Hydrated electrons induce the formation of interstrand cross-links in DNA modified by cisplatin adducts.

Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel electrophoresis analysis demonstrates the formation of cisplatin-interstrand crosslinks from the cisplatin-intrastrand species. The rate constant per base for the reaction between hydrated electrons and the double-stranded oligonucleotides with and without cisplatin containing a mismatched region was determined by pulse radiolysis to be 7 × 109 and 2 × 109 M-1 s-1, respectively. These results provide a better understanding of the radiosensitizing effect of cisplatin adducts in hypoxic tumors and of the formation of interstrand crosslinks, which are difficult for cells to repair.

Presence of parasite DNA in clinically unaffected nasal mucosa during cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis.

OBJECTIVES: We aimed to detect Leishmania DNA carriage in nasal mucosa of individuals with cutaneous leishmaniasis (CL) caused by Leishmania (Viannia) braziliensis. METHODS: A cross-sectional study was performed in all individuals with CL without nasal lesions (n = 153) attended within 2 years in an endemic area of L. (Viannia) braziliensis in Bahia (Brazil). An otorhinolaryngologist assessed the clinical status of the nasal mucosa by anterior rhinoscopy and endoscopic examinations. Swab samples were collected for parasite DNA detection by PCR from all individuals before standard treatment for leishmaniasis. A second evaluation 3 months after treatment was performed to assess clinical outcomes. RESULTS: Parasite DNA was detected in 7.8% (12/153) of clinically healthy nasal mucosa of individuals with CL. Interestingly, DNA was more frequently identified in individuals with more skin lesions (median 1.5, interquartile range (IQR) 1-3.5 versus 1.0, IQR 1-1.5; p 0.044), or larger injuries (median 2.7, IQR 2-3.8 versus 1.6, IQR 1-2.5; p 0.013). Additionally, the disease of those individuals with positive PCR evolved more frequently to unusual forms of leishmaniasis (recidiva cutis and disseminated) (45.5% (5/11) versus 11.5% (14/122); p 0.009), and required more cycles of treatment to reach clinical cure (median 2, IQR 1-4 versus 1, IQR 1-2; p 0.05). CONCLUSION: These findings suggest an early parasite tropism to nasal mucosa in L. (Viannia) braziliensis infection and a clinical phenotype of CL cases associated with parasite DNA in nasal mucosa. Future studies should evaluate whether PCR of nasal swab samples could serve as a prognostic tool for individuals at risk of mucocutaneous leishmaniasis.

Fertility Life Table of Tetranychus palmarum Flechtmann & Noronha (Acari: Tetranychidae) in Oil Palm.

Some species of spider mites belonging to the Tetranychidae family are known to associate with oil palm (Elaeis guineensis Jacq. - Arecaceae). The occurrence of Tetranychus palmarum Flechtmann & Noronha (Acari, Tetranychidae) was verified on oil palm seedlings under greenhouse conditions in the State of Pará in Northern Brazil. Plants with colonies of T. palmarum presented yellowish spots on leaflets and leaves with chlorosis. The objective of this study was to access the biology and fertility life table of T. palmarum in E. guineensis leaves. The experiment was conducted under four constant temperatures, 22, 25, 28, and 31°C, at 70 ± 10% RH under a 12:12 LD photoperiod. The duration of the egg-to-adult period was 18.4 and 9.8 days, at 22 and 31°C, respectively. The parameters of the fertility life table showed that 28°C is most suitable for the development and reproduction of T. palmarum, with higher values for reproductive parameters (R o , r m , and λ) and lower values for duplicating the population (TD). Therefore, it is apparent that the best temperature conditions for the development of T. palmarum are found in the warmer regions of Brazil, such as those observed in northern Brazil.

Scale Insects (Hemiptera: Coccoidea) on Myrciaria dubia (Myrtaceae) in Brazil.

Commercial cultivation of the fruit tree Myrciaria dubia (Myrtaceae) is being developed in Brazil but phytophagous insects, including scale insects (Hemiptera: Coccoidea), can become pests in plantations. The coccids Ceroplastes jamaicensis White, Coccus viridis (Green), Parasaissetia nigra (Nietner), Pseudokermes vitreus (Cockerell) (Coccidae), and the diaspidid Pseudaonidia trilobitiformis (Green) were collected on M. dubia in the municipality of Belém and Tomé-Açu, state of Pará (PA), metropolitan and Northeast Pará mesoregions, Brazil. A key to species of Coccoidea recorded on M. dubia, based on adult females, is provided. Photographs for all scale insects reported on M. dubia are provided. Ceroplastes jamaicensis is recorded for the first time for Brazil and is herein reported for the first time associated with this host.

Análise dos itens da Escala de Aconselhamento Profissional - EAP- pelo Modelo de Rasch / Analysis of items of Escala de Aconselhamento Profissional by the Rasch model

Esta pesquisa teve como objetivo analisar os itens da Escala de Aconselhamento Profissional segundoo modelo de Rasch, enfocando principalmente o funcionamento diferencial dos itens em relação aotipo de escola (particular ou pública). Participaram 615 estudantes do ensino médio (68% do sexofeminino) de instituições do interior do estado de São Paulo, sendo 179 de escola privada e 436 deescola pública, com idades variando entre 14 a 27 anos e média de 16,36. Os resultados mostraramque os itens tiveram, em geral, valores adequados de ajuste. Em relação à análise de DIF, observou-seque 20 itens estavam enviesados, sendo que o favorecimento ao tipo de escola mostrou-serelativamente equilibrado. Sugere-se uma análise mais aprofundada dos itens, para verificar se énecessária a separação da escala em duas versões, ou até mesmo se esse viés é parte do constructo(AU)

Antibacterial action of doped CoFe2O4 nanocrystals on multidrug resistant bacterial strains.

The bactericidal effect of pristine and doped cobalt ferrite nanoparticles has been evaluated against multiple drug resistant clinical strains by assessing the number of colony-forming units (CFU). Monophasic polycrystalline ferrites have been prepared by the malate-glycolate sol-gel autocombustion method as confirmed by the X-ray diffraction study. Various changes occurring during the preparative stages have been demonstrated using TG-DTA analysis which is well complemented by the FTIR spectroscopy. The antibacterial studies carried out demonstrate a bactericidal effect of the nanoparticles wherein the number of CFU has been found to decrease with doping. Cellular distortions have been revealed through SEM. Variation in the number of CFU with dopant type has also been reported herein.

Estudo correlacional entre interesses profissionais e autoeficácia com tecnologias / Correlational study between vocational interests and self-efficacy with technologists

No contexto da orientação profissional, interesses profissionais e autoeficácia são construtos de grande importância para o autoconhecimento dos orientandos. O presente estudo teve por objetivo verificar as relações entre os construtos junto a tecnólogos. Participaram 172 estudantes, com idades entre 19 e 57 anos. Os instrumentos utilizados foram a Escala de Aconselhamento Profissional (EAP) e a Escala de Autoeficácia para Atividades Ocupacionais (EAAOc). Os resultados indicaram correlações entre os interesses profissionais e a autoeficácia com magnitudes variando entre baixas e altas; para os interesses profissionais e as fontes de autoeficácia, muitos coeficientes variaram de baixos a muito baixos. A pesquisa possibilitou identificar outras evidências de validade, recomendando-se novos estudos com tecnólogos de diferentes cursos e instituições de ensino (AU)

Carcinoma ex pleomorphic adenoma in a Brazilian population: clinico-pathological analysis of 38 cases.

Carcinoma ex pleomorphic adenoma (CXPA) is a rare tumour, with different prevalence rates reported among studies. Epidemiological studies of large series of CXPAs in developing countries are scarce. The aim of the present study was to describe Brazilian patients with CXPA; this was a retrospective study of 38 patients. Demographic and clinico-pathological features were evaluated. No preferential gender was found, and the mean age at diagnosis was 57.6 years. The most commonly involved site was the parotid, followed by the submandibular and the minor salivary glands. A prevalence of clinical stages III and IV was observed at diagnosis. The most common histological subtypes were salivary duct carcinoma, adenocarcinoma not otherwise specified, myoepithelial carcinoma, and epithelial-myoepithelial carcinoma. Moreover, by invasive phase, most were frankly invasive carcinoma. Recurrence was observed in seven out of 24 patients with outcome information available, and all were invasive cases. All seven patients died of causes related to the disease. The distributions of cases according to age, gender, tumour location, and clinical stage were similar to those reported in the literature. Frankly invasive cases presented a worse prognosis. More information is needed to further our understanding of the clinico-pathological aspects of CXPA.

Detection of Leishmania (L.) chagasi in canine skin.

Canine visceral leishmaniasis (CVL) is caused by a protozoa parasite of the specie Leishmania (L.) chagasi endemic for humans and dogs in many regions of Brazil. The purpose of the present study was the detection of (L.) chagasi in canine skin tissues from three different groups of clinical signs: asymptomatic, oligosymptomatic and polysymptomatic Leishmania-infected dogs. Lesional or non-lesional skin tissue samples from 34 naturally infected dogs were obtained and processed by histochemistry (HE) and immunohistochemistry (IMHC) for direct parasitological examination and the results were compared with a polymerase chain reaction (PCR) method. IMHC and HE methods detected intact Leishmania-amastigote parasites in lesional and no lesional skin, particularly in asymptomatic and oligosymptomatic dogs. 50% of skin samples collected from asymptomatic and 21.4% from oligosymptomatic dogs had parasites in their skins even though with mild inflammatory reaction or without any macroscopic dermatological alterations. On the other hand, 100% of polysymptomatic dogs showed several forms of clinical dermatological alterations and 91.7% had intact amastigotes with parasite load ranging from mild to intense. By PCR, DNA of Leishmania spp. was detected in 97.8% skin samples regardless clinical status of the dogs or IMHC/HE test results. PCR on skin was a sensitive procedure for CVL diagnosis, but direct observation of intact parasite in skin biopsies, particularly by IMHC, may be also considered to support the diagnosis.

Ácaros (Arachnida: Acari) associados a plantas ornamentais tropicais na região litoral sul da Bahia / Mites (Arachnida: Acari) associated with tropical ornamental plants in the southern coastal region of Bahia, Brazil

Em razão da expansão do agronegócio de flores tropicais na região Litoral Sul da Bahia e da inexistência de estudos com ácaros associados a essas culturas na região foram realizadas coletas no período de setembro de 2006 a junho de 2007 em 34 espécies/cultivares de plantas ornamentais tropicais das famílias Costaceae, Heliconiaceae, Musaceae e Zingiberaceae de onze propriedades localizadas em seis municípios (13º 21' a 14º 58' de latitude Sul e 39º 04' a 39º 27' de longitude Oeste), com o objetivo de se determinar a composição de grupos funcionais nos cultivos analisando-se a comunidade no nível de família por meio de índices faunísticos. Os ácaros foram coletados, mensalmente, em folhas e inflorescências. Foram registradas 22 famílias. Mais da metade dos ácaros pertenceu a famílias predominantemente predadoras, com destaque para os fitoseídeos. Com base em índices faunísticos, as famílias Phytoseiidae e Tetranychidae atingiram os índices máximos de dominância, abundância, frequência e constância. Tetraniquídeos (Tetranychus aff. abacae Baker & Pritchard) foram registrados em Alpinia purpurata (Viell.) Schum, Etlingera elatior (Jack) R. M. Smith, Musa coccinea H.C. Andrews, Strelitzia reginae Aiton, Zingiber spectabilis Griffith, Heliconia latispatha Benth., Heliconia rivularis L. Emygd. & E. Santos, Heliconia rostrata Ruiz & Pavon, Heliconia wagneriana Petersen e nos cultivares de helicônias 'Nappi Yellow', 'Jacquinii', 'She', 'Golden Torch', 'Red Opal', 'Alan Carle', 'Fire Bird' e 'Nappi Red'. As espécies/cultivares com maior número de famílias de ácaros foram H. latispatha. H. rostrata. M. coccinea, 'Fire Bird', E. elatior 'Vermelha', Z. spectabilis. E. elatior 'Rosa', A. purpurata 'Vermelha' e helicônias 'Alan Carle', 'Sassy' e 'She'. Não foram detectados nas plantas danos que causassem prejuízos econômicos aos produtores. As pequenas populações de fitófagos sugerem um eficiente controle natural por predadores, patógenos ou outros fatores.

Due to the expansion of the tropical flower agribusiness in the southern coastal region of Bahia State, Brazil, and the lack of studies on mites associated to these cultures in the region, mite surveys were conducted from September 2006 to June 2007 in 34 species/cultivars of ornamental plants of the families Costaceae, Heliconiaceae, Musaceae and Zingiberaceae on 11 properties located in 6 counties (13º 21' to 14º 58' of south latitude and 39º 04' to 39º 27' of west longitude) with the aim of determining the composition of functional groups in the field through the analysis of the community at the family level using faunistic indexes. Mites were collected monthly from leaves and inflorescences. Twenty-two families were recorded. More than half of the mites pertained to predominantly predatory families, mainly to phytoseiids. Based on faunistic indexes, the families Phytoseiidae and Tetranychidae showed the maximum indexes of dominance, abundance, frequency and constancy. Tetranychids (Tetranychus aff. abacae Baker & Pritchard) were reported on Alpinia purpurata (Viell.) Schum, Etlingera elatior (Jack) R. M. Smith, Musa coccinea H.C. Andrews, Strelitzia reginae Aiton, Zingiber spectabilis Griffith, Heliconia latispatha Benth., Heliconia rivularis L. Emygd. & E. Santos, Heliconia rostrata Ruiz & Pavon, Heliconia wagneriana Petersen and on the cultivars of heliconia 'Nappi Yellow,' 'Jacquinii,' 'She,' 'Golden Torch,' 'Red Opal,' 'Alan Carle,' 'Fire Bird' and 'Nappi Red.' The species/cultivars with the largest number of mite families were H. latispatha. H. rostrata. M. coccinea, 'Fire Bird,' E. elatior 'Vermelha,' Z. spectabilis. E. elatior 'Rosa,' A. purpurata 'Vermelha' and heliconias 'Alan Carle,' 'Sassy' and 'She.' No mite-induced economic losses on tropical flower cultures were observed. The low population levels of phytophagous mites suggest an efficient natural control by predators, pathogens and other factors.

Desempenho animal e produtividade de pastagens tropicais no noroeste do Rio Grande do Sul / Animal performance and productivity of tropical pasture in Northwest of Rio Grande do Sul

Avaliou-se a produtividade do capim-elefante anão e do tifton 85 sob pastejo contínuo no noroeste do Rio Grande do Sul, utilizando-se 12 vacas da raça Holandesa, multíparas e com cerca de 100 dias de lactação. Foi aplicada a técnica dos animais reguladores para ajustes da carga animal de forma a manter a oferta de lâminas foliares de 4 por cento. No primeiro ano experimental, o capim-elefante anão e o tifton 85 apresentaram diferenças significativas quanto às taxas médias de acúmulo de lâminas foliares (31,2 vs 22,6kg/ha/dia) e produção animal (17,4 vs 20kg de leite/vaca/dia). No segundo, o tifton 85 foi superior ao capim-elefante anão quanto à taxa de acúmulo de matéria seca de lâminas foliares (38,8 vs 21,9kg/ha/dia), capacidade de suporte (2157 vs 1084kg de peso vivo/ha) e produções por área (70 vs 41,3kg de leite/ha/dia). No segundo ano, em relação ao primeiro, o tifton 85 manteve 88 por cento da capacidade de suporte e 80 por cento da produção por área, enquanto o capim-elefante anão apenas 46 por cento e 56 por cento. A produção média de 17kg de leite/vaca/dia indica um potencial pouco explorado das gramíneas tropicais em sistemas de produção de leite, especialmente na região Sul do Brasil.

Productivity of dwarf elephantgrass (Pennisetum purpureum Schum. cv. Mott) and tifton 85 (Cynodon dactylon x Cynodon nlemfuensis) pastures was evaluated under continuous grazing, in the Northwest area of Rio Grande do Sul. Twelve multiparous Holstein cows, at 100 days of lactation were evaluated and the put-and-take technique was used to regulate the stocking rate to maintain 4 percent of leaf lamina on offer. In the first year, dwarf elephantgrass and tifton 85 were different in leaf accumulation rates (31.2 vs 22.6kg/ha/day) and animal production (17.4 vs 20kg of milk/cow/day). In the second year, tifton 85 had higher leaf accumulation rates (38.8 vs 21.9kg/ha/day), stocking rate (2,157 vs 1,084kg of live weight/ha), and production per area (70 vs 41.3kg of milk/ha/day) than dwarf elephantgrass. Comparing the second to the first years, tifton 85 maintained 88 percent of stocking rate and 80 percent of production per area, while dwarf elephantgrass only 46 percent and 56 percent, respectively. Average individual production of 17kg of milk/cow/day indicates an unexplored potential of tropical grasses in dairy production systems, especially in the South of Brazil.

Effects of creating a non-specific, virus-hostile environment in the nasopharynx on symptoms and duration of common cold.

The Common Cold remains the most frequent symptomatic viral infection in man. Current best therapies are all symptomatic. New pharmacological therapies are likely to be prescription-bound, and as most Common Cold infections are successfully treated without the intervention of a Physician, there is a need for effective non-prescription therapy options. Aim of this study is to propose a new type of approach, based on the concept of making a hostile biological environment for virus survival and spreading at the point of infection, the nasopharynx. The hypothesis was advanced that infections could be controlled using a physical biological approach to create an environment at the point of infection, that is inhibitory to the survival, and persistence of infecting virus, and of viruses newly released from infected mucosal epithelial cells. A nasal irrigation spray, designed to deliver a low pH gel to the nasal cavity, was developed and tested in this study. The study was a randomised, parallel, double-blind, placebo-controlled evaluation of three formulations of irrigation nasal spray in 441 subjects. The objective was to test whether the formulations reduced Cold severity and Cold duration compared to a placebo nasal spray. Subjects were recruited, and supplied with the product when healthy, and were instructed to begin treating and recording symptom severity once they experienced the "first signs" of a Common Cold. To qualify, subjects had to volunteer that they had at least one of the symptoms: sore/scratchy throat, runny nose or congested nose. The product was used 4 times daily, with at least 4 hours separating each dose, for a maximum of 7 days. Efficacy was assessed by an Interactive Voice Recall System whereby subjects were required to contact the investigation site, by telephone, twice daily when they were asked to assess the severity of their symptoms using a four point ordinal scale where 0 = "absent", and 3 = "severe". The symptoms assessed were sore throat, runny nose, blocked nose, cough and tired/run-down feeling. Two formulations demonstrated significant effects. A hydroxy methyl propyl cellulose based formulation reduced symptom severity compared with placebo by 17% and a Poloxamer based formulation reduced severity by 21%. Duration of illness was reduced with a hydroxy methyl propyl cellulose based formulation by 1.5 days to 2.4 days (according to the dose) and by a Poloxamer based formulation by 2.5 days. Results of this study suggest that the creation of a non virus-specific, inhibitory environment in the nasopharynx holds promise as an effective method of controlling the severity and duration of the Common Cold.

Neutralizing antibodies to interferon beta-1b are not associated with disease worsening in multiple sclerosis.

The clinical impact of neutralizing antibodies (NAbs) on interferon beta (IFNbeta) efficacy was studied in three large patient cohorts comprising 6698 multiple sclerosis (MS) patients receiving IFNbeta-1b across North America, Europe, and Australia. In North America and Europe, NAb testing was generally undertaken because of a poor clinical response; in Australia, it was mandatory for every patient. Of the 6697 patients tested, 28.9% had at least one NAb titre > or = 20 neutralizing units (NU)/ml, 14.4% had NAb titres > or = 100 NU/ml and 7.7% had NAb titres > or = 400 NU/ml. The NAb-positive rate of 37.0% in Australia was significantly greater than those in North America (21.3%) and Europe (27.6%), and this was observed at every NAb titre level. Our results suggest that NAbs are not responsible for poor clinical responses and that NAb status is of little clinical value. These findings will need to be confirmed in a large independent study.

Plasmodium falciparum-infected erythrocytes induce tissue factor expression in endothelial cells and support the assembly of multimolecular coagulation complexes.

BACKGROUND: Plasmodium falciparum malaria infects 300-500 million people every year, causing 1-2 million deaths annually. Evidence of a coagulation disorder, activation of endothelial cells (EC) and increase in inflammatory cytokines are often present in malaria. OBJECTIVES: We have asked whether interaction of parasitized red blood cells (pRBC) with EC induces tissue factor (TF) expression in vitro and in vivo. The role of phosphatidylserine-containing pRBC to support the assembly of blood coagulation complexes was also investigated. RESULTS: We demonstrate that mature forms of pRBC induce functional expression of TF by EC in vitro with productive assembly of the extrinsic Xnase complex and initiation of the coagulation cascade. Late-stage pRBC also support the prothrombinase and intrinsic Xnase complex formation in vitro, and may function as activated platelets in the amplification phase of the blood coagulation. Notably, post-mortem brain sections obtained from P. falciparum-infected children who died from cerebral malaria and other causes display a consistent staining for TF in the EC. CONCLUSIONS: These findings place TF expression by endothelium and the amplification of the coagulation cascade by pRBC and/or activated platelets as potentially critical steps in the pathogenesis of malaria. Furthermore, it may allow investigators to test other therapeutic alternatives targeting TF or modulators of EC function in the treatment of malaria and/or its complications.

Is the number of antennal plate organs (sensilla placodea) greater in hygienic than in non-hygienic Africanized honey bees?

Hygienic behavior is a desirable trait in honey bees (Apis mellifera L.), as hygienic bees quickly remove diseased brood, interrupting the infectious cycle. Hygienic lines of honey bees appear to be more sensitive to the odors of dead and diseased honey bee brood, and Africanized honey bees are generally more hygienic than are European honey bees. We compared the number of sensilla placodea, antennal sensory structures involved in the perception of odor, in 10 bees from each of six hygienic and four non-hygienic colonies of Africanized honey bees. The sensilla placodea of three of the terminal segments (flagellomeres) of the right antenna of each bee were counted with a scanning electron microscope. There were no significant differences in the mean numbers of sensilla placodea between the hygienic and non-hygienic bees, though the variance was higher in the hygienic group. Flagellomere 4 had significantly more sensilla placodea than flagellomeres 6 and 8. However, there was no significant difference between the other two flagellomeres. As hygienic bees are capable of identifying dead, injured, or infested brood inside a capped brood cell, sensilla placodea probably have an important role in enabling worker bees to sense sick brood. However, we did not find greater numbers of this sensory structure in the antennae of hygienic, compared to non-hygienic Africanized honey bees

Central nervous system mechanisms in alcohol relapse.

BACKGROUND: Alcohol relapse is a major problem in the treatment of alcohol abuse and alcoholism. Understanding the long-term neuronal alterations that promote relapse of alcohol drinking is critical for the development of pharmacotherapies to treat alcoholism and alcohol abuse. The major objectives of this workshop were to present recent findings, by using rodent models, on behavioral and neurobiological factors that may underlie alcohol relapse and the results of clinical and pharmacological treatment strategies for preventing relapse. METHODS: Prolonged ethanol drinking and repeated periods of alcohol deprivation were studied in nonselected rats and in rats selectively bred for high alcohol preference (P rat). The expression of a robust alcohol deprivation effect (ADE) was used as a model for alcohol relapse in rodents. Operant techniques were used to examine responding for ethanol after deprivation in both rats and C57BL/6J mice. Environmental cues and stress were used to assess their effects on reinstatement of alcohol responding. Microdialysis and [14C]-2-deoxyglucose techniques were used to examine neuronal alterations associated with alcohol relapse. RESULTS: Prolonged free-choice ethanol drinking followed by deprivation produced an ADE in both stock and P rats. These rats demonstrated loss of control on reinstatement after chronic drinking and after prolonged deprivation. Acamprosate and naltrexone effectively reduced the ADE in stock rats. Stress reinstated operant responding for alcohol, and rats trained to associate a cue with ethanol presentation increased responding on the ethanol-associated lever in the absence of ethanol. After repeated deprivations, P rats shifted their preference toward drinking higher concentrations of ethanol, which increased the magnitude and duration of the ADE. Stock rats also shifted their preference toward solutions with higher ethanol concentrations and demonstrated a loss of control after prolonged ethanol drinking and deprivation. Long-lasting alterations in neuronal activity, serotonin-3 receptor function, and dopamine neurotransmission within the mesolimbic system were evident after chronic drinking that followed a prolonged deprivation period. CONCLUSIONS: The ADE is a useful model for studying alcohol relapse in both rats and mice. The potential validity of this model is supported by the findings that acamprosate and naltrexone are effective in preventing the ADE in rodents, and both compounds have gained recognition for their therapeutic effects in clinical populations. Genetics, stress, and environmental cues are all important factors that influence alcohol relapse. Long-term alterations in neuronal activity within the mesolimbic system, which possibly involve dopamine and serotonin, may underlie alcohol relapse.

Solution structure of an arabinonucleic acid (ANA)/RNA duplex in a chimeric hairpin: comparison with 2'-fluoro-ANA/RNA and DNA/RNA hybrids.

Hybrids of RNA and arabinonucleic acid (ANA) as well as the 2'-fluoro-ANA analog (2'F-ANA) were recently shown to be substrates of the enzyme RNase H. Although RNase H binds to double-stranded RNA, no cleavage occurs with such duplexes. Therefore, knowledge of the structure of ANA/RNA hybrids may prove helpful in the design of future antisense oligonucleotide analogs. In this study, we have determined the NMR solution structures of ANA/RNA and DNA/RNA hairpin duplexes and compared them to the recently published structure of a 2'F-ANA/RNA hairpin duplex. We demonstrate here that the sugars of RNA nucleotides of the ANA/RNA hairpin stem adopt the C3'-endo (north, A-form) conformation, whereas those of the ANA strand adopt a 'rigid' O4'-endo (east) sugar pucker. The DNA strand of the DNA/RNA hairpin stem is flexible, but the average DNA/RNA hairpin structural parameters are close to the ANA/RNA and 2'F-ANA/RNA hairpin parameters. The minor groove width of ANA/RNA, 2'F-ANA/RNA and DNA/RNA helices is 9.0 +/- 0.5 A, a value that is intermediate between that of A- and B-form duplexes. These results rationalize the ability of ANA/RNA and 2'F-ANA/RNA hybrids to elicit RNase H activity.

Effect of substituting arabinonucleosides for deoxynucleotides in the DNA priming strand on the polymerase action of HIV-1 RT.

The ability of 5'-DNA-araN-3' chimeras to serve as primers during HIV-1 RT-catalyzed DNA synthesis was assessed. It is shown that while the structural changes imparted by the arabinose units are minimal, the biological outcome is significant. For example, a DNA strand with arabinocytidine (araC) at the 3'-terminus was found to serve as a primer of DNA synthesis but significant pausing of HIV-RT was observed after the addition of 4 dNTP's. This phenomenon was not observed for the analogous DNA primer containing a riboC unit or an all-DNA strand.

Syntheses of DNA duplexes containing a C-C interstrand cross-link.

Short DNA duplexes that contain a N4C-ethyl-N4C interstrand cross-link were prepared on controlled pore glass supports using a DNA synthesizer. The C-C cross-link was introduced via a convertible nucleoside on the support or by using a protected C-C cross-link phosphoramidite. An orthogonal protection scheme allowed selective chain growth in either a 3'-->5' or 5'-->3' direction. The cross-linked duplexes were purified by HPLC and characterized by MALDI-TOF mass spectrometry and/or by enzymatic digestion.