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Biomedical subjects

F L Sun

Publications and source records attributed to F L Sun.

17 recordsLinked to original sources
PubMed2001

Long-range nucleosome ordering is associated with gene silencing in Drosophila melanogaster pericentric heterochromatin.

We have used line HS-2 of Drosophila melanogaster, carrying a silenced transgene in the pericentric heterochromatin, to investigate in detail the chromatin structure imposed by this environment. Digestion of the chromatin with micrococcal nuclease (MNase) shows a nucleosome array with extensive long-range order, indicating regular spacing, and with well-defined MNase cleavage fragments, indicating a smaller MNase target in the linker region. The repeating unit is ca. 10 bp larger than that observed for bulk Drosophila chromatin. The silenced transgene shows both a loss of DNase I-hypersensitive sites and decreased sensitivity to DNase I digestion within an array of nucleosomes lacking such sites; within such an array, sensitivity to digestion by MNase is unchanged. The ordered nucleosome array extends across the regulatory region of the transgene, a shift that could explain the loss of transgene expression in heterochromatin. Highly regular nucleosome arrays are observed over several endogenous heterochromatic sequences, indicating that this is a general feature of heterochromatin. However, genes normally active within heterochromatin (rolled and light) do not show this pattern, suggesting that the altered chromatin structure observed is associated with regions that are silent, rather than being a property of the domain as a whole. The results indicate that long-range nucleosomal ordering is linked with the heterochromatic packaging that imposes gene silencing.

Animals↗
PubMed2000

The fourth chromosome of Drosophila melanogaster: interspersed euchromatic and heterochromatic domains.

The small fourth chromosome of Drosophila melanogaster (3.5% of the genome) presents a puzzle. Cytological analysis suggests that the bulk of the fourth, including the portion that appears banded in the polytene chromosomes, is heterochromatic; the banded region includes blocks of middle repetitious DNA associated with heterochromatin protein 1 (HP1). However, genetic screens indicate 50-75 genes in this region, a density similar to that in other euchromatic portions of the genome. Using a P element containing an hsp70-white gene and a copy of hsp26 (marked with a fragment of plant DNA designated pt), we have identified domains that allow for full expression of the white marker (R domains), and others that induce a variegating phenotype (V domains). In the former case, the hsp26-pt gene shows an accessibility and heat-shock-inducible activity similar to that seen in euchromatin, whereas in the latter case, accessibility and inducible expression are reduced to levels typical of heterochromatin. Mapping by in situ hybridization and by hybridization of flanking DNA sequences to a collection of cosmid and bacterial artificial chromosome clones shows that the R domains (euchromatin-like) and V domains (heterochromatin-like) are interspersed. Examination of the effect of genetic modifiers on the variegating transgenes shows some differences among these domains. The results suggest that heterochromatic and euchromatic domains are interspersed and closely associated within this 1.2-megabase region of the genome.

Animals↗
PubMed1998

Epidermal growth factor signaling and mitogenesis in Plcg1 null mouse embryonic fibroblasts.

Gene targeting techniques and early mouse embryos have been used to produce immortalized fibroblasts genetically deficient in phospholipase C (PLC)-gamma1, a ubiquitous tyrosine kinase substrate. Plcg1(-/-) embryos die at embryonic day 9; however, cells derived from these embryos proliferate as well as cells from Plcg1(+/+) embryos. The null cells do grow to a higher saturation density in serum-containing media, as their capacity to spread out is decreased compared with that of wild-type cells. In terms of epidermal growth factor receptor activation and internalization, or growth factor induction of mitogen-activated protein kinase, c-fos, or DNA synthesis in quiescent cells, PLcg1(-/-) cells respond equivalently to PLcg1(+/+) cells. Also, null cells are able to migrate effectively in a wounded monolayer. Therefore, immortalized fibroblasts do not require PLC-gamma1 for many responses to growth factors.

Animals↗
PubMed1997

Transactivation of Igf2 in a mouse model of Beckwith-Wiedemann syndrome.

The gene IGF2, which encodes a fetal insulin-like growth factor, is imprinted, so only one of two parental copies of the gene is expressed. The altered expression of IGF2 has been implicated in Beckwith-Wiedemann syndrome, a human fetal overgrowth syndrome, which is characterized by overgrowth of several organs and an increased risk of developing childhood tumours. We have introduced Igf2 transgenes into the mouse genome by using embryonic stem cells, which leads to transactivation of the endogenous Igf2 gene. The consequent overexpression of Igf2 results in most of the symptoms of Beckwith-Wiedemann syndrome, including prenatal overgrowth, polyhydramnios, fetal and neonatal lethality, disproportionate organ overgrowth including tongue enlargement, and skeletal abnormalities. These phenotypes establish Igf2 overexpression as a key determinant of Beckwith-Wiedemann syndrome.

Animals↗
PubMed1996

[Influence of different combination of mental activity and respiratory cycle on heart rate variability].

By means of spectral analysis of P-R interval, different characteristics of heart rate variability in different form of respiratory exercise was observed. The results of observation on 32 volunteers showed that mental activity that affected respiration can influence the function of autonomic nerve system in a different way. When the mind was concentrated at the inspiration, the function of autonomic nerve system was kept in balance, and both the sympathetic and the vagal activities enhanced significantly and while mind concentrated at the expiration could induce a reduction of vagal activity so as to produce marked change in the sympathovagal balance.

Breathing Exercises↗
PubMed1992

[Effects of various qigong breathing pattern on variability of heart rate].

The effects of four various Qigong breathing pattern on variability of heart rate have been observed by R-R interval spectral analysis in 26 healthy volunteers. The differences in the shape of peaks in spectra were found to be correlated with the Qigong breathing pattern. The amplitude of peak in high-frequency area increased with a reduction of the low-frequency 2/high-frequency (LF2/HF) ratio during the Qigong breathing pattern A, B, and C, indicating the vagal activity increased during above-mentioned three Qigong breathing pattern. However, the amplitude of peak decreased and LF2/HF ratio increased during the Qigong breathing pattern D, it reflected the increase of sympathetic activities. Thus, the results suggested that the Qigong could indirectly regulate the function of viscera after controlling the direct breathing pattern.

Aged↗
PubMed1989

[Power spectral analysis of heart rate in qi deficiency and both qi and yin deficiency in patients with coronary heart disease].

Qi deficiency (QD) and both Qi and Yin deficiency (QYD) are most common in TCM classification of CHD patients with insufficiency syndrome. The authors used the power spectrum of spontaneous heart rate fluctuation (PSHF) to analyze the function of cardiac regulation in 30 QD patients and 27 QYD patients with CHD and compare with the control group of 30 cases for discussing the association between different TCM syndrome patterns and the function of cardiac nerve regulation. The main results were as follows: (1) Low-frequency areas of PSHF in QYD (34.15 +/- 11.60%) were significantly higher than those in QD group (26.24 +/- 11.57%) and the control group (27.80 +/- 11.65%). The L/H ratio in QYD (1.78 +/- 0.96) was significantly higher than those in QD (0.91 +/- 0.64) and the control group (0.98 +/- 0.58). The changes of PSHF in QYD could have some relations with the increasing of the activity of sympathetic nervous system. (2) The change in body posture was used as a load test to study cardiovascular regulation in different TCM patterns of insufficiency syndrome with CHD. In control group the L/H ratio increased with the change of body posture from 0.98 +/- 0.58 to 4.29 +/- 0.89 (P less than 0.001), while in QD group and QYD group increased from 0.91 +/- 0.64 to 1.67 +/- 0.83 (P less than 0.05) and 1.78 +/- 0.96 to 1.85 +/- 0.87 (P greater than 0.2) respectively. The results suggested that cardiovascular baroreceptor reflex was decreased in CHD patients, and QYD group was inferior to DQ group.

Aged↗
PubMed1989

[Clinical method of evaluating declined intelligence with aging and its application in traditional Chinese medicine research].

A practical program edited by BASIC was used in this test. The test included 7 indexes of fluid intelligence by using the method of talking between man and computer: speed of mental mathematic, digit-symbol, choice reaction time, counting visual number span, tracing reaction and recognition of meaningless figures. Through the principal component analysis and multiple stepwise regression techniques, the authors found out the mathematical model of the intelligence aging from 506 normal subjects and established a measuring system for the declined fluid intelligence and physiological age could be measured with the system. The correlation of the repetition of the test was 0.9528. This method was suitable for mental workers of 46-75 years old. The measured accuracy among the subjects of 50-70 years old was higher. The method was applied practically in clinical evaluation of the effects of traditional herbal medicines and Qigong on fluid intelligence with aging. Through the analysis of validity and reliability, it was proved that this method was suitable for geriatric research.

Age Factors↗
PubMed1989

[Effects of an ever-young pill on decreased intelligence and symptoms associated with aging].

A test was carried out to evaluate the effect of Ever-Young Pill (EYP) on decreased fluid intelligence and symptoms associated with aging. Nootropil and placebo were used as control drugs. Random, single-blind and self-control observation methods were applied. 90 days were spent for the clinical study. 154 older persons were divided into three groups (EYP 63, nootropil 60, placebo 31). The method of measuring intelligence was talking between man and computer. The computerized program was worked out by our department. The measure included eight parameters. A semi-quantitative method was used to evaluate the symptoms of aging. The main results were as follows: In the group of EYP, there were significant differences (P less than 0.01) in speed of calculation (SC, 5.92 +/- 2.5, 5.1 +/- 2.1), speed of digits and pictures (SDP, 24.2 +/- 6.2, 21.7 +/- 6.7), two digits span (2.8 +/- 1.0, 3.2 +/- 0.8) and other two parameters before and after treatment. In the group of nootropil, SDP and SC were also improved significantly. In the normal control's there was not any evident change. In the early declined health group treated with EYP and nootropil separately, four parameters were improved in each group. The best effect of EYP obtained was on Kidney Yang deficiency and Kidney and Heart Qi Yang deficiency Syndromes. In other syndromes, the results were less satisfactory. By using EYP for treating symptoms of aging the total effective rate was 96.8%, nootropil 71.7% and placebo 44.2%. There were noticeable differences in three groups. Those results suggested that EYP was one of the effective therapies for decreased fluid intelligence with aging.

Aged↗