Size dependent chaperon properties of gold nanoparticles

Citrate synthase is a heat labile enzyme showing a loss of activity even in response to a modest shift of temperature (35 degrees-45 degrees C). Gold nanoparticle is shown to prevent the thermal aggregation of this enzyme. The chaperon like activity of the nanoparticle diminishes if the particle size is reduced from 40 nm to 20 nm keeping the atomic concentration of gold constant. This implies that the effect is not merely due to enhanced surface area offered by the nano-surfaces. The effect is reversible as the protein separated out from nanoparticles behaves similar to control. The observed coupling between chaperon activity of the nanoparticle and its cluster forming ability is illustrated in terms of a thermal cage model.

Nanoparticle induced conformational change in DNA and chirality of silver nanoclusters

Nano-clusters formed on macromolecular templates carry the symmetry information of the template. Templates with broken symmetry thus lead to formation of asymmetric clusters. In response, such clusters induce a compensatory stress on the embedded template. Silver nanoparticles grown on a covalently closed negatively supercoiled plasmid DNA (pUC19) exhibit chiral behavior and as a reciprocal response, one observes alteration in DNA conformation. The inference was drawn using gel mobility-shift studies in which a silver nanoparticle (but not ions) induces a mobility shift implying a drift from supercoiled to relaxed state of the plasmid. Supporting evidences for such structural alterations were obtained from circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR). Silver ion and silver nanoparticles induce differential FT-IR signals reflected in the fingerprint regions 1720, 1666, 1611, 1529 cm(-1) that respectively corresponds to binding in GT, ATGC, C, and AC (A, T, G, and C representing the four nucleotides). Existence of CD signal in the silver plasmon region (350-550 nm) suggests formation of a chiral clustering of nanoparticles. The reciprocal effect on the covalently closed circular (CCC) pUC19 DNA, namely the transition to a relaxed state, can be regarded as a mimicry of the topological enzyme acting on such CCC DNA.

Insensitivity to the α2-adrenergic receptor blocker yohimbine hydrochloride and occurrence of spontaneous platelet macroaggregation (SPMA) in diabetes

We report here a study of platelet aggregation in diabetes, induced by epinephrine and its inhibition by yohimbine hydrochloride (YH), an alpha(2)-adrenergic receptor-blocking agent. Interestingly, emergence of spontaneous platelet macroaggregation (SPMA) was observed in six out of 75 cases in the absence of any agonist. The SPMA cases were strongly associated with insensitivity to YH (in contrast with non-SPMA cases) when epinephrine was used as an agonist. We suggest that the observed correlation is a result of over expression of platelet alpha(2)-adrenoceptors in such subjects. The quantitative nature of the effect is supported by the observation that addition of YH at higher concentration (more than 5 microM) led to restoration of the adrenergic receptor-blocking activity of the said agent. Eventually for non-SPMA subjects YH exhibited blocking activity even at lower concentration. The aggregation profile and the platelet morphology of the SPMA cases had distinctive features as compared to microaggregates formed in other diabetic subjects (non-SPMA cases).

Platelet responsiveness to yohimbine hydrochloride and MRS2179 in the context of the interaction between collagen and epinephrine in acute coronary syndrome

Acute coronary syndrome (ACS) covers a spectrum of clinical conditions ranging from unstable angina, Non-ST segment elevation myocardial infarction (NSTEMI), or ST segment elevation myocardial infarction (STEMI). This study encompasses patients with acute coronary syndrome, who were receiving the dual antiplatelet therapy of aspirin and clopidogrel. The focus of the study was to gain insight into the role of selective P2Y1 antagonism using MRS2179 in such cases as well as its effects, if any, on collagen-epinephrine interaction. All the cases showed greater potency of inhibition of the interaction when yohimbine hydrochloride (YH), a blocker of alpha2A-adrenoreceptor, was used compared to MRS2179, a P2Y1 antagonist, although there was variability in responsiveness to the antiplatelet drugs. These findings indicate that alpha2A-adrenoreceptors of platelets in this group play a major role in precipitating the interactive effect of collagen and epinephrine. The dose-response effect as studied by platelet aggregometry showed that the required molar concentration to block the interactive effect in the case of YH was less than that of MRS2179. Hence, it is postulated that although there may be an impairment of collagen-induced aggregation by MRS2179, the interactive effect of collagen-epinephrine may not be impaired by MRS2179 as efficaciously as YH.

Dual antiplatelet drug resistance in patients with acute coronary syndrome

AIMS AND OBJECTIVES

Antiplatelet therapy is a cornerstone in the management of the atherosclerotic vascular disease. Aspirin and clopidogrel are the two most commonly used antiplatelet drugs in its management. Recently, there has been a concern about the development of resistance to one or both antiplatelet agents with potentially devastating consequences. In this study we tried to assess the in vitro resistance to antiplatelet agents in patients presenting with acute coronary syndrome (ACS).

MATERIALS AND METHODS

144 patients presenting with ACS, who were not on any antiplatelet therapy prior to hospital admission were evaluated in this study. Baseline clinical data was obtained before giving the oral loading dose of aspirin and clopidogrel. Patients received a loading dose of 325 mg of aspirin and 300 mg of clopidogrel followed by a daily dose of 150 mg. of aspirin and 75 mg.of clopidogrel. After 7 days of dual antiplatelet therapy, platelet aggregation pattern was analyzed using optical aggregometer (chrono-log). Response to aspirin and clopidogrel was assessed by interaction with collagen (2microg/ml) and Adenosine diphosphate (ADP) (10micro/ml) respectively. The results were analyzed. Response to doubling the dose of antiplatelet agents was also observed in 6 aspirin resistant patients, 12 clopidogrel resistant patients and in 6 patients resistant to the effect of dual antiplatelet agents.

RESULTS

There were 22 patients (15.27%) who showed poor response to aspirin, 28 patients (19.44%) to clopidogrel (primary non-responder) and 18 patients (12.5%) showed a primary non-responsiveness to both the antiplatelet agents in the usual doses. After dose doubling, all 6 aspirin resistant patients showed adequate response but 4 out of 12 clopidogrel resistant patients showed inadequate response.

CONCLUSIONS

This pilot study brings out a disquieting picture of 12.5% patients suffering from ACS showing resistance to the antiplatelet effects of both aspirin and clopidogrel in the conventional dose. A long-term prospective randomized controlled trial is required to give an insight into this problem and its clinical consequences.

Platelet aggregation profile as a marker of hydroxyurea bioavailability through nitric oxide generation in chronic myelogenous leukemia

Platelet aggregation profiles were studied in chronic myelogenous leukemia patients who were undergoing hydroxyurea therapy. Nitric oxide (NO) generation induced by hydroxyurea was measured from the altered aggregatory response, in which the platelet suspension exhibits a de-aggregatory behaviour. NO caused platelet de-aggregation by generation of cyclic guanidine monophosphate through the activation of soluble guanylate cyclase (SGC). The fact that the observed response is specific to NO was confirmed by the reversal of the de-aggregatory behaviour in the presence of (1)H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of SGC. Among the subjects studied, one subset showed an hydroxyurea-induced de-aggregatory effect that was inhibited by ODQ, whereas another subset did not show any such effect. The observed inter-individual variability in platelet aggregometric response after the ingestion of drugs may be an indicator for NO generation from hydroxyurea, and this may help to explain the drug efficacy encountered in such cases.

Protein seeding of gold nanoparticles and mechanism of glycation sensing

The plasmon resonance of gold nanoparticles (GNPs) synthesized on a protein template senses formation of advanced glycosylated end products (AGEs). A graded alteration of plasmon resonance (both the peak and intensity are affected) is observed as the glycation progresses. Transmission electron microscopy shows significant shift of the size distribution of GNPs in presence of glycation. The higher plasmon resonance is thus caused by increased formation of GNPs, which in turn is attributed to a larger number of smaller particles. To study the binding of the protein with the GNP, infrared (IR) spectroscopy and circular dichroism (CD) studies were undertaken. Whereas the CD studies confirmed the emergence of beta-structure and loss of alpha-helix, the IR data indicated glycation-induced alterations in the amide I region. The proposed sensor for formation of AGEs thus apparently operates by direct or indirect conjugation with amino groups. Incidentally, glycation and AGE formation are responsible for a number of diabetes-related clinical conditions, and the present approach could be adopted for use for a simple colorimetric assay for the AGEs.

Cell selective response to gold nanoparticles

Gold nanoparticles (GNPs) are considered a potential probe to detect cancer. The present article investigates whether GNPs, even in the absence of any specific functionalization, induce any cell-specific response. We report GNP-induced death response in human carcinoma lung cell line A549. In contrast, the two other cell lines tested, BHK21 (baby hamster kidney) and HepG2 (human hepatocellular liver carcinoma), remained unaffected by GNP treatment. The specificity of the induction of the death response in A549 cells implies that GNPs do not universally target all cell types. Flow-cytometric studies indicated that the response was dose dependent and had a threshold effect (in A549). Gradual increase in GNP concentration induces a proportional cleavage of poly(ADP-ribose) polymerase. The programmed nature of the death response is implied, because such cleavage follows activation of caspases. Notably, at higher GNP concentration there was an asymmetric accumulation of GNPs in the periphery outside the cell nucleus of the A549 cells. This was confirmed by confocal microscopy, a green scattering (possibly, surface-enhanced Raman effect) appearing on selective z-slices of the image.

Gold nanoparticle-based tool to study protein conformational variants: implications in hemoglobinopathy

The size of gold nanoparticles is shown here to gradually decrease if it is allowed to grow on a protein template, and the protein is subjected to unfolding by a nonionic denaturant. The correlation between size of the gold nanoparticle formed and the plasmon frequency observed remains linear, except at stages where protein folding intermediates are formed. Higher population of exposed tyrosine residues, number of sulfhydryl groups of the protein, and the overall exposition of the inner hydrophobic core may lead to the generation of smaller particles. The method provides a simple colorimetric sensing of protein conformation and has been tested for both nonheme and heme proteins (hemoglobin and bovine serum albumin). Similarly, protein variants with defects in folding (caused by subunit misassembly or mutation) can also be classified. Possible application of this approach in hemoglobinopathy (e.g., thalassemia carrier detection) is discussed in the text.

Compensatory secondary structure alterations in protein glycation

Glycation, a local covalent interaction, leads to alterations in secondary and tertiary structures of hemoglobin, the changes produced by fructose being more pronounced than those caused by glucose. The Stokes diameter of hemoglobin increases upon glycation from 7 to 14 nm and a concurrent inter-chain cross-linking and heme loss are also observed, particularly in the later stage of glycation. An initial increase of tryptophan (trp) fluorescence was observed in both glucation and fructation. In case of frucation however there was a decrease in tryptophan fluorescence that was accompanied by an increase in fluorescence of the advanced glycosylation end products (AGEs). This fluorescence behavior is indicative of energy transfer between tryptophan and the AGEs formed during the late stage of glycation. Emergence of an isosbestic point in the fluorescence spectra (taken at different time intervals) implies existence of two distinct glycation stages. The late glycation stage is also marked by an increase of beta structure and random coil at the expense of alpha helix. It is further observed that this compensatory loss of alpha helix (reported for the first time) and increase in beta sheet and random coil elements depend on the number of solvent-accessible glycation sites (rather than total number of such sites) and the subunit assembly of the protein.

Potential of cadmium sulphide nanorods as an optical microscopic probe to the folding state of cytochrome C

The folding behavior of cytochrome C (Cyt-C) conjugated with CdS nanorods (CdSnr) is amenable to monitoring by bright field microscopy, the porosity and percolating behavior of such protein conjugated nanoclusters depending on the folding history prior to the conjugation. The method has been used to predict the thermal melting behavior as well as guanidine hydrochloride induced unfolding of Cyt-C. Dynamic light scattering studies indicate that the size distribution of the nanoforms widens in presence of the protein. Furthermore, there is emergence of clusters with higher conductivity and altered zeta potential. Increase of second virial coefficient of CdS nanoforms in the presence of Cyt-C (obtained from static light scattering experiments) implies presence of protein coat over the hydrophobic nanosurface. The results are supported by morphological changes observed through scanning electron microscopy (SEM). Accordingly, the X-ray diffraction pattern shows a change of crystallographic orientations of CdSnr in presence of Cyt-C.

Interaction of hemoglobin and copper nanoparticles: implications in hemoglobinopathy

Here we study the interaction of copper nanoparticles (CuNPs) with different variants of hemoglobin (Hb). The study reports analysis with HbA0 (the major component of human Hb) and HbA2 (a variant that is associated with beta-thalassemia). In the case of HbA0, the major fraction of human Hb, the CuNPs trigger protein aggregation, and this is followed by the precipitation of the protein. The aggregative response is largely attenuated in the case of HbA2. The difference between the two variants is thus amenable to detection by simple optical methods. We verified that CuNPs co-precipitated with specific Hb variants using atomic absorption spectroscopy (AAS) and high-pressure liquid chromatography (HPLC). An associated observation was the reversal of zeta potential of HbA0 induced by the CuNPs (from -11 mV to +13 mV). Dynamic light-scattering (DLS) studies indicated that in the case of HbA0, protein initially broke the nanoclusters into smaller sizes (4 nm), and this was followed by a gradual increase in cluster size. Assays of heme peroxidase activity indicated that the protein unfolded during the process. It is suggested that interaction between the CuNPs and HbA0 stimulates the molten-globule state of the protein, leading to the onset of such an aggregative pathway. When studied for other variants, HbE, a common mutant of Hb, showed similar aggregative behavior, and on the other hand, rare variants such as HbC tended to remain in solution. A suitable scaling up of the approach may have important implications in screening hemoglobinopathies such as beta-thalassemia.

Structural insights in platelet receptor synergism-antiplatelet therapy in post-ischemic cerebrovascular events

Synergy between agonists of platelet aggregation, namely, ADP and epinephrine, has been studied in patients having a history of cerebrovascular ischemic event. There is a significant variability of responsiveness among individuals towards clopidogrel, which is a specific inhibitor of the low-affinity human purinergic receptor (P2Y12). For responders of clopidogrel, simultaneous application of ADP and epinephrine at sub-threshold concentrations (i.e., concentration below the threshold concentration at which aggregation occurs) leads to platelet aggregation, which is followed by deaggregation. For non-responders of the drug, the synergism seems to be stronger, showing no deaggregatory pattern. The inhibition of synergism by yohimbine hydrochloride (YH), a blocker of alpha2A-adrenoreceptors is more pronounced in non-responders. A simple structural model based on receptor-receptor interaction is proposed to explain the synergism. The model explains synergy in terms of cooperative interaction between the low-affinity ADP receptor P2Y12 (Swiss Prot:Q9H244) and the alpha2A-adrenoreceptor (Swiss Prot:P08913). It follows that the synergistic effect can be achieved in only one of the two 3D structures for the alpha2A-adrenoreceptor P08913 permitted by homology modeling, as there is a better docking interface with the Q9H244. The synergism itself and the observed dichotomous phenomenon in relation to inhibition of synergism among responders and non-responders can be accounted for, if the interacting receptors on the dynamic membrane interface compete with the clopidogrel binding.

A size dependent folding contour for cytochrome C

The paper describes an experimental construct of the folding route of the heme protein cytochrome-C. The construct highlights a slowing down near the nose of the folding funnel caused by the multiplicity of the energy traps near the native conformation created as a result of complex heme-peptide interaction. Interestingly the hydrodynamic size, the size heterogeneity and peroxidase activity serve as a triple measure of the distance of this near equilibrium departure from native conformation. Accordingly, the folding process is marked with a gradual and reversible reduction of mean hydrodynamic size, size heterogeneity and peroxidase activity (higher in unfolded state). The Dynamic Light Scattering based straightforward illustration of hydrodynamic size variation may serve as a model to slow folding observed in case of heme proteins, the heme itself serving as a natural facilitator for the native peptide conformation.

Simultaneous determination of itraconazole and hydroxyitraconazole in human plasma by high-performance liquid chromatography

The development and validation of a high-performance liquid chromatography (HPLC) method for the simultaneous determination of itraconazole and its metabolite, hydroxyitraconazole, in human plasma is described. The method involved liquid-phase extraction of itraconazole and hydroxyitraconazole using a hexane-dichloromethane (70:30) mixture, after addition of loratidine as an internal standard (IS). Separation was achieved with a reversed-phase C18 column (250 mm x 4.6 mm) employing fluorescence detection (excitation: 264 nm, emission: 380 nm). The mobile phase consisted of [0.01% triethylamine solution adjusted to pH 2.8 with orthophosphoric acid-acetonitrile (46:54)]-isopropanol (90:10, v/v) at a flow rate of 1.0 ml/min. For both the drug and metabolite, the standard curve was linear from 5.0 to 500 ng/ml with goodness of fit (r2) greater than 0.98 observed with four precision and accuracy batches during validation. An observed recovery was more than 70% for drug, metabolite and internal standard. The applicability of this method to pharmacokinetic studies was established after successful application during 35 subjects bioavailibity study. The method was found to be precise, accurate and specific during the study.

Determination of mycophenolic acid in human plasma by high-performance liquid chromatography

The development, validation and evaluation of high-performance liquid chromatography (HPLC) method for quantifying mycophenolic acid in human plasma is described. The method involved protein precipitation using acetonitrile, after addition of terazosin as an internal standard. Separation was achieved with a reversed-phase C18 column (250 mm x 4.6 mm) employing UV detection at 215 nm. The mobile phase consisted of 0.02 M potassium dihydrogenphosphate solution adjusted to pH 6.9 with 2 M potassium hydroxide solution-acetonitrile (80:20 (v/v)) at a flow rate of 1.5 ml/min. The total run time was 21.0 min. The assay was linear from 0.2 to 25 microg/ml with goodness of fit (r2) greater than 0.99 observed with three precision and accuracy batches during validation. The observed mean recoveries were 89.3 and 98.0% for drug and internal standard, respectively. The applicability of this method to pharmacokinetic studies was established after successful application during a 34-subject bioavailability study. The method was found to be precise, accurate and specific during the study.

Onset of Percolation and Fractal Classification Scheme for Multilamellar Lipid Vesicles

Percolation, like phase transition, expresses a critical property of an assembly. The paper provides a brief description of the onset of percolation and the fractal behavior of clusters formed as a result of spontaneous assembly of multilamellar lipid vesicles (MLVs). The onset of percolation was studied using a series of mixed lipid systems. The percolation threshold showed a strong linear dependence on the net charge of the constituent lipids. Second, the vesicular clusters were characterized using a canonical coordinate frame spanned by the fractal dimension and the porosity of the cluster images. MLVs made of different lipid constituents formed different domains on such representations. The location of the individual domains relative to a simulated random cluster seemed to provide a measure of order-element present in such clusters. The specificity of the domain locations and their sensitivity to alteration in a microenvironment was studied in some detail. Copyright 1999 Academic Press.

Post-traumatic epilepsy: its complications and impact on occupational rehabilitation--an epidemiological study from India

The objective of this study was to assess the prevalence of seizure disorder, neuropsychiatric disorders and reproductive outcome of employees with post-traumatic epilepsy (PTE) and their effect on occupational rehabilitation. A case-comparison group study design was used to compare 30 subjects with PTE with (1) 129 non-PTE and (2) 55 non-PTE matched control employees. The 55 non-PTE matched controls were selected from the 129 non-PTE employees on the basis of age, age at onset of seizure, age at marriage and length of employment. The PTE group had a lower fertility rate than the controls and more neuropsychiatric disorders and seizure disability. PTE employees were more occupationally rehabilitated than non-PTE employees (p = 0.033). Of the 30 PTE subjects, thirteen who were rehabilitated by placement had more seizure disability (p = 0.007) and a higher fertility rate (p = 0.018). High prevalence of seizure disability and increased fertility rate among the placed PTE employees suggested that there might be some association between severity of seizures and increased production of live offspring and work placement. Work suitability or placement should not be judged on clinical assessment only but psychosocial seizure assessment, disability evaluation and other psychometric tests which are of equal importance.

Multilamellar vesicular clusters of phosphatidylcholine and their sensitivity to spectrin: a study by fractal analysis

The cluster patterns of multilamellar vesicles (MLV) of dimyristoylphosphatidylcholine (DMPC) were analyzed using a combination of fractal analysis and lattice simulation. Self-assembly of DMPC MLVs resulted in two types of microscopically observable clusters. The clusters were classified on the basis of their mass fractal dimension, two-dimensional porosity, and the light scattering properties. Spectrin, a cytoskeletal protein, well known for its role in determining the cellular morphology, was used to perturb such spontaneously formed clusters. The fragmentation of the clusters by hydrodynamic perturbation followed a power law, implying again a fractal behavior. A lattice-based simulation was performed generating different class of cluster patterns. The observed correspondence between the cluster patterns and their stability was discussed in the framework of the proposed lattice simulation.

The performance of the ICEROSS prostheses amongst transtibial amputees with a special reference to the workplace--a preliminary study. Icelandic Roll on Silicone Socket

A clinical trial was conducted to evaluate the efficiency of ICEROSS on randomly selected 46 male transtibial amputees. After rejection, only 27 (58.69%) amputees volunteered for various stages of the ICEROSS trial. All 27 were categorized into Group A-persons in employment (n = 16) and Group B-persons out of employment or economically inactive (n = 11). The study was conducted on the basis of questionnaire information, clinical examination and objective tests. The pre- and post-ICEROSS status were compared between the groups. Group A was younger and did better. Trauma was the main cause of amputation. There were certain changes of the stump before and after ICEROSS. The amputees with ICEROSS suspension performed better and had improved mobility in Group A. At the workplace, dynamic activities were less than the static activities (p < 0.001) and there were overall improvements in comfort and performance of amputees with ICEROSS.

The possible role of surface charge in membrane organization in an acidophile

Thiobacillus ferrooxidans, an obligate acidophile, possesses an electron transport chain that uses oxidation of ferrous iron to generate proton motive force. The cells possess an efficient machinery for inter-conversion of the two components of the free energy, namely pH gradient and membrane potential. Incidentally, unlike most of the naturally occurring membranes, surface in T. ferrooxidans appears to be positively charged at or near its physiological pH. Independent estimate of such charge was obtained from binding studies with anionic optical and fluorescent probes. When the external pH is lowered below a critical value the inter-conversion of the two components of the proton motive force was no longer operative. A surface charge mediated phase separation of membrane is suggested as one of the possible mechanisms for the failure of such inter-conversion process.

Effects of vibration on the hand-arm system of miners in India

Sixty-six Jackhammer drillers and 35 blasters from two mines were clinically screened for hand-arm vibration syndrome (HAVS). The screening consisted of questionnaire-based information, clinical examination including measurement of phalangeal circumferences of fingers (FCT) and motor nerve conduction (MCV) studies. In a warm environment, the prevalence of symptom complexes suggested the existence of peripheral neuropathy and musculoskeletal abnormalities rather than any peripheral circulatory disorders. Clinical examination revealed soft tissue wasting in the hands (26 cases), ulnar nerve impairment (23 cases), median nerve impairment (16 cases) and Dupuytren's contracture (4 cases). Mean motor nerve conduction velocities of 59 out of 66 drillers who volunteered for this assessment were not significantly different from those of the 35 blasters. The results of their correlation coefficients varied considerably for MCVs when age and years of vibration exposure underwent regression analysis. However, comparison of MCV and FCT of 30 drillers with 30 matched blasters revealed that the mean MCV of the right median nerve in the vibration exposed group was significantly decreased (p < 0.01) and for the mean FCT, the proximal phalanxes of the right index finger, left thumb and left ring fingers were thinner in the vibration exposed group (p < 0.05).

Epilepsy and employability: a comparative evaluation of epileptic employees working in the steel plants of India

Information on seizures and provoking factors, occupational status, shift work, overtime, home and work place adjustment was obtained from 176 epileptic employees working in hazardous, less and non-hazardous areas of steel plants in India. Accidents at work and sickness absence were also assessed in 44 epileptics. An overall comparison was made between Group A hazardous (63) and Group B less/non-hazardous (76) of the total of 139 epileptic employees over a three year period. Group A performed better than Group B. When compared with 77 employees with occupational dermatoses, 139 epileptics did more fixed shifts and had less promotion.

Metoclopramide on rat phrenic hemidiaphragm

The effect of metoclopramide on skeletal muscle and its neurotransmission was studied employing innervated and denervated rat diaphragm. Metoclopramide, at concentrations from 0.035 to 0.14 mM, inhibited the twitch contractions of rat diaphragm stimulated either directly or indirectly. Inhibition was greater in indirectly stimulated preparations, at a given concentration of metoclopramide, than in directly stimulated preparations. Inhibition of indirect twitch by metoclopramide could be intensified by raising the concentration of magnesium chloride, but was unaffected by physostigmine or d-tubocurarine. Metoclopramide also inhibited the submaximal contractures of denervated diaphragm elicited by potassium chloride and acetylcholine. In calcium-free physiological solution, metoclopramide inhibited the caffeine-induced contractures of denervated diaphragm as a function of its concentration. It is suggested that metoclopramide possesses a calcium antagonistic action in the rat diaphragm.