The Chilean socio-ethno-genomic cline.

Studies of the current Chilean population performed using classical genetic markers have established that the Chilean population originated primarily from the admixture of European people, particularly Spaniards, and Amerindians. A socioeconomic-ethno-genetic cline was established soon after the conquest. Spaniards born in Spain or Chile occupied the highest Socioeconomic Strata, while Amerindians belonged to the lowest. The intermediate strata consisted of people with different degrees of ethnic admixture; the larger the European admixture, the higher the Socioeconomic Level. The present study of molecular genomic markers sought to calculate the percentage of Amerindian admixture and revealed a finer distribution of this cline, as well as differences between two Amerindian groups: Aymara and Mapuche. The use of two socioeconomic classifications - Class and Socioeconomic Level - reveals important differences. Furthermore, Self-reported Ethnicity (self-assignment to an ethnic group) and Self-reported Ancestry (self-recognition of Amerindian ancestors) show variations and differing relationships between socioeconomic classifications and genomic Amerindian Admixture. These data constitute a valuable input for the formulation of public healthcare policy and show that the notions of Ethnicity, Socioeconomic Strata and Class should always be a consideration in policy development.

Thermal stabilization of putative karyoskeletal protein-enriched fractions from Saccharomyces cerevisiae.

Elevated growth temperature (heat shock) promoted the structural stability of karyoskeletal protein-enriched fractions isolated from Saccharomyces cerevisiae. Similar stabilization could be induced by brief incubation of nuclei at 37 degrees C in vitro. These results are similar to those reported for higher eucaryotes and have practical implications for investigation of the karyoskeleton in S. cerevisiae.

p75, a polypeptide component of karyoskeletal protein-enriched fractions associated with transcriptionally active loci of Drosophila melanogaster polytene chromosomes.

A 75-kilodalton polypeptide has been identified which copurifies with karyoskeletal protein-enriched fractions prepared from Drosophila melanogaster embryos. Results of indirect immunofluorescence experiments suggest that this protein, here designated p75, is primarily associated with puffed regions of larval salivary gland polytene chromosomes. In nonpolytenized Schneider 2 tissue culture cells, p75 appeared to be localized throughout the nuclear interior during interphase. In mitotic cells, p75 was redistributed diffusely. A possible role for karyoskeletal elements in transcriptional regulation is discussed.

Alterations in chromosomal synapses and DNA repair in apoptotic spermatocytes of Mus m. domesticus.

We investigated whether apoptotic spermatocytes from the mouse Mus m. domesticus presented alterations in chromosomal synapses and DNA repair. To enrich for apoptotic spermatocytes, the scrotum's temperature was raised by partially exposing animals for 15 min to a 42ºC water bath. Spermatocytes in initial apoptosis were identified in situ by detecting activated Caspase-9.  SYCP1 and SYCP3 were markers for evaluating synapses or the structure of synaptonemal complexes and Rad51 and γH2AX for detecting DNA repair and chromatin remodeling. Apoptotic spermatocytes were concentrated in spermatogenic cycle stages III-IV (50.3%), XI-XII (44.1%) and IX-X (4.2%). Among apoptotic spermatocytes, 48% were in middle pachytene, 44% in metaphase and 6% in diplotene. Moreover, apoptotic spermatocytes showed several structural anomalies in autosomal bivalents, including splitting of chromosomal axes and partial asynapses between homologous chromosomes. gH2AX and Rad51 were atypically distributed during pachytene and as late as diplotene and associated with asynaptic chromatin, single chromosome axes or discontinuous chromosome axes. Among apoptotic spermatocytes at pachytene, 70% showed changes in the structure of synapses, 67% showed changes in gH2AX and Rad51 distribution and 50% shared alterations in both synapses and DNA repair. Our results showed that apoptotic spermatocytes from Mus m. domesticus contain a high frequency of alterations in chromosomal synapses and in the recruitment and distribution of DNA repair proteins. Together, these observations suggest that these alterations may have been detected by meiotic checkpoints triggering apoptosis.

Antimitochondrial antibody detection by indirect immunofluorescence on mouse sperms.

Antimitochondrial antibodies (AMA) are characteristically present in the serum of patients with primary biliary cirrhosis (PBC). AMA detection constitutes an important step for the clinical diagnosis of PBC, the indirect immunofluorescence against cryostat sections of rat of mouse organs being the most common method used. This study presents an alternative method for AMA detection by indirect immunofluorescence using mouse sperms as substrate. Sera of 17 patients with PBC were examined for AMA using mouse sperms and frozen sections of rat kidney. With mouse sperms as substrate, all PBC sera were found to be AMA positive showing an intense fluorescent reaction on the mitochondrial sheath of mouse sperms (100% sensitivity). No false positive results were obtained with normal sera. Sera of 22 patients with collagen diseases (systemic lupus erithematosus and progressive systemic sclerosis) having defined reactivity to antigens other than mitochondrial antigens were also examined for AMA with both substrates; 19 of them resulted AMA negative. AMA diagnosis on mouse sperm substrate was found to be more sensitive than conventional rat kidney substrate. In addition, it has the advantage that it facilitates for the observer the visualization and reading of the fluorescent reaction on the mitochondria, due to the particular distribution of them on mouse sperms.

Tissue and sex differences in the expression of nucleoli in mouse somatic cells.

In Mus musculus, the nucleolus organizer regions (NORs), or sites of ribosomal RNA-encoding genes, map at three chromosomal pairs. A silver procedure was modified to stain nucleoli in interphasic somatic cells of mice. The number of nucleoli per cell nucleus was determined in squashed cells of kidney, liver and pancreas obtained from male and female mice. In liver and pancreas cells the average number of nucleoli per cell was 4.84 and 4.66, respectively, and only 2.83 in kidney cells (p < 0.001). Less than 8% of pancreas cells and about 15% of liver cells contained more than 6 nucleoli per cell, which was the maximum expected number. In addition, the number of nucleoli per cell was significatively different (p < 0.01) when male and female liver or pancreas cells (not kidney cells) were compared. In both cases, female cells presented more nucleoli than the respective male cells. Assuming that the available NORs are the same, the variable number of nucleoli in the examined cell types would be the consequence of a tissue specific NOR regulation. The apparent influence of sex on this regulation is noted.

Dolor torácico y hemotórax como presentación atípica de secuestro pulmonar en adulto / Chest pain and hemothorax: an atypical presentation of a pulmonary sequestration

Resumen El secuestro pulmonar es una malformación pulmonar rara, presentándose generalmente en edades tempranas. Se presenta mayoritariamente con neumonías e infecciones repetidas, distrés respiratorio y falla cardíaca; raramente en pacientes de mayor edad se presenta con hemoptisis y dolor torácico. En este artículo se describe el caso clínico de un paciente de 60 años de edad que se presenta con un infarto de un secuestro pulmonar y hemotórax.

Bronchopulmonary sequestration is a rare pulmonary malformation, usually occurring at an early age. It presents mainly with pneumonia and repetitive infections, respiratory distress and heart failure; rarely in aged patients presents with hemoptysis and chest pain. This article describes the clinical case of a 60-year-old male patient who presented an ischemic pulmonary sequestration and hemothorax.

Absceso mediastínico con extensión espontánea a través de la pared torácica / Mediastinal abscess with spontaneous across chest wall extension

Introduction: Mediastinal abscess (MA) is a rare disease in the adult population. Generally presents as a systemic inflammatory response syndrome (SIRS) with high morbidity and mortality. The prognosis improves with an early diagnosis associated with an aggressive surgical drainage. Clinical case: We report a clinical case with a MA with an unusual spontaneous extension across the chest wall.

Introducción: Los abscesos mediastínicos (AM) son una patología poco frecuente en la población adulta. Su presentación clínica más habitual es la de un síndrome de respuesta inflamatoria sistémica (SIRS) con una elevada morbimortalidad. Su pronóstico mejora con un diagnóstico temprano asociado a un drenaje quirúrgico agresivo y precoz. Caso clínico: Presentamos un caso clínico de un AM con una inusual extensión espontánea a través de la pared torácica.

Análisis comprensivo de los traumatismos torácios penetrantes atendidos en Hospital Padre Hurtado de Santiago / Penetrating chest trauma

Objectives: Penetrating chest trauma (PCT) is a life threatening condition that challenges emergency surgeons daily. The aim of this study is to make an epidemiological characterization of these patients, and secondarily analyze their treatment and outcome. Methods: A retrospective analysis of a series of consecutive patients experiencing PCT who presented at our hospital, was performed from 1st May 2009 to 30th April 2013. Results: Of 274 consecutive patients who presented to the emergency department (ED) with PCT, 257 (94 percent) were male and 17 (6 percent) were female. The median age was 26 (range 15-66) years. Stab wounds (SW) accounted for 185 (68 percent) of the injuries, and 80 (29 percent) suffered from gunshot wounds (GSW). As first treatment, chest tube drainage was performed in 229 (84 percent) patients, emergent thoracotomy in 21 (8 percent) and observation, in 13 (5 percent). 26 (9 percent) patients died: 21 (81 percent) from GSW and 4 (15 percent) with SW P<0.0001; 20 (77 percent) had heart or thoracic great vessels involvement. Thoracic complications occurred in 30 (12 percent) patients. There was no mortality associated with thoracic complications. The median hospital stay was 4 days. Conclusions: PCT is frequent in our hospital compared with historical series. The majority of the patients who died had cardiac or thoracic great vessels involvement due to GSW. Therefore, healthcare improvements are needed to reduce mortality in this group of patients.

Objetivos: Los traumatismos torácicos penetrantes (TTP) son graves y desafían diariamente a los cirujanos de urgencia. El objetivo de este estudio es realizar una caracterización epidemiológica de los pacientes con TTP, y como objetivo secundario analizar el tratamiento efectuado y su evolución. Métodos: Se realizó un estudio retrospectivo de los pacientes atendidos en el Hospital Padre Hurtado de Santiago que presentaron un TTP desde el 1 de mayo de 2009 hasta el 30 de abril de 2013. Resultados: 274 pacientes que se consultaron al servicio de urgencia con un TTP, 257 (94 por ciento) eran hombres y 17 (6 por ciento) eran mujeres. La mediana de edad fue 26 (15-66) años. Lesiones por arma blanca 185 (68 por ciento), y 80 (29 por ciento) fueron por arma de fuego. Como primer tratamiento la pleurostomía fue realizada en 229 (84 por ciento) pacientes. La toracotomía de emergencia fue realizada en 21 (8 por ciento) pacientes. No se realizó tratamiento y solo observación en 13 (5 por ciento) de los casos. 26 (9 por ciento) de los pacientes murieron, 21 (81 por ciento) fueron consecuencia de lesiones por arma de fuego y 4 (15 por ciento) por arma blanca P<0,0001, 20 (77 por ciento) tenían lesiones cardíacas o de grandes vasos torácicos. 30 (12 por ciento) pacientes presentaron complicaciones torácicas. No hubo mortalidad asociada a complicaciones torácicas. La mediana de días de hospitalización fue 4. Conclusiones: El TTP es frecuente en nuestro hospital comparado con series históricas. La mayoría de los pacientes fallecidos presentaban TTP por arma de fuego con lesiones cardíacas o de grandes vasos torácicos. Se precisan mejoras asistenciales en este grupo para disminuir su mortalidad.

Resección traqueal y anastomosis primaria en traumatismo traqueo esofágico por arma de fuego / Tracheal resection and primary anastomosis in tracheoesophagueal gunshot trauma

Introduction: even though tracheoesophagueal lesions due to cervicothoracic gunshot wound are infrecuent, they should always be considered in a lesion of this kind, based on the proximity of the structures in this area, as well as the rapid compromise and deterioration that can develop these patients if the air way or vascular structures are damaged. Clinical case: we present a patient with a tracheoesophageal gunshot trauma and the surgical repair.

Introducción: las lesiones traqueo esofágicas secundarias a heridas de bala en cuello, a pesar de ser infrecuentes, siempre deben descartarse frente a un mecanismo de este tipo, no sólo por la proximidad de las estructuras sino también por el importante compromiso y rápido deterioro que pudieran presentar estos pacientes si la vía aérea o estructuras vasculares se vieran comprometidas. Caso clínico: se presenta en este trabajo un paciente con lesión traqueo esofágica secundaria a herida de bala, además de la técnica de reparación utilizada.

Hernia diafragmática complicada con rotura de víscera hueca dentro de la cavidad torácica / Complicated diaphragmatic hernia with hollow viscus rupture in thoracic cavity

Introduction: diaphragmatic hernias (DH) are a rare condition in adult patients. Most of the cases are asymptomatic findings in imaging studies. Rarely do they present as complicated cases. Clinical cases: we report two clinical cases of complicated DH, one of Bochdalek and another with history of a penetrating thoracic trauma two years before, both with hollow viscus rupture in the thoracic cavity.

Introducción: las hernias diafragmáticas (HD) son una patología relativamente poco frecuente en adultos. La gran mayoría son hallazgos asintomáticos en exámenes de imágenes, y en ocasiones debutan con complicaciones de éstas. Casos clínicos: se presentan dos casos clínicos de HD, una de Bochdalek y otra con antecedente de trauma penetrante torácico hace 2 años, ambas complicadas con rotura de víscera hueca en la cavidad torácica.

Congelación ultra rápida de espermatozoides humanos: efecto sobre la función espermática y producción de especies reactiva de oxígeno / Ultra rapid freezing in human spermatozoa: effect on sperm function and reactive oxygen species production

El incremento del número de pacientes que desean mantener su fertilidad, ya sea por motivos oncológicos o de fertilidad, como son los pacientes con enfermedades infecciosas virales trasmitidas por vía sexual, o que se someten en forma voluntaria a la esterilización quirúrgica, requieren de métodos de congelación que preserven en forma adecuada la función de los espermatozoides. En el área de la criobiología, la utilización de técnicas de congelación ultrarrápida ha permitido preservar en forma exitosa ovocitos, embriones y tejido ovárico. Este método se ha incorporado recientemente para preservar el gameto masculino. El presente estudio evalúa el efecto de la congelación ultrarrápida (vitrificación) sobre la función espermática de 10 donantes normozoospérmicos. Los espermatozoides se seleccionaron por Swim-up y la solución espermática se dividió en dos subfracciones. Una fracción se vitrificó sumergiéndola directamente en nitrógeno líquido mientras que la segunda se utilizó como control. En ambas fracciones se determinaron viabilidad, movilidad, potencial de membrana mitocondrial (YMMit), integridad del ADN, reacción de acrosoma espontánea e inducida, y superóxido intracelular (O2.-). Se observó que la vitrificación preserva una adecuada función celular en un alto número de espermatozoides, siendo además un método simple, rápido y de menor costo, ya que no necesita equipo de congelación. No obstante, existe una significativa activación de la producción de especies reactivas de oxígeno, que conlleva a una prematura capacitación espermática, evento que es necesario de modular, especialmente si se utilizan estas células en técnicas de inseminación intrauterina. Futuros estudios con adición de antioxidantes a los medios de congelación parecen necesarios para optimizar esta técnica.

The number of patients who wish to maintain their fertility is ever increasing. This group of patients includes cancer patients, those with fertility problems or viral infectious diseases acquired through sexual contact and others submitting to voluntary surgical sterilization; all of the above requiring freezing methods to adequately preserve sperm function. In the field of cryobiology the use of ultra-rapid freezing techniques has successfully preserved oocytes, embryos and ovarian tissue. This method has recently been incorporated in preserving male gametes. This study evaluates the effect of ultra-rapid freezing (vitrification) on sperm function of 10 normozoospermic donors. The sperm were selected by swim-up technique and the solution divided into two fractions. One fraction is vitrified by dipping directly into liquid nitrogen and the second fraction is used as control. In both fractions, viability, motility, mitochondrial membrane potential (YMMit) DNA integrity, spontaneous and induced acrosome reaction and intracellular superoxide (O2.-) were determined. It was noted that vitrification preserves cell function in a great number of spermatozoon, and is also simple, rapid and cost effective as this method does not require freezing equipment. There is however, significant activation of the production of reactive oxygen species, which leads to premature sperm capacitation, an event necessary to modulate particularly when using these cells in intrauterine insemination techniques. Future studies with addition of antioxidants to freezing media are necessary to further improve this technique.

Calidad de vida en pacientes con hiperhidrosis primaria sometidos a simpatectomía videotoracoscópica / Quality of life after videothoracic simpathectomy in patients with primary hyperhidrosis

Introduction: Primary hyperhidrosis is characterized by excessive sweating that exceeds the physiological needs to maintain thermal homeostasis of the body. This study aims to assess the change in quality of life of patients operated on videothoracoscopic sympathectomy. Materials and Methods: We included all patients operated with this technique in the period between 2004 and 2010, in FACh Hospital. A standardized cuestionary was used to measure severity of hyperhidrosis and quality of life during pre and postoperative. Results: 61 patients, 57 percent female and mean age of 25 years. Preoperative sweating was barely tolerable or unacceptable in 81 percent, and preoperative quality of life was poor or very poor in 82 percent of patients. After surgery sweating was never noticed or tolerable at 85 percent and the quality of life was better in 84 percent of patients. 78 percent of patients developed compensatory sweating; however the 87 percent were satisfied with the outcome of surgery. Conclusion: Videothoracoscopic sympathectomy offers excellent results that are measurable in terms of improvement of quality of life, but often associated with the phenomenon of compensatory sweating. Despite the development of this sequel, the majorities of operated patients are satisfied with the surgical results and improve their quality of life.

Introducción: La hiperhidrosis primaria se caracteriza por sudoración excesiva que supera las necesidades fisiológicas para mantener la homeostasis térmica del cuerpo. El objetivo de este trabajo es evaluar el cambio en la calidad de vida de los pacientes operados de simpatectomía videotoracoscópica. Material y Método: Estudio de tipo transversal del total de pacientes operados con esta técnica en el Hospital Fuerza Aérea de Chile (FACh) en el período entre 2004 y 2010. Se utilizó una encuesta estandarizada y validada en la literatura para medir severidad de la hiperhidrosis y calidad de vida en período pre y postoperatorio. Resultados: 61 pacientes, 57 por ciento de género femenino y promedio de edad 25 años. La sudoración preoperatoria era apenas tolerable o intolerable en 81 por ciento y la calidad de vida preoperatoria era pobre o muy pobre en 82 por ciento de los pacientes. Posterior a la cirugía la sudoración nunca se notaba o era tolerable en 85 por ciento y la calidad de vida era mejor en 84 por ciento de los pacientes. El 78 por ciento de los pacientes operados desarrolló sudoración compensatoria, sin embargo, el 87 por ciento de los pacientes estaban satisfechos con el resultado de la cirugía. Conclusión: La simpatectomía videotoracoscópica ofrece excelentes resultados que son medibles en términos de mejoría de la calidad de vida, pero asociado frecuentemente al fenómeno de sudoración compensatoria. Pese al desarrollo de esta secuela, la mayoría de los pacientes operados están satisfechos con los resultados quirúrgicos y mejoran su calidad de vida.

Nuclear architecture of human pachytene spermatocytes: quantitative analysis of associations between nucleolar and XY bivalents.

Nucleolar association and heterochromatin coalescence have both been invoked as mechanisms involved in the origin of chromosomal associations between nucleolar bivalents themselves, as well as between these bivalents and the XY pair, during meiotic prophase in human spermatocytes. However, these mechanisms do not satisfactorily explain how associating bivalents meet each other within the nuclear space. To elucidate this problem, we have characterized different types of nucleolar-nucleolar and nucleolar-XY bivalent associations, and their frequencies, in light and electron microscope serial sections of spermatocyte nuclei. In the pachytene nucleus, nucleolar bivalent associations were found to involve only one nucleolar sphere of RNP granules connected through a fibrillar center to a chromatin mass composed of two, or more, nucleolar-bivalent short arms. Structural relationships between these elements were examined using 3D computer models of various nucleolar associations. XY and nucleolar bivalents were usually located towards the nuclear periphery associated with the inner face of the nuclear envelope. Some nucleolar bivalents, whether single or associated appeared beside or over XY chromatin. When nucleolar-bivalent short arms (BK) were found over nucleolar or over XY chromatin, their telomeres were unattached to the nuclear envelope and the corresponding synaptonemal complexes were not observed. Ninety nucleoli were found in sixty pachytene nuclei. Thirty six percent of these nucleoli were bound to associated BKs and the remaining 64% to single BKs. Over 40% of individual spermatocytes showed at least one cluster of associated BKs and about 20% presented single or multiple BKs associated with the XY pair. The frequencies of random BK associations, over the total or restricted areas of the nuclear envelope, were calculated according to a probabilistic nuclear model. A correspondence was found in comparing the observed frequencies of associated BKs with those calculated on the basis of bouquet formation. Such an analysis strongly suggests that the occurrence of associations between nucleolar bivalents may arise at random within the bouquet. Thus, the architecture of the meiocyte nucleus, particularly the organization of the bouquet, may be the primary mechanism by which nucleolar bivalents meet each other and, consequently, become associated either through common nucleolus formation or by heterochromatin coalescence.

Position of the nucleolus within the nuclei of pachytene spermatocytes of Dromiciops australis and Marmosa elegans (Didelphoidea-Marsupialia).

The location of the nucleoli within the nuclei of pachytene spermatocytes, and their relation with the position of the nucleolar organizer region (NOR) was studied. It appears that a terminal NOR determines a peripheral location of the nucleolus, due to the position of the NOR over the synaptonemal complex and to the attachment of the nucleolar chromosome telomeres at the nuclear membrane.

[A new substrate for the detection of antimitochondrial antibodies in human serum]. / Un nuevo sustrato para la deteccion de anticuerpos antimitocondriales en suero humano.

This work describes a new method to detect antimitochondrial antibodies using indirect immunofluorescence on mouse sperm as substrate. As controls conventional substrates and mitochondrial protein immunoblots were used. An intense fluorescent reaction was visualized in the mitochondrial sheet of mouse sperms allowing a straightforward diagnosis of positive sera. Sera coming from 10 patients with progressive systemic sclerosis, 12 patients with systemic lupus erythematosus and 17 patients with primary biliary cirrhosis were tested with this method, confirming results obtained with conventional tests that use indirect immunofluorescence and rat frozen kidney slices as substrate. The new method is simpler, more accurate and has a lower margin of error.

Organisation of complex nuclear domains in somatic mouse cells.

The number and associations of heterochromatin chromocenters, nucleoli, centromeres and telomeres were studied in the nucleus of different somatic cells of Mus domesticus. Fibroblasts of the cell line 3T3, kidney cells (primary culture), and bone marrow cells were used. The above mentioned nuclear and chromosome markers were identified by DAPI/actinomycin D, indirect immunofluorescence with anti-centromere antibodies, silver impregnation for nucleolar proteins and fluorescence in situ hybridisation (FISH) with telomeric probes. The quantitative analysis of the nuclei showed that the pericentromeric heterochromatin is organised in about 18 chromocenters per nucleus in the 3T3 cells, and about seven in kidney and bone marrow cells, having generally a peripheral distribution in the nucleus of all the studied cells. Several aggregated centromeres were participating in each of the chromocenters, about four centromeres per 3T3 cell and about six centromeres per kidney and bone marrow cells. Some of the chromocenters were also in close association with nucleoli. The number of telomeric labels per nucleus was as expected for each chromosome set (2n = 68-70 and 2n = 40). About half of the telomeric signals were loosely aggregated within the heterochromatic blocks while the rest were distributed in the nucleus as unrelated units not bound with chromocenters. The three cell types have complex nuclear territories formed by different chromosomal domains: the pericentromeric heterochromatin, centromeres, proximal telomeres and nucleoli. With the exception of some bone marrow cells, we have not found a nuclear polarisation of the analysed chromosomal markers compatible with the Rabl configuration. However, Rabl anaphasic polarisation allows the contact of centromeric regions making possible that centromeric associations arise. If in addition, associative elements such as constitutive heterochromatin or nucleoli are close to the centromeric regions, like in Mus domesticus chromosomes, then the associations might be consolidated and persist until the interphase. These associations may be the origin of the nuclear domains described here for Mus domesticus somatic cells.

Non-random distribution of the pericentromeric heterochromatin in meiotic prophase nuclei of mammalian spermatocytes.

The central or peripheral distribution of condensed chromatin (CC) was studied in pachytene spermatocyte nuclei in Mus domesticus, 2n = 40; Pudu puda, 2n = 70; Ctenomys opimus, 2n = 26 and Octodon degus, 2n = 58. Species were chosen according to the morphological characteristics of their chromosomal complements and in particular, the terminal or medial chromosomal localisation of the pericentromeric constitutive heterochromatin. Counts were made by defining the areas corresponding to peripheral and central location in each nuclear section from a series. The null hypothesis (i.e. random distribution of CC) was rejected. In the nuclear sections of Mus domesticus and Pudu puda, 69% and 74% of CC, respectively, was found in the peripheral nuclear space, while in those of Octodon degus and Ctenomys opimus, 69% and 65% of CC, respectively, was found in the central nuclear space. We estimate that if the CC measured in spermatocyte nuclei corresponds mainly to pericentromeric constitutive heterochromatin, the distribution found is consistent with that expected in accordance with the nuclear architecture model for meiocytes (Fernández-Donoso, 1982; Fernández-Donoso & Berrios, 1985). This model proposes a peripheral nuclear localisation for pericentromeric heterochromatin of telocentric bivalents and a relatively central nuclear localisation for pericentromeric heterochromatin of metacentric bivalents. We also discuss some of the biological consequences that could arise from the conservation of such distributions.

Alteration of nuclear architecture in male germ cells of chromosomally derived subfertile mice.

The mammalian cell nucleus consists of numerous compartments involved in the regular unfolding of processes such as DNA replication and transcription, RNA maturation, protein synthesis and cell division. Knowledge is increasing of the relationships between high-order levels of chromatin organization and its spatial organization, and of how these relationships contribute to the various functions carried out in the nucleus. We have studied the spatial arrangement of mouse telocentric chromosomes 5, 11, 13, 15, 16 and 17, some of their metacentric Robertsonian derivatives, and X and Y chromosomes by whole chromosome painting in male germ (spermatogonia, pachytene spermatocytes and spermatids) and Sertoli cells of homozygous and heterozygous individuals. Using dual-colour fluorescence in situ hybridization we found that these chromosomes occupy specific nuclear territories in each cell type analysed. When chromosomes are present as Robertsonian metacentrics in the heterozygous state, that is, as Robertsonian metacentrics and their homologous telocentrics, differences in their nuclear positions are detectable: heterozygosity regularly produces a change in the nuclear position of one of the two homologous telocentrics in all the cell types studied. In the Robertsonian heterozygotes, the vast majority of the Sertoli cells show the sex chromosomes in a condensed state, whereas they appear decondensed in the Robertsonian homozygotes. As the Robertsonian heterozygosities we studied produce a chromosomally derived impairment of male germ-cell differentiation, we discuss the possibility that changes in chromosome spatial territories may alter some nuclear machinery (e.g., synapsis, differential gene expression) important for the correct unfolding of the meiotic process and for the proper functioning of Sertoli cells.