Blood Flow VelocityRegional Blood FlowBlood PressureUltrasonography, Doppler, TranscranialCerebrovascular CirculationMiddle Cerebral ArteryHypertensionHypotensionUltrasonography, DopplerOphthalmic ArteryCerebral ArteriesPulsatile FlowHeart RateRats, Inbred SHRUltrasonography, Doppler, ColorUltrasonography, Doppler, PulsedCoronary CirculationVascular ResistanceRats, Inbred WKYLaser-Doppler FlowmetryHemodynamicsHypocapniaCiliary ArteriesRetinal ArteryEchocardiography, DopplerEchoencephalographyBlood GlucoseRheologyUmbilical ArteriesAntihypertensive AgentsHyperventilationMicrocirculationCarbon DioxideDiastoleUltrasonography, PrenatalAnterior Cerebral ArteryRats, Sprague-DawleyHyperemiaKidneyUltrasonographyModels, CardiovascularArteriesReference ValuesIntracranial PressureSystoleHeart Rate, FetalCeliac ArteryCoronary VesselsHomeostasisVasodilationAcetazolamideGestational AgeVasodilator AgentsDogsDoppler EffectPregnancyTime FactorsOxygenMesenteric Artery, SuperiorFetal Growth RetardationBrainCircle of WillisEchocardiography, Doppler, ColorCarotid Artery, InternalPlacental CirculationProspective StudiesCollateral CirculationReproducibility of ResultsHemorheologyTilt-Table TestFetal HeartPosterior Cerebral ArteryVasomotor SystemHypotension, OrthostaticEchocardiographySplanchnic CirculationHypercapniaFlow CytometryBlood ViscosityPulmonary CirculationBlood Circulation TimePostureBlood VolumePartial PressurePapaverineRetinal VesselsUterusEchocardiography, TransesophagealVasoconstrictionEchocardiography, Doppler, PulsedCardiac OutputAdenosineRenal CirculationCarotid ArteriesOxygen ConsumptionMitral ValveVentricular Function, LeftOrthostatic IntoleranceInfant, NewbornMicrospheres