Chemotransduction in the carotid body: K+ current modulated by PO2 in type I chemoreceptor cells

The ionic currents of carotid body type I cells and their possible involvement in the detection of oxygen tension (Po2) in arterial blood are unknown. The electrical properties of these cells were studied with the whole-cell patch clamp technique, and the hypothesis that ionic conductances can be altered by changes in PO2 was tested. The results show that type I cells have voltage-dependent sodium, calcium, and potassium channels. Sodium and calcium currents were unaffected by a decrease in PO2 from 150 to 10 millimeters of mercury, whereas, with the same experimental protocol, potassium currents were reversibly reduced by 25 to 50 percent. The effect of hypoxia was independent of internal adenosine triphosphate and calcium. Thus, ionic conductances, and particularly the O2-sensitive potassium current, play a key role in the transduction mechanism of arterial chemoreceptors.

Local calcium transients triggered by single L-type calcium channel currents in cardiac cells

Excitation-contraction coupling was studied in mammalian cardiac cells in which the opening probability of L-type calcium (Ca2+) channels was reduced. Confocal microscopy during voltage-clamp depolarization revealed distinct local transients in the concentration of intracellular calcium ions ([Ca2+]i). When voltage was varied, the latency to occurrence and the relative probability of occurrence of local [Ca2+]i transients varied as predicted if Ca2+ release from the sarcoplasmic reticulum (SR) was linked tightly to Ca2+ flux through L-type Ca2+ channels but not to that through the Na-Ca exchanger or to average [Ca2+]i. Voltage had no effect on the amplitude of local [Ca2+]i transients. Thus, the most efficacious "Ca2+ signal" for activating Ca2+ release from the SR may be a transient microdomain of high [Ca2+]i beneath an individual, open L-type Ca2+ channel.

Local control of excitation-contraction coupling in rat heart cells

1. Cytosolic free calcium ion concentration ([Ca2+]i) and whole-cell L-type Ca2+ channel currents were measured during excitation-contraction (E-C) coupling in single voltage-clamped rat cardiac ventricular cells. The measurements were used to compute the total cellular efflux of calcium ions through sarcoplasmic reticulum (SR) Ca2+ release channels (FSR,rel) and the influx of Ca2+ via L-type Ca2+ channels (FICa). 2. FSR,rel was elicited by depolarizing voltage-clamp pulses 200 ms in duration to membrane potentials from -30 to +80 mV. Over this range, peak FSR,rel had a bell-shaped dependence on clamp pulse potential. In all cells, the 'gain' of the system, measured as the ratio, FSR,rel(max)/FICa(max), declined from about 16, at 0 mV, to much lower values as clamp pulse voltage was made progressively more positive. We named this phenomenon of change in gain as a function of membrane potential, 'variable gain'. At clamp pulse potentials in the range -30 to 0 mV, the gain differed from cell to cell, being constant at about 16 in some cells, but decreasing from high values (approximately 65) at -20 mV in others. 3. At clamp pulse potentials at which Ca2+ influx (FICa) was maintained, FSR,rel also had a small maintained component. When macroscopic Ca2+ influx was brief (1-2 ms, during 'tails' of FICa), FSR,rel rose rapidly to a peak after repolarization and then declined with a half-time of about 9 ms (typically). 4. The rising phase of [Ca2+]i transients could be interrupted by stopping Ca2+ influx rapidly (by voltage clamp). We therefore termed this phenomenon 'interrupted SR Ca2+ release'.(ABSTRACT TRUNCATED AT 250 WORDS)

Low pO2 selectively inhibits K channel activity in chemoreceptor cells of the mammalian carotid body

The hypothesis that changes in environmental O2 tension (pO2) could affect the ionic conductances of dissociated type I cells of the carotid body was tested. Cells were subjected to whole-cell patch clamp and ionic currents were recorded in a control solution with normal pO2 (pO2 = 150 mmHg) and 3-5 min after exposure to the same solution with a lower pO2. Na and Ca currents were unaffected by lowering pO2 to 10 mmHg, however, in all cells studied (n = 42) exposure to hypoxia produced a reversible reduction of the K current. In 14 cells exposed to a pO2 of 10 mmHg peak K current amplitude decreased to 35 +/- 8% of the control value. The effect of low pO2 was independent of the internal Ca2+ concentration and was observed in the absence of internal exogenous nucleotides. Inhibition of K channel activity by hypoxia is a graded phenomenon and in the range between 70 and 120 mmHg, which includes normal pO2 values in arterial blood, it is directly correlated with pO2 levels. Low pO2 appeared to slow down the activation time course of the K current but deactivation kinetics seemed to be unaltered. Type I cells subjected to current clamp generate large Na- and Ca-dependent action potentials repetitively. Exposure to low pO2 produces a 4-10 mV increase in the action potential amplitude and a faster depolarization rate of pacemaker potentials, which leads to an increase in the firing frequency. Repolarization rate of individual action potentials is, however, unaffected, or slightly increased. The selective inhibition of K channel activity by low pO2 is a phenomenon without precedents in the literature that explains the chemoreceptive properties of type I cells. The nature of the interaction of molecular O2 with the K channel protein is unknown, however, it is argued that a hemoglobin-like O2 sensor, perhaps coupled to a G protein, could be involved.

Local, stochastic release of Ca2+ in voltage-clamped rat heart cells: visualization with confocal microscopy

1. Confocal microscopy and the fluorescent Ca2+ indicator fluo-3 (K+ salt) were used to measure cytosolic free calcium ion concentration ([Ca2+]) during excitation-contraction (E-C) coupling in single, voltage-clamped, rat cardiac ventricular cells. 2. Local [Ca2+]i transients were measured nearly simultaneously in different, separate, subcellular volumes of approximately 2.0 microns 3. During depolarization, local [Ca2+]i transients were distinctly different from each other and from whole-cell [Ca2+]i transients. These differences were particularly apparent during small depolarizations, and were substantially reduced by ryanodine. 3. Components of the local [Ca2+]i transients, particularly those evoked by small depolarizations, were closely similar, in time course and amplitude, to spontaneous local [Ca2+]i transients, or 'sparks' (which have been shown previously to be Ca2+ released from sarcoplasmic reticulum). 4. Analysis of local [Ca2+]i transients in the spatial frequency domain (power spectrum) revealed that high power at spatial frequencies of 0.05-0.2 microns-1 was always associated with spontaneous calcium 'sparks' and with local [Ca2+]i transients evoked by small depolarizing pulses (e.g. to -31 mV). Evoked local [Ca2+]o transients in the presence of ryanodine, and those evoked by depolarization to very positive clamp-pulse potentials (+45 mV), were associated with considerably lower power at this frequency. 5. The results suggest that whole-cell [Ca2+]i transients evoked by voltage-clamp depolarization, and thus by L-type Ca2+ current, are comprised of local [Ca2+]i transients that are similar to the spontaneous calcium 'sparks'. At very positive clamp-pulse potentials, however, the electrically evoked local [Ca2+]i transients may be smaller, perhaps as a result of smaller unitary L-type Ca2+ current.

O(2) modulates large-conductance Ca(2+)-dependent K(+) channels of rat chemoreceptor cells by a membrane-restricted and CO-sensitive mechanism

Hypoxic inhibition of large-conductance Ca(2+)-dependent K(+) channels (maxiK) of rat carotid body type I cells is a well-established fact. However, the molecular mechanisms of such inhibition and the role of these channels in the process of hypoxic transduction remain unclear. We have examined the mechanisms of interaction of O(2) with maxiK channels exploring the effect of hypoxia on maxiK currents recorded with the whole-cell and the inside-out configuration of the patch-clamp technique. Hypoxia inhibits channel activity both in whole-cell and in excised membrane patches. This effect is strongly voltage- and Ca(2+)-dependent, being maximal at low [Ca(2+)] and low membrane potential. The analysis of single-channel kinetics reveals a gating scheme comprising three open and five closed states. Hypoxia inhibits channel activity increasing the time the channel spends in the longest closed states, an effect that could be explained by a decrease in the Ca(2+) sensitivity of those closed states. Reducing maxiK channels with dithiothreitol (DTT) increases channel open probability, whereas oxidizing the channels with 2,2'-dithiopyridine (DTDP) has the opposite effect. These results suggest that hypoxic inhibition is not related with a reduction of channel thiol groups. However, CO, a competitive inhibitor of O(2) binding to hemoproteins, fully reverts hypoxic inhibition, both at the whole-cell and the single-channel level. We conclude that O(2) interaction with maxiK channels does not require cytoplasmic mediators. Such interaction could be mediated by a membrane hemoprotein that, as an O(2) sensor, would modulate channel activity.

Kvbeta1.2 subunit coexpression in HEK293 cells confers O2 sensitivity to kv4.2 but not to Shaker channels

Voltage-gated K+ (KV) channels are protein complexes composed of ion-conducting integral membrane alpha subunits and cytoplasmic modulatory beta subunits. The differential expression and association of alpha and beta subunits seems to contribute significantly to the complexity and heterogeneity of KV channels in excitable cells, and their functional expression in heterologous systems provides a tool to study their regulation at a molecular level. Here, we have studied the effects of Kvbeta1.2 coexpression on the properties of Shaker and Kv4.2 KV channel alpha subunits, which encode rapidly inactivating A-type K+ currents, in transfected HEK293 cells. We found that Kvbeta1.2 functionally associates with these two alpha subunits, as well as with the endogenous KV channels of HEK293 cells, to modulate different properties of the heteromultimers. Kvbeta1.2 accelerates the rate of inactivation of the Shaker currents, as previously described, increases significantly the amplitude of the endogenous currents, and confers sensitivity to redox modulation and hypoxia to Kv4.2 channels. Upon association with Kvbeta1.2, Kv4.2 can be modified by DTT (1,4 dithiothreitol) and DTDP (2,2'-dithiodipyridine), which also modulate the low pO2 response of the Kv4.2+beta channels. However, the physiological reducing agent GSH (reduced glutathione) did not mimic the effects of DTT. Finally, hypoxic inhibition of Kv4.2+beta currents can be reverted by 70% in the presence of carbon monoxide and remains in cell-free patches, suggesting the presence of a hemoproteic O2 sensor in HEK293 cells and a membrane-delimited mechanism at the origin of hypoxic responses. We conclude that beta subunits can modulate different properties upon association with different KV channel subfamilies; of potential relevance to understanding the molecular basis of low pO2 sensitivity in native tissues is the here described acquisition of the ability of Kv4. 2+beta channels to respond to hypoxia.

Quality of life related to oral health and its impact in adults

Oral health is part of general health, and is recognized as an essential component of quality of life (QoL). For years, oral health was determined solely by the clinic, which did not allow an evaluation of the true impact of oral diseases on the patients' daily lives. The development of instruments for assessing QoL related to oral health has occurred due to the urgency of determining the effects of changes in the oral cavity of individuals. This study aims, through a bibliographical survey, to describe issues involving the relationship between QoL and oral health focusing on methodological and conceptual aspects as well as considering how oral health of adult individuals affects their QoL in a general way. Research in this area has developed the concept of "quality of life related to oral health", which comprises four categories: functional factors, psychological factors, social factors and existence of discomfort or pain. The negative impacts that poor oral health of the population have on their QoL makes this issue a relevant problem for public health. Although most oral problems do not represent an immediate risk of death, they are responsible for decreasing the QoL of individuals as they prolong states of pain and suffering, and cause functional, aesthetic, nutritional and psychological problems. Actions focused on health education with emphasis on self-perception, self-protection and self-care should be explored. Programs based on equity seeking to reduce inequalities and their negative effects on people's QoL should also be explored.

Ionic currents in dispersed chemoreceptor cells of the mammalian carotid body

Ionic currents of enzymatically dispersed type I and type II cells of the carotid body have been studied using the whole cell variant of the patch-clamp technique. Type II cells only have a tiny, slowly activating outward potassium current. By contrast, in every type I chemoreceptor cell studied we found (a) sodium, (b) calcium, and (c) potassium currents. (a) The sodium current has a fast activation time course and an activation threshold at approximately -40 mV. At all voltages inactivation follows a single exponential time course. The time constant of inactivation is 0.67 ms at 0 mV. Half steady state inactivation occurs at a membrane potential of approximately -50 mV. (b) The calcium current is almost totally abolished when most of the external calcium is replaced by magnesium. The activation threshold of this current is at approximately -40 mV and at 0 mV it reaches a peak amplitude in 6-8 ms. The calcium current inactivates very slowly and only decreases to 27% of the maximal value at the end of 300-ms pulses to 40 mV. The calcium current was about two times larger when barium ions were used as charge carriers instead of calcium ions. Barium ions also shifted 15-20 mV toward negative voltages the conductance vs. voltage curve. Deactivation kinetics of the calcium current follows a biphasic time course well fitted by the sum of two exponentials. At -80 mV the slow component has a time constant of 1.3 +/- 0.4 ms whereas the fast component, with an amplitude about 20 times larger than the slow component, has a time constant of 0.16 +/- 0.03 ms. These results suggest that type I cells have predominantly fast deactivating calcium channels. The slow component of the tails may represent the activity of a small population of slowly deactivating calcium channels, although other possibilities are considered. (c) Potassium current seems to be mainly due to the activity of voltage-dependent potassium channels, but a small percentage of calcium-activated channels may also exist. This current activates slowly, reaches a peak amplitude in 5-10 ms, and thereafter slowly inactivates. Inactivation is almost complete in 250-300 ms. The potassium current is reversibly blocked by tetraethylammonium. Under current-clamp conditions type I cells can spontaneously fire large action potentials. These results indicate that type I cells are excitable and have a variety of ionic conductances. We suggest a possible participation of these conductances in chemoreception.

Periapical and endodontic status of type 2 diabetic patients in Catalonia, Spain: a cross-sectional study

INTRODUCTION

The aim of this study was to investigate radiographically the prevalence of apical periodontitis (AP) and endodontic treatment in a sample of adult type II diabetic patients and control subjects.

METHODS

In a cross-sectional study, the radiographic records of 50 adult patients reporting a history of well-controlled type 2 diabetes mellitus (DM) (study group) and 50 age- and sex-matched subjects who reported no history of DM (control group) were examined. Periapical status of all teeth was assessed using the periapical index score.

RESULTS

The average number of teeth per patient in the diabetic and control groups was 21.9 and 24.6 teeth, respectively (P = .012). AP in one or more teeth was found in 37 diabetic patients (74%) and in 21 control subjects (42%) (odds ratio = 3.9, P = .002). One or more root-filled teeth were found in 35 (70%) and 25 (50%) of diabetic and control subjects, respectively (odds ratio = 2.3, P = .043). Among diabetic patients with root-filled teeth, 16 (46%) had AP affecting at least one treated tooth. Among controls with root-filled teeth, 6 (24%) had AP affecting at least one treated tooth (P > .05). Adjusting for teeth number, multivariate logistic regression analysis showed that periapical status (odds ratio = 3.3, P = .0071) and the number of root-filled teeth (odds ratio = 1.7; P = .0035) were significantly associated with diabetic status.

CONCLUSIONS

The results showed that in adult patients, type 2 DM is significantly associated with an increased prevalence of AP and endodontic treatment.

Diabetes mellitus, periapical inflammation and endodontic treatment outcome

The possible connection between chronic oral inflammatory processes, such as apical periodontitis and periodontal disease (PD), and systemic health is one of the most interesting aspects faced by the medical and dental scientific community. Chronic apical periodontitis shares important characteristics with PD: 1) both are chronic infections of the oral cavity, 2) the Gram-negative anaerobic microbiota found in both diseases is comparable, and 3) in both infectious processes increased local levels of inflammatory mediators may have an impact on systemic levels. One of the systemic disorders linked to PD is diabetes mellitus (DM); is therefore plausible to assume that chronic apical periodontitis and endodontic treatment are also associated with DM. The status of knowledge regarding the relationship between DM and endodontics is reviewed. Upon review, we conclude that there are data in the literature that associate DM with a higher prevalence of periapical lesions, greater size of the osteolityc lesions, greater likelihood of asymptomatic infections and worse prognosis for root filled teeth. The results of some studies suggest that periapical disease may contribute to diabetic metabolic dyscontrol.

Key words: Apical periodontitis, diabetes mellitus, endodontics, root canal treatment.

Characterization of the Kv channels of mouse carotid body chemoreceptor cells and their role in oxygen sensing

As there are wide interspecies variations in the molecular nature of the O(2)-sensitive Kv channels in arterial chemoreceptors, we have characterized the expression of these channels and their hypoxic sensitivity in the mouse carotid body (CB). CB chemoreceptor cells were obtained from a transgenic mouse expressing green fluorescent protein (GFP) under the control of tyrosine hydroxylase (TH) promoter. Immunocytochemical identification of TH in CB cell cultures reveals a good match with GFP-positive cells. Furthermore, these cells show an increase in [Ca(2+)](i) in response to low P(O(2)), demonstrating their ability to engender a physiological response. Whole-cell experiments demonstrated slow-inactivating K(+) currents with activation threshold around -30 mV and a bi-exponential kinetic of deactivation (tau of 6.24 +/- 0.52 and 32.85 +/- 4.14 ms). TEA sensitivity of the currents identified also two different components (IC(50) of 17.8 +/- 2.8 and 940.0 +/- 14.7 microm). Current amplitude decreased reversibly in response to hypoxia, which selectively affected the fast deactivating component. Hypoxic inhibition was also abolished in the presence of low (10-50 microm) concentrations of TEA, suggesting that O(2) interacts with the component of the current most sensitive to TEA. The kinetic and pharmacological profile of the currents suggested the presence of Kv2 and Kv3 channels as their molecular correlates, and we have identified several members of these two subfamilies by single-cell PCR and immunocytochemistry. This report represents the first functional and molecular characterization of Kv channels in mouse CB chemoreceptor cells, and strongly suggests that O(2)-sensitive Kv channels in this preparation belong to the Kv3 subfamily.

Properties of ionic currents from isolated adult rat carotid body chemoreceptor cells: effect of hypoxia

1. The electrical properties of chemoreceptor cells from neonatal rat and adult rabbit carotid bodies (CBs) are strikingly different. These differences have been suggested to be developmental and/or species related. To distinguish between the two possibilities, the whole-cell configuration of the patch-clamp technique was used to characterize the ionic currents present in isolated chemoreceptor cells from adult rat CBs. Since hypoxia-induced inhibition of O2-sensitive K+ currents is considered a crucial step in O2 chemoreception, the effect of hypoxia on the adult rat chemoreceptor cell currents was also studied. 2. Outward currents were carried mainly by K+, and two different components could be distinguished: a Ca(2+)-dependent K+ current (IK(Ca)) sensitive to Cd2+ and charybdotoxin (CTX), and a Ca(2+)-insensitive, voltage-dependent K+ current (IK(V)). IK(V) showed a slow voltage-dependent activation (time constant (tau) of 87.4 ms at -20 mV and 8.8 ms at +60 mV) and a very slow inactivation, described by the sum of two exponentials (tau 1 = 684 +/- 150 ms and tau 2 = 4.96 +/- 0.76 s at + 30 mV), that was almost voltage insensitive. The kinetic and pharmacological properties of IK(V) are typical of a delayed rectifier K+ channel. 3. Voltage-dependent Ca2+ currents (ICa) were present in nineteen of twenty-seven cells. TTX-sensitive Na+ currents were also observed in about 10% of the cells. 4. Low PO2 (< 10 mmHg) reduced the whole outward current amplitude by 22.17 +/- 1.96% (n = 27) at +20 mV. This effect was absent in the presence of Cd2+. Since low PO2 did not affect ICa, we conclude that hypoxia selectively blocks IK(Ca). 5. The properties of the currents recorded in adult rat chemoreceptor cells, including the specific inhibition of IK(Ca) by hypoxia, are similar to those reported in neonatal rat CB cells, implying that the differences between rat and rabbit chemoreceptor cells are species related.

Properties of a transient K+ current in chemoreceptor cells of rabbit carotid body

1. Adult rabbit carotid body chemoreceptor cells, enzymatically dispersed and short-term cultured, exhibit an inactivating outward K+ current that is reversibly inhibited by low PO2. In the present work we have characterized the biophysical and pharmacological properties of this current using the whole-cell voltage clamp recording technique. 2. Inactivating current was recorded after blockage of Ca2+ currents with extracellular Co2+, Cd2+, or after complete washing out of Ca2+ channels. 3. The threshold of activation of this inactivating current was about -40 mV. Current activated very quickly (mean rise time 4.8 +/- 0.42 ms at +60 mV) but inactivated more slowly. Inactivation was well fitted by two exponentials with time constants of 79.7 +/- 6.6 and 824 +/- 42.8 ms (at +40 mV). The inactivation process showed a little voltage dependence. 4. The steady-state inactivation was well fitted by a Boltzman function. Inactivation was fully removed at potentials negative to -80 mV and was complete at voltages near -10 mV; 50% inactivation occurred at -41 mV. 5. Recovery from inactivation had several components and was voltage dependent. Initial recovery was fast, but full recovery, even at -100 mV, required more than 30 s. 6. Inactivating current was selectively blocked by 4-aminopyridine (4-AP), in a dose-dependent manner (IC50, 0.2 mM). The duration of chemoreceptor cells action potentials was augmented by 1 mM 4-AP from 2.3 +/- 0.36 to 7.0 +/- 0.25 ms at 0 mV. Tetraethylamonium (TEA), at concentrations above 5 mM, blocked inactivating and non-inactivating components of the whole K+ current. 7. Inactivating current was modulated by cyclic AMP (cAMP). Bath application of 2 mM dibutyryl cAMP reduced peak amplitude by 18.7 +/- 2.9% (at +30 mV) and slowed down the rise time of the current. The effect was not voltage dependent. Forskolin (10-20 microM) also affected inactivating current, by accelerating the inactivation process. In the same preparations neither dibutyryl cAMP nor forskolin affected Ca2+ currents. 8. It is concluded that modulation of K+ channels by cAMP might play a physiological role potentiating the low PO2 inhibition of K+ channels.

Oral manifestations of Diabetes Mellitus. A systematic review

BACKGROUND

Diabetes Mellitus has become a global epidemic and presents many complications, usually proportional to the degree and duration of hyperglycemia. The aim of this systematic review was to investigate the different oral manifestations associated with Diabetes Mellitus.

MATERIAL AND METHODS

A MEDLINE search for "Diabetes Mellitus and oral manifestations" was performed. A further search was conducted for "diabetes" and its individual oral manifestation. Inclusion criteria were as follows: human clinical studies with a minimum of 30 patients; studies published in relevant scientific journals between January 1998 and January 2016. Nineteen studies fulfilled the inclusion criteria and were analyzed, assessing the strength of scientific evidence according to recommendations made by the Centre for Evidence-Based Medicine, Oxford (OCEBM), which permits adequate assessment of prevalence studies.

RESULTS

A total 3,712 patients (2,084 diabetics) were included in the studies reviewed. Of the 19 studies analyzed, 4 were longitudinal studies and 15 cross-sectional studies. Periodontal disease, periapical lesions, xerostomia and taste disturbance were more prevalent among diabetic patients. An association between diabetes and caries and mucosal lesions proved positive in 5 out of 10 studies.

CONCLUSIONS

Despite multiple oral manifestations associated with DM, awareness of the associations between diabetes, oral health, and general health is inadequate. It is necessary for doctors and dentists to be aware of the various oral manifestations of diabetes in order to make an early diagnosis.

Time course of K+ current inhibition by low oxygen in chemoreceptor cells of adult rabbit carotid body. Effects of carbon monoxide

K+ currents recorded from adult rabbit chemoreceptor cells are reversibly inhibited on lowering the pO2 in the bathing solution. Bath application of a hypoxic TTX-containing solution revealed that inhibition of K+ current by low pO2 proceeds faster than TTX inhibition of Na+ currents, the apparent t1/2 being 3.68 and 7.14 s, respectively. Addition of carbon monoxide to the hypoxic gas mixture used to equilibrate the bathing solution reversed the inhibition of K+ currents by approx. 70%.

Release of dopamine and chemoreceptor discharge induced by low pH and high PCO2 stimulation of the cat carotid body

1. Cat carotid bodies were incubated with the precursor [3H]tyrosine to label the catecholamine deposits and then mounted in a superfusion chamber which allowed simultaneous collection of the released [3H]dopamine (DA) and recording of action potentials from the carotid sinus nerve. 2. Low pH (7.2-6.6) superfusion of the carotid bodies for periods of 10 min produced a parallel increase in the release of [3H]DA and chemoreceptor discharge. 3. Carotid sinus nerve denervation of the carotid body 12-15 days prior to the experiments did not modify the release of [3H]DA elicited by low pH. 4. Superfusion of the carotid bodies with Ca(2+)-free, high-Mg2+ (1.6 mM) media reduced basal release of [3H]DA and chemoreceptor discharge by about 30%. Release evoked by low pH was reduced by 82%. Peak and average chemoreceptor discharge recorded in response to low pH were reduced by 28%. 5. Solutions containing weak acids (sodium acetate, 10 mM), adjusted at pH 7.4, elicited release of [3H]DA and increased chemoreceptor discharge. 6. With HCO3-CO2-buffered superfusion media, a reduction of bicarbonate to 5.6 mM (pH 6.8), an increase in CO2 to 20% (pH 6.8), or a simultaneous increase in CO2 to 20% and bicarbonate to 90 mM (pH 7.4), resulted in all cases in a corresponding increase in [3H]DA release and chemoreceptor discharge. The most effective stimulus was 20% CO2-pH 6.8 and the least effective 5% CO2-5.6 mM-HCO3-pH 6.8. 7. Inhibition of carbonic anhydrase with acetazolamide while perfusing the carotid bodies with a 20% CO2-equilibrated (pH 7.4) solution resulted in comparable reductions in the release of [3H]DA and chemoreceptor discharge. 8. It is concluded that the effective acidic stimulus at the carotid body chemoreceptors is an increase in hydrogen ion concentration in type I cells. It is also concluded that DA plays a critical role in the genesis of carotid sinus nerve discharges.

Probiotics and oral health: A systematic review

Background

Probiotics are microorganisms, mainly bacteria, which benefit the host’s health. Many studies support the role of probiotics as a contributor to gastrointestinal health, and nowadays many authors are trying to prove its influence in oral health maintenance.

Objectives

To review the published literature with the purpose of knowing the importance of using probiotics as a preventive and therapeutic method for oral infectious diseases management.

Material and Methods

An electronic search in PubMed database with the keywords “oral health AND probiotics AND dentistry” was conducted. The inclusion criteria were: randomized clinical trials (RCTs) that assess the action of any probiotic strain in the treatment and / or prevention of an infectious oral disease, RCTs that assess the action of any probiotic strain on counting colony forming units (CFU) of oral pathogens, systematic reviews and meta-analysis. The Jadad scale was used to assess the high quality of RCTs.

Results

Fifteen articles were considered for this review. Of which, 12 were RCTs of good / high quality (Jadad scale), two meta-analysis and one systematic review.

Conclusions

The literature reviewed suggests probiotics usage could be beneficial for the maintenance of oral health, due to its ability to decrease the colony forming units (CFU) counts of the oral pathogens. However, randomized clinical trials with long-term follow-up periods are needed to confirm their efficacy in reducing the prevalence/incidence of oral infectious diseases. Furthermore, the recognition of specific strains with probiotic activity for each infectious oral disease is required, in order to determine exact dose, treatment time and ideal vehicles.

Key words:Probiotics, periodontal diseases, dental caries, oral health.

Contribution of Kv channels to phenotypic remodeling of human uterine artery smooth muscle cells

Vascular smooth muscle cells (VSMCs) perform diverse functions that can be classified into contractile and synthetic (or proliferating). All of these functions can be fulfilled by the same cell because of its capacity of phenotypic modulation in response to environmental changes. The resting membrane potential is a key determinant for both contractile and proliferating functions. Here, we have explored the expression of voltage-dependent K+ (Kv) channels in contractile (freshly dissociated) and proliferating (cultured) VSMCs obtained from human uterine arteries to establish their contribution to the functional properties of the cells and their possible participation in the phenotypic switch. We have studied the expression pattern (both at the mRNA and at the protein level) of Kvalpha subunits in both preparations as well as their functional contribution to the K+ currents of VSMCs. Our results indicate that phenotypic remodeling associates with a change in the expression and distribution of Kv channels. Whereas Kv currents in contractile VSMCs are mainly performed by Kv1 channels, Kv3.4 is the principal contributor to K+ currents in cultured VSMCs. Furthermore, selective blockade of Kv3.4 channels resulted in a reduced proliferation rate, suggesting a link between Kv channels expression and phenotypic remodeling.

Morse taper dental implants and platform switching: The new paradigm in oral implantology

The aim of this study was to conduct a literature review on the potential benefits with the use of Morse taper dental implant connections associated with small diameter platform switching abutments. A Medline bibliographical search (from 1961 to 2014) was carried out. The following search items were explored: “Bone loss and platform switching,” “bone loss and implant-abutment joint,” “bone resorption and platform switching,” “bone resorption and implant-abutment joint,” “Morse taper and platform switching.” “Morse taper and implant-abutment joint,” Morse taper and bone resorption,” “crestal bone remodeling and implant-abutment joint,” “crestal bone remodeling and platform switching.” The selection criteria used for the article were: meta-analysis; randomized controlled trials; prospective cohort studies; as well as reviews written in English, Portuguese, or Spanish languages. Within the 287 studies identified, 81 relevant and recent studies were selected. Results indicated a reduced occurrence of peri-implantitis and bone loss at the abutment/implant level associated with Morse taper implants and a reduced-diameter platform switching abutment. Extrapolation of data from previous studies indicates that Morse taper connections associated with platform switching have shown less inflammation and possible bone loss with the peri-implant soft tissues. However, more long-term studies are needed to confirm these trends.

Inferior alveolar nerve injury resulting from overextension of an endodontic sealer: non-surgical management using the GABA analogue pregabalin

AIM

  To describe a case of endodontic sealer (AH Plus) penetration within the mandibular canal after root canal treatment with resolution of pain and paraesthesia after a non-surgical approach, including treatment with prednisone and pregabalin.

SUMMARY

  A 37-year-old woman underwent root canal treatment of the left mandibular second molar tooth. Postoperative periapical radiographs revealed the presence of radiopaque canal sealer in the mandibular canal. The day after, the patient reported severe pain in the tooth and paraesthesia/anaesthesia in the region innervated by the left inferior alveolar and mental nerve. Diagnosis of injury to the inferior alveolar nerve because of extrusion of AH Plus was established. The non-surgical management included 1 mg kg(-1) per day prednisone, two times per day, in a regimen on a daily basis, and 150 mg per day pregabalin, two doses per day, monitoring the progress with periodic follow-up visits. One month after the incident, the signs and symptoms were gone.

KEY LEARNING POINTS

This case illustrates the care required when performing root canal treatment, especially when the root apices are in close proximity to the inferior alveolar nerve canal. The complete resolution of paraesthesia and the control of pain achieved in the present case suggests that a non-surgical approach combining prednisone and pregabalin is a good option in the management of the inferior alveolar when it is contacted by extruded root filling material.

Differential modulation of Kv4.2 and Kv4.3 channels by calmodulin-dependent protein kinase II in rat cardiac myocytes

In this work we have combined biochemical and electrophysiological approaches to explore the modulation of rat ventricular transient outward K+ current ( Ito) by calmodulin kinase II (CaMKII). Intracellular application of CaMKII inhibitors KN93, calmidazolium, and autocamtide-2-related inhibitory peptide II (ARIP-II) accelerated the inactivation of Ito, even at low [Ca2+]. In the same conditions, CaMKII coimmunoprecipitated with Kv4.3 channels, suggesting that phosphorylation of Kv4.3 channels modulate inactivation of Ito. Because channels underlying Ito are heteromultimers of Kv4.2 and Kv4.3, we have explored the effect of CaMKII on human embryonic kidney (HEK) cells transfected with either of those Kvα-subunits. Whereas Kv4.3 inactivated faster upon inhibition of CaMKII, Kv4.2 inactivation was insensitive to CaMKII inhibitors. However, Kv4.2 inactivation became slower when high Ca2+ was used in the pipette or when intracellular [Ca2+] ([Ca2+]i) was transiently increased. This effect was inhibited by KN93, and Western blot analysis demonstrated Ca2+-dependent phosphorylation of Kv4.2 channels. On the contrary, CaMKII coimmunoprecipitated with Kv4.3 channels without a previous Ca2+ increase, and the association was inhibited by KN93. These results suggest that both channels underlying Ito are substrates of CaMKII, although with different sensitivities; Kv4.2 remain unphosphorylated unless [Ca2+]i increases, whereas Kv4.3 are phosphorylated at rest. In addition to the functional impact that phosphorylation of Kv4 channels could cause on the shape of action potential, association of CaMKII with Kv4.3 provides a new role of Kv4.3 subunits as molecular scaffolds for concentrating CaMKII in the membrane, allowing Ca2+-dependent modulation by this enzyme of the associated Kv4.2 channels.