From sequence to consequence and back

The genotype–phenotype relation is at the core of theoretical biology. It is argued why a mathematically based explanatory structure of this relation is in principle possible, and why it has to embrace both sequence to consequence and consequence to sequence phenomena. It is suggested that the primary role of DNA in the chain of causality is that its presence allows a living system to induce perturbations of its own dynamics as a function of its own system state or phenome, i.e. it capacitates living systems to self-transcend beyond those morphogenetic limits that exist for non-living open physical systems in general. Dynamic models bridging genotypes with phenotypic variation in a causally cohesive way are shown to provide explanations of genetic phenomena that go well beyond the explanatory domains of statistically oriented genetics theory construction. A theory originally proposed by Rupert Riedl, which implies that the morphospace that is reachable by the standing genetic variation in a population is quite restricted due to systemic constraints, is shown to provide a foundation for a mathematical conceptualization of numerous evolutionary phenomena associated with the phenotypic consequence to sequence relation. The paper may be considered a call to arms to mathematicians and the mathematically inclined to rise to the challenge of developing new formalisms capable of dealing with the deep defining characteristics of living systems.     

Developmental Abnormalities of Female Sexual Organs in Swine

One thousand reproductive organs from gilts were collected during the period March-August at a slaughterhouse in central Sweden. The organs were inspected in respect of congenital defects and certain reproductive physiological data. The results are recorded in Tables 1–6. Figs. 1–7 show some types of malformations. The total frequency of malformations was 22.1 %, of which 14 % cysts in mesosalpinx and 4.1 % partial duplication of the vagina. The remainder consisted of general developmental defects and of local defects in the tubular genital tract. Malformations with presumed effect on fertility were found in 4.5 % of all organs examined, of which 0.8 % presumably caused permanent sterility and 3.7 % lowered fertility (small litters). Hydrometra was found in 33 cases, 2 of which in sexually mature gilts. The left ovary contained more corpora lutea than the right, and the mean weight of the left ovary was greater than that of the right, both in sexually mature and prepuberal gilts. Of 202 sexually mature gilts examined 16.9 % had cystic corpora lutea in their ovaries as a rule 2–4 in each ovary.     

The determination of acetaldehyde in blological samples by head-space gas chromatography

A method for the determination of acetaldehyde (AcH) in biological samples by head-space gas chromatography is presented. Human venous blood (antecubital), rat blood (heart-punctured) rat liver (freeze-clamped), and rat and mouse brain (freeze-clamped) were used as the biological samples. The method involves two steps, in the first of which the samples are deproteinized with perchloric acid (PCA). Rat blood can, alternatively, be hemolyzed with water. In the second step, the deproteinized supernatant or hemolyzed blood is pipetted into a serum bottle, which is sealed with a rubber stopper and brought to 65°C in a sampling turntable. Head-space samples are then automatically taken for GLC analysis. Ethanol causes a nonenzymatic formation of AcH in the PCA supernatants of liver and brain, which can be inhibited by the use of thiourea. This reaction is minor in the blood supernatants and cannot be inhibited there by thiourea. The method described measures the total AcH content without regard to any binding. Some of the AcH in rat blood was shown to be bound.     

A methodological basis for description and analysis of systems with complex switch-like interactions

 A wide range of complex systems appear to have switch-like interactions, i.e. below (or above) a certain threshold x has no or little influence on y, while above (or below) this threshold the effect of x on y saturates rapidly to a constant level. Switching functions are frequently described by sigmoid functions or combinations of these. Within the context of ordinary differential equations we present a very general methodological basis for designing and analysing models involving complicated switching functions together with any other non-linearities. A procedure to determine position and stability properties of all stationary points lying close to a threshold for one or several variables, so-called singular stationary points, is developed. Such points may represent homeostatic states in models, and are therefore of considerable interest. The analysis provides a profound insight into the generic effects of steep sigmoid interactions on the dynamics around homeostatic points. It leads to qualitative as well as quantitative predictions without using advanced mathematical methods. Thus, it may have an important heuristic function in connection with numerical simulations aimed at unfolding the predictive potential of realistic models. Received 25 January 1996; received in revised form 29 June 1997     

Effect of back reactions in the S-cycle on photosynthesis in very weak light

Photosynthesis in light which is so weak that excitation rates are comparable to the decay rates of S-states is modelled. It is found that oxygen evolution rate varies in a non-linear way with Photosystem II excitation rate in this region, but asymptotically approaches a linear relationship (with a slope of one oxygen molecule per four excitations) as excitation rate increases. The asymptote gives an intercept (zero oxygen evolution rate) on the excitation rate axis. The question is raised, whether this model is compatible with photoautotrophy in a red alga found at 268 m depth and able to carry out photosynthesis in extremely weak light. It is found that no unorthodox mechanisms for the S-cycle in this alga have to be assumed to explain its performance.     

Long-term development in a Baltic fish community exposed to bleached pulp mill effluent

Observations near a Swedish pulp mill at the Bothnian Sea during 1982-1992 revealed low fish abundance and a disturbed community structure. The presence of endocrine disrupting or toxic substances in effluent water was indicated by biomarker responses, impaired reproduction and stimulated growth in perch (Perca fluviatilis). In 1992 the bleaching process was altered and a secondary treatment system was installed, improving the quality and decreasing the amount of effluent. This paper presents the results of follow-up studies during 1995-1998 with the objective to analyse any recovery of the fish community due to changes in mill operations. Although abundance and diversity of the fish community did recover, an effect of enrichment, indicated by high catches of cyprinids, was still visible in the vicinity of the mill outlet. Sexual maturation was delayed, gonad development was retarded, average growth rate was faster, and the condition factor was higher in perch caught in the vicinity of the effluent outlet, than in perch captured elsewhere. It is concluded that substances inhibiting reproduction and causing growth disturbance were still present in the effluents in effective concentrations.     

Einige Gesichtspunkte zur Benutzung der Statistik im Versuchswesen

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