Differences in cerebral activation during perception of optokinetic computer stimuli and video clips of living animals: an fMRI study.

Aims: There is behavioral evidence of increased spontaneous recruitment of visual attention to ancestral evolved categories, such as animals, compared with expertise-derived categories, such as a computer. In order to investigate the association between visual perception and spontaneous visual attention, a study was performed to determine if brain activation whilst viewing moving animals was increased compared with optokinetic computer stimuli.

Methods: Functional MRI was performed in 12 healthy volunteers using a standard block-design paradigm, consisting of three consecutive experiments.

Cycle and gender-specific cerebral activation during a verb generation task using fMRI: comparison of women in different cycle phases, under oral contraception, and men.

Recent observations have revealed some evidence of the influence of sex and menstrual cycle on cognitive functions. In order to examine further differences depending on different phases of menstrual cycle, the use of oral contraception, and gender, fMRI during verb generation tests was performed in 12 female volunteers at menstrual phase and at luteal phase, 12 female volunteers under oral contraception, and in 12 men. Females under oral contraception compared to females in the menstrual or luteal phase revealed superior activation during verb generation in the right hemisphere; compared to menstrual phase in the superior temporal and in the luteal phase in the inferior frontal cortex.

Clinical characteristics of patients with late-onset multiple sclerosis.

We evaluated clinical presentation, cerebrospinal fluid (CSF), and magnetic resonance imaging (MRI) in patients with late-onset multiple sclerosis (LOMS). Fifty-two patients with definitive multiple sclerosis (MS) diagnosed after the age of 50 years were identified between 1991 and 2002. Data pertaining to clinical characteristics, CSF analysis, and cerebral and spinal MRI were compared with those of 52 young-onset MS (YOMS) patients matched for sex and disease duration.

Kinetic modeling of the photosynthetic electron transport chain.

A simulation model of the photosynthetic electron transport chain operating under steady state conditions is presented. The model enables the calculation of (1) the rates of electron transport and transmembrane proton translocation, (2) the proton/electron stoichiometry, (3) the number of electrons stored in the different redox centers and (4) the stationary transmembrane pH difference. Light intensity and proton permeability of the thylakoid membrane are varied in order to compare the predictions of the model with experimental data.

Kinetic modeling of rotary CF0F1-ATP synthase: storage of elastic energy during energy transduction.

F0F1-ATP synthase uses proton-motive force to produce ATP from ADP and Pi. With regard to its rotary mechanics, this energy transducing molecular machine assumes a unique position among all enzymes. In the work presented here we put forward a detailed functional model which is based on experimental results obtained with ATP synthase from spinach chloroplasts.

Proton to electron stoichiometry in electron transport of spinach thylakoids.

According to the concept of the Q-cycle, the H+/e- ratio of the electron transport chain of thylakoids can be raised from 2 to 3 by means of the rereduction of plastoquinone across the cytochrome b6f complex. In order to investigate the H+/e- ratio we compared stationary rates of electron transport and proton translocation in spinach thylakoids both in the presence of the artificial electron acceptor ferricyanide and in the presence of the natural acceptor system ferredoxin+NADP. The results may be summarised as follows: (1) a variability of the H+/e- ratio occurs with either acceptor.

Kinetic modelling of the proton translocating CF0CF1-ATP synthase from spinach.

The rate of both ATP synthase and hydrolysis catalysed by the thiol-modulated and activated ATP synthase from spinach is measured as a function of all substrates including the protons inside the thylakoid lumen. The most important findings are: (1) sigmoid kinetics with respect to H+in, (2) hyperbolic kinetics with respect to ADP, ATP and phosphate, with Km for phosphate and ADP decreasing upon increasing H+in, (3) binding of ADP and phosphate in random order and competitive to ATP. Simulation of the complete set of experimental data is obtained by a kinetic model featuring Boyer's binding-chain mechanism.

The H+/ATP coupling ratio of the ATP synthase from thiol-modulated chloroplasts and two cyanobacterial strains is four.

In this paper the authors emphasise that the proton translocating ATP synthase from thiol-modulated chloroplasts and two cyanobacterial strains has a coupling ratio of 4 protons per ATP synthesised or hydrolysed. This ratio is determined by several thermodynamic studies at equilibrium between phosphate potential (Delta Gp) and proton gradient (Delta(mu)H+), and is confirmed by measurement of proton flux during ATP hydrolysis. Ratios lower than 4 H+/ATP that have been published in the past have predominantly been determined with the oxidised chloroplast enzyme.

Kinetics and energetics of redox regulation of ATP synthase from chloroplasts.

The rate of ATP hydrolysis catalyzed by the membrane-bound CF0F1 ATP synthase from chloroplasts served as a probe for the determination of the reduction grade of the enzyme treated with dithiothreitol (DTT) or thioredoxin. Rate constants for reduction were obtained. It turns out that reduction by thioredoxin is about a factor of 6,000 more effective than DTT reduction.

Activation of the H(+)-ATP synthase in the photosynthetic bacterium Rhodobacter capsulatus.

The regulation of the membrane-bound H(+)-ATPase from the photosynthetic bacterium Rhodobacter capsulatus was investigated. In the presence of uncouplers the rate of ATP hydrolysis was about 40 mM ATP/M bacteriochlorophyll (Bchl)/s. Without uncouplers this rate increased and if, additionally, the chromatophores were illuminated, it was almost doubled.