Effect of body posture on chewing behaviours in healthy volunteers.

Mastication is essential to the eating process and forms an important part of feeding behaviour. Many factors related to the food bolus, such as bolus texture and size, are known to influence mastication. The aim of this study was to determine the effects of body posture on (i) chewing duration prior to the first swallow and (ii) patterns of mastication-related EMG activity. We asked 10 healthy adults to chew 8 g of steamed rice with barium sulphate while we recorded masseter, suprahyoid and infrahyoid muscle activity and simultaneously collected videofluorographic images. Participants chewed in either an upright or reclining position. Chewing duration, which was defined as the time from the start of mastication to the first swallow, was not different between the positions. However, the variability of chewing duration was larger in the upright versus reclining position, and the chewing duration in the reclining position was distributed around 15 s. Masseter activity gradually decreased in a time-dependent manner and was significantly larger at the early versus late stage of mastication. Suprahyoid activity was significantly larger at the early versus middle stage of mastication in the upright position only. Finally, masseter activity per second was negatively correlated with changes in chewing duration, that is, the larger the increase in chewing duration in the reclining position, the more the decrease in masseter activity per second. These results suggest that position-dependent changes in chewing behaviours, as described by chewing duration and EMG activity, may vary among participants.

Cold thermal oral stimulation produces immediate excitability in human pharyngeal motor cortex.

BACKGROUND: Current strategies of swallowing therapy include facilitation of swallowing initiation by sensory modulation. Although thermal tactile oral stimulation is a common method to treat dysphagic patients to improve swallowing movement, little is known about the possible mechanisms. This study is aimed to investigate whether thermal oral (tongue) stimulation can modulate the cortico-pharyngeal neural motor pathway in humans. METHODS: Eighteen healthy volunteers participated and were intubated with an intraluminal catheter for recording pharyngeal electromyography. Each participant underwent baseline transcranial magnetic stimulation (TMS) cortico-pharyngeal motor evoked potential (MEP) measurements bilaterally. MEPs were then measured during thermal stimulation over the dorsal tongue, applied using the Peltier device at three different temperatures; 45°C, 37°C, and 15°C, in a pre-ordered manner. Each of the three temperatures was given twice with a 5-min resting time between each trial. Averaged MEP amplitude changes were analyzed using ANOVA and post-hoc t-tests. KEY RESULTS: Two-way repeated measures ANOVA with factors of Temperature × Trial in amplitude of MEP demonstrated a significant effect of Temperature both in the stronger (F2,34  = 5.775, P = .007) and weaker (F2,34  = 4.771, P = .017) pharyngeal hemispheres. Subsequent post-hoc tests showed the significant increase in pharyngeal MEPs at 15° compared to 37° in both hemispheres (P < .05). CONCLUSIONS & INFERENCES: Cold oral stimulation was able to induce significant changes in pharyngeal cortical excitability, demonstrating evidence for a sensorimotor interaction between oral and pharyngeal cortical areas.

Exploring the effects of synchronous pharyngeal electrical stimulation with swallowing carbonated water on cortical excitability in the human pharyngeal motor system.

BACKGROUND: Previous reports have revealed that excitation of human pharyngeal motor cortex can be induced by pharyngeal electrical stimulation (PES) and swallowing carbonated water (CW). This study investigated whether combining PES with swallowing (of still water, SW or CW) can potentiate this excitation in either cortical and/or brain stem areas assessed with transcranial and transcutaneous magnetic stimulation (TMS). METHODS: Fourteen healthy volunteers participated and were intubated with an intraluminal catheter to record pharyngeal electromyography and deliver PES. Each participant underwent baseline corticopharyngeal, hand and craniobulbar motor-evoked potential (MEP) measurements. Subjects were then randomized to receive each of four 10-min interventions (PES only, ShamPES+CW, PES+CW, and PES+SW). Corticobulbar, craniobulbar and hand MEPs were then remeasured for up to 60 min and data analyzed using anova and post hoc t-tests. KEY RESULTS: A two-way rmanova for Interventions × Time-point showed a significant corticopharyngeal interaction (p = 0.010). One-way anova with post hoc t-tests indicated significant cortical changes with PES only at 45 (p = 0.038) and 60 min (p = 0.023) and ShamPES+CW immediately (p = 0.008) but not with PES+CW or PES+SW. By contrast, there were immediate craniobulbar amplitude changes only with PES+CW (p = 0.020) which were not sustained. CONCLUSIONS & INFERENCES: We conclude that only PES produced long-term changes in corticopharyngeal excitability whereas combination stimuli were less effective. Our data suggest that PES alone rather than in combination, may be better for the patients who have difficulty in performing voluntary swallows.

The effect of variation in powder particle size on the doughing and manipulation times and some mechanical properties of acrylic resin.

In this study, the hypothesis examined is that differences in polymer particle size affect the doughing and manipulation times and the mechanical properties of the cured product. Six batches of polymers were used varying in particle size from <38 micrometers diameter to > 75 micrometers diameter. A penetration test was undertaken to investigate the influence of polymer particle size on the doughing and manipulation times of acrylic resin. It was demonstrated that the particle size in the range examined influenced the doughing and manipulation times, the smaller particle sizes having shorter times. No significant difference was demonstrated in the impact resistance of surface hardness of acrylic resin specimens constructed from polymers of varying particle size and although there were some significant differences in the transverse (flexural) strength these were small in real terms. Further, the molecular weight of the polymerised product was found to be consistently higher than that of the original powder component.

Activity of agricultural chemicals to modify mitomycin C induced growth inhibition of Bacillus subtilis in the rec assay.

Rec assay of agricultural chemicals, MCPA-E, MCPA, CNP and PCNB was conducted. It was found that MCPA-E and MCPA accelerated the growth-inhibition originally induced by Mitomycin C in the rec- strain.

Co-mutagenic activity of phenoxyherbicides MCPA- and MCPB-ethylester in the Ames assay.

Mutagenicity and co-mutagenicity of MCPA- and MCPB-ethylester were examined in the Ames assay. It was found that they enhance the mutagenic action of 2-aminoanthracene in the Ames assay, although they were not mutagenic.

Rec-assay of human bile for mutagenicity and co-mutagenicity.

Spore rec-assay of human bile was conducted by the Bacillus subtilis test system to examine possible mutagenicity and co-mutagenicity. Of 26 samples examined, 8 (30.8%) showed mutagenic activity and 23 (88.5%) enhanced the mutagenic activity of mitomycin C.

Cytogenetic analysis of human bile for mutagenicity and co-mutagenicity.

Cytogenetic analysis was used to test whether or not human bile induced chromosome abnormalities in lymphocytes grown in culture. Bile was obtained from gallbladders resected for various reasons such as cholecystitis, cholelithiasis, polypus and cancers of the biliary tract, stomach and pancreas. After adding human bile to a final concentration of 25 microliters/ml or 12.5 microliters/ml, the culture medium was incubated at 37 degrees C for 72 hr. Air-dried slides were stained with conventional Giemsa and the numerical and structural chromosome abnormalities were scored. Positive and negative controls in terms of chromosome abnormalities were established by using 0.03 micrograms/ml mitomycin C (MMC) and 0.9% normal saline, respectively. Cytogenetic analysis was successfully performed in 6 out of 10 bile samples (60.0%). Bile alone did not induce numerical or structural chromosome abnormalities. Structural abnormalities increased significantly in the 25 microliters/ml bile + 0.03 micrograms/ml MMC group, compared with the 0.03 micrograms/ml MMC group: 36.0% vs. 20.7% in the chromatid-type gaps and breaks, 27.8% vs. 22.7% in the chromosome-type gaps and breaks, and 8.3% vs. 3.2% in the exchange-type abnormalities. It is likely that the interaction between bile and MMC is synergistic rather than additive.

Bartonella henselae serostatus is not correlated with neurocognitive decline in HIV infection.

Bartonella henselae has been implicated as a significant cause of HIV-associated dementia. We attempted to confirm this association by utilizing the database of the San Diego HIV Neurobehavioral Research Center, which collects longitudinal neurocognitive and laboratory data on over 500 HIV-infected participants. Utilizing an immunofluorescent assay we found that 11% of 177 subjects, half of whom had documented neurocognitive decline, were seropositive for B. henselae. There was no correlation between B. henselae seropositivity and neurocognitive decline. The role of B. henselae in HIV-associated dementia remains ambiguous.