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Biomedical subjects

Q Chen

Publications and source records attributed to Q Chen.

At least 667 records · Page 37Linked to original sources
PubMed1993

Type II collagen during cartilage and corneal development: immunohistochemical analysis with an anti-telopeptide antibody.

We have examined the pattern of immunoreactivity of a monoclonal antibody, II-5B2, with specificity for an epitope which resides within the NH2-terminal extension peptide (telopeptide) of the avian type II collagen molecule. This epitope is available in regions of matrix where de novo synthesis of the molecule is ongoing, but not where synthesis has ceased and maturation and crosslink formation have occurred. Within the cartilaginous growth plate, the epitope disappears from the matrix soon after the chondrocytes become hypertrophic; within the cornea, the epitope disappears subjacent to the epithelium. The II-5B2 epitope is not made available by a variety of procedures shown to remove potentially masking substances and to disrupt fibrillar organization. It is rendered available, however, when covalent crosslink formation between collagen molecules is blocked through administration of beta-aminopropionitrile or penicillamine. In contrast, the epitope of another monoclonal antibody against type II collagen, II-II6B3, which resides in the triple-helical domain of the molecule, in cartilage is present throughout the growth plate including the hypertrophic zone, and in cornea extends for a considerable distance into the stroma. Thus, it is available for antibody binding regardless of fibril maturation and crosslinking. These data suggest that the II-5B2 epitope becomes unavailable when the telopeptide becomes crosslinked. By using these two monoclonal antibodies in serial sections, one can establish the crosslinking pattern of type II collagen in the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminopropionitrile↗
PubMed1993

Chicken tibial dyschondroplasia: a limb mutant with two growth plates and possible defects of collagen crosslinking.

In the cartilaginous epiphyseal growth plate, extracellular matrix molecules such as collagens are believed to play important roles during both normal and abnormal development. One defect of the epiphyseal plate occurs in chickens with a condition termed tibial dyschondroplasia (TD). This abnormality occurs in certain strains of juvenile chickens and other rapidly developing animals. It is characterized by the presence of a mass of avascular, uncalcified cartilage which is retained in the proximal metaphysis of the tibiotarsus. To elucidate the developmental events which may be involved in this lesion, we have performed both immunohistochemistry and in situ hybridizations for collagen types II and X, known components of the extracellular matrix of the growth plate. By immunohistochemical analyses, the TD lesion contains both of these collagen types; therefore, the presence of these molecules per se is not sufficient for calcification of vascularization to occur. Since type X collagen is expressed exclusively in hypertrophic cartilage, the chondrocytes in the lesion must have undergone hypertrophy before their developmental arrest. The matrix of the lesion also reacted with a monoclonal antibody which is directed against an epitope in the NH2-terminal telopeptide of the alpha 1(II) chain. Our previous data suggest that this epitope is rendered unavailable in type II collagen which has undergone crosslink formation; its availability in the lesion suggests that crosslinking may be abnormal. Lastly, analyses by in situ hybridization failed to detect mRNA for either type II or type X collagen within the lesion, but chondrocytes distal to the lesion do contain mRNAs for these collagens in a spatial pattern suggesting the presence of a second growth plate.

Animals↗
PubMed1993

Properties and amino acid sequence of huwentoxin-I, a neurotoxin purified from the venom of the Chinese bird spider Selenocosmia huwena.

By means of reverse phase and ion-exchange high performance liquid chromatography, a neurotoxic peptide named huwentoxin-I was purified from the venom of the Chinese bird spider Selenocosmia huwena. The intraperitoneal and intracisternal LD50 in mice of the toxin were 0.70 mg/kg and 9.40 micrograms/kg, respectively. This toxin at the concentration of 1 x 10(-5) g/ml can irreversibly block the neuromuscular transmission of the isolated mouse phrenic nerve-diaphragm preparation in 13.4 +/- 1.3 min (mean +/- S.D., n = 5). The isoelectric point is 8.95 determined by isoelectric focusing electrophoresis. It consists of 33 amino acids including 6 Cys and 6 Lys determined by amino acid analysis. The complete amino sequence of huwentoxin-I was determined. The N-terminal and C-terminal residues were Ala and Leu, respectively. The primary structure showed partial homology with that of mu-agatoxins from the funnel-web spider Agelenopsis aperta.

Amino Acid Sequence↗
PubMed1993

Targeting of saporin to CD25-positive normal and neoplastic lymphocytes by an anti-saporin/anti-CD25 bispecific monoclonal antibody: in vitro evaluation.

This study has been designed to verify the specific toxicity of saporin, a type 1 ribosome-inactivating protein (RIP), with the same activity as ricin A chain, targeted by a bispecific monoclonal antibody (bimAb) recognising both the CD25 antigen and the RIP. The CD25 antigen is expressed by lymphoid populations upon activation and by leukaemias and lymphomas with an activated membrane phenotype (Hodgkin's lymphoma, anaplastic large cell lymphoma, adult T cell leukaemia). The bimAb-saporin mixture was tested on CD25+ targets at different bimAb and saporin concentrations. Saporin, in the presence of a bimAb concentration of 10(-9) M, inhibited protein synthesis by CD25+ neoplastic lymphocytes (L540 and MT2 cell lines) with IC50S (concentrations giving 50% of inhibition) ranging from 8 x 10(-12) M to 3 x 10(-11) M. The saporin-bimAb mixture was also effective in blocking the phytohaemagglutinin-driven proliferation of normal lymphocytes, whereas it displayed the same level of toxicity exerted by saporin alone on an irrelevant CD25-negative cell line (EBV-infected B lymphoblastoid cell line). From these results it is possible to envisage a clinical use of this bimAb as a cytotoxic agent for CD25+ leukaemias and lymphomas, as well as an immunosuppressive agent for severe immune disorders such as graft-vs-host disease (GVHD) and transplanted organ rejection.

Animals↗
PubMed1993

Temperature modulation of cerebral depolarization during focal cerebral ischemia in rats: correlation with ischemic injury.

The role of cerebral depolarizations in focal cerebral ischemia is unknown. We therefore measured the direct current (DC) electrical activity in the cortex of Wistar rats subjected to transient occlusion of the middle cerebral artery (MCA). Focal ischemia was induced for 90 min by insertion of an intraluminal filament to occlude the MCA. To modulate cell damage, we subjected the rats to hypothermic (30 degrees C, n = 4), normothermic (37 degrees C, n = 4), and hyperthermic (40 degrees C, n = 6) ischemia. Controlled temperatures were also maintained during 1 h of reperfusion. Continuous cortical DC potential changes were measured using two active Ag-AgCl electrodes placed in the cortical lesion. Animals were killed 1 week after ischemia. The brains were sectioned and stained with hematoxylin and eosin, for evaluation of neuronal damage, and calculation of infarct volume. All animals exhibited an initial depolarization within 30 min of ischemia, followed by a single depolarization event in hypothermic animals, and multiple periodic depolarization events in both normothermic and hyperthermic animals. Hyperthermic animals exhibited significantly more (p < 0.05) DC potential deflections (n = 6.17 +/- 0.67) than normothermic animals (n = 2.75 +/- 0.96). The ischemic infarct volume (% of hemisphere) was significantly different for the various groups; hypothermic animals exhibited no measurable infarct volume, while the ischemic infarct volume was 10.2 +/- 12.3% in normothermic animals and 36.5 +/- 3.4% in hyperthermic animals (p < 0.05). A significant correlation was detected between the volume of infarct and number of depolarization events (r = 0.90, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Does the bile salt-stimulated lipase of human milk have a role in the use of the milk long-chain polyunsaturated fatty acids?

Long-chain polyunsaturated (LCP) fatty acids derived from linoleic (18:2 n-6) and alpha-linolenic (18:3 n-3) acids are considered essential nutrients in preterm infants. The efficiency by which such fatty acids are released as absorbable products from triacylglycerol was explored in vitro using rat chylomicron triacylglycerol as substrate. When incubated with purified human pancreatic colipase-dependent lipase and colipase, arachidonic acid (20:4 n-6) was released less efficiently than linoleic acid from such triacylglycerol. This difference was not seen when purified human milk bile salt-stimulated lipase (BSSL) was incubated with the triacylglycerol substrate, and it was almost abolished when colipase-dependent lipase (with colipase) and BSSL acted simultaneously, as they do in breast-fed infants. There was no difference in arachidonic acid and eicosapentaenoic acid (20:5 n-3) release rates with either colipase-dependent lipase or BSSL, albeit the release was more rapid with the milk enzyme than with colipase-dependent lipase. Again, the most efficient release as absorbable free fatty acids was achieved when the two lipases operated together. The relative resistance to hydrolysis of arachidonic acid and eicosapentaenoic acid by colipase-dependent lipase was best explained by the localization of the first double bond to the delta-5 position of the respective fatty acid. The results obtained suggest that BSSL is of importance for the efficient use of human milk LCP fatty acids.

Animals↗
PubMed1993

Characterization of two cytosolic diacylglycerol kinase forms.

Two forms of rat brain cytosolic diacylglycerol kinase (EC2.7.1.107) were separated by heparin-agarose column chromatography. These forms, designated DGK-I and DGK-II, were not interconvertible as determined by rechromatography. DGK-I and DGK-II had respective molecular masses of 88 and 180 kDa, as measured by Sepharose 6B chromatography. Both forms preferred diacylglycerol over monoacylglycerol and were insensitive to R59022. DGK-II, but not DGK-I, was activated by an activator substance prepared from chicken egg yolk. DGK-II was activated by a rat brain cytosolic activator and was exclusively sensitive to 5'-AMP-mediated inactivation. Further studies revealed that these two forms had the following distinct characteristics: (a) substrate specificity, (b) inhibition by heparin, (c) sensitivity to lysine-containing polyamino acids, and (d) responses to different phospholipids. In general, DGK-II was more responsive to various inhibitors and activators, making it a prime candidate for a regulatable enzyme.

Adenosine Monophosphate↗
PubMed1993

The superficial buffer barrier in venous smooth muscle: sarcoplasmic reticulum refilling and unloading.

1. The interaction of Ca2+ transport in the plasmalemma and the sarcoplasmic reticulum (SR) was investigated in smooth muscle of the rabbit inferior vena cava. We tested the possibility of direct refilling of the SR with extracellular Ca2+ and of the existence of a vectorial Ca2+ extrusion pathway from the SR lumen to the extracellular space suggested by earlier results. 2. After depletion with caffeine the SR was loaded with Ca2+ to increasing levels by incubation in a high potassium 1.5 mM Ca2+ solution and a 10 mM Ca2+ zero Na+ solution, respectively. Thapsigargin, 2 microM, (a specific SR Ca(2+)-ATPase blocker) completely blocked refilling of the SR in either of the above solutions, indicating that the SR Ca(2+)-ATPase is essential for this process. 3. Three different agents, caffeine, ryanodine and thapsigargin, which inhibit Ca2+ accumulation by the SR, increased the steady state intracellular Ca2+ concentration in the rabbit inferior vena cava. 4. Measurements of Mn2+ induced quenching of the intracellular fura-2 signal during pharmacological manipulation of the SR content showed that these three agents did not stimulate divalent cation entry. 5. On the other hand, stimulation with noradrenaline caused a marked increase in Mn2+ influx, which was blocked by 2 mM Ni2+. Mn2+ entry stimulated by high K+ solution was blocked by 1 microM diltiazem. 6. We conclude that the SR refilling has to be mediated by the SR Ca(2+)-ATPase. Inhibition of Ca2+ accumulation by the SR causes an increase in the steady state intracellular Ca2+ concentration. This observation cannot be explained by an increase in Ca2+ influx into the smooth muscle cells of the rabbit inferior vena cava. Alternatively these results suggest the existence of a continuous vectorial release of Ca2+ from the SR lumen to the extracellular space.

Animals↗
PubMed1993

Immunostaining of human autopsy aortas with antibodies to modified apolipoprotein B and apoprotein(a).

A systematic immunohistochemical study of different stages of atherosclerosis in human aortas was performed using several antibodies. Because oxidation of lipoproteins could be a key event in atherogenesis, an antibody against apolipoprotein B (apoB) from low-density lipoprotein (LDL) modified with the lipid peroxidation-specific aldehyde, 4-hydroxynonenal (4-HNE) (anti-4-HNE-apoB), was raised in rabbits. This antibody recognizing 4-HNE protein adducts was used in concert with an antibody to apo(a) from lipoprotein(a), considered also potentially atherogenic, as well as with an antibody and a monoclonal antibody (mAb) to apoB. Autopsy material from 12 corpses was investigated. The immunohistochemical investigation by the alkaline-phosphatase technique included control specimens regarding postmortem artifacts by autolysis and oxidation. The results from six specimens from five corpses are presented. A positive staining with the antibody to apoB but not with anti-4-HNE-apoB was seen in the normal intima. The thickened intima of early, transitional, and advanced atherosclerotic lesions and atheromata showed a predominantly extracellular staining with all antibodies and the applied mAb. To test the specificity of the staining, antibodies preadsorbed by the appropriate antigens and nonimmune sera were used, giving negative results. These findings indicated a colocalization of epitopes derived from lipid peroxidation of polyunsaturated fatty acids and epitopes specific for apoB and apo(a) during atherogenesis in humans.

Aged↗
PubMed1993

Potentiation of the vasospastic response to angioplasty by pretreatment with fluoxetine. A study in the atherosclerotic rabbit.

There is evidence that angioplasty-induced vasospasm is mediated by serotonin (5-hydroxytryptamine [5-HT]) release from platelets. We tested the hypothesis that pretreatment of the atherosclerotic rabbit with fluoxetine, a platelet-uptake inhibitor of 5-HT, would reduce vasospasm after balloon angioplasty. Short-term administration of fluoxetine reduced platelet 5-HT uptake to 4% of baseline. Daily administration of fluoxetine for 7 days reduced whole-blood 5-HT levels to 28% of baseline. Thus, fluoxetine inhibited platelet 5-HT uptake in this model as predicted. Contrary to our expectations and despite the substantial reduction in whole-blood 5-HT levels, pretreatment with fluoxetine for 1 week resulted in augmentation of angioplasty-induced vasospasm in atherosclerotic rabbits. Intraperitoneal administration of fluoxetine produced vasoconstriction in normal rabbits that was augmented by 5-HT and not reversed with LY53857, a specific serotonin receptor antagonist. We postulate that this new observation is probably a result of the inhibition of the clearance mechanism for serotonin, with resultant enhancement of the effect of serotonin released by the activated platelets that are deposited on the vessel wall surface at the time of angioplasty. A direct effect of fluoxetine on serotonergic receptors is a second possible mechanism for the observed effect.

Angioplasty↗
PubMed1993

Genomic elements involved in transcriptional regulation of the rabbit surfactant protein-A gene.

Expression of the surfactant protein-A (SP-A) gene is lung specific and is developmentally and hormonally regulated in fetal lung tissue. Cyclic AMP analogs and glucocorticoids stimulate transcriptional activity of the SP-A gene in fetal rabbit lung tissue in culture; an additive effect is observed when the agents are added in combination. To analyze the genomic regions that regulate SP-A promoter activity, fusion genes comprised of -1766, -991, -378, and -47 basepairs (bp) of DNA flanking the 5'-end of the SP-A gene, the transcription initiation site, and 20 bp of exon I linked to the human GH (hGH) structural gene were subcloned into a replication-defective human adenovirus vector and transfected into differentiated rat type II cells in primary culture. SP-A promoter activity was analyzed by RIA of hGH protein in the culture medium. In type II cells transfected with SP-A-1766:hGH and SP-A-991:hGH fusion genes, hGH production was induced 30- to 40-fold by (Bu)2AMP (Bt2cAMP; 1 mM). When type II cells were transfected with the SP-A-378:hGH fusion gene, basal levels of expression were reduced by more than 50%; however, Bt2cAMP caused an 11-fold increase in hGH production. In type II cells transfected with the SP-A-47:hGH fusion gene, basal levels of hGH production were essentially undetectable, and no stimulatory effect of Bt2cAMP was apparent. Cyclic AMP stimulation of expression of the SP-A-1766:hGH, SP-A-991:hGH, and SP-A-378:hGH fusion genes was limited to type II pneumonocytes in primary culture and was absent in two lung adenocarcinoma cell lines (NCl-H358 and A549), which do not express SP-A, and in cAMP-responsive adrenal Y1 cells. Mutations of a putative cAMP-responsive element (TGACCTCA) at -261 bp revealed its functional importance in mediating cAMP regulation of SP-A gene expression. Unexpectedly, dexamethasone (Dex; 10(-7) M) antagonized the stimulatory effect of Bt2cAMP on expression of SP-A:hGH fusion genes containing from -378 to -1766 bp of 5'-flanking DNA as well as that of a fusion gene construct containing -991 bp of 5'-flanking DNA, the first exon, the first intron, and 20 bp of the second exon (SP-A-991+670:hGH). The inhibitory effect of Dex was dose dependent, with half-maximal inhibition occurring at a Dex concentration of 8 x 10(-10) M. The inhibitory effect of Dex was prevented by the glucocorticoid receptor antagonist RU486.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1993

Elemental analysis of renal slices by proton-induced X-ray emission.

We optimized proton-induced X-ray emission (PIXE) for tissue analysis in a toxicity-disposition study. We used cultured rabbit renal slices as the biological system to demonstrate the use of PIXE analysis. The renal slices were exposed to HgCl2, CdCl2, K2Cr2O7, or NaAsO2 alone or in a mixture. The PIXE analysis provides information on concentrations of elements above atomic number 11, and it is the only analytical technique that can determine 20-30 elements nondestructively in a single, small sample (approximately 5 mg) with detection limits of 1-5 ppm (dry weight). The renal slices are thin targets that yield X-ray emission spectra with low backgrounds and high elemental sensitivities. The nondestructive nature of PIXE and the ability to simultaneously measure uptake of multiple metals and endogenous elements are unique to this methodology.

Animals↗
PubMed1993

Antioxidant properties of fractions and polyphenol constituents from green, oolong and black teas.

Green, oolong and black teas were extracted with water, and then the water extracts were extracted separately with three types of solvent, chloroform, ethyl acetate and butanol, to obtain eight fractions. Major flavanol was extracted by EtOAc, while most of the alkaloid was in the chloroform fraction. Thearubigin was greatest in the butanol fraction, and most of the amino acid remained in the water fraction. All fractions were systematically analyzed by UV spectrophotometer and reverse phase HPLC for those important components existing in green tea, oolong tea, and black tea. The pure compounds of (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), free theaflavin, theaflavin monogallate-A, theaflavin monogallate-B, and theaflavin digallate were separated by LH-20 chromatography and reverse phase HPLC. All fractions and pure compounds were assayed for antioxidant activity and lipoxygenase inhibition activity. Flavanol showed very strong antioxidant activity and lipoxygenase inhibition.

Antioxidants↗
PubMed1993

[Clinical and pathological analysis on 44 cases of lid haemangioma].

Forty four cases of lid haemangioma are reported. 6 cases were diagnosed as cavernous haemangioma and treated by sclerosis therapy. The postoperative pathology examination to the other 38 cases showed that there were 9 cases of capillary haemangioma, 18 cases of cavernous, 8 cases of benign haemangioendothelioma, 1 case of racemose and 2 cases of mixed type. The age of these patients ranged from 2 months to 60 years and the disease history from 6 days to 26 years. From the clinical and pathological aspects the angioma is briefly discussed. The result suggest that the recurrence of the tumor may be associated with enlarged and deformed nutritious vessels. We advocate that the operation should be performed as early as possible.

Adolescent↗