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PubMed1980

Transfer factor: failure to transfer reactivity in normal human subjects.

Transfer factor was prepared from highly selected normal donors. One lot was made from donors strongly reactive to coccidioidin and negative to Dharmendra antigen in in vivo and in vitro testing. The other lot was made from donors without reactivity to coccidioidin and strongly reactive to Dharmendra. Aliquots of each lot were injected into eight normal recipients. Eight additional normal recipients were given placebo injections. Before and after injection, skin test reactivity and in vitro testing were evaluated by an individual who did not know which preparation the patient received. Changes in immunologic reactivity in subjects receiving transfer factor could not be distinguished from those in subjects receiving placebo. I conclude that transfer factor does not cause enhancement of immunologic reactivity in normal subjects. A well designed, critical study is needed to determine whether or not it does, in fact, cause enhancement of immunologic reactivity in patients with impaired cellular immune reactivity.

Antigens↗

PubMed1994

[Comparison of pregnancies issued from frozen embryo transfers and pregnancies issued from fresh embryo transfers in fertilization in vitro. FIVNAT].

The French in vitro fertilization registry FIVNAT allowed us to describe the most important cohort of pregnancies resulting from the replacement of frozen-thawed embryos, and to compare them with pregnancies issued from fresh embryos transfers. From 1987 to 1992, 465 and 8,757 clinical pregnancies were respectively collected, and resulted in the birth of 386 et 8729 babies. Whereas the miscarriage rate was higher, pregnancy evolution was more normal after transfer of frozen-thawed embryos. Multiple pregnancies were less frequent; preterm birth rates and low birth rate were also significantly lower. Nevertheless, after cryopreservation of embryos, more complications were noted. However, further analysis involving more pregnancies after transfer of frozen-thawed embryos is necessary before reaching conclusion. Finally, congenital malformation rate was not different between the two groups.

Abortion, Spontaneous↗

PubMed1994

A conjugative transfer system for the rumen bacterium, Butyrivibrio fibrisolvens, based on Tn916-mediated transfer of the Staphylococcus aureus plasmid pUB110.

A limitation of genetic studies of the rumen bacterium, Butyrivibrio fibrisolvens, has been the availability of suitable vectors and transfer systems. Using the conjugative tetracycline resistant transposon, Tn916, the Staphylococcus aureus plasmid, pUB110, and the pUB110-based shuttle vector, pUBLRS, a conjugative transfer system was developed for B. fibrisolvens. B fibrisolvens donor strains H17c2 and H17c12, containing Tn916 and pUB110 or pUBLRS, respectively, were used in mating experiments with selected B. fibrisolvens strains. Kanamycin resistant transconjugants, containing pUB110, of strains 193, 194, and 195 were detected at a combined average frequency of 7.78 x 10(-7) per donor and 1.11 x 10(-5) per recipient. Transconjugants of strains 193 and 194, containing pUBLRS, were detected at an average frequency of 1.22 x 10(-6) per donor and 4.70 x 10(-8) per recipient. Southern hybridization analysis confirmed the presence of pUB110 and pUBLRS in transconjugants. Results indicated that Tn916 was necessary for mobilization of pUB110 as transconjugants were not detected when the transposon was absent from the donor strains. The ability to mobilize pUB110 and pUBLRS between B. fibrisolvens strains provides a conjugative transfer system that circumvents problems encountered with electroporation.

Animals↗

PubMed1987

Facilitation of discrimination transfers under amphetamine: the relative control by S+ and S- and general transfer effects.

Rats were trained in a Y-maze on a two-choice simultaneous black-white discrimination with either black or white as S+. Animals were then transferred to one of three discrimination tasks. In task 1 (New S-), a new stimulus, either vertical or horizontal stripes, was substituted for the original S-. In task 2 (New S+), a new stimulus, either vertical or horizontal stripes as in task 1, was substituted for the original S+. In task 3 (New S+/S-) animals were trained on horizontal-vertical discrimination. The pre-trial administration of 1 mg/kg d-amphetamine facilitated the acquisition of the original black-white discrimination with both black as S+ and white as S+. Likewise, the drug improved performance in all three transfer conditions. However, the course of learning in the three transfer tasks was different in the placebo- and amphetamine-treated animals. Amphetamine-treated animals were disrupted more by a change in S+ than by a change in S-, whereas the opposite pattern was evident in the placebo controls. When both discriminative stimuli were changed, placebo animals exhibited pronounced decrement in performance, whereas amphetamine animals exhibited excellent learning. The implications of these findings for the effects of amphetamine on discrimination learning are discussed.

Animals↗

PubMed1997

Cadmium leads to stimulated expression of the lipid transfer protein genes in barley: implications for the involvement of lipid transfer proteins in wax assembly.

In order to investigate the nature of genes expressed in leaf epidermal cells of higher plants, we have identified the nucleotide sequence of a cDNA designated ltp 7a2b encoding a novel nonspecific lipid transfer protein of barley (Hordeum vulgare L. cv. Gerbel). The cDNA of 755 basepairs contains an open reading frame of 366 nucleotides coding for a 12.3-kDa polypeptide. The first 29 amino acids constitute the putative signal peptide, characteristic for targeting to the secretory pathway. Analysis of mRNA levels by Northern blotting indicated that ltp 7a2b is preferentially expressed in the leaf epidermis. Levels of mRNA decreased during ageing of leaf tissue. Expression of ltp 7a2b was stimulated by a factor of 2 - 3 when the seedlings were grown in the presence of cadmium (10 - 1600 microM). Concomitantly, the primary leaves of Cd-exposed seedlings contained elevated levels of abscisic acid and thicker was layer of the cuticle. At 100 microM Cd in the hydroponic medium, the was cover was increased by 50%. The increase in abscisic acid content, ltp 7a2b mRNA and was coverage was either not seen, or seen much less, in Ni- and Zn-stressed seedlings. The data add circumstantial evidence to the recently proposed hypothesis that nonspecific lipid transfer proteins function in transfer of cutin and/or wax monomers from the site of synthesis in the cell to the cuticle.

Amino Acid Sequence↗

PubMed1992

Laser flash photolysis studies of electron transfer mechanisms in cytochromes: an aromatic residue at position 82 is not required for cytochrome c reduction by flavin semiquinones or electron transfer from cytochrome c to cytochrome oxidase.

The influence of an aromatic side chain at position 82 of yeast iso-1-cytochrome c on the kinetics of its electron transfer reactions has been investigated using laser flash photolysis methods to compare a series of site-specific mutant cytochromes in their reduction by free flavin semiquinone and in electron transfer from reduced cytochrome to bovine cytochrome c oxidase. Although small (approximately 10%) but significant differences are observed between some of the mutants (S82, Y82, I82) and wild-type (F82) or G82 cytochrome in the second-order rate constant for reduction by lumiflavin semiquinone, these do not correlate with side-chain aromaticity. In the reaction between the ferrocytochromes and cytochrome c oxidase, significantly larger deviations from exponentiality are found for those mutants having aliphatic residues at position 82 than for wild type or Y82. We interpret the nonexponential behavior in terms of multiple orientations of the cytochromes within the oxidase binding site; the extent to which this occurs is apparently influenced by the character of the residue at position 82. However, a comparison of the average rate constants for electron transfer to cytochrome oxidase for the various mutants reveals that all are closely comparable to WT, except for I82 which is significantly slower (approximately threefold). These results, combined with those obtained previously from steady-state kinetic and thermodynamic measurements, suggest that the observed differences among the mutants are due to alterations in the mode of binding of the cytochrome to the oxidase, rather than to a specific requirement for the presence of an aromatic group at position 82.

Animals↗

PubMed1987

Studies of the role of mast cells in contact sensitivity responses. Passive transfer of the reaction into mast cell-deficient mice locally reconstituted with cultured mast cells: effect of reserpine on transfer of the reaction with DNP-specific cloned T cells.

The role of mast cells in the elicitation of contact sensitivity (CS) responses was evaluated by transferring different aliquots of the same preparations of immune lymph node cells (I-LNC) into naive, genetically mast cell-deficient (WBB6F1-W/Wv or WCB6F1-S1/S1d) mice and the corresponding congenic normal (+/+) mice. We found that the 24-hr CS responses elicited in the recipient mast cell-deficient mice were statistically indistinguishable from those in the congenic +/+ mice according to four different criteria: micrometer measurements of ear swelling, ratios of the weight or [125I]iododeoxyuridine-labeled leukocyte infiltration-associated cpm in challenged and contralateral control ears, and amount of 125I-fibrin deposition. We also transferred I-LNC into WBB6F1-W/Wv mice which, 5 months earlier, had undergone local repair of their mast cell deficiency by the intradermal injection (into the left ear only) of growth factor-dependent cultured mast cells derived from congenic +/+ mice. When 24-hr CS responses were elicited in both ears of these mice, the reactions in the mast cell-reconstituted left ears were similar to those in the mast cell-deficient right ears. We also found that treatment of antigen-specific cloned T cells with reserpine in vitro markedly impaired their ability to transfer reactivity for CS, providing further evidence that reserpine can interfere with the expression of T-cell-mediated responses through effects independent of its action on mast cells.

Animals↗

PubMed1992

The precursor form of the rat liver non-specific lipid-transfer protein, expressed in Escherichia coli, has lipid transfer activity.

The cDNA encoding the precursor form of non-specific lipid-transfer protein (pre-nsL-TP) from rat liver was cloned into the expression vector pET3d. The resulting plasmid was transformed to the Escherichia coli strain BL21(DE3). After induction of the bacteria with isopropyl-beta-D-thiogalactopyranoside (IPTG) pre-nsL-TP was purified from the bacterial lysate by anion exchange chromatography followed by gelfiltration. From 11 of culture, 6-7 mg of pre-nsL-TP was obtained, equal to approximately 7% of the cytoplasmic protein. By use of a fluorescence lipid transfer assay, pre-nsL-TP was found to have lipid transfer activity identical to mature nsL-TP.

Animals↗

PubMed1986

Microcell-mediated chromosome transfer from human tumor cells to human recipient cells evidenced by premature condensation of the transferred chromosomes.

Micronucleation was induced by vincristine, colcemid, and colcemid in combination with cytochalasin B in cells of a human metastatic breast carcinoma cell line (MDA MB 231). Cells treated with the latter combination were enucleated subsequently by centrifugation in the presence of cytochalasin B. The resulting "microcell" fraction was fused with mitotic human primary fibroblasts or mitotic HeLa cells using polyethyleneglycol (PEG). The success of the microcell-mediated chromosome transfer thus could be demonstrated as premature condensation in the mitotic recipient of the transferred micronuclei. This technique of cytogenetic analysis allowed a fast and simple control of the influence of different conditions on micronucleation and fusion of micronuclei with recipient cells. It could be shown that microcell-mediated chromosome transfer from human tumor cells into human normal, as well as human tumor, recipient cells is practicable if the techniques figured out by the present study are employed.

Breast Neoplasms↗

PubMed2006

Bidirectional electron transfer in photosystem I: replacement of the symmetry-breaking tryptophan close to the PsaB-bound phylloquinone A1B with a glycine residue alters the redox properties of A1B and blocks forward electron transfer at cryogenic temperatures.

A conserved tryptophan residue located between the A(1B) and F(X) redox centres on the PsaB side of the Photosystem I reaction centre has been mutated to a glycine in Chlamydomonas reinhardtii, thereby matching the conserved residue found in the equivalent position on the PsaA side. This mutant (PsaB:W669G) was studied using EPR spectroscopy with a view to understanding the molecular basis of the reported kinetic differences in forward electron transfer from the A(1A) and the A(1B) phyllo(semi)quinones. The kinetics of A(1)(-) reoxidation due to forward electron transfer or charge recombination were measured by electron spin echo spectroscopy at 265 K and 100 K, respectively. At 265 K, the reoxidation kinetics are considerably lengthened in the mutant in comparison to the wild-type. Under conditions in which F(X) is initially oxidised the kinetics of charge recombination at 100 K are found to be biphasic in the mutant while they are substantially monophasic in the wild-type. Pre-reduction of F(X) leads to biphasic kinetics in the wild-type, but does not alter the already biphasic kinetic properties of the PsaB:W669G mutant. Reduction of the [4Fe-4S] clusters F(A) and F(B) by illumination at 15 K is suppressed in the mutant. The results provide further support for the bi-directional model of electron transfer in Photosystem I of C. reinhardtii, and indicate that the replacement of the tryptophan residue with glycine mainly affects the redox properties of the PsaB bound phylloquinone A(1B).

Algal Proteins↗

PubMed2005

Evaluation of nuclear transfer and transcription of plasmid DNA condensed with protamine by microinjection: the use of a nuclear transfer score.

In the present study, the nuclear delivery of a green fluorescence protein (GFP)-encoding pDNA condensed by protamine was investigated in terms of trans-gene expression after cytoplasmic (E(cyt)) and nuclear (E(nuc)) microinjection. To compare the nuclear transfer process, a novel parameter; the nuclear transfer (NT) score was introduced. The E(cyt) value for protamine/pDNA particles increased in a charge ratio-dependent manner. The calculated NT score showed that this increase results from an enhancement in nuclear transfer efficiency, which was also quantitatively confirmed by a recently developed confocal image-assisted three-dimensionally integrated quantification (CIDIQ) method. Moreover, E(nuc) for protamine/pDNA particles was significantly higher than that for poly-L-lysine/pDNA particles, suggesting that pDNA, when condensed with protamine, is more accessible to intra-nuclear transcription. Collectively, protamine is an excellent DNA condenser, with bi-functional advantages: improvement in nuclear delivery and efficient intra-nuclear transcription.

Cell Nucleus↗

PubMed1977

Photo-induced charge transfer. A critical test of the mechanism and range of biological electron transfer processes.

The vibronic coupling theory of electron tunneling between biomolecules requires that all such tunnelings involve vibronic coupling, finds temperature dependence to tunneling at finite temperatures, and predicts relatively short tunneling distances. This theory might be expected to apply to most electron transfers involved in the membrane-bound electron transfer reactions of photosynthesis and oxidative phosphorylation. This paper calculates the properties of a weak charge-transfer optical absorption band, whose predicted characteristics are a direct and simple consequence of the model that describes vibronically coupled tunneling. The new absorption band provides the basis for a critical experimental test of the constructs and parameters of the tunneling theory. If the tunneling theory is valid, the oscillator strength of such bands will be the most reliable measure of the tunneling matrix element and of the distance between the sites exchanging an electron.

Electron Transport↗

PubMed1997

Purification and properties of a lipid transfer particle from Bombyx mori: comparison to the lipid transfer particle from Manduca sexta.

A lipid transfer particle (LTP) was purified from the hemolymph of the silkworm Bombyx mori. Like other insect LTPs, the B. mori LTP is a very high density lipoprotein containing 21% lipid and three apoproteins of mass approximately 350 kDa, approximately 85 kDa, and approximately 60 kDa. B. mori LTP catalyzes the exchange of lipids between different density class lipoproteins found in adult hemolymph and between adult lipoproteins and vitellogenin. However, in no case was net lipid transfer observed. Manduca sexta LTP also catalyzed exchange of lipids, but not net transfer of lipids, between different density class lipoproteins found in adult hemolymph.

Animals↗

PubMed2001

Charge-transfer emission of compact porphyrin-fullerene dyad analyzed by Marcus theory of electron-transfer.

A porphyrin-fullerene dyad, which is characterized by a close proximity of the porphyrin donor and the fullerene acceptor, was found to undergo a photoinduced electron transfer both in solutions and in solid films. Near-infrared charge-transfer (CT) emission was observed and analyzed in frame of the semi-classical Marcus electron-transfer theory yielding values for the reaction free energy, -deltaG degrees = 1.75 eV, the internal reorganization energy, lambdav = 0.05 eV, and the donor-acceptor vibrational energy, hv(v) = 0.14 eV, both in solution and in solid film. The influence of the environment on the CT properties of the dyad is described by a single parameter, the outer-sphere reorganization energy, lambdas, which varies from 0.05 eV in non-polar solvents and films to 0.13 eV in solvents of moderate polarity. At low temperatures (T< 200 K), the CT emission consists of distinct bands shifted from each other by value hv(v). This is the first direct observation of the vibrational frequencies of a porphyrin-fullerene donor-acceptor system.

Biophysical Phenomena↗

PubMed1989

Time-dependent 31P saturation transfer in the phosphoglucomutase reaction. Characterization of the spin system for the Cd(II) enzyme and evaluation of rate constants for the transfer process.

Time-dependent 31P saturation-transfer studies were conducted with the Cd2+-activated form of muscle phosphoglucomutase to probe the origin of the 100-fold difference between its catalytic efficiency (in terms of kcat) and that of the more efficient Mg2+-activated enzyme. The present paper describes the equilibrium mixture of phosphoglucomutase and its substrate/product pair when the concentration of the Cd2+ enzyme approaches that of the substrate and how the nine-spin 31P NMR system provided by this mixture was treated. It shows that the presence of abortive complexes is not a significant factor in the reduced activity of the Cd2+ enzyme since the complex of the dephosphoenzyme and glucose 1,6-bisphosphate, which accounts for a large majority of the enzyme present at equilibrium, is catalytically competent. It also shows that rate constants for saturation transfer obtained at three different ratios of enzyme to free substrate are mutually compatible. These constants, which were measured at chemical equilibrium, can be used to provide a quantitative kinetic rationale for the reduced steady-state activity elicited by Cd2+ relative to Mg2+ [cf. Ray, W.J., Post, C.B., & Puvathingal, J.M. (1989) Biochemistry (following paper in this issue)]. They also provide minimal estimates of 350 and 150 s-1 for the rate constants describing (PO3-) transfer from the Cd2+ phosphoenzyme to the 6-position of bound glucose 1-phosphate and to the 1-position of bound glucose 6-phosphate, respectively. These minimal estimates are compared with analogous estimates for the Mg2+ and Li+ forms of the enzyme in the accompanying paper.

Binding Sites↗

PubMed2002

The N-terminal 1000 residues of apolipoprotein B associate with microsomal triglyceride transfer protein to create a lipid transfer pocket required for lipoprotein assembly.

Apolipoprotein (apo) B, the major protein component of the atherogenic low-density lipoprotein (LDL), has a pentapartite structure, NH2-betaalpha1-beta1-alpha2-beta2-alpha3-COOH, the beta domains containing multiple amphipathic beta strands and the alpha domains containing multiple amphipathic alpha helixes. We recently reported that the first 1000 residues of human apoB-100 have sequence and amphipathic motif homologies to the lipid-pocket of lamprey lipovitellin (LV) [Segrest, J. P., Jones, M. K., and Dashti, N. (1999) J. Lipid Res. 40, 1401-1416]. The lipid-pocket of LV is a small triangular space lined by three antiparallel amphipathic beta sheets, betaA, betaB, and betaD. The betaA and betaB sheets are joined together by an antiparallel alpha helical bundle, alpha domain. We proposed [Segrest, J. P., Jones, M. K., and Dashti, N. (1999) J. Lipid Res. 40, 1401-1416] that formation of a LV-like lipid-pocket is necessary for lipid-transfer to apoB-containing lipoprotein particles and that this pocket is formed by association of the region of the betaalpha1 domain homologous to the betaA and betaB sheets of LV with a betaD-like amphipathic beta sheet from microsomal triglyceride transfer protein (MTP). To test this hypothesis, we generated four truncated cDNA constructs terminating at or near the juncture of the betaalpha1 and beta1 domains: Residues 1-800 (apoB:800), 1-931 (apoB:931), 1-1000 (apoB:1000), and 1-1200 (apoB:1200). Characterization of particles secreted by stable transformants of the McA-RH7777 cell line demonstrated that (i) ApoB:800, missing the betaB domain, was secreted as a lipid-poor aggregate. (ii) ApoB:931, containing most, but not all, of the betaB domain, was secreted as lipid-poor particles unassociated with MTP. (iii) ApoB:1000, containing the entire betaB domain, was secreted as a relatively lipid-rich particle associated hydrophobically with MTP. (iv) ApoB:1200, containing the betaalpha1 domain plus 200 residues of the beta1 domain, was secreted predominantly as a lipid-poor particle but also as a minor relatively lipid-rich, MTP-associated particle. We thus have captured an intermediate in apoB-containing particle assembly, a lipid transfer competent pocket formed by association of the complete betaalpha1 domain of apoB with MTP.

Animals↗

PubMed2006

Cation mediation of radical transfer between Trp48 and Tyr356 during O2 activation by protein R2 of Escherichia coli ribonucleotide reductase: relevance to R1-R2 radical transfer in nucleotide reduction?

A tryptophan 48 cation radical (W48(+)(*)) forms concomitantly with the Fe(2)(III/IV) cluster, X, during activation of oxygen for tyrosyl radical (Y122.) production in the R2 subunit of class I ribonucleotide reductase (RNR) from Escherichia coli. W48(+)(*) is also likely to be an intermediate in the long-range radical transfer between R2 and its partner subunit, R1, during nucleotide reduction by the RNR holoenzyme. The kinetics of decay of W48(+)(*) and formation of tyrosyl radicals during O(2) activation (in the absence of R1) in wild-type (wt) R2 and in variants with either Y122, Y356 (the residue thought to propagate the radical from W48(+)(*) into R1 during turnover), or both replaced by phenylalanine (F) have revealed that the presence of divalent cations at concentrations similar to the [Mg(2+)] employed in the standard RNR assay (15 mM) mediates a rapid radical-transfer equilibrium between W48 and Y356. Cation-mediated propagation of the radical from W48 to Y356 gives rise to a fast phase of Y. production that is essentially coincident with W48(+)(*) formation and creates an efficient pathway for decay of W48(+)(*). Possible mechanisms of this cation mediation and its potential relevance to intersubunit radical transfer during nucleotide reduction are considered.

Amino Acid Sequence↗

PubMed1997

Catalytic role of monovalent cations in the mechanism of proton transfer which gates an interprotein electron transfer reaction.

Within the methylamine dehydrogenase (MADH)-amicyanin protein complex, long range intermolecular electron transfer (ET) occurs between tryptophan tryptophylquinone (TTQ) of MADH and the type I copper of amicyanin. The reoxidations of two chemically distinct reduced forms of TTQ were studied, a quinol (O-quinol) generated by reduction by dithionite and the physiologically relevant aminoquinol (N-quinol) generated by reduction by methylamine. The latter contains a substrate-derived amino group which displaces the C6 carbonyl oxygen on TTQ. ET from N-quinol MADH to amicyanin is gated by the transfer of a solvent exchangeable proton [Bishop, G. R., & Davidson, V. L. (1995) Biochemistry 34, 12082-12086]. The factors which influence this proton transfer (PT) reaction have been examined. The rate of PT increases with increasing pH and with increasing salt concentration. The salt effect is due to specific monovalent cations and is not a general ionic strength effect. The rate enhancements by pH and cations do not reflect an elimination of the PT step that gates ET. Over the range of pH from 5.5 to 9.0 and with cation concentrations from 0 to 200 mM, the observed rate of the redox reaction is still that of PT. This is proven by kinetic solvent isotope effect studies which show that a primary isotope effect persists even at the highest values of pH and cation concentration. A model is presented to explain how specific cations contribute to catalysis and influence the rate of PT in this reaction. The pH dependence is attributed to an ionizable group that is involved in cation binding. The effect of the cation is stabilization of a negatively charged reaction intermediate that is formed during the deprotonation of the N-quinol, and from which rapid ET to the copper of amicyanin occurs. The relevance of these findings to other enzymes which exhibit reaction rates that are influenced by monovalent cations is also discussed.

Bacterial Proteins↗