• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.759-764
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• 2015

Antimicrobial peptides (AMPs) are one of the critical components in host innate immune responses to imbalanced and invading microbial pathogens. Although the antimicrobial activity and mechanism of action have been thoroughly investigated for decades, the exact biological properties of AMPs are still elusive. Most AMPs generally exert the antimicrobial effect by targeting the microbial membrane, such as barrel stave, toroidal, and carpet mechanisms. Thus, the mode of action in model membranes and the discrimination of AMPs to discrepant lipid compositions between mammalian cells and microbial pathogens (cell selectivity) have been studied intensively. However, the latest reports suggest that not only AMPs recently isolated but also well-known membrane-disruptive AMPs play a role in intracellular killing, such as apoptosis induction. In this mini-review, we will review some representative AMPs and their antimicrobial mechanisms and provide new insights into the dual mechanism of AMPs.

• Smart Structures and Systems
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• v.14 no.2
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• pp.71-83
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• 2014

The purpose of this paper is to investigate the flexible structure of parabolic shell using photostrictive actuators. The analysis is made to know its dynamic behavior and light-induced control forces for coupled parabolic shell. The effects of an actuator location as well as membrane and bending components under the control action have been analyzed considering the approximate spherical model. The parabolic membrane shell accuracy is being mathematically approximated and validated comparing the light induced control forces using approximate equivalent spherical shell model. The parabolic shell with kapton smart material and photostrictive actuators has been used to formulate the governing equation in the transverse direction. The Kirchhoff-Love assumptions are used to obtain the governing equation of shell with actuator. The mechanical membrane forces and bending moments for parabolic thin shell with actuator is used to analyze the dynamic effect. The results show that membrane control action is much more significant than bending control action. Photostrictive actuators oriented along circumferential direction (actuator-2) can give better control effect than actuators placed along longitudinal direction (actuator-1). The slight difference is observed between spherical and parabolic shell for a surface with focal length to the diameter ratio of 1.00 or more than unity. Space applications often have the shape of parabolical shells or shell of revolution, due to their required focusing, aiming, or reflecting performance. The present approach is focused that photostrictive actuators can effectively control the vibration of parabolical membrane shell. Also, the actuator's location plays an important role in defining the control force.

• The Korean Journal of Physiology
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• v.10 no.1
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• pp.1-5
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• 1976

The trypanocidal drug suramin, an impermeant polyanion, has been shown to be a powerful inhibitor of the calcium uptake and calcium-stimulated ATPase activity of sarcoplasmic reticulum (Fortes et al., 1974). In view of this finding, an attempt was made to investigate the effect of suramin on $Ca^{++}$ transport in resealed red cells and on $Ca^{++}$-activated ATPase in red blood cell membrane fragments (RBCMF). The results obtained are summarized as follows. 1. $Ca^{++}$ outflux from the resealed RBC was inhibited by suramin and the inhibitory action of suramin is proportional to the concentration of drug added inside the RBC preparation. When suramin is added both inside and outside the RBC preparation simultaneously, the magnitude of the inhibitory effect was more pronounced, suggesting that suramin inhibits both active $Ca^{++}-^{45}Ca$ exchange diffusion across the RBC membrane. 2. Suramin inhibits the $Ca^{++}$-activated ATPase of the RBCMF and the effect of inhibition by the drug was also concentration dependent. From the above results, it may be concluded that suramin inhibits $Ca^{++}$ transport across RBC membrane by inhibiting $Ca^{++}$-activated ATPase activity which has been known to be linked with active $Ca^{++}$ transport.

• Molecules and Cells
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• v.28 no.5
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• pp.473-477
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• 2009

Previously, the 9-mer analog peptides, 9Pbw2 and 9Pbw4, were designed based on a defensin-like peptide, protaetiamycine isolated from Protaetia brevitarsis. In this study, antifungal effects of the analog peptides were investigated. The antifungal susceptibility testing exhibited that 9Pbw4 contained more potent antifungal activities than 9Pbw2. A PI influx assay confirmed the effects of the analog peptides and demonstrated that the peptides exerted their activity by a membrane-active mechanism, in an energy-independent manner. As the noteworthy potency of 9Pbw4, the mechanism(s) of 9Pbw4 were further investigated. The membrane studies, using rhodamine-labeled giant unilamellar vesicle (GUV) and fluorescein isothiocyanate (FITC)-dextran loaded liposome, suggested that the membrane-active mechanism of 9Pbw4 could have originated from the pore-forming action and the radii of pores was presumed to be anywhere from 1.8 nm to 3.3 nm. These results were confirmed by 3D-flow cytometric contour-plot analysis. The present study suggests a potential of 9Pbw4 as a novel antifungal peptide.

• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1457-1466
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• 2012

Antimicrobial peptides (AMPs) exert antimicrobial activity against Gram-positive and Gram-negative bacteria, fungi, and viruses by various mechanisms. AMPs commonly possess particular characteristics by harboring cationic and amphipathic structures and binding to cell membranes, resulting in the leakage of essential cell contents by forming pores or disturbing lipid organization. These membrane disruptive mechanisms of AMPs are possible to explain according to the various structure forming pores in the membrane. Some AMPs inhibit DNA and/or RNA synthesis as well as apoptosis induction by reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. Specifically, mitochondria play a major role in the apoptotic pathway. During apoptosis induced by AMPs, cells undergo cytochrome c release, caspase activation, phosphatidylserine externalization, plasma or mitochondrial membrane depolarization, DNA and nuclei damage, cell shrinkage, apoptotic body formation, and membrane blebbing. Even AMPs, which have been reported to exert membrane-active mechanisms, induce apoptosis in yeast. These phenomena were also discovered in tumor cells treated with AMPs. The apoptosis mechanism of AMPs is available for various therapeutics such as antibiotics for antibiotic-resistant pathogens that resist to the membrane active mechanism, and antitumor agents with selectivity to tumor cells.

• Biomolecules & Therapeutics
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• v.18 no.4
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• pp.420-425
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• 2010

The antifungal effects and action mechanisms of styraxjaponoside A and B were investigated. Devoid of hemolytic effect, the compounds had significant effect against several human pathogenic fungal strains, with energy-independent manners. To understand the action mechanisms of the compounds, the flow cytometric analysis plotting the forward scatter and the side scatter, $DiBAC_4$(3) staining and DPH fluorescence analysis were conducted. The results indicated that the actions of the compounds were dependent upon the membrane-active mechanisms. The present study suggests that styraxjaponoside A and B exert their antimicrobial effects via membrane-disruptive mechanisms.

• Journal of Microbiology
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• v.35 no.4
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• pp.284-289
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• 1997

A Gram (-), rod-shaped bacterium $2.3{\sim}2.8{\times}0.45{\mu}m$ in size which exhibited growth-inhibiting effects against a cyanobacterium (Anabaena cylindrica) was isolated from Daechung Dam Reservoir. This isolate was identified as Moraxella sp. and designated Moracella sp. CK-1. Hollow zones formed around bacterial colonies on the cyanobacterial lawn. In a mixed-culture of A. cylindrica and the isolate, each microorganism grew inverse-proportionally, and the cyanobacterial vegetative cells completely disappeared within 24 hours. On treatment with Moraxella sp. CK-1, cell walls of A. cylindrica disappeared, but sheathes remained in a more electron dense form. The unit membrane such as thylakoidal membrane was stable to bacterial lysing activity. This bacterium showed a broad action spectrum against cyanobacteria. The growth-inhibiting activity of Moracella sp. CK-1 against A. cylindrica is believed to be performed through the excretion of active substances.

• The Korean Journal of Physiology
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• v.27 no.2
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• pp.123-138
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• 1993

The mechanism of insulin action to increase glucose transport is attributed to glucose transporter translocation from intracellular storage pools to the plasma membrane in insulin-sensitive cells. The present study was designed to visualize the redistribution of the glucose transporter by means of an immunogold labelling method. Our data clearly show that glucose transporter molecules were visible by this method. According to the method this distribution of glucose transporters between cell surface and intracellular pool was different in adipocytes. The glucose transporter molecules were randomly distributed at the cell surface whereas the molecules at LDM were farmed as clusters. By insulin treatment the number of homogeneous random particles increased at the cell surface whereas the cluster forms decreased at the intracellular storage pools. It suggests that the active molecules needed to be evenly distributed far effective function and that the inactive molecules in storage pools gathered and termed clusters until being transferred to the plasma membrane.

• The Korean Journal of Zoology
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• v.32 no.2
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• pp.153-162
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• 1989

Expedments were perfonned to examine the role of cAMP-dependent protein kinase (PK-A) and diacylglycerol-dependent protein kinase (PK-C) during the meiodc resumption and the first mitotic cell cycle of mouse embryogenesis. Mejoric GV oocytes and one-cell embryos derived from in vitro fertilization were cultured in vitro, and morphological changes in response to activators of PK-A and PK-C were examined. Treatments with a membrane-permeable cAMP analog, dbcAMP (0.1 mg/mi), phosphodiesterase inhibitor, IBMX (0.1 mM), biologically active phorbol ester, WA (10 nglmi), or a synthetic diacylglycerol, sn-diC8 inhibited resumption of melosis. Combination of PK-A and PK-C activator brought about furiher inhibition. On the contrary, dbcAMP (0.1 mg/mi), IBMX (0.2 mM), WA (10 nglml), and sn-diC8 (0.5 mM) did not inhibit pronucleus membrane breakdown (PNBD) when added S or G2 phase of cell cycle. However, activators of PK-C inhibited cleavage of one-cefl embryos. This result indicates that the action mechanism of PK-A and PK-C on dissolution of nuclear membrane in primary meiotic arrest oocytes may be different from that of mitotic one-cell embryos.

• The Korean Journal of Physiology
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• v.16 no.2
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• pp.119-128
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• 1982

The frog truncus arterious were studied with conventional glass microelectrode technique in order to elucidate the underlying mechanism of spontaneous pacemaker activity. The analyses were focussed on the ionic nature of pacemaker current by changing the concentrations of extracellular $K^+$ and, $Na^+$, or by using blockers of K- and Ca-current and chronotropic transmitters. 1) The action potential of the spontaneously active truncus arteriosus has some characteristic feature of maximal distolic potential ranged from -65 to -75 mV, resting potential from -45 to -50 mV and overshoot voltage about +30 mV, respectively. Duration of the action potential taken from rapid upstroke to maximal diastolic potential was about 600 msec. Usual discharge rate was $25{\sim}30/min$ at room temperature $(18{\sim}20^{\circ}C)$. 2) The sensitivity of the resting membrane potential to change extracellular potassium concentrations $(0{\sim}12\;mM)$ was relatively low. Transient hyperpolarization was appeared in the 12 mM K Ringer after 10 min exposure to 0 mM K and it could be related to Na-pump reactivation by high potassium. 3) Reduction of extracellular sodium concetrations diminished the amplitude and frequency of the action potential. In Ringer solution containing 30% Na (substituted by equimolar Tris), spontaneous activity stopped but reappeared as very slow and small action potential. There was no spotaneous activity in zero Na Ringer solution. 4) Caesium(10 mM), K-current blocker decreased the frequency of the action potential and also pacemaker depolarization. Manganese (2 mM) known to be Ca-current antagonist, blocked spontaneous activity completely. 5) Adrenaline and acetylcholine had no chronotropic effect. But adrenaline increased the duration of plateau phase and the magnitude of the action potential in the follower cell. It is concluded that K-, Na-and Ca-current components are involved in the genesis of spontaneous activity of the frog truncus arteriosus like cardiac pacemaker tissues. But the insensitivity of truncus arteriosus to adrenaline and acetylcholine indicates that there are some different control mechanisms of spontaneous rhythm in two tissues.