Images reproducibility of an electrical impedance tomography (EIT) prototype. Analysis of the EIT sensibility in rats in pathological in vivo conditions

The development of a 16 electrode-electrical impedance tomography (EIT) prototype to be applied in neurological fields such as epilepsy in rats has been previously reported. Approaching residual problems in order to improve its performance, this work reports results about changes made in the system hardware as follows: 1) replacing the current source demultiplexing circuit that could impact on a better spatial localization, and 2) a new current source design that increases the current amplitude up to 5 mA/sub rms/. System was evaluated by means of: a) image reproducibility starting from 4 test elements in homogeneous conditions; and b) spatial localization evaluation in conductivity perturbation conditions; this feature is evaluated too in preliminary acute in vivo experiments where an epileptic seizure is induced, and an impedance increase is expected. Results show a 95% of proper images for a) analysis. Spatial localization reports improvement up to 20% transversely and 5.5% longitudinally with regard to previous results. In vivo results are lack of interpretation due poor changes obtained in images. In order to conclude or not a reliable correlation between the perturbation measured and the seizure activity, a new definition of grey scale or other changes could be proposed.

Characterization of benzodiazepine receptor binding in immature rat brain after kainic acid administration

PURPOSE

To evaluate the effects of status epilepticus on benzodiazepine (BDZ) receptor binding in immature rat brain.

METHODS

Twenty-four immature (15 days old) and six adult (90 days old) rats were used in this study. Status epilepticus was induced in immature animals by administration of kainic acid (7 mg/kg intraperitoneal), whereas adults rats received saline. Animals were killed 72 hours or 35 days after treatment, and their brains were used for in vitro autoradiography experiments to determine BDZ binding.

RESULTS

In basal conditions and compared with the adult group, immature animals presented reduced BDZ binding in the entorhinal cortex, substantia nigra pars reticulata, and periaqueductal gray. Seventy-two hours after kainic acid-induced status epilepticus, immature rats showed significantly increased BDZ in the frontal (48%), cingulate (39%), sensorimotor (39%), piriform (57%), and entorhinal (59%) cortices, the medial (84%) and basolateral (27%) amygdaloid nuclei, the dentate gyrus (51%), and the substantia nigra pars reticulata (43%). Thirty-five days after status epilepticus, immature rats displayed decreased BDZ binding in the entorhinal cortex (48%), dentate gyrus (36%), and fields CA1, CA2, and CA3 of Ammon's horn (30%).

CONCLUSIONS

The present study demonstrates that status epilepticus and temporal lobe epilepsy produce a characteristic pattern of BDZ binding changes in the immature rat brain that differs from the one previously seen in adults.

Mutations affecting mRNA splicing are the most common molecular defects in patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders in humans and is caused by mutations in the NF1 gene. To date, the majority of the reported NF1 mutations are predicted to result in protein truncation, but very few studies have correlated the causative NF1 mutation with its effect at the mRNA level. We have applied a whole NF1 cDNA screening methodology to the study of 80 unrelated NF1 patients and have identified 44 different mutations, 32 being novel, in 52 of these patients. Mutations were detected in 87% of the familial cases, but in 51% of the sporadic ones. At least 15 of the 80 NF1 patients (19%) had recurrent mutations. The study shows that in 50% of the patients in whom the mutations were identified, these resulted in splicing alterations. Most of the splicing mutations did not involve the conserved AG/GT dinucleotides of the splice sites. One frameshift, two nonsense and two missense mutations were also responsible for alterations in mRNA splicing. The location and type of mutation within the NF1 gene, and its putative effect at the protein level, do not indicate any relationship to any specific clinical feature of NF1. The high proportion of aberrant spliced transcripts detected in NF1 patients stresses the importance of studying mutations at both the genomic and RNA level. It is possible that part of the clinical variability in NF1 could be due to mutations affecting mRNA splicing, which is the most common molecular defect in NF1.

Prenatal diagnosis of sporadic neurofibromatosis type 1 (NF1) by RNA and DNA analysis of a splicing mutation

Neurofibromatosis type 1 (NF1) is one of the most common genetic disorders in humans with an incidence of 1 in 3500. Most of the NF1 mutations reported so far (over 240 mutations) are unique. Specific prenatal diagnosis can only be provided to familial cases by an indirect linkage analysis or to families with a previously identified mutation. Here we report the first prenatal diagnosis in sporadic NF1 by direct characterization of the mutation. We first identified the skipping of exon 10b of NF1 in the mRNA from a woman affected by NF1 and without familial history of the disease. The analysis of genomic DNA identified mutation IVS10b+1G-->A as the cause of the skipping of exon 10b. Chorionic villus sampling (CVS) was performed at 10 weeks of gestation and total RNA was directly extracted from the sample. After reverse transcription (RT) and polymerase chain reaction (PCR) of the cDNA, the skipping of exon 10b was not identified in the CVS upon agarose gel electrophoresis. The fetal origin of the CVS was confirmed via polymorphic markers and the absence of the IVS10b+1G-->A mutation was confirmed by genomic analysis.

A clinical variant of neurofibromatosis type 1: familial spinal neurofibromatosis with a frameshift mutation in the NF1 gene

Spinal neurofibromatosis (SNF) has been considered to be an alternative form of neurofibromatosis in which spinal cord tumors are the main clinical characteristic. Familial SNF has been reported, elsewhere, in three families-two linked to markers within the gene for neurofibromatosis type 1 (NF1) and the other not linked to NF1-but no molecular alterations have been described in these families. We describe a three-generation family that includes five members affected by SNF. All the affected members presented multiple spinal neurofibromas and café au lait spots, one member had cutaneous neurofibromas, and some members had other signs of NF1. Genetic analysis, performed with markers within and flanking the NF1 gene, showed segregation with the NF1 locus. Mutation analysis, performed with the protein-truncation test and SSCP/heteroduplex analysis of the whole coding region of the NF1 gene, identified a frameshift mutation (8042insA) in exon 46, which should result in a truncated NF1 protein. The 8042insA mutation was detected in all five family members with the SNF/NF1 phenotype. To our knowledge, this is the first time that a mutation in the NF1 gene has been associated with SNF. The clinical homogeneity in the severity of the disease among the affected members of the family, which is unusual in NF1, suggests that a particular property of the NF1 mutation described here, a gene closely linked to NF1, or posttranscriptional events are involved in this severe neurological phenotype.

Confirmation of a double-hit model for the NF1 gene in benign neurofibromas

Neurofibroma is a benign tumor that arises from small or large nerves. This neoplastic lesion is a common feature of neurofibromatosis type 1 (NF1), one of the most common autosomal dominant disorders. The NF1 gene codes for a protein called "neurofibromin." It possesses a region that shares a high homology with the family of GTPase-activating proteins, which are negative regulators of RAS function and thereby control cell growth and differentiation. The evidence points to the NF1 gene being a tumor-suppressor gene. NF1 patients also have an increased incidence of certain malignant tumors that are believed to follow the "two hit" hypothesis, with one allele constitutionally inactivated and the other somatically mutated. Recently, somatic loss of heterozygosity (LOH) has been described for neurofibromas, and mutations in both copies of the NF1 gene have been reported for a dermal neurofibroma. The aim of our study was the analysis of the NF1 locus in benign neurofibromas in NF1 patients. We performed LOH analysis on 60 neurofibromas belonging to 17 patients, 9 of them with family history of the disease and 8 of them sporadic. We have analyzed five intragenic NF1 markers and six extragenic markers, and we have found LOH in 25% of the neurofibromas (corresponding to 53% of the patients). In addition, we found that in the neurofibromas of patients from familial cases the deletions occurred in the allele that is not transmitted with the disease, indicating that both copies of the NF1 gene were inactivated in these tumors. Therefore, the recent reports mentioned above, together with our findings, strongly support the double inactivation of the NF1 gene in benign neurofibromas.

Sex differences in mutational rate and mutational mechanism in the NF1 gene in neurofibromatosis type 1 patients

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a prevalence of around 1 in 3500, affecting all ethnic groups. The clinical manifestations of the disease are variable, even among members of the same family, and affect a variety of tissues and cell types, including skin, iris, central and peripheral nervous systems and skeletal system. It has been reported that the majority of sporadic mutations in NF1 arise in paternally inherited alleles. We present here a collaborative study of the parental origin and type of mutation in individuals with de novo NF1, who account for up to a half of all cases of clinically diagnosed NF1. We have studied intragenic and extragenic markers in 470 NF1 families. In 32 of these families it was possible to assess the parental origin of a de novo NF1 mutation either by linkage analysis (in families with three generations) or by the detection of an intragenic deletion in a sporadic NF1 case. Eleven of these 32 families have three generations (the second and third generation being affected), with the mutation (not a large deletion) being of paternal origin in 82% of them (P < 0.05). In the other 21 families an intragenic deletion was detected, in 76% being in the maternal chromosome and in 24% in the paternal one (P < 0.05). Our results suggest that in NF1 the majority of deletions occur in oogenesis, while other types of mutations should account for the paternally derived NF1 mutations.

Molecular characterization of the breakpoints of a 12-kb deletion in the NF1 gene in a family showing germ-line mosaicism

Neurofibromatosis type 1 (NF1) is caused by deletions, insertions, translocations, and point mutations in the NF1 gene, which spans 350 kb on the long arm of human chromosome 17. Although several point mutations have been described, large molecular abnormalities have rarely been characterized in detail. We describe here the molecular breakpoints of a 12-kb deletion of the NF1 gene, which is responsible for the NF1 phenotype in a kindred with two children affected because of germline mosaicism in the unaffected father, who has the mutation in 10% of his spermatozoa. The mutation spans introns 31-39, removing 12,021 nt and inserting 30 bp, of which 19 bp are a direct repetition of a sequence located in intron 31, just 4 bp before the 5' breakpoint. The 5' and 3' breakpoints contain the sequence TATTTTA, which could be involved in the generation of the deletion. The most plausible explanation for the mechanism involved in the generation of this 12-kb deletion is homologous/nonhomologous recombination. Since sperm of the father does not contain the corresponding insertion of the 12-kb deleted sequence, this deletion could have occurred within the NF1 chromosome through loop formation. RNA from lymphocytes of one of the NF1 patients showed similar levels of the mutated and normal transcripts, suggesting that the NF1-mRNA from mutations causing frame shifts of the reading frame or stop codons in this gene is not degraded during its processing. The mutation was not detected in fresh lymphocytes from the unaffected father by PCR analysis, supporting the case for true germ-line mosaicism.

Two further cases of mutation R1947X in the NF1 gene: screening for a relatively common recurrent mutation

We present two further cases of mutation R1947X in the neurofibromatosis type 1 gene. To date, a total of nine cases of mutation R1947X have been reported giving a frequency of about 2% and confirming the recurrence of this mutation. R1947X occurs within a CpG dinucleotide and supports the hypothesis that the mutation rate for this dinucleotide is higher than that of other dinucleotides. As routine analysis for R1947X is advisable, we have developed an allele-specific oligonucleotide hybridization assay for the efficient screening of a large number of samples.

[Electrolytic changes in children with acute lymphoblastic leukemia during remission induction]

The alterations of the water-electrolyte balance are among the commonest early complications of treatment in children with acute lymphoblastic leukaemia (ALL). A study was carried out in thirteen patients with ALL aged between 1.5 and 14 years. Four had high risk ALL and nine had standard risk ALL. All patients received intravenous epirubicin and vincristine, per os prednisone, allopurinol and bicarbonate, and intrathecal methotrexate and hydrocortisone. Venous blood was drawn before starting therapy and on days second and sixth of treatment in order to assay sodium, potassium, calcium, phosphate, magnesium, albumin, urea nitrogen, creatinine and uric acid concentrations. The following alterations were found: hyponatraemia in 4 cases, hypokalemia in 9, hypomagnesaemia in 9, hypocalcaemia in 11, hypophosphataemia in 9, hypouricemia in 3 and hyperuricaemia in 3 others. None of the patients developed acute renal insufficiency. These abnormalities could be due to the leukaemia itself or appear as a consequence of the remission induction treatment.

Prenatal diagnosis of neurofibromatosis type 1: from flanking RFLPs to intragenic microsatellite markers

Even though the neurofibromatosis type 1 (NF1) gene was cloned more than 3 years ago, the process of identifying mutations has not been fruitful, and genetic counselling is mainly based on the use of linked markers. Since 1990, we have analysed 130 NF1 families and have performed six prenatal diagnoses. In each case, genetic counselling has relied on linked markers and informativity was achieved in all of them. The use of intragenic microsatellite polymorphisms (IVS27AAAT2.1, IVS27AC28.4, IVS27AC33.1, and IVS38GT53.0) has increased the informativeness in our series of NF1 families to an average of 90 per cent, providing accurate diagnosis and confirmation of the disease status.

Neurofibromatosis type 1 due to germ-line mosaicism in a clinically normal father

BACKGROUND

The mutation rate of the neurofibromatosis type 1 (NF1) gene is one of the highest in the human genome, with about 50 percent of cases being due to new mutations. We describe a family in which neurofibromatosis type 1 occurred in two siblings with clinically normal parents, and we demonstrate germ-line mosaicism in the father.

METHODS

We studied lymphocyte DNA from each member of the family and the father's spermatozoa for several polymorphic intragenic markers of the NF1 gene. Southern blots of DNA digested with several enzymes were hybridized with complementary DNA and individual NF1 exon probes to search for alterations in the gene.

RESULTS

The affected siblings, with a clinically severe form of neurofibromatosis type 1, showed no inheritance of paternal alleles for a marker in intron 38 of the NF1 gene, whereas they received alleles from both parents for other NF1 markers. Analysis with probes from this region of the NF1 gene showed a 12-kb deletion of the NF1 gene, involving exons 32 to 39, in the affected offspring. Ten percent of the father's spermatozoa carried the same NF1 deletion, but the abnormality was not detected in DNA from his lymphocytes.

CONCLUSIONS

The presence of the NF1 mutation in 10 percent of the clinically normal father's spermatozoa supports the hypothesis that most germ-line mutations occur in precursors of gametes. In cases of spontaneous mutation, analyzing the specific NF1 mutation in the father's sperm might help in the detection of mosaicism and thus facilitate genetic counseling about further pregnancies.

Two CA/GT repeat polymorphisms in intron 27 of the human neurofibromatosis (NF1) gene

We describe two polymorphic microsatellites in intron 27 of the neurofibromatosis type 1 (NF1) gene. The microsatellites consist of TG/AC and AC/TG dinucleotide repeats detecting five and seven alleles and with heterozygosities of 0.46 and 0.72, respectively. These microsatellites are useful tools both for direct and indirect genetic analysis of NF1.

A highly informative CA/GT repeat polymorphism in intron 38 of the human neurofibromatosis type 1 (NF1) gene

We describe a polymorphic microsatellite in intron 38 of the neurofibromatosis type 1 (NF1) gene. The microsatellite consists of a CA/GT dinucleotide repeat detecting 8 alleles; it has a heterozygosity of 82%.

Novel alleles, hemizygosity and deletions at an Alu-repeat within the neurofibromatosis type 1 (NF1) gene

Neurofibromatosis type 1 (NF1) (von Recklinghausen) is a common autosomal dominant disorder, characterised by the presence of peripheral neurofibromas, café-au-lait spots and Lisch nodules of the iris. Due to the high mutation rate at the NF1 locus, most patients are expected to have different mutations, limiting molecular analysis and genetic counseling to the identification of the mutation in each patient or family, or to the use of DNA polymorphisms. We have analysed an Alu-repeat polymorphic sequence (AAAT), located in intron 27 of the NF1 gene, in 70 NF1 and 40 CEPH families and we have detected several genetic and molecular abnormalities. In two families the NF1 individuals were hemizygous at the AAAT-repeat and/or at the CA-repeat of intron 27 of NF1, due to interstitial deletions, which include intron 27 to exon 37 of the NF1 gene. A 71-bp deletion at the Alu sequence was detected in non-NF1 chromosomes of members of three NF1 families. New alleles at the AAAT-repeat were found in one NF1 family and in three CEPH families giving a mutation rate for this AAAT-repeat of 0.36% per allele, which is one of the highest detected for a microsatellite locus.

Cystic fibrosis in Spain: high frequency of mutation G542X in the Mediterranean coastal area

We have determined the frequency of deletion delta F508 and mutation G542X, a nonsense mutation in exon 11 of the cystic fibrosis (CF) gene, in a sample of 400 Spanish CF families. Mutation G542X represents 8% of the total number of CF mutations in Spain, making it the second most common mutation after the delta F508 deletion, which accounts for 48% of CF chromosomes. G542X has a higher frequency in the Mediterranean coastal area (14%) and in the Canary Islands (25%). About 70% of G542X chromosomes are from Andalucia, Múrcia, Valencia, Catalunya and the Canary Islands. The delta F508 deletion has its highest frequency in the Basque Country (83%). Mutation G542X is associated with the same rare haplotype that is found in association with the delta F508 mutation. The haplotype homogeneity found for G542X, even when intragenic microsatellites (IVS8CA, IVS17BTA and IVS17BCA) are considered, allows us to postulate that this mutation arose from a single mutational event. The geographic distribution of mutations delta F508 and G542X suggests that delta F508 was present in the Iberian Peninsula before the Indo-European invasions, and that G542X was introduced into Spain, via the Mediterranean Sea, probably by the Phoenicians, between 2500 and 3000 years ago.

A frameshift mutation (2869insG) in the second transmembrane domain of the CFTR gene: identification, regional distribution, and clinical presentation

Images

Cystic fibrosis patients with mutation 1949del84 in exon 13 of the CFTR gene have a similar clinical severity as delta F508 homozygotes

The majority of the identified cystic fibrosis (CF) mutations are very uncommon in the total patient population, making the correlation between the clinical presentation and the molecular alterations difficult. The largest deletion that has been described so far in CF is of 84 bp in exon 13, which corresponds to the regulatory (R) domain of the CF transmembrane conductance regulator (CFTR) protein. We have analysed 340 Spanish CF patients for this deletion, named 1949del84, and found three further compound heterozygous patients for mutations 1949del84 and delta F508, and one for 1949del84 and an unknown mutation. Evaluation of the clinical data in these patients suggests that this in-frame deletion, when associated with delta F508, has a similar disease severity to that of delta F508 homozygous patients.

Analysis of 14 cystic fibrosis mutations in five south European populations

We have analysed five Southern European populations (Albanian, Greek, Italian, Spanish and Yugoslavian) for 14 cystic fibrosis (CF) mutations. The most frequent mutations, apart from delta F508, were G542X (6.04%), R1162X (3.61%) and N1303K (3.24%). Each of the other analysed mutations were present at a frequency of less than 1% (R347P, R334W, S549RA, S549I, G551D, R553X and W1282X), and four mutations (D110H, delta I507, S549RT, and S1255X) were not found in this sample. The data presented here allows the use of mutation analysis in 69.5% of Spanish, 58% of Greek, and 56.5% of Italian CF cases.

The search for south European cystic fibrosis mutations: identification of two new mutations, four variants, and intronic sequences

The major mutation in the cystic fibrosis (CF) gene is a 3-bp deletion (delta F508) in exon 10. About 50% of the CF chromosomes in Southern Europe carry this mutation, while other previously described mutations account for less than 4%. To identify other common mutations in CF patients from the Mediterranean area, we have sequenced, exon by exon, 16 chromosomes that did not show the delta F508 deletion from a selected panel of eight unrelated CF patients. We describe here one missense and one nonsense mutation, and four sequence polymorphisms. We have also found two previously reported mutations in three chromosomes. Overall, these mutations may account for about 20% of CF alleles in the Italian and Spanish populations. No other mutations were detected in 10 out of 16 CF chromosomes after analyzing about 90% of the coding region of the CF gene, and 39 out of 54 intron/exon boundaries. Therefore, about 26% of CF mutations remain to be identified. In addition we provide the intron/exon boundary sequences for exons 4 to 9. These results together with previously reported linkage data suggest that in the Mediterranean populations further mutations may lie in the promoter region, or in intron sequences not yet analyzed.