Nutrient and chlorophyll a temporal patterns in eutrophic mountain ponds with contrasting macrophyte coverage

Hydrobiologia - In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of...     

Papain fragmentation of the gastric (H+ + K+)-ATPase

Membrane-bound (H+ + K+)-ATPase purified from hog gastric mucosa was exposed to limited papain digestion. Such treatment resulted in a rapid inhibition of the K+-stimulated adenosine triphosphatase and p-nitrophenyl phosphatase activities, with about 90% of these activities lost after 3 min incubation at 37 degrees C with 0.1 units of papain per mg of enzyme protein. Parallel to the inhibition of the enzyme activities, there was a production of a 77 kDa membrane-bound fragment containing the aspartyl phosphate residue of the phospho-intermediate. This fragment accounted for about 45% of the total enzyme protein after the 3 min papain treatment. The digestion barely affected the steady-state level of phosphorylation, allowed the aspartyl phosphate of the 77 kDa fragment to undergo the transition to the E2P form, and did not significantly alter the fraction of ADP-sensitive phosphoenzyme. The presence of KCl, however, depressed the steady-state level of phosphoenzyme formed from [gamma-32P]ATP considerably less than that of the control enzyme. With further exposure to papain the 77 kDa peptide became fragmented into a 28 kDa soluble peptide that retained the phosphorylating site. Binding of fluorescein 5'-isothiocyanate (FITC) to the native enzyme did not affect the sites of papain hydrolysis because the same peptide fragments were obtained. The FITC reaction site was also in the 28 kDa soluble peptide fragment.     

Modified inoculum for radiometric susceptibility testing ofMycobacterium tuberculosis

Two-hundred and fifteen isolates ofMycobacterium tuberculosis were evaluated with the BACTEC 460 radiometric method for susceptibility to isoniazid, rifampin, ethambutol, and streptomycin (SM); a revised protocol for inoculum preparation was used. Fresh clinical isolates were subcultured into 7H9 broth and then photometrically adjusted to the equivalent of a 0.5 McFarland standard, one-half the recommended inoculum density. This method produced an overall 98.3% correlation with a conventional agar method. The sensitivity of this procedure was good for all drugs tested except for the lowest concentration of SM (2 g/ml). Specificity was excellent for all drugs tested. After repeat testing, only four discrepancies were found, yielding a 99.8% correlation between the two systems. The time required for susceptibility tests averaged 4.6 days. This method for inoculum preparation effectively minimized the number of susceptibility tests exceeding the threshold value before the fourth day of incubation. This allowed for definite trends of the growth index values to become established before interpretation of results.     

Life history and species composition of the damselfly assemblage along the urban tract of a river in central Italy

The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution were different between the sampling sites showing that the life history of both species examined were influenced by a degradation of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites. This revised version was published online in August 2006 with corrections to the Cover Date.     

Application of an image analysis system to the determination of biomass (ash free dry weight) of pond macroinvertebrates

The absence of a rapid and inexpensive method for estimating macroinvertebrate individual biomass is a limit to the study of freshwater communities, given that traditional methods are time- and money-consuming. We propose an inexpensive method to quickly estimate individual biomass from video-recorded images of pond macroinvertebrates. We used a software that automatically measures several body dimensions (area, perimeter, minor and major axes) on each individual and linear regression to relate these body dimensions to dry weight. Area was found to be the best predictor of dry weight. The method allows individual measures of macroinvertebrates at a reasonable speed and accuracy, and may be useful for biomass size spectra or secondary production studies.     

A molecular phylogeny of antarctic chironomidae and its implications for biogeographical history

The chironomid midges Belgica antarctica, Eretmoptera murphyi (subfamily Orthocladiinae) and Parochlus steinenii (subfamily Podonominae), are the only Diptera species currently found in Antarctica. The relationships between these species and a range of further taxa of Chironomidae were examined by sequencing domains 1 and 3–5 of 28S ribosomal RNA. The resulting molecular relationships between B. antarctica and E. murphyi, within Orthocladiinae, were highly supported by validation analyses, confirming their position within Chironomidae, as generated by classical taxonomy. Within Podonominae, P. steinenii from the Maritime Antarctic was more closely related to material from sub-Antarctic South Georgia than to material from Patagonia. Taking advantage of the availability of a molecular substitution rate calculated for this gene in Diptera, a dating of divergence between our study taxa was tentatively established. The divergence dates obtained were 49 million years (Myr), between B. antarctica and E. murphyi, and 68.5 Myr between these species and the closest Orthocladiinae taxon tested from Patagonia, suggesting that B. antarctica and E. murphyi were representatives of an ancient lineage. As both are endemic to their respective tectonic microplates, their contemporary distribution is, therefore, likely to have been shaped by vicariance rather than dispersal.     

Structural and Functional Alterations of Subcutaneous Small Resistance Arteries in Severe Human Obesity

Obese persons are at increased cardiovascular risk and exhibit increased arterial stiffness and impaired endothelial function of large‐ and medium‐size arteries. We hypothesized that normotensive subjects suffering from severe obesity would also present remodeling and endothelial dysfunction of small resistance arteries. A total of 16 lean (age: 49.6 ± 2.9 years, BMI: 22.9 ± 0.3 kg/m², mean ± s.e.m.) and 17 age‐matched severely obese (BMI: 41.1 ± 2.3 kg/m²) normotensive subjects were investigated. None had glucose or lipid metabolic abnormalities except for insulin resistance. Resistance arteries, dissected from abdominal subcutaneous tissue, were assessed on a pressurized myograph. For superimposable blood pressure, the media thickness, media cross‐sectional area (CSA), and media‐to‐lumen ratio values of resistance arteries were markedly and significantly greater in obese compared to lean subjects (media thickness 26.3 ± 0.6 vs. 16.2 ± 0.6 µm, CSA 22,272 ± 1,339 vs. 15,183 ± 1,186 µm², and media‐to‐lumen ratio 0.113 ± 0.006 vs. 0.059 ± 0.001, respectively, P < 0.01). Acetylcholine‐induced relaxation was impaired in vessels from obese subjects compared to the lean individuals (?40.4 ± 1.3%, P < 0.01), whereas endothelium‐independent vasorelaxation was similar in all groups. Stiffness of small arteries as assessed by the stress/strain relationship was similar in lean and severely obese subjects. We conclude that severe human obesity is associated with profound alterations in structural and functional characteristics of small arteries, which may be responsible for the presence of elevated cardiovascular risk and increased incidence of coronary, cerebrovascular and renal events reported in obesity.     

An Effective Automatic Procedure for Testing Parameter Identifiability of HIV/AIDS Models

Realistic HIV models tend to be rather complex and many recent models proposed in the literature could not yet be analyzed by traditional identifiability testing techniques. In this paper, we check a priori global identifiability of some of these nonlinear HIV models taken from the recent literature, by using a differential algebra algorithm based on previous work of the author. The algorithm is implemented in a software tool, called DAISY (Differential Algebra for Identifiability of SYstems), which has been recently released (DAISY is freely available on the web site ). The software can be used to automatically check global identifiability of (linear and) nonlinear models described by polynomial or rational differential equations, thus providing a general and reliable tool to test global identifiability of several HIV models proposed in the literature. It can be used by researchers with a minimum of mathematical background.