Different sensitivities of native and oxidized forms of Na+/K(+)-ATPase to intracellular proteinases

Inactivation of Na+/K(+)-ATPase by partially reduced oxygen metabolites has been implicated in ischemia-reperfusion injury to heart and other organs. Because oxidation of many proteins makes them more susceptible to degradation by intracellular proteinases, we studied the effects of several such proteinases on native and H2O2-oxidized preparations of Na+/K(+)-ATPase from canine kidney (containing alpha 1 isoform of the catalytic subunit) and rat axolemma (containing alpha 2 and alpha 3 isoforms). Lysosomal cathepsin D degraded the native and the oxidized preparations at acid pH, but it was significantly more effective against the oxidized forms. m-Calpain had little or no effect on the native Na+/K(+)-ATPase preparations, but it digested the oxidized alpha-subunits of the axolemma and the kidney enzymes. mu-Calpain's effects were similar to those of m-calpain. Multi-catalytic proteinase which is known to degrade a large number of oxidized proteins, did not affect the native or the oxidized forms of Na+/K(+)-ATPase. The findings suggest that (a) during oxidative stress there may be accelerated degradation of the oxidatively damaged Na+/K(+)-ATPase, either through internalization and transport to lysosomes, or by the action of calpains at the membrane; and (b) those isoforms of the enzyme that are more sensitive to oxidants are more susceptible to degradation by the above processes.

[The roles of macrophage in immune dysfunction following severe thermal injury]

This experimental study in serious scald mice showed that the cytosolic free calcium ion concentration and the capacity of secreting TNF-alpha of macrophage (M phi) were obviously increased while the secretion of IL-1 was significantly decreased, and accompanied with simultaneous apparent rising of serum TNF-alpha in early postburn period. These indicate that M phi have been highly or even over activated after burn. But the ability of antigen presentation of M phi during this period was deeply suppressed rendering the obvious declination of activity and proliferation response of antigen pulsed lymphocytes. It might be concluded that the defective antigen presentation of M phi played a critical role in early immune dysfunction of severe scald mice, and the highly activated or even overactivated M phi by excessive secretion of TNF-alpha were the molecular basis of the alterations of M phi function.

Differential regulation of superoxide dismutase in copper-deficient rat organs

The effects of dietary copper deprivation on the activities, immunoreactive protein concentrations, and mRNA abundance of copper/zinc- and manganese-superoxide dismutase (Cu/Zn- and Mn-SOD) were examined in liver, heart, and brain of weanling rats fed a Cu-deficient diet for 4 weeks. Hepatic Cu/Zn-SOD activity, enzyme content, and mRNA abundance were significantly reduced, and, conversely, the activity, protein, and mRNA levels of Mn-SOD were significantly elevated in Cu-deficient rats. In Cu-deficient heart, the activity and protein content for Cu/Zn-SOD were reduced, whereas those for Mn-SOD were increased; the levels of mRNAs for these two enzymes was unaffected. Dietary Cu deficiency was without effect on the activities, enzyme contents, and mRNA abundance of brain Cu/Zn- and Mn-SOD. These results indicate that SODs from liver, heart, and brain exhibit differential sensitivities to dietary Cu deprivation, and that different mechanisms (transcriptional, posttranscriptional, or posttranslational) may be involved in their regulation.

Different sensitivities of the Na+/K(+)-ATPase isoforms to oxidants

Inhibition of Na+/K(+)-ATPase by partially reduced oxygen metabolites has been suggested to be involved in ischemia-reperfusion injury to heart and other organs. Since various isoforms of the enzyme have different sensitivities to ouabain and several other inhibitors, we studied the effects of H2O2 and the hydroxyl radical on enzyme activity and phosphoenzyme formation in Na+/K(+)-ATPase preparations with known alpha-subunit isoform composition in order to assess the oxidant sensitivities of the isoforms. Rat axolemma enzyme (alpha 2 and alpha 3) which has higher sensitivity than the rat kidney enzyme (alpha 1) to ouabain also showed higher oxidant sensitivity than the kidney enzyme. No significant difference between the oxidant sensitivities of the alpha 2 and alpha 3 of the axolemma was noted. In the ferret heart enzyme (alpha 1 and alpha 3), we confirmed that alpha 3 has higher ouabain sensitivity than alpha 1, and we established that alpha 3 also has higher oxidant sensitivity than alpha 1. The rat kidney enzyme (alpha 1) and the canine kidney enzyme (a variant of alpha 1 with much higher ouabain sensitivity than the rat kidney enzyme) exhibited similar oxidant sensitivities. The findings suggest that (a) oxidant sensitivity is related to structural features that distinguish alpha 1 from alpha 2 and alpha 3, rather than to features that control ouabain sensitivity; and (b) different isoform compositions of the various tissues may contribute to their relative susceptibilities to oxidant stress.

The significance of changes in serum tumour necrosis factor (TNF) activity in severely burned patients

In order to explore the pathogenesis of postburn internal organ injury (OI) and multiple organ failure (MOF), serum TNF activity was measured by biological assay in 24 severely burned patients. Parameters related to internal organ functions were simultaneously measured. The results showed an obvious increase in serum TNF activity accompanied by increased serum myocardial and hepatic enzymes, plasma lactate and aggregations of WBC in internal organ tissues. Serum protein levels decreased substantially. These changes were more marked in patients suffering from both OI and MOF. It is suggested that large amounts of TNF are produced postburn and might have an important role in the development of OI and MOF.

[Teratoma of testis--a case report]

A case of mature testicular teratoma in a 5-year-old child is presented. The level of serum beta-human chorionic gonadotropin (beta-HCG), alpha-fetoprotein (alpha-AFP), and carcinoembryonic antigen (CEA) were all within normal limit one year post-operatively. We discussed the clinical features, treatment and the result of this patient and reviewed the literature.

Serosurveys of spotted fever and murine typhus in local residents of Taiwan and Thailand compared with Japan

To estimate the prevalence of spotted fever (SF) and murine typhus (MT) rickettsioses in Southeast Asia, we performed serosurvey by immunoperoxidase test on local residents in Taiwan and Thailand, comparing them with those of Japan. In Japan, the prevalence of antibodies (1:80 as cut-off level) to some SF/MT antigens was noticeable in Japanese SF-endemic areas or a high-risk groups. In Tainan, Taiwan, SF antibodies were not so prevalent (3.5 to 4.4%), but MT antibodies were more prevalent (23.9%). In Chiang Rai in northern Thailand SF antibodies were markedly prevalent (9.0 to 21.3%); the reactivity with Thai tick 118 strain alone was 8.2%, but MT was less (2.5%). These results suggest that these rickettsioses may be latently distributed in various parts of Asia.

Allosteric regulation of the access channels to the Rb+ occlusion sites of (Na+ + K+)-ATPase

Previous work on the role of occluded Rb+ (a K+ substitute) in the reaction cycle of (Na+ + K+)-ATPase has focused on the kinetics of the dissociation of the enzyme-Rb+ complex at 20-24 degrees C. Doing experiments at 4 degrees C, we have made the following observations on the equilibrium binding levels and the kinetics of binding and release of Rb+. 1) The plot of bound Rb+ as a function of [Rb+] showed occupancy of high affinity sites, followed by binding to sites of lower affinity. The estimated number of Rb+ sites/active site was two to three, but a higher number was not ruled out. Release of bound Rb+ was slow and not monoexponential, the major portion being in a pool with a half-life of 4-5 h. Dissociation curves were identical at different levels of site occupancy. Rb+ binding also had fast and slow phases, requiring about 24 h to reach steady state at vastly different [Rb+]. These data suggest that (a) Rb+ occlusion sites are confined within the protein matrix and connected to the medium by narrow access channels that are heterogeneous in size, and (b) channel heterogeneity is distinct from differences in occlusion site affinities. 2) ATP, at a low affinity allosteric site, had no significant effect on the maximal level of bound Rb+ at any [Rb+], but it accelerated both the fast and the slow phases of Rb+ binding and release, and it increased the ratio of fast to slow phases. Evidently, ATP activates the channels (lowers the energy barrier for access) without altering binding site affinities. 3) Na+ was a competitive inhibitor of Rb+ at the occluded sites, but it also acted at an allosteric site to activate the access channels. Rb+ and K+ also had allosteric effects: although they did not affect the access channels directly, they blocked the allosteric effect of Na+. 4) Ouabain was an access channel inhibitor. It reduced the rates of binding and release of Rb+, blocked channel activation by ATP and Na+, but seemed to have no effect on the events at the occluded sites. The existence of heterogeneous access channels to the ion transport sites and the demonstration of channel regulation by the physiological ligands of the enzyme suggest the necessity of the inclusion of such allosteric mechanisms in the reaction cycle of (Na+ + K+)-ATPase.

[Metabolism of serum lipoprotein in hypothyroidism]

The changes of serum lipids concentrations in 15 patients with primary hypothyroidism were studied. 9 euthyroid persons in the similar age group with patients were selected as a control group. The serum levels of total and LDL cholesterol, TG, ApoAI, ApoB and ApoCII in patients before treatment were all higher than those of the control group. They decreased to normal level after treatment. The mean values of total cholesterol decreased from 6.7 mmol/L to 4.1 mmol/L, TG decreased from 2.5 mmol/L to 1.0 mmol/L, LDI-ch from 3.9 mmol/L to 2.4 mmol/L, ApoAI from 1.9 g/L, to 1.3g/L, ApoB from 1.2 g/L to 0.7 g/L and ApoCII decreased from 6.9 mg/dl to 3.9 mg/dl. There were no differences of HDI-ch level between patients before treatment and normal controls, HDI-ch level of patients only slightly decreased after treatment. Soon after the thyroid hormone treatment, all parameters of serum lipids, not including HDI-ch, were improved, as TT, level became normal, although the levels of TT4 was still not reached to normal level.

Race and diabetes as death risk predictors in hemodialysis patients

Case mix and laboratory predictors of death risk were evaluated in 17,185 hemodialysis patients. The laboratory variables most closely associated with the increased death risk borne by diabetic patients (relative to non-diabetics) and White patients (relative to non-Whites) were identified. The analyses of laboratory death risk predictors were similar to those previously reported. Serum albumin concentration is the most powerful death risk predictor among all of the variables, both case mix and laboratory. Statistical models including only case mix variables reveal both race (RRWhites = 1.42) and diabetes (RRdiabetes = 1.43) as significant predictors. Adding creatinine, albumin, and BUN concentrations to the model eliminated diabetes as a significant predictor. Creatinine and albumin accounted for most of the change. Adding only creatinine eliminated race. The data suggest that reduced visceral and somatic protein mass and/or metabolism may be important determinants of mortality in dialysis patients. Because differences in the concentrations of creatinine and albumin explain much of the risk associated with being White or diabetic, differences in nutritional status may explain the reduced survival observed in those groups. Therefore, clinicians should not simply accept without question the notion that diabetics and Whites are doomed to inferior survival.

Ionic mechanisms responsible for the antiarrhythmic action of dehydroevodiamine in guinea-pig isolated cardiomyocytes

1. Dehydroevodiamine alkaloid (DeHE), an active ingredient of a Chinese herbal medicine Wu-Chu-Yu (Evodiae frutus), has been shown to decrease aterial blood pressure in experimental animals and prolong action potential duration in cardiac cells. The aim of the present study was to explore the ionic basis of its possible antiarrhythmic effects. 2. Guinea-pig atrial and ventricular myocytes were isolated enzymatically and the ionic currents were recorded under whole-cell patch-clamp with single suction pipettes. 3. DeHE at a concentration of 0.1 microM inhibited reversibly the time-dependent outward K current (delayed rectifier, Ik) and the Na-dependent inward current (INa). 4. In low-K (1 mM) and high-Ca (9 mM) solution, DeHE also depressed the delayed afterdepolarizations (DAD) and the transient inward current (Iti) induced by 2 microM strophanthidin. On the other hand, DeHE occasionally induced early afterdepolarizations and slow response action potentials at a depolarized level. 5. At higher concentrations (1 microM and above), the L-type Ca current (ICa,L) was moderately inhibited. 6. The present findings indicate that DeHE may depress triggered arrhythmias in Ca-overloaded guinea-pig cardiac myocytes through its inhibitory actions on INa, Iti and, to a smaller extent, ICa. DeHE may also exert class III antiarrhythmic effect through a reduction of outward K currents (Ik) across the sarcolemma.

[Study of the abnormal plasma proteins after burn injury]

In our previous study at least 4 abnormal bands were found in burned sera when analyzed by SDS-PAGE. In this paper further exploration of the characteristics of these abnormalities of burned sera were presented. By way of western blotting, 12 kinds of antisera against different human proteins as detecting antibodies were used. Results showed that bands developed by anti-haptoglobin antiserum corresponded well with the abnormal bands in SDS-PAGE. If the burned serum was separated by ion-exchange chromatography and its collected eluates containing protein peaks were tested for the immunosuppressive activities on normal murine spleen lymphocytes, the immunosuppressive eluates were usually found in the 6th protein peak. When these immunosuppressive eluates were further analyzed by SDS-PAGE and Western blotting, bands stained with anti-haptoglobin antiserum still coincided with the abnormal bands found in SDS-PAGE of burned serum. Result of this study suggests that one of the immunosuppressive factors found in burned serum may be a haptoglobin-like substance.

Mesiodens in the primary dentition stage: a radiographic study

Five hundred and forty-three Chinese patients in the primary dentition stage were evaluated for mesiodens with maxillary, anterior occlusal films. Compared with other studies, a higher prevalence was found, using different age-groups and diagnostic methods. The distributions of mesiodens by sex, location, and direction were also studied. Because mesiodens could interfere with normal development of the occlusion, especially in the early mixed dentition stage, early diagnosis, using appropriate radiographs during the primary dentition stage, could lead to more comprehensive treatment planning.

(Na+ + K+)-ATPase: inactivation and degradation induced by oxygen radicals

1. Purified (Na+ + K+)-ATPase was irreversibly inhibited upon exposure to hydrogen peroxide, the superoxide anion, and the hydroxyl radical. 2. Comparison of the SDS-gel electrophoretic patterns of the ATPase samples exposed to these oxidants revealed that inhibition occurred either without gross structural changes, or concomitant with fragmentation and cross-linking of the enzyme subunits. 3. The oxidant modified ATPase was also shown to be more susceptible to degradation by several proteolytic enzymes.

[Renal pelvic tumor associated with contralateral renal cyst--a case report]

A 74-year-old female presented with a two years history of malaise, weakness and intermittent gross hematuria. Two years earlier, left renal cyst had been diagnosed by excretory urography, abdominal sonography and computed-tomography. Initially she was treated conservatively with oral antibiotics, however medical management had not been successful in improving her condition. Finally she was transfer to our ward for further evaluation and treatment. Cystoscopic examination demonstrated no abnormality, except for bloody urine efflux from the right ureteric orifice. Right retrograde pyelograms confirmed a solitary filling defect in the upper calyx of right kidney. Because of immediate concern for right renal pelvic tumor and contralateral renal cyst, a midline transperitoneal exploration was made. The right nephroureterectomy with cuff of bladder was removed and left unroofing of cyst was carried out. Convalescence was uneventful. The pathologic examination revealed moderately differentiated transitional cell carcinoma of right kidney with a simple renal cyst of left kidney. We suggest that cases with a clinical diagnosis of renal cyst based on the presence of gross hematuria, a normals excretory urogram and computed tomogram, generally require further evaluation especially by cystoscope and retrograde pyelogram to determine the source of bleeding.

Further explorations of abnormalities in serum proteins following burns

This report extends our earlier studies of the abnormal protein bands found in burn sera by use of Western blotting and ion exchange chromatography. The current studies indicated that some of the protein bands contained materials with immunosuppressive activity. One of these materials cross reacted with anti human haptoglobin antibody. Many of the other proteins in the bands were found to be acute phase reactant proteins without immunosuppressive activity. Some proteins in these bands have not yet been characterized or tested for immunosuppressive activity.

Predictors of in-hospital mortality after DC catheter ablation of atrioventricular junction. Results of a prospective, international, multicenter study

BACKGROUND

The Catheter Ablation Registry was the first international, multicenter, prospective study of the safety and efficacy of catheter ablation.

METHODS AND RESULTS

From August 1987 through March 1990, the study comprised 136 patients in whom only DC energy was used in attempted production of third-degree atrioventricular block to treat uncontrollable supraventricular tachycardias. Eight patients died during hospitalization for ablation. In seven (5.1%), the ablation may have contributed to their deaths. Causes of death included ventricular fibrillation (five patients, three with polymorphic ventricular tachycardia), progressive heart failure (one patient), and respiratory failure (two patients, one dying after resuscitation from ventricular fibrillation). Compared with survivors, patients who died were more likely to have had prior aborted sudden death (38% versus 2%, p less than 0.05), congestive heart failure (88% versus 22%, p less than 0.001), cardiomyopathy (50% versus 16%, p less than 0.05), lower baseline systolic blood pressure (106 versus 138 mm Hg, p less than 0.001), prolonged baseline and postablation corrected QT interval (p less than 0.01), and markedly reduced ejection fraction (27% versus 52%, p less than 0.001). Ablation successfully produced third-degree atrioventricular block in 88% of the patients who died and in 83% of survivors.

CONCLUSIONS

Catheter ablation of the atrioventricular junction with DC energy carries a significant, previously unrecognized risk of death (5.1%), particularly from lethal arrhythmias, when applied to patients with severe left ventricular dysfunction. Great care should be taken in these seriously ill patients to guard against postablation ventricular arrhythmias.

A second messenger role for monoacylglycerols is suggested by their activating effects on the sodium pump

Receptor-mediated activation of the sodium pump has been noted in several intact tissues. To test the hypothesis that this may be due to the direct effects of the second messenger diacylglycerols on the pump, we studied the effects of various long-chain acylglycerols on the purified Na+/K(+)-ATPase. With optimal ATP, acylglycerols had no effect on enzyme activity. When ATP was suboptimal, tri- and diacylglycerols had no effects, but monoacylglycerols caused up to 3-fold increase in ATPase activity. Using sealed vesicles of red cell membranes and cardiac sarcolemma, stimulation of the ion transport function of the enzyme by monoacylglycerols in the presence of suboptimal ATP was also shown. Since the sodium pump may not be saturated with ATP in the intact cell, the possibility arises that monoacylglycerols are the second messengers for the receptor-mediated regulation of the pump.