Search

The development, growth and regeneration of nerve cells remain an unresolved issue. The up-to-date reported brain repair mechanisms are numerous and evidence suggests that, apart from the required trophism, tropism, microenvironment and specificity of the brain, a plethora of chemical, physiological and immunological compounds can contribute to such events. Among these compounds, we concentrated our interest on l-carnitine (l-Cn), which regulates the β-oxidation of long chain fatty acids necessary for brain development, myelinization and growth. In contrast to fetal brain cells that grow easily in culture, adult brain cells show limited neurogenesis. Here, using adult brain cells from experimental mice, we show that although l-Cn does not improve their proliferative activity in short-term cultures, it accelerates the growth and differentiation of neurons, astrocytes, oligodendrocytes and ependymal cells from neurospheres in long-term cultures. Thus, the formation of a confluent neural network requires a 2-month period in culture. These observations provide new insights for in vivo use of l-Cn to support brain cell development in cases of injury or brain degenerative diseases. [Copyright &y& Elsevier]

Objective To investigate whether stepwise selection of resistance mutations may mirror the continued bacterial exposure to antibiotics that occurs in the clinical setting. Methods We examined the in vitro development of resistance to a number of commonly used antibiotics (cefepime, cefpirome, ceftazidime, cefotaxime, piperacillin and imipenem) in Pseudomonas aeruginosa, a significant nosocomial pathogen. Stepwise resistance was assessed by serial passage of colonies located nearest to the inhibition zone on antibiotic-containing gradient plates. Results The lowest frequencies of spontaneous resistance mutations were found with cefepime and imipenem; these drugs also resulted in the slowest appearance of resistance of spontaneous resistance mutations. In five wild-type P. aeruginosa strains, cefepime-selected isolates required a mean of 30 passages to reach resistance; resistance occurred more rapidly in strains selected with other cephalosporins. P. aeruginosa strains that produced β-lactamase or non-enzymatic resistance generally developed resistance more rapidly than wild-type strains. For most strains, resistance to all antibiotics except imipenem correlated with increased levels of β-lactamase activity. Cross-resistance of cephalosporin-selected resistant mutants to other cephalosporins was common. Cephalosporin-resistant strains retained susceptibility to imipenem and ciprofloxacin. Conclusions From our in vitro study, we can conclude that the rate of development of resistance of P. aeruginosa is lower with cefepime compared with other cephalosporines. [ABSTRACT FROM AUTHOR]