A fluorimetric method for the determination of tryptophan in animal tissues

CERTAIN PARAMETERS OF THE HEMOSTASIS SYSTEM, AS WELL AS INDICATORS OF TRYPTOPHANE METABOLISM IN PATIENTS WITH CORONARY HEART DISEASE

The hemostasis system is a functional system of the human body that ensures the integrity and patency of the vessels of the circulatory system, prevents or stops bleeding, and also maintains the blood in a liquid state. The functioning of the hemostasis system is based on a balanced interaction between its coagulation, anticoagulation and fibrinolytic links. According to modern concepts, destabilization of hemovascular homeostasis is one of the main mechanisms of progression of coronary heart disease (CHD). Biologically active substances of endogenous origin can play the role of triggers of cardiovascular events, along with generally accepted factors such as obesity, arterial hypertension, diabetes and smoking. Establishing the nature of genesis factors and mechanisms of progression of cardiovascular symptoms will increase the probability of a positive prognosis for patients with coronary heart disease, which remains the most common cause of mortality in the population of developed countries. The purpose of this study was to find out the level of some biologically active substances, including certain factors of the coagulation cascade and the fibrinolysis system, parameters of tryptophan metabolism and heat shock proteins (namely, HPS 60 and HPS 70), in patients with coronary artery disease. 66 patients diagnosed with coronary artery disease took part in the study: 20 of them had a confirmed diagnosis of stable angina, 28 had progressive unstable angina, and 18 had myocardial infarction. The results of the study showed an increased production of prothrombotic mediators (Willebrand factor, serotonin) in the blood plasma of patients with coronary artery disease. An imbalance between tissue plasminogen activator and its inhibitor was also noted, which may be the main factor in reducing the fibrinolytic potential of blood plasma under cardiovascular events. It has been established that patients with coronary heart disease, regardless of the form of the disease, are characterized by a significant increase in the plasma content of heat shock protein, namely HPS 60. Such results suggest the possible involvement of this protein in the pathological reactions that occur during coronary heart disease, and the possibility of its use as a biomarker of cardiovascular diseases.

Enhancing selectivity in spectrofluorimetric determination of tryptophan by using graphene oxide nanosheets

Reaction of formaldehyde with amino acids followed by oxidation with hydrogen peroxide to produce a fluorophore Norharman product is well known and was used for the spectrofluorimetric determination of l-tryptophan (Trp). This study aimed to use graphene oxide (GO) to enhance the selectivity and sensitivity of Trp in presence of other amino acids and possible interfering compounds. Different parameters such as pH, temperature, incubation time, and concentrations of formaldehyde, H2O2 and GO were studied to optimize the condition of determination. Experimental data showed that the maximum fluorescence intensity was achieved in pH 7.0-9.0 phosphate buffer mixed with 7-10% (v/v) formaldehyde and 1-2% (v/v) H2O2 as oxidizing agent at 60°C for 1h. On the basis of calibration curve of various concentrations of Trp in the presence of 20 μg mL(-1) GO, the lower limit of detection (LOD) of Trp was determined as 0.092 nmol mL(-1) and the lower limit of quantification (LOQ) was 0.3 nmol mL(-1). The selectivity of Trp in presence of other amino acids and possible interfering compounds were studied with and without GO. The data obtained after inner filter effect corrections revealed that the selectivity of Trp in presence of amino acids and other possible interfering agents was improved in the range of 76-96%, compared with that in absence of GO. The enhancement of selectivity in the presence of GO indicates that the Trp and other amino acid and possible interfering compounds were adsorbed by GO, and the selective uptaking of Trp-by the reaction with formaldehyde followed by oxidation with H2O2 at 60°C with high selectivity and sensitivity was achieved successfully.

Studies on the mechanism of shock. Central serotoninergic neuron activity after trauma in the rat

An attempt has been made to assess the effect of injury (limb ischaemia, scald) on the central serotoninergic system of the rat by studying the effect of these injuries on the tryptophan concentration, the tryptophan hydroxylase activity and the metabolism of serotonin in the hypothalamus, mid-brain and hind-brain. The effects of a serotonin uptake inhibitor and an antagonist on the survival time and mortality rate after limb ischaemia have been examined as well as the effects of central lesions produced by the injection of 5.6- and 5.7-dihydroxytryptamine into a lateral cerebral ventricle and the i.p. injection of (+/-)-4-chloroamphetamine. A few changes indicative of increased activity in the central serotoninergic system were found--an increase in tryptophan hydroxylase activity after 4 h bilateral hind-limb ischaemia, better survival of fed rats pre-treated with 5,6-dihydroxytryptamine--but for the most part the changes were not as great as those produced by starving or exposure to cold. Hence the effect of trauma on this system seems small.

The effects of diet, lipolysis and limb ischaemia on the distribution of plasma tryptophan in the rat

A non-linear relationship between the plasma non-esterified fatty acid concentration and the percentage of free plasma tryptophan was found in rats in different nutritional states, although non-esterified fatty acids are not the only factors determining the percentage of free tryptophan. This relationship was not seen in rats injured by limb ischaemia. The effect of drugs causing rapid increases in the plasma non-esterified fatty acid concentration was also studied. Isoprenaline decreased the total plasma tryptophan concentration. Dichloroisoprenaline caused a sustained increase in the plasma non-esterified fatty acid concentration which was accompanied by an increase in the concentration of free plasma tryptophan and followed by a fall in the concentration of total tryptophan. The loss of tryptophan from the plasma was attributed to an altered distribution of tryptophan in the extracellular space rather than to increased metabolism. This interpretation was supported by determinations of the irreversible disposal rate of plasma tryptophan which in uninjured rats was unaffected by the concentration of free plasma tryptophan. In the injured rats this rate was unaltered during limb ischaemia but was decreased after removal of the tourniquets; increased competition for tissue entry by other neutral amino acids and the fall in body temperature could be factors in this fall.