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S R Chen

Publications and source records attributed to S R Chen.

At least 55 records · Page 3Linked to original sources
PubMed1994

[The correlation between cytology and histopathology of primary adenocarcinoma of the uterine cervix].

Cytodiagnosis is a simple, non-invasive and economical screening method for uterine cervical malignancy. Adenocarcinoma as a primary tumor of uterine cervix, although relatively rare, is increasing recently. The first part of the study consisted of 113 patients, seen during a 10-year period, with adenocarcinoma of the uterine cervix proven by tissue diagnosis with prior and/or coincident Papanicolaou smears available in our hospital. Their cytology were as follows: positive/suspicious for adenocarcinoma in 72 cases (63.7%) and incorrect diagnosis for adenocarcinoma in 41 cases (36.3%). These included epidermoid carcinoma, 21 cases (18.6%); atypia, 8 cases (7.1%); negative smears, 8 cases (7.1%); inadequate specimens, 3 cases (2.7%) and radiation effect, 1 case (0.8%). The second part of the study is concerned with the 82 cases whose smear diagnosis was adenocarcinoma in the same period. The results of their tissue diagnosis and accuracy were as follows: adenocarcinoma in 62 cases (75.6%); epidermoid carcinoma in 9 and epidermoid carcinoma in situ in 3 cases totalling 12 cases (14.6%); and false positive in 8 cases (9.8%). The cytomorphology and its correlation to underdiagnosis and overdiagnosis is discussed. Our data revealed that cervicovaginal smears served as a routine for the screening of primary adenocarcinoma of the uterine cervix and for follow-up and detection of recurrence. In order to increase the accuracy, screening cytotechnicians and cytopathologists should acquaint themselves with the morphology of cervical adenocarcinoma by comparing cervicovaginal smear with histopathology.

Adenocarcinoma↗
PubMed1993

The role of the calcium release channel of skeletal muscle sarcoplasmic reticulum in malignant hyperthermia.

In this short review, we have described studies that have identified Arg415 in the Ca2+ release channel as a residue that influences channel sensitivity to Ca2+ induced Ca2+ release, rate of Ca2+ release, and channel closing. We have also described studies that confirm Dr. Numa's predictions that residues 4246-4267, 4382-4417, and 4478-4512 contain Ca2+ binding sites. The site between residues 4483 and 4494 (the PE repeat sequence) may be a key binding site for Ca2+ activation of the channel. Other residues in the sequence 4478-4512 may also contribute to activation of the channel. Thus our studies have contributed to basic knowledge of regulation of Ca2+ release function. They have also provided practical benefits in defining a disease gene, in development of a diagnostic test for porcine MH that is of economic benefit, and in laying the foundation for human MH diagnostic tests that may prevent anesthesia-induced morbidity and mortality.

Amino Acid Sequence↗
PubMed1993

Positioning of major tryptic fragments in the Ca2+ release channel (ryanodine receptor) resulting from partial digestion of rabbit skeletal muscle sarcoplasmic reticulum.

Site-specific antibodies against different regions of the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum (ryanodine receptor) were developed and used as probes for immunoblotting of the major tryptic fragments resulting from partial digestion of the ryanodine receptor in sarcoplasmic reticulum membranes. Five major tryptic fragments, some of which migrated as doublets, with apparent masses of 150/140, 110/100, 55, 170/160, and 76 kDa were ordered so that they covered the bulk of the protein from the NH2 to the COOH terminus. Tryptic subfragments of 53, 63, and 115/95 kDa were also derived from the 150/140-, 110/100-, and 170/160-kDa fragments, respectively. All of these fragments and subfragments were detected only in the insoluble membrane fraction of the trypsinized sarcoplasmic reticulum. Upon Na2CO3 extraction, the 150/140-, 110/100-, and 55-kDa fragments could be solubilized, suggesting their origin in the cytoplasmic domain of the ryanodine receptor. The 170/160- and 76-kDa fragments and the 115/95-kDa subfragment remained insoluble, suggesting their origin in the transmembrane region of the ryanodine receptor. The 150/140-, 110/100-, 170/160-, and 76-kDa fragments and the 115/95 subfragment co-migrated near the bottom of a sucrose density gradient after CHAPS solubilization, suggesting that they were associated in an oligomeric complex. By contrast, the 53- and 63-kDa subfragments and the 55-kDa fragment were detected near the top of the sucrose gradient after CHAPS solubilization, suggesting that they were not involved in the formation of the core of the oligomeric complex. These studies identify 7 sites that are exposed to trypsin in the ryanodine receptor in sarcoplasmic reticulum, 3 of which are novel and 4 of which are in the same location as proteolytic cleavage sites identified previously (Marks, A. R., Fleischer, S., and Tempst, P. (1990) J. Biol. Chem. 265, 13143-13149).

Animals↗
PubMed1993

Antibodies as probes for Ca2+ activation sites in the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum.

In earlier studies (Chen, S. R. W., Zhang, L., and MacLennan, D. H. (1992) J. Biol. Chem. 267, 23318-23326), an amino acid sequence, designated 13c2, lying between amino acid residues 4478 and 4512 in the skeletal muscle ryanodine receptor was shown, through the use of a polyclonal antibody, to be involved in Ca(2+)-induced Ca2+ release. In the present study, an immobilized synthetic peptide, PEPEPEPEPE, corresponding to part of the predicted high affinity Ca2+ binding site between residues 4489 and 4499, was used to purify specific antibodies from an anti-13c2 rabbit antiserum. The effect of this affinity-purified, anti-peptide (anti-13cp1) antibody on Ca2+ release channel function was then characterized using single channel recordings across planar lipid bilayers. The anti-peptide antibody inhibited Ca(2+)- or caffeine-activated channel activities without closing the channel but did not diminish ATP-activated channel activity. The addition of ATP reversed the inhibition of the Ca(2+)- or caffeine-activated channel by the antibody, and the antibody-bound, ATP-activated channel was further modulated by Mg2+, ryanodine, and ruthenium red. The major epitopes in the anti-13c2 antibody, previously shown to activate the Ca2+ release channel by increasing the Ca2+ sensitivity of the channel, did not lie in the PE repeat. These results suggest that the PE repeat sequence forms a site involved in the Ca2+ activation pathway.

Adenosine Triphosphate↗
PubMed1993

Functional expression of cDNA encoding the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum in COS-1 cells.

A full-length cDNA encoding the ryanodine receptor of rabbit skeletal muscle sarcoplasmic reticulum was transiently expressed in COS-1 cells. Immunoblotting studies showed that the expressed ryanodine receptor and the native ryanodine receptor of rabbit skeletal muscle were indistinguishable in molecular size and immunoreactivity. Scatchard analysis of [3H]ryanodine binding to transfected COS-1 cell microsomes resulted in a Bmax of 0.22 pmol/mg of protein and a Kd of 16.2 nM. Expressed ryanodine receptors were solubilized in CHAPS and were shown to cosediment with native ryanodine receptors in a sucrose density gradient. Thus, the expressed receptor, like the native receptor, is assembled as a large oligomeric complex. Single-channel recordings in planar lipid bilayers were used to investigate the functional properties of the sucrose gradient-purified complex. The expressed ryanodine receptor formed a large conductance channel activated by ATP and Ca2+ and inhibited by Mg2+ and ruthenium red. Ryanodine reduced the conductance and increased the mean open time in a manner consistent with that of native channels. These results demonstrated that functional binding sites for the physiological ligands (Ca2+, Mg2+, and ATP) and pharmacological ligands (ruthenium red and ryanodine) controlling gating of the Ca2+ release channel are encoded in the ryanodine receptor cDNA and are faithfully expressed in COS-1 cells. Ryanodine receptors expressed in COS-1 cells displayed several conductance states > or = 1 nS not present in native channels. Such anomalous conductance states of the expressed channel might be referable to lack of muscle-specific posttranslational processing or to the need for components not present in COS-1 cells, which may be required to stabilize the channel structure.

Adenosine Triphosphate↗
PubMed1993

Breakpoint clusters of the PML gene in acute promyelocytic leukemia: primary structure of the reciprocal products of the PML-RARA gene in a patient with t(15;17).

DNA studies of the translocation t(15;17) in acute promyelocytic leukemia (APL) have shown that the retinoic acid receptor alpha (RARA) gene on chromosome 17 is juxtaposed to the promyelocytic leukemia (PML) gene on chromosome 15. The PML breakpoints have been mapped to 3 clusters: bcr1, bcr2, and bcr3. We have examined the PML breakpoint distribution in a series of 33 Chinese patients with APL. Twenty-two patients fell within bcr1, 2 within bcr2, and 9 within bcr3. The primary structure of the reciprocal chromosome translocation joints of one patient and that of their normal counterparts have been determined and compared to those of 2 previously reported cases. These studies revealed possible topoisomerase II cleavage sites close to the breakpoints and suggested implications of DNA attachment sites to nuclear matrix. We propose that these features are relevant to the process of illegitimate recombination generating the translocation.

Base Sequence↗
PubMed1993

Effects of intentional hemodilution on pulmonary stasis and edema in patients and experimental animals.

The therapeutic effects of intentional hemodilution (IHD) on 64 patients of rheumatic mitral valvular disease with chronic pulmonary stasis were estimated. The mean hematocrit was decreased from 0.50 +/- 0.06 to 0.41 +/- 0.04 by withdrawing blood and replacing it with diluent. The whole blood ratio viscosity was decreased from 11.7 +/- 2.4 to 6.4 +/- 0.8 (P < 0.01), the pulmonary arterial pressure was reduced from 6.4 +/- 0.6 to 4.1 +/- 0.5 kPa (0.133 kPa = 1 mmHg) (P < 0.01), the pulmonary vascular resistance brought down from 536.0 +/- 108.0 to 315.0 +/- 62.0 dynes.s.cm-5 (P < 0.01), the cardiac output increased from 3.4 +/- 0.4 to 5.6 +/- 0.5 L/min (P < 0.01), the cardiac index increased from 2.2 +/- 0.5 to 3.5 +/- 0.4 L/min/m2 (P < 0.01), and venous oxygen saturation and oxygen content increased from 28.5 +/- 3.4%, 5.1 +/- 0.5% to 56.0 +/- 5.0%, 11.3 +/- 1.2%, respectively (P < 0.01). The patients' symptoms and signs improved significantly. The protective role of IHD in the early stage of lethal pulmonary edema induced by epinephrine in 39 rabbits and 27 rats was also observed. The experimental data show that intentional hemodilution increased the animals' survival rate (P < 0.01), reduced the pulmonary coefficient, permeability index of Evans blue and protein content in broncho-alveolar lavage fluid (BALF) (all P < 0.01), and alleviated the pathomorphological changes of the lungs of animals in Group IHD were alleviated. The results suggest that IHD acts well in both chronic pulmonary stasis and acute pulmonary edema.

Adolescent↗
PubMed1992

Characterization of a Ca2+ binding and regulatory site in the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum.

A region in the skeletal muscle ryanodine receptor between amino acids 4014 and 4765 was expressed as a trpE fusion protein. Overlay studies revealed that this region bound Ca2+ and ruthenium red, an indicator of Ca(2+)-binding sites. Ca2+ binding was mapped to subregion 13b between amino acids 4246 and 4377, encompassing a predicted high affinity Ca(2+)-binding site, and to subregion 13c between amino acids 4364 and 4529, encompassing two predicted high affinity Ca(2+)-binding sites. Ca2+ binding was then mapped to three shorter sequences, 22(13b1), 36(13c1), and 35(13c2), amino acids long, each encompassing one of the three predicted Ca(2+)-binding sites. Site-directed polyclonal antibodies were raised against these three short sequences and purified on antigen affinity columns. The antibody against sequence 13c2, lying between residues 4478 and 4512, specifically recognized both denatured and native forms of the ryanodine receptor, suggesting that at least part of the 35 amino acid sequence containing the Ca(2+)-binding site is surface-exposed. The affinity purified antibody increased the Ca2+ sensitivity of ryanodine receptor channels incorporated into planar lipid bilayers, resulting in increased open probability and opening time without altering channel conductance. The antibody-activated channel was still modulated by Ca2+, Mg2+, ATP, ryanodine, and ruthenium red. These observations suggest that sequence 13c2 may be involved in Ca(2+)-induced Ca2+ release.

Animals↗
PubMed1991

Protein kinase C in the promyelocytic leukemia cell differentiation of granulocytes.

When the leukemia cells in 14 patients with acute promyelocytic leukemia (APL) were induced by all-trans retinoic acid (RA) treatment, the activity of protein kinase C (PKC) increased with the differentiation. In the control cells, the activity of PKC was only 47 +/- 39.3 pmol.mg-1/min, while it was 149.3 +/- 150.1 pmol.mg-1/min after differentiation. There were 90.1 +/- 7.2% promyelocytes in the control group, and 8.9 +/- 5.6% in the induction group. Therefore, we think that there is a close correlation between PKC and the differentiation of promyelocytic leukemia cells.

Adult↗
PubMed1990

Effects of 1-beta-D-arabinofuranosylcytosine on DNA replication intermediates monitored by pH-step alkaline elution.

The pH-step alkaline elution method enables the isolation and quantification of nascent DNA (nDNA) replication intermediates, including Okazaki fragments, short length nDNA from replicon origins, longer lengths of nascent but subgenomic length nDNA (molecular weight, 20-30 x 10(6)), and full (or genomic) length nDNA (L. C. Erickson et al., Chromosoma, 74: 125-139, 1979). We utilized this technique to study, in HL-60 cells, the effects of 1-beta-D-arabinofuranosylcytosine (ara-C) on the formation of these replication intermediates and the kinetics of transit of radiolabel from [3H]thymidine ([3H]dThd) or [3H]-ara-C through these nDNA fragments and into full length nDNA. In the continuous presence of [3H]-ara-C (4 microM), the majority of radiolabel (greater than 85%) remained in the nascent subgenomic fractions, with 30-50% remaining in Okazaki fragments. These proportions did not change substantially with increasing time of exposure to [3H]-ara-C (from 1 to 24 h), although the total amount of [3H]-ara-C incorporated into DNA continued to increase with increasing time of exposure. In contrast, when cells were exposed to [3H]-ara-C for 1 h, placed in drug-free medium, and studied by the pH-step method at various times thereafter, the transit of radiolabel through progressively larger nDNA intermediates and into full length nDNA was rapid and equal to that of [3H]dThd in cells not exposed to drug. The observed elution of [3H]-ara-C in the subgenomic-length DNA fragments was not due to ara-C-induced breaks in template (parental) DNA and subsequent incorporation of [3H]-ara-C into the template strand, since ara-C treatment of cells prelabeled with [14C]dThd failed to cause substantial elution of the 14C label at the various pH steps used. In studies of the effects of ara-C on [3H]dThd incorporation into nDNA, concentrations of 1 to 10 microM ara-C inhibited total incorporation of radiolabel into DNA by greater than 90% and incorporation into full length nDNA by greater than 97%. In contrast, these concentrations of ara-C failed to decrease the amount of [3H]dThd incorporated into Okazaki fragments or other non-mitochondrial low molecular weight nDNA, compared to control. These studies demonstrate that, in HL-60 cells, ara-C causes profound inhibition of nascent chain elongation, does not cause chain termination, and does not inhibit initiation. In fact, ara-C may stimulate initiation, leading credence to recent theories proposing endoreduplication or reinitiation as consequences of ara-C incorporation into DNA.

Arabinonucleotides↗
PubMed1990

Treatment of acute promyelocytic leukemia with all-trans retinoic acid in China.

Seventy patients with acute promyelocytic leukemia (APL) were entered in this study. Fifty-seven cases received all-trans retinoic acid (RA) as sole agent and 48 cases (84.2%) attained complete remission (CR) in about 42 days. While the other 8 cases (14%) obtained partial remission (PR) during some time. Thirteen patients received combinations of RA and chemotherapy. 9 cases (69.2%) attained CR in about two months and 4 other cases (30.8%) got PR. Total CR rate reached 95.9% after continuing the treatment. Fifty cases were closely followed after CR. Three kinds of continuation therapy were administered including RA as sole agent (Group A), chemotherapy alone (Group B) and RA and chemotherapy alternatively (Group C). The results showed Group C gave the longest duration of CR and longest duration of survival.

Adolescent↗
PubMed1990

Genetic evidence indicating the identity of the cytochalasin B photolabelled components in rat myoblasts.

While photolabelling with cytochalasin B (CB) has been widely used in the identification of eukaryotic glucose transporters, there is presently no unequivocal evidence indicating that the CB-labelled components are indeed the glucose transporters. A combination of biochemical, physiological and genetic manipulations was used in the present investigation to demonstrate that the plasma membrane hexose transporters can indeed by photolabelled by CB. In this study, plasma membranes from glucose-grown and glucose-starved hexose transport mutant D23 and its parental L6 cells were photolyzed in the presence of 3H-CB. The amount of CB bound to the 40-60 kDa region (CB50) was found to be differentially inhibited by D-glucose, 2-deoxy-D-glucose (dGlc) and 3-O-methyl-glucose (MeGlc). Mutant D23 exhibited not only reduced hexose transport activity but also significantly lower level of CB50. Glucose-starvation resulted not only in elevated hexose transport activity but also increased level of CB50. It should be noted glucose-starvation did not have much effect on the hexose transport activity and on the level of CB50 in mutant D23. The present study provides the first genetic evidence indicating that the CB-labelled component(s) are indeed associated with the hexose transport systems.

Animals↗
PubMed1989

Regulation of hexose transport in rat myoblasts during growth and differentiation.

We report here the effects of growth conditions and myogenic differentiation on rat myoblast hexose transport activities. We have previously shown that in undifferentiated myoblasts the preferred substrates for the high (HAHT)- and low (LAHT)-affinity hexose transport systems are 2-deoxyglucose (2-DG) and 3-O-methyl-D-glucose (3-OMG), respectively. The present study shows that at cell density higher than 4.4 x 10(4) cells/cm2, the activities of both transport processes decrease with increasing cell densities of the undifferentiated myoblasts. Since the transport affinities are not altered, the observed decrease is compatible with the notion that the number of functional hexose transporters may be decreased in the plasma membrane. Myogenic differentiation is found to alter the 2-DG, but not the 3-OMG, transport affinity. The Km values of 2-DG uptake are elevated upon the onset of fusion and are directly proportional to the extent of fusion. This relationship between myogenesis and hexose transport is further explored by using cultures impaired in myogenesis. Treatment of cells with 5-bromo-2'-deoxyuridine abolishes not only myogenesis but also the myogenesis-induced change in 2-DG transport affinity. Similarly, alteration in 2-DG transport affinity cannot be observed in a myogenesis-defective mutant, D1. However, under myogenesis-permissive condition, the myogenesis of this mutant is also accompanied by changes in its 2-DG transport affinity. The myotube 2-DG transport system also differs from its myoblast counterpart in its response to sulfhydryl reagents and in its turnover rate. It may be surmised from the above observations that myogenesis results in the alteration of the turnover rate or in the modification of the 2-DG transport system. Although glucose starvation has no effect on myogenesis, it is found to alter the substrate specificity and transport capacity of HAHT. In conclusion, the present study shows that hexose transport in rat myoblasts is very sensitive to the growth conditions and the stages of differentiation of the cultures. This may explain why different hexose transport properties have been observed with myoblasts grown under different conditions.

3-O-Methylglucose↗
PubMed1989

[Isolation and identification of polysaccharides from radix Bupleuri].

A polysaccharide--Chai-III-5311 had been isolated from hot water extract of Radix Bupleuri through ultrafiltration and dialysis. Chai-III-5311 was homogeneous with an average molecular weight of about 8000. Acid hydrolysis has proved that Chai-III-5311 is composed of galacturonic acid, galactose, glucose, arabinose, xylose, ribose, rhamnose and an unknown component.

Drugs, Chinese Herbal↗
PubMed1988

Cytochalasin B as a probe for the two hexose-transport systems in rat L6 myoblasts.

We have recently demonstrated that two hexose-transport systems are present in undifferentiated rat L6 myoblasts: D-glucose and 2-deoxy-D-glucose are preferentially transported by the high-affinity system, whereas 3-O-methyl-D-glucose is transported primarily by the low-affinity system. Mutant D23 is found to be defective only in the high-affinity hexose-transport system. The low-affinity transport system is much more sensitive to inhibition by cytochalasin B (CB). The present study examines the identity, properties and regulation of the CB-binding sites by measuring CB binding to both whole cells and plasma membrane. Scatchard analysis of the binding data revealed the presence of two CB-binding sites, namely CBH and CBL. These two sites differ not only in their affinity for CB, but their levels can also be differentially altered by various biochemical, physiological and genetic manipulations. CBL resembles the high-affinity hexose-transport system in that it is absent in mutant D23 and is present in larger quantities in glucose-starved cells. Moreover, CB binding to this site is inhibited by D-glucose and 2-deoxy-D-glucose, the preferred substrates of the high-affinity hexose-transport system. On the other hand, CBH is found to be unaltered in mutant D23, which also retains the normal low-affinity hexose-transport system. CBH also resembles the low-affinity transport system in that it is not elevated in glucose-starved cells. Furthermore, binding of CB to this site can be inhibited by 3-O-methyl-D-glucose, the preferred substrate of the low-affinity transport system. It should be noted that 2-deoxy-D-glucose does not have much effect on CBH, and vice versa. Studies with purified membrane preparations indicate that both CB-binding sites are present in similar ratios in the plasma membrane and the low-density microsomal fraction. Plasma-membrane studies also reveal that D-glucose 6-phosphate, but not 2-deoxy-D-glucose 6-phosphate, is very effective in activating CB binding. Data presented suggest that CB binding may be regulated by sugar analogues in an allosteric manner.

Binding Sites↗