What can be learnt from analysing insect orientation flights using probabilistic SLAM?

In this paper, we provide an analysis of orientation flights in bumblebees, employing a novel technique based on simultaneous localisation and mapping (SLAM) a probabilistic approach from autonomous robotics. We use SLAM to determine what bumblebees might learn about the locations of objects in the world through the arcing behaviours that are typical of these flights. Our results indicate that while the bees are clearly influenced by the presence of a conspicuous landmark, there is little evidence that they structure their flights to specifically learn about the position of the landmark.     

The use of webcam images to determine tourist–climate aptitude: favourable weather types for sun and beach tourism on the Alicante coast (Spain)

Climate has an obvious influence on tourism as a resource and as a location factor for tourist activities. Consequently, the tourist phenomenon in general is heavily controlled by meteorological conditions—in short, by the climate. In this article, the author proposes a set of weather types with which to establish the climate aptitude for sun and beach tourism. To determine these types, the density of use of one of the beaches with the lowest seasonality in continental Europe, the Levante Beach in Benidorm (Alicante, Spain), was analysed. Beach attendance was monitored using a webcam installed by the “Agencia Valenciana de Turismo”. The relationship between the density of use of the lower and upper beach areas on the one hand, and meteorological variables on the other, allowed comfort (physiological equivalent temperature) and enjoyment (fractions of solar radiation) thresholds to be established. The appropriate hydric comfort values were obtained by comparing the ranges proposed by Besancenot in 1989 [Besancenot (1989) Clima et turismes. Massom, París] with numbers of visitors to the beach. The wind velocity and precipitation thresholds were selected following consultation with the literature and considering the climatic characteristics of the environment under analysis. Based on a combination of these thresholds, weather types suitable for this specific tourist activity are defined. Thus, this article presents a method for assessing the extent to which a day on the beach can be enjoyed. This has a number of applications, for planners, the tourism business and consumers alike. The use of this (filter) method in climate databases and meteorological forecasts could help determine the tourist season, the suitability of setting up a business associated with sun and beach tourism, as well as help plan holidays and program a day’s leisure activities. Thus, the article seeks to improve our understanding of the climate preferences of that tourist activity par excellence: sun and beach tourism.     

Nap1 regulates Dictyostelium cell motility and adhesion through SCAR-dependent and -independent pathways

SCAR--also known as WAVE--is a key regulator of actin dynamics. Activation of SCAR enhances the nucleation of new actin filaments through the Arp2/3 complex, causing a localized increase in the rate of actin polymerization . In vivo, SCAR is held in a large regulatory complex, which includes PIR121 and Nap1 proteins, whose precise role is unclear. It was initially thought to hold SCAR inactive until needed , but recent data suggest that it is essential for SCAR function . Here, we show that disruption of the gene that encodes Nap1 (napA) causes loss of SCAR function. Cells lacking Nap1 are small and rounded, with diminished actin polymerization and small pseudopods. Furthermore, several aspects of the napA phenotype are more severe than those evoked by the absence of SCAR alone. In particular, napA mutants have defects in cell-substrate adhesion and multicellular development. Despite these defects, napA(-) cells move and chemotax surprisingly effectively. Our results show that the members of the complex have unexpectedly diverse biological roles.     

Immune thrombocytopenic purpura associated with hepatitis A

A 23-year-old man developed thrombocytopenic purpura at the end of the second week of the clinical evolution of hepatitis A confirmed by viral markers. The bone marrow of this patient showed megakaryocytic hyperplasia. Circulating in his serum immune complexes were demonstrated by solid phase conglutinin enzymo-immunoassay. Platelet-reactive serum factors were also detected by an indirect immunofluorescence test using fresh donor platelets as targets. The evolution of both the hepatitis and the purpura were benign with no therapy other than bedrest. Platelet count normalized within five weeks of the onset of purpura, and IgM antibodies against hepatitis A virus as well as circulating immune complexes dropped to normal levels. It is postulated that the thrombocytopenia of this case was caused by nonspecific deposition of immune complexes at the platelet surface.     

Localization of the C-terminus of rat glutathione S-transferase A1-1: crystal structure of mutants W21F and W21F/F220Y

Twelve C-terminal residues of human glutathione S-transferase A1-1 form a helix in the presence of glutathione-conjugate, or substrate alone, and partly cover the active site. According to X-ray structures, the helix is disordered in the absence of glutathione, but it is not known if it is helical and delocalized, or in a random-coil conformation. Mutation to a tyrosine of residue 220 within this helix was previously shown to affect the pK(a) of Tyr-9 at the active site, in the apo form of the enzyme, and it was proposed that an on-face hydrogen bond between Tyr-220 and Tyr-9 provided a means for affecting this pK(a). In the current study, X-ray structures of the W21F and of the C-terminal mutation, W21F/F220Y, with glutathione sulfonate bound, show that the C-terminal helix is disordered (or delocalized) in the W21F crystal but is visible and ordered in a novel location, a crystal packing crevice, in one of three monomers in the W21F/F220Y crystal, and the proposed hydrogen bond is not formed. Fluorescence spectroscopy studies using an engineered F222W mutant show that the C-terminus remains delocalized in the absence of glutathione or when only the glutathione binding site is occupied, but is ordered and localized in the presence of substrate or conjugate, consistent with these and previous crystallographic studies. Proteins 2001;42:192-200.     

Multiple Mass Isotopomer Tracing of Acetyl-CoA Metabolism in Langendorff-perfused Rat Hearts: CHANNELING OF ACETYL-CoA FROM PYRUVATE DEHYDROGENASE TO CARNITINE ACETYLTRANSFERASE*

We developed an isotopic technique to assess mitochondrial acetyl-CoA turnover (≈citric acid flux) in perfused rat hearts. Hearts are perfused with buffer containing tracer [¹³C₂,²H₃]acetate, which forms M5 + M4 + M3 acetyl-CoA. The buffer may also contain one or two labeled substrates, which generate M2 acetyl-CoA (e.g. [¹³C₆]glucose or [1,2-¹³C₂]palmitate) or/and M1 acetyl-CoA (e.g. [1-¹³C]octanoate). The total acetyl-CoA turnover and the contributions of fuels to acetyl-CoA are calculated from the uptake of the acetate tracer and the mass isotopomer distribution of acetyl-CoA. The method was applied to measurements of acetyl-CoA turnover under different conditions (glucose ± palmitate ± insulin ± dichloroacetate). The data revealed (i) substrate cycling between glycogen and glucose-6-P and between glucose-6-P and triose phosphates, (ii) the release of small excess acetyl groups as acetylcarnitine and ketone bodies, and (iii) the channeling of mitochondrial acetyl-CoA from pyruvate dehydrogenase to carnitine acetyltransferase. Because of this channeling, the labeling of acetylcarnitine and ketone bodies released by the heart are not proxies of the labeling of mitochondrial acetyl-CoA.     

The relevance of in vitro anthelmintic screening tests employing the free-living stages of trichostrongylid nematodes

The response of the free-living stages of Nippostrongylus brasiliensis, Nematospiroides dubius, Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia ostertagi to a wide variety of antiparasitic agents in vitro was investigated. All the major broad spectrum veterinary anthelmintics showed good activity against each of these worms with EC50 values varying from about 0.0002 mg/l for certain benzimidazoles and ivermectin to about 6.5 mg/l for febantel. Of 22 known narrow spectrum anthelmintics useful only against H. contortus and/or helminths other than trichostrongyles, only 10% showed good activity at concentrations equal to or less than 10.0 mg/l. Further, only one of 15 antiprotozoal agents showed good activity in these tests at the 10.0 mg/l level. The screening test employing free-living Nippostrongylus brasiliensis was selected for an extended trial where the evaluation of 1400 miscellaneous organic chemicals was undertaken. Approximately 10% of these showed activity at concentrations equal to or less than 10.0 mg/l. It is concluded that in vitro screening tests employing the free-living stages of these five genera of nematodes afford simple yet effective means for selecting relevant compounds for further evaluation as possible leads to new broad spectrum anthelmintics for use in ruminants. However, tests using the free-living stages of these worms, including H. contortus, are unsuitable for detecting narrow spectrum 'specifics', e.g., for the treatment of haemonchiasis.     

Comparison of different elution conditions for the immunopurification of recombinant hepatitis B surface antigen

An immunoaffinity chromatographic method was developed using a mAb immunosorbent to purify recombinant hepatitis B surface antigen (r-HBsAg) from yeast. Elution conditions using a mAb-coated ELISA were improved to select the best conditions to purify r-HBsAg. The optimum results in terms of total quantitative recovery were obtained using 20 mM Tris pH 11.6. An increase in the CB.Hep-1 mAb (anti-HBsAg) useful immunosorbents half-life and in its yield per cycle was obtained when alkaline elution conditions were used. Moreover, the basic conditions do not affect either the antigenic characteristics or the purity or the molecular integrity of r-HBsAg.