The influence of menstrual cycle and oral contraceptive pill phases on the vascular response to hypoxia and sympathetic activation in healthy young women

INTRODUCTION: Hypoxia elicits peripheral vasodilation to preserve blood flow to metabolically active tissue and is accompanied by an increase in muscle sympathetic nervous system activity (MSNA). Prior data predominantly in male subjects, demonstrated the vasoconstrictive effects of MSNA are preserved in the setting of hypoxia. Because women are better able to attenuate or ignore the vasoconstrictive effects of MSNA at rest, we hypothesized women would exhibit greater hypoxic vasodilation (Aim 1). We further hypothesized women would attenuate the vasoconstrictive effects of sympathetic activation during both normoxia (Aim 2) and in the setting of hypoxia (Aim 3). The female sex hormone, estrogen, has been purported to be responsible for mediating the attenuated vasoconstriction to MSNA. As synthetic estrogen found in oral contraceptives is more biologically potent, we further hypothesized women taking oral contraceptives (OCPs) will better attenuate vasoconstriction relative to naturally cycling (NC) women during normoxia and hypoxia and this will be greatest during the high hormone phase of the pill or menstrual cycle. METHODS: Ten NC women, (25[plus or minus]1 yrs, 23[plus or minus]1 kg/m2) and ten women on OCPs, (24[plus or minus]1 yrs, 21[plus or minus]1 kg/m2) participated (N=20). Women were studied twice, once during the low hormone of the menstrual or pill cycle (menstrual cycle day, NC: 3.1[plus or minus]0.4; pill cycle day: OCP: 5.2[plus or minus]0.4) and once during the high hormone phase of the menstrual or pill cycle (menstrual cycle day, NC: 14.9[plus or minus]0.9; pill cycle day OCP: 16.6[plus or minus]0.6). Heart rate (ECG), blood pressure (finger photoplethysmography), forearm blood flow (venous occlusion plethysmography) and systemic blood flow (Modelflow) were continuously measured across three trials: 1) steady state hypoxia (80 percent SpO2); 2) sympathetic activation via two-minute cold pressor test (CPT); and 3) concomitant steady-state hypoxia and sympathetic activation via two-minute CPT. Forearm and systemic blood flow were normalized for blood pressure and expressed as forearm vascular conductance (FVC) and total vascular conductance (TVC), respectively. Data are reported from the last one minute of each trial. RESULTS: Hypoxia elicited a relative increase in FVC ( percent change from baseline) that was greater during the high hormone phase of the menstrual or pill cycle compared to the low hormone phase in both NC and women taking OCPs (p[less than]0.01). Sympathetic activation via CPT caused paradoxical local vasodilation in women taking OCPs, whereas NC women exhibited local vasoconstriction (p[less than]0.01). Concomitant hypoxia and sympathetic activation via CPT resulted in less systemic vasoconstriction compared to normoxia that was not different between groups or hormone phases (p=0.71). CONCLUSION: The hypoxic vasodilatory response is augmented during the high hormone phase of the menstrual or pill cycle. Exogenous estrogen found in OCPs may cause paradoxical vasodilation to sympathetic activation, whereas sympathetic activation in NC women with endogenous hormones elicits vasoconstriction. We observed a hypoxia-mediated attenuation of the systemic vasoconstrictor response to sympathetic activation in both NC women and women taking OCPs across all hormone phases. These data demonstrate the vascular response to autonomic and environmental stressors are influenced by female sex hormones and menstrual/pill cycle phase.Includes bibliographical references

The noise-lovers: cultures of speech and sound in second-century Rome

This chapter provides an examination of an ideal of the ‘deliberate speaker’, who aims to reflect time, thought, and study in his speech. In the Roman Empire, words became a vital tool for creating and defending in-groups, and orators and authors in both Latin and Greek alleged, by contrast, that their enemies produced babbling noise rather than articulate speech. In this chapter, the ideal of the deliberate speaker is explored through the works of two very different contemporaries: the African-born Roman orator Fronto and the Syrian Christian apologist Tatian. Despite moving in very different circles, Fronto and Tatian both express their identity and authority through an expertise in words, in strikingly similar ways. The chapter ends with a call for scholars of the Roman Empire to create categories of analysis that move across different cultural and linguistic groups. If we do not, we risk merely replicating the parochialism and insularity of our sources.Accepted manuscrip

Tactical interactions : dialogues between Greece and Rome in the military manuals of Aelian and Arrian

This chapter looks at two interconnected texts which were published within two or three decades of each other: Aelianus Tacticus’ Tactical Theory (addressed to Trajan) and Arrian’s Tactics, published two or three decades later under Hadrian. Both texts appear to draw on the same source material, and it is reasonable to suppose that Arrian was aware of Aelian’s earlier treatise, although there is no direct interaction between them. Their different approaches to the same material offer an opportunity to explore different models of literary and cross-cultural interaction, and also to examine our go-to metaphors and interpretative models for analysing them. While Aelian establishes a series of polemical comparisons between age-old Greek military theory and currently effective Roman military practice, Arrian hints at overlaps between Greek and Roman traditions, both by incorporating a section on Roman cavalry manoeuvres and by interacting with a speech delivered by Hadrian to the Roman army at Lambaesis in 128. Both approaches are equally tactical; and both are revealing of the complex dynamics of cross-cultural interaction, which took place on and off the page, and in literary and less literary forms of writing.PostprintPeer reviewe

Introduction

This introduction, co-written with Rebecca Langlands and James Uden, sets up important contextual and methodological questions for the volume to come