Prolonged antibacterial action of synthetic suture materials containing gentamicin]

A new sutural material in the form of polyacrylamide threads containing gentamicin in an amount of 10 per cent by the thread weight was studied. After storage for a year under refrigerator conditions the threads preserved their antibacterial activity when studied in vitro. Since gentamicin was included within the threads by means of the ionic links its release from the threads to the environment either in vitro or in vivo was gradual and uniform within at least 10 days. The quantity of the released antibiotic depended on its content per unit of thread length. The marked antibacterial effect within the prolonged period is a basis for the use of the threads in surgical practice for the prevention of infections in the early postoperative period.     

Prolonged action of tuftsin in penicillin epilepsy]

The free behaviour experiments on rats showed during the first day the tuftsin-induced (0.3 mg/kg i. p.) increment of epileptic discharge in all the structures simultaneously. Open field behaviour depended on the sequence of penicillin and tuftsin injections. The rats with tuftsin used after the epileptiformic activity has been developed showed the behaviour analogical to the penicillin-injected animals. The preventive injections of tuftsin resulted in restoration of all behavioural indications by the third day. The optimal corrective effect has been obtained with tuftsin used preventively.     

Mechanisms of action of antibacterial biocides

Antibacterial biocides are represented by a wide range of chemical agents. This chemical diversity offers a multiplicity of potentially damaging interactions with the bacterial cell. Only rarely, however, are these interactions non-specific in nature; more frequently, the morphology and physiology of the cell, when combined with the physicochemical properties of the biocide, will dictate specific targets or target regions. A knowledge and understanding of these lesions offers a powerful tool in the search for novel chemistries and improved biocidal capabilities.     

Prolonged action potentials from single nodes of Ranvier

The duration of action potentials from single nodes of Ranvier can be increased by several methods. Extraction of water from the node (e.g. by 2 to 3 M glycerin) causes increased durations up to 1000 msec. 1 to 5 min. after application of the glycerin the duration of the action potential again decreases to the normal value. Another type of prolonged action potential can be observed in solutions which contain K or Rb ions at concentrations between 50 mM and 2 M. The nodes respond only if the resting potential is restored by anodal current. The kinetics of these action potentials is slightly different. Their maximal durations are longer (up to 10 sec.). Like the normal action potential, they are initiated by cathodal make or anodal break. They also occur in external solutions which contain no sodium. The same type of action potentials as in KCl is found when the node is depolarized for some time (15 to 90 sec., 100 to 200 mv.) and is then stimulated by cathodal current. These action potentials require no K or Na ions in the external medium. Their maximal duration increases with the strength and duration of the preceding depolarization. The possible origin of the action potentials in KCl and after depolarization, and their relation to the normal action potentials and the negative after-potential are discussed.     

V型羊毛硫肽雷可肽的抑菌机制

[背景]雷可肽(Lexapeptide)为首例V型羊毛硫肽家族化合物,具有较好的抗革兰氏阳性菌活性,对耐甲氧西林金黄色葡萄球菌(Methicillin-Resistant Staphylococcus aureus,MRSA)和表皮葡萄球菌(Methicillin-Resistant Staphylococcus ep...     

Mode of antibacterial action by gramicidin S

To elucidate the mode of antibacterial action by gramicidin S (GS), a detailed experiment on GS distribution on bacteria cells was carried out. 14C-Labeled gramicidin S ([14C]GS) was incubated with cells of Gram-positive Bacillus subtilis and Gram-negative Escherichia coli, and the amount of [14C]GS adsorbed on the cells was measured. Adsorption on B. subtilis cells was observed from 1 microgram/ml of [14C]GS. As the concentration of [14C]GS increased, the amount adsorbed on B. subtilis increased discontinuously, producing a curve which had three plateaus. On the other hand, [14C]GS was not easily adsorbed on E. coli cells at lower concentrations, but the amount adsorbed increased above 6 micrograms/ml, and the cells were temporarily saturated with GS at 10 micrograms/ml, which is the minimum inhibitory concentration for E. coli. The amount of [14C]GS adsorbed on the protoplast membrane of B. subtilis was the same as that of natural cells. However, the amount of [14C]GS adsorbed on the cell wall dropped to about 20% of that of natural bacteria. These facts indicate that GS is adsorbed on the cell membrane of bacteria particularly. The uptake of amino acid or glucose in B. subtilis was inhibited by GS. Therefore, it is concluded that GS damages the phospholipid bilayer of the cell membrane by adsorption, and prevents the functioning of the cell membrane. The amount of [14C]GS adsorbed on the spheroplast membrane of E. coli increased remarkably as compared with natural cells, even at a lower concentration of GS. The poor GS adsorption on E. coli cells may be due to the permeability barrier of the E. coli cell wall.