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Some meteorological and geo‐orographical factors related to cloud‐to‐ground flashes in Castilla‐Leon (Spain) are studied. The relationship between flash density and the number of days with thunderstorms (thunderdays) is analysed, and a clear dependence and geographical variability is found. It is also shown that flashes have an average delay of four hours with respect to the time of the beginning of convection. The effect on flashes of dry static instability and moisture content is analysed by classifying days into four types according to the average values of the 850–700 hPa temperature difference and the 850 hPa dew‐point temperature. A similar classification using the 700 hPa wind direction is used to analyse the effect of the mean‐level flow on flashes. The results suggest that the daily number of flashes is mainly affected by the moisture content. Finally, a relationship between the cloud‐to‐ground flash density and geo‐orographical factors (altitude, latitude and longitude) is deduced using multiple linear analysis. Copyright © 2001 Royal Meteorological Society

Abstract: Ozone is a secondary air pollutant that has received extensive attention in the literature, mainly because of the adverse effects that exposure to it can cause, particularly in vegetation during the growing season. Because meteorological conditions strongly influence the efficiency of photochemical processes leading to ozone formation and destruction, ground-level ozone air pollution is currently being considered as a regional-scale phenomenon rather than a local one. This role of O3 as a regional-scale pollutant often implies the handling of large data sets in order to obtain information about its spatial and temporal variability patterns over a given broad region. Rotated principal component analysis (RPCA) is known to be one of the most powerful mathematical tools that can be used to achieve this aim. RPCA was applied in this paper to the summer and winter hourly time series of ground-level O3, concentrations recorded during 2 consecutive years (1996–1997) at 26 urban and suburban sites in Castilla-Len (Spain). This procedure permitted the identification of different subregions where O3 concentrations show different spatio-temporal variability patterns. These variability patterns are mainly associated with the interaction of regional-level meteorological and anthropogenic factors. Some differences between winter and summer patterns were also found.

Programmed cell death is an established developmental process in the nervous system. Whereas the regulation and the developmental role of neuronal cell death have been widely demonstrated, the relevance of cell death during early neurogenesis, the cells affected and the identity of regulatory local growth factors remain poorly characterized. We have previously described specific in vivo patterns of apoptosis during early retinal neurogenesis, and that exogenous insulin acts as survival factor (Díaz, B., Pimentel, B., De Pablo, F. and de la Rosa, E. J. (1999) Eur. J. Neurosci. 11, 1624-1632). Proinsulin mRNA was found to be expressed broadly in the early embryonic chick retina, and decreased later between days 6 and 8 of embryonic development, when there was increased expression of insulin-like growth factor I mRNA, absent or very scarce at earlier stages. Consequently, we studied whether proinsulin and/or insulin ((pro)insulin) action in prevention of cell death has physiological relevance during early neural development. In ovo treatment at day 2 of embryonic development with specific antibodies against (pro)insulin or the insulin receptor induced apoptosis in the neuroretina. The distribution of apoptotic cells two days after the blockade was similar to naturally occurring cell death, as visualized by TdT-mediated dUTP nick end labeling. The apoptosis induced by the insulin receptor blockade preferentially affected to the Islet1/2 positive cells, that is, the differentiated retinal ganglion cells. In parallel, the insulin survival effect on cultured retinas correlated with the activation of Akt to a greater extent than with the activation of MAP kinase. These results suggest that the physiological cell death occurring in early stages of retinal development is regulated by locally produced (pro)insulin through the activation of the Akt survival pathway.

Early neurogenesis progresses by an initial massive proliferation of neuroepithelial cells followed by a sequential differentiation of the various mature neural cell types. The regulation of these processes by growth factors is poorly understood. We intend to understand, in a well-defined biological system, the embryonic chicken retina, the role of the insulin-related growth factors in neurogenesis. We demonstrate the local presence of signaling elements together with a biological response to the factors. Neuroretina at days 6-8 of embryonic development (E6-E8) expressed proinsulin/insulin and insulin-like growth factor I (IGF-I) mRNAs as well as insulin receptor and IGF type I receptor mRNAs. In parallel with this in vivo gene expression, E5 cultured neuroretinas synthesized and released to the medium a metabolically radiolabeled immunoprecipitable insulin-related peptide. Furthermore, insulin-related immunoreactive material with a HPLC mobility close to that of proinsulin was found in the E6-E8 vitreous humor. Exogenous chicken IGF-I, human insulin, and human proinsulin added to E6 cultured neuroretinas showed relatively close potencies stimulating proliferation, as determined by [methyl-3H]thymidine incorporation, with a plateau reached at 10(-8) M. These factors also stimulated neuronal differentiation, indicated by the expression of the neuron-specific antigen G4. Thus, insulin-related growth factors, interestingly including proinsulin, are present in the developing chicken retina and appear to play an autocrine/paracrine stimulatory role in the progression of neurogenesis.

We have isolated and partially characterized an ca. 20-kilobase-pair Strongylocentrotus purpuratus genomic clone, using a mouse alpha 1 (type IV) collagen cDNA probe. A 1-kilobase-pair HindIII fragment of the clone hybridizes strongly to the probe; this has been subcloned and sequenced. It contains 212 base pairs of sequence coding for (Gly-Xaa-Yaa)n (where Xaa and Yaa are different unspecified amino acids), characteristic of all known collagen genes. There is a single point of discontinuity within the repeating pattern in this exon, similar to the genomic structure of mouse type IV collagen. The (Gly-Xaa-Yaa)n-encoding element is flanked by consensus splicing sequences, and the intervening sequences on either side of it have multiple in-phase termination codons. Electron microscopy of R loops between the phage lambda recombinant clone and poly(A)+ RNA reveals multiple short exons, a feature also seen in vertebrate collagen genes. The (Gly-Xaa-Yaa)n protein-encoding sequence hybridizes to a developmentally regulated 9-kilobase mRNA; the message appears during the morula stage, rises sharply in abundance at the blastula stage, and decreases in proportion to total RNA later in development.

Insulin is a multifunctional polypeptide hormone that regulates metabolic processes and promotes mitogenesis and differentiation in vitroin the cells and tissues of several species. Its role in vivoduring embryogenesis is still poorly understood. We have previously found insulin mRNA in mature Xenopus laevisoocytes and in embryos during neurulation (before organogenesis of the pancreas takes place). We have now measured insulin immunoactivity in mature oocytes, unfertilized eggs and day-2 tadpoles. Using reversed phase high performance liquid chromatography, we found low levels of insulin in extracts of oocytes (stage VI). Both Xenopusinsulin I and II were detected in unfertilized eggs. The day-2 tadpoles (stages 31–33) also contained immunoactive insulin, and in swimming tadpoles (stage 46) a few clusters of cells containing insulin immunoactivity could be identified by indirect immunofluorescence. Immunoblot analysis was relatively insensitive, detecting insulin only in the adult Xenopuspancreas. In summary, insulin (from maternal origin and embryonic expression) appears to be present early enough in Xenopus laevisto influence developmental processes such as neurulation.Journal of Endocrinology(1994) 141,123–129

Normal development of the chicken embryo requires insulin and insulin receptors. Insulin and also insulinlike growth factor I (IGF-I) can stimulate embryonic growth when applied in vivoat the beginning of organogenesis (Girbau, M., Gomez, J. A., Lesniak, M. A., and De Pablo, F. (1987) Endocrinology121, 1477–1482). In the present work we chose the developing eye lens, an avascular organ composed of a single cell type, to characterize further the specific effects of insulin and IGF-I upon cell differentiation and gene expression. Epithelial cells (before terminal differentiation) and fiber cells (terminally differentiated) were cultured in the presence of the hormones. δ-Crystallin mRNA steady-state levels as well as nuclear d-erystallin gene transcription were measured. Either insulin or IGF-I (0.1–10 ng/ml) increased (2–4-fold) 5-crystallin mRNA in epithelial and fiber lens cells from day 6 embryos. The effect of insulin was largely blocked by the Fab fragment of anti-insulin receptor antibody (B-10). By contrast, as it had been shown for metabolic actions in other systems, bivalent B-10 IgG itself mimicked insulin action, i.e. it induced an increase on δ-crystallin mRNA levels. Thus, insulin appears to act through its own receptor in regulating the levels of δ-crystallin mRNA. There was a differential transcriptional component in insulin and IGF-I effects on δ-crystallin gene expression, IGF-I induction of transcription, as measured by nuclear run-on assay, is greater than insulin induction (≈2.5-foid versus1.4-fold) and faster. The δ-crystallin gene will provide the opportunity to analyze the action of insulin and IGF-I on the expression of a structural protein marker of cell differentiation during early embryonic development.

We, and others, have recently reported that insulin-like growth factor I (IGF-I) mRNA is expressed in multiple tissues during embryogenesis and in whole embryos during early organogenesis. Therefore, it is likely that, in addition to any effect on embryo growth, IGF-I plays a paracrine/autocrine role in development. The embryonic chicken lens, an avascular organ composed by a single type of cell that undergoes differentiation in vivo and in vitro, is an ideal model to characterize the paracrine/autocrine action of IGF-I. The lens cells express IGF-I receptors, and respond to exogenous IGF-I with induction of fiber cells differentiation and stimulation of delta-crystallin gene transcription. Whether embryonic lens cells express IGF-I was uncertain. In the present study, we used a sensitive semiquantitative method (reverse transcription of RNA followed by amplification with the polymerase chain reaction) to analyze IGF-I gene expression. An amplified product of the expected length (209 base pairs) was found in days 8, 12, 15, and 19 lenses. At all embryo ages studied, the product was more readily detected in the lens than in the liver, while in eye tissues (excluding lens), IGF-I expression was relatively high. After microdissection of the epithelial cells from the fully differentiated fiber cells, IGF-I expression was detected exclusively in the epithelial cells. IGF-I immunoactivity was found using high performance liquid chromatography followed by radioimmunoassay in the days 8-19 lens extracts, and in primary cultures of isolated epithelial cells. Our previous and present findings show that the lens has all the elements for IGF-I autocrine/paracrine action in development.

Insulin and insulin-like growth factor I (IGF-I) initiate their metabolic, growth, and differentiation effects through binding to the insulin receptor and the IGF-I receptor, two members of the tyrosine kinase family of receptors. To study the role of these peptides and receptors in early development, we used the polymerase chain reaction and embryo-derived RNA to generate partial cDNA sequences of the insulin receptor and IGF-I receptor from the amphibian Xenopus laevis. Three unique tyrosine kinase-related sequences were obtained. Two of the nucleotide sequences, XTK 1a and XTK 1b, corresponded to peptide that share 92% amino acid identity, and each is 89% identical to the human insulin receptor. The third sequence, XTK 2, corresponds to a peptide that has 92% amino acid identity with the human IGF-I receptor but only 80% identity with XTK 1a and XTK 1b. On the basis of these similarities, the pattern of conserved amino acids, and the tetraploid nature of the Xenopus genome, we suggest that XTK 1a and XTK 1b most likely represent the product of two different nonallelic insulin receptor genes, while XTK 2 may be one of the probable two Xenopus IGF-I receptor genes. By reverse transcription-polymerase chain reaction and gene-specific hybridization, expression of the three XTK sequences was detected in the oocyte, unfertilized egg, and embryos through gastrulation, neurulation, and tailbud stages. Competition binding assays with Xenopus membrane preparations demonstrated insulin receptors and IGF-I receptors in older tadpoles. IGF-I receptors were also present in oocytes, eggs, and gastrula embryos. By contrast, insulin binding was present but atypical in oocytes and was barely detected in eggs and gastrula embryos. The expression of receptors for insulin and IGF-I in early Xenopus embryos and their apparent distinct developmental regulation suggest that these molecules and their ligands may be important in early Xenopus development.

Abstract:  The primary aim of the present work is to describe and analyze the temporal trends of concurrent hourly observations and its daily averaged series of the pollutants CO, NO2, NO and SO2 in the urban area of the City of Salamanca (environmental survey station SA001) for the period between 1 December 1993 and 30 November 1994. Using daily series corresponding to different meteorological variables recorded at the same site for the same period (wind direction, relative humidity, pressure, radiation, temperature and wind speed), linear regression techniques are used to study the relationships of these variables with each of the polluntants on both an individual and multivariate basis. The results obtained explain 40% of the variance of the series for NO2 and 66% in the case of SO2. Finally, in the modelling phase it was observed that the series of polluntants themselves have sufficient ’’information’’ to enable, by means of autoregressive and integrated moving average techniques (A.R.I.M.A.), the determination of future pollution. Once predicted, these were contrasted with the measured or observed values to check the goodness of the model.

Insulin-like growth factor I (IGF-I) and insulin regulate expression of the endogenous delta 1-crystallin gene in embryonic lens cells that express receptors for both peptides. To further analyze the transcriptional component of this hormonal effect, transient transfections of lens cells were prepared with DNA constructs containing deletions of the delta 1-crystallin promoter and the chloramphenicol acetyltransferase reporter gene. A 77-nucleotide DNA segment of the delta 1-crystallin promoter from nucleotide positions-120 to -43 confers sensitivity to insulin and IGF-I. The hormonal effect is dose-dependent, and maximal stimulation of promoter activity (2- to 2.5-fold induction) is obtained with 10(-8) M IGF-I and 10(-7) M insulin. Mobility-shift DNA-binding analysis shows specific binding of nuclear protein(s) to the delta 1-crystallin promoter DNA between positions -120 and +23, which appears to be regulated by IGF-I. An SP1-binding motif is involved in this DNA-protein interaction. The bivalent IgG fraction of an anti-insulin receptor antiserum (B-10), known to mimic insulin action in other systems, stimulates promoter activity to the same extent as insulin.

Insulin, traditionally regarded as a metabolic hormone, also can potently stimulate growth and differentiation in many cell types. To study further the potential role of insulin during early embryogenesis, we have used the amphibian Xenopus laevis, a versatile model of vertebrate development. Using (i) nucleotide sequences of two previously cloned cDNAs that correspond to two different nonallelic Xenopus insulin genes (both of which are expressed in the adult pancreas) and (ii) a modification of the highly sensitive reverse transcription-polymerase chain reaction (RT-PCR) method developed in our laboratory, designated RNA template-specific PCR (RS-PCR), we now find that mRNAs for both Xenopus insulins I and II are present in mature (stage VI) oocytes but not in less-mature oocytes (stages I and IV) or in unfertilized eggs. The Xenopus insulin II gene is differentially expressed during early neurulation (stage 13), while only the insulin I gene is expressed at stage 21, when the neural tube is closing and cephalization is beginning. During later stages (i.e., stage 26) there is a region in the head that appears to be transcribing only the insulin I gene, while mRNAs for both insulins I and II are present in the body region. These findings show that the two nonallelic insulin genes are expressed differentially in Xenopus embryos in a stage- and region-specific manner; because appropriate receptors are also present, we suggest a role for insulin during early nervous system development well before the emergence of pancreatic beta cells.

We previously reported specific cross-linking of 125I-labeled insulin and 125I-labeled insulin-like growth factor I (IGF-I) to the alpha subunit of their respective receptors in chicken embryos of 20 somites and older. To achieve adequate sensitivity and localize spatially the receptors in younger embryos, we adapted an autoradiographic technique using whole-mounted chicken blastoderms. Insulin receptors and IGF-I receptors were expressed and could be localized as early as gastrulation, before the first somite is formed. Relative density was analyzed by a computer-assisted image system, revealing overall slightly higher binding of IGF-I than of insulin. Structures rich in both types of receptors were predominantly of ectodermal origin: Hensen's node in gastrulating embryos and neural folds, neural tube and optic vesicles during neurulation. The signal transduction capability of the receptors in early organogenesis was assessed by their ability to phosphorylate the exogenous substrate poly(Glu80Tyr20). Ligand-dependent tyrosine phosphorylation was demonstrable with both insulin and IGF-I in glycoprotein-enriched preparations from embryos at days 2 through 6 of embryogenesis. There was a developmentally regulated change in ligand-dependent tyrosine kinase activity, with a sharp increase from day 2 to day 4, in contrast with a small increase in the ligand binding. Binding of 125I-labeled IGF-I was, with the solubilized receptors, severalfold higher than binding of 125I-labeled insulin. However, the insulin-dependent phosphorylation was as high as the IGF-I-dependent phosphorylation at each developmental stage.

Analysis of the total, intracloud and cloud‐to‐ground lightning flash density and the intracloud (IC) to cloud‐to‐ground (CG) ratio (Z= IC/CG) over the Iberian Peninsula (IP) has been performed using 5 years of combined data from the Spanish lightning detection network and the NASA Optical Transient Detector (OTD). The spatial distributions of total flash density and CG flash density show significant differences, especially on the northwest of the IP, the southern island of the Balearic Islands, and the southern/southeastern Mediterranean coastline. The spatial average of the annual value of Zis 3.48. A correlation was found between Zand latitude (correlation coefficient: −0.9). A relationship between Z and the total flash density was also observed (Z∼ f0.5; correlation coefficient: 0.48). The spatial pattern of Zis reminiscent of that of the percentage of positive CG‐flashes, and high Zvalues seem to occur where the percentage of positive flashes is high.