Influence of feeding schedules on the chronobiology of renin activity,urinary electrolytes and blood pressure in dogs

The contribution of the renin–angiotensin–aldosterone system (RAAS) to the development of congestive heart failure (CHF) and hypertension (HT) has long been recognized. Medications that are commonly used in the course of CHF and HT are most often given with morning food for the sake of convenience and therapeutic compliance. However, biological rhythms and their responsiveness to environmental clues such as food intake may noticeably impact the effectiveness of drugs used in the management of cardiovascular disorders. Only sparse information about the effect of feeding schedules on the biology of the RAAS and blood pressure (BP) is presently available. Two studies were designed to explore the chronobiology of renin activity (RA), BP, renal sodium (U_Na,fe) and potassium (U_K,fe) handling in relation to meal timing in dogs. In a first experiment (Study a), blood and urinary samples for measurement of RA, U_Na,fe and U_K,fe were drawn from 18 healthy beagle dogs fed a normal-sodium diet at either 07:00, 13:00 or 19:00?h. In a second experiment (Study b), BP was recorded continuously from six healthy, telemetered beagle dogs fed a similar diet at 07:00, or 19:00?h. Data were collected throughout 24-h time periods, and analyzed by means of nonlinear mixed-effects models. Differences between the geometric means of early versus late time after feeding observations were further compared using parametric statistics. In agreement with our previous investigations, the results indicate that RA, U_Na,fe, U_K,fe, systolic, and diastolic BP oscillate with a circadian periodicity in dogs fed a regular diet at 07:00?h. A cosine model with a fixed 24-h period was found to fit the variations of RA, U_K,fe and BP well, whereas cyclic changes in U_Na,fe were best characterized by means of a combined cosine and surge model, reflecting a postprandial sodium excretion followed by a monotonous decay. Our data show that feeding time has a marked influence on the chronobiology of the renin cascade, urinary electrolytes, and BP. Introducing a 6- or 12-h delay in the dogs’ feeding schedule caused a shift of similar magnitude (05:06 and 12:32?h for Studies a and b, respectively) in the rhythm of these biomarkers. In all study groups, RA and BP exhibited a marked fall just after food intake. The drop in RA is consistent with sodium and water-induced body fluid expansion, while the reduction of BP could be related to the decreased activity of renin and the secretion of vasodilatory gut peptides. An approximately 1.5-fold (1.2–1.6-fold) change between the average early and late time after feeding observations was found for RA (p?<?0.0001), U_Na,fe (p?<?0.01) and U_K,fe (p?<?0.05). Postprandial variations in BP, albeit small (ca. 10?mmHg), were statistically significant (p?<?0.01) and supported by the model-based analysis.

In conclusion, the timing of food intake appears to be pivotal to the circadian organization of the renin cascade and BP. This synchronizing effect could be mediated by feeding-related signals, such as dietary sodium, capable of entraining circadian oscillators downstream of the master, light–dark-adjusted pacemaker in the suprachiasmatic nucleus.     

Neurobiological mechanisms of the meridian and the propagation of needle feeling along the meridian pathway

The present experiments attempt to find the meridian phenomenon and how the needle feeling propagates along the given meridian channels. The neurobiological mechanisms of the meridian were studied with neuroelectrical recording from the motor neurons and CB-HRP retrograde histochemistry technique in both rats and cats. The results demonstrated that most, but not all, of alpha motor neurons supplying a muscle group of a given meridian were selectively activated by afferent inputs originating not only from homonymous or heterogeneous, but synergistic muscle, but also from the skin nerve overlying the muscle group of the homonymous meridian. However, the afferent inputs from the heterogeneous meridian have very weak or no effect. On the other hand, the labeled motor neurons supplying a given meridian muscles form a discrete longitudinal column with a definite bound in the lateral ventral horn. There are oriented dendro-dendristes projections between the labeled motor neurons.The characteristics of both sel     

The specification of metameric order in the insectCallosobruchus maculatus Fabr. (Coleoptera)

Summary Mechanically dividing an insect egg into anterior and posterior fragments results in a segment gap (Sander 1976), a loss of non-terminal segments in the constricted region. By altering the stage and duration of constriction, we produced different types of egg fragments in the pea beetleCallosobruchus. The patterns formed by these fragments suggest the existence of interactions between anterior and posterior egg regions that influence segment patterning and placement. Segments in excess of the numbers expected on the basis of permanent constrictions were produced in fragments when: (1) the constriction was released before cellularization occurred and (2) in addition the complementary fragment degenerated. Apparently the degenerating fragment induced the formation of excess segments in the developing fragment. Differences in the time and extent of excess segment formation in anterior versus posterior fragments suggest an asymmetric distribution of prerequisites for segment formation. This conclusion is consistent with our finding that a partial reversal of segment sequence (double abdomen formation) can be induced only in posterior fragments by a degenerating fragment, but not in anterior fragments (see companion paper).The formation of excess segments shows that the segment gap observed after permanent separation cannot be due to non-specific damage, caused by the process of constriction as such, to the egg or to localized putative segment precursors.     

What Are the Health Risks of Eating Red Meat,and How Should We Assess Them?

This paper discusses possible mechanisms that might lead to misinterpretations of collected data and makes new evidence-based medicine (EBM) recommendations to oppose the previously accepted preventive measures, or treatment options. It is focused on the danger of the “red meat” consumption, and the question whether eating pungent food is good or bad for our health and finally whether the “bad luck” concept of getting several cancer types is valid or not. These three topics got and still have significant media attention. Several mechanisms are proposed as possible causes of these apparent conflicts. Some of them have already been recognized but sadly remained less known to medical readers and also to the general population. Also see the video abstract here https://youtu.be/owjoRXrNShA .     

The neurobiology of adaptation to seasons: Relevance and correlations in bipolar disorders

ABSTRACT

Bipolar disorders (BDs) are severe and common psychiatric disorders. BD pathogenesis, clinical manifestations and relapses are associated with numerous circadian rhythm abnormalities. In addition, infradian fluctuations of mood, social activity, weight and sleep patterns are very frequent in BD. Disease course with a seasonal pattern (SP) occurs in approximately 25% of depressive and 15% of manic episodes, which is coupled to a more severe disease symptomatology. The pathophysiological mechanisms of seasonal effects in BD await clarification, with likely important clinical consequences. This review aims at synthesizing available data regarding the underlying pathophysiological mechanisms of seasonality in BD patients, with implications for future research directions in the study of seasonality in BD. Three factors are suggested to play significant roles in BD with SP, namely the suprachiasmatic nuclei, as well as the melatonergic and photoperiodism systems. It is proposed that BD with SP may be considered as a complex disorder resulting from the interaction of clock gene vulnerabilities and biological clock neuroplasticity, with environmental factors, such as the response to light. Light seems to play a key role in BD with SP, mainly due to two seasonal signaling pathways: a light to cortex serotonin transporter pathway, as well as a pathway connecting light to melatonin synthesis. This provides a theoretical framework for BD with SP, including for future research and clinical management. The review proposes that future research should explore markers of seasonality in BD, such as plasma melatonin, sleep–wake rhythms (with actigraphy) and genetic or epigenetic variants within the melatonin synthesis pathway. The role of light in driving BD with SP is an active area of research. Seasonality may also be intimately linked to wider aspects of BD, including via interactions with the gut microbiome, the gut–liver axis, cholesterol regulation, aspects of metabolic syndrome, vitamin D, decreased longevity, suicide risk and medication treatment targets. Further research on the role of seasonality in BD is likely to clarify the etiology, course and treatment of BD more widely.     

24-Hour Changes in Circulating Prolactin,Follicle-Stimulating Hormone,Luteinizing Hormone,and Testosterone in Young Male Rats Subjected to Calorie Restriction

This work analyzes the effect of calorie restriction on the 24 h variation of pituitary-testicular function in young male Wistar rats by measuring the circulating levels of prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone. Control animals were provided an equilibrium calorie diet and the experimental animals a calorie-restriction diet equivalent to 66% of food restriction for four weeks starting on day 35 of life. Different groups of control and experimental rats were killed at 6 h intervals around the clock, beginning 1 h after light on (HALO). Compared to the control animals, the mean secretion of prolactin was augmented and that of LH and testosterone decreased in calorie-restricted rats, whereas FSH release remained unchanged. Significant changes in the 24 h secretory pattern of circulating prolactin, LH, and testosterone occurred in the calorie-restricted rats. These include the appearance of a second maximum of plasma prolactin at 21 HALO, blunting of the LH peak seen at 13 HALO, and phase-shift of the testosterone peak from 13 HALO in controls to 17 HALO in calorie-restricted rats. The significant positive correlation between individual LH and testosterone levels found in controls was no longer observed in calorie-restricted rats. Availability of nutrients presumably affects the mechanisms that modulate the circadian variation of the pituitary-gonadal axis in growing male rats.     

Diurnal Variation in Wingate-Test Performance and Associated Electromyographic Parameters

The present study was designed to evaluate time-of-day effects on electromyographic (EMG) activity changes during a short-term intense cycling exercise. In a randomized order, 22 male subjects were asked to perform a 30-s Wingate test against a constant braking load of 0.087?kg·kg^?1 body mass during two experimental sessions, which were set up either at 07:00 or 17:00?h. During the test, peak power (P_peak), mean power (P_mean), fatigue index (FI; % of decrease in power output throughout the 30 s), and evolution of power output (5-s span) throughout the exercise were analyzed. Surface EMG activity was recorded in both the vastus lateralis and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root mean square (RMS) and mean power frequency (MPF) of EMG were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Resting core temperature, P_peak, P_mean, and FI were significantly higher (p?<?.05) in the evening than morning test (e.g., P_peak: 11.6?±?0.8 vs. 11.9?±?1 W·kg^?1). The results showed that power output decreased following two phases. During the first phase (first 20s), power output decreased rapidly and values were higher (p?<?.05) in the evening than in the morning. During the second phase (last 10s), power decreased slightly and appeared independent of the time of day of testing. This power output decrease was paralleled by evolution of the MPF and NME. During the first phase, NME and MPF were higher (p <?.05) in the evening. During the second phase, NME and MPF were independent of time of day. In addition, no significant differences were noticed between 7:00 and 17:00?h for EMG RMS during the whole 30 s. Taken together, these results suggest that peripheral mechanisms (i.e., muscle power and fatigue) are more likely the cause of the diurnal variation of the Wingate-test performance rather than central mechanisms. (Author correspondence: n_souissi@yahoo.fr)     

New Insights into the Circadian Rhythm of Acute Myocardial Infarction in Subgroups

The aim of this study was to determine the existence of the circadian rhythm (CR) in the onset of acute myocardial infarction (AMI) in different patient subgroups. Information was collected about 41,244 infarctions from the database of the ARIAM (Analysis of Delay in AMI) Spanish multicenter study. CR in AMI were explored in subgroups of cases categorized by age, gender, previous ischemic heart disease (PIHD), outcome in coronary care unit, infarction electrocardiograph (ECG) characteristics (Q wave or non‐Q wave), and location of AMI. Cases were classified according to these variables in the different subgroups. To verify the presence of CR, a simple test of equality of time series based on the multiple‐sinusoid (24, 12, and 8 h periods) cosinor analysis was developed. For the groups as a whole, the time of pain onset as an indicator of the AMI occurrence showed a CR (p<0.0001), with a morning peak at 10:10 h. All the analyzed subgroups also showed CR. Comparison between subgroups showed significant differences in the PIHD (p<0.01) and infarction ECG characteristics (p<0.01) groups. The CR of the subgroup with Q‐wave infarction differed from that of non‐Q wave subgroup (p<0.01) when the patients had PIHD (23% in Q wave infarction vs. 39.2% in non‐Q wave). AMI onset followed a CR pattern, which is also observed in all analyzed subgroups. Differences in the CR according to the Q/non‐Q wave infarction characteristics could be determined by PIHD. The cosinor model fit with three components (24, 12, and 8 h periods) showed a higher sensitivity than the single 24 h period analysis.