Protein metal-binding sites.

Metal ions have a role in a variety of important functions in proteins including protein folding, assembly, stability, conformational change, and catalysis. The presence or absence of a given metal ion is crucial to the conformation or activity of over one third of all proteins. Recent developments have been made in the understanding and design of metal-binding sites in proteins, an important and rapidly advancing area of protein engineering.     

Interrelation of the changes in the blood rheological properties and the microcirculatory disorders in the early and late stages of experimental hyperlipoproteinemia

Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked.     

Changes in the ultrastructure of the adrenal medulla and cortex during endotoxic shock

Electron microscopy of the adrenal medulla and cortex during the intermediate period of endotoxin shock has revealed severe destructive changes in parenchymal cells. These changes are the reason for synthetic, secretory and trophic disturbances of glandular functions. Ultrastructural lesions indicate that stress exposure exceeds the adaptive capacity of cells, the majority of which are exhausted and killed.     

Influence of oxytocin on human memory processes: Validation by a control study

An earlier report (1) of an adverse effect of high doses of oxytocin on human memory included results of studies on women receiving oxytocin as part of the treatment to induce 2nd trimester therapeutic abortion. These women served as their own controls. We have now been able to study a group of women who have been treated in all ways like the original group, with the exception that they did not receive oxytocin. The results from this external control corroborate the finding that oxytocin affected memory.     

Energy and biological evolution—I. The equilibrium states of biochemical processes

The Thom gradient model of morphogenesis poses the followinga posteriori problem: “From the observed morphology of a given natural process (effect) determine the dynamics of the process (cause)”. In this paper we consider the classicala priori problem: “Given the cause (dynamics) determine the effect (resultant morphology)”. We find that in biochemical processes the mechanisms for energy activation, energy-matter interaction and energy dissipation determine the dynamics. Furthermore there exists basic energy mechanisms which drive the equilibrium states through the elementary catastrophes of Thom. A comparison with current theories shows that our models describe open ecological food chains and their dynamical systems generalize the equations of organisation posed by M. Eigen. Work supported by a Research Associateship of the International Centre for Theoretical Physics, P.O.B. 586, Miramare, 34100 Trieste, Italy.     

Hepatic reactions in erythropoietic protoporphyria (author's transl)

The main hepatic change in erythropoietic protoporphyria is the deposition of protoporphyrin. Brown deposits of this pigment occur in bile canaliculi and ductules, discretely in hepatocytes, and secondarily in macrophages and Kupffer cells. The pigment is deposited in a crystalline form. Under the fluorescence microscope with a mercury maximum pressure burner (HO 50) at a wave length of 380--500 nm, it shows a typical red fluorescence even after paraffin embedding. Its crystalline structure results in a characteristic double refraction under the polarising microscope. Light-microscopically, hepatocellular reactions are characterised mainly by discrete alterations in the ergastoplasm. However, cell damage is indicated by diffusely distributed, hyaline single cell necrosis and by cytolytic piecemeal necrosis at the peripheries of hepatic lobules. Numerous, often disturbed mitoses produce binuclear and multinuclear hepatocytes. The obligatory secretion of protoporphyrin into the bile ducts leads to an alteration in the canalicular and ductular excretion apparatus which involves distinct ductular proliferation and accompanying fibrosis. Piecemeal necrosis is a further consequence of this process. The resulting histological picture is similar to sclerosing cholangitis with which it also has in common the slowly progressive development of hepatic cirrhosis.     

Mechanism of action of ryanodine on cardiac sarcoplasmic reticulum

Ryanodine was found to initially inhibit calcium uptake by cardiac sarcoplasmic reticulum. This initial depression was followed by a later marked stimulation of calcium uptake. These effects were noted when calcium uptake was measured in the presence or absence of oxalate. The requirement for preincubation with ryanodine was highly dependent on ryanodine concentration and temperature. The mechanism of action of ryanodine clearly was not an effect on oxalate entry or calcium oxalate precipitation because the effects were also observed in the absence of oxalate. Ryanodine also had no effect on passive calcium efflux from actively loaded vesicles. Because ryanodine had no effect on Ca2+-ATPase activity under defined conditions of an ATP-regenerating system and no calcium gradient, we suggest ryanodine does not change the stoichiometry of the pump. Our results are consistent with the hypothesis that ryanodine closes a calcium channel in a subpopulation of the vesicles.