A blind circadian clock in cavefish reveals that opsins mediate peripheral clock photoreception

The circadian clock is synchronized with the day-night cycle primarily by light. Fish represent fascinating models for deciphering the light input pathway to the vertebrate clock since fish cell clocks are regulated by direct light exposure. Here we have performed a comparative, functional analysis of the circadian clock involving the zebrafish that is normally exposed to the day-night cycle and a cavefish species that has evolved in perpetual darkness. Our results reveal that the cavefish retains a food-entrainable clock that oscillates with an infradian period. Importantly, however, this clock is not regulated by light. This comparative study pinpoints the two extra-retinal photoreceptors Melanopsin (Opn4m2) and TMT-opsin as essential upstream elements of the peripheral clock light input pathway.     

Randomized trial of time-limited interruptions of protease inhibitor-based antiretroviral therapy (ART) vs. continuous therapy for HIV-1 infection

Background

The clinical outcomes of short interruptions of PI-based ART regimens remains undefined.

Methods

A 2-arm non-inferiority trial was conducted on 53 HIV-1 infected South African participants with viral load <50 copies/ml and CD4 T cell count >450 cells/µl on stavudine (or zidovudine), lamivudine and lopinavir/ritonavir. Subjects were randomized to a) sequential 2, 4 and 8-week ART interruptions or b) continuous ART (cART). Primary analysis was based on the proportion of CD4 count >350 cells(c)/ml over 72 weeks. Adherence, HIV-1 drug resistance, and CD4 count rise over time were analyzed as secondary endpoints.

Results

The proportions of CD4 counts >350 cells/µl were 82.12% for the intermittent arm and 93.73 for the cART arm; the difference of 11.95% was above the defined 10% threshold for non-inferiority (upper limit of 97.5% CI, 24.1%; 2-sided CI: −0.16, 23.1). No clinically significant differences in opportunistic infections, adverse events, adherence or viral resistance were noted; after randomization, long-term CD4 rise was observed only in the cART arm.

Conclusion

We are unable to conclude that short PI-based ART interruptions are non-inferior to cART in retention of immune reconstitution; however, short interruptions did not lead to a greater rate of resistance mutations or adverse events than cART suggesting that this regimen may be more forgiving than NNRTIs if interruptions in therapy occur.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00100646","term_id":"NCT00100646"}}NCT00100646     

Achieving yield gains in wheat

Wheat provides 20% of calories and protein consumed by humans. Recent genetic gains are <1% per annum (p.a.), insufficient to meet future demand. The Wheat Yield Consortium brings expertise in photosynthesis, crop adaptation and genetics to a common breeding platform. Theory suggest radiation use efficiency (RUE) of wheat could be increased ～50%; strategies include modifying specificity, catalytic rate and regulation of Rubisco, up-regulating Calvin cycle enzymes, introducing chloroplast CO(2) concentrating mechanisms, optimizing light and N distribution of canopies while minimizing photoinhibition, and increasing spike photosynthesis. Maximum yield expression will also require dynamic optimization of source: sink so that dry matter partitioning to reproductive structures is not at the cost of the roots, stems and leaves needed to maintain physiological and structural integrity. Crop development should favour spike fertility to maximize harvest index so phenology must be tailored to different photoperiods, and sensitivity to unpredictable weather must be modulated to reduce conservative responses that reduce harvest index. Strategic crossing of complementary physiological traits will be augmented with wide crossing, while genome-wide selection and high throughput phenotyping and genotyping will increase efficiency of progeny screening. To ensure investment in breeding achieves agronomic impact, sustainable crop management must also be promoted through crop improvement networks.     

Circadian timing of injury-induced cell proliferation in zebrafish

In certain vertebrates such as the zebrafish, most tissues and organs including the heart and central nervous system possess the remarkable ability to regenerate following severe injury. Both spatial and temporal control of cell proliferation and differentiation is essential for the successful repair and re-growth of damaged tissues. Here, using the regenerating adult zebrafish caudal fin as a model, we have demonstrated an involvement of the circadian clock in timing cell proliferation following injury. Using a BrdU incorporation assay with a short labeling period, we reveal high amplitude daily rhythms in S-phase in the epidermal cell layer of the fin under normal conditions. Peak numbers of S-phase cells occur at the end of the light period while lowest levels are observed at the end of the dark period. Remarkably, immediately following amputation the basal level of epidermal cell proliferation increases significantly with kinetics, depending upon the time of day when the amputation is performed. In sharp contrast, we failed to detect circadian rhythms of S-phase in the highly proliferative mesenchymal cells of the blastema. Subsequently, during the entire period of outgrowth of the new fin, elevated, cycling levels of epidermal cell proliferation persist. Thus, our results point to a preferential role for the circadian clock in the timing of epidermal cell proliferation in response to injury.     

Systematic Identification of Rhythmic Genes Reveals camk1gb as a New Element in the Circadian Clockwork

A wide variety of biochemical, physiological, and molecular processes are known to have daily rhythms driven by an endogenous circadian clock. While extensive research has greatly improved our understanding of the molecular mechanisms that constitute the circadian clock, the links between this clock and dependent processes have remained elusive. To address this gap in our knowledge, we have used RNA sequencing (RNA–seq) and DNA microarrays to systematically identify clock-controlled genes in the zebrafish pineal gland. In addition to a comprehensive view of the expression pattern of known clock components within this master clock tissue, this approach has revealed novel potential elements of the circadian timing system. We have implicated one rhythmically expressed gene, camk1gb, in connecting the clock with downstream physiology of the pineal gland. Remarkably, knockdown of camk1gb disrupts locomotor activity in the whole larva, even though it is predominantly expressed within the pineal gland. Therefore, it appears that camk1gb plays a role in linking the pineal master clock with the periphery.     

Genetic correlation and path analysis of transpiration efficiency for wheat flag leaves

A 4 × 4 complete diallel cross was set up with four different types of drought-resistant winter wheat varieties to define mutual relations among main quantitative traits and the contribution of each trait to the flag leaf transpiration efficiency (TE) in the grain filling phase. Through genetic correlative and path analysis, the influence of five physiological traits, net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO₂ concentration (Ci), transpiration rate (Tr), and leaf temperature (Tl), on flag leaf TE was observed. The results of variance analysis showed that there were very significant differences between TE and the related five traits, as well as between these five traits. The results of genetic correlation analysis showed also that the absolute values of the correlation coefficients of corresponding traits to TE should be ordered as Pn > Gs > Tl > Tr > Ci in the early grain filling stage, Ci > Tr > Pn > Gs > Tl in the middle grain filling stage, and Pn > Ci > Tl > Tr > Gs in the late grain filling stage, respectively. The results of the combined analysis of genetic correlation and path analysis showed that at the early filling stage, there existed a strong positive genetic correlation between Pn and TE, and at the same time Pn had a direct positive contribution to TE. With the progression of grain filling, the stress of high temperature and drought strengthened and the function of flag leaves weakened, so that at the late grain filling phase Ci, Tr and Tl were strongly negatively correlated with TE and all these traits conferred direct negative contributions to TE. The results of this research showed that the selection of wheat genetic materials with slow-ageing, high-photosynthesis, low-transpiration and low leaf temperature should assist breeding of wheat with more efficient use of water in north western China.     

Molecular genetics of ovarian cancer

This is a review of the approaches that can be used to analyze genetic changes in ovarian cancer. Traditional gene localization methods are discussed, followed by a section on gene identification techniques. Once a putative disease-associated gene has been cloned, mutations have to be identified and analyzed. There are numerous mutation detection methods, and the most common ones are outlined. In the penultimate section, the role of immunohistochemistry as a surrogate method for mutation analysis is considered. Finally, the possible use of functional assays is discussed. At present, it would appear that DNA chip technology for the detection of mutations, and microarray analysis of gene expression, are two important techniques likely to have a significant impact on the genetic analysis of ovarian cancer.     

A NEUROCHEMICAL STUDY OF FIELD CASES OF THE DELAYED SPINAL FORM OF SWAYBACK (ENZOOTICATAXIA) IN LAMBS

Abstract— Spinal cords of 5-8 week-old lambs affected with the delayed or spinal form of swayback were deficient in myelin lipid components such as cholesterol, cerebrosides and phospholipids and contained less water than cords obtained from clinically and histologically unaffected lambs. The rate of synthesis in vitro of cerebrosides containing hydroxy fatty acids was reduced but the fatty acid composition of this and of the "non-hydroxy cerebroside' fractions were quite normal. Isolated myelin was deficient in copper compared with healthy controls and there was a deficiency in one of its basic protein constituents. This suggested an inherent instability of myelin in affected lambs while the presence of some 4 per cent of cholesterol in the esterified form (none normally present) was indicative of degenerative changes. Five out of eight clinically unaffected lambs obtained from the same flocks proved to be sub-clinical cases when the spinal cord was examined histologically and showed some of the neurochemical abnormalities of the overt clinical disease. When affected lambs were kept at the laboratory until 16 weeks old and fed a copper sufficient diet some of the spinal lesions showed signs of regression and there were fewer neurochemical abnormalities. In particular, cholesterol esters could not be detected in the spinal cord lipids.