Hypomagnesemia is a frequent finding in the emergency department in patients with chest pain

STUDY OBJECTIVE--To evaluate the frequency of low blood levels of total and ultrafilterable magnesium (total and ultrafilterable hypomagnesemia) in patients with chest pain in the emergency department, and to determine if hypomagnesemia is associated with other clinically important diagnostic and outcome variables in cardiac care. SETTING--An emergency department of a university teaching hospital. DESIGN--Prospective study of extracellular magnesium homeostasis in patients with chest pain in the emergency department and a cohort of patients without chest pain with a clinical indication for blood sampling. PATIENTS--During a 4-month period, 147 patients presenting to the emergency department were studied: 67 patients (mean +/- SD age, 61.4 +/- 13 years) with a chief complaint of chest pain (study group) and 80 patients (55.6 +/- 19 years) with other diagnoses (control group). RESULTS--Total and ultrafilterable hypomagnesemia occurred more frequently in patients with chest pain (20/67 [30%] and 9/67 [13%]) than in the control group (12/80 [15%] and 3/80 [4%]). Patients with a chief complaint of chest pain who were receiving diuretic medications were hypomagnesemic more frequently (9/16 [56%]) than patients not receiving diuretics (12/51 [23%]). In patients with chest pain admitted to the hospital with a diagnosis of "rule out" myocardial infarction, the frequency of hypokalemia was greater among hypomagnesemic patients (6/14 [43%]) than normomagnesemic patients (3/31 [10%]). A similar frequency of hypomagnesemia was noted in patients with a final diagnosis of myocardial infarction (4/15 [27%]) when compared with other patients admitted with chest pain (10/31 [32%]) in whom myocardial infarction was excluded. No association was noted among hypomagnesemia and length of hospital stay or the occurrence of hypotension or dysrhythmias. CONCLUSIONS--Total and ultrafilterable hypomagnesemia are frequent occurrences in patients with and without chest pain in the emergency department. Diuretic use is associated with hypomagnesemia in patients presenting with chest pain in the emergency department. These results support the concept that hypomagnesemia is common in patients with chest pain in the emergency department and is associated with hypokalemia but is not predictive of whether the patient with chest pain has had an acute myocardial infarction.     

Protein kinase-C activation stimulates synthesis of gonadotropin-releasing hormone (GnRH) receptors, but does not mediate GnRH-stimulated receptor synthesis.

Gonadotropes respond to GnRH with LH synthesis and release, desensitization, changes in GnRH receptor number, and GnRH receptor synthesis. Activation of protein kinase-C (PKC) appears to be involved in LH beta gene expression, but is not required for acute LH release, desensitization, or receptor down-regulation. The present studies were conducted to determine whether PKC mediates GnRH-stimulated receptor synthesis. We have adapted the density shift technique to measure the synthesis of GnRH receptors in pituitary culture. Pituitary cells from female weanling rats were exposed to medium containing treatments, dense amino acids (greater than 95% 13C, 15N, and 2H), dialyzed horse serum (10%, vol/vol), and fetal calf serum (2.5%, vol/vol). Treatments consisted of medium alone, phorbol myristate acetate (PMA), phorbol dibutyrate (PdBu), or GnRH. To deplete cells of PKC, cultures were exposed for 8-16 h to 1 microM PMA. Short term treatment with PKC activators (PMA or PdBu, 1 microM) or GnRH (0.1 nM) was given for 30 min. After treatment, GnRH receptors were covalently linked to [125I]Tyr5-azidobenzoyl-D-Lys6-GnRH and solubilized. Newly synthesized (densely labeled) GnRH receptors were separated from normal receptors by velocity sedimentation (156,000 X g; 24 h; 0-20% sucrose) and quantified by gamma-spectroscopy. Treatment with GnRH significantly stimulated the synthesis of GnRH receptors. Treatment of pituitary cell cultures with PMA (8-16 h) also stimulated the synthesis of GnRH receptors, although to a lesser extent than that observed after GnRH treatment. The synthesis of GnRH receptors in response to 0.1 nM GnRH was not different in cells with a normal complement of PKC compared to those depleted of PKC activity. This indicates that the ability of GnRH to stimulate the synthesis of its own receptor is not mediated by PKC. Short term treatment of cell cultures with 1 microM PMA or PdBu (30 min) stimulated GnRH receptor synthesis similar to treatment with 0.1 nM GnRH. When PMA and GnRH were administered simultaneously, GnRH receptor synthesis was stimulated to a greater extent than with either agent alone, suggesting differing mechanisms of action. These results indicate that although activators of PKC can stimulate the synthesis of GnRH receptors, PKC does not mediate the effects of GnRH on homologous receptor synthesis.     

Short-term effects of propranolol on portal venous pressure

The present study was designed to investigate the effect of propranolol on portal pressure of patients with alcoholic cirrhosis and portal hypertension and to correlate these effects with clinical and laboratory parameters. The mean baseline hepatic venous pressure gradient in the 50 patients studied was of 18.2 +/- 4.1 mm Hg. It decreased significantly 2 hr after the oral administration of 40 mg of propranolol to 15.7 +/- 4.2 mm Hg (a mean reduction of 13.4 +/- 17%). This reduction in hepatic venous pressure gradient resulted mainly from a decrease in mean wedged hepatic venous pressure. There was no correlation between the decrease in hepatic venous pressure gradient and the decrease in heart rate. When results were analyzed individually, only 15 (30%) showed a large decrease in hepatic venous pressure gradient (greater than 20%), 15 (30%) showed a moderate decrease (10 to 19%), and in 20 patients (40%) there was no reduction or an increase in hepatic venous pressure gradient. Comparison of "responders" (those that reduced hepatic venous pressure gradient greater than 10%) and "nonresponders" (hepatic venous pressure gradient reduction less than 10%) showed no significant differences in baseline laboratory and hemodynamic parameters, in the severity of the liver disease, in the heart rate and blood pressure response to propranolol, nor in the propranolol plasma levels achieved 2 hr after propranolol administration. Propranolol plasma levels correlated with the reduction in heart rate but not with the reduction in hepatic venous pressure gradient. Of 14 nonresponders to 40 mg of propranolol who received additional doses, six showed a reduction in hepatic venous pressure gradient.(ABSTRACT TRUNCATED AT 250 WORDS)     

A New Variant of Hereditary Hemolytic Anemia With Stomatocytosis and Erythrocyte Cation Abnormality

A new variant of congenital hemolyticanemia associated with stomatocytosis,reticulocytosis, decreased osmotic fragility, type I autohemolysis and shortened erythrocyte survival without specific splenic sequestration was discoveredin three siblings of Swiss-German ancestry. Increased intracellular sodium(two to three times normal) and slightlydecreased intracellular potassium weredetected. Total sodium efflux was eight-fold greater than normal but total potassium influx was normal and ouabain-sensitive potassium influx was decreased.The ouabain-sensitive sodium efflux:potassium influx ratio was 26:1 ratherthan the 3:2 ratio noted in normal cells.The consanguineous parents, four othersiblings, and 44 other family membershad mild stomatocytosis, reticulocytosis,and, when studied, decreased osmoticfragility, increased autohemolysis, intermediate abnormalities of cation content,cation flux, and moderate shortening oferythrocyte survival. Autosomal dominant inheritance was suggested. Noabnormalities of RBC enzymes, hemoglobin or lipids were observed. No abnormalities of membrane protein weredetected on acrylamide gel. Substratedepletion of these hypermetabolic cellsresulted in intracellular dehydrationwith potassium loss in excess of sodiumgain and decreased deformability. Although the exact nature of the defectresponsible for hemolysis is unknown,this syndrome differs from other hereditary hemolytic anemias associated withstomatocytosis.

Submitted on December 21, 1970 Revised on March 16, 1971 Accepted on March 29, 1971     

Stimulation of luteinizing hormone release by sodium fluoride is independent of protein kinase-C activity and unaffected by desensitization to gonadotropin-releasing hormone

GnRH stimulates secretion of pituitary LH by increasing intracellular calcium. Increased calcium may result from activation of phospholipase-C, since there is an increase in inositol phosphates and diacylglycerol, and a redistribution of protein kinase-C (PKC) from cytosolic to a particulate cell fraction in GnRH-stimulated pituitary cultures. A GTP-binding protein (G-protein) may mediate GnRH actions, since GTP stimulates LH release in permeabilized gonadotropes and decreases receptor affinity for a GnRH analog. In the present study we have used sodium fluoride, an exogenous activator of G-proteins, to investigate the possibility of a G-protein link between GnRH receptor activation, phospholipase-C activity, and LH release. Treatment of primary pituitary cell cultures from immature female rats with sodium fluoride stimulated the release of 20% total cellular LH and increased inositol phosphate accumulation. Sodium fluoride-stimulated LH release was insensitive to cholera toxin and pertussis toxin. Sodium fluoride-stimulated LH release was additive with a maximally effective concentration of phorbol 12-myristate 13-acetate and was not inhibited by depletion of cellular PKC, suggesting that PKC does not mediate sodium fluoride effects. Treatment of cultures with 3 mM EGTA and 10 nM GnRH for 5 and 16 h reduced pituitary responsiveness to subsequent treatment with GnRH, but had no effect on sodium fluoride-stimulated LH release. Although the precise mechanism of sodium fluoride-stimulated LH release remains to be described, our results support a role for a G-protein in regulation of LH release by the releasing hormone.     

The contribution of protease-activated receptor 1 to neuronal damage caused by transient focal cerebral ischemia

The serine proteases tissue plasminogen activator, plasmin, and thrombin and their receptors have previously been suggested to contribute to neuronal damage in certain pathological situations. Here we demonstrate that mice lacking protease-activated receptor 1 (PAR1) have a 3.1-fold reduction in infarct volume after transient focal cerebral ischemia. Intracerebroventricular injection of PAR1 antagonist BMS-200261 reduced infarct volume 2.7-fold. There are no detectable differences between PAR1-/- and WT mice in cerebrovascular anatomy, capillary density, or capillary diameter, demonstrating that the neuroprotective phenotype is not likely related to congenital abnormalities in vascular development. We also show that the exogenously applied serine proteases thrombin, plasmin, and tissue plasminogen activator can activate PAR1 signaling in brain tissue. These data together suggest that if blood-derived serine proteases that enter brain tissue in ischemic situations can activate PAR1, this sequence of events may contribute to the harmful effects observed. Furthermore, PAR1 immunoreactivity is present in human brain, suggesting that inhibition of PAR1 may provide a novel potential therapeutic strategy for decreasing neuronal damage associated with ischemia and blood-brain barrier breakdown.     

Platelet glycoproteins IIb and IIIa as a calcium channel in liposomes

Human platelet membrane glycoproteins IIb and IIIa (GPIIb and IIIa) were incorporated into phospholipid vesicles by the reverse-phase technique to assess the ability of GPIIb and IIIa to function as a Ca2+ channel. Movement of Ca2+ across the lipid bilayer was quantitated by injection of proteoliposomes with encapsulated Fura-2 into Ca2+ buffers and measurement of Fura-2 fluorescence as an indicator of Ca2+ influx. Reciprocally, to assess the function of proteins in an inside-out orientation, Ca2+-loaded vesicles were injected into Ca2+-free buffer and Ca2+ efflux monitored by a calcium electrode. Incorporation of the IIb-IIIa complex produced significant facilitation of Ca2+ movement across the lipid bilayer. No net transmembrane Ca2+ movement was seen with dissociated IIb and IIIa. Movement of Ca2+ was proportional to the transmembrane Ca2+ gradient. Ca2+ movement into the vesicles was inversely proportional to extravesicular NaCl from 25 to 150 mmol/L, analogous to several studies in the intact platelet. Adenosine triphosphate had no effect on Ca2+ movement into or out of the vesicles. Specific inhibition of a Ca2+ shift into the vesicles was seen with M148, a monoclonal antibody to IIb/IIIa, while no inhibition was observed with a panel of other anti-IIb/IIIa monoclonal antibodies. This suggests that a specific site on the complex or orientation of the complex is essential for calcium channel function. These data demonstrate that the GPIIb/IIIa complex can serve as a passive Ca2+ channel across a phospholipid bilayer and has the potential to play a role in Ca2+ flux across the platelet plasma membrane.     

A randomized trial of Chinese herbal medicines for the treatment of symptomatic hepatitis C

BACKGROUND: Many patients with the hepatitis C virus (HCV) cannot be successfully treated with interferon-based regimens. Chinese herbal medicines have been widely prescribed for HCV in Asia, and many infected patients in the United States have used these agents. However, data to support the efficacy of these medications are limited and, to our knowledge, no published trials have been conducted in a US population. METHODS: In a double-blinded design, 45 patients with HCV and fatigue were randomized to receive a combination of Chinese herbal medications or a matched placebo for 12 weeks. The main outcome measures were changes in health-related quality of life using the role physical and vitality scale scores from the validated Hepatitis Quality of Life Questionnaire and alanine aminotransferase levels. In addition, other Hepatitis Quality of Life Questionnaire variables, HCV load, and adverse effects were monitored. RESULTS: In patients with HCV, the herbal medications had no effect on any quality-of-life variables, as measured by the Hepatitis Quality of Life Questionnaire. In addition, no significant changes in alanine aminotransferase or serum HCV RNA levels were noted. No significant adverse effects were observed. CONCLUSIONS: In this study, a regimen of Chinese herbal medicines did not improve quality of life, liver chemistry results, or viral load in a cohort of patients with HCV. Patients and practitioners should remain cautious about the use of herbal medicines for HCV, because studies have not shown a clear benefit of these agents.