Release of ( 3 H)noradrenaline and ( 3 H)dopamine from field stimulated cerebral cortex slices. Effect of tyrosine hydroxylase and dopamine- -hydroxylase inhibition

Rat cerebral cortex slices were incubated in vitro with [³H]dopamine (DA) or [³H]noradrenaline (NA) (10^?7M), superfused by fresh buffer and stimulated by an electric field. The stimulation-induced overflow of [³H]DA and [³H]NA was determined. In slices from untreated rats about 16 ng [³H]NA/g tissue was formed from [³H]DA, corresponding to about 5 per cent of the endogenous NA concentration. Stimulation markedly enhanced the overflow of [³H]NA. The [³H]NA newly formed from [³H]DA was overflowing to a greater extent than [³H]NA previously taken up from the incubation medium, indicating a preferential release of newly synthesized transmitter. The stimulation-induced overflow of [³H]DA and [³H]NA was increased in slices of rats pretreated with a tyrosine hydroxylase inhibitor (H44/68). It seems that depletion of the endogenous NA stores of central NA neurons by tyrosine hydroxylase inhibition makes the [³H]cate-cholamines more available for release. Pretreatment of the rats with the DA-β-hydroxylase inhibitors FLA63 or FLA69 considerably diminished the formation of [³H]NA from [³H]DA. Stimulation markedly enhanced the overflow of [³H]DA indicating that DA can act as a ‘false transmitter’ in central NA neurons after DA-β-hydroxylase inhibition.     

Relationship Between Amino Sugars and Meat Microbial Quality

The amino sugar content of spoiling beef increased with the microbial count and appeared to be responsible for the increased hydration capacity of spoiled meats.     

Concentrations of Amino Acids in Extracellular Fluid After Opening of the Blood-Brain Barrier by Intracarotid Infusion of Protamine Sulfate

Abstract: This article evaluates the influence of an opening of the blood-brain barrier (BBB) on compounds in brain extracellular fluid. The concentrations of amino acids and some other primary amines were determined in dialysates sampled from the right parietal cortex of rats before and after an intracarotid infusion of protamine sulfate. Extravasated plasma proteins were visualized by Evans blue/albumin and immunohistochemistry. CSF albumin— an indicator of blood-CSF barrier opening—was quantified with immunoelectrophoresis. The brains were macroscopically edematous after 10 mg but not after 5 mg of protamine sulfate. The higher dose led to a 50% death rate. The concentrations of amino acids did not change 10 min after the BBB opening. No significant alterations in the amino acid concentrations were observed after the lower dose. The concentrations of glutamate, aspartate, GABA, glycine, taurine, and phosphoethanolamine increased significantly within 50–80 min after the infusion of 10 mg of protamine sulfate. CSF albumin levels were significantly increased 1 h after infusion. We conclude that a dysfunction of the BBB, of a degree known to induce brain edema (10 mg of protamine sulfate), significantly increases the extracellular concentration of excitatory amino acids, GABA, taurine, and phosphoethanolamine in the extracellular space.     

Effects of Prostaglandin E2 and Capsaicin on Behavior and Cerebrospinal Fluid Amino Acid Concentrations of Unanesthetized Rats: A Microdialysis Study

Abstract: Prostaglandin E₂ (PGE₂) delivered to the spinal cord produces an increased sensitivity to noxious (hyperalgesia) and innocuous (allodynia) stimuli. The mechanisms that underlie this effect remain unknown, but a PGE₂-evoked enhancement of spinal neurotransmitter release may be involved. To address this hypothesis, we examined the effect of PGE₂ on CSF concentrations of amino acids and also the modulatory effect of PGE₂ on capsaicin-evoked changes of spinal amino acid concentrations using a microdialysis probe placed in the lumbar subarachnoid space. Amino acids were quantified using HPLC with fluorescence detection. Addition of 1 mM, but not 10 or 100 µM, PGE₂ to the perfusate for a 10-min period (flow rate, 5 µl/min) evoked an immediate increase (80–100%) in glutamate (Glu), aspartate (Asp), taurine (Tau), glycine (Gly), and γ-aminobutyric acid (GABA) concentrations. Similarly, capsaicin infusion (0.1–10 µM) induced a dose-dependent increase in Glu, Asp, Tau, Gly, GABA, and ethanolamine levels. Significant increases in amino acid levels evoked by PGE₂ or capsaicin were associated with a touch-evoked allodynia. The combination of PGE₂ (10 µM) and capsaicin (0.1 or 1.0 µM) at concentrations that individually had no effect together evoked a significant increase (60–100%) in Glu, Asp, Tau, Gly, and GABA concentrations and produced tactile allodynia. These data demonstrate that spinally delivered PGE₂ or capsaicin substantially elevates CSF concentrations of both excitatory and inhibitory amino acids. The capacity of PGE₂ to enhance and prolong capsaicin-evoked amino acid concentrations may be one of the mechanisms by which spinal PGE₂ produces hyperalgesia and allodynia.     

The influence of early protein-calorie malnutrition on neuronal and glial protein synthesis

The effect of pre- and postnatal undernutrition, produced according to the method of Chow and Lee (3), on the rate of protein synthesis in the brains of rats 11, 21, 34 and 90 days of age was studied by measuring the incorporation ofl-[¹⁴C]valine in vivo andl-[³H]lysine in vitro. Both in vivo and in vitro experiments were performed with high concentration of the precursor to decrease the effects of pool variations and protein degradation. Particular interest was given to the effects of this form of early protein-calorie malnutrition (PCM) on neuronal and glial cells which were isolated from the brains by gradient centrifugation. Brain protein synthesis measured in vivo which showed a peak at 21 days in both animal series, was depressed by PCM at 11 days but stimulated at 34 days of animal age. Small effect was observed in the 90-day-old animals. A similar response as in whole brain was seen for neuronal cells, while glial cells showed a different reaction. Studies of in vitro protein synthesis did not reveal appreciable effects of undernutrition in whole brain. Both neuronal and glial cells showed a moderate but not statistically significant elevation of protein synthesis in animals subjected to early PCM.     

Neuronal and Glial Marker Proteins in the Evaluation of the Protective Action of MK 801

A quantitative dot immunobinding procedure was used to quantify glial [the S-100 protein and the glial fibrillary acidic (GFA) protein] and neuronal (the 68- and 200-kDa neurofilament polypeptides, neuron-specific enolase, and neuronal cell adhesion molecule) markers. A single intraperitoneal administration of 10 mg/kg of MK 801 blocked the increase of glial parameters and the decrease in content of neuronal marker proteins that occurred as the response to an N-methyl-D-aspartate (NMDA) lesion in the rat hippocampus. The degradation products of GFA protein and the 68-kDa neurofilament polypeptide that were induced by the NMDA lesion did not appear after MK 801 treatment. This study shows that brain-specific proteins are a set of precise tools for the evaluation of neuroprotective effects of antagonists to excitatory amino acids.     

Synaptosomal phospholipid pool in rabbit brain and its effect on GABA uptake

Rabbit synaptosomes have been used to study the effect of the base-exchange reaction in membrane phospholipids on -aminobutyric acid (GABA) transport in vitro. The uptake of GABA was measured after a base-exchange reaction with ethanolamine, choline, orl-serine and after subsequent displacement of these exchanged moieties from lipid by bases of similar or different structures which were added to the synaptosomal medium. Serine incorporation stimulated GABA transport, but its displacement from membrane lipid by choline or ethanolamine induced an inhibition of GABA transport. Ethanolamine incorporation inhibited GABA transport, but its displacement by serine or choline resulted in stimulation of GABA uptake. Choline incorporation also inhibited GABA transport, although less than ethanolamine. The pool size of synaptosomal phospholipids, presumably involved in GABA uptake, accounted for 0.2 to 10% of the total content of membrane phospholipid. Thus, alteration of phospholipid compositior by exchange of the lipid hydrophilic head-groups influences the extent GABA uptake into rabbit synaptosomes.     

Cyclic AMP formation of isolated human corpora lutea in response to HCG - interference by PGF2 alpha.

Human corpora lutea of defined ages were excised at operation, cut into pieces and incubated in the presence of HCG, PGF2 alpha and PGE2 alone or in combination. Following incubation cAMP formation in tissue and medium was determined. HCG-stimulated tissue cAMP content was most pronounced at a corpus luteum age of 7-10 days after ovulation. This stimulation was antagonized by PGF2 alpha in corpora lutea older than 6 days. PGE2 stimulated cAMP formation per se and this effect was more pronounced when HCG and PGE2 were combined. A possible role for PGF2 alpha as a luteolytic substance in the human is suggested.     

DMSO Represses Inflammatory Cytokine Production from Human Blood Cells and Reduces Autoimmune Arthritis

Dimethyl sulfoxide (DMSO) is currently used as an alternative treatment for various inflammatory conditions as well as for cancer. Despite its widespread use, there is a paucity of data regarding its safety and efficacy as well as its mechanism of action in human cells. Herein, we demonstrate that DMSO has ex-vivo anti-inflammatory activity using Escherichia coli- (E. coli) and herpes simplex virus-1 (HSV-1)-stimulated whole human blood. Specifically, we found that between 0.5%– 2%, DMSO significantly suppressed the expression of many pro-inflammatory cytokines/chemokines and prostaglandin E₂ (PGE₂). However, a significant reduction in monocyte viability was also observed at 2% DMSO, suggesting a narrow window of efficacy. Anti-inflammatory concentrations of DMSO suppressed E. coli-induced ERK1/2, p38, JNK and Akt phosphorylation, suggesting DMSO acts on these signaling pathways to suppress inflammatory cytokine/chemokine production. Although DMSO induces the differentiation of B16/F10 melanoma cells in vitro, topical administration of DMSO to mice subcutaneously implanted with B16 melanoma cells was ineffective at reducing tumor growth, DMSO was also found to block mouse macrophages from polarizing to either an M1- or an M2-phenotype, which may contribute to its inability to slow tumor growth. Topical administration of DMSO, however, significantly mitigated K/BxN serum-induced arthritis in mice, and this was associated with reduced levels of pro-inflammatory cytokines in the joints and white blood cell levels in the blood. Thus, while we cannot confirm the efficacy of DMSO as an anti-cancer agent, the use of DMSO in arthritis warrants further investigation to ascertain its therapeutic potential.