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Biomedical subjects

V Neuhoff

Publications and source records attributed to V Neuhoff.

At least 127 records · Page 7Linked to original sources
PubMed1975

The effect of the chronic administration of D-amphetamine upon circadian changes in amino acids in the pineal and pituitary glands of the rat.

The formation of dansyl derivatives of amino acids, 5-hydroxyindoleacetic acid and histamine, and their separation on polyamide plates provided a reliable and sensitive method for studying circadian changes in single pineal and pituitary glands of the rat. There appears to be no correlation between the circadian changes in concentrations of these substances in the pineal and pituitary glands. Chronically administered D-amphetamine altered the circadian rhythms of five amino acids in the pituitary, including the putative transmitters taurine, glycine, and glutamate; in the pineal gland only the rhythmical changes of lysine and 5-hydroxyindoleacetic acid were affected.

Amino Acids↗
PubMed1975

Neurochemical changes in the cat's spinal cord due to orthodromic tetanic stimuli. I: phospholipids.

Posttetanic potentiation of monosynaptic reflexes has been used as a paradigm for neuronal plasticity. The explanation for this phenomenon is an increased responsiveness of the synaptic junctions. This would basically require chemical changes of the nervous structures involved. The ventral horn area of the spinal cord was therefore analyzed neurochemically. The determination of the phospholipids revealed an alteration of their composition. Sphingomyelin, phosphatidylcholine and phosphatidylinositide/serine behaved differently, whereas phosphatidylethanolamine and the total phospholipid content remained unchanged.

Animals↗
PubMed1975

Proteinuria and distribution of fibrinogen split products in various forms of glomerulonephritis.

The microelectrophoresis on gradient gels allows differentiation between the different types of proteinuria in 1 h in a one-step procedure. Due to their different molecular weights and forms, fibrinogen split products are separated by this method. The determination of fibrinogen split products not only offers a possibility for dicrimination between the various forms of glomerulonephritis but also offers a possibility for following the course of the disease.

Electrophoresis, Polyacrylamide Gel↗
PubMed1975

Kinetic studies on microsomal glucose dehydrogenase in rat liver.

Glucose dehydrogenase from rat liver microsomes was found to react not only with glucose as a substrate but also with glucose 6-phosphate, 2-deoxyglucose 6-phosphate and galactose 6-phosphate. The relative maximum activity of this enzyme was 29% for glucose 6-phosphate, 99% for 2-deoxyglucose 6-phosphate, and 25% for galactose 6-phosphate, compared with 100% for glucose with NADP. The enzyme could utilize either NAD or NADP as a coenzyme. Using polyacrylamide gradient gel electrophoresis, we were able to detect several enzymatically active bands by incubation of the gels in a tetrazolium assay mixture. Each band had different Km values for the substrates (3.0 x 10(-5)M glucose 6-phosphate with NADP to 2.4M glucose with NAD) and for coenzymes (1.3 x 10(-6)M NAD with galactose 6-phosphate to 5.9 x 10(-5)M NAD with glucose). Though glucose 6-phosphate and galactose 6-phosphate reacted with glucose dehydrogenase, they inhibited the reaction of this enzyme only when either glucose or 2-deoxyglucose 6-phosphate was used as a substrate. The Ki values for glucose 6-phosphate with glucose as substrate were 4.0 x 10(-6)M with NAD, and 8.4 x 10(-6)M with NADP; for galactose 6-phosphate they were 6.7 x10(-6)M with NAD and 6.0 x 10(-6)M with NADP. The Ki values for glucose 6-phosphate with 2-deoxyglucose 6-phosphate as substrate were 6.3 x 10(-6)M with NAD and 8.9 x 10(-6)M with NADP; and for galactose 6-phosphate, 8.0 x 10(-6)M with NAD and 3.5 x 10(-6)M with NADP. Both NADH and NADPH inhibited glucose dehydrogenase when the corresponding oxidized coenzymes were used (Ki values: 8.0 x 10(-5)M by NADH and 9.1 x 10(-5)M by NADPH), while only NADPH inhibited cytoplasmic glucose 6-phosphate dehydrogenase (Ki: 2.4 x 10(-5)M). The results indicate that glucose dehydrogenase cannot directly oxidize glucose in vivo, but it might play a similar role to glucose 6-phosphate dehydrogenase. The differences in the kinetics of glucose dehydrogenase and glucose 6-phosphate dehydrogenase show that glucose 6-phosphate and galactose 6-phosphate could be metabolized in quite different ways in the microsomes and cytoplasm of rat liver.

Alcohol Oxidoreductases↗
PubMed1975

Neurochemical aspects of post-tetanic potentiation of monosynaptic reflexes in the cat spinal cord. II. Determination of phospholipids at maximum of potentiation.

A monosynaptic reflex pathway was used to produce a post-tetanic potentiation (PTP). in ten experiments (cats) one side was tetanized (via N. gastrocnemius) whereas the other one was taken as control. Tissue was punched out of the ventral horn area of the spinal cord (segment height L7/S1) for the analysis of the phospholipid content. The results demonstrate that PTP significantly increases phosphatidyl-inositol in the potentiated alpha-motoneurone area. Phosphatidylserine showed a trend towards a decrease; sphingomyelin, phosphatidylcholine and phosphatidylethanolamine remained almost unchanged. The effect of a different tetanizing time on the phospholipid content is discussed as is the intention of the present experiments.

Action Potentials↗
PubMed1975

[Microeletrophoresis in continuous polyacrylamide gel gradients. IV. The effect of reducing agents on the electrophoresis of proteins in sodium dodecylsulfate buffer systems (author's transl)].

The migration of reducing agents (e.g. 2-mercaptoethanol, dithiothreitol and thioglycolic acid) was analysed in various electrophoretic buffer systems containing sodium dodecylsulfate. It is shown that proteins loaded with dodecylsulfate and previously not reduced can be reduced during the electrophoretic separation.

Bence Jones Protein↗
PubMed1975

Neurochemical aspects of post-tetanic potentiation of monosynaptic reflexes in the cat spinal cord. III. Analysis of amino acids after long-term potentiation.

Following 30-min intermittent post-tetanic potentiation of monosynaptic reflexes in the ventral horn of the spinal cord of 10 cats, the amino acid composition was analyzed after reacting with 14C-dansylchloride and by two-dimensional chromatography. The amino acids in comparable segments of the spinal cord from eight animals after ether anesthesia and from five animals who were operated on but not stimulated were also analyzed. In the latter the operation itself influenced the amino acid composition as compared to those animals who were anesthetized. Comparison between the different control groups showed that the operated animals can be used as a control for calculation of the changes caused by potentiation. The amino acids glycine, glutamic acid and aspartic acid, which act as either inhibitory or excitatory neurotransmitters, increased significantly after potentiation, as did the amino acids lysine, histidine, leucine, isoleucine, and proline.

Amino Acids↗
PubMed1975

Neurochemical aspects of post-tetanic potentiation of monosynaptic reflexes in the cat spinal cord. I. Analysis of amino acids at maximum of potentiation.

In order to determine the chemical changes which might occur during post-tetanic potentiation, amino acids from the motor regions of the ventral horn of the spinal cord (potentiated and unpotentiated sides) of 10 different cats were analyzed. The intermittent tetanic stimulation of the Nn. gastroc. (only on the potentiated side) was carried out until a maximum of potentiation was reached (3--4 min). The monosynaptic reflexes were obtained from the ventral roots (L7 or S1) of both sides. The amino acids of the potentiated side were compared to those of the unpotentiated side (control) using a 14-C-dansyl chloride procedure. The two main amino acids considered to be excitatory neurotransmitters, glutamic acid and aspartic acid, showed a more than 20 per cent increase on the potentiated side as compared to the control side. Glycine, which plays an inhibitory role, especially in the spinal cord, reacted with 6 per cent decrease, whereas GABA which is also considered as an inhibitory neurotransmitter showed a change of + 11 per cent on the potentiated side as compared to the unpotentiated side. The importance of the potentiation time for those changes is pointed out.

Action Potentials↗