Ontogenetic differences in convulsive action and cerebral uptake of uremic guanidino compounds in juvenile mice

Severe Encephalatrophy and Related Disorders From Long-Term Ketamine Abuse: A Case Report and Literature Review

Ketamine is a glutamate N-methyl D-aspartate receptor antagonist and an anaesthetic agent that has been effectively used to treat depression. However, ketamine has also been increasingly used for recreational purposes. The dissociative side-effects of ketamine use, such as hallucinations, are the reason for abuse. Additionally, long-term ketamine abuse has been highly associated with liver-gallbladder and urinary symptoms. The present study reports the case of a 28-year-old young male adult with an 8-year history of daily inhalation of ketamine. We investigated the association between ketamine abuse and the mechanism of its adverse effects, particularly encephalatrophy, and attempted to find a link between these disorders. These results would help us to better understand ketamine usage, ketamine abuse effects and the addictive mechanism. To the best of our knowledge, the present case is the first report of severe brain atrophy related to ketamine abuse. Details of the patient are presented and the mechanism of the encephalatropy-associated ketamine abuse is discussed. Furthermore, organ dysfunction following chronic ketamine abuse may indicate that the side effects are the result of comprehensive action on multiple regions in the brain.

Overexpression of arginase alters circulating and tissue amino acids and guanidino compounds and affects neuromotor behavior in mice

Arginine is an intermediate of the ornithine cycle and serves as a precursor for the synthesis of nitric oxide, creatine, agmatine and proteins. It is considered to be a conditionally essential amino acid because endogenous synthesis only barely meets daily requirements. In rapidly growing suckling neonates, endogenous arginine biosynthesis is crucial to compensate for the insufficient supply of arginine via the milk. Evidence is accumulating that the intestine rather than the kidney plays a major role in arginine synthesis in this period. Accordingly, ectopic expression of hepatic arginase in murine enterocytes by genetic modification induces a selective arginine deficiency. The ensuing phenotype, whose severity correlates with the level of transgene expression in the enterocytes, could be reversed with arginine supplementation. We analyzed the effect of arginine deficiency on guanidine metabolism and neuromotor behavior. Arginine-deficient transgenic mice continued to suffer from an arginine deficiency after the arginine biosynthetic enzymes had disappeared from the enterocytes. Postweaning catch-up growth in arginine-deficient mice was characterized by increased levels of all measured amino acids except arginine. Furthermore, plasma total amino acid concentration, including arginine, was significantly lower in adult male than in adult female transgenic mice. Decreases in the concentration of plasma and tissue arginine led to significant decreases in most metabolites of arginine. However, the accumulation of the toxic guanidino compounds, guanidinosuccinic acid and methylguanidine, corresponded inversely with circulating arginine concentration, possibly reflecting a higher oxidative stress under hypoargininemic conditions. In addition, hypoargininemia was associated with disturbed neuromotor behavior, although brain levels of toxic guanidino compounds and ammonia were normal.

Biochemical, histological and behavioral consequences of nephrectomy in young and aged mice

BACKGROUND

This study investigates the effect of nephrectomy in young and aged mice on some biochemical, histological and behavioural aspects.

METHODS

Each age group, 2- and 12-months-old, comprised a sham-operated group, a unilaterally nephrectomized group and a subtotally nephrectomized group. Consequences of nephrectomy were examined 10 days postsurgery on urea and guanidino compound levels in body fluids and brain; the remaining kidney by light-microscopic examination; and learning and memory abilities using the Morris water maze task.

RESULTS

Effect of nephrectomy on urea and guanidino compound levels in plasma, urine and brain was significantly more pronounced in the young age group. Some guanidino compounds show a tendency to decrease with aging in the sham-operated group and the two nephrectomized groups. Higher compensatory kidney hypertrophy was found in younger nephrectomized mice whereas in older mice glomerular mesangial expansion was a common feature. Finally, young mice with subtotal nephrectomy displayed a slight but significant impairment in memory and learning; whilst old nephrectomized mice manifested no impairment.

CONCLUSIONS

Nephrectomy induces more changes in younger mice than in older mice as observed in higher variation of urea and guanidino compound levels, glomerular volume and kidney hypertrophy and decline in spatial learning and memory.