Properties of Transient K+ Currents and Underlying Single K+ Channels in Rat Olfactory Receptor Neurons

The transient potassium current, I(K)(t), of enzymatically dissociated rat olfactory receptor neurons was studied using patch-clamp techniques. Upon depolarization from negative holding potentials, I(K)(t) activated rapidly and then inactivated with a time course described by the sum of two exponential components with time constants of 22.4 and 143 ms. Single-channel analysis revealed a further small component with a time constant of several seconds. Steady-state inactivation was complete at -20 mV and completely removed at -80 mV (midpoint -45 mV). Activation was significant at -40 mV and appeared to reach a maximum conductance at +40 mV (midpoint -13 mV). Deactivation was described by the sum of two voltage-dependent exponential components. Recovery from inactivation was extraordinarily slow (50 s at -100 mV) and the underlying processes appeared complex. I(K)(t) was reduced by 4-aminopyridine and tetraethylammonium applied externally. Increasing the external K+ concentration ([K+]o) from 5 to 25 mM partially removed I(K)(t) inactivation, usually without affecting activation kinetics. The elevated [K+]o also hyperpolarized the steady-state inactivation curve by 9 mV and significantly depolarized the voltage dependence of activation. Single transient K+ channels, with conductances of 17 and 26 pS, were observed in excised patches and often appeared to be localized into large clusters. These channels were similar to I(K)(t) in their kinetic, pharmacological, and voltage-dependent properties and their inactivation was also subject to modulation by [K+]o. The properties of I(K)(t) imply a role in action potential repolarization and suggest it may also be important in modulating spike parameters during neuronal burst firing. A simple method is also presented to correct for errors in the measurement of whole-cell resistance (R(o)) that can result when patch-clamping very small cells. The analysis revealed a mean corrected R(o) of 26 G-OMEGA for these cells

Cyclic Nucleotide-Gated Channels of Rat Olfactory Receptor-Cells - Divalent-Cations Control the Sensitivity to Camp

cAMP-gated channels were studied in inside-out membrane patches excised from the apical cellular pore of isolated olfactory receptor cells of the rat. in the absence of divalent cations the dose-response curve of activation of patch current by cAMP had a K-M Of 4.0 mu M at -50 mV and of 2.5 mu M at +50 mV. However, addition of 0.2 or 0.5 mM Ca2+ shifted the K-M of cAMP reversibly to the higher cAMP concentrations of 33 or 90 mu M, respectively, at -50 mV. Among divalent cations, the relative potency for inducing cAMP affinity shifts was: Ca2+ > Sr2+ > Mn2+ > Ba2+ > Mg2+, of which Mg2+ (up to 3 mM) did not shift the K-M at all. This potency sequence corresponds closely to that required for the activation of calmodulin. However, the Ca2+-sensitivity is lower than expected for a calmodulin-mediated action. Brief(60 s) transient exposure to 3 mM Mg2+, in the absence of other divalent cations, had a protective effect in that following washout of Mg2+, subsequent exposure to 0.2 mM Ca2+ no longer caused affinity shifts. This protection effect did not occur in intact cells and was probably a consequence of patch excision, possibly representing ablation of a regulatory protein from the channel cyclic nucleotide binding site. Thus, the binding of divalent cations, probably via a regulatory protein, controls the sensitivity of the cAMP-gated channels to cAMP. The influx of Ca2+ through these channels during the odorant response may rise to a sufficiently high concentration at the intracellular membrane surface to contribute to the desensitization of the odorant-induced response. The results also indicate that divalent cation effects on cyclic nucleotide-gated channels may depend on the sequence of pre-exposure to other divalent cations

Properties of Cyclic-Nucleotide Gated Channels Mediating Olfactory Transduction - Activation, Selectivity, and Blockage

Cyclic nucleotide-gated channels (cng channels) in the sensory membrane of olfactory receptor cells, activated after the odorant-induced increase of cytosolic cAMP concentration, conduct the receptor current that elicits electrical excitation of the receptor neurons. We investigated properties of cng channels from frog and rat using inside-out and outside-out membrane patches excised from isolated olfactory receptor cells. Channels were activated by cAMP and cGMP with activation constants of 2.5-4.0-mu-M for cAMP and 1.0-1.8 for cGMP. Hill coefficients of dose-response curves were 1.4-1.8, indicating cooperativity of ligand binding. Selectivity for monovalent alkali cations and the Na/Li mole-fraction behavior identified the channel as a nonselective cation channel, having a cation-binding site of high field strength in the pore. Cytosolic pH effects suggest the presence of an additional titratable group which, when protonated, inhibits the cAMP-induced current with an apparent pK of 5.0-5.2. The pH effects were not voltage dependent. Several blockers of Ca2+ channels also blocked olfactory cng channels. Amiloride, D 600, and diltiazem inhibited the cAMP-induced current from the cytosolic side. Inhibition constants were voltage dependent with values of, respectively, 0.1, 0.3, and 1 mM at - 60 mV, and 0.03, 0.02, and 0.2 mM at + 60 mV. Our results suggest functional similarity between frog and rat cng channels, as well as marked differences to cng channels from photoreceptors and other tissues

Glycine receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABAA, nicotinic acetylcholine and 5-HT3 receptors [63]. The receptor is expressed either as a homo-pentamer of α subunits, or a complex now thought to harbour 2α and 3β subunits [30, 7], that contain an intrinsic anion channel. Four differentially expressed isoforms of the α-subunit (α1-α4) and one variant of the β-subunit (β1, GLRB, P48167) have been identified by genomic and cDNA cloning. Further diversity originates from alternative splicing of the primary gene transcripts for α1 (α1INS and α1del), α2 (α2A and α2B), α3 (α3S and α3L) and β (βΔ7) subunits and by mRNA editing of the α2 and α3 subunit [80, 91, 18]. Both α2 splicing and α3 mRNA editing can produce subunits (i.e., α2B and α3P185L) with enhanced agonist sensitivity. Predominantly, the mature form of the receptor contains α1 (or α3) and β subunits while the immature form is mostly composed of only α2 subunits. RNA transcripts encoding the α4-subunit have not been detected in adult humans. The N-terminal domain of the α-subunit contains both the agonist and strychnine binding sites that consist of several discontinuous regions of amino acids. Inclusion of the β-subunit in the pentameric glycine receptor contributes to agonist binding, reduces single channel conductance and alters pharmacology. The β-subunit also anchors the receptor, via an amphipathic sequence within the large intracellular loop region, to gephyrin. The latter is a cytoskeletal attachment protein that binds to a number of subsynaptic proteins involved in cytoskeletal structure and thus clusters and anchors hetero-oligomeric receptors to the synapse [86, 51, 53]. G-protein βγ subunits enhance the open state probability of native and recombinant glycine receptors by association with domains within the large intracellular loop [122, 121]. Intracellular chloride concentration modulates the kinetics of native and recombinant glycine receptors [94]. Intracellular Ca2+ appears to increase native and recombinant glycine receptor affinity, prolonging channel open events, by a mechanism that does not involve phosphorylation [24]

Glycine receptors in GtoPdb v.2021.3

The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABA_{A}, nicotinic acetylcholine and 5-HT_{3} receptors and Zn2^{+}_{-} activated channels. The receptor is expressed either as a homo-pentamer of α subunits, or a complex now thought to harbour 2α and 3β subunits [33, 7], that contain an intrinsic anion channel. Four differentially expressed isoforms of the α-subunit (α1-α4) and one variant of the β-subunit (β1, GLRB, P48167) have been identified by genomic and cDNA cloning. Further diversity originates from alternative splicing of the primary gene transcripts for α1 (α1^{INS} and α1^{del} ), α2 (α2A and α2B), α3 (α3S and α3L) and β (βΔ7) subunits and by mRNA editing of the α2 and α3 subunit [83, 93, 21]. Both α2 splicing and α3 mRNA editing can produce subunits (i.e., α2B and α3P185L) with enhanced agonist sensitivity. Predominantly, the adult form of the receptor contains α1 (or α3) and β subunits whereas the immature form is mostly composed of only α2 subunits. The &a;pha;4 subunit is a pseudogene in humans. High resolution molecular structures are available for the α1 and α3 homomeric receptors [50, 20]. As in other Cys-loop receptors, the orthosteric binding site for agonists and the competitive antagonist strychnine is formed at the interfaces between the subunits’ extracellular domains. Inclusion of the β-subunit in the pentameric glycine receptor contributes to agonist binding, reduces single channel conductance and alters pharmacology. The β-subunit also anchors the receptor, via an amphipathic sequence within the large intracellular loop region, to gephyrin. This a cytoskeletal attachment protein that binds to a number of subsynaptic proteins involved in cytoskeletal structure and thus clusters and anchors hetero-oligomeric receptors to the synapse [56, 54, 88]. G protein βγ subunits enhance the open state probability of native and recombinant glycine receptors by association with domains within the large intracellular loop [124, 123]. Intracellular chloride concentration modulates the kinetics of native and recombinant glycine receptors [96]. Intracellular Ca^{2+} appears to increase native and recombinant glycine receptor affinity, prolonging channel open events, by a mechanism that does not involve phosphorylation [27]. Extracellular Zn^{2+} potentiates GlyR function at nanomolar concentrations [86]. and causes inhibition at higher micromolar concentrations (17)

Do early life cognitive ability and self-regulation skills explain socio-economic inequalities in academic achievement? An effect. decomposition analysis in UK and Australian cohorts

Socio-economic inequalities in academic achievement emerge early in life and are observed across the globe. Cognitive ability and “non-cognitive” attributes (such as self-regulation) are the focus of many early years’ interventions. Despite this, little research has compared the contributions of early cognitive and self-regulation abilities as separate pathways to inequalities in academic achievement. We examined this in two nationally representative cohorts in the UK (Millennium Cohort Study, n = 11,168; 61% original cohort) and Australia (LSAC, n = 3028; 59% original cohort). An effect decomposition method was used to examine the pathways from socio-economic disadvantage (in infancy) to two academic outcomes: ‘low’ maths and literacy scores (based on bottom quintile) at age 7–9 years. Risk ratios (RRs, and bootstrap 95% confidence intervals) were estimated with binary regression for each pathway of interest: the ‘direct effect’ of socio-economic disadvantage on academic achievement (not acting through self-regulation and cognitive ability in early childhood), and the ‘indirect effects’ of socio-economic disadvantage acting via self-regulation and cognitive ability (separately). Analyses were adjusted for baseline and intermediate confounding. Children from less advantaged families were up to twice as likely to be in the lowest quintile of maths and literacy scores. Around two-thirds of this elevated risk was ‘direct’ and the majority of the remainder was mediated by early cognitive ability and not self-regulation. For example in LSAC: the RR for the direct pathway from socio-economic disadvantage to poor maths scores was 1.46 (95% CI: 1.17–1.79). The indirect effect of socio-economic disadvantage through cognitive ability (RR = 1.13 [1.06–1.22]) was larger than the indirect effect through self-regulation (1.05 [1.01–1.11]). Similar patterns were observed for both outcomes and in both cohorts. Policies to alleviate social inequality (e.g. child poverty reduction) remain important for closing the academic achievement gap. Early interventions to improve cognitive ability (rather than self-regulation) also hold potential for reducing inequalities in children's academic outcomes

Household item ownership and self-rated health: material and psychosocial explanations

BACKGROUND: There has been an ongoing debate whether the effects of socioeconomic factors on health are due to absolute poverty and material factors or to relative deprivation and psychosocial factors. In the present analyses, we examined the importance for health of material factors, which may have a direct effect on health, and of those that may affect health indirectly, through psychosocial mechanisms. METHODS: Random national samples of men and women in Hungary (n = 973) and Poland (n = 1141) were interviewed (response rates 58% and 59%, respectively). The subjects reported their self-rated health, socioeconomic circumstances, including ownership of different household items, and perceived control over life. Household items were categorised as "basic needs", "socially oriented", and "luxury". We examined the association between the ownership of different groups of items and self-rated health. Since the lists of household items were different in Hungary and Poland, we conducted parallel identical analyses of the Hungarian and Polish data. RESULTS: The overall prevalence of poor or very poor health was 13% in Poland and 25% in Hungary. Education, material deprivation and the number of household items were all associated with poor health in bivariate analyses. All three groups of household items were positively related to self-rated health in age-adjusted analyses. The relation of basic needs items to poor health disappeared after controlling for other socioeconomic variables (mainly material deprivation). The relation of socially oriented and luxury items to poor health, however, persisted in multivariate models. The results were similar in both datasets. CONCLUSIONS: These data suggest that health is influenced by both material and psychosocial aspects of socioeconomic factors

Socioeconomic considerations in the health of urban areas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45780/1/11524_2006_Article_BF02345090.pd

Can Waterlow score predict 30-day mortality and length of stay in acutely admitted medical patients (aged ≥65 years)? Evidence from a single centre prospective cohort study

OBJECTIVE: This study aimed to explore the potential for the Waterlow score (WS) to be used as a predictor of 30-day mortality and length of hospital stay (LHS) in acutely admitted medical patients aged 65 years and older. DESIGN: Prospective observational cohort study. SETTING: UK District General Hospital. SUBJECTS: 834 consecutive patients aged 65 years and older admitted acutely to medical specialties between 30 May and 22 July 2014. METHODS ADMISSION: WS (range 4–64) assessment paired with the patient’s status at 30 days in terms of mortality and their LHS. PRIMARY OUTCOMES: 30-day mortality and length of inpatient stay. RESULTS: 834 consecutive acute medical admissions had their WS recorded. 30-day mortality was 13.1% (109 deaths). A significant difference in the distribution of WS (p<0.001) was seen between those who survived (median 12) and those who died (median 16) within 30 days, particularly within respiratory (p<0.001), stroke (p<0.001), cardiology (p<0.016), non-respiratory infections (p<0.018) and trauma (p<0.044) subgroups. Odds of dying within 30 days increased threefold for every 10-unit increase in the WS (p<0.001, 95% CI 2.1 to 4.3). LHS was also positively linearly associated with the WS in those who survived 30 days (median=5, IQR=10; r=0.32, p<0.01). A five-unit increase in WS was associated with approximately 5 days increase in LHS. On the other hand, quadratic regression showed this relationship was curvilinear and negative (concave) for those who died within 30 days where a five-unit increase in WS was associated with an approximately 10 days decrease in LHS. CONCLUSION: This study demonstrates an association between a high WS and both 30-day mortality and LHS. This is particularly significant for mortality in patients in the respiratory, stroke and cardiac subcategories. The WS, a nursing-led screening tool that is carried out on virtually all admissions to UK hospitals, could have additional use at the time of patient admission as a risk assessment tool for 30-day mortality as well as a predictor of LHS

β Subunit M2–M3 Loop Conformational Changes Are Uncoupled from α1 β Glycine Receptor Channel Gating: Implications for Human Hereditary Hyperekplexia

Hereditary hyperekplexia, or startle disease, is a neuromotor disorder caused mainly by mutations that either prevent the surface expression of, or modify the function of, the human heteromeric α1 β glycine receptor (GlyR) chloride channel. There is as yet no explanation as to why hyperekplexia mutations that modify channel function are almost exclusively located in the α1 to the exclusion of β subunit. The majority of these mutations are identified in the M2–M3 loop of the α1 subunit. Here we demonstrate that α1 β GlyR channel function is less sensitive to hyperekplexia-mimicking mutations introduced into the M2–M3 loop of the β than into the α1 subunit. This suggests that the M2–M3 loop of the α subunit dominates the β subunit in gating the α1 β GlyR channel. A further attempt to determine the possible mechanism underlying this phenomenon by using the voltage-clamp fluorometry technique revealed that agonist-induced conformational changes in the β subunit M2–M3 loop were uncoupled from α1 β GlyR channel gating. This is in contrast to the α subunit, where the M2–M3 loop conformational changes were shown to be directly coupled to α1 β GlyR channel gating. Finally, based on analysis of α1 β chimeric receptors, we demonstrate that the structural components responsible for this are distributed throughout the β subunit, implying that the β subunit has evolved without the functional constraint of a normal gating pathway within it. Our study provides a possible explanation of why hereditary hyperekplexia-causing mutations that modify α1 β GlyR channel function are almost exclusively located in the α1 to the exclusion of the β subunit