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Biomedical subjects

S Z Chen

Publications and source records attributed to S Z Chen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Pharmacological effects and pathological changes induced by the venom of Pseudechis australis in isolated skeletal muscle preparations.

The venom from the Australian king brown snake Pseudechis australis produced a concentration-dependent and progressive inhibition of directly and indirectly evoked twitches of the mouse hemidiaphragm: 2, 5 and 10 micrograms/ml of venom produced complete blockade of directly evoked twitches after 87 +/- 26 min, 66 +/- 28 min and 56 +/- 13 min, respectively, whereas twitches elicited by indirect stimulation were blocked after 43 +/- 4 min, 34 +/- 2 min and 21 +/- 2 min, respectively. Two, 5 and 10 micrograms/ml of the venom also progressively inhibited the twitch responses of the chick biventer cervicis muscle evoked by nerve stimulation: the time (min) to 90% blockade of the twitches were 127 +/- 12, 41 +/- 8 and 26 +/- 6, respectively. Light and electron microscopic studies confirmed that the venom caused severe muscle damage and necrosis in the chick and mouse skeletal muscle. The degree of muscle damage was proportional to the concentration of venom used. The muscle degeneration was characterized by disorganized myofibrils, dilatation of the sarcoplasmic reticulum and swollen or broken-down mitochondria. Depletion and a decrease in population of storage vesicles in the neuromuscular junction were also observed. Thus, the inhibition of neuromuscular function by the venom of P. australis was a consequence of the extensive morphological damage to muscle fibres, motor nerve terminals and cytoplasmic organelles which could be attributed to a direct myotoxic action presumably mediated by the enzymatic action of phospholipase A2 present in the venom of P. australis.

Animals↗
PubMed1994

Protein crystallization in space.

The microgravity environment of space is an ideal place to study the complicated protein crystallization process and to grow good-quality protein crystals. A series of crystal growth experiments of 10 different proteins was carried out in space on a Chinese re-entry satellite FSW-2 in August, 1992. The experiments were performed for about two weeks at a temperature of 18.5 +/- 0.5 degrees C using a tube-like crystallization apparatus made in the Shanghai Institute of Technical Physics, Academia Sinica. More than half of 48 samples from 6 proteins produced crystals, and the effects of microgravity on protein crystal growth were observed, especially for hen-egg white lysozyme and an acidic phospholipase A2 from the venom of Agkistrodon halys Pallas. Analyses of the crystallization of these two enzymes in this mission showed that the microgravity environment in space may be beneficial to improve size, external perfection, morphology, internal order, and nucleation of protein crystals. Some of these positive microgravity effects were also demonstrated by the growth of protein crystals in gelled solution with the above two enzymes. A structural analysis of the tetragonal lysozyme crystal grown in space is in progress.

Ancrod↗
PubMed1994

[Effects of Paeonia-glycyrrhiza decoction on changes induced by cisplatin in rats].

In order to study the effects of Paeonia-Glycyrrhiza decoction (PGD) on the changes induced by cisplatin in rats, platinum-wire bipolar electrodes were inserted into the serosal membrane of the small intestine and migrating myoelectric complex (MMC) was used as index. After intravenous injection of cisplatin at doses of 4 mg/kg, the duration of the MMC cycles was significantly shorter than that of normal MMC cycles (P < 0.05) while the duration of phase III was remarkably prolonged comparing with that of normal phase III (P < 0.01) with latent period of 53.2 +/- 20.4 minutes. Taking PGD orally, cisplatin no longer induced the changes of MMC. The results suggest that PGD has marked adjusting effects on the changes of MMC induced by cisplatin. This might be one of the causes of PGD in relieving diarrhea induced by cisplatin in rats.

Animals↗
PubMed1994

Protein c-fos induction in rat brain and spinal dorsal horn by sincalide and opioids in vitro.

Sincalide (CCK-8) is an antiopioid substance. In this study, we investigated the effects of sincalide and opioids on c-fos expression and their interaction in brain and spinal dorsal horn in vitro. Immunoprecipitation was used for detection of c-fos protein. The results indicated that 0.1 mumol.L-1 sincalide induced c-fos expression markedly in both brain (a 3.8-fold increase in c-fos protein level) and in spinal dorsal horn (a 3.6-fold increase). NDAP (a kappa receptor agonist) 0.1 mumol.L-1 showed some activating effects on c-fos expression, the c-fos protein level increased 2.7 and 2.6 times respectively in brain and spinal dorsal horn. Ohmefentanyl (Ohm, a mu receptor agonist) 0.1 mumol.L-1 also exhibited an inducing effect on c-fos protein production. Sincalide and NDAP exerted some additive effects on c-fos protein production in spinal cord. In contrast, the effect of sincalide on c-fos protein production is antagonistic to that of Ohm. The results suggested that there were changing patterns of interaction on c-fos expression between sincalide and opioids.

Animals↗
PubMed1994

Pathological changes of oxytalan fibers in the human gingiva of chronic periodontitis.

The gingiva samples were obtained from 40 patients with chronic periodontitis after flap operation and 20 cases having healthy gingiva after ectopic wisdom tooth extraction. We investigated the oxytalan fibers by light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results demonstrated that under normal conditions numerous oxytalan fibers were widely and evenly distributed throughout the periodontal tissues. There was marked degeneration of the oxytalan fibers in chronic peridontitis. The predominant features were disintegration, fragmentation or disappearance of the oxytalan fibers under the basement membrane. Around the blood vessels, the oxytalan fibers decreased in density with fragmentation of the fibers and sometimes they disappeared almost completely. These results indicated that degeneration and destruction of the oxytalan fibers were closely correlated with the chronic periodontitis process, leading to reduced function occlusion of teeth.

Adult↗
PubMed1994

[Electron microscopic observation of the denervated flap reinnervation after implantation of sensory nerve].

Flap reinnervation was studied by electron microscopy in the rabbit cervico-shoulder flap with great auricular nerve implanted. After transferring the flap to the dorsal defect of the rabbit's ear and division of its pedicle, the original nerve fibers of the flap underwent a degenerative process which would persist over 2 months. The great auricular nerve implanted into the flap regenerated axons by entering into old endoneurial rube of the flap and sprouting. The development process of the regenerating nerves showed that the unmyelinated fibers appeared first in the 2nd month, and the myelinated ones in the 4th month. The regenerating nerve fibers had often accompanied by blood vessels.

Animals↗
PubMed1994

Protein crystal growth in microgravity.

Protein crystal growth is quite important for the determination of protein structures which are essential to the understanding of life at molecular level as well as to the development of molecular biotechnology. The microgravity environment of space is an ideal place to study the complicated protein crystallization and to grow good-quality protein crystals. A number of crystal-growth experiments of 10 different proteins were carried out in August, 1992 on the Chinese re-entry satellite FSW-2 in space using a tube crystallization equipment made in China. A total of 25 samples from 6 proteins produced crystals, and the effects of microgravity on protein crystal growth were observed, especially for an acidic phospholipase A2 and henegg-white lysozyme which gave better crystals in space than earth-grown crystals in ground control experiments. The results have shown that the microgravity in space favors the improvement of the size, perfection, morphology and internal order of the grown protein crystals.

Crystallization↗
PubMed1994

High frequency electroacupuncture induced changes of IP3 level in rat brain and spinal cord.

In the present study, the radioreceptor binding method was used to determine the changes of IP3 content in rat brain and dorsal spinal cord of high frequency (100 Hz) electroacupuncture (EA) analgesia and EA tolerance rat. The control levels of IP3 in rat brain (less cerebellum and cortex) and dorsal spinal cord were 6.3 +/- 0.78 pmol/mg protein and 3.4 +/- 0.60 pmol/mg protein, respectively. The results showed that IP3 in brain increased gradually within 45 min after stimulation in EA analgesia rat. Meanwhile, the dorsal spinal cord IP3 content decreased significantly 15 min, 30 min after EA stimulation and recovered to control level 45 min after EA stimulation. In EA tolerance rat, IP3 contents markedly increased in brain. And IP3 content in the spinal cord also increased dramatically within 30 min, but decreased rapidly to control level 45 min after EA stimulation. The IP3 level in EA tolerance rat brain and spinal cord was much higher than that in EA analgesia rat (P < 0.01). The studies first reported that high frequency (100 Hz) EA may be linked to PI system in its signal transduction pathways.

Acupuncture Analgesia↗
PubMed1994

[Cholecystokinin octapeptide antagonized the effect of NDAP on CaM in rat dorsal spinal synaptosome].

To elucidating the molecular mechanisms underlying CCK-8 anti-opioid effects, we have observed the effects and interactions of CCK-8 and kappa opiate agonist NDAP on CaM activity in rat dorsal spinal cord synaptosomes. The result indicated that 10 nmol/L-1 mumol/L NDAP produced dose-dependent decrease in CaM activity of rat spinal synaptosomes (P < 0.01). This suppressive effect was completely blocked by specific kappa receptor antagonist Nor-BNI at 1 mumol/L. In contrast, CCK-8 (10-100 nmol/L) induced a significant increase in CaM activity (P < 0.05-0.01), and was capable of antagonizing the suppressive effect induced by NDAP. Specific CCK-B receptor antagonist L365, 260 could partially block the effects of CCK-8 increased CaM activity at 1 mumol/L. The above results suggest that CCK-8 can antagonize the suppressive effect of NDAP on CaM activity in rat spinal synaptosomes via activation of CCK-B receptor, an effect that may constitute one of the mechanisms for the anti-opioid activity of CCK-8.

Animals↗
PubMed1994

Refined structure of trichosanthin at 1.73 A resolution.

An X-ray reflection data set of the orthorhombic crystal of Trichosanthin (TCS) at 1.73 A resolution had been collected using the area detector. We determined TCS crystal structure by the molecular replacement method using the data of the known alpha-momocharin model and TCS intensities, and then TCS structure refinement at 1.73 A resolution was performed with the restrained least-squares refinement. A final R-factor of 0.186 was obtained with a model obeying standard geometry within 0.013 A in bond lengths and 2.48 degrees in bond angles. The final model contains 133 solvent molecules in the asymmetric unit. This paper gives a detailed description of TCS molecule structure, temperature factors, hydrogen bonds, bound water, the distribution of conserved residues and the interactions between the TCS molecules. The hydrogen bond between the hydroxyl group of conserved residue 14Tyr and O157 plays an important role in maintaining the active site conformation. Conserved residue 160Glu and its conformation at the active site play a key role in the catalytic activity.

Crystallography, X-Ray↗
PubMed1993

[Polarographic determination of carbamazepine in the presence of sodium lauryl sulfate].

The electrochemical characteristics of carbamazepine (CBZ) have been studied. In a solution containing 0.40 mol.L-1 NaOH, 0.15 mol.L-1 KNO3 and 0.0020% sodium lauryl sulfate (SLS) CBZ gives a sensitive polarographic wave which can be used to determine trace amounts of the drug, the detection limit being 1.0 x 10(-6) mol.L-1. The cyclic voltammetric data show that SLS promotes adsorption of CBZ at the mercury electrode.

Carbamazepine↗
PubMed1992

[Variation of WGA and PNA binding glycoproteins in early pregnant rabbit uterine fluid].

The qualitative and quantitative changes of two kinds of lectin (WGA, PNA) binding glycoproteins in early pregnant rabbit uterine fluid (D4-D12) were measured by Western blot and Video densitometer scanning methods. During peri-implantation stage (D6, D7 and D9), there are two WGA binding glycoproteins with MW about 42 kd, 28 kd and a PNA binding glycoprotein with MW 75 kd. It is suggested that the three proteins are stage-specific glycoproteins in rabbit uterine fluid in the course of implantation.

Animals↗
PubMed1992

[The expression of MG7 corresponding antigen in gastrointestinal polyps and its relation with cancer].

We studied 112 patients with polyps of the stomach, gallbladder and colorectum by immunohistochemical staining with monoclonal antibody (MG7) against gastric cancer and avidin-biotin complex (ABC) technique. The positive expression of the MG7-corresponding antigen (MG7-Ag) was 100%, 100%, and 60.0% respectively in villous, mixed and tubular polyps. A close correlation was shown between dysplasia of grade II and the positive expression of MG7-Ag (p < 0.05). The positive expression was significantly related to canceration (P < 0.025). No malignancy was found in 45 patients with negative expression. But 12 of 67 patients with positive expression developed cancers in 3 to 38 months. The patients with positive expression of MG7-Ag were high risk group developing cancer.

Adenosine Triphosphate↗
PubMed1992

Variations of lectin-binding glycoproteins in early pregnant rabbit embryo.

In the present study, the quantitative and qualitative changes of three kinds of lectin-binding glycoproteins of early pregnant rabbit embryos (D4-D12) were analyzed. The technique of Western blot, as well as video densitometer scanning and its analytic software was used for analysis. Results found that there were five specific lectin-binding glycoproteins in Day 4 to Day 6 blastocyst fluids: one ConA-binding glycoprotein about 70 kD, two WGA-binding glycoproteins respectively about 42 kD and 25 kD and two PNA-binding glycoprotein respectively about 180 kD and 75 kD. They disappeared immediately after implantation. It is demonstrated that there are stage-specific glycoproteins in rabbit blastocyst fluid which might be relevant to the recognition of pregnancy and implantation.

Animals↗
PubMed1991

Crystallization and chemical modification of disulfide bond of calf chymosin.

In order to carry out protein engineering of chymosin, purification, crystallization and chemical modification of calf chymosin were undertaken. The resolution of iso-enzymes A,B and the degraded product, fraction C was improved and the period of purification was shortened by using fast protein liquid chromatograph (FPLC). Crystal of approximately cubic shape was obtained from 10 mg/ml purified chymosin B at 4 degrees C after successive dialysis against 1.4, 1.8 and 2.0 M NaCl in 0.1 M sodium phosphate buffer. One disulfide bond located on the surface of chymosin molecule was reduced by 0.72 mM dithiothreitol (DTT) at pH 6.3. The reduced disulfide bond was identified as Cys250-Cys283 by using the method of cyanogen bromide cleavage and peptide separation. The reduction of one disulfide bond resulted in the loss of about 25% activity. Carboxymethylated and mercurated derivatives exhibit the similar activity to that of the reduced enzyme suggesting that Cys250-Cys283 plays some role in keeping the conformation with full activity.

Animals↗
PubMed1991

[Re-establishment of sensory function of flaps by nerve implantation].

Taking the afferent sensory fiber discharges as an indicator, re-establishment of sensation of the abdominal island flap was investigated in rabbits. The flap, being fed by the superficial epigastric artery, was transplanted to the leg, and the saphenous nerve was implanted into it. The restoration of flap sensation was studied neuroelectrophysiologically. It was shown that nerve fiber discharges were detected within the boundary of the flaps, and mainly in the central portion of the flap along the course of the implanted nerve, in the nerve implantation animals. There was definite evidence of re-establishment of tactile, pressure, pain and temperature sensations in the flap, except that the unit discharges evoked by lower threshold stimulation were less than normal. In the flaps without nerve implantation nerve fiber discharge was rare, and pain and temperature sensation discharges could not be recorded. In 8 patients, nerve implantation was done in an attempt to re-establish sensations in the fingers. Altogether, 11 lateral antebrachial cutaneous nerve grafts were implanted to 10 fingers. The longest nerve graft was 9cm, and the shortest 2.5cm. They were implanted under the dermis of the denervated palmar skin of fingers or flaps. The follow-up time was 97-924 days. The results were very satisfactory.

Adolescent↗
PubMed1991

[Detection of Plasmodium falciparum infection in humans by (Dig)-DNA probe].

In this study, we used Digoxigenin, (Dig)-11-dUTP, in the Genius kit purchased from Boehringer Mannheim to label the Plasmodium falciparum (P.f.) DNA fragment by random primed labelling method. The P. falciparum DNA fragment was isolated from the recombinant clone pPF14 by enzyme digestion and agarose electrophoresis. This probe is designated pPF14-F-Dig. Purified P.f. DNA and blood samples from malaria patients in Hainan Province of China were detected by the probe in dot-blot hybridization. Thirty-eight patients with falciparum malaria, three with falciparum malaria and vivax malaria and four with vivax malaria were detected with the pPF14-F-Dig probe. The results showed that the pPF14-F-Dig probe could detect at least 40 pg of P.f. DNA and a parasitemia of 0.005 percent. Out of 38 detected P.f. patients' blood samples, 33 hybridized positively with this probe. The positivity rate was 86.8%. Twenty-one normal blood samples all showed negative. In addition, 2 of 3 samples with P.f. and P.v. were positive. Three of 4 samples with P.v. were negative and one was doubtful. The preliminary result of this study indicates that the pPF14-F-Dig probe could detect the patients of falciparum malaria with good sensitivity and specificity, and that this probe can be used to detect the patients with P. falciparum in Hainan Province.

Animals↗