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Biomedical subjects

D Sen

Publications and source records attributed to D Sen.

At least 19 recordsLinked to original sources
PubMed2006

Temperature effects on the composition and microstructure of spray-dried nanocomposite powders.

Porous composite powders, prepared by spray drying of silica and polybromostyrene nanoparticles, were calcined at various temperatures up to 750 degrees C. The structure in these powders are quantitatively investigated by ultra small-angle X-ray scattering, thermogravimetric analysis, and nuclear magnetic resonance measurements. It has been found that the polybromostyrene latex is efficient in templating mesopores. However, polybromostyrene remains almost completely in the interstitial micropores in the grain after the spray-drying process. A post thermal treatment of the powders has been applied from 250 up to 750 degrees C. We found that the hydrocarbon part of the polybromostyrene is decomposed and leaves the micropores at around 350 degrees C. However, it is demonstrated that a significant amount of bromine remains in the interstitial micropores between the silica particles. At around 600 degrees C, the silica nanoparticles start to fuse with each other and a coalescence of the micropores takes place. At still higher temperature, around 750 degrees C, the micropore network totally disappears, and the growth in pore size occurs due to the coalescence of the mesopores with a significant decrease of the total porosity. During this process, the silica network densification is accompanied by a lowering of the specific surface area.

Journal Article↗
PubMed2006

Epidemiology and outcome of sepsis in a tertiary-care hospital in a developing country.

Sepsis continues to have a substantial mortality and morbidity despite advances in the diagnosis and management of this condition. We retrospectively analysed hospital charts of patients diagnosed to have sepsis between January 2002 and June 2003. Demographic characteristics of patients, microbiological findings and predictors of survival were evaluated. Sixty-nine sepsis episodes that occurred in 63 patients were analysed. The most common underlying diseases were hypertension, malignancies and diabetes mellitus. Renal insufficiency, respiratory distress and disseminated intravascular coagulation developed in 52.2, 30.4 and 30.4% of the episodes respectively; 47.7% of the blood cultures yielded an organism. Gram-negative bacteria were the predominant microorganisms (65.9%). Fifty-five patients (87.3%) died. Mechanical ventilation and underlying renal disease were significant determinants of mortality. In conclusion, Gram-negative bacteria remain the major pathogens in sepsis. The mortality remains very high, and a change in the clinical approach to the septic patient should be employed to improve the outcome.

Adult↗
PubMed2004

Dynamical scaling of the structure factor of some non-Euclidean systems.

Predictions of nonlinear theories on dynamics of new phase formation have been examined for the hydration of calcium silicates with light water and heavy water. In the case of hydration with light water, reasonable agreement has been observed with dynamical scaling hypothesis with a new measure of the characteristic length. The characteristic length does not follow a power law relation with time. Hydrating mass is found to be mass fractal throughout hydration, with mass fractal dimension increasing with time. But, in the case of hydration with heavy water, no agreement has been observed with the scaling hypothesis. Hydrating mass undergoes transition from mass fractal to surface fractal and finally again to mass fractal. The qualitative features of the kinetics of hydration, as measured in small-angle scattering experiments, are strikingly different for hydration with light water and heavy water.

Journal Article↗
PubMed2004

Diagnostic features and treatment modalities in solitary rectal ulcer syndrome.

Solitary rectal ulcer syndrome (SRUS) is a traumatic lesion of the anterior or circular rectal wall caused by straining due to functional disorders of defecation. Defecography, transrectal ultrasonography or anorectal manometry are suitable procedures that may be used to detect the causative disorder and should, therefore, be performed in patients with solitary rectal ulcer syndrome. Histopathological features of SRUS are characteristic and pathognomonic, nevertheless the endoscopic and clinical presentations may be confusing. The lesions may mimic other rectal pathologies and lead to wrong diagnosis. We retrospectively evaluated 34 patients with SRUS who had various treatments. Rectosigmoidoscopy, defecography, transrectal ultrasonography and anorectal manometry were performed for evaluation of cases. The operative management was rectopexy in 26 patients, rectal mucosectomy in 4 patients, segmental colonic resection in 2 patients, local excision in 1 patient and colostomy in 1 patient. Total regression and healing of the ulcer occurred in 32 of 34 patients. Partial regression of symptoms in 2 patients, who underwent rectopexy and rectal mucosectomy, occurred, but we could not get complete healing.

Adult↗
PubMed2004

The retentive effects of pre-fabricated posts by luting cements.

The purpose of this study was to compare the retention of two different pre-fabricated posts cemented to the root canal with four different adhesive luting cements and a zinc phosphate cement. The crowns of 100 freshly extracted human mandibular central and lateral incisors were removed at the cementoenamel junction and divided into two main groups (A = ParaPost and B = Flexi-Post) and further divided into five subgroups to evaluate the effects of five different cements (Rely-X ARC, Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor) each with 10 samples. Post-holes were prepared on all of the roots following the manufacturer's instructions. Each sample was placed into a specialized jig and tensile strength tests performed by using testing machine with a crosshead speed of 0.638 cm min(-1) and force applied until failure. The data were analysed with one-way anova (Post Hoc a Scheffe's S test) and two-way anova (P < 0.001). The Flexi-Post dowels had a mean of 54.21 kg (s.d. = 9.37) and demonstrated statistically higher retention than ParaPost dowels with a mean of 33.93 kg (s.d. = 10.69) for all of the cement groups (P < 0.001). In Flexi-Post and ParaPost dowel groups; Rely-X ARC was statistically higher than the Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor (P < 0.05). Adhesor was significantly lower than the other subgroups (P < 0.05). Resin luting cements have demonstrated very high tensile strength potential for a strong bond to dentin.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2004

Effect of hyperbaric oxygen on experimental acute distal colitis.

It has been demonstrated that hyperbaric oxygen (HBO) is useful as an adjunctive therapy for Crohn's disease. However, its effects on ulcerative colitis have not been investigated. In the present study, HBO was tested for acetic acid-induced colitis, and antioxidant systems were evaluated to clarify its possible mode of action. Thirty-six Sprague-Dawley rats were randomly divided into three groups: sham control (Group I), colitis induced by acetic acid without any therapy (Group II), colitis induced by acetic acid and treated with HBO (Group III). HBO was given for 5 days, 2 sessions per day at 2.5-fold absolute atmosphere pressure (ATA) for a period of 90 min in rats in which colitis had been induced (Group III). Rats were sacrificed on the 5th day after the procedure. Superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GSH Px) activity were measured in the intestinal tissue and erythrocyte lysate. MDA and GSH Px were also determined in the plasma. Whereas MDA levels in erythrocyte, plasma and intestinal tissue were decreased, the levels of GSH Px and SOD were significantly increased in Group III as compared to those of Group II. The results of our study suggest that hyperbaric oxygen therapy has beneficial effects on the course of experimental distal colitis and that antioxidant systems may be involved in its mode of action.

Acetic Acid↗
PubMed2003

Acute renal failure due to intrinsic renal diseases: review of 1122 cases.

In this study we have analyzed incidence, causes and clinical course of ARF due to primary intrarenal disease other than acute tubular necrosis. Thousand hundred and twenty two cases of ARF of diverse etiology were studied over a period of 16 years; July 1984 to Dec, 1999. Surgical ARF 231 (20.6%) were not included in the present study. Intrinsic renal diseases were responsible for ARF in 891 (79.4%) of cases. The most common intrinsic renal diseases 705 (79.4%) causing ARF were ischemic/toxic acute tubular necrosis, but not included in this study. Acute renal failure was related to acute glomerulonephritis (9.3%), acute interstitial nephritis (7%), and renal cortical necrosis in (4.6%) of cases. Therefore intrinsic renal diseases other than ATN were the causative factor for acute renal failure in 186 (20.8%) patients in our study. Crescentic (51.8%) and endocapillary proliferative glomerulonephritis (34.9%), were the main glomerular diseases responsible for ARF and 75.9% of GN was related to infectious etiology. Fifty three percent of acute interstitial nephritis was drug induced and in 25 (40%) patients it was related to an infectious etiology. Renal cortical necrosis due to HUS was observed in 16 (39%) children and majority (76.47%) of the cases had a diarrhoeal prodrome. Obstetrical complications were the main causes (61%) of cortical necrosis in adults with acute renal failure. Thus, intrinsic renal diseases other than ATN were responsible for ARF in 186 (20.8%) cases. Post-infectious glomerulonephritis, acute interstitial nephritis and renal cortical necrosis (complicating HUS in children and obstetrical complications in adult) are the main causes of acute renal failure in our study. Both acute GN and interstitial nephritis had excellent prognosis, however renal cortical necrosis was associated with a very high mortality.

Acute Disease↗
PubMed2003

Antineutrophil cytoplasmic autoantibodies in systemic lupus erythematosus.

Although antineutrophil cytoplasmic antibodies (ANCA) were first associated with the primary vasculitides, it is now clear that 15-20% of patients with lupus have detectable ANCA. In this short review we confirm that the major link is with perinuclear ANCA (pANCA) but not cytoplasmic ANCA (cANCA). ANCA to myeloperoxidase are associated with drug-induced lupus. There may be a link between pANCA levels and disease activity in some patients although the links to specific organ involvement are not proven. ANCA in lupus must be interpreted cautiously with particular attention paid to laboratory technique, the size, age and genetic background of the populations studied.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed2003

The effect of hyperbaric oxygen treatment on oxidative stress in experimental acute necrotizing pancreatitis.

Various protocols may be used for acute pancreatitis treatment. Recently, the benefit of hyperbaric oxygen (HBO) has been demonstrated. To clarify the mechanism of HBO on the process of the acute pancreatitis, we determined the levels of antioxidant enzymes in an acute pancreatitis model. Forty-five Sprague-Dawley rats were randomly divided into three groups: Group I: sham group (n=15), Group II: pancreatitis group (n=15), Group III: pancreatitis group undergoing HBO therapy (n=15). HBO was applied postoperatively for 5 days, two sessions per day at 2.5 fold absolute atmospheric pressure (ATA) for 90 min. Superoxide dismutase (Cu/Zn-SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH Px) activity were measured in pancreatic tissue and erythrocyte lysate. MDA and GSH Px were also determined in plasma. In addition, amylase levels were measured in the serum. While serum amylase levels and MDA values in erythrocyte, plasma and pancreatic tissue were decreased, the levels of GSH Px and SOD were found to be significantly increased in the Group III as compared to those of the Group II. The findings of our study suggest that HBO has beneficial effects on the course of acute pancreatitis and this effect may occur through the antioxidant systems.

Animals↗
PubMed2002

Lead exposure in scaffolders during refurbishment construction activity--an observational study.

The toxic effects of lead have been known for centuries. Occupational exposure to this chemical hazard has also been well documented in relation to various industry groups, including construction, where workers are recognized as being significantly exposed during refurbishment work, in particular through inhalation and ingestion of lead fumes and dust. It is easy to see how so-called 'burners', 'cutters' and 'blasters'--workers directly involved in removing old lead paint--may become exposed; the influence of personal hygiene, smoking, eating/drinking and nail biting has also been documented in the literature. We now report on one group, the scaffolders, not previously considered to be at risk. Although not directly involved in the paint removal, anecdotal and personal experience of the authors indicate that these workers, who erect and later dismantle access structures during the renovation of previously lead-painted surfaces, may take up significant amounts of lead, mainly by ingestion, to raise their personal blood lead levels (and body burden) in line with recognized 'lead workers'. Exposures of this magnitude would also bring the scaffolders involved in such refurbishment work under the Control of Lead at Work Regulations 1998. The authors make various recommendations on measures to minimize and control exposure of scaffolders to lead.

Construction Materials↗
PubMed2002

Carpal tunnel syndrome.

Carpal tunnel syndrome is the most commonly diagnosed entrapment neuropathy. This review looks at the current body of evidence to help determine optimal practice for the diagnosis and management of this condition.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

A new and efficient DNA enzyme for the sequence-specific cleavage of RNA.

A new DNA enzyme, the "Bipartite DNAzyme", suitable for the sequence-specific cleavage of RNA, was obtained from a random DNA library by in vitro selection. Only a single family of catalytic molecules emerged from the selection, and a 22 nucleotide consensus sequence common to all clones defined a putative catalytic core. The most abundant clone self-cleaved at a single internal ribonucleotide phosphodiester with a relatively fast k(obs) value of 1.7 min(-1), in 10 mM MgCl(2) at 23 degrees C. This DNAzyme ("Bipartite I") required divalent cations, with magnesium and manganese most optimally supporting cleavage. A reselection from a mutagenized DNAzyme pool for the ability to cleave at extended RNA substrates yielded an unchanged catalytic core sequence. From this re-selection a DNAzyme ("Bipartite II") capable of sequence-specifically cleaving extended stretches of RNA was derived. A rate versus pH analysis of the Bipartite II DNAzyme revealed a two-phase profile, similar to that reported for the hepatitis delta virus (HDV) ribozyme, suggesting that the Bipartite II DNAzyme and the HDV ribozyme may share similar catalytic strategies. Multiple-turnover kinetics, measured in 30 mM MgCl(2), at 37 degrees C, with an HIV-1-derived RNA substrate, yielded a k(cat) value of approximately 1.4 min(-1) and a K(M) value of approximately 230 nM, which were of the same order as k(cat) and K(M )values measured for other ribozymes and DNAzymes in general use for RNA cleavage. The Bipartite DNAzyme therefore represents a new and potentially useful reagent, both for the processing of RNA transcripts in vitro and for mRNA ablation procedures in vivo.

Base Sequence↗
PubMed2001

A DNA oligonucleotide-hemin complex cleaves t-butyl hydroperoxide through a homolytic mechanism.

Both electron paramagnetic resonance (EPR) and electronic absorption spectroscopy have been employed to investigate the reaction of a guanine-rich DNA nucleotide-hemin complex (PS2.M-hemin complex) and organic peroxide (t-Bu-OOH). Incubation of the PS2.M-hemin complex with t-Bu-OOH resulted in the time-dependent decrease in the heme Soret with concomitant changes to the visible bands of the electronic absorbance spectrum for the PS2.M-hemin complex. Parallel EPR studies using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) combined with spectral simulation demonstrated the presence of tert-butyloxyl, carbon-centered methyl, and methyl peroxyl radicals as well as a simple nitroxide (triplet) signal. Experiments, performed by maintaining a constant ratio of t-Bu-OOH/PS2.M-hemin complex ( approximately 35 mol/mol) while varying DMPO concentration, indicated that the relative contributions of each radical adduct to the composite EPR spectrum were significantly influenced by the DMPO concentration. For example, at DMPO/PS2.M-hemin of 10-50 mol/mol, a complex mixture of radicals was consistently detected, whereas at high trapping efficiency (i.e., DMPO/PS2.M-hemin of approximately 250 mol/mol) the tert-butyloxyl-DMPO adduct was predominant. In contrast, at relatively low DMPO/PS2.M-hemin complex ratios of < or =5 mol/mol, a simple nitroxide three-line EPR signal was detected largely in the absence of all other radicals. Together, these data indicate that tert-butyloxyl radical is the primary radical likely formed from the homolytic cleavage of the O-O peroxy bond of t-Bu-OOH, while methyl and methyl peroxyl radicals result from beta-scission of the primary tert-butyloxyl radical product.

DNA↗
PubMed2001

A novel mode of regulation of an RNA-cleaving DNAzyme by effectors that bind to both enzyme and substrate.

We describe a novel and general strategy for controlling the activity of RNA-cleaving nucleic acid enzymes (ribozymes and DNAzymes) via the use of RNA and DNA effectors. Whereas in conventional heteroallosteric enzymes (including ribozymes) control of catalysis is achieved by the binding of effector molecules to the enzyme, in our strategy DNA and RNA regulators bind to both the enzyme and the substrate. The design of this system permits the control of catalysis even in the absence of a detailed knowledge of the secondary and tertiary structure of the relevant ribozyme or DNAzyme. Here, we utilize the ability of RNA and DNA to form branched three-way junctions to regulate the RNA-cleaving activity of the in vitro selected "10-23" DNAzyme by three orders of magnitude. Control is exercised by the ability of a DNA or RNA "regulator" to induce formation of stable and catalytically competent "three-way" enzyme-substrate-regulator complexes, relative to otherwise unstable and catalytically poor enzyme-substrate complexes. Such expansively regulated "three-way" ribozyme/DNAzyme systems might find utility in vivo to bring about the catalyzed destruction of one RNA transcript contingent on the presence in its immediate environment of another gene transcript.

Base Sequence↗
PubMed2001

The peroxidase activity of a hemin--DNA oligonucleotide complex: free radical damage to specific guanine bases of the DNA.

A specific DNA oligonucleotide--hemin complex (PS2.M--hemin complex) that exhibits DNA-enhanced peroxidative activity was studied by EPR and UV--visible spectroscopy and by chemical probing analysis. EPR data obtained from low-temperature experiments on the PS2.M--hemin complex showed both a low-field g approximately 6 and a high-field g approximately 2 signal. These EPR signals are typical of high-spin ferric heme with axial symmetry as judged by the EPR spectrum of six-coordinate heme iron in acidic Fe(III)-myoglobin. This similarity is consistent with the presence of two axial ligands to the heme iron within the PS2.M--hemin complex, one of which is a water molecule. Optical analyses of the acid-base transition for the hemin complex yielded a pK(a) value for the water ligand of 8.70 +/- 0.03 (mean +/- SD). Low-temperature EPR analysis coupled with parallel spin-trapping investigations following the reaction of the PS2.M--hemin complex and hydrogen peroxide (H(2)O(2)) indicated the formation of a carbon-centered radical, most likely on the PS2.M oligonucleotide. Chemical probing analysis identified specific guanine bases within the PS2.M sequence that underwent oxidative damage upon reaction with H(2)O(2). These and other experimental findings support the hypothesis that the interaction of specific guanines of PS2.M with the bound hemin cofactor might contribute to the superior peroxidative activity of the PS2.M--hemin complex.

DNA Adducts↗
PubMed2001

Self-reported skin problems among physical processors in the chemical industry in Great Britain.

Contact dermatitis is common in the chemical industry. A cross-sectional study was conducted to investigate the prevalence of self-reported skin problems in employees involved in the drying, blending, milling, grinding and filling/bagging end of chemical manufacture in small- to medium-sized contract manufacturing/processing chemical companies in Great Britain. There were several secondary aims. Twenty-three per cent of the employees interviewed reported having had a skin problem in the previous 12 months. Of those reporting problems, 46% were always/nearly always involved in blending and 56% were always/nearly always involved in filling and bagging. These same processes were also more commonly associated with continuous or recurring skin problems. Seventy-five per cent reported a problem involving the upper limbs; most had more than one body area affected. Forty-three per cent had consulted a doctor (67% their general practitioner) and 9% took time off work as a result of their skin condition. Skin problems seemed to peak (34% employees) in those who had spent between 1 and 2 years in their current job. Solvents, known skin irritants, were the most frequent, single category of chemicals encountered in the study. Over 92% had been told how to avoid skin problems; 85% reported that they always/almost always wore protective clothing. Despite these measures, a significant number had reported having had a skin problem related to their work in the previous 12 months. Particular attention to control measures based on risk assessment is recommended for these physical processors in the chemical industry. Further research is also recommended into the whole area of personal protective clothing and the individual worker's perception of risks to health in the workplace.

Adult↗
PubMed2001

Osteoporosis in systemic lupus erythematosus: prevention and treatment.

The patient with systemic lupus erythematosus (SLE) is at risk of osteoporosis through several factors: the inflammatory disease itself, disease-related co-morbidity, and its treatment. Bone loss is apparent early in the disease and this may be confounded primarily by treatment with corticosteroids. Patients should be assessed for additional risk factors for osteoporosis and general lifestyle measures adopted. Bone mineral density measurement should be considered in SLE patients at high risk of osteoporosis, particularly those starting corticosteroids and in postmenopausal women. Calcium and vitamin D supplementation provide general prophylaxis and are a suitable first-line option. Hormone replacement should be used in hypogondal subjects unless contra-indicated. In subjects at high fracture risk, particularly in postmenopausal women, bisphosphonate therapy should be considered as these agents have been shown to significantly reduce vertebral fracture risk. These measures should reduce the burden of osteoporosis and fracture in patients with lupus.

Calcium↗