Photosynthetic membrane development in Rhodopseudomonas sphaeroides. Spectral and kinetic characterization of redox components of light-driven electron flow in apparent photosynthetic membrane growth initiation sites

The kinetics of light-driven electron flow and the nature of redox centers at apparent photosynthetic membrane growth initiation sites in Rhodopseudomans sphaeroides were compared to those of intracytoplasmic photosynthetic membranes. In sucrose gradients, these membrane growth sites sediment more slowly than intracytoplasmic membrane-derived chromatophores and form an upper pigmented band. Cytochromes c1, c2, b561, and b566 were demonstrated in the upper fraction by redox potentiometry; c-type cytochromes were also detected electrophoretically. Signals characteristic of light-induced reaction center bacteriochlorophyll triplet and photooxidized reaction center bacteriochlorophyll dimer states were observed by EPR spectroscopy but the Rieske iron-sulfur signal of the ubiquinol-cytochrome c2 oxidoreductase was present at a 3-fold reduced level on a reaction center basis in comparison to chromatophores. Flash-induced absorbance measurements of the upper pigmented fraction demonstrated reaction center primary and secondary semiquinone anion acceptor signals, but cytochrome b561 photoreduction and cytochrome c1/c2 reactions occurred at slow rates. This fraction was enriched approximately 2- and 4-fold in total b- and c-type cytochromes, respectively, per reaction center over chromatophores, but photoreducible b-type cytochrome was lower. Measurements of respiratory activity indicated a 1.6-fold higher level of succinate-cytochrome c oxidoreductase/reaction center than in chromatophores, but the apparent turnover rates in both preparations were low. Overall, the results suggest that complete cycles of rapid, light-driven electron flow do not occur merely by introduction of newly synthesized reaction centers into respiratory membrane, but that subsequent synthesis and assembly of appropriate components of the ubiquinol-cytochrome c2 oxidoreductase is required.     

Classification of cDNA array genes that have a highly significant discriminative power due to their unique distribution in four brain regions

Novel statistical methods were used to distinguish functionally distinct brain regions using their cDNA array gene expression profiles, and it was found that one of four specific factors is often associated with the most regionally discriminative genes. The gene expression profiles for the substantia nigra (SN), striatum (STR), parietal cortex (PC), and posterolateral cortical amygdaloid nucleus (PLCo) brain regions were determined from each brain region. An F-test identified 339 genes of the 1185 array genes as having a P < or = 0.01 and applied a gene ranking and selection method based on Soft Independent Modeling of Class Analogy (SIMCA) to obtain 59 of the most discriminative genes. Their discriminative power was validated in three steps. The most convincing step showed their ability to correctly predict the brain regional classifications for 18 "test" gene expression sets obtained from the four regions. A two-way Hierarchical Cluster Analysis organized the 59 genes in six clusters according to their expression differences in the brain regions. Expression patterns in the SN and STR regions greatly differed from each other and the PC and PLCo. The closer similarity in the gene expression patterns of the PC and PLCo was probably due to their functional similarity. The important factors in determining differences in the regional gene expression profiles in six clusters were (1) regional myelin/oligodendrocyte levels, (2) resident neuron types, (3) neurotransmitter innervation profiles, and (4) Ca++-dependent signaling and second messenger systems.     

Effect of arylformamidase (kynurenine formamidase) gene inactivation in mice on enzymatic activity, kynurenine pathway metabolites and phenotype

The gene coding for arylformamidase (Afmid, also known as kynurenine formamidase) was inactivated in mice through the removal of a shared bidirectional promoter region regulating expression of the Afmid and thymidine kinase (Tk) genes. Afmid/Tk -deficient mice are known to develop sclerosis of glomeruli and to have an abnormal immune system. Afmid-catalyzed hydrolysis of N-formyl-kynurenine is a key step in tryptophan metabolism and biosynthesis of kynurenine-derived products including kynurenic acid, quinolinic acid, nicotinamide, NAD, and NADP. A disruption of these pathways is implicated in neurotoxicity and immunotoxicity. In wild-type (WT) mice, Afmid-specific activity (as measured by formyl-kynurenine hydrolysis) was 2-fold higher in the liver than in the kidney. Formyl-kynurenine hydrolysis was reduced by approximately 50% in mice heterozygous (HZ) for Afmid/Tk and almost completely eliminated in Afmid/Tk knockout (KO) mice. However, there was 13% residual formyl-kynurenine hydrolysis in the kidney of KO mice, suggesting the existence of a formamidase other than Afmid. Liver and kidney levels of nicotinamide plus NAD/NADP remained the same in WT, HZ and KO mice. Plasma concentrations of formyl-kynurenine, kynurenine, and kynurenic acid were elevated in KO mice (but not HZ mice) relative to WT mice, further suggesting that there must be enzymes other than Afmid (possibly in the kidney) capable of metabolizing formyl-kynurenine into kynurenine. Gradual kidney deterioration and subsequent failure in KO mice is consistent with high levels of tissue-specific Afmid expression in the kidney of WT but not KO mice. On this basis, the most significant function of the kynurenine pathway and Afmid in mice may be in eliminating toxic metabolites and to a lesser extent in providing intermediates for other processes.     

Intraspecific variation in an Ediacaran skeletal metazoan: Namacalathus from the Nama Group,Namibia

Namacalathus hermanastes is one of the oldest known skeletal metazoans, found in carbonate settings of the terminal Ediacaran (~550–541 million years ago [Ma]). The palaeoecology of this widespread, goblet‐shaped, benthic organism is poorly constrained yet critical for understanding the dynamics of the earliest metazoan communities. Analysis of in situ assemblages from the Nama Group, Namibia (~548–541 Ma), shows that Namacalathus exhibited size variation in response to differing water depths, hydrodynamic conditions and substrate types. In low‐energy, inner ramp environments, Namacalathus attains the largest average sizes but grew in transient, loosely aggregating, monospecific aggregations attached to microbial mats. In high‐energy mid‐ramp reefs, Namacalathus spatially segregated into different palaeoecological habitats with distinct size distributions. In outer ramp environments, individuals were small and formed patchy, dense, monospecific aggregations attached to thin microbial mats. Asexual budding is common in all settings. We infer that variations in size distribution in Namacalathus reflect differences in habitat heterogeneity and stability, including the longevity of mechanically stable substrates and oxic conditions. In the Nama Group, long‐lived skeletal metazoan communities developed within topographically heterogeneous mid‐ramp reefs, which provided diverse mechanically stable microbial substrates in persistently oxic waters, while inner and outer ramp communities were often ephemeral, developing during fleeting episodes of either oxia and/or substrate stability. We conclude that Namacalathus, which forms a component of these communities in the Nama Group, was a generalist that adapted to various palaeoecological habitats within a heterogeneous ecosystem landscape where favourable conditions persisted, and was also able to opportunistically colonise transiently hospitable environments. These early skeletal metazoans colonised previously unoccupied substrates in thrombolitic reefs and other microbial carbonate settings, and while they experienced relatively low levels of interspecific competition, they were nonetheless adapted to the diverse environments and highly dynamic redox conditions present in the terminal Ediacaran.     

Sleep Extension Normalizes ERP of Waking Auditory Sensory Gating in Healthy Habitually Short Sleeping Individuals

Chronic sleep loss has been associated with increased daytime sleepiness, as well as impairments in memory and attentional processes. In the present study, we evaluated the neuronal changes of a pre-attentive process of wake auditory sensory gating, measured by brain event-related potential (ERP) – P50 in eight normal sleepers (NS) (habitual total sleep time (TST) 7 h 32 m) vs. eight chronic short sleeping individuals (SS) (habitual TST ≤6 h). To evaluate the effect of sleep extension on sensory gating, the extended sleep condition was performed in chronic short sleeping individuals. Thus, one week of time in bed (6 h 11 m) corresponding to habitual short sleep (hSS), and one week of extended time (∼ 8 h 25 m) in bed corresponding to extended sleep (eSS), were counterbalanced in the SS group. The gating ERP assessment was performed on the last day after each sleep condition week (normal sleep and habitual short and extended sleep), and was separated by one week with habitual total sleep time and monitored by a sleep diary. We found that amplitude of gating was lower in SS group compared to that in NS group (0.3 µV vs. 1.2 µV, at Cz electrode respectively). The results of the group × laterality interaction showed that the reduction of gating amplitude in the SS group was due to lower amplitude over the left hemisphere and central-midline sites relative to that in the NS group. After sleep extension the amplitude of gating increased in chronic short sleeping individuals relative to their habitual short sleep condition. The sleep condition × frontality interaction analysis confirmed that sleep extension significantly increased the amplitude of gating over frontal and central brain areas compared to parietal brain areas.     

Young Bighorn (Ovis canadensis) Males: can they Successfully Woo Females?

Mating by young males or low male‐to‐female ratios can decrease pregnancy rates and postpone birthdates in ungulates, thereby hindering population growth. Young (2.5–3.5 yr old) male bighorn (Ovis canadensis) behave differently than older males, and age, horn size, mating behavior, and social rank help determine reproductive success. We estimated birthdates in two populations of bighorn sheep in Utah, USA, to determine if mating by young males or low male‐to‐female ratios resulted in fewer young born per female, a shift in mean timing of births, or asynchronous births. When reintroduced, the Rock Canyon population consisted of four males (two each of 2.5 yr old and 1.5 yr old) and a 1 to 7.5 ratio of males (>2 yr old) to adult females (≥3.5 yr old); the Mount Nebo population consisted of four males ≤1.5 yr old and a 0 to 12 ratio of males to adult females. For both populations, the number of young born per female did not differ between the first parturition period after reintroduction (where females were impregnated by males from their source populations) and the second period of parturition (where females were impregnated by young, reintroduced males). Mean birthdates and synchrony (SD) of births did not differ for Rock Canyon (May 12, 2001 ± 4.5 d, May 14, 2002 ± 3.2 d) or Mount Nebo (May 23, 2005 ± 8.1 d, May 22, 2006 ± 10.2 d) between the first and second years following reintroduction. Mating by young males or low male‐to‐female ratios had no demonstrable effect on the number of young born per female or timing and synchrony of births in these populations.     

Solubilisation of ferricytochrome c in methanol using a crown ether: absorption, circular dichroism and EPR spectral properties

Ferricytochrome c is normally insoluble in methanol, but its solution is facilitated by complexation with 18-crown-6. Absorption, circular dichroism and EPR spectroscopy indicate that the solubilised protein in MeOH exists in at least three conformational states, all different from the native state in neutral aqueous solution. In two states the haem iron (III) is low spin and in one state it is high spin, but it seems likely that all three forms are globular. The proportion in the high spin form increases at increasing crown ether concentration and on ageing the protein solution. The protein appears to return to its native conformation when it is restored to an aqueous environment.