Characteristics of C-4 photosynthesis in stems and petioles of C-3 flowering plants

Most plants are known as C-3 plants because the first product of photosynthetic CO2 fixation is a three-carbon compound. C-4 plants, which use an alternative pathway in which the first product is a four-carbon compound, have evolved independently many times and are found in at least 18 families. In addition to differences in their biochemistry, photosynthetic organs of C-4 plants show alterations in their anatomy and ultrastructure. Little is known about whether the biochemical or anatomical characteristics of C-4 photosynthesis evolved first. Here we report that tobacco, a typical C-3 plant, shows characteristics of C-4 photosynthesis in cells of stems and petioles that surround the xylem and phloem, and that these cells are supplied with carbon for photosynthesis from the vascular system and not from stomata. These photosynthetic cells possess high activities of enzymes characteristic of C-4 photosynthesis, which allow the decarboxylation of four-carbon organic acids from the xylem and phloem, thus releasing CO2 for photosynthesis. These biochemical characteristics of C-4 photosynthesis in cells around the vascular bundles of stems of C-3 plants might explain why C-4 photosynthesis has evolved independently many times

Oral and anal sex practices among high school youth in Addis Ababa, Ethiopia

<p>Abstract</p> <p>Background</p> <p>Understanding the full range of sexual behaviors of young people is crucial in developing appropriate interventions to prevent and control sexually transmitted infections including HIV. However, such information is meager in developing countries. The objective of this study was to describe oral and anal sex practices and identify associated factors among high school youth.</p> <p>Methods</p> <p>A cross-sectional study was conducted among high school youth in Addis Ababa, Ethiopia. A multi-stage sampling procedure was followed to select a representative sample of school youth. The total sample size for this study was 3840. Data were collected using a self-administered questionnaire. Data analysis was guided by the ecological framework.</p> <p>Results</p> <p>The overall proportion of people who reported ever having oral sex was 5.4% (190) and that of anal sex was 4.3% (154). Of these 51.6% (98) had oral sex and 57.1% (87) had anal sex in the past 12 months. Multiple partnerships were reported by 61.2% of the respondents who had oral sex and 51.1% of students practicing anal sex. Consistent condom use was reported by 12.2% of those practicing oral sex and 26.1% of anal sex. Reasons for oral and anal sex included prevention of pregnancy, preserving virginity, and reduction of HIV and STIs transmission. Oral sex practice was strongly and significantly associated with perception of best friends engagement in oral sex (AOR = 5.7; 95% CI 3.6-11.2) and having illiterate mothers (AOR = 11.5; 95%CI 6.4-18.5). Similarly, anal sex practice was strongly and significantly associated with favorable attitude towards anal sex (AOR = 6.2; 95%CI 3.8-12.4), and perceived best friends engagement in anal sex (AOR = 9.7; 95%CI 5.4-17.7).</p> <p>Conclusion</p> <p>Considerable proportion of adolescents had engaged in oral and anal sex practices. Multiple sexual partnerships were common while consistent condom use was low. Sexual health education and behavior change communication strategies need to cover a full range of sexual practices.</p

Ebola: translational science considerations

We are currently in the midst of the most aggressive and fulminating outbreak of Ebola-related disease, commonly referred to as “Ebola”, ever recorded. In less than a year, the Ebola virus (EBOV, Zaire ebolavirus species) has infected over 10,000 people, indiscriminately of gender or age, with a fatality rate of about 50%. Whereas at its onset this Ebola outbreak was limited to three countries in West Africa (Guinea, where it was first reported in late March 2014, Liberia, where it has been most rampant in its capital city, Monrovia and other metropolitan cities, and Sierra Leone), cases were later reported in Nigeria, Mali and Senegal, as well as in Western Europe (i.e., Madrid, Spain) and the US (i.e., Dallas, Texas; New York City) by late October 2014. World and US health agencies declared that the current Ebola virus disease (EVD) outbreak has a strong likelihood of growing exponentially across the world before an effective vaccine, treatment or cure can be developed, tested, validated and distributed widely. In the meantime, the spread of the disease may rapidly evolve from an epidemics to a full-blown pandemic. The scientific and healthcare communities actively research and define an emerging kaleidoscope of knowledge about critical translational research parameters, including the virology of EBOV, the molecular biomarkers of the pathological manifestations of EVD, putative central nervous system involvement in EVD, and the cellular immune surveillance to EBOV, patient-centered anthropological and societal parameters of EVD, as well as translational effectiveness about novel putative patient-targeted vaccine and pharmaceutical interventions, which hold strong promise, if not hope, to curb this and future Ebola outbreaks. This work reviews and discusses the principal known facts about EBOV and EVD, and certain among the most interesting ongoing or future avenues of research in the field, including vaccination programs for the wild animal vectors of the virus and the disease from global translational science perspective

Whiting–related sediment export along the Middle Miocene carbonate ramp of Great Bahama Bank.

International audienc

U-Pb dating of a diabase dike resolves the problem of mutually crosscutting relationships within the Fraser-Strathcona Deep Copper vein system, Sudbury Basin

A geologic problem has been addressed in the Fraser-Strathcona Deep Copper mine, Sudbury, wherein diabase dikes and the chalcopyrite vein system have a mutually crosscutting relationship. In any situation where crosscutting relationships are mutual there is ambiguity, and it is important to independently test and verify the ages of the events in question, thus avoiding erroneous conclusions about the controls on mineralization. To this end detailed underground geologic mapping and U-Pb dating have been applied to a diabase dike that crosscuts the 1850 Ma Sudbury Igneous Complex and footwall Cu-Ni-PGE vein mineralization. The dike has a minimum 1.5 km strike length, 2.2 km dip length, and a width of 20 m. Where the dike cuts the Cu-Ni-PGE vein system there are (1) sharp contacts with the dike clearly cutting chalcopyrite veins, (2) laminated chalcopyrite-pyrrhotite-pentlandite veins along the hanging-wall or footwall contacts of the dike, and (3) back veining in the form of 0.5- to 2 m-wide remobilized sulfide veins and stockworks that cut the dike. Magmatic zircons from the diabase have a concordant 206Pb/238U age of 506 ± 4 Ma, whereas abundant xenocrystic zircons have ages of 1810 to 1840 Ma and appear to have been derived from the Sudbury Igneous Complex. Magmatic titanite from the dike defines a highly discordant array of points with an upper intercept at 530 ± 21 Ma, although the titanite analyses are not precise. The discordance results from recent Pb loss, which may have been related to brittle fracturing and fluid infiltration during exhumation and mild deformation. The diabase dike is interpreted to be part of the 500 to 600 Ma extension and rifting that formed the Ottawa-Bonnechere graben and related features during rifting of eastern North America prior to the opening of the Iapetus Ocean. It represents the youngest intrusive event within the post-impact geologic history of the Sudbury structure

Evaluation of Calibration Curve-Based Approaches to Predict Clinical Inducers and Noninducers of CYP3A4 with Plated Human Hepatocytes

Cytochrome P450 (P450) induction is often considered a liability in drug development. Using calibration curve-based approaches, we assessed the induction parameters R3 (a term indicating the amount of P450 induction in the liver, expressed as a ratio between 0 and 1), relative induction score, Cmax/EC50, and area under the curve (AUC)/F2 (the concentration causing 2-fold increase from baseline of the dose-response curve), derived from concentration-response curves of CYP3A4 mRNA and enzyme activity data in vitro, as predictors of CYP3A4 induction potential in vivo. Plated cryopreserved human hepatocytes from three donors were treated with 20 test compounds, including several clinical inducers and noninducers of CYP3A4. After the 2-day treatment, CYP3A4 mRNA levels and testosterone 6beta-hydroxylase activity were determined by real-time reverse transcription polymerase chain reaction and liquid chromatography-tandem mass spectrometry analysis, respectively. Our results demonstrated a strong and predictive relationship between the extent of midazolam AUC change in humans and the various parameters calculated from both CYP3A4 mRNA and enzyme activity. The relationships exhibited with non-midazolam in vivo probes, in aggregate, were unsatisfactory. In general, the models yielded better fits when unbound rather than total plasma Cmax was used to calculate the induction parameters, as evidenced by higher R(2) and lower root mean square error (RMSE) and geometric mean fold error. With midazolam, the R3 cut-off value of 0.9, as suggested by US Food and Drug Administration guidance, effectively categorized strong inducers but was less effective in classifying midrange or weak inducers. This study supports the use of calibration curves generated from in vitro mRNA induction response curves to predict CYP3A4 induction potential in human. With the caveat that most compounds evaluated here were not strong inhibitors of enzyme activity, testosterone 6beta-hydroxylase activity was also demonstrated to be a strong predictor of CYP3A4 induction potential in this assay mode