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Biomedical subjects

B Feng

Publications and source records attributed to B Feng.

99 records · Page 6Linked to original sources
PubMed1991

[The effects of upstream region of SUC2 gene on its expression].

A series of deletions were made at upstream region of SUC2 gene with the direction from about -900 bp to the initiation codon. The DNA fragments, which contain SUC22 gene and its deleted upstream region, were inserted into multicopy plasmid. After transforming resulted plasmid into SUC strain, the invertase activities produced by the transformants were determined. Under glucose repressing condition, the glycosylated invertase produced by transformants with deletion from -636 bp to -179 bp of SUC2 gene were gradually increased. The transformants with deletion down to -223 bp and -179 bp could produce about 100 times higher glycosylated invertase activity as compared to wild type. Under glucose derepressing condition, the glycosylated invertase produced by transformants with deletion from -395 bp to -179 bp of SUC2 gene were only slightly more than that produced under glucose repressing condition. Under either glucose repressing or derepressing condition, the transformants with deletion at -89 bp and -41 bp produced only a little of glycosylated invertase, while they produced remarkably higher nonglycosylated invertase activity.

Amino Acid Sequence↗
PubMed1990

Transcriptional regulation of glutamine synthetase gene expression by dexamethasone in L6 muscle cells.

Dexamethasone increases glutamine synthetase activity and mRNA abundance in L6 muscle cells in culture, apparently by a glucocorticoid receptor-mediated process. The data in this report reveal that increased glutamine synthetase mRNA abundance is attributable at least in part to an enhanced rate of transcription of the glutamine synthetase gene. "Nuclear runoff" assays of glutamine synthetase gene expression were performed with purified myonuclei from dexamethasone-treated or untreated L6 skeletal muscle cells. These assays showed glutamine synthetase transcription to be increased approximately 2-fold as early as 1 h after incubation of cells with dexamethasone (10(-7) M); there was no increase in the rate of transcription of the beta-tubulin gene, which served as a control. The increase in glutamine synthetase gene transcription correlates with increased glutamine synthetase enzymatic activity after dexamethasone treatment. Studies with actinomycin D indicated that the half-life of glutamine synthetase mRNA (7-8 h) is not altered by dexamethasone. Therefore, the degradation of glutamine synthetase mRNA is not affected by dexamethasone, and the increased glutamine synthetase mRNA level is attributable to increased transcription. The dexamethasone-mediated increase in glutamine synthetase mRNA abundance is glucocorticoid receptor-mediated; RU38486 (a glucocorticoid receptor blocker) completely blocked the effect of dexamethasone. The dexamethasone-mediated increase in glutamine synthetase gene transcription and steady-state mRNA level was not blocked by cycloheximide, indicating a direct effect.

Blotting, Northern↗
PubMed1990

Glutamine regulates glutamine synthetase expression in skeletal muscle cells in culture.

Metabolite control of glutamine synthetase expression (by glutamine) was studied in L6 skeletal muscle cells. Depletion of glutamine from the culture medium for 24 hours resulted in a 3-4-fold increase in glutamine synthetase activity. This effect was blocked by cycloheximide but not by actinomycin D. Addition of glutamine to L6 cells maintained in glutamine-free medium caused a rapid return of glutamine synthetase activity to the control level. As reported, dexamethasone caused a striking increase in the glutamine synthetase mRNA level. In contrast, neither depletion nor addition of glutamine caused a change in the glutamine synthetase mRNA level. Therefore, regulation of glutamine synthetase by glutamine is exerted at a post-transcriptional level.

Animals↗
PubMed1990

Neural control of glutamine synthetase activity in rat skeletal muscles.

The mechanism of glutamine synthetase induction in rat skeletal muscle after denervation or limb immobilization was investigated. Adult male rats were subjected to midthigh section of the sciatic nerve. At 1, 2, and 5 h and 1, 2, and 7 days after denervation, rats were killed and denervated, and contralateral control soleus and plantaris muscles were excised, weighted, homogenized, and assayed for glutamine synthetase. Glutamine synthetase activity increased approximately twofold 1 h after denervation in both muscles. By 7 days postdenervation enzyme activity had increased to three times the control level in plantaris muscle and to four times the control level in soleus muscle. Increased enzyme activity after nerve section was associated with increased maximum velocity with no change in apparent Michaelis constant. Immunotitration with an antiglutamine synthetase antibody suggested that denervation caused an increase in the number of glutamine synthetase molecules in muscle. However, Northern-blot analysis revealed no increase in the steady-state level of glutamine synthetase mRNA after denervation. A mixing experiment failed to yield evidence for the presence of a soluble factor involved in regulating the activity of glutamine synthetase in denervated muscle. A combination of denervation and dexamethasone injections resulted in additive increases in glutamine synthetase. Thus the mechanism underlying increased glutamine synthetase after denervation appears to be posttranscriptional and is distinct from that of the glucocorticoid-mediated glutamine synthetase induction previously described by us.

Animals↗
PubMed1990

Effect of diabetes on glutamine synthetase expression in rat skeletal muscles.

The regulation of glutamine synthetase expression in muscles from normal and diabetic (streptozotocin-treated) rats was studied. Muscle and body weights were markedly reduced in diabetic animals. Glutamine synthetase activity was significantly (2-fold) elevated 7 days after induction of diabetes. Increased enzyme activity persisted for at least 14 days after induction of diabetes, and it was apparent in both slow (soleus) and fast (plantaris) muscles. The diabetes-induced increase in enzyme activity was reflected in an increased steady-state level of glutamine synthetase mRNA. The increases in glutamine synthetase activity and mRNA level in muscle from diabetic rats were reversed by insulin administration. Increased expression of glutamine synthetase may be important for accelerated glutamine production by muscle from diabetic rats.

Adrenalectomy↗
PubMed1989

[Dermatoglyphics parameters and cluster analysis of seven minority nationalities].

This paper reports the normal values of dermatoglyphics parameters of seven minority nationalities in Yunnan Province which are Bai, Blang, Yi, Hui, Lisu, Nu and Jinuo. The test of difference signification and cluster analysis show different parameters in several nationalities and the greatest most remarkable difference between Jinou and other nationalities. Han is very different from several nationalities. In each nationality, the symmetry pattern of same name finger or area is highly unanimous, the symmetry between left and right does not show random combination.

China↗
PubMedDate not supplied

Ca2+ is essential for the motility of plasma membrane-intact, but not of demembranated, hamster spermatozoa.

Extracellular Ca2+ is essential for the flagellar motility of membrane-intact hamster spermatozoa. When suspended in a medium completely free of Ca2+, most spermatozoa quickly lost their motility, and remained motionless until they were transferred back to Ca2+-containing medium. The motility could not be restored after the spermatozoa had been in Ca2+-free medium for more than 2 hr. Unlike membrane-intact spermatozoa, demembranated spermatozoa (spermatozoa without plasma membranes) exhibited active movement in Ca2+-free medium, and their motility was inhibited by Ca2+. In view of these facts, we suggest that the "hyperactivated motility" which membrane-intact spermatozoa display upon capacitation may be due to the activation of a Ca2+-dependent adenylate cyclase (and the resultant increase in intracellular cAMP), rather than being a direct effect of a rise in the intracellular Ca2+ concentration.

Animals↗
PubMedDate not supplied

Small proteins that modulate calmodulin-dependent signal transduction: effects of PEP-19, neuromodulin, and neurogranin on enzyme activation and cellular homeostasis.

Neuromodulin (GAP-43), neurogranin (RC3), and PEP-19 are small acid-stable proteins that bind calcium-poor calmodulin through a loosely conserved IQ-motif. Even though these proteins have been known for many years, much about their function in cells is not understood. It has recently become appreciated that calmodulin activity in cells is tightly controlled and that pools of otherwise free calmodulin are sequestered so as to restrict its availability for activating calcium/calmodulin-dependent enzymes. Neuromodulin, neurogranin, and PEP-19 appear to be major participants in this type of regulation. One way in which they do this is by providing localized increases in the concentration of calmodulin in cells so that the maximal level of target activation is increased. Additionally, they can function as calmodulin antagonists by directly inhibiting the association of calcium/calmodulin with enzymes and other proteins. Although neuromodulin, neurogranin, and PEP-19 were early representatives of the small IQ-motif-containing protein family, newer examples have come to light that expand the number of cellular systems through which the IQ-peptide/calmodulin interaction could regulate biological processes including gene transcription. It is the purpose of this review to examine the behavior of neuromodulin, neurogranin, and PEP-19 in paradigms that include both in vitro and in situ systems in order to summarize possible biological consequences that are linked to the expression of this type of protein. The use of protein:protein interaction chromatography is also examined in the recovery of a new calmodulin-binding peptide, CAP-19 (ratMBF1). Consistent with earlier predictions, at least one function of small IQ-motif proteins appears to be that they lessen the extent to which calcium-calmodulin-dependent enzymes become or stay activated. It also appears that these polypeptides can function to selectively inhibit activation of intracellular targets by some agonists while simultaneously permitting activation of these same targets by other agonists. Much of the mechanism for how this occurs is unknown, and possible explanations are examined. One of the biological consequences for a cell that expresses a calmodulin-regulatory protein could be an increased resistance to calcium-mediated toxicity. This possibility is examined for cells expressing PEP-19 and both anatomical and cell-biological data is described. The study of IQ-motif-containing small proteins has stimulated considerable thought as to how calcium signaling is refined in neurons. Current evidence suggests that signaling through calmodulin is not a fulminating and homogenous process but a spatially limited and highly regulated one. Data from studies on neuromodulin, neurogranin, and PEP-19 suggest that they play an important role in establishing some of the processes by which this regulation is accomplished.

Alzheimer Disease↗