Expression and distribution of carboxypeptidase B in the hippocampal subregions of normal and Alzheimer's disease brain

Earlier neurochemical studies suggested that human brain carboxypeptidase B may play a significant role in the degradation of amyloid-beta1-42 in the brain. Using an immimohistochemical technique we report here on the neuronal expression and distribution of this enzyme in the segments (CA1a, CA1b and CA1c) of the CA1 subfield and in area CA4 of the hippocampus in normal and Alzheimer's disease brain samples. Its distribution was compared with the appearance of neurofibrillary tangles in the same brain sample. For immunohistochemical localization of carboxypeptidase B, a specific C14-module antibody was applied, together with the Gallyas silver impregnation technique for the demonstration of neurofibrillary tangles. The results revealed that, in the control samples, most of the immunoreactivity appeared in segment CA1a in the pyramidal cells, less in segment CA1b and least in segment CA1c. In the Alzheimer's disease samples, there was no particular immunostaining in the neurons, but, a large number of silver-impregnated degenerated neurons appeared. The results support the suggestion that carboxypeptidase B may play a significant role in elimination of the intracellular accumulation and toxicity of amyloid-beta in the human brain and thereby protect the neurons from degeneration.     

Application of the maximum entropy method to absorption kinetic rate processes

The maximum entropy method, originally developed for astronomical image restoration, has already been successfully applied to a variety of biophysical problems. Through numerical inverse Laplace transformation, the method determines the lifetime distribution function with the largest informational entropy. Starting from a flat distribution, it results in the consistent selection of a single distribution from the numerous possible ones that correctly fit the data. In this paper, we discuss the application of the method to kinetic processes that have both rise and decay components, and test the algorithm with different signal to noise ratio generated data. It is proved that the mass conservation constraint can be taken into account by reducing the search to a lower dimensional subspace. The effect of noise on the width of lifetime distribution is studied and it is shown that an inherent entropy connected to the underlying kinetics can be separated from the noise generated entropy. The possibility of the application of the method to the photocycle kinetics of bacteriorhodopsin is also shown.     

Reduction of the endoplasmic reticulum accompanies the oxidative damage of diabetes mellitus

The endoplasmic reticulum (ER), similary to other subcompartments of the eukaryotic cell possesses a relatively oxidizing environment. The special milieu of ER lumen is important for many ER-specific processes (redox protein folding, glycoprotein synthesis, quality control of secreted proteins, antigen presentation, etc.). Despite of the vital importance of redox regulation in the ER, we have a surprisingly fragmented knowledge about the mechanisms responsible for the ER redox balance. Moreover, new observations on disulfide bridge synthesis and on glutathione functions urge us to revise our recent theories based on many indirect and in vitro results. We have also very little information about the effects of different pathological conditions on the thiol metabolism and redox folding in the ER. Examining the role of molecular chaperones in the cellular pathology of diabetes mellitus we found that the ER redox environment shifted to a more reducing state, which was followed by changes of the thiol metabolism and structural-functional changes of the protein machinery involved in the redox folding process in diabetes. The possible consequences of these unexpected changes are also discussed.     

Molecular chaperones,stress proteins and redox homeostasis

Protection against oxidative stress is highly interrelated with the function of the most ancient cellular defense system, the network of molecular chaperones, heat shock, or stress-proteins. These ubiquitous, conserved proteins help other proteins and macromolecules to fold or re-fold and reach their final, native conformation. Redox regulation of protein folding becomes especially important during the preparation of extracellular proteins to the outside oxidative milieu, which should take place in a gradual and step-by-step controlled manner in the endoplasmic reticulum or in the periplasm. Several chaperones, such as members of the Hsp33 family in yeast and the plethora of small heat shock proteins as well as one of the major chaperones, Hsp70 are able to act against cytoplasmic oxidative damage. Abrupt changes of cellular redox status lead to chaperone induction. The function of several chaperones is tightly regulated by the surrounding redox conditions. Moreover, our recent data suggest that chaperones may act as a central switchboard for the transmission of redox changes in the life of the cell.     

Glutamate decarboxylase activity in Trichoderma viride conidia and developing mycelia

Glutamic acid decarboxylase (GAD) activity was measured in homogenates of conidia and both submerged and aerial mycelia of Trichoderma viride. The GAD activity in conidia had a temperature optimum at 30 degrees C and a pH optimum at pH 4. GAD was stimulated by EDTA (2 mM) and was insensitive to treatment with calmodulin antagonists calmidazolium (10 microM) or phenothiazine neuroleptics (60 microM). Cyclosporin A (up to 300 microM) partially inhibited GAD in the homogenate, but not in the supernatant obtained after centrifuging the homogenate. Attempts to release GAD activity from the homogenate using high ionic strength, detergents, or urea failed. Freezing-thawing led to the partial increase of activity in the conidial homogenate. These results indicate that GAD is a membrane-bound enzyme. The highest specific activity of GAD was present in the mitochondrial/vacuolar organellar fraction. Germination of conidia in the submerged culture led to a temporary decrease in GAD activity. After prolonged cultivation, the activity displayed quasi-oscillatory changes. The stationary state was characterized by a high GAD activity. The presence of gamma-aminobutyric acid in the submerged mycelia was demonstrated. In surface culture in the dark, GAD activity increased in a monophasic manner until conidia formation. The illumination of dark-cultivated mycelia by a white-light pulse caused a dramatic increase in GAD activity. Light-induced changes were not observed in mutants with delayed onset of conidiation. In the dark or upon illumination by light pulse, the increase of GAD activity preceded the appearance of conidia. Thus, GAD activity in T. viride is closely associated with its developmental status and may represent a link between differentiation events and energy metabolism.     

Effect of glibenclamide and glimepiride treatment on the development of myocardial infarction in rats

The effect of glibenclamide and glimepiride, two orally active antidiabetic sulphonylurea derivatives, on the development of myocardial infarction has been compared. Permanent coronary artery ligation was induced in rats and the development of infarction was evaluated by a computer-assisted method after nitroblue-terazolium staining. Seven-day coronary ligation produced enlargement of the left ventricular cavity, scar thinning and thickening of the non-infarcted myocardium. Glibenclamide treatment (5 mg/kg b.i.d. intraperitoneally) decreased the infarct volume (29.1 +/- 3.5% vs. 39.1 +/- 3.2% in controls), that occurred primarily as a result of more significant thinning of the scar tissue (1.6 +/- 0.04 mm vs. 2.0 +/- 0.13 mm in controls). Glibenclamide also inhibited the thickening of the non-infarcted ventricular septum (2.1 +/- 0.10 mm vs. 2.9 +/- 0.10 mm in controls). In contrast to the effects of glibenclamide, glimepiride treatment (5 mg/kg b.i.d. intraperitoneally) inhibited the enlargement of the left ventricular cavity (15.2 +/- 1.1% vs. 19.9 +/- 1.2% of the left ventricular volume in controls), it did not precipitate scar thinning and did not influence the development of hypertrophy of the non-infarcted myocardium. These results suggest that glimepiride treatment might inhibit the development of left ventricular dilatation after myocardial infarction. Glibenclamide treatment, however, producing a thinning of the scar tissue may further precipitate morphological changes that can contribute to the development of heart failure.     

The roles of platelet function, thromboxane, blood lipids and nitric oxide in hypertension of children and adolescents

The roles of platelet function, plasma lipids and nitric oxide (NO) were studied in adolescent patients with essential hypertension (JEHT group), with chronic renal failure (CRF) associated with hypertension (CRFH group), and CRF patients with normal blood pressure (CRF group), as compared with normal controls (cont. group). Platelet aggregation and the thromboxane B(2)(TxB(2)) level were significantly higher in the JEHT and CRFH groups as compared with the cont. group, whereas they were significantly lower in the CRF group. On the other hand, the platelet cAMP level was significantly lower in the JEHT and CRFH groups than in the cont. group. The plasma NO level was significantly higher only in the JEHT as compared with the cont. group (120 +/- 39 and 89 +/- 21 microM, respectively). The plasma total cholesterol, triglyceride and LDL cholesterol concentrations were normal in the JEHT group, but high in the CRF and CRFH group, the HDL cholesterol level was lower in the CRF and CRFH groups as compared with the cont. and JEHT groups. There was a positive correlation between the platelet aggregation and the TxB(2)level and between the BP and the platelet aggregation. In conclusion, hyperlipidaemia is commonly present in uraemia with haemodialysis, but is not specific for hypertension in children, while an increased platelet function is frequently associated with hypertension. The increased NO level might play a compensatory role in JEHT.     

Metabolic Changes in Rat Brain After Prolonged Ethanol Consumption Measured by 1H and 31P MRS Experiments

SUMMARY 1. In vivo ¹H and ³¹P magnetic resonance spectroscopy techniques were applied to reveal biochemical changes in the rat brain caused by prolonged ethanol consumption.2. Three models of ethanol intoxication were used.3. ¹H MRS showed a significant decrease in the concentration of myo-inositol in the brain of rats fed with 20% ethanol for 8 weeks. This change is consistent with perturbances in astrocytes. On the other hand, N-acetyl aspartate and choline content did not differ from controls.4. ³¹P MRS did not reveal any significant changes in the high-energy phosphates or intracellular free Mg²⁺ content in the brain of rats after 14 weeks of 20% ethanol drinking. The intracellular pH was diminished.5. By means of a ³¹P saturation transfer technique, a significant decrease was observed for the pseudo first-order rate constant k _for of the creatine kinase reaction in the brain of rats administered 30% ethanol for 3 weeks using a gastric tube.6. The ¹H MRS results may indicate that myo-inositol loss, reflecting a disorder in astrocytes, might be one of the first changes associated with alcoholism, which could be detected in the brain by means of in vivo ¹H MRS.7. The results from ³¹P MRS experiments suggest that alcoholism is associated with decreased brain energy metabolism.8. ³¹P saturation transfer, which provides insight into the turnover of high-energy phosphates, could be a more suitable technique for studying the brain energetics in chronic pathological states than conventional ³¹P MRS.     

Lack of effects of glycineB receptor ligands on the psychostimulant-induced discriminative stimuli in rats

To examine the role of glycineB receptors in the stimulus effects induced by psychostimulants, separate groups of rats were trained to discriminate amphetamine (AMPH; 1 mg/kg) from saline (SAL), or cocaine (COC; 10 mg/kg) from SAL, using a two-lever operant procedure. Substitution studies showed that neither 1-aminocyclopropanecarboxylic acid (ACPC; 200 mg/kg) nor 7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-(H)quinolone (L-701,324; 3 mg/kg), being a partial agonist or an antagonist at glycineB receptors, respectively, generalized for the training drugs. Combination tests of glycineB ligands demonstrated that injection of a fixed dose of ACPC (200 mg/kg) or L-701,324 (3 mg/kg) together with different doses of AMPH or COC practically did not modify dose-response curves of the psychostimulants, nor did it affect their ED50 values. Our results indicate that glycineB receptors do not play a role in the discriminative effects of AMPH and COC.     

The possible role of information technology in radiotherapy II. The development of a biological dose distribution model in the 3-dimensional treatment planning of brain tumours

OBJECTIVE: Developing a new medical software based on the utilisation of information technology required in 3-dimensional treatment planning and modern radiotherapy. METHODS: The physical dose distribution programs were converted into biological meaning with the insertion of biological equivalence equations based on LQ model. Biological dose distributions and biological dose-volume histograms were generated. The treatment plans of a brain tumour patient were investigated to determine the dose burdening of the normal central nervous system tissues. RESULTS: Employing 3D conformal method, the dose of the vital mid-line structures decreased significantly, which possesses a more meaningful biological importance. Different treatment plans and different fractionation regimens could be compared to each other by utilising this kind of biological model. CONCLUSION: By employing information technology we succeeded in establishing a theoretical biological dose distribution system that could be visualised. The advantages of 3D treatment planning proved unambiguous. In the future this method will probably be suitable to choose the best therapeutic regimens.