Biomedical subjects

P Clausing

Publications and source records attributed to P Clausing.

At least 19 recordsLinked to original sources

PubMed2001

Inhalation studies with the Göttingen minipig.

A method for inhalative exposure of minipigs to aerosols and gases has been developed. Minipigs are exposed via mask inhalation to the test substance using a computer-controlled exposure system that permits simultaneous exposure of groups of four animals in parallel to different controlled dose levels. We studied inhalation treatment of verapamil, a cardiovascular drug, and show good absorption and favorable pharmacokinetics when compared with iv drug application. The results shown in this study encourage inhalation studies with the Göttingen minipig.

Aerosols↗

PubMed1999

d-Fenfluramine produces neuronal degeneration in localized regions of the cortex, thalamus, and cerebellum of the rat.

d-Fenfluramine is a potent serotonin (5-HT) reuptake inhibitor/releaser and, until its recent recall, was prescribed as an anoretic agent. This study demonstrates that 10 mg/kg d-fenfluramine i.p., when administered to rats in a warm (27 degrees C) environment, produces neuronal degeneration within select brain regions. Degeneration was detected and localized using a recently developed fluorescent marker of neuronal degeneration, Fluoro-Jade. The most extensive cortical damage was in the anterior cingulate region. In the medial thalamus, degeneration was frequently seen within the intralaminar nuclei, and somewhat less frequently observed within the paraventricular nucleus, the mediodorsal nucleus, and the gelatinosis nucleus. Cerebellar damage occurred primarily in medial Purkinje cells and occasionally in granule cells or basket cells. Degeneration was not observed in either saline-injected control animals or in rats given even higher doses of 25 mg/kg d-fenfluramine but kept in a cooler environment (23 degrees C). The degeneration was clearly most prominent in animals with body temperatures of 41 degrees to 42 degrees C, but this degeneration was not seen in animals given saline that became extremely hyperthermic in a 37 degrees C environment. Behavioral signs such as tremors, myoclonus, rigidity, and splayed legs were seen in all animals with extensive neurodegeneration. The areas damaged by d-fenfluramine, when hyperthermia occurs, could play a role in the expression of the serotonin syndrome. Elevated extracellular 5-HT levels alone are probably not sufficient for neurotoxicity, and additional factors such as hyperthermia, regional specificity of 5-HT receptor subtypes, blood flow, and/or neuronal networks may be involved.

Animals↗

PubMed1999

Time course of brain temperature and caudate/putamen microdialysate levels of amphetamine and dopamine in rats after multiple doses of d-amphetamine.

Brain temperature monitoring and microdialysis were performed simultaneously in the caudate/putamen (CPu) of conscious, freely moving rats dosed with d-amphetamine (AMPH). The brain temperature was determined via a thermistor inserted through a microdialysis guide cannula located in the left CPu, while the microdialysis probe was positioned in the right CPu. The peak AMPH and dopamine (DA) levels were reached 40 to 60 min after dosing, while peak brain temperature was not achieved until 20 to 40 min thereafter in rats becoming moderately hyperthermic. Those rats becoming severely hyperthermic (temperatures above 41.0 degrees C) had microdialysate concentrations of AMPH and DA almost 2-fold higher than those with moderate hyperthermia after the second dose of 5 mg/kg AMPH. However, these peaks were not reached until 60 to 80 min after dosing. This was probably due, in part, to the longer half-life of AMPH in the severely hyperthermic group. The changes in brain temperature observed after exposure to neurotoxic doses of AMPH closely paralleled core body temperature changes previously reported during AMPH exposure. Temperature plays an important role in many types of neurotoxicity, and monitoring brain temperature during microdialysis studies can be done continuously, and with less chance of damage to the microdialysis equipment than most of the traditional methods used to measure core body temperature.

Amphetamine↗

PubMed1998

Fenfluramine and norfenfluramine levels in brain microdialysate, brain tissue and plasma of rats administered doses of d-fenfluramine known to deplete 5-hydroxytryptamine levels in brain.

The relationship between dose, frontal cortex (brain) microdialysate and brain tissue levels of fenfluramine (FEN) and norfenfluramine (NF), as well as the effect that these levels have on body temperature, was determined after systemic d-FEN. FEN and NF levels were monitored continuously in the microdialysate of adult male Sprague-Dawley rats dosed with 3 x 5 mg/kg s.c. (spaced 2 hr apart), 1 x 2 mg/kg s.c. or 1 x 10 mg/kg i.p. d-FEN (at ambient temperatures of either 23 degrees C or 27 degrees C). Drug concentrations in plasma and brain regions were also determined 1 hr after one or three doses of 5 mg/kg of d-FEN and 1 and 8 hr after 10 mg/kg d-FEN, and the levels of 5-hydroxytryptamine and 5-hydroxyindole acetic acid in the frontal cortex of FEN and controls were determined 4 days after dosing. Peak microdialysate FEN levels, occurring between 40 and 60 min after the first dose, were 0.24 +/- 0.07 microM after 2 mg/kg, 0.33 +/- 0.04 microM after 5 mg/kg and 1.65 microM after 10 mg/kg. After multiple doses of 5 mg/kg FEN the time-to-peak level was greater than 80 min with peaks of 0.68 +/- 0.04 microM after the second dose and 1.20 +/- 0.07 microM after the third dose. There was a positive correlation between combined (FEN + NF) peak levels in microdialysate and the increase in body temperature after 10 mg/kg d-FEN at 27 degrees C; however, the group mean and peak levels of FEN and NF in microdialysate were statistically the same at either 23 degrees C or 27 degrees C. The indole-depleting effect of d-FEN at 4 days after dosing was exacerbated at 27 degrees C when hyperthermia occurred. Thus, hyperthermia does not affect the pharmacokinetics of d-FEN but pharmacokinetics can influence the degree of hyperthermia in a 27 degrees C environment. Plasma levels, brain extracellular and brain levels of approximately 1 microM, 2.5 microM and 50 microM FEN (respectively), or greater, result from 5-hydroxytryptamine-depleting doses of 5 mg/kg s.c. FEN.

Animals↗

PubMed1998

Long-term effects of amphetamine neurotoxicity on tyrosine hydroxylase mRNA and protein in aged rats.

Four injections (intraperitoneal) of 3 mg/kg amphetamine (2 hr apart) produced pronounced hyperthermia and sustained decreases in dopamine levels and tyrosine hydroxylase (TH) protein levels in the striatum of 15-month-old male rats. A partial recovery of striatal dopamine levels was observed at 4 months after amphetamine. In contrast, TH mRNA and TH protein levels in the midbrain were unaffected at all time points tested up to 4 months after amphetamine treatment. The number of TH-immunopositive cells in the midbrain was also unchanged at 4 months after amphetamine, even though the number of TH-positive axons in the striatum remained dramatically decreased at this time point. Interestingly, TH-immunopositive cell bodies were observed 4 months after amphetamine in the lateral caudate/putamen, defined anteriorly by the genu of the corpus collosum and posteriorly by the junction of the anterior commissures; these striatal TH-positive cells were not observed in saline- or amphetamine-treated rats that did not become hyperthermic. In addition, low levels (orders of magnitude lower than that present in the midbrain) of TH mRNA were detected using reverse transcription-polymerase chain reaction in the striatum of these amphetamine-treated rats. Our results suggest that even though there is a partial recovery of striatal dopamine levels, which occurs within 4 months after amphetamine treatment, this recovery is not associated with increased TH gene expression in the midbrain. Furthermore, new TH-positive cells are generated in the striatum at this 4-month time point.

Aging↗

PubMed1997

Determination of D-fenfluramine, D-norfenfluramine and fluoxetine in plasma, brain tissue and brain microdialysate using high-performance liquid chromatography after precolumn derivatization with dansyl chloride.

A HPLC method is described for the simultaneous determination of D-fenfluramine (FEN), D-norfenfluramine (NF) and fluoxetine (FLX) using fluorometric detection after precolumn derivatization with dansyl-chloride. The method has limits of quantitation of 200 fmol for FEN and NF, 500 fmol for FLX in brain microdialysate, and 1 pmol for NF and FEN, and 2 pmol for FLX in plasma. Brain tissue standards were linear between 5 and 200 pmol/mg for all three compounds. The inter-assay variability (relative standard deviation) was 6.6%, 6.9% and 9.3% for FEN, 4.6%, 3.7% and 7.9% for NF and 10.4%, 4.9% and 12.2% for FLX, for brain microdialysate (2 pmol/microl), plasma (2 pmol/ microl) and brain tissue (50 pmol/mg), respectively. Intra-assay variability was always lower, typically several times lower than inter-assay variability. Extraction recovery was 108% and 48% for FEN, 105% and 78% for NF and 94% and 45% for FLX, in plasma (2 pmol/microl) and brain tissue (5 pmol/mg), respectively. Due to the stability of the dansyl-chloride derivatives this method is well suited for an autoinjector after manual derivatization with dansyl chloride at room temperature for 4 h.

Animals↗

PubMed1997

Differential effects of communal rearing and preweaning handling on open-field behavior and hot-plate latencies in mice.

On day 2 after delivery, dams of the DBA/1 mouse inbred strain (n = 20/group) with their litter were allocated to one of the following groups: NH21, nonhandling, housed 1 litter/cage, weaned on postnatal day (PND) 21;H21, handling, housed 1 litter/cage, weaned on PND 21; NH30, nonhandling, group-housed (5 litters/cage), weaned on PND 30; H30, handling, group-housed (5 litters/cage), weaned on PND 30. Two male pups of each litter were color marked on PND 2. From PND 8-21 they were removed from their cage, gently held in the experimenter's hand for 5 min/day. The two marked males of each litter were housed together after weaning, and tested in the open-field on PNDs 51-53, and one of each of these siblings was tested for hot-plate latencies on PND 54. Being raised in group-housing and weaned on PND 30 resulted in offspring exhibiting shorter latencies to initiate behavior and higher percentages of centerfield entries in the open field, hot-plate latencies, however, remained unaffected. Preweaning handling increased hot-plate latencies and the number of grooming episodes in the open field, and it decreased defecation, percent centerfield entries and open-field activity in general. It is concluded that the two forms of early experience have different effects on neurobehavioral endpoints 8 weeks after birth.

Animals↗

PubMed1996

Methamphetamine-stimulated striatal dopamine release declines rapidly over time following microdialysis probe insertion.

To investigate changes in striatal dopamine release over a series of brief methamphetamine (METH) exposures, METH was pulsed three times at 2-h intervals, with the first exposure occurring 2 h after microdialysis probe insertion. Whether METH was administered directly into the striatum via the microdialysate (20 microM of METH for 10 min), or via peripheral intraperitoneal (i.p.) injection (1 mg/kg METH, i.p.), the dopamine (DA) peak elicited by the third METH exposure was only 50% as large as that elicited by the first exposure, 4 h earlier. This decline in the magnitude of METH-induced DA release probably continued over at least 24 h, since the magnitude of a single peak 26 h after probe implantation was only one-seventh of that at 2 h. This reduction in the response to METH was a function of time post-probe insertion, and not of prior METH exposure. Thus, peak size was the same at 6 h post-implantation in animals which received two prior METH pulses or no prior METH pulses, and in both cases this 6-h peak was substantially lower than that at 2 h post-implantation. Circadian influences were also excluded as a factor, because size of the initial METH-induced DA peak did not vary as a function of time of probe implantation. It is concluded that METH-stimulated striatal DA release declines rapidly over time post-probe insertion. When METH exposures occur repeatedly at short intervals, this decline can mimic, but is not caused by, desensitization or depletion in response to prior METH exposure.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1996

Parenterally administered 3-nitropropionic acid and amphetamine can combine to produce damage to terminals and cell bodies in the striatum.

The combined effects of amphetamine (AMPH) and 3-nitropropionic acid (3-NPA) were investigated to determine how the energy depletion proposed to be produced by AMPH interacts with an inhibitor of mitochondrial respiration to produce striatal neurotoxicity. Neither two doses (2 h apart) of 3.75 mg/kg AMPH alone nor a single dose of 30 mg/kg 3-NPA i.p. produced neurotoxicity in the striatum or lowered striatal dopamine content in rat. Administration of 40 mg/kg of 3-NPA alone almost invariably produced either lethality or did not produce neurotoxicity in the striatum of surviving animals. However, 30 mg/kg of 3-NPA administered along with 2 doses of 3.75 mg/kg AMPH to 47 animals produced striatal damage in the 31 survivors with 15 of the surviving rats showing muscle rigidity/catatonia for several days after dosing, along with decreased food consumption. Thirteen of these 15 rats showed degeneration of axons and cell bodies in the medial caudate-putamen with minimal damage to the globus pallidus. However, two rats exhibited hindlimb paralysis and signs of axonal and neuronal soma degeneration in the thalamus and cerebellar nuclei as well as striatum. Sixteen of the rats given both AMPH and 3-NPA exhibited only torpidity and loss of muscle tone 1-3 h after dosing. Such rats showed no signs of neuronal cell degeneration in the striatum, but did show significant dopamine depletions (60% of control) and reductions in tyrosine hydroxylase immunoreactivity at 14 days postexposure. The mitochondrial dysfunction produced by 3-NPA combined with activation of neuronal pathways by AMPH may have predisposed terminals, axons and cell bodies in striatum to degeneration.

Amphetamine↗

PubMed1996

Central and peripheral neurochemical alterations and immune effects of prenatal ethanol exposure in rats.

In contrast to the well known effects of prenatal ethanol exposure on the central nervous system, data about its peripheral effects are scarce. Here, Sprague Dawley rats were fed a liquid diet (gestational days 0-20) containing 36% ethanol-derived calories (EDCs, group H) or were pair-fed with 18% EDCs (group L) or 0% EDCs (group C). On postnatal day 20, one male and one female from each of 10 litters per group were killed. Norepinephrine (NE) was analyzed in the frontal cortex, spleen and thymus, and dopamine, 5-hydroxytryptamine (serotonin, 5-HT) and their metabolites 3,4-dihydroxyphenylacetic acid, homevanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were analyzed in the striatum by high-performance liquid chromatography with electrochemical detection. Lymphocyte subpopulations in the spleen and thymus were also assessed in half of these litters. Significant decreases in splenic NE concentration were seen in both sexes of group H (males 27%, females 28%). Decreases in striatal 5-HT and 5-HIAA of group H subjects appeared to be sex specific (only females were significantly affected: 23% decrease in 5-HT, 37% decrease in 5-HIAA). Pronounced, dose-dependent reductions in T cell percentages were observed in both the thymus and spleen. Splenic CD8+ and CD4+ cell percentages were positively correlated with the splenic NE concentrations. It is concluded that the decreases seen in splenic T cell percentages subsequent to prenatal ethanol exposure may be caused, at least partially, by impaired noradrenergic control of this organ.

Animals↗

PubMed1996

Individual differences in dopamine release but not rotational behavior correlate with extracellular amphetamine levels in caudate putamen in unlesioned rats.

It has been postulated that differences in pharmacokinetics do not contribute to the well-known individual variability in response to amphetamine (AMPH), but this is yet to be investigated thoroughly. Therefore, rotational behavior of outbred rats (Sprague-Dawley, 4 months old) was recorded during microdialysis sessions and striatal microdialysate was analyzed concomitantly for AMPH and dopamine concentrations after a single injection of 2.5 mg/kg AMPH SC. Three hours later these rats received three doses of 5 mg/kg AMPH SC (spaced 2 h apart) and their brain temperature was recorded every 20 min. The most important findings were: 1) the increase in extracellular dopamine was highly correlated with the corresponding peak AMPH levels in the microdialysate; 2) the peak dopamine level in response to 2.5 mg/kg AMPH was predictive of the hyperthermic response observed during 3 x 5 mg/kg AMPH and 3) high versus low rotators differed neither in their AMPH nor in their dopamine extracellular striatal concentrations.

Amphetamine↗

PubMed1995

Nitric oxide regulation of methamphetamine-induced dopamine release in caudate/putamen.

A possible role for NO modulation of dopamine (DA) release in the caudate/putamen (CPU) during methamphetamine (METH) exposure was investigated using in vivo microdialysis in rats. Inclusion of the nitric oxide synthase (NOS) inhibitors NG-nitro-L-arginine (NOARG), NG-nitro-L-arginine methyl ester (L-NAME) or D-NAME (less potent inhibitor) in the microdialysis buffer prior to METH minimally affected basal levels of DA, DOPAC or HVA in CPU microdialysate. However, L-NAME and NOARG produced concentration-dependent decreases of up to 64% (100 microM) in CPU DA levels in microdialysate during exposure to four doses of METH (5 mg/kg i.p./2 h), with lesser effects on DOPAC or HVA. Reversal of the NOARG inhibition was produced by inclusion of 500 microM of either L-arginine or L-citrulline in the microdialysate. D-NAME (100 microM) minimally affected levels of DA or metabolites. Paradoxically, inclusion of from 20 to 2 microM of the NOx generators isosorbide dinitrate (ISON) or sodium nitroprusside (SNP) in the microdialysis buffer decreased DA and DOPAC levels in microdialysate during METH exposure. This paradox might result from the concentrations of NOx produced by SNP or ISON being great and not regionally specific resulting in inhibition of DA release and/or synthesis while the NO generated endogenously during METH exposure may have localized and site-specific actions. Alternatively, NOx may inhibit NOS or other enzymes in the NO synthesis pathway, thereby reducing levels of an intermediate (other than NO) which potentiates DA release. In their entirety, our results indicate that NO generation in the CPU may augment the release of DA during METH exposure.

Animals↗

PubMed1995

Determination of d-amphetamine in biological samples using high-performance liquid chromatography after precolumn derivatization with o-phthaldialdehyde and 3-mercaptopropionic acid.

An HPLC method is described for the determination of amphetamine using fluorometric detection after derivatization with o-phthaldialdehyde and 3-mercaptopropionic acid. This procedure is more sensitive (detection limit 370 fmol in microdialysate buffer standards, 1.5 pmol in extracted plasma and tissue samples) than most of the previous methods described for the determination of amphetamine with HPLC-fluorescence detection. Due to the stability of the derivative it is also suitable for autosampling after manual derivatization. Investigators currently using o-phthaldialdehyde derivatization and fluorometric detection for amino acid determination should be able to rapidly implement this method.

3-Mercaptopropionic Acid↗

PubMed1995

Amphetamine levels in brain microdialysate, caudate/putamen, substantia nigra and plasma after dosage that produces either behavioral or neurotoxic effects.

Extracellular levels of d-amphetamine (AMPH) in caudate/putamen were determined using microdialysis and HPLC quantitation after s.c. doses that produced increased motor activity (1 mg/kg), stereotypic behavior (2.5 mg/kg) or dopamine depletion in the caudate/putamen (4 x 5 mg/kg). In 6-mo-old rats exposed to neurotoxic doses of AMPH sulfate (4 x 5 mg/kg in a 23 degrees C environment), extracellular caudate/putamen AMPH rose to levels of 7.9 +/- 0.9 microM after the first dose and peaked at 15.1 +/- 2.5 microM after the third dose with no further increases after the fourth dose. After one or three doses of 5 mg/kg, peak plasma and tissue levels of AMPH were 1.7 +/- 0.2 and 2.9 +/- 0.3 microM in plasma, 36 +/- 6 and 73 +/- 10 in substantia nigra and 25 +/- 4 and 50 +/- 8 in caudate/putamen, respectively. Caudate/putamen extracellular AMPH levels were about three times higher (in either 6- or 12-mo-old rats) after 4 x 15 mg/kg in a 10 degrees C environment and tissue levels in caudate/putamen and substantia nigra were three to five times higher after three doses of AMPH. However, these higher levels did not produce dopamine depletion in the caudate/putamen, while the lower doses (4 x 5 mg/kg) given at 23 degrees C did. Estimated caudate/putamen extracellular AMPH levels of 2.5 to 5 microM after single doses (1 and 2.5 mg/kg) that caused hyperactivity and stereotypic behavior are compatible with the 2 to 10 microM AMPH concentrations reported to be necessary to produce pronounced dopamine release in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Social isolation modifies the response of mice to experimental Mengo virus infection.

To investigate the effects of social isolation on host resistance male mice were housed either individually (IH) or in groups of four or five (GH). All animals were infected with MengoM,L virus. Incubation time (INCUB), duration of illness (ILL), death rate (DR), histopathological changes, and serum corticosterone levels (CORT) were recorded. First, the effect of IH starting 4 days prior to infection was studied in 5 different inbred strains. Next, the effect of different IH length was examined, and the role of T-cells was investigated by comparing euthymic (+/+) and athymic (nu/nu) NMRI mice. Finally, the effects of the infection on CORT in IH and GH mice were compared in C57BL/6 mice. The major findings were: 1. IH significantly increased ILL in all but the DBA/2 strain, whereas DR was not affected except in C57BL/6. 2. Longer IH (starting 35 [DBA/2] or 10 [NMRI] days prior to virus inoculation) significantly shortened INCUB and prolonged ILL, but IH starting on the day of virus inoculation [DBA/2] significantly prolonged INCUB and shortened ILL. 3. NMRI nude mice exhibited an unaltered DR accompanied by a tremendously prolonged INCUB. 4. Investigations in C57BL/6 mice revealed a significant rise of CORT after infection. This increase was higher in IH compared to GH mice. It is suggested that IH attenuates T-cell mediated inflammatory processes and/or increases macrophage activation, which in turn results in a prolonged course of the disease.

Animals↗

PubMed1992

Cholinergic and adrenergic drugs affect delayed type hypersensitivity in C57BL/6 mice.

The present study examined the influence of systemic administration of neuroactive drugs on delayed-type hypersensitivity (DTH) in C57BL/6 mice. The cholinergic agonist nicotine and the acetylcholinesterase inhibitor physostigmine decreased DTH, whereas the alpha-adrenergic agonist clonidine stimulated DTH. In contrast isoprenaline, a specific beta-adrenergic agonist suppressed DTH. It is concluded from these observations that the autonomic nervous system modulates those processes governing DTH. It seems that the alpha-adrenergic subsystem stimulates, whereas the beta-adrenergic subsystem and the parasympathicus inhibit DTH.

Animals↗

PubMed1991

Diurnal variation of cytochrome P-450 dependent parameters after administration of the phenoxyacid herbicide dichlorprop to rats.

The circadian rhythm of ethylmorphine N-demethylase (ND) and hexobarbital sleeping time (HBS) was studied in noninduced and dichlorophenoxy propionic acid (DP) induced adult male rats. DP was gavaged (40 mg/kg bw) at 1.00, 7.00, 13.00 or 19.00 hr. After 21 days the above mentioned parameters were determined corresponding to the time point of DP administration. ND showed a biphasic oscillation (peak activities at 1.00 and 13.00 hr), whereas HBS was significantly shortened only at 1.00 hr. The effects of DP--ND-induction and HBS-shortening--were significant only, when the circadian phase of these parameters was low (i.e. at 7.00 and 19.00 hr for ND and at 7.00 hr for HBS). Consequently, attention should be paid not only to circadian rhythms of the cytochrome P-450 system per se but also to circadian alterations of the inducibility of this system.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1990

Estimated soil ingestion by children.

The amount of soil ingested by young children was estimated by measuring the titanium, aluminum, and acid-insoluble residue in soil and feces. As intake of each of these tracers is also possible from sources other than soil ingestion, the amount of soil ingested was estimated to be not higher than the lowest of the three separate estimates. This estimate, the limiting tracer method (LTM) value, was then corrected for the similarly calculated mean LTM value for a group of hospitalized children without access to soil and dust. The study groups included children in three different environmental situations: day-care centers, campgrounds, and hospitals. The day-care center groups were sampled twice. From these groups, 162 children produced usable feces samples during both sampling periods. The camping groups and the hospitalized (control) group were sampled once. For the day-care center groups, the estimated geometric mean soil intake varied from 0 to 90 mg/day and for the camping groups these estimates ranged from 30 to 200 mg/day (in dry weight). Using estimates of the "true" between-child GSD values, the 90th percentile of the estimated soil intakes was shown to be typically 40-100 mg/day higher than the geometric means of these estimates. In the day-care center groups few correlations with the geometric mean LTM values were found for variables concerning living conditions, mouthing behavior, playing habits, etc. A strong correlation was found with weather. During dry weather the younger children especially showed higher LTM values. In the camping group the weather also influenced the mean LTM value only in the younger age groups. Analysis of variance showed that a single LTM value of a child has a low predictive value with regard to the LTM value of the next few days or that of a few months later. Therefore it seems reasonable to use group statistics as estimates of soil ingestion in health risk assessments of soil pollution incidents.

Aluminum↗