P. T. T. Wong

Alteration of Gene Expression in Normal-Appearing Colon Mucosa of APCmin Mice and Human Cancer Patients

The expression of many genes is altered in colon cancer, but the roles of these genes in carcinogenesis are unclear. Using real-time quantitative PCR, we demonstrated that several genes previously implicated in human colon cancer undergo altered expression in the APCmin mouse adenomatous polyp, a precursor of cancer, as well as in normal-appearing surrounding mucosa. The five genes that were most highly up-regulated in mouse polyp were also significantly up-regulated in polyp-free colon mucosa. Similar changes occurred in morphologically normal mucosa of surgical sections taken from human cancer patients, frequently extending to the margins. Thus, morphologically normal colon mucosa in APCmin mice and in human cancer patients is not metabolically normal. Altered gene expression in this tissue does not appear to result from a field effect because there was no correlation between extent of altered regulation and distance from polyp or tumor. Our data suggest that alterations of expression levels of these genes may be an early event in carcinogenesis and a marker of risk for the development of colon cancer.

Crystalline Quartz as an Internal Pressure Calibrant for High-Pressure Infrared Spectroscopy

Raman spectra of aqueous phospholipid bilayers and aqueous micellar solution of surfactants at high pressure have been studied in this laboratory. However, some normal modes in these systems are Raman inactive or weakly active, and most of the normal modes of the methylene chains in these systems are highly dispersed. In order to further understand the pressure effects on the vibrational dynamics in these systems, we have extended our pressure studies to the Fourier transform infrared spectra of these aqueous systems, using a diamond anvil cell.

A New Internal Pressure Calibrant for High-Pressure Infrared Spectroscopy of Aqueous Systems

Pressure-induced correlation field splitting of the CH2 rocking mode in the infrared spectra of methylene chain systems such as polyethylene, n-alkanes, surfactants, fatty acids, and model and biomembranes provides important information concerning the interchain structural and dynamic properties of these systems. The pressure at which the correlation field splitting starts is a measure of the orientational disorder of methylene chains along the chain axis. Moreover, the integrated intensity ratio between the correlation field component bands of the CH2 rocking mode is a measure of the relative orientation of the zig-zag planes between neighboring methylene chains.

Optical spectra of orientationally disordered crystal. V. Raman spectrum of ice Ih in the range 4000–350 cm−1

The Raman spectrum of polycrystalline ice Ih has been investigated using laser excitation in the frequency range 4000−350 cm−1. The relative intensities have been discussed in a semiquantitative way that takes explicit account of the intermolecular coupling of the molecular vibrations in the crystal. The principal conclusions from the work are summarized at the end of the paper.The Raman spectrum of polycrystalline ice Ih has been investigated using laser excitation in the frequency range 4000−350 cm−1. The relative intensities have been discussed in a semiquantitative way that takes explicit account of the intermolecular coupling of the molecular vibrations in the crystal. The principal conclusions from the work are summarized at the end of the paper.

Interactions of Laurdan with phosphatidylcholine liposomes: a high pressure FTIR study

The interactions of 6-lauroyl-2-dimethylaminonaphthalene (Laurdan) with L-alpha-dimyristoylphosphatidylcholine (DMPC) have been studied isothermally at 28 degrees C by Fourier-transform infrared spectroscopy (FTIR) at two pH values (6.8 and 3.0) and over the pressure range of 0.001-25 kbar. The results obtained with Laurdan are compared with those previously obtained with 6-propionyl-2-dimethylaminonaphthalene (Prodan) (Chong et al. (1989) Biochemistry 28, 8358-8363). The objective of this study is to delineate the differential interactions of Prodan and Laurdan with lipid membranes. The Laurdan carbonyl and naphthalene vibrational bands as well as the correlation field splitting of the methylene scissoring mode all indicate that in phospholipid model membrane systems, Laurdan behaves differently from Prodan. The data suggest that the chromophore of Laurdan is embedded somewhat deeper in the membrane than that of Prodan. The correlation field splitting pressure suggests that Laurdan causes more perturbation to DMPC vesicles than Prodan. Instead of being relocated to the exterior of the membrane as is the case of Prodan, Laurdan is found to remain in the membrane even when it is partially positively charged at pH 3. Apparently the stabilizing forces come from the strong van der Waals and hydrophobic interactions between the lauroyl chain and its neighboring lipid molecules. Laurdan seems to remain in the membrane at high pressures (up to 25 kbar). Using deuterated DMPC (d-DMPC) and deuterated L-alpha-dipalmitoylphosphatidylcholine (d-DPPC), we have demonstrated that, at 1 atm, there is a void space between the lauroyl chain of Laurdan and the acyl chain of the matrix lipid, regardless of the physical state of the matrix lipid. This void space, probably caused by the bulky naphthalene ring, is eventually diminished by elevated pressures.

Raman spectrum of ice VIII

The Raman spectra of H2O and D2O ice VIII recovered at ∼100 K and zero pressure have been measured in the range 4000–50 cm−1. The three stretching, three rotational, and four translational bands expected from the symmetry of the crystal have been identified. Two bending bands are expected and have been tentatively identified among some weak bands. The relative intensity of the rotational and stretching bands is much smaller than in the vapor, and so if the intensity of the stretching bands is not greatly changed, the anisotropy of the polarizability is appreciably smaller in ice VIII than in the vapor.

Infrared Spectra of Microtome Sections of Human Colon Tissues

The development of a pressure-tuned infrared spectroscopic technique for biological tissues in our Ottawa laboratory has made possible the use of Fourier transform infrared spectroscopy for the study of cells and tissue sections. Recently, using this technique we investigated structural properties of biomolecules in tissue specimens of human colon cancer. During this work we discovered that malignant colon tissue can be distinguished from normal colon tissue by a series of high-pressure infrared spectroscopic parameters. Furthermore, we observed that some infrared parameters of malignant colonic tissue obtained at atmospheric pressure were significantly different from those of normal colonic tissue. For example, there is a 2–3 cm−1 difference in the frequency of the symmetric phosphate stretching band of the nucleic acids between normal and malignant colon tissues.

Effect of pressure on molecular conformations. II. Trans–gauche equilibrium of 1,2‐dichloroethane and 1,2‐dibromoethane

The effect of pressure on the trans–gauche equilibrium of 1,2‐dichloroethane in n‐hexane solution and of 1,2‐dibromoethane in 2‐methylbutane and acetonitrile solutions has been measured by the Raman spectrum. The relative integrated intensities of the carbon–halogen stretching vibrations of the two conformers has been taken as a measure of their relative concentrations. The volume change at the trans–gauche transformation for 1,2‐dichloroethane is −3.8 ± ∼0.2 and −3.5 ± ∼0.2 cm3 mol−1, respectively, in 20% and 30% v/v solution in n‐hexane at 21 °C, and for 1,2‐dibromoethane it is −4.5 ± ∼0.7 cm3 mol−1 in 10% and 20% v/v solution in 2‐methylbutane and −2.0 and −1.8±∼0.7 cm3 mol−1, respectively, in 10% and 20% solutions in acetonitrile at 21 °C. The contributions to the volume change due to the overlapping of the halogen atoms in the gauche conformation and to the electrostatic effects as represented by the interaction of molecules having dipole and quadrupole moments with a dielectric continuum have been c...

Hydrostatic optical cell with glass windows for 25 kilobar

An optical cell with three glass windows for hydrostatic pressures up to 25 kilobar has been made. Its collecting angle is 13°, and it has been used mainly for Raman spectroscopy. The fundamental Raman spectrum of diamond has been recorded.

Pressure-Tuning FT-IR Study of Human Cervical Tissues

Infrared spectra of the normal connective, the normal epithelial, and the malignant epithelial tissues of cervix from seven patients have been measured as a function of pressure. Extremely high quality spectra of these tissue samples have been obtained. Consequently, structural differences at the molecular level among these three types of cervical tissues have been extracted from their pressure-tuning infrared spectra in the regions of the symmetric and antisymmetric stretching modes of phosphodiester groups, the C-O stretching mode, the CH2 bending mode, and the amide I mode. Significant differences in many features between the infrared spectra of the normal and the malignant cervical tissues and cells suggest that the infrared spectra of exfoliated cells and the biopsy of cervical tissues may be used in rapid evaluation of cervical cancer or in screening of large-volume normal cervical specimens. The infrared spectrum of the normal connective tissue of cervix in the frequency region 950 to 1100 cm−1 is similar to that of the malignant cervical tissue and cells. Therefore, if only this region of the spectrum is examined, the normal connective tissue will be misinterpreted as malignant tissue. However, the normal connective tissue can be differentiated unambiguously from the malignant tissue or the normal epithelial tissue by the infrared spectra in the frequency region 1200 to 1500 cm−1, where several well-defined sharp bands are unique for the normal connective tissue.