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Biomedical subjects

D B Das

Publications and source records attributed to D B Das.

17 recordsLinked to original sources
PubMed2006

3D bone tissue growth in hollow fibre membrane bioreactor: implications of various process parameters on tissue nutrition.

New experimental evidence shows that hollow fibre membrane bioreactor (HFMB) may be applied to grow bulky bone tissues which may then be implanted into patients to repair skeletal defects. To design effective bone tissue engineering protocols, it is necessary to determine the quantitative relationships between the cell environment and tissue behaviour in HFMBs and their relationship with nutrient supply. It is also necessary to determine under what conditions nutritional limitations may occur and, hence, may cause cell death. These require that the appropriate bioreactor conditions for generating neotissues, and the nutrient transfer behaviour and chemical reaction during cell growth and extracellular matrix formation are studied thoroughly. In this paper, we aim to use an existing mathematical framework to analyse the influence of various relevant parameters on nutrient supply for bone tissue growth in HFMB. We adopt the well-known Krogh cylinder approximation of the HFMB. The model parameters (e.g., cell metabolic rates) and operating conditions for the mathematical model have been obtained from, or correspond to, in-house experiments with the exception of a few variables which have been taken from the literature. The framework is then used to study oxygen and glucose transport behaviour in the HFMB. Influence of a number of important process parameters, e.g., reaction kinetics, cell density, inlet concentration of nutrients, etc, on the nutrient distributions have been systematically analysed. The work presented in this paper provides insights on unfavourable system designs and specifications which may be avoided to prevent mass transfer limitations for growing bone tissues in HFMB.

Bioreactors↗
PubMed2002

Development of a new mathematical model for subsurface water quality management.

The interfaces between free (e.g., groundwater) and porous (e.g., soil) flow zones in the subsurface represent important transition zones across which many important transfer/exchange processes occur. The understanding of these interactive phenomena and the way these regions behave in combination is, therefore, critical for management of subsurface water quality. Indispensable to this is numerical modelling and simulation as they can handle complex flow domains and minimise the analysis cost and time. In the present work, the hydrodynamic conditions for a combined free and porous flow domain in the subsurface are analysed. An investigation into the fluid dynamical behaviour for different aspect ratios of the domains is of most interest.

Conservation of Natural Resources↗
PubMed2001

Development of an effluent discharge policy for the Tay Estuary based on a finite element model.

The tidal hydrodynamics and effluent distribution in estuaries involve a complicated range of solute transport phenomena modelled by partial differential equations. Therefore, the quantitative estimation of the risks of water and soil contamination of coastal areas as a result of polluted estuary flows, or effects of the effluent input on the chemical loads, involves the solution of these equations. Generally, the pollutants load in an estuary is determined by the nature of land use which by altering the watershed hydrology or chemical detention/release in the river banks affect the water quality of the estuaries. The present modelling work aims to investigate the solute transport behaviour in the Tay Estuary in Scotland. Based on this study, an attempt to devise an estuary specific discharge strategy for the Tay has been made. The numerical calculations are based on using 2D Galerkin finite element discretisation of the governing equations in an Eulerian co-ordinate system. The flexibility of the formulation allows it to be extended to moving boundary situations encountered in most tidal water systems.

Environmental Monitoring↗
PubMed2001

LANDFLOW: a 3D finite volume model of combined free and porous flow of water in contaminated land sites.

Free and porous flow of water in lands often occurs in combination under different physical circumstances. To model such configurations, open and porous flow regions need to be studied independently and also to integrate them through well-posed mathematical formulations. This paper presents a computational investigation (modelling and simulation) on flow of water and contaminants' mobility in soil. The governing partial differential equations of the flow were discretised and reduced to algebraic forms by finite volume method for simulation purposes. Dirichlet boundary conditions were used at the inlet. For sidewalls, no slip conditions were imposed while for the outer boundary, stress free boundary conditions were used.

Algorithms↗
PubMed1999

Anaemia in acute, Plasmodium falciparum malaria in children from Orissa state, India.

The severity of anaemia associated with acute, Plasmodium falciparum malaria and the extent to which haemolysis, bone-marrow suppression, and pre-existent iron deficiency contribute to the anaemia were assessed in 102 Indian children aged 2-12 years. Blood haemoglobin (Hb), plasma unconjugated bilirubin and haptoglobin, serum iron and transferrin concentrations and transferrin saturation, red cell morphology and reticulocyte response were investigated in the patients and in 50 control children. Twenty-three patients with severe anaemia (< 70 g Hb/litre) were investigated further, by bone-marrow biopsy followed by iron staining of sections or touch smears of the biopsy material. There was evidence of haemolysis in the malaria cases: in the peripheral blood smears and the significantly higher plasma concentrations of unconjugated bilirubin, lower plasma concentrations of haptoglobin and lower blood concentrations of Hb than those seen in the controls. Haemoglobin concentration correlated directly with haptoglobin (r = 0.489; P < 0.001) and inversely with unconjugated bilirubin in malaria patients (r = -0.526; P < 0.001) but not in controls (r = -0.140 and -0.061, respectively). Parasitaemia (parasites/microliter) was not significantly correlated with Hb, haptoglobin or unconjugated bilirubin. Compared with the earlier samples, follow-up samples from the patients, collected 2 weeks after discharge from hospital and antimalarial therapy, showed significant increase in Hb, haematocrit, haptoglobin and decreases in both total and unconjugated bilirubin. There was evidence of hypercellularity and mild-moderate erythroid hyperplasia, mainly of normoblastic maturation with adequate reticulocyte response, in the bone-marrow samples from the cases of severe anaemia; dyserythropoiesis was only noticed in one case and no stainable iron was detectable in 17 of the 23 cases. These observations indicate that haemolysis is the prime cause of the anaemia seen in acute falciparum malaria, although destruction of parasitised erythrocytes is not the sole cause of the haemolytic process. Bone-marrow suppression appears to have an insignificant role but pre-existent iron deficiency aggravates the severity of the anaemia.

Acute Disease↗
PubMed1997

Influence of malaria on markers of iron status in children: implications for interpreting iron status in malaria-endemic communities.

To investigate Fe nutritional indices in malaria infection in children, haematology (blood haemoglobin, plasma ferritin, transferrin, Fe, and transferrin saturation), acute phase markers (albumin and caeruloplasmin) and liver function tests were studied in fifty consecutive cases of severe and mild falciparum malaria, fifty matched controls and twenty-three cases of asymptomatic malaria. Blood haemoglobin and transferrin were lower, while ferritin and transferrin saturation were higher, in groups with symptomatic malaria in comparison with the control group. The differences were greatest with the severest form of the disease. There were no differences between any of the groups in plasma Fe. Plasma transferrin correlated directly with albumin in asymptomatic, mild and severe malaria groups (r 0.48, 0.65 and 0.83; P < 0.05, P < 0.05, P < 0.01 and P < 0.001 respectively), and inversely with caeruloplasmin (r -0.65, -0.34 and -0.43; P < 0.01, P < 0.05 and P < 0.01 respectively). For ferritin, the correlation was inverse with albumin (r -0.65, -0.57 and -0.64; P < 0.01, P < 0.001 and P < 0.001 respectively and direct with caeruloplasmin (r 0.83, 0.21 and 0.49, P < 0.001, NS and P < 0.001 respectively). Multiple regression analysis on data from all patients combined indicated that albumin, and to a lesser extent alanine aminotransferase (EC 2.6.1.2) activity, explained 62 % of the variance in transferrin. Caeruloplasmin, parasite count and albumin explained 59 % of the variance in ferritin, and transferrin and unconjugated bilirubin explained 62 % of the variance in Fe values. In conclusion, these data suggest that low transferrin and high ferritin values are primarily due to the acute phase response. High transferrin saturation and lack of differences in plasma Fe between the groups are probably due to Fe released from lysed erythrocytes. Finally, in both symptomatic and asymptomatic malaria, indices of Fe status can be misleading and may be especially problematic in community studies in malaria-endemic areas where asymptomatic malaria may be common.

Acute Disease↗
PubMed1996

Plasma alpha-tocopherol, retinol, and carotenoids in children with falciparum malaria.

Cross-sectional interactions by malaria status were investigated between plasma alpha-tocopherol, retinol, and several carotenoids (lutein, beta-cryptoxanthin, lycopene, and alpha- and beta-carotene) and indicators of disease severity (blood parasite count, hemoglobin concentration), acute-phase response (plasma albumin and ceruloplasmin concentrations), hepatic involvement (plasma alanine aminotransferase), oxidant status and antioxidant status (plasma thiobarbituric acid-reactive material and ascorbate), nutritional (weight-for-age) and carrier protein [retinol binding protein (RBP)] status, and cholesterol concentration (as a proxy for lipoprotein) in 100 consecutively admitted children with malaria. There were 50 children with severe and 50 with mild malaria and 50 age- and sex-matched control subjects. alpha-Tocopherol, retinol, and all the carotenoid concentrations were lower in the patients than in the control subjects (P < 0.001). The differences were greater in severe than in mild malaria, except for lutein. In severe malaria only, both retinol and alpha-tocopherol correlated with albumin, ceruloplasmin, and RBP concentrations whereas in all three groups retinol correlated with RBP and alpha-tocopherol correlated with cholesterol (all P < 0.01)). Using multivariate analysis on data from all patients combined, cholesterol was the most significant factor explaining the variance in alpha-tocopherol (29%) whereas RBP was responsible for 95% of the variance in retinol. Plasma cholesterol and RBP values in turn (in the absence of alpha-tocopherol and retinol, respectively) were influenced primarily by acute-phase markers (mainly albumin and ceruloplasmin). Alanine aminotransferase (r = -0.17) and thiobarbituric acid-reactive material (r = -0.17) also showed a small contribution to the variance of RBP but 60-70% remained unexplained. In conclusion, low plasma lipid-soluble micronutrient concentrations in malaria are strongly influenced by the reductions in their carrier molecules, which, in turn, are low as a consequence of the acute-phase response.

Carotenoids↗
PubMed1992

Incidence of hypoglycaemia in children with severe Plasmodium falciparum malaria around Rourkela, Orissa state.

To determine the incidence of hypoglycaemia in children suffering from severe falciparum malaria, 23 patients from Rourkela (Orissa), were investigated. Plasma glucose and immunoreactive insulin were estimated before and at hourly intervals during quinine infusion. No child had hypoglycaemia at the time of admission. Correlation between parasite count and prequinine plasma glucose was not significant. In the period of quinine infusion, 20 patients showed fall in plasma glucose during all the three hours (P less than 0.05, P less than 0.01, P less than 0.01 at the end of 1st, 2nd, and 3rd h respectively) but the decrease to hypoglycaemic level (plasma glucose less than or equal to 40 mg/dl) was observed in only one child. Concomitant increase in plasma insulin was noticed in 18 of these patients. Decrease in plasma glucose and increase in plasma insulin was found to correlate well (r-0.78, P less than 0.001). Hypoglycaemia was found to be an infrequent complication of severe falciparum malaria in children from the area studied. Though decrease in plasma glucose was observed after quinine infusion, it was less severe and did not reach the hypoglycaemic level.

Blood Glucose↗
PubMed1990

Secular trend in birthweight in an industrial hospital in India.

Measurement of birthweight is an indicator of community health. The mean birthweight (MBW) of babies born in 1963, 1983 and 1986 were measured in 2254, 3550 and 3368 babies, respectively. Mean (SD) birthweight was found to be 2652 (553) g in 1963, 2724 (502) g in 1983 and 2726 (478) g in 1986. There was a rise in MBW (72 g) between 1963 and 1983 and a reduction in the percentage incidence of low birthweight from 34.29% to 26.06%. A change in birthweight distribution (was also seen, except in extreme weight groups. The improvement in birthweight is statistically significant (p less than 0.001). A trend for increase has been noticed in birthweights, and the mean birthweight values are the same as the national average.

Age Factors↗
PubMed1990

Increased plasma lipid peroxidation in riboflavin-deficient, malaria-infected children.

Plasma lipid peroxides were measured as malonyldialdehyde (MDA) by the thiobarbituric acid (TBA) method in 75 children suffering from Plasmodium falciparum malaria. Their riboflavin status was assessed by measuring erythrocyte glutathione reductase activation coefficients (EGRACs), and values greater than 1.40 were regarded as indicating biochemical deficiency. Plasma MDA was higher (p less than 0.001) in patients than in control subjects; the concentrations were 3.65 +/- 0.70 and 1.77 +/- 0.45 mumol/L (means +/- SD), respectively. The riboflavin-deficient group had higher plasma MDA values (3.98 +/- 0.70 mumol/L) than did the nondeficient group (3.30 +/- 0.68 mumol/L, p less than 0.001). Plasma MDA concentrations correlated with EGRACs (r = 0.46, p less than 0.01) in the patients. It is proposed that riboflavin deficiency restricts regeneration of reduced glutathione making the parasitized erythrocytes more vulnerable to destructive lipid peroxidation and increasing plasma lipid hydroperoxides.

Animals↗
PubMed1988

Riboflavin deficiency and severity of malaria.

The riboflavin status of 64 children suffering from malarial infection was assessed by measuring the activation coefficient of erythrocyte glutathione reductase. Thirty-five children were found to be deficient in riboflavin whereas in 29 children riboflavin status was within the normal range. The median parasite count and its range on admission in the deficient group (2.7 per cent, range 0.3-13.6) was lower than that in the non-deficient group (5.3 per cent, range 0.6-30.2). The correlation between activity coefficient and parasite count was significant (R = -0.49). The recovery process was slower in the deficient group even though they had a relatively lower parasite count. It is inferred that riboflavin deficiency leads to inhibition of growth and multiplication of plasmodia. Its beneficial effects in malaria infection needs further evaluation.

Animals↗