Synthesis and analysis of ethylated tetracycline, an antibiotic derivative that inhibits the growth of tetracycline-resistant XL1-Blue bacteria.

Bacterial resistance to antibiotics is a significant problem in medical care facilities, causing increased fatalities due to infection. The present study demonstrates that antibiotic structures can be selectively altered in a manner that revives their ability to inhibit bacterial growth. The antibiotic tetracycline was ethylated at the position of the phenolic hydroxy group with the use of diazoethane, forming an ethyl ether functional group. This derivative was dissolved in Luria-Bertani (LB) agar medium, then placed in tissue culture for screening against a tetracycline-resistant bacterial strain. The growth of this bacterial strain, designated XL1-Blue, was inhibited by the ethylated form of tetracycline. The procedure for synthesizing ethylated tetracycline utilizes diazoethane and is presented with the molecular structures and IR spectra. The ethylated form of tetracycline was stable at -20 degrees C for many weeks, and was soluble in LB agar plate medium. Ethylated tetracycline induced growth inhibition of XL1-Blue bacteria within the first 24 h of incubation. The level of bacterial growth inhibition was greater than 30%. Calculation of the partition coefficient, log P, was accomplished and indicates that ethylated tetracycline has an increased lipophilic tendency relative to unmodified tetracycline, and therefore has greater solubility in lipid bilayers.

Modified antibiotics-methylated ampicillin and ethylated ampicillin-inhibit growth of ampicillin-resistant strain of bacteria.

Bacterial resistance to antibiotics is a significant problem in health facilities and results in higher costs for health care and increased fatalities due to infection. The work presented here suggests that antibiotic molecular structure can be altered in a selected manner, which will revive the bacterial growth inhibiting capability. A bacterial strain PKK3535(DH1), which is resistant to the antibiotic ampicillin, was found to be highly growth inhibited by these altered forms of ampicillin when tested in tissue culture. The level of growth inhibition of bacterial strain PKK3535(DHI) was greater than 50%, for both molecular variants of ampicillin that were investigated. The bacteria strain used for testing was a clinical isolate obtained from the University Hospital of the University of Nebraska, Omaha. These two antibiotic variants were methylated ampicillin and ethylated ampicillin. The synthetic procedure for generating these variants is presented as well as the molecular structure. The methylated and ethylated ampicillin were found to be stable at 0 degrees C for many weeks, were somewhat less soluble than normal ampicillin, but dissolved in LB plate media. The resistant bacteria strain was plated onto LB media with altered ampicillin and profound inhibition of bacteria growth was seen within the first 24 hours of incubation. These molecular variants of ampicillin provide evidence of a means to combat the proliferation of resistant bacterial strains. The molecular alteration of antibiotics may provide a suitable means to study and combat the appearance of antibiotic-resistant bacteria.

[The detection of the sites of mediator release in a motor nerve ending]. / Vyiavlenie tochek osvobozhdeniia mediatora v dvigatel'noi nervnoi terminali.

A model of the postsynaptic current generation in response to a release of the quantum mediator from the nerve terminal is suggested. In its terms the law of the current density attenuation is determined as j = I/rb, where I is the current density in the site of generation, while j--current densities at the distance r from the site of generation. Experiments with extracellular recording have shown that coefficient b equals approximately 1. Assuming that sites of the quantum release and a site of the postsynaptic current generation are spatially identical, the new method is suggested to determine coordinates of the transmitter release sites in the motor nerve terminal. This method consists in the measuring of a uniquantal signal amplitude by three extracellular microelectrodes, arranged at a distance of 5-10 microns from each other. The construction of spatial pictures of the transmitter secretion on the basis of the analysis of several hundreds of signals in the cutaneous pectoris frog muscle has shown that release sites are organized in groups transversal to the nerve terminal. It is supposed that these groups of sites reflect the transmitter secretion in the active zones of the nerve ending. Advantages, shortcomings and errors of the method are shown.

[An analysis of mediator secretion in the active zone of the motor nerve ending]. / Analiz sekretsii mediatora v aktivnoi zone dvigatel'nogo nervnogo okonchaniia.

The topography of transmitter release sites at the motor-nerve terminal of the cutaneous-pectoris frog muscle has been determined using three extracellular electrodes. It is shown that release sites are united in groups arranged transversally to the nerve endings and reflecting the transmitter release in the active zones (AZ) of the nerve terminal. The quantitative analysis of revealed groups has permitted concluding that the maximal level of secretion is at the centre of AZ, decreasing to the edge and aside from AZ. At the low extracellular Ca2+ concentration all the AZ take part in the spontaneous release process, while in the evoked one--only some of AZ. Advantages of the three-microelectrode method over the two-microelectrode one are analyzed. It is found that the transmitter secretion in spatially isolated AZ leads to the polymodality in uniquantal signal amplitude distribution at extracellular recording. The role of AZ in the transmitter release process is discussed.