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Biomedical subjects

J D Chen

Publications and source records attributed to J D Chen.

At least 109 records · Page 6Linked to original sources
PubMed1996

Molecular cloning, characterization, and sequencing of the hemolysin gene from Edwardsiella tarda.

Hemolysis is a major symptom of diseased eels infected by Edwardsiella tarda. The hemolysin gene of E. tarda strain ET16 was cloned into plasmid pSK and expressed in Escherichia coli. The mol. mass of the functional beta-hemolysin was estimated to be approximately 34 kDa by gel filtration and by SDS-PAGE followed by in situ hemolysin activity analysis. The cloned fragment containing the beta-hemolysin locus from E. tarda strain ET16 expressed in E. coli was estimated to be 5.3 kb in length; the deduced gene product was identical in mol. mass and properties to the extracellular products of E. tarda strain ET16. The presence of EcoRI and XbaI sites within the beta-hemolysin gene of E. tarda was determined from the loss of hemolytic activity in subclones. Analysis of the DNA sequence of a 2,436-bp HaeIII-HindIII fragment that included EcoRI and XbaI sites revealed three ORFs organized as an operon that encoded three predicted polypeptides of 15,874, 7,055, and 34,804 Da. A 34-kDa polypeptide expressing hemolytic activity in cell lysates of the clone DH5 alpha(pETH3E) is very likely the beta-hemolysin encoded by the third ORF. The observation that hemolytic activity appeared in the culture medium of E. tarda, but not in that of E. coli strain DH5 alpha(pETH3E) indicates the existence of a mechanism for transporting the hemolysin across the cell envelope in E. tarda that is different from that of E. coli.

Amino Acid Sequence↗
PubMed1996

Historical development of Chinese dietary patterns and nutrition from the ancient to the modern society.

Actually, food, diet and diet therapy germinated together with the change of meal patterns and traditional Chinese medicine from very ancient China; they appeared in an embryonic form till the Shang and Zhou Dynasties and received great importance from the governors who arranged officials to manage their diets and banquets. Moreover, food, diet and meal patterns were replenished through the Zhou, Qin, Han and Jin Dynasties and epitomized and reached thriving and prosperous standards till the Tang Dynasty. They then became perfected, developed, and formed a complete theory in the dynasties of Song, Jin, Yuan, Ming and Qing. The basis of modern nutrition was made up until the end of 19th century and the beginning of 20th century, which was the time when natural science, including microbiology, chemistry, food industry, etc. were extended into China, yet it was not fully formed until the established of the People's Republic of China. Practicing, teaching, training and research activities started regularly in 1950. With a big population and poor economy basis, the first problem that the Chinese people has now been basically solved. Chinese nutritional scientists worked hard to find out the nutritional problems and status of the people. Through the broad-scale 'Nationwide Nutrition Survey', we now understand our main problems. On this basis, RDA, dietary goal and dietary guidance have been put forward. Although the problem of adequate food and clothing has been basically solved, the Chinese are still facing both the problem of nutrition insufficiency and nutrition excess. However, although nutrition insufficiency and deficiency still extensively exist, nutrition excess and imbalance are emerging in other sections of the population. There is still a shortage of qualified nutritional scientists and technicians, and the training of nutritionists is urgent. Food supplies, including milk, beef, green vegetables and fruit should be increased, especially for some rural and remote areas. The good traditional eating habits and meal patterns should be kept, e.g., breakfast and lunch cannot be neglected, and plant protein meals and Chinese medicinal diets should be promoted. Animals fat intake and fried foods should be reduced, and exercise and fitness programs should be recommended for the overweight population. In the future, our meal pattern take on a mixed form with the advantages of both the eastern and western diets. Chinese scientists are confident of solving the nutritional problems and improving the whole nation's physical fitness and physique under the situation of gradual improvements of the economy and nutritional status of people.

Aged↗
PubMed1996

Advances in time-frequency analysis of biomedical signals.

The frequency content of many biomedical signals can change rapidly with time. Conventional Fourier spectral analysis techniques are insufficient for analyzing the time-varying spectral content of these signals. By mapping a one-dimensional function of time (or frequency), the time-frequency representation can localize the signal energy in both the time and frequency directions. It has been shown that many biomedical signal problems may benefit from time-frequency analysis. The objective of this paper is to review the advances in time-frequency analysis of biomedical signals. Relevant theoretical methodologies and practical considerations are introduced, and five application areas are reviewed: electroencephalography (EEG), electrocardiography, phonocardiography, electrogastrography, and electromyography.

Algorithms↗
PubMed1996

The effect of a chocolate bar supplementation on moderate exercise recovery of recreational runners.

To study the effects of a chocolate bar supplementation before exercise on improving recovery of physiological and metabolic changes induced by exercise, 16 male students aged 18-20 years voluntarily served as subjects. A crossover design was employed. Each subject took part in two trials and ran an hour on a treadmill with the intensity of keeping heart rate at 148-150 min for each trial. Results showed that plasma glucose levels of subjects increased significantly (5.42 +/- 0.83 mmol/L) at 15 min after ingestion of a chocolate bar and maintained in moderate high levels (4.92 +/- 0.57 mmol/L) until 30 min after an hour's running while the glucose levels were low and dropped to under normal ranges (3.84 +/- 0.31 mmol/L) at 30 min after exercise as they were with a supplement of placebo. Results of plasma FFA, blood lactate and plasma urea nitrogen levels and RPE all indicated that chocolate bar supplementation before exercise benefits to create the necessary prerequisite for exercise and recovery.

Adolescent↗
PubMed1996

MR imaging of rotator cuff impingement: correlation with full-thickness rotator cuff tear.

BACKGROUND: Rotator cuff tears usually derive from shoulder impingement, and need surgical treatment. This study is to verify the Magnetic Resonance Image (MRI) findings of rotator cuff impingement which are related to full-thickness rotate cuff tear (FTRCT). METHODS: Totally 68 patients with shoulder impingement syndrome were studied, including 39 shoulders with surgically-proven FTRCT, and 29 shoulders without FTRCT. MRI findings of shoulder impingement were evaluated for peribursal fat plane, subacromial distance, acromion shape, subacromioclavicular space, irregularity of coracoacromial ligament and presence of subacromial spurs. The correlation with FTRCT was also determined. RESULTS: Peribursal fat plane obliteration (p = 0.0001), hook-shaped acromion (p = 0.0148), subacromioclavicular indentation (p = 0.0004), and decreased subacromial distance (p = 0.0005) showed significant correlation with FTRCT; however, subacromial spurs (p = 0.6238) and thickened irregular coracoacromial ligament (p = 0.1611) showed poor correlation. CONCLUSIONS: Specific MRI findings of rotator cuff impingement are fairly reliable and helpful for discrimination of FTRCT from non-FTRCT cases, and can be used preoperatively and noninvasively to determine the necessity of surgical repair of rotator cuff.

Adult↗
PubMed1995

A transcriptional co-repressor that interacts with nuclear hormone receptors.

Transcriptional silencing mediated by nuclear receptors is important in development, differentiation and oncogenesis. The mechanism underlying this effect is unknown but is one key to understanding the molecular basis of hormone action. Here we identify a receptor-interacting factor, SMRT, as a silencing mediator (co-repressor) for retinoid and thyroid-hormone receptors. SMRT is a previously undiscovered protein whose association with receptors both in solution and bound to DNA-response elements is destabilized by ligand. The interaction with mutant receptors correlates with their transcriptional silencing activities. In vivo, SMRT functions as a potent co-repressor, and a GAL4 DNA-binding domain fusion of SMRT behaves as a frank repressor of a GAL4-dependent reporter. Together, our results identify a new class of cofactors which may be important mediators of hormone action.

Amino Acid Sequence↗
PubMed1995

Inhibitory effects of cholecystokinin on postprandial gastric myoelectrical activity.

While a number of studies have investigated the effects of cholecystokinin (CCK) on gastrointestinal motility, little is known on the effects of CCK on gastric myoelectrical activity, which regulates gastric motility. The aim of this study was to investigate the effects of intravenous infusion of CCK-8 on gastric myoelectrical activity in normal humans. Gastric myoelectrical activity was measured in 10 healthy subjects with a noninvasive electrogastrographic technique by placing abdominal electrodes on the epigastric area. Two study sessions were performed in each subject on two separate days with double-blinded infusion of either saline or CCK (24 pmol/kg/hr). The procedure for each session was as follows: (A) 30-min baseline fasting electrogastrogram (EGG); (B) start infusion, another 30-min EGG; (C) give meal, 60-min EGG; and (D) stop infusion, another 60-min EGG. The dominant frequency and peak power (amplitude) of the EGG, and the percentage of normal 2-4 cycles/min slow waves during each recording session were computed and compared between placebo and CCK. It was found that normal 3 cpm slow waves were recorded in all EGGs. Infusion of CCK had no effect on the frequency of the gastric slow wave and did not induce gastric dysrhythmias. It was also found that intravenous infusion of CCK significantly decreased the EGG peak power (amplitude) during the first hour after the meal (the infusion was given during this period) in comparison with placebo (P < 0.05). This inhibitory effect on EGG peak power was sustained but not significant during the second postprandial hour (the infusion was not given during this period). It was concluded that intravenous infusion of CCK at a physiological concentration significantly decreased the postprandial EGG amplitude in normal humans, suggesting an inhibitory effect on postprandial gastric motility, but did not change the frequency and regularity of the gastric slow wave.

Adult↗
PubMed1995

Non-invasive identification of gastric contractions from surface electrogastrogram using back-propagation neural networks.

Gastric contractions play an important role in the digestive process of the stomach. The established method for the measurement of gastric contractions is invasive and involves the insertion through the nose of a manometric probe into the stomach. A non-invasive method is introduced in this paper for the identification of gastric contractions using the surface electrogastrogram. The electrogastrogram (EGG) was measured by placing surface electrodes on the abdominal skin over the stomach in ten subjects. Gastric contractions were simultaneously monitored using an intraluminal manometric probe. The back-propagation neural network was applied to identify gastric contractions from the EGG. The input of the neural network was composed of spectral data points of the EGG which was computed using the exponential distribution method. Experiments were conducted to optimize network structures and parameters. Using the EGG data in five subjects as the training set and the EGG data in another five subjects as the testing set, an overall accuracy of 92% was achieved in the identification of gastric contractions with an optimized three-layer back-propagation neural network (number of nodes for input:hidden:output layers being 64:10:2).

Adult↗
PubMed1995

Ganglioside GT1b inhibits keratinocyte adhesion and migration on a fibronectin matrix.

Highly sialylated gangliosides have been shown to alter cellular adhesion to a fibronectin matrix. The effect of these gangliosides on the adhesion, spreading, and migration of cultured keratinocytes on a fibronectin matrix has not been explored. Ganglioside GT1b significantly prevented attachment of keratinocytes to fibronectin and also detached previously adherent keratinocytes in a concentration-dependent manner without cell toxicity. GT1b did not affect adhesion of keratinocytes to wells coated with laminin, type I or type IV collagen, 804G extracellular matrix, or albumin. GT1b also inhibited keratinocyte migration on fibronectin in a concentration-dependent manner at concentrations as low as 5 nM GT1b, but had no effect on migration of keratinocytes plated on other matrices. GT1b binds to intact fibronectin and to the 120-kD RGDS-containing cell-binding fibronectin fragment, but not to the heparin- or gelatin-binding fragments of fibronectin. Although RGDS competes with GT1b in inhibiting adhesion, GT1b does not diminish binding of keratinocytes to a derivatized RGDS substratum, suggesting that the GT1b effect involves a non-RGDS site in the cell-binding region that modulates RGDS/alpha 5 beta 1 integrin receptor interaction. Through a specific effect on keratinocyte interaction with fibronectin, GT1b may participate in the regulation of cell adhesion and migration on a fibronectin substratum, which are important events during wound healing and the spreading of cutaneous neoplasia.

Cell Adhesion↗
PubMed1995

Interleukin-1 alpha stimulates keratinocyte migration through an epidermal growth factor/transforming growth factor-alpha-independent pathway.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) stimulate keratinocyte migration on collagen by up-regulating the alpha 2 subunit of the collagen integrin, alpha 2 beta 1. Interleukin-1 (IL-1) is an autocrine factor, produced by keratinocytes themselves, that is modulated by ultraviolet light and increases the proliferative potential of keratinocytes in culture. The autocrine nature of keratinocyte-derived IL-1 alpha is emphasized by the fact that it induces the keratinocyte to synthesize IL-1 alpha and TGF-alpha, a cytokine known to induce keratinocyte motility. Further, topical application of IL-1 alpha has been shown to promote wound healing in animals. In this study, we used a well-defined keratinocyte migration assay to assess the effect of IL-1 alpha on keratinocyte motility and to examine whether the IL-1 alpha/TGF alpha pathway is involved. The addition of recombinant human IL-1 alpha to keratinocytes produced a statistically significant and concentration-dependent increase in migration on matrices of collagen types I and IV, but not on laminin. Maximal levels of keratinocyte migration obtained on these matrices with IL-1 alpha were comparable to those obtained with stimulation by EGF and TGF-alpha. The effects of TGF-alpha and IL-1 alpha on keratinocyte migration are additive; however, the maximal level of migration achieved by using IL-1 alpha and TGF-alpha in combination never exceeds the maximal level of migration found by using either cytokine alone. The time course of keratinocyte migration induced by IL-1 alpha is delayed (onset of migration 9-12 h after addition) as compared with that induced by TGF-alpha (onset of migration 6-9 h after addition) even if the cells are preincubated in IL-1 alpha. Flow cytometry analysis demonstrated no change in surface expression of integrin subunits, specifically that of integrin subunit alpha 2, previously shown to be up-regulated by EGF/TGF-alpha. These results suggest that IL-1 alpha stimulates keratinocyte migration on collagen via a mechanism distinct from that of EGF/TGF-alpha.

Cell Movement↗
PubMed1995

Seven-up inhibits ultraspiracle-based signaling pathways in vitro and in vivo.

Seven-up (Svp), the Drosophila homolog of the chicken ovalbumin upstream transcription factor (COUP-TF); Ultraspiracle (Usp), the Drosophila homolog of the retinoid X receptor; and the ecdysone receptor are all members of the nuclear/steroid receptor superfamily. COUP-TF negatively regulates hormonal signaling involving retinoid X receptor in tissue culture systems. Here we demonstrate that Svp, like COUP-TF, can modulate Ultraspiracle-based hormonal signaling both in vitro and in vivo. Transfection assays in CV-1 cells demonstrate that Seven-up can inhibit ecdysone-dependent transactivation by the ecdysone receptor complex, a heterodimeric complex of Usp and ecdysone receptor. This repression depends on the dose of Svp and occurs with two different Drosophila ecdysone response elements. Ectopic expression of Svp in vivo induces lethality during early metamorphosis, the time of maximal ecdysone responsiveness. Concomitant overexpression of Usp rescues the larvae from the lethal effects of Svp. DNA binding studies show that Svp can bind to various direct repeats of the sequence AGGTCA but cannot bind to one of the ecdysone response elements used in the transient transfection assays. Our results suggest that Svp-mediated repression can occur by both DNA binding competition and protein-protein interactions.

Animals↗
PubMed1994

Vitronectin-driven human keratinocyte locomotion is mediated by the alpha v beta 5 integrin receptor.

Vitronectin is a soluble serum factor that is known to promote epiboly of keratinocytes in explant cultures and enhance cell spreading and attachment to matrix. Recently, vitronectin was demonstrated to promote human keratinocyte locomotion. The mechanism(s) by which vitronectin enhances keratinocyte migration is unknown. In this study, we quantitated the vitronectin-driven migration of human keratinocytes in the presence of antibodies to vitronectin receptors. We found that vitronectin's effect of promoting human keratinocyte migration was inhibited by antibody-directed against the alpha v beta 5 receptor. In addition, we surface-labeled human keratinocytes, chromatographed extracts of the cell membranes on a vitronectin column, and then immunoprecipitated the bound and eluted proteins with antibodies to specific vitronectin receptors. We identified the vitronectin receptors on human keratinocytes as bands of 150,000 and 100,000 daltons without reduction and as 125,000 and 110,000 daltons under reducing conditions. Immunoprecipitation with specific antibodies identified the major receptor to be the alpha v beta 5 integrin. In addition, we quantitated vitronectin-driven migration of human keratinocytes in the presence of Arg-Gly-Asp (RGD) and control peptides. We found that the presence of RGD, but not control peptide, inhibited vitronectin-driven migration of human keratinocytes. These studies demonstrate that human keratinocytes express vitronectin receptors and use the alpha v beta 5 receptor for cellular locomotion.

Antibodies↗
PubMed1994

A novel macromolecular structure is a target of the promyelocyte-retinoic acid receptor oncoprotein.

Acute promyelocytic leukemia (APL) is associated with a t(15;17) translocation that creates the promyelocyte-retinoic acid receptor alpha (PML-RAR alpha) fusion gene. Immunohistochemistry demonstrates that PML is a part of a novel macromolecular organelle (including at least three other nuclear proteins) referred to as PML oncogenic domains (PODs). In APL cells, the POD is disrupted into a microparticulate pattern as a consequence of the expression of the PML-RAR oncoprotein. RA treatment of APL cells triggers a reorganization of PML to generate normal-appearing PODs. We propose that PML-RAR is a dominant negative oncoprotein that exerts its putative leukomogenic effect by inhibiting assembly of the POD. According to this proposal, not only is the POD a novel structure, but it can be ascribed an imputed function such that its disruption leads to altered myeloid maturation; this may represent a novel oncogenic target.

Cell Nucleus↗
PubMed1994

Recursive running DCT algorithm and its application in adaptive filtering of surface electrical recording of small intestine.

A rhythmic electrical signal is present in the human small intestine and can be recorded using surface electrodes. Surface electrical recordings of the small intestine contain severe interference that obscures the electrical signal of the small intestine. An adaptive system is proposed in the paper for the enhancement of the small-intestinal signal. To obtain better performance, adaptive signal enhancement is performed in the transform domain using a discrete cosine transform (DCT). A fast recursive algorithm is developed for the calculation of running DCT. The computational complexity of the proposed recursive algorithm is only 2/N (N = length of the adaptive filter) of the direct calculation of the running DCT. A series of simulations are conducted to investigate the performance of the proposed transform-domain adaptive filtering using DCT in comparison with time-domain adaptive filtering and with transform-domain adaptive filtering using a discrete Fourier transform (DFT). The parameters of the proposed adaptive system are optimised, and their effects on system performance are investigated. The application of the proposed method for the enhancement of the small-intestinal signal is presented and discussed.

Algorithms↗
PubMed1994

Developmental expression of a novel murine homeobox gene (Chx10): evidence for roles in determination of the neuroretina and inner nuclear layer.

Few potential regulatory proteins of vertebrate retinal development have been identified. We describe a 39 kDa murine polypeptide (Chx10) with a homeodomain 82% identical to that of the nematode protein ceh-10. In the developing mouse, the Chx10 transcript is expressed throughout the anterior optic vesicle and all neuroblasts of the optic cup. In the mature retina, the Chx10 protein is restricted to the inner nuclear layer, in which its expression decreases from the outer to the inner margin. Chx10 transcripts are also detected in regions of the developing thalamus, hindbrain, and ventral spinal cord. The data suggest that Chx10 plays critical roles in the formation of the neuroretina and in the development and maintenance of the inner nuclear layer.

Amino Acid Sequence↗