1Alpha,25-dihydroxyvitamin D3 inhibits hepatic chromosomal aberrations, DNA strand breaks and specific DNA adducts during rat hepatocarcinogenesis.

The possible promoting effect of streptozotocin (STZ; 65 mg/kg body weight, intraperitoneal)-induced diabetes during 2-acetylaminofluorene (2-AAF; 0.04% in basal diet)-initiated hepatocarcinogenesis and modulatory effect of 1alpha,25-dihydroxyvitamin D3 (VD3; 0.3 microg/0.1 ml in propylene glycol, per os) were investigated by monitoring chromosomal aberrations (CAs), DNA strand breaks and specific DNA adducts in rat liver. VD3 treatment (twice a week) was started 4 weeks before the 2-AAF regimen and continued throughout the study. Aberrant metaphase chromosomes were counted from the regenerating hepatocytes 15, 30 or 45 weeks after STZ injection, while DNA strand break and adduct assays were performed 45 days post-STZ treatment. Dietary exposure to 2-AAF elicited a substantial increase in CAs and elevated the extent of DNA strand breaks and formation of N-(deoxyguanosin-8-yl)-2-aminofluorene. A promoting effect of STZ was evident from CAs coupled with DNA strand break analysis. VD3 treatment substantially reducted 2-AAF+STZ-induced CAs as well as DNA strand breaks and adducts. Thus, VD3 appears to be effective in suppressing liver-specific early chromosomal as well as DNA damage during the process of rat hepatocarcinogenesis initiated with 2-AAF and promoted by STZ contributing to its promise as a cancer chemotherapeutic agent.

Free radical-initiated and gap junction-mediated bystander effect due to nonuniform distribution of incorporated radioactivity in a three-dimensional tissue culture model.

To investigate the biological effects of nonuniform distribution of radioactivity in mammalian cells, we have developed a novel three-dimensional tissue culture model. Chinese hamster V79 cells were labeled with tritiated thymidine and mixed with unlabeled cells, and multicellular clusters (approximately 1.6 mm in diameter) were formed by gentle centrifugation. The short-range beta particles emitted by (3)H impart only self-irradiation of labeled cells without significant cross-irradiation of unlabeled bystander cells. The clusters were assembled in the absence or presence of 10% dimethyl sulfoxide (DMSO) and/or 100 microM lindane. DMSO is a hydroxyl radical scavenger, whereas lindane is an inhibitor of gap junctional intercellular communication. The clusters were maintained at 10.5 degrees C for 72 h to allow (3)H decays to accumulate and then dismantled, and the cells were plated for colony formation. When 100% of the cells were labeled, the surviving fraction was exponentially dependent on the mean level of radioactivity per labeled cell. A two-component exponential response was observed when either 50 or 10% of the cells were labeled. Though both DMSO and lindane significantly protected the unlabeled or bystander cells when 50 or 10% of the cells were labeled, the effect of lindane was greater than that of DMSO. In both cases, the combined treatment (DMSO + lindane) elicited maximum protection of the bystander cells. These results suggest that the bystander effects caused by nonuniform distributions of radioactivity are affected by the fraction of cells that are labeled. Furthermore, at least a part of these bystander effects are initiated by free radicals and are likely to be mediated by gap junctional intercellular communication.

Radiation protection by cysteamine against the lethal effects of intracellularly localized Auger electron, alpha- and beta-particle emitting radionuclides.

The mechanisms by which DNA-incorporated radionuclides impart lethal damage to mammalian cells were investigated by examining the capacity of cysteamine (MEA) to protect against lethal damage to V79 cells caused by unbound tritium (3H2O), DNA-incorporated 131/125I-iododeoxyuridine (IdU) and the alpha-particle emitter 210Po-citrate. Radiolabeled cells were maintained at 10.5 degrees C for 72 h in the absence or presence of MEA (0.65-2.6 mM) and the surviving fraction was determined. Protection against lethal damage caused by 3H2O, 131IdU or 125IdU and 210Po-citrate depended on the concentration of MEA with maximum protection at 1.3-1.9 mM. The dose modification factors obtained at 1.3 mM for the radiochemicals were 2.5 +/- 0.3, 1.8 +/- 0.2, 1.7 +/- 0.1 and 1.4 +/- 0.1, respectively. MEA provides more protection against indirect than direct effects of ionizing radiation, and indirect effects play a role in the radiotoxicity of Auger electron emitters incorporated into the DNA of mammalian cells.

Vanadium chemoprevention of 7,12-dimethylbenz(a)anthracene-induced rat mammary carcinogenesis: probable involvement of representative hepatic phase I and II xenobiotic metabolizing enzymes.

Vanadium, a non-platinum group metal and dietary micronutrient, is now proving to act as a promising antitumor agent. The present study was conducted to ascertain its antineoplastic potential against an experimental mammary carcinogenesis. Female Sprague-Dawley rats, at 50 days of age, were treated with 7,12-dimethylbenz(a)anthracene (DMBA) (0.5 mg/100 g body weight) by a single tail vein injection in an oil emulsion. Vanadium (ammonium monovanadate) at the concentration of 0.5 ppm was supplemented in drinking water and given ad libitum to the experimental group immediately after the carcinogen treatment and it continued until the termination of the study (24 weeks for histological and biochemical observations and 35 weeks for morphological findings). It was found that vanadium treatment brought about a substantial protection against DMBA-induced mammary carcinogenesis. This was evident from histological findings that showed no sign of hyperplasia or abnormality after vanadium treatment. There was a significant reduction in incidence (P < 0.05), total number, multiplicity (P < 0.01) and size of palpable mammary tumors and delay in mean latency period of tumor appearance (P < 0.001) following vanadium supplementation compared to DMBA control. From the cumulative results of various hepatic biochemical indices namely, lipid peroxidation, reduced glutathione level, superoxide dismutase activity, cytochrome P450 content and glutathione S-transferase activity, the anticarcinogenic potential of vanadium was well reflected through stabilization of these parameters. Results of the study indicate that the anticarcinogenic activity of vanadium during DMBA-initiated mammary carcinogenesis is mediated through alteration of hepatic antioxidant status as well as modulation of phase I and II drug metabolizing enzymes. On the basis of the observed results, vanadium can be considered as a readily available, promising and novel cancer chemopreventive agent.

Further evidence for chemopreventive potential of beta-carotene against experimental carcinogenesis: diethylnitrosamine-initiated and phenobarbital-promoted hepatocarcinogenesis is prevented more effectively by beta-carotene than by retinoic acid.

The comparative effectiveness of beta-carotene (BC) and retinoic acid (RA) was investigated against two-stage rat liver carcinogenesis initiated by a single injection of diethylnitrosamine (DEN, 200 mg/kg i.p.) followed by promotion with phenobarbital (PB, 0.05%) in a basal diet. BC (500 mg/kg) or RA (200 mg/kg) was administered per os daily throughout the entire experiment, before the initiation, or during the promotional stage. Treatment with BC throughout the experiment or before initiation significantly reduced the incidence (p < 0.01), multiplicity (p < 0.05), and size of visible subcapsular hepatocyte nodules (HNs) and reduced (p < 0.001 or 0.05) nodular volume as a percentage of liver volume. The results with RA were of lesser extent than those observed with BC. There was a considerable depletion of hepatic BC and total vitamin A (retinol + ester) in HNs and nonnodular surrounding parenchyma (NNSP) of rats subjected to the DEN-PB regimen than their control counterparts. Treatment with BC significantly elevated hepatic BC and total vitamin A contents in HNs and NNSP compared with DEN-PB control, and the elevation was proportional to the duration of BC treatment. Long-term BC or RA treatment elicited a substantial decrement in reduced glutathione content and gamma-glutamyltranspeptidase activity and an increment in cytochrome P-450 content and glutathione peroxidase and glutathione S-transferase activities in the HNs and NNSP, which were otherwise reversed in rats that received DEN-PB treatment alone. Our results suggest that BC or RA has the potential to inhibit DEN-induced hepatocarcinogenesis through selective modulation of the antioxidant defense system and xenobiotic detoxification in the liver. It is also apparent that the beneficial effect of BC or RA is primarily exerted on the initiation phase and secondarily during the promotional stage of DEN-initiated rat liver carcinogenesis and that BC affords a better chemopreventive response than RA.

Beta-carotene prolongs survival, decreases lipid peroxidation and enhances glutathione status in transplantable murine lymphoma.

Carotenoids of dietary origin have recently been the subject of renewed research interest because of epidemiological evidence indicating an inverse relationship between intake of carotenoids-rich plant substances and risk of certain cancers. This study was attempted to understand the biological actions of dietary beta-carotene (BC) on Dalton's lymphoma (DL), a rapidly proliferating transplantable tumor, in effecting the survival of the lymphoma-bearing mice. The glutathione (GSH) level and the extent of lipid peroxidation in the liver, kidney and brain were monitored in BC-treated (100 mg/kg food) mice transplanted with DL. These markers showed substantial alterations during the whole length of tumor progression in lymphoma-bearing mice without BC supplementation. When treated with BC, both malondialdehyde contents (evidence of lipid peroxidation) and the GSH levels in different organs were found to be closer to normal values in the initial period of tumor progression. BC-mediated protection against lipid peroxidation was maximally found to be in hepatic tissue throughout the study following DL transplantation. This was fairly reflected in the higher BC concentration in hepatic tissue of BC-treated lymphoma group compared to untreated lymphoma control. Significantly higher survival time (51-55 days) was observed in BC-treated animals in comparison to their untreated DL counterparts (35-38 days). The prolonged survival observed in the BC-supplemented animals may be attributed to the higher resistance offered by animals receiving BC towards lipid peroxidation-related tissue injury.

Marrow toxicity of 33P-versus 32P-orthophosphate: implications for therapy of bone pain and bone metastases.

UNLABELLED: Several bone-seeking radiopharmaceuticals, such as 32P-orthophosphate, 89Sr-chloride, 186Re-1,1 hydroxyethylidene diphosphonate (HEDP), and 153Sm-ethylene diamine tetramethylene phosphonic acid (EDTMP), have been used to treat bone pain. The major limiting factor with this modality is bone marrow toxicity, which arises from the penetrating nature of the high-energy beta particles emitted by the radionuclides. It has been hypothesized that marrow toxicity can be reduced while maintaining therapeutic efficacy by using radionuclides that emit short-range beta particles or conversion electrons. In view of the significant clinical experience with 32P-orthophosphate, and the similarity in pain relief afforded by 32P-orthophosphate and 89Sr-chloride, this hypothesis is examined in this study using 32P- and 33P-orthophosphate in a mouse femur model. METHODS: Survival of granulocyte macrophage colony-forming cells (GM-CFCs) in femoral marrow was used as a biologic dosimeter for bone marrow. 32P- and 33P-orthophosphate were administered intravenously, and GM-CFC survival was determined as a function of time after injection and, at the nadir, as a function of injected activity. The kinetics of radioactivity in the marrow, muscle, and femoral bone were also determined. The biologic dosimeter was calibrated by assessing GM-CFC survival at its nadir after chronic irradiation of Swiss Webster mice with exponentially decreasing dose rates of gamma rays (relative biologic effectiveness equivalent to that of beta particles) from a low-dose rate 137Cs irradiator. Dose-rate decrease half-times (Td) (time required for 137Cs gamma ray dose rate to decrease by one half) of 62, 255, and 425 h and infinity were used to simulate the dose rate patterns delivered by the radiopharmaceuticals as dictated by their effective clearance half-times from the mouse femurs. These data were used to experimentally determine the mean absorbed dose to the femoral marrow per unit injected activity. Finally, a theoretical dosimetry model of the mouse femur was developed, and the absorbed doses to the femoral marrow, bone, and endosteum were calculated using the EGS4 Monte Carlo code. RESULTS: When the animals were irradiated with exponentially decreasing dose rates of 137Cs gamma rays, initial dose rates required to achieve 37% survival were 1.9, 0.98, 0.88, and 0.79 cGy/h for dose rate decrease half-times of 62, 255, and 425 h and infinity, respectively. The D37 values were 144 +/- 15, 132 +/- 12, 129 +/- 3, and 133 +/- 10 cGy, respectively, compared with a value of 103 cGy for acute irradiation. When 32P and 33P were administered, the injected activities required to achieve 37% survival were 313 and 2,820 kBq, respectively. Theoretical dosimetry calculations show that 33P offers a 3- to 6-fold therapeutic advantage over 32P, depending on the source and target regions assumed. CONCLUSION: The low-energy beta-particle emitter 33P appears to offer a substantial dosimetric advantage over energetic beta-particle emitters (e.g., 32p, 89Sr, 186Re) for irradiating bone and minimizing marrow toxicity. This suggests that low-energy beta or conversion electron emitters may offer a substantial advantage for alleviation of bone pain as well as for specifically irradiating metastatic disease in bone.

Protection by DMSO against cell death caused by intracellularly localized iodine-125, iodine-131 and polonium-210.

The mechanisms by which DNA-incorporated radionuclides impart lethal damage to mammalian cells were investigated by examining the capacity of dimethyl sulfoxide (DMSO) to protect against lethal damage to Chinese hamster V79 cells caused by unbound tritium ((3)H(2)O), DNA-incorporated (125)I- and (131)I-iododeoxyuridine ((125)IdU, (131)IdU), and cytoplasmically localized (210)Po citrate. The radionuclides (3)H and (131)I emit low- and medium-energy beta particles, respectively, (125)I is a prolific Auger electron emitter, and (210)Po emits 5.3 MeV alpha particles. Cells were radiolabeled and maintained at 10.5 degrees C for 72 h in the presence of different concentrations of DMSO (5-12.5% v/v), and the surviving fraction compared to that of unlabeled controls was determined. DMSO afforded no protection against the lethal effects of the high-LET alpha particles emitted by (210)Po. Protection against lethal damage caused by unbound (3)H, (131)IdU and (125)IdU depended on the concentration of DMSO in the culture medium. Ten percent DMSO provided maximum protection in all cases. The dose modification factors obtained at 10% DMSO for (3)H(2)O, (131)IdU, (125)IdU and (210)Po citrate were 2.9 +/- 0.01, 2.3 +/- 0.5, 2.6 +/- 0.2 and 0.95 +/- 0.07, respectively. These results indicate that the toxicity of Auger electron and beta-particle emitters incorporated into the DNA of mammalian cells is largely radical-mediated and is therefore indirect in nature. This is also the case for the low-energy beta particles emitted by (3)H(2)O. In contrast, alpha particles impart lethal damage largely by direct effects. Finally, calculations of cellular absorbed doses indicate that beta-particle emitters are substantially more toxic when incorporated into the DNA of mammalian cells than when they are localized extracellularly.

Marrow-sparing effects of 117mSn(4+)diethylenetriaminepentaacetic acid for radionuclide therapy of bone cancer.

UNLABELLED: Several bone-seeking radionuclides (32P, 89Sr, 186Re, and 153Sm) have been used to treat bone pain. The limiting factor in this modality is marrow toxicity. Our hypothesis is that marrow toxicity can be reduced while maintaining therapeutic efficacy using radionuclides that emit short-range beta particles or conversion electrons (CEs). A recent study on 47 patients using the short-range CE emitter 117mSn(4+)diethylenetriaminepentaacetic acid (117mSn(4+)DTPA) supports this hypothesis. The hypothesis is now tested using 117mSn(4+)DTPA in a mouse femur model. METHODS: The survival of granulocyte-macrophage colony-forming cells (GM-CFCs) in femoral marrow is used as a biologic dosimeter for bone marrow. The dosimeter is calibrated by irradiating mice with exponentially decreasing dose rates of 137Cs gamma-rays with a dose-rate decrease half-time, Td, equal to the effective clearance half-time of 117mSn(4+)DTPA from the femur (222 h). When Td = 222 h, the mean absorbed dose required to achieve a survival fraction of 37% is 151 cGy. After calibration, 117mSn(4+)DTPA is administered and GM-CFC survival is determined as a function of injected activity. These data are used to experimentally determine the mean absorbed dose to the femoral marrow per unit injected activity. The kinetics of radioactivity in the marrow, muscle, and femoral bone are also determined. Finally, a theoretic dosimetry model of the mouse femur is used, and the absorbed doses to the femoral marrow and bone are calculated. RESULTS: The experimental mean absorbed dose to the femoral marrow per unit injected activity of 117mSn(4+)DTPA is 0.043 cGy/kBq. The theoretic mean absorbed dose to the femoral bone per unit injected activity is 1.07 cGy/kBq. If these data are compared with those obtained previously for 32P-orthophosphate, the radiochemical 117mSn(4+)DTPA yields up to an 8-fold therapeutic advantage over the energetic beta emitter 32P. CONCLUSION: The CE emitter 117mSn offers a large dosimetric advantage over energetic beta-particle emitters for alleviating bone pain, and possibly for other therapeutic applications, while minimizing marrow toxicity.

Characterization of selective induction and alteration of xenobiotic biotransforming enzymes by vanadium during diethylnitrosamine-induced chemical rat liver carcinogenesis.

Our recent studies have shown that vanadium, a dietary micronutrient, has an inhibitory response against experimentally induced rat liver carcinogenesis. In the present study, the effect of vanadium on hepatic xenobiotic biotransformation in rats exposed to diethylnitrosamine (DENA, 200 mg/kg, IP) was investigated to elucidate a possible mechanism of vanadium-mediated prevention of chemical carcinogenesis. Supplementary vanadium in drinking water at 0.5 parts per million (ppm) was employed ad lib before and after the intiation with DENA, before the initiation only, or during the promotional event. After 20 weeks, there was a significant reduction of hepatocyte nodules (HNs) (P<0.01), nodule multiplicity (P<0.001), and the number of nodules more than 3 mm in size in the long-term vanadium-supplemented rats than their DENA control counterparts. Total cytochrome P450 and b5 contents as well as cytochrome P450 2E1 (CYP2E1, EC 1.5.99), aryl hydrocarbon hydroxylase (AHH, EC 1.14.14.2), and UDP-glucuronyl transferase (UDPGT, EC 2.4.1.17) activities in the microsomal fractions of HNs and nonnodular surrounding parenchyma (NNSP) were found to be significantly decreased in DENA control group compared to untreated normal control. Though supplementary vanadium had little or no influence on the contents of cytochrome P450 and b5 and activities of CYP2E1 and AHH in HNs and NNSP, it substantially elevated the UDPGT activity in both HNs and NNSP liver areas. DENA treatment alone also brought about a sharp decrease in cytosolic UDP-glucose dehydrogenase (EC 1.1.1.22), DT-diaphorase (EC 1.6.99.2), and glutathione S-transferase (EC 2.5.1.18) activities in HNs and NNSP compared to normal liver. Supplementary vanadium was found to exert a marked induction in these cytosolic enzymes in HNs as well as NNSP when compared to DENA control. A positive correlation of phase I and phase II drug metabolizing enzymes in HNs or NNSP was always observed in DENA or DENA plus long-term vanadium-treated group. It is concluded that the chemoprotective effect of vanadium may be attributed to the substantial elevation of phase II conjugating enzymes, which may lead to a move and shift of the metabolic profile that may reduce the intracellular concentration of carcinogen-derived reactive intermediates.

Phosphorylation of tyrosine 992, 1068, and 1086 is required for conformational change of the human epidermal growth factor receptor c-terminal tail.

We reported previously that a conformation-specific antibody, Ab P2, to a 16-amino acid peptide (Glu-Gly-Tyr-Lys-Lys-Lys-Tyr-Gln-Gln-Val-Asp-Glu-Glu-Phe-Leu-Arg) of the cytoplasmic domain of the beta-type platelet-derived growth factor receptor also recognizes the epidermal growth factor (EGF) receptor. Although the antibody is not directed to phosphotyrosine, it recognizes in immunoprecipitation the activated and hence phosphorylated form of both receptors. In P2 peptide, there are two tripeptide sequences, Asp-Glu-Glu and Tyr-Gln-Gln, that are also present in the EGF receptor. Our present studies using either EGF receptor C-terminal deletion mutants or point mutations (Tyr-->Phe) and our previous studies on antibody inhibition by P2-derived peptides suggest that Gln-Gln in combination with Asp-Glu-Glu forms a high-affinity complex with Ab P2 and that such complex formation is dependent on tyrosine phosphorylation. Of the five phosphate acceptor sites in the EGF receptor, clustered in the extreme C-terminal tail, phosphorylation of three tyrosine residues (992, 1068, and 1086) located between Asp-Glu-Glu and Gln-Gln is necessary for Ab P2 binding. In contrast, the acceptor sites Tyr 1173 and 1148 play no role in the conformation change. Asp-Glu-Glu and Gln-Gln are located 169 amino acids apart, and it is highly likely that the interactions among three negatively charged phosphotyrosine residues in the receptor C terminus may result in the bending of the peptide chain in such a way that these two peptides come close to each other to form an antibody-binding site. Such a possibility is also supported by our finding that receptor dephosphorylation results in complete loss of Ab P2-binding activity. In conclusion, we have identified a domain within the cytoplasmic part of the EGF receptor whose conformation is altered by receptor phosphorylation; furthermore, we have identified the tyrosine residues that positively regulate this conformation.

Conformational analysis of the phosphorylated epidermal growth factor receptor.

Phosphorylation-induced conformational changes have been well documented with different receptor tyrosine kinases. However. the susceptible epitopes and the tyrosine residue(s) involved in particular structural alteration mostly remain to be determined. Using a conformation-specific anti-peptide antibody, we have not only identified one such domain in the C-terminal tail of the EGF receptor but also identified the phosphate acceptor sites that are involved in the conformational change.

Radioprotection against lethal damage caused by chronic irradiation with radionuclides in vitro.

To examine the capacity of chemical protectors to mitigate damage caused by chronic irradiation by incorporated radionuclides in vitro, cells must be maintained in the presence of the protector during the course of the irradiation. Such long exposures to chemical protectors at concentrations high enough to afford protection usually results in extreme chemotoxicity. To overcome this problem, experimental conditions were developed to allow Chinese hamster V79 cells to be maintained in 5% DMSO for prolonged periods (up to 72 h) with no observable chemotoxicity. Under these conditions, the capacity of DMSO to protect against damage to V79 cells caused by unbound 32P and 3H2O and DNA-incorporated (131)IdU, [3H]dThd and 125IdU was examined. The dose modification factors for 32P, 3H2O, (131)IdU, [3H]dThd and 125IdU were 2.6+/-0.5, 2.3+/-0.3, 1.0+/-0.1, 1.16+/-0.07 and 1.07+/-0.02, respectively. These results show that 5% DMSO is capable of protecting cultured V79 cells against lethal damage caused by beta particles emitted by unbound 32P and 3H2O, whereas little or no protection is afforded against damage caused by beta particles emitted by DNA-incorporated (131)I and 3H or low-energy Auger electrons emitted by DNA-incorporated 125I.

Alterations in total iron, zinc, and calcium levels and their influence on the hepatic activities of gamma-glutamyl transferase and glucose-6-phosphatase in the host bearing transplantable murine lymphoma.

The levels of iron, zinc, and calcium in liver as well as serum, together with the enzymatic activities of gamma-glutamyl transferase (GGT, EC 2.3.2.2) and glucose-6-phosphatase (G-6-Pase, EC 3.1.3.9) in liver, were critically monitored over various periods in male Swiss albino mice bearing Dalton's lymphoma (DL), a transplantable ascites-producing tumor. Both hepatic and serum contents of iron, zinc, and calcium were found to be maximally elevated (p < 0.001) on day 15 after tumor transplantation as compared with their contents in normal animals. There was a gradual increase in the activity of GGT in liver in lymphoma-bearing mice in comparison with their normal counterparts, which showed a maximum peak (p < 0.001) on day 15, followed by a continuous and sharp fall. Hepatic G-6-Pase activity was found to decrease continuously throughout the progression of lymphoma as compared with its levels to normal animals. Tumor-cell counts in peritoneal lymph fluids of mice containing DL yielded a maximum count of 155.7 x 10(3) cells/mm3 on day 15. A significant correlation was observed among the levels of different metals, enzymatic activities, and tumor-cell counts at different periods of study. From these results, it can be concluded that the metals studied may have a role in initiating and controlling cellular proliferations, through their effects on modulating the activities of the possibly preneoplastic and neoplastic marker enzymes named above.

Evaluation of cyanide exposure and its effect on thyroid function of workers in a cable industry.

A thyroid-hormone evaluation of workers dealing with cyanide compounds in an electroplating process of a cable industry was carried out. Serum thiocyanate (SCN) levels of 35 nonsmoking copper-ply employees were assayed by a ferric-chloride color test. The mean SCN concentration of these employees was 316 +/- 15 mumol/L, which was significantly (P < 0.01) higher than that of control subjects (90.8 +/- 9.02 mumol/L). Serum thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) concentrations of exposed workers were compared with those of 35 control subjects. Cyanide exposure resulted in a decrease in T4 and T3 concentrations (P < 0.05) and an increase in TSH concentration (P < 0.05), compared with the control subjects. The serum T4 level was found to be negatively correlated (r = -0.363, P < 0.05), whereas the TSH level was positively correlated (r = 0.354, P < 0.05), with SCN concentration in the exposed group. The study suggests that occupational cyanide exposure in the industry impairs thyroid function.

Vanadium-mediated chemoprotection against chemical hepatocarcinogenesis in rats: haematological and histological characteristics.

The trace element vanadium was investigated for its anti-neoplastic role in relation to haematological status, hepatic histopathology and histochemical analysis of glycogen in liver. Its impact on the survival of male Sprague-Dawley rats subjected to a two-stage hepatocarcinogenesis regimen was also assessed. Initiation was performed using a single intraperitoneal injection of diethylnitrosamine (DENA) (200 mg/kg) followed by promotion with phenobarbital (0.05%) in a basal diet. Vanadium supplementation as ammonium monovanadate at 0.5 ppm vanadium in drinking water was given ad libitum throughout the experiment (20 weeks), before the initiation (4 weeks), or during the promotional period (14 weeks). At the end of the study, there was a significant decrease in red blood cell count, haemoglobin content, haematocrit value, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma volume change and total white cell count, with a concurrent alteration in lymphoid:myeloid ratio in DENA control animals compared with their normal counterparts. Vanadium supplementation throughout the study or before the initiation significantly reversed the DENA-induced alterations in most of the haematological indices. A single intraperitoneal injection of DENA also depleted the plasma albumin concentration, raised the plasma globulin content, and decreased the ratio of albumin to globulin. These altered features began to return to normal following vanadium supplementation. Supplementary vanadium also elicited substantial protection against DENA-mediated rat liver carcinogenesis. This was fairly evident from hepatic histology and evaluation of glycogen accumulation by periodic acid-Schiff reaction. The survival of DENA-treated animals was considerably increased in the presence of vanadium. The critical involvement of vanadium in modulating several factors associated with erythropoiesis under carcinogenic challenge may thus have a possible impact on the eventual increased survival of the host.

Beta-carotene inhibits rat liver chromosomal aberrations and DNA chain break after a single injection of diethylnitrosamine.

Beta-carotene (BC) has recently been found to possess potent anti-tumour activity in chemically induced rat liver carcinogenesis. In the present study, attempts have been made to understand the basic cytogenetic and molecular mechanism of the anti-tumour effect of BC by monitoring its effect on rat liver chromosomal aberrations (CAs) and DNA chain breaks during the early preneoplastic stage of diethylnitrosamine (DEN)-induced hepatocarcinogenesis in male rats. DNA chain breaks, however, can be detected with great sensitivity by exposing crude cell lysates to alkaline solutions and monitoring the rate of strand unwinding so that one strand break per chromosome can easily be detected. Supplementary BC, in basal diet (120 mg kg[-1]), was given to rats 15 days before carcinogenic threat with DEN. Under these experimental conditions, BC was found to afford a unique protection against DEN-induced CAs 96 h after DEN injection. Long-term treatment with BC also triggered a protective effect on induction of CAs 15, 30 or 45 days after DEN treatment, which was maximal on structural aberrations followed by numerical and physiological types. BC treatment for 15 days before DEN injection was found to offer a significant (P < 0.001) protection in the generation of single-strand breaks compared with DEN control. Thus, BC ranks as a potential chemopreventive agent for the future so far as chemical rat liver carcinogenesis is concerned.

Vanadium-mediated suppression of diethylnitrosamine-induced chromosomal aberrations in rat hepatocytes and its correlation with induction of hepatic glutathione and glutathione S-transferase.

Vanadium, a dietary micronutrient, has recently been found to possess a potent antitumor activity during chemically induced rat liver carcinogenesis. In the present study, attempts have been made to understand the basic mechanism of the antitumor response of vanadium by monitoring its effect on chromosomal aberrations (CA) in rat liver cells during the early preneoplastic steps of diethylnitrosamine (DENA)-induced hepatocarcinogenesis. Supplementary vanadium at 0.5 ppm was found to afford a unique protection against DENA-evoked CA 96 h after DENA injection. Concurrent administration of glutathione (GSH) at 200 mg/kg 2 h before DENA treatment potentiated the suppressive effect of vanadium against CA when the rats were sacrificed 96 h after the carcinogenic insult. Pretreatment nf rate with buthionine sulfoximine (890 mg/kg) and/or diethylmaleate (600 mg/kg) 0.5 or 2 h prior to DENA injection resulted in a significant inhibition of vanadium-mediated protection of CA with a concomitant fall in hepatic GSH level. Rats given injection of bromosulfophthalein (250 mg/kg), a substrate inhibitor of glutathione S-transferase (GST), 0.5 h before DENA treatment displayed a prominent suppression of the protective effect of vanadium on DENA-induced CA. Long-term supplementation of vanadium also triggered protective effect against the induction of CA 15, 30 or 45 days following DENA treatment which was maximally observed on structural aberrations followed by numerical aberrations. At these time points, vanadium was found to lower the mitotic index of hepatic cells which was otherwise elevated with DENA alone. Vanadium restored DENA-dependent decrement in the ratio of polychromatic erythrocytes (PCE) to normochromatic erythrocytes (NCE) in rat liver cells. The DENA-induced increased frequency of micronucleated PCE as well as NCE was also attenuated following vanadium supplementation. The anticlastogenic effect of vanadium was found to be parallel to its ability to induce the activity of hepatic GST with a concurrent induction of hepatic GSH pool which were rather decreased in DENA control group. The results of this study, thus, provide evidence that vanadium-dependent induction of GSH-mediated GST-catalyzed detoxificational capacity of the host is presumably related to its suppressive effect against CA. This may explain, in part, the antitumor efficacy of this trace element.

Prevention of alcohol-carbon tetrachloride-induced signs of early hepatotoxicity in mice by Trianthema portulacastrum L.

The antihepatotoxic potential of an ethanolic extract of the whole plant of Trianthema portulacastrum L. (excluding the roots) was evaluated against alcohol-carbon tetrachloride (CCl(4))-induced acute liver damage in mice. The extract at a dose of 50,100 or 150 mg/kg was administered per os once daily for successive three days concomitant with alcohol-CCl(4) treatment. The substantially elevated serum enzymatic activities of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase, alkaline phosphatase, sorbitol and glutamate dehydrogenase due to alcohol-CCl(4) treatment were dose-dependently restored towards normalization following the extract therapy. There was a marked inhibition of serum bilirubin und urea levels in the plant extract-treated groups which were otherwise drastically increased in alcohol-CCl(4) control animals. The extract also significantly prevented the elevation of hepatic malondialdehyde formation (evidence of lipid peroxidation) and depletion of reduced glutathione content in liver of mice intoxicated with alcohol-CCl(4) in a dose-responsive fashion. The results of this study clearly indicate that the plant possesses a potent hepatoprotective action against alcohol-CCl(4)-induced hepatocellular injury which corroborates its use in hepatic disorders as well as alcohol-evoked liver ailments in traditional oriental medicine.