Isolation and characteristics of yeasts able to grow at low concentrations of nutrients

Seven oligotrophic yeasts, which can grow in a 10⁴-fold dilution of malt–yeast–glucose–peptone medium (10⁻⁴ YM), were mainly isolated from soil. These yeasts belong to the Cryptococcaceae. When inoculated at about 10² cells/ml in 10⁻⁴ YM, the isolates grew to 1·4×10³–2·4×10⁵ cells/ml after 3 days. Some culture collection yeasts fell into three groups according to their growth characteristics in 10⁻⁴ YM, one group showing characteristics of the oligotrophic yeasts. The half-saturation values of uptake by the five isolated oligotrophic yeasts for D-glucose, L-leucine and L-amino acids were 6·0–25·0, 1·7–43·3 and 3·5–21·6 μM, respectively. The oligotrophic yeasts suspended in 10 mM-phosphate buffer (pH 6·0) had high tolerances for starvation, and remained more than 15% viable after 90 days of starvation. © 1998 John Wiley & Sons, Ltd.     

Alzheimer’s Disease and Type 2 Diabetes Mellitus: The Use of MCT Oil and a Ketogenic Diet

Recently, type 2 diabetes mellitus (T2DM) has been reported to be strongly associated with Alzheimer’s disease (AD). This is partly due to insulin resistance in the brain. Insulin signaling and the number of insulin receptors may decline in the brain of T2DM patients, resulting in impaired synaptic formation, neuronal plasticity, and mitochondrial metabolism. In AD patients, hypometabolism of glucose in the brain is observed before the onset of symptoms. Amyloid-β accumulation, a main pathology of AD, also relates to impaired insulin action and glucose metabolism, although ketone metabolism is not affected. Therefore, the shift from glucose metabolism to ketone metabolism may be a reasonable pathway for neuronal protection. To promote ketone metabolism, medium-chain triglyceride (MCT) oil and a ketogenic diet could be introduced as an alternative source of energy in the brain of AD patients.     

New approaches to fabrication of multilayer Fresnel zone plate for high-energy synchrotron radiation X-rays

A multilayer (sputtered-sliced) Fresnel zone plate (FZP) is one of the promising focusing optics with high spatial resolution for the high-energy X-ray region. This is because a large “aspect ratio” can be realized easily. In addition, it is important that the kinoform FZP (theoretical diffraction efficiency=100%) can be fabricated by the sputtered-sliced method. This paper presents the experimental results of two new approaches for fabrication of a multilayer FZP for X-rays. (1) To achieve higher diffraction efficiency, a multilevel-type (4-step: quasi-kinoform type) FZP was fabricated. This FZP was composed of concentric multilayers of alternating high-Z, low-Z, and composite materials. The composite material layer was deposited by co-sputtering of high-Z and low-Z materials. (2) To achieve smoother zones (multilayer interfaces) at the conventional-type FZP, each target of a sputtering apparatus with two DC-sputtering guns was surrounded by a cover with an aperture, and Ar gas was supplied inside the cover, which led to the deposition at lower Ar gas pressure. As a result, for the former, the efficiency was improved markedly as compared with conventional FZP, and for the latter, the zone roughness was reduced, which has resulted in the improvement of the spatial resolution of the FZP.     

Solidification of Sn-0.7Cu-0.15Zn Solder: In Situ Observation

High resolution time-resolved X-ray imaging with synchrotron radiation was used for in situ observation of four distinct events during solidification of a Sn-0.7Cu-0.15Zn solder despite small composition and density differences. These included βSn dendrite growth, Sn-Cu₆Sn₅ univariant eutectic growth, microporosity formation, and a polyphase reaction in the last stages of freezing. The development of microstructure was described quantitatively by tracking the loci of dendrite tips during grain growth. The results have implications for microstructure control and the understanding of structure–property relationships in Sn-Cu-Zn lead-free solders.     

Chemical forms of mercury and cadmium accumulated in marine mammals and seabirds as determined by XAFS analysis

Marine mammals and seabirds tend to exhibit high accumulations of mercury, cadmium, and selenium in their livers and kidneys. In this study, chemical forms of mercury, cadmium, and selenium accumulated in the livers and kidneys of northern fur seal (Callorhinus ursinus), Risso's dolphin (Grampus griseus), and black-footed albatross (Diomedea nigripes) were studied by extended X-ray absorption fine structure (EXAFS) spectroscopy to reveal the detoxification mechanisms of these metals. It was found that mercury and selenium exist in the form of HgSe in the liver of northern fur seal. Mercury levels were found to be higher than those of Se, based on their molar ratio, in black-footed albatross. XAFS analysis disclosed an existence of chalcogenide containing both Hg-Se and the Hg-S bonds, suggesting the existence of a solid solution Hg(Se, S) as granules in black-footed albatross. In contrast, Cd concentrations in the kidney were higher than those in the liver for northern fur seal, black-footed albatross, and Risso's dolphin. It was found that Cd was bound to sulfur, which was probably derived from the metallothionein. The Cd-O bond was observed in the tissues of northern fur seal.     

Enzymatic preparation of arbutin derivatives: Lipase-catalyzed direct acylation without the need of vinyl ester as an acyl donor

Direct and regioselective acylation of arbutin with aromatic or aliphatic acid using a lipase obtained from Candida antarctica in an organic solvent was investigated. We achieved the enzymatic synthesis of feruloyl arbutin and lipoyl arbutin without the need of vinyl ferulate and vinyl lipoate as acyl donors, respectively.     

Comparison of two possible routes of pathogen contamination of spinach leaves in a hydroponic cultivation system

The route of pathogen contamination (from roots versus from leaves) of spinach leaves was investigated with a hydroponic cultivation system. Three major bacterial pathogens, Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes, were inoculated into the hydroponic solution, in which the spinach was grown to give concentrations of 10? and 103 CFU/ml. In parallel, the pathogens were inoculated onto the growing leaf surface by pipetting, to give concentrations of 10? and 103 CFU per leaf. Although contamination was observed at a high rate through the root system by the higher inoculum (10? CFU) for all the pathogens tested, the contamination was rare when the lower inoculum (103 CFU) was applied. In contrast, contamination through the leaf occurred at a very low rate, even when the inoculum level was high. For all the pathogens tested in the present study, the probability of contamination was promoted through the roots and with higher inoculum levels. The probability of contamination was analyzed with logistic regression. The logistic regression model showed that the odds ratio of contamination from the roots versus from the leaves was 6.93, which suggested that the risk of contamination from the roots was 6.93 times higher than the risk of contamination from the leaves. In addition, the risk of contamination by L. monocytogenes was about 0.3 times that of Salmonella enterica subsp. enterica serovars Typhimurium and Enteritidis and E. coli O157:H7. The results of the present study indicate that the principal route of pathogen contamination of growing spinach leaves in a hydroponic system is from the plant's roots, rather than from leaf contamination itself.     

The thermal mechanism of warm in winter and cool in summer in China traditional vernacular dwellings

Yaodong is one representative of western China vernacular dwellings. Its indoor thermal environment is cool in summer and warm in winter. This study interprets the characteristic of warm in winter and cool in summer in such a dwelling by measuring the indoor, outdoor and wall’s temperatures in winter and summer. The human thermal comfort theory is used to evaluate thermal environment, and the periodic heat transfer mechanism is used to analyze the thermal transfer through the wall. The results show that the Yaodong thick wall effectively damping external temperature wave and keeping steady inner surface temperature are the chief causes of warm in winter and cool in summer in Yaodong, which lays a scientific basis for low energy building design.