Notes on Diatoms V. : Epilithic Diatom Biomass in the Des Moines River

Luxuriant epilithic growths of the diatom, Gomphonema olivaceum (Lyngbye) Kutz., were observed to be growing throughout a 320 km section of the Des Moines River. Flat rocks covered with the diatom growth were collected and the live weight of the diatom biomass per square centimeter was determined to be 0.7 gm. This included 0.021 gm dry weight of organic matter. Using these values, the standing epilithic diatom biomass in one 6 km section of the river was estimated to be 1260 metric tons (live weight) containing 37.6 metric tons dry weight of organic matter. The bulk of the growth consisted of polysaccharide material secreted as tubular stalks by G. olivaceum. Extensive growths were usually limited to rocky shoals and riffle areas, composed of either cobbles and boulders of glacial origin, or of rock rubble of local origin

Diatoms In The Des Moines River

Diatoms were observed to be the dominant algal group in all seasons in the 860 km long Des Moines River, from April 1961 through September 1964. The 9 most abundant diatom taxa were: Diatoma vulgare, Gomphonema olivaceum, Melosira granulata, Nitzschia dissipata, N. palea, Stephanodiscus hantzschii, Synedra acus and S.ulna. Of the 60 most abundant diatom taxa in the Des Moines River, 36 are important components of diatom floras in other major United States Rivers. From over 600 samples collected year around and throughout the length of the river, 274 diatom taxa representing 38 genera were identified. No new diatom taxa were recognized. Diatoms and a water sample were collected weekly. Water samples were analysed for: temperature, pH, turbidity, sulfate, iron, phosphate, silica, nitrite, nitrate, methyl orange alkalinity, chloride, calcium hardness, total hardness, oxygen, and manganese. The river basin climate produced 5 distinct positive growth periods for diatoms each year; these were characterized by heavy benthic, attached, and planktonic (except in winter) diatom growth; and delimited or terminated by one of 5 distinct respective \u27\u27antigrowth periods\u27\u27 of highwater. The latter periods were typified by heavy silt loads, and removal of most diatoms from the river by flushing and scouring. Sources of diatoms for repopulating the river were the two headwater lakes, numerous tributaries, migratory animals, and impoundments in the upper and middle zones of the river itself. Motility is an important survival factor for diatoms settling out with silt in river impoundments, and 80% of the Des Moines River diatoms are motile forms. Flow (water volume) and available light were probably the most important limiting factors for diatom growth in all seasons in the Des Moines River, both in turn limited by precipitation in the drainage basin. Light penetration most probably was limited by ice and snow cover and turbidity; in addition to precipitation, high turbidity was also caused by effluents from commercial washing of sand and gravel. Seasonal temperature variation also regulated the kinds of dominant and abundant diatoms. Ample nutrients, especially nitrates and phosphates, for diatom growth were provided by inorganic fertilizers washed from farmlands and sewage and related effluents from over 500,000 people. The intrinsic fertility of the Des Moines River is insignificant under these conditions. It is estimated that during positive growth periods over l000 tons per month of diatoms and other algae were produced in and carried out of the river; the vast amount of diatom primary production in the Des Moines River is probably utilized negligibly by other organisms. Two large dams, at Saylorville and Red Rock, will alter the diatom growth patterns in the Middle and Lower portions of the river as well as providing the opportunity for a stratified sedimentary deposition of diatoms. The impoundments from these dams will probably result in a change in the kinds of dominant diatoms and increase the number of taxa collectable

Notes on Iowa Diatoms III. Occurrence of the Genus Pleurosigma in the Des Moines River

A member of the diatom genus Pleurosigma was collected from the Des Moines River from 12 stations. Earlier investigators did not report it. This organism may be suitable as an ecological indicator, since most members of the genus occur in salt or brackish water. Positive identification was not made, the organism is probably a variety of P. delicatulum Wm. Smith

Notes on Iowa Diatoms. VI. Frustular Aberrations in Surirella Ovalis

Two types of frustular aberrations in cultures of Surirella ovalis Breb. have been observed. The first is a notch deformity occurring in approximately 0.1% of the population. It is produced by mechanical distortion where the cells are crowded. This deformity is passed to daughter cells in each successive vegetative division. The second type is characterized by the presence of one or more aberrant raphe canals crossing the valve face in various directions. It occurred only in cultures exposed to continuous light for two weeks. Little or no cell division occurred during this period. The raphe canal aberrations, which occurred in about 0.01% of the exposed population, may have resulted from abortive cell divisions. They were not observed to continue in later transfers of the exposed populations to normal growth conditions

Conformational changes of calmodulin upon Ca2+ binding studied with a microfluidic mixer

A microfluidic mixer is applied to study the kinetics of calmodulin conformational changes upon Ca2+ binding. The device facilitates rapid, uniform mixing by decoupling hydrodynamic focusing from diffusive mixing and accesses time scales of tens of microseconds. The mixer is used in conjunction with multiphoton microscopy to examine the fast Ca2+-induced transitions of acrylodan-labeled calmodulin. We find that the kinetic rates of the conformational changes in two homologous globular domains differ by more than an order of magnitude. The characteristic time constants are ≈490 μs for the transitions in the C-terminal domain and ≈20 ms for those in the N-terminal domain of the protein. We discuss possible mechanisms for the two distinct events and the biological role of the stable intermediate, half-saturated calmodulin

A Metabolomic Analysis Of Thiol Response For Standard And Modified N-Acetyl Cysteine Treatment Regimens In Patients With Acetaminophen Overdose

Abstract N‐acetylcysteine (NAC) is an antidote to prevent acetaminophen (paracetamol‐APAP)‐induced acute liver injury (ALI). The 3‐bag licensed 20.25 h standard regimen, and a 12 h modified regimen, are used to treat APAP overdose. This study evaluated the redox thiol response and APAP metabolites, in patients with a single APAP overdose treated with either the 20.25 h standard or 12 h modified regimen. We used liquid chromatography tandem mass spectrometry to quantify clinically important oxidative stress biomarkers and APAP metabolites in plasma samples from 45 patients who participated in a randomized controlled trial (SNAP trial). We investigated the time course response of plasma metabolites at predose, 12 h, and 20.25 h post‐start of NAC infusion. The results showed that the 12 h modified regimen resulted in a significant elevation of plasma NAC and cysteine concentrations at 12 h post‐infusion. We found no significant alteration in the metabolism of APAP, mitochondrial, amino acids, and other thiol biomarkers with the two regimens. We examined APAP and purine metabolism in overdose patients who developed ALI. We showed the major APAP‐metabolites and xanthine were significantly higher in patients with ALI. These biomarkers correlated well with alanine aminotransferase activity at admission. Receiver operating characteristic analysis showed that at admission, plasma APAP‐metabolites and xanthine concentrations were predictive for ALI. In conclusion, a significantly higher redox thiol response with the modified NAC regimen at 12 h postdose suggests this regimen may produce greater antioxidant efficacy. At baseline, plasma APAP and purine metabolites may be useful biomarkers for early prediction of APAP‐induced ALI

Anthrax Toxin Receptor 2 Determinants that Dictate the pH Threshold of Toxin Pore Formation

The anthrax toxin receptors, ANTXR1 and ANTXR2, act as molecular clamps to prevent the protective antigen (PA) toxin subunit from forming pores until exposure to low pH. PA forms pores at pH ∼6.0 or below when it is bound to ANTXR1, but only at pH ∼5.0 or below when it is bound to ANTXR2. Here, structure-based mutagenesis was used to identify non-conserved ANTXR2 residues responsible for this striking 1.0 pH unit difference in pH threshold. Residues conserved between ANTXR2 and ANTXR1 that influence the ANTXR2-associated pH threshold of pore formation were also identified. All of these residues contact either PA domain 2 or the neighboring edge of PA domain 4. These results provide genetic evidence for receptor release of these regions of PA as being necessary for the protein rearrangements that accompany anthrax toxin pore formation

Age at disability onset and self-reported health status

Background: The critical importance of improving the well-being of people with disabilities is highlighted in many national health plans. Self-reported health status is reduced both with age and among people with disabilities. Because both factors are related to health status and the influence of the age at disability onset on health status is unclear, we examined the relationship between disability onset and health status. Methods: The U.S. 1998–2000 Behavioral Risk Factor Surveillance system (BRFSS) provided data on 11,905 adults with disability. Bivariate logistic regression analysis modeled the relationship between age at disability onset (based on self-report of duration of disability) and fair/poor self-perceived health status, adjusting for confounding variables. Results: Key variables included demographics and other measures related to disability and general health status. Disability onset after 21 years of age showed significant association with greater prevalence of fair/poor health compared to early disability onset, even adjusting for current age and other demographic covariates. Compared with younger onset, the adjusted odds ratios (OR) were ages 22–44: OR 1.52, ages 45–64: OR 1.67, and age ≥65: OR 1.53. Conclusion: This cross-sectional study provides population-level, generalizable evidence of increased fair or poor health in people with later onset disability compared to those with disability onset prior to the age of 21 years. This finding suggests that examining the general health of people with and those without disabilities might mask differences associated with onset, potentially relating to differences in experience and self-perception. Future research relating to global health status and disability should consider incorporating age at disability onset. In addition, research should examine possible differences in the relationship between age at onset and self-reported health within specific impairment groups.This is the publisher’s final pdf. The published article is copyrighted by BioMed Central Ltd. and can be found at: http://www.biomedcentral.com/bmcpublichealth