Trematode parasites as indicators of an animal component in the diet of the Water Vole Arvicola amphibius.

The intestinal trematode fauna of the Water Vole Arvicola amphibius, (previously A. terrestris), was investigated to determine whether it might provide evidence of an animal component in the diet of this aquatic herbivorous small mammal. Interrogation of the electronic Host-Parasite Database of the Natural History Museum London revealed the presence of fourteen species of intestinal trematode in water voles, infection with each of which would require the ingestion of tissue from an animal intermediate host. The results obtained using these parasite indicators provide convincing evidence of animal components in the diet of A. amphibius and support anecdotal reports of water voles feeding on animal material in the field.

Chyle leak following an axillary sentinel lymph node biopsy for breast cancer in a patient with superior vena caval thrombosis - a case report and review of the literature.

Chyle leak is a very rare complication following an axillary lymph node dissection. We report a case of chyle leak following sentinel lymph node biopsy in a patient with breast cancer with superior vena caval thrombosis. To our knowledge, this is the first case report of chyle leakage following axillary sentinel lymph node biopsy. We describe the aetiology, prevention and treatment strategy that can be adopted in these patients.

Combinatorial Preconditioning of Rat Brain Cultures with Subprotective Ethanol and Resveratrol Concentrations Promotes Synergistic Neuroprotection.

Preconditioning brain cultures with moderate concentrations of ethanol (EtOH) or trans-resveratrol (RES), key red wine constituents, can prevent amyloid-ß (Aß) neurotoxicity. Past studies have indicated that moderate EtOH activates synaptic N-methyl-D-aspartate receptors (NMDAR) that, in part, signal via protein kinase C (PKC) to increase protective antioxidant proteins such as peroxiredoxin-2 (Prx2). RES preconditioning also is reported to involve NMDAR and PKC. However, although moderate, the EtOH and RES concentrations used have been noticeably above circulating levels from two glasses of wine, a daily intake linked to reduced risk of cognitive decline among older social drinkers. Given their mechanistic parallels, we speculated that subprotective EtOH and RES concentrations in a combinatorial preconditioning paradigm might elicit synergistic neuroprotection. To examine this notion, rat cerebellar cultures were pretreated with 10 mM EtOH (circulating concentration after ~ 2 drinks), 5 µM RES, EtOH + RES combinatorially, or media alone (controls). After 3 days, media were removed, and fresh media aliquots containing Aß25-35 (25 µM) were added. Assessing apoptosis 24 h later with Hoescht 33342, neurodegeneration did not differ from controls in cultures separately preconditioned with 10 mM EtOH or 5 µM RES. However, apoptosis was prevented in combinatorially preconditioned cultures. Also, immunoblotting revealed elevated Prx2 levels due to combinatorial pretreatment that correlated with subsequent neuroprotection, whereas Prx2 was unchanged in separately pretreated cultures. Although the protective mechanisms require clarification, synergistically upregulated NMDAR-PKC-Prx2 (and other antioxidant proteins) is a reasonable component. These findings imply that EtOH + RES antioxidant synergy could be involved in neurobenefits attributed to low-moderate wine consumption.

Trophodynamics of Protomyctophum (Myctophidae) in the Scotia Sea (Southern Ocean).

This study investigated spatial and temporal patterns in distribution, population structure and diet of Bolin's lanternfish Protomyctophum bolini, Tenison's lanternfish Protomyctophum tenisoni and gaptooth lanternfish Protomyctophum choriodon in the Scotia Sea using data collected by midwater trawl during spring, summer and autumn. Protomyctophum bolini was the most abundant species of the genus encountered throughout the Scotia Sea with the greatest concentrations occurring around the Antarctic Polar Front (APF). This species had a life cycle of 2+ years, but spatial differences in population structure were apparent as the I-group was absent from all regions south of the APF, suggesting that the species does not recruit in the Scotia Sea. Protomyctophum tenisoni occurred mostly in waters characteristic of the APF and was absent from the southern Scotia Sea. It had a limited size range, but there was clear size-related sexual dimorphism with males significantly larger than females. The species had a life cycle of c. 2 years, but the I-group (c. 1 year old, 1 November to 31 October the next year) occurred only in regions close to the APF suggesting that recruitment is restricted to these waters. A seasonal southward migration for P. choriodon is likely as the species occurred mostly to the south-west of South Georgia in summer, but extended to the sea-ice sectors in autumn. Protomyctophum choriodon had a life cycle of 4+ years in the Scotia Sea and the population was dominated by age classes >3 years old. Larval stages were absent during the surveys for all species. Diurnal variations in vertical distribution were apparent for all three species. Interspecific variations in diet were evident, but all species were primarily copepod feeders, with Metridia spp., Rhincalanus gigas and Calanus simillimus generally dominating their diet. Small euphausiids, principally Thysanoessa spp., were also an important component of their diets, particularly for P. choriodon which had the largest body size. The spatial and temporal variations in diet for both P. bolini and P. tenisoni were broadly consistent with underlying abundance patterns within the mesozooplankton community.

Does diisocyanate exposure result in neurotoxicity?

CONTEXT: Diisocyanates have been associated with respiratory and dermal sensitization. Limited number of case reports, and a few case studies, media, and other references suggest potential neurotoxic effects from exposures to toluene diisocyanate (TDI), 1,6 hexamethylene diisocyanate (HDI), and methylene diisocyanate (MDI). However, a systematic review of the literature evaluating the causal association on humans does not exist to support this alleged association. OBJECTIVE: To perform systematic review examining the body of epidemiologic evidence and provide assessment of causal association based on principles of the Sir Austin Bradford Hill criteria or considerations for causal analysis. METHODS: A comprehensive search of public databases for published abstracts, case reports, cross-sectional surveys, and cohort studies using key search terms was conducted. Additional searches included regulatory reviews, EU IUCLID and EU Risk Assessment databases, and unpublished reports in the International Isocyanate Institute database. An expert panel consisting of physicians, toxicologists, and an epidemiologist critically reviewed accepted papers, providing examination of epidemiologic evidence of each report. Finally, the Hill criteria for causation were applied to the summative analysis of identified reports to estimate probability of causal association. RESULTS: Twelve papers reporting exposed populations with a variety of neurological symptoms or findings suitable for analysis were identified, including eleven case or case series reports, and one cross-sectional study. Three papers reported on the same population. Each of the papers was limited by paucity of diisocyanate exposure estimates, the presence of confounding exposures to known or suspected neurotoxicants, a lack of objective biological measures of exposure or neurotoxic effects, and lack of relative strength of association measures. Additionally, reported health symptoms and syndromes lacked consistency or specificity. No plausible mechanism of toxicity was found. Application of a predictive mathematical model for determining probability of causal association for neurotoxicity was calculated to be 21%. CONCLUSION: There is insufficient evidence for a causal association of neurotoxic effects and diisocyanate exposure based on lack of evidence in all categories of the Hill criteria for causality except for temporal association of reported symptoms and alleged exposure. Future reports should attempt to address more rigorous exposure assessment and control for confounding exposures.

Jugular venous neurone specific enolase (NSE) increases following carotid endarterectomy under general, but not local, anaesthesia.

INTRODUCTION: Previous studies indicate that local (LA) rather than general anaesthesia (GA) for carotid endarterectomy (CEA) is associated with reflex hypertension and preservation of cerebral cytochrome oxidase after carotid clamping. The hypothesis that LA offers protection against ischaemic cerebral injury has been investigated by measuring ipsilateral jugular venous neurone specific enolase (NSE: neuronal glycolytic enzyme) and S-100B (glial cell protein) during and after CEA. METHODS: 27 patients with symptomatic carotid artery disease (70-99% stenosis) underwent CEA, 14 under LA and 13 under GA. Jugular venous blood samples were assayed for NSE and S-100B before carotid clamping and at 5min before and 5min, 2, 4, 6, 8, 12 and 24h after clamp release. RESULTS: No neurological complications occurred. S-100B levels were low and did not increase from baseline in either group. Pre-clamp NSE levels were similar in both groups (LA: 17.6 (15.2-20.7)microg/l, GA: 21.5 (11.3-26.2)microg/l; p=0.37) but increased significantly 2h after clamp release in GA patients (LA: 25.5 (16.6-27.8)microg/l, GA: 48.2 (31.4-61.3)microg/l, p=0.05) with a significant rise from baseline in GA patients (p=0.04). CONCLUSIONS: CEA performed under GA is associated with greater rises in jugular venous NSE, and hence cerebral injury, than CEA performed under LA.

Long-term changes in deep-water fish populations in the northeast Atlantic: a deeper reaching effect of fisheries?

A severe scarcity of life history and population data for deep-water fishes is a major impediment to successful fisheries management. Long-term data for non-target species and those living deeper than the fishing grounds are particularly rare. We analysed a unique dataset of scientific trawls made from 1977 to 1989 and from 1997 to 2002, at depths from 800 to 4800 m. Over this time, overall fish abundance fell significantly at all depths from 800 to 2500 m, considerably deeper than the maximum depth of commercial fishing (approx. 1600 m). Changes in abundance were significantly larger in species whose ranges fell at least partly within fished depths and did not appear to be consistent with any natural factors such as changes in fluxes from the surface or the abundance of potential prey. If the observed decreases in abundance are due to fishing, then its effects now extend into the lower bathyal zone, resulting in declines in areas that have been previously thought to be unaffected. A possible mechanism is impacts on the shallow parts of the ranges of fish species, resulting in declines in abundance in the lower parts of their ranges. This unexpected phenomenon has important consequences for fisheries and marine reserve management, as this would indicate that the impacts of fisheries can be transmitted into deep offshore areas that are neither routinely monitored nor considered as part of the managed fishery areas.

Effects of different feed additives alone or in combination on broiler performance, gut microflora and ileal histology.

1. The objectives of this experiment were to investigate the effects of different xylanases, alone or in combination with different organic acid and oligosaccharide sources, on bird performance, gut microflora and ileal histology. 2. Birds were given a diet based on a commercial formulation, which was split into 8 batches. Batch 1 contained the antibiotic growth promoter Avilamycin and acted as the positive control. To batch 2 the enzyme Allzyme PT was added and to batch 3 Allzyme PT was added with the organic acid and oligosaccharide mixture Avimos. To batch 4, Allzyme PT was added with the oligosaccharide mixture Biomos. To batch 5, yeast extract 2012 was added with the organic acid mixture Gustor and the enzyme xylanase XP20. To batch 6, yeast extract 2012 and feed acidifier Gustor were added as before, with the enzyme Avizyme 1300. Batches 7 and 8 both acted as negative experimental controls, with no added growth promoters. 3. A total of 64 birds were housed in individual wire cages in each of three consecutive experimental replicates (24 birds/treatment). Birds were fed ad libitum from 7 to 28 d and a 7-d excreta collection was carried out to determine apparent metabolisable energy (AME) content. 4. At 28 d, the birds were killed and viscosity of jejunal digesta supernatant and gizzard weight were determined. Samples were taken from the crop, ileum and caecum and analysed for viable presumptive lactic acid bacteria and coliforms. The overall microbial flora was determined using denaturing gradient gel electrophoresis of 16S ribosomal DNA followed by DNA sequence analysis in order to assign amplicons to a bacterial species. Ileal sections were also collected for histological analysis. 5. Total live weight gain (12%) and gain:feed (9%) were significantly improved for all diets containing additives, compared to the negative control diets. All diets containing xylanases gave significantly lower in vivo viscosity values than the positive and negative controls. Diet treatment significantly affected viable coliform numbers in the ileum and also viable lactobacilli in the ileum and caecum. A substantial proportion of the bacteria present in the GI tract (40%) belong to unknown species. No effects of diet treatment on histological measurements were observed in this study. 6. All the additive combinations studied were at least as effective as the antibiotic growth promoter and the results for Allzyme PT suggest that xylanase alone is as effective as any of the combinations studied.

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web.

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell-Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño-Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts.

Tamoxifen effect on L-DOPA induced response complications in parkinsonian rats and primates.

The contribution of striatal protein kinase C (PKC) isoform changes in levodopa (L-DOPA) induced motor response complications in parkinsonian rats was investigated and the ability of tamoxifen, an antiestrogen with a partial PKC antagonist property, to prevent these response alterations in 6-hydroxydopamine (6-OHDA) lesioned rats as well as in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treated cynomologous monkeys was studied. Following treatment of adult male rats with L-DOPA twice daily for 3 weeks, protein levels of left (lesioned) and right (intact) striatal PKC isoforms were measured. Western blot analysis showed increased protein expression of both the novel PKC epsilon isoform and the atypical PKC lambda isoform ipsilateral to the lesion (174+/-17% for epsilon, 140+/-9% for lambda, of intact striatum in 6-OHDA lesioned plus chronic L-DOPA treated animals) in acute L-DOPA treated rats. No enhancement was observed in PKC immunoreactivity for other isoforms. Tamoxifen (5.0 mg/kg p.o.) significantly attenuated the L-DOPA induced augmentation of protein expression of PKC epsilon and PKC lambda, but had no effect on immunoreactivity for other PKC isoforms. In chronic L-DOPA treated parkinsonian rats, tamoxifen prevented (5.0 mg/kg p.o.) as well as ameliorated (5.0 mg/kg p.o.) the characteristic shortening in duration of motor response to L-DOPA challenge. In MPTP lesioned primates, similar to the ameliorative effect seen in rats, tamoxifen (1 and 3 mg/kg p.o) reduced the appearance of L-DOPA induced dyskinesia by 61% and 55% respectively (p<0.05). These results suggest that changes in specific striatal PKC isoforms contribute to the pathogenesis of L-DOPA induced motor complications and further that drugs able to selectively inhibit these signaling kinases might provide adjunctive benefit in the treatment of Parkinson's disease.

Combined blockade of AMPA and NMDA glutamate receptors reduces levodopa-induced motor complications in animal models of PD.

AMPA and NMDA receptors, abundantly expressed on striatal medium spiny neurons, have been implicated in the regulation of corticostriatal synaptic efficacy. To evaluate the contribution of both glutamate receptor types to the pathogenesis of motor response alterations associated with dopaminergic treatment, we studied the ability of the selective AMPA receptor antagonist GYKI-47261 and the selective NMDA receptor antagonists, MK-801 and amantadine, to mitigate these syndromes in rodent and primate models of Parkinson's disease. The effects of GYKI-47261 and amantadine (or MK-801), alone and in combination, were compared for their ability to modify dyskinesias induced by levodopa. In rats, simultaneous administration of subthreshold doses of AMPA and NMDA receptor antagonists completely normalized the wearing-off response to acute levodopa challenge produced by chronic levodopa treatment (P < 0.05). In primates, the glutamate antagonists GYKI-47261 and amantadine, co-administered at low doses (failing to alter dyskinesia scores), reduced levodopa-induced dyskinesias by 51% (P < 0.05). The simultaneous AMPA and NMDA receptor blockade acts to provide a substantially greater reduction in the response alterations induced by levodopa than inhibition of either of these receptors alone. The results suggest that mechanisms mediated by both ionotropic glutamate receptors make an independent contribution to the pathogenesis of these motor response changes and further that a combination of both drug types may provide relief from these disabling complications at lower and thus safer and more tolerable doses than required when either drug is used alone.

Trends in body size across an environmental gradient: a differential response in scavenging and non-scavenging demersal deep-sea fish.

Body size trends across environmental gradients are widely reported but poorly understood. Here, we investigate contrasting relationships between size (body mass) and depth in the scavenging and predatory demersal ichthyofauna (800-4800 m) of the North-east Atlantic. The mean size of scavenging fish, identified as those regularly attracted to baited cameras, increased significantly with depth, while in non-scavengers there was a significant decline in size. The increase in scavenger size is a consequence of both intra and inter-specific effects. The observation of opposing relationships, in different functional groups, across the same environmental gradient indicates ecological rather than physiological causes. Simple energetic models indicate that the dissimilarity can be explained by different patterns of food distribution. While food availability declines with depth for both groups, the food is likely to be in large, randomly distributed packages for scavengers and as smaller but more evenly distributed items for predators. Larger size in scavengers permits higher swimming speeds, greater endurance as a consequence of larger energy reserves and lower mass specific metabolic rate, factors that are critical to survival on sporadic food items.

Application of the modified Shepard interpolation method to the determination of the potential energy surface for a molecule-surface reaction: H2 + Pt(111).

We have used a modified Shepard (MS) interpolation method, initially developed for gas phase reactions, to build a potential energy surface (PES) for studying the dissociative chemisorption of H2 on Pt(111). The aim was to study the efficiency and the accuracy of this interpolation method for an activated multidimensional molecule-surface reactive problem. The strategy used is based on previous applications of the MS method to gas phase reactions, but modified to take into account special features of molecule-surface reactions, like the presence of many similar reaction pathways which vary only slightly with surface site. The efficiency of the interpolation method was tested by using an already existing PES to provide the input data required for the construction of the new PES. The construction of the new PES required half as many ab initio data points as the construction of the old PES, and the comparison of the two PESs shows that the method is able to reproduce with good accuracy the most important features of the H2 + Pt(111) interaction potential. Finally, accuracy tests were done by comparing the results of dynamics simulations using the two different PESs. The good agreement obtained for reaction probabilities and probabilities for rotationally and diffractionally inelastic scattering shows clearly that the MS interpolation method can be used efficiently to yield accurate PESs for activated molecule-surface reactions.

Completed sequence of plasmid pIP501 and origin of spontaneous deletion derivatives.

The sequence of plasmid pIP501 (30,603 bp) was completed using previously published and newly acquired data. The sites at which two spontaneous deletions had occurred were identified. One was between tracts of repeated heptamers and the other between regions of secondary structure associated with plasmid replication. A high level of identity ( >95%) between plasmid pIP501 and part of plasmid pRE25, which had been isolated from Enterococcus faecalis associated with a food source, was confirmed.

Cross section for the H+H2O abstraction reaction: experiment and theory.

The absolute value of the cross section for the abstraction reaction between fast H atoms and H2O has been determined experimentally at a mean collision energy of 2.46 eV. The OH population distribution at the same mean energy has also been determined. The new measurements are compared with state-of-the-art quantum mechanical and quasiclassical scattering calculations on the most recently developed potential energy surface.

Human immunodeficiency virus type 1 gp120 and ethanol coexposure in rat organotypic brain slice cultures: Curtailment of gp120-induced neurotoxicity and neurotoxic mediators by moderate but not high ethanol concentrations.

Human immunodeficiency virus type 1 (HIV-1) envelope protein gp120, implicated with other retroviral proteins in acquired immunodeficiency syndrome (AIDS)-related dementia, causes neuronal degeneration by inciting cascades of neurotoxic mediators from glia. It also may facilitate neuronal glutamate (N-methyl-D-aspartate, NMDA) receptor-mediated excitotoxicity by interacting at the glycine coagonist site. The authors reported that preconditioning rat organotypic hippocampal-cortical slice cultures subchronically with ethanol at concentrations occurring during moderate drinking (20 to 30 mM) prevented gp120's induction of neurotoxic mediators and intracellular calcium, as well as neuronal death. The authors now find that the acute copresence of ethanol in moderate as opposed to high concentrations similarly blocks the retroviral protein's neurotoxic effects in brain slice cultures, assessed with lactate dehydrogenase (LDH) release and propidium iodide (PI) labeling. As with ethanol preconditioning, neuroprotection against gp120 by moderate ethanol coexposure appears secondary to abrogation of the retroviral protein's early induction of arachidonic acid (AA), glutamate, and superoxide (but not nitric oxide) elevations/release. Additionally, experiments indicate that 30 mM ethanol is sufficient to inhibit the NMDA receptor, particularly in the presence of added glycine, thus hindering potential direct neuronal stimulation by gp120. However, in contrast to moderate ethanol, 100 mM ethanol, a concentration tolerated only in chronic alcoholics, potentiates gp120-dependent neurotoxicity (PI labeling) in the hippocampal CA1 region, augments LDH release, and fails to curtail gp120's actions on AA, glutamate, and superoxide-but does suppress nitric oxide induction. The results indicate dominant roles for AA, superoxide, and glutamate-mediated oxidative stress in gp120's neurotoxic mechanism, but perhaps a less important role for NMDA receptor stimulation, which would be constrained at both ethanol concentrations employed. We suggest that ethanol's concentration-dependent, two-edged sword behavior could alter the development of dementia in HIV-1-infected individuals during social consumption or abuse. Further studies are needed to elucidate the differing apparently glial effects of the two concentrations of ethanol.

DNA cloning in Lactobacillus helveticus by the exconjugation of recombinant mob-containing plasmid constructs from strains of transformable lactic acid bacteria.

A system developed for the genetic transfer of plasmids between strains of nontransformable bacteria (P. Langella, Y. le Loir, S. D. Ehrlich and A. Gruss, 1993, J. Bacteriol., 175, 5806-5813) by the specific inclusion of a mobilization (mob) region into a nonconjugative shuttle vector was used successfully to deliver the genetic determinants for beta-glucanase, beta-glucuronidase, and green fluorescent protein to Lactobacillus helveticus. Expression of two of the genes could be detected in the new host. Data suggested that resolution of cointegrates into components could release the original recombinant plasmid or generate a cointegrate deletion. All the recombinant plasmids were segregationally unstable in Lb. helveticus and there was some evidence for structural instability. Intrinsic instability in the mob-containing vector was reduced by replacing the duplicated pBluescript polylinker with that from pUC19. Sites at which cointegrate formation could occur were localized at two distinct tracts close to the D-loop that forms at the primosome during plasmid replication.

Effect of race and resistance training status on the density of fat-free mass and percent fat estimates.

The impact of race and resistance training status on the assumed density of the fat-free mass (D(FFM)) and estimates of body fatness via hydrodensitometry (%Fat(D)) vs. a four-component model (density, water, mineral; %Fat(D,W,M)) were determined in 45 men: white controls (W; n = 15), black controls (B; n = 15), and resistance-trained blacks (B-RT; n = 15). Body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by dual-energy X-ray absorptiometry were used to estimate %Fat(D,W,M). D(FFM) was not different between B and W (or 1.1 g/ml); however, D(FFM) in B-RT was significantly lower (1.091 +/- 0.012 g/ml; P < 0.05). Therefore, %Fat(D) using the Siri equation was not different from %Fat(D,W,M) in W (17.5 +/- 5.0 vs. 18.3 +/- 5.4%) or B (14.9 +/- 5.6 vs. 15.7 +/- 5.7%) but significantly overestimated %Fat(D,W,M) in B-RT (14.0 +/- 5.9 vs. 10.4 +/- 6.0%; P < 0.05). The use of a race-specific equation (assuming D(FFM) = 1.113 g/ml) did not improve the agreement between %Fat(D) and %Fat(D,W,M), resulting in a significantly greater mean (+/-SD) discrepancy for B (1.7 +/- 1.8% fat) and B-RT (6.2 +/- 4.3% fat). Thus race per se does not affect D(FFM) or estimates of %Fat(D); however, B-RT have a D(FFM) lower than 1.1 g/ml, leading to an overestimation of %Fat(D).

Use of air displacement plethysmography for estimating body fat in a four-component model.

PURPOSE: To compare measurements of body density (D(b)) obtained from air displacement plethysmography (AP) and hydrostatic weighing (HW) and to determine the accuracy of substituting D(b) via AP (D(b)-AP) for D(b) via HW (D(b)-HW) in estimating body fatness (%Fat(4C)) and the composition and density of the fat-free mass (Dffm) from a four-component model (fat, mineral, water, and protein). METHODS: D(b) was measured in 50 young adults using AP and HW. Total body water via deuterium dilution, bone mineral content via dual-energy x-ray absorptiometry, and D(b) were used to estimate %Fat(4C). RESULTS: D(b)-AP and D(b)-HW were highly correlated (r = 0.89, SEE = 0.008 g x mL(-1)), but D(b)-AP (1.065 +/- 0.003 g x mL(-1)) was significantly higher (P < 0.05) than D(b)-HW (1.058 +/- 0.003 g x mL(-1)), resulting in a mean difference of 2.8%fat. Differences between %Fat(4C-AP) (17.8 +/- 1.2%) and %Fat(4C-HW) (19.3 +/- 1.2%) were significant (P < 0.05), but the SD of the differences (2.3%) was low. When D(b)-AP was used in a four-component model in place of D(b)-HW, the calculated Dffm was significantly higher (1.109 +/- 0.002 vs 1.105 +/- 0.002 g x mL(-1)) based on a higher (P < 0.05) protein fraction (22.0 +/- 0.4% vs 20.6 +/- 0.4%) and lower (P < 0.05) water (71.1 +/- 0.4% vs 72.4 +/- 0.4%) and mineral fractions (7.0 +/- 0.1% vs 7.1 +/- 0.1%). CONCLUSIONS: AP yields a higher D(b) than HW and may not be a valid method for measuring D(b) or estimating %fat using densitometry. However, due to relatively small bias and low individual error, D(b)-AP is an acceptable substitute for D(b)-HW when estimating %fat with a four-component model in young adults.