Microsurgical thrombectomy: where the ancient art meets the new era.

Mechanical thrombectomy (MT) is the leading treatment for acute large vessel occlusion (LVO). However, surgical thrombectomy (ST) may have a role in well selected LVO patients where MT failed to re-establish flow, the endovascular route is inaccessible, or where MT is a financially prohibitive or absent option (developing and poor countries). We compared the efficacy and efficiency between ST and MT, and described our operative experience and its potential application in the developing world. Clinical outcomes, procedural times, and efficacy of treatment were compared between the MT and ST of acute LVO between 2012 and 2022. Propensity score-matched analysis was also conducted to compare MT and ST. One-hundred nine patients fulfilled the study criteria (77 MTs vs 32 STs). Factors driving outcome were age (aOR: 0.95, 95%CI, 0.91-0.98), hemisphere side (aOR: 0.38, 95%CI, 0.15-0.96), and DWI-ASPECT (aOR: 1.39, 95%CI, 1.09-1.77) at presentation by the multivariate analysis. Times from door-start of procedure (P = 0.45) and start of procedure-recanalization (P = 0.13) were similar between treatment options. Propensity score-matched analysis found no significant difference for 2 treatment methods about time of door to recanalization (P = 0.155) and outcome (P = 0.221). The prognosticators of thrombectomy for acute LVO in patients with successful recanalization were age, affected hemisphere side, and DWI-ASPECT score. Our evidence shows that the efficacy of ST is similar to that of MT. There should be a place of ST for cases of mechanical failure or tandem cervical ICA and MCA occlusion. ST may be a temporizing LVO treatment option in healthcare systems where MT is inexistent or financially prohibitive to patients.

A case of facial nerve palsy caused by severe head injury treated by translabyrinthine approach.

Background: Several treatments for traumatic facial paralysis have been reported, but the role of surgery is still controversial. Case Description: A 57-year-old man was admitted to our hospital with head trauma due to a fall injury. A total body computed tomography (CT) scan showed a left frontal acute epidural hematoma associated with a left optic canal and petrous bone fractures with the disappearance of the light reflex. Hematoma removal and optic nerve decompression were performed immediately. The initial treatment was successful with complete recovery of consciousness and vision. The facial nerve paralysis (House and Brackmann scale grade 6) did not improve after medical therapy, and thus, surgical reconstruction was performed 3 months after the injury. The left hearing was lost entirely, and the facial nerve was surgically exposed from the internal auditory canal to the stylomastoid foramen through the translabyrinthine approach. The facial nerve's fracture line and damaged portion were recognized intraoperatively near the geniculate ganglion. The facial nerve was reconstructed using a greater auricular nerve graft. Functional recovery was observed at the 6-months follow-up (House and Brackmann grade 4), with significant recovery in the orbicularis oris muscle. Conclusion: Interventions tend to be delayed, but it is possible to select a treatment method of the translabyrinthine approach.

A case of anterior choroidal artery occlusion test under MEP monitoring for a recurrent internal carotid artery-anterior choroidal artery bifurcation aneurysm clipping.

A 59-year-old female with recurrent Anterior Choroidal Artery (AchA) aneurysm was elected for surgery at our institution through a standard pterional approach. Two thin perforating branches were found to origin from the dome of the aneurysm during operation, and therefore complete aneurysm clipping preserving these branches was not feasible. These perforating branches were temporarily occluded under motor-evoked potential (MEP) monitoring. The MEPs remained stable during 10 min of temporary clipping, and we concluded that these branches could be sacrificed, and therefore neck clipping was performed occluding these tiny AchA perforators. Although postoperative magnetic resonance imaging with diffusion-weighted images showed ischemic signs in left AchA territory after the operation, the patient remained asymptomatic and was discharged home with mRS 0.

Emergent Subarachnoid Clot Removal with Aneurysm Repair for Subarachnoid Hemorrhage Might Improves Clinical Outcome.

BACKGROUND: The goal in treating patients with subarachnoid hemorrhage (SAH) is shifting to preventing early brain injury. Intracranial pressure must be controlled to manage such an injury. We retrospectively analyzed the impact of aggressive removal of cisternal subarachnoid clots with simultaneous aneurysm repair for all grades of SAH. METHODS: Our study included 260 consecutive patients with SAH treated through aggressive subarachnoid clot removal with simultaneous aneurysm repair. Baseline patient characteristics, history, radiographic findings, and time of SAH onset to arrival in the operating room were retrospectively collected. Factors related to poor outcome (modified Rankin Scale score >2) were analyzed. RESULTS: Multivariate analysis revealed several characteristics were significantly associated with poor outcome: advanced age (adjusted odds ratio [aOR] 1.07, 95% confidence interval [CI] 1.04-01.10); time of SAH onset to operating room per 1-hour increments (aOR 1.03, 95% CI 1.01-01.05; postoperative hematoma volume (aOR 1.04, 95% CI 1.01-01.06); and poorer World Federation of Neurosurgical Societies grade (aOR 2.18, 95% CI 1.63-02.92). According to a receiver operating characteristic analysis, the cut-off time of SAH onset to operating room was 6.0 hours (area under the curve 0.61, P = 0.01, 95% CI 0.52-0.69, sensitivity = 0.79, specificity = 0.43) as the threshold between modified Rankin Scale scores of 0-2 and 3-6. CONCLUSIONS: Prognostic factors of SAH in patients undergoing emergent aneurysm repair with simultaneous removal of a cisternal subarachnoid clot are advanced age, poorer World Federation of Neurosurgical Societies grade, postoperative hematoma volume, and a longer time from SAH onset to operating room. The clinical outcome may improve with emergent reduction of intracranial pressure through removal of the subarachnoid clot as soon as possible.

A Novel Technique to Retrieve a Snagged Stent Retriever: Technical Note.

Objective: Currently, there are no established approaches for removal of devices, such as stents, which sometimes become difficult to recover during endovascular treatment. We report a new method to successfully remove a stent that has become snagged during thrombus removal. Case Presentation: An 82-year-old female who had undergone a mitral valve annuloplasty developed sudden aphasia, right hemiplegia, and right unilateral spatial neglect on postoperative day 10. Cranial MRI indicated occlusion of the horizontal segment of the left middle cerebral artery. During mechanical thrombectomy, a vasospasm snagged the stent, and re-sheathing attempts failed repeatedly. We wedged the microcatheter into the spasm site and slowly injected a solution containing 1 cc of nicardipine, 2 cc of contrast medium, and 2 cc of heparin in normal saline intra-arterially. After several minutes, we retracted the Trevo wire slightly and easily removed the stent. The thrombus adhered to the retrieved stent. Post-retrieval imaging showed that the branch was completely recanalized. Conclusion: In cases wherein a microwire or stent retriever becomes difficult to remove, we propose switching to a microcatheter with a sufficient diameter to allow vasodilator injection. If the microcatheter is difficult to remove, our method can be utilized by severing the hub, inserting a larger-bore catheter, and injecting vasodilators. Adding contrast medium to the intra-arterial injectate allows visualization of whether the solution has reached the spasm site. Furthermore, by injecting the solution through the wedged catheter, pooling of the solution at the spasm site can be confirmed.

Imaging of Oral SCC Cells by Raman Micro-Spectroscopy Technique.

We used Raman micro-spectroscopy technique to analyze the molecular changes associated with oral squamous cell carcinoma (SCC) cells in the form of frozen tissue. Previously, Raman micro-spectroscopy technique on human tissue was mainly based on spectral analysis, but we worked on imaging of molecular structure. In this study, we evaluated the distribution of four components at the cell level (about 10 µm) to describe the changes in protein and molecular structures of protein belonging to malignant tissue. We analyzed ten oral SCC samples of five patients without special pretreatments of the use of formaldehyde. We obtained cell level images of the oral SCC cells at various components (peak at 935 cm-1: proline and valine, 1004 cm-1: phenylalanine, 1223 cm-1: nucleic acids, and 1650 cm-1: amide I). These mapping images of SCC cells showed the distribution of nucleic acids in the nuclear areas; meanwhile, proline and valine, phenylalanine, and amide I were detected in the cytoplasm areas of the SCC cells. Furthermore, the peak of amide I in the cancer area shifts to the higher wavenumber side, which indicates the α-helix component may decrease in its relative amounts of protein in the ß-sheet or random coil conformation. Imaging of SCC cells with Raman micro-spectroscopy technique indicated that such a new observation of cancer cells is useful for analyzing the detailed distribution of various molecular conformation within SCC cells.

[Clipping of a Large Unruptured Basilar Artery Trunk Large Aneurysm Using Rapid Ventricular Pacing:A Case Report].

Neck clipping of basilar trunk aneurysms, particularly those of a large size, is challenging because of its location. Here, we report a case of a basilar artery aneurysm successfully treated with neck clipping using rapid ventricular pacing(RVP). A 67-year-old woman was referred to our hospital for treatment of a large basilar artery aneurysm. Although coiling was considered, we performed neck clipping of this aneurysm because of the expected radical therapeutic effect. The patient was positioned in the right park-bench position, and right suboccipital craniotomy was performed. The aneurysm was mainly approached via the right supracerebellar route. RVP softened the aneurysm for easy dissection and insertion of multiple clips. The postoperative course was uneventful, and she was discharged 1 week later without neurological deficits. RVP should be considered for the treatment of complex aneurysms as adjunctive techniques.

[Determining the tumor-cell density required for macroscopic observation of 5-ALA-induced fluorescence of protoporphyrin IX in cultured glioma cells and clinical cases].

We investigated the association between the cell density and intensity of 5-aminolevulinic acid-induced fluorescence of protoporphyrin IX in 3-dimensionally cultured C6 glioma cells. The ratio between 636-nm red fluorescence excited by a 405-nm laser and 513-nm green autofluorescence of the tissue was measured as the fluorescence intensity. A ratio exceeding 0.68 was macroscopically judged as fluorescence-positive by observers, and the cell density at this fluorescence intensity was 1×107< cells/mL. In clinical surgical fields, the fluorescence ratio was about 0.65 in cases judged as fluorescence-positive, similarly to that in cultured cells. Neurosurgeons and pathologists should recognize that tumor cells are present in fluorescence-negative regions. It is necessary to develop a device which measures fluorescence more simply than macroscopic observation for cutting-edge brain surgery.

Targeting of sebaceous glands by δ-aminolevulinic acid-based photodynamic therapy: An in vivo study.

BACKGROUND AND OBJECTIVES: Wide application of ALA-PDT for acne is limited due to relative strong side effects, such as pain and erythema. The objective of this study was to establish a protocol for ALA-PDT that would provide specific destruction of sebaceous glands at the lowest concentrations and shortest contact times of ALA. MATERIALS AND METHODS: The rhino (hr(rh) hr(rh) ) murine model, an experimental acne model, was used in this study. A freshly prepared hydrophilic ALA hydrochloride ointment (2.5%, 5%, and 20%) was applied to the backs of 16-week-old male rhino mice. The fluorescence intensity (FI) of ALA-induced protoporphyrin IX (ALA-PpIX) on the skin was measured by spectrofluorometry. Skin samples were taken at 1, 2, and 4 hours after ALA application to determine the tissue distribution of ALA-PpIX by fluorescence microscopy. Light irradiation was also performed with a broadband light source (600-1100 nm, 15 J/cm² , 60 mW/cm²) with subsequent histological examination 1 day after treatment. RESULTS: Prominent increases of ALA-PpIX were observed 1 hour after application of 5% and 20% ALA, while no increase was observed with 2.5% ALA until 2 hours. A direct correlation was found between ALA concentration and ALA-PpIX FI. While no fluorescence was detected 1 hour after application of 2.5% or 5% ALA, 20% ALA produced a strong fluorescence in the epidermis, utricle walls, and sebaceous glands. Histological evaluation showed no damage to skin treated with 2.5% ALA-PDT incubated for 1 hour. Damage was still focused within the sebaceous glands with longer incubation times. Increased ALA concentrations resulted in more prominent damage to the epidermis and sebaceous glands, with deeper damage to the dermis when longer incubation times were used. CONCLUSION: Focused damage of sebaceous glands can be achieved with ALA-PDT when low concentrations of ALA (2.5-5.0%) and short incubation times (to 2 hours) were used.

Enhancement of 5-Aminolevulinic acid-induced oxidative stress on two cancer cell lines by gold nanoparticles.

5-Aminolevulinic acid (5-ALA) and its methyl ester (5-ALA-Me) at mM concentration levels induce oxidative stress via the production of reactive oxygen species (ROS). Human cancer cell lines (MCF-7 and HepG2) incubated in the dark in the simultaneous presence of 5.0 mM or more 5-ALA or 5-ALA-Me (for MCF-7) and 7 microg/mL of 15 nm citrate capped gold nanoparticles (AuNPs) were damaged more seriously compared to those in the presence of the levulinic acid alone. Damage is visible in electron micrographs which reveal similar morphology both in the presence or absence of AuNPs. Cytotoxicity was observed irrespective of the presence of serum and medium. Production of ROS in cell free samples containing 5-ALA-Me was monitored by EPR as the DMPO-OH spin adduct and also showed a catalytic effect of AuNPs. Both SOD and CAT inhibited the production of ROS and also reduced cytotoxicity in the cell samples. These observations can be explained by initial attack on the cell membrane by ROS produced in the medium outside the cell and provide insight into possible uses of 5-ALA in cancer chemotherapy.

Dynamic adsorption properties of n-alkyl glucopyranosides determine their ability to inhibit cytolysis mediated by acoustic cavitation.

Suspensions of human leukemia (HL-60) cells readily undergo cytolysis when exposed to ultrasound above the acoustic cavitation threshold. However, n-alkyl glucopyranosides (hexyl, heptyl, and octyl) completely inhibit ultrasound-induced (1057 kHz) cytolysis (Sostaric, et al. Free Radical Biol. Med. 2005, 39, 1539-1548). The efficacy of protection from ultrasound-induced cytolysis was determined by the n-alkyl chain length of the glucopyranosides, indicating that protection efficacy depended on adsorption of n-alkyl glucopyranosides to the gas/solution interface of cavitation bubbles and/or the lipid membrane of cells. The current study tests the hypothesis that "sonoprotection" (i.e., protection of cells from ultrasound-induced cytolysis) in vitro depends on the adsorption of glucopyranosides at the gas/solution interface of cavitation bubbles. To test this hypothesis, the effect of ultrasound frequency (from 42 kHz to 1 MHz) on the ability of a homologous series of n-alkyl glucopyranosides to protect cells from ultrasound-induced cytolysis was investigated. It is expected that ultrasound frequency will affect sonoprotection ability since the nature of the cavitation bubble field will change. This will affect the relative importance of the possible mechanisms for ultrasound-induced cytolysis. Additionally, ultrasound frequency will affect the lifetime and rate of change of the surface area of cavitation bubbles, hence the dynamically controlled adsorption of glucopyranosides to their surface. The data support the hypothesis that sonoprotection efficiency depends on the ability of glucopyranosides to adsorb at the gas/solution interface of cavitation bubbles.

Ultrasound-induced cytolysis of cancer cells is enhanced in the presence of micron-sized alumina particles.

Micron-sized alumina particles have been shown to enhance sonochemical free radical formation in aqueous solutions and simultaneously increase the solution temperature and acoustic (white) noise, effects attributable to enhanced inertial cavitation [T. Tuziuti, J. Phys. Chem. A 109 (2005) 4869-4872]. In the current study, the same ultrasound exposure system was applied to in vitro cancer cells as a model system to determine the effect of alumina particles on the long-term survival of cells and on the major pathways of cell death, i.e., either apoptosis or necrosis. Following 6h of incubation after ultrasound treatment, it was found that the cells died mainly through necrosis, irrespective of whether the exposure was conducted in the presence of alumina particles or not. Alumina particles were non-toxic to cells alone, but were found to decrease the long-term survivability of cells that survived the initial exposure. This effect depended on the size and concentration of particles. These results correlated well with the effect of alumina particles on the sonochemical oxidation of KI under the same exposure conditions. Spin-trapping with 5,5-dimethyl-pyroline N-oxide (DMPO) and electron spin resonance spectroscopy indicated that the sonochemical formation of *OH radicals increased in the presence of alumina particles. The current study is consistent with the well known observation that micron-sized particles enhance the acoustic cavitation process.

Fluorescence-guided resection of metastatic brain tumors using a 5-aminolevulinic acid-induced protoporphyrin IX: pathological study.

We performed a pathological study to identify the locus of production of protoporphyrin IX (PPIX) in human metastatic brain tumors. Patients with metastatic brain tumors (n = 11) received 1 g of 5-aminolevulinic acid (5-ALA) perorally 2 h before undergoing surgery. The target region was exposed to laser light with a peak wavelength of 405 +/- 1 nm and an output of 40 mW. Tissue samples from the tumor bulk and surrounding areas were examined by histological and fluorescence methods. Of the 11 tumors, 9 manifested PPIX fluorescence in the tumor bulk and peritumoral brain tissue. Our findings indicate that PPIX fluorescence can be observed in peritumoral edematous areas that are free of neoplastic cells, because PPIX produced by neoplastic cells leaks into the surrounding edematous area.

Massive apoptotic cell death of human glioma cells via a mitochondrial pathway following 5-aminolevulinic acid-mediated photodynamic therapy.

The basic mechanism of cell death induced by 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) (ALA-PDT) in glioma cells has not been fully elucidated. In this study, the details of the cell death mechanism induced by ALA-PDT were investigated in three human glioma cell lines (U251MG, U87MG, and U118MG) in vitro. To evaluate the manner of accumulation of protoporphyrin IX (PpIX), intracellular PpIX contents were measured by flow cytometry after incubation with 5-ALA. To analyze the mechanism of cell death, U251MG cells were assayed by the terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick end-labeling (TUNEL) method, and the caspase activity was measured after ALA-PDT. Furthermore, the mitochondrial membrane potential (MMP) and the release of mitochondrial cytochrome c were determined. PpIX fluorescence reached a plateau 4 h after exposure to 5-ALA. The proportion of dead cells increased with increases in the dosage of light. These cells were confirmed by TUNEL staining to be apoptotic. Increases in the activity of both caspase-3 and -9, a decrease in MMP, and a marked increase in cytochrome c in the cytosolic fraction were found after cells were subjected to PDT. These results indicate that a dysfunction of MMP is followed by mitochondrial cytochrome c release, which triggers apoptosis through a mitochondrial pathway. ALA-PDT induces massive apoptosis due to the direct activation of a mitochondrial pathway, which is resistant to many anti-apoptotic processes, in human glioma cells. This finding implies that ALA-PDT is a promising therapy for the treatment of apoptosis-reluctant tumors such as malignant gliomas.

Reinforcement therapy using nitric oxide synthase inhibitors against endotoxin shock in dogs.

PURPOSE: Nitric oxide synthase (NOS) inhibitors were confirmed to correct the hypotension associated with septic shock, but the overall prognosis is often pessimistic. The histological findings failed to show any improvement. In fact, some patients even exhibited signs of exacerbation. The purpose of this study was to investigate the therapeutic effects of NOS inhibitors and catecholamines in dogs suffering from endotoxin shock. The histological changes produced by these agents were also evaluated. METHODS: Mongrel dogs were used under midazolam anesthesia. A PiCCO continuous cardiac output monitoring catheter was placed in the femoral artery, and a central venous monitoring catheter was placed in the external carotid artery. RESULTS: Endotoxin (0.5 mg/kg, i.v.) was administered to cause shock. After this shock state was observed, the NOS inhibitors and catecholamines raised the blood pressure, and norepinephrine (NA, 2 microg/kg/h) was found to be more potent than S-methylisothiourea (SMT, 20 microg/kg/h). The combined effects of SMT-NA or SMT-DOB were greater than those of NA or dobutamine (DOB) alone. The histological changes induced by endotoxin shock were not ameliorated by the administration of NOS inhibitors but instead appeared to be exacerbated to some degree. CONCLUSION: NOS inhibitors combined with cathecholamines were thus suggested to be able to reduce the cathecolamine dosage in patients suffering from septic shock; They are thus considered to be hemodynamically effective agents.

n-Alkyl glucopyranosides completely inhibit ultrasound-induced cytolysis.

The mechanism(s) responsible for sudden cytolysis observed when cells are exposed to ultrasound could be mechanical and/or free radical in nature. Free radical reactions are initiated in the core and in the interfacial regions of collapsing acoustic cavitation bubbles. Because cyclic sugars are known to inhibit free radical chain reactions, we investigated the effects of n-alkyl-beta-d-glucopyranosides of varying hydrophobicity on ultrasound (1.057 MHz)-induced cytolysis of HL-60 cells in vitro. n-Alkyl glucopyranosides with hexyl- (5 mM), heptyl- (3 mM), or octyl- (2 mM) n-alkyl chains protected 100% of the cell population from ultrasound-induced cytolysis under a range of conditions that resulted in 35 to 100% cytolysis in the absence of glucopyranosides. The protected cell populations also possessed long-term reproductive viability. However, the hydrophilic methyl-beta-D-glucopyranoside could not protect cells, even up to a concentration of 30 mM. Furthermore, none of the glucopyranosides could prevent cytolysis of cells from a mechanically induced shear stress. Spin trapping and electron spin resonance experiments confirmed the presence of inertial cavitation in cell suspensions both in the presence and in the absence of the surfactants. It is concluded that surface-active glucopyranosides efficiently quench cytotoxic radicals and/or their precursors at the gas/solution interface of collapsing cavitation bubbles.

Correlation between acoustic cavitation noise and yield enhancement of sonochemical reaction by particle addition.

The mechanism of the effect of particle addition on sonochemical reaction is studied through the measurements of frequency spectrum of sound intensity for evaluating the cavitation noise and the absorbance for the liberation of iodine from an aqueous solution of KI as an index of oxidation reaction by ultrasonic irradiation in the presence or absence of alumina particles. As it is expected that both the acoustic noise and a rise in temperature in the liquid irradiated by intense ultrasound will increase with the number of collapsing bubbles, these are supposed to be the best tools for evaluating the relative number of bubbles. In the present investigation, it has been shown that the addition of particles with appropriate amount and size results in an increase in the absorbance when both the acoustic noise and the rise in the liquid temperature due to cavitation bubbles also increase. This suggests that the enhancement in the yield of sonochemical reaction by appropriate particle addition comes from an increase in the number of cavitation bubbles. The existence of particle in liquid provides a nucleation site for cavitation bubble due to its surface roughness, leading to the decrease in the cavitation threshold responsible for the increase in the number of bubbles when the liquid is irradiated by ultrasound. Thus, from the present investigation, it is clarified that the particle addition has a potential to enhance the yield in the sonochemical reaction.

Irrigational therapy of a dentigerous cyst in a geriatric patient: a case report.

Dentigerous cysts are recognized as one of the most common lesions of the jaws. Although surgical enucleation is usually the preferred treatment method, it is not always the best choice for elderly patients who have other medical complications. With cyst irrigational therapy, repeated irrigation allows bone regeneration around the cyst to progress more rapidly than that around a cyst treated operatively with marsupialization. We used irrigational therapy to treat a dentigerous cyst in a 72-year-old man who did not agree to surgery because he had no symptoms associated with the cyst, and he had other medical complications. After one year, remarkable bone regeneration was observed. We conclude that irrigational therapy appears to be an effective, less-invasive alternative to surgery for geriatric patients.

Correlation between sonochemistry of surfactant solutions and human leukemia cell killing by ultrasound and porphyrins.

The synergistic effect of ultrasound and drugs on cells is known as sonodynamic therapy. The use of sonodynamic therapy for the potential clinical treatment of certain tumors is promising, however, the mechanism of sonodynamic therapy could be due to either sonomechanical and/or sonochemical effects on the cells. The aim of the current study is to determine the importance of the sonochemical mechanism for sonodynamic therapy. Sonochemical effects arise from the formation of radical species following collapse of cavitation bubbles. The synergistic effect of ultrasound (47 kHz) and analogues of a gallium-porphyrin derivative (ATX-70) on cytolysis of Human leukemia cells (HL-525 and HL-60) suspended in a cell culture medium were studied. Organic surfactants preferentially accumulate and subsequently decompose at the gas/solution interface of cavitation bubbles, producing secondary radicals that can diffuse to the bulk solution. The gallium porphyrin analogues used in the current study possess two n-alkyl side chains (ATX-C(x), where x = number of carbon atoms, ranging from x = 2 to x = 12). By varying the n-alkyl chain length, thereby modifying the surfactant properties of the ATX-C(x) derivatives, cell killing in relation to the accumulation of ATX-C(x) derivatives at the gas/solution interface of cavitation bubbles was determined. Following sonolysis in the presence of ATX-C(x), a strong correlation for the yield of carbon-centered radicals and cell killing was observed. These results support the hypothesis that a sonochemical mechanism is responsible for the synergistic effect of ultrasound and ATX-C(x) on HL-525 and HL-60 cells.

Singlet oxygen trapping by DRD156 in micellar solutions.

Recently, 4.4'-bis(1-p-carboxyphenyl-3-methyl-5-dydroxyl)-pyrazol (DRD156) has been developed as a new sensitive reagent that reacts specifically with singlet oxygen. The specificity of DRD156 for singlet oxygen in a biomimetic solution (micellar solution) and the effects of its coexistence with other reagent were examined with electron spin resonance (ESR). Singlet oxygen was generated using photosensitization reaction. The ESR spectrum of the radical derived from DRD156 after the reaction with singlet oxygen in phosphate buffered salines (PBS) was comprised of twenty-nine lines, whereas that in cetyltrimethylammonium bromide (CTAB) micelles was comprised of nine lines. Both 2,2,6,6-tetramethyl-4-piperidine (TMPD) and 1,3-diphenyl-isobenzofuran (DPBF) reduced the singlet oxygen-DRD156 signal intensity, and TMPD-mediated decrease in PBS (to 62%) was almost the same as that in CTAB micelle (to 65%). In contrast, DPBF reduced the DRD156 signal intensity more effectively in CTAB micelle (to 12%) than PBS (to 38%). These results indicate that the specificity of DRD156 for singlet oxygen is dependent on microenvironment.