The Biology of Arctic Charr, Salvelinus Alpinus, of Gander Lake, A Large, Deep, Oligotrophic Lake in Newfoundland, Canada

Resident Arctic charr, Salvelinus alpinus, are widespread throughout the island of Newfoundland. This study examines aspects of the biology and spatial and temporal distributions of the charr of Gander Lake, the third largest in Newfoundland (surface area = 11320ha, maximum depth = 288m, mean depth = 105.4m). The deepest part of the lake is approximately 258m below sea level. The lake is well oxygenated from the surface to the bottom during all seasons. Sampling was conducted with Lundgren multiple-mesh experimental gillnets and baited hooks. There appears to be two morphs present, based on colour (dark and pale) and certain meristic characteristics. Dark charr were caught mainly in benthic nets (at depths from 1 to 100m inclusive) with only a few pelagic captures. Pale charr were caught only in benthic nets at depths between 20 and 100m inclusive. The maximum depth sampled was 196m, but there was no catch. There was a tendency for dark charr to be found in deeper, cooler water as the upper water column and inshore areas warmed during summer. There was no apparent trend in size of charr with depth sampled. Dark and pale charr both fed on benthic macroinvertebrates; sticklebacks were consumed only by dark charr and the importance of this prey item increased with size of predator. Zooplankton and surface food were not utilised by Gander Lake charr. Results of the study are compared with findings reported for other water bodies in Newfoundland and Labrador, North America, and Europe, particularly Loch Ness which has similarities in morphometry and trophic status to Gander Lake.     

The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre

Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.     

Interaction of Topotecan,DNA Topoisomerase I Inhibitor,with Double-stranded Polydeoxyribonucleotides. 4. Topotecan Binds Preferably to the GC Base Pairs of DNA

Interaction of topotecan (TPT) with synthetic double-stranded polydeoxyribonucleotides has been studied in solutions of low ionic strength at pH 6.8 by linear flow dichroism (LD), circular dichroism (CD), UV-Vis absorption, and Raman spectroscopy. The complexes of TPT with poly(dG-dC)·poly(dG-dC), poly(dG)·poly(dC), poly(dA-dC)·poly(dG-dT), and poly(dA)·poly(dT), as well as complexes of TPT with calf thymus DNA and coliphage T4 DNA studied by us previously, have been shown to have negative LD in the long-wavelength absorption band of TPT, whereas the complex of TPT with poly(dA-dT)·poly(dA-dT) has positive LD in this absorption band of TPT. Thus, there are two different types of TPT complex with the polymers. TPT has been established to bind preferably to GC base pairs because its affinity to the polymers of different composition decreases in the following order: poly(dG-dC)·poly(dG-dC) > poly(dG)·poly(dC) > poly(dA-dC)·poly(dG-dT) > poly(dA)·poly(dT). The presence of DNA has been shown to shift the monomer–dimer equilibrium in TPT solutions toward dimer formation. Several duplexes of the synthetic polynucleotides bound together by bridges of TPT dimers may participate in the formation of the studied type of TPT–polynucleotide complex. Molecular models of TPT complex with linear and circular supercoiled DNAs and with deoxyguanosine have been considered. TPT (and presumably the whole camptothecin family) proved to represent a new class of DNA-specific ligands whose biological action is associated with formation of dimeric bridges between two DNA duplexes.     

Cowdria Ruminantium Antibodies in Acaricide-Treated and Untreated Cattle Exposed to Amblyomma Variegatum Ticks in The Gambia

An indirect enzyme-linked immunosorbent assay (ELISA), based on the major antigenic protein 1 fragment B (MAP1-B) of Cowdria ruminantium, was used to assess seroprevalence in cattle in The Gambia. Two groups of 20 N'Dama and 20 Gobra zebu cattle were monitored for 12 months with flumethrin treatment and for another 10 months without acaricidal treatment. Two groups of 20 N'Dama and 20 Gobra cattle served as untreated controls. During the period of acaricidal treatment, the cumulative proportions of positive serum samples were 25.6±5.6% (±confidence interval) and 34.7±6.8% in treated N'Dama and Gobra cattle respectively; the proportion of positive sera in untreated cattle was 52.2±6.9% in N'Damas and 61.4±7.3% in Gobras. Within breed, difference in antibody prevalence between treated and untreated cattle was significant (P<0.001) but between breed differences were not significant. In the 10 months following suspension of acaricide application, there was an increase of proportion of positive serum samples in previously treated N'Dama and Gobra cattle. In both previously treated and untreated animals the peak of positive seroreactions occurred during and subsequent to the period of activity of Amblyomma variegatum adults. Cumulative seroprevalences in previously treated N'Dama and Gobra cattle were 32.6±6.9% and 44.7±8.5%, respectively; in untreated animals seroprevalence was 38.6±7.2% in N'Dama and 65.3±8.4% in Gobra cattle. Throughout the study period, within the N'Dama breed, the seropositive rate in previously treated cattle did not differ from that in untreated animals. Conversely, within the Gobra breed, the number of positive seroreactions was higher (P<0.002) in untreated animals than in previously treated cattle. These results provide a support for designing A. variegatum and heartwater control strategies, if necessary, in The Gambia in relation to cattle breeds.     

Light utilization and competition between Echinacea purpurea, Panicum virgatum and Ratibida pinnata under greenhouse and field conditions

Competitive interactions were compared under field and greenhouse conditions for three representative tallgrass prairie species, Echinacea purpurea, Panicum virgatum and Ratibida pinnata. These were planted in monoculture and in mixtures of two species using a replacement series design with groups of four or eight plants. Competition was determined from shoot dry weight data collected during 120days in the greenhouse and after 415days in the field. Yields declined with increased density of a single species in the greenhouse from 40days onward and in the field. Relative yields were up to 100% higher in mixtures than in monocultures for all species early on in the greenhouse experiment. Later in the experiment and in the field relative yields of E.purpurea decreased in the presence of P.virgatum and R.pinnata, whereas relative yields of these two species increased in the presence of E.purpurea. There were correlations in relative yield between the field and the greenhouse experiment at 80 and 120days. In the greenhouse P.virgatum maintained higher net assimilation rates than the other species. Relative growth rates of all species were higher in monoculture and in mixtures up to 40days, after which they declined, especially for E.purpurea in mixtures. In the field, higher light intensities occurred in pure stands of E.purpurea than in mixed stands with other species. The order of competitive ability that was apparent from these field and greenhouse studies, P.virgatum=R.pinnata>E.purpurea, could be partially explained by photosynthetic rates in relation to canopy light interception.     

Larval development and food habits of the marbled parrotfish, <Emphasis Type="Italic">Leptoscarus vaigiensis</Emphasis>, associated with drifting algae

The larval development and food habits of the marbled parrotfish, Leptoscarus vaigiensis (Scaridae) associated with drifting algae were studied. In this study, 628 L. vaigiensis of various developmental stages ranging from postflexion larvae (9.4mm in standard length, SL) to adults (192.0mmSL) were sampled from drifting algae at two fishing ports in Nakagusuku Bay of Okinawa Island. In 3969 fish comprising 65 taxa in 34 families of Teleostei collected with drifting algae, L. vaigiensis occupied 15.8% of samples and occurred generally throughout the whole year. A large number of L. vaigiensis were collected from July to October accompanied by an occurrence of drifting algae composed of Sargassum spp. Larvae and early juveniles ranging from 11.1 to 14.9mmSL appeared sporadically throughout the year, and postflexion larvae 11mmSL occurred from July to November. Their food shifted from planktonic copepods in postflexion larvae and juveniles ranging from 10.0 to 14.9mmSL to seaweed in the juveniles ranging from 15.0 to 24.9mmSL. Furthermore, adults and young over 25mmSL fed almost exclusively on seaweed, with Sargassum spp. constituting the drifting algae. These facts indicate that drifting algae may have a role concerning food and habitat, and may act as a nursery for L. vaigiensis.     

Carbon dynamics and budget in a <Emphasis Type="Italic">Miscanthus sinensis</Emphasis> grassland in Japan

We investigated the carbon dynamics and budget in a grassland of Miscanthus sinensis, which is widely distributed in Japan, over a 2-year period (2000–2001). Plant biomass began to increase from May and peaked in September, then decreased towards the end of the growing season (October). Soil respiration rates also exhibited seasonal fluctuations that reflected seasonal changes in soil temperature and root respiration. The contribution of root respiration to total soil respiration was 22–41% in spring and summer, but increased to 52–53% in September. To determine the net ecosystem production (carbon budget), we estimated annual net primary production, soil respiration, and root respiration. Net primary production was 1207 and 1140gCm^–2 in 2000 and 2001, respectively. Annual soil respiration was 1387gCm^–2 in 2000 and 1408gCm^–2 in 2001; root respiration was 649 and 695gCm^–2 in 2000 and 2001, respectively. Moreover, some of the carbon fixed as net production (457–459gCm^–2) is removed by mowing in autumn in this grassland. Therefore, the annual carbon budget was estimated to be –56gCm^–2 in 2000 and – 100gCm^–2 in 2001. These results suggest that the Miscanthus sinensis grassland in Japan can act as a source of CO₂.     

Patterns of Fish Movement on Eastern Tasmanian Rocky Reefs

We assessed small-scale movement patterns of fishes on three eastern Tasmanian reefs by divers visually resighting 1040 individuals of 16 species marked with unique colour-coded tags. With the possible exception of the monacanthid Acanthaluteres vittiger, common species showed high fidelity to site, with individuals generally resighted <100m from the initial tagging site and remaining near the tagging site throughout the 1 year duration of study. The wrasses Pictilabrus laticlavius and Notolabrus tetricus were more sedentary than Notolabrus fucicola and the monacanthids Meuschenia australis and Meuschenia freycineti. Body length, sex, water temperature and time since tagging had little influence on distance moved compared to variation between individuals, other than movement distance increasing with body length for N. tetricus. Movement patterns were generally consistent at all three sites, although mean distance moved by N. fucicola was double at Swanport and Return Point compared to Lobster Point. N. tetricus but not P. laticlavius emigrated from areas artificially cleared of macroalgae. The sedentary nature of most small- to medium-sized reef fish species, particularly labrids, indicates that relatively small (1km diameter) marine protected areas should generally provide conservation benefits for these fishes but few `spillover' benefits in surrounding areas.     

Recombinant Components of the EcoRII Restriction–Modification System: Restriction Endonuclease Can Interact with DNA · RNA Duplexes

To obtain recombinant restriction endonuclease (R) and methylase (M) of the EcoRII restriction–modification system, bacterial strains overproducing their functional hexahistidine derivatives were constructed. Active full-length R·EcoRII was produced only in cells that also expressed M·EcoRII from a multicopy plasmid. Recombinant R·EcoRII bound with hybrid DNA·RNA duplexes.     

Descriptive morphology of the reared eggs,larvae, and juveniles of the marine atherinid fish <Emphasis Type="Italic">Atherinomorus duodecimalis</Emphasis>

Embryonic, larval, and juvenile development of the marine atherinid Atherinomorus duodecimalis are described from laboratory-reared specimens. The eggs, measuring 1.15–1.24mm in diameter, were demersal and almost spherical in shape with numerous chorionic filaments. Hatching occurred 7 or 8 days after spawning, the newly hatched larvae measuring 4.5–5.1mm in body length (BL) and having 5+34=39 myomeres. Notochord flexion started at 6.9mm BL and finished at 8.3mm BL. Aggregate numbers of all fin rays were completed by 14mm BL. Eggs of this species could be distinguished from other known atherinid eggs on the basis of egg diameter and the arrangement, length, and number of chorionic filaments. Larvae were also distinctive in myomere counts, pigmentation, and locations of the anus and second dorsal fin origin.     

Larvae of <Emphasis Type="Italic">Arnoglossus elongatus</Emphasis> (Pleuronectiformes: Bothidae) from northwestern Australia

Eleven postflexion larvae (9.1–23.9mm standard length: SL) of a bothid, Arnoglossus elongatus, from northwestern Australian waters were described. These specimens were characterized by vertebral numbers of 11–12+32–34=43–45, slender body, remarkably elongated second dorsal fin ray, and presence of melanophores on and slightly above midlateral line of body, plus on dorsal wall of abdominal cavity and air bladder (specimens >12.6mm SL), proximally on caudal fin rays (>16.5mm SL), and on pterygiophore zones of dorsal fin and anal fin (>23.8mm SL).     

Inoculation of sugar mill by-products compost with N2-fixing bacteria

Inoculation of sugar mill by-products compost with N₂-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter vinelandii(ATCC 478), Beijerinckia derxii (ATCC 49361), and Azospirillumsp. TS8, each alone and all three together. Numbers of all N₂-fixing bacteria in compost declined from an initial population of 5×10⁵cellsg^–1 during incubation. The population of Azotobacter declined to approximately 2×10²cellsg^–1 and the population of Beijerinckia and Azospirillum declined to approximately 9×10³ and 3.5×10⁴cellsg^–1 respectively, at day 50. Inoculation with N₂-fixing bacteria increased acetylene reduction, total N by 6–16 and available P by 25–30% in comparison to the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefit from providing N₂ fixing bacteria.     

Conversion of food waste into hydrogen by thermophilic acidogenesis

Conversion of food waste into hydrogen by thermophilic acidogenesis was investigated as a function of organic loading rate (OLR), hydraulic retention time (HRT) and pH in a continuous stirred tank reactor. In order to identify hydrogen-producing microorganisms, denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) – amplified V3 region of 16S rDNA analysis was conducted at each tested pH. The conversion of food waste into hydrogen was strongly influenced by the operational conditions. The hydrogen production was increased as OLR increased up to 8gVSl^-1d^-1, but drastically decreased at 10gVSl^-1d^-1. The yield of hydrogen was decreased from 2.2 to 1.0mol-H₂/mol-hexose consumed as HRT decreased from 5 to 2days. More carbohydrates in the food waste were decomposed at longer HRT, 76–90%, at HRT of 2–5days. The hydrogen production peaked at pH 5.5±0.1 and significantly decreased at pH 5.0±0.1. The biogas produced was composed of hydrogen and carbon dioxide, but no methane was detected at all tested conditions. The hydrogen contents in the gas produced were more than 55% (v/v) and not sensitive to all tested conditions. The optimum operational condition for continuous hydrogen production from the food waste was obtained at 8gVSl^-1d^-1, 5 days HRT and pH 5.5±0.1 where the hydrogen production rate, content, yield and the efficiency of carbohydrate decomposition were 1.0l H₂/l-d, 60.5% (v/v), 2.2mol-H₂/mol-hexose consumed and 90%, respectively. The hydrogen production was related with the concentration of total organic acids (TOA) which was strongly dependent on that of butyrate indicating that the reaction was mainly butyrate fermentation. The hydrogen-producing microorganism of Thermoanaerobacterium thermosaccharolyticum that involved in acetate/butyrate fermentation, was detected with strong intensity at all tested pHs by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) – amplified V3 region of 16S rDNA analysis and sensitive to the tested pHs. The experimental results indicated that effective hydrogen production from the food waste could be obtained continuously by thermophilic acidogenesis at proper operational condition.     

Indirect method to estimate convective gas flow through culms of a <Emphasis Type="Italic">Phragmites australis</Emphasis> stand

We propose an indirect method to estimate continuously the rate of convective gas flow in a Phragmites australis stand. In this method, the rate of gas flow is estimated using the dynamic pressure differential in a culm and the convective conductance of the culm. The rate of gas flow obtained by this indirect method coincided well with that obtained by the direct method in which a culm is detached and then reconnected to the stubble using a mass flow meter. We monitored the total gas flux through a P. australis stand in a field and found that it fluctuated diurnally with the dynamic pressure differential in culms, showing a highest rate of 26lairm^–2 ground area h^–1 at noon. The total daily gas flux was about 170lairm^–2. Our indirect method has advantages in simultaneous and continuous measurements for a cluster of culms. This method will be of use not only to quantify various gas dynamics through aquatic plants in aquatic ecosystems but also to elucidate the ecosystem processes and properties that regulate these gas dynamics.     

The Effect of Ration on Acclimation to Environmental Acidity in Rainbow Trout

Freshwater salmonids exposed to low environmental pH typically suffer a net loss of ions, primarily Na⁺ and Cl^–, across the gills, resulting in reduced plasma and tissue ion concentrations. However, in recent experiments in our laboratory, juvenile rainbow trout, Oncorhynchus mykiss, fed a ration of 1% body weight d^–1 or greater showed no ionoregulatory disturbance during chronic, sublethal acidification. This raised the possibility that these fish had acclimated to low pH in that they would be better able to withstand further, more severe acidification than fish that had no prior experience of acid conditions: previous studies had concluded that such acclimation does not occur. This hypothesis was tested by measuring unidirectional ion fluxes during a 24h acute acid challenge (pH 4.2) in juvenile rainbow trout that had previously been exposed to either ambient pH 6.2 (naive fish) or sublethal low pH 5.2 (acid pre-exposed fish) for 90 days, and fed a ration of either 1.0 or 0.25% d^–1 (wet basis). No mortalities were observed during the acute acid challenge in the fish fed the higher ration and no differences between the two groups in the response of Na⁺ fluxes were observed. Sodium influx in both groups was significantly inhibited throughout the challenge and Na⁺ net flux was significantly stimulated over the first 6h. Prior to the acute acid challenge, the fish fed the lower ration that had previously been exposed to pH 5.2 had significantly lower plasma ion concentrations than those fish previously exposed to pH 6.2. Both groups suffered mortalities; those of the naive fish (22% by 24h) being markedly lower than those of the acid pre-exposed fish (68% by 24h). However, there were no significant differences in either Na⁺ or Cl^– fluxes between the two groups of fish during the acid challenge: both showed significant inhibition of ion influxes and significantly greater net ion losses, resulting in reduced plasma ion concentrations. These results indicate that rainbow trout are unable to acclimate to environmental acidification irrespective of the availability of dietary salts.     

Summer forage biomass and the importance of litterfall for a high-density sika deer population

The biomass of summer forage and their contributions were surveyed to show that litterfall supported a high-density population of sika deer (Cervus nippon Temminck) in summer on Nakanoshima Island, Toya Lake, Japan. In July 1974, the grassland had the highest productivity among understory vegetations (228±55kgha^–1: mean±SE). In deciduous forests, palatable plants occupied only 0.1% of the biomass of 0.872±0.366kgha^–1, and deciduous leaves within the reach of deer (=220cm at height) produced 0.208±0.070kgha^–1. However, litterfall during this period had the highest productivity, 28.7± 5.3kgha^–1. The deer consumed litterfall (75.6% in dry weight), short grasses (17.2%), deciduous forest understory (4.1%), deciduous leaves within the reach of deer (3.0%) and conifer plantation under story (0.1%). It is suggested that the high-density deer population would be maintained by litterfall through the year instead of browsing in deciduous forests, which has been overlooked.     

Developmental morphology of the cyprinid fish Chela dadiburjori

Embryonic, larval, and juvenile development of an Indian cyprinid fish, Chela dadiburjori, is described from laboratory-reared specimens. The eggs, measuring 0.7–0.9mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk and no oil globule. Hatching occurred 50–61h after fertilization at ca. 27°C. The newly hatched larvae, measuring 2.4–2.6mm in body length (BL), had melanophores on the body with 14–16+14–17=29–31 myomeres. Two dark transverse bands on the ventral body surface and one melanophore on the lower margin of the eye in newly hatched larvae were diagnostic. Additionally, a cement organ for adhering to objects was present on the forehead of yolk sac larvae <3.1mm BL. The yolk was completely absorbed at 3.5mm BL. Notochord flexion was initiated at 5.0mm BL and finished at 6.0mm BL. Aggregate numbers of all fin rays were completed at 9.2mm BL. Squamation was initiated on the caudal peduncle at 8.0mm BL and completed at 10mm BL. The eggs of C. dadiburjori resembled those of the closely related species Devario malabaricus and Danio rerio. The larvae and juveniles of C. dadiburjori were also similar to those of the latter species in general morphology, especially the presence of body melanophores in newly hatched individuals and a distinctive lateral streak on the head during the period from yolk sac to postflexion larvae. However, early yolk sac larvae of C. dadiburjori were more similar to those of Devario malabaricus than Danio rerio in having a cement organ on the forehead. Larvae and juveniles of C. dadiburjori differed from those of the latter two species in pigmentation on the ventral body surface at hatching and around the mouth during the period from preflexion to early postflexion larvae and in having a dark lateral streak or band on the body in postflexion larvae and juveniles.     

Isolation and characterization of a thermophilic bacterium, Geobacillus thermocatenulatus, degrading nylon 12 and nylon 66

A thermophilic bacterium, identified as a neighboring species to Geobacillus thermocatenulatus, having a growth optimum at 55 °C and, capable of degrading nylon 12, was isolated from soil by enrichment culture technique at 60 °C. At this temperature, the strain grew on 5 g nylon 12 l^–1 with a decrease in its molecular weight from 41000 to 11000 over 20 d. The degradation was assumed to be due to endogenous hydrolysis of amide bond in nylon 12. The strain degraded also nylon 66 with a decrease in its molecular weight from 43000 to 17000 in 20 d at 60 °C. Nylon 6 was not degraded.     

Ethanol production in multistage continuous, single stage continuous, Lactobacillus-contaminated continuous, and batch fermentations

Saccharomyces cerevisiae-based ethanol fermentations were conducted in batch culture, in a single stage continuous stirred tank reactor (CSTR), a multistage CSTR, and in a fermentor contaminated with Lactobacillus that corresponded to the first fermentor of the multistage CSTR system. Using a glucose concentration of 260 g l^–1 in the medium, the highest ethanol concentration reached was in batch (116gl^–1), followed by the multistage CSTR (106gl^–1), and the single stage CSTR continuous production system (60gl^–1). The highest ethanol productivity at this sugar concentration was achieved in the multistage CSTR system where a productivity of 12.7gl^–1h^–1 was seen. The other fermentation systems in comparison did not exceed an ethanol productivity of 3gl^–1h^–1. By performing a continuous ethanol fermentation in multiple stages (having a total equivalent working volume of the tested single stage), a 4-fold higher ethanol productivity was achieved as compared to either the single stage CSTR, or the batch fermentation.     

Taurine protected myocardial mitochondria injury induced by hyperhomocysteinemia in rats

Summary. Taurine can protect against cardiovascular diseases, whereas elevated levels of plasma homocysteine are associated with atherosclerotic and thromboembolic cardiovascular diseases. To illustrate the effects of taurine on hyperhomocysteinemia, we observed the myocardial mitochondria dysfunction in the rats with hyperhomocysteinemia induced by diet methionine loading, and the therapeutic effect of taurine. A methionine diet increased plasma homocysteine concentration (133.51±27.91mol/L vs 12.31±2.58mol/L in control, P<0.01), stimulated the production of reactive oxygen species (ROS) in the myocardial mitochondria, and inhibited the activities of mitochondrial Mn-superoxide dismutase and catalase. The ⁴⁵Ca uptake and Ca²⁺-ATPase activity in the myocardial mitochondria were significantly lowered in rats with hyperhomocysteinemia. Taurine supplements effectively attenuated the hyperhomocysteinemia-induced ROS production and inhibition of Mn-superoxide dismutase and catalase activities in the myocardial mitochondria, and increased its ⁴⁵Ca uptake and Ca²⁺-ATPase activity. Thus, taurine antagonizes the oxidative stress injury in the myocardial mitochondria induced by the hyperhomocysteinemia.