Kv4 Channels Underlie the Subthreshold-Operating A-type K+-current in Nociceptive Dorsal Root Ganglion Neurons

The dorsal root ganglion (DRG) contains heterogeneous populations of sensory neurons including primary nociceptive neurons and C-fibers implicated in pain signaling. Recent studies have demonstrated DRG hyperexcitability associated with downregulation of A-type K+ channels; however, the molecular correlate of the corresponding A-type K+ current (IA) has remained hypothetical. Kv4 channels may underlie the IA in DRG neurons. We combined electrophysiology, molecular biology (Whole-Tissue and Single-Cell RT-PCR) and immunohistochemistry to investigate the molecular basis of the IA in acutely dissociated DRG neurons from 7- to 8-day-old rats. Whole-cell recordings demonstrate a robust tetraethylammonium-resistant (20 mM) and 4-aminopyridine-sensitive (5 mM) IA. Matching Kv4 channel properties, activation and inactivation of this IA occur in the subthreshold range of membrane potentials and the rate of recovery from inactivation is rapid and voltage-dependent. Among Kv4 transcripts, the DRG expresses significant levels of Kv4.1 and Kv4.3 mRNAs. Also, single small-medium diameter DRG neurons (∼30 μm) exhibit correlated frequent expression of mRNAs encoding Kv4.1 and Nav1.8, a known nociceptor marker. In contrast, the expressions of Kv1.4 and Kv4.2 mRNAs at the whole-tissue and single-cell levels are relatively low and infrequent. Kv4 protein expression in nociceptive DRG neurons was confirmed by immunohistochemistry, which demonstrates colocalization of Kv4.3 and Nav1.8, and negligible expression of Kv4.2. Furthermore, specific dominant-negative suppression and overexpression strategies confirmed the contribution of Kv4 channels to IA in DRG neurons. Contrasting the expression patterns of Kv4 channels in the central and peripheral nervous systems, we discuss possible functional roles of these channels in primary sensory neurons

Understanding EFL Students’ Errors in Writing

Writing is the most difficult skill in English, so most EFL students tend to make errors in writing. In assisting the learners to sucessfully acquire writing skill,  the analysis of errors and the understanding of their sources are neccessary. This study attempts to explore the major sources of errors occurred in the writing of EFL students. It also investigates the types of errors and the linguistic level that presents the most errors in their writing. Forty narrative essays composed by Thai university students were collected and analysed.  Results showed that the mostly frequent types of errors were translated words from Thai, word choice, verb tense, preposition, and comma. The errors derived from two sources: interlingual and intralingual.  Interlingual or native language interference was found to be the dominant source of errors. This study provides pedagogical implications for EFL instructors. Instructors should pay attention to the influence of learners’ native language. Keywords: errors, error analysis, interlingual, intralingual, writing, English as a foreign languag

BIOLOGICAL ACTIVITY OF ß-GLUCANS FROM EDIBLE MUSHROOM, SCHIZOPHYLLUM COMMUNE IN THAILAND

Objective: The objective of this research was to determine the antioxidant of ß-glucans from an edible mushroom, Schizophyllum commune in Thailand.Methods: The antioxidant activity of ß-glucans was measured in terms of hydrogen donating or radical scavenging ability by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method,2,2´-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity analysis, and total phenoliccompounds. The ß-glucans structure was analyzed using Fourier-transform infrared spectrophotometer.Results: The ß-glucans were extracted from S. commune and tested biological activities. Using the Folin–Ciocalteu Reactive method, we found thatthe phenolic compound contents of ethanol extracts of the mushroom sample were 284.41±1.22 mgGAE/g extract. The IC50 radical scavenging ability(DPPH) and IC50 radical scavenging activity (ABTS) of ß-glucans were 0.829±0.006 and 0.724±0.021 mg/mL, respectively.Conclusion: The ß-glucans from S. commune in Thailand showed a potent antioxidant activity and it will be able to apply in pharmaceutical cosmetics

Expression of Kv4 channels in dorsal root ganglion neurons: Major determinants of the A-type potassium current

The dorsal root ganglion (DRG) contains a heterogeneous population of sensory neurons which include primary nociceptive neurons and the C-fibers implicated in pain signaling. Recent studies have demonstrated DRG neuron hyperexcitability associated with a reduction in the A-type potassium current (IA); however, the molecular identity of the underlying voltage gated potassium (Kv) channels has remained unknown. Kv channels that underlie the somatodendritic A-type current (ISA) in the central nervous system may also underlie the IA in DRG neurons. Patch-clamp electrophysiology, molecular genetics (RT-PCR) and immunohistochemistry were applied to investigate the molecular composition of the IA in acutely dissociated DRG neurons from 7-8 day-old rats. Whole-cell recordings demonstrated a TEA-resistant (20 mM) IA current that is inhibited by 4-aminopyridine (5 mM). Consistent with the presence of Kv4 channel complexes, the midpoint voltages of the activation and steady-state inactivation curves are relatively hyperpolarized and the rate of recovery from inactivation is rapid and voltage dependent. At the whole-tissue and single-cell levels, Kv4.1 mRNA is the predominant Kv4 channel transcript in DRG neurons; and Kv4.1 positive neurons were associated with Nav1.8 mRNA expression, a typical DRG nociceptive marker. Kv4 protein expression was confirmed by immunohistochemistry, which revealed heavy anti-Kv4.1 staining in populations of small neurons. Furthermore, the role of Kv4 channels in DRG neuron excitibility was demonstrated in over- and knock-down expression experiments utilizing Kv4.2-WT and Kv4.2-W362F constructs, respectively. In conclusion, Kv4.1 channels are major determinants of the IA in DRG neurons and play a major role in regulating electrical excitibility resulting from nociceptive stimuli

Prevalence of Antibiotic-resistant Salmonella in Vegetables and Fermented Foods and their Control by Lactic Acid Bacteria

Salmonella is the leading cause of foodborne disease and a public health concern. In this study, food samples were collected from fresh markets within northeastern Thailand. Antibiotic-resistant Salmonella were detected in fresh vegetables and fermented meat products. Of 172 collected food samples, 25 (14.53%) were contaminated with Salmonella resistant to at least 1 of 9 antibiotics. Eight strains of 7 serovars, including S. Derby, S. Paratyphi B, S. Stanley, S. Dabou, S. Rissen, S. Hvittingfoss, and S. Brenderup, were resistant to S, TE, CN, SXT, and NA, accounting for 20%, 16%, 12%, 12%, and 12% of all antibiotics, respectively. To determine the anti-Salmonella activity of lactic acid bacteria, Pediococcus pentosaceus PS34 isolated from fermented fish was selected from 5 strains of food-derived lactic acid bacteria according to the antibacterial and acid-resistance properties. When added to 3 log CFU/ml cultures of Salmonella, the PS34 cell-free supernatant (CFS) reduced the numbers of Salmonella after 1, 15, 30, and 60 minutes of incubation; the reduction reached 99.9% within 30 minutes. The minimal arbitrary inhibition concentration of freeze-dried PS34 CFS was a 1:4 dilution. With the exception of neutralization to pH 6.5, treatment with proteolytic enzymes and heating at 100°C and 120°C did not reduce the freeze-dried PS34 CFS anti-Salmonella activity, indicating that the extracellular PS34 bioactive substances were heat stable and highly effective against Salmonella in vitro. Thus, bioactive substances produced by P. pentosaceus PS34 have the potential to reduce the risk of antibiotic-resistant Salmonella from contaminated food reaching consumers

Advances in computing science--ASIAN '99 : 5th Asian Computing Science Conference, Phuket, Thailand, December 10-12, 1999 : proceedings

xi, 395 p. : ill. ; 24 cm