In vivo bioluminescent imaging of a new model of infectious complications in head-injury rats.

Infectious complications are responsible for 10-25% of mortality in head-injured patients. In the present work we developed a model of infectious complications in head-injury rats using Escherichia coli (E. coli) with a stable copy of the lux operon, and monitored the infection in vivo by optical imaging. Rats were randomized into three groups: AL (healthy rats), HI (head-injury rats), and HI-EC (HI rats+single enteral bolus of E. coli, 1.3×10(9)/rat given 2 days after HI). Infection was evaluated with a camera at 2 and 6 h after E. coli challenge. Blood and organs were sampled to assess biological parameters. HI was associated with body weight loss, muscle atrophy, and plasma amino acid disturbances, in particular glutamine depletion (AL 919±37 versus HI 647±25 and HI-EC 717±20 µmol/L; p<0.05). In the HI-EC rats, the luminescence signal was observed at T+2 (mean [range]: 34,778 cpm [1617-2,918,810]), and was significantly decreased at T+6 (0 cpm [0-847,922]; p<0.05). Bacterial challenge was associated with a specific body weight loss and a decrease in gastrocnemius protein content, in alanine (AL 512±41 versus HI-EC 395±29 µmol/L; p<0.05), and in sulfur plasma amino acids. In conclusion, we propose a controlled model of HI with infectious complications characterized by specific metabolic alterations. Combined with the in vivo monitoring of the infection by bioluminescence, this model offers a valuable tool to evaluate specific strategies for HI patients.

Tolerance and efficacy of a new enteral formula specifically designed for elderly persons: an experimental study in the aged rat.

For the first time, a formula was specifically designed for the nutritional support of tube-fed elderly patients (Elderly-Specific Formula [ESF], Nestlé, Switzerland). It was tested against a standard formula (Sondalis Iso [SI], Nestlé Clinical Nutrition, Marne la Vallée, France) in sixteen 22-month-old Sprague Dawley rats fed by total continuous enteral infusion for 7 days. Body weight, stool weight, and nitrogen balance were measured daily. After death, muscle weight, plasma levels of amino acids, tissue protein, and amino acid content were measured. The ESF curbed weight loss, improved cumulative nitrogen balance, and increased jejunum protein content. Plasma levels of threonine, leucine, and isoleucine and the sum of total amino acids were higher in ESF-fed than in SF-fed rats. Threonine and isoleucine content in the soleus and gastrocnemius were higher in ESF-fed rats than SI-fed ones. ESF improved intestinal transit. Thus, in old rats, the ESF favored nutritional status more than a standard formula.