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At least 1,117 records · Page 62Linked to original sources
PubMed1989

Multiple in vitro interactions with and differential in vivo regulation of muscarinic receptor subtypes by tetrahydroaminoacridine.

Tetrahydroaminoacridine (THA) is known to be a potent centrally acting cholinesterase inhibitor. In this report, the effects of THA in vivo and in vitro on the binding of muscarinic agonists and antagonists to putative M1 and M2 receptor subtypes were assessed in rat brain membranes. THA competitively inhibited labeled agonist and antagonist binding to membranes prepared from M1 and M2 enriched brain regions. The dissociation of radiolabeled antagonists from muscarinic receptors was decelerated markedly by THA. The half-time for dissociation of [3H]oxotremorine-M from the high affinity state of M1 and M2 receptors was unaffected by THA. Chronic THA administration resulted in a selective down regulation in the number of M1 receptors assayed directly with the M1-selective antagonist, [3H]pirenzepine. The decrease in the binding capacity of [3H]pirenzepine was correlated positively with the duration of drug treatment. Saturation analysis of [3H]pirenzepine binding confirmed that this loss in binding capacity was due to a reduction in the number of binding sites and not an altered affinity of the receptor for [3H]pirenzepine. Carbachol-[3H]pirenzepine competition revealed no change in the ratio of high and low affinity agonist states of the M1 receptor with chronic THA administration. In vivo studies demonstrate further that the total number of muscarinic receptors was decreased significantly, whereas putative M2 receptors, measured directly with the agonist [3H]oxotremorine-M or estimated by pirenzepine-[3H]quinuclidinyl benzilate competition, were unchanged. Thus, THA exhibits multiple actions at primary and secondary recognition sites on putative M1 and M2 subclasses of muscarinic receptors. The results suggest further that the clinical pharmacology of THA may represent a composite efficacy of THA at multiple sites on cholinergic synapses.

Allosteric Regulation↗
PubMed1971

Doctor shortage.

Explore the source record for details and available documents.

Physicians↗
PubMed1978

Farnesyl pyrophosphate synthetase. Mechanistic studies of the 1'-4 coupling reaction with 2-fluorogeranyl pyrophosphate.

The mechanism of the 1'-4 coupling reaction between isopentenyl pyrophosphate and geranyl pyrophosphate catalyzed by farnesyl pyrophosphate synthetase from porcine liver was studied with the allylic substrate analogue 2-fluorogeranyl pyrophosphate. 2-Fluorogeranyl pyrophosphate is an alternate substrate for the enzyme, yielding 6-fluorofarnesyl pyrophosphate upon condensation with isopentenyl pyrophosphate. The Michaelis constant for the fluoroanalogue, Km = 1.1 micron, is similar to that measured for geranyl pyrophosphate, Km = 0.7 micron. However, the rate of condensation with the fluoroanalogue was only 8.4 X 10(-4) that of the normal reaction. A similar rate of depression (4.4 X 10(-3)) was found for solvolysis of geranyl methanesulfonate and the corresponding 2-fluoro derivative, reactions known to proceed via cationic intermediates. In contrast, displacement of chlorine from geranyl chloride and 2-fluorogeranyl chloride by cyanide showed a small (2-fold) rate enhancement for the fluoro compound. Finally, 2-fluorogeranyl pyrophosphate is a competitive inhibitor against geranyl pyrophosphate. These data are interpreted in terms of an ionization-condensation-elimination mechanism for the 1'-4 coupling reaction.

Animals↗
PubMed1982

A comparison of the mother-child interactions of younger and older hyperactive and normal children.

The mother-child interactions of both younger (means age = 4.11) and older (means age = 8.4) hyperactive children were compared and contrasted with those observed in comparable age groups of normals. Interactions were observed in an unstructured-play and structured-task situation. Mothers of hyperactives were generally more directive and negative during play and less responsive to child-initiated interactions. Hyperactive children asked more questions and were generally more negative and noncompliant during play, particularly younger hyperactives. Hyperactives did not differ from normals in their reactions to mother-initiated behavior during play but engaged in less independent activity when their mothers were noninteractive. During the structured-task situation mothers of hyperactives were more directive and negative and less interactive and approving, even when their child was interacting appropriately. In general, between-group differences in mother-child interactions were greatest when comparing dyads with a younger hyperactive child with the other 3 groups, especially during the structured-task situation.

Age Factors↗
PubMed1994

Selective labeling and localization of the M4 (m4) muscarinic receptor subtype.

We report here a novel strategy for the selective labeling and localization of the M4 (m4) muscarinic receptor subtype, based on the distinct kinetics of the muscarinic antagonists dexetimide and N-methylscopolamine (NMS) and on the selectivity profile of guanylpirenzepine and AF-DX 116 for the m1-m5 muscarinic receptor subtypes expressed in CHO-K1 cells. Incubation with 10 nM dexetimide, a nonselective antagonist, resulted in > 90% occupancy of each of the m1-m5 receptor subtypes. The relatively rapid rates of dexetimide dissociation from the m1, m2, and m4 receptor subtypes (t1/2 values of < 12.5 min) and the slower rates of dexetimide dissociation from the m3 and m5 receptor subtypes (t1/2 values of 65 and 75 min, respectively) favored the labeling of the m1, m2, and m4 receptor subtypes with short incubations with [3H]NMS. Inclusion of 200 nM guanylpirenzepine and 250 nM AF-DX 116 prevented the binding of [3H]NMS to the majority of the m1 and m2 receptor subtypes, respectively, resulting in primary labeling of the m4 receptor subtype. Brief dissociation of the radioligand in the presence of 1 microM atropine improved the ratio of m4 to m2 labeling by selectively removing [3H]NMS from the m2 subtype. Under these conditions, the ratio of [3H]NMS binding to the m4 versus m1, m2, m3, and m5 receptor subtypes was 4:1. In vitro autoradiography combined with these m4-selective labeling conditions demonstrated that the M4 (m4) receptor subtype was localized to the primary visual area (V1, area 17, occipital cortex) and the basal ganglia, a distribution distinct from that demonstrated for the M1 (m1), M2 (m2), and M3 (m3) receptor subtypes. These results demonstrate that a combination of the distinct kinetics of dexetimide and NMS and the receptor subtype selectivity of guanylpirenzepine and AF-DX 116 provides a valuable labeling strategy to examine the distribution and localization of the M4 (m4) muscarinic receptor subtype in brain, peripheral tissues, and cell lines.

Animals↗
PubMed1994

High affinity cocaine recognition sites on the dopamine transporter are elevated in fatal cocaine overdose victims.

Cocaine mediates its powerful reinforcement by binding to recognition sites on the dopamine (DA) transporter. The pharmacological identity of cocaine recognition sites and their relevance to dopamine transport function has remained unclear. Ligand binding studies with transport inhibitors and cocaine congeners have provided evidence for multiple sites or "states" of the DA transporter. The potent cocaine congener [3H]WIN 35,428 ((CFT), 2B-carbomethoxy-3 beta-(4-fluorophenyl)-tropane) has been shown to recognize high and low affinity binding sites on the DA transporter. We have used [3H]WIN 35,428 to map and quantify the high affinity cocaine recognition site on the DA transporter in victims of fatal cocaine overdose. Region-of-interest densitometric analysis of the autoradiograms demonstrated a 2- to 3-fold elevation in the apparent density of [3H]WIN 35,428 binding in particular sectors of the striatum from victims of cocaine overdose as compared to age-matched and drug-free control subjects. The most marked increase in [3H]WIN 35,428 binding was seen in the nucleus accumbens. The apparent increase in the density of high affinity sites was confirmed by saturation binding analysis of [3H]WIN 35,428 to putamen membranes. Saturation analysis revealed high and low affinity binding components with affinities (KD values) of 4.3 +/- 1.2 and 84.7 +/- 19.7 nM (mean +/- S.E.) and densities of 9.9 +/- 4.0 and 193.0 +/- 28.6 pmol/g of tissue, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Preliminary laboratory studies of inactivation of HIV-1 in needles and syringes containing infected blood using undiluted household bleach.

To evaluate the effectiveness of bleach disinfection of injection equipment, we tested HIV-1 inactivation by household bleach in needles and syringes. We obtained blood from HIV-1 infected injecting drug users (IDUs), placed small aliquots in needles and syringes. Blood with and without anticoagulant was incubated at room temperature for 3, 6, 18, and 24 h, and some needles and syringes from each condition were exposed to undiluted bleach for 15 and 30 s. The needles and syringes were then rinsed and the rinses were used to inoculate peripheral blood mononuclear cells (PBMNCs). HIV-1 replication was monitored using p24 enzyme linked immunosorbent assay (ELISA). We describe results that HIV-1 is inactivated in clotted and unclotted blood allowed to stand at room temperature for 3, 6, 18, and 24 h in needles and syringes using undiluted household bleach at 30 s of exposure time. These results are consistent with earlier findings that micropellets of HIV-1 were inactivated by bleach under similar conditions of exposure to bleach; 10% bleach was not effective at an exposure time of 30 s and undiluted bleach was not effective at an exposure time of 15 s to inactivate HIV-1 in clotted blood. Bleach concentration and exposure time are critical and HIV disinfection may not occur with inadequate exposure to bleach HIV.

Disinfection↗
PubMed1993

Restorative considerations for special needs patients.

Individuals are living longer with more chronic and disabling conditions than previous generations of adults. In addition, they are retaining more of their natural dentition than ever before. As a result, it will be common for a dentist in practice in the next 20 to 30 years to care for many patients with special needs. These individuals offer unique challenges to the dental practitioner. Dentists must be knowledgeable in the oral aspects of various medical conditions and the systemic manifestation of oral diseases. In addition to the oral medicine aspects of practice, dentists must be skilled clinically to care for the unique restorative needs with which these patients present. As individuals age or become chronically ill, people deserve the opportunity to select from all that modern dentistry has to offer. Patients must be involved intimately in the decision-making process. No dental professional should assume because a patient is old or chronically ill that he or she lacks the financial resources or the desire to maintain his or her oral health.

Aged↗
PubMed1996

Interobserver reliability of the Teller Acuity Card procedure in pediatric patients.

PURPOSE: To compare interobserver agreement for Teller Acuity Card estimates of grating acuity between children with ocular or neurologic abnormalities, or both, and age-matched healthy preterm children. METHODS: Subjects were 57 children, 3 to 38 months of age, who were referred for visual assessment because of diagnosed or suspected visual impairment (clinical group), and 57 healthy preterm children with no known visual or neurologic abnormalities (control group), each of whom was matched to a clinical subject, based on corrected age at the time of testing, and type of testing (monocular or binocular). Each child's grating acuity was tested by two independent observers. RESULTS: Interobserver agreement of 1 octave or better was found in 91% of the monocular and 96% of the binocular clinical test-retest comparisons and in 95% of the monocular and 96% of the binocular control comparisons. For estimates of interocular acuity difference, interobserver agreement of 1 octave or better was found in 88% of clinical subjects and 88% of control subjects. Average test time was significantly longer in the clinical group (4.1 minutes [SD = 1.9] for monocular and 3.6 minutes [SD = 1.9] for binocular tests) than in the control group (2.5 minutes [SD = 0.9] for monocular and 2.4 minutes [SD = 0.6] for binocular tests), suggesting that children in the clinical group were more difficult to test. CONCLUSIONS: Teller Acuity Card testing conducted by experienced testers is as reliable in children with mild to severe ocular or neurologic abnormalities as it is in healthy children, even though children with abnormalities may be more difficult to test.

Child, Preschool↗
PubMed1996

Adaptive increase in D3 dopamine receptors in the brain reward circuits of human cocaine fatalities.

The mesolimbic dopaminergic system plays a primary role in mediating the euphoric and rewarding effects of most abused drugs. Chronic cocaine use is associated with an increase in dopamine neurotransmission resulting from the blockade of dopamine uptake and is mediated by the activation of dopamine receptors. Recent studies have suggested that the D3 receptor subtype plays a pivotal role in the reinforcing effects of cocaine. The D3 receptor-preferring agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) is a reinforcer in rhesus monkeys trained to self-administer cocaine, but not in cocainenaive monkeys. In vitro autoradiographic localization of [3H]-(+)-7-OH-DPAT binding in the human brain demonstrated that D3 receptors were prevalent and highly localized over the ventromedial sectors of the striatum. Pharmacological characterization of [3H]-(+)-7-OH-DPAT binding to the human nucleus accumbens demonstrated a rank order of potency similar to that observed for binding to the cloned D3 receptor expressed in transfected cell lines. Region-of-interest analysis of [3H]-(+)-7-OH-DPAT binding to the D3 receptor demonstrated a one- to threefold elevation in the number of binding sites over particular sectors of the striatum and substantia nigra in cocaine overdose victims as compared with age-matched and drug-free control subjects. The elevated number of [3H]-(+)-7-OH-DPAT binding sites demonstrates that adaptive changes in the D3 receptor in the reward circuitry of the brain are associated with chronic cocaine abuse. These results suggest that the D3 receptor may be a useful target for drug development of anticocaine medications.

Adaptation, Physiological↗
PubMed1997

Fatal excited delirium following cocaine use: epidemiologic findings provide new evidence for mechanisms of cocaine toxicity.

We describe an outbreak of deaths from cocaine-induced excited delirium (EDDs) in Dade County, Florida between 1979 and 1990. From a registry of all cocaine-related deaths in Dade County, Florida, from 1969-1990, 58 EDDs were compared with 125 victims of accidental cocaine overdose without excited delirium. Compared with controls, EDDs were more frequently black, male, and younger. They were less likely to have a low body mass index, and more likely to have died in police custody, to have received medical treatment immediately before death, to have survived for a longer period, to have developed hyperthermia, and to have died in summer months. EDDs had concentrations of cocaine and benzoylecgonine in autopsy blood that were similar to those for controls. The epidemiologic findings are most consistent with the hypothesis that chronic cocaine use disrupts dopaminergic function and, when coupled with recent cocaine use, may precipitate agitation, delirium, aberrant thermoregulation, rhabdomyolysis, and sudden death.

Adult↗