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En la piña se han utilizado protocolos de crioconservación basados en un procedimiento de vitrificación. Sin embargo, se desconoce aún la influencia de algunos factores técnicos para lograr una estrategia criogénica con una aplicación de rutina a un amplio número de genotipos. Además hasta la fecha, no se han realizado ningún análisis histológico para visualizar cambios estructurales durante un procedimiento de crioconservación. En la presente investigación se determinaron diferentes aspectos técnicos de una estrategia criogénica para aumentar los niveles de supervivencia de los ápices a la inmersión en nitrógeno líquido. Estos fueron: tipo de ápice, compuesto por 3-4 primordios foliares con un tamaño aproximado de 2,5-3mm; precultivo en 0,3 mol L-1 de sacarosa; aplicación de la solución de carga 0,4 mol L-1+2 0,4 mol L-1 glicerol; temperatura de aplicación de la solución vitrificadora PVS2 a 0 °C durante 420 min. El análisis de la visualización de los cambios estructurales ocurridos en los ápices crioconservados reveló que las células meristemática presentes en el domo apical y los primordios foliares en formación, sufrieron pocas alteraciones celulares y mantuvieron casi intacta sus características morfo-fisiológica en las mejores condiciones de supervivencia. Se aplicó de manera exitosa un procedimiento de vitrificación para nueve accesiones del banco de germoplasma in vitro del centro de Bioplantas. Lo anterior constituye una importante etapa para el establecimiento de un banco de germoplasma a larga plazo del cultivo de la piña.

Pineapple producing countries lack good quality propagation material to expand cultivars into new areas. Previously, research protocols may increase the offer of high quality plantlets and speed the introduction of new pineapple cultivars. The present work is to evaluate the morpho-physiological changes in plantlets of pineapple [Ananas comosus (L.) Merr. 'MD-2'] during the acclimatization phase. Plantlets were acclimatized under 80% relative humidity, 25.5 °C temperature and photosynthetic photon flux of 400-500 µmol m-2 s-1 as average for 45 d under natural photoperiods. All measurements (plant length, number of leaves and roots, fresh weight, width and length of leaf 'D', net photosynthesis and total transpiration rate) were carried out at the end of in vitro rooting phase coincident with 0 d of acclimatization and at 15, 30 and 45 d thereafter. Photosynthetic activity of in vitro plantlets did not increase during the first 30 d of the acclimatization phase. After 30 d, photosynthetic activity ranged from 5.72 to 9.36 µmol CO2 m-2 s-1 while total transpiration ranged from 6.0 to 1.42 mmol H2O m-2 s-1. During the first 30 days there were no significant differences in number of leaves, length or width of the longest ('D') leaf (cm) or plant length (cm). However, after 45 days plant fresh weight (g), length and width of the 'D' leaf (cm) and root number all increased significantly, while transpiration (mmol H2O m-2 s-1) declined. There were small but significant decreases in chlorophyll a and b (µg g-1 mf.). Increased photosynthetic activity after 30 d shows that the increase in light intensity and the reduction of relative humidity during acclimatization did not constitute inhibitory factors.Os países produtores do abacaxi precisam de mudas de boa qualidade para a introdução de novas culturas nas áreas de cultivo. Os protocolos de pesquisa podem aumentar a oferta de mudas de alta qualidade e acelerar a introdução de novas culturas do abacaxi. O estudo apresentado teve como objetivo avaliar as alterações morfofisiológicas de mudas de abacaxi [Ananas comosus (L.) Merr. 'MD-2'], durante a fase de aclimatação. As plantas foram aclimatizadas baseadas em um regímen de 80% de humidade relativa, uma temperatura de 25°C e um fluxo médio de fótones fotossinteticamente ativos de 400-500 µmol m-2 s-1, durante 45 dias em condições naturais de iluminação. As medições todas (comprimento da planta, número de folhas, comprimento, largura da folha maior 'D', taxa fossintetica e taxa transpiratória total) foram feitas no final da fase do enraizamento in vitro a coincidir com a aclimatização no período de 0, 15, 30 e 45 dias após aclimatização. Depois de 30 dias, a atividade fotossintética variou entre 5,72 e 9,36 µmol CO2 m-2 s-1, enquanto a transpiração total variou de 6,0 a 1,42 mmol H2O m-2 s-1. Durante os primeiros 30 dias, não foram registradas diferenças significativas entre o e comprimento da planta, número de folhas e comprimento e largura da folha maior 'D'. No entanto, após 45 dias a massa fresca da planta (g), comprimento e largura da lâmina 'D' (cm) e o número de raízes aumentarem significativamente, enquanto a transpiração (mmol H2O m-2 s-1) foi reduzida. As clorofilas a e b (µg g-1 mf) diminuíram e mostraram diferenças pequenas, mas significativas. O aumento da atividade fotossintética após 30 dias mostrou que o aumento da intensidade luminosa e redução da umidade relativa não são fatores inibidores desta atividade durante a aclimatização.

In this work, a virus isolate collected from squash plants (Cucurbita pepo L.), showing severe symptoms of mosaic and leaf deformation, grown in Cuba, was analyzed using indicator plants, electron microscopy, and phylogenetic analysis. Plants of Squash, cv. Caserta, inoculated with this virus isolate showed mosaic, leaf distortion and blistering symptoms, whereas papaya plants were immune and did not show any symptoms. A transmission electron microscopic examination of leaf dip preparations made from infected squash leaves revealed the presence of elongated and flexuous particles, approximately 780-800 x 12 nm in size. Genomic fragments containing the coat protein (CP) and HC-Pro genes, amplified by specific primers for Papaya ringspot virus, W strain (PRSV-W), showed amino acid identities of both genes higher than 94% when compared to other PRSV-W isolates from America. In the phylogenetic tree, this virus isolate has grouped with other virus isolates from America, Australia, and India and was more distant from the Asian isolates. Taken together, the analyses allow the conclusion that this virus isolate is a W strain of PRSV, detected for the first time in Cuba.

Gibberellins control various aspects of plants growing and development, including seed germination, stem elongation, leaves expansion, flower and seed development. They are also involved in phase changes in some species, as from vegetative transition to reproductive. Most of these aspects seem to be regulated by DELLA proteins, which are negative regulators of the induced growth by GAs. The asynchronism in flowering processes of coffee and pineapple plants is recognized. This is also directly associated with the low quality of productions of both species. Studies that allow understanding this process are very important. This article shows a characterization in silico of supposed DELLA proteins in the database of CAFEST genome, gene bank of pineapple and GenBank to understand the role of DELLA proteins in the coffee and pineapple flowering processes. Structural similarity and expression profile in silico showed by probable DELLA genes in coffee corroborated the classification of DELLA proteins and suggest the presence of two of them in this specie. In pineapple, after an exhausted search, none of the bank genes proteins from this specie and the GenBank showed DELLA motifs in the four domains with structural functions related to the control of GAs. Nevertheless, in the future these analyses should be repeated due to the possibility that the corresponding sequences of these genes may not be present in the analyzed database. Key words: bioinformatics, CAFEST, flowering process, gibberellins. Abreviaturas:ácido desoxirribonucleico (ADN), ácido desoxirribonucleico complementario (ADNc), banco de secuencias expresadas en cafeto (CAFEST), giberelinas (GAs), Marco abierto de lectura (ORFs), secuencias expresadas contiguas (EST-contigs), secuencias expresadas únicas (EST-singlets).

Cincuenta y ocho machos enteros, producidos y sacrificados en la región oriental de Venezuela, fueron categorizados en canal bajo los criterios de dos decretos: 181 (D181) ó 1896 (D1896), para determinar la variación por cuadrados mínimos en características de rendimiento, calidad, culinaria y composición química según la categoría (A vs. B con D181; A vs. B vs. C con D1896) o el índice de rendimiento ( 2 vs. 3 vs. 4 con D1896) como variable independiente. Por el D181 se encontró diferencia significativa entre categorías en la proporción de solomo abierto+pecho+cogote (SAPC) (A > B; P < 0,05), costillar y lagarto anterior con hueso (B > A; P < 0,01), variando los cortes de “mediano valor” (A > B; P < 0,05), con tendencia inversa a los de “bajo valor” (B > A; P < 0,05). Bistés de solomo (longissimus) de categoría A (D181) mostraron menor humedad y cenizas (P < 0,05) que los de B. Los índices D1896 de rendimiento variaron significativamente en Muchacho Cuadrado (3 y 4 > 2), Punta Trasera y SACP (2 > 3 y 4), cortes de mediano valor y delanteros (2 > 3 y 4). La categoría de calidad por D1896 solo afectó la humedad (A > C) del longissimus. Ninguna categorización (D181 o D1896) hizo variar la fuerza de corte, variables culinarias o atributos sensoriales, impidiendo discriminar y ordenar adecuadamente las canales con base en calidad.

Bromeliads are ornamentals plants very attractive due to leaves coloration and the beautiful inflorescences. Vrieseas is a genus of a great commercial interest among them. Traditional propagation techniques are limited to introduce new hybrids to market. Then, in vitro propagation technique gains a great interest. Effect of paclobutrazol combined with Kinetin and BA to different immersion frequency in shoots proliferation and quality, using two concentrations of GA3 in shoots growth were evaluated to establish a protocol for in vitro propagation in Temporary Immersion Systems. Integration of these results is the elemental procedure for an in vitro propagation protocol of Vriesea using temporary immersion technique. Key words: bromeliads, ornamentals, paclobutrazol

The technique of Temporary Immersion constitutes an effective tool for the plant propagation; it increases the multiplication coefficient and the quality of the same ones. Little it is known until the moment about the echophysiology of this new cultivation technique where the plants are subjected to an immersion between liquid and the physiologic changes that take place during this stage will be those responsible for the plants quality. To evaluate the effects of these conditions in the physiologic change of plantain plants, a descriptive experiment was directed during the elongation phase. Enzymes related with the carbon metabolism were measure of the plant heterotrophic behaviour during the studied phase. High levels of acid invertase (AI) activities and pyruvato kinase (PK) accompanied by first floor levels of sucrose phosphate synthase (SPS) and phosphoenolpyruvate carboxylase (PEPC), evidence these behaviours. The changes induced by the atmosphere and the indicative net photosynthesis and transpiration demonstrate the tendency from the plants to be a less autotrophy systems. The plants during the in vitro conditions don’t depend totally on the photosynthesis but rather they present photomixotrophic behaviour. Key words: acid invertase (AI), Phosphoenolpyruvate carboxylase (PEPC), pyruvato kinase (PK), sucrose phosphate synthase (SPS)

In the last few years the productions levels of pineapple have decreased. The lack of planting material is one of the factors responsible for such a decrement. Two protocols for pineapple micropropagation have been recently developed: that described by Daquinta (1998), and the one of Escalona (1999). The first one uses conventional micropropagation methods, while the second one employs temporary immersion biorreactors. The critical step of these procedures is the acclimatization stage, because of the low survival and growth rates reaching the plants in this phase. The aim of this work was to evaluate the effect of gibberelins and fertilizer sprays on vitroplants growth. Doses of 0, 5, 100, 150 and 200 mg.l-1 of GA3 (BDH) were tested. Also three frequencies were evaluated: each 5, 10 and 15 days respectively. In a second experiment, four doses of the fertilizer Combi II were spayed on the plants: 0 (distilled water), 5,10 and 15 ml.l-1. Later, the combined application of GA3 and Combi II was measured compared to a control treatment (distilled water). Finally, the effects of GA3 (BDH) and the gibberelins produced by ICIDCA were compared. The sprays of GA3 (BDH) at 100 mg.l-1 twice a month, increased vitroplants growth; however, they caused undesirable morphological abnormalities of the plants. The sprays with the fertilizer Combi II at 5 mg.l-1 also improved plant growth. Its combined application with gibberelins (ICIDCA) at 100 mg.l-1 provoked an homogeneous and significant increment of plant growth. Key words: biotechnology, gibberelic acid, plant growth regulators

Single chamber, rata-responsive pacing is emerging as a new modality in cardiac pacing and in the near future dual chamber rate-responsive pacing may be the optimal for most pacemaker patients. In this report we describe our short- and long-term clinical experience with two different rate-responsive pacemakers: the RS4, an asynchronous atrial sensing ventricular pacemaker, and the TX-pacemaker, which senses the evoked QT after a ventricular paced beat, as an indicator of metabolic demand. Both systems use a single ventricular lead. Nine patients received RS4 and 10 patients received TX units. All of these patients had AV block and good ventricular function except for three patients with sinus node disease in the TX group. Between 1 and 3 months after implantation, a 24-hour Holter monitoring was performed, during which two maximal symptom-limited treadmill exercise tests (Bruce protocol) were conducted in VVI (70 bpm) and rate-responsive modes, in a random fashion. The mean follow-up was 25 months in RS4 group and 10 months in TX group. Significant improvements in patient exercise tolerance were found in the rate-responsive mode (9.0 vs. 6.6 METs in VVI) with similar results in both groups [RS4 and TX] despite higher ventricular pacing rates in the TX group [121 bpm vs. 102 bpm in RS4]. An autolimited rate-responsive pacemaker-mediated tachycardia, induced by retrograde ventriculo-atrial conduction, was observed in a patient with an RS4. There are still many problems with these units; at the end of follow-up, only 4 out of 9 with the RS4 unit and 9 out of 10 with the TX unit have pacers that are functioning properly. Single chamber rate-responsive pacing should be considered as a step forward in cardiac pacing. [ABSTRACT FROM AUTHOR]

Atrial systole and ineffective pacemaker stimuli. An unusual case of pacemaker failure induced by atrial activity is presented. The pacemaker stimulus was ineffective for ventricular capture not only with low energy output (decreased pulse duration) of the generator, but also with pulse width two to three times the stimulation threshold. The two possible mechanisms of this phenomenon, one electrotonic and the other mechanical, are discussed. This report strongly supports the mechanical hypothesis. [ABSTRACT FROM AUTHOR]

Intranasal meningoencephaloceles have historically been managed by neurosurgeons, although their main clinical manifestations are rhinological. Recent advances in endoscopic skull base surgery has significantly improved the treatment of these lesions and consequently diminished appreciable surgical morbidity. We report an ethmoidal meningoencephalocele case operated on by endonasal endoscopic approach for removal of the lesion and reconstructing the associated skull base. From this experience, we conclude that removal of the lesion and watertight closure of the skull base irrespective of the size of the mass and anterior skull base defect are the operation’s most important aspects.