Differential sensitivity of plant-associated bacteria to sulfonylurea and imidazolinone herbicides

The side effects of sulfonylurea and imidazolinone herbicides on plant-associated bacteria were investigated under pure culture conditions. Eighteen isolates, belonging to the genera Azotobacter, Azospirillum, Bacillus, Enterobacter Pseudomonas and Serratia, were exposed to four active compounds at concentration ranges similar to those in field soil. The sulfonylureas chlorsulfuron and rimsulfuron inhibited the growth of one of two Azospirillum and one of four Pseudomonas strains, while the imidazolinones imazapyr and imazethapyr were effective on two out of five Bacillus isolates. Surfactants in commercial formulation significantly enhanced rimsulfuron toxicity. With the exception of one Azospirillum strain, the differential tolerance of rhizobacteria to these herbicides was related to a differential sensitivity of their target, the activity of the first enzyme in branched-chain amino acid biosynthesis, acetohydroxyacid synthase (AHAS).Greenhouse pot studies were performed to assess the occurrence of inhibitory effects on bacterial growth in field conditions. Maize seedlings were bacterized with the two strains which had shown in vitro sensitivity to sulfonylureas. Following the application to the soil of a commercial formulation of rimsulfuron at rates of 0, 0.2 and 0.5 mol a.i. kg^–1, significative differences in the resulting degree of bacterial root colonization were found. Moreover, upon co-inoculation with two strains, one tolerant and one sensitive to the herbicide, the presence of rimsulfuron significantly enhanced root occupancy by resistant bacteria, suggesting that shifts in the microbial community structure of crop rhizosphere could indeed result as a consequence of weed control by AHAS inhibitors.Abbreviations AHAS acetohydroxyacid synthase - CETAB cetyltrimethylammonium bromide - ID₅₀ concentration causing 50% inhibition of enzyme activity - LD₅₀ concentration causing 50% decrease of growth constant value     

Enhanced thermotolerance by hydrostatic pressure in the deep-sea hyperthermophile Pyrococcus strain ES4

Abstract: The combined effect of hydrostatic pressure and heat shock on thermotolerance was examined in the deep-sea hyperthermophilic archaeon Pyrococcus strain ES4. Pressure equivalent to the depth of isolation (22 MPa) enhanced ES4's survival at super-optimal temperatures (101–108°C) relative to low pressure (3 MPa). Pressure also raised the temperature at which a putative heat-shock protein (98 kDa) accumulated. ES4 grown at 95°C and 3 MPa displayed immediate enhanced thermotolerance to 105°C after being shifted to 22 MPa. Cultures grown at 95°C and 22 MPa and then heat shocked at 105°C and 3 MPa retained enhanced thermotolerance after decompression. These results suggest that this deep-sea hyperthermophile has developed pressure-induced responses that include increased survival to hyperthermal conditions.     

Alternative male reproductive strategies in the peacock blenny

A 4-year study (1989–1992) of a population of Lipophrys pavo living in a brackish lagoon (Maugio, France) revealed three types of male during the spawning season (April to September): (i) nest-breeder males which are territorial, and have well-developed secondary sexual characteristics; (ii) non-functional males which were abundant only in 1991 when population density was very high and (iii) 1-year-old kleptogamic males with small body size which possess neither secondary sexual organs nor a testicular gland, although their testes are functional and hyperdeveloped (up to 10.5% of carcass weight). The percentage of kleptogamic males was fairly stable in the population (from 7.9 to 10.0%) and highly variable in their age class (from 8.5 to 51.3%). It is suggested that kleptogamy is a conditional strategy adopted by smaller males.     

Macrophage colony-stimulating factor induces thrombospondin I production by cultured human macrophages

The role of colony-stimulating factors (CSFs) in regulating the synthesis of thrombospondin 1 (TSP1) by cultured human macrophages is investigated. Macrophage (M)-CSF is shown rapidly and transiently to induce two predominant species of TSP1 mRNA. One of these species was 3.2 kb in size and appeared to be specific to M-CSF-stimulated macrophages. Adherent M-CSF-treated macrophages are also shown to express abundant surface cell-associated TSP rapidly when examined by indirect immunofluorescence staining. Granulocyte-macrophage (GM)-CSF induced TSP1 mRNA at a later time point, and this was attributable to the effects of endogenous M-CSF induced by the GM-CSF; the GM-CSF-treated cells did not display surface-associated TSP after 3 hr of treatment. Analysis of the TSP1 protein synthesised by the M-CSF-treated macrophages revealed the expected trimeric form of the molecule. In addition, an unidentified 95-kDa protein was found to be covalently associated with immunoreactive TSP1, and this appeared to be specific to the macrophages as it was not found in TSP1 precipitated from other cell types. It is suggested that the induction of TSP1 by M-CSF may play an important role in the major physiological functions of macrophages. © 1995 Wiley-Liss, Inc.     

Polygenic Mutation in Drosophila Melanogaster: Non-Linear Divergence among Unselected Strains

A highly inbred strain of Drosophila melanogaster was subdivided into 20 replicate sublines that were maintained independently with 10 pairs of randomly sampled parents per generation for 180 generations. The variance between lines in abdominal and sternopleural bristle number increased little after 100 generations, in contrast to the neutral expectation of a linear increase; and the covariances of line means between different generations declined with increasing number of generations apart, in contrast to the neutral expectation of constant covariance. Thus, under a neutral model, the estimates of mutational variance were lower than for previous estimates from the first 100 generations of subline divergence. An autoregressive model was fitted to the variance of line means that indicated strong natural selection. There is no single unequivocal explanation for the results. Possible and nonexclusive alternatives include stabilizing selection on bristle number and deleterious effects on fitness of bristle mutations. The inferred strengths of selection on both traits are too high for stabilizing selection alone, and the between-line variance did not continue to increase sufficiently for pleiotropy alone to account for the observations. A third potential explanation that does not invoke selection is duplicate epistasis between mutations affecting bristle number.     

The mATPase histochemical profile of rat type IIX fibres: correlation with myosin heavy chain immunolabelling

Summary In the present study we report a novel histochemical method which, by sequential pre-incubations in alkaline and acidic media, selectively differentiates muscle fibres expressing myosin heavy chain IIX, on the basis of a specific profile for myofibrillar actomyosin ATPase (mATPase) activity. The enzyme reactions were tested for specificity by means of anti-myosin heavy chain monoclonal antibodies, which were characterized on Western blots of muscle homogenates. Enzyme histochemical reactions with the traditional pH buffers were compared to those of the new method and, in conjunction with the immunoreactions, used to confirm the relationship between MyHC expression and the distinct profiles for mATPase. Imrnunohistochemical reactions demonstrated that the new method only differentiates those fibres expressing myosin heavy chain IIX. The method revealed a continuum in which the intermediate staining intensities corresponded to hybrid fibres expressing myosin heavy chain IIX in combination with either the IIA or IIB forms. Quantitative histochemistry and immunohistochemistry (by image analysis), used to examine the relationship between staining intensities for mATPase and amounts of myosin heavy chain IIX expression, revealed that the new method discriminates well between hybrid fibres expressing variable amounts of the IIX isoform (r² = 0.93).     

Interferon antibodies in patients with infectious diseases

Interferons (IFNs) are generally recognized as the most important therapeutic agent in some infectious diseases such as chronic hepatitis B and C. Since the early clinical trials it was documented that the therapeutic use of IFNs could be complicated by the development of antibodies able to neutralize or to bind to the IFN molecule. After several years of research it is now widely accepted that the presence of circulating anti-IFN antibodies may affect the response to IFN. Here we summarize what is currently know on the clinical significance of antibodies to IFN in IFN-treated viral diseases patients.     

Retrospective study of concussive convulsions in elite Australian rules and rugby league footballers: phenomenology,aetiology, and outcome.

OBJECTIVES: To study the ictal phenomenology, aetiology, and outcome of convulsions occurring within seconds of impact in violent collision sport. DESIGN: Retrospective identification of convulsions associated with concussive brain injury from case records from medical officers of football clubs over a 15 year period. SUBJECTS: Elite Australian rules and rugby league footballers. MAIN OUTCOME MEASURES: Neuroimaging studies, electroencephalography, neuropsychological test data, and statistics on performance in matches to determine presence of structural or functional brain injury. Clinical follow up and electroencephalography for evidence of epilepsy. RESULTS: Twenty two cases of concussive convulsions were identified with four events documented on television videotape. Convulsions began within 2 seconds of impact and comprised an initial period of tonic stiffening followed by myoclonic jerks of all limbs lasting up to 150 seconds. Some asymmetry in the convulsive manifestations was common, and recovery of consciousness was rapid. No structural or permanent brain injury was present on clinical assessment, neuropsychological testing, or neuroimaging studies. All players returned to elite competition within two weeks of the incident. Epilepsy did not develop in any player over a mean (range) follow up of 3.5 (1-13) years. CONCLUSIONS: These concussive or impact convulsions are probably a non-epileptic phenomenon, somewhat akin to convulsive syncope. The mechanism may be a transient traumatic functional decerebration. In concussive convulsions the outcome is universally good, antiepileptic treatment is not indicated, and prolonged absence from sport is unwarranted.