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  • 1
    Electronic Resource
    Electronic Resource
    An in-vitro growth system for studying the parasitism of cowpea (Vigna unguiculata) by Striga gesnerioides (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 31 (1991), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An in-vitro growth system for investigating the behaviour of S. gesnerioides on cowpea has been developed. The roots of young cowpea plants were spread over glass fibre filter paper in a shallow plastic tray, and a known number of germinated Striga seeds were placed on the cowpea root surface. This allowed the infection process of the parasite to be quantified. Good access to the host-parasite association enabled the entire infection process to be easily monitored and tissue removed for cytological studies. Observations revealed for the first time that contact of S. gesnerioides radicles with host roots stimulated the development of radicular hairs and swelling of the tip of these radicles. Furthermore, penetration of cowpea roots by Striga was shown to be localized and to cause very little damage to the host roots. Swollen parasite tubercles developed on the surface of the roots only after the host stele had been penetrated by invading Striga cells. This growth system is suitable for in-vestigating the mechanisms of host resistance. and also for rapidly screening cowpea germplasm for new sources of resistance to the Parasite. Resistant cowpea cultivars offer the best potential solution for control of this Parasite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1991.tb01760.x
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  • 2
    Electronic Resource
    Electronic Resource
    Errors in the gerdien measurement of atmospheric electric conductivity (1991)
    Springer
    Meteorology and atmospheric physics 46 (1991), S. 101-112 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The measurement of conductivity has been an essential part of most atmospheric electricity research programs during the past century. This measurement is known to be vulnerable to a variety of potentially significant errors which can be separated into those resulting from diffusion of ions and those produced by electrical forces. Diffusion errors are caused by inlet tubing, screens, and inlet covers; and electrically produced errors may result from the effect of the accelerating potential or the potential of the apparatus itself. Detection and quantification of these errors has been the subject of several past studies which are discussed in detail. In this paper, a series of measurements and theoretical analyses is described in which the effects of each error mechanism are isolated, measured, and analyzed, and in which prior error reduction schemes are tested. It is shown that diffusive losses in inlet ducting and structures can be significant, and analytical estimations of these losses are presented which agree well with the measurements. The losses produced by electrical forces may also be significant even when plausible ameliorative measures are taken, and operating constraints to avoid this error source are developed. Past measurements of diffusive loss are found to be consistent with these results except in one case where improper operating conditions are indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026627
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  • 3
    Electronic Resource
    Electronic Resource
    31P NMR and 13C NMR studies of recombinant Saccharomyces cerevisiae with altered glucose phosphorylation activities (1991)
    Springer
    Bioprocess and biosystems engineering 6 (1991), S. 273-284 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Manipulation of cellular metabolism to maximize the yield and rate of formation of desired products may be achieved through genetic modification. Batch fermentations utilizing glucose as a carbon source were performed for three recombinant strains of Saccharomyces cerevisiae in which the glucose phosphorylation step was altered by mutation and genetic engineering. The host strain (hxk1 hxk2 glk) is unable to grow on glucose or fructose; the three plasmids investigated expressed hexokinase PI, hexokinase PII, or glucokinase, respectively, enabling more rapid glucose and fructose phosphorylation in vivo than that provided by wild-type yeast. Intracellular metabolic state variables were determined by 31P NMR measurements of in vivo fermentations under nongrowth conditions for high cell density suspensions. Glucose consumption, ethanol and glycerol production, and polysaccharide formation were determined by 13C NMR measurements under the same experimental conditions as used in the 31P NMR measurements. The trends observed in ethanol yields for the strains under growth conditions were mimicked in the nongrowth NMR conditions. Only the strain with hexokinase PI had higher rates of glucose consumption and ethanol production in comparison to healthy diploid strains in the literature. The hexokinase PII strain drastically underutilized its glucose-phosphorylating capacity. A regulation difference in the use of magnesium-free ATP for this strain could be a possible explanation. Differences in ATP levels and cytoplasmic pH values among the strains were observed that could not have been foreseen. However, cytoplasmic pH values do not account for the differences observed among in vivo and in vitro glucose phosphorylation activities of the three recombinant strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369557
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  • 4
    Electronic Resource
    Electronic Resource
    A re-examination of phosphorus-lime interactions in perennial ryegrass (1991)
    Springer
    Plant and soil 135 (1991), S. 185-196 
    Details
    ISSN: 1573-5036
    Keywords: calcium ; critical phosphorus concentration ; gypsum ; lime ; perennial ryegrass ; root membranes ; soluble carbohydrate ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The results of a previous study had suggested that under conditions of limited P availability, Ca may be able to compensate for P in the shoot tissue of perennial ryegrass. To verify this preliminary finding, a factorial experiment was set up which simultaneously tested the effects of Ca and P fertilization on the yield and chemical composition of perennial ryegrass. Calcium was supplied as either lime or gypsum in order to differentiate between the effects of Ca and pH on the response of perennial ryegrass to P fertilization. In the final stage of the experiment a Zn treatment was included, to see whether altering the P/Zn ratios of plant shoots had any influence on the purported interaction between Ca and P. The results demonstrated that the P-sparing effect of lime occurs, at least partly, because Ca application improves the efficiency of absorbed P for DM production. However, it was reasonably clear that the site of the interaction between Ca and P was the soil-root interface, and not shoot tissue. It was suggested that under conditions of limited P supply, Ca stablizes root membranes and thereby minimizes both the efflux losses of nutrients from root tissue, and the compensatory flow of photosynthates from shoots to roots. No interaction was observed between P and Zn treatments in this study. Instead, a positive interaction was found between lime and Zn treatments, which suggests that the stabilizing action of Ca on root membranes requires Zn as a co-stabilizing factor. It is proposed that chemical analysis of shoot tissue alone may not be sufficient to accurately diagnose the P, Ca or Zn status of whole plants, since the critical levels of these elements in shoots appear to bear little relation to their requirements in the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010906
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  • 5
    Electronic Resource
    Electronic Resource
    A test of the maternal stress theory of human male homosexuality (1991)
    Springer
    Archives of sexual behavior 20 (1991), S. 277-293 
    Details
    ISSN: 1573-2800
    Keywords: maternal stress ; sexual orientation ; etiology ; homosexuality ; familiality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract Both the neurohormonal theory of sexual orientation and previous research on humans and animals suggest that male homosexuality may arise from prenatal stress during the brain's sexual differentiation. Stress-proneness and retrospective reports of stress during pregnancy were obtained from mothers of male and female heterosexuals, bisexuals, and homosexuals. Each mother also rated pregnancy stress for a heterosexual sibling of the subject. For males, neither between-family nor within-family analyses revealed a maternal stress effect for either sexual orientation or childhood gender nonconformity. However, mothers of effeminate children reported more stress-proneness than other mothers. Male homosexuality nevertheless was strongly familial, suggesting a reconsideration of genetic and familial environmental mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01541847
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  • 6
    Electronic Resource
    Electronic Resource
    Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins (1991)
    Springer
    Behavior genetics 21 (1991), S. 75-96 
    Details
    ISSN: 1573-3297
    Keywords: sexual orientation ; twins ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchial tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067668
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  • 7
    Electronic Resource
    Electronic Resource
    Increased heritability for lower IQ levels? (1991)
    Springer
    Behavior genetics 21 (1991), S. 397-404 
    Details
    ISSN: 1573-3297
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Dettermanet al. (1990) presented evidence based on twins that the heritability of IQ may be higher in the lower part of the IQ range. We first offer an alternative test for differential heritability across the IQ range, based on the analysis of absolute intrapair differences of monozygotic versus dizygotic twins. We then review two previous studies, each containing more twins than the sample of Dettermanea al., which examined the distribution of intrapair absolute differences. In contrast to the study of Dettermanet al., both yielded results more compatible with higher heritability in the upper range of IQ. We discuss various interpretations of these findings and show how our proposed test might aid in distinguishing among them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065975
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  • 8
    Electronic Resource
    Electronic Resource
    Comments on a segregated model of recombinant cultures: Authors' reply (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1364-1365 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260381114
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  • 9
    Electronic Resource
    Electronic Resource
    Production of slow muonic hydrogen isotopes in vacuum (1991)
    Springer
    Hyperfine interactions 65 (1991), S. 1007-1013 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Muonic hydrogen isotopes (μ− p, μ− d, and μ−t) are simple quantum mechanical systems ideally suited for studies of numerous fundamental phenomena in electroweak and strong interactions as well as in applied areas such as muon chemistry or muon catalyzed fusion. Emission of muonic hydrogen isotopes into vacuum helps to overcome the limitations which are normally imposed on conventional investigations with gaseous and liquid targets. A proof of principle experiment for this new technique was performed at TRIUMF last year. Negative muons with 30 MeV/c momentum were stopped in a thin film of solid hydrogen and produced very low energy μ−d in vacuum. The distribution center of the normal velocity components of emitted μ−d atoms was measured to be ∼1 cm/μs. The yield of μ−d in vacuum is an increasing function of H2 film thickness δ up to a value of δ≥1 mm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397756
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  • 10
    Electronic Resource
    Electronic Resource
    Plasmid presence changes the relative levels of many host cell proteins and ribosome components in recombinant Escherichia coli (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 736-745 
    Details
    ISSN: 0006-3592
    Keywords: computer image analysis ; electrophoresis patterns ; DNA manipulations ; recombinant Escherichia coli ; metabolic analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Relative levels of many individual proteins in Escherichia coli HB101 strains with 0, 37, 56, and 240 plasmids per chromosome were determined by computer image analysis of two-dimensional gel electrophoresis patterns. The plasmids investigated had very similar sequences except for small domains encoding the represser of plasmid replication. At the intermediate plasmid copy number of 56, levels of several of the TCA cycle enzymes (oxoglutarate dehydrogenase complex, succinate thiokinase, and succinate dehydrogenase) as well as in aspartate transcarbamoylase increased. At a plasmid copy number of 240, higher amounts of PEP carboxylase as well as several of the heat shock proteins were observed. Furthermore, at high plasmid levels, significant decreases occurred in growth rate, pyruvate kinase I, pyruvate dehydrogenase complex, unadenylated glutamine synthetase, aspartate transcarbamoylase as well as in several of the proteins involved in translation. Decreases in ribosome content as well as in the free 30S and 50S ribosomal subunit pool fractions were also observed in separate analyses. These results indicate that recombinant DNA manipulations can cause major alterations in numerous host cell properties which could significantly influence cloned protein production or metabolic engineering endeavors.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370808
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