Biomedical subjects

Hubert M Pollock

Publications and source records attributed to Hubert M Pollock.

6 recordsLinked to original sources

PubMed2006

ATR microspectroscopy with multivariate analysis segregates grades of exfoliative cervical cytology.

Although cervical cancer screening in the UK has led to reductions in the incidence of invasive disease, this programme remains flawed. We set out to examine the potential of infrared (IR) microspectroscopy to allow the profiling of cellular biochemical constituents associated with disease progression. Attenuated total reflection-Fourier Transform IR (ATR) microspectroscopy was employed to interrogate spectral differences between samples of exfoliative cervical cytology collected into liquid based cytology (LBC). These were histologically characterised as normal (n = 5), low-grade (n = 5), high-grade (n = 5) or severe dyskaryosis (? carcinoma) (n = 5). Examination of resultant spectra was coupled with principal component analysis (PCA) and subsequent linear discriminant analysis (LDA). The interrogation of LBC samples using ATR microspectroscopy with PCA-LDA facilitated the discrimination of different categories of exfoliative cytology and allowed the identification of potential biomarkers of abnormality; these occurred prominently in the IR spectral region 1200 cm(-1) - 950 cm(-1) consisting of carbohydrates, phosphate, and glycogen. Shifts in the centroids of amide I (approximately 1650 cm(-1)) and II (approximately 1530 cm(-1)) absorbance bands, indicating conformational changes to the secondary structure of intracellular proteins and associated with increasing disease progression, were also noted. This work demonstrates the potential of ATR microspectroscopy coupled with multivariate analysis to be an objective alternative to routine cytology.

Female↗

PubMed2006

IR microspectroscopy: potential applications in cervical cancer screening.

Screening exfoliative cytology for early dysplastic cells reduces incidence and mortality from squamous carcinoma of the cervix. In the developed world, screening programmes have adopted a 3-5 years recall system. In its absence, cervical cancer would be the second most common female cancer in these regions; instead, it is currently eleventh. However, there exist a number of limitations to the smear test even given the removal of contaminants using liquid-based cytology. It is prohibitively expensive, labour-intensive and subject to inaccuracies that give rise to significant numbers of false negatives. There remains a need for novel approaches to allow efficient and objective interrogation of exfoliative cytology. Methods that variously exploit infrared (IR) microspectroscopy are one possibility. Using IR microspectroscopy, an integrated 'biochemical-cell fingerprint' of the lipid, protein and carbohydrate composition of a biomolecular entity may be derived in the form of a spectrum via vibrational transitions of individual chemical bonds. Powerful statistical approaches (e.g. principal component analysis) now facilitate the interrogation of large amounts of spectroscopic data to allow the extraction of what may be small but extremely significant biomarker differences between disease-free and pre-malignant or malignant samples. An increasing wealth of literature points to the ability of IR microspectroscopy to allow the segregation of cells based on their disease status. We review the current evidence supporting its diagnostic potential in cancer biology.

Female↗

PubMed2006

Infrared spectroscopy with multivariate analysis potentially facilitates the segregation of different types of prostate cell.

The prostate gland is conventionally divided into zones or regions. This morphology is of clinical significance as prostate cancer (CaP) occurs mainly in the peripheral zone (PZ). We obtained tissue sets consisting of paraffin-embedded blocks of cancer-free transition zone (TZ) and PZ and adjacent CaP from patients (n = 6) who had undergone radical retropubic prostatectomy; a seventh tissue set of snap-frozen PZ and TZ was obtained from a CaP-free gland removed after radical cystoprostatectomy. Paraffin-embedded tissue slices were sectioned (10-mum thick) and mounted on suitable windows to facilitate infrared (IR) spectra acquisition before being dewaxed and air dried; cryosections were dessicated on BaF(2) windows. Spectra were collected employing synchrotron Fourier-transform infrared (FTIR) microspectroscopy in transmission mode or attenuated total reflection-FTIR (ATR) spectroscopy. Epithelial cell and stromal IR spectra were subjected to principal component analysis to determine whether wavenumber-absorbance relationships expressed as single points in "hyperspace" might on the basis of multivariate distance reveal biophysical differences between cells in situ in different tissue regions. After spectroscopic analysis, plotted clusters and their loadings curves highlighted marked variation in the spectral region containing DNA/RNA bands ( approximately 1490-1000 cm(-1)). By interrogating the intrinsic dimensionality of IR spectra in this small cohort sample, we found that TZ epithelial cells appeared to align more closely with those of CaP while exhibiting marked structural differences compared to PZ epithelium. IR spectra of PZ stroma also suggested that these cells are structurally more different to CaP than those located in the TZ. Because the PZ exhibits a higher occurrence of CaP, other factors (e.g., hormone exposure) may modulate the growth kinetics of initiated epithelial cells in this region. The results of this pilot study surprisingly indicate that TZ epithelial cells are more likely to exhibit what may be a susceptibility-to-adenocarcinoma spectral signature. Thus, IR spectroscopy on its own may not be sufficient to identify premalignant prostate epithelial cells most likely to progress to CaP.

Algorithms↗

PubMed2006

Characterization of putative stem cell populations in the cornea using synchrotron infrared microspectroscopy.

PURPOSE: High-resolution synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy coupled with multivariate analysis was used to investigate the characteristics of putative adult stem cell (SC), transiently amplified (TA) cell, and terminally differentiated (TD) cell populations of the corneal epithelium. METHODS: Spectra of individual cells in situ in cryosections of bovine cornea were collected by using a synchrotron microspectroscopy facility at Daresbury Laboratory (United Kingdom). The resultant spectra were analyzed by multivariate analysis. RESULTS: The median spectra of the three different cell populations showed marked differences, which correlated with their degree of differentiation and proliferative capacity. Multivariate (principal component) analysis (PCA) showed that the three cell populations could be segregated into discrete clusters, with only a slight overlap between the SC and TA cell populations. Further analysis (Mann-Whitney test) indicated that the most significant (P<0.001) spectral differences between the SC and TA cell populations were chiefly associated with changes in nucleic acid conformation. CONCLUSIONS: SR-FTIR microspectroscopy coupled with PCA appears to enable the identification of SC, TA cell, and TD cell populations. The results also suggest that a small subpopulation of cells in the corneal epithelial SC niche possess TA cell-like characteristics. The most significant spectral characteristics associated with the SCs appear to relate to differences in nucleic acid conformation. This finding is consistent with recent theories suggesting that the control of differentiation is related to major changes in chromatin structure.

Animals↗

PubMed2005

Monitoring cell cycle distributions in MCF-7 cells using near-field photothermal microspectroscopy.

Microspectroscopic techniques such as Fourier transform infrared (FTIR) have played an important role in "fingerprinting" the biochemical composition of cellular components. Based on structure and function, complex biomolecules absorb energy in the mid-infrared (lambda = 2-20 microm) yielding characteristic vibrational infrared (IR) spectra. However, optical detection FTIR microspectroscopy may not be suitable for IR-absorbing sample materials. Photothermal microspectroscopy (PTMS) permits the direct measurement of heat generated as a result of sample material absorbing radiation. This approach generates true absorption spectra and is implemented by interfacing a scanning probe microscope and an FTIR spectrometer. Detection is performed using a near-field ultra-miniaturized temperature sensor. Employing PTMS, IR spectra of MCF-7 cells were examined in spectral regions (900-2000 cm(-1)) corresponding to proteins, DNA, RNA, glycoproteins, carbohydrates, lipids, and levels of protein phosphorylation. As a cell passes through the cell cycle, its nuclear material decondenses and condenses and this has led to ambiguity as to whether the intensity of such spectral regions may be associated with the G(1)-, S- or G(2)-phases of the cell cycle. Cultured cells were tracked over a time course known to correspond to marked alterations in cell-cycle distributions, as determined using flow cytometry. Experiments were carried out in the absence or presence of lindane, a pesticide known to induce G(1)-arrest in MCF-7 cells. Significant (P < 0.05) elevations in spectral intensities were associated with exponentially growing cell populations, predominantly in S-phase or G(2)-phase, compared to more quiescent populations predominantly in G(1)-phase. Increases in the absorption band at 970 cm(-1), associated with elevated protein phosphorylation, were observed in vibrational spectra of exponentially growing cell populations compared to those exhibiting a slowing in their growth kinetics. These results seem to suggest that intracellular bulk changes, associated with transit through the cell cycle, can be tracked using PTMS.

Analysis of Variance↗

PubMed2004

Frictional forces between cohesive powder particles studied by AFM.

A range of commercially important powders (hydrated alumina, limestone, titania and zeolite) and glass ballotini were attached to atomic force microscope cantilevers, and inter-particle friction forces studied in air using lateral force microscopy (LFM). The in situ calibration procedure for friction forces is described. LF images, line profiles, LF histograms, surface roughness, pull-off forces, and the load dependence of friction in the range 0-25 nN were studied for both particle-particle and particle-wall (steel) contacts. The single-particle friction results are discussed in terms of contact mechanics theory. Particle-particle contacts showed load-dependent friction, involving single asperity contacts (non-linear behaviour) or multi-asperity contacts (linear behaviour). Particle-wall contacts usually showed little load dependence and were more adhesive. The results are also related to shear stress-normal stress data (yield loci) for the same materials from bulk shear testers.

Friction↗