1,300 research outputs found

    Mechanisms Underlying the Morning Increase in Platelet Aggregation: A Flow Cytometry Study

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    ObjectivesMechanisms underlying the morning increase in platelet aggregation produced by arising and assuming the upright posture were studied by examining 1) the expression on the platelet surface of activation-dependent markers; 2) platelet aggregation in whole blood; and 3) hematologic factors likely to influence aggregation.BackgroundThe morning increase in thrombotic cardiovascular events has been attributed, in part, to the morning surge in platelet aggregability, but its mechanisms are poorly understood.MethodsExpression of seven platelet surface antigens (including P-selectin, activated GPIIb-IIIa and GPIb-IX), whole-blood platelet aggregation, platelet count and hematocrit were measured before and after arising in 17 normal volunteers. The fibrinolytic variables, tissue-type plasminogen activator, plasminogen activator inhibitor 1 and catecholamine levels were also measured.ResultsOn arising and standing, platelet aggregation increased by 71% (p ≤ 0.01) and 27% (p ≤ 0.03) in response to collagen and adenosine diphosphate, respectively. However, there was no change in any of the activation-dependent platelet surface markers. Whole-blood platelet count and hematocrit increased by 15% and 7% (both p < 0.0001), respectively. Norepinephrine and epinephrine levels increased by 189% (p < 0.0001) and 130% (p < 0.01), respectively. Tissue-type plasminogen activator antigen increased (31%, p < 0.01), but there was no significant increase in plasminogen activator inhibitor 1, suggesting an overall increase in fibrinolysis on standing. Prothrombin fragment 1.2 increased by 28% (p < 0.02), indicating a small increase in thrombin generation. The increases in hematocrit and platelet count that occurred on standing were carefully mimicked in vitro and resulted in a 115% (p < 0.05) increase in platelet aggregation in response to adenosine diphosphate.ConclusionsThese data demonstrate that the morning increase in platelet aggregation is not accompanied by expression of activation-dependent platelet surface receptors and suggest that the increase in whole-blood aggregation may be primarily due to the increases in catecholamine levels, platelet count and hemocon-centration

    Pliocene-Pleistocene marine cyclothems, Wanganui Basin, New Zealand: a lithostratigraphic framework

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    The Rangitikei River valley between Mangaweka and Vinegar Hill and the surrounding Ohingaiti region in eastern Wanganui Basin contains a late Pliocene to early Pleistocene (c. 2.6-1.7 Ma), c. 1100 m thick, southward-dipping (4-9deg.), marine cyclothemic succession. Twenty sedimentary cycles occur within the succession, each of which contains coarse-grained (siliciclastic sandstone and coquina) and fine-grained (siliciclastic siltstone) units. Nineteen of the cycles are assigned to the Rangitikei Group (new). Six new formations are defined within the Rangitikei Group, and their distribution in the Ohingaiti region is represented in a new geologic map. The new formations are named: Mangarere, Tikapu, Makohine, Orangipongo, Mangaonoho, and Vinegar Hill. Each formation comprises one or more cyclothems and includes a previously described and named distinctive basal horizon. Discrete sandstones, siltstones, and coquinas within formations are assigned member status and correspond to systems tracts in sequence stratigraphic nomenclature. The members provide the link between the new formational lithostratigraphy and the sequence stratigraphy of the Rangitikei Group. Base of cycle coquina members accumulated during episodes of sediment starvation associated with stratigraphic condensation on an open marine shelf during sea-level transgressions. Siltstone members accumulated in mid-shelf environments (50-100 m water depth) during sea-level highstands, whereas the overlying sandstone members are ascribed to inner shelf and shoreface environments (0-50 m water depth) and accumulated during falling eustatic sea-level conditions. Repetitive changes in water depth of 50-100 m magnitude are consistent with a glacio-eustatic origin for the cyclothems, which correspond to an interval of Earth history when successive glaciations in the Northern Hemisphere are known to have occurred. Moreover, the chronology of the Rangitikei River section indicates that Rangitikei Group cyclothems accumulated during short duration, 41 ka cycles in continental ice volume attributed to the dominance of the Milankovitch obliquity orbital parameter. The Ohingaiti region has simple postdepositional structure. The late Pliocene formations dip generally to the SSW between 4deg. and 9deg.. Discernible discordances of c. 1deg. between successively younger formations are attributed to synsedimentary tilting of the shelf concomitant with migration of the tectonic hingeline southward into the basin. The outcrop distribution of the Rangitikei Group is strongly influenced by this regional tilt and also by three major northeast-southwest oriented, high-angle reverse faults (Rauoterangi, Pakihikura, and Rangitikei Faults)

    Moving Toward Patient-Centered Care in Africa: A Discrete Choice Experiment of Preferences for Delivery Care among 3,003 Tanzanian Women

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    Objective: In order to develop patient-centered care we need to know what patients want and how changing socio-demographic factors shape their preferences. Methods: We fielded a structured questionnaire that included a discrete choice experiment to investigate women’s preferences for place of delivery care in four rural districts of Pwani Region, Tanzania. The discrete choice experiment consisted of six attributes: kind treatment by the health worker, health worker medical knowledge, modern equipment and medicines, facility privacy, facility cleanliness, and cost of visit. Each woman received eight choice questions. The influence of potential supply- and demand- side factors on patient preferences was evaluated using mixed logit models. Results: 3,003 women participated in the discrete choice experiment (93% response rate) completing 23,947 choice tasks. The greatest predictor of health facility preference was kind treatment by doctor (β = 1.13, p<0.001), followed by having a doctor with excellent medical knowledge (β = 0.89 p<0.001) and modern medical equipment and drugs (β = 0.66 p<0.001). Preferences for all attributes except kindness and cost were changed with changes to education, primiparity, media exposure and distance to nearest hospital. Conclusions: Care quality, both technical and interpersonal, was more important than clinic inputs such as equipment and cleanliness. These results suggest that while basic clinic infrastructure is necessary, it is not sufficient for provision of high quality, patient-centered care. There is an urgent need to build an adequate, competent, and kind health workforce to raise facility delivery and promote patient-centered care

    Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand

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    Pliocene limestone formations in central Hawke's Bay (eastern North Island, New Zealand) accumulated on and near the margins of a narrow forearc basin seaway within the convergent Australia/Pacific plate boundary zone. The active tectonic setting and varied paleogeographic features of the limestone units investigated, in association with probable glacioeustatic sea-level fluctuations, resulted in complex stratigraphic architectures and contrasting types of carbonate accumulation on either side of the seaway. Here, we recognise recurring patterns of sedimentary facies, and sequences and systems tracts bounded by key physical surfaces within the limestone sheets. The facies types range from Bioclastic (B) to Siliciclastic (S) end-members via Mixed (M) carbonate-siliciclastic deposits. Skeletal components are typical cool-water associations dominated by epifaunal calcitic bivalves, bryozoans, and especially barnacles. Siliciclastic contents vary from one formation to another, and highlight siliciclastic-rich limestone units in the western ranges versus siliciclastic-poor limestone units in the eastern coastal hills. Heterogeneities in facies types, stratal patterns, and also in diagenetic pathways between eastern and western limestone units are considered to originate in the coeval occurrence in different parts of the forearc basin of two main morphodynamic carbonate systems over time
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