Intercellular signal communication among odontoblasts and trigeminal ganglion neurons via glutamate

Various stimuli to the exposed surface of dentin induce changes in the hydrodynamic force inside the dentinal tubules resulting in dentinal pain. Recent evidences indicate that mechano-sensor channels, such as the transient receptor potential channels, in odontoblasts receive these hydrodynamic forces and trigger the release of ATP to the pulpal neurons, to generate dentinal pain. A recent study, however, has shown that odontoblasts also express glutamate receptors (GluRs). This implies that cells in the dental pulp tissue have the ability to release glutamate, which acts as a functional intercellular mediator to establish inter-odontoblast and odontoblast-trigeminal ganglion (TG) neuron signal communication. To investigate the intercellular signal communication, we applied mechanical stimulation to odontoblasts and measured the intracellular free Ca²⁺ concentration ([Ca²⁺]_i). During mechanical stimulation in the presence of extracellular Ca²⁺, we observed a transient [Ca²⁺]_i increase not only in single stimulated odontoblasts, but also in adjacent odontoblasts. We could not observe these responses in the absence of extracellular Ca²⁺. [Ca²⁺]_i increases in the neighboring odontoblasts during mechanical stimulation of single odontoblasts were inhibited by antagonists of metabotropic glutamate receptors (mGluRs) as well as glutamate-permeable anion channels. In the odontoblast-TG neuron coculture, we observed an increase in [Ca²⁺]_i in the stimulated odontoblasts and TG neurons, in response to direct mechanical stimulation of single odontoblasts. These [Ca²⁺]_i increases in the neighboring TG neurons were inhibited by antagonists for mGluRs. The [Ca²⁺]_i increases in the stimulated odontoblasts were also inhibited by mGluRs antagonists. We further confirmed that the odontoblasts express group I, II, and III mGluRs. However, we could not record any currents evoked from odontoblasts near the mechanically stimulated odontoblast, with or without extracellular Mg²⁺, indicating that N-methyl-d-aspartic acid receptor does not contribute to inter-odontoblast signal communication. The results suggest that a mechanically stimulated odontoblast is capable of releasing glutamate into the extracellular space via glutamate-permeable anion channels. The released glutamate activates mGluRs on the odontoblasts in an autocrine/paracrine manner, forming an inter-odontoblasts communication, which drives dentin formation via odontoblast-odontoblast signal communication. Glutamate and mGluRs also mediate neurotransmission between the odontoblasts and neurons in the dental pulp to modulate sensory signal transmission for dentinal sensitivity.

High pH-Sensitive TRPA1 Activation in Odontoblasts Regulates Mineralization

Calcium hydroxide and mineral trioxide aggregate are widely used for indirect and direct pulp capping and root canal filling. Their dissociation into Ca(2+) and OH(-) in dental pulp creates an alkaline environment, which activates reparative/reactionary dentinogenesis. However, the mechanisms by which odontoblasts detect the pH of the extracellular environment remain unclear. We examined the alkali-sensitive intracellular Ca(2+) signaling pathway in rat odontoblasts. In the presence or absence of extracellular Ca(2+), application of alkaline solution increased intracellular Ca(2+) concentration, or [Ca(2+)]i Alkaline solution-induced [Ca(2+)]i increases depended on extracellular pH (8.5 to 10.5) in both the absence and the presence of extracellular Ca(2+) The amplitude was smaller in the absence than in the presence of extracellular Ca(2+) Each increase in [Ca(2+)]i, activated by pH 7.5, 8.5, or 9.5, depended on extracellular Ca(2+) concentration; the equilibrium binding constant for extracellular Ca(2+) concentration decreased as extracellular pH increased (1.04 mM at pH 7.5 to 0.11 mM at pH 9.5). Repeated applications of alkaline solution did not have a desensitizing effect on alkali-induced [Ca(2+)]i increases and inward currents. In the presence of extracellular Ca(2+), alkaline solution-induced [Ca(2+)]i increases were suppressed by application of an antagonist of transient receptor potential ankyrin subfamily member 1 (TRPA1) channels. Ca(2+) exclusion efficiency during alkaline solution-induced [Ca(2+)]i increases was reduced by a Na(+)-Ca(2+) exchanger antagonist. Alizarin red and von Kossa staining revealed increased mineralization levels under repeated high pH stimulation, whereas the TRPA1 antagonist strongly reduced this effect. These findings indicate that alkaline stimuli-such as the alkaline environment inside dental pulp treated with calcium hydroxide or mineral trioxide aggregate-activate Ca(2+) mobilization via Ca(2+) influx mediated by TRPA1 channels and intracellular Ca(2+) release in odontoblasts. High pH-sensing mechanisms in odontoblasts are important for activating dentinogenesis induced by an alkaline environment.

Effects of sleep deprivation: the phosphorus metabolism in the human brain measured by 31P-magnetic resonance spectroscopy

Sleep deprivation (SD) has an antidepressant effect in some, but not all, patients with depression, although its biological mechanisms have not yet been characterized. We previously reported altered brain phosphorus metabolism measured by phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in patients with bipolar depression. We preliminarily examined effects of SD on phosphorus metabolism in the frontal lobes of 15 normal subjects using 31P-MRS. No significant differences of membrane phospholipid metabolism, high-energy phosphate metabolism and intracellular pH were found between before and after SD in these subjects. Further studies will be necessary to elucidate the physiological mechanism of SD for depressive patients.

Calcium inflow of hamster Merkel cells in response to hyposmotic stimulation indicate a stretch activated ion channel

The aim of this study was to investigate the existence of the stretch activated ion channels in single Merkel cell using microfluorimetric techniques. Single Merkel cells were dissociated enzymatically from the touch domes in the cheek pouch mucosa of 4-8 week old golden hamsters. They were loaded with calcium (Ca2+) fluorescent indicator fura-2/AM. The increase in intracellular Ca2+ concentration ([Ca2+]i) of a single Merkel cell (quinacrine fluorescent cell) was induced by hyposmotic solution in normal Krebs solution, while it was not induced by Ca2+-free hyposmotic solution in Ca2+-free physiological solution. Gadolinium ion (10 microM) in normal Krebs solution partially blocked the increase in [Ca2+]i of Merkel cells induced by hyposmotic solution. Hence, this study revealed that stretch activated ion channels existed on the Merkel cell membrane.

Results of a qualitative and field study using the WHOQOL instrument for cancer patients

The main purpose of the study was to evaluate quality of life (QOL) among cancer patients using the WHOQOL-100 instrument and to see if any significant differences were seen in cancer stages, treatment status and prognosis. This study consisted of two parts; qualitative and quantitative. For the qualitative study, two focus groups were conducted by medical professionals to establish the applicability of the WHOQOL instrument in evaluating the QOL of cancer patients, but most participants were negative about using a generic instrument such as WHOQOL. For the quantitative study, 197 cancer patients (average age 55.86) from eight medical centers using the WHOQOL instrument, in addition to each patient's information sheet filled in by their own physicians, were analyzed. The average overall QOL score was 3.39. There was high reliability (Cronbach's alpha = 0.9685) and a high correlation between the psychological and the environmental domains (r = 0.7021), the physical domain and the level of independence (r = 0.6031) and social relations and the environment (r = 0.6856) and between health conditions perceived by patients and QOL scores. In addition, differences by gender, treatments and cancer sites were also found to be significantly different at the 5% significance level. The results indicated that the WHOQOL core instrument was sensitive enough to evaluate the QOL of cancer patients.

Distribution of organized sensory nerve endings in the human periodontal ligament

The purpose of the present study was to clarify the distribution pattern of organized nerve endings in human-periodontal ligament. The materials investigated were obtained from the first premolar teeth. The fresh periodontal ligament of the extracted tooth was stained using the methylene blue vital staining method. Then the whole-mount preparations of the periodontal ligament were observed by light microscope. Three kinds of receptors (encapsulate corpuscles, bush-like endings and free-nerve endings) were located in the ligament. The ratio of total number of encapsulated corpuscles to bush-like endings was one to three. The density of the encapsulated corpuscles ranged from 0.2/mm2 to 1.2/mm2 and the bush-like endings ranged from 1.3/mm2 to 3.2/mm2. The most organized nerve endings were distributed at the middle one third in the ligament. The distribution of bush-like endings, which differed from that of encapsulated corpuscles, might contribute to their response thresholds and static properties.

Reconstitution of the isobutene-forming reaction catalyzed by cytochrome P450 and P450 reductase from Rhodotorula minuta: decarboxylation with the formation of isobutene

An isobutene-forming activity was reconstituted with cytochrome P450rm and cytochrome P450 reductase purified from Rhodotorula minuta. The nonionic detergent. Emulgen 911, present in the preparation of purified P450rm, inhibited the reconstitution. Bovine serum albumin enhanced the activity of the reconstituted system. Branching of the beta carbon of the substrate carboxylic acid was important for formation of isobutene. In a comparative study with isovalerate and 3-deuterio-3-methylbutanoate, a very large isotopic effect (kH/kD = 14) was observed. This result indicates that formation of isobutene might be initiated by abstraction of hydrogen from the beta carbon of isovalerate and might be followed by decarboxylation.

Merkel cell-neurite complexes in touch domes of hamster cheek pouch

Morphological study has been done in touch domes of hamster cheek pouch as a preparation for further electrophysiological study. The touch domes were examined by light and electron microscopy. There were one or two primary ridges (epithelial ridges) in the center of the touch dome, and each dome was supplied by one to three nerve fibres. Tactile cells (Merkel cells) were localized within primary ridges of touch domes and Merkel cell-neurite complexes were observed in every one. Since Merkel cell-neurite complexes are slow adapting mechanoreceptors, these results suggest that they might be involved in touch sensation.

The oscillation from pacinian corpuscles to external stimuli in cat mesentery

Single Pacinian corpuscles isolated from cat mesentery elicited fast-adapting responses and/or oscillation to displacement and vibratory stimuli at temperatures of 24-43 degrees C. The displacement threshold of oscillation increased by decreasing the temperature of the room or of the corpuscles to below 26 degrees C. Further cooling made the corpuscles elicit only fast-adapting responses to displacement stimuli of identical strength. When a single Pacinian corpuscle was stimulated by the same displacement the impulse patterns depended on the temperature of the experimental plate on which the corpuscle was situated. It is therefore suggested that, in temperatures higher than 28 degrees C and lower than 43 degrees C, constant displacement stimuli or vibratory stimuli (10-0.01 Hz) induced oscillation of the receptor potential from the Pacinian corpuscles.

Two reactions are simultaneously catalyzed by a single enzyme: the arginine-dependent simultaneous formation of two products, ethylene and succinate, from 2-oxoglutarate by an enzyme from Pseudomonas syringae

A single enzyme isolated from Pseudomonas syringae pv. phaseolicola PK2 simultaneously catalyzed two reactions, namely, the formation of ethylene and succinate from 2-oxoglutarate, at a molar ratio of 2:1. In the main reaction, 2-oxoglutarate was dioxygenated to produce one molecule of ethylene and three molecules of carbon dioxide. In the sub-reaction, both 2-oxoglutarate and L-arginine were mono-oxygenated to yield succinate plus carbon dioxide and L-hydroxyarginine, respectively, the latter being further transformed to guanidine and L-delta 1-pyrroline-5-carboxylate. We propose a dual-circuit mechanism for the entire reaction, in which the binding of L-arginine and 2-oxoglutarate in a Schiff-base structure generates a common intermediate for two reactions.

Purification and properties of an ethylene-forming enzyme from Pseudomonas syringae pv. phaseolicola PK2

A novel ethylene-forming enzyme that catalyses the formation of ethylene from 2-oxoglutarate was purified from a cell-free extract of Pseudomonas syringae pv. phaseolicola PK2. It was purified about 2800-fold with an overall yield of 53% to a single band of protein after SDS-PAGE. The purified enzyme had a specific activity of 660 nmol ethylene min-1 (mg protein)-1. The molecular mass of the enzyme was approximately 36 kDa by gel filtration and 42 kDa by SDS-PAGE. The isoelectric point and optimum pH were 5.9 and ca. 7.0-7.5, respectively. There was no homology between the N-terminal amino acid sequence of the ethylene-forming enzyme of Ps. syringae pv. phaseolicola PK2 and the sequence of the ethylene-forming enzyme of the fungus Penicillium digitatum IFO 9372. However, the two enzymes have the following properties in common. The presence of 2-oxoglutarate, L-arginine, Fe2+ and oxygen is essential for the enzymic reaction. The enzymes are highly specific for 2-oxoglutarate as substrate and L-arginine as cofactor. EDTA, Tiron, DTNB [5,5'-dithio-bis(2-nitrobenzoate)] and hydrogen peroxide are all effective inhibitors.

Ultrastructure of the encapsulated corpuscles in the lower lip mucosa of the mouse

Under the light microscope, the encapsulated corpuscles of the mouse lower lip mucosa were only classified into 4 types, simple, ramifying, branched-axon, and clew-like corpuscles. The ultrastructural characteristics of the branched-axon and clew-like corpuscles, however, were not reported. Five male mice, aged 4 to 8 weeks, were used. The mouse lower lip mucosa were examined with a electron microscope. Two types of corpuscles were distinguished. The first type had numerous branched axon terminals and bilaterally symmetrical and/or asymmetrical Schwann cell cytoplasmic lamellae in a few perineural capsules. The second type did not have perineural capsules. We concluded that these two types fell into the categories of branched-axon and/or clew-like corpuscles in the light microscopical observations. We concluded also that first type fit the category of coiled simple corpuscles and second type fit the category of Meissner-like corpuscles according to the electron microscopical observations.

An NADH:Fe(III)EDTA oxidoreductase from Cryptococcus albidus: an enzyme involved in ethylene production in vivo?

An ethylene-forming enzyme which forms ethylene from 2-oxo-4-methylthiobutyric acid (KMBA) was purified to an electrophoretically homogeneous state from a cell-free extract of Cryptococcus albidus IFP 0939. The presence of KMBA, NADH, Fe(III) chelated to EDTA and oxygen were essential for the formation of ethylene. When ferric ions, as Fe(III)EDTA, in the reaction mixture were replaced by Fe(II)EDTA under aerobic conditions, the non-enzymatic formation of ethylene was observed. Under anaerobic conditions in the presence of Fe(III)EDTA and NADH, the enzyme reduced 2 mol of Fe(III) with 1 mol of NADH to give 2 mol of Fe(II) and 1 mol NAD+, indicating that the ethylene-forming enzyme is an NADH-Fe(III)EDTA oxidoreductase. The role of NADH:Fe(III)EDTA oxidoreductase activity in the formation in vivo ethylene from KMBA is discussed.

Morphological study of the sensory innervation of the rat labial mucosa

The sensory innervation of the rat labial mucosa was investigated by means of methylene blue vital staining and osmic acid staining. Sensory receptors in this region were of three kinds (free nerve endings, encapsulated corpuscles and bush-like nerve endings) which constituted separate sensory units respectively. The encapsulated corpuscles were observed in the deep part of lamina propria, and distributed mainly in the margin of labial mucosa. Almost all (78.8%) of encapsulated corpuscles were of a simple type which had a non-branched axon terminal. No clew-like type corpuscles or glomerular-Meissner corpuscles were observed. The bush-like nerve endings were located in the lamina propria close to the epithelium, and localized in the central part of labial mucosa where the formation of papillae was remarkable. The density of the encapsulated corpuscles in the entire mucosa was 3.5-5.3/mm2, and that of the bush-like nerve endings in the densely distributed area was 38.9-60.6/mm2.

Slow-adapting responses of the Pacinian corpuscles of cat planta

Slow-adapting impulses were recorded from the single nerve fiber innervating the Pacinian corpuscle of the cat planta, which was stimulated by constant pressure. Slow-adapting Pacinian corpuscles responded to both low-frequency (0.1-0.01 Hz) and high-frequency (400-800 Hz) vibrations. Simultaneously performed electron microscopy showed that there were no definite ultrastructural differences between slow- and fast-adapting Pacinian corpuscles.