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Factors which can affect the Hill slope are particularly the presence of more than one population of receptors with different affinities for the agonist contributing to the response (nH 5 1) buy digoxin 0.25mg online blood pressure chart athlete, occurrence of receptor desensitisation (nH 5 1) discount digoxin 0.25 mg without prescription blood pressure definition, the presence of more than one agonist binding site on the receptor (as occurs with the ligand-gated ion channel receptors) where more than one site needs to be occupied for efficient activation of the receptor (nH 4 1), and the presence of spare receptors in the tissue (nH 4 1). Concentration±response curves are often fitted empirically by the expression nH A y ymax nH nH A3:5 A50 A where nH is the Hill coefficient and ymax is the maximum response. However, the constant K obtained by fitting the Hill equation does not correspond to an equilibrium constant as defined above when deriving the Hill±Langmuir equation. This is a great advantage and has allowed electrophysiological techniques to be used to study ion channel activation and drug block of ion channels in great detail. The first physically plausible mechanism for receptor activation was proposed by del Castillo and Katz (1957). However, recent results suggest that G- protein-coupled receptors (and potentially other receptors) can exist in the active state in the absence of agonist. These constitutively active receptors give rise to interesting new predictions for the shape of the dose±response curve and an alternative interpretation for the difference between agonists, partial agonists and antagonists (Lefkowitz et al. If L combines with R* there will be an increase in active receptors and so L will behave as a conventional agonist. Where L has equal affinity for R and R*, it will not affect the fraction of receptors in the active state. However, it will reduce the binding of either a conventional or an inverse agonist, and so will behave as an antagonist. Del Castillo, J and Katz, B (1957) Interaction at endplate receptors between different choline derivatives. Current status of the nomenclature for nicotinic acetylcholine receptors and their subunits. Sautel, M and Milligan, G(2000) Molecular manipulation of G-protein-coupled receptors: a new avenue into drug discovery. Unwin, N (2000) Nicotinic acetylcholine receptor and the structural basis of fast synaptic transmission. Vernier, P, Cardinaud, B, Valdenaire, O, Philippe, H and Vincent, J-D (1995) An evolutionary view of drug±receptor interaction: the bioamine receptor family. This wave of excitation causes the opening of voltage-gated Ca2-channels or mobilisation of Ca2 from intracellular stores (e. As a result, there is a phasic increase in free intracellular Ca2, probably to a concentration of about 0. The subsequent fusion of neurotransmitter storage vesicles with the axolemma, together with the extrusion of their contents into the synapse, is thought to take about 100±200 ms; this cascade is therefore fast enough to effect rapid signalling between neurons. While this chapter is concerned primarily with the neurochemical mechanisms which bring about and control impulse-evoked release of neurotransmitter, some of the methods used to measure transmitter release are described first. This is because important findings have emerged from studies of the effects of nerve stimulation on gross changes in transmitter release and intraneuronal stores. The actual processes that link neuronal excitation and release of transmitter from nerve terminals have been studied only relatively recently. The neurochemical basis of this stimulus±secretion coupling, which is still not fully understood, is described next. The final sections will deal with evidence that, under certain conditions, appreciable amounts of transmitter can be released through Ca2-independent mechanisms which do not depend on neuronal activation. However, under resting conditions, the transmitter content of any given organ or brain region is remarkably constant. The store of classical transmitters (monoamines and acetylcho- line)in nerve terminals is rarely depleted by physiologically relevant rates of neuronal stimulation. Although this approach is rarely used nowadays, it is outlined here because it uncovered some important findings which are relevant to current studies of the regulation of transmitter release. Transmitter synthesis can be monitored by administering [3H]- or [14C]-labelled precursors in vivo; these are eventually taken up by neurons and converted into radiolabelled product (the transmitter). The rate of accumulation of the radiolabelled transmitter can be used to estimate its synthesis rate. One limitation of this method is that the specific activity of the radiolabel is progressively diluted as the radiolabelled transmitter is released from neurons and replaced by that derived from unlabelled substrate. This method also assumes that there is no compartmentalisation of the terminal stores, yet there is ample evidence that newly synthesised acetylcholine and monoamines are preferentially released. An alternative approach is to monitor the rate at which the store of neurotransmitter is depleted after inhibition of its synthesis (Fig.
It respects and incorporates their individual discount digoxin 0.25 mg visa blood pressure medication ramipril, family purchase digoxin 0.25mg with mastercard blood pressure medication causing dizziness, and cultural realities and perspectives. Summarized version of proposal: efectve implementaton of a structured psychoeducaton programme among caregivers of schizophrenia patents in the community. Used with permission from authors Increasingly, mental health facilities are feeling pressure to meet the demands of service and productivity. Mental health program leaders fnd they need to direct services that will satisfy these demands without sacrifcing the quality of care being offered. At the same time, program leaders are concerned about practitioners’ level of satisfaction. In the Cochrane analysis of Pekkala et al, 2002, such interventions were accompanied by a higher level of compliance, lower rate of relapse, and improved psychopathological status. Only a few studies have been carried out with Chinese or Asian populations, in which great importance is attached to intimate interpersonal relationships and interactions with family members (Li Z. The application of family psychoeducation in Malaysia has been rather limited and very recent. Healthy lifestyle – diet and exercise Following the initiation of this programme, there was encouraging results from both the client as well as their care-givers. Notably, there was an increase in the quality of life in both the client as well as their care-givers. Relapse rates were also lower as they were able to recognize the early warning signs of possible relapse (Ghaus Z. As this is a pioneering initiative, the researchers have decided to study the effectiveness of the structured psychoeducation programme among care-givers of schizophrenics in the community. Summarized version of proposal: efectve implementaton of a structured psychoeducaton programme among caregivers of schizophrenia patents in the community. Used with permission from authors The main aim of this study is to assess if a structured psychoeducation programme can be effectively implemented among schizophrenia patients in the community. The researchers aim to look at sustainability, will attempt to standardize the delivery of the psychoeducation programme and monitor defaulter and drop-out rates with a view to improve the health outcome for schizophrenics and their families. The researchers hope to be able to make recommendations with regards to a uniformed national psychoeducation programme for schizophrenia patients. Lack ofLack of motivationmotivation PoorPoor PoorPoor Lack of budgetLack of budget & Incentive& Incentive insightinsight knowledgeknowledge aboutabout aboutabout diseasedisease diseasedisease IncreasedIncreased Lack ofLack of burden ofburden of staffstaff workwork Lack ofLack of Defaulters/Defaulters/ InfrastructureInfrastructure dropoutdropout & Resources& Resources PoorPoor ratesrates attitudeattitude Can we effectivelyCan we effectively implement a structured psychoeducationimplement a structured psychoeducation Patient/ care-giver factorsPatient/ care-giver factors programme among caregivers ofprogramme among caregivers of Staff factorsStaff factors schizophrenia patients in theschizophrenia patients in the community? To determine if the use of a structured psychoeducation program will signifcantly: a. To make recommendations regarding the implementation of a structured psychoeducation program in the community. Summarized version of proposal: efectve implementaton of a structured psychoeducaton programme among caregivers of schizophrenia patents in the community. The intervention to be used is the introduction of a structured psycho education program. Specifc health staffs in the interventional group will be trained in the structured psycho education module, after which will administer the structured psycho education to the caregivers. The control group will be those caregivers of patients who follow the standard treatment without any structured intervention. Phase 2 Specifcally identifed health staff in the interventional group, from the respective clinics will be trained in the use of the modules of the structured psychoeducation (see Appendix). Summarized version of proposal: efectve implementaton of a structured psychoeducaton programme among caregivers of schizophrenia patents in the community. Used with permission from authors Phase 3 Respondents in the interventional group will be taken through the structured psychoeducational program. To ensure the modules were taught adequately and in a standard manner, all the staff involved in giving the psychoeducation program will be required to complete a checklist. The patients in the interventional groups will be given the psychoeducation mainly in the clinics. The teaching materials that will be provided to the trainers during the training sessions will be used during the teaching. For the interventional group the post-test questionnaire will be done immediately after the completion of the modules to assess the quality of the training.
Maternal use of high-dose aspirin is associated with increased frequency of post-term pregnancies (Collins and Turner cheap digoxin 0.25mg online blood pressure medication ed, 1975) order 0.25mg digoxin with amex blood pressure machine name, low birth weight (Lewis and Schulman, 1973), neonatal bleeding disorders, and intracranial hemorrhage in premature infants (Rumack et al. However, these complications are not associated with aspirin use when pharmacologically con- trolled doses of salicylates were used (Sibai and Amon, 1988). This implies that gravi- das may be self-adjusting their doses and/or frequency regimens upward, increasing the risk of untoward outcomes. In one study, a significantly increased frequency of placental abruption was found among women taking low-dose aspirin therapy compared to controls (Sibai et al. However, meta-analysis of 11 clinical trials found no significant difference in the incidence of placental abruption among women taking aspirin compared to controls (Hauth et al. In summary, aspirin at therapeutic or low doses is not associated with a significant risk of birth defects, although in very large, chronic doses close to the time of delivery, aspirin may be associated with an increase in bleeding disorders in the mother and fetus. Forty- one percent of pregnant women reported acetaminophen use during pregnancy in a large longitudinal study (Streissguth et al. The frequency of congenital birth defects in several studies was not increased above background among more than 1200 offspring whose mothers used acetaminophen during the first trimester (Aselton et al. Nonsteroidal antiinflammatory agents 153 The potential association of maternal acetaminophen use and polyhydramnios is unclear, but is based upon one case report of one single infant (Char et al. Ingestion of large doses of acetaminophen or the protracted use of this drug may result in renal and hepatic failure in the adult and could result in the same complications in the fetus (see Chapter 14). In summary, acetaminophen is one of the safest nonnarcotic analgesics available for use in the pregnant woman when doses are kept in the therapeutic range. It is often used in combination with other analgesics, and one of its major metabolites is acetamin- ophen. The frequency of malformations was not increased among more than 18 000 off- spring of mothers who utilized this analgesic either alone or in combination with other agents (Heinonen et al. It is commonly used to treat women with arthritic conditions (rheumatoid arthritis, degenerative joint disease). No scientific stud- ies are published regarding the safety and efficacy of this medication in pregnant women. Two major congenital anomalies were among 27 infants exposed to phenylbutazone, but these data were not peer reviewed (Rosa, personal communication, cited in Briggs et al. Some of the prostaglandin synthetase inhibitors are associated with premature clo- sure of the ductus arteriosus in the newborn (Csaba et al. It is used for the treatment of rheumatoid arthritis and osteoarthritis, bursitis, and ten- donitis. It has also been used to treat premature labor in the second and third trimesters of pregnancy (Niebyl et al. In addition, intravenous indomethacin has been used to close a hemodynamically significant patent ductus arteriosus in premature infants. Indomethacin has also been used for the treatment of symptomatic leiomyomata during pregnancy (Dildy et al. The frequency of congenital anomalies among more than 400 infants following expo- sure to indomethacin during the first trimester is no different from the population back- ground rate (Aselton et al. Congenital anomalies have also not been found to be increased in several reports in which animals received several times the adult human dose of indomethacin (Kalter, 1973; Klein et al. Indomethacin is associated with premature closure of the ductus arteriosus and pul- monary hypertension in the fetus and newborn in several reports (DeWit et al. Ductal constriction was found by echocardiography in seven of 14 fetuses in 13 pregnant women who received indomethacin for premature labor at 25–31 weeks gestation (Moise et al. Ductal 154 Analgesics during pregnancy constriction was transient and resolved within 24 h after discontinuation of the indomethacin. Fetal ductus arteriosus closure in the fetus was also associated with indomethacin exposure in several animal models (Harker et al. No evidence was reported of either premature closure of the ductus arteriosus or pulmonary hypertension in 15 fetuses whose mothers had received indomethacin in a randomized trial (Niebyl et al. Among 818 women who received indomethacin during pregnancy near the time of delivery, perinatal complications occurred in 13 percent compared to 1. In contrast, among 15 infants exposed to indomethacin chronically during gestation, no instances of patent ductus occurred (Al-Alaiyan et al.
The extracellular structure is stabilised by the disulphide bond joining the first and second extracellular loop 0.25 mg digoxin visa hypertension handout. The third intracellular loop determines the class of G-protein activated by the receptor with the second intracellular loop and C-terminus also influencing G- protein binding in some cases buy digoxin 0.25mg line blood pressure xls. Four classes of G-protein are known: (1) Gs Ð activates adenylyl cyclase (irreversibly activated by cholera toxin) (2) Gi Ð inhibits adenylyl cyclase (inactivated by Pertussis toxin) (3) Gq Ð activates phospholipase-C (not activated by Pertussis toxin or cholera toxin) (4) G Ð inhibits voltage-dependent Ca2 and K channels (inactivated by Pertussis o toxin) Using chimaeric receptors it has been shown that swapping the third intracellular loop between receptors also swaps their G-protein selectivity. Different subtypes of G-protein-coupled receptor have evolved which couple to different G-proteins (Table 3. A similar effect has recently also been described for dopamine and somatostatin receptors (Rocheville et al. The significance of this in terms of the pharmacology of the receptors is unclear, or indeed whether dimerisation affects mechanisms such as desensitisation. Ligand binding outside the transmembrane domains on cell surface (3) Metabotropic glutamate receptors and chemosensor (Ca2) receptors. These are also the largest group of receptors in number as they include receptors not only for the monoamines, nucleotides, neuropeptides and peptide hormones, but they also include the odorant receptors which number several hundreds of related receptors. In some cases the C-terminus is myristolyated which by tying the C- terminus to the cell membrane generates a fourth intracellular loop. While the agonist binding domain is thought to be within the transmembrane domains for the monoamine and nucleotide receptors, neuropeptides are thought to bind close to the membrane surface on the extracellular domains of the receptor. It is still not clear whether non-peptide antagonists bind at the same or a different site on the receptor. Small ligands such as monoamines, nucleotides and lipids bind within the transmembrane domains while peptide and glycoprotein hormones bind outside the transmembrane region. Metabotropic glutamate receptors have agonist binding on the large N-terminal domain while the thrombin receptor is activated by cleavage of the N-terminal domain by thrombin (reproduced from Schwartz 1996). Metabotropic glutamate receptors and chemosensor (Ca2) receptors The metabotropic glutamate receptors are a distinct family of G-protein-coupled receptors which are homologous only to the Ca2 sensors of the parathyroid and kidney. These receptors have an extremely large extracellular N-terminal domain of 500±600 amino acids (cf. Thrombin receptors The thrombin receptor is unusual in that the receptor is activated by the enzymatic action of thrombin which cleaves the N-terminus of the receptor leaving the receptor constitutively active. Two forms of desensitisation have been characterised: homologous and heterologous. Homologous desensitisation refers to desensitisation of the response to an agonist due to prior application of the same agonist. Heterologous desensitisation refers to the desensitisation of the response to one agonist by the application of a different agonist. Phosphorylation disrupts the receptor±G-protein interaction and induces the binding of specific proteins, arrestins which enhance receptors internalisa- tion via clathrin-coated pits. Thus desensitisation of G-protein-coupled receptors results in a decrease in the number of functional receptors on the cell surface. Thermodynamically, in this freely reversible mechanism receptors may occasionally adopt the active conformation in the absence of ligand and may then cause G-protein activation. Constitutive activity has been produced by specific point mutations of the b-adrenoceptor where conversion of Ala-293 to glu-293 results in a tenfold increase in constitutive activity. Clearly the ability to manipulate the degree of constitutive receptor activity using drugs could provide a therapeutic strategy in these diseases. These same receptors are therefore ideal targets for drug action because of their central role in the activity of the nervous system. A rational approach to the development of new therapeutic strategies involving the action of drugs at receptors in the nervous system is based on knowledge of receptor structure, distribution and function. Thus the rate of the forward reaction is proportional to ARk1AR, where k1 is the association rate constant (with units of MÀ1 sÀ1). Its derivation assumes that the con- centration of A does not change as drug receptor complexes are formed.