Seasonal environmental changes regulate the expression of the histone variant macroH2A in an eurythermal fish.

Adaptation to cold and warm conditions requires dramatic change in gene expression. The acclimatization process of the common carp Cyprinus carpio L. in its natural habitat has been used to study how organisms respond to natural environmental changes. At the cellular level, adaptation to cold condition is accompanied by a dramatic alteration in nucleolar structure and a down regulation of the expression of ribosomal genes. We show that the enrichment of condensed chromatin in winter adapted cells is not correlated with an increase of the heterochromatin marker trimethyl and monomethyl K20H4. However, the expression of the tri methyl K4 H3 and of the variant histone macroH2A is significantly increased during the winter season together with a hypermethylation of CpG residues. Taking into account the properties of macroH2A toward chromatin structure and dynamics and its role in gene repression our data suggest that the increased expression of macroH2A and the hypermethylation of DNA which occurs upon winter-acclimatization plays a major role for the reorganization of chromatin structure and the regulation of gene expression during the physiological adaptation to a colder environment.

[A scientometric view of Revista Médica de Chile]. / Una mirada epistemométrica de la Revista Médica de Chile y su aporte al conocimiento en Medicina.

BACKGROUND: During the last decade Revista Médica de Chile increased its visibility, measured on citations and impact factor. AIM: To perform a scientometric analysis to assess the performance of Revista Médica de Chile. MATERIAL AND METHODS: Thomson's-ISI Web of Science and Journal Citation Reports QCR) were consulted for performance indicators of Revista Médica de Chile and Latin American journals whose subject is General and Internal Medicine. We also report the h-index of the journal, which infers quality linked to the quantity of the output. RESULTS: According to the h-index, Revista Médica de Chile ranks 4 among the 36 journals indexed and published by Argentina, Brazil, Chile and México. The top ten articles published by Revista Médica de Chile and the institutions with the higher contribution to the journal, were identified using citations. In the Latin American region, Brazil relevantly increased its scientific output. However, Argentina, Chile and México maintain a plateau during the last decade. CONCLUSIONS: Revista Médica de Chile increased notoriously its performance. Its contribution to the Chilean scientific community dedicated to Medicine appears to be of central value.

Gene structure and seasonal expression of carp fish prolactin short receptor isoforms.

The complex adaptive mechanisms that eurythermal fish have evolved in response to the seasonal changes of the environment include the transduction of the physical parameter variations into neuroendocrine signals. Studies in carp (Cyprinus carpio) have indicated that prolactin (PRL) and growth hormone (GH) expression is associated with acclimatization, suggesting that the pituitary gland is a relevant physiological node in this adaptive process. Also, the distinctive pattern of expression that carp prolactin receptor (PRLr) protein depicts upon seasonal acclimatization supports the hypothesis that PRL and its receptor clearly are involved in the new homeostatic stage that the eurythermal fish needs to survive during the cyclical changes of its habitat. Here, we characterize the first prolactin receptor gene in a teleost and show that its expression is not associated with alternative promoters, unlike in humans and rodents. Using the regulatory region to direct the transcription of green fluorescent protein (GFP) in zebrafish embryos, we mapped the appearance of this hormone receptor during fish development. This is the first report identifying a fish prolactin receptor gene expressing transcript isoforms encoding for short forms of the protein (45 kDa). These have been found in osmoregulatory tissues of the carp and are regulated in connection with the seasonal acclimatization of the fish.

Ultrastructural changes of the carp (Cyprinus carpio) hepatocyte nucleolus during seasonal acclimatization.

BACKGROUND INFORMATION: The eurythermal fish carp (Cyprinus carpio) adjusts to the seasonal changes in the temperature and photoperiod of its habitat through diverse cellular and molecular mechanisms. We have observed that ribosomal biogenesis is modulated during the acclimatization process and correlates with profound phenotypic changes, reflecting a seasonal-dependent ultrastructural appearance of the nucleolar components. Previous studies using classical techniques showed that in winter-adapted carp the nucleolus appears to be segregated. In the present work, we have reassessed the nucleolar ultrastructural organization of the carp in summer- and winter-adapted fish by using more specific cytochemical and immunocytological techniques. RESULTS: The acetylation method provided evidence that the nucleolar organization is different between winter- and summer-adapted carp. In winter-adapted fish the fibrillar component appears as a unique mass surrounded by several granular caps, whereas in summer-adapted carp the fibrillar component forms few cordons surrounded by granular masses. The nucleolar structure and distribution of the condensed chromatin observed varies upon seasonal acclimatization. In winter the nucleolar chromatin is densely packed in masses that surround the nucleolus, whereas during summer it displays a rather looser organization formed by filaments that not only surround the nucleolus, but also go through the nucleolar body. Using the TdT (terminal deoxynucleotidyl transferase)-immunogold labelling technique, we detected condensed and decondensed nucleolar chromatin, and found some labelling of fibrillar components in both seasons. When liver tissue from summer-adapted carp was treated with AMD (actinomycin D), we observed that the rearrangement of the nucleolar components and condensed chromatin were similar to that found in winter-adapted fish, with differences in the distribution of the perinucleolar chromatin. CONCLUSIONS: The acetylation and TdT-immunogold labelling experiments indicated that the rearrangement of the nucleolar components of winter-adapted carp is very similar to the AMD-treated summer-adapted carp nucleolus, with the latter representing the repression of the ribosomal biogenesis that occurs during the cold season. Nevertheless, the distribution of the condensed perinucleolar chromatin in winter-adapted carp compared with AMD-treated cells suggests that the transcription of rRNA genes in winter-adapted fish is less strongly inhibited and does not lead to the classical segregation of the nucleolus of that described after AMD treatment. In addition, we have confirmed that carp hepatocyte nucleoli comprise only two main structural compartments: a fibrillar component and a granular component. Fibrillar centres were not observed.

[A epistemometric view of some biological disciplines in Chile]. / Una visión epistemométrica de algunas disciplinas biológicas en Chile.

During the last decade the articles published by Chilean Research Centers grew 1,73 which compares to the 2.34 fold increase of mainstream research articles registered as a whole in Latin America. However, the relative impact of the Chilean publications surpassed that of Latin America. In Biological Sciences, traditionally the strongest research area within Chile, Latin America also shows a steeper slope of growth. Qualitatively, biological disciplines in Chile are comparable to those published in Latin America although in Chile there are specialties as Physiology that surpass the average world's impact. The scientometric data is consistent with the fall in individual grants that the Chilean Research Fund (FONDECYT) has been allocating during the last decade.

Gene structure of the carp fish ribosomal protein L41: seasonally regulated expression.

The seasonal acclimatization of the carp fish demands physiological compensatory responses. The process involves profound nucleolar adjustments and remarkable changes in rRNA synthesis, which affect ribosomal biogenesis. We have documented that protein kinase CK2, whose activity is related to ribosomal protein L41 and the regulation of rRNA synthesis, was expressed in notably higher amounts in summer-acclimatized carp compared to the cold-season adapted fish. Thus, we approached the study of the functional genomics of carp L41 protein. We report the first cloning of a fish L41 gene encoding the highly conserved 25 amino acids, including approximately 1700 bp regulatory upstream region and the 3(') polyadenylation signal, plus the isolation and characterization of two different L41 cDNAs. We found a clear differential expression of L41, which follows the same pattern as protein kinase CK2beta that transcribes at higher levels in the summer-acclimatized carp than it does in the winter-adapted fish.

Seasonal environmental changes modulate the prolactin receptor expression in an eurythermal fish.

Eurythermal fish have evolved compensatory responses to the cyclical seasonal changes of the environment. The complex adaptive mechanisms include the transduction of the physical parameters variations into molecular signals. Studies in carp have indicated that prolactin and growth hormone expression is associated with acclimatization, suggesting that the pituitary gland is a relevant physiological node in the generation of the homeostatic rearrangement that occurs in this adaptive process. Here, we report the cloning and characterization of a full-length carp prolactin receptor cDNA, which codes for the long form of the protein resembling that found in mammalian prolactin receptors. We identified up to three receptor transcript isoforms in different tissues of the teleost and assessed cell- and temporal-specific transcription and protein expression in carp undergoing seasonal acclimatization. The distinctive pattern of expression that carp prolactin receptor (cPRLr) depicts upon seasonal acclimatization supports the hypothesis that prolactin and its receptor are clearly involved in the new homeostatic stage that the eurythermal fish needs to survive during the cyclical changes of its habitat.

Genomic organization of the rDNA cistron of the teleost fish Cyprinus carpio.

The seasonal adaptation of the teleost Cyprinus carpio to the cyclical changes of its habitat demands physiological compensatory responses. The process involves profound nucleolar adjustments and remarkable changes in rRNA synthesis, which affects ribosomal biosynthesis. In this context, we have demonstrated that the synthesis of several proteins involved in ribosomal biogenesis as protein kinase CK2, ribosomal protein L41 and nucleolin, as well as U3 snoRNP, are differentially regulated in summer-acclimatized carp compared to the cold-season adapted fish. To understand the mechanisms involved in the seasonal regulation of rRNA gene transcription, we have been studying the carp rDNA cistron structure. Because the cis-elements that regulate the expression of the tandem organized ribosomal genes are located in the non-transcribed intergenic spacer (IGS), we analyzed the primary structure of the carp rDNA gene IGS. The gene organization is similar to that described from other vertebrate species, including numerous repetitive sequences, the transcription start site, and some potential cis-elements such as ribosomal enhancers, proximal terminator and transcriptional terminators. Ribosomal DNA is a remarkable case of gene duplication and has been used as a model to test the concerted evolution theory. We performed sequence comparison analyses of 18S rRNA coding sequences from carp with different species, data with which an unrooted phylogram was constructed.

Una mirada epistemométrica de la Revista Médica de Chile y su aporte al conocimiento en Medicina / A scientometric view of Revista Médica de Chile

Background: During the last decade Revista Médica de Chile increased its visibility, measured on citations and impact factor. Aim: To perform a scientometric analysis to assess the performance of Revista Médica de Chile. Material and methods: Thomson's-ISI Web of Science and Journal Citation Reports QCR) were consulted for performance indicators of Revista Médica de Chile and Latin Amerícan journals whose subject is General and Internal Medicine. We also report the h-index of the journal, which infers quality ¡inked to the quantity of the output. Results: According to the h-index, Revista Médica de Chile ranks 4 among the 36 journals indexed and published by Argentina, Brazil, Chile and México. The top ten articles published by Revista Médica de Chile and the institutions with the higher contríbution to the journal, were identified using citations. In the Latin Amerícan región, Brazil relevantly increased its scientific output. However, Argentina, Chile and México maintain a plateau during the last decade. Conclusions: Revista Médica de Chile increased notoriously its performance. Its contríbution to the Chilean scientific community dedicated to Medicine appears to be of central value.

Una visión epistemométrica de algunas disciplinas Biológicas en Chile / A scientometric view of some biological disciplines in Chile

During the last decade the articles published by Chilean Research Centers grew 1,73 which compares to the 2.34 fold increase of mainstream research articles registered as a whole in Latin America. However, the relative impact of the Chilean publications surpassed that of Latin America. In Biological Sciences, traditionally the strongest research area within Chile, Latin America also shows a steeper slope of growth. Qualitatively, biological disciplines in Chile are comparable to those published in Latin America although in Chile there are specialties as Physiology that surpass the average world's impact. The scientometric data is consistent with the fall in individual grants that the Chilean Research Fund (FONDECYT) has been allocating during the last decade.

In situ hybridization of somatolactin transcripts in the pituitary glands from acclimatized carp (Cyprinus carpio)

We isolated and cloned a carp somatolactin SL DNA fragment, of which 78 per cent of the nucleotides were identical to the corresponding salmon SL sequence. The results obtained upon Northern blot hybridization of carp pituitary RNA allowed the identification of two transcripts as described for other fish. When the content of SL transcripts in pituitary sections from summer- and winter-acclimatized carp was quantified by in situ hybridization assays, we found no significant differences between the two seasons. In salmonids, plasma SL reaches higher levels in summer than in winter in synchrony with the water temperature cycle; in the eurythermal carp, however, the complex adaptive responses imposed by seasonal environmental changes do not seem to include the regulation of the somatolactin detected with the probe used at the transcriptional level in pituitary glands.

Genomic organization of the rDNA cistron of the teleost fish Cyprinus carpio

The seasonal adaptation of the teleost Cyprinus carpio to the cyclical changes of its habitat demands physiological compensatory responses. The process involves profound nucleolar adjustments and remarkable changes in rRNA synthesis, which affects ribosomal biosynthesis. In this context, we have demonstrated that the synthesis of several proteins involved in ribosomal biogenesis as protein kinase CK2, ribosomal protein L41 and nucleolin, as well as U3 snoRNP, are differentially regulated in summer-acclimatized carp compared to the cold-season adapted fish. To understand the mechanisms involved in the seasonal regulation of rRNA gene transcription, we have been studying the carp rDNA cistron structure. Because the cis-elements that regulate the expression of the tandem organized ribosomal genes are located in the non-transcribed intergenic spacer (IGS), we analyzed the primary structure of the carp rDNA gene IGS. The gene organization is similar to that described from other vertebrate species, including numerous repetitive sequences, the transcription start site, and some potential cis-elements such as ribosomal enhancers, proximal terminator and transcriptional terminators. Ribosomal DNA is a remarkable case of gene duplication and has been used as a model to test the concerted evolution theory. We performed sequence comparison analyses of 18S rRNA coding sequences from carp with different species, data with which an unrooted phylogram was constructed

Visión de la investigación en Chile a través de algunos indicadores epistemométricos / Overview of research in Chile by several scientometric indicators

Scientific productivity in Chile was studied examining a data bank constructed with the publications indexed by the Institue for Scientific Information during 1987 and 1988. the bank excludes meeting abstracts and contains the full title of the publisched paper, the list of authors, addresses, field, and the nature of collaboration two or more institutions. The articles were classified in different fields and tabulated according to the institution from which they originated. Although remains to be the more productive subjective (26.5%) followed by medical sciences (23.9%) and chemistry (12.3%), articles in mathematics and physics continued theri increase as in previous years. Using the scientometric indicators published by Braun et al (see refs. 14-17), the impact of the research originated in Chile in biology, physics and mathematics was compared to that attained in Argentina, Brazil, Mexico and Venezuela. The role of the chilean National Research Fund and the output of the financed resarch projects were also analyzed. The succesful results obtained during the first years in which the National Research Fund has been involved in the support of the scientific activity in Chile, confirms the need to strenghten its budget, according to the foals stated in the National Plan for Science and Technology for Development

Uso de sondas no radiactivas para la determinación del número de copias de genes y para el diagnóstico de enfermedades moleculares / Use of non radioactive probes to assess gene copy numbers and for the diagnosis of molecular diseases

Se sintetizó un análogo fotoactivable de biotina, el que se utilizó para marcar sondas de ácidos nucleicos. La marca se reveló con dos sistemas de detección avidina-peroxidasa y estreptavidina-fosfatasa alcalina, siendo ésta última la que demostró una mayor sensibilidad. Los plasmidos pSS1.8 y pSP64/U1 fueron fotobiotinilados y utilizados en ensayos de hibridación en gota con DNA extraido de leucocitos humanos. Despues de la incubacion con estreptavidina y fosfatasa alcalina biotinilada, la actividad de la enzima se reveló con un sustrato soluble. Los resultados obtenidos demuestran diferencias cuantitativas consistentes con el número de copias para globina y U1snRNA humano. El plasmido pSS1.8 fotobiotinilado se utilizó para identificar fragmentos de restricción de DNA genómico alterados en un paciente afectado de anemia de células falciformes. El gen de la globina mutado se detectó por digestión del DNA del paciente con la endonucleasa de restricción Dde I, seguido de una hibridación "Southern" con la sonda marcada