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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 25 (1987), S. 275-288 
    ISSN: 1432-1416
    Keywords: Chemical mass recruitment ; Quality recruitment ; Damping ; Ants ; Delayed differential equation ; Functional differential equation ; Monotonicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Ant species on a “high evolutionary level” have evolved chemical recruitment systems such as mass recruitment or quality recruitment. The recruitment process from the nest to a food source may be damped by crowding effects at the source. For four patterns of behavior (mass/quality recruitment; with/without damping) we study mathematical models for the time development of the quantity of food at the source. Each of the models can be reduced to a second order time-delayed differential equation which will be studied in the equivalent form of a first order (nonlinear) functional differential equation. We discuss the complete exploitation of a given source. In case of mass recruitment there possibly remains a threshold quantity of food not worth exploiting. However, every source will be exploited completely (in finite time) provided that the volatility of the trail pheromone is small compared with the exploitation activities of the colony and the distance from the nest to the source. In addition, for the damped models the “capacity” of the crowded source must be large compared with the initial quantity of food offered. The efficiency of the exploitation activities of some species allows conclusions on their evolutionary development.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 375 (1990), S. 259-265 
    ISSN: 1435-2451
    Keywords: Islets of Langerhans transplantation ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Grenzen und Möglichkeiten der Transplantation von Langerhans-Inseln wurden am Schwein erprobt. Nach totaler Pankreatektomie wurden durch intraduktale Kollagenaseandauung zwischen 6mal 104 and 3mal 106 Inseln and inseltragende Fragmente pro Pankreas gewonnen. Nach Injektion des Transplantates in die Milz oder wahlweise in die Leber konnte bei den Tieren ein normoglykämischer Zustand mit normalen intravenösen Glukosetoleranztesten und ein Überleben bis zu 1 Jahr erreicht werden. Apankreatische Kontrollen verstarben im diabetischen Koma 10–12 Tage postoperativ. Eine gute Korrelation zwischen der Anzahl transplantierter Inseln und Normoglykämie nach Transplantation konnte demonstriert werden. Darüber hinaus war die synchrone In-vitro-Stimulation der Inseln mit Glukose und die daraus resultierende Inselsekretion ein wichtiger Indikator für die funktionelle Integrität der Inseln nach der Transplantation. Das Schwein bietet somit auch aufgrund der dem Menschen sehr ähnlichen immunologischen, physiologischen und anatomischen Eigenschaften bezüglich des Pankreas und der Ernährung ein gutes Modell zur weiteren präklinischen Erforschung der Inseltransplantation als Therapie des Diabetes mellitus.
    Notes: Summary Limits and possibilities of the transplantation of islets of Langerhans in pigs were studied. 6 × 104 to 3 × 106 islets and insulin producing fragments per pancreas were obtained by intraductal collagenase digestion of the pancreatic gland following total pancreatectomy. Islets grafted into the spleen or liver rendered normoglycemia to the pancreatectomized animals as demonstrated by normal fasting blood sugars and normal intravenous glucose tolerance tests as compared to not operated animals permitting a survival time of up to one year. Apancreatic controls died of ketoacidosis and diabetic coma 10 to 12 days posttransplant. The number of isolated and transplanted islets correlated well to the normoglycemic state of the animal. Beyond that the in vitro challenge of the islets with glucose and resulting insulin secretion was a very important indicator for the functional status and integrity of the islets after transplantation. Thus the pig appears to be a suitable model for the preclinical studying of islet transplantation especially since immunologic, physiologic and anatomic features of the pig are similar to those in the human regarding pancreas and nutrition.
    Type of Medium: Electronic Resource
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