Biomedical subjects

A Nag

Publications and source records attributed to A Nag.

At least 19 recordsLinked to original sources

PubMed2001

The p48 subunit of the damaged-DNA binding protein DDB associates with the CBP/p300 family of histone acetyltransferase.

DDB has been implicated in DNA repair as well as transcription. Mutations in DDB have been correlated with the repair-deficiency disease, xeroderma pigmentosum group E (XP-E). The XP-E cells exhibit deficiencies in global genomic repair, suggesting a role for DDB in that process. DDB also possesses a transcription stimulatory activity. We showed that DDB could function as a transcriptional partner of E2F1. But the mechanism by which DDB stimulates E2F-regulated transcription or carry out its DNA repair function is not understood. To investigate the mechanisms, we looked for nuclear proteins that interact with DDB. Here we show that DDB associates with the CBP/p300 family of proteins, in vivo and in vitro. We suggest that DDB participates in global genomic repair by recruiting CBP/p300 to the damaged-chromatin. It is possible that the histone acetyltransferase activities of the CBP/p300 proteins induce chromatin remodeling at the damaged-sites to allow recruitment of the repair complexes. The observation offers insights into both transcription and repair functions of DDB.

Acetyltransferases↗

PubMed2001

Lipase-catalyzed synthesis of fatty acid diethanolamides.

Diethanolamides are nonionic emulsifiers widely used in industries such as cosmetics and as corrosion inhibitors. Candida antarctica lipase (Novozym 435) was used to catalyze the amidation of various fatty acids with diethanolamine. Contents of fatty acids, metal ions, and water affected the yields of diethanolamides. Hexanoic acid was the best substrate among all acyl donors. Yields of hexanoyl diethanolamide (HADEA), lauroyl diethanolamide (LADEA), and oleoyl diethanolamide (OADEA), obtained after 24 h of lipase-catalyzed reaction at 50 degrees C and 250 rpm with 90 mM fatty acid and 360 mM diethanolamine in acetonitrile, were 76.5, 49.5, and 12.1%, respectively. Addition of 1 mM metal salts increased the yields of HADEA and LADEA. Kinetic analysis showed that the yields of HADEA and LADEA in lipase-catalyzed reactions were largely associated with the rate of the forward reaction constant k(1). Anhydrous enzyme was found to be the best for the amidation reaction. Study on the enzyme operational stability showed that C. antarctica lipase retained 95 and 85% of the initial activity for the syntheses of HADEA and LADEA, respectively (even after repeated use for 10 days). The reaction runs smoothly without the use of hazardous reactants, and the developed method is useful for the industrial application.

Amides↗

PubMed2001

DDB2 induces nuclear accumulation of the hepatitis B virus X protein independently of binding to DDB1.

The hepatitis B virus (HBV) X protein (HBx) is critical for the life cycle of the virus. HBx associates with several host cell proteins including the DDB1 subunit of the damaged-DNA binding protein DDB. Recent studies on the X protein encoded by the woodchuck hepadnavirus have provided correlative evidence indicating that the interaction with DDB1 is important for establishment of infection by the virus. In addition, the interaction with DDB1 has been implicated in the nuclear localization of HBx. Because the DDB2 subunit of DDB is required for the nuclear accumulation of DDB1, we investigated the role of DDB2 in the nuclear accumulation of HBx. Here we show that expression of DDB2 increases the nuclear levels of HBx. Several C-terminal deletion mutants of DDB2 that fail to bind DDB1 are able to associate with HBx, suggesting that DDB2 may associate with HBx independently of binding to DDB1. We also show that DDB2 enhances the nuclear accumulation of HBx independently of binding to DDB1, since a mutant that does not bind DDB1 is able to enhance the nuclear accumulation of HBx. HBV infection is associated with liver pathogenesis. We show that the nuclear levels of DDB1 and DDB2 are tightly regulated in hepatocytes. Studies with regenerating mouse liver indicate that during late G1 phase the nuclear levels of both subunits of DDB are transiently increased, followed by a sharp decrease in S phase. Taken together, these results suggest that DDB1 and DDB2 would participate in the nuclear functions of HBx effectively only during the late-G1 phase of the cell cycle.

Cell Nucleus↗

PubMed2001

The xeroderma pigmentosum group E gene product DDB2 is a specific target of cullin 4A in mammalian cells.

The damaged-DNA binding protein DDB consists of two subunits, DDB1 (127 kDa) and DDB2 (48 kDa). Mutations in the DDB2 subunit have been detected in patients suffering from the repair deficiency disease xeroderma pigmentosum (group E). In addition, recent studies suggested a role for DDB2 in global genomic repair. DDB2 also exhibits transcriptional activity. We showed that expression of DDB1 and DDB2 stimulated the activity of the cell cycle regulatory transcription factor E2F1. Here we show that DDB2 is a cell cycle-regulated protein. It is present at a low level in growth-arrested primary fibroblasts, and after release the level peaks at the G(1)/S boundary. The cell cycle regulation of DDB2 involves posttranscriptional mechanisms. Moreover, we find that an inhibitor of 26S proteasome increases the level of DDB2, suggesting that it is regulated by the ubiquitin-proteasome pathway. Our previous study indicated that the cullin family protein Cul-4A associates with the DDB2 subunit. Because cullins are involved in the ubiquitin-proteasome pathway, we investigated the role of Cul-4A in regulating DDB2. Here we show that DDB2 is a specific target of Cul-4A. Coexpression of Cul-4A, but not Cul-1 or other highly related cullins, increases the ubiquitination and the decay rate of DDB2. A naturally occurring mutant of DDB2 (2RO), which does not bind Cul-4A, is not affected by coexpression of Cul-4A. Studies presented here identify a specific function of the Cul-4A gene, which is amplified and overexpressed in breast cancers.

Animals↗

PubMed2001

Shiftwork in the hot environment.

The study examined the risks of heat induced workplace accidents (textile industry, N = 4125) and the heat tolerability of the rotating day (morning and afternoon, N = 16) and permanent night shift workers (N = 13) in hot-dry and hot-humid environment (34 to 49 degrees C, 50-80% RH; 31 to 42 degrees C ET, Basic). Accident prevalence was significantly high in the summer months (May-June) when the ambient temperature ranged between 42 and 48 degrees C (hot-dry). The influence of hot climate in accident causation was evident from the shift-wise variations in the occurrence of accidents. The longitudinal study showed that the night workers were more vulnerable and less tolerant to heat, the tolerance time being less by about 15% (31 degrees C ET) to 40% (39 degrees C ET), compared to the rotating day workers. The relationship of the segmental and compartmental temperatures (segmental triggering response) played a critical role in heat dissipation/accumulation mechanism, and reflected in the heat tolerability of the day and night workers.

Accidents, Occupational↗

PubMed1999

Cullin 4A associates with the UV-damaged DNA-binding protein DDB.

The damaged DNA-binding protein (DDB) is believed to be involved in DNA repair, and it has been linked to the repair deficiency disease xeroderma pigmentosum. DDB also exhibits transcriptional activities. DDB binds to the activation domain of E2F1 and stimulates E2F1-activated transcription. Here we provide evidence that DDB or DDB-associated proteins are targets of cullin 4A (CUL-4A). CUL-4A is a member of the cullin family of proteins, which are believed to be ubiquitin-protein isopeptide ligases (type E3). The CUL-4A gene has been shown to be amplified and up-regulated in breast carcinomas. In this study, we identify CUL-4A as one of the DDB-associated proteins. CUL-4A co-immunoprecipitates with DDB, but not with a naturally occurring mutant of DDB. Moreover, CUL-4A in HeLa nuclear extracts co-purifies with DDB, suggesting they are parts of the same complex. The observation provides insights how CUL-4A, through an interaction with DDB, might be playing a role in the development of breast carcinomas.

Amino Acid Sequence↗

PubMed1999

Assessment of targeting potential of galactosylated and mannosylated sterically stabilized liposomes to different cell types of mouse liver.

Galactose and Mannose residues were tagged on the surface of n-glutaryl-phosphatidylethanolamine (NGPE) containing liposomes with and without polyethylene glycol of molecular weight 2000 Da conjugated to distearoyl phosphatidylethanolamine (PEG-2000-DSPE). Biodistribution studies showed that sugar bearing liposomes were cleared more rapidly from circulation than those not bearing the sugar moieties. However, the rate of clearance of glycosylated conventional liposomes was much faster than the sugar bearing sterically stabilized liposomes. Intrahepatic distribution studies showed that a substantial amount of conventional liposomes without sugar residues were taken up by both parenchymal (P) (40%) and non-parenchymal (NP) cells (60%). However, incorporation of PEG-2000-DSPE shifted this uptake slightly in favour of parenchymal cells (47%). While ratio of distribution of galactosylated conventional liposomes to P and NP cells was found to be 74:26, galactosylation of sterically stabilized liposomes further enhanced the affinity of these vesicles towards P cells (P:NP ratio being 93:7). Thus, reduced uptake by Kupffer cells was observed with galactosylated sterically stabilized liposomes as compared to conventional liposomes. Whereas, mannosylation of both the liposomes shifted the distribution towards Kupffer cells in an analogous manner. These findings indicate that sterically stabilized liposomes tagged with galactose residues on their surface are more effective in targeting the entrapped material to hepatocytes as compared to conventional liposomes. This approach can therefore be employed for delivering therapeutic agents like drugs, enzymes, genetic materials, anti-sense oligonucleotides selectively to liver P cells for treatment of hepatic disorders.

Animals↗

PubMed1999

Exposure limits of women in hot environment.

The tolerance of six women to work in hot environments was examined under four environmental conditions from 38 to 44 degrees C dry bulb temperature and 50 to 80 per cent relative humidity, i.e., 32 to 36.5 degrees C effective temperature [ET (normal scale)] in a climatic chamber. The subjects performed bicycle ergometric work at an intensity of 50 W and the exposure duration was determined by the cardiorespiratory, body temperature and sweating responses. At the limit of tolerance, the body core temperature (Tcr) reached over 38.5 degrees C and the heart rates attained a peak level (i.e., about 172 beats/min). The total oxygen demand decreased significantly with higher environmental load, particularly beyond 33.5 degrees C ET (N). While the tolerance time decrement was evident with the higher heat stress, on an average, an increase or decrease of every liter of total oxygen demand was equivalent to a 0.8 min change in the tolerance time. As such, the women volunteers were not susceptible to heat; only in extreme hot situations beyond 33.5 degrees C ET (N), they had unacceptable levels of physiological and psychophysical reactions. Based on the distribution of tolerance time of the women in different exposure conditions, the safe exposure times were estimated, which varied from 43 min [32.0 degrees C ET (N)] to 16 min [36.5 degrees C ET (N)].

Adult↗

PubMed1998

Efficacy of a water-cooled garment for auxiliary body cooling in heat.

The efficacy of a water-cooled jacket for auxiliary body cooling was examined under a simulated hot environment. The personal garment comprised of a water re-circulating three-layered vest of cotton fabric lined with 2 mm diameter latex tubing and inter-spaced coating of rubberized solution. Four subjects wearing the water-cooled jacket were tested in the environment chamber (30, 35 and 40 degrees C DB, 50-60% RH, air velocity 0.3, 0.6 and 0.9 m/s, with corresponding average effective temperature of 26 +/- 2.3, 33 +/- 1.1 and 36 +/- 1.5 degrees C). The inlet water temperature was maintained at 10-12 degrees C, with flow rates of 2.6 +/- 0.3, 4.3 +/- 0.3 and 5.1 +/- 0.3 l/h). At 30 degrees C DB, variation in water flow had marginal effect on microclimate, while at higher temperatures (35 and 40 degrees C DB), the re-circulating cooled water had noticeable effects in lowering microclimate, trunk and other skin temperatures, and maintaining the body core within 36.7 +/- 0.2 to 37.5 +/- 0.2 degrees C, over 2 h exposure at 35 and 40 degrees C DB. The observation indicates that the water-cooled jacket provided auxiliary cooling to maintain comfortable microclimate, skin and body core temperatures. This enabled subjects to sustain comfortable heat balance over 2 h heat exposure without any noticeable heat strain.

Adult↗

PubMed1997

A colorimetric estimation of polyethyleneglycol-conjugated phospholipid in stealth liposomes.

The paper describes a colorimetric method for estimation of polyethyleneglycol (PEG)-conjugated phospholipid in either form, free or bound to liposomes. It provides a rapid, highly reproducible, and sensitive tool to detect PEG-coupled phospholipid in amounts as low as 1 microg giving a linear response over a range of 1-100 microg. The method makes use of the biphasic system comprising aqueous ammonium ferrithiocyanate and chloroform, developed by Stewart for estimation of phospholipids. The same system was also applied for quantitation of PEG in PEG-protein conjugates in a recent report. The samples were digested with phospholipase-C, prior to analysis, in order to eliminate the contributions from liposomal phospholipids other than the PEG-conjugated phospholipid. The technique can give valuable information regarding the retention of PEG coating on the surface of the vesicles when employed in combination with markers for the aqueous compartment. In addition, it does not suffer from interference by proteins. This makes it particularly suitable for monitoring the pharmacokinetics of stealth liposomes, using PEG-phospholipid as a lipid probe. Since it does not involve handling hazardous radioisotopes, the suggested technique could even be utilized in clinical trials.

Animals↗

PubMed1997

Human heat tolerance in simulated environment.

The heat tolerance of 11 male volunteers were examined under seven climatic conditions in a climatic chamber. The conditions were 38 to 49 degrees C dry bulb temperature and 45 to 80 per cent relative humidity, i.e., 32.3 to 40 degrees C effective temperature-basic [ET(B)]. The ET(B) values were equated to other heat stress indices, e.g., WBGT (Wet-bulb Globe Temperature Index) and Oxford Index. The subjects did ergometric work at an intensity of 60 per cent VO2max. The exposure durations were decided by the cardiorespiratory, body temperature and sweating responses. Of the climatic conditions studied, at 35.4, 38, 39 and 40 degrees C ET(B), the body core temperature (Tcr) reached over 39 degrees C and heart rates attained 172 to 182 beats/min, which were taken as the tolerance limit. The total oxygen demand significantly varied with the increase in environmental warmth, i.e., increase or decrease of one litre of oxygen demand was equivalent to one minute change in tolerance time. The volunteers were not susceptible to heat; only in extreme hot situations beyond 35.4 degrees C ET(B), were unacceptable levels of physiological and psychophysical reactions seen. The study suggests the acceptable and tolerable limits for human exposure in heat: (i) acceptable at 38 to 38.2 degrees C Tcr for a tolerance time of 80 to 85 min; and (ii) the tolerable limit of short duration (40-45 min) at 39 degrees C Tcr that corresponded to 31.5 and 36.5 degrees C ET(B).

Adolescent↗

PubMed1996

A colorimetric assay for estimation of polyethylene glycol and polyethylene glycolated protein using ammonium ferrothiocyanate.

A colorimetric method for quantitative assay of polyethylene glycol (PEG) described here is based on partitioning of a chromophore present in ammonium ferrothiocyanate reagent from an aqueous to a chloroform phase in the presence of PEG. The method is simple, reproducible, and can detect PEG in amounts as low as 5 microg. It gives a linear response over a range of 5-100 microg. The absence of any interference by proteins makes the assay equally suitable for the estimation of PEG in PEG-protein conjugates. The method was employed to monitor the separation profile of a mixture of free and PEG-5000 coupled to bovine serum albumin during purification through a gel filtration column. In this report we have also demonstrated for the first time an assay method which permits a critical evaluation of pharmacokinetic properties of any PEG-protein conjugate under in vivo conditions.

Animals↗

PubMed1996

Human work capacity under combined stress of work and heat.

The working capacity of young, healthy, unacclimatized men (N = 11) was studied under long-duration (8 to 9 days) exposure to combined work and heat (dry and humid). The dry (Gr A, N = 5) and humid (Gr B, N = 6) groups were exposed to 41.3 +/- 0.6 degrees C DB, 40-50% RH and 39.2 +/- 0.6 degrees C DB, 70-80% RH, respectively, for all days of exposure. The experimental protocol was divided into: (i) direct determination of maximal oxygen uptake (VO2max) by stepped increases in bicycle ergometry everyday in the morning in the initial hours before exposure to heat, after which the recovery process of oxygen debt contraction was examined; and (ii) exposure to heat in a climatic chamber for 2 h where the subjects performed two spells of ergometric work (10 to 12 min each) at a relative intensity of 50 +/- 12 to 69 +/- 11% VO2max. The average heat exposure time for Gr A was higher (108 +/- 12 min) as compared to Gr B (95 +/- 10 min), but Gr B sustained a high heat load as reflected from the high deep-body temperature maintained during the exposure. The high body temperature load of Gr B had a significant effect on the cardiorespiratory capacity, indicating an upward trend in VO2max. This was statistically significant (p < 0.05) for the first four days of exposure. Subjects of Gr B had a relatively higher working capacity compared to those in Gr A on all days. The VO2max and analysis of the fractions of oxygen debt contraction (fast and slow component) indicated that the subjects showed a better training/heat acclimatization effect under hot, humid conditions.

Adult↗

PubMed1995

Transplanted acellular allograft dermal matrix. Potential as a template for the reconstruction of viable dermis.

The use of allograft donor skin as a permanent skin transplant in full-thickness burns is limited by its immunogenic properties and by the inappropriateness of immunosuppression of a burn patient. Allograft skin will initially take on a full-thickness wound, but it is ultimately rejected. This immunogenic response to allograft skin is directed primarily against the cells of the epidermis and the endothelial cells in the dermis. To date, it has not been possible to remove these immunogenic cells while maintaining the integrity of the nonimmunogenic components of allograft dermis. In this study, we have investigated a method of processing porcine skin to produce an acellular, structurally intact, dermal matrix. We have developed a process that de-epidermizes and decellularizes fresh porcine skin, while maintaining the basement membrane complex and the extracellular matrix structure of the dermis. Porcine dermis processed by this method was initially assessed for toxicity in a rat subcutaneous implant study. In vivo assessment confirmed the absence of local and systemic toxicity. Subsequently, we investigated the potential use of this matrix in combination with a meshed split-thickness autograft (STSG) as a permanent allograft in full-thickness wounds in pigs. Histological analysis revealed that the dermal matrix supported fibroblast infiltration, neovascularization, and keratinocyte migration from an overlying STSG. There was no evidence of an inflammatory cell infiltrate or a cell-mediated immune response. This apparent lack of an immune response was also tested in vitro by assessing recipient lymphocyte proliferation in response to an extract of the dermal matrix. These results suggest that skin processed by this method has the potential to be used as a permanent dermal allograft to augment the performance of an STSG in the closure of full-thickness wounds.

Animals↗

PubMed1993

Chemical composition of two semi-aquatic plants for food use.

The seasonal variation in the nutrient composition of Enhydra fluctuans and Marsilea quadrifolia, two edible semi-aquatic plants, was studied in order to promote their consumption as green leafy vegetables. Both plants had a high crude protein content throughout all harvesting seasons. Enhydra fluctuans had a low ash content and was a good source of beta-carotene (3.7 to 4.2 mg/100 g on a fresh weight basis). Marsilea quadrifolia exhibited wide fluctuations between seasons and was not very promising in nutrient composition when compared to other commonly used green leafy vegetables.

Carotenoids↗

PubMed1993

Acute diarrhoea caused by Vibrio mimicus in Calcutta.

Out of 539 acute diarrhoea cases studied, Vibrio mimicus was isolated as a sole pathogen in the faeces of 7 (1.3%) cases. The chief clinical presentations of the seven cases were watery diarrhoea and vomiting. Bloody diarrhoea was observed in 2 (28.5%), abdominal pain in 2 (28.57%) and fever in one (14.29) cases. All cases could be effectively treated with ORS except 3 (42.85%) cases who required IV Ringer's lactate. All V. mimicus strains isolated in the study were uniformly susceptible to tetracycline, chloramphenicol, norfloxacin and ciprofloxacin.

Acute Disease↗

PubMed1992

Heat stress of women doing manipulative work.

Six women were exposed to nine environmental conditions, ranging from 26.0 to 35.8 degrees C effective temperature (ET), in a climatic chamber. They were involved in manipulative work in a seated position for a duration of 3 hr. The O2 uptake, heart rate, deep body (Tc) and skin temperature (Tsk), sweat loss, and perception of thermal comfort were noted. The O2 uptake increased with the time of exposure at different heat levels. The work energy demand, which was 19% of VO2max at 26 degree C ET, increased to 35% of VO2max at 35.8 degrees C ET. However, the work output declined with the increase in ET. Thus, the elevated metabolic demands were the results of the thermal stimuli. The Tsk was greatly influenced by the environmental heat; the Tc changes were gradual. The highest mean Tsk attained was 37.3 degrees C at 33.8 degrees C ET when the gradient of Tc-Tsk was only 0.5 degrees C. The rate of change in mean Tsk for 31.6 to 33.8 degrees C ET was much faster compared to the range between 26.0 and 31.6 degrees C ET. From 32.1 degrees C ET onward the Tc and heart rates rose rapidly, while the sweating rate tended to fall, indicating some hindrance for evaporative cooling. Also, thermal sensations were noted as extremely hot for the conditions 32.1 to 35.8 degrees C ET with the increase in exposure duration.

Adult↗

PubMed1992

Efficacy of norfloxacin for shigellosis: a double-blind randomised clinical trial.

In a double-blind, randomised, clinical trial on 122 adults with acute Shigella dysentery, 60 patients were treated with norfloxacin and 62 with nalidixic acid. Of these, 32 patients in the norfloxacin group and 28 patients in the nalidixic acid group had Shigella in their stool. Patients of the two treatment groups were clinically comparable on admission. No significant differences in clinical responses were observed in the two groups among the Shigella-positive cases, Shigella-negative cases and among the total cases. All isolates of Shigella were susceptible to norfloxacin, whereas 13.8% of the strains were resistant to nalidixic acid.

Adult↗