Persistent left sided superior vena cava.
Explore the source record for details and available documents.
Cardiac Catheterization↗
Biomedical subjects
J L Tan
Publications and source records attributed to J L Tan.
Cartilage injury and repair: assessment with magnetic resonance imaging.
Articular cartilage damage plays a major role in joint degeneration and dysfunction. Accurate assessment of the morphology and degree of cartilage wear is important in diagnosis, prognosis and management, particularly as many of these patients are young or participate in high-performance sports. Magnetic resonance imaging is able to directly evaluate such injuries, due to its high spatial resolution and excellent soft-tissue contrast resolution. This pictoral essay aims to demonstrate normal and damaged articular cartilage on MR imaging, as well as surgically-repaired cartilage.
Cartilage Diseases↗
Intrinsic histological abnormalities of aortic root and ascending aorta in tetralogy of Fallot: evidence of causative mechanism for aortic dilatation and aortopathy.
BACKGROUND: Dilatation of the aortic root is a known feature in tetralogy of Fallot (TOF) patients with pulmonary stenosis (PS) or pulmonary atresia (PA). We hypothesized that intrinsic histological abnormalities of the aortic wall present since infancy are an important causative factor leading to aortic root dilatation. METHODS AND RESULTS: We examined the aortic histology of 17 cases with TOF and PS/PA from our cardiac morphology archive and compared them with a control group of normal aortas. Measured circumference of the aortic root at the sinotubular junction and at the ascending aorta was indexed to the left ventricle. Aortic walls were studied by light microscopy with the use of various stains. Seventeen TOF cases (7 with PS, 10 with PA) including 7 infants, 2 children, and 8 adults were compared with 11 hearts with normal aorta. Aortic root circumference to left ventricular index and ascending aortic circumference to left ventricular index were 1.24+/-0.25 and 1.37+/-0.24, respectively, in the TOF group versus 0.89+/-0.10 and 0.88+/-0.11, respectively, in the control group (P<0.001). Histological changes of grade 2 or 3 were present in 29% (medionecrosis), 82% (fibrosis), 35% (cystic medial necrosis), and 59% (elastic fragmentation) in the ascending aorta of the TOF group. Histology grading scores were significantly higher in the TOF group (median score, 7; range, 1 to 12) compared with normal controls (median score, 2; range, 0 to 6) and correlated with the ascending aortic circumference to left ventricular index (r=0.525, P=0.03). CONCLUSIONS: There are marked histological abnormalities in the aortic root and ascending aortic wall of patients with TOF present from infancy, suggesting a causative mechanism for subsequent aortic root dilatation.
Adult↗
Septic arthritis after arthroscopic anterior cruciate ligament reconstruction.
INTRODUCTION: A retrospective review of postoperative infected anterior cruciate ligament (ACL) reconstruction was done on 472 consecutive cases in one institution. The purpose was to assess the incidence, diagnosis, treatment and outcome factors. MATERIALS AND METHODS: Out of 472 arthroscopic-assisted ACL reconstructions performed between 1999 and 2002, 7 (1%) postoperative deep intra-articular infections were detected. Seven males with a mean age of 23 years (range, 19 to 30 years) formed the study group; 3 had undergone prior knee surgery. RESULTS: Four patients had acute infection (<2 weeks), 3 had subacute infection (2 weeks to 2 months) and none had late infection (>2 months). All were admitted within 24 hours of onset of symptoms and underwent immediate arthroscopic lavage, incision and drainage of abscess, debridement with graft retention and intravenous (8 to 31 days) followed by oral (4 to 6 weeks) antibiotics. Staphylococcus aureus was present in 4 patients, Peptostreptococcus in 3, Klebsiella in 1, and Enterobacter in 1. The patients underwent an average of 1.4 arthroscopic procedures (range, 1 to 3 procedures), with an average hospital stay of 17.3 days per patient. All were evaluated at an average of 11.7 months (range, 5 to 26 months). In all cases, the infection resolved with stable knees and with all grafts and implants retained. Although rare, early diagnosis and prompt treatment of infection can result in successful eradication without sacrificing the graft.
Adult↗
Rising trend of anterior cruciate ligament injuries in females in a regional hospital.
INTRODUCTION: We see a rising trend in the number of anterior cruciate ligament (ACL) injuries in females over the past 4 years (1999 to 2002). This article seeks to identify and examine the rising trend in the number of ACL injuries in females in our institution over this period. MATERIALS AND METHODS: Two hundred and fifty-nine patients with ACL reconstructions were identified and their casenotes were retrieved from the medical records office. Of these, 13 were females. RESULTS: The number of ACL reconstructions has increased from 9 cases to 144 cases a year from 1999 to 2002. Over this period, 13 female cases (3 in 2001 and 10 in 2002) with an age range of 13 to 38 years were performed in our institution. Their injuries were mainly sustained from a bad landing or during pivoting on 1 leg. There were 8 patients (61.5 %) with prior conditioning and experience and 5 without (38.5 %). The mean number of years of prior training was 4.4 years. Of these 8, 4 were netball players. All were competitive players either at the school or club level and they were all playing as goal attackers. CONCLUSION: Linear regression analysis shows a significant increase in the number of ACL reconstructions performed for females in our institution over this time period. Netball was a common sport in our series. This suggests a likely relationship between netball and ACL injuries. All the patients were playing as goal attackers. The area of court covered and frequency of jump-stop and sudden deceleration activities could be a cause.
Adolescent↗
Immediate and mid-term safety and efficacy of single lead VDD pacemakers for patients with atrioventricular block and normal sinus node function--a single centre experience.
INTRODUCTION: Single lead atrial synchronous ventricular pacing (VDD) is increasingly being used in place of conventional dual chamber pacing (DDD) for patients with atrioventricular block and preserved sinus node function. Compared to the latter, VDD pacemakers provide similar haemodynamic benefits derived from atrial synchronous pacing, with the added benefit of an easier implant procedure. OBJECTIVE: To review the use, safety and efficacy of VDD pacing in a single tertiary referral centre. MATERIALS AND METHODS: A review of all patients with atrioventricular block and normal sinus node function implanted with a VDD pacemaker over a 2-year period at a local tertiary cardiac referral centre. Data on complications, atrial sensing performance and maintenance of atrioventricular synchrony during implant and at subsequent follow-up visits were obtained from a prospectively maintained registry and analysed. RESULTS: Forty-one patients (17 males, 24 females) with a mean age of 72 +/- 9 years received VDD pacing for various forms of high-grade atrioventricular block. The average implantation time was 46.8 +/- 17.1 minutes, and a pneumothorax in 1 patient was the only complication. Electrical measurements at implantation and subsequent follow-up visits revealed an initial rapid decrease in atrial signal amplitude (mean atrial P wave at implant 3.1 +/- 1.1 mV, predischarge 1.9 +/- 1.3 mV) which began to stabilise after 3 months, reaching a mean atrial P wave value of 1.3 +/- 0.3 mV at 24 months. The atrial sensing performance (percentage of atrial synchronous ventricular complexes) was 97% over a mean follow-up period of 9.9 months. Four patients (10%) developed paroxysmal atrial tachyarrhythmias. Sinus node dysfunction was not observed in any of our patients during the follow-up period. CONCLUSION: In patients with atrioventricular block and preserved sinus node function, single lead VDD pacing is safe and effective in maintaining a physiological atrial synchronous pacing mode.
Adult↗
Atrial flutter with 1:1 conduction.
Explore the source record for details and available documents.
Atrial Flutter↗
The lax shoulder in females. Issues, answers, but many more questions.
A review of the existing data on shoulder laxity in females reveals there are insufficient data to confirm the commonly held belief that shoulders in females are more lax than shoulders in males. Laxity is not synonymous with instability. Although females may have increased generalized joint laxity relative to males, generalized joint laxity does not correlate with shoulder laxity. There is conflicting data regarding shoulder laxity and gender. A review of patients with multidirectional instability who were treated operatively showed that 55% of the patients were female (N = 94) and 45% were male (N = 77), but the number or gender of patients who were treated nonoperatively was not reported. Multidirectional instability is reviewed in the context of the lax shoulder in the female. Initial treatment should be nonoperative, emphasizing physical therapy and dynamic stabilization of the shoulder. If nonoperative treatment fails, open or arthroscopic inferior capsular shift stabilization is recommended. Additional basic science and clinical trials are needed to determine whether thermal capsulorrhaphy should be considered in the treatment of patients with multidirectional instability of the shoulder.
Athletic Injuries↗
MLCK-A, an unconventional myosin light chain kinase from Dictyostelium, is activated by a cGMP-dependent pathway.
Dictyostelium myosin II is activated by phosphorylation of its regulatory light chain by myosin light chain kinase A (MLCK-A), an unconventional MLCK that is not regulated by Ca2+/calmodulin. MLCK-A is activated by autophosphorylation of threonine-289 outside of the catalytic domain and by phosphorylation of threonine-166 in the activation loop by an unidentified kinase, but the signals controlling these phosphorylations are unknown. Treatment of cells with Con A results in quantitative phosphorylation of the regulatory light chain by MLCK-A, providing an opportunity to study MLCK-A's activation mechanism. MLCK-A does not alter its cellular location upon treatment of cells with Con A, nor does it localize to the myosin-rich caps that form after treatment. However, MLCK-A activity rapidly increases 2- to 13-fold when Dictyostelium cells are exposed to Con A. This activation can occur in the absence of MLCK-A autophosphorylation. cGMP is a promising candidate for an intracellular messenger mediating Con A-triggered MLCK-A activation, as addition of cGMP to fresh Dictyostelium lysates increases MLCK-A activity 3- to 12-fold. The specific activity of MLCK-A in cGMP-treated lysates is 210-fold higher than that of recombinant MLCK-A, which is fully autophosphorylated, but lacks threonine-166 phosphorylation. Purified MLCK-A is not directly activated by cGMP, indicating that additional cellular factors, perhaps a kinase that phosphorylates threonine-166, are involved.
Actomyosin↗
Anthropometry of anterior cruciate ligament in Singaporean Chinese.
Accurate reproduction of the anatomy of the anterior cruciate ligament during reconstructive surgery is paramount for obtaining good functional results. Graft size and length are important components of the reconstruction and the references we have used are Western figures. We feel that these Western figures do not apply to our local population. We performed an anthropometric study to test the hypothesis that the anterior cruciate ligament in the Singaporean Chinese is smaller than that quoted in Western literature. The study revealed that the anterior cruciate ligament in Singaporean Chinese is shorter and narrower. More importantly, the anterior cruciate ligament orientation in our study population is more vertical. This suggests that placement of the femoral tunnel in anterior cruciate ligament reconstruction has to be in a more vertical position to reproduce the physiometry of the anterior cruciate ligament.
Aged↗
The relationship between presurgical hyoid bone position and 1-year postsurgical change in mandibular position following mandibular advancement surgery.
The presurgical hyoid bone position and its relationship to changes in the position of the mandible 1 year following mandibular advancement surgery was studied. Thirty-eight adult patients with mandibular deficiency underwent surgical correction with a bilateral sagittal split ramus osteotomy procedure and rigid fixation. Lateral cephalometric radiographs taken presurgically, 1 week postsurgically, and approximately 1 year postsurgically were hand traced and digitized. Horizontal and vertical measurements, made from the landmarks hyoidale and pogonion to a vertical reference line perpendicular to sellanasion line + 7 degrees and passing through basion point, were used to determine the position of the hyoid bone and the mandible, respectively. The presurgical hyoid bone position and the amount of postsurgical change in position of the mandible were compared using the Pearson's correlation coefficient (r). Results of this study indicate that no statistically significant correlation exists between the presurgical hyoid bone position and the degree of mandibular change 1 year following mandibular advancement surgery (P < .05).
Adolescent↗
Control of nonmuscle myosins by phosphorylation.
Explore the source record for details and available documents.
Acanthamoeba↗
Surgical treatment of metastatic long bone disease.
A retrospective study of the results of operative treatment of 60 long bones secondaries in 46 patients was carried out. The mean period of follow-up was 10 months. The most common primary in this study was carcinoma of the breast (28.2%), followed by carcinoma of the lung (21.7%) and unknown primary (10.9%). Three groups of patients were studied--pathological fracture group, prophylactic fixation group and a mixed group. In the pathological fracture group, 70% of patients achieved good to excellent pain relief and 60.9% was able to walk with or without walking aids. In the prophylactic group, all the patients achieved good to excellent pain relief and 60% were able to ambulate with or without walking aids. In the mixed group, all the patients achieved good to excellent pain relief and 66.6% of the patients were able to walk with aids. The operative mortality in both the pathological fracture group and prophylactic fixation group was 10% and 33.3% in the mixed group. Multiple internal fixation performed at one operative session was associated with high operative mortality (50%).
Adult↗
Characterization and bacterial expression of the Dictyostelium myosin light chain kinase cDNA. Identification of an autoinhibitory domain.
A full-length cDNA corresponding to the Dictyostelium myosin light chain kinase gene has been isolated and characterized. Sequence analysis of the cDNA confirms conserved protein kinase subdomains and reveals that the Dictyostelium sequence is highly homologous to those of calcium/calmodulin-dependent protein kinases, including myosin light chain kinases from higher eukaryotes. Despite the high homologies to calcium/calmodulin-dependent protein kinases, there is no recognizable calmodulin-binding domain within the Dictyostelium sequence. However, the Dictyostelium myosin light chain kinase possesses a putative auto-inhibitory domain near its carboxyl terminus. To further characterize this domain, the full-length enzyme as well as a truncated form lacking this domain were expressed in bacterial cells and purified. The full-length enzyme expressed in bacteria exhibits essentially the same biochemical characteristics as the enzyme isolated from Dictyostelium. The truncated form however exhibits a Vmax that is approximately ten times greater than that of the native enzyme. In addition, unlike the native kinase and the full-length kinase expressed in bacteria, the truncated enzyme does not undergo autophosphorylation. These results suggest that the Dictyostelium enzyme, like myosin light chain kinases from higher eukaryotes, is regulated by an autoinhibitory domain but that the specific molecular signals necessary for activation of the Dictyostelium enzyme are entirely distinct.
Amino Acid Sequence↗
Dictyostelium myosin light chain kinase. Purification and characterization.
A Dictyostelium myosin light chain kinase has been purified approximately 15,000-fold to near homogeneity. The purified kinase is a single polypeptide of approximately 34 kDa that phosphorylates only the 18-kDa Dictyostelium myosin regulatory light chain and itself among substrates tested. The enzyme was purified largely by ammonium sulfate fractionation and hydrophobic (butyl) interaction chromatography. Analysis using polyclonal antibodies raised against the purified 34-kDa protein confirms that this protein is responsible for myosin light chain kinase activity. Protein microsequence of the 34-kDa protein reveals conserved protein kinase sequences. The purified Dictyostelium myosin light chain kinase exhibits a Km for Dictyostelium myosin of 4 microM and a Vmax of 8 nmol/min/mg. Unlike other characterized myosin light chain kinases, this enzyme is not regulated by calcium/calmodulin. Western blot analysis demonstrates that the purified kinase is not a proteolytic fragment that has lost calcium/calmodulin regulation. The Dictyostelium myosin light chain kinase activity is not directly regulated by cyclic nucleotides. However, this kinase undergoes an intramolecular autophosphorylation that activates the enzyme.
Amino Acid Sequence↗
Developmentally regulated protein-tyrosine kinase genes in Dictyostelium discoideum.
Dictyostelium discoideum, an organism that undergoes development and that is amenable to biochemical and molecular genetic approaches, is an attractive model organism with which to study the role of tyrosine phosphorylation in cell-cell communication. We report the presence of protein-tyrosine kinase genes in D. discoideum. Screening of a Dictyostelium cDNA expression library with an anti-phosphotyrosine antibody identifies fusion proteins that exhibit protein-tyrosine kinase activity. Two distinct cDNAs were identified and isolated. Though highly homologous to protein kinases in general, these kinases do not exhibit many of the hallmarks of protein-tyrosine kinases of higher eucaryotes. In addition, these genes are developmentally regulated, which suggests a role for tyrosine phosphorylation in controlling Dictyostelium development.
Amino Acid Sequence↗
Prevalence of respiratory illnesses of school children in the industrial, urban and rural areas of Singapore.
An epidemiological survey of 3216 primary school children living in the industrial, urban and rural areas of Singapore revealed a high prevalence of various respiratory symptoms and illnesses, with 13.1% cough, 8.2% wheezy chest, 25.9% blocked/running nose, 4.3% sinusitis, 7.8% asthmatic attacks and 4.1% bronchitis/pneumonia. Differences in the prevalence of respiratory illnesses and lung function tests were observed among children in the three areas, but this could not be accounted for by the varying air pollution levels which have been maintained below the long-term standards set up by WHO. It was probably responsible for the differences noted.
Adolescent↗
A common source foodborne outbreak of cholera in Singapore.
An epidemiological investigation of an outbreak of Vibrio cholerae 01, biotype El Tor, serotype Ogawa, phage type 1, confined to a group of foreign construction workers in Singapore is described. A total of 22 workers were confirmed to have cholera and another 15 had asymptomatic Vibrio cholerae 01 infection between 3 November and 11 November 1982. The source of infection was traced to contaminated seafood prepared at the construction site canteen where two food handlers were found to be infected with V. cholerae 01 (one symptomatic and the other asymptomatic). The incubation period of cholera in this outbreak ranged from 4 to 203 hours with a median of 38 hours. Only two workers had moderate to severe dehydration and required intravenous therapy. Early recognition of the outbreak and prompt implementation of control measures prevented the outbreak from spreading to other parts of Singapore.
Adolescent↗