A Unified Approach to Linking Experimental,Statistical and Computational Analysis of Spike Train Data

A fundamental issue in neuroscience is how to identify the multiple biophysical mechanisms through which neurons generate observed patterns of spiking activity. In previous work, we proposed a method for linking observed patterns of spiking activity to specific biophysical mechanisms based on a state space modeling framework and a sequential Monte Carlo, or particle filter, estimation algorithm. We have shown, in simulation, that this approach is able to identify a space of simple biophysical models that were consistent with observed spiking data (and included the model that generated the data), but have yet to demonstrate the application of the method to identify realistic currents from real spike train data. Here, we apply the particle filter to spiking data recorded from rat layer V cortical neurons, and correctly identify the dynamics of an slow, intrinsic current. The underlying intrinsic current is successfully identified in four distinct neurons, even though the cells exhibit two distinct classes of spiking activity: regular spiking and bursting. This approach – linking statistical, computational, and experimental neuroscience – provides an effective technique to constrain detailed biophysical models to specific mechanisms consistent with observed spike train data.     

A 3-hydroxy-3-methylglutaryl-CoA synthase-based probe for the discovery of the acyltransferase-less type I polyketide synthases

Acyltransferase (AT)-less type I polyketide synthases (PKSs) produce complex natural products due to the presence of many unique tailoring enzymes. The 3-hydroxy-3-methylglutaryl coenzyme A synthases (HCSs) are responsible for β-alkylation of the growing polyketide intermediates in AT-less type I PKSs. In this study, we discovered a large group of HCSs, closely associated with the characterized and orphan AT-less type I PKSs through in silico genome mining, sequence and genome neighbourhood network analyses. Using HCS-based probes, the survey of 1207 in-house strains and 18 soil samples from different geographic locations revealed the vast diversity of HCS-containing AT-less type I PKSs. The presence of HCSs in many AT-less type I PKSs suggests their co-evolutionary relationship. This study provides a new probe to study the abundance and diversity of AT-less type I PKSs in the environment and microbial strain collections. Our study should inspire future efforts to discover new polyketide natural products from AT-less type I PKSs.     

Abnormal Whole Blood Thrombi in Humans with Inherited Platelet Receptor Defects

To delineate the critical features of platelets required for formation and stability of thrombi, thromboelastography and platelet aggregation measurements were employed on whole blood of normal patients and of those with Bernard-Soulier Syndrome (BSS) and Glanzmann’s Thrombasthenia (GT). We found that separation of platelet activation, as assessed by platelet aggregation, from that needed to form viscoelastic stable whole blood thrombi, occurred. In normal human blood, ristocetin and collagen aggregated platelets, but did not induce strong viscoelastic thrombi. However, ADP, arachidonic acid, thrombin, and protease-activated-receptor-1 and -4 agonists, stimulated both processes. During this study, we identified the genetic basis of a very rare double heterozygous GP1b deficiency in a BSS patient, along with a new homozygous GP1b inactivating mutation in another BSS patient. In BSS whole blood, ADP responsiveness, as measured by thrombus strength, was diminished, while ADP-induced platelet aggregation was normal. Further, the platelets of 3 additional GT patients showed very weak whole blood platelet aggregation toward the above agonists and provided whole blood thrombi of very low viscoelastic strength. These results indicate that measurements of platelet counts and platelet aggregability do not necessarily correlate with generation of stable thrombi, a potentially significant feature in patient clinical outcomes.     

The Protective Effect of Human Umbilical Cord Blood CD34+ Cells and Estradiol against Focal Cerebral Ischemia in Female Ovariectomized Rat: Cerebral MR Imaging and Immunohistochemical Study

Human umbilical cord blood derived CD34⁺ stem cells are reported to mediate therapeutic effects in stroke animal models. Estrogen was known to protect against ischemic injury. The present study wished to investigate whether the protective effect of CD34⁺ cells against ischemic injury can be reinforced with complemental estradiol treatment in female ovariectomized rat and its possible mechanism. Experiment 1 was to determine the best optimal timing of CD34⁺ cell treatment for the neuroprotective effect after 60-min middle cerebral artery occlusion (MCAO). Experiment 2 was to evaluate the adjuvant effect of 17β-estradiol on CD34⁺ cell neuroprotection after MCAO. Experiment 1 showed intravenous infusion with CD34⁺ cells before MCAO (pre-treatment) caused less infarction size than those infused after MCAO (post-treatment) on 7T magnetic resonance T2-weighted images. Experiment 2 revealed infarction size was most significantly reduced after CD34⁺ + estradiol pre-treatment. When compared with no treatment group, CD34⁺ + estradiol pre-treatment showed significantly less ADC reduction at 2 h and 2 d, less CBF reduction at 2 h and less hyperperfusion at 2 d. The immunoreactivity of c-Fos, c-Jun and GFAP was attenuated, and BDNF showed significant recovery from 2 h to 2 d after MCAO, especially after CD34⁺ + estradiol pre-treatment. The present study suggests pre-treatment with CD34⁺ cells with complemental estradiol can be most protective against ischemic injury, which may act through stabilization of cerebral hemodynamics and normalization of the expressions of immediate early genes and BDNF.