A survey of alkaloids in the genera Harpalyce and Brongniartia (Fabaceae—Brongniartieae)

The presence of alkaloids in six species of Brongniartia and three species of Harpalyce is reported. This survey revealed remarkable qualitative differences in the alkaloid profiles of these two genera. B. discolor, B. lupinoides, B. sousae and B. intermedia showed a typical -pyridone pattern, with cytisine, anagyrine and baptifoline as major alkaloids. In leaves of the first three species ormosanine-type alkaloids occurred additionally. B. flava and B. vazquezii are devoid of -pyridones, but accumulate lupanine, hydroxylated lupanines and ester alkaloids. All three species of Harpalyce were similar in accumulating -pyridones, but H. formosa differed from H. brasiliana and H. pringlei in the presence of epilupinine. In general the alkaloid profiles of Brongniartia and Harpalyce show similarities to those of the Australian genera Hovea, Lamprolobium, Plagiocarpus and Templetonia and support therefore the actual concept of the enlarged tribe Brongniartieae.     

Subject: Migration

Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressGeneral Biology: Migration

Subject: Migration     

High Pressure Homogenization of Porcine Pepsin Protease: Effects on Enzyme Activity,Stability, Milk Coagulation Profile and Gel Development

This study investigated the effect of high pressure homogenization (HPH) (up to 190 MPa) on porcine pepsin (proteolytic and milk-clotting activities), and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure). Although the proteolytic activity (PA) was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA) of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G’ value 92% higher after 90 minutes) when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network) and lower porosity (evidenced by confocal microscopy). These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese.     

An oxidative stress-mediated positive-feedback iron uptake loop in neuronal cells

Intracellular reactive iron is a source of free radicals and a possible cause of cell damage. In this study, we analyzed the changes in iron homeostasis generated by iron accumulation in neuroblastoma (N2A) cells and hippocampal neurons. Increasing concentrations of iron in the culture medium elicited increasing amounts of intracellular iron and of the reactive iron pool. The cells had both IRP1 and IRP2 activities, being IRP1 activity quantitatively predominant. When iron in the culture medium increased from 1 to 40 microm, IRP2 activity decreased to nil. In contrast, IRP1 activity decreased when iron increased up to 20 microm, and then, unexpectedly, increased. IRP1 activity at iron concentrations above 20 microm was functional as it correlated with increased (55) Fe uptake. The increase in IRP1 activity was mediated by oxidative-stress as it was largely abolished by N-acetyl-L-cysteine. Culturing cells with iron resulted in proteins and DNA modifications. In summary, iron uptake by N2A cells and hippocampus neurons did not shut off at high iron concentrations in the culture media. As a consequence, iron accumulated and generated oxidative damage. This behavior is probably a consequence of the paradoxical activation of IRP1 at high iron concentrations, a condition that may underlie some processes associated with neuronal degeneration and death.     

Dispersal of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in an urban endemic dengue area in the State of Rio de Janeiro,Brazil

Experimental releases of female Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus were performed in August and September 1999, in an urban area of Nova Igua u, State of Rio de Janeiro, Brazil, to estimate their flight range in a circular area of 1,600 m where 1,472 ovitraps were set. Releases of 3,055 Ae. aegypti and 2,225 Ae. albopictus females, fed with rubidium (Rb)-marked blood and surgically prevented from subsequent blood-feeding, were separated by 11 days. Rb was detected in ovitrap-collected eggs by atomic emission spectrophotometry. Rb-marked eggs of both species were detected up to 800 m from the release point. Eggs of Ae. albopictus were more numerous and more heterogeneously distributed in the area than those of Ae. aegypti. Eggs positively marked for Rb were found at all borders of the study area, suggesting that egg laying also occurred beyond these limits. Results from this study suggest that females can fly at least 800 m in 6 days and, if infected, potentially spread virus rapidly.     

Stem Mortality Following Fire in Kalahari Sand Vegetation: Effects of Frost,Prior Damage,and Tree Neighbourhoods

Fire is a key factor affecting the survivorship and dynamics of woody plants in savannas, but few empirical studies in savanna vegetation have investigated correlates of mortality following fire at the level of individual stems. A study of stem mortality as a function of size, neighbourhood effects, and prior damage (mainly caused by elephants) was undertaken in an area of Kalahari sand vegetation in western Zimbabwe. Stem and whole-plant mortality were quantified for the dominant stems of 557 trees in 4 plots following dry season unplanned fires in 2001. Two plots were located in areas that had been affected by frost earlier in the season, and 2 in areas that had not. Mortality was also recorded for 1762 trees in 20 unburned reference plots, also classified according to the presence of frost damage. Mortality estimators were constructed with a maximum likelihood regression method. Whole-plant mortality was low (on the order of 1–2%) compared with stem mortality, which in burned plots approximated 100% for the smallest size classes and declined as a function of stem diameter. Fire-driven mortality was lower in stems protected by the crowns of larger trees than in stems that were in the open. There was also evidence to suggest that the effects of fire are exacerbated by the prior action of frost and elephant herbivory.     

Benthic community metabolism and trophic conditions of four South American lakes

Oxygen uptake rates of undisturbed sediment columns have been used as an integrative measure of the metabolic activities of benthic communities. Since the intensity of metabolic processes of profundal lake is dependent on the production of organic matter in the pelagic zone, oxygen uptake rates reflect the trophic condition of the whole lake. Four small lakes of central Chile, differing strongly in trophic conditions, provided a possibility to compare benthic oxygen uptake rates, under different oxygen conditions (Quiñenco, Grande, Chica and Lleulleu). Our objective was to establish the relationship between the oxygen uptake rates and bottom characteristics of lakes with different trophic conditions. At 8 mg O₂ l^-1 in the overlying water of the cores studied, the oxygen uptake rates of the sediment were: Quiñenco 51.2–56.0 mg O₂ m² h^-1 (eutrophic), Grande 41.2–46.4 mg O₂ m² h^-1 (mesotrophic), Chica 23.2–18.1 mg O₂ m² h^-1 (mesotrophic) and Lleulleu 11.7–16.0 mg O₂ m² h^-1 (oligotrophic). By exposing the sediments to different oxygen levels in the laboratory, it was found that benthic community metabolism decreased with oxygen concentrations. The slope of regression lines, relating oxygen uptake rates to oxygen concentrations, differed for the different sites investigated, closely related with the trophic conditions of the lakes. It was positively correlated with the organic matter content of the sediment of the cores (r ²= 0.78, p<0,05) and the nutrients of the bottom waters (total-P: r ²= 0.73, p<0,05; total-N: r ²= 0.73, p<0,05), and negatively with the redox potential of the sediments (r ²= 0.88, p<0,05).     

Time-irreversible Subconductance Gating Associated with Ba2+ Block of Large Conductance Ca2+-activated K+ Channels

Ba²⁺ block of large conductance Ca²⁺-activated K⁺ channels was studied in patches of membrane excised from cultures of rat skeletal muscle using the patch clamp technique. Under conditions in which a blocking Ba²⁺ ion would dissociate to the external solution (150 mM N-methyl-d-glucamine⁺ _o, 500 mM K⁺ _i, 10 μM Ba²⁺ _i, +30 mV, and 100 μM Ca²⁺ _i to fully activate the channel), Ba²⁺ blocks with a mean duration of ∼2 s occurred, on average, once every ∼100 ms of channel open time. Of these Ba²⁺ blocks, 78% terminated with a single step in the current to the fully open level and 22% terminated with a transition to a subconductance level at ∼0.26 of the fully open level (preopening) before stepping to the fully open level. Only one apparent preclosing was observed in ∼10,000 Ba²⁺ blocks. Thus, the preopenings represent Ba²⁺-induced time-irreversible subconductance gating. The fraction of Ba²⁺ blocks terminating with a preopening and the duration of preopenings (exponentially distributed, mean = 0.75 ms) appeared independent of changes in [Ba²⁺]_i or membrane potential. The fractional conductance of the preopenings increased from 0.24 at +10 mV to 0.39 at +90 mV. In contrast, the average subconductance level during normal gating in the absence of Ba²⁺ was independent of membrane potential, suggesting different mechanisms for preopenings and normal subconductance levels. Preopenings were also observed with 10 mM Ba²⁺ _o and no added Ba²⁺ _i. Adding K⁺, Rb⁺, or Na⁺ to the external solution decreased the fraction of Ba²⁺ blocks with preopenings, with K⁺ and Rb⁺ being more effective than Na⁺. These results are consistent with models in which the blocking Ba²⁺ ion either induces a preopening gate, and then dissociates to the external solution, or moves to a site located on the external side of the Ba²⁺ blocking site and acts directly as the preopening gate.