Ultrasound of the shoulder

Ultrasound has been widely used for the evaluation of the shoulder, mainly for rotator cuff pathology. Developments in technology, as well as better knowledge of the pathology and the anatomy make this examination one of the most useful in the exploration of the shoulder, especially in the hands of the experienced radiologist. Ultrasound is low-cost, readily available and should be considered with plain films as the first step examination of the shoulder. Ultrasound is not only useful for the evaluation of the rotator cuff pathology and impingement syndrome, but is also performing in the evaluation of non rotator cuff pathology such as biceps tendon pathology, shoulder instability, mass evaluation, infection, degenerative and inflammatory arthropathies and nerve entrapment syndromes. Making a complete evaluation of the shoulder helps to differentiate between rotator cuff pathology and others that can mimic rotator cuff disorders. This article will review shoulder anatomy and examination technique and the different pathologies that can be assessed by ultrasound.

Analysis of oncogenic signaling networks in glioblastoma identifies ASPM as a molecular target

Glioblastoma is the most common primary malignant brain tumor of adults and one of the most lethal of all cancers. Patients with this disease have a median survival of 15 months from the time of diagnosis despite surgery, radiation, and chemotherapy. New treatment approaches are needed. Recent works suggest that glioblastoma patients may benefit from molecularly targeted therapies. Here, we address the compelling need for identification of new molecular targets. Leveraging global gene expression data from two independent sets of clinical tumor samples (n = 55 and n = 65), we identify a gene coexpression module in glioblastoma that is also present in breast cancer and significantly overlaps with the "metasignature" for undifferentiated cancer. Studies in an isogenic model system demonstrate that this module is downstream of the mutant epidermal growth factor receptor, EGFRvIII, and that it can be inhibited by the epidermal growth factor receptor tyrosine kinase inhibitor Erlotinib. We identify ASPM (abnormal spindle-like microcephaly associated) as a key gene within this module and demonstrate its overexpression in glioblastoma relative to normal brain (or body tissues). Finally, we show that ASPM inhibition by siRNA-mediated knockdown inhibits tumor cell proliferation and neural stem cell proliferation, supporting ASPM as a potential molecular target in glioblastoma. Our weighted gene coexpression network analysis provides a blueprint for leveraging genomic data to identify key control networks and molecular targets for glioblastoma, and the principle eluted from our work can be applied to other cancers.

A multiethnic study of Delta32ccr5 and ccr2b-V64I allele distribution in four Los Angeles populations

Mutant alleles of the chemokine receptors CCR5 and CCR2 affect the susceptibility to HIV infection as well as the rate of disease progression. In this article the authors report the results of a survey for presence of the common Delta32ccr5 and ccr2b-V64I mutant alleles in 472 individuals of a multiethnic cohort. Hispanic Americans had the highest observed frequency of the Delta32ccr5 allele (3.57%), whereas African Americans had a lower frequency (1.55%). The mutant allele was absent in Asian Americans and Native Americans. Thus, the Delta32ccr5 allele segregates in populations with a significant white admixture and is rare in genetically distant non-European groups. Native Americans had the highest occurrence of the ccr2b-V64I allele (31.13%), whereas African Americans, Asian Americans, and Hispanic Americans had much lower frequencies (14.36%, 11.94%, and 14.37% respectively). This mutation is probably an ancient one, occurring before the migration of the ancestors of Native Americans across the Bering Straits to the Americas. The twofold greater frequency of ccr2b-V64I in modern Native Americans probably reflects a founder effect. The observed population differences in Delta32ccr5 and ccr2b-V64I frequencies, considered together with their documented effects on sensitivity to HIV infection and rate of disease progression, have implications for HIV transmission patterns in the United States, as well as for AIDS prediction, monitoring, and treatment.

In vitro methionine oxidation of recombinant human leptin

PURPOSE

To investigate the role and importance of the four methionines in recombinant human leptin, and the effect of methionine oxidation in leptin structural stability and biological activity.

METHODS

Oxidized leptin derivatives were prepared in the presence of H2O2 and t-butylhydroperoxide, separated by RP-HPLC, and characterized by peptide mapping and LC/MS. Their biophysical and biological properties were studied.

RESULTS

Six major species of oxidized leptins were detected: two mono-oxidized, one di-oxidized, two tri-oxidized, and one tetra-oxidized. Further oxidation at cystine disulfide was also detected. Kinetic analysis indicated that oxidation at Met1 and Met69 proceeded first and independently. In 48 mM t-butylhydroperoxide, the pseudo first-order rate constants, k1 and k69, were 1.5 x 10(-3) and 2.3 x 10(-4) min-1. No change in the secondary or tertiary structure was detected for Met1 mono-oxidized and Met1, Met69 di-oxidized leptins. The Met1 mono-oxidized leptin retained full potency as compared to native leptin. A slight decrease of thermostability and a significant loss of the in vitro bioactivity were observed for Met1, Met69 di-oxidized leptin. Both Met55 and Met137 were not oxidized in t-butylhydroperoxide but only in H2O2. They appeared to be much less accessible to oxidation and might interact with the hydrophobic core structure of the leptin molecule.

CONCLUSIONS

The oxidation of leptin occurred in the order of Met1 > Met69 >> Met55 approximately Met137, and the importance for maintaining leptin structural integrity was Met55 approximately Met137 >> Met69 approximately Met1. Met69, but not Met1, plays a critical role in the protein stability and activity.

Mistranslation of a TGA termination codon as tryptophan in recombinant platelet-derived growth factor expressed in Escherichia coli

The mature 109-amino-acid human platelet-derived growth factor B (PDGF-B) peptide is derived by intracellular processing from a 241-amino-acid precursor synthesized in mammalian cells, with removal of 81 N-terminal and 51 C-terminal amino acids. In order to produce directly the mature 109-amino acid PDGF-B peptide as a recombinant protein in Escherichia coli, a CGA codon at position 110 of a DNA sequence encoding the full-length precursor form of PDGF-B was converted into the translation termination codon TGA by in vitro mutagenesis. Expression of this DNA via a plasmid vector in E. coli resulted in production of two distinct PDGF-B proteins having apparent molecular masses of 15 and 19 kDa, with the latter species predominating. Structural characterization employing N- and C-terminal amino acid sequencing and MS analyses indicated that the 15 kDa protein is the expected 109-amino-acid PDGF-B, and that the 19 kDa protein represents a C-terminal extended PDGF-B containing 160 amino acids. Characterization of a unique tryptic peptide derived from the 19 kDa protein revealed that this longer form of PDGF-B results from mistranslation of the introduced TGA termination codon at position 110 as tryptophan, with translation subsequently proceeding to the naturally occurring TAG termination codon at position 161. Owing to the high rate of translation readthrough of TGA codons in this and occasionally other proteins, it appears that the use of TGA as a translation termination codon for proteins to be expressed in E. coli should be avoided when possible.