Phosphoglucose isomerase isozymes in teleostean fishes from the Arabian Gulf

Two phosphoglucose isomerases (PGI) with different electrophoretic mobilities have been found in all groups of teleostean fishes studied, with the exception of the Clupeomorpha. PGI proved to be a good taxonomic criterion to differentiate members of the Nemipteridae, Sciaenidae, Platycephalidae and Stromateidae from the other teleost families.     

The invasion of Biomphalaria pfeifferi by Schistosoma mansoni miracidia and the development of daughter sporocysts

Laboratory experiments have been carried out to determine the susceptibility of Gezira Biomphalaria pfeifferi snails to S. mansoni miracidia and the relationship between miracidia and daughter sporocyst production at the 10–17 day development stage. The relationship between snail numbers, miracidia numbers and water volume has also been studied. Two non susceptible snails, Bulinus truncatus and Cleopatra bulimoides, both of which occur naturally in Gezira canals, were tested to see if they act as decoys for S. mansoni miracidia.The results showed that the B. pfeifferi are 100% susceptible to S. mansoni invasion, at least to the daughter sporocyst development stage. The more miracidia that penetrated the more daughter sporocysts were produced, however individual variation and overlap were great. When one miracidium was released to find one snail it succeeded in low water volumes (5 m, 50 ml), but failed in 5 litres. When 100 miracidia were released mortality of snails was high suggesting superinfection particularly when only one or five snails were available. Among survivors daughter sporocyst counts were very high. Cleopatra and Bulinus snails do have a decoy effect when present in large numbers. In their presence the number of infected snails was marginally reduced and the number of daughter sporocysts greatly reduced. However, if superinfection is reduced by decoy effect, it is conceivable that Biomphalaria may be protected by decoy snails in circumstances where miracidia counts are high.     

Spectral shifting by dyes to enhance algae growth

The photosynthetic growth action spectrum of a green alga at three bands of visible light (blue, orange, and red) at fixed quanta input and under light-limiting conditions was measured in a batch cultivation system. Quantum efficiencies (biomass dry weight increment per quanta absorbed) were better in the yellow-red region than in the blue region. Results served as a basis for the design and optimization of a dye system that would shift the energy of solar radiation to the required wavelength range by absorbing ultraviolet to blue radiation and emitting in the yellow-red, thus enhancing algae growth. Direct incorporation of dyes into the growth medium, although theoretically expected to enhance growth, in fact resulted in dye decomposition, toxicity to algae and consequently in growth inhibition. Indirect application of dyes in a double tubular reactor (algae inside and dye solution outside) demonstrated growth enhancement for certain dyes with high quantum yields and stability, which had suitable absorption/emission spectra for artificial light sources used. The maximum indirect growth enhancement was obtained using rhodamine 6G at a concentration of 3x10(-5)M with tungsten filament lamp sources.     

The effect of short-term fluctuations in pH on NO−3 uptake and intracellular constituents in Skeletonemacostatum (Grev.) Cleve

Measurements of uptake rates, intracellular nitrogen pools, and other key intracellular constituents were made during exponential growth in Skeletonema costatum (Grev.) Cleve under varying pH levels. An understanding of the overall effects of extracellular pH on the above mentioned cellular parameters is crucial in order to ascertain the degree to which pH must be regulated and monitored in laboratory experiments with marine phytoplankton.It was found that uptake rates and intracellular pool sizes of NO^?₃ were directly influenced by the extracellular pH level, whereas, other cellular compounds remained relatively unchanged. Therefore, nitrogen uptake and intracellular nitrogen storage are dependent on key H⁺ and OH_? ion transport mechanisms that are associated with phytoplankton metabolism. These findings reiterate the fact that investigators examining nitrogen uptake and assimilatory mechanisms in marine phytoplankton must be conscious of cellular H ⁺ and OH^? fluxes that contribute to intracellular pH regulation and changes in extracellular pH levels, both of which interact to affect phytoplankton metabolic processes.     

Recognition and response to alloantigens in vivo. I. Negative and positive selection of MLR reactivity in murine peripheral blood lymphocytes to major histocompatibility complex and Mls antigens

Specific mixed lymphocyte reaction (MLR) responsiveness to allogeneic major histocompatibility complex (MHC), or minor lymphocyte-stimulating (Mls) determinants, was depleted in the peripheral blood lymphocytes (PBL) obtained from mice 24 to 48 hr after i.v. injection of 5 to 7.5 X 10(7) MHC or Mlsa-incompatible spleen cells, respectively. Results of cell mixture experiments suggest that the generation of suppressor cells was not the explanation for this specific reduction in MLR proliferation occurring with these PBL responder cells. To gain additional insight into parameters involved in the recognition of allodeterminants in vivo, experimental manipulations of the host environment and donor cell inoculum utilized in the negative selection procedure were employed. For example, removal of the spleen in the recipient animal, an anatomic site in which injected allogeneic cells and corresponding host antigen-reactive cells (ARC) are trapped, still permitted the specific depletion in murine PBL of host ARC for donor foreign MHC antigens. This finding may implicate other sites such as the liver where unprimed host alloreactive clones are trapped. In addition, irradiation of allogeneic donor cells significantly reduced their capacity to trap alloreactive T cell clones in vivo, whereas heat treatment of the donor cells completely eliminated this ability, even though the Ia determinants were still expressed, measured by flow cytometry. After the negative selection period, kinetic analysis of proliferation showed that 3, 4, or 5 days after injection of MHC-incompatible allogeneic spleen cells, the PBL of the recipient showed specific hyperresponsiveness to the MHC-haplotype of the donor cells. Interestingly, these primed PBL responder cells had the volume distribution of small resting cells; thoracic duct lymphocytes (TDL), positively selected by adoptive transfer of T cells to irradiated semiallogeneic recipients, are reported to be mainly blast cells. In contrast to the MLR hyperresponsiveness that results from priming with MHC-incompatible splenocytes, PBL, obtained at these later time points from mice primed with Mlsa-incompatible, H-2-compatible splenocytes, showed complete unresponsiveness in MLR to these Mlsa-bearing stimulator cells, as well as some nonspecific reduction in proliferation to MHC-incompatible stimulator cells regardless of their Mls genotype.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ammonium-nitrogen metabolism and nitrogen fixation in azotobacter vinelandii

The probable effect of increasing levels of ammonium nitrogen on the growth, efficiency of nitrogen fixation, and main cellular constituents of Azotobacter vinelandii was studied under shaking and static culture conditions. The presence of NH₄⁺-N up to 50 mgl^-1 level has no harmful effect on the multiplication as well as the yield efficiency ratio of the tested organism. A. vinelandii was able to fix dinitrogen in the presence of NH₄⁺-N when both nitrogen sources were available in the culturing medium. The efficiency of nitrogen fixation was affected by the initial presence of NH₄⁺-N in the medium, it was quite low at the highest level. The crude protein efficiency ratio was correlated inversely with the initial NH₄⁺-N concentration, whereas the total carbohydrate efficiency ratio as well as the total lipid efficiency ratio were positively correlated with the NH₄⁺-N concentration. The presence of NH₄⁺-N in the culturing medium has no essential influence on the qualitative composition of the amino acids in the Azotobacter cells.     

Lineage-specific expression of c-fos and c-fms in human hematopoietic cells: Discrepancies with the in vitro differentiation of leukemia cells

In vitro differentiation studies using the bipotential human leukemia cell line, HL60, have indicated that high levels of expression of two proto-oncogenes, c-fos and c-fms, are restricted to the myelomonocytic lineage. No such expression has been detected in induced granulocytic cells. In striking contrast to these observations, we found that c-fos mRNA levels are very high in purified human granulocytes, but barely detectable in blood monocytes and tissue macrophages. Human granulocytes contain, however, relatively low levels of c-fos protein, indicating that c-fos mRNA is inefficiently translated or that the protein is rapidly degraded in these cells. In closer agreement with the in vitro results, the level of the expression of c-fms is high in purified blood monocytes and undetectable in granulocytes. We found, however, that the evolution of monocytes into tissue macrophages is accompanied by a significant decrease in c-fms expression, suggesting that the function of c-fms is restricted to specific stages of monocytic differentiation. Our observations also show that results obtained using in vitro differentiation systems have to be regarded with caution, since they may not reflect the in vivo situation.     

Serotypes of verocytotoxigenic Escherichia coli isolated from cattle and buffalo calf diarrhoea

Abstract Parasporal crystals of the recently isolated Bacillus thuringiensis var. tenebrionis are toxic for coleopteran larvae. Unlike those of other strains they are soluble either in aqueous solutions of NaBr at neutral pH or in water after titration to pH values above pH 10.0. The dissolved crystal protein readily forms crystals after removal of the salt or neutralization. The crystal protein was not found to differ much in the amino acid composition from other crystal proteins. The parasporal crystals are composed of subunits of M _r 68 000 which are not linked by disulfide bridges.     

A unique DR-related B cell differentiation antigen

The Ia or class II molecules in both mouse and man are the basis for the genetic control of the immune response. In addition to DR, other class II antigens have been described in man. We describe a new human Ia antigen K19, recognized by three monoclonal antibodies (HK-9, HK-19, and HK-20). This antigen has the general biochemical characteristics of an Ia antigen but is different from a DR antigen. Further, this antigen is found only on mature B lymphocytes and not on monocytes and activated T cells. Thus, this antigen may represent a new Ia-like molecule that is preferentially expressed on mature B cells.