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Biomedical subjects

P C Joshi

Publications and source records attributed to P C Joshi.

At least 19 recordsLinked to original sources
PubMed2003

Effect of bioaccumulation of cadmium on biomass productivity, essential trace elements, chlorophyll biosynthesis, and macromolecules of wheat seedlings.

Soil contamination with heavy metals has become a worldwide problem, leading to losses in agricultural yield and hazardous human health effects as they enter the food chain. The present investigation was undertaken to examine the influence of cadmium (Cd2+) on the wheat (Triticum aestivum L.) plant. Cd2+ accumulation and distribution in 3-wk-old seedlings grown in nutrient medium containing varying concentrations of Cd2+ (control, 0.25, 0.50, 1.0, 2.5, and 5.0 mg/L) was monitored. The effect of varying Cd2+ concentrations up to 21 d on biomass productivity, plant growth, photosynthetic pigments, protein, amino acids, starch, soluble sugars, and essential nutrients uptake was studied in detail to explore the level up to which the plant can withstand the stress of heavy metal. Plants treated with 0.5, 1.0, 2.5, and 5.0 mg/L Cd2+ showed symptoms of heavy-metal toxicity as observed by various morphological parameters which were recorded with the growth of plants. The root, shoot-leaf length and the root, shoot-leaf biomass progressively decreased with increasing Cd2+ concentration in the nutrient medium. Cd2+ uptake and accumulation was found to be maximum during the initial growth period. Cd2+ also interfered with the nutrients uptake, especially calcium (Ca2+), magnesium (Mg2+), potassium (K+), iron (Fe2+), zinc (Zn2+), and manganese (Mn2+) from the growth medium. Growth reduction and altered levels of major biochemical constituents such as chlorophyll, protein, free amino acids, starch, and soluble sugars that play a major role in plant metabolism were observed in response to varying concentrations of Cd2+ in the nutrient medium. In the present study, the effects of Cd2+ on growth, biomass productivity, mineral nutrients, chlorophyll biosynthesis, protein, free amino acid, starch, and soluble sugars in wheat plants was estimated to establish an overall picture of the Cd2+ toxicity at structural and functional levels.

Amino Acids↗
PubMed2002

Identification of new photoreduction products of pentachlorophenol.

Pentachlorophenol (PCP), a fungicide and insecticide, leaves behind considerable residue in the environment in the form of unreacted molecule, metabolites and photoreduction products. Most of the previously reported photoproducts have resulted from dechlorination of the parent molecule. We have shown that photoreduction of PCP also proceeds by photoreduction of the parent molecule at carbons 2 and 4. These products were identified and characterized as 2-dehydro-2,3,4,5,6-pentachlorocyclohexanone (II) and 2,3,4,5,6-pentachlorocyclohexanone (IV). Both of them display keto-enol tautomerism. Identification and characterization of new photoproducts of PCP is significant for determining its overall environmental impact in the ecosystem.

Environmental Monitoring↗
PubMed2002

Evaluation of UV-radiation induced singlet oxygen generation potential of selected drugs.

Photosensitization reaction of drugs leading to the formation of reactive oxygen species under ultraviolet radiation (UVR) can cause tissue injury, resulting in damage to various cellular macromolecules. The aim of this study was to determine the singlet oxygen generation potential of some commonly used antibiotics so that due precautions can be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce singlet oxygen (1O2) under artificial UVA (320-400 nm). Singlet oxygen generation of various screened antibiotics under UVA is of the following order: Nalidixic acid > Amphotericin-B > Cephradine > Cefazolin > Nafcillin > Cephalothin > Ampicillin > Cephalexin > Puromycin > Kanamycin > Lincomycin > Tetracycline > Nystatin > Gentamicin sulphate. Nalidixic acid, the most potent generator of 1O2 among the screened antibiotics, was selected to carry out further studies. Certain specific quenchers of 1O2 such as beta-carotene, 1,4-diazabicyclo[2.2.2] octane (DABCO), and sodium azide (NaN3) accorded significant inhibition in the production of 1O2. The results suggest that precautions are necessary to avoid ultraviolet radiation after the intake of photoreactive drugs, especially in tropical countries such as India. These findings are significant because UVB radiation is reportedly increasing on earth surface in part due to depletion of stratospheric ozone layer. The selected drugs are commonly used for the treatment of various diseases. Thus, the synergistic action of both can lead to undesirable phototoxic responses.

Anti-Bacterial Agents↗
PubMed2001

Prostaglandin E2 suppressed IL-15-mediated human NK cell function through down-regulation of common gamma-chain.

NK cell function is regulated by cytokines and certain biochemical mediators in a positive or negative manner. This study was performed to investigate the suppressive effects of PGE(2) on IL-15-activated human NK cell function. Purified NK cells were cultured with 200 ng/ml IL-15 for 2 days in the presence or absence of 10-200 ng/ml PGE(2). PGE(2) significantly suppressed NK cell-mediated cytotoxicity and IFN-gamma production at the secretional and the transcriptional levels. We also evaluated the effect of PGE(2) on the IL-15R complex that consists of IL-2Rbeta, common gamma-chain (gamma(c)-chain), and a specific chain IL-15Ralpha. Percentage of positive cells and number of binding sites for gamma(c)-chain were significantly increased after IL-15 treatment; however, a substantial decrease was observed with PGE(2) cotreatment. In contrast, constitutive expression of IL-2Rbeta was significantly decreased after IL-15 treatment, with no change detected in the presence of PGE(2.) At the transcriptional level, neither IL-15 nor PGE(2) had significant effects on the expression of beta- or gamma(c)-chains. There was a 3-fold increase in the expression of IL-15Ralpha at the transcriptional level that peaked at 8 h after IL-15 treatment; however, PGE(2) had no significant effect. Suppression of NK function by PGE(2) was not due to the endogenous production of IL-4, IL-10, or TGF-beta(1) by NK cells. These results suggest that down-regulation of surface expression of gamma(c)-chain on NK cells may be one mechanism through which PGE(2) mediates suppression of IL-15-activated NK cell function.

Cells, Cultured↗
PubMed2001

Effect of lindane on the growth and metabolic activities of cyanobacteria.

The effect of lindane was studied in Cyanobacteria (Anabaena) by estimating its growth pattern, biomass yield, chlorophyll content, and total starch and protein content. The results reveal that exposure of Anabaena with 0.5, 1.0, 1.5, and 2.0 ppm levels of lindane will have drastic effects on biomass production and photosynthetic rate. Since Cyanobacteria are a primary source of aquatic food web and important biofertilizer for rice cultivation, their protection from residual effects of lindane is essential for enriched soil fertility.

Algal Proteins↗
PubMed2001

An unusual photohaemolytic property of riboflavin.

Riboflavin (RF) is a known photoreactive and phototoxic molecule. However, unlike other photosensitizers, it does not induce photohaemolysis of erythrocytes by itself. On the other hand, illuminated RF caused haemolysis but in the presence of serum or plasma. The kinetics of photohaemolysis in the presence of serum/plasma has been studied by monitoring the rate of haemolysis spectrophotometrically and morphological changes at erythrocytes membrane by scanning electron microscopy. We found that the extent of mammalian RBC membrane damage was dependent on the concentration of RF or hematoporphyrin (HP) (0-20 microgram/ml) and dose of sunlight (0-20 min). The RBC membrane-damaging potential of illuminated HP was not affected by the presence of plasma in the reaction system. Furthermore, RF showed a protective role against photohaemolysis caused by photoexcited HP if erythrocytes were preincubated with RF in the absence of serum/plasma. For mechanistic studies, biochemical parameters such as acetylcholinesterase activity (AChE) and formation of TBA-reactive substance (TBA-RS) were analysed in RBC and RBC+plasma under a similar set of experimental conditions. We observed about a 25% decrease in AchE activity as a synergistic action of RF or HP (20 microgram/ml) and sunlight (30 min) in both cases (RBC or RBC+plasma). Interestingly, illuminated RF caused about a 125% increase of TBA-RS in a reaction system consisting of RBC+plasma. On the other hand, an increase in the production of TBA-RS by illuminated RF was not observed in the absence of plasma/serum, in the reaction system. These results suggested that photooxidation of RBC membrane lipids by illuminated RF, under the influence of plasma/serum, may be one of the causes of membrane modification leading to RBC lysis.

Acetylcholinesterase↗
PubMed2001

Evaluation of UV-induced superoxide radical generation potential of some common antibiotics.

Photosensitization reaction of drugs leading to the formation of reactive oxygen species (ROS) cause tissue injury causing damage to various cellular macromolecules. The aim of this study was to determine the superoxide anion (O2-) generation potential of commonly used antibiotics so that due precaution could be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce (O2-) under sunlight and artificial UVA (320-400 nm) and UVB (290-320 nm). Lincomycin, cephalothin and erythromycin generated significant amount of O2- under various irradiation conditions. Superoxide dismutase (SOD), an enzymatic quencher of O2- inhibited O2- production in all drugs tested. The results suggest that due precaution are necessary to avoid ultraviolet radiation (UVR) after the intake of photoreactive drugs, especially in tropical and sub tropical countries.

Anti-Bacterial Agents↗
PubMed2000

Trauma patients with positive cultures have higher levels of circulating macrophage migration inhibitory factor (MIF).

Macrophage migration inhibitory factor (MIF) is a pituitary "stress" hormone that plays a critical role in the host immune response. The aims of the study were to determine whether MIF was detectable in the circulation of trauma patients, to assess whether MIF levels were associated with injury severity, days post injury, infection, and to examine concentrations of other pro-inflammatory cytokines in circulation. We collected plasma samples from 35 trauma (multiple injury) patients and 18 healthy controls. Concentrations of MIF, TNF-alpha, IL-1beta, and IL-6 were measured by ELISA. Average MIF concentration in plasma of trauma patients was 14 fold higher than that of healthy controls (19,439+/-2,615 pg/ml in trauma vs 1,337+/-286 pg/ml in control; p=0.0002). There was no correlation between MIF values and injury severity score or days post injury. Average level of IL-6 in trauma patients was 587+/-85 pg/ml but was not correlated with MIF concentration. TNF-alpha and IL-1beta were not detectable in trauma patients or healthy controls. Higher MIF levels were associated with positive cultures (blood, urine, sputum, wound). These data suggest that MIF may be a possible indicator of infection in trauma patients.

Bacterial Infections↗
PubMed1999

Agricultural produce in the dry bed of the River Ganga in Kanpur, India--a new source of pesticide contamination in human diets.

Vegetables grown in the dry bed field of the River Ganga in Kanpur, an important industrial city of North India, were analysed for the pesticides hexachlorocyclohexane (HCH), dichlorodiphenyl trichloroethane (DDT), their isomers and metabolites at three different sites. Residues of both the pesticides were found in all the samples. Mean levels of 109.35, 136.76 and 145.93 microg HCH/kg and 6.64, 49.3 and 46.70 microg DDT/kg were found in the rural upstream, city and downstream industrial areas, respectively. The mean total HCH and DDT levels were within safe limits as per the Indian Standard but some samples had HCH levels above the WHO/FAO limit. The pesticide residue level in vegetables was several fold higher than their surrounding sandy soil and could pose health problems since these popular vegetables are consumed regularly by the population.

Crops, Agricultural↗
PubMed1999

Phototoxicity evaluation--Tetrahymena thermophila as an alternative model.

Interest in utilizing an alternative to animal method for toxicological evaluation has received considerable attention due to cost effectiveness and the ethical issues involving animal experimentation. Alternative methods for phototoxicity evaluation are significant because of growing concern over increasing health effects due to stratospheric ozone depletion resulting in an increasing penetration of ultraviolet light-B radiation (UVB, 290-320 nm) which contributes to activation of chemical and biological molecules to potential phototoxic agents. The classic rabbit eye-irritancy test referred to as Draize test has been the subject of severe criticism by animal welfare groups. Dermal toxicity test using guinea pigs and mouse tail phototoxicity test is time consuming and requires a large number of laboratory animals. In photohaemolysis assay some of the phototoxic agents (such as riboflavin) react with the membrane proteins of the erythrocyte. However, in vitro test system using protozoa offers a promising alternative means of phototoxicity evaluation. Our previous studies have demonstrated that synergistic action of photochemically reactive agents and sunlight produces lethal effects to Paramecium but the protozoan has not received serious consideration for use as an alternative model for phototoxicity evaluation. In the present communication we have described the potential application of Tetrahymena as an alternative model to study the radiation-induced changes both in the presence or absence of photoreactive chemical agents. This model is likely to provide scope for studying the biological effects of environmental UVB radiation, DNA damage and defence against oxidative stress.

Animal Testing Alternatives↗
PubMed1998

UVB-induced reduction in biomass and overall productivity of cyanobacteria.

Effect of middle wave ultraviolet radiation (UVB) was studied in three different species of cyanobacteria (Nostoc, Anabaena and Scytonema) by estimating their growth pattern, biomass yield, chlorophyll content, total starch and protein content. The results show that exposure of the cyanobacteria with UVB dose corresponding to an increase or decrease of 20% in its environmental flux will have drastic effects on biomass production, photosynthetic rate and nitrogen fixation. Cyanobacteria are primary sources of marine food web and an important biofertilizer; therefore, their protection from increasing threat of stratospheric ozone depletion will be necessary to maintain the ecological balance.

Anabaena↗
PubMed1998

Copper(II) as an efficient scavenger of singlet molecular oxygen.

Reactive oxygen species (ROS) are considered to play an important role in tissue injury that damages DNA, proteins, carbohydrates and lipids. Increased production of ROS and/or decreased efficiency of antioxidant defense system has been shown to contribute to a number of degenerative processes including cancer and AIDS. Among the various forms of ROS, singlet oxygen (1O2), which is generated predominantly in photosensitization reactions, is of particular physiologic significance because of its selectively long life in aqueous solution, its ability to cross the cell membrane barrier and high reactivity towards biomolecules. In the present study, the 1O2 scavenging potential of Cu(II) has been evaluated by (i) generating 1O2 by photosensitization of rose bengal (RB), (ii) establishing 1O2 quenching with recognized 1O2 scavengers like sodium azide, DABCO and (iii) examining the effect of Cu(II) in scavenging of 1O2. The results revealed that Cu(II) inhibited the rate of 1O2 production by 88%, 68%, 40%, 21% and 10% at a concentration of 10(-2) M, 5 x 10(-3) M, 10(-3) M; 5 x 10(-4) M, and 10(-4) M, respectively. Under similar experimental condition, sodium azide or DABCO at 10(-2) M inhibited the 1O2 production by 86% and 88%, respectively. Other 1O2 generating photosensitizer like hematoporphyrin, riboflavin and methylene blue also produced identical results with Cu(II) but Fe(II), Fe(III), Zn(II) or As(III) did not produce any quenching of 1O2. Presence of a copper binding peptide (Gly-Gly-His) in the reaction system reduced the 1O2 scavenging capacity of Cu(II) by 52-66% depending upon the UV dose. The 1O2 scavenging property of metal ion appears to have an advantage to reduce the oxidative damage of photodynamic reactions in order to prevent ROS-induced toxicity reactions.

Animals↗
PubMed1997

High sensitivity of tubifex for ultraviolet-B.

Phytoplankton and zooplankton serve as major food material for primary and secondary consumers in the marine food web. Although phytoplankton are primary targets to UV radiation damaging effects, we have demonstrated that stratospheric ozone depletion will affect zooplankton to contribute to inhibition in biomass production. In this study, an annilid Tubifex was irradiated under UVA, UVB, UVC or direct sunlight to demonstrate behavioral changes (motility and mortality). The organism showed varying degrees of sensitivity towards UVB and UVC. Even a small increment in UVB resulted in high degree of mortality. Interestingly, water turbidity seems to have a protective effect against UV exposure. These results strongly suggest that a change in UVB flux has direct impact on biomass production.

Animals↗
PubMed1996

Nitric oxide produced by cytokine-activated pulmonary artery smooth muscle cells is cytotoxic to cocultured endothelium.

BACKGROUND: We recently demonstrated that rat pulmonary artery smooth muscle (RPASM) generates maximal nitric oxide (NO) when exposed to inflammatory cytokines, such as tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. Our hypothesis is that NO produced by cytokine-stimulated RPASM has local cytotoxic effects on endothelium. Accordingly, we designed a pulmonary smooth muscle and endothelial coculture experiment in which the effects of NO on endothelium can be distinguished from the direct effects of cytokines. METHODS: RPASM cells were incubated with a mixture of TNF-alpha (500 units/ml) and IFN-gamma (100 units/ml) for 24 hours. This cytokine mixture was then removed and the NO-producing smooth muscle cells were incubated in a coculture transwell system with rat pulmonary artery endothelial (RPAE) cells. Subsequent NO production (as measured by nitrite concentration in cell supernatants), and the number of viable attached endothelial cells were then measured at 48 hours. RESULTS: RPASM continued to produce large amounts of NO, in the absence of further cytokine stimulation, after a 24-hour exposure to TNF-alpha and IFN-gamma. This RPASM-generated NO decreased the number of viable attached endothelial cells after 24 hour RPASM-RPAE coculture by 57%. The competitive stereospecific inhibitor of inducible NO synthase (iNOS), NG-monomethyl-L-arginine (NMA), returned the inducible NO production to basal levels and reversed the cytotoxic effects on endothelial cells. The number of viable attached endothelial cells returned to control levels. CONCLUSIONS: The NO produced by cytokine-activated RPASM has local cytotoxic effects on RPAE in coculture. Such NO produced in the vasculature may be a factor in the origin of acute lung injury under conditions of trauma and sepsis.

Animals↗
PubMed1996

Ultraviolet radiation-induced production of superoxide radicals by selected antibiotics.

The ability of certain drugs and chemicals to induce cutaneous phototoxicity and DNA damage has been attributed to free radical formation during photolysis. In this context we have observed that the synergistic action of commonly used antibiotics and ultraviolet radiation (UVR) exhibited strong superoxide radical (O2-) generation potential in the following order: benzylpenicillin > amphotericin > ampicillin > nystatin > spectinomycin > gentamicin. Commercially available penicillin, nystatin, ampicillin and gentamicin also generated O2- under similar conditions. The results suggest that due precaution are necessary to avoid UVR after the intake of photoreactive drugs.

Anti-Bacterial Agents↗
PubMed1996

Effect of aminoguanidine on in vivo expression of cytokines and inducible nitric oxide synthase in the lungs of endotoxemic rats.

Endotoxemia results in the release of multiple mediators such as tumor necrosis factor alpha (TNF-infinity), interleukin-1 beta (IL-1 beta), and nitric oxide (NO), which is thought to be responsible for the hypotension of septic shock. Although there are many reports on the presence of these mediators in serum, in vivo expression of TNF-infinity, IL-1 beta and inducible nitric oxide synthase (iNOS) at the tissue level has not been studied extensively. We investigated in vivo expression of these cytokines and iNOS in the lungs of rats that were injected with saline, endotoxin or endotoxin plus aminoguanidine (AG), an inhibitor of iNOS. Expression of TNF-infinity, IL-1 beta and iNOS was absent in control (saline treated) but was increased in endotoxin treated animals. In animals treated with endotoxin plus AG (400 mg/kg), expression of iNOS was markedly inhibited whereas there was no effect on expression of TNF-infinity and IL-1 beta. The inhibitory effect of AG was probably dose dependent because a lower concentration of AG (50 mg/kg) showed no change in the expression of iNOS.

Animals↗
PubMed1995

Ultraviolet-B effects on ocular tissues.

The enhancement of UVB on the surface of the earth due to stratospheric ozone depletion may increase the risk of photochemically induced cataract. In this study, changes in the content of certain biological parameters were used as a marker to study ocular toxicity. A significant enhancement in the level of H2O2, LP and Pi, along with the depletion of GSH (antioxidant-defence system) in serum, aqueous humor and lens of albino mice exposed to UVB was observed. The level of Ca++ increased in serum and aqueous humor but decreased considerably in the lens due to increase in UVB exposure. These observations provide further clues to support the involvement of oxidative stress and Ca++ in the events leading to the formation of cataract.

Animals↗