Urinary excretion of an intravenous 26Mg dose as an indicator of marginal magnesium deficiency in adults

BACKGROUND

Measurement of magnesium (Mg) status is problematic because tissue Mg deficiency can be present without low serum Mg concentrations.

OBJECTIVE

To evaluate a modified version of the Mg retention test using stable isotopes for the assessment of Mg status in general, and the detection of marginal Mg deficiency in particular.

DESIGN

A modified version of the Mg retention test using a small dose of (26)Mg was evaluated for assessment of Mg status in 22 healthy subjects. Muscle Mg concentration was used as reference for Mg status. A muscle biopsy was taken from the lateral portion of the quadriceps muscle from each subject. After 2 to 4 weeks, 11 mg of (26)Mg (as MgCl(2) in 14 ml water) were injected i.v. over a period of 10 min and all urine was collected for the following 24 h. Excretion of the isotopic label was expressed as percentage of the administered dose excreted in urine within 24 h.

RESULTS

Mean +/- s.d. Mg concentration in muscle was 3.85 +/- 0.17 mmol/100 g fat-free dried solids. Mean +/- s.d. excretion of the injected dose within 24 h was 7.9 +/- 2.1%. No correlation was found between muscle Mg concentration and excretion of the isotopic label (r (2 ) = 0.061, P = 0.27).

CONCLUSIONS

In this study, urinary excretion of an intravenous Mg tracer was not influenced by muscle Mg concentration and its usefulness for the detection of marginal Mg deficiency could therefore not be demonstrated.

SPONSORSHIP

Swiss Foundation for Nutrition Research and Swiss Federal Institute of Technology, Zurich, Switzerland.

Old Masters' lead white pigments: investigations of paintings from the 16th to the 17th century using high precision lead isotope abundance ratios

White lead (2PbCO(3).Pb(OH)(2)), a common component in 17c. artists' painting materials, was singled out to investigate the potential of lead isotope abundance ratios in the field of authentication and origin assignment. Paintings by Peter Paul Rubens, Anthony van Dyck and other Old Masters of the Northern and Southern schools were chosen for this study. An interdisciplinary approach was chosen using both analytical instrumental methods, art technological and art historical knowledge. Minute samples taken from paintings from selected art collections worldwide were investigated using mass spectrometry, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The high precision lead isotope abundance ratios were measured by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The determination of the calcium matrix influence with respect to possible bias effects to the isotope ratios gave clear decision support, to whether a result lies within the stated combined measurement uncertainty of the result, to eliminate time-consuming matrix separations. The scatter plots of the measured isotope abundance ratios for the painting pigments from P. P. Rubens, A. van Dyck and other Flemish painters exhibit a very narrow distribution forming a cluster. The range of the measured ratio (206)Pb/(204)Pb amounts to 0.55% and for the ratio (207)Pb/(204)Pb to 0.2%. The comparison of the data to cis-alpine (Italian) sample pigments from paintings from the same time period reveals a clear distinction between the two fields. With respect to the lead isotope data originating from the ores it is assumed that the pigment isotope ratio distribution can be explained by very distinct origin of raw materials. Presumably, no mixing of different lead ores from Europe took place. The comparison of the measured white lead isotope ratio values (Flemish paintings) and the data from ore samples led to the unexpected conclusion that local ores were not used for the pigment production but British or German sources.

Genetic typing of Corallium rubrum

Corallium rubrum taxonomy is based on morphologic criteria; little is known about its genome. We set up a rapid, easy method based on amplified fragment length polymorphism to characterize the genetic patterns of C. rubrum in an attempt to understand better the evolutionary relations between species from diverse geographic areas and to help define migration patterns. Applying this procedure to C. rubrum specimens from Spain and Italy, we identified 6 AFLP amplification fragments common to the 4 coral populations studied and 4 fragments that differentiated between these populations. Using this characterization we were able to plot a "genetic identity card" of this commercially harvested species, which is also a marker of pollution.

Evaluation of the combined measurement uncertainty in isotope dilution by MC-ICP-MS

The combination of metrological weighing, the measurement of isotope amount ratios by a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) and the use of high-purity reference materials are the cornerstones to achieve improved results for the amount content of lead in wine by the reversed isotope dilution technique. Isotope dilution mass spectrometry (IDMS) and reversed IDMS have the potential to be a so-called primary method, with which close comparability and well-stated combined measurement uncertainties can be obtained. This work describes the detailed uncertainty budget determination using the ISO-GUM approach. The traces of lead in wine were separated from the matrix by ion exchange chromatography after HNO(3)/H(2)O(2) microwave digestion. The thallium isotope amount ratio ( n((205)Tl)/ n((203)Tl)) was used to correct for mass discrimination using an exponential model approach. The corrected lead isotope amount ratio n((206)Pb)/ n((208)Pb) for the isotopic standard SRM 981 measured in our laboratory was compared with ratio values considered to be the least uncertain. The result has been compared in a so-called pilot study "lead in wine" organised by the CCQM (Comité Consultatif pour la Quantité de Matière, BIPM, Paris; the highest measurement authority for analytical chemical measurements). The result for the lead amount content k(Pb) and the corresponding expanded uncertainty U given by our laboratory was:k(Pb)=1.329 x 10-10mol g-1 (amount content of lead in wine)U[k(Pb)]=1.0 x 10-12mol g-1 (expanded uncertainty U=kxuc, k=2)The uncertainty of the main influence parameter of the combined measurement uncertainty was determined to be the isotope amount ratio R(206,B) of the blend between the enriched spike and the sample.

Uncertainty evaluation of mass values determined by electronic balances in analytical chemistry: a new method to correct for air buoyancy

A new method to correct for the largest systematic influence in mass determination-air buoyancy-is outlined. A full description of the most relevant influence parameters is given and the combined measurement uncertainty is evaluated according to the ISO-GUM approach [1]. A new correction method for air buoyancy using an artefact is presented. This method has the advantage that only a mass artefact is used to correct for air buoyancy. The classical approach demands the determination of the air density and therefore suitable equipment to measure at least the air temperature, the air pressure and the relative air humidity within the demanded uncertainties (i.e. three independent measurement tasks have to be performed simultaneously). The calculated uncertainty is lower for the classical method. However a field laboratory may not always be in possession of fully traceable measurement systems for these room climatic parameters.A comparison of three approaches applied to the calculation of the combined uncertainty of mass values is presented. Namely the classical determination of air buoyancy, the artefact method, and the neglecting of this systematic effect as proposed in the new EURACHEM/CITAC guide [2]. The artefact method is suitable for high-precision measurement in analytical chemistry and especially for the production of certified reference materials, reference values and analytical chemical reference materials. The method could also be used either for volume determination of solids or for air density measurement by an independent method.

Complementary therapy for severe Rh-alloimmunization

PURPOSE OF INVESTIGATION

This report describes successful treatment, using invasive and noninvasive techniques, of a 36-year-old woman (gravida 10, para 0) referred to our center at 13 weeks' gestation for severe Rh alloimmunization. Pre-pregnancy indirect Coombs titers ranged from 1:1024-2048. All nine past pregnancies (conceived with three different partners) had ended in abortion, intrauterine death or neonatal death

METHODS

The patient was treated with a single session of plasmapheresis (week 14) immediately followed by five days of immunoglobulin therapy and immunosuppressive therapy based on azathioprine and prednisone (weeks 15-22). Seven fetal transfusions (one intraperitoneal, six intravascular) were performed beginning at 16 weeks.

RESULTS

The pregnancy, which was characterized by insulin-dependent gestational diabetes, spontaneously resolving polyhydramnios and peak indirect Coombs titers of 1:65,536, ended at 27 weeks with cesarean section delivery of a viable female weighing 1,000 g. In spite of numerous neonatal complications, the child is physically well at age 3, with normal intellectual and psychomotor development.

CONCLUSION

In light of the negative outcomes of the patient's nine past pregnancies, our experience suggests that the early initiation of an integrated approach based on noninvasive and invasive techniques can play a potentially decisive role in the management of severe Rh-alloimmunization.

Ovine fetal growth curves in twin pregnancy: ultrasonographic assessment

PURPOSE OF INVESTIGATION

The fetal-lamb model is a fundamental tool for developing clinical applications for the treatment of human fetal pathology (e.g., open fetal surgery). Accurate estimation of gestational age is important to avoid size-related problems during surgery.

METHODS

To evaluate the effect of twinning on ovine fetal growth, we followed seven twin pregnancies in Comiso ewes from mating through parturition. Fetal growth indexes (muzzle-occipital and mean abdominal diameters, abdominal circumference, femoral and humeral length) were measured weekly using perimammary ultrasonography and analyzed with a linear quadratic regression model based on natural logarithms of each parameter and fetal age.

RESULTS

The model explained > 90% of the variability observed, with determination coefficients of 95% (femoral length, abdominal circumference), 94% (abdominal diameter, humeral length), and 89% (muzzle-occipital diameter).

CONCLUSION

Mean birth weight was lower than that reported for singleton fetal lambs, as it is in bigeminal pregnancies in humans, despite the uterine and placental differences between these two species. With the exception of slightly earlier growth deceleration, curves for head and long-bone growth resembled those for singleton ovine fetuses. Ovine fetal growth patterns (like those of humans) in singleton and twin pregnancies are similar.

Recent advances in the diagnosis of malignant hyperthermia susceptibility: how confident can we be of genetic testing?

Malignant hyperthermia (MH) is a condition that manifests in susceptible individuals only on exposure to certain anaesthetic agents. Although genetically heterogeneous, mutations in the RYR1 gene (19q13.1) are associated with the majority of reported MH cases. Guidelines for the genetic diagnosis for MH susceptibility have recently been introduced by the European MH Group (EMHG). These are designed to supplement the muscle biopsy testing procedure, the in vitro contracture test (IVCT), which has been the only means of patient screening for the last 30 years and which remains the method for definitive diagnosis in suspected probands. Discordance observed in some families between IVCT phenotype and susceptibility locus genotype could limit the confidence in genetic diagnosis. We have therefore assessed the prevalence of 15 RYR1 mutations currently used in the genetic diagnosis of MH in a sample of over 500 unrelated European MH susceptible individuals and have recorded the frequency of RYR1 genotype/IVCT phenotype discordance. RYR1 mutations were detected in up to approximately 30% of families investigated. Phenotype/genotype discordance in a single individual was observed in 10 out of 196 mutation-positive families. In five families a mutation-positive/IVCT-negative individual was observed, and in the other five families a mutation-negative/IVCT-positive individual was observed. These data represent the most comprehensive assessment of RYR1 mutation prevalence and genotype/phenotype correlation analysis and highlight the possible limitations of MH screening methods. The implications for genetic diagnosis are discussed.

Multivariate discriminant function based on six biochemical markers in blood can predict the cirrhotic evolution of chronic hepatitis

BACKGROUND

Serologic markers have been proposed for monitoring hepatic fibrosis in chronic active liver disease. Because none of these markers, when used singly, is totally satisfactory, we developed and evaluated a multivariate approach.

METHODS

We studied two cohorts of chronic hepatitis (54 patients) and cirrhosis patients (49 patients) to identify a panel of biochemical markers that discriminates between the two diseases. Using multivariate discriminant analysis, we selected a function, based on the concentrations of six biochemical markers (fibronectin, prothrombin, pseudocholinesterase, alanine aminotransferase, manganese superoxide dismutase, and N-acetyl-beta-glucosaminidase). We then prospectively validated this function on a second temporal cohort of patients.

RESULTS

Multivariate discriminant analysis correctly classified 93.7% of patients (94.3% of chronic hepatitis and 92.9% of cirrhosis patients) in the first cohort and 85% of patients (89.5% of chronic hepatitis patients and 81% of cirrhosis patients) in the second cohort.

CONCLUSIONS

Discriminant analysis of results of six inexpensive biochemical markers provides a high predictive value for differentiation between liver cirrhosis and chronic hepatitis. Consequently, these biochemical markers condensed into a multivariate discriminant analysis value for each patient provide information that can be contributory for subsequent options during the evolution of the natural history of chronic hepatitis.

Identification of a novel mutation in the ryanodine receptor gene (RYR1) in a malignant hyperthermia Italian family

Malignant hyperthermia (MH) is an inherited autosomal dominant pharmacogenetic disorder and is one of the main causes of death subsequent to anaesthesia. Around 50% of affected families are linked to the ryanodine receptor (RYR1) gene. To date, 19 mutations have been identified in the coding region of this gene and appear to be associated with the MH-susceptible phenotype. Here we report the identification by two independent methods of a novel mutation associated with the MH-susceptible phenotype in the RYR1 gene: the 6488G-->C transversion, resulting in the replacement of the Arg2163 with a proline residue.

Primary cardiac tumors: early and late results of surgical treatment in 91 patients

BACKGROUND

Between March 1980 and September 1997, 91 patients underwent evaluation and treatment for primary cardiac neoplasms.

METHODS

Tumors were grouped into three categories: atrial myxomas, benign nonmyxomas, and malignant tumors. Survivors were contacted; no one was lost to follow-up. The mean follow-up for this series is 7 +/- 5 years.

RESULTS

Eighty-three patients were diagnosed with atrial myxomas (Male/Female: 29/54), average age 55 +/- 13 years. The hospital mortality was 3.6% (3/83), the late mortality was 6.5% (5/80). No recurrent myxomas have been identified clinically or by echocardiography in any patient. Three patients were diagnosed with benign nonmyxoma tumors. (Male/Female: 2/1), average age 64 +/- 8 years. There were no perioperative deaths and 1 patient died 4 years postoperatively from fibroma, with no linked causes. No recurrent tumors have been identified. Five patients were diagnosed with malignant tumors. (M/F: 1/4), average age 53 +/- 16 years. The hospital mortality was 20% (1/5); in 3 patients a redo-operation was necessary after 8, 11, and 12 months because of tumor recurrence. All patients died within 3 years of the first operation (mean 13 +/- 14 months).

CONCLUSIONS

Surgical resection, when possible, is the treatment of choice for all primary cardiac tumors. Patients with benign tumors are probably cured by resection and in our experience there was no known tumor recurrence. Effective palliation is possible with resection of malignant tumors, but more effective adjuvant therapy will be necessary to improve long-term prognosis.

Left atrial approach to big myxoma with angiographically visible neovascularity. Report of one case

In this article, we report a 65-year-old man with a large atrial myxoma arising from the posterior wall and from the base of the right inferior pulmonary vein. The big neoplastic mass showed a large implant site. A rare atrial myxoma neovascularity arising from the atrial circumflex artery was very clearly visualized by selective coronary arteriography. The surgical approach used to resect this tumor was an isolated left atriotomy that provided excellent exposure and safe excision.

A case of discordance between genotype and phenotype in a malignant hyperthermia family

Malignant hyperthermia (MH) is an inherited autosomal dominant pharmacogenetic disorder and is the major cause of anaesthesia-induced death. Malignant hyperthermia susceptibility is usually diagnosed by the in vitro contracture test (IVCT) performed on fresh muscle biopsies exposed to caffeine and halothane, respectively. Around 50% of affected families are linked to the ryanodine receptor (RYR1) gene. The human RYR1 gene maps to chromosome 19q13.1 and encodes a protein that associates as a homotetramer and acts as a calcium-release channel from the sarcoplasmic reticulum. To date, 17 mutations have been identified in the coding region of the RYR1 gene and appear to be associated to the MH-susceptible phenotype. Here we describe a rare case of discordance between genotype (characterised by the presence of the Arg614Cys mutation in the RYR1 gene) and MH-normal typed phenotype. Although the IVCT remains a very reliable procedure for the assessment of MH status, genetic data can provide in some cases an additional aid to clinical diagnosis.

Macroenzyme investigation and monitoring in children with persistent increase of aspartate aminotransferase of unexplained origin

Ten children with asymptomatic persistent cryptogenic increased serum levels of aspartate aminotransferase (AST) were screened for detection and monitoring of AST macroenzyme (macroAST). MacroAST was found in 4 patients; their serum AST levels were significantly higher than in those without biochemical evidence of macroAST (mean +/- SD: 515 +/- 433 and 78 +/- 16 IU/L, respectively; P = .0095). MacroAST was a persistent, benign phenomenon and was probably not congenital.

Osteogenic response to hydroxyapatite-fibrin implants in maxillofacial bone defects

Bone formation in hydroxyapatite-fibrin implants has been reported several times. However, available studies refer to experimental animals, or are limited to short periods after implantation. We report the results of histological, histochemical and ultrastructural studies carried out 2.5-8 yr after implantation of non-resorbable, porous hydroxyapatite (HA) and fibrin glue in human maxillofacial bones. Prominent ossification was found in all cases, with the presence of normally structured spongy bone. HA granules were embedded in the calcified bone matrix. They had not elicited inflammatory reactions and did not induce bone resorption. Ossification was preceded by the appearance of alkaline phosphatase activity on fibroblast-like cells, and by the formation of dense collagenous layers, similar to osteoid borders, on the surface of HA granules. The early phases of the calcification process occurred in these borders, with the appearance of calcification nodules adjacent to alkaline phosphatase-positive osteoblast-like cells. A remodeling process similar to that occurring in normal bones was found in the newly formed bone. These results justify the conclusion that HA-fibrin implants lead to the formation of long-lasting bone that does not differ from that of the normal maxillofacial skeleton. Mixing the HA granules with fibrin has the advantage of creating an easily mouldable material which can be adapted to any skeletal surface and stays in place after surgery.

Ventricular septal rupture after a myocardial infarction: clinical features and long term survival

BACKGROUND

Ventricular septal defect (VSD) represents a serious complication after acute myocardial infarction (AMI) with an incidence of 1-2%. Surgical treatment is often mandatory in the early period after AMI because of the worsening of the hemodynamic and clinical conditions.

METHODS

We reviewed 34 patients complicating AMI who underwent surgical treatment at our Institution from January 1988 to December 1994 (23 males, 11 females, mean age 64.2+/-7.96, range 45-78). The localization of the AMI was anterior in 47.05% but inferior in 52.95% of the patients (p=NS). The mean time between AMI and VSD was 5.24+/-9.31 days. The preoperative NYHA functional class was III-IV in 93% of the patients. QP/QS ratio was 2.7+/-0.65 and the diameter of VSD ranged from 1 to 8 (mean 2.5+/-0.35). In 26 patients (76.4%) an intraortic balloon pump (IABP) was inserted before surgery. Surgical treatment was done after 10+/-17.7 days after VSD appearance through a left ventriculotomy. Ten patients received a concomitant myocardial revascularization.

RESULTS

Overall surgical mortality was significantly higher (p<0.05) in patients operated on in the early period after AMI (1+/-1.4 days) and with VSD complicating an inferior AMI. A complete follow-up was possible in all the survivors with a cumulative FU of 1453 month/patients. Two patients received a redo procedure after 30 and 40 days after the first correction because of a residual shunt. We observed 3 late deaths for re-AMI and one for complications after bronchial pneumonia. The actuarial survival rate is 70% at 1 year, 68% at 2 years and 65% at 7 years. NYHA functional class after operation is 1-11 in 91% of the patients.

CONCLUSIONS

The major determinant of hospital survival in VSD after AMI in our patient population was the anatomical localization and the early timing of the operation. We believe that a prompt diagnosis and immediate cardiac support (IABP or ventricular assist device) is recommended to obtain a hemodynamic stabilization and to achieve the shaping of stronger cicatricial tissue before surgery. Nevertheless surgical repair of VSD is mandatory when clinical and hemodynamic condition becomes unacceptable. The results in the long term assessment are very satisfying.

Comparison of new rapid methods for D-dimer measurement to exclude deep vein thrombosis in symptomatic outpatients

Eighty-seven outpatients consecutively admitted to the emergency unit of our hospital with clinically suspected first deep vein thrombosis (DVT) of a leg had D-dimer levels measured by the following recently introduced fast methods: VIDAS (bioMerieux), LPIA (Mitsubishi), Nephelotex (Biopool), Nycocard (Nycomed) and Instant.I.A. (Diagnostica Stago). A latex agglutination test (Minutex, Biopool) was also performed and a classical ELISA (Gold EIA, Agen) used as reference. Venography was performed in all patients, with DVT diagnosed in 42 (37 proximal). All the new methods can be adopted in emergency situations, since they are suited for individual tests, are rapid and the reagents ready to use. All the methods proved to have a good interassay reproducibility. The new D-dimer and latex agglutination tests showed negative (88-96%) and positive (63-81%) predictive values similar to those of ELISA (92% and 71%, respectively), though the still wide confidence intervals suggest larger patient population series be investigated. As regards clinical application, the use of these tests to rule out DVT should be tested in prospective clinical follow-up trials where anticoagulation is withheld in subjects with negative non-invasive reliable vascular tests and normal D-dimer levels.