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Biomedical subjects

K Lim

Publications and source records attributed to K Lim.

83 records · Page 5Linked to original sources
PubMed1988

Human placenta S-adenosylmethionine: protein carboxyl O-methyltransferase (protein methylase II). Purification and characterization.

1. Protein methylase II was purified from human placenta approx. 8700-fold with a yield of 14%. 2. Unlike protein methylase II from other sources, the activity of human placenta enzyme was completely inhibited by 2 mM Cu2+. Other divalent ions were without effect. 3. Human chorionic gonadotropin (HCG), immunoglobulin A and calf thymus histones served as good in vitro substrates for the enzyme, particularly HCG. 4. The Km for S-adenosyl-L-methionine and Ki for S-adenosyl-L-homocysteine were 2.08 x 10(-6) and 5.8 x 10(-7) M, respectively. 5. The protein methylase II activity in human placenta changed with gestational age, the activity at 1st and 2nd trimester being approximately twice that of term placenta.

Cations, Divalent↗
PubMed1967

WHO respiratory disease survey in children: a serological study.

This paper is a report on the first (serological) phase of a study organized by WHO in collaboration with the WHO International Reference Centre for Respiratory Virus Diseases other than Influenza in Bethesda, Md., USA, to define the viral etiology of severe respiratory infections in children, particularly in tropical areas. Paired sera from 528 children up to 5 years old admitted to hospital with severe respiratory illness of probable viral etiology were collected in 10 countries and sent frozen to the International Reference Centre, where standard complement-fixation tests were made for the following agents: parainfluenza virus types 1, 2 and 3, influenza virus types A and B, adenoviruses, respiratory syncytial virus, Mycoplasma pneumoniae, Coxiella burneti and psittacosis-ornithosis.Some 41% of paired sera showed rising antibody titres for one or more of these agents, multiple infections being observed in 8%. In most of the countries the pattern of infection was similar. RS virus was the most important respiratory tract pathogen of early life, particularly in the first year of life and in cases of bronchiolitis and pneumonia; the parainfluenza viruses were next in importance, particularly in cases of croup, but, in contra-distinction to RS virus infections, they were commoner in older children. Influenza, adenoviruses, and M. pneumoniae were of moderate importance, and C. burneti and the psittacosis-ornithosis agents were relatively rare. This pattern is similar to that which has been observed in temperate climates.

Africa↗
PubMedDate not supplied

Cell death in retinoblastoma: electron microscopic, immunohistochemical, and DNA fragmentation studies.

Apparent cell loss by apoptosis occurs in carcinomatous tissue. To investigate cell death in retinoblastoma (Rb), ultrastructural examination, ApopTag staining, electrophoresis to detect apoptotic DNA fragmentation, and flow cytometric studies were performed. Immunostaining for the oncogenic products bcl-2 and p53 was also carried out. Relationships between the proliferation fraction (PF), apoptotic index (AI), and the distribution of bcl-2 and p53 were investigated according to the degree of histologic differentiation of Rb. Ultrastructurally, two patterns of cell death were seen. Necrotic cells exhibited vacuolation of cytoplasmic organelles with a marked lytic change in the karyoplasm and cytoplasm. In contrast, apoptotic cells were characterized by crescentic margination of chromatin, condensation of karyoplasm and cytoplasm, and fragmentation of the nucleus. Differentiated Rb had a low AI value (< 1%), whereas undifferentiated Rb had a high AI value (> 8%). The PF of undifferentiated RB (31%) was significantly higher than that of differentiated RB (14%). Analysis of DNA fragmentation using 3'-end labeling with terminal transferase indicated that undifferentiated Rb has increased DNA cleavage. The distribution of apoptotic bodies within Rb was inversely correlated with the expression of bcl-2. A majority of tumor cells of differentiated Rb were negative for p53, whereas 20-40% of tumor cells of undifferentiated Rb showed a positive reaction for p53. These findings suggest that the degree of susceptibility to apoptosis is closely related to PF, is inversely related to the degree of differentiation of Rb, and is protected by oncogene bcl-2.

Apoptosis↗
PubMedDate not supplied

Testosterone regulation of proto-oncogene c-myc expression in primary Sertoli cell cultures from prepubertal rats.

The expression of c-myc has been associated with cell proliferation through changes of nuclear function. To evaluate the possibility that the proto-oncogene c-myc plays a role in testosterone-dependent gene regulation, the effects of testosterone on the expression of c-myc have been investigated in primary Sertoli cell cultures. Testosterone increased c-myc mRNA levels, with maximal stimulation reached in 16 hours. The induction of c-myc mRNA was dependent on the concentration of testosterone. Testosterone-induced c-myc mRNA levels were also increased in cells after addition of cycloheximide but reduced by actinomycin-D pretreatment. Even in the absence of hormone in culture medium, c-myc mRNA was clearly detectable in Sertoli cells from 8-day-old rats but hardly detectable in cells from 14 and 28 days of age. Testosterone stimulated c-myc mRNA expression in the Sertoli cells from only 8-/and 14-day-old rats. These results suggest that testosterone induces c-myc mRNA levels in the primary Sertoli cells from prepubertal rats, and then transient expression of c-myc may be responsible for some of the regulatory roles of testosterone-dependent genes in the Sertoli cells. The biological significance of testosterone-dependent c-myc induction is not known.

Animals↗