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B X Zhang

Publications and source records attributed to B X Zhang.

At least 19 recordsLinked to original sources
PubMed1992

Feedback inhibition of Ca2+ release by Ca2+ is the underlying mechanism of agonist-evoked intracellular Ca2+ oscillations in pancreatic acinar cells.

Oscillations of free intracellular Ca2+ concentration ([Ca2+]i) are known to occur in many cell types during physiological cell signaling. To identify the basis for the oscillations, we measured both [Ca2+]i and extracellular Ca2+ concentration ([Ca2+]o) to follow the fate of Ca2+ during stimulation of [Ca2+]i oscillations in pancreatic acinar cells. [Ca2+]i oscillations were initiated by either t-butyloxycarbonyl-Tyr(SO3)-Nle-Gly-Tyr-Nle-Asp-2-phenylethyl ester (CCK-J), which mobilized Ca2+ from the inositol 1,4,5-trisphosphate (IP3)-insensitive pool, or low concentration of cholecystokinin octapeptide (CCK-OP), which mobilized Ca2+ from the IP3-sensitive internal pool. Little Ca2+ efflux occurred during the oscillations triggered by CCK-J or CCK-OP in spite of a large average increase in [Ca2+]i. When internal store Ca2+ pumps were inhibited with thapsigargin (Tg) during [Ca2+]i oscillations, a rapid Ca2+ efflux occurred similar to that measured in intensely stimulated, nonoscillatory cells. Tg also stimulated 45Ca efflux from internal pools of cells stimulated with CCK-J or a low concentration of CCK-OP. Hence, a large fraction of the Ca2+ released during each spike is reincorporated by the internal store Ca2+ pumps. Surprisingly, when the increase in [Ca2+]i during stimulation of oscillations was prevented by loading the cells with 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid, a persistent activation of Ca2+ release and Ca2+ efflux occurred. This was reflected as a persistent increase in [Ca2+]o in cells suspended at low [Ca2+]o or persistent efflux of 45Ca from internal stores of cells maintained at high [Ca2+]o. Since agonist-stimulated Ca2+ release evidently remains activated when [Ca2+]i is highly buffered, the primary mechanism determining Ca2+ oscillations must include an inhibition of Ca2+ release by [Ca2+]i. Loading the cells with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid had no apparent effect on the levels or kinetics of IP3 formation in agonist-stimulated cells. This suggests that [Ca2+]i regulated the oscillation by inhibition of Ca2+ release independent of its possible effects on cellular levels of IP3.

Animals↗
PubMed1992

Simultaneous recording of cell volume changes and intracellular pH or Ca2+ concentration in single osteosarcoma cells UMR-106-01.

We present a new technique for the simultaneous measurement of cell volume changes and intracellular ionic activities in single cells. The technique uses measurement of changes in the concentration of intracellularly trapped fluorescent dyes to report relative cell volume. By using pH- or Ca(2+)-sensitive dyes and recording at the ion-sensitive and -insensitive (isosbestic) wavelengths, the method can measure both cell volume changes and intracellular ionic activities. The technique was used to study the mechanisms of regulatory volume decrease (RVD) in the osteosarcoma cell line UMR-106-01 grown on cover slips. Swelling cells in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)-buffered hypotonic medium was followed by stable cytosolic acidification and a decrease in cell volume back toward normal. The recovery of cell volume could be blocked by depolarization, treatment with ouabain, or depletion of cell Cl-. These suggest the conductive efflux of K+ and Cl- during RVD. The cytosolic acidification that accompanied cell swelling was not blocked by amiloride, bafilomycin A, or removal of Cl- and could not be reproduced by depletion of cellular ATP. These findings exclude Na+/H+ and Cl-/HCO-3 exchange, intracellularly generated acid, or increased metabolism, respectively, as the cause of the acidification. The cell swelling-induced acidification was inhibited by depolarization, suggesting the involvement of an electrogenic pathway. The acidification, as well as RVD, was inhibited by short incubation with deoxyglucose, and these effects could not be reversed by valinomycin. Thus, the anionic pathway(s) participating in RVD and the acidification are sensitive to the cellular level of ATP. Together, these studies indicate that RVD in UMR-106-01 cells in HEPES-buffered medium is mediated by the conductive efflux of K+, Cl-, and OH-.

Adenosine Triphosphate↗
PubMed1992

Regulatory volume decrease in the presence of HCO3- by single osteosarcoma cells UMR-106-01.

The technique for the simultaneous recording of cell volume changes and pHi in single cells was used to study the role of HCO3- in regulatory volume decrease (RVD) by the osteosarcoma cells UMR-106-01. In the presence of HCO3-, steady state pHi is regulated by Na+/H+ exchange, Na+ (HCO3-)3 cotransport and Na(+)-independent Cl-/HCO3- exchange. Following swelling in hypotonic medium, pHi was reduced from 7.16 +/- 0.02 to 6.48 +/- 0.02 within 3.4 +/- 0.28 min. During this period of time, the cells performed RVD until cell volume was decreased by 31 +/- 5% beyond that of control cells (RVD overshoot). Subsequently, while the cells were still in hypotonic medium, pHi slowly increased from 6.48 +/- 0.02 to 6.75 +/- 0.02. This increase in pHi coincided with an increase in cell volume back to normal (recovery from RVD overshoot or hypotonic regulatory volume increase (RVI)). The same profound changes in cell volume and pHi after cell swelling were observed in the complete absence of Cl- or Na+, providing HCO3- was present. On the other hand, depolarizing the cells by increasing external K+ or by inhibition of K+ channels with quinidine, Ba2+ or tetraethylammonium prevented the changes in pHi and RVD. These findings suggest that in the presence of HCO3-, RVD in UMR-106-01 cells is largely mediated by the conductive efflux of K+ and HCO3-. Removal of external Na+ but not Cl- prevented the hypotonic RVI that occurred after the overshoot in RVD. Amiloride had no effect, whereas pretreatment with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) strongly inhibited hypotonic RVI. Thus, hypotonic RVI is mediated by a Na+(out)-dependent, Cl(-)-independent and DIDS-inhibitable mechanism, which is indicative of a Na+(HCO3-)3 cotransporter. This is the first evidence for the involvement of this transporter in cell volume regulation. The present results also stress the power of the new technique used in delineating complicated cell volume regulatory mechanisms in attached single cells.

Animals↗
PubMed1992

Activation of the plasma membrane Ca2+ pump during agonist stimulation of pancreatic acini.

The role of internal stores and plasma membrane Ca2+ pumps in controlling [Ca2+]i during agonist stimulation and their regulation by agonists are not well understood. We report here measurements of intracellular ([Ca2+]i) and extracellular ([Ca2+]o) Ca2+ concentrations in agonist-stimulated pancreatic acini in an effort to directly address these questions. Stimulation of acini suspended in Ca(2+)-free or Ca(2+)-containing medium with Ca2+ mobilizing agonists resulted in a typical transient increase in [Ca2+]i. Thapsigargin, a specific inhibitor of internal Ca2+ pumps, inhibited the rate of [Ca2+]i reduction after agonist stimulation by approximately 40%. Under the same conditions, thapsigargin had no effect on the rate of the unidirectional Ca2+ efflux across the plasma membrane as revealed by measurements of [Ca2+]o. These findings suggest that internal Ca2+ pumps actively remove Ca2+ from the cytosol during continued agonist stimulation. The correlation between the reduction in [Ca2+]i and the increase in [Ca2+]o showed that Ca2+ efflux from cells stimulated with agonist and thapsigargin represent Ca2+ efflux across the plasma membrane. Inhibition of cells exposed to agonist and thapsigargin with a specific antagonist sharply reduced the rates of the [Ca2+]i decrease and the accompanied [Ca2+]o increase. Hence, at comparable [Ca2+]i, Ca2+ efflux from stimulated cells was about 3-fold faster than that from resting cells, indicating that agonists directly activate the plasma membrane Ca2+ pump. To study the role of [Ca2+]i increase in plasma membrane Ca2+ pump activation the acini were loaded with 1,2-bis-(2-aminophenoxyethane-N,N,N',N')-tetraacetic acid (BAPTA), and [Ca2+]o was measured during agonist stimulation. Surprisingly, although BAPTA completely prevented the increase in [Ca2+]i, Ca2+ efflux rate was reduced by only 34%. These findings provide the first evidence for Ca(2+)-independent activation of the plasma membrane Ca2+ pump by Ca2+ mobilizing agonists.

Animals↗
PubMed1992

Regulation of agonist-evoked [Ca2+]i oscillation by intracellular Ca2+ and Ba2+ in AR42J cells.

Measurements of intracellular Ca2+ ([Ca2+]i) and intracellular Ba2+ ([Ba2+]i) in single AR42J cells were used to evaluate the effect of [Ca2+]i and [Ba2+]i on agonist-evoked [Ca2+]i oscillations. Variations in [Ca2+]i and [Ba2+]i were imposed by gradual activation of entry through voltage-activated Ca2+ channels (VACC) present in the plasma membrane of these cells. Activation of high K+ was followed by partial inactivation of the channels and stabilization of [Ca2+]i at a new steady-state level depending on the extent of depolarization. Activation by BAY K 8644 was followed by complete inactivation and return of [Ca2+]i to resting levels. Ba2+ activated the channels and entered the cells but could not be removed from the cytosol by cellular Ca2+ pumps. The use of channel blockers and the ability to increase [Ca2+]i and [Ba2+]i by channel activation during [Ca2+]i oscillations showed that VACC do not contribute to or are activated during agonist-stimulated Ca2+ oscillation in this cell type. Graded activation of VACC showed that an increase in [Ca2+]i between the spikes to below 200 nM increased the frequency of the oscillation. Further increase in [Ca2+]i caused gradual reduction in the frequency. At [Ca2+]i above 500 nM, [Ca2+]i oscillations were inhibited. The inhibitory but not the stimulatory effects of [Ca2+]i on the oscillations can be mimicked by [Ba2+]i. These observations suggest that [Ca2+]i levels between the spikes play an important role in regulating the oscillations.

Barium↗
PubMed1992

[Observation on the phenotypic changes of tumor-infiltrating lymphocytes(TIL) during cultivation in vitro].

Tumor-infiltrating lymphocytes (TIL) were isolated from 5 malignant tumors and their phenotypes were analyzed by flow cytometry when co-cultured with recombinant human interleukin-2 (rIL-2). It was shown that 84% (+/- 8%) of TILs were OKT3+in phenotype after three weeks of cultivation. Among these, OKT8+subpopulations amounted to 77%(+/- 13%), while OKT4+subpopulations were only 14%(+/- 11), and the ratio of OKT4+/OKT8+changed from 0.5:1 (in the first week) to 0.18 (in the third week). Two parameters (mode and peak) in the histogram of flow cytometry varied in accordance with the variations of TIL's phenotypes. The results suggested that TILs stimulated by rIL-2 could be enriched predominantly in a single subpopulation (OKT8+), which might be related with their specific effects against tumor growth.

CD4-CD8 Ratio↗
PubMed1992

[Experimental expansion and antitumor effects of LAK cells from cancer patient's peripheral blood].

To augment the in vitro expansion of LAK cells, we added highly purified human recombinant interleukin-2, phytohemagglutinin and accessory cells (Uc cells) to the LAK culture system, with which huge number of LAK cells (LAK-L) were generated from originally small number of peripheral blood lymphocytes of cancer patients. These LAK-L cells exhibited similar antitumor activities in vitro and in vivo, as compared with LAK-S cells (LAK cells activated in short term culture). The phenotyping results suggested that there was more expression of IL-2 receptors in the LAK-L group than in the LAK-S group. The rapid proliferation of LAK-L cells was characterized by the expansion of OKT8 positive cells in the LAK-L populations.

Animals↗
PubMed1992

[The antitumor effects of tumor-infiltrating lymphocytes (TIL) being proliferated in vitro].

Tumor-infiltrating lymphocytes (TIL) were isolated from 19 solid tumors by means of in vitro digestion and discontinuous density gradient centrifugation. The average amount of TIL harvested from one gram of tumor tissue was 1.3 x 10(6). A four-week long term cultivation procedure was performed in 8 of the 19 specimens with rIL-2, and the number of TIL had then been expanded for 30 to 150 times more. Phenotypic analysis showed that most of TILs obtained were OKT3+ lymphocytes, and the ratio of OKT4+ and OKT8+ was decreased coincidently during the cultivation in vitro. The experiment showed that TILs exhibited stronger anti-autologous tumor effects than that to the allogeneic tumors through both in vitro and in vivo studies.

Animals↗
PubMed1991

Regulation of Na-K-2Cl cotransport in osteoblasts.

Uptake of 86Rb was used to follow the activity of Na-K-2Cl cotransport in the osteosarcoma cell line UMR-106-01. The ouabain-resistant fraction of 86Rb uptake was sensitive to bumetanide and furosemide. Furosemide-sensitive 86Rb uptake required the presence of Na+, K+, and Cl- in the incubation medium. These observations indicate the presence of a Na-K-2Cl cotransport system in osteoblasts. Cotransporter activity was stimulated by agonists which increase adenosine 3',5'-cyclic monophosphate (cAMP), cytosolic free Ca2+ ([Ca2+]i), and protein kinase C (PKC) activity such as parathyroid hormone (PTH) and prostaglandin E2 (PGE2). However, endothelin, which increases [Ca2+]i and PKC activity without affecting cellular levels of cAMP, was ineffective in stimulating the cotransporter. Accordingly, increasing cellular cAMP with forskolin was as effective as PTH and PGE2 in stimulating the cotransporter. Stimulation of PKC with TPA inhibited the cotransporter in a time- and concentration-dependent manner. No stimulation of cotransport could be demonstrated at any 12-O-tetradecanoyl-phorbol-13-acetate (TPA) concentration or incubation time. The Na-K-2Cl cotransporter was stimulated by cell shrinkage. Maximal stimulation was observed after swelling the cells in hypotonic medium and subsequent shrinkage in isotonic medium. Stimulation by cell shrinkage can be demonstrated in control, agonist-, cAMP-, and TPA-treated cells. These observations suggest that 1) the osteoblastic Na-K-2Cl cotransporter is activated by calciotropic hormones predominantly through an increase in cellular cAMP, and 2) in osteoblasts, the cotransporter is independently regulated by different biochemical pathways.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Regulation of cell volume by the osteosarcoma cell line UMR-106-01.

Determination of cell volume by an electronic cell-sizing technique was used to study the role of ion transporters in cell volume regulation by the osteosarcoma cell line UMR-106-01. Swelling the cells in hypotonic medium was followed by regulatory volume decrease (RVD). The rate of RVD was strongly dependent on the subpassage used and increased with increasing subpassages. Swelling-evoked changes in cytosolic free Ca2+ ([Ca2+]i) did not account for this behavior, since it was similar in cells from all subpassages. Increasing plasma membrane K+ permeability with valinomycin resulted in a similar rate of RVD in cells from different subpassages, suggesting increased K+ channel activity or other electrogenic transporter with increased subpassages. In contrast, the mechanisms responsible for regulatory volume increase (RVI) were fully active in cells from all subpassages. Increasing medium osmolarity of cells bathed in isotonic medium induced slow and incomplete RVI. In addition, shrinking cells exposed to hypotonic medium before completion of RVD resulted in impaired RVI. Effective RVI could be observed only after completion of RVD of cells exposed to hypotonic medium. Removal of extracellular Na+ or K+ completely blocked RVI, whereas removal of external Cl- partially blocked RVI. The effect of K+ removal probably reflects in part inhibition of Na-K-2Cl cotransport and in part inhibition of the Na+ pump.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1991

[Postoperative radiotherapy of renal carcinoma--analysis of 57 patients].

Retrospective analysis of 57 patients with carcinoma of kidney treated by radiotherapy postoperatively from 1970 to 1986 is reported. Thirty-six were male and 21 were female, with ages ranging from 19 to 75. All patients had unilateral nephrectomy followed by radiation therapy after an interval of 3-8 weeks. The kidney area was irradiated using either parallel opposing anterior and posterior portals or two oblique ones. 10-MV photon beam was used to deliver a total dose of 35-60 Gy with daily dose of 1.8 Gy, 5 times a week. The 3- and 5-year survival rates were 62.5% and 58.9%. The authors believe that for extra-capsular extension, tumors larger than 5 cm in diameter, presence of metastatic lymphnodes or local residual lesion, postoperative radiotherapy is indicated.

Adenocarcinoma↗
PubMed1991

A study of phlebotomine sandflies (Diptera: Psychodidae) in Yunnan Province, China. I. Phlebotomine sandflies of northeastern and western Yunnan.

From August to September, 1984 phlebotomine sandflies were collected with light-sticky traps by the authors in the following places viz., Weixin, Yanjian and Huize Counties, North-eastern Yunnan; Xiaguan, Baoshan, Shidian, Longling, Lùxi, Ruili, Yingjiang and Tengchong Counties, western Yunnan. A total of 9 species had been identified. Their systematical catalogue and zoogeographical distribution were given.

Animals↗
PubMed1990

[Long-term results of radiation therapy for pituitary adenoma--analysis of 386 cases].

A total of 386 cases of pituitary adenoma treated in our hospital from Jan. 1963 to Jan. 1986 is reported. Of them, 117 were treated by operation alone, 97 by radiotherapy alone and 172 by operation plus radiotherapy. 119 cases (group A) treated before April 1980 were mostly diagnosed by pneumoencephalography or cerebral angiography, treated, by conventional operation, followed by radiation therapy with 60Co or linear accelerator. 267 cases (group B) treated after April 1980 arrived at the correct diagnoses by CT scan and endocrine assay, treated by microsurgery, followed by radiotherapy with linear accelerator. All patients were followed for 2-23 years. The response rates of groups A and B were 90.7% and 94%. The results were better in patients treated by surgery combined with irradiation. The recurrence rate of radiation or surgery alone was higher than that of combined therapy. It is indicated that the optimal treatment for pituitary adenoma is surgery combined with radiotherapy. Besides, the introduction of CT scan and microsurgery has improved the diagnosis and treatment results of pituitary adenoma.

Adenoma, Acidophil↗
PubMed1990

[Primary non-squamous cell carcinoma of the trachea and main bronchus--analysis of 17 cases].

Seventeen patients with primary non-squamous cell carcinoma in the trachea and main bronchus are reported. Tomography and bronchoscopy are of great help in the diagnosis of this disease. CT scan is useful to show the extent of the tumor and lymph node metastasis. The treatment should depend on the extent of the lesion, pathologic type and general condition of the patient. Surgery is the treatment of choice for the early stage lesion, while pre- or post-operative irradiation is given to patients with larger tumor. In patients with localized lesion but unsuitable for operation because of late stage or poor differentiation of the tumor, radical radiotherapy alone should be used. A total dose of 70-80 Gy/7-8 weeks is suggested.

Adenocarcinoma↗
PubMed1989

Transposition of iliac periosteum with vascular pedicle and compression screw fixation for transcervical fracture of femur. Experimental research and clinical application.

The vascular pedicled periosteum was used in 11 cases in our hospital for the treatment of femoral neck fracture with good result. The follow-up period ranged from 2 to 6 years, with an average of 4 years. Animal experiment was made to elucidate the repairing process. It demonstrated that the pedicled periosteum played double roles, namely, blood supply and osteogenesis. The clinical and experimental results are presented.

Adolescent↗
PubMed1989

Cloning and expression of delta-endotoxin gene of Bacillus thuringiensis in Escherichia coli.

Fragments (larger than 4 kb) of partially Sau 3AI-digested plasmid DNA from Bacillus thuringiensis subsp. kenyae 7404 and kurstaki HD-1 were cloned into the BamH I site of pBR322. Four transformants, containing the corresponding delta-endotoxin gene and producing proteins that reacted with antiserum against crystalline protein, were selected on the basis of results from in situ colony hybridization, radioimmunologic screening, and Western blot analysis. Three of those tested, i.e., the lysates of one transformant (TK89) carrying the delta-endotoxin gene of B.t. 7404 and two transformants (TH12 and TH48) carrying the delta-endotoxin gene of HD-1, were toxic for tobacco budworm (Heliothis assulta) and armyworm (Leucania separata Walker) caterpillars. This is the first report on cloning of the delta-endotoxin gene from B.t. subsp. kenyae, which is different in serotype from the well-studied subsp. kurstaki.

Animals↗