A-kinase-anchoring protein 1 (dAKAP1)-based signaling complexes coordinate local protein synthesis at the mitochondrial surface

Compartmentalization of macromolecules is a ubiquitous molecular mechanism that drives numerous cellular functions. The appropriate organization of enzymes in space and time enables the precise transmission and integration of intracellular signals. Molecular scaffolds constrain signaling enzymes to influence the regional modulation of these physiological processes. Mitochondrial targeting of protein kinases and protein phosphatases provides a means to locally control the phosphorylation status and action of proteins on the surface of this organelle. Dual-specificity protein kinase A anchoring protein 1 (dAKAP1) is a multivalent binding protein that targets protein kinase A (PKA), RNAs, and other signaling enzymes to the outer mitochondrial membrane. Many AKAPs recruit a diverse set of binding partners that coordinate a broad range of cellular processes. Here, results of MS and biochemical analyses reveal that dAKAP1 anchors additional components, including the ribonucleoprotein granule components La-related protein 4 (LARP4) and polyadenylate-binding protein 1 (PABPC1). Local translation of mRNAs at organelles is a means to spatially control the synthesis of proteins. RNA-Seq data demonstrate that dAKAP1 binds mRNAs encoding proteins required for mitochondrial metabolism, including succinate dehydrogenase. Functional studies suggest that the loss of dAKAP1-RNA interactions reduces mitochondrial electron transport chain activity. Hence, dAKAP1 plays a previously unappreciated role as a molecular interface between second messenger signaling and local protein synthesis machinery.

Trastuzumab for the treatment of HER2-positive metastatic adenocarcinoma of the stomach or gastro-oesophageal junction

This paper presents a summary of the evidence review group (ERG) report into trastuzumab for the treatment of human epidermal growth factor receptor 2 (HER2)-positive metastatic adenocarcinoma of the stomach (mGC) or gastro-oesophageal junction. HER2 positivity is defined by immunohistochemistry (IHC)3+ or IHC2+/fluorescence in situ hybridisation (FISH)+. The decision problem addressed was the testing of the whole mGC population with IHC and, for IHC2+ patients, also with FISH, followed by treatment of HER2-positive patients with trastuzumab combined with cisplatin and either capecitabine or 5-fluorouracil (5-FU) [HCX (trastuzumab, cisplatin, capecitabine)/fluorouracil (F)] compared with current standard NHS therapy. The manufacturer's submission contained direct evidence from the ToGA trial, a well-conducted, multinational, phase III randomised controlled trial (RCT) that compared HCX/F with cisplatin and a fluoropyrimidine alone [cisplatin, capecitabine (CX)/F]. HCX/F showed statistically significantly better overall survival in the European Medicines Agency-licensed population subgroup (74%) (hazard ratio 0.65, 95% confidence interval 0.51 to 0.83), corresponding to median survival of 16 months versus 11.8 months. No other evidence exists for the efficacy of any therapy in a known HER2-positive mGC population; other comparisons extrapolate from trials in mixed HER2 status populations. The ERG accepted the manufacturer's view that a meaningful network meta-analysis to establish a comparison for HCX/F compared with current standard NHS therapy [epirubicin, cisplatin, capecitabine (ECX)/epirubicin, oxaliplatin, capecitabine (EOX)/epirubicin, cisplatin, 5-FU (ECF)] was not possible, but was unconvinced by arguments advanced in the alternative narrative synthesis. These involved disregarding evidence from a meta-analysis and interpreting non-significant results of small RCTs comparing epirubicin-containing triplets with cisplatin, 5-FU (CF)/capecitabine (X) doublets as evidence of no difference between triplet and doublet regimens. The high CX/F dose in the ToGA trial was an additional basis for the contention of equivalence. An appropriate de novo economic evaluation, including an economic model that separately compared HCX or trastuzumab, cisplatin, 5-FU (HCF) with the triplet regimens ECX, EOX and ECF, based on a simple, three-state cohort model (progression-free, disease, progression and death), was submitted. Utility weights were applied to estimate quality-adjusted life-years (QALYs). Costs were assessed from an NHS perspective, and incorporated the acquisition and monitoring costs of the alternative regimens, HER2 testing, adverse events and other supportive care costs. An 8-year time horizon was used to represent a lifetime analysis. Results from the ToGA trial were combined with a series of assumptions on relative treatment effects and testing strategies. The manufacturer's results produced an incremental cost-effectiveness ratio (ICER) of £ 53,010 per QALY for HCX versus ECX. Although the manufacturer undertook a detailed set of sensitivity analyses, several alternative model assumptions were not evaluated. The ERG undertook a series of alternative base-case analyses. As a result of these analyses, EOX replaced ECX as the appropriate comparator, and the ICER for the comparison of HCX vs EOX increased to between £ 66,982 and £ 71,636 per QALY. The impact of implementation of alternative testing strategies remained unclear. There is also considerable uncertainty surrounding the true estimate of effectiveness for the comparison between triplet regimens containing epirubicin (ECX/ECF/EOX) and doublet CX/F regimens. Consequently, the view of the ERG was that there is insufficient evidence on the efficacy of HCX/F compared with current NHS standard therapy for an ICER to be determined with any degree of certainty.

Trastuzumab for the treatment of HER2- positive metastatic adenocarcinoma of the stomach or gastro-oesophageal junction

This paper presents a summary of the evidence review group (ERG) report into trastuzumab for the treatment of human epidermal growth factor receptor 2 (HER2)-positive metastatic adenocarcinoma of the stomach (mGC) or gastro-oesophageal junction. HER2 positivity is defined by immunohistochemistry (IHC)3+ or IHC2+/fluorescence in situ hybridisation (FISH)+. The decision problem addressed was the testing of the whole mGC population with IHC and, for IHC2+ patients, also with FISH, followed by treatment of HER2-positive patients with trastuzumab combined with cisplatin and either capecitabine or 5-fluorouracil (5-FU) [HCX (trastuzumab, cisplatin, capecitabine)/fluorouracil (F)] compared with current standard NHS therapy. The manufacturer’s submission contained direct evidence from the ToGA trial, a well-conducted, multinational, phase III randomised controlled trial (RCT) that compared HCX/F with cisplatin and a fluoropyrimidine alone [cisplatin, capecitabine (CX)/F]. HCX/F showed statistically significantly better overall survival in the European Medicines Agency-licensed population subgroup (74%) (hazard ratio 0.65, 95% confidence interval 0.51 to 0.83), corresponding to median survival of 16 months versus 11.8 months. No other evidence exists for the efficacy of any therapy in a known HER2-positive mGC population; other comparisons extrapolate from trials in mixed HER2 status populations. The ERG accepted the manufacturer’s view that a meaningful network meta-analysis to establish a comparison for HCX/F compared with current standard NHS therapy [epirubicin, cisplatin, capecitabine (ECX)/epirubicin, oxaliplatin, capecitabine (EOX)/epirubicin, cisplatin, 5-FU (ECF)] was not possible, but was unconvinced by arguments advanced in the alternative narrative synthesis. These involved disregarding evidence from a meta-analysis and interpreting non-significant results of small RCTs comparing epirubicin-containing triplets with cisplatin, 5-FU (CF)/capecitabine (X) doublets as evidence of no difference between triplet and doublet regimens. The high CX/F dose in the ToGA trial was an additional basis for the contention of equivalence. An appropriate de novo economic evaluation, including an economic model that separately compared HCX or trastuzumab, cisplatin, 5-FU (HCF) with the triplet regimens ECX, EOX and ECF, based on a simple, three-state cohort model (progression-free, disease, progression and death), was submitted. Utility weights were applied to estimate quality-adjusted life-years (QALYs). Costs were assessed from an NHS perspective, and incorporated the acquisition and monitoring costs of the alternative regimens, HER2 testing, adverse events and other supportive care costs. An 8-year time horizon was used to represent a lifetime analysis. Results from the ToGA trial were combined with a series of assumptions on relative treatment effects and testing strategies. The manufacturer’s results produced an incremental cost-effectiveness ratio (ICER) of £53,010 per QALY for HCX versus ECX. Although the manufacturer undertook a detailed set of sensitivity analyses, several alternative model assumptions were not evaluated. The ERG undertook a series of alternative base-case analyses. As a result of these analyses, EOX replaced ECX as the appropriate comparator, and the ICER for the comparison of HCX vs EOX increased to between £66,982 and £71,636 per QALY. The impact of implementation of alternative testing strategies remained unclear. There is also considerable uncertainty surrounding the true estimate of effectiveness for the comparison between triplet regimens containing epirubicin (ECX/ECF/EOX) and doublet CX/F regimens. Consequently, the view of the ERG was that there is insufficient evidence on the efficacy of HCX/F compared with current NHS standard therapy for an ICER to be determined with any degree of certainty.

Capecitabine for the treatment of advanced gastric cancer

This paper presents a summary of the evidence review group (ERG) report into capecitabine for advanced gastric cancer (aGC). Capecitabine is an oral prodrug of 5-fluorouracil (5-FU). The decision problem addressed was the use of capecitabine (X) compared to 5-FU (F), in combination regimens with platinum agents [cisplatin (C) or oxaliplatin (O)] with or without epirubicin (E), in patients with inoperable aGC. Approximately 7000 new cases of gastric cancer are diagnosed in England and Wales every year. Of these, 80% are candidates for palliative chemotherapy and around 2900 receive such treatment. The standard UK practice for patients with aGC who are considered fit enough has consisted of a triplet regimen comprising intravenous 5-FU in combination with a platinum agent (capecitabine or oxaliplatin) and epirubicin. The manufacturer's submission (MS) focused on direct evidence from two phase III non-inferiority randomised controlled trials (RCTs), REAL-2 (Randomized ECF for Advanced and Locally advanced oesophagogastric cancer-2; n = 1002) and ML17032 (n = 316). REAL-2 randomised patients to four regimens (ECF, ECX, EOF and EOX) to compare 5-FU with capecitabine and cisplatin with oxaliplatin, whereas ML17032 compared CX with CF. Efficacy outcomes from these trials were pooled in an individual patient data (IPD) meta-analysis. Both RCTs demonstrated statistically significant non-inferiority of capecitabine on the outcome of overall survival (OS) assessed in the per-protocol population; equivalent results were also demonstrated for progression-free survival (PFS). The IPD meta-analysis found a statistically significant benefit in OS for capecitabine compared with 5-FU [unadjusted hazard ratio (HR): 0.87; 95% confidence interval (CI) 0.77 to 0.98, p = 0.027]. There was no evidence of a poorer safety profile for capecitabine overall, nor of any difference in quality of life (QoL) between the two fluoropyrimidines. The MS included a de novo economic evaluation based on a cost-minimisation analysis (CMA), where the costs of capecitabine-based regimens were compared with their equivalent 5-FU-based regimens in aGC. A time horizon of 5.5 cycles (each lasting for 21 days) was used in the base-case analysis, representing the duration of treatment. The results of the manufacturer's base-case analysis showed that capecitabine regimens are associated with mean net cost savings of 1620 pounds (ECX vs ECF), 1572 pounds (EOX vs EOF) and 4210 pounds (CX vs CF). The manufacturer failed to comment explicitly on the uncertainty around the estimates of efficacy and on the fact that the IPD meta-analysis suggests that capecitabine may actually be more effective on average. Further analyses exploring additional costs incurred by the UK NHS from extending survival duration showed that these are unlikely to have a material effect on conclusions. A full probabilistic analysis was not performed; however, the evidence explored by the MS and ERG is consistent in suggesting that capecitabine has a lower mean cost than 5-FU-based regimens. The submission was considered to contain convincing evidence of the non-inferiority of capecitabine to 5-FU on survival; this evidence was considered to be applicable to UK practice. Although some uncertainty remains, the ERG deemed CMA to be an appropriate framework with which to analyse this decision problem. Overall cost estimates for the CMA were generated appropriately and were robust to uncertainties regarding assumptions and sources. At the time of writing, the guidance document issued by NICE on 28 July 2010 states that capecitabine in combination with a platinum-based regimen is recommended for the first-line treatment of inoperable advanced gastric cancer.

Capecitabine for the treatment of advanced gastric cancer

This paper presents a summary of the evidence review group (ERG) report into capecitabine for advanced gastric cancer (aGC). Capecitabine is an oral prodrug of 5-fluorouracil (5-FU). The decision problem addressed was the use of capecitabine (X) compared to 5-FU (F), in combination regimens with platinum agents [cisplatin (C) or oxaliplatin (O)] with or without epirubicin (E), in patients with inoperable aGC. Approximately 7000 new cases of gastric cancer are diagnosed in England and Wales every year. Of these, 80% are candidates for palliative chemotherapy and around 2900 receive such treatment. The standard UK practice for patients with aGC who are considered fit enough has consisted of a triplet regimen comprising intravenous 5-FU in combination with a platinum agent (capecitabine or oxaliplatin) and epirubicin. The manufacturer’s submission (MS) focused on direct evidence from two phase III non-inferiority randomised controlled trials (RCTs), REAL-2 (Randomized ECF for Advanced and Locally advanced oesophagogastric cancer-2; n = 1002) and ML17032 (n = 316). REAL-2 randomised patients to four regimens (ECF, ECX, EOF and EOX) to compare 5-FU with capecitabine and cisplatin with oxaliplatin, whereas ML17032 compared CX with CF. Efficacy outcomes from these trials were pooled in an individual patient data (IPD) meta-analysis. Both RCTs demonstrated statistically significant non-inferiority of capecitabine on the outcome of overall survival (OS) assessed in the per-protocol population; equivalent results were also demonstrated for progression-free survival (PFS). The IPD meta-analysis found a statistically significant benefit in OS for capecitabine compared with 5-FU [unadjusted hazard ratio (HR): 0.87; 95% confidence interval (CI) 0.77 to 0.98, p = 0.027]. There was no evidence of a poorer safety profile for capecitabine overall, nor of any difference in quality of life (QoL) between the two fluoropyrimidines. The MS included a de novo economic evaluation based on a cost-minimisation analysis (CMA), where the costs of capecitabine-based regimens were compared with their equivalent 5-FU-based regimens in aGC. A time horizon of 5.5 cycles (each lasting for 21 days) was used in the base-case analysis, representing the duration of treatment. The results of the manufacturer’s base-case analysis showed that capecitabine regimens are associated with mean net cost savings of £1620 (ECX vs ECF), £1572 (EOX vs EOF) and £4210 (CX vs CF). The manufacturer failed to comment explicitly on the uncertainty around the estimates of efficacy and on the fact that the IPD meta-analysis suggests that capecitabine may actually be more effective on average. Further analyses exploring additional costs incurred by the UK NHS from extending survival duration showed that these are unlikely to have a material effect on conclusions. A full probabilistic analysis was not performed; however, the evidence explored by the MS and ERG is consistent in suggesting that capecitabine has a lower mean cost than 5-FU-based regimens. The submission was considered to contain convincing evidence of the non-inferiority of capecitabine to 5-FU on survival; this evidence was considered to be applicable to UK practice. Although some uncertainty remains, the ERG deemed CMA to be an appropriate framework with which to analyse this decision problem. Overall cost estimates for the CMA were generated appropriately and were robust to uncertainties regarding assumptions and sources. At the time of writing, the guidance document issued by NICE on 28 July 2010 states that capecitabine in combination with a platinum-based regimen is recommended for the first-line treatment of inoperable advanced gastric cancer.

Erythrocyte ghost-mediated gene delivery for prolonged and blood-targeted expression

This study reports the use of erythrocyte ghosts (EG) as a biocompatible nonviral delivery system for extended circulation and prolonged expression of plasmid DNA in the blood. Murine interleukin-2-expressing plasmid DNA was efficiently loaded to EG by electroporation in hypotonic condition. The presence of plasmid DNA in EG was confirmed by fluorescence-labeled plasmid DNA. At 21 min after intravenous administration into mice, the level of plasmid DNA in the blood was 92 000-fold higher following EG-mediated delivery as compared to the injection of naked form. EG-mediated gene delivery revealed higher and more prolonged mRNA expression levels of plasmid DNA in the blood until 9 days after the single intravenous injection. Moreover, plasmid DNA-loaded EG showed gene expression targeted to the blood cells. At 3 days post-dose, substantial expression levels of plasmid DNA delivered in EG were observed only in the blood and not in the other organs. Of the blood cells, the subpopulation containing granulocytes showed higher expression of plasmid DNA than mononuclear cells. These results indicate the potential of EG as a safe, prolonged and blood-targeted delivery system of therapeutic genes.

Polyethylenimine-mediated cellular uptake, nucleus trafficking and expression of cytokine plasmid DNA

Although polyethylenimine (PEI) has been widely used as a nonviral vector, there is little mechanistic understanding on PEI-mediated delivery. Here, we studied whether the expression of murine interleukin-2 (mIL-2) plasmids could be improved by complexation with PEI at various N/P ratios, and whether the cellular uptake, nuclear translocation, and retention of plasmids could be affected by the N/P ratios. Compared with the naked mIL-2, PEI/mIL-2 complexes showed at least two orders of magnitude higher expression at Raw264 cells in the N/P ratio-dependent manner. PEI-mediated cellular uptake and nuclear trafficking of plasmids, quantitated by competitive polymerase chain reaction, also depended on the N/P ratios showing the highest cell and nuclear levels of plasmids at 10/1. The higher cellular levels of plasmid DNA after PEI-mediated delivery were also observed in other cell lines. Unlike naked plasmids, PEI/mIL-2 complexes (N/P ratios >/=4/1) showed prolonged cellular and nuclear retention of mIL-2 plasmids. The nuclear translocation and higher cellular level of plasmids given in PEI complexes were similarly observed by fluorescence microscopy. Moreover, PEI/mIL-2 complexes revealed high stability against DNase I, partly explaining the prolonged subcellular retention. These results indicate that the expression of plasmid mIL-2 might be highly enhanced by complexation with PEI and that such increased expression could be attributed by the higher cellular uptake, nuclear translocation and prolonged retention.

Chronicle of advocacy to increase AAPI focused objectives in Healthy People 2010: implications for tobacco-related data and research

OBJECTIVES

The objectives of this chronicle is to illustrate key components of health polocy advocacy in increasing data availability and research for Asian Americans and Pacific Islanders (AAPIs).

METHODS

Through the examination of the evolution of AAPI data in Healthy People 2000 to Healthy People 2010, this chronicle cites parallel and convergent advocacy by AAPI health advocates and tobacco advocates with key external factors that resulted in an increase in AAPI data included in Healthy People 2010.

FINDINGS

In Healthy People 2000, there were eight objectives focusing on AAPIs. In Healthy People 2010, 98 objectives included some data for AAPIs and 120 objectives provided categorical reasons why AAPI data were not available. In Healthy People 2010, there was only one objective on tobacco use focusing on AAPIs. Healthy People 2010 includes 11 tobacco use objectives with either AAPI data or categorical reasons why the data were not available. Understanding why AAPI data are not available can direct advocacy efforts.

CONCLUSIONS

The AAPI data improvements in Healthy People 2010 have provided useful information on data availability and strategy for data development at the national level. At the same time, the limitations of the national data (lack of AAPI ethnic specific data, data collected only in English) calls for more appropriate data collection and research at the local and regional level.

Optimal solder and power density for diode laser tissue soldering (LTS)

BACKGROUND AND OBJECTIVE

Laser tissue soldering (LTS) using albumin and indocyanine green dye (ICG) is an effective technique utilized in various reconstructive surgical procedures. The purpose of this study was to describe in vivo and in vitro temperature profiles of an albumin-based solder while varying ICG concentration and laser power density (PD), and to describe immediate and short-term tensile strength measurements and histology of tissue with variable ICG concentrations and PD.

STUDY DESIGN/MATERIALS AND METHODS

ICG ranged from 0.31 to 20 mg/mL while PD ranged from 3.2 to 63.7 W/cm(2). Direct solder temperature measurements were obtained at 5-second intervals during laser activation. Differential temperature measurements were determined within the dermis of rat skin and the overlying solder. Eighteen rats were subjected to 2.0-cm incisions (n = 113) created on the dorsal skin followed by closure with LTS at varying PD and ICG concentrations. ICG concentrations included 0.31, 2.5, and 20 mg/mL, while PD ranged from 8.0 to 63.7 W/cm(2). Tensile strength (TS) profiles were measured immediately and 10 days post-operatively. Histological examination was performed at the time of sacrifice.

RESULTS

Temperature profiles of the ICG/albumin solder differed significantly only at the highest concentration of ICG (20 mg/mL), but showed statistically significant variability at different laser PD. Using solder color changes as an endpoint of LTS, average peak solder temperature ranged from 69 degrees C at a PD of 8.0 W/cm(2), 105 degrees -120 degrees C at PD 15.9-31.8 W/cm(2), and > 200 degrees C at PD > or = 47.7 W/cm(2). Peak intradermal temperatures remained below 50 degrees C at all PDs. Varying ICG concentration only had an effect on the immediate TS of wounds at the lowest power densities. Increasing PD resulted in statistically significant increases in immediate TS up to a PD of 23.9 W/cm(2) at an ICG concentrations of 0.31 and up to a PD of 15.9 W/cm(2) at a concentration of 2.5 mg/mL. Statistically insignificant decreases in 10-day would strength resulted from higher PD. Power densities > or = 23.9 W/cm(2) showed significant thermal injury upon histologic examination.

CONCLUSIONS

Power density, not ICG concentration, is the primary determinant of solder and tissue temperature during LTS. Effective and reproducible laser tissue soldering may be achieved primarily by power density control when using diode laser and ICG-based albumin solder. Alterations in PD show the most direct and predictable effects on the healing properties of skin closed by LTS. Optimal laser wound closure occurs with an ICG of 2.5 mg/mL and at a PD between 15.9 and 23.9 W/cm(2).

Contractile properties of adjacent segments of single human muscle fibers

A comparison of the contractile properties of adjacent segments of single human muscle fibers may help to explain the interaction among nuclear domains within the myofiber. Biopsy samples were obtained from the vastus lateralis muscle of 20 healthy untrained women (age 18-79 years). Single fibers (n = 38) were dissected and cut into halves (segments A and B). Segment diameter and depth were measured using an image analysis system. Maximal force (Po) was recorded during activation with calcium (pCa 4.5). Maximal unloaded shortening velocity (Vo) was calculated using the slack test. Myosin heavy chain (MyHC) expression was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). A significant difference ( approximately 7%) in Po was seen between adjacent segments expressing type I MyHC that could not be attributed to differences in fiber size. Significant differences were observed in Vo even after adjusting for fiber type. A positive correlation was seen in Po (concordance coefficient Rho_C = 0.803) and Vo (Rho_C = 0.690) between segments, but concordance was less than perfect in both cases. Possible explanations for nonuniformity of contractile properties include random variations in physiological systems or variability of protein expression among nuclear domains.

Age- and gender-related differences in maximum shortening velocity of skeletal muscle fibers

OBJECTIVE

To determine age- and gender-related differences in maximum unloaded shortening velocity (Vo) of Type I and IIA single muscle fibers. Muscle fibers must have a broad range of contractile velocities to generate the full range of power required for varied activities.

DESIGN

Percutaneous needle biopsies of the vastus lateralis were obtained from 31 healthy subjects (n = 7 young men [YM], n = 7 young women [YW], n = 12 older men [OM], n = 12 older women [OW]). The slack test was used to determine Vo of individual fibers; 916 muscle fibers were chemically skinned. Fiber type was determined by myosin heavy chain isoform identification.

RESULTS

Among men, Vo (fiber lengths/sec) was reduced with age in Type IIA fibers (OM vs. YM: 1.78 vs. 2.14; P < 0.05) but unchanged in Type I fibers. Among women, Vo was reduced with age in Type I fibers (OW vs. YW: 0.70 vs. 0.75; P < 0.05) but not IIA. OW had a lower Vo than did OM in both fiber types (Type I: OW = 0.70, OM = 0.77; Type IIA: OW = 1.51, OM = 1.78; P < 0.05). YW did not differ from YM.

CONCLUSIONS

Both age and gender affect Vo. Age- and gender-related differences in Vo may partially explain the impairments in muscle function that occur with aging and the greater impairment in muscle function observed in OW compared with that observed in OM.

Environments of ethidium binding to allosteric Dna: II. Accessibility, mobility and mode of binding

DNA binding compounds were previously shown to bind to the right-handed DNA forms and hybrid B-Z forms in a highly cooperative manner and indicate that structural specificity plays a key role in a ligand binding to DNA. In this study, the modes of binding and structural specificity of agents to unusual DNA are examined by a variety of fluorescence techniques (intensity, polarization and quenching, etc.) to explore a reliable method to detect the association environment of ligands to deoxyoligonucleotides initially containing a B-Z junction between the left-handed Z-DNA and right-handed B-DNA. The results of fluorescence energy transfer measurement demonstrated that the ligand molecules bind to the allosterically converted DNA structures by intercalation. In the absence of high-resolution structural data, this fluorescence energy transfer measurement allowed reliable measures and infer the binding environment of ligands to the allosteric DNA structures.

Skeletal muscle fiber quality in older men and women

Whole muscle strength and cross-sectional area (WMCSA), and contractile properties of chemically skinned segments from single fibers of the quadriceps were studied in 7 young men (YM, 36.5 +/- 3. 0 yr), 12 older men (OM, 74.4 +/- 5.9 yr), and 12 older women (OW, 72.1 +/- 4.3 yr). WMCSA was smaller in OM compared with YM (56.1 +/- 10.1 vs. 79.7 +/- 13.1 cm(2); P = 0.031) and in OW (44.9 +/- 7.5; P < 0.003) compared with OM. Age-related, but not sex-related, differences in strength were eliminated after adjusting for WMCSA. Maximal force was measured in 552 type I and 230 type IIA fibers. Fibers from YM (type I = 725 +/- 221; type IIA = 792 +/- 271 microN) were stronger (P < 0.001) than fibers from OM (I = 505 +/- 179; IIA = 577 +/- 262 microN) even after correcting for size. Type IIA fibers were stronger (P < 0.005) than type I fibers in YM and OM but not in OW (I = 472 +/- 154; IIA = 422 +/- 97 microN). Sex-related differences in type I and IIA fibers were dependent on fiber size. In conclusion, differences in WMCSA explain age-related differences in strength. An intrinsic defect in contractile proteins could explain weakness in single fibers from OM. Sex-related differences exist at the whole muscle and single fiber levels.

Contractile properties of single muscle fibers in myotonic dystrophy

Muscle fiber contractile dysfunction in myotonic dystrophy (MD) is poorly understood. We biopsied the tibialis anterior of two symptomatic and three asymptomatic subjects (aged 21-31 years) with the MD mutation. Biopsies were freeze dried. A total of 103 single muscle fibers were activated with Ca(++), allowing maximal force measurements and specific force (SF) estimates. The slack test was performed to calculate maximum unloaded shortening velocity (V(o)). The myosin heavy chain composition of each fiber was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Type I and IIA fibers of all subjects had reduced SF when compared with healthy control subjects (P < 0.001). In addition, the type I fibers of symptomatic subjects generated less SF than those of asymptomatic subjects (P < 0.001). Type I fibers from asymptomatic and symptomatic subjects did not differ in V(o), but V(o) was lower than in control subjects (P < 0.001). There was no significant difference in V(o) of type IIA fibers from symptomatic, asymptomatic, and control subjects. These results indicate that the MD mutation leads to a diminished force-generating capacity of the myofilaments in both symptomatic and asymptomatic individuals. The results further suggest that reduction in force-generating capacity at the cellular level develops prior to clinical weakness.

Social class, race/ethnicity, and incidence of breast, cervix, colon, lung, and prostate cancer among Asian, Black, Hispanic, and White residents of the San Francisco Bay Area, 1988-92 (United States)

BACKGROUND

To date only eight US studies have simultaneously examined cancer incidence in relation to social class and race/ethnicity; all but one included only black and white Americans. To address gaps in knowledge we thus investigated socioeconomic gradients in cancer incidence among four mutually exclusive US racial/ethnic groups-- Asian and Pacific Islander, black, Hispanic, and white-- for five major cancer sites: breast, cervix, colon, lung, and prostate cancer.

METHODS

We generated age-adjusted cancer incidence rates stratified by socioeconomic position using: (a) geocoded cancer registry records, (b) census population counts, and (c) 1990 census block-group socioeconomic measures. Cases (n = 70,899) were diagnosed between 1988 and 1992 and lived in seven counties located in California's San Francisco Bay Area.

RESULTS

Incidence rates varied as much if not more by socioeconomic position than by race/ethnicity, and for each site the magnitude - and in some cases direction - of the socioeconomic gradient differed by race/ethnicity and, where applicable, by gender. Breast cancer incidence increased with affluence only among Hispanic women. Incidence of cervical cancer increased with socioeconomic deprivation among all four racial/ethnic groups, with trends strongest among white women. Lung cancer incidence increased with socioeconomic deprivation among all but Hispanics, for whom incidence increased with affluence. Colon and prostate cancer incidence were inconsistently associated with socioeconomic position.

CONCLUSIONS

These complex patterns defy easy generalization and illustrate why US cancer data should be stratified by socioeconomic position, along with race/ethnicity and gender, so as to improve cancer surveillance, research, and control.

Cooperative binding interaction of ethidium with allosteric DNA

The specific association of drugs with deoxyoligonucleotides, containing a B-Z junction between left-handed Z-DNA and right-handed B-DNA, was examined by fluorescence and circular dichroism (CD) technique. Ethidium was chosen for a simple DNA binding compound because it binds to right-handed DNA and hybrid B-Z forms containing a B-Z junction in a highly cooperative manner. The binding isotherms were analyzed by an allosteric model in order to describe the cooperativity of association. Binding of ethidium to the DNA that are initially in the hybrid B-Z forms showed over an order of magnitude higher affinity than other DNA which were entirely in the B-form. The conformational transitions of deoxyoligonucleotides containing a B-Z junction as a result of ethidium binding were monitored by CD and the influence of NaCl on the complex formation was also determined by the CD spectra. The singular value decomposition (SVD) analysis was used to characterize a family of CD spectra of the species in binding equilibria. The results of SVD analysis showed a strikingly complex thermodynamic equilibria of cooperative binding of drugs to the allosterically converted DNA forms. The results also showed that these DNA forms in low- and high-salt were different in the absence or presence of drug. These results demonstrate that DNA-binding-drugs can preferentially interact with specific DNA structures and that these interactions are accompanied by allosteric changes of DNA conformations.

Binding of daunomycin to diaminopurine- and/or inosine-substituted DNA

The binding of the anticancer drug daunomycin to double-helical DNA has been investigated by DNase I footprinting and fluorescence titration, using a series of polymerase chain reaction (PCR) synthesized DNA fragments that contained systematic base substitutions to alter the disposition of functional groups within the minor groove. The 160 bp tyrT DNA fragment constituted the starting material. Fragments in which (i) inosine was substituted for guanosine, (ii) diaminopurine was substituted for adenine, and (iii) both inosine and diaminopurine were substituted for guanosine and adenine, respectively, were studied. These fragments permit the role of the 2-amino group in the minor groove to be systematically explored. The results of DNase I footprinting experiments confirmed that daunomycin binds preferentially to 5'(A/T)GC and 5'(A/T)CG triplets in the normal fragment. Substitution of inosine for guanosine, with the concomitant loss of the N-2 in the minor groove, weakened binding affinity but did not dramatically alter the sequence preference associated with daunomycin binding. Complete reversal of the location of the N-2 group by the double substitution, however, completely altered the sequence preference of daunomycin and shifted its binding from the canonical triplets to ones with a 5'IDD motif. These results have critically tested and confirmed the proposed key roles of the daunosamine moiety and the 9-OH group of daunomycin in dictating binding to preferred sites. In a parallel study, both macroscopic and microscopic binding to the normal tyrT fragment were investigated, experiments made possible by using PCR to prepare large quantities of the long, defined DNA sequence. The results of these experiments underscored the complexity of the interaction of the drug with the DNA lattice and revealed unequivocal heterogeneity in its affinity for different binding sites. A class of high-affinity sites, most probably corresponding to the 5'(A/T)GC and 5'(A/T)CG triplets, was identified and characterized in macroscopic binding isotherms.