Preoperative breast MRI and mortality in older women with breast cancer.

PURPOSE: The survival benefit from detecting additional breast cancers by preoperative magnetic resonance imaging (MRI) continues to be controversial. METHODS: We followed a cohort of 4454 women diagnosed with non-metastatic breast cancer (stage I-III) from 2/2005-6/2010 in five registries of the breast cancer surveillance consortium (BCSC). BCSC clinical and registry data were linked to Medicare claims and enrollment data. We estimated the cumulative probability of breast cancer-specific and all-cause mortality. We tested the association of preoperative MRI with all-cause mortality using a Cox proportional hazards model. RESULTS: 917 (20.6%) women underwent preoperative MRI. No significant difference in the cumulative probability of breast cancer-specific mortality was found. We observed no significant difference in the hazard of all-cause mortality during the follow-up period after adjusting for sociodemographic and clinical factors among women with MRI (HR 0.90; 95% CI 0.72-1.12) compared to those without MRI. CONCLUSION: Our findings of no breast cancer-specific or all-cause mortality benefit supplement prior results that indicate a lack of improvement in surgical outcomes associated with use of preoperative MRI. In combination with other reports, the results of this analysis highlight the importance of exploring the benefit of preoperative MRI in patient-reported outcomes such as women's decision quality and confidence levels with decisions involving treatment choices.

Consolidating new words from repetitive versus multiple stories: Prior knowledge matters.

Prior knowledge is proposed to support the consolidation of newly acquired material. The current study examined whether children with superior vocabulary knowledge show enhanced overnight consolidation, particularly when new words are encountered in varying stories. Children aged 10 and 11 years (N = 42) were exposed to two sets of eight spoken novel words (e.g., "crocodol"), with one set embedded in the same story presented twice and the other presented in two different stories. Children with superior vocabulary knowledge showed larger overnight gains in explicit phonological and semantic knowledge when novel words had been encountered in multiple stories. However, when novel words had been encountered in repetitive stories, existing knowledge exerted no influence on the consolidation of explicit phonological knowledge and had a negative impact on the consolidation of semantic knowledge. One full day (24 h) after story exposure, only very weak evidence of lexical integration (i.e., slower animacy decisions toward the basewords [e.g., "crocodile"] than toward the control words) was observed for novel words learned via repetitive (but not multiple) stories. These data suggest that although the consolidation of explicit new word knowledge learned through multiple contexts is supported by prior knowledge, lexical integration might benefit more from repetition.

Do naps benefit novel word learning? Developmental differences and white matter correlates.

Memory representations of newly learned words undergo changes during nocturnal sleep, as evidenced by improvements in explicit recall and lexical integration (i.e., after sleep, novel words compete with existing words during online word recognition). Some studies have revealed larger sleep-benefits in children relative to adults. However, whether daytime naps play a similar facilitatory role is unclear. We investigated the effect of a daytime nap (relative to wake) on explicit memory (recall/recognition) and lexical integration (lexical competition) of newly learned novel words in young adults and children aged 10-12 years, also exploring white matter correlates of the pre- and post-nap effects of word learning in the child group with diffusion weighted MRI. In both age groups, a nap maintained explicit memory of novel words and wake led to forgetting. However, there was an age group interaction when comparing change in recall over the nap: children showed a slight improvement whereas adults showed a slight decline. There was no evidence of lexical integration at any point. Although children spent proportionally more time in slow-wave sleep (SWS) than adults, neither SWS nor spindle parameters correlated with over-nap changes in word learning. For children, increased fractional anisotropy (FA) in the uncinate fasciculus and arcuate fasciculus were associated with the recognition of novel words immediately after learning, and FA in the right arcuate fasciculus was further associated with changes in recall of novel words over a nap, supporting the importance of these tracts in the word learning and consolidation process. These findings point to a protective role of naps in word learning (at least under the present conditions), and emphasize the need to better understand both the active and passive roles that sleep plays in supporting vocabulary consolidation over development.

Accessing and selecting word meaning in autism spectrum disorder.

BACKGROUND: Comprehension difficulties are commonly reported in autism spectrum disorder (ASD) but the causes of these difficulties are poorly understood. This study investigates how children with ASD access and select meanings of ambiguous words to test four hypotheses regarding the nature of their comprehension difficulties: semantic deficit, weak central coherence, reduced top-down control and inhibition deficit. METHODS: The cross-modal semantic priming paradigm was used. Children heard homonym primes in isolation or as final words in sentences biased towards the subordinate meaning and then named picture targets depicting dominant or subordinate associates of homonyms. RESULTS: When homonyms were presented in isolation, children with ASD and controls showed priming for dominant and subordinate pictures at 250ms ISI. At 1,000ms ISI, the controls showed dominant (but not subordinate) priming whilst the ASD group did not show any priming. When homonyms were presented in subordinate sentence contexts, both groups only showed priming for context-appropriate (subordinate) meanings at 250ms ISI, suggesting that context has an early influence on meaning selection. At 1,000ms ISI the controls showed context-appropriate (but not inappropriate) priming whereas the ASD group showed both appropriate and inappropriate priming. CONCLUSIONS: Children with ASD showed intact access to semantic information early in the time course of processing; however, they showed impairments in the selection of semantic representations later in processing. These findings suggest that a difficulty with initiating top-down strategies to modulate online semantic processing may compromise language comprehension in ASD. Implications for intervention are discussed.

Growing up with interfering neighbours: the influence of time of learning and vocabulary knowledge on written word learning in children.

Evidence suggests that new vocabulary undergoes a period of strengthening and integration offline, particularly during sleep. Practical questions remain, however, including whether learning closer to bedtime can optimize consolidation, and whether such an effect varies with vocabulary ability. To examine this, children aged 8-12-years-old (n 59) were trained on written novel forms (e.g. BANARA) in either the morning (long delay) or the evening (short delay). Immediately after training and the next day, lexical competition (a marker of integration) was assessed via speeded semantic decisions to neighbouring existing words (e.g. BANANA); explicit memory was measured via recognition and recall tasks. There were no main effects indicating performance changes across sleep for any task, counter to studies of spoken word learning. However, a significant interaction was found, such that children with poorer vocabulary showed stronger lexical competition on the day after learning if there was a short delay between learning and sleep. Furthermore, while poorer vocabulary was associated with slower novel word recognition speed before and after sleep for the long delay group, this association was only present before sleep for the short delay group. Thus, weak vocabulary knowledge compromises novel word acquisition, and when there is a longer period of post-learning wake, this disadvantage remains after a consolidation opportunity. However, when sleep occurs soon after learning, consolidation processes can compensate for weaker encoding and permit lexical integration. These data provide preliminary suggestion that children with poorer vocabulary may benefit from learning new words closer to bedtime.

Learning to live with interfering neighbours: the influence of time of learning and level of encoding on word learning.

New vocabulary is consolidated offline, particularly during sleep; however, the parameters that influence consolidation remain unclear. Two experiments investigated effects of exposure level and delay between learning and sleep on adults' consolidation of novel competitors (e.g. BANARA) to existing words (e.g. BANANA). Participants made speeded semantic decisions (i.e. a forced choice: natural versus man-made) to the existing words, with the expectation that novel word learning would inhibit responses due to lexical competition. This competition was observed, particularly when assessed after sleep, for both standard and high exposure levels (10 and 20 exposures per word; Experiment 1). Using a lower exposure level (five exposures; Experiment 2), no post-sleep enhancement of competition was observed, despite evidence of consolidation when explicit knowledge of novel word memory was tested. Thus, when encoding is relatively weak, consolidation-related lexical integration is particularly compromised. There was no evidence that going to bed soon after learning is advantageous for overnight consolidation; however, there was some preliminary suggestion that longer gaps between learning and bed-onset were associated with better explicit memory of novel words one week later, but only at higher levels of exposure. These findings suggest that while lexical integration can occur overnight, weaker lexical traces may not be able to access overnight integration processes in the sleeping brain. Furthermore, the finding that longer-term explicit memory of stronger (but not weaker) traces benefit from periods of wake following learning deserves examination in future research.

Eye-tracking the time-course of novel word learning and lexical competition in adults and children.

Lexical competition is a hallmark of proficient, automatic word recognition. Previous research suggests that there is a delay before a new spoken word becomes engaged in this process, with sleep playing an important role. However, data from one method - the visual world paradigm - consistently show competition without a delay. We trained 42 adults and 40 children (aged 7-8) on novel word-object pairings, and employed this paradigm to measure the time-course of lexical competition. Fixations to novel objects upon hearing existing words (e.g., looks to the novel object biscal upon hearing "click on the biscuit") were compared to fixations on untrained objects. Novel word-object pairings learned immediately before testing and those learned the previous day exhibited significant competition effects, with stronger competition for the previous day pairings for children but not adults. Crucially, this competition effect was significantly smaller for novel than existing competitors (e.g., looks to candy upon hearing "click on the candle"), suggesting that novel items may not compete for recognition like fully-fledged lexical items, even after 24h. Explicit memory (cued recall) was superior for words learned the day before testing, particularly for children; this effect (but not the lexical competition effects) correlated with sleep-spindle density. Together, the results suggest that different aspects of new word learning follow different time courses: visual world competition effects can emerge swiftly, but are qualitatively different from those observed with established words, and are less reliant upon sleep. Furthermore, the findings fit with the view that word learning earlier in development is boosted by sleep to a greater degree.

Effect of vitamin C deficiency on hydroxylation of trimethylaminobutyrate to carnitine in the guinea pig.

The effect of ascorbate deficiency on carnitine biosynthesis was investigated in young male guinea pigs. Liver and skeletal muscle carnitine levels were reduced in scorbutic animals. Heart and kidney concentrations remained unchanged. 14C-labeled 4-N-trimethylaminobutyrate was administered to control, pair-fed and scorbutic animals and distribution of isotope in compound present in the liver after 30 min was determined. Control and pair-fed animals converted trimethylaminobutyrate to carnitine faster than scorbutic animals. Injection of ascorbate with the [14C]trimethylaminobutyrate reversed the decline in trimethylaminobutyrate hydroxylase (EC 1.14.11.1) activity in scorbutic animals.

Absorption of D- and L-carnitine by the intestine and kidney tubule in the rat.

The process by which L- and D-carnitine are absorbed was investigated using the live rat and the isolated vascularly perfused intestine. A lumenal dose of 2-6 nmol in the perfused intestine resulted in less than 5% transport of either isomer to the perfusate in 30 min. The L-isomer was taken up by the intestinal tissue about twice as rapidly as the D-isomer by both the perfused intestine (52.8% and 21.6%, respectively) and the live animal (80% and 50%, respectively) in 30 min. After 1 h 90% of the L-carnitine had accumulated in the intestinal tissue and was released to the circulation over the next several hours. Accumulation of D-carnitine reached a maximum of 80% in 2 h and release to the circulations was similar to that of L-carnitine. Uptake of both L-[14C]carnitine and acetyl-L-[14C]carnitine was more rapid in the upper jejunal segment than in other portions of the small intestine. Acetylation occurred in all segments, resulting in nearly 50% conversion to this derivative in 5 min. Increasing the dose of L-carnitine reduced the percent acetylation. The uptake of both isomers was a saturable process and high concentrations of D-carnitine, acetyl-L-carnitine and trimethylaminobutyrate inhibited L-carnitine uptake. In the live animal after 5 h, the distribution of isotope from L-[14C]carnitine and D-[3H]carnitine differed primarily in the muscle where 29.5% of the L-carnitine and 5.3% of the D-carnitine was found and in the urine where 2.9% of the L-carnitine and 7.1% of the D-carnitine was found. The renal threshold for L-carnitine was 80 microM and for D-carnitine 30 microM, in the isolated perfused kidney. Approx. 40% of the L-carnitine but none of the D-carnitine excreted in the urine was acetylated. L-Carnitine and D-carnitine competed for tubular reabsorption.

Transport and metabolism of pantothenic acid by rat kidney.

Transport of [14C]pantothenic acid was studied using brush-border membrane vesicles prepared from rat kidney. In the presence of a Na+ gradient an accumulation of pantothenic acid 3-fold above equilibrium was observed. The Km and Vmax found were 7.30 microM and 23.8 pmol/mg protein per min, respectively. Isolated perfused rat kidneys were employed to study excretion of pantothenic acid at various concentrations in the perfusate. At physiological plasma concentrations, the filtered pantothenic acid was largely reabsorbed by the active process observed in the vesicles. At higher concentrations, pantothenic acid was found to undergo tubular secretion. Penicillin inhibited this secretory process indicating that both compounds share a secretory mechanism. Live animal studies indicated that the only compound excreted after injection of [14C]pantothenic acid was free pantothenic acid. After 1 week only 38% of the administered dose was excreted in the urine, indicating that effective conservation was taking place in the whole animal.

Transport and metabolism of pyridoxine in rat liver.

Evidence, obtained with in situ perfused rat liver, indicated that pyridoxine is taken up from the perfusate by a non-concentrative process, followed by metabolic trapping. These conclusions were reached on the basis of the fact that at low concentrations (0.125 microM), the 3H of [3H]pyridoxine accumulated against a concentration gradient, but high concentrations (333 microM) of pyridoxine or 4-deoxypyridoxine prevented this apparent concentrative uptake. Under no conditions did the tissue water:perfusate concentration ratio of [3H]pyridoxine exceed unity. The perfused liver rapidly converted the labeled pyridoxine to pyridoxine phosphate, pyridoxal phosphate and pyridoxamine phosphate and released a substantial amount of pyridoxal and some pyridoxal phosphate into the perfusate. Since muscle and erythrocytes failed to oxidize pyridoxine phosphate to pyridoxal phosphate, it is suggested that the liver plays a major role in oxidizing dietary pyridoxine and pyridoxamine as their phosphate esters to supply pyridoxal phosphate which then reaches to other organs chiefly as circulating pyridoxal.

Uptake of L-carnitine, D-carnitine and acetyl-L-carnitine by isolated guinea-pig enterocytes.

Uptake and metabolism of L-carnitine, D-carnitine and acetyl-L-carnitine were studied utilizing isolated guinea-pig enterocytes. Uptake of the D- and L-isomers of carnitine was temperature dependent. Uptake of L-[14C]carnitine by jejunal cells was sodium dependent since replacement by lithium, potassium or choline greatly reduced uptake. L- and D-carnitine developed intracellular to extracellular concentration gradients for total carnitine (free plus acetylated) of 2.7 and 1.4, respectively. However, acetylation of L-carnitine accounted almost entirely for the difference between uptake of L- and D-carnitine. About 60% of the intracellular label was acetyl-L-carnitine after 30 min, and the remainder was free L-carnitine. No other products were observed. D-Carnitine was not metabolized. Acetyl-L-carnitine was deacetylated during or immediately after uptake into intestinal cells and a portion of this newly formed intracellular free carnitine was apparently reacetylated. L-Carnitine and D-carnitine transport (after adjustment for metabolism and diffusion) were evaluated over a concentration range of 2-1000 microM. Km values of 6-7 microM and 5 microM, were estimated for L- and D-carnitine, respectively. Ileal-cell uptake was about half that found for jejunal cells, but the labeled intracellular acetylcarnitine-to-carnitine ratios were similar for both cell populations. Carnitine transport by guinea-pig enterocytes demonstrate characteristics of a carrier-mediated process since it was inhibited by D-carnitine and trimethylaminobutyrate, as well as being temperature and concentration dependent. The process appears to be facilitated diffusion rather than active transport since L-carnitine did not develop a significant concentration gradient, and was unaffected by ouabain or actinomycin A.

Transport and metabolism of carnitine precursors in various organs of the rat.

Isolated, vascularly perfused small intestine, liver, and kidney were used to investigate their interdependence in the absorption and metabolism of carnitine precursors in the rat. During 30 min of recirculating perfusion, the small intestine absorbed trimethyllysine, hydroxytrimethyllysine, and trimethylaminobutyrate fairly well when they were administered via the lumen or the perfusate. Trimethylaminobutyrate was synthesized from either trimethyllysine or hydroxytrimethyllysine by the small intestine, but further hydroxylation of trimethylaminobutyrate to carnitine did not occur. Trimethyllysine and hydroxytrimethyllysine were not readily absorbed by the liver. In contrast, trimethylaminobutyrate and trimethylaminobutyraldehyde were rapidly absorbed from the perfusate and readily incorporated into carnitine by the liver. Trimethyllysine and hydroxytrimethyllysine were taken up slowly by the kiodney and partially converted to trimethylaminobutyrate during 3409 min of perfusion. Trimethylaminobutyrate was neither absorbed readily by the kidney nor was it hydroxylated to carnitine. These results were compared to whole animal studies performed over an equivalent time period. The data suggest that the isolted small intestine absorbs trimethyllysine well, but it probably plays a minor role in metabolizing physiological quantities of this compound in the whole animal where other organs are competing for the same substrate. In both the isolated organ and in the whole animal, the kidney absorbs and metabolizes trimethyllysine more readily than the liver; whereas the liver absorbs trimethylaminobutyrate more rapidly than either the kidney or the small intestine and, unlike these organs, converts it to carnitine.

Effect of ascorbic acid deficiency on the in vivo synthesis of carnitine.

The effects of ascorbate deficiency on carnitine biosynthesis was investigated in young male guinea pigs. Liver and kidney carnitine levels were not affected by the deficiency, but scorbutic animals had 50% less carnitine in heart and skeletal muscle than control animals. Labeled carnitine precursors, 6-N-tri-methyl-L-lysine and 4-N-trimethylaminobutyrate, both of which require ascorbate for their enzymatic hydroxylation, were injected into the vena cava of control, pair-fed and scorbutic animals. The distribution of isotope in compounds present in the liver and kidney after 1 h was determined. The uptake of trimethyllysine by the liver was less than 2% in 1 h, while the kidney took up approx. 20% of the 14C. Control and pair-fed animals converted trimethyllysine to kidney trimethylaminobutyrate 8--10 times as well as did scorbutic animals. Trimethylaminobutyrate hydroxylase, present in the liver but almost absent from the kidney, converted nearly all of substrate taken up by the liver to carnitine in both the scorbutic and control animals.

Evidence that the product of the human X-linked CGD gene, gp91-phox, is a voltage-gated H(+) pathway.

Expression of gp91-phox in Chinese hamster ovary (CHO91) cells is correlated with the presence of a voltage-gated H(+) conductance. As one component of NADPH oxidase in neutrophils, gp91-phox is responsible for catalyzing the production of superoxide (O(2).(2)). Suspensions of CHO91 cells exhibit arachidonate-activatable H(+) fluxes (Henderson, L.M., G. Banting, and J.B. Chappell. 1995. J. Biol. Chem. 270:5909-5916) and we now characterize the electrical properties of the pathway. Voltage-gated currents were recorded from CHO91 cells using the whole-cell configuration of the patch-clamp technique under conditions designed to exclude a contribution from ions other than H(+). As in other voltage-gated proton currents (Byerly, L., R. Meech, and W. Moody. 1984. J. Physiol. 351:199-216; DeCoursey, T.E., and V.V. Cherny. 1993. Biophys. J. 65:1590-1598), a lowered external pH (pH(o)) shifted activation to more positive voltages and caused the tail current reversal potential to shift in the manner predicted by the Nernst equation. The outward currents were also reversibly inhibited by 200 microM zinc. Voltage-gated currents were not present immediately upon perforating the cell membrane, but showed a progressive increase over the first 10-20 min of the recording period. This time course was consistent with a gradual shift in activation to more negative potentials as the pipette solution, pH 6.5, equilibrated with the cell contents (reported by Lucifer yellow included in the patch pipette). Use of the pH-sensitive dye 2'7' bis-(2-carboxyethyl)-5(and 6) carboxyfluorescein (BCECF) suggested that the final intracellular pH (pH(i)) was approximately 6.9, as though pH(i) was largely determined by endogenous cellular regulation. Arachidonate (20 microM) increased the amplitude of the currents by shifting activation to more negative voltages and by increasing the maximally available conductance. Changes in external Cl(-) concentration had no effect on either the time scale or the appearance of the currents. Examination of whole cell currents from cells expressing mutated versions of gp91-phox suggest that: (a) voltage as well as arachidonate sensitivity was retained by cells with only the NH(2)-terminal 230 amino acids, (b) histidine residues at positions 111, 115, and 119 on a putative membrane-spanning helical region of the protein contribute to H(+) permeation, (c) histidine residues at positions 111 and 119 may contribute to voltage gating, (d) the histidine residue at position 115 is functionally important for H(+) selectivity. Mechanisms of H(+) permeation through gp91-phox include the possible protonation/deprotonation of His-115 as it is exposed alternatively to the interior and exterior faces of the cell membrane (see Starace, D.M., E. Stefani, and F. Bezanilla. 1997. Neuron. 19:1319-1327) and the transfer of protons across an "H-X-X-X-H-X-X-X-H" motif lining a conducting pore.

Treatment of diabetic neuropathy with gamma-linolenic acid. The gamma-Linolenic Acid Multicenter Trial Group.

OBJECTIVE: To compare the effects of placebo and GLA on the course of mild diabetic neuropathy over 1 yr. RESEARCH DESIGN AND METHODS: We entered 111 patients with mild diabetic neuropathy from seven centers into a randomized, double-blind, placebo-controlled parallel study of GLA at a dose of 480 mg/day. MNCV, SNAP, CMAP, hot and cold thresholds, sensation, tendon reflexes, and muscle strength were assessed by standard tests in upper and lower limbs. RESULTS: For all 16 parameters, the change over 1 yr in response to GLA was more favorable than the change with placebo, and for 13 parameters, the difference was statistically significant. Sex, age, and type of diabetes did not influence the result, but treatment was more effective in relatively well-controlled than in poorly-controlled diabetic patients. CONCLUSIONS: GLA had a beneficial effect on the course of diabetic neuropathy.

Considerations on photochemical genotoxicity: report of the International Workshop on Genotoxicity Test Procedures Working Group.

Recent toxicological observations have caused concern regarding the need to test, for example, pharmaceuticals and cosmetic products for photochemical genotoxicity. The objective of this report is to give assistance on how to adapt existing test methods to investigate the potential of light-absorbing compounds to induce genotoxic effects on photoactivation. In general, the Organization for Economic Co-Operation & Economic Development (OECD) draft guideline on in vitro phototoxicity testing served as a basis for consideration. Concomitant exposure of the cells to the test compound and solar simulated light was considered appropriate as the initial, basic test condition. Optimization of the exposure scheme, e.g., a change of the irradiation spectrum, might be indicated depending on the initial test results. Selection of test compound concentrations should be based on results obtained with the dark version of the respective test system but might have to be modified if phototoxic effects are observed. Selection of the irradiation dose has to be performed individually for each test system based on dose-effect studies. The irradiation should induce per se a small, reproducible toxic or genotoxic effect. The report includes a specification of necessary controls, discusses factors that might have an impact on the irradiation characteristics, and gives a rationale for the omission of an external metabolic activation system. It also addresses the question that physicochemical and pharmacokinetic properties might trigger the need to test a chemical for photochemical genotoxicity. Relevant experimental observations are presented to back up the recommendations. The working group did not reach a consensus as to whether a single, adequately perfomed in vitro test for clastogenicity would be sufficient to exclude a photogenotoxic liability or whether a test battery including a gene mutation assay would be needed for product safety testing regarding photochemical genotoxicity.

Cerebral arterial spasm. Part 4: in vitro effects of temperature, serotonin analogues, large nonphysiological concentrations of serotonin, and extracellular calcium and magnesium on serotonin-induced contractions of the canine basilar artery.

In vitro experiments were performed using a small volume chamber to study serotonin-induced contractions of the canine basilar artery. Temperature was found to have a profound effect on the artery's response to serotonin. Raising the temperature to 40 degrees C (104 degrees F) increased the maximum response by 20% and lowering the temperature by 10 degrees C caused a 40% reduction in the maximum contraction. Cumulative log-dose response curves for analogues of serotonin demonstrated a high degree of specificity for the serotonin receptor and large nonphysiological concentrations of serotonin caused relaxation of the contracted artery. Extracellular calcium was shown to be an absolute requirement for serotonin-induced contractions. Extracellular magnesium, in contrast, was shown to inhibit serotonin-induced contractions.

In vitro potency assays for nonreplicating veterinary vaccines: comparison to in vivo assays and considerations in assay development.

Each finished batch or serial of veterinary vaccine must be potency tested to assure the quality of marketed product. The potency assay must be correlated to efficacy in the target species. Potency assays of nonreplicating vaccines have traditionally measured the immune response to the vaccine in host or laboratory animals by serology or protection from challenge. Such tests are expensive, time-consuming, and raise animal welfare concerns. As disease agent protective antigens are described, in vitro techniques for quantitating them can be applied to vaccine potency measurement. However, in many cases the immunological adjuvants critical to the efficacy of the biological interfere with in vitro antigen quantitation techniques. The development of techniques that remove or compensate for the effect of adjuvants on the assays, sham vaccines containing no antigen, reference preparations containing a proven protective immunogen dose, characterization of the immunological reactants, and appropriate design and data analysis have contributed to the development of rapid, reproducible, humane, and relatively inexpensive in vitro potency assays to be used in the evaluation of veterinary biologicals.

Aneuploidy: a report of an ECETOC task force.

Aneuploidy plays a significant role in adverse human health conditions including birth defects, pregnancy wastage and cancer. Although there is clear evidence of chemically induced aneuploidy in experimental systems, to date there are insufficient data to determine with certainty if chemically induced aneuploidy contributes to human disease. However, since there is no reason to assume that chemically induced aneuploidy will not occur in human beings, it is prudent to address the aneugenic potential of chemicals in the safety assessment process. A wide range of methods has been described for the detection of chemically induced aneuploidy including subcellular systems, tests with fungi, plants and Drosophila as well as in vitro mammalian systems and in vivo mammalian somatic and germ cell assays. However, none of these methods is sufficiently validated or widely used in routine screening. Underlying the efforts to develop aneuploidy-specific assays is the presumption that current genetic toxicology tests do not detected chemicals that have aneuploidy-inducing potential. To address this, we have critically evaluated data from standard genetic toxicology assays for 16 known or suspected aneugens. The conclusions from the review are listed below. 1. At present there are only nine chemicals that can be classified as definitive aneugens, as determined by positive results in in vivo rodent assays. 2. As expected, the majority of definitive and suspected aneugens are negative in the bacterial mutation assay. 3. The majority of definitive aneugens evaluated induce polyploidy in vitro. With few exception, they also induced structural chromosome aberrations in vitro. 4. All of the definitive aneugens that have been sufficiently tested induce micronuclei in rodent bone marrow cells in vivo. A number of these chemicals also induced structural chromosome aberrations in vivo. 5. There is no evidence for a unique germ cell aneugen, that is a chemical that induces aneuploidy in germ cells and not in somatic cells. Furthermore, an analysis of several databases indicates the proportion of chemicals which induce polyploidy and not chromosome aberrations in vitro is low. Based on these conclusions, the following recommendations are made: for screening purposes, a standard genotoxicity test battery (including an in vitro cytogenetic assay with an assessment of polyploidy and clastogenicity at the same harvest time) should be performed; in the absence of polyploidy induction in vitro no further evaluation of aneuploidy-inducing potential is needed; if polyploidy is observed, in vitro follow-up testing to investigate further the aneuploidy-inducing potential should be conducted; such follow-up testing will generally start with the conduct of a standard in vivo somatic cell micronucleus assay; if the in vivo somatic cell micronucleus assay is negative, with adequate evidence of exposure of the bone marrow to the test compound, no further testing of aneuploidy-inducing potential is needed; if the in vivo somatic cell micronucleus assay is positive, further information on mechanisms of micronucleus induction can be obtained by using kinetochore/centromeric staining in vitro and/or in vivo; an assessment of potential germ cell aneuploidy activity may then be considered; aneuploidy induction which does not involve the direct interaction of a chemical or its metabolite(s) with DNA is expected to have a threshold. This must be considered in the risk assessment of such chemicals; this is not addressed by current risk assessment guidelines.