Nitric oxide-releasing polyacrylonitrile disperses biofilms formed by wound-relevant pathogenic bacteria.

AIMS: To test the antimicrobial and antibiofilm properties of a nitric oxide (NO)-releasing polymer against wound-relevant bacterial pathogens. METHODS AND RESULTS: Using a variety of 96-well plate assay systems that include standard well plates and the minimum biofilm eradication concentration biofilm assay well plate, a NO-releasing polymer based on (poly)acrylonitrile (PAN/NO) was studied for antimicrobial and antibiofilm activity against the common wound pathogens Pseudomonas aeruginosa (PAO1), Staphylococcus aureus (Mu50) and Enterococcus faecalis (V583). The polymer was capable of dispersing single-species biofilms of Ps. aeruginosa as well as a more clinically relevant multispecies biofilm that incorporates Ps. aeruginosa along with Staph. aureus and Ent. faecalis. PAN/NO also synergistically enhanced the susceptibility of the multispecies biofilms to the common broad-spectrum antibiotic, ciprofloxacin. Multiple in vitro biocompatibility assays show that PAN/NO has limited potential for mammalian cytotoxicity. CONCLUSION: This study demonstrates the feasibility of utilizing the NO-releasing polymer, PAN/NO, to manage biofilms formed by wound-relevant pathogens, and provides proof-of-concept for use of this NO-releasing polymer platform across multiple disciplines where bacterial biofilms pose significant problems. SIGNIFICANCE AND IMPACT OF STUDY: In the clinical sector, bacterial biofilms represent a substantial treatment challenge for health care professionals and are widely recognized as a key factor in prolonging patient morbidity. This study highlights the potential role for the ubiquitous signalling molecule nitric oxide (NO) as an antibiofilm therapy.

Microwave ablation of the liver: a description of lesion evolution over time and an investigation of the heat sink effect.

AIM: Microwave ablation has been successfully used to treat unresectable liver tumours for many years. However, despite its widespread use, there seems to be a relative paucity of experimental data regarding lesion evolution and the effects of any surrounding vasculature on ablation morphology. The aim of this study was to investigate the principal pathological changes in the liver following microwave ablation, in particular the heat sink effect. In addition we carefully reviewed the available literature to provide an overview of all relevant pathological studies. METHODS: Microwave ablation was carried out on male rats at various distances from the hilum. Histological (H&E) and immunocytochemical (caspase 3) analyses of the lesion were performed at various time points; 0, 4, 24, 48  hours, 2 weeks and 1 month. A literature review was carried out using Medline, Embase and the Cochrane database to identify all relevant histological studies. RESULTS: The lesion underwent complete coagulative necrosis and was extremely regular at the ablation edge with no evidence of any influence from surrounding blood vessels at all time points. H&E and caspase 3 results were consistent and microwave caused little collateral damage outside the intended ablation zone. CONCLUSION: This study suggests that microwave ablation is extremely concise and is minimally affected by the heat sink effect. Comparative investigations with other treatment modalities are required.

Cryotherapy of the liver: a histological review.

INTRODUCTION: Cryotherapy has been largely used in the past for palliation of unresectable liver tumors, but high local recurrence rates and peculiar systemic complications have determined its progressive abandonment. This review analyzes the histological changes produced to provide the basis for the local recurrences. MATERIALS AND METHODS: A detailed literature search was performed on studies focusing on liver cryotherapy. Included were only those that described the histological characteristics in detail. RESULTS: A total of 22 studies were found, one clinical and the others in-vivo animal studies. Similar to other ablative techniques, cryotherapy produces a lesion which is composed by a central zone of coagulative necrosis surrounded with a transitional inflammatory zone. The lesion's dimensions and morphology are influenced by numerous factors including the probe temperature, diameter, the duration of freezing time, fast cooling rate, slow thawing rate, the number of freezing cycles and the inflow occlusion (Pringle maneuver). The temporal evolution is consistent across studies and leads to a progressive inflammatory invasion of the necrosis with definitive fibrotic substitution. CONCLUSIONS: Lesions obtained after cryotherapy seem similar and behave as those obtained after other techniques of liver ablation. However, controversial areas still exist and include the optimum number of freeze thaw cycles, the place of inflow occlusion, the potential corrupting effects of intra-lesional or proximal blood vessels on ablation morphology. The influence of these factors on the local recurrences are still not fully understood.

Microwave ablation for unresectable hepatic tumours: clinical results using a novel microwave probe and generator.

BACKGROUND: Microwave ablation is an in situ method of tumour destruction used to treat patients with unresectable liver tumours. A new microwave generator and probe, designed to deliver high energy into solid tumours quickly has been developed at our institution. We report the results of its use in patients with unresectable liver tumours treated by a single surgeon in a single institution. METHODS: Thirty-one patients with 89 unresectable liver tumours were recruited into the study and underwent microwave ablation in a single procedure. RESULTS: There were no post-operative complications. At a median of 24 months post ablation, 15 patients were alive with 7 patients disease free. At a median of 26 months, 8 patients were alive with tumour recurrence but only 1 with local recurrence. The remaining 7 patients with recurrence were found to have new disease at locations remote from the ablation site. Fourteen patients died of disease progression at a median survival of 15 months, with only 1 patient with local and remote tumour recurrence. Of the total numbers of tumours treated (n=89), a local tumour recurrence rate of 2% was observed. Overall median survival was 29 months with 3 year survival of 40%. DISCUSSION: Microwave tissue ablation using this novel generator and probe has a low local recurrence and complication rate. Overall survival is comparable to alternative ablation modalities and its ability to treat, even large tumours, with a single insertion of the probe makes it an extremely attractive treatment option.

Liver ablation techniques: a review.

BACKGROUND: Ablation techniques for unresectable liver carcinomas have evolved immensely since their introduction. Results of studies involving these techniques are restricted to reports of patient case series, which are often not presented in a standardised manner. This review aims to summarise the major studies in ablation technologies and present them in a way that may make comparison between the major modalities easier. METHODS: All major databases (Medline, Cochrane, Embase and Pubmed) were searched for studies using microwave, radiofrequency or cryoablation to treat unresectable liver tumours. Only studies with at least 30 patients and 3-year follow-up were included. Complication, recurrence and survival rates of all studies are summarised and presented. RESULTS AND CONCLUSION: It is difficult to compare ablation modalities, as probe design and energy sources have evolved rapidly over the last decade. Ablation offers an invaluable palliative option and in some cases it may offer rates of cure approaching that of surgical resection with lower morbidity and mortality. Perhaps the time has come, therefore, for prospective large-scale randomised control trials to take place comparing ablation modalities to each other and surgical resection.

A comparative histological evaluation of the ablations produced by microwave, cryotherapy and radiofrequency in the liver.

AIMS: Complete tumour cell death is necessary for any ablative technique to be successful. Microwave tissue ablation (MTA), radiofrequency (RF) and cryotherapy (CT) are three methods of destroying liver tumours in situ. Unlike MTA, RF and CT rely on conduction of the thermal insult for their cytotoxicity, potentially affecting lesion uniformity. The aim of this study was to compare the uniformity of demarcation of lesions induced by MTA, RF and CT in the rat liver. METHODS: Twenty-one rats were assigned to each of the three ablative modalities. RESULTS: All specimens exhibited macroscopically well-demarcated lesions. Microscopically, the most clearly delineated lesions were induced by MTA with no intra-lesional viable hepatocytes or peri-vascular survival. All vessels and bile ducts had undergone complete necrosis. CT specimens showed more prominent inflammation at the lesion edge than MTA and peri-vascular hepatocyte survival within the ablated volumes. RF showed hepatocyte survival in the ablated area and conspicuous peri-vascular hepatocyte survival with evidence of a very irregular lesion edge. Cell viability was only assessed with H&E staining and not immunocytochemically. CONCLUSION: Unlike RF and CT, MTA induced microscopically well-demarcated lesions, with no intralesional hepatocyte survival. Intralesional cell survival in RF and CT may be due to the relatively prolonged treatment times needed, allowing thermal energy to dissipate via blood flow. This is known as the heat sink effect and may contribute to the high local recurrence rates following treatment of larger tumours with RF and CT.

Experimental study of large-volume microwave ablation in the liver.

BACKGROUND: Microwave coagulation therapy is useful in the destruction of small, irresectable liver tumours of primary and secondary origin. Unfortunately, the small lesion size produced by currently available equipment makes it difficult and time consuming completely to ablate lesions larger than 3 cm in diameter. A microwave system capable of producing large-volume ablations in very short periods of time has been developed. Using a large-animal model the ability of the equipment to produce large-volume lesions in a safe, predictable and dose-dependent manner was tested. METHODS: Fourteen large white pigs were anaesthetized and underwent multiple microwave treatments. The animals were killed at different timepoints to investigate lesion size and evolution. RESULTS: The microwave system was able to generate large-volume ablations of up to 6.5 cm in diameter in a controlled and dose-dependent manner. CONCLUSION: This novel microwave system allows the ablation of large volumes of liver tissue in a short period of time. The ability to produce lesions reproducibly and safely highlights the potential of this system in the future treatment of irresectable liver tumours.

Biodistribution and dosimetry of an aqueous solution containing sodium 3-(125I)iodo-4-hydroxybenzenesulfonate (Iotrex) for brachytherapy of resected malignant brain tumors.

UNLABELLED: Iotrex is an aqueous radiotherapy solution containing sodium 3-(125I)iodo-4-hydroxybenzenesulfonate (125I-HBS), which is used as the radiation source for the brachytherapy of resected of brain tumor cavity margins with the GliaSite catheter. During routine clinical use of this brachytherapy applicator and radiation source, approximately 0.1% of the afterloaded Iotrex will diffuse through the GliaSite balloon. Our purpose was to assess the radiation doses to normal organs under routine clinical use of the GliaSite. METHODS: Five groups of rats received intracerebral injections of an 131I-HBS solution (131I used as a surrogate for 125I in the synthesis of 125I-HBS) with one group sacrificed at 15 minutes, 30 minutes, 1 hour, 2 hours and 4 hours post-administration. Urine was collected and activity retention in numerous organs was measured. The biodistribution data were used to estimate radiation doses to normal organs of the Reference Adult Male and Female phantoms. RESULTS: Radioactivity was rapidly and completely cleared from the brain (98% cleared by 2 hours) and total body (urinary clearance; 93%@2 hours). No organ retained > 0.7% of the radioactivity at 4 hours. For 100% loss of the radiotherapy solution from the balloon catheter (device failure), all organs would receive less than 100 mGy (10 rad), except the bladder wall (2800 mGy, 280 rad), uterus (130 mGy, 13 rad) and distal colon (270 mGy, 27 rad). Under normal conditions, all organ doses are 1000-fold lower (< 3 mGy or 0.3 rad). CONCLUSIONS: Under routine clinical conditions, the radiation doses to normal organs are inconsequential. Should the maximum clinical load of Iotrex (16.7 GBq of 125I) be released intracerebrally, the radiation doses to all organs would be below the thresholds for deterministic effects.

Differential expression of the two human arginase genes in hyperargininemia. Enzymatic, pathologic, and molecular analysis.

Previous studies in our laboratory and others have demonstrated in humans and other mammals two isozymes of arginase (AI and AII) that differ both electrophoretically and antigenically. AI, a cytosolic protein found predominantly in liver and red blood cells, is believed to be chiefly responsible for ureagenesis and is the one missing in hyperargininemic patients. Much less is known about AII because it is present in far smaller amounts and localized in less accessible deep tissues, primarily kidney. We now report the application of enzymatic and immunologic methods to assess the independent expression and regulation of these two gene products in normal tissue extracts, two cultured cell lines, and multiple organ samples from a hyperargininemic patient who came to autopsy after an unusually severe clinical course characterized by rapidly progressive hepatic cirrhosis. AI was totally absent (less than 0.1%) in the patient's tissues, whereas marked enhancement of AII activity (four times normal) was seen in the kidney by immunoprecipitation and biochemical inhibition studies. Immunoprecipitation-competition and Western blot analysis failed to reveal presence of even an enzymatically inactive cross-reacting AI protein, whereas Southern blot analysis showed no evidence of a substantial deletion in the AI gene. Induction studies in cell lines that similarly express only the AII isozyme indicated that its activity could be enhanced severalfold by exposure to elevated arginine levels. Our findings suggest that the same induction mechanism may well be operative in hyperargininemic patients, and that the heightened AII activity may be responsible for the persistent ureagenesis seen in this disorder. These data lend further support to the existence of two separate arginase gene loci in humans, and raise possibilities for novel therapeutic approaches based on their independent manipulation.

Surgical management of gastroesophageal reflux in severely mentally retarded children.

Thirty-three severely mentally retarded children with profound malnutrition and aspiration pneumonitis were treated by gastrostomy and Nissen fundoplication. Early and late complications were 27.3% and 16.6% respectively. Mortality was 9.4%. All surviving patients gained weight. Time required for feeding was greatly reduced. This study supports earlier operative intervention for the mentally retarded child with gastroesophageal reflux, malnutrition and aspiration pneumonitis.

Enhanced glucose absorption in the jejunum of patients with cystic fibrosis.

After oral D-xylose ingestion, cystic fibrosis patients have significantly higher blood levels of xylose than controls. The aim of this study was to examine whether nutrient absorption at the mucosal level is altered in cystic fibrosis. Steady-state perfusion experiments using isotonic test solutions were performed in 11 healthy controls and 10 cystic fibrosis patients. Net D-glucose absorption was higher in cystic fibrosis when the perfusate contained a glucose concentration of less than or equal to 50 mM. Kinetic analysis by three different methods, including Lineweaver-Burk analysis, revealed a lower apparent Km as well as a lower apparent Vmax in cystic fibrosis as compared with healthy controls (33.9 mM and 52.5 mmol/20 cm . h vs. 81.8 mM and 68.3 mmol/20 cm . h, respectively, p less than 0.01). Absorption of D-fructose and glycine demonstrated a tendency for increased net absorption in cystic fibrosis but the results were not significantly different. L-Xylose absorption and electrolyte movement were not altered in cystic fibrosis. Among several possible mechanisms investigated, a decrease in the apparent Km for glucose absorption would be consistent with a decrease in diffusion barriers overlying the jejunal mucosa in cystic fibrosis. Using an electrical method, the unstirred water layer thickness was significantly decreased in cystic fibrosis (546 +/- 41 micron in cystic fibrosis vs. 780 +/- 110 micron in controls, p less than 0.05). A decrease in the mucosal surface area in the cystic fibrosis group or an intrinsic defect in the mucosal glucose transport system could account for differences in the apparent Vmax values. We suggest, however, that enhanced absorption in cystic fibrosis is most likely due to a decrease in intestinal diffusion barriers possibly due to abnormal mucus overlying the intestinal mucosa.

Results of treatment of gastroesophageal reflux with bethanechol.

Thirty-seven infants and children with gastroesophageal reflux were studied with prolonged esophageal pH monitoring before and during treatment with bethanechol. Total reflux scores improved by 69% (P = 6.47 X 10(-7) during bethanechol therapy. This improvement resulted primarily from decreases in the frequency and the duration of reflux episodes occurring more than two hours after feeding. Our findings indicate that infants and children with gastroesophageal reflux may safely be treated with bethanechol; thus the need for surgery is avoided.