Cholinesterase activity of capillaries in the rat brain. A light and electron microscopic study

Synopsis The presence of cholinesterase activity in association with capillaries of the central nervous system was investigated in the rat by means of both light and electron microscopic methods. Throughout most of the rat brain, the smaller blood vessels stain intensely for butyrylcholinesterase activity. In some areas, such as the commissural nucleus of the vagus and parts of the medial thalamus, the capillaries possess both acetylcholinesterase and butyrylcholinesterase activity. Blood vessels in those structures which lie outside the blood-brain barrier are completely devoid of cholinesterase activity. The electron microscope reveals that reaction product occurs within the matrix of the basement membrane, in the intermembranous space of the endothelial nuclear envelope and occasionally in the endothelial granular endoplasmic reticulum. It is suggested that the presence of cholinesterase within the basement membrane of brain capillaries is evidence of the role that the basement membrane may play in transfer mechanisms.     

Succinic dehydrogenase activity in liver,kidney and brain of rat

Summary A method is described for histochemical quantification of the activity of succinic dehydrogenase in various tissues of rat by means of Nitroblue tetrazolium. This method can be used for comparison of enzyme activities; the activities calculated correspond to values obtained by biochemical methods. The necessity to quantify the nothing dehydrogenase is established as well as the amount of half-formazan.Accepted as doctoral dissertation by the Faculty of Medicine, Westfälische Wilhelms-University Münster     

Effect of phenylpyruvate on pyruvate dehydrogenase activity in rat brain mitochondria

1. The effects of phenylpyruvate, a metabolite produced in phenylketonuria, on the pyruvate dehydrogenase-complex activity were investigated in rat brain mitochondria. 2. Pyruvate dehydrogenase activity was measured by two methods, one measuring the release of (14)CO(2) from [1-(14)C]pyruvate and the other measuring the acetyl-CoA formed by means of the coupling enzyme, pigeon liver arylamine acetyltransferase (EC 2.3.1.5). In neither case was there significant inhibition of the pyruvate dehydrogenase complex by phenylpyruvate at concentrations below 2mm. 3. However, phenylpyruvate acted as a classical competitive inhibitor of the coupling enzyme arylamine acetyltransferase, with a K(i) of 100mum. 4. It was concluded that the inhibition of pyruvate dehydrogenase by phenylpyruvate is unlikely to be a primary enzyme defect in phenylketonuria.     

Influence of starvation on lactic dehydrogenase activity in the serum and brain of rats of different ages.

The authors investigated the effect of 24 hours' acute deprivation of food and liquids on lactic dehydrogenase (LDH) activity in the serum, cerebral cortex, subcortical formations and medulla oblongata of 6- and 14-day-old and adult rats. Young rats were starved by separating half of a standard litter from the female for 24 hours. LDH activity was determined by means of Sevac-test-LDH (Imuna, Czechoslovakia) and was expressed in I.U./litre serum or 1 kg tissue wet weight. The samples were prepared at 0 degrees C. LDH activity in the various parts of the CNS was measured in the supernatant of homogenates of the above tissues and the greatest possible destruction of the tissues was ensured by freezing and thawing the homogenates prior to centrifugation. The specimens were incubated at 37 degrees C. Extinction was measured on a SPECOL (G.D.R.) apparatus at 505 nm wavelength. We found that 24 hours' deprivation of food and liquids, together with sensory deprivation in the youngest age groups, significantly reduced LDH activity in both the serum and the cerebral cortex of 6-day-old rats. In adult rats, starvation and thirst raised LDH activity, but the only statistically significant increase was in the medulla oblongata. Under our experimental conditions, LDH activity rose during development by 274% in the cerebral cortex, by 233% in subcortical formations and by 173% in the medulla oblongata. The differences betwen these developmental trends are statistically significant.     

Phenylpyruvic Acid decreases glucose-6-phosphate dehydrogenase activity in rat brain

Phenylketonuria is a recessive autosomal disorder that is caused by a deficiency in the activity of phenylalanine-4-hydroxylase, which converts phenylalanine to tyrosine, leading to the accumulation of phenylalanine and its metabolites phenyllactic acid, phenylacetic acid, and phenylpyruvic acid in the blood and tissues of patients. Phenylketonuria is characterized by severe neurological symptoms, but the mechanisms underlying brain damage have not been clarified. Recent studies have shown the involvement of oxidative stress in the neuropathology of hyperphenylalaninemia. Glucose-6-phosphate dehydrogenase plays an important role in antioxidant defense because it is the main source of reduced nicotinamide adenine dinucleotide phosphate (NADPH), providing a reducing power that is essential in protecting cells against oxidative stress. Therefore, the present study investigated the in vitro effect of phenylalanine (0.5, 1, 2.5, and 5?mM) and its metabolites phenyllactic acid, phenylacetic acid, and phenylpyruvic acid (0.2, 0.6, and 1.2?mM) on the activity of enzymes of the pentose phosphate pathway, which is involved in the oxidative phase in rat brain homogenates. 6-Phosphogluconate dehydrogenase activity was not altered by any of the substances tested. Phenylalanine, phenyllactic acid, and phenylacetic acid had no effect on glucose-6-phosphate dehydrogenase activity. Phenylpyruvic acid significantly reduced glucose-6-phosphate dehydrogenase activity without pre-incubation and after 1?h of pre-incubation with the homogenates. The inhibition of glucose-6-phosphate dehydrogenase activity caused by phenylpyruvic acid could elicit an impairment of NADPH production and might eventually alter the cellular redox status. The role of phenylpyruvic acid in the pathophysiological mechanisms of phenylketonuria remains unknown.     

Aspartate aminotransferase and glutamate dehydrogenase activity in the rat brain during infrared laser exposure

In experiments in vivo it was shown that upon low-intensity infrared irradiation changes in the activity of main enzymes of glutamic acid metabolism are a function of time of exposure and flux density.     

A detection method for lactic dehydrogenase activity in the inner ear

A method for the detection of lactic dehydrogenase enzymatic activity in outer hair cells of the rabbit is described. The membranous labyrinth with temporal bone was prefixed in glutaraldehyde. After being placed into the incubation medium, it was postfixed in osmium tetroxide. Specimens of the organ of Corti were removed. Then the specimens were embedded in water-soluble glycol and cut with a cryostat for light microscopy, and also they were embedded in Epon and cut for light and electron microscopy. Sectioning of the membranous labyrinth was very easily made when the specimens were embedded in both the water-soluble glycol and the Epon. The structures of the frozen sections as well as the Epon-embedded ones were well preserved. In the frozen sections the preservation and localization of reaction products were thoroughly kept, but monoformazan of the Epon-embedded sections was soluble.