Homogeneous BTK Occupancy Assay for Pharmacodynamic Assessment of Tirabrutinib (GS-4059/ONO-4059) Target Engagement

Bruton’s tyrosine kinase (BTK) is a clinically validated target for B-cell leukemias and lymphomas with FDA-approved small-molecule inhibitors ibrutinib and acalabrutinib. Tirabrutinib (GS-4059/ONO-4059, Gilead Sciences, Inc., Foster City, CA) is a second-generation, potent, selective, irreversible BTK inhibitor in clinical development for lymphoid malignancies, including chronic lymphocytic leukemia (CLL) and diffuse large B-cell lymphoma (DLBCL). An accurate pharmacodynamic assay to assess tirabrutinib target coverage in phase 1/2 clinical studies will inform dose and schedule selection for advanced clinical evaluation. We developed a novel duplex homogeneous BTK occupancy assay based on time-resolved fluorescence resonance energy transfer (TR-FRET) to measure free and total BTK levels in a multiplexed format. The dual-wavelength emission property of terbium-conjugated anti-BTK antibody served as the energy donor for two fluorescent energy acceptors with distinct excitation and emission spectra. The assay was characterized and qualified using full-length purified recombinant human BTK protein and peripheral blood mononuclear cells derived from healthy volunteers and patients with CLL. We demonstrated assay utility using cells derived from lymph node and bone marrow samples from patients with CLL and DLBCL. Our TR-FRET-based BTK occupancy assay provides accurate, quantitative assessment of BTK occupancy in the clinical trial program for tirabrutinib and is in use in ongoing clinical studies.

Discovery of potent and selective inhibitors of calmodulin-dependent kinase II (CaMKII)

We hereby disclose the discovery of inhibitors of CaMKII (7h and 7i) that are highly potent in rat ventricular myocytes, selective against hERG and other off-target kinases, while possessing good CaMKII tissue isoform selectivity (cardiac γ/δ vs. neuronal α/β). In vitro and in vivo ADME/PK studies demonstrated the suitability of these CaMKII inhibitors for PO (7h rat F = 73%) and IV pharmacological studies.

Abstract 1354: Developing 384-well and 1536-well cell growth inhibition assay workflow for screening drug-drug combination in tumor cell lines

Drug combination has been widely used in treating the most debilitating diseases such as cancer. The ideal drug-drug combination will broaden and/or deepen therapeutic efficacy while overcoming resistance and unwanted off-target effects. We have developed a 384-well combination compound plating method in 8×7 format (8 dilutions of Drug A and 7 dilutions of Drug B), and screened a number of compound pairs that showed synergistic effect in inhibiting tumor cell growth in either suspension or solid tumor lines. Compound vehicle DMSO was used as negative control and puromycin treatment as positive control for calculating% inhibition, and both HSA and Bliss independence synergy models were applied for calculating synergy scores. As 384-well 8×7 format contains one compound pair per plate, we aimed to increase the throughput by developing 384-well 5×5 format (5 dilutions of Drug A and 5 dilutions of Drug B) which contains 3 drug pairs per plate, and 1536-well 8×7 and 5×5 format which contains 4 and 12 drug pairs per plate, respectively. We compared EC50s and synergy scores generated from 384-well and 1536-well with both 8×7 and 5×5 formats, single agent EC50s within combination pairs were generally within 3 fold difference and synergy scores are largely consistent. Therefore, we have validated and enabled higher throughput drug-drug combination screen by using 384-well 5×5, 1536-well 8×7, or 5×5 format. The high-throughput method presented here can be readily adopted for combination studies in other disease areas.

Citation Format: Yvonne Li, Mike Ma, Julie Chan, Yang Tian, Nikos Pagratis, Derek Stonich, Victor Chen, Louis Zhang, Mark Kenney. Developing 384-well and 1536-well cell growth inhibition assay workflow for screening drug-drug combination in tumor cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1354.

Inhibitions of late INa and CaMKII act synergistically to prevent ATX-II-induced atrial fibrillation in isolated rat right atria

AIMS

Increases in late Na(+) current (late INa) and activation of Ca(2+)/calmodulin-dependent protein kinase (CaMKII) are associated with atrial arrhythmias. CaMKII also phosphorylates Nav1.5, further increasing late INa. The combination of a CaMKII inhibitor with a late INa inhibitor may be superior to each compound alone to suppress atrial arrhythmias. Therefore, we investigated the effect of a CaMKII inhibitor in combination with a late INa inhibitor on anemone toxin II (ATX-II, a late INa enhancer)-induced atrial arrhythmias.

METHODS AND RESULTS

Rat right atrial tissue was isolated and preincubated with either the CaMKII inhibitor autocamtide-2-related inhibitory peptide (AIP), the late INa inhibitor GS458967, or both, and then exposed to ATX-II. ATX-II increased diastolic tension and caused fibrillation of isolated right atrial tissue. AIP (0.3μmol/L) and 0.1μmol/L GS458967 alone inhibited ATX-II-induced arrhythmias by 20±3% (mean±SEM, n=14) and 34±5% (n=13), respectively, whereas the two compounds in combination inhibited arrhythmias by 81±4% (n=10, p<0.05, vs either AIP or GS458967 alone or the calculated sum of individual effects of both compounds). AIP and GS458967 also attenuated the ATX-induced increase of diastolic tension. Consistent with the mechanical and electrical data, 0.3μmol/L AIP and 0.1μmol/L GS458967 each inhibited ATX-II-induced CaMKII phosphorylation by 23±3% and 32±4%, whereas the combination of both compounds inhibited CaMKII phosphorylation completely.

CONCLUSION

The effects of an enhanced late INa to induce arrhythmic activity and activation of CaMKII in atria are attenuated synergistically by inhibitors of late INa and CaMKII.

Functional label-free assays for characterizing the in vitro mechanism of action of small molecule modulators of capsid assembly

HIV capsid protein is an important target for antiviral drug design. High-throughput screening campaigns have identified two classes of compounds (PF74 and BI64) that directly target HIV capsid, resulting in antiviral activity against HIV-1 and HIV-2 laboratory strains. Using recombinant proteins, we developed a suite of label-free assays to mechanistically understand how these compounds modulate capsid activity. PF74 preferentially binds to the preassembled hexameric capsid form and prevents disruption of higher-order capsid structures by stabilizing capsid intersubunit interactions. BI64 binds only the monomeric capsid and locks the protein in the assembly incompetent monomeric form by disrupting capsid intersubunit interactions. We also used these assays to characterize the interaction between capsid and the host protein cleavage and polyadenylation specific factor 6 (CPSF6). Consistent with recently published results, our assays revealed CPSF6 activates capsid polymerization and preferentially binds to the preassembled hexameric capsid form similar to the small molecule compound, PF74. Furthermore, these label-free assays provide a robust method for facilitating the identification of a different class of small molecule modulators of capsid function.

Abyssomicin 2 reactivates latent HIV-1 by a PKC- and HDAC-independent mechanism

Screening of a marine natural products library afforded three new analogues of the tetronic acid containing polyketide abyssomicin family and identified abyssomicin 2 as a selective reactivator of latent HIV virus. Examination of the mode of action of this new latent HIV reactivating agent demonstrated that it functions via a distinct mechanism compared to that of existing reactivating agents and is effective at reactivating latent virus in a subset of primary patient cell lines.

High-throughput kinetic screening of hybridomas to identify high-affinity antibodies using bio-layer interferometry

Kinetic analysis of antibodies is crucial in both clone selection and characterization. Historically, antibodies in supernatants from hybridomas are selected based on a solid-phase enzyme-linked immunosorbent assay (ELISA) in which the antigen is immobilized on the assay plate. ELISA selects clones based on a combination of antibody concentration in the supernatant and affinity. The antibody concentration in the supernatant can vary significantly and is typically unknown. Using the ELISA method, clones that express high levels of a low-affinity antibody can give an equivalent signal as clones that express low levels of a high-affinity antibody. As a consequence, using the ELISA method, superior clones can be overshadowed by inferior clones. In this study, we have applied Bio-Layer Interferometry to screen hybridoma clones based on disassociation rates using the OctetRED 384 platform. Using the OctetRED platform, we were able to screen 2000 clones within 24 hours and select clones containing high-affinity antibodies for further expansion and subsequent characterization. Using this method, we were able to identify several clones producing high-affinity antibodies that were missed by ELISA.

Medical, demographical and social aspects of syphilis: the case of infected sex workers in Greece during Interwar

The aim of this research is to present syphilis among women described as "indecent" according to the records of the Venereal Diseases Hospital "Andreas Syggros", which is located in Athens, during the period 1931-1935. In impoverished Greece of the Interwar period, factors such as criminal ignorance, or lack of information on sexually transmitted diseases (STDs) along with inadequate health controls of sex workers, resulted in a dramatic spread of syphilis, whereas "Andreas Syggros" hospital accommodated thousands of patients. The inflow of 1.300.000 Greek refugees from Asia Minor, after the Greek defeat by the Turkish army in the war of 1922, resulted in a notable change in the demographics of the country, while the combination of miserable living conditions, unemployment, economic crisis of the Interwar period, political instability and dysfunction of the State led to an increased number of illegal sex workers and syphilis outbreaks. Despite the introduction of an ad hoc Act to control STDs since 1923, the State was unable to limit the transmissibility of syphilis and to control prostitution. Unfortunately, the value of this historical paradigm is borne out by a contemporary example, i.e. the scandal of HIV seropositive sex workers in -beset by economic crisis- Greece in May 2012. It turns out that ignorance, failure to comply with the law, change in the mentality of the citizens in an economically ruined society, and most notably dysfunction of public services during periods of crisis, are all risk factors for the spread of serious infectious diseases.

Study of marine natural products including resorcyclic acid lactones from Humicola fuscoatra that reactivate latent HIV-1 expression in an in vitro model of central memory CD4+ T cells

An extract of Humicola fuscoatra (UCSC strain no. 108111A) was shown to reactivate latent HIV-1 expression in an in vitro model of central memory CD4+ T cells. We report the bioassay-guided isolation and structure determination of several resorcyclic acid lactones, including four known compounds, radicicol (1, aka. monorden) and pochonins B (2), C (3), and N (4), and three new analogues, radicicols B-D (5-7). Compounds 1-3 and 5 showed moderate activities in the memory T cell model of HIV-1 latency. Radicicol (1) displayed lower potency in reactivating latent HIV-1 (EC50 = 9.1 μM) relative to the HDAC inhibitors apicidin (EC50 = 0.3 μM), romidepsin (EC50 = 0.003 μM), and SAHA (EC50 = 0.6 μM); however, it achieved equivalent maximum efficacy relative to the positive control compounds (98% of SAHA and romidepsin).

A small-molecule inhibitor of hepatitis C virus infectivity

One of the most challenging goals of hepatitis C virus (HCV) research is to develop well-tolerated regimens with high cure rates across a variety of patient populations. Such a regimen will likely require a combination of at least two distinct direct-acting antivirals (DAAs). Combining two or more DAAs with different resistance profiles increases the number of mutations required for viral breakthrough. Currently, most DAAs inhibit HCV replication. We recently reported that the combination of two distinct classes of HCV inhibitors, entry inhibitors and replication inhibitors, prolonged reductions in extracellular HCV in persistently infected cells. We therefore sought to identify new inhibitors targeting aspects of the HCV replication cycle other than RNA replication. We report here the discovery of the first small-molecule HCV infectivity inhibitor, GS-563253, also called HCV infectivity inhibitor 1 (HCV II-1). HCV II-1 is a substituted tetrahydroquinoline that selectively inhibits genotype 1 and 2 HCVs with low-nanomolar 50% effective concentrations. It was identified through a high-throughput screen and subsequent chemical optimization. HCV II-1 only permits the production and release of noninfectious HCV particles from cells. Moreover, infectious HCV is rapidly inactivated in its presence. HCV II-1 resistance mutations map to HCV E2. In addition, HCV-II prevents HCV endosomal fusion, suggesting that it either locks the viral envelope in its prefusion state or promotes a viral envelope conformation change incapable of fusion. Importantly, the discovery of HCV II-1 opens up a new class of HCV inhibitors that prolong viral suppression by HCV replication inhibitors in persistently infected cell cultures.

Lipid-sensing high-throughput ApoA-I assays

Apolipoprotein A-I (ApoA-I), a primary protein component of high-density lipoprotein (HDL), plays an important role in cholesterol metabolism mediating the formation of HDL and the efflux of cellular cholesterol from macrophage foam cells in arterial walls. Lipidation of ApoA-I is mediated by adenosine triphosphate (ATP) binding cassette A1 (ABCA1). Insufficient ABCA1 activity may lead to increased risk of atherosclerosis due to reduced HDL formation and cholesterol efflux. The standard radioactive assay for measuring cholesterol transport to ApoA-I has low throughput and poor dynamic range, and it fails to measure phospholipid transfer. We describe the development of two sensitive, nonradioactive high-throughput assays that report on the lipidation of ApoA-I: a homogeneous assay based on time-resolved fluorescence resonance energy transfer (TR-FRET) and a discontinuous assay that uses the label-free Epic platform. The TR-FRET assay employs HiLyte Fluor 647-labeled ApoA-I with N-terminal biotin bound to streptavidin-terbium. When fluorescent ApoA-I was incorporated into HDL, TR-FRET decreased proportionally to the increase in the ratio of lipids to ApoA-I, demonstrating that the assay was sensitive to the amount of lipid bound to ApoA-I. In the Epic assay, biotinylated ApoA-I was captured on a streptavidin-coated biosensor. Measured resonant wavelength shift was proportional to the amount of lipids associated with ApoA-I, indicating that the assay senses ApoA-I lipidation.

Optimized high-throughput screen for hepatitis C virus translation inhibitors

Hepatitis C virus (HCV) is a considerable global health problem for which new classes of therapeutics are needed. The authors developed a high-throughput assay to identify compounds that selectively block translation initiation from the HCV internal ribosome entry site (HCV IRES). Rabbit reticulocyte lysate conditions were optimized to faithfully report on authentic HCV IRES-dependent translation relative to a 5' capped mRNA control. The authors screened a library of ~430,000 small molecules for IRES inhibition, leading to ~1700 initial hits. After secondary counterscreening, the vast majority of hits proved to be luciferase and general translation inhibitors. Despite well-optimized in vitro translation conditions, in the end, the authors found no selective HCV IRES inhibitors but did discover a new scaffold of general translation inhibitor. The analysis of these molecules, as well we the finding that a large fraction of false positives resulted from off-target effects, highlights the challenges inherent in screens for RNA-specific inhibitors.

Screening and identification of a novel class of TGF-β type 1 receptor kinase inhibitor

Transforming growth factor β (TGF-β) type I receptor (activin receptor-like kinase 5, ALK5) has been identified as a promising target for fibrotic diseases. To find a novel inhibitor of ALK5, the authors performed a high-throughput screen of a library of 420,000 compounds using dephosphorylated ALK5. From primary hits of 1521 compounds, 555 compounds were confirmed. In total, 124 compounds were then selected for follow-up based on their unique structures and other properties. Repeated concentration-response testing and final interference assays of the above compounds resulted in the discovery of a structurally novel ALK5 inhibitor (compound 8) (N-(thiophen 2-ylmethyl)-3-(3,4,5 trimethoxyphenyl)imidazo[1,2β]pyridazin 6-amine) with a low IC(50) value of 0.7 µM. Compound 8 also inhibited the TGF-β-induced nuclear translocation of SMAD with an EC(50) value of 0.8 µM. Kinetic analysis revealed that compound 8 inhibited ALK5 via mixed-type inhibition, suggesting that it may bind to ALK5 differently than other published adenosine triphosphate site inhibitors.

3,5-diarylazoles as novel and selective inhibitors of protein kinase D

The synthesis and preliminary studies of the SAR of novel 3,5-diarylazole inhibitors of Protein Kinase D (PKD) are reported. Notably, optimized compounds in this class have been found to be active in cellular assays of phosphorylation-dependant HDAC5 nuclear export, orally bioavailable, and highly selective versus a panel of additional putative histone deacetylase (HDAC) kinases. Therefore these compounds could provide attractive tools for the further study of PKD/HDAC5 signaling.

Kinetic mechanisms of Ca++/calmodulin dependent protein kinases

Many of the cellular responses to Ca++ signaling are modulated by a family of multifunctional Ca++/calmodulin dependent protein kinases (CaMKs): CaMK I, CaMK II and CaMK IV. In order to further understand the role of CaMKs, we investigated the kinetic mechanism of CaMK II isozymes in comparison with those of CaMK I and CaMK IV by analyzing their steady state kinetics using phospholamban as a phosphoacceptor. The results indicated that (a) the CaMK family's reaction mechanisms were of the sequential type in which all substrates must bind to enzyme before any product is released; (b) CaMK I and CaMK IV exhibited random sequential mechanism where either phospholamban or ATP can bind to the free enzyme; (c) the data of product inhibition for CaMK IIs best fit with an Ordered Bi Bi mechanism in which phospholamban is the first substrate to bind and ADP is the last product to be released; and (d) the constant α (ratio of apparent dissociation constants for binding peptide in the presence and absence of the second ligand) of all isozymes for ATP and peptide was higher than 1 indicating that the binding of phospholamban to CaMK decreased the enzyme's affinity toward ATP.

Identification of potent and selective amidobipyridyl inhibitors of protein kinase D

The synthesis and biological evaluation of potent and selective PKD inhibitors are described herein. The compounds described in the present study selectively inhibit PKD among other putative HDAC kinases. The PKD inhibitors of the present study blunt phosphorylation and subsequent nuclear export of HDAC4/5 in response to diverse agonists. These compounds further establish the central role of PKD as an HDAC4/5 kinase and enhance the current understanding of cardiac myocyte signal transduction. The in vivo efficacy of a representative example compound on heart morphology is reported herein.

Identification of orally available naphthyridine protein kinase D inhibitors

A novel 2,6-naphthyridine was identified by high throughput screen (HTS) as a dual protein kinase C/D (PKC/PKD) inhibitor. PKD inhibition in the heart was proposed as a potential antihypertrophic mechanism with application as a heart failure therapy. As PKC was previously identified as the immediate upstream activator of PKD, PKD vs PKC selectivity was essential to understand the effect of PKD inhibition in models of cardiac hypertrophy and heart failure. The present study describes the modification of the HTS hit to a series of prototype pan-PKD inhibitors with routine 1000-fold PKD vs PKC selectivity. Example compounds inhibited PKD activity in vitro, in cells, and in vivo following oral administration. Their effects on heart morphology and function are discussed herein.

Affinities between the binding partners of the HIV-1 integrase dimer-lens epithelium-derived growth factor (IN dimer-LEDGF) complex

The interaction between lens epithelium-derived growth factor/transcriptional co-activator p75 (LEDGF) and human immunodeficiency virus type 1 (HIV-1) integrase (IN) is essential for HIV-1 replication. Homogeneous time-resolved fluorescence resonance energy transfer assays were developed to characterize HIV-1 integrase dimerization and the interaction between LEDGF and IN dimers. Using these assays in an equilibrium end point dose-response format with mathematical modeling, we determined the dissociation constants of IN dimers (K(dimer) = 67.8 pm) and of LEDGF from IN dimers (K(d) = 10.9 nm). When used in a kinetic format, the assays allowed the determination of the on- and off-rate constants for these same interactions. Integrase dimerization had a k(on) of 0.1247 nm(-1) x min(-1) and a k(off) of 0.0080 min(-1) resulting in a K(dimer) of 64.5 pm. LEDGF binding to IN dimers had a k(on) of 0.0285 nm(-1).min(-1) and a k(off) of 0.2340 min(-1) resulting in a K(d) of 8.2 nm. These binding assays can also be used in an equilibrium end point competition format. In this format, the IN catalytic core domain produced a K(i) of 15.2 nm while competing for integrase dimerization, confirming the very tight interaction of IN with itself. In the same format, LEDGF produced a K(i) value of 35 nm when competing for LEDGF binding to IN dimers. In summary, this study describes a methodology combining homogeneous time-resolved fluorescence resonance energy transfer and mathematical modeling to derive the affinities between IN monomers and between LEDGF and IN dimers. This study revealed the significantly tighter nature of the IN-IN dimer compared with the IN-LEDGF interaction.

Comparative study of magnetic resonance angiography, digital subtraction angiography, duplex ultrasound examination with surgical and histological findings of atherosclerotic carotid bifurcation disease

This study was designed in order to determine the diagnostic accuracy in imaging of the extracranial arteries by using magnetic resonance angiography (MRA), digital subtraction angiography (DSA), B-mode duplex ultrasonic examination (DUE) in comparison with the surgical and histological findings of the specimen removed after endarterectomy. The degree of stenosis of the arterial lumen of the surgical specimen was compared with the imaging findings of MRA, DSA and DUE: a) the degree of agreement of stenosis with histologic findings was found in 89% of cases for MRA, in 93% for DSA and 88% for DUE; b) the correlation of morphology of the plaque showed agreement in 91% of the cases with MRA, in 94% with DSA and 87% with DUE; c) the constitution of the plaque was in agreement with DUE findings in 96% of cases. There is no significant difference between the three methods, as far as the estimation of degree of carotid stenosis and morphology of the atheromatous plaque in the carotid arteries. MRA findings are similar with those of DSA and DUE with a high sensitivity and specificity concerning the constitution of the plaque. The combination of MRA and DUE provides all the necessary information concerning the extracranial segments of the cerebral arteries for the preoperative evaluation of patients with carotid disease.

Is cerebral arteriography necessary for decision making in carotid endarterectomy?

The development of ultrasonic diagnostic imaging technics has recently been a competitive diagnostic method in cerebral arteriography. Many vascular surgeons, based on the high specificity and sensitivity of the ultrasonic imaging technics in carotid artery disease, have been performing carotid endarterectomy without arteriography with satisfactory results. In the last four years we have performed in our Department 62 carotid endarterectomies on 57 patients without using cerebral arteriography. In this paper diagnostic ultrasonic imaging and transcranial Doppler technics are presented and the immediate results of carotid endarterectomy in the above series of patients are reported. From our and other authors' experience it is concluded that carotid endarterectomy in patients with carotid artery disease is a safe procedure. Larger series of patients are needed with a longer follow-up in order that carotid endarterectomy without arteriography be accepted by the medical profession as a safe procedure.

Genome mapping and protein coding region identification using bacteriophage Mu

Transposons such as bacteriophage Mu provide a means to clone bacterial genes as alternatives to using standard recombinant DNA technologies. A DNA-cloning and gene-expressing system has been developed with a bacteriophage Mu (DNA capacity of 38 kb) vector that combines the Mu transposition capabilities and a specialized promoter from bacteriophage T7. Genes cloned with this vector can be identified by transcription in vivo with T7 RNA polymerase and subsequent host translation. This system, illustrated with the characterization of a 35-kb region of the Escherichia coli K-12 chromosome, is applicable to other Enterobacteriaceae, which are hosts for Mu phage, and is potentially applicable to other bacteria, including Pseudomonas aeruginosa, which have Mu-like phage, and to other organisms for which high-frequency transposons are available.

Detection of bacteriophage phi 6 minus-strand RNA and novel mRNA isoconformers synthesized in vivo and in vitro, by strand-separating agarose gels

Two urea-free agarose gel protocols that resolve the six individual strands of bacteriophage phi 6 dsRNA were developed and used to analyze phage RNA synthesis in vivo and in vitro. Citrate gels separate strands of the large and medium chromosomes while Tris-borate-EDTA (TBE) gels resolve the medium and small dsRNA segments. Minus strands migrate faster than plus strands on citrate gels but are retarded on TBE gels. A study of electrophoretic conditions showed that pH affects strand resolution on citrate gels, and that voltage gradient, agarose concentration, and ethidium bromide significantly alter strand migration on TBE gels. Analysis of native phi 6 RNA synthesized in vivo and in vitro showed that the large and medium message RNAs comigrate with the corresponding plus strands of denatured virion dsRNA. The small messenger RNA is exceptional. Native small mRNA was detected as three isoconformers in vivo and in vitro. The isoconformers were converted by heat denaturation to a single RNA species that comigrates with the virion s+ strand. Minus strands labeled in vivo were detected only after heat denaturation. Minus strand synthesis was detected also in heat-denatured samples from in vitro phi 6 nucleocapsid RNA polymerase reactions at pH values suboptimal for transcription.

Minus-strand RNA synthesis by the segmented double-stranded RNA bacteriophage phi 6 requires continuous protein synthesis

Bacteriophage phi 6 contains three dsRNA chromosomes. Strand-separating agarose gels were used to study plus- and minus-strand synthesis in vivo and the effect of protein synthesis inhibitors. Analysis of phi 6 RNA synthesis shows low levels of all three dsRNAs and ssRNAs at 10 min, increasing label uptake into all RNAs except the large message from 20 to 60 min, and a greater abundance of medium and small messages than large mRNAs at late times. Isoconformers of the small message are synthesized throughout infection. Northern analysis suggests that large messages made early may persist to direct continuing translation of L-segment-encoded transcription and replication proteins. The time course of phi 6 minus-strand RNA synthesis in vivo, in the absence of background label in host RNAs, is reported for the first time. Label in minus strands is detected only after heat denaturation of RNA samples and appears sequentially in the small, medium, and large strands beginning at 20 min. At both early and late times, chloramphenicol arrests minus-strand synthesis rapidly and all three mRNAs accumulate. The results are consistent with the reovirus asynchronous model for dsRNA viral replication: plus ssRNAs made first are used as templates for minus-strand synthesis. They also indicate that replication protein(s) acts stoichiometrically.

Vital capillaroscopy on microcirculation: pharmacodynamic activity of Daflon 500 mg in venous insufficiency

A group of ten female patients suffering from telengiectasia of the lower limbs was treated with Daflon 500 mg administered orally. The results obtained are presented and discussed.

Generation of cDNA clones of the bacteriophage phi 6 segmented dsRNA genome: characterization and expression of L segment clones

Bacteriophage phi 6 has three dsRNA genome segments of about 3.0, 4.0, and 6.4 kbp. More than 90% of the segmented phi 6 dsRNA genome has been cloned as subchromosomal cDNA fragments, generated by reverse transcription of denatured polyadenylated dsRNA, RNA removal, annealing, filling, size fractionation, tailing, and insertion at the PstI site of pBR322. All of the large (L) segment is represented by five overlapping fragments, 98% of the small (S) segment is present in three fragments, and 67% of the medium (M) segment is contained in two fragments. Fragments have been aligned in linear arrays by Southern blot hybridization and restriction enzyme analysis. The orientation of the ordered fragments with respect to genomic RNA and phi 6 transcriptional direction was determined by comparison of terminal DNA sequences with RNA sequences at the genomic ends of phi 6 RNA. Expression of L segment clones using both Escherichia coli minicells and T7 polymerase/promoter vectors indicate that the order of known phi 6 genes on the large chromosome is: 5'--gene 7, gene 2, gene 4, gene 1--3'. cDNA complementation of a ts mutant, ts411, has located this mutation in gene 4.