High-performance liquid chromatography of guanidino compounds using benzoin as a pre-column fluorescent derivatization reagent

Fluorometric determination of guanidino compounds by new postcolumn derivatization system using reversed-phase ion-pair high-performance liquid chromatography.

High-performance liquid chromatographic analyser for guanidino compounds using benzoin as a fluorogenic reagent.

Recent developments in amino acid analysis by gas-liquid chromatography.

Guanidinosuccinic acid (GSA) is one of the earliest uremic toxins isolated and its toxicity identified. Its metabolic origins have remained obscure until recently when a series of studies showed that it arose from the oxidation of argininosuccinic acid (ASA) by free radicals. The stimulus for this oxidation, occurring optimally in the presence of the failed kidney, is the rising level of urea which, through enzyme inhibition, results in a decline in hepatic levels of the semi-essential amino acid, arginine. It is further noted that concentrations of GSA in both serum and urine decline sharply in animals and humans exposed to the essential amino acid, methionine. In this review the argument is advanced that uremics suffer from a defective ability to generate methyl groups due to anorexia, dietary restrictions and renal protein leakage. This leads to the accumulation of homocysteine, a substance known to produce vascular damage. Even in healthy subjects intake of choline together with methionine is insufficient to satisfy total metabolic requirements for methyl groups. In end-stage renal disease, therefore, protein restriction contributes to the build-up of toxins in uremia. Replacement using specific amino acid mixtures should be directed toward identified deficiencies and adequacy monitored by following serum levels of the related toxins, in this case GSA and homocysteine.

Methyl group deficiency and guanidino production in Uremia

We present a method for separating and measuring guanidino acids by gas—liquid chromatography. Compared to ion-exchange techniques, this system is faster, more sensitive, requires smaller sample volumes, is independent of colorimetric reactions, and permits simultaneous determination of both amino and guanidino acids. N -Trifluoroacetyl- n -butyl esters are formed and then are separated by using a column containing a mixed silicone liquid phase coated on Chromosorb W-HP. Analytical recoveries from plasma ranged from 86 to 112% and were optimal when purification and derivatization were done without prior protein precipitation. Speculations as to the cause of this interference by protein include coprecipitation, protein-binding, and cyclization of the guanidines in the acids used for denaturation. Evidence presented suggests that all three occur: ultrafiltrability is diminished in the presence of protein and nuclear magnetic resonance demonstrates cyclization of some of these esters.

Gas-liquid chromatographic measurement of guanidino acids.

Among the many disturbances encountered in uremia are encephalopathy, erythrohemolysis, thrombaesthenia, and pyridoxine inhibition. Studies suggest that guanidino compounds, several of which are demonstrably increased in uremia,14 may be implicated in this toxicity. Natelson and Sherwin’ have shown that a number of these potential toxins, notably guanidinosuccinic acid (GSA), guanidine (G), methyl guanidine (MG), canaline, and canavanine,”’ originate in a pathway that parallels the urea cycle and is initiated by a cytochrome P-.QSO-dependent, mixed-function, microsomal oxidase. This report presents evidence in support of this hypothesis. Rats weighing 200-300 g were injected intraperitoneally for 4 days with 15 mg phenobarbital in 5 ml sterile water. On the fourth day we added 1.25 mmoles of methionine and/or 10 mmoles of urea. Control studies included animals that were either uninjected or received urea alone. Having demonstrated that GSA is a metabolically inert by-product,” we used the quantitative daily output of GSA calculated per milligram of creatinine as a marker reflecting activity of the guanidine cycle. The results are shown in TABLES 1 and 2 reported in terms of the ratio of experiment-to-control as labeled. Phenobarbital is a recognized inhibitor of the mixed-function oxidases acting competitively.” It is also an enzyme activator and has the disadvantage of an “escape” phenomenon as the buildup of enzyme surpasses the excess of substrate. This can be

The Effect of Inhibitors of Cytochrome P‐450 Microsomal Enzymes on the Biosynthesis of Potential Uremic Toxins

Disturbances in nitrogen balance are the hallmark of renal insufficiency. More sophisticated studies indicate that this is not simply a matter of balance. While failure to excrete adequate quantities may be the initiating event, a variety of adaptions and compensatory phenomena complicate the picture.

The Guanidine Cycle

Methionine and the Control of Creatine Synthesis

Aim: The purpose of this research is to assess the antibiotic prescription analysis of inpatients at a tertiary care hospital. Methods: The Department of Pharmacology conducted this prospective investigation. We examined the source of information for relevant features such as antimicrobial dose, frequency, and duration of antimicrobial usage, as well as whether or not such use was indicated by recorded culture sensitivity reports. A possible infective aetiology was evaluated if the patient showed any of the following symptoms prior to study inclusion: fever, elevated leukocyte count, signs and symptoms of infection of a specific organ system, and sepsis. Results: Antimicrobials were prescribed to 100 (43.48 percent) of the 230 patients. The referral note was the most often utilised source for obtaining information on antibiotic prescription. The prescription habits of these individuals were studied further. 59 patients (59%) were males, whereas 41 patients (41% were women). The research participants' mean (SD) age was 48.25 12.55 years. The most patients were between the ages of 35 and 45. (40 percent). 58 patients (58%) were recommended by public sector healthcare facilities, whereas 42 (42%) were referred by private clinics. Ceftriaxone and amoxicillin-clavulanic acid were the most often given medications (21 percent and 17 percent, respectively). Piperacillin-tazobactam was then administered to 12 (12%) of the patients. More than 57 percent of patients were given four antibiotics. Antibiotics with a broad range of action accounted for 70 percent of prescriptions. Conclusion: The results of this research aided in the development of several modules of an educational intervention tailored for healthcare settings with limited or no access to antimicrobial stewardship training. 

To assess the antibiotic prescription analysis of inpatients at a tertiary care hospital

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