| 1. |
- Rahman, Anisur, 1962-, et al.
(författare)
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Association of Arsenic Exposure during Pregnancy with Fetal Loss and Infant Death : A Cohort Study in Bangladesh
- 2007
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Ingår i: American Journal of Epidemiology. - : Oxford University Press (OUP). - 0002-9262 .- 1476-6256. ; 165:12, s. 1389-1396
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Tidskriftsartikel (refereegranskat)abstract
- The authors evaluated the effect of arsenic exposure on fetal and infant survival in a cohort of 29,134 pregnancies identified by the health and demographic surveillance system in Matlab, Bangladesh, in 1991-2000. Arsenic exposure, reflected by drinking water history and analysis of arsenic concentrations in tube-well water used by women during pregnancy, was assessed in a separate survey conducted in 2002-2003. Data on vital events, including pregnancy outcome and infant mortality, were collected by monthly surveillance at the household level. The risk of fetal loss and infant death in relation to arsenic exposure was estimated by a Cox proportional hazards model. Drinking tube-well water with more than 50 microg of arsenic per liter during pregnancy significantly increased the risks of fetal loss (relative risk = 1.14, 95% confidence interval: 1.04, 1.25) and infant death (relative risk = 1.17, 95% confidence interval: 1.03, 1.32). There was a significant dose response of arsenic exposure to risk of infant death (p = 0.02). Women of reproductive age should urgently be prioritized for mitigation activities where drinking water is contaminated by arsenic.
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| 2. |
- Vahter, Marie E., et al.
(författare)
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Arsenic exposure in pregnancy : A population-based study in Matlab, Bangladesh
- 2006
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Ingår i: Journal of Health, Population and Nutrition. - 1606-0997 .- 2072-1315. ; 24:2, s. 236-245
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Tidskriftsartikel (refereegranskat)abstract
- This study assessed the exposure of pregnant women to arsenic in Matlab, Bangladesh, an area with highly-elevated concentrations of arsenic in tubewells, by measuring concentrations of arsenic in urine. In a defined administrative area, all new pregnancies were identified by urine test in gestational week 6-8, and women were asked to participate in the assessment of arsenic exposure. Urine for analysis of arsenic was collected immediately and in gestational week 30. In total, 3,426 pregnant women provided urine samples during January 2002-March 2003. There was a considerable variation in urinary concentrations of arsenic (total range 1-1,470 mu g/L, adjusted to specific gravity 1.012 g/mL), with an overall median concentration of 80 mu g/L (25th and 75th percentiles were 37 and 208 mu g/L respectively). Similar concentrations were found in gestational week 30, indicating no trend of decreasing exposure, despite the initiation of mitigation activities in the area. Arsenic exposure was negatively associated with socioeconomic classes and achieved educational level. There were marked geographical variations in exposure. The results emphasize the urgent need for efficient mitigation activities and investigations of arsenic-related reproductive effects.
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| 3. |
- Li, Li, et al.
(författare)
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Nutritional status has marginal influence on the metabolism of inorganic arsenic in pregnant Bangladeshi women
- 2008
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Ingår i: Journal of Environmental Health Perspectives. - : Environmental Health Perspectives. - 0091-6765 .- 1552-9924. ; 116:3, s. 315-321
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The interindividual variation in metabolism of inorganic arsenic (iAs), involving methylation via one-carbon metabolism, has been well documented, but the reasons remain unclear. OBJECTIVES: In this population-based study we aimed to elucidate the effect of nutrition on As methylation among women in Matlab, Bangladesh, where people are chronically exposed to iAs via drinking water. METHODS: We studied effects of macronutrient status using body mass index (BMI) among 442 women in early pregnancy (gestational week 8), and effects of micronutrient status (plasma folate, vitamin B-12, zinc, ferritin, and selenium) among 753 women at gestational week 14. Arsenic metabolites in urine were measured by HPLC combined with hydride generation inductively coupled plasma mass spectrometry. RESULTS: The median concentration of As in urine was 97 mu g/L (range, 5-1,216 mu g/L, adjusted by specific gravity). The average proportions of iAs, monomethylarsonic acid, and dimethylarsinic acid in urine in gestational week 8 were 15%, 11%, and 74%, respectively. Thus, the women had efficient As methylation in spite of being poorly nourished (one-third had BMIs < 18.5 kg/m(2)) and having elevated As exposure, both of which are known to decrease As methylation. The metabolism of iAs was only marginally influenced by micronutrient status, probably because women, especially in pregnancy and with low folate intake, have an efficient betaine-mediated remethylation of homocysteine, which is essential for an efficient As methylation. CONCLUSIONS: In spite of the high As exposure and prevalent malnutrition, overall As methylation in women in early pregnancy was remarkably efficient. The As exposure level had the greatest impact on As methylation among the studied factors.
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| 4. |
- Masud, Mehedi, et al.
(författare)
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A hashing technique using separate binary tree
- 2006
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Ingår i: Data Science Journal. - Paris : Committee on Data for Science and Technology (CODATA) International Council for Science (ICSU). - 1683-1470. ; 5, s. 143-161
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Tidskriftsartikel (refereegranskat)abstract
- It is always a major demand to provide efficient retrieving and storing of data and information in a large database system. For this purpose, many file organization techniques have already been developed, and much additional research is still going on. Hashing is one developed technique. In this paper we propose an enhanced hashing technique that uses a hash table combined with a binary tree, searching on the binary representation of a portion the primary key of records that is associated with each index of the hash table. The paper contains numerous examples to describe the technique. The technique shows significant improvements in searching, insertion, and deletion for systems with huge amounts of data. The paper also presents the mathematical analysis of the proposed technique and comparative results.
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| 5. |
- Rahman, Anisur, 1962-, et al.
(författare)
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Arsenic exposure during pregnancy and size at birth : a prospective cohort study in Bangladesh
- 2009
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Ingår i: American Journal of Epidemiology. - : Oxford University Press (OUP). - 0002-9262 .- 1476-6256. ; 169:3, s. 304-312
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Tidskriftsartikel (refereegranskat)abstract
- The authors evaluated the association of prenatal arsenic exposure with size at birth (birth weight, birth length, head and chest circumferences). This prospective cohort study, based on 1,578 mother-infant pairs, was conducted in Matlab, Bangladesh, in 2002-2003. Arsenic exposure was assessed by analysis of arsenic in urine collected at around gestational weeks 8 and 30. The association of arsenic exposure with size at birth was assessed by linear regression analyses. In analysis over the full range of exposure (6-978 microg/L), no dose-effect association was found with birth size. However, significant negative dose effects were found with birth weight and head and chest circumferences at a low level of arsenic exposure (<100 microg/L in urine). In this range of exposure, birth weight decreased by 1.68 (standard error (SE), 0.62) g for each 1-microg/L increase of arsenic in urine. For head and chest circumferences, the corresponding reductions were 0.05 (SE, 0.03) mm and 0.14 (SE, 0.03) mm per 1 microg/L, respectively. No further negative effects were shown at higher levels of arsenic exposure. The indicated negative effect on birth size at a low level of arsenic exposure warrants further investigation.
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| 6. |
- Rahman, Anisur
(författare)
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Healing of tympanic membrane perforations : an experimental study
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most acute tympanic membrane perforations heal spontaneously without any residual complication, whereas a fraction transforms into a chronic perforation. The current treatment of a chronic perforation is surgical repair, which is a costly, time consuming and uncomfortable procedure particularly for the pediatric patients. The objective of this thesis is to evaluate the underlying mechanisms of the reparative process in acute and chronic perforations. This is done by monitoring the structural and mechanical properties of the tympanic membrane in various situations during healing. Furthermore, an aim is to test the efficacy of stem cells as a healing adjuvant both in acute and chronic perforations. On otomicroscopic examination the reduction of the laser perforation size was evident between day four and five after myringotomy. Histological analysis revealed thickening of the tympanic membrane at and around the myringotomy site at two and four weeks post-myringotomy in light microscopic sections. Transmission electron microscopic sections revealed a five-fold thickness increase in the lamina propria. Proliferation of fibroblasts and accumulation of large amounts of extra-cellular substances suggests an attempt of the body s reparative mechanism to revert the damage. The lamina propria is thickened still at six months after myringotomy. The fibers of the lamina propria are loosely packed with seemingly unorganized orientation. These findings suggest that the healing process is not yet finished after half a year. A striking histological feature was the larger thickening increase in the lamina propria of the tympanic membranes that were treated with stem cells, as compared to the untreated. Growth factors or other secreted substances from the stem cells might have influenced the proliferation of fibroblasts and the production of extra-cellular substances to contribute to this accentuated thickness. An in vitro model in the rat was developed and adjusted for moiré interferometry measurements in order to assess the stiffness of normal and healed myringotomized tympanic membranes. Moiré interferometry is an optical, non-contacting technique by which the shape and pressure-produced displacement of an object can be measured. This method provides a full-field, 3-dimensional, overall stiffness change along with local stiffness variation of different portions of the tympanic membrane. The stiffness of myringotomized and healed tympanic membranes is almost normal already at two weeks after myringotomy. A huge over-production of fibers during the proliferative phase of the healing seem to limit the damage caused by the myringotomy and thus provide extra strength to this area of reorganization. Long-term measurement of the myringotomized and healed tympanic membranes showed slightly reduced strength as compared to normal. Acute perforations treated with mouse embryonic stem cells did not show any enhanced healing as compared to untreated. Teratoma, which is a known complication to embryonic stem cell treatment, was not detected in any of the ears after a follow-up time of six months. The use of human mesenchymal stem cell treatment on chronic perforations showed better healing as compared to the untreated. Thus, it appears to be of great importance to continue to study this type of stem cells in the treatment of chronic tympanic membrane perforations.
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| 7. |
- Rahman, Anisur, et al.
(författare)
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Healing time, long-term result and effects of stem cell treatment in acute tympanic membrane perforation
- 2007
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Ingår i: International Journal of Pediatric Otorhinolaryngology. - : Elsevier BV. - 0165-5876 .- 1872-8464. ; 71:7, s. 1129-1137
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Tidskriftsartikel (refereegranskat)abstract
- Objective The incidence of otitis media in children between the age of 2 and 6 years is well documented. Repeated attacks may cause acute and chronic perforations. The surgical treatment for repairing chronic perforation is quite uncomfortable for the patients of this age group because of the invasiveness of this treatment. The aim of this study was to determine the long-term influence of embryonic stem cells on acute perforations and the effect of gelatin as a vehicle for applied stem cells. The possibility of teratogenic effects of the stem cells was also observed. Methods Bilateral laser myringotomy was performed in 17 adult Sprague–Dawley rats, divided into two groups. Gelatin, a substance suitable as vehicle for bioactive material was used bilaterally around the perforation in group A, to serve as a scaffold for repairing tissue. The stem cells were used in the right tympanic membrane perforation leaving the left tympanic membrane as a control. The animals in group B received the same treatment except for the use of gelatin and in addition received an immuno-suppressive agent. After half a year of observation the mechanical stiffness of the tympanic membrane was measured by moiré interferometry for group B and the morphological study was performed by light microscopy for both groups A and B and electron microscopy for group A. Results Stem cell treated ears did not show any enhanced healing of the perforation although a marked thickening of the lamina propria was observed compared with control group. After half a year the strength and the stiffness of the tympanic membrane was almost the same for both treated and untreated ears. No evidence of teratoma was found after half a year. Conclusion This study suggests that the stem cells stimulate the proliferation of connective tissue and fibers in the lamina propria, possibly mediated by secreted substances, although the stiffness properties do not seem to be altered. The use of gelatin does not seem to enhance the healing process of the tympanic membrane perforation.
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| 8. |
- Rahman, Anisur, 1962-
(författare)
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Prenatal Arsenic Exposure and Consequences for Pregnancy Outcome and Infant Health : Epidemiological Studies in Bangladesh
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to analyse possible effects of prenatal arsenic exposure on foetal and infant health. The setting is Bangladesh, where two cohorts were studied, both part of a health and demographic surveillance system in Matlab. A historical cohort 1991-2000 included 29,134 pregnant women with information on drinking water sources and arsenic testing of tube well water. A prospective cohort study included pregnant women 2002 - 2003 where urinary arsenic concentrations were assessed twice during pregnancy; 2,924 women and their pregnancy outcomes were evaluated for foetal loss, perinatal and infant mortality; 1,578 mother-infant pairs were analysed for size at birth; and 1,552 were analysed for morbidity during infancy. Women exposed to arsenic levels ≥ 50 µg/L in water had an increased risk of foetal loss and infant death in comparison with women exposed to arsenic levels < 50 µg/L. These findings were confirmed in the prospective cohort study. Women with urine arsenic concentrations at the 5th quintile had 62% increased risk of spontaneous abortion (OR 1.62, 95% CI 1.04 - 2.55) in comparison with women who had arsenic concentrations at the 1st quintile level. Increased risks of perinatal morality (RR 3.01, 95% CI 1.07 - 8.45) and infant mortality (RR 5.01; 95% CI: 1.41 - 17.84) were also observed at the 5th quintile of exposure. Significant negative dose-effect associations were found between arsenic exposure and birth weight, head and chest circumferences at a relatively low level of exposure (<100 µg/L in urine). In this range of exposure birth weight decreased by 1.68 g (SE 0.62) for each 1 µg/L increase of arsenic in urine. In comparison with exposure at the 1st quintile level the risk of lower respiratory tract infection was significantly increased (RR 1.68, 95% CI 1.35-2.07) for women who had urinary arsenic concentrations at the 5th quintile level. The risk was also increased for diarrhoeal diseases. The study findings highlight the negative effects of arsenic exposures on pregnancy outcomes and infant health. Mitigation programs need to be strengthened and women of reproductive ages should be prioritized in arsenic affected regions worldwide.
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| 9. |
- Rahman, Anisur, et al.
(författare)
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Stem cells and enhanced healing of chronic tympanic membrane perforation
- 2008
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Ingår i: Acta Oto-Laryngologica. - : Informa Healthcare. - 0001-6489 .- 1651-2251. ; 128:4, s. 352-359
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Tidskriftsartikel (refereegranskat)abstract
- CONCLUSIONS:Important information about the basic reparative process of tympanic membrane (TM) healing is shown, which can be incorporated for further clinical understanding. This provides a basis for the exploration of stem cell treatment for TM perforations and holds promise for future improvements.OBJECTIVES:This study aimed to analyse the healing of TM perforation by using stem cells and the stiffness of the membrane was tested in an acute and long-term study.MATERIALS AND METHODS:Sprague-Dawley rats were used in a model of TM perforation. The perforation was performed with a laser system. Stem cells were applied and the healing time and morphological analysis were performed with light and transmission electron microscope. Stiffness was examined by moiré interferometry.RESULTS:The stiffness of the perforated and healed TM was restored after just 2 weeks. In the chronic perforation model, mesenchymal stem cells enhanced the healing.
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| 10. |
- Rahman, Anisur, et al.
(författare)
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Structural and functional properties of the healed tympanic membrane : a long-term follow-up after laser myringotomy
- 2007
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Ingår i: Otology and Neurotology. - 1531-7129 .- 1537-4505. ; 28:5, s. 685-691
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: The short-term healing scar that forms after experimental laser myringotomy will revert to a normal lamina propria in the long run. The mechanical stiffness will stay normal. Background: Recent studies have shown severe structural changes in the fibrous layer in the early course after experimental laser myringotomy, whereas the scar quickly restored the strength of the tympanic membrane (TM). A reorganization of the fiber layer is expected to occur. Methods: Potassium titanyl phosphate laser myringotomy was made on one side of the TM in Sprague-Dawley rats. The ear of the other side was untouched and used for control. After half a year of observation, the stiffness and strength of the healed TMs were measured with moiré interferometry and examined with otomicroscopy and light and electron microscopy. Results: The interferometry readings showed a slightly reduced strength in the myringotomized and healed TMs. After half a year, still there were immense structural changes including increased thickness over a wide area of the pars tensa with increased amounts of fibers. An obvious reorganization of the fiber layer was lacking. Conclusion: Laser myringotomy causes profound, long-standing, or permanent structural changes in the lamina propria of the pars tensa, whereas the strength of the TM may become slightly reduced.
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