Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm

The purpose of the present study was to assess atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) mineralization by indigenous microbial communities and to investigate constraints associated with atrazine biodegradation in environmental samples collected from surface soil and subsurface zones at an agricultural site in Ohio. Atrazine mineralization in soil and sediment samples was monitored as ¹⁴CO₂ evolution in biometers which were amended with ¹⁴C-labeled atrazine. Variables of interest were the position of the label ([U-¹⁴C-ring]-atrazine and [2-¹⁴C-ethyl]-atrazine), incubation temperature (25°C and 10°C), inoculation with a previously characterized atrazine-mineralizing bacterial isolate (M91-3), and the effect of sterilization prior to inoculation. In uninoculated biometers, mineralization rate constants declined with increasing sample depth. First-order mineralization rate constants were somewhat lower for [2-¹⁴C-ethyl]-atrazine when compared to those of [U-¹⁴C-ring]-atrazine. Moreover, the total amount of ¹⁴CO₂ released was less with [2-¹⁴C-ethyl]-atrazine. Mineralization at 10°C was slow and linear. In inoculated biometers, less ¹⁴CO₂ was released in [2-¹⁴C-ethyl]-atrazine experiments as compared with [U-¹⁴C-ring]-atrazine probably as a result of assimilatory incorporation of ¹⁴C into biomass. The mineralization rate constants (k) and overall extents of mineralization (P _max ) were higher in biometers that were not sterilized prior to inoculation, suggesting that the native microbial populations in the sediments were contributing to the overall release of ¹⁴CO₂ from [U-¹⁴C-ring]-atrazine and [2-¹⁴C-ethyl]-atrazine. A positive correlation between k and aqueous phase atrazine concentrations (C _eq ) in the biometers was observed at 25°C, suggesting that sorption of atrazine influenced mineralization rates. The sorption effect on atrazine mineralization was greatly diminished at 10°C. It was concluded that sorption can limit biodegradation rates of weakly-sorbing solutes at high solid-to-solution ratios and at ambient surface temperatures if an active degrading population is present. Under vadose zone and subsurface aquifer conditions, however, low temperatures and the lack of degrading organisms are likely to be primary factors limiting the biodegradation of atrazine.Abbreviations C _eq solution phase atrazine concentration at equilibrium - C _s amount of atrazine sorbed - CLA [2-¹⁴C-ethyl]-atrazine - k first-order mineralization rate constant - K _d sorption coefficient - m slope - P _max maximum amount of CO₂ released - RLA [U-¹⁴C-ring]-atrazine     

Sister chromatid exchange analysis of the 15q11 region in Prader-Willi syndrome patients

Summary Prader-Willi syndrome (PWS) is a sporadic disorder in which about half of cases have a 15q12 deletion. Although a small number of cases have other rearrangements involving 15q12, the rest of the cases appear to have normal chromosomes. Clinical similarities among all these patients regardless of the karyotype strongly suggests a common etiology. To investigate the nature of this common etiology, we analyzed sister chromatid exchange (SCE) at the 15q11-13 region in 10 PWS patients with the chromosome deletion, 12 PWS patients with normal chromosomes, and 11 normal control individuals. While SCE at the q11-13 region was absent on the 15q12 deleted chromosome, the percentage of SCE on chromosome 15 at q11 was statistically higher for PWS with normal chromosomes (10.1%) compared to that for normal controls (1.9%) and the normal homologue (2.2%) in deleted patients (²=7.7982, df=2, P<0.025). The data suggest relative instability of DNA at the 15q11 region in PWS patients.     

Chromosomal evolution withinPiperaceae

Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed.     

Biosynthesis of δ-aminolevulinic acid from glutamate by Sulfolobus solfataricus

The extremely thermophilic, obligately aerobic bacterium Sulfolobus solfataricus forms the tetrapyrrole precursor, -aminolevulinic acid (ALA), from glutamate by the tRNA-dependent five-carbon pathway. This pathway has been previously shown to occur in plants, algae, and most prokaryotes with the exception of the -group of proteobacteria (purple bacteria). An alternative mode of ALA formation by condensation of glycine and succinyl-CoA occurs in animals, yeasts, fungi, and the -proteobacteria. Sulfolobus and several other thermophilic, sulfur-dependent bacteria, have been variously placed within a subgroup of archaea (archaebacteria) named crenarchaeotes, or have been proposed to comprise a distinct prokaryotic group designated eocytes. On the basis of ribosomal structure and certain other criteria, eocytes have been proposed as predecessors of the nuclear-cytoplasmic descent line of eukaryotes. Because aplastidic eukaryotes differ from most prokaryotes in their mode of ALA formation, and in view of the proposed affiliation of eocytes to eukaryotes, it was of interest to determine how eocytes form ALA. Sulfolobus extracts were able to incorporate label from [1-¹⁴C]glutamate, but not from [2-¹⁴C]glycine, into ALA. Glutamate incorporation was abolished by preincubation of the extract with RNase. Sulfolobus extracts contained glutamate-1-semialdehyde aminotransferase activity, which is indicative of the five-carbon pathway. Growth of Sulfolobus was inhibited by gabaculine, a mechanism-based inhibitor of glutamate-1-semialdehyde aminotransferase, an enzyme of the five-carbon ALA biosynthetic pathway. These results indicate that Sulfolobus uses the five-carbon pathway for ALA formation.Abbreviations AHA 4-amino-5-hexynoic acid - ALA -aminolevulinic acid, Gabaculine, 3-amino-2,3-dihydrobenzoic acid - GSA glutamate 1-semialdehyde     

Labidocera aestiva and L. scotti in Tamiahua Lagoon,Veracruz, Mexico

Labidocera aestiva and L. scotti were found in the Tamiahua Lagoon, Veracruz, Mexico. Fleminger (1957) found that the populations of these species may overlap geographically, although L. aestiva has affinity to the Carolinian province and L. scotti to the Caribbean province. This study describes the seasonal behavior and succession of this species in the Tamiahua Lagoon, a brackish water system with a high marine influence. A qualitative and quantitative analysis of samples was made in March, July, and September 1985 and January 1986. L. aestiva was found in temperatures below 26 °C in a wide salinity range. At temperatures above 26 °C and up to 32 °C, L. aestiva was present also with euryhaline character. In the Tamiahua Lagoon these two species did not overlap during this study. Both species are considered temporary inhabitants of this estuarine system in the Western Gulf of Mexico.     

Modulation by angiotensin III of nociception-related and arterial pressure-related neuronal responsiveness in the nucleus reticularis gigantocellularis of the rat

We evaluated possible modulation by angiotensin III (AIII) of the interactive effect of noxious stimuli and elevation in systemic arterial pressure on the responsiveness of neurons in the nucleus reticularis gigantocellularis (NRGC) of the medulla oblongata. Combined extracellular single-neuron recording and microiontophoresis were carried out on male, adult Sprague-Dawley rats anesthetized with pentobarbital sodium. The responsiveness of NRGC neurons to nociception (tail clamp) and/or transient hypertension elicited by phenylephrine (5 μg/kg, i.v.), in the absence or presence of AIII, was used as the experimental index. Microiontophoretic application of the heptapeptide suppressed the responses of spontaneously active NRGC neurons to individually delivered nociception or hypertension. Interestingly, the preferential reduction in responsiveness to tail clamp upon simultaneous elevation in arterial pressure was reversed to one that favored nociception in the presence of AIII. These actions of the heptapeptide appeared to be receptor-specific, since they were discernibly blocked by its selective antagonist, Ile⁷-angiotensin III. Our results reveal that neuropeptides such as AIII may differentially modulate neuronal responsiveness according to the prevailing physiologic input(s) to the central nervous system of the animal.     

Comparison of corn steep liquor with other nutrients in the fermentation of D-Xylose by Pichia stipitis CBS 6054

Summary Pichia stipitis CBS 6054 ferments D-Xylose to ethanol in a medium containing corn steep liquor as the only source of nitrogen, amino acids, vitamins and other nutrients. The ethanol yield and fermentation rate compare favorably to those obtained with media containing more expensive sources of nitrogen, vitamins and amino acids. Corn steep liquor is a good source of nutrients that can support growth and fermentation activity of this xylose fermenting yeast.     

International Society for Reef Studies

International Society for Reef Studies     

Cell-substrate adhesion and metastatic potential of cultured mesothelioma cells induced by asbestos

Cell-substrate adhesion was quantified for two cultured mesothelioma cell lines (epitheliomatus and sarcomatous) on glass, fibronectin and laminin substrates. Interference reflection microscopy (IRM) was used to image the adhesion patterns of cells and a grey level analysis was employed to quantify adhesion. Sarcomatous cells demonstrated marked adhesion to glass and fibronectin-coated substrates but not to laminin-coated substrate, with the greatest adhesion occurring on the fibronectin-coated surface. This adhesion was accompanied by cytoplasmic spreading. By contrast, epitheliomatous cells showed little tendency to adhere to any of the substrates and only showed significant spreading when in contact with the laminin substrate (P < 0.01). A bioassay was used to determine the metastatic potential of each of the cell lines. Via the intravenous route, the sarcomatous cells killed the host rats in 24.7 ± 1.5 (S.D.) days compared to 27.3 ± 0.9 (S.D.) days for the epitheliomatous cells (P < 0.01). After subcutaneous inoculation of tumour cells, the sarcomatous cells killed the host rats in 54.7 ± 0.7 (S.D.) days compared to 48.5 ± 0.5 (S.D.) days for the epitheliomatous cells (P < 0.01). We conclude that the results of the metastasis bioassays were consistent with the predicted behavior of these cell lines based on their ability to adhere to substrates in the in vitro adhesion assays.