Observations and comments on the reliability of muscle reconstruction in fossil vertebrates

In Canis and Ursus the largest proportion of attachments of muscles of the shoulder and brachium on the scapula and humerus is direct; fewer attachments are aponeurotic or tendinous. In both genera most attachments can be associated with superficial osteological features (scars or delimitable surfaces); attachments that lack such features are direct. Most aponeurotic attachments are associated with rugose scarring whereas tendinous attachments are often associated with smooth surfaces. Although most attachments can be associated with osteological features the areal extent of attachment is often not inferrable from the bone. The inference of muscle size or functional significance from osteological features is problematic. The amount of myological information that can be deciphered from the osteology in Canis and Ursus is greater than that reported for particular members of other vertebrate groups which suggests that there may be differences in the degree to which muscles can be reconstructed from superficial osteology alone. Nonetheless, even in mammals such as the Carnivora, detailed muscular reconstructions in extinct taxa cannot be achieved without reference to the musculature of extant relatives. Such reconstructions rely on assumptions, that often have not been adequately tested, regarding the similarity of musculature in closely related taxa. This testing and well corroborated hypotheses of phylogenetic relationship are essential for the evaluation of the accuracy of reconstructions of the musculature in fossil vertebrates.     

The bactericidal effect of isoascorbic acid combined with mild heat

The thermal inactivation of Salmonella thompson, Escherichia coli, Staphylococcus aureus, Clostridium perfringens, Candida zeylanoides, Enterococcus faecium and E. faecalis was accelerated by the addition of sodium isoascorbate (1 mmol/l) to phosphate-buffer heating medium but not to complex food mixtures. The lethal effect of isoascorbate was nullified by heating under anaerobic conditions or by the addition of catalase. The scavengers of hydroxyl radicals, mannitol and formate were not protective whereas histidine was. Histidine may have protected by slowing the rate of isoascorbate autoxidation, a property common to other amino acids tested. Superoxide dismutase was not protective. Dehydroascorbic acid also enhanced heat killing and its action was also reversed by catalase. The bactericidal effects of mild heat plus isoascorbate or dehydroascorbic acid both apparently depend on oxidative processes but their relative effectiveness was not related to their respective rates of oxygen consumption or peroxide production. We speculate that site-specific redox reactions, involving amino-carbonyl intermediates are involved in the inactivation mechanism.     

Integrating Biosystem Models Using Waveform Relaxation

Modelling in systems biology often involves the integration of component models into larger composite models. How to do this systematically and efficiently is a significant challenge: coupling of components can be unidirectional or bidirectional, and of variable strengths. We adapt the waveform relaxation (WR) method for parallel computation of ODEs as a general methodology for computing systems of linked submodels. Four test cases are presented: (i) a cascade of unidirectionally and bidirectionally coupled harmonic oscillators, (ii) deterministic and stochastic simulations of calcium oscillations, (iii) single cell calcium oscillations showing complex behaviour such as periodic and chaotic bursting, and (iv) a multicellular calcium model for a cell plate of hepatocytes. We conclude that WR provides a flexible means to deal with multitime-scale computation and model heterogeneity. Global solutions over time can be captured independently of the solution techniques for the individual components, which may be distributed in different computing environments.     

The Continuity Principle and the Evolution of Replication Fidelity

Evolution in modern life requires high replication fidelity to allow for natural selection. A simulation model utilizing simulated phenotype data on cellular probability of survival was developed to determine how self-replication fidelity could evolve in early life. The results indicate that initial survivability and replication fidelity both contribute to overall fitness as measured by growth rates of the cell population. Survival probability was the more dominant feature, and evolution was possible even with zero replication fidelity. A derived formula for the relationship of survival probability and replication fidelity with growth rate was consistent with the simulated empirical data. Quantitative assessment of continuity and other evidence was obtained for a saltation (non-continuous) evolutionary process starting from low to moderate levels of survival probability and self-replication fidelity to reach the high levels seen in modern life forms.

     

Clozapine induces hyperphagia in undeprived rats

Rats given either intragastric or intraventricular injections of clozapine showed a dose-dependent increase in food intake.