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PubMed1994

Retention of posts cemented with various dentinal bonding cements.

This investigation evaluated the retention of preformed posts with four different cements: C & B Metabond, Panavia, All-Bond 2, and Ketac-Cem. Sixty intact maxillary canines were selected for the study. The clinical crowns were removed and endodontic therapy done on each root, which was then prepared to receive prefabricated posts. The 60 samples were divided into four groups of 15, and the posts in each group were cemented with one of the four cements. The roots were mounted in acrylic resin blocks and the posts were separated from the canals with an Instron testing machine. Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive (p < 0.05). No difference in retention was recorded between Ketac-Cem and Panavia cements. All-Bond 2 cement was the least retentive of cements.

Analysis of Variance↗
PubMed1984

Corticosterone decreases the efficacy of adrenaline to affect passive avoidance retention of adrenalectomized rats.

Short-term (48h) adrenalectomy (ADX) resulted in a deficit in the retention of a passive avoidance response. An inverted U-shaped dose-response relationship was found following immediate post-learning administration of adrenaline (A). A in a dose range of 0.005 - 5 micrograms/kg s.c. facilitated later retention. While corticosterone (CS) replacement alone had no effect, pretreatment with CS (300 micrograms/kg) was followed by a shift in the dose-response curve of A in ADX rats. Ten thousand times higher doses of A were required to improve retention behavior. Administration of the potent synthetic glucocorticoid dexamethasone failed to affect the responsiveness to A. It is concluded that corticosterone decreases the efficacy by which adrenaline affects later retention behavior of ADX rats. The specificity of corticosterone in this interaction suggests the involvement of the corticosterone receptor system which has its predominant localization in hippocampal neurons.

Adrenal Glands↗
PubMed1985

Adrenalectomy fails to alter radial maze performance of rats at retention intervals of 24 hours or less.

Evidence suggests that the behavioral actions of adrenalectomy and glucocorticoid replacement therapy result from changes in the binding of corticosterone to specific receptors in the hippocampus. Efficient foraging for bait on the radial maze has been demonstrated to require a functionally intact hippocampal system. The present experiment examined the effect of adrenalectomy on the ability of rats to locate unexplored arms in the radial maze after various retention intervals midway through completion of the maze. Rats were very proficient at locating the unexplored arms after retention intervals of 3 hours or less; significantly more trials were required to locate all of the previously unvisited arms at retention intervals of 8 and 24 hours. However, adrenalectomy failed to alter maze performance at any retention interval tested. It was concluded that the neural substrates involved in the performance of this spatial/working memory task are not dependent upon the neuromodulatory effects of physiological levels of adrenal corticosteroids. The results are discussed in terms of behavior/contingency conflicts and innate versus learned responses as factors which may be important for revealing behavioral actions of adrenalectomy or corticosteroid therapy.

Adrenal Cortex Hormones↗
PubMed1989

Posttraining or pretest administration of nimodipine fails to affect retention of a simple learned association.

In previous experiments, the antagonist of voltage-sensitive calcium channels, nimodipine, given before training, enhanced the retention of an acquired preference for white-left relative to black-right in a two compartment apparatus. In the present experiments we attempted to determine if the retention effects produced by the drug could be attributed to effects occurring in the posttraining period. Various groups of rats received posttraining injections of nimodipine or its vehicle and two hours prior to testing received a second injection of nimodipine or its vehicle or no injection at all. All rats were tested for retention of the association twice, both 24 and 48 hr after acquisition. No posttraining or pretesting drug effects were found. This would support the view that the enhanced retention found after treatment with nimodipine found by ourselves and by others is due to a change in the animals at the time of acquisition.

Animals↗
PubMed1976

Facilitation of retention performance in mice by posttraining diethyldithiocarbamate.

These experiments examined the effects in mice of posttraining injections of diethyldithiocarbamate (DDC) upon retention (7 days after training) of active avoidance learning and upon whole brain catecholamine levels. When administered immediately following training, DDC enhanced retention performance. The degree of enhancement varied directly with dose. DDC did not significantly affect retention performance if the injections were delayed 1 or 4 hours after training. Also, DDC administered 30 min prior to training did not affect retention performance. DDC (900 mg/kg) produced a large but transient increase in whole brain dopamine (DA) levels while norepinephrine (NE) levels were lowered.

Animals↗
PubMed1981

Effects of cycloheximide and puromycin on learning and retention in the cockroach, P. americana.

A new one-session T-maze training procedure for cockroaches, in which animals were trained to turn right or left to avoid shock, is described. This paradigm was utilized to investigate effects of protein synthesis inhibiting drugs on learning and retention. Cycloheximide (CXM), which inhibited protein synthesis by over 90% during the training period, did not impair acquisition and did not produce retention deficits an any interval up to 1 day after training. Puromycin (PURO), which inhibited protein synthesis by about 70% during the training period, produced amnesia 5 hr after training, while acquisition was not affected. Thus invertebrates, as well as vertebrates, are susceptible to amnesic effects of puromycin. Although PURO-injected animals showed retention deficits as measured by the number of correct turns, no retention deficit occurred for the behavioral modification consisting of an increase in runway time during the training period. Therefore, PURO appears to show specificity for the different types of longer-term memories that are formed in a training situation.

Animals↗
PubMed1986

Repeated acquisition and delayed performance as a baseline to assess drug effects on retention in monkeys.

As an extension of previous research on repeated acquisition, a new baseline was developed to assess the effects of phencyclidine on retention in patas monkeys. Each session was divided into three phases: acquisition, delay, and performance. During acquisition, the subject acquired a four-response chain (which was different each session) by responding sequentially on three keys in the presence of four geometric forms. When the acquisition criterion (20 consecutive correct responses) was met, the keylights turned off and the delay (retention interval) began. After the delay, the keylights and a white light above the keys were turned on for 10 min (performance). The white light indicated that the response chain was the same as the chain acquired before the delay. Retention of the acquired response chain, as measured by percent "savings" in errors to criterion, decreased as the delay was increased from 5 to 180 min, and this "forgetting curve" tended to shift to the left with increasing doses of phencyclidine (administered IM 5 min before the performance phase). "Overlearning" the response chain before the 180-min delay increased retention and attenuated the disruptive effects of the lower dose of phencyclidine.

Animals↗
PubMed1995

Role of hippocampal nitric oxide in memory retention in rats.

The present study investigated the role of hippocampal nitric oxide (NO) in memory retention of an inhibitory avoidance learning task in rats. The anatomical locus was aimed at the dentate gyrus (DG). Results indicated that intra-DG administration of a NO generator, sodium nitroprusside (SNP), at moderate doses enhanced retention performance in a dose-response fashion in rats. SNP at higher doses, on the other hand, impaired memory retention. Intra-DG injection of a NO inhibitor, L-NG-monomethylarginine (L-MeArg), impaired retention performance at moderate doses. Coadministration of a NO precursor L-arginine (2.9 and 7.2 micrograms) reversed the memory-impairing effect of L-MeArg. An in vitro ADP-ribosylation experiment showed five protein bands with molecular weights around 118, 94, 54, 43, and 39 kDa that were labeled. The labeling intensity of these proteins decreased as the concentration of in vivo SNP increased. These results suggest that hippocampal NO plays a facilitatory role in the memory process of an inhibitory avoidance learning task in rats.

Adenosine Diphosphate Ribose↗
PubMed1990

Testosterone fails to reverse spatial memory decline in aged rats and impairs retention in young and middle-aged animals.

Recently, the vasopressin (AVP) innervation in the rat brain was shown to be restored in senescent rats following long-term testosterone administration. In order to investigate whether this restoration is accompanied by an improvement in learning and memory, both sham- and testosterone-treated young (4.5 months), middle-aged (20 months), and aged (31 months) male Brown-Norway rats were tested in a Morris water maze. All animals learned to localize a cued platform equally well, indicating that the ability to learn this task was not affected by sensory, motoric, or motivational changes with aging or testosterone treatment. There were no significant differences in retention following cue training. Subsequent training with a hidden platform in the opposite quadrant of the pool (place training) revealed impaired spatial learning in middle-aged and aged animals. Retention following place training was significantly impaired in the sham-treated aged rats as compared with sham-treated young rats. Testosterone treatment did not improve spatial learning nor retention of spatial information, but, on the contrary, impaired retention in young and middle-aged animals. The present results confirm earlier reports on an impairment of spatial learning and memory in senescent rats but fail to support a role of decreased plasma testosterone levels and central AVP innervation in this respect.

Aging↗
PubMed1992

Selective lesions in the temporal-hippocampal region of the rat: effects on acquisition and retention of a visual discrimination task.

The first purpose of this study was to investigate whether lesions in the temporal region may affect acquisition or retention of a discrimination task. In Experiment 1, rats with lesions of the temporal cortex (TC), the lateral entorhinal cortex (LEC), or their interconnections were tested postoperatively in simultaneous brightness discrimination. The results show that neither TC lesions nor LEC lesions affected acquisition of the task, and only LEC lesions impaired retention. TC/LEC transections impaired both acquisition and retention. The second purpose was to investigate effects of hippocampal lesions and perforant path transections on the discrimination task (Experiment 2). Both hippocampal and perforant path lesions impaired acquisition of the task, whereas retention was unaffected. It is suggested that TC and LEC are primarily involved in information storing and that hippocampal function is primarily involved in information processing.

Animals↗
PubMed1983

Lesions of the stria terminalis attenuate the enhancing effect of post-training epinephrine on retention of an inhibitory avoidance response.

This study investigated the effect of the stria terminalis (ST) lesions on the retention facilitation produced by post-training epinephrine. Rats with sham or bilateral ST lesions were trained on a one-trial step-through inhibitory avoidance task and, immediately after training, received saline or one of 3 doses (0.01, 0.1 or 1.0 mg/kg, s.c.) of epinephrine. In the rats with sham ST lesions, all 3 doses of epinephrine significantly enhanced retention performance. Lesions of the ST did not affect retention significantly. However, the lesions attenuated the facilitating effect of epinephrine on retention. These findings suggest that the integrity of the ST, which connects the amygdala and other brain structures, is essential for the effect of epinephrine on memory processes. The possible involvement of the brain structures processing visceral information in the memory modulatory effect of epinephrine is discussed.

Afferent Pathways↗
PubMed1988

Nigral 5-HT and substance P-induced enhancement of passive avoidance retention.

Peripheral, posttraining injection of substance P (SP) has been shown to facilitate the retention of aversive and appetitive learning tasks, suggesting that SP may play a role in information processing. In addition, SP may modulate the release of nigrostriatal monoamines, which have also been linked with avoidance learning. This paper examines the interaction between SP and nigrostriatal monoamines by observing the behavioral effects of neurochemical lesions on SP-induced avoidance retention, and by measuring changes in nigrostriatal monoamine activity and receptor regulation following avoidance training and SP injection. In Expt. 1, 5,7-dihydroxytryptamine lesions of the substantia nigra, but not the caudate, attenuated the retention-enhancing effects of posttraining SP injection. Further, 6-hydroxydopamine lesions of the substantia nigra produced a deficit in avoidance conditioning that was reversed by posttraining SP injection. Expts. 2 and 3 demonstrated that although passive avoidance training and posttraining SP injections did not significantly alter nigral 5-hydroxytryptamine (5-HT) activity, SP increased 5-HT1 receptor density. It was concluded that SP may affect avoidance retention by modulating nigral 5-HT activity.

Animals↗
PubMed1983

Memory retention: potentiation of cholinergic drug combinations in mice.

The amnesias characteristic of Alzheimer's disease and other age-related dementias are refractory to conventional pharmacotherapy. A recent strategy is to combine present drugs, to improve their memory enhancing effect. We utilize mice weakly trained on active avoidance in a T-maze in order to compare the effect on retention test performance of cholinergic drugs given alone and in two-drug and three-drug combinations. All drugs were injected intraventricularly immediately after training. Memory retention was tested one week later. A dose-response curve was determined for each of four drugs (arecoline, edrophonium, oxotremorine, deanol) and for several of their fixed-ratio combinations. The results indicate that each drug and each combination improved retention test performance up to an optimal dose; the improvement decreased with further increases in dose. A striking reduction (as much as 95%) in the optimal dose for enhanced retention was observed with these two-drug combinations, and further reduction with a three-drug combination. The practical implications of planned drug interactions as an improved means of treating amnesias associated with aging are under investigation.

Animals↗
PubMed1992

Value of guide planes in partial denture retention.

The retention of five nominally identical partial denture casting fitted to a master model was measured on an Instron testing machine in the direction of the guide planes and also at angles inclined to them. It was found that: the maximum retention was considerably reduced when the clasps were removed; the guide planes offered some frictional resistance to displacement, the magnitude being critically dependent on the fit; for frameworks with or without clasps a significant increase (P less than 0.01) in retention occurred when the pull was at 22 degrees but not at 12 degrees to the guide planes, and that there was no statistically significant difference between the retention in the forward and backward directions for either a 12 degrees or a 22 degrees tilt of the dislodging force.

Chromium Alloys↗
PubMed1990

Cholinergic modulation of aged-like retention deficits in young autoimmune mice.

Separate age groups of autoimmune NZB/BINJ and non-autoimmune C57BL/BNNia mice were compared for habituation of locomotor activity and its retention over four separate testing sessions spaced at 24-hr intervals. A decline in locomotion (distance in cm) or in the time spent in the center zone as a function of sessions was taken to indicate retention for habituation to stimuli within the test apparatus. The time spent in the center zone decreased as a function of sessions in young and mature C57BL/6NNia mice but failed to show reliable between-session decreases in old (24-26-months) C57BL/6NNia mice. When compared with the old C57BL/6NNia mice, young NZB/BINJ mice showed similar impairments. Habituation of locomotion was present in all age groups of C57BL/6NNia mice, but absent in NZB/BINJ mice regardless of age. The retention impairments of 2-4 month old NZB/BINJ mice were attenuated when i.p. injections of 0.04-0.16 mg physostigmine/kg were given just following each habituation session. The effectiveness of physostigmine was substantially reduced when injections were delayed by 20 min or longer following each habituation session. The time-dependent reversal of the aged-like retention deficits by the cholinesterase inhibitor, physostigmine, suggests that cholinergic modulation of memory storage processes may be impaired in NZB/BINJ mice.

Aging↗
PubMed2005

Age-related deficits in the retention of memories for cued fear conditioning are reversed by galantamine treatment.

Aging has diverse effects on different behaviors and underlying neural systems. This study utilized fear conditioning to determine if aged mice have deficits in the acquisition and/or retention of memories for contextual or cued fear conditioning, and to determine if galantamine, an acetylcholinesterase (AChE) inhibitor and allosteric modulator of nicotinic acetylcholinergic receptors, would alter acquisition and/or retention of fear conditioning memories in young (2-3 months) and aged (19-20 months) C57BL/6 mice. Mice were trained with two white-noise CS (85 dB, 30 s)-footshock US (0.57 mA, 2 s) presentations. In the initial study, separate groups were tested 24, 48, or 96 h post-training. All mice were retested 1 week after the initial test. Aged mice were impaired in freezing to the CS for the 48 and 96 h train-test intervals, but not the 24-h interval. When retested 1 week after the initial test, freezing to the CS was significantly lower for all train-test intervals. No age-related deficits were found in contextual fear conditioning. In the second study, 2 mg/kg galantamine was administered to young and aged mice before fear conditioning and conditioned fear was assessed 48 h later. No age-related deficits in cued fear conditioning were seen in galantamine-treated aged mice. Thus, aged C57BL/6 mice are impaired in the long-term retention of auditory cued fear conditioning, but not the acquisition of auditory cued or contextual fear conditioning. This retention deficit for cued fear conditioning is ameliorated by treatment with the AChE inhibitor galantamine.

Acoustic Stimulation↗
PubMed2004

Erosions and urinary retention following polypropylene synthetic sling: Australasian survey.

INTRODUCTION: There are few published reports on the incidence and management of urethral and vaginal erosions following the use of polypropylene synthetic slings. Moreover, there is very little Australasian data on their use for management of female urinary incontinence or on their associated complications. METHODS: A 1-page survey was mailed to the Australian and New Zealand members of the Urological Society of Australasia (N=326). The survey included questions on the use of polypropylene synthetic sling and the incidence and management of post-operative vaginal and urethral erosions and urinary retention. RESULTS: 198 surveys were returned (response rate: 61%). Polypropylene synthetic sling procedure is practiced by 39% of the respondents with a total of 1459 cases (TVT: 993, SPARC: 466). The incidence of vaginal erosions, urethral erosions and urinary retention was 1.2%, 0.6% and 6.5%, respectively. Thirty five percent of vaginal erosions were asymptomatic and only identified on routine post-operative vaginal examination. One third of urethral erosions presented more than 1 year after surgery and 89% of these were symptomatic. Thirty four percent of patients with urinary retention required surgical intervention to correct the retention. CONCLUSIONS: The incidence of urethral and vaginal erosions following polypropylene synthetic sling procedures is lower than that with other synthetic slings. However, a high index of suspicion and long-term follow-up are required to identify and manage these complications of this relatively new procedure.

Australia↗
PubMed2006

The effect of encoding time on retention by infants and young children.

Using a Visual Recognition Memory (VRM) procedure, we examined the effect of encoding time on retention by 1- and 4-year olds. Irrespective of age, shorter familiarization time reduced retention, and longer familiarization time prolonged retention. The amount of familiarization that yielded retention after a given delay decreased as a function of age.

Age Factors↗