Caracterización y resultados inmediatos en pacientes con tratamiento quirúrgico de bocio intratorácico / Characterization and immediate results in patients with surgical treatment of intrathoracic goiter

Objectives: To describe characteristics and immediate results of surgical treatment of patients with intrathoracic goiter (ITG). Methods: Retrospective review. Period: October 2003 - March 2010. We describe general characteristics, morbidity and mortality. Results: 33 patients, 23 women, mean age 59.1 +/- 14.3 years. Preoperative thyroid function: 32 euthyroid and 1 hyperthyroid. Asymptomatic 10 patients. ITG rate: 31 cervico-mediastinal and 2 mediastinal. Approach: 24 cervicotomy, 7 cervicotomy and sternotomy and 2 sternotomy. Type of resection: 19 total thyroidectomy and 14 subtotal thyroidectomy. Histology: 29 benign and 4 malignant neoplasms. Postoperative stay: median of 4.5 days. Complications in 12 patients: 10 hypo-parathyroidism (9 transient and 1 permanent), 2 dysphonia, 2 cervical hematoma (one redo), 1 wound infection and 1 ventilator associated pneumonia. One patient died (pneumonia). Conclusions: The ITG is more common in women, most are euthyroid and may be asymptomatic. Most can be resected by cervicotomy. The histology is benign in most but may represent malignancies. The surgery is not free of morbidity and mortality.

Objetivos: Describir características y resultados inmediatos del tratamiento quirúrgico de pacientes con Bocio Intratorácico (BIT). Material y Método: Revisión retrospectiva. Período: octubre de 2003 - marzo de 2010. Se describen características generales y morbi-mortalidad. Resultados: 33 pacientes, 23 mujeres, edad promedio 59,1 +/- 14,3 años. Comorbilidades: 12 hipertensos y 1 diabético. Función tiroidea preoperatoria: 32 eutiroideos y 1 hipertiroideo. Asintomáticos 10 pacientes. Tipo BIT: 31 cérvico-mediastínicos y 2 mediastínicos. Abordaje: 24 cervicotomía, 7 cervicotomía más esternotomía y 2 esternotomía. Tipo de resección: 19 tiroidectomía total y 14 tiroidectomía subtotal. Histología: 29 benignos y 4 neoplasias malignas. Estadía postoperatoria: mediana de 4,5 días. Complicaciones en 12 pacientes: 10 hipoparatiroidismos (9 transitorios y 1 permanente), 2 disfonías, 2 hematomas cervicales (uno se reexploró), 1 infección herida operatoria y 1 neumonía asociada a ventilación mecánica. Fallece un paciente (neumonía). Conclusiones: El BIT es más frecuente en mujeres, la mayoría son eutiroideos y pueden ser asintomáticos. La mayoría pueden ser resecados por cervicotomía. La histología es benigna en la mayoría aunque pueden corresponder a neoplasias malignas. La cirugía no está exenta de morbi-mortalidad.

Leiomiosarcoma primario de mediastino que compromete el sistema de la vena cava superior: resección quirúrgica asociada a reconstrucción venosa / Primary leiomyosarcoma of the mediastinum involving the superior vena cava system: surgical resection and venous reconstruction

Mediastinal tumors have multiple presentation forms and various pathological origins. Sometimes they reach a large size and can involve the system of superior vena cava by compression or infiltration. We present a 48 year old man admited for dyspnea, headache and palpitations in decubitus, for the last two months. The X-ray and chest computed tomography showed an anterior mediastinal tumor and the tru-cut pathological study concluded leiomyosarcoma. He underwent surgical treatment; the tumor compromised the system of the superior vena cava and was resected with ligation and resection the left brachiocephalic trunk. Part of the superior vena cava was reconstructed with autologous pericardium. The right phrenic nerve was surrounded by the tumor mass and was resected in block. The patient recovered satisfactorily and was discharged on the eleventh day post surgery. The histopathologic study of the surgical specimen confirmed a leiomyosarcoma G2 (3,100 gr). Full adjuvant radiotherapy was done. At 15 months after surgery the patient is in good condition without evidence of recurrence or superior vena cava syndrome.

Los tumores del mediastino pueden tener múltiples formas de presentación y diversos orígenes anato-mopatológicos. A veces alcanzan gran tamaño y pueden comprometer por compresión o infiltración el sistema de la vena cava superior. Presentamos el caso de un hombre de 48 años que consultó por disnea, cefalea y palpitaciones en decúbito de dos meses de evolución. En la radiografía y en la tomografía computada de tórax se demostró un tumor de mediastino anterior, el estudio anatomopatológico mediante biopsia trucut concluyó leiomiosarcoma. Se realizó tratamiento quirúrgico, se resecó la masa tumoral que comprometía el sistema de la vena cava superior, se ligó y resecó el tronco venoso braquiocefálico izquierdo o innominado y se reconstruyó parte de la vena cava superior con parche de pericardio autólogo. El nervio frénico derecho se encontraba rodeado por la masa tumoral y se resecó junto con el tumor. El paciente evolucionó satisfactoriamente y fue dado de alta al décimo primer día post operado. El estudio de anatomía patológica de la pieza operatoria confirmó un leiomiosarcoma G2 de 3.100 gramos. Se completó tratamiento con radioterapia post operatoria. A 15 meses post operado el paciente se encuentra en buenas condiciones generales, sin evidencias de recidiva y sin síndrome de vena cava superior.

Malformación arteriovenosa pulmonar: características clínicas, diagnóstico y rol del tratamiento quirúrgico en pacientes tratados con cirugía resectiva pulmonar / Pulmonary arteriovenous malformation: clinical features, diagnosis and role of surgical management in patients with lung resection surgery

Introducción: Las malformaciones arteriovenosas pulmonares (MAVP) son infrecuentes y la cirugía tiene un rol en casos seleccionados. Objetivos: Describir las características clínicas, métodos diagnósticos y rol del tratamiento quirúrgico en pacientes tratados con cirugía por MAVP. Materialy Método: Revisión retrospectiva, incluyendo todos los pacientes con diagnóstico de MAVP en quienes se realizó cirugía en el Instituto Nacional del Tórax, desde febrero de 2005 a febrero de 2010. El seguimiento fue por control médico o contacto telefónico. Resultados: Se analizó 8 pacientes, seis mujeres (relación 3:1), edad entre 16 y 68 años. Los síntomas y signos más frecuentes fueron: disnea, cianosis y acropaquia. La localización más frecuente fue el lóbulo inferior derecho. Cuatro pacientes tenían MAVP múltiples y cuatro cumplían con criterios de Enfermedad de Rendu-Osler-Weber Seis tenían policitemia y dos anemia. La radiografía fue anormal en todos los casos y la tomogrqfía computada definió la anatomía en siete. Angiogrqfia se realizó en tres casos. Dos tenían ecocardiograma con contraste y cuatro cintigrama. La cirugía más frecuente fue la lobectomía. La indicación de cirugía fue: tamaño de la MAVP en cinco, falla de embolización en dos y hallazgo intra operatorio en uno, intervenido por otra razón. Uno presentó hemorragia post-operatoria. La estadía post-operatoria fue entre 2 y 10 días. No hubo mortalidad. En el último control todos los pacientes estaban asintomáticos. Conclusión: Las MAVPpueden presentarse en un amplio espectro clínico y anatómico. Pueden generar síntomas y complicaciones graves, por esto se recomienda tratarlas. El estudio pre-operatorio se basa en demostrar el shunt y en determinar las características anatómicas de la lesión. En algunos casos seleccionados está indicada la cirugía resectiva pulmonar.

Background: Pulmonary arteriovenous malformations (PA VM) are rare and surgery has a role only in selected cases. Our objectives are to describe clinical features, diagnostic methods and role of surgical treatment in patients with PA VM. Methods: Retrospective review of all patients with PA VM, in whom surgery was performed in our institution, from February 2005 to February 2010. The follow up controls were done through physician or telephone contact. Results: 8 patients, six females (3:1), aged between 16-68 years were analyzed. Most common sigiis and symptoms were dyspnea, cyanosis and clubbing. Right lower lobe was the most frequent location. Four had multiple PA VM and four met criteria for Rendu-Osler- Weber disease. Six patients had polycythemia and two anemia. Radiography was abnormal in all and computed tomography defined anatomy in seven. Angiography was performed in three, two had contrasted echocardiography and four had scintigraphy. Most common surgical treatment was lobectomy. Indications for surgery were the size of PA VM in five cases, failure of embolization in two and one because of intra-operative findings, without a previous diagrwsis. One had postoperative bleeding. Discharge was between day 2 and 10 days after surgery. There was no mortality. At their last control all patients were asymptomatic. Conclusion: PA VM presents a wide and varied range of clinical and anatomical findings. They can cause major symptoms and serious complications, which justify their treatment. The preoperative study is based primarily on demonstrating the shunt and determining the anatomical characteristics of the lesion. In selected cases lung resection surgery is indicated.

Evaluación del compromiso linfonodal en el cáncer gástrico mediante Dímero D / No association between serum D Dimer levels and lymph node involvement among patients with gastric cancer

Background: D Dimer levels can be predictors of lymph node involvement in gastric cancer. Aim: To evaluate the association between D Dimer levels and lymph node involvement among patients with gastric cancer. Material and Methods: In 32 patients with gastric cancer, aged 38 to 86 years (24 males), subjected to a curative surgery, D Dimer was measured in the preoperative period. Its levels were associated with the number of regional lymph nodes involved and the tumor stage, according to the pathological report of the surgical piece. Results: There was no significant correlation between D Dimer levels and the number of involved lymph nodes (r = 0.18, p = NS). Conclusions: In this series of patients with gastric cancer, there was no association between serum D Dimer levels and the number of involved regional lymph nodes.

Introducción: En el cáncer gástrico resecado el principal factor pronóstico es el compromiso linfonodal. Estudios han demostrado que en el adenocarcinoma esofágico los niveles plasmáticos de Dímero D, se correlacionan con el compromiso linfonodal. Recientemente, Kwon HC demostró lo mismo en el adenocarcinoma gástrico. Objetivo: Establecer si el valor plasmático de Dímero D en el preoperatorio se correlaciona con el compromiso linfonodal en pacientes con adenocarcinoma gástrico resecado. Métodos: Estudio correlacional Durante un año, a los pacientes con diagnóstico de adenocarcinoma gástrico operados en el Hospital Base Valdivia, se les solicitó niveles plasmáticos de Dímero D, dentro del estudio preoperatorio. Causas de exclusión fueron: rechazo de ingreso al estudio, presencia de coagulopatía, los puncionados 48 horas antes del ingreso, los irresecables o con linfadenectomía insuficiente. El resultado del examen se correlacionó con el número de linfonodos comprometidos y el estadio tumoral (TNM) que informaba la biopsia definitiva de la pieza quirúrgica. Software utilizado: XLstat. Resultados: Para el análisis se incluyeron 32 casos. La mediana de edad: 66 años, la ubicación más frecuente fue tercio superior (52,94 por ciento) y el 28,13 por ciento de los pacientes se encontraban en estadio IIIA. El coeficiente de correlación entre nivel plasmático de Dímero D y el número de linfonodos comprometidos fue de 0,18 (p = 0,3411). Conclusión: De acuerdo a los resultados obtenidos en este estudio, existe correlación positiva débil entre los niveles plasmáticos de Dímero D y el número de linfonodos comprometidos en el adenocarcinoma gástrico, no concordando con lo actualmente publicado.

Yeast diversity in the oral microbiota of subjects with periodontitis: Candida albicans and Candida dubliniensis colonize the periodontal pockets.

The term periodontitis encompasses several polymicrobial infectious diseases, of multifactorial etiology, with chronic and aggressive forms. In spite of the etiopathogenic differences between these two forms of the disease, few studies have analyzed the subgingival colonization by yeast. The objective of this investigation was to analyze the composition of the yeast microbiota present in the mucosa and subgingival sites of healthy individuals and patients with aggressive and chronic periodontitis. For this, samples were recovered from these two locations and the yeast recovered identified by phenotypic and genotypic methods. Patients with chronic periodontitis showed significant differences in relation to the other groups with respect to carrier status (69.2% versus 35.7% of healthy individuals; [chi(i)(2) test; p=0.014]), the total number of isolated colony forming units or CFU (mean and ranges 281.6 (0-6048) [K-W(2)=6.998; p=0.03]), the Simpson diversity index (I) in site b (I(b)=0.344 versus healthy subjet and aggresive periodontitis where I=0 [multiple t-test comparisons with the Bonferronni correction, p<0.05]), and the species profile. Interestingly, in spite of the varied profiles of the species present in the mucosa of the three groups analyzed we noted that only C. albicans and C. dubliniensis were capable of colonizing the periodontal pockets in patients with chronic periodontitis, while only C. albicans was identified in the subgingiva of healthy individuals and patients with aggressive periodontitis.

Expression of the carotenoid biosynthesis genes in Xanthophyllomyces dendrorhous.

In the yeast Xanthophyllomyces dendrorhous the genes idi, crtE, crtYB, crtl and ast are involved in the biosynthesis of astaxanthin from isopentenyl pyrophosphate. The carotenoid production and the kinetics of mRNA expression of structural genes controlling the carotenogenesis in a wild-type ATCC 24230 and in carotenoid overproducer deregulated atxS2 strains were studied. The biosynthesis of carotenoid was induced at the late exponential growth phase in both strains. However, the cellular carotenoid concentration was four times higher in atxS2 than in the wild-type strain in the exponential growth phase, suggesting that carotenogenesis was deregulated in atxS2 at the beginning of growth. In addition, the maximum expression of the carotenogenesis genes at the mRNA level was observed during the induction period of carotenoid biosynthesis in the wild-type strain. The mRNA level of the crtYB, crtl, ast genes and to a lesser extent the idi gene, decayed at the end of the exponential growth phase. The mRNA levels of the crtE gene remained high along the whole growth curve of the yeast. In the atxS2 strain the mRNA levels of crtE gene were about two times higher than the wild-type strain in the early phase of the growth cycle.

Hernia inguinal: conceptos actuales / Inguinal hernia: updates

Este artículo tiene como objetivo revisar lo nuevo en el tratamiento de la hernia inguinal, en lo referente a su indicación quirúrgica, compromiso testicular por uso de malla, profilaxis antibiótica, manejo de infección de herida operatoria, prevención y manejo de inguinodinia, técnica quirúrgica de elección y tratamiento de hernia inguinal complicada. Se mencionan y describen las principales técnicas de reparación de hernia inguinal, tanto con malla como sin ella, con sus respectivas incidencias de dolor postoperatorio y recurrencia. Concluimos que la mejor técnica de reparación de la hernia inguinal es la Técnica de Lichtenstein (malla libre de tensión). La profilaxis antibiótica en la hernioplastía con malla no previene las infecciones de herida operatoria y por lo tanto no se recomienda. No se ha demostrado que la malla sea causal de infertilidad. Además frente a una herida operatoria infectada, en la cual se ha utilizado malla, no es necesario retirarla como primera medida. Por otro lado, las hernias complicadas no son una contraindicación absoluta de hernioplastía con malla y la identificación y preservación de los 3 nervios es lo ideal para evitar la inguinodinia crónica.

Expression of the carotenoid biosynthesis genes in Xanthophyllomyces dendrorhous

In the yeast Xanthophyllomyces dendrorhous the genes idi, crtE, crtYB, crtl and ast are involved in the biosynthesis of astaxanthin from isopentenyl pyrophosphate. The carotenoid production and the kinetics of mRNA expression of structural genes controlling the carotenogenesis in a wild-type ATCC 24230 and in carotenoid overproducer deregulated atxS2 strains were studied. The biosynthesis of carotenoid was induced at the late exponential growth phase in both strains. However, the cellular carotenoid concentration was four times higher in atxS2 than in the wild-type strain in the exponential growth phase, suggesting that carotenogenesis was deregulated in atxS2 at the beginning of growth. In addition, the maximum expression of the carotenogenesis genes at the mRNA level was observed during the induction period of carotenoid biosynthesis in the wild-type strain. The mRNA level of the crtYB, crtl, ast genes and to a lesser extent the idi gene, decayed at the end of the exponential growth phase. The mRNA levels of the crtE gene remained high along the whole growth curve of the yeast. In the atxS2 strain the mRNA levels of crtE gene were about two times higher than the wild-type strain in the early phase of the growth cycle.

Genetic polymorphism of clinical and environmental strains of Pichia anomala

In this work 20 clinical and 3 environmental yeast isolates were characterized by classical morphological and physiological methods, as well as molecular methods based on PCR of the ITS1-5.8S rDNA-ITS2 region. The characteristic morphology and biochemical profiles observed in these samples correspond to those described for the Pichia genera, more specifically to P. anomala. The profiles of susceptibility to five antifungal drugs were determined by two broth dilution methods. The results obtained by both methods were comparable and showed that clinical isolates presented more resistance to azoles, amphotericin B, and 5-fluorocytosine, than environmental ones did. By amplification and sequencing of internal transcribed spacers (ITS1 and ITS2) and the ribosomal 5.8S DNA, the yeast samples were divided into four groups, where the strains within each group had the same sequence. Of the analyzed yeast isolates, 78 por percent were identified as Pichia anomala. Using RAPD analysis with seven different Operon primers, polymorphism was observed within the four groups. Our study highlights the growing importance of P. anomala in fungemic episodes in premature neonates. Furthermore, the methodologies used provide a powerful tool to identify and determine differences in similar strains of this yeast.

Alternative splicing of transcripts from crtI and crtYB genes of Xanthophyllomyces dendrorhous.

Xanthophyllomyces dendrorhous is one of the relevant sources of the carotenoid astaxanthin. In this paper, we describe for the first time cloning of unexpected cDNAs obtained from the crtI and crtYB genes of X. dendrorhous strain UCD 67-385. The cDNA of the crtI gene conserves 80 bp of the first intron, while the cDNA of the crtYB gene conserves 55 bp of the first intron and lacks 111 bp of the second exon. The crtI and crtYB RNAs could be spliced in alternative splice sites, which produced alternative transcripts which could not be translated to active CRTI and CRTYB proteins since they had numerous stop codons in their sequences. The ratio of mature mRNA to alternative mRNA for the crtI gene decreased as a function of the age of the culture, while the cellular content of carotenoids increased. It is possible that splicing to mature or alternative transcripts could regulate the cellular concentrations of phytoene desaturase and phytoene synthase-lycopene cyclase proteins, depending on the physiological or environmental conditions.

Development of the sexual reproductive cycle of Xanthophyllomyces dendrorhous.

Conditions inducing the development of holobasidia with terminal basidiospores in wild-type and astaxanthin mutant strains of Xanthophyllomyces dendrorhous were reexamined. Important factors for the development of holobasidia were the incubation temperature and the medium composition. A temperature of 9 degrees C was demonstrated to enhance holobasidia formation. Minimal growth medium with glucose as sole carbon source at concentrations between 80 and 120 mM, and ammonium nitrate with concentrations of 28 mM gave optimal results. A period of 20 or more days was needed for the formation of holobasidia with basidiospores. Additionally, mutant strains of X. dendrorhous were observed to have different abilities to produce holobasidia and strains obtained after protoplast fusion, which have been called fusant in this study, to have an increased capacity to form holobasidia.

Hemoglobin affinity for oxygen in three subspecies of toads (Bufo sp.) living at different altitudes.

Blood oxygen affinity and red blood cell properties were measured in three subspecies of genus Bufo: Bufo spinulosus limensis, collected at sea level and at an average day temperature of 20 degrees C; Bufo spinulosus trifolium, from 3100 m, average day temperature of 15 degrees C; and Bufo spinulosus flavolineatus, from 4100 m, average day temperature of 10 degrees C. Electrophoresis of the hemoglobin showed the same component in each of the three subspecies. At 20 degrees C the blood oxygen affinities (P50) showed small differences between Bufo spinulosus limensis and Bufo spinulosus trifolium, whereas the value for Bufo spinulosus flavolineatus was markedly lower. At 10 degrees C, the ambient temperature of Bufo spinulosus flavolineatus, the P50 was extremely low compared with the other two subspecies at their corresponding ambient temperatures.

Reduced oxygen diffusion across the shell of Gray gull (Larus modestus) eggs.

Gray gulls, Larus modestus, nest 1500 m above sea level in northern Chile's Atacama Desert, one of the driest in the world. Their eggshell gas permeability, one third of that found in other Larus species, is an adaptation that reduces water loss, but at the expense of oxygen diffusion into the air cell with resultant hypoxia and reduced metabolic rate. This contrasts with characteristics found in birds nesting at very high altitudes where oxygen diffusion across the egg shell is maximized at the expense of water conservation. The oxygen consumption (MO2) of Larus modestus is 66% that of Larus argentatus; the oxygen conductance (GO2) is equivalent to 48% of that obtained in 5 other bird species. The oxygen partial pressure (PAO2) in the air chamber of Larus modestus (84 Torr) is lower than that of 10 other bird species whose average (PAO2) is 106 Torr. The CO2 partial pressure (PACO2) in the air chamber of Larus modestus is 68 Torr, a higher value than that found in 9 other bird species whose average (PACO2) is 39 Torr.

Reduced oxygen diffusion across the shell of Gray gull (Larus modestus) eggs

Gray gulls, Larus modestus, nest 1500 m above sea level in northern Chile's Atacama Desert, one of the driest in the world. Their eggshell gas permeability, one third of that found in other Larus species, is an adaptation that reduces water loss, but at the expense of oxygen diffusion into the air cell with resultant hypoxia and reduced metabolic rate. This contrasts with characteristics found in birds nesting at very high altitudes where oxygen diffusion across the egg shell is maximized at the expense of water conservation. The oxygen consumption (MO2) of Larus modestus is 66% that of Larus argentatus; the oxygen conductance (GO2) is equivalent to 48% of that obtained in 5 other bird species. The oxygen partial pressure (PAO2) in the air chamber of Larus modestus (84 Torr) is lower than that of 10 other bird species whose average (PAO2) is 106 Torr. The CO2 partial pressure (PACO2) in the air chamber of Larus modestus is 68 Torr, a higher value than that found in 9 other bird species whose average (PACO2) is 39 Torr.

Complementation analysis with new genetic markers in Phaffia rhodozyma.

Isolation and characterization of auxotrophic mutants from wild-type and astaxanthin mutant strains of Phaffia rhodozyma is described. Differences in survival were observed when u.v. irradiation of P. rhodozyma wild-type and astaxanthin mutant strains were incubated in the dark or exposed to photoreactivating light. Ultra-violet mutagenesis was not effective to produce auxotrophic mutants in this yeast. Auxotrophic mutants were obtained with high efficiency through a nystatin enrichment procedure after a N-methyl-N'-nitro-N-nitrosoguanidine (NGT) mutagenic treatment with a 0.12% survivor level. Stringent mutagenetic conditions were needed to obtain P. rhodozyma auxotrophs. The most frequent mutants were ade- and met- in a rather narrow auxotroph spectrum. These results may be associated with a possible diploid condition of this yeast. The high number of adenine auxotrophs obtained in relation to other auxotrophic mutants suggests the possibility of some degree of heterozygosity in the wild-type strain UCD 67-385.

Genetic transformation of astaxanthin mutants of Phaffia rhodozyma.

Stable red astaxanthin-producing transformants were obtained after genetic transformation of two Phaffia rhodozyma mutants. A yellow mutant, accumulating beta-carotene, and an albino mutant, accumulating phytoene, from P. rhodozyma were transformed using a genomic library of wild-type strain UCD 67-385 in the pBluescript vector. Hybridization assays, using the pBluescript DNA as a radioactive probe, indicate integration of vector sequences into the genome of the transformants. Transformants DNA was digested with restriction endonucleases, ligated with T4 DNA ligase and then used to transform E. coli. Ampicillin resistant plasmids, containing 0.1, 0.2, and 2.5 kb DNA inserts of P. rhodozyma, were rescued from the yeast red transformants. The molecular analysis indicate that transformation has occurred by an integration event of donor DNA into the genome of the host strains.

Genetics and electrophoretic karyotyping of wild-type and astaxanthin mutant strains of Phaffia rhodozyma.

In this work we establish the chromosomal composition of a wild-type, one astaxanthin and two beta-carotene overproducer strains of the red yeast Phaffia rhodozyma. The method used has been pulsed field gel electrophoresis, which has determined 9 DNA chromosomal bands in the yeast genome. The two largest bands are triplets and two other bands, VI and VIII, seem to be doublets. The size of the chromosomal bands varies between 0.35 and 2.5 Mb, suggesting a genome size of 25 Mb. The technique used, complemented with hybridization assays using specific DNA probes, provides direct information about the genomic organization of P. rhodozyma. We have also cloned and located in chromosomal bands different DNA sequences that code for the translation elongation factor 1 alpha (ef-1 alpha), a 7.6 kb BamHI fragment of repetitive DNA (possibly rDNA) and a randomly chosen fragment (named locus R2). Additionally, we have detected a chromosomal length polymorphism between wild-type strains and mutant strains affecting carotenogenesis obtained in our laboratory.

Presence of double-stranded RNA and virus-like particles in Phaffia rhodozyma.

Four double-stranded RNA (dsRNA) molecules were isolated from Phaffia rhodozyma UCD 67-385. Their molecular sizes were approximately 4.3, 3.1, 0.9 and 0.75 kilobase pairs (kbp) as determined by agarose-gel electrophoresis and they were designated as L, M, S1 and S2, respectively. By differential centrifugation in sucrose gradients, these dsRNAs copurified with isometric virus-like particles 36 nm in diameter. A cured strain, UV-S2, lacking the S2-dsRNA was obtained from P. rhodozyma UCD 67-385 by ultraviolet (UV) light treatment. UV-S2 strain contains identical virus-like particles to those from the wild-type strain, as determined by electron microscopy, suggesting that the S2-dsRNA was not essential for the expression of mycovirus structural polypeptides. On the other hand, both the UCD 67-385 and UV-S2 strains were able to kill P. rhodozyma UCD 67-383, a strain without dsRNAs. These results suggest that the dsRNA molecules also encode a killer system. Finally, the UV-S2 strain maintains killer ability, which suggests that S2-dsRNA is not involved in the killer phenotype expression.

Molecular cloning and expression in Saccharomyces cerevisiae and Neurospora crassa of the invertase gene from Neurospora crassa.

A plasmid (named pCN2) carrying a 7.6 kb BamHI DNA insert was isolated from a Neurospora crassa genomic library raised in the yeast vector YRp7. Saccharomyces cerevisiae suco and N. crassa inv strains transformed with pNC2 were able to grow on sucrose-based media and expressed invertase activity. Saccharomyces cerevisiae suco (pNC2) expressed a product which immunoreacted with antibody raised against purified invertase from wild type N. crassa, although S. cerevisiae suc+ did not. The cloned DNA hybridized with a 7.6 kb DNA fragment from BamHI-restricted wild type N. crassa DNA. Plasmid pNC2 transformed N. crassa Inv- to Inv+ by integration either near to the endogenous inv locus (40% events) or at other genomic sites (60% events). It appears therefore that the cloned DNA piece encodes the N. crassa invertase enzyme. A 3.8 kb XhoI DNA fragment, derived from pNC2, inserted in YRp7, in both orientation, was able to express invertase activity in yeast, suggesting that it contains an intact invertase gene which is not expressed from a vector promoter.