Sufficient intake of high amylose cornstarch maintains high colonic hydrogen production for 24 h in rats

Colonic hydrogen (H₂) can suppress oxidative stress and damage in the body. We examined the minimum requirement of high amylose cornstarch (HAS) to maintain high colonic H₂ production for 24 h. Ileorectostomized and sham-operated rats were fed a control diet supplemented with or without 20% HAS for 7 days. Colonic starch utilization was determined. Next, rats were fed the control diet with or without 10% or 20% HAS for 14 or 28 days, respectively. Breath and flatus H₂ excretion for 24 h was measured. 1.04 g of resistant fraction in HAS was utilized for 24 h by colonic bacteria. High H₂ excretion was not maintained for 24 h in rats fed the 10% HAS diet, from which only 0.89 g of resistant starch was estimated to be delivered. High colonic H₂ production for 24 h would be maintained by delivering more HAS to the large intestine than is utilized.     

Root endophyte symbiosis in vitro between the ectomycorrhizal basidiomycete Tricholoma matsutake and the arbuscular mycorrhizal plant Prunus speciosa

We previously reported that Tricholoma matsutake and Tricholoma fulvocastaneum, ectomycorrhizal basidiomycetes that associate with Pinaceae and Fagaceae, respectively, in the Northern Hemisphere, could interact in vitro as a root endophyte of somatic plants of Cedrela odorata (Meliaceae), which naturally harbors arbuscular mycorrhizal fungi in South America, to form a characteristic rhizospheric colony or “shiro”. We questioned whether this phenomenon could have occurred because of plant–microbe interactions between geographically separated species that never encounter one another in nature. In the present study, we document that these fungi formed root endophyte interactions and shiro within 140 days of inoculation with somatic plants of Prunus speciosa (=Cerasus speciosa, Rosaceae), a wild cherry tree that naturally harbors arbuscular mycorrhizal fungi in Japan. Compared with C. odorata, infected P. speciosa plants had less mycelial sheath surrounding the exodermis, and the older the roots, especially main roots, the more hyphae penetrated. In addition, a large number of juvenile roots were not associated with hyphae. We concluded that such root endophyte interactions were not events isolated to the interactions between exotic plants and microbes but could occur generally in vitro. Our pure culture system with a somatic plant allowed these fungi to express symbiosis-related phenotypes that varied with the plant host; these traits are innately programmed but suppressed in nature and could be useful in genetic analyses of plant–fungal symbiosis.     

Granuloma formation and killing functions of granuloma in congenitally athymic nude mice infected with Blastomyces dermatitidis and Paracoccidioides brasiliensis

We did this experiment to clarify the mechanism of granuloma formation and the killing functions of granuloma in nude mice against Blastomyces dermatitidis and Paracoccidioides brasiliensis infections. B. dermatitidis A-295 and P. brasiliensis B-1183 were the cultures used. Congenitally athymic nude (nu/ nu) mice and their heterozygous (nu/ +) littermates of BALB/ c background were the test animals. From culture A-295, 0.1% and 1% cell suspensions (wet weight) were prepared and from culture B-1183 0.2% and 2% cells suspensions were prepared. Ten nu/ + and 10 nu/ nu mice were allotted to each of four cell suspensions. For experimental blastomycosis each mouse was inoculated intravenously with 0.2 ml of the cell suspension of A-295 and for experimental paracoccidioidomycosis, with 0.15 ml of the cell suspension of B-1183. Two mice from each of the four groups were killed at 5, 8, 12, 18 and 25 days after inoculation, and histopathologic sections, stained with H&E or by PAS, were prepared from various internal organs.In the nu/ nu mice inoculated with B. dermatitidis A-295 granuloma was formed in the brain tissue after the 12th day. However, mononuclear cells, which formed the granuloma, did not kill the fungal cells, and the fungal cells continued to multiply in the granuloma. On the other hand, in the heart, kidney and fat tissue, their histopathological findings after the 18th day were clumps of fungal cells with slight cell reactions. In these organs the exertion of cell-mediated immunity was necessary for granuloma formation against the fungal infection.In the nu/ nu mice infected with P. brasiliensis B-1183, granuloma appeared in the brain and kidney after the 18th day and fungal cells continued to multiply within the granuloma as well as in those inoculated with culture A-295.These results show that the exertion of cell-mediated immunity plays an important role as the defense mechanisms of hosts against these fungal infections. However, PMNs also play an important role in the mouse's defense mechanisms against these fungal infections.We assume that the defense mechanisms of immunocompetent mice against B. dermatitidis or P. brasiliensis infection consist chiefly of two steps: in the first step phagocytosis by PMNs occurs and in the second step cell-mediated immunity enters into play.