Sharp, local synchrony among putative feed-forward inhibitory interneurons of rabbit somatosensory cortex

Many suspected inhibitory interneurons (SINs) of primary somatosensory cortex (S1) receive a potent monosynaptic thalamic input (thalamocortical SINs, SINstc). It has been proposed that nearly all such SINstc of a S1 barrel column (BC) receive excitatory synaptic input from each member of a subpopulation of neurons within the topographically aligned ventrobasal (VB) thalamic barreloid. Such a divergent and convergent network leads to several testable predictions: sharply synchronous activity should occur between SINstc of a BC, sharp synchrony should not occur between SINstc of neighboring BCs, and sharp synchrony should not occur between SINs or other neurons of the same BC that do not receive potent monosynaptic thalamic input. These predictions were tested by cross-correlating the activity of SINstc of the same and neighboring BCs. Correlations among descending corticofugal neurons of layer 5 (CF-5 neurons, identified by antidromic activation) and other neurons that receive little or no monosynaptic VB input also were examined. SINs were identified by a high-frequency (>600 Hz) burst of three or more spikes elicited by VB stimulation and had action potentials of short duration. SINstc were further differentiated by short synaptic latencies to electrical stimulation of VB thalamus (<1.7 ms) and to peripheral stimulation (<7.5 ms). The above predictions were confirmed fully. 1) Sharp synchrony (+/-1 ms) was seen between all SINstc recorded within the same BC (a mean of 4.26% of the spikes of each SINtc were synchronized sharply with the spikes of the paired SINtc). Sharp synchrony was not dependent on peripheral stimulation, was not oscillatory, and survived general anesthesia. Sharp synchrony was superimposed on a broader synchrony, with a time course of tens of milliseconds. 2) Little or no sharp synchrony was seen when CF-5 neurons were paired with SINstc or other neurons of the same BC. 3) Little or no sharp synchrony was seen when SINstc were paired with other SINstc located in neighboring BCs. Intracellular recordings obtained from three SINs in the fully awake state supported the assertion that SINs are GABAergic interneurons. Each of these cells met our extracellular criteria for identification as a SIN, each had a spike of short duration (0.4-0.5 ms), and each responded to a depolarizing current pulse with a nonadapting train of action potentials. These results support the proposed network linking VB barreloid neurons with SINstc within the topographically aligned BC. We suggest that sharp synchrony among SINstc results in highly synchronous inhibitory postsynpatic potentials (IPSPs)in the target neurons of these cells and that these summated IPSPs may be especially effective when excitatory drive to target cells is weak and asynchronous.     

Magnetization, magnetic susceptibility, and effective magnetic moment of the Fe3+ ions in Bi2Fe4O9

Bi₂Fe₄O₉ with an orthorhombic structure and lattice parameters a = 7.9595 Å, b = 8.4297 Å, c = 5.9912 Å, and V = 401.987 ų has been prepared by solid-state reactions method. Its molar magnetic susceptibility measured as a function of temperature in the range 5–950 K indicates that Bi₂Fe₄O₉ is an antiferromagnet with a Néel temperature of 258 K. In the range 280–750 K, its molar magnetic susceptibility exhibits Curie-Weiss behavior, which allowed us to determine the Weiss constant (Θ = ?1468 K) of this material and the effective magnetic moment of the Fe³⁺ ions $\left( {\mu _{eff}^{Fe^{3 + } } = 6.37\mu _B } \right)$ . Magnetization versus magnetic field data show no magnetic hysteresis, indicating that the Bi₂Fe₄O₉ sample studied exhibits no weak ferromagnetism.     

Statistical analysis of compression strength of single grains of SHM powders and improvement of the strength assessment procedure

A new approach to strength assessment of diamond powders has been proposed. It is based on the statistical theory of extremes and provides the small-sampling prediction of strength properties. A comparative statistical analysis of several powder batches has been performed. The strength of grains is shown to be satisfactorily approximated by a Weibull distribution rule over the entire range of grain sizes and grades considered. The relation between the Weibull parameters and the average strength has been studied. The convergence of empirical statistics is investigated and the criterion of sufficiency of a sample size for the assessment of average compression strength of diamond grains is stated. The authors have found the possibility to reduce the number of tests, thus significantly shortening the testing duration and minimizing the anvil wear, which results in lower investigations costs. These findings provide a theoretical basis for improving the existing methods of quality inspection of SHM powders and elaborating new methods.     

Effect of dexamethasone on IL-2 and IL-3 production by mononuclear cells in neonates and adults

The effect of dexamethasone on interleukin 2 (IL-2) and interleukin 3 (IL-3) production by mononuclear cells in preterm and term infants and adults was evaluated. The capacity of mononuclear cells to produce these cytokines, in preterm infants with bronchopulmonary dysplasia (BPD) and treated with dexamethasone, was compared with that before treatment. Twenty six preterm and 36 term neonates and 24 healthy adults were included in the study. Mononuclear cells isolated from neonatal cord blood (CBMC) and adult peripheral blood (PBMC) were stimulated with phytohaemagglutinin (PHA) in the absence or presence of dexamethasone at concentrations between 10(-8)M and 10(-5)M. IL-2 and IL-3 activities in the supernatant fluids were tested using bioassays. The in vivo effect of the drug on the production of these cytokines by PBMC in 10 preterms was determined before and 24 hours after dexamethasone administration (0.5 mg/kg/day). The production of both cytokines was inhibited in a dose dependent manner. A difference in the sensitivity of mononuclear cells to the inhibitory effect of the drug was found between neonatal cord blood cells and adult PBMC, the former being more sensitive. PBMC from preterm infants treated with dexamethasone for BPD produced significantly less IL-2 and IL-3 as early as 24 hours after the initiation of the treatment (43% and 31%; P < 0.05, respectively). It is concluded that mononuclear cells from preterm and term neonates are more sensitive to the inhibitory effect of dexamethasone on IL-2 and IL-3 production.     

Case study: Use of covert self-instruction for the elimination of psychotic speech.

Reports the systematic application of a self-instructional treatment program for the elimination of psychotic speech in a hospitalized 47-yr-old single male schizophrenic. Marked improvement of verbal behavior resulted in the patient's being discharged, and at 6-mo follow-up he was employed part-time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Voluntary control of human heart rate: Effect on reaction to aversive stimulation: A replication and extension.

In anticipation of receiving painful stimuli, 20 female Ss learned to regulate their heart rate (HR) when provided with meter biofeedback and monetary bonuses for HR changes and instructions to increase or decrease their rate. Voluntary slowing of HR was associated with a relative reduction in perceived aversiveness of the stimuli, particularly in those Ss who scored high on a cardiac-awareness questionnaire (i.e., reported experiencing cardiac reactions to fear situations in daily life). These fingings replicate and extend previous findings by the authors (see record 1974-31631-001) on HR self-regulation, perception of aversive stimulation, and individual differences in cardiac awareness. They also provide further support for the hypothesis that biofeedback training for relevant physiological responses may serve as a behavioral strategy for changing anxiety and fear reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phase transformation and dehydration of calcium sulphate dihydrate in solution studied by SEM

The transformation of separate crystals of CaSO₄·2H₂O (DH) into CaSO₄·O.5H₂O (HH) in an aqueous solution of H₃PO₄ and H₂SO₄ at 90–97°C was studied using a JSM-35CF SEM. The source DH and acids were reagent or commercial (taken from the production of H₃PO₄ by a wet process). DH was allowed to convert into HH and periodic samples of the suspension were drawn, filtered, and investigated in the solid phase by SEM. It was shown that the dehydration of reagent DH specimens occurred through the recrystallization mechanism, whereas the transformation of commercial DH into HH was basically topochemical and developed by a relay race mechanism without any phase transformation front. The observed difference between commercial and reagent DH specimens may be explained by differences in their crystalline structure, initial particle size and by the presence of impurities in DH and acids. It is established that chemical impurities can change the mechanism of the phase transformation of the crystals DH into HH.