Biomedical subjects

W J Wu

Publications and source records attributed to W J Wu.

At least 37 records · Page 2Linked to original sources

PubMed2000

Ethanol suppresses NK cell activation by polyinosinic-polycytidylic acid (poly I:C) in female B6C3F1 mice: role of endogenous corticosterone.

BACKGROUND: Acute administration of EtOH suppresses basal NK cell lytic function in mice, and this suppression is caused, in part, by neuroendocrine mediators induced by EtOH. There is also evidence that a smaller part of the suppression is caused by direct action of EtOH. However, activation of NK cells to higher levels of lytic activity may be more important than basal NK cell lytic function in resistance to cancer or infectious agents. Therefore, the study described here examined the effects of acute EtOH exposure on activation of NK cells by polyinosinic-polycytidilic acid (poly I:C). METHODS: Ethanol was administered by gavage as a 32% solution in water, and poly I:C was administered to activate NK cells. NK cell activity was measured using a standard 4 hr 51Cr release assay with YAC-1 tumor cells. The effects of corticosterone were evaluated by administration of a glucocorticoid antagonist (RU 486) or a dosage of corticosterone previously shown to induce similar blood levels as treatment with EtOH. RESULTS: EtOH at 5-7 g/kg suppressed poly I:C-induced increases in NK cell lytic activity, and at least the lower end of this dosage range yields blood EtOH levels that are relevant for humans (0.25-0.3%). This suppression was partially blocked in mice that were pretreated with a glucocorticoid antagonist, and administration of exogenous corticosterone also suppressed NK cell activation. CONCLUSIONS: EtOH-induced increases in corticosterone are apparently involved in the suppression of NK cell activation. This conclusion was supported by the lack of a direct effect of EtOH or its major metabolites (acetaldehyde and acetate) on NK cell activation by poly I:C in vitro.

Animals↗

PubMed2000

Orthotopic bladder substitution in women using the ileal neobladder.

Before 1990, orthotopic bladder substitution was limited to men and urethrectomy was routinely performed in women--making orthotopic reconstruction impossible. Following studies on pelvic exenteration for transitional cell bladder cancer patients, and after anatomic studies of the female urethra, the first report on orthotopic bladder substitution was published in 1994. Here, we present our ileal neobladder technique, which was applied for the treatment of bladder cancer in three women, and sigmoid colon cancer with vesical metastasis in one woman. This surgical procedure preserves the urethral sphincter, the endopelvic fascia, and the pubourethral ligaments. The innervation of the sphincter is also maintained. A 45-cm segment is isolated from the distal ileum and arranged in a W-shaped configuration. An anastomosis between the ileal bladder and the urethra is made and an antireflux ureteroileal implantation is created. Postoperatively, all patients reported daytime continence. The average urinary flow rate was 13.5 +/- 2.1 mL/sec 3 months after surgery. The reservoir had low pressure and high capacity. There was no reflux or deterioration of renal function. In properly selected female patients undergoing radical cystectomy, an ileal neobladder is now an option.

Aged↗

PubMed2000

[The effect of chronic ototoxicity of gentamicin on the function of auditory efferents].

OBJECTIVE: To study the effect of chronic ototoxicity of gentamicin on the function of the cochlea and auditory efferents. METHOD: The effect of chronic ototoxicity of gentamicin on the function of the cochlea was determined by recording thresholds of the compound action potentials (CAP) of the auditory nerves to tone pip at 4, 6, 8, 10 and 12 kHz. The function of the medial olivocochlear (MOC) system was determined, through the observation of the effect of the contralateral noise (CLN) on CAP, before and after gentamicin administration. RESULT: The suppression effects of CLN on CAP were irreversibly eliminated, and the effects were most obvious at the 11th week after gentamicin (P < 0.01), and the response threshold of CAP was raised about 10 dB and 25 dB, respectively, at the 3rd and 11th week after the application of gentamicin. These results were most related to the morphological changes on cochlear efferents and hair cells. CONCLUSION: The auditory efferents play an important role in the chronic ototoxicity of gentamicin.

Animals↗

PubMed1999

The late phase of ischemic preconditioning is abrogated by targeted disruption of the inducible NO synthase gene.

The goal of this study was to interrogate the role of inducible NO synthase (iNOS) in the late phase of ischemic preconditioning (PC) in vivo. A total of 321 mice were used. Wild-type mice preconditioned 24 h earlier with six cycles of 4-min coronary occlusion/4-min reperfusion exhibited a significant (P < 0.05) increase in myocardial iNOS protein content, iNOS activity (assessed as calcium-independent L-citrulline formation), and nitrite + nitrate tissue levels. In contrast, endothelial NOS protein content and calcium-dependent NOS activity remained unchanged. No immunoreactive neuronal NOS was detected. When wild-type mice were preconditioned 24 h earlier with six 4-min occlusion/4-min reperfusion cycles, the size of the infarcts produced by a 30-min coronary occlusion followed by 24 h of reperfusion was reduced markedly (by 67%; P < 0.05) compared with sham-preconditioned controls, indicating a late PC effect. In contrast, when mice homozygous for a null iNOS allele were preconditioned 24 h earlier with the same protocol, infarct size was not reduced. Disruption of the iNOS gene had no effect on early PC or on infarct size in the absence of PC. These results demonstrate that (i) the late phase of ischemic PC is associated with selective up-regulation of iNOS, and (ii) targeted disruption of the iNOS gene completely abrogates the infarct-sparing effect of late PC (but not of early PC), providing unequivocal molecular genetic evidence for an obligatory role of iNOS in the cardioprotection afforded by the late phase of ischemic PC. Thus, this study identifies a specific protein that mediates late PC in vivo.

Animals↗

PubMed1999

Ethanol decreases host resistance to pulmonary metastases in a mouse model: role of natural killer cells and the ethanol-induced stress response.

The present study was done to delineate cause-effect relationships between the ethanol (EtOH)-induced stress response, natural-killer (NK)-cell activity, and resistance to experimental metastases of B16F10 melanoma cells in mice. Increased numbers of metastatic nodules were noted in the lungs of mice treated with dosages of EtOH that produce peak blood levels of 0.25-0.4%. EtOH caused only a minor depletion of NK cells or NK-cell activity from the spleen or lungs of normal or B16F10-challenged mice. However, in earlier studies we have shown consistent, significant decreases in NK-cell activity (approx. 50%) in spleen preparations from EtOH-treated mice. Depletion of NK cells by a monoclonal antibody increased the number of B16F10 nodules in the lungs, confirming an important role for NK cells for resistance to B16F10 metastases. Treatment of NK-cell-depleted mice with EtOH caused no further decrease in resistance to B16F10 cells, indicating that suppression of NK-cell activity is the major mechanism by which EtOH suppresses resistance to B16F10 metastases. Adrenalectomy or a glucocorticoid antagonist partially prevented EtOH-induced increases in the number of metastatic nodules in the lungs. Administration of exogenous corticosterone increased the number of B16F10 nodules to an extent similar to that caused by EtOH. These results indicate a role for the EtOH-induced stress response in decreasing resistance to B16F10 metastases. EtOH-induced decreases in resistance to cancer have also been reported in rats. The findings of the present study support the possibility that this is a generalized phenomenon, which could occur in humans.

Adrenalectomy↗

PubMed1999

Glycosaminoglycans mediate the coacervation of human tropoelastin through dominant charge interactions involving lysine side chains.

Following cellular secretion into the extracellular matrix, tropoelastin is transported, deposited, and cross-linked to make elastin. Assembly by coacervation was examined for an isoform of tropoelastin that lacks the hydrophilic domain encoded by exon 26A. It is equivalent to a naturally secreted form of tropoelastin and shows similar coacervation performance to its partner containing 26A, thereby generalizing the concept that splice form variants are able to coacervate under comparable conditions. This is optimal under physiological conditions of temperature, salt concentration, and pH. The proteins were examined for their ability to interact with extracellular matrix glycosaminoglycans. These negatively charged molecules interacted with positively charged lysine residues and promoted coacervation of tropoelastin in a temperature- and concentration-dependent manner. A testable model for elastin-glycosaminoglycan interactions is proposed, where tropoelastin deposition during elastogenesis is encouraged by local exposure to matrix glycosaminoglycans. Unmodified proteins are retained at approximately 3 microM dissociation constant. Following lysyl oxidase modification of tropoelastin lysine residues, they are released from glycosaminoglycan interactions, thereby permitting those residues to contribute to elastin cross-links.

Exons↗

PubMed1999

Folding of the multidomain ribosomal protein L9: the two domains fold independently with remarkably different rates.

The folding and unfolding behavior of the multidomain ribosomal protein L9 from Bacillus stearothermophilus was studied by a novel combination of stopped-flow fluorescence and nuclear magnetic resonance (NMR) spectroscopy. One-dimensional 1H spectra acquired at various temperatures show that the C-terminal domain unfolds at a lower temperature than the N-terminal domain (Tm = 67 degrees C for the C-terminal domain, 80 degrees C for the N-terminal domain). NMR line-shape analysis was used to determine the folding and unfolding rates for the N-terminal domain. At 72 degrees C, the folding rate constant equals 2980 s-1 and the unfolding rate constant equals 640 s-1. For the C-terminal domain, saturation transfer experiments performed at 69 degrees C were used to determine the folding rate constant, 3.3 s-1, and the unfolding rate constant, 9.0 s-1. Stopped-flow fluorescence experiments detected two resolved phases: a fast phase for the N-terminal domain and a slow phase for the C-terminal domain. The folding and unfolding rate constants determined by stopped-flow fluorescence are 760 s-1 and 0.36 s-1, respectively, for the N-terminal domain at 25 degrees C and 3.0 s-1 and 0.0025 s-1 for the C-terminal domain. The Chevron plots for both domains show a V-shaped curve that is indicative of two-state folding. The measured folding rate constants for the N-terminal domain in the intact protein are very similar to the values determined for the isolated N-terminal domain, demonstrating that the folding kinetics of this domain is not affected by the rest of the protein. The remarkably different rate constants between the N- and C-terminal domains suggest that the two domains can fold and unfold independently. The folding behavior of L9 argues that extremely rapid folding is not necessarily functionally important.

Geobacillus stearothermophilus↗

PubMed1999

Conformational analysis of a set of peptides corresponding to the entire primary sequence of the N-terminal domain of the ribosomal protein L9: evidence for stable native-like secondary structure in the unfolded state.

There is considerable interest in the structure of the denatured state and in the role local interactions play in protein stability and protein folding. Studies of peptide fragments provide one method to assess local conformational preferences which may be present in the denatured state under native-like conditions. A set of peptides corresponding to the individual elements of secondary structure derived from the N-terminal domain of the ribosomal protein L9 have been synthesized. This small 56 residue protein adopts a mixed alpha-beta topology and has been shown to fold rapidly in an apparent two-state fashion. The conformational preferences of each peptide have been analyzed by proton nuclear magnetic resonance spectroscopy and circular dichroism spectroscopy. Peptides corresponding to each of the three beta-stands and to the first alpha-helix are unstructured as judged by CD and NMR. In contrast, a peptide corresponding to the C-terminal helix is remarkably structured. This 17 residue peptide is 53 % helical at pH 5.4, 4 degrees C. Two-dimensional NMR studies demonstrate that the helical structure is distributed approximately uniformly throughout the peptide, although there is some evidence for fraying at the C terminus. Detailed analysis of the NMR spectra indicate that the helix is stabilized, in part, by a native N-capping interaction involving Thr40. A mutant peptide which lacks Thr40 is only 32 % helical. pH and ionic strength-dependent studies suggested that charge charge interactions make only a modest net contribution to the stability of the peptide. The protein contains a trans proline peptide bond located at the first position of the C-terminal helix. NMR analysis of the helical peptide and of a smaller peptide containing the proline residue indicates that only a small amount of cis proline isomer (8 %) is likely to be populated in the unfolded state.

Amino Acid Sequence↗

PubMed1999

Deficient coacervation of two forms of human tropoelastin associated with supravalvular aortic stenosis.

Human tropoelastin associates by coacervation and is subsequently cross-linked to make elastin. In Williams syndrome, defective elastin deposition is associated with hemizygous deletion of the tropoelastin gene in supravalvular aortic stenosis (SVAS). Remarkably, point-mutation forms of SVAS correspond to incomplete forms of tropoelastin which include in-frame termination by nonsense mutations, yet the resulting phenotype of these disorders is not explained because expression variably occurs from both normal and mutant alleles. Proteins corresponding to two truncated tropoelastin mutants were expressed and purified to homogeneity. Coacervation of these proteins occurred as expected with increasing temperature, but substantially contrasted with that of the performance of a normal tropoelastin. Significantly, association by coacervation of the truncated SVAS tropoelastin molecules was negligible at 37 degrees C, which contrasted with the substantial coacervation seen for normal tropoelastin. Furthermore their midpoints of coacervation increased and correlated with the extent of deletion, in accord with the loss of hydrophobic regions required for tropoelastin association. Their secondary structures are similar, as evidenced by CD studies. We propose a model for point-mutation SVAS in which aberrant tropoelastin molecules are incompetent and are mainly excluded from participation in coacervation and consequently in elastogenesis. These forms of SVAS may consequently be considered functionally similar to a hemizygous deletion, and mark point-mutation SVAS as a disorder of defective coacervation.

Amino Acid Substitution↗

PubMed1999

Quantitative relationships between the suppression of selected immunological parameters and the area under the corticosterone concentration vs. time curve in B6C3F1 mice subjected to exogenous corticosterone or to restraint stress.

The neuroendocrine response to stressors increases the concentration of several endogenous mediators, some of which are immunosuppressive. However, quantitative aspects of these effects have been overlooked. Although it should be possible to predict the degree of suppression of particular immunological functions by measuring the concentrations of stress-related mediators such as corticosterone, this cannot be done with data presently available. This study was designed to develop regression models to predict the relationship between the area under the corticosterone concentration vs. time curve (AUC) and two immunological parameters. Models were developed using mice treated with exogenous corticosterone and mice subjected to various periods of restraint stress. The latter treatment was included to determine if the effects of corticosterone were different from those of corticosterone in association with the other mediators induced in a restraint-stress response. Models relating corticosterone AUC to expression of MHC class II proteins on splenocytes were very similar, whether the corticosterone was exogenous or produced as part of a restraint-stress response. This was also true for splenic natural killer (NK) cell activity. However, MHC class II expression was more sensitive to the effects of corticosterone or restraint than was NK cell activity. The corticosterone and restraint models predicted the previously published effect of a chemical stressor (ethanol) on MHC class II expression, but neither model predicted the suppression of NK cell activity by ethanol. These results have mechanistic implications, which are discussed in the context of previous studies. The quantitative models described here should be useful in determining and predicting the stress-related portion of chemical-induced immunosuppression. In addition, these models provide quantitative data essential for a complete understanding of stress-induced immunosuppression.

Animals↗

PubMed1998

Transformation activity of Cdc42 requires a region unique to Rho-related proteins.

The Rho subfamily GTP-binding protein Cdc42 mediates actin cytoskeletal rearrangements and cell cycle progression and is essential for Ras transformation. Expression of a Cdc42 mutant (Cdc42(F28L)) that undergoes spontaneous activation (guanine nucleotide exchange) results in transformation of NIH3T3 fibroblasts. In this report, we show that deletion of residues 120-139 from Cdc42(F28L), which comprise an insert region unique to Rho subfamily proteins but is missing in other GTP-binding proteins, yields a Cdc42 molecule that still undergoes spontaneous GTP-GDP exchange and stimulates both actin cytoskeletal changes and the activation of the cellular targets p21-activated kinase and the c-Jun kinase (JNK1). However, this Cdc42 mutant is unable to transform cells. These findings indicate that the Rho subfamily insert region is dispensable for many of the known signaling pathways initiated by activated Cdc42 but is essential for its regulation of cell growth.

3T3 Cells↗

PubMed1998

Direct evidence that protein kinase C plays an essential role in the development of late preconditioning against myocardial stunning in conscious rabbits and that epsilon is the isoform involved.

Brief ischemic episodes confer marked protection against myocardial stunning 1-3 d later (late preconditioning [PC] against stunning). The mechanism of this powerful protective effect is poorly understood. Although protein kinase C (PKC) has been implicated in PC against infarction, it is unknown whether it triggers late PC against stunning. In addition, the entire PKC hypothesis of ischemic PC remains controversial, possibly because the effects of PKC inhibitors on PC protection have not been correlated with their effects on PKC activity and/or translocation in vivo. Thus, conscious rabbits underwent a sequence of six 4-min coronary occlusion (O)/4-min reperfusion (R) cycles for three consecutive days (days 1, 2, and 3). In the control group (group I, n = 7), the recovery of systolic wall thickening after the six O/R cycles was markedly improved on days 2 and 3 compared with day 1, indicating the development of late PC against stunning. Administration of the PKC inhibitor chelerythrine at a dose of 5 mg/kg before the first O on day 1 (group II, n = 10) abrogated the late PC effect against stunning, whereas a 10-fold lower dose (0.5 mg/kg; group III, n = 7) did not. Administration of 5 mg/kg of chelerythrine 10 min after the sixth reperfusion on day 1 (group IV, n = 6) failed to block late PC against stunning. When rabbits were given 5 mg/kg of chelerythrine in the absence of O/R (group V, n = 5), the severity of myocardial stunning 24 h later was not modified. Pretreatment with phorbol 12-myristate 13-acetate (4 microg/kg) on day 1 without ischemia (group VI, n = 11) induced late PC against stunning on day 2 and the magnitude of this effect was equivalent to that observed after ischemic PC. In vehicle-treated rabbits (group VIII, n = 5), the six O/R cycles caused translocation of PKC isoforms epsilon and eta from the cytosolic to the particulate fraction without significant changes in total PKC activity, in the subcellular distribution of total PKC activity, or in the subcellular distribution of the alpha, beta1, beta2, gamma, delta, zeta, iota, lambda, and mu isoforms. The higher dose of chelerythrine (5 mg/kg; group X, n = 5) prevented the translocation of both PKC epsilon and eta induced by ischemic PC, whereas the lower dose (0.5 mg/kg; group XI, n = 5) prevented the translocation of PKC eta but not that of epsilon, indicating that the activation of epsilon is necessary for late PC to occur whereas that of eta is not. To our knowledge, this is the first demonstration that a PKC inhibitor actually prevents the translocation of PKC induced by ischemic PC in vivo, and that this inhibition of PKC translocation results in loss of PC protection. Taken together, the results demonstrate that the mechanism of late PC against myocardial stunning in conscious rabbits involves a PKC-mediated signaling pathway, and implicate epsilon as the specific PKC isoform responsible for the development of this cardioprotective phenomenon.

Alkaloids↗

PubMed1998

Local control of peptide conformation: stabilization of cis proline peptide bonds by aromatic proline interactions.

In the native state of proteins there is a marked tendency for an aromatic amino acid to precede a cis proline. There are also significant differences between the three aromatic amino acids with Tyr exhibiting a noticeably higher propensity than Phe or Trp to precede a cis proline residue. In order to study the role that local interactions play in these conformation preferences, a set of tetrapeptides of the general sequence acetyl-Gly-X-Pro-Gly-carboxamide (GXPG), where X = Tyr, Phe, Trp, Ala, or cyclohexyl alanine, were synthesized and studied by nmr. Analysis of the nmr data shows that none of the peptides adopt a specific backbone structure. Ring current shifts, the equilibrium constant, the Van't Hoff enthalpy, and the measured rate of cis-trans isomerization all indicate that the cis proline conformer is stabilized by favorable interactions between the aromatic ring and the proline residue. Analysis of the side chain conformation of the aromatic residue and analysis of the chemical shifts of the pyrrolidine ring protons shows that the aromatic side chain adopts a preferred conformation in the cis form. The distribution of rotamers and the effect of an aromatic residue on the cis-trans equilibrium indicate that the preferred conformation is populated to approximately 62% for the Phe containing peptide, 67% for the Tyr containing peptide, and between 75 and 80% for the Trp containing peptide. The interaction is unaffected by the addition of 8M urea. These local interactions favor an aromatic residue immediately preceding a cis proline, but they cannot explain the relative propensities for Phe-Pro, Tyr-Pro, and Trp-Pro cis peptide bonds observed in the native state of proteins. In the model peptides the percentage of the cis proline conformer is 21% GYPG while it is 17% for GFPG. This difference is considerably smaller than the almost three to one preponderance observed for cis Tyr-Pro peptide bonds vs cis Phe-Pro peptide bonds in the protein database.

Deuterium↗

PubMed1998

Endogenous glucocorticoids induced by a chemical stressor (ethanol) cause apoptosis in the spleen in B6C3F1 female mice.

Stress-induced increases in glucocorticoid levels can cause-apoptosis in immature thymocytes, but it is not known if glucocorticoids at these levels can also cause apoptosis in peripheral lymphocytes. In the present study, mice were exposed to ethanol (EtOH) in a model designed to represent binge drinking. This induces a substantial stress response, including an increase in corticosterone levels. Apoptosis in the spleen was evaluated using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) with fluorescein-labeled dUTP. Flow cytometric analysis demonstrated a significant increase in the percentage of apoptotic cells in the spleen 2-6 h after administration of EtOH (3-6% apoptotic cells in treated mice vs 0.2-2% in controls). This increase was blocked by the glucocorticoid antagonist, RU 486, and administration of exogenous corticosterone in a manner that produced similar blood levels and kinetics as noted in EtOH-treated mice produced similar levels of apoptosis. Fluorescein-labeled Annexin V was used to confirm increased numbers of apoptotic cells in the spleen in EtOH-treated mice. These results indicate that stress-induced glucocorticoids are sufficient to induce apoptosis in the spleen, and this may be one mechanism by which stress responses cause immunosuppression.

Administration, Oral↗

PubMed1998

Ethanol-induced activation of the hypothalamic-pituitary-adrenal axis in a mouse model for binge drinking: role of Ro15-4513-sensitive gamma aminobutyric acid receptors, tolerance, and relevance to humans.

A mouse model for binge drinking has been developed in this laboratory, and several aspects of this model have been characterized. Many of the immunosuppressive effects of ethanol (EtOH) in this model seem to be mediated by activation of the hypothalamic-pituitary-adrenal (HPA) axis and consequent increases in the concentration of glucocorticoids, catecholamines, and perhaps other immunosuppressive mediators. The purpose of the work described here is to examine three important issues regarding the EtOH-induced neuroendocrine response in this model: 1) Are Ro15-4513-sensitive gamma aminobutyric acid type A (GABA-A) receptors involved in activation of the HPA axis by EtOH? 2) Does daily administration of EtOH produce tolerance with regard to activation of the HPA axis or with regard to suppression of natural killer cell activity? 3) Is the HPA axis activated by similar blood EtOH concentrations in humans and in the mouse model? Ro15-4513, a partial inverse agonist of GABA-A receptors, did not affect EtOH-induced increases in blood corticosterone levels. This suggests that Ro15-4513-sensitive GABA-A receptors are not involved in EtOH-induced activation of the HPA axis and that inhibition of corticosterone production is not the mechanism by which Ro-15-4513 blocks EtOH-induced immunosuppression. To evaluate tolerance, mice were given a daily dose of EtOH (6.5 g/kg by gavage) or vehicle (water) for 10 days. Control groups received vehicle or EtOH only on the last day of the experiment. At the optimum time after EtOH administration serum corticosterone and splenic NK cell activity were measured. The results indicate no significant alterations in the response to EtOH of mice exposed to EtOH for 10 days compared to those exposed only once. To compare the HPA axis response of mice and humans, lower EtOH dosages than generally used in our model were administered to mice, and the corticosterone response was compared to published data for humans who had similar ranges of blood EtOH levels. The results suggest that humans and mice exhibit activation of the HPA axis only when blood EtOH levels exceed approximately 0.14%. Together these results further characterize a mouse model for binge drinking that seems to provide a reasonable representation of many aspects of binge drinking in humans.

Affinity Labels↗

PubMed1998

Changes in the activities of mitochondrial enzymes in the progress of tumorigenesis of bladder cancer.

To investigate changes in the activities of mitochondrial enzymes in the progress of tumorigenesis of bladder cancer, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) carcinogen was administered orally to male Sprague-Dawley rats for eight weeks. The urinary bladders were harvested periodically for the evaluation of tumorigenesis. The activities of NADH cytochrome c reductase (NCCR), succinate cytochrone c reductase (SCCR) and cytochrome c oxidase (CCO) were measured. The NCCR and SCCR activities elevated significantly by the exposure of BBN and decreased rapidly when BBN was withdrawn. However, the CCO activity increased and reached plateau at 18 weeks in spite of the discontinuance of BBN. The results indicated that the NCCR, SCCR and CCO activities were significantly elevated in the tumorigenesis. However, the CCO enzyme may be more related to the progress of tumorigenesis of bladder cancer.

Animals↗

PubMed1998

Demonstration of an early and a late phase of ischemic preconditioning in mice.

It is unknown whether ischemic preconditioning (PC; either early or late) occurs in the mouse. The goal of this study was to answer this question and to develop a reliable and physiologically relevant murine model of both early and late ischemic PC. A total of 201 mice were used. In nonpreconditioned open-chest animals subjected to 30 min of coronary occlusion followed by 24 h of reperfusion, infarct size (tetrazolium staining) averaged 52% of the region at risk. When the 30-min occlusion was performed 10 min after a PC protocol consisting of six cycles of 4-min occlusion and 4-min reperfusion, infarct size was reduced by 75%, indicating an early PC effect. When the 30-min occlusion was performed 24 h after the same PC protocol, infarct size was reduced by 48%, indicating a late PC effect. In mice in which the 30-min occlusion was followed by 4 h of reperfusion, infarct size was similar to that observed after 24 h of reperfusion, indicating that a 4-h reperfusion interval is sufficient to detect the final extent of cell death in this model. Fundamental physiological variables (body temperature, arterial oxygenation, acid-base balance, heart rate, and arterial pressure) were measured and found to be within normal limits. Taken together, these results demonstrate that, in the mouse, a robust infarct-sparing effect occurs during both the early and the late phases of ischemic PC, although the early phase is more powerful. This murine model is physiologically relevant, provides reliable measurements, and should be useful for elucidating the cellular mechanisms of ischemic PC in genetically engineered animals.

Animals↗

PubMed1998

The experiences of rectosigmoid pouch as a continent urinary diversion after radical cystectomy.

Thirty-five patients receiving cystectomy underwent rectosigmoid pouch. The technique of ureteral submucous implantation was described. The follow-up results were analyzed. The relationship of postoperative voiding frequency and preoperative anal closure pressure was assessed. The day and night time continence rate is 97% (34/35). There were no hydronephrosis, no ureterocolonic stricture or reflux. The complications are not unique to rectosigmoid pouch and not high when compared with other forms of urinary diversion. When the preoperative anal closure pressure reaches nearly 100 cmH2O a postoperative outcome with good quality of life will be predicted. With the advantages of high continence rate and simplicity of performance the rectosigmoid pouch will become one of the alternative forms of continent urinary diversion. For obtaining the favorable results a patient with normal renal function, good hepatic function and anal closure pressure more than 50 cmH2O is required.

Adult↗