Murine protein which binds preferentially to oligo-C-rich single-stranded nucleic acids.

Two single-stranded nucleic acid binding proteins mCBP and mCTBP were identified by means of their binding to a potential recombination hotspot in LTRs of mouse retro-transposons. Both are nuclear proteins of 35 and 55 kDa respectively. mCBP binds preferentially to oligo dC, mCTBP to oligo dCdT. mCBP was purified and its cDNA was isolated and sequenced.     

Synthesis and structure determination of some nonanomerically C-C-linked serine glycoconjugates structurally related to mannojirimycin

The Bucherer-Bergs reaction of methyl 2,3-O-isopropylidene-alpha-d-lyxo-hexofuranosid-5-ulose gave (4'S)-4'-carbamoyl-4'-[methyl (4R)-2,3-O-isopropylidene-beta-l-erythrofuranosid-4-C-yl]-oxazolidin-2'-one instead of expected hydantoins. A mixture of hydantoins--(5'R)-triphenylmethoxymethyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-l-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione and (5'S)-triphenylmethoxymethyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-l-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was obtained from the 5-ulose having protected primary OH group at C-6. The 4'-S configuration of 2 as well as 5'-S configuration of (5'S)-hydroxymethyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-l-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione (9) was confirmed by X-ray crystallography. Corresponding alpha-amino acid--methyl (5S)-5-amino-5-C-carboxy-5-deoxy-alpha-d-lyxo-hexofuranoside (alternative name: 2-[methyl (4R)-beta-l-erythrofuranosid-4-C-yl]-l-serine) (11) was obtained from the hydantoin 9 by acid hydrolysis of the isopropylidene and trityl groups followed by basic hydrolysis of the hydantoin ring. Analogous derivatives with 5-R configuration, formed in a minority, were also isolated and characterised.     

Neural control of quadrupedal and bipedal stance: implications for the evolution of erect posture

The transition among hominids from quadrupedalism to bipedalism resulted in modifications in their musculoskeletal morphology. It is unclear, however, whether changes in the circuitry of the CNS were also necessary in order to accommodate the unique balance requirements of two-limb support. This study addresses the issue of modifications in control strategies by investigating the rapid, automatic postural responses of feline and human subjects to sudden disturbances of balance in the anteroposterior (AP) direction while they stand quadrupedally and bipedally on movable platforms. Postural responses are characterized in terms of segmental adjustments, generated AP shear forces, and electromyographic activity. Feline and human subjects correct posture similarly when standing quadrupedally. Furthermore, both species correct stance primarily with their hindlimbs and use their forelimbs as supportive struts. In contrast, both species use completely different correctional strategies when standing bipedally. Morphological restrictions, however, prevent cats from adopting the pillar-like plantigrade posture of human beings. Thus, the correctional strategies of bipedal cats are distinct from those of bipedal human subjects. It is concluded that 1) automatic postural response patterns of quadrupedal Felis and bipedal Homo reflect the different biomechanical characteristics of the initial postures rather than species differences in CNS circuitry controlling stance; 2) hindlimb-dominated posture control is probably a common and relatively ancient pattern; and 3) reorganization of hominid CNS circuitry was probably unnecessary because hindlimb control was already a feature of the system.     

Changes of Ni biogeochemistry in the rhizosphere of the hyperaccumulator Thlaspi goesingense

Processes in the rhizosphere of metal hyperaccumulator species are largely unknown. We investigated root-induced changes of Ni biogeochemistry in the rhizosphere of Thlaspi goesingense Hálácsy in a rhizobox experiment and in related soil chemical and Ni uptake studies. In the rhizobox, a root monolayer was separated from rhizosphere soil by a nylon membrane. Rhizosphere soil was then sliced into 0.5 mm layers and analyzed for changes in soluble (water-extractable, Ni _S) and labile (1 M NH ₄NO ₃-extractable, Ni _L) Ni pools. Ni _L in the rhizosphere was depleted due to excessive uptake in T. goesingense. Ni _S in the rhizosphere increased in contrast to expectations based on the experimental Ni desorption isotherm. Mathematical simulations following the Tinker–Nye–Barber approach overestimated the depletion of the Ni _L and predicted a decrease of Ni _S in the rhizosphere. In a hydroponic experiment, we demonstrated that T. goesingense takes up Ni ²⁺ but excludes metal–organic complexes. The model output was then improved in later versions considering this finding. A sensitivity analysis identified I _max and K _m, derived from the Michaelis–Menten uptake kinetics experiment to be the most sensitive of the model parameters. The model was also sensitive to the accuracy of the estimate of the initial Ni concentration (C _Si) in soil solution. The formation of Ni–DOM complexes in solution could not explain the poor fit as in contrast to previous field experiments, the correlation between soluble Ni and dissolved organic carbon (DOC) was weak. Ion competition of Ni with Ca and Mg could be ruled out as explanation of enhanced Ni solubility in the rhizosphere as the molar ratio of Ni/(Ca + Mg) in solution was not affected. However, a decreased Vanselov coefficient Kv near the root plane indicated (an apparent) lower selectivity of the exchange complex for Ni, possibly due to adsorption of oxalate exuded by T. goesingense roots or associated rhizosphere microbes. This conclusion is supported by field data, showing enhanced oxalate concentrations in the rhizosphere of T. goesingense on the same experimental soil. The implications for phytoextraction and bio-available contaminant stripping (BCS) as well as for future modeling and experimental work are discussed.     

Adoptive immunotherapy of syngeneic murine leukemia is enhanced by the combination of recombinant IFN-gamma and a tumor-specific cytotoxic T cell clone

Mice with an established syngeneic T cell tumor (RBL5) received short term adoptive chemoimmunotherapy with CTL clone 1.B6 and murine rIFN-gamma. In comparison with treatment with either agent alone, the combination of 1.B6 and rIFN-gamma was associated with a dramatic increase in long term survival. No direct effects of rIFN-gamma on tumor cell proliferation, MHC Ag expression, or susceptibility to CTL-mediated lysis could be demonstrated to explain the prolongation of survival. However, rIFN-gamma induced a distinct increase in broad-spectrum cytolytic capacity of peritoneal exudate cells and further increased class II MHC expression on peritoneal macrophages. The explanation for enhanced adoptive chemoimmunotherapy after combined short term administration of a CTL clone and rIFN-gamma is uncertain. Potential mechanisms include direct tumor lysis by activated cells, indirect tumor lysis via sensitization to other lymphokines or monokines, improved Ag-specific activation of transferred CTL clones, and/or more effective development of de novo host anti-tumor immunity.     

The Use of Hybrid Somatic Cells as an Approach to Mitochondrial Genetics in Animals

We have studied the fate of parental mitochondrial DNA (mtDNA) in hybrid somatic cells derived by Sendai virus-induced fusion of human cells and mouse or rat cells. Many hybrid cell strains were obtained which contained sequences from both human and rodent mtDNA after 40 to 60 population doublings. Some strains were subcloned and cultured further for up to 150 doublings; a large fraction of these strains contained both parental mtDNA sequences at that time.The relation between human and rodent mtDNA sequences was tested in some of the hybrid cell strains. In a high fraction of strains tested the human and rodent mtDNA sequences were linked to each other by what are most likely covalent bonds. This linkage may be described as "recombination" of mtDNA sequences from two different animals.     

Oxidative phosphorylation in a hybrid system containing bovine heart membranes and pea mitochondrial F1-ATPase

Purified pea mitochondrial F1-ATPase reconstituted oxidative phosphorylation in both partially and completely F1-depleted bovine heart mitochondrial membranes. The isolated plant enzyme exhibited high rates of ATP synthesis when combined with bovine heart membranes, suggesting great evolutionary conservation of the ATP synthase complex in mitochondria.     

Monoclonal Antibodies to the [alpha]- and [beta]-Subunits of the Plant Mitochondrial F1-ATPase

We have generated nine monoclonal antibodies against subunits of the maize (Zea mays L.) mitochondrial F1-ATPase. These monoclonal antibodies were generated by immunizing mice against maize mitochondrial fractions and randomly collecting useful hybridomas. To prove that these monoclonal antibodies were directed against ATPase subunits, we tested their cross-reactivity with purified F1-ATPase from pea cotyledon mitochondria. One of the antibodies ([alpha]-ATPaseD) cross-reacted with the pea F1-ATPase [alpha]-subunit and two ([beta]-ATPaseD and [beta]-ATPaseE) cross-reacted with the pea F1-ATPase [beta]-subunit. This established that, of the nine antibodies, four react with the maize [alpha]-ATPase subunit and the other five react with the maize [beta]-ATPase subunit. Most of the monoclonal antibodies cross-react with the F1-ATPase from a wide range of plant species. Each of the four monoclonal antibodies raised against the [alpha]-subunit recognizes a different epitope. Of the five [beta]-subunit antibodies, at least three different epitopes are recognized. Direct incubation of the monoclonal antibodies with the F1-ATPase failed to inhibit the ATPase activity. The monoclonal antibodies [alpha]-ATPaseD and [beta]-ATPaseD were bound to epoxide-glass QuantAffinity beads and incubated with a purified preparation of pea F1-ATPase. The ATPase activity was not inhibited when the antibodies bound the ATPase. The antibodies were used to help map the pea F1-ATPase subunits on a two-dimensional map of whole pea cotyledon mitochondrial protein. In addition, the antibodies have revealed antigenic similarities between various isoforms observed for the [alpha]- and [beta]-subunits of the purified F1-ATPase. The specificity of these monoclonal antibodies, along with their cross-species recognition and their ability to bind the F1-ATPase without inhibiting enzymic function, makes these antibodies useful and invaluable tools for the further purification and characterization of plant mitochondrial F1-ATPases.     

D-mannose-modified iron oxide nanoparticles for stem cell labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide according to two methods. In the first method, precipitation was done in the presence of D-mannose solution (in situ coating); the second method involved oxidation of precipitated magnetite with sodium hypochlorite followed by addition of D-mannose solution (postsynthesis coating). Selected nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), elemental analysis, dynamic light scattering, infrared (IR), X-ray powder analysis, and ultrasonic spectrometry. While the first preparation method produced very fine nanoparticles ca. 2 nm in diameter, the second one yielded ca. 6 nm particles. Addition of D-mannose after synthesis did not affect the iron oxide particle size. UV-vis spectroscopy suggested that D-mannose suppresses the nonspecific sorption of serum proteins from DMEM culture medium on magnetic nanoparticles. Rat bone marrow stromal cells (rMSCs) were labeled with uncoated and d-mannose-modified iron oxide nanoparticles and with Endorem (Guerbet, France; control). Optical and transmission electron microscopy confirmed the presence of D-mannose-modified iron oxide nanoparticles inside the cells. D-mannose-modified nanoparticles crossed the cell membranes and were internalized well by the cells. Relaxivity measurements of labeled cells in gelatin revealed very high relaxivities only for postsynthesis D-mannose-coated iron oxide nanoparticles.     

Effect of interstage mixing in multistage culture systems on continuous biomass production

The significance of the interstage mixing on important process parameters of biomass production was studied. The experiments were performed in a multistage tower fermentor and in fermentors in series. The interstage mixing effect can be evaluated under conditions of geometrical similarity, identity of oxygen transfer rate, and identity of dilution rate per stage in the individual stages of both culture systems. Candida utilis was cultivated on a synthetic medium with ethanol as the sole carbon and energy source in the concentration range 10–100 g/liter. Dilution rate, temperature, and pH in each stage of both culture systems were kept constant. It was demonstrated that in the multistage tower fermentor the definite backflow which ensures the permanent reinoculation by adapted cells significantly decreases the inhibitory effect of higher ethanol concentrations on the cell growth and on the rate of ethanol utilization.