Oxygen consumption and biosynthetic function in perfused liver from rats at different stages of development

Changes in mitochondrial function were studied in perfused liver from rats aged 24 – 365 days. Oxygen consumption together with the rates of gluconeogenesis, urea synthesis and ketogenesis were determined. Basal mitochondrial respiration as well as the ability of the liver to synthesize glucose, urea and ketone bodies declined from 24- to 365-day-old rats. On the other hand, on transition from 24 to 60 days the liver oxidation rate of hexanoate, sorbitol and glycerol is enhanced, but not of ketone bodies or palmitate. Our results show that the transition from weaning to middle age is accompanied by defined changes in hepatic substrate oxidation. From the observed time course of the decrease in basal and substrate-stimulated oxygen consumption, it is concluded that in rat liver cells a decline in respiratory chain function, long-chain fatty acid and ketone body metabolism, gluconeogenesis and ureogenesis occurs at a relatively early life stage. Received 19 June 1998; received after revision 11 September 1998; accepted 11 September 1998     

The effects of thermogenic agents on hindlimb oxygen consumption in the dog: ICI D7114 and noradrenaline

The thermogenic action of beta-adrenoceptor agonists may be due, in part, to increased metabolism in skeletal muscle. Previous results suggest that vasoconstriction is also necessary, and that the effect can be blocked by vasodilators. Both noradrenaline and the beta-3 agonist, ICI D7114, were studied using two dog hindlimb protocols. During constant perfusion conditions, ICI D7114 caused a significant increase in hindlimb oxygen consumption although it is a vasodilator. Noradrenaline resulted in a smaller rise in oxygen consumption, and produced a marked vasoconstriction. Both noradrenaline and ICI D7114 resulted in decreased oxygen consumption when the blood flow was allowed to vary in response to the drug treatment. The results suggest that changes in tissue oxygen consumption caused by beta-agonists are not related to vasomotion.     

Bilateral lesions of suprachiasmatic nucleus eliminate circadian rhythms of oxygen consumption and the respiratory quotient in rats

Summary Bilateral lesions of the suprachiasmatic nucleus of the hypothalamus of rats abolished circadian rhythms of oxygen consumption and of the respiratory quotient (RQ). The RQ remained constant at a level intermediate between the maximum (about 1.0) and minimum (about 0.9) values in control animals.     

Ancient origin of reggie (flotillin), reggie-like, and other lipid-raft proteins: convergent evolution of the SPFH domain

Reggies (flotillins) are detergent-resistant microdomains involved in the scaffolding of large heteromeric complexes that signal across the plasma membrane. Based on the presence of an evolutionarily widespread motif, reggies/flotillins have been included within the SPFH (stomatin-prohibitin-flotillin-HflC/K) protein superfamily. To better understand the origin and evolution of reggie/flotillin structure and function, we searched databases for reggie/flotillin and SPFH-like proteins in organisms at the base and beyond the animal kingdom, and used the resulting dataset to compare their structural and functional domains. Our analysis shows that the SPFH grouping has little phylogenetic support, probably due to convergent evolution of its members. We also find that reggie/flotillin homologues are highly conserved among metazoans but are absent in plants, fungi and bacteria, where only proteins with ‘reggie-like’ domains can be found. However, despite their low sequence similarities, reggie/flotillin and ‘reggie-like’ domains appear to subserve related functions, suggesting that their basic biological role was acquired independently during evolution. Received 21 September 2005; received after revision 14 November 2005; accepted 21 November 2005     

The use of canonical correlation analysis to identify the order of multivariate ARMA models: simulation and application

This paper is concerned with how canonical correlation can be used to identify the structure of a linear multivariate time series model. We describe briefly methods that use the canonical correlation technique and present simulation results in order to compare and evaluate the performance of these methods. The methods are also applied to a well‐known multivariate time series. Copyright © 2000 John Wiley & Sons, Ltd.     

Implications of toxins in the ecology and evolution of plant pathogenic microorganisms: Bacteria

This review attempts to rationalise what is known about bacterial phytotoxins and associate it with the ecology and possible evolution of the producing organisms. Study of non-toxin producing variants gives insight into the ecological role of the toxin. Elucidation of chemical structures of phytotoxins has shown that many exist as families of analogous compounds. Studies on the variation of chemical structures and how they are distributed across species and genera can lead to development of hypotheses on evolutionary relationships. Knowledge on biosynthetic pathways to tosins allows recognition of specific enzymatic steps involved in developing the characteristic features of the structures. Phytotoxins often have a potent biochemical activity, and in some cases the producing organism has associated mechanisms to prevent action of the toxin upon itself; in such cases toxigenesis is clearly not a chance event. The various aspects of bacterial toxigenesis indicate that bacterial phytotoxins are special secondary metabolic products that play beneficial roles to the producing organisms in their various ecological niches.