The Effect of Academic Load and Work Conditions on the Sympathoadrenal Function and the Indices of Heart Rhythm Regulation in 17- to 18-Year-Old Girls

The dynamics of the sympathoadrenal function and the specific features of heart rhythm regulation were studied in female students and clothing factory female workers during their adaptation to academic and work conditions. Periods of the strongest functional tension in test systems were found in first-year students: the beginning of an academic year, the end of the first semester, and a period after winter examinations, all characterized by an increase in the central-circuit and sympathetic effects on sinus rhythm, acceleration of the heart rate, activation of sympathoadrenal mechanisms, and a decrease in sympathoadrenal reserves. The comparative analysis allowed us to disclose general trends typical of females of this age group such as the relative maturity of the sympathoadrenal system (SAS) and optimum correlation between autonomic and centralized heart rhythm regulation and to reveal the differences in the character and dynamics of functional shifts caused by a specific effect of academic load and work conditions. The degree of correlation between the indices characteristic of hormonal and mediator SAS mechanisms and the statistical characteristics of heart rhythm was proposed as the criteria for estimating the functional tension of the human body.     

18O-Labeling of guanosine monophosphate upon hydrolysis of cyclic guanosine 3':5'-monophosphate by phosphodiesterase

The hydrolysis of cGMP by phosphodiesterase was conducted in [18O]water to determine the site of bond cleavage and the stoichiometry of 18O incorporation into 5'-GMP. Three different forms of phosphodiesterase including a calmodulin-calcium-dependent enzyme in its basal and activated states were examined. The hydrolysis of cGMP catalyzed by each of the forms of phosphodiesterase proceeded with incorporation of 1 18O atom recoverable in the phosphate moiety of each molecule of 5'-GMP generated. No molecular species of phosphate deriving from the 5'-GMP generated containing two or three 18O were detectable. These results indicate that the phosphodiesterase-catalyzed hydrolysis of cGMP proceeds by nucleophilic substitution at phosphorus resulting in P-O bond cleavage. The stoichiometry of 18O incorporation indicates that the reaction proceeds without phosphate-water oxygen exchange when the hydrolytic reaction is catalyzed by diverse forms of phosphodiesterase in the basal or activated state. These considerations of the phosphodiesterase reaction help to establish the validity of monitoring the rate of enzyme-catalyzed hydrolysis of cGMP as a function of the rate of 18O-labeling of the phosphate of 5'-GMP when the reaction proceeds in a medium of predetermined 18O enrichment.     

Calcium control of glycogen synthase activities in mouse diaphragms, rat adipocytes and rat hepatocytes

The following article provides evidence that cellular calcium controls the activity of glycogen synthase in all three major glycogen storage tissues; muscle, fat, and liver. Depletion of cellular calcium resulted in a moderate increase of glycogen synthase %I activities in intact mouse diaphragms, in isolated rat adipocytes, and in rat hepatocytes. The increase in %I activity of glycogen synthase was more pronounced when the uridine di-phosphoglucose concentration in the glycogen synthase assay was lowered from 4.4 mM to 0.2 mM. Calcium depletion resulted in an approximately two-fold decrease in the Ka values for glucose-6-phosphate in all three tissues. The activities of glycogen synthase also correlated well with the content of cell-associated calcium in rat hepatocytes. The glucose-6-phosphate independent activities of glycogen synthase in extracts of calcium-replete and calcium-depleted tissue approached the same value following the exposure to crude phosphoprotein phosphatase. The activities of glycogen phosphorylase decreased in calcium-depleted tissues and cells. Insulin stimulated the activity of glycogen synthase in muscle and fat in the absence of added sugar and in the absence of extracellular calcium. It is concluded that glycogen synthase is under the control of calcium in the three main glycogen storage tissues. The actions of calcium are probably mediated through the actions of calcium-sensitive protein kinase(s).     

Purification of arogenate dehydrogenase from Phenylobacterium immobile

Phenylobacterium immobile, a bacterium which is able to degrade the herbicide chloridazon, utilizes for L-tyrosine synthesis arogenate as an obligatory intermediate which is converted in the final biosynthetic step by a dehydrogenase to tyrosine. This enzyme, the arogenate dehydrogenase, has been purified for the first time in a 5-step procedure to homogeneity as confirmed by electrophoresis. The Mr of the enzyme that consists of two identical subunits amounts to 69000 as established by gel electrophoresis after cross-linking the enzyme with dimethylsuberimidate. The Km values were 0.09 mM for arogenate and 0.02 mM for NAD+. The enzyme has a high specificity with respect to its substrate arogenate.     

Diffusion along intercellular spaces: An analysis of a transient situation

We present an analysis of the diffusion of a tracer in a model of a cell-intercellular space system. The problem reduces to the resolution of a system of a linear partial differential equation and of a linear integral differential equation. The mathematical results have been obtained in terms of their Laplace transforms, which have been inverted by a numerical procedure for some parameter values. The importance of considering gradients of concentrations in intercellular spaces instead of lumping them with the external mediums has been discussed together with the possibility of extending Ussing's relation to transient cases, in order to detect active transports. Some possible implementations of the model to take into account more general situations have been considered.     

Mobilization of iron from ferritin by isolated mitochondria effects of species compatibility between ferritin and mitochondria and iron content of ferritin

Mitochondria mobilize iron from ferritin by a mechanism that depends on external FMN. With rat liver mitochondria, the rate of mobilization of iron is higher from rat liver ferritin than from horse spleen ferritin. With horse liver mitochondria, the rate of iron mobilization is higher from horse spleen ferritin than from rat liver ferritin. The results are explained by a higher affinity between mitochondria and ferritins of the same species. The mobilization of iron increases with the iron content of the ferritin and then levels off. A maximum is reached with ferritins containing about 1 200 iron atoms per molecule. The results represent further evidence that ferritin may function as a direct iron donor to the mitochondria.     

Mutant alpha-synuclein-induced degeneration is reduced by parkin in a fly model of Parkinson's disease.

Parkinson's disease (PD) patients show a characteristic loss of motor control caused by the degeneration of dopaminergic neurons. Mutations in the genes that encode alpha-synuclein and parkin have been linked to inherited forms of this disease. The parkin protein functions as a ubiquitin ligase that targets proteins for degradation. Expression of isoforms of human alpha-synuclein in the Drosophila melanogaster nervous system forms the basis of an excellent genetic model that recapitulates phenotypic and behavioural features of PD. Using this model, we analysed the effect of parkin co-expression on the climbing ability of aging flies, their life span, and their retinal degeneration. We have determined that co-expression of parkin can suppress phenotypes caused by expression of mutant alpha-synuclein. In the developing eye, parkin reduces retinal degeneration. When co-expressed in the dopaminergic neurons, the ability to climb is extended over time. If conserved in humans, we suggest that upregulation of parkin may prove a method of suppression for PD induced by mutant forms of alpha-synuclein.     

Functional analysis of tryptophans alpha 62 and beta 120 on HLA-DM.

In the endocytic pathway of antigen-presenting cells, HLA-DM catalyzes the exchange between class II-associated invariant chain peptide (CLIP) and antigenic peptides onto major histocompatibility complex class II molecules. At low pH of lysosomal compartments, both HLA-DM and HLA-DR undergo conformational changes, and it was recently postulated that two partially exposed tryptophans on HLA-DM might be involved in the interaction between the two molecules. To define contact regions on HLA-DM, we have conducted site-directed mutagenesis on those two hydrophobic residues. The HLA-DM alphaW62A,betaW120A (DM(W62A/W120A)) double mutant was expressed in HLA-DR(+) HeLa cells expressing invariant chain, and the activity of this DM molecule was assessed. Flow cytometry analysis of cell surface DR-CLIP complexes revealed that DM(W62A/W120A) removes CLIP as efficiently as its wild-type counterpart. DM(W62A/W120A) was found in the endocytic pathway by immunofluorescence, and DM-DR complexes were immunoprecipitated from these cells at pH 5. Finally, mutations alphaW62A and betaW120A on HLA-DM did not affect the association with HLA-DO. The complex egresses the endoplasmic reticulum and accumulates in endocytic vesicles. Moreover, DO and DM(W62A/)W120A were co-immunoprecipitated at pH 7. We conclude that the alpha62 and beta120 tryptophan residues are not required for the activity of DM, nor are they directly implicated in the interaction with DR or DO.