Ca2Lib: Simple and Accurate LiDAR-RGB Calibration Using Small Common Markers

Modern visual perception techniques often rely on multiple heterogeneous sensors to achieve accurate and robust estimates. Knowledge of their relative positions is a mandatory prerequisite to accomplish sensor fusion. Typically, this result is obtained through a calibration procedure that correlates the sensors' measurements. In this context, we focus on LiDAR and RGB sensors that exhibit complementary capabilities. Given the sparsity of LiDAR measurements, current state-of-the-art calibration techniques often rely on complex or large calibration targets to resolve the relative pose estimation. As such, the geometric properties of the targets may hinder the calibration procedure in those cases where an ad hoc environment cannot be guaranteed. This paper addresses the problem of LiDAR-RGB calibration using common calibration patterns (i.e., A3 chessboard) with minimal human intervention. Our approach exploits the flatness of the target to find associations between the sensors' measurements, leading to robust features and retrieval of the solution through nonlinear optimization. The results of quantitative and comparative experiments with other state-of-the-art approaches show that our simple schema performs on par or better than existing methods that rely on complex calibration targets.

Biodegradable microspheres for prolidase delivery to human cultured fibroblasts

Prolidase deficiency (PD) is a rare autosomal recessive disorder caused by inadequate levels of the cytosolic exopeptidase prolidase (E.C. 3.4.13.9), for which there is not, as yet, a resolutive cure. We have investigated whether biodegradable microspheres loaded with prolidase could release active enzyme inside cells, to consider this system as a possible therapeutic approach for prolidase deficiency. Poly(lactide-co-glycolide) microspheres were prepared, modifying the classical double emulsion solvent evaporation method to mitigate the burst effect of the enzyme from the microspheres. Ex-vivo experiments were performed, by incubating microencapsulated prolidase with cultured fibroblasts from PD patients and from controls, to determine the amount of active enzyme delivered to the cells. The microparticulate drug delivery system described carried small amounts of active prolidase inside fibroblasts, ensuring a response to the intracellular accumulation of X-Pro dipeptides, the mechanism that is supposed to be responsible for the development of clinical manifestations of this disorder in man. A positive result of the presence of active enzyme inside cells was an improvement in fibroblast shape.

Polyethylenglycol-co-poly-D,L-lactide copolymer based microspheres: preparation, characterization and delivery of a model protein

PURPOSE

To prepare and characterize polyethylenglycol-co-poly-D,L-lactide (PEG-D,L-PLA) multiblock copolymer microspheres containing ovalbumin. Microsphere batches made of Poly-D,L-lactide (PLA) homopolymers were prepared in order to evaluate how the presence of PEG segments into PEG-D,L-PLA copolymer could affect the behaviour of microspheres as carrier of protein drugs.

METHODS

The PEG-D,L-PLA and PLA microspheres, loaded with the model protein ovalbumin, were prepared using double emulsion solvent evaporation method. The effect of PEG segments in the microparticles matrix, on the morphology, size distribution, encapsulation efficiency and release behaviour was studied.

RESULTS

According to the results, PEG-D,L-PLA microspheres were more hydrophilic than PLA microparticles and with lower glass transition temperature. The surface of PEG-D,L-PLA microspheres was not as smooth as that of PLA microparticles, the mean diameter of PEG-D,L-PLA microparticles was bigger than that of PLA microspheres. Protein release from the microspheres was affected by the morphological structure of PEG-D,L-PLA microspheres and properties of PEG-D,L-PLA copolymer. This study suggests that PEG-D,L-PLA multiblock copolymer may be used as carrier in protein delivery systems for different purposes.

gamma-Irradiation of PEGd,lPLA and PEG-PLGA multiblock copolymers. I. Effect of irradiation doses

To evaluate the effects of different gamma irradiation doses on PEGd,lPLA and PEG-PLGA multiblock copolymers. The behaviour of the multiblock copolymers to irradiation was compared to that of PLA, PLGA polymers. PEGd,lPLA, PEG-PLGA, PLA and PLGA polymers were irradiated by using a (60)Co irradiation source at 5, 15, 25 and 50 kGy total dose. Characterization was performed on all samples before and after irradiation, by nuclear magnetic resonance (NMR), infrared absorption spectrophotometry (FTIR) and gel permeation chromatography (GPC). The effect of gamma irradiation on polymer stability was also evaluated. Results of NMR and FTIR suggest an increase in -OH and -COOH groups, attributed to scission reactions induced by irradiation treatment. Data of GPC analysis showed that the weight average molecular weight (Mw) of polymer samples decreased with increasing irradiation dose. The extent of Mw degradation expressed as percentage of Mw reduction was more prominent for polymers with high molecular weight as PEGd,lPLA and PLA. The dominant effect of gamma-irradiation on both polymer samples was chain scission. The multiblock copolymer PEGd,lPLA presented higher sensitivity to irradiation treatment with respect to PLA, likely due to the presence of PEG in the matrix. The effect of gamma irradiation continues over a much longer period of time after gamma irradiation has been performed. It is suggested that the material reacts with oxygen to form peroxyl free radicals, which may further undergo degradation reactions during storage after irradiation.

Efficacy of oleuropein against UVB irradiation: preliminary evaluation

Oleuropein, a phenolic compound derived from olive leaves and oil, is known to possess several biological properties, many of which may be attributed to its antioxidant and free radical-scavenging activities. Nevertheless, up to now, the cosmetic activity of this molecule has not been extensively investigated. The aim of this work was to evaluate the cosmetic properties of oleuropein against UVB-induced erythema. To this end, an emulsion and an emulgel containing oleuropein were prepared, applied and evaluated on healthy volunteers who had undergone UVB irradiation to investigate its protective and/or lenitive activity. Protective effect was assayed by application of topical preparations before irradiation and lenitive effect was evaluated after erythema induction. Vitamin E was used as the reference compound. Our study was carried out by using noninvasive techniques to assess specific skin parameters: barrier function, skin colour and microcirculation. Results clearly showed that oleuropein formulations highlighted lenitive efficacy by reducing erythema, transepidermal water loss and blood flow of about 22%, 35% and 30% respectively. The study allowed us to point out the lenitive property of oleuropein, opening the way to further trials to deepen our specific knowledge about this natural molecule, which could be used in association with other active ingredients in cosmetics to repair UV damages.

Preparation and in vitro evaluation of thiolated chitosan microparticles

The objective of this study was to prepare a microparticulate drug delivery system being based on a new thiomer, namely a chitosan 2-iminothiolane conjugate (chitosan-TBA conjugate). Due to thiol groups being immobilized on chitosan, chitosan-TBA conjugate exhibits improved mucoadhesive and permeation enhancing properties. Because of these features microparticulate drug delivery systems based on chitosan-TBA conjugate might be a promising tool for the non-invasive administration of hydrophilic macromolecular drugs. Chitosan-TBA conjugate microspheres were prepared by the emulsification/solvent evaporation method. Fluorescein-isothiocyanate labelled dextran (FITC-dextran) was chosen as a model hydrophilic drug. Microspheres have been characterized by morphological analysis, thiol group content, swelling behaviour, polymer degradation drug load determination, dissolution test and mucoadhesion studies. Results reported in this work demonstrated the possibility to obtain stable microspheres without cross-linking agents. Thiolated chitosan microspheres seem to be more stable in aqueous media with respect to unmodified chitosan. The degradability by lysozyme appears quite similar for both polymers, showing that chemical modification does not influence the biodegradable properties of chitosan. Microspheres were able to control the drug release for at least 1 h, exhibiting comparatively strong mucoadhesive properties. The chitosan-TBA conjugate microparticles remain on the mucosa in a 2.5-fold higher concentration with respect to unmodified chitosan microparticles. These data suggest that chitosan-TBA conjugate microspheres have the potential to be used as a mucoadhesive drug delivery system.

PLGA microspheres for oral osteopenia treatment: preliminary "in vitro"/"in vivo" evaluation

The aim of this work was to prepare and to evaluate "in vitro"/"in vivo" microspheres based on poly(D,L-lactide-co-glycolide) copolymers containing ipriflavone, for the local treatment of oral bone loss. The first objective was the preparation and "in vitro" characterization of ipriflavone loaded microspheres, by emulsion/solvent evaporation method. Process parameters such as drug:polymer weight ratio, and molecular weight of copolymers, were also investigated. The second objective was to elaborate a suitable animal model of mandibular osteoporosis, to evaluate the efficacy of these microparticulate drug delivery systems. "In vivo" experiments were carried out on female rats, in which oral osteopenia was induced by gonadectomy and molar avulsion. Morphometric analysis of mandibular segment were carried out to quantify the development of oral osteopenia and the efficacy of drug loaded microspheres. Results showed that ipriflavone loaded PLGA microspheres can be successfully obtained with good "in vitro" characteristics, utilizing the emulsification/solvent evaporation method. "In vivo" experiments revealed that local administration of microspheres produced only mild inflammation on the injection site. Morphometric analyses showed, at the level of the third molar, a slight increase in spongy and total bone mass on rat jaw treated with microspheres with respect to control. Control animals exhibited a scarce degree of osteopenia demonstrating that this animal model is not suitable for this purpose.

Periodontal delivery of ipriflavone: new chitosan/PLGA film delivery system for a lipophilic drug

The aim of the present work was to design a film dosage form for sustained delivery of ipriflavone into the periodontal pocket. For this purpose, monolayer composite systems made of ipriflavone loaded poly(D,L-lactide-co-glycolide) (PLGA) micromatrices in a chitosan film form, were obtained by emulsification/casting/evaporation technique. Multilayer films, made of three layers of polymers (chitosan/PLGA/chitosan), were also prepared and compared to monolayer films for their "in vitro" characteristics. Morphology and physico-chemical properties of the different systems were evaluated. The influence of pH, ionic strength and enzymatic activity on film degradation, was also investigated. Significant differences in swelling, degradation and drug release were highlighted, depending on film structure and composition. In vitro experiments demonstrated that the composite micromatricial films represent a suitable dosage form to prolong ipriflavone release for 20 days.

Effect of nanoparticle encapsulation on the photostability of the sunscreen agent, 2-ethylhexyl-p-methoxycinnamate

The aim of this study was to investigate the influence of nanoparticle-based systems on the light-induced decomposition of the sunscreen agent, trans-2-ethylhexyl-p-methoxycinnamate (trans-EHMC). Ethylcellulose (EC) and poly-D,L-lactide-co-glycolide (PLGA) were used as biocompatible polymers for the preparation of the particulate systems. The "salting out" method was used for nanoparticle preparation and several variables were evaluated in order to optimize product characteristics. The photodegradation of the sunscreen agent in emulsion vehicles was reduced by encapsulation into the PLGA nanoparticles (the extent of degradation was 35.3% for the sunscreen-loaded nanoparticles compared to 52.3% for free trans-EHMC) whereas the EC nanoparticle system had no significant effect. Therefore, PLGA nanoparticles loaded with trans-EHMC improve the photostability of the sunscreen agent.

Evaluation of enzyme stability during preparation of polylactide-co-glycolide microspheres

This work was aimed at studying enzyme prolidase stability and its interactions with the reagents and the process conditions involved in preparation, by an emulsification process, of prolidase loaded poly(lactide-co-glycolide) (PLGA) microparticulate systems. Enzyme stability was tested with respect to contact with methylene chloride, ethyl acetate, PLGA polymers, and several agents used as emulsifiers such as polyvinyl alcohol (PVA), polyvinyl pyrolidone (PVP), carboxymethyl cellulose (CMC) and sodium oleate (NaOl). Enzyme stability to temperature and mechanical stirring was also evaluated. Prolidase-loaded PLGA microspheres were prepared and evaluated in terms of protein activity. The results obtained showed that the prolidase-loaded PLGA microspheres can be prepared only upon enzyme stabilization by addition of both BSA and MnCl(2) into its TRIS solution. Methylene chloride was the suitable organic solvent to be used in the double emulsion process, together with PVA as dispersing agent in the outer aqueous phase. Low temperatures during the emulsification step and very short process times are recommended, in order to maintain enzyme activity at its maximum. In these conditions spherical microspheres were obtained, releasing active prolidase for up to 15 days.

Enzyme loaded biodegradable microspheres in vitro ex vivo evaluation

Prolidase is a naturally occurring enzyme involved in the final stage of protein catabolism. Deficient enzyme activity causes prolidase deficiency (PD), a rare autosomal recessive inherited disorder whose main manifestations are chronic, intractable ulcerations of the skin, particularly of lower limbs. Although several attempts have been made towards the treatment of this pathology, a cure for this disease has yet to be found. The purpose of this work is to evaluate the possibility of enzyme replacement therapy through prolidase microencapsulation in biodegradable microspheres. The poly(D,L-lactide-co-glycolide) (PLGA) prolidase loaded microparticulate systems have been prepared utilizing the w-o-w double emulsion solvent evaporation method. They have been characterized "in vitro" by morphological analysis, total protein content and an in vitro dissolution test of active protein. "Ex vivo" evaluation of prolidase activity from the microspheres has been performed on cellular extracts of cultured skin fibroblasts from healthy subjects (controls) and from patients affected by PD. The results reported in this work on prolidase from pig kidney (available on the market) demonstrate the positive role of microencapsulation as a process of enzymatic activity stabilization inside PLGA microspheres achieving both in vitro and ex vivo active enzyme release. This formulation can be proposed as a parenteral depot drug delivery system.

Long-term release of clodronate from biodegradable microspheres

This paper describes the formulation of a biodegradable microparticulate drug delivery system containing clodronate, a bisphosphonate intended for the treatment of bone diseases. Microspheres were prepared with several poly(D,L-lactide-co-glycolide) (PLGA) copolymers of various molecular weights and molar compositions and 1 poly(D,L-lactide) (PDLLA) homopolymer by a water-in-oil-in-water (w/o/w) double emulsion solvent evaporation procedure. Critical process parameters and formulation variables (ie, addition of stabilizing agents) were evaluated for their effect on drug encapsulation efficiency and clodronate release rate from microparticles. Well-formed clodronate-loaded microspheres were obtained for all polymers by selecting suitable process parameters (inner water/oil volume ratio 1:16, temperature-raising rate in the solvent evaporation step 1 degree C/min, 2% wt/vol NaCl in the external aqueous phase). Good yields were obtained in all batches of clodronate microspheres (above 60%); drug encapsulation efficiencies ranged between 49% and 75% depending on the polymer used. Clodronate release from all copolymer microspheres was completed in about 48 hours, while those from PDLLA microspheres required about 20 days. The change of microsphere composition by adding a surfactant such as Span 20 or a viscosing agent such as carboxymethylcellulose extended the long-term release up to 3 months. Clodronate was successfully entrapped in PLGA and PDLLA microspheres, and drug release could be modulated from 48 hours up to 3 months by suitable selection of polymer, composition, additives, and manufacturing conditions.

Boron-loaded liposomes in the treatment of hepatic metastases: preliminary investigation by autoradiography analysis

Boronophenylalanine (BPA)-loaded conventional and stabilized liposomes were prepared by the reversed phase evaporation method to treat liver metastases by boron neutron capture therapy. Conventional vesicles were composed of phosphatidylcholine and cholesterol, molar ratio 1:1. To obtain stealth liposomes, GM1 or PEG were included in the lipidic bilayer at a concentration of 6.67 or 5 mol%, respectively. Large unilamellar vesicles were formulated encapsulating BPA in the liposome aqueous compartment as a complex with fructose; BPA free base also was embedded into the lipidic bilayer. In vivo experiments were carried out after intravenous injection of liposome suspensions in BD-IX strain rats in which liver metastases had been induced. Alpha particle spectroscopy associated with histological analysis was performed to visualize boron spatial distribution in liver. Simultaneously, tissue boron concentrations were determined using inductively coupled plasma-mass spectroscopy. Results showed that PEG-modified liposomes accumulated boron in therapeutic concentrations (> 30 micrograms boron/g tissue) in metastatic tissue. The PEG-liposomes could be further explored in enhancing boron delivery to tumor cells.

Study on glycolic acid delivery by liposomes and microspheres

Glycolic acid is used in many cosmetic products as exfoliant and moisturizer. Unfortunately, the greater glycolic acid cosmetic benefits the greater is the potential for skin irritation as far as burning. The aim of this work was to investigate the feasibility of topical controlled delivery systems loading glycolic acid in order to optimize the acid cosmetic properties lowering its side effects. For this purpose different types of microparticulate systems have been evaluated: liposomes, liposomes modified by chitosan addition and chitosan microspheres. Liposomes, composed of phosphatidylcholine and cholesterol (1:1 molar ratio) and with different glycolic acid/lipid molar ratio, were prepared by reverse phase evaporation method. Two types of interaction between liposomes and chitosan were investigated: chitosan addition into lipidic bilayer during liposome preparation and coating of already formed liposomes with chitosan. Glycolic acid loaded chitosan microspheres were prepared by the dry-in-oil emulsion method. The microparticulate systems were morphologically characterized by electron microscopy and particle size analysis. In vitro dissolution tests were performed to evaluate the feasibility of microparticulate systems in modulating glycolic acid release. The results obtained show that liposomes are always suitable to modulate glycolic acid release and that the best condition to achieve this control is obtained by the liposomal systems in which glycolic acid/lipid molar ratio is 5:1. Further significant release control is obtained by addition of chitosan into the liposomes, while chitosan microspheres are not able to control glycolic acid release even after crosslinking.

Microparticulate drug delivery systems

Chitosan was proposed as a drug carrier for mucosal administration in ocular, buccal, nasal, gastroenteric and vaginal-uterine therapies based on its bioadhesive properties and biodegradability in vivo under the action of hydrolases. Examples are the delivery of acyclovir via ocular administration, and the delivery of 5-aminosalicylic acid to the colon. Microparticles may need to be cross-linked to retard their degradation in acidic media; yet cross-linking with glutaraldehyde introduces cytotoxic characteristics and depresses bioadhesion. Alternative cross-linking approaches are discussed along with the suitability of chitosan for the oral delivery of vaccines.

Different molecular weight chitosan microspheres: influence on drug loading and drug release

Influence of chitosan molecular weight on drug loading and drug release of drug-loaded chitosan microspheres was studied. Chitosans of 70,000 (LC), 750,000 (MC), and 2,000,000 (HC) molecular weight were employed alone or as mixtures (HC/LC 1:1-1:2 w/w). Ketoprofen (ket) was chosen as the model drug to be encapsulated. Microspheres characterized by different theoretical polymer/drug ratios were prepared (2:1, 1:1, 1:2 w/w). Satisfactory ket contents were obtained for all batches of chitosan microspheres with the theoretical polymer/drug ratio 1:2 w/w; microspheres made of HC/LC (1:2 w/w) were characterized by good drug content and encapsulation efficiency independent by polymer/drug ratio. Prepared chitosan microparticulate delivery systems can modulate ket release within 48 hr. Microspheres consisting of HC/LC (1:2 w/w) were the most suitable formulation in controlling drug release.

Liposomes containing boronophenylalanine for boron neutron capture therapy

In the present work, liposomes loaded with Boronophenylalanine (BPA), with or without stabilization, were formulated for the application in boron neutron capture therapy. BPA was encapsulated into liposomes as a complex with fructose, but also as a free drug in two different pH buffers. The influence of critical variables (cholesterol content, drug:lipid molar ratio, osmotic stress of liposomes containing hyperosmotic drug solution) on liposome morphology and drug content was evaluated. The drug content and dissolution profile of different BPA loaded liposomes were also studied. The physical stability of liposomes in terms of changes in the size distribution in different osmotic pressure buffers and the chemical oxidation of phospholipids during storing conditions were investigated. The encapsulation efficiencies of all formulations were always satisfactory, being between 20-48%; even when the liposomes were exposed to high osmotic stress, the particle size was below 200 nm. The BPA-fructose complex loaded liposomes showed a slower drug release profile.

Bioadhesive microspheres for ophthalmic administration of acyclovir

The bioavailability of acyclovir to the ophthalmic epithelium is low and when the drug is administered in ophthalmic ointment it must be applied every four hours. An emulsification technique has been used to prepare acyclovir-loaded chitosan microspheres with the aim of promoting the prolonged release of drug and increasing its ocular bioavailability. The microparticulate drug-delivery systems obtained have been characterized for their morphology and physicochemical characteristics by in-vitro dissolution tests and in-vivo ocular administration to rabbits. The results show that the microspheres obtained are always quite small--the diameters of 90% of the particles are < or = 25 microns (i.e. d 90% never exceeds 25 microns) and physicochemical characterization shows that the drug is homogeneously dispersed in an amorphous state inside the microspheres. The in-vitro dissolution profile of acyclovir from chitosan microspheres is slower than that for the raw drug. Results from in-vivo ocular administration of acyclovir-loaded microspheres to the rabbit eye show prolonged high concentrations of acyclovir and increased AUC values. The microparticulate drug-carrier seems a promising means of topical administration of acyclovir to the eye.

Evaluation of process parameters involved in chitosan microsphere preparation by the o/w/o multiple emulsion method

Chitosans are interesting biopolymers largely studied for applications in the medical and pharmaceutical fields. In this work, an o/w/o multiple emulsion technique was used for the preparation of hydrophobic drug loaded microspheres. Moreover, the influence of critical variables (concentration of acetic acid in the polymer solution and drug-polymer ratio) on microsphere morphology and drug content was evaluated. Two chitosans of different molecular weights and deacetylation degree were employed; ketoprofen, a non-steroidal anti- inflammatory drug, was chosen as the hydrophobic model drug. The multiple emulsion method produced well-formed microspheres with good yields. Acetic acid concentration in the polymeric solutions influenced particle size and drug content of the microspheres. The highest drug encapsulation efficiencies were obtained for the lowest theoretical drug/chitosan ratio.

[The methods of using the echocardiogram in outpatients. The role of the cardiologist for more appropriate use of the procedure. The Ligurian Group of the Italian Society of Cardiovascular Echocardiography]

Concerns about the increasing medical care costs are causing the medical community to focus its attention on the appropriate of diagnostic tests such as echocardiography. Prerequisite to a better utilization of the limited economic resources assigned to our health care system is an analysis of how, why, and with which results diagnostic tests with a widespread use and relevant cost, like echocardiography, are requested. During the last 2 weeks of September 1994, a transversal, observational study was carried out at 13 hospital echocardiographic laboratories. Ordering physician characteristics, reasons for ordering the test, cardiological diagnostic tests previously performed and their relationship with the test results, were evaluated with a questionnaire completed by the physician who performed the test, in all the out-patients undergoing echocardiogram in that fortnight. Five hundred and sixteen consecutive questionnaires were successfully completed. Fourty-five percent of the echocardiograms were ordered by cardiologists, 35% by general practitioners, 10% by internists, and 10% by other specialists. Hypertension (16.4%) and ischemic heart disease (14.8%) were the most common indications for the test, followed by palpitations or arrhythmias (7.5%), mitral valve prolapse or mitral valve disease (7.3%), chest pain or angina pectoris (6.3%), cardiac murmur (5.5%), dyspnea or heart failure (5.2%), aortic valve disease (5%), prosthetic heart valve evaluation (4.6%), others (27%). Before undergoing the echocardiogram, 433 (84%) patients underwent an electrocardiogram, 242 (47%) a cardiological clinical evaluation, 196 (38%) a chest X-ray, and 191 (37%) had had a previous echocardiogram. The most common echocardiographic diagnosis was normal (29.2%) followed by hypertensive heart disease (16.2%), mitral valve disease (12.3%), aortic valve disease (10.5%), ischemic heart disease (9.3%), cardiomyopathy (4.9%) normal prosthetic heart valve function (4.5%), pericardial effusion (3.8%), others (11.3%). Among the echocardiograms ordered by cardiologists, 21.8% were normal in comparison with 35.4% of those ordered by general practitioners (p < 0.004), 35.3% of those ordered by internists (p = 0.04), 35.3% of those ordered by other specialists (p = 0.04). Among the 284 patients whose echocardiograms were not requested by a cardiologist, only 215 (76%) had undergone an electrocardiogram and only 68 (24%) a clinical evaluation by a cardiologist. In these patients, the frequency of normal echocardiograms was not influenced by having undergone a previous electrocardiogram or a chest X-ray. Conversely, patients in whom the echocardiogram was ordered after a cardiology consult showed a significant lower frequency of normal results compared to patients not evaluated by a cardiologist (23% vs 39%; p < 0.05). More than 50% of the echocardiograms performed in out-patients are ordered by physicians who are not cardiologists. Among these echocardiograms, about 1 out of 3 results normal. This finding suggests an improper use of echocardiogram as a screening tool by non-cardiologists in out-patients. A preceding clinical evaluation by a cardiologist, but not an electrocardiogram or a chest X-ray alone, may determine a more appropriate use of the test being associated with a reduced frequency of normal results.

[Effects of cimetidine on the cardiovascular system of normal subjects]

The effect of cimetidine on the cardiovascular system of normal subjects has been assessed. Eight healthy subjects were submitted to i.v. infusion on 200 mg of cimetidine in 2'; at a second stage, five of these were treated with placebo in equal volume and infusion speed. Polygraphic (LVET, PEP, PEP/LVET, triple product) and echocardiographic (systolic volume, cardiac capacity, velocity, circumferential shortening and ejection fraction) parameters were considered and heart frequency and arterial pressure measured. Measurements were carried out prior to infusion and for periods subsequent to the end of infusion. The results showed a statistically significant reduction only in heart frequency, triple product and cardiac output of subjects treated with cimetidine; no modifications were observed in subjects treated with placebo. It is concluded that cimetidine changes in heart frequency and its related parameters.