Etiology of cecal and hepatic lesions in mice after administration of gas-carrier contrast agents used in ultrasound imaging

Production of a Series of Long-Chain Isomaltooligosaccharides from Maltose by Bacillus subtilis AP-1 and Associated Prebiotic Properties

Bacillus subtilis strain AP-1, which produces α-glucosidase with transglucosidase activity, was used to produce a series of long-chain isomaltooligosaccharides (IMOs) with degree of polymerization (DP) ranging from 2 to 14 by direct fermentation of maltose. A total IMOs yield of 36.33 g/L without contabacillusmination from glucose and maltose was achieved at 36 h of cultivation using 50 g/L of maltose, with a yield of 72.7%. IMOs were purified by size exclusion chromatography with a Superdex 30 Increase column. The molecular mass and DP of IMOs were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Subsequently, linkages in produced oligosaccharides were verified by enzymatic hydrolysis with α-amylase and oligo-α-1,6-glucosidase. These IMOs showed prebiotic properties, namely tolerance to acidic conditions and digestive enzymes of the gastrointestinal tract, stimulation of probiotic bacteria growth to produce short-chain fatty acids and no stimulating effect on pathogenic bacteria growth. Moreover, these IMOs were not toxic to mammalian cells at up to 5 mg/mL, indicating their biocompatibility. Therefore, this research demonstrated a simple and economical method for producing IMOs with DP2–14 without additional operations; moreover, the excellent prebiotic properties of the IMOs offer great prospects for their application in functional foods.

Unusual Progressive Hepatic Echogenicity of the Pediatric Liver Following Intravenous Sonographic Contrast Administration

Contrast-enhanced ultrasound is a valuable tool to evaluate liver lesions in a pediatric patient cohort. Unusual progressive hepatic echogenicity (UPHE) is a self-limiting phenomenon noted in a cohort of children after administration of ultrasonographic contrast agents (UCAs). UPHE appears initially as heterogeneous branching similar to portal venous gas, culminating in a diffuse globular appearance. The etiology of UPHE is unclear and may be from underlying hepatic microvascular disease or altered gut permeability. This case series describes pediatric patients with UPHE following UCA bolus and discusses its potential mechanisms in children.

Nonclinical safety testing of imaging agents, contrast agents and radiopharmaceuticals

Drug development includes imaging agents, contrast agents and radiopharmaceuticals; these materials differ from therapeutic drugs in that they are largely used to diagnose and/or monitor diseases and not treat them. Consequently, nonclinical safety testing needs are different. An examination of testing packages supporting clinical entry and/or marketing of these materials has shown a common approach to some study types (eg, imaging, biodistribution and toxicity testing). Recent regulatory guidelines to support development are the United States Food and Drug Administration (FDA)'s "Guidance for Industry Microdose Radiopharmaceutical Diagnostic Drugs: Nonclinical Study Recommendations" and the European Medicines Agency (EMA)'s "Guideline on the Non-Clinical Requirements for Radiopharmaceuticals" (currently draft). It is hoped that these documents will allow developers to only perform nonclinical studies that are necessary to support functionality, follow distribution of the material and examine general safety/toxicity. However, as they are mainly focused on radiopharmaceuticals, companies are likely to apply knowledge of established testing packages to other new imaging agents and/or follow principles given in older regulatory guidelines, namely FDA's "Guidance for Industry Developing Medical Imaging Drug and Biological Products Part I Conducting Safety Assessments". Thus, in some cases, the need for regulatory agency interaction is still vital to avoid development surprises and delays due to an incomplete or badly performed testing package.

Therapeutic Dose Response of Acoustic Cluster Therapy in Combination With Irinotecan for the Treatment of Human Colon Cancer in Mice

Introduction: Acoustic Cluster Therapy (ACT) comprises coadministration of a formulation containing microbubble-microdroplet clusters (PS101) together with a regular medicinal drug and local ultrasound (US) insonation of the targeted pathological tissue. PS101 is confined to the vascular compartment and when the clusters are exposed to regular diagnostic imaging US fields, the microdroplets undergo a phase shift to produce bubbles with a median diameter of 22 µm. Low frequency, low mechanical index US is then applied to drive oscillations of the deposited ACT bubbles to induce biomechanical effects that locally enhance extravasation, distribution, and uptake of the coadministered drug, significantly increasing its therapeutic efficacy. Methods: The therapeutic efficacy of ACT with irinotecan (60 mg/kg i.p.) was investigated using three treatment sessions given on day 0, 7, and 14 on subcutaneous human colorectal adenocarcinoma xenografts in mice. Treatment was performed with three back-to-back PS101+US administrations per session with PS101 doses ranging from 0.40-2.00 ml PS101/kg body weight (n = 8-15). To induce the phase shift, 45 s of US at 8 MHz at an MI of 0.30 was applied using a diagnostic US system; low frequency exposure consisted of 1 or 5 min at 500 kHz with an MI of 0.20. Results: ACT with irinotecan induced a strong, dose dependent increase in the therapeutic effect (R2 = 0.95). When compared to irinotecan alone, at the highest dose investigated, combination treatment induced a reduction in average normalized tumour volume from 14.6 (irinotecan), to 5.4 (ACT with irinotecan, p = 0.002) on day 27. Median survival increased from 34 days (irinotecan) to 54 (ACT with irinotecan, p = 0.002). Additionally, ACT with irinotecan induced an increase in the fraction of complete responders; from 7% to 26%. There was no significant difference in the therapeutic efficacy whether the low frequency US lasted 1 or 5 min. Furthermore, there was no significant difference between the enhancement observed in the efficacy of ACT with irinotecan when PS101+US was administered before or after irinotecan. An increase in early dropouts was observed at higher PS101 doses. Both mean tumour volume (on day 27) and median survival indicate that the PS101 dose response was linear in the range investigated.

Microbial short-chain fatty acid production and extracellular enzymes activities during in vitro fermentation of polysaccharides from the seeds of Plantago asiatica L. treated with microwave irradiation

Effects of microwave irradiation on microbial short-chain fatty acid production and the activites of extracellular enzymes during in vitro fermentation of the polysaccharide from Plantago asiatica L. were investigated in this study. It was found that the apparent viscosity, average molecular weight, and particle size of the polysaccharide decreased after microwave irradiation. Reducing sugar amount increased with molecular weight decrease, suggesting the degradation may derive from glycosidic bond rupture. The polysaccharide surface topography was changed from large flakelike structure to smaller chips. FT-IR showed that microwave irradiation did not alter the primary functional groups in the polysaccharide. However, short-chain fatty acid productions of the polysaccharide during in vitro fermentation significantly increased after microwave irradiation. Activities of microbial extracellular enzymes xylanase, arabinofuranosidase, xylosidase, and glucuronidase in fermentation cultures supplemented with microwave irradiation treated polysaccharide were also generally higher than those of untreated polysaccharide. This showed that microwave irradiation could be a promising degradation method for the production of value-added polysaccharides.

Does contrast-enhanced cervical ultrasonography improve preoperative localization results in patients with sporadic primary hyperparathyroidism?

OBJECTIVE

Pre-operative localization studies are inevitable in patients with primary hyperparathyroidism (pHPT), who are eligible for focused or minimally invasive parathyroidectomy (MIP). High-resolution ultrasonography (US) in combination with planar (99m)Tc-Sestamibi-scintigraphy (MIBI) and additional single-photon emission computed tomography (SPECT) are the standard procedures to localize enlarged parathyroid glands. Our aim was to evaluate the practicability and significance of contrast-enhanced ultrasonography (CEUS) in patients with pHPT.

MATERIALS AND METHODS

All investigations were performed at the University Hospital Marburg. Totally, 25 patients with biochemical proven pHPT underwent preoperative US, MIBI/SPECT, and CEUS. For CEUS, a suspension of phospholipid-stabilized sulfur-hexafluoride (SF6) microbubbles in combination with a special 12 MHz linear US probe was used. All patients were investigated by two sonographers, who did not get to view the findings noted by the other. Finally, surgery was performed and histopathological results were obtained from 24 patients.

RESULTS

In 17 (68%) patients, US and MIBI/SPECT already raised suspicion of parathyroid lesions and all suspected lesions were reassessed by CEUS. However, no additional information was obtained using CEUS. Especially in eight patients with negative or inconsistent US and MIBI/SPECT results, CEUS did not provide additional information regarding the site of the suspected parathyroid adenoma. Overall, no side effects were observed using CEUS. Surgical cure was achieved in all patients.

CONCLUSION

In this limited cohort of patients, no additional information could be obtained using the costly CEUS compared to results of US and MIBI/SPECT.

Targeted microbubbles in the experimental and clinical setting

BACKGROUND

Microbubbles have improved ultrasonography imaging techniques over the past 2 decades. Their safety, versatility, and easiness of use have rendered them equal or even superior in some instances to other imaging modalities such as computed tomography and magnetic resonance imaging. Herein, we conducted a literature review to present their types, general behavior in tissues, and current and potential use in clinical practice.

METHODS

A literature search was conducted for all preclinical and clinical studies involving microbubbles and ultrasonography.

RESULTS

Different types of microbubbles are available. These generally improve the enhancement of tissues during ultrasonography imaging. They also can be attached to ligands for the target of several conditions such as inflammation, angiogenesis, thrombosis, apoptosis, and might have the potential of carrying toxic drugs to diseased sites, thereby limiting the systemic adverse effects.

CONCLUSIONS

The use of microbubbles is evolving rapidly and can have a significant impact on the management of various conditions. The potential for their use as targeting agents and gene and drug delivery vehicles looks promising.

Safety of ultrasound contrast agents

The use of ultrasound contrast agents has increased over recent years. The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) decided to review the safety of ultrasound contrast agents in humans and to draw up guidelines. A comprehensive literature search and review was carried out. The resulting report was discussed by the CMSC of ESUR and at the 11th European Symposium on Urogenital Radiology in Santiago de Compostela, Spain, in 2004. Ultrasound contrast agents approved for clinical use are well tolerated, and serious adverse reactions are rarely observed. Adverse events are usually minor (e.g. headache, nausea, altered taste, sensation of heat) and self-resolving. These symptoms may not be related to the ultrasound contrast materials as they have also been observed in placebo-control groups. Intolerance to some components may occur. Generalized allergy-like reactions occur rarely. Ultrasound contrast agents are generally safe. The ultrasound scanning time and the acoustic output should be kept to the lowest level consistent with obtaining diagnostic information. Adverse reactions should be treated symptomatically.

In vivo study of microbubbles as an MR susceptibility contrast agent

The potential application of gas microbubbles as a unique intravascular susceptibility contrast agent for MRI has not been fully explored. In this study, the MR susceptibility effect of an ultrasound microbubble contrast agent, Optison, was studied with rat liver imaging at 7 T. Optison suspension in two different doses (0.15 mL/kg and 0.4 mL/kg) was injected into rats, and induced transverse relaxation rate increases (deltaR2*) of 29.1 +/- 1.6 s(-1) (N = 2) and 61.5 +/- 12.9 s(-1) (N = 6), respectively, in liver tissue. Liver uptake of intact albumin microbubbles was observed 10 min after injection. Eight of the 16 rats studied showed no susceptibility enhancement. This is probably attributable to the intravascular microbubble growth due to transmural CO2 supersaturation in the cecum and colon in small animals that causes microbubble aggregation and trapping in the inferior vena cava (IVC). In vitro deltaR2* measurements of Optison suspension at different concentrations are also reported.

Intestinal and hepatic lesions in mice, rats, and other laboratory animals after intravenous administration of gas-carrier contrast agents used in ultrasound imaging

Single intravenous administration of three different gas-carrier contrast agents used in ultrasound imaging to mice caused inflammation, necrosis, and ulceration of cecum and proximal colon (cecocolonic area) and focal necrosis in the liver. Similar intestinal lesions were also found in rats after treatment with a single iv administration of a gas-carrier contrast agent. Strain differences in the incidences of these lesions were found in both rats and mice. HsdHan:NMRI mice were among the most sensitive of the strains of mice studied. Even at the lowest dose of Sonazoid technically possible to inject in HsdHan:NMRI mice, lesions were found and a no-effect dose could not be determined. In a time-course experiment in HsdHan:NMRI mice, it was found that the lesions began to develop in the cecum and colon within 15 to 30 min after dosing. Lesions in the liver were first observed 120-240 min after dosing. Diet played a role in the etiology of the lesions, as HsdHan:NMRI mice given a diet with reduced amounts of cellulose and starch had reduced incidences of lesions, and when glucose was the only carbohydrate source, no lesions were observed. No intestinal or hepatic lesions were found in guinea pigs or rabbits after repeated intravenous administrations of Sonazoid. In dogs, minimal to mild granulocytic inflammation of the cecum and/or colon was found after daily repeated intravenous injections for 28 days, but not after daily repeated administration for 14 days nor after a single administration. It is proposed that the intestinal and hepatic lesions in rats and mice after a single intravenous injection of gas-carrier contrast agents are caused by a common mechanism: intravascular growth of gas-carrier agents in tissues with gas supersaturation, as occurs in the cecal wall of rats and mice. In this particular environment the growing gas bubbles cause ischemia and necrosis in the cecal and colonic wall and liver. This proposed mechanism of action is consistent with the absence of clinical reports indicative of intestinal and/or hepatic lesions in humans after administration of gas-carrier contrast agents.