Crystallization of retinol dehydratase from Spodoptera frugiperda: improvement of crystal quality by modification by ethylmercurythiosalicylate.

Retinol dehydratase is a sulfotransferase which is presumed to catalyze the dehydration of its substrate via a transient retinyl sulfate intermediate. Crystals (space group P2(1), unit-cell parameters a = 82.05, b = 66.61, c = 84.90 A, beta = 111.29 degrees ) are significantly improved by covalent modification of the protein with ethylmercury.

Molecular cloning and functional characterization of the oxytocin receptor from a rat pancreatic cell line (RINm5F).

Oxytocin (OT) and vasopressin (AVP) stimulate insulin and glucagon release from the pancreas, and evoke insulin secretion from the rat insulinoma cell line, RINm5F. To determine which AVP/OT receptor subtype is expressed in RINm5F cells, we used PCR with degenerate primers to two transmembrane domains of the AVP (V1a, V1b (or V3), V2) and OT receptors (OTRs). The single PCR fragment identified was used to obtain a full length cDNA from a RINm5F cDNA library. Comparison of the deduced amino acid sequence of this clone with uterine OTR sequences from several species (human, sheep, bovine) and to the pig kidney epithelial cell (LLC-PK1) OTR reveals a very high degree of homology. After the RIN cell OTR cDNA was stably transfected into CHO cells (CHO-OTR), the cell membranes bound iodinated oxytocin antagonist with an apparent Kd comparable to that of RIN cell membranes and those from other OT target cells. Comparison of the ligand specificities of CHO-OTR and RIN cells membranes showed that the relative Ki values of a series of OT analogues were approximately equivalent in both preparations. The rank order of apparent Ki values also corresponded to published values for the rat myometrium, where OT elicits intracellular calcium transients, and increases inositol phosphate production. In uterin endometrium and amnion cells, OT stimulates prostaglandin release. Stimulation of CHO-OTR cells with OT caused an increase in cytosolic calcium concentration originating from both intracellular and extracellular sources, and a dose-dependent increase in inositol phosphate levels. Arachidonic acid release and PGE2 synthesis were also stimulated by OT. These findings (amino acid sequence homology, binding specificity, and signal transduction/second messenger production) suggest that OTRs from RINm5F cells are indistinguishable from OTRs that have been described in other tissues. The expression of OTR in pancreatic cells implies that OT plays a role in pancreatic function.

Pulmonary barotrauma as the cause of pneumoretropharynx in pulmonary lymphangioleiomyomatosis.

A 55-year-old white woman with pulmonary lymphangioleiomyomatosis (LAM) presented to the emergency department with odynophagia and subplatysmal emphysema after a paroxysm of coughing. Lateral neck films showed subcutaneous emphysema and a retropharyngeal air stripe. Chest radiographs showed neither pneumothorax nor pneumomediastinum. Patients with LAM frequently develop pulmonary barotrauma and pneumothoracies. This patient, however, had undergone prior bilateral talc pleuradesis as treatment for recurrent pneumothoracies and, thus, could not manifest this complication of barotrauma. This case illustrates the uncommon occurrence of superior dissection of air after pulmonary barotrauma.

Effects of dietary zinc restriction on postprandial changes in plasma zinc.

The principal objective of this study was to determine the effect of a short period of severe dietary zinc restriction on both prebreakfast and postbreakfast plasma zinc concentrations. After an overnight fast, plasma zinc was measured in five normal adults before and at 30-min intervals for 6 h after a standard zinc-free test meal. This test was performed after a week on a zinc-adequate diet and repeated after a week of severe dietary zinc restriction. Postabsorptive premeal plasma zinc did not change after a week of severe dietary zinc restriction but the posttest meal decline was significantly greater and the maximum decline less variable (15-23%). It is concluded that postprandial plasma zinc is more sensitive than prebreakfast plasma zinc to dietary zinc depletion. Recent zinc intake is one factor that determines the magnitude of the postprandial net efflux of zinc from the plasma compartment.

Iron chelation by deferoxamine in sickle cell patients with severe transfusion-induced hemosiderosis: a randomized, double-blind study of the dose-response relationship.

Transfusion-induced hemosiderosis is a serious and potentially life-threatening complication for some patients with sickle cell anemia. The use of high-dose intravenous deferoxamine (DFO) has become widespread in spite of a paucity of published data on safety and efficacy. We report a randomized double-blind study of the dose-response relationship of intravenous DFO in six subjects with sickle cell anemia and severe transfusion-induced hemosiderosis (serum ferritin 4100 to 14,176 ng/ml). Each subject received three different doses of intravenous DFO for 3 days each while consuming a constant diet. Total iron excretion (urine and fecal) was 91% greater at 180 mg/kg/day DFO than at 60 mg/kg/day DFO, and fecal iron excretion became a relatively larger proportion of total excretion at higher doses. Subsequent treatment for 3 months with 150 mg/kg/day DFO caused a 33% to 60% reduction in serum ferritin and demonstrable improvement in hepatic function in all patients. No toxicity was encountered, but DFO at 180 mg/kg/day was associated with a significant increase in fecal zinc excretion when compared with that observed at lower doses.