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Biomedical subjects

M Chan

Publications and source records attributed to M Chan.

At least 55 records · Page 3Linked to original sources
PubMed1999

Percutaneous embolization to control intractable epistaxis in nasopharyngeal carcinoma.

BACKGROUND: Epistaxis in patients with nasopharyngeal carcinoma (NPC) who have received radiotherapy can be difficult to control by conventional methods. The use of angiography and embolization to control problematic epistaxis has been well documented in other situations, but its use in severe or recurrent epistaxis following irradiation for NPC has not been described. METHODS: We retrospectively reviewed case notes of all patients with NPC initially seen with epistaxis over a 4-year period. Those patients with refractory epistaxis which could not be controlled by conventional methods and required angiography and embolization were assessed. RESULTS: Eight patients who underwent angiography were identified. Five patients showed hypervascularization and three patients had pseudoaneurysms or an aneurysm of the internal carotid artery seen on the angiogram. All these patients were successfully embolized. There were no significant complications after the procedure. CONCLUSION: We conclude that embolization is a safe and effective method of controlling refractory epistaxis in patients irradiated for NPC.

Adult↗
PubMed1999

Selective use of ultrasonography for acute appendicitis in children.

BACKGROUND: To evaluate the role of ultrasonography in children with equivocal signs of acute appendicitis, and correlate with initial clinical impression and pathological findings. METHODS: This is a prospective evaluation of all children presenting with a possible diagnosis of appendicitis during a 14-month study period. Patients with unequivocal clinical signs of appendicitis underwent appendectomy without ultrasonography. Patients with equivocal signs had documentation of the clinical impression and subsequent abdominal ultrasound. Statistical analysis of results was performed using the chi-square test (P <0.05 significant). RESULTS: Two hundred fifteen consecutive children were enrolled. Signs were unequivocal in 116 and equivocal in 99. Seven patients in the first group had a normal appendix at operation. Of the 99 patients with equivocal signs, there were 28 true positives, 3 false positives, 64 true negatives, and 4 false negatives. In equivocal cases, sensitivity of the initial clinical impression versus ultrasound was 50% and 88%, respectively (P <0.05). Specificity was 85% and 96%, respectively. The positive and negative predictive values improved from 63% to 90% and 78% to 94%, respectively, with the use of ultrasonography. CONCLUSIONS: The low false positive rate (6%) in clinically obvious cases of appendicitis does not, in our opinion, warrant ultrasonography. In clinically equivocal cases, ultrasonography is a fast, sensitive, and specific diagnostic modality to diagnose or rule out appendicitis, avoiding the need for prolonged observation and/or hospitalization.

Acute Disease↗
PubMed1999

A randomized trial comparing day and residential drug abuse treatment: 18-month outcomes.

Extending an earlier report of 6-month outcomes, this study reports 12- and 18-month follow-up data for clients (N = 188) entering a therapeutic community drug treatment program who were randomly assigned to day or residential treatment conditions. Outcomes included Addiction Severity Index composite scores and measures of depression, psychiatric symptoms, and social support. Both groups showed significant change over time. The pattern of change indicated decreased problem severity in the 1st 6 months and then maintenance of lowered problem severity. Comparisons between groups indicated greater improvement for residential treatment clients on social problems and psychiatric symptoms but no differences on the remaining outcomes. Although residential treatment may offer some specific advantages, the conclusion here is that improvement among day treatment clients was not significantly different from that of residential treatment clients.

Adult↗
PubMed1999

Experimental infection of emus (Dromaiius novaehollandiae) with avian influenza viruses of varying virulence: clinical signs, virus shedding and serology.

Two groups of emus were experimentally inoculated with a low and high pathogenic strain of avian influenza virus (AIV), type A to determine the virus susceptibility, pathogenicity, shedding and seroconversion. Emus were found susceptible to infection with AIV, with virus shedding detectable in tracheal and cloacal swabs between 3 and 10 days post-infection. Only the birds infected with the highly pathogenic viral isolate showed a brief period of mild clinical signs associated with infection. Virus recovered from the infected emus was found to be of similar pathogenicity to that of the virus inoculum. All the birds seroconverted by 10 days post-infection, as determined by haemagglutination inhibition, agar gel immunodiffusion and competitive ELISA assays. This study suggests that emus are similar to wild waterfowl in their response to AIV infection, in that they are susceptible and will replicate and shed the virus, but do not show any marked clinical signs of infection.

Journal Article↗
PubMed1999

Alarm communication network to help carers of the elderly for safety purposes: a survey of a project.

Over years, radical changes in engineering technology have taken place due to greatly improved instrumentation, enhanced computing power, new sensors and upgraded transmission mediums making it possible to achieve in the field what once could only be done on laboratory models. In daily life, the use of an active self-testing instrumentation endowed with a self-diagnostic capability built into the structural fabric of a machine permits us to monitor the initiation of breakdown, corrosion and erosion. This has become particularly important in such means of transportation as planes, boats and automobiles where advanced instrumentation, signal processing and pattern recognition systems operate in fairly conventional structures. By capitalizing on the technological progress in the field of instrumentation and data processing, help can be contemplated for elderly people in nursing homes through detection of abnormal situations. The continued assistance to elderly people is achieved by utilizing a technological system respectful of the elderly's privacy and operating without their active participation.

Activities of Daily Living↗
PubMed1998

Mesial temporal lobe measurements on magnetic resonance imaging scans.

Changes in the mesial temporal lobe, particularly in the hippocampus, amygdala, and entorhinal cortex, are reported to occur in several neuropsychiatric conditions. Neuroimaging provides a non-invasive means of studying these changes. We present a method for reliably measuring the hippocampus, amygdala, and entorhinal cortex on MRI. The advantages of our method include high reliability, the use of orthogonal views in delineating boundaries and circumscription of measurement such that no tissue of any one anatomic structure is included in the measurement of another structure.

Amygdala↗
PubMed1998

Selective internal radiation therapy for nonresectable hepatocellular carcinoma with intraarterial infusion of 90yttrium microspheres.

PURPOSE: To evaluate the efficacy of intraarterial 90yttrium (90Y) microspheres in nonresectable hepatocellular carcinoma (HCC). METHODS AND MATERIALS: Patients with nonresectable HCC, but without extrahepatic disease, who also had lung shunting < 15% and tumor-to-normal ratio > or =2, as determined by simulation using (99m)technetium macroaggregated albumin, were entered into the study. The radiation dose delivered to the lungs, tumor, and normal liver was estimated by a partition model. 90Y microspheres were infused into the hepatic artery at the time of hepatic angiography or through an implanted arterial portacatheter under fluoroscopy. Repeated treatments were given for residual or recurrent tumor. Response to treatment was monitored by serum alpha-fetoprotein or ferritin levels, together with serial computed tomography. RESULTS: Seventy-one patients, including 20 patients with postoperative recurrence, were initially treated with an activity of 0.8 to 5.0 Giga-Becquerel (GBq) (21.6-135.1 mCi) (median 3.0 GBq or 81.1 mCi) of 90Y microspheres. There was a 50% reduction in tumor volume in 19 (26.7%) patients after the first treatment. However, the overall objective response in terms of changes in alpha-fetoprotein levels was 89% [partial response (PR) 67%, complete response (CR) 22%] among the 46 patients with raised pretreatment levels. The serum ferritin level in the other 25 patients dropped by 34 to 99% after treatment. Treatment was repeated in 15 patients. The maximum number of treatments was 5 and the maximum total activity was 13.0 GBq (351.4 mCi), given in 3 treatments. The estimated radiation doses to the nontumorous liver ranged from 25 to 136 Gy (median 52 Gy) in the first treatment and the highest total radiation dose was estimated to be 324 Gy. For the tumors, the estimated radiation doses ranged from 83 to 748 Gy (median 225 Gy) in the initial treatment and the highest cumulative dose reached was 1580 Gy. The residual tumors were resected in 4 patients. Two of these had complete histological remission, but only occasional viable tumor cells were found in the necrotic centers of the tumors resected from the other 2 patients. The median survival of the 71 patients was 9.4 months (range 1.8 to 46.4 months). Treatment was well tolerated and there was no bone-marrow toxicity, or clinical evidence of radiation hepatitis or pneumonitis. CONCLUSIONS: Selective internal radiation therapy using 90Y microspheres is effective for selected cases of nonresectable HCC and is well tolerated. The objective response rate in terms of drop in tumor marker levels is higher than that based on reduction in tumor volume shown by computed tomography. The nontumorous liver appears more tolerant to internal radiation than external beam radiation. Selective internal radiation treatment may convert nonresectable tumors to resectable ones.

Adult↗
PubMed1998

Is there a limit to massive blood transfusion after severe trauma?

OBJECTIVE: To examine the hypothesis that the futility of short-term care for trauma patients requiring emergency operation can be determined based on the number of units of blood transfused and associated risk factors. DESIGN: A 4-year retrospective review of a cohort of critically injured patients who underwent an emergency operation. SETTING: A large-volume, academic level I, urban trauma center. PATIENTS: One hundred forty-one consecutive patients received massive blood transfusions of 20 U or more of blood during preoperative and intraoperative resuscitation (highest, 68 U). There were 43 survivors (30.5%) and 98 nonsurvivors (69.5%). MAIN OUTCOME MEASURES: Mortality. RESULTS: The number of blood units transfused did not differ between survivors and nonsurvivors (mean +/- SD, 31 +/- 11 vs 32 +/- 10; P = .52). Stepwise multiple regression analysis identified 3 independent variables associated with mortality: need for aortic clamping, intraoperative use of inotropes, and intraoperative time with a systolic blood pressure of 90 mm Hg or less. However, blood usage was not different among the subgroups of patients who had 1 or more of these risk factors. When patients were stratified according to the amount of massive blood transfusion (20-29, 30-39, 40-49, and 50-68 U), the incidence of risk factors was not different across the 4 subgroups. Survival in the presence of risk factors was not affected by the amount of blood transfused. CONCLUSIONS: Although mortality among critically injured patients requiring operation and massive blood transfusion can be correlated with independent risk factors, discontinuation of short-term care cannot be justified based on the need for massive blood transfusion of up to 68 units.

Adult↗
PubMed1998

Silicone synovitis: MR imaging in five patients.

Silicone synovitis is a known complication of silicone implants used in orthopedic surgery for joint reconstruction. It has been studied with routine radiography; however, no report on magnetic resonance imaging abnormalities of this condition exist in the literature. This article reports on five patients with silicone synovitis studied by magnetic resonance imaging. All patients showed hypointense implants that were deformed, fragmented or subluxed, and intra- and periarticular silicone particles were evident on T1- and T2-weighted images.

Adult↗
PubMed1998

Gene structure of human and mouse methylenetetrahydrofolate reductase (MTHFR)

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. A human cDNA for MTHFR, 2.2 kb in length, has been expressed and shown to result in a catalytically active enzyme of approximately 70 kDa. Fifteen mutations have been identified in the MTHFR gene: 14 rare mutations associated with severe enzymatic deficiency and 1 common variant associated with a milder deficiency. The common polymorphism has been implicated in three multifactorial diseases: occlusive vascular disease, neural tube defects, and colon cancer. The human gene has been mapped to chromosomal region 1p36.3 while the mouse gene has been localized to distal Chromosome (Chr) 4. Here we report the isolation and characterization of the human and mouse genes for MTHFR. A human genomic clone (17 kb) was found to contain the entire cDNA sequence of 2.2 kb; there were 11 exons ranging in size from 102 bp to 432 bp. Intron sizes ranged from 250 bp to 1.5 kb with one exception of 4.2 kb. The mouse genomic clones (19 kb) start 7 kb 5' exon 1 and extend to the end of the coding sequence. The mouse amino acid sequence is approximately 90% identical to the corresponding human sequence. The exon sizes, locations of intronic boundaries, and intron sizes are also quite similar between the two species. The availability of human genomic clones has been useful in designing primers for exon amplification and mutation detection. The mouse genomic clones will be helpful in designing constructs for gene targeting and generation of mouse models for MTHFR deficiency.

Amino Acid Sequence↗
PubMed1998

Expression and protective effects of urocortin in cardiac myocytes.

Reverse transcription PCR showed that mRNA encoding the CRH-like molecule, urocortin, is expressed in a rat cardiac myocyte cell line and in primary cultures of cardiac myocytes. Identity of the amplified with the published sequence was established by restriction mapping and direct sequencing. Expression of urocortin mRNA was increased 12-18 h after thermal injury. Urocortin peptide protected cardiac myocytes from cell death induced by hypoxia. The data suggest that urocortin is an endogenous cardiac myocyte peptide which modulates the cellular response to stress.

Animals↗
PubMed1998

De novo lipogenesis predicts short-term body-composition response by bioelectrical impedance analysis to oral nutritional supplements in HIV-associated wasting.

We studied the effects of enteral supplements on protein and energy intakes, body composition, energy expenditure, and gastrointestinal histology in 49 subjects with human immunodeficiency virus-associated weight loss (12.7 +/- 0.9% of body wt). We also determined whether a stable-isotope mass spectrometric measurement at baseline might predict the short-term response of fat-free mass (FFM) measured by bioelectrical impedance analysis. Thirty-nine subjects completed the study after being randomly assigned to receive either a whole-protein-based (n = 22) or a peptide-based (n = 17) formula. A nonsupplemented, nonrandomly assigned group (n = 13) was followed concurrently. Both formulas were well tolerated. Voluntary intakes of energy and protein from nonsupplement sources decreased significantly during supplementation [by 819-1638 kJ (196-382 kcal)/d and 5.6-14.4 g protein/d, respectively; P < 0.01] but to a lesser extent than the intake from the supplement [2300-2510 kJ(550-600 kcal)/d and 19-28 g protein/d, respectively], so that net increases in intakes of protein and energy (P < 0.03), as well as of several vitamins and trace elements were increased. Nevertheless, the mean FFM did not increase for the group as a whole, although there was considerable interindividual heterogeneity. Changes in FFM at 6 wk were significantly inversely correlated (r = 0.65, P < 0.01) with baseline synthesis of fat (de novo hepatic lipogenesis), but not with other potential measures of energy intake (insulin-like growth factor 1 or its binding protein) or inflammation (soluble tumor necrosis factor receptors I or II). The prospective identification of FFM response by measurement of de novo hepatic lipogenesis supported the hypothesis that the subset of wasting patients whose FFM is unresponsive to nutrient supplementation have altered nutrient metabolism.

Adult↗
PubMed1998

Pseudoaneurysm after high tibial osteotomy and limb lengthening.

A case of a young man with anterior tibial artery rupture and pseudoaneurysm formation that occurred during lengthening of a scarred limb is presented. Leg length discrepancy occurred because of previous distal femoral and proximal tibial fractures. Two corrective operations were performed 11 and 2 years earlier at another hospital. As limb deformity persisted, distal femoral and proximal tibial osteotomies combined with limb lengthening were performed. The aim was to achieve 120 mm (70 mm femoral, 50 mm tibial) lengthening. The operative and early postoperative course was uneventful. Twenty-six days after surgery (when femoral and tibial lengthening was 13.5 mm and 5.5 mm, respectively), blood began oozing from the operative scar during limb distraction. At 70 days after surgery (when femoral and tibia lengthening was 41.5 mm and 14 mm, respectively), a rupture and pseudoaneurysm of the anterior tibial artery became apparent. Documentation of a normal pulses in the foot after surgery, the late presentation of pseudoaneurysm, and the initiation of bleeding by limb distraction indicate that limb lengthening either aggravated an unrecognized arterial injury or precipitated de novo rupture of the anterior tibial artery scarred from previous trauma. The pseudoaneurysm was treated successfully by transarterial embolization.

Adult↗
PubMed1998

Heart Retransplantation.

Retransplantation of the heart is not a widely performed procedure, and few centers have large series. The most common indication for heart retransplantation is transplant graft coronary artery disease, followed by acute rejection and primary graft dysfunction. The outcome after heart retransplantation is not as good as with primary transplantation; the one year actuarial survival rate is lower and there are more perioperative complications. The number of episodes of infection and rejection, however, is not increased. The outcome of heart retransplantation for transplant graft coronary artery disease is better than that of retransplantation for rejection or primary graft failure. However, it is still inferior to that of primary heart transplantation. Because of this and the critical shortage of donor hearts, it is suggested that heart retransplantation should be limited to carefully selected patients.

Journal Article↗
PubMed1998

Mammogram screening of Chinese women in Kwong Wah Hospital, Hong Kong.

The incidence of primary carcinoma of the breast in Hong Kong has been rising. A screening team including radiologists, breast surgeons, cytopathologists, a full-time gynaecologist and mammographers was set up at Kwong Wah Hospital. The screening method includes a clinical breast examination (CBE) and two-view mammography. The target age group is 40-70. A total of 13,033 women were screened from March 1993 to March 1995 and 8504 mammograms were performed. A double reading system was used, with an experienced mammographer as the first reader. The films were then read by radiologists and were reported. All abnormal films and normal films with palpable masses or clinical symptoms were reviewed in a weekly meeting. A total of 113 biopsies were performed including 86 stereotactic-guided fine needle aspirations (FNA) and 27 stereotactic-guided hook-wire biopsies. Four FNA showed malignant cells and another five showed suspicious cells. Eleven hook-wire biopsies showed carcinoma. The benign to malignant ratio of the hook-wire biopsies was 16:11 (< 1.5). The total number of carcinomas disclosed was 42, and 16 of these were not palpable. Four palpable tumours were not detected by mammography. The overall carcinoma of the breast detection rate was 4.94/1000, with a rate of 4.61/1000 for the 40-49-year age group and a rate of 6.46/1000 for the over 50 years of age group. The incidence of ductal carcinoma in situ plus T1 tumours was 2.82/1000.

Adult↗
PubMed1998

Siderophore production by cystic fibrosis isolates of Burkholderia cepacia.

Sixty-one Burkholderia cepacia isolates from patients with cystic fibrosis (CF) and four plant isolates were screened for production of the siderophores salicylic acid (SA), pyochelin, cepabactin, and ornibactins and fingerprinted by a PCR-based randomly amplified polymorphic DNA (RAPD) method. Of the 24 RAPD types determined, 22 (92%) were associated with isolates that produced SA, 21 (87%) were associated with isolates that produced ornibactins, 15 (60%) were associated with isolates that produced pyochelin, and 3 (12%) were associated with isolates that produced cepabactin. Of the 24 RAPD types plus 2 phenotypic variants of types 1 and 9, 3 were associated with isolates that produced all four siderophores, 8 were associated with isolates that produced three siderophores, 12 were associated with isolates that produced two siderophores, and 3 were associated with isolates that produced only one siderophore. These results suggest that the numbers and types of siderophores produced by CF isolates of B. cepacia correlate with RAPD type and that SA and ornibactins are the most prevalent siderophores produced.

Burkholderia cepacia↗
PubMed1998

Multisensor system and artificial intelligence in housing for the elderly.

To improve the safety of a growing proportion of elderly and disabled people in the developed countries, a multisensor system based on Artificial Intelligence (AI), Advanced Telecommunications (AT) and Information Technology (IT) has been devised and fabricated. Thus, the habits and behaviours of these populations will be recorded without disturbing their daily activities. AI will diagnose any abnormal behavior or change and the system will warn the professionals. Gerontology issues are presented together with the multisensor system, the AI-based learning and diagnosis methodology and the main functionalities.

Activities of Daily Living↗