Studies on the Indochina I/CDC strain of Plasmodium falciparum in Colombian and Bolivian Aotus monkeys and different anophelines

The Indochina I/CDC strain of Plasmodium falciparum was isolated from a physician returning to the United States after working in the refugee camps along the Thailand-Kampuchean border. The strain was established in splenectomized Aotus monkeys from Colombia after being grown in vitro for 50 days. During the first three passages in Colombian monkeys, the parasites were not infective to Bolivian Aotus monkeys. After six intervening passages in Saimiri sciureus monkeys, the parasites produced high parasitemias in both Colombian and Bolivian Aotus, but gametocytes were no longer produced. Mosquito infections were obtained only during the first three passages in the Colombian monkeys. The most susceptible mosquito was Anopheles freeborni, followed by An. dirus, An. stephensi, An. maculatus, An. culicifacies, and, rarely, An. gambiae. Sporozoites were found in the salivary glands of the An. freeborni, An. dirus, An. stephensi, and An. maculatus.     

Conformational change in yeast tRNAAsp

The structure of yeast tRNA^Asp in aqueous solutions has been analyzed in the light of results obtained from Raman spectra recorded at from 5 to 82°C and compared to those of tRNA^Phe. Firm evidence is given of a reversible conformation transition for tRNA^Asp at 20°C. This transition is observed for the first time in the tRNA series. The low-temperature conformation appears to have a more regular ribose–phosphate backbone and a more effective G base-stacking. This conformational change, which occurs essentially in the D loop, could be connected to the existence of two (A and B) crystal forms obtained depending on crystallization conditions. The melting temperatures, which are different for each base stacking in tRNA^Asp, lie in a range of about 70°C, much higher than for tRNA^Phe. This fact is interpreted by a higher ratio of G-C base pairs in tRNA^Asp.     

Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.     

The promoter of filamentation (POF1) protein from <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> is an ATPase involved in the protein quality control process

Background

The gene YCL047C, which has been renamed promoter of filamentation gene (POF1), has recently been described as a cell component involved in yeast filamentous growth. The objective of this work is to understand the molecular and biological function of this gene.

Results

Here, we report that the protein encoded by the POF1 gene, Pof1p, is an ATPase that may be part of the Saccharomyces cerevisiae protein quality control pathway. According to the results, Δpof1 cells showed increased sensitivity to hydrogen peroxide, tert-butyl hydroperoxide, heat shock and protein unfolding agents, such as dithiothreitol and tunicamycin. Besides, the overexpression of POF1 suppressed the sensitivity of Δpct1, a strain that lacks a gene that encodes a phosphocholine cytidylyltransferase, to heat shock. In vitro analysis showed, however, that the purified Pof1p enzyme had no cytidylyltransferase activity but does have ATPase activity, with catalytic efficiency comparable to other ATPases involved in endoplasmic reticulum-associated degradation of proteins (ERAD). Supporting these findings, co-immunoprecipitation experiments showed a physical interaction between Pof1p and Ubc7p (an ubiquitin conjugating enzyme) in vivo.

Conclusions

Taken together, the results strongly suggest that the biological function of Pof1p is related to the regulation of protein degradation.

     

Partitioning of oxygen uptake and cost of surfacing during swimming in the air-breathing catfish Pangasianodon hypophthalmus

Though air-breathing has probably evolved mainly as a response to hypoxia, it may provide an important oxygen supplement when metabolism is elevated, as for example during swimming. Due to the increased travelling distance involved when an air-breathing fish swims to and from the surface, and the increased drag when the surface is breached, it can be proposed that air-breathing results in a rise in the apparent cost of transport. In order to investigate this hypothesis, it is necessary to use a fish that is able to swim equally well with and without access to air. The striped catfish Pangasianodon hypophthalmus has been shown to have a sufficiently high capacity for aquatic oxygen uptake in normoxia, to allow for such a comparison. Here, we measured the partitioning of oxygen uptake ( $ \dot{M}{\text{O}}_{2} $ ) during swimming and recovery, and calculated the apparent cost of transport with and without access to air, under normoxic conditions. Aerial $ \dot{M}{\text{O}}_{2} $ constituted 25–40 % of the total $ \dot{M}{\text{O}}_{2} $ during swimming and less than 15 % during recovery. The net cost of transport was 25 % lower in fish that did not air-breathe compared to fish that did, showing that the cost of surfacing can be substantial. This is the first study to measure partitioning in an air-breathing fish during swimming at velocities close to the critical swimming speed.     

The effect of oxysterols on the interaction of Alzheimer's amyloid beta with model membranes

The interaction of amyloid beta (Aβ) peptide with cell membranes has been shown to be influenced by Aβ conformation, membrane physicochemical properties and lipid composition. However, the effect of cholesterol and its oxidized derivatives, oxysterols, on Aβ-induced neurotoxicity to membranes is not fully understood. We employed here model membranes to investigate the localization of Aβ in membranes and the peptide-induced membrane dynamics in the presence of cholesterol and 7-ketocholesterol (7keto) or 25-hydroxycholesterol (25OH). Our results have indicated that oxysterols rendered membranes more sensitive to Aβ, in contrast to role of cholesterol in inhibiting Aβ/membrane interaction. We have demonstrated that two oxysterols had different impacts owing to distinct positions of the additional oxygen group in their structures. 7keto-containing cell-sized liposomes exhibited a high propensity toward association with Aβ, while 25OH systems were more capable of morphological changes in response to the peptide. Furthermore, we have shown that 42-amino acid Aβ (Aβ-42) pre-fibril species had higher association with membranes, and caused membrane fluctuation faster than 40-residue isoform (Aβ-40). These findings suggest the enhancing effect of oxysterols on interaction of Aβ with membranes and contribute to clarify the harmful impact of cholesterol on Aβ-induced neurotoxicity by means of its oxidation.     

Brominated Diphenyl Ethers Including a New Tribromoiododiphenyl Ether from the Vietnamese Marine Sponge Arenosclera sp. and Their Antibacterial Activities

A new tribromoiododiphenyl ether ( 1 ) and eight known brominated diphenyl ethers ( 2 – 9 ) were isolated from the MeOH extract of the sponge Arenosclera sp. collected in Vietnam, using repeated open column chromatography and preparative thin layer chromatography. The chemical structure of the new compound 1 was determined by analyses of spectroscopic (1D‐ and 2D‐NMR, and MS) data and by comparison of our data with those reported in the literature. Compounds 1 , 3 , and 8 exhibited strong antibacterial activities against the Gram‐positive bacteria Bacillus subtilis and Staphylococcus aureus and the Gram‐negative bacterium Klebsiella pneumoniae with MIC values ranging from 0.8 to 6.3 μm , while compounds 5 and 7 only displayed activities against Gram‐positive bacteria with MIC values from 0.5 to 3.1 μm . Compound 2 showed activities against the four tested bacteria with MIC values ranging from 0.5 to 6.3 μm .