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Biomedical subjects

A M Das

Publications and source records attributed to A M Das.

At least 19 recordsLinked to original sources
PubMed2006

Vaso-occlusion in Schimke-immuno-osseous dysplasia: is the NO pathway involved?

Schimke-immuno-osseous dysplasia (SIOD) is an autosomal recessive disorder with the main clinical findings of spondyloepiphyseal dysplasia, nephrotic syndrome, and defective cellular immunity. Vaso-occlusive processes, especially generalized atherosclerosis, are a life-limiting complication in patients with severe SIOD. The nitric oxide synthase (NOS) oxidizes L-arginine to nitric oxide (NO). NO is a potent vasodilator with inhibitory effects on platelet aggregation and the development of atherosclerosis. We hypothesized that reduced NO production due to antagonism of NOS by asymmetric dimethylarginine (ADMA) would be a possible pathophysiological mechanism for vaso-occlusion in SIOD. We tested this hypothesis in 10 patients with SIOD and 10 age-matched healthy controls. Plasma and urine levels of nitrite and nitrate, the indicators of NO synthesis, and of ADMA, an endogenous NOS inhibitor, in children suffering from SIOD were not significantly different from those in the age-matched healthy controls. Our results suggest that the L-arginine/NO pathway is not altered in SIOD. Antagonism of NOS by ADMA does not seem to be the cause of premature general atherosclerosis in SIOD. The underlying pathology of vaso-occlusion in SIOD still remains unclear.

Adolescent↗
PubMed2006

Biopharmaceutical therapeutics for asthma remodeling.

Current asthma therapy is aimed at controlling disease symptoms. A subset of asthma patients remains symptomatic despite optimal therapy indicating that an unmet medical need exists for these patients. Innovative therapeutics are needed to treat the unmet need in asthma and biopharmaceutical approaches may provide an opportunity for identifying these agents. It is proposed that airway remodeling contributes to asthma symptoms and this feature of disease pathology may be a target for future therapies. The current review focuses on the contribution of one feature of airway remodeling, subepithelial fibrosis, towards disease and highlights some of the mechanisms that may contribute to this feature of airway remodeling. Further, some potential molecular targets are identified for consideration for therapeutic intervention.

Animals↗
PubMed2006

Role of chemokines in severe asthma.

The severe asthma phenotype is exhibited by a subset of asthma patients whose asthma symptom is poorly controlled by current therapies. Severe asthma represents a high unmet medical need and warrants research into the mechanisms driving the underlying pathophysiology. It is hypothesized that the underlying pathology associated with severe asthma is driving the symptoms experienced by these patients, which may share common features with mild to moderate asthma or may represent a unique pathological phenotype. For the purpose of this review, the pathophysiology associated with asthma in general are described and extended to incorporate severe asthma. Chemokines may contribute towards multiple features of asthma pathophysiology and this current review focuses on the biology of chemokines pertaining to asthma pathophysiology. Chemokines are important recruiters and activators of inflammatory cells and these infiltrating cells interact with resident cells, such as fibroblasts and it is through these pathways that chemokines appear to exert multiple biological actions. Clinical trials are underway with therapeutics targeting chemokine pathways for other inflammatory diseases. It is hoped that the information generated from these studies will contribute towards furthering our understanding of chemokine biology and be applied towards targeting severe asthma.

Animals↗
PubMed2004

Branched chain amino acids as a parameter for catabolism in treated phenylketonuria.

This study was performed to study an association between nutritional status on one hand and BCAA- and Phe-concentrations on the other hand in PKU patients free of infection. AA profiles from 70 PKU patients were measured. 9 patients (subgroup I) with elevated Phe- and BCAA-concentrations as well as 23 patients (subgroup II) with only elevated Phe-levels were included. Dietary records were obtained from both groups; low caloric intake in subgroup I was increased with Duocal or p-am ANAMIX without modifying total protein- and Phe-intake. AA profiles were controlled after 2 weeks. Additionally, we investigated AA profiles from 26 liver transplanted patients with increased carbohydrate and caloric intake as an example for anabolism. In subgroup I Phe- and Isoleu-concentrations decreased sign. After dietary intervention. Leu, Val and Tyr levels decreased not sign. Initial Phe-levels correlated negatively with protein and caloric intake. BCAA concentrations of liver transplanted patients receiving high amounts of carbohydrates were in the lower range of normal. Increased caloric intake lowered most of the elevated Phe- and BCAA- concentrations.

Adolescent↗
PubMed2004

Agenesis of the corpus callosum, abnormal genitalia and intractable epilepsy due to a novel familial mutation in the Aristaless-related homeobox gene.

Mutations in the Aristaless-related homeobox (ARX) gene are associated with a broad spectrum of disorders including X-linked lissencephaly with abnormal genitalia (XLAG) and absent corpus callosum. Here, we describe a family with two male infants suffering from agenesis of the corpus callosum (ACC), intractable epilepsy, and abnormal genitalia. The phenotype of both affected patients differed in severity of the cerebral malformation with one showing no obvious evidence for lissencephaly. Both infants lacked any psychomotor development and died at the age of 17 weeks and 18 months, respectively. Genetic analysis of the ARX gene revealed a novel frameshift mutation in exon 4 (nt1419_1420insAC) leading to a shortened protein lacking the aristaless domain. In summary, analysis of the ARX gene should not only be considered in male patients with typical features of XLAG but also in those presenting with early onset epilepsy, ACC, and abnormal genitalia without obvious neuroradiological features of lissencephaly.

Abnormalities, Multiple↗
PubMed2003

Glutaric aciduria I: creatine supplementation restores creatinephosphate levels in mixed cortex cells from rat incubated with 3-hydroxyglutarate.

The pathogenesis of neurological sequelae in glutaric aciduria I (GA I) is still unclear. Some evidence exists for compromised energy generation in the brain of patients with GA I resulting in 'slow-onset' excitotoxicity. Previously, we have shown a reduced activity of the mitochondrial ATPsynthase in cultured mixed cortex cells from neonatal rats incubated with 2-4mM 3-hydroxyglutarate (3-OH glut) for 24h. In the present study we measured cellular contents of high energy phosphate compounds (creatinephosphate CP, ATP, and ADP) in this model after a 24h incubation period with 2-4mM glutarate (glut) or 3-OH glut. 3-OH glut specifically led to a reduction of CP content in a dose-dependent manner, whereas concentrations of ATP, ADP, and AMP remained unchanged. The drop in CP-concentration could be prevented by preincubation with the non-competitive NMDA-receptor antagonist MK 801 or coincubation with 1mM creatine. NMDA-receptor associated ion channels may be opened due to a lack of energy inside the neurons caused by a reduction of CP. This is followed by membrane depolarization which could impair electrogenic creatine transport into the cell.

Adenine Nucleotides↗
PubMed2002

Mitochondrial dysfunction in the neuronal ceroid-lipofuscinoses (Batten disease).

There are at least eight genetic entities known as the ceroid-lipofuscinoses in humans which share clinical and pathological features that have caused them to be grouped together under the eponym of Batten disease. They present pathologically as lysosomal storage diseases but are also characterised by severe neurodegeneration. Although the biochemical defects appear primarily centred on lysosomes and defects in proteolysis, the link between this and pathogenesis of neuronal death is poorly understood. The pathogenesis of neurodegeneration has been studied particularly in two animal models these being the English setter dog and the New Zealand Southhampshire sheep (OCL6). In these, and some of the human entities, there is evidence of mitochondrial dysfunction. This includes the accumulation of subunit c of ATP synthase as a component of storage material in at least six of eight genetic forms of the disease; structural abnormalities of mitochondria and selective loss of neurons in areas of the brain that are particularly metabolically active. Direct evidence of dysfunction comes from mitochondrial function tests in fibroblasts and, in animal models, isolated liver mitochondria. Supporting evidence of mitochondrial dysfunction was shown by disturbances in proportions of energy-rich phosphates in fibroblasts in some of these diseases. If these various defects were reflected in neurons, then it would support the hypothesis that neuron death was associated with energy-linked excitotoxicity.

Animals↗
PubMed2001

Morphological alteration of peritoneal mast cells and macrophages in the mouse peritoneal cavity during the early phases of an allergic inflammatory reaction.

We investigated the presence of mast cell granules in macrophages following an in vivo model of an allergic reaction. Injection of ovalbumin (100 microg) into the peritoneal cavity of sensitised mice produced a rapid (within 2 h) influx of neutrophils followed by a slower (after >4 h) eosinophil migration. Ovalbumin treatment induced a high incidence (approximately 50%) of mast cell degranulation compared to control phosphated-buffered saline-treated mice. The majority (approximately 90%) of peritoneal macrophages contained mast cell granules as early as 2 h post-ovalbumin, with lower values at later time-points, as determined by staining with Toluidine blue and Berberine sulphate. This was confirmed by electron microscopy which enabled us to identify the complex mast cell granule sub-structural components in macrophage phagosomes. In conclusion, we used histochemical and ultrastructural analyses to show that mast cell granules become internalised with macrophages during the early stages of an experimental allergic reaction.

Animals↗
PubMed2001

Altered levels of high-energy phosphate compounds in fibroblasts from different forms of neuronal ceroid lipofuscinoses: further evidence for mitochondrial involvement.

The pathogenesis of neurodegeneration in neuronal ceroid lipofuscinosis (NCL) is still not clear despite progress in mutation analysis of these diseases. We have recently observed anomalies at the level of the mitochondrial ATPsynthase (complex V of the respiratory chain) in fibroblasts from children with CLN1, CLN2, CLN3 and in an ovine model (OCL6). The measurements were carried out in vitro. If these alterations were of relevance in vivo as well, contents of high-energy phosphate compounds should be reduced. In the present study, we measured levels of creatine phosphate (CP), ATP, ADP and AMP in fibroblasts from children with CLN1, CLN2, CLN3 and in OCL6. ATP was reduced to about 50% of normal in CLN1, CLN2 and CLN3, ADP was about 30% of normal in these cells, and CP was 50% of normal in CLN1 and CLN2 but remained normal in CLN3. In fibroblasts of NCL-sheep, however, CP and ADP were increased to 690% and 220% of normal, respectively, while ATP remained normal. If the anomalies found in cellular energy metabolism in fibroblasts were expressed in neurons from NCL patients and NCL sheep 'slow-onset excitotoxicity' could occur leading to cellular dysfunction and eventually to cell death.

Adenosine Diphosphate↗
PubMed2000

Secondary respiratory chain defect in a boy with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: possible diagnostic pitfalls.

UNLABELLED: We report on a boy who suffered from microcephaly, growth retardation, cardiomyopathy and hepatic dysfunction. When he had his first febrile infection at the age of 3 months he showed metabolic decompensation. Laboratory parameters and clinical features were compatible with a beta-oxidation defect or a respiratory chain disorder. Measurement of beta-oxidation enzymes showed long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency; determination of respiratory chain complex activities revealed complete absence of complex I, II, III and IV activities in skeletal muscle and reduced activities of complexes II and IV in cultured fibroblasts, with secondary dysregulation of ATP synthase. The patient was found to be homozygous for the MTP:G1528 C mutation (LCHAD-deficiency). CONCLUSION: This patient had LCHAD deficiency as his primary metabolic disorder, leading to secondary inhibition of respiratory chain enzymes by 'toxic' metabolites.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2000

Glucocorticoid receptor activation reduces CD11b and CD49d levels on murine eosinophils: characterization and functional relevance.

In vitro incubation of mouse blood eosinophils with dexamethasone (DEX) resulted in concentration- and time-dependent reduction in CD11b and CD49d cell-surface expression as detected by flow cytometry. This inhibitory effect ranged between 20 and 40% for both integrins, and it was not related to alteration of cell survival. DEX was maximally effective at 1 microM, and it was prevented by coaddition of the glucocorticoid receptor antagonist RU486 (mifepristone; 10 microM). Budesonide, hydrocortisone, and prednisolone, but not the sex steroids testosterone and progesterone, reduced CD11b and CD49d cell-surface expression to a similar extent. Subchronic treatment of mice with 1 mg/kg DEX again reduced both CD11b and CD49d expression on circulating eosinophils, without alterations in CD11b messenger RNA expression as assessed by polymerase chain reaction analysis. In contrast, membrane but not intracellular protein expression of either CD11b or CD49d was inhibited by eosinophil incubation with DEX in vitro; thus, an interference with exportation of these adhesion molecules to the cell surface is proposed as the mechanism of action of the glucocorticoid. Finally, steroid effects on integrin expression were linked to a reduced eosinophil function as indicated by a lower degree of cell chemotaxis after incubation with DEX, an effect which was again prevented by 10 microM RU486. These observations may explain part of the therapeutic efficacy displayed by glucocorticoid hormones in the clinical control of tissue eosinophilia in allergic disease conditions.

Animals↗
PubMed1999

Regulation of macrophage inflammatory protein-1 alpha expression and function by endogenous interleukin-10 in a model of acute inflammation.

In this study we have determined the role of endogenous interleukin (IL)-10 on leucocyte recruitment and production of the CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) in a murine model of acute inflammation. Intraperitoneal injection of zymosan produced a dose-dependent cellular infiltration which was concomitant with MIP-1alpha release in the lavage fluids. Release of this chemokine had a functional role since treatment of mice with a specific anti-MIP-1alpha antibody reduced both neutrophil and monocyte accumulation into the peritoneal cavity. An unexpected increase in cell influx and MIP-1alpha production was measured following depletion of resident peritoneal macrophages, as achieved by a 3-day liposome treatment. A similar result was obtained when the zymosan peritonitis response was elicited in IL-10 knock-out mice. In summary we propose a functional cross talk between endogenous IL-10 and this CC chemokine during the host inflammatory response.

Acute Disease↗
PubMed1999

Role of resident peritoneal macrophages and mast cells in chemokine production and neutrophil migration in acute inflammation: evidence for an inhibitory loop involving endogenous IL-10.

The roles played by resident macrophages (Mphi) and mast cells (MCs) in polymorphonuclear leukocyte (PMN) accumulation and chemokine production within the mouse peritoneal cavity in response to administration of zymosan (0.2 and 1 mg), LPS (1 mg/kg), and thioglycolate (0.5 ml of a 3% suspension) were investigated. A marked reduction (>95%) in intact MC numbers was obtained by pretreatment with the MC activator compound 48/80, whereas resident Mphi were greatly diminished (>85%) by a 3-day treatment with liposomes encapsulating the cytotoxic drug dichloromethylene-bisphosphonate. No modulation of thioglycolate-induced inflammation was seen with either pretreatment. Removal of either MCs or Mphi attenuated LPS-induced PMN extravasation without affecting the levels of the chemokines murine monocyte chemoattractant protein-1 and KC measured in the lavage fluids. In contrast, MC depletion inhibited PMN accumulation and murine monocyte chemoattractant protein-1 and KC production in the zymosan peritonitis model. Removal of Mphi augmented the accumulation of PMN elicited by the latter stimulus. This was due to an inhibitory action of Mphi-derived IL-10 because there was 1) a time-dependent release of IL-10 in the zymosan exudates; 2) a reduction in IL-10 levels following Mphi, but not MC, depletion; and 3) an increased PMN influx and chemokine production in IL-10 knockout mice. In conclusion, we propose a stimulus-dependent role of resident MCs in chemokine production and the existence of a regulatory loop between endogenous IL-10 and the chemokine-mediated cellular component of acute inflammation.

Animals↗
PubMed1999

Anomalies of mitochondrial ATP synthase regulation in four different types of neuronal ceroid lipofuscinosis.

Several neuronal ceroid lipofuscinoses (NCL) show storage of subunit c of mitochondrial ATP synthase. The neurodegenerative process, however, remains obscure. We previously reported a decreased basal ATP synthase activity in fibroblasts from late-infantile NCL (CLN2) and juvenile NCL (CLN3) patients. We have now extended the study of the ATP synthase system to an ovine NCL (a model for the late-infantile NCL variant, CLN6) and the infantile NCL (CLN1). In fibroblasts from healthy sheep, active regulation of ATP synthase in response to cellular energy demand was present similar to human cells: ATP synthase was down-regulated under conditions of anoxia or functional uncoupling and was up-regulated in response to calcium. In fibroblasts from NCL sheep, basal ATP synthase activity was slightly elevated and down-regulation in response to anoxia or uncoupling of mitochondria also occurred. Calcium produced an unexpected down-regulation to 55% of basal activity. Activities of respiratory chain enzymes did not differ between healthy and NCL sheep. In fibroblasts from CLN1 patients, basal ATP synthase activity was reduced and regulation of the enzyme was absent. Activities of respiratory chain complexes II and IV were reduced. The defect of ATP synthase regulation found in fibroblasts from NCL sheep and infantile NCL patients is different from the ATP synthase deficiencies demonstrated in late-infantile and juvenile NCL, but problems of mitochondrial energy production, if also expressed in brain, would be a common feature of several NCL forms. Deficient ATP supply could result in degeneration of neurons, especially in those with high energy requirements.

Animals↗
PubMed1999

Contrasting roles for RANTES and macrophage inflammatory protein-1 alpha (MIP-1 alpha) in a murine model of allergic peritonitis.

Cell accumulation and CC chemokine production were assessed in the peritoneal cavity of ovalbumin (OVA)-sensitized mice following antigen challenge. Intraperitoneal challenge with OVA induced a significant eosinophil influx from 6 h post-challenge with increased numbers persisting at 24 h. At 6 h there was also a marked presence of neutrophils. Messenger RNA expression and protein levels for the chemokines RANTES and MIP-1 alpha were measured in the cell pellets and supernatants, respectively, from peritoneal washes following OVA challenge. RANTES mRNA was detected from 2 h to 4 h following OVA injection, whereas mRNA for MIP-1 alpha was only detectable at 4 h. RANTES protein was first detected from 4 h after OVA injection and by 24 h the protein levels had increased further. Basal levels of MIP-1 alpha were detected in peritoneal washes. These levels peaked at 2 h after OVA challenge and rapidly declined to basal levels by 6 h. A functional role for the chemokines was assessed using neutralizing polyclonal antibodies. Co-injection of OVA with anti-RANTES antibodies resulted in a significant inhibition of eosinophil infiltration into the cavity at 6 h and 24 h (63% and 52% inhibition, respectively) without significantly influencing the number of neutrophils present. In contrast, injection of anti-MIP-1 alpha antibodies only inhibited neutrophil migration at the 6 h time point by 44% without significantly affecting the accumulation of eosinophils. These results demonstrate an important role for RANTES in mediating eosinophil influx in allergic inflammation and a contrasting role for MIP-1 alpha in mediating neutrophil recruitment.

Animals↗
PubMed1998

Resident mast cells are important for eotaxin-induced eosinophil accumulation in vivo.

Eotaxin administration intraperitoneally, but not into dorsal air-pouches, of ovalbumin-sensitized mice exhibiting blood eosinophilia induced a threefold increase in eosinophil (E phi s) infiltration. Transfer of 1 x 10(6) mixed peritoneal cavity cells (PCC), containing 3.5 to 4.5 x 10(4) mast cells (MC), from donor mice to air-pouches of sensitized (but not unsensitized) recipient mice, established an E phi infiltration to eotaxin (vehicle, 0.86 +/- 0.27 x 10(6); eotaxin, 1.63 +/- 0.16 x 10(6) E phi s/air-pouch). Neutrophil numbers were also increased. When MC-depleted (-93%) PCC were injected into air-pouches of recipient animals, E phi infiltration was not supported (-52%). Injection of macrophage-depleted (-99%) PCC into air-pouches elicited a full E phi response to eotaxin but not neutrophil infiltration (-81%). Systemic dexamethasone treatment of recipient mice reduced E phi accumulation; treatment of donor mice only reduced neutrophil accumulation. Our study points to a crucial role for MC in E phi recruitment by eotaxin.

Animals↗