The influence of substratum age on patterns of protozoan assemblages in freshwater Aufwuchs — a case study

The sulfate reduction rate was measured for almost four years in the profundal sediments of Lake Kizaki, a mesotrophic lake in central Japan. The rate was generally highest in the surface layer and decreased with depth. Seasonally, sulfate reduction tended to be high in spring and summer, and then to decrease until the end of stratification (December) in spite of a constant in situ temperature of around 6 °C, although fluctuations were found in every year. The rate also fluctuated greatly according to year. The maximum rate of sulfate reduction was 0.33 mmol m⁻² d⁻¹ in May, 1990, and the minimum was 0.004 mmol m⁻² d⁻¹ in March, 1993. These relatively low rates, compared with those reported for freshwater sediments, seem to be due to low concentrations of sulfate in the sediments (5–23 μmol l⁻¹ in the surface layer). The rate was highly correlated with the concentration of sulfate in the sediments. The addition of sulfate stimulated sulfate reduction in all sediment samples tested, but adding lactate did not. Therefore, sulfate reduction should be limited mainly by the supply of sulfate. Measurements of sulfate reduction rates at different concentrations of added sulfate revealed a low concentration of half-saturation constant as low as 12 μmol l⁻¹.     

Urinary 6-Sulfatoxymelatonin Cycle-To-Cycle Variability

For either clinical or research purposes, the timing of the nocturnal onset in production of the urinary melatonin metabolite 6-sulfatoxymelatonin (UaMT6s-onset), has been proposed as a reliable and robust marker of circa-dian phase. However, given that most circadian rhythms show cycle-to-cycle variability, the statistical reliability of phase estimates obtained from a single study using UaMT6s-onset remains to be determined. Following 2 weeks of sleep diary and wrist actigraphy, 15 young, healthy good sleepers participated in four UaMT6s sampling sessions spaced 1 day apart. During the sampling sessions subjects remained indoors under low light conditions and hourly urine samples were collected from 19:00 to 02:00 h. Samples were subsequently assayed for UaMT6s using standard radioimmunographic techniques. UaMT6s-onset was determined by the time at which melatonin production exceeded the average of three proceeding trials by 100%. Sleep onset times were derived from sleep diary and actigraphic measures taken before the melatonin collection nights. We found that there was no significant variation between nights in group mean UaMT6s-onset times, and intraindividual variability was small. In addition, UaMT6s-onset times were highly and significantly correlated between nights (grand mean r = 0.804). Our results suggest that within 95% confidence interval limits, individual UaMT6s-onset estimates obtained from a single night UaMT6s-onset study can be used to predict subsequent UaMT6s-onset times within ±97 min. A close temporal relationship was also found between the timing of UaMT6s-onset and sleep onset. Overall, our results suggest that under entrained conditions single-session UaMT6s-onset studies can provide reliable individual UaMT6s-onset phase estimates and that the protocol described in this study is a practical and noninvasive methodology. (Chronobiology International, 13(6), 411-421, 1996)     

Secretion of a heat-stable fungalβ-glucanase from transgenic,suspension-cultured barley cells

Transgenic plant cell cultures have a potential for production and secretion of important proteins and peptides. To assess the possibilities of using a stable barley suspension culture for secretion of heterologous proteins in active form, we expressed the cDNA of the thermostable-glucanase (EGI) ofTrichoderma reesei in barley suspension cells. The cDNA coding for EGI and its signal sequence was placed under the control of the CaMV 35S promoter and the construction was transferred to the cells by particle bombardment. Stably transformed lines were obtained by selecting for a cotransformed antibiotic resistance marker. The expression of EGI cDNA led to accumulation of EGI in the culture medium, as shown by analysis with EGI-specific antibodies. Enzymatic assays confirmed that the EGI secreted by the suspension cells retained its activity and thermostable character. Furthermore, it was shown that the enzyme produced by the transgenic suspension culture could be used for degradation of soluble-glucans during mashing.     

Immunoaffinity column clean-up for the high-performance liquid chromatographic determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in urine

A method for the determination of aflatoxins B₁, B₂, G₁, G₂, M₁ and Q₁ in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B₁ 103%, B₂ 106%, G₁ 98% and G₂ 96% in the range 6.8–73 pg/ml of urine and M₁ 103% and Q₁ 100% in the range 18–97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B₁, B₂, G₁ and G₂ and 18 pg/ml for M₁ and Q₁.     

H-2T24 and Pema T24: orthologous expressed MHC class Ib genes from mouse and Peromyscus maniculatus

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers U03104 and L22338.     

Fertile transgenic barley by particle bombardment of immature embryos

Transgenic, fertile barley (Hordeum vulgare L.) from the Finnish elite cultivar Kymppi was obtained by particle bombardment of immature embryos. Immature embryos were bombarded to the embryonic axis side and grown to plants without selection. Neomycin phosphotransferase II (NPTII) activity was screened in small plantlets. One out of a total of 227 plants expressed the transferred nptII gene. This plant has until now produced 98 fertile spikes (T₀), and four of the 90 T₀ spikes analyzed to date contained the nptII gene. These shoots were further analyzed and they expressed the transferred gene. From green grains, embryos were isolated and grown to plantlets (T₁). The four transgenic shoots of Toivo (the T₀ plant) produced 25 plantlets as T₁ progeny. Altogether fifteen of these T₁ plants carried the transferred nptII gene as detected with the PCR technique, fourteen of which expressed the nptII gene. The integration and inheritance of the transferred nptII gene was confirmed by Southern blot hybridization. Although present as several copies, the transferred gene was inherited as a single Mendelian locus into the T₂ progeny.     

Distribution of two congeneric charrs in streams of Hokkaido Island,Japan: considering multiple factors across scales

Salvelinus leucomaenis (white-spotted charr) and S. malma (Dolly Varden) are distributed throughout Hokkaido Island, Japan, but sites where they occur in sympatry are rare. In general, S. malma inhabit upstream reaches and S. leucomaenis extend downstream to the ocean. Factors influencing their distribution were analyzed at four spatial scales ranging from the whole island to individual stream pools. At the island scale, S. leucomaenis were found in the warmer south-west region and at lower altitudes elsewhere, whereas S. malma were found in the colder north-east and at higher altitudes. At a regional scale, the downstream limit of S. malma and upstream limit of S. leucomaenis shifted to lower altitude from south-west to north-east across the island, coincident with the decrease in temperature. Further analysis showed that transition points from S. leucomaenis or sympatry to S. malma in individual watersheds were closely related to an index of cumulative mean monthly temperatures exceeding 5°C. However, at the scale of a single watershed, the transition occurred at different altitudes, gradients, and temperatures in two tributaries, apparently because stream discharge, habitat, and disturbances from floods interacted with these abiotic factors to limit distribution. The two charr species developed interspecific dominance hierarchies in individual pools, and there was strong complementary density compensation among stream pools that could be explained by interspecific competition but not by differences in habitat. However, patterns at watershed and regional scales suggested that interspecific competition interacts with temperature in complex ways. We conclude that the importance of various abiotic and biotic factors in shaping Hokkaido charr distributions depends on the scale at which they are viewed.     

Endocytosis of 1,3-β-glucans by broad bean cells at the penetration site of the cowpea rust fungus (haploid stage)

Te penetration hypha of basidiospore-derived infection structures of the cowpea rust fungus (Uromyces vignae Barclay) in epidermal cells of the nonhost, broad bean (Vicia faba L.), was studied with the electron microscope after high-pressure freezing and freeze substitution. After fungal invasion of the epidermis, a plug in the penetration hypha separated the infection structures on the cuticle from the intraepidermal vesicle of the fungus. The plug and the fungal cell wall reacted with a polyclonal 1,3-β-glucan antibody. The plug in the haploid stage seems to have a task similar to the septum formed in the diploid stage of the fungus. Around the penetration hypha, the plant wall stained darkly and a papilla was deposited by the plant. In the papilla, 1,3-β-glucans were labelled by a monoclonal and a polyclonal antibody. In the infected epidermal cell, clathrin-coated pits, coated vesicles, partially coated reticula and multivesicular bodies were found. The contents of the coated pits, coated vesicles, partially coated reticula and multivesicular bodies bound to monoclonal and polyclonal 1,3-β-glucan antibodies. Accumulation and uptake of this paramural material into the plant cell by endocytosis is concentrated at the fungal penetration site. It may influence the host-parasite interaction.