Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020050001&lang=en vol. 38 num. 1 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100001&lng=en&nrm=iso&tlng=en <![CDATA[<strong>Multiple imputation procedures allow the rescue of missing data</strong>: <strong>An application to determine serum tumor necrosis factor (TNF) concentration values during the treatment of rheumatoid arthritis patients with anti-TNF therapy </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100002&lng=en&nrm=iso&tlng=en Longitudinal studies aimed at evaluating patients clinical response to specific therapeutic treatments are frequently summarized in incomplete datasets due to missing data. Multivariate statistical procedures use only complete cases, deleting any case with missing data. MI and MIANALYZE procedures of the SAS software perform multiple imputations based on the Markov Chain Monte Carlo method to replace each missing value with a plausible value and to evaluate the efficiency of such missing data treatment. The objective of this work was to compare the evaluation of differences in the increase of serum TNF concentrations depending on the ­308 TNF promoter genotype of rheumatoid arthritis (RA) patients receiving anti-TNF therapy with and without multiple imputations of missing data based on mixed models for repeated measures. Our results indicate that the relative efficiency of our multiple imputation model is greater than 98% and that the related inference was significant (p-value < 0.001). We established that under both approaches serum TNF levels in RA patients bearing the G/A ­308 TNF promoter genotype displayed a significantly (p-value < 0.0001) increased ability to produce TNF over time than the G/G patient group, as they received successively doses of anti-TNF therapy. <![CDATA[<strong>Simultaneous Single Unit Recording in the Mitral Cell Layer of the Rat Olfactory Bulb under Nasal and Tracheal Breathing </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100003&lng=en&nrm=iso&tlng=en Odor perception depends on the odorant-evoked changes on Mitral/Tufted cell firing pattern within the olfactory bulb (OB). The OB exhibits a significant "ongoing" or spontaneous activity in the absence of sensory stimulation. We characterized this ongoing activity by simultaneously recording several single neurons in the mitral cell layer (MCL) of anesthetized rats and determined the extent of synchrony and oscillations under nasal and tracheal breathing. We recorded 115 neurons and found no significant differences in the mean firing rates between both breathing conditions. Surprisingly, nearly all single units exhibited a long refractory period averaging 14.4 ms during nasal respiration that was not different under tracheal breathing. We found a small incidence (2% of neurons) of gamma band oscillations and a low incidence (8.1%) of correlated firing between adjacent MCL cells. During nasal respiration, a significant oscillation at the respiratory rate was observed in 12% of cells that disappeared during tracheal breathing. Thus, in the absence of odorants, MCL cells exhibit a long refractory period, probably reflecting the intrinsic OB network properties. Furthermore, in the absence of sensory stimulation, MCL cell discharge does not oscillate in the gamma band and the respiratory cycle can modulate the firing of these cells <![CDATA[<strong>New invariants and dimensionless numbers</strong>: <strong>futile renaissance of old fallacies?</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100004&lng=en&nrm=iso&tlng=en The necessity of the mathematical description of living processes and the recent advances in theoretical syntheses that fit surprisingly well with real data have led many scientists to experiment with new "generalizations," beginning with allometric equations. I present here, briefly, why caution is needed when allometric equations are multiplied or divided to make new ones. This practice is flawed by old and recognized problems, such as the fallacy of averages combined with misunderstandings that include error propagation, misuse of statistics and confounding scale. <![CDATA[<strong>Fertility and life expectancy of the predator <i>Supputius</i> <i>cincticeps </i>(Heteroptera: Pentatomidae) exposed to sublethal doses of permethrin </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100005&lng=en&nrm=iso&tlng=en The stinkbug Supputius cincticeps (Stål) (Heteroptera: Pentatomidae) can be found in agricultural and forest ecosystems feeding primarily on larvae of Coleoptera and Lepidoptera, where it can be exposed to insecticide applications. This study therefore aimed to evaluate the reproductive potential of'S. cincticeps after exposition to sublethal doses of permethrin (5.74 x 10-3, 5.74 x 10-2, 5.74 x 10-1, 5.74 and 57.44 ppb) through the use of a fertility life table. The development cycle of this predator was determined in order to calculate its net reproductive rate (R0), the infinitesimal (r m) and finite (λ) rates of increase in addition to mean generation time (T). The net reproductive (18.31), infinitesimal (r m) (0.050) and finite (λ) (1.051) rates of increase were higher, while generation time (57.93 days) was shorter for S. cincticeps exposed to 5.74x10-1 ppb of permethrin than in the control. This indicates a higher rate of population increase of this predator when exposed to this permethrin dose <![CDATA[<strong>A radiographic method to estimate lung volume and its use in small mammals </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100006&lng=en&nrm=iso&tlng=en In this paper we develop a method to estimate lung volume using chest x-rays of small mammals. We applied this method to assess the lung volume of several rodents. We showed that a good estimator of the lung volume is: V*L = 0.496 · V RX ≈ 1/2·V RX , where V RX is a measurement obtained from the x-ray that represents the volume of a rectangular box containing the lungs and mediastinum organs. The proposed formula may be interpreted as the volume of an ellipsoid formed by both lungs joined at their bases. When that relationship was used to estimate lung volume, values similar to those expected from allometric relationship were found in four rodents. In two others, M. musculus and R. norvegicus, lung volume was similar to reported data, although values were lower than expected. <![CDATA[<strong>Two alternative models concerning the perialveolar microcirculation in mammalian lungs </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100007&lng=en&nrm=iso&tlng=en Despite the fact that the concept of sheet-flow in the pulmonary microcirculation of mammals was introduced more than three decades ago, the capillary circulatory model still prevails in the physiological literature. Since cardiac output is identical in the systemic and in pulmonary circulations, it is noteworthy that in the former, the resulting arterial pressure is five times higher than that of the latter, which means that the corresponding microcirculations must be radically different. The present study addresses this problem from both morphological and physiological perspectives. <![CDATA[<strong>Isolation, sequencing and phylogenetic analysis of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 and H3N8 </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100008&lng=en&nrm=iso&tlng=en We report here on the isolation and sequencing of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 (A⁄equi-1⁄Santiago⁄77, Sa77) and H3N8 (A⁄equi-2⁄Santiago⁄85, Sa85) . The sequences obtained allowed a variability analysis, which indicated significant differences when compared with other isolates. We found that Chilean isolates are more similar to the North American variety than to European isolates. Isolate Sa77 is a good candidate for inclusion in a vaccine as it is the latest isolate of the subtype H7N7 and is probably better-adapted to the equine host. Isolate Sa85, of subtype H3N8, also appears to be a good candidate since it has no significant differences in the main antigenic sites with recent isolates. <![CDATA[<strong>Production and immune response of recombinant Hsp60 and Hsp70 from the salmon pathogen <i>Piscirickettsia salmonis</i> </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100009&lng=en&nrm=iso&tlng=en We have isolated and sequenced the genes encoding the heat shock proteins 60 (Hsp60) and 70 (Hsp70) of the salmon pathogen Piscirickettsia salmonis. The sequence analysis revealed the expected two open reading frames that encode proteins with calculated molecular weights of 60,060 and 70,400. The proteins exhibit a 70-80% homology with other known prokaryotic Hsp60 and Hsp70 sequences. The coding regions have been expressed in E. coli as thioredoxin fusion proteins. Both recombinant proteins were shown to elicit a humoral response when injected intraperitoneally in Atlantic salmon and also conferred protection to fish challenged with P. salmonis. The present data will facilitate further studies on the involvement of heat shock proteins in protective immunity of fish to infection by P. salmonis and their potential use in recombinants vaccines against this intracellular pathogen. <![CDATA[<strong>A Rapid and Efficient Method for Purifying High Quality Total RNA from Peaches (<i>Prunus persica</i>) for Functional Genomics Analyses</strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100010&lng=en&nrm=iso&tlng=en Prunus persica has been proposed as a genomic model for deciduous trees and the Rosaceae family. Optimized protocols for RNA isolation are necessary to further advance studies in this model species such that functional genomics analyses may be performed. Here we present an optimized protocol to rapidly and efficiently purify high quality total RNA from peach fruits (Prunus persica). Isolating high-quality RNA from fruit tissue is often difficult due to large quantities of polysaccharides and polyphenolic compounds that accumulate in this tissue and co-purify with the RNA. Here we demonstrate that a modified version of the method used to isolate RNA from pine trees and the woody plant Cinnamomun tenuipilum is ideal for isolating high quality RNA from the fruits of Prunus persica. This RNA may be used for many functional genomic based experiments such as RT-PCR and the construction of large-insert cDNA libraries. <![CDATA[<strong>IP<sub>3</sub> production in the hypersensitive response of lemon seedlings against <i>Alternaria alternata</i> involves active protein tyrosine kinases but not a G-protein </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100011&lng=en&nrm=iso&tlng=en IP3 increase and de novo synthesis of scoparone are produced in the hypersensitive response (HR) of lemon seedlings against the fungus Alternaria alternata. To elucidate whether a G-protein and/or a protein tyrosine kinase (PTK) are involved in signal transduction leading to the production of such a defensive response, we studied the HR in this plant system after treatment with G-protein activators alone and PTK inhibitors in the presence of fungal conidia. No changes in the level of IP3 were detected in response to the treatment with the G-protein activators cholera toxin or mastoparan, although the HR was observed in response to these compounds as determined by the scoparone synthesis. On the contrary, the PTK inhibitors lavendustin A and 2,5-dihidroxy methyl cinnamate (DHMC) not only prevented the IP3 changes observed in response to the fungal inoculation of lemon seedlings but also blocked the development of the HR. These results suggest that the IP3 changes observed in response to A. alternata require a PTK activity and are the result of a G-protein independent Phospholipase C activity, even though the activation of a G-protein can also lead to the development of a HR. Therefore, it appears that more than one signaling pathway may be activated for the development of HR in lemon seedlings: one involving a G-protein and the other involving a PTK-dependent PLC. <![CDATA[<strong>Development of a BALB/c mouse model of <i>Helicobacter pylori </i>infection with fresh and frozen bacteria </strong>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602005000100012&lng=en&nrm=iso&tlng=en An experimental model for H. pylori infection was established by intragastrically challenging BALB/c mice with 1 ml (10(8) CFU/ml) of suspension for two consecutive days. Animals were divided into three groups. GA: mice inoculated with fresh bacteria; GB: mice inoculated with frozen bacteria, and GC: mice inoculated with brucella broth (control group). Animals were killed at 7, 14, 21, 28, 35 and 60 days pi and fragments of stomach and duodenum were collected, paraffin embedded and stained by hematoxylin-eosin and Giemsa. The results showed that challenged mice exhibited mild duodenitis and gastritis. In group GA, infiltration in the duodenum was lymphoplasmacytic until day 35; in group GB, it was lymphomonocytic for 60 days pi. In the stomach, H. pylori induced lymphomonocytic infiltration that was present from days 7 to 60 in group GA. In group GB, it was only present from days 14 to 35. In conclusion, our data suggested that freezing altered pathogenic properties of H. pylori and probably inhibited expression of bacterial antigens and consequently the establishment and maintenance of infection. Although the animals developed mild duodenitis and gastritis, the BALB/c mouse is not susceptible to developing peptic ulcers during H. pylori infection