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PubMed2000

Reversal reactions in the skin lesions of AMFES patients: incidence and risk factors.

Reversal reactions affect the skin and/or nerves of leprosy patients. This paper looks at reversal reactions involving the skin in 594 new patients in central Ethiopia, followed for between 6 and 11 years after the start of treatment. The incidence of reversal reaction declines steadily after the start of treatment, but the first episode may occur as long as 5 years after diagnosis in both paucibacillary (PB) and multibacillary (MB) patients. Recurrent episodes occurred up to 6 years after diagnosis. PB patients were at greatest risk for reversal reaction in the first year after diagnosis and MB patients in the first 4 years. The highest incidence rate was 18 episodes per 100 person years in MB patients during the first year after diagnosis. The ratio of the incidence rates for the first 3 years in MB versus PB patients is 2.4 (95% CI 1.6-3.8). This study confirms that starting effective treatment and borderline classification are risk factors for reversal reactions. Pregnancy/delivery in the 6 months prior to diagnosis was a significant risk factor for presenting with a reversal reaction [relative risk (RR) 5.9 (95% CI 2.1-16.5)], but later pregnancies were not associated with an increased risk. Being female was a significant risk factor for the late appearance of the first episode of reversal reaction. Having a reversal reaction in the first year after diagnosis was a highly significant risk factor for the development of later reactions [RR in PB cases 11.9 (95% CI 3.4-41.7); in MB cases 6.4 (95% CI 3.8-10.6)]. Being HIV positive was a risk factor for developing recurrent reversal reactions, although only three out of 29 recurrent cases were HIV positive [RR 2.7 (95% CI 1.4-5.1)].

Adult↗
PubMed2000

Treatment effects of simple fixed appliance and reverse headgear in correction of anterior crossbites.

The aim of this study was to compare the skeletal and dental changes contributing to the correction of Class III malocclusion using a 2 x 4 appliance and reverse headgear in the mixed dentition. Seventeen consecutive patients (mean age, 9.7 years) with pseudo-Class III malocclusions and an anterior functional shift and straight or concave facial profile were treated with a simple fixed appliance. Another 20 consecutive patients (mean age, 8.5 years) with Class III incisor relationship and straight or concave facial profiles, were treated with reverse headgear. Lateral cephalometric films taken at the beginning of treatment, the end of the treatment, and 1 year after the active treatment, were analyzed with the modified Pancherz analysis. After active treatment, the overjet correction, 5.2 mm and 6.5 mm on average, respectively, were achieved using the 2 x 4 and reverse headgear. The overjet correction by the 2 x 4 appliance was due to dental changes only. In the reverse headgear group, 60% of the overjet correction was due to dental changes and 40% due to skeletal changes. During the 12 months follow-up period, the overjet was unchanged in the 2 x 4 group (1.6 mm) and decreased in the reverse headgear group, the difference being statistically significant (P <.05). The change of jaw relationship was similar between the 2 x 4 and reverse headgear groups. During the follow-up period, a decrease in overjet in the reverse headgear group was mainly due to forward growth of the mandible and proclination of lower incisors. The overjet in the 2 x 4 group was unchanged due to dental compensation (1.6 mm). To conclude there was a similar amount of overjet correction in the 2 x 4 and reverse headgear groups. Overjet correction by the simple fixed appliance was produced by dental changes whereas in the reverse headgear group, it was produced by both dental and skeletal changes.

Cephalometry↗
PubMed1999

[Comparison between motion sickness induced by reversed vision and that by parallel swing].

OBJECTIVE: To make clear the characteristics of motion sickness induced by reversed vision and to see whether it can be used in motion sickness experiments. METHODS: 10 healthy young men experienced walking tests wearing up-down or left-right reversing prisms, and parallel swing test on different days with intervals of 5-7d. Ataxia and motion sickness symptoms induced by walking wearing reversing prisms and those by parallel swing were observed. The reversed vision tolerance index (RVTI) and linear acceleration tolerance index (LATI) were calculated by an empirical formula. RESULTS: Both types of reversing prisms can induce obvious ataxia and motion sickness symptoms. The ataxia is correlative (P<0.05) with the susceptibility to motion sickness. In comparison with symptoms of swing motion sickness, the symptoms of reversed vision motion sickness are not too serious and appear slowly. There are correlativities (P< 0.01) between the susceptibility to motion sickness induced by up-down and left-right reversing prisms. The susceptibilities to motion sickness induced by reversing prisms are not correlative completely with that by swing. CONCLUSION: Reversed vision test is simple and easy and can be used for simulating space motion sickness or training of adaptation to sensory conflict on the ground.

Acceleration↗
PubMed1992

Collins' solution for cold storage of the heart for transplantation must be reversed with cardioplegic solution before reperfusion. A functional and metabolic study in the rat heart.

The following hypotheses were tested using an isolated perfused working rat heart model: (1) Collins' solution for cold storage of the heart is harmful for the heart during reperfusion; (2) a "reverse" of the intracellular-type Collins' solution with an extracellular-type cardioplegic solution before reperfusion is able to prevent this disadvantage of Collins' solution. The following two major groups (I and II) and five subgroups (-a to -e) in each group were prepared. In group I (reversed group); the hearts were initially stored in Collins' solution but were reversed by a 1-minute flush with cardioplegic solution followed by storage in cardioplegic solution for the last 1 to 180 minutes of the total 3-hour storage, that is, groups I-a (reversed for 1 minute), I-b (10 minutes), I-c (30 minutes), I-d (90 minutes), and I-e (180 minutes). In group II (nonreversed control group); the hearts were stored in Collins' solution throughout 3 hours and were also divided into five subgroups of groups II-a, II-b, II-c, II-d, and II-e in which only a 1-minute flush with Collins' solution was performed at the point corresponding to group I. The coronary flow in any of group II showed a marked decrease during the early reperfusion period. In group I, however, the coronary flow increased significantly in proportion to the duration of the reversing phase. The recovery of the aortic flow and the cardiac output in group I showed a bell-shaped pattern in relation to the duration of the reversing phase, reaching their peak values when reversed for 30 minutes (group I-c). The prolonged reverse (180 minutes) resulted in a deterioration of functional recovery associated with a poorer preservation of high-energy phosphates and a larger enzyme leakage. These results suggest that the beneficial effects of intracellular-type Collins' solution for cold storage of the heart were further improved by reversing Collins' solution with the extracellular-type cardioplegic solution for the last 30 minutes of the 3-hour cold storage because the disadvantageous vasoconstriction due to Collins' solution during reperfusion was successfully prevented by the replacement of intravascular and extravascular Collins' solution with cardioplegic solution before the reperfusion.

Animals↗
PubMed2006

Dual regulation of soluble tumor necrosis factor-alpha induced activation of human monocytic cells via modulating transmembrane TNF-alpha-mediated 'reverse signaling'.

Transmembrane tumor necrosis factor-alpha (mTNF-alpha) is known to be the precursor of soluble TNF-alpha (sTNF-alpha). mTNF-alpha can act as a ligand on the TNF receptor- (TNFR)- bearing cell through 'forward signaling' or as a receptor on the TNF producing cell through 'reverse signaling'. In the current study, we investigated the role of mTNF-alpha-mediated reverse signaling in regulating sTNF-alpha-induced activation of human monocytic U937 cells. We demonstrated that pretreatment with sTNFRI, for inducing reverse signaling through mTNF-alpha, sensitized U937 cells to sTNF-alpha stimulation, as evidenced by an increase in reactive oxygen production and mRNA levels of proinflammatory cytokines (TNF-alpha, IL-1beta, and IL-8) in these cells. Further experiments revealed that IkappaB-alpha degradation was increased in the monocytic cells primed with sTNFRI, implying that reverse signaling of mTNF-alpha sensitizes U937 cells via an NF-kappaB-dependent mechanism. On the other hand, binding of sTNFRI to mTNF-alpha after sTNF-alpha-induced activation of U937 cells reduced mRNA stability (half-life) of IL-1beta and IL-8. The involvement of reverse signaling in the process was verified by using a mutated form of mTNF-alpha lacking the majority of the cytoplasmic domain. Our results clearly showed that enhanced mRNA degradation of the cytokines occurred only in U937 cells transfected with a wild-type mTNF-alpha, but not in those cells transfected with the mutant mTNF-alpha. Taken together, these data suggest that reverse signaling through mTNF-alpha may exert a double role in modulating sTNF-alpha bioactivity. It is positive when reverse signaling occurs prior to sTNF-alpha stimulation, while it is negative when reverse signaling occurs after the sTNF-alpha signal. Thus, our findings strengthen a role of mTNF-alpha-mediated reverse signaling in the regulation of immune-inflammatory response and control of inflammatory reaction.

Cell Line, Tumor↗
PubMed2006

[Bronchial obstruction reversibility test in the assessment of COPD severity--controversies].

UNLABELLED: The GOLD and ERS/ATS guidelines recommend the post-bronchodilator FEV1 (% predicted) to define the severity of chronic obstructive pulmonary disease (COPD). Yet in various publications authors analyze the pre-bronchodilator value or do not clearly state which value was used when the bronchial reversibility test was performed. The guidelines established by the Polish Respiratory Society (PRS) do not specify if performing the reversibility test is necessary to estimate the COPD severity and suggest a reversibility test evaluation which differs from that in the ERS/ ATS and GOLD recommendations. AIM: to assess the changes in the degree of severity of COPD in the classification based upon the pre- and post-bronchodilator FEV1 and to compare the interpretation of the reversibility test as suggested by GOLD and ATS/ ERS and the PRS. METHODS: 145 COPD patients (67F, 78M, mean age 67.5+/-8.9 yrs) with a negative bronchial obstruction reversibility test (salbutamol 400 microg) were enrolled to the study. For each patient the degree of COPD severity using the pre- and postbronchodilator FEV1 was established. The pre- and post-bronchodilator classifications were compared. Differences in the interpretation of the reversibility test according to the GOLD and ATS/ ERS and the Polish guidelines were analyzed. RESULTS: In 22 subjects (15.2%) the degree of disease severity changed after salbutamol. The changes were most frequent in the group of severe and very severe COPD (77.3% of changes). In 1 patient (0.7%) post-bronchodilator severity was greater than before salbutamol intake. In 7 patients (4.8%) the post-bronchodilator FEV1/FVC exceeded 70%, thus excluding the diagnosis of COPD. Of all the 145 negative (according to the ATS/ ERS and GOLD criteria) reversibility tests in 24 cases (16.6%) the test was positive when the criteria recommended by PRS were applied. CONCLUSIONS: the bronchial obstruction reversibility test is essential in the diagnosis and assessment of severity of COPD. Despite poor obstruction reversibility in this disease the use of pre-bronchodilator FEV1 in the assessment of COPD severity may be misleading and is an obstacle in the comparative analysis of studies in the domain of this disease. Differences in the guidelines for the management of COPD may also hinder comparative studies and influence epidemiologic data.

Aged↗
PubMedDate not supplied

[Prevalence of potentially reversible cognitive function disorders in patients of a memory dysfunction clinic].

UNLABELLED: Potentially reversible dementias are rarely detected in out-patient care facilities. Actual reversibility is virtually not known and has been occasionally reported in literature. AIM: To determine the prevalence of potentially reversible dementias among patients seen at the ambulatory care facility and to estimate their "real life" reversibility. METHOD: A retrospective analysis of medical records of 258 outpatients attending the Memory Clinic of the Central University Hospital of Lódź in the years 2002-2003. RESULTS: Potentially reversible dementia was diagnosed in 18 (5 women, mean age 60.9 +/- 4.9) subjects yielding 7% of all the subjects presented. These patients were significantly younger and the severity of their cognitive deficits milder as compared to the "non-reversible" cases. Treatment was successful only in 3 cases what translates into only 1.5% of those diagnosed as demented. Twenty seven cases with cognitive deficit but no dementia (depression or drugs side-effects) were claimed as potentially reversible and treated, in most cases (22 out of 27), successfully. However, within the 2 years period of follow-up in 13 of the 22 cases, the development of dementia was observed. CONCLUSIONS: Potentially reversible dementia is a rare phenomenon in ambulatory care facility. The majority of potentially reversible cases can be found among younger and less impaired patients. Even in cases treated successfully, the risk of developing dementia within 2 years is very high.

Aged↗
PubMed1990

Quantification of the reversibility of stress-induced thallium-201 myocardial perfusion defects: a multicenter trial using bull's-eye polar maps and standard normal limits.

A multicenter trial was performed on 140 patients from four centers to determine the accuracy of quantitative analysis of stress/delayed thallium-201 myocardial tomograms using normal limits to assess the relative amount of reversibility of stress-induced defects. The patients were found to have 85 fixed and 124 reversible defects, as determined by visual interpretation. Reversibility bull's-eye polar maps were compared to gender-matched normal limits from 36 normals. Regions were identified as reversible if their normalized difference between stress and 4 hr greater than 1.5 s.d.s. from the mean normal limits. Overall agreement between experts at multicenter sites and reversibility maps was 73% for reversible defects and 80% of fixed defects. Sensitivity in detecting reversibility was highest for the left circumflex (88%) and lowest for the right coronary (60%). These results indicate that reversibility polar maps and normal limits offer an objective, accurate technique for determining the reversibility of stress-induced perfusion defects.

Adult↗
PubMed1983

Biplane radiographic measurements of reversible displacement (including clinical loosening) and migration of total joint replacements.

UNLABELLED: We studied nineteen total knee replacements and thirty-three total hip replacements with simultaneous biplane radiography to measure in vivo micromotion at the cement-bone interface. Spherical cobalt-chromium markers were embedded in the cement and cortical bone. Relative motion of the cement-markers was measured with respect to the markers in the cortical bone. Reversible displacement (relative motion during a change from non-weight-bearing to weight-bearing) and migration (relative motion over time from one non-weight-bearing study to another) were calculated. The resolution of the measuring system was 0.2 millimeter. The range for symptomatic reversible displacement was 0.4 to 4.5 millimeters, while that for asymptomatic reversible displacement was 0.3 to 1.9 millimeters. All reversible displacement of less than 0.4 millimeter was asymptomatic. Migration of as much as 2.1 millimeters occurred without concomitant reversible displacement. All radiolucent lines correlated with measured reversible displacement. Half of the patients who were evaluated two weeks postoperatively had measurable reversible displacement. CLINICAL RELEVANCE: Our findings were based on a small series from a selected population. The incidence of measured reversible displacement (75 per cent) was based on in vivo techniques and included symptomatic and asymptomatic reversible displacement; therefore, it was higher than the incidence of clinical loosening (9.6 per cent in our series). Simultaneous biplane radiography may become an important adjunct in the postoperative management of patients with a total joint replacement.

Follow-Up Studies↗
PubMed1997

[Estimation of myocardial viability and clinical significance of reverse redistribution in resting technetium-99m sestamibi myocardial single photon emission computed tomography in patients with acute myocardial infarction].

The clinical significance of reverse redistribution of technetium-99m sestamibi (MIBI) was investigated in 36 patients with acute myocardial infarction and angiographically confirmed single-vessel disease, but without previous infarction using resting MIBI myocardial single photon emission computed tomography (SPECT) and exercise-reinjection thallium-201 (Tl) myocardial SPECT. MIBI myocardial SPECT was performed 90 min and 300 min after injection of MIBI 370 MBq at rest. Four hours after exercise Tl imaging was completed, reinjection imaging was obtained. Wall motion abnormalities on left ventriculograms were analyzed at the onset of infarction and 1 month later. The severity scores on the MIBI early image, MIBI delayed image and Tl reinjection image were 98 +/- 18, 170 +/- 22 and 90 +/- 18, respectively. The reverse redistribution of MIBI was marked in acute infarction. A significant correlation of severity score was found between the MIBI early image and Tl reinjection image (r = 0.89). In 18 patients with significant stenosis of an infarct-related artery, there was a significant correlation between the degree of reverse redistribution and that of Tl redistribution (r = 0.826). A good correlation was found between the severity score on the MIBI early image and wall motion abnormality at 1 month after infarction (r = 0.816). There was a significant correlation between the degree of reverse redistribution and wall motion improvement (r = 0.782). Despite stenosis of the infarct-related artery, the wall motion abnormality was less in 22 patients with marked reverse redistribution (defect score on the MIBI delayed image was double that on the early image) than the other 14 patients. In conclusion, the MIBI early image may reflect myocardial viability and the reverse redistribution of MIBI was observed frequently in patients with acute myocardial infarction. Marked reverse redistribution was observed in patients with preserved left ventricular function. Because of the close correlation of reverse redistribution with Tl redistribution and wall motion improvement, reverse redistribution of MIBI is considered to occur in areas at risk for acute myocardial infarction.

Adult↗
PubMed1998

Reversal of incipient and radiographic caries through the use of sodium and stannous fluoride dentifrices in a clinical trial.

Experimental evidence has clearly demonstrated that the early stages of lesion formation (enamel demineralization) are reversible following exposure to saliva and/or fluoride. Clinical evidence for remineralization has also been reported extensively in the literature. However, the literature is lacking with respect to data from well-controlled clinical studies regarding the quantitative contribution of remineralization to arrestment and reversal of caries. Retrospective analysis of an existing clinical trial database provided an opportunity to examine the incidence of clinical lesion reversals in a placebo-controlled, double-blinded caries clinical study. The clinical study examined three treatment groups: 1) 0.243% sodium fluoride/silica dentifrice, 2) 0.4% stannous fluoride/calcium pyrophosphate (positive control) dentifrice and 3) non-fluoridated placebo/calcium pyrophosphate (negative control) dentifrice. Clinical measures in this study included both radiographic and visual-tactile assessments of caries. Examination of all subjects revealed a statistically greater frequency for caries reversals in the sodium fluoride group as compared to the placebo group at Year 3, for both total and radiographic caries. In contrast, while caries reversals in the stannous fluoride group occurred with greater frequency than in the placebo group at Year 3, for both total and radiographic caries, the differences were not statistically significant. When only subjects who were "at risk" for potential reversals (i.e., those with a minimum of one carious lesion at baseline) were examined, a statistically greater frequency in caries reversals was observed in both the sodium fluoride (total, incipient, and radiographic caries) and stannous fluoride (total and radiographic caries) groups as compared to the placebo group at Year 3. Collectively, these data confirm the ability of both 0.243% sodium fluoride/silica and 0.4% stannous fluoride/calcium pyrophosphate dentifrices to clinically reverse caries. The results suggest that sodium fluoride may deliver a greater frequency of caries reversals than stannous fluoride, although these treatments were not found to be significantly different.

Adolescent↗
PubMed2001

The biological effects of structural variation at the meta position of the aromatic rings and at the end of the alkenyl chain in the alkenyldiarylmethane series of non-nucleoside reverse transcriptase inhibitors.

In an effort to elucidate a set of structure-activity relationships in the alkenyldiarylmethane (ADAM) series of non-nucleoside reverse transcriptase inhibitors, a number of modifications were made at two locations: (1) the meta positions of the two aromatic rings and (2) the end of the alkenyl chain. Forty-two new ADAMs were synthesized and evaluated for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cell culture and for inhibition of HIV-1 reverse transcriptase. The size of the aromatic substituents was found to affect anti-HIV activity, with optimal activity appearing with Cl, CH(3), and Br substituents and with diminished activity occurring with smaller (H and F) or larger (I and CF(3)) substituents. The substituents at the end of the alkenyl chain were also found to influence the antiviral activity, with maximal activity associated with methyl or ethyl ester groups and with diminished activity resulting from substitution with higher esters, amides, sulfides, sulfoxides, sulfones, thioesters, acetals, ketones, carbamates, ureas, and thioureas. Twelve of the new ADAMs displayed submicromolar EC(50) values for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cells. Selected ADAMs, 19 and 21, were compared to previously published ADAMs 15 and 17 for antiviral efficacy and activity against the HIV-1 reverse transcriptase enzyme. All four ADAMs were found to inhibit HIV-1 reverse transcriptase enzyme activity, to inhibit the replication of a variety of HIV-1 clinical isolates representing syncytium-inducing, nonsyncytium-inducing, and subtype representative isolates, and to inhibit HIV-1 replication in monocytes. Subsequent assessment against a panel of site-directed reverse transcriptase mutants in NL4-3 demonstrated no effect of the K103N mutation on antiviral efficacy and a slight enhancement (6- to 11-fold) in sensitivity to AZT-resistant viruses. Additionally, ADAMs 19 (44-fold) and 21 (29-fold) were more effective against the A98G mutation (found in association with nevirapine resistance in vitro), and ADAM 21 was 5-fold and 2-fold more potent against the Y181C inactivation mutation than the previously reported ADAMs 15 and 17, respectively. All four ADAMs were tested for efficacy against a multidrug-resistant virus derived from a highly experienced patient expressing resistance to the reverse transcriptase enzyme inhibitors AZT, ddI, 3TC, d4T, foscarnet, and nevirapine, as well as the protease inhibitors indinavir, saquinavir, and nelfinavir. ADAM 21 was 2-fold more potent than ADAM 15 and 6-fold more potent than ADAMs 17 and 19 at preventing virus replication. Thus, we have identified a novel series of reverse transcriptase inhibitors with a favorable profile of antiviral activity against the primary mutation involved in clinical failure of non-nucleoside reverse transcriptase inhibitors, K103N, and that retain activity against a multidrug-resistant virus.

Alkenes↗
PubMed2025

Viral genome sequence datasets display pervasive evidence of strand-specific substitution biases that are best described using non-reversible nucleotide substitution models.

Most phylogenetic trees are inferred using time-reversible evolutionary models that assume that the relative rates of substitution for any given pair of nucleotides are the same regardless of the direction of the substitutions. However, there is no reason to assume that the underlying biochemical mutational processes that cause substitutions are similarly symmetrical. We consider two non-reversible nucleotide substitution models: (1) a 6-rate non-reversible model (NREV6) that is applicable to analyzing mutational processes in double-stranded genomes in that complementary substitutions occur at identical rates; and (2) a 12-rate non-reversible model (NREV12) that is applicable to analyzing mutational processes in single-stranded (ss) genomes in that all substitution types are free to occur at different rates. Using likelihood ratio and Akaike Information Criterion-based model tests, we show that, surprisingly, NREV12 provided a significantly better fit than the General Time Reversible (GTR) and NREV6 models to 21/31 dsRNA and 20/30 dsDNA datasets. As expected, however, NREV12 provided a significantly better fit to 24/33 ssDNA and 40/47 ssRNA datasets. We tested how non-reversibility impacts the accuracy with which phylogenetic trees are inferred. As simulated degrees of non-reversibility (DNR) increased, the tree topology inferences using both NREV12 and GTR became more accurate, whereas inferred tree branch lengths became less accurate. We conclude that while non-reversible models should be helpful in the analysis of mutational processes in most virus species, there is no pressing need to use these models for routine phylogenetic inference.

Models of evolution↗
PubMed1993

Reversal of female sterilisation: outcome of 210 referrals.

AIMS: To determine the outcome of request for reversal of sterilisation and to compare demographic and social factors of women who subsequently withdrew their request with those who proceeded with the reversal assessment and operation. METHODS: Information relating to the sterilisation and regret intervals were sought from 210 women. Demographic and social factors were recorded and the outcome of the reversal request determined. Patients who withdrew or were deferred/declined were compared on relevant factors with the group who proceeded to, or are still planning, the reversal operation. RESULTS: Ninety-two (44%) withdrew before or during the assessment phase. Another 13 withdrew after laparoscopy identified a poor prognosis. Three declared their intention not to conceive after they underwent the reversal operation. To date, 83 have had surgery with the cumulative intrauterine pregnancy rate at 1, 2 and 3 years being 0.46, 0.62 and 0.78 respectively. In comparing those women who proceeded and withdrew, there were no differences in mean age at referral, age at sterilisation, the number of living children nor marital status. The regret interval prior to referral was significantly longer in the women who proceeded (27.9 and 19.5 months respectively, p = 0.03). Those who were highly motivated in their reversal request were also more likely to proceed (p = 0.003). CONCLUSIONS: There is a large dropout rate of women who seek a reversal of sterilisation. Women who regret sterilisation may have sought sterilisation as a solution to problems that were psychosocial rather than contraceptive in nature. We stress the importance of counselling for both sterilisation and its reversal, since in the latter many developmental personality and relationship problems remain unresolved.

Adult↗
PubMed1999

The fate of cryopreserved sperm acquired during vasectomy reversals.

PURPOSE: Intraoperative sperm banking has been recommended during vasectomy reversal. These specimens are maintained as insurance for possible future intracytoplasmic sperm injection. We evaluated the fate of specimens collected intraoperatively from 48 vasectomy reversal patients. MATERIALS AND METHODS: Of 75 men 48 (64.0%) agreed to intraoperative sperm banking during vasectomy reversal. A total of 135 vials of epididymal sperm, 81 vials of testicular tissue and 13 vials of vasal sperm were cryopreserved. RESULTS: Among couples who stored sperm 10 (20.8%) voluntarily discarded the specimens within 4 months of vasectomy reversal. Specimens from 31 couples (64.5%) remain in storage. Seven couples (14.6%) have used frozen sperm for intracytoplasmic sperm injection. In 3 of these couples the men were azoospermic after surgery, 2 men had 10,000 to 15,000 sperm per ml. in the ejaculate with limited motility and 2 had 1 to 2 million sperm per ml. with limited motility. The 7 women who underwent intracytoplasmic sperm injection ranged between 37 and 39 years old, which was older than the mean age of the remaining study group (32.7 years). With intracytoplasmic sperm injection fertilization was achieved in all cases and 20 of 47 eggs (42.5%) developed into embryos. Of 7 women 4 achieved biochemical pregnancies (57.1%) and 2 (28.6%) delivered newborns with epididymal sperm. Natural pregnancy occurred in 7 of 16 vasectomy reversal couples (43.7%) who were followed at least 18 months postoperatively but the time to pregnancy averaged 1 year. CONCLUSIONS: Cryopreservation of sperm collected at vasectomy reversal is recommended for patients undergoing vasoepididymostomy or vasovasostomy. The couples who used the cryopreserved sperm for intracytoplasmic sperm injection included husbands whose postoperative ejaculate remained azoospermic or severely oligospermic and wives who were approaching 40 years old. Only a limited number of couples (14.6% of the study group) have used the cryopreserved sperm but the delivered newborn rate (28.6%) was comparable to other intracytoplasmic sperm injection data. The natural pregnancy rate after vasectomy reversal was 43.7% but the time to pregnancy after surgery was lengthy (average 1 year). These findings may be helpful for counseling couples who are planning vasectomy reversal surgery and may be considering intraoperative sperm banking.

Adult↗
PubMed2005

Contextual modulation of spatial discrimination reversal in developing rats.

Reversal of discrimination learning is influenced by manipulation of the training context. In adult and developing rats, contextual changes made between acquisition and reversal aid the learning of the new discrimination, possibly by serving to release proactive interference from the originally acquired discrimination (M. E. Bouton & D. C. Brooks, 1993; N. Spear, G. Smith, R. Bryan, & W. Gordon, 1980). The present study sought to examine this effect in an appetitive T-maze task, as a function of different contextual manipulations. Rats of three ages, Postnatal Day (PND) 19, PND23, and PND30, were tested for their ability to acquire and reverse a position habit in a T-maze. Contextual changes were made between acquisition and reversal sessions and consisted of one of three manipulations: (a) texture; the texture of the maze floor was changed via the addition or subtraction of wire mesh; (b) maze; subjects were reversed in a different maze that was identical in construction to the training maze, but differed in spatial location; (c) texture and maze; subjects were shifted to the new maze, the floor of which differed in texture from the training maze but was otherwise identical in construction. Results showed that the texture-maze combination was an effective aid to reversal learning at all ages tested. The texture alone, however, was not effective at any age. The maze alone also was an effective cue for reversal, but proved to have the greatest effect for PND30 subjects. During ontogeny, the contextual modulation of reversal learning is importantly influenced by the nature and the salience of the contextual cue.

Age Factors↗
PubMed1991

Serial spatial reversal learning in rats: comparison of instrumental and automaintenance procedures.

Serial reversals of a spatial discrimination were trained in rats under automaintenance conditions, in which food reward occurred regardless of responding. This automaintained reversal learning was compared to instrumental reversal learning in other rats trained under a similar procedure which required responding for reward. In the automaintenance (AU) procedure, rats received food after every retraction of a "positive" response lever (S+); retraction of a second, "neutral" lever (So) was not paired with food delivery. Responses to the S+ were elicited at fairly constant rates during daily 100-trial conditioning sessions. Responses to the So occurred early in each session but rapidly diminished across trials. When the valences of the levers were reversed, responding shifted to the new S+ and diminished on the new So. Criterion for reversal was defined as a discrimination ratio (DR) of at least 90% responding to the S+ in two consecutive 10-trial blocks. With repeated reversals, acquisition of criterion performance occurred with increasing rapidity, reaching an asymptote below that required for the original discrimination. A second group of rats was trained on a similar instrumental schedule, in which at least one response to the S+ was required for food delivery. Response rates in this instrumental (IN) group were approximately double those of the AU group. However, ratios of S+ to So response rates were similar to those of the AU group, and the serial reversal curves generated were qualitatively similar. Thus rats can show improvement across serial reversals of a spatial discrimination based entirely on pairings of stimulus events (automaintenance), in a manner similar to that observed in instrumental procedures, in which reward is contingent upon correct responding.

Animals↗
PubMed1986

Learning sets, discrimination reversal, and hippocampal function.

Impairments of discrimination reversal are commonly found following lesions of the hippocampal system. In a recent experiment, however, acquisition of a reversed discrimination was actually facilitated, rather than impaired, by partial lesions of the fimbria-fornix (FFX), an extrinsic fiber connection to the hippocampus. That experiment differed from most previous reversal experiments in that the discriminative stimuli were olfactory rather than spatial or visual, and 3 discriminations were given prior to the reversal of the third discrimination, rather than a single discrimination. The present experiment was designed to determine the generality of the results obtained in the olfactory experiment. Rats with partial lesions of the FFX and operated controls were tested on a series of 3 Go, No-go spatial discriminations, a reversal of the third discrimination, and 4 subsequent discriminations, in that order. Control rats acquired a learning set in the first 3 discriminations, reaching criterion on the third discrimination in fewer trials than they took on the first discrimination. Their choice accuracy was not significantly affected by the reversal and discrimination performance reached an asymptotic level after the reversal. Rats with FFX lesions also acquired a learning set in the first 3 discriminations, but they consistently took longer than control rats to learn each of the 7 discriminations. These rats were especially impaired on the reversal. These results contrast markedly with those obtained when a similar procedure was used with olfactory discriminations. Identification of the variables responsible for these differences should help distinguish those behaviors that require hippocampal function from those that do not.

Acetylcholinesterase↗