Effect of direct injection of melanin-concentrating hormone into the paraventricular nucleus: further evidence for a stimulatory role in the adrenal axis via SLC-1.

Melanin-concentrating hormone (MCH) is implicated in the control of a number of hormonal axes including the hypothalamic-pituitary adrenal (HPA) axis. Previous studies have shown that there is evidence for both a stimulatory and an inhibitory action on the HPA axis; therefore, we attempted to further characterize the effects of MCH on this axis. Intracerebroventricular injection of MCH increased circulating adrenocorticotropic hormone (ACTH) at 10 min post injection. Injection of MCH directly into the paraventricular nucleus (PVN) was found to increase both circulating ACTH and corticosterone 10 min after injection. Additionally, MCH was found to increase corticotropin-releasing factor (CRF) release from hypothalamic explants, and this effect was abolished by the specific SLC-1 antagonist SB-568849. Neuropeptide EI, a peptide from the same precursor as MCH was also found to increase CRF release from explants. These results suggest that MCH has a stimulatory role in the HPA axis via SLC-1, and that MCH exerts its effects predominantly through the PVN CRF neuronal populations

Critical appraisal of two methods for determining aluminum in blood samples.

We report two methods for determining aluminum concentrations in blood. Method 1, proposed for routine monitoring of patients with chronic renal failure, includes a collection procedure that can be adopted by any renal dialysis unit, with a minimum of sample contamination. Plasma samples are diluted fourfold with HNO3/Triton X-100 matrix modifier. Method 2 is proposed for determining aluminum concentrations in patients with normal renal function, e.g., in drug studies and environmental monitoring. Samples are diluted with an equal volume of Mg(NO3)2 matrix modifier and atomized from a L'vov platform. By either method, analytical recovery of aluminum added to serum ranged between 92% and 105% throughout the linear calibration range. The reference interval (mean +/- SD) for aluminum in 22 healthy subjects by method 2 was 0.044 +/- 0.030 mumol/L.

Lithium determined in serum with an ion-selective electrode.

We evaluated the performance of the lithium ion-selective electrode (ISE) in the Du Pont Na/K/Li analyzer. Lithium concentrations in 106 serum samples from patients being treated with lithium were measured in duplicate with the ISE and by flame photometry. The slope of the regression line for the two methods was 1.004 with a standard error of the estimate of 0.049 mmol/L (x = flame photometry, y = ISE). Lithium measurements by the ISE method in serum or aqueous standards were linear to greater than 2.0 mmol/L. Within-run CVs for low (0.31 mmol/L) and high (1.15 mmol/L) lithium controls were 5.9% and 1.7%, respectively (n = 20). Day-to-day CVs for the same controls were 9.8% and 3.3%, respectively (n = 20). There was no significant interference when the concentrations of sodium, potassium, calcium, or magnesium were varied, nor did intervening urinary lithium analyses affect the measurement of serum lithium. Results for lithium measurement in four serum-based survey materials compared well with results by isotope dilution/mass spectrometry.