Novel insights into FGD3, a putative GEF for Cdc42, that undergoes SCF(FWD1/beta-TrCP)-mediated proteasomal degradation analogous to that of its homologue FGD1 but regulates cell morphology and motility differently from FGD1

We previously demonstrated that FGD1, the Cdc42 guanine nucleotide exchange factor (GEF) responsible for faciogenital dysplasia, is targeted by the ubiquitin ligase SCF^FWD1/β-TrCP upon phosphorylation of two serine residues in its DSGIDS motif and subsequently degraded by the proteasome. Here we show that FGD3, which was identified as a homologue of FGD1 but has been poorly characterized, has conserved the same motif and is down-regulated similarly by SCF^FWD1/β-TrCP. Although FGD3 and FGD1 share strikingly similar Dbl homology (DH) domains and adjacent pleckstrin homology (PH) domains, both of which are responsible for guanine nucleotide exchange, there also exist remarkable differences in their structures. Indeed, FGD1 and FGD3 induced significantly different morphological changes in HeLa Tet-Off cells: whereas FGD1 induced long finger-like protrusions, FGD3 induced broad sheet-like protrusions when the level of GTP-bound Cdc42 was significantly increased by the inducible expression of FGD3. Furthermore, FGD1 and FGD3 reciprocally regulated cell motility: when inducibly expressed in HeLa Tet-Off cells, FGD1 stimulated cell migration whereas FGD3 inhibited it. Thus we demonstrate that the highly homologous GEFs, FGD1 and FGD3 play different roles to regulate cellular functions but that their intracellular levels are tightly controlled by the same destruction pathway through SCF^FWD1/β-TrCP.     

For others: epistasis and the evolutionary survival of an extreme tail of the quantitative distribution of autistic assets

The ongoing paradigm shift from the traditional qualitative dichotomy concept to the quantitative framework increases the necessity of an evolutionary implication and interpretation of the presence of a hypo-reproductive behavioral extreme (autism) with strong genetic contribution. As a theoretical challenge to explain the survival of the dimensional distribution of autistic traits, an epistasis-associated oscillation of fitness outcomes is proposed. In this hypothesis, an allele could contribute to the existence of both phenotypic extreme tails and the hypothesized genetic machinery (quantitative trait loci) for autism would necessarily be common in the entire human population. The postulated autism genes would allow autistics to enjoy autistic traits and assets and all of the residual non-autistic individuals could owe their social skills and reproductive advantages to the same autism genes. Importantly, the reported modest correlations between core autistic dimensions can be illustrated using unsynchronized epistatic pleiotropy.     

Endurance exercise performance in Masters athletes: age-associated changes and underlying physiological mechanisms

Older ('Masters') athletes strive to maintain or even improve upon the performance they achieved at younger ages, but declines in athletic performance are inevitable with ageing. In this review, we describe changes in peak endurance exercise performance with advancing age as well as physiological factors responsible for those changes. Peak endurance performance is maintained until approximately 35 years of age, followed by modest decreases until 50-60 years of age, with progressively steeper declines thereafter. Among the three main physiological determinants of endurance exercise performance (i.e. maximal oxygen consumption , lactate threshold and exercise economy), a progressive reduction in appears to be the primary mechanism associated with declines in endurance performance with age. A reduction in lactate threshold, i.e. the exercise intensity at which blood lactate concentration increases significantly above baseline, also contributes to the reduction in endurance performance with ageing, although this may be secondary to decreases in . In contrast, exercise economy (i.e. metabolic cost of sustained submaximal exercise) does not change with age in endurance-trained adults. Decreases in maximal stroke volume, heart rate and arterio-venous O(2) difference all appear to contribute to the age-related reductions in in endurance-trained athletes. Declines in endurance exercise performance and its physiological determinants with ageing appear to be mediated in large part by a reduction in the intensity (velocity) and volume of the exercise that can be performed during training sessions. Given their impressive peak performance capability and physiological function capacity, Masters athletes remain a fascinating model of 'exceptionally successful ageing' and therefore are highly deserving of our continued scientific attention as physiologists.     

A novel autonomic activation measurement method for stress monitoring: non-contact measurement of heart rate variability using a compact microwave radar

We developed a novel method for non-contact monitoring of stress-induced autonomic activation through the back of a chair, using a compact 24 GHz microwave radar (8 x 5 x 3 cm), without large-scale equipment and placing a heavy burden on the monitored individual. Following a silent period of 120 s, audio stimuli using a composite tone of 2,120 and 2,130 Hz sine-waves at 95 dB were conducted for 120 s. From dorsal, LF/HF of HRV reflecting sympatho-vagal balance was determined by microwave radar with the maximum entropy method using eight volunteers (mean age 23 +/- 1 years). Mean LF/HF measured by non-contact and contact (using electrocardiography for reference) methods during audio stimuli increased 34 and 37%, respectively, as compared with those of the silent period. Maximum cross-correlations between contact and non-contact measurements averaged 0.73 +/- 0.10. Our method appears to be promising for future monitoring of stress-induced autonomic activation of operators and may reduce stress-induced accidents.     

B-type natriuretic peptide after hormone therapy in postmenopausal women with chest pain and normal coronary angiogram

OBJECTIVES: Coronary heart disease is relatively uncommon in premenopausal women but shows a sharp increase after menopause. The decline of endogenous ovarian hormones is commonly assumed to be a major component of this phenomenon. The effects of estrogens on the vasculature have been investigated extensively in previous studies. However, the effects of estrogens on myocardial function have not been evaluated in humans. We sought to examine the effects of hormone therapy (HT) on myocardial function and cardiac natriuretic peptides in postmenopausal women with chest pain and a normal coronary angiogram. DESIGN: Transdermal HT (estradiol: 0.72 mg/2 d) was administered to 15 postmenopausal women with chest pain and a normal coronary angiogram (mean age, 53 y) for 12 weeks, and oral HT (conjugated equine estrogens: 0.625 mg/d) was administered to another 15 postmenopausal women (mean age, 54 y) for 12 weeks. Echocardiography or cardiac catheterization showed no cardiac dysfunction in any woman at baseline. Cardiac function was evaluated by echocardiography, and plasma B-type natriuretic peptide was measured every 4 weeks. RESULTS: B-type natriuretic peptide levels increased after transdermal HT (baseline: 13.1 +/- 3.1, 4 wk: 22.1 +/- 2.9, 8 wk: 33.2 +/- 3.1, 12 wk: 38.4 +/- 3.3 pg/mL; P < 0.01 vs baseline). The levels were also augmented after oral HT (baseline: 14.1 +/- 3.8, 4 wk: 23.2 +/- 3.3, 8 wk: 35.6 +/- 3.9, 12 wk: 39.6 +/- 3.5 pg/mL; P < 0.01 vs baseline). Serial echocardiography showed no changes in ventricular function in either treatment group. At baseline the serum estradiol levels in the transdermal group were comparable with those in the oral group. CONCLUSIONS: The estradiol levels after HT increased in both groups, but there was no significant difference between the two groups. B-type natriuretic peptide levels increased without cardiac dysfunction, and the chest symptoms were relieved in some participants after HT. Thus, estrogen supplementation augments natriuretic peptide levels without harmful effects on ventricular function.     

MEK–ERK signaling in adult newt retinal pigment epithelium cells is strengthened immediately after surgical induction of retinal regeneration

Adult newt retinal pigment epithelium (RPE) cells are mitotically quiescent in the physiological condition, but upon a traumatic injury of the neural retina (NR) they re-enter the cell-cycle and eventually regenerate the missing NR. Here, to understand the mechanism underlying the cell-cycle re-entry of RPE cells following NR injury, we first investigated changes in MEK–ERK signaling activity in RPE cells upon removal of the NR (retinectomy) from the eye of living animals, and found that ERK-mediated signaling activity is elevated quickly (in 30 min) upon retinectomy. In addition, we found, in in vitro analyses, that immediate early activation of MEK–ERK signaling may occur in RPE cells upon NR injury, intensifying the MEK–ERK signaling itself through up-regulation of the expression of constituent molecules in the pathway, and that 1-h blockade of such early MEK–ERK signaling interferes with the cell-cycle re-entry, which occurs 5–10 days later. Together, these results provide us with insight that elevation of MEK–ERK signaling activity upon NR injury may be a key process for mitotically quiescent RPE cells to re-enter the cell-cycle, leading to retinal regeneration.     

Effects of aging and persistent prehypertension on arterial stiffening

An age-related association of blood pressure in the non-hypertensive range (non-hypertensive blood pressure) to the cardiovascular mortality has been demonstrated. This prospective study was conducted to examine the effects of age, persistence of pre-hypertension (preHYP) during the study period, and the interaction between these factors on the rate of progression of arterial stiffening. Among 1563 healthy Japanese subjects without hypertension (age range: 29-95 years), the brachial-ankle pulse wave velocity (baPWV) was measured twice (i.e., at baseline and 5-6 years later). The adjusted (including for blood pressure) value of the annual rate of increase of the baPWV during the study period (delPWV) increased in a linear manner along with the age category (categorized into 29-39 years, 40-59 years, and 60 years or older for this study) and the evolutional category of non-hypertensive blood pressure during the study period (categorized into persistence of normal blood pressure, borderline evolution, and persistence of preHYP), and a significant interaction between the two in relation to the delPWV was also noted (non-standardization coefficient=5.08 [95% confidence interval=3.24-6.92], F-value=29.40, P<0.01). In conclusion, the present study suggests that persistence of preHYP is associated with accelerated structural stiffening of the large- to middle-sized arteries, and that age may exert a synergistic effect on this acceleration of arterial stiffening. Thus, persistence of preHYP also appears, like hypertension, to be associated with progressive vascular damage, and this progression may be more pronounced in middle-aged and elderly subjects.