Application of Reactive Oxygen Species in Dental Treatment

Reactive oxygen species (ROS) and free radicals, which have been implicated in inflammation, pain, carcinogenesis, and aging, are actually used in dental treatments such as tooth bleaching and composite resin polymerization. Recently, numerous studies have investigated the application of ROS in the medical and dental fields. In previous studies, ROS were generated intentionally through pathways such as photolysis, photocatalytic methods, and photodynamic therapy, which are used in the medical field to target cancer. In the field of dentistry, generated ROS are applied mainly for periodontal treatment and sterilization of the root canal, and its effectiveness as an antibacterial photodynamic therapy has been widely reported.. Given this background, the present article aimed to review the basic effects of ROS in dental medicine, especially endodontic therapy, and to discuss future applications of ROS.

P-185 The migration speed of nucleolar precursor bodies in pronuclei affects in vitro fertilization-derived human embryo ploidy status

Study question

Does the migration speed of nucleolar precursor bodies (NPBs) in male and female pronuclei (mPN and fPN) affect in vitro fertilization (IVF)-derived embryo ploidy status?

Summary answer

The NPB migration speed in mPN impacts the IVF-derived human embryo ploidy status and this indicator could be an attractive marker for noninvasive embryo selection.

What is known already

NPBs are not considered as simple nucleolar components transmitted from an oocyte to an embryo, and they could participate in genome remodeling during embryo development. NPBs are essential only shortly after fertilization, suggesting that they may actively participate in centromeric chromatin establishment. A previous study demonstrated that NPBs migrated faster in intracytoplasmic sperm injection-derived zygotes having the potential to develop into a blastocyst and eventually into a baby (Inoue et al., 2021). However, the relationship between NPB migration speed and IVF-derived embryo ploidy status is unclear.

Study design, size, duration

The relationship between the NPB migration speed and embryo ploidy status was retrospectively analyzed in patients with recurrent assisted reproductive technology failure (euploid n =18; aneuploid n =19; and total = 219 NPBs). Archived time-lapse videos (images were recorded every 5 min; Geri+) from incubation after IVF were retrieved after the patients were identified for the study, and the NPB migration speed was analyzed. The retrospective analyses were performed with the patient’s identities masked.

Participants/materials, setting, methods

mPN and fPN were identified by appearance location in a zygote (fPN appearance is just below the polar bodies). The mPN, fPN, and 2–3 NPBs/PN central coordinates were measured by Kinovea (motion capture software). Their central coordinates were confirmed/revised every image and were decided. The migration distance of NPBs between two sequential images was calculated as the standard of the central PN coordinates. Thereafter, the migration speed of NPBs was calculated.

Main results and the role of chance

Both NPB speeds were significantly faster in the euploid than in the aneuploid groups (mPN: 4.08±0.61 vs. 3.54±0.54 µm/h, P =0.003, power [1-β]: 0.999, fPN: 4.03±0.89 vs. 3.26±0.45 µm/h, P <0.003, 1-β: 0.987). The NPB speed in mPN was correlated with that in fPN (rs =0.523, P =0.001). The ploidy status was related to the NPB speeds in mPN and fPN (P <0.05) in univariate logistic analysis including male/female ages, ICM/TE grades, and 29 morphokinetic parameters. The factors associated with ploidy status were the NPB speed in mPN (odds ratio [OR], 10.2; 95% confidence interval [CI], 1.90–54.90; P =0.007) and female age (OR, 0.8; 95%CI, 0.64–0.98; P =0.03) in multivariate logistic analysis. The cutoff value for the NPB speeds in mPN and fPN were 3.65 μm/h (specificity, 73.7%; sensitivity, 77.8%; AUC, 0.78; 95%CI, 0.62–0.93) and 3.77 μm/h (specificity, 89.5%; sensitivity, 66.7%; AUC, 0.78; 95%CI, 0.62–0.94). When the zygotes were categorized by their cutoff values, the euploid rate in zygotes with NPB speeds greater than the cutoff value was significantly higher than that in zygotes with the speeds less than the cutoff value (mPN = 73.7% vs. 22.2% [P =0.003]; fPN = 85.7% vs. 26.1% [P <0.001]).

Limitations, reasons for caution

The NPB migration in the z-axis direction could not be analyzed. NPB tracking could not be performed when NPBs were large in number or drastically moved. Our findings should help in elucidating the relationship, although they did not completely explain the relationship between NPB migration and embryo development.

Wider implications of the findings

The migration speed of NPBs impacts human embryo ploidy status. NPB migration speed may add clinical value for embryo selection, which may be associated with live birth, and consequently, the time of the live birth could be shorter. The indicator could be an attractive marker for noninvasive embryo selection.

Trial registration number

Not applicable

ADC Level is Related to DWI Reversal in Patients Undergoing Mechanical Thrombectomy: A Retrospective Cohort Study

BACKGROUND AND PURPOSE

In patients with ischemic stroke, DWI lesions can occasionally be reversed by reperfusion therapy. This study aimed to ascertain the relationship between ADC levels and DWI reversal in patients with acute ischemic stroke who underwent recanalization treatment.

MATERIALS AND METHODS

We conducted a retrospective cohort study in patients with acute ischemic stroke who underwent endovascular mechanical thrombectomy with successful recanalization between April 2017 and March 2021. DWI reversal was assessed through follow-up MR imaging approximately 24 hours after treatment.

RESULTS

In total, 118 patients were included. DWI reversal was confirmed in 42 patients. The ADC level in patients with reversal was significantly higher than that in patients without reversal. Eighty-three percent of patients with DWI reversal areas had mean ADC levels of ≥520 × 10^-6 mm²/s, and 71% of patients without DWI reversal areas had mean ADC levels of <520 × 10^-6 mm²/s. The mean ADC threshold was 520 × 10^-6 mm²/s with a sensitivity and specificity of 71% and 83%, respectively. In multivariate analysis, the mean ADC level (OR, 1.023; 95% CI, 1.013-1.033; P < .0001) was independently associated with DWI reversal. Patients with DWI reversal areas had earlier neurologic improvement (NIHSS at 7 days) than patients without reversal areas (P < .0001).

CONCLUSIONS

In acute ischemic stroke, the ADC value is independently associated with DWI reversal. Lesions with a mean ADC of ≥520 × 10^-6 mm²/s are salvageable by mechanical thrombectomy, and DWI reversal areas regain neurologic function. The ADC value is easily assessed and is a useful tool to predict viable lesions.

Evolution of the Magnetic Excitations in NaOsO_{3} through its Metal-Insulator Transition

The temperature dependence of the excitation spectrum in NaOsO_{3} through its metal-to-insulator transition (MIT) at 410 K has been investigated using resonant inelastic x-ray scattering at the Os L_{3} edge. High-resolution (ΔE∼56  meV) measurements show that the well-defined, low-energy magnons in the insulating state weaken and dampen upon approaching the metallic state. Concomitantly, a broad continuum of excitations develops which is well described by the magnetic fluctuations of a nearly antiferromagnetic Fermi liquid. By revealing the continuous evolution of the magnetic quasiparticle spectrum as it changes its character from itinerant to localized, our results provide unprecedented insight into the nature of the MIT in NaOsO_{3} [J. G. Vale, S. Calder, C. Donnerer, D. Pincini, Y. G. Shi, Y. Tsujimoto, K. Yamaura, M. M. Sala, J. van den Brink, A. D. Christianson, and D. F. McMorrow, Phys. Rev. B 97, 184429 (2018)PRBMDO2469-995010.1103/PhysRevB.97.184429].

Essential versus accessory aspects of cell death: recommendations of the NCCD 2015

Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is generally referred to as ‘accidental cell death' (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. ‘Regulated cell death' (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects in the mammalian system, but simply alters the kinetics of cellular demise as it shifts its morphologic and biochemical correlates. Conversely, bona fide cytoprotection can be achieved by inhibiting the transduction of lethal signals in the early phases of the process, when adaptive responses are still operational. Thus, the mechanisms that truly execute RCD may be less understood, less inhibitable and perhaps more homogeneous than previously thought. Here, the Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death.

New members of layered oxychloride perovskites with square planar coordination: Sr2MO2Cl2 (M = Mn, Ni) and Ba2PdO2Cl2

We have demonstrated high-pressure syntheses of Ruddlesden–Popper type layered oxychloride perovskites, Sr₂MnO₂Cl₂, Sr₂NiO₂Cl₂ and Ba₂PdO₂Cl₂, with a square planar coordination around the transition metal centres.

The effect of irradiation wavelengths and the crystal structures of titanium dioxide on the formation of singlet oxygen for bacterial killing

Safe and effective methods for oral bacterial disinfection have been desired, since bacteria cause many infectious diseases such as dental caries, periodontal disease, and endodontic infections. Singlet oxygen ((1)O(2)) is attractive, because it is toxic to prokaryotic cells, but not to eukaryotic cells. We selected irradiation of titanium dioxide (TiO(2)) as a source of (1)O(2), because it has been used in sunscreens and cosmetic products without complications. In order to establish the optimal oral photodynamic therapy conditions, we measured the rate of (1)O(2) formation from the irradiated anatase or rutile forms of TiO(2) using 365 or 405 nm lamps. The rate of (1)O(2) formation decreased in the following order: anatase, 365 nm > rutile, 405 nm > rutile, 365 nm > anatase, 405 nm. Therefore, we concluded that irradiation of the rutile form of TiO(2) by a 405 nm lamp is the most favorable photodynamic therapy condition, because visible light is more desirable than UV light from the viewpoint of patient safety. We also confirmed that there was no direct HO(•) formation from the irradiated TiO(2).

Magnetically driven metal-insulator transition in NaOsO3

The metal-insulator transition (MIT) is one of the most dramatic manifestations of electron correlations in materials. Various mechanisms producing MITs have been extensively considered, including the Mott (electron localization via Coulomb repulsion), Anderson (localization via disorder), and Peierls (localization via distortion of a periodic one-dimensional lattice) mechanisms. One additional route to a MIT proposed by Slater, in which long-range magnetic order in a three dimensional system drives the MIT, has received relatively little attention. Using neutron and x-ray scattering we show that the MIT in NaOsO(3) is coincident with the onset of long-range commensurate three dimensional magnetic order. While candidate materials have been suggested, our experimental methodology allows the first definitive demonstration of the long predicted Slater MIT.

Stimulatory Effects of CO(2) Laser, Er:YAG Laser and Ga-Al-As Laser on Exposed Dentinal Tubule Orifices

We investigated the effects of lasers irradiation on the exposed dentinal tubule. Human tooth specimens with exposed dentinal tubule orifices were used. Three types of lasers (CO₂ laser, Er:YAG laser and Ga-Al-As laser) were employed. The parameters were 1.0 W in continuous-wave mode with an irradiation time of 30 s for the CO₂ laser, 30 mJ in continuous-wave mode with an irradiation time of 60 s for the Er:YAG laser, and 1.0 W in continuous-wave mode with an irradiation time of 60 s for the Ga-Al-As laser. A non-irradiated group was used as a control. After laser irradiation, the dentinal surface of each sample was observed using SEM. Afterwards, all samples were immersed in methylene blue dye solution in order to evaluate the penetration of the dye solution and observe the change in dentinal permeability after laser irradiation. SEM observation showed that the control group had numerous exposed dentinal tubule orifices, whereas these orifices were closed in the laser-irradiated groups. There was consistent dye penetration into the pulp chamber in the control group, whereas no dye penetration was evident in the laser-irradiated groups. Therefore, laser appears to be a promising treatment for reducing permeation through exposed dentinal tubules.

Surface changes of mineral trioxide aggregate after the application of bleaching agents: electron microscopy and an energy-dispersive X-ray microanalysis

INTRODUCTION

The aim of this study was to investigate the changes in the surface structure and chemical composition after applying bleaching agents to completely hardened mineral trioxide aggregate.

METHODS

A total of 12 samples of MTA blocks were divided into three groups, two different bleaching agents, and a control group. The surface structure was observed using a scanning electron microscope. The changes in elemental composition were analyzed by an energy-dispersive x-ray microanalysis (EDX) system.

RESULTS

The surface of the MTA covered with each bleaching agent changed in terms of both color and structure compared with the control. EDX showed that both bleaching agents affected the elemental distribution. A decrease in Ca and an increase in Si were shown, and this tendency was especially pronounced in the higher hydrogen peroxide concentration group.

CONCLUSIONS

The acidic conditions induced by bleaching agents brought about the deterioration of the MTA surface. These findings suggest that MTA is an insufficient barrier against tooth bleaching.

Antioxidant effects of antioxidant biofactor on reactive oxygen species in human gingival fibroblasts

The purpose of this study was to investigate the effects of antioxidant biofactor (AOB) on reactive oxygen species (ROS). Generation of superoxide radical (O₂^•−) and hydroxyl radical (^•OH) was determined using an electron spin resonance (ESR) spin-trapping method. AOB was added at different concentrations to these free radical generating systems. The generation of both O₂^•− and ^•OH was scavenged by the addition of AOB in a dose-dependent manner. These results indicate that AOB has strong antioxidant properties against these radicals. We further investigated the anti-oxidative effect of AOB on human gingival fibroblasts (HGFs). HGFs were treated for 3 h with α-MEM containing a combination of AOB and H₂O₂ (AOB + H₂O₂ group), containing H₂O₂ (H₂O₂ group), or containing AOB alone (AOB group). Non-stimulated HGFs were used as a control group. The number of surviving cells was in the order of the AOB group > control group > AOB + H₂O₂ group > H₂O₂ group. The level of expression of type I collagen mRNA and production of collagen were also in the order of the AOB group > control group > AOB + H₂O₂ group > H₂O₂ group. In conclusion, our results suggest that AOB may protect HGFs against oxidative stress by reducing stress-induced ROS.

Involvement of JNK in the regulation of autophagic cell death

Programmed cell death is a crucial process in the normal development and physiology of metazoans, and it can be divided into several categories that include type I death (apoptosis) and type II death (autophagic cell death). The Bcl-2 family proteins are well-characterized regulators of apoptosis, among which multidomain pro-apoptotic members (such as Bax and Bak) function as a mitochondrial gateway at which various apoptotic signals converge. Although embryonic fibroblasts from Bax/Bak double-knockout (DKO) mice are resistant to apoptosis, we have previously reported that these cells still die by autophagy in response to various death stimuli. In this study, we found that jun N-terminal kinase (JNK) was activated in etoposide- and staurosporine-treated, but not serum-starved, Bax/Bak DKO cells, and that autophagic cell death was suppressed by the addition of a JNK inhibitor and by a dominant-negative mutant of JNK. Studies with sek1(-/-)mkk7(-/-) cells revealed that disruption of JNK prevented the induction of autophagic cell death. Co-activation of JNK and autophagy induced autophagic cell death. Activation of JNK occurred downstream of the induction of autophagy, and was dependent on the autophagic process. These results indicate that JNK activation is crucial for the autophagic death of Bax/Bak DKO cells.

Influence of sodium benzoate on the metabolism ofo-xylene in the rat

The main metabolites of o-xylene in urine are o-methylhippuric acid, o-toluic acid, o-toluic acid glucuronide, 3,4-dimethylphenol, 3,4-dimethylphenol conjugates and o-xylylmercapturic acid. The urinary excretion of o-toluic acid, o-toluic acid conjugates and o-xylene were increased by the prior administration of sodium benzoate. Conversely, the amounts of o-methylhippuric acid, 3,4-dimethylphenol conjugates and o-xylylmercapturic acid decreased by sodium benzoate pretreatment. In addition, the urinary excretion of o-methylhippuric acid was delayed by the pretreatment. The percentages of urinary excretion of the o-xylene metabolites were substantially changed by the pretreatment with sodium benzoate. These results therefore highlight a potential interaction of an air pollutant with a food additive, an interaction that remains to be established in man.

Stimulatory Effects of Hydroxyl Radical Generation by Ga-Al-As Laser Irradiation on Mineralization Ability of Human Dental Pulp Cells

The present study was conducted to investigate the effects of Ga-Al-As laser irradiation on the mineralization ability of human dental pulp (HDP) cells. HDP cells in vitro were irradiated once with a Ga-AL-As laser at 0.5 W for 500 s and at 1.0 W for 500 s in order to investigate free radicals as one mechanism for transmission of laser photochemical energy to cells. Production of the hydroxyl radical (*OH) was measured using the ESR spin-trapping method and was found to be increased by laser irradiation. The DMPO-OH was not detected in the presence of dimethyl sulfoxide (DMSO), a *OH scavenger. The formation of calcification nodule was also investigated by von Kossa staining. The number of calcified nodules was increased by 1.0 W-laser irradiation. Alkaline phosphatase (ALP) activity was higher in the 1.0 W-laser irradiation group. Expression of mRNAs for heat shock protein 27, bone morphogenetic proteins (BMPs) and ALP were greater in the 1.0 W-laser irradiation group. Expression of BMPs in the conditioned medium was also higher in the 1.0 W-laser irradiation group. In particular, DMSO decreased the number of calcified nodule produced by 1.0 W-laser irradiation. These results supposed that the mineralization of HDP cells is stimulated by laser irradiation, and that *OH generated by laser irradiation is a trigger for promotion of HDP cell mineralization.

Body fat mass and lean mass as predictors of survival in hemodialysis patients

A higher body mass index (BMI) is a predictor of better survival in hemodialysis patients, although the relative importance of body fat and lean mass has not been examined in the dialysis population. We performed an observational cohort study in 808 patients with end-stage renal disease on maintenance hemodialysis. At baseline, fat mass was measured by dual-energy X-ray absorptiometry and expressed as fat mass index (FMI; kg/m2). Lean mass index (LMI) was defined as BMI minus FMI. During the mean follow-up period of 53 months, 147 deaths, including 62 cardiovascular (CV) and 85 non-CV fatal events, were recorded. In univariate analysis, LMI was not significantly associated with CV or non-CV death, whereas a higher FMI was predictive of lower risk for non-CV death. Analyses with multivariate Cox models, which took other confounding variables as covariates, indicated the independent associations between a higher LMI and a lower risk of CV death, as well as between a higher FMI and a lower risk of non-CV death. These results indicate that increased fat mass and lean mass were both conditions associated with better outcomes in the dialysis population.

Antiapoptotic function of 17AA(+)WT1 (Wilms' tumor gene) isoforms on the intrinsic apoptosis pathway

The WT1 gene is overexpressed in human primary leukemia and a wide variety of solid cancers. The WT1 gene is alternatively spliced at two sites, yielding four isoforms: 17AA(+)KTS(+), 17AA(+)KTS(-), 17AA(-)KTS(+), and 17AA(-)KTS(-). Here, we showed that 17AA(+)WT1-specific siRNA induced apoptosis in three WT1-expressing leukemia cell lines (K562, HL-60, and Kasumi-1), but not in WT1-non-expressing lymphoma cell line (Daudi). 17AA(+)WT1-specific siRNA activated caspase-3 and -9 in the intrinsic apoptosis pathway but not caspase-8 in the extrinsic one. On the other hand, 17AA(-)WT1-specific siRNA did not induce apoptosis in the three WT1-expressing cell lines. The apoptosis was associated with activation of proapoptotic Bax, which was activated upstream of the mitochondria. Constitutive expression of 17AA(+)WT1 isoforms inhibited apoptosis of K562 leukemia cells induced by apoptosis-inducing agents, etoposide and doxorubicin, through the protection of mitochondrial membrane damages, and DNA-binding zinc-finger region of 17AA(+)WT1 isoform was essential for the antiapoptotic functions. We further studied the gene(s) whose expression was altered by the expression of 17AA(+)WT1 isoforms and showed that the expression of proapoptotic Bak was decreased by the expression of 17AA(+)KTS(-)WT1 isoform. Taken together, these results indicated that 17AA(+)WT1 isoforms played antiapoptotic roles at some points upstream of the mitochondria in the intrinsic apoptosis pathway.

Overexpressed Bcl-x(L) prevents bacterial superantigen-induced apoptosis of thymocytes in vitro

bcl-x, a homologous gene of bcl-2, has an anti-apoptotic function and appears to play a critical role in the development of lymphoid systems. To investigate the effect of overexpressed Bcl-x(L) on the development of T lymphocytes, we established two lines of transgenic mice by using Emu-chicken bcl-x(L) (cbcl-x(L)) transgene, where the cBcl-x(L) protein was expressed mainly in lymphoid cells. Although thymocytes and splenocytes from cbcl-x(L) transgenic mice are resistant to apoptosis in vitro, clonal deletion of thymocytes, recognizing endogenous self-superantigens in the thymus, still normally proceeded and no self-reactive T cells were found in the spleen of the transgenic mice. To dissect clonal deletion, we utilized two in vitro models, thymocytes/antigen presenting cells co-culture system and fetal thymus organ culture system. In both, bacterial superantigen staphylococcus aureus enterotoxin B (SEB) induces apoptosis of T cells with Vbeta8+ T cell receptor (TCR) reacting to SEB, which mimics clonal deletion of self-reactive thymocytes in vivo. SEB-induced depletion of Vbeta8+ T cells from thymocytes when taken from the transgenic mice was effectively inhibited. The data might raise the possibility that cell death process involved in clonal deletion in the thymus is a form of apoptosis inhibited by Bcl-x(L).

Opening of plasma membrane voltage-dependent anion channels (VDAC) precedes caspase activation in neuronal apoptosis induced by toxic stimuli

Apoptotic cell death is an essential process in the development of the central nervous system and in the pathogenesis of its degenerative diseases. Efflux of K(+) and Cl(-) ions leads to the shrinkage of the apoptotic cell and facilitates the activation of caspases. Here, we present electrophysiological and immunocytochemical evidences for the activation of a voltage-dependent anion channel (VDAC) in the plasma membrane of neurons undergoing apoptosis. Anti-VDAC antibodies blocked the channel and inhibited the apoptotic process. In nonapoptotic cells, plasma membrane VDAC1 protein can function as a NADH (-ferricyanide) reductase. Opening of VDAC channels in apoptotic cells was associated with an increase in this activity, which was partly blocked by VDAC antibodies. Hence, it appears that there might be a dual role for this protein in the plasma membrane: (1) maintenance of redox homeostasis in normal cells and (2) promotion of anion efflux in apoptotic cells.

Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.

Another way to die: autophagic programmed cell death

Programmed cell death (PCD) is one of the important terminal paths for the cells of metazoans, and is involved in a variety of biological events that include morphogenesis, maintenance of tissue homeostasis, and elimination of harmful cells. Dysfunction of PCD leads to various diseases in humans, including cancer and several degenerative diseases. Apoptosis is not the only form of PCD. Recent studies have provided evidence that there is another mechanism of PCD, which is associated with the appearance of autophagosomes and depends on autophagy proteins. This form of cell death most likely corresponds to a process that has been morphologically defined as autophagic PCD. The present review summarizes recent experimental evidence about autophagic PCD and discusses some aspects of this form of cell death, including the mechanisms that may distinguish autophagic death from the process of autophagy involved in cell survival.

N2O emissions at solid waste disposal sites in Osaka City

Nitrous oxide (N2O) is a trace gas contributing to stratospheric ozone depletion and global warming. Although a large quantity of information exists about N2O emissions from various ecosystems, this study was initiated to demonstrate the features of N2O emissions from sea-based waste disposal sites in Osaka City in relation to CH4 emissions. Average N2O emissions at an active landfill (S-Site) were several times higher than those at a closed landfill (N-Site). Average CH4 emissions were also much greater at the S-Site. Regarding the nature of N2O emissions, remarkable emissions often were observed with aerobic waste layers at the N-Site, suggesting almost inversely related N2O emissions with CH4 production at the N-Site. However, at the S-Site a few exceptionally high N2O emissions were noted in cases of high CH4 emissions.

An investigation into the role of Bcl-2 in neuroendocrine differentiation

INTRODUCTION

In addition to its role in apoptosis suppression, Bcl-2 has been reported to be co-expressed with neuroendocrine markers in several tissues, leading to speculation that this oncoprotein may promote neuroendocrine differentiation.

AIM

This study investigated whether Bcl-2 modulated neuroendocrine biopeptide expression.

METHODS

Levels of chromogranin A, neurone specific enolase, protein gene peptide 9.5, pancreatic polypeptide, and the chromogranin-derived peptides, intervening peptide and vasostatin-1 were examined by immunocytochemistry in rat phaeochromocytoma (PC12) cell lines genetically engineered to over-express Bcl-2 and their mock-transfected controls. Intensity of fluorescence was graded using a semi-quantitative scale from (-) indicating negative expression to (+++) indicating intense positivity.

RESULTS

Mann-Whitney U analysis indicated that no significant differences in expression existed between control and Bcl2 over-expressing cell lines for any of the six peptides examined.

CONCLUSIONS

The results of this study do not support the hypothesis that Bcl-2 promotes the acquisition of a neuroendocrine phenotype.

An Aneurinibacillus sp. strain AM-1 produces a proline-specific aminopeptidase useful for collagen degradation

AIMS

We have been for a species of thermophilic bacteria that can effectively decompose collagen and collagen peptides that tend to be hard-to-degrade proteins because of their high content of proline residues. This study focused upon the enzymatic degradation of prolyl peptides by thermophilic bacteria.

METHODS AND RESULTS

A strain, AM-1, producing a proline-specific aminopeptidase was isolated using a medium containing gelatin that was taken from soil samples collected at Arima Hot Spring located near Kobe, Japan. The strain showed the strongest level of hydrolysing activity toward prolyl-p-nitroanilide, and the activity proved to be thermostable. Phylogenetic analysis based on 16S rDNA sequences revealed that the isolated strain AM-1 was closest to Aneurinibacillus thermoaerophilus DSM10154T in its characteristics. Analysis of the purified proline-specific aminopeptidase suggested that the enzyme is an aminopeptidase containing metal that includes important disulphide bond(s). The strain AM-1 aminopeptidase has more similarities with leucyl aminopeptidases, but its activity level differs greatly with prolyl peptides.

CONCLUSIONS

The proline-specific aminopeptidase from strain AM-1 is the first from the genus Aneurinibacillus and may be a new type of aminopeptidase for hydrolysing prolyl peptide. This enzyme also contributed to the degradation of collagen when used in combination with another collagenolytic protease.

SIGNIFICANCE AND IMPACT OF THE STUDY

The proline-specific aminopeptidase obtained from strain AM-1 may be used in the treatment of wastewater containing collagen that is encountered in the meat industries, and for decreasing bitter peptides in milk products.

Effects of the hydroxyl radical and hydrogen peroxide on tooth bleaching

The mechanisms of bleaching of discolored coronal teeth using hydrogen peroxide (H2O2) were investigated. In a scanning-electron-microscopy study, the intertubular dentin and peritubular dentin were dissolved by high concentrations of H2O2, which is used for bleaching. The X-ray diffraction study showed that hydroxyapatite was not influenced by H2O2. In an electron-spin-resonance study, more hydroxyl radical (* OH) was detected as the H2O2 concentration was increased. When amino acids that are core components of dentin proteins, such as proline and alanine, were added to H2O2, the generation of * OH decreased, but there was no change when glycine was added. A nuclear-magnetic-resonance study showed that proline was degraded completely by H2O2, the structure of alanine changed slightly, and glycine was not affected by H2O2. It is suggested that H2O2 and * OH do not influence the inorganic tissue of dentin but attack the organic component of dentin. These facts suggest that * OH has the main role in tooth bleaching with H2O2.

Dentin Is Dissolved by High Concentrations of L-Ascorbic Acid 2-[3,4-Dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl-hydrogen Phosphate] Potassium Salt with or without Hydrogen Peroxide

L-Ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K(1)) is a conjugate of vitamin C and vitamin E that is water-soluble and stable at room temperature. EPC-K(1) has been developed as a hydroxyl radical (.OH) scavenger and antioxidant. In a previous tooth whitening experiment, it was accidentally found that tooth (dentin) blocks were dissolved by EPC-K(1) with H(2)O(2). In the current study, high concentrations of EPC-K(1) (2.5, 25 mM) with 3% H(2)O(2) dissolved and caused the collapse of dentin blocks. Similar concentrations of EPC-K(1) without 3% H(2)O(2), however, dissolved the dentin blocks without collapse over a 3-week period. In these cases, a.OH-like signal was detected using an ESR spin-trapping method. The volume of calcium in solution (including the dentin block) increased on the addition of EPC-K(1) in a concentration-dependent manner. In addition, the calcium : phosphorus ratio changed from 2 : 1 in sound dentin to 1 : 2 in the collapsed dentin block. High concentrations of EPC-K(1) are therefore considered to have calcium chelating and dentin dissolving activity. The dentin dissolving activity was enhanced when EPC-K(1) was used with H(2)O(2). EPC-K(1) had no protective effect when used in tooth whitening with H(2)O(2).

Gene cloning, expression, and crystallization of a thermostable exo-inulinase from Geobacillus stearothermophilus KP1289

The gene ( inuA) encoding exo-inulinase (EC 3.2.1.80) was cloned from the thermophilic Geobacillus stearothermophilus ( Bacillus stearothermophilus) KP 1289 growing at between 41 degrees C and 69 degrees C. The inuA gene consisted of 1,482 bp encoding a protein of 493 amino acids. The deduced polypeptide of molecular mass ( M) 56,744 Da showed strong sequence similarity to Pseudomonas mucidolens exo-inulinase, Bacillus subtilis levanase, Paenibacillus polymyxa ( Bacillus polymyxa) fructosyltransferase, and so on, indicating that the enzyme belonged to glycosyl hydrolase family 32. The M of the purified exo-inulinase, expressed in Escherichia coli HB101, was estimated as approximately 54,000 Da by both SDS-PAGE and gel filtration. These results suggested that the active form of the enzyme is a monomer. The enzyme was active between 30 and 75 degrees C with an optimum at 60 degrees C. The properties were identical to those of the native enzyme. Additionally, for the first time for a prokaryotic GH32 protein, crystals of the recombinant enzyme were obtained.