Clastogenic activity of strontium chloride on bone marrow cells in vivo

Oral administration of different concentrations of Strontium chloride to laboratory bred mice in vivo induced chromosomal aberrations in bone marrow cell metaphase preparations. The degree of clastogenicity was directly proportional to concentration used at 6, 12, and 24 h of treatment. Duration of treatment could only be related positively in the lower doses. The females showed greater susceptibility than the males at all concentrations used.     

Effects of etretinate on the distribution of elements in rats

We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations.     

Changes of concentrations of the elements Co,Cr, Sb,and Sc in tissues of persons with joint implants

Elevated levels of Co and Cr were found in several organs of deceased implant bearers (CoCr-alloy/polyethylene joint prostheses) by means of instrumental and radiochemical neutron activation analysis as compared to normal persons. For comparative purposes, concentrations of the elements Co, Cr, Sb, and Sc were measured in heart, kidney, liver, and spleen of the patients and normal persons. For Cr determination, a new radiochemical separation technique with sufficiently low determination limit was employed. The importance of such investigations for studying possible carcinogenic effects of corrosion products and wear particles of metallic prostheses is mentioned.     

Effect of long-term nickel ingestion on insulin binding and antilipolytic response in rat adipocytes

Male Wistar rats of the third generation of rats drinking 200 micrograms Ni2+/mL as NiCl2 in their drinking water were studied. Basal plasma glucose and insulin levels were unchanged. Epididymal adipocytes from Ni2(+)-fed rats showed an increased insulin binding with a slight increase in apparent insulin affinity (ED50: Ni2(+)-fed rats 2.8 x 10(-9) M and controls 5 x 10(-9) M) with no change in insulin receptor numbers (Ni2(+)-fed rats 143,000 +/- 12,000 (6) receptors/cell and controls 126,000 +/- 13,000 (5]. Moreover, a decreased sensitivity to the antilipolytic response of insulin was also observed in adipocytes from Ni2(+)-fed rats. These events could represent actions of Ni2+ both at the receptor and post-receptor insulin levels. Several possible mechanisms involved in the process are suggested.     

Dietary calcium and blood lead levels in women

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.     

The effects of cadmium on zinc absorption in isolated rat intestinal preparations

The effect of cadmium on zinc absorption was studied using an isolated vascularly and luminally perfused rat intestinal preparation.⁶⁵Zn as well as Zn and Cd (both as the chloride salt) were added to the luminal perfusion medium (LPM) at varying concentrations. Over a 90-min period, the amount of Zn appearing in the vascular perfusion medium (VPM) and that retained by the tissue post-perfusion was estimated. Cd at all levels studied (0.03, 0.10, 1.0, and 10.0 μg/mL) reduced the amount of Zn appearing in the VPM in comparison with control perfusions (no detectable Cd in the LPM) when the initial Zn concentration was 5 μg/mL. Similarly, with an initial Zn concentration of 10 or 20 μg/mL, the amount of Zn appearing in the VPM was reduced when the Cd concentration was 0.1 or 1.0 μg/mL. With these same Zn concentrations, the amount of Zn retained by the tissue was higher when the Cd concentration was 10 μg/mL. These results demonstrate that Cd at low concentrations is capable of reducing Zn appearance in the VPM.     

The in vitro transformation of a rat liver epithelial cell line with chromium

The transformation of a rat liver epithelial cell line under a wide range of doses of chromium was determined by anchorage-independent growth and tumor formation in syngeneic animals. Chronic exposure to low concentrations and brief exposure to high concentrations of hexavalent chromium (K₂CrO₄) transformed the cells, but one dose (1 mM K₂CrO₄, 2h) was clearly optimal in this regard. The cytotoxicity, effects on cell cycle, rates of chromium uptake, and mutagenic activity under the different treatment conditions were evaluated. The results showed that cells could adapt to the presence of chromium under certain treatment conditions, but this was not the case for the optimal transforming dose. Cells treated with chromium above the optimal transforming dose showed evidence of a transient G2 arrest, whereas all lower levels of treatment did not. A low level continuous exposure to chromate was mutagenic, whereas high level short exposures, including the optimal transforming dose, were not. An increase in the amount of protein complexed with isolated nucleic acids was detected in cells following treatment with the optimal transforming dose of chromate. The results indicate that the effects of chromium on this in vitro system vary with dose; and the identification of those events relevant to metal carcinogenesis will require consideration of treatment conditions.     

Mechanism of cadmium-induced cytotoxicity in rat hepatocytes

Exposure of rat hepatocytes to cadmium below 50 μM for a short period (10 min) resulted in cellular acidification. Conversely, exposure to Cd more than 50 μM for a long period (60 min) caused cellular alkalinization accompanied by membrane damage as reflected by decrease in cellular K content and loss of intracellular lactic dehydrogenase. In hepatocytes exposed to 5 μM Cd, a concentration sufficient to induce acidification without cytotoxicity, the metal was preferentially associated with the crude nuclei and cell debris fractions, suggesting an interaction between Cd and cell membranes to cause acidification. Omission of bicarbonate from the incubation medium induced cellular acidification. The presence of Cd in this medium did not potentiate the medium-induced acidification. Mg-ATP (25 μM) induced cellular acidification in relation to an increase in the concentration of cytosolic free Ca. The coexistence of Mg-ATP and Cd at the concentrations which had no effect on cellular pH in the presence of either agants induced cellular acidification. These observations suggest that Cd induced cellular acidification by modulating the process connected with the rise in cytosolic free Ca via interaction with plasma membranes. This acidification had no strong immediate cytotoxic actions but led to subsequent cellular alkalinization accompanied with severe cytotoxicity and membrane breakage.     

Enhancement of the kidney Cd burden by SH-containing chelating agents

The accumulation of Cd in the kidneys is enhanced markedly if chelating agents that contain SH-groups like 2,3 dimercaptopropanol (BAL) are injected immediately after the metal. This is not a transient effect but persists for more than 3 d. It is less pronounced at higher chelate doses or when the pH of urine is increased. Our experiments indicate that chelating agents, which form unstable complexes at acid pH and are able to pass through the cell membrane, will cause metal accumulation in the kidneys.     

Effect of time and sex on tissue selenium concentrations in chicks fed practical diets supplemented with sodium selenite or calcium selenite

An experiment was conducted with 384 1-d-old male and female broiler-chicks. The basal corn-soybean meal diet (.07 ppm Se DM basis) was supplemented with 0, .1, .2, or .3 ppm added Se as either sodium selenite (Na2SeO3) or calcium selenite (CaSeO3), and fed for 1, 3, or 5 wk. There was no effect of Se source or level on feed intake or gain, but males consumed more (P less than .01) feed than females. There was no effect (P greater than .10) of sex or Se source on plasma, liver, or kidney Se concentration. The Se concentration of all tissues increased (P less than .01) with time and increasing dietary Se concentration. Based on multiple regression slope ratios of liver, kidney, and plasma Se concentrations, Se from CaSeO3 was as available (103%) as Se from Na2SeO3.     

Oral and subcutaneous administration of cadmium chloride and the distribution of metallothionein and cadmium along the villus-crypt axis in rat jejunum

The route of Cd uptake influences the distribution of Cd, other metals, and metallothionein (MT). Although intestinal MT levels related to the tissue mass did not show proximodistal gradients after sc administration of CdCl₂, orally administered high doses of CdCl₂ increased mucosal MT levels longitudinally from the duodenum to the ileum. The gradient abolished when the mucosal MT level was related to the intestinal length. To further elucidate this finding, three groups of rats were studied: a control group, a group receiving dietary CdCl₂, and a group receiving sc injections of CdCl₂. The small intestine was removed after a 14-d treatment. Midjejunal segments were mounted in a cryomicrotome and cut transversally into five layers along the villus-crypt axis. Mucosal enzymes were measured to control these sections. Cd was measured by AAS and MT by RIA. Alkaline phosphatase and lactase activities exhibited the typical villus-crypt gradient. Mucosal MT levels paralleled those of Cd. Although Cd and MT concentrations were high at the tip of the villi and low in the crypts after oral administration, sc treatment reversed that profile. A molar Cd-MT ratio of approx 10 or 1 was reached after po or sc treatment, respectively. This demonstrates that only oral Cd may lead to an accumulation of Cd in the mucosal tissue fairly exceeding the binding capacity of small intestinal MT. The results show that different routes of Cd intake lead to a different MT-induction pattern in the intestinal wall and that longitudinal Cd and MT concentration gradients in the small intestine observed after high oral doses are a result of their high levels at the villus tips.     

Effects of doxorubicin on the sensitivity of L1210 leukemia cells to deformation-associated trauma

Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-μm pore-size Nuclepore® membranes, with or without prior incubation with 10^-7M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis.     

Effects of low copper and high zinc intakes and related changes in Cu,Zn-superoxide dismutase activity on DMBA-induced mammary tumorigenesis

The effect of low copper and high zinc intakes on Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity and mammary tumorigenesis induced by 9,10-dimethyl-1,2-benzanthracene (DMBA) was investigated. Groups of 40 weanling female Sprague-Dawley rats were fed a modified AIN-76 diet containing the following (/kg diet): 1 mg Cu (0.016 mmol) and 30 mg Zn (0.459 mmol); 6 mg Cu (0.094 mmol) and 30 mg Zn (0.459 mmol) (control); or 6 mg Cu (0.094 mmol) and 150 mg Zn (2.295 mmol) for 21 wk. At 5 wk, 30 rats/group were given 4 mg (15.6 mumol) DMBA in corn oil intragastrically, and controls (10/group) received corn oil alone. Erythrocyte Cu,Zn-SOD activity was measured at 3, 5 (just before DMBA), 9, 13, 17, and 21 wk. The group fed the high-Zn diet had a slightly lower weight gain and food consumption. DMBA treatment had no effect on these parameters. Plasma and liver Cu concentration decreased in the low-Cu group. Femur zinc was significantly elevated in the high-Zn group. Erythrocyte Cu,Zn-SOD activity was decreased in the low-Cu group from 3 to 21 wk and was significantly elevated in the high-Zn group at 3 and 5 wk. In the low-Cu group, there were 5 nonmalignant adenomas and 3 malignant adenocarcinomas; in the control group, there were 4 adenomas and 3 adenocarcinomas; in the high-Zn group, there were 5 adenomas and 3 adenocarcinomas. No relationship between Cu,Zn-SOD activity and the presence of tumors could be found.     

Nutritional copper deficiency does not affect sponge granuloma formation in the rat

Sponge granuloma formation was compared in copper-deficient and copper-sufficient rats following feeding of respective diets for 20, 40, or 60 d. Body weight, total blood hemoglobin, and activities of ceruloplasmin and Cu, Zn-superoxide dismutase in plasma were monitored to ascertain copper deficiency. Mean granuloma weights (mg +/- SEM) in copper-deficient and copper-sufficient groups of rats, respectively, were as follows: 37 +/- 2 and 38 +/- 2 after 20 d, 22 +/- 2 and 23 +/- 2 after 40 d, and 19 +/- 1 and 21 +/- 1 after 60 d on respective diets. Thus, nutritional copper deficiency did not have an effect on sponge granuloma formation in the rat.     

Interaction of dietary calcium,manganese, and manganese source (Mn oxide or Mn methionine complex) on chick performance and manganese utilization

Two trials were conducted to determine the utilization of manganese (Mn) as influenced by the level and source of Mn and the level of dietary calcium (Ca) in broiler chickens. Trial One was a 2 x 2 x 3 factorial arrangement of two Mn sources (Mn methionine or manganous oxide), two levels of dietary Ca (1.8 or 1.0), and three levels of supplemental Mn (30, 60, or 200 mg/kg) fed until 4 wk of age. Total phosphorus (available phosphorus) levels were 0.70% (0.48%) during all ages. High levels of dietary Ca caused a slower early rate of growth (0.53 vs. 0.64 kg) for chicks fed 1.8 vs 1.0% Ca, respectively. Chick weight was equivalent for all diets within the Ca-treatment group, except the dietary combination of high Ca and 200 mg/kg Mn as Mn methionine. Bone and liver Mn were significantly increased as the Mn level increased, but were not affected by the Mn source. Chicks fed 1.8% Ca had higher levels of bone Mn (9.28 ppm) than chicks fed 1.0% Ca (7.23 ppm). High levels of dietary Ca and 200 ppm Mn methionine dramatically depressed early growth, feed intake, and bone ash in this trial, raising the question of a diet x environment (heat-stress) effect. Trial Two was a 2 x 2 factorial arrangement of two levels of dietary Ca (1.8 or 1.0%) and two Mn sources (200 mg/kg Mn as Mn methionine or MnO) up to 3 wk of age in a controlled heat-stress environment. No growth depression in the chicks fed high levels of Ca and Mn methionine was observed. In the presence of high levels of dietary Ca, bone Mn was significantly higher when chicks were fed the MnO source. In summary, dietary Ca did not decrease Mn utilization in these trials, and availability of Mn in Mn methionine as a source compared to MnO depended on dietary Ca levels.     

Cell orientation induced by extracellular signals

Cells like fibroblasts and osteoblasts are oriented by different extracellular guiding signals like an electric field, a bent surface, and a periodically stretched surface. An automatic controller is responsible for the cell alignment. The controller contains both a deterministic and a stochastic signal. The following machine properties were determined: (1) The angle dependence of the cellular signal transformer is cos 2(psi 0 - psi). (2) The set point of the automatic controller is psi 0 = +/- 90 degrees. The cells like to orient their long axis perpendicular to the direction of the applied guiding signal. (3) The signal transformer measures the extracellular signal in a quadratic fashion. The cells cannot register the sign of the guiding field. (4) The stochastic signal in the automatic controller can be quantified by a characteristic time (approximately 130 min for fibroblasts). (5) The extracellular signal is registered in cell-made standards (ratio of the deterministic and stochastic signal equals one): 0.3 +/- 0.05 V/mm for human fibroblasts (electric field) and 85 +/- 3 microns for human fibroblasts and osteoblasts (cyclindrically bent surface). (6) The lag-time in the signal transduction system of fibroblasts is approximately 4 min.     

Zinc protection against cadmium effect on estrual cycle of wistar rat

A single dose of cadmium chloride (2.2 mg/kg of body wt) increased the estrual cycle period about two times. This effect could be prevented by means of simultaneous administration of zinc at the same dose.     

Effect of D-Penicillamine on iron uptake by isolated rat hepatocytes

d-penicillamine (β,β-dimethylcysteine) promotes the incorporation of iron into isolated rat hepatocytes. The mechanism for doing this remains unknown. No differences in iron distribution between control and treated cells has been observed. Ferritin appears as the main destination of internalized iron in both cases. Therefore, increasing iron storage may appear as a side effect of the use ofd-penicillamine as a therapeutic agent for several diseases.     

A new technique for the study of erythrocyte survival by double labeling and use of a well-type Ge detector

A double label procedure with⁵⁷Co and⁵⁸Co has been developed for detailed in vivo studies of erythrocyte survival. A well-type Ge detector is used in the measurements. The activities necessary for these experiments are very low, and the associated dose received by the test persons can be neglected.