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  • 1
    ISSN: 1432-0428
    Keywords: Insulin ; despentapeptide insulin ; deshexapeptide insulin ; negative cooperativity ; insulin demerisation ; lipogenesis ; insulin binding ; insulin metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The C-terminus of the insulin B chain is essential for dimerisation and expression of negative cooperativity. In order to evaluate the possible physiological role of these phenomena, we have studied the properties in vivo and in vitro of despentapeptide insulin (B 26–30 deleted), derived from beef insulin, and deshexapeptide insulin (B25–30 deleted), derived from pork insulin. These materials do not dimerise and have 15% and 0% retention of negative cooperativity respectively. Lipogenesis potencies in rat adipocytes were: despentapeptide insulin 19.9±0.3%; deshexapeptide insulin 19.9±1.5%. Binding potencies in adipocytes were: despentapeptide insulin 22.6±7.8%; deshexapeptide insulin 13.2±3.3%. Metabolic clearance rates were reduced compared to insulin (insulin = 19.1±0.9; despentapeptide insulin = 9.7±0.8; deshexapeptide insulin = 6.4±0.6ml·min−1·kg−1 at plasma concentration 0.5 nmol/l). Hypoglycaemic potencies were reduced for both analogues (40% and 30%) when calculated on the basis of plasma concentration although both analogues and insulin were equally effective at lowering plasma glucose concentration in equimolar doses. Plasma half-disappearance time was prolonged (despentapeptide insulin=7.3±0.5; deshexapeptide insulin=9.1±0.2 min). Both analogues were full agonists and conformed to the general relationship between in vitro and in vivo properties seen with a wide range of modified insulins. They resemble other analogues with modifications which reduce receptor affinity without impairing dimerisation or negative cooperativity. The results do not support a physiological role for dimerisation or negative cooperativity.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Insulin ; insulin analogues ; glucose metabolism ; euglycaemic clamp ; insulin action ; hepatoselectivity ; glucose production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin analogues with relatively greater effect on hepatic glucose production than peripheral glucose disposal could offer a more physiological approach to the treatment of diabetes mellitus. The fact that proinsulin exhibits this property to a minor degree may suggest that analogues with increased molecular size may be less able than insulin to obtain access to peripheral receptor sites. Covalent insulin dimers have previously been shown to possess lower hypoglycaemic potencies than predicted by their in vivo receptor binding affinities. Reduced rates of diffusion to peripheral target tissues-might be an explanation for the lower in vivo potency compared to insulin. To test the relative hepatic and peripheral effects of covalent insulin dimers, glucose clamp procedures with D-[3-3H] glucose tracer infusions were used in anaesthetised greyhounds to establish dose-response curves for rates of hepatic glucose production and glucose disposal with insulin, NαB1, NαB′ 1,-suberoyl-insulin dimer, and NεB29, NεB′ 29,-suberoyl-insulin dimer. With NαB1, NαB′ 1,-suberoyl-insulin dimer molar potencies relative to insulin were 68%, (34–133) (mean and 95% fiducial limits), for inhibition of hepatic glucose production and 14.7%, (10.3–20.9) for glucose disposal. With NεB29,NεB′ 29,-suberoyl-insulin dimer potencies were 75%, (31–184) and 2.5%, (1.5–4.3), for inhibition of hepatic glucose production and for glucose disposal, respectively. The demonstration that both dimers exhibit a significantly greater effect on glucose production than on glucose disposal supports the suggestion that analogues with increased molecular size may exhibit reduced ability to gain access to peripheral target cells.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6849
    Keywords: B chromosomes ; interphase chromatin ; rDNA organization ; rye
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Patterns of rye rDNA organization in interphase nuclei were studied through the use ofin situ hybridization in spreads of root meristem cells from plants with and without B chromosomes (Bs). In cells from plants without Bs each rDNA locus is organized as a single perinucleolar knob of condensed chromatin with decondensed chromatin inside the nucleolus. In plants with Bs there is a marked modification of the pattern, found in more than 23% of nuclei, which involves several regions of condensed chromatin interspersed with decondensed chromatin inside the nucleolus. This B-induced alteration in rDNA interphase organization suggests a change in expression of the rRNA genes located on the A chromosomes probably related to the reduction in nuclear RNA observed previously in plants with Bs. The influence of the Bs on the expression of A chromosome genes, through rearrangement of interphase chromatin, could provide the basis of an explanation for some of the known phenotypic effects of B chromosomes in rye.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-6849
    Keywords: B chromosomes ; genomicin situ hybridization ; nuclear architecture ; Secale cereale ; Triticum aestivum cv ; Lindström
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The B chromosomes (Bs) of rye (Secale cereale) have been studied at interphase in terms of their chromatin organization, patterns of nuclear disposition and physical association in plants with two, three, and four Bs. The study was made in the Lindström strain of hexaploid wheat, which carries the rye Bs as an addition line, byin situ hybridization with a B-specific probe and by genomicin situ hybridization (GISH) with rye genomic DNA, enabling whole chromosome painting. Repetive sequences common to the As and Bs of rye allow for visualization of the rye B at interphase in the wheat background. A B-specific probe enables the orientation of two or more Bs to be determined, and the combination of both probes used together gives information on the disposition of the Bs and on their patterns of physical association within the nucleus. The Bs form linear ‘strings’, and the ends of their long arms, which can be detected by the B-specific probe, are usually located within the hemisphere of the nucleus that has the least condensed chromatin. There is dose-dependent association, and even numbers (2B, 4B) have a greater preference for association than odd ones (3B).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 35 (1986), S. 575-582 
    ISSN: 1573-5060
    Keywords: Lycopersicon ; tomato ; salinity ; germination ; germplasm ; breeding ; salt-tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The potential to improve seed germination responses to salinity was evaluated for 13 accessions representing six wild Lycopersicon species and 20 accessions of L. esculentum. Germination response times increased in all accessions at 100 mM NaCl. Analysis indicated that one accession of L. peruvianum (PI126435) germinated faster under high salinity than all other accessions and was closely followed by L. pennellii (LA716). The fastest germinating L. esculentum accession, PI174263, ranked third. Additional wild ecotypes exhibiting rapid germination at 100 mM NaCl were identified among L. pimpinellifolium and L. peruvianum.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 40 (1989), S. 187-191 
    ISSN: 1573-5060
    Keywords: Lycopersicon esculentum ; tomato ; Pyrenochaeta lycopersici ; corky root ; brown root rot ; resistance ; greenhouse screening method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A greenhouse screening method for corky root (Pyrenochaeta lycopersici) resistance in the tomato (Lycopersicon esculentum) is described in detail. In determining the reliability of the method, known resistance sources within wild asccessions, commerical cultivars and breeding lines were evaluated for resistance in fields naturally infested with corky root and their response compared under greenhouse conditions in soil heavily infested with corky root and artifically maintained at temperatures between 10–13°C. The procedure developed can be used year round and improves the efficiency of recovering resistant progeny in large segregrating populations.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5060
    Keywords: Lycopersicon esculentum ; tomato ; cold tolerance ; seed germination ; genetic analysis ; missing data ; response-time data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In studies to determine the inheritance of response-time traits, such as time to seed germination, some viable individuals may fail to respond during an experiment. If these right-censored observations are ignored, sample means and variances will be underestimated. This is illustrated using data from time to seed germination at 9°C for Lycopersicon esculentum (Mill.) fast germinating PI 120256, slow-germinating T3 and their reciprocal F1, F2 and backcross progeny. This paper presents methods to detect and to accommodate right-censored data in generation means analysis. Genetic interpretations derived from corrected and uncorrected estimates of generation means and variances are compared. Correction for right-censoring increased estimates of environmental and phenotypic variances, and decreased heritability estimates.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 32 (1983), S. 845-855 
    ISSN: 1573-5060
    Keywords: Lycopersicon esculentum ; tomato ; flavor ; sensory evaluation ; soluble solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Advanced high sugar and acid breeding lines of tomatoes (Lycopersion esculentum Mill.) were rated higher in sweetness, sourness and overall flavor intensity than the standard cultivars Cal Ace or T3. Titratable acidity and soluble solids content were major contributors to differences in overall flavor intensity. The results demonstrate that significant improvement in tomato flavor can be attained by increasing sugar and acid contents in tomato fruits by genetic manipulation. Current evidence indicates that breeding for high soluble solids in horticulturally acceptable tomato cultivars is justified.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Genetica 97 (1996), S. 65-72 
    ISSN: 1573-6857
    Keywords: Secale cereale ; rye ; B chromosomes ; inbred lines ; pairing ; pollen mitosis ; transmission genotypes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract B chromosomes from an experimental population of the Japanese JNK strain of rye, isogenic for its Bs, have been backcrossed into twelve different inbred lines. The experiment is a way of studying the effects of the Bs against a range of different homozygous A chromosome backgrounds. This publication deals with pairing effects of both the As and the Bs, and their interactions, and with pollen mitosis. At meiosis there is a genotypic component to B effects, and they do not appear to act solely through a physical disturbance within the nucleus. In pollen the Bs are always present in more than 50% of the grains regardless of their pairing behaviour during meiosis; this result fits with a ‘parasitic’ model of the activity of rye Bs.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromosome research 5 (1997), S. 177-181 
    ISSN: 1573-6849
    Keywords: B chromosomes ; interphase chromosome arrangement ; meiosis ; Secale cereale ; Triticum aestivum cv. Lindstro¨m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Probes for B chromosome-specific sequences in the distal region of the long arm of the rye B have been used to investigate the interphase arrangement of the Bs in rye and in hexaploid wheat. The Lindstro¨m strain of wheat carries the rye Bs as additions. The number of in situ signals in nuclei with two, three and four Bs is often less than the maximum B number, and it seems that the Bs may be grouped together in various ways rather than being randomly dispersed throughout the nucleus. The degree of physical association is greater in rye than in the alien wheat background. The results are discussed in relation to the pairing and recombination preferences of the Bs in rye and in Lindstro¨m wheat.
    Type of Medium: Electronic Resource
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