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  • Polymer and Materials Science  (17)
  • Lycopersicon  (4)
  • Carotid body  (3)
  • Insulin  (3)
  • 1
    Electronic Resource
    Electronic Resource
    An examination of the role of insulin dimerisation and negative cooperativity using the biological properties of the despentapeptide and deshexapeptide insulins (1987)
    Springer
    Diabetologia 30 (1987), S. 733-738 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00296998
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  • 2
    Electronic Resource
    Electronic Resource
    Demonstration of a relatively hepatoselective effect of covalent insulin dimers on glucose metabolism in dogs (1995)
    Springer
    Diabetologia 38 (1995), S. 1007-1013 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00402169
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  • 3
    Electronic Resource
    Electronic Resource
    Assessment of evidence for K+-H+ exchange in isolated type-1 cells of neonatal rat carotid body (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 429-437 
    Details
    ISSN: 1432-2013
    Keywords: Key words pHi ; SNARF ; Carotid body ; Type-1 cell ; Potassium-hydrogen exchange ; K+-H+ exchanger (KHE) ; Nigericin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Intracellular pH (pHi) was measured in enzymically isolated, neonatal rat carotid body type-1 cells, using the fluorophore carboxy-SNARF-1 (AM-loaded), and using the nigericin technique for in situ fluorescence calibration (nigericin is a membrane-soluble K+-H+ exchanger). In CO2/HCO3 –-free media, inhibiting Na+-H+ exchange produced a prompt fall of pHi (background acid-loading), the rate of which was reduced by raising the extracellular K+ concentration, [K+]o. pHi recovery from an intracellular acid or alkali load was also sensitive to changes of [K+]o. These results are similar to those of Wilding et al. (J Gen Physiol 100:593–608, 1992), who proposed the existence of an acid-loading, K+-H+ exchanger (KHE) in the type-1 cell. However, when nigericin was not used for post-experimental calibration, and the superfusion system was flushed exhaustively with strong detergent, alcohol and distilled water, then background acid-loading was attenuated, and the K+ o sensitivity of pHi insignificant. Background loading was increased again, and K+ o sensitivity restored, when cells were monitored in a superfusion system which had previously been exposed to a single nigericin-calibration protocol (followed by a short system wash with strong detergent and distilled water). We conclude that the previously reported expression of KHE in carotid body type-1 cells is an artefact caused by nigericin contamination. We have therefore quantified the pHi dependence of background loading in uncontaminated type-1 cells. We consider the possible implications of our work for reports of KHE in other cell types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050417
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  • 4
    Electronic Resource
    Electronic Resource
    Application of a new pH-sensitive fluoroprobe (carboxy-SNARF-1) for intracellular pH measurement in small, isolated cells (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 234-239 
    Details
    ISSN: 1432-2013
    Keywords: Intracellular pH ; SNARF-1 ; Carotid body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the use of a new pH-sensitive dualemission fluoroprobe, carboxy-seminaphthorhodafluor-1 (carboxy-SNARF-1) for ratiometric recording of intracellular pH (pHi) in small isolated cells. The method is illustrated with pHi measurement in single type-1 cells (cell diameter ∼10 μm) isolated from the carotid body of the neonatal rat. Carboxy-SNARF-1 is loaded using bath application of the acetoxymethyl ester. When excited at 540 nm, the fluoroprobe gives strong, inversely related emission signals at 590 nm and 640 nm. Stable ratiometric recordings of pHi can be achieved from a single cell (pHi 8.5-6.5) for up to 50 min. Photobleaching of the probe is minimised by illuminating at relatively low light intensity (50 W xenon lamp with 0.2% transmission neutral density filter). The probe can be calibrated in situ using the nigericin technique and this is in good quantitative agreement with the independent null-point technique (extracellular weak acid/weak base application) of Eisner et al. (1989). This fluoroprobe offers certain advantages over the other commonly used probe for pHi 2′,7′-bis-(2-carboxyethyl)-5(and -6)-carboxyfluorescein (BCECF): (i) because of its two strong pH-sensitive peak emissions, SNARF displays a good signal-to-noise ratio for ratiometric recording at low light intensities; (ii) unlike BCECF, the dual emisson of SNARF requires no sequential mechanical switching of excitation filters, thus simplifying the epifluorescence set-up; (iii) because carboxy-SNARF-1 emission signals are at the yellow/red end of the visible spectrum, fluorescent drugs like amiloride, ethyl-isopropyl-amibride (EIPA), 4,4′-diisothiocyanostilbene 2,2′-disulphonic acid (DIDS) and cinnamate analogues do not interfere with the pHi recording, even when used at high concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370705
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of acidic stimuli on intracellular calcium in isolated type I cells of the neonatal rat carotid body (1993)
    Springer
    Pflügers Archiv 425 (1993), S. 22-27 
    Details
    ISSN: 1432-2013
    Keywords: Carotid body ; Chemoreceptor ; Intracellular calcium ; Intracellular pH ; Extracellular pH ; Acidosis ; Hypercapnia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated the effects of acidic stimuli upon [Ca2+]i in isolated carotid body type I cells from the neonatal rat using indo-1 (AM-loaded). Under normocapnic, non-hypoxic conditions (23 mM HCO3 −, 5% CO2 in air, pHo=7.4), the mean [Ca2+]i for single cells was 102±5.0 nM (SEM, n=55) with 58% of cells showing sporadic [Ca2+]i fluctuations. A hypercapnic acidosis (increase in CO2 to 10%–20% at constant HCO3 −, pHo 7.15–6.85), an isohydric hypercapnia (increase in CO2 to 10% at constant pHo=7.4) and an isocapnic acidosis (pHo=7.0, constant CO2) all increased [Ca2+]i in single cells and cell clusters. The averaged [Ca2+]i response to both hypercapnic acidosis and isohydric hypercapnia displayed a rapid rise followed by a secondary decline. The averaged [Ca2+]i response to isocapnic acidosis displayed a slower rise and little secondary decline. The rise of [Ca2+]i in response to all the above stimuli can be attributed to no single factor other than to a fall of pHi. The hypercapnia-induced rise of [Ca2+]i was almost completely abolished in Ca2+-free solution, suggesting a role for Ca2+ influx in triggering and/or sustaining the [Ca2+]i response. These results are consistent with a role for type I cell [Ca2+]i in mediating pH/PCO2 chemoreception.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374499
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  • 6
    Electronic Resource
    Electronic Resource
    Low temperature effect on selective fertilization by pollen mixtures of wild and cultivated tomato species (1981)
    Springer
    Theoretical and applied genetics 59 (1981), S. 235-238 
    Details
    ISSN: 1432-2242
    Keywords: Low temperature adaptation ; Lycopersicon ; Pollen mixtures ; Selective fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In vitro pollen germination of cultivated tomato, Lycopersicon esculentum Mill., is inhibited by an ambient temperature of 5°C, more so than pollen from a Peruvian ecotype of Lycopersicon hirsutum Humb. & Bonpl. originating from an altitude of 3200 m. The frequency of L. hirsutum gametes contributing to hybrid zygote formation is more than doubled when controlled fertilizations with pollen mixtures of the two species occurs at 12/6°C as compared to crosses with the same mixtures at 24/19°C. The results suggest that differential selection at the gametophytic level occurs in response to low temperature regimes. To our knowledge this is the first time in higher plants that alteration of an environmental factor has been demonstrated to change selection values of male gametophytes in a fashion predicted by the ecology of the parental sporophytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265501
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  • 7
    Electronic Resource
    Electronic Resource
    Mapping QTLs conferring salt tolerance during germination in tomato by selective genotyping (1997)
    Springer
    Molecular breeding 3 (1997), S. 269-277 
    Details
    ISSN: 1572-9788
    Keywords: Lycopersicon ; marker-assisted selection (MAS) ; quantitative trait loci (QTLs) ; restriction fragment length polymorphism (RFLP) ; salt tolerance ; seed germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to identify genomic regions (quantitative trait loci, QTLs) affecting salt tolerance during germination in tomato. Germination response of an F2 population of a cross between UCT5 (Lycopersicon esculentum, salt-sensitive) and LA716 (L. pennellii, salt-tolerant) was evaluated at a salt-stress level of 175 mM NaCl + 17.5 mM CaCl2 (water potential ca. −950 kPa). Germination was scored visually as radicle protrusion at 6 h intervals for 30 consecutive days. Individuals at both extremes of the response distribution (i.e., salt-tolerant and salt-sensitive individuals) were selected. The selected individuals were genotyped at 84 genetic markers including 16 isozymes and 68 restriction fragment length polymorphisms (RFLPs). Trait-based marker analysis (TBA) which measures changes (differences) in marker allele frequencies in selected lines was used to identify marker-linked QTLs. Eight genomic regions were identified on seven tomato chromosomes bearing genes (QTLs) with significant effects on this trait. The results confirmed our previous suggestion that salt tolerance during germination in tomato is polygenically controlled. The salt-tolerant parent contributed favorable QTL alleles on chromosomes 1, 3, 9 and 12 whereas the salt sensitive parent contributed favorable QTL alleles on chromosomes 2, 7 and 8. The identification of favorable alleles in both parents suggests the likelihood of recovering transgressive segregants in progeny derived from these parental genotypes. The results can be used for marker-assisted selection and breeding of salt-tolerant tomatoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009668325331
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  • 8
    Electronic Resource
    Electronic Resource
    High salt tolerance potential in Lycopersicon species during germination (1986)
    Springer
    Euphytica 35 (1986), S. 575-582 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00021866
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  • 9
    Electronic Resource
    Electronic Resource
    Low temperature seed germination of Lycopersicon species evaluated by survival analysis (1982)
    Springer
    Euphytica 31 (1982), S. 869-883 
    Details
    ISSN: 1573-5060
    Keywords: Lycopersicon ; tomato ; low temperature germination ; survival analysis ; high altitude ecotypes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Low temperature germination responses were evaluated for 18 high altitude accessions representing five wild Lycopersicon species and 19 accessions of L. esculentum which have reputed ability to germinate in the cold. Survival analysis indicated that one accession of L. chilense germinates better at 10°C than PI 120256, the fastest-germinating L. esculentum genotype, and that PI 120256 germinates as well as PI 126435 (L. peruvianum). Additional wild ecotypes exhibiting rapid germination at 10°C were identified from L. peruvianum and L. hirsutum. These ecotypes may possess genetic potential for introgressing cold germination ability into L. esculentum cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039227
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  • 10
    Electronic Resource
    Electronic Resource
    A theoretical study of liquid-film spread heights in the calendering of newtonian and power law fluids (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 2771-2784 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The relationship between spread height and upstream reservoir thickness, with power low coefficient as parameter, was obtained analytically. At all values of n studied, the value of r (ratio of spread height to nip width) increases with increasing values of H/ho where H is upstream reservoir thickness and ho is nip width. At higher values of H/ho, the curves of r, versus H/ho tend to “flatten” out, and r approaches an asymptotic value. For example, the asymptotic value of r for Newtonian fluids (power law constant of 1) is 1.226. Asymptotic values of r increase with decreasing values of the power law constant.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1970.070141111
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