Evaluation of Antimicrobial and Lipopolysaccharide-Neutralizing Effects of a Synthetic CAP18 Fragment against Pseudomonas aeruginosa in a Mouse Model

CAP18 (cationic antimicrobial protein; 18 kDa) is a neutrophil-derived protein that can bind to and inhibit various activities of lipopolysaccharide (LPS). The 37 C-terminal amino acids of CAP18 make up the LPS-binding domain. A truncated 32-amino-acid C-terminal fragment of CAP18 had potent activity against Pseudomonas aeruginosa in vitro. We studied the antimicrobial and LPS-neutralizing effects of this synthetic truncated CAP18 peptide (CAP18_106–137) on lung injury in mice infected with cytotoxic P. aeruginosa. To determine its maximal effect, the CAP18_106–137 peptide was mixed with bacteria just prior to tracheal instillation, and lung injury was evaluated by determining the amount of leakage of an alveolar protein tracer (¹²⁵I-albumin) into the circulation and by the quantification of lung edema. The lung injury caused by the instillation of 5 × 10⁵ CFU of P. aeruginosa was significantly reduced by the concomitant instillation of CAP18_106–137. However, the administration of CAP18_106–137 alone, without bacteria, induced lung edema, suggesting that it has some toxicity. Also, the peptide did not significantly reduce the number of bacteria that had been simultaneously instilled, nor did it significantly improve the survival of the infected mice. The addition of CAP18_106–137 to aztreonam along with the bacteria did decrease the level of antibiotic-induced release of inflammatory mediators including tumor necrosis factor alpha, interleukin-6, and nitric oxide and also improved the survival of the mice. Therefore, more investigations are needed to confirm the toxicities and the therapeutic benefits of CAP18_106–137 as an adjunctive therapy to antibiotics in the treatment of infections caused by gram-negative bacteria.     

Identification of zebrafish ARNT1 homologs: 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity in the developing zebrafish requires ARNT1

To use the zebrafish (Danio rerio) as a model to study 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) developmental toxicity, it is essential to know which proteins are involved in mediating toxicity. Previous work has identified zfAHR2 as the receptor that binds TCDD mediating downstream responses. Although zfARNT2b can form a functional heterodimer with zfAHR2 in vitro, zfarnt2 null mutants show no protection against endpoints of TCDD developmental toxicity, demonstrating that zfARNT2b cannot be the physiological dimerization partner for zfAHR2 mediating responses to TCDD in zebrafish embryos. The purpose of the current study was to identify an alternate dimerization partner(s) for zfAHR2 that may function to mediate TCDD developmental toxicity. By searching zebrafish genomic sequence and using the polymerase chain reaction-based rapid amplification of cDNA ends technique, three forms of cDNA that seem to be alternate mRNA splice variants of a zebrafish homolog of ARNT1 were detected. Analysis of the zfARNT1 proteins in vitro demonstrates that the two longest forms of zfARNT1, zfARNT1b and zfARNT1c, can form functional heterodimers with zfAHR2. However, the shortest form, zfARNT1a, seems to be nonfunctional with zfAHR2 in vitro. To determine whether a zfARNT1 protein functions with zfAHR2 in vivo, a morpholino targeted against the 5' end of zfARNT1 (zfarnt1-MO) was used. Injection of the zfarnt1-MO before TCDD treatment significantly decreases the induction of zfCYP1A mRNA and protein. In addition, zfarnt1 morphants show complete protection against TCDD-induced pericardial edema and show partial protection against reduced blood flow and craniofacial malformations caused by TCDD, demonstrating the role of zfARNT1 proteins in mediating these responses.     

Prevalence and associations of epiretinal membranes in the visual impairment project

PURPOSE: To determine the prevalence and factors associated with epiretinal membranes in a random sample of the population aged 40 years and older in Victoria, Australia. DESIGN: Population-based cross-sectional study. METHODS: Detailed eye examinations, including retinal photographs, were conducted in 1992 and 1997 in 3271 people (83% of the eligible) in Melbourne and 1473 (92% of the eligible) in rural Victoria. Eyes present with either cellophane macular reflex (CMR) or preretinal macular fibrosis (PMF) were classified as having epiretinal membranes. Eyes with both CMR and PMF present were classified as having PMF. Age-standardized prevalence rates and 95% confidence limits were calculated by the direct methods using Segi's world population. RESULTS: Epiretinal membranes were observed in 253 of 4313 participants (6.0%; 95% confidence interval [CI] 5.2 to 6.7), bilaterally in 19%. Prevalence increased significantly by age group (0.5% for 40 to 49 years, 2.6% for 50 to 59 years, 9.4% for 60 to 69 years, 15.1% for 70 to 79 years, and 11.3% for 80 years and older). Prevalence was similar in males and females after adjusting for age. The overall age- and gender-standardized prevalence of CMR was 4.8% (95% CI 4.0 to 5.6) and PMF was 1.7% (95% CI 1.2 to 2.3). A decrease in visual acuity (<6/6) was significantly associated with idiopathic PMF (odds ratio [OR] 1.9; 95% CI 1.0 to 3.6) and CMR (OR 1.5; 95% CI 1.1 to 2.0) after adjusting for age. CONCLUSIONS: The prevalence of epiretinal membranes was similar to that reported in other population-based studies. Population shifts in the age distribution to older ages could lead to an increase in mild visual impairment caused by epiretinal membranes.     

Toxicity study of diethyl phthalate on freshwater fish Cirrhina mrigala

Diethyl phthalate (DEP) is used as a plasticizer, a detergent base, in aerosol sprays, as a perfume binder in incense sticks and after-shave lotions. It is known to be a contaminant of freshwater and marine ecosystems. Therefore, a study was designed to determine the toxic effects of DEP on a freshwater fish, Cirrhina mrigala. The fish was treated with 25, 50, 75, and 100 ppm (w/v) DEP dissolved in acetone to determine the LC50. Positive controls were treated with acetone only. There was 100% mortality observed within 24 h in 75 and 100 ppm, and 50% mortality in 50 ppm treated fish in 72 h. Those treated at 25 ppm showed only 10% mortality within 72 h and remaining fish continued to survive. The surviving fish were treated with 25 ppm DEP once daily for 3 days with every change of water (Group III). One group was maintained as negative control in dechlorinated water (Group I) and the other group received acetone once daily for 3 days with every change of water and was used as positive control (Group II). Fish were killed by cold narcosis on an ice block and dissected to obtain liver, muscle, and brain samples; 10% homogenates in ice-cold saline were prepared. Brain and muscle acetylcholinesterase (AchE) activity was measured. Liver aspartate (AST) and alanine aminotransferase (ALT), and liver and muscle succinate dehydrogenase (SDH) alkaline and acid phosphate (ALP and ACP) were measured. There was a significant increase in liver and muscle ACP and ALP in DEP-treated fish compared with positive and negative controls. There was a significant increase in muscle SDH and liver ALT (ALT) in DEP-treated fish compared with positive and negative controls. Brain AchE level was significantly decreased in DEP-treated fish compared to positive and negative controls. These results indicate that DEP brings about significant changes in the activity of certain liver and muscle enzymes. These alterations in enzyme activity may have long-term effects on that are continuously exposed to low doses of DEP in the aquatic environment.     

Amorphous calcific tumor of the mitral annulus echocardiographically mimicking a vegetation

We describe echocardiographic findings in an elderly patient with histologically proven amorphous tumor involving the posterior mitral annulus, mimicking a vegetation.