Pyridostigmine Restores Cardiac Autonomic Balance after Small Myocardial Infarction in Mice

The effect of pyridostigmine (PYR) - an acetylcholinesterase inhibitor - on hemodynamics and cardiac autonomic control, was never studied in conscious myocardial infarcted mice. Telemetry transmitters were implanted into the carotid artery under isoflurane anesthesia. Seven to ten days after recovery from the surgery, basal arterial pressure and heart rate were recorded, while parasympathetic and sympathetic tone (ΔHR) was evaluated by means of methyl atropine and propranolol. After the basal hemodynamic recording the mice were subjected to left coronary artery ligation for producing myocardial infarction (MI), or sham operation, and implantation of minipumps filled with PYR or saline. Separate groups of anesthetized (isoflurane) mice previously (4 weeks) subjected to MI, or sham coronary artery ligation, were submitted to cardiac function examination. The mice exhibited an infarct length of approximately 12%, no change in arterial pressure and increased heart rate only in the 1st week after MI. Vagal tone decreased in the 1^st week, while the sympathetic tone was increased in the 1^st and 4^th week after MI. PYR prevented the increase in heart rate but did not affect the arterial pressure. Moreover, PYR prevented the increase in sympathetic tone throughout the 4 weeks. Concerning the parasympathetic tone, PYR not only impaired its attenuation in the 1^st week, but enhanced it in the 4^th week. MI decreased ejection fraction and increased diastolic and systolic volume. Therefore, the pharmacological increase of peripheral acetylcholine availability by means of PYR prevented tachycardia, increased parasympathetic and decreased sympathetic tone after MI in mice.     

A Fast-Start Pacing Strategy Speeds Pulmonary Oxygen Uptake Kinetics and Improves Supramaximal Running Performance

The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake () kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min) visited the laboratory for a series of tests that were performed until exhaustion: 1) an incremental test; 2) three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3) two to four constant speed tests for the determination of the highest constant speed (HS) that still allowed achieving maximal oxygen uptake; and 4) an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; P = 0.029); subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; P = 0.037). Moreover, the mean response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; P = 0.025). In conclusion, middle-distance running performances with a duration of 2–3 min are improved and response time is faster when a fast-start is adopted.     

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass <Emphasis Type="Italic">(Paspalum Paspalodes</Emphasis>)

We examined the variability of macroinvertebrate assemblage structure, species identities, and functional feeding group composition in relation to stream size, tributary position, and in-stream factors in a boreal watershed in Finland. Our study included three riffle sites in each of three stream sections in each of three stream size classes. Multi-response permutation procedure, indicator value method, and canonical correspondence analysis revealed clear differences in assemblage structure among the stream size classes, with a gradual increase of species richness as the stream size increased. Significant differences in assemblage structure were also found among the tributary river systems. The functional feeding group composition broadly followed the river continuum concept, i.e., headwaters were dominated by shredders, gatherers, or filterers, whereas scrapers increased in relative abundance with stream size. There was, however, considerable variation in the functional feeding group composition both among and within the headwater stream sections. Our findings refer to a strong influence of stream size on macroinvertebrate assemblages, but also factors prevailing at the scale of individual riffles should be considered in biodiversity conservation of lotic ecosystems.     

Regional analysis of litter quality in the central grassland region of North America

Abstract. The central grassland region of North America is characterized by large gradients of temperature and precipitation. These climatic variables are important determinants of the distribution of plant species, and strongly influence plant morphology and tissue chemistry. We analysed regional patterns of plant litter quality as they vary with climate in grassland ecosystems throughout central North America including tall‐grass prairie, mixed grass prairie, shortgrass steppe, and hot desert grasslands. An extensive database from the International Biological Program and the Long‐Term Ecological Research Program allowed us to isolate the effects of climate from those of plant functional types on litter quality. Our analysis of grass species confirms a previously recognized positive correlation between C/N ratios and precipitation. Precipitation exhibited a similar positive relationship with lignin/N and percent lignin. Although there was no significant correlation between temperature and C/N, there was a significant positive relationship between temperature and both percent lignin and lignin/N. Among functional types, C₃ grasses had a slightly lower C/N ratio than C₄ grasses. Tall grass species exhibited higher C/N, lignin/N, and percent lignin than short grass species. This understanding of the regional patterns of litter quality and the factors controlling them provides us with a greater knowledge of the effect that global change and the accompanying feedbacks may have on ecosystem processes.     

Classification and regression tree (CART) model to predict pulmonary tuberculosis in hospitalized patients

ABSTRACT: BACKGROUND: Tuberculosis (TB) remains a public health issue worldwide. The lack of specific clinical symptoms to diagnose TB makes the correct decision to admit patients to respiratory isolation a difficult task for the clinician. Isolation of patients without the disease is common and increases health costs. Decision models for the diagnosis of TB in patients attending hospitals can increase the quality of care and decrease costs, without the risk of hospital transmission. We present a predictive model for predicting pulmonary TB in hospitalized patients in a high prevalence area in order to contribute to a more rational use of isolation rooms without increasing the risk of transmission. METHODS: Cross sectional study of patients admitted to CFFH from March 2003 to December 2004. A classification and regression tree (CART) model was generated and validated. The area under the ROC curve (AUC), sensitivity, specificity, positive and negative predictive values were used to evaluate the performance of model. Validation of the model was performed with a different sample of patients admitted to the same hospital from January to December 2005. RESULTS: We studied 290 patients admitted with clinical suspicion of TB. Diagnosis was confirmed in 26.5% of them. Pulmonary TB was present in 83.7% of the patients with TB (62.3% with positive sputum smear) and HIV/AIDS was present in 56.9% of patients. The validated CART model showed sensitivity, specificity, positive predictive value and negative predictive value of 60.00%, 76.16%, 33.33%, and 90.55%, respectively. The AUC was 79.70%. CONCLUSIONS: The CART model developed for these hospitalized patients with clinical suspicion of TB had fair to good predictive performance for pulmonary TB. The most important variable for prediction of TB diagnosis was chest radiograph results. Prospective validation is still necessary, but our model offer an alternative for decision making in whether to isolate patients with clinical suspicion of TB in tertiary health facilities in countries with limited resources.     

Microscopy images as interactive tools in cell modeling and cell biology education

The advent of genomics, proteomics, and microarray technology has brought much excitement to science, both in teaching and in learning. The public is eager to know about the processes of life. In the present context of the explosive growth of scientific information, a major challenge of modern cell biology is to popularize basic concepts of structures and functions of living cells, to introduce people to the scientific method, to stimulate inquiry, and to analyze and synthesize concepts and paradigms. In this essay we present our experience in mixing science and education in Brazil. For two decades we have developed activities for the science education of teachers and undergraduate students, using microscopy images generated by our work as cell biologists. We describe open-air outreach education activities, games, cell modeling, and other practical and innovative activities presented in public squares and favelas. Especially in developing countries, science education is important, since it may lead to an improvement in quality of life while advancing understanding of traditional scientific ideas. We show that teaching and research can be mutually beneficial rather than competing pursuits in advancing these goals.     

Alkaline-sulfite pretreatment and use of surfactants during enzymatic hydrolysis to enhance ethanol production from sugarcane bagasse

Sugarcane bagasse is a by-product from the sugar and ethanol industry which contains approximately 70 % of its dry mass composed by polysaccharides. To convert these polysaccharides into fuel ethanol it is necessary a pretreatment step to increase the enzymatic digestibility of the recalcitrant raw material. In this work, sugarcane bagasse was pretreated by an alkaline-sulfite chemithermomechanical process for increasing its enzymatic digestibility. Na₂SO₃ and NaOH ratios were fixed at 2:1, and three increasing chemical loads, varying from 4 to 8 % m/m Na₂SO₃, were used to prepare the pretreated materials. The increase in the alkaline-sulfite load decreased the lignin content in the pretreated material up to 35.5 % at the highest chemical load. The pretreated samples presented enhanced glucose yields during enzymatic hydrolysis as a function of the pretreatment severity. The maximum glucose yield (64 %) was observed for the samples pretreated with the highest chemical load. The use of 2.5 g l^?1 Tween 20 in the hydrolysis step further increased the glucose yield to 75 %. Semi-simultaneous hydrolysis and fermentation of the pretreated materials indicated that the ethanol yield was also enhanced as a function of the pretreatment severity. The maximum ethanol yield was 56 ± 2 % for the sample pretreated with the highest chemical load. For the sample pretreated with the lowest chemical load (2 % m/m NaOH and 4 % m/m Na₂SO₃), adding Tween 20 during the hydrolysis process increased the ethanol yield from 25 ± 3 to 39.5 ± 1 %.     

Effects of general,specific and combined warm-up on explosive muscular performance

The purpose of this study was to compare the acute effects of general, specific and combined warm-up (WU) on explosive performance. Healthy male (n = 10) subjects participated in six WU protocols in a crossover randomized study design. Protocols were: passive rest (PR; 15 min of passive rest), running (Run; 5 min of running at 70% of maximum heart rate), stretching (STR; 5 min of static stretching exercise), jumping [Jump; 5 min of jumping exercises – 3x8 countermovement jumps (CMJ) and 3x8 drop jumps from 60 cm (DJ60)], and combined (COM; protocols Run+STR+Jump combined). Immediately before and after each WU, subjects were assessed for explosive concentric-only (i.e. squat jump – SJ), slow stretch-shortening cycle (i.e. CMJ), fast stretch-shortening cycle (i.e. DJ60) and contact time (CT) muscle performance. PR significantly reduced SJ performance (p =0.007). Run increased SJ (p =0.0001) and CMJ (p =0.002). STR increased CMJ (p =0.048). Specific WU (i.e. Jump) increased SJ (p =0.001), CMJ (p =0.028) and DJ60 (p =0.006) performance. COM increased CMJ performance (p =0.006). Jump was superior in SJ performance vs. PR (p =0.001). Jump reduced (p =0.03) CT in DJ60. In conclusion, general, specific and combined WU increase slow stretch-shortening cycle (SSC) muscle performance, but only specific WU increases fast SSC muscle performance. Therefore, to increase fast SSC performance, specific fast SSC muscle actions must be included during the WU.     

Impacts of inter-basin water transfer on the water quality of receiving reservoirs in a tropical semi-arid region

Inter-basin water transfer (IBWT) involves the transport of water from one geographically distinct basin to another to balance the distribution of water resources. Although the socio-economic benefits of implementing these projects are well recognized, little is known about the subsequent effects on the water quality of the receiving systems. We evaluated the effects of an IBWT on the water quality of three receiving reservoirs of an intermittent river in a semi-arid region. We compared the similarity among the reservoirs before and after the IBWT to assess how the reservoirs responded to the introduction of water. Although the last two reservoirs that have received water have become similar in terms of physical and chemical characteristics and algal biomass (chlorophyll-a), the first reservoir has not. The IBWT resulted in an improvement in the water quality of the first reservoir but a decrease in the water quality of the two successive reservoirs, along with a significant increase in algal biomass. Long river sections located upstream that were dry at the time of IBWT probably contributed nutrients to the water as it moved downstream and into the reservoirs. Significant differences in the water quality were observed for different sampling months after the IBWT, but not for different sampling depths. Before the IBWT, the predictor variables for algal biomass were basically transparency and non-algal turbidity, with which it established a positive relationship. After IBWT, however, algal biomass also showed a positive relationship with pH and temperature. We conclude that IBWT affects the water quality of receiving reservoirs and that the responses are reservoir specific. IBWT also increases the complexity of the correlations of physical and chemical variables with algal biomass.