Biomedical subjects

S K Das

Publications and source records attributed to S K Das.

At least 19 recordsLinked to original sources

PubMed1992

Partial characterization, progressive development and correlations of some neoplastic characters in 20-methylcholanthrene-induced transformed murine embryonal fibroblasts.

Non-trypsinized primary fibroblast cells from 20-day-old Swiss mouse embryo was transformed by 20-methylcholanthrene (MCA) and was designated as CNCI-PM-20. The progressive development of some transformation related characters such as morphological alterations, reduced population doubling time, increased saturation density, reduced serum requirement, increased plating efficiency, loss of density dependent growth inhibition, anchorage-independent growth and tumorigenicity in mice clearly demonstrated the multistep process of carcinogenesis as well as the neoplastic nature of the cell line. Furthermore, the association of reduced requirement of serum and loss of density-dependent growth inhibition with tumorigenicity were also observed. Finally, anchorage-independent growth, greater malignant nature of transformed foci and increased number of giant cells may be required for tumorigenicity of this cell line.

Animals↗

PubMed1992

Identification of calcium-dependent phospholipid-binding proteins (annexins) from guinea pig alveolar type II cells.

A new group of calcium-regulating proteins, called annexins or Ca(++)-dependent phospholipid-binding proteins (PLBP), have been detected in different species, organs and cell types. In the present study, we have identified and quantitated PLBP from guinea pig lung, lavage fluid and alveolar type II cells to elucidate the possible role of PLBP in lung surfactant biogenesis and secretion. Lungs were lavaged and type II cells from lavaged lung were isolated by elastase digestion and purified by centrifugal elutriation. For the quantitative identification of PLBP, we performed ELISA assays and Western blot analysis by using an antiserum raised in guinea pigs against a pure rabbit lung 36 kDa PLBP. The lavage fluid, cytosol from lung and type II cells contained 784, 167 and 435 ng per mg protein, respectively, of PLBP. The SDS-PAGE electrophoretic pattern and Western blot confirmed that all lung samples have band corresponding to a 36 kDa protein. This indicates that both alveolar type II cells and lavage fluid have higher levels of PLBP than whole lung cytosol.

Animals↗

PubMed1992

Genotoxicity of chryseno[4,5-bcd]thiophene and its sulfone derivative.

Our recent syntheses of chryseno[4,5-bcd]thiophene together with its potential sulfone metabolite, chryseno[4,5-bcd]thiophene-4,4-dioxide, have made these compounds available for genotoxicity testing. Such toxicity testing is of interest as this thiophene is an isoster of the established carcinogen benzo[a]pyrene and is one of the thiaarenes which are potential environmental contaminants found in fossil fuels. Although the thiophene was less mutagenic than benzo[a]pyrene in Salmonella strains TA98 and TA100 after S9 activation, it exhibited in vivo chromosomal aberration activity equal to that of benzo[a]pyrene in the bone-marrow cells of mice. A reduced activity with Salmonella as well as in the bone-marrow cell assay for the sulfone does not support its role as the key active metabolic intermediate for the genotoxicity of the thiophene. Our molecular orbital calculations would be consistent with the concept of activation through a diol-epoxide mechanism and offers an explanation for the reduced genotoxicity of the sulfone via this mechanism. These genotoxicity studies support the concern that sulfur isosters of established carcinogenic polycyclic aromatic hydrocarbons could themselves be toxic.

Animals↗

PubMed1992

A comparison of heparinised saline irrigation solutions in a model of microvascular thrombosis.

The use of heparinised irrigation solutions has become common in microvascular surgery, but the concentration of heparin has been determined empirically. A laboratory model of microvascular thrombosis, employing a crush injury, intimal abrasion, and stasis to the rat superficial femoral artery was used to compare heparinised saline irrigation solutions of various concentrations. The solutions included normal saline (Group I, controls) and heparinised normal saline in concentrations of 10 U/ml (Group III), 250 U/ml (Group IV), and 500 U/ml (Group V). Group I animals had a patency rate of 25% at 20 min and 0% at 24 h. Group II showed a patency rate of 75% at 20 min but fell to 37.5% at 24 h. Patency in Group III was 87.5% at 20 min and at 24 h. Group IV had a 100% patency rate at 20 min and at 24 h. Group V animals were 100% patent at 20 min and 87.5% patent at 24 h. The activated partial thromboplastin time was prolonged in animals exposed to 250 U/ml and 500 U/ml of heparinised saline. Patency was significantly improved in animals exposed to 100 U/ml, 250 U/ml and 500 U/ml when compared to the control group (p less than 0.001). These results suggest that topical heparinised saline administration is of benefit in the prevention of microvascular thrombosis. Higher concentrations tested in this study resulted in a significant increase in patency, but also prolonged the activated partial thromboplastin time. 100 U/ml is the ideal concentration of heparinised saline irrigation because it significantly improved patency but did not produce detectable systemic effects in this model.

Animals↗

PubMed1992

An in vitro study on the effect of UVA radiation on human gingival fibroblasts.

The recent availability of a 99.9% UVA source has made possible studies that show that low energy wavelengths, previously considered innocuous, significantly affected wound healing in hairless guinea pigs. Decreased wound tensile strength and a slower rate of wound contraction in irradiated animals were among the changes noted. Because of their advocated role in the wound healing process, fibroblasts were chosen to study the effects of pure UVA exposure at a cellular level. 3H-thymidine uptake levels were measured in 8 groups of fibroblast cultures (12 samples/group). The cultures were exposed to varying concentrations of pure UVA. Previously incorporated 14C-thymidine levels were used to compensate for differences in cell numbers between samples. At a fluence of 3.65 x 10(-3) watts/cm2, a significant decrease in 3H-thymidine incorporation (compared to controls) was seen for all exposure periods and there was a dose-dependent decrease only in 3H-thymidine uptake for cells exposed to 1-4 min of UVA. Using post-exposure incubations of 2-16 h, a time-dependent recovery of 3H-thymidine uptake was also demonstrated, from 40% of control at 4 h, to 75% at 8 h, and 99% at 16 h. The near-complete recovery at 16 h was seen in exposures up to 2.73 joules/cm2 (12 min), whereas higher concentrations showed only partial recovery. These studies demonstrated the deleterious, though reversible, effects of UVA on fibroblasts and suggest a possible pathophysiologic process for UVA's effect on wound healing in this animal model.

Cells, Cultured↗

PubMed1992

The effects of ultraviolet irradiation on wound contraction in the hairless guinea pig.

Ultraviolet radiation has been shown to alter wound tensile strength and evoke a number of intracellular changes in fibroblasts. We examined the effects of relatively high doses of ultraviolet radiation on subsequent wound contraction of circular wounds in the hairless guinea pig model. Female hairless guinea pigs were divided into two experimental groups receiving 80 J/cm2 or 480 J/cm2 every other day for 16 weeks. Age-matched unirradiated animals were used as controls. After exposure, all animals had either a 4 mm punch biopsy (80 J/cm2) or a 2.4 cm diameter ((480 J/cm2) Groups 3 and 4) circular area excised from the dorsum. The extent of wound enlargement immediately following wounding of the irradiated animals was decreased as compared to the controls. The rate of wound contraction was significantly lower during early stages of wound contraction in each group of irradiated animals, and wound contraction was significantly slower overall in both groups of irradiated animals compared to controls.

Animals↗

PubMed1992

The in vivo and in vitro genotoxicity of aromatic amines in relationship to the genotoxicity of benzidine.

Benzidine and 12 related aromatic amines have been studied for the effects of substituent groups and pi orbital conjugation on their genotoxicity as measured by their mutagenicity in vitro with Salmonella and by chromosomal aberrations (CA) in vivo in the bone-marrow cells of mice. The in vitro studies indicated increases in mutagenicity with increases in the electron withdrawing ability of para' substituents. Mutagenicity also increases with increased conjugation as shown by the degree of planarity of the biphenyl compounds and by comparing the mutagenicities of biphenyl amines to stilbenes as well as to ethylene bridged diphenyl compounds. The relative in vitro mutagenicity results were not predictive of relative in vivo CA results. The 3 most genotoxic compounds in vivo were the conjugated amines without substituents in the para' position. The CA values for 4-aminostilbene were exceptionally high. These in vivo results indicate increased genotoxicity for benzidine analogs without substitution in the para' position.

Aminobiphenyl Compounds↗

PubMed1992

beta-Carotene-mediated inhibition of a DNA adduct induced by 7,12-dimethylbenz(a)anthracene and 7-hydroxymethyl-12-methylbenz(a)anthracene in mouse mammary gland in vitro.

The influence of beta-carotene on the formation of DNA-adducts induced by 7,12-dimethylbenz(a)anthracene (DMBA) and 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA) during transformation of mouse mammary cells in organ culture was analysed. Treatment with beta-carotene (10(-8)-10(-5) mol/l) caused inhibition (48.8-94.4%) of an adduct (VI), which was detectable in DNA samples from DMBA-treated mammary glands. Out of six adducts, derived from further analysis of DNA samples from 7-OHM-12-MBA-treated glands, adduct f eluted in the same fraction as adduct (VI), indicating these adducts were analogous. Likewise, adduct f was also inhibited by beta-carotene. Boronate chromatographic analysis revealed this particular adduct was a syn-dihydrodiol epoxide product. Adduct inhibition was detectable both at the start and after DMBA treatment. alpha-Tocopherol and canthaxanthin were ineffective in inhibiting adducts. It is reasonable to conclude that beta-carotene-mediated modification of adducts is associated with the inhibition of a syn-adduct, which is derived from further metabolism of a 7-OHM-12-MBA intermediate.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1992

Protection against the effects of anticholinesterases on the latencies of action potentials in mouse skeletal muscles.

1. Adult male albino mice were injected subcutaneously with an organophosphorous anticholinesterase to initiate excessive variability in the latency of indirectly elicited muscle action potentials (jitter) when assessed 5 days later. 2. Pretreatment of the mice with a single dose of pyridostigmine prevented the development of jitter after subsequent dosing with an organophosphate. 3. Treatment with one dose of pralidoxime (2PAM) prevented the development of jitter if given less than 1 h after treatment with ecothiopate, a reactivatable inhibitor of cholinesterase. Similar treatment with 2PAM after a non-reactivatable inhibitor did not prevent the development of jitter. The repeated administration of 2PAM over 12 h did ameliorate jitter. 4. Pretreatment of mice orally with alpha-tocopherol and N-acetylcysteine, known to prevent ecothiopate-induced myopathy, did not prevent the development of jitter after ecothiopate. 5. It is concluded that the development of jitter was a consequence of the inhibition of acetylcholinesterase, and although jitter did not develop acutely, the potential for the full development of jitter was achieved about 1 h after intoxication with ecothiopate. The development of jitter did not involve the generation of free radicals. Reduction of the early effects of intoxication with anticholinesterases by pyridostigmine or 2PAM prevented the development of jitter.

Acetylcholinesterase↗

PubMed1992

Effects of physical stress on complete blood count and venous blood gas profile of individuals with sickle cell trait.

The association between sickle cell trait (SCT) and adverse effects of exercise has been controversial. While individuals with SCT are at higher risk of sudden death, the mechanism for this outcome remains to be elucidated. In order to shed light on this controversy, we have monitored venous blood count and blood gas parameter values in normal and SCT subjects during treadmill exercise. White and red blood cell counts and hemoglobin changed significantly over time in both the SCT and normal groups, with peak exercise values different from pre-exercise or post-exercise values. Red blood cell counts showed significant group-time interaction; increase in count during exercise was accentuated in SCT subjects. All blood gas parameters showed significant changes over time in both groups. O2 content was significantly higher in SCT than AA at all time intervals. O2 saturation, pO2 and CO binding to hemoglobin showed significant group-time interaction. Furthermore, O2 saturation for the combined groups was significantly greater at peak exercise and at rest than before exercise. It is possible that treadmill exercise causes microvascular shunting in SCT subjects, leading to a decrease in the peripheral utilization of oxygen.

Adult↗

PubMed1992

Hyperoxia elevates Cu,Zn-superoxide dismutase of endothelial cells as detected by a sensitive ELISA.

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of bovine Cu,Zn-SOD. Accuracy of the ELISA and specificity of the antibody for cell-free extracts was established by: (1) measurement of antigen levels of bovine endothelial cell extracts reconstituted with pure antigen, and (2) immunoblotting with affinity purified antibody. The ELISA was highly sensitive and 0.05-0.10 ng of pure antigen could be accurately detected, which allowed the measurement of Cu,Zn-SOD in as few as 250 endothelial cells. With utilization of the ELISA for detection, DEAE-cellulose chromatography patterns of endothelial cell Cu,Zn-SOD overlapped those of pure bovine erythrocyte Cu,Zn-SOD. Exposure of cells in culture to 80% O2 for 48 h increased the relative abundance of the Cu,Zn-SOD as measured by the ELISA by 1.8-fold. Thus, endothelial cells in culture respond to hyperoxia by enhanced production of Cu,Zn-SOD protein. The ELISA developed in this study may be useful for assessing other factors that regulate cellular production of Cu,Zn-SOD.

Animals↗

PubMed1992

Reduction of glutathione is associated with growth restriction and enlargement of bovine pulmonary artery endothelial cells produced by transforming growth factor-beta 1.

In addition to inhibiting proliferation and causing enlargement of bovine pulmonary artery endothelial cells in culture, porcine platelet transforming growth factor-beta 1 (TGF-beta 1) (2 ng/ml) lowered glutathione (GSH) of these cells by 48% after 96 h in culture when GSH levels were normalized for cell counts. This lowering of cellular GSH was more marked when corrections were made for approximated cell volume. TGF-beta 1 produced only moderate inhibition of pulmonary artery smooth muscle cell proliferation and did not significantly reduce the GSH content of these cells, even at concentrations as high as 8 ng/ml. Elevation of GSH of endothelial cells above control levels by 0.05 mM diethylmaleate or 1 mM cystine prevented the inhibition of cellular proliferation produced by TGF-beta 1. Lowering cellular GSH levels by approximately 85% for 24 to 72 h with 0.01 mM buthionine sulfoximine (BSO) in the absence of TGF-beta 1 had no effect on proliferation or size of the endothelial cells. However, 0.01 mM BSO potentiated the inhibitory effect of TGF-beta 1 on endothelial cell proliferation and in combination with TGF-beta 1 caused cellular detachment at low endothelial cell densities. Thus, although TGF-beta 1 lowers the level of endothelial cellular GSH, this in itself does not appear to account for the inhibition of proliferation and enlargement of these cells produced by TGF-beta 1. Rather, the combination of another unidentified action of TGF-beta 1 in the presence of reduced cellular GSH likely accounts for these effects.

Animals↗

PubMed1992

Modulation of transforming growth factor-beta 1 antiproliferative effects on endothelial cells by cysteine, cystine, and N-acetylcysteine.

Early passaged bovine pulmonary artery endothelial cells exposed to 0.1-2.0 ng/ml transforming growth factor-beta 1 (TGF-beta 1) showed concentration-dependent growth inhibition, as assessed by [3H]thymidine labeling and cell counts, over a 96-h interval. Most of the inhibition of [3H]thymidine labeling measured at 96 h persisted when the medium was replaced with TGF-beta 1-free medium after 24 h, but the inhibition of labeling was prevented by the presence of anti-TGF-beta 1 antibody in the replacement medium. Additions of 2 mM cysteine, 1 mM cystine, or 2 mM N-acetylcysteine at the time of the initial addition of TGF-beta 1 blocked the inhibitory effect of TGF-beta 1 on [3H]-thymidine labeling when this was assessed after 72-96 h, but not at earlier times. Prevention of the inhibitory effect on cellular proliferation produced by cysteine, cystine and N-acetylcysteine was associated with elevation of cellular glutathione that was present at 48-96 h. There was no evidence for direct inactivation of TGF-beta 1 by the thiol-amino acids. Conditioned medium from TGF-beta 1-treated endothelial cells inhibited proliferation of mink lung carcinoma (CCL64) cells, supporting a previously reported concept of autocrine production of TGF-beta 1 by the endothelial cells. The inhibitory action of the conditioned medium was partially prevented when 1 mM cysteine was added during conditioning. Thus, TGF-beta 1 treatment of endothelial cells appears to set off autocrine production by these cells of TGF-beta 1 that perpetuates the inhibition of cellular proliferation. Replenishment of cellular glutathione with thiol-amino acids counteracts the growth-inhibitory effect of TGF-beta 1 through a currently undefined mechanism.

Acetylcysteine↗

PubMed1992

Expression of transforming growth factor-beta isoforms (beta 2 and beta 3) in the mouse uterus: analysis of the periimplantation period and effects of ovarian steroids.

Expression of beta-type transforming growth factor genes (TGF beta 2 and TGF beta 3) in the mouse uterus during the periimplantation period and in response to an acute exposure to 17 beta-estradiol (E2) and progesterone (P4) was studied using Northern blot hybridization and/or immunocytochemistry. Polyclonal antipeptide antibodies specific for TGF beta 2 or TGF beta 3 were employed for immunocytochemistry. In the preimplantation uterus [days (D) 1-4 of pregnancy; day 1 = vaginal plug], immunostaining for TGF beta 2 was observed in luminal and glandular epithelia as well as in myometrium and vascular smooth muscle. In the postimplantation period (D5-D8), TGF beta 2 immunostaining was also detected in decidual cells. In contrast, TGF beta 3 immunostaining was restricted to the myometrium and vascular smooth muscle throughout the periimplantation period (D1-D8). Antisense TGF beta 2 and TGF beta 3 RNA probes were employed for Northern blotting. Northern blot hybridization revealed four TGF beta 2 transcripts (approximately 6.0, 5.0, 4.0, and 3.5 kilobases) in total uterine poly(A)+ RNA on D1-D6 and in poly(A)+ RNA from the deciduum and myometrium collected on D7 and D8 of pregnancy. These TGF beta 2 transcripts were also detected in isolated samples of deciduomata or myometrium obtained from D8 pseudopregnant mice in which the decidual cell reaction was induced experimentally on D4. The levels of these transcripts remained relatively constant during the periimplantation period. Northern blot analysis detected a 3.8-kilobase TGF beta 3 transcript in total uterine poly(A)+ RNA on D1-D6. This transcript was detected in myometrial RNA samples on D7 and D8 of pregnancy or D8 of pseudopregnancy, but was not detected in RNA from the deciduum on D7 and D8 or in that from deciduomata on D8. The effects of ovarian steroids on TGF beta 2 and TGF beta 3 mRNAs were examined in uteri of adult ovariectomized mice. Uterine TGF beta 2 or TGF beta 3 mRNA persisted in ovariectomized mice. However, an injection of E2 induced a rapid (6 h), but transient, induction (approximately 3- to 4-fold) of TGF beta 2 mRNA. An injection of P4 had no effect on TGF beta 2 mRNA levels, and coinjection of P4 with E2 did not antagonize the E2-stimulated transient accumulation of TGF beta 2 mRNA. In comparison, neither an injection of E2 nor one of P4 exerted significant effects on TGF beta 3 mRNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Thrombo-embolic prophylaxis in total knee replacement. Evaluation of the A-V Impulse System.

We performed a prospective randomised controlled trial of a new mechanical method of prophylaxis for venous thrombo-embolism in 60 patients undergoing knee replacement surgery. The method uses the A-V Impulse System to produce cyclical compression of the venous reservoir of the foot. The overall incidence of deep-vein thrombosis was 68.7% in patients receiving no prophylaxis and 50% in those using the device. The difference was not significant. There was, however, a reduction of the extent of thrombosis in the treated group. There were 13 major calf-vein thrombi and six proximal-vein thrombi in the control group compared with only five major calf-vein thrombi in the treated group. This difference was significant (p = 0.014). No patient developed clinical features of a pulmonary embolism.

Aged↗

PubMed1992

Enhanced production of antibody with specific antigen.

On inoculation of nonspecific stimulator of immunity (NSI), prepared from Mycobacterium phlei (M. phlei), simultaneously along with sheep pox virus (SPV) in sheep, the recipient has exhibited appreciable level of SPV specific antibody as early as on 10th day which reached at peak level on 20th day and remained unaltered on 30th day of postimmunisation as evinced by serum neutralisation test (SNT), enzyme linked immunosorbant assay (ELISA) indirect, fluorescent antibody technique (FAT) indirect, counter immunoelectrophoresis (CIEP) and finally by virulent SPV challenge. On the contrary, sheep, when immunised with SPV only could not produce appreciable level of antibody on 10th day but did so on 20th day of inoculation. SPV and NSI immunised sheep produced enhanced protection against virulent SPV challenge in comparison with sheep immunised with SPV only. Healthy control sheep, however, could not resist challenge.

Animals↗

PubMed1992

Characteristics of retinoid-induced adhesion in a cultured human oral carcinoma cell line.

Cultured epidermoid oral carcinoma cells KB were easily detached from plastic surface in an ethylene diamine tetra acetic acid (EDTA) mediated detachment assay. Treatment of KB cells with retinol (vitamin A) or retinoic acid (RA) induced growth inhibition and caused reversible enhanced adhesion to the substratum in a similar fashion as well. Different synthetic retinoids were tested for their ability to induce growth inhibition and adhesion. A relationship between structure and activity of retinoids was found to exist. Possible mechanisms of retinoid-induced enhanced adhesion are discussed.

Carcinoma, Squamous Cell↗

PubMed1992

Macrophage interleukin 1 response to injected silicone in a rat model.

Observations of silicone granuloma formation and migration of silicone to regional lymph nodes have indicated a need for more research into the possible immunological responses to silicone. The present study was undertaken to assess the effect of injected silicone particles on the ability of splenic macrophages to produce interleukin 1 (IL-1) and to determine the relative quantities produced. Lewis rats were divided into 4 groups: Group 1 animals (n = 3) were injected subcutaneously with sterile saline (2.5 ml) and served as control animals; Group 2 animals (n = 3) also served as control subjects, but macrophages isolated from these animals were exposed to lipopolysaccharide (LPS); Group 3 animals (n = 3) were injected subcutaneously with Freund's complete adjuvant (FCA) (2.5 ml) to serve as FCA control animals; and Group 4 animals (n = 3) received a subcutaneous injection of a sonicated slurry of equal parts FCA and silicone (2.5 ml each). IL-1 production was not significantly increased in splenic macrophages from animals exposed to the silicone slurry (p greater than 0.20) 8 months after injection as compared with control animals or animals given FCA alone. Macrophages exposed to LPS, a known mitogen, had significantly elevated IL-1 production. Subcutaneously injected silicone particles did not elicit an increase in IL-1 production in rat macrophages.

Animals↗