[Tomographic studies of myocardial perfusion normality with 99m Tc-Tetrofosmin. Spanish multicenter study]

This objective of this study was to obtain a pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers having a less than or equal to 5% likelihood of coronary artery disease that represents normalcy in the Spanish population. A total of 169 volunteers from 15 hospitals were studied. The volunteers were divided into 5 groups: Groups 1, 2 or 3 corresponding to men < 30 years (n = 33), men between 30 and 50 years (n = 32), or men > 50 years (n = 31); Groups 4 or 5: premenopausal (n = 38) or postmenopausal women (n = 35). A clinical history, physical examination, clinical laboratory parameters, echocardiography and a symptom limited exercise stress test were performed in all of them and had to be normal. The mean likelihood of coronary artery disease was 1.15 +/- 1.07%.Twenty-four segments were analyzed in each study and were classified into 5 grades of uptake (1 = normal, 2, 3, 4 = mild, moderate or severe defect and 5 = no uptake). Defects were then analyzed according to sex and location. Considering the stress and rest studies separately (8,112 segments), only 19 moderate and 75 mild defects were found, these corresponding to 16 volunteers, with more inferior defects in men and anterior defects in women. These data validate the normalcy of our population. A pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers that represents Spanish normal values was obtained.

Oleate, linoleate and cholesterol differently modify aspartyl- and glutamyl-aminopeptidase activities in primary cultures of rat astrocytes

The intake of mono- and polyunsaturated fatty acids has been associated with a minor risk of cardiovascular diseases including hypertension. Changes in levels of fatty acids may also modify the cell activity and may be related with alterations in different regulatory processes. Aminopeptidases are zinc-metalloenzymes which metabolise circulating peptide hormones in several tissues. Glutamyl-aminopeptidase (GluAP) and to a lesser extent, aspartyl-aminopeptidase (AspAP), are related with angiotensin metabolism in the renin-angiotensin system. The present work was designed to study the effect of a range of concentrations (1-100 microM) of oleic and linoleic acids and cholesterol present in the culture medium on the activity of GluAP and AspAP in the culture of rat cerebral cortical astrocytes taken from 21-day-old fetuses. The results showed that oleic acid inhibits, while linoleic acid stimulates the activity of AspAP. Both fatty acids inhibit the activity of GluAP. Cholesterol stimulates the activity of both enzymes. On the basis of these results, a functional link may exit between the effects of fatty acids on hypertension and the modulation of aminopeptidase activity by these compounds in rat astrocytes, as an example of target cell type in the central nervous system.

Identification of surfactant degradation products as toxic organic compounds present in sewage sludge

A cost-effective strategy combining chemical analysis and bioassays for the identification of polar toxic compounds in sewage sludge is reported. ToxAlert 100 bioluminescence inhibition assay was used in combination with chemical analysis involving extraction, clean-up, chromatographic separation and mass spectrometry detection. This methodology was applied to real samples of sludge from three wastewater treatment plants (WWTP) located in Catalonia (Spain) during a 3 month period. In the first step, sewage sludge was lyophilized, treated by sonication with a mixture of methanol and chloroform and finally cleaned up using a sequential solid phase extraction (SSPE) with an octadecylsilica cartridge (C18) in series with a polymeric Lichrolut EN cartridge (Lic EN). In the second step, the toxicity of each fraction of the sludge sample was investigated using the ToxAlert 100. The unequivocal identification and quantification of polar organic cytotoxic substances present in the fractionated extracts were determined by liquid chromatography-mass spectrometry (LC-MS). Major toxic compounds identified were: non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their intermediates (polyethylene glycol polyethoxylated, nonylphenol carboxylates and polyethoxylated alcohol carboxylates), linear alkylbenzenesulfonates and heavy metals. The toxic response (in terms of bioluminescence inhibition using ToxAlert 100), defined by the 50% effective concentration (EC50), and the toxicity units (TU) for every standard non-ionic surfactant were calculated. The results provided the identification of polar cytotoxic compounds as well as the evaluation of their contribution to the total toxicity observed in sewage sludge.

Calcium-dependent modulation by ethanol of mouse synaptosomal pyroglutamyl aminopeptidase activity under basal and K(+)-stimulated conditions

We studied the in vitro effects of ethanol (25, 50 and 100 mM) on pyroglutamyl aminopeptidase activity (pGluAP), which has been reported as thyrotrophin-releasing-hormone-degrading activity. pGluAP was measured in presence or absence of calcium, under basal and K(+)-stimulated conditions, in synaptosomes and their incubation supernatant, using pyroglutamyl-beta-naphthylamide as substrate. In basal conditions, in synaptosomes, pGluAP was inhibited by ethanol in a calcium-independent way. In the supernatant, the response differed depending on the concentration of ethanol. Depolarization with K(+) modified pGluAP in synaptosomes and supernatant depending on the presence or not of calcium. In synaptosomes, in absence of calcium, the activity was inhibited at the highest concentrations of ethanol. In contrast, in the supernatant, under depolarizing conditions, ethanol increases pGluAP in absence of calcium. These changes may be in part responsible of the behavioural changes associated to alcohol intake.

Hypermethylation of P16ink4a and P15ink4b genes as a marker of disease in the follow-up of non-Hodgkin's lymphomas

The hypermethylation of p16ink4a and p15ink4b genes have been described as an inactivating mechanism alternative to deletions and mutations that accounts for a relatively high proportion of cancers, including non-Hodgkin's lymphomas (NHLs). To investigate whether detection of abnormal methylation could have clinical applications in the management and follow-up of lymphomas, we have analysed the behaviour and evolution of p16ink4a and p15ink4b methylation in 13 NHL cases undergoing chemotherapy. All cases were also analysed for the presence of monoclonal rearrangements of immunoglobulin or T-cell receptor genes. Six patients showed methylation in at least one of these genes at diagnosis, whereas in two other cases methylation appeared during the treatment. The other five cases were always unmethylated. Methylation was detected when any histological or molecular evidence of disease was present, suggesting a good correlation between methylation and disease. In some cases, we were able to detect methylation in patients at complete remission and without evidence of monoclonal cell population, indicating a high sensitivity of the PCR to detect methylation. These results suggest that p16ink4a and p15ink4b methylation could be good markers of disease and could be helpful in identifying lymphoma patients at risk of relapse.

Potential relationship between genotype and clinical outcome in propionic acidaemia patients

Propionic acidaemia (PA) is an autosomal recessive disorder caused by mutations in either of the PCCA or PCCB genes which encode the alpha and beta subunits, respectively, of the mitochondrial enzyme propionyl-CoA carboxylase (PCC). In this work we have examined the biochemical findings and clinical outcome of 37 Spanish PA patients in relation to the mutations found in both PCCA and PCCB genes. We have detected 27 early-onset and 101 late-onset cases, showing remarkably similar biochemical features without relation to either the age of onset of the disease or the defective gene they have. Twenty-one of the patients have so far survived and three of them, now adolescents, present normal development. Different biochemical procedures allowed us to identify the defective gene in 9 PCCA deficient and 28 PCCB deficient patients. Nine putative disease-causing mutations accounting for 77.7% of mutant alleles were identified among PCCA deficient patients, each one carrying a unique genotypic combination. Of PCCB mutant alleles 98% were characterised. Four common mutations (ins/del, E168K, 1170insT and A497V) were found in 38/52 mutant chromosomes investigated, whereas the remainder of the alleles harbour 12 other different mutations. By examining the mutations identified both in PCCA and PCCB genes and the clinical evolution of patients, we have found a good correlation between certain mutations which can be considered as null with a severe phenotype, while certain missense mutations tend to be related to the late and mild forms of the disease. Expression studies, particularly of the missense mutations identified are necessary but other genetic and environmental factors probably contribute to the phenotypic variability observed in PA.

Prenatal exposure to valproic acid during pregnancy and limb deficiencies: a case-control study

We conducted a case-control study using data from the Spanish Collaborative Study of Congenital Malformations (ECEMC) on the relationship between prenatal exposure to valproic acid (VPA) and the presence of limb deficiencies in newborn infants. Among a total of 22,294 consecutive malformed infants (once we excluded genetic syndromes) and 21,937 control infants with specified data on antiepileptic drugs during gestation, 57 malformed infants and 10 control infants were exposed to VPA during the first trimester of pregnancy. Of the total of malformed infants exposed to VPA, 36.8% (21/57) presented with congenital limb defects of different types (including overlapping digits, talipes, clubfoot, clinodactyly, arachnodactyly, hip dislocation, pre- and postaxial polydactyly, etc.), three of them having limb deficiencies. The result of the case-control analysis shows a risk for limb deficiencies of odds ratio = 6.17 [confidence interval (CI) 1.28-29.66, P = 0.023], after controlling for potential confounder factors. If we consider that in our population the prevalence at birth of this type of defect is 6.88 per 10,000 livebirths (95% CI 6.43-7.36) we can estimate that the risk for women treated with VPA of having a baby with limb deficiencies would be around 0.42%. The limb deficiencies in the three patients exposed to VPA were the following: the first case was a newborn infant with hypoplasia of the left hand, the second patient was a newborn infant with unilateral forearm defect and hypoplastic first metacarpal bone in the left hand, and the third patient presented with short hands with hypoplastic first metacarpal bone, absent and hypoplastic phalanges, retrognathia, facial asymmetry, hypospadias, teleangiectatic angioma in skull, and hypotonia.

[In vitro study of the effect of ethanol on pyroglutamyl aminopeptidase activity in mouse synaptosomes under basal and stimulated conditions]

INTRODUCTION AND OBJECTIVE

Pyroglutamyl aminopeptidase (pGluAP) is an omega peptidase which removes pyroglutamyl N-terminals residues from peptides and arylamidase derivatives. This activity is thought to be involved in the regulation of several physiological mechanisms on the central nervous system. pGluAP can modulate various susceptible endogenous substrates such as thyrotrophin-releasing hormone (TRH). It is well known that TRH plays an important role in the modulation of the behavioral changes induced by ethanol and others drugs. The aim of this work was to study the in vitro effects of ethanol (25, 50 and 100 mM) on the pGluAP activity and its ability for modulating the TRH.

MATERIAL AND METHODS

pGluAP activity was measured in synaptosomes from cerebral cortex of mouse, using pyroglutamyl-beta-naphthylamide as substrate in basal and stimulated (K+ 25 mM) conditions, and in presence or absence of calcium on the buffer.

RESULTS

In basal conditions, ethanol produced an inhibition of the pGluAP activity in presence or absence of calcium, being this inhibition non dose-related. However, the stimulation with K+ 25 mM did not produce a modification of pGluAP activity in presence of calcium, but produced a light increase in absence of it. Depolarization in presence or absence of calcium and ethanol produced an inhibition of pGluAP activity, which changed in function of the ethanol concentration used.

CONCLUSIONS

Ethanol modifies pGluAP activity in basal conditions by a mechanism independent of calcium, but the changes observed after the stimulation with high K+ may be due to a calcium-dependent mechanism. These variations of pGluAP activity induced by ethanol, and their effects on their endogenous substrates, specially TRH, may be responsible for the behavioral changes associated to the alcoholism and mediated by TRH.

[Diagnosis and treatment of postmenopausal osteoporosis after a Colles' fracture]

OBJECTIVES

To investigate whether the presence of Colles fracture leads to diagnostic studies or treatment of osteoporosis in postmenopausal women.

DESIGN

Retrospective study with follow-up of incident cases.

SETTING

Hospital General de Vic and Primary Care Centre Osona. Vic. Barcelona.

PARTICIPANTS AND METHODS

We studied 80 postmenopausal women with Colles' fracture during 1995-1996. The clinical records were systematically reviewed and treatment with antiosteoporotic drugs before and after Colles' fracture were compared.

MEASUREMENTS AND MAIN RESULTS

Diagnostic studies were found in 3 (3.8%) patients. 6 patients (7.5%) took antiosteoporotic drugs before the fracture while 21 (26.3%, p < 0.001) did so after it.

CONCLUSIONS

A recent Colles' fracture induces few osteoporosis diagnostic studies. However, it leads to a significant increase in the use of antiosteoporotic drugs.

Selenium, copper, and zinc indices of nutritional status: influence of sex and season on reference values

The objective was to estimate the possible influence of season or season and sex on the selenium, glutathione peroxidase (GSH-Px), copper, zinc, and superoxide dismutase (SOD) values in plasma with a view to establishing reference values. For this purpose, 55 healthy volunteers (36 women and 19 men) were selected and their whole-blood samples were collected four times a year at the beginning of each season. In the population as a whole, no statistically significant seasonal differences were detected in copper, selenium, and GSH-Px values in plasma, whereas zinc and SOD values in plasma depended on the season. In general, the variability was higher among the women. In view of the differences detected according to sex and/or season in the parameters studied, we recommend taking samples from men and women and from different seasons to establish reference values.

Genetic and phenotypic aspects of phenylalanine hydroxylase deficiency in Spain: molecular survey by regions

We present an extensive study of the genetic diversity of phenylalanine hydroxylase deficiency in the Spanish phenylketonuria population. We have analysed 195 PKU patients by DGGE analysis identifying 67 different mutations which represent 89% of the total mutant chromosomes. Seventeen mutations first described in Spain have not yet been detected elsewhere; ten of these are reported here for the first time. The clinical significance of this high genetic heterogeneity was examined by analysing the genotype-phenotype correlations, mainly focusing on the mild hyperphenylalaninaemia (MHP) phenotype. The genotypes found in a group of 93 MHP patients, the largest analysed so far, are described in detail, as well as the relative frequencies of the MHP mutations identified. From the total pool of mutations, 27 can be considered severe, 18 can be defined as mild and 13 as associated with MHP. The prevalent mutations correspond to one severe mutation (IVS10nt-11), one MHP mutation (A403V) and two mild mutations (165T and V388M). The high frequency of mutations with a low degree of severity can explain the relatively higher prevalence of MHP and mild PKU phenotypes in Spain compared with NOrthern European populations. We have looked at the geographical distribution in Spain of the more common mutations, finding evidence of local mutation clustering, which could be the result of differences in the ethnic background and/or of genetic drift within each region.

[Clinical factors that affect the detection of BCR-ABL transcripts after allogenic bone marrow transplantation for chronic myeloid leukemia]

BACKGROUND

To evaluate the relationship between clinical parameters and the ability to detect BCR-ABL-positive cells in a series of 27 long survivor patients after allogeneic bone marrow transplantation (BMT) for chronic myelogenous leukemia (CML).

PATIENTS AND METHODS

A total of 78 samples obtained between 1 and 160 months after BMT were analyzed for the presence of the BCR-ABL transcript detected by the reverse-transcription polymerase chain reaction (PCR) using nested primers. Median follow up was 83 months.

RESULTS

16 patients were persistently PCR-positive and 7 patients persistently PCR-negative. The original transcript became negative in four patients. Only two of the positive cases developed hematologic relapse during the period of study. High white blood cell counts before BMT (17.88 vs 10.12 x 10(9)/l; p = 0.008) and immunosuppressive therapy for chronic graft-versus-host disease (p < 0.05) were associated with an increased ability to detect residual BCR-ABL positive cells.

CONCLUSIONS

Our data show that most patient are persistently BCR-ABL positive after BMT for CML. If these findings represents a dynamic balance between the tumour burden prior BMT and the immunological capability of the graft must be confirmed in further studies.

Hypermethylation of p15/ink4b/MTS2 gene is differentially implicated among non-Hodgkin's lymphomas

P15 (MTS2) gene is a candidate tumor suppressor gene localized adjacent to the p16 gene at 9p21. Deletions at the 9p21 region frequently affect both p16 and p15 genes, however, mutations in the coding sequence of the p15 gene have not been found in the majority of tumors analyzed, including non-Hodgkin's lymphomas. Abnormal methylation of the promoter region of p15 has been recently described as an alternative mechanism of inactivation of this gene. We analyzed 72 non-Hodgkin's lymphomas (NHL) for methylation at p15 exon 1 by PCR and Southern blot techniques using methylation-sensitive restriction enzymes. Abnormal methylation was found in eight cases (11%), most of them (three MALT, one anaplastic T cell lymphoma, one Burkitt and one follicular lymphoma) showing hypermethylation in the p16 gene also. In contrast, two pleomorphic T cell NHL showed a selective methylation at p15 gene, while the p16 gene remained unmethylated. The results show that methylation at the p15 gene is frequently associated with p16 methylation in NHL, and suggest that selective methylation of p15, although uncommon, could be a specific alteration implicated in T cell NHL.

Importance of mixed chimerism to predict relapse in persistently BCR/ABL positive long survivors after allogeneic bone marrow transplantation for chronic myeloid leukemia

Determination of hematological chimerism could be helpful in understanding the biology of leukemic relapse after allogeneic bone marrow transplant (BMT) for chronic myeloid leukemia (CML), because the detection of malignant residual cells carrying the bcr/abl message by qualitative RT-PCR is of limited value in predicting disease progression for individual patients. We have studied the chimerism pattern and the bcr/abl status by Southern-blot in 15 CML patients (M/F:6/9) transplanted with unmanipulated BM from HLA identical sibling donors, persistently bcr/abl positive by RT-PCR. The median age of the series was 31 years (18-49) and disease status at BMT was: chronic phase: 11, accelerated phase: 3 and blast crisis: 1 patient. Of the 15 patients, 9 are alive and in complete remission (CR), 4 have died in CR and 2 are alive but suffered relapse at + 19 and +26 months post-BMT. The median follow-up is 81 months (13,7-168). Rearrangement of the BCR gene was performed by Southern-blot using P32-labeled transprobe-1. PCR analysis of chimerism was assessed using primers for the following VNTR loci: D1S80, D1S111, 33.1, APO-B, YNZ-22, lambdag3 and DXS52. Seventy-nine samples were analyzed (median per patient 5 (range 2-9)). Thirteen patients showed complete chimerism and lacked BCR rearrangement over time by Southern-blot. The 2 patients who relapsed showed mixed chimera status from +9 and +5 months respectively until the end of the study. Persistent BCR rearrangement was observed in these 2 patients from +12 and +11 months respectively. Our data suggest that mixed chimerism may predict hematologic or cytogenetic relapse by several months in those patients who are persistently PCR-positive post-BMT.

[Correlation of flow and static cytometry; their application to the study of anaplastic lymphomas]

PURPOSE

DNA study by cytometric methods is one of the prognosis factors considered in malignant tumours. Flow cytometry (FCM) was the most frequently used techniques in cell suspensions. Image cytometry (ICM) was also applied in cellular smears and it is possible to measure the results with an Image Analyzer, which supposes a substancial advantage over DNA studies. To confirm the results and correlation of the two techniques a controversial subtype of lymphoid tumour was selected: Anaplastic large cell lymphoma (ALCL).

MATERIAL AND METHODS

Fifty four cases of ALCL (23 classical type and 31 ACL-Hodgkin related) were studied. Cytometry was performed in paraffin-embedded tissues previously dewaxed, rehydrated and minced. FCM was done in suspensions incubated with ribonuclease A and stained with propidium iodide in an EPICS-C flow cytometer. ICM study was performed in Feulgen-stained smears and measured by an Image Analyzer CAS-200.

RESULTS

All cases were aneuploid. ALCL were 30.5% hypodiploid (HpD) and 69.5% hyperdiploid (HrD) by FCM; 43.5% HpD and 56.5% HrD by ICM. ALCL-HR were 58% HpD and 42% HrD by FCM; 68% HpD and 32% HrD by ICM. There was a lack of correlation of 22% between both methods but it was not statistically significant.

CONCLUSIONS

We can conclude the obtained results by FCM and ICM are almost similar.

Description of the characteristics of cases with noncontiguous neural tube defects identified in a series of consecutive births

Van Allen et al. [(1973) Am. J. Med. Genet. 47:723-743] provided evidence for multisite closure of the neural tube in humans. Reynolds et al. [(1995) Proceedings of the Greewood Genetic Center 14:70-71] and Seller [(1995) J. Med. Genet. 32:205-207] described 13 and seven cases of noncontiguous neural tube defects (NTDs) respectively and concluded that the presence of noncontiguous NTDs cannot be explained on the basis of the model of a single initiation site with bidirectional closure. Here we present a series of 14 consecutive infants with noncontiguous NTDs, describing their characteristics. These show that noncontiguous NTDs are clinically heterogeneous, may have differences in sex ratio, and could have causal heterogeneity. The different combinations of closure failure defects have shown proportions in our population that are different from those in the populations studied by Reynolds et al. and Seller.

An unusual late-onset case of propionic acidaemia: biochemical investigations, neuroradiological findings and mutation analysis

We report a 5-year-old boy with propionic acidaemia who developed a rapidly fatal necrosis of the basal ganglia after an episode of clinical deterioration. Neither metabolic acidosis nor hyperammonaemia were present. Organic acid analysis in both urine and CSF showed increased levels of methylcitric and 3-hydroxypropionic acids. Propionic acidaemia was confirmed by demonstrating a propionyl-CoA carboxylase deficiency (11% of control value) in skin fibroblasts. DNA analysis revealed that the patient was a compound heterozygote for two mutations in the PCCB gene.

CONCLUSION

Propionic acidaemia can present as a sudden and fatal neurological disease and not only as an organic aciduria with severe biochemical dis-turbances and progressive neurological deterioration.

Severe limb deficiencies, vertebral hypersegmentation, and mirror polydactyly: two additional cases that expand the phenotype to a more generalized effect on blastogenesis

We report on 2 unrelated fetuses with a multiple congenital anomaly pattern of severe limb deficiencies, vertebral/rib alterations, and mirror polydactyly similar to that described previously by us [Urioste et al., Hum Genet 97:214-217, 1996]. In addition, the two cases we present here have a more extense alteration of blastogenesis, expanding the phenotype of the cases previously reported. We have suggested [Urioste et al., Hum Genet 97:214-217, 1996] that this condition may be caused by a mutation in a developmental control gene that affects body-plan organization. The minimal estimate of the prevalence of this new entity in our population (the Spanish Collaborative Study of Congenital Malformations, ECEMC) is 3.0/ 1,000,000 live births.

katGI and katGII encode two different catalases-peroxidases in Mycobacterium fortuitum

It has been suggested that catalase-peroxidase plays an important role in several aspects of mycobacterial metabolism and is a virulence factor in the main pathogenic mycobacteria. In this investigation, we studied genes encoding for this protein in the fast-growing opportunistic pathogen Mycobacterium fortuitum. Nucleotide sequences of two different catalase-peroxidase genes (katGI and katGII) of M. fortuitum are described. They show only 64% homology at the nucleotide level and 55% identity at the amino acid level, and they are more similar to catalases-peroxidases from different bacteria, including mycobacteria, than to each other. Both proteins were found to be expressed in actively growing M. fortuitum, and both could also be expressed when transformed into Escherichia coli and M. aurum. We detected the presence of a copy of IS6100 in the neighboring region of a katG gene in the M. fortuitum strain in which this element was identified (strain FC1). The influence of each katG gene on isoniazid (isonicotinic acid hydrazide; INH) susceptibility of mycobacteria was checked by using the INH-sensitive M. aurum as the host. Resistance to INH was induced when katGI was transformed into INH-sensitive M. aurum, suggesting that this enzyme contributes to the natural resistance of M. fortuitum to the drug. This is the first report showing two different genes encoding same enzyme activity which are actively expressed within the same mycobacterial strain.

[Neuropsychological deficits, obstetric complications and premorbid adjustment in patients with the first psychotic episode]

In spite of the great number of studies that have proved the existence of cognitive disturbances in schizophrenic subjects, conflicting results have not allowed to glimpse a typical pattern of neuropsychological deficits in schizophrenia. On the contrary, these results have raised important controversies regarding the nature of such cognitive impairment. Thus, questions concerning the existence of generalized versus focal cognitive impairment or in relation lo the static versus progressive nature of these deficits remain unresolved. In the middle of these debates, the need for prospective research, which focuses on the neuropsychological deficits of schizophrenia and other psychotic disorders from the beginning of the illness, has been pointed out. In these lines we present the results obtained in our study in which 59 subjects, who were admitted in our hospital for presenting a first psychotic episode, were assessed. Measures of premorbid adjustment, obstetric complications and clinical symptoms were taken and correlated to measures of cognitive performance obtained by using a minibattery of neuropsychological tests at time of dismissal. Results showed, as in previous research, that neuropsychological deficits are already present in psychotic patients at the beginning of the illness. These deficits in our sample were related lo obstetric complications especially in males, and disturbances of premorbid adjustment occurred in early stages of development. These results support the neurodevelopmental hypothesis of schizophrenia.

Relationship between mutation genotype and biochemical phenotype in a heterogeneous Spanish phenylketonuria population

Genotyping of the phenylalanine hydroxylase (PAH) gene offers a new tool for characterizing patients with phenylketonuria (PKU), refining the diagnosis and aiding in the prediction of the clinical outcome and in the implementation of a more adequate treatment. The primary goal of this work was the detailed study of the different allele combinations and the metabolic phenotypes in Spanish PKU patients in order to understand better the clinical heterogeneity of PAH deficiency in our population. The results show that the disease phenotype is a consequence of a combination of mutations at the PAH locus and this observation is valid throughout the spectrum of clinical and biochemical varieties found in Spanish PKU patients. A stronger correlation was found between the predicted residual activity, when known from previous in vitro studies of the mutant proteins, and the Phe tolerance than between the predicted residual activity and the inverse of Phe levels at diagnosis. The observed genotype-phenotype correlations and the available data on the in vitro residual activity of the mutant proteins has enabled the estimation of the severity of most of the mutations found in Spain. This study includes relevant data for clinicians and pediatricians adding to the present knowledge which relates allelic PAH genotypes to biological phenotypes.

Population pharmacokinetics of caffeine in premature neonates

OBJECTIVE

To determine population pharmacokinetic parameters of caffeine in premature neonates.

METHODS

This population analysis was done using 145 serum concentration measurements gathered from 75 hospitalized patients during their routine clinical care. The data were analysed by use of NONMEM (mixed effects modeling) according to a one-compartment open model with either zero or first-order absorption and first-order elimination. The effect of a variety of developmental, demographic and clinical factors (gender, birth weight, current weight, gestational age, postnatal age, postconceptional age and concurrent treatment with phenobarbital and parenteral nutrition) on clearance and volume of distribution was investigated. Forward selection and backward elimination regression identified significant covariates.

RESULTS

The final pharmacostatistical model with influential covariates were as follows: clearance (m1.h-1) = 5.81-current weight (kg) + 1.22.postnatal age (weeks), multiplied by 0.757 if gestational age < or = 28 weeks and 0.836 if the current primary source of patients' nutrition is parenteral nutrition, and volume of distribution (ml) = 911.current weight (kg). The inter-individual variability in clearance and the residual variability, expressed as coefficients of variation, were 14.8%, and 18.44%, respectively. Due to the lack of information on the data set we were unable to characterize the interindividual variability for volume of distribution.

CONCLUSION

In this study, which involved on average only two serum concentrations of caffeine per patient, the use of NONMEM gave us significant and consistent information about the pharmacokinetic profile of caffeine when compared with available bibliographic information. Additionally, parenteral nutrition and low gestational age (< or = 28 weeks) may even come to be considered as risk factors, and their presence may serve as an indicator of the need for periodic monitoring of caffeine concentrations in premature infants.

Selenium and glutathione peroxidase reference values in whole blood and plasma of a reference population living in Valencia, Spain

In order to assess the reference values for selenium nutritional status, adequate indicators (selenium concentration and glutathione peroxidase activity) were determined in whole blood and blood derivates of a healthy population (n = 287) from the province of Valencia, Spain. The reference population was selected by applying preestablished criteria. Selenium in whole blood and plasma was measured by graphite furnace atomic absorption spectrometry (GFAAS), with a deuterium correction, after addition of Pd/Mg(NO3)2 as the matrix modifier and appropriate dilution. Accuracy was checked by means of a reference material (Seronorm Trace Metals serum and whole blood). The population's reference intervals for selenium content at a 95% confidence level were: 53.03-108.96 and 66.71-119.4 mg/L for plasma and whole blood selenium concentration respectively. GPX activity was measured using a modification of the Paglia and Valentine method, and the reference intervals obtained ranged from 196 to 477 U/L in plasma, from 49 to 93 U/gHb in erythrocytes and from 52 to 96 U/gHb in whole blood. The only statistically significant differences detected between men and women are for to the GPX activity in whole blood. The results obtained are in the range of values found by others authors in healthy populations residing in different European countries.