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PubMed1993

Amalgam retention using pins, boxes, and Amalgambond.

The purpose of this study was to evaluate and compare the retentive strength of amalgam to tooth structure by utilizing pins, boxes, Amalgambond adhesive only, and Amalgambond adhesive plus retentive boxes. There was no statistical difference (P = 0.05) in retentive strength of the amalgam between the group utilizing pins alone and the group utilizing Amalgambond plus retentive boxes. However, both of these sample groups demonstrated statistically greater retentive strengths than either the boxes only or Amalgambond only groups.

Analysis of Variance↗
PubMed1975

An evaluation of the Coulter thrombocounter in counting platelets before and after contact with foreign surfaces and its use in tests of platelet retention.

The counting of platelets by electronic methods has become widely accepted by laboratories and the methods is considered to give better reproducibility than the conventional microscope count. Prompted by an impression that prior contact of whole blood with glass beads or cellulose-based dialysis membranes resulted in platelet counts showing a poor correlation between the electronic and microscopic methods of counting, an evaluation of the Coulter Thrombocounter was carried out with regard to its ability in counting platelets before and after contact with such foreign surfaces in two tests for the measurement of platelet retention. The effect of citrate and heparin anticoagulation with and without the addition of EDTA on the efficiency of the Thrombocounter was also studied. The results indicate that an excellent correlation is obtained between microscopic and electronically estimated platelet counts before foreign surface contact when EDTA is included in the anticoagulation, and that the Thrombocounter gives good reproducibility over a wide range of platelet counts. After contact with the foreign surfaces, the Thrombocounter significantly underestimated the platelet counts and thus overestimated the platelet retention values. Using the membrane test cell system with citrate plus EDTA anticoagulation, platelet retention results estimated by Thrombocounter platelet counts were significantly higher than those estimated by microscopic platelet counts but there was a good linear correlation between the two sets of results. Thus, the Thrombocounter may be used with this method. However, using the glass-bead column technique and the same anticoagulation, although the platelet retention results gave the same mean value with both methods of platelet counting, there was no correlation between the two sets of results indicating that microscopy alone should be used with this method. The other anticoagulant regimens rendered the Thrombocount inefficient for use in these tests of platelet retention.

Blood Cell Count↗
PubMed1975

Learning and retention by monkeys with epileptogenic implants in anteromedial temporal cortex.

Alumina cream was implanted bilaterally in anteromedial temporal cortex of monkeys. After the onset of epileptic discharges eight implanted and eight normal monkeys were trained on tasks of visual and somesthetic discriminations and delayed alternation. All monkeys were tested for retention on the three tasks at 3-week intervals, for a total experimental period of 52 weeks. The normal monkeys received epileptogenic implants after their first retention tests. Serial scalp EEGs were recorded and several monkeys were implanted with cortical recording electrodes. On acquisition training the epileptic group was significantly retarded in comparison with the normals, but also exhibited significantly greater variabilities in individual learning rates. On the retention tests the majority of epileptic monkeys showed little or no deficits. In these monkeys the epileptic discharges remained restricted to the implanted areas. The retention deficits in several monkeys could be related to propagations of epileptiform patterns and secondary foci. These results are consistent with earlier findings with focal epileptogenic implants in different cortical areas of deficient acquisition rates on tasks specific to the focal areas, but unimpaired retention performance. The finding can be explained in relation to labile and consolidated mnemonic processes.

Animals↗
PubMed1993

Myocardial kinetics of carbon-11-meta-hydroxyephedrine: retention mechanisms and effects of norepinephrine.

Carbon-11-labeled meta-hydroxyephedrine (HED, N-methyl-metaraminol) is a catecholamine analog developed for the PET imaging of sympathetic nerve terminals of the heart. The retention mechanisms of this tracer and interactions with norepinephrine were investigated in isolated working rat hearts. Externally monitored time-activity curves showed a strong uptake process in control hearts (K1 = 2.66 +/- 0.39 ml/g/min) and relatively slow monoexponential clearance rates (k2 = 0.011 +/- 0.003 min-1). Comparative studies with the neuronal uptake inhibitor desipramine indicated little extraneuronal distribution and a strong dependence of clearance rate on neuronal reuptake of tracer. Norepinephrine (< or = 10 nM) increased HED clearance rate without affecting initial uptake rates. This effect may be related to competitive inhibition of neuronal reuptake and/or accelerated neuronal release of HED. These results indicate that the uptake and retention of HED by the myocardium is highly specific to sympathetic nerve terminals. However, its retention in the myocardium is not directly related to neuronal processing of catecholamines (i.e., metabolism and vesicular turnover). Thus, important differences may exist in the physiologic information indicated by retention measurements of HED and radiolabeled catecholamines. The finding of increased clearance rates with NE in the perfusion medium recommends the consideration of potential effects of circulating and endogenous catecholamines on PET measurements of myocardial retention of HED, especially in subjects with elevated plasma catecholamines or high sympathetic tone.

Animals↗
PubMed1993

Transmembrane domain length affects charge-mediated retention and degradation of proteins within the endoplasmic reticulum.

Previous studies have shown that the presence of potentially charged amino acid residues within the transmembrane domains of type I integral membrane proteins can result in protein retention and, in some cases, degradation within the endoplasmic reticulum (ER). An apparent exception to this observation is the CD3-epsilon chain of the T-cell antigen receptor complex, which is relatively stable in spite of having a transmembrane aspartic acid residue. A chimeric protein (T epsilon T) made by replacing the transmembrane domain of the Tac antigen with that of CD3-epsilon was normally transported to the cell surface, indicating that the transmembrane domain of CD3-epsilon was essentially unable to confer the phenotype of ER retention and degradation to another protein. Progressive shortening of the T epsilon T transmembrane domain, however, resulted in increasing retention and degradation of the mutant proteins in the ER. Conversely, a mutant Tac protein containing a single aspartic acid residue in its transmembrane domain was found to be retained and degraded in the ER, but when the transmembrane domain was lengthened, ER retention and degradation of the protein were abrogated. The aspartic acid residue in the transmembrane domain of all of these mutant proteins could mediate assembly with another protein having an arginine residue in its transmembrane domain, independent of the length of the transmembrane sequence. These findings demonstrate that the length of the hydrophobic transmembrane sequence has a critical influence on the ability of potentially charged transmembrane residues to cause protein retention and degradation in the ER.

Amino Acid Sequence↗
PubMed1993

Uncleaved signals for glycosylphosphatidylinositol anchoring cause retention of precursor proteins in the endoplasmic reticulum.

Glycosylphosphatidylinositol (GPI)-anchored proteins are generally absent from the surface of cells that are defective in GPI biosynthesis. The current study was undertaken to: (a) examine in detail the intracellular localization and fate of precursors of GPI-anchored proteins in cells that fail to add GPI groups and (b) define structural characteristics of the precursor proteins that determine their intracellular localization. By examining GPI-deficient cells, we show that the uncleaved precursor of the GPI-anchored protein, Q7b, is retained in the cisternae of the endoplasmic reticulum (ER) and is largely lost intracellularly with a half-time of 2-4 h. Only a small amount (1-10%) of a proteolytically cleaved form of the protein is secreted into the medium. In cells competent for GPI anchor addition, mutation of the putative cleavage/attachment site for GPI addition in Q7b results in a similar phenotype of ER retention of the uncleaved precursor. An aspartic acid residue (Asp316) within the Q7b GPI anchoring signal, previously found to be essential for GPI anchor addition (Waneck, G. L., Stein, M. E., and Flavell, R. A. (1988) Science 241, 697-699), is also shown to be critical for ER retention. Information leading to ER retention is transferable to another protein leading to ER retention is transferable to another protein by fusion of the GPI anchoring signals from either Q7b or the GPI-anchored form of the IgG Fc receptor type III. Analysis by sedimentation on sucrose gradients shows that Q7b species retained in the ER are multimeric, whereas species that exit the ER are monomeric. This correlation suggests that the presence of an uncleaved signal for GPI anchoring induces changes in the aggregation state of the precursor proteins, which may lead to their retention in the ER.

Amino Acid Sequence↗
PubMed1996

Cellular basis of ECD brain retention.

UNLABELLED: Clinical observations have shown discrepancies between ECD and HMPAO regional cerebral perfusion, particularly in brain tumors and during stroke recovery. We investigated the nature of the process(es) involved in ECD accumulation in vitro at the cellular level. METHODS: Time course incorporation of ECD was studied in a fast-growing human premonocytic line, U937, in a human astrocytic-derived cell line, U373, and a human hybridized endothelial cell line, EaHy926. Cells were further used in experiments aiming to correlate esterase activity and ECD retention. RESULTS: Significant differences in ECD retention between these cell lines were observed: %UECD (cpm cells/cpm standard of injected) plateaued within 2 hr in all cases but %UECD was significantly higher in U937 cells (25.1 +/- 3.9% at 120 min) than in the other cell lines (6.1 +/- 0.7% and 8.2 +/- 2.0% at 120 min for U373 and EaHy926, respectively). Contrary to what we expected, total cellular esterase activity (EATOT) was inversely correlated to %UECD.EATOT was 5-fold lower in U937 cells than in U373 and 20-fold lower than in EaHy926. Thus, we compared the membranar to the cytosolic esterase activity of U937 and analyzed the influence of temperature and diisopropylfluorophosphate (DFP, an inhibitor of cytosolic esterase activity) on both ECD retention and enzymatic activities. When cells were exposed to DFP, %UECD was reduced by 80%; while when cells were maintained at 4 degrees C, %UECD continuously increased, corresponding to a passive diffusion since both cytosolic and membranar esterase activities were inhibited. CONCLUSION: For optimal uptake of ECD, the membranar fraction of the esterase activity has to be low, while, in contrast, the cytosolic fraction of the esterase activity plays an important role in ECD cell retention. ECD-SPECT is likely able to reflect regional cerebral blood flow in normal and pathological states accurately, but in the event of unusual observations, the membranar esterase activity should be considered to explain reduced ECD retention.

Brain↗
PubMed1997

Fractional retention of technetium-99m-sestamibi as an index of P-glycoprotein expression in untreated breast cancer patients.

UNLABELLED: The multidrug-resistant phenotype is characterized by the reduced intracellular retention of several structurally and functionally unrelated cytotoxic compounds due to the energy-dependent pump activity of P-glycoprotein (Pgp). Because 99mTc-sestamibi is a suitable transport substrate of Pgp, we tested whether the time-dependent fractional retention of this tracer could be used as an index of Pgp expression in untreated breast carcinomas. METHODS: Twenty-seven patients with histologically confirmed breast carcinoma were intravenously injected with 740 MBq (20 mCi) of 99mTc-sestamibi, and static planar images of the breast were obtained at 10, 60 and 240 min. The fractional retention of 99mTc-sestamibi was then calculated as the ratios between 60 and 10 min (R60/10) and between 240 and 10 min (R240/10) of decay-corrected counts/pixel registered in the region of interest drawn around the tumor. Surgically excised tumors were then obtained from each patient, and Pgp levels were determined using 125I-labeled MRK16 monoclonal antibody and in vitro quantitative autoradiography. RESULTS: The fractional retention of 99mTc-sestamibi at 60 and 240 min was significantly higher in tumors with low Pgp levels (Group I, n = 18) as compared to that measured in tumors with high Pgp expression (Group II, n = 9) (p < 0.001). In particular, R60/10 values were 0.86 and 0.59 in breast carcinomas of Groups I and II, respectively, whereas the values of R240/10 were 0.56 and 0.25 in low- and high-Pgp-expressing tumors, respectively. CONCLUSION: The determination of fractional retention of 99mTc-sestamibi may be used as a simple functional test for Pgp expression in untreated breast cancer. A preliminary estimate of the sensitivity and the specificity of the test indicates its potential use in clinical practice to identify patients with a high probability of developing multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Intracellular routes and selective retention of antigens in mildly acidic cathepsin D/lysosome-associated membrane protein-1/MHC class II-positive vesicles in immature dendritic cells.

Immature dendritic cells (DC) use both macropinocytosis and mannose receptor-mediated endocytosis to internalize soluble Ags efficiently. These Ags are ultimately presented to T cells after DC maturation and migration into the lymph nodes. We have previously described the immortalized myeloid cell line FSDC as displaying the characteristics of early DC precursors that efficiently internalize soluble Ags. To describe the different routes of Ag uptake and to identify the Ag retention compartments in FSDC, we followed the intracellular fate of FITC-coupled OVA, dextran (DX), transferrin, and Lucifer Yellow using flow cytometry, confocal microscopy, and immunoelectron microscopy. OVA and DX gained access into macropinosomes and early endosomes. DX was preferentially sorted into endosomal compartments, while most of the OVA entered macropinosomes via fluid phase uptake. We found a long-lasting retention of DX and OVA of up to 24 h. After 6 h of chase, these two molecules were concentrated in common vesicular compartments. These retention compartments were distinct from endosomes and lysosomes; they were much larger, only mildly acidic, and lacked the small GTP binding protein rab7. However, they were positive for lysosome-associated membrane protein-1, the protease cathepsin D, and MHC class II molecules, thus representing matured macropinosomes. These data suggest that the activity of vacuolar proteases is reduced at the mildly acidic pH of these vesicles, which explains their specific retention of an Ag. The retention compartments might be used by nonlymphoid tissue DC to store peripheral Ags during their migration to the lymph node.

Animals↗
PubMed1997

von Willebrand factor mediates increased platelet retention in recurrent thrombotic thrombocytopenic purpura.

The plasma cryoprecipitate of two brothers with recurrent thrombotic thrombocytopenic purpura (TTP) was previously found to mediate increased platelet retention and contain ultra-large von Willebrand factor (vWF) multimers during remissions. We conducted this study to examine if vWF is involved in the increased platelet retention in TTP. Platelet retention decreased when the patients' plasma was incubated with a monoclonal antibody directed to the vWF epitope which interacts with the platelet receptor glycoprotein Ib or when incubated with a Fab-fragment directed to the platelet receptor glycoprotein IIb/IIIa. Replacement of patient vWF with an equivalent concentration of a factor VIII/vWF concentrate containing no ultra-large vWF multimers was accompanied by a normalization of platelet retention. These results indicate that vWF is involved in the increased platelet retention. Analysis of polymorphic markers in the vWF gene demonstrated that a recessive mutation in this gene is unlikely.

Adolescent↗
PubMed1997

Predictors of patient retention in a newly established methadone maintenance treatment programme.

AIMS: To identify predictors of patient retention in methadone maintenance. DESIGN: Prospective study. SETTING: Methadone maintenance treatment programme newly established in Geneva, Switzerland. PARTICIPANTS: All patients who initiated treatment between February 1991 and January 1995. MEASUREMENTS: Baseline patient characteristics, dose of methadone, year of enrollment and retention in treatment. FINDINGS: Overall, 111 patients contributed 164.4 person-years of follow-up. The retention rate was 84% after 12 months. In multivariate analysis, the risk of dropping out was significantly higher for patients who had been using opioids for < or = 7 years (relative hazard (RH) 3.0, 95% confidence interval (CI) 1.2-7.4), and for patients who had no stable income at baseline (RH 3.3, 95% CI 1.2-9.1). Dropouts were less frequent at the highest doses of methadone (65-110 mg/day, RH 1.0) than at middle doses (45-60 mg/day, RH 2.0, 95% CI 0.7-5.5) but, quite unexpectedly, dropouts were least likely at the lowest doses (15-40 mg/day, RH 0.5, 95% CI 0.1-1.8). Dropouts were more likely among patients who enrolled in the first (RH 6.2, 95% CI 2.3-16.7) and second (RH 1.9, 95% CI 0.6-5.6) years of the programme, compared with subsequent years (RH 1.0). CONCLUSIONS: Patients who have a long history of drug use and who have a stable income were more likely to stay in methadone maintenance treatment. Independent of patient characteristics, retention improved dramatically in the first years of programme functioning, suggesting that patient retention is a sensitive indicator of programme performance.

Adolescent↗
PubMed1997

Comparison of intravenous retention of fentanyl and lidocaine on local analgesia in propofol injection pain.

BACKGROUND: With a tourniquet on arm for arresting venous blood flow, we evaluated the efficacy of intravenous (i.v.) retention of fentanyl and lidocaine in reducing the pain on i.v. propofol injection during general anesthesia. METHODS: One hundred and twelve patients were studied. Following a venous occlusion by a tourniquet inflated to 70 mmHg, patients in Group A (n = 38) received normal saline (NS) 3 ml, while those in Group B (n = 37) and in Group C (n = 37) respectively received fentanyl 150 micrograms or 3 ml and 2% lidocaine 3 ml (60 mg). The venous retention of drug was maintained for 1 min, followed immediately by tourniquet release and propofol 100 mg i.v. injection over 20 s. RESULTS: Both fentanyl and lidocaine treatments (Groups B and C) were significantly better than placebo (Group A) in reducing pain on propofol injection (p < 0.005). Lidocaine 60 mg was more effective than fentanyl 150 micrograms in reduction of pain associated with i.v. propofol (p < 0.001). Injection of fentanyl itself caused pain in 28% of patients as compared to 2% in the lidocaine group. Mild local skin erythema was noted in 14% of patients with fentanyl venous retention versus 0% of patients with lidocaine venous retention. CONCLUSIONS: Intravenous retention of fentanyl 150 micrograms, although less effective than that of lidocaine (p < 0.001), showed local analgesic effect in reducing the pain on propofol injection. The hypothetic mechanisms of action were speculated.

Adolescent↗
PubMed1998

[Discrepancy between 99mTc-HMPAO and 99mTc-ECD in Alzheimer's disease: does the retention mechanism depend on the disease?].

The discrepancy between 99mTc-hexamethyl-propyleneamine oxime (HMPAO) and 99mTc-ethyl cysteinate dimer (ECD) in Alzheimer's disease (AD) was investigated and compared with in cerebral ischemic disease (CID). The subjects were fourteen AD and thirty-one CID patients with clinically reasonable rCBF reduced lesion on 133Xe SPECT. The subjects did not include the cases of acute and subacute CID. These SPECT were performed within two weeks by ring-type dynamic SPECT (HEADTOME, Shimadzu, Japan). In the CID group, both of HMPAO and ECD SPECT could hardly detect the mildly reduced rCBF lesion on 133Xe SPECT but normal on X-CT. In the case of AD group, the rCBF-reduced lesion on 133Xe SPECT could be detected well by ECD SPECT, but the HMPAO hardly detected the reduced lesion. This discrepancy between HMPAO and ECD may be due to the difference of the retention mechanism. In the case of AD, the injury of esterase activity that participates with the ECD retention may be more notable than that of glutathione activity for the HMPAO retention. These results suggest suggest that the reduction of ECD or HMPAO density depends directly on the insufficiency of retention mechanism rather the than rCBF reduction. And the insufficiency of this retention mechanism depends on also type of the disease i.e. AD or CID.

Alzheimer Disease↗
PubMed1999

Prevention of postherniorrhaphy urinary retention with prazosin.

Urinary retention that necessitates catheterization after herniorrhaphy is a well known, but usually ignored, situation. Increased sympathetic activity resulting from surgery may be the contributing factor. Blockade of alpha receptors in the bladder neck and urethral sphincter may prevent postoperative urinary retention. In this prospective placebo-controlled study, the efficacy of prazosin in preventing postoperative urinary retention after herniorrhaphy was investigated in 156 patients. Patients were randomized into two groups. Patients in Group I (control) were given placebo orally 12 hours before surgery, just before surgery, and 12 and 24 hours after surgery. In Group II, 1 mg of prazosin was given in the same manner of placebo. Nine of 84 patients (10.8%) in the prazosin group and 18 of 72 patients (25%) in the placebo group developed urinary retention. Catheterization was required in only 3 patients (3.5%) in the prazosin group compared to 10 patients (13.8%) in placebo-treated group (P < 0.05). In conclusion, prophylactic use of prazosin after herniorrhaphy significantly reduced the incidence of urinary retention and catheterization.

Adrenergic alpha-Antagonists↗
PubMed1976

[An animal experimental study on the retention rate of polycyclic aromatic hydrocarbons in the lung and in the subcutaneous tissue (author's transl)].

The retention rate of five polyaromatic hydrocarbons (PAH) (benzo(a)pyrene, dibenz(ah)anthracene, chrysene, pyrene, benz(a) anthracene) was studied after intratracheal instillation into syrian hamsters and subcutanous injection into mice. For subcutanous injection the PAH were solved in 0.5 ml tricaprylin, for intratracheal instillation a suspension in NaCl was used. The results were the following: 1. With respect to the retention rate of the five PAH the largest difference was found comparing the application modes. The ratio of the averaged half-time-values for the intratracheal test to the subcutanous test is about 1:35. 2. The retention rates for each polycyclic hydrocarbon differs significantly. An interrelation of PAH after application of a PAH-mixture was not detectable. 3. The retention rates determined in the lung and in the subcutanous tissue do not give a constant ratio concerning each PAH. Thus DBahA is retained in the lung as well as in the subcutanous tissue definitely longer than BaP. Chrysene and benz(a)anthracene behave - respecting the retention rate - in the subcutanous test like BaP. In lung tissue, however, the different behaviour becomes obvious: while benz(a)anthracene is eliminated most rapidly, chrysene can be detected for a relative long time.

Animals↗
PubMed1997

Ontogenetic differences in retention of spatial learning tested with the Morris water maze.

Two experiments examined retention of spatial learning in rats using a Morris water maze. Retention was scored in terms of probe trial performance when the platform was removed. Latency to reach the platform location, percent of time in the quadrant that had contained the platform, and relative frequency of visits to the platform location were analyzed. Results of the first experiment showed that preweanlings and juveniles exhibited substantial forgetting at 3- and 7-day retention intervals. Forgetting in adults was much lower than that found in the younger animals, and no differences in amount of forgetting appeared between the 3- and 7-day retention intervals at any age. The second experiment showed that forgetting in juveniles was alleviated by a single training trial administered just prior to the probe trial. These results are discussed in terms of ontogenetic differences in memory processing and measurement issues pertinent to the Morris water maze test procedure.

Aging↗
PubMed2001

The etiology of urinary retention after surgery for genuine stress incontinence.

Transient postoperative urinary retention after stress incontinence surgery is common, and there is no widely accepted method of hastening the return to normal voiding. The etiology of this retention is poorly understood. Failure of the relaxation of the striated external urethral sphincter has been proposed as an etiologic agent, but has not been documented. Ten patients about to undergo a Burch colposuspension or sub-urethral sling, who demonstrated normal preoperative voiding, were recruited to a study of postoperative retention. Hook-wire electromyographic (EMG)probes were placed into the external urethral sphincter while the patients were under anesthesia, and a suprapubic catheter was placed. We performed instrumented voiding trials 1 or 2 days after surgery while continuously recording urethral EMG and intravesical pressure. Two patients demonstrated normal voiding. Two patients were able to void but demonstrated no EMG silencing. Six patients were unable to void and demonstrated persistent EMG activity. Four of these demonstrated no detrusor contraction, whereas two demonstrated detrusor contractions. All patients resumed normal voiding by clinical parameters within 14 days of surgery. Our study supports other research that suggests that failure of relaxation of the striated urethral sphincter contributes to postoperative urinary retention.

Aged↗
PubMed1976

Acquisition and retention of habituation in the preweanling rat.

The acquisition and retention of habituation to air-puff was studied in rats on Days 1-19 postpartum. Animals of all ages demonstrated habituation but the rate of habituation varied with age: slower on each successive day from Day 1 to Day 8, but thereafter more rapid on each successive day. This peak of elicited responding is discussed in relation to the peak of spontaneous activity at Day 16 and to the pattern of neural development, including changes in acetylcholinesterase, norepinephrine, and serotonin, measured during the preweaning period. All ages showed 30-min retention of habituation, with 60-min retention developing after the 1st week. No evidence of 24-hr retention appeared at any age.

Acetylcholinesterase↗