Characterization of a murine thymic CD4+ T cell subset-TCRαβ+ 3G11− 6C10− CD4+ CD8− thymocytes

The presence of a relatively mature CD4⁺ CD8⁻ (SP) T cell subset in mouse thymus has been demonstrated. Composing of 10% of total CD4SP thymocytes, this subset is defined by the absence of 3G11 and 6C10 expression with a phenotype of CD69^+/−, HSA^med/lo and heterogeneous for Qa-2 expression. The proliferation capability of TCRαβ⁺ 3Gl l⁻ 6C10⁻ CD4⁺ CD8⁻ thymocytes was high while using Con A stimulus. And Con A stimulation could result in secretion of IL4, IL-10, IL-6 and a little amount of IFNγ. IL-2 was barely detectable. This is distinct from typical Th0 type cytokines. The cells of this subset were NK1.1 negative, but strongly expressed GATA-3 mRNA. The results suggest that the CD4⁺ subset of 3G11⁻ 6C10⁻ NK1.1⁻ phenotype possesses immunocompetent cells with functions characteristic of Th2-like cytokines, which may indicate the cells at transitional status from Th0 to Th2, with a propensity to Th2.     

The effect of ice formation on the function of smooth muscle tissue stored at −21 or −60 °C

The mechanisms by which single cells are injured during freezing are relatively well understood, but it is likely that additional factors apply to tissues and organs, factors that may be responsible for the poor suecess of attempts to cryopreserve complex multicellular systems. One such factor may be the formation of extracellular ice.

This study was designed to discover whether ice formation as such is detrimental to the contractile recovery of pieces of mammalian smooth muscle after storage at subzero temperatures. Strips of taenia coli muscle were equilibrated with 2.56 M Me₂SO in a buffered solution, cooled at either 0.3 or 2 °C/min to ?21 °C and then held at this temperature in the frozen state. Other muscle strips were bathed in a solution the composition of which mimicked that of the unfrozen phase of the previous solution at ?21 °C; it contained 4.49 M Me₂SO and 1.75 times the normal concentration of salts, and muscles equilibrated with this solution were also cooled at either 0.3 or 2 °C/min to ?21 °C, and then held unfrozen for the same length of time.It was shown that exposure to ?21 °C and the increased concentration of solutes had little effect on the contractile recovery of the muscles, whereas ice formation was damaging. Furthermore, the rate of cooling had a marked effect upon functional recovery in the frozen muscles, and this could be correlated with the known effect of these cooling rates on the pattern of ice formation in the tissue. The effect was also seen in muscles frozen at ?60 °C. Improved buffering increased the functional recovery of all groups, but the effect of ice, and of cooling rate in the presence of ice, was confirmed. These findings may have significant implications for attempts to cryopreserve complex tissues and organs.     

水溶性C60与C60衍生物的生物学效应研究进展

本文对近几年来有关C_(60)及其衍生物的生物学效应的研究作了较为系统的评述,包括对生物酶活性的抑制、对DNA的选择性剪切作用、对细胞生长的影响、C_(60)及其衍生物的作用机理以及应用前景等5方面的内容。     

Orbital landscapes for reductive 2e− activation of dihydrogen molecule

The various spatial arrangements of frontier orbitals that may lead to facile reductive splitting of the H2 molecule at mono- or binuclear catalysts containing s, p, d or f-block metals, and on surfaces of solids are briefly reviewed. The postulation is also made that binuclear divalent titanium (Ti(II)) and mononuclear silicon (Si(II)) species might serve as active sites for the H2 attachment reaction for hydridoalanates doped with Ti salts and hydridoborates doped with SiO2, respectively.     

Short-term carbon-isotope discrimination in C3−C4 intermediate species

Short-term discrimination in assimilation of stable isotopes of carbon was measured for leaves of the C₃ speciesPhaseolus vulgaris L. cv. Hawkesbury Wonder andFlaveria pringlei Gandoger, the C₄ speciesAmaranthus edulis Speg., and the C₃–C₄ intermediate speciesPanicum milioides Nees ex. Trin,Flaveria floridana Johnson, andFlaveria anomala B.L. Robinson. Discriminations in the C₃ and C₄ species were similar to those expected from theoretical considerations. When ambient CO₂ pressure was 330 bar the mean discriminations in the C₃ species andPanicum milioides were similar, whereas the mean discriminations inF. floridana andF. anomala were less than discrimination in C₃ species andPanicum milioides. When ambient CO₂ pressure was 100 bar the mean discriminations inPanicum milioides andF. anomala were greater, and that inF. floridana was less, than that inPhaseolus vulgaris. We conclude that the pattern of discrimination inPanicum milioides is consistent with the presence of a glycine shuttle; inF. floridana andF. anomala, discrimination is consistent with the presence of a C₄ pathway coupled with the operation of a glycine shuttle.Abbreviations and symbols PEP phosphoenolpyruvate - Rubisco ribulose, 1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39) - p _a ambient CO₂ pressure - p _i intercellular CO₂ pressure - carbon-isotope discrimination - carbonisotope composition relative to PeeDee Belemnite     

Cryopreservation at −20 and −70 °C of Pleurotus ostreatus on Grains

Alternative substrates for cryopreservation at −20 °C have been little explored for basidiomycetes and could bring new possibilities of lower cost cryopreservation. Nevertheless, freezing temperatures between −15 and −60 °C are very challenging because they frequently result in cryoinjuries. The objective of this study was to evaluate substrates associated to cryoprotective agents for Pleurotus ostreatus cryopreservation at −20 or −70 °C in order to develop alternative techniques for basidiomycete cryopreservation. P. ostreatus was grown on potato dextrose agar or whole grains of oat, wheat, rice or millet and transferred to cryovials with cryoprotective solution with 1 % dimethyl sulfoxide, 5 % glycerol, 10 % saccharose, 4 % glucose, 6 % polyethylene glycol-6000 or 5 % malt extract. The mycelium in the cryovials were cryopreserved at −20 or −70 °C and recovered for evaluation of the mycelial growth viability after 1 and 3 years. Both substrates and cryoprotectants affect the viability of the mycelial growth cryopreserved at −20 or −70 °C; wheat grains combined with cryoprotectants such as saccharose or glucose are effective for keeping mycelium viable after cryopreservation at −20 °C for 1 or 3 years; for cryopreservation at −70 °C after 1 or 3 years, any substrate combined with any cryoprotectant is effective for preserving the mycelium viable, except for millet grains with polyethylene glycol after 3 years; semi-permeable cryoprotective agents such as saccharose and glucose are the most effective for cryopreservation at −20 or −70 °C for at least 3 years.     

Vasopressin alters the mechanism of apical Cl− entry from Na+:Cl− to Na+:K+:2Cl− cotransport in mouse medullary thick ascending limb

Summary Experiments were performed usingin vitro perfused medullary thick ascending limbs of Henle (MTAL) and in suspensions of MTAL tubules isolated from mouse kidney to evaluate the effects of arginine vasopressin (AVP) on the K⁺ dependence of the apical, furosemide-sensitive Na⁺:Cl^– cotransporter and on transport-related oxygen consumption (QO₂). In isolated perfused MTAL segments, the rate of cell swelling induced by removing K⁺ from, and adding onemm ouabain to, the basolateral solution [ouabain(zero-K⁺)] provided an index to apical cotransporter activity and was used to evaluated the ionic requirements of the apical cotransporter in the presence and absence of AVP. In the absence of AVP cotransporter activity required Na⁺ and Cl^–, but not K⁺, while in the presence of AVP the apical cotransporter required all three ions.⁸⁶Rb⁺ uptake into MTAL tubules in suspension was significant only after exposure of tubules to AVP. Moreover,²²Na⁺ uptake was unaffected by extracellular K⁺ in the absence of AVP while after AVP exposure²²Na⁺ uptake was strictly K⁺-dependent. The AVP-induced coupling of K⁺ to the Na⁺:Cl^– cotransporter resulted in a doubling in the rate of NaCl absorption without a parallel increase in the rate of cellular²²Na⁺ uptake or transport-related oxygen consumption. These results indicate that arginine vasopressin alters the mode of a loop diuretic-sensitive transporter from Na⁺:Cl^– cotransport to Na⁺:K⁺:2Cl^– cotransport in the mouse MTAL with the latter providing a distinct metabolic advantage for sodium transport. A model for AVP action on NaCl absorption by the MTAL is presented and the physiological significance of the coupling of K⁺ to the apical Na⁺:Cl^– cotransporter in the MTAL and of the enhanced metabolic efficiency are discussed.     

Photosynthetic/photorespiratory characteristics of C3−C4 intermediate species

The extent of photorespiration, the inhibition of apparent photosynthesis (APS) by 21% O₂, and the leaf anatomical and ultrastructural features of the naturally occurring C₃–C₄ intermediate species in the diverse Panicum, Moricandia, and Flaveria genera are between those features of representative C₃ and C₄ plants. The greatest differences between the photosynthetic/photorespiratory CO₂ exchange characteristics of the C₃–C₄ intermediates and C₃ plants occur for the parameters which are measured at low pCO₂ (i.e., the CO₂ compensation concentration and rates of CO₂ evolution into CO₂-free air in the light). The rates of APS by the intermediate species at atmospheric pCO₂ are similar to those of C₃ plants.The mechanisms which are responsible for reducing photorespiration in the C₃–C₄ intermediate species are poorly understood, but two proposals have been advanced. One emphasizes the importance of limited C₄ photosynthesis which reduces O₂ fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase, and, thus, reduces photorespiration by a CO₂-concentrating mechanism, while the other emphasizes the importance of the internal recycling of photorespiratory CO₂ evolved from the chloroplast/mitochondrion-containing bundle-sheath cells. There is no evidence from recent studies that limited C₄ photosynthesis is responsible for reducing photorespiration in the intermediate Panicum and Moricandia species. However, preliminary results suggest that some, but not all, of the intermediate Flaveria species may possess a limited C₄ cycle. The importance of a chlorophyllous bundle-sheath layer in the leaves of intermediate Panicum and Moricandia species in a mechanism based on the recycling of photorespiratory CO₂ is uncertain.Therefore, although they have yet to be clearly delineated, different strategies appear to exist in the C₃–C₄ intermediate group to reduce photorespiration. Of major importance is the finding that some mechanism(s) other than Crassulacean acid metabolism or C₄ photosynthesis has (have) evolved in at least the majority of these terrestrial intermediate species to reduce the seemingly wasteful metabolic process of photorespiration.Abbreviations APS apparent (net) photosynthesis - CAM Crassulacean acid metabolism - CE carboxylation efficiency - T CO₂ compensation concentration - IRGA infrared gas analysis - P_i orthophosphate - PEP phosphoenolpyruvate - RuBP ribulose 1,5-bisphosphate Published as Paper No. 7383, Journal Series, Nebraska Agricultural Experiment Station.     

Intestinal HCO 3 − secretion inAmphiuma: Stimulation by mucosal Cl− and serosal Na+

Summary The requirement for Na⁺ and Cl^– in the bathing media to obtain a maximal HCO ₃ ^– secretory flux ( ) across isolated short-circuitedAmphiuma duodenum was investigated using titration techniques and ion substitution. Upon substitution of media Na⁺ with choline, HCO ₃ ^– secretion was markedly reduced. Replacement of media Cl^– produced a smaller reduction of . The presence of Cl^– enhanced HCO ₃ ^– secretion only if Na⁺ was also in the media. Elevation of media Na⁺ or Cl^– in the presence of the other ion produced a saturable increase of . In the presence of Na⁺, Cl^– stimulated when added to the mucosal but not the serosal medium. In the presence of Cl^–, Na⁺ elevated when added to the serosal but not the mucosal medium. The ability of mucosal Cl^– to stimulate was not apparently dependent on mucosal Na⁺. Simultaneous addition of 10mm Cl^– to the Na⁺-free mucosal medium and 10mm Na⁺ to the Cl^–-free serosal medium stimulated above levels produced by serosal Na⁺ alone. In conclusion, intestinal HCO ₃ ^– secretion required mucosal Cl^– and serosal Na⁺ and did not involve mucosal NaCl cotransport. The results are consistent with a mucosal Cl^– absorptive mechanism in series with parallel basolateral Na⁺–H⁺ and Cl^––HCO ₃ ^– exchange mechanisms.     

富勒烯C60的生物学研究

富勒烯Ｃ６０是１９８５年发现的一种新型纯碳分子,具有独特的三维球状结构。近几年来Ｃ６０的研究发展非常迅速,并有可能在生物学研究方面起到重要作用。本文主要从Ｃ６０的水溶性、光电导效应、光动力作用和生物富勒烯四个方面论述了Ｃ６０在生物学方面的有关研究结果和进展。     

The influence of amino acid starvation on the UV reversibility of the strains ofEscherichia coli B/rthy − trp − Hcr + andEscherichia coli B/rthy − trp − Hcr −

The fraction of inducedtrp ⁺ reversions in the strains ofEscherichia coli B/rthy ⁻ trp ⁻ Hcr ⁺ andEscherichia coli B/rthy ⁻ trp ⁻ Hcr ⁻ was studied in the course of starvation for an essential amino acid. UV light as a mutagenic factor was used. It was found that there is a decrease in the proportion of inducedtrp ⁺ reversions in the strain ofHcr ⁺ type during starvation. Such a decrease was however observed only with that fraction oftrp ⁺ reversions which is expressed in selective plates where several divisions of irradiated cells are caused. The proportion oftrp ⁺ reversions expressed on minimal plates does not change during starvation. With the strain ofHcr ⁻ type the proportion of inducedtrp ⁺ mutations remains unaltered irrespective of the nature of the selective plates.     

Phase labeling of C−H and C−C spin-system topologies: Application in constant-time PFG-CBCA(CO)NH experiments for discriminating amino acid spin-system types

Summary Triple-resonance experiments facilitate the determination of sequence-specific resonance assignments of medium-sized ¹³C, ¹⁵N-enriched proteins. Some triple-resonance experiments can also be used to obtain information about amino acid spin-system topologies by proper delay tuning. The constant-time PFG-CBCA(CO)NH experiment allows discrimination between five different groups of amino acids by tuning (phase labeling) independently the delays for proton-carbon refocusing and carbon-carbon constant-time frequency labeling. The proton-carbon refocusing delay allows discrimination of spin-system topologies based on the number of protons attached to C and C atoms (i.e. C-H phase labeling). In addition, tuning of the carbon-carbon constant-time frequency-labeling delay discriminates topologies based on the number of carbons directly coupled to C and C atoms (i.e. C-C phase labeling). Classifying the spin systems into these five groups facilitates identification of amino acid types, making both manual and automated analysis of assignments easier. The use of this pair of optimally tuned PFG-CBCA(CO)NH experiments for distinguishing five spin-system topologies is demonstrated for the 124-residue bovine pancreatic ribonuclease A protein.     

Nature of the neutral Na+-Cl− coupled entry at the apical membrane of rabbit gallbladder epithelium: IV. Na+/H+, Cl−/HCO 3 − double exchange,hydrochlorothiazide-sensitive Na+-Cl− symport and Na+-K+-2Cl− cotransport are all involved

Transepithelial fluid transport was measured gravimetrically in rabbit gallbladder (and net Na+ transport was calculated from it), at 27 degrees C, in HCO(3-)-free bathing media containing 10(-4) M acetazolamide. Whereas luminal 10(-4) M bumetanide or 10(-4) M 4-acetamido-4'-iso-thiocyanostilbene-2,2'-disulfonate (SITS) did not affect fluid absorption, 25 mM SCN- abolished it; hydrochlorothiazide (HCTZ) in the luminal medium reduced fluid absorption from 28.3 +/- 1.6 (n = 21) to 8.6 +/- 1.6 microliters cm-2 hr-1 (n = 10), i.e., to about 30%. This maximum effect was already obtained at 10(-3) M concentration; the apparent IC50 was about 2 x 10(-4) M. The residual fluid absorption, again insensitive to SITS, was completely inhibited by SCN- or bumetanide. Cl- influx at the luminal border of the epithelium, measured under the same conditions and corrected for the extracellular space and paracellular influx, proved insensitive to 10(-4) M bumetanide, but was slowly inhibited by 10(-3) M HCTZ, with maximum inhibition (about 54%) reached after a 10-min treatment; it subsequently rose again, in spite of the presence of HCTZ. However, if the epithelium, treated with HCTZ, was exposed to 10(-4) M bumetanide during the measuring time (45 sec), inhibition was completed and the subsequent rise of Cl- influx eliminated. Intracellular Cl- accumulation with respect to the predicted activity value at equilibrium decreased significantly upon exposure to 10(-3) M HCTZ, reached a minimum within 15-30 min of treatment, then rose again significantly at 60 min. Simultaneous exposure to HCTZ and bumetanide decreased the accumulation to a significantly larger extent as compared to HCTZ alone, already in 15 min, and impeded the subsequent rise. Intracellular K+ activity rose significantly within 30 min treatment with HCTZ; the increase proved bumetanide dependent. The results obtained show that Na(+)-Cl- symport, previously detected under control conditions, is the HCTZ-sensitive type; its inhibition elicits bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport. Thus, the three forms of neutral Na(+)-Cl(-)-coupled transport so far evidenced in epithelia, Na+/H+, Cl-/HCO3- double exchange (in the presence of exogenous bicarbonate), HCTZ-sensitive Na(+)-Cl- symport and bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport, are all present in the apical membrane of rabbit gallbladder.     

Molecular properties of phosphoenolpyruvate carboxylase from C3, C3−C4 intermediate,and C4 Flaveria species

Phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) from Flaveria trinervia Mohr (C₄), F. floridana Johnston (C₃–C₄), and F. cronquistii Powell (C₃) leaves were compared by electrotransfer blotting/enzyme-linked immunoassay (Western-blot analysis), mobility of the native enzyme in polyacrylamide gels and in isoelectric focusing (IEF) gels, peptide mapping, and in-vitro translation of RNA isolated from each plant. The PEPCases from the C₃ and C₃–C₄ plants were very similar to each other in terms of electrophoretic mobilities on gels and isoenzyme patterns on IEF gels, and identical in peptide mapping. Quantitative differences were noted, however, in that the C₃–C₄ intermediate plant contained more PEPCase overall and that the relative activity of individual isoenzymes shifted between the C₃ and C₃–C₄ intermediate PEPCases. The PEPCase from the C₄ plant had a different isoenzyme pattern, a different peptide map, and was far more abundant than the other two enzymes. Western blot analysis demonstrated the cross-reactivity of PEPCases from all three Flaveria species with antibody raised against maize PEPCase. The results provide evidence, at the molecular level, that supports the view of C₃–C₄ intermediate species as C₃-like plants with some C₄-like photosynthetic characteristics, but there are differences from the C₃ plant in the quantity and properties of the PEPCase from the C₃–C₄ intermediate plant.Abbreviations IEF isoelectric focusing - kDa kilodalton - PEPCase phosphoenolpyruvate carboxylase - Rubisco Ribulose-1,5-bisphosphate carboxylase/oxygenase     

Symbiotic efficiency of Hup+ and Hup− strains ofRhizobium japonicum

Summary Relative efficiency of Hup⁺ and Hup^– R. japonicum strains with Pusa 16 cultivar of soybean was studied. Inoculation with the Hup⁺ strain (A 1014) reduced the protein content in grain as compared to uninoculated control.     

Association between tumor necrosis factor-α promoter −308 A/G, −238 A/G, interleukin-6 −174 G/C and −572 G/C polymorphisms and periodontal disease: a meta-analysis

The aim of this study was to determine whether tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) promoter polymorphisms confer susceptibility to periodontitis in ethnically different populations. A literature search was performed using PubMed and Embase and a meta-analysis of the identified studies was conducted to explore the associations between TNF-α ?308 A/G, ?238 A/G, IL-6 promoter ?174 G/C and ?572 G/C polymorphisms and periodontitis. Seventeen comparison studies for the TNF-α ?308 A/G polymorphism and three studies for the TNF-α ?238 A/G polymorphism were included in the meta-analysis. And 16 separate studies for the IL-6 ?174 G/C polymorphism and 10 studies for the IL-6 ?572 G/C polymorphism were considered in our meta-analysis. Analysis after stratification by ethnicity indicated that the TNF-α ?308 A allele was associated with periodontitis in Brazilian, Asian, and Turkish populations (OR = 0.637, 95 % CI = 0.447–0.907, p = 0.013; OR = 0.403, 95 % CI = 0.204–0.707, p = 0.009; OR = 1.818, 95;  % CI = 1.036–3.189, p = 0.037). The meta-analysis showed no association between the TNF-α ?238 A/G polymorphism and periodontitis. The meta-analysis indicated an association of the IL-6 ?174 G/C polymorphisms with periodontitis in Brazilian populations (OR for GG + GC = 2.394, 95 % CI = 1.081–5.302, p = 0.031). Stratification by ethnicity and disease type indicated an association between the IL-6 ?572 G allele and chronic periodontitis (OR = 1.585, 95 % CI = 1.030–2.439, p = 0.036), and periodontitis in Europeans (OR = 2.118, 95 % CI = 1.254–3.577, p = 0.005). This meta-analysis demonstrates that the TNF-α ?308 A/G polymorphism confers susceptibility to periodontitis in Brazilian, Asian and Turkish populations. The IL-6 ?174 G/C polymorphism may confer susceptibility to periodontitis in Brazilians, and the IL-6 ?572 G/C polymorphism may be associated with susceptibility to periodontitis in Europeans, and chronic periodontitis.     

Ecotypic differences in the C3 and C4 photosynthetic activity in Mollugo verticillata,a C3−C4 intermediate

Four populations of Mollugo verticillata L. were compared on the basis of their photosynthetic products, photosynthetic rates, enhancement under low oxygen concentration, and CO₂ compensation points. In addition, pulse-chase labeling experiments were conducted using one of the four populations. Depending on the plant population, C₄ acids ranged from 40% to 11% of the primary products under short-term exposure to ¹⁴CO₂. These compounds were also metabolized during pulse-chase experiments. All four populations had significantly different photosynthetic rates and those rates were correlated with the amounts of labelled C₄ acids produced and C₄-acid turnover. Three populations of M. verticillata had similar compensation points (40 l/l) and degrees of photosynthetic enhancement under low [O₂] (20%), the fourth population was much lower in both characteristics (CO₂ compensation, 25 l/l; low-O₂ enhancement, 12%). The results verify the intermediate nature of photosynthesis in this species, and illustrate populational differences in its photosynthetic and photorespiratory carbon metabolism.Abbreviations PGA 3-phosphoglyceric acid - Kan Kansas - Mass Massachusetts - Mex Mexico     

Trichothecene biosynthesis inGibberella pulicaris: Inheritance of C−8 hydroxylation

Summary Naturally occurring strains ofGibberella pulicaris (Fusarium sambucinum) produce different kinds and levels of trichothecene toxins. Progeny from crosses between strains which produce trichothecenes with an oxygen-containing group at C–8 (C8+) and those that do not (C8–) can segregate in a 11 ratio for this trait. These results define a genetic locus, which we have designatedTox1. The segregation patterns observed for progeny obtained from crosses between high-toxin producers and low-toxin producers indicate that the level of toxin production is determined by several loci. One gene which controls quantitative aspects of toxin production segregates independently of both theTox1 locus and another locus which controls toxin levels. These results suggest that multiple, unlinked nuclear loci are involved in the control of trichothecene biosynthesis.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.