Acetyl-L-carnitine affects nonassociative learning processes in the leech Hirudo medicinalis.

Acetyl-L-carnitine is a natural molecule widely distributed in vertebrate and invertebrate nervous system. It is known to have significant effects on neuronal activity playing a role as neuroprotective and anti-nociceptive agent, as well as neuromodulatory factor. About its capability of affecting learning processes the available data are controversial. In the present study, we utilized the simplified model system of the leech Hirudo medicinalis to analyze the effects of acetyl-L-carnitine, assessing whether and how it might affect elementary forms of nonassociative learning processes. In leeches with the head ganglion disconnected from the first segmental ganglion, repetitive application of weak electrical shocks onto the caudal portion of the body wall induces habituation of swim induction whereas brush strokes on the dorsal skin produces sensitization or dishabituation when the nociceptive stimulus is delivered on previously habituated animals. Herein, the effects of different concentrations of acetyl-L-carnitine (2 mM - 0.05 mM) have been tested at different times on both sensitization and dishabituation. The results show that a single treatment of acetyl-L-carnitine blocked the onset of sensitization in a dose- and time-dependent manner. In fact, the most effective concentration able to block this process was 2 mM, which induced its major effects 11 days after the treatment, whereas 0.05 mM was unable to affect the sensitization process at all considered time points. On the contrary, acetyl-L-carnitine did not completely abolish dishabituation at the tested concentrations and at every time point. Finally, acetyl-L-carnitine also impaired the habituation of swim induction, but only 11 days after treatment.

A comparative study of protein immobilization techniques for optical immunosensors.

This paper presents the results of a study of a number of antibody immobilization techniques for application to optical immunosensors. In particular, well-known methods such as covalent binding and physical adsorption have been extended to the Langmiur-Blodgett method in an attempt to improve the density and possibly the uniformity of orientation of monoclonal antibodies on an optical surface. The surface density of active immobilized antibodies was determined from enzyme immunoassay and their thickness and refractive index were deduced from ellipsometry. It is shown that, although high surface densities (500 ng/cm2) of antibody can be obtained, the major obstacle to the detection of low concentrations of antigens or haptens is the non-specific binding of foreign molecules to the sensing surface.

Design of immunization programmes for developing countries.

PIP: Factors to be considered in designing immunization programs in developing countries are summarized. The limiting factors will usually be costs of vaccines, administration equipment and supplies, transport and maintenance of the cold chain. Choices have to be made about the sources of vaccines, whether produced locally or imported, size of vaccine lots and type of package, and quality control of vaccines. Selection of vaccines is treated in a separate appendix, but generally 3 groups are recognized: 1) recommended for general use: smallpox, diphtheria, tetanus, pertussis, BCG, typhoid and measles; 2) recommended for special cases: polio and yellow fever; 3) not recommended for developing countries: rubella, mumps, influenza, cholera; and 4) vaccines in development stage only: arbovirus, rickettsia, trachoma, meningococci, plague and shigella. Schedules for vaccine administration are suggested, such as plans for vaccination every 2 years, plans for 4 courses of vaccinations including 1 at school entry, and special programs such as smallpox campaigns and immunization of adolescent girls and fertile women with tetanus. Finally the importance of recording of vaccinees and assessment of programs is discussed.^ieng

Vi serology in detection of chronic Salmonella typhi carriers in an endemic area.

A passive haemagglutination assay measuring antibody to highly purified Vi antigen, known to be sensitive and specific for the detection of chronic Salmonella typhi carriers in a non-endemic area, was assessed in an endemic area. A reciprocal serum Vi antibody titre of 160 was found to have a sensitivity of 75%, specificity of 92%, and a high predictive value in screening for chronic S typhi carriers in high-risk population group (eg, women over 40 years). This simple assay can screen for chronic S typhi carriers even in areas where typhoid fever is highly endemic.