Effect of Voluntary Contraction in Motor Evoked Potential and Silent Period by Transcranial Magnetic Stimulation

OBJECTIVE: To determine the effects of the voluntary contraction of muscles and magnetic stimulation intensity on the motor evoked potential (MEP) and the silent period (SP). METHOD: We studied MEPs and SPs in opponens pollicis muscle in 30 healthy adults (male: 16, female: 14) while varying the amount of the voluntary contraction and the stimulation intensity. We analyzed MEPs and SPs in relation to sex, recording site, opposition power and height. RESULTS: 1) During the contraction, the latencies of MEP were significantly shorter than during the relaxation. 2) The amplitudes of MEP reached plateau at 30% of maximal voluntary contraction and increased with increment of stimulation intensity without limitation. The amplitudes of MEP of right hand were bigger than left hand. There were no significant differences according to sex and recording site. 3) The durations of SP were directly proportional to the degrees of voluntary contraction and the stimulation intensity. CONCLUSION: Transcranial magnetic stimulation should be performed under the same voluntary contraction and magnetic stimulation intensity.

Development of a Mycobacterial Gene Knock-out System using Sequence-specific Recombinase FLP/FRT and its Application to the Construction of a Rhamnose Biosynthetic Gene rmlD Deletion Mutant

Development of a new and effecient tuberculosis vaccine is very important since the efficacy of the only available vaccine against tuberculosis, BCG, is variable among races and different ages. Attempts to develop attenuated vaccines by disrupting virulence gene(s) specifically in Mycobacterium tuberculosis are now actively being tried after the release of whole genome sequence of M. tuberculosis in 1998. However, disruption of specific genes in M. tuberculosis is still very difficult due to the lack of effective gene knock-out system(s) in mycobacteria. In this study, we developed a novel method to delete specific genes in both Escherichia coli and mycobacteria. This knock-out system is operated by a sequence-specific recombinase FLP and its recognition sequence FRT (FLP/FRT system). Two shuttle vectors (an FLP expressing vector and a gene targeting vector) between Escherichia coli and Mycobacteria were developed. The gene targeting vector contains a kanamycin resistance gene (KmR) flanked by two neighboring genes and two FRTs (FLPrecognition targets). We applied this system to knock-out the rhamnose biosynthetic gene rmlD of Escherichia coli. The upstream and downstream genes of rmlD, rmlB and rmlA, were cloned into the gene targeting vector. After and allelic exchange of E. coli chromosomal rmlB, rmlD, rmlA with vectoral rmlB, FRT-KmR-FRT, rmlA by homologous recombination, FLP-expressing plasmid was introduced to induce the excision of KmR cassette remaining one FRT sequence between rmlB and rmlA. We also demonstrated our shuttle vector could disrupt a target gene (kanamycin resistance gene) in M. smegmatis. These results suggest that our gene knock-out system can be used for the development of an attenuated tuberculosis vaccines and for the functional genomic study of mycobacteria.

Expression of Brain-Derived Neurotrophic Factor and its mRNA in Catecholaminergic Neurons of the Rat Lower Brainstem after Colohicine Treatment or Hemorrhage / 대한해부학회지

Widespread brain-derived neurotrophic factor (BDNF) mRNA expression has been detected in the region of catecholamine groups of the rat lower brainstem, while few BDNF-immunoreactive cells were found in this area. In the present study, a double-color immunofluorescence (IF) technique for BDNF and tyrosine hydroxylase (TH) after colchicine treatment was employed to evaluate the possible presence of BDNF immunoreactivity in the catecholamin-ergic cells of rat lower brainstem. Additionally, a double-color IF technique for BNDF and TH and in situ hybridiza-tion for BDNF mRNA were performed to see effects of hemorrhage on the expression of BDNF and its mRNA. We detected many new BDNF-immunoreactive cells in the A1, A2, A4, A6-A10 and C1-C3 cell groups and in the other lower brainstem nuclei where, without colchicine treatment, BDNF mRNA was expressed, but not BDNF immunoreactivity. In addition, the catecholaminergic neurons were found to express BDNF immunoreactivity with the co-existence being greatest, in percentage terms, in medullary catecholaminergic cell groups. Hypotensive hemorrhage, which activates medullary catecholaminergic neurons, induced the expression of BDNF immunoreactivity in catecholaminergic neurons (A1/C1 and C2) and increased the number of BDNF mRNA-containing neurons in the area. These results demonstrate that BDNF is regulated by activity in medullary catecholaminergic cell groups involved in central cardiovascular regulation.

Effects of Peripheral Inflammation on Brain-Derived Neurotrophic Factor and TrkB in Rat Dorsal Root Ganglia and Spinal Cord / 대한해부학회지

Recent study showed that peripheral inflammation induced an increased expression of brain-derived neurotrophic factor (BDNF) mRNA which was mediated by nerve growth factor in the dorsal root ganglion (DRG). Therefore, it is conceivable that peripheral inflammation may induce an increase in BDNF synthesis in DRG and consequently enhance the level of BDNF in the spinal cord and that gene expression of trkB mRNA may be altered. In the present study, we evaluated changes in BDNF-immunoreactivity and trkB mRNA in the DRG and spinal cord by means of immunohis-tochemistry and RT-PCR, respectively, following peripheral tissue inflammation produced by intraplantar injection of Freund's adjuvant into rat paws. In addition, coexistence of BDNF and preprotachykinin (PTT) mRNAs, BDNF and CGRP mRNAs or BDNF and trkB mRNAs in the DRG following inflammation was observed by means of in situ hybridization. The results obtained were as follows; 1. Inflammation induced a significant increase of the number of BDNF-immunoreactive (IR) neurons in the ipsilateral DRGs. The increase was observed 1 and 3 days after injection of adjuvant, and the levels had returned to normal by 7 days. In the spinal cord, inflammation also induced an elevation in the expression of BDNF-IR terminals in the medial superficial layers of the ipsilateral dorsal horn and in lamina V 1 and 3 days after injection. 2. There was significant increase of truncated trkB (t-trkB) mRNA in the ipsilateral DRG 3 days following inflammation. Changes in the expression of trkB mRNA in the DRG or trkB and t-trkB mRNAs in the spinal cord were not observed. 3. Many neurons showed increased coexistence of BDNF and PTT mRNAs or BDNF and CGRP mRNAs in the DRG following inflammation. 4. Few neurons showed coexistence of BDNF and trkB mRNAs in the DRG following inflammation. The results suggest a paracrine function for BDNF within the DRG in addition to an important role related with nociception following peripheral inflammation.

Change in the Synthesis of Brain-Derived Neurotrophic Factor in the Dorsal Root Ganglion Following Peripheral Inflammation / 대한해부학회지

It is well known that nerve growth factor (NGF) may serve as a link between inflammation and hyperalgesia. However, there is little information whether brain-derived neurotrophic factor (BDNF), another family of neurotrophin, may related with nociception. In the present study, in situ hybridization was used to evaluate i) the change in the level of BDNF mRNA, ii) colocalization of the trkA mRNA and BDNFmRNA and iii) colocalization of the preprotachykinin (PTT)mRNA and BDNFmRNA following peripheral inflammation produced by an intraplantar injection of Freund's adjuvant into the rat paws. The results obtained were as follows: 1. Peripheral tissue inflammation significantly increased BDNFmRNA levels in the DRG. 2. Many neurons expressing trkAmRNA showed increased expression of BDNFmRNA following peripheral inflammation. 3. Many neurons expressing PTT mRNA showed increased expression of BDNFmRNA following peripheral inflammation. 4. Intraplantar injection of antibody to NGF together with Freund's adjuvant prevent the increase in BDNFmRNA. The present results indicate that the peripheral inflammation induces an increased synthesis of BDNF which is mediated by NGF and BDNF coexist with substance P in the DRG and that BDNF may play an important role related with nociception.