The influx of amino acids into the brain of the rat in vivo : the essential compared with some non-essential amino acids

1973 ◽  
Vol 183 (1070) ◽  
pp. 59-70 ◽  
Keyword(s):  
Amino Acids ◽  
Specific Activity ◽  
Essential Amino Acids ◽  
Transport Processes ◽  
Carrier Mediated Transport ◽  
A New Technique ◽  
High Degree ◽  
The Brain

The cerebral influx rates of fifteen amino acids were measured directly in living rats by means of a new technique which makes it possible to maintain a constant specific activity of a radioactively labelled amino acid in the bloodstream. A wide variation in the influx rates of the amino acids was found. These rates differed from those found by other workers using in vitro preparations, but are consistent with the theory that amino acids enter the brain mainly by carrier mediated transport processes with a high degree of specificity. There are a number of important differences between the behaviour of the transport processes in vivo and in vitro . The influx rates of the various amino acids were directly proportional to their concentra­tions in blood plasma (over the range of concentrations studied). All the nutritionally essential amino acids had relatively high influx rates as did other amino acids which the brain does not seem to be able to synthesize. On the other hand, amino acids that the brain can readily synthesize and two amino acids which are not normally found in mammalian tissues had low influx rates.

scholarly journals A novel PET tracer 18F-deoxy-thiamine: synthesis, metabolic kinetics, and evaluation on cerebral thiamine metabolism status

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Changpeng Wang ◽  
Siwei Zhang ◽  
Yuefei Zou ◽  
Hongzhao Ma ◽  
Donglang Jiang ◽  
...  
Keyword(s):  
High Performance ◽  
Specific Activity ◽  
High Accumulation ◽  
Metabolic Kinetics ◽  
Thiamine Metabolism ◽  
Pet Tracer ◽  
The Status ◽  
The Brain

Abstract Background Some neuropsychological diseases are associated with abnormal thiamine metabolism, including Korsakoff–Wernicke syndrome and Alzheimer’s disease. However, in vivo detection of the status of brain thiamine metabolism is still unavailable and needs to be developed. Methods A novel PET tracer of 18F-deoxy-thiamine was synthesized using an automated module via a two-step route. The main quality control parameters, such as specific activity and radiochemical purity, were evaluated by high-performance liquid chromatography (HPLC). Radiochemical concentration was determined by radioactivity calibrator. Metabolic kinetics and the level of 18F-deoxy-thiamine in brains of mice and marmosets were studied by micro-positron emission tomography/computed tomography (PET/CT). In vivo stability, renal excretion rate, and biodistribution of 18F-deoxy-thiamine in the mice were assayed using HPLC and γ-counter, respectively. Also, the correlation between the retention of cerebral 18F-deoxy-thiamine in 60 min after injection as represented by the area under the curve (AUC) and blood thiamine levels was investigated. Results The 18F-deoxy-thiamine was stable both in vitro and in vivo. The uptake and clearance of 18F-deoxy-thiamine were quick in the mice. It reached the max standard uptake value (SUVmax) of 4.61 ± 0.53 in the liver within 1 min, 18.67 ± 7.04 in the kidney within half a minute. The SUV dropped to 0.72 ± 0.05 and 0.77 ± 0.35 after 60 min of injection in the liver and kidney, respectively. After injection, kidney, liver, and pancreas exhibited high accumulation level of 18F-deoxy-thiamine, while brain, muscle, fat, and gonad showed low accumulation concentration, consistent with previous reports on thiamine distribution in mice. Within 90 min after injection, the level of 18F-deoxy-thiamine in the brain of C57BL/6 mice with thiamine deficiency (TD) was 1.9 times higher than that in control mice, and was 3.1 times higher in ICR mice with TD than that in control mice. The AUC of the tracer in the brain of marmosets within 60 min was 29.33 ± 5.15 and negatively correlated with blood thiamine diphosphate levels (r = − 0.985, p = 0.015). Conclusion The 18F-deoxy-thiamine meets the requirements for ideal PET tracer for in vivo detecting the status of cerebral thiamine metabolism.

Cannabinoid effects on adenylate cyclase and phosphodiesterase activities of mouse brain

1977 ◽  
Vol 55 (4) ◽  
pp. 934-942 ◽  
Author(s):  
Thomas W. Dolby ◽  
Lewis J. Kleinsmith
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Mouse Brain ◽  
Biogenic Amine ◽  
Specific Activity ◽  
Intraperitoneal Administration ◽  
The Brain

The experiments presented in this paper examine the mechanisms underlying the ability of cannabinoids to alter the in vivo levels of cyclic adenosine 3′,5′-monophosphate (cyclic AMP) in mouse brain. It was found that changes in cyclic AMP levels are a composite result of direct actions of cannabinoids on adenylate cyclase (EC 4.6.1.1) activity and indirect actions involving the potentiation or inhibition of biogenic amine induced activity of adenylate cyclase. Furthermore, the long-term intraperitoneal administration of 1-(−)-Δ-tetrahydrocannabinol to mice produced a form of phosphodiesterase (EC 3.1.4.17) in the brain whose activity is not stimulated by Ca2+, although its basal specific activity is similar to that of control animals. In vitro, the presence of the cannabinoids caused no significant changes in activity of brain PDE at the concentrations tested. Some correlations are presented which imply that many of the observed behavioral and physiological actions of the cannabinoids in mammalian organisms may be mediated via cyclic AMP mechanisms.

Proteinsynthese in grünen Blättern

1964 ◽  
Vol 19 (3) ◽  
pp. 235-248 ◽  
Author(s):  
Benno Parthier
Keyword(s):  
Amino Acids ◽  
Specific Activity ◽  
Subcellular Fractions ◽  
Mechanical Destruction ◽  
Cell Organization ◽  
Specific Activities ◽  
Short Time ◽  
Natural Cell

In the green leaves of Nicotiana rustica, protein synthesis of various subcellular fractions has been investigated in vivo after 14CO2-photosynthesis and also in vitro by incorporation of radioactive amino acids. Following photosynthesis, homogenization of the tissues, and differential centrifugation of the homogenates, the results show that all structural particles of the cell are able to use photosynthetically formed amino acids for the incorporation into their proteins. The proteins with the highest specific activities are found in the mitochondria-rich fractions, and with the lowest in the soluble cytoplasma supernatant. High specific activities are also observed in the ribosomal-rich fraction in short-time experiments, and also in the chloroplasts after exposure of the leaves to light. After an osmotic-mechanical destruction of the isolated 14C-labelled chloroplasts, the specific activities of lamellar proteins exceed the colourless soluble proteins of the chloroplasts. A green fraction, sedimented at 1,000 g, and perhaps mainly consisting of broken and leached chloroplasts, shows the highest specific activity of all chloroplast fractions. Obviously, due to the destruction of the natural cell organization, in vitro experiments give not only drastically decreased specific activities but also another distribution of the incorporated amino acids between the subcellular fractions, compared with experiments in vivo.

THE STIMULATION OF INSULIN RELEASE BY ESSENTIAL AMINO ACIDS FROM RABBIT PANCREAS IN VITRO

1970 ◽  
Vol 47 (3) ◽  
pp. 347-356 ◽  
Author(s):  
R. D. G. MILNER
Keyword(s):  
Amino Acids ◽  
Insulin Release ◽  
Incubation Medium ◽  
Statistical Significance ◽  
Adenosine Monophosphate ◽  
Essential Amino Acids ◽  
Isoleucine Leucine ◽  
Rabbit Pancreas

SUMMARY Pieces of rabbit pancreas were incubated in vitro in an incubation medium containing no glucose or 1·5 mg. glucose/ml. In each of these conditions the effect on insulin release of each of the essential amino acids at 5 mm concentration was studied. Leucine was the only essential amino acid that stimulated insulin release to a level which reached statistical significance in an incubation medium containing no glucose. In medium containing 1·5 mg. glucose/ml., arginine, isoleucine, leucine and lysine stimulated insulin release and phenylalanine inhibited insulin release. Glucagon, theophylline or dibutyryl cyclic adenosine monophosphate stimulated insulin release significantly in the presence of leucine but not in the presence of arginine. Arginine stimulated insulin release in the presence of leucine. The results of these experiments characterize further the difference in the mechanism of action of leucine and arginine on the pancreatic β-cell and indicate possible explanations for results obtained in other species in vivo.

scholarly journals Human CNS barrier-forming organoids with cerebrospinal fluid production

Science ◽  
2020 ◽  
Vol 369 (6500) ◽  
pp. eaaz5626 ◽  
Author(s):  
Laura Pellegrini ◽  
Claudia Bonfio ◽  
Jessica Chadwick ◽  
Farida Begum ◽  
Mark Skehel ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Fluid Secretion ◽  
Fluid Production ◽  
New Compounds ◽  
High Degree ◽  
The Brain ◽  
Degree Of Similarity ◽  
By Products

Cerebrospinal fluid (CSF) is a vital liquid, providing nutrients and signaling molecules and clearing out toxic by-products from the brain. The CSF is produced by the choroid plexus (ChP), a protective epithelial barrier that also prevents free entry of toxic molecules or drugs from the blood. Here, we establish human ChP organoids with a selective barrier and CSF-like fluid secretion in self-contained compartments. We show that this in vitro barrier exhibits the same selectivity to small molecules as the ChP in vivo and that ChP-CSF organoids can predict central nervous system (CNS) permeability of new compounds. The transcriptomic and proteomic signatures of ChP-CSF organoids reveal a high degree of similarity to the ChP in vivo. Finally, the intersection of single-cell transcriptomics and proteomic analysis uncovers key human CSF components produced by previously unidentified specialized epithelial subtypes.

scholarly journals Mutagenesis of solvent-exposed amino acids in Photinus pyralis luciferase improves thermostability and pH-tolerance

2006 ◽  
Vol 397 (2) ◽  
pp. 305-312 ◽  
Author(s):  
G. H. Erica Law ◽  
Olga A. Gandelman ◽  
Laurence C. Tisi ◽  
Christopher R. Lowe ◽  
James A. H. Murray
Keyword(s):  
Amino Acids ◽  
Specific Activity ◽  
Green Light ◽  
Firefly Luciferase ◽  
Wild Type ◽  
Photinus Pyralis ◽  
Wild Type Enzyme ◽  
Ph Tolerance

Firefly luciferase catalyses a two-step reaction, using ATP-Mg2+, firefly luciferin and molecular oxygen as substrates, leading to the efficient emission of yellow–green light. We report the identification of novel luciferase mutants which combine improved pH-tolerance and thermostability and that retain the specific activity of the wild-type enzyme. These were identified by the mutagenesis of solvent-exposed non-conserved hydrophobic amino acids to hydrophilic residues in Photinus pyralis firefly luciferase followed by in vivo activity screening. Mutants F14R, L35Q, V182K, I232K and F465R were found to be the preferred substitutions at the respective positions. The effects of these amino acid replacements are additive, since combination of the five substitutions produced an enzyme with greatly improved pH-tolerance and stability up to 45 °C. All mutants, including the mutant with all five substitutions, showed neither a decrease in specific activity relative to the recombinant wild-type enzyme, nor any substantial differences in kinetic constants. It is envisaged that the combined mutant will be superior to wild-type luciferase for many in vitro and in vivo applications.

scholarly journals A novel PET tracer 18F-deoxy-thiamine: synthesis, metabolic kinetics, and evaluation on cerebral thiamine metabolism status

2020 ◽  
Author(s):  
Changpeng Wang ◽  
Siwei Zhang ◽  
Yuefei Zou ◽  
Hongzhao Ma ◽  
Donglang Jiang ◽  
...  
Keyword(s):  
High Performance ◽  
Specific Activity ◽  
High Accumulation ◽  
Metabolic Kinetics ◽  
Thiamine Metabolism ◽  
Pet Tracer ◽  
The Status ◽  
The Brain

Abstract Background: Some neuropsychological diseases are associated with abnormal thiamine metabolism, including Korsakoff-Wernicke syndrome and Alzheimer’s disease. However, in vivo detection of the status of brain thiamine metabolism is still unavailable and needs to be developed. Methods: A novel PET tracer of 18F-deoxy-thiamine was synthesized using an automated module via a two-step route. The main quality control parameters, such as specific activity, radiochemical purity, radiochemical concentration, were evaluated by high performance liquid chromatography (HPLC). Metabolic kinetics and brain level of 18F-deoxy-thiamine in mice and marmosets were studied by micro-positron emission tomography/computed tomography (PET/CT). In vivo stability, renal excretion rate, biodistribution of 18F-deoxy-thiamine in the mice were assayed using HPLC and γ-counter. Also, the correlation between the retention of cerebral 18F-deoxy-thiamine in 60 minutes after injection as represented by the area under the curve (AUC) and blood thiamine levels were investigated. Results: The 18F-deoxy-thiamine was stable both in vitro and in vivo. The uptake and clearance of 18F-deoxy-thiamine were quick in the mice. It reached the max standard uptake value (SUVmax) of 4.61±0.53 in the liver within 1 minute, 18.67±7.04 in the kidney within half a minute. The SUV dropped to 0.72±0.05 and 0.77±0.35 after 60 minutes of injection in the liver and kidney, respectively. After injection, kidney, liver, and pancreas exhibited high accumulation level of 18F-deoxy-thiamine, while brain, muscle, fat, and gonad showed low accumulation concentration, consistent with previous reports on thiamine distribution in mice. Within 90 minutes after injection, the level of 18F-deoxy-thiamine in the brain of C57BL/6 mice with thiamine deficiency by thiamine-deprived diet (TD) was 1.9 times higher than that in control mice, and was 3.1 times higher in ICR mice with TD than that in control mice. The AUC of the tracer in the brain of marmosets within 60 minutes was 29.33 ± 5.15 and negatively correlated with blood thiamine diphosphate levels (r = -0.985, p = 0.015).Conclusion: The 18F-deoxy-thiamine meets the requirements for ideal PET tracer for in vivo detecting the status of cerebral thiamine metabolism.

Studies on the toxicity of copper. I. The toxic action of copper in vivo and in vitro

1966 ◽  
Vol 166 (1004) ◽  
pp. 273-284 ◽  
Keyword(s):  
Microsomal Fraction ◽  
Specific Activity ◽  
Membrane Surface ◽  
High Specific Activity ◽  
Rapid Onset ◽  
Significant Inhibition ◽  
Low Concentrations ◽  
The Brain

With the object of throwing light upon the brain damage found in patients with Wilson’s disease (hepato-lenticular degeneration) due to the accumulation of copper, the effect of Cu 2+ has been investigated in pigeons. Subarachnoid injections of Cu 2+ (10 to 25 µ g) led to rapid onset of convulsions and death. These concentrations of Cu 2+ inhibited pigeon and rat b rain mitochondria; more organized tissue breis or slices showed no significant inhibition of oxygen up take at Cu +2 concentration inducing convulsions in vivo . Studies with radioactive copper ( 64 Cu) showed that the injected copper was widely distributed in the brain, though maximal near the site of injection. Centrifugation showed a high specific activity in the ATP -ase-rich microsomal fraction. Thorium in concentrations similar to Cu 2+ was not toxic. From this we suggest that the Cu 2+ does not alter the charge on some membrane surface. Since the effect of the copper is immediate, and since it does not affect respiration of slices in these low concentrations, we conclude that it is exerting its convulsive effect directly upon the cell surfaces.

scholarly journals Increase of essential amino acids in the bovine uterine lumen during preimplantation development

Reproduction ◽  
2011 ◽  
Vol 141 (5) ◽  
pp. 685-695 ◽  
Author(s):  
Anna E Groebner ◽  
Isabel Rubio-Aliaga ◽  
Katy Schulke ◽  
Horst D Reichenbach ◽  
Hannelore Daniel ◽  
...  
Keyword(s):  
Amino Acids ◽  
Essential Amino Acids ◽  
Peptide Transporter ◽  
Bovine Embryo ◽  
Endometrial Cells ◽  
Culture Model ◽  
Uterine Fluid ◽  
Liquid Chromatography Tandem Mass

Amino acids (AAs) are crucial for the developing conceptus prior to implantation. To provide insights into the requirements of the bovine embryo, we determined the AA composition of the uterine fluid. At days 12, 15, and 18 post-estrus, the uteri of synchronized pregnant and non-pregnant Simmental heifers were flushed for the analysis of 41 AAs and their derivatives by liquid chromatography–tandem mass spectrometry. The ipsilateral endometrium was sampled for quantitative PCR. In addition to a pregnancy-dependent increase of the essential AAs (P<0.01), we detected elevated concentrations for most non-essential proteinogenic AAs. Histidine (His) and the expression of the His/peptide transporter solute carrier 15A3 (SLC15A3) were significantly increased at day 18 of pregnancyin vivo. In addition,SLC15A3was predominantly stimulated by trophoblast-derived interferon-τ in stroma cells of anin vitroco-culture model of endometrial cells. Our results show an increased concentration of AAs most likely to optimally provide the elongating pre-attachment conceptus with nutrients.

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