Molecular analysis of 23 exons of the CFTR gene in Brazilian patients leads to the finding of rare cystic fibrosis mutations

To define mutations present in 23 exons and flanking intronic sequences of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in 95 patients from Rio de Janeiro, Brazil, we carried out single-strand conformation polymorphism analysis and automated direct sequencing. Mutation detection was achieved in 45% of the alleles presented, and complete genotyping (two mutated alleles) was accomplished in 34.7% of the patients. Twenty patients (21.1%) were found to carry only one mutation, whereas mutated alleles could not be observed in 42 patients (44.2%). Eleven mutations were found, of which four were characterized as rare mutations: P205S (1.05%), Y1092X (0.53%), S549R (0.53%), and S4X (0.53%). The DF508 mutation in this population sample showed a frequency of 28.42%. The low number of individuals (10 of 95; 10.5%) with compound heterozygous (DF508/non-DF508) genotypes could indicate the presence of another severe mutation leading to the premature death of these individuals. In 4 of the aforementioned 10 individuals with compound heterozygous genotypes, the D-7-2-1-2 (XV2c-KM19-IVS6a-TUB9-M470-T854) haplotype was defined.     

Tissue-specific localization of gibberellins and expression of gibberellin-biosynthetic and signaling genes in wood-forming tissues in aspen

Bioactive gibberellins (GAs) are known regulators of shoot growth and development in plants. In an attempt to identify where GAs are formed, we have analyzed the expression patterns of six GA biosynthesis genes and two genes with predicted roles in GA signaling and responses in relation to measured levels of GAs. The analysis was based on tangential sections, giving tissue-specific resolution across the cambial region of aspen trees (Populus tremula). Gibberellin quantification by GC/MS-SRM showed that the bioactive GA1 and GA4 were predominantly located in the zone of expansion of xylem cells. Based on co-localization of the expression of the late GA biosynthesis gene GA 20-oxidase 1 and bioactive GAs, we suggest that de novo GA biosynthesis occurs in the expanding xylem. However, expression levels of the first committed GA biosynthesis enzyme, ent-copalyl diphosphate synthase, were high in the phloem, suggesting that a GA precursor(s) may be transported to the xylem. The expression of the GA signaling and response genes DELLA-like1 and GIP-like1 coincided well with sites of high bioactive GA levels. We therefore suggest that the main role of GA during wood formation is to regulate early stages of xylem differentiation, including cell elongation.     

Glyconeogenic pathway in isolated skeletal muscles of rats

Although the conversion of lactate to glycogen (glyconeogenesis) in muscle was demonstrated a long time ago, the biochemical reactions responsible for this process are still a controversial matter. In the present study, advantage was taken from the specific inhibition induced by phenylalanine on muscle pyruvate kinase (PK) to investigate the role of reverse PK activity in muscle glyconeogenesis. Addition of phenylalanine to the incubation medium of a preparation of isolated, intact skeletal muscles that maintain metabolic activity for several hours reduced by 50% the rate of incorporation of [14C]lactate or [14C]bicarbonate into muscle glycogen. Muscle extracts presented high levels of maximal activity of PK in the reverse direction, which was completely blocked in the presence of phenylalanine. In contrast, mercaptopicolinic acid, an inhibitor of phosphoenolpyruvate carboxykinase (PEPCK), did not affect the incorporation of 14C from either lactate or bicarbonate into muscle glycogen. Maximal PEPCK activity was much lower in muscle extracts than in gluconeogenic or glyceroneogenic tissues and was suppressed in the presence of mercaptopicolinic acid. The data suggest that a reversal of the metabolic flux through the reaction catalyzed by PK contributes to the accumulation of lactate-derived glycogen that occurs in skeletal muscle under certain physiological conditions.     

Immunological thresholds in neurological gene therapy: highly efficient elimination of transduced cells might be related to the specific formation of immunological synapses between T cells and virus-infected brain cells

First-generation adenovirus can be engineered with powerful promoters to drive expression of therapeutic transgenes. Numerous clinical trials for glioblastoma multiforme using first generation adenoviral vectors have either been performed or are ongoing, including an ongoing, Phase III, multicenter trial in Europe and Israel (Ark Therapeutics, Inc.). Although in the absence of anti-adenovirus immune responses expression in the brain lasts 6-18 months, systemic infection with adenovirus induces immune responses that inhibit dramatically therapeutic transgene expression from first generation adenoviral vectors, thus, potentially compromising therapeutic efficacy. Here, we show evidence of an immunization threshold for the dose that generates an immune response strong enough to eliminate transgene expression from the CNS. For the systemic immunization to eliminate transgene expression from the brain, > or = 1 x 10(7) infectious units (iu) of adenovirus need to be used as immunogen. Furthermore, this immune response eliminates >90% of transgene expression from 1 x 10(7)-1 x 10(3) iu of vector injected into the striatum 60 days earlier. Importantly, elimination of transgene expression is independent of the nature of the promoter that drives transgene expression and is accompanied by brain infiltration of CD8(+) T cells and macrophages. In conclusion, once the threshold for systemic immunization (i.e. 1 x 10(7) iu) is crossed, the immune response eliminates transgene expression by >90% even from brains that receive as little as 1000 iu of adenoviral vectors, independently of the type of promoter that drives expression.     

Delayed development of interstitial cells of Cajal in the ileum of a human case of gastroschisis

The Interstitial Cells of Cajal (ICC) are responsible for rhythmic electrical activity. A paralytic ileus is present in gastroschisis (GS), a malformation due to a defective closure of the abdominal wall through which part of the intestine herniates during pregnancy. In experimental GS, ICC morphological immaturity was shown in the rat foetus at-term but it could not be demonstrated whether differentiation is accomplished post-natally. For this purpose we morphologically investigated ICC, as well as enteric neurons and smooth muscle cells, in a case of human GS at birth and 1 month later when peristaltic activity had initiated. A 36 weeks gestation female was born by c/section with prenatal diagnosis of GS and possible volvulus of the herniated intestine. At birth, the necrotic intestine was resected and both ileostomy and colostomy were performed. The intestine continuity was restored after 4 weeks. Intestinal specimens, taken during both operations at the level of the proximal stoma, were immunostained with c-kit, neuron-specific-enolase and alpha-smooth-muscle-actin antibodies and some processed for electron microscopy. ICC were present at the myenteric plexus only. At birth, these cells were rare and ultrastructurally immature; 1 month later, when partial enteral feeding was tolerated, they formed rows or groups and many of them were ultrastructurally differentiated. Neurons and smooth muscle cells, immature at birth, had developed after 1 month. Therefore, ICC differentiation, as well as that of neurons and smooth muscle cells, is delayed at birth and this might explain the paralytic ileus in GS. One month later, differentiation quickly proceeded at all cellular levels paralleling the increasing tolerance of enteral nutrition.     

Changes in the protein synthesis pattern during a nutritional shift-down transition in Saccharomyces cerevisiae

In Saccharomyces cerevisiae cells (strain A364A) during a shift-down from glucose to raffinose, a rapid reduction in the rate of RNA accumulation was observed whereas the rate of protein accumulation was unaffected for at least 2 h. Following the transition the percentage of unbudded cells slightly increased and the cell volume distribution showed a newly formed subpopulation of smaller cells. To study the effects of the shift-down on the protein synthesis pattern, total [35S]-methionine pulse-labeled extracts were fractionated by high-resolution two-dimensional gel electrophoresis. The synthesis of two classes of proteins (I and II) was modulated during the transitory state of growth: one positively, the other negatively. Two polypeptides of 57 kDa showed the most dramatic increase in synthesis during the shift-down. Also a heat-shock protein (HSP 256) appeared to be positively correlated to the shift-down transition.     

Interaction of trout hemoglobin with H2O2: a chemiluminescence study

Erythrocytes from trout Salmo irideus are characterized by four different hemoglobin components (HbI, HbII, HbIII and HbIV), HbI and HbIV being predominant. In this study we describe the interaction between trout hemoglobin (HbI and HbIV) and H₂O₂ using a chemiluminescence assay. Our data show that the reaction of hemoglobins with H₂O₂ produces a time-limited and significant increase of chemiluminescence signal. The half-life of the decay of this chemiluminescence signal was characteristic for each type of hemoglobin used. These results indicate the formation of excited molecules related to the interaction between trout hemoglobin and H₂O₂. © 1997 John Wiley & Sons, Ltd.