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Systemic gabapentin and S(+)-3-isobutyl-gamma-aminobutyric acid block secondary hyperalgesia.

Gabapentin (GBP) and S(+)-3-isobutyl-gamma-aminobutyric acid (IBG) are anticonvulsant agents which are effective against many clinical and experimental neuropathic pain states. We examined the efficacy of these agents in a new rat model of secondary mechanical hyperalgesia generated by a mild thermal injury. Under brief halothane anesthesia, an injury was induced by applying one heel to a hot surface (52.5 degreesC) for 45 s. GBP, IBG or saline was injected i.p. just prior to the injury. Mean mechanical withdrawal threshold (MWT) was determined using von Frey hairs before and at 30 min intervals for 3 h following the injury. MWT outside the injury area decreased post-injury (secondary hyperalgesia, allodynia), but primary (site of injury) mechanical hyperalgesia was not observed. Secondary hyperalgesia exhibited a tendency toward recovery over time. Time to onset of the anti-allodynic effect of GBP was 30-60 min. The minimum effective GBP dose was 100 mg/kg; 300 mg/kg GBP totally inhibited the drop in MWT, but was accompanied by pronounced sedation. Anti-allodynic effects of IBG were apparent at the first post-injury measure of MWT (30 min). Thirty milligrams per kilogram was the minimum effective dose; 100 mg/kg IBG totally blocked the allodynia with minimal side effects. Our findings demonstrate a dose-dependent blockade of the mechanical sensitivity caused by a mild thermal injury by both GBP and IBG. Results indicate that IBG is more effective than GBP in this model at doses which do not cause sedation. These observations support the suggested use of these or related gamma-amino acid analogues as an effective treatment for post-operative pain.

Acetates↗

Tranexamic acid and traumatic hyphaema. A prospective study.

112 patients with traumatic hyphaema were investigated prospectively over a period of 3 years. 53 had conservative treatment and 59 tranexamic acid treatment. They were hospitalized, but fully mobilized. Both groups were given supplementary local therapy with glucocorticoids and mydriatics as well as monocular patching. In neither group was any re-bleeding seen. The resorption of blood was delayed in the tranexamic treated patients, which may be taken as indirect proof of the efficacy of the treatment. The longer persistence of blood in the anterior chamber in the tranexamic acid treated group caused no complication. The treatment was well tolerated. In both departments treatment with tranexamic acid had replaced the bed rest treatment.

Adolescent↗

[Possibilities of immunostimulation in oncology. I. In vitro functional activity of rat peritoneal macrophages in presence of tranexamic acid].

Peritoneal macrophages from Wistar rats were examined in vitro to evaluate the effects of tranexamic acid on their spreading activity. The results suggested that some concentrations of the drug (10(-5), 10(-6)) may activate in vitro the function of the peritoneal adherent cells. This finding support the concept that tranexamic acid enhances host resistance by a mechanism to be elucidated.

Adjuvants, Immunologic↗

[Further clinical observations on the treatment of noncirrhotic alcoholic liver disease].

After an experiment comparative clinical study, the authors could point out that biohumoral, semeiological and histopathological alterations in alcoholic hepatopaties, can retrograde only by the suspending the pathogenic alcoholic noxa, and that the improvement can be accelerated by a contemporary administration of a. cycloxilic, thiazolidine carboxylic of argynin, EPL: all antisteatosis substances helping the oxidation of alcohol and fat acids, potentiating the rigeneration of the hepatocyte and resolving the hepatosecretory function alterated.

Adult↗

New bradykinin analogues substituted in positions 7 and 8 with sterically restricted 1-aminocyclopentane-1-carboxylic acid.

A sterically constrained non-coded amino acid, 1-aminocyclopentane-1-carboxylic acid (Apc), was introduced in position 7 or 8 of the bradykinin (BK) B(2) receptor antagonist, [D-Arg(0), Hyp(3), Thi(5, 8), D-Phe(7)]BK, previously synthesized by Stewart's group. This modification is believed to reduce the flexibility of the peptides, thereby forcing the peptide backbone and side chains to adopt specific orientations. Apc substitution was combined with acylation of the N-terminus with 1-adamantaneacetic acid (Aaa). The activity of four new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated that the Apc residue inserted in position 7 led to a reduction of antagonistic properties in the rat uterus assay or even restored the agonism in the blood pressure test, whereas Apc at position 8 enhanced antagonistic potency in both the tests. In both cases, acylation of the N-terminus led to the enhancement of the antagonistic potency. On the basis of these findings, new potent and selective B(2) blockers might be designed.

Amino Acids, Cyclic↗

Novel cyclopropyl beta-amino acid analogues of pregabalin and gabapentin that target the alpha2-delta protein.

As part of a program aimed at generating compounds with affinity for the alpha(2)-delta subunit of voltage-gated calcium channels, several novel beta-amino acids were prepared using an efficient nitroalkane-mediated cyclopropanation as a key step. Depending on the ester that was chosen, the target amino acids could be prepared in as few as three steps. The cyclopropyl amino acids derived from ketones proved to be potent binders of the alpha(2)-delta subunit of voltage-gated calcium channels, but did not interact with the large neutral amino acid system L (leucine) transporter. Anticonvulsant effects were observed in vivo with compound 34 but only after intracerebroventricular (icv) administration, presumably due to inadequate brain concentrations of the drug being achieved following oral dosing. However, pregabalin 1 was active in the DBA/2 model after oral (and icv) dosing, supporting a hypothesis that active transport is a prerequisite for such zwitterionic species to cross the blood-brain barrier.

Administration, Oral↗

Down-regulation of N-type voltage-activated Ca2+ channels by gabapentin.

1. Although the cellular and molecular mechanisms of the anticonvulsant action of gabapentin (GBP) remain incompletely described, in vitro studies have shown that GBP binds to the alpha2delta subunit of the high voltage-activated (HVA) Ca2+ channels. 2. In this report, we analyzed the effects of GBP on the functional expression of HVA Ca2+ channels in the PC12 cell line model system. Negligible inhibition of Ca2+ channel activity was observed after acute treatment, but a significant decrease in Ca2+ current amplitude was promoted by chronic exposure to GBP. 3. Consistent with this, radioligand binding experiments showed a comparable reduction in the total number of membrane HVA N-type channels after GBP treatment.

Acetates↗

Purification and functional characterization of glutamate-1-semialdehyde aminotransferase from Chlamydomonas reinhardtii.

The formation of delta-aminolevulinic acid, the first committed precursor of chlorophyll biosynthesis, occurs in the chloroplast of plants and algae by the C5-pathway, a three-step, tRNA-dependent transformation of glutamate. Previously, we reported the purification and characterization of the first two enzymes of this pathway, glutamyl-tRNA synthetase and Glu-tRNA reductase from the green alga Chlamydomonas reinhardtii (Chen, M.-W., Jahn, D., Schön, A., O'Neill, G. P., and Söll, D. (1990) J. Biol. Chem. 265, 4054-4057 and Chen, M.-W., Jahn, D., O'Neill, G. P., and Söll, D. (1990) J. Biol. Chem. 265, 4058-4063). Here we present the purification of the third enzyme of the pathway, the glutamate-1-semialdehyde aminotransferase from C. reinhardtii. The enzyme was purified from the membrane fraction of a whole cell extract employing four different chromatographic separations. The apparent molecular mass of the protein was approximately 43,000 Da as analyzed by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis, by nondenaturing rate zonal sedimentation on glycerol gradients, and by gel filtration. By these criteria, the enzyme in its active form is a monomer of 43,000 Da. In the presence of pyridoxal 5'-phosphate, purified glutamate-1-semialdehyde aminotransferase converts synthetic glutamate 1-semialdehyde to delta-aminolevulinic acid. The enzyme is inhibited by gabaculine and aminooxyacetate, both typical inhibitors of aminotransferases. The purified glutamate-1-semialdehyde aminotransferase successfully reconstitutes the whole C5-pathway in vitro from glutamate in the presence of purified glutamyl-tRNA synthetase, glutamyl-tRNA reductase, Mg2+, ATP, NADPH, tRNA, and pyridoxal 5'-phosphate.

Aminooxyacetic Acid↗

Special considerations with regard to the dosage of tranexamic acid in patients with chronic renal diseases.

Tranexamic acid is a potent antifibrinolytic drug frequently used in the treatment of haematuria and a number of other haemorrhagic conditions. Since it is eliminated mainly in the urine, the drug accumulates in patients with uraemia. The excretion of tranexamic acid in patients with renal failure has been investigated and dosage recommendations are given for tranexamic acid therapy in cases of renal failure.

Biological Availability↗

The role of anticonvulsants in preventive migraine therapy.

The mainstay of migraine treatment is pharmacotherapy. There have been numerous medications used to prevent migraine headaches, including b-blockers, calcium-channel blockers, anticonvulsants, and nonsteroidal anti-inflammatory drugs. Sodium valproate is the only antiepileptic drug approved by the Food and Drug Administration for migraine prevention. Newer antiepileptics, including gabapentin and topiramate, are being evaluated for their role in preventive therapy. The mechanism of action of antiepileptics is not fully understood, but they all share a common role in enhancing gamma-aminobutyric acid-mediated inhibition. This article reviews the role of anticonvulsants in preventive migraine therapy.

Acetates↗

Tranexamic acid in the prevention of periventricular haemorrhage.

Increased fibrinolytic activity in the ganglionic eminence of the preterm human brain has been proposed as a factor in the aetiology of periventricular haemorrhage. The effect of tranexamic acid in preventing periventricular haemorrhage was evaluated in 100 infants in a double blind, randomised controlled trial. Haemorrhages developed in 22 infants who received tranexamic acid and in 20 of those who received placebo. A significant reduction in fibrin degradation products in treated infants was seen. Our study suggests that excessive fibrinolytic activity is not an important factor in the aetiology of periventricular haemorrhage and that treatment with tranexamic acid will not prevent its occurrence.

Cerebral Hemorrhage↗

Pulmonary embolism: emboli and fibrinolysis inhibition in isolated canine lungs.

The effect of fibrinolysis inhibition with tranexamic acid on pulmonary microvascular permeability during glass bead embolization was investigated in the isolated lung. Lung lobes from nonheparinized dogs were treated in vivo with the equivalent of 0.6 g/kg 100 microns glass bead emboli alone, emboli after tranexamic acid, tranexamic acid alone, or the bead vehicle alone. After 40-50 min, the lobes were isolated for ex vivo perfusion with heparinized autologous blood. There were no changes in any parameter over the 120-min perfusion period. Blood flow at 120 min was decreased after both emboli alone and emboli with tranexamic acid, reflecting an increase in vascular resistance compared with the Tween or tranexamic acid controls. Furthermore, tranexamic acid increased the ratio of pre- to postcapillary resistance in embolized lobes compared with that after emboli alone or in the Tween or tranexamic acid controls. The isogravimetric capillary pressure and the osmotic reflection coefficient were not significantly decreased by tranexamic acid compared with those after emboli alone; however, it did result in an increase in the capillary filtration coefficient compared with that after emboli alone or in the control groups. We conclude that although fibrinolysis inhibition does not clearly exacerbate the lung injury seen after emboli, the tranexamic acid-induced changes in hemodynamics would tend to accelerate edema formation.

Animals↗

[Tranexamic acid in the prevention of oropharyngeal radiomucositis].

The therapeutic effect of tranexamic acid in prevention of radiomucositis has been evaluated in a double blind study. The results suggest that tranexamic acid can be the useful for the treatment of radiomucositis in head and neck cancer patients submitted to radiotherapy.

Cyclohexanecarboxylic Acids↗