Endovascular management of isolated iliac artery aneurysms.

Isolated iliac artery aneuryms are detected increasingly as a result of expanding use of diagnostic imaging, and screening programmes. This present review describes endovascular solutions for the management of isolated iliac artery aneurysms. This was a review of the published literature on endovascular treatment of iliac aneurysms. Most of the papers were case series, and there are no randomized studies. Aneurysms of the common iliac artery are most common, followed by internal, then external iliac aneurysms. Indications for intervention remain unclear, but are generally based on diameter. Endovascular solutions exist for at least half the aneurysms that required treatment, including as an emergency. Often a standard bifurcated solution, as for abdominal aortic aneurysm is indicated, however, there are a number of other novel solutions to deal with variable anatomy. Endovascular treatment of iliac aneurysms is less painful and reduces hospital stay. However, outcome data remain limited, and formal comparison with open surgery is awaited.

Renal and gastrointestinal amyloidosis in an HIV-infected injection drug user.

A 30-year-old HIV-infected intravenous drug user presented with sepsis, acute renal failure, oedema, proteinuria and iron deficiency anaemia. After extensive investigation, a diagnosis of reactive systemic AA (amyloid, serum amyloid A protein) amyloidosis was made on the basis of renal, gastric and duodenal biopsies.

The role of insulin, corticosterone and other factors in the acute recovery of muscle protein synthesis on refeeding food-deprived rats.

Measurements of changes in muscle protein synthesis, insulin and corticosterone in vivo in refed food-deprived rats, some after pretreatment with anti-insulin serum or corticosterone, indicate that the acute increase in protein synthesis (20-40 min) requires (a) insulin, (b) a fall in corticosterone, since corticosterone acts at least in part by blocking insulin action, and (c) at least one other independent anabolic factor.

Time course of the effect of catabolic doses of corticosterone on protein turnover in rat skeletal muscle and liver.

The time course of the response of protein synthesis in muscle and liver to catabolic doses of corticosterone (10 mg/day per 100 g body wt.) was studied in vivo in growing rats over a 12-day period. The rate of protein synthesis in muscle and liver and the rate of actomyosin synthesis in muscle were measured by the phenylalanine-flooding technique, and 3-methylhistidine (N tau-methylhistidine) synthesis was measured by injection of labelled histidine. 3-Methylhistidine concentrations in tissue free pools and urinary excretion were also measured to compare directly with the rate of muscle protein degradation determined as the difference between synthesis and growth each day during the treatment. The overall rate of protein synthesis in muscle fell gradually over the first 4 days, reaching a rate after 5 days that was 36% of the initial rate, and this lower rate was then maintained for the following week. This decrease in the overall rate was accompanied with changes in the relative rate of synthesis in muscle proteins, since during the first 4 days there was a disproportionate decrease in the rate of actomyosin synthesis, and specifically 3-methylhistidine synthesis. In the latter case the synthesis rate was decreased to only 4% of its initial rate after 4 days. These changes in protein synthesis in muscle were accompanied by a transient increase in the rate of protein degradation, which was more than doubled on days 2 and 3 of treatment but which returned to the original rate on day 5, and a similar pattern of response was indicated by urinary 3-methylhistidine excretion, which also exhibited a transient increase. Thus in this case 3-methylhistidine excretion and measured rates of protein degradation in muscle do correlate. The transient effects of the glucocorticoids on degradation compared with the sustained effect on synthesis suggest that these two responses are achieved by different mechanisms. The hepatic size and protein mass were increased by the treatment, and protein synthesis was well maintained until after 12 days, when the rate was suppressed. Although the fractional synthesis rate was transiently increased for 24 h, it is argued that the enlarged liver most likely reflects a decrease in protein degradation resulting from the increased amino acid supply to the liver. This would result from the cessation of muscle growth while dietary supply was maintained.

L-Phenylalanine inhibition of muscle pyruvate kinase.

The allosteric inhibition of M1-type pyruvate kinase from rabbit skeletal muscle by phenylalanine is reciprocally dependent on Mg2+ and phosphoenolpyruvate concentrations. At pH 8, phenylalanine acts as a competitive inhibitor with respect to Mg2+ and phosphoenolpyruvate, and vice versa. Phenylalanine introduces sigmoidicity into the dependence of the reaction velocity on [Mg2+]. In vitro kinetic analysis indicates that phenylalanine inhibition of muscle pyruvate kinase is unlikely to have regulatory significance in vivo.

Effect of corticosterone treatment on muscle protein turnover in adrenalectomized rats and diabetic rats maintained on insulin.

The effect of corticosterone on protein turnover in skeletal muscle was investigated in growing rats. Protein synthesis was measured in vivo by the constant infusion of [(14)C]tyrosine. The extent to which any effect of corticosterone is modulated by the hyperinsulinaemia induced by steroid treatment was examined by giving the hormone not only to adrenalectomized rats but also to streptozotocin-induced diabetic rats maintained throughout the treatment period on two dosages of insulin by an implanted osmotic minipump. Approximate rates of protein degradation were also estimated in some cases as the difference between synthesis and net change in muscle protein mass. Measurements were also made of free 3-methylhistidine concentration in muscle and plasma. At 10mg of corticosterone/100g body wt. per day, growth stopped and muscle wasting occurred, whereas at 5 mg of corticosterone/100g body wt. per day no net loss of protein occurred. However, this low dose did induce muscle wasting when insulin concentration was regulated by a dose of 1.2 units/day. Protein synthesis was markedly depressed in all treated groups, the depression in the insulin-maintained rats being marginally more than in the hyperinsulinaemic adrenalectomized rats. The oxidative soleus muscle appeared to be less susceptible to the effect of the corticosterone than was the more glycolytic plantaris or gastrocnemius muscle. Any effect of the corticosterone on protein degradation was much less than its effects on protein synthesis. Where increases in the degradation rates appeared to occur in the rats treated with 10mg of corticosterone/100g body wt. per day, the increases were less than 20%. The free intracellular 3-methylhistidine concentrations were doubled in all groups treated with 5 mg of corticosterone/100g body wt. per day and increased 5-fold in the adrenalectomized rats treated with 10mg of corticosterone/100g body wt. per day, with no change in plasma concentration in any of the groups. It is therefore concluded that: (a) the suppression of protein synthesis is the main effect of glucocorticoids in muscle; (b) marked increases in insulin afford only minor protection against this effect; (c) stimulation of protein degradation may occur, but to a much lesser extent.

Muscle protein synthesis in the streptozotocin-diabetic rat. A possible role for corticosterone in the insensitivity to insulin infusion in vivo.

The effect of insulin infusion in vivo on muscle protein synthesis was investigated in rats. In 10-days-streptozotocin-diabetic rats infused in vivo with amino acids and glucose, the rate of protein synthesis per unit of RNA (RNA activity) was markedly decreased. Pre-treatment with large doses of insulin at 17 and 1 h before the infusion fully restored RNA activity to normal. Infusion of insulin for 6 h with amino acids and glucose did not restore RNA activity to normal in the diabetic rats. However, in diabetic-adrenalectomized rats similar infusions of insulin fully restored RNA activity to normal. Measurements of plasma corticosterone concentrations indicated a 50% increase in the diabetic rats. Since pre-treatment with corticosterone suppressed the stimulatory effect of insulin infusion on RNA activity in adrenalectomized rats, and since corticosterone treatment for 6 days suppressed RNA activity even though insulin concentrations were elevated, it is suggested that increased concentrations of corticosterone are responsible for the lag in response to insulin in the diabetic rat. This means that the catabolic effects of glucocorticoids must be also considered together with the catabolic effect of insulin lack in diabetes.

A putative pathway of glyconeogenesis in skeletal muscle.

Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U]-14C]glutamate exert a glycogen-sparing action, but 14C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased 14C-incorporation from L-[U-14C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with "malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle.