Alterations in the biomass-specific productivity of periphyton assemblages mediated by fish grazing

1. In an experimental flume, we examined the effects of a biomass reduction and alteration of taxonomic composition, because of grazing by the fish Plecoglossus altivelis, on the net biomass accumulation of periphyton. 2. Grazed and ungrazed assemblages with different biomass and taxonomic composition were first prepared in fish enclosures and exclosures, respectively. These assemblages were then set out in the flume and incubated for 2 days under grazing‐free conditions to examine (i) the relationship between biomass and biomass accumulation rate and (ii) the effect of taxonomic composition on the relationship between these two. 3. The grazed and ungrazed assemblages were dominated by upright filamentous cyanobacteria and diatoms, respectively. The rate of biomass accumulation decreased with increasing periphyton biomass in both the grazed and ungrazed assemblages, and was lower in the grazed than the ungrazed assemblages at any biomass level. 4. The results showed that the reduction in biomass and the alteration of taxonomic composition due to fish grazing have opposite effects on biomass‐specific productivity. Biomass accumulation rate increased in response to biomass reduction, although a shift in dominance from diatoms to upright filamentous cyanobacteria decreased the overall productivity of the periphyton.     

Nitrogen delivery to maize via mycorrhizal hyphae depends on the form of N supplied

Arbuscular mycorrhizal fungi can enhance nutrient acquisition by a plant via their extraradical hyphae. This is particularly true for phosphorus, but the case for nitrogen (N) has been less clear. In our growth systems there was a small air-gap between root and hyphal compartments, which eliminated diffusion of nutrients between compartments. Moreover, our methods allowed us to distinguish between nitrate and ammonium. We found that N transfer to Zea maize L. depends on the sources fed to the hyphae of Glomus aggregatum Schenck & Smith. In experiment 1, despite the fact that plant demand for N was already met, plants received 10 times as much ¹⁵N from ammonium than from nitrate. In experiment 2, 74% of shoot-N was derived from the slow-release urea added to the hyphal compartment while only 2.9% was derived from the nitrate-N. Intraradical hyphae isolated from roots contained a considerable amount of ¹⁵N in the cell wall even when ¹⁵N-nitrate was the source. We conclude that the mycorrhizal fungus can rapidly deliver ammonium-N to the plants, and that while the fungus can absorb nitrate, it apparently lacks the capacity to transfer it to the plant.     

Generation of multivirus-specific T cells by a single stimulation of peripheral blood mononuclear cells with a peptide mixture using serum-free medium

Background: Restoration of virus-specific immunity by virus specific T cells (VSTs) offers an attractive alternative to conventional drugs, and can be highly effective in immunocompromised patients, including hematopoietic stem cell transplant (HSCT) recipients. However, conventional VSTs manufacture requires preparation of specialized antigen-presenting cells (APCs), prolonged ex vivo culture in serum-containing medium and antigen re-stimulation with viruses or viral vectors to provide viral antigens for presentation on APCs. Methods: To simplify this complex process, we developed a method to generate multiple VSTs by direct stimulation of peripheral blood mononuclear cells (PBMCs) with overlapping peptide libraries in serum-free medium. Results: We generated VSTs that targeted seven viruses (cytomegalovirus [CMV], Epstein-Barr virus [EBV], adenovirus [AdV], human herpesvirus 6 [HHV-6], BK virus [BKV], JC virus [JCV] and Varicella Zoster virus [VZV]) in a single line. The phenotype, growth and specificity of multiple VSTs produced in serum-free medium were equivalent to those generated in conventional serum-containing medium. Discussion: The use of serum-free medium allows this approach to be readily introduced to clinical practice with lower cost, greater reproducibility due to the absence of batch-to-batch variability in serum and without concerns for infectious agents in the serum used. This simplified approach will now be tested in recipients of Human Leukocyte Antigen (HLA)–matched sibling HSCT.     

Uptake and loss of water in diapause and non-diapause eggs of crickets

ABSTRACT. In laboratory-laid eggs of the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), water absorption occurs at an early stage of embryogenesis (stage II) at 30°C but is delayed until later stages at lower temperatures. This is related to the variation in diapause stage at different temperatures. No egg developed beyond stage VII (the end of anatrepsis) without water absorption.
A. fasciatus shows seasonal variation in the stage of water absorption. At 30°C, eggs collected in August absorb water at the early stage while many of those collected in September avert diapause and absorb water at a later stage.
Diapause also influenced the water absorption of eggs in A. socius Scudder. Eggs of short-day females enter diapause and absorb water at stage II, while those of long-day females develop without diapause and absorb water at a later stage (around stage IV).
The susceptibility to desiccation (r.h. 50%) was examined at 20°C with A. fasciatus eggs. The percentage water loss and mortality of eggs varied with the time and duration of exposure to desiccation. Eggs are most sensitive to desiccation during the first several days after being laid and during the period of water absorption.     

PGD variants in several wild pig populations of East Asia

PGD (6-phosphogluconate dehydrogenase) gene frequencies were reported in wild pigs, Sus scrofa, of three subspecies, i.e. Japanese wild pig, S.s. leucomystax, Ryukyu wild pig, S.s. riukiuanus, and Formosan wild pig, S.s. taivanus. Five phenotypes (A, AB, B, AC' and C') were observed. The C' variant was found only in the S.s. leucomystax, and may be identical to PGD-C reported by Archibald & McTeir (1988). PGD-A was a common variant in all the species in the genus Sus including wild pig, Sus scrofa, Javan pig, Sus verrucosus, and Bearded pig, Sus barbatus, and predominated in the whole populations examined except some of those of the S.s. riukiuanus. This suggested that the PGDA appeared before the other two alleles (B and C') during the evolution of the genus Sus.     

Effects of Surfactant Protein-A on the Interaction of Pneumocystis murina with its Host at Different Stages of the Infection in Mice

ABSTRACT. We examined the effects of surfactant protein A (SP-A), a collectin, on the interaction of Pneumocystis murina with its host at the beginning, early to middle, and late stages of infection. Pneumocystis murina from SP-A wild-type (WT) mice inoculated intractracheally into WT mice (WT_S-WT_R) adhered well to alveolar macrophages, whereas organisms from SP-A knockout (KO) mice inoculated into KO mice (KO_S-KO_R) did not. Substitution of WT mice as the source of organisms (WT_S-KO_R) or recipient host macrophages (KO_S-WT_R) restored adherence to that found with WT_S-WT_R mice. In contrast, when immunosuppressed KO and WT mice were inoculated with P. murina from a homologous source (KO_S-KO_R, WT_S-WT_R) or heterologous source (WT_S-KO_R, KO_S-WT_R) and followed sequentially, WT_S-KO_R mice had the highest levels of infection at weeks 3 and 4; these mice also had the highest levels of the chemokine macrophage inflammatory protein-2 and neutrophils in lavage fluid at week 3. Surfactant protein-A administered to immunosuppressed KO_S-KO_R mice with Pneumocystis pneumonia for 8 wk as a therapeutic agent failed to lower the organism burden. We conclude that SP-A can correct the host immune defect in the beginning of P. murina infection, but not in the middle or late stages of the infection.     

Patients With Various Types of Human Papillomavirus: Covariation and Diagnostic Relevance of Cytological Findings In Papanicolaou Smears

Human papillomavirus (HPV) infection in the genital tract is associated with a number of cytological changes which are accepted as standard criteria for a cytological diagnosis. We evaluated the covariation and diagnostic accuracy of these criteria in 210 patients, i.e. 150 cases who were positive for HPV types 6, 11, 16, 18, 31, 33 or 35, and 60 cases who were HPV-negative by simultaneous Southern blot analysis. This was done by re-examining cervical smears obtained at the same time, without knowing the results of the Southern blot analysis, for the presence of koilocytosis, dyskeratosis-parakeratosis, nuclear smudging, hyperchromasia, binucleation, multinucleation, karyorrhexis and macrocytosis. We found that all these cytological changes correlated with the presence of an HPV infection. However, analysis of variance showed that koilocytosis, dyskeratosis-parakeratosis and karyorrhexis were of particular diagnostic value, while the other features provided little or no additional information. By omitting these features and making the diagnosis when two out of three of the key criteria, i.e. koilocytosis, dyskeratosis-parakeratosis and karyorrhexis were present, we diagnosed HPV infection with a specificity of 100% in 36% of the 150 cases, which were positive by Southern blot analysis. the various HPV types produced different morphological patterns which may reflect differences in action on the host cell. In the individual patient, however, such differences in cytology do not provide a sound basis for distinguishing between viral types.     

Inhibitory effects of monoamine oxidase inhibitors on the growth of pea and rice seedlings

Two monoamine oxidase inhibitors of the hydrazine-type, safrazineand nialamide, inhibited growth in seedlings of rice and pea.We demonstrated histochemically that monoamine oxidase is locatedchiefly in sieve tubes and in the epidermis of pea seedling.Activity of this enzyme was high in the apical part of the epicotyl,decreasing toward the base. Inhibition of pea monoamine oxidaseby safrazine and nialamide was observed histochemically andwith an extract from the epicotyl. This supports the hypothesisthat indole-3-acetic acid (IAA) is formed from tryptamine byamine oxidase and that inhibition of this enzyme causes loweringof the auxin level, resulting in growth inhibition. Inhibitionof growth in rice seedlings by safrazine was reversed by theaddition of IAA to the culture medium. (Received May 6, 1970; )