Dark starvation and chloroplast function

Summary Mature spinach plants were held in the dark for several days. The photochemical activities and the activity of some enzymes related to NADP reduction were follwed in the chloroplasts isolated from leaves after dark starvation. Photosystem-II, measured by reduction of DPIP, remained stable during 6 days of darkening. The decrease of NADP reduction which appeared after 2 days of starvation was found to be due to protein autolysis rather than inactivation of the photosystems. The stability of photosystem-I was demonstrated by reactivation of NADP reduction after addition of purified ferredoxin and ferredoxin-NADP-reductase. After 4 days of starvation the restoration of the NADP reduction required in addition another, low-molecular-weight factor. From the isolation procedure and from its properties this factor is assumed to be identical with FRS. However, even in the presence of FRS only half of the total activity is restored after 7 days. The activity of the NADP-reducing system is restored in vivo when plants kept for 7 days in the dark are again illuminated.Abbreviations NADP nicotinamide-adenine-dinucleotide phosphate - DPIP 2,6-dichlorophenolindophenol - DCMU (3,4-dichlorophenyl)-1,1-dimethylurea - FRS ferredoxin-reducing-substance     

Eicosanoid-mediated increase in glucose and lactate output as well as decrease and redistribution of flow by complement-activated rat serum in perfused rat liver

Rat serum, in which the complement system had been activated by incubation with zymosan, increased the glucose and lactate output, and reduced and redistributed the flow in isolated perfused rat liver clearly more than the control serum. Heat inactivation of the rat serum prior to zymosan incubation abolished this difference. Metabolic and hemodynamic alterations caused by the activated serum were dose dependent. They were almost completely inhibited by the cyclooxygenase inhibitor indomethacin and by the thromboxane antagonist 4-[2-(4-chlorobenzesulfonamide)-ethyl]-benzene-acetic acid (BM 13505), but clearly less efficiently by the 5'-lipoxygenase inhibitor nordihydroguaiaretic acid and the leukotriene antagonist N-(3-[3-(4-acetyl-3-hydroxy-2-propyl-phenoxy)-propoxy]-4-chlorine-6-meth yl- phenyl)-1H-tetrazole-5-carboxamide sodium salt (CGP 35949 B). Control serum and to a much larger extent complement-activated serum, caused an overflow of thromboxane B2 and prostaglandin F2 alpha into the hepatic vein. It is concluded that the activated complement system of rat serum can influence liver metabolism and hemodynamics via release from nonparenchymal liver cells of thromboxane and prostaglandins, the latter of which can in turn act on the parenchymal cells.     

Uptake of the aromatic retinoids Ro 10-9359 (etretinate) and Ro 10-1670 (acitretin), its main metabolite, delivered to cultured human fibroblasts by serum proteins. Lack of evidence for perturbation of LDL catabolism

Etretinate or acitretin are efficiently delivered to cultured human fibroblasts in the presence of low density lipoproteins, high density lipoproteins or human serum albumin. In contrast to acitretin, delivery of etretinate to fibroblasts is more efficiently achieved with human serum albumin than with lipoproteins. The uptake of etretinate and acitretin via low density lipoproteins delivery, does not take place via the low density lipoprotein-receptor endocytotic pathway but mostly through a passive exchange with the plasma membrane. However, in contrast to acitretin, the exchange of etretinate seems to occur alter binding of etretinate-loaded low density lipoproteins to the apolipoprotein B receptors. No differences are observed in binding, internalization and degradation of native, etretinate-loaded low density lipoproteins and acitretin-loaded low density lipoproteins, suggesting that the presence of these retinoids in low density lipoproteins does not alter their processing by the cells. Furthermore, the presence of these retinoids in the cells does not notably affect, under our experimental conditions, the catabolism of native low density lipoproteins.     

Bacteriophage-resistance mechanisms examined by transfection of Lactococcus lactis subsp. lactis 4513-5 mediated by high voltage electroporation

Summary Phage adsorption tests and transfection by electroporation were carried out to decide whether phage-resistance in Lactococcus lactis subsp. lactis strain 4513-5 is based on intracellular or extracellular mechanisms. Using high voltage (12.5 kV/cm) electroporation, untreated phage DNA was introduced into phage-sensitive and phage-resistant cells. Since phages showed low adsorption frequencies on resistant bacteria, resistance is localized in the cell wall preventing phage DNA from entering the cell. This is the only mechanism responsible for the resistance of L. lactis subsp. lactis 4513-5 against its homologous phage P4513-K12 and non-homologous phages P05M-13 and P05M-47, but not against phage P530-7 and phage P530-12. In the case of the latter two phage strains, intracellular resistance mechanisms are involved and discussed.     

Colonization and extinction of land planarians (Platyhelminthes,Tricladida) in a Brazilian Atlantic Forest regrowth remnant

Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two initially most abundant species, which are native to the study site, Notogynaphallia ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed in lab conditions. Júlio Pedroni: Granted by CNPQ–Brazil.     

Methods in clinical hemorheology: the continuous measurement of arterial blood density and blood sound speed in man

Both blood density and sound speed are closely related to total protein concentration in blood and, as a consequence, to rheologically important parameters of blood. Two methods that permit continuous measurement of these properties, the mechanical oscillator technique and the new ultrasonic technique, were used for measuring blood protein concentration over a continuous period of time in a group of hemodialysis patients and in volunteers. It was seen that the concentration of the components of blood varies considerably. This variability is related to transport phenomena within as well as to the flow of masses across the cardiovascular compartment. From the continuous measurement of concentrations during hemodialysis treatment, relative changes in blood volume can be recorded in order to control the fluid balance of the patient. Rapid fluctuations at the macroscopic scale with periods of 5 to 30 seconds are due to heterogeneities at the microscopic scale and to the particular rheological behaviour of the red blood cells at the level of the capillaries and the small blood vessels. The amplitude of rapid oscillations increased up to 1.2% in terms of hematocrit values when there was rhythmic, spontaneous breathing at various frequencies. The measurement of concentrations at an accessible measuring site may be used to investigate the rheology of blood in the human microvasculature.