Partial pneumonectomy of telomerase null mice carrying shortened telomeres initiates cell growth arrest resulting in a limited compensatory growth response.

Telomerase mutations and significantly shortened chromosomal telomeres have recently been implicated in human lung pathologies. Natural telomere shortening is an inevitable consequence of aging, which is also a risk factor for development of lung disease. However, the impact of shortened telomeres and telomerase dysfunction on the ability of lung cells to respond to significant challenge is still largely unknown. We have previously shown that lungs of late generation, telomerase null B6.Cg-Terc(tm1Rdp) mice feature alveolar simplification and chronic stress signaling at baseline, a phenocopy of aged lung. To determine the role telomerase plays when the lung is challenged, B6.Cg-Terc(tm1Rdp) mice carrying shortened telomeres and wild-type controls were subjected to partial pneumonectomy. We found that telomerase activity was strongly induced in alveolar epithelial type 2 cells (AEC2) of the remaining lung immediately following surgery. Eighty-six percent of wild-type animals survived the procedure and exhibited a burst of early compensatory growth marked by upregulation of proliferation, stress response, and DNA repair pathways in AEC2. In B6.Cg-Terc(tm1Rdp) mice carrying shortened telomeres, response to pneumonectomy was characterized by decreased survival, diminished compensatory lung growth, attenuated distal lung progenitor cell response, persistent DNA damage, and cell growth arrest. Overall, survival correlated strongly with telomere length. We conclude that functional telomerase and properly maintained telomeres play key roles in both long-term survival and the early phase of compensatory lung growth following partial pneumonectomy.

L1CAM mutation in association with X-linked hydrocephalus and Hirschsprung's disease.

X-linked hydrocephalus (XLH) is characterized by increased intracranial ventricle size and head circumference secondary to aqueduct of Sylvius congenital stenosis. Exceedingly rare is the concurrence of XLH and Hirschsprung's disease (HSCR) with a theoretical incidence of 1 in 125-250 million cases. Herein, we are describing a case of a patient with concurrent XLH and HSCR. The patient was delivered via cesarean section at 37 weeks gestation and underwent uneventful ventriculoperitoneal shunt placement. As a part of a workup for constipation, we performed a rectal biopsy, which was consistent with HSCR. Genetics testing showed hemizygous for R558X hemizygous mutation in the L1CAM gene. A C --> T nucleotide substitution in exon 13 resulted in replacement of an arginine codon with a stop codon, a nonsense mutation. Although it is widely accepted that HSCR represents the failure of early embryonic neural crest cells to migrate properly, the exact mechanism is not known. The association of HSCR with XLH in the presence of L1CAM mutations remains quite interesting because cell adhesion molecules are involved in the proper migration of neural components throughout the body. Additional studies are necessary to fully elucidate the relationship between XLH and HSCR in the presence of L1CAM mutations.

A modified technique for partial pneumonectomy in the mouse.

BACKGROUND: Partial pneumonectomy (PNX) in mice results in compensatory growth in the remaining lung and is a useful model for lung repair. However, common pitfalls to the technique present a challenge for researchers. A complete description of murine PNX is thus provided, with a modification that, in our hands, enhanced animal survival. MATERIALS AND METHODS: 10 ± 2 weeks old mice were anesthetized using 5% inhalational isoflurane via tracheotomy. Mechanical ventilation was provided using a Harvard Model 687 ventilator. In a procedure optimized to be performed in ≤20 min, left lateral thoracotomy was used to access to the left lung, which was grasped with a blunt forceps just distal to the hilum and clipped using a single 5-mm neuro clip. The left lung was resected, leaving a small rim of lung tissue immediately adjacent to the clip. The thoracotomy was closed, and while anesthesia was titrated, sterile saline was injected subcutaneously to replace insensible fluid losses. Upon return of spontaneous breaths, the trachea was decannulated, and the tracheotomy was closed. RESULTS: Even when performed by a single operator, this modified technique produced a survival rate of >85% during the procedure and >90% up to seven days postoperatively in wild-type C57BL/6J mice. CONCLUSIONS: Minimizing the time required to perform left lobe pneumonectomy is critical for animal survival. Using a 5-mm neuro clip, rather than silk suture, to isolate the lobe streamlines the procedure, helps reduce cardiac arrythmia, and results in significantly increased rates of intraoperative and immediate postoperative survival.

Utility of bilateral bronchoalveolar lavage for the diagnosis of ventilator-associated pneumonia in critically ill surgical patients.

BACKGROUND: Bronchoalveolar lavage (BAL) is recommended to facilitate the diagnosis of ventilator-associated pneumonia (VAP). It is unclear if bilateral sampling improves the accuracy of BAL. METHODS: Consecutive patients with clinical suspicion for VAP were analyzed. All patients underwent bilateral BAL. A threshold of >10(4) colony-forming units (cfu)/mL was diagnostic for VAP (VAP positive). Samples were concordant if the organism(s) and thresholds from both lungs were diagnostically consistent. Organisms 10(4) cfu/mL were considered false-negative samples. RESULTS: Between November 2005 and April 2006, 73 patients were considered clinically suspicious for VAP. Forty-four (60%) patients were VAP positive. Twenty-eight (64%) VAP patients had concordant samples. Overall, there were 15 false-negative samples. Sole use of the unilateral samples to guide treatment would have inappropriately directed antibiotic avoidance and/or discontinuation in 25% of VAP patients. Influence of the chest radiograph was equivocal because of the presence of bilateral infiltrates in 80% of discordant samples. CONCLUSIONS: Bilateral BAL improves the accuracy of bronchoscopy in diagnosing VAP. Unilateral BAL may be insensitive in patients with clinically significant contralateral infection.