Lowering Effect of Phenolic Glycosides on the Rise in Postprandial Glucose in Mice

Glycosides were screened for their lowering effect on the postprandial blood glucose rise in vivo. The effect of phlorizin and other phenolic glycosides on the postprandial blood glucose response to glucose ingestion was evaluated in Std ddY mice. When phlorizin was simultaneously added, the peak blood glucose level was significantly decreased by 51% (p < 0.01) compared to vehicles following glucose ingestion by mice, while the blood insulin responses were generally similar. Screening experiments were conducted with different classes of phenolic glycosides added to a glucose solution. Reductions of 40–52% (p < 0.05) were observed in vehicles containing arbutin, 4-hydroxyphenyl-α-d-glucopyranoside (hydroquinone-α-glucoside) or glycyrrhizin, and of only 15–31% (not significant) in vehicles containing neohesperidin dihydrochalcone, glycyrrhetinic acid monoglucuronide, or 3,4-dimethoxyphenyl-β-d-glucopyranoside. No lowering effect was observed in vehicles containing salicin. Since glycyrrhizin, arbutin, and hydroquinone-α-glucoside blunted to varying degrees the postprandial blood glucose rise following glucose ingestion, they may be useful adjuvants for the treatment of diabetic subjects.     

Studies on the Metabolism of Pantothenic Acid in Microorganisms

The ability of the formation of coenzyme A from pantothenic acid and cysteine in the presence of AMP or ATP was searched in yeasts and bacteria. The result of screening showed that the activity was found in several yeasts and the bacteria belonging to the genera Sarcina, Corynebacterium and Brevibacterium. Particularly, Brevibacterium ammoniagenes IFO 12071 (ATCC 6871) accumulated a large amount of coenzyme A.

Isolation of the reaction products, which were synthesized by Brevibacterium ammoniagenes IFO 12071, were carried out. The isolates were identified as coenzyme A, dephosphocoenzyme A and phosphopantothenic acid.

The possibility for the formation of coenzyme A in a larger amount from pantothenic acid and cysteine was investigated with baker’s yeast under the condition coupled with ATP-generating system.

Effect of various factors affecting the accumulation of coenzyme A was investigated. Among them, glucose concentration and inorganic phosphorus concentration were the most important factors for its accumulation. Coenzyme A was not accumulated without the phosphorylation of AMP to ATP. Several cationic surfactants stimulated the accumulation of coenzyme A.

The amount of coenzyme A accumulated reached about 200 μg per ml of the reaction mixture under the suitable reaction conditions employed.     

Purification and Properties of a Pectate Lyase in Erwinia aroideae

A strain of Erwinia aroideae produced an extracellular pectolytic enzyme under growth conditions with pectin or pectic acid as the inducer. This strain also produced a pectin lyase when nalidixic acid is added to a culture medium. The pectolytic enzyme produced under the growth conditions was purified approximately 40-fold from the culture fluid by carboxy- methyl cellulose and Sephadex G-75 gel column chromatographies. The purified enzyme was almost homogeneous on sodium dodecyl sulfate polyacrylamide gel electrophoresis, having a molecular weight of about 36,000 to 38,000. This enzyme, with optimal activity at pH 9.0 to 9.2, produced reaction products which had a strong absorption at 230 nm indicating a lyase type of the reaction. The enzyme activity was markedly stimulated by calcium ion and completely inhibited by cobalt and mercuric ions and by ethylenediaminetetraacetate. Pectic acid or pectin with lower methoxyl content was a good substrate for this enzyme, while no significant activity was observed when pectin with higher methoxyl content was used as a substrate. It was concluded that the enzyme produced under the normal growth conditions is an endo-pectate lyase and differs from the pectin lyase induced by nalidixic acid.     

Distribution and Solubilization of Particulate Gluconate Dehydrogenase and Particulate 2-Ketogluconate Dehydrogenase in Acetic Acid Bacteria

The distribution of two particulate enzymes, gluconate dehydrogenase (GDH) and 2-ketogluconate dehydrogenase (2KGDH), was investigated with cell free extract through 26 strains of genus Acetobacter and genus Gluconobacter. GDH activity was found in the cell free extracts from all strains of genus Gluconobacter and two species of genus Acetobacter, A. aceti and A. aurantium. High activity of 2KGDH was also found in the pigment-producing strains of genus Gluconobacter.

Best solubilization of particulate enzymes was attained with the highest recovery when 10 mg of Triton X–100 and 30 mg of protein of particulate fractions in 1 ml of 0.01 m phosphate buffer, pH 6.0, are incubated for 9 hr at 5°C with continuous stirring.

By comparison of the total enzyme activity of particulate enzymes with that of NAD(P)-linked enzymes in the cell free extract, it was obvious that the formation of ketogluconates by particulate enzymes was much more predominant, roughly over 100 times higher, as that of NAD(P)-linked enzymes.     

Establishment of a New Cross of the Rice Blast Fungus Derived from Japanese Differential Strain Ina168 and Hermaphroditic Rice Pathogen Guy11

Mating experiments between Magnaporthe grisea Japanese rice pathogens and Guy11, a hermaphroditic fertile rice pathogen, were done aimed at identification of avirulence genes. A cross named cross 2107 with thirty-six random progenies was obtained. Segregation analyses of genetic markers found that the cross was less suitable for genetic analysis. Backcrosses with cross 2107 progenies and Guy11 were done and another cross named cross 5307 with sixty-five progenies was obtained. A locus controlling kasugamycin resistance named Ksg1R was identified and used for a model case of genetic mapping. Bulked segregant analysis was done to find adjacent RAPD markers for mapping of the gene. Three adjacent markers to Ksg1R were obtained and a genetic map around the Ksg1R was made, but these markers were not located on a single chromosome. These results suggest that genetic analysis to identify a gene locus is available in cross 5307. Infection assay of parental strains of cross 5307 to Japanese differential rice cultivars suggested the possibility of genetic analysis of cultivar specificity toward four rice cultivars: Aichiasahi, Kusabue, Tsuyuake, and K59.     

Antitumor effects of MutT homolog 1 inhibitors in human bladder cancer cells

ABSTRACT

As standard second-line regimen has not been established for patients who are refractory to or relapse with cisplatin-based chemotherapy, an effective class of novel chemotherapeutic agents is needed for cisplatin-resistant bladder cancer. Recent publications reported that MutT homolog 1 (MTH1) inhibitors suppress tumor growth and induce impressive therapeutic responses in a variety of human cancer cells. Few studies investigated the cytotoxic effects of MTH1 inhibitors in human bladder cancer. Accordingly, we investigated the antitumor effects and the possible molecular mechanisms of MTH1 inhibitors in cisplatin-sensitive (T24) and – resistant (T24R2) human bladder cancer cell lines. These results suggest that TH588 or TH287 may induce cancer cell suppression by off-target effects such as alterations in the expression of apoptosis- and cell cycle-related proteins rather than MTH1 inhibition in cisplatin-sensitive and – resistant bladder cancer cells.

Abbreviations: MTH: MutT homolog; ROS: reactive oxygen species; CCK-8: cell counting kit-8; DCFH-DA: dichlorofluorescein diacetate; PARP: poly (ADP-ribose) polymerase     

Host–parasite genotypic interactions in the honey bee: the dynamics of diversity

Parasites are thought to be a major driving force shaping genetic variation in their host, and are suggested to be a significant reason for the maintenance of sexual reproduction. A leading hypothesis for the occurrence of multiple mating (polyandry) in social insects is that the genetic diversity generated within‐colonies through this behavior promotes disease resistance. This benefit is likely to be particularly significant when colonies are exposed to multiple species and strains of parasites, but host–parasite genotypic interactions in social insects are little known. We investigated this using honey bees, which are naturally polyandrous and consequently produce genetically diverse colonies containing multiple genotypes (patrilines), and which are also known to host multiple strains of various parasite species. We found that host genotypes differed significantly in their resistance to different strains of the obligate fungal parasite that causes chalkbrood disease, while genotypic variation in resistance to the facultative fungal parasite that causes stonebrood disease was less pronounced. Our results show that genetic variation in disease resistance depends in part on the parasite genotype, as well as species, with the latter most likely relating to differences in parasite life history and host–parasite coevolution. Our results suggest that the selection pressure from genetically diverse parasites might be an important driving force in the evolution of polyandry, a mechanism that generates significant genetic diversity in social insects.     

The bacterial parasite Pasteuria ramosa is not killed if it fails to infect: implications for coevolution

Strong selection on parasites, as well as on hosts, is crucial for fueling coevolutionary dynamics. Selection will be especially strong if parasites that encounter resistant hosts are destroyed and diluted from the local environment. We tested whether spores of the bacterial parasite Pasteuria ramosa were passed through the gut (the route of infection) of their host, Daphnia magna, and whether passaged spores remained viable for a “second chance” at infecting a new host. In particular, we tested if this viability (estimated via infectivity) depended on host genotype, whether or not the genotype was susceptible, and on initial parasite dose. Our results show that Pasteuria spores generally remain viable after passage through both susceptible and resistant Daphnia. Furthermore, these spores remained infectious even after being frozen for several weeks. If parasites can get a second chance at infecting hosts in the wild, selection for infection success in the first instance will be reduced. This could also weaken reciprocal selection on hosts and slow the coevolutionary process.     

High genetic diversity is not essential for successful introduction

Some introduced populations thrive and evolve despite the presumed loss of diversity at introduction. We aimed to quantify the amount of genetic diversity retained at introduction in species that have shown evidence of adaptation to their introduced environments. Samples were taken from native and introduced ranges of Arctotheca populifolia and Petrorhagia nanteuilii. Using microsatellite data, we identified the source for each introduction, estimated genetic diversity in native and introduced populations, and calculated the amount of diversity retained in introduced populations. These values were compared to those from a literature review of diversity in native, confamilial populations and to estimates of genetic diversity retained at introduction. Gene diversity in the native range of both species was significantly lower than for confamilials. We found that, on average, introduced populations showing evidence of adaptation to their new environments retained 81% of the genetic diversity from the native range. Introduced populations of P. nanteuilii had higher genetic diversity than found in the native source populations, whereas introduced populations of A. populifolia retained only 14% of its native diversity in one introduction and 1% in another. Our literature review has shown that most introductions demonstrating adaptive ability have lost diversity upon introduction. The two species studied here had exceptionally low native range genetic diversity. Further, the two introductions of A. populifolia represent the largest percentage loss of genetic diversity in a species showing evidence of substantial morphological change in the introduced range. While high genetic diversity may increase the likelihood of invasion success, the species examined here adapted to their new environments with very little neutral genetic diversity. This finding suggests that even introductions founded by small numbers of individuals have the potential to become invasive.     

Differential physiological responses to environmental change promote woody shrub expansion

Direct and indirect effects of warming are increasingly modifying the carbon-rich vegetation and soils of the Arctic tundra, with important implications for the terrestrial carbon cycle. Understanding the biological and environmental influences on the processes that regulate foliar carbon cycling in tundra species is essential for predicting the future terrestrial carbon balance in this region. To determine the effect of climate change impacts on gas exchange in tundra, we quantified foliar photosynthesis (A_net), respiration in the dark and light (R_D and R_L, determined using the Kok method), photorespiration (PR), carbon gain efficiency (CGE, the ratio of photosynthetic CO₂ uptake to total CO₂ exchange of photosynthesis, PR, and respiration), and leaf traits of three dominant species – Betula nana, a woody shrub; Eriophorum vaginatum, a graminoid; and Rubus chamaemorus, a forb – grown under long-term warming and fertilization treatments since 1989 at Toolik Lake, Alaska. Under warming, B. nana exhibited the highest rates of A_net and strongest light inhibition of respiration, increasing CGE nearly 50% compared with leaves grown in ambient conditions, which corresponded to a 52% increase in relative abundance. Gas exchange did not shift under fertilization in B. nana despite increases in leaf N and P and near-complete dominance at the community scale, suggesting a morphological rather than physiological response. Rubus chamaemorus, exhibited minimal shifts in foliar gas exchange, and responded similarly to B. nana under treatment conditions. By contrast, E. vaginatum, did not significantly alter its gas exchange physiology under treatments and exhibited dramatic decreases in relative cover (warming: −19.7%; fertilization: −79.7%; warming with fertilization: −91.1%). Our findings suggest a foliar physiological advantage in the woody shrub B. nana that is further mediated by warming and increased soil nutrient availability, which may facilitate shrub expansion and in turn alter the terrestrial carbon cycle in future tundra environments.