Evidence that neomycin inhibits binding of herpes simplex virus type 1 to the cellular receptor.

The effect of neomycin, a phosphoinositide-binding aminoglycoside, on herpes simplex virus type 1 (HSV-1) infection of BHK cells was studied. We showed earlier that it specifically inhibits HSV-1 production but not HSV-2 production (Langeland et al., Biochem Biophys. Res. Commun. 141:198-203, 1986). We now show that neomycin had no effect on cellular protein synthesis, as judged by the appearance of 35S-labeled polypeptides separated by polyacrylamide gel electrophoresis. Virus-induced polypeptides, however, were strongly inhibited at neomycin concentrations above 2 mM. Comparison among different aminoglycosides showed a variation in inhibition of HSV-1 production that paralleled the cationic charge of the aminoglycosides. HSV-1 receptor binding at 4 degrees C was completely inhibited by neomycin. At 37 degrees C both receptor binding and internalization, as measured by an indirect assay, appeared to be inhibited by more than 90%. The effect of neomycin on the infection was almost immediate upon the addition of the drug and preceded virus internalization. Possible mechanisms of the neomycin effect are discussed.     

Herpes simplex virus-1-specific proteins are involved in alteration of polyphosphoinositide metabolism in baby-hamster kidney cells.

Herpes simplex virus type 1 (HSV-1) induces altered phosphoinositide metabolism in baby hamster kidney (BHK) cells, measured as incorporation of [3H]inositol or [32P]Pi [Langeland, Haarr & Holmsen (1986) Biochem. J. 237, 707-712]. We now report that this response in the inositol phospholipids is dependent on virus-specific proteins synthesized in the beta (early) stage of virus protein synthesis. This was demonstrated both by resistance to the inhibitory effect of cycloheximide after this stage of infection, and by the use of temperature-sensitive (ts) mutants of HSV-1; ts mutants in which protein synthesis was blocked so that only the alpha proteins were expressed showed a PIP2/PIP (phosphatidylinositol 4,5-bisphosphate/phosphatidylinositol 4-monophosphate) ratio similar to uninfected cells, while ts mutants which were defective in protein synthesis at a late beta stage or later showed increased PIP2/PIP ratios similar to cells infected by wild type HSV-1.     

Evidence that neomycin inhibits HSV 1 infection of BHK cells

The effect of neomycin on the Herpes Simplex Virus (HSV) type 1 and 2 infection of baby hamster kidney cells was studied. Neomycin concentrations of 3 mM or more caused a more than 90% inhibition of HSV 1 proliferation, while it had no effect on HSV 2 proliferation, measured as plaque-forming units. Furthermore, neomycin must be present at the time of infection in order to exert full effect, addition 1 hour postinfection was comparable to untreated cells. This indicates that neomycin may specifically interfere with very early stages of HSV 1 infection.     

Activated platelet-derived growth factor autocrine pathway drives the transformed phenotype of a human glioblastoma cell line

Human glioblastoma cells (A172) were found to concomitantly express PDGF-BB and PDGF β-receptors. The receptors were constitutively autophosphorylated in the absence of exogenous ligand, suggesting the presence of an autocrine PDGF pathway. Neutralizing PDGF antibodies as well as suramin inhibited the autonomous PDGF receptor tyrosine kinase activity and resulted in up-regulation of receptor protein. The interruption of the autocrine loop by the PDGF antibodies reversed the transformed phenotype of the glioblastoma cell, as determined by (1) diminished DNA synthesis, (2) inhibition of tumor colony growth, and (3) reversion of the transformed morphology of the tumor cells. The PDGF antibodies showed no effect on the DNA synthesis of another glioblastoma cells line (U343MGa 31L) or on Ki-ras-transformed fibroblasts. The present study demonstrates an endogenously activated PDGF pathway in a spontaneous human glioblastoma cell line. Furthermore, we provide evidence that the autocrine PDGF pathway drives the transtormed phenotype of the tumor cells, a process that can be blocked by extracellular antagonists. © 1994 Wiley-Liss, Inc.     

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.     

Interactions between zooplankton and fish in a fertilized lake

The effects of fish predation on the zooplankton community in an oligotrophic lake, Langvatn, near Trondheim in Central Norway, were investigated during a six-year period (1973–1978), together with the added effects of changes produced by adding artificial fertilizer in 1975 and 1976. The improved nutrient conditions in 1975 resulted in a rapid increase in biomass and production of the largest herbivore zooplankton species and of the fish population. A change in the behaviour and food habits of the arctic char was recorded; they became more pelagic and fed mainly on zooplankton. An increased survival rate of 0-group and biomass of planktivorous fish in 1975 enhanced the degree of fish predation on the zooplankton during subsequent years (1976–1978). As a consequence of fish predation, the composition of the zooplankton changed, from a mainly large-sized to a mainly small-sized community, dominated by Bosmina longirostris and rotifers. Since fish predation is size-selective and visibility-dependent, it induced a decrease in mean size and in body length at onset of maturity of the cladoceran populations and probably also weakened their ability to produce resting eggs.     

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.