Summary Research in animals and humans has shown that mastication maintains cognitive function in the hippocampus, a brain area important for learning and memory. Reduced mastication, an ...epidemiological risk factor for the development of dementia in humans, attenuates spatial memory and causes hippocampal neurons to deteriorate morphologically and functionally, especially in aged animals. Active mastication rescues the stress‐attenuated hippocampal memory process in animals and attenuates the perception of stress in humans by suppressing endocrinological and autonomic stress responses. Active mastication further improves the performance of sustained cognitive tasks by increasing the activation of the hippocampus and the prefrontal cortex, the brain regions that are essential for cognitive processing. Abnormal mastication caused by experimental occlusal disharmony in animals produces chronic stress, which in turn suppresses spatial learning ability. The negative correlation between mastication and corticosteroids has raised the hypothesis that the suppression of the hypothalamic–pituitary–adrenal (HPA) axis by masticatory stimulation contributes, in part, to preserving cognitive functions associated with mastication. In the present review, we examine research pertaining to the mastication‐induced amelioration of deficits in cognitive function, its possible relationship with the HPA axis, and the neuronal mechanisms that may be involved in this process in the hippocampus.
Previous studies demonstrated that treatment involving eccentric training was effective in the conservative management of chronic tendinosis. However, the mechanisms for these phenomena are unknown. ...The purpose of this study was to compare changes in blood circulation of the tendons after the repeated concentric and eccentric contractions. 11 healthy males volunteered for this study. Subjects performed the repeated concentric (CON) and eccentric (ECC) contractions (5 sets of 10 maximal voluntary contractions) of the plantar flexors. During and after repeated contractions, oxyhemoglobin (Oxy), deoxyhemoglobin (Deoxy), total hemoglobin (THb), and oxygen saturation (StO2) of the Achilles tendons were measured using red laser lights. Oxy and THb increased during and after ECC, but not CON. Deoxy decreased during both CON and ECC. Increase in StO2 during and after ECC was greater than that during and after CON. These results suggested that changes in blood circulation of the Achilles tendon during and after repeated eccentric contractions were more remarkable than those during and after repeated concentric contractions.
The VAHINE mesocosm experiment, conducted in the low-nutrient low-chlorophyll waters of the Noumea lagoon (coastal New Caledonia) was designed to trace the incorporation of nitrogen (N) fixed by ...diazotrophs into the food web, using large volume (50 m3) mesocosms. This experiment provided a unique opportunity to study the succession of different N2-fixing microorganisms (diazotrophs) and calculate in situ net growth and mortality rates in response to fertilization with dissolved inorganic phosphate (DIP) over a 23-day period, using quantitative polymerase chain reaction (qPCR) assays targeting widely distributed marine diazotroph lineages. Inside the mesocosms, the most abundant diazotroph was the heterocyst-forming Richelia associated with Rhizosolenia (Het-1) in the first half of the experiment, while unicellular cyanobacterial Group C (UCYN-C) became abundant during the second half of the experiment. Decreasing DIP concentrations following the fertilization event and increasing temperatures were significantly correlated with increasing abundances of UCYN-C. Maximum net growth rates for UCYN-C were calculated to range between 1.23 ± 0.07 and 2.16 ± 0.07 d−1 in the mesocosms, which are among the highest growth rates reported for diazotrophs. Outside the mesocosms in the New Caledonia lagoon, UCYN-C abundances remained low, despite increasing temperatures, suggesting that the microbial community response to the DIP fertilization created conditions favorable for UCYN-C growth inside the mesocosms. Diazotroph community composition analysis using PCR targeting a component of the nitrogenase gene (nifH) verified that diazotrophs targeted in qPCR assays were collectively among the major lineages in the lagoon and mesocosm samples, with the exception of Crocosphaera-like phylotypes, where sequence types not typically seen in the oligotrophic ocean grew in the mesocosms. Maximum net growth and mortality rates for nine diazotroph phylotypes throughout the 23-day experiment were variable between mesocosms, and repeated fluctuations between periods of net growth and mortality were commonly observed. The field population of diazotrophs in the New Caledonian lagoon waters appeared to be dominated by Het-1 over the course of the study period. However, results from both qPCR and PCR analysis indicated a diverse field population of diazotrophs was present in the lagoon at the time of sampling. Two ecotypes of the Braarudosphaera bigelowii symbiont unicellular group A (UCYN-A) were present simultaneously in the lagoon, with the recently described B. bigelowii/UCYN-A2 association present at higher abundances than the B. bigelowii/UCYN-A1 association.
The purpose of this study was to investigate changes in muscle oxygenation of knee extensor and plantar flexor muscles during repeated muscle contractions under the same condition. In addition, we ...compared changes in muscle oxygenation between superficial and deep regions of both muscles.
Eleven healthy males participated in this study. During repeated knee extensions and plantar flexions (50 repetitions at 50% of the isometric maximum voluntary contraction for 3 s with 3 s relaxations), blood volume and oxygen saturation (StO₂) of the vastus lateralis and medial gastrocnemius muscles (superficial and deep region of each muscle) were measured using near infrared spectroscopy.
The decrement of StO₂at the end of exercises was greater in plantar flexor muscle than in knee extensor muscle (P<0.001). For both muscles, the decrement of StO₂at the end of exercises was greater in the deep region than in the superficial one (both P<0.001).
These results suggested that the oxygen utilization of plantar flexor muscle and deep regions of each muscle were higher than that of knee extensor muscle and superficial regions of each muscle.
Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world’s oceans. Differential preferences for specific N substrates may be important in ...controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate (
NO
3
−
), ammonium (
NH
4
+
), and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the oligotrophic waters of the North Pacific Ocean. All N substrates tested significantly stimulated phytoplankton growth and productivity. Urea resulted in the greatest (>300%) increases in chlorophyll a (<0.06 μg L−1 and ∼0.19 μg L−1 in the control and urea addition, respectively) and productivity (<0.4 μmol C L−1 d−1 and ∼1.4 μmol C L−1 d−1 in the control and urea addition, respectively) at two experimental stations, largely due to increased abundances of Prochlorococcus (Cyanobacteria). Two abundant clades of Prochlorococcus, High Light I and II, demonstrated similar responses to urea, suggesting this substrate is likely an important N source for natural Prochlorococcus populations. In contrast, the heterotrophic community composition changed most in response to
NH
4
+
. Finally, the time and magnitude of response to N amendments varied with geographic location, likely due to differences in microbial community composition and their nutrient status. Our results provide support for the hypothesis that changes in N supply would likely favor specific populations of phytoplankton in different oceanic regions and thus, affect both biogeochemical cycles and ecological processes.
•Controversial results in literature about non-thermal effects of electric fields.•Unreliable methods and assumptions can compromise results and conclusions.•Control and distribution of temperature ...and electric field are key factors.•Comparison with conventional process must be fair.•Depending on field frequency, effects may be subtle and difficult to assess.
The use of microwave and ohmic heating in food processing has the advantage of a fast volumetric heating due to ionic and dielectric mechanisms, depending on field frequency. One topic that has been under debate is whether or not the electric field has a non-thermal effect that enhances the inactivation of microorganisms and enzymes. Numerous studies with controversial have been conducted using different approaches, experimental designs and methodologies. This review discusses important factors for accurately assessing non-thermal effects, such as distribution and control of electric field and temperature, measurement of time temperature history, sample homogeneity, fair comparison with conventional processed samples. Current theories for non-thermal inactivation of enzymes (structure and functionally changes) and micro-organisms (cell membrane changes) are also reviewed.
Dunite formation processes in highly depleted peridotites are discussed based upon a detailed study of the Iwanaidake peridotite, Hokkaido, Japan, which consists mainly of harzburgite with a small ...amount of dunite. In the harzburgites, the Mg# = 100 × Mg/(Mg + Fe2+) of olivine ranges from 91·5 to 92·5, and the Cr# = 100 × Cr/(Cr + Al) of spinel from 30 to 70; in the dunites, the Mg# of olivine ranges from 92·5 to 94 and the Cr# of spinel from 60 to 85, respectively. The NiO wt % of olivine in harzburgites ranges from 0·38 to 0·44, and in dunites from 0·35 to 0·37. The Mg# and Cr# are higher and NiO wt % is lower in the dunites than in the harzburgites surrounding the dunites. The Mg# and Cr# exhibit normal depletion trends expected from simple partial melting, whereas the NiO wt % shows an abnormal trend. On the basis of mass balance calculations, dunites are considered to be derived from the harzburgites by a process involving incongruent melting of orthopyroxene (orthopyroxene olivine + Si-rich melt). Hydrous conditions were necessary to lower the solidus, and thus melting of harzburgite was probably triggered by the introduction of hydrous silicate melt. The dunite in this massif may have formed in the mantle wedge above a subduction zone.
The purpose of this study was to investigate growth changes in human plantar flexor muscle and tendons. In addition, we ascertained whether growth changes in muscle and tendon were more closely ...related to skeletal age than chronological age. 22 elementary school children (ESC), 19 junior high school students (JHS), and 23 young adults (ADT) men participated in this study. Maximal strain and hysteresis of tendon structures and cross-sectional area of Achilles tendon were measured using ultrasonography. In addition, skeletal age was assessed using Tanner-Whitehouse III method. Maximal strain of ESC was significantly greater than that of other groups, while no significant difference was observed between JHS and ADT. There was no difference in hysteresis among 3 groups. Relative cross-sectional area (to body mass(2/3)) of ADT was significantly smaller than that of other groups. For ESC and JHS, measured variables of muscle and tendon were significantly correlated to both chronological and skeletal ages. These results suggested that immature musculoskeletal system was protected by more extensible and larger tendon structures in ESC and only by larger tendon structures in JHS, respectively. Furthermore, there were no differences in correlation coefficient values between measured variables of muscle and tendon and chronological or skeletal ages.
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