Adverse effects of Sudanese toombak vs. Swedish snuff on human oral cells

J Oral Pathol Med (2010) 39 128–140 Background: The high incidence of oral cancer in Sudan has been associated with the use of toombak, the local type of smokeless tobacco. However, its specific effects on human oral cells are not known. We aimed to investigate the effects of toombak on primary normal human oral keratinocytes, fibroblasts, and a dysplastic oral keratinocytic cell line, and to compare them with the effects induced by Swedish snuff. Method: Aqueous extracts were prepared from moist toombak and Swedish snuff and added in serial dilutions on in vitro monolayer cultured cells. Cell viability, morphology and growth, DNA double‐strand breaks (γH2AX staining), expression of phosphatidylserine (Annexin V staining), and cell cycle were assessed after various exposure time periods. Results: Significant decrease in cell number, occurrence of DNA double‐strain breaks, morphological and biochemical signs of programmed cell death were detected in all oral cell types exposed to clinically relevant dilutions of toombak extract, although to a lesser extent in normal oral fibroblasts and dysplastic keratinocytes. G2/M‐block was also detected in normal oral keratinocytes and fibroblasts exposed to clinically relevant dilutions of toombak extract. Swedish snuff extract had less adverse effects on oral cells, mainly at non‐clinically relevant dilutions. Conclusion: This study indicates a potential for toombak, higher than for Swedish snuff, to damage human oral epithelium. Dysplastic oral keratinocytes were less sensitive than their normal counterparts, suggesting that they might have acquired a partially resistant phenotype to toombak‐induced cytotoxic effects while still being prone to DNA damage that could lead to further malignant progression.     

Transpupillary thermotherapy for choroidal neovascular membrane in age related macular degeneration

PURPOSE: To evaluate the efficacy of transpupillary thermotherapy (TTT) in choroidal neovasularisation (CNVM) secondary to age related macular degeneration (AMD). MATERIAL AND METHODS: Retrospective, non-randomized study of 28 eyes of 28 patients with subfoveal CNVM (classic, occult or mixed) secondary to AMD. RESULTS: Fifteen patients (53.57%) maintained their pre-treatment vision, 2 (7.14%) patients showed improvement of more than 2 lines and 11 (39.28%) patients showed deterioration of vision by >2 lines. Angiographic and clinical regression of CNVM was noted in 19 patients (67.8%) on an average follow up of 15.32 +/- 3.31 months. CONCLUSION: TTT leads to stabilisation of vision in 60% of treated eyes with CNVM due to AMD.     

Cyclooxygenase-2 expression in stromal tumors of the gastrointestinal tract

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid to prostaglandins, prostacyclin, and thromboxane. COX-2 is expressed in many epithelial malignancies, particularly those of the gastrointestinal (GI) tract. COX-2 has been implicated in the pathogenesis of cancers and has a significant negative effect on survival. To date, little is known about the expression of COX-2 in nonepithelial tumors. The objective of this study was to evaluate the expression of COX-2 in GI stromal tumors (GISTs). We evaluated 15 GISTs using tissue microarray. Tissue blocks were retrieved and stained with hematoxylin and eosin to evaluate the histological tumor type. In addition, immunohistochemistry was performed for COX-2, the macrophage marker, CD68 (KP-1), and KIT (CD117). Two pathologists then evaluated the tissues to determine the extent and intensity of COX-2 expression. The location of CD68-positive cells, and whether these cells were COX-2 positive, was also evaluated. The results showed that 80% (12 of 15) of the tumors expressed COX-2. Expression was noted in the cytoplasm of the tumor cells, with variable intensity of staining among the tumors. COX-2 was expressed in both epithelial cell and spindle cell tumors, but appeared stronger in epithelial lesions. In mixed lesions, COX-2 was expressed to a greater extent in epithelial areas. There was a greater extent of COX-2 expression in malignant tumors and tumors located within the stomach. Tumor-infiltrating macrophages (CD68-positive cells) were identified in all of the lesions; in 80% of cases, those macrophages also expressed COX-2. This study is the first to demonstrate COX-2 expression in stromal lesions of the GI tract. The enzyme may play a role in the proliferation of these lesions, suggesting the potential use of nonsteroidal anti-inflammatory drugs in treatment.     

The novel R211Q POP1 homozygous mutation causes different pathogenesis and skeletal changes from those of previously reported POP1‐associated anauxetic dysplasia

Processing of Precursor RNA 1 (POP1) is a core protein component shared by two essential closely related eukaryotic ribonucleoprotein complexes: RNase MRP (the mitochondrial RNA processing ribonuclease) and RNase P. Recently, five patients harboring mutations in POP1 have been reported with severe spondylo‐epi‐metaphyseal dysplasia and extremely short stature. We report a unique clinical phenotype resulting from the novel homozygous R211Q POP1 mutation in three patients from one family, presenting with severe short stature but only subtle skeletal dysplastic changes that are merely metaphyseal. The RNA moiety of the RNase‐MRP complex quantified in RNA extracted from peripheral lymphocytes was dramatically reduced in affected patients indicating instability of the enzymatic complex. However, pre5.8s rRNA, a substrate of RNase‐MRP complex, was not accumulated in patients' RNA unlike in the previously reported POP1 mutations; this may explain the uniquely mild phenotype in our cases, and questions the assumption that alteration in ribosomal biogenesis is the pathophysiological basis for skeletal disorders caused by POP1 mutations. Finally, POP1 mutations should be considered in familial cases with severe short stature even when skeletal dysplasia is not strongly evident.     

Loss of heterozygosity of chromosome 9p and loss of p16INK4A expression are associated with malignant gastrointestinal stromal tumors.

Gastrointestinal stromal tumors GISTs are distinctive KIT-positive mesenchymal neoplasms. The genetic alterations leading to the malignant behavior of these tumors are not well characterized. In this study, 21 cases of GISTs (eight low malignant potential, nine primary malignant and four intra-abdominal recurrences) were characterized by immunohistochemistry and evaluated for loss of heterozygosity of the short arm of chromosome 9, using six microsatellite markers. Loss of heterozygosity with at least one microsatellite marker at 9p region was a common finding in high-risk GISTs (malignant and recurrent group) but was absent in the low malignant potential group. Recurrent GISTs showed more frequent deletions than their primary tumors. All cases with loss of heterozygosity showed deletions at 9p21. Similarly, all low malignant potential GISTs were immunoreactive for p16, whereas malignant tumors were negative for p16. These results suggest that loss of p16(INK4A) gene on 9p may contribute to the progression and/or malignant transformation of GISTs.     

The R172W mutation in peripherin/rds causes a cone-rod dystrophy in transgenic mice

Peripherin/rds (P/rds) is a membrane glycoprotein essential for the photoreceptor outer segment disc morphogenesis and maintenance. More than half of the disease-causing mutations in P/rds have been linked to different forms of macular dystrophy; the most common one is substitution of tryptophan for arginine at position 172 (R172W). Here we confirm the patient phenotype associated with the expression of R172W mutation in transgenic mice. Functional, structural and biochemical analyses showed that, while R172W P/rds is appropriately localized, a direct correlation exists between transgene expression levels and the onset/severity of the phenotype. In the wild-type background, both cone and rod photoreceptors' structure and function were significantly diminished, which indicates a dominant-negative, cone-rod defect. Whereas rds(+/-) mice maintained the normal cone function at early ages, cone responses in R172W/rds(+/-) mice were diminished to 41% of the wild-type level signifying a preferential damaging effect of the mutation on cones. Conversely, R172W/rds(+/-) mice showed a significant rescue of rod function and improvement of rod outer segment structure. Although rds(-/-) mice have no detectable rod or cone responses, R172W/rds(-/-) animals retained 30% of wild-type structure and rod function, but no significant rescue of cone function was detected at 1 month of age. No biochemical abnormalities were observed in complex formation and association with Rom-1; however, R172W protein was more sensitive to tryptic digestion, indicative of a change in protein conformation, possibly contributing to the cone-dominated phenotype. As the first animal model for P/rds-associated cone-rod dystrophy, R172W mice provide a valuable tool for studying the pathophysiology of P/rds-associated human retinal dystrophies and the development of therapeutic strategies to intervene in these diseases.