Phytoplankton production and biomass at frontal zones in the Atlantic sector of the Southern Ocean

A high resolution study of chlorophyll a and primary production distribution was carried out in the Atlantic sector of the Southern Ocean during the austral summer of 1990–91. Primary production (¹⁴C assimilation) and photosynthetic capacity levels at frontal systems were among the highest recorded during the cruise (2.8–6.3 mgC·m^–3·h^–1, and 1.3–4.7mgC·mgChl a ^–1·h^–1, respectively). Blooms at ocean fronts were strongly dominated by specific size classes and species. This suggests that the increase in biomass was probably the result of an enhancement of in situ production by selected components of the phytoplankton assemblage, rather than accumulation of cells through hydrographic forces. This hypothesis is supported by the high variability of photosynthetic capacities at adjacent stations along the transects. Blooms (ca 2.7–3.5 mg Chl a·m^–3) were found at three oceanic fronts (the Subtropical, Subantarctic and Antarctic Polar Fronts) during the early summer. These were equivalent to, or denser than, blooms in the Marginal Ice Zone and at the Continental Water Boundary. Seasonal effects on phytoplankton community structure were very marked. In early summer (December), netphyto-plankton (>20 m) was consistently the major component of the frontal blooms, with the chain-forming diatoms Chaetoceros spp. and Nitzschia spp. dominating at the Subantarctic and Antarctic Polar Fronts, respectively. During late summer (February), nanophytoplankton (1–20 m) usually dominated algal communities at the main frontal areas. Only at the Antarctic Polar Front did netphytoplankton dominate, with the diatom component consisting almost exclusively of Corethron criophilum. An early to late summer shift of maximum phytoplankton biomass from north to south of the Antarctic Polar Front was observed. Spatial covariance between silicate levels and water-column stability appeared to be the main factor controlling phytoplankton production at the Antarctic Polar Front. Low silicate concentrations may have limited diatom growth at the northern edge of the front, while a deep mixed layer depth reduced production at the southern edge of the front.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.     

Economic evaluation of water loss saving due to the biological control of water hyacinth at New Year’s Dam,Eastern Cape province,South Africa

Water hyacinth Eichhornia crassipes is considered the most damaging aquatic weed in the world. However, few studies have quantified the impact of this weed economically and ecologically, and even fewer studies have quantified the benefits of its control. This paper focuses on water loss saving as the benefit derived from biological control of this plant between 1990 and 2013 at New Year’s Dam, Alicedale, Eastern Cape, South Africa. Estimates of water loss due to evapotranspiration from water hyacinth vary significantly; therefore, the study used three different rates, high, medium and low. A conservative raw agriculture value of R 0.26 per m³ was used to calculate the benefits derived by the water saved. The present benefit and cost values were determined using 10% and 5% discount rates. The benefit/cost ratio at the low evapotranspiration rate was less than one, implying that biological control was not economically viable but, at the higher evapotranspiration rates, the return justified the costs of biological control. However, at the marginal value product of water, the inclusion of the costs of damage to infrastructure, or the adverse effects of water hyacinth on biodiversity, would justify the use of biological control, even at the low transpiration rate.     

The Tau/A152T mutation,a risk factor for frontotemporal‐spectrum disorders,leads to NR2B receptor‐mediated excitotoxicity

We report on a novel transgenic mouse model expressing human full‐length Tau with the Tau mutation A152T (hTau^AT), a risk factor for FTD‐spectrum disorders including PSP and CBD. Brain neurons reveal pathological Tau conformation, hyperphosphorylation, mis‐sorting, aggregation, neuronal degeneration, and progressive loss, most prominently in area CA3 of the hippocampus. The mossy fiber pathway shows enhanced basal synaptic transmission without changes in short‐ or long‐term plasticity. In organotypic hippocampal slices, extracellular glutamate increases early above control levels, followed by a rise in neurotoxicity. These changes are normalized by inhibiting neurotransmitter release or by blocking voltage‐gated sodium channels. CA3 neurons show elevated intracellular calcium during rest and after activity induction which is sensitive to NR2B antagonizing drugs, demonstrating a pivotal role of extrasynaptic NMDA receptors. Slices show pronounced epileptiform activity and axonal sprouting of mossy fibers. Excitotoxic neuronal death is ameliorated by ceftriaxone, which stimulates astrocytic glutamate uptake via the transporter EAAT2/GLT1. In summary, hTau^AT causes excitotoxicity mediated by NR2B‐containing NMDA receptors due to enhanced extracellular glutamate.     

In vitro evaluation of native entomopathogenic fungi and neem (Azadiractha indica) extracts on Spodoptera frugiperda

The control of Spodoptera frugiperda is based on synthetic insecticides, so some alternatives are the use of entomopathogenic fungi (EF) and neem extract. The objective of the study was to evaluate in vitro effectiveness of native EF and neem extracts on S. frugiperda larvae. Six EF were identified by DNA sequencing of ITS regions from three EF (Fusarium solani, Metarrhizium robertsii, Nigrospora spherica and Penicillium citrinum). They were evaluated in concentrations of 1 × 10⁸ spores/ mL. In addition, a second bioassay was carried out evaluating only F. solani, M. robertsii and N. sphaerica and the addition of vegetable oil. On the other hand, extraction of secondary metabolites from neem seed (Azadirachta indica) was carried out by performing, mass (g) and solvent volume (mL ethanol and water) combinations, which were subjected to microwaves and ultrasound. Subsequently, these extracts were evaluated in concentrations of 3%, 4% and 5%. A survival analysis was performed for each of the bioassays. With respect to the results of the first bioassay, F. solani obtained a probability of survival of 0.476 on the seventh day, while in the second bioassay, M. robertsii obtained 0.488 survival probability. This suggests that the expected percentage of larvae that stay alive on the sixth day is 48.8%. However, in the evaluation of the neem extract the combination 1:12/70% to 4% caused 84% mortality of larvae. The use of native HE and neem extracts has potential for the control of S. frugiperda.     

Effects of a prudent diet containing either lean beef and mutton or fish and skinless chicken on the plasma lipoproteins and fatty acid composition of triacylglycerol and cholesteryl ester of hypercholesterolemic subjects

In this two-phase crossover study, 39 hypercholesterolemic subjects followed a prudent diet with either lean red meat or fish and skinless chicken (treatment groups), and 13 subjects (reference group) followed their habitual diet. Fasting blood samples were analyzed for plasma total cholesterol, triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein one- and two-cholesterol, apolipoprotein-B, very low density lipoprotein cholesterol, and very low density lipoprotein TAG, and fatty acid composition of plasma TAG and cholesteryl ester (CE). Body mass and blood pressure were determined. Seven-day dietary records were kept once at baseline and twice during the treatment periods. Significant differences were observed in dietary intake between the baseline and treatment diets and between the two treatment diets. HDL-C (P < 0.05) and diastolic blood pressure (P < 0.01) were higher in patients on the red meat diet than in those on the chicken-fish diet. No other significant differences in lipoproteins were observed between the effects of the two treatment diets. The linoleic acid (%), eicosapentaenoic acid (%), and the eicosapentaenoic acid/arachidonic acid ratios in TAG and CE were higher (P < 0.01) in subjects on the chicken-fish diet than in those on the red meat diet. In conclusion, this study showed that the effect of two lipid-lowering diets containing either lean red meat or skinless chicken and fish on the atherogenic lipoproteins did not differ significantly. A prudent diet with skinless chicken and fish, however, had a more favorable effect on the fatty acid composition of the plasma TAG and the CE than did the lean red meat diet.