Geographically diverse canid sampling provides novel insights into pre-industrial microbiomes.

Canine microbiome studies are often limited in the geographic and temporal scope of samples studied. This results in a paucity of data on the canine microbiome around the world, especially in contexts where dogs may not be pets or human associated. Here, we present the shotgun sequences of fecal microbiomes of pet dogs from South Africa, shelter and stray dogs from India, and stray village dogs in Laos. We additionally performed a dietary experiment with dogs housed in a veterinary medical school, attempting to replicate the diet of the sampled dogs from Laos. We analyse the taxonomic diversity in these populations and identify the underlying functional redundancy of these microbiomes. Our results show that diet alone is not sufficient to recapitulate the higher diversity seen in the microbiome of dogs from Laos. Comparisons to previous studies and ancient dog fecal microbiomes highlight the need for greater population diversity in studies of canine microbiomes, as modern analogues can provide better comparisons to ancient microbiomes. We identify trends in microbial diversity and industrialization in dogs that mirror results of human studies, suggesting future research can make use of these companion animals as substitutes for humans in studying the effects of industrialization on the microbiome.

The effect of dietary sodium octanoate on Ghrelin concentration and feed intake in chickens and turkeys: a comparative study.

Active ghrelin (AG) is produced through the post-translational addition of n-octanoic acid to the amino residue Ser-3, making it the natural ligand for the ghrelin receptor. The synthesis of AG is contingent upon specific dietary fatty acids as substrates for the acylation process. Prior studies have demonstrated that AG infusion can lead to reduced feed intake (FI) in broiler chickens, suggesting that manipulating AG may serve as an alternative to quantitative feed restriction in broiler breeders. In this study, we evaluated the effect of dietary sodium octanoate (Octanoate) on FI, water intake (WI), BW, total ghrelin, and ß-hydroxybutyrate (BHB) concentration in two avian species. Broiler chickens and turkeys were reared as recommended by the industry. At 3 wk of age, birds were randomly assigned to a 2 × 3 factorial. The first factor included two species (chickens and turkeys), and the second included doses (0, 4, and 8 mg/mL) of Octanoate in drinking water for 30 d. Feed and WI were recorded daily, while body weight and blood samples were obtained weekly. In chickens, Octanoate doses increased ghrelin and BHB concentrations linearly, while FI and BW decreased linearly with rising Octanoate doses (P < 0.05). However, Octanoate doses did not affect ghrelin, BHB, FI, or BW in turkeys. In conclusion, our data indicate that sodium octanoate administration elicits a differential response in feed intake and body weight gain in chickens and turkeys.

Bisphosphonates as a supplement to exercise to protect bone during long-duration spaceflight.

UNLABELLED: We report the results of alendronate ingestion plus exercise in preventing the declines in bone mass and strength and elevated levels of urinary calcium and bone resorption in astronauts during 5.5 months of spaceflight. INTRODUCTION: This investigation was an international collaboration between NASA and the JAXA space agencies to investigate the potential value of antiresorptive agents to mitigate the well-established bone changes associated with long-duration spaceflight. METHODS: We report the results from seven International Space Station (ISS) astronauts who spent a mean of 5.5 months on the ISS and who took an oral dose of 70 mg of alendronate weekly starting 3 weeks before flight and continuing throughout the mission. All crewmembers had available for exercise a treadmill, cycle ergometer, and a resistance exercise device. Our assessment included densitometry of multiple bone regions using X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) and assays of biomarkers of bone metabolism. RESULTS: In addition to pre- and post-flight measurements, we compared our results to 18 astronauts who flew ISS missions and who exercised using an early model resistance exercise device, called the interim resistance exercise device, and to 11 ISS astronauts who exercised using the newer advanced resistance exercise device (ARED). Our findings indicate that the ARED provided significant attenuation of bone loss compared with the older device although post-flight decreases in the femur neck and hip remained. The combination of the ARED and bisphosphonate attenuated the expected decline in essentially all indices of altered bone physiology during spaceflight including: DXA-determined losses in bone mineral density of the spine, hip, and pelvis, QCT-determined compartmental losses in trabecular and cortical bone mass in the hip, calculated measures of fall and stance computed bone strength of the hip, elevated levels of bone resorption markers, and urinary excretion of calcium. CONCLUSIONS: The combination of exercise plus an antiresoptive drug may be useful for protecting bone health during long-duration spaceflight.

Effects of artificial gravity during bed rest on bone metabolism in humans.

We report results from a study designed to explore the utility of artificial gravity (AG) as a countermeasure to bone loss induced by microgravity simulation. After baseline testing, 15 male subjects underwent 21 days of 6 degrees head-down bed rest to simulate the deconditioning associated with spaceflight. Eight of the subjects underwent 1 h of centrifugation (AG; 1 G(z) at the heart, 2.5 G(z) at the feet) each day for 21 days, whereas seven of the subjects served as untreated controls (Con). Blood and urine were collected before, during, and after bed rest for bone marker determinations. Bone mineral density (BMD) and bone mineral content (BMC) were determined by dual-energy X-ray absorptiometry and peripheral quantitative computerized tomography before and after bed rest. Urinary excretion of bone resorption markers increased during bed rest, but the AG and Con groups did not differ significantly. The same was true for serum C-telopeptide. During bed rest, bone alkaline phosphatase (ALP) and total ALP tended to be lower in the AG group (P = 0.08, P = 0.09). Neither BMC nor BMD changed significantly from the pre-bed rest period in AG or Con groups, and the two groups were not significantly different. However, when AG and Con data were combined, there was a significant (P < 0.05) effect of time for whole body total BMC and total hip and trochanter BMD. These data failed to demonstrate efficacy of this AG prescription to prevent the changes in bone metabolism observed during 3 wk of bed rest.

Resistive exercise in astronauts on prolonged spaceflights provides partial protection against spaceflight-induced bone loss.

Bone loss in astronauts during spaceflight may be a risk factor for osteoporosis, fractures and renal stone formation. We previously reported that the bisphosphonate alendronate, combined with exercise that included an Advanced Resistive Exercise Device (ARED), can prevent or attenuate group mean declines in areal bone mineral density (aBMD) measured soon after ~ 6-month spaceflights aboard the International Space Station (ISS). It is unclear however if the beneficial effects on postflight aBMD were due to individual or combined effects of alendronate and ARED. Hence, 10 additional ISS astronauts were recruited who used the ARED (ARED group) without drug administration using similar measurements in the previous study, i.e., densitometry, biochemical assays and analysis of finite element (FE) models. In addition densitometry data (DXA and QCT only) were compared to published data from crewmembers (n = 14-18) flown prior to in-flight access to the ARED (Pre-ARED). Group mean changes from preflight (± SD %) were used to evaluate effects of countermeasures as sequentially modified on the ISS (i.e., Pre-ARED vs. ARED; ARED vs. Bis+ARED). Spaceflight durations were not significantly different between groups. Postflight bone density measurements were significantly reduced from preflight in the Pre-ARED group. As previously reported, combined Bis+ARED prevented declines in all DXA and QCT hip densitometry and in estimates of FE hip strengths; increased the aBMD of lumbar spine; and prevented elevations in urinary markers for bone resorption during spaceflight. ARED without alendronate partially attenuated declines in bone mass but did not suppress biomarkers for bone resorption or prevent trabecular bone loss. Resistive exercise in the ARED group did not prevent declines in hip trabecular vBMD, but prevented reductions in cortical vBMD of the femoral neck, in FE estimate of hip strength for non-linear stance (NLS) and in aBMD of the femoral neck. We conclude that a bisphosphonate, when combined with resistive exercise, enhances the preservation of bone mass because of the added suppression of bone resorption in trabecular bone compartment not evident with ARED alone.

Recovery of spaceflight-induced bone loss: bone mineral density after long-duration missions as fitted with an exponential function.

The loss of bone mineral in NASA astronauts during spaceflight has been investigated throughout the more than 40 years of space travel. Consequently, it is a medical requirement at NASA Johnson Space Center (JSC) that changes in bone mass be monitored in crew members by measuring bone mineral density (BMD), with dual-energy X-ray absorptiometry (DXA) before and after flight, of astronauts who serve on long-duration missions (4-6 months). We evaluated this repository of medical data to track whether there is recovery of bone mineral that was lost during spaceflight. Our analysis was supplemented by BMD data from cosmonauts (by convention, a space traveler formally employed by the Russia Aviation and Space Agency or by the previous Soviet Union) who had also flown on long-duration missions. Data from a total of 45 individual crew members - a small number of whom flew on more than one mission - were used in this analysis. Changes in BMD (between 56 different sets of pre- and postflight measurements) were plotted as a function of time (days after landing). Plotted BMD changes were fitted to an exponential mathematical function that estimated: (i) BMD change on landing day (day 0) and (ii) the number of days after landing when 50% of the lost bone would be recovered ("50% recovery time") in the lumbar spine, trochanter, pelvis, femoral neck and calcaneus. In sum, averaged losses of bone mineral after long-duration spaceflight ranged between 2% and 9% across all sites with our recovery model predicting a 50% restoration of bone loss for all sites to be within 9 months.

Flax seed oil and flax seed meal reduce the formation of aberrant crypt foci (ACF) in azoxymethane-induced colon cancer in Fisher 344 male rats.

Flax seed oil and flax seed meal are good sources of omega-3 fatty acids. The objective of this study was to explicate the effects of feeding flax seed oil and flax seed meal on AOM-induced aberrant crypt foci (ACF) in Fisher 344 male rats. Following an acclimatization period, rats were divided into six groups and fed AIN 93G diet Control (C), C+7 and 14% soybean oil (SBO), C+7 and 14% flax seed oil (FSO) and C+10 and 20% flax seed meal (FSM). All rats received 16 mg/kg body weight of AOM at 7 and 8 weeks of age. The rats were euthanized with CO2 at 17 weeks of age. FSM and FSO reduced the incidence of ACF which are putative precursor lesions in the development of colon cancer in the distal colon by 88% and 77%, in the proximal colon by 86% and 87% with a total reduction of 87.5% and 84%, respectively. Glutathione-S-transferase (GST) activities were significantly (P<0.05) higher in rats fed C+7 and 14% FSO and C+10 and 20% FSM, as compared to rats fed C+SBO diets. Results of this study showed that FSO and FSM reduced the incidence of AOM-induced ACF formation and may therefore be effective chemopreventive agents.

Selected fruits reduce azoxymethane (AOM)-induced aberrant crypt foci (ACF) in Fisher 344 male rats.

Phytochemicals contribute to the vibrant colors of fruits and it is suggested that the darker the fruit the higher the antioxidative or anticarcinogenic properties. In this study we investigated the possible effects of blueberries (BLU), blackberries (BLK), plums (PLM), mangoes (MAN), pomegranate juice (POJ), watermelon juice (WMJ) and cranberry juice (CBJ) on azoxymethane (AOM)-induced aberrant crypt foci (ACF) in Fisher 344 male rats. Forty-eight male Fisher 344 rats were randomly assigned to eight groups (n=6). The groups were fed AIN-93G as a control (C) diet, the rats fed fruits received AIN-93G+5% fruits and the groups that were given fruits juices received 20% fruit juice instead of water. The rats received subcutaneous injections of AOM at 16 mg/kg body weight at seventh and eighth weeks of age. At 17th week of age, the rats were killed by CO(2) asphyxiation. Total ACF numbers (mean+/-SEM) in the rats fed CON, BLU, BLK, PLM, MNG, POJ, WMJ and CBJ were 171.67+/-5.6, 11.33+/-2.85, 24.0+/-0.58, 33.67+/-0.89, 28.67+/-1.33, 15.67+/-1.86, 24.33+/-3.92 and 39.0+/-15.31. Total glutathione-S-transferase (GST) activity (mICROmol/mg) in the liver of the rats fed fruits (except BLK) and fruit juices were significantly (p<0.05) higher in the rats fed fruits and fruit juices compared with the control. Our findings suggest that among the fruits and fruit juices, BLU and POJ contributed to significant (P<0.05) reductions in the formation of AOM-induced ACF.

Red palm oil suppresses the formation of azoxymethane (AOM) induced aberrant crypt foci (ACF) in Fisher 344 male rats.

Red palm oil (RPO) contains significant levels of carotenoids and Vitamin E. In this experiment we compared the inhibitory effects of RPO (7% and 14% levels) and soybean oil (7% and 14%) on azoxymethane (AOM) induced aberrant crypt foci (ACF). Thirty-two male Fisher 344 rats were randomly assigned to four groups. Two groups received AIN-93 G control (C) diet containing 7% and 14% soybean oil (SBO), respectively. Groups 3 and 4 received a treatment diet consisting of 7% and 14% RPO, respectively. The rats received subcutaneous injections of AOM at 16 mg/kg body weight at 7 and 8 weeks of age. At 17 weeks of age rats were killed by CO(2) asphyxiation. Numbers of ACF (mean+/-SE) in the proximal and distal colon were: 39.9 +/- 0.9, 53.8 +/- 2.8, 26.0 +/- 3.0, 27.5 +/- 1.5 and 118.2 +/- 1.7, 125.6 +/- 3.2, 41 +/- 7, 52.3 +/- 1.8 in rats fed 7% SBO, 14% SBO, 7% RPO and 14% RPO, respectively. The results of this study showed that RPO reduced the incidence of AOM induced ACF and may therefore have a beneficial effect in reducing the incidence of colon cancer.

Future human bone research in space.

Skylab crewmembers demonstrated negative calcium (Ca) balance reaching about -300 mg/day by flight day 84. Limited bone density (BMD) measurements documented that bone was not lost equally from all parts of the skeleton. Subsequent BMD studies during long duration Russian flights documented the regional extent of bone loss. These studies demonstrated mean losses in the spine, femur neck, trochanter, and pelvis of about 1%-1.6% with large differences between individuals as well as between bone sites in a given individual. Limited available data indicate postflight bone recovery occurred in some individuals, but may require several years for complete restoration. Long duration bedrest studies showed a similar pattern of bone loss and calcium balance (-180 mg/day) as spaceflight. During long duration bedrest, resorption markers were elevated, formation markers were unchanged, 1,25 vitamin D (VitD) and calcium absorption were decreased, and serum ionized Ca was increased. Although this information is a good beginning, additional spaceflight research is needed to assess architectural and subregional bone changes, elucidate mechanisms, and develop efficient as well as effective countermeasures. Space research poses a number of unique problems not encountered in ground-based laboratory research. Therefore, researchers contemplating human spaceflight research need to consider a number of unique problems related to spaceflight in their experimental design.

Resistance exercise as a countermeasure to disuse-induced bone loss.

During spaceflight, skeletal unloading results in loss of bone mineral density (BMD). This occurs primarily in the spine and lower body regions. This loss of skeletal mass could prove hazardous to astronauts on flights of long duration. In this study, intense resistance exercise was used to test whether a training regimen would prevent the loss of BMD that accompanies disuse. Nine subjects (5 men, 4 women) participated in a supine maximal resistance exercise training program during 17 wk of horizontal bed rest. These subjects were compared with 18 control subjects (13 men, 5 women) who followed the same bed rest protocol without exercise. Determination of treatment effect was based on measures of BMD, bone metabolism markers, and calcium balance obtained before, during, and after bed rest. Exercisers and controls had significantly (P < 0.05) different means, represented by the respective following percent changes: lumbar spine BMD, +3% vs. -1%; total hip BMD, +1% vs. -3%; calcaneus BMD, +1% vs. -9%; pelvis BMD, -0.5% vs. -3%; total body BMD, 0% vs. -1%; bone-specific alkaline phosphatase, +64% vs. 0%; alkaline phosphatase, +31% vs. +5%; osteocalcin, +43% vs. +10%; 1,25 dihydroxyvitamin D, +12% vs. -15%; parathyroid hormone intact molecule, +18% vs. -25%; and serum and ionized calcium, -1% vs. +1%. The difference in net calcium balance was also significant (+21 mg/day vs. -199 mg/day, exercise vs. control). The gastrocnemius and soleus muscle volumes decreased significantly in the exercise group, but the loss was significantly less than observed in the control group. The results indicate that resistance exercise had a positive treatment effect and thus might be useful as a countermeasure to prevent the deleterious skeletal changes associated with long-duration spaceflight.

Muscle volume, MRI relaxation times (T2), and body composition after spaceflight.

Postflight changes in muscle volume, calf muscle transverse relaxation time, and total body composition were measured in 4 crewmembers after a 17-day mission and in 14-16 crewmembers in multiple shuttle/Mir missions of 16- to 28-wk duration. During the 17-day mission, all muscle regions except the hamstrings significantly decreased 3-10% compared with baseline. During the shuttle/Mir missions, there were significant decreases in muscle volume (5-17%) in all muscle groups except the neck. These changes, which reached a new steady state by 4 mo of flight or less, were reversed within 30-60 days after landing. Postflight swelling and elevation of calf muscle transverse relaxation time persisted for several weeks after flight, which suggests possible muscle damage. In contrast to the 17-day flight, in which loss in fat, but not lean body mass, was found (25), losses in bone mineral content and lean body mass, but not fat, were seen after the longer shuttle/Mir missions. The percent losses in total body lean body mass and bone mineral content were similar at approximately 3.4-3.5%, whereas the pelvis demonstrated the largest regional bone loss at 13%.

Invited review: gender issues related to spaceflight: a NASA perspective.

This minireview provides an overview of known and potential gender differences in physiological responses to spaceflight. The paper covers cardiovascular and exercise physiology, barophysiology and decompression sickness, renal stone risk, immunology, neurovestibular and sensorimotor function, nutrition, pharmacotherapeutics, and reproduction. Potential health and functional impacts associated with the various physiological changes during spaceflight are discussed, and areas needing additional research are highlighted. Historically, studies of physiological responses to microgravity have not been aimed at examining gender-specific differences in the astronaut population. Insufficient data exist in most of the discipline areas at this time to draw valid conclusions about gender-specific differences in astronauts, in part due to the small ratio of women to men. The only astronaut health issue for which a large enough data set exists to allow valid conclusions to be drawn about gender differences is orthostatic intolerance following shuttle missions, in which women have a significantly higher incidence of presyncope during stand tests than do men. The most common observation across disciplines is that individual differences in physiological responses within genders are usually as large as, or larger than, differences between genders. Individual characteristics usually outweigh gender differences per se.

Otological and habilitative management of children with Down syndrome.

It has been well-established that children with Down syndrome experience a high incidence of persistent conductive hearing loss because of their predisposition to stenosis of the external auditory canal (EAC), cerumen impaction, serous otitis media (SOM), and cholesteatoma. Because this hearing problem may be a primary cause of the spoken communication skills in these children being far below their cognitive ability, assertive management is required. The authors present an aggressive multi-discipline treatment model that is instituted during the first year of life in an infant with Down syndrome. Reconstruction of the EAC, amplification technology, and speech/language intervention that emphasizes auditory-verbal (A/V) therapy are discussed. In a pilot study, we compared the language development of six infants with Down syndrome who received aggressive treatment during their first year of life (group A) to six infants who did not (group B). The results showed age-appropriate oral language development for the infants in group A.

Bone mineral and lean tissue loss after long duration space flight.

The loss of bone and muscle is a major concern for long duration space flight. In December of 1989, we established a collaboration with Russian colleagues to determine the bone and lean tissue changes in cosmonauts before and after flights on the Mir space station lasting 4-14.4 months. Eighteen crew members received a lumbar spine and hip DEXA scan (Hologic 1000W) before and after flight; 17 crew members received an additional whole body scan. All results were expressed as percent change from baseline per month of flight in order to account for the different flight times. The pre-and post-flight data were analyzed using Hotelling's T(2) for 3 groups of variables: spine, neck of femur, trochanter; whole body BMD and subregions; lean (total, legs, arms) and fat (total only). A paired t-test was used as a follow-up to the Hotelling's T(2) to identify the individual measurements that were significantly different. These data define the rate and extent of bone and lean tissue loss during long duration space flight and indicate that the current in-flight exercise program is not sufficient to completely ameliorate bone and muscle loss during weightlessness.

Alendronate as an effective countermeasure to disuse induced bone loss.

Microgravity, similar to disuse immobilization on earth, causes rapid bone loss. This loss is believed to be an adaptive response to the reduced musculoskeletal forces in space and occurs gradually enough that changes occurring during short duration space flight are not a concern. Bone loss, however, will be a major impediment for long duration missions if effective countermeasures are not developed and implemented. Bed rest is used to simulate the reduced mechanical forces in humans and was used to test the hypothesis that oral alendronate would reduce the effects of long duration (17 weeks) inactivity on bone. Eight male subjects were given daily oral doses of alendronate during 17 weeks of horizontal bed rest and compared with 13 male control subjects not given the drug. Efficacy was evaluated based on measurements of bone markers, calcium balance and bone density performed before, during and after the bed rest. The results show that oral alendronate attenuates most of the characteristic changes in bone that are associated with long duration bed rest and presumably space flight.

Chemopreventive potential of synergy1 and soybean in reducing azoxymethane-induced aberrant crypt foci in fisher 344 male rats.

Synergy1, a prebiotic composed of Inulin and Oligofructose (1 : 1). Soybean meal is a natural source of isoflavones. The objective was to investigate the effects of feeding Synergy1 and SM on the incidence of azoxymethane- (AOM-) induced aberrant crypt foci (ACF) in Fisher 344 male rats. Rats (54) were randomly assigned to 9 groups (n = 6). Control group (C) was fed AIN-93G and treatment groups Syn1 and SM at 5% and 10% singly and in combinations. Rats were injected with two s/c injections of AOM at 7 and 8 weeks of age at 16 mg/kg body weight and killed at 17 weeks by CO(2) asphyxiation. Colonic ACF enumeration and hepatic enzyme activities were measured. Reductions (%) in total ACF among treatment groups fed combinations were higher (67-77) compared to groups fed singly (52-64). Synergistic mechanisms among phytochemicals may be responsible suggesting protective role in colon carcinogenesis with implications in food product development.

Combinational Effects of Prebiotics and Soybean against Azoxymethane-Induced Colon Cancer In Vivo.

Prebiotic fructans are nondigestible carbohydrates with numerous health benefits. Soybean is a rich source of phytonutrients such as isoflavones. The objective of this study was to evaluate the chemopreventive effects of prebiotics (Synergy1) and soybean meal (SM) at 5% and 10% levels alone and in combination on azoxymethane- (AOM-) induced colon carcinogenesis. After one wk of acclimatization, Fisher 344 male rats (N = 90) were randomly assigned to 9 groups (n = 10). Control rats (C) were fed AIN-93G/M. Two s/c injections of AOM were administered to rats at 7 and 8 wk of age at 16 mg/kg body weight. Rats were killed by CO(2) asphyxiation at 45 wk. Tumor incidence (%) in treatment groups ranged from 40 to 75 compared to 100 in C. Results indicate that feeding prebiotics and soybean in combination significantly reduced incidence of AOM-induced colon tumors with implications for food industry in the food-product development.

Further evaluation of the superficial and deep tendons of the human temporalis muscle.

The superficial and deep tendons of the human temporalis muscle and their fasciae were examined for specific attachments. It was found that as they pass inferiorly along the ramus of the mandible, a structure consisting of tendon and fascia (herein referred to as the fascial-tendinous complex of FTC) is projected anteromedially and inferiorly. The FTC is a unifying structure in the oral-buccal area, serving as a common point of attachment for three muscles of mastication (temporalis, masseter, and medial pterygoid) as well as the buccinator, superior pharyngeal constrictor (SPC), and the mylohyoid muscles, and their corresponding fasciae. The FTC creates a defined fascial space containing loose connective tissue, the buccal nerve, and corresponding blood vessels between the posterior buccal region and the anterior ramus and posterior body of the mandible. The FTC has two components: (1) a medial part which merges into the posterior buccal region in the area of the pterygomandibular depression and (2) a lateral part which continues inferiorly to the posterior area of the body of the mandible. A distinct slip of the medial pterygoid muscle was found to attach to the FTC which caused the lingual nerve to be sandwiched between this slip and the main bulk of the medial pterygoid as it inserts into the mandible. The pterygomandibular raphe, as previously described, was not found. Because of the FTC, the buccinator and SPC do not have simple hamulus-raphe-mylohyoid line attachments. The exact relationship of the buccinator and SPC is dependent upon the extent of the FTC. The larger the FTC, the greater are the muscle attachments and vice versa. In large FTCs a separate muscle (Hamular-FTC muscle) was found attaching from the hamulus to the FTC. The pterygomandibular fold was found not to coincide with the "raphe." The concavity of the pterygomandibular depression upon depression of the mandible was found to be the result of the FTC.

Hologic QDR 2000 whole-body scans: a comparison of three combinations of scan modes and analysis software.

This study reports on the short-term in vivo precision and absolute measurements of three combinations of whole-body scan modes and analysis software using a Hologic QDR 2000 dual-energy X-ray densitometer. A group of 21 normal, healthy volunteers (11 male and 10 female) were scanned six times, receiving one pencil-beam and one array whole-body scan on three occasions approximately 1 week apart. The following combinations of scan modes and analysis software were used: pencil-beam scans analyzed with Hologic's standard whole-body software (PB scans); the same pencil-beam analyzed with Hologic's newer "enhanced" software (EPB scans); and array scans analyzed with the enhanced software (EA scans). Precision values (% coefficient of variation, %CV) were calculated for whole-body and regional bone mineral content (BMC), bone mineral density (BMD), fat mass, lean mass, %fat and total mass. In general, there was no significant difference among the three scan types with respect to short-term precision of BMD and only slight differences in the precision of BMC. Precision of BMC and BMD for all three scan types was excellent: < 1% CV for whole-body values, with most regional values in the 1%-2% range. Pencil-beam scans demonstrated significantly better soft tissue precision than did array scans. Precision errors for whole-body lean mass were: 0.9% (PB), 1.1% (EPB) and 1.9% (EA). Precision errors for whole-body fat mass were: 1.7% (PB), 2.4% (EPB) and 5.6% (EA). EPB precision errors were slightly higher than PB precision errors for lean, fat and %fat measurements of all regions except the head, although these differences were significant only for the fat and % fat of the arms and legs. In addition EPB precision values exhibited greater individual variability than PB precision values. Finally, absolute values of bone and soft tissue were compared among the three combinations of scan and analysis modes. BMC, BMD, fat mass, %fat and lean mass were significantly different between PB scans and either of the EPB or EA scans. Differences were as large as 20%-25% for certain regional fat and BMD measurements. Additional work may be needed to examine the relative accuracy of the scan mode/software combinations and to identify reasons for the differences in soft tissue precision with the array whole-body scan mode.