The interaction of dietary vitamin C, protein, and calcium with fluoride: effects in guinea pigs in relation to breaking strength and radiodensity of bone

Guinea pigs were maintained on semisynthetic diets with or without the adequate amounts of dietary vitamin C, protein, and calcium, and were exposed to 25 ppm of fluoride in drinking water. Bone radiodensity was increased in the guinea pig humerus and tibia by fluoride supplementation, while femur and pelvic bones showed no density increases. Fluoride administration did not affect the torsion or bending strength of the bones of guinea pigs fed normal diets but increased the tensile strength. These physical properties of bones were not altered by low vitamin C or low protein diets. Low calcium diet significantly reduced the tensile strength of guinea pig humeri while the simultaneous administration of fluoride counteracted this effect.

The subcellular distribution of gold in monkey liver, kidney and spleen, in vivo

1. The subcellular distribution of gold in the livers, kidney cortex and the spleens of rhesus monkeys was determined at 2, 10 and 20 days after the administration of sodium (195Au)-aurothiomalate. The serum gold levels were also determined over the period of study. 2. With the continued decrease in the serum gold levels from day 1 to day 20, a continued increase in the tissue levels of the organs studied was observed. The corresponding subcellular fractions of the tissues also showed continued increases in the radioactive concentrations of gold. 3. Gold was found to localise in all the organelles of the cells in the liver, kidney cortex and the spleen, though in varying amounts. The largest increases in the concentrations of gold from day 2 to day 20 were found in the lysosomal bodies of liver and kidney. The concentrations in the kidney cortex increased from approximately five times those in the liver or the spleen on day 2 to about eight times those on day 20.

The development of SS'-polymethylenebis(methanethiosulphonates) as reversible cross-linking reagents for thiol groups and their use to form stable catalytically active cross-linked dimers within glyceraldehyde 3-phosphate dehydrogenase

The synthesis of a series of SS'-polymethylenebis(methanethiosulphonates) including the pentane, hexane, octane, decane and dodecane derivatives is described. These derivatives were synthesized by condensation between dibromoalkanes and potassium methanethiosulphonate in refluxing methanol and this seems an especially versatile reaction for the synthesis of asymmetric thiosulphonate derivatives. The synthesis of SS'-[1,8-3H4]-octamethylenebis(methanethiosulphonate) was also perfomed. Cross-linking was demonstrated in the four enzymes lactate dehydrogenase, phosphofructokinase, pyruvate kinase and glyceraldehyde 3-phosphate dehydrogenase. For all four enzymes cross-linking was efficiently reversed by reducing conditions in denaturing solvents. The reaction with glyceraldehyde 3-phosphate dehydrogenase was unique in that only the cross-linked dimer was produced in significant amounts (greater than 90% of total products as dimer). This reaction was followed in detail with radioactive cross-linking reagent. Inhibition of enzyme activity was extremely fast and showed an asymmetric distribution of enzyme activity on subunits. Thus complete modification of only one subunit resulted in up to 75% inhibition of enzyme activity. Reaction of glyceraldehyde 3-phosphate dehydrogenase with 1.25 mol of SS'-octamethylenebis(methanethiosulphonate) per mol of enzyme subunit produced two species of protein. The first species was obtained in 20% yield and was only partially re-activated on mild reduction with 2-mercaptoethanol. The second species was isolated in 66% yield and was completely re-activated on mild reduction. Before reduction there was 4 mol of inhibitor per tetramer for the latter species, and more than 95% of the enzyme was present as a dimer on non-reducing electrophoresis. After mild reduction 2 mol of inhibitor was still bound per tetramer, the enzyme was now catalytically active and the dimer was still the major structure on non-reducing electrophoresis. Thus mild reduction of SS'-octamethylenebis(methanethiosulphonate-treated glyceraldehyde 3-phosphate dehydrogenase enabled the production of active enzyme in which there is a stable cross-link across one of the molecular axes of the tetrameric enzyme. This cross-link was only reversed if reduction was performed when the enzyme was denatured. The molecular weight of cross-linked and re-activated cross-linked glyceraldehyde 3-phosphate dehydrogenase was established as 144000 (tetramer) by sucrose-density-gradient centrifugation. These observations are interpreted in terms of the molecular structure of glyceraldehyde 3-phosphate dehydrogenase.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on splenic lymphocyte transformation in mice after single and repeated exposures

Male CD-1 mice were orally treated with 0.01, 0.1, 1 and 10 micrograms TCDD/kg body wt./week for up to 8 weeks. Randomly selected animals were sacrificed at 2, 4, and 8 weeks of exposure. An additional group was given orally 10 micrograms TCDD/kg and the animals similarly sacrificed. Splenic lymphocytes from these animals were cultured in vitro with or without the presence of phytomitogens, phytohemagglutinin, and pokeweed mitogen. The incorporation of 3H-thymidine was measured as an indication of relative blast formation. Exposure of animals to TCDD, even at the lowest level (0.01 microgram/kg/wk for 2 weeks) caused a marked increase in the thymidine uptake by cultured lymphocytes. The blastogenic response of mitogens was reduced at high levels of TCDD exposure, indicating an immunosuppressive effect. Following a single treatment with 10 micrograms TCDD/kg, the increase in the blast formation was noted at 2 weeks, the effect reduced at 4 weeks, and no difference noticed in treated vs. control cultures 8 weeks after the treatment. Small doses of TCDD stimulate the splenic lymphocyte transformation and this effect, although somewhat dose-related, can be reversed in a relatively short period of time.

Immunologic effects of vinyl chloride in mice

Male CD-1 mice were exposed to 10, 100 or 1000 ppm vinyl chloride (VC) for 2--8 weeks at 6 hr/day, 5 days/week. A slight increase in the spleen weight of mice was noted at the highest exposure level. Spleens were obtained from these animals (4 mice/group after 2, 4, and 8 weeks of exposure) and their lymphocytes cultured in vitro with or without the presence of phytomitogens, phytohemagglutinin (PHA) and pokeweed mitogen (PWM). Relative blast formation and the DNA synthesis was measured by the incorporation of 3H-thymidine in the cultured cells. The response of splenic lymphocytes to the phytomitogens was increased several-fold by VC exposure. The effects were apparent at 1000 ppm VC after 2 weeks of exposure and at all levels of VC exposure after 4--8 weeks. The effects were generally more pronounced at 100 ppm VC exposure than those at 1000 ppm. In vitro culture of splenic lymphocytes from control or VC-exposed mice in the VC atmosphere did not show an enhancement of blast formation. Alteration of VC metabolism during the VC exposure in vivo yielded results that indicated that metabolites of VC may be responsible for the stimulation of lymphocyte transformation observed in splenic cultures.

A detailed investigation of the properties of lactate dehydrogenase in which the 'Essential' cysteine-165 is modified by thioalkylation

The reaction of pig heart lactate dehydrogenase with methyl methanethiosulphonate resulted in the modification of one thiol group per protomer, and this was located at cysteine-165 in the enzyme sequence. On reduction, both the thiomethylation of cysteine-165 and any changes in kinetic properties of the enzyme were completely reversed. Cysteine-165 has been considered essential for catalytic activity; however, cysteine-165-thiomethylated dehydrogenase possessed full catalytic activity, although the affinity of the enzyme for carbonyl-or hydroxy-containing substrates was markedly decreased. The nicotinamide nucleotide-binding capacity was unaffected, as judged by the formation of fluorescent complexes with NADH. The enzyme-mediated activation of NAD+, as judged by sulphite addition, was unaffected in thiomethylated lactate dehydrogenase. However, the affinity of oxamate for the enzyme--NADH complex was decreased by 100-fold and it was calculated that this constituted a net increase of 10.4 kJ/mol in the activation energy for binding. Thiomethylated lactate dehydrogenase was able to form an abortive adduct between NAD+ and fluoropyruvate. However, the equilibrium constant for adduct formation between pyruvate and NAD+ was too low to demonstrate this complex at reasonable pyruvate concentrations. A conformational change in the protein structure on selective thiomethylation was revealed by the decreased thermostability of the modified enzyme. The alteration of lactate dehydrogenase catalytic properties on modification depended on the bulk of the reagent used, since thioethylation resulted in an increase in Km for pyruvate (13.5 +/- 3.5 mm) and an 85% decrease in maximum catalytic activity. The implications of all these findings for the catalytic mechanism of lactate dehydrogenase are discussed.

Cadmium uptake from feed and its distribution to food products of livestock

Distribution of cadmium (Cd) into the edible products of three species of food-producing animals was investigated during long-term dietary administration of supplemental cadmium chloride. Cows were exposed to 0.2 (control), 2.4, and 11.3 ppm Cd on whole ration basis for a period of three months followed by a three-month period on control ration. No accumulation of Cd occurred in milk, muscle, or bone at any of the time periods. A dose-related increase of Cd was observed in liver and kidney. The Cd concentration in these organs showed a gradual rise even when the animals were given control ration for three months after an initial three-month exposure to Cd; this observation suggests a mobilization and redistribution of this metal from other tissues. Dietary Cd levels in swine rations were 0.2, 2.4, and 10.1 ppm. The highest level of Cd produced a slightly reduced growth rate in swine. No accumulation of Cd was observed in muscle, bone, or brain. Liver and kidney showed a treatment and time-related increase in cadmium values at 6 and 12 weeks on experiment. During a three-month depletion phase after an initial three months of Cd administration, no further change in liver and kidney Cd levels was observed. White Leghorn chickens were treated by administering 0.3, 1.9, and 13.1 ppm Cd in their diets for up to 6 months. No accumulation of Cd occurred in eggs or bones. A slight increase of Cd level was observed in chicken muscle after six months of exposure. Liver and kidney had the highest levels of Cd, which showed a dose and time-related increase in these organs. No depletion of liver and kidney Cd was seen during seven weeks following a six-week treatment period. In all three species, the kidney Cd levels were severalfold higher than those of liver at all dietary levels. In swine, the renal cortex and medulla had similar Cd concentration in control animals but in all animals exposed to supplemental Cd, a dramatic rise in Cd levels in renal cortex was observed. Medullary Cd did not show a proportional time and dose-related increase in Cd levels, although the levels showed some increase. In kidney and liver of all three species the Cd levels showed a positive correlation with the amount of Cd-binding protein in these tissues. Induced levels of this metal-binding protein may explain accumulation and persistence of Cd-residues in these organs. In all three species, the concentrations of renal Cd-binding protein increased at a rate greater than those in liver. Although the food-producing animals may act as an effective filter of Cd in the case of an environmental increase of this metal, consumption of visceral organs from such animals may pose a hazard. This is particularly critical since the daily intake of Cd in human diet is already estimated to exceed the tolerance limits suggested by WHO/FAO.

Hepatic and renal metallothionein concentrations in cows, swine, and chickens given cadmium and lead in feed

Dairy cows, growing swine, and laying chickens were given supplemental cadmium (Cd) at concentrations of approximately 2 and 10 ppm in feed as cadmium chloride and were given lead at concentrations of 5 and 25 ppm in feed as lead acetate for 12 to 24 weeks. Metallothionein (MT) and Cd concentrations increased more in renal than in hepatic tissues of the Cd-treated animals. The hepatic MT values in pigs and chickens and the renal MT values in all species continued to increase for several weeks after Cd feeding was stopped. A significant correlation between Cd and MT concentrations of the hepatic and the renal tissues was observed, except in bovine liver. The feeding of lead did not have any effect on the hepatic or the renal MT concentrations in cows, pigs, and chickens. Dietary Cd and possibly some other metals, but not lead, may be determinants of concentration of metal binding protein in tissues.

Accumulation and depletion of vanadium in selected tissues of rats treated with vanadyl sulfate and sodium orthovanadate

Experiments were conducted to determine the distribution and effects of selected vanadium (V) salts in male rats following continuous ingestion. Wistar rats were continuously fed drinking water ad. Lib. containing 5 and 50 ppm V as vanadyl sulfate and sodium orthovanadate for a 3 month period. At the end of the 3rd, 6th, 9th, and 12th week, blood, kidney, liver, bone, muscle, and digestive tract were collected and analyzed for V utilizing flame atomic absorption spectrophotometry. In addition, the decline of vanadium residues in tissues after 6 weeks of continuous exposure was studied in selected groups. At the 5 and 50 ppm levels, V had no significant effect on body weights or hematocrit values. In the tissues of animals given 5 ppm of V salt, the V contents were essentially the same as those in controls. The tissues of animals given 50 ppm of V salt showed increased levels of vanadium. Kidney had the highest concentration, followed by bone, liver, and muscle. In general, the tissue concentrations of V in animals given 50 ppm as sodium orthovanadate were higher than those exposed to similar levels as vanadyl sulfate. The V concentration in kidney of the animals given 50 ppm sodium orthovanadate continued to rise until the 9th week of sampling, whereas the V content of other tissues analyzed for the treated animals plateaued from the 3rd week. The concentration of V in tissues after cessation of exposure declined rapidly except in the bone. After 6 weeks of the depletion phase the concentration of vanadium in animals given vanadyl sulfate returned to control values except in bone and kidneys. The animals exposed to sodium orthovanadate contained relatively high concentrations of V even after a 6 week depletion phase.

Teratogenic potential of blighted potato concentrate in rabbits, hamsters, and miniature swine

Freeze-dried preparations of potatoes infected with phytophthora infestans or Alternaria solani were fed to pregnant hamsters, rabbits, and miniature swine. No evidence was observed that these diets or the extracts of respective blights were capable of producing teratologic effects in hamsters. Lesions of neurulation and anencephaly were noticed in rabbits and swine, respectively. The need for further pharmacological and toxicological evaluation in sensitive species is emphasized.

Use of methanethiolation to investigate the catalytic role of sulphydryl groups in rabbit skeletal muscle pyruvate kinase

Incubation of rabbit skeletal muscle pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) with methyl methanethiosulphonate resulted in the time- and inhibitor concentration-dependent loss of enzyme activity. Substrates or products of the catalytic reaction prevented the loss of activity caused by methanethiolation. Their effectiveness as protecting agents was placed in the order ADP greater than ATP greater than Mg2+ greater than phosphoenolpyruvate greater than pyruvate. The essential catalytic cation, K+, had no effect on the methanethiolation reaction. [Me-3H]Methanethiosulphonate modified all the available cysteine thiol groups which correlated to the incorporation of four SC3H3 groups per protomer. Four radioactive peptides were obtained on tryptic peptide mapping. When methanethiolation was carried out in the presence of Mg2+ alone or with Mg2+ and ATP together, then only three SC3H3 groups were incorporated into each subunit. If MgATP protected methanethiolated pyruvate kinase was reacted with iodo[2-3H]acetic acid then 1.37 +/- 0.2 groups per protomer were carboxymethylated. 70% of the radioactivity was located in a single peptide on tryptic peptide mapping. This peptide was isolated and contained the segment carboxymethyl cysteine (Glx, Asx, Ser) Arg. Collectively these data indicate that although all thiol groups are equally accessible to methyl methanethiosulphonate, only a single thiol group participates in the catalytic event. An additional role in the maintenance of structure for this thiol group was also shown in studied of reduction and thermal denaturation of the enzyme.

Effect of vitamin E on selenium cytotoxicity in chick ganglia cultures

Short term exposure of cultured chick ganglia nerve fibers and neuroglia to selenite produced half maximal inhibitory growth effects in concentrations of 6.2 (2.9--13.0) X 10(-5) M and 1.1 (0.7--1.7) X 10(-4) M, respectively. Complete inhibition of growth for both cell types was apparent at 1 X 10(-3) M, while slight stimulation of nerve fiber outgrowth occurred at 1 X 10(-6) M. The addition of vitamin E to these mixed nerve elements produced effects not distinguishable from controls, while on the other hand affording significant protection to the cytotoxic effects of selenite (1 X 10(-4) M). Nerve fibers were more sensitive to selenite than were glial cells. Furthermore, selenite with and without vitamin E exerted a darkening effect on the explant cultures at 1 X 10(-4) M, which became absent or reduced above or below this concentration. The high affinity and binding properties of selenium for the non-polar hydrophobic bi-lipid layer and SH functions of membranes may be implicated in this metal-membrane interaction. The cytotoxic effects of selenite in vitro even though non-specific are protected by the simultaneous presence of vitamin E.

Crystal structure of Tris(pyridine-2-carboxylato)manganese(III) monohydrate

The crystal structure of the title compound, [Mn(C5H4NCO2)3],H2O, has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.053 for 2234 'observed' reflections. Crystals are monoclinic, C2/c, a 30.50(2), b 8.387(8), c 13.903(7) Ǻ, β 94.15(3)°, Z 8. The geometry of the manganese environment displays a pseudo-tetragonal distortion, the axial atoms being nitrogen (Mn-N 2.254(6), 2.217(6) Ǻ). The equatorial atoms are at distances Mn-N 2.059(5) Ǻ, Mn-O 1.891(5), 1.908(5), 1.942(5) Ǻ, the latter being trans to the nitrogen. The occupancy of the water molecule site is 0.54(1).

Crystal structures of 2-Hydroxyimino-1-phenylethan-1-one and ethyl 3-Oxo-2-sodiooxyiminobutanoate

The crystal structures of the title compounds, PhCOCH=NOH (5) and Na+[MeCOC(=NO-)CO2Et],-2H2O (10), have been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to R 0.051, 0.062 (815, 1199 'observed' reflections) respectively. Crystals of (5) are monoclinic, P21/n, a 14.177(6), b 5.075(4), c 11.049(6) Ǻ, β 112.89(3)°, Z4. Crystals of (10) are tetragonal, 141/a, a 19.41(1), c 10.643(5)Ǻ Z 16. In (5), within the C=NOH group, C-N is 1.263(4) and N-O is 1.375(4)Ǻ; in (10) C-N is 1.318(6) and N-O is 1.321(5)Ǻ. In (10), the (presumably) negative C=NO- group does not coordinate the sodium ion; the latter is bridged by water molecules, occupying four close coordination positions [2.405(4)-2.552(4)Ǻ] in an interesting bridged polymeric array while the remaining two coordination positions are occupied by two ligand C=O groups [2.363(4), 2.393(4) Ǻ], the ligands also bridging sodium ions.

Crystal structure of diammonium aquapentachloroferrate(III)

The crystal structure of the title compound, (NH4)2 [FeCl5(H2O)], has been redetermined by single-crystal X-ray diffraction at 295 K and refined by full matrix least squares to a residual of 0.054 for 1662 'observed' reflections. Crystals are orthorhombic, Pnma, a 13.706(2), b 9.924(1), c 7.024(1)Ǻ Z 4. Fe-O is 2.110(4)Ǻ; Fe-Cl range between 2.323(1)Ǻ (trans to OH2) and 2.350(1)-2.390(1) Ǻ (cis), the latter distances being very dependent upon hydrogen-bonded interactions with nearby species.

Crystal structure of ab-Bis(3-methylpyridine)-dc,fe-bis(pentane-2,3,4-trione 3-oximato)iron(II)

The crystal structure of the title compound has been determined at 295 K by single-crystal X-ray diffraction and refined by least squares to a residual of 0.062. Crystals are monoclinic, P2/c, a 19.102(8), b 8.117(4), c 16.610(8) Ǻ, β 111.90(3)°, Z. Unlike the tris(α-oxyimino ketonato)iron(II) complexes which are fac, the present derivative is based upon substitution of the two picoline moieties into a mer derivative, trans to the nitrogen atoms of the chelate ligands. <Fe- N(picoline)> is 2.020; <Fe-N, O(chelate)> 1.880, 1.952 Ǻ.

Crystal structure of fac-Tris(pentane-2,3,4-trione 3-oximato)cobalt(III)

The crystal structure of the title compound has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.058 for 2363 'observed' reflections. Crystals are triclinic, Pī, Z 4, a 15.517(8), b 11.772(7), c 11.282(7) Ǻ, α 112.10(4), β 94.80(3), γ 90.60(4)°. <Co-N, O>| distances are 1.883, 1.925 Ǻ respectively, the disposition of the three bidentate ligands within each of the two independent molecules being fac.

Evaluation of cytotoxic responses caused by selected organophosphorus esters in chick sympathetic ganglia cultures

Ten day old chick sympathetic ganglia cultured in a microslide assembly were treated with a selected group of organophosphate pesticides to evaluate their cytotoxicity ranges, and the usefulness of such a model for screening pesticides. Examination by phase contrast and light microscopy for chemically-induced morphological alteration of nerve fibers, glial cells and neurons provided the criteria for quantitation and assessment of the toxic effects. Concentrations that produced half-maximal effects ranged from 1 x 10(-6)M (severely toxic) for methylparathian, diazinon, paraoxon, mevinphos, diisopropylfluorophosphate, tri-o-tolyl phosphate and its mixed isomers to a 1 x 10(-3)M (intermediate) for malathion, leptophos, coumaphos, mono- and dicrotophos. Some or no effects were evident at 1 x 10(2-)M for O'ethyl-O-p-nitrophenyl phenyl phosphonothioate, tri-m-tolylphosphate, chlorpyriphos and triphenyl phosphate. In all instances, nerve fibers were more sensitive than neurons or glial cells to insecticides. All cellular growth was inhibited at 1 x 10(-2)M (except triphenyl phosphate). Below 1 x 10(-7)M, no inhibitory effects were evident. The secondary abnormalities included decreased cellular migration, diffuse cellular growth pattern, increased vacuolization, nerve fiber swelling and cellular degeneration. The cytotoxic effects of these chemicals do not appear to be related to in vivo toxicity or cholinesterase inhibition potential.

Locoweed poisoning in sheep: electroencephalographic and brain amine changes

The effects in sheep of locoweed poisoning on electroencephalograms and on levels of the brain amines serotonin and norepinephrine were measured. Lucoweed-induced EEG changes in sheep were characterized by episodes of high voltage, slow activity (HVSA). There was no effect on brain norephinephrine levels. The mean brain serotonin level of the sheep fed locoweed was approximately 57% higher than the control but was not significant.

Fluoride accumulation in bone and the effect on their physical properties in guinea pigs given different levels of fluoridated water

Guinea pigs were exposed to fluoridated water (2-20 ppm) for a period ranging from 15 to 42 weeks. The fluoride content of the bones increased in proportion to the concentration of fluoride in drinking water and the period of exposure. The rate constant of accumulation of fluoride in guinea pig bones was estimated to be 2.5 X 10(-2) week-1, with a half-life of plateau formation in the order of 28 weeks. This indicated that maximum accumulation of fluoride during a continuous exposure, or a computed complete elimination of fluoride after exposure, will take approximately four years. Although fluoridated water improved the weight gain of guinea pigs, no effect on physical properties of bones was observed. No other toxic effects of fluoride under these conditions were noted.

Synaptosomal adenosine triphosphatase (ATPase) inhibition by organophosphates

Chicken spinal cord adenosine triphosphatases (both Na+, K+ stimulated and ouabain insensitive) were inhibited by tri-o-tolyl phosphate (TOTP, a neurotoxic organophosphate which is not a cholinesterase inhibitor) and mevinphos (a non-neurotoxic compound but inhibitor of cholinesterases). The inhibition was concentration and time dependent, with an initial rapid drop in activity followed by a gradual exponential decline.

Lymphatic tissue response in chickens treated with tri-o-tolyl phosphate

Indices of immunologic response elicited by tri-o-tolyl phosphate (TOTP) in chickens were investigated. Histopathologic evaluation of lymphatic organs (spleen, cecal tonsil, bursa of Fabricius) and selected immuno-related visceral organs containing lymphatic infiltrations (liver, kidney, duodenum, pancreas) was conducted. Liver and spleen showed a consistent and definite increase of diffuse lymphatic tissue in TOTP-treated animals. Total plasma protein levels of treated animals were increased from 7 to 20% over 4-14 days after TOTP administration. A similar increased pattern was noted in gamma-globulin:albumin ratios of the treated group. The data suggested stimulation of immunologic response in chickens treated with TOTP.

Giemsa banding and heterochromatin distribution in Ornithogalum

In Ornithogalum virens, following Giemsa staining, the mitotic chromosomes revealed distinct C-banding pattern. Interphase nucleus also showed 12 chromocentres corresponding to the number of C-bands. Based on the measurements of C-bands, about 13.5% of the genome is heterochromatic.

Innate metabolic differences and mutagen sensitivity of Drosophila melanogaster. I. Radiosensitivity of hyperkinetic mutant

The sensitivity to gamma-rays of a hyperkinetic mutant (HK1), characterized by high metabolic activity, has been studied and compared with gamma-ray sensitivity of the wild-type Oregon-K. Radiation damage, as measured by the frequency of induced dominant lethals (DL) and sex-linked recessive lethals (SLRL), was more in HK1 as compared with Or-K. The maximal sensitivity differences for these parameters were observed in the first brood. Translocations, on the contrary, were in general fewer in the HK1 compared with Or-K. These results have been interpreted in terms of reduced repair of mutational lesions in the energy-stressed cells of KH1.