Photochemical Mechanism of an Atypical Algal Phytochrome

Phytochromes are bilin‐containing photoreceptors that are typically sensitive to the red/far‐red region of the visible spectrum. Recently, phytochromes from certain eukaryotic algae have become attractive targets for optogenetic applications because of their unique ability to respond to multiple wavelengths of light. Herein, a combination of time‐resolved spectroscopy and structural approaches across picosecond to second timescales have been used to map photochemical mechanisms and structural changes in this atypical group of phytochromes. The photochemistry of an orange/far‐red light‐sensitive algal phytochrome from Dolihomastix tenuilepis has been investigated by using a combination of visible, IR and X‐ray scattering probes. The entire photocycle, correlated with accompanying structural changes in the cofactor/protein, are reported. This study identifies a complex photocycle for this atypical phytochrome. It also highlights a need to combine outcomes from a range of biophysical approaches to unravel complex photochemical and macromolecular processes in multi‐domain photoreceptor proteins that are the basis of biological light‐mediated signalling.     

Wear testing of a DJOA finger prosthesis in vitro

Although the market for replacement of diseased metacarpophalangeal (MCP) joints is dominated by single-piece silicone prostheses, several two-piece designs have been implanted. One such is the Digital Joint Operative Arthroplasty (DJOA) which consists of a part-spherical stainless steel metacarpal component which articulates within a matching concave phalangeal component made of ultra high molecular weight polyethylene (UHMWPE). A DJOA MCP prosthesis was tested using a clinically-validated finger simulator while a second DJOA prosthesis acted as a statically-loaded soak-control. Testing ran to 7.1 million cycles of flexion–extension. It was found that the UHMWPE components, both test and control, gained in weight by a similar amount. Therefore apparently there was no wear of the test components. However, the initial and final surface finish values of the test stainless steel metacarpal head were relatively high. Calculations based on this roughness data, plus recent dynamically-loaded soak data, may explain the apparent lack of wear.     

Categorical shape and color coding by pigeons.

Two studies with 32 pigeons assessed the categorical coding of shapes and the existence of a higher-order color category (all colors). Ss were trained on 2 independent tasks (matching-to-sample and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials, 1 of the 2 comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the 2 stimuli from the other task was introduced suggested categorical coding rules. In Exp I, evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Exp II replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Results support the view that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Apoptosis-prone phenotype of human colon carcinoma cells with a high level amplification of the c-myc gene

Although apoptosis can be induced by the enforced expression of exogenously introduced c-myc genes, it is not clear whether overexpression resulting from the amplification of the resident c-myc gene in tumor cells is sufficient to induce apoptosis. We have investigated the relationship between c-myc gene amplification and the propensity of tumor cells to undergo apoptosis, using the SW613-12A1 and SW613-B3 cell lines, which are representatives, respectively, of tumorigenic and non-tumorigenic clones isolated from the SW613-S human colon carcinoma cell line. Tumorigenic clones are characterized by a high level of amplification and expression of the c-myc gene, whereas cells of non-tumorigenic clones have a small number of copies and a lower level of expression of this gene. Analysis of c-myc mRNA level in cells cultured under low serum conditions indicated that the expression of the gene is tightly regulated by serum growth factors in non-tumorigenic B3 cells, whereas it is poorly regulated in tumorigenic 12A1 cells, the level of mRNAs remaining relatively high in serum-starved 12A1 cells. Under these conditions, 12A1 cells showed clear evidence of apoptosis, whereas B3 cells were completely refractory to the induction of apoptosis. Moreover, the study of cell lines derived from non-tumorigenic apoptosis-resistant clones following the introduction by transfection of exogenous c-myc gene copies showed that they have acquired an apoptosisprone phenotype. Altogether, our results strongly suggest that deregulated c-myc expression due to high-level amplification confers an apoptosis-prone phenotype to tumor cells. The possible consequences of these observations for cancer therapy are discussed.     

Weight suppression predicts weight gain over treatment but not treatment completion or outcome in bulimia nervosa.

The authors attempted to replicate previous findings that weight suppression is a significant predictor of treatment completion and treatment outcome (M. L. Butryn, M. R. Lowe, D. L. Safer, & W. S. Agras, 2006) and weight gain over treatment (M. R. Lowe, W. Davis, D. Lucks, R. A. Annunziato, & M. L. Butryn, 2006) among women with bulimic disorders. The authors also examined 2 alternative measures of weight variability. Participants were 132 women with bulimia nervosa treated with cognitive-behavioral therapy. Participants who dropped out of treatment did not have significantly higher levels of weight suppression than did treatment completers. Among those who completed treatment, weight suppression did not significantly predict binge eating and purging at post-treatment. Weight suppression did significantly predict weight change and, in particular, weight gain (≥5 kg) over treatment. Alternative measures of weight variability did not significantly predict treatment completion or treatment outcome, but 1 measure significantly predicted weight gain over treatment. In conclusion, the authors failed to replicate the previous finding that weight suppression predicts treatment compliance and treatment outcome, but they did replicate the finding that weight suppression predicts weight gain over treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation between catastrophizing and depression in chronic pain patients.

The relation between catastrophizing, depression, and pain was examined in 125 chronic pain patients. The Coping Strategies Questionnaire (CSQ) developed by A. K. Rosenstiel and F. J. Keefe (see record 1984-18170-001) assessed patients' use of cognitive and behavioral strategies to cope with chronic pain. A significant association between catastrophizing and depression was found. In order to address questions of measurement redundancy, 6 clinical psychologists rated the degree to which items on the CSQ reflected depressive symptomatology. All items contained in the Catastrophizing subscale were rated by all psychologists as being reflective of symptoms of depression and were removed from the CSQ. When this subscale was excluded, none of the remaining CSQ subscales were significantly related to depression. The discussion addresses the interpretive difficulties that arise from hypothesizing mediating relations between variables that are conceptually and operationally confounded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spectral methods for the Stokes problem in stream-function formulation

We propose and analyse two recent spectral type algorithms to approximate the Stokes problem in a square. The first one is a collocation method in which the only unknown is the stream-function, the second one is a Galerkin method involving numerical integration and using the stream-function and the vorticity as two dependent variables.     

Synaptic plasticity and physiological interactions between dopamine and glutamate in the striatum

All vertebrates develop with a distinct, invariant, left-right (L-R) body asymmetry. Recently, a number of molecules have been shown to be expressed asymmetrically with respect to the L-R axis during early embryogenesis. The temporal expression patterns of these molecules, in combination with embryo manipulation and genetic experiments, indicate that they may represent elements of a conserved pathway governing embryonic handedness.