cases, no increase in pH was noticed. However, some transformation of AFG₁ to AFB₃ by both fungi was observed when the initial pH of the media was adjusted to 9.0. The rate of transformation increased to 15 – 20% in the static culture where the same medium was adsorbed onto vermiculite andRhizopus andAspergilli gave the highest increase in AFB₃ yield.     

Changes in force, cross-sectional area and neural activation during strength training and detraining of the human quadriceps

Four male subjects aged 23-34 years were studied during 60 days of unilateral strength training and 40 days of detraining. Training was carried out four times a week and consisted of six series of ten maximal isokinetic knee extensions at an angular velocity of 2.09 rad.s-1. At the start and at every 20th day of training and detraining, isometric maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG) and quadriceps muscle cross-sectional area (CSA) assessed at seven fractions of femur length (Lf), by nuclear magnetic resonance imaging, were measured on both trained (T) and untrained (UT) legs. Isokinetic torques at 30 degrees before full knee extension were measured before and at the end of training at: 0, 1.05, 2.09, 3.14, 4.19, 5.24 rad.s-1. After 60 days T leg CSA had increased by 8.5% +/- 1.4% (mean +/- SEM, n = 4, p less than 0.001), iEMG by 42.4% +/- 16.5% (p less than 0.01) and MVC by 20.8% +/- 5.4% (p less than 0.01). Changes during detraining had a similar time course to those of training. No changes in UT leg CSA were observed while iEMG and MVC increased by 24.8% +/- 10% (N.S.) and 8.7% +/- 4.3% (N.S.), respectively. The increase in quadriceps muscle CSA was maximal at 2/10 Lf (12.0% +/- 1.5%, p less than 0.01) and minimal, proximally to the knee, at 8/10 Lf (3.5% +/- 1.2%, N.S.). Preferential hypertrophy of the vastus medialis and intermedius muscles compared to those of the rectus femoris and lateralis muscles was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy cost of walking and running at extreme uphill and downhill slopes.

The costs of walking (Cw) and running (Cr) were measured on 10 runners on a treadmill inclined between -0.45 to +0.45 at different speeds. The minimum Cw was 1.64 +/- 0.50 J. kg(-1). m(-1) at a 1.0 +/- 0.3 m/s speed on the level. It increased on positive slopes, attained 17.33 +/- 1.11 J. kg(-1). m(-1) at +0.45, and was reduced to 0.81 +/- 0.37 J. kg(-1). m(-1) at -0.10. At steeper slopes, it increased to reach 3.46 +/- 0.95 J. kg(-1). m(-1) at -0.45. Cr was 3.40 +/- 0.24 J. kg(-1). m(-1) on the level, independent of speed. It increased on positive slopes, attained 18.93 +/- 1.74 J. kg(-1). m(-1) at +0.45, and was reduced to 1.73 +/- 0.36 J. kg(-1). m(-1) at -0.20. At steeper slopes, it increased to reach 3.92 +/- 0.81 J. kg(-1). m(-1) at -0.45. The mechanical efficiencies of walking and running above +0.15 and below -0.15 attained those of concentric and eccentric muscular contraction, respectively. The optimum gradients for mountain paths approximated 0.20-0.30 for both gaits. Downhill, Cr was some 40% lower than reported in the literature for sedentary subjects. The estimated maximum running speeds on positive gradients corresponded to those adopted in uphill races; on negative gradients they were well above those attained in downhill competitions.     

Assessment of the Microbiological Potential for the Natural Attenuation of Petroleum Hydrocarbons in a Shallow Aquifer System

Abstract A multidisciplinary field study investigating the fate and transport of petroleum hydrocarbons commonly associated with jet-fuel contamination is currently underway at Columbus Air Force Base (AFB), Mississippi. Sixty sediment cores from 12 boreholes were recovered from the study aquifer. The goal of this initial sampling was to characterize the potential microbial activity using 14C-labeled substrates, as well as the presence, abundance, and distribution of specific hydrocarbon degrading genotypes using DNA:DNA hybridization. Enumeration of total microbial abundance using a 16S rDNA universal oligonucleotide probe was compared to traditional enumeration methods. Total culturable populations determined by spread plate analysis ranged from a low of 10(4) to more than 10(6) organisms per gram sediment. Microbial abundance estimated by DNA hybridization studies with 16S rDNA genes ranged from 10(7) to 10(8) organisms per gram sediment. Molecular analysis of aquifer samples using DNA probes targeting genes encoding the degradative enzymes alkane hydroxylase (alkB), catechol 2,3-dioxygenase (nahH), naphthalene dioxygenase (nahA), toluene dioxygenase (todC1C2), toluene monooxygenase (tomA), and xylene monooxygenase (xylA), as well as two probes measuring methanogenic microorganisms, codh (carbon monoxide dehydrogenase) and mcr (methyl coenzyme reductase), revealed that each target gene sequence was present in nearly all 60 samples. The presence of organisms demonstrating the phenotype to degrade BTEX and naphthalene was further supported using mineralization assays with 14C-labeled benzene, toluene, naphthalene, and phenanthrene. Minimal activity occurred during the first 24 hours. After a period of 5-7 days, greater than 40% of the target compounds were mineralized in aquifer sediments.