Modulation of A1 and A2B adenosine receptor activity: a new strategy to sensitise glioblastoma stem cells to chemotherapy

Therapies that target the signal transduction and biological characteristics of cancer stem cells (CSCs) are innovative strategies that are used in combination with conventional chemotherapy and radiotherapy to effectively reduce the recurrence and significantly improve the treatment of glioblastoma multiforme (GBM). The two main strategies that are currently being exploited to eradicate CSCs are (a) chemotherapeutic regimens that specifically drive CSCs toward cell death and (b) those that promote the differentiation of CSCs, thereby depleting the tumour reservoir. Extracellular purines, particularly adenosine triphosphate, have been implicated in the regulation of CSC formation, but currently, no data on the role of adenosine and its receptors in the biological processes of CSCs are available. In this study, we investigated the role of adenosine receptor (AR) subtypes in the survival and differentiation of CSCs isolated from human GBM cells. Stimulation of A₁AR and A_2BAR had a prominent anti-proliferative/pro-apoptotic effect on the CSCs. Notably, an A₁AR agonist also promoted the differentiation of CSCs toward a glial phenotype. The differential effects of the two AR agonists on the survival and/or differentiation of CSCs may be ascribed to their distinct regulation of the kinetics of ERK/AKT phosphorylation and the expression of hypoxia-inducible factors. Most importantly, the AR agonists sensitised CSCs to the genotoxic activity of temozolomide (TMZ) and prolonged its effects, most likely through different mechanisms, are as follows: (i) by A_2BAR potentiating the pro-apoptotic effects of TMZ and (ii) by A₁AR driving cells toward a differentiated phenotype that is more sensitive to TMZ. Taken together, the results of this study suggested that the purinergic system is a novel target for a stem cell-oriented therapy that could reduce the recurrence of GBM and improve the survival rate of GBM patients.

Temporal dynamics in the evolution of the sunflower genome as revealed by sequencing and annotation of three large genomic regions

Improved knowledge of genome composition, especially of its repetitive component, generates important informations in both theoretical and applied research. In this study, we provide the first insight into the local organization of the sunflower genome by sequencing and annotating 349,380 bp from 3 BAC clones, each including one single-copy gene. These analyses resulted in the identification of 11 putative gene sequences, 18 full-length LTR retrotransposons, 6 incomplete LTR retrotransposons, 2 non-autonomous LTR-retroelements (LINEs), 2 putative DNA transposons fragments and one putative helitron. Among LTR-retrotransposons, non-autonomous elements (the so-called LARDs), which do not carry any protein-encoding sequence, were discovered for the first time in the sunflower. The insertion time of intact retroelements was measured, based on sister LTRs divergence. All isolated elements were inserted relatively recently, especially those belonging to the Gypsy superfamily. Retrotransposon families related to those identified in the BAC clones are present also in other species of Helianthus, both annual and perennial, and even in other Asteraceae. In one of the three BAC clones, we found five copies of a lipid transfer protein (LTP) encoding gene within less than 100,000 bp, four of which are potentially functional. Two of these are interrupted by LTR retrotransposons, in the intron and in the coding sequence, respectively. The divergence between sister LTRs of the retrotransposons inserted within the genes indicates that LTP gene duplication started earlier than 1.749 MYRS ago. On the whole, the results reported in this study confirm that the sunflower is an excellent system to study transposons dynamics and evolution.

An analysis of sequence variability in eight genes putatively involved in drought response in sunflower (Helianthus annuus L.)

With the aim to study variability in genes involved in ecological adaptations, we have analysed sequence polymorphisms of eight unique genes putatively involved in drought response by isolation and analysis of allelic sequences in eight inbred lines of sunflower of different origin and phenotypic characters and showing different drought response in terms of leaf relative water content (RWC). First, gene sequences were amplified by PCR on genomic DNA from a highly inbred line and their products were directly sequenced. In the absence of single nucleotide polymorphisms, the gene was considered as unique. Then, the same PCR reaction was performed on genomic DNAs of eight inbred lines to isolate allelic variants to be compared. The eight selected genes encode a dehydrin, a heat shock protein, a non-specific lipid transfer protein, a z-carotene desaturase, a drought-responsive-element-binding protein, a NAC-domain transcription regulator, an auxin-binding protein, and an ABA responsive-C5 protein. Nucleotide diversity per synonymous and non-synonymous sites was calculated for each gene sequence. The π (a)/π (s) ratio range was usually very low, indicating strong purifying selection, though with locus-to-locus differences. As far as non-coding regions, the intron showed a larger variability than the other regions only in the case of the dehydrin gene. In the other genes tested, in which one or more introns occur, variability in the introns was similar or even lower than in the other regions. On the contrary, 3'-UTRs were usually more variable than the coding regions. Linkage disequilibrium in the selected genes decayed on average within 1,000 bp, with large variation among genes. A pairwise comparison between genetic distances calculated on the eight genes and the difference in RWC showed a significant correlation in the first phases of drought stress. The results are discussed in relation to the function of analysed genes, i.e. involved in gene regulation and signal transduction, or encoding enzymes and defence proteins.

HACRE1, a recently inserted copia-like retrotransposon of sunflower (Helianthus annuus L.)

In this paper we report on the isolation and characterization, for the first time, of a complete 6511 bp retrotransposon of sunflower. Considering its protein domain order and sequence similarity to other copia elements of dicotyledons, this retrotransposon was assigned to the copia retrotransposon superfamily and named HACRE1 (Helianthus annuus copia-like retroelement 1). HACRE1 carries 5' and 3' long terminal repeats (LTRs) flanking an internal region of 4661 bp. The LTRs are identical in their sequence except for two deletions of 7 and 5 nucleotides in the 5' LTR. Based on the sequence identity of the LTRs, HACRE1 was estimated to have inserted within the last approximately 84 000 years. The isolated sequence contains a complete open reading frame with only one complete reading frame. The absence of nonsense mutations agrees with the very high sequence identity between LTRs, confirming that HACRE1 insertion is recent. The haploid genome of sunflower (inbred line HCM) contains about 160 copies of HACRE1. This retrotransposon is expressed in leaflets from 7-day-old plantlets under different light conditions, probably in relation to the occurrence of many putative light-related regulatory cis-elements in the LTRs. However, sequenced cDNAs show less variability than HACRE1 genomic sequences, indicating that only a subset of this family is expressed under these conditions.

Genetic variability in sunflower (Helianthus annuus L.) and in the Helianthus genus as assessed by retrotransposon-based molecular markers

The inter-retrotransposon amplified polymorphism (IRAP) protocol was applied for the first time within the genus Helianthus to assess intraspecific variability based on retrotransposon sequences among 36 wild accessions and 26 cultivars of Helianthus annuus L., and interspecific variability among 39 species of Helianthus. Two groups of LTRs, one belonging to a Copia-like retroelement and the other to a putative retrotransposon of unknown nature (SURE) have been isolated, sequenced and primers were designed to obtain IRAP fingerprints. The number of polymorphic bands in H. annuus wild accessions is as high as in Helianthus species. If we assume that a polymorphic band can be related to a retrotransposon insertion, this result suggests that retrotransposon activity continued after Helianthus speciation. Calculation of similarity indices from binary matrices (Shannon's and Jaccard's indices) show that variability is reduced among domesticated H. annuus. On the contrary, similarity indices among Helianthus species were as large as those observed among wild H. annuus accessions, probably related to their scattered geographic distribution. Principal component analysis of IRAP fingerprints allows the distinction between perennial and annual Helianthus species especially when the SURE element is concerned.

Phylogenetic relationships between annual and perennial species of Helianthus: evolution of a tandem repeated DNA sequence and cytological hybridization experiments

The amplification and chromosomal localization of tandem repeated DNA sequences from Helianthus annuus (clone HAG004N15) and the physical organization of ribosomal DNA were studied in annual and perennial species of Helianthus. HAG004N15-related sequences, which did not show amplification in other Asteraceae except for Viguiera multiflora, were redundant in all the Helianthus species tested, but their frequency was significantly higher in perennials than in annuals. These sequences were located at the ends and intercalary regions of all chromosome pairs of annual species. A similar pattern was found in the perennials, but a metacentric pair in their complement was not labelled. Ribosomal cistrons were carried on two chromosome pairs in perennials and on three pairs in annuals except for H. annuus, where rDNA loci were on four pairs. No difference was observed between cultivated H. annuus and its wild accessions in the hybridization pattern of the HAG004N15 and ribosomal probes. These findings support the hypothesis that the separation between annual and perennial Helianthus species occurred through interspecific hybridization involving at least one different parent. However, GISH in H. annuus using genomic DNA from the perennial Helianthus giganteus as blocking DNA failed to reveal different genomic assets in annual and perennial species.

Characterization of the chromosome complement of Helianthus annuus by in situ hybridization of a tandemly repeated DNA sequence

A tandemly repeated sequence isolated from a clone (HAG004N15) of a nebulized genomic DNA library of sunflower (Helianthus annuus L., 2n = 34) was characterized and used to study the chromosome complement of sunflower. HAG004N15 repeat units (368 bp in length) were found to be highly methylated, and their copy number per haploid (1C) genome was estimated to be 7800. After in situ hybridization of HAG004N15 repeats onto chromosome spreads, signals were observed at the end of both chromosome arms in 4 pairs and at the end of only one arm in 8 other pairs. Signals were also observed at the intercalary (mostly subtelomeric) regions in all pairs, in both arms in 8 pairs, and in only one arm in the other 9 pairs. The short arm of 1 pair was labelled entirely. The chromosomal location of ribosomal DNA was also studied by hybridizing the wheat ribosomal probe pTa71. Four chromosome pairs contained ribosomal cistrons at the end of their shorter arm, but a satellite was seen in only 3 pairs. These hybridization patterns were the same in the 3 sunflower lines studied (HA89, RA20031, and HOR). The chromosomal localization of HAG004N15-related sequences allowed all of the chromosome pairs to be distinguished from each other, in spite of small size and similar morphology.

Distribution of Ty3-gypsy- and Ty1-copia-like DNA sequences in the genus Helianthus and other Asteraceae

Two repeated DNA sequences, pHaS13 and pHaS211, which revealed similarity to the int gene of Ty3-gypsy retrotransposons and the RNAse-H gene of Ty1-copia retroelements, respectively, were surveyed in Asteraceae species and within the genus Helianthus. Southern analysis of the genome of selected Asteraceae that belong to different tribes showed that pHaS13- and pHaS211-related subfamilies of gypsy- and copia-like retroelements are highly redundant only in Helianthus and, to a lesser extent, in Tithonia, a Helianthus strict relative. However, under low stringency posthybridization washes, bands were observed in almost all the other Asteraceae tested when pHaS13 was used as a probe, and in several species when pHaS211 was hybridized. FISH analysis of pHaS13 or pHaS211 probes was performed in species in which labelling was observed in Southern hybridizations carried out under high stringency conditions (Helianthus annuus, Tithonia rotundifolia, Ageratum spp., Leontopodium spp., Senecio vulgaris for pHaS13, and H. annuus, Tithonia rotundifolia, and S. vulgaris for pHaS211). Scattered labelling was observed over all metaphase chromosomes, indicating a large dispersal of both Ty3-gypsy- and Ty1-copia-like retroelements. However, preferential localization of Ty3-gypsy-like sequences at centromeric chromosome regions was observed in all of the species studies but one, even in species in which pHaS13-related elements are poorly represented. Ty1-copia -like sequences showed preferential localization at the chromosome ends only in H. annuus. To study the evolution of gypsy- and copia-like retrotransposons in Helianthus, cladograms were built based on the Southern blot hybridization patterns of pHaS13 or pHaS211 sequences to DNA digests of several species of this genus. Both cladograms agree in splitting the genomes studied into annuals and perennials. Differences that occurred within the clades of perennial and annual species between gypsy- and copia-like retroelements indicated that these retrotransposons were differentially active during Helianthus speciation, suggesting that the evolution of the 2 retroelement families was, within limits, independent.Key words: Asteraceae, FISH, genome evolution, Helianthus, retrotransposons, Ty1-copia, Ty3-gypsy.

Analysis of a dehydrin encoding gene and its phylogenetic utility in Helianthus

Dehydrins are ubiquitous plant proteins, synthesized in late stages of plant embryo development and following any environmental stress involving dehydration. With the aim to study the evolution of such a stress-responsive gene within Helianthus and to test the possibility of using this gene for phylogenetic studies, fragments of the same dehydrin gene were isolated by PCR and sequenced in 16 wild Helianthus species or subspecies. All isolated sequences included the typical dehydrin domains (Y, S and K), a portion of 3'-UTR and an intron, inserted in the same position within the S domain-encoding region. The number of nucleotide substitutions (both synonymous and nonsynonymous) was calculated keeping separate the different gene regions, and differences occur even among coding domains, indicating that evolutionary constraints act differently on each region. The occurrence of indels and/or insertions was also observed. At the deduced protein level, the calculation of isoelectric point, molecular weight and the percentage of alpha-helix showed a diversification of biochemical properties of this protein between annual and perennial Helianthus species. Phylogenetic trees were built by the maximum-likelihood, maximum-parsimony, and neighbor-joining methods. In all cases the same topology was observed; perennial and annual species form a supported clade, and H. annuus was separated from the other annuals and from perennials. These data support the use of this stress-responsive gene to study the phylogeny of Helianthus.

Sequence variability of a dehydrin gene within Helianthus annuus

Dehydrins are proteins produced during the late stages of plant embryo development and following any environmental stimulus involving dehydration. In order to investigate the variability of a dehydrin-encoding gene (Dhn1) in cultivated and wild sunflower (Helianthus annuus) genotypes, near-complete alleles were isolated by the polymerase chain reaction and sequenced. All of the isolated sequences were found to contain the typical dehydrin domains, and interrupted by an intron. The number of nucleotide substitutions and indels per site was calculated. With respect to the overall sequence, variation in both the coding and noncoding [intron and 3'-UTR (untranslated region)] sequences was much larger among wild accessions than among cultivars. No variation was observed in 3'-UTRs from cultivated sunflowers. Different coding regions showed a different numbers of synonymous and nonsynonymous substitutions. The Y and K domains were the most conserved in both wild and cultivated genotypes. Sequence analysis of the deduced dehydrin proteins showed that nucleotide substitutions in wild accessions should also determine large biochemical differences at the protein level. All of the isolated alleles were however functional, at least at the transcription level. To our knowledge these are the first data on intraspecific genetic variability of such a stress response gene. The low variability of dehydrin genes from cultivated sunflower is discussed in relation to the origin of sunflower cultivars. The possibility of rescuing general genetic variability through crosses to wild accessions of H. annuus rather than using wild Helianthus species is also discussed.

Ty1 /copia- and Ty3 /gypsy-like DNA sequences in Helianthus species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.

Cancer testis antigens expression in mesothelioma: role of DNA methylation and bioimmunotherapeutic implications

Recent evidences suggest that malignant mesothelioma may be sensitive to immunotherapy; however, little is known about malignant mesothelioma-associated tumour antigens. Focusing on cancer/testis antigens, the expression of well-characterised immunogenic tumour-associated antigens was investigated in malignant mesothelioma cells. At variance with MAGE-4 and NY-ESO-1, malignant mesothelioma cells frequently expressed MAGE-1, -2 and -3, GAGE 1-2, GAGE 1-6, SSX-2 and SSX 1-5, and distinct malignant mesothelioma cells concomitantly expressed at least four cancer/testis antigens. Additionally, the tumour-associated antigens RAGE-1 was expressed at high levels in both benign and malignant mesothelial cells. Lastly, treatment with the DNA hypomethylating agent 5-aza-2'-deoxycytidine induced and up-regulated the expression of the cancer/testis antigen examined in malignant mesothelioma cells. Overall, these findings strongly suggest that cancer/testis antigens-based immunotherapy may represent a suitable therapeutic approach to malignant mesothelioma, and foresee the clinical use of 5-aza-2'-deoxycytidine to design new chemo-immunotherapeutic strategies in malignant mesothelioma patients.

White and UV light effects on cell nuclei in the aurea genotype of Lycopersicum esculentum L

The effects of white light and UV light on chromosome endoreduplication, chromatin conformation and RNA synthesis were analysed in the hypocotyl cortical cylinder of the cv UC-105 of tomato and its isogenic mutant aurea, deficient in photoactive phytochrome A at the etiolated stage. Short white light or UV irradiations were administered to 4-day-old seedlings grown in the dark. White light had no effect on the mean ploidy level in the cv UC-105, but it increased the ploidy level in the aurea mutant. This is explained by hypothesizing that phytochrome inhibits endoreduplication, while cryptochrome stimulates it. UV light produced a higher ploidy in both genotypes, possibly because of residual action of cryptochrome at this wavelength or of specific UV-responsive photoreceptor. White light or UV light transiently increased heterochromatin amounts in the diploid nuclei of cv UC-105, and produced higher levels of RNA transcription than continuous dark. It is suggested that these responses were mediated by phytochrome, because they were lacking in the aurea mutant.

Characterization and expression of DNA sequences encoding putative type-II metallothioneins in the seagrass Posidonia oceanica

Posidonia oceanica is a marine phanerogam, largely widespread in the Mediterranean sea, representing an important food substrate for many marine organisms. A progressive reduction of P. oceanica meadows has been reported, due to anthropogenic coastal activity. Studying mechanisms by which this species responds to environmental stresses, three DNA sequences putatively encoding metallothioneins (MTs) have been isolated, by PCR. Two sequences, Pomt2a (accession no. AJ249603) and Pomt2b (accession no. AJ249602), show high similarities with genes encoding type-II MTs and are interrupted by two and one intron, respectively. The third sequence, Pomt2c (accession no. AJ249604), is supposed to be a pseudogene, originated by retrotranscription of the Pomt2b mRNA. These sequences belong to a multigene family with at least five members. Northern hybridizations indicated that MT transcripts accumulation is constitutive and seasonally regulated. MT encoding RNAs increase after rhyzome harvesting and (at a lesser extent) after 15 d of cultivation in an aquarium. As for animal MTs, transcripts accumulation is observed also after exposure to trace metals such as copper and cadmium. In the case of copper, the effect depends on concentration. Finally, taking into consideration the great interest in studying the biogeochemical cycle of mercury in the Mediterranean basin and since P. oceanica is commonly considered a bioindicator of this metal, the effect of mercury treatments on the accumulation of MT transcripts has been analyzed: in only a few experiments a small increase in the level of transcripts was recorded, suggesting that MTs are not key elements in the mercury accumulation by this species.

Expression of a dehydrin gene during embryo development and drought stress in ABA-deficient mutants of sunflower (Helianthus annuus L.)

The synthesis of a particular class of proteins, the dehydrins, is a common response to drought in plants. Dehydrins are known to be synthesized by the cell in response to abscisic acid, which represents a link between environment and nuclear activity, though dehydrin genes may be expressed even constitutively. We have investigated the relationship between abscisic acid (ABA) and accumulation of a dehydrin mRNA in sunflower, in which a dehydrin cDNA (HaDhnla) was isolated. In particular, we studied changes in the steady-state level of dehydrin transcripts in two mutants for ABA synthesis and accumulation: nd-1 (an albino, non-dormant and lethal mutant with a very low ABA content and no ABA accumulation in response to stress) and w-1 (a wilty mutant, with reduced ABA accumulation) during embryo and plantlet development and drought stress. Differences between genotypes were observed through embryogenesis: w-1 shows a lower content of dehydrin transcripts in the early stages compared to control plants, indicating that ABA affects dehydrin mRNA accumulation; however, dehydrin transcripts level appears independent of ABA content in late embryogenesis. Also during drought stress in w-1 adult leaves, ABA is not quantitatively related to the steady-state level of the HaDhn1a transcripts. Finally, data on nd-1 mutant show a high level of dehydrin transcripts after drought stress in plantlet cotyledons and leaflets. These results indicate the existence of two regulation pathways of HaDhn1a transcripts accumulation, an ABA-dependent and an ABA-independent one, which may have cumulative effects.

Circadian rhythms of fibrinogen antithrombin III and plasminogen in chronic liver diseases of increasing severity

Acquired deficiencies of fibrinogen, antithrombin III and plasminogen are reported in liver disease, and it is known that their plasma levels fluctuate during the day. The aim of this study was to investigate the circadian rhythms of these three factors in chronic liver disease. Five groups of subjects were considered: (A) 15 healthy controls: (B) 15 patients with hepatic alcoholic steatosis; (C) 15 patients with chronic active hepatitis; (D) 15 patients with compensated cirrhosis of the liver, and (E) 15 patients with decompensated cirrhosis with ascites. The levels of fibrinogen, antithrombin III and plasminogen were determined in blood samples drawn in each subject during the span of a day every 3 h starting from midnight. The time-related values were analyzed using the 'population-mean cosinor' method. Groups A and B presented a significant (p < 0.05) circadian rhythm for each variable, group C a significant (p < 0.05) circadian rhythm for fibrinogen and antithrombin III and groups D and E no significant (p > 0.05) circadian rhythms. Statistically significant differences (p < 0.05) were demonstrated among the groups in the mean daily levels of the three variables by ANOVA, the concentrations decreasing with disease severity. These data confirm the existence of a significant diurnal periodicity in the circulating levels of fibrinogen, antithrombin III and plasminogen in controls and suggest that liver disease is associated with progressive circadian modifications in the temporal structure of fibrinogen, antithrombin III and plasminogen, related to the stage of the liver disease. The rhythm derangements may be considered markers of evolution in liver disease.

Variation of repetitive DNA sequences in progenies of regenerated plants of Pisum sativum

The frequency variation of highly repeated (HR) DNA sequences was studied in plants regenerated through in vitro culture of macerated vegetative apices of Pisum sativum and their progenies. Feulgen cytophotometry showed that regenerated plants (R1) have 6-7% more DNA per nucleus than control plants; this difference is maintained in the subsequent generation (R2). Slot-blot analyses using isolated highly repeated sequences as probe indicated that an increased frequency of these sequences occurs in regenerated plants and their progenies. These results were confirmed by a series of experiments: (a) metaphase chromosomes were longer in R2 than in control plants; (b) cytophotometric analyses of chromatin structure after Feulgen-staining showed that condensed chromatin is more represented in R2 than in control plants; and (c) thermal denaturation of isolated HR sequences indicated that a new HR family appears in R1 and is maintained in R2 plants. These results suggest that, in this species, the DNA extrasynthesized during in vitro culture is, at least in part, integrated in the chromosomes and transmitted to the progeny.

Cytophotometric and biochemical analyses of DNA in pentaploid and diploid Agave species

Nuclear DNA content, chromatin structure, and DNA composition were investigated in four Agave species: two diploid, Agave tequilana Weber and Agave angustifolia Haworth var. marginata Hort., and two pentaploid, Agave fourcroydes Lemaire and Agave sisalana Perrine. It was determined that the genome size of pentaploid species is nearly 2.5 times that of diploid ones. Cytophotometric analyses of chromatin structure were performed following Feulgen or DAPI staining to determine optical density profiles of interphase nuclei. Pentaploid species showed higher frequencies of condensed chromatin (heterochromatin) than diploid species. On the other hand, a lower frequency of A-T rich (DAPI stained) heterochromatin was found in pentaploid species than in diploid ones, indicating that heterochromatin in pentaploid species is made up of sequences with base compositions different from those of diploid species. Since thermal denaturation profiles of extracted DNA showed minor variations in the base composition of the genomes of the four species, it is supposed that, in pentaploid species, the large heterochromatin content is not due to an overrepresentation of G-C repetitive sequences but rather to the condensation of nonrepetitive sequences, such as, for example, redundant gene copies switched off in the polyploid complement. It is suggested that speciation in the genus Agave occurs through point mutations and minor DNA rearrangements, as is also indicated by the relative stability of the karyotype of this genus. Key words : Agave, DNA cytophotometry, DNA melting profiles, chromatin structure, genome size.

Nuclear DNA changes within Helianthus annuus L.: variations in the amount and methylation of repetitive DNA within homozygous progenies

Complex alterations in the redundancy and methylation of repeated DNA sequences were shown to differentiate the nuclear genome of individuals belonging to single progenies of homozygous plants of the sunflower. DNA was extracted from seedlings obtained from seeds collected at the periphery of flowering heads (P DNA) or from seedlings obtained from seeds collected in their middle (M DNA). Three fractions of repeated sequences were isolated from genomic DNA: a highly repetitive fraction (HR), which reassociates within an equivalent Cot of about 2 × 10(-1), and two medium repetitive fractions (MR1 and MR2) having Cot ranges of about 2 × 10(-1)-2 and 2-10(2), respectively. Denaturation kinetics allowed different sequence families to be recognized within each fraction of repetitive DNA, and showed significant differences in sequence redundancy to occur between P and M DNA, particularly as far as the MR2 fraction is concerned. Most DNA sequence families are more represented in P DNA than in M DNA. However, the redundancy of certain sequences is greater in the latter than in the former. Each repetitive DNA fraction was hybridized to Southern blots of genomic P or M DNA which was digested to completion by three pairs of isoschizomeric restriction endonucleases which are either insensitive or sensitive to the methylation of a cytosine in the recognition site. The results obtained showed that the repetitive DNA of H. annuus is highly methylated. Clear-cut differences in the degree of methylation of P and M DNA were found, and these differences were particularly apparent in the MR2 fraction. It is suggested that alterations in the redundancy of given DNA sequences and changes in their methylation patterns are complementary ways to produce continuous genotypic variability within the species which can be exploited in environmental adaptation.

Cytophotometric determination of heterochromatin base composition in interphase nuclei of plant cells

The use of DNA base-specific fluorochromes and static cytophotometry at different thresholds of fluorescence intensity is proposed for studying the base composition of differently condensed chromatin fractions in plant interphase nuclei. Results are reported of such analyses on nuclei from leaflets of Posidonia oceanica and Helianthus annuus, which confirm other findings obtained on the same materials by biochemical and molecular methods.

Heterochromatin and repetitive DNA frequency variation in regenerated plants of Helianthus annuus L

Plant regeneration from cotyledons of seeds of a single progeny of a pure line of Helianthus annuus was studied in respect of the nuclear DNA contents of control and regenerated plants. Control plants were divided into two groups: those developed from seeds at the periphery of the inflorescence (showing a high basic 4C DNA content) and those from seeds developed in the middle of the inflorescence (showing a low basic 4C DNA content). It was observed that plants from peripheral seeds have a higher morphogenetic potential than those from central seeds. Cytophotometric analyses indicated that plants regenerated from cotyledons of both peripheral and central seeds show the same basic 4C DNA amount, which is higher that that observed in vivo in peripheral seeds. Molecular analysis by slot blotting and hybridization with different DNA families showed that the difference in nuclear DNA content between plants from peripheral and central seeds in vivo are mainly related to differences in the frequency of highly repeated, "slow" medium repeated (MR2), and ribosomal DNA families; by contrast, the increase in DNA amount in regenerated plants is mainly due to "fast" medium repeated sequences (MR1). Moreover, the frequency of kinetically isolated "unique" sequences was higher in peripheral seeds than in central ones and still higher in regenerated plants. Optical-density measurements of interphase nuclei showed an increase of heterochromatin in regenerated plants, suggesting that, whatever DNA is amplified in these plants, it remains condensed and probably inactive.

Treatment of type C chronic active hepatitis with interferon-alpha 2a. Treatment duration does not influence biochemical remission but does decrease the relapse rate

Few data are as yet available on the influence of interferon (IFN) treatment duration on biochemical remission and posttreatment relapse of chronic type C hepatitis. We investigated whether duration of recombinant IFN-alpha 2a treatment influences the remission and relapse rates in type C chronic active hepatitis (CAH). Sixty-two CAH patients were randomly assigned to receive 3 MU of i.m. recombinant IFN-alpha 2a three times per week for either 3 (group A, 32 patients) or 6 (group B, 30 patients) months. A complete biochemical remission was cumulatively observed in 62.5 and 63.3% of patients in groups A and B, respectively (p = NS). One and two patients in groups A and B, respectively, showed a biochemical relapse during treatment. In all cases biochemical remission was observed within the first 3 months of treatment. Among responders, 84.2 and 52.9% (p = 0.04) cumulatively had relapses in groups A and B, respectively. We conclude that IFN treatment duration does not influence the biochemical remission rate in type C CAH, but lowers the relapse rate of those who are treated for a longer period. The IFN treatment should be stopped if the patient is a nonresponder after 3 months of treatment. In responders, treatment should be continued for at least 6 months.

Nuclear DNA changes within Helianthus annum L.: changes within single progenies and their relationships with plant development

The variations in the basic nuclear DNA content, which previous results indicated to occur within one and the same progeny of Helianthus annuus, were studied in detail and correlated with certain developmental features of the plants. The size and organization of the genome of seedlings obtained from seeds (achenes) collected at the periphery (P-seedlings) or in the middle (M-seedlings) of the flowering heads of plants belonging to a line selfed for 10 years were compared. Cytophotometric determinations indicated that the nuclear DNA content of P-seedlings is 14.7% higher than that of M-seedlings. Thermal denaturation and reassociation kinetics of extracted DNAs showed that variations in the redundancy of repetitive DNA, in particular of a family of medium repeated sequences with a Cot range of 2-100, account for the differences in genome size. These findings were confirmed by the results of molecular hybridizations (slot blots), which also indicated a higher amount of ribosomal DNA in the P-seedlings than in the M-seedlings. Cell proliferation is affected by DNA content, and mitotic cycle time is 1h30' longer in the P-seedlings. By studying mature plants, positive correlations were also found between genome size and both the surface area of leaf epidermal cells (P≤0.01) and flowering time (P≤0.001). It is suggested that the variations of nuclear DNA content and organization observed play a role in determining developmental variability in plant populations, which may be of importance in buffering the effects of changing environmental conditions.

DNA variations in regenerated plants of pea (Pisum sativum L.)

The aim of this study was to determine whether DNA variations could be detected in regenerated pea plants. Two different genotypes were analyzed by cytogenetic and molecular techniques: the "Dolce Provenza" cultivar and the "5075" experimental line. "Dolce Provenza" regenerated plants showed a reduction in DNA content, particularly at the level of unique sequences and ribosomal genes. Moreover, regeneration was associated with an increase in DNA methylation of both internal and external cytosines of the CCG sequence. On the other hand, the DNA content of the "5075" line remained stable after regeneration. DNA reduction was found only in "5075" plants regenerated from callus cultures maintained for long incubation periods (about a year). The DNA variations observed are discussed both in relation to the genotype source and the role of tissue-culture stress.

[Assessment of gallbladder motility in patients with alcoholic hepatic cirrhosis after a fatty meal. A real-time ultrasonography study]

Gallbladder emptying after fatty meal administration was investigated by real-time ultrasonography in 10 patients with alcoholic cirrhosis of the liver, and 10 normal controls. Gallbladder volume was measured using the sum of cylinders method before and 5', 15', 20', 30', 60', 90', and 120' after fatty meal administration. Patients with liver cirrhosis presented the gallbladder volume significantly increased after 15' and 20', and significantly reduced after 60' and 90' in respect to controls. A significant difference was found between the groups in the two curves, patients showing a retarded contraction of gallbladder. The mechanism for sluggish gallbladder emptying in liver cirrhosis is unknown, however impaired emptying with bile stasis provides a potential pathophysiology basis for the high frequency of cholelithiasis in this disease.

Incidence and indications for cholecystectomy in a public health district of a small town in central Italy

There are major differences in cholecystectomy rates between different countries. We prospectively recorded all gallbladder operations in L'Aquila, Italy (a small town in central Italy with a population of about 98,700 inhabitants) from June 15, 1987 to June 14, 1988. During that year 210 cholecystectomies were performed (women and girls = 71.4%), for a calculated yearly incidence rate of 0.212%. Cholecystectomy was elective in 85.2%, urgent in 8.6%, and was performed in the course of other abdominal operations (mainly colon cancer) in the remaining 6.2%. Half (44.3%) of the patients were operated on because of at least one episode of biliary colic, and 9.0% because of an acute complication. Respectively 16.2% and 30.5% were operated on because of dyspeptic symptoms or to prevent symptoms or complications. Gallstones were not found in six, while exploration of the common bile duct revealed gallstones in seven patients. The chemical analysis showed that 84.7% were cholesterol stones (mixed or pure). We presume that most observed differences in cholecystectomy rates between different Western countries are more likely owing to differences in indications for surgery rather than to differences in prevalence of gallstones.

Nuclear DNA changes within Helianthus annuus L.: origin and control mechanism

Previous results suggested that the amount of nuclear DNA varies in one and the same progeny of Helianthus annuus, depending on the head portion in which seeds have developed. Accordingly, cytophotometric determinations were carried out in a selfed line, after Feulgen-staining, to obtain information on the developmental stages at which DNA changes are produced and on the mechanism controlling the variation. It was found that the Feulgen absorption values of mitotic prophases in immature anthers and pistils and of meiotic prophases I are the same in any flower of the head. In contrast, the Feulgen/DNA contents of early prophases in heart-shaped embryos differ significantly, increasing from those developing at the centre of the head to those developing at its periphery, and remaining unchanged in each embryo during further development and seed germination. Variations in the number of chromosomes do not account for the differences observed in nuclear DNA contents in which sequences comprised in heterochromatic nuclear regions are involved. The Feulgen absorption values of seedlings obtained from seeds developed in different portions of single heads increase or diminish starting from those found in the mother plant. This depends on whether these latter are relatively low or high and on the gradient of seed location in the head. The variation occurring within each single progeny covers the whole range existing within the line.

5-azacytidine-induced tumorous transformation and DNA hypomethylation in Nicotiana tissue cultures

The phenomenon of habituation is considered in plant tissue cultures to be a real process of chemical tumorogenesis; the cultures acquire the capacity of autonomous growth in a hormone-free medium under the influence of a variety of chemical and physical agents. Treatments with 5-azacytidine (AzaC) of in vitro cultured cells of the Nicotiana glauca x N. langsdorffii nontumorous hybrid (NNT) during the culture cycle led to the induction of a habituated phenotype. The repetitive DNA sequences showed a significant lower level of endogenous methylation in the treated cells in comparison with the normal ones. It is worth noting that it was impossible until now to habituate this strain by conventional methods and that the treatments were effective only in the first 5 days of subculturing; various evidence (cytological and biochemical) pointed out a phenomenon of DNA amplification, occurring in the same period. Moreover, analysis of DNA from control and treated cells shows the induction of variations in the endogenous methylation pattern by AzaC in a critical period of cell culture. These results suggest that demethylation can act as a switch from hormone-dependent to autonomous proliferation by activation of genes coding for or regulating the synthesis of growth factors.

Hepatic encephalopathy: lack of changes of gamma-aminobutyric acid content in plasma and cerebrospinal fluid

The aim of the study was to verify the role of gamma-aminobutyric acid in the pathogenesis of hepatic encephalopathy occurring in cirrhotic patients by attempting to correlate plasma and cerebrospinal fluid content of authentic gamma-aminobutyric acid with the neurological manifestations of hepatic encephalopathy. For this purpose, plasma and cerebrospinal fluid gamma-aminobutyric acid levels were measured by means of mass fragmentography in 17 cirrhotic patients with hepatic encephalopathy and in 6 cirrhotics without neurological symptoms. Moreover, in all patients, a second sample was obtained during the clinical course of hepatic encephalopathy. The mean plasma and cerebrospinal fluid gamma-aminobutyric acid levels were not different in patients with or without hepatic encephalopathy and did not change during the evolution of the neurological symptoms. The lack of changes in the gamma-aminobutyric acid content in plasma and cerebrospinal fluid during hepatic encephalopathy is in contrast with the hypothesized importance of increased entry into the brain of gamma-aminobutyric acid in the pathogenesis of hepatic encephalopathy.

Eosinophilic fasciitis: a case with IgA deficiency

A case of eosinophilic fasciitis with IgA deficiency is presented. The increased recognition of this association suggests that IgA deficiency may be pathogenetically involved in the etiology of eosinophilic fasciitis.

[Serum levels of magnesium in hepatic cirrhosis]

In a group of 50 patients with liver cirrhosis compared with a group of 50 clinically healthy subjects serum magnesium levels were determined. The patients were divided according the aetiology of liver cirrhosis and to the presence or not of ascite and cholestasis. The serum magnesium levels were related to the main laboratory tests used in liver cirrhosis. The patients present a significant decrease of serum magnesium levels in comparison to controls. The patients with alcoholic cirrhosis of the liver and with ascite have significant lower magnesium levels in comparison with the patients with post-hepatitis cirrhosis and with patients without ascite. There is a significant correlation between serum magnesium levels and serum levels of aldosterone, albumin, gamma-glutamyl transpeptidase and total pool of bile acids. Direct and indirect effects of alcohol, a secondary hyperaldosteronism, the use of diuretics, and hypoalbuminaemia could account for magnesium serum level decrease in liver cirrhosis.

Nuclear DNA changes within Helianthus annuus L.: cytophotometric, karyological and biochemical analyses

Cytophotometric measurement of the root meristems of seedlings after Feulgen-staining reveals that large differences (up to 58.16%) in nuclear DNA content may occur in the thirty-one cultivated varieties or lines of Helianthus annuus tested. Significant variations (not exceeding 25%) in the amount of DNA, which does not differ between the root and the shoot meristems of a single seedling, are also found to exist within cultivars or lines; even seedlings obtained from seeds collected from different portions of single heads of plants belonging to a selfed line may vary one from the other in this respect. Variations in the number of chromosomes or alterations in the chromosome structure do not account for the differences observed in nuclear DNA content. Karyometric analyses demonstrate that the surface area of squashed interphase nuclei and metaphase chromosomes and the total length of the latter increase with the increase in Feulgen/DNA absorption. DNA thermal denaturation and reassociation kinetics indicate that a frequency variation in repeated DNA sequences goes hand in hand with changes in the size of the genome. These results, supporting the concept that a plant genome is highly flexible, are discussed in relation to other data to be found in the literature on the intraspecific variation in the nuclear DNA content and in relation to the way in which it is produced in H. annuus.

Amplification of nuclear DNA sequences during induced plant cell dedifferentiation

Cell dedifferentiation has been induced in Vicia faba roots by removing the whole meristem (decapitation). When centrifuged to equilibrium in CsCl density gradient, the DNA from dedifferentiating tissues forms a heavier satellite, not occurring in the DNA from differentiated tissues. Most of the radioactivity after [3H]thymidine feeding is found in the satellite DNA. Its sequences have a well defined nuclear localization, as shown by in situ hybridization experiments. These results indicate amplification of G + C-rich nuclear DNA sequences during cell dedifferentiation.