PubMed Health⌕ Search

Biomedical subjects

D F Chen

Publications and source records attributed to D F Chen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Prospective multimodality treatment of SCLC--experience during the past 18 years.

Lung cancer has been one of the leading malignancies in China. Since 1989 it has ranked first among common malignancies in the male population, and second in females. In 1975, a multimodality treatment study group for lung cancer was organized in our institute. The group has since expanded to 15 institutions in the Beijing and Tianjin area during the past four years. The present communication is based on our experiences and data, and tries to explain the treatment strategy of our study group.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

A polymerase chain reaction-sequence-specific oligonucleotide procedure for HLA class II typing using biotin- and digoxigenin-labeled probes simultaneously in hybridization.

To simplify PCR-SSO HLA-DRB generic typing, we labeled eight of 15 oligonucleotide probes with DIG and the others with biotin, and hybridized each dot blot with both a biotin-labeled probe and a DIG-labeled probe simultaneously. We chose oligonucleotide pairs which require the same hybridization and stringent washing conditions and do not compete with each other during hybridization. After incubation with a mixture of anti-DIG Fab fragment-alkaline phosphatase and streptavidin-peroxidase conjugates, specific binding of the DIG-labeled probe was revealed by a chemiluminescent substrate (CSPD) and specific binding of the biotin-labeled probe was subsequently visualized by a chromogenic substrate (TMB). The sensitivity of both probes was similar and gave comparable hybridization signals. Using this simplified procedure, the number of hybridizations or dot blots can be reduced to half the usual amount and the labor involved in PCR-SSO typing significantly reduced.

Base Sequence↗
PubMed1994

[HLA-DR typing using PCR-SSO with simultaneous hybridization of each dot blot membrane with a digoxigenin- and a biotin-marked probe].

Here we present a PCR-SSO procedure designed to simplify HLA-DR typing. We labelled 8 of a total of 16 oligonucleotide probes with digoxigenin, the others with biotin, and formed 8 pairs, each containing a digoxigenin- as well as a biotin-labelled probe. Each pair was hybridized simultaneously to one of eight dot blot membranes containing the DNA to be typed. Specific binding was detected by incubation with a mixture of the appropriate conjugates followed by sequential addition first of a chemiluminescent substrate to detect the digoxigenin-labelled probe and then a chromogenic substrate for detection of the biotin-labelled probe. With this procedure, the specific binding of two different probes to the same dot blot membrane could be evaluated, considerably reducing the labor inherent in PCR-SSO typing.

Biotin↗
PubMed1993

Prospective study of abdominal ultrasonography before laparoscopic cholecystectomy.

To investigate the role of abdominal ultrasonography (US) in predicting possible difficulties during laparoscopic cholecystectomy, we performed preoperative US evaluation prospectively in 82 consecutive patients. We correlated our predictions of "easy" and "difficult" with difficulties experienced at operation in surgery. The binary outcomes were analyzed by taking both easy category of US and surgical operation as positive results and both difficult category as negative results. We obtained satisfactory sensitivity (93.8%), accuracy (81.4%), and positive predictive value (84.7%), but low specificity (35.3%) and negative predictive value (60%). The highly positive results were the result of careful US examination. The low specificity and negative predictive value were attributed to the fact that most surgically difficult cases were due to adhesions around the gallbladder, difficult indeed to detect at US. We conclude that thorough abdominal US examination before laparoscopic cholecystectomy is useful in preoperative evaluation of patients undergoing laparoscopic cholecystectomy, even if it not infrequently fails to predict the surgically difficult cases mainly due to adhesions around the gallbladder.

Abdomen↗
PubMed1992

Isolation of novel lignans, heteroclitins F and G, from the stems of Kadsura heteroclita, and anti-lipid peroxidative actions of heteroclitins A-G and related compounds in the in vitro rat liver homogenate system.

From the stems of Kadsura heteroclita, two new lignans named heteroclitins F and G were isolated and their structures were determined by various spectroscopic means including an X-ray diffraction method. Dibenzocyclooctadiene type lignans and related compounds isolated from the stems of K. heteroclita, potently inhibited the lipid peroxidation in the rat liver homogenate stimulated by Fe(2+)-ascorbic acid, CCl4-reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine 5'-diphosphate-NADPH.

Animals↗
PubMed1992

Anti-lipid peroxidative effect of an extract of the stems of Kadsura heteroclita and its major constituent, kadsurin, in mice.

Three-days successive p.o. administration of an EtOH extract of the stems of Kadsura heteroclita (Schizandraceae) or its major constituent, kadsurin, resulted in significant decreases of CCl4-induced lipid-peroxidation products, such as thiobarbituric acid reactive substances (TBA-RS), conjugated dienes and fluorescent products in the liver of mice. In contrast, a significant restoration of superoxide dismutase (SOD) activity reduced by CCl4-intoxication was observed in the administered groups, suggesting that the subchronic treatment of mice with the EtOH extract or kadsurin induce enzymes capable of scavenging oxygen radical species in the liver, though the extract and kadsurin themselves may have an anti-oxidant property.

Animals↗
PubMed1992

Complications of laparoscopic cholecystectomy: an analysis of 200 cases.

Complications of the initial 200 cases of laparoscopic cholecystectomy (LC) at the Cathay General Hospital within a period of 11 months were reviewed from video documents of the operations and clinical records. The major complication rate was 3.5%, including one common bile duct (CBD) injury (0.5%), three retained CBD stones (1.5%), one subphrenic fluid accumulation (0.5%), one liver abscess (0.5%) and one cystic duct stump bile leakage (0.5%). All major complications were cholecystectomy-related, and only one of the seven occurred in cases of acute cholecystitis. Age and sex were not related to its occurrence. The rate of minor complications ranged from 0.5% to 10%; they were: shoulder and back pain (10%), gall bladder perforation (10%), retained stones in the abdominal cavity (5%), transient nausea and diarrhea (5%), extension of umbilical port to a mini-laparotomy (3.5%), prolonged operation time > three hours (2%), subcutaneous emphysema (1.5%), wound infection (1.5%) and prolonged ileus (0.5%). The minor complications occurred largely in patients with acute cholecystitis. The complications occurred mostly during the early period of our study, indicating a learning period phenomenon. These could have been avoided if we had had a thorough knowledge of the potential complications and had strictly followed the principles of laparoscopic surgery. We conclude that LC is safe and the complication rate is not higher than that for open cholecystectomy. Most of the complications are preventable if LC is performed by qualified biliary surgeons following strict precautions.

Adult↗
PubMed1991

The inhibition of restriction endonuclease PvuII cleavage activity by methylation outside its recognition sequence.

The recombinant plasmid pGEM4Z-ras DNA which was methylated on dam and dcm sites outside the PvuII recognition sequence was digested with restriction endonuclease PvuII, and one of the three PvuII sites was about 16-fold less efficient to cleave than either of the other two. On the contrary, the three PvuII sites were cleaved at about the same rate on the unmethylated DNA molecule. The results show that the cleavage inhibition of the methylated DNA on the certain PvuII site was caused by methylation outside the PvuII recognition sequence. Maybe a adjacent methylated dam site *A was responsible for the less efficient cleavage. This observation suggests that methylation outside the recognition sequence may be considered a new factor in the kinetic experiment of restriction endonuclease.

Base Sequence↗
PubMed1991

Comparison of neural activity in the supplementary motor area and in the primary motor cortex in monkeys.

Neuronal activity recorded from the primary motor cortex (MI) and from the supplementary motor area (SMA) was compared in two monkeys trained to perform conditioned arm movements. A handle had to be held in a central waiting position until a visual go and cueing signal indicated to the monkey to move the handle either to a medial or to a lateral target zone (choice reaction time paradigm). Unit and representative electromyographic data were analyzed in relation either to the go signal or to movement onset. In 240 penetrations, 431 SMA neurons and 353 MI neurons were found with activity related to the task. The majority of neurons (303 in MI, 290 in SMA) displayed activity changes after the go signal and before movement onset. Of these "short-lead neurons", 71% in MI and 41% in SMA were clearly related to movement execution. The distribution of lead times in MI and SMA neurons was completely overlapping without any statistical difference among subgroups. The remaining neurons were as well related to the go signal as to movement onset, or were better related to the visual go signal. The response latencies to this signal were not statistically different in SMA and MI neurons. Activity changes during the waiting period was observed more frequently in SMA (47%) than in MI (32%); modulations restricted to the waiting period occurred in 14% of SMA neurons, but were exceptional in MI neurons (3%). It is concluded from these experiments that a surprisingly large proportion of SMA neurons have "MI-like" properties, in that they are temporally recruited together with MI neurons, with similar patterns of discharges during the task. This then suggests that the two interconnected areas operate in parallel. A population of SMA neurons is involved in some processing that is not as predominantly expressed in MI. This activity could relate to sensory, timing, or other higher-order aspects of response preparation, and/or motor functions such as postural stabilization.

Animals↗
PubMed1991

[Laparoscopic cholecystectomy: the first 50 patients].

Laparoscopic cholecystectomy (LC) has rapidly gained wide acceptance in the United States. The applicability, safety and efficacy of this new procedure for the treatment of cholelithiasis in Taiwan, however, needs evaluation. We performed LC in 50 out of 98 cases of cholelithiasis at Cathay General Hospital from 28 December 1990 to 28 April 1991. We found that the applicability rate was 51%. The reasons for not selecting LC in the 48 open cases were: acute and gangrenous cholecystitis (13), common bile duct stones (11), concomitant intra-abdominal malignancy (5), intrahepatic stones (5), multiple upper abdominal incisions (4), pancreatitis or pancreatic abscesses (3) and other causes (7). In the LC group, there were 44 patients with symptomatic chronic calculus cholecystitis, 3 patients with acute calculus cholecystitis and 3 patients with gall bladder polyps. The age of the patients ranged from 27 to 79. There were 14 males and 36 females. All of the patients had a detailed preoperative workup including complete liver function test and sonographic examination of the hepatobiliary system. Additional pre-operative endoscopic retrograde cholangiopancreatographies were done in 3 and operative cholangiograms were done in another 3 to confirm the absence of common bile duct stones or to delineate anatomy. Although we encountered a few problems during the operations, such as severe adhesion, bleeding, difficult dissection, CO2 leakage, difficult insufflation, or large stones, all of the 50 patients completed the LC successfully without conversion to open cholecystectomy. The average operation time was 60 minutes, ranging from 30 to 135 minutes. Drain tubes were used in 7 cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Curative radiotherapy of early operable non-small cell lung cancer.

The results of 44 patients with early operable non-small cell lung cancer treated from January 1975 through 1981 are retrospectively analysed. All were proven by pathology and/or cytology and denied surgery in our joint Chest Clinic for various reasons. 55-70 Gy/6-7 weeks was delivered by conventional fractionation through A-P portals by telecobalt and/or 25-35 MeV high energy electron beam or 8 MV X-ray. 40 Gy/4 weeks was given prophylactically to the mediastinum. The 1-, 3-, and 5-year survival rates, 93, 55, and 32%, are superior to what is reported in the literature. In the present series, the favorable factors are: (1) patients without any intercurrent disease but refused operation; (2) T1 lesions; (3) complete regression of the lesion at the conclusion of radiotherapy; (4) doses ranging from 69 to 70 Gy. It is shown that early non-small cell lung cancer can be cured by radiotherapy alone giving survival rates comparable to surgery. Prospective randomized clinical trials are warranted.

Adult↗
PubMed1989

What is the role of the supplementary motor area in movement initiation?

The hierarchical position of the supplementary motor area (SMA) relative to the primary motor cortex is discussed on the basis of neurological observations and of animal experiments. In the last 10 years evidence has accumulated, especially from studies on the human brain, that the supplementary motor area is a hierarchically superior structure involved in the processes of movement initiation. Single unit studies in subhuman primates also revealed neuronal populations related to aspects of movement preparation rather than to the movement per se. However, we report that a surprisingly large subpopulation of SMA neurones has features classically found in the primary motor cortex (MI). These MI-like neurones precede movement onset by a relatively short interval. The occurrence of such "short-lead neurones" was somewhat higher in MI, but the histograms of lead-times were completely overlapping in the two areas. Taken together with the fact that the SMA is microexcitable and is part of the origin of the pyramidal tract, these findings suggest that the SMA functions also in parallel with MI as concluded by Woolsey and coworkers (1952). Finally, the SMA and MI are reciprocally interconnected, a situation which is not unlike that of the cortical visual areas.

Animals↗
PubMed1989

Sequence specific inhibition of in vitro translation of mutated or normal ras p21.

Antisense methylphosphonate-modified oligomers (ONMP) complementary to 8 nucleotides spanning the twelfth amino acid codon of human c-Ha-ras have been synthesized to explore their inhibitory effect on ras p21 translation. The ONMP Ras 0, perfectly complementary to the specific target region in normal c-Ha-ras, inhibits cell-free translation of p21 from a normal c-Ha-ras mRNA template in a dose-dependent manner. At 200uM Ras 0, p21 translation is inhibited by almost 90% in a rabbit reticulocyte lysate; at 100uM, p21 is reduced by over 60%. Ras I and Ras II contain, internally, a single and double base mismatch, respectively. The inhibitory activity of these ONMPs is reduced in proportion to the number of mismatches. When the target mRNA encodes the activated c-Ha-ras differing by a single nucleotide at the twelfth amino acid codon from normal c-Ha-ras, the magnitude of the inhibitory effect of Ras I increased significantly because Ras I is now perfectly complementary to its target mRNA. In turn, Ras 0, now only partially complementary, is considerably less effective at the same concentrations. Therefore, the inhibitory effect is exquisitely sensitive to the extent of the sequence complementarity between the antisense ONMP and the targeted mRNA.

Amino Acids↗
PubMed1987

Input and output organization of the supplementary motor area.

Recent work on the supplementary motor area (SMA) in Macaca fascicularis led to the conclusion that this area is involved mainly in the preparation of self-paced movements. Results are presented indicating that the posterior portion of the SMA is also directly involved in movement execution and that it receives various sensory inputs. The main results are as follows: (1) The SMA has direct access to the spinal cord by way of corticospinal neurons, but the density of these neurons is lower than in the primary motor cortex (MI). (2) Intracortical microstimulation effects can be elicited in the SMA. Facilitatory effects on ongoing EMG activity can even be produced by single micropulses (8/s). The shortest latencies are compatible with an oligosynaptic or monosynaptic transmission. (3) SMA neurons respond (as do MI neurons) to external perturbations. (4) Anatomical tracing studies revealed that basal ganglia outflow to the SMA via the thalamus is important; our results suggest that dentate outflow contributes as well. (5) Many cells of the SMA may covary with conditioned movements in the same way as MI neurons do. It is argued that it is difficult to compare the lead-time of MI and SMA neurons since 'early' discharges may be coupled with anticipatory postural events.

Animals↗
PubMed1987

The adrenergic agonist tizanidine has differential effects on flexor reflexes of intact and spinalized rat.

Tizanidine with its predominant alpha 2-adrenergic properties is a potent myorelaxant drug used clinically in spastic patients. The aim of this study is to analyse further the mechanisms by which this substance exerts its influence on spinal reflexes. It was found that tizanidine dose-dependently diminished flexor reflexes in intact chloralose-anaesthetized rats, and also, but slightly less, in unanaesthetized decerebrate rats. In spinalized rats (1-5 days postoperatively), flexor reflexes were, however, enhanced by tizanidine, especially by the higher doses. Pretreatment with the alpha 2-blocker yohimbine antagonized the depressant action of tizanidine in intact rats whereas the alpha 1-blocker prazosin antagonized the facilitatory action of tizanidine in the spinalized rats. The reflex depression might be explained by a removal of a tonic facilitation of spinal neurons by the descending noradrenergic fibres, because tizanidine is likely to reduce, like clonidine, the spontaneous activity of locus coeruleus neurons by presynaptic autoinhibition. In spinalized preparations, a net facilitatory alpha 1-mediated action may be revealed by the higher doses of tizanidine that would be unopposed by the alpha 2-mediated disfacilitation.

Adrenergic alpha-Agonists↗
PubMed1987

cDNA sequence, protein structure, and chromosomal location of the human gene for poly(ADP-ribose) polymerase.

Recently we described a full-length cDNA for the human nuclear enzyme poly(ADP-ribose) polymerase. Here, we report the chromosomal localization and partial map of the human gene for this enzyme as well as the complete coding sequence for this protein. The nucleotide sequence reveals a single 3042-base open reading frame encoding a protein with a predicted Mr of 113,135. A comparison of this deduced amino acid sequence with the amino acid sequence of three peptides derived from human poly(ADP-ribose) polymerase revealed a match of 27 amino acid residues. A computer-derived structural analysis of the enzyme and a search for similarities with other proteins confirmed that the polymerase belongs to a subfamily of DNA/NAD-binding proteins and DNA-repair proteins. Possible Zn2+-binding "fingers," a nucleotide-binding fold, and a nuclear transport signal were noted. Additionally, chromosomal mapping has identified polymerase-hybridizing sequences on human chromosomes 1 (the active gene), 13, and 14 (processed pseudogenes). Using the polymerase cDNA as a probe, we also have detected several DNA restriction fragment length polymorphisms in normal humans.

Amino Acid Sequence↗