Involvement of microtubule-associated protein 2 (MAP2) in oral cancer cell motility: a novel biological function of MAP2 in non-neuronal cells

Microtubule-associated protein 2 (MAP2) has been better known for its well-defined role primarily in neurite outgrowth during neuronal development. However, the biological functions of MAP2 in non-neuronal cells, such as epithelial cells, remain largely unknown. In the present study, we sought to investigate the cellular functions of MAP2 by separately establishing stable expression of two MAP2 isoforms, MAP2A and MAP2C, in oral squamous cell carcinoma, Ca9-22. Ectopic expression of MAP2A or MAP2C results in microtubule bundling predominantly at the cell periphery. Remarkably, overexpression of MAP2A but not MAP2C significantly promotes migration of Ca9-22 cells, whereas knockdown of MAP2A expression by specific siRNA oligos dramatically decreases cell migration of HaCaT, an immortalized keratinocyte cell line with abundant endogenous MAP2A. Furthermore, by immunohistochemical studies, MAP2A was shown to highly and selectively express in invasive oral cancer tissues, consistent with its motility-promoting cellular function revealed through in vitro assays. Thus, our findings have not only identified a novel role of MAP2 in non-neuronal cells, but also provided the first implication of MAP2 in malignant oral cancer tissues.     

Identification of further elongation and branching of dimeric type 1 chain on lactosylceramides from colonic adenocarcinoma by tandem mass spectrometry sequencing analyses

Mammalian glycan chain elongation is mostly based on extending the type 2 chain, Galbeta1-4GlcNAc, whereas the corresponding type 1 chain, Galbeta1-3GlcNAc, is not normally extended. In a broader context of developing high sensitivity mass spectrometry methodologies for glycomic identification of Le(a) versus Le(x) and linear versus branched poly-N-acetyllactosamine (polyLacNAc), we have now shown that the dimeric type 1 glycan chain, as carried on the lactosylceramides of a human colonic adenocarcinoma cell line, Colo205, not only can be further extended linearly but can likewise be branched at C6 of 3-linked Gal in a manner similar to polyLacNAc. A combination of chemical and enzymatic derivatization coupled with advanced mass spectrometry analyses afforded unambiguous identification of a complex mixture of type 1 and 2 hybrids as well as those fucosylated variants founded exclusively on linear and branched trimeric type 1 chain. We further showed by in vitro enzymatic synthesis that extended type 1 and the hybrid chains can be branched by all three forms of the human I branching enzymes (IGnT) currently identified but with lower efficiency and stringency with respect to branching site preference. Importantly, it was found that a better substrate is one that carries a Gal site for branching that is extended at the non-reducing end by a type 2 and not a type 1 unit, whereas the IGnTs are less discriminative with respect to whether the targeted Gal site is itself beta3- or beta4-linked to GlcNAc at the reducing end.     

雪霸公园雪山主峰线之承载量研究

本研究之目的在于取得雪山主峰线登山步道最适承载量计量值,以供雪霸公园管理处日后进行承载量管理之参考。研究结果表明,就社会心理承载量而言,登山者对于同时进行登山活动者的承载程度为11-40人或甚至可以更多;实质的设施承载量则依据雪山主峰线目前现况设施可容纳的最大登山人数为296人;每日最大实质生态承载量于平常日为109人,公休日以不超过218人为宜。稀有生物繁殖期最好禁止登山者入山,若无可避免时,每日以不超过65人为宜。本研究建议后继研究应进行长期游憩冲击所带来的环境影响程度的监测,每三年或五年再检查一次生态资料的变化,或有稀有动、植物的消长,配合长期游憩冲击监测指标,以适时修正承载量管制的人数,适度地调整登山人数。     

Pre- and postsynaptic effects of nicotine on the mouse phrenic nerve-diaphragm preparation

Nicotine at less than or equal to 33 microM enhanced the single twitch response to indirect stimulation but potentiated the blocking effect of tubocurarine. Failure of tetanic contraction (tetanic fade) occurred on stimulation at 100 Hz. At 76 microM, nicotine induced a first phase rapid (10 min) inhibition of twitch response followed later (60-90 min) by a second phase complete block. Neostigmine partially restored the response at either phase of block whereas diaminopyridine completely antagonized the blockade. The end-plate was depolarized maximally by only 10-15 mV within 30 min with 43 microM nicotine. The depolarization was maintained but was antagonized by tubocurarine. The twitch response induced by direct stimulation was unchanged indicating no depolarization block ensued. The amplitudes of both EPP (0.7 Hz) and MEPP were markedly depressed in parallel indicating a curare-like postsynaptic inhibition without an effect on the release of transmitter. It is concluded that nicotine blocks the neuromuscular transmission by a dual mechanism by its partial agonist action. At higher frequencies of transmission, nicotine (greater than or equal to 22 microM) also produced a remarkable run-down of EPP just like other receptor antagonists suggesting that the nerve terminal acetylcholine receptors are not particularly sensitive to nicotine as those on the autonomic ganglia.     

Molecular evolution of snake venom toxins

Summary Phylogenetic trees were constructed for 62 venom toxins of snakes ofProteroglyphae suborder using matrix method. The resulting tree fromMinimum Spanning Tree-Cluster Analysis technique had the lowest percent deviation (8.55). The taxonomic relationship of these toxins agrees very well with zoological opinions. However, the appearance of the tree did not directly provide a plausible evolutionary model for the toxins. A model was derived from nodal ancestral sequence calculations, comparisons between intra-and inter-generical rates of amino acid change, and generally held ideas about protein evolution. According to the model, short neurotoxin is the ancient form of snake venom toxins. The courses of evolution leading to the present intraspecific homologous toxins are explained by gene duplication and allelomorphism.     

Induction of contracture and extracellular Ca<Superscript>2+</Superscript> influx in cardiac muscle by sanguinarine: a study on cardiotoxicity of sanguinarine

Summary In this study, the toxic effect of sanguinarine (SANG) on heart was studied with isolated cardiac muscle strip isolated from Wistar rat. SANG induced positive inotropic action followed by contracture on the left ventricle and both atria strips. In addition, SANG dose-dependently inhibited spontaneous beat of the right atrium. SANG-induced contracture was completely suppressed by pretreatment with La³⁺ or in a Ca²⁺ free Tyrode solution containing 2.5 mM EGTA. Incubating isolated cardiomyocytes with SANG enhanced the ⁴⁵Ca²⁺ influx, which could be inhibited by pretreatment with La³⁺. However, the SANG-induced ⁴⁵Ca²⁺ influx could not be inhibited by pretreatment with other Ca²⁺ channel blockers, such as nifedipine, verapamil, diltiazem, nickel and manganese, and amiloride. Although antioxidants can inhibit the SANG-induced lipid peroxidation, they could not prevent the SANG-induced contracture. N-acetylcysteine and dithiothreitol, the sulfhydryl reducing agents, were shown to be effective in preventing the SANG-induced contracture. These data suggested that the SANG-induced contracture is caused by the influx of extracellular Ca²⁺ through a La³⁺-sensitive Ca²⁺ channel.     

Brain asymmetry: switching from left to right

The relationship between structural and functional asymmetries in the brain remains unclear. A recent report describes a zebrafish mutant that provides us with some enticing clues about this relationship.     

Corticospinal Excitability of Trunk Muscles during Different Postural Tasks

Evidence suggests that the primary motor cortex (M1) is involved in both voluntary, goal-directed movements and in postural control. Trunk muscles are involved in both tasks, however, the extent to which M1 controls these muscles in trunk flexion/extension (voluntary movement) and in rapid shoulder flexion (postural control) remains unclear. The purpose of this study was to investigate this question by examining excitability of corticospinal inputs to trunk muscles during voluntary and postural tasks. Twenty healthy adults participated. Transcranial magnetic stimulation was delivered to the M1 to examine motor evoked potentials (MEPs) in the trunk muscles (erector spinae (ES) and rectus abdominis (RA)) during dynamic shoulder flexion (DSF), static shoulder flexion (SSF), and static trunk extension (STE). The level of background muscle activity in the ES muscles was matched across tasks. MEP amplitudes in ES were significantly larger in DSF than in SSF or in STE; however, this was not observed for RA. Further, there were no differences in levels of muscle activity in RA between tasks. Our findings reveal that corticospinal excitability of the ES muscles appears greater during dynamic anticipatory posture-related adjustments than during static tasks requiring postural (SSF) and goal-directed voluntary (STE) activity. These results suggest that task-oriented rehabilitation of trunk muscles should be considered for optimal transfer of therapeutic effect to function.