Comparison of the Ames assay and the induction of sister chromatid exchanges: Results with ten pharmaceuticals and five selected agents

Seven antischistosomal drugs, two antimalarial drugs, and one antiamoebic drug were tested in all five Ames strains for induction of mutation, as well as for induction of cytotoxicity, inhibition of cellular progression, and the induction of sister chromatid exchanges in two cultured mammalian cell lines. We found that two agents shown to be negative in the Ames test were positive for sister chromatid exchange induction. Based on qualitative and quantitative evaluation, we find that all but three of the pharmaceuticals should be considered to be potential human carcinogens.Abbreviations AA 2-aminoanthracene - 9AACC 9-aminoacridine - AM amoscanate - BrdUU bromodeoxyuridine - CA chloroquine diphosphate - CHO Chinese hamster ovary - CQ chloroquine - DAPI 46-diamidino-2-phenylindole - DHY dehydroemetine - DMSO dimethyl sulfoxide - EB ethidium bromide - FCS fetal calf serum - FN 4-fluoro-3-nitrophenyl azide - HY hycanthone - ICP inhibiting cell progression - LU lucanthone - MEM minimal essential medium - 2NF 2-nitrofurantoin - 4NPD 4-nitro-O-phenylenediamine - NZ niridazole - OL oltipraz - OX oxaminiquine - PBS phosphate buffered saline - PQ primaquine - PZ praziquantel - SA sodium azide - SCE sister chromatid exchange     

Comparison of the properties of active Ca2+ transport by the islet-cell endoplasmic reticulum and plasma membrane

The properties of active or ATP-dependent calcium transport by islet-cell endoplasmic reticulum and plasma membrane-enriched subcellular fractions were directly compared. These studies indicate that the active calcium transport systems of the two membranes are fundamentally distinct. In contrast to calcium uptake by the endoplasmic reticulum-enriched fraction, calcium uptake by islet-cell plasma membrane-enriched vesicles exhibited a different pH optimum, was not sustained by oxalate, and showed an approximate 30-fold greater affinity for ionized calcium. A similar difference in affinity for calcium was exhibited by the Ca²⁺-stimulated ATPase activities which are associated with these islet-cell subcellular fractions. Consistent with the effects of calmodulin on calcium transport, calmodulin stimulated Ca²⁺-ATPase in the plasma membranes, but did not increase calcium-stimulated ATPase activity in the endoplasmic reticulum membranes. The physiological significance of the differences observed in calcium transport by the endoplasmic reticulum and plasma membrane fractions relative to the regulation of insulin secretion by the islets of Langerhans is discussed.     

Metabolic heterogeneity of the proximal and distal kidney tubules

Proximal and distal tubule suspensions were prepared from kidneys of Sprague-Dawley rats by an isolation procedure on a Percoll^R gradient. The marker enzymes alkaline phosphatase (brush border) and hexokinase (cytoplasmic) as well as p-aminohippurate transport capacity, gluconeogenic activity and electron microscopy were used to characterize the two kidney tubule suspensions. The results of this study indicate that cytochrome P-450 is localized to the proximal tubular cells and that the O-deethylation of 7- ethoxycoumarin was higher in the proximal than distal fraction. Both proximal and distal tubules showed glucuronidation and deacetylation capacities and a relatively equal distribution of non-protein sulfhydryls. These studies demonstrate metabolic heterogeneity of the nephron, the proximal tubule being the main site of renal xenobiotic metabolism. Understanding of metabolic heterogeneity of proximal and distal kidney tubules should provide important information regarding cell specific mechanisms of nephrotoxicity.     

The effect of grazing intensity on phosphorus spiralling in autotropic streams

The effect of grazing on primary productivity and phosphorus cycling in autotrophic streams was studied using the snail Goniobasis clavaeformes. Snails were added to each of three replicate laboratory stream channels, receiving once-through flow of groundwater, in densities of 2.1, 3.0, and 4.2 g ash free dry mass (AFDM)/m². A fourth channel received no snails and served as an ungrazed control. Presence of snail grazers resulted in a large reduction in aufwuchs biomass, primary productivity, and biotic phosphorus uptake; a modest reduction in fine particulate organic matter (FPOM); and an increase in the fraction of stream particulate organic matter (POM) exported as seston. Although primary production and aufwuchs biomass continued to decline with increasing snail density, phosphorus uptake increased. This increased phosphorus uptake is attributed to abiotic sorption to inorganic surfaces exposed as a result of efficient removal of aufwuchs at high snail densities. Although snail densities were chosen to bracket the density measured in a natural stream, the experimental densities may result in considerably higher grazing pressure on aufwuchs due to the absence of alternate food sources (e.g., coarse particulate organic matter) usually found in natural streams. Presence of snail grazers increased the spiralling length of phosphorus, primarily by reducing aufwuchs biomass and consequently reducing uptake of phosphorus from the water. Presence of snails also increased downstream transport velocity of phosphorus bound to organic particles. These results follow the patterns predicted in a previous theoretical analysis for mildly phosphorus-limited streams.     

13C NMR Analysis of some simple tetrahydroisoquinolines

¹³C NMR resonances of 15 simple tetrahydroisoquinolines have been assigned on the basis of chemical shift theory, ¹³C-¹H coupling constants     

Lymphocyte zinc metabolism in disease

Lymphocytes were obtained from two patients with paroxysmal nocturnal hemoglobinuria as well as from apparently healthy controls and from patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia. Subsequently, several aspects of zinc metabolism were studied in vitro in short-term cultures of these lymphocytes in order to assess lymphocyte functional capacity. The results of mitogen stimulation and zinc uptake studies for lymphocytes from donors with paroxysmal nocturnal hemoglobinuria were similar to those obtained for leukemic lymphocytes. The results of studies to determine the inducibility of the low molecular weight zinc-binding protein, metallothionein, by zinc were complicated by the decrease in overall protein synthesis in lymphocytes from donors in the paroxysmal nocturnal hemoglobinuria. It is proposed that paroxysmal nocturnal hemoglobinuria is indeed a clonal disorder and the relationship between lymphocytes in this disorder and leukemic lymphocytes is discussed.     

Applicability of radiotracer methods of measuring14CO2 assimilation for determining microbial activity in soil including a newin situ method

The applicability of two methods (pyrolysis gas chromatography and acidification-wet oxidation) for determining¹⁴CO₂ incorporation into soil microorganisms was investigated. Both methods were able to distinguish biologically incorporated¹⁴C from abiotically adsorbed¹⁴C, but to varying degrees, there being a larger carryover of abiotic¹⁴C into the organic fraction and a higher percentage of assimilated¹⁴C in the organic fraction with the wet oxidation method. Using¹⁴C assimilation as a measure, it was possible to determine microbial activities in soils of diverse properties under a variety of conditions, including polar soils under harsh environmental conditions. Both light and dark¹⁴CO₂ fixation was measurable.¹⁴CO₂ assimilation was not always proportional to the enumerable microorganisms. A new design for measurement of microbial activityin situ enabled measurement of total C influx (primary productivity) into soils with minimal perturbation to the natural soil ecosystem.     

Evaluation of Factors Related to Growth of Rift Valley Fever Virus in Suspended Cell Cultures

The effect of several controlled variables on the peak titer and fold increase of Rift Valley fever virus grown in suspension culture on two variants of Earle's L cell, L-DR and L-MA clone 1-1, was studied. No significant amount of cell-associated virus was found at 24 hr, indicating a release of virus soon after its formation. Mild sonic treatment of the virus produced in serum-free medium increased the infective titer about 10x. This difference was not observed with virus produced in medium supplemented with serum. Peak titer was not affected by medium used during the infection period, by multiplicity of inoculum (MOI), or by initial cell concentration within the test range of 10(4) to 2 x 10(6) cell/ml. Cell strain employed influenced titer, because the L-DR cell did not produce virus efficiently at low MOI and low initial cell concentration. The time of peak titer and fold replication was dependent on MOI and initial cell concentration. Differences in virus propagation in monolayer and suspension systems are discussed.