Abiotic factors drives floristic variations of fern's metacommunity in an Atlantic Forest remnant / Fatores abióticos regulam as variações florísticas na metacomunidade de samambaias em um remanescente de Floresta Atlântica

Abstract We analyzed floristic variations in fern's metacommunity at the local scale and their relationship with abiotic factors in an Atlantic Forest remnant of northeastern Brazil. Floristic and environmental variations were accessed on ten plots of 10 × 20 m. We performed cluster analyses, based on Bray-Curtis dissimilarity index to establish the floristic relationship. The influence of abiotic factors: luminosity, temperature, relative air humidity and relative soil moisture was evaluated from a redundancy analysis. We found 24 species belonging to 20 genera and 12 families. The fern's flora showed high floristic heterogeneity (>75% for most of the plot's associations). The fern's metacommunity was structured along an abiotic gradient modulated by temperature, luminosity, and relative soil moisture.

Resumo Analisamos as variações florísticas na metacomunidade de samambaias em escala local e sua relação com fatores abióticos em um remanescente de Floresta Atlântica no Nordeste do Brasil. Variações florísticas e ambientais foram acessadas a partir de dez parcelas de 10 × 20 m. Realizamos análises de cluster, baseado no índice de similaridade de Bray-Curtis para estabelecer relações florísticas. A influência de fatores abióticos: luminosidade, temperatura, umidade relativa do ar e umidade relativa do solo foram avaliadas a partir da análise de redundância. Encontramos 24 espécies pertencentes a 20 gêneros e 12 famílias. A flora de samambaias exibiu uma elevada heterogeneidade florística (>75% para a maioria das associações entre plots). Observou-se que a metacomunidade de samambaias estava estruturada ao longo de um gradiente abiótico modulado pela temperatura, luminosidade e umidade relativa do solo.

Abiotic factors drives floristic variations of fern's metacommunity in an Atlantic Forest remnant.

We analyzed floristic variations in fern's metacommunity at the local scale and their relationship with abiotic factors in an Atlantic Forest remnant of northeastern Brazil. Floristic and environmental variations were accessed on ten plots of 10 × 20 m. We performed cluster analyses, based on Bray-Curtis dissimilarity index to establish the floristic relationship. The influence of abiotic factors: luminosity, temperature, relative air humidity and relative soil moisture was evaluated from a redundancy analysis. We found 24 species belonging to 20 genera and 12 families. The fern's flora showed high floristic heterogeneity (>75% for most of the plot's associations). The fern's metacommunity was structured along an abiotic gradient modulated by temperature, luminosity, and relative soil moisture.

Edge effects on fern community in an Atlantic Forest remnant of Rio Formoso, PE, Brazil.

We have investigated how edge effects influence the fern community of Jaguarão Forest (08º 35' 49" S and 35º 15' 39" W), located in the district of Rio Formoso, Pernambuco, Brazil. A comparative analysis was made of the interior and edge of the fragment of forest, regarding the richness, abundance and diversity of ferns in the two areas. Six plots of 10 × 20 m were chosen, three in each area. A total of 381 ferns were recorded, which were distributed among 25 species, 17 genera and 12 families. The two areas (edge and interior) were found to differ, with distinct relative air humidities and temperatures (p = 0.00254 and p = 0.00019, respectively). The interior showed higher diversity (t = 7.251 and p = 0.018) and richness (t = 6.379 and p = 0.023) than the edge area, but the same abundance (t = 1.728; p = 0.226) as the edge. Regarding the composition of the flora, it was clear that the interior is a habitat completely distinct from the edge with regard to the fern community, given that only one species, Adiantum petiolatum Desv., was common to both environments. It was concluded that the edge effect causes a decrease in richness and abundance of the fern species found in Jaguarão Forest, where the more sensitive species are being replaced by species that are tolerant to the disturbance caused by the creation of an edge.

Kinetic disposition of (+)-S- and (-)-R-sotalol enantiomers in cardiac patients with tachyarrhythmias using an improved HPLC-fluorescence stereoselective method.

Since the enantioselective pharmacokinetic profiles of R,S-sotalol in cardiac patients are controversial, the present investigation aimed to study the kinetic disposition of sotalol enantiomers in patients with tachycardia. Thirteen cardiac patients, who gave their written consent, were included (6F/7M; 53 +/- 12 yrs, 66 +/- 13 kg, 163 +/- 8 cm height). They had tachycardia, normal renal function and had been chronically treated with tablets of sotalol 160 mg b.i.d. The patients were submitted to blood samples collection at zero, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10 and 12 h after drug administration. The quantitation of sotalol enantiomers were performed by a stereoselective HPLC method with fluorescence detection previously published. A one open compartment model was applied and the main pharmacokinetic parameters obtained for R-/S-sotalol were, respectively (Mean +/- SD): CSSMAX = 1007 +/- 307/1040 +/- 340 ng/mL; TMAX = 1.82 +/- 0.6/1.83 +/- 0.6 h; AUCSST = 6959 +/- 2153/7388 +/- 2563 ng.h/mL; CISSr/F = 2.7 +/- 1.2/2.5 +/- 1.2 mL/min/kg and VdSS/F = 1.9 +/- 0.9/2.0 +/- 1.0 L/kg. The pharmacokinetic parameters of R,S-sotalol were within the published range and the kinetic parameters for the isomers were grouped as two independent samples and statistically compared. In conclusion, stereoselective pharmacokinetic for sotalol was not observed in cardiac arrhythmic patients, i.e., both R- and S-sotalol enantiomers have the same pharmacokinetic profile.

An improved HPLC-fluorescence stereoselective method for analysis of (+)-S- and (-)-R-sotalol enantiomers in plasma sample.

A simplified high performance chromatographic method (HPLC) was performed for sotalol enantiomers in plasma samples for purposes of investigation of the kinetic disposition of racemic sotalol in cardiac arrhythmic patients under multiple dose and multidrug therapy regimens. After addition of NaCl:Na2CO3 (4:1) and plasma protein precipitation by acetonitrile:methanol mixture (1:1) the supernatant was evaporated. The residue containing sotalol racemate was submitted to derivatization reaction with (-)-menthylcloroformate to R(-)- and S(+)-sotalol diastereoisomers. The diastereoisomers were resolved in HPLC, by a C18 column with fluorescent detection under lexcitation = 235 nm and lemission = 310 nm. The retention times for R- and S-sotalol were 20 and 22 minutes while that of internal standard S(-)-atenolol, was 17 minutes. The detection limit for each enantiomer was 12.5 ng/mL and intra-day/inter-day coefficients of variation were less than 10% for each enantiomer within a concentration range of 200 and 2000 ng/mL. The method was appropriate for the objective proposed.

Electrophysiological effects of somatostatin at the supraventricular level of isolated guinea pig hearts.

1. The objective of the present study was to evaluate the electrophysiological effects of the peptide somatostatin (SST) at the supraventricular level in isolated guinea pig hearts. 2. ECG recording from isolated hearts perfused by the Langendorff method indicated that 1.0 microM SST induced a decrease in heart rate from 174 +/- 15 to 157 +/- 9 bpm (N = 6, P < 0.05), blocked AV conduction (the PR interval increased from 92 +/- 11 ms to 106 +/- 5 ms, N = 5, P < 0.05) and increased the QTc interval from 210 +/- 0 to 232 +/- 4 ms (N = 5, P < 0.05). The supraventricular effects of SST, particularly upon the AV conduction, were potentiated by a reduction in calcium concentration from 2.5 to 0.5 mM in the perfusing solution. Thus, 1.0 microM SST induced 2nd degree AV conduction block progressing to AV dissociation in 75% of the hearts in the low calcium medium instead of the first degree conduction block observed in all hearts in normal calcium medium. 3. His bundle electrogram evidenced a complete A-H dissociation without significant change in the H-V interval and microelectrode studies showed a complete abolition of the AV node action potential in the presence of 1.0 microM SST. Both results demonstrate that the site of AV conduction block induced by SST is at the AV node. 4. All the supraventricular effects of SST were transitory, subsiding within about 10 min of hormone exposition, showing desensitization. 5. The effects of somatostatin here described were not blocked by 10 microM atropine, indicating that they are not mediated by muscarinic receptors. 6. These data provide a direct electrophysiological demonstration of the supraventricular effects of SST, and suggest that this peptide decreases calcium influx during the action potential.

Electrophysiological effects of somatostatin at the supraventricular level of isolated guinea pig hearts

The objective of the present study was to evaluate the electrophysiological effects of the peptide somatostatin (SST) at the supraventricular level in isolated guinea hearts. ECG recording from isolated hearts perfused by the Langendorff method i9ndicating that 1.0 uM SST induced a decrease in heart rate from 174 ñ 15 to 157 ñ 9 bpm (N=6, P<0.05), blocked AV conductio9n (the PR interval increased from 92 ñ 11 ms to 106 ñ 5 ms, N+5, P<0.05) and increased the QTc interval from 210 ñ 0 to 232 ñ 4 ms (N+5, P<0.05). The supraventricular effect of SST, particulary upon the AV conduction , were potentiated by a reduction in calcium concentration from 2.5 to 0.5 mM in the perfusing solution. Thus, 1.0 uM SST induced 2nd degree AV conduction block progressing to AV dissociation in 75% of thye hearts in the low calcium medium instead of the first degree conduction block observed in all hearts in normal calcium medium. His bundle electrogram evidence a complete A-H dissociation withouth significant change in the H-V interval and microelectrode studies showed a complete abolition of the AV node action potential in the presence of 1.0 uM SST. Both results demonstrate that the site of AV conduction block induced by SST is at the AV node. All the supraventricular effects of SST were transitory, subsiding within abouth 10 min of hormone exposition, showing desensitization. The effects of somatostatin here described were not blocked by 10 uM atropine, indicating that they are not mediated by muscarinic receptors. These data provide a direct electrophysiological demonstration of the supraventricular effects of SST, and suggest that this peptide decreases calcium influx during the action potential