Genetic transformation system for the aflatoxin-producing fungus Aspergillus flavus.

A heterologous transformation system was developed for Aspergillus flavus with efficiencies greater than 20 stable transformants per micrograms of DNA. Protoplasts of uracil-requiring strains of the fungus were transformed with plasmid and cosmid vectors containing the pyr-4 gene of Neurospora crassa. Transformants were selected for their ability to grow and sporulate on medium lacking uracil. Vector DNA appeared to integrate randomly into the genome of A. flavus with a tendency for multiple, tandem insertion. Transformants with single or multiple insertions were stable after five consecutive transfers on medium containing uracil. Uracil-requiring recipient strains were obtained either by UV-irradiating conidia and selecting colonies resistant to 5-fluoroorotic acid or by transferring the mutated pyr locus to strains by parasexual recombination. This is the first report of a transformation system for an aflatoxin-producing fungus. The transformation system and the availability of aflatoxin-negative mutants provide a new approach to studying the biosynthesis and regulation of aflatoxin.     

Mercury translocation in and evaporation from soil. I. soil lysimeter experiments with 203Hg‐radiolabeled compounds

Due to a considerable increase of anthropogenic mercury emissions, the mercury load of many soils has risen significantly, for instance in northern Europe. Understanding the fate of mercury in soils is a prerequisite for assessing the effects of ecotoxicological concern. This paper presents a method for obtaining qualitative and quantitative information about mercury translocation in and evaporation from soil. Soil lysimeters were treated with ²⁰³Hg‐labeled HgCl₂ and CH₃HgCl and irrigated with artificial rain. It was demonstrated that the leaching of Hg can be detected by measuring the relative y‐activity throughout the soil profile by means of Na(TI)I detectors. Furthermore, the set‐up was designed to allow detection of Hg volatilization from soil by using traps of iodized charcoal, followed by a potassium peroxodisulfate solution and measuring the γ‐activity. The amount of radioactive Hg in soil leachate was measured by a Na(Tl)I well‐type detector after upconcentration. The determination of monomethyl ²⁰³Hg was been performed by extraction procedures that isolate the methyl mercury compounds. The amount of ²⁰³Hg retained in the soil profile and the real depth of leaching were determined by stratifying the soil profile at the end of the experiment and measuring the y‐activity. With control of all pathways of Hg, the experimental design allows performance of a mass balance analysis.     

Bloom Syndrome and Maternal Uniparental Disomy for Chromosome 15

Bloom syndrome (BS) is an autosomal recessive disorder characterized by increases in the frequency of sister-chromatid exchange and in the incidence of malignancy. Chromosome-transfer studies have shown the BS locus to map to chromosome 15q. This report describes a subject with features of both BS and Prader-Willi syndrome (PWS). Molecular analysis showed maternal uniparental disomy for chromosome 15. Meiotic recombination between the two disomic chromosomes 15 has resulted in heterodisomy for proximal 15q and isodisomy for distal 15q. In this individual BS is probably due to homozygosity for a gene that is telomeric to D15S95 (15q25), rather than to genetic imprinting, the mechanism responsible for the development of PWS. This report represents the first application of disomy analysis to the regional localization of a disease gene. This strategy promises to be useful in the genetic mapping of other uncommon autosomal recessive conditions.     

Different responses to changes in phosphorus,P, among lakes. A study of slopes in chl-a = f(P) graphs

The least squares estimator of a linear regression coefficient _L will give an overall expression for the change in with x. In fresh water ecology, however, subgroups, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaSGaci% 4Aaaaa!37BE!\[P\operatorname{k}\], of a parent population may have slopes which differ from the overall slope, _L. By constructing frequency histograms for the set of angles: Arctang % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4uaSGaam% yAaiaadQgaaaa!38AE!\[\operatorname{S} ij\],% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4uaSGaam% yAaiaadQgaaaa!38AE!\[\operatorname{S} ij\]= para sa y and x% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiaadM% faliaadMgakiabgkHiTiaadMfaliaadQgakiaacMcacaGGVaGaaiik% aiaadIhaliaadMgakiabgkHiTiaadIhaliaadQgakiaacMcaaaa!42F0!\[(Yi - Yj)/(xi - xj)\], i < j, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiEaSGaam% yAaOGaeyiyIKRaamiEaSGaamOAaaaa!3BAB!\[xi \ne xj\], peaks in the distribution may be identified and related to ecological phenomenon. To identify peaks we fit Gaussian distributions to the frequency histograms. For a set consisting of 142 observations of chlorophyll-a and total phosphorus (nutrient) concentrations (TP) from 16 lakes we found four Gaussian peaks corresponding to four subgroups, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaSGaci% 4Aaaaa!37BE!\[P\operatorname{k}\]k = 1,4. One group identified a response of chl-a to changes in TP which correspond approximately to the average slope found by least square regression (the slope was 0.49). The second group consisted of steeper response than the average (1.28). A third group showed that there is an enhanced proportion of cases where chl-a does not respond to TP (zero slope, all the three deep lakes > 10 m, included in the date set contributed to this group). The size of the last group, spanning a wide range of slopes, suggested that about 30% of the inter annual changes in chl-a is unrelated to TP. The results are compared to result obtained by simple least squares regression and to the Theil non-parametric slope estimator.     

Mercury translocation in and evaporation from soil. III. quantification of evaporation of mercury from podzolized soil profiles treated with Hg Cl

Mercury evaporation from undisturbed iron‐humus podzol lysimeters was measured over 3 months after treatment with HgCl₂ spiked with radioactive ²⁰³Hg. The relative evaporation rate from HgCl₂ treated soils followed the sum of two exponential functions. Because evaporation asymptotically approaches zero with time, the integral of the fit curve represents the evaporative loss in percent of atmospheric deposition. For the soil investigated, about 5% of atmospheric Hg deposition was reemitted into the atmosphere. It is hypothesized that mercury evaporation can decrease the leaching of mercury in and from soil significantly; this effect is probably increasing with decreasing rain acidity or soil acidity. Mercury deposited as soluble salt remains susceptible to reemission to air for 300 d after incorporation into the soil matrix. Indications are found that Hg evaporation from soils in geological background areas predominantly derives from recent atmospheric Hg deposition and not from geological sources.     

Drug induced changes in cardio-vascular parameters in the Atlantic cod,Gadus morhua

Summary Ventral (VAP) and dorsal (DAP) aortic blood pressure, heart rate (HR) and cardiac output ( ) were recorded simultaneously in unanaesthetized Atlantic cod, and the effects of vasoactive drugs on the cardio-vascular parameters studied. Mean resting values for the parameters were VAP=4,39 kPa, DAP=2,49 kPa, HR=41 beats/min, and = 29,1 ml/min×kg. Adrenaline constricted the systemic vasculature, dilated the branchial vasculature and caused a decrease of HR and due to a cholinergic reflex. After atropine pre-treatment this reflex was abolished, and the effect of adrenaline on blood pressure enhanced. A small decrease in persisted after atropine, presumably reflecting the effect of an increased end-systolic afterload.Phenylephrine produced a weak increase in systemic vascular resistance, while isoprenaline lowered both systemic and branchial vascular resistance. The effect of isoprenaline is probably mediated by beta adrenoceptors in both vascular beds, since propranolol antagonizes the effect.Acetylcholine in low doses produces a drop in without affecting HR, while higher doses also stop the heart. There is no significant change in either branchial and systemic vascular resistance after acetylcholine.Abbreviations VAP mean ventral aortic blood pressure - DAP mean dorsal aortic blood pressure - TBPD trans-branchial blood pressure drop - HR heart rate - SV stroke volume - cardiac output (ventral aortic blood flow) - VR _g branchial vascular resistance - VR _s systemic vascular resistance