Essential role for p38alpha mitogen-activated protein kinase in placental angiogenesis

The p38 family of mitogen-activated protein kinases (MAPKs) mediates signaling in response to environmental stresses and inflammatory cytokines, but the requirements for the p38 MAPK pathway in normal mammalian development have not been elucidated. Here, we show that targeted disruption of the p38alpha MAPK gene results in homozygous embryonic lethality because of severe defects in placental development. Although chorioallantoic placentation is initiated appropriately in p38alpha null homozygotes, placental defects are manifest at 10.5 days postcoitum as nearly complete loss of the labyrinth layer and significant reduction of the spongiotrophoblast. In particular, p38alpha mutant placentas display lack of vascularization of the labyrinth layer as well as increased rates of apoptosis, consistent with a defect in placental angiogenesis. Furthermore, p38alpha mutants display abnormal angiogenesis in the embryo proper as well as in the visceral yolk sac. Thus, our results indicate a requirement for p38alpha MAPK in diploid trophoblast development and placental vascularization and suggest a more general role for p38 MAPK signaling in embryonic angiogenesis.

Fix and flap: the radical orthopaedic and plastic treatment of severe open fractures of the tibia

We performed a retrospective review of the case notes of 84 consecutive patients who had suffered a severe (Gustilo IIIb or IIIc) open fracture of the tibia after blunt trauma between 1990 and 1998. All had been treated by a radical protocol which included early soft-tissue cover with a muscle flap by a combined orthopaedic and plastic surgery service. Our ideal management is a radical debridement of the wound outside the zone of injury, skeletal stabilisation and early soft-tissue cover with a vascularised muscle flap. All patients were followed clinically and radiologically to union or for one year. After exclusion of four patients (one unrelated death and three patients lost to follow-up), we reviewed 80 patients with 84 fractures. There were 67 men and 13 women with a mean age of 37 years (3 to 89). Five injuries were grade IIIc and 79 grade IIIb; 12 were site 41, 43 were site 42 and 29 were site 43. Debridement and stabilisation of the fracture were invariably performed immediately. In 33 cases the soft-tissue reconstruction was also completed in a single stage, while in a further 30 it was achieved within 72 hours. In the remaining 21 there was a delay beyond 72 hours, often for critical reasons unrelated to the limb injury. All grade-IIIc injuries underwent immediate vascular reconstruction, with an immediate cover by a flap in two. All were salvaged. There were four amputations, one early, one mid-term and two late, giving a final rate of limb salvage of 95%. Overall, nine pedicled and 75 free muscle flaps were used; the rate of flap failure was 3.5%. Stabilisation of the fracture was achieved with 19 external and 65 internal fixation devices (nails or plates). Three patients had significant segmental defects and required bone-transport procedures to achieve bony union. Of the rest, 51 fractures (66%) progressed to primary bony union while 26 (34%) required a bone-stimulating procedure to achieve this outcome. Overall, there was a rate of superficial infection of the skin graft of 6%, of deep infection at the site of the fracture of 9.5%, and of serious pin-track infection of 37% in the external fixator group. At final review all patients were walking freely on united fractures with no evidence of infection. The treatment of these very severe injuries by an aggressive combined orthopaedic and plastic surgical approach provides good results; immediate internal fixation and healthy soft-tissue cover with a muscle flap is safe. Indeed, delay in cover (>72 hours) was associated with most of the problems. External fixation was associated with practical difficulties for the plastic surgeons, a number of chronic pin-track infections and our only cases of malunion. We prefer to use internal fixation. We recommend primary referral to a specialist centre whenever possible. If local factors prevent this we suggest that after discussion with the relevant centre, initial debridement and bridging external fixation, followed by transfer, is the safest procedure.

International cancer seminars: a focus on esophageal squamous cell carcinoma

The International Agency for Research on Cancer (IARC) and the US National Cancer Institute (NCI) have initiated a series of cancer-focused seminars [Scelo G, Hofmann JN, Banks RE et al. International cancer seminars: a focus on kidney cancer. Ann Oncol 2016; 27(8): 1382-1385]. In this, the second seminar, IARC and NCI convened a workshop in order to examine the state of the current science on esophageal squamous cell carcinoma etiology, genetics, early detection, treatment, and palliation, was reviewed to identify the most critical open research questions. The results of these discussions were summarized by formulating a series of 'difficult questions', which should inform and prioritize future research efforts.

The functional outcome of severe, open tibial fractures managed with early fixation and flap coverage

We studied the outcome and functional status of 33 patients with 34 severe open tibial fractures (Gustilo grade IIIb and IIIc). The treatment regime consisted of radical debridement, immediate bony stabilisation and early soft-tissue cover using a muscle flap (free or rotational). The review included standardised assessments of health-related quality of life (SF-36 and Euroqol) and measurement of the following parameters: gait, the use of walking aids, limb-length discrepancy, knee and ankle joint function, muscle wasting and the cosmetic appearance of the limb. Personal comments and overall patient satisfaction were also recorded. The mean follow-up was 46 months (15 to 80). There were 30 Gustilo grade IIIb fractures and and four grade IIIc fractures. Of the 33 patients, 29 had primary internal fixation and four, external fixation; 11 (34%) later required further surgery to achieve union and two needed bone transport procedures to reconstruct large segmental defects. The mean time to union was 41 weeks (12 to 104). Two patients (6.1%) developed deep infection; both resolved with treatment. The mean SF-36 physical and mental scores were 49 and 62 respectively. The mean state of health score for the Euroqol was 68. Patients with isolated tibial fractures had a better outcome than those with other associated injuries on both scoring systems. Knee stiffness was noted in seven patients (21%) and ankle stiffness in 19 (56%); 12 patients (41%) returned to work. Our results compare favourably with previous outcome measurements published for both limb salvage and amputation. All patients were pleased to have retained their limbs.

A functional update of the Escherichia coli K-12 genome

BACKGROUND

Since the genome of Escherichia coli K-12 was initially annotated in 1997, additional functional information based on biological characterization and functions of sequence-similar proteins has become available. On the basis of this new information, an updated version of the annotated chromosome has been generated.

RESULTS

The E. coli K-12 chromosome is currently represented by 4,401 genes encoding 116 RNAs and 4,285 proteins. The boundaries of the genes identified in the GenBank Accession U00096 were used. Some protein-coding sequences are compound and encode multimodular proteins. The coding sequences (CDSs) are represented by modules (protein elements of at least 100 amino acids with biological activity and independent evolutionary history). There are 4,616 identified modules in the 4,285 proteins. Of these, 48.9% have been characterized, 29.5% have an imputed function, 2.1% have a phenotype and 19.5% have no function assignment. Only 7% of the modules appear unique to E. coli, and this number is expected to be reduced as more genome data becomes available. The imputed functions were assigned on the basis of manual evaluation of functions predicted by BLAST and DARWIN analyses and by the MAGPIE genome annotation system.

CONCLUSIONS

Much knowledge has been gained about functions encoded by the E. coli K-12 genome since the 1997 annotation was published. The data presented here should be useful for analysis of E. coli gene products as well as gene products encoded by other genomes.

A 52-week open-label study of the safety and tolerability of paliperidone palmitate in patients with schizophrenia

The safety and tolerability of paliperidone palmitate, an injectable atypical antipsychotic agent, were assessed in a 1-year open-label extension of a double-blind study in patients with schizophrenia. Patients from the double-blind study who experienced a recurrence, remained recurrence free until study end, or who were in the transition, maintenance or double-blind phases and had received at least one injection of paliperidone palmitate when enrollment was stopped, were eligible for the open-label extension. Patients received gluteal injections of paliperidone palmitate once every 4 weeks: starting dose 50 mg eq. followed by 25, 50, 75, or 100 mg eq. flexible dosing. Of the 388 patients enrolled, 288 completed the open-label extension. During the open-label extension, the median (range) duration of exposure to paliperidone palmitate was 338 days (10; 390), and 74% of patients received all 12 open-label injections of paliperidone palmitate. The most frequent (≥ 5% in total group) adverse events were insomnia (7%); worsening of schizophrenia; nasopharyngitis; headache; and weight increase (6% each). Potentially prolactin-related adverse events occurred in 13 (3%) patients, mostly women, and none resulted in study discontinuation. Extrapyramidal treatment-emergent adverse events were reported in 25 (6%) patients; tremor was the most frequently reported (n = 8, 2%). At open-label extension endpoint, investigator-rated redness at the injection site was observed in ≤ 4% of patients in each group. Injection-site pain was rated by investigators as absent in 82-87% of patients. Schizophrenia symptoms measured by Positive and Negative Syndrome Scale and personal and social performance changes improved during the open-label extension.

Self-reported photophobic symptoms in migraineurs and controls are reliable and predict diagnostic category accurately

OBJECTIVES

To assess the reliability of self-reported photophobia across different patient populations and to examine how visual stress thresholds and photophobic symptoms may be predictive of diagnosis.

BACKGROUND

Relatively little is known about interictal photophobia in migraine. In particular, the variability of photophobia across different patient groups has not previously been studied, and a pathophysiological hypothesis to account for the symptoms is not agreed upon.

METHODS AND RESULTS

Study 1 compared 99 self-selected Dutch patients and 101 headache-free controls using survey methods. Patients both with and without aura were significantly more likely to report symptoms, such as the wearing of sunglasses in normal daylight, consistent with interictal photophobia. Study 2 replicated these findings in a series of consecutive referrals to a headache clinic in the United States. Study 3 used a specially designed laboratory test to examine the threshold for visual stress in those patients who had participated in study 2. Visual stress thresholds were significantly lower in patients than in controls. A discriminant function analysis of data from both studies 2 and 3 showed that diagnostic category (migraine; control) could be predicted from photophobic symptoms and visual stress thresholds at a level significantly better than chance.

CONCLUSIONS

We suggest that interictal photophobia is common in migraine and similar across different patient populations. One pathophysiological hypothesis is that interictal photophobia is associated with cortical hypersensitivity to stimulation. The predictive validity of interictal photophobic symptoms suggests that clinical diagnosis may be aided by questioning the patient about light sensitivity in the period between attacks.

Mutagenesis of organophosphorus hydrolase to enhance hydrolysis of the nerve agent VX

Organophosphorus hydrolase (OPH) is capable of hydrolyzing a wide variety of organophosphorus pesticides and chemical warfare agents. However, the hydrolytic activity of OPH against the warfare agent VX is less than 0.1% relative to its activity against parathion and paraoxon. Based on the crystal structure of OPH and the similarities it shares with acetylcholinesterase, eight OPH mutants were constructed with the goal of increasing OPH activity toward VX. The activities of crude extracts from these mutants were measured using VX, demeton-S methyl, diisopropylfluoro-phosphate, ethyl parathion, paraoxon, and EPN as substrates. One mutant (L136Y) displayed a 33% increase in the relative VX hydrolysis rate compared to wild type enzyme. The other seven mutations resulted in 55-76% decreases in the relative rates of VX hydrolysis. There was no apparent relationship between the hydrolysis rates of VX and the rates of the other organophosphorus compounds tested.

Practical guidance for dosing and switching paliperidone palmitate treatment in patients with schizophrenia

OBJECTIVE

This article overviews the recommended dosing strategies for the treatment of schizophrenia patients using the recently FDA-approved once-monthly long-acting injectable atypical antipsychotic, paliperidone palmitate.

METHODS

Using pharmacokinetic (PK), efficacy and safety data from clinical trials and a comprehensive population PK simulation model, dosing recommendations for paliperidone palmitate have been generated.

RESULTS

The recommended initiation regimen is 150 mg eq. paliperidone palmitate (234 mg) on Day 1 followed by 100 mg eq. paliperidone palmitate (156 mg) on Day 8, each administered into the deltoid muscle, using a 1-inch 23 gauge (G) needle in those <90 kg and a 1.5-inch 22 G needle in those > or =90 kg. No oral supplementation is required. Monthly maintenance doses of paliperidone palmitate range from 25-150 mg eq. (39-234 mg; recommended dose of 75 mg eq. [117 mg]) injected into the deltoid (using weight-adjusted needle) or gluteal (using 1.5 inch 22 G needle) muscle. The Day 8 dose may be administered +/-2 days and monthly doses +/-7 days, without a clinically significant impact on plasma concentrations. In patients with mild renal impairment (creatinine clearance [CrCL]: 50-80 mL/min), dosage should be adjusted. No dose adjustment is required in patients with mild or moderate hepatic impairment; no data currently exist regarding severe hepatic impairment. Elderly patients with normal renal function should receive the same dosage as younger adult patients with normal renal function. In the event of an age-related decline in CrCL, dosage should be adjusted accordingly. Paliperidone palmitate treatment can be initiated the day after discontinuing previous oral antipsychotic treatment. Paliperidone palmitate should be initiated at the next scheduled injection, and monthly thereafter, in patients switching from other long-acting injectable antipsychotics, including long-acting risperidone.

CONCLUSIONS

These data provide practical guidance to clinicians on how to use paliperidone palmitate in adult patients with schizophrenia.

Homology-based annotation yields 1,042 new candidate genes in the Drosophila melanogaster genome

The approach to annotating a genome critically affects the number and accuracy of genes identified in the genome sequence. Genome annotation based on stringent gene identification is prone to underestimate the complement of genes encoded in a genome. In contrast, over-prediction of putative genes followed by exhaustive computational sequence, motif and structural homology search will find rarely expressed, possibly unique, new genes at the risk of including non-functional genes. We developed a two-stage approach that combines the merits of stringent genome annotation with the benefits of over-prediction. First we identify plausible genes regardless of matches with EST, cDNA or protein sequences from the organism (stage 1). In the second stage, proteins predicted from the plausible genes are compared at the protein level with EST, cDNA and protein sequences, and protein structures from other organisms (stage 2). Remote but biologically meaningful protein sequence or structure homologies provide supporting evidence for genuine genes. The method, applied to the Drosophila melanogaster genome, validated 1,042 novel candidate genes after filtering 19,410 plausible genes, of which 12,124 matched the original 13,601 annotated genes. This annotation strategy is applicable to genomes of all organisms, including human.

Pilot randomized trial of nutritional supplementation in patients with tuberculosis and HIV-tuberculosis coinfection receiving directly observed short-course chemotherapy for tuberculosis

OBJECTIVE

To investigate the effects of nutritional supplementation on the outcome and nutritional status of south Indian patients with tuberculosis (TB) with and without human immunodeficiency virus (HIV) coinfection on anti-tuberculous therapy.

METHOD

Randomized controlled trial on the effect of a locally prepared cereal-lentil mixture providing 930 kcal and a multivitamin micronutrient supplement during anti-tuberculous therapy in 81 newly diagnosed TB alone and 22 TB-HIV-coinfected patients, among whom 51 received and 52 did not receive the supplement. The primary outcome evaluated at completion of TB therapy was outcome of TB treatment, as classified by the national programme. Secondary outcomes were body composition, compliance and condition on follow-up 1 year after cessation of TB therapy and supplementation.

RESULTS

There was no significant difference in TB outcomes at the end of treatment, but HIV-TB coinfected individuals had four times greater odds of poor outcome than those with TB alone. Among patients with TB, 1/35 (2.9%) supplemented and 5/42(12%) of those not supplemented had poor outcomes, while among TB-HIV-coinfected individuals, 4/13 (31%) supplemented and 3/7 (42.8%) non-supplemented patients had poor outcomes at the end of treatment, and the differences were more marked after 1 year of follow-up. Although there was some trend of benefit for both TB alone and TB-HIV coinfection, the results were not statistically significant at the end of TB treatment, possibly because of limited sample size.

CONCLUSION

Nutritional supplements in patients are a potentially feasible, low-cost intervention, which could impact patients with TB and TB-HIV. The public health importance of these diseases in resource-limited settings suggests the need for large, multi-centre randomized control trials on nutritional supplementation.

Refractory thrombotic thrombocytopenic purpura following influenza vaccination

Thrombotic thrombocytopenic purpura (TTP) is characterised by the systemic microvascular aggregation of platelets causing ischaemia of the brain and other organs. We describe the case of a 54 year-old man who presented with neurological signs, fever, severe thrombocytopenia, microangiopathic haemolytic anaemia and renal failure 5 days after receiving an influenza vaccination. He was diagnosed with acute refractory TTP caused by autoantibody-mediated ADAMTS-13 deficiency. He required stabilisation on the critical care unit before being successfully treated with 3 l plasma exchanges for 21 days and rituximab (MabThera) at a dose of 375 mg x m(-2), given weekly for a total of 4 weeks. Vaccination is an important part of preventative medicine and reduces morbidity and mortality. Only in a few rare cases has vaccination been associated with autoimmune pathology. We could find only one similar case report of thrombotic thrombocytopenic purpura following influenza vaccination. In addition to plasma exchange, rituximab appears to be effective and well tolerated in the treatment of refractory thrombotic thrombocytopenic purpura.

Alpha-actinin interactions with syndecan-4 are integral to fibroblast-matrix adhesion and regulate cytoskeletal architecture

All cells of the musculoskeletal system possess transmembrane syndecan proteoglycans, notably syndecan-4. In fibroblasts it regulates integrin-mediated adhesion to the extracellular matrix. Syndecan-4 null mice have a complex wound repair phenotype while their fibroblasts have reduced focal adhesions and matrix contraction abilities. Signalling through syndecan-4 core protein to the actin cytoskeleton involves protein kinase Cα and Rho family G proteins but also direct interactions with α-actinin. The contribution of the latter interaction to cell-matrix adhesion is not defined but investigated here since manipulation of Rho GTPase and its downstream targets could not restore a wild type microfilament organisation to syndecan-4 null cells. Microarray and protein analysis revealed no significant alterations in mRNA or protein levels for actin- or α-actinin associated proteins when wild type and syndecan-4 knockout fibroblasts were compared. The binding site for syndecan-4 cytoplasmic domain was identified as spectrin repeat 4 of α-actinin while further experiments confirmed the importance of this interaction in stabilising cell-matrix junctions. However, α-actinin is also present in adherens junctions, these organelles not being disrupted in the absence of syndecan-4. Indeed, co-culture of wild type and knockout cells led to adherens junction-associated stress fibre formation in cells lacking syndecan-4, supporting the hypothesis that the proteoglycan regulates cell-matrix adhesion and its associated microfilament bundles at a post-translational level. These data provide an additional dimension to syndecan function related to tension at the cell-matrix interface, wound healing and potentially fibrosis.

Functional profiling in Streptococcus mutans: construction and examination of a genomic collection of gene deletion mutants

A collection of tagged deletion mutant strains was created in Streptococcus mutans UA159 to facilitate investigation of the aciduric capability of this oral pathogen. Gene-specific barcoded deletions were attempted in 1432 open reading frames (representing 73% of the genome), and resulted in the isolation of 1112 strains (56% coverage) carrying deletions in distinct non-essential genes. As S. mutans virulence is predicated upon the ability of the organism to survive an acidic pH environment, form biofilms on tooth surfaces, and out-compete other oral microflora, we assayed individual mutant strains for the relative fitness of the deletion strain, compared with the parent strain, under acidic and oxidative stress conditions, as well as for their ability to form biofilms in glucose- or sucrose-containing medium. Our studies revealed a total of 51 deletion strains with defects in both aciduricity and biofilm formation. We have also identified 49 strains whose gene deletion confers sensitivity to oxidative damage and deficiencies in biofilm formation. We demonstrate the ability to examine competitive fitness of mutant organisms using the barcode tags incorporated into each deletion strain to examine the representation of a particular strain in a population. Co-cultures of deletion strains were grown either in vitro in a chemostat to steady-state values of pH 7 and pH 5 or in vivo in an animal model for oral infection. Taken together, these data represent a mechanism for assessing the virulence capacity of this pathogenic microorganism and a resource for identifying future targets for drug intervention to promote healthy oral microflora.

Development and validation of a sensitive analytical method for the simultaneous determination of buprenorphine and norbuprenorphine in human plasma

A sensitive, specific, and robust capillary gas chromatography-mass spectrometry method has been developed and validated for simultaneous determination of buprenorphine and its active metabolite, norbuprenorphine, in human plasma. Sample preparation involved a clean-up procedure using a Bond Elut Certify cartridge followed by derivatization with pentafluoropropionic anhydride. Separation was carried out on a HP-1 fused silica capillary column using helium as the carrier gas. Selected ion monitoring was used in the electron impact mode. Excellent linearity was found between 0.10 and 20.0 ng/ml with a limit of quantitation of 0.05 and 0.10 ng/ml for buprenorphine and norbuprenorphine, respectively. Interday and intraday assay precisions (%CV) and accuracies were within 15.0% for buprenorphine and norbuprenorphine, respectively. Recoveries were quantitative and concentration-independent. This method will be applied to pharmacokinetic/pharmacodynamic/bioequivalence studies of buprenorphine in humans.

Review: Head and neck squamous cell carcinoma in sub-Saharan Africa

AIM

Review the literature from 1990 to 2013 to determine known anatomic sites, risk factors, treatments, and outcomes of head and neck squamous cell carcinoma (HNSCC) in sub-Saharan Africa.

METHODS

Using a systematic search strategy, literature pertaining to HNSCC in sub-Saharan Africa was reviewed and patient demographics, anatomic sites, histology, stage, treatment, and outcomes were abstracted. The contributions of human immunodeficiency virus (HIV), human papillomavirus (HPV) and behavioural risk factors to HNSCC in the region were assessed.

RESULTS

Of the 342 papers identified, 46 were utilized for review, including 8611 patients. In sub-Saharan Africa, the oropharyngeal/oral cavity was found to be the most common site, with 7750 cases (90% of all cases). Few papers distinguished oropharyngeal from oral cavity, making identification of possible HPV-associated oropharyngeal squamous cell carcinoma (SCC) difficult. SCC of the nasopharynx, nasal cavity, or paranasal sinuses was identified in 410 patients (4.8% of all cases). Laryngeal SCC was found in 385 patients (4.5% of all cases), and only 66 patients (0.8% of all cases) with hypopharyngeal SCC were identified. In 862 patients with data available, 43% used tobacco and 42% used alcohol, and reported use varied widely and was more common in laryngeal SCC than that of the oropharyngeal/oral cavity. Toombak and kola nut use was reported to be higher in patients with HNSCC. Several papers reported HIV-positive patients with HNSCC, but it was not possible to determine HNSCC prevalence in HIV-positive compared to negative patients. Reports of treatment and outcomes were rare.

CONCLUSIONS

The oropharyngeal/oral cavity was by far the most commonly reported site of HNSCC reported in sub-Saharan Africa. The roles of risk factors in HNSCC incidence in sub-Saharan Africa were difficult to delineate from the available studies, but a majority of patients did not use tobacco and alcohol.

The Quilty lesion enigma: focal apoptosis/necrosis and lymphocyte subsets in human cardiac allografts

Quilty lesions, as first described by Billingham in 1981, or 'Quilty Effect' (QE) are distinct endomyocardial mononuclear cell infiltrates that have been observed in human heart transplant recipients, as well as in experimental models of heart transplantation. In the present investigations, the pattern and extent of apoptosis (programmed cell death) and myocyte necrosis, as well as specific lymphocyte subsets in Quilty lesions was assessed. Endomyocardial biopsies obtained from 13 patients at 10-3362 days post-transplant were examined. Apoptosis, as identified by DNA nick end-labeling, was found in myocytes at the periphery of Quilty lesions in 11 of 13 cases (85%), and 'early' stages of myocyte necrosis, as demonstrated by specific staining with alpha light chain myosin monoclonal antibodies (mAb), was observed at the same sites in 10 of 13 cases (77%) of both Quilty type A and type B lesions. Apoptosis was not identified in the lymphocyte infiltrates of any of the lesions examined. Lymphocyte subsets were characterized using mAb for T cell receptor (CD3), for helper/inducer T cells (CD4), for cytotoxic/suppressor T cells (CD8) and for mature B cells (CD20). Immunostaining revealed separate clusters of T lymphocytes with less prevalent B cells within the Quilty lesions. CD4+ cells were found in larger numbers than CD8+ cells in all cases. Non-B, non-T large lymphocytes were occasionally present. Except for the extent of the cellular infiltrate, no major cytochemical lymphocyte distribution differences were found between Quilty type A and B lesions. Myocyte apoptosis and early necrosis at the periphery of Quilty lesions suggest that early myocyte injury occurring in B lesions may represent initial or 'abortive stages' of cardiac allograft rejection. Why these lesions do not progress to overt rejection indeed warrant further detailed studies.

Conformational insights into the lesion and sequence effects for arylamine-induced translesion DNA synthesis: 19F NMR, surface plasmon resonance, and primer kinetic studies

Adduct-induced DNA damage can affect transcription efficiency and DNA replication and repair. We previously investigated the effects of the 3′-next flanking base (G*CT vs G*CA; G*, FABP, N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl; FAF, N-(2′-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene) on the conformation of arylamine-DNA lesions in relation to E. coli nucleotide excision repair (JainV., HiltonB., LinB., PatnaikS., LiangF., DarianE., ZouY., MackerellA. D.Jr., and ChoB. P. (2013) Nucleic Acids Res., 41, 869−88023180767). Here, we report the differential effects of the same pair of sequences on DNA replication in vitro by the polymerases exofree Klenow fragment (Kf-exo^–) and Dpo4. We obtained dynamic ¹⁹F NMR spectra for two 19-mer modified templates during primer elongation: G*CA [d(5′-CTTACCATCG*CAACCATTC-3′)] and G*CT [d(5′-CTTACCATCG*CTACCATTC-3′)]. We found that lesion stacking is favored in the G*CT sequence compared to the G*CA counterpart. Surface plasmon resonance binding results showed consistently weaker affinities for the modified DNA with the binding strength in the order of FABP > FAF and G*CA > G*CT. Primer extension was stalled at (n) and near (n – 1 and n + 1) the lesion site, and the extent of blockage and the extension rates across the lesion were influenced by not only the DNA sequences but also the nature of the adduct’s chemical structure (FAF vs FABP) and the polymerase employed (Kf-exo^– vs Dpo4). Steady-state kinetics analysis with Kf-exo^– revealed the most dramatic sequence and lesion effects at the lesion (n) and postinsertion (n + 1) sites, respectively. Taken together, these results provide insights into the important role of lesion-induced conformational heterogeneity in modulating translesion DNA synthesis.

ATP-Dependent colchicine transport by human erythrocyte glutathione conjugate transporter

We have recently demonstrated mutually inhibitory ATP-dependent transport of dinitrophenyl-S-glutathione (DNP-SG) and doxorubicin by DNP-SG ATPase purified from human erythrocyte membranes (S. Awasthi et al., 1998a,b). Our previous studies indicate a broad substrate specificity for this transport mechanism, including some P-glycoprotein substrates. Present studies were carried out to determine whether colchicine (COL), a classical P-glycoprotein substrate, could be transported by purified human erythrocyte DNP-SG ATPase reconstituted in artificial liposomes. We also investigated whether leukotriene C4 (LTC4), an endogenous proinflammatory glutathione-conjugate derived from arachidonic acid, would inhibit colchicine transport. Uptake of COL was compared in proteoliposomes reconstituted with the purified DNP-SG ATPase as well as control liposomes in the presence or absence of ATP. Increased colchicine uptake was observed upon addition of ATP to proteoliposomes, but not control liposomes. Uptake was linear with respect to the amount of vesicle protein used. Sensitivity to osmolarity was consistent with intravesicular COL accumulation. The ATP-dependent colchicine uptake was sensitive to temperature in a manner consistent with a protein-mediated transport process with activation energy of 7.3 kcal/mol. Time-dependent COL uptake by proteoliposomes in the presence of ATP was consistent with a single compartment model with an apparent rate constant of 0.21 +/- 0.02 min-1. Kinetic studies indicated a saturable behavior with respect to ATP (Km 2.3 +/- 0.7 mM) and colchicine (Km 4.3 +/- 0.2 microM). LTC4 was found to be a competitive inhibitor of COL transport (Kis 16.4 microM). Since DNP-SG ATPase is present in many tissues, it may play an important role in determining colchicine accumulation in cells. Increased LTC4 would tend to increase cellular COL accumulation.