Results of a hybrid cardiovascular rehabilitation program (in-hospital plus home) in patients with low income

Background

One of the main problems facing cardiovascular rehabilitation (CR) is patient care and adherence. However, due to the low level of economic income of the patients who are cared for in our center, the possibility of going to CR in a conventional way is very difficult since they do not have the necessary resources to cover transportation, cost of the sessions, among others.

It has been shown that the greater the number of sessions attended by the patient, the greater the reduction in cardiovascular risk, however the role of a hybrid program with a decreased number of face-to-face sessions has not been established.

Purpose

Present the results of a hybrid training program (in-hospital plus home) in a low-income population. Education through supervised sessions plus home physical training in a patient with bases for exercise can improve their adherence with better results.

Methods

A cohort of patients with heart disease who were referred to the Cardiovascular Rehabilitation program between May 2017 and February 2019 was included. The socioeconomic level was classified into 6 strata according to occupation, income, housing, economic dependents, place of origin and family health status. After risk stratification, the patients participated in a hybrid program that consisted of 6 in-hospital sessions, once a week, in which the training to be carried out at home was prescribed by means of a triptych. An exercise test was performed before and after completing the program, as well as psychological and nutritional intervention. Statistical analysis was performed using SPSS 21.0 software. All p values less than 0.05 were considered significant.

Results

In the study period, of the total number of patients discharged for heart disease from the hospital, 61% were referred to cardiovascular rehabilitation, of which only 45% (n=39) completed the program, the reasons for dropping out were multiple and the lowest socioeconomic level (1) was the most frequent (figure 1). The main referral diagnosis was ischemic heart disease in 82%. The majority of patients were men, 95%. A significant improvement was observed in load METs, maximum heart rate, heart rate recovery (figure 2).

Conclusion

The implementation of a hybrid cardiovascular rehabilitation program (in-hospital + home) was associated with an improvement in the exercise test parameters of patients who successfully completed the program.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Severity of depression and its relationship with the parameters obtained in the cardiopulmonary exercise test in patients of a cardiac rehabilitation program

Background

Cardiovascular diseases are the leading cause of global morbidity and mortality. Depression causes specific disorders such as autonomic nervous system dysfunction, neurohormonal axis imbalance, proinflammatory and prothrombotic states. The alteration profiles in the parameters measured in the cardiopulmonary exercise testing (CPET) associated with the different severities of depression have not yet been characterized.

Purpose

To determine the association of the degree of depression and the parameters obtained in the CPET in patients undergoing a cardiac rehabilitation program.

Methods

Observational, comparative, cross-sectional, retrospective study of adult patients examined in the period from January 1, 2010 to December 31, 2017. Independent variables were degrees of depression according to Beck depression inventory, dependent variables were parameters reported in the CPET. Categorical variables were reported in frequency and continuous variables as averages. The comparison between groups was made with x2, T test, ANOVA according to type and number of variables and their distribution. Pearson's correlation to determine association.

Results

From a total of 594 patients: 490 were men (82.4%), age 57.34±11.3. Maximum METs 7.49±2.42, heart rate (HR) response (percentage of theoretical maximum heart rate achieved) 82.79±12.69 and systolic blood pressure response (SBP) (ratio of peak SBP to resting SBP) 1.29±0.18. Bivariate analysis found significant differences between Beck's depression scale and study variables: Male (p<0.0001), married (p=0.022), diabetes (p=0.012), surgical revascularization (p=0.05), use of angiotensin II receptor antagonists (p=0.027).

Conclusions

The present study found association of depressive symptoms with male gender, married marital status, diabetes, surgical myocardial revascularization and treatment with angiotensin II receptor antagonists. In the CPET, significant differences were found in exercise tolerance measured by METs, HR response and SBP response between subjects without depression and those with mild and moderate depression.

Depression and Exercise Tolerance

Funding Acknowledgement

Type of funding source: None

Detection and characterization of silver nanoparticles and dissolved species of silver in culture medium and cells by AsFlFFF-UV-Vis-ICPMS: application to nanotoxicity tests

A methodology based on Asymmetric Flow Field-Flow Fractionation (AsFlFFF) coupled with UV-Vis absorption spectrometry and ICP mass spectrometry (ICPMS) has been developed and applied to the study of silver nanoparticles (AgNPs) and dissolved species of silver in culture media and cells used in cytotoxicity tests. The effect of a nano-silver based product (protein stabilized silver nanoparticles ca. 15 nm average diameter) on human hepatoma (HepG2) cell viability has been studied. UV-Vis absorption spectrometry provided information about the nature (organic vs. nanoparticle) of the eluted species, whereas the silver was monitored by ICPMS. A shift towards larger hydrodynamic diameters was observed in the AgNPs after a 24 hour incubation period in the culture medium, which suggests a "protein corona" effect. Silver(I) associated with proteins present in the culture medium has also been detected, as a consequence of the oxidation process experimented by the AgNPs. However, the Ag(I) released into the culture medium did not justify the toxicity levels observed. AgNPs associated with the cultured HepG2 cells were also identified by AsFlFFF, after applying a solubilisation process based on the use of tetramethylammonium hydroxide (TMAH) and Triton X-100. These results have been confirmed by transmission electronic microscopy (TEM) analysis of the fractions collected from the AsFlFFF. The effect of AgNPs on HepG2 cells has been compared to that caused by silver(I) as AgNO3 under the same conditions. The determination of the total content of silver in the cells confirms that a much larger mass of silver as AgNPs with respect to AgNO3 (16 to 1) is needed to observe a similar toxicity.

Direct determination of uric acid in serum by a fluorometric-enzymatic method based on uricase

The present paper describes a method for the fluorometric determination of uric acid in blood serum by its reaction with uricase (UOx). The procedure is based on the changes in fluorescence that take place during the enzymatic reaction of UOx with uric acid when the solution is excited at 287 nm and the emission is measured at 330 nm. A mathematical model which relates the analytical signal to the analyte concentration was developed and the model also served to obtain some of the thermodynamic constants of the system (the Michaelis constant and the turnover number). The optimum reaction conditions and its analytical characteristics were studied, linear response range (3x10(-5)-6x10(-4) M) and reproducibility (4%, n=7). The method was applied to the determination of uric acid in three blood serum samples. The results were compared with those obtained by a commercial clinical analyzer and no systematic errors were observed.

Multielement characterization of metal-humic substances complexation by size exclusion chromatography, asymmetrical flow field-flow fractionation, ultrafiltration and inductively coupled plasma-mass spectrometry detection: a comparative approach

The use of three different separation techniques, ultrafiltration (UF), high performance size exclusion chromatography (HPSEC) and asymmetrical flow field-flow fractionation (AsFlFFF), for the characterization of a compost leachate is described. The possible interaction of about 30 elements with different size fractions of humic substances (HS) has been investigated coupling these separation techniques with UV-vis absorption spectrophotometry and inductively coupled plasma-mass spectrometry (ICP-MS) as detection techniques. The organic matter is constituted by a polydisperse mixture of humic substances ranging from low molecular weights (around 1kDa) to significantly larger entities. Elements can be classified into three main groups with regard to their interaction with HS. The first group is constituted by primarily the monovalent alkaline metal ions and anionic species like B, W, Mo, As existing as oxyanions all being not significantly associated to HS. The second group consists of elements that are at least partly associated to a smaller HS size fraction (such as Ni, Cu, Cr and Co). A third group of mainly tri- and tetravalent metal ions like Al, Fe, the lanthanides, Sn and Th are rather associated to larger-sized HS fractions. The three separation techniques provide a fairly consistent size classification for most of the metal ions, even though slight disagreements were observed. The number-average molecular weight (Mn), the weight-average molecular weight (Mw) and the polydispersity (rho) parameters have been calculated both from AsFlFFF and HPSEC experiments and compared for HS and some metal-HS species. Differences in values can be partly explained by an overloading effect observed in the AsFlFFF experiments induced by electrostatic repulsion effects in the low ionic strength, high pH carrier solution. Size information obtained from ultrafiltration is not as resolved as for the other methods. Molecular weight cut-offs (MWCO) of the individual filter membranes refer to globular proteins and molecular weight information may therefore, deviate from that given by the other methods after calibration with polystyrene sulfonate (PSS) standards.

Comparison of biosensors based on entrapment of cholesterol oxidase and cholesterol esterase in electropolymerized films of polypyrrole and diaminonaphthalene derivatives for amperometric determination of cholesterol

Cholesterol amperometric biosensors constructed with enzymes entrapped in electropolymerized layers of polypyrrole and poly-naphthalene derivative polymers are compared. The biosensors are based on entrapment of cholesterol oxidase and/or cholesterol esterase in monolayer or multilayer films electrochemically synthesised from pyrrole, 1,8-diaminonaphthalene (1,8-DAN), and 1,5-diaminonaphthalene (1,5-DAN) monomers. Seven configurations were assayed and compared, and different analytical properties were obtained depending on the kind of polymer and the arrangement of the layers. The selectivity properties were evaluated for the different monolayer and bilayer configurations proposed as a function of the film permeation factor. All the steps involved in the preparation of the biosensors and determination of cholesterol were carried out in a flow system. Sensitivity and selectivity depend greatly on hydrophobicity, permeability, compactness, thickness, and the kind of the polymer used. In some cases a protective outer layer of non-conducting poly( o-phenylenediamine) polymer improves the analytical characteristics of the biosensor. A comparative study was made of the analytical performance of each of the configurations developed. The biosensors were also applied to the flow-injection determination of cholesterol in a synthetic serum.

SEC-ICP-MS studies for elements binding to different molecular weight fractions of humic substances in compost extract obtained from urban solid waste

In this work, the speciation of elements in compost was studied with emphasis on their binding to humic substances. In order to assess the distribution of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, U, Th and Zn among molecular weight fractions of humic substances, the compost extract (extracted by 0.1 mol l(-1) sodium pyrophosphate) was analyzed by size exclusion chromatography coupled on-line with UV-Vis spectrophotometric and ICP-MS detection. Similar chromatograms were obtained for standard humic acid (Fluka) and for compost extract (254 nm, 400 nm) and three size fractions were operationally defined that corresponded to the apparent molecular weight ranges > 15 kDa, 1-15 kDa and < 1 kDa. The percentage of total element content in compost that was leached to the extract ranged from 30% up to 100% for different elements. The elution profiles of Co, Cr, Cu, Ni and Pb (ICP-MS) followed that of humic substances, while for other elements the bulk elution peak matched the retention time observed for the element in the absence of compost extract. Spiking experiments were carried out to confirm elements' binding and to estimate the affinity of individual elements for humic substances derived from compost. The results obtained indicated the following order of decreasing affinity: Cu > Ni > Co > Pb > Cd > (Cr, U, Th) >> (As, Mn, Mo, Zn). After standard addition, further binding of Cu, Ni and Co with the two molecular weight fractions of humic substances was observed, indicating that humic substances derived from compost were not saturated with these elements.

Chemical vapor generation for sample introduction into inductively coupled plasma atomic emission spectroscopy: vaporization of antimony(III) with bromide

A new method for antimony determination in soils is proposed. It is based on the chemical vapor generation of Sb(III) with bromide, after a reaction in sulfuric acid media and transport of the gaseous phase into an inductively coupled plasma for atomic emission spectrometry. The experimental variables influencing the method were delimited by experimental design and the most important were finally optimized by the modified Simplex method. In optimized conditions the method involves the reaction of 579 microl concentrated sulfuric acid with 120 microl 5% w/v KBr and 250 microl antimony solution. Measurement of antimony emission intensity at 217.581 nm provides a method with an absolute detection limit of 3.5 ng and a precision (RSD) of 5.8% for the injection of five replicates of 175 ng Sb(III) (250 microl of 0.7 microg ml(-1) solution). The interference of common anions and cations on the antimony signal was evaluated. A 21% Sb(III) volatilization efficiency was calculated from the mean of six experiments at optimum conditions. The accuracy of the methodology was checked by the analysis of one standard reference soil after acid decomposition heating in a microwave oven.

Reagent injection FIA system for lead determination by hydride generation - quartz-tube atomic absorption spectrometry

A method is proposed for the determination of lead by generation of its hydride and detection by quartz-tube AAS using a reagent injection FIA system based on the injection of sodium tetrahydroborate. Lead hydride generation was carried out using a combination of 0.5 M nitric acid, 10% m/ v hydrogen peroxide and 10% m/ v sodium tetrahydroborate. The characteristic concentration obtained was 3.1 ng mL(-1) and the detection limit was 2.6 ng mL(-1) for an injected volume of 0.125 mL of tetrahydroborate.

Intrinsic fluorescence of enzymes and fluorescence of chemically modified enzymes for analytical purposes: a review

In recent years our research group has developed new alternatives for fluorescence enzymatic determinations. First, we observed that the intrinsic fluorescence of enzymes changes during enzymatic reactions, proportionally to the substrate concentration, avoiding the combination of the enzymatic reaction with a fluorophore-involving reaction. The main disadvantage of this method is that the excitation and emission wavelengths of the enzymes are in the UV region of the spectrum. An alternative to overcome this problem consisted of covalently bonding the enzyme to a fluorophore. In this paper, an overview is given of all of the applications and future developments on both types of alternatives that we have developed. Apart from the analytical characteristics of the methods, we have also reviewed all of the information about mathematical models we have elaborated to date.

Strategies for the improvement of an amperometric cholesterol biosensor based on electropolymerization in flow systems: use of charge-transfer mediators and platinization of the electrode

Different configurations based on an amperometric biosensor with cholesterol oxidase entrapped in a polypyrrole film have been developed with a view to improving the analytical properties of this biosensor. The alternatives considered involve the simultaneous entrapment of the enzyme and a charge-transfer mediator as well as previous platinization of the surface of the Pt electrode. Both artificial (a ferrocene derivative) and natural (flavin nucleotides) mediators were studied as constituents of the charge-transfer process between the enzyme and the electrode. The comparative study of these biosensors, which were prepared in situ in a continuous flow system, made it possible to determine the advantages and disadvantages of each configuration when applied to flow-injection determination of cholesterol.

Determination of direct-bilirubin by a fluorimetric-enzymatic method based on bilirubin oxidase

A method for the determination of direct bilirubin by reaction with bilirubin oxidase (BOx) is reported. The procedure is based on the changes in fluorescence which take place during the enzymatic reaction of BOx with any of the three forms of bilirubin (free, conjugated and with albumin) when the solution is excited at 240 nm and the emission is measured at 440 nm. The change in fluorescence was studied thoroughly. It seems mainly due to the fluorescence of one of the reaction products. A theoretical study was carried out to relate the changes in fluorescence observed to the species taking part in the reaction and to establish some of the enzymatic reaction constants. The optimum reaction conditions were studied for each of the three types of bilirubin together with their analytical characteristics (linear range and precision). Selective determination of direct bilirubin was carried out for various synthetic samples with good results. A linear response up to 7 mg L(-1) of direct bilirubin was obtained. Using optimum conditions, the precision for free and conjugated bilirubin was 3.4% (n = 5) and 3.0% (n = 5), respectively.

Classification of ancient Roman glazed ceramics using the neural network of Self-Organizing Maps

Artificial neural networks with unsupervised learning strategy known as Self-Organizing Maps were applied to classify ancient Roman glazed ceramics. Their clay ceramic bodies were analyzed by Inductively Coupled Plasma-Atomic Emission Spectroscopy and the chemical composition obtained was processed by this neural algorithm. The results obtained provide two types of information: firstly, classification of ceramic samples with identification of several groups and secondly, differentiation between the elemental chemical information. It was found that there are certain chemical elements which can be considered as principal and which can serve to differentiate between ceramics, whereas other elements give redundant information and do not contribute to sample differentiation. Seven chemical elements were considered principal and provide the necessary information. Two types of element were identified: 1- a group formed by common elements, such as: Ca, Fe, Mg, Mn and 2- another formed by optional elements: K or Na and Ba or Sr and Al or Ti.

[Safety of meningococcal A and C vaccine. Data from the Spanish drug surveillance system. Meningococcal Vaccine Research Group of the Spanish System of Drug Surveillance]

OBJECTIVE

Data on meningococcal vaccines safety are scanty. In 1997 several vaccination campaign took place in Spain. Thus, this situation was used to improve our knowledge about the safety profile of this vaccine.

METHODS

An inquiry was carried out to the Regional Centers of the Spanish Pharmacovigilance System to know the number of vaccinated people and the type and number of suspected cases of adverse reactions.

RESULTS

There were 133 identified cases of suspected adverse reactions associated with meningococcal A and C vaccine until June 1st, 1998. Most of them affected the skin (25,3%) or nervous system (similar proportion). Those of allergic reactions accounted for 35,2%. Two cases were considered as severe, although they were resolved without secuelae.

CONCLUSIONS

Serious risks were not detected. The Spanish Pharmacosurveillance System as an epidemiological surveillance resource has been useful to know the safety problems associated with antimeningococcal vaccine in the community.

Three approaches to the development of selective bilayer amperometric biosensors for glucose by in situ electropolymerization

Three different glucose oxidase biosensors for the enzymatic determination of glucose, based on bilayer polymer coatings consisting of polypyrrole (PPy) and poly(o-phenylenediamine), were developed. The electrode substrates are Pt metal, carbon paste and an organic conducting salt (tetrathiafulvalene-tetracyanoquinodimethane), which introduces appreciable variability in the electrode construction process. The three sensors were compared with one another and with bare and PPy monolayer-coated sensors in terms of performance in the determination of glucose in a synthetic serum sample. These configurations provide improved selectivity against the interferences of electroactive species such as ascorbic acid and uric acid, frequently present in biological samples, and the differences between them can be taken advantage of in application to different kinds of samples.

Electropolymerization of pyrrole and immobilization of glucose oxidase in a flow system: influence of the operating conditions on analytical performance

The in situ potentiostatic electropolymerization of pyrrole (Py) on a Pt electrode in a thin-layer amperometric cell and the entrapment of the enzyme glucose oxidase (GOx) for the determination of glucose are reported. Polypyrrole (PPy) is directly formed by continuous passage of a buffered solution of the monomer (0.4 M) and enzyme (250 U mL-1) at pH 7 at a flow rate of 0.05-0.1 mL min-1 under a constant applied potential of +0.85 V vs Ag/AgCl decreases. The electrosynthesis of PPy by injection of 500 microL of a Py + GOx solution in a carrier electrolyte consisting of 0.05 M phosphate buffer and 0.1 M KCl at pH 7.0 was also assayed. The influence of the electropolymerization conditions on the analytical response of the sensor to glucose was investigated. The analytical performance of the PPy/GOx sensor was also studied in terms of durability and storage life, as well as selectivity against electroactive species such as ascorbic acid and uric acid as a function of the thickness of the polymer film formed.

Intrinsic molecular fluorescence of lactate dehydrogenase: an analytical alternative for enzymic determination of pyruvate

A method for the enzymic determination of pyruvate based on changes in the fluorescence intensity of lactate dehydrogenase (LDH) is described. These changes are due to the differential quenching effect produced by NAD and NADH on the LDH fluorescence. The NADH quenching is due to both an inner filter effect and LDH-NADH complex formation; the LDH-NADH complex is also fluorescent. However, the NAD quenching is based only on the inner filter effect. From these suppositions, the equilibrium constant of the reaction and the formation constant of the LDH-NADH complex were obtained. Given this, an appropriate analytical signal for the quantification of pyruvate and a mathematical model explaining the effect of each parameter are proposed. The linear response range of the method depends on the NADH concentration used during the determination; it is possible to determine pyruvate concentrations down to 8.8 x 10(-7) mol dm-3. The method was applied to the determination of pyruvate in synthetic blood samples with good accuracy.

Absence of effect of trimethoprim-sulfamethoxazole on pharmacokinetics of zidovudine in patients infected with human immunodeficiency virus

Pharmacokinetic parameters of zidovudine (ZDV) were not altered in 16 patients receiving concomitant therapy with ZDV and trimethoprim-sulfamethoxazole by oral administration. ZDV areas under the concentration-time curves were (means +/- standard deviations) 1.80 +/- 0.70 and 1.69 +/- 0.64 micrograms.h/ml in the absence and presence of trimethoprim-sulfamethoxazole, respectively. ZDV clearances were 1.57 +/- 0.61 and 1.74 +/- 0.66 liters/h/kg, respectively.

Human SP-10: acrosomal distribution, processing, and fate after the acrosome reaction

SP-10 is a testis-specific acrosomal protein that has been detected in several species including humans. Extracts from whole human testis and epididymal, ejaculated, and capacitated sperm were analyzed by Western blot for SP-10 polypeptides. The testis extracts contained a full-length SP-10 protein at approximately 45 kDa as well as other immunoreactive SP-10 peptides at 32, 30, 28, and 26 kDa. Extracts from epididymal, ejaculated, and capacitated sperm contained several immunoreactive SP-10 peptides that co-migrated with the 32-26-kDa SP-10 peptides in the testis extracts. Epididymal, ejaculated, and capacitated sperm extracts did not contain the 45-kDa SP-10 peptide observed in testis extracts, but did contain immunoreactive SP-10 peptides from 25 to 18 kDa that were not detected in testis extracts. These results indicate that a full-length 45-kDa SP-10 precursor protein is present in the testis and that SP-10 peptides of 32, 30, 28, and 26 kDa result from proteolytic processing of the SP-10 precursor protein in the testis and/or alternative splicing. In addition, SP-10 peptides of 25-18 kDa were first detected in extracts of caput epididymal sperm and probably resulted from the proteolytic processing of the 45- and 32-26-kDa SP-10 peptides in the initial segment or caput epididymidis. Also, no additional SP-10 bands were detected in extracts of cauda epididymal, ejaculated, or capacitated sperm, suggesting that no further processing of the 32-18-kDa SP-10 peptides occurred during epididymal transit, ejaculation, and capacitation. Electron microscopic immunocytochemical observations of epididymal, ejaculated, and capacitated sperm revealed that colloidal gold labeling of SP-10 was most abundant within the principal segment and posterior bulb of the equatorial segment of the acrosome, while the colloidal gold labeling of SP-10 was sparse in the anterior equatorial segment of the acrosome. After a follicular fluid-induced acrosome reaction, SP-10 was detected on the inner acrosomal membrane in the equatorial segment and was associated with hybrid vesicles. This localization after the acrosome reaction is consistent with the hypothesis that SP-10 may be involved in sperm-zona binding or penetration.

Production in Escherichia coli, purification and immunogenicity of acrosomal protein SP-10, a candidate contraceptive vaccine

The testis-specific human sperm antigen, SP-10, has been designated a 'primary vaccine candidate' by the World Health Organization Taskforce on Contraceptive Vaccines. Molecular cloning and sequencing of the cDNAs coding for human (h) and baboon (b) SP-10 have been reported. To produce large amounts of pure antigen for ongoing studies of the immunogenicity and anti-fertility effects of SP-10, we used an efficient Escherichia coli expression system. The full-length open reading frames for hSP-10 and bSP-10 were placed under the inducible T7 bacteriophage RNA polymerase/promoter system. An in-frame fusion was made such that a His6 stretch was produced at the C terminus of SP-10. Upon induction of gene expression, large amounts of hSP-10 or bSP-10 were synthesized and the recombinant (re-) protein segregated into an insoluble fraction. The protein was then solubilized in 6 M guanidine.HCl and purified by immobilized metal affinity chromatography (IMAC). The yield of purified bSP-10 preparation was approx. 20 micrograms/ml of culture. Immunoreactivity of the purified re-SP-10 with MHS-10, a monoclonal antibody specific to SP-10, and rabbit polyclonal sera raised against SP-10, indicated that the synthesized antigen was suitable for immunization studies. Four female baboons were then immunized with the re-bSP-10 antigen. Immunoblots using pre-immune and immune sera from these animals indicated that all four baboons produced antibodies that reacted with native SP-10 extracted from human sperm in a manner identical to that of MHS-10, the positive control. Immune sera also stained the acrosome region of human and baboon sperm heads by immunofluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

[Gastric leiomyoblastoma. Histomorphologic and immunologic analysis of 3 cases]

We present three cases of Leiomioblastomas of stomach, diagnosed at the unit of Pathology of the Gastrointestinal Cancer Center "Dr Luis E. Anderson" -San Cristóbal-Táchira State Venezuela. The lesions are analyzed from the clinical, morphological and immunohistological points of view, utilizing Queratine and Vimentin techniques. This neoplasm is not frequent but it is interesting because its biologic behavior not always correspond to its histology-pattern.

Fluorometric-enzymatic lactate determination based on enzyme cytochrome b2 fluorescence

This paper presents a procedure for fluorometric-enzymatic lactate determination based on the modification of the fluorometric properties of the enzyme L-lactic dehydrogenase (cytochrome b2). during the enzymatic oxidation of the analyte with ferricyanide. During the reaction one can observe an irreversible fall in the intensity of the enzyme's fluorescence, the rate of which is proportional to the concentration of the lactate. The source of this signal has been investigated and it has been shown that, besides the formation of a complex between the enzyme and the ferricyanide (the constant of which can be determined), this signal loss can be explained by simultaneous inner filter effects caused by the ferricyanide and the ferrocyanide (generated in the enzymatic reaction). A mathematical model has been developed which makes it possible to establish a linear response between the enzyme's analytical signal of fluorescence and the concentrations of the lactate, the cytochrome, and the ferricyanide. The procedure makes it possible to determine the lactate in concentrations ranging from 0.2 to 45 mg/L. Determination of the analyte has been carried out in milk samples with great precision and accuracy.

[Pharmacokinetic study of zidovudine in parenteral drug addicts with human immunodeficiency virus infection]

BACKGROUND

The aim of this study was to know the pharmacokinetics of zidovudine (ZDV) in steady state in patients with infection by the human immunodeficiency virus (HIV) in whom the risk factor was intravenous drug use.

METHODS

The study was carried out in 8 patients in stage IV of the Centers for Disease Control (CDC) with no acute intercurrent process, with normal liver and renal function, orally receiving 250 mg of ZDV every 6 hours. Blood samples were taken between 30 and 360 minutes from the last doses taken during fasting. Plasma concentrations of ZDV and glucuronide zidovudine (G-ZDV) were determined by radioimmunoassay with the data being adapted to a monocompartmental pharmacokinetic model.

RESULTS

The maximum concentration (Cmax) of ZDV was 0.81 +/- 0.38 microgram/ml demonstrating high interindividual variability with values between 0.35 microgram/ml and 1.45 microgram/ml. The mean Cmax of G-ZDV was 1.44 +/- 0.64 microgram/ml. The mean t1/2 of ZDV and G-ZDV was 1.63 +/- 0.75 hours and 1.12 +/- 0.32 hours, respectively, with values oscillating between 0.99 and 3.14 h in the case of ZDV. The area below the curve concentration/time (AUC) of ZDV was 1.43 +/- 0.34 microgram-h/ml and in the case of G-ZDV the AUC was 2.73 +/- 0.91 microgram-h/ml. Total body clearance (Clb) of ZDV was 2.11 +/- 0.64 l/kg/h and the volume of distribution (Vd) of ZDV was 5.6 +/- 1.73 l/kg.

CONCLUSIONS

The results of this study demonstrate that there is a marked interindividual variability in the pharmacokinetics of zidovudine suggesting the need for adapting dosage to patients weight and monitoring plasma concentration.

Pharmacokinetics of zidovudine in end-stage renal disease: influence of haemodialysis

OBJECTIVE

To study the pharmacokinetics of zidovudine (ZDV) and its glucoronide metabolite (G-ZDV) in a patient with end-stage renal disease in haemodialysis.

DESIGN

Pharmacokinetics study performed during and between haemodialysis sessions.

METHODS

The patient was treated with oral ZDV (100 mg every 8 h). Concentrations of ZDV and G-ZDV were measured by radioimmunoassay. A monocompartmental model was used to calculate pharmacokinetic parameters.

RESULTS

The peak plasma concentrations of ZDV and G-ZDV after drug administration between haemodialysis sessions were 0.57 and 10.01 micrograms/ml, respectively. The half-lives of ZDV and G-ZDV rose to 3.2 and 14.2 h, respectively. The total body clearance for ZDV in the period between haemodialysis sessions (0.44 l/kg/h) was 66% lower than normal values. The ZDV half-life was normalized by haemodialysis, the total body clearance of ZDV increased (1.12 l/kg/h) and the G-ZDV half-life shortened (5.9-7.9 h). Neither G-ZDV accumulation nor derived ZDV toxicity occurred.

CONCLUSIONS

Our data suggest that ZDV is safe and an efficient drug when administered at a dosage of 100 mg three times daily in patients with end-stage renal disease in haemodialysis sessions, and that ZDV and G-ZDV are cleared by haemodialysis.

Effect of PK 11195, an antagonist of benzodiazepine receptors, on platelet aggregation in a model of anxiety in the rat

1. Anxiety induced by forced swimming increases maximal intensity (h) of platelet aggregation (PAG) and time to reach it (t). 2. PK 11195 pretreatment (12.5 and 25 mg/kg) reverses anxiety-induced PAG changes. At 6.25 mg/kg it inhibits PAG. 3. Changes induced by anxiety on PAG may be mediated by peripheral-benzodiazepine receptors.