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J Philo

Publications and source records attributed to J Philo.

9 recordsLinked to original sources
PubMed1997

Comparison of solution properties of human and rat ciliary neurotrophic factor.

The solution structure and stability of rat and human ciliary neurotrophic factor (CNTF) were examined by circular dichroism (CD), Fourier transform infrared (FTIR) and fluorescence spectroscopy and sedimentation equilibrium analyses. The secondary structure of both proteins, as assessed by CD and FTIR, consists primarily of alpha-helix, consistent with CNTF being a member of the four-helical bundle family of cytokines and neurokines, with rat CNTF containing slightly less helix (about 10% less) and slightly more disordered structure. The environment of the tyrosine and tryptophan residues, assessed by intrinsic fluorescence emission spectroscopy, appears to be the same in both proteins. Binding of anilinonaphthalene sulfonate is identical for both proteins, indicating that these two proteins have similar surface hydrophobicities in the native state. The thermal stability of the human CNTF is significantly less than that of the rat CNTF, yet their stabilities to guanidine HCl-induced denaturation are equivalent. This apparent discrepancy in stability between the two proteins may be explained by solubility differences upon thermal unfolding. Although the human protein precipitates as it is denatured by heat, the rat protein does not. It thus appears that the unfolded state of human CNTF is less soluble and more prone to aggregation than that of the rat protein upon heating, although their conformational stability is similar. Both proteins remain largely folded at pH 3.0. Sedimentation equilibrium analysis demonstrates that both rat and human CNTF exist primarily as monomers; however, significant dimer formation occurs as the protein concentrations are increased to greater than 3 mg/mL, particularly in the presence of ammonium sulfate.

Anilino Naphthalenesulfonates↗
PubMed1996

ErbB receptor activation, cell morphology changes, and apoptosis induced by anti-Her2 monoclonal antibodies.

A panel of mAbs were generated against the purified soluble form of erbB2/Her2 receptor, corresponding to the extracellular region of the receptor, and examined for their ability to mimic the receptor ligand. Some of the mAbs strongly induced tyrosine phosphorylation of 180-185 kDa proteins, including not only Her2 but also Her3 and Her4 receptors, when they were expressed on the surface of breast cancer cells. These mAbs do not cross-react with Her3 or Her4 as demonstrated by competition study. Receptor phosphorylation was also observed with the cell lines transfected with Her2 or a chimeric receptor consisting of the extracellular domain of Her2 and the transmembrane and cytoplasmic domains of epidermal growth factor receptor. Selected mAbs were tested for their ability to change cell morphology, and one specific mAb, mAb74, induced cell morphology changes and apoptosis.

Animals↗
PubMed1996

Dimerization of the extracellular domain of granuloycte-colony stimulating factor receptor by ligand binding: a monovalent ligand induces 2:2 complexes.

Granulocyte-colony stimulating factor (G-CSF) binds to a specific cell surface receptor and induces signals for growth and differentiation in cells of granulocyte hematopoietic lineage. In order to understand how G-CSF binding initiates signals into these cells, we have studied its interactions with the entire extracellular domain of the receptor (sG-CSFR). The sG-CSFR was purified from CHO cell conditioned media with a G-CSF affinity column, resting in a preparation fully competent for ligand binding. However, when sG-CSFR was purified by conventional means, i.e., without affinity chromatography, only about half was competent. Therefore, all studies were carried out using affinity-purified material. The sG-CSFR exhibited a weak self-association into a dimer with a dissociation constant of 200microM in the absence of G-CSF. Addition of G-CSF dimerizes the receptor, with a preferred stoichiometry of 2 G-CSF molecules plus 2 receptors. Unexpectedly, receptor-receptor interactions rather than through two receptors binding to the same G-CSF molecule; i.e., G-CSF is a monovalent ligand. G-CSF binding to the receptor monomer occurs with high affinity. The binding of G-CSF also enhances the receptor-receptor dimerization; when G-CSF is bound to both receptors, dimerization is enhanced 2000-fold, while the interaction of a 1:1 receptor-ligand complex with a second ligand-free receptor is enhanced 80-fold. Thus, the mechanism of receptor dimerization is fundamentally different than that of related cytokine receptors such as growth hormone and erythropoietin receptors. Circular dichroic spectra showed a small but significant conformational change of receptor upon binding G-CSF. This is consistent with the idea that G-CSF binding alters the conformation of the receptor, resulting in an increase in receptor-receptor interactions.

Animals↗
PubMed1994

Interactions of neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF), and the NT-3.BDNF heterodimer with the extracellular domains of the TrkB and TrkC receptors.

Interactions of three neurotrophin dimers, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and a NT-3.BDNF heterodimer with extracellular, soluble TrkB and TrkC receptors were studied using native gels, light scattering, and sedimentation equilibrium. These three neurotrophins showed binding of two TrkB receptors per neurotrophin dimer, with a tendency to dissociate into one TrkB per dimer for NT-3 and the heterodimer, as determined by native gels, light scattering, and sedimentation equilibrium. For TrkC, native gels suggested binding of NT-3, heterodimer, and BDNF but not of nerve growth factor. Sedimentation equilibrium revealed that all three neurotrophin molecules bind to TrkC at two receptors per dimer but that BDNF binds much more weakly and that the heterodimer has an intermediate binding strength. Light scattering/size exclusion chromatography showed complexes with two TrkC receptors per NT-3 dimer and one TrkC per heterodimer but did not detect binding of BDNF to TrkC. This latter result is not inconsistent with the sedimentation data, because the weak binding of BDNF to TrkC may be easily dissociated by nonspecific interactions of BDNF with the size exclusion column. The relative binding constants for these neurotrophins and the soluble receptor extracellular domains, as determined by sedimentation equilibrium, are correlated with their biological activity. However, the magnitude of these binding constants is insufficient by approximately 3 orders of magnitude to promote receptor dimerization at physiologically active concentrations.

Animals↗
PubMed1994

Structure and solubility of interleukin-2 in sodium dodecyl sulfate.

The solubility of an interleukin-2 (C125A) in an aqueous sodium dodecyl sulfate (SDS) solution was examined as a function of SDS concentration. A stock interleukin-2 solution at 1.1 or 0.31 mg/mL was mixed with one-tenth volume of a stock SDS solution at various concentrations. At intermediate SDS concentrations, the interleukin-2 showed nearly complete precipitation, while lower or higher SDS concentrations resulted in an increase in protein solubility. Circular dichroic analysis indicated that the protein remaining in the supernatant at low or high SDS concentrations has an altered conformation. Sedimentation velocity analysis of interleukin-2 in 0.1% SDS showed that about half the protein was monomeric, with the remainder as large aggregates with a broad size distribution from 20 to 100 S (M(r) approximately 10(5) - 10(7). In contrast, interleukin-2 in 0.01% SDS has a much smaller distribution of aggregates, sedimenting at ca. 2-10 S.

Chemical Phenomena↗
PubMed1981

Does bacteremia follow upper gastrointestinal endoscopy?

To determine the risk of bacteremia, 53 patients had blood collected for culture before and five, ten and 15 minutes following fiberoptic endoscopy of the upper digestive tract. One patient had transient bacteremia with Acinetobacter Sp. five minutes after endoscopy. Combining our study with four others, 447 patients have been evaluated of which 6% had bacteremia after upper gastrointestinal endoscopy. Biopsy or other endoscopic operation does not increase the likelihood of bacteremia. We recommend careful attention to instrument and accessory cleaning and prophylactic antibiotics (probably penicillin or oxacillin alone suffices) only for patients with prosthetic heart valves.

Acinetobacter Infections↗
PubMed1980

Proctosigmoidoscopic examinations by gastroenterology assistants.

Four gastroenterology assistants learned proctosigmoidoscopy by each performing 200 examinations with a physician. The assistants then examined a total of 7557 patients independently. The quality of their examination was assessed by reexamination of about every 10th patient by a physician. The data from all examinations were processed for computer tabulation and periodically reviewed. The patients accepted the examination by the gastroenterology assistant in all but three instances. The time spent by the patient for proctosigmoidoscopy, including preparation and examination, averaged 47 minutes before the assistant program and was reduced to an average of 34 minutes by the gastroenterology assistants. Ten patients had polyps (all smaller than 0.4 cm in diameter) undetected by the gastroenterology assistant but discovered by the physician. All 31 cancers and all of 371 polyps 0.5 cm or larger were discovered by the assistants. We conclude that a satisfactory proctosigmoidoscopy examination can be performed by a properly trained gastroenterology assistant, that it will conserve the physician's time, and that it reduces the waiting time of patients.

Gastroenterology↗
PubMed1976

Does bacteremia follow colonoscopy?

In order to determine the risk of bacteremia from colonoscopy, we cultured blood specimens from 40 patients the day before laxative and enema preparation; right after such preparation; and 15 min, 1 hr, and 4 hr after colonscopy. Bacteremia was not induced by either the vigorous preparation or the colonscopy which, in 27 patients, included polypectomy, biopsy, and/or fulgurations. On the basis of our data, we conclude that the risk of bacteremia following colonoscopy is small, and we doubt the need of antibiotic prophylaxis for those with susceptible hearts.

Colon↗