Significance of short chain fatty acid transport by members of the monocarboxylate transporter family (MCT).

Metabolism of short-chain fatty acids (SCFA) in the brain, particularly that of acetate, appears to occur mainly in astrocytes. The differential use has been attributed to transport, but the extent to which transmembrane movement of SCFA is mediated by transporters has not been investigated systematically. Here we tested the possible contribution of monocarboxylate transporters to SCFA uptake by measuring fluxes with labelled compounds and by following changes of the intracellular pH in Xenopus laevis oocytes expressing the isoforms MCT1, MCT2 or MCT4. All isoforms mediated significant transport of acetate. Formate, however, was transported only by MCT1. The contribution of MCT1 to SCFA transport was determined by using phloretin as a high-affinity inhibitor, which allowed a paired comparison of oocytes with and without active MCT1.

Outcomes of dental fracture injury as related to laser Doppler flow measurements of pulpal blood-flow level.

Laser Doppler flowmetry (LDF) is a non-invasive method to assess pulpal blood flow (PBF). Dental fracture injuries have been associated with significant PBF reduction The purpose of this study was: (i) to evaluate whether the severity of outcomes of dental fracture injuries may be related to LDF measurements of PBF, and (ii) to investigate whether outcomes of dental fracture injuries may predict PBF levels. The relationship between outcomes and PBF measurements was analyzed in 72 permanent maxillary incisors of 52 consecutive dental trauma patients. The diagnostic outcome group comprised 72 incisors with a type I (absence of sensitivity, periapical radiolucency, and grey discoloration of crown) (n = 42), type II (loss of sensitivity) (n = 16), or type III (loss of sensitivity, periapical radiolucency, and/or grey discoloration of crown) diagnosis. At each session, when an injured permanent maxillary incisor was recorded, a contralateral homologous tooth was used as a control. An ordinal stepwise regression was completed to assess the degree of association between PBF measurements and diagnostic outcomes. A logistic regression analysis was used to compute the odds ratios for the outcome features for incisor non-injury controls vs two outcome groups: type II (n = 16) and type III (n = 14). PBF measurements that were significantly associated with more severe outcome were PBF levels of

Use of laser Doppler flowmetry to predict vitality of luxated or avulsed permanent teeth.

OBJECTIVE: Splinting of traumatically displaced or avulsed permanent teeth has been described as an effective modality in the treatment of patients with dental injuries. The purpose of this study was to investigate whether laser Doppler flowmetry (LDF) measurements of pulpal blood flow (PBF) and/or dental injury type may predict treatment outcome of splinting of permanent maxillary incisors. STUDY DESIGN: The study comprised 64 patients undergoing dental trauma splinting, who were characterized by the presence of a single permanent maxillary incisor affected by a subluxation, luxation, or avulsion type injury. Perfusion units (PU) were taken in 2 sessions, on the day of splint removal (6 weeks after trauma; session I) and 12 weeks after splint removal (session II). At each session, when an injured permanent maxillary central incisor was recorded, the respective contralateral homologous tooth was used as a control. An adverse outcome occurring 36 weeks after splint removal was defined as the presence of "periapical radiolucency and/or grey discoloration." A multiple logistic regression analysis was used to compute the odds ratio for session-related PBF characteristics and dental injury type for adverse outcome (n=22) versus nonadverse outcome (n=42). RESULTS: There was a significant increase in PBF values from session I to session II (P=.047) for teeth without an adverse outcome, whereas teeth affected by an adverse outcome showed a significant decrease in PBF values (P=.001). PBF measurements did not change over time for the control group of contralateral incisors (P=.185). For the outcome criterion of "presence of periapical radiolucency and/or grey discoloration," there was a significant association between the treatment outcome groups and the variables of dental injury type (P=.049), session-related PBF difference (P=.000), and session II-related PBF level (P=.000). Significant increase in risk of an adverse outcome occurred with a session-related PBF difference (PBF(Session I) - PBF(Session II)) of >/=0 PU (8.6 odds ratio) (P=.014), and a session II-related PBF level of

Influence of rBAT-mediated amino acid transport on cytosolic pH.

rBAT, together with its subunit b(0,+) AT mediates the hetero- and homoexchange of neutral and dibasic amino acids. Since the heteroexchange of dibasic amino acids against neutral amino acids is coupled to net transport of positive charge, this transport is electrogenic. Extracellular addition of histidine could create an inward or an outward current depending on extracellular pH (pH(e)) and cell membrane potential. It has been concluded that histidine may be transported in both its protonated and its neutral form. In this study measurements of cytosolic pH (pH(i)) were performed to test this hypothesis. As a result, addition of protonated histidine at acidic pH(e) to Xenopus oocytes expressing rBAT creates an inward current which is paralleled by cytosolic acidification. Both can be reduced by increase of pH(e). At alkaline pH(e) and simultaneous depolarization of the cell membrane the effect of histidine on pH(i) is virtually abolished. The neutral amino acid leucine does not alter cytosolic pH at neither pH 6.0 nor at pH 8.0. In conclusion, histidine can be transported in either its neutral or its protonated form. Transport of the protonated form is facilitated by extracellular acidification and hyperpolarization of the cell membrane.