Anti-tuberculosis drugs and liver toxicity.
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Antitubercular Agents↗
Biomedical subjects
S Leung
Publications and source records attributed to S Leung.
Regulation of STAT-dependent pathways by growth factors and cytokines.
Polypeptide growth factors and cytokines elicit their effects by activating specific cell-surface receptors, thereby initiating signaling cascades that culminate in the induction of specific subsets of genes. Initially identified as the primary mediators of interferon-dependent signaling, JAKs and STATs are now known to be utilized by many different extracellular signaling proteins. In this report we describe how JAK-STAT pathways transduce signals initiated by both cytokines and growth factors, focusing on how specificity is achieved through STAT-receptor interactions and on how receptor-associated kinases function in STAT activation. We also summarize current information on interactions between signaling pathways, particularly STAT-Ras cross-talk and the relative importance of these two pathways in regulating the transcription of target genes.
Animals↗
Combinatorial association and abundance of components of interferon-stimulated gene factor 3 dictate the selectivity of interferon responses.
Genes containing the interferon-stimulated response element (ISRE) enhancer have been characterized as transcriptionally responsive primarily to type I interferons (IFN alpha/beta). Induction is due to activation of a multimeric transcription factor, interferon-stimulated gene factor 3 (ISGF3), which is activated by IFN alpha/beta but not by IFN gamma. We found that ISRE-containing genes were induced by IFN gamma as well as by IFN alpha in Vero cells. The IFN gamma response was dependent on the ISRE and was accentuated by preexposure of cells to IFN alpha, a treatment that increases the abundance of ISGF3 components. Overexpression of ISGF3 polypeptides showed that the IFN gamma response depended on the DNA-binding protein ISGF3 gamma (p48) as well as on the 91-kDa protein STAT91 (Stat1 alpha). The transcriptional response to IFN alpha required the 113-kDa protein STAT113 (Stat2) in addition to STAT91 and p48. Mutant fibrosarcoma cells deficient in each component of ISGF3 were used to confirm that IFN gamma induction of an ISRE reporter required p48 and STAT91, but not STAT113. A complex containing p48 and phosphorylated STAT91 but lacking STAT113 bound the ISRE in vitro. IFN gamma-induced activation of this complex, preferentially formed at high concentrations of p48 and STAT91, may explain some of the overlapping responses to IFN alpha and IFN gamma.
Animals↗
Engineering a unique glycosylation site for site-specific conjugation of haptens to antibody fragments.
A natural N-linked glycosylation site (Asn-Val-Thr) at amino acid positions 18-20 (Kabat's numbering) was identified in the framework-1 (FR-1) region of the light chain variable (V kappa) domain of a murine anti-B cell lymphoma Ab, LL-2. Our earlier studies demonstrated that no contact between the V kappa-appended oligosaccharide and the Ag binding site was evident, because glycosylation at this site did not affect the Ag binding property of the Ab. By using the murine LL-2 F(ab')2 fragment (which is devoid of constant region-appended oligosaccharide) as substrate, as much as five bifunctional chelator molecules per F(ab')2 fragment could be site specifically conjugated at the V kappa-appended carbohydrate moiety with no reduction in immunoreactivity. The resulting conjugates labeled efficiently with both 90Y and 111In, with no significant effect on Ab affinity. In contrast, conjugation of less than five chelates/Ab fragment randomly at lysine residues resulted in a three- to fivefold reduction in affinity. By a single Arg to Asn mutation, an N-linked glycosylation site similar to that of LL-2 was introduced in the FR-1 segment of a nonglycosylated, humanized anti-carcinoembryonic Ag (CEA) Ab, MN-14 (hMN-14). Glycosylation at the engineered carbohydrate-addition site was demonstrated by SDS-PAGE analysis. Neither glycosylation nor site-specific conjugation of chelate at the V kappa-appended carbohydrate moiety resulted in the loss of immunoreactivity. The glycosylated hMN-14 conjugate labeled efficiently with 90Y.
Amino Acid Sequence↗
Treatment of pediatric genitourinary malignancy with interstitial brachytherapy: Peter MacCallum Cancer Institute experience with four cases.
PURPOSE: To describe early outcome and technical treatment aspects of four patients with pediatric genitourinary malignancy receiving local therapy using interstitial brachytherapy at the Peter MacCallum Cancer Institute since 1991. METHODS AND MATERIALS: Two patients with primary bladder tumors and two patients with primary vaginal tumors received interstitial brachytherapy with needle-template techniques following chemotherapy. Two patients were treated for salvage following local failure after primary chemotherapy and two patients electively after initial induction chemotherapy, one following limited surgical excision. Three patients were treated exclusively with brachytherapy with doses of 50-55 Gy (LDR), and one patient also received external beam radiation. RESULTS: Resultant implants, dosimetry, and dose prescriptions are described and illustrated. Follow-up is short (14-27 months), but all patients remain well without significant sequelae. One child required salvage surgery for local failure. CONCLUSION: Interstitial brachytherapy using needle-template techniques described is an ideal method of local ablative therapy for pediatric genitourinary malignancy. Functional and late sequelae should be less than that of radical surgery or external beam radiation. There are technical and practical advantages compared with other brachytherapy techniques described in the literature.
Antineoplastic Agents↗
Preference for static or revolving cane tips by visually impaired travellers.
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Adolescent↗
Role of STAT2 in the alpha interferon signaling pathway.
We have isolated U6A, a mutant cell line which lacks the STAT2 subunit of the transcription factor interferon (IFN)-stimulated gene factor 3 (ISGF3). The response of U6A cells to IFN-alpha is almost completely defective, but the response to IFN-gamma is normal. Complementation of U6A cells with a cDNA encoding STAT2 restores the IFN-alpha response, proving that STAT2 is required in this pathway. Binding of IFNs to their receptors triggers tyrosine phosphorylation and activation of the receptors, JAK family kinases, STAT1, and STAT2. In IFN-alpha-treated U6A cells, phosphorylation of the essential tyrosine kinases TYK2 and JAK1 is normal, but the phosphorylation of STAT1 is weak. A mutant STAT2 protein in which the phosphorylated tyrosine at position 690 is changed to phenylalanine does not restore normal phosphorylation of STAT1 in response to IFN-alpha. The dependence of STAT1 phosphorylation on the presence of STAT2 but not vice versa (T. Improta, C. Schindler, C. M. Horvath, I. M. Kerr, G. R. Stark, and J. E. Darnell, Jr., Proc. Natl. Acad. Sci. USA 91:4776-4780, 1994) indicates that in the formation of ISGF3, these two proteins may be phosphorylated sequentially in response to IFN-alpha and that phosphorylated STAT2 may be required to allow unphosphorylated STAT1 to bind to the activated IFN-alpha receptor.
Antibodies↗
Norplant removals spur suits. Some recipients report problems.
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Americas↗
Regulation by nerve growth factor and protein phosphorylation of Na/K/2Cl cotransport and cell volume in PC12 cells.
PC12 cells possess a bumetanide-sensitive Na/K/2Cl cotransport system similar to that found in other cell types. Between 10-15% of the total 86Rb influx in these cells is mediated by this pathway under normal conditions. The cotransporter has affinities of 16.5 mM for Nao and 0.7 mM for Ko, is absolutely dependent on Clo and is loop diuretic inhibitable (benzmetanide > bumetanide > piretanide > furosemide). The cotransporter can be activated (up to 8-fold) by cell shrinkage or (up to 4-fold) by treatment with the protein phosphatase inhibitors okadaic acid (EC50 approximately 650 nM) or calyculin A (EC50 approximately 8 nM). Cell shrinkage is followed by a bumetanide-sensitive regulatory volume increase as determined in cell sizing experiments. Calyculin A rapidly elevates normal cell volume in a diuretic-inhibitable manner. Cotransport activity and cell volume are also increased by nerve growth factor (NGF) treatment. The effect of NGF on cotransport rate is biphasic, with an initial rapid approximately 2.5-fold increase followed by a prolonged plateau, and is blocked by pretreatment of the cells with K252a (IC50 approximately 30 nM). By contrast, agents that raise cAMP or phorbol esters lead to an inhibition of cotransport, indicating that the NGF effect is not mediated by stimulation of either cAMP-dependent protein kinase or protein kinase C. Long term NGF treatment (> 2 days) leads to neurite formation and a maintained approximately 2-fold increase in cotransport activity. Bumetanide treatment does not affect the ability of cells to extend neurites, nor is the growth rate of cells in normal medium affected by the diuretic. These results suggest that the cotransport system in PC12 cells is acutely regulated by protein phosphorylation and dephosphorylation as well as cell shrinkage and that cotransport activity may be up-regulated during neuronotypic differentiation.
Animals↗
Infant feeding and growth of Chinese infants: birth to 2 years.
A cohort of 174 healthy full-term Chinese infants was followed up regularly for 2 years for their weight, length, head circumference, triceps and subscapular skinfold thickness, and their feeding practice. The majority of babies (92% at 2 months) were bottle fed with full strength infant formula. The energy intake over the first year of life was comparable with that of healthy Caucasian infants. The mean protein intake during the weaning period exceeded fourfold that of the WHO recommendation. At 2 years, infants were -0.6 standard deviation score (SDS) lighter and -0.4 SDS shorter than the National Centre for Health Statistics (NCHS) reference.
Anthropometry↗
Myb and Ets related transcription factors are required for activity of the human lck type I promoter.
The lck gene, which encodes a lymphoid-specific Src family tyrosine kinase, is transcribed from two promoters that are differentially utilized during T cell development. We have shown previously that the human lck type I promoter, which is preferentially expressed in immature thymocytes, requires a binding site (-97 to -90) for the Ets family of transcription factors for its activity in Jurkat T leukemia cells. Three putative Myb binding sites (-86 to -82, -77 to -72 and -59 to -54) were analysed for their ability to activate the lck type I promoter. In vitro assays demonstrated specific binding of purified, bacterially expressed c-Myb DNA binding domain to the Myb (-59 to -54) site. Transient transfection assays using the site-directed mutants of the lck type I promoter in Jurkat cells revealed that mutation of the Myb (-59 to -54) site abolished transcriptional activity. In transiently transfected HeLa cells, the lck type I promoter was activated by co-transfection with a vector that expresses c-Myb. This c-Myb dependent activation required the presence of intact Myb and Ets binding sites, indicating that the expressed c-Myb functions with endogenous Ets related transcription factors to activate the lck type I promoter. This effect was further enhanced by co-transfection with vectors that express either Ets1 or Ets2. These results demonstrate that Myb and Ets related transcription factors synergistically activate the human lck type I promoter.
Base Sequence↗
Use of extended field radiation in cancer of the cervix and endometrium.
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Endometrial Neoplasms↗
Radical radiation therapy for carcinoma of the vagina--impact of treatment modalities on outcome: Peter MacCallum Cancer Institute experience 1970-1990.
To determine the outcome of radical radiation therapy for carcinoma of the vagina, a retrospective analysis has been made of 103 patients referred with this diagnosis to the Peter MacCallum Cancer Institute from 1970 to 1989. Eighty-four patients were treated for cure, seventy-four patients with definitive radical radiotherapy and 10 patients with adjuvant post-operative radiotherapy. Results were analyzed from two eras--before and after 1985--reflecting changes in referral pattern, treatment policy, and outcome. Forty-eight patients were treated before 1985 (Stage I--24, Stage II--6, Stage III--15, Stage IV--3) and 36 patients after 1985 (Stage I--20, Stage II--3, Stage III--6, Stage IV--7). After 1985 more patients were treated with combined beam radiation and brachytherapy (23/36 vs. 16/48 prior to 1985). More extensive tumors were systematically implanted (Ir 192). (No implants before 1985; 15 implants and 8 intracavitary applications post 1985). Fewer were treated with external beam alone after 1985; 11/36 (31%) vs. 27/48 (55%) before 1985. A small number (7/84-8%) were treated with brachytherapy alone. Survival results were markedly improved after 1985 (22/36-61% vs 16/48-33%) due partly to the shorter period of follow-up, but due also to marked improvement in local control particularly in early stage disease. (1/23 vs. 12/30 recurrences in Stage I, II disease). Results indicate optimal results with radical radiation therapy occur only with adequate dose delivery best achieved with a judicious combination of external beam radiotherapy and brachytherapy. Interstitial implantation plays a crucial role.
Adenocarcinoma↗
Inhibition of Na-K-2Cl cotransport and bumetanide binding by ethacrynic acid, its analogues, and adducts.
The inhibitory effect of ethacrynic acid (EA) and a variety of its derivatives on Na-K-2Cl cotransport in avian erythrocytes was investigated. The most potent compound tested was the adduct of EA with L-cysteine, with an IC50 of 7.2 x 10(-7) M. EA itself, dihydro-EA, EA-D-cysteine, and adducts of EA with other sulfhydryl (-SH) compounds were much less potent. The mechanism of action of EA and EA-L-cysteine differed in several respects: 1) EA-L-cysteine acted more rapidly than EA (half times of < 1 and 4 min, respectively, at 37 degrees C); 2) the action of EA-L-cysteine was reversible by washing, whereas that of EA was not; and 3) the degree of inhibition by EA-L-cysteine varied with medium [K], whereas that of EA did not. The inhibitory effects of both EA-L-cysteine and EA were affected by medium [Na] and [Cl]. We conclude that EA-L-cysteine does not "deliver" EA to transport-related -SH residues or act as an alkylating agent but has some stereospecific effect on cotransport that is a property of the entire molecule. EA does appear to inhibit cotransport by alkylating -SH residues, as closely related compounds lacking the ability to covalently react with such groups were reversible, and other -SH reagents (e.g., N-ethylmaleimide) also inhibited cotransport. EA, EA-L-cysteine, and EA-D-cysteine all inhibited [3H]bumetanide binding to membranes from activated avian erythrocytes at concentrations similar to those that inhibited cotransport. It is possible that the EA and bumetanide types of diuretics interact with closely apposed sites on the Na-K-2Cl cotransporter.
Animals↗
Requirement of an ETS-binding element for transcription of the human lck type I promoter.
The requirement for cis-acting DNA sequences for transcriptional activity of the human lck type I promoter was investigated in two human cell lines that express type I transcripts, the leukemic T-cell line, Jurkat, and the colon carcinoma line, SW620. Transient transfection assays in Jurkat and SW620 cells revealed negative and positive cis-acting regulatory elements in the lck type I promoter between -570 and -480 and between -128 and -63 respectively. For the latter, a triple point mutation of a sequence, GCAGGAAGT, from -99 and -91 resulted in complete loss of lck type I promoter activity in both Jurkat and SW620 cells. In vitro binding assays indicated that this sequence, denoted the ETS-binding element or EBE, can interact with the lymphoid-specific transcription factor ETS-1. Thus, a protein(s) in the ETS family appears to be required for transcription of the lck type I promoter in T cells and may be important for the activation of the lck gene in human colon carcinoma.
Adult↗
Postoperative adjuvant radiotherapy in Astler-Coller stages B2 and C rectal cancer.
Between 1979 and 1983, 127 patients with Stages B2 or C rectal cancer treated with surgery plus postoperative adjuvant radiotherapy (RT group) and 122 patients treated with surgery alone (S group) were compared to evaluate the effect of postoperative radiotherapy on survival and disease recurrence. Each group was stratified into subgroups according to stage and tumor differentiation as follows: Subgroups BW (Stage B2 and well-differentiated tumor), BM (Stage B2 and moderately differentiated tumor), CW (Stage C and well-differentiated tumor), CM (Stage C and moderately differentiated tumor), and P (poorly differentiated tumor). Ninety-five percent of the patients were followed until death or, if alive, to five years after surgery. Postoperative radiotherapy was associated with a reduced five-year survival rate in Subgroup BW (67 vs. 87 percent; P = 0.02). In the remaining subgroups of the RT group, there was a statistically insignificant trend toward a worse survival rate (56 vs. 65 percent, 47 vs. 64 percent, 41 vs. 46 percent, and 50 vs. 36 percent for Subgroups BM, CW, CM, and P, respectively). The local failure rates for the S group and RT group were 10 vs. 23 percent (P = 0.15) in Subgroup BW, 32 vs. 21 percent (P = 0.4) in Subgroup BM, 24 vs. 25 percent (P = 0.6) in Subgroup CW, and 18 vs. 18 percent (P = 0.6) in Subgroup CM, respectively. Eight percent (9/127) had severe or life-threatening radiation-related complications. Postoperative adjuvant radiotherapy alone did not improve the survival of patients with Stages B2 or C rectal cancers. It may have led to worsened survival in the subgroup of patients with well-differentiated Stage B2 rectal cancer.
Adenocarcinoma↗
Differential expression of two classes of lck transcripts upon phorbol ester treatment of human leukemic T cells.
The human lymphocyte-specific tyrosine kinase gene, lck, is transcribed from two distinct promoters, resulting in two classes of transcripts (type I and II) differing in their 5' untranslated regions. The steady-state levels of the type I and II lck transcripts were measured in a variety of lymphoid and non-lymphoid human tumor cell lines by S1 nuclease mapping and by a sensitive assay system using the polymerase chain reaction. Human thymocytes and all the leukemic T cell lines tested express both type I and II lck transcripts, albeit at different relative levels. Peripheral blood T cells express mainly type II lck transcripts, whereas two colonic carcinoma lines, COLO 201 and COLO 205, express exclusively type I lck transcripts. Treatment of the leukemic T cell lines, P30/OKUBO and Jurkat, by the phorbol esters tetradecanoylphorbol acetate (TPA) or phorbol dibutyrate (PDB) results in the down-regulation of the type I, and the up-regulation of the type II, lck transcript levels. The effect of PDB on the in vitro differentiation of Jurkat cells, and the expression of lck transcripts, is reversible. The modulation of lck transcript levels in TPA-treated Jurkat cells is not due to differential RNA stability, suggesting that the two lck promoters are utilized differentially during T cell differentiation. The leukemic T cell line, Jurkat, may thus serve as a model for the elucidation of molecular mechanisms that regulate lck transcription and T cell differentiation.
Cell Line↗
Segmentally restricted, cephalic expression of a leucine zipper gene during Drosophila embryogenesis.
The expression pattern and DNA sequence of a newly identified gene, CNC (cap'n'collar), suggest a role for this gene in cephalic patterning during Drosophila embryogenesis. In situ hybridization reveals transcripts localized to the mandibular segment and the hypopharyngeal and labral primordia first detectable in late blastoderm stages. Sequence analysis of cDNA clones from the CNC locus shows the CNC gene product to be related to transcription factors of the leucine zipper (bZIP) class. Based on its protein sequence, we propose that CNC is a subunit of a heterodimeric regulatory protein involved in the control of head morphogenesis.
Amino Acid Sequence↗