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PubMed1989

Micronucleus test with potassium chromate(VI) administered intraperitoneally and orally to mice.

The effect of route of administration, intraperitoneal (i.p.) or oral gavage (p.o.), in the mouse micronucleus test was studied with K2CrO4 in 2 mouse strains (MS/Ae and CD-1). A simplified acute toxicity test to estimate the toxic dose levels of K2CrO4 showed that the LD50S were 50 mg/kg i.p. and 300 mg/kg p.o. for MS/Ae and 32 mg/kg i.p. and 180 mg/kg p.o. for CD-1. Based on results of a pilot micronucleus test to determine appropriate dose levels and the optimal sampling time, it was decided to sample bone marrow cells of both strains of mice 24 h after i.p. doses of 10-80 mg/kg and p.o. doses ranging from 20 to 320 mg/kg. K2CrO4 administered i.p. induced micronucleated polychromatic erythrocytes (MNPCEs) dose-dependently in both strains. In contrast, when administered p.o. the chemical failed to induce MNPCEs. These results suggest that this difference between i.p. and p.o. routes is related to a difference of absorption or metabolic fate of chromate in vivo.

Administration, Oral↗
PubMedDate not supplied

Induction of micronucleated reticulocytes by potassium bromate and potassium chromate in CD-1 male mice.

Micronucleus tests of potassium bromate (KBrO3) and potassium chromate (K2CrO4) were conducted with peripheral blood reticulocytes (PB-RETs) of CD-1 male mice dose intraperitoneally. Peripheral blood cells collected from the tail were stained supravitally with acridine orange (AO) using AO-coated glass slides. Both KBrO3 and K2CrO4 induced micronuclei in PB-RETs in the same manner as in polychromatic erythrocytes of bone marrow.

Animals↗
PubMed1995

Chromosome aberrations in cultured rat bone marrow cells treated with inorganic fluorides.

The genotoxic effects of inorganic fluorides were investigated by treating cultured rat bone marrow cells with varying concentrations (0.1-100 microM) of potassium fluoride (KF) and sodium fluoride (NaF) for different durations (12, 24 and 36 h) and measuring the incidence of cells with aberrations and number of breaks per cell. Both forms of fluoride were found to be weak mutagens relative to the positive control N-methyl-N-nitro-N-nitrosoguanidine (MNNG). A specificity of fluoride ion in inducing chromosome aberrations (CA) was indicated by the observation that both NaF and KF behaved almost equivalently in this study and at significantly higher variations from the results with potassium chloride (KCl) and sodium chloride (NaCl).

Animals↗
PubMed1985

The effect of fluoride on chromosome aberration and sister-chromatid exchange frequencies in cultured human lymphocytes.

Sodium fluoride, at concentrations of up to 60 times the level normally used in drinking water for the prevention of dental decay, was compared with 2 other inorganic salts for its ability to induce chromosome aberrations and sister-chromatid exchanges (SCE) in cultured human lymphocytes. No significant increases in the frequencies of aberrations of SCEs were found.

Cells, Cultured↗
PubMed1993

A sequential study on the use of the cytokinesis-block micronucleus method in mouse splenocytes.

Several known clastogens and mutagens have been tested for their ability to induce micronuclei (MN) using the cytokinesis-block method in mouse splenocytes. The chemicals were harringtonine, cisplatin, cytosine arabinoside, vincristine sulfate, colchicine, potassium chromate, methyl methanesulfonate and 2-acetylaminofluorene. All chemicals tested induced a dose-dependent increase in MN and a delay in cell-cycle progression. The results suggest that the cytokinesis-block micronucleus method in mouse splenocytes is reliable, economical and sensitive enough for detecting mutagenic agents in vivo and in vitro.

2-Acetylaminofluorene↗
PubMed1994

Identification of Norwalk virus in artificially seeded shellfish and selected foods.

A rotavirus dsRNA purification protocol was adapted to extract Norwalk ssRNA from artificially contaminated shellfish, and a sensitive reverse transcription-polymerase chain reaction assay for Norwalk virus was devised to identify an estimated 20-200 genomic copies. The technique includes deproteinization with guanidinium isothiocyanate, adsorption of RNA to hydroxyapatite, and sequential precipitation with cetyltrimethylammonium bromide and ethanol. The protocol allows high recovery of viral RNA free of enzymatic inhibitors from oysters, clams, and a variety of food matrices. Norwalk virus sequences were copied and amplified by using primers selected from the polymerase gene. Digestion of the amplified products with restriction enzymes ensured the specificity of the test. This rapid and sensitive assay may significantly improve the prospect for the routine screening of the uncultivatable Norwalk virus in food stuffs.

Animals↗
PubMed1984

Purification and crystallization of bovine liver phosphorylase.

We have purified and crystallized bovine liver phosphorylase a. Starting from 2.5 kg of liver, we obtain 250 mg of phosphorylase a, with a specific activity of 90 units/mg, representing 15% recovery. SDS polyacrylamide gels show three bands, a 95 kDa band with the same mobility as muscle phosphorylase, and two smaller bands of 55 kDa and 40 kDa, which are probably proteolytic fragments. These fragments remain associated and have native conformation and catalytic activity. Crystals which diffract to 2.8 A resolution, were prepared by the hanging drop method using polyethylene glycol PEG 4000 as precipitant. The crystals were prepared in the presence of activators maltotriose and phosphite and crack when placed in solutions containing the inhibitors glucose and caffeine. This suggests phosphorylase is present in an active conformation.

Animals↗
PubMed1985

Temperature-dependent structural rearrangement of apotryptophanase in potassium phosphate.

Apotryptophanase (L-tryptophan indole-lyase, EC 4.1.99.1) from Escherichia coli B/1t7A shows, in the presence of potassium phosphate, a temperature-dependent structural rearrangement which is not observed in the presence of sodium phosphate or imidazole plus KC1. This rearrangement can be described by a two-state equilibrium between two forms of the apoenzyme. The midpoint temperature of the rearrangement (TM) and the van't Hoff enthalpy (delta H) at different potassium phosphate concentrations and pH values, respectively, were determined by measuring the temperature-dependence of the ultraviolet absorbance of apotryptophanase. Increasing the potassium phosphate concentration at pH 7.8 causes a simultaneous increase in total absorbance and the delta H value, whereas the TM increases between pH 7.0 and 7.8 but starts to decrease at pH values above 7.8. In 0.1 M potassium phosphate at the pH optimum of the enzyme (7.8) TM and delta H were found to be 293.1 K and 167 kJ X mol-1, respectively. Moreover, the tyrosine residues of apotryptophanase dissociate in potassium phosphate and in imidazole plus KCl with pK values of 8.6 and 9.8, respectively, indicating that potassium phosphate favors the formation of tyrosinate. The rearrangement might be interpreted as the formation of specific hydrogen bonds between tyrosine and potassium phosphate which are ruptured at higher temperature. Such hydrogen bonds cannot be formed at all or only to a small extent in the presence of imidazole plus KCl or sodium phosphate. Those hydrogen bonds stabilize the structure of apotryptophanase. In contrast, holotryptophanase requires only K+ for enzymatic activity.

Apoenzymes↗
PubMed1987

Enzyme action in polymer and salt solutions. I. Stability of penicillin acylase in poly(ethylene glycol) and potassium phosphate solutions in relation to water activity.

The stability of penicillin acylase (penicillin aminohydrolase, EC 3.5.1.11) was studied in poly(ethylene glycol) and potassium phosphate solutions. Enzyme stability measured as the half-life of the enzymatic activity and the transition temperature determined by differential scanning calorimetry, correlated well. The enzyme stability could not be related to the water activity as a measure of solute-solvent interaction. It seems to be related more to the concentration of the solutes and much less to the molecular weight of poly(ethylene glycol). The stabilizing effect of poly(ethylene glycol) is also discussed in terms of poly(ethylene glycol)-protein interactions.

Amidohydrolases↗
PubMed1987

Enzyme action in polymer and salt solutions. II. Activity of penicillin acylase in poly(ethylene glycol) and potassium phosphate solutions in relation to water activity.

Increasing concentrations of poly(ethylene glycol) and potassium phosphate solutions decreased the enzymatic activity of penicillin acylase (penicillin aminohydrolase, EC 3.5.1.11). Low molecular weight poly(ethylene glycol) reduced the penicillin acylase activity more than high molecular weight poly(ethylene glycol). The decrease in enzymatic activity seemed to be related to the decrease in water activity in solutions containing poly(ethylene glycol), irrespective of the molecular weight of the polymer. The decrease in enzymatic activity in potassium phosphate solutions was lower than in poly(ethylene glycol) solutions and did not fit the water activity relationship. The decreased enzymatic activity is discussed in relation to the enzyme stability in these solutions.

Amidohydrolases↗
PubMed1988

Study of pH- and temperature-induced transitions in F-protein (phosphofructokinase) by spectroscopy and microcalorimetry methods.

The temperature- and pH-induced transitions in F-protein (phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11] have been studied by means of microcalorimetry and fluorescence and CD spectroscopy. An increase in pH from approx. 6.0 to approx. 8.0 causes a change in the protein state which seems to correspond to a shift of the dimer-tetramer equilibrium in favour of the tetramers. In the absence of phosphate, stability of the protein to temperature- and urea-induced denaturation at pH 6.0 is higher than that at pH 8.0. An addition of 150 mM phosphate results in a pronounced increase in the protein's stability in such a way that the protein becomes more stable at pH 8.0 than at pH 6.0. The shift of the denaturational heat capacity peak induced by the phosphate binding exceeds 25 degrees C at pH 8.0 and 9 degrees C at pH 6.0.

Animals↗
PubMed1989

Structure-function relationships in the inorganic salt-induced precipitation of alpha-chymotrypsin.

alpha-Chymotrypsin (alpha CT) was used as a model protein to study the effects of salt-induced precipitation on protein conformation. Process parameters investigated included the type and amount of salt used to induce precipitation. The salts studied included Na2SO4, NaCl, NaBr, KBr and KSCN. Precipitate secondary structure content was examined via laser Raman spectroscopy. Conventional and saturation transfer electron paramagnetic resonance spectroscopy were employed to probe the tertiary structure of the active site in spin-labelled alpha CT precipitates. As the molal surface tension increment of the inducing salt increased, the beta-sheet content increased and the alpha-helix content decreased. There was no significant variation in secondary structure with the amount of salt used. The fraction of precipitate that recovered activity on redissolution was correlated with the change in secondary structure content. Spin-labelled precipitate spectra indicated that the active site remains unaltered during precipitation. Molecular modelling was employed to investigate how physical property of alpha CT were affected by these types of conformational change. Estimated physical property changes could not account entirely for observed deviations from current equilibrium theory for salt-induced precipitation. The spectroscopic observations were also combined with activity/solubility results to propose a mechanism for the salt-induced precipitation of globular proteins.

Animals↗
PubMed1993

Quasi-irreversible inactivation of the sarcoplasmic reticulum Ca(2+)-ATPase by simultaneous tight binding of magnesium and fluoride to the catalytic site.

The sarcoplasmic reticulum Ca(2+)-ATPase was inactivated quasi-irreversibly by the treatment with KF in the presence of Mg2+ and absence of Ca2+. This inactivation was Mg(2+)-dependent, and prevented by high-affinity Ca2+ binding. The enzyme was completely protected by ATP against the inactivation with an affinity consistent with that of the catalytic site for ATP. The affinity for Mg2+ in this inactivation was in agreement with that for Mg2+ in phosphorylation of the enzyme with Pi. Mg.ATP did not bind to the inactivated enzyme, whereas metal-free ATP did bind to it with a high affinity. These findings suggest that the Mg2+ binding sub-site in the catalytic site of the inactivated enzyme is occupied by tightly-bound Mg2+. The enzyme was completely protected by Pi against the inactivation with an affinity consistent with that of the catalytic site for Pi. The inactivated enzyme showed neither phosphorylation with Pi nor high-affinity vanadate binding. These findings suggest that the phosphorylation site of the inactivated enzyme is occupied by tightly-bound F-. The contents of tightly-bound Mg2+ and F- in the inactivated enzyme were determined after unbound Mg2+ and F- were removed by gel filtration. 2.3 mol of Mg2+ and 3.7 mol of F- per mol of phosphorylation sites were tightly bound to the enzyme. The tight binding of these ligands depended on the presence of each other, and was completely prevented by high-affinity Ca2+ binding. Linear relationships were found between the contents of the tightly-bound ligands and the extent of the enzyme inactivation. The tightly-bound Mg2+ and F- were entirely released by low-affinity Ca2+ binding, and correspondingly the ATPase activity was restored. It is concluded that the observed enzyme inactivation is caused by simultaneous tight binding of Mg2+ and F- to the catalytic site.

Adenosine Triphosphate↗
PubMed1996

Yersinia spp. and numbers, with particular reference to Y. enterocolitica bio/serotypes, occurring on Irish meat and meat products, and the influence of alkali treatment on their isolation.

Samples (n = 340) of Irish meat and meat products were examined to determine the incidence and initial numbers of Yersinia spp. present. In cases where no typical Yersinia colonies were observed, samples were cold enriched up to 21 days at 4 degrees C and streaked out on CIN agar with and without post-enrichment alkali treatment. The highest isolation rates of Yersinia were found using post-enrichment alkali treatment and an incubation temperature of 37 degrees C. All Yersinia isolates were identified to species level and Y. enterocolitica isolates were biotyped and serotyped. Pathogenic isolates (biotypes 1B-5) were examined for the presence of a virulence plasmid using dye binding reactions and agglutination tests. The incidence of Yersinia spp. was high on raw (89%) and cooked meats (49%) obtained fromdelicatessen counters but lower in pre-packaged cooked meats (18.8%). Initial numbers of Yersinia were generally < 2.7 log10cfu/g on raw meats and < 0.7 log10cfu/g on cooked.

Food Microbiology↗
PubMed1990

Reduction of anthralin-induced inflammation by application of amines.

Twenty-two primary, secondary, and tertiary amines were studied to determine whether they could reduce anthralin-induced inflammation. Amine solutions of 0.18 mol/L were applied after anthralin application to normal forearm skin. Inflammation was measured with the use of Harpenden calipers by the increase in skin thickness at 48 hours. Inflammation was reduced by 66% to 95% with the use of nine different amines. There was no overall correlation between the inhibiting effect and either amine basicity or octanol/water partition coefficient. However, within each of the series of primary, secondary, and tertiary alkylamines there appeared to be some correlation between inhibitory effect and alkyl chain size, which may reflect differences in transdermal flux. Some of these amines are used in cosmetics and skin cleansers and could help reduce the inflammation that accompanies anthralin therapy for psoriasis.

Administration, Cutaneous↗
PubMed1991

The effects of potassium chromate and citrinin on rat renal membrane transport.

Both chromate and citrinin have been shown to produce acute renal damage. Although both substrates act on the proximal tubule in the rat, they affect different parts of that nephron segment. As with most nephrotoxicants, the mechanism(s) or subcellular target(s) for citrinin or chromate is unknown. The availability of methodology for isolation of functional membrane vesicles has afforded the opportunity to study the plasma membrane as a target for the effects of citrinin and chromate. Whether studied solely with in vitro conditions or after administration to the rat, chromate exhibited its primary action on the basolateral (BL) membrane vesicles. This was exhibited by a reduction in the p-aminohippurate (PAH) overshoot. At both 3 and 16 hr after treatment (40 mg/kg, sc) there was a significant, but relatively modest, effect on glucose transport by brush border (BB) vesicles. Citrinin, when studied in vitro, inhibited PAH transport (BL vesicles), but had only equivocal effects on BB glucose transport. However, after pretreatment of the rats with citrinin (60 mg/kg, ip), both BL and BB membrane vesicle function was reduced markedly at 3 hr. By 16 hr, an overshoot had returned for both transport substrates, although the glucose overshoot was still significantly below control. These data demonstrate that both citrinin and chromate alter proximal tubular cell membrane function and do so relatively early after administration to the rat. This effect suggests that alteration of membrane function by these nephrotoxicants is an early, if not initiating, event in the production of acute tubular necrosis.

Animals↗
PubMed1994

Interfacial reactions of osteoblasts to dental and implant materials.

Scanning electron microscopy was used to study the response of osteoblasts to various surfaces including ceramics and glasses as well as steel and titanium. Hydroxylapatite, tricalcium phosphate, bioglass, steel, and titanium supported cell adhesion. However, the toxic effects of the In-Ceram (Vita, Bad Säckingen, Germany), and feldspar ceramic and glaze were severe enough to cause verrucous necrosis that was identifiable after 2 days of culture. After 10 days in culture only the peripheral portions of these specimens were still occupied by cells; the cells in the central portion of the circular specimens had succumbed to necrosis. It was concluded that scanning electron microscopy is useful in identifying the response of cells to materials. Pathologic changes are not recognizable if they are limited to the internal structure of the cell, but readily discernible when they impinge on the morphologic integrity of the cell surface.

Aluminum Oxide↗
PubMed1990

Two-year oral chronic toxicity and carcinogenicity study in rats of diets fumigated with methyl bromide.

A chronic toxicity and carcinogenicity study was conducted by feeding diets containing 80, 200 or 500 ppm total bromine following fumigation with methyl bromide, a diet containing 500 ppm potassium bromide, or a basal diet alone to groups of 60 male and 60 female Fischer (F344) rats for up to 2 yr. Ten males and ten females from each group were killed after wk 52 and 104 for urinalysis, haematology, blood biochemistry and pathology. Rats that were killed in extremis or found dead during the study and all rats that survived to the end of the study were also subjected to pathological examinations. In rats fed the diets fumigated with methyl bromide there were no marked toxic changes, except for a slight depression of body-weight gain from wk 60 onwards in males of the 500-ppm group, and tumour incidence was unaffected. Rats given a diet containing potassium bromide did not show any treatment-related changes. It was concluded that residues of up to 500 ppm total bromine in diets fumigated with methyl bromide are not carcinogenic in F344 rats of either sex and that the maximum no-effect level is 200 ppm (6.77 mg total bromine/kg body weight/day) in males. The maximum no-effect level could not be determined in females.

Animals↗