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Biomedical subjects

J M Polak

Publications and source records attributed to J M Polak.

At least 19 recordsLinked to original sources
PubMed2007

Enhanced differentiation and mineralization of human fetal osteoblasts on PDLLA containing Bioglass composite films in the absence of osteogenic supplements.

This study investigates the cellular response of fetal osteoblasts to bioactive resorbable composite films consisting of a poly-D,L-lactide (PDLLA) matrix and bioactive glass 45S5 Bioglass (BG) particles at three different concentrations (0% (PDLLA), 5% (P/BG5), and 40% (P/BG40)). Using scanning electron microscopy (SEM) we observed that cells were less spread and elongated on PDLLA and P/BG5, whereas cells on P/BG40 were elongated but with multiple protrusions spreading over the BG particles. Vinculin immunostaining revealed similar distribution of focal adhesion contacts on all cells independent of substratum, indicating that all materials permitted cell adhesion. However, when differentiation and maturation of fetal osteoblasts was examined, incorporation of 45S5 BG within the PDLLA matrix was found to significantly (p < 0.05) enhance alkaline phosphatase enzymatic activity and osteocalcin protein synthesis compared to tissue culture polystyrene controls and PDLLA alone. Alizarin red staining indicated extracellular matrix mineralization on both P/BG5 and P/BG40, with significantly more bone nodules formed than on PDLLA. Real time RT-PCR revealed that expression of bone sialoprotein was also affected by the BG containing films compared to controls, whereas expression of Collagen Type I was not influenced. By performing these investigations in the absence of osteogenic factors it appears that the incorporation of BG stimulates osteoblast differentiation and mineralization of the extracellular matrix, demonstrating the osteoinductive capacity of the composite.

Antigens, Differentiation↗
PubMed2006

Biocompatibility of poly-DL-lactic acid (PDLLA) for lung tissue engineering.

This study explores the possibility of growing lung cells on poly-DL-lactic acid (PDLLA) scaffolds, with a view to in future engineer pulmonary tissue for human implantation. As a first step in this process, the ability of PDLLA to maintain the growth of lung epithelium is tested using a robust cell line. Poly-DL-lactic acid has been investigated in two forms, as planar discs and as 3-D foams, and it has been demonstrated that PDLLA is not only nontoxic to pneumocytes but it also actively supports their growth. The initial findings suggest that the material is an appropriate matrix for engineering of distal lung tissue.

Animals↗
PubMed2005

Pantoprazole in severe acid-peptic disease: the effectiveness and safety of 5 years' continuous treatment.

OBJECTIVE: This is our final report on the clinical effectiveness and safety of long-term pantoprazole in patients with severe peptic ulcer or reflux disease during continuous treatment for up to 5 years. METHODS: Patients (n= 150) with peptic ulcer or reflux erosive oesophagitis running an aggressive course or with complications, and refractory to H2-receptor antagonists, were entered into this 5-year programme. Assessment was by serial endoscopy, clinical examination, serum gastrin estimation, gastric mucosal histology and mucosal endocrine cell quantification. RESULTS: Healing results were presented earlier. The estimated rates of remission on maintenance treatment with pantoprazole (n = 115) were 82% at 1 year, 75% at 2 years, 72% at 3 years, 70% at 4 years and 68% at 5 years. Helicobacter pylori infection appeared not to influence the outcome in reflux patients, with roughly two-thirds continuing in remission irrespective of infection. Only four patients had adverse events considered to be definitely related to pantoprazole. Median gastrin levels rose by 1.5-2-fold and were higher in those with H. pylori infection; 13 patients had levels >500 ng/L on at least one occasion, but these high levels were not sustained. Histological changes were more marked in patients infected with H. pylori: chronic gastritis decreased in the antrum and increased in the corpus, which also showed atrophic changes. The total number of endocrine cells in the antrum showed little variation over 60 months but fell by around one-third in the corpus. CONCLUSION: Long-term treatment with pantoprazole is effective and safe.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2004

Initial observations on the effect of medium composition on the differentiation of murine embryonic stem cells to alveolar type II cells.

The pluripotency and high proliferative index of embryonic stem (ES) cells make them a good potential source of cells for tissue engineering purposes. We have shown that ES cells can be induced to differentiate in vitro into pulmonary epithelial cells (type II pneumocytes) using a serum-free medium designed for the maintenance of mature distal lung epithelial cells in culture (SAGM). However, the resulting cell cultures were heterogeneous. Our aim in this study was to attempt to increase pneumocyte yield and differentiation state by determining which medium components enhance the differentiation of pneumocytes and modifying the medium accordingly. Quantitative RT-PCR was used to measure changes in the expression of a type II pneumocyte-specific gene, surfactant protein C (SPC), in response to alterations in the cell culture medium. Results suggested that most individual SAGM growth factors were inhibitory for type II pneumocyte differentiation, with the largest increases in SPC expression (approximately threefold) being observed upon removal of retinoic acid and triiodothryonine. However, large standard deviations occurred between replicates, illustrating the highly variable nature of ES cell differentiation. Nevertheless, these observations represent an initial step towards achieving directed differentiation of pneumocytes from stem cells that could lead to their purification for tissue engineering purposes.

Animals↗
PubMed2004

A histological study of the hph-1 mouse mutant: an animal model of phenylketonuria and infantile hypertrophic pyloric stenosis.

AIM: To quantify the chronological sequence of changes in the morphology and immunoreactivity for neurotransmitters in the pylorus of an animal model of infantile hypertrophic pyloric stenosis and phenylketonuria. METHOD: Thirty specimens of pylorus from hph-1 mice and age/sex matched controls (age range: 10-180 days) were examined using conventional histology and immunohistochemistry for a variety of antigens: protein gene product 9.5, a pan neuronal marker; vasoactive intestinal polypeptide; nitric oxide synthase two antigens coalesced to the same inhibitory neurons in humans; substance P, a potent excitatory neurotransmitter; and calcitonin gene related peptide, a neurotransmitter implicated in the somatic afferent innervation of the stomach. The changes in the morphology of the muscle layers were quantified and statistically analysed for each age group (10, 20, 40, 90 and 180 days). RESULTS: Between 10 and 90 days of age, all muscle layers of the hph-1 mice were hypertrophied, for example, 10 days, hph-1 longitudinal muscle mean diameter = 3.4, control = 1.8; hph-1 circular muscle width = 11.5, control = 4.7. The hph-1 mice were significantly smaller during this period (40 days, hph-1 weight = 10 g, control = 25 g). There was no change in the pattern of expression of the antigens examined within the hph-1 mice compared with the controls. CONCLUSION: Hph-1 mice develop a transient smooth muscle hypertrophy of the pylorus attended by gastric distension and failure to gain weight. These changes resolve as the pyloric muscle hypertrophy resolves.

Age Factors↗
PubMed2004

Apoptosis--a significant cause of bone cell death in osteonecrosis of the femoral head.

Osteonecrosis of the femoral head usually affects young individuals and is responsible for up to 12% of total hip arthroplasties. The underlying pathophysiology of the death of the bone cells remains uncertain. We have investigated nitric oxide mediated apoptosis as a potential mechanism and found that steroid- and alcohol-induced osteonecrosis is accompanied by widespread apoptosis of osteoblasts and osteocytes. Certain drugs or their metabolites may have a direct cytotoxic effect on cancellous bone of the femoral head leading to apoptosis rather than purely necrosis.

Apoptosis↗
PubMed2003

Spectroscopic study of human lung epithelial cells (A549) in culture: living cells versus dead cells.

The noninvasive analysis of living cells grown on 3-dimensional scaffold materials is a key point in tissue engineering. In this work we show the capability of Raman spectroscopy for use as a noninvasive method to distinguish cells at different stages of the cell cycle and living cells from dead cells. The spectral differences between cells in different stages of the cell cycle are characterized mainly by variations in DNA vibrations at 782, 788, and 1095 cm(-1). The Raman spectrum of dead human lung derived (A549 line) cells indicates the breakdown of both phosphodiester bonds and DNA bases. The most sensitive peak for identifying dead cells is the 788 cm(-1) peak corresponding to DNA Obond;Pbond;O backbone stretching. The magnitude of this peak is reduced by 80% in the spectrum of dead cells. Changes in protein peaks suggest significant conformational changes; for example, the magnitude of the 1231 cm(-1) peak assigned to random coils is reduced by 63% for dead cells. The sharp peak of phenylalanine at 1005 cm(-1) drops to half, indicating a decrease of stable proteins associated with cell death. The differences in the 1190-1385 cm(-1) spectral region also suggest a decrease in the amount of nucleic acids and proteins. Using curve fitting, we quantify these spectral differences that can be used as markers of cell death.

Biomarkers↗
PubMed2003

Scaffolds and biomaterials for tissue engineering: a review of clinical applications.

Tissue engineering is a multidisciplinary area of research aimed at regeneration of tissues and restoration of organ function. This is achieved through implantation of cells/tissues grown outside the body or by stimulating cells to grow into an implanted matrix. In this short review, we discuss the use of biomaterials, in the form of scaffolds, for tissue engineering and review clinical applications to otorhinolaryngology-head and neck surgery.

Biocompatible Materials↗
PubMed2002

Stem cells: sources and applications.

Tissue engineering is a multidisciplinary area of research aimed at regeneration of tissues and restoration of function of organs through implantation of cells/tissues grown outside the body, or stimulating cells to grow into implanted matrix. In this short review, some of the most recent developments in the use of stem cells for tissue repair and regeneration will be discussed. There is no doubt that stem cells derived from adult and embryonic sources hold great therapeutic potential but it is clear that there is still much research required before their use is commonplace. There is much debate over adult versus embryonic stem cells and whether both are required. It is probably too early to disregard one or other of these cell sources. With regard to embryonic stem cells, the major concern relates to the ethics of their creation and the proposed practice of therapeutic cloning.

Animals↗
PubMed2002

Gene expression: a review of clinical applications in otorhinolaryngology-head and neck surgery.

Tissue engineering is a multidisciplinary area of research aimed at regeneration of tissues and restoration of function of organs through implantation of cells/tissues grown outside the body or stimulating cells to grow into implanted matrix. In this short review, we aim to examine current techniques in gene expression analysis and their relevant clinical applications to the field of otorhinolaryngology-head and neck surgery.

Gene Expression↗
PubMed2002

A quantitative study of the neural changes underlying pyloric stenosis in dogs.

This study aimed to quantify the neural changes in congenital pyloric stenosis in dogs and to study the comparative anatomy between this condition in dogs and that in infantile hypertrophic pyloric stenosis. Eight specimens from the pylorus of dogs with pyloric stenosis and six control specimens were examined using conventional histology and immunohistochemistry for a range of neural antigens. The changes in the proportion of nerves immunoreactive for each antigen were quantified and analysed statistically. The morphology of the nerves in the diseased dogs was similar to that in controls. Only vasoactive intestinal peptide was reduced in expression in dogs (median proportion in control dogs 0.57, in diseased dogs 0.17; P = 0.065). This study demonstrates both morphological similarities and significant differences between closely related conditions in dogs, humans and other species.

Animals↗
PubMed2002

Modulation of hydrogen peroxide induced injury to corneal endothelium by virus mediated catalase gene transfer.

AIM: To examine the effect of catalase gene transfer on survival of corneal endothelial cells (EC) following challenge with hydrogen peroxide (H(2)O(2)) in an ex vivo model of oxidative stress. METHODS: A recombinant adenovirus vector (AdCL) was used to transfer human catalase cDNA into EC of whole thickness rabbit corneas ex vivo. The resulting catalase protein concentration was measured in corneal lysates by ELISA; catalase functional activity in lysates was determined using a H(2)O(2) activity assay. To examine the morphological effects of catalase gene transfer in modulation of H(2)O(2) induced injury, transduced corneas were maintained in ex vivo culture and challenged with H(2)O(2). Laser scanning confocal microscopy was used to image EC injury. Cell density, cell morphology, and ratios of viable to necrotic cells were determined. RESULTS: Following incubation with AdCL, catalase expression reached maximum at 5-7 days. Corneas transduced with AdCL showed increased EC cell survival following challenge with H(2)O(2) on day 3 when compared to null vector control or mock infected corneas. CONCLUSIONS: Ex vivo catalase gene transfer can protect EC from death mediated by H(2)O(2). This gene based approach to the protection of corneal endothelium from oxidative stress may have application in prevention of EC loss in pathological conditions in which H(2)O(2) is involved and in ex vivo donor corneal storage before transplantation.

Adenoviridae↗
PubMed2001

Quantitative myocardial cytokine expression and activation of the apoptotic pathway in patients who require left ventricular assist devices.

BACKGROUND: Molecular mechanisms underlying the deterioration of patients undergoing LV assist device (LVAD) implantation remain poorly understood. We studied the cytokines tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta and IL-6 and the terminal stage of the apoptotic pathway in patients with decompensating heart failure who required LVAD support and compared them with patients with less severe heart failure undergoing elective heart transplantation. METHODS AND RESULTS: Myocardial and serum samples from 23 patients undergoing LVAD implantation were compared with those from 36 patients undergoing elective heart transplantation. Myocardial TNF-alpha mRNA (1.71-fold; P<0.05) and protein (3.43+/-0.19 versus 2.95+/-0.10 pg/mg protein; P<0.05) were elevated in the LVAD patients. Immunocytochemistry demonstrated TNF expression in the myocytes. Serum TNF-alpha was also elevated (12.5+/-1.9 versus 4.0+/-0.4 pg/mL; P<0.0001) in the LVAD patients. IL-6 mRNA (2.57-fold higher; P<0.005) and protein (27.83+/-9.35 versus 4.26+/-1.24 pg/mg protein; P<0.001) were higher in the LVAD candidates, as was serum IL-6 (79.3+/-23.6 versus 7.1+/-1.6 pg/mL; P<0.0001). Interleukin-1beta mRNA expression was 9.78-fold higher in the LVAD patients (P<0.001). iNOS mRNA expression was similar to that in advanced heart failure patients and was not further elevated in the LVAD patients. Levels of procaspase-9 (8.02+/-0.91 versus 6.16+/-0.43 oligodeoxynucleotide [OD] units; P<0.01), cleaved caspase-9 (10.02+/-1.0 versus 7.34+/-0.40 OD units; P<0.05), intact and spliced DFF-45 (4.58+/-0.75 versus 2.84+/-0.23 OD units; P<0.05) were raised in LVAD patients, but caspase-3 and human nuclease CPAN were not. CONCLUSIONS: Elevated TNF-alpha, IL-1beta, and IL-6 and alterations in the apoptotic pathway were found in the myocardium and elevated TNF-alpha and IL-6 in serum of deteriorating patients who required LVAD support. These occurrences may have therapeutic implications and influence the timing of LVAD insertion.

Adolescent↗
PubMed2001

Abdominal aortic calcific deposits are an important predictor of vascular morbidity and mortality.

BACKGROUND: The impact of abdominal arterial calcific deposits on the prediction of cardiovascular disease (CVD) over a long follow-up interval deserves greater scrutiny. METHODS AND RESULTS: Lateral lumbar radiographs were studied as a predictor of incident coronary heart disease (CHD), CVD, and CVD mortality in 1049 men and 1466 women (mean age, 61 years) who were followed from 1967 to 1989. Anterior and posterior wall calcific deposits in the aorta at the level of the first through fourth lumbar vertebrae were graded according to increasing severity using a previously validated rating scale for abdominal aortic calcium (AAC) that ranges from 0 to 24 points. There were 454 cases of CHD, 709 cases of CVD, and 365 CVD deaths. Proportional hazards logistic regression was used to test for associations between AAC and later events after adjustment for age, cigarette use, diabetes mellitus, systolic blood pressure, left ventricular hypertrophy, body mass index, cholesterol, and HDL cholesterol. In comparisons with the lowest AAC tertile, the multivariate age-adjusted relative risks (RR) for CVD were increased in tertile 2 (men: RR, 1.33; 95% confidence interval [CI], 1.02 to 1.74; women: RR, 1.25; 95% CI, 0.95 to 1.65) and tertile 3 (men: RR, 1.68; 95% CI, 1.25 to 2.27; women: RR, 1.78; 95% CI, 1.33 to 2.38). Similar results were obtained with CHD and CVD mortality. CONCLUSIONS: AAC deposits, detected by lateral lumbar radiograms, are a marker of subclinical atherosclerotic disease and an independent predictor of subsequent vascular morbidity and mortality.

Aorta, Abdominal↗
PubMed2001

Gene-expression profiling of human osteoblasts following treatment with the ionic products of Bioglass 45S5 dissolution.

The effect of the ionic products of Bioglass 45S5 dissolution on the gene-expression profile of human osteoblasts was investigated by cDNA microarray analysis of 1,176 genes. Treatment with the ionic products of Bioglass 45S5 dissolution increased the levels of 60 transcripts twofold or more and reduced the levels of five transcripts to one-half or less than in control. Markedly up-regulated genes included RCL, a c-myc responsive growth related gene, cell cycle regulators such as G1/S specific cyclin D1, and apoptosis regulators including calpain and defender against cell death (DAD1). Other significantly up-regulated genes included the cell surface receptors CD44 and integrin beta1, and various extracellular matrix regulators including metalloproteinases-2 and -4 and their inhibitors TIMP-1 and TIMP-2. The identification of differentially expressed genes by cDNA microarray analysis has offered new insights into the mode of action of bioactive glasses and has proven to be an effective tool in evaluating their osteoproductive properties.

Biocompatible Materials↗