Effects of nicotine on K+ channel currents in vascular smooth muscle cells from rat tail arteries

Intake of nicotine has been related in many cases to acute or chronic hypertension. Using the patch-clamp technique the effect of nicotine on voltage-dependent K+ channel currents in rat tail artery smooth muscle cells was studied. Nicotine at concentrations of 1-100 microM or 0.3-3 mM increased or decreased, respectively, the amplitude of the tetraethylammonium-sensitive K+ currents. Pretreatment of cells with 10 microM dihydro-beta-erythroidine hydrobromide, a nicotinic receptor antagonist, abolished the excitatory effect (n=6), but not the inhibitory effect (n=10), of nicotine on K+ channel currents. The activation of nicotinic receptors with 100 microM 1,1-dimethyl-4-phenylpiperazinium iodide increased K+ channel currents by 27.4+/-3.8% (n=13, P < 0.01). Our results indicate that the excitatory and inhibitory effects of nicotine on K+ channels are respectively mediated by a nicotinic receptor-dependent mechanism and by a direct interaction of nicotine with K+ channels.     

Biodegradation of benzene, toluene, ethylbenzene, and o-xylene by a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in a fibrous-bed bioreactor

A fibrous-bed bioreactor containing the coculture of Pseudomonas putida and P. fluorescens immobilized in a fibrous matrix was developed to degrade benzene (B), toluene (T), ethylbenzene (E), and o-xylene (X) in synthetic waste streams. The kinetics of BTEX biodegradation by immobilized cells adapted in the fibrous-bed bioreactor and free cells grown in serum bottles were studied. In general, the BTEX biodegradation rate increased with increasing substrate concentration and then decreased after reaching a maximum, showing substrate-inhibition kinetics. However, for immobilized cells, the degradation rate was much higher than that of free cells. Compared to free cells, immobilized cells in the bioreactor tolerated higher concentrations (> 1000 mg l-1) of benzene and toluene, and gave at least 16-fold higher degradation rates for benzene, ethylbenzene, and o-xylene, and a 9-fold higher degradation rate for toluene. Complete and simultaneous degradation of BTEX mixture was achieved in the bioreactor under hypoxic conditions. Cells in the bioreactor were relatively insensitive to benzene toxicity; this insensitivity was attributed to adaptation of the cells in the bioreactor. Compared to the original seeding culture, the adapted cells from the fibrous-bed bioreactor had higher specific growth rate, benzene degradation rate, and cell yield when the benzene concentration was higher than 100 mg l-1. Cells in the fibrous bed had a long, slim morphology, which is different from the normal short-rod shape found for suspended cells in solution.     

Tools for Visual and Numerical Data Entry

While developing a two-dimensional sequence stratigraphy simulation to be used by geologists, our research group found tools such as portable graphics libraries and cross-platform compilers useful for supporting the simulation. The resources for developing the interface aspect of our work were inadequate, however. We have created several tools which aided the development of data entry mechanisms for large sets of numerical data. A major concern in designing our tool set was to enable our graphically oriented users to work in a natural manner, while still retaining the ability to achieve the precision required for an accurate simulation. Our Plotter mechanism allows users to view and edit curve data using the mouse on an X Window terminal. The DataSheet we developed provides a means for precise data entry from the keyboard. The Calculator works with ranges of values in the DataSheet to make large-scale changes. Although these tools were designed with a specific purpose in mind, they are more general and could be used for other applications.     

Peroxisome synthesis in the absence of preexisting peroxisomes

Zellweger syndrome and related diseases are caused by defective import of peroxisomal matrix proteins. In all previously reported Zellweger syndrome cell lines the defect could be assigned to the matrix protein import pathway since peroxisome membranes were present, and import of integral peroxisomal membrane proteins was normal. However, we report here a Zellweger syndrome patient (PBD061) with an unusual cellular phenotype, an inability to import peroxisomal membrane proteins. We also identified human PEX16, a novel integral peroxisomal membrane protein, and found that PBD061 had inactivating mutations in the PEX16 gene. Previous studies have suggested that peroxisomes arise from preexisting peroxisomes but we find that expression of PEX16 restores the formation of new peroxisomes in PBD061 cells. Peroxisome synthesis and peroxisomal membrane protein import could be detected within 2-3 h of PEX16 injection and was followed by matrix protein import. These results demonstrate that peroxisomes do not necessarily arise from division of preexisting peroxisomes. We propose that peroxisomes may form by either of two pathways: one that involves PEX11-mediated division of preexisting peroxisomes, and another that involves PEX16-mediated formation of peroxisomes in the absence of preexisting peroxisomes.     

Improved simulated annealing with step width adaptation for Langmuir probe tuning

In a previous investigation, a simulated annealing (SA) method was developed to optimize 14 Fourier terms in a radio-frequency waveform for active compensation of a Langmuir probe system. This approach was shown to find better solutions in less time than skilled human operators. However, variations in fitness indicated that the SA algorithm did not always find the precise global solution, although it came consistently close to it. This variability was caused by the limited number of fitness evaluations available due to time constraints. In this research, the chosen maximum step width has been shown to have a significant effect on the overall performance of the algorithm. A scaling function has been developed to adapt the maximum step width of the SA algorithm, on-line, as a function of the number of elapsed iterations. The modified algorithm has been shown to find fitter solutions with reduced variability in fitness.     

Soliton self-frequency shift effects in photonic crystal fibre

Using a femtosecond Ti:sapphire laser operating at a wavelength of 810nm we have demonstrated infrared generation in photonic crystal fibre at distinct wavelengths which can be attributed to the soliton self-frequency shift effect. The maximum observed shift produced spectra centred at 1260nm and the frequency-shifted light accounted for up to 80% of the fibre output power. We show that the shifts can be explained by the dispersion properties of the fundamental and higher-order waveguide modes of the fibre.     

Variation in the region of the angiotensin-converting enzyme gene influences interindividual differences in blood pressure levels in young white males

BACKGROUND: The renin-angiotensin system regulates blood pressure through its effects on vascular tone, renal hemodynamics, and renal sodium and fluid balance. METHODS AND RESULTS: Using data from a large population-based sample of 1488 siblings having a mean age of 14.8 years and belonging to the youngest generation of 583 randomly ascertained three-generation pedigrees from Rochester, Minn, we carried out variance components-based linkage analyses to evaluate the contribution of variation in four renin-angiotensin system gene regions (angiotensinogen, renin, angiotensin I-converting enzyme, and angiotensin II receptor type 1) to interindividual variation in systolic, diastolic, and mean arterial pressure. We rejected the null hypothesis that allelic variation in the region of the angiotensin-converting enzyme (ACE) gene does not contribute to interindividual blood pressure variability. After conditioning on measured covariates, variation in this region accounted for 0%, 13% (P=0.04), and 16% (P=0.04) of the interindividual variance in systolic, diastolic, and mean arterial pressures, respectively. These estimates were even greater in a subset of subjects with a positive family history of hypertension (0%, 29% [P=0.005], and 32% [P<0.005], respectively). In sex-specific analyses, genetic variation in the region of the ACE gene significantly influenced interindividual blood pressure variation in males (37% for SBP [P=0.03], 38% for DBP [P=0.04], and 53% for MAP [P<0.005]) but not in females. CONCLUSIONS: Although it is possible that variation in a gene near the ACE gene may explain the observed results, knowledge about the physiological involvement of ACE in blood pressure regulation supports the proposition that the ACE gene itself influences blood pressure variability in a sex-specific manner.     

Tryptophan substitutions surrounding the nucleotide in catalytic sites of F1-ATPase

Novel tryptophan substitutions, surrounding the nucleotide bound in catalytic sites, were introduced into Escherichia coli F1-ATPase. The mutant enzymes were purified and studied by fluorescence spectroscopy. One cluster of Trp substitutions, consisting of beta-Trp-404, beta-Trp-410, beta-Asp-158 (lining the adenine-binding pocket), and beta-Trp-153 (close to the alpha/beta-phosphates), showed the same fluorescence responses to MgADP, MgAMPPNP, and MgATP and the same nucleotide binding pattern with MgADP and MgAMPPNP, with one site of higher and two sites of lower affinity. Therefore, in absence of catalytic turnover (and of gamma-subunit rotation), sites 2 and 3 appeared similar in affinity, and the region of the catalytic site sensed by these Trp substitutions did not change conformation with different nucleotides. In contrast, alpha-Trp-291 and beta-Trp-297, both close to the gamma-phosphate, showed very different fluorescence responses to MgADP versus MgAMPPNP, and in these cases the response was due exclusively or predominantly to nucleotide binding at the first, high-affinity catalytic site, thus allowing specific detection of this site. Titration with MgATP showed that the high-affinity site was present under conditions of steady-state, Vmax MgATP hydrolysis.     

Updates in interventional ultrasonography

Interventional ultrasonography, including diagnostic, therapeutic, and intraoperative interventions, is a rapidly developing field in both human and veterinary medicine. Growing expertise and significant improvements in the technology have contributed to the innovation of numerous ultrasound-assisted procedures. Ultrasound-guided biopsy and fine-needle aspiration are now commonly performed. New techniques and the indications for other procedures such as cavity drainage, indwelling catheter placement, and intraoperative procedures are presented.