Exercise stimulates the mitogen-activated protein kinase pathway in human skeletal muscle

Physical exercise can cause marked alterations in the structure and function of human skeletal muscle. However, little is known about the specific signaling molecules and pathways that enable exercise to modulate cellular processes in skeletal muscle. The mitogen-activated protein kinase (MAPK) cascade is a major signaling system by which cells transduce extracellular signals into intracellular responses. We tested the hypothesis that a single bout of exercise activates the MAPK signaling pathway. Needle biopsies of vastus lateralis muscle were taken from nine subjects at rest and after 60 min of cycle ergometer exercise. In all subjects, exercise increased MAPK phosphorylation, and the activity of its downstream substrate, the p90 ribosomal S6 kinase 2. Furthermore, exercise increased the activities of the upstream regulators of MAPK, MAP kinase kinase, and Raf-1. When two additional subjects were studied using a one-legged exercise protocol, MAPK phosphorylation and p90 ribosomal S6 kinase 2, MAP kinase kinase 1, and Raf-1 activities were increased only in the exercising leg. These studies demonstrate that exercise activates the MAPK cascade in human skeletal muscle and that this stimulation is primarily a local, tissue-specific phenomenon, rather than a systemic response to exercise. These findings suggest that the MAPK pathway may modulate cellular processes that occur in skeletal muscle in response to exercise.     

Some comments on frequently used multiple endpoint adjustment methods in clinical trials

Confirmatory clinical trials often classify clinical response variables into primary and secondary endpoints. The presence of two or more primary endpoints in a clinical trial usually means that some adjustments of the observed p-values for multiplicity of tests may be required for the control of the type I error rate. In this paper, we discuss statistical concerns associated with some commonly used multiple endpoint adjustment procedures. We also present limited Monte Carlo simulation results to demonstrate the performance of selected p-value-based methods in protecting the type I error rate.     

Biological and conformational examination of stereochemical modifications using the template melanotropin peptide, Ac-Nle-c[Asp-His-Phe-Arg-Trp-Ala-Lys]-NH2, on human melanocortin receptors

Examination of conformationally constrained melanotropin peptide (Ac-Nle4-c[Asp5-His-Phe7-Arg-Trp9-Ala-Lys]-NH2) on four human melanotropin receptors (hMC1R, hMC3R, hMC4R, and hMC5R) resulted in identifying the importance of ligand stereochemistry at positions 5, 7, and 9 for agonist binding affinity and receptor selectivity. A trend in ligand structure-activity relationships emerged for these peptides, with the hMC1R and hMC4R possessing similar tendencies, as did the hMC3R and hMC5R. alpha-MSH (Ac-Ser-Tyr-Ser-Met4-Glu-His-Phe7-Arg-Trp-Gly-Lys-Pro-Val-NH2), NDP-MSH (Ac-Ser-Tyr-Ser-Nle4-Glu-His-D-Phe7-Arg-Trp-Gly-Lys-Pro-Val-NH2), and MTII (Ac-Nle4-c[Asp5,D-Phe7,Lys10]-alpha-MSH(4-10)-NH2) were also examined at each of these melanocortin receptors. Interestingly, the linear NDP-MSH possessed greater binding affinity for the hMC3R and hMC5R than did the cyclic analogue MTII. The peptide Ac-Nle-c[Asp-His-Phe-Arg-D-Trp9-Ala-Lys]-NH2 demonstrated the greatest differentiation in binding affinity between the hMC1R and hMC4R (78-fold). Analogue Ac-Nle-c[Asp-His-Phe7-Arg-Trp-Ala-Lys]-NH2 resulted in micromolar binding affinity (or greater) at the hMC3R and hMC5R, demonstrating the importance of D-Phe7 for ligand binding potency at these receptors. Ac-c[Asp-His-Phe-Arg-Trp-Ala-Lys]-NH2 resulted in loss of binding affinity at the hMC5R, implicating the importance of Nle4 (or a hydrophobic residue in this position) for binding to this receptor. Ac-Nle-c[D-Asp5-His-Phe-Arg-Trp-Ala-Lys]-NH2 was unable to competitively displace [125I]NDP-MSH binding at micromolar concentrations on the hMC3R and hMC5R, suggesting the importance of chirality of Asp5 either for ligand-receptor interactions or for orientation of the side chain lactam bridge and the structural integrity of the peptide conformation. Energy calculations performed for these peptides resulted in the identification of a low-energy ligand conformer family that is common to all the ligands. The differences in ligand binding affinities observed in this study are postulated to be a result of different ligand-receptor complexed interactions and not solely to the ligand structure.     

Deoxyribonuclease treatment improves the homogeneity of single-stranded DNA preparations

The isolation of single-stranded (ss) phagemid DNA using standard protocols often results in impure preparations, which contain undesirable quantities of chromosomal and/or double-stranded (ds) phagemid DNA. Here we report a simple and efficient method for elimination of virtually all dsDNA by incubation of phagemid viral particles with deoxyribonuclease I. In addition to analyzing the ratio of linear-to-circular topological forms of ssDNA after deoxyribonuclease I treatment, we verified that no decrease in transformation efficiency occurred and demonstrated that ssDNA molecules covered by capsid proteins remained intact following such treatment.     

Expression of pro form of prostate-specific antigen by mammalian cells and its conversion to mature, active form by human kallikrein 2

To study the expression, biosynthesis, and processing of prostate-specific antigen (PSA) in mammalian cells, recombinant PSA was expressed in Syrian hamster tumor cell line AV12-664 (AV12-PSA). Expression of PSA was monitored by the Tandem-MP PSA assay. PSA was secreted into the medium during the logarithmic phase of cell growth at >9 microg/ml and was stable. The PSA purified from spent medium of AV12-PSA cells did not exhibit any enzymatic activity and did not complex with the protease inhibitor, alpha-1-antichymotrypsin. These findings indicated that an inactive form of PSA was expressed by AV12-PSA cells. NH2-terminal sequencing confirmed the identity of the PSA purified from the spent medium of AV12-PSA cells to be pro-PSA. This demonstrates that PSA is expressed as pro-PSA by mammalian cells and suggests that pro-PSA may be present in biological fluids. Human kallikrein 2 (hK2), another member of the hK family, is also expressed predominantly in prostate epithelium. Although hK2 has been shown to exhibit trypsin-like activity, little is known about its natural substrates. Using purified proteins, we show that hK2 can convert pro-PSA to mature, enzymatically active PSA, thus establishing a physiological connection between hK2 and PSA. These findings imply that hK2 may be regulating PSA activity in vivo.     

Breast conservation and prolonged chemotherapy for locally advanced breast cancer: the University of Michigan experience

PURPOSE: To determine whether breast conservation and prolonged neoadjuvant chemotherapy have efficacy in locally advanced breast cancer (LABC), as measured by survival and rate of breast conservation. MATERIALS AND METHODS: Eighty-nine patients with stage III disease were enrolled at the University of Michigan (UM) onto a prospective nonrandomized trial. Patients received nine 21-day cycles of neoadjuvant chemohormonal therapy that consisted of doxorubicin 30 mg/m2 and cyclophosphamide 750 mg/m2 intravenously on day 1, conjugated estrogens 0.625 mg orally twice daily on days 6 to 8, methotrexate 40 mg/m2 and fluorouracil 500 mg/m2 intravenously on day 8, and tamoxifen 10 mg orally twice daily on days 9 to 14. Patients with a negative biopsy received radiation only, while those with residual disease underwent mastectomy and postoperative radiotherapy. Eight more cycles of chemohormonal therapy were administered after local-regional therapy. RESULTS: The clinical response rate to neoadjuvant therapy was 97%, 28% of patients had a complete pathologic response evaluated at biopsy. Five-year overall and disease-free survival probabilities were 54% and 44%, respectively. The median disease-free survival time was 2.4 years. The 5-year actuarial rates of local-regional control with local failure as only first failure were 82% and 78% following radiotherapy, and mastectomy and radiotherapy, respectively (P = .99). CONCLUSION: Prolonged neoadjuvant chemohormonal therapy and biopsy-driven local therapy have efficacy in LABC, with 28% of patients being candidates for breast conservation and a 5-year overall survival rate of 54%.     

Vitrectomy for retained lens fragments after phacoemulsification

PURPOSE: Posterior lens fragments after phacoemulsification can be a serious complication of cataract surgery. This study is designed to evaluate the clinical features of eyes after pars plana vitrectomy has been performed to remove posteriorly dislocated lens fragments after phacoemulsification. METHODS: The authors performed a retrospective chart review of 126 consecutive eyes of 126 patients with dislocated lens fragments after phacoemulsification, managed with pars plana vitrectomy at Associated Retinal Consultants of Michigan. These eyes were operated on from January 1986 through January 1996. RESULTS: The relation of the intervals between cataract surgery and vitrectomy to various postoperative clinical parameters was studied. Clinical features at presentation included elevated intraocular pressure (IOP over 25 mmHg) in 52.4% of the eyes, uveitis in 69.6%, and corneal edema in 50.8%. Initial visual acuity was 20/400 or worse in 73.8% of the eyes. The mean preoperative visual acuity was 20/278 (median, 20/400), whereas the mean final visual acuity was 20/40 (median, 20/50) after a mean follow-up of 18.9 months. Retinal detachments were found in 20 eyes: 7 before vitrectomy and 13 during or after it. After surgery, 44% of eyes achieved a final visual acuity of 20/40 or better and 90% were 20/400 or better. The distribution of best-corrected final visual acuities among the eyes showed statistically significant differences based on the type of intraocular lens (IOL) used, with posterior chamber IOL greater than anterior chamber IOL, and anterior chamber IOL greater than aphakia. Reasons for a poor visual outcome included persistent corneal edema (four eyes), retinal detachment (two eyes), central retinal vein occlusion (two eyes), age-related macular degeneration (two eyes) glaucoma (one year), and endophthalmitis (one eye). CONCLUSIONS: There were no statistically significant differences between early (< 7 days) and delayed (8 days or more) vitrectomy when increased IOP, corneal edema, choroidal effusions, cystoid macular edema, and visual acuity were analyzed. The use of vitrectomy to remove posteriorly dislocated lens fragments has been shown to be an effective treatment method that significantly reduces the inflammatory response and hastens visual recovery.     

Genetic construction, properties and application of a green fluorescent protein-tagged ciliary neurotrophic factor

The in vitro and in vivo actions of ciliary neurotrophic factor (CNTF) suggest that endogenous CNTF plays a role in nervous system development and maintenance. CNTF produces most, possibly all, of its effects by binding to a protein referred to as CNTF receptor alpha (CNTFRalpha). Information on CNTFRalpha tissue expression and dynamics would be advanced by the availability of reagents suitable for studying the subcellular localization and trafficking of CNTFRalpha. This paper describes the genetic construction, synthesis, purification and properties of a chimeric protein in which a highly fluorescent form of the green fluorescent protein (GFP) has been fused to human CNTF. The fusion protein, termed GFP-CNTF, was expressed in Escherichia coli. Histidine tagging of GFP-CNTF permitted ready purification by means of immobilized Ni(II) chromatography. Under non-reducing conditions GFP- CNTF migrated on SDS-PAGE with an apparent molecular mass of 50 kDa, although under reducing conditions it behaved electrophoretically as a 67 kDa species. Despite these discrepancies, the molecular mass of GFP- CNTF determined by mass spectrometry (54755) agreed well with its deduced relative molecular mass of 54536. Importantly, the absorbance profile of the GFP chromophore in GFP-CNTF was not modified by the presence of the CNTF domain. Moreover, the fluorescence emission spectrum of GFP-CNTF overlapped that of GFP, showing neither a change in absorbance shift nor a difference in the fluorescence quantum yield. Circular dichroism spectroscopy confirmed that the CNTF and GFP domains of GFP-CNTF folded independently of each other. GFP-tagged CNTF was equipotent to human CNTF in supporting the survival of cultured embryonic chicken sensory and ciliary ganglion neurons. GFP-CNTF, but not GFP, bound to immobilized CNTFRalpha and was displaced by an excess of human CNTF. GFP-CNTF specifically labeled the Purkinje cell layer in cerebellar slices from adult rat. This report is the first to describe a GFP chimera with a neurotrophic factor as the fusion partner. GFP- CNTF should provide a valuable tool for elucidating the role of CNTFRalpha in nervous system function.      

High stroke volume para-aortic counterpulsation device versus centrifugal pump in cardiogenic shock: experimental study

During the last decades a number of left ventricular assist devices has been used especially for patients resistant to pharmacologic treatment and to intraaortic balloon pump (IABP) support for left ventricular failure. A high stroke volume para-aortic counterpulsation device (PACD) has been developed utilizing the principle of the diastolic counterpulsation technique. In this study the hemodynamic effects of the valveless PACD were compared to those of the centrifugal blood pump (CBP) in nine dogs in acute experimental cardiogenic shock. Hemodynamic measurements were obtained at baseline with both devices off, PACD on and CBP off, or PACD off and CBP on. There was no difference in mean aortic pressure between PACD on (60.0 +/- 11.5 mmHg) and CBP on (69.0 +/- 26.8 mmHg). Similarly, there was no difference in left ventricular end-diastolic pressure with the PACD on (11.9 +/- 5.4 mmHg) versus the CBP on (9.9 +/- 5.2 mmHg) or the cardiac index with the PACD on (84 +/- 36 ml/kg/min) versus the CBP on (77 +/- 36 ml/kg/min). However, the left ventricular systolic pressure (55.0 +/- 19.0 with PACD versus 73.0 +/- 26.0 with CBP,p < 0.001), the tension time index (712 +/- 381 versus 1333 +/- 694,p < 0.01), and the double product (5629 +/- 2574 versus 7440 +/- 3294,p < 0.01) were significantly lower during assistance with the PACD than with the CBP. It was concluded that PACD is at least as effective as CBP for restoring hemodynamic status during acute experimental cardiogenic shock. Moreover, the PACD unloads the left ventricle more effectively than CBP, making it suitable for left ventricular mechanical support in cases with reversible myocardial damage.