The relation between morphology and behaviour during ontogenetic and evolutionary changes

During development, form and function (behaviour) change while the match between them must be maintained. The quality of this match determines the importance of morphological parameters in constraining behaviour. If the match is close, the morphology of organisms will be more constraining to the behaviour than when there is a large reserve capacity that creates a certain flexibility. This leads to two questions: (1) How good is the match between form and function during development? The quality of the match necessarily changes during development because changes in structural capacity often cannot proceed at the same speed as changes in functional demand. The evidence for these changes is discussed. (2) What are the mechanisms that maintain the match between form and function during developmental and evolutionary changes? Two mechanisms for maintaining the match are discussed: (a) reserve capacity and (b) flexible muscle activity patterns. Special emphasis is given to fish examples throughout this review.     

Isolation of viable deletion mutants of Streptomyces actinophage (Pal 6) and their molecular characterization

Summary Deletion mutants of bacteriophage Pal 6 were isolated by successive treatments of either heat (60° C) or pyrophosphate (10 mM). These mutants were characterized by restriction enzyme cleavage analysis. The pyrophosphate resistant clones lost the whole Eco R1 fragment in which the Sal I site is located, as well as an unrelated Hind III fragment. These results show that the region containing the Sal I site in the phage genome is not essential for phage viability. This single Sal I site is therefore suitable as a potential insertion site for DNA cloning. On the other hand, the heat resistant clones that were isolated and characterized do not appear to have detectable deletions as indicated by their Eco R1 DNA digestion pattern.     

Membrane Contact Sites between Apicoplast and ER in Toxoplasma gondii Revealed by Electron Tomography

Toxoplasma gondii is an obligate intracellular parasite from the phylum Apicomplexa. A hallmark of these protozoans is the presence of a unique apical complex of organelles that includes the apicoplast, a plastid acquired by secondary endosymbiosis. The apicoplast is indispensible for parasite viability. It harbours a fatty acid biosynthesis type II (FAS II) pathway and plays a key role in the parasite lipid metabolism. Possibly, the apicoplast provides components for the establishment and the maturation of the parasitophorous vacuole, ensuring the successful infection of the host cell. This implies the presence of a transport mechanism for fast and accurate allocation of lipids between the apicoplast and other membrane-bound compartments in the parasite cell. Using a combination of high-pressure freezing, freeze-substitution and electron tomography, we analysed the ultrastructural organization of the apicoplast of T. gondii in relation with the endoplasmic reticulum (ER). This allowed us to clearly show the presence of four continuous membranes surrounding the apicoplast. We present, for the first time, the existence of membrane contact sites between the apicoplast outermost membrane and the ER. We describe the morphological characteristics of these structures and discuss their potential significance for the subcellular distribution of lipids in the parasite.     

Is vasoactive intestinal polypeptide (VIP) a sleep factor?

Vasoactive intestinal peptide (VIP) was tested in order to determine its hypnogenic properties in cats. VIP was administered intraventricularly in doses of 10 and 100 ng and compared to Ringer controls. In addition the dose of 100 ng was tested in cats pretreated with 150 mg/kg of chloramphenicol (CAP). The results showed that the 100 ng dose of VIP had small but significant REM enhancing properties, but that it did not protect the animals from the specific REM inhibiting properties of CAP. The results suggest that VIP may participate in the regulation of REM sleep.     

Inhibition of [3H] Dexetimide binding by a homologous series of methylfurthrethonium analogues at the peripheral muscarinic receptor

The interaction of a homologous series of methylfurthrethonium analogues, in which there is a gradual transition from full agonists via partial agonists to antagonists, with the peripheral muscarinic receptor was investigated by concentration-dependent inhibition of [³H] Dexetimide binding. The antagonists give normal sigmoid inhibition curves, but those of agonists follow a much flatter course. The results can be explained by assuming the presence of two non-interconverting muscarinic binding sites for which agonists have different and antagonists have identical affinities.The affinity ratio for the two binding sites decreases from 61 for methylfurthrethonium to 1 for its isopropyl analogue and parallels the decrease in intrinsic activity.     

Glucose is essential for the initiation of fatty acid oxidation in ATP-depleted cultured ventricular myocytes

Cultured cardiac myocytes were depleted of ATP by incubation with oligomycin (1 mg/ml). Then the ability of the cells to oxidize various substrates and to restore ATP levels was studied. Following ATP depletion, the cells were found to be able to oxidize glucose given alone, but not palmitate. However, with both substrates, palmitate was oxidized in the presence of glucose and ATP recovery was enhanced. Pyruvate had a minor effect on palmitate oxidation, while acetate given alone was oxidized, but did not enhance cellular ATP content. These results show that glucose is essential for restoration of mitochondrial function and the coupling between oxidation and ATP synthesis.