PubMed Health⌕ Search

Biomedical subjects

A Sun

Publications and source records attributed to A Sun.

At least 73 records · Page 4Linked to original sources
PubMed1996

Comparing techniques of measuring tumor hypoxia in different murine tumors: Eppendorf pO2 Histograph, [3H]misonidazole binding and paired survival assay.

Using five transplantable murine tumors (SCC-VII, B16F1, KHT-C, KHT-LP1, RIF-1), measurements of tumor hypoxia have been made with two techniques which have the potential to be used for assessing oxygenation in human tumors (the Eppendorf pO2 Histograph and binding of [3H]misonidazole) and have been compared with an established radiobiological technique, the paired survival assay. There were significant differences in the pO2 measurements made in individual tumors both within and between the five different tumor types. Significant differences between the tumor types were also found for the [3H]misonidazole binding. A correlation was observed between the mean values of the hypoxic proportion as measured by the paired survival assay and the mean binding of [3H]misonidazole as measured by both tumor activity in dpm/100 mg tissue (r = 0.94, P = 0.02) and the tumor-to-muscle activity ratio (r = 0.87, P = 0.06). No biologically significant correlation was seen between the mean values of the hypoxic proportion from anesthetized mice as measured by the paired survival assay (range 20-58%) and the pooled Eppendorf pO2 Histograph measurements made on groups of tumors. These results with the Eppendorf pO2 Histograph are similar to those reported by others. When both Eppendorf pO2 Histograph measurements and paired survival measurements were made on the same individual KHT-C tumors, it was again found that there was no correlation between the two measurements of hypoxia.

Animals↗
PubMed1996

[Effects of levonorgestrel subdermal implants on estradiol and progesterone receptors of endometrium and ovarian tissues in rats].

OBJECTIVE: To study the influence of subdermal implantation of levonorgestrel (LNG) on the levels of estradiol receptor (ER) and progesterone receptor (PR) in ovaries and endometrium of rats. METHODS: 45 female mature rats were divided into 3 groups: control group, silicon tube group and LNG implants group. Using single-point determination at saturating concentration method, ER and PR levels of both ovaries and endometrium were measured at 15, 30 and 45 days after subdermal implantation of LNG or silicon tube, and compared with that of the control group. RESULTS: ER and PR levels in LNG group were significantly lower than those in the other 2 groups (P < 0.01). The concentration of ER and PR decreased gradually as implantation prolonged. CONCLUSION: subdermal implantation of LNG resulted in the reduction of ER and PR levels in ovaries and endometrium of rats, which may be related to the mechanism of contraception and breakthrough bleeding after implantation.

Animals↗
PubMed1996

[Reversal of adriamycin or vincristine resistance by tetrandrine in human cancer cells in vitro].

In an in vitro culture system of human cancer cells MCF-7 and its adriamycin-resistant line MCF-7/Ad or KB and its vincristine-resistant line KBv200, tetrandrine was found to exhibit significantly selective anticancer activity against the drug-resistant cancer cell MCF-7/Ad. In addition, essentially complete reversal effects of tetrandrine on drug resistance were observed in MCF/Ad or KBv200.

Alkaloids↗
PubMed1995

Simultaneous determination of copper and zinc in the hair of children by pH gradient construction in a flow-injection system.

A flow-injection method is described for the simultaneous determination of copper and zinc with a single detector using the pH gradient technique. Zincon is used as the colour reagent for the spectrophotometric determination. The linear range for the determination of zinc is 0.4-12 micrograms ml-1 and for copper is 0.1-3.0 micrograms ml-1. About 20-30 samples can be determined in one hour. The proposed method has been applied to the determination of zinc and copper in childrens' hair.

Child↗
PubMed1995

[Laparoscopic treatment of endometriosis with Nd: YAG laser and microwave].

A series of 200 cases of endometriosis were treated laparoscopically by Nd: YAG laser and microwave at Peking Union Medical College Hospital. All the operations were performed under local and topical anesthesia follow-up for 10-48 months revealed good results. Of 76 cases with infertility, 46 (60.5%) conceived after treatment. Of 114 cases with ovarian endometriomas, the cysts were no longer found in 81 cases (71.1%), decreased in size in 24 cases (21.0%). Of 180 cases with pain symptoms, 105 patients (58.3%) were achieved complete relief, Partial relief in 61 cases (33.9%). It has been found that laparoscopic surgery is effective to improve fertile rate for the patients with all the stages of endometriosis. The results showed that the microwave and Nd: YAG laser can be achieved with safety and success. The microwave is safer than Nd: YAG laser and is easier to operate and less expensive.

Adult↗
PubMed1994

Critical role for intracellular calcium in tight junction biogenesis.

Using the Madin Darby canine kidney (MDCK) cell "calcium switch," we have previously demonstrated that, as MDCK cells establish contact and ultimately form tight junctions, there are marked global and localized changes in intracellular calcium at the sites of cell-cell contact (Nigam et al., 1992, Proc. Natl. Acad. Sci. USA, 89:6162-6166). We have now examined whether intracellular Ca++ is critical to the biogenesis of tight junctions by chelating this ion and monitoring the formation of junctions by electrical, immunocytochemical, and biochemical criteria. Intracellular Ca++ was chelated with the cell-permeant chelators, dimethyl-BAPTA-AM and BAPTA-AM. By digital imaging of fura-2 loaded cells, it was demonstrated that both agents efficiently chelated Ca++ during the "switch" in a dose-dependent manner which paralleled their respective in vitro affinities for Ca++. Chelation of Ca++ during the switch markedly attenuated the development of transepithelial electrical resistance (TER), a measure of tight junction assembly. Immunofluorescent staining of the tight junctional protein, zonula occludens-1 (ZO-1), revealed that chelation of intracellular Ca++ retarded the movement of ZO-1 from intracellular sites to the plasma membrane during the switch. During the development of tight junctions, a fraction of ZO-1 redistributed from the Triton X-100 soluble to the Triton X-100 insoluble pool; chelation of Ca++ during the induction of cell-cell contact prevented this stabilization into the Triton X-100 insoluble fraction. Taken together, these data indicate an important role for intracellular Ca++ in tight junction biogenesis and suggest a specific role for calcium in the early sorting and possible cytoskeletal association of tight junction components.

Animals↗
PubMed1994

Cyclic guanosine monophosphate responses to atrial natriuretic factor, brain natriuretic peptide, but not C-type natriuretic peptide, and the characterization of their receptors in rat medullary thick ascending limb.

The effects of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on renal medullary thick ascending limb (mTAL) have not been fully understood. The aim of this study is to examine the second-messenger responses of rat mTAL to ANF, BNP, and CNP. Characterizations of the ANF, BNP, and CNP receptors in mTAL were also performed by radioligand studies. Results showed that ANF and BNP were both capable of eliciting cyclic guanosine monophosphate (cGMP) responses in mTAL. Conversely, no cGMP response was observed upon stimulation by CNP in mTAL. The presence of ANF receptors was demonstrated by radioligand studies. One receptor site was found, and the Kd and maximum binding capacity were 4.0 +/- 0.45 nmol/L and 277.8 +/- 47.7 fmol/mg protein, respectively. BNP receptors were also found in mTAL, and ANF and BNP were sharing the same receptor. On the contrary, no CNP receptor could be shown by radioligand studies. These results suggest that guanylyl cyclase-coupled receptors (atrial natriuretic peptide receptor-A [ANPR-A]) specific for ANF and BNP are present in rat mTAL, while those for CNP (ANPR-B) are absent. ANF and BNP but not CNP act on mTAL to control water excretion.

Animals↗
PubMed1994

Immunomodulation by levamisole in patients with recurrent aphthous ulcers or oral lichen planus.

The purpose of this study was to evaluate the effect of levamisole on the immune system of patients with recurrent aphthous ulcers (RAU) or oral lichen planus (OLP) in an open trial. Lymphocyte subsets, serum immunoglobulins, and circulating immune complexes (CIC) in patients with RAU or OLP and in normal control subjects were determined by an indirect immunofluorescence (IIF) technique with monoclonal anti-lymphocyte antibodies, by single radial immunodiffusion, and by precipitation with 3% polyethylene glycol, respectively. In addition, the anti-nuclear antibodies (ANA) and anti-basal cell antibodies (anti-BCA) in sera were detected by an IIF technique. We found a significant improvement in clinical symptoms and normalization of the decreased CD4/CD8 ratio in RAU patients after levamisole treatment. Moreover, the decreased CD4/CD8 ratio, which persisted until the remission stage in the untreated RAU patients, reverted to normal in the active late stage in the levamisole-treated patients. This reversion of aberrant cellular immunity in an earlier stage of the ulcer cycle may explain why RAU patients experience symptom improvement after levamisole treatment. Although RAU patients treated with levamisole for 1 to 3 or 4 months still had higher than normal levels of CIC and serum immunoglobulins, the levels of their IgA and IgM returned to normal values after 4 months of levamisole treatment. The serum ANA detected in 6 patients with RAU and 3 patients with erosive OLP disappeared after 1-22 months of levamisole treatment. The disappearance of serum anti-BCA was also observed in 50% of the anti-BCA-positive patients with erosive OLP after 3-13 months of levamisole treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Generation of alginate-poly-l-lysine-alginate (APA) biomicrocapsules: the relationship between the membrane strength and the reaction conditions.

Alginate-poly-l-lysine-alginate (APA) microcapsules have proven effective in protecting enclosed live cells from immune rejection following transplantation into experimental animals, thereby eliminating the need for immunosuppressive therapy. However, in order for the capsules to remain intact for extended periods in vivo, the thickness of the membrane material must be optimized. In this study, the membrane thickness was examined as an indicator of membrane strength and measured under different reaction conditions. The thickness was found to increase 1) from 4.6 microns to 6.6 microns with an increase in the concentration of sodium alginate from 1.25 (w/v) to 2.0% (w.v); 2) from 4.2 microns to 6.2 microns with an increase in the concentration of the calcium solution from 20 mM to 100mM; 3) from 3.9 microns to 10.3 microns with an increase in the concentration of poly-l-lysine (PLL) from 0.02% (w/v) to 0.08% (w/v); and 4) from 2.3 microns to 7.4 microns with an increase in the reaction time with the PLL from two to seven minutes. On the other hand, membrane thickness decreased 1) from 9.8 microns to 8.6 microns with an increase of the pH in the PLL solution from 5.8 to 9.2; 2) from 13.2m to 5.8 microns with an increase in the molecular weight of PLL from 14,000 to 57,000; 3) from 8.4 microns to 6.0 microns with an increase in the treatment time with 0.9 (w/v) NaCl solution from zero to fifteen minutes and; 4) from 7.5 microns to 6.1 microns with an increase in the treatment time of the second sodium alginate coating from zero to ten minutes. Membrane thickness was inversely proportional to capsule volume expansion during membrane synthesis. By replacing calcium chloride by calcium lactate and eliminating the use of CHES in the construction of capsule membranes, we improved the strength and biocompatibility of our capsules, as evidenced by marked improvements in the survival rates of diabetic mice treated with islet transplants enclosed in the new capsules. These results indicate that it is possible to obtain optimal membrane thickness for a given purpose by creating specific reaction conditions under which membranes are synthesized.

Alginates↗
PubMed1993

Cloning and characterization of an extracellular Ca(2+)-sensing receptor from bovine parathyroid.

Maintenance of a stable internal environment within complex organisms requires specialized cells that sense changes in the extracellular concentration of specific ions (such as Ca2+). Although the molecular nature of such ion sensors is unknown, parathyroid cells possess a cell surface Ca(2+)-sensing mechanism that also recognizes trivalent and polyvalent cations (such as neomycin) and couples by changes in phosphoinositide turnover and cytosolic Ca2+ to regulation of parathyroid hormone secretion. The latter restores normocalcaemia by acting on kidney and bone. We now report the cloning of complementary DNA encoding an extracellular Ca(2+)-sensing receptor from bovine parathyroid with pharmacological and functional properties nearly identical to those of the native receptor. The novel approximately 120K receptor shares limited similarity with the metabotropic glutamate receptors and features a large extracellular domain, containing clusters of acidic amino-acid residues possibly involved in calcium binding, coupled to a seven-membrane-spanning domain like those in the G-protein-coupled receptor superfamily.

Amino Acid Sequence↗
PubMed1993

Studies of a sperm/placenta cross-reacting antigen, STX-10.

A monoclonal antibody, HSA-10 initially produced against acrosome-reacted human sperm was also shown to cross-react with human placenta/trophoblast. Transmission electron microscopy, as well as indirect immunofluorescent assay, demonstrated that HSA-10 was found to react with antigen on the inner acrosome of human sperm. The cognate antigen, designated as STX-10, was found to exist as an aggregate in the native form when analyzed by Sephacryl S-300 gel filtration chromatography. When purified by HSA-10-immunoaffinity chromatography from human placenta extract, STX-10 was found to be predominantly a group of glycoproteins with a subunit molecular mass in the range of 75 +/- 5 kDa, whereas an additional group of three proteins with subunit molecular mass less than 20 kDa were copurified from human sperm extract. A sandwich enzyme immunoassay was designed to quantitatively determine the immunoactivity of STX-10 in solution, using HSA-10 monoclonal antibody for coating and for signal detection via enzyme conjugation. Based on this assay, it was found that STX-10 could be detected only in human sperm and placenta extract, but not in any other human somatic tissues, such as serum, brain, heart, muscle, kidney and liver. The immunoactivity of STX-10 was found to be sensitive to proteolytic digestion, low pH, in the presence of reducing agent, but resistant to treatment with sodium periodate. This observation suggests that HSA-10 specific epitope is a peptide in nature and not a carbohydrate moiety. Results of antifertility studies revealed that HSA-10 significantly inhibited human sperm penetration to zona-free hamster ova. Thus, the results of this study are consistent with those of WHO Workshop evaluations that seem to suggest that STX-10 is a highly gamete-specific antigen localized on the inner acrosome of human sperm and in human trophoblast/placenta. Therefore, it may play an important role during human fertilization and embryo development.

Animals↗
PubMed1993

HLA-DR and DQ antigens in Chinese patients with Behçet's disease.

The frequencies of HLA-DR and DQ antigens in 24 Chinese patients with Behçet's disease (BD) were calculated and compared with those in 130 healthy control Chinese and those in 80 Chinese patients with recurrent oral ulcers (ROU). Although an increased trend of DRw6 and DRw8 antigens in patients with BD was noted, there was no significant difference in frequencies of HLA-DR and DQ antigens between patients with BD and healthy control subjects or patients with ROU after correction of P values (Pc > 0.05). Further analysis of our data of the phenotype frequencies of DRw6 and DRw8 antigens according to the subtypes of BD also showed the increased frequencies of DRw6 and DRw8 antigens in patients with mucocutaneous type of BD as compared with those in healthy control subjects. However, only the phenotype frequency of DRw8 antigen in patients with mucocutaneous type of BD was significantly higher than that in patients with ROU (P < 0.005, Pc < 0.05, relative risk = 17.7, and etiologic fraction = 0.30). This significant increase of the phenotype frequency suggests that the gene coding for HLA-DRw8 antigen in patients with ROU was only partially (30%) responsible for susceptibility to the mucocutaneous type of BD.

Adolescent↗
PubMed1993

Laser light-scattering system for studying cell volume regulation and membrane transport processes.

A simple and relatively inexpensive device utilizing laser light scattering for the study of volume regulatory behavior and membrane transport phenomena in cells cultured on or affixed to a rigid substrate is described in detail. Validation of the method is provided by study of cell types with known volume regulatory responses. The method we describe has numerous advantages over currently available techniques used to monitor cell volume changes. These advantages include 1) the ability to rapidly detect and quantify small cell volume changes on-line, 2) the ability to maintain natural cell morphology, cell surface contacts, and cell-to-cell interactions, 3) the ability to easily control solution temperature and gas and solute composition, and 4) the ability to perform multiple perturbations in a single experiment. The light-scattering system we describe can be modified to allow for simultaneous measurement of light-scattering signals and fluorescence emission from intracellular ion-sensitive probes and membrane potential dyes. In addition, our method may be useful for the study of apical and basolateral membrane transport processes in epithelial monolayer cell cultures.

Animals↗
PubMed1992

Presence of anti-basal cell antibodies in oral lichen planus.

BACKGROUND: An autoimmune hypothesis for oral lichen planus (OLP) has been proposed, but no anti-basal cell antibodies (anti-BCA) have been found in the sera of patients with OLP. OBJECTIVE: Our purpose was to test whether the negative results of anti-BCA assays in sera have been due to the insensitivity of the substrates. Rat esophagus, monkey esophagus, as well as human oral mucosa and skin were used to detect anti-BCA in sera of OLP patients. METHODS: By indirect immunofluorescence technique, the rat esophagus was found to be the most sensitive substrate. Therefore it was used as the only substrate to test the presence of anti-epithelial cell antibodies (anti-ECA) in a large group of patients with OLP and other oral mucosal diseases or normal control subjects. RESULTS: The results showed that anti-ECA were detected in 54% (34 of 63) of patients with OLP, 71% (15 of 21) of patients with aphthous ulcers, 29% (6 of 21) of patients with oral carcinoma, 20% (2 of 10) of patients with traumatic ulcer, and 7% (1 of 15) of patients with periodontitis but none of the healthy control subjects (n = 41). The presence of anti-BCA in OLP patients' sera was persistent and lasted for a few months or years. There was a decrease in the serum anti-BCA titers in six of eight anti-BCA-positive OLP patients after topical application of triamcinolone. CONCLUSION: These anti-BCA that persist longer in OLP patients' sera may be autoantibodies that are raised against altered basal cell-specific antigens.

Adult↗
PubMed1992

Cellular NH4+/K+ transport pathways in mouse medullary thick limb of Henle. Regulation by intracellular pH.

Fluorescence and electrophysiological methods were used to determine the effects of intracellular pH (pHi) on cellular NH4+/K+ transport pathways in the renal medullary thick ascending limb of Henle (MTAL) from CD1 mice. Studies were performed in suspensions of MTAL tubules (S-MTAL) and in isolated, perfused MTAL segments (IP-MTAL). Steady-state pHi measured using 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) averaged 7.42 +/- 0.02 (mean +/- SE) in S-MTAL and 7.26 +/- 0.04 in IP-MTAL. The intrinsic cellular buffering power of MTAL cells was 29.7 +/- 2.4 mM/pHi unit at pHi values between 7.0 and 7.6, but below a pHi of 7.0 the intrinsic buffering power increased linearly to approximately 50 mM/pHi unit at pHi 6.5. In IP-MTAL, NH4+ entered cells across apical membranes via both Ba(2+)-sensitive pathway and furosemide-sensitive Na+:K+(NH4+):2Cl- cotransport mechanisms. The K0.5 and maximal rate for combined apical entry were 0.5 mM and 83.3 mM/min, respectively. The apical Ba(2+)-sensitive cell conductance in IP-MTAL (Gc), which reflects the apical K+ conductance, was sensitive to pHi over a pHi range of 6.0-7.4 with an apparent K0.5 at pHi approximately 6.7. The rate of cellular NH4+ influx in IP-MTAL due to the apical Ba(2+)-sensitive NH4+ transport pathway was sensitive to reduction in cytosolic pH whether pHi was changed by acidifying the basolateral medium or by inhibition of the apical Na+:H+ exchanger with amiloride at a constant pHo of 7.4. The pHi sensitivities of Gc and apical, Ba(2+)-sensitive NH4+ influx in IP-MTAL were virtually identical. The pHi sensitivity of the Ba(2+)-sensitive NH4+ influx in S-MTAL when exposed to (apical+basolateral) NH4Cl was greater than that observed in IP-MTAL where NH4Cl was added only to apical membranes, suggesting an additional effect of intracellular NH4+/NH3 on NH4+ influx. NH4+ entry via apical Na+:K+ (NH4+):2Cl- cotransport in IP-MTAL was somewhat more sensitive to reductions in pHi than the Ba(2+)-sensitive NH4+ influx pathway; NH4+ entry decreased by 52.9 +/- 13.4% on reducing pHi from 7.31 +/- 0.17 to 6.82 +/- 0.14. These results suggest that pHi may provide a negative feedback signal for regulating the rate of apical NH4+ entry, and hence transcellular NH4+ transport, in the MTAL. A model incorporating these results is proposed which illustrates the role of both pHi and basolateral/intracellular NH4+/NH3 in regulating the rate of transcellular N H4+ transport in the MTAL.

Amiloride↗
PubMed1992

The value of hysteroscopy in the diagnosis of infertility and habitual abortion.

Ninety cases of infertility and habitual abortion were analyzed by hysteroscopy between April 1983 and July 1990 in PUMC hospital. Abnormal changes of the uterine cavity were seen in 74.4%. The result of hysterosalpingography corresponded with that of hysteroscopy in 62.5%, and the result of B-ultrasound corresponded to that of hysteroscopy in 52.5%. The diagnosis of adhesion and polyps of the uterine cavity was made accurately by hysteroscopy, and both could be operated under hysteroscopy. After operative removal of the adhesion, an IUD should be put into the uterine cavity for 3 months. In 60 cases operations were performed during or after hysteroscopy. Of the 45 patients followed, 19 achieved pregnancy. Five patients achieved pregnancy after operative removal of the adhesion. It is concluded that hysteroscopy is more important than B-ultrasound and hysterosalpingography in the examination and treatment of infertility.

Abortion, Habitual↗
PubMed1991

Vasopressin alters the mechanism of apical Cl- entry from Na+:Cl- to Na+:K+:2Cl- cotransport in mouse medullary thick ascending limb.

Experiments were performed using in vitro perfused medullary thick ascending limbs of Henle (MTAL) and in suspensions of MTAL tubules isolated from mouse kidney to evaluate the effects of arginine vasopressin (AVP) on the K+ dependence of the apical, furosemide-sensitive Na+:Cl- cotransporter and on transport-related oxygen consumption (QO2). In isolated perfused MTAL segments, the rate of cell swelling induced by removing K+ from, and adding one mM ouabain to, the basolateral solution [ouabain(zero-K+)] provided an index to apical cotransporter activity and was used to evaluate the ionic requirements of the apical cotransporter in the presence and absence of AVP. In the absence of AVP cotransporter activity required Na+ and Cl-, but not K+, while the presence of AVP the apical cotransporter required all three ions. 86Rb+ uptake into MTAL tubules in suspension was significant only after exposure of tubules to AVP. Moreover, 22Na+ uptake was unaffected by extracellular K+ in the absence of AVP while after AVP exposure 22Na+ uptake was strictly K(+)-dependent. The AVP-induced coupling of K+ to the Na+:Cl- cotransporter resulted in a doubling in the rate of NaCl absorption without a parallel increase in the rate of cellular 22Na+ uptake or transport-related oxygen consumption. These results indicate that arginine vasopressin alters the mode of a loop diuretic-sensitive transporter from Na+: Cl- cotransport to Na+: K+: 2Cl- cotransport in the mouse MTAL with the latter providing a distinct metabolic advantage for sodium transport. A model for AVP action on NaCl absorption by the MTAL is presented and the physiological significance of the coupling of K+ to the apical Na+: Cl- cotransporter in the MTAL and of the enhanced metabolic efficiency are discussed.

Animals↗