Example of a system which is computation universal but not effectively programmable

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.     

Countershading by physiological colour change in the fish louse Anilocra physodes L. (Crustacea: Isopoda)

Summary Specimens of the fish louse Anilocra physodes L. from the Mediterranean Sea exhibited a striking colour asymmetry in their dorsal pigmentation: one longitudinal half of their back was dark, the opposite half was lightcoloured. The dark side corresponded with the physiological upper side when the fish louse was attached to the flank of a host fish.The colour pattern derives from the different shape (stellate/punctate) of chromatophores, which lie immediately beneath the epidermis. The appearance and distribution of the chromatophore stages indicate the possibility of physiological colour change in Anilocra. In this way the fish louse probably achieves adaptive countershading and thus additional protection from predators, advantageous for both parasite and host.     

Photobehaviour of Paramecium bursaria infected with different symbiotic and aposymbiotic species of Chlorella

The endosymbiotic unit of Paramecium bursaria and Chlorella spec. shows two types of photobehaviour: 1) A step-up photophobic response which possibly depends on photosensitive agents in the ciliate cell itself — as is also shown by alga-free Paramecium bursaria - and can be drastically enhanced by photosynthetic activity of symbiotic algae; and 2) a step-down photophobic response. The step-down response leads to photoaccumulation of green paramecia. Both types of photobehaviour in Paramecium bursaria do not depend on any special kind of algal partners: The infection of alga-free Paramecium bursaria with different Chlorella species results in new ciliatealgae-associations. They are formed not only by combination of the original symbiotic algae with their host, but also by infection with other symbiotic or free-living (aposymbiotic) chlorellae, respecitively. Systems with other than the original algae are not permanently stable — algae are lost under stress conditions — but show the same types of photobehaviour. Photoaccumulation in general requires algal photosynthesis and occurs only with ciliates containing more than fifty algae/cell. It is not mediated by a chemotactic response to oxygen in the medium, since it occurs at light fluence rates not sufficient for a release of oxygen by the symbiotic system, e.g., below its photosynthetic compensation point. Photoresponses can be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Sensory transduction does not depend on any special symbiotic features of the algae, e.g., sugar excretion. The participation of oxygen in the Paramecium cell, of its cytoplasmic pH and of ions released or taken up by endosymbiotic algae in sensory transduction is discussed.     

Water permeability of Betula periderm

The water permeability of periderm membranes stripped from mature trees of Betula pendula Roth was investigated. The diffusion of water was studied using the system water/membrane/water, and transpiration was measured using the system water/membrane/water vapor. Betula periderm consists of successive periderm layers each made up of about 5 heavily suberized cell layers and a varying number of cell layers that are little suberized, if at all. It is shown that these layers act as resistances in series. The permeability coefficient of the diffusion of water (P _d) can be predicted with 79% accuracy from the reciprocal of the membrane weight (x in mg cm^-2) by means of the linear equation P _d=14.69·10^-7 x-0.73·10^-7. For example, the P _d of a periderm membrane having a weight of 10 mg cm^-2 (approx. 250 m thick) is 7.4·10^-8 cm s^-1, which is comparable to the permeability of cuticles. This comparison shows that on a basis of unit thickness, Betula periderm is quite permeable to water as cuticles have the same resistance with a thickness of only 0.5 to 3 m. It is argued that this comparatively high water permeability of birch periderm is due to the fact that middle lamellae and the primary walls of periderm cells are not at all, or only incompletely suberized and, therefore, form a hydrophilic network within which the water can flow. This conclusion is based on the following observations: (1) Middle lamellae and primary walls stain strongly with toluidine blue, which shows them to be polar. (2) If silver ions are added as tracer for the flow of water, they are found only in the middle lamellae, primary walls, and in plasmodesmata, while no silver can be detected in the suberized walls. (3) Permeability coefficients of transpiration strongly depend on water activity. This shows conclusively that water flows across Betula periderm via a polar pathway. It is further argued that liquid continuity is likely to be maintained under all physiological conditions in the network formed by middle lamellae and primary walls. On the other hand, the lumina of periderm cells, intercellular air spaces in the lenticels, and even the pores in the suberized walls (remainders of plasmodesmata) will drain at a humidity of 95% and below. Due to the presence of intercellulars the permeability coefficient of lenticels is much greater than that of the periderm. A substantial amount of the total water, therefore, flows as vapor through lenticels even though they cover only 3% of the surface.Abbreviations PM perideron membrane - P _d permeability coefficient for diffusion of water - P _tt permeability coefficient of transpiration - MES (N-morpholino)ethane sulfonic acid     

Physiological factors determining formation of plastocyanin and plastidic cytochrome c-553 in Scenedesmus

Physiological conditions necessary for the formation of plastocyanin and the concurrent cessation of cytochrome c-553 formation were studied in cells of copper-deficient Scenedesmus acutus after the addition of copper. Plastocyanin is formed after a lag-phase, leaving constant the content of plastidic cytochrome c-553. Therefore, the concentration of plastocyanin per cell increases and the concentration of cytochrome c-553 decreases during growth. Formation of plastocyanin during the induction period studied is dependent on light intensity. In the dark, there is a 90% inhibition, whereas under light intensities above 50 Wm^-2, a ratio of 1.3 molecules plastocyanin per 1,000 molecules chlorophyll is attained.Plastocyanin formations is inhibited by the uncoupler carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), but not by moderate concentrations of 3-[3,4-dichlorophenyl]-1,1-dimethylurea (DCMU), and by keeping the algae under a nitrogen atmosphere without CO₂. Concurrently, the cultures treated with FCCP show a decreased endogenous ATP level. The ATP is necessary for plastocyanin formation.Abbreviations FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - DCMU 3-[3,4-dichlorophenyl]-1,1-dimethylurea - pcv packed cell volume     

Species differences in biotransformation of 17α-cyanomethylestradiol 3-methyl ether

Following oral administration of 9,11- ³H-17α-cyano-methylestra-1,3,5(10)-triene-3,17-diol 3-methyl ether, urinary metabolites were studied in man, baboon, beagle dog, minipig and rat. The metabolite pattern revealed remarkable species differences, especially in quantitative respects. 17α-Cyanomethylestra-1,3,5(10)-triene-3,17-diol, 17α-cyanomethylestra-1,3,5(10)-triene-2,3,17-triol 2-methyl ether, 17α-hydroxymethylestra-1,3,5(10)-triene-3,17-diol and 17α-cyanomethylestra-1,3,5(10)-triene-3,16$\text{6}\text{5}$,17-triol were isolated as principal metabolites. In rat bile, a metabolite was tentatively identified as aγ-lactone of a 17α-carbozymethyl-16α-hydroxy compound.     

Genetics of the anti-dextran B512 and the autoanti-idiotypic response: codominant expression in F1 hybrids and dichotomy of response and allotype-linked idiotype

The IgM plaque-forming response to the alpha 1-6 epitope of dextran B512 is linked to the Ig-1 heavy chain allotypes j and b characteristic of CBA and C57BL strains, respectively, and the response typically induces the formation of autoanti-idiotypic antibodies that can distinguish between anti-dextran antibodies of CBA and C57BL origin. Nevertheless, some substrains of Balb/c mice (allotype a) and some Bailey recombinant stains give a PFC response although they do not possess allotypes j or b. The anti-dextran antibodies in these strains lack the idiotypes characteristic of either CBA and C57BL antibodies to dextran, but they possess their own particular idiotype. F1 hybrids between two responder strains possessing different idiotypes on their antibodies against dextran, produce both idiotypes and two different autoanti-idiotypic antibodies. CBA(Ig-1b) mice were high responders to dextran and possessed the idiotype of C57BL, whereas C57BL/6(Ig-1a) mice were low responders. The V(H) recombinant strains BAB.14 and CB-8KN that possess the Ig-1b allotype of C57BL, but have some of the V(H) genes from Balb/c and the rest from C57BL/6 were high responders to dextran, but did not possess the C57BL idiotype, suggesting that the genes determining the response against dextran and the idiotype may have different locations in the heavy chain locus.     

Calcium alginate immobilized cells of clostridium acetobutylicum for solvent production

Conclusions Immobilized vegetative cells ofC. acetobutylicum has a similar product formation pattern when incubated in a simple glucose-salts solution as ordinary growing cells. If vegetative cells of the organism are immobilized in the solvent production phase, solvents are continuously produced on extended incubation.By immobi1izing spores of the organism the disturbance of the cells metabolic activity during the immobilization procedure was avoided. After the outgrowth of viable cells within the gel, the washed gel preparation retained at a high production capacity in the non-growth stage and the results indicate that continuous production might be fully possible. The butanol productivity was also found to be higher with immobilized cells than in a normal batch process.     

Molecular distribution of zinc in biliary and pancreatic secretions

Rat bile and pancreatic fluid were examined for the presence of low molecular weight zinc complexes. Fluids were collected separately by cannulation, and zinc distribution in collected samples was analyzed by gel filtration on Sephadex G-50. Most of the zinc in bile was associated with low molecular weight zinc complexes; only a small amount of zinc was present in the high molecular weight fraction. In contrast, pancreatic secretions did not contain low molecular weight zinc complexes, but there were considerable amounts of zinc bound to high molecular weight compounds. The addition of zinc to bile resulted in an increased amount of zinc in the low molecular weight fraction, while the addition of zinc to pancreatic fluid resulted primarily in an increase in zinc bound to the high molecular weight components. Like pancreatic fluid, homogenates of pancreatic tissue had no low molecular weight zinc complex. In rats whose bile and pancreatic fluid were removed and not returned into the intestine, the amount of zinc bound to low molecular weight complexes in intestinal homogenates was reduced. This alteration of the molecular distribution of zinc in intestinal homogenates by removal of bile and pancreatic fluid suggests the potential importance of low molecular weight zinc complexes for zinc homeostasis.