Prognostic Implication of Right Ventricular Free Wall Longitudinal Strain and Right Atrial Pressure Estimated By Echocardiography in Patients With Severe Functional Tricuspid Regurgitation

BACKGROUND

The interaction between right ventricular (RV) function and pulmonary hypertension is crucial for prognosis of patients with severe functional tricuspid regurgitation. RV free wall longitudinal strain (RVFWLS) has been reported to detect RV systolic dysfunction earlier than other conventional parameters. Although pulmonary artery systolic pressure measured by Doppler echocardiography is often underestimated in severe functional tricuspid regurgitation, right atrial pressure (RAP) estimated by echocardiography may be viewed as a prognostic factor. Impact of RAP and RVFWLS on outcome in patients with severe functional tricuspid regurgitation remains unclear. The aim of the present study was to investigate prognostic implication of RAP, RVFWLS, and their combination in this population.

METHODS AND RESULTS

We retrospectively examined 377 patients with severe functional tricuspid regurgitation. RAP, pulmonary artery systolic pressure, RV fractional area change, and RVFWLS were analyzed. RAP of 15 mm Hg was classified as elevated RAP. All-cause death at 2-year follow-up was defined as the primary end point. RVFWLS provided better prognostic information than RV fractional area change by receiver operating characteristic curve analysis. In the multivariable Cox regression analysis, elevated RAP and RVFWLS of ≤18% were independent predictors of clinical outcome. Patients with RVFWLS of ≤18% had higher risk of all-cause death than those without by Kaplan-Meier curve analysis. Furthermore, when patients were stratified into 4 groups by RAP and RVFWLS, the group with elevated RAP and RVFWLS of ≤18% had the worst outcome.

CONCLUSIONS

Elevated RAP and RVFWLS of ≤18% were independent predictors of all-cause death. The combination of elevated RAP and RVFWLS effectively stratified the all-cause death.

Long-Term Impact of Small Mitral Valve Orifice Area after Transcatheter Edge-to-Edge Mitral Valve Repair on Clinical Outcome: A Three-Dimensional Echocardiography Study

BACKGROUND

Iatrogenic mitral stenosis is a complication associated with transcatheter edge-to-edge mitral valve repair. Some reports revealed the impact of mean transmitral pressure gradient after procedure on long-term clinical outcomes. However, the association between prognosis and mitral valve orifice area (MVA) after the procedure has been poorly studied. This study aimed to investigate the association between postprocedural small MVA, derived from three-dimensional (3D) transesophageal echocardiography (TEE), and long-term clinical outcomes in 2 cohorts: the degenerative mitral regurgitation (MR) cohort and the functional MR cohort.

METHODS

This retrospective study assessed 279 consecutive patients with 3D TEE data during transcatheter edge-to-edge mitral valve repair between January 2010 and December 2016. Mitral valve orifice area after device implantation was measured by 3D planimetry. The patients with degenerative and functional MR were stratified separately into 2 groups according to postprocedural MVA: normal MVA (MVA > 1.5 cm2) group and small MVA (MVA ≤ 1.5 cm2) group.

RESULTS

Of the 279 patients, 142 (51%) had degenerative MR and 137 (49%) had functional MR. The number of degenerative MR patients with small MVA was 38, whereas 42 patients were in the functional MR cohort. Patients with small MVA had higher rate of all-cause mortality in the degenerative MR group (log-rank test: P = .01) but not in the functional MR group (log-rank test: P = .52). In multivariate analysis small MVA was independently associated with all-cause mortality but not postprocedural transmitral pressure gradient. Neither small MVA nor transmitral pressure gradient was associated with all-cause mortality in patients with functional MR.

CONCLUSION

Small MVA measured by 3D TEE after transcatheter mitral edge-to-edge repair was associated with poor prognosis in patients with degenerative MR.

Impact of stroke volume assessment by three-dimensional transesophageal echocardiography on the classification of low-gradient aortic stenosis

BACKGROUND

Accurate assessment of flow status is crucial in low-gradient aortic stenosis (AS). However, the clinical implication of three-dimensional transesophageal echocardiography (3DTEE) on flow status evaluation remains unclear. This study aimed to investigate the assessment of flow status using 3D TEE in low-gradient AS patients.

METHODS

We retrospectively reviewed patients diagnosed with low-gradient AS and preserved ejection fraction at our institution between 2019 and 2022. Patients were categorized into low-flow/low-gradient (LF-LG) AS or normal-flow/low-gradient (NF-LG) AS based on two-dimensional transthoracic echocardiography (2DTTE). We compared the left ventricular outflow tract (LVOT) geometry between the two groups and reclassified them using stroke volume index (SVi) obtained by 3DTEE.

RESULTS

Among 173 patients (105 with LF-LG AS and 68 with NF-LG AS), 54 propensity-matched pairs of patients were analyzed. 3DTEE-derived ellipticity index of LVOT was significantly higher in LF-LG AS patients compared to NF-LG AS patients (p = 0.012). We assessed the discordance in flow status classification between SVi2DTTE and SVi3DTEE in both groups using a cutoff value of 35 ml/m2. The LF-LG AS group exhibited a significantly higher discordance rate compared to the NF-LG AS group, with rates of 50% and 2%, respectively. The optimal cutoff values of SVi3DTEE for identifying low flow status, based on 2DTTE-derived cutoff values, were determined to be 43 ml/m2.

CONCLUSIONS

LVOT ellipticity in low-gradient AS patients varies depending on flow status, and this difference contributes to discrepancies between SVi3DTEE and SVi2DTTE, particularly in LF-LG AS patients. Utilizing SVi3DTEE is valuable for accurately assessing flow status.

Echocardiographic Characteristics of Left and Right Ventricular Longitudinal Function in Patients With a History of Cardiac Surgery

Previous studies have indicated a reduction in right ventricular (RV) longitudinal motion after cardiac surgery. However, the long-term effect of cardiac surgery on longitudinal motion and the involvement of left ventricular (LV) motion remains unclear. Therefore, this study aimed to comprehensively investigate the longitudinal function of the right ventricle and left ventricle in patients who underwent cardiac surgery. The study included patients who underwent comprehensive transthoracic echocardiography with 3-dimensional RV data sets. By propensity score matching of the clinical and echocardiographic variables, including LV and RV ejection fraction, the echocardiographic parameters were compared between patients with and without a history of cardiac surgery (the surgery and nonsurgery groups, respectively). In this study, the surgery group had significantly lower LV global longitudinal strain values than the nonsurgery group, despite having similar LV ejection fraction. The tricuspid annular plane systolic excursion (TAPSE), tricuspid annular velocity, and RV free wall longitudinal strain were also significantly smaller in the surgery group, whereas the RV ejection fraction was comparable between the 2 groups. In addition, a subgroup analysis based on the time from previous surgery to transthoracic echocardiography (≤1 and >1 year) revealed that TAPSE was reduced in both postoperative phases. In conclusion, LV and RV longitudinal parameters were reduced after cardiac surgery, despite preserved LV and RV global functions. Moreover, TAPSE was reduced even after a long time after cardiac surgery. These findings emphasize the need for careful interpretation of biventricular longitudinal motion in patients with a history of cardiac surgery.

Comparison of prognostic value among echocardiographic surrogates of right ventricular-pulmonary arterial coupling: A three-dimensional echocardiographic study

OBJECTIVES

Right ventricular (RV)-pulmonary arterial (PA) coupling is important in various cardiac diseases. Recently, several echocardiographic surrogates for RV-PA coupling have been proposed and reported to be useful in predicting outcomes. However, it remains unclear which surrogate is the most clinically relevant. This study aimed to comprehensively compare the prognostic value of different echocardiographic RV-PA coupling surrogates.

METHODS

We retrospectively reviewed 242 patients with various cardiac conditions who underwent comprehensive transthoracic echocardiography with three-dimensional RV data. In addition to conventional parameters including tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), and PA systolic pressure (PASP), we analyzed RV free wall and global longitudinal strain (FWLS and GLS). We also obtained RV ejection fraction (RVEF), stroke volume (SV), and end-systolic volume (ESV) using three-dimensional RV analysis. RV-PA coupling surrogates were calculated as TAPSE/PASP, FAC/PASP, FWLS/PASP, GLS/PASP, RVEF/PASP, and SV/ESV. The study endpoint was a composite outcome of all-cause death or cardiovascular hospitalization within 1 year.

RESULTS

In multivariable analysis, all the RV-PA coupling surrogates were independent predictors of the outcome. Among the surrogates, the model with TAPSE/PASP showed the lowest prognostic value in model fit and discrimination ability, whereas the model with RVEF/PASP exhibited the highest prognostic value. The partial likelihood ratio test indicated that the model with RVEF/PASP was significantly better than the model with TAPSE/PASP (p < .024).

CONCLUSION

All the RV-PA coupling surrogates were independent predictors of the outcome. Notably, RVEF/PASP had the highest prognostic value among the surrogates.

Impact of eccentric jet on outcomes in patients with atrial functional mitral regurgitation: An echocardiographic study

BACKGROUND

Previous studies have reported the mechanisms underlying atrial functional mitral regurgitation (A-FMR). Recently, A-FMR subtypes based on mitral regurgitation (MR) mechanisms were proposed: "central jet" due to insufficient leaflet remodeling and "eccentric jet" due to atriogenic tethering. However, their prognostic value remains unclear. Therefore, this study investigated the impact of A-FMR subtypes on clinical outcomes.

METHODS

Outpatients with significant A-FMR between January 2013 and December 2016 were retrospectively reviewed. They were classified into two subtypes according to the MR jet's direction. All-cause mortality, heart failure hospitalization, and any mitral valve interventions were the primary composite endpoint.

RESULTS

Among 101 patients with significant A-FMR, 32% had eccentric jet. The primary endpoint was observed in 56 patients during the follow-up period (median 0.7 years, range 0.1-4.2 years). Kaplan-Meier curves demonstrated that the composite endpoint was higher among patients with eccentric jet than those with central jet (log-rank p < 0.001). Eccentric jet (hazard ratio [HR] 2.46, 95% confidence interval [CI] 1.28-4.73; p = 0.007), age (HR 1.06, 95% CI 1.02-1.11; p = 0.002), symptoms (HR 6.22, 95% CI 2.18-17.8; p < 0.001), severe MR (HR 3.97, 95% CI 1.92-8.18; p < 0.001), and significant tricuspid regurgitation (TR; HR 2.00, 95% CI 1.01-3.97; p = 0.047) were independent predictors of the composite endpoint.

CONCLUSIONS

Patients with eccentric jet had poorer outcomes than those with central jet. Eccentric jet, age, symptoms, severe MR, and significant TR were independently associated with poor outcomes.

Implication of Right Atrial Pressure Estimated by Echocardiography in Patients with Severe Tricuspid Regurgitation

BACKGROUND

Little is known about how tightly right atrial pressure (RAP) is associated with prognosis in patients with severe tricuspid regurgitation (TR). The aim of this study was to investigate the association of RAP estimated by echocardiography (RAP-echo) with cardiovascular events in patients with severe TR.

METHODS

Two hundred forty outpatients (median age, 75 years; 130 women) who underwent two-dimensional transthoracic echocardiography and were diagnosed with severe TR were retrospectively studied. According to RAP-echo using the diameter of the inferior vena cava and its response to a sniff, patients were classified into two groups: low or middle and high RAP-echo. Cardiovascular events were defined as cardiovascular death and admission for heart failure.

RESULTS

During follow-up (median, 428 days; range, 87-1,229 days), 64 patients experienced cardiovascular events. By multivariate analysis, high RAP-echo was independently associated with cardiovascular events (hazard ratio, 2.46; 95% CI, 1.17-5.18). Also, jugular venous distention and leg edema were not independently associated with cardiovascular events.

CONCLUSIONS

The significant and stronger association of RAP-echo with clinical outcome compared with estimates of RAP on physical examination suggests that recognition of high RAP-echo can be a valuable surrogate for the clinical management of severe TR patients.

Effect of right ventricular free wall longitudinal strain on all-cause death in patients with isolated severe tricuspid regurgitation and atrial fibrillation

Background

With the aging population and advanced catheter-based therapy, isolated tricuspid regurgitation (TR) with atrial fibrillation (AF) has gained increased attention; however, data on the prognostic effect of isolated TR with AF are limited because of the small number of patients among those with severe TR. Recently, right ventricular (RV) longitudinal strain by two-dimensional speckle-tracking echocardiography has been reported as an excellent indicator of RV dysfunction in severe TR. However, the prognostic implications of RV longitudinal strain in isolated severe TR associated with AF remain unclear. Therefore, this study aimed to reveal the prognostic value of this index in this population.

Methods

We retrospectively studied patients with severe isolated TR associated with AF in the absence of other etiologies in the Cedars-Sinai Medical Center between April 2015 and March 2018. Baseline clinical and echocardiographic data were studied including RV systolic function evaluated by RV free wall longitudinal strain (FWLS) and conventional parameters. All-cause death was defined as the primary endpoint.

Results

In total, 53 patients (median age, 85 years; female, 60%) with a median follow-up of 433 (60-1567) days were included. Fourteen patients (26%) died, and 66% had right heart failure (RHF) symptoms. By multivariable analysis, reduced RVFWLS was independently associated with all-cause death. Patients with RVFWLS of ≤18% had higher risk of all-cause death adjusted for age (log-rank P = 0.030, adjusted hazard ratio 4.00, 95% confidence interval, 1.11-14.4; P = 0.034). When patients were stratified into four groups by RHF symptoms and RVFWLS, the group with symptomatic and reduced RVFWLS had the worst outcome.

Conclusion

Reduced RVFWLS was independently associated with all-cause death in patients with isolated severe TR and AF. Our subset classification showed the worst outcome from the combination of RHF symptoms and reduced RVFWLS.

Outcome of Patients With Both Moderate Aortic Stenosis and Moderate Mitral Stenosis

Aims

This study aimed to investigate the symptoms and prognosis of patients with both moderate aortic stenosis (AS) and mitral stenosis (MS).

Methods and Results

We studied 82 patients with moderate AS and MS diagnosed via transthoracic echocardiography. The patients had a mean age of 79 ± 13 years and 95% of patients had degenerative MS. Out of 82 patients, 34 (41%) had heart failure (HF) symptoms (New York Heart Association class ≥ Ⅱ) or a history of HF admission. Left ventricular ejection fraction, stroke volume index, atrial fibrillation, and right ventricular systolic pressure were independent determinants of HF symptoms. The median follow-up duration was 3.2 (interquartile range, 1.0-4.9) years and clinical events occurred in 48 (59%) patients, including death in 11 (13%) patients, aortic or mitral valve interventions in 22 (27%) patients, and HF hospitalization in 15 (18%) patients. The 5-year survival free of the combined endpoint of aortic or mitral valve interventions, HF hospitalization, or death was 19%. A multivariate predictor of clinical events was HF symptoms (hazard ratio [HR], 2.32; 95% confidence interval [CI], 1.30-4.14; p = 0.0045). Kaplan-Meier survival at 5 years was 61% without intervention and HF symptoms were not associated with mortality.

Conclusions

Among patients with both moderate AS and MS, left ventricular ejection fraction, stroke volume index, atrial fibrillation, and right ventricular systolic pressure were strong determinants of HF symptoms. HF symptoms were independently predictive of clinical events.

Synergistic cytoprotection by co-treatment with dexamethasone and rapamycin against proinflammatory cytokine-induced alveolar epithelial cell injury

Background

One of the main pathophysiological manifestations during the acute phase of sepsis is massive production of proinflammatory mediators. Clinical trials involving direct suppression of inflammatory mediators to relieve organ dysfunction in sepsis have been extensively performed; however, the clinical outcomes of such trials remain far from satisfactory. Given the need for better sepsis treatments, we have screened various agents with anti-inflammatory properties for cytoprotective effects. In this study, we identified dexamethasone and rapamycin as clinically applicable candidates with favorable synergistic effects against inflammatory cytokine-induced cytotoxicity in vitro and further explored the molecular mechanisms underlying the augmented cytoprotective effects exerted by co-treatment with both drugs.

Methods

Human alveolar epithelial cell-derived A549 cells were stimulated with a mixture of inflammatory cytokines, TNF-alpha, IL-1beta, and IFN-gamma, which induce cellular injury, including apoptosis. This in vitro model was designed to simulate acute lung injury (ALI) associated with sepsis. The cells were co-treated with dexamethasone and rapamycin under cytokine stimulation. Conditioned medium and cell lysates were subjected to further analysis.

Results

Either dexamethasone or rapamycin significantly attenuated cytokine-induced cytotoxicity in A549 cells in a dose-dependent manner. In addition, the simultaneous administration of dexamethasone and rapamycin had a synergistic cytoprotective effect. The applied doses of dexamethasone (10 nM) and rapamycin (1 nM) were considerably below the reported plasma concentrations of each drug in clinical setting. Interestingly, distinct augmentation of both of c-Jun inhibition and Akt activation were observed when the cells were co-treated with both drugs under cytokine stimulation.

Conclusions

A synergistic protective effect of dexamethasone and rapamycin was observed against cytokine-induced cytotoxicity in A549 cells. Augmentation of both of c-Jun inhibition and Akt activation were likely responsible for the cytoprotective effect. The combined administration of anti-inflammatory drugs such as dexamethasone and rapamycin offers a promising treatment option for alveolar epithelial injury associated with sepsis.

Lysophosphatidic acid is associated with neuropathic pain intensity in humans: An exploratory study

The underlying mechanisms of neuropathic pain remain to be elucidated. Basic animal research has suggested that lysophosphatidic acids, which are bioactive lipids produced by autotaxin from lysophosphatidylcholine, may play key roles in the initiation and maintenance of neuropathic pain. Here, we investigated the clinical relevance of lysophosphatidic acids signaling on neuropathic pain in humans. Eighteen patients who had been diagnosed with neuropathic pain with varied etiologies participated in the study. Cerebrospinal fluid samples were obtained by lumbar puncture and the concentrations of 12 species of lysophosphatidic acids and lysophosphatidylcholine, autotaxin, and the phosphorylated neurofilament heavy subunit were measured. Pain symptoms were assessed using an 11-point numeric rating scale and the Neuropathic Pain Symptom Inventory regarding intensity and descriptive dimensions of neuropathic pain. The total lysophosphatidic acids were significantly associated with both pain intensity and symptoms. 18:1 and 20:4 lysophosphatidic acids in particular demonstrated the most correlations with dimensions of pain symptoms. Autotaxin and the phosphorylated neurofilament heavy subunit showed no association with pain symptoms. In conclusions, lysophosphatidic acids were significantly associated with pain symptoms in neuropathic pain patients. These results suggest that lysophosphatidic acids signaling might be a potential therapeutic target for neuropathic pain.

Phenotypic and Molecular Characterization of Antimicrobial Resistance in Klebsiella spp. Isolates from Companion Animals in Japan: Clonal Dissemination of Multidrug-Resistant Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae

The emergence of antimicrobial resistance in Klebsiella spp., including resistance to extended-spectrum cephalosporins (ESC) and fluoroquinolones, is of great concern in both human and veterinary medicine. In this study, we investigated the prevalence of antimicrobial resistance in a total of 103 Klebsiella spp. isolates, consisting of Klebsiella pneumoniae complex (KP, n = 89) and K. oxytoca (KO, n = 14) from clinical specimens of dogs and cats in Japan. Furthermore, we characterized the resistance mechanisms, including extended-spectrum β-lactamase (ESBL), plasmid-mediated AmpC β-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and assessed genetic relatedness of ESC-resistant Klebsiella spp. strains by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility testing demonstrated that resistance rates to ampicillin, cephalothin, enrofloxacin, ciprofloxacin, trimethoprim/sulfamethoxazole, cefotaxime, gentamicin, tetracycline, chloramphenicol, amoxicillin-clavulanic acid, and cefmetazole were 98.1, 37.9, 37.9, 35.9, 35.0, 34.0, 31.1, 30.1, 28.2, 14.6, and 6.8%, respectively. Phenotypic testing detected ESBLs and/or AmpC β-lactamases in 31 of 89 (34.8%) KP isolates, but not in KO isolates. Resistances to 5 of the 12 antimicrobials tested, as well as the three PMQRs [qnrB, qnrS, and aac(6′)-Ib-cr], were detected significantly more frequently in ESBL-producing KP, than in non-ESBL-producing KP and KO. The most frequent ESBL was CTX-M-15 (n = 13), followed by CTX-M-14 (n = 7), CTX-M-55 (n = 6), SHV-2 (n = 5), CTX-M-2 (n = 2), and CTX-M-3 (n = 2). Based on the rpoB phylogeny, all ESBL-producing strains were identified as K. pneumoniae, except for one CTX-M-14-producing strain, which was identified as K. quasipneumoniae. All of AmpC β-lactamase positive isolates (n = 6) harbored DHA-1, one of the PABLs. Based on MLST and PFGE analysis, ST15 KP clones producing CTX-M-2, CTX-M-15, CTX-M-55, and/or SHV-2, as well as KP clones of ST1844-CTX-M-55, ST655-CTX-M-14, and ST307-CTX-M-15, were detected in one or several hospitals. Surprisingly, specific clones were detected in different patients at an interval of many months. These results suggest that multidrug-resistant ESBL-producing KP were clonally disseminated among companion animals via not only direct but also indirect transmission. This is the first report on large-scale monitoring of antimicrobial-resistant Klebsiella spp. isolates from companion animals in Japan.

Phenotypic and molecular characterization of antimicrobial resistance in Proteus mirabilis isolates from dogs

Large-scale monitoring of resistance to 14 antimicrobial agents was performed using 103 Proteus mirabilis strains isolated from dogs in Japan. Resistant strains were analysed to identify their resistance mechanisms. Rates of resistance to chloramphenicol, streptomycin, enrofloxacin, trimethoprim/sulfamethoxazole, kanamycin, ampicillin, ciprofloxacin, cephalothin, gentamicin, cefoxitin and cefotaxime were 20.4, 15.5, 12.6, 10.7, 9.7, 8.7, 5.8, 2.9, 2.9, 1.9 and 1.9%, respectively. No resistance to ceftazidime, aztreonam or imipenem was found. Class 1 and 2 integrases were detected in 2.9 and 11.7% of isolates, respectively. Class 1 integrons contained aadB or aadB-catB-like-blaOXA10-aadA1, whereas those of class 2 contained sat-aadA1, dhfr1-sat-aadA1 or none of the anticipated resistance genes. Of five distinct plasmid-mediated quinolone-resistance (PMQR) genes, only qnrD gene was detected in 1.9% of isolates. Quinolone-resistance determining regions (QRDRs) of gyrA and parC from 13 enrofloxacin-intermediate and -resistant isolates were sequenced. Seven strains had double mutations and three had single mutations. Three of nine ampicillin-resistant isolates harboured AmpC-type β-lactamases (i.e. blaCMY-2, blaCMY-4 and blaDHA-1). These results suggest that canine Proteus mirabilis deserves continued surveillance as an important reservoir of antimicrobial resistance determinants. This is the first report, to our knowledge, describing integrons, PMQRs and QRDR mutations in Proteus mirabilis isolates from companion animals.

Anesthetic management of pregnant women with stroke

Stroke during pregnancy is rare, but after occurring, most patients develop serious neurological conditions. Hemorrhagic stroke, including intracerebral hemorrhage and subarachnoid hemorrhage, often requires emergency surgical intervention. In addition to significant maternal physiological changes, the potential for fetal harm should be considered during anesthetic management of these patients. Whether cesarean section or neurosurgical intervention should be prioritized or performed simultaneously in pregnant women with stroke is an important issue. Whether the patients receive general or spinal and epidural anesthesia is another clinically significant issue. Finally neurosurgeons, anesthesiologists, and obstetricians should cooperate to manage pregnant women with stroke.

[Intraoperative body temperature changes and short-term outcomes of open and minimally invasive esophagectomy]

BACKGROUND

Esophagectomy is a highly invasive procedure, and recently the use of minimally invasive esophagectomy (MIE) via thoracoscopy and laparoscopy increased, since this technique possibly enhances the recovery and outcomes of the patient compared with open esophagectomy (OE). However there is little data about intraoperative changes in body temperature during OE and MIE.

METHODS

We retrospectively investigated the intraoperative body temperature and the postoperative short-term outcomes of patients undergoing OE (n = 33) or MIE (n = 24). The rectal temperature was recorded at 5 time points (at the start of the surgery, 1, 3, and 5 h after the start of the surgery, and at the end of the surgery).

RESULTS

The average body temperature at the start was similar between the OE and MIE groups (36.5 +/- 0.4 vs. 36.6 +/- 0.5 degrees C, P = 0.497). Throughout the surgery, the temperature of the OE group increased to 37.1 +/- 0.6 degrees C, but the temperature in the MIE group decreased to 36.1 +/- 0.8 degrees C. There was no significant difference in 30-day mortality and short-term complications between the two groups.

CONCLUSIONS

Our study showed that the intraoperative temperature during MIE tended to decrease compared with OE, but the short-term outcomes were comparable.

Deep hypothermic circulatory arrest for hemiarch replacement in a pediatric patient with moyamoya disease

Moyamoya disease is a chronic cerebrovascular occlusive disease, occurring predominantly in young populations, that causes cerebral ischemia and hemorrhage. Patients with moyamoya disease are at high risk of neurological complications during cardiac surgery because of perioperative hemodynamic changes. However, there is no established evidence on temperature management during cardiopulmonary bypass. Previous reports described normothermia or mild to moderate hypothermia during cardiopulmonary bypass in patients with moyamoya disease; however, surgical conditions, such as not having enough space to clamp the aorta or a clean surgical field, sometimes force us to use deep hypothermic circuratory arrest. We report a successful case of a pediatric patient with moyamoya disease who underwent deep hypothermic circulatory arrest (18 °C) for hemiarch replacement without neurological complications. Deep hypothermia may be an alternative technique for achieving cerebral protection in the context of moyamoya disease.

Chaperonin-affected folding of globular proteins

We studied the effect of GroEL on the kinetic refolding ofα-lactalbumin by stopped-flow fluorescence techniques. We usedwild-type GroEL and its ATPase-defficient mutant D398A, and studied thebinding constants between GroEL and the molten globule foldingintermediate at various concentrations of ADP and ATP. The results arecompared with titration of GroEL with the nucleotides, ADP, ATP-analogs(ATP-γS and AMP-PNP) and ATP, which have shown that bothADP and the ATP analogs are bound to GroEL in a non-cooperativemanner but that ATP shows a cooperative effect. Similarly, the bindingconstant between GroEL and the folding intermediate decreased in acooperative manner with an increase in ATP concentration although itshowed non-cooperative decrease with respect to ADP concentration. Itis shown that the allosteric control of GroEL by the nucleotides isresponsible for the above behavior of GroEL and that the observeddifference between the ATP- and ADP-induced transitions of GroEL isbrought about by a small difference in an allosteric parameter (the ratio ofthe nucleotide affinities of GroEL in the high-affinity and the low-affinitystates), i.e., 4.1 for ATP and 2.6 for ADP.

[Bladder temperature versus tympanic temperature in patients undergoing abdominal aortic aneurysm surgery]

BACKGROUND

Inaccurate measurements of body temperature might be associated with complications during the perioperative period. We conducted a retrospective cohort study to compare the bladder temperature and the tympanic membrane temperature in patients undergoing open repair of abdominal aortic aneurysm.

METHODS

Fifteen adult patients who had undergone general anesthesia with/without epidural anesthesia were included in the present cohort. The bladder and the tympanic temperatures were simultaneously recorded at 6 points during surgery. One-way repeated measures ANOVA and Bland-Altman analysis were performed to assess statistical significance. The two-tailed P values less than 0.05 were considered statistically significant.

RESULTS

No difference was found between the bladder and the tympanic temperatures before abdominal aortic cross-clamping. However, during and after cross-clamping, the bladder temperature values were likely to be lower compared with the tympanic values. The average temperature difference (+/- 2 SD) was 0.4 degrees C (+/- 1.1 degrees C) (95% CI: -1.21-0.78).

CONCLUSIONS

The tympanic membrane might be a reliable site for core body temperature measurement in abdominal aortic aneurysm surgery patients.

[Intraoperative coronary spasm during caesarean section under spinal anesthesia]

A 37-year-old woman without history of ischemic heart disease or any coronary risk factors was scheduled for caesarean section. Under spinal anesthesia, the patient's blood pressure (BP) decreased to 93/72 mmHg. Although 6 mg of ephedrine was administered intravenously, BP continued to decrease to 75/40 mmHg and she complained of nausea. In addition to additional ephedrine (12 mg), phenylephrine (0.1 mg) and atropine (0.5 mg) were administered. BP increased to 170/100 mmHg, but electrocardiogram (ECG) showed ST elevation in I and aV(L), ST depression in II, III, aV(F), and frequent premature ventricular beats, and the patient complained of chest discomfort. Coronary dilators and lidocaine promptly reversed the ST elevation, premature ventricular beats and discomfort. The operation was started promptly and was uneventful. Although BP decreased again to 75/45 mmHg at the beginning of the operation, we did not use vasopressors to avoid the relapse of myocardial ischemia. The anesthetic course was uneventful thereafter. This cardiac event seemed to be derived from coronary spasm caused by acute sympathetic stimulation. The observations in this case suggest that the possibility of intraoperative coronary spasm should be considered even in a healthy patient.

Contribution of Thr29 to the thermodynamic stability of goat alpha-lactalbumin as determined by experimental and theoretical approaches

The Thr29 residue in the hydrophobic core of goat alpha-lactalbumin (alpha-LA) was substituted with Val (Thr29Val) and Ile (Thr29Ile) to investigate the contribution of Thr29 to the thermodynamic stability of the protein. We carried out protein stability measurements, X-ray crystallographic analyses, and free energy calculations based on molecular dynamics simulation. The equilibrium unfolding transitions induced by guanidine hydrochloride demonstrated that the Thr29Val and Thr29Ile mutants were, respectively, 1.9 and 3.2 kcal/mol more stable than the wild-type protein (WT). The overall structures of the mutants were almost identical to that of WT, in spite of the disruption of the hydrogen bonding between the side-chain O-H group of Thr29 and the main-chain C=O group of Glu25. To analyze the stabilization mechanism of the mutants, we performed free energy calculations. The calculated free energy differences were in good agreement with the experimental values. The stabilization of the mutants was mainly caused by solvation loss in the denatured state. Furthermore, the O-H group of Thr29 favorably interacts with the C=O group of Glu25 to form hydrogen bonds and, simultaneously, unfavorably interacts electrostatically with the main-chain C=O group of Thr29. The difference in the free energy profile of the unfolding path between WT and the Thr29Ile mutant is discussed in light of our experimental and theoretical results.

Nucleotide-induced transition of GroEL from the high-affinity to the low-affinity state for a target protein: effects of ATP and ADP on the GroEL-affected refolding of alpha-lactalbumin

We studied the refolding kinetics of alpha-lactalbumin in the presence of wild-type GroEL and its ATPase-deficient mutant D398A at various concentrations of nucleotides (ATP and ADP). We evaluated the apparent binding constant between GroEL and the alpha-lactalbumin refolding intermediate quantitatively by numerical simulation analysis of the alpha-lactalbumin refolding curves in the presence and absence of GroEL. The binding constant showed a co-operative decrease with an increase in ATP concentration, whereas the binding constant decreased in a non-co-operative manner with respect to ADP concentration. For the D398A mutant, the ATP-induced decrease in affinity occurred much faster than the steady-state ATP hydrolysis by this mutant, suggesting that ATP binding to GroEL rather than ATP hydrolysis, was responsible for the co-operative decrease in the affinity for the target protein. We thus analyzed the nucleotide-concentration dependence of affinity of GroEL for the target protein using an allosteric Monod-Wyman-Changeux model in which GroEL underwent an ATP-induced co-operative conformational transition between the high-affinity and low-affinity states of the target protein. The transition midpoint of the ATP-induced transition of GroEL has been found to be around 30 microM, in good agreement with the midpoint evaluated in other structural studies of GroEL. The results show that the observed difference between ATP and ADP-induced transitions of GroEL are brought about by a small difference in an allosteric parameter (the ratio of the nucleotide affinities of GroEL in the high-affinity and the low-affinity states), i.e. 4.1 for ATP and 2.6 for ADP.

Nucleotide binding to the chaperonin GroEL: non-cooperative binding of ATP analogs and ADP, and cooperative effect of ATP

Chaperonin-assisted protein folding proceeds through cycles of ATP binding and hydrolysis by GroEL, which undergoes a large structural change by the ATP binding or hydrolysis. One of the main concerns of GroEL is the mechanism of the productive and cooperative structural change of GroEL induced by the nucleotide. We studied the cooperative nature of GroEL by nucleotide titration using isothermal titration calorimetry and fluorescence spectroscopy. Our results indicated that the binding of ADP and ATP analogs to a single ring mutant (SR1), as well as that to GroEL, was non-cooperative. Only ATP induces an apparently cooperative conformational change in both proteins. Furthermore, the fluorescence changes of pyrene-labeled GroEL indicated that GroEL has two kinds of nucleotide binding sites. The fluorescence titration result fits well with a model in which two kinds of binding sites are both non-cooperative and independent of each other. These results suggest that the binding and hydrolysis of ATP may be necessary for the cooperative transition of GroEL.

Folding-unfolding of goat alpha-lactalbumin studied by stopped-flow circular dichroism and molecular dynamics simulations

Folding reaction of goat alpha-lactalbumin has been studied by stopped-flow circular dichroism and molecular dynamics simulations. The effects of four single mutations and a double mutation on the stability of the protein under a native condition were studied. The mutations were introduced into residues located at a hydrophobic core in the alpha-domain of the molecule. Here we show that an amino acid substitution (T29I) increases the native-state stability of goat alpha-lactalbumin against the guanidine hydrochloride-induced unfolding by 3.5 kcal/mol. Kinetic refolding and unfolding of wild-type and mutant goat alpha-lactalbumin measured by stopped-flow circular dichroism showed that the local structure around the Thr29 side chain was not constructed in the transition state of the folding reaction. To characterize the local structural change around the Thr29 side chain to an atomic level of resolution, we performed high-temperature (at 400 K and 600 K) molecular dynamics simulations and studied the structural change at an initial stage of unfolding observed in the simulation trajectories. The Thr29 portion of the molecule experienced structural disruption accompanied with the loss of inter-residue contacts and with the water molecule penetration in the 400-K simulation as well as in four of the six 600-K simulations. Disruption of the N-terminal portion was also observed and was consistent with the results of kinetic refolding/unfolding experiments shown in our previous report.

[A case of bilateral coronal craniosynostosis with the P250R mutation in FGFR3 gene]

Recently, the substitution of proline 250 by arginine in the fibroblast growth factor receptor 3 (FGFR3) gene, has been identified in patients with craniosynostosis and defines a new syndrome on a molecular basis. We report a 1-year-1-month-old female with bilateral coronal craniosynostosis who had the P250R mutation in FGFR3 gene detected by DNA sequencing. She had brachycephaly, temporal bossing, high and flat forehead, hypertelorism, mild proptosis, low set ears and no digital abnormalities. She underwent surgical repair at 7 months and her cosmetic problems were improved. Her development was normal up to 13 months of age. DNA analysis from her parents showed that her father had the same mutation. The phenotypes of the P250R mutation in the FGFR3 syndrome are variable even within the same family, but main characteristic clinical features are follows, 1) lateral or bilateral coronal craniosynostosis, 2) mild hand and foot anomalies, and 3) sensory deafness. In FGFR3 syndrome the diagnosis of P250R mutation by polymerase chain reaction (PCR) is very easy and important for early diagnosis and genetic counseling.

Equilibrium and kinetic studies on folding of the authentic and recombinant forms of human alpha-lactalbumin by circular dichroism spectroscopy

The equilibrium and kinetics of the unfolding and refolding of authentic and recombinant human alpha-lactalbumin, the latter of which had an extra methionine residue at the N-terminus, were studied by circular dichroism spectroscopy, and the results were compared with the results for bovine and goat alpha-lactalbumins obtained in our previous studies. As observed in the bovine and goat proteins, the presence of the extra methionine residue in the recombinant protein remarkably destabilized the native state, and the destabilization was entirely ascribed to an increase in the rate of unfolding. The thermodynamic stability of the native state against the unfolded state was lower, and the thermodynamic stability of the molten globule state against the unfolded state was higher for the human protein than for the other alpha-lactalbumins previously studied. Thus, the population of the molten globule intermediate was higher during the equilibrium unfolding of human alpha-lactalbumin by guanidine hydrochloride. Unlike the molten globule states of the bovine and goat proteins, the human alpha-lactalbumin molten globule showed remarkably more intense circular dichroism ellipticity than the native state in the far-ultraviolet region below 225 nm. During refolding from the unfolded state, human alpha-lactalbumin thus exhibited overshoot kinetics, in which the alpha-helical peptide ellipticity exceeded the native value when the molten globule folding intermediate was formed in the burst phase. The subsequent folding involved reorganization of nonnative secondary structures. It should be noted that the rate constant of the major refolding phase was approximately the same among the three types of alpha-lactalbumin and that the rate constant of unfolding was accelerated 18-600 times in the human protein, and these results interpreted the lower thermodynamic stability of this protein.

Folding of green fluorescent protein and the cycle3 mutant

Although the correct folding of green fluorescent protein (GFP) is required for formation of the chromophore, it is known that wild-type GFP cannot mature efficiently in vivo in Escherichia coli at 37 degrees C or higher temperatures that the jellyfish in the Pacific Northwest have never experienced. Recently, by random mutagenesis by the polymerase chain reaction (PCR) method, a mutant called Cycle3 was constructed. This mutant had three mutations, F99S, M153T, and V163A, on or near the surface of the GFP molecule and was able to mature correctly even at 37 degrees C [Crameri et al. (1996) Nat. Biotechnol. 143, 315-319]. In the present study, we investigated the differences in their folding behavior in vitro. We observed the folding and unfolding reactions of both wild-type GFP and the Cycle3 mutant by using green fluorescence as an indicator of the formation of the native structure and examining hydrogen-exchange reactions by Fourier transform infrared spectroscopy. Both proteins showed unusually slow refolding and unfolding rates, and their refolding rates were almost identical under the native state at 25 and at 35 degrees C. On the other hand, aggregation studies in vitro showed that wild-type GFP had a strong tendency to aggregate, while the Cycle3 mutant did not. These results indicated that the ability to mature efficiently in vivo at 37 degrees C was not due to the improved folding and that reduced hydrophobicity on the surface of the Cycle3 mutant was a more critical factor for efficient maturation in vivo.

Hydrogen exchange study of canine milk lysozyme: stabilization mechanism of the molten globule

The native state (1)H, (15)N resonance assignment of 123 of the 128 nonproline residues of canine milk lysozyme has enabled measurements of the amide hydrogen exchange of over 70 amide hydrogens in the molten globule state. To elucidate the mechanism of protein folding, the molten globule state has been studied as a model of the folding intermediate state. Lysozyme and alpha-lactalbumin are homologous to each other, but their equilibrium unfolding mechanisms differ. Generally, the folding mechanism of lysozyme obeys a two-state model, whereas that of alpha-lactalbumin follows a three-state model. Exceptions to this rule are equine and canine milk lysozymes, which exhibit a partially unfolded state during the equilibrium unfolding; this state resembles the molten globule state of alpha-lactalbumin but with extreme stability. Study of the molten globules of alpha-lactalbumin and equine milk lysozyme showed that the stabilities of their alpha-helices are similar, despite the differences in the thermodynamic stability of their molten globule states. On the other hand, our hydrogen exchange study of the molten globule of canine milk lysozyme showed that the alpha-helices are more stabilized than in alpha-lactalbumin or equine milk lysozyme and that this enhanced stability is caused by the strengthened cooperative interaction between secondary structure elements. Thus, our results underscore the importance of the cooperative interaction in the stability of the molten globule state.

Limitations of urinary telomerase activity measurement in urothelial cancer

The reported frequency of detectable telomerase activity in spontaneously voided urine samples from patients with urothelial cancer varied from 0 to 85%. We examined stasis in the bladder and specimen storage as interfering conditions in this assay. Telomerase activity in exfoliated cells was measured by a polymerase-chain-reaction-based assay in spontaneously voided urine from urothelial cancer patients. Effects of retention in the bladder and specimen storage from voiding to measurement of telomerase activity were modeled by suspending 10(6) cells from the cancer-derived T24 line in normal urine (pH 6.5) at 37 degrees C and 25 degrees C, respectively. Hematuria was modeled by adding hemoglobin. In T24 cells suspended in urine at 37 degrees C, telomerase activity had decreased to approximately 20% of preincubation activity after 1 h, and had disappeared after 3 h. In urine at 25 degrees C, telomerase activity in T24 cells had decreased to approximately 40% of preincubation activity at 1 h and to <10% at 6 h. When we examined telomerase activity in exfoliated cells in spontaneously voided urine from urothelial cancer patients (excluding first-voided morning specimens), telomerase activity was detected in only 21% of samples (four of 19) despite measurement with 1 h of voiding and steps to avoid hemoglobin interference. Measurement of telomerase activity in spontaneously voided urine is insufficiently sensitive and reliable for the diagnosis of urothelial cancer.

Fast folding of Escherichia coli cyclophilin A: a hypothesis of a unique hydrophobic core with a phenylalanine cluster

Escherichia coli cyclophilin A, a 164 residue globular protein, shows fast and slow phases of refolding kinetics from the urea-induced unfolded state at pH 7.0. Given that the slow phases are independent of the denaturant concentration and may be rate-limited by cis/trans isomerizations of prolyl peptide bonds, the fast phase represents the true folding reaction. The extrapolation of the fast-phase rate constant to 0 M urea indicates that the folding reaction of cyclophilin A is extraordinarily fast and has about 700 s(-1) of the rate constant. Interrupted refolding experiments showed that the protein molecules formed in the fast phase had already been fully folded to the native state. This finding overthrows the accepted view that the fast folding is observed only in small proteins of fewer than 100 amino acid residues. Examination of the X-ray structure of cyclophilin A has shown that this protein has only one unique hydrophobic core (phenylalanine cluster) formed by evolutionarily conserved phenylalanine residues, and suggests that this architecture of the molecule may be responsible for the fast folding behavior.

Structure and thermodynamics of the extraordinarily stable molten globule state of canine milk lysozyme

Here, we show that an unfolded intermediate of canine milk lysozyme is extraordinarily stable compared with that of the other members of the lysozyme-alpha-lactalbumin superfamily, which has been studied previously. The stability of the intermediate of this protein was investigated using calorimetry, CD spectroscopy, and NMR spectroscopy, and the results were interpreted in terms of the structure revealed by X-ray crystallography at a resolution of 1.85 A to an R-factor of 17.8%. On the basis of the results of the thermal unfolding, this protein unfolds in two clear cooperative stages, and the melting temperature from the intermediate to the unfolded states is about 20 degrees C higher than that of equine milk lysozyme. Furthermore, the (1)H NMR spectra of canine milk lysozyme at 60 degrees C, essentially 100% of which exists in the intermediate, showed that small resonance peaks that arise from ring-current shifts of aliphatic protons are still present in the upfield region from 0 to -1 ppm. The protein at this temperature (60 degrees C) and pH 4.5 has been found to bind 1-anilino-naphthalene-8-sulfonate (ANS) with enhancement of the fluorescence intensity compared with that of native and thermally unfolded states. We interpret that the extraordinarily stable intermediate is a molten globule state, and the extraordinary stabilization of the molten globule state comes from stronger protection around the C- and D-helix of the aromatic cluster region due to the His-21 residue. The conclusion helps to explain how the molten globule state acquires its structure and stability.

Effect of an alternative disulfide bond on the structure, stability, and folding of human lysozyme

Human lysozyme has four disulfide bonds, one of which, Cys65-Cys81, is included in a long loop of the beta-domain. A cysteine-scanning mutagenesis in which the position of Cys65 was shifted within a continuous segment from positions 61 to 67, with fixed Cys81, has previously shown that only the mutant W64CC65A, which has a nonnative Cys64-Cys81 disulfide, can be correctly folded and secreted by yeast. Here, using the W64CC65A mutant, we investigated the effects of an alternative disulfide bond on the structure, stability, and folding of human lysozyme using circular dichroism (CD) and fluorescence spectroscopy combined with a stopped-flow technique. Although the mutant is expected to have a different main-chain structure from that of the wild-type protein around the loop region, far- and near-UV CD spectra show that the native state of the mutant has tightly packed side chains and secondary structure similar to that of the wild-type. Guanidine hydrochloride-induced equilibrium unfolding transition of the mutant is reversible, showing high stability and cooperativity of folding. In the kinetic folding reaction, both proteins accumulate a similar burst-phase intermediate having pronounced secondary structure within the dead time of the measurement and fold into the native structure by means of a similar folding mechanism. Both the kinetic refolding and unfolding reactions of the mutant protein are faster than those of the wild-type, but the increase in the unfolding rate is larger than that of the refolding rate. The Gibbs' free-energy diagrams obtained from the kinetic analysis suggest that the structure around the loop region in the beta-domain of human lysozyme is formed after the transition state of folding, and thus, the effect of the alternative disulfide bond on the structure, stability, and folding of human lysozyme appears mainly in the native state.

Is folding of beta-lactoglobulin non-hierarchic? Intermediate with native-like beta-sheet and non-native alpha-helix

The refolding of beta-lactoglobulin, a beta-barrel protein consisting of beta strands betaA-betaI and one major helix, is unusual because non-native alpha-helices are formed at the beginning of the process. We studied the refolding kinetics of bovine beta-lactoglobulin A at pH 3 using the stopped-flow circular dichroism and manual H/(2)H exchange pulse labeling coupled with heteronuclear NMR. The protection pattern from the H/(2)H exchange of the native state indicated the presence of a stable hydrophobic core consisting of betaF, betaG and betaH strands. The protection pattern of the kinetic intermediate obtained about one second after initiating the reaction was compared with that of the native state. In this relatively late kinetic intermediate, which still contains some non-native helical structure, the disulfide-bonded beta-hairpin made up of betaG and betaH strands was formed, but the rest of the molecule was fluctuating, where the non-native alpha-helices may reside. Subsequently, the core beta-sheet extends, accompanied by a further alpha-helix to beta-sheet transition. Thus, the refolding of beta-lactoglobulin exhibits two elements: the critical role of the core beta-sheet is consistent with the hierarchic mechanism, whereas the alpha-helix to beta-sheet transition suggests the non-hierarchic mechanism.

Hydrophilic residues at the apical domain of GroEL contribute to GroES binding but attenuate polypeptide binding

The GroES binding site at the apical domain of GroEL, mostly consisting of hydrophobic residues, overlaps largely with the substrate polypeptide binding site. Essential contribution of hydrophobic interaction to the binding of both GroES and polypeptide was exemplified by the mutant GroEL(L237Q) which lost the ability to bind either of them. The binding site, however, contains three hydrophilic residues, E238, T261, and N265. For GroES binding, N265 is essential since GroEL(N265A) is unable to bind GroES. E238 contributes to rapid GroES binding to GroEL because GroEL(E238A) is extremely sluggish in GroES binding. Polypeptide binding was not impaired by any mutations of E238A, T261A, and N265A. Rather, these mutants, especially GroEL(N265A), showed stronger polypeptide binding affinity than wild-type GroEL. Thus, these hydrophilic residues have a dual role; they help GroES binding on one hand but attenuate polypeptide binding on the other hand.

Chaperonin-affected refolding of alpha-lactalbumin: effects of nucleotides and the co-chaperonin GroES

We have studied how nucleotides (ADP, AMP-PNP, and ATP) and the co-chaperonin GroES influence the GroEL-affected refolding of apo-alpha-lactalbumin. The refolding reactions induced by stopped-flow pH jumps were monitored by alpha-lactalbumin tryptophan fluorescence. The simple single-exponential character of the free-refolding kinetics of the protein allowed us to quantitatively analyze the kinetic traces of the GroEL-affected refolding with the aid of computer simulations, and to obtain the best-fit parameters for binding between GroEL and the refolding intermediate of alpha-lactalbumin by the non-linear least-squares method. When GroES was absent, the interaction between GroEL and alpha-lactalbumin could be well represented by a "cooperative-binding" model in which GroEL has two binding sites for alpha-lactalbumin with the affinity of the second site being tenfold weaker than that of the first, so that there is negative cooperativity between the two sites. The affinity between GroEL and alpha-lactalbumin was significantly reduced when ATP was present, while ADP and AMP-PNP did not alter the affinity. A comparison of this result with those reported previously for other target proteins suggests a remarkable adjustability of the GroEL 14-mer with respect to the nucleotide-induced reduction of affinity. When GroES was present, ATP as well as ADP and AMP-PNP were effective in reducing the affinity between GroEL and the refolding intermediate of alpha-lactalbumin. The affinity at a saturating concentration of ADP or AMP-PNP was about ten times lower than with GroEL alone. The ADP concentration at which the acceleration of the GroEL/ES-affected refolding of alphaLA was observed, was higher than the concentration at which the nucleotide-induced formation of the GroEL/ES complex took place. These results indicate that GroEL/ES complex formation itself is not enough to reduce the affinity for alpha-lactalbumin, and that further binding of the nucleotide to the GroEL/ES complex is required to reduce the affinity.

An AciI polymorphism in the 3' untranslated region of the human phosphomannomutase 2 (PMM2) gene

We found an AciI polymorphism in the 3' untranslated region of the phosphomannomutase 2 (PMM2) gene located at 16p13. A G-to-C transition at nucleotide position 96 bp downstream from the PMM2 stop codon was detected in polymerase chain reaction (PCR) products after AciI digestion. The heterozygosity of the polymorphic alleles was 0.375 in a Japanese population. This polymorphism is useful for genetic analysis in patients with carbohydrate-deficient glycoprotein syndromes, of which there are four subtypes.

Missense mutations in the phosphomannomutase 2 gene of two Japanese siblings with carbohydrate-deficient glycoprotein syndrome type I

Carbohydrate-deficient glycoprotein syndrome type I (CDG1) is an autosomal recessive disorder characterized by severe nervous system involvement and a carbohydrate moiety deficiency in N-linked glycoproteins. Clinical symptoms are psychomotor retardation, stroke-like episodes or hemorrhagic episodes, hepatic dysfunction, polyneuropathy, and cerebellar ataxia. Marked atrophy of the cerebellar hemispheres and pons is recognizable on CT scan or MRI. CDGI has been mapped to human chromosome 16p by linkage studies. Recently, missense mutations in the gene for phosphomannomutase (PMM2) have been detected in Caucasian patients with CDG1. We studied DNA mutations in PMM2 in a Japanese family with CDG1. DNA sequencing of PMM2 in the siblings showed missense mutations of maternal origin in exon 5 and of paternal origin in exon 8. No such mutations were detected in 50 unrelated healthy Japanese. These findings suggest that the PMM2 is responsible for CDG1 in the Japanese as well as in Caucasians, and CDG1 may be the diagnosis in OPCA of neonatal onset, more often than currently thought.

Thermodynamics of nucleotide binding to the chaperonin GroEL studied by isothermal titration calorimetry: evidence for noncooperative nucleotide binding

We characterized the thermodynamics of binding reactions of nucleotides ADP and ATPgammaS (a nonhydrolyzable analog of ATP) to GroEL in a temperature range of 5 degrees C to 35 degrees C by isothermal titration calorimetry. Analysis with a noncooperative binding model has shown that the bindings of nucleotides are driven enthalpically with binding constants of 7x103 M-1 and 4x104 M-1 for ADP and ATPgammaS, respectively, at 26 degrees C and that the heat capacity change DeltaCp is about 100 cal/mol.K for both the nucleotides. The stoichiometries of binding were about 8 and 9 molecules for ADP and ATPgammaS, respectively, per GroEL tetradecamer at 5 degrees C, and both increased with temperature to reach about 14 (ADP) and 12 (ATPgammaS) for both nucleotides at 35 degrees C. The absence of initial increase of binding heat as well as Hill coefficient less than 1.2, which were obtained from the fitting to the model curve by assuming positive cooperativity, showed that there was virtually no positive cooperativity in the nucleotide bindings. Incorporating a difference in affinity for the nucleotide (ADP and ATPgammaS) between the two rings of GroEL into the noncooperative binding model improved the goodness of fitting and the difference in the affinity increased with decreasing temperature.

Expression of a synthetic gene encoding canine milk lysozyme in Escherichia coli and characterization of the expressed protein

A high-expression plasmid of the canine milk lysozyme, which belongs to the family of calcium-binding lysozymes, was constructed in order to study its physico-chemical properties. Because the cDNA sequence of the protein has not yet been determined, a 400 base-pair gene encoding canine milk lysozyme was first designed on the basis of the known amino acid sequence. The gene was constructed by an enzymatic assembly of 21 chemically synthesized oligonucleotides and inserted into an Escherichia coli expression vector by stepwise ligation. The expression plasmid thus constructed was transformed into BL21(DE3)/pLysS cells. The gene product accumulated as inclusion bodies in an insoluble fraction. Recombinant canine milk lysozyme was obtained by purification and refolding of the product and showed the same characteristics in terms of bacteriolytic activity and far- and near-UV circular dichroism spectra as the authentic protein. The NMR spectra of refolded lysozyme were also characteristic of a native globular protein. It was concluded that recombinant canine milk lysozyme was folded into the correct native structure. Moreover, the thermal unfolding profiles of the refolded recombinant lysozyme showed a stable equilibrium intermediate, indicating that the molten globule state of this protein was extraordinarily stable. This expression system of canine milk lysozyme will enable biophysical and structural studies of this protein to be extended.

Folding-unfolding equilibrium and kinetics of equine beta-lactoglobulin: equivalence between the equilibrium molten globule state and a burst-phase folding intermediate

The denaturant-induced equilibrium unfolding transition of equine beta-lactoglobulin was investigated by ultraviolet absorption, fluorescence, and circular dichroism (CD) spectra. An equilibrium intermediate populates at moderate denaturant concentrations, and its CD spectrum is similar to that of the molten globule state previously observed for this protein at acid pH [Ikeguchi, M., Kato, S., Shimizu, A., and Sugai, S. (1997) Proteins: Struct., Funct., Genet. 27, 567-575]. The unfolding and refolding kinetics were also investigated by the stopped-flow CD and fluorescence. A significant change in the CD intensity was observed within the dead time of measurements (25 ms) when the refolding reaction was initiated by diluting the urea-unfolded protein solution, indicating the transient accumulation of the folding intermediate. The CD spectrum of this burst-phase intermediate agrees well with that of the molten globule state at acid pH. The stability of the burst-phase intermediate was also estimated from the urea-concentration dependence of the burst-phase amplitude, and it shows a fair agreement with that of the equilibrium intermediate. These results indicate that the molten globule state of equine beta-lactoglobulin populates at moderate urea concentration as well as at acid pH and it is equivalent with the kinetic folding intermediate.