Biomedical subjects

M L Ng

Publications and source records attributed to M L Ng.

At least 19 recordsLinked to original sources

PubMed1997

Interaction of kunjin virus with octyl-D-glucoside extracted Vero cell plasma membrane.

Initial experiments using whole cells have shown that there were specific and saturable interactions between kunjin (KUN) virus and receptor molecules on the Vero cell surfaces. Solubilisation of Vero cell plasma membranes with octyl-D-glucoside (OG) yielded an extract which also interacted specifically with KUN virus. This was proven using electron microscopy. When the virus-OG-extract complex was exposed onto Vero cell monolayers, no KUN virus was observed to enter into the whole cells. This would imply that there was virus-receptor interaction with the OG-extract leaving no free virus to attach to the whole cells. The attachment kinetics of KUN virus was studied further using the Scatchard analysis which indicated the involvement of more than one interactive macromolecule in the attachment event.

Animals↗

PubMed1997

Speech performance of adult cantonese-speaking laryngectomees using different types of alaryngeal phonation.

The purpose of the present study was to compare the speech performance of four types of alaryngeal phonation-electrolaryngeal (EL), pneumatic artificial laryngeal (PA), tracheoesophageal (TE), and standard esophageal (SE) speech-by adult Cantonese-speaking laryngectomees. Subjective ratings of (1) voice quality, (2) articulation proficiency, (3) quietness of speech, (4) pitch variability, and (5) overall speech intelligibility were given by eight naive individuals who had no prior experience with any form of alaryngeal speech. Results indicated that SE and TE speech was perceived to be more hoarse than PA and EL speech. EL speech was associated with significantly less pitch variability, and PA speakers produced speech with the least amount of perceived noise. However, articulation proficiency and overall speech intelligibility were found to be comparable in all four types of alaryngeal speakers.

Aged↗

PubMed1997

Some aerodynamic and acoustic characteristics of acute laryngitis.

The purpose of the present study was to describe the effects of acute laryngitis on some aerodynamic, acoustic, and perceptual measures. Eleven subjects with diagnosed acute laryngitis due to upper respiratory infection were recorded during a laryngitic episode and 1 week to 10 days after amelioration of the laryngitic condition. Fundamental frequency, values, collapsed across the five vowels, were significantly reduced in the laryngitic compared with the normal speaking condition. The decrease in fundamental frequency associated with acute laryngitis suggests an increase in the mass of the vocal folds. In addition, aerodynamic values differed significantly for the laryngitic condition compared with the normal speaking condition, suggesting the presence of laryngeal hypofunction. Perceptual data indicated that speakers in the laryngitic condition were judged to have a hoarse voice when compared with the normal speaking condition.

Acute Disease↗

PubMed1996

Perinatal vitamin A (retinol) status of northern Canadian mothers and their infants.

Vitamin A (retinol) status was determined in two groups living in the northern part of Canada: native (Indian and Inuit) and non-native (Caucasian). The dietary intake of vitamin A and its plasma concentration were measured prenatally, at delivery and postnatally in mothers. Plasma concentrations were also measured at birth and postnatally in their infants. The mean vitamin A intake of native mothers was significantly lower than that of non-native mothers, 661 +/- 485 versus 1,377 +/- 1,418 retinol equivalents (p < 0.00005), with a higher risk of deficiency without supplementation, 35% versus 8%. Plasma retinol concentrations, although not in the deficient range, were significantly lower in native than non-native mothers prenatally and postnatally. Infant mean plasma retinol concentrations at birth averaged only 52% of those of their mothers and were significantly lower among native than non-native infants although no clinical evidence of vitamin A deficiency was noted. We speculate that vitamin A supplementation in native Northern Canadian mothers during pregnancy and in their neonates during infancy may have a role to play in the prevention of vitamin A deficiency. We also postulate that plasma retinol concentrations of 50-60% of maternal levels and between 0.7 and 2.5 mumol/l represent a 'normal' range for newborn infants.

Canada↗

PubMed1996

Immunochemical and genetic analysis of the p53 gene in liver preneoplastic nodules from aflatoxin-induced rats in one year.

Mutations of the p53 tumour-suppressor gene in human hepatocellular carcinomas from certain geographic areas appear to be associated with high dietary exposure to aflatoxin B1 (AFB1). In this study, the effects of AFB1 on p53 locus at the preneoplastic stage of rat liver oncogenesis were assessed. Male Wistar rats were treated with a single dose of 1.5 mg AFB1/kg body weight by a gastric tube. Liver biopsies over a period of one year were examined for aberrations of the p53 gene together with the expression of placental glutathione-S transferase (GST-P), a marker for preneoplasia. Immunohistochemistry, Western blot, polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing techniques were used. AFB1 induction resulted in GST-P overexpression, forming GST-P-positive multi-foci and nodules of hepatocytes, but no aberrations in the p53 expression and the microstructure of exons 5-8 of the p53 gene. These results suggested that p53 mutation(s) might not occur at this early stage of AFB1-induced hepatocarcinogenesis.

Aflatoxins↗

PubMed1995

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↗

PubMed1995

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↗

PubMed1994

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↗

PubMed1994

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↗

PubMed1994

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗

PubMed1993

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↗