Serum magnesium aberrations in furosemide (frusemide) treated patients with congestive heart failure: pathophysiological correlates and prognostic evaluation.

OBJECTIVES: To determine the prevalence of hypomagnesaemia and hypermagnesaemia, to discern various factors associated with abnormal serum magnesium, and to estimate prognostic significance of serum magnesium aberrations in patients with congestive heart failure. DESIGN: Observational study. SETTING: Medical department of a university hospital (tertiary referral centre). PATIENTS: 404 consecutive patients admitted with congestive heart failure as one of the diagnoses and previously treated with furosemide (frusemide) for at least three months. MAIN OUTCOME MEASURES: Clinical, biochemical, and electrocardiographic variables were analysed with respect to serum magnesium aberrations. Following discharge, mortality rates, including sudden death, were registered. RESULTS: Hypomagnesaemia was found in 50 patients (12.3%) and 20 (4.9%) were hypermagnesaemic. Female sex (p < 0.04), diabetes mellitus (p < 0.006), hypocalcaemia (p = 0.03), hyponatraemia (p < 0.05), malignant disease (p = 0.05), and high fever (p = 0.05) were statistically associated with hypomagnesaemia. Renal failure, severe congestive heart failure, and high dose furosemide treatment (> 80 mg/day) were associated with hypermagnesaemia (p < 0.001, p = 0.05, and p < 0.03, respectively). Hypermagnesaemic patients were older and weighed less. On follow up (median duration 43 months), 169 (41.8%) died, with 22 (13%) sudden deaths. Mortality was highest with hypermagnesaemia, lowest with normomagnesaemia, and intermediate with hypomagnesaemia. After adjustment for renal failure, old age, and severity of congestive heart failure, hypomagnesaemia but not hypermagnesaemia emerged as being significantly associated with shorter survival (p = 0.009). No statistical association was found between sudden death and magnesium concentrations. CONCLUSIONS: While hypermagnesaemia seems to represent a prognostic marker only, hypomagnesaemia appears to have an adverse pathophysiological effect. The subgroup of patients at risk for hypomagnesaemia requires frequent serum magnesium determinations and magnesium replacement for as long as hypomagnesaemia persists.

Insulin-like growth factor I and II preserve myocardial structure in postinfarct swine.

BACKGROUND: Insulin-like growth factors (IGF) I and II improve myocardial function after coronary occlusion in different animal models. OBJECTIVES: To investigate the mechanism of improved myocardial function after administration of IGF-I or IGF-II in acute myocardial infarction. METHODS: Female pigs (mean (SD) weight 25 (5) kg) were subjected to acute myocardial infarction by microembolisation with 75-150 micrometer affigel blue beads. The beads contained and slowly released 150 microgram/pig of IGF-I (n = 6), IGF-II (n = 6), or pig albumin (n = 6). Echocardiography, perfusion imaging, and haemodynamic measurements were performed before infarction and during four weeks after infarction. Regional wall motion of different left ventricular segments was scored semiquantitatively on the basis of a three point scoring system, from normal = 0 to dyskinesia = 3. Serum cardiac troponin I concentration was measured before, immediately after, and three hours after the infarct. Excised hearts were analysed for actin, desmin, blood vessel density, and DNA laddering within the infarct, border, and normal myocardial areas. RESULTS: Myocardial function of the infarct related area improved significantly during the four weeks of follow up in both the IGF groups (p = 0.01). Myocardial perfusion, heart rate, and blood pressure were similar in all the animals during the study. Treated animals had lower serum cardiac troponin I concentration (p = 0.001), more actin in the border area (p = 0.01) and infarct area (p = 0.0001), and reduced DNA laddering in the infarct area compared with the controls (p < 0.05). IGF groups had more blood vessels in the border area (p = 0.04) and the infarct area (p = 0.003). CONCLUSIONS: Both types of IGF improved myocardial function and the improvement was associated with preservation of myocardial structure. IGF-I was more effective than IGF-II.

Heliox use in the treatment of acute hyperammonemia.

The objective of this study was to evaluate a new method for the treatment of acute hyperammonemia with a helium-oxygen mixture (heliox). We conducted a prospective, randomized, controlled study of male Sprague-Dawley rats. Experimental hyperammonemia was induced by 7 days of a high-ammonia diet. Subsequently, the animals were randomly divided into two groups: the study group treated with heliox breathing for 24 hours and a control group breathing room air for 24 hours. A prospective, randomized, controlled laboratory animal study was conducted at an animal research facility. The baseline plasma ammonia level was 9.49 +/- 10.96 micromol/L. After 7 days of a high-ammonia diet, the plasma ammonia level rose to 31.53 +/- 8.86 micromol/L. There was a significant statistical difference between the plasma ammonia level following 24 hours of heliox therapy (23.14 +/- 13.97 micromol/L) and the ammonia level in the control group (42.31 +/- 24.25 micromol/L) (P < .05). Heliox breathing was found to be an efficient treatment modality for decreasing plasma ammonia levels in an animal model. Further studies are required to evaluate its potential application in the treatment of patients with hyperammonemia.

Vitamin B(6) therapy does not improve hematocrit in hemodialysis patients supplemented with iron and erythropoietin.

BACKGROUND/AIM: Pyridoxine deficiency may be the cause of failure to respond appropriately to iron and erythropoietin (EPO) administration in hemodialysis patients. METHOD: We studied 36 patients on chronic hemodialysis amply supplemented with iron and EPO, who failed to raise hematocrit levels >33%. Patients were divided into three equal groups and evaluated for 6 months as follows: Group A -- no additional therapy; group B -- supplemented with oral pyridoxine 50 mg/day, and group C received 100 mg/day pyridoxine orally. RESULTS: In all our patients, erythrocyte pyridoxine levels were initially within reference range for a healthy population and did not vary significantly during the study period. Likewise, ferritin levels and iron saturation values remained normal and constant. Hemoglobin and/or hematocrit levels remained practically unchanged in all three groups. CONCLUSIONS: The results indicate that in hemodialysis patients with normal pyridoxine status who, despite appropriate supplementation of iron and EPO, fail to reach optimal hematocrit levels, additional pyridoxine treatment does not produce any hematocrit elevation.

False-high blood salicylate levels in neonates with hyperbilirubinemia.

Drug assays may yield false-positive results caused by cross-reacting compounds. After finding a serum salicylate concentration of 81 microg/mL by using Trinder's colorimetric method, in a comatose child admitted to the authors' pediatric intensive care unit, in the absence of reported salicylate intake, the authors aimed to compare this situation with the phenomenon involving endogenous digoxin-like substances, which cross-react with the routine assay of digoxin. None of the participants in the study had been exposed to salicylate. Salicylate concentration was measured in all patients using Trinder's colorimetric method and in the second stage of the study also by AxSYM salicylate assay. Salicylate concentration using Trinder's method was 18 +/- 25 (4-81) microg/mL among nine seriously ill children in the pediatric intensive care unit, of whom two children with extensive burns had salicylate levels of 30 and 81 microg/mL, respectively. Salicylate concentrations were 107 +/- 24 (45-143) microg/mL and 60 +/- 25 (28-92) microg/mL, among 18 premature newborns and 18 term newborns, with hyperbilirubinemia, respectively. In the second stage, which involved 22 jaundiced term newborns and cord blood from 21 pregnant women, Trinder's method yielded elevated salicylate blood levels among the hyperbilirubinemic infants: 82 +/- 5 (73-89) microg/mL; however, the AxSYM assay yielded significantly lower blood levels: 2.5 +/- 3.4 (0-10.9) microg/mL (P < 0.0001). Among the pregnant women, salicylate cord blood levels were found to be low-within the limit error of the assay with both assay methods. In conclusion, when salicylate intoxication is suspected, particularly during the neonatal period, it is advisable to measure salicylate levels by immunoassay technology.

The effect of diazepam in the recovery of rabbits from acute acetaminophen intoxication.

We have recently shown that diazepam can reduce mortality of acute iron overdose in rats. The mechanism for that effect is not yet defined. Our objective in the present study was to assess whether diazepam can similarly reduce mortality of experimental acute acetaminophen intoxication. Survival of rabbits was compared among four groups receiving 3 g/kg (body weight) of acetaminophen (LD40) orally each, followed by: 1) nothing (group I), 2) one oral dose of 140 mg/kg N-acetylcystein (NAC) an hour later (group II), 3) intramuscular injection of 7 mg/kg diazepam (group III), 4) intramuscular injection of 7 mg/kg diazepam and one oral dose of 140 mg/kg NAC an hour later (group IV). 37.5% of rabbits in group I died after 16 hours, whereas none of the rabbits in group III died, (p = 0.04). No animal died during the 96-hour observation period in groups II and IV. Two and four hours post drug administration, acetaminophen plasma concentrations (APC) were significantly lower among rabbits in group III than in group I (p = 0.0007 and 0.01, respectively) and significantly lower among rabbits in group IV than in those in group II (p<0.0001 and p = 0.03, respectively). Acetaminophen plasma concentrations 2 hours after drug administration were also significantly lower among rabbits in group III than in those in group II (p = 0.0002). Seven and 24 hours after dosage, APC tended to be higher among rabbits in group III than in those in group I, but not significantly so. Administration of diazepam without NAC did not prevent liver and renal dysfunction. We conclude that early administration of diazepam in acute experimental acetaminophen overdose in rabbits reduced APC and mortality, probably by slowing intestinal motility, which resulted in delayed acetaminophen absorption from the gastrointestinal tract.

Small G proteins are expressed ubiquitously in lymphoid cells and do not correspond to Bcl-2.

The bcl-2 gene is consistently associated with t(14; 18) chromosomal translocations observed in a large fraction of human B-cell lymphomas. The t(14; 18) translocation results in deregulated expression of the bcl-2 gene and synthesis of inappropriately high levels of the Bcl-2 protein. Gene transfer studies suggest a role for Bcl-2 in cell survival, growth enhancement and oncogenic transformation. To test the suggestion that GTP-binding by Bcl-2 may mediate its biological effects we characterized the GTP-binding proteins in lymphoid cells expressing Bcl-2. Expression of several small GTP-binding proteins was found to be ubiquitous and did not vary with levels of Bcl-2. By using immunological, electrophoretic and cell-fractionation techniques, we separated Bcl-2 from G proteins of small relative molecular mass (Mr) and showed that it is incapable of binding GTP. Our results show that small Mr G proteins are widely expressed in lymphoid cells and that Bcl-2 is not a novel member of this GTP-binding protein family.

Membrane topology of the Bcl-2 proto-oncogenic protein demonstrated in vitro.

The Bcl-2 oncogenic protein was synthesized in vitro and shown to post-translationally integrate asymmetrically into microsomal membranes with no requirement for an amino-terminal signal sequence. Instead, a carboxyl-terminal hydrophobic domain of Bcl-2 served as an insertion sequence essential for membrane assembly since a Bcl-2 mutant lacking this domain completely lost its ability to associate with microsomal membranes. The data demonstrate that Bcl-2 is tightly associated with the lipid bilayer with the nature of an integral membrane protein. The membrane orientation of Bcl-2 was determined using a protease protection assay, which showed that it is predominantly localized to the cytoplasmic face of membranes. A similar type of membrane processing has been shown for cytochrome b5 and also suggested for the viral oncogenic protein polyoma middle-T antigen.

The bcl-2 candidate proto-oncogene product is a 24-kilodalton integral-membrane protein highly expressed in lymphoid cell lines and lymphomas carrying the t(14;18) translocation.

We have identified a 24-kilodalton protein that is the product of the human bcl-2 gene, implicated as an oncogene because of its presence at the site of t(14;18) translocation breakpoints. The Bcl-2 protein was detected by specific, highly sensitive rabbit antibodies and was shown to be present in a number of human lymphoid cell lines and tissues, as well as in mouse B cells transfected with a bcl-2 cDNA construct. Characterization of the Bcl-2 protein demonstrated that it has a lipophilic nature and is associated with membrane structures, probably by means of its hydrophobic carboxy-terminal membrane-spanning domain. In t(14;18)-carrying cell lines, the protein is predominantly localized to the perinuclear endoplasmic reticulum, with a minor fraction in the plasma membrane. These properties, together with the observations that Bcl-2 does not have a characteristic signal peptide and is not glycosylated, suggest that it is an integral-membrane protein that spans the bilayer at its C-terminal hydrophobic region but is exposed only at the cytoplasmic surface. The relative abundance of the Bcl-2 protein in various human lymphoid cell lines correlated with transcription of the bcl-2 gene. The protein was abundant in all t(14;18)-carrying cell lines and lymphomas and was also found at lower levels in pre-B-cell lines and nonmalignant lymphoid tissues that do not carry t(14;18) translocations. These results suggest that the Bcl-2 protein is functional in normal B lymphocytes and that a quantitative difference in its expression may play a role in the pathogenesis of lymphomas carrying the t(14;18) translocation.

Expression in non-Hodgkin's lymphoma of the bcl-2 protein associated with the t(14;18) chromosomal translocation.

For many non-Hodgkin's lymphomas, the bcl-2 gene has been implicated as a likely proto-oncogene, since it is consistently located at or near the breakpoint sites of t(14;18) chromosomal translocations. To define the role of the protein product of the bcl-2 gene in lymphoid cancers, we used anti-bcl-2 antibodies to perform immunohistochemical studies of frozen sections of 136 tissue specimens affected by lymphoma or non-neoplastic lymphoid disorders. Immunoreactive bcl-2 protein was observed in the neoplastic cells in almost all the follicular lymphomas, whereas no bcl-2 protein was detected in follicles affected by non-neoplastic processes or in normal lymphoid tissue. Every tumor with molecular-genetic evidence of t(14;18) translocation expressed detectable levels of bcl-2 protein, regardless of whether the breakpoint was located in or at a distance from the bcl-2 gene. These data show consistent expression of a proto-oncogenic protein in a large proportion of non-Hodgkin's lymphomas and provide further support of a role for bcl-2 in the pathogenesis of all lymphomas with the t(14;18) karyotypic abnormality. Increased expression of bcl-2 after t(14;18) translocations may be a specific marker for B-cell cancers, and demonstration of the protein with use of anti-bcl-2 antibodies could be useful in the diagnosis of many non-Hodgkin's lymphomas.