PslD Is a Secreted Protein Required for Biofilm Formation by Pseudomonas aeruginosa

The function of pslD, which is part of the psl operon from Pseudomonas aeruginosa, was investigated in this study. The psl operon is involved in exopolysaccharide biosynthesis and biofilm formation. An isogenic marker-free pslD deletion mutant of P. aeruginosa PAO1 which was deficient in the formation of differentiated biofilms was generated. Expression of only the pslD gene coding region restored the wild-type phenotype. A C-terminal, hexahistidine tag fusion enabled the identification of PslD. LacZ and PhoA translational fusions with PslD indicated that PslD is a secreted protein required for biofilm formation, presumably via its role in exopolysaccharide export.     

2‐(Undecyloxy)‐ethanol is a major component of the male‐produced aggregation pheromone of Monochamus sutor

The small white‐marmorated longicorn beetle, Monochamus sutor (L.) (Coleoptera: Cerambycidae), is widely distributed throughout Europe and Asia. It is a potential vector of the pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, the causal agent of the devastating pine wilt disease. Volatiles were collected from both male and female beetles after maturation feeding. In analyses of these collections using gas chromatography (GC) coupled to mass spectrometry, a single male‐specific compound was detected and identified as 2‐(undecyloxy)‐ethanol. In analyses by GC coupled to electroantennography the only consistent responses from both female and male antennae were to this compound. Trapping tests were carried out in Spain, Sweden, and China. 2‐(Undecyloxy)‐ethanol was attractive to both male and female M. sutor beetles. A blend of the bark beetle pheromones ipsenol, ipsdienol, and 2‐methyl‐3‐buten‐2‐ol was also attractive to both sexes in Spain and Sweden, and further increased the attractiveness of the 2‐(undecyloxy)‐ethanol. The host plant volatiles α‐pinene, 3‐carene, and ethanol were weakly attractive, if at all, in all three countries and did not significantly increase the attractiveness of the blend of 2‐(undecyloxy)‐ethanol and bark beetle pheromones. 2‐(Undecyloxy)‐ethanol is thus proposed to be the major, if not only, component of the male‐produced aggregation pheromone of M. sutor, and its role is discussed. This compound has been reported as a pheromone of several other Monochamus species and is another example of the parsimony that seems to exist among the pheromones of many of the Cerambycidae. Traps baited with 2‐(undecyloxy)‐ethanol and bark beetle pheromones should be useful for monitoring and control of pine wilt disease, should M. sutor be proven to be a vector of the nematode.     

Functional expression and characterization of the wild-type mammalian renal cortex sodium/phosphate cotransporter and an 215R mutant in Saccharomyces cerevisiae.

The wild-type and an R215E mutant of the rat renal cortex sodium/phosphate cotransporter type 2 (NaPi-2) were functionally expressed in the yeast Saccharomyces cerevisiae strain MB192, a cell line lacking the high-affinity endogenous H+/P(i) cotransporter. The expression of the mRNA molecules and corresponding proteins was confirmed by Northern and Western blot analysis, respectively. As detected by indirect immunofluorescence and antibody capture assay, both wild-type and mutant NaPi-2 proteins are expressed in the yeast plasma membrane in comparable amounts. In the presence of 5 microM phosphate, Na+ promotes phosphate uptake into yeast cells expressing the wild-type NaPi-2 with a K(0.5) of 5.6 +/- 1.1 mM. The maximum uptake of phosphate (649 +/- 30 pmol/10 min) is approximately 8-fold higher than the uptake obtained with nontransformed cells (76.8 +/- 8 pmol/10 min). Yeast cells expressing the R215E mutant of NaPi-2 accumulate 213 +/- 9 pmol of phosphate/10 min under the same conditions. The K(0.5) for the stimulation of phosphate uptake by Na+ is 4.2 +/- 0.8 mM for the R215E mutant and thus not significantly different from the value obtained with cells expressing the wild-type cotransporter. The reduced level of accumulation of phosphate in yeast cells expressing the R215E mutant is probably due to a reduction of the first-order rate constant k for phosphate uptake: while cells expressing wild-type NaPi-2 accumulate phosphate with a k of 0.06 min(-1), the rate for phosphate uptake into cells expressing the R215E mutant (k) is 0.016 min(-1) and therefore about 4-fold lower. In comparison, the rate for phosphate uptake into nontransformed cells (k) is 0.0075 min(-1). Phosphate uptake into yeast cells that express the wild-type NaPi-2 in the presence of 150 mM NaCl is promoted by extracellular phosphate with a K(0.5) of 45 +/- 4 microM. A phosphate-dependent phosphate accumulation is also observed with cells expressing the R215E mutant, but the K(0.5) is twice as high (86 +/- 5 microM) as that obtained with the wild-type cotransporter. We conclude that the yeast expression system is a useful tool for the investigation of structure-function relationships of the renal sodium/phosphate cotransporter and that (215)R, although not involved in Na+ recognition, is a part of the structure involved in phosphate recognition and considerably influences the rate of phosphate uptake by the NaPi-2 cotransporter.     

Resilience of predators to fishing pressure on coral patch reefs

Numbers and biomass of piscivorous fish and their predation on other fish may often be high in undisturbed coral reef communities. The effects of such predation have sometimes been studied by removal of piscivores (either experimentally or by fishermen). Such perturbations have usually involved removal of large, highly vulnerable, mobile piscivores that are often actively sought in fisheries. The effects of fishing on smaller, demersal, semi-resident piscivores have been little studied. We studied such effects on the fish communities of patch reefs at Midway atoll by experimentally removing major resident, demersal, piscivorous fishes. First, four control reefs and four experimental reefs were selected, their dimensions and habitats mapped, and their visible fish communities censused repeatedly over 1 year. Census of all control and experimental reefs was continued for the following 39 months, during which known piscivores were collected repeatedly by hand spearing. Records were kept of catch and effort to calculate CPUE as an index of predator density. Spearfishing on the experimental reefs removed 2504 piscivorous fish from 12 families and 43 taxa (mostly species). The species richness of the catch did not show an overall change over the duration of the experiment. Spearman rank correlation analysis showed some unexpected positive correlations for density in numbers and biomass of major fished piscivorous groups (especially lizardfish) over the experiment. Only two relatively minor fished piscivorous taxa declined in abundance over the experiment, while the overall abundance of piscivores increased. Visual censuses of fish on the experimental reefs also failed to show reduction of total piscivores over the full experimental period. No significant trend in the abundance of lizardfish censused over the full period was apparent on any of the control reefs. The high resilience of piscivores on these experimental reefs to relatively intense fishing pressure could result from their protracted recruitment seasons, high immigration rates, cryptic habits, or naturally high abundances. A major factor was the high immigration rates of lizardfish, replacing lizardfish and other less mobile piscivores removed from the reefs by spearing. On the fished reefs, the removed lizardfish population replaced itself >20 times during the experiment; other piscivorous taxa replaced themselves only 5 times.     

Comparison of the Morphology Development of Polymer–Fullerene and Polymer–Polymer Solar Cells during Solution‐Shearing Blade Coating

In this work, the detailed morphology studies of polymer poly(3‐hexylthiophene‐2,5‐diyl) (P3HT):fullerene(PCBM) and polymer(P3HT):polymer naphthalene diimide thiophene (PNDIT) solar cell are presented to understand the challenge for getting high performance all‐polymer solar cells. The in situ X‐ray scattering and optical interferometry and ex situ hard and soft X‐ray scattering and imaging techniques are used to characterize the bulk heterojunction (BHJ) ink during drying and in dried state. The crystallization of P3HT polymers in P3HT:PCBM bulk heterojunction shows very different behavior compared to that of P3HT:PNDIT BHJ due to different mobilities of P3HT in the donor:acceptor glass. Supplemented by the ex situ grazing incidence X‐ray diffraction and soft X‐ray scattering, PNDIT has a lower tendency to form a mixed phase with P3HT than PCBM, which may be the key to inhibit the donor polymer crystallization process, thus creating preferred small phase separation between the donor and acceptor polymer.     

Understanding the dual nature of CD44 in breast cancer progression

CD44 has been the subject of extensive research for more than 3 decades because of its role in breast cancer, in addition to many physiological processes, but interestingly, conflicting data implicate CD44 in both tumor suppression and tumor promotion. CD44 has been shown to promote protumorigenic signaling and advance the metastatic cascade. On the other hand, CD44 has been shown to suppress growth and metastasis. Histopathological studies of human breast cancer have correlated CD44 expression with both favorable and unfavorable clinical outcomes. In recent years, CD44 has garnered significant attention because of its utility as a stem cell marker and has surfaced as a potential therapeutic target, necessitating a greater understanding of CD44 in breast cancer. In this review, we attempt to unify the literature implicating CD44 in both tumor promotion and suppression, and explain its dualistic nature.     

Analysis for linkage between F13A and three chromosome 6 marker loci: evidence for 6pter: F13A:HLA:GL01:cen gene order

Summary The results of the present study provide independent support for F13A:HLA linkage and refine the F13A: HLA and F13A: GLO1 linkage relationships. Analysis of the corresponding recombination fractions for the total paternal F13A:HLA and F13A:GLO1 peak lod scores() indicates a locus order of 6pter: F13A:HLA:GLO1:cen. Lod scores between F13A and PLG, a locus recently assigned to chromosome 6, exclude close linkage between these loci.     

Changes in certain kinetic properties of hepatic microsomal aniline hydroxylase and ethylmorphine demethylase associated with postnatal development and maturation in male rats

1. Changes in certain kinetic properties (V(max.) and apparent K(m)) of hepatic microsomal mixed-function oxidases have been studied as a function of postnatal development and maturation in male rats. 2. Microsomal cytochrome P-450 content changed only slightly between 1 and 12 weeks of age. 3. Aniline hydroxylase activity (V(max.)) increased abruptly between 1 and 2 weeks of age to greater than adult activities and then returned to a plateau value between 4(1/2) and 12 weeks of age. Ethylmorphine demethylase activity remained low and relatively constant between 1 and 3 weeks of age and then increased markedly ( approximately 100%) between 3 and 4(1/2) weeks. 4. The apparent Michaelis constant (K(m)) for aniline hydroxylation increased almost linearly with time between 1 and 6 weeks of age and tended to reach a plateau value thereafter. The apparent K(m) for ethylmorphine demethylation increased between 1 and 3 weeks of age and then decreased abruptly to a constant value between 6 and 12 weeks. 5. The data indicate that developmental changes in the activity of these microsomal oxidases do not correlate temporally with each other or with changes in microsomal cytochrome P-450 content. 6. The most dramatic changes in enzyme activity were associated with early development (1-3 weeks) and weaning (3-4 weeks). 7. Changes in weight of seminal vesicle, a criterion of sexual maturation in male rats, were most prominent between 6 and 8 weeks of age and thus appeared to be separated in time from the prominent changes in enzyme activity.     

Recruitment of plasma membrane voltage-dependent calcium-permeable channels in carrot cells.

Numerous biological assays and pharmacological studies have led to the suggestion that depolarization-activated plasma membrane Ca2+ channels play prominent roles in signal perception and transduction processes during growth and development of higher plants. The recent application of patch-clamp techniques to isolated carrot protoplasts has led to direct voltage-clamp evidence for the existence of Ca2+ channels activated by physiological depolarizations in the plasma membrane of higher plant cells. However, these voltage-dependent Ca2+ channels were not stable and their activities decreased following the establishment of whole-cell recordings. We show here that large pre-depolarizing pulses positive to 0 mV induced not only the recovery of Ca2+ channel activities, but also the activation of initially quiescent voltage-dependent Ca2+ channels in the plasma membrane (recruitment). This recruitment was dependent on the intensity and duration of membrane depolarizations, i.e. the higher and longer the pre-depolarization, the greater the recruitment. Pre-depolarizing pulses to +118 mV during 30 s increased the initial calcium currents 5- to 10-fold. The recruited channels were permeable to Ba2+ and Sr2+ ions. The data suggested that voltage-dependent Ca(2+)-permeable channels are regulated by biological mechanisms which might be induced by large pre-depolarizations of the plasma membrane. In addition, this study provides evidence for the existence in the plasma membrane of higher plant cells of a large number of voltage-dependent Ca2+ channels of which a major part are inactive and quiescent. It is suggested that quiescent Ca2+ channels can be rapidly recruited for Ca(2+)-dependent signal transduction.     

Effect of Diurnal Temperature Cycles on the Production of Aflatoxin

Exposures to short periods of high temperature (40 to 50 C) in each 24-hr diurnal temperature cycle (average temperature ca. 25 C) reduced growth of Aspergillus parasiticus and production and accumulation of the aflatoxins when compared with cultures held continuously at 25 C. In contrast, diurnal cycles with an average temperature of ca. 25 C but with minima as low as 10 C did not appreciably affect either growth or toxin production. The ratio of production of aflatoxin B to aflatoxin G increased as the maximal temperature was raised but remained essentially unchanged with decreasing minimal temperatures.