Showing papers by "National University of Singapore published in 1975"

Nasopharyngeal carcinoma. X. Presence of epstein-barr genomes in separated epithelial cells of tumours in patients from Singapore, Tunisia and Kenya.

Abstract: Nasopharyngeal carcinoma (NPC) biopsies from Singapore, Tunisia and Kenya were compared, before and after separation of epithelial and lymphoid cells, for their EBV-DNA content, using the cellular DNA-EBV-cRNA hybridization test. In all instances where successful separation of the two cell types was achieved, epithelial tumour cells showed a higher EBV-DNA content than lymphoid cells or tumour before cell separation. It is, therefore, suggested that EBV-DNA is mostly limited to epithelial cells. No significant difference was observed between NPC tumours originating from various geographical areas.

The vortex-street structure of ‘turbulent’ jets. Part 1

Abstract: It was suggested by Lau, Fisher & Puchs (1972) that the basic structure of a ‘turbulent’ round jet might consist, essentially, of an axial array of fairly evenly spaced vortices moving downstream in the mixing region of the jet. The present experimental study is an attempt to establish this hypothesis on a sound footing. The problem which was posed was first to find proof of the existence of a fairly regular pattern in the mixing region, and second to extract detailed information on the component parts of this pattern to identify the nature of the structure.Hot-wire signals in the mixing layer are known to possess a predominance of spikes. In the region closer to the high velocity side of the layer, these spikes tend to be downward ones whilst in the opposite region, they are upward. These spikes have been attributed to the entrainment mechanism in the mixing layer and had been thought to be random. A closer study of time-history curves of these hotwire signals suggests that they might not be as random as would appear at first glance. A probability analysis was conducted of the time intervals between the successive downward spikes in the u′ signals, and it was found that indeed the highest probability occurred when the time interval corresponded to a frequency equal to the vortex passing frequency.A time-domain averaging (or eduction) technique was used to try to identify the nature of the flow structure using the spikes to trigger the eduction process. On the basis of these results it would seem that the suggestion of a vortex street is well founded. Furthermore, it appears that, as the individual vortices in the street move downstream, they are continuously transporting fluid masses across the mixing layer, and it is this effect which is producing the Reynolds stresses in the mixing layer, and causing the spikes in the u’ signals in this region.

Arsenic poisoning from anti-asthmatic herbal preparations.

Abstract: Arsenic poisoning, a disease of the past, was recently found in 74 patients in Singapore over a 15-month period. Most victims (70%) had a chronic form of poisoning and 64% of the cases were caused by a local anti-asthmatic herbal preparation containing 12,000 ppm of inorganic arsenic sulphide. The other patients were poisoned by six other brands of herbal preparations used for the treatment of asthma and a variety of other illnesses. Subsequent investigations revealed another 22 other brands of Chinese herbal preparations containing high concentrations of inorganic arsenic ranging from 25 to 107,000 ppm, of which most were imported. Nearly 40% of the patients had taken the medicine for less than six months, but the others had a longer history of exposure ranging from one to 15 years. Systemic involvement was confined mainly to the skin (91%), nervous system (51%), gastrointestinal system (23%) and blood (23%). Malignancy of the skin was present in six patients, and of the visceral samples, toxicological confirmation was found in half of the cases investigated. There was no correlation between the clinical status of the patients and their tissue arsenic content. The importance of arsenic poisoning by herbal preparations is discussed, as there are no known reports of their association.

Light and electron microscopic observations of the life cycle of Sarcocystis orientalis sp. n. in the rat (Rattus norvegicus) and the Malaysian reticulated python (Python reticulatus).

Abstract: A light and electron microscopic study of Sarcocystis orientalis sp. n. was made. The life cycle of this parasite is in two hosts. Gametogony is in the intestinal epithelial cells of a predator, Python reticulatus. Isospora-like oocysts developed. Sporocysts average 9.1 by 7.7 μm. Rats (Rattus norvegicus) were infected with sporocysts and asexual stages developed. Ten days after infection large zoites (average 7.85 by 2.48 μm) were observed free in peripheral blood and within white blood cells. Small schizonts producing merozoites 2–3 μm long were seen in lung tissue. Tissue cysts developed in skeletal muscle and produced numerous cystozoites (average 5.53 by 1.38 μm). Fine structure was similar to previously described Sarcocystis spp.

Comparison of the effectiveness of single-direction and double-direction phototherapy for neonatal jaundice.

Abstract: Two matched groups of Chinese infants with "idiopathic" jaundice were subjected to phototherapy, one group to "single-direction" phototherapy and the other to "double-direction" phototherapy. The total energy output on the skin of the infants was similar in both groups. The 24hour fall in bilirubin levels was almost identical in the two groups; the number of infants in each group achieving bilirubin levels less than 11 mg/100 ml at 24, 48, and 72 hours was statistically very similar too. Where the energy output can be adjusted to supply a constant dose on the infant (by varying the energy output in inverse proportion to the skin area exposed), the effect of varying the skin area under phototherapy is minimal. However, the total area of skin exposed to phototherapy under uniform lighting conditions is important because it determines the dose of energy output acting on it, and hence the effectiveness of the procedure.

Fine structure of the gastric epithelium of the coral fish, Chelmon rostratus Cuvier.

Abstract: The gastric lining of higher vertebrates is known to consist of the following cell types : surface epithelial cells, mucous neck cells, zymogenic cells, parietal or oxyntic cells and argentaffin. cells (Ham, 1969 ; Bloom and Fawcett, 1968). Except for the epithelial cells, all the other cell types are found in the gastric glands. The mucosal lining of the gastrointestinal tract of terrestrial vertebrates have been well described (Helander, 1962 ; Sedar, 1962 ; Ito and Winchester, 1963 ; Schofield and Silva, 1968), but similar studies of the gut of aquatic animals, especially fishes, are relatively few. Most of the digestive tract of fishes have been at the light-microscopic level. AlHussani (1949a, b) reported the histological features of the gut of some cyprinids ; Bullock (1963) described the intestinal histology of some salmonids ; Gupta (1971) studied the gut of carnivorous fish, Xenentodon cancila ; and Weisel (1973) reported on the digestive tract of the paddlefish, Polyodon spat hula. Recently, Iwai (1967, 1968) described the digestive tract of some teleost larvae at the electron microscopic level. The present study is to further the observations made by Tan and Teh (1974a, b) on the gastrointestinal tract of a tropical coral fish, Chelmonrostratus Cuvier. This paper emphasizes on the ultrastructural features of the mucosal lining of the stomach of this fish.

Panniculitis (Rothmann-Makai), with good response to tetracycline.

Abstract: SUMMARY A case of idiopathic circumscribed panniculitis of the legs, with features consistent with that of the Rothmann-Makai syndrome, is reported. The response to a 10-week course of oral tetracycline therapy was impressive. It is suggested that the anti-lipase activity of tetracycline could account for this response.

Ultrastructural and functional differentiation of the midgut of the sugar cane beetle, Protaetia acuminata (F.) (Coleoptera: Cetoniidae)

Abstract: The midgut of Protaetia is a simple straight tube. Ultrastructural, cytochemical and simple physiological studies show that it is differentiated into anterior, mid, and posterior regions, carrying out different functions. The anterior midgut cells have numerous rough endoplasmic reticulum, multivesicular bodies and dense vesicles at the luminal side. Basally, there are abundant intracellular sinuses. The mid midgut contains glycogen deposits. The posterior midgut differs cytochemically from the anterior midgut and the cells are characterized by deep narrow basal invaginations. It is suggested that enzyme secretion and nutrient absorption mainly occur at the anterior midgut, intermediary metabolism occurs at the mid midgut and the posterior midgut functions in ion secretion. The lumen of a regenerative crypt is filled with a “fuzz”, which is probably a mucoprotein. The significance of this “fuzz” is unknown.

Immunodeficiency to hepatitis B virus infection and genetic susceptibility to development of hepatocellular carcinoma.

Abstract: The high frequency of hepatitis B antigen (HBsAg) in hepatocellular carcinoma (HCC) patients has led to the hypothesis that immunoresponsiveness to hepatitis B virus (HBV) may be deficient in some patients, and that the immune response deficiency may have a genetic basis. Radioelectrocomplexing (REC), a radioimmunoassay in gel based on the principle of counterimmunoelectrophoresis (CIE), has been used to identify four HBV immune status subgroups: 1) HBsAg +ve/HBsAb +ve; 2) HBsAg +ve/HBsAb -ve; 3) HBsAb -ve/HBsAb +ve; 4) HBsAg -ve/HBsAb -ve/HBsAb -ve. These subgroups comprise 2, 6, 70, and 22 percent, respectively, among blood donors, and 32, 19, 23, and 26 percent, respectively, among HCC patients. Although the HBV exposure rates in the two groups were similar, the immune complexemic rates and HBs antigenemic rates were significantly higher in HBB patients than in the blood donors. It is proposed that the failure of termination of HBV infection revealed by these high rates reflects an immunodeficiency state characterized by an inability to produce high-avidity HBsAb. The immunodeficiency might have a primary genetic basis, or it might be secondary to the immunodepressive effects of concurrent viral or parasitic infections.

The significance of the fovea palatini in complete denture prosthodontics

Abstract: Clinical, radiographic, and histologic studies of the fovea palatini indicate that they were positioned 1.31 mm. (mean of 100 subjects) in front of the vibrating line. Radiographically and histologically, the foveae were located in soft tissue covering the hard palate in all specimens. Histologically, complex nerve endings were found just anterior to the foveae and spreading to the soft palate. The findings were related to clinical aspects of complete dentures.

The biosynthesis of 3-methoxy-4-hydroxyphenylglycol sulphate by liver and brain.

Abstract: —3-Methoxy-4-hydroxyphenylglycol (MHPG) formed a sulphate conjugate when incubated with ATP, Mg2+ ions, Na235SO4 and the high-speed supernatant preparations of rabbit or rat brain. The same reactions could be catalysed by similar enzyme preparations from liver. The sulphated product was separated and identified by paper chromatography. On acid hydrolysis, it released both Na235SO4 and the free glycol. The measurement of this labelled sulphate was used as a specific assay procedure for determining the overall sulphoconjugatory process. The pH optimum of the reaction is 7.8. For rabbit brain, the Km for Na2SO4 determined for the activating system is 3.6 × 10−4m, and that for MHPG for the sulphotransferase reaction is 1.05 × 10−4m. The specific enzyme activity, expressed as nmol 35SO4 incorporated/h/mg protein for a 30-min assay is as follows: rat brain, 2.8; rabbit brain, 1.6; rat liver, 33.4and rabbit liver, 15.0. Dithiothreitol at 3 mm concentration had no significant effect on the sulphation of MHPG in all these preparations.

An ultrastructural study of the synaptic glomeruli in the intermediolateral nucleus of the rat.

Abstract: On a constate que le neuroptile du noyau intermedio-lateral du rat contient de nombreux glomerules synaptiques gliaux encapsules dans lesquels se trouve habituellement un dentrite ou axe terminal tres visible surmonte par de petits boutons et des dentrites. Les glomerules sont accompagnes de synapses axo-axonaux qui peuvent etre le corrolaire structural d'une inhibition presynaptique. La signification fonctionnelle des glomerules et des synapses axo-axonaux est discutee.