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Biomedical subjects

L Ma

Publications and source records attributed to L Ma.

At least 433 records · Page 24Linked to original sources
PubMed1996

Failed pharyngoplasty and subsequent management.

An investigation of 18 patients who had experienced "surgical failure' following pharyngoplasty for the correction of velopharyngeal dysfunction was undertaken in an attempt to identify the causes. These included poor case selection, poor surgical design and execution. Subsequent management of this group included three modalities of treatment; of the three, a carefully designed and executed surgical procedure produced the most satisfactory results in this particular patient cohort.

Adolescent↗
PubMed1996

A model of practice for the management of velopharyngeal dysfunction.

This paper reviews normal speech production, the speech characteristics associated with velopharyngeal dysfunction, the investigations required and treatment options. A model of service delivery is proposed which has been in place over the past 4 years. This model highlights multidisciplinary management by a specialist team. An audit of the service has been undertaken. Of the 225 patients audited, some interesting findings are presented on aetiology, diagnosis and trends in management. Systematic and comprehensive collection of data on large numbers of patients permits meaningful audit of process and outcome.

Articulation Disorders↗
PubMed1996

Effects of beta-blockade and atropine on ischemic responses in left ventricular regions subtending coronary stenosis during dobutamine stress echocardiography.

OBJECTIVES: This study was designed to examine the effects of a beta-adrenergic blocking agent on the ischemic response to dobutamine stress and to determine the degree to which these effects can be abolished by the addition of atropine. BACKGROUND: Whether beta-blockade affects the sensitivity of dobutamine stress echocardiography for the diagnosis of coronary artery disease has been controversial. METHODS: In nine pigs, a left anterior descending coronary artery stenosis was created to reduce flow reserve (maximal/rest flow) to 1.1 to 1.9 without baseline regional wall motion abnormalities. This corresponded to a 50% to 90% diameter stenosis. Wall thickening was measured using epicardial echocardiography. Regional lactate production and coronary venous pH were monitored from an adjacent cardiac vein. A standard protocol of dobutamine stress echocardiography was first performed. After normalization of the ischemic abnormalities elicited with this infusion, esmolol was infused at 50 micrograms/kg body weight per min and the dobutamine test was repeated, with 1.0 mg of atropine added at the maximal dobutamine dose. RESULTS: Without esmolol, dobutamine stress induced myocardial ischemia with a reduction in regional wall thickening and lactate production in all nine pigs. Multiple regression analysis revealed that coronary flow per heartbeat (p < 0.01) and lactate production (p < 0.05) independently correlated with regional wall thickening during dobutamine stress. The beta-blocker significantly reduced heart rate and regional oxygen consumption and altered the relation between coronary flow per heartbeat and regional wall thickening (p < 0.05) during dobutamine stress. Esmolol prevented dobutamine-induced ischemia (lactate production and wall motion abnormalities) in seven of nine pigs. The addition of atropine induced lactate production and a reduction in wall thickening in five of seven pigs in which ischemia had been prevented by beta-blockade. However, lactate production was higher and regional venous pH was lower with the baseline dobutamine infusion than with that performed after esmolol with atropine added at the maximal dobutamine dose (p < 0.05). CONCLUSIONS: A correlation between regional wall thickening and coronary flow per heartbeat was demonstrated during baseline dobutamine stress. Beta-blockade shifted this relation so that dobutamine stress-induced myocardial ischemia was attenuated. The mechanisms by which beta-blockade prevents dobutamine-induced ischemia appeared to be mainly through decreases in heart rate and rate of rise in left ventricular pressure, improvement of regional coronary flow per heartbeat and attenuation of regional ischemic lactate production. Adding atropine in conventional doses enhanced the ability of dobutamine stress to induce myocardial ischemia but did not completely abolish the effects of beta-blockade on either the severity of dobutamine-induced wall thickening abnormalities or regional metabolic disturbances.

Adrenergic beta-Antagonists↗
PubMed1996

The molecular basis of Boston-type craniosynostosis: the Pro148-->His mutation in the N-terminal arm of the MSX2 homeodomain stabilizes DNA binding without altering nucleotide sequence preferences.

Craniosynostosis, Boston type is an autosomal dominant disorder that results in the premature fusion of calvarial bones and ensuing abnormalities in skull shape. We showed previously that this disorder is tightly linked to the Msx2 homeobox gene on the long arm of chromosome 5, and that affected individuals bear a mutated copy of Msx2. In addition, transgenic mice in which either mutant or wild-type mouse Msx2 is overexpressed in the developing skull also exhibit craniosynostosis. That both mutant and wild-type Msx2 elicit craniosynostosis in transgenic mice and that the Boston type mutation is dominant led us to hypothesize that the mutation might enhance the normal function of Msx2. The mutation is located in position 7 of the N-terminal arm of the homeodomain, a region implicated in both target sequence recognition and protein-protein interactions. Here we test the hypothesis that the Pro148-->His mutation alters the DNA binding properties of Msx2. Using gel shift and binding site selection analyses, we show that the mutation enhances the affinity of Msx2 for a set of known Msx2 target sequences but has little or no effect on the site specificity of Msx2 binding. The enhancement of Msx2 binding is due largely if not entirely to an increased stability of the mutant Msx2-DNA complex. These data provide a molecular-level explanation of how the Pro148-->His mutation enhances Msx2 function and thus leads to the dominant craniosynostosis phenotype.

Animals↗
PubMed1996

Case report: lysosomal glycogen storage disease with normal acid maltase: an unusual form of hypertrophic cardiomyopathy with rapidly progressive heart failure.

A 14-year-old boy with mild mental retardation, myopathy, and nonobstructive hypertrophic cardiomyopathy (HCM) with clinical and histopathologic features consistent with lysosomal glycogen storage disease with normal acid maltase is described. The case illustrates the aggressive nature of the cardiomyopathy of this syndrome. This condition is associated with malignant ventricular arrhythmias, relentlessly progressive ventricular dilatation, dysfunction, and sudden death. It is important to recognize this unusual and malignant form of HCM to precipitate low early diagnosis by muscle biopsy. Patients with this condition would be excellent candidates for life-saving heart transplant as the myopathy and mental retardation are mild and nonprogressive. The underlying biochemical defect and mode of inheritance of this syndrome are unclear. However, a significant proportion are genetically related and thus, relatives may benefit from family screening.

Adolescent↗
PubMed1996

Follicular dendritic cell tumor of the liver. Evidence for an Epstein-Barr virus-related clonal proliferation of follicular dendritic cells.

Tumors of the follicular dendritic cell are uncommon, and most occur as primary lymph node tumors. We report a case of primary follicular dendritic cell tumor of the liver that was initially reported as an inflammatory pseudotumor. The neoplasm recurred as two separate tumor masses 30 months after complete resection of the "hepatic inflammatory pseudotumor." It showed a wide spectrum of morphologic features ranging from areas with fascicles of very bland spindle cells amidst a background population of lymphocytes, reminiscent of inflammatory pseudotumor, to areas of dispersed sheets of highly pleomorphic tumor cells with a relative paucity of reactive inflammatory cells. The diagnosis was confirmed by positive immunohistochemical staining with CD21, CD35, R4/23, and Ki-M4 and by ultrastructural demonstration of convoluted interdigitating cell processes joined by desmosomes. The background lymphocytes were oligoclonal, CD8-positive T cells. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA was positive in the tumor cells in the original and recurrent tumors. More importantly, the cells showed identical episomal clonal EBV on Southern blot analysis, implying that the initial and recurrent tumors are due to clonal proliferation of EBV-positive neoplastic follicular dendritic cells. The tumor cells expressed latent membrane protein but not EBV-encoded nuclear antigen 2 (EBNA2) or ZEBRA. Such gene expression is very similar to that of Hodgkin's disease and nasopharyngeal carcinoma. The strong expression of latent membrane protein restricted to the tumor cells and the clonality of the EBV suggest that the virus may be involved in the pathogenesis of this tumor and not present merely as a "bystander."

Adult↗
PubMed1996

Inflammatory cell-rich gastrointestinal autonomic nerve tumor. An expansion of its histologic spectrum.

Gastrointestinal autonomic nerve (GAN) tumor is an uncommon neoplasm of the gastrointestinal tract. Its histologic appearance is similar to other gastrointestinal stromal tumors. Ultrastructural demonstration of neural differentiation is required for its definitive diagnosis. Recently, we encountered two examples of GAN tumor that occurred in the body of the stomach and the cervical esophagus; the latter site has never been reported previously. These tumors showed unequivocal evidence of neural differentiation ultrastructurally, confirming the diagnosis of GAN tumor. Histologically, they were composed of swirling fascicles of spindle cells as well as a minor component of epithelioid cells, similar to that described previously. In addition, a cuff of lymphoid cells was noted at the peripheral part of both tumors and a scattering of mature plasma cells, lymphocytes, and foam cells was intermingled with the tumor cells. Such histologic features have not been described hitherto and can potentially be misinterpreted as features of inflammatory pseudotumor, inflammatory fibrosarcoma, or follicular dendritic cell tumor. There is a lack of CD34 expression in both tumors, but it would be premature to draw any conclusions about the potential usefulness of this observation.

Adult↗
PubMed1996

Recent status of the antisense oligonucleotide approaches in oncology.

Antisense oligonucleotides designed to complement a region of a particular messenger RNA may inhibit gene expression potentially through sequence-specific hybridization. Their inhibiting effect has been shown in a variety of in vitro and in vivo models in oncology, whereas much rarer clinical trials have been carried out. Rigorous demonstration of in vitro and in vivo specific effects upon their targets is mandatory before their use as drugs in cancer therapy.

Animals↗
PubMed1996

Use of flow cytometry in the analysis of stage III squamous cell carcinoma of the oesophagus and its association with MIB-1.

AIMS: To examine the prognostic and pathobiological importance of DNA content in oesophageal squamous cell carcinomas in Hong Kong Chinese subjects; to evaluate its association with the immunohistochemical proliferative marker MIB-1. METHODS: Paraffin wax embedded tumour tissue and adjacent normal tissue (control tissue) samples from 45 resected stage III oesophageal squamous cell carcinomas were studied using flow cytometric analysis. The DNA content and the clinicopathological data of these patients were analysed together with the MIB-1 labelling index. RESULTS: DNA aneuploidy was present in 14 (31%) of the 45 cases. However, the DNA content did not correlate significantly with the age, sex, or survival of the patients, nor the length, location, differentiation and MIB-1 labelling index of the oesophageal carcinomas. The synthetic (S) phase fraction of diploid tumours bore no relation to the patients' survival or MIB-1 score. CONCLUSIONS: Flow cytometry was not as useful as the MIB-1 labelling index in predicting the biological characteristics of the tumours and the prognosis of patients with oesophageal squamous cell carcinomas. This study does not support the routine use of DNA flow cytometric analysis in oesophageal cancers.

Aged↗
PubMed1996

Analysis of CA repeat polymorphisms places three human gene loci on the 8p linkage map.

The gene loci for luteinizing hormone-releasing hormone (LHRH), the beta-3 adrenergic receptor (ADRB3), and heregulin (HGL) have been assigned to the short arm of human chromosome 8, but the positions of these loci on the human genetic linkage map have not been previously reported. We have isolated simple tandem repeat polymorphisms (STRPs) for these loci. These STRPs enabled us to determine the genetic map locations for these genes.

Base Sequence↗
PubMed1996

Paclitaxel-induced cardiotoxicity. An ultrastructural study.

The ultrastructural appearance of the myocardium in a fatal case of paclitaxel-induced cardiotoxicity is reported, which includes swelling of the sarcoplasmic reticulum, loss of myofibrils, and accumulation of lipofuscin as well as laminated myelinoid figures. Such changes are very similar to those seen in anthracycline-induced cardiotoxicity and may suggest a pathogenetic final common pathway. While endomyocardial biopsy is a recognized means of monitoring anthracycline-induced cardiotoxicity, whether more liberal use of endomyocardial biopsy can prevent fatal cases of paclitaxel-induced cardiotoxicity needs to be further assessed.

Antineoplastic Agents, Phytogenic↗
PubMed1996

The combination of melphalan, cyclophosphamide and cytosine arabinoside as a conditioning regimen for autologous bone marrow transplantation for acute leukemia.

OBJECTIVE: To explore more effective and less toxic conditioning regimen without total body irradiation for autologous bone marrow transplantation (ABMT) for acute leukemia (AL). MATERIAL AND METHODS: Twenty patients with AL were treated with ABMT, including 13 cases of acute myelocytic leukemia (AML) and 7 cases of acute lymphocytic leukemia (ALL). A median of 1.06 (range, 0.69-1.75) x 10(8) nucleated BM cells/kg was harvested and stored in normal salt solution containing heparin at 4 degrees C. The conditioning regimen (MAC) consisted of high-dose melphalan (M, 140-160 mg/m2), cyclophosphamide (CY, 120 mg/kg) and cytosine arabinoside (Ara-C, 2.0 g/m2). These 3 drugs were administered within 25 hours and the unpurged autologous marrow infusion began after another 24-hour interval. RESULTS: MAC regimen could result in myeloblastic efficacy in a week. All marrow cells were reinfused within 56 hours after the harvest so that hemopoietic reconstitutions could occur in all the patients. The median time to reach a neutrophil count of > 1.0 x 10(9)/L and a platelet count of > 50 x 10(9)/L was 20 and 26 days respectively. With a median observation period of 25 months, the median duration on continuous complete remission in our patients was 22 months, and the longest reached 56 months. The median survival was 33 months, and the longest was over 6 years. The event-free survival at 2 years had reached 72%. In seven patients with leukemic relapse, six (86%) relapsed within 8 months after ABMT. The relapse rate and mortality in AML patients were significantly lower than those in ALL patients. In 7 patients with M3, relapse had not yet been observed. The nonhematologic toxic effects of MAC conditioning regimen occurred mainly in the gastrointestinal tract. CONCLUSIONS: The preliminary results indicated that the ABMT using MAC conditioning regimen had some advantages in stronger antileukemic efficacy, less extrahematologic toxicity and earlier recovery of platelet and could greatly prolong the duration of remission and survival in some patients with AL.

Adolescent↗
PubMed1996

Fatigue of isotropic pyrolytic carbon used in mechanical heart valves.

This study shows that the strength of silicon-alloyed pyrolytic carbon is not affected by long-life cyclic stress up to 6 x 10(8) cycles at stress levels which are two, four and eight times higher than the estimated peak service stress of a mechanical heart valve. It is demonstrated that there is clearly a threshold size for cyclic fatigue crack propagation below which the cracks do not grow at all when cycled up to 6 x 10(8) cycles at strain levels that are two and four times higher than the estimated peak service stress of the heart valve. The large sample size of the fatigue test gives a high statistical confidence in the intrinsic fatigue behavior of pyrolytic carbon, which has been demonstrated in over three million implants of the material in actual devices with an accumulated experience of over ten million patient years. Nevertheless, mechanical heart valve designers are cautioned to consider the effects of extrinsically introduced flaws.

Biocompatible Materials↗
PubMed1996

High resolution view of the true cytosolic membrane surface of phagosomes of known ages purified from Paramecium.

Techniques were used for viewing the true cytosolic surfaces of the membranes of intracellular organelles by field emission scanning electron microscopy (SEM). Cells of Paramecium multimicronucleatum were fed briefly with magnetic beads followed by a chase which advanced the newly formed digestive vacuoles (DVs) to predetermined ages. These bead-containing phagosomes were isolated from the whole cell homogenates with a magnet and were determined to be intact by fluorescence microscopy. Antigenically, these DVs were similar to those in situ. The DVs prepared for transmission electron microscopy or SEM showed extensive adherence of cellular debris. The use of 0.2 M KCl in the wash buffer eliminated much of this debris and exposed the true vacuolar surfaces. Three populations of tightly bound vesicles and numerous globular particles of 10 to 20 nm became visible on the DV surfaces. The attached vesicles, having diameters of approximately 300 and approximately 200 nm each, corresponded to the acidosomes and lysosomes that are known to be associated with the DV-I and DV-II, respectively. High resolution SEM also revealed a third set of small vesicles (50-150 nm), which were previously not known to be associated with DVs. The 10 to 20 nm globular particles were judged to be the cytosolic extensions of transmembrane protein complexes as their patterns of distribution on DVs of various ages corresponded to the transmembrane particles previously seen in these membranes in freeze-fracture studies.

Acid Phosphatase↗
PubMed1996

[Intestinal lymphatic circulation is one of the important portals for microbial translocation after thermal injury].

The goal of this study was to determine whether the bacteria and endotoxin from GI tract could pass through the intestinal lymph circulation to the systemic circulation after severe thermal injury. Lymphatic fistula of intestine was created in 46 Wistar rats the rats were then divided randomly in scald and control groups. In scald group, animals were sustained with 30% TBSA full-thickness scald. The items studied were, the dynamic changes in intestinal lymph endotoxin level, the qualitative and quantitative bacterial culture, and pathological alterations in ileal mucosa within 24 hours postburn. Results showed that the levels of intestinal lymph endotoxin and the positive culture rate and counting of bacteria were evidently increased, and ileal mucosal lacteals were dilated and epithelial cells were necrotic and denudated in scald group. These suggested that the intestinal lymph circulation is one of the important portals for endotoxin and microbial translocation after severe thermal injury, and the intestinal mucosal damage is an important factor in pathogenesis.

Animals↗
PubMed1996

[Correction of alveolar cleft by bone graft in the patients with cleft lip and palate].

Treatment of alveolar cleft using bone graft has been developed to the stage of team approach. We summarized the clinical material of 80 cases treated by bone grafting. This study revealed that bone grafting for cleft alveolar repair was an effective procedure valuable to be popularized. Properly forming the bed of bone grafting and perfectly closing the recipient site is the key to a successful operation. Patients should accept orthodontic treatment before and after the operation. We discuss the indications, technique, result evaluation and management before and after the operation.

Adolescent↗