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Biomedical subjects

A Linden

Publications and source records attributed to A Linden.

At least 55 records · Page 3Linked to original sources
PubMed1999

Cardiovascular response to intravenous administration of 5-hydroxytryptamine after type-2 receptor blockade, by metrenperone, in healthy calves.

The cardiovascular response to 5-hydroxytryptamine (5-HT) challenge has been previously described in cattle. Abrupt bradycardia, followed by tachycardia, triphasic systemic blood pressure response, and pulmonary hypertension were the major changes elicited by 5-HT. The purpose of the present study was to determine whether the cardiovascular response to 5-HT in calves was attributable to 5-HT2 receptors. A specific 5-HT2 antagonist (metrenperone, 0.05 mg/kg) was administered intramuscular to six unsedated Friesian calves 30 min before the animals were given a 5-min intravenous 5-HT infusion. Mean systemic arterial (SAP), mean pulmonary arterial (PAP), pulmonary capillary wedge (PW) pressures were obtained by means of fluid-filled catheters, and cardiac output (CO) was measured by the thermodilution technique. Heart rate, stroke volume, systemic (SVR) and pulmonary (PVR) vascular resistances were calculated. Administration of 5-HT after metrenperone induced a short-lasting period of severe bradycardia followed by tachycardia and increased CO. The systemic blood pressure response was exclusively hypotensive and associated with a decrease in SVR. Conversely, PAP, PW, and PVR were not modified by 5-HT administration. The results establish that 5-HT induced systemic as well as pulmonary hypertension is mediated through the activation of type-2 serotonergic or alpha-adrenergic receptors, or both. In contrast, neither apnoea, bradycardia and hypotension, nor the positive chronotropic effect induced by 5-HT in cattle are mediated through such receptors.

Animals↗
PubMed1998

Antiplasmodial and cytotoxic metabolites from the Maltese sponge Agelas oroides.

From a Maltese sample of the marine sponge Agelas oroides, five compounds: oroidin (1), 2-cyano-4,5-dibromopyrrole (2), 4,5-dibromopyrrole-2-carboxylic acid (3), 4,5-dibromopyrrole-2-carboxylic acid methyl ester (4), and 4 alpha-methyl-5 alpha-cholest-8-en-3 beta-ol (5) have been isolated. For compounds 1-5, completely assigned 1H- and 13C-NMR data are reported for the first time. For 2 a single crystal X-ray crystallographic analysis proved its structure unambiguously. The X-ray analysis of 2 indicated it to crystallise in an unexpected polar space group. Biological activity assessment of all isolates indicate 5 to have moderate antiplasmodial activity, as well as being cytotoxic, and 2 to be moderately cytotoxic towards several cancer cell lines.

Animals↗
PubMed1997

[Infection by Vibrio vulnificus after a prick from from the spine of a Tilapia].

Vibrio vulnificus is a Gram-negative bacterium living in warm salty water that produces a spectrum of human disease which may progress to devastating, sometimes fatal infections in susceptible individuals. Such infections have rarely been reported in Israel. However, over the past few months we have been seeing a sharp increase in V. vulnificus infections with a common history of injury to extremities by the sharp spines of Tilapia zillii, ("amnon" or St. Peter's fish). Clinical suspicion and prompt intervention prevent the untoward consequences of misdiagnosis or delay.

Adult↗
PubMed1997

Pulmonary function values in Friesian and double-muscled calves during acute poikilocapnic hypoxia.

The effects of an acute non-isocapnic hypoxia on ventilation and pulmonary mechanics were investigated in 6 healthy unsedated Holstein-Friesian (HF) calves and in 7 double-muscled calves of the Belgian White and Blue (BWB) breed known to develop more severe hypoxemia during exercise and respiratory diseases. Data were collected at 1 min intervals throughout the following protocol: breathing air (FIO2 = 21%), then breathing hypoxic gas mixture (FIO2 = 10%) for 5 min, and, finally, breathing air again for 5 min of recovery. Arterial blood was sampled at rest and at the 4th min of hypoxia for blood gas analysis. In HF and BWB calves, hypoxia induced a significant increase in tidal and minute volume, but did not change respiratory rate, dynamic lung compliance and total pulmonary resistance. However, with regard to their ventilation during normoxia at rest, BWB calves showed a comparatively greater rise in ventilation than HF calves during the first 4 min of hypoxia. On the contrary, by the 5th minute of hypoxia, ventilation of BWB calves declined to the normoxic level while HF calves largely sustained hyperventilation. This hypoxic ventilatory depression in BWB calves could be explained by the proportionately greater initial increase in ventilation. It was concluded that BWB calves supported this hypoxic challenge less easily than HF calves.

Animals↗
PubMed1997

Ventilatory effects of the single-breath CO2 test, compared with eructation, in cattle.

OBJECTIVE: To assess the peripheral chemoreceptor-induced ventilatory response to single tidal-breath CO2 (SB CO2) tests, compared with eructations, in 2 breeds of calves. ANIMALS: 13 conscious unsedated Holstein-Friesian and 8 Belgian White and Blue hypermuscled calves. PROCEDURE: An SB of +/- 50% CO2 in equal parts of O2 and N2 was inhaled. Ventilatory response was determined from the increase in ventilation (delta Ve) during the first 20 seconds after the test breath or eructation and from the difference in end-tidal PCO2 between the stimulus and preceding control breaths. RESULTS: Because no difference was found between the 2 breeds of calves, all data were pooled. The increase in Ve peaked during the fifth breath after the SB CO2 test on average, corresponding to a delay of 12.4 seconds. The SB CO2 responses ranged from 0.037 to 0.151 L/min.mm of Hg.m2, with a mean +/- SD of 0.082 +/- 0.032 L/min.mm of Hg.m2 for all calves. The SB CO2 tests, similar to eructations, modified the breathing pattern significantly and in the same direction, by principally shortening expiratory time and increasing mean inspiratory flow. After eructations, Ve peak increase was more important for lower difference in end-tidal PCO2 between the stimulus and preceding control breaths and took place more rapidly than after SB CO2 tests. Accordingly, eructation responses were more marked than SB CO2 responses and averaged 0.925 +/- 0.276 L/min.mm of Hg.m2. CONCLUSIONS AND CLINICAL RELEVANCE: In cattle, the pattern of breathing and ventilation under basal conditions is characterized by a cyclic variability coupled to eructation.

Animals↗
PubMed1996

Cold air-induced bronchoconstriction is mediated by tachykinin and kinin release in guinea pigs.

In the present study, we investigated the role of acetylcholine, tachykinins and kinins in the bronchoconstriction induced by cold air inhalation. Cold air was delivered to anaesthetised, artificially ventilated guinea pigs through a tracheal cannula. Inhalation of cold air increased the maximum total pulmonary resistance (RL) in a time-dependent manner, reaching a maximum after 15 min of exposure. The increase in RL induced by exposure to cold air for 10 min was not affected by pretreatment with atropine (1.4 mu mol/kg, i.v.); it was abolished by the tachykinin NK2 receptor antagonist, SR 48968 (0.3 mu mol/kg, i.v.) and was reduced by 58% by the kinin B2 receptor antagonist, HOE 140 (0.1 mu mol/kg, i.v.). These findings suggest that cold air induces bronchoconstriction in guinea pigs via a cascade that involves the release of kinins and tachykinins.

Animals↗
PubMed1996

Relationship of plasma lactate production to cortisol release following completion of different types of sporting events in horses.

Fifty-eight healthy horses were studied during five sporting events of various intensities and durations, namely show-jumping (n = 6), cross-country in a three-day event (n = 30), trotting races (n = 7), galloping races (n = 7) and endurance rides (n = 8). Venous blood samples were collected at rest and immediately after exercise and analysed for plasma cortisol (CORT) and lactate (LA) levels. The experimental procedure was the same throughout the investigation so as to permit a reliable comparison between the five types of exercise. The type of event significantly affected both the resting (p < or = 0.05) and the post-exercise (p < or = 0.01) plasma CORT. The degree of exercise-induced hypercortisolaemia was related to both the intensity and the duration of exercise for all five sporting events, but the endurance ride induced the most and show-jumping the least serious post-exercise CORT changes. LA production was much more closely related to the intensity of the exercise than was CORT. It is concluded that simultaneous measurements of plasma CORT and LA levels may be useful to discriminate between different types of exercise, adjust training programmes, and improve our comprehension of the physiology of sport horses at exercise.

Analysis of Variance↗
PubMed1996

Effect of serotonergic blockade on calf pulmonary function after the intravenous administration of 3-methylindole.

This study was designed to investigate whether 3-methylindole (3-Mi), a tryptamine analogue, could cause pulmonary injury in calves other than by cytotoxicity. Injection of 3-Mi resulted in a marked increase of respiratory rate, decrease of tidal volume and increase in minute ventilation. Pulmonary mechanics values were also profoundly affected, lung dynamic compliance being reduced to approximately one-third of its baseline value and total pulmonary resistance being increased two-fold. Arterial oxygen partial pressure was dramatically reduced. Successive challenges with 3-Mi after physiological saline pretreatment resulted in quantitatively identical alterations of pulmonary function values. Conversely, all these ventilatory, mechanical and gas exchange changes were abolished by pretreatment with serotonergic antagonists. It was concluded that intravenous administration of 3-Mi to healthy calves induced immediate and reversible bronchoconstriction which affected both central and peripheral airways. Because the effect was abolished by pretreatment with antiserotonin drugs, it is suggested that 3-Mi acts either directly by stimulating serotonergic receptors or indirectly through the release of serotonin from platelets. Current concepts of the physiopathological cascade underlying the toxicity of 3-Mi should, therefore, be re-evaluated in the light of this pharmacological mechanism.

Analysis of Variance↗
PubMed1996

Antimalarial activity: the search for marine-derived natural products with selective antimalarial activity.

In this short review, an approach to the isolation of potential antimalarial agents and lead compounds is outlined. A discussion of organism collection, followed by a description of biological testing and isolation methodologies, is also given. For two organisms, details of their secondary metabolite chemistry are reported. From one of these, Laurencia papillosa, the two aromatic compounds p-hydroxybenzaldehyde (1) and p-methoxybenzyl alcohol (2) were isolated. From the other, the tropical marine sponge Cymbastela hooperi, 15 diterpenes (3-17), which contain isonitrile, isothiocyanate, and isocyanate functionalities, are reported. Together with the diterpenes, three sesquiterpene hydrocarbons, 18-20, and the thiol, 21, were obtained. All structures were established by spectroscopic methods, particularly 1H-1H and 1H-13C shift-correlated 2D NMR spectroscopy and accurate mass measurement (HREIMS). The majority of isolates demonstrate significant and selective in vitro antimalarial activity. For compounds 4-17 a brief description of their possible structure-activity relationships is provided.

Animals↗
PubMed1996

Hemodynamic responses to Pasteurella haemolytica inoculation in calves given type 2 serotonergic antagonist.

The effects of saline (control, group C) and metrenperone (treated, group M) on systemic and pulmonary hemodynamics were determined in conscious 7- to 15-day-old calves after they were intratracheally inoculated with Pasteurella haemolytica. Metrenperone, a specific serotonin (5-hydroxytryptamine) receptor antagonist, was injected intramuscularly (100 micrograms.kg-1) 2 h after the calves were inoculated. Central venous, pulmonary arterial and capillary wedge, and systemic arterial pressures were measured, using fluid-filled catheters. Cardiac output was measured by the thermodilution technique. Heart rate, stroke volume, and pulmonary and systemic vascular resistances were calculated. The parameters were measured hourly from the 1st to the 10th h after inoculation. In group C, cardiovascular response to P. haemolytica inoculation was marked and typically consisted of two systemic hypotensive phases and two pulmonary hypertensive phases. The first phase occurred by the 2nd h post inoculation and was induced by a transient bradycardia and a systemic vasodilation, leading to profound hypotension and reduced venous return. Cardiac performance then transiently recovered, but systemic hypotension persisted. The second hypotensive hypodynamic phase occurred by the 7th h after inoculation, and was associated with a decline in stroke volume, an increase in heart rate, and pulmonary hypertension and vasoconstriction. In group M, the early response to P. haemolytica exposure was similar to that in controls, indicating that, as in sheep, 5-hydroxytryptamine does not contribute to the early hypodynamic response to endotoxemia. In contrast, metrenperone completely abolished late increases in pulmonary arterial pressure and pulmonary vascular resistance, suggesting that 5-hydroxytryptamine contributes to the late pulmonary vasoconstriction. Metrenperone treatment also allowed better restoration of heart rate, and hence, cardiac output was maintained. In conclusion, 5-hydroxytryptamine might have a role in mediating pasteurellic endotoxin induced changes in pulmonary hemodynamics through its type-2 receptors.

Analysis of Variance↗
PubMed1995

2,2',3,3'-Tetra-O-benzoyl-6,6'-dideoxy-4,4'-di-O-mesyl-6,6'- dithiocyanato-alpha,alpha-trehalose.

The low-temperature X-ray crystal structure of 2,3-di-O-benzoyl-6-deoxy-4-O-mesyl-6-thiocyanato-alpha-D-glu copyranosyl 2,3-di-O-benzoyl-6-deoxy-4-O-mesyl-6-thiocyanato-alpha-D-glu copyranoside (the title compound), C44H40N2O17S4, is reported. The absolute configuration has been determined. The molecule has only approximate C2 symmetry but the differences in the orientation of the C(5) substituents and the torsion angles about the glycosidic linkage are very much less than in alpha,alpha-trehalose and its derivatives. Each of the hexopyranosyl residues has a nearly perfect 4C1 conformation. The planes of the phenyl rings of the benzoyl groups are oriented such that they are approximately perpendicular to the plane of the parent pyranose ring.

Carbohydrate Sequence↗
PubMed1995

3-O-benzoyl-4,6;4',6'-di-O-benzylidene-2,2'-dideoxy,alpha,alpha-ribo- trehalose.

The low-temperature X-ray structure of an asymmetrically substituted derivative of alpha,alpha-trehalose, 3-O-benzoyl-4,6;4',6'-di-O-benzylidene-2,2'-dideoxy-alpha,alpha-ribo-tre halose (3-O-benzoyl-4,6-O-benzylidene-2-deoxy-alpha-D-ribo-hexopyranosyl 4,6-O-benzylidene-2-deoxy-alpha-D-ribo-hexopyranoside, C33H34O10), is reported. The hexopyranosyl rings and the 1,3-dioxane rings have normal 4C1 chair conformations, so that each half of the molecule has a double-chair conformation, resembling a trans-decalin ring system. Each benzylidene acetal group takes the form of the thermodynamically more stable (R)-diastereomer with its phenyl group attached to the 1,3-dioxane ring in an equatorial orientation. The conformations about the glycosidic linkages are stabilized by the anomeric effect and by an intramolecular hydrogen bond between the lone hydroxy group and the glycosidic O atom.

Carbohydrate Conformation↗
PubMed1995

Validation of creatine, glycogen and L-(+)-lactate determination in biopsy samples of bovine Musculus diaphragma.

Whereas reliable measurements of diaphragmatic force and electrical activity are now available in calves, evidence that substrate contents in the bovine diaphragm can be accurately measured is still lacking. The purposes of the present study were therefore a) to describe and test the reliability of methods and procedures used for sampling, lyophilisation, extraction and dosage of muscular lactate, glycogen and creatine contents and b) to report the variation in their levels found along the bovine diaphragm and among individuals. The repeatability of the results yielded by a) assaying the extracts, b) processing and assaying the extracts and c) taking samples at different sites in the muscle was assessed. Neither assay, nor processing effects were significant (P < or = 0.05). Substrates were found to be homogeneously distributed within the two muscles studied. Substrate contents expressed per unit of muscle weight or total creatine were neither more or less variable than when expressed per unit of dry matter.

Animals↗
PubMed1995

Pulmonary ventilation, mechanics, gas exchange and haemodynamics in calves following intratracheal inoculation of Pasteurella haemolytica.

A Pasteurella haemolytica A1 broth was injected intratracheally in eight calves and measurements of pulmonary function values (PFV) were made once before and hourly post inoculation (p.i.). Changes in PFVs, included increased respiratory rate and minute ventilation (up to 158% of baseline 2 h p.i.) and decreased tidal volume and lung dynamic compliance (up to 33% of baseline 3 h p.i.). Total pulmonary resistance was not affected. At and after 3 h p.i. there was a progressive impairement of gas exchange, as judged from arterial O2 tension which decreased up to 65% of baseline. In contrast, arterial CO2 tension was not affected. Pulmonary hypertension was observed during the 3 last h of the study and was attributable to an increased pulmonary vascular resistance. Severe neutropenia was observed at 3 h p.i. and post-mortem histological findings were consistent with an acute fibrinohemorragic bronchopneumonia. In conclusion, P. haemolytica airway challenge unequiovocally resulted in acute pneumonia, providing a reproducible pathophysiological model for investigations regarding new therapeutic strategies.

Animals↗
PubMed1995

Pathophysiological response of bovine diaphragm function to gastric distension.

Because of the anatomic association of an exceptionally bulky stomach with a striking compartmentation of the chest wall, leading to the most cranial insertion of the diaphragm among mammals, gastric overdistension in the bovine species offers a unique pathophysiological condition for the diaphragm. The purpose of the present study was to determine whether increased intragastric pressure (Pga) (1, 2, 3, 4, and 5 kPa) leads to perturbations of respiratory and diaphragm function in calves. Changes in diaphragmatic strength and inspiratory action followed a biphasic pattern: 1) transdiaphragmatic pressure (Pdi) in response to constant bilateral maximal phrenic nerve stimulation at 30 Hz increased with moderate gastric distension and then fell abruptly as Pga continued to rise and 2) the magnitude of the ratio of the fall in pleural pressure to total Pdi was maintained up to a Pga amounting to 2 kPa but declined at higher pressures. We conclude that gastric distension in the bovine species provokes physiologically significant alterations of the diaphragm excitation-to-pressure generation coupling as well as of its capacity to convert Pdi into useful inspiratory pleural pressure. We suggest that these perturbations resulted from the combination of 1) altered tension-generating capacity due to compromised perfusion, 2) altered diaphragm geometry capable of altering tension-to-pressure generation coupling, and 3) modified coupling of the diaphragm with the chest wall that reduced its ability to drive inspiration.

Animals↗
PubMed1994

2,2',3,3'-Tetra-O-acetyl-4,4',6,6'-tetradeoxy-alpha,alpha-xylo-trehalose.

The low-temperature X-ray crystal structure of 2,2',3,3'-tetra-O-acetyl-4,4',6,6'-tetradeoxy-alpha,alpha-xylo-trehalose (I) (2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranosyl 2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranoside) is reported. The crystals were found to contain approximately 16% of 2,3-di-O-acetyl-6-chloro-4,6-dideoxy-alpha-D-xylo-hexopyranosyl 2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranoside (II) as a result of incomplete hydrodechlorination of the intermediate 2,2',3,3'-tetra-O-acetyl-4,4',6,6'-tetrachloro-4,4',6,6'-tetradeoxy- alpha,alpha-trehalose. Except for the chloro substituent, the two molecules are crystallographically identical and the structure may be refined using a disordered model with one H atom being replaced by a Cl atom in 16% of the molecules. The two hexopyranosyl residues in both molecules have 4C1 conformations, with one of the residues adopting a nearly perfect chair conformation. The crystal packing places the Cl atom of (II) in a very crowded environment with a C-Cl bond length of 1.527 (7) A and a short intermolecular Cl...C contact of 2.884 (9) A.

Carbohydrate Conformation↗
PubMed1994

Measurement of right ventricular ejection fraction and volume by the thermodilution technique in the unsedated calf.

This study was designed to test the applicability and the reproducibility of the thermodilution method in the measurement of right ventricular ejection fraction (EF), end-diastolic volume (EDV) and end-systolic volume (ESV) in unsedated cattle. In the 16 healthy calves studied, it was possible, using a fast response thermodilution catheter, to obtain characteristic exponential steplike washout curves, allowing the calculation of right ventricular EF, EDV and ESV. Five to 10 successive thermodilution curves were recorded within a few minutes and two to five similar sets of measurements were performed throughout the same day to test the reproducibility of the technique. The same protocol was repeated the following day. Right ventricular EF, EDV and ESV were reproducible successively, throughout a given day and on following days. The mean intraset, intraday and interdays coefficients of variation ranged from a mean of 4.0 (SD 4.1) per cent to a mean of 18.2 (SD 7.9) per cent. Values of right ventricular volumes and EF agreed with those previously reported in various animal species. Thermodilution was, therefore, shown to be a useful method for measuring with a satisfactory reproducibility, right ventricular EF, EDV and ESV in the unsedated healthy calf.

Animals↗