A test and calibration process for microcalorimeters used a thermal power meters

A test and calibration process for microcalorimeters is described. The method has been developed with particular reference to instruments used for measurements of thermal power produced by suspensions of living cells. The process investigated is the hydrolysis of triacetin in imidazole/acetic acid buffer. The power levels are regulated by changing the buffer composition. The power will decrease slowly and very nearly linearly with time. Five test solutions, power levels 7–90 μW·ml^?1, have been characterized at 37°C and one of them at 25°C (13 μW·ml^?1). The power values for these reaction mixtures can be accurately calculated (±0.5%) as a function of time during extended reaction periods, about 20 h or more.     

Biochemistry of Parkinson's disease with special reference to the dopaminergic systems

The cardinal neurochemical abnormality in Parkinson's disease is the decreased dopamine content in the striatum, resulting from the loss of dopaminergic neurons in the mesencephalon. Precise analysis of the dopaminergic neurons in the midbrain demonstrates, however, that this cell loss is not uniform. Some dopaminergic cell groups are more vulnerable than others. The degree of cell loss is severe in the substantia nigra pars compacta, intermediate in the ventral tegmental area and cell group A8, but nonexistent in the central gray substance. This heterogeneity provides a good paradigm for analyzing the factors implicated in this differential vulnerability. So far, the neurons that degenerate have been shown to contain neuromelanin, high amounts of iron, and no calbinding_28K, and to be poorly protected against oxidative stress. By contrast, the neurons that survive in Parkinson's disease are free of neuromelanin, calbindin_D28-positive, contain low amounts of iron, and are better protected against oxidative stress. The analysis of the pattern of cell loss in Parkinson's disease may thus bring new clues as to the mechanism of nerve cell death in Parkinson's disease.     

The kinetics of linear systems with special reference to periodic reactions

It is shown on the basis of (1) conservation of mass, (2) positive concentrations, and (3) the principle of detail balancing that periodic reactions cannot occur in a closed system described bylinear differential equations. The matrix,A, of the rate equations must be such that |A|=0,a _ij>0 fori≠j,a _ii<0, andVAV ⁻¹=B, whereV is diagonal andB is symmetric. These properties ofA imply that the latent roots are real and non-positive and that neither catalysis nor inhibition can be described bylinear equations. It is further shown that periodic reactions cannot occur in anopen system for which the matrix associated with the chemical reactions has the above properties and in which thesimple law of diffusion is obeyed. The relation of these results to Onsager's reciprocal relations and to previous work on periodic and cyclic chemical reactions is discussed. The utility of certain of these results for the treatment of isotope kinetics is indicated. A portion of this work was performed while the author was in the Department of Physiology, University of Chicago, and was supported by a grant from the Dr. Wallace C. and Clara A. Abbott Memorial Fund.     

Partition and counter-current distribution of membrane particles in aqueous dextran-poly(ethylene glycol) two-phase systems with special reference to synaptosomes

Aqueous two-phase systems composed of water, dextran and poly(ethylene glycol) can be used for the separation of biological particles. The adjustment of the partition of such particles between the two phases and the interface between them has been studied by using a preparation of synaptosomes (from calf brain cortex) also containing free mitochondria. The partition has been affected by variation of polymer concentrations and addition of salts, e.g. phosphates and chloride. The time for separation of the phases showed a bimodal behaviour with an initially rapid formation of bulk phases followed by a slow phase separation. The relative amount of mixed phases at the time of the transition was proportional to the amount of particles included. Counter-current distribution with moderate time for the phase separation was carried out in such way that the interface material travelled with approximately half the speed of the moving upper phase. In this way the distribution of the particles between the upper phase and the interface as well as between the interface and the lower phase could be studied in the same experiment. The heterogeneity of the synaptosome preparation was clearly demonstrated by counter-current distribution at low polymer concentrations while no separation was obtained when the system contained larger amounts of polymers. Possible reasons for this behaviour are discussed.     

The specific heat of red cells,with special reference to the paracrystalline rat red cell

The specific heat of the rat red cell, kept in cold sodium citrate, changes in the neighborhood of 6°C., the temperature near which the cell passes from its paracrystalline state to a state of greater disorder. The change in the specific heat is from 0.74 with a standard deviation of ±0.022 (paracrystalline state) to 0.87 with a standard deviation of ±0.021 (normal state). Although it has been looked for, no evidence of a change in specific heat has been found, between 1°C. and 15°C., in the case of the human red cell or of the fresh rat red cell in saline or plasma.     

Diagnostic and prognostic criteria for heat stroke with special reference to plasma enzyme and isoenzyme release patterns.

1. The aim of this study was to investigate the potential value of isoenzyme release patterns as parameters of hyperthermic injury in improving the diagnostic protocol for heat stroke. 2. Rats were exposed to combinations of exercise and hyperthermic stress. Following exposure, respective release patterns of isoenzymes were determined. 3. Isoenzyme release patterns following hyperthermic injury portray both the type and extent of tissue damage more clearly than do plasma total enzyme release patterns. 4. The sensitivity of isoenzymes as a diagnostic criterion is extended to include both a temporal component (i.e. an accurate diagnosis will be possible at an earlier stage subsequent to hyperthermic exposure) and at the same time to be indicative of the exposure.     

The tonicity-volume relations for human red cells subjected to the action of heat,with special reference to prolytic K loss

1. The volume-tonicity relations for human red cells exposed to a temperature of 48 degrees C. for 2 minutes remain the same as those for unheated human red cells. The heated systems show lysis in higher tonicities than the unheated systems do; this is probably largely due to fragmentation with its effect on the geometry of the situation, as suggested by Ham, Shen, Fleming and Castle. When the cells are heated to 48 degrees C. for longer times, the amount of fragmentation becomes considerable, but the volume-tonicity relation remains the same as before; the properties which are usually referred to as the osmotic properties of the red cell are accordingly not necessarily dependent on the integrity of the cell as a unit. 2. Heating to 52 degrees C. for 2 minutes profoundly modifies the volume-tonicity relation, very little swelling now occurring even in tonicities as low as 0.6. This is partly accounted for by the large K losses and K-Na exchanges which occur and which become greater as the tonicity is reduced and as the temperature is increased. Fragmentation and hemolysis also increase, the latter out of proportion to the expected effects of the former. Direct effects of heat on the cohesion of the red cell ultrastructure are probably involved.     

Lytic and inhibition responses to bacteriophages among marine bacteria,with special reference to the origin of phage-host systems

The results of phage-host cross-reaction tests reported by Moebus & Nattkemper (1981) were re-examined using serially diluted bacteriophage suspensions to elicit the actual type of reaction between the bacteria and phage lysates tested. More than 1450 phage-host systems were studied at 25 °C incubation temperature. Among the nearly 300 phage strains used, 29 were identified as temperate ones. In about 65 % of the phage-host systems bacteriophage propagation was indicated by plaque formation. The remaining systems were characterized by the inhibition reaction of bacteria to phage lysates indicated by homogenously reduced bacterial growth within the test area without production of progeny phages. Since crude phage lysates had to be used, it remains obscure whether agents other than infective phage particles (defective ones or bacteriocins) caused this reaction. Among 269 systems of the inhibition type which were also tested at 5° and 15 °C, 54 were observed to propagate phages at one of or both the lower temperatures. Plaques produced at 15 °C with several phage-host systems were found to yield only few progeny phages which generally could not be propagated to produce high-titer phage stocks. With one system temperature-sensitive phage mutants were isolated. The probability of inhibition reactions occurring was found to be higher with phage-host systems isolated east of the Azores than with systems derived from the western Atlantic. With systems from the last mentioned area the proportion of inhibition versus lytic responses of bacteria to phages was observed to increase with the distance between the stations where both parts of the systems were derived. The latter findings are discussed in view of the assumption that bacterial and bacteriophage populations undergo genetic changes while being transported from west to east.