Dopamine precursors and brain function in phenylalanine hydroxylase deficiency

Phenylalanine and tyrosine constitute the two initial steps in the biosynthesis of dopamine, which, in its turn, is the metabolic precursor of noradrenaline and adrenaline. The extracellular phenylalanine concentration influences brain function in phenylalanine deficiency (PHD) by decreased dopamine synthesis. It has been shown to induce EEG slowing, and prolonged the performance time on neuropsychological tests. The tyrosine concentration in the CNS is reduced in PHD, possibly implying insufficient substrate (= tyrosine) for catecholamine synthesis due to competition inhibition, for instance across the blood brain barrier. In experimental studies it has been shown that the synthesis and release of dopamine can be influenced by an increase in the availability of tyrosine. In PHD an extra dietary intake of three doses of tyrosine (160mg/kg/24h) induced a shortsning of reaction time and decreased variability, and in a double-blind crossover study a similar dose has been reported to induce an improvement on psychological tests. In a study with lower doses of tyrosine (110mg/kg/24h) no effect was found on reaction time tests. These findings need to be substantiated, and more detailed information should be obtained.     

A role for Ubc9 in tumorigenesis

The post-translational modifications ubiquitination and sumoylation have been implicated in regulating many critical cellular pathways. Like ubiquitination, sumoylation is a multistep process involving maturation, activation, conjugation and deconjugation. Ubc9 is a sole E2-conjugating enzyme essential for sumoylation. We have previously shown that alterations of Ubc9 expression affect tumor drug responsiveness. However, it is not clear whether there is any link between sumoylation and tumorigenesis, even though alterations of the ubiquitination pathway can lead to the development of cancer. In this study, we found that Ubc9 expression levels were elevated in ovarian tumors compared to the matched normal ovarian specimens, suggesting that Ubc9 may play a role in tumorigenesis. To test this, we overexpressed a dominant-negative mutant of Ubc9 (Ubc9-DN) and wild-type Ubc9 (Ubc9-WT) in the MCF-7 human breast tumor cells. Inoculating these cells as xenografts in mice revealed that tumors expressing Ubc9-WT grew better than the vector control, while tumors expressing Ubc9-DN exhibited reduced growth. This pattern was also seen in these cells when grown in culture. To better understand the mechanism behind this observation, we profiled gene expressions in these cells by microarray analysis and found alterations in expression of the pro-oncogene bcl-2 in these Ubc9-DN- and Ubc9-WT-expressing cells. Consistent with the bcl-2 results, subsequent studies revealed a higher rate of apoptosis and poor survival for the MCF-7 cells expressing Ubc9-DN, which are associated with downregulation of bcl-2. Together, these results suggest a role for Ubc9 in tumorigenesis at least partially through regulation of bcl-2 expression.     

Transesophageal echocardiography-related gastrointestinal complications in cardiac surgical patients

OBJECTIVE: The aim of this audit was to determine the incidence of major gastrointestinal (GI) complications associated with intraoperative transesophageal echocardiography (TEE) in adult cardiac surgical patients in this institution. DESIGN: Retrospective database audit. SETTING: University-affiliated teaching hospital. PARTICIPANTS: Eight hundred fifty-nine consecutive cardiac surgical patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The records of all patients who developed a major upper GI complication within 30 days of cardiac surgery between January 2001 and May 2003 were examined. The patients were identified by cross-referencing cardiac surgery and endoscopy databases. A major GI complication was defined as a perforation of the esophagus or stomach or upper GI bleeding requiring transfusion, endoscopic, or surgical intervention. Early presentation was defined as <24 hours; late presentation was defined as >24 hours. During the audit period, 859 patients underwent cardiac surgery. Five hundred sixteen patients had cardiac surgery with TEE (group 1), and 343 patients had cardiac surgery without TEE (group 2). Six patients were identified, 1.2% (95% confidence interval [CI], CI, 0.5%-2.5%) in group 1 who had a major upper GI complication consistent with TEE injury. Two patients, 0.38% (95% CI, 0.05%-1.40%), presented early, and 4 patients, 0.76% (95% CI, 0.21%-1.98%), presented late. One patient in group 2 developed a major upper GI complication, 0.29% (95% CI, 0.01%-1.6%). CONCLUSION: The incidence of major GI complications attributed to TEE in this group of cardiac surgical patients was higher than previously reported. Late presentation was more common than early presentation. Previous studies that have not included late presentations may have underestimated the true incidence of major GI complications related to TEE.     

Generalised anxiety disorder in Singapore: prevalence, co-morbidity and risk factors in a multi-ethnic population

BACKGROUND: There has been a relative lack of epidemiological data on generalised anxiety disorder (GAD) in Southeast Asia. A previous study reported a lifetime prevalence of 1.5% and highlighted low preference for seeking professional help and consultation by persons suspected to be suffering from mental health problems. The present study is part of a National Mental Health survey of adults conducted from February 2003-March 2004 specifically assessing anxiety and depression in Singapore. In this paper we report on prevalence, co-morbidity and risk factors associated with GAD. METHODS: We interviewed 2,847 households from an ethnically stratified random sample of adults aged 20-59 years who were Singapore citizens or permanent residents. The General Health Questionnaire and Schedule for Clinical Assessment of Neuropsychiatry were administered, which generated Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) diagnoses of GAD. We assessed socio-demographic correlates, life events, medical and other psychiatric co-morbidities related to GAD. RESULTS: Lifetime prevalence of GAD was 3.3%, current prevalence is 3.0%. Female to male ratio is 3.6:1. GAD was significantly associated (p<0.001) with the presence of other psychiatric co-morbidities, including major depressive disorder, dysthymia, panic disorder, agoraphobia and social phobia. Prevalence increased in older individuals, with the odds of association greatest in subjects with three or more co-morbid medical conditions [adjusted odds ratio (OR) 3.66]. Those who had experienced one or more threatening life events showed increased odds of association with GAD. Chinese ethnicity, the divorced and persons from both the upper and the lowest socio-economic status had highest odds of association with GAD. CONCLUSIONS: We challenge established notions that GAD tends to be a disorder of the socially disadvantaged. Life events are important as precipitating factors in GAD, and uniquely different types of events appear to affect both extremes of social classes. High co-morbidity associations with current GAD are grounds for concern. This may suggest failure to seek treatment, hence giving rise to an increase in severity of the primary condition.     

Development of a Western blot assay for detection of antibodies against coronavirus causing severe acute respiratory syndrome

To identify a major antigenic determinant for use in the development of a rapid serological diagnostic test for severe acute respiratory syndrome (SARS) coronavirus infection and to study the immune response during SARS coronavirus infection in humans, we cloned the full length and six truncated fragments of the nucleocapsid gene, expressed them, and purified them as glutathione S-transferase-tagged recombinant proteins. The reactivities of the recombinant proteins to a panel of antibodies containing 33 SARS coronavirus-positive sera and 66 negative sera and to antibodies against other animal coronaviruses were screened. A truncated 195-amino-acid fragment from the C terminus of the nucleocapsid protein (N195) was identified that had a strong ability to detect antibodies against SARS coronavirus. No cross-reaction was found between the N195 protein and antibodies against chicken, pig, and canine coronaviruses. The N195 protein was used to develop a Western blot assay to detect antibodies against SARS coronavirus in 274 clinically blinded samples. The specificity and sensitivity of this test were 98.3 and 90.9%, respectively. The correlation between our Western blotting assay and an immunofluorescence assay (IFA) was also analyzed. The results of our Western blot assay and IFA for the detection of SARS coronavirus-positive sera were the same. Thus, the N195 protein was identified as a suitable protein to be used as an antigen in Western blot and other possible assays for the detection of SARS coronavirus infection.     

Immunological characterization of the spike protein of the severe acute respiratory syndrome coronavirus

Severe acute respiratory syndrome (SARS) is a novel infectious disease caused by the SARS-associated coronavirus (SARS-CoV). There are four major structural proteins in the SARS-CoV, including the nucleocapsid, spike, membrane, and small envelope proteins. In this study, two sets of truncated fragments of spike protein were generated, the first were approximately 210-bp nonoverlapping fragments and the second were overlapping segments of 750 to 900 bp. From these 23 fragments, we identified a fragment of 259 amino acids (amino acids 441 to 700) that is a major immunodominant epitope. This fragment was highly expressed, and the purified fragment C could detect all 33 SARS patient serum samples tested, collected from 7 to 60 days after the onset of fever, but had no reactivity with all 66 healthy human serum samples tested. Thus, fragment C of spike protein was identified as an immunodominant antigen and could be used for serological detection of SARS-CoV infection.     

MR renography using a dynamic gradient-echo sequence and low-dose gadopentetate dimeglumine as an alternative to radionuclide renography

OBJECTIVE: Our aim was to evaluate the feasibility of acquiring an MR signal intensity-time renographic curve and dynamic serial images in a way similar to that of acquiring radionuclide renograms, with a dynamic gradient-echo sequence and a low-dose gadopentetate dimeglumine technique, using a commonly available 1.5-T MR scanner. SUBJECTS AND METHODS. Patients who underwent both radionuclide and MR renographic studies within a 3-month period were included in the analysis. This yielded 21 studies from 19 patients. Nineteen of the 21 studies were available for analysis. Two studies were excluded because of technical errors during MR renographic acquisition. Serial MR renograms were obtained using a dynamic two-dimensional spoiled gradient-echo fast low-angle shot T1-weighted sequence. Low-dose IV furosemide and gadopentetate dimeglumine (0.025 mmol/kg of body weight) were administered. Intensity-time curves were obtained from the manually selected regions of interest over the renal parenchyma and whole kidney for calculation of split renal function and assessment of urinary excretion, respectively. Results were compared with those obtained with radionuclide renography. RESULTS: Good correlation (Pearson's correlation coefficient, r = 0.97, p < 0.001) was observed when the volume-corrected split renal function acquired with MR renography was compared with that obtained with radionuclide renography. There was also good agreement in the excretory curve patterns (weighted kappa(observer 1) = 0.77 and kappa(observer 2) = 0.81) between the two techniques. CONCLUSION: Dynamic MR gradient-echo imaging with a low-dose gadopentetate dimeglumine technique can produce an intensity-time curve and serial dynamic images of the urinary system, in a way similar to that of radionuclide renography. This technique allows assessment of split renal function and urinary excretory status and is a feasible alternative to radionuclide renography.