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The regrowth delay assay was used to assess hypoxic fraction in the RIF-1 tumor. Results approximating those of earlier paired survival curve data were obtained for previously untreated tumors and tumors treated with a single dose of 15 Gy. Further studies showed that after 5 daily fractions of 5 Gy, the hypoxic fraction returned to approximate pretreatment values within 24 hr.
Phosphorus-31 magnetic resonance spectra were obtained from the RIF-1 tumor in C3H mice before and up to 2 days after various doses of X rays. Parallel studies were performed to measure relative changes in tumor blood perfusion using [14C]iodo-antipyrine and changes in % tumor necrosis using Chalkley's method. Tumor ratios of phosphocreatine to inorganic phosphate (PCr/Pi) and nucleotide triphosphates to inorganic phosphate (NTP/Pi) as well as pH as measured by 31P-MRS increased significantly at most time points after irradiation with doses of 5, 10, and 20 Gy. Tumor blood perfusion was found to significantly improve after a dose of 20 Gy but not after a dose of 2 Gy. Percent tumor necrosis increased to about 3 times its control level at 1 day after a dose of 20 Gy and then declined to about twice its control value at 2 days. The magnitude of the changes in the 31P-MRS parameters makes it unlikely that any of them are entirely due to radiation-induced changes in the radiobiologically hypoxic fraction of these tumors. Changes in the necrotic fraction did not appear to influence the tumor spectra. However, the observed improvement in tumor blood perfusion may have resulted in an increase in oxidative phosphorylation of the whole tumor population as well as a clearance of inorganic phosphate and acid metabolites, so that 31P-MRS changes may indirectly reflect changes in tumor blood perfusion.
RIF-1 tumors contain a small number of cells (1 to 100 per 10(6) cells) that are resistant to 5-fluorouracil, methotrexate, or adriamycin. The frequency of drug-resistant cells among individual untreated tumors is highly variable. Radiation, delivered in vivo at doses of 3 to 12 Gy, increases the frequency of methotrexate- and 5-fluorouracil-resistant cells, but not the frequency of adriamycin-resistant cells. The magnitude of induction of 5-fluorouracil and methotrexate resistance shows a complex dependence on the radiation dose and on the interval between irradiation and assessment of drug resistance. For a dose of 3 Gy, induced 5-fluorouracil and methotrexate resistance is seen only after an interval of 5 to 7 days, whereas for a dose of 12 Gy, high levels of induced resistance are observed 1 to 3 days after irradiation. The maximum absolute risk for induction of resistance is 4 per 10(4) cells per Gy for methotrexate, and 3 per 10(6) cells per Gy for 5-fluorouracil. These results indicate that tumor hypoxia may play a role in the increased levels of drug resistance seen after irradiation, and that both genetic and environmental factors may influence radiation-induction of drug resistance. These studies provide essential data for models of the development of tumor drug resistance, and imply that some of the drug resistance seen when chemotherapy follows radiotherapy may be caused by radiation-induced drug resistance.
The proportion of hypoxic cells in the RIF-1 tumor was observed for 24 hr after treatments with bleomycin, cisplatin, cyclophosphamide, and mitomycin C. The assays were based upon the paired survival curve method for determining the hypoxic fraction using irradiation of aerobic and artificially hypoxic tumors. It was observed that at 1/2 hr after bleomycin, hypoxic fraction was elevated but returned to baseline levels by 2 hr. Following cisplatin, hypoxic fraction did not rise above baseline. However, after cyclophosphamide, hypoxic fraction was elevated and did not return to baseline over the 24-hr observation period of this study. At 1/2 hr after mitomycin treatment, the hypoxic fraction was raised but within 1 hr returned to baseline. These results indicate that tumor reoxygenation varies after different drug treatments and that the determination of drug specificity for aerobic versus hypoxic cells may be strongly biased by the choice of the time after treatment for making the determination.
5-Chlorodeoxycytidine (CldC), coadministered with modulators of pyrimidine metabolism, is an effective radiosensitizer of murine tumors. Past studies that utilized RIF-1 tumors in C3H mice and Lewis lung carcinoma (LLC) in BDF1 mice have been extended with an emphasis on using multiple cycles of drug administration followed by irradiation of LLC and the use of two additional tumor models. Four of seven cures of BDF1 mice bearing LLC were obtained with three doses of 20 Gy irradiation, in which the first and third dose were preceded by a "Standard Protocol" that includes N-(phosphonacetyl)-L-aspartic acid (PALA), 5-fluorodeoxycytidine (FdC), tetrahydrouridine, and the radiosensitizer, 5-chlorodeoxycytidine. No cures were obtained in groups of mice receiving radiation alone or drugs alone, and there were no "no takes" in untreated control groups (six mice/group). Extensive tumor inhibition, exceeding that obtained with drugs or radiation alone, was obtained with two cycles of drugs and radiation combined when a dimethybenzanthracene-induced mammary adenocarcinoma was used in BALB/c mice. With the EMT-6 tumor in BALB/c mice, doses of 10 and 20 Gy were administered 9 and 16 days after tumor implantation, each preceded with the Standard Protocol; this resulted in a tumor growth delay of 24 days. No tumor growth delay occurred with drugs or radiation alone. The omission of PALA, FdC or CldC from the Standard Protocol resulted in loss of tumor control, which was obtained with the complete protocol. The fact that 5-chlorodeoxycytidine is an effective radiosensitizer in four rodent tumor systems is compelling evidence that it has potential as a radiosensitizer of human tumors, especially in view of its tumor selectivity and its resistance to catabolism when used with modulators of its metabolism, and in view of the high levels of the key enzymes in human tumors, which can convert 5-chlorodeoxycytidine to 5-chlorodeoxyuridine triphosphate, the proximate radiosensitizer.
The metabolic consequences of increased glucose availability were examined in subcutaneous RIF-1 tumors in vivo, using 13C and 31P NMR spectroscopy. Significant increases in the levels of nucleotide triphosphates and phosphocreatine relative to low energy phosphates and in tumor pH were observed within 30 min following injection of 1 g/kg of glucose directly into the tumor. These changes did not occur following an equivalent intratumoral dose of the non-metabolizable sugar alcohol, mannitol. When [1-13C]-glucose was administered, [3-13C]-lactate and [3-13C]-alanine were the only labeled metabolites detected in the in vivo 13C NMR spectra during the period of bioenergetic improvement. Biochemical analysis revealed a substantial increase in tumor and plasma glucose concentration, but no increase in either tumor or plasma lactate, consistent with the absence of acidosis. Evaluation of the distribution of glucose in the tumor by quantitative autoradiography of [1-14C]-2-deoxyglucose administered with the glucose indicated that, on average, 7 mM of the added glucose distributed over the entire tumor within 10 min. The significant improvement in overall metabolic status of the tumors following glucose administration is attributed to the existence of substrate limited regions within the tumor.
PURPOSE: Previous studies from our laboratory have suggested that pooling of ammonium in tumor tissues may be caused by its inefficient removal due to the poor vasculature commonly found in tumors. The purpose of these experiments was to validate the relationship between tumor ammonium ion concentration and tumor blood flow, and to determine whether large concentrations of ammonium ion detected by Nuclear Magnetic Resonance (NMR) spectroscopy are either produced within the tumor or simply imported into the tumor through the blood stream. METHODS AND MATERIALS: To test this hypothesis, we reduced blood flow in subcutaneously grown Radiation Induced Fibrosarcoma-1 (RIF-1) tumors, either by creating partial ischemia with a bolus injection of hydralazine or by occlusion with surgical sutures. 14N and 31P NMR spectroscopy were used to detect the presence of ammonium, and to assess the bioenergetic status of the tumors, respectively. RESULTS: A correlation between ammonium ion concentration and PCr/Pi ratio was established for untreated tumors. An increase in the in vivo tumor ammonium ion concentration was observed for every tumor that experienced a reduction in blood flow caused by either hydralazine injection or suture ligation. Changes in ammonium ion concentration paralleled changes in the bioenergetics of hydralazine-treated tumors. CONCLUSION: Our results support the hypothesis that a reduction in tumor blood flow is responsible for the accumulation of ammonium in tumors, and that detected ammonium originated from within the tumor.
Tumor blood volume (TBV) is an important factor in the metabolism of a tumor and in its response to therapy. Until recently, the only methods to determine TBV were highly invasive and many involved radioisotopes. In this study, a perfluorocarbon (PFC) emulsion, Oxypherol, was monitored by 19F magnetic resonance spectroscopy (MRS). TBVs as determined by 19F MRS of in situ and excised radiation-induced fibrosarcoma (RIF-1) tumors (n = 9), were strongly correlated with the TBV measured by a radioisotope labeled albumin method (slopes of 1.1 and 0.8 with R = 0.86 and 0.91, respectively, by linear regression). In general, the TBV as calculated from the in situ MRS measurements (n = 24) decreased from 28 to 5 ml/100 g tumor mass for tumors ranging in mass from 0.15 to 2 g. However, there was an indication of an initial increase of TBV in tumors smaller than 0.5 g.
OBJECTIVES: Plaque accumulation, leading to inflammatory processes and bone loss, is one of the main reasons for failure of dental implants. Pellicle formation plays a key role in bacterial adhesion and plaque accumulation. The influence of experimental bioactive implant surface coatings on the initial process of pellicle formation was investigated in a model system. METHODS: TiO2-films were modified by covalent binding of laminin and human epidermal growth factor (EGF) to promote adhesion of epithelial cells. Adsorption and dissociation behavior of bovine serum albumin (BSA) and salivary proteins on these surfaces were monitored by time-resolved reflectometric interference spectroscopy (RIfS). RESULTS: The thickness of the irreversibly adsorbed salivary protein layer was reduced from 2.78 +/- 0.71 nm on unmodified TiO2 to 0.78 +/- 0.22 nm on laminin-coated surfaces and to 1.18 +/- 0.29 nm on EGF-coated surfaces. The percentage of initially adsorbed proteins remaining irreversibly bound was reduced from 51 +/- 8% on titanium to 23 +/- 5% by laminin coating and to 44 +/- 11% on EGF-coated surfaces. The highest reduction of protein adsorption (layer thickness lower than 0.05 nm) was achieved on DC-PEG-layers used as spacer for protein coupling. SIGNIFICANCE: Laminin and EGF were shown to be promising candidates for use as biological coatings on the transmucosal part of titanium dental implants where the objective is to enhance epithelial adhesion and inhibit adsorption of salivary proteins and bacteria.
The aim of the present paper is to present information about a kif preparation smoked by the Moroccan population. Results are considered as an advance of our actual investigations undertaken in the Rif zone to observe an improvement in night vision after smoking kif [Ethan et al., 2002. International Cannabinoid Research Society (ICRS) meeting, in preparation].
The effects of pentobarbital anesthetic and physical restraint have been evaluated in murine RIF-1 tumors in terms of their suitability in providing minimal temporal variations in core and tumor temperatures, intracellular (pHMR) and extracellular (pHF) tumor pH, and tumor bioenergetics. pHF was measured using a fibreoptic pH probe. The implications of the changes in these parameters on the combined studies of in vivo MRS and hyperthermia have been discussed. The temporal variations of core and tumor temperatures, pHF and pHMR between the anesthetised and restrained mice were statistically significant (p < 0.0001, p < 0.005, and p < 0.0001, respectively). Differences in the temperatures between the two groups varied with time, and were maximum at about 2 h after pentobarbital. In the anesthetised mice, while there was a net increase of 0.28 pH units in pHF, there was a drop by 0.32 pH units in pHMR (p < 0.001). Temporal variations of both pHF and pHMR in the restrained mice were relatively constant. In light of these findings, wherever possible, physical restraint in a suitably designed holder is suggested for immobilizing animals for magnetic resonance spectroscopy studies.
BACKGROUND: The ansamycin class of antibiotics are produced by various Actinomycetes. Their carbon framework arises from the polyketide pathway via a polyketide synthase (PKS) that uses an unusual starter unit. Rifamycin (rif), produced by Amycolatopsis mediterranei, is the archetype ansamycin and it is medically important. Although its basic precursors (3-amino-5-hydroxy benzoic acid AHBA, and acetic and propionic acids) had been established, and several biosynthetic intermediates had been identified, very little was known about the origin of AHBA nor had the PKS and the various genes and enzymes that modify the initial intermediate been characterized. RESULTS: A set of 34 genes clustered around the rifK gene encoding AHBA synthase were defined by sequencing all but 5 kilobases (kb) of a 95 kb contiguous region of DNA from A. mediterranei. The involvement of some of the genes in the biosynthesis of rifamycin B was examined. At least five genes were shown to be essential for the synthesis of AHBA, five genes were determined to encode the modular type I PKS that uses AHBA as the starter unit, and 20 or more genes appear to govern modification of the polyketide-derived framework, and rifamycin resistance and export. Putative regulatory genes were also identified. Disruption of the PKS genes at the end of rifA abolished rifamycin B production and resulted in the formation of P8/1-OG, a known shunt product of rifamycin biosynthesis, whereas disruption of the orf6 and orf9 genes, which may encode deoxysugar biosynthesis enzymes, had no apparent effect. CONCLUSIONS: Rifamycin production in A. mediterranei is governed by a single gene cluster consisting of structural, resistance and export, and regulatory genes. The genes characterized here could be modified to produce novel forms of the rifamycins that may be effective against rifamycin-resistant microorganisms.
The effect has been studied of adding either misonidazole (MISO) or metronidazole (METRO) to cytotoxic drug treatment of C3H mice bearing the RIF-1 sarcoma. The nitroimidazoles were injected 30 min before the cytotoxic drugs at a dose of 2 . 5 mmol/kg. Both clonogenic-cell survival and growth delay were measured as indicators of tumour response and depression in WBC count and acute lethality were used to indicate normal-tissue response. For melphalan, neither pretreatment agent produced any change in tumor response. For cyclophosphamide, no change was produced by METRO but a minimal increase in tumour response occurred with MISO. An enhancement of cell killing by CCNU was seen with MISO pretreatment, but there was no increase in tumour growth delay. METRO, however, did not enhance tumour response by either endpoint. WBC depression by CCNU was not enhanced by MISO pretreatment, and there was no significant reduction in the acute LD50. This indicates a therapeutic advantage from the addition of MISO to CCNU in this model system. For chlorambucil, considerable enhancement of tumour response followed either MISO or METRO pretreatment (dose-modifying factors of 2 . 0 and 1 . 4 respectively). However, the modification by MISO of normal-tissue response to chlorambucil was also enhanced by about a factor of 2, with no therapeutic gain.
The effect of inhibitors of nuclear ADP-ribosyl transferase (ADPRT) on the cytotoxicity of melphalan (L-PAM) in the RIF-1 tumour in vivo was investigated. A large single dose of nicotinamide (1000 mg kg-1) enhanced the tumour cell killing by L-PAM as measured by tumour cell survival. This enhancement was maximum when nicotinamide was administered within 1 h before injecting the L-PAM. When given at this time, the nicotinamide had a dose-modifying effect on all L-PAM doses tested, giving rise to a mean enhancement ratio (ER) of 2.2. Nicotinamide did not appear to inhibit the recovery from L-PAM induced potentially lethal damage. L-PAM (6 mg kg-1) produced a transient drop in mouse body temperature. This effect was both increased and prolonged by nicotinamide. In addition the inhibitor also delayed the clearance of L-PAM from the plasma of C3H mice, such that the half-life of the chemotherapeutic agent was extended from 41 min to 143 min. The effect of combining L-PAM with nicotinamide doses below 1000 mg kg-1 was also investigated. The results showed that as the nicotinamide dose was decreased, the enhancement of the effects on body temperature, pharmacokinetics and white blood cell counts were reduced. However, a concomitant loss in the enhancement of tumour cell killing was also observed. Similar results were obtained using 3-aminobenzamide, a more efficient inhibitor of ADPRT.
The effect of combining photodynamic therapy (PDT) and bioreductive drugs has been investigated using the RIF-1 experimental murine tumour. Light was delivered interstially to the tumour at 675 nm using a single optical fibre attached to an argon-ion dye laser. The photosensitizer was disulphonated aluminium phthalocyanine (AlS2Pc) and the bioreductive drugs were the dual function nitroimidazole RSU1069 and its pro-drug RB6145. Varying the time between administration of the photosensitizer and light delivery (TL) from 30 min to 24 h had little influence on the extent of the anti-tumour effect of PDT alone, as measured by the regrowth delay endpoint. When the bioreductive drug was included in the treatment, administered 20 min before light irradiation, regrowth delay was greatly increased. The effectiveness of the combined treatment was optimum for short values of TL (about 1 h). Fluorescence microscopy was used to investigate the distribution of the photosensitizer within the tumours. This showed that the compound was mainly confined to the tumour vasculature over the first few hours post-treatment. The high efficacy of the combined treatment of PDT and bioreductive drugs for short values of TL suggest that photodynamic action, during the period when the photosensitizer AlS2Pc is confined to the vasculature, enhances the severity of tumour hypoxia which is sufficient to induce activation of the bioreductive drugs.
Magnetic resonance spectroscopy (MRS) in situ was used to study changes in 31P metabolism occurring during and after treatment of murine RIF-1 tumours with photodynamic therapy (PDT). Tumours were irradiated using a fibreoptic light delivery system while the mice were in position within the magnet. Changes in 31P-MRS were observable during and immediately after treatments of several minutes' duration. Both the extent and duration of the increase in the Pi/total ratio were light dose dependent. The effect on the metabolism was also affected by the time interval (TL) between administering the photosensitiser disulphonated phthalocyanine, (A1S2Pc) and the light. With a dose of 50 J the increase in Pi/total was much faster when TL was 1 h than when TL was 24 h. This difference in rate probably reflects differences in the distribution of A1S2Pc within the tumour. Significant decreases in pH were only seen after a light dose of 50 J when TL was 1 h. Blood flow measurements using deuterium uptake were also carried out using MRS. These experiments showed that for a dose of 50 J the level of blood flow was reduced by approximately 90% of the control value within 10 min from the end of the 8 min light treatment. This occurred irrespective of the value of TL. The data indicate that it is possible to observe very early changes in 31P metabolism that can be attributed to direct cellular damage as opposed to the later changes indicative of overall tumour hypoxia caused by vascular damage.
The strategy of combining carbogen breathing and nicotinamide to overcome chronic and acute hypoxia respectively is being evaluated clinically. The effects of both agents individually and in combination on relative perfusion of 400-700 mm3 RIF-1 tumours and normal tissues were measured by 86Rb extraction. Carbogen breathing alone for 6 min increased relative tumour perfusion by 50-70% compared with control at flow rates of 50 to 200 ml min-1, but the effect was lost at 300 ml min-1. All flow rates also produced similar increases in relative perfusion of lung, of between 36% and 58%, and smaller increases in skin, of between 20% and 34%. The minimum breathing time at 150 ml min-1 to produce a significant increase in relative tumour perfusion was 4.5 min, and the effect was maintained up to 9 min. Nicotinamide alone at 1000 mg kg-1 60 min before assay did not alter relative tumour perfusion. Comparing the combination of nicotinamide with 6 min carbogen breathing at 150 ml min-1 with carbogen breathing alone showed no difference in relative tumour perfusion; increases were of 36% and 42% respectively. Nicotinamide-induced alterations in microcirculation associated with reduction of acute hypoxia have therefore not been detected by 86Rb extraction. The perfusion-enhancing effect of carbogen in this tumour is probably an important component of its radiosensitising ability, in addition to its known ability to increase the oxygen-carrying capacity of the blood, and should be taken into consideration in clinical studies.
The influence of photodynamic therapy (PDT) on vascular perfusion and the development of hypoxia was investigated in the murine RIF-1 tumour. Image analysis was used to quantify changes in perfusion and hypoxia at 5 min after interstitial Photofrin-mediated PDT. The fluorescent stain Hoechst 33342 was used as an in vivo marker of functional vascular perfusion and the antibody anti-collagen type IV as a marker of the tumour vasculature. The percentage of total tumour vasculature that was perfused decreased to less than 30% of control values after PDT. For the lower light doses this decrease was more pronounced in the centre of the tumour. The observed reduction in vascular perfusion showed a good linear correlation (r = 0.98) with previously published tumour perfusion data obtained with the 86Rb extraction technique. The image analysis technique provides extra information concerning the localisation of (non)-perfused vessels. To detect hypoxic tumour areas in vivo, an immunohistochemical method was used employing NITP [7-(4'-(2-nitroimidazol-1-yl)-butyl)-theophylline]. A large increase in hypoxic areas was found for PDT-treated tumours. More than half the total tumour area was hypoxic after PDT, compared with < 4% for control tumours. Our studies illustrate the potential of image analysis systems for monitoring the functional consequences of PDT-mediated vascular damage early after treatment. This provides direct confirmation that the perfusion changes lead to tissue hypoxia, which has implications for the combined treatment of PDT with bioreductive drugs.