Torsten Alvager

Reaction of malonaldehyde with mitochondrial membranes

Malonaldehyde formed by lipid oxidation is regarded as a main crosslinker in the formation of natural age pigment. To elucidate the mechanism of pigment formation the reaction of malonaldehyde with biomembranes using fluorescence spectroscopy has been studied. Rat liver mitochondrial ghosts or bovine serum albumin were reacted with malonaldehyde. In both cases two main fluorescence changes were observed: protein fluorescence decreased to 50% of its initial value in about two hours; aminoiminopropene fluorescence reached a maximum at a much slower rate. The kinetics support a two-step reaction hypothesis. First, malonaldehyde reacts with protein quenching its fluorescence. Next fluorescent interprotein aminoiminopropene (AIP) crosslinks are formed. The fluorescence lifetime value of the induced AIP fluorophore was shown to be similar to the lifetime of naturally occurring age pigment previously reported for mitochondrial ghosts prepared from aged animals (5.4 ns +/- 0.3 and 5.9 ns +/- 0.6, respectively).

MAGNETOHYDRODYNAMIC WAVE RESONANCE AND THE EVOCATION OF EPILEPTIFORM ACTIVITY BY MILLITESLA DC MAGNETIC FIELDS

DC magnetic fields of low- to medium-flux density (nTesla to mTesla) affect a variety of brain activities. The cellular mechanism underlying these effects is unknown. A model involving magnetohydrodynamic waves and corresponding resonance phenomena is offered here as a solution. The model is discussed in relation to the evocation of epileptiform activity due to external DC magnetic fields in the mTesla range. The assumed existence of a resonance wave makes it possible to calculate the size of the involved area.

Age related changes in fluorescence and respiratory properties of liver mitochondria

Fluorescence and respiratory properties of rat liver mitochondrial membranes in young and old animals have been measured. A trend toward decreasing specific activity of malate + glutamate supported state 4 respiration in mitochondria from 18 month old animals as compared to 1 month old animals is found. A concomitant decrease in membrane protein tryptophane fluorescence and an increase in a membrane fluorophore proposed to be aminoiminopropene has also been observed using nanosecond fluorescence spectroscopy techniques.

Data compression in brains

Data compression involves packaging data in an efficient manner. It is a common phenomenon in man-made computers. If is reasonable to assume that something similar occurs in brains. It is proposed that experimental evidence for this is given by the data on decreasing density of synaptic connections in brains with age. The proposed effect is reviewed in relation to computations with simple brain models in the form of a specific artificial neural network.

Nanosecond fluorescence decay study of mitochondria and mitochondrial membranes

Summary The nanosecond fluorescence decay of the tryptophan residues of rat liver mitochondria and mitochondrial membranes has been measured. Apparent fluroescence lifetimes of 3 to 11 nanoseconds have been observed. Authentic membrane proteins suspended in 50% DMSO exhibit fluorescence properties almost identical to membrane proteins in situ . It is found that the fluorescent membrane components appear to remain firmly bound to the membranes in fresh preparations, but can be, at least in part, released into the solvent phase as a consequence of freeze thaw procedures.

DNA, proteins and compressibility

The possibility is considered that the average number of amino acids in proteins is influenced by the complexity of the corresponding DNA sequence. Complexity is regarded as a quantity related to the compressibility of a sequence. This makes a computation manageable using artificial neural network techniques. A neural network computation is performed on a section of several E. coli DNA coding sequences to illustrate the procedure.

Mathematical modeling of objects of physical reality through artificial neural networks

It is often regarded as a mystery by many authors that mathematics, a product of human thought, can explain physical reality. Here we explore the possibility that a model of physical objects is created by a computational system that is equivalent to an artificial neural network. Since it is believed that human thought is created in the brains neural networks the mystery disappears due to similarities between neural networks. Our 3-dimensional space is discussed as a possible application of the model.

An artificial neural network study of the relationship between arousal, task difficulty and learning

We compare the performance of a backpropagation neural network and a recirculation neural network when they are used to simulate the interactions between arousal, task difficulty and learning. We use number strings that vary in terms of their randomness as the stimuli to be learned and the bias unit to simulate arousal. We find that the recirculation neural network shows an interaction between task difficulty and arousal which is typical of that observed when living organism learn a task. This interaction is not observed with the backpropagation algorithm. We conclude that the recirculation neural network provides a better model of arousal and learning than the backpropagation algorithm.

Neural network analysis of DNA sequences

Summary form only given. Attention is given to a project which investigates the applicability of recently developed neural network programs to analyze DNA sequences in a few simple cases to determine parameters such as learning times. Specifically, the ability of various macromolecules to bind to nucleic acid with a recognizable pattern has been considered. The group of enzymes known as restriction endonucleases was considered as an example. These molecules bind and cut DNA at specific nucleotide sites. The neural network is taught to recognize a set of patterns of interest and is then tested on its performance on extended DNA sequences.<<ETX>>

Reinstatement of Ovarian Cycles in Aged Female Rats by Placement of L-Dopa in the Medial Preoptic Area

Systemic treatment with the catecholamine precursor 1-dopa has been shown to reinstate ovarian cycles in the aged female rat (Quadri et al., 1973; Linnoila and Cooper, 1976). In an effort to determine if this effect is mediated via the action of 1-dopa on CNS catecholamines, we observed ovarian function after placing small amounts of 1-dopa directly into selected brain regions of aged rats (14 to 22 months old) bearing chronically implanted cannulae. Ovarian cycles could be reliably reinstated when 1-dopa was placed in the medial preoptic area of constant estrus or recurrently pseudopregnant females. This treatment was more effective (i.e. greater proportion of females responding.) and of longer duration (i.e. greater number of cycles observed) in 14–16 month old females than in the 22 month old females. Placement of 1-dopa in the septum, hippocampus or cortex had no effect on ovarian function. Placement of the norepinephrine precursor dlthreo-dihydroxyphenylserine (DOPS) or the neutral amino acid leucine in the four brain regions was without effect on ovarian function. The results will be discussed in terms of possible regional changes in brain amines with age.