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Biomedical subjects

S Kong

Publications and source records attributed to S Kong.

36 records · Page 2Linked to original sources
PubMed1997

Distinct tissue and cellular distribution of two major isoforms of calcineurin.

The protein phosphatase calcineurin is known to be an essential intracellular signal transducer involved in the TCR-mediated signal transduction pathway and is the common target of the immunosuppressive drugs cyclosporin A (CsA) and FK506. The catalytic subunit of calcineurin exists in multiple isoforms, but their functional differences are not known. It has been assumed that the alpha isoform of calcineurin is the relevant isoform mediating TCR signaling. Recently, calcineurin alpha was knocked out in mice, but no defect in the TCR-mediated IL-2 production was observed, suggesting that another isoform of calcineurin mediates the TCR signal transduction pathway. We have generated specific polyclonal antibodies against the alpha and the beta2 isoforms of calcineurin and examined their distribution in murine tissues and immune cells by immunohistochemical staining and Western blot analysis. We found that the beta2 isoform of calcineurin is predominant in T and B lymphocytes as well as in thymus compared to the alpha isoform, suggesting that the beta2 isoform may play a key role in TCR signaling. Furthermore, we observed that the two isoforms exhibit distinct expression patterns in both kidney and thymus, indicating that the two isoforms of calcineurin have distinct cellular functions. Together, these findings raise the possibility that the nephrotoxicity associated with CsA and FK506 can be reduced by designing novel inhibitors of calcineurin that target specific isoforms of the enzyme.

Amino Acid Sequence↗
PubMed1997

Transcription of the HS2 enhancer toward a cis-linked gene is independent of the orientation, position, and distance of the enhancer relative to the gene.

The locus control region (LCR) regulates transcription of the downstream beta-like globin genes 10 to 50 kb away. Among hypersensitive sites HS4, -3, -2, and -1, which define the LCR in erythroid cells, HS2 possesses prominent enhancer function. The mechanism by which the HS2 enhancer and other functional components of the LCR act over the distance is not clear. We have used reverse transcription-PCR and RNase protection assays to analyze the transcriptional statuses of both the endogenous and the transfected HS2 enhancer in erythroid K562 cells. A novel pattern of HS2 enhancer transcription was observed. The endogenous HS2 enhancer was transcribed predominantly in the direction toward the downstream globin genes. The HS2 enhancer in transfected recombinant chloramphenicol acetyltransferase (CAT) plasmids was also transcribed predominantly toward the CAT gene, regardless of whether the enhancer was placed (i) in the genomic or reverse genomic orientation, (ii) in a position 5' or 3' to the gene, or (iii) at various distances up to 6 kb from the gene. The orientation, position, and distance independence in gene-tropic transcription of the HS2 enhancer correlates with the observed orientation, position, and distance independence of HS2 enhancer function and suggests that enhancer transcription may play a role in enhancer function.

Animals↗
PubMed1995

Formation of novel hydrophobic complexes between cationic lipids and plasmid DNA.

An ability to generate a well defined lipid-based carrier system for the delivery of plasmid DNA in vivo requires the characterization of factors governing DNA/lipid interactions and carrier formation. We report that a hydrophobic DNA/lipid complex can be formed following addition of cationic lipids to DNA in a Bligh and Dyer monophase consisting of chloroform/methanol/water (1:2.1:1). Subsequent partitioning of the monophase into a two-phase system allows for the extraction of DNA into the organic phase. When using monovalent cationic lipids, such as dimethyldioctadecylammonium bromide, dioleyldimethylammonium chloride, and 1,2-dioleyl-3-N,N,N-trimethylaminopropane chloride, greater than 95% of the DNA present can be recovered in the organic phase when the lipid is added at concentrations sufficient to neutralize DNA phosphate charge. When the polyvalent cationic lipids 2,3-dioleyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl- 1- propanaminium trifluoroacetate and diheptadecylamidoglycyl spermidine are used, efficient extraction of the DNA into the organic phase is also achieved when the charge ratio between lipid and DNA is approximately equal. Formation of the hydrophobic DNA complex can only be achieved with cationic lipids. In the absence of added cations or in the presence of excess Ca2+, L-lysine, or poly(L-lysine), 100% of the DNA is recovered in the aqueous fraction. The monovalent cationic lipid/DNA complexes can also be prepared in the presence of detergent; however, low concentrations of NaCl (< 1 mM) lead to dissociation of the complex. Importantly, these results clearly demonstrate that cationic lipid binding does not lead to DNA condensation. The methods described, therefore, enable DNA/lipid complexes to be characterized in the absence of DNA condensation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cations↗
PubMed1994

[Gynecology and obstetrics of the Song Dynasty].

There are great gynecological achievements in the Song Dynasty, featuring the establishment of a discipline on obstetrics with an obstetrical professor who specialized in the training of students in gynecology and obstetrics and pushed forward the development of these departments; the appearance of obstetricians and gynecologists as well as relevant monographs; accomplishment of basic theories, and technical know-how on diagnosis and therapy. By then, obstetrics and gynecology were developed into an independent discipline.

China↗
PubMed1993

Protein phosphatase inhibition and in vivo hepatotoxicity of microcystins.

Administration of microcystin (MCYST)-YM or -LR (peptide hepatotoxins produced by the cyanobacterium Microcystis aeruginosa) to mice resulted in the inhibition of liver protein phosphatase 1 and 2A activity. In all cases significant inhibition preceded or accompanied clinical changes due to MCYST intoxication. Fifteen minutes after intraperitoneal injection of lethal doses of MCYST-YM protein phosphatase activity was already decreased to 44% of controls, and by 60 min was further decreased to 22% of controls. The inhibition was dose dependent: intraperitoneal injection with 84 nmol/kg of MCYST-YM and 48 nmol/kg of MCYST-LR were the minimum doses required for significant inhibition at 60 min. Pretreatment of mice with 200 mumol/kg of rifamycin prevented the inhibition of liver protein phosphatase. The inhibition was tissue specific, with none detected in the kidneys, an organ that, unlike the liver, does not accumulate MCYST. In contrast to MCYST intoxication, lethal doses of phalloidin, a peptide hepatotoxin that produces clinical and pathological changes similar to MCYST, did not cause any inhibition of protein phosphatases.

Animals↗
PubMed1992

Transcription of the hypersensitive site HS2 enhancer in erythroid cells.

In the human genome, the erythroid-specific hypersensitive site HS2 enhancer regulates the transcription of the downstream beta-like globin genes 10-50 kilobases away. The mechanism of HS2 enhancer function is not known. The present study employs RNA protection assays to analyze the transcriptional status of the HS2 enhancer in transfected recombinant chloramphenicol acetyltransferase (CAT) plasmids. In erythroid K562 cells in which the HS2 enhancer is active, the HS2 sequence directs the synthesis of long enhancer transcripts that are initiated apparently from within the enhancer and elongated through the intervening DNA into the cis-linked CAT gene. In nonerythroid HL-60 cells in which the HS2 enhancer is inactive, long enhancer transcripts are not detectable. Splitting the HS2 enhancer between two tandem Ap1 sites abolishes the synthesis of a group of long enhancer transcripts and results in loss of enhancer function and transcriptional silencing of the cis-linked CAT gene. In directing the synthesis of RNA through the intervening DNA and the gene by a tracking and transcription mechanism, the HS2 enhancer may (i) open up the chromatin structure of a gene domain and (ii) deliver enhancer binding proteins to the promoter sequence where they may stimulate the transcription of the gene at the cap site.

Base Sequence↗
PubMed1992

Aluminum(III) facilitates the oxidation of NADH by the superoxide anion.

Al(III) augments the oxidation of reduced nicotinamide adenine dinucleotide (NADH) by enzymatic or photochemical sources of O2-. Superoxide dismutase, but not catalase, inhibited this action of Al(III). It thus appears that Al(III) forms a complex with O2-, which is a stronger oxidant than is O2- itself and which may contribute to the adverse biological effects of Al(III).

Aluminum↗
PubMed1990

In vivo induction of lymphokine-activated killer cells by interleukin-2 splenic artery perfusion in advanced malignancy.

In an effort to stimulate in vivo LAK cell activity at relatively nontoxic doses, 20 patients with advanced metastatic malignancy (13 renal cell carcinoma, 6 melanoma, 1 lymphoma) were treated with recombinant human interleukin-2 (IL-2) by continuous 5-day splenic artery perfusion using the femoral approach. Two treatment cycles were administered 3 weeks apart; IL-2 doses ranged from 1.5-4 x 10(4) Cetus units/kg/day. Peripheral blood lymphocyte cytotoxicity in a 4-h 51Cr release assay was measured using as tumor cell targets K562 for natural killer (NK) activity, Daudi for LAK, and Daudi plus in vitro IL-2 for inducible LAK (I-LAK). For the 20 patients, an increase in mean peak percent cytotoxicity from pretreatment levels was seen for NK (36% to 53%), LAK (8% to 37%) and I-LAK (20% to 53%) activity, all significant at P = 0.001. On day 43, 16 days after completing the second cycle of treatment, NK activity remained elevated at 47% and I-LAK at 40% (P = 0.008 and 0.01, respectively). Lymphocyte phenotype analysis by flow cytometry demonstrated increases from pretreatment levels in Leu 11+ (13 to 23%), Leu 19+ (10 to 21%), Leu 11+ 19+ (7 to 17%), IL-2r+ (4 to 17%), and HLA-DR+ (12 to 25%) subsets, all significant at P less than or equal to 0.01. Dose effect was studied at 3 dose levels: 1.5, 3, and 4 x 10(4) Cetus units/kg/day. At the higher doses mean peak NK (57%) and I-LAK (57%) activity were greater than at the low dose (42 and 31%, respectively), both significant at P less than 0.05. A trend to positive dose effect was seen in LAK activity (P = 0.08). Splenic artery perfusion with IL-2 can result in significant in vivo peripheral LAK cell generation as well as enhancement of I-LAK and NK activity that persists at least 16 days after the cessation of treatment. Such sustained activity would not be expected with conventional high dose i.v. therapy.

Antigens, CD↗
PubMed1988

Survival, response and immune effects in a prospectively randomized study of dose strategy for alpha-N1 interferon.

Several tumour sites have now demonstrated objective responses to alpha interferons in a diversity of doses and schedules. Since effectiveness should be enhanced with the identification of an optimal dose strategy, we undertook a prospectively randomized study to compare an intermittent high dose escalating strategy (HDS) vs. a fixed low dose treatment in relation to clinical outcome and laboratory correlates of immune function. HDS patients received interferon alpha-N1 (lymphoblastoid interferon) 5M units m-2 by continuous i.v. infusion over 24 h, escalating by 5 M units m-2 day-1 as tolerated over 10 days, and repeated every 28 days. The low dose strategy (LDS) consisted of a fixed dose of 2 M units m-2 by intramuscular injection daily for 28 days, then daily for 7 days every other week. There were 53 evaluable patients. In keeping with earlier preliminary results there was evidence of improved immune function for HDS patients. They demonstrated a significant increase in the number of CD2+ (sheep red blood cell binding) cells and CD4+ (helper-inducer/suppressor-inducer) cells along with enhanced activity of natural killer cell, and mixed leukocyte culture activity. In addition to improved immune function, HDS patients survived longer than LDS (P = 0.04). Analysis of survival in relation to response suggested that monitoring of minor responses may be of interest for biological agents such as interferon.

Adult↗
PubMed1983

Effect of lymphoblastoid interferon on lymphocyte subsets in cancer patients.

The effect of interferon dose on lymphocyte subsets is unclear for humans, especially with prolonged intermittent administration. Enumeration of T4 and T8 cells and natural killer (NK) cell activity against K562 cells were examined as part of our ongoing randomized clinical study comparing low- and high-dose treatment strategies. Fifty-four patients have been entered into study, of which 46 are now evaluable. High-dose patients showed no significant changes during actual interferon infusion. However, over the entire period on study, there was a significant increase in NK cell activity (p = 0.001), a concurrent decrease in T8 (p = 0.004), and an increase in T4/T8 (p = 0.02). By contrast, for low-dose patients there was a trend of increasing NK activity during interferon administration, but no change during the total time on study, with a concurrent trend of decreasing T4/T8 and a significant increase in T8 (p = 0.01). Although there is as yet no significant response difference between high- and low-dose treatments, a favourable response was associated with an overall increase in NK activity (p = 0.005), a decrease in T8 (p = 0.02), and an increase in T4/T8 (p = 0.03). In a preliminary study of immune complexes in selected patients, an inverse relationship between NK cell activity and immune complex concentration was suggested. This was supported by in vitro addition of autologous immune complex-containing sera during NK cell assay.

Breast Neoplasms↗
PubMed1981

The relative effectiveness of .OH, H2O2, O2-, and reducing free radicals in causing damage to biomembranes. A study of radiation damage to erythrocyte ghosts using selective free radical scavengers.

The relative effectiveness of oxidizing (.OH, H2O2), ambivalent (O2-) and reducing free radicals (e- and CO2-) in causing damage to membranes and membrane=bound glyceraldehyde-3-phosphate dehydrogenase of resealed erythrocyte ghosts has been determined. The rates of damage to membrane-bound glyceraldehyde-3-phosphate dehydrogenase (R(enz)) were measured and the rates of damage to membranes (R(mb)) were assessed by measuring changes in permeability of the resealed ghosts to the relatively low molecular weight substrates of glyceraldehyde-3-phosphate dehydrogenase. Each radical was selectively isolated from the mixture produced during gamma-irradiation, using appropriate mixtures of scavengers such as catalase, superoxide dismutase and formate. .OH, O2- and H2O2 were approximately equally effective in inactivating membrane-bound glyceraldehyde-3-phosphate dehydrogenase, while e- and CO2- were the least effective. R(enz) values of O2- and H2O2 were 10-times and of .OH 15-times that of e-. R(mb) values were quite similar for e- and H2O2 (about twice that of O2-), while that of .OH was 3-times that of O2-. Hence, with respect to R(mb): .OH greater than e- = H2O2 greater than O2-, and with respect to R(enz): .OH greater than O2- = H2O2 much greater than e-. The difference between the effectiveness of the most damaging and the least damaging free radicals was more than 10-fold greater in damage to the enzyme than to the membranes. Comparison between H2O2 added as a chemical reagent and H2O2 formed by irradiation showed that membranes and membrane-bound glyceraldehyde-3-phosphate dehydrogenase were relatively inert to reagent H2O2 but markedly susceptible to the latter.

Catalase↗
PubMed1981

Actions of gamma-radiation on resealed erythrocyte ghosts. A comparison with intact erythrocytes and a study of the effects of oxygen.

With respect to both permeability and inactivation of membranous GAPDH, ghosts were more susceptible than erythrocytes to free radicals produced in the gamma-irradiation of aqueous solutions. The rate of increase in the permeability of irradiated ghosts was immeasurably greater than that of irradiated erythrocytes, while the rate of inactivation of GAPDH was 21-fold greater. The sensitivity of ghosts to radiation damage was affected strongly by the presence of oxygen during irradiation. In the presence of air, the rates of increase of permeability and inactivation of GAPDH were 2.8- and 1.5-fold of those in the presence of N2. The use of buffer saturated with oxygen accelerated the aerobic rates of increase of permeability and inactivation of GAPDH by 60- and 2.7-fold. These results indicate that inactivation of GAPDH is somewhat sensitive to oxygen, particularly at high concentration of oxygen. Nevertheless, in air or under nitrogen, the rate of enzymic inactivation was almost an order of magnitude greater than that of increase of permeability, indicating that the former is much more sensitive to irradiation. The major mechanism of the oxygen effect observed is the ability of oxygen to increase the branching of the free radical chain reactions which propagate damage after initiation within the membrane.

Cell Membrane Permeability↗
PubMedDate not supplied

Adequate relief as an endpoint in clinical trials in irritable bowel syndrome.

Irritable bowel syndrome is characterized by recurrent abdominal pain and altered bowel function. In designing studies to evaluate new treatments for this disease, however, it is difficult to select appropriate endpoints to reflect improvement in the range of symptoms of the syndrome. In the present study we evaluated the parameter of adequate relief of abdominal pain and discomfort, as perceived by the patients, as a key endpoint for efficacy in the treatment of patients with irritable bowel syndrome. Abdominal pain and bowel function data were collected daily from 370 patients with the disease during treatment with placebo or a novel potent 5HT3 receptor antagonist. Once every 7 days adequate relief of pain and discomfort was assessed. Quality-of-life data were collected using self-administered questionnaires. The endpoint of adequate relief was significantly (P < 0.05) correlated with improvement in pain severity scores, percentage of pain-free days, percentage of days with urgency, improvement in stool frequency and consistency, and quality-of-life parameters. Adequate relief of pain and discomfort is significantly correlated with changes in multiple parameters associated with irritable bowel syndrome and can be used as an endpoint for assessing response to therapy in these patients.

Abdominal Pain↗