Aggressive management of acute myocardial infarction: successful outcome in an older patient with cardiogenic shock

A 71-year-old man was referred to our emergency department presenting with acute inferior and right ventricular myocardial infarction with cardiogenic shock. He developed ventricular fibrillation 80 minutes after arrival. Immediate defibrillation, mechanical ventilatory support with oxygenation, and inotropic agents were instituted. Despite restoration of sinus rhythm, his hypotension persisted. He promptly received intra-aortic balloon pump (IABP) counterpulsation and cardiac catheterisation. Coronary angiography revealed a subtotal occlusion of the left anterior descending coronary artery and complete occlusion of the right coronary artery. Since the right coronary artery was considered to be the infarct-related coronary artery, percutaneous coronary intervention (PCI) was carried out to the right coronary artery only. The patient was extubated and IABP was removed on the second and third admission day, respectively. He was discharged from the hospital eight days later. A second PCI to the left anterior descending coronary artery was performed successfully three weeks later. This case illustrates that in patients with acute myocardial infarction and cardiogenic shock, prompt application of IABP and PCI of the infarct-related coronary artery may be beneficial in reducing the catastrophic morbidity and mortality, especially in older patients.

Development of interesting step-climbing styles

OBJECTIVES

This study was to investigate the influence of stepping styles (forward, side, and cross steppings) and inclinations (25 and 45 degrees) on cardiorespiratory responses (C-R responses).

METHODS

Twenty volunteers were recruited and randomly arranged into two ten-people groups, exercising on step-climbing machines respectively of 25 and 45 degrees of inclination. C-R responses were recorded during each test which lasted for six minutes at 50 steps per minute on a step-climbing machine.

RESULTS

The group on 25-degree inclination had significantly lower C-R responses than the group on 45-degree inclination. Although only small differences, probably statistically insignificant, were found among the three step-climbing styles, these differences showed interesting trends independent of inclination.

CONCLUSIONS

Climbing stairs with the three interesting step-climbing styles in this study could be considered as an exercise of moderate intensity (60-80% HRmax ). Climbing on 25-degree inclination at 50 steps per minute is recommended for less fit individuals because of lower cardiovascular stress as compared with on 45-degree inclination.

Neuromuscular hamartoma arising in the brachial plexus

We report a case brachial plexus neuromuscular hamartoma (choristoma) in a 28-year-old man who complained of numbness of the left hand and forearm for several years. MRI revealed a circumscribed, rounded mass in the left brachial plexus. The patient is well 2 years after surgery, with no neurological deficit.

Serum soluble transferrin receptor reflects erythropoiesis but not iron availability in erythropoietin-treated chronic hemodialysis patients

BACKGROUND

The diagnosis of iron deficiency using the current commonly used tests is usually difficult in hemodialysis patients. Soluble transferrin receptor (sTfR) has caught the attention of physicians recently as regards its use as a parameter for the evaluation of iron status. This study was conducted in order to evaluate the correlation of serum soluble transferrin receptor (sTfR) concentration with hematological parameters and iron profiles, in the role of identifying iron deficiency among dialysis patients.

METHODS

Seventy-three patients having received chronic hemodialysis and stable maintenance recombinant human erythropoietin (rHuEPO) therapy were included. Iron, total iron-binding capacity, ferritin and sTfR were measured in the first week. Following this, these patients began to receive intravenous iron dextran (2 mg/kg/week) for 4 weeks. The hematocrit (Hct), hemoglobin (Hb) levels and reticulocyte counts were evaluated weekly. At the beginning of fifth week, the sTfR level was measured again. Patients were classified as belonging to one of the following groups: serum ferritin < 100 microg/L - absolute iron-deficient group; initial ferritin level > or = 100 microg/L with an increase in hemoglobin of greater than 1 g/dL at the end of the study occult iron deficiency group; others - non iron-deficient group.

RESULTS

Seventy-one patients completed the study. The concentration of sTfR was positively correlated with Hct, Hb and reticulocyte index at the beginning (r = 0.236, p = 0.047; r = 0.257, p = 0.04; r = 0.401, p < 0.01, respectively) and at the end of the study (r = 0.384, p < 0.01; r = 0.338, p < 0.01; r = 0.427, p < 0.001, respectively). After 4 weeks of iron and rHuEPO therapy, the sTfR concentration increased, rather than declined, from 21.85 +/- 8.06 nM to 23.76 +/- 7.42 nM (p = 0.04) and the change was positively correlated with the changes in Hct, Hb and reticulocyte index. The administered rHuEPO doses did not differbetween the iron deficiency group (absolute deficiency, n = 3; occult deficiency, n = 10) and non-iron deficiency group (n = 58). The sTfR levels failed to identify the occult iron deficiency group because there was no difference between occult iron-deficient and non-iron-deficient patients (24.73 +/- 9.09 nM versus 21.60 +/- 7.89 nM, p = 0.34). Instead, transferrin saturation (TS) could be a differential marker between the 2 groups (19.0 +/- 10.9% versus 30.1 +/- 12.7%, p = 0.012).

CONCLUSION

The serum sTfR concentration is indeed an appropriate marker for erythropoiesis. The erythropoitic effect of administered rHuEPO could mask the effect of iron status on the sTfR concentration. This might make the sTfR concentration no longer an appropriate index to identify the presence of occult iron deficiency. Thus, TS and ferritin currently remain better methods for the evaluation of iron status in rHuEPO-treated chronic hemodialysis patients.

Color encoding of the two-dimensional echocardiograms to analyze the echo texture of thickened mitral leaflets

OBJECTIVE

The visual identification of different brightness of two-dimensional echocardiograms has natural limitations. The aim of this study was to perform a color-encoding technique on the echocardiograms and to evaluate whether the thickened mitral valve due to different etiologies may exhibit different colors and textures.

DESIGN

Two-dimensional echocardiograms in parasternal long axis view in late diastole were digitized in 28 patients with thickened mitral valves and 14 age-matched control subjects. These 28 patients included 14 patients with mitral valve prolapse (MVP) and 14 patients with rheumatic change of mitral valve (RMV). The mean gray level of the anterior mitral valve and the skewness of the histogram of gray level distribution of the anterior mitral valve were studied in all cases.

RESULTS

A significantly greater mean gray level of mitral valves in patients with RMV (114 +/- 20, p < 0.001) and lesser mean gray level in patients with MVP (49 +/- 12, p = 0.041) compared to that of control subjects (62 +/- 18) were noted. The mitral valves of the echocardiograms of patients with MVP tended to show a blue-to-green color, while those of RMV tended to show a yellow-to-orange color by this image processing system. Significant differences in skewness of the gray level distribution of mitral valves in control vs RMV (p = 0.001), control vs MVP (p = 0.005), and RMV vs MVP (p < 0.001) were also found.

CONCLUSION

This study demonstrates that the thickened mitral valves due to MVP and RMV may exhibit different colors and textures. Digital image processing can provide additional information to conventional echocardiograms in characterizing different echo textures of the heart valves.

High resistive index of the radial artery is related to early primary radiocephalic hemodialysis fistula failure

Forty-nine patients who had received radiocephalic hemodialysis fistula construction were evaluated with duplex Doppler ultrasonography to characterize the Doppler indices of the feed radial arteries just proximal to the site of anastomosis. Forty-four patients had fistulas with good function, and 5 patients had fistulas with inadequate blood flow or thrombosis within 4 weeks after the operation. A preliminary study showed extensive variability in peak systolic velocity and end-diastolic velocity in the feed arteries. The resistive index dropped significantly 1 week after the operation and remained relatively constant over the following 5 weeks. In the success group, the mean resistive index measured 1 week after operation was 0.40+/-0.06. It was higher than that of the failure group (mean resistive index: 0.52+/-0.06). Among patients with well-functioning fistulas, diabetic patients had higher resistive indices than did non-diabetic patients (0.44+/-0.04 vs. 0.37+/-0.06). Our results suggest that a higher resistive index of the feed artery is closely related to early autogenous primary hemodialysis fistula failure.

An ultrasensitive chemical method for polysialic acid analysis

An ultrasensitive method for analysis of polysialic acid (polySia) chains, using fluorescence-assisted high-performance liquid chromatography was developed. The new method is a substantial improvement of our earlier method in which the reducing terminal Sia residues of a homologous series of oligo/polySia hydrolytically released during derivatization reaction were simultaneously labeled with a fluorogenic reagent, 1,2-diamino-4,5-methylenedioxybenzene (DMB) in situ. We first studied extensively the stability of oligo/polySia in the acid (0.02 M trifluoracetic acid) used for 1,2-diamino-4,5-methylenedioxybenzene derivatization under various conditions of reaction time and temperature, analyzing the hydrolytic products by high-performance anion exchange chromatography with pulsed electrochemical detection (HPAEC-PED). Then we optimized the reaction conditions to minimize degradation of the parent polySia while maintaining high derivatization rate. Using a DNAPac PA-100 column rather than a MonoQ column, baseline resolution of polySia peaks up to DP 90 with a detection threshold of 1.4 femtomol per resolved peak was achieved. The new method was used to analyze the degree of polymerization of a polySia-containing glycopeptide fraction derived from embryonic chicken brain, and the results were compared with those obtained by HPAEC-PED.

Prediction of in-hospital mortality in patients with myocardial infarction using APACHE II system

BACKGROUND

The acute physiology and chronic health evaluation (APACHE) scoring system has been validated in many different patient populations, however, patients with myocardial infarction (MI) were not included in the original data base. To evaluate the ability of APACHE scoring system in predicting in-hospital mortality, 694 patients with MI were studied.

METHODS

Data had been collected prospectively in an ICU computer database in the past 3 years. Patients admitted in coronary care unit with acute MI or acute coronary syndrome who had previous history of MI were all included. Patients were divided into survivor and non-survivor data sets. Multiple logistic regression analysis was evaluated on the variables of APACHE II score to determine which variables could predict in-hospital mortality. A logistic regression model was used to study the mortality curves. The differences of APACHE II scores between survivors and non-survivors were compared. Correlation between observed and predicted mortality was also assessed.

RESULTS

According to the statistical analysis, the non-survivors tended to have significantly greater APACHE II scores than those of survivors. The APACHE II values of non-survivors and survivors were 23.64 +/- 9.41 versus 13.35 +/- 7.14 (p < 0.001), respectively. Using multiple logistic regression analysis, we found that age, creatinine, coma scale, sodium and APACHE II score were capable of predicting the in-hospital mortality (p < 0.05). With use of the logistic model, a good correlation of predicted mortality rate to observed mortality rate was found (r = 0.992). This study demonstrated that lower APACHE II scores predicted survival while high scores predicted mortality. Mortality rate increased significantly when APACHE II score was > 25. An APACHE II score greater than 28.25 predicted a more than 50% in-hospital mortality.

CONCLUSIONS

This study demonstrates that the APACHE II scoring system is capable of predicting mortality in patients with MI, which makes this modality more applicable in the busy intensive care unit.

External biliary drainage plus bile acid feeding is not equal to internal drainage in preserving the cellular immunity following prolonged obstructive jaundice

This study investigates the importance of intestinal bile flow in cellular immunity. Sprague-Dawley rats undergoing bile duct ligation (BDL) and sham ceiliotomy (Sham) for 14 and 21 days were investigated. Experimental animals following BDL were further divided into an external drainage (ED) group, an ED group with rat chow mixed with 2:2:1 cholic acid, chenodeoxycholic acid, and deoxycholic acid (ED + BF), and an internal drainage (ID) group. Fourteen days later, they were killed and analyzed for spleen lymphocytic [3H] thymidine uptake (LHU) under mitogen stimulation with phytohemagglutinin, blood biochemistry, hemogram, and liver pathology. In the 14-day BDL experiment, LHU and serum albumin level were decreased in the BDL group (P < 0.05). After drainage, they were not significantly different among sham, ED, ED + BF, and ID groups. In the 21-day BDL experiment, the red cell volume was decreased (P < 0.05). After drainage, the ED, ED + BF, and ID groups still had a significantly lower LHU than the sham group (P < 0.05). However, the ID group had higher LHU than the ED and ED + BF groups (P < 0.05). The ED + BF group had a slightly higher LHU than the ED group but not statistically significant. Liver pathology returned to normal after drainage in the 14-day BDL model. In contrast, the 21-day BDL group had prominent periportal necrosis and developed periportal fibrosis after drainage. The present study reveals the duration of BDL determines the severity of hepatic damage. In the 14-day BDL groups, all kinds of drainage completely reverse the impaired liver function and cellular immunity. In the 21-day BDL group, 14-day drainage is inadequate for recovery because irreversible pathological changes are found. The reversal of cellular immunity in ID is better and faster, because it provides a better hepatic functional, nutritional, and hematological recovery besides the presence of primarily secreted bile acids.

Comparison of the APACHE II and APACHE III scoring systems in patients with respiratory failure in a medical intensive care unit

BACKGROUND AND PURPOSE

This retrospective study compared the capability of the Acute Physiology and Chronic Health Evaluation (APACHE) II and APACHE III scoring systems to predict outcome and determined the independent predictors of survival in these scoring systems for patients with respiratory failure in a medical intensive care unit (ICU).

MATERIALS AND METHODS

Seven hundred and eight patients with respiratory failure admitted to the medical ICU throughout a 9-year period were studied. Patients with an ICU stay of less than 24 hours, patients under 12 years of age, and burn and surgery patients were excluded. APACHE scores were calculated at 24 hours after admission. Student's t-test was used to compare the total APACHE scores of survivor and non-survivor groups. Multivariate logistic regression analysis was used to determine which variables were predictors of mortality. The discriminative power of APACHE scores to predict in-hospital mortality was studied by the area under the receiver operating characteristic curves of the APACHE II and APACHE III systems, respectively.

RESULTS

Both systems showed a significant association between higher scores and higher mortality. The APACHE II system under-predicted the actual hospital mortality rate. The APACHE III systems had a higher discriminative power (area 0.7462) than the APACHE II systems (area 0.6856; p < 0.05). The independent predictors of survival as assessed by APACHE II and III systems were respiratory rate, arterial oxygen pressure, oxygen gradient between alveoli and artery, serum creatinine concentration, and the presence of neurologic abnormalities.

CONCLUSIONS

The APACHE III systems has greater discriminative power than the APACHE II systems for predicting in-hospital mortality. The variables of oxygenation, mean artery pressure, respiratory rate, serum creatinine concentration, and Glasgow Coma Scale play important roles in predicting survival for patients with respiratory failure.

Significance of cardiac troponin I and creatine kinase release after coronary intervention

BACKGROUND

Cardiac troponin I is a highly sensitive and specific marker for early detection of myocardial injury. Whether it can be used to monitor myocardial injury after coronary intervention is uncertain. This study was designed to measure the cardiac troponin I and creatine kinase (CK) after coronary intervention and investigate their clinical significance.

METHODS

We measured cardiac troponin I and CK levels before intervention and 4 hours, 8 hours, 12 hours and 24 hours after apparently successful coronary intervention in 106 eligible patients. Nine patients were excluded due to missing data. We also followed up the clinical outcome to record major cardiac events (MACE).

RESULTS

The frequency of cardiac troponin I increase after coronary intervention was higher than that of CK increase (40.2% vs 8.2%). The frequency of cardiac troponin I increase in the stent group was significantly higher than that in the PTCA group (49.2% vs 21.9%, p < 0.001). The frequency of cardiac troponin I increase was also higher than that of CK increase in patients with in-hospital events (58.8% vs 14.7%).

CONCLUSIONS

Cardiac troponin I is more sensitive than creatine kinase in detecting myocardial injury after coronary intervention. The incidence of cardiac troponin I increase is significantly higher in patients undergoing stenting than in patients treated with balloon angioplasty only. The cardiac troponin I increase is more highly correlated with in-hospital events than is creatine kinase.

Extremely low sodium hypotonic rehydration solution for young children with acute gastroenteritis

BACKGROUND

The clinical efficacy and safety of a low-sodium hypotonic oral rehydration solution (LSORS) was compared in a pilot study with that of a standard World Health Organization oral rehydration solution (STORS) in young children with acute diarrhea.

METHODS

One hundred and seventeen boys aged 3 to 18 months with acute diarrhea were randomly assigned to groups and received low-sodium (sodium 28 mmol/L) hypotonic oral rehydration solution and standard oral rehydration solution (sodium 90 mmol/L). Outcomes of therapy such as stool volume, duration of diarrhea and fluid intake were recorded at 24 hours, 48 hours, and the discontinuation of disease. Serum electrolytes levels were calculated before and after therapy.

RESULTS

The stool output (gm/kg) in the first 24 hours was 69.2 +/- 38.5 in the LSORS group versus 105 +/- 39.8 in the STORS group (p < 0.05), while the total stool output during the 48-hour period was 151.4 +/- 68.9 in the LSORS group versus 232 +/- 97.3 in the STORS group (p < 0.05). No significant (p > 0.05) reduction in duration of diarrhea was noted (72.3 +/- 25.5 hours versus 69.8 +/- 29.4 hours). Four patients in the LSORS group and 7 patients in the STORS were classified as treatment failure. Forty-four (80%) achieved successful treatment in the LSORS group and 34 (56.7%) in the STORS group (p = 0.07).

CONCLUSION

LSORS is as safe as STORS in treating young children with acute gastroenteritis. No evidence of hyponatremia was found after patient received LSORS. LSORS afforded more efficacious therapy than STORS.

Tumor amplified protein expression therapy: Salmonella as a tumor-selective protein delivery vector

Attenuated strains of Salmonella typhimurium, VNP20009 and YS7212, when injected systemically to tumor-bearing mice, accumulated preferentially in tumors at levels at least 200-fold and, more commonly, 1000-fold greater than in other normal tissues. This selectivity occurred in subcutaneously implanted murine tumors, including B16F10 melanoma, M27 lung carcinoma, and colon 38 carcinoma. The preferential accumulation was also manifested in animals bearing human tumor xenografts, including Lox, C8186, DLD1, SW620, HCT116, HTB177, DU145, MDA-MB-231, and Caki. Four to five days after a single IV injection of 1 x 10(6) colony-forming unit (cfu)/mouse, we routinely detected VNP20009 proliferation and accumulation at levels ranging from 1 x 10(8) to 2 x 10(9) cfu/g tumor. The amount of VNP20009 accumulated in the liver ranged from 3 x 10(4) to 2 x 10(6) cfu/g. The distribution of Salmonella in tumors was homogenous; YS7212 could be detected from the periphery to the interior portion of the tumors. Using mice with various immunodeficiencies, we also discovered the same preferential accumulation of Salmonella in tumors implanted in these mice. The use of Salmonella as a protein delivery vector was shown by IV administration of the bacteria expressing either green fluorescent protein (GFP) or cytosine deaminase (CD) into tumor-bearing mice. GFP and CD were detected in tumors, but not in livers, taken from mice inoculated with Salmonella carrying these genes. Bacteria accumulation and CD expression persisted in the tumors for up to 14 days after a single bolus IV administration of bacteria to tumor-bearing mice.

Influence of erythropoietin treatment on gonadotropic hormone levels and sexual function in male uremic patients

OBJECTIVE

The purpose of this study was to evaluate whether levels of sex hormones and sexual function differ in renal failure patients with and without uremia and the effect of treatment with recombinant human erythropoietin (rhuEPO).

MATERIAL AND METHODS

Fifteen males with chronic renal failure who were not receiving hemodialysis and 25 male renal failure patients with uremia who were undergoing hemodialysis were enrolled before and after rhuEPO therapy. Fifteen male volunteers matched for age and weight were also studied. Levels of various blood biochemicals were measured in all patients before and 1 week after rhuEPO treatment. Sexual function was also studied in all patients before and 6 months after rhuEPO treatment.

RESULTS

The control group had significantly higher levels of testosterone (6.21 +/- 1.21 ng/ml) and hematocrit (Hct) (43.2 +/- 2.1%) and significantly lower levels of prolactin (5.27 +/- 1.21 ng/ml), follicular-stimulating hormone (FSH) (7.51 +/- 2.36 mIU/ml) and leutinizing hormone (LH) (4.23 +/- 2.10 mIU/ml) than the two patient groups (p < 0.05 for all comparisons). Patients with renal failure only had significantly lower levels of testosterone and Hct (2.54 +/- 0.53 ng/ml and 21.4 +/- 1.4%, respectively) than those with uremia (3.65 +/- 0.52 ng/ml and 24.3 +/- 2.5%, respectively; p < 0.001 for both comparisons). After rhuEPO therapy, the testosterone and Hct levels of the two patient groups did not reach the level of the control subjects (p < 0.05 for both comparisons). Similarly, the levels of prolactin, FSH and LH were significantly higher in both patient groups than those of control subjects after rhuEPO therapy (p < 0.001 for both comparisons). However, after rhuEPO therapy, significant increases in testosterone and Hct levels were found in both patient groups (p < 0.001 for both comparisons). Sexual function was also markedly improved in the hemodialysis patient group. While 20/25 (80%) male hemodialysis patients reported improved sexual function after rhuEPO treatment, only 3/15 (20%) chronic renal failure patients reported improvement.

CONCLUSIONS

In patients with advanced uremia, rhuEPO therapy may result in improved gonadotropic hormone levels and sexual function. Good dialysis quality may contribute to the increase in the incidence of patients with better sexual function.

A Novel mRNA-cDNA interference phenomenon for silencing bcl-2 expression in human LNCaP cells

The templates required for inducing posttranscriptional gene silencing (PTGS) effects have been investigated in human prostate cancer LNCaP cells. Transfection of a mRNA-cDNA hybrid construct was found to result in a relatively long-term interference of specific gene expression. Androgen-stimulated expression of bcl-2 has been reported to increase the tumorigenic and metastatic potentials of human prostate cancer LNCaP cells, as well as their resistance to many apoptotic stimuli. The addition of bcl-2 antisense oligonucleotides, however, restored apoptosis. Our studies demonstrate gene silencing effects of the mRNA-cDNA transfection that is similar to those of PTGS/RNAi in this in vitro prostate cancer cell model. A potential RNA-directed RNA polymerase activity was also detected which is alpha-amanitin-sensitive. These findings indicate that a novel gene silencing system may exist in mammalian cells.

Laparoscopic closure of patent canal of Nuck for female indirect inguinal hernia

STUDY OBJECTIVE

To determine the efficacy of concomitant laparoscopic closure of the patent canal of Nuck in treatment of indirect inguinal hernias in women.

DESIGN

Prospective clinical trial (Canadian Task Force classification II-2).

SETTING

University-associated tertiary care referral center.

PATIENTS

Six women scheduled for laparoscopy for gynecologic indications. Intervention. Concomitant simple closure of the patent canal of Nuck from the peritoneal cavity during laparoscopic surgery.

MEASUREMENTS AND MAIN RESULTS

Inguinal hernias were repaired in all six patients, with no recurrence.

CONCLUSION

l Laparoscopic closure of the patent canal of Nuck is an easy, safe, and effective treatment of indirect inguinal hernias in women. (J Am Assoc Gynecol Laparosc 8(1):143-146, 2001)

A unique sialidase that cleaves the Neu5Gcalpha2-->5-O(glycolyl)Neu5Gc linkage: comparison of its specificity with that of three microbial sialidases toward four sialic acid dimers

We found that the hepatopancreas of oyster, Crassostrea virginica, contained a sialidase capable of releasing Neu5Gc from the novel polysialic acid chain (-->5-O(glycolyl)Neu5Gcalpha2-->)n more efficiently than from the conventional type of polysialic acid chains, (-->8Neu5Acalpha2-->)n, or (-->8Neu5Gcalpha2-->)n. We have partially purified this novel sialidase and compared its reactivity with that of microbial sialidases using four different sialic acid dimers, Neu5Gcalpha2-->5-O(glycolyl)Neu5Gc (Gg2), Neu5Acalpha2-->8Neu5Ac (A2), Neu5Gcalpha2-->8Neu5Gc (G2), and KDNalpha2-->8KDN (K2) as substrates. Hydrolysis was monitored by high performance anion-exchange chromatography with a CarboPac PA-100 column and pulsed amperometric detection, the method by which we can accurately quantitate both the substrate (sialiac acid dimers) and the product (sialic acid monomers). The oyster sialidase effectively hydrolyzed Gg2 and K2, whereas A2 and G2 were poor substrates. Neu5Ac2en but not KDN2en effectively inhibited the hydrolysis of Gg2 by the oyster sialidase. Likewise, the hydrolysis of K2 by the oyster sialidase was inhibited by a cognate inhibitor, KDN2en, but not by Neu5Ac2en. Using the new analytical method we found that Gg2 was hydrolyzed less efficiently than A2 but much more readily than G2 by Arthrobacter ureafaciens sialidase. This result was at variance with the previous report using the thiobarbituric acid method to detect the released free sialic acid [Kitazume, S., et al. (1994) Biochem. Biophys. Res. Commun. 205, 893-898]. In agreement with previous results, Gg2 was a poor substrate for Clostridium perfringens sialidase, while K2 was refractory to all microbial sialidases tested. Thus, the oyster sialidase is novel and distinct from microbial sialidases with regards to glycon- and linkage-specificity. This finding adds an example of the presence of diverse sialidases, in line with the diverse sialic acids and sialic acid linkages that exist in nature. The new sialidase should become useful for both structural and functional studies of sialoglycoconjugates.

Crystal structure of the oligomerization domain of NSP4 from rotavirus reveals a core metal-binding site

During the maturation of rotaviral particles, non-structural protein 4 (NSP4) plays a critical role in the translocation of the immature capsid into the lumen of the endoplasmic reticulum. Full-length NSP4 and a 22 amino acid peptide (NSP4(114-135)) derived from this protein have been shown to induce diarrhea in young mice in an age-dependent manner, and may therefore be the agent responsible for rotavirally-induced symptoms. We have determined the crystal structure of the oligomerization domain of NSP4 which spans residues 95 to 137 (NSP4(95-137)). NSP4(95-137) self-associates into a parallel, tetrameric coiled-coil, with the hydrophobic core interrupted by three polar layers occupying a and d-heptad positions. Side-chains from two consecutive polar layers, consisting of four Gln123 and two of the four Glu120 residues, coordinate a divalent cation. Two independent structures built from MAD-phased data indicated the presence of a strontium and calcium ion bound at this site, respectively. This metal-binding site appears to play an important role in stabilizing the homo-tetramer, which has implications for the engagement of NSP4 as an enterotoxin.

Acid-base properties of the reaction product of sialic acid with fluorogenic reagent, 1,2-diamino-4,5-methylenedioxybenzene (DMB)

N-Acetylneuraminic acid (Neu5Ac) forms the highly fluorophoric quinoxalinone derivative (Q) when treated with 1,2-diamino-4,5-methylenedioxybenzene (DMB). Effects of protonation and deprotonation on the fluorescence of Q were examined at room temperature. The strong fluorescence was found to be caused by the neutral form Q but not the protonated form of its excited state [Q]* and at pH below 1 the emission was completely quenched. The deprotonated singlet form [Q-]* was a less efficient fluorescer than [Q]*.