The Menstrual Cycle and Human Performance: An Overview

Physiological events during the normal menstrual cycle are determined by feedback loops within the hypothalamic-pituitary-ovarian axis. Hormonal changes within the menstrual cycle have potential impact on human performance. Relevant stages to consider are pre-menses and menses, the follicular and luteal phases separated by an abrupt elevation in lutenizing hormone and characterised by a sharp rise in body temperature coinciding with ovulation. Strenuous athletic training may affect the normal menstrual cycle. Such disruptions include delayed menarche in ballet dancers and gymnasts, shortened luteal phase and secondary amenorrhea associated with high training loads and competitive stress. Amenorrhea is also noted in flight attendants, linked with an inhibiting effect of disrupted circadian rhythm on lutenizing hormone. The so-called 'athlete triad' considers secondary amenorrhea, abnormal eating behaviour and osteoporosis (attributed to chronic hypoestrogenia). The normal cycle may also be disrupted when circadian rhythms are disturbed, for example in rapid time-zone transitions. Fluctuations in the steroid hormones have been associated with changes in muscle strength. There is evidence also of elevations in heart rate: changes may be partly specific to time of day. Effects on muscle strength may be determined at selected stages of the menstrual cycle, using whole-body performance, local muscle groups or isolated individual muscles. Whilst oestrogen has been implicated in the ergogenic effect of steroid hormones, there is accumulating evidence that a role for progesterone cannot be discounted. The isolation of the ovarian hormones separately is feasible with studies of IVF patients or groups on hormone replacement therapy.     

Life-history responses of larviparous Boettcherisca formosensis (Diptera: Sarcophagidae) to larval competition for food, including comparisons with oviparous Hemipyrellia ligurriens (Calliphoridae)

Abstract. 1 The effect of larval rearing density on life-history parameters of Boettcherisca formosensis Kirner & Lopes (Sarcophagidae) was investigated. Increases in rearing density resulted in lowered larval survivorship, shortened larval development time and production of smaller, shorter-lived adults with reduced fecundity.
2. B. formosensis is larviparous. Average brood size was 17.5±1.0 (mean±M) larvae, which was much less than the average number of mature larvae inside gravid females. Females apparently produced a series of small broods, distributing their offspring over a number of carcasses.
3. Compared with the oviparous species Hemipyrellia ligurriens (Wiedemann) (Calliphoridae), B. formosensis adults were larger and longer-lived, with a longer larval development time but shorter larval feeding period. However, females had a shorter pre-reproductive period, were less fecund, and had a lower life time reproductive investment.
4. B. formosensis had lower relative performance (measured by the composite index of performance, r') than H. ligurriens over the larval rearing density range, and was more sensitive to increases in density. Although the r' values suggest that the sarcophagid may be a competitively inferior species, other features which are not included in the index (such as larvipary, short larval feeding period and spreading of offspring from a single brood among carcasses) may be of significant adaptive value to B. formosensis.     

The effect of exercise and zinc supplement on the hematological parameters in rats

This study evaluates the consequences of a session of intensive short-duration exercise and Zn supplementation on different hematological variables. Forty male Wistar rats were divided into four groups (n=10): the first nonsupplemented, maintained at rest (R); the second nonsupplemented, undergoing exercise (E); the third supplemented with Zn, kept at rest (ZnR); and the fourth supplemented with Zn, undergoing exercise (ZnE). Zinc supplements (200 ppm) were given in drinking water. The exercise consisted of a single session of swimming until exhaustion. At rest, RBC, Hb, and Hto fell (p<0.05), whereas red cell indices, MCV, and MCH rose (p<0.05) in +ZnR compared with R; MCHC remained unchanged (ZnR vs R). After exercise, RBC, Hb, and Hto increased significantly in E and in ZnE compared with R and ZnR, respectively. In addition, RBC and Hb were lower (p<0.01) in ZnE compared with E; however, MCV and MCH were higher (p<0.05) in the group ZnE vs E. With respect to white blood cells—leukocytes (WBC), limphocytes (LYMPH), and neutrophiles (NEUT)—no significant differences were observed between groups at rest (ZnR vs R). WBC and LYMPH increased significantly in E with respect to the rest situation (E vs R), but this did not happen in supplemented animals (ZnE vs ZnR). Level of pH decreased after exercise both in E and in ZnE, but the fall was lower in the latter. We believe that a single session of swimming until exhaustion leads to an increase in RBC, Hb, and Hto without causing changes in MCV, MCH, and MCHC. On the other hand, Zn supplementation leads to an increase of MCV and MCH, although they remain within normal levels. Furthermore, this supplementation produces lower metabolic acidoses after exercise that leads to leukocyte stability.     

Monosynaptic excitation of lateral giant fibres by proprioceptive afferents in the crayfish

Giant interneurones mediate a characteristic `tail flip' escape response of the crayfish, Procambarus clarkii, which move it rapidly away from the source of stimulation. We have analysed the synaptic connections of proprioceptive sensory neurones with one type of giant interneurone, the lateral giant. Spikes in sensory neurones innervating an exopodite-endopodite chordotonal organ in the tailfan, which monitors the position and movements of the exopodite, are followed at a short and constant latency by excitatory postsynaptic potentials in a lateral giant interneurone (LG) recorded in the terminal abdominal ganglion. These potentials are unaffected by manipulation of the membrane potential of LG, by bath application of saline with a low calcium concentration, or by one containing the nicotinic antagonist, curare. The potentials evoked in LG by chordotonal organ stimulation are thus thought to be monosynaptic and electrically mediated. This is the first demonstration that LG receives input from sensory receptors other than exteroceptors in the terminal abdominal ganglion. Accepted: 7 April 1997     

Determination of kinetic parameters from chemical relaxation data discrimination between coupled two-step binding reactions differing in stoichiometry

The chemical relaxation times of two different two-step equilibrium reactions, characterized by a 1:1 binding process followed by a subsequent rearrangement step and a stepwise 1:2 binding reaction, are analyzed for the purpose of qualitative model discrimination and quantitative determination of kinetic parameters. The equations describing the dependences of the two reciprocal relaxation times on suitable concentrations are given for both models in the general case as well as for four different limiting situations which are characterized by well separated relaxation times. The conditions corresponding to the limiting cases are expressed in terms of strong, weak and no coupling between the two partial equilibrium steps involved in both models. The coupling strength depends on the rate constants as well as on the total concentrations of the reactants. Criteria to discriminate between these two reaction models under defined limiting conditions are developed. In the general case, the product of both reciprocal relaxation times can be used to distinguish both models. If only one relaxation time can be resolved experimentally, it is possible under conditions described to determine only a reduced set of individual rate constants for most of the limiting cases considered. If both relaxation times are observed, all rate constants are determinable in the general case as well as in most of the limiting cases discussed.     

Configural Frequency Analysis as a Parametric Method for the Search of Types and Antitypes

The article introduces Parametric Configural Frequency Analysis (CFA). It is argued that there are two types of parameters that can be of importance in CFA models. The first is effect parameters that are estimated from the data. This type of parameter is involved in almost all models of Classical, nonparametric CFA. The second type involves a priori or distributional parameters that can be used for estimation of expected frequencies. These parameters are specified a priori rather than estimated from data. A combination of models from Classical CFA and Parametric CFA is introduced as Semi-Parametric CFA. Data examples illustrate the new CFA models in comparison with the Classical CFA. Interpretational issues are discussed.     

Nitroxide Radicals Prevent Metal-aggravated Reperfusion Injury in Isolated Rat Heart

The effects of Cu(II) and the stable nitroxide radical 4-OH-2, 2, 6, 6-tetramethyl-piperidine-1-oxyl (TPL) on reperfusion injury following global myocardial ischemia have been studied using the isolated rat heart model in the Langendorff configuration. Hearts were equilibrated with Krebs-Henseleit buffer (KH-buffer) for 10 min and subjected to 18 min of normothermic global ischemia. After 20 min reperfusion, hemodynamic parameters recovered as follows: ventricular developed pressure (77%), dP/dt (71%) and -dP/dt (80%), heart rate (91%), and work index (70%). End-diastolic pressure was 16 mm Hg. When 10μM Cu-nitrilotriacetate or Cu-(histidine)₂ was included in the perfusate before, during, and following ischemia, the heart injury was more extensive and the work index only recovered to 17% of the preischemic value. The inclusion of 100μM TPL during reperfusion abolished the copper-induced sensi-tization. In the absence of copper, TPL did not provide any protection against ischemia-reperfusion damage to the heart. The inclusion of 100μM 1, 4-dihydroxy-2, 2, 6, 6-tetramethylpiperidine (TPL-H) during reperfusion, partially abolished the copper-induced sensitization. Since conversion between TPL and TPL-H takes place, the fact that both forms provide protection can increase their protective efficacy.     

Influence of the single‐strand linker composition on the structural/dynamical properties of a truncated octahedral DNA nano‐cage family

The structural/dynamical properties of three truncated octahedral DNA nano‐cages composed by identical double helices but single strand linkers with different composition, namely 7 thymidines, 7 adenines, and 7 alternated thymidines and adenines, have been investigated through classical molecular dynamics simulations. Trajectories have been analyzed to investigate the role of the linkers in defining nano‐cages stability and flexibility, including possible influence on the internal cages motions. The data indicate that the cages behavior is almost identical and that the structural/dynamical parameters measured along the trajectories are not particularly affected by the presence of different bases. These results demonstrate that the constraints imposed by the nano‐structure geometry are the main factor in modulating these properties. © 2014 Wiley Periodicals, Inc. Biopolymers 101: 992–999, 2014.     

Influence of newly designed monorail pressure sensor catheter on coronary diagnostic parameters: An in vitro study

The decision to perform intervention on a patient with coronary stenosis is often based on functional diagnostic parameters obtained from pressure and flow measurements using sensor-tipped guidewire at maximal vasodilation (hyperemia). Recently, a rapid exchange Monorail Pressure Sensor catheter of 0.022″ diameter (MPS22), with pressure sensor at distal end has been developed for improved assessment of stenosis severity. The hollow shaft of the MPS22 is designed to slide over any standard 0.014″ guidewire (G14). Hence, influence of MPS22 diameter on coronary diagnostic parameters needs investigation. An in vitro experiment was conducted to replicate physiologic flows in three representative area stenosis (AS): mild (64% AS), intermediate (80% AS), and severe (90% AS), for two arterial diameters, 3 mm (N2; more common) and 2.5 mm (N1). Influence of MPS22 on diagnostic parameters: fractional flow reserve (FFR) and pressure drop coefficient (CDP) was evaluated both at hyperemic and basal conditions, while comparing it with G14. The FFR values decreased for the MPS22 in comparison to G14, (Mild: 0.87 vs 0.88, Intermediate: 0.68 vs 0.73, Severe: 0.48 vs 0.56) and CDP values increased (Mild: 16 vs 14, Intermediate: 75 vs 56, Severe: 370 vs 182) for N2. Similar trend was observed in the case of N1. The FFR values were found to be well above (mild) and below (intermediate and severe) the diagnostic cut-off of 0.75. Therefore, MPS22 catheter can be used as a possible alternative to G14. Further, irrespective of the MPS22 or G14, basal FFR (FFR_b) had overlapping ranges in close proximity for clinically relevant mild and intermediate stenoses that will lead to diagnostic uncertainty under both N1 and N2. However, CDP_b had distinct ranges for different stenosis severities and could be a potential diagnostic parameter under basal conditions.