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PubMed2006

Expression of human telomerase reverse transcriptase and correlation with telomerase activity in placentas with and without intrauterine growth retardation.

BACKGROUND: Human telomerase reverse transcriptase has been found in telomerase-positive tumor tissues, but not in telomerase-negative nonmalignant somatic cells. METHODS: Thirty-two first-trimester chorionic villi specimens (Group A), 33 second- and third-trimester placenta specimens without asymmetric intrauterine growth retardation (Group B) and 13 specimens of placenta tissue from cases with intrauterine growth retardation (Group C) were examined for telomerase activity and expression of human telomerase reverse transcriptase by reverse transcription polymerase chain reaction and quantitative reverse transcription polymerase chain reaction. RESULTS: Telomerase activity was detected in 29 of the 32 specimens (90.6%) in Group A, in 20 of the 33 specimens (60.6%) in Group B and none of the 13 specimens (0.0%) in Group C. Human telomerase reverse transcriptase was identified in all 32 specimens of Group A (100%), all 33 specimens of Group B (100%) and 2 of the 13 specimens in Group C (15.4%) by nested reverse transcription polymerase chain reaction. Copy numbers of human telomerase reverse transcriptase were 202.3 +/- 73.0 (n=32), 8.8 +/- 2.9 (n=33) and 0 (n=13) in Groups A, B, and C, respectively. Significant differences were observed between Groups A and B, Groups A and C, and Groups B and C (p <0.01, p < 0.01, and p < 0.01, respectively). CONCLUSIONS: Our findings indicate that human telomerase reverse transcriptase expression is the rate-limiting determinant of telomerase activity in chorionic villi during the first trimester. Telomerase activity was not detected in placentas with intrauterine growth retardation, whereas human telomerase reverse transcriptase was expressed in some placentas with intrauterine growth retardation.

Chorionic Villi Sampling↗
PubMed2000

Diminished human immunodeficiency virus type 1 reverse transcription and nuclear transport in primary macrophages arrested in early G(1) phase of the cell cycle.

Previously, we and others have demonstrated that the process of reverse transcription of human immunodeficiency virus type 1 (HIV-1) is disturbed in nondividing macrophages and quiescent T lymphocytes. Here we analyzed which phase of the cell cycle in macrophages is crucial for early steps in the HIV-1 replication cycle. HIV-1 Ba-L-inoculated macrophages arrested early in the G(1) phase by n-butyrate contained incomplete products of reverse transcription. In gamma-irradiated macrophages, reverse transcription was successfully completed but proviral integration could not be detected. In these cells, nuclear import was disturbed as reflected by the absence of two-long-terminal-repeat circles. In macrophages arrested late in G(1) phase by aphidicolin or 5, 6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DRB), reverse transcription was unaffected. Proviral integration occurred efficiently in DRB-treated macrophages, whereas integrated proviral DNA could not be detected after aphidicolin treatment. Arrest at G(2) phase of the cell cycle by nocodazole did not affect reverse transcription or proviral integration. Treatment of macrophages with hydroxyurea (HU), which reduces the intracellular deoxynucleoside triphosphate (dNTP) pool by blocking the de novo synthesis of dNTP, resulted in a dose-dependent inhibition of HIV-1 reverse transcription. This could partially be restored by the addition of nucleoside precursors. Addition of nucleoside precursors enhanced both reverse transcription and cell proliferation. However, the disturbed reverse transcription observed in the nonproliferating and n-butyrate-treated macrophages could not be restored by addition of nucleoside precursors. Similar to observations in quiescent T lymphocytes, incomplete proviral DNA species were arrested in the cytoplasm of the macrophages. Our results indicate that also in primary macrophages the intracellular nucleotide pools and other cellular factors that coincide with late G(1) phase of the cell cycle may contribute to efficient reverse transcription and nuclear localization.

Biological Transport↗
PubMed2006

Intracytoplasmic maturation of the human immunodeficiency virus type 1 reverse transcription complexes determines their capacity to integrate into chromatin.

BACKGROUND: The early events of the HIV-1 life cycle include entry of the viral core into target cell, assembly of the reverse transcription complex (RTCs) performing reverse transcription, its transformation into integration-competent complexes called pre-integration complexes (PICs), trafficking of complexes into the nucleus, and finally integration of the viral DNA into chromatin. Molecular details and temporal organization of these processes remain among the least investigated and most controversial problems in the biology of HIV. RESULTS: To quantitatively evaluate maturation and nuclear translocation of the HIV-1 RTCs, nucleoprotein complexes isolated from the nucleus (nRTC) and cytoplasm (cRTC) of HeLa cells infected with MLV Env-pseudotyped HIV-1 were analyzed by real-time PCR. While most complexes completed reverse transcription in the cytoplasm, some got into the nucleus before completing DNA synthesis. The HIV-specific RNA complexes could get into the nucleus when reverse transcription was blocked by reverse transcriptase inhibitor, although nuclear import of RNA complexes was less efficient than of DNA-containing RTCs. Analysis of the RTC nuclear import in synchronized cells infected in the G2/M phase of the cell cycle showed enrichment in the nuclei of RTCs containing incomplete HIV-1 DNA compared to non-synchronized cells, where RTCs with complete reverse transcripts prevailed. Immunoprecipitation assays identified viral proteins IN, Vpr, MA, and cellular Ini1 and PML associated with both cRTCs and nRTCs, whereas CA was detected only in cRTCs and RT was diminished in nRTCs. Cytoplasmic maturation of the complexes was associated with increased immunoreactivity with anti-Vpr and anti-IN antibodies, and decreased reactivity with antibodies to RT. Both cRTCs and nRTCs carried out endogenous reverse transcription reaction in vitro. In contrast to cRTCs, in vitro completion of reverse transcription in nRTCs did not increase their integration into chromatin. CONCLUSION: These results suggest that RTC maturation occurs predominantly in the cytoplasm. Immature RTCs containing RT and incomplete DNA can translocate into the nucleus during mitosis and complete reverse transcription, but are defective for integration.

Cell Division↗
PubMed2004

Properties of the reverse transcription reaction in mRNA quantification.

BACKGROUND: In most measurements of gene expression, mRNA is first reverse-transcribed into cDNA. We studied the reverse transcription reaction and its consequences for quantitative measurements of gene expression. METHODS: We used SYBR green I-based quantitative real-time PCR (QPCR) to measure the properties of reverse transcription reaction for the beta-tubulin, glyceraldehyde-3-phosphate dehydrogenase, Glut2, CaV1D, and insulin II genes, using random hexamers, oligo(dT), and gene-specific reverse transcription primers. RESULTS: Experimental variation in reverse transcription-QPCR (RT-QPCR) was mainly attributable to the reverse transcription step. Reverse transcription efficiency depended on priming strategy, and the dependence was different for the five genes studied. Reverse transcription yields also depended on total RNA concentration. CONCLUSIONS: RT-QPCR gene expression measurements are comparable only when the same priming strategy and reaction conditions are used in all experiments and the samples contain the same total amount of RNA. Experimental accuracy is improved by running samples in (at least) duplicate starting with the reverse transcription reaction.

Animals↗
PubMed2001

Thermal effects on reverse transcription: improvement of accuracy and processivity in cDNA synthesis.

Reverse transcription, coupled with DNA amplification, has been widely used for molecular analysis of RNAs. Reverse transcriptases are retroviral DNA polymerases that can synthesize DNA from both RNA and DNA. In general, because of the lack of 3'-->5' exonuclease activity in retroviral reverse transcriptases, the reverse transcription step is error prone. Mutations created during the reverse transcription step of cDNA synthesis or RT-PCR are delivered to the final products to be analyzed, interfering with accurate analysis of the RNAs. In addition, because reverse transcription uses RNA as a template, processive DNA synthesis by reverse transcriptase is frequently interrupted by secondary structures of the RNA templates, causing difficulties in full-length cDNA synthesis. Here, we report that an increase in reaction temperature greatly enhances both the accuracy and the processivity of reverse transcription catalyzed by murine leukemia virus (MuLV) and human immunodeficiency virus type 1 (HIV-1) reverse transcriptases.

DNA, Complementary↗
PubMed1997

[Relationship between microsurgical tubal reversal and ectopic pregnancy].

OBJECTIVE: To study the correlation between microsurgical tubal reversal after tubal sterilization and ectopic pregnancy. METHODS: 1029 women who underwent microsurgical tubal reversal were followed up. The causes of ectopic pregnancy were analysed and discussed. RESULTS: 960 intrauterine pregnanciess and 12 ectopic pregnancies occurred. The 12 ectopic pregnancies were all tubal ones, among which 2 had intrauterine pregnancies. The rate of ectopic pregnancy in the 1029 women was 1.17%, and in the pregnant cases was 1.23%. The ratio of intrauterine pregnancy to ectopic pregnancy was 1:80. The rates of ectopic pregnancy in the 1st, 2nd year and 2 years later after tubal reversal were not significantly different respectively among the tubal reversal and among the pregnant cases. The rates of ectopic pregnancy in the 1st and 2nd 6 months after tubal reversal were not statistically different. The early tubal hydrapertubation could only increase the chance of ectopic pregnancy. The sterilization method, reversal mode, and interval between sterilization and reversal were not related to the ectopic pegnancy. CONCLUSION: When the lesion in the sterilized position is completely removed, the sutures being through the tubal mucosa and the early tubal hydrapertubation not carried out, the chance of ectopic pregnancy can not be increased after tubal reversal. The contraception 6 months after tubal reversal is not related to ectopic pregnancy.

Adult↗
PubMed1996

Absence of correlation between Sry polymorphisms and XY sex reversal caused by the M. m. domesticus Y chromosome.

Mus musculus domesticus Y chromosomes (YDOM Chrs) vary in their ability to induce testes in the strain C57BL/6J. In severe cases, XY females develop (XYDOM sex reversal). To identify the molecular basis for the sex reversal, a 2.7-kb region of Sry, the testis-determining gene, was sequenced from YDOM Chrs linked to normal testis determination, transient sex reversal, and severe sex reversal. Four mutations were identified. However, no correlation exists between these mutations and severity of XYDOM sex reversal. RT-PCR identified Sry transcripts in XYDOM sex-reversed fetal gonads at 11 d.p.c., the age when Sry is hypothesized to function. In addition, no correlation exists between XYDOM sex reversal and copy numbers of pSx1, a Y-repetitive sequence whose deletion is linked to XY sex reversal. We conclude that SRY protein variants, blockade of Sry transcription, and deletion of pSx1 sequences are not the underlying causes of XYDOM sex reversal.

Animals↗
PubMed1999

An Experimental Study on the Relationship between the Physical Properties of CTAB/Hexanol/Water Reverse Micelles and ZrO2-Y2O3 Nanoparticles Prepared.

Based on the studies of their physical properties such as aqueous solution uptake, electric conductivity, and microstructure, CTAB/hexanol/water reverse micelles (CTAB, cetyltrimethyl ammonium bromide) were used to prepare ZrO2-Y2O3 nanoparticles. The relationship between the micelle microstructure and size, morphology, and aggregate properties of particles prepared was also investigated. It has been found that with high CTAB concentration ([CTAB] > 0.8 mol/l), the reverse micelles can solubilize a sufficient amount of aqueous solution with high metallic ion concentration ( approximately 1.0 mol/L), while the microstructure of the reverse micelles keeps unchanged. The most important factor affecting the size and shape of reverse micelles was found to be the water content w0 (w0, molar ratio of water to surfactant used). When both the CTAB concentration and the w0 values are low, the diameters of reverse micelles are below 20 nm, and the ZrO2-Y2O3 particles prepared are also very small. However, the powders obtained were found to form a lot of aggregates after drying and calcination. High CTAB concentration, high w0 value, and high metallic ion concentration in the aqueous phase for high powder productivity were found to be the suitable compositions of reverse micelles for preparing high-quality ZrO2-Y2O3 nanoparticles. Under these conditions, the reverse micelles are still spherical in shape even the reverse micellar system is nearly saturated with aqueous solutions. These reverse micelles were found to have a diameter of between 60 and 150 nm and the ZrO2-Y2O3 particles prepared therefrom range from 30 to 70 nm with spherical shape and not easy to form aggregates. Copyright 1999 Academic Press.

Journal Article↗
PubMed2001

Formation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty Acids.

The formation of reversed micellar systems composed of phosphatidylcholine (PC) and fatty acid was newly demonstrated by a significant increase in water content in the organic ethyl oleate phase when the micelles were prepared by the contact method. The solubilized water concentration in the reversed micellar organic phase reached 3 wt%. The new systems are expected to be used as highly biocompatible reversed micellar systems. The structure of the reversed micelles composed of PC and oleic acid was characterized by determining the water concentration and by small-angle X-ray scattering analysis. The reversed micelles composed of PC and oleic acid formed in ethyl oleate were spherical. The radius of gyration was between 30 and 50 Å. The size of the reversed micelles decreased with an increase in the oleic acid concentration and was independent of the PC concentration. Experimental results indicated that the structure of the reversed micellar system was determined by the oleic acid concentration. An increase in the PC concentration caused an increase in the number of reversed micelles of the same size. These reversed micellar systems are expected to be used as solubilization media in pharmaceutical and food industries because they are not toxic. Copyright 2001 Academic Press.

Journal Article↗
PubMed1994

Reverse redistribution of thallium-201 represents a low-risk finding in thrombolysed patients following myocardial infarction.

The aim of the study was to evaluate the prevalence and clinical significance of reverse redistribution on thallium-201 imaging in post-myocardial infarction patients who have undergone thrombolytic therapy. Sixty-two patients aged 35-79 (mean 60) years with proven myocardial infarction who had undergone thrombolysis were studied 6 weeks post infarction. Standard stress and 4-h redistribution imaging was performed with 201Tl following treadmill exercise. Separate day rest injection of 201Tl was given after sublingual nitroglycerine; imaging was performed at 1 h. Planar images were acquired in three standard views and semiquantitative segmental analysis of the images was performed from the unprocessed images. All patients had radionuclide ventriculography for the assessment of left ventricular ejection fraction and wall motion abnormality. Thirty-three patients also had coronary angiography. 201Tl scintigraphy revealed fixed defects in 19 patients, reversible defects in 22, and reverse redistribution in 21. Those with reverse redistribution had a significantly higher exercise capacity (P < 0.01). Mean (SD) left ventricular ejection fraction was 46 (12)% for those with fixed defects, 47 (9)% for those with reversible defects and 45 (15)% for patients with reverse redistribution (P = NS). The regional wall motion abnormality score was 8 (5), 11.8 (2.2) and 14.2 (6) respectively in patients with reverse redistribution, redistribution alone and fixed defects. Regions with reverse redistribution revealed less regional wall motion abnormality compared to the other two groups (P < 0.01). Fifteen patients demonstrated significant 201Tl uptake in the region showing reverse redistribution, with rest injection of 201Tl following sublingual nitroglycerine, suggesting viable myocardium in that region.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed2005

Hartmann's reversal is associated with high postoperative adverse events.

PURPOSE: The aim of this study was to ascertain the preva lence and pattern of surgical and medical adverse events in patients undergoing Hartmann's reversal for diverticular dis ease. A comparison of postoperative outcomes is made be tween Hartmann's reversal and primary resection and anas tomosis. METHODS: Data were collected from patients who underwent successful Hartmann's reversal (Group 1 n=121) and primary resection and anastomosis (Group 2 n=731) for diverticular disease in a single center from January 1981 to May 2003. Multivariate logistic regression was used to compare early postoperative mortality, medical and surgical complications and readmission rates between the two groups. RESULTS: Hartmann's reversal was associ ated with a higher prevalence of surgical or medical com plications compared with primary resection and anastomo sis (43.8 percent and 9.1 percent for Hartmann's reversal vs. 26.0 percent and 4.8 percent for primary resection and anastomosis). There was no difference in the readmissior rates (7.2 percent vs. 7.6 percent, respectively, P = 0.88) or early postoperative mortality (1.7 percent vs. 0.7 percent, P = 0.25) between Hartmann's reversal and primary resection and anastomosis. The need for reoperation, prolonged ileus respiratory tract infections, and renal failure were more common adverse events in the Hartmann's reversal group (P < 0.01). Having controlled for the number of comorbid conditions, extent of diverticular disease, severity of peri toneal contamination (Mannheim Peritonitis Index), and op erative urgency, patients who underwent Hartmann's rever sal were 2.1 times more likely to have adverse surgical events during their postoperative period (95 percent confidence interval for odds ratio = 1.3-3.3). CONCLUSIONS: Hartmann's reversal is a complex surgical procedure that is associated with a high prevalence of postoperative adverse events in comparison with primary resection and anastomosis. To minimize the prevalence of such adverse events, patients who undergo Hartmann's reversal need careful preoperative evaluation and close monitoring in their postoperative period.

Adult↗
PubMed1994

Why do ambiguous figures reverse?

For much of this century the dominant theory of reversal of ambiguous figures has been neural satiation. We suggest a very different kind of theory based on the consequences of the typical instructions given to subjects in experiments on reversal. In analyzing these instructions in preliminary experiments we conclude that what matters is the subject's knowledge that the figure is reversible and specific knowledge of how its alternative construals appear. This leads to an intention to reverse the figure. In one experiment we demonstrate that recent experience with the ambiguous figure and its two modes of appearance does not lead to its reversal if the subject does not know the figure is reversible. In another experiment we demonstrate that when the subject does know the ambiguous figure is reversible, it nonetheless will not tend to reverse if the intention to do so is contravened by a different intention. We suggest that the intention to reverse cannot succeed unless the subject "knows" how to carry it out and, further, that the intention may become involuntary and automatic.

Female↗
PubMed1991

Frequency of late reversibility in stress-redistribution thallium-201 SPECT using an early reinjection protocol.

To assess the efficacy of an early thallium-201 reinjection protocol for reducing the need for late redistribution imaging, the frequency of thallium-201 late reversibility was prospectively assessed in 62 patients who had stress-redistribution thallium-201 studies by single-photon emission computerized tomography (SPECT), and who received 1 mCi of thallium-201 reinjection immediately following stress tomographic acquisition. These patients also demonstrated greater than or equal to 2 segments with nonreversible defects at 4-hour imaging and underwent late (18-to 72-hour) redistribution imaging. When the criterion of late reversibility was defined as greater than or equal to 1 segment with a 4-hour nonreversible defect demonstrating late reversibility, late reversibility was present in 36 (58%) of the 62 patients and in 88 (24%) of 368 SPECT segments. When the criterion of greater than or equal to 2 segments was used, late reversibility was found in 21 (34%) of the 62 patients and in 73 (20%) of the 368 segments. Of the 21 patients who had greater than or equal to 2 late reversible segments, 12 (57%) exhibited late reversibility in greater than or equal to 3 segments. The frequency of detected reversible defects increased from 32% by 4-hour imaging to 48% by combined 4-hour and late imaging (p less than 0.0001). The patients who demonstrated late reversibility could not be distinguished from those who had only late nonreversible defects by analysis of the clinical, exercise, and electrocardiographic (ECG) variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Reversibility of the effects of dietary fish oil on the fatty acid composition of the brain and retina of growing chicks.

Dietary fish oil increases levels of (n-3) fatty acids in the brain and retina of younger animals but has less effect in adults. The duration of the effects of fish oil in young animals, as well as the extent of reversibility of the effects, are unknown. Laying hens were fed either a fish oil diet or a soybean oil-based control diet. Resulting chicks were assigned to three diet groups: chicks from fish oil and soybean oil hens were continued on fish oil and soybean oil diets, respectively, for 0, 3, 6, or 9 weeks, and additional chicks from the fish oil hens were fed the fish oil diet for 0, 3, or 6 weeks and then reversed to the soybean oil diet for a period of 3 weeks. The fatty acid composition of the brain, retina, liver, and serum of the reversal chicks was compared with chicks fed the fish oil diet only or the soybean oil diet only. Brain levels of docosahexaenoic acid (22:6(n-3)) decreased substantially when reversal from the fish oil diet to the control diet was begun at hatching, but did not decrease when reversal was begun at later times. Other (n-3) fatty acids in the brain, docosapentaenoic acid (22:5(n-3)) and eicosapentaenoic acid (20:5(n-3)), decreased substantially at all ages, and to a greater extent than 22:6(n-3). Brain arachidonic acid (20:4(n-6)), which was low in fish oil chicks, rose to control after reversal at hatching, but recovered only partially when reversal was begun at later times. A similar patterns was observed in the retina. Serum and liver (n-3) fatty acids fell to control in all reversal chicks, and (n-6) fatty acids increased to control, except in chicks reversed at 6 weeks. This study demonstrates that by 3 weeks of age the chick brain strongly resists diet-induced lowering of high levels of 22:6(n-3).

Analysis of Variance↗
PubMed1987

Radiation-induced forward and reverse specific locus mutations and dominant cataract mutations in treated strain BALB/c and DBA/2 male mice.

Strain BALB/c and DBA/2 mice were chosen to investigate the effects of genetic background on the radiation-induced mutation rate since they exhibit differences in their radiation sensitivity. Males were exposed to 3 + 3-Gy X-irradiation and mated to untreated specific locus Test-stock females. Offspring resulting from treated spermatogonia were screened for induced specific locus forward and reverse mutations and dominant cataract mutations. Since BALB/c mice are homozygous brown and albino, specific locus forward mutations could be screened at 5 of the 7 specific loci (a, d, se, p, s), while reverse mutations could be screened at the b and c loci. Strain DBA/2 is homozygous non-agouti, brown and dilute. Therefore, specific locus forward mutations could be screened at 4 loci (c, se, p, s) and reverse mutations were screened at the a, b and d loci. Results indicate no effect of genetic background on the sensitivity to mutation induction of specific locus forward mutations, while for the dominant cataract alleles strain DBA/2 exhibited a higher mutation rate than either strain BALB/c or similarly treated (101/El X C3H/El)F1 mice. If, by confirmation, these differences should be demonstrated to be real, it is interesting that strain DBA/2 should exhibit a greater sensitivity to radiation-induced dominant mutations. First, strain DBA/2 was chosen as radiation resistant or repair competent. The observation that DBA/2 exhibited a higher sensitivity to radiation-induced mutation may indicate a role for repair, albeit misrepair, in the mutation process. Second, that the effect of genotype was only observed for the mutation rate to dominant cataract alleles may reflect a difference in the spectrum of DNA alterations which result in dominant or recessive alleles. A dominant allele is more likely misinformation, such that as heterozygote it interferes with the wild-type allele. By comparison, a recessive allele may result from any DNA alteration leading to the loss of a functional gene product. One reverse mutation at each of the a and d loci was recovered in the present experiments. The similarities of the present results for radiation-induced reverse mutations with the extensive data on the spontaneous reverse mutation rates are interesting. Reverse mutations were recovered only at the a and d loci. Further, the reverse mutations recovered at the a locus were to alternate alleles (at, Aw or Asy) while true reverse mutations were apparently recovered at the d locus.

Abnormalities, Radiation-Induced↗
PubMed1987

Reversal of methylmercury-induced block of nerve-evoked release of acetylcholine at the neuromuscular junction.

Acute bath application of micromolar concentrations of methylmercury (MeHg) blocks the nerve-evoked release of acetylcholine at the neuromuscular junction by presynaptic effects. The goal of the present study was to try to reverse this block of stimulus-evoked release. Experiments were conducted using the phrenic nerve hemidiaphragm of the rat and conventional intracellular microelectrode techniques. Myofibers were cut ("cut muscle") to prevent contractions elicited by stimulation of the phrenic nerve. End-plate potentials (EPPs) were recorded before and during MeHg application and during subsequent reversal attempts. MeHg (100 microM) blocked the EPP within 8-9 min of application. The time to block did not differ if Sr2+ (2 mM) was substituted for Ca2+ prior to exposure to MeHg. Washing the preparation with MeHg-free physiological saline at the time the EPP was blocked failed to reverse the block of synaptic transmission even during protracted washing. Increasing the extracellular [Ca2+] from 2 to 4 mM, or application of 4-aminopyridine (50 or 100 microM) failed to reverse block of the EPP. D-Penicillamine was also ineffective at reversing transmission block when applied at 0.4 mM; however, when applied at 1 mM D-penicillamine caused a return of EPPs in three of eight experiments within 5-20 min of wash. Longer periods of washing with D-penicillamine or use of higher concentrations of D-penicillamine were not effective in reversing transmission block in the refractory preparations. Increasing the intensity or duration of stimulation at the time of EPP block was uniformly successful in reversing MeHg-induced block; in 9 of the 10 preparations tested, EPPs could again be elicited from MeHg-blocked preparations merely by increasing the intensity and/or duration of stimulation, despite the continued presence of MeHg. Following reversal of transmission block by MeHg, continued exposure to MeHg resulted in a subsequent block of the EPP within approximately 3 min. During this subsequent block of the EPP by MeHg, increasing extracellular [Ca2+] or adding 4-aminopyridine did restore synaptic transmission. These results indicate that a temporary reversal of MeHg-induced block of synaptic transmission can be produced and that this effect does not require extracellular Ca2+ during the initial stages, but does seem to require extracellular Ca2+ during later stages.

Acetylcholine↗
PubMed1990

ISI produces reverse apparent motion.

A moving random-dot stimulus was presented in two sequential frames separated by an interstimulus interval (ISI) during which the field was spatially uniform with luminance equal to either the average luminance of the stimulus field (grey) or that of the black dots (black). In Experiment 1, black ISIs did not affect perception of motion direction but grey ISIs produced motion in the direction opposite to the physical displacement (reverse motion). In Experiment 2, the contrast of the stimulus was reversed simultaneously with the displacement of the random-dot fields so that reverse motion would be seen with no ISI [Anstis & Rogers, Vision Research, 15, 957, 1975]. In this condition, grey ISIs reversed the reverse motion to produce a veridical perception. Finally, in Experiment 3, we examined whether the negative image that follows the stimulus offset was the source of the reversal in motion direction. A gradual offset of the stimulus necessarily reduces the amplitude of the negative response at stimulus offset and also reduced the frequency of seeing reverse motion, suggesting that the apparent reversal of motion direction with ISI can be attributed to the negative phase of a biphasic impulse response function. A simulation of the temporal response to the displacements of random-dot fields demonstrated that the negative phase of a biphasic impulse response function is sufficient to produce the reverse motion. We therefore claim that there is a significant biphasic temporal response function that precedes the analysis of motion in the visual system. This indicates that the overall temporal response function of the visual system is the result of a cascade of functions from early through late stages and that only a portion of the overall temporal response function can be attributed to stages involved in motion analysis.

Contrast Sensitivity↗
PubMed1989

RO15-4513 but not FG-7142 reverses anticonvulsant effects of ethanol against bicuculline- and picrotoxin-induced convulsions in rats.

The reversal of anticonvulsant effect of ethanol against chemoconvulsions by RO15-4513 was investigated in rats as this novel imidazobenzodiazepine (ethyl-8 azido-5, 6-dihydro-5-methyl-6-Oxo-4H-imidazo [1,5a] [1,4] benzodiazepine-3-carboxylate) is reported to antagonize the acute behavioral and biochemical effects of ethanol in animals. Reversal of ethanol effects on onset of myoclonic jerks, tonic extensor phase, mortality time and percent protection against mortality were compared with not only other anticonvulsant pentobarbital but also with another inverse agonist FG-7142. Pretreatment with RO15-4513 (4 mg/kg) reversed the protective effect of ethanol against bicuculline-induced tonic extensor phase and mortality (87%). This response was sensitive to reversal by RO15-1788 (10 mg/kg). However, onset of myoclonic jerks and duration of clonus were not significantly altered. It also reversed the effect against picrotoxin but the reversal against mortality was up to 50%. As compared to ethanol, RO15-4513 reversed partially the protective effect of pentobarbital against bicuculline- and picrotoxin-induced convulsions. FG-7142 failed to reverse the protective effect of ethanol and pentobarbital against bicuculline-induced tonic extensor phase although it reversed the effect against onset and mortality. It had no effect on the protective effect against picrotoxin-induced convulsions. Both RO15-4513 and FG-7142 possessed proconvulsant effects against bicuculline but not against picrotoxin. These observations suggest that RO15-4513 has a more preferential action against ethanol effects as compared to the other inverse agonist.

Affinity Labels↗