Siderophore production by a marine Pseudomonas aeruginosa and its antagonistic action against phytopathogenic fungi.

A marine isolate of fluorescent Pseudomonas sp. having the ability to produce the pyoverdine type of siderophores under low iron stress (up to 10 microM iron in the succinate medium) was identified as Pseudomonas aeruginosa by using BIOLOG Breathprint and siderotyping. Pyoverdine production was optimum at 0.2% (w/v) succinate, pH 6.0, in an iron-deficient medium. Studies carried out in vitro revealed that purified siderophores and Pseudomonas culture have good antifungal activity against the plant deleterious fungi, namely, Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Fusarium oxysporum, and Sclerotium rolfsii. Siderophore-based maximum inhibition was observed against A. niger. These in vitro antagonistic actions of marine Pseudomonas against phytopathogens suggest the potential of the organism to serve as a biocontrol agent.

Siderophoregenic Bradyrhizobia boost yield of soybean.

After screening for siderophore (microbial iron chelator) production, of seven available cultures of soybean (Glycine max L.) root nodule bradyrhizobia, one strain, Bradyrhizobium japonicum NCIM 2746, was selected to confirm its phytopathogenic suppression and soybean growth promotion. Based on chromatographic and spectrophotometric studies, two different siderophores, a hydroxamate type (MW 734) and another catecholate type (MW 1000), were observed. Randomized block design (RBD) analysis of sick-pot studies (soil inoculated with phytopathogens) with an MACS 124 variety of soybean, bacterized with siderophoregenic B. japonicum, showed a marked increase in the percentage of germination, nodulation, chlorophyll, oil, protein content, and number of pods. Field trial study confirmed these pot results, which were evident from enhancement in shoot length, number of branches, chlorophyll content, number of nodules, root length, and number of pods. These results suggest the possibility of exploiting B. japonicum NCIM 2746 as a potential bioinoculant.

A phase I study of RSR13, a radiation-enhancing hemoglobin modifier: tolerance of repeated intravenous doses and correlation of pharmacokinetics with pharmacodynamics.

PURPOSE: Preclinical studies indicate that RSR13 oxygenates and radiosensitizes hypoxic solid tumors by decreasing the oxygen (O(2))-binding affinity of hemoglobin (Hb). A Phase I open-label, multicenter dose and frequency escalation study was conducted to assess the safety, tolerance, pharmacokinetics, and pharmacodynamic effect of daily RSR13 administration to cancer patients receiving concurrent palliative radiotherapy (RT). METHODS AND MATERIALS: Eligibility criteria included the following: ECOG performance status < or =2; resting and exercise arterial oxygen saturation (SaO(2)) > or =90%; an indication for palliative RT, 20-40 Gy in 10-15 fractions. RSR13 was administered i.v. via central vein over 60 min immediately before RT. Patients received supplemental O(2) via nasal cannula at 4 L/min during RSR13 infusion and RT. Plasma, red blood cell (RBC), and urine RSR13 concentrations were assayed. The pharmacodynamic effect of RSR13 on Hb-O(2) binding affinity was quantified by multipoint tonometry and expressed as an increase in p50, defined as the partial pressure of O(2) that results in 50% SaO(2). The RSR13 dose in the first cohort was 75 mg/kg once a week for two doses; successive cohorts received higher, more frequent doses up to 100 mg/kg/day for 10 days during RT. RESULTS: Twenty patients were enrolled in the study. Repeated daily doses of RSR13 were generally well tolerated. Two adverse events of note occurred: (1) A patient with pre-existing restrictive lung disease had transient persistent hypoxemia after the sixth RSR13 dose; (2) a patient with a recurrent glioma receiving high-dose corticosteroids had edema after the seventh RSR13 dose, likely due to the daily high-volume fluid infusions. Both patients recovered to baseline status with conservative management. Maximum pharmacodynamic effect occurred at the end of RSR13 infusion and was proportional to the RBC RSR13 concentration. After an RSR13 dose of 100 mg/kg, the peak increase in p50 averaged 8.1 mm Hg, consistent with the targeted physiologic effect, and then diminished with a half-life of approximately 5 h. CONCLUSIONS: RSR13 was well tolerated in daily doses up to 100 mg/kg administered for 10 days during RT. The combined administration of RSR13 with 4 L/min supplemental O(2) yielded pharmacodynamic conditions in which hypoxic tumor radiosensitization can occur. Ongoing Phase II and Phase III studies are evaluating the combination of RT and RSR13 for selected indications, including primary brain tumors, brain metastases, and non-small-cell lung cancer.

RSR13, an allosteric effector of haemoglobin, and carbogen radiosensitize FSAII and SCCVII tumours in C3H mice.

Pre-clinical evaluation has demonstrated that 2-[4-(((3,5-dimethylanilino)carbonyl)methyl)phenoxy]-2-methylpropi onic acid (RSR13) acts as an allosteric effector of haemoglobin (Hb). RSR13 binding to Hb results in decreased haemoglobin-oxygen (Hb-O2) affinity, improved tumour oxygenation, and enhanced radiation-induced cell killing in several experimental tumour systems. In the present work, ex vivo clonogenic survival analyses are applied in two murine tumour systems to characterize the relationship between the magnitude of decrease in Hb-O2 affinity and radiosensitization, the influence of inspired pO2 upon this effect, and the efficacy of combining RSR13 and radiation during a course of repeated radiation exposures. For FSaII tumours in C3H mice breathing air, 100 mg kg(-1) RSR13 administered intraperitoneally produced an enhancement ratio (ER) of 1.3, but there was marked desensitization at a RSR13 dose of 300 mg kg(-1) (ER 0.6). The most likely reason for the increased radioresistance was insufficient oxygen loading of Hb in the pulmonary circulation due to reduced haemoglobin-oxygen affinity because carbogen breathing combined with 300 mg kg(-1) RSR13 reversed the effect and produced an ER of 1.8. In SCCVII tumours in C3H mice irradiated with eight fractions of 2.5 Gy over 4 days, the surviving fraction was reduced to 58-67% of control values when RSR13 was combined with radiation on days 1 and 2, days 3 and 4, or days 1-4. These results confirm that combining RSR13 and irradiation within a fractionated course of clinically relevant low-dose exposures provides significant radiosensitization. Additional preclinical experimentation is needed to define better the optimum dose-scheduling conditions for clinical applications.

Clinical use of a digital simulator for rapid setup verification in high dose rate brachytherapy.

PURPOSE: Fractionated high dose rate (HDR) brachytherapy provides a number of technical advantages over conventional implant therapy in that (a) it can be carried out on an outpatient basis, (b) personnel exposure is reduced to insignificant levels, and (c) patient motion during irradiation is minimized, resulting in a more accurate delivery of the planned radiation dose distribution to the target and critical structures. The patient discomfort associated with the repeated applicator insertions and/or treatment setups can be alleviated to the extent that the setup time is held to a minimum. This work describes the use of a prototype digital simulator to obtain fast, high-quality digital images for rapid setup verification. METHODS AND MATERIALS: The digital imaging system of the prototype simulator consists of a charge-coupled device (CCD) camera, which views the x-ray image optically transmitted from a conventional phosphor screen. Treatment is carried out with a remote afterloading HDR unit immediately after setup verification with the patient on the simulator stretcher. The high-resolution digital images are processed and displayed in about 5 s, as opposed to a minimum of approximately 2 min for film. RESULTS: The imaging system has been evaluated for a variety of implant types, both intracavitary and interstitial. The digital radiographs provided permanent high-resolution images as required in most cases for precise applicator positioning. The gray scale manipulation capabilities were found to be useful for imaging in regions of different density, such as lung and soft tissue, in the same radiograph. The advantages of short image acquisition and display times were observed in all cases, but were most evident in the intraluminal procedures, which sometimes involved several pretreatment applicator adjustments at a time of considerable patient discomfort. CONCLUSION: Pretreatment imaging is necessary to fully exploit the technical advantages of HDR brachytherapy. High-quality digital radiography offers unique advantages in HDR setup and verification by providing fast high-resolution, undistorted images with software manipulation capabilities and permanent storage of images.

The influence of quantitative tumor volume measurements on local control in advanced head and neck cancer using concomitant boost accelerated superfractionated irradiation.

PURPOSE: Current methods to clinically define head and neck tumor bulk are qualitative and imprecise. Although the American Joint Committee on Cancer (AJCC) staging system is important for this purpose, limitations exist. This study will investigate the prognostic value of computed tomography (CT) derived tumor volume measurements in comparison to AJCC stage and other significant variables. MATERIALS AND METHODS: Seventy-six patients with advanced head and neck squamous cell carcinoma were treated with concomitant boost accelerated superfractionated irradiation. Doses ranged from 68.4-73.8 Gy (median 70.2 Gy). Good quality pretherapy CT scans were available in 51 patients. Total tumor volume (TTV) estimates were derived from these scans using digital integration of primary tumor and metastatic lymphadenopathy. Actuarial and multivariate statistical techniques were applied to analyze local control. RESULTS: Thirty-six-month local control was 63%. TTV ranged from 5-196 cm3 (median 35 cm3) for all cases, 5-142 cm3 (median 17 cm3) for those controlled, and 16-196 cm3 (median 47 cm3) for local failures. There was a significant increase in failures above 35 cm3. Univariate analysis found that TTV, T-stage, N-stage, and primary site were each significant prognostic variables. Local control for TTV < or = 35 cm3 was 92% at 36 months vs. 34% for TTV > 35 cm3 (p = 0.0001). Multivariate analysis, however, found that TTV, primary site, and sex were important as independent variables; T and N stage were not independently significant unless TTV was removed from the model. CONCLUSIONS: This study demonstrates the prognostic significance of TTV in advanced carcinoma of the head and neck. This variable appears to be a more predictive than AJCC clinical stage. Quantitative tumor volume measurements may prove to be a useful parameter in future analyses of head and neck cancer.

Enhanced oxygenation in vivo by allosteric inhibitors of hemoglobin saturation.

The in vivo effects on hemoglobin (Hb)-O2 affinity and tissue PO2 were investigated after intraperitoneal administration of 2-[4-(((dichloroanilino)-carbonyl)methyl)phenoxyl]-2-methyl propionic acid (RSR4; 150 mg/kg) or its 3,5-dimethyl derivative (RSR13; 300 mg/kg) in C3Hf/Sed mice. The Hb-O2 dissociation curve was plotted from tail vein blood samples using an O2 dissociation analyzer before and up to 160 min after compound administration. Twenty to 40 min after injection, the PO2 at 50% saturation of hemoglobin (Hb P50) increased by a mean of 25% (range 18-31%) after RSR4 and 53% (range 36-76%) after RSR13. Tissue PO2 was continuously measured using an O2 microelectrode in thigh muscle before and up to 40 min after RSR4 or RSR13 injection. Twenty to 40 min after administration, tissue PO2 increased by a mean of 78% (range 30-127%) after RSR4 and 66% (range 39-97%) after RSR13 administration in anesthetized mice. No change in tissue PO2 was seen in anesthetized controls.