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Biomedical subjects

M L Ng

Publications and source records attributed to M L Ng.

At least 55 records · Page 3Linked to original sources

Structural features of tracheal tube biofilm formed during prolonged mechanical ventilation.

The dissemination of tracheal tube biofilm into the mechanically ventilated lung has been proposed as a contributory factor in the pathogenesis of ventilator-associated pneumonia. In the present study, conventional light microscopy, confocal laser scanning microscopy, and scanning electron microscopy were used to examine luminal tracheal tube biofilm in tubes from ten consecutive medical intensive care patients. Biofilms also were cultured. No tube contained a predominantly microbial aggregate. Microorganisms were either dispersed throughout the biofilm or restricted to the most superficial layer. Neutrophil polymorphonuclear cells were present in all biofilms in a pattern suggesting that a layering or stratification had taken place. The distribution of neutrophils and microorganisms was consistent with a progressive accretion of respiratory secretions, rather than formation of a predominantly microbial biofilm.

Adult↗

Sexual dysfunction in China.

In recent years, many sexual dysfunction cases cropped up in various parts of China. The number of hospital with sexual dysfunction clinics has also increased. They are concentrated more in the big or coastal cities. In these clinics, compared with those of the west, there is a greater proportion of retarded ejaculation cases and a lower proportion of female patients. Deficient sexual knowledge is the commonest cause of sexual dysfunction especially with respect to the sexual problems of the aged. The treatment approaches used by these clinics combine psychotherapy, behavioural therapy, medication and the application of physical aids, and are in line with modern international trends. However, these clinics are only in their infancy and still face many obstacles. The government is still quite stringent on the control of drugs for treatment of sexual dysfunctions and also sees many sex aids as obscene. However, in view of the rapid development, the Chinese readiness to accept new ideas, the diligence of the Chinese medical professionals and the establishment of the Chinese Sexology Association in 1994, it is hoped that China will soon become one of the more advanced countries in Asia for the treatment of sexual dysfunctions.

China↗

Flavivirus West Nile (Sarafend) egress at the plasma membrane.

West Nile (Sarafend) virus was distinctly observed to bud from the plasma membrane rather than mature intracellularly. This has been observed with transmission electron microscopy. Using conventional scanning electron microscopy, budding at the plasma membrane especially at the filopodia was clearly illustrated. Immunogold labelling against the virus envelope protein was also performed to confirm this mode of exit. The gold particles were observed to be located at the sites where virus budding was seen under the field emission scanning electron microscope.

Animals↗

Cryosubstitution technique reveals new morphology of flavivirus-induced structures.

Cryotechniques in combination with electron microscopy were used in an attempt to obtain more precise morphological details of flavivirus-induced structures. From conventional chemical fixation procedure, proliferation of endoplasmic reticulum, formation of microtubule paracrystals and clusters of smooth membrane vesicles (with 'thread-like' enclosures) were observed. These induced changes are typical for flavivirus infections. The images obtained from cryosections were disappointing as the structures were not well preserved. On the other hand, cryosubstituted-infected cells gave revealing images of the virus-induced structures. The most obvious difference between the cryosubstituted and chemical fixed processes was on the morphology of the 'thread-like' structure. The 'thread-like' structures instead appeared as dense cores. The morphology of the virus particles was also better defined. The envelope of the virus appeared clearly differentiated from the nucleocapsid. The most important finding was that the cryosubstituted technique was able to preserve the structures of the flavivirus nucleocapsids which so far has not been convincing reported with chemical processing.

Animals↗

Thyroid function and pubertal development in malnutrition.

Thyroid function and pubertal development of aborigines (Orang Asli) and Malays at different socioeconomic strata were assessed among 1136 subjects aged 7 years and above. Anthropometric measurements, goitre and pubertal staging were done. Serum thyroxine (T4), triiodothyronine (T3) and growth hormone were measured using radioimmunoassays (RIA) and serum thyroid stimulating hormone (TSH) by immunoradiometric assays (IRMA). It was found that serum T3 in children was significantly higher in Malays from rural areas, girls and children aged less than 13 years. However, in adults, T3 was significantly associated with anthropometric indices. On the contrary, serum T4 levels were higher among children from urban areas. In adults, serum T4 levels were significantly related to nutritional status and they increased according to the levels of social development, being lowest in remote areas and highest in urban areas. However, serum TSH levels were significantly higher in Orang Asli at all ages and among malnourished children. By using multiple regression, apart from age, gender and ethnicity, nutritional status was a significant predictor for T3 levels in children and adults. Presence of goitre was an important factor which determined the T4 levels in children and adults after controlling for other factors. It was also a predictor for TSH levels in children but not in adults. Fasting serum growth hormone (GH) levels were significantly higher among less privileged groups and decreased according to social development. Serum growth hormone was negatively correlated with anthropometric indices and had a significant association with malnutrition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Brefeldin A affects West Nile virus replication in Vero cells but not C6/36 cells.

A fungal metabolite brefeldin A (BFA) was used to study virus-host interaction in glycoprotein processing in West Nile virus-infected Vero and C6/36 cells. The results indicated that as little as 1 microgram/ml of BFA resulted in complete breakdown in the Golgi organelle in infected Vero cells. This led to modifications of the glycoproteins which could not be efficiently used in infectious virion formation. In contrast, as much as 10 micrograms/ml of BFA in culture medium did not affect either glycoprotein formation or production of infectious particles in C6/36 cells. The results showed that in Vero cells, the transport of glycoproteins to the Golgi apparatus is important in West Nile virus infection. It also showed that BFA could be used as a tool to understand further the trafficking of glycoprotein from the ER to Golgi in flavivirus infection in Vero cells.

Animals↗

The effect of time between doses on serological response to a recombinant multivalent pilus vaccine against footrot in sheep.

The response of sheep to a recombinant multivalent footrot vaccine containing pilus antigens was examined after the administration of two doses of vaccine at intervals ranging from 2 to 52 weeks. Agglutinating antibody titres were measured 3 weeks after the second vaccination and showed that lengthening of the interdose interval results in higher agglutinin titres. The capability of sheep to mount an increasingly strong immune response as the interval between doses is increased provides an opportunity to maximise the usefulness of vaccination by administering the first dose well before an expected footrot transmission period. This advantage of increasing the interdose interval has not been reported for traditional, whole-cell footrot vaccines, and use of the new pilus vaccine in this manner may improve prospects for disease control. Furthermore, sheep given a third dose either 6 or 12 months after their initial two-dose vaccination program achieved significantly higher titres than those elicited after the second dose, suggesting the likelihood of further improvement in disease control in successive seasons.

Agglutination Tests↗

Prevalence of NIDDM and impaired glucose tolerance in aborigines and Malays in Malaysia and their relationship to sociodemographic, health, and nutritional factors.

OBJECTIVE: To determine the prevalence of diabetes mellitus and IGT in different ethnic groups living in the same physical environment and to find their relationship to nutritional status and dietary intake. RESEARCH DESIGN AND METHODS: The study was conducted among Malays and Orang Asli in six rural and urban locations in Malaysia. OGTTs were performed on 706 adult subjects > or = 18 yr of age. WHO criteria were used for diagnosing diabetes mellitus and IGT. RESULTS: The overall prevalence of diabetes mellitus and IGT among Orang Asli was 0.3 and 4.4% compared with 4.7 and 11.3%, respectively, among Malays. This increased prevalence of glucose intolerance among Malays was associated with higher levels of social development. Among rural Malays, the crude prevalence of diabetes in a traditional village was 2.8% and in the land scheme was 6.7%, whereas urban Malays had a prevalence of 8.2%. In contrast, the prevalence of IGT (10.5-14.8%) was higher among rural Malays, compared with 9.6% among urban Malays. Ethnic group, > or = 40 yr of age, an income > M$250, fewer daily activity, and obesity were associated with a higher prevalence of diabetes. CONCLUSIONS: Diabetes mellitus and IGT, which were more common among Malays than Orang Asli, were associated with more affluent life-styles and modernization.

Adult↗

Usefulness and limitations of thyrotropin measurements as a first-line test for follow-up of Graves' patients.

We evaluated the usefulness of sensitive thyrotrophin hormone (TSH) measurements in determining the thyroid status in the follow-up of Graves' patients undergoing medical treatment with thionamides. Out of a total of 186 serum samples tested, TSH levels were suppressed in 123 (66.1%), normal in 32 (17.2%) and elevated in 31 (16.7%) cases. Total T4, or T3 or both were elevated only in 97 (74.8%) cases of TSH-suppressed patients, indicating that TSH is less discriminatory as a first-line test for patients under treatment due to the hypothalamic-pituitary lag period. No comparisons with free T4 or free T3 were done in this study. Both total T4 (120 +/- 28 nmol/l) and TBII (23 +/- 21%) levels were significantly greater (p < 0.02) in the euthyroid group with suppressed TSH. This may suggest that persistence of a thyrotoxic state may still be present.

Adolescent↗

Fasting growth hormone levels in diabetes mellitus.

Fasting serum growth hormone (GH) levels of different groups of diabetic patients were measured and compared to age-matched normal subjects. Insulin-dependent diabetes mellitus (IDDM) children (aged 12-17 years) were found to have significantly lower fasting GH levels than age-matched normal children (p < 0.001). In the adult age groups of 18-44 and 45-76 years, the IDDM patients showed increased fasting GH levels compared to age-matched normal subjects (p < 0.06 and p < 0.001 respectively) and non-insulin-dependent diabetes mellitus (NIDDM) patients (p < 0.05 and p < 0.001 respectively). The fasting GH levels of IDDM patients of the age group 18-44 years also showed significant correlations with glycated haemoglobin (r = 0.510, p = 0.002) and fasting blood sugar levels (r = 0.571, p = 0.01).

Adolescent↗

Effect of gender and age on fasting serum growth hormone levels in normal subjects.

Fasting growth hormone (GH) level is an important reference level in dynamic tests of GH secretion. Other studies have demonstrated sex and age variation in the rate of GH secretion. We analysed fasting serum samples from 377 normal subjects (193 males and 184 females, age range 6 to 81 years old), using our in-house enzyme immunoassay. We found sex differences in fasting GH levels to be only significant in the prepubertal children (Tanner stage I), being higher in girls than in age-matched boys (p < 0.05). Both sexes showed age-dependent changes in fasting GH levels (p < 0.001); highest levels were achieved at puberty and subsequently declined with advancing age. Hence, the physiological sex difference and age-dependency in GH secretion can also be demonstrated in single fasting samples.

Adolescent↗

Thyroid hormones and autoantibodies in pregnant patients with thyroid diseases.

Serum concentrations of thyroid stimulating hormone (TSH) and thyroid autoantibodies in pregnant patients with thyroid disease at various stages of pregnancy were determined by in-house ELISAs. In normal pregnancy, serum TSH levels were significantly elevated (p < 0.05) from 13 weeks of gestation. The normal reference ranges for TSH for the second (0.6-5.0 mIU/l) and third trimester (0.6-5.6 mIU/l) were significantly higher (p < 0.05; p < 0.01 respectively) compared to 0.4-4.5 mIU/l for the first trimester. In pregnant thyroid patients, serum TSH levels correlated highly (p < 0.001) to T4 (r = 0.740), FT4I (r = 0.683) and MicAb (microsomal antibodies) (r = 0.825) but weaker (p < 0.01) to T3 (r = -0.512), FT3I (r = 0.520) and TgAb (thyroglobulin antibodies) (r = 0.618). Thus, measurement of TSH with the highly sensitive ELISA (enzyme linked immunosorbent assay) would form a useful first line test for thyroid dysfunction in pregnancy while measurement of thyroid autoantibodies would aid in the diagnosis of autoimmune hypothyroidism.

Adult↗

Serum thyroid stimulating hormone (TSH) in malnutrition: preliminary results.

This is a report of a cross sectional study involving 3 groups of children, moderately malnourished (BMI < 15), mildly malnourished (BMI 15-18) and well nourished (BMI > 18) to determine the differences in hormonal and biochemical parameters between the groups. The children were of age range from 7-17 years old. The children were from the same area with exposure to the same food, drinking water and environment. There were significant differences in the nutritional indices between the three groups. No differences were observed in levels of triiodothyronine (T3), thyroxine (T4) and T3:T4 ratio. Significant difference however was found in the TSH levels using highly sensitive IRMA TSH assays. Moderately malnourished children had higher TSH levels (p < 0.05) compared to mildly malnourished and well-nourished children. No difference was found between the mildly malnourished and well-nourished groups. There were no significant differences in serum cortisols done at similar times, fasting growth hormone and calcium. Serum alanine transminase (ALT) however was higher in moderately malnourished than in well-nourished children. Thus using highly sensitive IRMA TSH assays, we were able to detect differences in TSH levels even though T3, T4 and T3:T4 ratio, cortisol, growth hormone and calcium were normal, implying in moderately malnourished children, a higher TSH drive to maintain euthyroid state.

Adolescent↗

An in-house enzyme-linked immunoabsorbant assay for human growth hormone.

A simple, non-isotopic in-house enzyme-linked immunoabsorbant assay (ELISA) for human growth hormone (GH) was developed. The assay involved using in-house polyclonal anti-GH adsorbed onto 96-well microtitre plates, commercially prepared mouse monoclonal anti-GH, and goat anti-mouse IgG horseradish peroxidase detection system. Results of recovery and parallelism studies ranged from 95%-106% and 98%-101% respectively, of the expected values. The detection limit of the assay was 0.008 mIU/well or the equivalent to 0.4 mIU/L of undiluted serum. Intra- and interassay coefficients of variations were 4.8%-7.9% and 6.5%-8.7% respectively. Serum GH levels measured in this assay correlated well with those measured in established in-house radioimmunoassays (r = 0.985, p < 0.001) and immunoradiometric assay from NETRIA (r = 0.984, p < 0.001).

Animals↗

The effect of cassava leave intake on thyroid hormone and urinary iodine.

The effect of consuming large amounts of cassava leaves on thyroid function and urinary iodine was studied. Twenty volunteers were given 200 gm of boiled cassava leaves twice a day for 12 consecutive days. Thyroid hormones triiodothyronine and thyroxine were significantly lower by 9 days. Urinary iodine excretion was also significantly decreased. Cassava leaves, consumed in large amounts by aborigines, probably caused goitres by decreasing iodine absorption.

Adult↗

Detection of flavivirus antigens in purified infected Vero cell plasma membranes.

The types of Kunjin virus-specified proteins present in purified Vero cell plasma membrane were studied. Immunofluorescence of unfixed Kunjin virus-infected whole cell monolayers, indicated that two structural proteins (envelope and prM) and three non-structural proteins (NS1, 3 and 5) were found at the plasma membrane. There was no obvious progressive accumulation of the observed antigens over the time periods between 8 to 24 h p.i. Thus SDS-PAGE analysis was performed using purified radiolabelled Vero cell plasma membranes. From the protein profiles, all five antigens detected by immunofluorescent staining were also present. In addition, two smaller molecular weight non-structural proteins NS4B and NS2B were also observed. Generally, all the non-structural proteins found in the purified plasma membranes were of the same molecular weights as those found in infected whole cell lysate. Interestingly, both the structural proteins, i.e., envelope (E) and prM proteins in the plasma membrane sample were of higher molecular weights as compared to the counterparts in the infected whole cell lysate. The envelope protein of purified extracellular Kunjin virus was also lower in molecular weight compared to the same protein in the plasma membrane.

Animals↗

The community meeting: a review.

Community meetings are conducted in many psychiatric units and institutions. The formats, methods and theoretical backgrounds of the meetings however are very diversified. Most of the claims for beneficial effects are based on clinical impressions or indirect observations. The few structured studies that have been performed show that community meetings have the effect of reducing unfavorable ward incidents, especially aggressive ones. Much research remains to be done to confirm these findings and to elucidate the basic ingredients of the community meeting in providing beneficial effects.

Communication↗