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PubMed1983

Persistence of tetrachlorophenol and pentachlorophenol in exposed woodworkers.

The decline in urinary concentrations of pentachlorophenol (PCP) and 2,3,4,6-tetrachlorophenol (TCP) were observed for a group of woodworkers chronically exposed to Permatox 100 (3% PCP, 21% TCP) during a 16 day vacation and plant shutdown. The group was monitored annually for two years, with sampling occurring on the last working day prior to shutdown and on the first day after the shutdown. Among those workers with the highest pre-shutdown levels, uniform TCP reductions of 90 +/- 6% were observed, indicating elimination rates similar to those reported for PCP in a single dose human exposure study. Four workers were sampled on alternate days during the shutdown in the second year. Of these, two workers had significant pre-shutdown levels, and showed declines in urine TCP levels over this period consistent with simple one-compartment first order decay. The possible effect of environmental PCP exposure on observed biological decay rates when occupational PCP exposures are low was indicated by the wide variation in urinary PCP reduction and slight decreases or actual increases observed over the shutdown period.

Chlorophenols↗

PubMed1983

Monoamine oxidase inhibition and furazolidone-induced cardiomyopathy in turkey poults.

Furazolidone (FZ), a potent inhibitor of monoamine oxidase (MAO), fed at concentrations of 700 ppm to turkey poults 2 through 5 weeks of age, produces cardiomyopathy and cardiomegaly. To determine the role of MAO inhibition in FZ-induced cardiomyopathy, the effects of FZ were compared with those of a chemically different MAO inhibitor, tranylcypromine (TCP), and a chemically similar non-MAO inhibitor, nitrofurazone (NFZ). At 14 days of age, poults were divided randomly into four groups. Control poults were fed a standard turkey starter ration, and poults in the experimental groups were fed the standard ration that included one of the following drugs at the given concentrations: 700 ppm FZ, 350 ppm NFZ, or 50 ppm TCP. Activity of MAO was assayed in liver and kidney homogenates from poults chosen at random at 14, 17, 21, 28, and 35 days of age in one trial and on heart homogenates at 14, 15, 17, 19, and 28 days of age in another trial. Development of cardiomyopathy was assessed using an electrocardiographic (ECG) technique and substantiated with necropsy examination. Inhibition of MAO was observed only in the heart in FZ-fed poults, only in the kidney in NFZ-fed poults, and in all three tissues studied in TCP-fed poults. Under the conditions of this study, an increase in the incidence of cardiomyopathy, based on ECG data and necropsy results, occurred only in the FZ-fed group. The inability of the potent MAO inhibitor, TCP, to produce cardiomyopathy in this study supports the conclusion that the primary mechanism of FZ-induced cardiomyopathy in turkey poults is probably not due to MAO inhibition.

Animals↗

PubMed2002

Adjunctive use of ultraporous beta-tricalcium phosphate bone void filler in spinal arthrodesis.

Spinal fusion is one of the most common clinical indications for bone grafting. However, synthetic bone substitutes are needed to ameliorate limited availability, donor site morbidity, and potential disease transmission concerns associated with autograft and allograft. One new synthetic bone substitute, Vitoss (Orthovita, Malvern, Pa), is an ultraporous formulation of beta-tricalcium phosphate (beta-TCP). This study examines 50 patients who received ultraporous beta-TCP bone void filler as an adjunct to autogenous bone graft while undergoing spinal fusion procedures. All patients underwent decompressive laminectomy with bilateral posterolateral intertransverse fusion (PLITF) using bone graft mixed with ultraporous beta-TCP, with and without instrumentation. Some patients also underwent posterior lumbar interbody fusion (PLIF) using cages and bone graft. Thirty-two patients were studied for at least 5-7 months postoperatively. Of these patients, 100% demonstrated good consolidation on follow-up radiographs. The use of iliac crest bone graft (ICBG) was avoided entirely in 7 (14%) of the 50 patients, and 30% less ICBG volume was required on average in others. Only 3 patients (7%) had donor site-associated pain. Controlled studies are being conducted to support the clinical impression that ultraporous beta-TCP used as a bone void filler in spinal arthrodesis facilitates bone healing at both the spinal and donor operative sites, and contributes to less overall morbidity.

Adult↗

PubMed2002

Use of an advanced formulation of beta-tricalcium phosphate as a bone extender in interbody lumbar fusion.

Despite numerous advances in the development of bone graft substitutes over the past 20 years, iliac crest autograft remains the gold standard for lumbar spinal fusion. However, donor site morbidity associated with the harvesting of iliac crest autograft remains problematic. Acute and chronic pain, prolonged operative time, bleeding, infection, deformity, and nerve and vascular injury still produce significant postoperative morbidity, even in the presence of careful surgical technique. Although allograft circumvents donor site morbidity, the growing number of spinal fusions performed in the United States and worldwide is creating a shortage of cadaver bone acceptable for use. Additionally, the extensive processing and storage of allograft is expensive. Synthetic materials, such as beta-tricalcium phosphate (beta-TCP), have been developed as alternatives to both autograft and allograft. A novel formulation of ultraporous beta-TCP (Vitoss, Orthovita, Malvern, Pa) offers interconnected microporosity, providing it with good wicking and hydrophilic properties. These properties allow the migration of nutrients, growth factors, and osteogenic cells into the ultraporous beta-TCP scaffold, thereby promoting new bone growth and concurrent scaffold resorption. This study presents a retrospective review of 7 patients who underwent anterior (ALIF) or posterior (PLIF) interbody fusion at 12 levels with a 3- to 6-month follow-up. At the patients' last radiographic examination, all 12 levels were solidly fused with interbody grafting material consisting only of allograft plus a combination of ultraporous beta-TCP and venous blood as an extender. Additionally, all 7 patients had segmental pedicle-screw fixation.

Adult↗

PubMed1998

Development of calcium phosphate cement for rapid crystallization to apatite.

The purpose of this study was to develop an alpha-tricalcium phosphate (alpha-TCP) cement which transforms to hydroxyapatite (HAP) in a relatively short period. We used calcium and phosphate solutions as the liquid phase for the alpha-TCP cement. The alpha-TCP powder was first mixed with CaCl2 solution, and then mixed with NaH2PO4 or Na2HPO3 solution for a total powder/liquid ratio of 1.8. The setting time became shorter with the increase in the concentration of calcium and phosphate solutions, reaching 5 min, whereas the setting time was longer than 30 min when distilled water was used as the liquid phase. X-ray diffraction analysis revealed that the cement was mostly transformed to HAP within 24 h when kept in an incubator. We concluded that alpha-TCP should be mixed with calcium and phosphate solutions since this results in a moderate setting time and fast transformation to HAP even if the method of mixing becomes a little complex.

Calcium Phosphates↗

PubMed2006

Effects of different sizes of beta-tricalcium phosphate particles on bone augmentation within a titanium cap in rabbit calvarium.

This study evaluated the effects of different sizes of beta-TCP particles on bone augmentation within a titanium cap. In 20 rabbits, the calvarium was exposed and a circular groove was prepared. After marrow penetration, a standardized hemispherical titanium cap was placed in the circular grove. The cap was filled with small-sized (100-250 microm) or medium-sized (250-500 microm) beta-TCP particles for the experimental site and without beta-TCP for the control site. After one and three months of healing, the animals were euthanized and examined histologically. There was a statistically significant difference in the amount of mineralized bone generated between the experimental and control groups in the three-month specimens. Furthermore, the medium-sized particles showed significantly more mineralized bone than did the small-sized particles. Based on these findings, we suggested that beta-TCP might be effective for bone formation and that medium-sized particles are more useful than small-sized particles in bone maturation.

Animals↗

PubMed2006

Detection of biofilm formation among the clinical isolates of Staphylococci: an evaluation of three different screening methods.

PURPOSE: The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. METHODS: For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. RESULTS: Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. CONCLUSION: The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices.

Agar↗

PubMed2006

Guided bone regeneration with beta-tricalcium phosphate and poly L-lactide-co-glycolide-co-epsilon-caprolactone membrane in partial defects of canine humerus.

This study was performed to evaluate the effect of betatricalcium phosphate and poly L-lactide-co-glycolide-coepsilon- caprolactone (TCP/PLGC) membrane in the repair of partial bone defects in canine proximal humerus. Three adult mixed-breed dogs were used during the experimental period. The length of the defect was quarter of the full length of humerus, and width of the defect was quarter of middle diameter of the lateral aspect of humerus. The humeri of each dog were divided into treatment (TCP/ PLGC) and control groups. The defect was covered with TCP/PLGC membrane in treatment group. To evaluate regeneration of the bone, computerized tomography (CT) and histopathologic examination were performed. The radiopaque lines were appeared at the original defect sites in TCP/PLGC group but below the original site in control at 4th week. Radiopacity and thickness of the defect sites, and radiopaque lines were more increased at 8th week than those of 4th week. Histopathologic findings revealed fibrous connective tissue migration into the defect and the migration inhibited the structure of new cortex to be placed in the original level in control whereas new cortex growth was found in the level of original line in TCP/ PLGC group. However, the new cortical bone in the TCP/ PLGC group was thinner and less organized than the adjacent intact cortex, and the amount of new cancellous bones were also scanty. The result suggested that TCP/ PLGC membrane is a good guided bone regeneration material to restore the original morphology of humerus in partial defect.

Absorbable Implants↗

PubMed2000

[Study on regeneration of mandibular bone with bioabsorbable organic/inorganic composite membrane].

Guided bone regeneration (GBR) has attracted much attention as a means to treat bone defects and congenital malformation. However, presently available materials are not ideal and further improvements are necessary. Hence we have been developing a novel bioabsorbable composite material beta-TCP/CPLA for the GBR technique. The polymeric matrix is a copolymer of poly-L-lactide acid and fatty polyester (CPLA) that is biodegradable by hydrolysis, and the ceramic filler is beta-tricalcium phosphate (beta-TCP) that is bioabsorbable and has good osteoconductivity. The materials were evaluated by in vivo and in vitro experiments. Furthermore, animal experiments with mandibular bones defects in dogs were carried out. Good bone regeneration was observed in the case of the treatment with beta-TCP/CPLA membrane whereas almost no bone regenerated in the cases without the membrane. beta-TCP/CPLA membranes were suggested to have promising properties for bone defect treatment.

Absorbable Implants↗

PubMedDate not supplied

Reference values of urinary 3,5,6-trichloro-2-pyridinol in the Italian population--validation of analytical method and preliminary results (multicentric study).

The interlaboratory validation of analytical procedures for the assay of urinary 3,5,6-trichloro-2-pyridinol (TCP) in the general Italian population is reported. The determinations were performed by high-resolution gas chromatography (HRGS) with electron capture detection and HRGS with mass spectrometry (MS) in 2 laboratories. The urine samples were from 42 participants from 3 regions of Italy. The results were evaluated by interlaboratory quality control. Urinary TCP concentrations were above the detection limit (1.2 micrograms/L) in 88% of the population, with a mean detectable concentration [GM (GSD)] of 2.8 (1.9) micrograms/g creatinine (creat). (GM, geometric mean; GSD, geometric standard deviation.) The Mann-Whitney U test showed that wine consumption was a statistically significant variable (p < 0.05) for urinary concentrations of TCP. Analysis of variance of the logarithm of urinary TCP versus wine consumption and diet showed a statistically significant fit. The model used explained 30% of the total variance: wine consumption and diet accounted for 37 and 17% respectively of the explained variance.

Adult↗

PubMed1999

Organophosphate-induced delayed neurotoxicity of triarylphosphates.

This paper reviews the characteristics of organophosphate-induced delayed neurotoxicity, its mechanism, lesions, species sensitivities and structure activity-relationships as they relate to the class of compounds known as triaryl phosphates. The triaryl phosphates have been widely used in commerce for over thirty years as flame retardants in fluids and plastics. Concern has been raised regarding their potential to cause organophosphate-induced delayed neurotoxicity (OPIDN), due to structural similarities to the potent neurotoxicant, tri-ortho cresyl phosphate (TOCP). Based on research on many pure isomers, Johnson (1975a, 1975b) found that certain structural features are required for a triaryl phosphate to react with the enzyme, neuropathy target enzyme (NTE), in a manner which induces OPIDN. Results of acute hen OPIDN studies, the experimental model of choice, support his findings as regards the structure-activity relationships for commercial triaryl phosphates. Thus, standard acute hen OPIDN studies on triphenyl phosphate and butylated triaryl phosphates fail to demonstrate a potential to elicit OPIDN by these products after a single dose. Studies on the mixed isopropyl phenyl phosphates indicate that, while some are neurotoxic, they are much less potent than tricresyl phosphate (TCP) and TOCP in the induction of OPIDN. Most commercial isopropylated triaryl phosphates lacked the potential to induce acute OPIDN using a limit dose of 2000 mg/kg. Although in early studies these compounds appeared to be neurotoxic, they were generally tested at excessively high doses, often exceeding 10,000 mg/kg in acute hen OPIDN studies. In contrast to the isopropylated and butylated triaryl phosphate products, TCP, and especially its ortho substituted isomer, TOCP, were found to be neurotoxic in both acute and subchronic hen OPIDN studies. Recent advances in the synthesis of commercial TCP products have resulted in products with reduced neurotoxic potential (McCormick et al, 1993). As an example, when 3% TCP in aviation oil was dosed acutely at 5000 mg/kg, or for 90 days at 1000 mg/kg/day, no delayed neurotoxicity was noted (Daughtrey et al., 1990, 1996). These data are indicative of the safety of these aviation lubricants at use levels currently employed.

Animals↗

PubMed1999

Biochemical markers evaluation of RAW transformed cells during treatment with various biomaterials.

Upon introduction into the human body, biomaterials initially trigger a foreign-body inflammatory response. Furthermore, the wear debris associated with such materials as those used for orthopedic implants, artificial heart valves, and dental implants can cause the body to mount an inflammatory response. This involves the production of phagocytic macrophages that ingest the foreign material while simultaneously producing cytokines that serve as chemotactic agents for an amplified immune response. Currently titanium (Ti), polyethylene (PE), tricalcium phosphate (TCP) and hydroxyapatite (HA) are widely used as biomaterials in medical implants, and particle size is an important factor in the development of orthopedic, dental, and medical implants. The objective of this study was to investigate the effect of various biomaterials (Ti, mixed particle size polyethylene (MPE), ultra high molecular weight polyethylene (UHMWPE), mixed particle size TCP (MTCP), < 0.38 micron TCP (S-TCP), and hydroxyapatite (HA)) on the inflammatory reactions expressed by transformed RAW macrophages. RAW transformed monocytes were obtained from the American Cell Culture Line, (Rockville, MD). The cells were allowed to incubate in contact with the materials for intervals of 24, 48, and 72 hours. Biochemical tests and morphological evaluations were performed after each time point, including screening for cell number, cell protein levels, supernatant protein levels, lactate dehydrogenase (LDH), Maliondialdehyde (MDA), catalase by following standard lab protocols.

Biocompatible Materials↗

PubMed1999

Bioceramics surface modification by means of osteoclasts in culture.

The specific objectives of this study was: (I) to investigate the effect of various biomedical ceramics such as tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum-calcium-phosphorous oxide (ALCAP) on the adherence and viability of mice osteoclasts (OT) in vitro, and (II) to evaluate the role of OT that might have on the surfaces of such bioceramics. The OT cells were isolated from adult male mice and seeded at a density of 5 x 10(5) cells/well according to standard laboratory procedures. Cells were plated in each micrometer-well pretreated with ceramic capsules (HA, TCP and ALCAP) and buffered control. At the end of 1, 2, 3 and 5 days, the viability and cell number of OT were determined using an established assay. Cell number was determined in control wells with known number of cells, and a standard curve was generated by plotting absorbency units versus cell number. Biochemical analysis was performed on the aliquots obtained from the experimental and control wells at the end of each phase of the investigation. The data from this experiment suggest that: (I) OT are capable of adhering to the surface of HA, TCP and ALCAP in an in vitro environment for over a 5-day period. (II) Long-term incubation of ceramic capsules with OT revealed that the cells experienced gradual disassociation phenomenon with a greater numbers of cell detachments seen in the ALCAP contained wells. (III) SEM analysis of representative capsules demonstrated that there was an increase in the number of micro/macropores on the surface of the materials after contacting a cellular environment. This observation suggest that the material surface has been modified (TCP > HA = ALCAP). Information obtained from this study provided new insights on the interrelationship between bioceramics and the possible OT response during chronic inflammation at the site of implantation.

Aluminum Compounds↗

PubMed2001

[Two-cusp plasty using a pedicled auto pericardial patch for the right ventricular outflow tract in complete repair of tetralogy of Fallot].

BACKGROUND: Pulmonary stenosis (PS) and regurgitation (PR) are major concerns late after transannular patching for tetralogy of Fallot (TOF). In this study, we reviewed the TOF patients undergoing transannular patching to reveal whether the valvuloplasty technique (two cusp plasty) improved long-term results. We also reviewed potential for grow of the pedicled autopericardial patch. METHODS AND RESULTS: Since 1977, 151 patients underwent corrective surgery for TOF. Transannular patching was required in 58 (38.4%). PS and PR in the postoperative long-term period of these 59 cases were reviewed. 25 patients had the standard transannular patching (S-TAP), and 33 had two-cusp plasty (TCP). Pedicled autologous pericardial patch were used in 9 patients of TCP. Actuarial freedom from PS at 7 years was 70.8 +/- 9.2% in S-TAP and 79.2 +/- 8.3% in TCP, and there was no significant difference. Incidence of severe PR was significantly higher in S-TAP (7/24) than TCP (1/24) (p < 0.05). Actuarial freedom from PR at 7 year was 69.6 +/- 9.6% in the former and 95.8 +/- 4.2% in the later, respectively. The diameter of the pulmonary arterial annuals was augmented with the somatic growth in 6 patients with the pedicled pericardial patch. CONCLUSIONS: Two cusp plasty was more effective to prevent PR in the postoperative long-term period, comparing to S-TAP. As the material of the patch, pedicled autologous pericardium showed satisfactory outcome.

Blood Vessel Prosthesis Implantation↗

PubMed2001

Standard anatomical medullary locking (AML) versus tricalcium phosphate-coated AML femoral prostheses.

OBJECTIVES: To compare the preliminary rate and amount of bony ingrowth and calcar resorption between patients receiving either a standard anatomical medullary locking (AML) or a tricalcium phosphate (TCP)-coated AML femoral prosthesis and to compare preliminary clinical results. DESIGN: A prospective, randomized, double-blind clinical trial. SETTING: An acute care tertiary institution. PATIENTS: Between January 1993 and March 1995, 92 patients underwent primary total hip arthroplasty (THA). They were randomized to 2 groups of 46--a control group or a treatment group. Of the 46 subjects enrolled in each group, no significant differences were seen preoperatively with respect to age, sex, diagnosis, clinical and radiographic assessment. Seventy-one patients were followed up for 24 months. INTERVENTIONS: Insertion of either a standard AML femoral implant (control group) or a TCP-coated AML femoral implant (treatment group). OUTCOME MEASURES: The degree of hypertrophy, calcar atrophy and the number of spot welds on standard postoperative radiographs at 6, 12 and 24 months. Clinically, assessment according to the Société internationale de chirurgie orthopédique et de traumatologie (SICOT) scale and a 100-point visual analogue scale (VAS) for pain. RESULTS: There were no prosthetic stem revisions in either group at the 24-month follow-up. Radiographically, bony ingrowth was not significantly different in the TCP-coated stem, by chi2 analysis of the degree of hypertrophy and number of spot welds present. Also by chi2 analysis, the degree of calcar atrophy was not significantly different between groups. The mean VAS score for pain at 24 months was 12.5 for the control and 12.1 for the treatment group. No significant differences were seen in any of the clinical categories of the SICOT Scale over the 24-month interval. CONCLUSION: The objective of TCP-coating--to increase the rate and amount of bony ingrowth while reducing the rate of calcar resorption in non-cemented THA--was not achieved by 24 months postoperatively in our study.

Arthroplasty, Replacement, Hip↗

PubMed2003

Guided osteogenesis using synthetic membranes and alloplastic materials: a pilot study.

OBJECTIVE: The aim of this study was to develop an experimental model for the assessment of bone augmentation, and in doing so, compare the use of beta-tricalcium phosphate (TCP) bone grafts in combination with Gore-Tex augmentation material (GTAM) and GTAM without TCP. METHOD AND MATERIALS: Calvarial sites in eight Sprague Dawley rats were prepared for bone augmentation. Graft materials and Hermann stainless steel bone pins were used for localized bone augmentation. Specimens were subjected to macroscopic and histological evaluation at the sixth week. RESULTS: Bone formation was significantly higher in the group with the graft support. CONCLUSION: TCP bone grafts used in conjunction with supporting pins may contribute to successful bone regeneration by osseoconduction and by maintaining the membrane-created space. At the sixth week, guided bone regeneration utilizing Gore-Tex augmentation material and TCP bone grafts resulted in the formation of viable new bone.

Animals↗

PubMed1992

4-Methoxytranylcypromine, a monoamine oxidase inhibitor: effects on biogenic amines in rat brain following chronic administration.

4-Methoxytranylcypromine (MeOTCP), a ring-substituted analogue of the monoamine oxidase (MAO)-inhibiting antidepressant tranylcypromine (TCP), was investigated in the rat after chronic (28-day) administration and the results compared with those observed with TCP using equimolar doses of both drugs. At the dose tested, MeOTCP produced a greater inhibition of type A MAO in brain, liver, and heart than did TCP. Both drugs caused a reduction in the specific binding to beta-adrenergic and tryptamine receptors in cortex from brain. MeOTCP produced a marked increase in 5-hydroxytryptamine levels in pons-medulla, hypothalamus, and hippocampus relative to values in vehicle-treated rats and also produced a significant increase in these levels over those observed in the TCP-treated rats.

Animals↗

PubMed1992

High affinity [3H]dextrorphan binding in rat brain is localized to a noncompetitive antagonist site of the activated N-methyl-D-aspartate receptor-cation channel.

[3H]Dextrorphan recognition sites were characterized in rat brain membranes. The pharmacological profile and regional distribution of [3H]dextrorphan binding sites appear to distinguish these sites from those labeled either by [3H]dextromethorphan or by putative sigma receptor radioligands. Data from thoroughly washed forebrain membranes suggest that [3H]dextrorphan predominantly labels a high affinity site defined by the activated state of the N-methyl-D-aspartate (NMDA) receptor-channel complex. Regulation of [3H]dextrorphan binding by specific modulators of NMDA receptor function suggests that [3H]dextrorphan binding is predominantly localized to a domain of the receptor-channel complex also recognized by the prototypical noncompetitive antagonist radioligands (+)-[3H]5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne (MK-801) and [3H]1-[1-(2-thienyl)cyclohexyl]piperidine (TCP). The critical relationship between [3H]dextrorphan binding and activation of the NMDA receptor-complex is suggested by the profound dependence of [3H]dextrorphan binding on glutamate in well washed membranes. Basal specific [3H]dextrorphan binding is nearly totally suppressed by the specific competitive NMDA antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP5), in a glutamate- but not glycine-surmountable manner. Glutamate and glycine each stimulate [3H]dextrorphan binding in a concentration-dependent manner, effecting maximal increases from control of up to 30- and 14-fold, respectively. The NMDA receptor specificity of the modulation of [3H]dextrorphan binding by glutamate and glycine is indicated by the sensitivity of their effects to competitive antagonism by D-AP5 and 3-amino-1-hydroxy-2-pyrrolidone (HA-966), respectively, and by the accordant rank orders of potency of glycine analogs as modulators of [3H]dextrorphan binding and as ligands at the strychnine-insensitive glycine site. The divalent cations Mg2+ and Zn2+ and the polyamines spermine and spermidine regulate [3H]dextrorphan binding in a manner consistent with radioligand interaction at the noncompetitive NMDA antagonist domain. Mg2+ and spermidine regulate [3H]dextrorphan binding biphasically in well washed forebrain membranes, whereas Zn2+ monotonically inhibits [3H]dextrorphan binding. Mg2+ and spermidine regulate [3H]dextrorphan binding with qualitative similarity and in a contrasting fashion to their regulation of [3H]MK-801 and [3H]TCP binding. First, spermidine and Mg2+ are significantly more potent modulators of [3H]dextrorphan binding than of [3H]MK-801 and [3H]TCP binding in well washed membranes; second, whereas the potencies of spermidine and Mg2+ as modulators of [3H]MK-801 and [3H]TCP binding are significantly increased by glutamate and glycine in well washed membranes, their potencies as regulators of [3H]dextrorphan binding appear to be unaffected by glutamate and glycine.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗