Fundamental calcium release events revealed by two-photon excitation photolysis of caged calcium in guinea-pig cardiac myocytes

In cardiac muscle, ‘Ca2+ sparks’ have been proposed to underlie Ca2+-induced Ca2+ release (CICR), and to result from openings of clusters of Ca2+ channels (ryanodine receptors; RyRs) located in the sarcoplasmic reticulum membrane.To investigate the elementary nature of these Ca2+ signals directly, a diffraction-limited point source of Ca2+ was created in single cardiac myocytes by two-photon excitation photolysis of caged Ca2+. Simultaneously, concentration profiles of released Ca2+ were imaged at high temporal and spatial resolution with a laser-scanning confocal microscope.This approach enabled us to generate and detect photolytic Ca2+ signals that closely resembled the Ca2+ sparks occurring naturally, not only in amplitude and size, but also in their ability to trigger additional Ca2+ sparks or Ca2+ waves.Surprisingly, at low photolytic power minuscule events with estimated Ca2+ release fluxes 20–40 times smaller than those calculated for a typical Ca2+ spark were directly resolved. These events appeared to arise from the opening of a more limited number of RyRs (possibly one) or from RyRs exhibiting a different gating mode and may correspond to the elusive ‘Ca2+ quark’.The Ca2+ quark represents the fundamental Ca2+ release event of excitable cells implementing hierarchical Ca2+ signalling systems with Ca2+ release events of various but distinct amplitude levels (i.e. Ca2+ quarks, Ca2+ sparks and full cellular Ca2+ transients).A graded recruitment of nanoscopic Ca2+ release domains (i.e. Ca2+ quarks) exhibiting variable degrees of spatial coherence and coupling may then build up intermediate Ca2+ signalling events (i.e. Ca2+ sparks). This mechanism suggests the existence of Ca2+ sparks caused by gating of a variable fraction of RyRs from within an individual cluster. Additional mobilization of a variable number of these Ca2+ sparks enables cardiac cells to show graded cellular Ca2+ transients. Similar recruitment processes may underlie regulation of Ca2+ signalling on the cellular level in general

Re-Envisioning RCx: Achieving Max Potential HVAC Controls Retrofits through Modernized BAS Hardware and Software

Most existing buildings have sub-optimal heating, ventilation, and air conditioning (HVAC) controls, resulting in wasted energy and occupant discomfort. Retro-commissioning (RCx) addresses many of these issues, but it is a lengthy and highly customized process. Limited capabilities of existing building automation system hardware restricts the scope of most RCx projects. Incentive programs consider building automation system (BAS) hardware retrofits to be high-capital investments and do not allow them in typical RCx programs. This paper describes work that the authors are leading to facilitate technical and market innovation in the BAS industry to unlock large savings in existing commercial buildings through deep retrofits of BAS hardware and software. California and New York research projects are demonstrating BAS retrofits leveraging the American Society of Heating, Refrigeration, and Air Conditioning Engineers’ (ASHRAE) new Guideline 36 high performance sequences of operation to achieve greater than 20 percent whole building energy savings, while saving costs and reducing risk through streamlined processes and standardization across BAS manufacturer product lines and across implementation practices. This paper describes market barriers that impede achieving deep savings from BAS retrofits in custom incentive and traditional RCx programs and presents a new maximum potential BAS retrofit model that addresses these barriers. The new model leverages the authors’ efforts in market enablement through open standards, BAS industry partnerships, and tools for cost-effective scaling that includes tools for project screening, savings calculations, and measurement and verification (M&V). This approach is widely applicable and will be ready for at-scale implementation within two years

Re-Envisioning RCx: Achieving Max Potential HVAC Controls Retrofits through Modernized BAS Hardware and Software

Most existing buildings have sub-optimal heating, ventilation, and air conditioning (HVAC) controls, resulting in wasted energy and occupant discomfort. Retro-commissioning (RCx) addresses many of these issues, but it is a lengthy and highly customized process. Limited capabilities of existing building automation system hardware restricts the scope of most RCx projects. Incentive programs consider building automation system (BAS) hardware retrofits to be high-capital investments and do not allow them in typical RCx programs. This paper describes work that the authors are leading to facilitate technical and market innovation in the BAS industry to unlock large savings in existing commercial buildings through deep retrofits of BAS hardware and software. California and New York research projects are demonstrating BAS retrofits leveraging the American Society of Heating, Refrigeration, and Air Conditioning Engineers’ (ASHRAE) new Guideline 36 high performance sequences of operation to achieve greater than 20 percent whole building energy savings, while saving costs and reducing risk through streamlined processes and standardization across BAS manufacturer product lines and across implementation practices. This paper describes market barriers that impede achieving deep savings from BAS retrofits in custom incentive and traditional RCx programs and presents a new maximum potential BAS retrofit model that addresses these barriers. The new model leverages the authors’ efforts in market enablement through open standards, BAS industry partnerships, and tools for cost-effective scaling that includes tools for project screening, savings calculations, and measurement and verification (M&V). This approach is widely applicable and will be ready for at-scale implementation within two years

Differential distribution of six calcium-binding proteins in the rat olfactory epithelium during postnatal development and adulthood.

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. Ca2+ acceptors, such as calmodulin, may mediate between the change in intracellular calcium and the conductance mechanism underlying the initial electrical event. Ca2+ acceptors also may participate in subsequent processing of olfactory information. The identification and characterization of these molecules, therefore, should provide important information about the complex signal transduction pathway involving calcium in olfaction as well as other sensory systems. The present study describes the distribution of six calcium-binding proteins in the rat main olfactory epithelium during postnatal development to determine when different Ca2+ acceptors can be detected and whether they segregate into different layers or portions of the epithelium. Calmodulin, calretinin, calbindin-D28k, neurocalcin, and recoverin were detected immunohistochemically in olfactory receptors but not in basal cells. S-100 immunoreactivity was restricted to glial cells primarily around the cribriform plate. During postnatal development (from P1 to P20), calmodulin, calretinin, calbindin-D28k, and neurocalcin formed a gradient of immunoreactivity descending from the central to the lateral areas in the nasal cavity, whereas recoverin was expressed only in sporadic, mature receptors in the proximal region of the mucosa. At P20, the immunoreactivity pattern for each calcium-binding protein was identical to the adult profile, indicating that the olfactory epithelium had reached maturity by this stage. Olfactory nerve fiber bundles displayed a differential staining pattern from P1 until adulthood for calbindin-D28k and calretinin (internal portions of bundles). Differential calmodulin immunoreactivity of olfactory nerves (large external portions of bundles) appeared at P10. The immunoreactivity of the nerve fiber bundles may reflect a further degree of organization relevant to odor discrimination.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.FLWNAinfo:eu-repo/semantics/publishe