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Biomedical subjects

J Sun

Publications and source records attributed to J Sun.

At least 721 records · Page 40Linked to original sources
PubMed1989

Extensive diversity of branched-RNA-linked multicopy single-stranded DNAs in clinical strains of Escherichia coli.

Recently it was shown that a clinical strain of Escherichia coli contains a reverse transcriptase that is essential for the synthesis of a branched-RNA-linked multicopy single-stranded DNA (msDNA). We now have examined 113 independent clinical isolates of E. coli for the existence of msDNA and found that 7 strains contained msDNA. Four of them were further analyzed by hybridization analysis, which indicated that three of the msDNAs were different, having little sequence homology. When the reverse transcriptase gene associated with one of these msDNAs was used as a probe, it did not hybridize with chromosomal DNA from the other strains containing msDNA. These results indicate that some clinical E. coli strains carry their own unique msDNA-synthesizing systems; msDNAs produced by these systems have little, if any, sequence homology in their RNA and DNA molecules and the reverse transcriptases required for the production of msDNA also have little sequence similarity. Such extensive diversity of the msDNA-synthesizing systems supports the notion that they were acquired by the E. coli genome late during the evolution of E. coli.

Blotting, Southern↗
PubMed1989

Improved brain metabolism with fructose 1-6 diphosphate during insulin-induced hypoglycemic coma.

The effect of fructose 1-6 diphosphate (FDP) on brain metabolism and brain function was investigated in hypoglycemic rabbits. The electroencephalogram and differences in oxygen content of arterial and cerebral venous blood were used as indicators for brain metabolic activity. Hypoglycemic coma was induced and maintained for 1 hour by insulin administration. At the onset of isoelectric EEG, six rabbits were treated with FDP and five rabbits received 0.9% saline. The animals were killed by an overdose of barbiturate 60 minutes after hypoglycemic recovery with glucose. FDP-treated rabbits had lower arterial glucose concentration after 40 minutes of treatment (p less than .05) and a significantly greater difference between the oxygen content of arterial and venous blood after 40 minutes (p less than .01), and after 60 minutes (p less than .025) of FDP infusion than saline-treated rabbits. FDP-treated rabbits also had a lower cerebral glucose-oxygen index than did saline-treated rabbits (p less than .005, after 20 and 40 minutes of FDP infusion). FDP administration was followed by a return of EEG activity during hypoglycemia, whereas saline produced no such effect. After glucose infusion, EEG activity was improved in FDP-treated rabbits; in saline-treated rabbits, minimal or no EEG activity was observed. The data suggest the possibility that, at the doses given in this study, FDP is taken up and used as a metabolic substrate by the brain.

Animals↗
PubMed1989

Association of RFLP of HLA class I genes with Chinese ankylosing spondylitis patients.

By serum typing, it is indicated that HLA B27 may be associated with the susceptibility to ankylosing spondylitis (AS). We analyzed DNA restriction fragment length polymorphism (RFLP) in 28 Chinese AS patients and 99 healthy controls, using a 1.4 Kb HLA class I cDNA probe. The results showed that the frequencies of the 8.1 Kb EcoRI, 5.2 Kb EcoRI and 21.9 Kb XbaI fragments were found to be significantly increased in affected patients (P less than 0.0001, P = 0.0015, respectively), but that of 19.2 Kb XbaI fragment was decreased (P = 0.0021). The data suggest that AS may be a polygenic disease; furthermore, B27 and 8.1 Kb EcoRI band may be two different factors responsible for the susceptibility or just in linkage disequilibrium with the susceptible gene(s).

Asian People↗
PubMed1989

[Acetylcholinesterase in the cochlea on normal guinea pigs by light and electron microscopy].

The distribution of AchE activity in the cochleae of 42 normal guinea pigs was studied with thiocholine Cu-ferrocyanide method. Light microscopy revealed the AchE activity in the following areas: 1. the inner spiral bundle, 2. the spiral tunnel bundle, 3. the upper tunnel radial fibers, and 4. the large nerve endings at the base of the outer hair cells. Activity of AchE was most abundant in the basal turn and decreased gradually towards the apex. There was also a decreasing AchE from the first to the third row of outer hair cells. In the fourth turn, AchE activity was demonstrated only in the large nerve endings under the first row of outer hair cells. Under electron microscopy, the reaction was found to be localized to the following structures: 1. the axolemma of the small efferent fibers and their presynaptic enlargements in the inner spiral bundle, 2. the outer surface of the upper tunnel radial fibers and the spiral tunnel bundle, and 3. the large efferent nerve endings in contact with the base of the outer hair cells.

Acetylcholinesterase↗
PubMed1989

Comparative study of metastatic behavior of a human tumor cell line in athymic (nu/nu) and beige nude mice (bg/bg-nu/nu).

In this experiment, the "nu" gene was introduced into "beige" mutant mice, which are immunodeficient in NK cell activity. The resultant beige nude mice (bg/bg-nu/nu) have combined immunodeficiency in both T and NK cell activities. The level of NK cell activity in beige nude mice is slightly higher than that in beige mice, but much lower than that in nude mice. This is consistent with other studies. In order to elucidate the role of the metastatic behavior of a human tumor cell line PAa in both athymic nude mice and beige nude mice. The PAa cell line was originally established from a human lung adenocarcinoma and maintained as a solid tumor by serial s.c. passage in nude mice. During the first 18 passages in nude mice, PAa cells were found to have metastasized spontaneously to regional lymph nodes in only 4 animals, but metastases were no longer found in subsequent passages. The total incidence of metastasis in nude mice was 9% (4/44). However, when inoculated s.c. into beige nude mice, the metastatic rate of PAa cells was 43% (9/21) to the regional lymph nodes and 10% (2/21) to the lungs in two separate experiments. We conclude from the results that NK cells may play an important, if not exclusive, role in host resistance to tumor metastasis. Beige nude mice could serve as a useful in vivo model in studies of the biology and heterogeneity of human tumor metastasis.

Adenocarcinoma↗
PubMed1988

Effects of pyrethroid insecticides on subjects engaged in packaging pyrethroids.

A health survey was conducted on 199 workers engaged in dividing and packaging pyrethroids. The subjects were exposed to fenvalerate at 0.012-0.055 mg/m3 and deltamethrin at 0.005-0.012 mg/m3 in the air with simultaneous skin contact for 0.5-4.5 months. Burning sensations and tightness or numbness on the face appeared in two thirds of the subjects and one third had sniffs and sneezes. Abnormal facial sensations, dizziness, fatigue, and miliary red papules on the skin were more evident in summer than in winter. Neither abnormalities in other organs or systems nor symptoms or signs of acute pyrethroid poisoning were found by interviews, examinations, and laboratory tests. There was no significant difference in plasma levels of NA, cAMP, and cGMP between the examined subjects and the control group. The urine concentration of fenvalerate in the study group ranged from 1.02 to 18.6 micrograms/l; deltamethrin in the urine was present in trace amounts.

Adolescent↗
PubMed1988

[Snoring].

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Humans↗
PubMed1988

[In vivo metastasis of human tumor transplant in T and NK cell immune-deficient mice].

Beige-nude mice with combined T and NK cell deficiency were produced by introducing "nu" gene into the beige mice of C57BL/6 background. The beige-nude mice were characterized by morphological features, level and activity of the NK cell in spleen and peripheral blood. NK cell level of the beige-nude mice was higher than the beige mice and similar to the ordinary nude mice though its NK cell activity was markedly lower than the nude mice. Human lung adenocarcinoma (PAa) was transplanted subcutaneously to the beige-nude mice and nude mice of BALB/cA background. No metastasis was found in BALB/cA nude mice (0/7), while in beige-nude mice, spontaneous lymph node metastasis rate was 36.3% (4/11). It should be noted that the transplanted PAa metastasized to lungs, which had never been seen in BALB/cA nude mice in previous experiments. The increase of metastatic rate is correlated with the relative low NK cell activity of the beige-nude mice. Our observation is that the beige-nude mice could be a suitable experimental model for in vivo study on metastatic behavior of the human tumors.

Adenocarcinoma↗
PubMed1987

[Different effects of selenium on proliferation of human lung adenocarcinoma cells and human embryonic lung diploid cells in vitro].

After treating human lung adenocarcinoma cells by Na2SeO3 (1 microgram/ml) for 24 hours, its mitotic index decreased by 50%. The reduction rate was directly proportional to selenite concentration (1-5 micrograms/ml). In the meantime, the labelling index, growth rate and progression of the cell cycle were also inhibited. In contrast to the above observation, there was no marked change in the cell count, mitotic index, labelling index and the average silver granule number in the human embryonic lung diploid cells treated by Na2SeO3 (1-5 micrograms/ml) for 1-3 days. When human embryonic lung diploid cells were mix-cultured with human lung adenocarcinoma cells in the presence of 5 micrograms/ml Na2SeO3 for 24 hours, the former maintained a normal morphology, while the lung cancer cells showed heavily vacuolated cytoplasms and distorted nuclei.

Adenocarcinoma↗