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H van Aken

Publications and source records attributed to H van Aken.

36 records · Page 2Linked to original sources
PubMed1992

The effects of intraventricular administration of eltoprazine, 1-(3-trifluoromethylphenyl)piperazine hydrochloride and 8-hydroxy-2-(di-n-propylamino)tetralin on resident intruder aggression in the rat.

Various serotonergic agents may reduce aggression in rats, but how they act in different parts of the brain is unknown. This study attempted to unravel part of this question by application of different serotonergic ligands into the lateral ventricle (i.c.v.) of male rats (resident-intruder aggression). 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin; 1 and 10 micrograms), a specific 5-HT1A agonist, affected neither aggression nor any other behaviour. The mixed 5-HT1A,B,C agonist, TFMPP (1-(3-trifluoromethylphenyl)piperazine hydrochloride), and the 5-HT1A/1B agonist, eltoprazine ((1-(2,3)-dihydro-1,4-benzodioxin-5-yl)piperazine hydrochloride), suppressed aggression at i.c.v. doses of 10 and 30 micrograms. This reduction was not caused by sedation. These data suggest a role of postsynaptic 5-HT1B receptors in mediating the anti-aggressive effects of mixed 5-HT1 agonists.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

[The reuse of 29-gauge spinal needles following combined spinal-epidural anesthesia].

The technique of combined spinal epidural anaesthesia (CSE) combines the versatility of spinal with the variability of epidural anaesthesia. Spinal application of the local anaesthetic achieves a fast response, reliable sensorial and motor block at a low dose with little toxicity. The epidural catheter allows for the duration of surgical anaesthesia to be extended and provides analgesia for the postoperative period. As the incidence of post dural puncture headache (PDPH) is inversely related to the size of the spinal needle, PDPH rarely or never occurs when 29 gauge needles are used. In 1775 parturients receiving spinal anaesthesia for caesarean section, Dittmann et al. [4] reported an incidence of PDPH of 1.37% with 29 gauge needles. The 29 gauge needle produced by Becton-Dickinson is the one now most frequently used for this technique. It is recommended that these needles be reused after resterilization. The objective of this study was to examine how clean 29 gauge spinal needles really are after resterilization. MATERIALS AND METHODS. Fifteen needles (29 gauge; Becton-Dickinson) were routinely used for combined spinal epidural anaesthesia. After identification of the epidural space at the L3-4 spinal segment with the 18 gauge Tuohy needle, the 29 gauge needle was advanced through the Tuohy needle. Immediately after use the needles were cleaned, rinsed with 20 ml distilled water, dried with pressurized air and subsequently resterilized in gas. Preparation of the used needles was in accordance with the manufacturer's recommendations ("wash, rinse, dry, sterilize before initial and each subsequent use") and with generally accepted principles [6]. Two needles were additionally cleaned in an ultrasonic bath for 15 min. The needles were examined using a scanning electron microscope. After this analyses, eight needles were sterilized again and then taken for hygienic examination. They were incubated with trypticase soy broth and checked for bacterial growth. RESULTS. Scanning electron microscopy (ScEM) showed organic impurities on all needles. These impurities were equally distributed among all needles. Even the two cleaned in the ultrasonic bath were not free of organic particles. However, no material defects or damage could be seen. Hygienic evaluation proved sterility as no bacterial growth could be detected. CONCLUSION. Owing to the possibility of medico-legal consequences, which sometimes occur a long time after anaesthesia has been given, we think it is unwise to reuse such needles. We hope that disposable and cheap 29 gauge needles will soon become available.

Anesthesia, Epidural↗
PubMed1991

Light-induced photon emission by rat hepatocytes and hepatoma cells.

We have investigated spontaneous and light-induced photon emission of suspensions of rat hepatocytes and of HTC hepatoma cells. Rat hepatocytes exhibit spontaneous biophoton emission, but from hepatoma cells this was not detectable. In contrast, after irradiation with white light, the reemission intensity was found to be lower for hepatocytes than for the tumor cell line. Induced photon emission was neither influenced by anaerobiosis nor by the intactness of the cells. Cell-fractionation studies demonstrate that the induced photon emission was caused by the nuclear fraction and by isolated chromatin. Phenol-extracted DNA, however, has lost this capacity. Our data suggest that differences in the chromatin structure may explain the cell-specific induced photon emission.

Anaerobiosis↗
PubMed1991

Postsynaptic 5-HT1 receptors and offensive aggression in rats: a combined behavioural and autoradiographic study with eltoprazine.

The present study was designed to assess whether the antiaggressive effects of eltoprazine are mediated via presynaptic and/or postsynaptic 5-HT1 receptors. We describe the effects of central 5-HT depletion 1) on the behaviour of resident TMD-S3 rats in a territorial situation, 2) on the efficacy of eltoprazine to inhibit offensive aggression, and 3) on the 5-HT1A, 5-HT1B and 5-HT1C receptor binding in brains of rats previously used in behavioural studies. Male resident rats were given combined 5,7-dihydroxytryptamine (5,7-DHT) injections into the dorsal and median raphe nuclei. Two to four weeks after the lesions, rats were confronted with an intruder Wiser rat in their home cage for a 10-min period. The 5,7-DHT treatment resulted in a modest reduction of offensive behaviour, while having no effects on other social and nonsocial behaviours. Oral administration of eltoprazine (1 mg/kg) specifically reduced offensive aggression in both sham- and 5,7-DHT-lesioned animals, leaving social interest and exploration intact or even increasing it. A low dose (0.3 mg/kg) of eltoprazine did not affect the behavioural repertoire of sham-operated rats, whereas this dose significantly reduced offense behaviours in the 5,7-DHT-lesioned residents. Quantitative autoradiographic studies 5 weeks after 5,7-DHT treatment revealed a significant increase in radioligand binding to 5-HT1A, 5-HT1B and 5-HT1C sites in many brain regions studied, except for the raphe nuclei where [3H]8-OH-DPAT binding to 5-HT1A sites was markedly reduced. The concentrations of 5-HT and 5-HIAA in frontal cortex were reduced to approximately 10% of controls. The results indicate that serotonin has a stimulatory rather than an inhibitory influence on offensive aggressive behaviour. Central 5-HT depletion does not prevent the antiaggressive effects of eltoprazine, indicating a role for postsynaptic 5-HT1 receptors in the modulation of offensive aggression. The 5,7-DHT-induced overall upregulation of 5-HT1A, 5-HT1B and 5-HT1C binding sites suggests that these three receptor subtypes receive a tonic serotonergic influence. It is conceivable that this postsynaptic 5-HT1 receptor supersensitivity is reflected by the increased efficacy of eltoprazine to inhibit offensive aggression.

5,7-Dihydroxytryptamine↗
PubMed1990

[Hemo- and cardiodynamic action of halothane or isoflurane following peroral long-term pretreatment with nifedipine. An animal experimental study].

This study investigated the influence of chronic oral nifedipine on the hemodynamic effects of halothane or isoflurane anesthesia in dogs. Under general anesthesia with fentanyl 0.3 microgram/kg/min i.v. and 3:1 N2O/O2 inhalation mixture a left thoracotomy was performed and two needle force probes were placed in the left ventricular wall to measure myocardial force of contraction. In the halothane group (n = 12) a Hall-effect sensor was placed on the anterior surface of the left ventricle, which in combination with a magnet on the posterior surface allowed measurements of left ventricular diameter. In the isoflurane group (n = 15) a Widney gauge was placed around the left ventricle to measure left ventricular circumference changes. The dogs were also monitored with left ventricular tip manometers, pulmonary arterial thermodilution catheters, and femoral arterial and venous catheters. Prior to surgery, in the halothane group 6 dogs were pretreated with nifedipine 6 mg/kg p.o. for 10 days; the other 6 served as controls. In the isoflurane group, 8 dogs were pretreated with nifedipine in the same way and 7 served as controls. Three hours after instrumentation baseline hemodynamic measurements were performed and repeated 15 min after adding 1 MAC and then 2 MAC halothane or isoflurane. Oral pretreatment with nifedipine caused vasodilation with a significant decrease in systemic vascular resistance (SVR) and mean arterial pressure (MAP); heart rate (HR) and dp/dt max were unchanged in comparison to the control group. The cardiac output (CO) increased. Halothane (1 MAC/2 MAC) had a dose-related circulatory depressant effect. This occurred to the same extent in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

[The effect of urapidil and sodium nitroprusside on intrapulmonary right-left shunt and arterial oxygenation in the treatment of hypertension following coronary surgery].

20 patients who developed arterial hypertension following coronary artery bypass grafting were randomly treated with either sodium nitroprusside (SNP) or urapidil. Both drugs led to a significant decrease in blood pressure. A significant tachycardia was noted only in the SNP-group. A decrease in peripheral and pulmonary vascular resistance was seen in both groups. Following application of SNP, alveolarterial oxygen difference and venous admixture increased significantly, whereas PaO2 showed a significant decrease. Three patients had to be taken out of the SNP group because of an increase of venous admixture. Alveoloarterial oxygen difference and venous admixture showed no significant changes following application of urapidil.

Antihypertensive Agents↗
PubMed1988

Permeation of the blood-brain barrier by urapidil and its influence on intracranial pressure in man in the presence of compromised intracranial dynamics.

We studied eight patients undergoing craniotomy for intracerebral tumour surgery requiring monitoring of intracranial pressure. All these patients showed significantly increased systolic arterial pressure, during anaesthesia. Following an average dose of 0.8 +/- 0.22 mg/kg urapidil, systolic arterial pressure returned to baseline values without a significant change in intracranial pressure. In nine patients, urapidil concentrations in plasma and cerebrospinal fluid were assayed following an intravenous injection of urapidil. Urapidil was found in the cerebrospinal fluid in concentrations between 5 and 99 ng/ml after total cumulative bolus injections of 10-75 mg. There is evidence that in clinically applied doses urapidil permeates the blood-brain barrier and reaches cerebrospinal fluid concentrations that allow an interaction with central 5-hydroxytryptamine-1A receptors.

Antihypertensive Agents↗
PubMed1983

Treatment of hypertension with labetalol in neurosurgical practice. Influence of labetalol on cerebral perfusion pressure in dogs without and with intracranial mass lesions.

In neurosurgical patients autoregulation of cerebral perfusion is often lost. Therefore, a sudden increase in blood pressure may lead to an increase in cerebral blood flow and cerebral oedema may follow. The influence of labetalol, a new alpha- and beta-adrenoceptor blocking agent, on intracranial pressure and cerebral perfusion pressure was investigated in dogs without and with mass lesions. During hypotension with labetalol the intracranial pressure remained unchanged and the cerebral perfusion pressure decreased to the same extent as mean arterial pressure (30%). Labetalol seems to be suitable to treat hypertension perioperatively in neurosurgical patients but it is not a suitable drug for induced hypotension.

Animals↗
PubMed1980

[Anaesthesia and intraocular pressure (author's transl)].

Almost every modern anaesthetic has an impact on the complex physiology of the intraocular pressure. The different factors influencing the intraocular pressure are discussed. With the exception of succinylcholine and ketamine all other substances used in modern anaesthesia produce a more or less significant reduction of the intraocular pressure. Hence, the anaesthesiologist disposes in general of a great variety of drugs to conduct an anaesthesia that is well adapted to the physiological requirements of the eye. Yet, he may still encounter some difficulties in emergency-situations, like a perforating eye trauma in a patient with a full stomach. Fazadinium may be a usefull alternative to succinylcholine in these situations, as its rapid onset of action is not accompanied by a rise in the intraocular pressure. Some other measures to reduce the intraocular pressure intraoperatively are also mentioned, like controlled hypotension, osmotic diuresis and inhibition of the carbonic anhydrase.

Anesthesia, General↗
PubMedDate not supplied

Induction of thermotolerance and heat-shock protein synthesis during nutritional deprivation.

Under various conditions of heating, H35 cells were submitted to acute nutritional deprivation by omitting a number of substrates (L15D medium). At 37 degrees C cell death starts after a lag-period of 3-5 h. During hypothermia cell death is delayed, whereas during hyperthermia it is accelerated especially as a result of thermosensitization. In L15D the ATP level decreases approximately 3 times faster in combination with hyperthermia than at 37 degrees C. In non-thermotolerant cells thermosensization is very high at 41 degrees C and decreases with increasing temperature; in thermotolerant cells it is comparatively decreased at 41 degrees C and increased at 42.5 degrees C and above. In response to a heat shock of 30 min at 42.5 degrees C only 10% of the cell population expresses acute thermotolerance after incubation at 37 degrees C in L15D as compared to nearly 100% in complete medium (L15C). Chronic development of thermotolerance appears to be even more repressed in the presence of L15D, which partly explains the high thermosensitization at 41 degrees C. Changes in the rate of protein synthesis for combinations of nutritional deprivation and hyperthermia show a correlation with the cell survival data. Development of acute thermotolerance in L15D is accompanied by an increase in heat-shock protein synthesis relative to total protein. At 41 degrees C in L15D no heat-shock protein induction could be detected. Of the omitted substrates only glutamine can effectively abolish thermosensitization and the effects of L15D on protein and heat-shock protein synthesis depending on the condition of the cells, thermotolerant or non-thermotolerant, and to a different extent for the various proteins considered.

Adenosine Triphosphate↗
PubMedDate not supplied

Effects on the expression of heat shock proteins by step-down heating and hypothermia in rat hepatoma cells with a different degree of heat sensitivity.

Thermosensitization induced by pretreatment at supra- and subnormal temperatures, rate of protein synthesis and expression of the major heat shock proteins under such conditions was investigated in relation to intrinsic heat sensitivity of rat hepatoma cells, i.e. Reuber H35 and HTC. The high degree of heat susceptibility of H35 cells was reflected by a high degree of thermosensitization after pretreatment by heat (step-down heating) at temperatures of 42-44 degrees C for 30 min or cold for 16 h at temperatures ranging from 0 to 25 degrees C. Sensitization under step-down heating conditions was found to be paralleled by a delayed recovery of protein synthesis. Despite an increased relative rate, enhancement of the absolute rate of synthesis of the major heat shock proteins, HSP28, HSP60, HSP68, HSP70, HSP84 and HSP100, was less pronounced during step-down exposure. Comparable results were obtained during recovery of sensitized H35 cells at 37 degrees C after exposure to heat following pretreatment at 0 degrees C. Furthermore, clear differences in the regulation of the specific HSP synthesis, depending on the particular treatment protocol, were observed.

Animals↗