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1.
Eur J Prosthodont Restor Dent ; 32(1): 109-119, 2024 Feb 29.
Article in English | MEDLINE | ID: mdl-37988616

ABSTRACT

This study aims to investigate the effects of laser-activated irrigation on root canal dentin using different laser wavelengths. Sixty-six roots were prepared and split longitudinally. First, lasers with different power settings were tested on 34 samples, pre-etched with phosphoric acid, or remaining with a smear-layer to determine the test parameters. Selected parameters were then applied on thirty roots (9 groups) covered with smear layer: 1. Smear-layer removed; 2. Smear-layer untouched; 3. Conventional needle irrigation with NaOCl and EDTA; 4. ER:YAG laser; 5. 9.3 µm CO2 laser; 6-9. Diode lasers. All lasers were applied in ultra-pure water as an irrigant. Root halves were examined by scanning electron microscope to analyze the intracanal dentin micromorphology on 9 consequent photos per specimen @ a magnification of 1000X. The results showed that conventional needle irrigation was effective in removing the smear-layer from coronal and middle root parts, while laser-activated irrigation had two main mechanisms: cleaning and opening of the dentinal tubules by removing the smear layer (Er:YAG laser) and melting of dentin (CO2 and diode lasers) in all root parts. The study concluded that laseractivated irrigation with different wavelengths impacted the smear layer and root canal dentin differently through pure physical/mechanical effects.


Subject(s)
Lasers, Solid-State , Smear Layer , Humans , Dental Pulp Cavity , Root Canal Preparation , Root Canal Irrigants/pharmacology , Lasers , Microscopy, Electron, Scanning , Edetic Acid/pharmacology , Dentin , Sodium Hypochlorite/pharmacology
2.
Biochem Pharmacol ; 91(4): 426-35, 2014 Oct 15.
Article in English | MEDLINE | ID: mdl-25130547

ABSTRACT

The divalent cation, zinc is the second most abundant metal in the human body and is indispensable for life. Zinc concentrations must however, be tightly regulated as deficiencies are associated with multiple pathological conditions while an excess can be toxic. Zinc plays an important role as a cofactor in protein folding and function, e.g. catalytic interactions, DNA recognition by zinc finger proteins and modulation ion channel activity. There are 24 mammalian proteins specific for zinc transport that are subdivided in two groups with opposing functions: ZnT proteins reduce cytosolic zinc concentration while ZIP proteins increase it. The mammalian brain contains a significant amount of zinc, with 5-15% concentrated in synaptic vesicles of glutamatergic neurons alone. Accumulated in these vesicles by the ZnT3 transporter, zinc is released into the synaptic cleft at concentrations from nanomolar at rest to high micromolar during active neurotransmission. Low concentrations of zinc modulate the activity of a multitude of voltage- or ligand-gated ion channels, indicating that this divalent cation must be taken into account in the analysis of the pathophysiology of CNS disorders including epilepsy, schizophrenia and Alzheimer's disease. In the context of the latest findings, we review the role of zinc in the central nervous system and discuss the relevance of the most recent association between the zinc transporter, ZIP8 and schizophrenia. An enhanced understanding of zinc transporters in the context of ion channel modulation may offer new avenues in identifying novel therapeutic entities that target neurological disorders.


Subject(s)
Brain/physiology , Zinc/physiology , Brain/drug effects , Dose-Response Relationship, Drug , Humans , Mental Disorders/drug therapy , Nervous System Diseases/drug therapy , Synaptic Transmission/physiology , Zinc/therapeutic use , Zinc/toxicity
3.
Article in English | MEDLINE | ID: mdl-17017901

ABSTRACT

The generation of cardiac pacemaker activity is a complex phenomenon which requires the coordinated activity of different membrane ionic channels, as well as intracellular signalling factors including Ca(2+) and second messengers. The precise mechanism initiating automaticity in primary pacemaker cells is still matter of debate and certain aspects of how channels cooperate in the regulation of pacemaking by the autonomic nervous system have not been entirely elucidated. Research in the physiopathology of cardiac automaticity has also gained a considerable interest in the domain of cardiovascular pharmacology, since accumulating clinical and epidemiological evidence indicate a link between an increase in heart rate and the risk of cardiac mortality and morbidity. Lowering the heart rate by specific bradycardic agents in patients with heart disease constitutes a promising way to increase cardioprotection and improve survival. Thus, the elucidation of the mechanisms underlying the generation of pacemaker activity is necessary for the development of new therapeutic molecules for controlling the heart rate. Recent work on genetically modified mouse models provided new and intriguing evidence linking the activity of ionic channels genes to the generation and regulation of pacemaking. Importantly, results obtained on genetically engineered mouse strains have demonstrated that some channels are specifically involved in the generation of cardiac automaticity and conduction, but have no functional impact on the contractile activity of the heart. In this article, we will outline the current knowledge on the role of ionic channels in cardiac pacemaker activity and suggest new potential pharmacological targets for controlling the heart rate without concomitant negative inotropism.


Subject(s)
Heart Conduction System/physiology , Ion Channels/physiology , Animals , Arrhythmias, Cardiac/etiology , Calcium Channels/physiology , Diastole , Humans , Potassium Channels, Voltage-Gated/physiology , Sodium Channels/physiology , Sympathetic Nervous System/physiology
4.
Adv Cardiol ; 43: 17-30, 2006.
Article in English | MEDLINE | ID: mdl-16936469

ABSTRACT

The slow diastolic depolarization phase in cardiac pacemaker cells is the electrical basis of cardiac automaticity. The hyperpolarization-activated current (I(f)) is one of the key mechanisms underlying diastolic depolarization. Particularly, I(f) is unique in being activated on membrane hyperpolarization following the repolarization phase of the action potential. I(f) has adapted biophysical properties and voltage-dependent gating to initiate pacemaker activity. I(f) possibly constitutes the first voltage-dependent trigger of the diastolic depolarization. For these reasons, I(f) is a natural pharmacological target for controlling heart rate in cardiovascular disease. In this view, I(f) inhibitors have been developed in the past, yet the only molecule to have reached the clinical development is ivabradine. At the cellular level, the remarkable success of ivabradine is to be ascribed to its relatively high affinity for f-channels. Furthermore, ivabradine is the most I(f)-specific inhibitor known to date, since moderate inhibition of other voltage-dependent ionic currents involved in automaticity can be observed only at very high concentrations of ivabradine, more than one order of magnitude from that inhibiting I(f). Finally, the mechanism of block of f-channels by ivabradine has particularly favorable properties in light of controlling heart rate under variable physiological conditions. In this article, we will discuss how I(f) inhibition by ivabradine can lead to reduction of heart rate. To this aim, we will comment on the role of I(f) in cardiac automaticity and on the mechanism of action of ivabradine on f-channels. Some aspects of the cardiac pacemaker mechanism that improve the degree of security of ivabradine will also be highlighted.


Subject(s)
Benzazepines/pharmacology , Cardiotonic Agents/pharmacology , Cardiovascular Diseases/drug therapy , Cardiovascular Diseases/physiopathology , Heart Conduction System/drug effects , Heart Conduction System/physiology , Heart Rate/drug effects , Heart Rate/physiology , Animals , Diastole/drug effects , Diastole/physiology , Humans , Ion Channels/drug effects , Ivabradine
5.
Reprod Nutr Dev ; 31(6): 703-16, 1991.
Article in English | MEDLINE | ID: mdl-1777062

ABSTRACT

Propylthiouracil (PTU), thyroxine (T4) or thyreoliberin (TRH) were injected in ovo to modify the thyroid state of chicken embryos. Significant sexual differences were observed in the effects of these treatments on the plasma concentrations of thyroid hormones and on plantaris muscle characteristics (DNA, RNA, populations of muscle fibers) in 3- and 35-day old male and female chickens. The T4 plasma concentration is lower in control males; it is decreased in PTU treated females and in the T4 treated females at 35 days. The T3 plasma concentration is lowered at 3 days in all treated chickens and also at 35 days in the TRH treated animals. The slow (STnO) and the fast (FTOG) fibers of the plantaris are always more numerous in males. In controls, the number of FTOG fibers remains steady between 3 and 35 days; at the same time, the number of STnO fibers rises in males only. Both PTU and T4 treatments increase the number of the FTOG and the STnO fibers respectively before and after the 3rd day. TRH treatment increases the number of STnO fibers at 3 and 35 days in males, but reduces it at 3 days in females. Thus changes in the number of FTOG fibers can be induced during in ovo myogenesis, whereas the number of STnO fibers may increase after hatching.


Subject(s)
Chickens/physiology , Muscles/anatomy & histology , Thyroid Gland/embryology , Thyroid Hormones/blood , Animals , Chick Embryo , Chickens/anatomy & histology , Female , Male , Organ Size , Propylthiouracil/pharmacology , Sex Characteristics , Thyroid Gland/drug effects , Thyroid Gland/physiology , Thyrotropin-Releasing Hormone/pharmacology , Thyroxine/blood , Thyroxine/pharmacology , Triiodothyronine/blood
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