Browsing by Autor "Henry Yamashiro"

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Augmented uterine artery blood flow and oxygen delivery protect Andeans from altitude-associated reductions in fetal growth
(American Physiological Society, 2009) Colleen G. Julian; Megan J. Wilson; M. de la Flor; Henry Yamashiro; Wilma Téllez; Armando Rodríguez; Abigail W. Bigham; Mark D. Shriver; Carmelo Rodriguez; Enrique Vargas
The effect of high altitude on reducing birth weight is markedly less in populations of high- (e.g., Andeans) relative to low-altitude origin (e.g., Europeans). Uterine artery (UA) blood flow is greater during pregnancy in Andeans than Europeans at high altitude; however, it is not clear whether such blood flow differences play a causal role in ancestry-associated variations in fetal growth. We tested the hypothesis that greater UA blood flow contributes to the protection of fetal growth afforded by Andean ancestry by comparing UA blood flow and fetal growth throughout pregnancy in 137 Andean or European residents of low (400 m; European n = 28, Andean n = 23) or high (3,100-4,100 m; European n = 51, Andean n = 35) altitude in Bolivia. Blood flow and fetal biometry were assessed by Doppler ultrasound, and maternal ancestry was confirmed, using a panel of 100 ancestry-informative genetic markers (AIMs). At low altitude, there were no ancestry-related differences in the pregnancy-associated rise in UA blood flow, fetal biometry, or birth weight. At high altitude, Andean infants weighed 253 g more than European infants after controlling for gestational age and other known influences. UA blood flow and O(2) delivery were twofold greater at 20 wk in Andean than European women at high altitude, and were paralleled by greater fetal size. Moreover, variation in the proportion of Indigenous American ancestry among individual women was positively associated with UA diameter, blood flow, O(2) delivery, and fetal head circumference. We concluded that greater UA blood flow protects against hypoxia-associated reductions in fetal growth, consistent with the hypothesis that genetic factors enabled Andeans to achieve a greater pregnancy-associated rise in UA blood flow and O(2) delivery than European women at high altitude.
High-end arteriolar resistance limits uterine artery blood flow and restricts fetal growth in preeclampsia and gestational hypertension at high altitude
(American Physiological Society, 2011) Vaughn A. Browne; Lilian Toledo‐Jaldin; R. Daniela Dávila; Luis P. Lopez; Henry Yamashiro; Darleen Cioffi‐Ragan; Colleen G. Julian; Megan J. Wilson; Abigail W. Bigham; Mark D. Shriver
The reduction in infant birth weight and increased frequency of preeclampsia (PE) in high-altitude residents have been attributed to greater placental hypoxia, smaller uterine artery (UA) diameter, and lower UA blood flow (Q(UA)). This cross-sectional case-control study determined UA, common iliac (CI), and external iliac (EI) arterial blood flow in Andeans residing at 3,600-4,100 m, who were either nonpregnant (NP, n = 23), or experiencing normotensive pregnancies (NORM; n = 155), preeclampsia (PE, n = 20), or gestational hypertension (GH, n = 12). Pregnancy enlarged UA diameter to ~0.62 cm in all groups, but indices of end-arteriolar vascular resistance were higher in PE or GH than in NORM. Q(UA) was lower in early-onset (≤34 wk) PE or GH than in NORM, but was normal in late-onset (>34 wk) illness. Left Q(UA) was consistently greater than right in NORM, but the pattern reversed in PE. Although Q(CI) and Q(EI) were higher in PE and GH than NORM, the fraction of Q(CI) distributed to the UA was reduced 2- to 3-fold. Women with early-onset PE delivered preterm, and 43% had stillborn small for gestational age (SGA) babies. Those with GH and late-onset PE delivered at term but had higher frequencies of SGA babies (GH=50%, PE=46% vs. NORM=15%, both P < 0.01). Birth weight was strongly associated with reduced Q(UA) (R(2) = 0.80, P < 0.01), as were disease severity and adverse fetal outcomes. We concluded that high end-arteriolar resistance, not smaller UA diameter, limited Q(UA) and restricted fetal growth in PE and GH. These are, to our knowledge, the first quantitative measurements of Q(UA) and pelvic blood flow in early- vs. late-onset PE in high-altitude residents.
PlGF is greater and sFLT‐1 lower in multigenerational vs. shorter‐term pregnant residents of high altitude
(Wiley, 2008) R. Daniela Dávila; Colleen G. Julian; Vaughn A. Browne; Megan J. Wilson; Jennifer L. Hageman; Henry Yamashiro; Armando Rodríguez; Carmelo Rodriguez; Enrique Vargas; Lorna G. Moore
INTRODUCTION. An imbalance between angiogenic and anti‐angiogenic factors likely plays an etiological role in fetal growth restriction. Since multigenerational high‐altitude (HA) Andean (AND) vs. shorter‐term, European (EUR) ancestry protects against fetal growth restriction at HA, we hypothesized that the angiogenic factor PlGF was elevated and the anti‐angiogenic factor sFlt‐1 reduced. MATERIALS AND METHODS. Pregnant women residing at low (400 m; AND n=36, EUR n=39) or high (3600m; AND n=46, EUR n=33) altitude in Bolivia were studied at 20 and 36 wk of pregnancy and 4 mo postpartum. Plasma sFlt1 and PlGF levels were determined by ELISA and data analyzed by ANOVA. RESULTS. Pregnancy increased PlGF and sFlt‐1 in EUR and AND women (p<0.001). PlGF increased in AND women at HA in early pregnancy and declined at 36 wk compared EUR values (interaction between pregnancy, altitude and ancestry, p<0.05). At HA, sFlt‐1 was greater in EUR than AND women at 20 and 36 wk (p<0.001). The sFlt‐1/PlGF ratio rose from 20 wk to 36 wk in EUR women at both altitudes and in HA AND women but not in the LA AND, and tended to be lower in AND vs. EUR women near term (p<0.10). CONCLUSIONS. Lower sFLT‐1 and higher PlGF levels may help protect multigenerational AND compared with shorter‐term EUR HA‐residents from fetal growth restriction. (NIH HL079647 and HL 14985)
The role of antioxidant & oxidative status in the protection against altitude‐associated reductions in uterine artery (UA) blood flow & fetal growth afforded by Andean ancestry
(Wiley, 2008) Colleen G. Julian; Enrique Vargas; Joe M. McCord; Jennifer L. Hageman; R. Daniela Dávila; Henry Yamashiro; Megan J. Wilson; Carmelo Rodriguez; Armando Rodríguez; Vaughn A. Browne
Objective: To determine the role of antioxidant & oxidative status in the protection of uterine artery blood flow (UAVF) & fetal growth at high altitude in Andean populations. Methods: Erythrocyte catalase (CAT) & superoxide dismutase (SOD), plasma isoprostanes (8‐ISO‐PGF‐2α) & UA VF were measured at 20 & 36w of pregnancy & and in the non‐pregnant state in Andean (AND) & European (EUR) women at low (LA, 416m) or high (HA, 3600m) altitude. CAT, SOD & 8‐iso‐PGF‐2α were assessed by spectrometry, UA VF by Doppler ultrasound & birth weight (BW) by medical records review. Data was analyzed by t‐tests, 1‐ & 2‐way ANOVA. Results: At LA, ancestry had no effect on CAT or SOD. AND had higher CAT (20 & 36w p<0.05) & SOD activity (36w p<0.05) than EUR at HA. At HA, UA diameter and UA VF were greater in AND than EUR. Altitude decreased BW in AND (p<0.05) and EUR (p<0.01), and at HA EUR ancestry reduced BW (β= − 0.238 p<0.05). Small‐for‐gestational age (SGA) infants occurred 2‐times more frequently at HA than LA in EUR. SOD was lower at 20w in SGA at both altitues, or HA alone (all p<0.05). In EUR, CAT tended to be lower at 20w in SGA. 8‐ISO‐PGF2α reduced UA diam (p<0.05) & UA VF (p<0.01) in all women. Conclusion: Elevated endogenous antioxidant activity may contribute to the protection against altitude‐associated reductions in UA blood flow & fetal growth afforded by Andean ancestry. NIH HL079647 ,AHA 0610129Z & NSF BCS‐064719.