Another factor besides hydrophobicity can affect signal peptide interaction with signal recognition particle

Translocation of alkaline extracellular protease (AEP) into the endoplasmic reticulum of Yarrowia lipolytica is cotranslational and signal recognition particle (SRP)-dependent, whereas translocation of P17M AEP (proline to methionine at position 17, second amino acid in the pro-region) is posttranslational and SRP-independent. P17M signal peptide mutations that resulted in more rapid SRP-dependent translocation of AEP precursor were isolated. Most of these mutations significantly increased hydrophobicity, but the A12P/P17M mutation did not. The switch from SRP-dependent to SRP-independent translocation without a decrease in hydrophobicity (wild type to P17M) and restoration of SRP-dependent translocation without an increase in hydrophobicity (P17M to A12P/P17M) indicate that some factor(s) in addition to hydrophobicity determines selection of targeting pathway. Models of extended forms of wild type and A12P/P17M signal peptides are kinked, whereas the P17M signal peptide is relatively straight. Possibly the conformation/orientation of signal peptides at the ribosomal surface affects SRP binding and consequently the targeting route to the endoplasmic reticulum. Kinked signal peptides might approach SRP more closely more often. Most likely, these effects were only detectable because of the short length and low average hydrophobicity of the AEP signal peptide.     

Effects of three prepubertal body growth rates on performance of Holstein heifers during first lactation

beta1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from beta1-null stem cells. beta1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active alpha5 beta1 and alpha6 beta1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive beta1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type beta1A or beta1A with the D759A activating mutation of a conserved membrane-proximal aspartate, Y783, 795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing beta1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type beta1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility.     

Bronchiolitis obliterans syndrome: thin-section CT diagnosis of obstructive changes in infants and young children after lung transplantation

PURPOSE: To characterize the thin-section computed tomographic (CT) appearance of bronchiolitis fibrosa obliterans syndrome in infants and young children after lung transplantation. MATERIALS AND METHODS: Thin-section CT studies in six patients with bronchiolitis obliterans syndrome (age range, 2 months to 5 1/2 years) and in 15 control patients without obstructive airway disease (age range, 2 months to 7 years) who underwent bilateral lung transplantation were retrospectively reviewed. The thin-section CT scans were obtained during quiet sleep at a median of 24 months (range, 6-36 months) after transplantation. The CT studies were evaluated for mosaic perfusion, bronchial dilatation, bronchial wall thickening, and mucous plugging Final diagnoses in all patients were based pulmonary function test results. RESULTS: Thin-section CT findings in the six patients with clinically proved bronchiolitis obliterans syndrome were mosaic perfusion in five (83%) bronchial dilation in three (50%), and bronchial wall thickening in one (17%). Of the 15 control patients with normal pulmonary function test results, six (40%) had mosaic perfusion; none had bronchial dilatation or bronchial wall thickening. Mucous plugging was not seen in either group. Only the association of bronchial dilatation with bronchiolitis obliterans syndrome was significant (P = .02). CONCLUSION: Infants and young children with bronchiolitis obliterans syndrome after lung transplantation are more likely to have CT abnormalities than those with normal pulmonary function test results.     

Charge exchange at molecular-orbital pseudocrossings as an important mechanism for nonkinetic-electron emission in slow-multicharged-ion (v

KJ Snowdon  CC Havener  FW Meyer  SH Overbury  DM Zehner  W Heiland 《Canadian Metallurgical Quarterly》1988,38(5):2294-2304

Conservative treatment of plantar fasciitis. A prospective study

A randomized, prospective study was conducted to compare the individual effectiveness of three types of conservative therapy in the treatment of plantar fasciitis. One hundred three subjects were randomly assigned to one of three treatment categories: anti-inflammatory, accommodative, or mechanical. Subjects were treated for 3 months, with follow-up visits at 2, 4, 6, and 12 weeks. For the 85 patients who completed the study, a statistically significant difference was noted between groups, with mechanical treatment with taping and orthoses proving to be more effective than either anti-inflammatory or accommodative modalities.     

The estrogen receptor from a tamoxifen stimulated MCF-7 tumor variant contains a point mutation in the ligand binding domain

The nonsteroidal antiestrogen tamoxifen (TAM) is the most commonly used endocrine treatment for all stages of breast cancer in both pre- and postmenopausal women. However, the development of resistance to the drug is common, as most patients treated with TAM eventually experience a recurrence of tumor growth. One of the potential mechanisms of treatment failure is the acquisition by the tumor of the ability to respond to TAM as a stimulatory rather than inhibitory ligand. We (Gottardis and Jordan, Cancer Res 48:5183-5187, 1988; Wolf et al., J Natl Cancer Inst 85:806-812, 1993) and others (Osborne et al., Eur J Cancer Clin Oncol 23: 1189-1196, 1987; Osborne et al., J Natl Cancer Inst 83: 1477-1482, 1991) have extensively described the reproducible development of TAM stimulated growth in a laboratory model system using MCF-7 human breast cancer cells grown as solid tumors in athymic mice. In this paper we report on the isolation of an estrogen receptor (ER) from a TAM stimulated tumor (MCF-7/MT2) which contains a point mutation that causes a tyrosine for aspartate substitution at amino acid 351 in the ligand binding domain. The mutant appears to the major form of ER expressed by this tumor. We also report that only wild type ER was detected in three other TAM stimulated MCF-7 tumor variants, suggesting that multiple mechanisms are possible for the development of TAM stimulated growth. The implications of these findings are discussed.     

Genotypic variation in the transforming growth factor-beta1 gene: association with transforming growth factor-beta1 production, fibrotic lung disease, and graft fibrosis after lung transplantation

BACKGROUND: Transforming growth factor (TGF)-beta1 is a profibrogenetic cytokine that has been implicated in the development of fibrosis in transplanted tissues. In this study, we have analyzed the genetic regulation of TGF-beta1 production in lung transplant recipients. METHOD: A polymerase chain reaction-single-stranded conformational polymorphism technique was used to detect polymorphisms in the TGF-beta1 gene from genomic DNA. Polymorphisms were shown to correlate with in vitro TGF-beta1 production by stimulated lymphocytes. A single-specific oligonucleotide probe hybridization method was devised to screen for these polymorphisms in lung transplant groups and controls. RESULTS: We have identified five polymorphisms in the TGF-beta1 gene: two in the promoter region at positions -800 and -509, one at position +72 in a nontranslated region, and two in the signal sequence at positions +869 and +915. The polymorphism at position +915 in the signal sequence, which changes codon 25 (arginine-->proline), is associated with interindividual variation in levels of TGF-beta1 production. Stimulated lymphocytes of homozygous genotype (arginine/arginine) from control individuals produced significantly more TGF-beta1 in vitro (10037+/-745 pg/ml) compared with heterozygous (arginine/proline) individuals (6729+/-883 pg/ml; P<0.02). In patients requiring lung transplantation for a fibrotic lung condition, there was an increase in the frequency of the high-producer TGF-beta1 allele (arginine). This allele was significantly associated with pretransplant fibrotic pathology (P<0.02) (n=45) when compared with controls (n=107) and with pretransplant nonfibrotic pathology (P<0.004) (n=50). This allele was also associated with allograft fibrosis in transbronchial biopsies when compared with controls (P<0.03) and with nonallograft fibrosis (P<0.01). CONCLUSION: The production of TGF-beta1 is under genetic control, and this in turn influences the development of lung fibrosis. Hence, the TGF-beta1 genotype has prognostic significance in transplant recipients.