DNA strand-breaking activity and mutagenicity of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP), a Maillard reaction product of glucose and glycine

Aqueous solution of glucose and glycine was heated under reflux for 4 h and extracted with ethyl acetate. Reversed phase HPLC of the extract revealed a new DNA strand-breaking substance, which was purified by repeated HPLC and identified as 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP). DDMP induced DNA strand breaking in a dose- and time-dependent manner. It was active to break DNA strands at pH 7.4 and 9.4. Its pyranone skeleton was destroyed at the pH values. DNA strand breaking by DDMP was inhibited by superoxide dismutase, catalase, scavengers for hydroxyl radical, spin trapping agents and metal chelators, and the breaking was enhanced by Fe(III) ion. A mixture of DDMP and a spin trap DMPO gave electron spin resonance signals of a spin adduct DMPO-OH, indicating generation of hydroxyl radical. DDMP was found to be mutagenic to Salmonella typhimurium TA100 without metabolic activation. These results show DDMP generated active oxygen species to cause DNA strand breaking and mutagenesis.     

Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats

Sadamoto, Tomoko, and Kanji Matsukawa. Cardiovascularresponses during spontaneous overground locomotion in freely movingdecerebrate cats. J. Appl. Physiol.83(5): 1454-1460, 1997.To examine whether the cerebrum isessential for producing the rapid cardiovascular adjustment at thebeginning of overground locomotion, we examined heart rate (HR), meanarterial blood pressure (MAP), and integrated electromyogram (iEMG) ofthe forelimb triceps brachialis muscle in freely moving decerebratecats during locomotion. Two to four days after decerebration surgeryperformed at the level of the precollicular-premammillary body, theanimals spontaneously produced coordinated overground locomotion,supporting body weight. HR began to increase immediately before theonset of iEMG, and MAP began to rise almost simultaneously with theiEMG onset. Their increases in HR and MAP (24 ± 3 beats/min and 22 ± 4 mmHg) were sustained during locomotion. Sinoaortic denervation(SAD) did not affect the abrupt changes in HR and MAP at the beginningof locomotion (0-4 s from the onset of iEMG), whereas SAD had acontrasting effect during the subsequent period, a decrease in the HRresponse (9 ± 1 beats/min) and an increase in the MAP response (30 ± 3 mmHg). These results suggest that the cerebrum and the rostral part of the diencephalon are not essential for producing the rapid cardiovascular adjustment at the beginning of spontaneous overground locomotion. The arterial baroreflex does not contribute to this rapidadjustment but plays an important role in regulating the cardiovascularresponses during the later period of spontaneous locomotion.

     

Lazy gene (la) responsible for both an agravitropism of seedlings and lazy habit of tiller growth in rice (Oryza sativa L.)

Using an isogenic line of rice having lazy gene (la), we studied the correlation between the agravitropic response at the young seedling stage and the lazy habit (prostrate growth of tillers) at the more advanced stage of growth. In this study, it was found that both agravitropism and lazy habit were controlled by the single recessivela gene. That is, F₂ segregants of Kamenoo×lazy-Kamenoo, which had an agravitropic response at their young seedling stage, showed a lazy habit of growth in the more advanced stage of vegetative growth. On the other hand, seedlings that showed normal gravitropic curvature at their early stage of growth had an upright growth in the mature stage.     

Characteristics and Pathogenicity of Non-Melibiose-Fermenting Strains of Yersinia pseudotuberculosis O3

The biological properties of non-melibiose-fermenting (NMF) strains of Yersinia pseudotuberculosis 03 were investigated. These strains were clearly distinguished from representative melibiose-fermenting (MF) strains of Y. pseudotuberculosis 03 by their pathogenicity in mice, sensitivity to some phages, production of catalase, restriction endonuclease analysis of virulence plasmid DNA with BamHI, detection of specific yersinia outer-membrane proteins with SDS-PAGE, antigenicity of the outer-membrane proteins and neutrophil resistance to phagocytosis. The pathogenicity of NMF strains was clearly less than that of MF strains. In addition, the resistance of NMF strains to phagocytosis and catalase activity was evidently weaker than that of MF strains. These results suggested that the difference of pathogenicity was due to the ability of catalase production. Although the relationship between the above characteristics and melibiose-fermentation was not analysed, the pathogenicity of Y. pseudotuberculosis 03 strains can probably be predicted by testing melibiose-fermentation and catalase production.     

Contrasting traits,contrasting environments,and considerations on population dynamics under a changing climate: an ecophysiological field study of two co‐dominant tree species

The increase in light availability resulting from canopy changes or opening is not always beneficial and can inhibit photosynthesis of tree seedlings already under other environmental stress. Tree seedlings' responses to compounded abiotic stress depend on their life‐history traits, and understanding the variations of such responses is important for understanding population dynamics under a changing climate. In this study we investigate how the photosynthesis of juveniles of two canopy tree species with different life‐history traits, Abies sachalinensis and Betula ermanii, differs in two contrasting sites at a sub‐boreal forest in northern Japan—one under a deciduous canopy (Closed site) and the other at a wide canopy opening (Open site). Seedlings at the Open site had low F_v/F_m (quantum yield of photosystem II) for a longer period than those at the Closed site. Abies sachalinensis at the Closed site showed lower F_v/F_m in spring than those at the Open site, but recovered after the canopy's new leaves flushed, indicating its acclimation to the shaded condition. Mean P_max (light‐saturated photosynthetic rate at ambient CO₂ levels) of A. sachalinensis seedlings was affected by site and air temperature, while B. ermanii seedlings were also affected by precipitation. Only B. ermanii's seedlings presented growth in the period studied, in spite of observed mid‐day drops to F_v/F_m attributed to water‐deficit‐related photoprotection. Results suggest that the climate change predicted for the Hokkaido area may increase the competitive advantage of broad‐leaved deciduous species, such as B. ermanii, in relation to evergreen conifers like A. sachalinensis.     

Changes in Polyamine Concentrations in Amygdaloid-Kindled Rats

Concentrations of the polyamines putrescine, spermidine, and spermine were investigated in the left and right amygdala and in the remaining cerebrum, in which kindling was induced by repeated application of electrical stimulation of the left amygdala of rats. In kindled rats, the concentrations of spermidine and spermine increased slightly, but elevations did not reach significant levels in any brain regions. The most profound increase was detected in the putrescine concentration in all parts of the cerebrum 1-8 h after the final stimulation. These results suggest that the increases in concentrations of polyamines, particularly of putrescine, are involved in the pathogenesis of amygdaloid kindling.     

Intestinal metaplasia and altered enzyme expression in propylnitrosamine-induced Syrian hamster cholangiocellular and gallbladder lesions

Intrahepatic bile duct and gallbladder preneoplastic and neoplastic lesions induced in Syrian golden hamsters by propylnitrosamine treatment were investigated for the presence of polysaccharides and assayed immunohistochemically for expression of the enzymes glucose-6-phosphate dehydrogenase (G6PD) and glutathione-S-transferase (GST) molecular forms. On the basis of an increase in G6PD and the GST-placental form, a sequence of altered cell populations ranging from simple ductular proliferation through dysplasia and cholangiofibroma to cholangiocellular carcinoma could be established, the latter three lesions being characterized by marked increase in polysaccharide production. While similar goblet cell (intestinal) metaplasia and increased polysaccharide storage were also evident in carcinogen-induced gallbladder lesions G6PD and GST-P expression was decreased when compared with control epithelium.     

Glucose Modulates the Release of Histamine from the Mouse Hypothalamus In Vitro

The effect of glucose concentration on the in vitro release of histamine (HA) was examined, using two different preparations of the mouse hypothalamus. The HA and tele-methylhistamine released from whole blocks of the hypothalamus into the medium linearly increased during 2-h incubation in normal Krebs-Ringer bicarbonate solution in the absence of external depolarizing stimuli. The release of HA from this preparation depended on the temperature and Ca2+ in the medium and was progressively increased with decrease in the glucose concentration from 11.5 to 1 mM. The rate of the HA release was dependent on the absolute concentration of glucose and not on an abrupt change in the concentration. When slices of the hypothalamus were incubated in high K+ medium, a temperature- and Ca2+-dependent HA release was observed. At low concentrations of glucose, the K+ (20 mM)-induced HA release from the hypothalamic slices was also enhanced. Tetrodotoxin (10 microM) inhibited the enhancing effect of a low glucose concentration (2 mM) on the HA release by 60%, in both preparations of the hypothalamus. The possibility that the release of HA from the mouse hypothalamus is regulated by glucose concentration and that activation of neuronal Na+ channels is involved in the enhancement of the HA release by low glucose concentrations warrants further attention.     

<Emphasis Type="Italic">Cachaça</Emphasis> yeast strains: alternative starters to produce beer and bioethanol

This work was performed to verify the potential of yeast strains isolated from cachaça distilleries for two specific biotechnological applications: beer and bioethanol production. In the beer production, the strains were tested for characteristics required in brewery practices, such as: capacity to ferment maltose and maltotriose, ability to grow at lowest temperatures, low H₂S production, and flocculation profile. Among the strains tested, two of them showed appropriate characteristics to produce two different beer styles: lager and ale. Moreover, both strains were tested for cachaça production and the results confirmed the capacity of these strains to improve the quality of cachaça. In the bioethanol production, the fermentation process was performed similarly to that used by bioethanol industries: recycling of yeast biomass in the fermentative process with sulfuric acid washings (pH 2.0). The production of ethanol, glycerol, organic acids, dry cell weight, carbohydrate consumption, and cellular viability were analyzed. One strain presented fermentative parameters similar to PE2, industrial/commercial strain, with equivalent ethanol yields and cellular viability during all fermentative cycles. This work demonstrates that cachaça distilleries seem to be an interesting environment to select new yeast strains to be used in biotechnology applications as beer and bioethanol production.     

Characterization of cynomolgus monkey cytochrome P450 (CYP) cDNAs: is CYP2C76 the only monkey-specific CYP gene responsible for species differences in drug metabolism?

Cynomolgus monkey CYP2C76 does not have a corresponding ortholog in humans, and it is at least partly responsible for differences in drug metabolism between monkeys and humans. To determine if CYP2C76 is the only monkey-specific CYP gene, we identified cynomolgus monkey cDNAs for CYP2A23, CYP2A24, CYP2E1, CYP2J2, CYP3A5, CYP3A8, CYP4A11, CYP4F3, CYP4F11, CYP4F12, and CYP4F45. These CYP cDNAs showed a high sequence identity (93-96%) to the homologous human CYP cDNAs. The monkey CYPs were preferentially expressed in liver among the analyzed tissues. Moreover, all five analyzed monkey CYPs (CYP2A23, CYP2A24, CYP2E1, CYP3A5, and CYP3A8) metabolized typical substrates for human CYPs in the corresponding subfamilies. These results suggest that these 11 monkey CYP cDNAs are closely related to the human CYP cDNAs and thus, unlike CYP2C76, are not apparent monkey-specific cDNAs.