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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The absence of soy phosphatidylcholine (PC) in purified diets fed to juvenile lobstrs causes a significant decrease in the concentrations of total cholesterol and phospholipids in the serum. When egg PC, bovine PC, phosphatidylinositol, and ovine cephalin are used as substitutes for the soy PC, cholesterol and phospholipid levels in the serum are also significantly reduced. Cholesterol and phospholipid concentrations in the serum are highly correlated. Analysis of levels of hepatopancreatic cholesterol indicate that intestinal absorption of cholesterol is not impaired by the absence of dietary PC or by the presence of a phospholipid substitute. We suggest that the PC molecule is an important component of a lipoprotein complex that effectively transfers cholesterol, an essential nutrient for lobsters, from the hepatopancreas to the hemolymph.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A knowledge-based approach to crystal structure determination is presented. The approach integrates direct-methods and artificial-intelligence strategies to rephrase the structure determination process as an exercise in scene analysis. A general joint probability distribution framework, which allows the incorporation of isomorphous replacement, anomalous scattering and a priori structural information, forms the basis of the direct-methods strategies. The accumulated knowledge on crystal and molecular structures is exploited through the use of artificial-intelligence strategies, which include techniques of knowledge representation, search and machine learning.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 31 (1959), S. 1598-1599 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 45 (1953), S. 1586-1591 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden , USA : Blackwell Publishing Ltd/Inc
    Journal of fish biology 64 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of the timing of first feeding (3, 4, 5, 6, 7 and 8 days post-hatch, dph) on laboratory-reared California halibut Paralichthys californicus larvae was evaluated by means of morphologic, morphometric and histological criteria. Larvae began to feed exogenously at 3 dph (2·7 ± 0·01 mm standard length, LS) at 18° C. Eye pigmentation, rather than mouth opening was the most distinctive trait of California halibut larvae at first feeding. Larval growth was significantly affected by the time of first exogenous feeding. At notochord flexion (21 dph), the LS of larvae fed for the first time at 3 dph was significantly larger (5·1 ± 0·1 mm) than that of those fed at 4 and 5 dph (4·9 ± 0·1 mm), although the latter fish had a more uniform size distribution. The point of no return was reached at 7 dph. Survival of larvae initially fed at 3, 4 and 5 dph was similar (58·4–60%), while no larvae were able to survive when food was offered for the first time between 6 and 8 dph. Food deprivation resulted in a progressive deterioration of the larval digestive system and atrophy of skeletal muscle fibres. Significant changes in the anterior and posterior enterocyte height were detected after 2 days of food deprivation. Similarly, tail height: LS and trunk length: LS ratios were the most sensitive morphometric indices to detect the effect of fasting on larval condition. Present results show that a combination of morphometric and histological variables can be used to evaluate the nutritional condition of California halibut larvae.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 61 (2002), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Morphological development, allometric growth and behaviour of hatchery-reared California halibut Paralichthys californicus were studied from hatching to metamorphosis (42 days post hatch, dph) at 187° C. Mean standard length (LS) of larvae and juveniles increased from 2.1 mm at hatching to 10.5 mm at metamorphosis with the increase in length being approximately linear. Stages of morphological development were described using the alphabetic staging (A–I) used for other flatfish species. Organogenesis and differentiation were more rapid and complex in yolk-sac (hatching, stage A–3 dph, stage B), preflexion (3–19 dph, stages B–C), and flexion larvae (from 20 to 23 dph, stages D–E), as larvae developed most of their sensory, feeding, respiratory and swimming systems. After notochord flexion at 24–25 dph (stage F), most morphological changes were related to the progressive transformation from a bilateral symmetrical larva to an asymmetrical benthic juvenile (42 dph, stages G–I).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 535-549 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The rapid growth of crystallographic databases has created a demand for novel and efficient techniques for the analysis of molecular conformations, in order to derive new concepts and rules and to generate useful classifications of the available data. This paper presents a conceptual clustering approach, termed IMEM (image memory), which discovers the conformational diversity present in a dataset of crystal structures. In contrast to numerical clustering methods, IMEM views a molecular structure as comprising qualitative relationships among its parts, i.e. the structure is viewed as a molecular scene. In addition, IMEM does not require the user to have any a priori knowledge of an expected number of conformational classes within a given dataset. The IMEM approach is applied to several datasets derived from the Cambridge Structural Database and, in all cases, chemically correct and sensible conformational classifications were discovered. This is confirmed by a rigorous comparison of IMEM results with published conformational data obtained by energy-minimization and numerical clustering methods. Conformational analysis tools have an important part to play in the conversion of raw molecular databases to knowledge bases.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Helgoland marine research 20 (1970), S. 443-454 
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary 1. Fertility stops after a few aseptic generations in cultures ofArtemia salina, Tigriopus japonicus andDaphnia magna fed algae. 2. Fertility was restored in amphigonic and parthenogeneticArtemia salina subjected to low-salinity stress by addition of milligram concentrations of yeast and liver extract. 3. Fertility ofTigriopus japonicus andDaphnia magna was restored by addition of vitamin mixtures to the algae/crustacean medium. 4. The vitamins act directly on the algae by increasing their nutritional value for the crustaceans cultivated. 5. Continuous aseptic culture ofMoina macrocopa was obtained in an artifical medium enriched with egg yolk and vitamins E and D. Such a medium supports only 5 to 6 generations ofDaphnia magna. 6. Lipid factors seem essential for sustained fertility inMoina macrocopa andDaphnia magna. 7. Some suggestions are made for improving partially gnotobiotic cultures of filter-feeders.
    Notes: Kurzfassung Nur die kontinuierliche Kultivierung eines Organismus gewährt Sicherheit, daß alle ernährungsphysiologischen und kulturtechnischen Erfordernisse erfüllt worden sind. Keimfreie Zuchten von Insekten und Krebsen zeigen, daß die Voraussetzungen für eine uneingeschränkte Fertilität komplexer sind als für die Produktion einer oder mehrerer sukzessiv aufeinanderfolgender Generationen. Ähnliche Ergebnisse sind mit aseptisch gehaltenenArtemia salina, Daphnia magna undTigriopus japonicus erhalten worden. Die Schlußfolgerungen sind daher möglicherweise auch auf weitere Arten ausdehnbar. Nur in seltenen Fällen vermag eine Algenart alle ernährungsphysiologischen Erfordernisse des zu züchtenden Tieres zu erfüllen; oft werden zwei oder mehrere Algenarten benötigt. Jedoch selbst in diesen Fällen versiegt die Fertilität häufig nach einigen wenigen aseptischen Generationen. BeiT. japonicus kompensierte der Zusatz von Vitaminen die ernährungsphysiologische Unzulänglichkeit von 2 Futteralgen. Zugabe von einigen Milligramm Hefe und Leberextrakt zu dem Kulturmedium, in dem Algen und Krebse gehalten wurden, restaurierte die Fertilität vonA. salina (die durch osmotischen Stress geschwächt waren) und gestattete eine kontinuierliche Kultur vonD. magna in synthetischen Mineralmedien. Offensichtlich beeinflussen die organischen Anreicherungen nicht direkt die Ernährung vonD. magna, sondern vielmehr den ernährungsphysiologischen Wert, welchen die Algen fürD. magna besitzen. Qualität und Quantität der organischen Substanz in natürlichen Gewässern sind daher möglicherweise von Bedeutung für die Fertilität von Crustaceen. Die ernährungsphysiologischen Ansprüche vonA. salina, D. magna undMoina macrocopa, welche aseptisch in künstlichen Medien kultiviert werden, sind sehr ähnlich. Alle Arten beanspruchen Cholesterin, Thiamin, Biotin, Phyridoxin und Nicotin-, Fol- und Pantothensäure zur Produktion von Adulti; es werden jedoch höchstens 1 oder 2 Generationen bei geringer Fruchtbarkeit erreicht. 6 Generationen vonD. magna und 50 Generationen vonM. macrocopa wurden erhalten, nachdem Eidotter und die Vitamine E und D zugesetzt worden waren; Carotin war inaktiv. Fettlösliche Wirkstoffe spielen sicher eine Rolle. Ihre Identifikation wird gegenwärtig betrieben.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 165 (1996), S. 518-526 
    ISSN: 1432-136X
    Keywords: Blood vessels ; Gravity ; Catecholamines ; Vasoactive agents ; Snake ; Elaphe obsoleta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of vasoactive agonists on systemic blood vessels were examined with respect to anatomical location and gravity acclimation in the semi-arboreal snake, Elaphe Obsoleta. Major blood vessels were reactive to putative neurotransmitters, hormones or local factors in vessel specific patterns. Catecholamines, adenosine triphosphate, histamine and high potassium (80 mM) stimulated significantly greater tension per unit vessel mass in posterior than anterior arteries. Anterior vessels were significantly more sensitive to catecholamines than midbody and posterior vessels. Angiotensin II stimulated significantly greater tension in carotid artery than in midbody and posterior dorsal aorta. Arginine vasotocin strongly contracted the left and right aortic arches and anterior dorsal aorta. Veins were strongly contracted by catecholamines, high potassium and angiotensin II, but less so by adenosine triphosphate, arginine vasotocin and histamine. Precontracted vessels were relaxed by acetylcholine and sodium nitroprusside, but not by atrial natriuretic peptide or bradykinin. Chronic exposure of snakes to intermittent hypergravity stress (+1.5 Gz at tail) did not affect the majority of vessel responses. These data demonstrate that in vitro tension correlates with known patterns of sympathetic innervation and suggest that catecholamines, as well as other agonists, are important in mediating vascular responses to gravitational stresses in snakes.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 163 (1994), S. 657-663 
    ISSN: 1432-136X
    Keywords: Fish veins ; Contraction ; Catecholamines ; Vasoactive peptides ; Trout, Oncorhynchus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Systemic veins have a profound influence on cardiac output in mammals. Venoregulatory mechanisms have not been adequately studied in fish and their existence has been questioned. In the present study, two characteristics of vascular mechanics, compliance and agonist-induced tension development, were investigated in rainbow trout vessels in vitro. Rapid compliance in the anterior cardinal vein and efferent branchial artery was calculated from step-wise changes in the volume-pressure curve of isolated vessel segments. Agonist-induced tension development was examined in four veins; anterior and posterior cardinals, intestinal and duct of Cuvier. Venous compliance was not altered in response to epinephrine, norepinephrine or angiotensin II, while efferent branchial artery compliance was decreased by 10-6 mol·l-1 epinephrine and norepinephrine but not angiotensin II. The ratios of venous to arterial compliance in vessels from two rainbow trout strains were similar (21:1 and 32:1) and consistent with the ratio reported for mammalian viens (24:1). Trout veins contracted in response to agonists in both an, agonist- and vesselspecific manner. The greatest tension per vessel wet weight was produced in anterior cardinal vein. The response pattern of anterior cardinal vein and duct of Cuvier were similar; acetylcholine, arginine vasotocin, epinephrine and norepinephrine, and the thromboxane A2 agonist, U-44,069, produced approximately identical contractions, whereas angiotensin II was virtually ineffective. Conversely, angiotensin II was more potent than epinephrine in posterior cardinal vein. In cumulative dose-response experiments, epinephrine was equipotent in anterior cardinal vein and duct of Cuvier, whereas the latter was less sensitive to acetylcholine. Both atrial natriuretic peptide and sodium nitroprusside relaxed precontracted veins. This is the first study to determine compliance in fish vessels and the contractile nature of different rainbow trout veins. These findings suggest that venous tone and therefore cardiac output in fish may be regulated by neural or humoral mechanisms.
    Type of Medium: Electronic Resource
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