Norepinephrine (NE, 10−6 M) stimulated melatonin accumulation in the incubation medium of rat (but not Syrian hamster) pineals taken at the end of the light phase. However, NE elevated melatonin accumulation in the medium of pineals taken after 20 min of light exposure of animals of either species at 6 h into the 10‐h dark phase. A dose response to 10−7−10−5 M NE was observed in both the medium and pineals upon incubation of pineals taken from rats at 4 h into the light phase and from hamsters after 20 min light exposure at 6 h into the dark phase. Approximately 95% of the melatonin present was in the medium. The incubation time was 4 h in all cases. Subcutaneous injection of 1 μg/g NE (either at the end of the light phase or after 30 min of light at 6 h into the dark phase) did not stimulate in vivo Syrian hamster pineal melatonin content determined 1 or 2 h after injection, whether the hamsters were placed in light or darkness after the injection. However, after 30 min of light beginning at 6 h into dark, injection of 5 μg/g desipramine (DMI, a blocker of catecholamine uptake into nerve endings) allowed a dramatic hamster pineal melatonin response to additional injection of 1 μg/g NE, observed at 1 and 2 h in light after injection. A small effect of DMI alone was seen. DMI also potentiated the effect of NE (each 10−6 M) on melatonin accumulation in the medium of incubated hamster pineals taken after a short light exposure at night. No significant stimulatory effect of NE and/ or DMI was seen in vivo or in vitro near the middle of the light phase. Measurement of melatonin in the incubation medium is a useful method for studying pineal function. The Syrian hamster pineal has rhythm of sensitivity to NE (sensitivity evident at night) and even at night is protected by neuronal uptake from circulating NE‐induced stimulation of melatonin production. NE appears to be the neurotransmitter for stimulation of pineal melatonin production in the Syrian hamster. The sensitivity rhythm and uptake protection might provide specificity of control of the nightly melatonin signal by reducing the chance of a melatonin response during the day or a response to circulating catecholamines from general sympathetic stimuli.

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Ratios of lactulose/mannitol excretion in urine have been signed to assess perturbations of intestinal permeability I • used to assess the extent of intestinal permeability in after burn injury. Seven men with burns ranging from _ various disease and trauma conditions. Reported studies 31% to 78% of the total body surface area (mean 58%) have used this technique to correlate altered gastrointeswere used in this preliminary study to develop our assay (• tinal mucosal permeability totranslocation of bacteria and technique. On the fourth day after the burns were endotoxin, leading to occult sepsis in bum patients.sustained, the patients were given 5 g of mannitol and Enzymatic methods of analysis for urine concentrations of 10 g of lactulose in 100 mL of de-ionized water. A 6-h mannitol and lactulose were used in these studies. We urine collection was initiated after ingestion of the test have found that urine from patients with severe burns solution. We added 1 mL of a 200 g/L chlorhexidine frequently contains compounds that interfere with the solution to the total urine collected. Aliquots of the enzymatic methods. We describe using gas-liquid chrourine samples were frozen at -20 'C until analyses matography to determine mannitol and lactulose simultawere perfbrmed. neously in the urine of burn patients. To avoid the multiple Sample preparation: We added 125 AL of 1 mmoIIL peaks for the anomeric forms of the reducing sugars methylmannopyranoside reagent as an internal standuring precolumn trimethylsilyl derivatization, we condard to 50Al of fivefold-diluted (with de-ionized water) verted the sugars to oximes before the silylation step. The drd ThL of ved-iltedn(withnde ed wer) method gave good recoveries of mannitol and lactulose urine. The sample and internal standard were dried added to burn patients' urine samples. Unlike the enzyunder nitrogen in a heating block at 75 °C. Aftr these matic methods, gas-liquid chromatography eliminates the cooled, we added 100 ML of oxin' solution (25 mg of effect of interfering compounds and allows for the simulhydroxylamine hydrochloride per inilliliter of pyridine), taneous determination of both sugars in urine samples.capped the samples, and incubated them at 75 0C for 30 min. After letting the samples cool, we added 100 AL of Several investigators have proposed that thermal n-trimethylsilyl imidazole reagent (Pierce Chemical, injury alters gastrointestinal mucosal permeability, Rockford, IL 61105-9976) and incubated the solutions causing translocation of bacteria and endotoxin and for 15 min at 75 'C. leading to occult sepsis and multiple organ failure (1-3).Standard preparation: Stock solutions of mannitol (5 Ratios of lactulose/mannitol urine excretion have been mmol/L) and lactulose (0.5 mmol/L) were made in deused to monitor changes in intestinal permeability in ionized water. From the stock mannitol solution, we various disease conditions (4,5). We have found that the pipetted 20, 40, 60, 80, and 100 AL into disposable enzymatic methods commonly used to determine mani...

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