Search PubMed⌕ Search

Biomedical subjects

R van den Hoven

Publications and source records attributed to R van den Hoven.

At least 19 recordsLinked to original sources
PubMed2006

Clenbuterol affects the expression of messenger RNA for interleukin 10 in peripheral leukocytes from horses challenged intrabronchially with lipopolysaccharides.

On four occasions, four horses with heaves and four horses with small airway inflammatory diseases inhaled 0.9% saline based aerosol mixtures with or without lipopolysaccharides (LPS). Prior to the first saline and LPS inhalation, horses were untreated, while three and a half days prior to the third and forth inhalation horses had received 0.8 microg/kg clenbuterol intravenously twice daily. The messenger RNA (mRNA) expression of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-4, IL-6, IL-8, IL-10 and interferon- gamma (IFN- gamma) was investigated by RT-PCR, all of which were expressed in the white blood cells of samples collected. Inhalation of LPS only changed the cytokine expression profile of IL-10, IL-4 and TNF-alpha mRNA which were higher after challenge with LPS. However in those horses that were treated with clenbuterol the LPS-induced IL-10 mRNA expression was shown to be suppressed. Further changes in IL-4 and TNF-alpha were not significant. Thus the results of this study indicated that clenbuterol can modulate the expression of IL-10 mRNA in peripheral white blood cells in those horses with small airway diseases that have been exposed to LPS.

Animals↗
PubMed2006

Individual differences and repeatability of post-prandial changes of plasma-free amino acids in young horses.

Few data are available on post-prandial changes of plasma amino acids (AAs) in horses and on the repeatability and the individual variance on different sampling days. The objective of the present study was to measure pre- and post-prandial concentrations of plasma AA in 10 yearling horses. Blood samples were taken on days 1 and 40 of the study before feeding of hay, oats and soya meal and over an 8 h post-prandial period in 2-h intervals. The plasma AAs were measured by high-pressure liquid chromatography after ortho-phthalaldehyde derivatization. Mean fasting concentrations of the AAs were not significantly influenced by the individuum and sampling day. Repeatability of the fasting AA levels in the individual horses on two different sampling days was only found for histidine, 3-methylhistidine, methionine, tryptophan and taurine. While the absolute post-prandial AA concentrations differed between sampling days, the relative changes were comparable. All AA concentrations except 3-methylhistidine increased after feeding by 13% to more than 200% of their fasting values if the combined data of both days were analysed. Four hours after feeding the concentrations of arginine, asparagine, lysine, leucine, isoleucine and threonine, decreased more than 20%. Histidine, methionine, phenylalanine, valine, tryptophan, glutamine, glycine, tyrosine and taurine concentrations decreased by less than 20%. Concentrations of aspartic acid, glutamic acid, ornithine, serine and citrulline remained elevated. Most AA approached the fasting concentrations at 8 h, only glycine increased between 6 and 8 h after meal and 3-methyl-histidine concentrations were constant throughout the entire period. In conclusion, the pre-prandial plasma AA in horses appeared less influenced by individuum or sampling day than post-prandial plasma AA concentrations. Therefore, plasma AA concentrations should be interpreted only under well-defined conditions, especially regarding the feeding regimen.

Amino Acids↗
PubMed2005

Improvement of the lung function of horses with heaves by treatment with a botanical preparation for 14 days.

The effects of an oral preparation containing a mixture of extracts from yellow gentian, garden sorrel, cowslip, verbena and common elder on the lung function of nine horses suffering from heaves were determined in a longitudinal crossover study. The horses were divided at random into a group of five (group 1) and a group of four (group 2). The horses in group 1 were each given 15 tablets of the preparation twice daily, while the horses in group 2 were left untreated. Fourteen days later, the horses in group 2 were given the same course of treatment while the horses in group 1 were left untreated. On being subjected to a histamine inhalation provocation test, five of eight horses tested appeared to be hyperresponsive to histamine. The treatment decreased the histamine sensitivity of three of them; it also caused a significant decrease in maximal intrapleural pressure difference of all the horses. The treatment had no significant effects on the clinical signs, the mucociliary activity or the cytology of the bronchoalveolar lavage fluid of the horses.

Administration, Oral↗
PubMed2003

Study of the effect of Bronchipret on the lung function of five Austrian saddle horses suffering recurrent airway obstruction (heaves).

The effects of an oral preparation containing an extract of thyme and primula (Bronchipret; Bionorica) on the lung function of five horses suffering heaves were determined in a longitudinal study. The horses accepted the product well. The plasma concentrations of the marker substance, thymol, indicated that at least one of the substances in the extract had been absorbed from the gastrointestinal tract. The compliance, pulmonary pressure and airway resistance of the horses' lungs were all significantly improved after one month of treatment However, the severity of their clinical signs and their arterial oxygen partial pressure had not improved significantly.

Administration, Oral↗
PubMed2003

Intramuscular dosing strategy for ampicillin sodium in horses, based on its distribution into tissue chambers before and after induction of inflammation.

The Pharmacokinetics (PK) and distribution into tissue chamber fluid (TCF) of intramuscularly (i.m.) administered ampicillin sodium were examined in horses in order to design adequate dosing strategies. Concentration-time curves of ampicillin in plasma and TCF were determined in six horses following administration of 15 mg/kg ampicillin sodium, before and after the induction of local inflammation with 0.5% carrageenan. The calculated parameters were used to simulate various dosage-dosing interval combinations. Ampicillin was absorbed very rapidly following i.m. administration. Plasma concentrations were maximual between 18 and 21 min after administration. None of the plasma PK parameters were affected significantly by local (TC) inflammation. Penetration of ampicillin into and elimination from the TCF were affected significantly by inflammation and the half-life of elimination from the tissue fluid t1/2(d) was significantly shorter in inflammation. In the simulated dosage-dosing interval scenarios, only a dosage of 15 mg ampicillin/kg four times daily would successfully treat all ampicillin-susceptible bacterial isolates in well vascularized tissues. However a dosage as low as 10 mg/kg twice daily, would, in theory, treat all ampicillin-susceptible isolates in the inflamed poorly vascularized tissues. Decreasing the dosage results in loss of efficacy that cannot be completely compensated for by increasing the frequency of dosing.

Ampicillin↗
PubMed2003

The effect of orally administered marbofloxacin on the pharmacokinetics of theophylline.

As certain quinolones can interfere with the metabolism of theophylline by competitive inhibition of the hepatic microsomal cytochrome P450 system, concomitant use of these drugs with theophylline could result in theophylline toxicity. This study investigated the effect of orally administered marbofloxacin (2 and 5 mg/kg each once daily) on steady-state plasma pharmacokinetics of theophylline after concomitant oral administration of a sustained release theophylline preparation in dogs. Marbofloxacin caused some alteration in theophylline metabolism. A 2 mg/kg dose of marbofloxacin did not clearly result in an increased area under the concentration--time curve (AUC) or decreased clearance of theophylline, but at a dose of 5 mg/kg, a statistically significant increase in AUC and a decrease in the total clearance of theophylline was found. The 26% reduction in theophylline clearance is probably not clinically significant in healthy dogs, but for dogs with renal impairment, there might be a chance of theophylline accumulation when dosed concomitantly with marbofloxacin.

Administration, Oral↗
PubMed2002

Area under the curve calculations as a tool to compare the efficacy of equine influenza vaccines--a retrospective analysis of three independent field trials.

Using the area under the curve (AUC) concept as is commonly used in pharmaceutical bioequivalence studies, the bioequivalence of three equine influenza vaccines was demonstrated. A retrospective analysis was performed using this technique on data generated in three trials in which each of the three vaccines had been used. In total, data from 63 pony and horse foals were used. The AUC of the single radial hemolysis (SRH) titres against Influenza A/equi-1/Prague/56 (Pr/56), A/equi-2/Newmarket-1/93, and A/equi-2/Suffolk/89 (Suf/89) were calculated for each horse. It was concluded that calculation of the AUC from four time-points permitted a suitable estimate for vaccine potency. Using pooled data, it appeared that the AUC permitted better evaluation of vaccine potency than simply considering the highest post vaccinal titre (Titremax). In two studies, a minimal value for the AUC was associated with protection against Influenza (H3N8) challenge 50-153 days later.

Animals↗
PubMed2001

Clinical and virological evaluation of the efficacy of an inactivated EHV1 and EHV4 whole virus vaccine (Duvaxyn EHV1,4). Vaccination/challenge experiments in foals and pregnant mares.

Pregnant mares and young foals were vaccinated with Duvaxyn EHV1,4, an inactivated and adjuvanted vaccine containing both the EHV-1 and 4 antigens. SN and CF antibody titres were induced two weeks after first vaccination. Antibody levels were boosted after second vaccination, however they never reached the levels induced after virus challenge. Young foals were challenged with virulent EHV-1 and EHV-4 field viruses. Pregnant mares were challenged with the highly abortigenic EHV-1 strain Ab4. Vaccinated animals showed a clear reduction in clinical signs and virus excretion compared to unvaccinated control animals. Log transformed antibody levels could be correlated to duration of virus excretion. The incidence of EHV-1 induced abortions was drastically reduced in vaccinated mares. Therefore, although vaccinated animals are not fully protected against disease, Duvaxyn EHV1,4 clearly reduces clinical symptoms, the duration of virus shedding and the quantity of virus shed. It can be concluded that vaccination of foals and pregnant mares with Duvaxyn EHV1,4 significantly reduces the risk of abortions and outbreaks of respiratory disease caused by circulating field viruses.

Abortion, Veterinary↗
PubMed2001

Duration of immunity induced by an adjuvanted and inactivated equine influenza, tetanus and equine herpesvirus 1 and 4 combination vaccine.

An adjuvanted vaccine containing inactivated equine influenza, herpesvirus antigens, and tetanus toxoid was administered to young seronegative foals of 8 months of age by deep intramuscular injection in the neck (Group A). The first two vaccinations were given 4 weeks apart. The third was administered 6 months later. Another group of foals (Group B) was vaccinated according to the same scheme at the same time with monovalent equine herpes virus (EHV) vaccine (EHV1.4) vaccine. Antibody responses to the equine influenza (single radial haemolysis; SRH) and tetanus (ToBi ELISA) components of the vaccines were examined from first vaccination until 1 year after the third vaccination. The influenza components of the combination vaccine induced high antibody titres at two weeks after the second vaccination whereafter titres declined until the time of the third vaccination. After the third vaccination, the titres rose rapidly again to remain high for at least 1 year. Antibody titres against tetanus peaked only after the third vaccination but remained high enough to offer protective immunity for at least 1 year. Foals vaccinated with monovalent EHV1.4 remained seronegative for influenza and tetanus throughout the study. Four and a half months after the third vaccination of groups A and B, a third group of animals was vaccinated twice with monovalent EHV1.4 vaccine 4 weeks apart (Group C). Two weeks after the administration of the second dose in the later group, all groups (A, B, C and an unvaccinated control group D) were challenged with EHV-4. Vaccinated foals (Group A, B, C) showed a clear reduction of clinical symptoms and virus excretion after EHV-4 challenge compared with the unvaccinated control foals. No difference could be demonstrated among the vaccinated groups, suggesting that the combination vaccine protects as well as the monovalent vaccine. In EHV1.4-vaccinated foals both antigenic fractions induced clear protection up to 6 months after vaccination (9). It can therefore be anticipated that the efficacy of the combination vaccine against EHV-1 challenge is similar to the efficacy against EHV-1 induced by EHV1.4 vaccination.

Adjuvants, Immunologic↗
PubMed2000

In vitro activity of difloxacin against canine bacterial isolates.

The in vitro activity of difloxacin against canine bacterial isolates from clinical cases was studied in the United States and The Netherlands. Minimal inhibitory concentrations (MIC), the postantibiotic effect, the effect of pH on antimicrobial activity, and the bacterial killing rate tests were determined according to standard techniques. The MICs of American and Dutch isolates agreed in general. The MICs of the American gram-negative isolates ranged from 0.06 to 2.0 microg/ml, and the MICs of the Dutch gram-negative isolates ranged from 0.016 to 8.0 microg/ml. A few European strains of Proteus mirabilis and Klebsiella pneumoniae had relatively high MICs. Bordetella bronchiseptica also was less susceptible to difloxacin. The MICs of the American gram-positive cocci ranged from 0.125 to 4.0 microg/ml, and the MICs of Dutch isolates ranged from 0.125 to 2.0 microg/ ml. Difloxacin induced a concentration-dependent postantibiotic effect that lasted 0.2-3 hours in cultures with Escherichia coli, Staphylococcus intermedius, Streptococcus canis, Proteus spp., and Klebsiella pneumoniae. There was no postantibiotic effect observed against canine Pseudomonas aeruginosa. Decreasing the pH of the medium increased the MIC of Proteus mirabilis for difloxacin. The MICs of Escherichia coli and Klebsiella pneumoniae were lowest at neutral pH and were slightly increased in acid or alkaline media. At a neutral pH, most tested bacterial species were killed at a difloxacin concentration of 4 times the MIC. Similar results were obtained when these same bacteria were tested against enrofloxacin. A Klebsiella pneumoniae strain in an acidic environment was readily killed at difloxacin or enrofloxacin MIC, but at neutral pH the drug concentration had to be raised to 4 times the MIC for a bactericidal effect. After 24 hours of incubation at pH 7.1, difloxacin and enrofloxacin had similar bactericidal activity for all bacteria tested except Staphylococcus intermedius. Against S. intermedius, difloxacin was more bactericidal than enrofloxacin.

Animals↗
PubMed1998

Efficacy of difloxacin in growing broiler chickens for the control of infection due to pathogenic Mycoplasma gallisepticum.

Chickens 14 days old were experimentally inoculated with Mycoplasma gallisepticum (MG) R-P10 strain. After development of respiratory symptoms, birds were left unmedicated or medicated for 5 consecutive days with Difloxacin 5, 7.5 or 10 mg/kg body weight per day or Enrofloxacin at the dose level of 10 mg/kg body weight per day. Evaluation of efficacy was based on body weight, symptoms, post-mortem findings, re-isolation of MG and serology. Results indicated that under the conditions of this experiment, treatment with 7.5 mg Difloxacin per kg body weight for 5 days was already effective against pathogenic MG infection. The dose of 10 mg/kg Difloxacin was equally effective as a dose of 10 mg/kg Enrofloxacin in treating respiratory symptoms.

Animals↗
PubMed1994

[An outbreak of equine arteritis virus infection in a riding school].

A major part of the residing horses and ponies of a riding school in Noord-Holland became affected by a febrile disorder that included anorexia, depression, conjunctivitis, urticaria, edema of the legs and laborious locomotion. All remaining horses fell ill within one week. Based on the clinical symptoms the disorder was diagnosed as vasculitis. With serology the causative agent of the disorder appeared to be equine arteritis virus.

Animals↗
PubMed1991

Effect of an isoxsuprine-resin preparation on blood flow in the equine thoracic limb.

The effects of an oral isoxsuprine-resin preparation on the blood flow in the thoracic limb of seven horses was determined by thermography. Treatment with the oral resin preparation resulted in increased skin temperatures compared with the non-medicated controls. The maximal temperature differences, 2.2 degrees C for the horses treated with 0.9 mg/kg and 1.8 degrees C for the horses treated with 1.2 mg/kg, occurred four hours after dosing. Plasma total isoxsuprine, determined in three horses, was detectable two hours after oral dosing and maximal eight hours after dosing, but free isoxsuprine could not be detected. Receptor binding studies demonstrated strong alpha-receptor binding, and this binding was so strong that even at isoxsuprine concentrations below the detection level receptors could have been stimulated.

Animals↗
PubMed1990

[Histochemical and biochemical changes in skeletal muscles of rhabdomyolysis-sensitive racehorses following exertion. III: Elevated activity of various antioxidant enzymes].

In this communication, the results of a histochemical and biochemical enzyme study on gluteus medius muscle of horses, sensitive to exertional myopathy, during attacks of rhabdomyolysis are presented. For the biochemical study the biopsy specimens investigated were selected by means of histological and enzyme histochemical staining methods. Dissected specimens were used which contained groups of muscle fibres with a high or low activity of glucose-6-phosphate dehydrogenase. The activity of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase was measured microbiochemically in these dissected specimens. A rise in activity of glucose-6-phosphate dehydrogenase in pathologically changed muscle fibres was always found to be coupled with a significant rise in activity of phosphogluconate dehydrogenase, glutathione reductase, and glutathione peroxidase. In these muscle fibres, the activity of superoxide dismutase and catalase was not significantly increased. On the basis of the combined histochemical and biochemical findings it is concluded that the application of the histochemical method for the demonstration of glucose-6-phosphate dehydrogenase activity can be highly recommended for the study of antioxidant enzymes in skeletal muscles with neuromuscular defects.

Animals↗
PubMed1989

[Histochemical changes in skeletal muscles of racehorses susceptible to rhabdomyolysis after exertion. I. Early myopathological changes].

In this communication, the results of an enzyme histochemical study on m. gluteus medius of horses, sensitive to exertional myopathy, during attacks of rhabdomyolysis are presented. The activity and location of about 25 enzymes were examined. In the present report, the early metabolic changes are discussed. Within 6 min after an attack, some large rounded fibres (approximately 2%) were seen, which showed an intense red staining in the haematoxylin and eosin sections. These hypercontracted fibres showed an increase in activity of mitochondrial adenosine triphosphatase, indicating the presence of uncoupling and/or loose coupling of the mitochondria. This finding may point to a deficient production of ATP in the m. gluteus medius of horses sensitive for exertional myopathy and this deficiency may lead to pathological alterations in the skeletal muscles. The pathological fibres revealed a changed activity of other mitochondrial enzymes as well.

Animals↗