PHOTOOXIDATIVE CONSUMPTION AND PHOTOREDUCTIVE FORMATION OF ASCORBIC ACID IN GREEN LEAVES

1. From leaves of barley and spinach, cellular components wereisolated and brought together under various conditions to investigatethe fate of ascorbic acid as affected by the components in thelight and dark. 2. A new colorimetric method for assaying ascorbic acid andsome other reducing substances was devised, measuring the colorof molybdenum-blue developed by the substances in the presenceof excess amounts of phosphomolybdate and inorganic acid. 3. The photooxidation of ascorbic acid by green and yellow filtrates,prepared from green and etiolated leaves of barley, was studiedby the ordinary as well as the new colorimetric method. In thepresence of oxygen, the oxidation of ascorbic acid was foundto be accelerated by light in the green filtrate, but not inthe yellow filtrate. 4. The oxidation of the endogenous reducing substance containedin the supernatant fraction of spinach leaf extracts was studiedin the presence of washed chloroplasts (spinach). In the presenceof oxygen, the rate of oxidation in the light was markedly higherthan in the dark. From the changes in absorption spectrum accompanyingthe reaction, the endogenous reducing substance in questionwas identified as ascorbic acid. 5. The occurrence of an endogenous precursor of ascorbic acidin spinach leaf extracts was disclosed. The photoreduction ofthis precursor into ascorbic acid was studied in the precenceof spinach chloroplasts. A specific inhibition of this reactionby phosphoglycerate and glycerophosphate was discovered. 6. The experimental results obtained were discussed in connectionwith the role of ascorbic acid in photosynthesis. (Received September 13, 1960; )     

Effects of Asobara japonica venom on larval survival of host and nonhost Drosophila species

Abstract Ovipositing Asobara japonica females inject venom (containing paralysis‐inducing factors) immediately after the insertion of their ovipositors into Drosophila larvae, and lay eggs a little later. Interruption of their oviposition behaviour before egg laying causes high larval mortality in host Drosophila species, whereas normal oviposition does not. This suggests that venom of this parasitoid is toxic to larvae of these host species but its toxicity is suppressed by factor(s) provided by parasitoid females at the time of laying egg or by parasitoid embryos developing in the hosts. On the other hand, venom does not show toxicity to larvae of nonhost Drosophia species. Possible functions of venom are discussed.     

Host plant variation in plant-mediated indirect effects: moth boring-induced susceptibility of willows to a specialist leaf beetle

Abstract.  1. We examined the plant-mediated indirect effects of the stem-boring moth Endoclita excrescens (Lepidoptera: Hepialidae) on the leaf beetle Plagiodera versicolora (Coleoptera: Chrysomelidae) in three willow species, Salix gilgiana , S. eriocarpa , and S. serissaefolia.
2. When the stem-boring moth larvae damaged stems in the previous year, willows were stimulated to produce vigorously growing lateral shoots on these stems. These new lateral shoots were significantly longer and the upper leaves had significantly higher nitrogen and water content than current-year shoots on unbored stems, although the carbon content and leaf dry mass were not different between lateral and current-year shoots.
3. In the field, leaf beetle larvae and adults had significantly greater densities on lateral shoots of bored stems than on current-year shoots of unbored stems. A laboratory experiment showed that female beetles had significantly greater mass and fecundity when fed on leaves of newly-emerged lateral shoots. Thus, the stem-boring moth had a positive effect on the temporally and spatially separated leaf beetle by increasing resource availability by inducing compensatory regrowth.
4. The strength of the indirect effects on the density and performance of the leaf beetle differed among willow species, because there was interspecific variation in host quality and herbivore-induced changes in plant traits. In particular, we suggest that the differences in magnitude of the changes among willow species in shoot length and leaf nitrogen content greatly affected the strength of the plant-regrowth mediated indirect effect, coupled with host-plant preference of the leaf beetle.     

Light intensity regulates growth and reproduction of a snail grazer (Gyraulus chinensis) through changes in the quality and biomass of stream periphyton

1. The light : nutrient hypothesis (LNH) proposes that herbivore growth rates are maximised at intermediate light‐to‐nutrient ratios. A reduction to light intensity (i.e. decreased light‐to‐nutrient ratio) should lead to reduced food availability for herbivores while excessive light intensity in oligotrophic environments (i.e. increased light‐to‐nutrient ratios) should increase the C : N and C : P ratios of producers. However, this hypothesis has not yet been supported by studies on stream ecosystems. 2. We tested the LNH by experimental application of controlled natural gradients in light intensity to oligotrophic laboratory channels that included periphyton and the freshwater snail Gyraulus chinensis. 3. The results in this oligotrophic environment indicate that light regulated the flow of matter between trophic levels and grazer reproduction by controlling C : P ratios of the producers.     

日本三宅岛火山土壤中硫代硫酸盐氧化菌的分离、生物学特性及鉴定

【目的】利用培养法从日本三宅岛火山土壤(堆积年限131年)中分离到一株能氧化分解硫代硫酸盐的细菌MU2A-22T。【方法】用培养法对该菌株MU2A-22T进行了生理生化性质以及分类学位置上的确定。【结果】菌株MU2A-22T为革兰氏阴性,短杆状或球状。理化性质表明该菌株能利用葡萄糖、L-阿拉伯糖、葡萄糖酸盐、己二酸酯、dL-苹果酸钠、硫代硫酸钠(最适浓度为2.5 mmol/L)为唯一碳源进行自养生长。最适生长温度为25°C 30°C,最适pH为6.0 8.0。菌株MU2A-22T的16S rRNA序列与菌株Paracoccus solventivorans 6637T亲缘关系最近,序列相似性为97%,编码核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)的基因也被确定。对Paracoccus属内几种近缘菌的脂肪酸分析,证明菌株MU2A-22T中含有Paracoccus属的特征氨基酸,其中含量大于10%的分别为C18:1(74.7%)和C18:0(12.1%)。DNA-DNA杂交实验表明,菌株MU2A-22T与Paracoccus solventivorans 6637TDNA的相似度为49.3%。MU2A-22T菌株G+C含量为66.5%66.7%。【结论】菌株MU2A-22T为Paracoccus属内的一新种菌(登录号GQ452286),命名为Paracoccus scorialis sp.nov.。     

Contribution of hyperglycemia on diabetic complications in obese type 2 diabetic SDT fatty rats: effects of SGLT inhibitor phlorizin

The spontaneously diabetic torii (SDT) fatty rat is a new model of type 2 diabetes showing overt obesity, hyperglycemia and hyperlipidemia. With early onset of diabetes mellitus, diabetic microvascular complications, including nephropathy, peripheral neuropathy and retinopathy, are observed at young ages. In the present study, blood glucose levels of female SDT fatty rats were controlled with phlorizin, a non-selective SGLT inhibitor, to examine whether and how these complications are caused by hyperglycemia. Phlorizin treatment adequately controlled plasma glucose levels during the experiment. At 29 weeks of age, urinary albumin excretion considerably increased in SDT fatty rats. Glomerulosclerosis and tubular pathological findings also indicate diabetic nephropathy. These renal parameters tended to decrease with phlorizin; however, effects were partial. Sciatic nerve conduction velocities were significantly delayed in SDT fatty rats compared with Sprague-Dawley (SD) rats. Intraepidermal nerve fiber density, an indicator of subclinical small nerve fiber neuropathy, significantly decreased in SDT fatty rats. Retinal dysfunction (prolongation of peak latency for oscillatory potential in electroretinograms) and histopathological eye abnormalities, including retinal folding and mature cataracts were also observed. Both nerve and eye disorders were prevented with phlorizin. These findings indicate that severe hyperglycemia mainly causes diabetic complications in SDT fatty rats. However, other factors, such as hyperlipidemia and hypertension, may affect diabetic nephropathy. These characteristics of diabetic complications will become helpful in evaluating new drugs for diabetic complications using SDT fatty rats.     

Morphological difference and reproductive isolation: morphometries in the millipede Parafontaria tonominea and its allied forms

Thin-plate spline and other multivariate statistical methods were used to examine the variation in genital morphology and body size in 74 populations of the millipede Parafontaria tonominea and its allied forms in central Japan. Although the study populations included nine sympatric pairs of two reproductively isolated forms, the variations in genital morphology and body size observed were continuous across the study group. Analyses of the sympatric pairs using bootstrapping revealed that the degree of morphological difference between sympatric populations varied considerably from pair to pair. These results demonstrate that the degree of difference in genital morphology and body size may not correspond with the establishment of reproductive isolation. Significant correlation in the pattern of geographic variation was observed for many combinations of morphological components. However, it was not possible to detect a significant correlation between morphology and geographic distance in many of the morphological components studied. This study suggests that the incorporation of genital characters in classification should be done carefully, particularly for animal groups with low vagility, such as millipedes.     

Cyst distribution and excystment conditions for the dinoflagellate Peridinium penardii (Lemm.) Lemm. in a reservoir

SUMMARY. 1. Cyst distribution and a possible excystment site of the dinoflagellate Peridinium penardii (Lemm.) Lemm. in a reservoir were surveyed.
2. The presence of vegetative cells of P. penardii from all lake bottom mud samples, taken from several sites throughout the reservoir and cultured in vitro , showed that viable cysts of P. penardii were ubiquitous on the bottom of the reservoir.
3. Culture bottles containing bottom mud with cysts of P. penardii were suspended at several depths at four stations in the reservoir. Vegetative cells of P. penardii were found in all bottles suspended at 0.5 m and almost none deeper than 20.0 m. Water depth was a critical environmental factor in preventing excystment.
4. The place where P. penardii first excysts annually was predicted to be at the head of the reservoir using the data of cyst distribution, excystment conditions and morphology of the lake basin.