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PubMed1992

The effects of rubidium, caesium and quinine on 5-HT-mediated behaviour in rat and mouse--3. Quinine.

It has been shown that caesium, which shares properties with quinine as a K(+)-channel blocker, enhanced 5-HT-mediated behaviour in both rats and mice. It was therefore of interest to investigate the effects of quinine on 5-HT-mediated behaviour in the rat and mouse. Quinine, dose-dependently (ED50 = 5 mg/kg), produced the 5-HT behavioural syndrome in rats pre-treated with tranylcypromine (TCP) (15 mg/kg, i.p.). p-Chlorophenylalanine (i.p., 300 mg/kg x2) or (-)-propranolol (20 mg/kg, i.p.), pindolol (4 mg/kg, i.p.) and ritanserin (0.4 mg/kg, s.c.), all prevented the behavioural syndrome induced by quinine (72 mg/kg, i.p.) plus TCP. The administration of quinine (72 mg/kg, i.p.) enhanced the 5-HT syndrome elicited by p-chloramphetamine (4 mg/kg, i.p.) and the 5-HT agonists, 8-OH-DPAT (0.5 mg/kg, s.c.), 5-MeODMT (2 mg/kg, i.p.), DOI (8 mg/kg, s.c.) and quipazine (25 mg/kg, i.p.) in rats. Pretreatment with quinine also potentiated the 5-HT2-mediated head-twitch in the mouse but had no effect on the hypothermia in the mouse, induced by 8-OH-DPAT (0.5 mg/kg, s.c.). Quinine also enhanced the rate of synthesis of 5-HT in the brain of the rat. On the basis of these findings, together with those in the preceding two papers, it is suggested that the effects of rubidium, caesium and quinine, to enhance differentially various aspects of 5-HT function are mediated by actions on 5-HT-modulated K(+)-channels. This conclusion is also discussed in relation to the actions of lithium and electroconvulsive shock on 5-HT function in brain and the treatment of manic-depressive disease.

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

PubMed1989

Effects of the beta-isomer of hexachlorocyclohexane on estrogen-sensitive human mammary tumor cells.

The effects of the beta-isomer of hexachlorocyclohexane (beta-HCH) on the induction of the cytosolic progesterone receptor (PgRc), on the redistribution of the estrogen receptor (ER), and its affinity for ER were investigated in the estrogen-sensitive human mammary tumor cell line MCF-7. The effects of beta-HCH were compared to those of estradiol-17 beta (E2) and 2,4,6-trichlorophenol (TCP), a major urinary metabolite of beta-HCH in rats. beta-HCH in concentrations higher than 1 microM caused induction of PgRc whereas TCP was essentially without effect up to a cytotoxic concentration of 100 microM. Furthermore, beta-HCH (10 microM) caused redistribution of ER, i.e., decrease of cytosolic ER concentration and increase of nuclear ER concentration, in a way similar to E2. In contrast to this, beta-HCH up to a molar excess of 6 X 10(4) (concentration 30 microM) caused no significant displacement of [3H]E2 from ER indicating that beta-HCH has no substantial affinity for ER. It is concluded that beta-HCH has estrogenic properties which are at variance with the failure to demonstrate binding of beta-HCH to ER.

Animals↗

PubMed1991

Chlorpyrifos pharmacokinetics and metabolism following intravascular and dietary administration in channel catfish.

The pharmacokinetics and metabolism of a model organophosphorothioate, chlorpyrifos, was investigated in channel catfish (Ictalurus punctatus). Chlorpyrifos exhibited multicompartmental disposition after oral and intravascular administration, indicating slower distribution to peripheral storage tissues. The oral bioavailability of chlorpyrifos was 41%, substantially higher than in mammals. Muscle contained less than 5% of the oral dose, with an elimination half-life of about 3.3 days. Residues in the whole fish were greater than 95% chlorpyrifos, while excreta (bile and urine) primarily contained metabolites. The dephosphorylated metabolite, trichloropyridinol (TCP), was the major metabolite in the blood, while the glucuronide conjugate of TCP was the major metabolite in urine and bile. The toxic metabolite, chlorpyrifos oxon, was not detected in any samples of blood, tissues, or excreta. The metabolism of chlorpyrifos in catfish appeared similar to other species of fish and mammals. Extensive metabolism resulted in a low potential for chlorpyrifos to accumulate in catfish from dietary exposure.

Animals↗

PubMed1993

Phencyclidine-binding sites in mouse cerebral cortex during development and ageing: effects of inhibitory amino acids.

The binding of N-[1-(2-thienyl)cyclohexyl]-[3H]piperidine ([3H]TCP) to the phencyclidine-binding sites in the N-methyl-D-aspartate (NMDA) receptor complex-associated ion channel was characterized in cerebral cortical membranes from 3-day-old to 24-month-old mice. The binding was saturable, exhibiting only one binding component during the whole life-span studied. The maximal binding capacity Bmax, calculated per protein content, decreased during postnatal development until 3 months of age, remaining thereafter constant in ageing mice, thus indicating the greatest availability of phencyclidine-binding sites in the immature cerebral cortex. The binding constant KD increased during the first postnatal week, remained thereafter unchanged and increased again during the second year of life, indicating a decreased affinity of the receptor sites for the ligand. The general properties of the binding; potentiation by glutamate and NMDA, as well as by glycine in a strychnine-insensitive manner, prevailed during development and ageing, certain of these effects being however less pronounced in the immature brain. Taurine and beta-alanine stimulated TCP binding, acting probably at the glycine modulatory site. The actions of these inhibitory amino acids were weak and inconsistent when compared to that of glycine. Since NMDA receptors have been suggested to be involved in neuronal plasticity and learning and memory processes, these modifications in the properties of cortical phencyclidine-binding sites might be of importance in the regulation of excitatory amino acid functions during development and ageing.

Aging↗

PubMed1995

Differential effects of aging on binding sites of the activated NMDA receptor complex in mice.

The NMDA receptor site has been shown to be vulnerable to the effects of aging. Decreases in binding to the receptor site of up to 50% have been reported in aged animals. The present study was designed to quantitate and compare the effects of aging on multiple binding sites of the NMDA receptor complex in various brain regions. Autoradiography with [3H]glutamate, [3H]CPP, [3H]glycine, [3H]MK801 and [3H]TCP was performed on brain sections from 3, 10 and 28-30 month old C57B1/6 mice. The percent declines between 3 and 28-30 months of age in [3H]-glutamate (15-35% declines) and [3H]CPP (20-42% declines) binding were similar within most cortical regions and the caudate nucleus but [3H]glutamate binding showed less change (0-11% declines) than [3H]CPP (13-27% declines) in the occipital/temporal cortex and hippocampal regions. [3H]MK801 and [3H]TCP binding, stimulated by 10 microM glutamate, exhibited intermediate aging changes between the glycine and NMDA sites, both in percent decline (3-28% and 0-26%, respectively) and in the number of brain regions involved. [3H]Glycine binding, stimulated by 10 microM glutamate, showed no significant overall effect of age (declines ranged from 0-34%). [3H]CPP binding was significantly more affected than [3H]glycine binding in many regions. These results suggest that aging has heterogeneous effects on different sites on the NMDA receptor complex throughout the brain and on NMDA receptor agonist versus antagonist binding in selected brain regions.

Aging↗

PubMed1989

Role of the aromatic group in the inhibition of phencyclidine binding and dopamine uptake by PCP analogs.

Thirty-seven arylcyclohexylamines including phencyclidine (PCP) and derivatives, N[1-(2-thienyl)cyclohexyl]piperidine (TCP) and derivatives and N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine (BTCP) were assessed for their ability to inhibit [3H]PCP binding and [3H]dopamine ([3H]DA) synaptosomal uptake. Their pharmacological property (ataxia) was measured by means of the rotarod test. A very good correlation was observed between the inhibition of [3H]PCP binding and the [3H]DA uptake only for arylcyclohexylamines bearing an unmodified phenyl group. Conversely the comparison between the inhibition of [3H]PCP binding and the activity in the rotarod test shows a good correlation with arylcyclohexylamines having any aromatic group (phenyl, substituted phenyl and thienyl rings). This study outlined a new compound (BTCP) without ataxic effect, which is one of the more potent inhibitors of the [3H]DA uptake (IC50 = 8 nM) and which seems very specific since it has a low affinity for [3H]PCP receptors (IC50 = 6 microM). These data show that the aromatic group of the compounds leads to molecules that bind differently to the PCP receptor and to the DA uptake complex. They also suggest that the behavioral properties of arylcyclohexylamines revealed by the rotarod test occur essentially as a result of an interaction with the sites labeled with [3H]PCP and that TCP is more selective than PCP itself in this recognition.

Animals↗

PubMed1989

Phencyclidine/SKF-10,047 binding sites: evaluation of function.

Results of correlation analyses comparing rank-order affinities with rank-order potencies of (+)SKF-10,047, phencyclidine (PCP), and several PCP analogs support the involvement of [3H]-1-[1-(2-thienyl)cyclohexyl]piperidine binding sites (TCP sites) in mediating both the discriminative stimulus properties of PCP and production of 180 degrees perseveration in a 4-arm radial maze. For the same group of drugs, no significant relationship was found to exist between affinities at haloperidol-sensitive (+)[3H]SKF-10,047 binding sites (H-S-SKF sites) and potencies. Also, H-S-SKF sites were found to lack pharmacological selectivity and to be localized in the microsomal fraction of cells. It is concluded that TCP sites may represent receptors which mediate effects not only of PCP, but also of (+)SKF-10,047. In addition, the possibility that H-S-SKF sites may represent a type of membrane-bound enzyme is discussed.

Animals↗

PubMed1983

A diversified set of testicular cell proteins specified by genes within the mouse t complex.

We have conducted a comparative high-resolution, two-dimensional gel analysis of testicular cell proteins synthesized by inbred mice congenic for a series of t haplotypes on the 129/SvJ background. At least nine t haplotype-specific proteins can be identified within the 1000 most prominent proteins observed. Apparent allelic wild-type forms of six of these t complex proteins (TCPs) have also been identified, and evidence from cell-free translation experiments indicates that all of these are coded for directly by genes within the t complex. Eight of the mutant t-haplotype-specific proteins are expressed in an identical form by testicular cells carrying any one of the complete t haplotypes analyzed. The ninth protein is polymorphic among different t haplotypes, as well as among different inbred strains of mice. Partial t haplotypes were used to map the genes specifying the expression of each TCP protein to a subregion of the t complex. The accumulated data suggest a subset of TCP proteins that are most likely to be involved in t haplotype effects on germ cell differentiation and fertility.

Animals↗

PubMed1989

Calcium phosphate cements: action of setting regulators on the properties of the beta-tricalcium phosphate-monocalcium phosphate cements.

Various additives were tested as setting retarders of the beta-tricalcium phosphate-monocalcium phosphate monohydrate (beta-TCP-MCPM) cements. Calcium pyrophosphate (CPP), calcium sulphate dihydrate (CSD) and calcium sulphate hemihydrate (CSH) were found to increase the setting time from 30 s to about 10 min. Moreover, the use of CSH resulted in a marked increase of the final diametral strength of the cement, which could be raised from 1 MPa to about 3 MPa. The best results were obtained when CSH and CPP were added together to the cement, while the addition of CSD and CPP alone only retarded the setting, without improving the final strength. A particular cement composition (64 wt% beta-TCP, 16 wt% MCPM, 15 wt% CSH and 5 wt% CPP), selected for its optimum final strength, was aged in vitro for 8 d at 37 degrees C in saline solution (0.9 wt% NaCl in water). After a moderate decrease, the diametral strength of the specimen was found to level off at about 60% of its initial value (3.2 MPa), for ageing times beyond 1 d. This behaviour has been ascribed to the progressive dissolution of the CSD fraction of the hardened cement, compensated by the crystallization of further amounts of DCPD.

Bone Cements↗

PubMed1990

Behaviour of tricalcium phosphate and hydroxyapatite granules in sheep bone defects.

Granules of hydroxyapatite (HA) and tricalcium phosphate (TCP) were implanted in separate holes drilled in mandibular bone of sheep to check the bone growth and in vivo behaviour of the materials. The experiment was performed in three sheep, killed respectively at 4, 8, 12 month. Samples of bone with the materials were explanted, microradiographed and sectioned to evaluate the interface under optical and electron scanning electron microscope. The hole, left empty as a reference, showed no full repair; whereas 4 month after implantation the TCP granules induce total repair of the hole. HA granules crumbled and no new bone induction was seen even 12 month after implantation.

Animals↗

PubMed1992

Crystallographic changes in calcium phosphates during plasma-spraying.

Coating hydroxyapatite (HA) onto metal implant surfaces using the plasma-spraying technique has been investigated in several laboratories as a means of improving the mechanical properties of the bulk ceramic. This study describes crystallographic changes which can occur during the plasma-spraying of calcium phosphate powders. A precipitated calcium-deficient apatite and a high temperature near-stoichiometric HA were each sprayed onto metal substrate in an argon plasma using several hydrogen gas flow conditions at various temperatures. The surfaces were examined by X-ray diffraction and scanning electron microscopy. The plasma-sprayed products were identified as a mixture of calcium phosphates including HA, beta-tricalcium phosphate (beta-TCP) and calcium oxide. Stoichiometric HA when plasma-sprayed showed the least (5%) degradation. Since beta-TCP is more resorbable than HA in vivo, varying the HA/beta-TCP ratio on the plasma-sprayed surface may provide a method to control surface dissolution of the coating.

Biocompatible Materials↗

PubMed1993

Osseointegration of macroporous calcium phosphate ceramics having a different chemical composition.

Calcium phosphate macroporous ceramics are biocompatible for bone surgery. Their osseointegration is, however, sometimes very poor. To measure the effect of the calcium phosphate content of the ceramic on its osseointegration, macroporous ceramics, differing in their chemical composition, were implanted into sheep femurs. The ceramics were composed of different percentages of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP). All other characteristics were the same. Results were assessed histologically with image analysis and showed significant differences in the amount of bone formed at the contact of the different ceramics. Ceramics containing beta-TCP induced better osseointegration than pure HA ceramics.

Animals↗

PubMed1994

Evaluation of the osteogenic potential of biomaterials implanted in the palatal connective tissue of miniature pigs using undecalcified sections.

Calcium phosphate or calcium carbonate biomaterials are widely used as bone substitutes in periodontal surgery. This study evaluates the osteogenic potential of five different alloplastic biomaterials implanted in the connective tissue of the palatal papilla in miniature pigs. A porous hydroxyapatite (PHA), a dense hydroxyapatite (DHA), a semi-porous hydroxyapatite (SPHA), a tricalcium phosphate (TCP) and a calcium carbonate natural coral (NC) were implanted in a tunnel in the palatal papillae of seven miniature pigs. Undecalcified sections were examined histologically at 1, 2, 3, 4, 8, 12 and 24 wk intervals. Resorbable materials (TCP and NC) were totally resorbed by 24 wk. DHA, PHA and HA showed very limited resorption, although there were multinucleated giant cells in contact with PHA and SPHA. There was no histologically detectable bone formation in contact with or near any of the biomaterials tested. However, several particles of NC, and sometimes of PHA, were surrounded by a dense, mineralized matrix. It is concluded that none of these biomaterials, in their presently available forms, has any bone inducing capacity.

Animals↗

PubMed1994

Microstructural characterization of glass-reinforced hydroxyapatite composites.

The influence of phosphate-based glasses and a bioactive silica glass on the sintering mechanism of hydroxyapatite was studied over a wide range of temperatures. The composites were microstructurally characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Small additions of phosphate-based glasses proved to be beneficial to the sintering process and fully dense materials were obtained. A significant improvement in mechanical properties was achieved. beta-TCP and alpha-TCP were found in the microstructure depending on the sintering temperature. Additions of bioactive glass led to the development of calcium phosphate silicate.

Biocompatible Materials↗

PubMed1994

Histological and microradiographic evaluation of hydrated and hardened alpha-tricalcium phosphate/calcium phosphate dibasic mixtures.

Bone tissue response to pre-hardened alpha-tricalcium phosphate (alpha-TCP) and calcium phosphate dibasic (DCPD) mixture by hydration was studied histologically and microradiographically after implanting on the inferior aspect of the mandible in rabbits. In 1-month implants, new bone formation was observed along the surface of the material near the host bone, and connection of new and host bone through thin bone bridges was seen in some places. In 3-month implants, newly formed bone filled the greater part of the gap between material and host bone, and in 6-month implants, it surrounded almost all the surface of the material. New bone was in direct contact with the material in all implant periods. The bone response was essentially consistent with that to hydroxyapatite (HA). Resorption of the material was noticed in 3- and 6-month implants. It was concluded that pre-hardened alpha-TCP/DCPD mixture has good biocompatibility with bone tissue equal to HA and that it resorbs when implanted in rabbit. Further research should be performed to evaluate the material changes of resorption and formation of the white zone.

Animals↗

PubMed1994

Long-term in vivo study of plasma-sprayed coatings on titanium alloys of tetracalcium phosphate, hydroxyapatite and alpha-tricalcium phosphate.

In order to study the interaction of calcium phosphate coatings with bone tissue, coated titanium plugs of standard size were implanted in dog femora. The bone bonding and bone formation of hydroxyapatite, alpha-tricalcium phosphate (alpha-TCP) and tetracalcium phosphate plasma-sprayed coatings were evaluated by mechanical push-out tests and histological observations after 3, 5, 15 and 28 months of implantation. During this time all coating types degraded. alpha-TCP showed the most significant degradation after 3 months of implantation. Hydroxyapatite and tetracalcium phosphate showed significant signs of degradation after about 5 months of implantation. All coatings showed a small increase in bone bonding after 5 months of implantation. In general, all types of implants showed similar bone response, some bone contact and several remodelling lacunae along the surfaces after long-term implantation.

Alloys↗

PubMed1996

Sintering effects in a glass reinforced hydroxyapatite.

Glass was incorporated into hydroxyapatite (HA) to act as a sintering aid in order to improve the mechanical properties. The glass was added at 2 and 4 wt% and the powders compacted uniaxially. The compacts were sintered at a variety of temperatures (1200, 1250, 1300 and 1350 degrees C) and the effects of the glass addition and the firing temperature were studied to determine their effects on the sintering process. It was found that the glass promoted some phase changes, related to the amount of glass added to the composite. At 1200 and 1250 degrees C, some beta-tricalcium phosphate (TCP) was found with the residual being HA. However, at 1300 and 1350 degrees C, both beta- and alpha-TCP were formed. The 4 wt% addition, as expected, promoted higher levels of secondary phases in the composite. The flexural bend strength (FBS) showed high values and also significant differences dependent on the amount of glass added. A 2 wt% addition gave a gradual increase in FBS with temperature. With a 4 wt% addition there was an increase in FBS, but above 1300 degrees C there was a rapid decrease. These effects were mirrored in the linear shrinkage. Both the linear shrinkage and the FBS results were attributed to both the phase changes occurring and also change in grain size with increasing firing temperature.

Chemical Phenomena↗

PubMedDate not supplied

Rat brain PCP receptors: alterations in binding parameters following chronic administration of opiate agonists and antagonists.

Phencyclidine (PCP) is a widely abused drug of the arylcyclohexylamine class which is capable of producing symptoms of acute psychosis in man. PCP interacts with a specific CNS receptor, for which a putative endogenous peptide ligand has been identified. We have investigated whether PCP receptor binding parameters are modulated by activity in central opiate pathways. We have found that chronic administration of both an opiate agonist (etonitazene) and an opiate antagonist (naloxone) are able to decrease the affinity of the PCP receptor for TCP, a thienyl derivative of PCP. Furthermore, naloxone, but not etonitazene, resulted in a significant increase in the Bmax of TCP binding to the PCP receptor. These results suggest that neural activity mediated by CNS opioids systems is capable of affecting the binding parameters of the PCP receptor.

Animals↗