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At least 991 records · Page 55Linked to original sources
PubMed1992

Effects of a new triazinoaminopiperidine derivative on adriamycin accumulation and retention in cells displaying P-glycoprotein-mediated multidrug resistance.

A new triazinoaminopiperidine derivative, Servier 9788 (S9788), was investigated for its ability to increase Adriamycin (ADR) accumulation and retention in two rodent (P388/ADR and DC-3F/AD) and three human (KB-A1, K562/R and COLO 320DM) cell lines displaying the P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) phenotype. Depending on the cell line S9788 was shown to be two to five times more active and five to 15 times more potent than Verapamil (VRP) in increasing ADR accumulation in resistant cells. ADR retention in KB-A1 cells maintained in a concentration of 10 microM S9788 was twice that in VRP-treated cells, and similar to that measured in the untreated sensitive KB-3-1 cells. Although 5 microM S9788 and 50 microM VRP gave the same values of ADR uptake in KB-A1 cells, S9788 was shown to induce a greater ADR retention following cell wash and post-incubation in resistance modifier- and ADR-free medium. Taking into account that S9788 had no effects on ADR accumulation and retention in sensitive KB-3-1 cells, it can be suggested that S9788 inhibits specifically the P-gp dependent ADR efflux, and in a manner less reversible than that observed with VRP. Moreover, [3H]azidopine photolabeling of P-gp, in P388/ADR plasma membranes, was completely inhibited by 100 microM S9788. Although S9788, as VRP, had no effect on the cell cycle of P388 cells, 5 microM S9788 increased 700-fold the efficacy of ADR to block P388/ADR cells in the G2+M phase of the cell cycle. Together, these results show that the sensitization, by S9788, of cell lines resistant to ADR is mainly due to an increase in ADR accumulation and retention, leading to an increase in the number of resistant cells blocked in the G2+M phase.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Changes in blood glucose concentration in the carotid body-sinus modify brain glucose retention.

To test whether blood glucose concentration in the carotid body-sinus may influence the amount of glucose retained by the brain, the isolated carotid sinus was perfused with glucose-rich blood or glucose-poor blood from a second animal. The circulation of the right carotid body-sinus was temporarily isolated in rat A, and perfused with blood coming from rat B. Blood glucose in rat B was modified by injections of glucose or insulin. Changes in glucose retention by the brain were measured in rat A. When the isolated carotid body-sinus in rat A was perfused with hyperglycemic blood (16.7 mM), brain glucose retention in rat A decreased significantly from 0.14 +/- 0.02 mumol/g/min (t = 0) to 0.08 +/- 0.01 mumol/g/min at 4 min after the beginning of perfusion. In contrast, the perfusion of the isolated carotid body-sinus of rat A with hypoglycemic blood (2.7 mM) from rat B, had the opposite effect. Brain glucose retention in rat A increased (0.23 +/- 0.03 mumol/g/min) at t = 4 min in comparison to control values (0.13 +/- 0.01 mumol/g/min). Chemoreceptor activity was also manipulated by the injection of cyanide (NaCN) in rat B, under these conditions, brain glucose retention in rat A increased from 0.13 +/- 0.01 mumol/g/min to 0.28 +/- 0.03 mumol/g/min between 4 to 8 min after the beginning of perfusion. These results indicate that chemosensory activity within the carotid body-sinus, superfused in vivo with different glucose concentrations, modify glucose retention by the brain.

Animals↗
PubMed1985

The retention and ultrastructural appearances of various extracellular matrix molecules incorporated into three-dimensional hydrated collagen lattices.

Artificial extracellular matrices composed of collagen, glycosaminoglycans (GAG), proteoglycans (PG), plasma fibronectin (FN), and a hyaluronate-binding protein (HABP) have been prepared that morphologically resemble embryonic extracellular matrices in vivo at the light and electron microscope level. The effect of each of the above matrix molecules on the structure and "self-assembly" of these artificial matrices was delineated. (1) Matrix components assembled in vitro morphologically resemble their counterparts in vivo, for the most part. Scanning and transmission electron microscopy indicate that under our assembly and fixation conditions, collagen forms striated fibrils that are 125 nm in diameter, FN forms 30- to 60-nm granules, chondroitin sulfate proteoglycan (CSPG) forms 27- to 37-nm granules, chondroitin sulfate (CS) assembles into 100- to 250-nm spheres, and hyaluronate (HA) appears either as granular mats when fixed with cetylpyridinium chloride (CPC) or as 1.5- to 3-nm microfibrils when preserved with ruthenium red plus tannic acid. These molecules are known to assume the same configurations in embryonic matrices when the same preservation techniques are used with the exception of FN, which generally forms fibrillar arrays. (2) Addition of various matrix molecules can radically change the appearance of the collage gels. HA greatly expands the volume of the gel and increases the space between collagen fibrils. CSPG at low concentrations (less than 1 mg/ml) and CS at high concentrations (greater than 20 mg/ml) bundle the collagen fibrils into twisted ropes. (3) A variety of assays were used to examine binding between various matrix components and retention of these components in the hydrated collagen lattices. These assays included solid-phase binding assays, negative staining of spread mixtures of matrix components, cryostat sections of unfixed mixtures of matrix components, and retention of radiolabeled matrix molecules in fixed and washed gels. A number of these binding interactions may play a role in the assembly and stabilization of the matrix. (a) HA, CSPG, and FN bind to collagen. CS appears to only weakly bind to collagen, if at all. (b) FN promotes the increased retention of HA, CSPG, and to a very small degrees, CS, in collagen gels. Conversely, the GAG increase the retention of 3H-FN in the gels. Furthermore, FN binds to HA, CS, and CSPG as demonstrated by solid surface binding assays and morphological criteria. The increased retention of GAG and CSPG by the addition of FN may be due to both stabilization of binding to the collagen and trapping of matrix complexes within the gel. (c) HA binds to both CS and CSPG.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Naloxone and [Met5]enkephalin effects on retention: attenuation by adrenal denervation.

This study investigated the effect of posttraining administration (i.p.) of naloxone and [Met5]enkephalin on retention in intact and adrenal-denervated mice. Naloxone (0.3 mg/kg) enhanced and [Met5]enkephalin (0.5 or 2.0 micrograms/kg) impaired retention in both inhibitory avoidance and Y-maze discrimination tasks. Further, [Met5]enkephalin antagonized the facilitative effect of naloxone on retention while naloxone attenuated the retention deficit produced by [Met5]enkephalin. However, neither naloxone nor [Met5]enkephalin affected retention in adrenal denervated mice. These findings suggest that endogenous hormones of the adrenal medulla, including [Met5]enkephalin, may be involved in the modulating influence of opiate peptides on memory storage.

Adrenal Glands↗
PubMed1991

Restoration of daunomycin retention in multidrug-resistant P388 cells by submicromolar concentrations of SDZ PSC 833, a nonimmunosuppressive cyclosporin derivative.

Overexpression of P-glycoprotein may cause increased efflux of a variety of anticancer drugs (ACD) leading to multidrug resistance (MDR) of tumor cells. Two sublines of murine monocytic leukemia P388 cells were used, one parental (Par-P388) and one multidrug resistant (MDR-P388). In cell growth inhibition assays in vitro, the Par-P388 cells showed a normal sensitivity to daunomycin (DAU) while the MDR-P388 cells were 200-fold resistant. In cellular fluorescence assays, DAU retention in MDR-P388 cells reached only 5% of the level achieved in Par-P388 cells. This cell line pair was used to compare the nonimmunosuppressive cyclosporin analog PSC 833 with several resistance-modifying agents (RMAs) for their in vitro chemosensitizing activity and for their restoration of DAU retention. PSC 833 sensitized the MDR-P388 cells 60- and 140-fold when used at 0.1 and 0.3 micrograms/ml (0.08 and 0.25 microM), respectively, a complete restoration of sensitivity being obtained at 1.0 micrograms/ml PSC 833. Similarly as little as 0.1 micrograms/ml (0.08 microM) PSC 833 was sufficient to restore intracellular DAU retention to 60% of the level found in Par-P388 cells, a 3-fold higher concentration restoring virtually the whole DAU retention. For both these activities, PSC 833 was at least one order of magnitude more active than CsA, which was itself an order of magnitude stronger than verapamil, another RMA already used in clinic. Since PSC 833 had no effect on the PAR-P388 cells, neither on chemosensitization nor on drug retention, it is assumed that it acts on the P-glycoprotein, which is highly expressed on the membrane of the MDR-P388 cells, by inhibiting the function of the P-glycoprotein pump and thus restoring a normal ACD-sensitivity of the MDR-P388 cells.

Amiodarone↗
PubMed1990

Controlling the retention of clopenthixol and other basic drug substances by reversed-phase ion-pair chromatography on bonded-phase materials using two counter-ions of opposite charge.

In the reversed-phase chromatography of nitrogen-containing bases on chemically bonded ODS-silica, peak tailing and prolonged retention are often considerable problems. These effects are due to residual silanols on the surface of the column material and may be remedied by adding suitable amines or quaternary ammonium ions to the eluent as anti-tailing agents. However, further addition of an anionic compound is often needed to achieve a suitable retention. The retention mechanism in such systems is complex as interaction takes place between the anionic compound and the solute molecules, anti-tailing agent and column packing material. The influence of the nature of the anti-tailing agent and anionic counter-ion on the retention of cis- and trans-clopenthixol and of other basic drug substances was investigated and it was found that both the retention and the selectivity were greatly affected.

Alkanesulfonates↗
PubMed1991

Retention behaviour of a template-assembled synthetic protein and its amphiphilic building blocks on reversed-phase columns.

The retention behaviour of a six-helix bundle template-assembled synthetic protein (TASP) molecule and its amphiphilic building blocks was investigated. The TASP consists of a circular template, cyclo(1-12)[KG]6, and six identical potentially alpha-helical peptides of the sequence KLALKLALKALKLALKLA. As an alpha-helix, this peptide is amphiliphilic along the axis of its helix. Based on this sequence, the retention times of a set of acetylated peptides containing from seven to twenty amino acids on a Nucleosil C18 column were compared with another set of peptides with the same amino acid composition but a non-amphiphilic structure. Peptide elution was effected with linear trifluoroacetic acid (TFA)-water to TFA-acetonitrile gradients. The difference in retention times increased with peptide length; the 9-mers eluted at the same time, but there was a difference of 3.5 min for the 13-mers and 22.3 min for the 20-mer, indicating the induction of secondary structure on binding to the stationary phase. The same pair of 20-mers on Vydac C18, C4 and biphenyl columns gave differences in retention times of 23.2, 16.7 and 12.3 min respectively. The TASP molecule was irreversibly adsorbed to C18 stationary phases, whereas it was eluted from C4 and biphenyl columns as a single sharp peak. Several side-products resulting from the synthesis of the TASP molecule were identified by matrix-assisted laser desorption ionization mass spectroscopy. A comparison of the retention times of these side-products and the results of pre-column denaturation experiments indicated that the tertiary structure of the TASP molecule is maintained on binding to biphenyl and C4 columns.

Amino Acid Sequence↗
PubMed1994

Gas chromatographic retention behaviour of polychlorinated naphthalenes on non-polar, polarizable, polar and smectic capillary columns.

Six commercially available gas chromatography columns were investigated for performance in separating polychlorinated naphthalenes (PCNs). Retention behaviour on the investigated phases is compared and retention data for 40 congeners on a 5% phenyl-methylpolysiloxane column is reported. For all columns, except the octylmethylpolysiloxane and the smectic, a relation between substitution pattern and retention was found, where substitution in adjacent positions as well as alpha-substitution increase the retention time. A mathematical model based on these findings was developed and used to predict the relative retention of all congeners from di- up to octachloronaphthalene, on a 5% phenyl-methylpolysiloxane column.

Chromatography, Gas↗
PubMed1979

Comparison of the retentive strength of two cast gold pin techniques.

The retention contributed by the use of pins with gold castings can be substantially increased by the technique of placing a threaded pin in the dentin and making a casting with a threaded receptacle to fit the pin. The basis for the improvement is the greater retention of threaded pins to dentin compared to that of smooth, cemented pins that are part of the casting. The limitation on the retention achieved with the new technique is the cohesive strength of the cement. Zinc phosphate cement provided the highest retention, and EBA and polycarboxylate cements provided lower and similar retention when threaded pins were cemented to threaded receptacles.

Cementation↗
PubMed1986

Proactive and retroactive effects of repeated electroconvulsive shock on passive avoidance retention in rats.

In spite of technical modifications, the therapeutic administration of electroconvulsive shock (ECS) to humans is still associated with significant memory impairment. Studies aimed at elucidating the neurobiologic basis of this impairment and developing appropriate treatment approaches have been limited by the absence of an appropriate animal model. We report here that ECS administered daily for 1-7 days to male albino rats (ECS X 1-ECS X 7) cumulatively impaired retention of passive avoidance when animals were trained 24 hours after the last ECS and tested 24 hours after training. Retention was directly proportional to the interval between training and testing; animals trained 24 hours after ECS X 7 and tested 1 hour later showed no deficit while animals tested after 24 hours showed maximal impairment. Retention was significantly improved by 10 days following the last of ECS X 7 and intact by 21 days. These findings parallel the effects of ECS on memory function in humans. The retrograde effects of ECS also paralleled those demonstrated in humans; while retention of a passive avoidance task learned 24 hours before ECS X 7 was grossly impaired, retention was intact if learning took place 7 days before the ECS course. The application of these findings as an animal model of ECS-induced memory impairment in humans, is discussed.

Amnesia↗
PubMed1981

Simultaneous reduction of radioactive strontium, caesium and iodine retention by single treatment in rats.

The effect of a mixture of calcium alginate, iron (III) ferrocyanide and potassium iodide added to rat diet on 85Sr, 137Cs and 131I metabolism and health was investigated in female rats after four weeks of treatment. The retention of these radioisotopes was determined in the whole body and critical organs six days after 85 Sr and 137CS and one day after 131I oral administration. The health effect of the mixture was evaluated by measuring body weights, haematological parameters, concentrations of iron, zinc and manganese in the kidneys, liver and femur, bone parameters (femur composition and morphometry) and by a histopathological examination. The mixture reduced 85Sr retention in the femur 11 times, 137Cs retention in the thigh muscle 102 times and 131I retention in the thyroid 134 times. Treated animals were in good health and the only differences found between the control and experimental rats were slightly lower haemoglobin values in the blood and a slightly lower iron concentration in the liver. It is concluded that the mixture was very efficient for decreasing body retention of three important fission products and that it can be used over long periods without causing adverse health effects.

Alginates↗
PubMed1990

Female urinary retention.

The urodynamic results in 68 females with urinary retention were reviewed. There were two groups: 39 patients with neurologic causes for retention, and 29 patients in whom possible causes for retention included: psychological history (15 patients), gynecologic pathology, and urinary tract infection. Nine patients in the neurogenic group and 13 patients in the non-neurogenic group had undergone urethral dilatation with no improvement. Upper urinary tract evaluation was unremarkable. Detrusor failure was the prominent bladder pattern in both groups. In the neurogenic group, low pressure detrusor activity was also present in 10 patients, 3 of whom had sphincter dyssynergia. Flow rate, surface electromyography, and bethanechol supersensitivity test could not help differentiate neurogenic from non-neurogenic detrusor failure. The notation of abnormal bladder sensation did significantly differ between the groups, but was of limited accuracy as an indicator of neurogenic retention. Self-intermittent catheterization was the most effective treatment for both groups, with some patients voiding adequately in follow-up. Although no one test can accurately differentiate neurogenic from nonneurogenic female urinary retention, careful neurourologic evaluation will help guide us to more appropriate management.

Bethanechol↗
PubMed1981

Time-dependent retention deficits induced by post-training injections of atropine into the caudate nucleus.

Rats were trained on a one-trial passive avoidance task, and retention of the task measured 24 hr later. Atropine was injected bilaterally into the anterior caudate nuclei (ACN) of rats from independent groups at one of several intervals after training. Application of atropine 2 min after training produced a lack of retention of passive avoidance. An intermediate degree of impairment was seen when the treatment was given 3 min 45 sec after the learning experience, and interference with retention was still noted when an interval of 7 min 30 sec was studied. In contrast, no deficits were observed in groups of animals injected with atropine 15 or 30 min after training. Rats injected with atropine into the parietal cortex 2 min after training showed only a minimal reduction of retention, and a group injected with saline solution into the ACN performed as well as non-treated animals. These results suggest that there is a time-dependent process that mediates the retention of passive avoidance, and that this process requires the activation of cholinergic synapses within the anterior caudate nucleus.

Animals↗
PubMed1994

Ketamine: acquisition and retention of classically conditioned responses during treatment with large doses.

Two experiments were conducted in rabbits to examine the effects of ketamine (0, 100, and 200 mg/kg) on the acquisition and retention of the classically conditioned nictitating membrane response (NMR). Classical conditioning of the NMR was accomplished by pairing tone and light conditioned stimuli (CS) with paraorbital shock as the unconditioned stimulus (UCS). Experiment 1 assessed the effects of the drug on acquisition and retention of conditioned responses (CR) and determined the role of previous exposure to the experimental environment. Ketamine blocked the display of CR. However, data from subsequent retention testing under nondrug conditions revealed that rabbits that had previously received 100 mg/kg ketamine learned faster than saline-treated rabbits during the acquisition phases. Rabbits that received 100 mg/kg ketamine and were placed in the experimental chambers, but not presented with stimuli during the acquisition phase, did not learn faster during the retention phase than naive rabbits. Experiment 2 controlled further for the effects of nonassociative, unlearned processes. Control groups were presented with unpaired CS and UCS training after drug administration, and subsequently received conventional acquisition sessions under nondrug conditions. Their data indicated that the ketamine group's rapid acquisition during retention testing could not be attributed to nonassociative factors. We conclude that, although it was impossible directly to observe acquisition in rabbits under the influence of ketamine, it was possible that learning occurred as manifested by "savings" in subsequent learning trials.

Animals↗
PubMed1993

Effects of a long-interval retention on the hypoxia-induced impairment of performance in a fixed-interval schedule.

Retention of the fixed-interval (FI) responding was studied in rats after a chronic hypoxic treatment. The rats were trained over a 25-day period on a FI 60 s schedule. The rats were then given a normoxic or hypoxic (3.5% O2 for 10 min) treatment once a day for 4 days after which they were maintained in the animal quarters for 6 supplementary days. A retention test consisting of 4 daily FI 60 session followed the 10-day interval. The results showed that the performance during the retention test was very similar for both groups of rats. These data contrast with the deficit of retention observed when the retention FI 60 session were undertaken 24 h after the same hypoxic treatment. It is suggested that the results are due to a recovery from hypoxia-induced retrieval deficits rather than to the progressive attenuation of non-specific effects of hypoxia, such as anhedonia, hypoactivity, motivational changes or structural brain damage.

Amnesia, Retrograde↗
PubMed1993

Calcium and phosphorus retention in the preterm infant during total parenteral nutrition. A comparative randomised study between organic and inorganic phosphate as a source of phosphorus.

The preterm infant fed parenterally is prone to some demineralisation due in part to insufficient Calcium (Ca) and Phosphorus (P) retention. In an attempt to augment Ca and P retention, we prepared a standardised parenteral solution containing calcium gluconate and glucose-1-phosphate (Phocytan) as source of phosphorus, yielding a daily supply of 75 mg/kg Ca and 45 mg/kg P. 28 very low birthweight infants were randomly assigned to receive either this solution (high Ca P ; n = 15) or a conventional formulation containing calcium gluconate and potassium mono- and dibasic phosphate delivering 42 mg/kg Ca and 36 mg/kg P daily (low Ca P ; n = 13). In the high Ca P daily retention was respectively 80% and 99% for Ca and P whereas in the low Ca P group, retention was 70% and 82%. Serum parathormone levels were significantly lower in the high Ca P group. We conclude that parenteral nutrition with a new high Ca P supplement results in an augmented Ca and P retention in very low birthweight infants. This may help to prevent neonatal bone demineralization.

Journal Article↗
PubMed1995

Tetrahydroaminoacridine modulates technetium-99m labelled ethylene dicysteinate retention in Alzheimer's disease measured with single photon emission computed tomography imaging.

The present study investigated if acute treatment with tetrahydroaminoacridine (THA) (25 or 75 mg, p.o.) affects technetium-99m labelled ethylene dicysteinate (ECD) retention abnormalities in patients with mild to moderate Alzheimer's disease (AD; mean age 69 years). THA (75 mg) increased temporal, prefrontal and occipital ECD retention (normalized to cerebellum) in mildly demented AD patients, but 25 mg of THA had no effect on ECD retention. After 75 mg THA, prefrontal and temporal ECD retention correlated with improved executive and memory functioning, respectively. THA (25 or 75 mg) had no measurable effect on ECD retention of moderately demented patients.

Aged↗
PubMed1991

N6-cyclopentyladenosine impairs passive avoidance retention by selective action at A1 receptors.

The effects of N6-cyclopentyladenosine (CPA), a highly selective agonist for adenosine A1 receptors, on retention of one-trial inhibitory avoidance behavior were examined in mice. Water-deprived animals were trained to avoid drinking by pairing foot-shock with licks from a water spout. Retention was measured as the suppression of drinking (latency to drink) 48 h following training. Administration of CPA (0.15-2.25 mumol/kg) 30 min prior to training produced a dose-dependent impairment in memory of the original avoidance task. The CPA-elicited deficits in retention performance were blocked by pretreatment with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective A1 receptor antagonist; DPCPX (15 mumol/kg) administration alone had no effect on retention performance. These findings suggest that selective activation of a presumably central population of A1 receptors may impair retention performance and influence information processing.

Adenosine↗