scholarly journals Mathematical Analysis of Electrical Responses in Photoreceptor Cells Reveals Distinct Chemical Control of Visual Signal Transduction in Rods and Cones.

2021 ◽  
Author(s):  
Yukari Takeda ◽  
Kazuma Sato ◽  
Yukari Hosoki ◽  
Shuji Tachibanaki ◽  
Chieko Koike ◽  
...  
Keyword(s):  
Light Intensity ◽  
Current Model ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Visual Signal ◽  
Visual Transduction ◽  
Rods And Cones ◽  
Experimental Systems ◽  
Lower Light

Abstract Retinal photoreceptor cells, rods and cones, convert photons of light into chemical and electrical signals as the first step of the visual transduction cascade. Although the chemical processes in the phototransduction system are very similar to each other in these photoreceptors, the light sensitivity and time resolution of the photoresponse in rods are functionally different than those in the photoresponses of cones. To systematically investigate how photoresponses are divergently regulated in rods and cones, we have developed a detailed mathematical model on the basis of the Hamer model. The current model successfully reconstructed light intensity-, ATP- and GTP-dependent changes in concentrations of phosphorylated visual pigments (VPs), activated transducins (Tr*s) and phosphodiesterases (PDEs), as well as cyclic nucleotide-gated currents (ICNG) in rods and cones. In comparison to rods, the lower light sensitivity of cones was attributed not only to the lower affinity of activated VPs for Trs but also to the faster desensitization of the VPs. The assumption of an intermediate inactive state, MIIi, in the thermal decay of activated VPs was pivotal for inducing faster inactivation of VPs. In addition to the faster inactivation of VPs, calculating a faster rate of RGS9 intervention for PDE-induced Tr* inactivation in cones was indispensable for simulating the electrical waveforms of the light intensity-dependent ICNG at higher temporal resolution in experimental systems in vivo.

scholarly journals Shedding light on dark adaptation

2020 ◽  
Vol 42 (5) ◽  
pp. 44-50
Author(s):  
Ellen Weiss
Keyword(s):  
Dark Adaptation ◽  
Bright Light ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Visual Sensitivity ◽  
Rods And Cones ◽  
Light Sensing ◽  
Light Intensities ◽  
Visual Signalling ◽  
G Protein Coupled

The retina is famous for its ability to operate under a broad range of light intensities. This is partly due to the presence of two types of photoreceptor cells, rods and cones. Rods are used mostly for dim light vision, and cones are used for bright light and colour vision. These cells are also able to adapt to a broad range of light intensities using light- and dark-adaptation mechanisms. Dark adaptation is used by the vertebrate retina to increase its visual sensitivity when moving from a brightly lit environment to a dark environment. The brighter the surrounding light, the longer it takes for the retina to adapt to the dark. Most retina biologists have studied dark adaptation by exposing animals to a 90% bleach, meaning that 90% of the light-sensing proteins in these photoreceptor cells have been activated, followed by transfer of these animals to a dark room and analysis of their light sensitivity using electrophysiological methods. In this report, we introduce the basic elements of the visual system and describe how the system might operate during dark adaptation. We also introduce a novel role for cAMP-mediated phosphorylation of G protein-coupled receptor kinase 1 (GRK1), a major kinase in visual signalling.

scholarly journals Generalizing game-changing species across microbial communities

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jie Deng ◽  
Marco Tulio Angulo ◽  
Serguei Saavedra
Keyword(s):  
Microbial Communities ◽  
Context Dependency ◽  
Heuristic Rules ◽  
Resident Species ◽  
Experimental Systems ◽  
Environment And Health ◽  
Structuralist Theory ◽  
Context Specific

AbstractMicrobes form multispecies communities that play essential roles in our environment and health. Not surprisingly, there is an increasing need for understanding if certain invader species will modify a given microbial community, producing either a desired or undesired change in the observed collection of resident species. However, the complex interactions that species can establish between each other and the diverse external factors underlying their dynamics have made constructing such understanding context-specific. Here we integrate tractable theoretical systems with tractable experimental systems to find general conditions under which non-resident species can change the collection of resident communities—game-changing species. We show that non-resident colonizers are more likely to be game-changers than transients, whereas game-changers are more likely to suppress than to promote resident species. Importantly, we find general heuristic rules for game-changers under controlled environments by integrating mutual invasibility theory with in vitro experimental systems, and general heuristic rules under changing environments by integrating structuralist theory with in vivo experimental systems. Despite the strong context-dependency of microbial communities, our work shows that under an appropriate integration of tractable theoretical and experimental systems, it is possible to unveil regularities that can then be potentially extended to understand the behavior of complex natural communities.

Differential use of SCL/TAL-1 DNA-binding domain in developmental hematopoiesis

Blood ◽  
2008 ◽  
Vol 112 (4) ◽  
pp. 1056-1067 ◽  
Author(s):  
Mira T. Kassouf ◽  
Hedia Chagraoui ◽  
Paresh Vyas ◽  
Catherine Porcher
Keyword(s):  
Dna Binding ◽  
Molecular Mechanisms ◽  
Binding Activity ◽  
Hematopoietic Stem ◽  
Helix Loop Helix ◽  
Experimental Systems ◽  
Dna Binding Activity ◽  
Independent Functions

Abstract Dissecting the molecular mechanisms used by developmental regulators is essential to understand tissue specification/differentiation. SCL/TAL-1 is a basic helix-loop-helix transcription factor absolutely critical for hematopoietic stem/progenitor cell specification and lineage maturation. Using in vitro and forced expression experimental systems, we previously suggested that SCL might have DNA-binding–independent functions. Here, to assess the requirements for SCL DNA-binding activity in vivo, we examined hematopoietic development in mice carrying a germline DNA-binding mutation. Remarkably, in contrast to complete absence of hematopoiesis and early lethality in scl-null embryos, specification of hematopoietic cells occurred in homozygous mutant embryos, indicating that direct DNA binding is dispensable for this process. Lethality was forestalled to later in development, although some mice survived to adulthood. Anemia was documented throughout development and in adulthood. Cellular and molecular studies showed requirements for SCL direct DNA binding in red cell maturation and indicated that scl expression is positively autoregulated in terminally differentiating erythroid cells. Thus, different mechanisms of SCL's action predominate depending on the developmental/cellular context: indirect DNA binding activities and/or sequestration of other nuclear regulators are sufficient in specification processes, whereas direct DNA binding functions with transcriptional autoregulation are critically required in terminal maturation processes.

scholarly journals Parameters Influencing Zinc in Experimental Systems in Vivo and in Vitro

Metals ◽  
2016 ◽  
Vol 6 (3) ◽  
pp. 71 ◽  
Author(s):  
Johanna Ollig ◽  
Veronika Kloubert ◽  
Inga Weßels ◽  
Hajo Haase ◽  
Lothar Rink
Keyword(s):  
Experimental Systems

scholarly journals Optical Measurement of Blood Oxygen Saturation of Dental Pulp

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Satoko Kakino ◽  
Shinya Kushibiki ◽  
Azusa Yamada ◽  
Zenzo Miwa ◽  
Yuzo Takagi ◽  
...  
Keyword(s):  
Light Intensity ◽  
Oxygen Saturation ◽  
Dental Pulp ◽  
Optical Measurement ◽  
Blood Oxygen ◽  
Arterial Pulse ◽  
Blood Oxygen Saturation ◽  
Visible Wavelengths

The applicability of arterial pulse oximetry to dental pulp was demonstrated using in vitro and in vivo measurements. First, porcine blood of known oxygen saturation (SO2) was circulated through extracted human upper incisors, while transmitted-light plethysmography was performed using three different visible wavelengths. From the light intensity waveforms measured in vitro, a parameter that is statistically correlated to SO2 was calculated using the pulsatile/nonpulsatile component ratios of two wavelengths for different SO2. Then, values were measured in vivo for living incisors, and the corresponding SO2 values were calculated using the results of in vitro measurements. The estimated SO2 values of the upper central incisors measured in vivo were from 71.0 to 92.7%. This study showed the potential to measure the oxygen saturation changes to identify the sign of pulpal inflammation.

scholarly journals Left-right and upper-lower light sensitivity asymmetry in visual field defects caused by pituitary adenoma: a retrospective observational study

2019 ◽  
Author(s):  
Yumi Kotoda ◽  
Masakazu Kotoda ◽  
Masakazu Ogiwara ◽  
Hiroyuki Kinouchi ◽  
Hiroyuki Iijima
Keyword(s):  
Pituitary Adenoma ◽  
Visual Field ◽  
Light Sensitivity ◽  
Visual Field Defects ◽  
Lower Visual Field ◽  
Lower Quadrant ◽  
Lower Light ◽  
Left And Right ◽  
Left Right Asymmetry ◽  
Field Defects

Abstract Background While bitemporal visual field defects are characteristic in pituitary adenoma cases, it is rare to have complete bitemporal hemianopsia that is symmetrical in both eyes and has absolute scotoma throughout both temporal hemifields. Although several researches have investigated asymmetric visual field defects in patients with pituitary adenoma, no precise investigation with statistical analysis regarding the inter-eye and intra-eye symmetry of visual field defects has yet been reported. In this study, we conducted quantitative analysis to explore the asymmetric properties of visual field defects in pituitary adenoma patients. Methods Preoperative Humphrey 30-2 perimetry results were reviewed retrospectively using the charts of 28 pituitary adenoma patients who underwent surgery. Inter-eye light sensitivity comparisons of the temporal and nasal hemifields between the left and right eyes were conducted in each patient to study left-right asymmetry. Upper-lower asymmetry was investigated by comparing the frequency of severe scotoma (light sensitivity 5 dB or less) in the upper and lower visual field quadrants in the temporal and nasal hemifields. Results Left-right asymmetry was demonstrated in 61% of cases in the temporal hemifield and in 57% of cases in the nasal hemifield. Severe scotoma test points were investigated in the worse eye of each patient and were more frequent in the superotemporal quadrant of the visual field compared with the inferotemporal quadrant (P = 0.00029) and in the inferonasal quadrant compared to the superonasal quadrant (P = 0.00268). Conclusions Asymmetric visual field defects between left and right eyes are common in patients with pituitary adenoma. Severe scotoma is more frequent in the upper quadrant of the temporal hemifield and in the lower quadrant of the nasal hemifield.

scholarly journals Unstressing intemperate models: how cold stress undermines mouse modeling

2012 ◽  
Vol 209 (6) ◽  
pp. 1069-1074 ◽  
Author(s):  
Christopher L. Karp
Keyword(s):  
Cold Stress ◽  
Biomedical Research ◽  
Current Model ◽  
Environmental Variable ◽  
Model System ◽  
Laboratory Mice ◽  
Therapeutic Approaches ◽  
Mechanistic Analysis ◽  
Mouse Modeling

Mus musculus enjoys pride of place at the center of contemporary biomedical research. Despite being the current model system of choice for in vivo mechanistic analysis, mice have clear limitations. The literature is littered with examples of therapeutic approaches that showed promise in mouse models but failed in clinical trials. More generally, mice often provide poor mimics of the human diseases being modeled. Available data suggest that the cold stress to which laboratory mice are ubiquitously subjected profoundly affects mouse physiology in ways that impair the modeling of human homeostasis and disease. Experimental attention to this key, albeit largely ignored, environmental variable is likely to have a broad transformative effect on biomedical research.

JAM-C maintains VEGR2 expression to promote retinal pigment epithelium cell survival under oxidative stress

2017 ◽  
Vol 117 (04) ◽  
pp. 750-757
Author(s):  
Xin Jia ◽  
Chen Zhao ◽  
Qishan Chen ◽  
Yuxiang Du ◽  
Lijuan Huang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Retinal Pigment Epithelium ◽  
Cell Survival ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Pigment Epithelium Cell ◽  
Photoreceptor Cells ◽  
Rpe Cells

SummaryJunctional adhesion molecule-C (JAM-C) has been shown to play critical roles during development and in immune responses. However, its role in adult eyes under oxidative stress remains poorly understood. Here, we report that JAM-C is abundantly expressed in adult mouse retinae and choroids in vivo and in cultured retinal pigment epithelium (RPE) and photoreceptor cells in vitro. Importantly, both JAM-C expression and its membrane localisation are downregulated by H2O2-induced oxidative stress. Under H2O2-induced oxidative stress, JAM-C is critically required for the survival of human RPE cells. Indeed, loss of JAM-C by siRNA knockdown decreased RPE cell survival. Mechanistically, we show that JAM-C is required to maintain VEGFR2 expression in RPE cells, and VEGFR2 plays an important role in keeping the RPE cells viable since overexpression of VEGFR2 partially restored impaired RPE survival caused by JAM-C knockdown and increased RPE survival. We further show that JAM-C regulates VEGFR2 expression and, in turn, modulates p38 phosphorylation. Together, our data demonstrate that JAM-C plays an important role in maintaining VEGR2 expression to promote RPE cell survival under oxidative stress. Given the vital importance of RPE in the eye, approaches that can modulate JAM-C expression may have therapeutic values in treating diseases with impaired RPE survival.

scholarly journals A COMPARATIVE STUDY OF ANTIMICROBIAL PROFILE HAVING BROAD SPECTRUM BACTERIOCINS AGAINST ANTIBIOTICS

2017 ◽  
Vol 10 (9) ◽  
pp. 44 ◽  
Author(s):  
Sabiha Imran ◽  
Twinkle Gupta ◽  
Aarti Arora ◽  
Nilanjan Das
Keyword(s):  
Broad Spectrum ◽  
Cationic Peptides ◽  
Promising Alternative ◽  
Bacterial Diseases ◽  
Adverse Side Effects ◽  
Experimental Systems ◽  
Improper Use ◽  
Physical And Chemical

  Bacteriocins are ribosomally synthesized antimicrobial peptides produced by microbes owned by different eubacterial taxonomic branches. Most of them are small cationic membrane-active compounds that form pores in the targeted cells, disrupting membrane possibilities, and triggering cell fatality. The availability of small cationic peptides with antimicrobial activity is a protection strategy found not only in bacteria but also in plants and animals. The antibiotics which have extensive applications in the treatment of various bacterial diseases have developed alarming resistance against them in many pathogens due to improper use besides this antibiotics have adverse side effects also. There are an extensive variety of bacteriocins made by different bacterial genera have promising alternative to antibiotics that needs to be further studied to show the no existence of undesirable effects, which must be performed both in vitro and in vivo experimental systems. Most of the bacteriocin have narrow spectrum of their activity and effective only on the related species. There is an urgent need for the identification of broad-spectrum bacteriocins isolated from the species from different habitats that can be effective against both Gram-positive and Gram-negative pathogens. In this review, we focus on the main physical and chemical characteristics of broad-spectrum bacteriocin and discuss their application as an alternative option to antibiotics.

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