Panfilo S. Belo

Translocation and fluxes of mercury in neonatal and maternal rats treated with methyl mercuric chloride during gestation.

Summary Pregnant rats, during the 16th day of gestation, were force-fed a tracer dose of 203Hg as methyl mercuric chloride. At parturition, 7, 14,21, and 28 days after parturition, the 203Hg radioactivities in the different brain parts and organs of maternal and neonatal rats were determined. The concentration of 203Hg in the brain, brain parts, and organs of mothers and pups decreased with time after force-feeding. At all time periods, cerebrum contained the greatest quantity of 203Hg and pituitary the lowest in both mothers and pups due primarily to the size of the tissue. The blood concentration of 203Hg in the pups at birth was 27% higher than that of the darns. Similarly, at birth, the concentration of 203Hg in the different brain parts and organs of the pups, except in the kidney, was higher than corresponding tissues in the dams. Mercury pool size in the brain and brain parts of maternal and neonatal rats also primarily reflected the size of the tissues studied. In general, a faster turnover of mercury in the pups was observed. The half-life of mercury in the maternal brain, kidneys, liver, and gastrocnemius were 10.79, 27.61,9.38, and 6.73 days, respectively. In the pups, corresponding half-life values were 10.00, 20.20, 13.50, and 12.86 days. In another study, foster rearing of pups originally contaminated in utero with the radioactive mercury demonstrated that mercury excreted by pups recirculated to the foster dams. The uptake of 203Hg in the brain, brain parts and organs of foster dams ranged from 0.0001 to 0.067% of the original dose administered to the mothers of the contaminated pups.

Carbon-Mercury Bond Cleavage in Blood of Rats Fed Methyl Mercuric Chloride

Summary Methyl mercuric chloride labeled with 14C or 203Hg or both were forcefed to rats in order to quantitatively determine breakage of the carbon–mercury bond in different fractions of blood. Based on the hypothesis that a change in the ratio of 14C to 203Hg radioactivities in the tissue from that in the compound fed to rats would indicate breakage, values ranging from 5.1% to 10.6% were observed depending upon the blood fraction studied. Since the site of deposition of mercurial compounds is important in determining toxicities, the concentrations of either 14C or 203Hg radioactivities in blood fractions were determined after force-feeding the single or double-labeled methyl mercuric chloride. One day after force-feeding, the highest concentration in the erythrocytes was in the hemoglobin. In the plasma, fat contained the highest concentration. However, plasma fat radioactivities constitute only 0.1% of the whole blood radioactivities whereas plasma protein radioactivities constitute 0.7%. Nearly 99% of blood radioactivities was in the hemoglobin.

Determination of glucose-utilization in the dog with [2-3H], [6-3H]-, and [U-14C]glucose.

Summary Parameters of in vivo glucose metabolism in adult female dogs fasted for 48 hr were estimated after a single injection of [2-3H]- or [6-3H]glucose in combination with [U-14C]glucose. The glucose replacement rate estimated with [2-3H]glucose averaged 4.6 mg/min/kg and was about 25% higher than the values obtained with [6-3H]glucose. Estimates of glucose-carbon recycling were more than twice as high (31 vs 14%) when [2-3H]glucose was utilized as tracer than when [6-3H]glucose was utilized. These differences suggest the presence of a “futile” cycle between glucose and glucose-6-phosphate in the dog.

Carbon–Mercury Bond Breakage in Milk, Cerebrum, Liver, and Kidney of Rats Fed Methyl Mercuric Chloride

Summary A double-label technique was used to determine the carbon–mercury bond breakages in milk and milk fractions, cerebrum, liver and kidneys of rats one day after force-feeding double-labeled methyl mercuric chloride. Breakages of the carbon–mercury bond occurred mainly in the fat and casein fractions and not in the whey of milk. In the cerebrum, liver and kidney, the breakages of the bond were respectively 6.2%, 6.2%, and 8.0%. The 14C and 203Hg concentrations (percent of dose/g) were high in fat and casein fractions and low in whey fraction of milk. The 14C radioactivities in milk were distributed 46.2% in fat, 32.3% in casein and 21.5% in whey. For 203Hg radioactivities in milk, distribution was 55.1% in whey, 41.0% in casein and 3.9% in fat. Of the three organs studied, the kidney contained the highest percent of dose/gram tissue whereas the cerebrum contained the lowest.

Methylazoxymethanol-Acetate Induced Neurotoxicity of Chick Embryos

Summary Six-day-old chick embryos were treated with either methylazoxymethanol acetate (MAM-acetate) or saline and allowed to hatch. When 4 μl of the neurotoxic compound were introduced into the yolk sacs of the embryos, motor function was impaired when the chicks were tested for their perching ability at 1, 2, and 3 days of age. No statistical differences were observed when the chicks were 4- or 5-days of age. Treatment with 2 μl of MAM-acetate produced motor impairment only during the 1st day post hatching. The higher level of MAM-acetate was also accompanied by a significantly reduced adenyl cyclase activities 1-day post hatching. The activity, however, became normal when the chicks reached 3 and 5-days of age. No histological lesions were detected in the brain of the chick. It was concluded that chicks are useful subjects for detection of subtle neurological changes produced by MAM-acetate using a simple perching test.