Effects of temperature on microbial ethanol production. III. The influence of the temperature on the relation existing between the specific ethanol formation rate of the yeast Saccharomyces cerevisiae Sc 5 and the ethanol concentration in the culture medium

The ethanol-inhibitory behaviour of the yeast Saccharomyces cerevisiae Sc 5 was found to be characterized by a continual-linear relation between the specific ethanol formation rate and the ethanol concentration. Therefore the simple equation could be applied for it. It is shown that this model is correct only then, if all of the process parameters are in their optimum. Out of the optimum temperature range the characteristics of the function ν = f(P) change in such a way that in regard to the ethanol concentration P twc linear relations exist for each suboptimum temperature: and a non-linear equation is current for each superoptimum temperature: where b_T is also a function of the temperature and always less than 1. Taking as a basis these equations the specific ethanol formation rate of the used strain can be calculated for the whole biokinetic P/T-sphere of ethanol production.     

Ca2+ release from mitochondria induced by prooxidants

A variety of chemically different prooxidants causes Ca2+ release from mitochondria. The prooxidant-induced Ca2+ release occurs from intact mitochondria via a route which is physiologically relevant and may be regulated by protein ADP-ribosylation. When the released Ca2+ is excessively cycled by mitochondria they are damaged. This leads to uncoupling, a decreased ATP supply, and a decreased ability of mitochondria to retain Ca2+. Excessive Ca2+ cycling by mitochondria will deprive cells of ATP. As a result, Ca2+ ATPases of the endoplasmic (sarcoplasmic) reticulum and the plasma membrane are stopped. The rising cytosolic Ca2+ level cannot be counterbalanced due to damage of mitochondria which, under normoxic conditions, act as safety device against increased cytosolic Ca2+. It is proposed that prooxidants are toxic because they impair the ability of mitochondria to retain Ca2+.     

Resistance ofSpodoptera frugiperda [Lep.: Noctuidae] to a nuclear polyhedrosis virus in the field and laboratory

Median lethal doses (LD₅₀s) of nuclear polyhedrosis virus (NPV) were determined in neonatal offspring ofSpodoptera frugiperda (J. E. Smith) (Sf) larvae captured in southeastern Louisiana in 1981, 1982, and 1984. These LD₅₀s ranged from 1.8 to 16.3 polyhedral inclusion bodies (PIB)/insect. The LD₅₀s significantly (P<0.05) increased during the season of 1982 but had no pattern in 1981 or 1984. However, the Sf populations increased in heterogeneity of response to the NPV during all 3 years. The LD₅₀ increased from 4.1 to 18.7 PIB/insect in a Sf laboratory colony exposed to the NPV LD₈₀ for 7 generations, whereas in a control colony not exposed to NPV the LD₅₀ was 5.9 PIB/insect after 7 generations.     

In situ hybridization of corticotropin-releasing factor-encoding messenger RNA in the hypothalamus of the white sucker,Catostomus commersoni

Summary In situ hybridization procedure with a ³²P-labelled synthetic oligonucleotide probe was used to detect corticotropin-releasing factor-encoding messenger RNA (CRF mRNA) in the hypothalamus of the white sucker, Catostomus commersoni. Adjacent sections were immunostained by a sucker CRF-specific antiserum. CRF mRNA-containing neurons were identified by autoradiography in the magnocellular and parvocellular subdivisions of the preoptic nucleus (PON). Many of these neurons were also immunostained by sucker antiserum, showing the same distribution patterns. These results confirm the presence of CRF mRNA and CRF peptide in the white sucker hypothalamus and support the view that the magnocellular and parvocellular neurons of the PON may be involved in the control of adrenocorticotropic hormone secretion from the pituitary in the white sucker.     

Redox cycling of potential antitumor aziridinyl quinones

The formation of reactive oxygen intermediates (ROI) during redox cycling of newly synthesized potential antitumor 2,5-bis (1-aziridinyl)-1,4-benzoquinone (BABQ) derivatives has been studied by assaying the production of ROI (superoxide, hydroxyl radical, and hydrogen peroxide) by xanthine oxidase in the presence of BABQ derivatives. At low concentrations (< 10 microM) some BABQ derivatives turned out to inhibit the production of superoxide and hydroxyl radicals by xanthine oxidase, while the effect on the xanthine-oxidase-induced production of hydrogen peroxide was much less pronounced. Induction of DNA strand breaks by reactive oxygen species generated by xanthine oxidase was also inhibited by BABQ derivatives. The DNA damage was comparable to the amount of hydroxyl radicals produced. The inhibiting effect on hydroxyl radical production can be explained as a consequence of the lowered level of superoxide, which disrupts the Haber-Weiss reaction sequence. The inhibitory effect of BABQ derivatives on superoxide formation correlated with their one-electron reduction potentials: BABQ derivatives with a high reduction potential scavenge superoxide anion radicals produced by xanthine oxidase, leading to reduced BABQ species and production of hydrogen peroxide from reoxidation of reduced BABQ. This study, using a unique series of BABQ derivatives with an extended range of reduction potentials, demonstrates that the formation of superoxide and hydroxyl radicals by bioreductively activated antitumor quinones can in principle be uncoupled from alkylating activity.     

Differential detachment from resting hosts of replete larval and nymphal Ixodes ticks

To determine whether replete subadult Ixodes ticks detach more frequently from resting than from active hosts, diverse rodents and lizards were caged in an apparatus designed to record the ticks' sites of detachment relative to the resting site of the host. Replete larval Ixodes ricinus and Ixodes dammini accumulated mainly beneath the resting places of the mice (Apodemus agrarius and Peromyscus leucopus) most frequently parasitized in nature. Although nymphal I. ricinus similarly detached where these mice rested, nymphal I. dammini detached more randomly. When lizards were used as hosts, both subadult stages of I. ricinus tended to detach away from their main resting sites; these ticks detached from squirrels more randomly. Detachment ratios for other rodent hosts, that are abundantly infested by the larvae of these ticks in nature (Apodemus flavicollis and Clethrionomys glareolus), could not be derived because nymphs generally failed to attach. Our observations are consistent with reports that both subadult stages of I. dammini, but not the adult, feed on the same kind of nest-dwelling hosts and that the host range of I. ricinus is less focused. Detachment of mouse-feeding larvae from resting mice promotes subsequent nymphal attachment to conspecific hosts, and the absence of such behavior among nymphs facilitates access of the resulting adults to deer.     

Gene expression during induction of somatic embryogenesis in carrot cell suspensions

We report the identification, via their cDNAs, of genes which are temporarily transcribed during the initiation of somatic embryogenesis in carrot (Daucus carota L.) cells cultured in an auxin-free medium. Their expression is roughly associated with the first morphogenetic, or globular, stage. A cDNA library ( gt 10) was established using poly(A)⁺ -rich RNAs from cells deprived of auxin for 8 d. By differential screening a number of clones corresponding to early-induced embryogenic genes were identified. For several a temporary accumulation of the specific mRNA between 6 and 16 d after induction was observed. With regard to the nucleotide sequence and the respective deduced amino-acid sequence, two glycine-rich proteins and a polypeptide with a proline-rich domain were among the products of genes activated at the onset of somatic embryogenesis.Abbreviations b, bp bases, basepairs - 2,4-D 2,4-dichlorophenoxyacetic acid Sequence data reported here will appear in the EMBL Genbank and DDBJ Nucleotide Sequence Databases under the following accession numbers: X 15436 for clone DC 2.15 (proline-rich protein), X 15706 for clone DC 7.1 (glycine-rich protein, DCGRP) and X 14067 for clone DC 9.1 (glycine-rich protein, DCGRP)This research was supported by the Deutsche Forschungsgemeinschaft. We thank Mrs. I. Liebscher for her competent assistance.     

Chromosomal Organization of Rrna Operons in Bacillus Subtilis

Integrative mapping with vectors containing ribosomal DNA sequences were used to complete the mapping of the 10 rRNA gene sets in the endospore forming bacterium Bacillus subtilis. Southern hybridizations allowed the assignment of nine operons to distinct BclI restriction fragments and their genetic locus identified by transductional crosses. Nine of the ten rRNA gene sets are located between 0 and 70 degrees on the genomic map. In the region surrounding cysA14, two sets of closely spaced tandem clusters are present. The first (rrnJ and rrnW) is located between purA16 and cysA14 closely linked to the latter; the second (rrnI, rrnH and rrnG) previously mapped within this area is located between attSPO2 and glpT6. The operons at or near the origin of replication (rrnO,rrnA and rrnJ,rrnW) represent "hot spots" of plasmid insertion.     

Reconstitution of the H+-ATPase complex of Rhodospirillum rubrum by the beta subunit of the chloroplast coupling factor 1

A method is described for isolating the beta subunit from spinach chloroplast F1 (CF1). The isolated beta subunit reconstituted an active F1 hybrid with the F1 of Rhodospirillum rubrum chromatophores from which the beta subunit had been removed. The CF1 beta subunit was similar to the isolated beta subunit of Escherichia coli F1 (Gromet-Elhanan, Z., Khananshivili, D., Weiss, S., Kanazawa, H., and Futai, M. (1985) J. Biol. Chem. 260, 12635-12640) in that it restored a substantial rate of ATP hydrolysis and low, but significant light-dependent ATP synthesis to the beta-less chromatophores. The low rate of photophosphorylation observed with the hybrid enzyme probably resulted from a looser coupling of the CF1 beta subunit to proton translocation in the R. rubrum Fo-F1 complex. The hybrid enzyme exhibited a high specificity for Mg2+-ATP as substrate for ATP hydrolysis and both ATP synthesis and hydrolysis were strongly inhibited by the antibiotic tentoxin. In contrast, chromatophores reconstituted with the native R. rubrum beta subunit actively hydrolyzed both Mg2+-ATP and Ca2+-ATP and were insensitive to tentoxin. These results indicate a close functional homology between the beta subunits of the prokaryotic and eukaryotic H+-ATPases and suggest a role for the beta subunit in conferring the different metal ion specificities and inhibitor sensitivities upon the enzymes. They also demonstrate the feasibility of isolating the beta subunit from CF1 in a reconstitutively active form.     

Biomanipulation and its feasibility for water quality management in shallow eutrophic water bodies in The Netherlands

Biomanipulation as a tool for lake restoration is discussed mainly using literature data. It is based on the exploitation of the interactions both within and between the trophic levels in an aquatic ecosystem. Important among the interactions are: competition for light and nutrients between aquatic macrophytes and phytoplankton and among different phytoplankton species; grazing by planktonic and benthic filter feeders; and size-selective predation by fish. In several case studies biomanipulation has proved to be successful in restorating mildly eutrophic small waterbodies. However, for long-term stability of the restored ecosystems supplementary measures like reducing the external nutrient loadings are needed. The feasibility of the different biomanipulation measures to improve the water quality in shallow Dutch lakes is discussed. Preliminary results on biomanipulation experiments in enclosures withOscillatoria agardhii and the benthic filter feederDreissena polymorpha are given.