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Biomedical subjects

M Ng

Publications and source records attributed to M Ng.

At least 73 records · Page 4Linked to original sources
PubMed1997

Resolution rates of low grade vesicoureteral reflux stratified by patient age at presentation.

PURPOSE: Most children with grades I to III primary vesicoureteral reflux are monitored for years on antibiotic prophylaxis until reflux resolves. While the overall resolution rate of these grades is known, the rates for various patient ages at presentation are unknown. Therefore, we examined resolution rates of these grades for different ages at presentation. MATERIALS AND METHODS: From 1985 through 1990, 168 boys (245 ureters) and 433 girls (590 ureters) with all grades of reflux were enrolled in the study and monitored through the end of 1993. Urine cultures were obtained every 4 months and contrast voiding cystourethrography was repeated every 18 months. Age at presentation was stratified into groups younger than 1, 1 to 3, 4 to 6, 7 to 9, and 10 years and older. Resolution rates were then calculated for grades I to III reflux for each age at presentation. Time to resolution was also evaluated for each age and grade. RESULTS: There were no significant differences between rates of resolution at different ages for each grade. Children less than 10 years old had as high a likelihood of resolution as infants. Neither sex nor bilaterality versus unilaterality was a helpful predictor of resolution. Time to resolution varied widely and it was also not helpful for identifying the cases of reflux that resolved. CONCLUSIONS: Low grade vesicoureteral reflux may not resolve until adolescence and age at presentation is not a reliable predictive factor. Children should remain on prophylaxis for many years unless definitive correction is undertaken.

Age Factors↗
PubMed1997

Experience with vesicoureteral reflux in children: clinical characteristics.

PURPOSE: We reviewed our 9-year experience with a large population of children with vesicoureteral reflux who were evaluated and treated according to contemporary concepts. MATERIALS AND METHODS: From 1985 to 1993 we followed 288 boys and 752 girls with vesicoureteral reflux. If surgery was not performed, patients were on antibiotic prophylaxis and evaluation was done every 18 months with contrast voiding cystography and radionuclide renal imaging. Urine cultures were obtained every 4 months. Two negative voiding cystourethrograms 1 year apart were required to discontinue prophylaxis. RESULTS: The major reasons for initial evaluation were urinary tract infection in 560 children (54%), voiding dysfunction without urinary tract infection in 156 (15%), sibling surveys in 122 (12%) and prenatal hydronephrosis in 23 (2%). In 150 kidneys (10%) in 132 children scarring at presentation was grade 0 in 10 (7%), I in 18 (12%), II in 27 (18%), III in 30 (20%), IV in 48 (32%) and V in 17 (11%). Of these 132 patients 17 presented at ages less than 1 year (13%), 29 at ages 1 to 3 (22%), 50 at ages 4 to 6 (38%), 24 at ages 7 to 9 (18%) and 12 at ages greater than 10 (9%). No new scars were seen in children on prophylaxis without breakthrough infection. After 1 negative voiding cystourethrogram reflux was noted again in 27% of the cases. Breakthrough infections developed in 62 children of whom a third were older than 7 years. Reimplantation in 205 children (20%) was performed for grade IV to V reflux (101), breakthrough infection (62), advanced age (18), large periureteral diverticulum (12) and noncompliance (3). Five boys and 57 girls (30% of all children) had urinary tract infections after successful reimplantation. CONCLUSIONS: Almost half of the children with vesicoureteral reflux have no history of culture proved urinary tract infection. Scarring may be associated with any reflux grade and it may be initially diagnosed at any age. Only half of the scars are noted with higher grades of reflux (IV and V). Continuous prophylaxis prevents new scarring. Breakthrough infections are rare but they can occur at ages greater than 7 years. Two consecutive negative cystograms are necessary before discontinuing prophylaxis. Children should be monitored after reimplantation for recurrent urinary tract infection.

Child↗
PubMed1997

Better survival in women with resected hepatocellular carcinoma is not related to tumor proliferation or expression of hormone receptors.

OBJECTIVE: There is a well known male predominance in hepatocellular carcinoma (HCC). Moreover, female patients with HCC have better survival and lower recurrence rates after surgical resection. We previously showed that the better prognosis in female patients is related to a higher incidence of tumor encapsulation and less invasive tumors. However, the underlying mechanism is still obscure. METHODS: In this study, we examined the cell proliferative indices (expression of proliferative cell nuclear antigen (PCNA) and Ki-67 antigen using MIB1 antibody) and expression of the estrogen and progesterone receptors (ERs and PRs, respectively) in 71 patients with resected HCC. These were correlated with the pathological features of the tumors and the survival rates of patients. RESULTS: Female patients with HCC had significantly better actuarial and disease-free survival rates than male patients (p = 0.010 and 0.004, respectively). Tumor PCNA scores, represented by positively stained nuclei per 1000 tumor cells, were significantly higher in tumors showing venous permeation (p = 0.034), positive resection margins (p = 0.011), and absence of bile production (p = 0.008). Higher tumor MIB1 scores were seen in tumors that had poorer cellular differentiation (p = 0.002) and no tumor capsules (p = 0.042). However, both tumor PCNA and MIB1 scores did not differ significantly between female and male patients. ERs were detected in the tumor cells in 23.9% of tumors, and PRs were detected in 14.3%. Expression of both ER and PR was not influenced by gender. CONCLUSIONS: Women with HCC had significantly better survival and lower tumor recurrence rates. However, significant differences in cellular proliferation indices and expression of ER and PR were not observed between men and women to explain the difference in survival rate.

Adult↗
PubMed1997

Changes in diagnostic decision-making after a computerized decision support consultation based on perceptions of need and helpfulness: a preliminary report.

We examined the degree to which attending physicians, residents, and medical students' stated desire for a consultation on difficult-to-diagnose patient cases is related to changes in their diagnostic judgments after a computer consultation, and whether, in fact, their perceptions of the usefulness of these consultations are related to these changes. The decision support system (DSS) used in this study was ILIAD (v4.2). Preliminary findings based on 16 subjects' (6 general internists, 4 second-year residents in internal medicine, and 6 fourth-year medical students) workup of 136 patient cases indicated no significant main effects for 1) level of experience, 2) whether or not subjects indicated they would seek a diagnostic consultation before using the DSS, or 3) whether or not they found the DSS consultation in fact to be helpful in arriving at a diagnosis (p > .49 in all instances). Nor were there any significant interactions. Findings were similar using subjects or cases as the unit of analysis. It is possible that what may appear to be counter-intuitive, and perhaps irrational, may not necessarily be so. We are currently examining potential explanatory hypotheses in our ongoing current, larger study.

Attitude to Computers↗
PubMed1996

Two distinct mechanisms for long-range patterning by Decapentaplegic in the Drosophila wing.

Secreted signalling molecules provide cells with positional information that organizes long-range pattern during the development of multicellular animals. Evidence is presented that localized expression of Decapentaplegic instructs cells about their position along the anterior-posterior axis of the Drosophila wing in two distinct ways. One mechanism is based on the local concentration of the secreted protein; the other is based on the ability of the cells to retain an instruction received at an earlier time when their progenitors were in close proximity to the signal. Both mechanisms are involved in axis formation.

Animals↗
PubMed1996

Specification of the wing by localized expression of wingless protein.

Limb development in Drosophila depends on subdivision of the limb primordia into functional units called compartments. Cell interactions across compartment boundaries establish pattern-organizing centres that control growth and specify cell fates along the anteroposterior (AP) and dorsoventral (DV) axes of the limbs. AP subdivision of the disc primordia is inherited from the embryonic ectoderm. DV subdivision of the wing disc occurs during the second larval instar through localized expression of the apterous protein (Apterous) in dorsal cells. A third major subdivision of the wing disc into wing and body-wall compartments also occurs in the second instar. Here we show that specification of the wing primordium in early second instar depends on activity of the AP patterning system but not the DV system. These results define two distinct roles for the wingless gene: a primary role in specifying the wing primordium, and a subsequent role mediating the patterning activities of the DV compartment boundary.

Animals↗
PubMed1996

Purified recombinant EBV desoxyribonuclease in serological diagnosis of nasopharyngeal carcinoma.

To evaluate applications of highly purified recombinant EBV DNAase in the diagnosis and prognosis of NPC, we tested sera from patients with NPC, other EBV-associated diseases and EBV-seropositive and -seronegative healthy subjects by immunoblotting and DNAase inhibitory assay. The results were compared with those obtained by the conventional immunofluorescence assays against the EBV-specified early antigens and capsid antigens. The antigenic specificity of the immunoblotting assay for IgG antibody against the viral enzyme, but not that for the IgA antibody, was correlated with DNAase-inhibitory activity of the sera and their titers of IgG antibodies against the viral early antigens. Purified IgA as well as IgG from NPC sera inhibited enzyme activity with similar efficiency. The use of highly purified viral DNase has increased the sensitivity of detection of the corresponding antibodies by immunoblotting, with the IgG antibody being detected in all but one, and IgA antibody in all but 2, of the 174 NPC sera tested. The IgG antibody was also commonly detected in the other groups of control sera, while the IgA antibody was detected in about 10% of African Burkitt's lymphoma and Algerian Hodgkin's lymphoma patients and less than 3% of the other control subjects. These results suggest that IgA antibody against recombinant EBV DNAase may be useful in the diagnosis of NPC, but the level of this antibody did not appear to be related to clinical stages of this cancer.

Animals↗
PubMed1996

An analysis of social and economic factors associated with followup of patients with vesicoureteral reflux.

PURPOSE: Nonsurgical treatment of vesicoureteral reflux requires antibiotic prophylaxis and long-term surveillance. We examined factors that affect followup compliance and influence quality of care in these children. MATERIALS AND METHODS: We retrospectively reviewed the records of 288 boys and 742 girls with vesicoureteral reflux. RESULTS: Of the children treated nonsurgically for vesicoureteral reflux 34% were lost to followup and the majority (80%) were not monitored beyond the 1-year followup appointment. Older maternal age (36 years or older) was significantly associated with improved followup compliance. Paternal age, primary physician type, medical insurance type, income, education level and environment (urban, suburban or rural) were not significant. CONCLUSIONS: Approximately a third of children treated nonsurgically for vesicoureteral reflux will be lost to followup. Only older maternal age predicts for good compliance. Preconceptions about compliance on the basis of other factors, such as socioeconomic status and primary physician type, may be incorrect. Furthermore, the notion that certain forms of medical insurance plans may help to promote followup may also be unsupported. These children would benefit from efforts to improve compliance with a medical regimen or early correction of reflux.

Child↗
PubMed1996

Clinical and histological features of gastric antral vascular ectasia: successful treatment with endoscopic laser therapy.

Gastric antral vascular ectasia is a rare but important cause of chronic gastrointestinal bleeding. We report five patients in whom endoscopic laser therapy successfully controlled repeated blood loss. The patients were elderly (age range: 61-84 years; mean age: 75 years) and three of them were female. Endoscopically, all patients presented with a characteristic antral appearance of either ecstatic vascular 'stripes' radiating out from the pylorus, or multiple cherry-red spots. In all patients, the gastric mucosal biopsy specimens showed dilatation of the capillaries with focal fibrin thrombi and fibromuscular hyperplasia. Marked improvement of both endoscopic and histological features was achieved with endoscopic laser treatment using Nd-YAG laser photocoagulation. Its importance lies in its recognition and successful treatment with endoscopic laser therapy, which offers an effective and relatively safe alternative to surgery, particularly in elderly patients.

Aged↗
PubMed1996

Sibling reflux: a dual center retrospective study.

PURPOSE: Siblings of index patients with vesicoureteral reflux are known to have an increased incidence of reflux. Previous reports may be biased due to significantly more female siblings undergoing screening. In addition, it has been suggested that screening is unnecessary in older children. MATERIALS AND METHODS: We retrospectively reviewed the records of probands with vesicoureteral reflux. A total of 422 families comprising 622 siblings was identified at our centers from 1985 to 1994. Of the 255 boys and 277 girls newborn to 16 years old (mean age 6.2 years) 85% were evaluated. Almost 43% of the probands (225) were older than 7 years. RESULTS: Vesicoureteral reflux was noted in 144 siblings (52 boys and 92 girls, 27%). The majority had low grade reflux but in 111 (77%) maximum reflux grade was II or III. Reflux nephropathy was demonstrated on a nuclear renal scan in 18 of the 132 tested siblings (13.6%). In all of these children reflux was grades II to IV and 27% were older than 10 years. CONCLUSIONS: When vesicoureteral reflux is discovered, all siblings should be considered for screening. The evaluation of older siblings remains controversial, since they comprise only a small fraction of all siblings with reflux but may have a significant portion of reflux nephropathy. There was a 27% overall incidence with a 33% rate in girls. The incidence of reflux in siblings decreased after age 7 years but reflux nephropathy was identified even in the older children.

Adolescent↗
PubMed1995

Cloning and characterization of a murine macrophage lipoxygenase.

We have isolated a murine macrophage cDNA encoding a 12-lipoxygenase, that represents the homolog of the human 15-lipoxygenase. The predicted amino acid sequence of this lipoxygenase is highly similar to the rat 12-lipoxygenase isolated from brain and human 15-lipoxgenase. The recombinant enzyme expressed in Cos-7 cells oxidizes arachidonic acid to 12- and 15-HETE with a profile similar to that obtained from peritoneal macrophages. A polyclonal antibody generated against a putative peptide recognizes a 75 kDa protein in cell extracts from mouse peritoneal macrophages and transfected Cos-7 cells. The lipoxygenase cDNA hybridizes to a 2.5 kb mRNA present in peritoneal macrophages, lung, spleen, heart and liver. RT-PCR analysis indicates that the same lipoxygenase is expressed in mouse reticulocytes. A partial genomic clone for this lipoxygenase has also been characterized. Southern blot analysis of mouse genomic DNA indicates that this is a single copy gene.

Amino Acid Sequence↗
PubMed1995

Ultrastructure of Blastocystis hominis cysts.

Blastocystis hominis cysts were concentrated from human faeces by repeated washing in distilled water and centrifugation on Ficoll-Paque. This procedure gave a concentrated suspension of cysts without yielding any non-cystic forms. The cysts were examined by both transmission (TEM) and scanning electron microscopy (SEM). Cysts were surrounded by a fibrillar layer that appeared porous in SEM. Many naked cysts without the fibrillar layer were also visible in SEM. They were variable in shape but mostly circular to oval. The diameter of the cyst without the fibrillar layer was 3.5 microns in both TEM and SEM. The nuclear structure was typical of Blastocystis and exhibited multiple mitochondria with poorly developed cristae. Glycogen was present in small to large clumps in the cytoplasm. The cyst wall was 5-100 nm thick and was bounded internally by an electron-dense plasmalemma.

Animals↗
PubMed1995

Living with a chronic illness: Chinese-Canadian and Euro-Canadian women with diabetes--exploring factors that influence management.

The study reported on here was designed to address how Euro-Canadian and Chinese-Canadian women living with diabetes experience and manage their illness in their day to day lives, and the factors that influence daily management (diet, exercise, medication and blood testing). It was hypothesized that women's patterns of diabetes management would be associated with (a) ethnicity and/or (b) fluency in English. It was also hypothesized that the extent to which women with diabetes (whether Chinese- or Euro-Canadian, fluent or not fluent in English) would carry out daily management in accordance with western health care practices would be associated with: (i) the extent to which desired professional care is experienced; (ii) the women's awareness of facts as endorsed by health professionals (biomedical knowledge); and (iii) her satisfaction with the support received from family and friends. A total of 196 women were interviewed to explore these hypotheses. While we do not yet know the magnitude or relative importance of each of the independent variables, the findings from this study suggest that the management of diabetes is a complex construct, comprised of several components, each being influenced by a number of factors. How a woman managed her illness was not reducible to her ethnicity. Instead, the contextual features of her life, coupled with her ability to access resources seemed to organize the ways in which she managed her illness. Diabetes management therefore becomes a multifaceted phenomenon, which has to be understood within the mediating circumstances of a woman's life.

Adaptation, Psychological↗
PubMed1995

Ki-67 antigen expression in hepatocellular carcinoma using monoclonal antibody MIB1. A comparison with proliferating cell nuclear antigen.

To evaluate the prognostic significance and clinicopathologic correlation of proliferative activity in patients with hepatocellular carcinoma, Ki-67 antigen expression was examined using immunohistochemical staining with monoclonal antibody MIB1. Seventy-two patients (65 men, 7 women; age range 24-77 years, mean, 52 years) having hepatocellular carcinoma surgically resected were studied. Tumor and nontumorous tissues were stained with monoclonal antibody MIB1 with microwave oven pretreatment. Tumor and nontumor MIB1 (T-MIB1 and NT-MIB1) scores were assessed by counting the positive staining nuclei per 1,000 cells. The T-MIB1 score ranged from 5-630 per 1,000 cells (mean +/- standard deviation [SD] = 145 +/- 162). It was found to be significantly higher in less well-differentiated tumors (Edmondson's grades III and IV) than in well-differentiated ones (Edmondson's grades I and II) (P = .017). The T-MIB1 score was also higher in nonencapsulated tumors than in encapsulated ones, although it did not reach statistical significance (P = .069). It had no influence on tumor size, tumor invasiveness, the background disease in the nontumorous livers, patients' HBsAg status, or serum alpha-fetoprotein levels. Diseases in the nontumorous livers or patients' HBsAg status had no influence on the NT-MIB1 scores. When the tumors were stratified into two groups with T-MIB1 score < or = 20 and T-MIB1 score > 20, those patients with score < or = 20 had significantly longer disease-free survival (DFS) than those with scores > 20 (median DFS: 34 months and 4.7 months, respectively; P = .011). In addition, MIB1 and PCNA were closely correlated (P < .01). The authors conclude that proliferative activity in hepatocellular carcinoma, as defined by MIB1 immunohistochemical analysis, is significantly related to tumor cellular differentiation. It is also a potentially valuable prognostic factor in patients with this tumor.

Adult↗
PubMed1995

Nubbin encodes a POU-domain protein required for proximal-distal patterning in the Drosophila wing.

The nubbin gene is required for normal growth and patterning of the wing in Drosophila. We report here that nubbin encodes a member of the POU family of transcription factors. Regulatory mutants which selectively remove nubbin expression from wing imaginal discs lead to loss of wing structures. Although nubbin is expressed throughout the wing primordium, analysis of genetic mosaics suggests a localized requirement for nubbin activity in the wing hinge. These observations suggest the existence of a novel proximal-distal growth control center in the wing hinge, which is required in addition to the well characterized anterior-posterior and dorsal-ventral compartment boundary organizing centers.

Animals↗
PubMed1994

Prognostic significance of proliferating cell nuclear antigen expression in hepatocellular carcinoma.

BACKGROUND: Proliferating cell nuclear antigen (PCNA) is a nuclear protein synthesized in G1/S-phase of the cell cycle and therefore is related to cell proliferative activity. In an attempt to evaluate its prognostic significance and clinicopathologic correlation in patients with hepatocellular carcinoma (HCC), the proliferative activity was studied using immunohistochemical staining with monoclonal antibody to PCNA. METHODS: Seventy-two patients (64 men, 8 women; mean age, 52 years [range, 24-77 years]) having HCC surgically resected were studied. Tumor and nontumor tissues were selected from each case and stained with PCNA antibody. Tumor and nontumor PCNA (T-PCNA and NT-PCNA) scores were assessed by counting the positive staining nuclei per 1000 cells. RESULTS: The T-PCNA score ranged from 10 to 894 per 1000 cells (mean +/- standard deviation = 333 +/- 263). It was found to be significantly and positively associated with positive margin (P = 0.003), direct liver invasion by tumor (P = 0.021), and venous permeation (P = 0.020), features directly or indirectly related to tumor invasiveness. However, it had no significant association with tumor size, cellular differentiation, or patients' hepatitis B surface antigen (HBsAg) status. When the tumors were stratified into two groups with a T-PCNA score less than or equal to 200 and a T-PCNA score greater than 200, those patients with a T-PCNA score less than or equal to 200 had significantly longer disease-free survival (DFS) and actual survival (AS) rates than those with scores greater than 200 (median DFS and AS, 34.6 and 49.3 months and 7.7 and 19.1 months, respectively; P = 0.019 and 0.035 for DFS and AS, respectively). T-PCNA and NT-PCNA scores had no significant correlation with the HBsAg status of the patients. CONCLUSIONS: Proliferative activity in HCC, as defined by PCNA immunohistochemical analysis, is significantly related to tumor invasiveness. It is also a potentially valuable prognostic factor in patients with this tumor.

Adult↗
PubMed1994

Cisplatin-based chemotherapy for ovarian germ cell malignancies: the Australian experience.

PURPOSE: This study was performed to evaluate the Australian experience with cisplatin-based treatment of ovarian germ cell tumors (OGCT) with respect to survival and toxicity of treatment. PATIENTS AND METHODS: A retrospective review was undertaken based on a standardized questionnaire, which was sent to all major gynecologic oncology centers in Australia. RESULTS: Data on 58 patients were obtained. Overall survival at 5 years for all patients was 87%. There was one death from disease among 14 patients with dysgerminoma, and four deaths from disease among 44 patients with nondysgerminomas. Cisplatin-based chemotherapy was associated with a low incidence of serious complications, with only one treatment-related death (from bleomycin-induced respiratory failure). CONCLUSION: Our large series demonstrates that cisplatin-based chemotherapy is highly effective for patients with OGCT. Although direct comparisons cannot be made, the survival of our patients with advanced tumors was comparable to that seen in male germ cell tumors, rather than inferior as is commonly believed. Future studies should aim to refine treatment to minimize toxicity, while further increasing curability.

Adolescent↗