SEARCH · PubMed Health

Results for “Retention”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources

PubMed2000

Permanent and temporary inactivation of the hippocampus impairs T-maze footshock avoidance acquisition and retention.

The hippocampus is widely recognized as playing an important role in learning and memory. Lesions of the hippocampus can disrupt spatial navigational learning and memory and injection of drugs into the hippocampus can affect both spatial navigational and nonspatial tasks. In the current studies we tested the effects of bilateral of electrolytic lesions and reversible inactivation of the hippocampus on acquisition and retention of T-maze footshock avoidance conditioning. Electrolytic lesions, which destroyed 31+/-0.04% of the hippocampus, significantly impaired acquisition and retention for T-maze footshock avoidance. No differences were found in motivation to avoid shock, open field activity, or foot shock sensitivity between lesion and control groups. Temporary inactivation of the hippocampus with lidocaine administered immediately before training disrupted acquisition and retention for T-maze footshock avoidance. Temporary hippocampal inactivation performed just prior to retention testing and post-training inactivation in mice trained to first avoidance had no effect on retention. However, temporary post-training inactivation in 'undertrained' (enough trials to remember 1 week later if treated with saline, but not allowed to make the avoidance response) mice impaired retention. The current findings indicate that the hippocampus plays an important role in learning and memory processing in the aversive T-maze paradigm.

Animals↗

PubMed1997

Effect of different surface textures on retentive strength of tapered posts.

STATEMENT OF PROBLEM: Tapered posts allow for the preservation of tooth substance in the fragile apical area and are advantageous in clinical situations where they conform to the root and canal configuration of endodontically treated teeth. However, their lower retention compared with passive parallel-sided or active threaded posts is a disadvantage. PURPOSE: This study determined the retentive strength of tapered titanium posts with different surface textures and examined the effect of roughening dentinal walls of the prepared post space. MATERIAL AND METHODS: Posts with four surface configurations (smooth, with and without grooves, and sandblasted, with and without grooves) were examined when cemented in extracted anterior teeth. RESULTS: The smooth post showed the lowest retentive strength. Sandblasting the smooth post more than doubled its retentive strength. The retentive strength of both smooth and sandblasted posts could be further increased by the addition of circumferential grooves. Roughening the dentinal walls of the prepared post space increased the retentive strength of sandblasted posts with and without grooves even more. CONCLUSIONS: These findings indicated that, when a tapered post is used, roughening the dentin canal wall, as well as sandblasting and grooving the post, can provide statistically significant additional resistance to dislodgment.

Analysis of Variance↗

PubMed1997

Effect of friction coefficient on Akers clasp retention.

STATEMENT OF PROBLEM: Retentive force control of clasp retainers is one of the most essential factors for the successful function of removable partial dentures. However, it is not yet known how the friction coefficients differ among restored abutments and clasp materials, and how the friction coefficients affect the retention of clasps. PURPOSE: The purposes of this study were to clarify the friction coefficients among restored abutments and clasp materials and to estimate the effect of friction coefficients on the retention of clasps. MATERIAL AND METHODS: The coefficients of static friction between three clasp materials (type IV gold, high Pd, and cobalt-chromium [Co-Cr] alloys) of two surface treatments (polished and sandblasted) and four abutment materials (human enamel, porcelain, type IV gold, and high Pd alloys) were evaluated under three conditions (dry, wet with water, and wet with saliva), and theoretically, the effect of the friction coefficients on clasp retention was estimated. RESULTS: The friction coefficients under various conditions ranged from 0.08 (polished Co-Cr clasp on type IV abutment in dry condition) to 0.37 (sandblasted Co-Cr clasp on high Pd abutment in dry condition). The theoretical estimation clarified that the retentive force of the clasp was linear to the friction coefficient. CONCLUSION: The retentive force increased linearly with increasing friction coefficient between abutment material and clasp material according to the newly developed formula. This study suggested that clasp designs should be changed depending on abutment materials.

Analysis of Variance↗

PubMed1999

Clinical methods for adjusting retention force of cast clasps.

Careless adjusting methods to increase or decrease retention by grinding, polishing, or bending the clasp arm can lead to instability of the removable partial denture, damage to the surrounding tissues, and fracture of the clasp arm. This article describes systematic evaluation criteria and adjusting methods of retention force of a cast clasp. Excessive retention can be reduced by using a proper adjustment method, which depends on the cause. Poor retention can be increased temporarily, but it will decrease again. Evaluations and adjustment of poor retention will contribute to the diagnosis of the cause and will establish clinical and laboratory procedures that will lead to making clasps with proper retention in the future.

Dental Clasps↗

PubMed1999

Effect of tooth surface roughness on marginal seating and retention of complete metal crowns.

STATEMENT OF PROBLEM: Retention and marginal adaptation factors have major influence on the failure of cemented complete veneer crowns. PURPOSE: This study investigated the effect of axial surface roughness on the marginal seating and retention of silver-palladium crowns luted with zinc phosphate, glass ionomer, and resin cements. MATERIAL AND METHODS: Coarse and fine diamond stones were used to create various surface roughnesses of premolars. A milling machine was used to control the height and angle of the axial walls of tooth preparations. Ten cast metal crowns in 6 subgroups were luted with 3 cements (Phosphacap, Fuji Cap I, and Panavia 21). Marginal seating was recorded with a Digimatic indicator. Retention was determined by measuring the tensile force required to remove a metal crown with a Lloyd testing machine. RESULTS: Two-way analysis of variance revealed statistically significant differences (P <.001) in retention for both luting cements and surface roughness. No significant difference was recorded for marginal seating relative to roughness (P =.860) and interaction effects (P =.204). Tukey-HSD tests revealed substantial differences in retention among Phosphacap, Fuji Cap I, and Panavia 21 cements. Significant differences were not confirmed in marginal seating between Fuji Cap I and Phosphacap cements with coarse diamonds, and Phosphacap and Panavia 21 cements with fine diamonds. CONCLUSIONS: The best retention for complete metal crown was demonstrated for tooth preparations ground with coarse diamonds and cemented with Panavia 21 cement. Differences in axial surface roughness had no effect on the marginal seating of the complete metal crowns.

Analysis of Variance↗

PubMed1999

Urinary retention after bilateral extravesical ureteral reimplantation: does dissection distal to the ureteral orifice have a role?

PURPOSE: We evaluated the outcome and incidence of urinary retention after bilateral detrusorrhaphy using 2 modifications of the original Lich-Gregoir procedure. MATERIALS AND METHODS: We evaluated the charts of 220 patients who underwent correction of bilateral vesicoureteral reflux using the extravesical approach from January 1991 to December 1997. Inverted Y detrusorrhaphy was performed in 154 patients and the advancing suture modification was done in 66. RESULTS: The success rate using the advancing suture technique was 92.4 and 95.4% at 3 and 12 months, respectively. The Y detrusorrhaphy technique was successful in 91.6 and 97.4% of cases at 3 and 12 months, respectively. The difference in the techniques was not statistically significant. Urinary retention developed in 8.4% of the patients who underwent Y detrusorrhaphy compared to 15.2% of those who underwent the advancing suture technique (not statistically significant). However, patients with grades IV and V reflux, children younger than 3 years and boys had significantly (p <0.05) higher postoperative retention rates of 24.6, 35.6 and 20.3%, respectively, when all 220 patients were considered. CONCLUSIONS: Each modification of the original Lich-Gregoir technique is highly effective for treating bilateral vesicoureteral reflux and each is associated with a low rate of temporary urinary retention. Although there seems to be a lower incidence of retention with the Y detrusorrhaphy technique, this was not statistically significant. Because of the higher incidence of urinary retention in young children, boys and/or patients with high grade reflux, we recommend that physicians consider a longer period of catheterization regardless of the technique chosen.

Child↗

PubMed2002

Maximum urethral closure pressure and sphincter volume in women with urinary retention.

PURPOSE: In 1988 a syndrome of isolated urinary retention in young women that is associated with electromyographic abnormality of the striated urethral sphincter was described. It was hypothesised that urinary retention resulted from a failure of sphincter relaxation. The electromyographic abnormality causes overactivity of the muscle and may induce changes of work hypertrophy. If the hypothesis that the electromyographic abnormality is the cause of urinary retention is correct, we would expect the urethral sphincter to be enlarged and the urethral pressure profile to be increased in these women. We evaluated the role of static urethral pressure profilometry and transvaginal ultrasound in women in urinary retention. MATERIALS AND METHODS: A total of 66 women in complete or partial urinary retention underwent electromyography of the striated urethral sphincter using a concentric needle electrode, followed by urethral pressure profile and/or urethral sphincter volume measurement by transvaginal ultrasound. RESULTS: Maximum urethral closure pressure plus or minus standard deviation was significantly increased in patients with versus without the electromyographic abnormality (103 +/- 26.4 versus 76.7 +/- 18.4 cm. water, p <0.001). Maximum urethral sphincter volume was also increased in women with versus without the abnormality (2.29 +/- 0.64 versus 1.62 +/- 0.32 cm.3, p <0.001). CONCLUSIONS: The results of this study are consistent with the hypothesis that a local sphincter abnormality is the cause of urinary retention in a subgroup of women. Urethral pressure profilometry and sphincter volume measurement are useful for assessing these cases, especially when sphincter electromyography is not readily available.

Adolescent↗

PubMed1996

Unconditioned stimulus intensity and retention interval effects.

In single-element taste-aversion learning, retention interval effects are seen if taste aversions are paradoxically weak when they are tested 1 day after conditioning than when they are tested 3 or more days after conditioning. One explanation of this phenomenon is that weaker taste aversions may increase in strength across a retention interval. To test this possibility, rats were given saccharin followed by an unconditioned stimulus (US) of weak, medium, or high intensity; testing occurred after a 1-day or a 5-day retention interval. The results showed retention-interval effects only at medium and high dosage levels, but not following a weak-intensity US. Furthermore, at the 5-day retention interval, aversion strength increased as the intensity of the US increased. However, at the 1-day retention interval, there were no significant differences due to US intensity. In accordance with previous experiments, this outcome suggests that nonassociative factors, such as US novelty, and not associative factors (e.g., US intensity), modulate taste aversion performance on a 1-day test.

Animals↗

PubMed1983

Retention deficit after d-amphetamine treatment: memory defect or performance change?

Retention deficits in discrete trial delayed alternation and delayed matching to sample tasks following administration of d-amphetamine have been interpreted to support the view that arousal facilitates the decay of information from shortterm memory (STM) (Kesner, 1973). But since amphetamine causes numerous changes in performance, alternative explanations of the deficit are also plausible. In an attempt to separate drug effects on memory from those on performance, the effects of d-amphetamine on spatial memory in the radial maze were studied in rats. The unusually long span of accurate working memory in this setting permits drug administration within the retention interval as well as prior to the to-be-remembered event (TBRE). In rats tested at a 5-hr retention interval d-amphetamine (2 mg/kg) disrupted retention when given 0.5 hr before or 4.5 hr after the TBRE, but the same treatment 0 or 2 hr after the TBRE or 3 hr before the TBRE was without effect. At a 5-hr retention interval 3 mg/kg d-amphetamine impaired performance if given 2 hr after the TBRE, but not when given 0 hr after the TBRE or 3 hr before the TBRE. However, when the retention interval was lengthened to 7 hr, administering 3 mg/kg d-amphetamine 2 hr after the TBRE did not disrupt performance. The effects of d-amphetamine on spatial memory are best explained in terms of the well established effects of the drug on motor activity and appetite. Similar changes in performance may account for the "memory" impairments observed after amphetamine treatment in other tasks.

Animals↗

PubMed1986

Epinephrine modulates long-term retention of an aversively motivated discrimination.

These experiments examined the effects of post-training epinephrine (Epi) on retention of an aversively motivated discrimination task. Male CFW mice were trained to escape from footshock by entering one of two alleys of a Y-maze. On a 24-h retention test (six trials) the correct alley was reversed. The findings of Experiment 1 indicate that errors on the discrimination reversal varied directly with number of trials (criterion of 0, 3, or 6 successive correct choices) on the original training. These findings indicate that errors on discrimination reversal training provide a sensitive index of retention of the original training. In Experiment 2, mice were trained to a criterion of three successive correct choices and were given post-training injections of saline or Epi (0.1, 0.3, or 1.0 mg/kg ip). On a 24-h discrimination reversal test mice given the low doses of Epi made more errors than did saline controls while mice given the high dose made fewer errors. In Experiment 3, mice trained as in Exp 2 received post-training saline or Epi (0.3 or 1.0 mg/kg) and were tested for retention either 1 week or 1 month later. At each retention interval, performance was comparable to that found with a 24-h retention interval. The findings provide additional evidence that post-training Epi produces long-lasting dose-dependent modulating effects on memory storage.

Animals↗

PubMed1987

Effect of novel experiences on retention of inhibitory avoidance behavior in mice: the influence of previous exposure to the same or another experience.

Mice were trained and tested in a step-through inhibitory avoidance task with a 24-h interval between training and testing. At one of several intervals prior to the test session (9 h, 6 h, 3 h, or 6 min), they were given one of the following novel experiences: 4 min in a small Plexiglas box containing an empty water bottle, or 4 min hanging from the wire mesh ceiling of a large Plexiglas box. When given 3 h or 6 min before testing, both novel experiences enhanced retention test performance. The effect was antagonized by naltrexone and mimicked by an administration of beta-endorphin 6 min prior to testing. Thus, the findings are consistent with previous evidence suggesting that the effects of novel experiences on retention test performance are due to an activation of the brain beta-endorphin system. When one of the novel experiences given 3 h or 6 min prior to testing was preceded by the same experience given 6 h earlier retention test performance was not enhanced. Thus, the enhancing effect is obtained only if the experience is novel. Further, an experience given prior to retention testing did not affect performance if either the same or a different experience was given 3 h earlier. This finding is consistent with previous evidence indicating that following a novel experience, the brain beta-endorphin remains unresponsive for several hours. These results provide additional evidence that novel experiences prior to retention testing affect retention performance and provide additional support for the view that the effect may involve the release of beta-endorphin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Mecamylamine prevents the enhancement of retention induced by lysine vasopressin in mice.

Lysine vasopressin (0.03 microgram/kg, sc) enhanced retention of a one-trial, step-through inhibitory avoidance task when injected into male Swiss mice immediately post-training, as indicated by retention performance 48 h later. A low dose of the vasopressin antagonist, AAVP (0.01 microgram/kg, sc), did not significantly affect retention, whereas a higher dose (0.03 microgram/kg, sc) impaired retention. Neither lysine vasopressin nor AAVP modified latencies to step-through of mice that had not received a footshock during training. The simultaneous injection of AAVP (0.01 microgram/kg, sc) prevented the enhancement of retention induced by lysine vasopressin. The influence of lysine vasopressin on retention was antagonized by the simultaneous administration of mecamylamine (5 mg/kg, sc) but not by hexamethonium (5 mg/kg, sc), atropine (0.5 mg/kg, sc), or methylatropine (0.5 mg/kg, sc). A modulatory role of vasopressin on the activity of central cholinergic nicotinic mechanisms which participate in memory formation is suggested.

Animals↗

PubMed2003

Parafascicular electrical stimulation attenuates nucleus basalis magnocellularis lesion-induced active avoidance retention deficit.

Previous experiments from our laboratory showed that retention of two-way active avoidance learning is improved by post-training intracranial electrical stimulation (ICS) of the parafascicular nucleus (PF) and impaired by pre-training electrolytic lesions of the nucleus basalis magnocellularis (NBM). The question investigated here was whether post-training PF ICS is able to attenuate the active avoidance retention deficit observed in rats lesioned pre-training in the NBM. To this goal, the following experimental design was used: rats bilaterally lesioned in the NBM and stimulated in the PF, rats lesioned in the NBM, rats stimulated in the PF, control rats implanted in the PF, and sham-operated rats were first trained in a shuttle-box for a single 30-trial session and tested again following two successive retention intervals (24 h and 11 days). The results showed that: (1) NBM lesions impaired the 11-day performance without affecting either the acquisition or the 24-h retention of the avoidance learning; (2) PF ICS treatment in unlesioned rats improved performance in both retention sessions only when the stimulation was applied in the posterior region of the nucleus; and (3) stimulation of the posterior PF compensated the 11-day retention impairment induced by NBM lesions. These results are discussed in relation to the interaction of arousal systems in the modulation of cognitive processes.

Animals↗

PubMed2003

Effect of circumferential undercut placement in the root canal wall on the retention of a tapered post in large and small root canals.

OBJECTIVES: This study examined the influence of root canal space and circumferential undercut placement in the dentine wall on the retention of a prefabricated Root Keeper post. METHODS: Twenty-four extracted single-rooted teeth, having narrow root canal spaces, were decoronated, treated endodontically, and then centrally embedded in resin blocks. All canal spaces were prepared with a no. 2 Peeso reamer to an 8mm depth, and half the specimens were successively treated with a no. 3 Peeso to depths of 5 and 8mm for the small canal group (SC) and large canal group (LC), respectively. An L-type keeper post (Aichi Steel Co.) was luted to each canal with resin cement. The assembly was thermocycled 2000 times (4-60 degrees C), and post retention was measured. Afterwards the dislodged post with the intact structure was sandblasted, and the canal was cleaned and slightly undercut using an inverted cone bur. Six treated posts were recemented for both grooved large canal (GLC) and grooved small canal (GSC) groups, and the repaired retentive strengths were measured. RESULTS: Keeper posts cemented in SC (84.26+/-31.85N) showed better (p<0.05) retention than those cemented in LC (41.92+/-22.36N). Interestingly, the repaired strengths of the recemented post increased in both GSC (104.29+/-11.89N) and GLC (96.65+/-6.91N). All posts, except for one in the GLC, failed at the keeper-post joint. CONCLUSIONS: Prefabricated Root Keeper posts had lower retentive strength in roots with a large canal space. Placement of a circumferential undercut in the root canal wall significantly enhanced the retention of the short tapered posts.

Cementation↗

PubMed1997

Post-partum urinary retention: a comparison between two methods of epidural analgesia.

OBJECTIVE: To compare two methods of epidural labor analgesia regarding the incidence of post-partum urinary retention. STUDY DESIGN: One thousand parturients who requested epidural analgesia for the relief of labor pain received, at random, either bupivacaine 0.25% with adrenaline 1:200 000 (n = 500) or bupivacaine 0.125% with 10 micrograms sufentanil (n = 500). During the same observation period all women with clinically significant urinary retention (> 500 ml, requiring indwelling catheter) were registered. RESULT: Altogether 30/3.364 parturients had clinically significant urinary retention. Twenty-seven of these had received epidural analgesia (EDA) (17 with bupivacaine/adrenaline and ten with bupivacaine/sufentanil, a non-significant differences). The number of parturients with urinary retention was highly increased following EDA (27/1000) as compared to those not receiving EDA (3/2364), P < 0.001 (Fisher's exact test). In patients with EDA and urinary retention there were no difference between the groups in the incidence of instrumental deliveries or vaginal/perirectal tears. All parturients regained normal bladder function. CONCLUSION: EDA significantly increased the risk of post-partum urinary retention but no difference was found between the two epidural techniques.

Adult↗

PubMed2004

GABAergic system and imipramine-induced impairment of memory retention in rats.

In this study, the influence of GABAergic agents, imipramine and their interactions on memory retention have been investigated. Intracerebroventricular (i.c.v.; 1-6 microg/rat) or intraperitoneal (i.p.; 5-40 mg/kg) injection of imipramine decreased memory retention. i.c.v. administration of GABA receptor agonists baclofen and muscimol also reduced memory retention. The combination of i.p. or i.c.v. injection of imipramine with a low dose of muscimol (1 microg/rat, i.c.v.) induced a higher decrease in memory retention. The higher dose of GABA(B) receptor antagonist CGP35348 [p-(3-aminopropyl)-p-diethoxymethyl-phosphinic acid] (10 microg/rat) increased memory retention by itself, and decreased the response induced by baclofen or imipramine. Bicuculline (1, 2 and 4 microg/rat, i.c.v.) tends to increase memory retention by itself. Furthermore, bicuculline in same doses reduced the response induced by muscimol or imipramine, but it did not show interaction with the latter drugs. It is concluded that the GABA(B) receptor mechanism is involved in memory impairment induced by imipramine.

Animals↗

PubMed2004

Memory for objects and their locations: the role of the hippocampus in retention of object-place associations.

Computational models of hippocampal function have suggested that the hippocampus is involved in the formation and storage of arbitrary associations. Previous studies have shown that rats with hippocampal lesions are impaired in object-place associative learning. However, few studies have examined the role of the hippocampus in the retention of previously learned arbitrary associations. In the present study, male Long-Evans rats with either cortical control or hippocampal lesions were tested on a task measuring the retention of previously learned arbitrary associations using an object-place paired-associate task. To assess retention, each animal was trained on the paired-associate task for 360 trials, then received a lesion, and was retested to examine retention of the previously learned associations. The results indicate that all rats learned the task prior to surgery. Following surgery, rats with cortical control lesions were not impaired in the retention of object-place associations. In contrast, hippocampal lesions resulted in an initial deficit in retention of the paired-associate task followed by recovery. Therefore, the hippocampus may play a role in the retrieval of previously learned arbitrary association.

Animals↗

PubMed2005

The role of the IPSS (International Prostate Symptoms Score) in predicting acute retention of urine in patients undergoing major joint arthroplasty.

BACKGROUND: Acute urinary retention following major joint arthroplasty is common. It does necessitate instrumentation, puts patients at risk of complications, and causes discomfort and embarrassment. The aim of the study was to find a test to help the surgeon to predict the possibility of acute retention of urine. METHODS: Male patients admitted for elective major joint arthroplasty filled in an IPSS (International Prostate Symptoms Score) during the pre-operative visit. They were observed post-operatively to document if they passed urine spontaneously or went into acute retention. RESULTS: There was a strong correlation between the IPSS and the likelihood of developing acute retention. Patients with moderate to high IPSS had a 55% to 100% chance of developing acute retention of urine, respectively. CONCLUSION: The IPSS proved to be a simple and reliable test to help the surgeon in predicting the possibility of developing acute retention. It might be a good addition to the pre-admission clinic investigations in patients undergoing major surgery. It could consolidate the decision to pre-emptive catheterisation in patients at risk.

Acute Disease↗