Succession of sessile organisms on experimental plates immersed in Nabeta Bay,Izu Peninsula,Japan III. Temporal changes in community structure

From percentage covers of sessile organisms obtained over about 3 yr by suspending concrete plates at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, Pacific coast of Japan, changes of five indices of community structure, i.e. number of species (S), Shannon-Weaver diversity (H′), evenness (J′), McNaughton's dominance (MD) and Horn's similarity (HS), were investigated throughout succession. Colonization curves became horizontal after reaching a maximum at 6 months after immersion at all depths. The number of species appeared to approach equilibrium during the first year of immersion. In the period from 13 to 37 months after immersion, the five indices indicated that communities at the upper two depths had stabilized structures within a limited range of variation, as represented by low HS values, whereas those at the lower two depths had simplified structures, as indicated by low S orH′ values. Furthermore, the results of cluster analysis of samples at four depths indicated that 13 to 37-month communities at the upper two depths had advanced, converged structures, whereas those at the lower depths had young, non-converged structures. The stability of community structure observed at the upper two depths could be due to domination of two long-lived species, the kelpEisenia bicyclis and the oysterCrassostrea nippona. On the other hand, the simplification of community structure at the lower two depths seems to be due to reduced domination of these two species as a result of disturbances such as scouring by sand. Contributions from the Shimoda Marine Research Center, No. 514.     

Succession of sessile organisms on experimental plates immersed in Nabeta Bay,Izu Peninsula,Japan V. An integrated consideration on the definition and prediction of succession

Successional changes of sessile organisms over about 3 years on concrete plates immersed at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, Pacific coast of Japan, were investigated from their species composition, percentage cover, and the structure, metabolism, biomass and maturity of the community for the purpose of verifying the hypothesis of succession by Margalef (1968) and Odum (1969). The process of succession was divided into five stages from a cluster analysis based on Horn's (1966) similarity in community structure. The five stages were characterized from dominant, species and 18 community attributes in terms of structure, metabolism, biomass and maturity. With the advance of stages, two large-sized, long-lived species, the kelpEisenia bicyclis and the oysterCrassostrea nippona, dominated; 18 community attributes showed a directional succession ending in a constant community structure, low community metabolism, accumulation of community biomass except chlorophylla and an enhanced degree of community maturity. This directionality in succession of community attributes was valid for the prediction of Margalef and Odum, despite a tendency for estimated daily energy budget to be more heterotrophic in such an open system. From these results, it was suggested that the definition of succession by Odum (1969) should be interpreted as the regularity in shift of dominant species, not individual species, and as the control of system by feedback mechanism developing with succession rather than community-controlled mechanism.     

Vertical distribution and seasonal variation of eelgrass beds in Iwachi Bay,Izu Peninsula,Japan

The vertical distribution and population structure of eelgrass beds were surveyed in Iwachi Bay, along the Pacific coast of central Japan. Samplings were conducted from May through November 1977 by SCUBA. Eelgrass was distributed between 3 and 11 m in depth. The relative light intensity at 12 m depth was 11% at the lower range. The highest population density was 290 shoots/m² in September and the fresh weight of biomass was 888 g/m² in July at 7 m depth. The maximum mean leaf area index was about 3 at 10 m depth in July. The ratio of reproductive shoots to the total shoots was about 36% at 7 m depth in June. Eelgrass showed good growth at 7–10 m depth, which is comparatively deeper than other eelgrass habitations. The high values of water transparency and sunshine duration, as well as solar radiation compared with other localities was believed to contribute to the growth of eelgrass in deeper waters in Iwachi Bay.     

Quantitative and qualitative analyses of dissolved organic matter released from Ecklonia cava Kjellman, in Oura Bay, Shimoda, Izu Peninsula, Japan

Release of dissolved organic matter (DOM) was studied on macroalga, Ecklonia cava Kjellman, by in situ field bag experiments, which were designed to keep the algal body under natural field condition, in Oura Bay, Shimoda, Izu Peninsula, Japan, from August 2003 to May 2005. The experiments were conducted 6 times in different seasons. The concentrations of dissolved organic carbon (DOC) in the experimental bag generally increased during the first 1-2 days, showing the release of DOC from algae. The daily release rates of DOC varied between 0.12 and 5.8 mgC per g (dry wt) of the algal blades per day. The seasonal variability of the DOC release rate was similar to those of the growth and the photosynthetic rates reported by the previous studies on E. cava in the same location. The fractions of the DOC release of the net primary production accounted for 18-62%. These contributions are comparable to other macroalgae in the previous studies (27-43%) using other macroalgae. Analysis of organic composition of DOM using gas chromatography (neutral aldose composition) and spectrometry (UV-visible and fluorescence) indicates that E. cava usually release extracellular products containing mucilaginous polysaccharides containing fucose as a main constituent and colored dissolved organic matter (CDOM). The release of these organic compounds is likely performed as the ordinary metabolism of brown algae. An exceptional release of a considerable amount of protein and carbohydrates mainly composed of mannose was found in June 2004, probably reflecting leakage of the intracellular material by an autolysis of the algal cells. The high DOM release rate in the present study suggests that macroalgae would be one of the important DOM producers in coastal regions.     

Temporal and spatial macrofaunal community changes along a salinity gradient in seagrass meadows of Akkeshi-ko estuary and Akkeshi Bay,northern Japan

Changes in water clarity (secchi disc transparency) in relation to the presence/absence of introduced, exotic fish, including rudd (Scardinius erythrophthalmus), tench (Tinca tinca), perch (Perca fluviatilis), brown bullhead catfish (Ameiurus nebulosus), goldfish (Carassius auratus), and koi carp (Cyprinus carpio) were determined for 49 small, North Island, New Zealand lakes. There was a negative association between water clarity and the presence of exotic fish independent of lake depth. Moreover, a ‘before-and-after’ comparison and examination of case-studies indicated that introductions of exotic fish reduce water clarity. The number of species introduced affected the relationship between lake depth and water clarity but the specific role of each species could not be distinguished because most of the lakes (83%) contained more than one exotic fish species. A model incorporating the known mechanisms by which planktivorous, benthivorous and herbivorous fish can influence water clarity in lakes showed that control over just one species or feeding guild may not result in an improvement in water clarity because of the additive and synergistic effects of different species on lake trophic processes. Handling editor J. Cambray     

Seasonal variation in the physical properties of agar and biomass of Gracilaria sp. (chorda type) from Tosa Bay,southern Japan

Plants of Gracilaria sp.(chorda type), which grow along the coast of Uranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26 °C to 31 °C) and spring season (15.1 °C to 24.9 °C). Maximum biomass was 6952 g m^–2 in July, but gradually decreased in the autumn (30.5 °C in September to 20 °C in November) and winter (19.5 °C in December to 14.9 °C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali treatment (5% NaOH, 2 h) at three different temperatures (70, 80, and 90 °C), the agars showed gel strengths essentially that of commercial grade agars, with the best gel obtained at 80 °C. Maximum gel strength (1455 g cm^–2 of 1.5% agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spring. Gel strength was inversely correlated with agar yield, but was positively correlated with apparent viscosity. Maximum viscosity was 40 cP. in December. Gelling temperatures, pH of 1.5% agar gel, and moisture content in agars showed little variation.     

Influence of synthetic sheep urine on the microbial biomass,activity and community structure in two pastures in the Scottish uplands

The impact of urine on the microbial biomass, activity and community structure was compared in the soil beneath two pastures in the Scottish uplands; Fasset, a natural Agrostis capillaris–Festuca ovina–Galium saxatile grassland and Strathfinella, a semi-natural grassland, improved with fertiliser addition. Community level physiological profiles (CLPP) were used to characterise the microbial communities. The utilisation of sugars, oligosaccharides, alcohols, carboxylic acids, long chain aliphatic acids, acidic, basic and neutral amino acids, amide N, phenolic acids and long chain aliphatic acids was used to compare the soils and the impact of synthetic urine addition. In the untreated soils, the utilisation of all the substrates decreased from the first week in May through to October. Averaged over all times and urine treatment, the potential utilisation of all substrates except for phenolic acids, long chain aliphatic acids and carboxylic acids was greater in the improved and more intensively grazed Strathfinella site. When averaged over all sample times, urine increased the utilisation of sugars, oligosaccharides, basic amino acids and amide N and the increases were greater in the unimproved, less intensively grazed, Fasset soil than that at Strathfinella. The effect of urine tended to be greatest during the period between 2 and 5 weeks after urine addition when utilisation of alcohols, acidic and neutral amino acids was also increased. Microbial biomass C in the control soils was 155.9 and 112.7 g C m⁻² at Fasset and Strathfinella, respectively. Values did not change significantly with time and were unchanged by the addition of urine. However, urine addition significantly increased basal respiration rates at Fasset and decreased them at Strathfinella. Urine also increased bacterial numbers in both soils, but had no consistent effect on fungi or yeasts. The significance of these findings for studies of soil microbial community structure and activity in grazed upland grasslands is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Laboratory investigation on community composition, emergence patterns and biomass of wood-inhabiting Chironomidae (Diptera) from a sandy lowland stream in Central Europe (Germany)

Wood-inhabiting chironomid communities were investigated from June 1998 to July 1999 by laboratory rearing of randomly collected submerged branches from a headwater and mid-reach site of a sandy lowland stream, separated by an impoundment used for fishery purposes. Total annual emergence (males and females) from headwater samples was higher (2551 ind m^–2 y^–1) compared to the mid-reach (1576 ind m^–2 y^–1), which could be due to disturbances caused by frequent impoundment openings resulting in high discharge events. Chironomid community from branches comprised three subfamilies, with Orthocladiinae (18 species, 2189 ind m^–2 y^–1) clearly predominating at the headwater (total of 36 species). Mid-reach samples (total of 48 species) showed similar emergent numbers of Orthocladiinae (19 species, 786 ind m^–2 y^–1) and Chironominae (26 species, 764 ind m^–2 y^–1). Tanypodinae were caught very rarely in the laboratory emergence (12 ind m^–2 y^–1 at both sites). Shannon-Wiener diversity index for the mid-reach chironomid community was higher (2.52) than for the headwater community (1.68). Chironomid species composition on woody debris was similar between stream sites, with a Sørensen index of 0.75, but showed different dominance structures indicated by a Wainstein index of 0.26. Total adult biomass (in the manner of dry mass) during the study period was higher for wood-dwelling chironomids from the headwater (158.2 mg m^–2 y^–1) compared to the mid-reach (123.8 mg m^–2 y^–1), but individual biomass was higher for mid-reach chironomids (0.079 mg ind^–1 vs. 0.062 mg ind^–1 at the headwater), indicating the predominance of larger species. Total biomass of wood-inhabiting chironomids in the investigated lowland stream was low compared to other field emergence studies, which could be attributed to the laboratory approach for investigating the emergence from a single substrate type (submerged wood) instead of the integrative field surveys where chironomids from all habitats were caught. Main reason for the lack of chironomid species closely associated to wood in this sandy lowland stream could be infrequent but episodic disurbances caused by the anthropogenic induced highly fluctuating discharge regime of the downstream study site.     

A field experiment on the effects of interspecific competition from roach, Rutilus rutilus (L.), on age at maturity and gonad size in perch, Percafluviatilis L.

The effects of interspecific competition from roach on gonad development in O+ and 1+ perch were studied in a pond experiment by varying the roach density between treatments. The proportion of mature O+ males first increased and, thereafter, decreased with increasing roach density and increasing somatic weight. O f females were immature and all I+ males were mature. The proportion of mature 1+ females decreased with increasing roach density and decreasing somatic weight. The gonad weight of O+ and 1+ males as well as 1+ females decreased with increasing roach density and decreasing somatic weight. For 1+ males, which were individually marked, both start weight as well as somatic end weight were positively related to gonad weight. One possibleexplanation for the hump shaped relationship between the proportion of mature O+ males and somatic weight is that behavioural interactions between O+ and I+ males in the absence of roach affected maturing in O+ males. This study supports previous suggestions that annual variation in resource availability may give rise to variance in fecundity-body size relationships.     

Temporal changes in the cyst densities of Pyrodinium bahamense var. compressum and other dinoflagellates in Manila Bay, Philippines

Temporal variation in the type and abundance of dinoflagellate cysts in Manila Bay, Philippines, is established using ²¹⁰Pb-dated sediment cores. At least 17 dinoflagellate cyst species, including those of the toxic species, Pyrodinium bahamense var. compressum, were identified. P. bahamense may have been present in the area since at least the 1920s. Total cyst density has increased beginning about 1988 to 1998 coinciding with records of P. bahamense blooms in the area. Heterotrophs have always dominated the cysts assemblage. These changes in the dinoflagellate record and the P. bahamense blooms in recent years may have been induced by the interplay of warmer temperatures, high rainfall leading to higher river discharge and less turbulent waters due to passage of few tropical cyclones.     

Accumulation of phenolic acid conjugates and betacyanins,and changes in the activities of enzymes involved in feruloylglucose metabolism in cell-suspension cultures ofChenopodium rubrum L.

Cell-suspension cultures ofChenopodium rubrum accumulate various soluble secondary phenolic metabolites such as the hydroxybenzoic acid glycosides 4-hydroxybenzoic acid--glucoside, vanillic acid--glucoside, the hydroxycinnamic acid acylglycosides 1-O-(4-coumaroyl)--glucose, 1-O-feruloyl--glucose, 1-O-sinapoyl--glucose and 1-O-feruloyl-(-1,2-glucuronosyl)--glucose, the hydroxycinnamic acid amide N-feruloylaspartate, and the betacyanins betanin, amaranthin and celosianin II. In addition, accumulation of the insoluble cell wall-bound hydroxycinnamic acids with ferulic acid as the major component occurs parallel to culture growth. The changes of three pivotal enzymatic activities, all O-transferases which are involved in the formation of the dominant ferulic acid conjugates, were determined. These are (i) uridine 5-diphosphate(UDP)glucose-hydroxycinnamic acid O-glucosyltransferase (EC 2.4.1), (ii) UDP-glucuronic acid:1-O-hydroxycin-namoyl--glucose O-glucuronosyltransferase (EC 2.4.1) and (iii) 1-O-hydroxycinnamoyl--glucose:amaranthin O-hydroxycinnamoyltransferase (EC 2.3.1). The patterns of metabolite accumulation associated with these enzyme activities show that the hydroxycinnamic acid-glucose esters play a central role as metabolically active intermediates in the secondary metabolism ofCh. rubrum. Two cell lines of this culture (CH, CHN), differing in their betacyanin content, were compared with respect to this metabolism. A markedly higher total betacyanin content in the CHN line might possibly be the consequence of an increased supply of the key precursor for betalain biosynthesis, i.e. 3,4-dihydroxyphenylalanine (DOPA). In addition, the enhanced accumulation of celosianin II in the CHN line correlates well with a higher activity of the enzyme catalyzing the transfer of ferulic acid from 1-O-feruloyl--glucose to amaranthin.Abbreviations CH line red-coloured betalain-producing cell-suspension cultures ofChenopodium rubrum (lower betacyanin content) - CHN line deep-red-coloured betalain-producing cell-suspension cultures ofCh. rubrum (higher betacyanin content), selected from CH line - DOPA 3,4-dihydroxyphenylalanine - glucosyltransferase uridine 5-diphosphate-glucose hydroxycinnamic acid O-glucosyltransferase (EC 2.4.1) - glucuronosyltransferase uridine 5-diphosphate-glucuronic acid: 1-O-hydroxycinnamoyl--glucose O-glucuronosyltransferase (EC 2.4.1) - HPLC high-performance liquid chromatography - hydroxycinnamoyltransferase 1-O-hydroxycinnamoyl--glucose:amaranthin O-hydroxycinnamoyltransferase (EC 2.3.1) - NMR nuclear magnetic resonance Support by the Deutsche Forschungsgemeinschaft and by the Fonds der Chemischen Industrie to D.S. is gratefully acknowledged. We thank Sabine Fehling for help in cell wall analyses and Heike Steingaß for optimization of enzyme assays. Our special thanks are due to Dr H. Harms (FAL, Braunschweig, FRG) and Dr J. Berlin (BBA, Braunschweig) for establishing and providing the CH and CHN lines, respectively, of theChenopodium rubrum cell culture. We are grateful to Christel Kokoschka, H. Dirks and Inge Schweer (GBF, Braunschweig) for recording the NMR, FAB MS and EI MS data, respectively.     

Experimental study of trophic cascade effect of silver carp (Hypophthalmichthys molitrixon) in a subtropical lake, Lake Donghu: on plankton community and underlying mechanisms of changes of crustacean community

An enclosure experiment was carried out to test trophic cascade effect of filter-feeding fish on the ecosystem: growth of crustacean zooplankton, and possible mechanism of changes of crustacean community structure. Four fish biomass levels were set as follows: 0, 116, 176 and 316 g m^-2, and lake water (containing ca. 190 g m^-2 of filter-feeding fishes) was comparatively monitored. Nutrient levels were high in all treatments during the experiment. Lowest algal biomass were measured in fishless treatment. Algal biomass decreased during days 21–56 as a function of fish biomass in treatments of low (LF), medium (MF) and high (HF) fish biomass. Crustaceans biomass decreased with increasing fish biomass. Small-bodied cladocerans, Moina micrura, Diaphanosoma brachyurum and Scapholeberis kingii survived when fish biomass was high whilst, large-bodied cladocerans Daphnia spp. and the cyclopoids Theromcyclops taihokuensis, T. brevifuratus, Mescyclops notius and Cyclops vicinus were abundant only in NF enclosures. Evasive calanoid Sinodiaptomus sarsi was significantly enhanced in LF, but decreased significantly with further increase of fish biomass. Demographic data indicated that M. micrura was well developed in all treatments. Our study indicates that algal biomass might be controlled by silver carp biomass in eutrophic environment. Changes of crustacean community are probably affected by the age of the first generation of species. Species with short generation time were dominant and species with long generation time survived less with high fish biomass. Evasive calanoids hardly developed in treatments with high fish biomass because of the (bottle neck) effect of nauplii. Species abundance were positively related to fish predation avoidance. Other than direct predation, zooplankton might also be suppressed by filter-feeding fish via competition.     

Seasonal changes in composition and biomass of epiphytic algae on the macrophyte Ranunculus penicillatus in a chalk stream,with estimates of production,and observations on the epiphytes of Cladophora glomerata

The epiphytic algae on surfaces of the macrophyte Ranunculus penicillatus (Dumort.) Bab. var. calcareus (R. W. Butcher) C. D. K. Cook and on Cladophora glomerata (L.) Kütz growing in the River Itchen at Otterbourne near Southampton were studied between February 1984 and June 1985. The river at this site has a mean flow rate of 0.33 m s^–1, and is about 16 m wide and on average 20 cm deep, with a discharge ranging through the year between 0.34 and 2.46 m³ s^–1. The pH of the river varies little around 8.2, with a mean alkalinity of 236 mg HCO_inf3^sup1l^–1, because of its origin from chalk springs.Ranunculus grows throughout the year, with peaks of biomass in spring and autumn. It forms a very large surface for attachment of epiphytes, and covers on average 40% of the stream bed. Numbers of epiphyte cells removed from Ranunculus ranged through the year between 52 × 10³ and 271 × 10³ cells mm^–2 stream floor, with maximum numbers in April, and a secondary peak in October. This pattern partly reflects fluctuations in the biomass of Ranunculus; the number of cells per unit area of plant surface showed a broader spring peak and lower fluctuations in other seasons. Diatoms formed 65 to 98% of these epiphyte cells, with chlorophytes reaching their peak (10%) in summer and cyanophytes (25%) in autumn. Estimates of biomass of these epiphytic forms, derived from measurements of chlorophyll c, indicate a range between 30 and 100 g dry weight m^–2 of weed bed. Colonisation studies showed that the algae grow and reproduce throughout the year, with a mean generation time of about 5 days, suggesting an annual production of about 3 kg dry weight m^–2 of weed bed, which makes epiphytic algae the principal primary producers in the stream. The numbers and biomass of epiphytic algae on Cladophora are considerably less.The species of epiphytic algae found on Ranunculus were generally similar to those growing on Cladophora, and to epilithic algae on pebbles of the stream bed, but different species were dominant on the different substrata. Algal cells in the water column were all derived from benthic habitats, although their relative abundance was very different.     

Effects of outbreak of the train millipede Parafontaria laminata armigera Verhoeff (Diplopoda: Xystodesmidae) on litter decomposition in a natural beech forest in Central Japan. 1. Density and biomass of soil invertebrates

Soil invertebrates were studied to determine the animals important in litter decomposition and soil formation in a natural forest of Fagus crenata Blume mixed with Quercus mongolica var. grosseserrata Rehd. et Wils., where outbreak of the adult train millipede, Parafontaria laminata armigera Verhoeff was recorded in 1980. The density and biomass of soil invertebrates, and their distribution in soil, were surveyed largely by hand sorting and also using Tullgren and Baermann apparatuses. The densities of soil macroinvertebrates were 10²–10³ individuals/m². Diplopoda was the most abundant among them, 87.3% of which was the train millipede. The total biomass in wet weight of soil macro-invertebrates was 34.9–70.5g/m² in 1980–1981, when the millipede was pre-adult or adult, and it decreased to 3.5–6.7g/m² in 1982–1984, when it was young. The density of soil invertebrates extracted by apparatuses was 10⁴–10⁶ individuals/m². The total biomass of these was estimated to be 5.8–10.8g/m². The majority of soil invertebrates lived in the A₀ horizon, whereas the train millipede lived in soil of the A₁+A₂ horizon. These results suggest that the train millipede is one of the most important soil invertebrates affecting soil properties. For evaluating the importance of the species, more than 8 years survey of hand-sorting together with the Tullgren apparatus was necessary, as the train millipede grew synchronously and had an 8-year life span and young stages of 1.5–3.5mm long.     

Induction of a Crassulacean acid like metabolism in the C4 succulent plant,Portulaca oleracea L.: physiological and morphological changes are accompanied by specific modifications in phosphoenolpyruvate carboxylase

The induction of a Crassulacean acid like metabolism (CAM) was evidenced after 21–23 days of drought stress in the C₄ succulent plant Portulaca oleracea L. by changes in the CO₂ exchange pattern, in malic acid content and in titratable acidity during the day–night cycle. Light microscopy studies also revealed differences in the leaf structure after the drought treatment. Following the induction of the CAM-like metabolism, the regulatory properties of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), the enzyme responsible for the diurnal fixation of CO₂ in C₄ plants but nocturnal in CAM plants, were studied. The enzyme from stressed plants showed different kinetic properties with respect to controls, notably its lack of cooperativity, higher sensitivity to L-malate inhibition, higher PEP affinity and lower enzyme content on a protein basis. In both conditions, PEPC's subunit mass was 110 kDa, although changes in the isoelectric point and electrophoretic mobility of the native enzyme were observed. In vivo phosphorylation and native isoelectrofocusing studies indicated variations in the phosphorylation status of the enzyme of samples collected during the night and day, which was clearly different for the control and stressed groups of plants. The results presented suggest that PEPC activity and regulation are modified upon drought stress treatment in a way that allows P. oleracea to perform a CAM-like metabolism. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spindle disturbances in mammalian cells. IV. The action of some glutathione-specific agents in V79 Chinese hamster cells, changes in levels of free sulfhydryls and ATP, c-mitosis and effects on DNA metabolism

The glutathione-specific agents diamide, diethyl maleate and 1-chloro-2,4-dinitrobenzene were found to induce a low frequency of c-mitosis (15%) at non-toxic concentrations concomitant with a 30-40% decrease of non-protein sulfhydryls. The frequency of c-mitosis did not increase further with increased concentrations until non-protein sulfhydryl levels were obtained suggesting depletion of reduced glutathione. The observed shape of the concentration-response curve for c-mitosis is particular to these 3 agents and caffeine among 22 different compounds being tested under comparable conditions. This suggests a similar mechanism of action and from what is known about caffeine this mechanism probably involves an impaired control of cytoplasmic free Ca2+. It is speculated that this impairment with the glutathione-specific agents is primarily due to depletion of a particular pool of reduced glutathione. Tertiary butylhydroperoxide which is a substrate for glutathione peroxidase(s) also causes c-mitosis when there is no significant decrease of non-protein sulfhydryls. The c-mitotic response was found to be biphasic with maintained control levels at an intermediate concentration. The humps in the concentration-response curve for c-mitosis appeared coincident with a mitogenic response (G1----S). Since the latter type of effect most probably is Ca2+ dependent and since the spindle is sensitive to Ca2+ it is tentatively suggested that the c-mitotic effect of tertiary butylhydroperoxide is due to an increase of cytoplasmic Ca2+. Measurements performed imply that an increase of glutathione disulfide (diamide) is more inhibitory to uptake and incorporation of thymidine than a decrease of reduced glutathione per se (diethyl maleate). This difference is probably due to secondary effects on pertinent protein sulfhydryls with diamide, one possible target being the ribonucleotide reductase. All compounds were found to cause an increase of ATP with some of the applied concentrations. The results with diethyl maleate suggest that an increase of ATP is favored by an attack on mitochondrial reduced glutathione. The possible analogy between this effect and an increase of ATP and Ap4A in bacteria during oxidative stress is considered.     

Effects of ingested fruiting bodies, submerged culture biomass, and acidic polysaccharide glucuronoxylomannan of Tremella mesenterica Retz.:Fr. on glycemic responses in normal and diabetic rats

Mushroom polysaccharides have been shown to regulate glucose metabolism. Using male Wistar rats injected with saline (normal rats), streptozotocin (STZ-NT rats), or streptozotocin plus nicotinamide (STZ+NT rats), we investigated the hypoglycemic activity of orally ingested fruiting bodies (FB), submerged culture biomass (CM), or the acidic polysaccharide glucuronoxylomannan (GXM) of Tremella mesenterica, an edible jelly mushroom. Our results demonstrated that FB ingestion significantly attenuated the elevated blood glucose levels in an oral glucose tolerance test (OGTT) in STZ-NT rats. However, in STZ+NT rats, FB, CM, and GXM ingestion significantly attenuated the increases in food and water intake, 2-h postprandial blood glucose concentrations, and blood glucose levels in OGTT. Moreover, FB and GXM ingestion significantly decreased serum concentration of fructosamine in STZ+NT rats. Our results indicated that T. mesenterica might be developed as a potential oral hypoglycemic agent or functional food for diabetic patients and for persons with high risk for diabetes mellitus.     

Effects of dimethylnitrosamine on metabolism of N,N-dimethylaniline by rat liver microsomes. A comparative study of treatment in vivo,in isolated liver perfusion and in the microsomal system

The effect of dimethylnitrosamine (DMN) on rat liver microsomal detoxication was studied, using the non-carcinogenic aromatic amine N,N-dimethylaniline (dimethylaniline) as substrate. Prior to the preparation of microsomes, the rat liver was exposed to DMN either in vivo (by i.p. injection) or in the isolated liver perfusion system (by addition to the perfusion medium). DMN treatment in vivo (20 mg/kg body wt.) caused a 40% increase in dimethylaniline N-oxygenation and a 30% decrease in dimethylaniline C-oxygenation. When DMN was added to the perfusion medium to a final concentration of 5 or 25 mM, a similar effect was observed. With the 5 mM dose, C-oxygenation was decreased by 20% with a non-significant increase in N-oxygenation. The higher dose caused a 50% increase in N-oxygenation, whereas the decrease in C-oxygenation remained at 20%.When microsomes were incubated with both DMN (5 mM) and dimethylaniline (5 mM) in the system, a small but significant decrease in both N- and C-oxygenation of dimethylaniline was observed. The effect of DMN on the amino acid incorporation into liver and plasma proteins was also studied in the liver perfusion system. The synthesis of both liver and plasma proteins was reduced by DMN.     

Seasonal changes in needle water content and needle ABA concentration of Japanese red pine, Pinus densiflora, in declining forests on Mt. Gokurakuji, Hiroshima prefecture, Japan

To evaluate the effects of air pollution on the decline of Pinus densiflora forests, various research has been conducted around Mt. Gokurakuji (34° 23N, 132° 19E, 693 m a.s.l.) north of the Seto Inland Sea, west Japan. To investigate the mechanisms responsible for decreases in photosynthesis (Pn) and stomatal conductance (gl), ¹³C of needles and seasonal changes in the water content (WC) and abscisic acid concentration (ABA) of needles were measured in various stands. The ¹³C values were less negative in declining stands and younger needles. ABA and WC were not correlated with each other. WC decreased consistently with needle age while the ABA showed a minimum in August and a smaller content in older needles. Monthly precipitation and the daily maximum vapor pressure were not correlated with ABA and WC. In declining stands, WC and ABA tended to be higher and lower, respectively, than in nondeclining stands. These results suggest that the trees in declining stands received less water stress than those in nondeclining stands and the differences in gl and ¹³C are not caused by the difference in water stress. The possibilities of the effects of air pollution and the infection of pine-wood nematode on the physiological decline on the pine needles are discussed.     

Effects of acclimation temperature on thermal tolerance, locomotion performance and respiratory metabolism in Acheta domesticus L. (Orthoptera: Gryllidae)

The effects of acclimation temperature on insect thermal performance curves are generally poorly understood but significant for understanding responses to future climate variation and the evolution of these reaction norms. Here, in Acheta domesticus, we examine the physiological effects of 7-9 days acclimation to temperatures 4 °C above and below optimum growth temperature of 29 °C (i.e. 25, 29, 33 °C) for traits of resistance to thermal extremes, temperature-dependence of locomotion performance (jumping distance and running speed) and temperature-dependence of respiratory metabolism. We also examine the effects of acclimation on mitochondrial cytochrome c oxidase (CCO) enzyme activity. Chill coma recovery time (CRRT) was significantly reduced from 38 to 13 min with acclimation at 33-25 °C, respectively. Heat knockdown resistance was less responsive than CCRT to acclimation, with no significant effects of acclimation detected for heat knockdown times (25 °C: 18.25, 29 °C: 18.07, 33 °C: 25.5 min). Thermal optima for running speed were higher (39.4-40.6 °C) than those for jumping performance (25.6-30.9 °C). Acclimation temperature affected jumping distance but not running speed (general linear model, p = 0.0075) although maximum performance (U_MAX) and optimum temperature (T_OPT) of the performance curves showed small or insignificant effects of acclimation temperature. However, these effects were sensitive to the method of analysis since analyses of T_OPT, U_MAX and the temperature breadth (T_BR) derived from non-linear curve-fitting approaches produced high inter-individual variation within acclimation groups and reduced variation between acclimation groups. Standard metabolic rate (SMR) was positively related to body mass and test temperature. Acclimation temperature significantly influenced the slope of the SMR-temperature reaction norms, whereas no variation in the intercept was found. The CCO enzyme activity remained unaffected by thermal acclimation. Finally, high temperature acclimation resulted in significant increases in mortality (60-70% at 33 °C vs. 20-30% at 25 and 29 °C). These results suggest that although A. domesticus may be able to cope with low temperature extremes to some degree through phenotypic plasticity, population declines with warmer mean temperatures of only a few degrees are likely owing to the limited plasticity of their performance curves.