Structural changes in the innercortex cells of soybean root nodules are induced by short-term exposure to high salt or oxygen concentrations

After a 2 h exposure of intact soybean nodules to high concentrations of NaCl (100mol m_?3) or oxygen (8OkPa O₂), morphometric computations carried out using an image analysis technique on semi-thin sections showed that both treatments induced a decrease in the area of the inner-cortex cells, which were then characterized by a tangential elongation. In contrast, no significant change in area occurred in the middle-cortex cells although their elongation decreased. Electron microscopic observations showed that in the inner-cortex cells changes included the presence of wall infoldings, an enlarged periplasmic space and a lobate nucleus whose chromatin distribution differed from that of the control. Structural changes also occurred in the endoplasmic reticulum, microbodies, mitochondria and plastids. From several of these changes, which are similar to those noted in osmocontractil cells in response to external stimuli, it can be hypothesized that the inner cortex may provide a potential mechanism for the control of oxygen diffusion through the nodules.     

Intracellular flux analysis applied to the effect of dissolved oxygen on hybridomas

Quantitative estimates of intracellular fluxes and measurements of intracellular concentrations were used to evaluate the effect of dissolved oxygen (DO) concentration on CRL 1606 hybridoma cells in batch culture. The estimates of intracellular fluxes were generated by combining material balances with measurements of extracellular metabolite rates of change. Experiments were performed at DO levels of 60% and 1% air saturation, as well as under oxygen-limited conditions. Cell extracts were analyzed to evaluate the effect of DO on the intracellular concentrations of the glutamate dehydrogenase reactants, as well as the redox state of the pyridine nucleotides in the cytosol and mitochondria. The relationship between cell density and pyridine nucleotide redox state was also investigated. Dissolved oxygen concentration had a significant effect on nitrogen metabolism and the flux through glutamate dehydrogenase was found to reverse at low DO, favoring glutamate formation. The NAD in the cytosol and mitochondria was more reduced under low DO conditions while the cytosolic NAD was more oxidized at low DO. Cytosolic NAD was reduced at higher cell densities while the redox states of cytosolic NADP and mitochondrial NAD did not exhibit significant variation with cell density. These results point to the fundamental role of the intracellular oxidation/reduction state in cell physiology and the possibility of controlling physiological processes through modulation of the dissolved oxygen level or the oxidation/reduction potential of the culture.     

Malaria-induced reduction of fecundity during the first gonotrophic cycle of Anopheles Stephensi mosquitoes

Abstract. Anopheles stephensi mosquitoes which had fed upon mice infected with Plasmodium yoelii nigeriensis malaria parasites produced significantly fewer eggs than mosquitoes fed on an uninfected mouse. Fecundity reduction was more pronounced when the bloodmeal contained malaria gametocytes and the mosquitoes developed oocysts. Egg production and haematin excretion were correlated for uninfected bloodfed mosquitoes; the presence of P.y. nigeriensis in the blood affected this relationship. Reduced fecundity was associated with a significant reduction of bloodmeal size (measured by haematin excretion) in mosquitoes which ingested gametocytaemic blood. The bloodmeal size in mosquitoes fed on parasitaemic blood without gametocytes was not significantly reduced. The use of haematin assays for determination of bloodmeal size in mosquitoes is discussed.     

Protective effects of anti-antiidiotypic IgE antibodies obtained from an IgE monoclonal antibody specific for a 26-kilodalton Schistosoma mansoni antigen

A rat IgE mAb specific for larval Ag (26 kDa, 56 kDa) has been shown to protect rats against Schistosoma mansoni infection. Immunizations of Lou/M rats performed with this IgE (Ab1) induced the production of antiidiotypic antibodies (Ab2). Moreover, after this Ab2 production, anti-antiidiotypic antibodies (Ab3) were revealed. The screening of Ab3 isotypes showed the presence of IgG Ab3 and more interestingly of IgE Ab3, i.e., the same isotype as Ab1. These IgE and IgG antibodies recognized predominantly the 26-kDa Ag and were cytotoxic for schistosomula in the presence of platelets for IgE Ab3 and eosinophils for IgG Ab3. Both IgE and IgG Ab3 conferred by passive transfer protective immunity to infected rats (up to 50%). Thus the immunization with an IgE mAb led in part to the production of Ab3 of the same isotype as Ab1. In conclusion, these results suggest that the isotype selection of the antibodies of the third generation (Ab3) might be influenced by the Ab1. The respective role of the idiotope and isotype of Ab1 in isotype regulation is discussed.     

Expression of mosquitocidal crystal protein genes in non-insecticidal Bacillus thuringiensis subsp. israelensis

Bacillus thuringiensis NTB-1 isolated from soil samples in Korea produces ovoidal parasporal inclusions with proteins of approximately 24–40 kDa in size. Although serological study indicated that the isolate has a flagella (H) antigen identical with subsp. israelensis , it seemed to be non-insecticidal against Lepidoptera and Coleoptera as well as Diptera. To investigate the activity of non-insecticidal B. thuringiensis transformed with insecticidal crystal protein genes, cryIVD and cytA genes of B. thuringiensis subsp. morrisoni PG-14, highly toxic to mosquito larvae, were introduced into the isolate NTB-1. The expression of mosquitocidal crystal protein genes in NTB-1 was characterized by SDS–PAGE analysis and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were stably expressed in the transformant. However, the mosquitocidal activity of transformant was similar to that of B. thuringiensis subsp. kurstaki Cry⁻ B harbouring cryIVD and cytA genes, demonstrating that a synergistic effect by an interaction of both introduced insecticidal and resident non-insecticidal crystal proteins was not observed.     

Artificial light and sun compass orientation in the sandhopper Talitrus saltator (Crustacea, Amphipoda)

Experiments on compass orientation under artificial light were conducted with adult individuals of Talitrus saltator. The aim was to reproduce in the laboratory an orientation based on the sun compass corresponding to that recorded in conditions of the true sun and sky. This was obtained by the creation within an opaque Plexiglas dome of a scenario that permitted variation of the brightness of the artificial sky and sun. The results show that it is possible to obtain sun compass orientation corresponding to the natural situation even in an artificial environment. It can be concluded that sandhoppers identify an artificial light source as the sun if the artificial sky is also illuminated and if the intensities of the artificial sun and sky exceed certain threshold values (1.13 and 10 μW cm⁻², respectively). The results of other experiments under the natural blue sky with an artificial sun and with the real sun attenuated are discussed. Accepted: 23 May 1997     

The incidence of Weeksella- and Bergeyella-like bacteria in the food environment

Eighty-five catalase- and oxidase-positive Gram-negative rods and cocci susceptible to penicillin G were isolated from a variety of food sources. The phenotypic relationships of these isolates with reference cultures of Bergeyella -like, Chryseobacterium, Empedobacter, Myroides , Moraxella , Sphingobacterium and Weeksella -like strains were examined by numerical taxonomy. Seventy-three isolates were recovered in five groups; 80% of the isolates clustered in groups 1, 2 and 3 and produced indole, bearing a strong resemblance to Weeksella and Bergeyella . They could not, however, be regarded as belonging to the known species of W. virosa and B. zoohelcum . It is suggested that three species may be necessary to accommodate the environmental Weeksella - or Bergeyella -like bacteria. The isolates in groups 4 and 5 had white colonies and were unable to produce indole, in this way resembling the Moraxella genus.