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PubMed2002

Does ileal reverse segment in rats with short bowel syndrome change intestinal morphology?

BACKGROUND: The primary goal of surgical therapy for short bowel syndrome is to increase intestinal absorptive capacity. Many surgical procedures have been described for this purpose. One of these is ileal reverse-segment procedure. This procedure after massive small-bowel resection is an alternative way to treat short bowel syndrome, but how it affects intestinal morphology in short bowel syndrome has not been investigated. The aim of this study is to investigate macroscopic and microscopic effects of reverse-segment procedure on the short bowel. METHODS: Twenty rats underwent resection of 80% of the small bowel. The rats were separated into two groups (n = 10). In the first group (reverse group), a reverse segment was formed by twisting a 2-cm ileal segment 180 degrees, without damaging its vascularity. In the second group (control group), a 2-cm ileal segment was resected, preserving its mesentery, and end-to-end anastomosis was performed to maintain the intestinal passage. The segment was not twisted 180 degrees. The 2-cm proximal (jejunal) and distal (ileal) segments of the resected bowel were reserved for histologic investigation. Two months later, the rats were killed and the jejunal and ileal segments were evaluated morphologically. RESULTS: In the reverse group, body weight and total intestinal length significantly increased (14% more than in the control group). The diameter of both proximal (jejunal) and distal (ileal) segments in the reverse group also increased 53.8% and 22.8%, respectively ( P < 0.05). Histologically, crypt depth and villus height of the ileal segment in the reverse group increased 15.2% and 18.2% more than in the control group ( P < 0.05). No histologic change was observed at the jejunal level except for intestinal muscle thickness. CONCLUSIONS: Ileal reverse-segment procedure in rats with short bowel syndrome 1) does not cause intestinal obstruction, 2) increases total bowel length and body weight, 3) increases the diameter of both jejunal and ileal segments, and 4) increases villus height and crypt depth only at the ileal level. For this reason, reverse-segment procedure positively affects intestinal adaptation.

Adaptation, Physiological↗
PubMed2004

Should all urologists performing vasectomy reversals be able to perform vasoepididymostomies if required?

PURPOSE: While vasectomy reversal is a highly successful procedure 10% to 30% of reversals may fail. Despite the general consensus that an epididymal obstruction may occur following a vasectomy and that some men should undergo vasoepididymostomy (VE) rather than vasovasostomy (VV), the practice of many urologists in our region has been to offer only VV for vasectomy reversal. We examined the potential causes for vasectomy reversal failure in patients who had undergone VV without an attempt at VE. MATERIALS AND METHODS: We conducted a retrospective review of patients who had undergone redo vasectomy reversal from January 1999 to September 2001. A total of 22 patients underwent redo reversal with a minimum followup of 2 years. The medical records of all patients were then reviewed. Patients and partners seen postoperatively in the clinic were questioned regarding any pregnancy or deliveries. RESULTS: We examined 22 patients who had undergone redo vasectomy reversal. Of 22 patients 9 (40.9%) underwent repeat VV, 8 (36.3%) underwent bilateral VE for a presumed unrecognized epididymal obstruction and 5 (22.7%) had a combination of VE and VV. Of the 44 reproductive units studied 23 (52.3%) had a failed vasal anastomosis while 21 (47.7%) had an unrecognized epididymal obstruction. Based on semen analysis patency was observed in 75% of patients who had undergone vasovasostomy as a redo procedure. A patency rate of 60% was found in patients who underwent vasoepididymostomy and vasovasostomy unilaterally, and patency rates for bilateral VE were 63%. CONCLUSIONS: Our study indicates that a large proportion of men (48%) have an epididymal obstruction as the etiology for vasectomy reversal failure. We recommend that all surgeons offering vasectomy reversals be able to offer VE if required based on intraoperative findings to serve the patient adequately as well as his partner and their future fertility.

Anastomosis, Surgical↗
PubMed1987

Spectroscopic properties of horse liver alcohol dehydrogenase in reversed micellar solutions.

Catalytic and spectroscopic properties of alcohol dehydrogenase from horse liver, incorporated in reversed micellar media, have been studied. Two different reversed micellar systems have been used, one containing an anionic [sodium bis(2-ethylhexyl)sulfosuccinate, AOT], the other containing a cationic (cetyltrimethylammonium bromide, CTAB) surfactant. With 1-hexanol as substrate the turnover number of the enzyme in AOT-reversed micelles is strongly dependent on the water content of the system. At low wo ([H2O]/[surfactant]) (wo less than 20) no enzymatic activity can be detected whereas at high wo (wo = 40) the turnover is only slightly lower than in aqueous solution. In CTAB-reversed micelles the dependence of the turnover number on wo is much less. The enzymatic activity is in this case significantly lower than in aqueous solution and increases only slightly with an increasing water content of the reversed micelles. Possible interactions of the protein with the surfactant interfaces in the reversed micellar media were studied via circular dichroism and fluorescence measurements. From the circular dichroism of the protein backbone it is observed that the protein secondary structure is not significantly affected upon incorporation in the reversed micelles since the far-ultraviolet spectrum is not altered. Results from time-resolved fluorescence anisotropy experiments indicate that, especially in AOT-reversed micelles, interactions between the protein and the surfactant interface are largely electrostatic in nature, as evident from the dependence on the pH of the buffer used. In CTAB-reversed micellar solutions such interactions appear to be much less pronounced than in AOT.

Alcohol Dehydrogenase↗
PubMed1990

Enzyme kinetics in reversed micelles. 3. Behaviour of 20 beta-hydroxysteroid dehydrogenase.

The kinetic parameters of 20 beta-hydroxysteroid dehydrogenase were determined in aqueous solutions and in reversed micellar media composed with either an anionic, a cationic or a nonionic surfactant, at low and at high ionic strength. The velocity data were analysed in two ways: first by extrapolation to infinite concentrations of both substrates to determine 'apparent' Michaelis constants and V values, and secondly by comparison to reaction rates calculated using the model presented (see first of this series of papers in this issue of the journal). Data analysis according to the first method reveals some differences in the kinetic parameters in reversed micelles as compared to those in aqueous solution, though the kinetic parameters of the enzyme seem not to be much affected by enclosure in reversed micelles. It is shown that the changes that do occur are not caused by a shift of the intramicellar pH or by electrostatic interactions between the enzyme and the surfactant head groups. Interpretation of the data using the second method assumes that the enzyme is not affected by the enclosure in reversed micelles, and that deviations with respect to the aqueous parameters are caused by exchange phenomena between distinct aqueous droplets in the organic phase and by a high effective intramicellar substrate concentration. This model is able to predict reaction rates that agree rather well with experimentally determined rates and explains why the enzyme mechanism in reversed micelles is, at all progesterone concentrations used, the same as observed at high progesterone concentrations in aqueous solution. Furthermore it clarifies the occurrence of substrate inhibition in sodium-di(ethylhexyl)sulphosuccinate-reversed micelles and the observed low activity in Triton-reversed micelles, as arising from the high partition coefficient of progesterone and the slow rate of diffusion of progesterone into the reversed micelles. From these results, and those reported for enoate reductase (see preceding paper in this issue of the journal) it can be concluded that the theory presented before (see first of this series of papers in this issue of the journal) offers a good explanation for the observed kinetic behaviour in reversed micelles, and emphasizes the importance of exchange processes between micelles.

20-Hydroxysteroid Dehydrogenases↗
PubMed1994

Possible kinetic mechanism of human placental alkaline phosphatase in vivo as implemented in reverse micelles.

Human placental alkaline phosphatase is an integral membrane protein. It catalyzes the hydrolysis of phosphoester linkage of a broad-range substrate. We have embedded the enzyme in a reverse micellar system prepared by dissolving the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane. Linear Lineweaver-Burk and Eadie-Hofstee plots for the substrate and linear Arrhenius plot for the temperature-dependent enzyme reaction were obtained in reverse micelles suggesting that the substrate diffusion limitation was not a rate-limiting step in the system and exchange of materials between reverse micelles was very rapid. The catalytic constant (kcat) of the enzyme was decreased, and the Km for the substrate was increased in reverse micelles, both in an exponential way with the [H2O]/ AOT] ratio (omega O). The enzyme was more stable in reverse micelles than in aqueous solution at 30 degrees C but was unstable at higher temperature (65 degrees C). The activation energy of the enzyme in reverse micelles was 46.5 +/- 2.6 kJ/mol, which was about 20 kJ/mol higher than that in aqueous solution and reflected in the lower Kcat value at low omega O. The binding affinity between the substrate 4-nitrophenyl phosphate and the enzyme in reverse micelles was decreased as implemented by the higher Km and higher Ki for phosphate values. In aqueous solution, the log kcat/pH plot suggested that amino acid residues with pKa values of 9.03 +/- 0.03 and 11.37 +/- 0.10 are involved in catalysis. The former should be deprotonated and the latter should be protonated for the reaction to proceed. In reverse micelles, both the above-mentioned pKa values were detected. However, both groups have to deprotonated to give the optimum catalytic function. In aqueous solution, the enzyme's specificity was highly dependent on pH and buffer. The pKa value of the amino acid residues involved in substrate binding was found to be 8.69 +/- 0.07 in carbonate buffer, but changed to 9.80 +/- 0.06 in Tris buffer. Our results suggested that the rate-limiting step of the enzyme-catalyzed reaction may be changed from phosphate releasing in aqueous solution to another critical step in the reverse micelles.

Alkaline Phosphatase↗
PubMed2005

Feasibility and morbidity of reversal of Hartmann's.

OBJECTIVE: Reversal of Hartmann's is a major surgical procedure and associated with substantial morbidity and mortality. METHOD: This study retrospectively analysed the data at a single centre over an eight-year period to assess the clinical results and morbidity of reversal of Hartmann's. RESULTS: One hundred and ten Hartmann's procedures were performed during the period. Only 66 (61%) of patients had a reversal. Advanced age and comorbidity were the primary reasons for not reversing. Complications among the 66 patients (36 males and 30 females) who underwent reversal occurred in 26 (41%). There were no deaths. Patients who underwent reversal were ASA 2 (60%), ASA 3 (25%) and ASA 4 (4.6%). Univariate analysis demonstrated a significant association between complications following reversal and ASA grade (P =0.01), and hypertension (P = 0.03) There was no correlation between the patient variables and anastomotic leakage. Multiple logistic regression analysis showed a significant influence of hypertension, smoking and ASA grade on complications. CONCLUSIONS: About 40% of patients who undergo Hartmann's procedure will not have a reversal. Reversal is a feasible operation for selected patients, but there is a high complication rate.

Adult↗
PubMed2006

Mechanism-based inactivation and reversibility: is there a new trend in the inactivation of cytochrome p450 enzymes?

Recent studies with cytochrome P450 (P450) enzymes from the 2E and 2B subfamilies have shed light on what may be a new trend in the mechanism-based inactivation of P450s: reversibility. The reversible inactivation of P450-type enzymes was first reported in the mid-1990s by Dexter and Hager [Dexter AF and Hager LP (1995) J Am Chem Soc 117:817-818], who studied the transient heme N-alkylation of chloroperoxidase by allylbenzene and 1-hexyne. While characterizing small tert-butyl acetylenes as mechanism-based inactivators of P450s 2E1 and 2B4, Hollenberg and coworkers observed the reversible inactivation of an acetylene-inactivated T303A mutant of P450 2E1. The mechanism of reversibility was a combined product of the structure of the inactivator and the positioning of conserved amino acid residues, threonine 303 (alanine in the mutant) and glutamate 302, in the enzyme active site. Reversibility was also observed with both wild-type P450 2B4 and the T302A mutant of 2B4, although this inactivation and reversibility did not seem to depend on the T302 residue. Subsequent studies have attempted to elucidate the chemical/structural requirements of the inactivator in determining reversibility and have shown that both the size and the chemical nature of functional groups play an important role. At this time, reversibility has only been observed with P450 2E and 2B enzymes during their mechanism-based inactivation by terminal alkynes. Future studies with P450s from other subfamilies and structurally distinct inactivators will greatly aid our understanding of the molecular and chemical determinants of reversibility.

Acetylene↗
PubMed1977

Inhibitory protein controls the reversion of protoplasts and L forms of Bacillus subtilis to the walled state.

When the cell wall of Bacillus subtilis is removed by lysozyme and the resultant protoplasts are plated on hypertonic soft agar medium, each protoplast forms an L colony. L bodies from such L colonies again plate as L-colony-forming units (CFU). However, if protoplasts or L bodies are "conditioned" by 1 h of incubation in 0.4% casein hydrolysate medium and then incubated in 25% gelatin medium for 1 h, 60 to 100% of the formerly naked cells give rist to bacillary colonies. The present experiments largely explain the mechanism responsible for the "heritable" persistence of the wall-less state in B. subtilis. It is shown that protoplasts produce a reversion inhibitory factor (RIF) which blocks reversion when the cell concentration exceeds 5 x 105 CFU/ml. This inhibitor is nondialyzable and sensitive to trypsin, heat, and detergent. Efficient reversion at 2 x 107 CFU/ml is obtained if the protoplasts are treated with trypsin after conditioning and chloramphenicol is incorporated into the gelatin reversion medium. In the presence of 500 mug of trypsin per ml, the requirement for gelatin is sharply reduced, and reversion occurs rapidly in liquid medium containing only 10% gelatin. Trypsin also stimulates reversion in L colonies growing on soft agar. Latent RIF is activated by beta-mercaptoethanol. This reagent blocks reversion of protoplast suspensions at densities of 5 x 105 CFU/ml. Comparison of the autolytic behavior of B. subtilis and of the RIF revealed that several or the properties of the two activities coincide: both are inhibited by high concentrations of gelatin, both are activated by beta-mercaptoethanol, and both have high affinity for cell wall. Going on the assumption that RIF is autolysin, models for protoplast reversion is suggested by the finding that mutants with altered teichoic acid show altered reversion behavior.

Bacillus subtilis↗
PubMed1992

Incompletely reverse-transcribed human immunodeficiency virus type 1 genomes in quiescent cells can function as intermediates in the retroviral life cycle.

Using a quantitative polymerase chain reaction (PCR) method, we have previously shown that a molecularly cloned isolate of human immunodeficiency virus type 1 (HIV-1) can efficiently enter quiescent primary lymphocytes; however, the reverse transcription process is not completed in these cells. In this study, we further characterized the reverse transcription of HIV-1 in quiescent cells, and our results indicate that while initiation of reverse transcription occurs simultaneously in both activated and quiescent lymphocytes, it not only ends prematurely but also proceeds more slowly in quiescent cells. We also performed experiments to address the role of partial reverse transcripts as intermediates in the viral life cycle. We used azidothymidine either before or after infection with HIV-1 to prevent formation of and further DNA synthesis by partial reverse transcripts, respectively. Decreases in virus production from these cells following mitogenic stimulation indicated that partial reverse transcripts can contribute significantly to virus rescue from infected quiescent cells stimulated subsequent to infection. Furthermore, we established that mitogenic stimulation of infected quiescent cells induces reinitiation of DNA synthesis from partial reverse transcripts. However, the virus rescue is inefficient relative to the initial multiplicity of infection, and this is explained by inefficient completion of DNA synthesis from the partial reverse transcript. Thus, the arrest of reverse transcription in quiescent cells may play an important role in HIV-1 pathogenesis by contributing to the inefficient infection of potential target cells in the peripheral blood of HIV-1-infected individuals.

Base Sequence↗
PubMed1997

Nucleotide substitutions within U5 are critical for efficient reverse transcription of human immunodeficiency virus type 1 with a primer binding site complementary to tRNA(His).

Sequence analysis of integrated proviruses of human immunodeficiency virus type 1 (HIV-1) which utilize tRNA(His) to initiate reverse transcription [virus derived from pHXB2(His-AC-TGT)] revealed five additional nucleotide substitutions in the U5 and primer binding site (PBS) regions (ATGAC for CCTGT at nucleotides 152, 160, 174, 181, and 200, respectively) (Z. Zhang et al., Virology 226:306-317, 1996). We constructed a mutant proviral genome [pHXB2(His-AC-GAC)] which contained the ATGAC substitutions to test if they represented a necessary adaptation by the virus for use of tRNA(His) to initiate reverse transcription. Viruses from pHXB2(His-AC-TGT) and pHXB2(His-AC-GAC) were infectious. Sequence analysis of the U5 and PBS regions of integrated provirus from a cell culture infected with virus derived from pHXB2(His-AC-TGT) revealed a G-to-A change in CCTGT at nucleotide 181 after limited in vitro culture, suggesting that this nucleotide change represented an adaptation by the virus to efficiently utilize tRNA(His) to initiate reverse transcription. To further address this possibility, we used a specific mutation in reverse transcriptase (RT), a methionine-to-valine change in the highly conserved YMDD amino acid motif of HIV-1 RT (M184V), which has been shown in previous studies to influence the fidelity and activity of the enzyme. The M184V RT mutation was cloned into pHXB2(His-AC-GAC) and pHXB2(His-AC-TGT). Virus derived from pHXB2(His-AC-GAC) with M184V RT had slightly delayed replication compared to the virus from pHXB2(His-AC-GAC) with wild-type RT; in contrast, virus from pHXB2(His-AC-TGT) with M184V RT was severely compromised in replication. Using an endogenous reverse transcription-PCR assay to analyze the reverse transcription of viruses obtained after transfection, we found that viruses derived from pHXB2(His-AC-GAC) with the wildtype RT were slightly faster in the initiation of reverse transcription than viruses with M184V RT. The initiation of reverse transcription was delayed in viruses derived from pHXB2(His-AC-TGT) with wild-type RT and M184V RT compared to viruses derived from pHXB2(His-AC-GAC). Finally, sequence analysis of U5 and PBS regions of proviruses from pHXB2(His-AC-GAC) with wild-type RT revealed considerably more nucleotide substitutions than in viruses derived from pHXB2(His-AC-GAC) containing the M184V mutation in RT after extended in vitro culture. Our studies point to a role for these additional nucleotide substitutions in U5 as an adaptation by the virus to utilize an alternative tRNA to initiate reverse transcription.

Animals↗
PubMed2000

The majority of duck hepatitis B virus reverse transcriptase in cells is nonencapsidated and is bound to a cytoplasmic structure.

The hepadnavirus reverse transcriptase binds cotranslationally to the viral pregenomic RNA. This ribonucleoprotein complex is then encapsidated into nascent viral core particles, where the reverse transcriptase copies the viral RNA into DNA. Here we report that 75% of the duck hepatitis B virus reverse transcriptase present in transfected LMH cells does not follow this well-known pathway but rather exists in the cell separate from the core protein or nucleocapsids. The nonencapsidated reverse transcriptase is also abundant in infected duck liver. The nonencapsidated reverse transcriptase exists as a complex set of isoforms that are most likely produced by posttranslational modification. Interestingly, only the smallest of these isoforms is encapsidated into viral core particles. The nonencapsidated reverse transcriptase is bound to a large cellular cytoplasmic structure(s) in a detergent-sensitive complex. The cellular distribution of the reverse transcriptase only partially overlaps that of the core protein, and this distribution is unaffected by blocking encapsidation. These observations raise the possibilities that the metabolic fate of the reverse transcriptase may be posttranscriptionally regulated and that the reverse transcriptase may have roles in the viral replication cycle beyond its well-known function in copying the viral genome.

Animals↗
PubMed2003

Persistence of systolic coronary flow reversal predicts irreversible dysfunction after reperfused anterior myocardial infarction.

OBJECTIVE: To investigate serial assessments of systolic coronary flow reversal in the infarct related artery for predicting poor left ventricular functional recovery after reperfused acute myocardial infarction. SETTING: Regional hospital. PATIENTS AND METHODS: 49 patients with anterior acute myocardial infarction had transthoracic Doppler echocardiography to record coronary flow velocity in the left anterior descending coronary artery immediately after successful primary coronary angioplasty (day 0), and at 48 hours, one week, and three weeks. MAIN OUTCOME MEASURES: Coronary flow velocity at each time point; regional wall motion score index (RWMSI) at day 0 and at three weeks. Irreversible dysfunction was defined as a decrease in RWMSI to < 0.22. RESULTS: Measurements of coronary flow velocity could be made in 45 patients. Patients were divided into three groups: no systolic flow reversal (group 1, n = 27), systolic flow reversal observed only on day 0 (group 2, n = 8), and systolic flow reversal persisting until 48 hours (group 3, n = 10). Although baseline RWMSI was similar among the three groups, the value at three weeks was significantly higher in group 3 than in the other two groups. In predicting irreversible dysfunction, the persistence of systolic flow reversal up to 48 hours had a higher positive predictive value (100%) than the presence of systolic flow reversal on day 0 (67%, p < 0.04). The negative predictive value of systolic flow reversal at 48 hours (83%) was comparable in accuracy to the presence of systolic flow reversal on day 0 (85%, NS). CONCLUSIONS: In reperfused anterior acute myocardial infarction, serial assessment of coronary flow velocity in the left anterior descending coronary artery is feasible using transthoracic Doppler echocardiography, and the persistence of systolic flow reversal at 48 hours is a more specific marker of irreversible dysfunction than peak creatine kinase or diastolic deceleration time.

Adult↗
PubMed2003

The trends of vasectomy reversal in the forces.

A reversal of a vasectomy is required in about 3% of men who undergo vasectomy. We set out to examine the relationships between the age at which vasectomy was performed and the interval before subsequent reversal within the context of the armed forces. Thirty seven patients were identified from hospital records, as having undergone a reversal of vasectomy in the preceding two years, and thirty one sets of notes were available for inspection. Ages at vasectomy and at reversal were recorded and, where stated in the notes, if there had been a change in partner prior to the reversal request. Twelve (39%) men were under the age of thirty years at the time of their vasectomy, with a mean time to reversal of 4.4 years. Nineteen (61%) were over the age of thirty years at time of the vasectomy and their mean time to reversal was 7.2 years. Where recorded, the reason for requesting a reversal was a change in partner in 90% of men. Men who had their vasectomies before reaching the age of thirty were more likely to undergo reversal in a significantly shorter period of time when compared to those over thirty years. The disseminated criteria for vasectomy should be adhered to and appropriate preoperative counselling by surgeons may be useful.

Adult↗
PubMed1976

Reversal properties of climbing fiber potential in cat Purkinje cells: an example of a distributed synapse.

1. The electrophysiological properties of the EPSP generated in Purkinje cells by the activation of CFs were studies in the cat cerebellar cortex. 2. CF-EPSPs were evoked by electrical stimulation of the cerebellar white matter and recorded intracellularly from the soma of the Purkinje cells. 3. Current was injected into the Purkinje cells via the recording micropipette using a bridge amplifer in order to study the reversal properties of the EPSP. 4. The CF-EPSP reversal was biphasic with the early portion reversing first. 5. The reversed EPSP waveform was not a mirror image of the EPSP, but displayed a briefer time course. 6. A four-compartment computer stimulation showed that the reversal properities of the CF-EPSP were explicable in terms of a distributed synapse on a cable. 7. The biphasic reversal and asymmetry were shown to be due to the spatially nonuniform potential distribution created by the somatic current injection, which predominantly reversed the proximal part of the distributed synapse. Delayed rectification may also have contributed to the reversal asymmetry. 8. The advantages of a distributed synapse over a point synapse are discussed and the reversal properties of the CF-EPSP compared to those of the Ia-evoked EPSP in motoneurons.

Animals↗
PubMed1993

Low-dose dobutamine echocardiography detects reversible dysfunction after thrombolytic therapy of acute myocardial infarction.

BACKGROUND: Dysfunction after thrombolytic therapy of acute myocardial infarction (MI) may be reversible. Early after myocardial infarction, both reversible and irreversible injury may be manifested by regional wall motion abnormalities. Improved wall thickening during dobutamine infusion (dobutamine-responsive wall motion) may accurately identify reversibly injured segments. METHODS AND RESULTS: To determine whether dobutamine-responsive wall motion accurately detects reversible postischemic dysfunction irrespective of infarct location, multistage (baseline, 4 and 12 micrograms.kg-1.min-1, and peak) dobutamine echocardiography (DE) was performed within 7 days of thrombolytic therapy. Resting echocardiography was repeated > or = 4 weeks after MI, and reversible dysfunction was defined as improved wall motion. The accuracy of dobutamine-responsive wall motion was compared with that of signs of early reperfusion, non-Q-wave MI, and peak creatine kinase (CK). Sixty-three patients underwent DE without complications. Follow-up echocardiograms were done in 51 (81%) of these patients, and wall motion improved in 22 (41%). Dobutamine-responsive wall motion during all stages of DE was very specific for reversible dysfunction (90% to 93%) but sensitive (86%) only when hemodynamics were not altered (low dose, 4 micrograms.kg-1.min-1). Non-Q-wave MI and a low peak CK (< 1000 IU/mL) were also specific (89% to 93%) but less sensitive (64% [P = .16] and 55% [P < .05], respectively). Signs of early reperfusion did not identify postischemic dysfunction. Low-dose dobutamine-responsive wall motion and non-Q-wave MI independently identified reversible dysfunction, but only dobutamine-responsive wall motion was sensitive in all infarct locations. Non-Q-wave MI was sensitive only in anterior infarction. CONCLUSIONS: Multistage dobutamine echocardiography can be performed safely early after thrombolytic therapy. Low-dose dobutamine-responsive wall motion accurately detected reversible dysfunction in all infarct locations. Dobutamine-responsive wall motion and non-Q-wave infarction may be very useful for accurately identifying reversible dysfunction early after thrombolytic therapy for acute MI.

Adult↗
PubMed1998

Stress-induced reversible and mild-to-moderate irreversible thallium defects: are they equally accurate for predicting recovery of regional left ventricular function after revascularization?

BACKGROUND: In patients with coronary artery disease, stress-redistribution-reinjection thallium scintigraphy provides important information regarding myocardial ischemia and viability. Although both reversible and mild-to-moderate irreversible thallium defects retain metabolically active, viable myocardium, we hypothesized that stress-induced reversible thallium defects may better differentiate reversible from irreversible regional left ventricular dysfunction after revascularization. METHODS AND RESULTS: Twenty-four patients with chronic coronary artery disease underwent prerevascularization and postrevascularization exercise-redistribution-reinjection thallium single photon emission CT, gated MRI, and radionuclide angiography. After revascularization, mean left ventricular ejection fraction increased from 30+/-9% to 37+/-13% at rest (P<0.001). Before revascularization, abnormal contraction at rest was observed in 56 of 110 reversible and 20 of 37 mild-to-moderate irreversible thallium defects (51% and 54%, respectively). After revascularization, regional contraction improved in 44 of 56 reversible compared with 6 of 20 mild-to-moderate irreversible thallium defects (79% and 30%, respectively; P<0.001). The final thallium content (maximum tracer uptake on redistribution-reinjection images) was significantly higher in regions with reversible defects that improved than in those that did not improve after revascularization (86+/-16% versus 66+/-9%, P<0.001). In contrast, final thallium content was similar in regions with mild-to-moderate irreversible defects that improved and in those that did not improve after revascularization (69+/-9% versus 65+/-10%, P=NS). Furthermore, when asynergic regions were grouped according to the final thallium content, at 60% threshold value, functional recovery was observed in 83% of regions with reversible defects compared with 33% of regions with mild-to-moderate irreversible defects (P<0.001). CONCLUSIONS: These findings suggest that although both reversible and mild-to-moderate irreversible thallium defects after stress retain viable myocardium, the identification of reversible thallium defect on stress in an asynergic region more accurately predicts recovery of function after revascularization. Even at a similar mass of viable myocardial tissue (as reflected by the final thallium content), the presence of inducible ischemia is associated with an increased likelihood of functional recovery.

Adult↗
PubMed1984

Complete reversibility of cat right ventricular chronic progressive pressure overload.

Chronic, progressive pressure overload of the cat right ventricle produces persistent, ongoing abnormalities of contractile, energetic, and biochemical function in vitro at a time when in vivo pump function is still normal. The present study tested the reversibility of the in vitro changes in this clinically relevant hypertrophy model. Fourteen sham-operated and 14 reversal cats were studied. After banding the animals as 1-kg kittens, right ventricular pressures were normal. Before band removal (25.2 +/- 0.5 weeks later for the control group and 25.5 +/- 0.3 weeks later for the hypertrophy reversal group), systolic right ventricular pressures were 24 +/- 1 mm Hg for controls and 71 +/- 5 mm Hg for the hypertrophy reversal group (P less than 0.05). At study, 19.5 +/- 1.1 weeks after a second sham operation for controls or 18.7 +/- 0.7 weeks after band removal for the hypertrophy reversal group, these pressures were 24 +/- 1 mm Hg for controls and 23 +/- 1 mm Hg for the hypertrophy reversal group (P = NS); cardiac output was 0.18 +/- 0.01 liters/kg per min for controls and 0.19 +/- 0.01 liters/kg per min for the hypertrophy reversal group (P = NS). The ratio of right ventricle to body weight was normal in both groups, as was the right ventricular papillary muscle myocyte cross-sectional area and the myocardial collagen concentration. A right ventricular papillary muscle from each cat was studied at 29 degrees C in a polarographic myograph. Preloaded shortening velocity was 0.79 +/- 0.04 muscle lengths/sec for controls and 0.86 +/- 0.03 muscle lengths/sec for the hypertrophy reversal group (P = NS); extent of shortening was 0.15 +/- 0.01 muscle lengths for controls and 0.16 +/- 0.01 muscle lengths for the hypertrophy reversal group (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Modification of the behavioral effects of drugs after repeated administration--special reference to the reverse tolerance of amphetamines].

It has been well-known that a chronic abuse of amphetamines induces schizophrenia-like psychotic symptoms, namely amphetamine psychosis. When amphetamines are repeatedly administered to rodents, a reverse tolerance (behavioral sensitization) to the ambulation-increasing and/or stereotypy-producing effect is observed. The process of the reverse tolerance is affected by various factors. A clear reverse tolerance is produced when optimal doses of the drug (2 mg/kg, s.c. for mice, and 0.5-1 mg/kg, s.c., for rats) is administered at intervals of longer than 1 day rather than a shorter interval. Furthermore, the animal has to be put into a freely mobile situation during the presence of the acute drug effect. A cross reverse tolerance is observed between certain types of drugs that show an ambulation-increasing effect, although the potencies are different among the drugs. A reverse tolerance to the stereotypy (in particular sniffing and head-bobbing)-producing effect is also observed when comparatively higher doses of methamphetamine are repeatedly administered. The process is qualitatively identical with the reverse tolerance to the ambulation-increasing effect produced by the repeated administration of comparatively smaller doses. The reverse-tolerance, once established, to both ambulation-increasing and stereotypy-producing effects is almost irreversible even with various treatments such as repeated post-treatment with antipsychotics. The characteristics of reverse tolerance to methamphetamine in animals might be closely correlated to the amphetamine psychosis in humans. It is also necessary to search for a method that effectively reduces the established reverse tolerance to amphetamines.

Age Factors↗