Structural analysis of female and hermaphroditic flowers of a gynodioecious tree, Ocotea tenera (Lauraceae)

The evolution of gynodioecy from hermaphroditism involves modifications of floral structure such that male or female fitness is enhanced in hermaphrodites and females, respectively. We present an analysis of structural specialization of flowers of Ocotea tenera, in order to evaluate gender system evolution in this tropical tree species. Significant morphological and anatomical variation was found between high fruiting and low or nonfruiting trees. Female flowers were significantly smaller than hermaphroditic flowers, produced no viable pollen, and made relatively greater allocation to structures that increase female fitness. Hermaphroditic flowers were significantly larger than female flowers, produced copious quantities of pollen, and made relatively greater allocation to male structures. Analyses indicated that changes in allometries between whole-flower growth and growth of reproductive structures may have occurred, which enhance function of the flower and plant as a male or female. Efficiency of nutrient allocation for reproduction is argued to be a factor driving gender system evolution in Ocotea tenera.     

Seasonality of thermophilic Campylobacter populations in chickens

The small intestines and caeca of chickens were monitored for seasonal variation of thermophilic campylobacters over a 12-month period. There was a significant seasonal fluctuation in the carriage rate which correlated with the following environmental parameters: sunshine hours (P = 0.0003) and minimum (P = 0.007) and maximum temperatures (P = 0.003). The number of campylobacters in the small intestine and caeca also showed significant seasonal variation (P = 0.0008); however, the periodicity in the caeca was significantly different from that in the small intestine (P = 0.007). The numbers of Campylobacter in the caeca were significantly higher than those in the small intestine (P = 0.001). No significant correlation was found between the numbers of campylobacters in the caeca and small intestines and the environmental parameters monitored.     

Impact of Ramadan intermittent fasting on cognitive function in trained cyclists: a pilot study

This study assessed selected measures of cognitive function in trained cyclists who observed daylight fasting during Ramadan. Eleven cyclists volunteered to participate (age: 21.6±4.8 years, VO₂max: 57.7±5.6 ml kg⁻¹·min⁻¹) and were followed for 2 months. Cognitive function (Cambridge Neuropsychological Test Automated Battery (CANTAB), Reaction Time index (RTI) and Rapid Visual Information Processing (RVP) tests) and sleep architecture (ambulatory EEG) were assessed: before Ramadan (BR), in the 1st week (RA1) and 4th week of Ramadan (RA4), and 2 weeks post-Ramadan (PR). Both cognitive tests were performed twice per day: before and after Ramadan at 8-10 a.m. and 4-6 p.m., and during Ramadan at 4-6 p.m. and 0-2 a.m., respectively. Training load (TL) by the rating of perceived exertion (RPE) method and wellness (Hooper index) were measured daily. If the TL increased over the study period, this variable was stable during Ramadan. The perceived fatigue and delayed onset muscle soreness (DOMS) increased at RA4. Sleep patterns and architecture showed clear disturbances, with significant increases in the number of awakenings and light sleep durations during Ramadan (RA1 and RA4), together with decreased durations of deep and REM sleep stages at PR. RTI (simple and multiple reaction index) reaction and movement times did not vary over the study period. The RVP test showed reduced false alarms during Ramadan, suggesting reduced impulsivity. Overall accuracy significantly increased at RA1, RA4 and PR compared to baseline. At RA4, the accuracy was higher at 0-2 a.m. compared to 4-6 p.m. Despite the observed disturbances in sleep architecture, Ramadan fasting did not negatively impact the cognitive performance of trained cyclists from the Middle East.     

The self-association of chicken-erythrocyte histones.

The self-association of the separate histone fractions isolated from chicken erythrocytes has been studied in solution at a number of different pH values and ionic strengths. The apparent molecular weights of the histones were determined over a range of macromolecular concentrations using the techniques of osmotic pressure and sedimentation equilibrium. Histone F2c (H5) did not associate under any of the conditions investigated whereas the other histone fractions all appeared to undergo self-association forming dimers, dimers of dimers, etc. The degree of association increased with the pH and ionic strength of the medium. The tendency to aggregate increased in the order; histone F2c (H5) (non-aggregating), histone F2b (H2B), histone F2a2 (H2A), histone F3 (H3), histone F2a1 (H4) (highly aggregating). In the case of histone F2a2 (H2A) at pH 3.0 and ionic strength 0.1, the apparent weight-average molecular weight was determined at a number of macromolecular concentrations at five different temperatures. The self-association was analysed according to the method of Adams (published by Beckman Instruments Inc. in 1967) and shown to be a monomer-dimer-tetramer equilibrium. The association constants were evaluated at each of the temperatures studied and from their variation with temperature the values of the enthalpy and entropy of association were calculated. The intermolecular association was characterised by only a small change in enthalpy but a large, positive, change in entropy. This suggests that the association of histones at acid pH is due to hydrophobic interactions between the relatively uncharged segments of like polypeptide chains.