Neuroplasticity of face primary motor cortex control of orofacial movements.

We have carried out a series of studies to address the role of the face primary motor area (MI) in the cerebral cortex in trained or semi-automatic orofacial motor behaviours and in behavioural adaptations to an altered oral environment. These studies have utilized intracortical microstimulation (ICMS), reversible cold block or single neurone recordings in face MI. Our studies in monkeys have revealed that face MI plays a strategic role in elemental and learned motor behaviours and in certain aspects of chewing and swallowing. Furthermore, successful training of awake monkeys in a novel tongue-protrusion task is associated with significant neuroplastic changes in face MI. These findings in monkeys are supported by correlated findings in humans which have revealed significantly enhanced corticomotoneuronal excitability when humans learn the novel tongue-protrusion task. Our related ICMS studies in rats reveal that trimming or extraction of the rat's lower incisors or damage to the rat's lingual nerve can result in significant changes in the MI representations of the tongue or jaw muscles. These various findings suggest that the face MI is important in orofacial motor skill acquisition and adaptation to an altered occlusion or loss of teeth or lingual sensory function, and that it reflects dynamic and modifiable constructs that are modelled by behaviourally significant experiences and that are critical to learning and adaptive processes.

Response properties of slowly and rapidly adapting periodontal mechanosensitive neurones in the primary somatosensory cortex of the cat.

Periodontal mechanosensitive neurones in the primary somatosensory (SI) cortex are classified as either slowly or rapidly adapting. The responses of cortical neurones and their projection pathways were studied using mechanical and electrical stimulation of the teeth and electrical stimulation of the thalamic posteromedial ventral (VPM) nuclei and contralateral SI cortex. A total of 247 periodontal mechanosensitive units were recorded from the SI cortex in 35 anaesthetized cats, distributed mainly in area 3b: 14% were slowly adapting and 86% rapidly adapting units; 62% of the slowly adapting and 9% of the rapidly adapting units were single-tooth units sensitive to stimulation of only one tooth. The incidence of slowly adapting units with an ipsilateral receptive field was almost equal to that of slowly adapting units with a contralateral receptive field, and more than half of the units were directionally selective to mechanical tooth stimulation. The majority of rapidly adapting units had their receptive field in the contralateral teeth and were directionally non-selective to tooth stimulation. The latencies of the cortical responses of the slowly and rapidly adapting units were 7.3 and 10.7 ms, respectively, on electrical stimulation of the contralateral teeth, and 1.8 and 2.0 ms, respectively, on electrical stimulation of the ipsilateral VPM nucleus. From these findings, it is inferred that slowly adapting neurones are useful for discriminating the tooth stimulated, the stimulus direction, the stimulus intensity and the change of pressure applied to the tooth, while rapidly adapting neurones could function to signal initial contact with food or the opposing teeth.

Correlations between response properties of periodontal mechanosensitive neurones in the primary somatosensory cortex of the rabbit and cortically induced rhythmical jaw movements.

The response properties of incisor- and molar-sensitive periodontal mechanosensitive (PM) neurones in the primary somatosensory (SI) cortex of rabbits were examined and rhythmical jaw movements induced by repetitive electrical stimulation of the recording sites of cortical PM neurones were observed. PM units were recorded from the rostromedial (RM) and rostrolateral (RL) areas of the SI cortex. In the RM area, most PMs (85%) were lower incisor-sensitive. Electrical stimulation of the RM area produced chopping-type rhythmical jaw movements. In the RL area, both incisor- and molar-sensitive PM units were recorded, and molar-sensitive units were located more rostromedially than incisor-sensitive units. More than half (66%) of the incisor-sensitive PM units were upper incisor-sensitive. The incidences of sustained-response type units were 8 and 10% for upper incisor- and lower incisor-sensitive units and 28 and 34% for upper molar- and lower molar-sensitive units, respectively. The optimal stimulus directions for the upper molar-sensitive units were predominantly labial or lingual, whereas those for most of the lower molar-sensitive units were lingual. Electrical stimulation of the PM unit-recording sites in the RL area induced grinding-type rhythmical jaw movements. Based on these findings, the lower incisor-sensitive neurones in the RM area of the SI cortex might mainly contribute to a neural network that controls jaw movements during ingestion. Furthermore, the response properties of molar-sensitive cortical neurones might be useful for discriminating the magnitude and direction of the biting force during grinding. Further studies are needed to clarify the role of upper incisor-sensitive neurones in the RL area in triggering grinding-type rhythmical jaw movements.

An epidemiological analysis of the foot-and-mouth disease epidemic in Miyazaki, Japan, 2010.

An epidemic of foot-and-mouth disease occurred in Miyazaki, Japan, beginning in late March 2010. Here, we document the descriptive epidemiological features and investigate the between-farm transmission dynamics. As of 10 July 2010, a total of 292 infected premises have been confirmed with a cumulative incidence for cattle and pig herds of 8.5% and 36.4%, respectively, for the whole of Miyazaki prefecture. Pig herds were more likely to be infected than cattle herds (odds ratio = 4.3 [95% confidence interval (CI): 3.2, 5.7]). Modelling analysis suggested that the relative susceptibility of a cattle herd is 4.2 times greater than a typical pig herd (95% CI: 3.9, 4.5), while the relative infectiousness of a pig herd is estimated to be 8.0 times higher than a cattle herd (95% CI: 5.0, 13.6). The epidemic peak occurred around mid-May, after which the incidence started to decline and the effective reproduction numbers from late May were mostly less than unity, although a vaccination programme in late May could have masked symptoms in infected animals. The infected premises were geographically confined to limited areas in Miyazaki, but sporadic long-distance transmissions were seen within the prefecture. Given that multiple outbreaks in Far East Asian countries have occurred since early 2010, continued monitoring and surveillance is deemed essential.

Usefulness of the assessment of urinary enzyme leakage in monitoring acute fluoride nephrotoxicity.

A single oral dose of sodium fluoride (NaF) in aqueous solution was given to male Wistar rats. Twenty-four-hour urine samples were collected and examined to evaluate fluoride-induced acute renal damage. The following parameters were measured in 24-h urine: urine volume and urinary excretion of fluoride, N-acetyl-beta-d-glucosaminidase (NAG), alpha-glutathione-S-transferase (alpha-GST), and creatinine (CR). Fluoride exposure produced specific, dose-dependent changes of these parameters. Significant increases of fluoride and fluoride-induced polyuria were observed. NAG as specific marker of proximal convoluted tubule (PCT) function showed a significant increase when the lowest dose of fluoride was administered. At this minimal dose, alpha-GST, a specific marker for the S3 segment, did not show a significant increase but presented the strongest relationship (r = 0. 83) to fluoride dose. No significant changes were measured for CR excretion, which showed a low correlation coefficient (r = 0.36) to administered fluoride. The specific differences in the increase pattern of these parameters show that the PCT is more susceptible to damage by low-dose fluoride than the S3 segment or the glomerulus. We concluded that both NAG and alpha-GST are useful for the diagnosis of fluoride-induced acute nephrotoxicity. Proper evaluation of these urinary indices may be of help to establish the site and extent of kidney injury in acute fluoride toxicity.

Boron diffusion across the dialysis membrane during hemodialysis.

To investigate the movement of boron across the dialysis membrane, serum and dialysate boron levels of long-term hemodialysis (HD) patients (n = 17) were determined using inductively coupled plasma emission spectrometry in both the inlet and the outlet side of the dialyzer. Results revealed that 77.8% of the serum boron in the inlet side of the dialyzer was filterable and 94.4% of filterable boron was actually filtered during HD. Boron dialysance was found to be 138.6 +/- 16.1 ml/min, and this value was higher than the clearance value of blood urea nitrogen (not significant), phosphorus and creatinine (p < 0.001). It is concluded that HD is effective in eliminating serum boron even at low concentrations, and boron can be classified as an element that is easily diffusible across the dialysis membrane. There seems to be relatively little relation of boron to serum constituents of macromolecules that are reported to have a major impact on the diffusion of trace elements across the HD membrane.

Urinary biomarkers monitoring for experimental fluoride nephrotoxicity.

An excess of sodium fluoride (135 mg F/kg body weight) was given in a single oral dose to male Wistar rats. Effects were investigated of fluoride-induced acute kidney intoxication on the time-dependent variations of urine volume. Also, of urinary fluoride ion (F-), alpha-glutathione-S-transferase (alpha-GST), N-acetyl-beta-D-glucosaminidase (NAG), and creatinine (CR) concentrations. Fluoride administration strongly affects these urinary biochemical indices. Of the several biomarkers studied, alpha-GST is particularly useful as marker of S3 proximal tubule damage. We found that alpha-GST shows the strongest and more durable changes as a result of the large dose of F- given to the experimental animals. Our results suggest that the toxic effect of F- on the kidney may be more pronounced in the proximal tubule than the glomeruli region, and that the disorder of the proximal tubule is more serious in the S3 segment than S1 or S2 segment. Alpha-GST proved to be a useful marker for the early detection and long-term observation of proximal renal tubular injury resulting from F- intoxication. The animal model should help to establish guidelines for the treatment of industrial workers suffering from acute renal failure resulting from accidental exposure to fluoride.