Stem cells for ocular tissue engineering and regeneration

With advances in stem cell biology, tissue engineering is becoming increasingly powerful for tissue regeneration. Stem cells with capacity of multilineage and self-renewal are an ideal cell source for tissue engineering. This review focus on discussing the potential strategies including stem cell sources, bio-scaffolds, mechanical stimulation, genetic modification and co-culture techniques to direct ocular-lineage differentiation of stem cells for complete or partial eye regeneration and research. Attempts to use embryonic and somatic stem cells as seed cells for ocular tissue engineering have achieved encouraging results. The combination of chemical and physical signals in stem cell microenvironment could be regulated to induce differentiation of the embryonic stem cells into ocular tissue. This paper present here a broad introduction to the stem cell mediated correction of eye ailments and provide extensive references for the interested reader. This paper also looks into the different aspects of using stem cells for drug development for treating eye ailments.     

LC determination of rofecoxib in bulk and pharmaceutical formulations

An isocratic reversed phase-liquid chromatographic (RP-LC) method has been developed for the determination and purity evaluation of rofecoxib in bulk and pharmaceutical dosage forms using photodiode array detection set at 225 nm. The method is simple, rapid and selective. The method is capable of detecting all process intermediates and other related compounds, which may be present at trace levels in finished products. Hence the method is very useful for process monitoring during the production of rofecoxib. Chlorophenyl methyl sulphone has been used as internal standard for the quantitative determination of rofecoxib. The method is linear in the range of 125-500 microg. The precision for inter- and intra-day assay variation of rofecoxib is below 1.6% relative standard deviation (R.S.D.). The accuracy determined as relative mean error (R.M.E.) for the intra-day assay is within +/-2.0%. The drug was extracted from tablets (Vioxx) using acetonitrile. The percentage recoveries from dosage forms were ranged from 98.2 to 102.6.     

Cellular manifestations of human papillomavirus infection in laryngeal tissues

BACKGROUND AND OBJECTIVES: Although epidemiologic studies have suggested human papillomavirus (HPV) to be an etiological agent in laryngeal carcinogenesis, little is known on the cellular manifestations of HPV infection in these tumors. In this study, we investigated the frequency of HPV infection in various neoplastic and non-neoplastic laryngeal tissue and its association with expression of the proliferating cell nuclear antigen (PCNA) and the tumor suppressor protein p53. METHODS: Tissues were analyzed by polymerase chain reaction (PCR) for the presence of HPV and by immunocytochemistry for the expression of p53 and PCNA. RESULTS: None of the six normal laryngeal tissues showed the presence of HPV. Thirteen out of the 16 papillomas were positive for HPV, while 15 out of the 44 invasive cancers were HPV positive. PCNA expression increased as the lesion progressed through increasing histological abnormality (r = 0.64400, P = 0.00000). The correlation between the type of laryngeal neoplasm and p53 accumulation was significant (r = 0.54839, P = 0.00000). Significant correlation was also evident between presence of HPV and p53 accumulation (r = 0.34259, P = 0.00424) and PCNA expression (r = 0.036024, P = 0.00266) indicating that HPV positive tumors showed significant p53 accumulation and increased proliferation.There was also correlation between p53 and PCNA expression (r = 0.67475, P = 0.00000) indicating that in all tumors with p53 accumulation, there was a corresponding increase in PCNA expression. CONCLUSIONS: The results suggests that changes in p53 and PCNA expression may be associated with HPV infection, and could play a role in laryngeal carcinogenesis.     

Polymorphisms in DNA repair gene <Emphasis Type="Italic">XRCC1</Emphasis> and increased genetic susceptibility to breast cancer

X-ray repair cross-complementing 1 (XRCC1) gene encodes for a scaffolding protein, which plays an important role in base excision DNA repair by bringing together DNA polymerase beta, DNA ligase III and poly(ADP-Ribose) polymerase (PARP) at the site of DNA damage. Three polymorphisms of the XRCC1 gene at codons 194, 280 and 399 leading to a mino acid changes at evolutionary conserved regions are found to alter the efficiency of the resulting protein and may therefore constitute potential breast cancer risk. In the present study we sought to determine whether these genetic variants of the XRCC1 gene was associated with any increased risk of breast cancer among the South Indian women in a hospital based case control study using PCR-RFLP and DNA sequencing techniques. Our data showed a positive association between the polymorphisms of codons 194 (OR=1.98, 95% CI=1.13--3.48 for Trp allele) and 399 (OR=2.14, 95% CI=1.29--3.58 for Gln allele) and breast cancer risk. However, XRCC1 codon 280 genotype analysis showed no evidence for an association with increased risk of breast cancer. A combined analysis of the effect of XRCC1 codon 194 and 399 revealed the highest risk (OR=3.64, 95% CI=1.57--8.46) for carriers of the polymorphic alleles in both these codons. In conclusion, the present study suggested involvement of XRCC1 codon 194 and 399 polymorphisms in the genetic predisposition to breast cancer among South Indian women. Our preliminary results based on the analysis of functionally relevant polymorphisms in XRCC1 low penetrance gene may provide a better model that would exhibit additive effects on individual susceptibility to breast cancer.     

Clinicopathological significance of tissue homeostasis in Indian breast cancer

BACKGROUND: Tissue homeostasis and the maintenance of cell populations depend on a delicate balance between the rates of cell proliferation and cell death. Disruption of this balance is an important factor in development and progression of tumors. In the present study we evaluated the growth index in a large group of breast cancer patients and correlated it with various clinical and histopathological features of the tumor. METHODS: Estimation of apoptosis was determined by TUNEL assay while immunocytochemistry for proliferating nuclear cell antigen (PCNA) was used as a measure of proliferation. Necrosis was identified morphologically by haematoxylin and eosin staining. RESULTS: A positive correlation was observed between the percentage of PCNA positive cells and the frequency of mitosis (r=0.6117, p<0.0001). A highly statistical significant correlation was observed between type of tissue analyzed and growth index (r=0.46869, p<0.0001). No significant association was observed between hormone receptor status and growth index. CONCLUSIONS: The growth index was found to be higher in carcinoma cells that metastasised into lymph nodes compared with primary lesions with no nodal metastasis. Growth index was particularly prominent in high-grade tumors in which increased proliferative activity was evident. Apoptotic cells were detected more frequently in tumor cells with higher rather than lower proliferative activity. This suggests that not only proliferative activity but also capacity for apoptosis is altered in breast tumors.     

Evaluation of a collapsed-cone convolution algorithm for esophagus and surface mold 192Ir brachytherapy treatment planning

PurposeTG43 does not account for a lack of scatter and tissue and applicator heterogeneities. The advanced collapsed-cone engine (ACE) algorithm available for use in the Oncentra Brachy treatment planning system (Elekta AB, Stockholm, Sweden) can model these conditions more accurately and is evaluated for esophageal and surface mold brachytherapy treatments.Methods and MaterialsACE was commissioned for use then compared against TG43 for five esophageal and five surface mold treatment plans. Dosimetric differences between each algorithm were assessed using superimposed comparisons and dose-volume histogram statistics.ResultsEsophagus (6 Gy per fraction): Compared with TG43, ACE demonstrated up to a 0.63% and 0.05 Gy reduction in planning target volume (PTV) V100% and PTV D98, respectively. Lung D2cc and bone D2cc deviated by up to 0.09 Gy and 0.03 Gy, respectively. Lung D0.1 cc and bone D0.1 cc both deviated by up to 0.12 Gy.Surface mold (4.5 Gy per fraction): Compared with TG43, ACE demonstrated up to a 12.5% and 0.18 Gy reduction in PTV V80% and PTV D98, respectively. Bone D2cc and D0.1 cc both reduced by up to 0.2 Gy when modeled with ACE. Increasing mold size laterally increased the dosimetric differences between TG43 and ACE.ConclusionsTG43 generally overestimated dose delivered to the target volume and organs at risk for the sites investigated. Dosimetric differences observed for esophageal treatments were minimal; however, surface mold treatments would benefit from the increased dosimetric accuracy offered by ACE.Implementation should be considered for surface mold ¹⁹²Ir treatment planning, but increased calculation time, additional contouring, and mass density assignment requirements should be scrutinized with regard to their potentially negative impact on current clinical practice.     

Frequency and predictors for angiographically improved inflow of contrast medium after carotid angioplasty and stenting

Percutaneous transluminal carotid angioplasty and stenting (PTAS) can result in immediate improvement in cerebral blood flow (CBF) evident through faster transit of contrast medium on angiography. To evaluate frequency and predictors of changes in inflow of contrast medium before and after PTAS, we reviewed 86 patients (mean age 68.6 ± 9.1 years) treated for symptomatic or asymptomatic carotid stenosis. Clinical data and lesion characteristics were extracted from charts and digital angiograms, respectively. Perfusion change was assessed qualitatively by comparing pre- and poststenting images matched for projection and time from injection. Improved inflow was defined on the basis of spatial or temporal distribution of contrast medium: grade –1: fewer vessels visible after stenting; 0: no change; 1: more distal small arteries visible; 2: time-matched poststenting image showing a capillary blush; 3: time-matched poststenting image showing small veins, 4 time-matched poststenting image showing large veins and sinuses. Faster inflow of contrast medium was observed in 74 % of patients (grades 1: 34 %,and 4: 4.7 %). In linear regression analysis, higher degrees of ipsilateral stenosis were associated with greater changes in inflow of contrast medium (P < 0.05). Right internal carotid lesions were associated with greater change in inflow than left-sided lesions (P < 0.01). In 31 patients (36 %) we initially showed contralateral anterior cerebral artery (ACA) filling, and in 39 % of these, normal filling was restored after stenting. Lesser contralateral carotid stenosis was associated with crossed ACA filling and with restoration of normal filling pattern after stenting. Faster appearance of a contrast-medium blush is seen in most cases of carotid angioplasty and stenting and depends on the degree of hemodynamic inflow obstruction relieved by stenting. Received: 1 December 2000/Accepted: 10 January 2001