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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 1,225 records · Page 68Linked to original sources
PubMed1995

Analogical transfer: from schematic pictures to problem solving.

A series of experiments was conducted to explore whether individuals can solve problems by transferring conceptual information gained from schematic pictures and to examine the mechanisms involved in this transfer process. Subjects viewed a schematic picture and then attempted to solve an insight problem to which the conceptual information from the picture could be applied. The results indicate that the degree of similarity--specifically, superficial and procedural similarity--between a source schematic picture and the target problem determined transfer performance. Discussion focuses on the relationship between these two types of similarity and the two key cognitive components involved in transferring pictorial analogies to solve problems: accessing the pictorial analogues and executing the solutions.

Adult↗
PubMed1995

Precue effects in visual search: data or resource limited?

Precuing an observer as to where a target is more likely to occur in a subsequent visual array can increase the detectability (d') of a target at that location. This is often attributed to the observer's increased allocation of some limited cognitive resource ("attention") to the cued location. Two experiments are reported which are difficult to interpret in this way even though they involve similar cue effects. The first involves postcuing a location well after the array but before the observer responds, so that the cue can influence the response but not the observation. The second involves precuing, but with slow sequential presentation of array elements prior to the response, so the observer need not share any limited resource while processing each element in turn. Enhanced detectability similar to that produced with precues and simultaneous presentation of elements is shown to occur in each experiment. An alternative data-limited (rather than resource-limited) interpretation of these effects is provided by a mathematical model in which the observer integrates equally noisy or degraded internal representations of the array elements, but gives more weight to cued elements in selecting a response. Theoretical parameters of the model are shown to provide separate measures of both an observer's overall sensitivity and precue effects in cost-benefit analyses of cuing data.

Adult↗
PubMed1995

[Preliminary clinical study of endodontic antiseptic in monotithic type chlorhexidine controlled release delivery system]

The purpose of clinical study was to assess the bacteriological status of the root canal after disinfection with the monotithic type chlorhexidine enrolled release delivery system (CCROS).In experiments the monotithic type CCRDS was found to be more effective than the reservoir type CCRDS.The root canals of 24 teeth with apical periodontitis were completely instrumented and irrigated with sodium hypochloride.After the instrumentations,12 teeth were treated with the monotitihic type CCRDS,12 teeth were treated with formocresol.Bacterological samples from the root canals were taken after 5 days using an anaerobic technique.The results indicated that monotithic type CCRDS was more effective than formocresol in obtaining bacteria-free root canals(Chi-square test P<0.05).The advantages of an antiseptic with along lasting effect for the elimination of bacteria form the root canal and for the prevention of reinfection were emphasized.

Journal Article↗
PubMed1995

[Role of afferent renal nerves in 2K2C Goldblatt hypertension].

In order to study the role of afferent renal nerves in 2K2C Goldblatt hypertension, the renal afferent nerves were selectively lesioned by bilateral T9-L2 spinal dorsal rhizotomy before clipping (internal diameter, 0.3 mm) of birenal arteries. Systolic blood pressure of the rat was measured by tail-cuff method. Concentrations of catecholamines, Ang II, and aldosterone were determined respectively by HPLC-EC and RIA, and vascular structural changes were measured by blood vessel micro-image analysis system coupled with a computer. The results showed that the concentrations of NE and E in medulla oblongata, adrenal gland and plasma, and of plasma Ang II and aldosterone as well as body weight of the rat were all significantly increased. The heart coefficient (heart wt/body wt), the media thickness, and the media thickness/lumen diameter in superior mesenteric arteries were also increased in 2K2C hypertensive rats (clipping, 6 wk) as compared with those in control rats. Bilateral rhizotomy delayed development of 2K2C hypertension and prevented above-mentioned vascular structural changes, the NE and E concentrations of medulla oblongata, adrenal gland and plasma were all decreased, hypothalamic NE and E were increased, and plasma Ang II level was not significantly changed. These results suggest that afferent renal nerves may play a partial role in the development of hypertension in 2K2C rats by activating sympathetic nervous system as a result of affecting metabolic activities of brain catecholaminergic neurons, and that high-plasma Ang II and aldosterone as well as heart hypertrophy and proliferation of vascular smooth muscle cells may also participate in the pathogenesis of hypertension in 2K2C rats.

Afferent Pathways↗
PubMed1995

Purification and characterization of prostate-specific antigen (PSA) complexed to alpha 1-antichymotrypsin: potential reference material for international standardization of PSA immunoassays.

We describe for the first time a protocol to purify to apparent homogeneity an in vitro-prepared complex of prostate-specific antigen (PSA) and alpha 1-antichymotrypsin (ACT) by using a combination of gel filtration and ion-exchange chromatography. The purity of the PSA-ACT complex was confirmed by gel electrophoresis and Western blot. The PSA-ACT complex was stable in the pH range 6.0 to 7.8; it was also stable in various matrices, temperatures, and high concentrations of salt. Purification of the PSA-ACT complex was highly reproducible. An absorptivity of 0.99 L x g-1 x cm-1 at 280 nm was assigned to the PSA-ACT complex, based on amino acid analysis. Because PSA and ACT bind in a 1:1 molar ratio, we determined the molecular mass of the PSA-ACT complex as the mass encoded by the cDNA of ACT (plus 26% carbohydrate) plus the molecular mass of PSA (28,430 Da), which totals 89,280 Da. Using this material, we made two common calibrators, one of 100% PSA-ACT complex and one of 90% PSA-ACT complex plus 10% free PSA by volume (90:10 calibrator). Substitution of these calibrators for the manufacturers' calibrators in nine commercial immunoassays substantially reduced differences between immunoassays, especially for serum PSA values between 4 and 10 micrograms/L. The 90:10 calibrator is recommended as a universal calibrator for international standardization of PSA immunoassays.

Amino Acid Sequence↗
PubMed1995

A new animal model of coronary thrombosis and effects of antithrombotic agents.

The model was established in male rabbits with experimental atherosclerosis, which was induced by diet cholesterol (0.5 g per day for 8 weeks), by means of intravenous injection of one unit of pituitrin (P.P.). To evaluate the effects of aspirin, heparin and viper venom (VV) on this model, 26 male rabbits were divided randomly into four groups: group A (GA) as control, group B (GB) treated with heparin (10mg, i.v.), group C (GC) with VV (0.08 arginine esterase activity units), group D (GD) with both heparin and VV. Aspirin (30 mg) was given orally before experiment. The results showed that the rate of coronary thrombosis was 11.26% in GA, 8.10% in GB, 9.17% in GC, and 7.56% in GD respectively. The difference between each of three treated groups and the control one was significant (P < 0.005, 0.05, 0.001, respectively). Such a difference can also be found between GA and that without oral aspirin (11.26% vs 16.39%, P < 0.001). The beneficial effects of heparin and VV may be due to their inhibitory effects on different steps of thrombosis, i.e., heparin can prolong the coagulation time, and VV can inhibit platelet aggregation and decrease the concentration of plasma fibrinogen. It is concluded that heparin, viper venom, and especially their combination would be useful in the treatment of human acute coronary syndromes.

Animals↗
PubMed1995

[Epidemiological studies on risk for adverse pregnancy outcomes in women neighboring a petrochemical works].

Data of 7695 deliveries during 1985-1992 in four general hospitals neighboring a petrochemical works in Guangzhou were collected. Relationship between air pollution surrounding the plant and adverse pregnancy outcomes (APO) in women living there, including congenital malformation, stillbirth, low birth weight and preterm birth, was analyzed with air monitoring data and exposure assessment indices. Results showed there was difference in incidence rates of APO between lying-in women living in the places with various distance from the plant, and the incidence lowered with the distance prolonging, with a P-value of less than 0.05. Unconditional logistic model was used to control confounding and to estimate relative risks in a study of 325 cases of APO and 390 randomly sampled normal controls. Results indicated the distance between the places where the women living and the plant related to incidence of APO. It suggested air pollution caused by the petrochemical works may be a risk factor for APO in neighbored women.

Air Pollutants↗
PubMed1995

[Foraminal and extraforaminal lumbar disc herniations].

Between August 1992 to November 1994, 7 cases of foraminal and 3 cases of extraforaminal lumbar disc herniation were diagnosed and operated on, which represented an incidence of 4.1% of all operated lumber disc herniations. Contrasted to the typical disc herniation, foraminal and extraforaminal disc herniations involved the upper nerve root mainly. The dominent symptoms and signs were severe anterior thigh and lower leg pain, positive femoral nerve strech test, impairment of knee jerk reflex and weakness of the quadriceps muscle. Sequestration and extrusion were the most common type of disc pathology. CT/MRI showed the protruded disc in and outside of the foramen clearly. It was thought to be ideal method for the precise diagnosis and guidance of surgery. However the variations of the nerve root or other diseases related to it should be identified. All of the 10 cases underwent surgical treatment with the approach by outer edge of pars interarticularis in 8. The result was encouraging with complete improvement in 8 cases, obvious improvement in 1 case, and partial improvement in another case. It was found that the approach had the advantage of good exposure and effect with the minimal destruction of pars interarticularis and facet joint which would not give rise to lumbar instability.

Adult↗
PubMed1995

Reduction of bovine plasma cholesterol concentration by partial interruption of enterohepatic circulation of bile salts: a novel hypocholesterolemic model.

Interruption of enterohepatic circulation (EHC) of bile salts in several species is known to cause a significant decrease in plasma concentrations of low density lipoprotein (LDL) cholesterol, but to have little effect on high density lipoprotein (HDL) cholesterol. The present study, for the first time, demonstrates that partial interruption of EHC dramatically reduces both plasma LDL and HDL cholesterol concentrations in cattle. Five adult Holstein cows were surgically altered to allow controlled portions of bile flow to be diverted from the body. The animals were fed a low-fat, cholesterol-free diet. In two experiments, bile was diverted at 50% and 22% of total flow rates. By day 8 of diversion, both rates reduced mean plasma cholesterol from baseline (85 mg/dl) to about 8 and 18 mg/dl, respectively. Cholesterol was reduced in equal proportions in all lipoprotein fractions. In addition, plasma concentrations of triglycerides and phospholipids were also dramatically reduced. All of these plasma lipids returned to baseline within 1 week after restoration of bile flow. To determine the hepatic response to bile diversion, liver cholesterol concentrations, cholesterol synthesis rates, and LDL receptor-binding activities were determined in biopsy samples. In response to bile diversion, hepatic cholesteryl esters were markedly depleted while hepatic cholesterol synthesis rates were increased by more than 10-fold. Nevertheless, because the basal cholesterol synthesis rate was so low, it was estimated that the increase in synthesis would have supplied no more than 5% of the sterols depleted during bile diversion (1.2 vs. 25 mmol/day). LDL receptor-binding activity was significantly elevated, suggesting an increased uptake of plasma lipoprotein cholesterol by the liver. These results suggest that the unique sensitivity of bovine plasma cholesterol to enterohepatic circulation interruption might occur as a result of the inherently low rate of hepatic cholesterol synthesis in cattle. This hypocholesterolemic model might serve as an interesting tool for the study of factors regulating plasma HDL cholesterol.

Animals↗
PubMed1995

[Experimental studies of glomerular endothelial cell culture and its production of extracellular matrixes].

We successfully cultured human fetal and bovine glomerular endothelial cells by cell cloning and maintained seven passages. The glomerular endothelial cells were identified by indirect immunofluorescence method. We found that the fetal and bovine glomerular endothelial cells could produce factor VIII related antigen, fibronectin, type IV collagen and laminin. The extracellular matrixes in the cultured supernatant were determined at various stages. The results showed that the glomerular endothelial cells could produce extracellular matrixes steadily without any stimulating factor.

Animals↗
PubMed1995

[Involvement of opioid peptides in corticofugal modulation of pain].

The effect of opioid peptides on corticofugal modulation of nociceptive response in thalamic ventrobasal nucleus (VB) produced by cortical sensorimotor area II (Sm II) was observed. Single unit activities of VB neurons were extracellularly recorded by glass microelectrodes. The results showed that the nociceptive responses of VB neurons were attenuated at 0-7.5 minutes after stimulating Sm II (n = 14, P < 0.05). The inhibitory effect of stimulation of Sm II was reduced after ventriculer microinjection of 20ul of naloxone (n = 9), while marked inhibition was shown at 0-2.5 minutes after stimulating Sm II in the saline control group (n = 9, P < 0.05). There was a statistical difference at 0-2.5 minutes after stimulating Sm II between the two groups (P < 0.05). These studies suggest that opioid peptides might be involved in corticofugal modulation of pain.

Animals↗
PubMed1995

[Influence of SmI lesion on acupuncture-induced analgesia in thalamic Pf neurons and effects of iontophoretic ACh on their nociceptive responses].

This study aimed to investigate the role of ACh in SmI emanating descending modulation of thalamic Pf neurons in acupuncture analgesia. Multi-micropipettes were used for both extracellularly recording responses of thalamic Pf neurons to noxious stimulation of the plantar area and drug application in rats. It was found that (1) lesion of SmI obviously attenuated the inhibitory effect of EA applied at "Zusanli" and "Huantiao" points on nociceptive responses in Pfneurons; (2) after lesion of SmI iontophoretic application of ACh markedly suppressed the nociceptive responses of Pf neurons, which was significantly different from the effect of iontophoretic NaCl (as the control) showing no influence on them; (3) the inhibition induced by iontophoretic ACh applied in the rats with lesion of SmI was similar to that produced by EA applied in those with SmI intact. It is indicated that EA can activate SmI to release ACh to exert descending modulation, in which ACh is involved in SmI originating descending regulation of Pf neruons in acupuncture analgesia.

Acetylcholine↗
PubMed1995

[A study on the relationship between morphology and gene heterogeneity in acute promyelocytic leukemia].

Aucte promyelocytic leukemia (APL) can be treated by all-trans retinoic acid (ATRA) with high complete remission rate. 50 cases of APL diagnosed morphologically were studied on their cytogenetics, molecular biology and response to treatment with ATRA. Forty-five cases showed chromosomal translocation t(15; 17) and PML/RAR alpha fusion gene (PML + RAR alpha + APL). They had typical morphologic change, in which hypergranular cells appeared more frequently in L type of PML/RAR alpha and microgranular cells in S type of PML/RAR alpha. Among the 45 PML + RAR alpha + APL patients 8 died early and 37 had complete remission with ATRA. In the remainging 5 patients, three had typical APL morphologic features in cytology, but one of them displayed t (11; 17) with PLZF+RARA alpha +, the second showed RAR alpha + PML - (PML - RAR alpha + APL) and the third PML - RAR alpha -(PML - RAR alpha - APL). They did not respond to ATRA treatment. These data indicate that APL is not a homogeneous disease. The other a patients had neither chromosomal translocation nor rearrangements of the two genes. On careful morphological reexamination, these two cases were not APL, but one of them responded well to ATRA. It is shown that morphology is the important diagnostic basis of APL, but in a few APL cases diagnosis should be made with the help of cytogenetics and molecular biology. Response of ATRA treatment may be of diagnostic value of APL, but is not a specific criterion.

Adolescent↗
PubMed1995

[Epidemiological investigation of Campylobacter Jejuni infection in children].

Epidemiological studies on campylobacter jejuni infection in children were carried out in Chengdu during December 1987 to October 1989. Detection rate of campylobacter in 1,092 children with diarrhea was 11.36%, with the highest in children aged 1-2 and the lowest in babies within six months. Campylobacter jejuni could be detected in young children with acute diarrhea all the year round, with a higher detection rate in the spring and summer and lower in the autumn and winter. Campylobacter jejuni could be detected in 5.09% of healthy children, with a significant difference between kindergartens due to their living conditions. Use of spectrum of drug-resistance and plasmid analysis in children of nurseries and kindergartens to study campylobacter infection suggested campylobacter jejuni infection in children could be caused by a lot of distant-associated strains with genetic homogeneity.

Age Factors↗
PubMed1995

[The inhibitory effect of intraperitoneal hyperthermic and hypotonic chemotherapy on ascites cancer cells in mice].

To study the effect of inhibition of intraperitoneal hyperthermic hypotonic chemotherapy on the ascites cacer cells, LACA mice were given intraperitoneal injection of H22 cancer cells (2 x 10(7) tumor cell, each mouse). At 24 hours after the cancer injection, intraperitoneal simple hyperthermic (43 C) hypotonic fluid group (I), isotonic fluid group (II), cis-Diamminodichloroplatinum (DDP) group (IV) and hyperthermic hypotonic fluid perfusion combined with DDP group (V) were processed. The results showed that cancer cells in LACA mice peritoneal cavity were seriously damaged, the ascites growing was obviously inhibited, and the survival days of LACA mice were prolonged in all groups; however, the intraperitoneal hyperthermic hypotonic fluid perfusion with DDP group (V) presented greater effect compared with the other groups. This might be a new therapeutic procedure for the prevention and treatment of cancer ascites in the patients with digestive tract malignancies.

Animals↗
PubMed1995

[Organ regeneration and somatic embryogenesis from young stems of Fritillaria sinica].

Regenerated bulbs and embryogenetic calli were inducted from young stems of Fritillaria sinica cultured on Murashige and Skoog (MS) medium supplemented with alpha-naphthale-neacetic acid (NAA), 2, 4-dichlophenexy-acetin acid (2, 4-D), 6-benzylaminopurine (6BA) and kenetin (Kt) respectively. The callus cultures used for the organ regeneration and somatic embryogenesis were subcultured at intervals of 30-40 days on MS medium+NAA 1mg/L + 6BA 0.5mg/L. In general, the bulbs can be obtained from cultured Fritillaria sinica through three ways: (1) induction from explants; (2) production of adventitious buds or (3) somatic embryogenesis.

Culture Media↗
PubMed1995

V-J junctional sequences of T cell receptor gamma gene in acute lymphocytic leukemia.

T cell receptor TCR gamma gene rearrangement in a series of acute lymphocytic leukemia (ALL) patients was studied using PCR technique. 18 V-J junctional sequences (designated by N sequence) of TCR gamma gene were amplified with the V gamma and J gamma primers, using an unsymmetrical PCR and analysed by direct sequencing, demonstrating that in Chinese ALLs, the N sequences of TCR gamma gene are indeed clone-specific. Based on the known N sequences, several oligo-nucleotides were synthesized as probes, which were specific for the leukemic clone, and were used to detect the minimal residual disease (MRD) in 4 ALL cases. The sensitivity of this method was 0.1%-0.01%.

Adult↗