Mitochondrial membrane potential regulates PINK1 import and proteolytic destabilization by PARL

Differential localization to the inner and outer mitochondrial membranes regulates PINK1 stability and function

3D finite element electrical model of larval zebrafish ECG signals

Assessment of heart function in zebrafish larvae using electrocardiography (ECG) is a potentially useful tool in developing cardiac treatments and the assessment of drug therapies. In order to better understand how a measured ECG waveform is related to the structure of the heart, its position within the larva and the position of the electrodes, a 3D model of a 3 days post fertilisation (dpf) larval zebrafish was developed to simulate cardiac electrical activity and investigate the voltage distribution throughout the body. The geometry consisted of two main components; the zebrafish body was modelled as a homogeneous volume, while the heart was split into five distinct regions (sinoatrial region, atrial wall, atrioventricular band, ventricular wall and heart chambers). Similarly, the electrical model consisted of two parts with the body described by Laplace’s equation and the heart using a bidomain ionic model based upon the Fitzhugh-Nagumo equations. Each region of the heart was differentiated by action potential (AP) parameters and activation wave conduction velocities, which were fitted and scaled based on previously published experimental results. ECG measurements in vivo at different electrode recording positions were then compared to the model results. The model was able to simulate action potentials, wave propagation and all the major features (P wave, R wave, T wave) of the ECG, as well as polarity of the peaks observed at each position. This model was based upon our current understanding of the structure of the normal zebrafish larval heart. Further development would enable us to incorporate features associated with the diseased heart and hence assist in the interpretation of larval zebrafish ECGs in these conditions

Neurochemical identification of stereotypic burst-firing neurons in the rat dorsal raphe nucleus using juxtacellular labelling methods.

Recent electrophysiological studies have discovered evidence of heterogeneity of 5-hydroxytryptamine (5-HT) neurons in the mesencephalic raphe nuclei. Of particular interest is a subpopulation of putative 5-HT neurons that display many of the electrophysiological properties of presumed 5-HT-containing neurons (regular and slow firing of single spikes with a broad waveform) but fire spikes in short, stereotyped bursts. In the present study we investigated the chemical identity of these neurons in rats utilizing in vivo juxtacellular labelling methods. Of ten dorsal raphe nucleus (DRN) neurons firing short stereotyped bursts within an otherwise regular firing pattern, all exhibited immunoreactivity for either 5-HT (n = 6) or the 5-HT synthesizing enzyme, tryptophan hydroxylase (TRH; n = 2) or both (n = 2). Supporting pharmacological experiments demonstrated that the burst firing DRN neurons demonstrated equal sensitivity to 5-HT(1A) agonism and alpha(1)-adrenoceptor antagonism to single spiking DRN neurons that we have previously identified as 5-HT-containing. Collectively these data provide direct evidence that DRN neurons that exhibit stereotyped burst firing activity are 5-HT containing. The presence of multiple types of electrophysiologically distinct midbrain 5-HT neurons is discussed

Phage abortive infection of Bacillus licheniformis ATCC 9800; identification of the abiBL11 gene and localisation and sequencing of its promoter region.

The virulent bacteriophage BL11 infects almost all Bacillus licheniformis strains tested, including the industrial bacitracin-producing B. licheniformis 19. B. licheniformis ATCC 9800, however, was virtually insensitive to phage BL11 infection, and all of the few surviving progeny phages proved to be mutants. The phage-resistance mechanism was neither inhibition of adsorption, nor restriction or exclusion provided by a resident prophage, but was, instead, of another type. Phage BL11 adsorbed well on to ATCC 9800 cells, its DNA was injected, but replication of phage DNA was inhibited and the infected cells died. Thus, the mechanism of phage resistance was identified as abortive infection (AbiBL11). The so-called abiBL11 gene was identified on the chromosome of strain ATCC 9800 by Tn917PF1 transposon mutagenesis. Part of the abiBL11 gene from the phage-sensitive ATCC 9800::Tn917PFI was cloned. Gene-disruption analysis, based on Campbell-type integration, showed that a 0.3-kb EcoRI fragment contained the 5' end of abiBL11. The promoter region of abiBL11 was identified using promoter- and terminator-probe plasmids. The deduced sequence (206 amino acids) of the N-terminal part of abiBL11 showed no significant homology to known abortive-infection genes, but did show homology to a Saccharomyces cerevisiae gene coding for a serine/threonine protein kinase (RCK1)

Regulation of fast-spiking basket cell synapses by the chloride channel ClC-2

Parvalbumin-expressing, fast-spiking basket cells play key roles in the generation of synchronous, rhythmic population activities in the hippocampus. Here we show that GABAA receptor-mediated synaptic inputs from murine parvalbumin-expressing basket cells are selectively modulated by the membrane voltage- and intracellular chloride-dependent chloride channel ClC–2. These data demonstrate a novel cell type-specific regulation of intracellular chloride homeostasis in the perisomatic region of hippocampal pyramidal neurons. Keywords interneuron; GABAA receptor; excitability; microcircuit; intracellular chloride There are two distinct basket cell classes specialized to provide GABAergic innervation to the perisomatic region of principal cells, the parvalbumin- or cholecystokinin- expressing basket cells (PVBCs or CCKBCs, respectively). The intrinsic and synaptic properties of PVBCs enable them to perform circuit functions related to precise time keeping and generation of network oscillations, whereas CCKBCs are thought to serve as modulators that adapt network activity to behavioral states1,2. Because synapses from PVBCs and CCKBC

Permeant anions contribute to voltage dependence of ClC-2 chloride channel by interacting with the protopore gate

It has been shown that the voltage (Vm) dependence of ClC Cl− channels is conferred by interaction of the protopore gate with H+ ions. However, in this paper we present evidence which indicates that permeant Cl− ions contribute to Vm-dependent gating of the broadly distributed ClC-2 Cl− channel. The apparent open probability (PA) of ClC-2 was enhanced either by changing the [Cl−]i from 10 to 200 mm or by keeping the [Cl−]i low (10 mm) and then raising [Cl−]o from 10 to 140 mm. Additionally, these changes in [Cl−] slowed down channel closing at positive Vm suggesting that high [Cl−] increased pore occupancy thus hindering closing of the protopore gate. The identity of the permeant anion was also important since the PA(Vm) curves were nearly identical with Cl− or Br− but shifted to negative voltages in the presence of SCN− ions. In addition, gating, closing rate and reversal potential displayed anomalous mole fraction behaviour in a SCN−/Cl− mixture in agreement with the idea that pore occupancy by different permeant anions modifies the Vm dependence ClC-2 gating. Based on the ec1-ClC anion pathway, we hypothesized that opening of the protopore gate is facilitated when Cl− ions dwell in the central binding site. In contrast, when Cl− ions dwell in the external binding site they prevent the gate from closing. Finally, this Cl−-dependent gating in ClC-2 channels is of physiological relevance since an increase in [Cl−]o enhances channel opening when the [Cl−]i is in the physiological range