Evaluation of Delivered Doses in Proton Beam Therapy for Prostate Cancer Using Positron Emission Tomography/Computed Tomography Imaging

AIMS

Proton beams deposit energy along their paths and stop abruptly without penetrating the opposite side, making it difficult to detect their actual paths. However, confirming the path may lead to evaluating the actual doses to organs at risk in proton therapy for prostate cancer. As proton beams produce positron emitters through nuclear fragmentation reactions, theoretically, proton beam paths can be measured by positron emission tomography/computed tomography (PET/CT). Therefore, this study investigated whether conducting PET/CT examinations immediately after proton beam therapy helps to assess the doses delivered to the rectal and urinary bladder walls, which are the major sites of radiation-related toxicity.

MATERIALS AND METHODS

Between June 2022 and June 2023, 51 consecutive patients with prostate cancer who underwent proton beam therapy were enrolled and imaged with PET/CT to measure these radioactive particles and validate the actual dose delivered to the rectal and urinary bladder walls.

RESULTS

The delivered doses assessed using PET/CT after proton beam therapy strongly correlated with the planned volume for proton beam treatment.

CONCLUSIONS

PET/CT exhibited potential as a valuable tool for validating the irradiated dose to organs at risk.

Generation and purification of ACTH-secreting hPSC-derived pituitary cells for effective transplantation

Pituitary organoids are promising graft sources for transplantation in treatment of hypopituitarism. Building on development of self-organizing culture to generate pituitary-hypothalamic organoids (PHOs) using human pluripotent stem cells (hPSCs), we established techniques to generate PHOs using feeder-free hPSCs and to purify pituitary cells. The PHOs were uniformly and reliably generated through preconditioning of undifferentiated hPSCs and modulation of Wnt and TGF-β signaling after differentiation. Cell sorting using EpCAM, a pituitary cell-surface marker, successfully purified pituitary cells, reducing off-target cell numbers. EpCAM-expressing purified pituitary cells reaggregated to form three-dimensional pituitary spheres (3D-pituitaries). These exhibited high adrenocorticotropic hormone (ACTH) secretory capacity and responded to both positive and negative regulators. When transplanted into hypopituitary mice, the 3D-pituitaries engrafted, improved ACTH levels, and responded to in vivo stimuli. This method of generating purified pituitary tissue opens new avenues of research for pituitary regenerative medicine.

Selective dysfunction of fast-spiking inhibitory interneurons and disruption of perineuronal nets in a tauopathy mouse model

In Alzheimer's disease (AD), network hyperexcitability is frequently observed and associated with subsequent cognitive impairment. Dysfunction of inhibitory interneurons (INs) is thought to be one of the key biological mechanisms of hyperexcitability. However, it is still unknown how INs are functionally affected in tau pathology, which is a major pathology in AD. To clarify this, we evaluated the neuronal activity of cortical INs in 6-month-old rTg4510 mice, a model of tauopathy. Calcium imaging with mDlx enhancer-driven labeling revealed that neuronal activity in INs was decreased in rTg4510 mice. In the patch clamp recording, the firing properties of fast-spiking INs were altered so as to reduce their activity in rTg4510 mice. In parallel with microglial activation, perineuronal nets around parvalbumin-positive INs were partially disrupted in rTg4510 mice. Taken together, our data indicate that the excitability of cortical fast-spiking INs is decreased, possibly because of the disruption of perineuronal nets.

P-218 Mitochondria transfer from adipose stem cell ameliorates the development potential of cryopreserved oocytes

Study question

Could autologous adipose stem cell (ASC) mitochondria supplementation restore the post-fertilization development potentialin vitrified-thawed oocytes?

Summary answer

Autologous ASC mitochondria supplementation could rejuvenate the quality of vitrified-thawed oocytes and enhance the embryo’s developmental capacity.

What is known already

Pre- and post-implantation developmental potential of embryos derived from vitrified oocytes are remarkedly lower than those of fresh oocytes. Despite its’ low efficacy, oocyte cryopreservation is becoming prevalent in assisted reproductive technologies to cater the growing demands due to patients' sociological and pathological conditions. Unfavorable effects to mitochondrial membrane potential, mitochondrial structure, ATP production, reactive oxygen species (ROS), meiotic spindle and microfilaments, and Ca2+ ion regulation are reported as detrimental damages in oocytes following the cryopreservation, that adversely affect the development potential. Furthermore, autologous stem cell mitochondria supplementation can rescue the aging-related oocyte mitochondrial damages.

Study design, size, duration

The mature oocytes, autologous ASC, and mitochondria were collected from young mice and analyzed at Osaka City University, Japan. In total, 600 young mouse mature oocytes were occupied in this prospective study.

Participants/materials, setting, methods

Young C57BL/6JJmsmouse (8weeks) mature oocytes that have been pre-vitrified were thawed before the start of the ICSI procedure.ASC specificity and ASC mitochondria function and ultrastructure were pre-analyzed. ASC mitochondria were isolated on the same day and supplemented with intracellular sperm injection (ICSI) and as the control, the mitochondrial buffer was injected. The survival rate, fertilization rate, blastulation, mitochondria function, ROS level in 2 cell embryos, and live birth rates were compared between the 2 groups.

Main results and the role of chance

The ASC mitochondriashowed higher membrane potential compared to the somatic cells and were spherical in shape with low cristae numbers. The survival rate and the fertilization ratewere comparable in both mitochondria supplemented and control groups. However, theASC mitochondria supplementation seemed to havesignificantly improvedthe blastocyst development capacity from 2cell embryos compared to the control group (P < 0.05;56.8% & 38.2%, respectively).And interestingly, a significantly higher ATP level was found in the mitochondria supplemented group’s 2 cell embryos thanin the control group (P < 0.05;905.6pmol & 561.1pmol respectively). And though it was not statistically significant, a higher potential ofgetting live birth was found in the mitochondria supplemented group thanthe control group after 2 cell embryo transfer.

Limitations, reasons for caution

We acknowledge that the absence of compared data with fresh oocytes’ ICSI, the detailed cellular mechanism behind theimprovement of embryo development, and transgenerational safety in offspring developed fromthe mitochondria supplementation werethe limitations of this study.

Wider implications of the findings

With these results, we propose that ASC mitochondria supplementation could rejuvenate the quality of cryopreserved oocytes and enhance the embryo developmental capacity, signifying another possible approach of mitochondrial transplantation therapy.

Trial registration number

not applicable

A novel orexin antagonist from a natural plant was discovered using zebrafish behavioural analysis

OBJECTIVE

Phenotypic screening is one of the most practical approaches to the identification of mediators of behaviour, since it is difficult to model brain function in vitro, at a cellular level. We used a zebrafish (Danio rerio) behavioural assay to discover novel, natural, neuroactive compounds.

MATERIALS AND METHODS

A zebrafish behavioural assay was performed for seven natural compounds, obtained from plants. The behavioural profiles were compared to those of known psychoactive drugs. We characterised a natural compound exhibiting a behaviour profile similar to that of suvorexant, using in silico, in vitro and microarray expression analysis.

RESULTS

The behavioural analysis performed in this study classified central nervous system drugs according to their mechanism. Zebrafish treated with a natural compound, 8b-(4'-Hydroxytigloyloxy) costunolide (8b), showed behaviour profiles similar to those of zebrafish treated with suvorexant, a known orexin antagonist. This behavioural assay was validated using in silico and in vitro assays, which revealed that the new compound was a dual orexin receptor antagonist. In addition, transcriptome analysis suggested that 8b might regulate the nuclear factor-κB (NF-κB) related pathway.

CONCLUSIONS

We conclude that zebrafish phenotypic screening, combined with in silico assays and gene expression profiling, is a useful strategy to discover and characterize novel therapeutic compounds, including natural products.

Glomerular hyperfiltration with hyperglycemia in the spontaneously diabetic Torii (SDT) fatty rat, an obese type 2 diabetic model

Glomerular hyperfiltration is observed in an early stage of kidney diseases including diabetic nephropathy. A better understanding of pathophysiological changes in glomerular hyperfiltration is essential for development of new therapies to prevent kidney disease progression. In this study, we investigated glomerular changes including glomerular filtration rate (GFR) and glomerular size in the Spontaneously Diabetic Torii (SDT) fatty rat, an obese type 2 diabetic model, and we also evaluated pharmacological effects of the sodium glucose cotransporter 2 inhibitor dapagliflozin on the renal lesions. Dapagliflozin was administered to SDT fatty rats from 5 to 17 weeks of age. Blood and urinary biochemical parameters were periodically measured. GFR was determined by transdermal GFR monitor at 16 weeks of age and histopathological analysis was performed at 17 weeks of age. SDT fatty rat developed severe hyperglycemia and exhibited pathophysiological abnormalities in the kidney, such as an increased GFR, glomerular hypertrophy and tissue lesions. Dapagliflozin achieved good glycemic control during the experimental period, inhibited the increase in GFR, and improved histopathological abnormalities in tubules. These results suggest that the SDT fatty rat is a useful model for analyzing the pathogenesis of diabetic nephropathy during its early stage and dapagliflozin improves not only hyperglycemia but also glomerular hyperfiltration and tubule lesions in SDT fatty rat.

All-polarization-maintaining Er-doped dual comb fiber laser using single-wall carbon nanotubes

We demonstrated a bi-directional, Er-doped dual comb fiber laser consisting of all-polarization-maintaining fiber devices. Polyimide films in which single-wall carbon nanotubes (SWNTs) were dispersed were used as the in-line saturable absorber. In order to avoid synchronization of the two combs and associated damage to the SWNT film, a two-branch configuration with two SWNT films was employed. Soliton pulses with almost the same optical spectra were generated stably in each direction, and dual comb beats were observed simply by overlapping the two outputs. The repetition frequency was 28 MHz, and the frequency difference was 105-140 Hz. Thanks to the small frequency difference, dual comb beats corresponding to the whole optical spectrum were observed without any overlapping. Fourier transform spectroscopy using the developed dual comb source was examined, and the characteristics of an optical filter were successfully obtained.

RNA-seq analysis of diet-driven obesity and anti-obesity effects of quercetin glucoside or epigallocatechin gallate in Drosophila adults

OBJECTIVE

High-fat diet (HFD) feeding stimulates fat accumulation in mammals and Drosophila. In the present study, we examined whether simultaneous feeding of familiar anti-obesity drugs, quercetin glycosides (QG) and epigallocatechin gallate (EGCG), to Drosophila has the same suppressive effect on fat accumulation as previously reported in rats and mice. To understand the underlying molecular mechanisms of HFD diet-induced obesity and the suppression effect of the drugs, we performed transcriptome analyses.

MATERIALS AND METHODS

We induced extra fat accumulation by feeding Drosophila fly food containing 20% coconut oil and quantified the triglyceride accumulated in flies. The effects of anti-obesity drugs were also evaluated. We isolated total RNA from each sample and performed RNA-seq analyses and quantitive Real Time-Polymerase Chain Reaction (qRT-PCR) to investigate altered gene expression.

RESULTS

The mRNA levels of several genes involved in lipid metabolism, glycolysis/gluconeogenesis, and anti-oxidative stress changed in HFD-fed adults. Moreover, the levels altered in those fed an HFD with QG or EGCG. The qRT-PCR further confirmed the RNA-seq data, suggesting that the expression of five essential genes for lipid metabolism changed in HFD-fed flies and altered in the flies treated with anti-obesity drugs. The most remarkable alteration was observed in the dHSL gene encoding a lipase involved in lipid-storage after HFD feeding and HFD with QG or EGCG. These alterations are consistent with HFD-induced fat accumulation as well as the anti-obesity effects of the drugs in mammals, suggesting that the genes play an important role in anti-obesity effects.

CONCLUSIONS

These are the first reports to date of entire profiles of altered gene expression under the conditions of diet-induced obesity and its suppression by anti-obesity drugs in Drosophila.

POU3F2 participates in cognitive function and adult hippocampal neurogenesis via mammalian-characteristic amino acid repeats

POU3F2/BRN-2 is a transcription factor that is mainly expressed in the central nervous system and plays an important role in brain development. The transactivation domain of POU3F2 includes multiple mammalian-characteristic tandem amino acid repeats (homopolymeric amino acid repeats). We previously generated knock-in mice (Pou3f2^Δ/Δ mice) in which all three homopolymeric amino acid repeats were deleted from the Pou3f2 transactivation domain and identified phenotypic impairments in maternal behavior and pup recognition. Yet, the exact biological implications of homopolymeric repeats are not completely understood. In this study, we investigated cognitive function and hippocampal neurogenesis in Pou3f2^Δ/Δ mice. Pou3f2^Δ/Δ mice exhibited cognitive impairment in object recognition and object location tests. Immunohistochemistry for doublecortin, a marker of immature neurons, showed a lower number of newborn neurons in the dentate gyrus of adult Pou3f2^Δ/Δ mice compared with wild-type mice. Consistent with this observation, adult Pou3f2^Δ/Δ mice had lower numbers of 5-bromo-2'-deoxyuridine (BrdU) and NeuN double-positive cells at 4 weeks after BrdU injection compared with control mice, indicating the decreased generation of mature granule cells in Pou3f2^Δ/Δ mice. Taken together, these results suggest that POU3F2 is involved in cognitive function as well as adult hippocampal neurogenesis, and that homopolymeric amino acid repeats in this gene play a functional role.

Possible selection of viable human blastocysts after vitrification by monitoring morphological changes

PURPOSE

Morphological assessment of human blastocysts has been effective for selecting embryos with high potential. However, they often show repeated shrinkage and expansion toward their hatching. Here we assessed whether capturing morphological changes over time of vitrified-warmed blastocysts could lead to a better selection of viable embryos from shrunken blastocysts.

METHODS

The implantation rates of vitrified-warmed blastocysts that were shrunken or expanded (developing) at the time of loading for transfer were compared among 2,729 cycles that were subjected to single blastocyst transfer. Vitrified (107) and fresh blastocysts (17) were donated for the experimental study. To assess the relationship between morphology (expanded vs. shrunken) and the mitochondrial respiration of blastocysts, the oxygen consumption rate (OCR) was analyzed for 55 specimens using an uncoupler of oxidative phosphorylation. The remaining 69 blastocysts were used for recording morphological changes every 15 min for 48 h after warming.

RESULTS

Because there were no surplus embryos, 7 % of the vitrified-warmed blastocysts were shrunken and transferred. The shrunken embryos had sufficient implantation ability (40 %). The OCR of the shrunken embryos was significantly lower than that of their expanded counterparts. Upon exposure to the uncoupler, the OCR of some shrunken embryos increased to levels similar to the expanded specimens. Time-lapse images revealed some shrunken embryos which formed blastocoel by 5 h following warming exhibited developmental competence to the hatched stage.

CONCLUSIONS

Data of the present study suggest a group of shrunken blastocysts contains many viable and clinically available embryos and time-lapse observation of vitrified-warmed blastocysts is a potential method to distinguish viable embryos from shrunken blastocysts.

Reactive oxygen species enhance excitatory synaptic transmission in rat spinal dorsal horn neurons by activating TRPA1 and TRPV1 channels

Central neuropathic pain (CNP) in the spinal cord, such as chronic pain after spinal cord injury (SCI), is an incurable ailment. However, little is known about the spinal cord mechanisms underlying CNP. Recently, reactive oxygen species (ROS) have been recognized to play an important role in CNP of the spinal cord. However, it is unclear how ROS affect synaptic transmission in the dorsal horn of the spinal cord. To clarify how ROS impact on synaptic transmission, we investigated the effects of ROS on synaptic transmission in rat spinal cord substantia gelatinosa (SG) neurons using whole-cell patch-clamp recordings. Administration of tert-butyl hydroperoxide (t-BOOH), an ROS donor, into the spinal cord markedly increased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) in SG neurons. This t-BOOH-induced enhancement was not suppressed by the Na(+) channel blocker tetrodotoxin. However, in the presence of a non-N-methyl-D-aspartate glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, t-BOOH did not generate any sEPSCs. Furthermore, in the presence of a transient receptor potential ankyrin 1 (TRPA1) channel antagonist (HC-030031) or a transient receptor potential vanilloid 1 (TRPV1) channel antagonist (capsazepine or AMG9810), the t-BOOH-induced increase in the frequency of sEPSCs was inhibited. These results indicate that ROS enhance the spontaneous release of glutamate from presynaptic terminals onto SG neurons through TRPA1 and TRPV1 channel activation. Excessive activation of these ion channels by ROS may induce central sensitization in the spinal cord and result in chronic pain such as that following SCI.

Electrical Properties of 3C-SiC and its application to FET

Electrical and luminescent properties of nondoped, and N-doped n-type 3C-SiC layers epitaxially grown on Si(100) by chemical vapor deposition were studied. Nondoped n-type epilayers with carrier concentration of 1×1016cm−3 and the Hall mobility of 750cm2/Vs at room temperature have the activation energy of donors, Ed=2OmeV, which is different from that of the donors in the N-doped layers. The photoluminescence spectra of nondoped layers are different from those of N-doped ones. These results suggest that the donors in the unintentionally doped n-type 3C-SiC are not due to N impurities. 45–70 % of N-donors in the N-doped epilayers are compensated.

Schottky-barrier and MOS-type field-effect transistors have been fabricated from 3C-SiC. The transistor operations of MESFETs and MOSFETs were studied at elevated temperatures up to 440°C. Transconductances of 1.7mS/mm and 0.15mS/mm for MESFET and 0.8 and 0.05mS/mm for MOSFET at room temperature and 440°C, respectively, were obtained. The drain currentvoltage characteristics of both the FETs at room temperature did not change in the least after heating up to 440°C in the air.

Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni

Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.

EFFECT OF LIFESTYLE FACTORS ONINFERTILITY IN MEN

Environmental factors, changes in lifestyle and occupational exposures are responsible for declining human semen quality. We investigated the effects of history of surgery and lifestyle choices on infertility of 271 infertile men and 251 healthy volunteers. The frequency of varicocelectomy was significantly higher in infertile men (2.9%) than in controls (0.4%; P < 0.05). Alcohol use was significantly more common in infertile men (92%) than in controls (80%; P < 0.01). Satisfaction with sexual life was greater in controls (85%) than in infertile men (77%; P < 0.05). Other factors had no effect.

Climacteric-Like Disorders in Prostate Cancer Patients Treated With LHRH Agonists

We assessed long-term side effects with characteristics of female climacteric disorders in prostate cancer patients treated with luteinizing hormone-releasing hormone (LHRH) agonists. Such side effects are not considered to be serious, though they can significantly affect patient quality of life. Sixty-four prostate cancer patients treated with LHRH agonists and 30 benign prostatic hyperplasia patients, as a control group, were surveyed by questionnaire. The median age of the cancer patients was 74.9 years old, ranging from 60 to 94 years, and the median LHRH agonist dosing period was 16.5 months, ranging from 1 to 64 months. The results of the questionnaires were compared between the patients and the controls, as well as between different variables. Sixty (93.8%) of 64 patients claimed symptoms similar to female climacteric disorders. Further, more than 50% of the symptoms included in the questionnaire were reported by 14 (21.9%) of the patients. Symptoms reported by the patients were more severe than those by the controls. Hot flashes, sleep disturbance, and fatigue recorded high scores in the patient questionnaires as compared with those of the controls. In addition, as the term of LHRH agonist use increased, complaints of sweating or coldness in hands and feet increased. Patients without bone metastasis frequently experienced heaviness in the head and headaches compared to those with bone metastasis. The results of our questionnaire-based outcome study showed that side effects similar to female climacteric disorders in prostate cancer patients treated with LHRH agonists were more severe than in the control group, which could be detrimental to quality of life and general well-being.

Intermittent administration of brain-derived neurotrophic factor (BDNF) ameliorates glucose metabolism and prevents pancreatic exhaustion in diabetic mice

We previously demonstrated that repetitive administration of brain-derived neurotrophic factor (BDNF) ameliorates glucose metabolism and energy expenditure in obese diabetic db/db mice. However, we have not evaluated in detail the effect of single or intermittent BDNF administration on glucose metabolism in a diabetic animal model. The objectives of this study were to examine the dose-response effect and dosing interval of BDNF administration in db/db mice and to evaluate the effect of intermittent BDNF administration on pancreatic function in db/db mice. We evaluated the dose-response effect of BDNF by single administration in db/db mice. First, single administration of BDNF greater than 70 mg/kg significantly reduced blood glucose concentration one day after administered, and the BDNF effect was maintained for 6 d. Next, the effects of BDNF administered twice a week at 4, 10, 25, and 62.5 mg/kg on blood glucose concentration, and the effects of BDNF administered once a week at 10, 20, 30, 50, and 70 mg/kg on blood glucose concentration were examined in db/db mice. In the intermittent treatment studies, BDNF dose-dependently ameliorated glucose metabolism by not only the twice-a-week administration but also the once-a-week administration. Lastly, because BDNF reduces the food intake of obese hyperphagic diabetic mice, the effects of BDNF administered once or twice a week on the blood glucose concentration and plasma and pancreatic insulin concentrations in db/db mice were compared with those of the vehicle under pair-fed conditions. Under pair-fed conditions, the intermittent administration of BDNF (25 mg/kg, twice a week, or 50 mg/kg, once a week) significantly reduced the blood glucose concentration and increased the plasma and pancreatic insulin concentrations compared with those in the pair-fed vehicle-treated db/db mice. This indicates that the prolonged hypoglycemic effect of BDNF is not simply due to the reduction of food intake. In conclusion, we demonstrated that the intermittent administration of BDNF ameliorates glucose metabolism and prevents pancreatic exhaustion in obese diabetic mice. These findings indicate that BDNF may have potential as a unique hypoglycemic agent for the treatment of diabetes at a fundamental level with good patient compliance.

Comparison of the antidiabetic effects of brain-derived neurotrophic factor and thiazolidinediones in obese diabetic mice

AIMS

Brain-derived neurotrophic factor (BDNF) ameliorates glucose metabolism in obese diabetic db/db mice. The antidiabetic effect of BDNF is dependent on plasma insulin levels, and BDNF enhances insulin action by modulating insulin signalling in peripheral tissues. The aim of the study was to compare the antidiabetic effects of BDNF with those of thiazolidinediones (TZDs), which are insulin-sensitizing agents, through evaluation of the effects of BDNF and TZDs on glucose metabolism, energy expenditure, pancreatic function and hepatic steatosis in db/db mice.

METHODS

The effects of BDNF, pioglitazone and rosiglitazone on blood glucose concentration, body weight and pancreatic insulin and glucagon contents and the effects of BDNF and troglitazone treatment for 3 weeks on blood glucose concentration, body and liver weights and histological liver images were examined in db/db mice. Furthermore, since BDNF reduces food intake in obese hyperphagic diabetic mice, the effects of BDNF treatment for 3 weeks on blood glucose concentration, body weight, fat pad and liver weights and rectal temparature in db/db mice were compared with those of troglitazone under pair-fed conditions.

RESULTS

BDNF, pioglitazone and rosiglitazone all ameliorated hyperglycaemia in db/db mice, but BDNF increased the pancreatic insulin content more effectively than pioglitazone and rosiglitazone. The pancreatic glucagon content decreased with BDNF, but increased with pioglitazone and rosiglitazone compared with vehicle, and body weight and liver weight increased with troglitazone, but decreased with BDNF compared with vehicle. Histological analysis of the liver showed that BDNF treatment reduced the massive vacuolization observed with vehicle, whereas troglitazone worsened the vacuolization. Body weight, fat pad and liver weights in BDNF-treated mice were significantly lower than those in pair-fed troglitazone-treated db/db mice, and rectal temperature in BDNF-treated mice was significantly higher than that in pair-fed troglitazone-treated mice, suggesting that BDNF enhances energy expenditure.

CONCLUSIONS

These data suggest that compared with TZDs, BDNF potently ameliorates pancreatic dysfunction, fatty liver and energy expenditure, thereby exerting favourable antidiabetic effects in type 2 diabetic mice.

Controlling the dissociative ionization of ethanol with 800 and 400nm two-color femtosecond laser pulses

Ethanol molecules were irradiated with a pair of temporally overlapping ultrashort intense laser pulses (10(13)-10(14) Wcm(2)) with different colors of 400 and 800 nm, and the dissociative ionization processes have been investigated. The yield ratio of the C-O bond breaking with respect to the C-C bond breaking was varied in the range of 0.17-0.53 sensitively depending on the delay time between the two laser pulses, and the absolute value of the yield of the C-O bond breaking was found to be increased largely when the Fourier-transform limited 800 nm laser pulse overlaps the stretched 400 nm laser pulse, demonstrating an advantage of the two-color intense laser fields in controlling chemical bond breaking processes.