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Biomedical subjects

M H Ma

Publications and source records attributed to M H Ma.

At least 19 recordsLinked to original sources
PubMed2001

Hypoxanthine impairs morphogenesis and enhances proliferation of a neuroblastoma model of Lesch Nyhan syndrome.

Extracellular purines have essential roles in neuronal development; hence, disruptions in their metabolism as reported in Lesch Nyhan syndrome (LNS) could result in developmental abnormalities. The deficiency of hypoxanthine-guanine phosphoribosyl transferase (HGPRT) in LNS leads to increased hypoxanthine and uric acid production. We have reported that HGPRT-deficient B103-4C neuroblastoma, a neuronal model of LNS, proliferated less and differentiated more than their HGPRT-positive B103 counterparts. Here, we sought to determine whether differences in proliferation and differentiation would occur when these cells were cultured in the presence of hypoxanthine or in a hypoxanthine-/serum-free chemically defined media (NBMN2). In media with 1% serum, hypoxanthine (50 microM) significantly increased the proliferation of both cell lines with a greater effect on B103-4C cells. In 1% serum media, hypoxanthine increased differentiation of B103 but decreased B103-4C differentiation. In NBMN2, B103 proliferated far more than B103-4C, but both cell types differentiated to the same extent. These results are interpreted to suggest that elevated levels of central nervous system (CNS) hypoxanthine as reported in LNS may affect neuronal development, and to implicate hypoxanthine and abnormal neuronal development as causative factors in the etiology of LNS.

Animals↗
PubMed2001

Ambulance utilization in metropolitan and rural areas in Taiwan.

BACKGROUND AND PURPOSE: Emergency medical services (EMS) have expanded rapidly in the Asian developing countries recently. However, the patterns of ambulance utilization in the rural and urban areas of these countries have not been thoroughly described. This study investigated the patterns of ambulance utilization in two urban areas and the larger rural area of Taiwan formerly designated Taiwan Province. METHODS: We studied a total of 304,368 ambulance missions during 1997 in Taiwan. We analyzed the differences in the characteristics of emergency calls and the interventions performed on the scene in two urban areas, Taipei City and Kaohsiung City, and in the rural area formerly designated Taiwan Province. RESULTS: The call volume and percentage of non-transport calls were higher in the more developed of the two urban areas, Taipei City, than in Kaohsiung (p < 0.01). The incidence of calls with trauma-related causes was higher in both urban areas. However, the percentage of calls placed for trauma-related reasons was higher in the rural area (p < 0.01). More calls for acute medical illness were placed in Taipei City (p < 0.01) than in the rural area. The number of interventions performed by ambulance staff was higher in Taipei City and Kaohsiung City than in the rural area (p < 0.01). The availability of acute illness management was generally lower than needed in all areas. CONCLUSIONS: Call volume and the number of interventions performed were higher in the urban area, whereas the percentage of trauma-related calls was higher in the rural area. These findings suggest that EMS use patterns in Taiwan are transitioning towards a pattern characteristic of a more developed country. The differences in ambulance utilization patterns must be considered in plans to further develop EMS services in these areas.

Ambulances↗
PubMed2000

Abnormalities in cellular adhesion of neuroblastoma and fibroblast models of Lesch Nyhan syndrome.

Lesch Nyhan syndrome is a neurological paediatric condition characterized by mental retardation, choreathotosis and self-mutilation. Biochemically, this condition has been attributed to a deficiency in the purine enzyme, hypoxanthine guanine phosphoribosyltransferase, however, the way this affects the development of the nervous system is still unknown. Ma et al.(15) and Stacey et al.(25) found that hypoxanthine guanine phosphoribosyltransferase-deficient neuroblastoma, differentiated significantly more than cells with this enzyme. Here, we report that adhesion of hypoxanthine guanine phosphoribosyltransferase-deficient neuroblastoma as well as fibroblasts from patients with Lesch Nyhan syndrome, exhibited dramatically enhanced adhesion compared to control cells. This increase in adhesion was dependent upon the cell type, density of the cells and upon the substrate used. Development of the nervous system is dependent on adhesion, in particular in the processes of migration, nucleation, differentiation and fasciculation. Our results suggest that the increased adhesion of hypoxanthine guanine phosphoribosyltransferase-deficient neuroblastoma and fibroblasts in vitro underpins the neuropathology of Lesch Nyhan syndrome.

Animals↗
PubMed1999

ED overcrowding in Taiwan: facts and strategies.

The objective of this study was to quantity the extent of emergency department (ED) overcrowding in Taiwan and to identify possible solutions. The ED log was reviewed for all patients who presented to the National Taiwan University Hospital's ED from January 16, 1996 through February 15, 1996. Charts from patients held longer than 72 hours were reviewed. Among 5,810 patients, 213 (3.6%) were held in the ED for more than 72 hours (7.1 patients per day). In 149 (70.0%) of them, admission was indicated but delayed (42 because more than one subspecialty were involved, 57 because of unavailability of bed, and 50 because of the disparity in admission priority between the emergency physicians and house staffs). Eighteen (8.4%) patients did not meet admission criteria (13 could have been treated in outpatient clinics, 3 needed placement in nursing homes, 2 because of personal problems). The others (22%) recovered while waiting. Significant overcrowding exists in EDs in Taiwan. Four solutions are proposed: (1) creation of a holding unit; (2) flexible ward assignment; (3) pre-established rules for admission priority-setting; and (4) active interfacility transfer. Only through these efforts can EDs in Taiwan guarantee an optimal level of care in the face of a growing patient demand.

Appointments and Schedules↗
PubMed1999

Compliance with prehospital triage protocols for major trauma patients.

BACKGROUND: The extent to which severely injured patients receive definitive care at trauma centers is determined by the accuracy of prehospital major trauma criteria in predicting severe injuries and by the level of compliance with these triage instructions by prehospital providers. This study was conducted to evaluate the level of compliance with triage criteria in an established trauma system. METHODS: The study involved a retrospective analysis of the 1995 Maryland statewide prehospital ambulance data. Prehospital providers in Maryland are instructed to consider transporting patients meeting any of the three nonexclusive major trauma criteria-physiology, injury, and mechanism-to designated trauma centers. Compliance with these criteria was defined as the proportion of patients transported to designated trauma centers among those meeting prehospital triage criteria as documented on the ambulance trip report. Special emphasis was placed on differences in the levels of compliance by age of the trauma patients. RESULTS: A total of 32,950 transports were analyzed. Patients meeting injury criteria were most likely to be transported to trauma centers (86%), followed by those meeting mechanism criteria (46%), and physiology criteria (34%). When the level of compliance was stratified by age, there was no age difference in the level of compliance for patients meeting injury criteria (90.5% for patients aged 0-54 years vs. 88.7% for patients aged 55+ years; p = 0.197). For older patients meeting physiology criteria only or for those meeting mechanism criteria only, however, compliance was differentially low. For patients meeting physiology criteria only, the compliance was 40.3% for patients aged 0 to 54 years and 23.9% for patients aged 55 years and older (p = 0.0001); for patients meeting mechanism criteria only, compliance was 47.0% for patients aged 0 to 54 years and 39.7% for patients aged 55+ years (p = 0.002). CONCLUSION: The majority of patients meeting prehospital major trauma criteria were transported to designated trauma centers. Patients meeting only physiology criteria, however, were much less likely to be transported to trauma centers, and there was a differentially low compliance for elderly trauma patients meeting physiology criteria alone. The causes and consequences of lower compliance with triage instructions for the elderly population deserve further investigation.

Adolescent↗
PubMed1996

Comparison of modes of oral hygiene instruction in improving gingival health.

195 Hong Kong Chinese employees from a single company participated in a 10-month longitudinal study on the effects of various modes of delivery of oral hygiene messages on their gingival health. Subjects were allocated to one of the following modes of oral hygiene education: (1) personal instruction; (2) self-education manual; (3) video; (4) a combination of 2 or more of these modes of instruction. Scaling or any other form of periodontal treatment was not given throughout the study period. Full mouth clinical examinations were carried out using a Williams Periodontal probe to examine for the presence or absence of plaque and bleeding on probing from the gingival sulcus. At 2 weeks, 4 months and 10 months, results showed significant reductions in the mean % of plaque and bleeding when compared with baseline. No significant differences were found between the groups given the various modes of oral hygiene education. The study does confirm the effectiveness of oral hygiene alone in improving gingival health, but the lack of difference in the outcome of various oral hygiene education approaches indicates that the mode of instruction is not crucially important to the end result. However, it has to be acknowledged that improvement in oral hygiene may be related to factors other than the oral hygiene programme itself. The findings have significant implications in oral health promotion programmes to improve the periodontal status of the local community.

Adult↗
PubMed1995

Transesophageal echocardiographic assessment of mitral valve position and pulmonary venous flow during cardiopulmonary resuscitation in humans.

BACKGROUND: The mechanisms of blood flow during closed-chest cardiopulmonary resuscitation (CPR) in humans have been debated since the technique was first described in 1960. Two competing models, the cardiac pump theory and the thoracic pump theory, have been proposed, and some investigators have used mitral valve position during the downstroke of chest compression to distinguish between them. Previous studies using either transthoracic or transesophageal echocardiography have yielded conflicting results, and there have been few, if any, hemodynamic or echocardiographic studies on pulmonary venous flow (PVF) during CPR. METHODS AND RESULTS: In this study, transesophageal two-dimensional and pulsed Doppler echocardiography were used to study mitral valve position and flow, together with PVF, in 20 adult patients undergoing manual CPR. In the 17 patients who could be analyzed, the mitral valve closed in 5 patients (group 1) during chest compression but stayed open or opened further in the remaining 12 patients (group 2). Peak forward mitral flow occurred during the release phase in group 1 but during the compression phase in group 2. During chest compression, PVF occurred in the forward direction (from the pulmonary vein to the left atrium) in 8 of the group 2 patients (group 2a) and in the backward direction (from the left atrium to the pulmonary vein) in all group 1 patients and the remaining 4 patients in group 2 (group 2b). The downtime (time from collapse to CPR) was significantly shorter (P < .05) for those in group 1 (7.0 +/- 4.4 minutes) than in groups 2a (19.8 +/- 7.7 minutes) and 2b (17.8 +/- 6.8 minutes). CONCLUSIONS: Transesophageal echocardiography performed during manual CPR in humans disclosed three different patterns of mitral valve position and PVF during chest compression. The presence of an opened mitral valve with forward mitral flow and backward pulmonary venous flow during chest compression in a small number of subjects underscores this heterogeneity in blood flow and suggests the possible existence of a "left atrium pump" in addition to the currently known "left ventricle pump" and "chest pump" mechanisms.

Adult↗
PubMed1991

[Effects of GABA and bicuculline on the properties of visual superior colliculus neurons in golden hamsters].

Visual response properties of single neurons in the superior colliculus of golden hamsters could be altered by iontophoretically applied gamma-aminobutyric acid (GABA) and its antagonist, bicuculline (Bicu). GABA decreased the responses of the superficial cells to stationary flashing stimuli, while Bicu increased the responses and suppressed the inhibition exerted by the surround. The number of spikes evoked by a moving bar/spot decreased after applying GABA in 76.6% of the cells (n = 60) and increased in 90.0% (n = 60) of the cells after Bicu. Similar effects on the spontaneous activities were observed. In addition, 65.0% of the 60 cells recorded have enlarged movement receptive fields after application of Bicu. GABA and Bicu have some effects on the orientation selectivity of the collicular cells too.

Animals↗