Reproducibility of an oral fat tolerance test is influenced by phase of menstrual cycle.

Knowledge of the reproducibility of oral fat tolerance tests is important for experimental design and data interpretation. In this study, seven normolipidaemic men underwent two fat tolerance tests (blood taken fasting and for six hours after a meal containing 1.2 g fat, 1.2 g carbohydrate per kg body mass) with an interval of one week. Eleven normolipidaemic women underwent two fat tolerance tests--one during the follicular phase of the menstrual cycle, the other during the mid-luteal phase. Dietary intake was controlled for two days and subjects refrained from exercise for three days before each test. There was no significant difference in postprandial triglyceride responses between the two tests in the men (10.20 +/- 3.45 mmol/l.h vs. 9.68 +/- 2.77 mmol/l.h, NS) (mean +/- SD); intraclass correlation coefficient between the two tests was 0.93, and within-subject coefficient of variation was 10.1 %. In the women, the postprandial triglyceride response was lower in the luteal phase (6.75 +/- 1.83 mmol/l.h) than in the follicular phase (8.36 +/- 3.71 mmol/l.h) (p = 0.05), intraclass correlation was 0.65 and within-subject coefficient of variation was 23.2 %. These results suggest that, with adequate control of preceding lifestyle, reproducibility of postprandial triglyceride responses is high in men, but menstrual phase should be taken into consideration when studying these responses in women.     

Diurnal and menstrual cycles in body temperature are regulated differently: A 28-day ambulatory study in healthy women with thermal discomfort of cold extremities and controls

Diurnal cycle variations in body-heat loss and heat production, and their resulting core body temperature (CBT), are relatively well investigated; however, little is known about their variations across the menstrual cycle under ambulatory conditions. The main purpose of this study was to determine whether menstrual cycle variations in distal and proximal skin temperatures exhibit similar patterns to those of diurnal variations, with lower internal heat conductance when CBT is high, i.e. during the luteal phase. Furthermore, we tested these relationships in two groups of women, with and without thermal discomfort of cold extremities (TDCE). In total, 19 healthy eumenorrheic women with regular menstrual cycles (28–32 days), 9 with habitual TDCE (ages 29?±?1.5 year; BMI 20.1?±?0.4) and 10 controls without these symptoms (CON: aged 27?±?0.8 year; BMI 22.7?±?0.6; p?<?0.004 different to TDCE) took part in the study. Twenty-eight days continuous ambulatory skin temperature measurements of distal (mean of hands and feet) and proximal (mean of sternum and infraclavicular regions) skin regions, thighs, and calves were carried out under real-life, ambulatory conditions (i-Buttons® skin probes, sampling rate: 2.5?min). The distal minus proximal skin temperature gradient (DPG) provided a valuable measure for heat redistribution from the core to the shell, and, hence, for internal heat conduction. Additionally, basal body temperature was measured sublingually directly after waking up in bed. Mean diurnal amplitudes in skin temperatures increased from proximal to distal skin regions and the 24-h mean values were inversely related. TDCE compared to CON showed significantly lower hand skin temperatures and DPG during daytime. However, menstrual cycle phase did not modify these diurnal patterns, indicating that menstrual and diurnal cycle variations in skin temperatures reveal additive effects. Most striking was the finding that all measured skin temperatures, together with basal body temperature, revealed a similar menstrual cycle variation (independent of BMI), with highest and lowest values during the luteal and follicular phases, respectively. These findings lead to the conclusion that in contrast to diurnal cycle, variations in CBT variation across the menstrual cycle cannot be explained by changes in internal heat conduction under ambulatory conditions. Although no measurements of metabolic heat production were carried out increased metabolic heat generation during the luteal phase seems to be the most plausible explanation for similar body temperature increases.     

Two-stage functional mixed models for evaluating the effect of longitudinal covariate profiles on a scalar outcome

The Daily Hormone Study, a substudy of the Study of Women's Health Across the Nation (SWAN) consisting of more than 600 pre- and perimenopausal women, includes a scalar measure of total hip bone mineral density (BMD) together with repeated measures of creatinine-adjusted follicle stimulating hormone (FSH) assayed from daily urine samples collected over one menstrual cycle. It is of scientific interest to investigate the effect of the FSH time profile during a menstrual cycle on total hip BMD, adjusting for age and body mass index. The statistical analysis is challenged by several features of the data: (1) the covariate FSH is measured longitudinally and its effect on the scalar outcome BMD may be complex; (2) due to varying menstrual cycle lengths, subjects have unbalanced longitudinal measures of FSH; and (3) the longitudinal measures of FSH are subject to considerable among- and within-subject variations and measurement errors. We propose a measurement error partial functional linear model, where repeated measures of FSH are modeled using a functional mixed effects model and the effect of the FSH time profile on BMD is modeled using a partial functional linear model by treating the unobserved true subject-specific FSH time profile as a functional covariate. We develop a two-stage nonparametric regression calibration method using period smoothing splines. Using the connection between smoothing splines and mixed models, we show that a key feature of our approach is that estimation at both stages can be conveniently cast into a unified mixed model framework. A simple testing procedure for constant functional covariate effect is also proposed. The proposed methods are evaluated using simulation studies and applied to the SWAN data.     

Comparison of seasonal variation in the fasting respiratory quotient of young Japanese, Polish and Thai women in relation to seasonal change in their percent body fat

Background

From the viewpoint of human physiological adaptability, we previously investigated seasonal variation in the amount of unabsorbed dietary carbohydrates from the intestine after breakfast in Japanese, Polish and Thai participants. In this investigation we found that there were significant seasonal variations in the amount of unabsorbed dietary carbohydrates in Japanese and Polish participants, while we could not find significant seasonal variation in Thai participants. These facts prompted us to examine seasonal variations in the respiratory quotient after an overnight fast (an indicator of the ratio of carbohydrate and fat oxidized after the last meal) with female university students living in Osaka (Japan), Poznan (Poland) and Chiang Mai (Thailand).

Methods

We enrolled 30, 33 and 32 paid participants in Japan, Poland and Thailand, respectively, and measurements were taken over the course of one full year. Fasting respiratory quotient was measured with the participants in their postabsorptive state (after 12 hours or more fasting before respiratory quotient measurement). Respiratory quotient measurements were carried out by means of indirect calorimetry using the mixing chamber method. The percent body fat was measured using an electric bioelectrical impedance analysis scale. Food intake of the participants in Osaka and Poznan were carried out by the Food Frequency Questionnaire method.

Results

There were different seasonal variations in the fasting respiratory quotient values in the three different populations; with a significant seasonal variation in the fasting respiratory quotient values in Japanese participants, while those in Polish and Thai participants were non-significant. We found that there were significant seasonal changes in the percent body fat in the three populations but we could not find any significant correlation between the fasting respiratory quotient values and the percent body fat.

Conclusions

There were different seasonal variations in the fasting respiratory quotient values in the three different populations. There were significant seasonal changes in the percent body fat in the three populations but no significant correlation between the fasting respiratory quotient values and the percent body fat.     

Copeptin Levels Remain Unchanged during the Menstrual Cycle

Background

Copeptin, a surrogate marker for arginin vasopressin production, is evaluated as an osmo-dependent stress and inflammatory biomarker in different diseases. We investigated copeptin during the menstrual cycle and its relationship to sex hormones, markers of subclinical inflammation and estimates of body fluid.

Methods

In 15 healthy women with regular menstrual cycles, blood was drawn on fifteen defined days of their menstrual cycle and was assayed for copeptin, progesterone, estradiol, luteinizing hormone, high-sensitive C-reactive protein, tumor necrosis factor-alpha and procalcitonin. Symptoms of fluid retention were assessed on each visit, and bio impedance analysis was measured thrice to estimate body fluid changes. Mixed linear model analysis was performed to assess the changes of copeptin across the menstrual cycle and the relationship of sex hormones, markers of subclinical inflammation and estimates of body fluid with copeptin.

Results

Copeptin levels did not significantly change during the menstrual cycle (p = 0.16). Throughout the menstrual cycle, changes in estradiol (p = 0.002) and in the physical premenstrual symptom score (p = 0.01) were positively related to copeptin, but changes in other sex hormones, in markers of subclinical inflammation or in bio impedance analysis-estimated body fluid were not (all p = ns).

Conclusion

Although changes in estradiol and the physical premenstrual symptom score appear to be related to copeptin changes, copeptin does not significantly change during the menstrual cycle.     

Menstrual variations in thermal properties of the human breast.

Menstrual variations in breast skin temperature (Tbr), heat flow (HF), volume (Vol), surface area (A), and core temperature (Tre) have been measured in 13 women. Measurements were made twice weekly on resting subjects throughout one cycle. Twelve of thirteen subjects showed increased Vol and A during the second half of the menstrual cycle; six also showed a minor peak prior to the midcycle rise in Tre. Eight of thirteen subjects had significant peaks in Tbr which preceded the estimated day of ovulation. Breast HF was generally low during the first half of the cycle, rising following estimated ovulation. Analysis of core-to-breast conductance indicates that a decrease in resistance to heat transfer occurs both during the luteal phase and at the Tbr peak. It is hypothesized that the control mechanism underlying the Tbr peak is independent of that controlling the postovulatory increases in Vol, HF, and Tre.     

Women at altitude: ventilatory acclimatization at 4,300 m.

Women living at low altitudes or acclimatized to high altitudes have greater effective ventilation in the luteal (L) compared with follicular (F) menstrual cycle phase and compared with men. We hypothesized that ventilatory acclimatization to high altitude would occur more quickly and to a greater degree in 1) women in their L compared with women in their F menstrual cycle phase, and 2) in women compared with men. Studies were conducted on 22 eumenorrheic, unacclimatized, sea-level (SL) residents. Indexes of ventilatory acclimatization [resting ventilatory parameters, hypoxic ventilatory response, hypercapnic ventilatory response (HCVR)] were measured in 14 women in the F phase and in 8 other women in the L phase of their menstrual cycle, both at SL and again during a 12-day residence at 4,300 m. At SL only, ventilatory studies were also completed in both menstrual cycle phases in 12 subjects (i.e., within-subject comparison). In these subjects, SL alveolar ventilation (expressed as end-tidal PCO(2)) was greater in the L vs. F phase. Yet the comparison between L- and F-phase groups found similar levels of resting end-tidal PCO(2), hypoxic ventilatory response parameter A, HCVR slope, and HCVR parameter B, both at SL and 4,300 m. Moreover, these indexes of ventilatory acclimatization were not significantly different from those previously measured in men. Thus female lowlanders rapidly ascending to 4,300 m in either the L or F menstrual cycle phase have similar levels of alveolar ventilation and a time course for ventilatory acclimatization that is nearly identical to that reported in male lowlanders.     

Menstrual cycle variation in spatial ability: relation to salivary cortisol levels

This study examined whether menstrual cycle phase was associated with performance on the Primary Mental Abilities Test of Spatial Relations, a test of mental rotation, in undergraduate students (N = 82). As cortisol levels also vary across the menstrual cycle under conditions of stress and influence cognitive performance, saliva samples were obtained before and after the test session to examine whether cortisol levels were related to between- and within-group differences in spatial performance. Men scored higher on the spatial test than all the groups of women, although the difference between men and women in the menstrual phase was not significant. Women in the luteal phase scored lower than the menstrual, follicular, and oral contraceptive user groups of women. There were no sex or menstrual cycle differences in cortisol levels, and no association between cortisol levels and spatial performance. The poorer performance of women in the luteal phase was not related to differences in ratings of perceived stress, perceived success on the test, or mood. Although menstrual cycle phase accounted for a significant proportion of the variance (15%) in performance on the spatial test, this does not explain why men outperformed women regardless of the phase of the cycle. Thus, there are clearly several other variables, sociocultural and physiological, involved in mediating individual differences in spatial performance.     

Influence of vibration on the excitability of spinal α-motoneurons under static conditions and during evoked stepping in humans

The excitability of spinal α-motoneurons in healthy humans was investigated with vibrostimulation (20–60 Hz) applied to different groups of muscles both under stationary conditions and during vibration-evoked stepping movements with leg suspension. In 15 subjects, the H-reflex amplitude was compared under the conditions of vibration of the left leg quadriceps femoris (QFM) or biceps femoris (BFM) muscle, as well as under the conditions of vibration of the contralateral, motionless leg QFM muscle in three spatial positions of the body: upright, supine, and lying on the side with the left leg suspended. Under dynamic conditions, the H-reflex value was compared during evoked and voluntary steppings at eight intervals of the step cycle. In all body positions, the vibration of each ipsilateral leg muscle caused a significant H-reflex suppression, this suppression being more prominent under the air-stepping conditions. The vibration of the contralateral leg QFM had weak influence on the H-reflex amplitude. In seven subjects, the vibration of the ipsilateral and contralateral leg muscles generated stepping movements. During vibration-evoked air-stepping, the H-reflex had different amplitudes in different phases of the step cycle. At the same time, the differences between responses under voluntary and involuntary stepping conditions were revealed only in the step cycle phase corresponding to the stance phase. Thus, the different degrees of the H-reflex suppression by vibration in different spatial positions of the body seem to depend on the summary afferent inflows to the spinal cord interneurons involved in the regulation of locomotion and posture. Apparently, an increase in the spinal cord neuronal excitability, which is necessary for activating locomotor automatism under the leg unloading conditions, occurs during evoked air-stepping in the swing phase.     

Changes in Total Body Water and Body Fat in Young Women in the Course of Menstrual Cycle

This paper reports on the changes in total body water and body fat in young women in during the course of the menstrual cycle. We followed 40 young women with an average age of 21.52 years, and took bioelectrical impedance measurements during two menstrual cycles. The measurements were taken in three phases of the menstrual cycle. We found that body mass and total body water fluctuate during the menstrual cycle. Both parameters are highest in the luteal phase and lowest in the late folicular phase; 65% of the young women demonstrated these changes. The presence or absence of premenstrual symptoms had no influence on these values.     

Menstrual cycle effects on performance of mental arithmetic task

The purpose of this research was to identify the relationship between task performance and menstrual cycle. The difference of performance on menstrual cycle phase was investigated. The task was the mental arithmetic task which involved the non-sequential and higher order cognitive processes. The duration of the experiment was twenty minutes. Two-way analysis of variance by repeated-measures design was used to examine the differences in task performance between phases and temporal variations. Results showed that there was a significant difference in correct input time during temporal variations though there was no significant difference between phases. Moreover, the relationships between phases and intra-individual variations in task performance were examined using coefficient of variance (CV). CVs were plotted in three dimensions to examine the relationships between intra-individual variations and phases. Based on CVs, the subjects who showed differences were classified into two groups: those with a small difference in three phases and those with a difference every phase. The phase which indicated large CV changed with individuals.     

Circadian Rhythms in Human Body Composition

The study investigates how the human body composition (BC) changes as a function of the day-night cycle. The BC was investigated using bioelec-trical impedance analysis (BIA) of 10 clinically healthy subjects (CHS), mon-itored in supine position (readings at 2-h intervals), avoiding mealtimes, di-etary abuses, and bladder and intestinal retention. Time series data were analyzed for their temporal characteristics and circadian rhythm (CR). Ail the variables of BC (lean body mass, fat body mass, body cell mass, total body water, intracellular and extracellular body water, sodium and potassium exchangeable pool) showed a within-day variability with nighttime crests. Such an oscillatory synchronism corroborates the hypothesis that the rest time plays a fundamental role, via its anabolic effects, in conferring the noc-turnal phase to the CR of the human BC.     

The influence of vibration on spinal alpha-motoneurons excitability in static conditions and during evoked stepping in human

In healthy human the excitability of spinal alpha-motoneurons under application of vibrostimulation (20-60 Hz) to different leg muscles was investigated both in stationary condition and during stepping movements caused by vibration in the condition of suspended leg. In 15 subjects the amplitude of H-reflex were compared under vibration of rectus femoris (RF) and biceps femoris (BF) muscles of left leg as well during vibration of rectus femoris of contralateral, motionless leg in three spatial positions: upright, supine and on right side of body with suspended left leg. In dynamic conditions the amount of H-reflex was compared during evoked and voluntary stepping at 8 intervals of step cycle. In all body positions the vibration of each ipsilateral leg muscles caused significant suppression of H-reflex, this suppression was more prominent in the air-stepping conditions. The vibration of contralateral leg RF muscle had a weak influence on the amplitude of H-reflex. In 7 subjects the muscle vibration of ipsilateral and contralateral legs generated stepping movements. During evoked "air-stepping" H-reflex had different amplitudes in different phases of step cycle. At the same time the differences between responses under voluntary and non-voluntary stepping were revealed only in stance phase. Thus, different degree of H-reflex suppression by vibration under different body position in space depends on, it seems to be, from summary afferent inflows to spinal cord interneurons, which participate in regulation of posture and locomotion. Seemingly, the increasing of spinal cord neurons excitability occurs under involuntary air-stepping in swing phase, which is necessary for activation of locomotor automatism under unloading leg conditions.     

Menstrual cycle characteristics and predictability of ovulation of Bhutia women in Sikkim, India

Although a woman's menstrual history can have significant implications for health outcomes, few studies have examined menstrual cycle variability in non-western, non-clinically based populations. This study presents menstrual cycle characteristics from Bhutia women living in Gangtok, Sikkim, India. The Bhutia are one of two indigenous populations residing in this small, northeastern state of India. A total of 1067 cycles were recorded by 200 Bhutia women over the course of 12 months. Mean cycle length in this population was similar to reported mean cycle lengths for populations in the U.S (30 days vs. 28 days). Menstrual cycles in this sample were highly variable with most women experiencing more than one short or long menstrual cycle. The frequency of irregular menstrual cycles experienced by individuals also varied significantly by season. A body mass index (BMI) above or below the WHO defined normal range was associated with higher rates of irregular cycles. Leutenizing hormone (LH) and follicle stimulating hormone (FSH) levels were also determined from urine samples collected just before mid-cycle, based on median cycle lengths. Although menstrual cycles in this sample were highly variable, median cycle length was still useful in predicting timing of the pre-ovulatory hormone surges of LH and FSH. Frequency of irregular cycles did impact the successful capture of the LH and FSH peak values.     

Determinants and interindividual variation of R-R interval dynamics in healthy middle-aged subjects

Determinants and intersubject variations of fractal and complexity measures of R-R interval variability were studied in a random population of 200 healthy middle-aged women (age 51 +/- 6 yr) and 189 men (age 50 +/- 6 yr) during controlled conditions in the supine and sitting positions. The short-term fractal exponent (alpha(1)) was lower in women than men in both the supine (1.18 +/- 0.20 vs. 1.12 +/- 0.17, P < 0.01) and sitting position (P < 0.001). Approximate entropy (ApEn), a measure of complexity, was higher in women in the sitting position (1.16 +/- 0.17 vs. 1.07 +/- 0.19, P < 0.001), but no gender-related differences were observed in ApEn in the supine position. Fractal and complexity measures were not related to any other demographic, laboratory, or lifestyle factors. Intersubject variations in a fractal measure, alpha(1) (e.g., 1.15 +/- 0.20 in the supine position, z value 1.24, not significant), and in a complexity measure, ApEn (e.g., 1.14 +/- 0.18 in the supine position, z value 1.44, not significant), were generally smaller and more normally distributed than the variations in the traditional measures of heart rate variability (e.g., standard deviation of R-R intervals 49 +/- 21 ms in the supine position, z value 2.53, P < 0.001). These results in a large random population sample show that healthy subjects express relatively little interindividual variation in the fractal and complexity measures of heart rate behavior and, unlike the traditional measures of heart rate variability, they are not related to lifestyle, metabolic, or demographic variables. However, subtle gender-related differences are also present in fractal and complexity measures of heart rate behavior.     

How Body Orientation Affects Concepts of Space,Time and Valence: Functional Relevance of Integrating Sensorimotor Experiences during Word Processing

The aim of the present study was to test the functional relevance of the spatial concepts UP or DOWN for words that use these concepts either literally (space) or metaphorically (time, valence). A functional relevance would imply a symmetrical relationship between the spatial concepts and words related to these concepts, showing that processing words activate the related spatial concepts on one hand, but also that an activation of the concepts will ease the retrieval of a related word on the other. For the latter, the rotation angle of participant’s body position was manipulated either to an upright or a head-down tilted body position to activate the related spatial concept. Afterwards participants produced in a within-subject design previously memorized words of the concepts space, time and valence according to the pace of a metronome. All words were related either to the spatial concept UP or DOWN. The results including Bayesian analyses show (1) a significant interaction between body position and words using the concepts UP and DOWN literally, (2) a marginal significant interaction between body position and temporal words and (3) no effect between body position and valence words. However, post-hoc analyses suggest no difference between experiments. Thus, the authors concluded that integrating sensorimotor experiences is indeed of functional relevance for all three concepts of space, time and valence. However, the strength of this functional relevance depends on how close words are linked to mental concepts representing vertical space.     

Potential applications of electrical impedance techniques in female mammalian reproduction

The measurement of electrical impedance is one of many methods that can be used for monitoring various reproductive events in female mammals. This paper summarizes the key findings in this research area that have been achieved during the past four decades. The electrical impedance in the vagina, vaginal vestibule and vulva during the estrous/menstrual cycle shows significant changes that vary among these reproductive organs, different locations in these organs and mammalian species. The changes of vaginal and vulvar impedance during periestrus are temporarily associated with the preovulatory luteinizing hormone (LH) peak and are significantly correlated with systemic levels of estradiol and progesterone. In humans, significant impedance changes during the menstrual cycle and their close association with the LH peak and ovulation have been found not only in the vagina, but also in the tongue. Findings of a number of studies suggest the possibility of using vaginal, vestibular and vulvar impedance to predict and confirm the fertile period of the estrous/menstrual cycle. There is some evidence that vulvar and cervical impedance may be a reliable indicator of impending parturition. Results in several studies also indicate the possibility of using electrical impedance methods to confirm the existence of ovarian follicular cysts, endometriosis and cervical neoplasia. However, physical and biological factors that may affect the impedance variation in the female reproductive system and tongue are still poorly understood. Their detection allows us to improve our ability to predict more precisely various reproductive processes by impedance techniques. This review also provides some considerations about the origin of impedance changes in the female reproductive system and tongue that may be useful for the systematic development of impedance methods in the field of female mammalian reproduction.     

Twenty-four-Hour Rhythmic Variations of Histamine in Human Female Blood

We have previously observed that blood histamine levels undergo rhythmic 24 hour variations in male normal subjects. In the present study we examined whether similar 24 hour modifications were also present in female subjects. To this purpose, 60 healthy cycling women were enrolled for a chronobiological transverse study. To achieve experimental conditions as homogeneous as possible, the study was carried out on the first day of the menstrual flow. Histamine was determined in whole venous blood by a spectrophotofluorimetric method. The blood histamine levels showed significant rhythmic changes depending on the time of blood sampling, with 1 maximum and 1 minimum within a period of 24 h, with percentage rhythm 15.1, MESOR 0.15 μg/ml, amplitude 0.02 μg/ml and acrophase at 01:20 h. These results reveal the presence of 24 h cyclic variations of histamine levels in the female, as it occurred in male. However, the differences observed in the chronobiological rhythms of histamine between the two sexes may represent a peculiar feature of the first day of the menstrual cycle.     

A 30-year study of body temperature variations correlated with menstrual cycle,seasonality, and aging

Studies of human body temperature typically involve a small number of subjects or measurements taken over a relatively short timeframe. To enhance the size of the data-set and more reliably distinguish outlying values, oral temperature was measured each evening in a single female subject for 30 years. The results confirmed the well-known temperature variations during the menstrual cycle and the decreased temperature in older adults compared to young adults. The present study’s large data-set extended these results, revealing a gradual decline in temperature with advancing age during middle-age and a rapid decline in temperature during menopause. The results also revealed a convincing seasonal variation in body temperature that peaked in August and were lowest in February–March. A modest shift in body temperature was also related to daylight-saving time change. These results confirm and extend the findings of earlier studies, showing the relationship of body temperature to the menstrual cycle, seasonality, and aging.