Age-related changes in auditory nerve-inner hair cell connections, hair cell numbers, auditory brain stem response and gap detection in UM-HET4 mice.

This study compared the timing of appearance of three components of age-related hearing loss that determine the pattern and severity of presbycusis: the functional and structural pathologies of sensory cells and neurons and changes in gap detection (GD), the latter as an indicator of auditory temporal processing. Using UM-HET4 mice, genetically heterogeneous mice derived from four inbred strains, we studied the integrity of inner and outer hair cells by position along the cochlear spiral, inner hair cell-auditory nerve connections, spiral ganglion neurons (SGN), and determined auditory thresholds, as well as pre-pulse and gap inhibition of the acoustic startle reflex (ASR). Comparisons were made between mice of 5-7, 22-24 and 27-29 months of age. There was individual variability among mice in the onset and extent of age-related auditory pathology. At 22-24 months of age a moderate to large loss of outer hair cells was restricted to the apical third of the cochlea and threshold shifts in the auditory brain stem response were minimal. There was also a large and significant loss of inner hair cell-auditory nerve connections and a significant reduction in GD. The expression of Ntf3 in the cochlea was significantly reduced. At 27-29 months of age there was no further change in the mean number of synaptic connections per inner hair cell or in GD, but a moderate to large loss of outer hair cells was found across all cochlear turns as well as significantly increased ABR threshold shifts at 4, 12, 24 and 48 kHz. A statistical analysis of correlations on an individual animal basis revealed that neither the hair cell loss nor the ABR threshold shifts correlated with loss of GD or with the loss of connections, consistent with independent pathological mechanisms.

Impaired sensorimotor gating in Fmr1 knock out and Fragile X premutation model mice.

Fragile X syndrome (FXS) is a common inherited cause of intellectual disability that results from a CGG repeat expansion in the FMR1 gene. Large repeat expansions trigger both transcriptional and translational suppression of Fragile X protein (FMRP) production. Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is an allelic neurodegenerative disease caused by smaller "pre-mutation" CGG repeat expansions that enhance FMR1 transcription but lead to translational inefficiency and reduced FMRP expression in animal models. Sensorimotor gating as measured by pre-pulse inhibition (PPI) is altered in both FXS patients and Fmr1 knock out (KO) mice. Similarly, FXTAS patients have demonstrated PPI deficits. Recent work suggests there may be overlapping synaptic defects between Fmr1 KO and CGG knock-in premutation mouse models (CGG KI). We therefore sought to interrogate PPI in CGG KI mice. Using a quiet PPI protocol more akin to human testing conditions, we find that Fmr1 KO animals have significantly impaired PPI. Using this same protocol, we find CGG KI mice demonstrate an age-dependent impairment in PPI compared to wild type (WT) controls. This study describes a novel phenotype in CGG KI mice that can be used in future therapeutic development targeting premutation associated symptoms.

Eosinophilic infiltration of the esophagus following endoscopic ablation of Barrett's neoplasia.

To assess the incidence of esophageal intra-epithelial eosinophilic infiltration following endoscopic ablation of Barrett's esophagus (BE), a retrospective study of consecutive cases of endoscopic ablation of BE with dysplasia or cancer using radiofrequency ablation (RFA) and spray cryotherapy at two centers in the United States was performed. Post-ablation eosinophilia was defined as ≥ 5 eosinophils per high power field during post-treatment surveillance. Twenty of 122 patients (16%) undergoing ablation developed esophageal eosinophilia after ablation, including 8/77 (10%) treated with RFA and 12/44 (27%) treated with cryotherapy. No patient had clinical or endoscopic findings of or risk factors for eosinophilic esophagitis. Esophageal eosinophilia persisted in 30% over a median of 20.2 months. On multivariate analysis, post-ablation eosinophilia was independently associated with increasing BE segment length (adjusted odds ratio 1.46 for every 2-cm increase, 95% confidence interval 1.24-1.71) and cryotherapy as the ablation modality (adjusted odds ratio 5.23, 95% confidence interval 1.67-16.39). Esophageal eosinophilic infiltration after endoscopic ablation with RFA and cryotherapy is common and is associated with the BE segment length and treatment modality. The clinical significance of post-ablation eosinophilia is unclear.

Recurrent disease following endoscopic ablation of Barrett's high-grade dysplasia with spray cryotherapy.

BACKGROUND AND AIMS: Recurrent disease after endoscopic ablation of Barrett's esophagus should be detected early to prevent malignant progression. We assessed the incidence and patterns of disease recurrence in patients after liquid nitrogen spray cryotherapy ablation of Barrett's esophagus with high grade dysplasia (HGD), including the area below the neosquamocolumnar junction (NSCJ). PATIENTS AND METHODS: This is a single-center, retrospective study of prospectively collected data on consecutive cases of endoscopic ablation with liquid nitrogen spray cryotherapy for Barrett's HGD. Post-treatment surveillance biopsies were obtained of suspicious lesions and in 4 quadrants every 1 cm in the treated esophagus and just below the NSCJ. Primary outcome measures were location and histology of recurrent disease. RESULTS: 36 patients (median age 62 years, 92% men) were enrolled, and 11 (30%) developed recurrent disease in a median of 6.5 months; three developed a second recurrence. Ten recurrences (71%) were identified below the NSCJ in 9 patients, including HGD (4), low grade dysplasia (LGD) (2), and intestinal metaplasia (4). Six recurrences were identified in the treated esophagus in five patients, including intramucosal cancer (1), HGD (1), and intestinal metaplasia (4). Two patients had recurrent disease involving both locations. Ultimately 33 patients (92%) achieved a complete response. Diagnosis in the remaining three was LGD (1) and intestinal metaplasia (2). CONCLUSION: Most patients with recurrent intestinal metaplasia with or without dysplasia after ablation achieve a complete response. Recurrent disease commonly involves the area just below the NSCJ. Surveillance endoscopies should include this area to accurately identify patients with disease recurrence.

Propionate inactivation of butane monooxygenase activity in 'Pseudomonas butanovora': biochemical and physiological implications.

Butane monooxygenase (BMO) catalyses the oxidation of alkanes to alcohols in the alkane-utilizing bacterium 'Pseudomonas butanovora'. Incubation of alkane-grown 'P. butanovora' with butyrate or propionate led to irreversible time- and O2-dependent loss of BMO activity. In contrast, BMO activity was unaffected by incubation with lactate or acetate. Chloramphenicol inhibited the synthesis of new BMO, but did not change the kinetics of propionate-dependent BMO inactivation, suggesting that the propionate effect was not simply due to it acting as a repressor of BMO transcription. BMO was protected from propionate-dependent inactivation by the presence of its natural substrate, butane. Although both the time and O2 dependency of propionate inactivation of BMO imply that propionate might be a suicide substrate, no evidence was obtained for BMO-dependent propionate consumption, or 14C labelling of BMO polypeptides by [2-(14)C]propionate during inactivation. Propionate-dependent BMO inactivation was also explored in mutant strains of 'P. butanovora' containing single amino acid substitutions in the alpha-subunit of the BMO hydroxylase. Propionate-dependent BMO inactivation in two mutant strains with amino acid substitutions close to the catalytic site differed from wild-type (one was more sensitive and the other less), providing further evidence that propionate-dependent inactivation involves interaction with the BMO catalytic site. A putative model is presented that might explain propionate-dependent inactivation of BMO when framed within the context of the catalytic cycle of the closely related enzyme, soluble methane monooxygenase.

Role of pulmonary alveolar macrophages in defense of the lung against Pseudomonas aeruginosa.

Alveolar macrophages (AM) provide one of the first lines of defense against microbial invasion in the lower airways. The role of AM in the clearance of Pseudomonas aeruginosa in mice after intrapulmonary challenge was evaluated. AM were depleted by intranasal administration of liposome-encapsulated dichloromethylene diphosphonate. At 24 h following the instillation of liposomes, a sublethal dose of P. aeruginosa was inoculated intranasally. Spleen, liver, and lung tissue was then evaluated for viable bacteria and for histopathology. AM depletion of 78 to 88% did not affect the survival rate of infected mice or clearance of P. aeruginosa from the spleen, liver, or lung, compared to the control group, but the mice's susceptibility to Klebsiella pneumoniae was greatly enhanced. The recruitment of neutrophils to the lung was also not affected. Freshly explanted AM were not competent to phagocytose unopsonized P. aeruginosa but were able to phagocytose zymosan particles. Further studies were conducted to assess the in situ phagocytic activities of AM. Three hours after the intranasal instillation of P. aeruginosa or other particles, bronchoalveolar lavage was performed. AM phagocytosis of zymosan particles and latex beads exceeded that of P. aeruginosa. Neutrophils were recruited to the lung in response to a high-dose bacterial challenge. These results suggest that AM do not play an important role in defense of the lung against P. aeruginosa.

A murine model for infection with Burkholderia cepacia with sustained persistence in the spleen.

Burkholderia cepacia is an opportunistic pathogen that causes severe systemic infections in patients with chronic granulomatous disease (CGD) or with cystic fibrosis (CF), but its mechanisms of virulence are poorly understood. We developed a murine model of systemic infection in wild-type (WT) and gamma interferon knockout (GKO) BALB/c mice to facilitate dissection of components of pathogenicity and host defense. Both WT and GKO mice were susceptible to chronic splenic infection with B. cepacia, but not with Pseudomonas aeruginosa. B. cepacia strains from patients with CGD persisted longer than those from CF patients. C57BL/6 mice were the most susceptible murine strain; bacteria persisted in the spleen for 2 months. DBA/2, BALB/c, and A/J strains of mice were relatively resistant to infection. Certain strains of B. cepacia complex can persist in the murine spleen after systemic infection; this may provide clues to its virulence in compromised hosts, such as those with CGD and CF.