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1.
H K Wolf G R Dagenais J G Fodor R S Fynes S P Handa R B Haynes G A Klassen M G Myers N M Robitaille 《CMAJ》1988,139(6):507-512
Causal blood pressure measurements were recorded in two groups of men aged 40 to 64 years; of the 7024 men in metropolitan Saint John, NB, and the 4044 men in seven suburbs of Quebec who were asked, 5840 (83.1%) and 3097 (76.6%) respectively agreed to participate. Of the Saint John group 9.0% were taking antihypertensive drugs, as compared with only 3.3% of the Quebec group (p less than 0.0001). Among the treated subjects 33% in Saint John and 53% in Quebec still had a diastolic pressure greater than 95 mm Hg (p less than 0.01). Among the participants not taking antihypertensive drugs the systolic blood pressure increased with age, but the diastolic blood pressure increased only slightly up to 55 years of age and then decreased. On average the subjects in Saint John who were not being treated had a systolic pressure 6.2 mm Hg lower and a diastolic blood pressure 3.6 mm Hg lower than their Quebec counterparts (p less than 0.0001). This difference was observed in all the age groups and was not the result of the treatment of a greater proportion of the Saint John cohort. Despite the higher blood pressures and the smaller number receiving adequate treatment in the Quebec group, the rate of death due to coronary artery disease was 10% lower than that in the Saint John group. A bias in the data from Quebec may have influenced the magnitude of the differences between the two samples, but if present it should have underestimated the blood pressures in the Quebec group and therefore not have changed the outcome. 相似文献
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Transmitter release increases intracellular calcium in perisynaptic Schwann cells in situ. 总被引:9,自引:0,他引:9
Glial cells isolated from the nervous system are sensitive to neurotransmitters and may therefore be involved in synaptic transmission. The sensitivity of individual perisynaptic Schwann cells to activity of a single synapse was investigated, in situ, at the frog neuromuscular junction by monitoring changes in intracellular Ca2+ in the Schwann cells. Motor nerve stimulation induced an increase in intracellular Ca2+ in these Schwann cells; this increase was greatly reduced when transmitter release was blocked. Furthermore, local application of the cotransmitters acetylcholine and ATP evoked Ca2+ responses even in the absence of extracellular Ca2+. Successive trains of nerve stimuli or applications of transmitters resulted in progressively smaller Ca2+ responses. We conclude that transmitter released during synaptic activity can evoke release of intracellular Ca2+ in perisynaptic Schwann cells. This Ca2+ signal may play a role in the maintenance or modulation of a synapse. These data show that synaptic transmission involves three cellular components with both postsynaptic and glial components responding to transmitter secretion. 相似文献
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Fluorinated calcium-sensitive indicators such as 5,5'-difluoro-1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (difluoro-BAPTA) will often be less sensitive under in vivo conditions than gyromagnetic ratio considerations alone would have predicted. This is due to the very broad line widths displayed by these molecules within the living cell. In order to provide a spectroscopic alternative to these molecules, we have synthesized 13C-enriched 1-(2-aminophenoxy)-2-(2-aminoethoxy)ethane-N,N,N',N'-tetraac etic acid or AATA. The rationale for the design of this molecule was the increased signal to noise ratio available by selective detection of 13C-attached protons in AATA using proton-observe carbon-edited spectroscopy or multiple-quantum coherence. AATA has the advantage of increased number of detectable nuclei and narrow line widths. As such, it should provide a 6-10-fold improvement in the signal to noise ratio over existing fluorinated indicators. As a hybrid between EGTA and BAPTA, AATA should display intermediate pKa's, exchange rates, and KD values. We have measured pKa values of 5.94 +/- 0.05 and 9.03 +/- 0.05 for AATA. KD values of 350 +/- 80 nM and 6.6 +/- 2.0 mM were obtained for the AATA-Ca2+ and AATA-Mg2+ interactions, respectively, at 37 degrees C in 0.1 M KCl. As such, this new ligand displays the expected selectivity for Ca2+ over Mg2+. This new approach to detection of intracellular probes with NMR can be readily extended to other probes for intracellular ions, pH, and membrane potential. In addition, the move toward carbon-selected proton spectroscopy should also permit more flexibility in synthetic approaches since the strong electronegativity of fluorine often hampers synthetic design. 相似文献
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Fishers are mid-sized forest carnivores indigenous to North America that experienced sharp population declines from the early 1800s through to the mid-1900s. To evaluate levels of genetic variation within and subdivision among northern fisher populations 459 individuals were genotyped using 13 microsatellite loci. Genetic diversity was found to be slightly lower in re-introduced populations than in adjacent indigenous populations. Furthermore, fisher populations revealed much more genetic structuring than two closely related mustelids. Further investigation is needed to determine if fishers are more philopatric than martens and wolverines or if barriers to dispersal explain the levels of structure identified in this study. 相似文献
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