Proteolysis Coupled to ATP Hydrolysis: Regulation of the Activity of Proteolytic Sites of Lon Protease from Escherichia coli

Regulation of activity of the proteolytic sites of Lon protease was studied. It was found that ATP–Mg has the properties of a noncompetitive activator of peptidase sites. The processive mechanism of the hydrolysis of protein substrates by Lon protease was experimentally confirmed under the conditions of ATP hydrolysis. It was shown that the oligomeric state of the enzyme is the necessary prerequisite for the processive proteolysis by native Lon protease. The study of the properties of the mixed mutant Lon-K362Q/S679A confirmed the existence of intra- and intersubunit pathways of signal transduction from the ATPase to proteolytic sites. The mutual influence of substrates of Lon protease was studied, and the existence of cooperative interactions between the peptidase sites in the oligomeric enzyme was suggested.     

Fucosyltransferase expression in human platelets and leucocytes

The activities of -2-l-fucosyltransferase and -3-l-fucosyltransferase were measured in human platelets and leucocytes from normal donors, -2-l-Fucosyltransferase was found in platelets but not in leucocytes. In contrast -3-l-fucosyltransferase was not detected in platelets but was present in leucocytes where it was demonstrated in the neutrophil, monocyte and lymphocyte fractions.     

Variation in stable isotope signatures of seston and a zooplanktivorous fish in a eutrophic Chinese lake

Temporal and spatial changes in ¹³C and ¹⁵N of seston (mainly phytoplankton) and isotopic relationship between seston and the lake anchovy (Coilia ectenes) were studied in the large eutrophic freshwater Lake Chaohu in China. Much of the spatial and temporal variation in ¹³C of lake anchovies was explained by variation in seston, indicating a strong link between pelagic primary production and higher order consumers. Because the lake is shallow, there were no significant differences in ¹³C and ¹⁵N of seston between surface and overlying waters. Spatially, the relatively high ¹³C and ¹⁵N of seston in the western part of the lake might be due to high levels of anthropogenically derived N and C introduced from the surrounding cities through sewage drainage systems. The trophic position of the lake anchovy in the food web of Lake Chaohu was estimated to be 2.9–4.1 (3.5 ± 0.4), which agrees well with the previous stomach content analysis suggesting that the lake anchovy fed both on zooplankton and small planktivorous fishes.     

Role ofCandida in indirect pathogenesis of antibiotic associated diarrhoea in infants

One hundred and thirty seven isolates ofCandida species were isolated from antiobiotic associated diarrhoea cases and were examined to study the role ofCandida in the pathogenesis of diarrhoea in infants. The quantitative estimation of yeast population by simple gram stain smear revealed more than 70% of the cases had 3+ score. The isolates further screened for detection of-lactamases. Among the isolatedCandida sp,-lactamases was secreted byC. albicans, C. tropicalis, C. krusei andC. parapsilosis. Further, 46% of theCandida isolates were found to be produced 741–1110 mU/ml of-lactamases, suggesting that these enzyme would inactivate penicillin group of drugs and cause failure in the therapy directed against other diarrhoegenic bacteria.Abbreviation AAD antibiotic associated diarrhoea     

β-1-3- and β-1-4-glucan synthesis by membrane fractions from the fungus Saprolegnia

The -glucan synthetase activity of the fungus Saprolegnia monoica was assayed by supplying UDP-glucose to membrane fractions of mycelial homogenate. The analysis of glucan products by hydrolysis with various -glucanases and by chromatography show that both -1-3- and -1-4-linkages are formed at high substrate concentrations. In the absence of MgCl₂, -1-3-linked glucans are mainly produced. By increasing MgCl₂ concentrations the total synthesis activity and -1-3-linkages production are reduced. At low substrate concentrations in the presence of MgCl₂, -1-4-linked glucans are the only polysaccharide synthesized. Electron microscopy of radioactive products, synthesized by original membrane fractions or by membrane fractions isolated from continuous sucrose density gradients, shows microfibrils when the assays are conducted at high substrate concentrations in the absence of MgCl₂.Abbreviations G.S. I glucan synthetase I - G.S. II glucan synthetase II - Dol. P dolichol phosphate     

β-Oxidation enzymes in the mitochondria of Arum and oilseed rape

-Oxidation enzymes were detected both in the mitochondria and microbodies of Arum maculatum L. spadices and Brassica napus L. seeds. It is apparent that the mitochondrial membrane barrier, which remains intact after sucrose-density-gradient centrifugation, prevents rapid access of acyl-GoA substrates to matrix oxidation tes. Thus intact mitochondria showed little -oxidation enzyme activity. Rupturing of the mitochondrial membrane allowed rapid access of acyl CoAs to matrix sites. Consequently, in ruptured mitochondria, high -oxidation enzyme activities were measured.C. Masterson thanks the Science and Engineering Research Council for the award of a postgraduate student maintenance grant. D.R. Thomas and C. Wood thank their relatives for continuing financial support. The authors also thank West Cumberland Farmers Ltd., Hexham, UK for their gift of oilseed rape seeds.     

Influence of field bed position,ground surface color,mycorrhizal fungi,and high root-zone temperature in woody plant container production

High root-zone temperatures can stress plants and reduce nursery productivity of container produced crops. Field studies were conducted to study position of containers in field beds, ground surface color, mycorrhizal fungi and high root-zone temperatures in the production of selected woody plants. Root-zone temperature profiles in containers were established to determine nursery production conditions for white and black ground bed surfaces. White surfaces increased container medium temperatures in beds of plants with open canopies by 2–4°C compared to full canopied plants. Under field conditions with container medium temperatures as high as 40–50°C, the open canopiedBerberis thunbergii DC. Atropurpurea,Pinus eldarica Medw. andBuxus microphylla Seibold and Zucc. were more susceptible to temeprature stress compared to the more close canopiedPittosporum tobira (Thunb.) Ait. Wheeler's dwarf. When compared to controls,P. tobira colonized with mycorrhizal fungi [Glomus etunicatus Baker and Gerd. andGlomus fasciculatum (Thax.sensu Gerd.) Gerd. and Trappe] had increased shoot growth in all bed areas except the western exposure, and increased root growth in western and eastern bed regions. Greatest root damage generally occurred in containers of colonized and noncolonizedB. thunbergii in southern and western bed exposures. Mycorrhizal colonization did not improve plant growth of the more high temperature susceptibleB. thunbergii.     

The Determination of Total Concentration and Activity of Antioxidants in Foodstuffs

We developed a new method for the analysis of active antioxidants that is based on their reactions with the BTS⁺ cation radical obtained by oxidation of ABTS, 2,2"-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt. The feasibility of this method was confirmed by electrochemical and kinetic studies of model antioxidants. BTS⁺ was shown to react rapidly with active and slowly with weak antioxidants, which allows it to be used as a model radical for the quantitative determination of the total content of natural antioxidants (antioxidant equivalent) in natural extracts and wines. Another analytical method based on the competitive oxidation of Pyrogallol Red (a detecting molecule) and the examined antioxidants by radicals derived from peroxynitrite was used for measuring the relative activity of antioxidants. A combination of both methods helped measure the total concentration of antioxidants and their average specific activities (per molecule of active compound) in extracts from grape, olive, and tomato and in various popular beverages (wines, beers, and juices), as well as in the commercial concentrated food product Kréto-A^®, made from grape, red wine, tomato, and olive. Red wine and red grape juice were shown to be the most rich in antioxidants (up to 20 mM), with their activity being similar to that of polyphenols.     

Rotala cookii: A new species ofLythraceae from India showingHippuris syndrome

A new aquatic species ofRotala (Rotala cookii) is described from Kerala, India. Growing in the flooded lowlands, along the coastal belt, the plant is a Hippuris mimic.     

Detection and partial characterization of two antigenically distinct β-amylases in developing kernels of wheat

A -amylase (EC 3.2.1.2) was identified in the outer pericarp (P) of developing seeds of wheat (Triticum aestivum L.) and compared with the well known -amylase which is synthesized during seed development in the starchy endosperm (E). The enzyme P already exists in the tissues before anthesis and vanishes at the time when E starts to accumulate. The isoelectric-focusing patterns of P and E are very similar. The relative molecular weight (M_r) of P is slightly higher than that of E (66 and 64.5 kDa, respectively). Both P and E exhibit common epitopes in addition to epitopes specific for each of them. The two enzymes were identified in small amounts in the green tissues of the developing seeds (inner pericarp and testa). No antigenic difference was detected between P and the -amylases of roots and leaves.Abbreviations P pericarp -amylase - E endosperm -amylase - IS1 anti--amylase immune serum - IS2 anti- and anti- amylase immune serum - IS3 anti- amylase immune serum - IEF isoelectric focusing - IgG immunoglobulin G The authors thank Dr. P. Ziegler (Universität Bayreuth, FRG) for stimulating discussion and for useful suggestions during the writing of the text. The authors thank Miss C. Mayer for her skillful technical assistance.     

Development of spectrophotometric method for monitoring trans-sialidase reaction and its application

A spectrophotometric method that can monitor the trans-sialidase catalyzed reaction was devised by using a chromogenic substrate, o-nitrophenyl--d-galactopyranoside (ONPG), as a sialic acid acceptor. This method yielded results that were consistent with those from HPLC, and could be very conveniently used in the screening of sialic acid donor or inhibitor of trans-sialidase.     

Variants within the 5′-flanking regions of bovine milk-protein-encoding genes. III. Genes encoding the Ca-sensitive caseins αs1, αs2 and β

The 5-flanking regions of the Ca-sensitive casein-encoding gene family were analysed for DNA variants by automated DNA sequencing of 13 cows belonging to seven breeds. About 1 kbp of each 5-flanking region, including non-coding exon I, was amplified by PCR and sequenced bidirectionally. A total number of 34 variable sites (17 for the _s1, 10 for the _s2, and 7 for the casein encoding gene) was identified. Variants were computer-analysed for location in putative regulatory sites in order to predict potential influences on gene expression.     

Are active oxygen species involved in induction of β-carotene in Dunaliella bardawil?

The purpose of this work was to test whether induction of massive -carotene synthesis in the alga Dunaliella bardawil is triggered by oxygen radicals. The following results were obtained: (i) The induction of -carotene synthesis is preceded by a lag period of about 4 h during which the cells swell and photosynthesis is partially inhibited, (ii) Addition of promoters of oxygen radicals or of azide (an inhibitor of catalase and superoxide dismutase) during the induction period, under conditions which are suboptimal for massive -carotene accumulation, greatly enhances -carotene synthesis, photodegradation of chlorophyll and inhibition of photosynthesis, (iii) High irradiance, which induces massive -carotene accumulation, also induces a high catalase activity. It is suggested that photosynthetically produced oxygen radicals are involved in triggering massive -carotene accumulation in D. bardawil.     

Tree diversity change in remaining primary mixed-broadleaved Korean pine forest under climate change and human activities

Studying biodiversity change in existing typical ecosystems of the world under possible global climate change and local human activities is important for diversity conservation. An adapted forest dynamics model is used to simulate tree diversity change of the remaining primary mixed-broadleaved Korean pine forest (RPMKPF) in northeast China under global climate change and local human activities for the next 50 years. Human activities include logging, which removes all big trees (DBH > 50 cm), removing all individuals of each single species and all species of each functional type (shade tolerant, shade intolerant and medium type tree species). As results for RPMKPF, the index of tree diversity decreases under climate change, but it increases significantly under a combination of climate change and logging. Removing all individuals of each single species significantly affects the tree diversity of the ecosystem. After the removal of shade tolerant species, both and _c indices of tree diversity experience a significant change. The index decreases significantly under climate change when shade intolerant or medium type tree species are removed, but the _c index does not change significantly. The results of this study have implications for tree diversity management in RPMKPF under climate change and human activities.     

Behavioral responses of a leaf beetle to injury-related changes in its salicaceous host

Summary Adults of the leaf beetle Plagiodera versicolora Laich, avoided previously injured shoots of Salix alba Tristis in favor of nearby uninjured ones. The response was rapid and persisted for five days of study. During brief periods of observation, the vast majority of beetles engaged in behaviors other than locomotion such as feeding and resting. Furthermore, the proportions of beetles walking were similar on injured and uninjured shoots. It appears that under these experimental conditions previous injury did not greatly increase searching behavior of the beetles. Leaves on previously injured shoots received less subsequent herbivory than uninjured ones. Findings of these experiments are consistent with patterns of herbivory observed in the field and known reproductive responses of beetles to diets of injured leaves. These results provide new information toward understanding relatively low levels of herbivory on individual willow leaves associated with the feeding of P. versicolora.