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Biomedical subjects

C Freund

Publications and source records attributed to C Freund.

At least 19 recordsLinked to original sources
PubMed2005

[Breastfeeding and breast cancer].

The objective of this review is to summarize the current knowledge about the impact of pregnancy and lactation on the risk of breast cancer and possibility of breastfeeding after breast cancer treatment. A Pubmed search was carried out for publications in English or French from 1974 through 2004, related to breast cancer, pregnancy and breastfeeding. There is a transient increase in risk of breast cancer in the first three to four years after pregnancy, whereas during lifetime, the risk seems lower than in nulliparity. Lactation reduced the risk for breast cancer. This protective effect seems greater for women who had extended periods of breastfeeding during their lifetime, particularly in case of BRCA1 mutation. Various physiopathological mechanisms are involved in the protective effect of breastfeeding: anovulation, cellular differentiation of the mammary cells and excretion in the milk of breast carcinogens. After breast cancer treatment, there is no evidence that breastfeeding increases the risk of breast cancer recurrence, nor that it carries any health risk to the newborn. Women previously treated for breast cancer and free of recurrence are allowed to breastfeed their children. Beneficial effects of breastfeeding for the mother and the newborn should lead physicians and midwives to encourage prolonged breastfeeding in their medical practice.

Breast Feeding↗
PubMed2001

Vsx1, a rapidly evolving paired-like homeobox gene expressed in cone bipolar cells.

The paired-like homeodomain (HD) protein Chx10 is distinguished by the presence of the CVC domain, a conserved 56 amino acid sequence C-terminal to the HD. In mammals, Chx10 is essential both for the proliferation of retinal progenitor cells and for the formation or survival of retinal bipolar interneurons. We describe the cloning and characterization of a mouse Chx10 homologue, Vsx1; phylogenetic analysis suggests that Vsx1 and its putative vertebrate orthologues have evolved rapidly. Vsx1 expression in the adult is predominantly retinal. Whereas Chx10 is expressed both in retinal progenitors in the developing eye and apparently in all bipolar cells of the mature retina, Vsx1 expression is first detected in the eye at postnatal day 5, where it is restricted to cone bipolar cells.

Amino Acid Sequence↗
PubMed2000

SH3 domain recognition of a proline-independent tyrosine-based RKxxYxxY motif in immune cell adaptor SKAP55.

Src-homology 3 (SH3) domains recognize PXXP core motif preceded or followed by positively charged residue(s). Whether SH3 domains recognize motifs other than proline-based sequences is unclear. In this study, we report SH3 domain binding to a novel proline-independent motif in immune cell adaptor SKAP55, which is comprised of two N-terminal lysine and arginine residues followed by two tyrosines (i.e. RKxxYxxY). Domains capable of binding to class I proline motifs bound to the motif, while the class II domains failed to bind. Peptide precipitation, alanine scanning and in vivo co-expression studies demonstrated a requirement for the arginine, lysine and tandem tyrosines of the motif. Two-dimensional NMR analysis of the peptide bound FYN-SH3 domain showed overlap with the binding site of a proline-rich peptide on the charged surface of the SH3 domain, while resonance signals for other residues (W119, W120, Y137) were not perturbed by the RKGDYASY based peptide. Expression of the RKGDYASY peptide potently inhibited TcRzeta/CD3-mediated NF-AT transcription in T cells. Our findings extend the repertoire of SH3 domain binding motifs to include a tyrosine-based motif and demonstrate a regulatory role for this motif in receptor signaling.

Amino Acids, Diamino↗
PubMed1999

The GYF domain is a novel structural fold that is involved in lymphoid signaling through proline-rich sequences.

T cell activation through the CD2 cell surface receptor is transmitted by proline-rich sequences within its cytoplasmic tail. A membrane-proximal proline-rich tandem repeat, involved in cytokine production, is recognized by the intracellular CD2 binding protein CD2BP2. We solved the solution structure of the CD2 binding domain of CD2BP2, which we name the glycine-tyrosine-phenylalanine (GYF) domain. The GYF sequence is part of a structurally unique bulge-helix-bulge motif that constitutes the major binding site for the CD2 tail. A hydrophobic surface patch is created by motif residues that are highly conserved among a variety of proteins from diverse eukaryotic species. Thus, the architecture of the GYF domain may be widely used in protein-protein associations.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Identification of a proline-binding motif regulating CD2-triggered T lymphocyte activation.

An intracellular protein termed CD2 binding protein 2 (CD2BP2), which binds to a site containing two PPPGHR segments within the cytoplasmic region of CD2, was identified. Mutagenesis and NMR analysis demonstrated that the CD2 binding region of CD2BP2 includes a 17-aa motif (GPY[orF]xxxxM[orV]xxWxxx GYF), also found in several yeast and Caenorhabditis elegans proteins of unknown function. In Jurkat T cells, over-expression of the isolated CD2BP2 domain binding to CD2 enhances the production of interleukin 2 on crosslinking of CD2 but not the T cell receptor. Hence, a proline-binding module distinct from SH3 and WW domains regulates protein-protein interactions.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Parallel pathways in the folding of a short-term denatured scFv fragment of an antibody.

BACKGROUND: Antibodies are prototypes of multimeric proteins and consist of structurally similar domains. The two variable domains of an antibody (VH and VL) interact through a large hydrophobic interface and can be expressed as covalently linked single-chain Fv (scFv) fragments. The in vitro folding of scFv fragments after long-term denaturation in guanidinium chloride is known to be slow. In order to delineate the nature of the rate-limiting step, the folding of the scFv fragment of an antibody after short-term denaturation has been investigated. RESULTS: Secondary structure formation, measured by H/D-exchange protection, of a mutant scFv fragment of an antibody after short incubation in 6 M guanidinium chloride was shown to be multiphasic. NMR analysis shows that an intermediate with significant proton protection is observed within the dead time of the manual mixing experiments. Subsequently, the folding reaction proceeds via a biphasic reaction and mass spectrometry analyses of the exchange experiments confirm the existence of two parallel pathways. In the presence of cyclophilin, however, the faster of the two phases vanishes (when followed by intrinsic tryptophan fluorescence), while the slower phase is not significantly enhanced by equimolar cyclophilin. CONCLUSIONS: The formation of an early intermediate, which shows amide-proton exchange protection, is independent of proline isomerization. Subsequently, a proline cis-trans isomerization reaction in the rapidly formed intermediate, producing 'non-native' isomers, competes with the fast formation of native species. Interface formation in a folding intermediate of the scFv fragment is proposed to prevent the back-isomerization of these prolines from being efficiently catalyzed by cyclophilin.

Immunoglobulin Fragments↗
PubMed1997

Comparison of the amide proton exchange behavior of the rapidly formed folding intermediate and the native state of an antibody scFv fragment.

We have investigated the stability of backbone amide protons of the intermediate and the native state of the scFv fragment of an antibody. Stopped flow experiments analyzed by MS and NMR detected the formation of an exchange protected intermediate within the deadtime of the stopped flow apparatus (17 ms). H/D exchange rates of the native protein identified a number of very stable backbone amide protons in the V(L) and the V(H) domains. In the V(L) domain, this slowly exchanging core of the scFv fragment is similar to the folding core of the intermediate, while the V(H) domain possesses a great number of very stable amide protons which are not stabilized to a significant degree in the folding intermediate of the scFv fragment.

Amides↗
PubMed1996

Folding nuclei of the scFv fragment of an antibody.

The folding kinetics of the variable domains of the phosphorylcholine-binding antibody McPC603, combined into a scFv fragment [VH-(Gly4Ser)3-VL], were investigated by the use of fluorescence spectroscopy, nuclear magnetic resonance (NMR), and mass spectrometry (MS). All three methods gave evidence for the occurrence of a major kinetic intermediate during the refolding of the denatured, oxidized scFv fragment. This intermediate is formed within the first 30 s of folding and comprises exchange-protected amide protons of hydrophobic and aromatic amino acids, most of which are localized within the inner beta-sheet of the V(L) domain. In the subsequent slow step, most of the amide protons become protected with rate constants that are very similar for residues of both domains. These data are in agreement with the MS results, which indicate a cooperative folding event from the intermediate to the native state of the scFv fragment.

Amino Acid Sequence↗
PubMed1996

Transcription factor genes and the developing eye: a genetic perspective.

We review the current knowledge of transcription factors in mammallan eye development. The 14 transcription factors presently known to be required for eye formation are examined in some detail, incorporating data from both humans and rodents. Aspects of the biochemistry, expression patterns, genetics, mutant phenotypes, and biological insights acquired from the examination of loss-of-function mutations are summarized. The other 32 tissue-restricted transcription factors that are currently known to be expressed in the developing or mature mammallan eye are tabulated, together with the timing and site of their ocular expression; the requirement for most of these genes in the eye is unknown. Contributions to mammallan eye development from the study of the genetics of the Drosophila eye are discussed briefly. Identification of the entire cohort of transcription factors required for eye development is an essential first step towards understanding the mechanisms underlying eye morphogenesis and differentiation, and the molecular basis of inherited eye abnormalities in humans.

Animals↗
PubMed1994

Structural and dynamic properties of the Fv fragment and the single-chain Fv fragment of an antibody in solution investigated by heteronuclear three-dimensional NMR spectroscopy.

Fv fragments, heterodimers of the variable light (VL) and variable heavy chain (VH) domains, are the smallest functional antibody units with molecular masses of approximately 26 kDa. The structural and dynamic properties of the Fv fragment and the corresponding single-chain Fv fragment (scFv: VH-linker-VL, 252 amino acids) of the phosphorylcholine-binding antibody McPC603 in the presence of hapten have been studied in solution by heteronuclear multidimensional NMR spectroscopy. Both 15N TOCSY-HMQC and triple-resonance experiments (HNCA and HN(CA)H, with 15N-13C-labeled protein) gave poor spectra, due to short T2 relaxation times for most of the backbone 1H, 15N, and 13C alpha atoms. The assignment procedure therefore relied upon the combination of amino acid and domain (VL) specifically labeled spectra and the 3D NOESY-HMQC spectrum of the uniformly 15N labeled Fv and scFv fragments. Approximately 80% of the 15N and 1H backbone and 60% of the 1H side-chain resonances have been assigned. Short- and long-range NOEs were used to determine the extent of beta-sheet structure and were compared to the X-ray crystallographic data. The 1H-15N NOE data indicate that the scFv backbone has a well-defined structure of limited conformational flexibility. However, the linker of the scFv fragment exhibits substantial fast internal motion (on the picosecond to nanosecond time scale) compared with the overall rotational correlation time of the whole molecule. Several residues in the CDRs, in turns, or at the C-terminal end of the protein have smaller NOEs, reflecting some degree of rapid motion in the protein backbone.

Amino Acid Sequence↗
PubMed1993

[Vaginal bleeding in the first trimester].

Significant changes in attitudes towards patients with vaginal bleeding during the first trimester of pregnancy are taking place at the moment, and it is with this in mind that the relevant literature dealing with these patients is reviewed. The rate of miscarriage in an asymptomatic population of pregnant women is 2-4%. If vaginal bleeding occurs, about half the fetuses will have no detectable heartbeat by the time symptoms appear and miscarriage is taking place. Of the remainder, where heartbeat is demonstrated, only ten percent will miscarry despite the bleeding. The presence of an intrauterine haematoma will at most have marginal significance for the prognosis. There is no treatment that has a documented effect amongst these patients, which is why hospitalization can no longer be recommended. A possible investigational program is suggested.

Abortion, Threatened↗
PubMed1993

Characterization of the linker peptide of the single-chain Fv fragment of an antibody by NMR spectroscopy.

A comparison of the single-chain Fv fragment of the antibody McPC603 (scFv) with its corresponding unlinked Fv fragment has been carried out with 15N-edited NMR spectroscopy. The two Fv fragments adopt the same structure, indicating that the linker does not perturb the folding of the domains. This also directly demonstrates that folding in vivo (Fv fragment) and in vitro (scFv fragment) leads to the same structure. The main differences in the spectra of the uniformly 15N-labeled scFv and Fv fragments are due to signals of Gly and Ser from the linker peptide of the scFv fragment. The linker peptide has been mapped with NMR spectra of 15N-glycine- and 15N-glycine/15N-serine-labeled scFv fragments. The 15N T2 relaxation data indicate that the linker peptide is more flexible than the rest of the molecule.

Glycine↗
PubMed1992

Premarital HIV-1 testing in New Jersey.

To answer questions related to the usefulness of premarital testing for human immunodeficiency virus type 1 (HIV-1), two "blinded" or "nonlinked" HIV-1 serosurveys were done in New Jersey, a state with a high incidence of AIDS, on blood specimens submitted for a premarital serologic test for syphilis. The first survey involved premarital blood specimens submitted to the New Jersey Department of Health laboratory for the year starting September 1987. The second survey involved premarital specimens submitted to five private or hospital clinical laboratories in the spring of 1989, of which approximately 1,000 consecutive premarital specimens from each laboratory were sent to the Department of Health laboratory for HIV-1 testing. Of 4,247 specimens tested in the 1987-1988 survey, 21 (0.49%) were positive for antibodies to HIV-1, while among 4,696 specimens in the 1989 survey, 29 (0.62%) were positive. When the survey results were weighted by the number of marriages by geographic regions of the state, the weighted premarital HIV-1 seroprevalence was 0.55% for the 1987-1988 survey and 0.62% for the 1989 survey. The male/female ratio of positive tests was 2.7:1 in 1987-1988 and 1.6:1 in 1989. Of the 8,943 specimens in both surveys, 5 (0.06%) gave an indeterminate immunoblot result, compared with 50 positive results. These percentages of premarital HIV-1 infections are much higher than earlier estimates and reports and are of the same magnitude as recently reported blinded premarital HIV-1 testing elsewhere. Results of this magnitude support a recommendation in New Jersey of voluntary HIV-1 counseling and testing for marriage applicants.

Adult↗
PubMed1991

Isolation and properties of a nitrile hydratase from the soil fungus Myrothecium verrucaria that is highly specific for the fertilizer cyanamide and cloning of its gene.

A protein was purified from crude extracts of the soil fungus Myrothecium verrucaria by gel filtration and hydrophobic chromatography to homogeneity; this protein catalyzed the stoichiometric hydration of the fertilizer cyanamide to urea with high substrate specificity. This cyanamide hydratase (urea hydro-lyase; EC 4.2.1.69) contained zinc and consisted of six identical subunits with Mr = 27,700. It was partially sequenced. The protein was detectable only when the fungus was grown on cyanamide as the sole nitrogen source. Genomic DNA from the fungus was cloned, and the gene encoding the enzyme was mapped with an oligonucleotide probe derived from the amino acid sequence within a 25,800-base-pair DNA region. The subunit of the enzyme is encoded by a 795-base-pair DNA sequence containing a 63-base-pair intron. A cDNA clone containing the intronless gene with an open reading frame encoding a sequence of 244 amino acids expressed the enzyme in active form in Escherichia coli with excellent yield.

Amino Acid Sequence↗
PubMed1990

Genetic instability of clathrin-deficient strains of Saccharomyces cerevisiae.

Saccharomyces cerevisiae strains carrying a mutation in the clathrin heavy chain gene (CHC1) are genetically unstable and give rise to heterogeneous populations of cells. Manifestations of the instability include increases in genome copy number as well as compensatory genetic changes that allow better growing clathrin-deficient cells to take over the population. Increases in genome copy number appear to result from changes in ploidy as well as alterations in normal nuclear number. Genetic background influences the frequency at which cells with increased genome content are observed in different Chc- strains. We cannot distinguish whether genetic background affects the rate at which aberrant nuclear division events occur or a growth advantage of cells with increased nuclear and/or genome content. However, survival of chc1-delta cells does not require an increase in genome copy number. The clathrin heavy chain gene was mapped 1-2 cM distal to KEX1 on the left arm of chromosome VII by making use of integrated 2 mu plasmid sequences to destabilize distal chromosome segments and allow ordering of the genes.

Canavanine↗