Predictability of exogenous hormone effect on subgroups of migraineurs

OBJECTIVE

To evaluate whether self-reported past migraine response to reproductive life events (menses, pregnancy, menopause) alters the likelihood of worsening of migraine with exogenous hormone use.

METHODS

A retrospective study was conducted on 451 female patients at the University Headache Center who had a diagnosis of migraine with or without aura.

RESULTS

The majority of migraineurs recalled no change in headaches with oral contraceptive use or hormone replacement therapy (67.2% and 77%, respectively). Worsening of migraines with oral contraceptive use was associated with a menstrual trigger, worsening during pregnancy, and a diagnosis of migraine without aura. Worsening with hormone replacement therapy was associated with worsening during prior oral contraceptive use, improvement during pregnancy, worsening during menopause, and a diagnosis of migraine without aura.

CONCLUSIONS

Prospective studies are needed to confirm these associations.

Glaucoma and race: a case for screening in Connecticut

This study is a review of the current literature regarding the relationship of primary open angle glaucoma and race. There is strong evidence that blacks have a much higher prevalence rate of this disease. They also tend to have a more severe clinical course. Glaucoma is the leading cause of irreversible blindness in blacks. The number of blacks in Connecticut with glaucoma is estimated to be between 14,000 and 21,000, and it is estimated that up to half of these cases are currently undetected. New technology has made screening for glaucoma more practical and cost-effective. This study suggests that glaucoma screening would be beneficial for the black population of Connecticut.

Living-donor liver transplantation in children

INTRODUCTION

Living-related liver transplantation (LRLT) for paediatric recipients was developed 10 years ago to overcome the high mortality on the waiting list. Since then, liver transplantation programs around the world have begun to employ this method with encouraging results. This review describes the actual status of LRLT in children, aspects of donor selection, donor risks, and surgical technique, as well as an update of the results of the leading LRLT programs in the world. The donor operation has matured to the stage of being a standardised, teachable procedure with a low risk of morbidity or mortality. However, there is a percentage of potential donations that have to be declined for medical or socio-psychological reasons. LRLT provides grafts of excellent quality and short cold ischemic times. A major advantage is the fact that the optimal moment for the transplantation procedure can be chosen. Together with split-liver techniques, LRLT has a positive effect on the general situation of the paediatric waiting list for liver transplantation, with a reduction of pre-transplant mortality to nearly 0%.

Sex-specific induction of apoptosis by cyproterone acetate in primary rat hepatocytes

The synthetic steroid cyproterone acetate (CPA) has been reported to be hepatogenotoxic in female rats depending on sex-specific expression of a hydroxysteroid sulfotransferase (HST) which is involved in the bioactivation of CPA to reactive metabolites. In the present study the ability of CPA to initiate apoptosis in rat hepatocytes in vitro was investigated with respect to sex-specific effects and dependency on HST activity. Incubation of primary hepatocytes of female rats with CPA (0.1-30 microM) caused a strong increase in percent of cells undergoing apoptosis. The lowest concentration leading to apoptosis was 0.3 microM. In contrast, hepatocytes isolated from male rats showed a very weak response at high exposure to CPA (30 microM) only. Treatment with transforming growth factor-beta1 induced high levels of apoptotis in hepatocytes of both genders. Megestrol acetate and chlormadinone acetate, two structural analogues of CPA with a much lower genotoxic potency, did not induce apoptosis. Pre-addition of 10 or 50 microM dehydroepiandrosterone (DHEA), a known inhibitor of hepatic HST, almost completely inhibited CPA-induced apoptosis in hepatocytes of female rats. Using similar test concentrations, DHEA also reduced CPA-induced DNA excision repair as measured in the unscheduled DNA synthesis test. The results suggest that apoptosis induction is directly related to DNA damage induced by HST-dependent CPA metabolites.

Retinoid X receptor (RXR) agonist-induced activation of dominant-negative RXR-retinoic acid receptor alpha403 heterodimers is developmentally regulated during myeloid differentiation

The multiple biologic activities of retinoic acid (RA) are mediated through RAR and retinoid X receptor (RXR) nuclear receptors that interact with specific DNA target sequences as heterodimers (RXR-RAR) or homodimers (RXR-RXR). RA receptor activation appears critical to regulating important aspects of hematopoiesis, since transducing a COOH-terminally truncated RARalpha exhibiting dominant-negative activity (RARalpha403) into normal mouse bone marrow generates hematopoietic growth factor-dependent cell lines frozen at the multipotent progenitor (EML) or committed promyelocyte (MPRO) stages. Nevertheless, relatively high, pharmacological concentrations of RA (1 to 10 microM) overcome these differentiation blocks and induce terminal granulocytic differentiation of the MPRO promyelocytes while potentiating interleukin-3 (IL-3)-induced commitment of EML cells to the granulocyte/monocyte lineage. In the present study, we utilized RXR- and RAR-specific agonists and antagonists to determine how RA overcomes the dominant-negative activity of the truncated RARalpha in these different myeloid developmental stages. Unexpectedly, we observed that an RXR-specific, rather than an RAR-specific, agonist induces terminal granulocytic differentiation of MPRO promyelocytes, and this differentiation is associated with activation of DNA response elements corresponding to RAR-RXR heterodimers rather than RXR-RXR homodimers. This RXR agonist activity is blocked by RAR-specific antagonists, suggesting extensive cross-talk between the partners of the RXR-RARalpha403 heterodimer. In contrast, in the more immature, multipotent EML cells we observed that this RXR-specific agonist is inactive either in potentiating IL-3-mediated commitment of EML cells to the granulocyte lineage or in transactivating RAR-RXR response elements. RA-triggered GALdbd-RARalpha hybrid activity in these cells indicates that the multipotent EML cells harbor substantial nuclear hormone receptor coactivator activity. However, the histone deacetylase (HDAC) inhibitor trichostatin A readily activates an RXR-RAR reporter construct in the multipotent EML cells but not in the committed MPRO promyelocytes, indicating that differences in HDAC-containing repressor complexes in these two closely related but distinct hematopoietic lineages might account for the differential activation of the RXR-RARalpha403 heterodimers that we observed at these different stages of myeloid development.

LC/ESI-MS allows simultaneous and specific quantification of SDZ RAD and cyclosporine, including groups of their metabolites in human blood

An analytic technique using liquid chromatography (LC) coupled with electrospray-mass spectrometry (ESI-MS) has been developed for the simultaneous determination of the new immunosuppressant SDZ RAD (40-O-[2-hydroxy)ethylrapamycin) and cyclosporine (Cs), including their metabolites in blood. With the time-sparing, automated on-line extraction technique, the recovery of SDZ RAD averaged 95% and that of Cs, 94%. The calibration lines were linear from 0.5 to 100 microg/L (r2 = 0.99) for SDZ RAD and from 10 to 1,000 microg/L (r2 = 0.99) for Cs. The method has been tested on blood samples from renal transplant recipients taken between 1 and 5 hours after oral SDZ RAD and Cs administration. In blood, we found the following metabolites: Hydroxy-SDZ RAD, dihydroxy-SDZ RAD, demethyl-SDZ RAD, and the ring-opened form of SDZ RAD. The main metabolite of SDZ RAD in blood was hydroxy-SDZ RAD. This novel LC/ESI-MS technique provided an excellent method for simultaneous quantitative monitoring of SDZ RAD and Cs, including their relevant groups of metabolites in patients treated simultaneously with these immunosuppressants.

Smoking in women

Smoking has numerous increased health risks for women, including the risks for cancer, cardiovascular disease, chronic obstructive pulmonary disease, gastric and duodenal ulcers, reduced fertility, ovulatory dysfunction, ectopic pregnancy, spontaneous abortion, sudden infant death, and earlier menopause. Such health risks, smoking cessation therapy, and unique obstacles to smoking cessation in women are the focus of this article.

Tunable alignment of macromolecules by filamentous phage yields dipolar coupling interactions

Dipolar coupling interactions represent an extremely valuable source of long-range distance and angle information that was previously not available for solution structure determinations of macromolecules. This is because observation of these dipolar coupling data requires creating an anisotropic environment for the macromolecule. Here we introduce a new method for generating tunable degrees of alignment of macromolecules by addition of magnetically aligned Pf1 filamentous bacteriophage as a cosolute. This phage-induced alignment technique has been used to study 1H-1H, 1H-13C, and 1H-15N dipolar coupling interactions in a DNA duplex, an RNA hairpin and several proteins including thioredoxin and apo-calmodulin. The phage allow alignment of macromolecules over a wide range of temperature and solution conditions and thus represent a stable versatile method for generating partially aligned macromolecules in solution.

CCU patient survey tool: all-out recovery

Studies show that patients' recall of their CCU stays is extremely limited due to various factors. To monitor patient satisfaction in this area, a team of CCU managers developed a survey and began an "All-Out Recovery Program."

Backbone and side chain dynamics of uncomplexed human adipocyte and muscle fatty acid-binding proteins

Adipocyte lipid-binding protein (A-LBP) and muscle fatty acid-binding protein (M-FABP) are members of a family of small ( approximately 15 kDa) cytosolic proteins that are involved in the metabolism of fatty acids and other lipid-soluble molecules. Although highly homologous (65%) and structurally very similar, A-LBP and M-FABP display distinct ligand binding characteristics. Since ligand binding may be influenced by intrinsic protein dynamical properties, we have characterized the backbone and side chain dynamics of uncomplexed (apo) human A-LBP and M-FABP. Backbone dynamics were characterized by measurements of 15N T1 and T2 values and ¿1H¿-15N NOEs. These data were analyzed using model-free spectral density functions and reduced spectral density mapping. The dynamics of methyl-containing side chains were charaterized by measurements of 2H T1 and T1rho relaxation times of 13C1H22H groups. The 2H relaxation data were analyzed using the model-free approach. For A-LBP, 15N relaxation data were obtained for 111 residues and 2H relaxation data were obtained for 42 methyl groups. For M-FABP, 15N relaxation data were obtained for 111 residues and 2H relaxation data were obtained for 53 methyl groups. The intrinsic flexibilities of these two proteins are compared, with particular emphasis placed on binding pocket residues. There are a number of distinct dynamical differences among corresponding residues between the two proteins. In particular, many residues display greater backbone picosecond to nanosecond and/or microsecond to millisecond time scale mobility in A-LBP relative to M-FABP, including F57, K58, and most residues in alpha-helix 2 (residues 28-35). Variations in the dynamics of this region may play a role in ligand selectivity. The side chains lining the fatty acid binding pocket display a wide range of motional restriction in both proteins. Side chains showing distinct dynamical differences between the two proteins include those of residues 20, 29, and 51. This information provides a necessary benchmark for determining dynamical changes induced by ligand binding and may ultimately lead to an enhanced understanding of ligand affinity and selectivity among fatty acid-binding proteins.

Human RanBP3, a group of nuclear RanGTP binding proteins

A group of novel human Ran-binding proteins, RanBP3, was identified using the yeast two-hybrid system via Ran-mediated interaction with the nucleotide exchange factor RCC1. Several open reading frames, representing putative alternatively spliced products, were established by cDNA cloning. Two of them, RanBP3-a and RanBP3-b, encode nuclear hydrophilic proteins of 499 and 562 amino acid residues. The sequences contain FXFG motifs, characteristic of a subgroup of nucleoporins, and a C-terminal domain showing similarity to the Ran-binding protein RanBP1. These proteins are localized in the nucleus, preferentially bind RanGTP and may be nuclear effectors of the Ran pathway.

Superinduction of IL-8 in T cells by HIV-1 Tat protein is mediated through NF-kappaB factors

Elevated levels of circulating IL-8, a potent chemotactic factor for granulocytes and T lymphocytes, are found in HIV-infected individuals. The HIV-1 transactivator protein Tat increased IL-8 secretion in T cell lines following CD3- and CD28-mediated costimulation. Full-length Tat (Tat101) enhanced IL-8 transcription through up-regulated transcription factor binding to the CD28-responsive element (CD28RE) in the IL-8 promoter. Expression of the Tat splice variant Tat72 (72 amino acids) also enhanced IL-8 production following T cell stimulation via a different, most likely post-transcriptional, mechanism. The CD28RE in the IL-8 promoter was characterized as a low-affinity NF-kappaB binding site recognized by the transcription factors p50 (NF-kappaB1), p65 (RelA) and c-rel. Transcription factor binding to "classical" NF-kappaB sites in the HIV-1, the human IL-2, and lymphotoxin promoters, recognized by p50 and p65 following CD3+28-mediated costimulation, was unaffected by Tat101 as was binding to the AP-1 motif in the IL-8 promoter. These experiments identify the CD28RE in the IL-8 promoter as a c-rel recognition site and a Tat101-responsive element. The effect of Tat101 on CD28REs in the IL-8 promoter and the subsequent up-regulation of IL-8 secretion is likely to contribute to the immune dysregulation observed during HIV-1 infection.

Retroviral gene transfer into cord blood stem/progenitor cells using purified vector stocks

Cord blood (CB) progenitor/stem cells (P/SC) are ideal targets for early gene therapy in individuals prenatally diagnosed with genetic disorders. Most retroviral transduction protocols were developed using adult peripheral blood stem cells (PBSC) and bone marrow (BM). Less is known about retroviral transduction of CB P/SC. We examined how timing, multiplicity of infection (MOI), and polycations in the transduction media affect transduction efficiency. Rates of transduction were determined in recently isolated CD34+ enriched CB cells and in colonies derived after various times in liquid cultures (LC). CB mononuclear cells (MNC) were separated by ficoll-hypaque centrifugation and enriched for CD34+ cells. Purity was assessed by flow cytometry. Transduction were performed with clinical-grade retroviral stocks at MOIs of 1-20. Transduction was performed with fetal bovine serum (FBS) or autologous plasma, IL-3, GM-CSF, IL-6, and SCF. The retroviral vector contained LacZ and neomycin resistance (neo) reporter genes. Transduction was determined by X-gal stain and by PCR amplification of the reporter genes. No drug selection was used. Twenty-five experiments were done. CB volumes ranged from 35-150 ml. MNC and CD34+ cell counts ranges were: 0.14-840 x 10(6) and 0.1-4.2 x 10(6), respectively. Transduction efficiency in liquid cultures ranged from 4-63%. Higher rates were seen using MOI > or = 10, 2 microg/ml polybrene, and 10% autologous CB plasma. In colonies, transduction rates were 63 to 72% by PCR and 32% by X-gal staining. In LTC-IC derived colonies, transduction was 7% by PCR. Short incubations of CD34+ CB cells with purified retroviral stocks, polybrene, and autologous sera result in high transduction rates of committed progenitors and moderately low efficiencies of transduction of LTC-IC in the absence of drug selection.

Trends in infant mortality in Connecticut, 1981-1992

Assessing infant mortality rates (IMRs) is important in public health planning. However, single year fluctuations in IMRs often receive attention without consideration of long-term trends. Trends in IMR over 12 years in Connecticut were examined using linked birth and death files. Overall, there was an exponential decline in IMR from 12.2/1,000 live births in 1981 to 7.3/1,000 live births in 1992. However, differential declines in IMRs resulted in an increased relative risk of infant death over time for infants of Black women compared with infants of White women. IMRs were also higher for infants of Black, teenaged, and less educated mothers. Targeted local maternal and child health programs are needed if IMRs are to continue to decline for all sections of the population in Connecticut.

Ran-binding protein 5 (RanBP5) is related to the nuclear transport factor importin-beta but interacts differently with RanBP1

We report the identification and characterization of a novel 124-kDa Ran binding protein, RanBP5. This protein is related to importin-beta, the key mediator of nuclear localization signal (NLS)-dependent nuclear transport. RanBP5 was identified by two independent methods: it was isolated from HeLa cells by using its interaction with RanGTP in an overlay assay to monitor enrichment, and it was also found by the yeast two-hybrid selection method with RanBP1 as bait. RanBP5 binds to RanBP1 as part of a trimeric RanBP1-Ran-RanBP5 complex. Like importin-beta, RanBP5 strongly binds the GTP-bound form of Ran, stabilizing it against both intrinsic and RanGAP1-induced GTP hydrolysis and also against nucleotide exchange. The GAP resistance of the RanBP5-RanGTP complex can be relieved by RanBP1, which might reflect an in vivo role for RanBP1. RanBP5 is a predominantly cytoplasmic protein that can bind to nuclear pore complexes. We propose that RanBP5 is a mediator of a nucleocytoplasmic transport pathway that is distinct from the importin-alpha-dependent import of proteins with a classical NLS.

Multiple isoforms of GAGA factor, a critical component of chromatin structure

The GAGA transcription factor of Drosophila melanogaster is ubiquitous and plays multiple roles. Characterization of cDNA clones and detection by domain- specific antibodies has revealed that the 70-90 kDa major GAGA species are encoded by two open reading frames producing GAGA factor proteins of 519 amino acids (GAGA-519) and 581 amino acids (GAGA-581), which share a common N-terminal region that is linked to two different glutamine-rich C-termini. Purified recombinant GAGA-519 and GAGA-581 proteins can form homomeric complexes that bind specifically to a single GAGA sequence in vitro. The two GAGA isoforms also function similarly in transient transactivation assays in tissue culture cells and in chromatin remodeling experiments in vitro . Only GAGA-519 protein accumulates during the first 6 h of embryogenesis. Thereafter, both GAGA proteins are present in nearly equal amounts throughout development; in larval salivary gland nuclei they colocalize completely to specific regions along the euchromatic arms of the polytene chromosomes. Coimmunoprecipitation of GAGA-519 and GAGA-581 from crude nuclear extracts and from mixtures of purified recombinant proteins, indicates direct interactions. We suggest that homomeric complexes of GAGA-519 may function during early embryogenesis; both homomeric and heteromeric complexes of GAGA-519 and GAGA-581 may function later.

Solution structure of human CTLA-4 and delineation of a CD80/CD86 binding site conserved in CD28

The structure of human CTLA-4 reveals that residues Met 99, Tyr 100 and Tyr 104 of the M99YPPPY104 motif are adjacent to a patch of charged surface residues on the A'GFCC' face of the protein. Mutation of these residues, which are conserved in the CTLA-4/CD28 family, significantly reduces binding to CD80 and/or CD86, implicating this patch as a ligand binding site.

Methylergonovine maleate as a cluster headache prophylactic: a study and review

Methylergonovine maleate (Methergine), an ergot derivative with vasoconstrictive properties, has been cited as an effective treatment for vascular headaches. Few studies are available to support its use in headache management. An uncontrolled pilot study of 20 episodic cluster headache patients confirmed its effectiveness and tolerability as an adjunct cluster headache prophylactic. Decreased headache frequency was reported by 19 of 20 patients (95%), and 15 of 20 patients (75%) reported decreased intensity of headaches within 1 week of initiating therapy. A review of methylergonovine's pharmacokinetic, molecular, and tolerability profile clarifies its mechanisms and clinical role in headache management.

Characterization of NADP+ binding to perdeuterated MurB: backbone atom NMR assignments and chemical-shift changes

Backbone-atom resonances have been assigned for both the substrate-free and the NADP+-complexed forms of UDP-N-acetylenolpyruvylglucosamine reductase (MurB), a monomeric, 347-residue (38.5 kDa) flavoenzyme essential for bacterial cell-wall biosynthesis. NMR studies were performed using perdeuterated, uniformly 13C/15N-labeled samples of MurB. In the case of substrate-free MurB, one or more backbone atoms have been assigned for 334 residues (96%). The assigned backbone atoms include 309 1HN and 15N atoms (94%), 315 13CO atoms (91%), 331 13C(alpha) atoms (95%), and 297 13C(beta) atoms (93%). For NADP+-complexed MurB, one or more backbone atoms have been assigned for 313 residues (90%); these include 283 1HN and 15N atoms (86%), 305 13CO atoms (88%), 310 13C(alpha) atoms (89%), and 269 13C(beta) atoms (84%). The strategies used for obtaining resonance assignments are described in detail. Information on the secondary structure in solution for both the substrate-free and NADP+-complexed forms of the enzyme has been derived both from 13C(alpha) and 13C(beta) chemical-shift deviations from random-coil values and from 1HN-1HN NOEs. These data are compared to X-ray crystallographic structures of substrate-free MurB and MurB complexed with the UDP-N-acetylglucosamine enolpyruvate (UNAGEP) substrate. NADP+ binding induces significant chemical-shift changes in residues both within the known UNAGEP and FAD binding pockets and within regions known to undergo conformational changes upon UNAGEP binding. The NMR data indicate that NADP+ and UNAGEP utilize the same binding pocket and, furthermore, that the binding of NADP+ induces structural changes in MurB. Finally, many of the residues within the UNAGEP/NADP+ binding pocket were difficult to assign due to dynamic processes which weaken and/or broaden the respective resonances. Overall, our results are consistent with MurB having a flexible active site.

Solution structure of the Grb2 N-terminal SH3 domain complexed with a ten-residue peptide derived from SOS: direct refinement against NOEs, J-couplings and 1H and 13C chemical shifts

Refined ensembles of solution structures have been calculated for the N-terminal SH3 domain of Grb2 (N-SH3) complexed with the ac-VPPPVPPRRR-nh2 peptide derived from residues 1135 to 1144 of the mouse SOS-1 sequence. NMR spectra obtained from different combinations of both 13C-15N-labeled and unlabeled N-SH3 and SOS peptide fragment were used to obtain stereo-assignments for pro-chiral groups of the peptide, angle restraints via heteronuclear coupling constants, and complete 1H, 13C, and 15N resonance assignments for both molecules. One ensemble of structures was calculated using conventional methods while a second ensemble was generated by including additional direct refinements against both 1H and 13C(alpha)/13C(beta) chemical shifts. In both ensembles, the protein:peptide interface is highly resolved, reflecting the inclusion of 110 inter-molecular nuclear Overhauser enhancement (NOE) distance restraints. The first and second peptide-binding sub-sites of N-SH3 interact with structurally well-defined portions of the peptide. These interactions include hydrogen bonds and extensive hydrophobic contacts. In the third highly acidic sub-site, the conformation of the peptide Arg8 side-chain is partially ordered by a set of NOE restraints to the Trp36 ring protons. Overall, several lines of evidence point to dynamical averaging of peptide and N-SH3 side-chain conformations in the third subsite. These conformations are characterized by transient charge stabilized hydrogen bond interactions between the peptide arginine side-chain hydrogen bond donors and either single, or possibly multiple, acceptor(s) in the third peptide-binding sub-site.

E3, a hematopoietic-specific transcript directly regulated by the retinoic acid receptor alpha

Retinoic acid (RA)-induced maturation mediated by the retinoic acid receptor alpha (RAR alpha) has been implicated in myeloid development. We have used differential hybridization analysis of a cDNA library constructed from the murine RA-inducible MPRO promyelocyte cell line to identify immediate-early genes induced by RA during granulocytic differentiation. E3, one of nine sequences identified, was upregulated in an immediate-early manner, with transcript levels peaking after 60 minutes exposure to RA. E3 transcripts were RA-inducible in HL60 cells, but not in an RA-resistant subclone, HL60R, that harbors a mutated RAR alpha gene. However, when HL60R cells were transduced with a functional copy of the RAR alpha gene, RA induced a 10-fold increase in E3 mRNA levels. E3 transcripts are present in the myeloid, B-lymphoid, and erythroid lineages, absent in nonhematopoietic cells, and encode a highly hydrophobic, potentially phosphorylated polypeptide of unknown function with significant homology to a putative protein expressed in myeloid cells. The murine E3 promoter harbors a single bipartite retinoic acid response element which in transient transfection assays conferred RA sensitivity. These results indicate that E3 is a hematopoietic-specific gene that is an immediate target for the activated RAR alpha during myelopoiesis.

Time-related induction of DNA repair synthesis in rat hepatocytes following in vivo treatment with cyproterone acetate

Cyproterone acetate (CPA), a synthetic steroid hormone widely used as a human pharmaceutical, has recently been shown to induce unscheduled DNA synthesis (UDS) in vitro in primary cultures of rat and human hepatocytes. In the present study CPA was evaluated for its ability to initiate UDS in the liver of female rats in vivo by means of the in vivo/in vitro hepatocyte DNA repair test. Using the standard sampling time of 16 h after single oral dosing, a dose-related UDS response at >50 mg CPA/kg body wt was observed. In order to examine the time course of CPA-induced UDS, different sampling times (4, 16, 48, 72, 96 and 144 h) after a single oral administration of 100 mg CPA/kg body wt were used. Whereas no UDS was induced in liver cells isolated 4 h after treatment, continuous DNA repair activity was observed after 16 h, with a maximum effect of approximately 10 net nuclear grains on day 4 after dosing. After a post-application period of 6 days the net grain counts returned to near control level. In contrast to the data with CPA, DNA damage induced by the positive control compound 2-acetylaminofluorene was removed much faster, within 2 days after administration. The time course of UDS activity during the first 4 days after administration of CPA parallels the previously reported time course of DNA adduct formation. However, a subsequent decrease and final cessation of UDS on day 6 takes place, although significant levels of CPA-DNA adducts have been reported to occur at that time point in rat liver cells. Whereas the time-related onset of UDS is suggested to reflect the pharmacokinetics of the activation of CPA to DNA-reactive intermediates, it remains unclear why the excision repair of DNA adducts did not continue. In addition to DNA repair synthesis, CPA was also shown to clearly increase the incidence of S phase cells under the test conditions applied, confirming the known mitogenic potential of CPA in rat liver.

The three-dimensional solution structure of the SH2 domain from p55blk kinase

Signal transduction in B cells is mediated, in part, by the interaction of the cytoplasmic components of the antigen receptor complex and various members of the src family tyrosine kinases. Key to this process appears to be the interaction of the tyrosine kinase SH2 domains with the tyrosine-phosphorylated cytoplasmic domain of Ig-alpha, a disulfide-bonded heterodimeric (with Ig-beta or Ig-gamma) transmembrane protein that noncovalently associates with the antigen receptor immunoglobin chains. In addition to binding to the phosphorylated cytoplasmic domains of Ig-alpha and Ig-beta, blk and fyn(T), two members of the src family kinases, have been shown to bind overlapping but distinct sets of phosphoproteins [Malek & Desiderio (1993) J. Biol. Chem. 268. 22557-22565]. A comparison of their three-dimensional structures may elucidate the apparently subtle differences required for phosphoprotein discrimination. To begin characterizing the blk/fyn/phosphosphoprotein interactions, we have determined the three-dimensional solution structure of the SH2 domain of blk kinase by nuclear magnetic resonance (NMR) spectroscopy. 1H, 13C, and 15N resonances of the SH2 domain of blk kinase were assigned by analysis of multidimensional, double- and triple-resonance NMR experiments. Twenty structures of the blk SH2 domain were refined with the program X-PLOR using a total of 2080 experimentally derived conformational restraints. The structures converged to a root-mean-squared (rms) distance deviation of 0.51 and 0.95 A for the backbone atoms and for the non-hydrogen atoms, respectively. The blk SH2 domain adopts the prototypical SH2 fold. Structurally, blk SH2 is most similar to the crystal structure of the v-src SH2 domain [Waksman et al. (1993) Nature 358.646-653] and superimposes on the crystal structure with an rmsd of 1.52 A for the backbone atoms. The largest deviations occur in the four loops interconnecting beta-strands A-E, which are the least well-defined regions in the NMR structure. Exclusion of these loops lowers this rmsd to 0.82 A. The conformation of the BC loop in the blk SH2 domain is similar to the open conformation in the apo lck SH2 domain, suggesting that, like the lck SH2 domain, the blk SH2 domain may have a gated phosphopeptide binding site. Finally, it is proposed that the amino acid substitution of Lys 88 (blk) for Glu [fyn(T)] is important for the observed differences in specificity between blk and fyn(T) SH2 domains.

Vasospasm-induced myocardial infarction with sumatriptan

Sumatriptan, a 5-hydroxytryptamine1, (5-HT1) receptor agonist is an effective abortive agent for migraine headaches. A common side effect in 3% to 7.9% of patients is chest pain. Although most cases of chest pain are not thought to be of cardiac origin, its mechanism is not entirely understood. Rare examples of electrocardiogram changes consistent with transient ischemia have been reported. Isolated instances of angina, arrhythmia, myocardial infarction, and death have been temporally associated with sumatriptan administration. In most cases, it is unclear whether underlying cardiovascular disease existed or contributed to this adverse event. We report the history of a 56-year-old female patient with migraine who experienced a myocardial infarction shortly after using sumatriptan, despite having had a normal cardiovascular evaluation. As she had a normal cardiac catheterization after the event, we find it probable that sumatriptan induced coronary vasospasm and myocardial infarction.