Serum cystatin C may be a better marker of renal impairment than creatinine.
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Aged↗
Biomedical subjects
David J Newman
Publications and source records attributed to David J Newman.
Diazonamide A and a synthetic structural analog: disruptive effects on mitosis and cellular microtubules and analysis of their interactions with tubulin.
The marine ascidian Diazona angulata was the source organism for the complex cytotoxic peptide diazonamide A. The molecular structure of this peptide was recently revised after synthesis of a biologically active analog of diazonamide A in which a single nitrogen atom was replaced by an oxygen atom. Diazonamide A causes cells to arrest in mitosis, and, after exposure to the drug, treated cells lose both interphase and spindle microtubules. Both diazonamide A and the oxygen analog are potent inhibitors of microtubule assembly, equivalent in activity to dolastatin 10 and therefore far more potent than dolastatin 15. This inhibition of microtubule assembly is accompanied by potent inhibition of tubulin-dependent GTP hydrolysis, also comparable with the effects observed with dolastatin 10. However, the remaining biochemical properties of diazonamide A and its analog differ markedly from those of dolastatin 10 and closely resemble the properties of dolastatin 15. Neither diazonamide A nor the analog inhibited the binding of [3H]vinblastine, [3H]dolastatin 10, or [8-14C]GTP to tubulin. Nor were they able to stabilize the colchicine binding activity of tubulin. These observations indicate either that diazonamide A and the analog have a unique binding site on tubulin differing from the vinca alkaloid and dolastatin 10 binding sites, or that diazonamide A and the analog bind weakly to unpolymerized tubulin but strongly to microtubule ends. If the latter is correct, diazonamide A and its oxygen analog should have uniquely potent inhibitory effects on the dynamic properties of microtubules.
Animals↗
Cystatin C: what more do we need to know?
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Biomarkers↗
Cystatin C improves the detection of mild renal dysfunction in older patients.
BACKGROUND: Conventional estimates of glomerular dysfunction, including serum creatinine and creatinine clearance, are inadequate in older people. In this study we have compared the diagnostic accuracy of a novel test of kidney disease, cystatin C, against these markers in older patients with a range of renal function. METHODS: Fifty-three patients (mean age 79.6 years, range 69-92 years) with a variety of medical diagnoses were recruited via outpatient clinics. Exclusion criteria included active rheumatoid disease, known current malignancy, renal replacement therapy/renal transplantation and cognitive impairment. (51)Cr-EDTA was used as the reference method against which the other markers of glomerular filtration rate were compared using regression analyses. RESULTS: The best fit with glomerular filtration rate was given by Cockcroft and Gault calculated clearance (R(2) = 0.83), followed by serum cystatin C (R(2) = 0.79), serum creatinine (R(2) = 0.76) and creatinine clearance (R(2) = 0.73). The accuracy for glomerular filtration rate prediction was poor for all markers. Serum cystatin C detected nearly all patients with mild renal impairment whereas serum creatinine only detected half of these cases. Regression modelling predicted that the upper limit of normal for serum cystatin C would be exceeded as glomerular filtration rate fell below 64 mL/min/1.73 m(2), compared with 44 mL/min/1.73 m(2) for serum creatinine. CONCLUSION: Serum cystatin C is a simple and sensitive screening test for kidney dysfunction in older people.
Aged↗
The thioredoxin redox inhibitors 1-methylpropyl 2-imidazolyl disulfide and pleurotin inhibit hypoxia-induced factor 1alpha and vascular endothelial growth factor formation.
Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays a critical role in tumor growth by increasing resistance to apoptosis and the production of angiogenic factors such as vascular endothelial growth factor (VEGF). HIF-1 is a heterodimer comprised of oxygen-regulated HIF-1alpha and constitutively expressed HIF-1beta subunits. The redox protein thioredoxin-1 (Trx-1), which is found at high levels in many human cancers, increases both aerobic and hypoxia-induced HIF-1alpha protein in cells leading to increased expression of HIF-regulated genes. We have investigated whether two cancer drugs that inhibit Trx-1 signaling, PX-12 (1-methylpropyl 2-imidazolyl disulfide) and pleurotin, decrease HIF-1alpha protein levels and the expression of downstream target genes. Treatment of MCF-7 human breast cancer and HT-29 human colon carcinoma cells with PX-12 and pleurotin prevented the hypoxia (1% oxygen)-induced increase in HIF-1alpha protein. HIF-1-trans-activating activity, VEGF formation, and inducible nitric oxide synthase were also decreased by treatment with PX-12 and pleurotin under hypoxic conditions. PX-12 and pleurotin also decreased HIF-1alpha protein levels and HIF-1 trans-activation in RCC4 renal cell carcinoma cells that constitutively overexpress HIF-1alpha protein because of loss of the pVHL gene, indicating that HIF-1alpha is inhibited independently of the pVHL pathway. HIF-1alpha and VEGF protein levels in MCF-7 tumor xenografts in vivo were decreased by PX-12 treatment of mice. The results suggest that inhibition of HIF-1alpha by Trx-1 inhibitors may contribute to the growth inhibitory and antitumor activity of these agents.
Animals↗
Oxygen-evoked changes in transcriptional activity of the 5'-flanking region of the human amiloride-sensitive sodium channel (alphaENaC) gene: role of nuclear factor kappaB.
Expression of the alpha-subunit of the amiloride-sensitive sodium channel (alphaENaC) is regulated by a number of factors in the lung, including oxygen partial pressure (PO2). As transcriptional activation is a mechanism for raising cellular mRNA levels, we investigated the effect of physiological changes in PO2 on the activity of the redox-sensitive transcription factor nuclear factor kappaB (NF-kappaB) and transcriptional activity of 5'-flanking regions of the human alphaENaC gene using luciferase reporter-gene vectors transiently transfected into human adult alveolar carcinoma A549 cells. By Western blotting we confirmed the presence of NF-kappaB p65 but not p50 in these cells. Transiently increasing PO2 from 23 to 42 mmHg for 24 h evoked a significant increase in NF-kappaB DNA-binding activity and transactivation of a NF-kappaB-driven luciferase construct (pGLNF-kappaBpro), which was blocked by the NF-kappaB activation inhibitor sulphasalazine (5 mM). Transcriptional activity of alphaENaC-luciferase constructs containing 5'-flanking sequences (including the NF-kappaB consensus) were increased by raising PO2 from 23 to 142 mmHg if they contained transcriptional initiation sites (TIS) for exons 1A and 1B (pGL3E2.2) or the 3' TIS of exon 1B alone (pGL3E0.8). Sulphasalazine had no significant effect on the activity of these constructs, suggesting that the PO2-evoked rise in activity was not a direct consequence of NF-kappaB activation. Conversely, the relative luciferase activity of a construct that lacked the 3' TIS, a 3' intron and splice site but still retained the 5' TIS and NF-kappaB consensus sequence was suppressed significantly by raising PO2. This effect was reversed by sulphasalazine, suggesting that activation of NF-kappaB mediated PO2-evoked suppression of transcription from the exon 1A TIS of alphaENaC.
Base Sequence↗
Detection of low-molecular-weight proteins in urine by dipsticks.
BACKGROUND: Testing of urines with dipsticks for proteinuria, glycosuria, etc., is common practice. A deficiency with currently available dipsticks is their lack of chemical sensitivity and underestimation of low-molecular-weight proteins such as light chains. METHODS: We experimented with a number of dyes that gave an easily recognized color change on dipsticks for various low-molecular-weight proteins such as alpha-1-glycoprotein, alpha-1- and beta-2-microglobulin, and kappa and lambda light chains. We were successful in formulating a dye for impregnating dipsticks that gave a color change with low-molecular-weight proteins. RESULTS: Most dipsticks will measure proteins down to about 1 g/l. Our composite of two dyes (described here as the "TPR" dipsticks) gave reproducible results for protein concentrations of >/=300 mg/l, and detected low-molecular proteins. The TPR reagent is resistant to interferences from many compounds; also, the protein results are not altered in a given urine at a pH between 5 and 8. CONCLUSIONS: We have developed a dipstick that detects low-molecular-weight proteins. The dipsticks are easy to use and are suitable for outpatient or point-of-care testing. The precision of the dipsticks is satisfactory and is only marginally lower than quantitative spectrophotometric methods using pyrogallol red (PYR).
Coloring Agents↗
Chemical diversity: a function of biodiversity.
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Biological Products↗
Cystatin C.
Clinical biochemists have long known the analytical and clinical limitations of creatinine and creatinine clearance measurement in the assessment of glomerular filtration rate (GFR). This background is reviewed in the article before assessing the utility of cystatin C, the most promising replacement biochemical marker yet identified. Cystatin C has been used in clinical research studies for more than 20 years and yet has been introduced into clinical practice in very few centres, firstly in Lund in Sweden and now Carshalton in the UK. Why is this? The review compares our ability to measure creatinine and cystatin C and their relative sensitivity and specificity for changes in GFR. Comparison is made of cystatin C with creatinine as screening tests for early renal dysfunction and for monitoring its progression where issues of reference ranges and within-individual variation are important. The superiority of cystatin C as a screening test is probably accepted but there are still concerns about non-renal influences upon its circulating concentration, particularly steroid therapy, insufficient data on the influence of malignancy and a general lack of prospective clinical studies confirming the prognostic significance of cystatin C.
Biomarkers↗
Natural products and derivatives as leads to cell cycle pathway targets in cancer chemotherapy.
The influence of natural products upon drug discovery in general has been quite impressive; one only has to look at the number of clinically active drugs that are in use in cancer therapy to see how many either are natural products or have a natural pro-duct pharmacophore. What is now becoming quite apparent is that materials from natural sources are excellent probes (indicators) for cellular targets that when modulated, may well have a deleterious effect upon the cycling of a tumor cell through the conventional cell cycle. If the particular target is not expressed in normal cell cycling, then a directed "perturbation" of the tumor cell's cycle may well lead to a novel method of treatment for specific tumor types. In this review we have not attempted to be exhaustive but have given a current overview of how natural products from marine, microbial and plant sources have permitted in-depth analyses of various parts of the cell cycle under varying conditions with the ultimate aims of attempting to "control or perturb" the cycling of tumor cells in a fashion that permits their ultimate removal via cellular death, with a minimum of trauma to the host.
Animals↗
Mother nature's combinatorial libraries; their influence on the synthesis of drugs.
Natural products or secondary metabolites, whether from the microbial, plant or marine worlds, represent the results of evolutionary pressures to preserve and enhance the life of their producing organism. They have evolved into structurally and usually stereochemically complex compounds with specific bioactivities. They thus represent a diverse 'combinatorial library' that may have potential pharmaceutical use. In principle, the combination of this diverse library with the methods of combinatorial chemistry could lead to an unlimited supply of diverse and complex structures, and is recommended as a fruitful approach for future drug development. Examples of the application of combinatorial methods to nature's combinatorial library will be presented and discussed, with an emphasis on the antitumor, anti-infective and pain control disease areas.
Analgesics↗