Activation of ion secretion via proteinase-activated receptor-2 in human colon

Proteinase-activated receptor (PAR) type 2 (PAR-2) has been shown to mediate ion secretion in cultured epithelial cells and rat jejunum. With the use of a microUssing chamber, we demonstrate the role of PAR-2 for ion transport in native human colonic mucosa obtained from 30 normal individuals and 11 cystic fibrosis (CF) patients. Trypsin induced Cl- secretion when added to the basolateral but not luminal side of normal epithelia. Activation of Cl- secretion by trypsin was inhibited by indomethacin and was further increased by cAMP in normal tissues but was not present in CF colon, indicating the requirement of luminal CF transmembrane conductance regulator. Effects of trypsin were largely reduced by low Cl-,by basolateral bumetanide, and in the presence of barium or clotrimazole, but not by tetrodotoxin. Furthermore, trypsin-induced secretion was inhibited by the Ca2+-ATPase inhibitor cyclopiazonic acid and in low-Ca2+ buffer. The effects of trypsin were almost abolished by trypsin inhibitor. Thrombin, an activator of PAR types 1, 3, and 4, had no effects on equivalent short-circuit currents. The presence of PAR-2 in human colon epithelium was confirmed by RT-PCR and additional experiments with PAR-2-activating peptide. PAR-2-mediated intestinal electrolyte secretion by release of mast cell tryptase and potentiation of PAR-2 expression by tumor necrosis factor-alpha may contribute to the hypersecretion observed in inflammatory processes such as chronic inflammatory bowel disease.

Inhibition of rat platelet aggregation by the diazeniumdiolate nitric oxide donor MAHMA NONOate

1 Inhibition of rat platelet aggregation by the nitric oxide (NO) donor MAHMA NONOate (Z-1-{N-methyl-N-[6-(N-methylammoniohexyl)amino]}diazen-l-ium-1,2-diolate) was investigated. The aims were to compare its anti-aggregatory effect with vasorelaxation, to determine the effects of the soluble guanylate cyclase inhibitor, ODQ (1H-[1,2,4]oxadiazolo[4,3-ajquinoxalin-1-one), and to investigate the possible role of activation of sarco-encloplasmic reticulum calcium-ATPase (SERCA), independent of soluble guanylate cyclase, using thapsigargin. 2 MAHMA NONOate concentration-dependently inhibited sub-maximal aggregation responses to collagen (2 - 10 mug ml(-1)) and adenosine diphosphate (ADP; 2 mum) in platelet rich plasma. It was (i) more effective at inhibiting aggregation induced by collagen than by ADP, and (ii) less potent at inhibiting platelet aggregation than relaxing rat pulmonary artery. 3 ODQ (10 mum) caused only a small shift (approximately half a log unit) in the concentration-response curve to MAHMA NONOate irrespective of the aggregating agent. 4 The NO-independent activator of soluble guanylate cyclase, YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzy] indazole; 1 - 100 mum), did not inhibit aggregation. The cGMP analogue, 8-pCPT-cGMP (8-(4-chlorophenylthio)guanosine 3'5' cyclic monophosphate; 0.1 - 1 mm), caused minimal inhibition. 5 On collagen-aggregated platelets responses to MAHMA NONOate (ODQ 10 PM present) were abolished by thapsigargin (200 nm). On ADP-aggregated platelets thapsigargin caused partial inhibition. 6 Results with S-nitrosoglutathione (GSNO) resembled those with MAHMA NONOate. Glyceryl trinitrate and sodium nitroprusside were poor inhibitors of aggregation. 7 Thus inhibition of rat platelet aggregation by MAHMA NONOate (like GSNO) is largely ODQ-resistant and, by implication, independent of soluble guanylate cyclase. A likely mechanism of inhibition is activation of SERCA.

Genetic and Environmental Influences on Migraine: A Twin Study Across Six Countries

Migraine is a common neurovascular brain disorder that is manifested in recurrent episodes of disabling headache. The aim of the present study was to compare the prevalence and heritability of migraine across six of the countries that participate in GenomEutwin project including a total number of 29,717 twin pairs. Migraine was assessed by questionnaires that differed between most countries. It was most prevalent in Danish and Dutch females (32% and 34%, respectively), whereas the lowest prevalence was found in the younger and older Finnish cohorts (13% and 10%, respectively). The estimated genetic variance (heritability) was significant and the same between sexes in all countries. Heritability ranged from 34% to 57%, with lowest estimates in Australia, and highest estimates in the older cohort of Finland, the Netherlands, and Denmark. There was some indication that part of the genetic variance was non-additive, but this was significant in Sweden only. In addition to genetic factors, environmental effects that are non-shared between members of a twin pair contributed to the liability of migraine. After migraine definitions are homogenized among the participating countries, the GenomEUtwin project will provide a powerful resource to identify the genes involved in migraine.

Molecular and functional characterization of an octopamine receptor from honeybee (Apis mellifera) brain

Biogenic amines and their receptors regulate and modulate many physiological and behavioural processes in animals. In vertebrates, octopamine is only found in trace amounts and its function as a true neurotransmitter is unclear. In protostomes, however, octopamine can act as neurotransmitter, neuromodulator and neurohormone. In the honeybee, octopamine acts as a neuromodulator and is involved in learning and memory formation. The identification of potential octopamine receptors is decisive for an understanding of the cellular pathways involved in mediating the effects of octopamine. Here we report the cloning and functional characterization of the first octopamine receptor from the honeybee, Apis mellifera . The gene was isolated from a brain-specific cDNA library. It encodes a protein most closely related to octopamine receptors from Drosophila melanogaster and Lymnea stagnalis . Signalling properties of the cloned receptor were studied in transiently transfected human embryonic kidney (HEK) 293 cells. Nanomolar to micromolar concentrations of octopamine induced oscillatory increases in the intracellular Ca2+ concentration. In contrast to octopamine, tyramine only elicited Ca2+ responses at micromolar concentrations. The gene is abundantly expressed in many somata of the honeybee brain, suggesting that this octopamine receptor is involved in the processing of sensory inputs, antennal motor outputs and higher-order brain functions.

Autosomal dominant hypocalcemia: A novel activating mutation (E604K) in the cysteine-rich domain of the calcium-sensing receptor

We report a novel activating mutation (E604K) of the calcium-sensing receptor in a family with autosomal dominant hypocalcemia. Whereas all affected individuals exhibited marked hypocalcemia, some cases with untreated hypocalcemia exhibited seizures in infancy, whereas others were largely asymptomatic from birth into adulthood. The missense mutation E604K (G2182A, GenBank accession no. U20759), which affects an amino acid residue in the C terminus of the cysteine-rich domain of the extracellular head, co-segregated with hypocalcemia in all seven individuals for whom DNA was available. Two unaffected, normocalcemic members of the family did not exhibit the mutation. The molecular impact of the mutation on two key components of the signaling response was assessed in HEK-293 cells transiently transfected with cDNA corresponding to either the wild-type calcium-sensing receptor or the E604K mutation derived by site-directed mutagenesis. There was a significant leftward shift in the concentration response curves for the effects of extracellular Ca2+ on both intracellular Ca2+ mobilization (determined by aequorin luminescence) and MAPK activity (determined by luciferase expression). The C terminus of the cysteine-rich domain of the extracellular head may normally act to suppress receptor activity in the presence of low extracellular Ca2+ concentrations.

Ventricular performance and Na+-K+ ATPase activity are reduced early and late after myocardial infarction in rats

Myocardial infarction leads to compensatory ventricular remodeling. Disturbances in myocardial contractility depend on the active transport of Ca2+ and Na+, which are regulated by Na+-K+ ATPase. Inappropriate regulation of Na+-K+ ATPase activity leads to excessive loss of K+ and gain of Na+ by the cell. We determined the participation of Na+-K+ ATPase in ventricular performance early and late after myocardial infarction. Wistar rats (8-10 per group) underwent left coronary artery ligation (infarcted, Inf) or sham-operation (Sham). Ventricular performance was measured at 3 and 30 days after surgery using the Langendorff technique. Left ventricular systolic pressure was obtained under different ventricular diastolic pressures and increased extracellular Ca2+ concentrations (Ca2+e) and after low and high ouabain concentrations. The baseline coronary perfusion pressure increased 3 days after myocardial infarction and normalized by 30 days (Sham 3 = 88 �� 6; Inf 3 = 130 �� 9; Inf 30 = 92 �� 7 mmHg; P < 0.05). The inotropic response to Ca2+e and ouabain was reduced at 3 and 30 days after myocardial infarction (Ca2+ = 1.25 mM; Sham 3 = 70 �� 3; Inf 3 = 45 �� 2; Inf 30 = 29 �� 3 mmHg; P < 0.05), while the Frank-Starling mechanism was preserved. At 3 and 30 days after myocardial infarction, ventricular Na+-K+ ATPase activity and contractility were reduced. This Na+-K+ ATPase hypoactivity may modify the Na+, K+ and Ca2+ transport across the sarcolemma resulting in ventricular dysfunction.

Lead reduces tension development and the myosin ATPase activity of the rat right ventricular myocardium

Lead (Pb2+) poisoning causes hypertension, but little is known regarding its acute effects on cardiac contractility. To evaluate these effects, force was measured in right ventricular strips that were contracting isometrically in 45 male Wistar rats (250-300 g) before and after the addition of increasing concentrations of lead acetate (3, 7, 10, 30, 70, 100, and 300 ��M) to the bath. Changes in rate of stimulation (0.1-1.5 Hz), relative potentiation after pauses of 15, 30, and 60 s, effect of Ca2+ concentration (0.62, 1.25, and 2.5 mM), and the effect of isoproterenol (20 ng/mL) were determined before and after the addition of 100 ��M Pb2+. Effects on contractile proteins were evaluated after caffeine treatment using tetanic stimulation (10 Hz) and measuring the activity of the myosin ATPase. Pb2+ produced concentration-dependent force reduction, significant at concentrations greater than 30 ��M. The force developed in response to increasing rates of stimulation became smaller at 0.5 and 0.8 Hz. Relative potentiation increased after 100 ��M Pb2+ treatment. Extracellular Ca2+ increment and isoproterenol administration increased force development but after 100 ��M Pb2+ treatment the force was significantly reduced suggesting an effect of the metal on the sarcolemmal Ca2+ influx. Concentration of 100 ��M Pb2+ also reduced the peak and plateau force of tetanic contractions and reduced the activity of the myosin ATPase. Results showed that acute Pb2+ administration, although not affecting the sarcoplasmic reticulum activity, produces a concentration-dependent negative inotropic effect and reduces myosin ATPase activity. Results suggest that acute lead administration reduced myocardial contractility by reducing sarcolemmal calcium influx and the myosin ATPase activity. These results also suggest that lead exposure is hazardous and has toxicological consequences affecting cardiac muscle.

Eucalyptol, an essential oil, reduces contractile activity in rat cardiac muscle

Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50% at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50% but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker.

Reactivity of the isolated perfused rat tail vascular bed

Isolated segments of the perfused rat tail artery display a high basal tone when compared to other isolated arteries such as the mesenteric and are suitable for the assay of vasopressor agents. However, the perfusion of this artery in the entire tail has not yet been used for functional studies. The main purpose of the present study was to identify some aspects of the vascular reactivity of the rat tail vascular bed and validate this method to measure vascular reactivity. The tail severed from the body was perfused with Krebs solution containing different Ca2+ concentrations at different flow rates. Rats were anesthetized with sodium pentobarbital (65 mg/kg) and heparinized (500 U). The tail artery was dissected near the tail insertion, cannulated and perfused with Krebs solution plus 30 ��M EDTA at 36oC and 2.5 ml/min and the procedures were started after equilibration of the perfusion pressure. In the first group a dose-response curve to phenylephrine (PE) (0.5, 1, 2 and 5 ��g, bolus injection) was obtained at different flow rates (1.5, 2.5 and 3.5 ml/min). The mean perfusion pressure increased with flow as well as PE vasopressor responses. In a second group the flow was changed (1.5, 2, 2.5, 3 and 3.5 ml/min) at different Ca2+ concentrations (0.62, 1.25, 2.5 and 3.75 mM) in the Krebs solution. Increasing Ca2+ concentrations did not alter the flow-pressure relationship. In the third group a similar protocol was performed but the rat tail vascular bed was perfused with Krebs solution containing PE (0.1 ��g/ml). There was an enhancement of the effect of PE with increasing external Ca2+ and flow. PE vasopressor responses increased after endothelial damage with air and CHAPS, suggesting an endothelial modulation of the tone of the rat tail vascular bed. These experiments validate the perfusion of the rat tail vascular bed as a method to investigate vascular reactivity.

Effects of ouabain on vascular reactivity

Ouabain is an endogenous substance occurring in the plasma in the nanomolar range, that has been proposed to increase vascular resistance and induce hypertension. This substance acts on the a-subunit of Na+,K+-ATPase inhibiting the Na+-pump activity. In the vascular smooth muscle this effect leads to intracellular Na+ accumulation that reduces the activity of the Na+/Ca2+ exchanger and to an increased vascular tone. It was also suggested that circulating ouabain, even in the nanomolar range, sensitizes the vascular smooth muscle to vasopressor substances. We tested the latter hypothesis by studying the effects of ouabain in the micromolar and nanomolar range on phenylephrine (PE)-evoked pressor responses. The experiments were performed in normotensive and hypertensive rats in vivo, under anesthesia, and in perfused rat tail vascular beds. The results showed that ouabain pretreatment increased the vasopressor responses to PE in vitro and in vivo. This sensitization after ouabain treatment was also observed in hypertensive animals which presented an enhanced vasopressor response to PE in comparison to normotensive animals. It is suggested that ouabain at nanomolar concentrations can sensitize vascular smooth muscle to vasopressor stimuli possibly contributing to increased tone in hypertension.

Indicadores de qualidade do solo e determina����o de n��veis de degrada����o de pastagens

A utiliza����o do solo no Brasil foi realizada de forma explorat��ria, com a convers��o de sistemas naturais em sistemas agr��colas extrativistas. Grande parte das ��reas de sistemas naturais deu lugar ��s ��reas de cultivo, posteriormente sucedidas por pastagens, encontrando-se boa parte em elevado est��gio de degrada����o. Diante do exposto, o presente trabalho tem como objetivo avaliar a sensibilidade de alguns atributos f��sicos, qu��micos, compartimentos da mat��ria org��nica e determina����es de campo como indicadores de qualidade do solo estabelecendo rela����es entre os mesmos. O estudo foi desenvolvido no munic��pio de Governador Valadares-MG, para tal foram escolhidos n��veis de pastagens progressivamente degradadas observadas visualmente (pastagem 1, pastagem 2, pastagem 3 e pastagem 4), duas ��reas de capoeira em est��gios de regenera����o natural (capoeira 1 e capoeira 2) e mata (refer��ncia). O solo em estudo foi um Argissolo Vermelho, textura argilosa. As determina����es dos indicadores f��sicos, qu��micos e compartimentos da mat��ria org��nica foram realizadas em quatro profundidades (0-5, 5-10, 10-20 e 20-40 cm). Foram realizadas tamb��m determina����es de campo, todos os atributos foram determinados no ter��o m��dio de uma pedoforma convexa, em dois per��odos, chuvoso e seco. Atrav��s dos atributos do solo utilizados como indicadores do solo, foi poss��vel separar dois n��veis de pastagens degradadas, baixa degrada����o (pastagem 1 e pastagem 2) e elevada degrada����o (pastagem 3 e pastagem 4). A melhor qualidade do solo foi observada na ��rea de mata. Entre os atributos do solo utilizados como indicadores de qualidade do solo os mais sens��veis aos n��veis de pastagens degradadas s��o os atributos qu��micos pH, Ca2+, Mg2+, Al3+, H+Al, satura����o por bases (V), satura����o por alum��nio (m), seguidos pelos atributos f��sicos macroporosidade e porosidade total. Os compartimentos da mat��ria org��nica do solo, mat��ria org��nica particulada (MOP), mat��ria org��nica leve (MOL) e carbono sol��vel em ��gua (CSA) utilizados como indicadores de qualidade do solo s��o eficientes em diferenciar a qualidade do solo nas convers��es de sistema, mata/pastagens e pastagens/capoeiras, n��o sendo sens��vel aos n��veis de pastagens degradadas, o que sugere estudos futuros utilizado compartimentos mais sens��veis a pequenas varia����es. As determina����es de campo espessura do horizonte ���A���, profundidade do sistema radicular e taxa de cobertura do solo s��o sens��veis aos n��veis de pastagens degradadas, e apresentam uma boa correla����o com os indicadores de laborat��rio macroporosidade (Ma), mat��ria org��nica particulada (MOP), satura����o por bases (V), satura����o por alum��nio (m) sugerindo assim a utiliza����o dessas determina����es como indicadores de qualidade do solo em pastagens degradadas, para o solo e a regi��o estudados.

Efeitos dos ��cidos h��micos provenientes de aterro sanit��rio em plantas

O processo de tratamento biol��gico dos lixiviados de aterros sanit��rios resulta na gera����o de grandes quantidades de lodo, caracterizados por conterem altas taxas de mat��ria org��nica. Por meio do fracionamento qu��mico da mat��ria org��nica s��o obtidos os ��cidos h��micos (AH), fra����o de comprovada efici��ncia sobre o crescimento vegetal, promovendo melhorias no desenvolvimento das plantas. Este trabalho teve como objetivo caracterizar quimicamente os AH extra��dos do lodo de lixiviado de aterro sanit��rio e avaliar os efeitos da aplica����o de diferentes doses dos AH por meio de an��lises biol��gicas em plantas, visando minimizar os potenciais riscos da utiliza����o do lodo in natura. Por meio de caracteriza����es qu��micas, o ��cido h��mico apresentou elevados teores de carbono e nitrog��nio, podendo constituir uma importante fonte de nutrientes para as plantas. Al��m disso, foram observadas altera����es nas taxas de absor����o, na bioconcentra����o e na translocação de alguns nutrientes. Com rela����o �� an��lise das enzimas antioxidantes, foi poss��vel observar aumento na atividade de algumas enzimas com a aplica����o de diferentes doses de AH. Al��m disto, foram constatadas altera����es citogen��ticas por meio da an��lise de c��lulas meristem��ticas e F1 de Allium cepa. Influ��ncias sobre o crescimento da planta tamb��m s��o reportadas, por meio de aumentos expressivos na ��rea radicular e na altura de Zea mays. Em geral, os dados de crescimento revelaram um maior investimento da planta na parte a��rea, provavelmente associado com a melhor efici��ncia do sistema radicular. Al��m disso, tamb��m foram reportadas altera����es na espessura da epiderme. Neste contexto, apesar dos benef��cios nutricionais e da comprovada atua����o dos AH sobre o metabolismo vegetal, os seus efeitos biol��gicos sobre enzimas do estresse oxidativo e a sua capacidade citot��xica precisam ser melhor investigados. Devido �� complexidade do res��duo, a utiliza����o de an��lises qu��micas, gen��ticas, enzim��ticas, fisiol��gicas e anat��micas foi uma importante ferramenta para a avalia����o da poss��vel aplica����o dos ��cidos h��micos em plantas.

Efici��ncia nutricional do milho cv. BRS 1030 submetido �� omiss��o de macronutrientes em solu����o nutritiva

Em casa de vegeta����o, desenvolveu-se experimento com delineamento inteiramente casualizado, com sete tratamentos e tr��s repeti����es, a fim de estudar a influ��ncia da omiss��o de nutrientes nas rela����es de efici��ncia (efici��ncia de absor����o, translocação e utiliza����o) deplantas de milho cv. BRS 1030 crescidas em solu����o nutritiva de Hoagland &amp; Arnon (1950), completa e com omiss��o de N, P, K, Ca, Mg e S, durante 30 dias. Ap��s esse per��odo, as plantas foram coletadas, separadas em parte a��rea e raiz, secadas e em seguida pesadas e mo��das, para determina����o dos teores de macronutrientes e obten����o dos ��ndices de efici��ncia. A omiss��o de macronutrientes promove diminui����o na produ����o de massa seca da planta inteira e na efici��ncia de absor����o dos nutrientes, quando comparada �� do tratamento completo. A omiss��o de P, Mg e S resulta em maior efici��ncia de utiliza����o, comparada com o tratamento completo. Plantas deficientes retranslocam os nutrientes, tentando manter seu conte��do nas folhas medianas (ou parte a��rea) em rela����o aos demais ��rg��os.

Din��mica dos micronutrientes em cafeeiros enxertados

As respostas �� disponibilidade dos nutrientes variam entre esp��cies distintas dentro de um mesmo g��nero, por causa, principalmente, das exig��ncias nutricionais vari��veis, capacidade de absor����o, translocação e utiliza����o dos nutrientes. O objetivo deste trabalho foi avaliar a efici��ncia de absor����o, translocação e uso dos micronutrientes por diferentes cultivares de Coffea arabica L., enxertados em Apoat�� IAC 2258 (Coffea canephora). O experimento foi instalado em casa de vegeta����o, utilizando-se o m��todo de cultivo em solu����o nutritiva. Foi utilizado um fatorial 7 x 3 + 2, sendo sete cultivares de Coffea arabica L. (Palma II, Catuca�� 2 SL, Oeiras MG 6851, Obat�� IAC 1669-20, Acau��, Top��zio MG 1190 e Para��so MG H 419-1), tr��s tipos de mudas (p�� franco, autoenxertada e enxertada sobre o cultivar Apoat�� IAC 2258) e duas testemunhas (Apoat�� autoenxertado e Apoat�� p�� franco). O porta-enxerto utilizado influenciou negativamente na absor����o de boro, ferro e mangan��s. A translocação dos micronutrientes boro e cobre obteve maiores ��ndices nas mudas enxertadas. O cultivar Palma II, quando enxertado, apresentou o maior ��ndice de utiliza����o dos nutrientes, mostrando-se pass��vel de ser enxertado. O porta-enxerto utilizado mostrou-se apto para a enxertia, por n��o sofrer influ��ncia negativa, tanto pela enxertia, quanto pelos cultivares utilizados.

Cristaliza����o de Biomateriais Vitrocer��micos e Mineraliza����o em Meio Fisiol��gico Simulado

We propose new theoretical models, which generalize the classical Avrami-Nakamura models. These models are suitable to describe the kinetics of nucleation and growth in transient regime, and/or with overlapping of nucleation and growth. Simulations and predictions were performed for lithium disilicate based on data reported in the literature. One re-examined the limitations of the models currently used to interpret DTA or DSC results, and to extract the relevant kinetic parameters. Glasses and glass-ceramics with molar formulation 0.45SiO2? (0.45-x)MgO?xK2O?0.1(3CaO.P2O5) (0?x?0.090) were prepared, crystallized and studied as potential materials for biomedical applications. Substitution of K+ for Mg2+ were used to prevent devritification on cooling, to adjust the kinetics of crystallization and to modify the in vitro behaviour of resulting biomaterials. The crystallization of the glass frits was studied by DTA, XRD and SEM. Exothermic peaks were detected corresponding to bulk crystallization of whitlockite-type phosphate, Ca9MgK(PO4)7, at approximately 900��C, and surface crystallization of a predominant forsterite phase (Mg2SiO4) at higher temperatures. XRD also revealed the presence of diopside (CaMgSi2O6 in some samples. The predominant microstructure of the phosphate phase is of the plate-type, seemingly crystallizing by a 2-dimensional growth mechanism. Impedance spectroscopy revealed significant changes in electrical behaviour, associated to crystallization of the phosphate phase. This showed that electrical measurements can be used to study the kinetics of crystallization for cases when DTA or DSC experiments reveal limitations, and to extract estimates of relevant parameters from the dependence of crystallization peak temperature, and its width at half height. In vitro studies of glasses and glass-ceramics in acelular SBF media showed bioactivity and the development of apatite layers The morphology, composition and adhesion of the apatite layer could be changed by substitution of Mg2+ by K+. Apatite layers were deposited on the surface of glass-ceramics of the nominal compositions with x=0 and 0.09, in contact with SBF at 37��C. The adhesion of the apatite layer was quantified by the scratch test technique, having been related with SBF?s immersion time, with composition and structure of the glass phase, and with the morphology of the crystalline phase of the glass-ceramics. The structure of three glasses (x=0, 0.045 and 0.090) were investigated by MAS-NMR ( 29Si and 31P), showing that the fraction of Q3 structural units increases with the contents of Mg, and that the structure of these glasses includes orthophosphate groups (PO43-) preferentially connected to Ca2+ ions. Mg2+ ions show preference towards the silicate network. Substitution of Mg2+ by K+ allowed one to change the bioactivity. FTIR data revealed octacalcium phosphate precipitation (Ca8H2(PO4)6.5H2O) in the glass without K, while the morphology of the layer acquires the shape of partially superimposed hemispheres, spread over the surface. The glasses with K present a layer of acicular hidroxyapatite, whose crystallinity and needles thickness tend to increase along with K content.