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1.
Life expectancy curves have a characteristic ominous shape that has fascinated scientists for centuries. Medawar was the first to explain this shape, specifically the steeply rising proneness of an average individual to die as a function of age, in evolutionary terms. The idea was that the "selective value" of the individual decreases as it has triggered other individuals taking its place (and carrying its genes) into existence. We demonstrate that this idea can be turned into a quantitative model. The resulting 4-parameter function reproduces well two well-known life expectancy curves from the first half of this century. Moreover, the easily interpretable parameters (3 of the 4) seem intuitively reasonable. 相似文献
2.
The incorporation of a chaotic component in a computing system is incompatible with its being effectively programmable. The
example presented shows that concepts of programming suitable for biological systems may differ from those which have grown
out of our experience with present day digital computers. 相似文献
3.
Otto E. Rössler 《Bulletin of mathematical biology》1978,40(1):45-58
For certain environments, the Darwinian model allows unique prediction of a function that any surviving system adapted to
such an environment has to perform. This is the case for those environments that determine a “survival functional” of position
in space-time of known shape. Purely temporal survival functionals can be distinguished from spatial and mixed ones. In each
case, there exists an optimum path in combined physical and (reduced) metabolic space. Dependent on the admissible error,
approximate solutions of different complexity are sufficient. All solutions possess an afferent, a central, and an efferent
part. Within this general frame, specific, “probably simplest”, solutions are proposed for adaptive chemotaxis, insect locomotion,
lower vertebrates locomotion, higher vertebrates locomotion, chronobiological systems, and immune systems, respectively—or
rather, for the underlying functionals.
Presented at the Society for Mathematical Biology Meeting, University of Pennsylvania, Philadelphia, August 19–21, 1976. 相似文献
4.
Rabbits treated daily and for seven consecutive days with 6-mercaptopurine bovine gamma globulin conjugates (MPI--n-BGG; 'I'--characterizes the king of chemical binding and 'n' the number of coupled MP-residues per one mole BGG) show an altered immunological reactivity. A following intradermal immunization with BGG alum adsorbate results in a suppressed anti BGG antibody production on the third day after antigen application (antibody titer 1:320, antibody titer of control animals--pretreated with BGG and uncoupled 6-MP equals 1:5120). Already three days later the antibody titers of the test groups show a significant increase and are two dilution stages higher than the titers of the controls. A suppressive effect on the third day is induced by MPI--13-BGG, MPI--26-BGG, MPI--36-BGG and MPI--46-BGG; the later adjuvant effect can only be seen in the MPI--26-BGG, MPI--36-BGG and MPI--46-BGG but not in the MPI--13-BGG pretreated animal group. While the short time suppression was antigen specific--the humoral immune response against a second unrelated antigen was not reduced--the adjuvans effect was not antigen specific. A pretreatment with the substances mentioned above results in an increased anti BGG and anti HSA serum antibody level. Comparing investigations on the unspecific immunosuppression in rabbits by 6-mercaptopurine shows that application of 10 mg 6-MP/kg/day for seven days at first leads to a suppression but later on to an enhancement of antibody production. Application of 10 mg 6-MP/kg/day for 10 days results in a long lasting suppression without enhancement effect. As a reason for these differences the different catabolism of immunosuppressive agent and antigen is discussed. For the phenomena following antigen specific immunosuppression, similar mechanisms can be responsible. 相似文献
5.
A simple and fast method is presented for the isolation and separation of human cardiac myosin light chains. The method requires only a crude myosin for splitting into heavy and light chains. The separation of the light chains is made by isoelectric precipitation with good yield. 相似文献
6.
The mechanism of suppression of humoral immune response to dinitrophenylated bovine gamma globulin (DNP23-BGG), human serum albumin (HSA), and trinitrophenylated sheep red blood cells (TNP-SRBC) by 6-mercaptopurine (6-MP) was studied in guinea pigs. Following the intradermal application of the antigens emulsified in complete (CFA) or incomplete Freund's adjuvant (IFA) each test animal was given 6-MP, 10 mg/kg/day for 7 days. This treatment resulted in a significant suppression of the anti BGG and anti SRBC agglutinating and complement binding antibody production. The latter was only significantly suppressed if the TNP-SRBC were applied together with CFA and not if TNP-SRBC were given in IFA. The anti DNP and anti HSA antibody formation was not influenced. 相似文献
7.
U. Bässler 《Biological cybernetics》1976,24(1):47-49
In inactive stick insects ramp-wise stretching of the femoral chordotonal organ excites the slow extensor tibiae motoneuron. In active animals the same stimulus decreases the firing rate of this motoneuron. The time-course of increased and decreased activity of this motoneuron can be seen with triangular stimulation.Supported by the Deutsche Forschungsgemeinschaft 相似文献
8.
Otto E. Rössler 《Bulletin of mathematical biology》1975,37(2):181-192
On the basis of an abstract, simple bistable reaction system (‘homogeneous Eccles-Jordan trigger’) used as anRS flip-flop, an abstract homogeneousastable flip-flop is devised. It can be run also as amonostable flip-flop and as aT flip-flop. The qualitative behavior of the three systems can be understood, in the limiting case, with the aid of Poincaré's notion of bifurcation of steady states. The reaction system is proposed as a paradigm for a specific class of ‘decomposable’ chemical and dynamical systems (so-called DC-type dynamical automata). Two possible biological applications are mentioned. 相似文献
9.
Arrhenotokously reproducing Hymenoptera and Acarina include many important natural enemies. This reproductive system offers
the opportunity of selection on hemizygous (♂ ♂), with the attendant advantages of an unmasked genotype fully exposed to selection,
in creased frequency of genotypes expressing rare genes, and enhanced discrimination of characters, in all-♂ populations produced
by virgin (♀ ♀). Increased selection intensity and reduced genetic drift may offer additional advantages. The method is limited
to characters displayed by (♂ ♂), and may require labor-intensive techniques and species-specific research. The method has
been shown to be practicable withAphytis holoxanthus DeBach (Hymenoptera: Aphelinidae), an important parasite of the Florida red scale,Chrysomphalus aonidum (L.) (Homoptera: Diaspididae).
相似文献
10.