Piperazine derivatives as iron chelators: a potential application in neurobiology.

Polysubstituted piperazine derivatives, designed as new iron chelators, were synthesized and fully characterized by nuclear magnetic resonance and mass spectroscopy. Their potential to prevent iron-induced neurotoxicity was assessed using a cellular model of Parkinson disease. We demonstrated their ability to provide sustained neuroprotection to dopaminergic neurons that are vulnerable in this pathology. The iron chelating properties of the new compounds were determined by spectrophotometric titration illustrating that high affinity for iron is not associated with important neuroprotective effects.

Design and synthesis of 3-isoxazolidone derivatives as new Chlamydia trachomatis inhibitors.

Chlamydia trachomatis (Ct) is a bacterial human pathogen responsible for the development of trachoma, the worldwide infection leading to blindness, and is also a major cause of sexually transmitted diseases. As iron is an essential metabolite for this bacterium, iron depletion presents a promising strategy to limit Ct proliferation. The aim of this study is to synthesize 3-isoxazolidone derivatives bearing known chelating moieties in an attempt to develop new bactericidal anti-Chlamydiaceae molecules. We have investigated the paths by which these new compounds affect Ct serovar L2 development in HeLa cells, in the presence or absence of exogenously added iron. The iron-chelating properties of these molecules were also determined. Our data reveal important bactericidal effects which are distinguishable from those due to iron chelation.

Clinical experience with the MicroMed DeBakey ventricular assist device.

BACKGROUND: The MicroMed DeBakey ventricular assist device (VAD) (MicroMed Technology, Inc, Houston, TX) is the first long-term axial flow circulatory assist device to be introduced into clinical trials as a bridge to transplantation. Clinical trials began in Europe in November 1998 and in the United States in June 2000. METHODS: To qualify for the study, the patients must be listed for cardiac transplantation and must have demonstrated profound cardiac failure. There were no exclusions to the MicroMed DeBakey VAD implant other than those patients who would typically be excluded from cardiac transplantation. RESULTS: As of September 2000, 51 patients have been implanted with the MicroMed DeBakey VAD. A detailed evaluation of the first 32 patients has been completed. With current data, the probability of survival at 30 days after VAD implant is 81%. CONCLUSIONS: The clinical trial demonstrated that the MicroMed DeBakey VAD is capable of providing adequate circulatory support in patients with severe heart failure, sufficient to recover and return to normal activities while awaiting a heart transplantation. Much has been learned about the function of the device and its continuous flow in humans.

Turbine blood pumps.

After years of development and preclinical testing, clinical trials of the MicroMed DeBakey VAD began in November 1998 in Europe and in June 2000 in the United States. As of August 2000, 44 patients in Europe and 3 patients in the United States have undergone implantation with the MicroMed DeBakey VAD. In conclusion, data from the European clinical trial of the MicroMed DeBakey VAD support the safety and performance of the device. Results show that the device provides adequate left ventricular and circulatory support in patients with end-stage heart failure without unduly jeopardizing patient safety. Moreover, the device provides advantages not inherent to commercially available pulsatile devices: (1) miniature size, enabling implantation in smaller patients; (2) ease of implantation; (3) reduced surgical bleeding; and (4) a low incidence of postoperative infections, often a limiting factor with other devices. The MicroMed DeBakey VAD European clinical trial is the first demonstration of the compatibility of continuous blood flow with adequate tissue perfusion and overall maintenance of life for up to 4.5 months. This initial experience with the MicroMed DeBakey VAD suggests that the pump can provide circulatory support to bridge patients to cardiac transplantation and may provide an improved quality of life for the patient with end-stage heart failure.

Impaired energy homeostasis in C/EBP alpha knockout mice.

Mice homozygous for the targeted deletion of the c/ebp alpha gene, which expresses the CCAAT/enhancer-binding protein alpha (C/EBP alpha), did not store hepatic glycogen and died from hypoglycemia within 8 hours after birth. In these mutant mice, the amounts of glycogen synthase messenger RNA were 50 to 70 percent of normal and the transcriptional induction of the genes for two gluconeogenic enzymes, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, was delayed. The hepatocytes and adipocytes of the mutant mice failed to accumulate lipid and the expression of the gene for uncoupling protein, the defining marker of brown adipose tissue, was reduced. This study demonstrates that C/EBP alpha is critical for the establishment and maintenance of energy homeostasis in neonates.

Autoregulation of the human C/EBP alpha gene by stimulation of upstream stimulatory factor binding.

The human C/EBP alpha gene promoter shares significant sequence homology with that of the mouse but has a different mechanism of autoregulation. Activation of the murine promoter by direct binding of C/EBP alpha to a site within 200 bp of the transcriptional start was shown to elevate activity by approximately threefold (R. J. Christy, K. H. Kaestner, D. E. Geiman, and M. D. Lane, Proc. Natl. Acad. Sci. USA 88:2593-2597, 1991; K. Legraverend, P. Antonson, P. Flodby, and K. G. Xanthapoulos, Nucleic Acids Res. 21:1735-1742, 1993). Unlike its murine counterpart, the human C/EBP alpha gene promoter does not contain a cis element that binds the C/EBP alpha protein. Neither C/EBP alpha nor C/EBP beta (NF-Il-6) binds the human C/EBP alpha promoter within 437 bp. However, cotransfection studies show that C/EBP alpha stimulates transcription of a reporter gene driven by 437 bp of the C/EBP alpha promoter. Our studies show that the human C/EBP alpha protein stimulates USF to bind to a USF consensus element within C/EBP alpha promoter and activates it by two- to threefold. We propose that the human gene employs the ubiquitously expressed DNA-binding protein factor USF to carry out autoregulation. Autoregulation of the human C/EBP alpha promoter was abolished by deletion of the USF binding site, CACGTG. Expression of human C/EBP beta following transfection did not stimulate USF binding. These studies suggest a mechanism whereby tissue-specific autoregulation can be achieved via a trans-acting factor that is expressed in all cell types. Thus, direct binding of the C/EBP alpha protein to the promoter of the C/EBP alpha gene is not required for autoregulation.