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Both nonlinear and fractal properties of beat-to-beat R-R interval variability signal (RRV) of freely moving lizards (Gallotia galloti) were studied in baseline and under autonomic nervous system blockade. Nonlinear techniques allowed us to study the complexity, chaotic behavior, nonlinearity, stationarity, and regularity over time of RRV. Scaling behavior of RRV was studied by means of fractal techniques. The autonomic nervous system blockers used were atropine, propranolol, prazosin, and yohimbine. The nature of RRV was linear in baseline and under [beta]-, [[alpha].sub.1]- and [[alpha].sub.2]-adrenoceptor blockades. Atropine changed the linear nature of RRV to nonlinear and increased its stationarity, regularity and fractality. Propranolol increased the complexity and chaotic behavior, and decreased the stationarity, regularity, and fractality of RRV. Both prazosin and yohimbine did not change any of the nonlinear and fractal properties of RRV. It is suggested that 1) the use of both nonlinear and fractal analysis is an appropriate approach for studying cardiac period variability in reptiles; 2) the cholinergic activity, which seems to make the [[alpha].sub.1]-, [[alpha].sub.2]- and [beta]-adrenergic activity interaction unnecessary, determines the linear behavior in basal RRV; 3) fractality, as well as both RRV regularity and stationarity over time, may result from the balance between cholinergic and [beta]-adrenergic activities opposing actions; 4) [beta]-adrenergic activity may buffer both the complexity and chaotic behavior of RRV, and 5) neither the [[alpha].sub.1]-nor the [[alpha].sub.2]-adrenergic activity seem to be involved in the mediation of either nonlinear or fractal components of RRV. autonomic nervous system; fractal analysis; nonlinear analysis; recurrence plot; telemetry

Aminiature perifusion system, comprising of two pH sensors, is able to indicate modifications in extracellular protons following the application of metabolic perturbants. A convolution technique applied to the perifusion system facilitates the analysis of the response of HeLa cells to carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Convolution evaluation can give new insights into metabolism and cellular responsiveness.

White noise analyis was used to study physiological processes with recordings less than 30 seconds. It serves as a probe which facilitates comparisons between systems. This was applied to the visual system where input of light to the retina was transformed into electrical signals in photoreceptors and measured using white noise analysis. The mathematical computations involved present an enormous task to the neurophysiologist, but it is an effective tool especially when used intracellularly.

During the perinatal period the newborn must adapt to a different environment from that of the womb. After birth, maternal supplies of nutrient ceases requiring changes in glucose and fatty acid metabolism stimulated by alterations in hormone secretion. The suckling-weaning transition also changes nutritional patterns in the neonate resulting in further metabolic adaptations of glucose and fat metabolism.