Carbohydrazones of Substituted Salicylaldehydes as Potential Lead Compounds for the Development of Narrow-Spectrum Antimicrobials

Certain substituted salicylaldehydes are known to have highly potent antimicrobial activity against bacteria and fungi, but the mechanism underlying this remarkable activity is not known, and almost nothing has been reported on the effects of further modification of the structures, such as the formation of hydrazone-type derivatives. We report now a study on the antimicrobial properties of the carbohydrazone derivatives of several substituted salicylaldehydes. The compounds studied were synthesized from ring-substituted salicylaldehydes and carbohydrazide in the mole ratio 2:1. They were tested against Aspergillus niger, Bacillus cereus, Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Saccharomyces cerevisiae and Staphylococcus epidermidis using the agar diffusion method. The carbohydrazone derived from 2,3,4-trihydroxybenzaldehyde had distinctly higher activity than the parent aldehyde in the same molar concentration. This activity was limited to one test organism (S. epidermidis), while the free aldehyde had at least some (in some cases even high) activity against all of the microbes studied. All other ones of the effective carbohydrazone compounds were distinctly less active than the parent salicylaldehydes as such. The hydrazones studied had in general a narrower antimicrobial spectrum than the free aldehydes and are thus of interest as potential lead compounds for the development of narrow-spectrum antimicrobial drugs. The mechanism of action of the aldehydes as well as that of the carbohydrazones is discussed

Comparison of an Indirect Format ELISA on Modified Graphite and Polystyrene Surfaces against Triazines

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods (Ø 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6- diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. ε-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.

Streptococcus pneumoniae Type 14 Polysaccharide-Conjugate Vaccines: Length Stabilization of Opsonophagocytic Conformational Polysaccharide Epitopes

ABSTRACT A simple and convenient method was developed for the preparation of Streptococcus pneumoniae type 14 polysaccharide (Pn14PS)-tetanus toxoid (TT) conjugate vaccines, using terminally linked Pn14PS fragments of different lengths. Native Pn14PS was simultaneously depolymerized and activated for conjugation by partial N-deacetylation followed by nitrous acid deamination which yielded fragments (1.4 to 150.0 kDa) having a free aldehyde at the reducing end. These were then conjugated to TT through their terminal aldehydic groups, using the reductive amination procedure. All of the above conjugates, when injected in rabbits, induced anti-Pn14PS antibodies, whereas the native Pn14PS did not. The amounts of anti-Pn14PS antibodies elicited by these conjugates, as determined by enzyme-linked immunosorbent assay, followed a trend with conjugates containing the highest-molecular-weight Pn14PS eliciting the highest titers. The same trend was also observed in the ability of the antibodies to opsonize and kill live type 14 pneumococci, although the increase in opsonophagocytic activity was more pronounced and did not correlate linearly with increases in antibody titer. Competitive inhibition of the binding of different conjugate antisera to the native Pn14PS, using Pn14PS fragments as inhibitors, established that the conjugates induced antibodies with specificities for different lengths of Pn14PS beginning at 2 repeating units (RU). It was also established, both immunologically and antigenically, that at least 4 RU of Pn14PS were required to form an extended conformational epitope and that approximately 22 RU of Pn14PS were required to duplicate the same epitope on the same saccharide chain. The conformational epitope was found to be essential for the induction of antibodies with high opsonophagocytic activity and that augmentation of opsonophagocytic activity was also dependent on further chain extension.

Endothelialization of Porcine Aortic Valves Postfixed with L-Glutamic Acid

Endothelial cells from rat aorta were cultured before seeding onto porcine aortic valve leaflet surfaces. Primary adherence, growth kinetics, and characteristics of the endothelialization were investigated at different time periods. There were 4 experimental groups: (1) preserved with glutaraldehyde alone, (2) non-preserved, (3) presented with glutaraldehyde and L-glutamic acid, and (4) preserved with glutaraldehyde, epoxy chloropropane, and L-glutamic acid. In group 1 there were no cells growing on the leaflet surfaces after 3 days but in groups 2, 3, and 4 there was distinctive cell growth. Immunostaining and morphologic examinations showed that the growing cells comprised mainly endothelial cells with some fibroblasts. The results showed that L-glutamic acid treatment could neutralize the effect of residual free aldehyde in tanned tissue, thereby allowing endothelial cells to grow on the valve leaflet surfaces.