Differentiation between vergence and saccadic functional activity within the human frontal eye fields and midbrain revealed through fMRI

Purpose

Eye movement research has traditionally studied solely saccade and/or vergence eye movements by isolating these systems within a laboratory setting. While the neural correlates of saccadic eye movements are established, few studies have quantified the functional activity of vergence eye movements using fMRI. This study mapped the neural substrates of vergence eye movements and compared them to saccades to elucidate the spatial commonality and differentiation between these systems.

Methodology

The stimulus was presented in a block design where the ‘off’ stimulus was a sustained fixation and the ‘on’ stimulus was random vergence or saccadic eye movements. Data were collected with a 3T scanner. A general linear model (GLM) was used in conjunction with cluster size to determine significantly active regions. A paired t-test of the GLM beta weight coefficients was computed between the saccade and vergence functional activities to test the hypothesis that vergence and saccadic stimulation would have spatial differentiation in addition to shared neural substrates.

Results

Segregated functional activation was observed within the frontal eye fields where a portion of the functional activity from the vergence task was located anterior to the saccadic functional activity (z>2.3; p<0.03). An area within the midbrain was significantly correlated with the experimental design for the vergence but not the saccade data set. Similar functional activation was observed within the following regions of interest: the supplementary eye field, dorsolateral prefrontal cortex, ventral lateral prefrontal cortex, lateral intraparietal area, cuneus, precuneus, anterior and posterior cingulates, and cerebellar vermis. The functional activity from these regions was not different between the vergence and saccade data sets assessed by analyzing the beta weights of the paired t-test (p>0.2).

Conclusion

Functional MRI can elucidate the differences between the vergence and saccade neural substrates within the frontal eye fields and midbrain.     

Role of sedoheptulose-1,7 bisphosphatase in low light tolerance of rice (Oryza sativa L.)

Rice grain yield is drastically reduced under low light especially in kharif (wet) season due to cloudy weather during most part of crop growth. Therefore, 50–60% of yield penalty was observed. To overcome this problem, identification of low light tolerant rice genotypes with a high buffering capacity trait such as photosynthetic rate has to be developed. Sedoheptulose-1,7 bisphosphatase, a light-regulated enzyme, plays pivotal role in the Calvin cycle by regenerating the substrate (RuBP) for RuBisCo and therefore, indirectly regulates the influx of CO₂ for this crucial process. We found a potential role of SBPase expression and activity in low light tolerant and susceptible rice genotypes by analyzing its influence on net photosynthetic rate and biomass. We observed a significant relationship of yield with photosynthesis, SBPase expression and activity especially under low light conditions. Two tolerant and two susceptible rice genotypes were used for the present study. Tolerant genotypes exhibited significant but least reduction compared to susceptible genotypes in the expression and activity of SBPase, which was also manifested in its photosynthetic rate and finally in the grain yield under low light. However, susceptible genotypes showed significant reduction in SBPase activity along with photosynthesis and grain yield suggesting that tracking the expression and activity of SBPase could form a simple and reliable method to identify the low light tolerant rice cultivars. The data were analyzed using the Indostat 7.5, Tukey–Kramer method through Microsoft Excel 2019 and PAST4.0 software. The significant association of SBPase activity with the grain yield, net assimilation rate, electron transfer rate, biomass and grain weight were observed under low light stress. These traits should be considered while selecting and breeding for low light tolerant cultivars. Thus, SBPase plays a major role in the low light tolerance mechanism in rice.Electronic supplementary materialThe online version of this article (10.1007/s12298-020-00905-z) contains supplementary material, which is available to authorized users.     

Proteomic changes at 8 weeks after infection are associated with chronic liver pathology in experimental schistosomiasis

Chronic Schistosoma mansoni infection can present as a moderate or severe disease, termed intestinal or hepatosplenic schistosomiasis, respectively. Similarly, either moderate splenomegaly or hypersplenomegaly syndrome develops in CBA/J mice by 20 weeks of infection and is similar to intestinal or hepatosplenic schistosomiasis respectively. Using this mouse model and two-dimensional differential in gel electrophoresis, the liver proteomic signatures of uninfected mice and mice infected for 6, 8, 12, or 20 weeks were compared, and significant protein spots identified using mass spectrometry. We found the greatest number of changes at 12 weeks suggesting that this period represents the peak time of change. Pathway analysis identified specific proteins and pathways that correlated to the pathological changes indicative of severe disease, and these pathways were involved as early as 8 weeks after infection. These findings provide insight into the development of severe liver pathology in schistosomiasis and may aid in developing biomarkers for hepatosplenic schistosomiasis.     

Chronic cigarette smoke causes oxidative damage and apoptosis to retinal pigmented epithelial cells in mice

The purpose of this study was to determine whether mice exposed to chronic cigarette smoke develop features of early age-related macular degeneration (AMD). Two month old C57Bl6 mice were exposed to either filtered air or cigarette smoke in a smoking chamber for 5 h/day, 5 days/week for 6 months. Eyes were fixed in 2.5% glutaraldehyde/2% paraformaldehyde and examined for ultrastructural changes by transmission electron microscopy. The contralateral eye was fixed in 2% paraformaldehyde and examined for oxidative injury to the retinal pigmented epithelium (RPE) by 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) immunolabeling and apoptosis by TUNEL labeling. Mice exposed to cigarette smoke had immunolabeling for 8-OHdG in 85+/-3.7% of RPE cells counted compared to 9.5+/-3.9% in controls (p<0.00001). Bruch membrane was thicker in mice exposed to smoke (1086+/-332 nm) than those raised in air (543+/-132 nm; p = 0.0069). The two most pronounced ultrastructural changes (severity grading scale from 0-3) seen were a loss of basal infoldings (mean difference in grade = 1.98; p<0.0001), and an increase in intracellular vacuoles (mean difference in grade = 1.7; p<0.0001). Ultrastructural changes to Bruch membrane in cigarette-smoke exposed mice were smaller in magnitude but consistently demonstrated significantly higher grade injury in cigarette-exposed mice, including basal laminar deposits (mean difference in grade = 0.54; p<0.0001), increased outer collagenous layer deposits (mean difference in grade = 0.59; p = 0.002), and increased basal laminar deposit continuity (mean difference in grade = 0.4; p<0.0001). TUNEL assay showed a higher percentage of apoptotic RPE from mice exposed to cigarette smoke (average 8.0+/-1.1%) than room air (average 0+/-0%; p = 0.043). Mice exposed to chronic cigarette smoke develop evidence of oxidative damage with ultrastructural degeneration to the RPE and Bruch membrane, and RPE cell apoptosis. This model could be useful for studying the mechanism of smoke induced changes during early AMD.     

Response to darkness of late-responsive dark-inducible genes is positively regulated by leaf age and negatively regulated by calmodulin-antagonist-sensitive signalling in Arabidopsis thaliana

Induction after prolonged darkness distinguishes the late-responsive genes din2 and din9 from the early-responsive gene din3 in Arabidopsis. The former genes were coincidently induced with the senescence marker gene YLS4 in rosette leaves of different ages and in the early-senescence mutant hys1. The calmodulin antagonists W-7, trifluoperazine, and fluphenazine accelerated the expression of the former genes in darkness but not in light, and had little effect on the latter gene. Our results suggest that Ca(2+)/calmodulin signalling conveys a negative signal that suppresses the responses of late-responsive din genes to prolonged darkness. The results are discussed in relation to natural senescence.     

The 2microm-plasmid-encoded Rep1 and Rep2 proteins interact with each other and colocalize to the Saccharomyces cerevisiae nucleus.

The efficient partitioning of the 2microm plasmid of Saccharomyces cerevisiae at cell division requires two plasmid-encoded proteins (Rep1p and Rep2p) and a cis-acting locus, REP3 (STB). By using protein hybrids containing fusions of the Rep proteins to green fluorescent protein (GFP), we show here that fluorescence from GFP-Rep1p or GFP-Rep2p is almost exclusively localized in the nucleus in a cir+ strain. Nuclear localization of GFP-Rep1p and GFP-Rep2p, though discernible, is less efficient in a cir(0) host. GFP-Rep2p or GFP-Rep1p is able to promote the stability of a 2microm circle-derived plasmid harboring REP1 or REP2, respectively, in a cir(0) background. Under these conditions, fluorescence from GFP-Rep2p or GFP-Rep1p is concentrated within the nucleus, as is the case in cir+ cells. This characteristic nuclear accumulation is not dependent on the expression of the FLP or RAF1 gene of the 2microm circle. Nuclear colocalization of Rep1p and Rep2p is consistent with the hypothesis that the two proteins directly or indirectly interact to form a functional bipartite or high-order protein complex. Immunoprecipitation experiments as well as baiting assays using GST-Rep hybrid proteins suggest a direct interaction between Rep1p and Rep2p which, in principle, may be modulated by other yeast proteins. Furthermore, these assays provide evidence for Rep1p-Rep1p and Rep2p-Rep2p associations as well. The sum of these interactions may be important in controlling the effective cellular concentration of the Rep1p-Rep2p complex.     

Modified Radioimmunoassay for Murine Sarcoma-Leukemia Virus Group-Specific Antigen

Iodination of disrupted Moloney strain murine sarcoma-leukemia virus resulted in labeled group-specific (gs) protein which was subsequently purified on an isoelectrofocusing column. This iodinated purified gs antigen, prepared from a relatively small quantity of purified virus, was used in a radioimmunoassay. A radioimmunoassay inhibition method was developed so that antibody specific for mammalian C-type gs antigen could be measured in undiluted or low dilutions of test serum without altering the known reagents of the test. The gs antigen isolated from purified Moloney strain murine sarcoma-leukemia virus has an isoelectric point (pH 5.95) which is significantly lower than that reported for other murine leukemia viruses.     

Characterization of Intracellular Ribonucleic Acid Specific for the Murine Sarcoma-Leukemia Virus Complex

Virus particles were continuously produced by a cell line (78A1) of rat embryo fibroblasts that had been transformed by the murine sarcoma-leukemia virus complex. Since most of the mature virions were found in the extracellular fluid and were not cell-associated, a measurable quantity of viral ribonucleic acid (RNA) could not be extracted from these cells. Cycloheximide, a protein inhibitor, was successfully used to accumulate viral RNA within the cells. This ribonuclease-sensitive RNA, with a sedimentation coefficient of 71S, had the same base composition as the high molecular weight RNA (S(20,w) = 71) isolated from purified virions released by the transformed cells.