Endogenous levels of polyamines in the organs of cucumber plant (Cucumis sativus) and factors affecting leaf polyamine contents

Polyamine compositions of various organs from hydroponically cultivated cucumber plants ( Cucumis sativus L. cv. Sharp-1) and factors affecting the leaf polyamine content were examined. Diamine putrescine was found most abundantly in the root, while a relatively large amount of spermine was detected in the reproductive organs such as the immature fruit and the calyx (+stamen). Spermidine was present at the highest level in rapidly growing tissues such as newly expanded leaf and fruit at an early developing stage, implying the possible involvement of spermidine in the growth and development of these young tissues. Polyamine content of cucumber leaves changed during the day. Especially, the putrescine content of upper leaves showed a striking decrease from the morning to the night. Alterations of leaf Ca or Mg content did not significantly affect leaf polyamine composition. On the other hand, abnormal cucumber leaves showed altered polyamine composition. Yellowing of the leaf intervein resulted in a striking decrease in spermidine content without a significant change in putrescine and spermine content. By contrast, the leaves infected with the phytopathogen, powdery mildew, showed decreased putrescine and increased spermine content in response to the degree of fungi infection. The possible usefulness of polyamines as a diagnostic marker of plant development and physiological disorder is discussed.     

Enantioselective synthesis of derivatives and structure–activity relationship study in the development of NA255 as a novel host-targeting anti-HCV agent

Hepatitis C virus (HCV) infection represents a serious health-care problem. Previously we reported the identification of NA255 from our natural products library using a HCV sub-genomic replicon cell culture system. Herein, we report how the absolute stereochemistry of NA255 was determined and an enantioselective synthetic method for NA255 derivatives was developed. The structure–activity relationship of the NA255 derivatives and rat pharmacokinetic profiles of the representative compounds are disclosed.     

Distinct modulations of the hexokinase1-mediated glucose response and hexokinase1-independent processes by HYS1/CPR5 in Arabidopsis

The Arabidopsis mutant hypersenescence 1 (hys1), that is allelic to constitutive expresser of pathogenesis-related genes 5 (cpr5), displays phenotypes related to glucose signalling and defence responses. In the present study, it is shown that the hys1 mutation boosts the inhibitory effects of glucose upon the greening of seedlings and reduces the antagonistic activities of ethylene and cytokinin toward this inhibition. Neither the glucose content nor the sensitivities to ethylene, cytokinin, and abscisic acid were found to differ between wild-type and hys1 seedlings. However, disruption of the gene encoding hexokinase1 (HXK1), which acts as a glucose sensor, partially suppressed the glucose hypersensitive phenotype of the hys1 mutant. These results thus suggest that the hys1 mutation promotes a process associated with the HXK1-mediated glucose response during greening. By contrast, additional hys1 phenotypes, including an increase in salicylic acid (SA), production of abnormal trichomes, and early senescence, were not suppressed by the loss of HXK1. Surprisingly, the hxk1 and hys1 mutations acted synergistically towards an increased SA accumulation. Hence, HYS1/CPR5 appears to be a versatile protein that modulates both the HXK1-mediated glucose response and various HXK1-indepndent processes that are involved in growth control. A possible role for HYS1/CPR5 as a component of the networks that regulate growth control is discussed.     

Influence of long-term exposure to an air-conditioned environment on the diurnal cortisol rhythm

In the present study, the influence of the long-term use of air-conditioning in summer on the cortisol rhythm was examined by measuring the rhythm in subjects who had been exposed to air-conditioning for a short [S] or long [L] time. Investigations were conducted twice in July and September. Atmospheric temperature and relative humidity near the subjects were measured for three days in each season. Saliva samples for cortisol analysis were collected every 2 hours during the daytime beginning at 8:00 h with subsequent sampling times at 10:00, 12:00, 14:00, 16:00, 18:00, 20:00 and 22:00 h. A questionnaire on sleep and duration of air-conditioning use was also undertaken. Ambient mean temperature was higher in the S group (mean+/-SD; 30.8+/-1.2 degrees C in July, 28.0+/-0.8 degrees C in September) than in the L group (28.0+/-1.2 degrees C in July, 27.3+/-1.0 degrees C in September) (p<0.01), while mean relative humidity did not differ. There were no differences in bedtime, waking time and sleeping hours either between groups or months. Diurnal patterns of salivary cortisol rhythm in July and September were similar in the S group, but the L group had a delayed rise of morning cortisol secretion in September compared with July. These results suggest that long-term exposure to an air-conditioned environment might adversely affect the human cortisol rhythm.     

Potassium uptake by Chinese cabbage (Brassica pekinensis Rupy.) from fused potassium silicate,a slow-releasing fertilizer

Fused potassium silicate (FPS), which contains K₂Ca₂Si₂O₇, has been prepared as a slow-releasing potassium fertilizer. Moreover, it is difficult to estimate the proportion of nutrients utilized by plants that come from the soil versus the slow-releasing fertilizer applied. To trace the uptake of potassium (K) by plants from FPS supplied to the soil, the fertilizer K was partially replaced with rubidium (Rb). The growth and K+Rb uptake (moles) of Chinese cabbage (Brassica pekinensis Rupy. cv. Kekkyu) plants in sand culture experiments were not affected by the replacement of K with Rb. In pot experiments using a volcanic ash Ando soil, Chinese cabbage was grown with no application of K, with K and Rb salts, or with Rb-containing FPS for three cycles of 40 days each. The amounts of fertilizer-derived K in the shoots estimated by the Rb-tracer method were smaller than those estimated by the difference of K accumulation between K fertilized and unfertilized plants. Such result suggests the involvement of `K priming', a process by which the addition of K fertilizers enhances plant K uptake from the soil. The amount of K absorbed from FPS, calculated by the Rb-tracer method, indicated that the sparingly soluble K, that is soluble in 0.2 g L^–1 citric acid solution but not in water, was absorbed at least partly through direct contact with the roots without prior exchange with soil K. Moreover, the plant absorption of sparingly soluble K from FPS was also confirmed by the difference method in K uptake.     

Amino acid metabolism in plant leaf IV. The effect of light on ammonium assimilation and glutamine metabolism in the cells isolated from spinach leaves

Comparison of incorporation of ¹⁵N-labeled ammonium into aminoacids in cells isolated from spinach leaves showed that ammoniumwas most actively incorporated into the amido-group of glutamine.The ¹⁵N contents of other amino acids were less than one-tenththat of the amido-group of glutamine. L-Methionine-DL-sulfoximine(MS) suppressed the incorporation of ammonium not only intothe amido-group of glutamine, but also into glutamic acid. Turningoff the light after 1 min illumination increased die 15N contentof glutamine while it decreased that of the glutamic acid, asparticacid and alanine. Illumination of the cells after die applicationof ammonium had a more significant effect on ammonium assimilationthan illumination before the application of ammonium. When ¹⁴C-U-¹⁵N(amido labeled)-glutamine was added to the cell suspension,the transfer of amido-group of glutamine was completely inhibitedin the dark, but no difference in the flow of ¹⁴C was observed. These results suggest that glutamine synthetase (GS) and glutamatesynthase (GOGAT) pathways operate in ammonium assimilation inthe cells isolated from spinach leaves, and that the formeris light-independent but die latter is light-dependent. (Received December 23, 1977; )     

The bactericidal activity of tea and coffee

Extracts of black tea, green tea, pu-erh tea or coffee inhibited the growth of various bacteria known to cause diarrhoeal diseases. Tea or coffee also showed bactericidal activity against Staphylococcus aureus and Vibrio parahaemolyticus.