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Biomedical subjects

F Cheng

Publications and source records attributed to F Cheng.

63 records · Page 4Linked to original sources
PubMed1987

Increased glucose increases glomerular basement membrane in metanephric culture.

A model of in vitro renal development has been used to examine the effect of glucose on the glomerular basement membrane. Glomerular differentiation in this system progresses to an arborizing tuft of podocytes overlying well-formed basal lamina. The proportional amount of lamina densa and dense fibrillary matrix was increased in blastemas grown in an increased amount of glucose during the last 4 of 7 days in culture. These observations indicate that glucose itself can stimulate an accumulation of basement membrane, an excess of which is characteristic of diabetic microangiopathy.

Animals↗
PubMed1985

Characterization of nutritionally variant streptococci by biochemical tests and penicillin-binding proteins.

A comparative study of 60 strains of nutritionally variant streptococci (NVS) with 34 strains of Streptococcus mitis and 37 strains of Streptococcus sanguis II showed the presence of a red chromophore which was absent in the other streptococcal species. By using the conventional microbiological tests, only small differences were found between the NVS and the two other related species. In contrast a clear-cut delineation was found by the API 20 Strep system of identification. All NVS contained pyrrolidonylarylamidase, an enzyme which was absent in S. mitis and S. sanguis II strains, and lacked the alkaline phosphatase enzyme which was present in 56% of S. mitis strains and 62% of S. sanguis II strains. According to the additional enzymatic and biochemical tests of the API 20 Strep system, there were three biotypes among NVS. The major biotype included 33 of 60 strains which were characterized by the presence of both alpha- and beta-galactosidases and the capacity to hydrolyze trehalose. This biotype also showed a specific pattern of penicillin-binding proteins. These results show that NVS are recognized as a separate variety distinct from S. mitis and S. sanguis II species, despite some common biochemical properties. Moreover, the delineation of 33 strains with a specific biotype and a specific penicillin-binding protein pattern strongly suggests that a large part of NVS strains belong to an individual species.

Bacterial Proteins↗
PubMed1985

Respiratory abnormalities among workers in an iron and steel foundry.

A study of the health of 78 workers in an iron and steel foundry in Vancouver, British Columbia, was carried out and the results compared with those found in 372 railway repair yard workers who were not significantly exposed to air contaminants at work. The foundry workers were exposed to PepSet, which consists of diphenyl methane diisocyanate (MDI) and phenol formaldehyde and their decomposition products as well as to silica containing particulates. A questionnaire was administered by trained interviewers, and chest radiography, allergy skin tests, pulmonary function tests, and methacholine inhalation tests were carried out as well as measurement levels of dust and MDI. Compared with the controls, the foundry workers had more respiratory symptoms and a significantly lower mean FEV1 and FEF25-75% after adjustments had been made for differences in age, height, and smoking habit. Three workers (4.8%) had radiographic evidence of pneumoconiosis and 12 (18.2%) had asthma defined as presence of bronchial hyperreactivity, cough, and additional respiratory symptoms such as wheeze, chest tightness, or breathlessness. Sensitisation to MDI is probably the cause of asthma in these workers.

Adult↗
PubMed1984

Localization of collagen types IV and V, laminin, and heparan sulfate proteoglycan to the basal lamina of kidney epithelial cells in transfilter metanephric culture.

Mouse metanephric mesenchyme and embryonic spinal cord were cultured on opposite sides of a filter membrane. This resulted in formation of prenephronic vesicles after 36 hours in culture, S-shaped bodies after 2-3 days, and glomeruli and tubules after 4-7 days. The glomeruli consisted of an arborizing tuft of podocytes lying on a basement membrane without vascularization or a mesangial ingrowth. We have used antibodies to study the molecular composition of the nephron basement membrane at each stage of development. By immunofluorescence light microscopy, collagen Types IV and V, laminin, and heparin sulfate proteoglycan were expressed within the pericellular/intercellular matrix at the onset of morphologic differentiation. The molecules were organized into a linear basement membrane associated with epithelial cells during the prenephronic vesicle, S-shaped body, and glomerulus and tubule stages of development.

Animals↗
PubMed1981

Glomerular differentiation in metanephric culture.

Undifferentiated metanephric blastema, grown in transfilter culture with embryonic inductor, undergoes differentiation to nephrons, including glomeruli and tubules. As in natural nephrogenesis, mesenchymal cells aggregate and form a vesicle that elongates into an s-shaped loop; a bilaminar disc at the end of the s-shaped loop becomes the glomerulus. The glomerular tuft in culture is an arborizing structure of basement membrane covered with epithelium. The epithelial cells have foot processes separated by slit pores and bridged by slit diaphragms. The cells are coated with polyanionic material, demonstrable before the appearance of foot processes. The basement membrane of the tuft continues at a hilum with the basement membrane of Bowman's capsule. Laminae of basement membrane, lying between apposed layers of epithelium, enclose spaces that can be envisioned as vascular spaces for the ingrowth of glomerular capillaries in vivo. The glomerular structure creates, therefore, a sling for holding capillaries, as suggested by Zimmermann when he proposed the concept of the mesangium. There are, however, no blood vessels in the metanephric culture, and the glomerulus develops and differentiates without capillary ingrowth. The glomeruli lack mesangial cells and juxtaglomerular complex, suggesting that those are vascular derivatives. The development of the tuft does not depend upon invagination by sprouting blood vessels; it is inherent in the glomerular epithelium.

Animals↗
PubMedDate not supplied

A successful control programme for lymphatic filariasis in Hubei, China.

This paper describes the epidemiology and control of human lymphatic filariasis in Hubei province, China from the 1950s to the 1990s. Brugia malayi, transmitted by Anopheles sinensis, and Wuchereria bancrofti, transmitted by Culex quinquefasciatus, were found in 69 of 78 counties and cities. The distribution of filaria species was distinct, with B. malayi endemic in the plains, mixed infections in hilly areas, and W. bancrofti in the mountains. Before 1979, the microfilaria rate (mfr) in some villages was as high as 30.69%. Since 1979, large scale control programmes have been carried out and 27,875,267 blood examinations have been made. Up to 1988, the mfr in all endemic villages decreased to below 1%. From 1989 to 1991 about 200,000 people had their blood examined yearly and few cases were detected. The continued use of mass blood examination for filariasis surveillance is not economic at such low levels of infection, and it is suggested that selective treatment of microfilaremic persons should be the main control measure at this stage.

Adolescent↗
PubMedDate not supplied

Surveillance for low-level malaria.

Due to good detection and control, malaria has reached very low levels in China with the result that existing methods of surveillance, taking blood slides from all fever cases and those with a common cold, are finding very few malaria cases among the millions of persons examined. Passive case detection agents in areas of moderate and low endemicity in Hubei Province, China, were instructed to indicate on the form associated with each slide whether the patient was considered to be a clinical case of malaria (group 1), was thought to have malaria but did not have all the features (group 2), had fever alone and was not thought to be a case of malaria (group 3), or merely had a common cold (group 4). In the low endemic area (slide positivity rate 0.23%), only 5 cases in group 3 and 4 in group 2 were detected per 10,000 examinations. It is recommended that these categories be discontinued in malarious areas of low endemicity, to encourage greater efficiency in detecting cases in groups 1 and 2. In the moderately endemic area, with a slide positivity rate of 4.19%, all categories, including group 4, were considered valuable for detecting malaria cases.

Adolescent↗