[Statement of the Spanish Interdisciplinary Vascular Prevention Committee on the updated European Guidelines on Cardiovascular Disease Prevention]

Statement of the Spanish Interdisciplinary Vascular Prevention Committee on the updated European Guidelines on Cardiovascular Disease Prevention. We present the Spanish adaptation of the 2021 European Guidelines on Cardiovascular Disease (CVD) prevention in clinical practice. The current guidelines besides the individual approach greatly emphasize on the importance of population level approaches to the prevention of cardiovascular diseases. Systematic global CVD risk assessment is recommended in individuals with any major vascular risk factor. Regarding LDL-Cholesterol, blood pressure, and glycemic control in patients with diabetes mellitus, goals and targets remain as recommended in previous guidelines. However, it is proposed a new, stepwise approach (Step 1 and 2) to treatment intensification as a tool to help physicians and patients pursue these targets in a way that fits patient profile. After Step 1, considering proceeding to the intensified goals of Step 2 is mandatory, and this intensification will be based on 10-year CVD risk, lifetime CVD risk and treatment benefit, comorbidities and patient preferences. The updated SCORE algorithm-SCORE2, SCORE-OP- is recommended in these guidelines, which estimates an individual's 10-year risk of fatal and non-fatal CVD events (myocardial infarction, stroke) in healthy men and women aged 40-89 years. Another new and important recommendation is the use of different categories of risk according different age groups (< 50, 50-69 ≥ 70 years). Different flow charts of CVD risk and risk factor treatment in apparently healthy persons, in patients with established atherosclerotic CVD, and in diabetic patients are recommended. Patients with chronic kidney disease are considered high risk or very high-risk patients according to the levels of glomerular filtration rate and albumin-to-creatinine ratio. New lifestyle recommendations adapted to the ones published by the Spanish Ministry of Health as well as recommendations focused on the management of lipids, blood pressure, diabetes and chronic renal failure are included.

Cost-effectiveness of the Hall Technique in a Randomized Trial

Clinical and patient-reported outcomes were reported for carious primary molars treated with the Hall technique (HT) as compared with conventional carious tissue removal and restorations (i.e., conventional restoration [CR]) in a 5-y randomized controlled practice-based trial in Scotland. We interrogated this data set further to investigate the cost-effectiveness of HT versus CR. A total of 132 children who had 2 matched occlusal/occlusal-proximal carious lesions in primary molars ( n = 264 teeth) were randomly allocated to HT or CR, provided by 17 general dental practitioners. Molars were followed up for a mean 5 y. A societal perspective was taken for the economic analysis. Direct dental treatment costs were estimated from a Scottish NHS perspective (an NHS England perspective was taken for a sensitivity analysis). Initial, maintenance, and retreatment costs, including rerestorations, endodontic treatments, and extractions, were estimated with fee items. Indirect/opportunity costs were estimated with time and travel costs from a UK perspective. The primary outcome was tooth survival. Secondary outcomes included 1) not having pain or needing endodontic treatments/extractions and 2) not needing rerestorations. Cost-effectiveness and acceptability were estimated from bootstrapped samples. Significantly more molars in HT survived (99%, 95% CI: 98% to 100%) than in CR (92%; 87% to 97%). Also, the proportion of molars retained without pain or requiring endodontic treatment/extraction was significantly higher in HT than CR. In the base case analysis (NHS Scotland perspective), cumulative direct dental treatment costs (Great British pound [GBP]) of HT were 24 GBP (95% CI: 23 to 25); costs for CR were 29 (17 to 46). From an NHS England perspective, the cost advantage of HT (29 GBP; 95% CI: 25 to 34) over CR (107; 86 to 127) was more pronounced. Indirect/opportunity costs were significantly lower for HT (8 GBP; 95% CI: 7 to 9) than CR (19; 16 to 23). Total cumulative costs were significantly lower for HT (32 GBP; 95% CI: 31 to 34) than CR (49; 34 to 69). Based on a long-term practice-based trial, HT was more cost-effective than CR with HT retained for longer and experiencing less complications at lower costs.

Comparison and critical appraisal of dengue clinical guidelines and their use in Asia and Latin America

The World Health Organization (WHO) dengue classification scheme for dengue fever (DF) and dengue haemorrhagic fever (DHF)/dengue shock syndrome (DSS) has been adopted as the standard for diagnosis, clinical management and reporting. In recent years, difficulties in applying the WHO case classification have been reported in several countries. A multicenter study was carried out in Asia and Latin America to analyze the variation and utility of dengue clinical guidelines (DCGs) taking as reference the WHO/PAHO guidelines (1994) and the WHO/SEARO guidelines (1998). A document analysis of 13 dengue guidelines was followed by a questionnaire and Focus Group discussions (FGDs) with 858 health care providers in seven countries. Differences in DCGs of the 13 countries were identified including the concept of warning signs, case classification, use of treatment algorithms and grading into levels of severity. The questionnaires and FGDs revealed (1) inaccessibility of DCGs, (2) lack of training, (3) insufficient number of staff to correctly apply the DCGs at the frontline and (4) the unavailability of diagnostic tests. The differences of the DCGs and the inconsistency in their application suggest a need to re-evaluate and standardise DCGs. This applies especially to case classification and case management.

Identification of a novel pseudodeficiency allele in the GLB1 gene in a carrier of GM1 gangliosidosis

The term 'pseudodeficiency' is used in lysosomal storage diseases to denote the situation in which individuals show greatly reduced enzyme activity but remain clinically healthy. Pseudodeficiencies have been reported for several lysosomal hydrolases. GM1 gangliosidosis is a rare autosomal recessive lysosomal storage disorder caused by beta-galactosidase hydrolase deficiency as a result of mutations in the GLB1 gene. Until now, two variants altering the beta-galactosidase activity have been described, p.Arg521Cys and p.Ser532Gly. Here we report the new variant p.Arg595Trp in the GLB1 gene, which markedly reduces beta-galactosidase activity when expressed in COS-1 cells. The variant was identified in the healthy father of a girl with GM1 gangliosidosis. He was a heterozygous compound with p.Arg595Trp in trans with one of the disease-causing mutations identified in his daughter; in leukocytes and plasma he showed lower beta-galactosidase activity than that observed in GM1 gangliosidosis carriers. As this family originated from the Basque Country in the north of Spain, we decided to analyse individuals of Basque and non-Basque origin, finding the p.Arg595Trp allele in 3.2% of Basque and in 0.8% of non-Basque alleles. The detection of the presence of alterations resulting in pseudodeficient activity in leukocytes and plasma is important for the correct diagnosis of GM1 gangliosidosis.

Identification of 14 novel GLB1 mutations, including five deletions, in 19 patients with GM1 gangliosidosis from South America

GM1 gangliosidosis is a lysosomal storage disorder caused by the absence or reduction of lysosomal beta-galactosidase activity because of mutations in the GLB1 gene. Three major clinical forms have been established: type I (infantile), type II (late infantile/juvenile) and type III (adult). A mutational analysis was performed in 19 patients with GM1 gangliosidosis from South America, mainly from Argentina. Two of them were of Gypsy origin. Main clinical findings of the patients are presented. All 38 mutant alleles were identified: of the 22 different mutations found, 14 mutations are described here for the first time. Among the novel mutations, five deletions were found. Four of them are relatively small (c.435_440delTCT, c.845_846delC, c.1131_1145del15 and c.1706_1707delC), while the other one is a deletion of 1529 nucleotides that includes exon 5 and is caused by an unequal crossover between intronic Alu sequences. All the described patients with GM1 gangliosidosis were affected by the infantile form, except for four unrelated patients classified as type II, III, and II/III (two cases). The two type II/III patients bore the previously described p.R201H mutation, while the adult patient bore the new p.L155R. The juvenile patient bore two novel mutations: p.S434L and p.G554E. The two Gypsy patients are homozygous for the p.R59H mutation as are all Gypsy patients previously genotyped.

Selectivity of a model zeolite ring over hydrocarbons with different symmetry, travelling with different orientations and speeds

We explore the selectivity of a model zeolite ring over representative hydrocarbons of crude oil. The model ring consists of 7 silicon tetrahedral units and one chemically active aluminum site through which hydrocarbons with symmetries varying from almost spherically symmetric to linear chains (1D), planar (2D), and pyramidal (3D) structures diffuse. The selectivity is further investigated when the hydrocarbons travel with different orientations and speeds. The semiclassical Born-Oppenheimer molecular dynamics approximation is used to characterize the chemical dynamics, as well as to determine the energetics and reaction products. The simulations reveal noticeable differences in energy profiles and charge populations. Our results are important to understand aspects of mass transport and some of the factors that control the catalytic activity in zeolites.

Functional and molecular modelling studies of two hereditary fructose intolerance-causing mutations at arginine 303 in human liver aldolase

We have identified a novel hereditary fructose intolerance mutation in the aldolase B gene (i.e. liver aldolase) that causes an arginine-to-glutamine substitution at residue 303 (Arg(303)-->Gln). We previously described another mutation (Arg(303)-->Trp) at the same residue. We have expressed the wild-type protein and the two mutated proteins and characterized their kinetic properties. The catalytic efficiency of protein Gln(303) is approx. 1/100 that of the wild-type for substrates fructose 1,6-bisphosphate and fructose 1-phosphate. The Trp(303) enzyme has a catalytic efficiency approx. 1/4800 that of the wild-type for fructose 1,6-bisphosphate; no activity was detected with fructose 1-phosphate. The mutation Arg(303)-->Trp thus substitution impairs enzyme activity more than Arg(303)-->Gln. Three-dimensional models of wild-type, Trp(303) and Gln(303) aldolase B generated by homology-modelling techniques suggest that, because of its larger size, tryptophan exerts a greater deranging effect than glutamine on the enzyme's three-dimensional structure. Our results show that the Arg(303)-->Gln substitution is a novel mutation causing hereditary fructose intolerance and provide a functional demonstration that Arg(303), a conserved residue in all vertebrate aldolases, has a dominant role in substrate binding during enzyme catalysis.

Microstructure and properties of pitch-based carbon composites

Pitches prepared in the laboratory by thermal treatment and air-blowing of a commercial coal-tar pitch were used as matrix precursors of carbon composites using granular petroleum coke, foundry coke, amorphous graphite and anthracite. Pitches were characterized by standard procedures (elemental analysis, softening point, solubility tests and carbon yield) and light microscopy (mesophase content). Pitch pyrolysis behaviour was monitored by thermogravimetric analysis and from the optical texture of cokes. Pitch wettability to the different carbons, at different temperatures, was also studied. Experimental conditions selected for the preparation of composites were based on pitch composition and properties. The main microstructural features of composites were determined by light microscopy and scanning electron microscopy. Composite properties were described in terms of their density, porosity and compressive strength, and related to composite microstructure and the characteristics of the precursors. Thermal treatment and air-blowing of pitch improved carbon composite structure and properties. The lowest porosities and best mechanical properties were observed in those composites obtained with the thermally treated pitches combined with foundry coke and anthracite.

Novel six-nucleotide deletion in the hepatic fructose-1,6-bisphosphate aldolase gene in a patient with hereditary fructose intolerance and enzyme structure-function implications

Hereditary fructose intolerance (HFI) is an autosomal recessive human disease that results from the deficiency of the hepatic aldolase isoenzyme. Affected individuals will succumb to the disease unless it is readily diagnosed and fructose eliminated from the diet. Simple and non-invasive diagnosis is now possible by direct DNA analysis that scans for known and unknown mutations. Using a combination of several PCR-based methods (restriction enzyme digestion, allele specific oligonucleotide hybridisation, single strand conformation analysis and direct sequencing) we identified a novel six-nucleotide deletion in exon 6 of the aldolase B gene (delta 6ex6) that leads to the elimination of two amino acid residues (Leu182 and Val183) leaving the message inframe. The three-dimensional structural alterations induced in the enzyme by delta 6ex6 have been elucidated by molecular graphics analysis using the crystal structure of the rabbit muscle aldolase as reference model. These studies showed that the elimination of Leu182 and Val183 perturbs the correct orientation of adjacent catalytic residues such as Lys146 and Glu187.

Molecular basis of hereditary fructose intolerance in Italy: identification of two novel mutations in the aldolase B gene

We screened the aldolase B gene in 14 unrelated Italian patients with hereditary fructose intolerance (HFI), and found two novel disease related mutations: a single nucleotide deletion in exon 2 (delta A20) that leads to an early stop codon, and a C-->T transition in exon 8 that substitutes an Arg with a Trp residue at codon 303 (R303W).

The molecular basis of hereditary fructose intolerance in Italian children

We investigated the molecular defects of the aldolase B gene in five unrelated patients affected by hereditary fructose intolerance. The techniques used were DNA amplification, direct sequencing and allele-specific oligonucleotide (ASO) hybridization. The most frequent substitutions found in the hereditary fructose intolerance alleles analysed were the A174D and the A149P mutations, which account for 50% and 30% of the alleles, respectively. In two unrelated families, we found a rare mutation, the MD delta 4 previously described only in one British family, which may be an important cause of the disease in Italy.

Extracellular complementation of a developmental mutation implicates a small sporulation protein in aerial mycelium formation by S. coelicolor

The filamentous bacterium S. coelicolor differentiates by forming aerial hyphae, which protrude into the air and metamorphose into chains of spores. Aerial hyphae formation is associated with the production of a small, abundant protein, SapB, which is present in a zone around colonies of differentiating bacteria. Production of SapB is impaired in bld mutants, which are blocked in aerial hyphae formation, but not in whi mutants in which spore formation is prevented. We report that aerial hyphae formation by a newly identified bld mutant is restored by juxtaposition of the mutant near colonies of SapB-producing bacteria or by the application of the purified protein near mutant colonies. These observations implicate SapB in aerial mycelium formation and suggest that SapB is a morphogenetic protein that enables hyphae on the surface of colonies to grow into the air.

Assignment of human aldolase C gene to chromosome 17, region cen----q21.1

The mapping of the gene coding for human aldolase C has been studied using a specific cDNA probe and genomic blots from a panel of human-hamster somatic cell hybrids. The results show that the aldolase C gene is on chromosome 17. In situ experiments have restricted the mapping to the region 17cen----q21.1. Using the same panel of human-hamster somatic cell hybrids, we have confirmed the localization of aldolase A and B on chromosomes 16 and 9, respectively.

Visualizing gene expression in time and space in the filamentous bacterium Streptomyces coelicolor

Streptomycetes are prokaryotic microorganisms that exhibit a complex, mycelial fungus-like cycle of morphological differentiation. Development involves at least two spatially separated types of cells: the branching hyphae of the substrate mycelium, which penetrate the stratum upon which the colony feeds, and the upwardly protruding hyphae of the aerial mycelium, which undergo metamorphosis into spores. The luciferase-encoding luxA and luxB operon of the luminescent marine bacterium Vibrio harveyi was used as a promoter probe to visualize gene expression in differentiating colonies of Streptomyces coelicolor. Promoters for developmental genes of several kinds gave distinctive temporal and spatial patterns of light emission.

Promoter determining the timing and spatial localization of transcription of a cloned Streptomyces coelicolor gene encoding a spore-associated polypeptide

Streptomyces coelicolor is a filamentous, gram-positive bacterium that exhibits a complex cycle of morphological differentiation involving the formation of an aerial mycelium of multinucleoid hyphae which undergo septation to form long chains of spores. We report the identification of two proteins of 13 and 3 kilodaltons, designated SapA and SapB, respectively, that are produced during formation of the aerial mycelium and are found in assocation with purified, mature spores. We cloned the structural gene (sapA) for one of these spore-associated proteins. Nucleotide sequence analysis suggests that the 13-kilodalton polypeptide is derived from a larger pre- or preproprotein containing a leader sequence of 37 amino acids. Nuclease protection-hybridization analysis and experiments using the Vibrio harveyi, luciferase-encoding luxAB operon as a gene tag demonstrated that expression of sapA is controlled from a promoter contained within a region of less than 110 base pairs in length, whose transcription start site is located approximately 50 base pairs upstream from the initiation codon for the sapA open reading frame. Transcription of sapA was induced at the time of appearance of the aerial mycelium, and the level of sapA transcripts was significantly reduced in certain mutants blocked in aerial mycelium (bld) and or spore (whi) formation. As further evidence of the association of sapA transcription with morphological differentiation, experiments in which we monitored sapA transcription topographically by use of a sapA-luxAB operon fusion demonstrated a close spatial correlation between colony regions undergoing aerial mycelium formation and zones of sapA-promoted light emission.

Mapping of a restriction fragment length polymorphism within the human aldolase B gene

Peripheral blood DNA was hybridized to the full-length cDNA and the cloned structural gene of human aldolase B. With PvuII endonuclease a restriction fragment length polymorphism was detected that was present in the heterozygous state in about 21% of the individuals tested. A map of the human aldolase gene was constructed for the two groups of individuals found to produce different fragments after PvuII digestion. This allowed the localization of the polymorphic site within the gene, which was found to be due to the loss of a PvuII site in the last intron upstream from the 3' end. This polymorphism may be used as a genetic marker to study individuals affected by hereditary fructose intolerance.

Mapping through somatic cell hybrids and cDNA probes of protein C to chromosome 2, factor X to chromosome 13, and alpha 1-acid glycoprotein to chromosome 9

The previously unassigned gene coding for the anti-coagulatory protein C has been mapped on chromosome 2 using a cDNA probe and genomic blots from a human-hamster somatic cell hybrid panel. The assignments of the genes coding for the coagulation factor X to chromosome 13, and for alpha 1-acid glycoprotein to chromosome 9 have been confirmed using a similar direct approach.

Human aldolase B cDNA detects a Pvu II RFLP in healthy individuals

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Calcium blocking properties of piprofurol

Piprofurol is a benzofuran chalcon derivative. It was studied under various experimental conditions which allow the recognition of calcium antagonistic activity. Piprofurol inhibited in a concentration-dependent manner the calcium-induced contractions in isolated potassium depolarized preparations of rat aorta (pA2: 9.29) and relaxed the K+-induced contraction of the dog coronary artery and the rabbit basilar artery (IC's 50: 2 10(-8) M; 3 10(-9) M). Piprofurol also inhibited noradrenaline-induced vascular smooth muscle contractions but the antagonism was clearly noncompetitive and the contractions induced were altered by concentrations two orders of magnitude higher than the concentration inhibiting calcium-induced contractions. Calcium antagonism was demonstrated in cardiac muscle: calcium mediated slowly rising action potentials were evoked in partially depolarized guinea-pig papillary muscle by electrical stimulation in the presence of isoprenaline. Piprofurol decreased the rate of rise of these slow action potentials. The inhibitory effect was reversed by an elevation of the calcium concentration in the bath fluid. Piprofurol exerts a negative inotropic effect (IC50: 5 10(-6) M) on guinea-pig papillary muscle. The ratio IC50 inotropic action/IC50 relaxant activity was 230, i.e. higher than that obtained with verapamil or diltiazem, and near that observed for cinnarizine. The pharmacological profile from in vivo dog experiments is in agreement with its in vitro properties: coronary sinus blood flow was increased and heart rate decreased. These effects suggested a potentially anti-ischaemic activity. This is confirmed in anaesthetized dogs, where piprofurol reduced the epicardial ST-segment elevation following coronary artery occlusion, and in isolated heart preparations, where it decreased the leakage of LDH during periods of anoxia and reoxygenation.

Isolation and nucleotide sequence of a full-length cDNA coding for aldolase B from human liver

Two recombinant clones, pA2 and pA3, containing cDNA sequences for human aldolase B have been isolated from a full length human liver cDNA library. The larger one, pA3, has been subcloned in M13 phage and completely sequenced with the chain terminator method. The sequence covers 1,600 nucleotides including the whole coding region (1,050 nucleotides), 67 nucleotides from the 5' non-coding region and the whole 3' non-coding region, 440 nucleotides long, down to the poly-A tail. Comparison with rabbit aldolase A and with a partial sequence of rat aldolase B, shows a homology of about 76% for aldolase A and of about 94% for aldolase B, which indicates that the sequenced cDNA codes for the liver isoenzyme. This is the first complete sequence reported for human aldolase B. The pA3 clone strongly hybridizes to 18S mRNA from human adult liver as expected from the size of the isolated cDNA.

Electrophysiological effects of carocainide (770207) on the dog heart

The electrophysiological effects of carocainide (770207) were assessed in "in vivo" and "in vitro" experiments on dogs' hearts. Intravenous administration of 5 mg/kg body weight of carocainide significantly lengthened the following: A-H interval, the shortest atrial pacing cycle length maintaining 1:1 atrioventricular (A-V) nodal conduction, H-V interval, left bundle-ventricle (LB-V) interval, the shortest His bundle pacing cycle length maintaining 1:1 His-Purkinje conduction, QRS duration, right atrial and right ventricular effective refractory periods. In Purkinje fiber-papillary muscle junction preparations driven at a constant cycle length of 1000 msec, perfusion of carocainide at the concentration of 1.25 10(-5) M and 2.5 10(-5) M, increased conduction time between Purkinje and muscle fibers and decreased the rate of depolarization of Purkinje fibers and papillary muscle. These results suggest that carocainide depresses conduction and lengthens refractory periods at atrial and ventricular levels and provide an explanation for the positive effect of this compound against experimental cardiac arrhythmias.

Electrophysiological effects of carocainide (770207) on canine ventricular muscle and Purkinje fibers

Carocainide is a new benzofuran derivative showing antiarrhythmic properties in animal models. In isolated papillary muscles and Purkinje fibers it decreases the maximum rate of rise of the action potential and in Purkinje fibers it decreases the plateau amplitude and the duration of the action potential. Carocainide increases the ratio of the effective refractory period to the action potential duration at 90% of repolarization, shifts the membrane responsiveness curve towards more negative membrane potentials and slows down the recovery of the maximum rate of rise of the action potentials of the Purkinje fibers. Carocainide also increases the conduction time at the Purkinje papillary muscle junction.

Effects of MD770207 (carocainide) on experimental ventricular arrhythmias

Administered by intravenous or oral route, carocainide, MD770207, abolished experimental ventricular arrhythmias in anaesthetized and conscious dogs. Slow rate intravenous infusion (0.5 mg/kg/min) studies in conscious coronary ligated dogs demonstrated a good arrhythmia conversion as well as a wide margin of safety; mean conversion to 95% of normal sinus rhythm was achieved at 10.5 +/- 2.1 mg/kg while first signs of reversible neuro and cardio-toxicity occurred at 37.8 +/- 8 mg/kg. The reference agents disopyramide and lidocaine showed less favourable safety margin. Carocainide reduced epicardial ST-segment elevation produced by short coronary artery occlusion and prevented the occurrence of ventricular fibrillation resulting from reperfusion after acute coronary artery ligation. At antiarrhythmic dose levels there were no undesirable effects noted on cardiovascular function. Given intravenously the compound increased the ventricular fibrillation threshold in spontaneously hypertensive rats.

Isolation and characterization of a tRNA(guanine-7-)-methyltransferase from Salmonella typhimurium

The tRNA modifying enzyme, S-adenosylmethionine:tRNA(guanine-7-)-methyltransferase, has been extensively purified from Salmonella typhimurium. A rapid and efficient purification method using phosphocellulose chromatography followed by ammonium sulfate precipitation and Sephadex G-100 gel filtration is described. The enzyme appears to be a single polypeptide chain with a molecular weight of approximately 25 000--30 000 daltons. The Km for S-adenosylmethionine and for undermethylated tRNA is 53 microM and 3.4 microM, respectively. The methylation reaction is dependent on added monovalent or divalent cations; 5 mM spermidine, 3 mM MgCl2 and 1 mM spermine are the most effective. The enzyme, though not homogeneous, is free from contaminating ribonucleases and other tRNA methyltransferases.

Functional assay of tRNA molecules transcribed from a purified gene

Purified tRNA genes are expressed when microinjected into the nucleus of X.laevis oocytes. In this paper we describe a method to assay the capacity to be aminoacylated of the tRNA transcribed in the frog oocytes. The method exploits the radiochemical purity of the transcript and relies on the binding of aminoacyl-tRNA but not of uncharged tRNA to purified elongation factor EF-Tu. We also present some preliminary results on several single point mutants of tRNAPro from Caenorhabditis elegans. We show that nucleotide 73 of tRNAPro can be substituted by any other nucleotide without loss of acceptor activity. A double mutant, causing transition from G45G46 to A45A46 has lost acceptor activity. Also inactive is a mutant carrying an insertion of a single base in the anticodon loop.

Effects of 5-hydroxytryptamine on canine isolated coronary arteries

The effects of 5-hydroxytryptamine (5-HT) were studied in vitro on proximal and distal portions of canine interventricular and circumflex coronary arterial strips. 5-HT produced concentration-related contractions in the proximal portion whether contracted previously with KCl or not. These responses were still present after either chemical sympathetic denervation or release of noradrenaline induced by K+-free salt solution. In contrast, the distal portions of coronary arteries did not respond to 5-HT. Concentration-response curves to 5-HT exhibited a classical hyperbolic shape with a calculated Hill-coefficient of approximately 1. Methysergide and phentolamine but not morphine shifted to the right and depressed the maximum of the dose-response curves to 5-HT. It is concluded that the contractions produced by 5-HT in the proximal portion of the interventricular and circumflex coronary arteries are not due to the release of endogenous noradrenaline. The vessels appear to possess separate receptors for 5-HT and noradrenaline and the 5-HT responses belong to neither the M nor the D type.

[Thermodynamic analysis of oxygen/transport to the turtle heart]

Isolated turtle hearts were perfused, at constant flow, with human erytrocytes suspensions containing different levels of 2,3-DPG. PO2 measurements, in the blood leaving the heart, resulted in lower figures when the tissue was perfused with low affinity blood compared with perfusion of high affinity blood. Thermodynamic analysis was, also, carried out at four different levels of temperature. The results suggest that, in severe hypoxia, oxygen delivery to the tissue is increased when perfusion is performed with high oxygen affinity blood.