Aged Beagle Dogs Research Articles

The effects of Novifit on cognitive function in aged beagle dogs

s 39 breed and sex were treated as independent variables (SAS , 2008). Behavioral reactivity analysis revealed significant differences at different levels for breed, sex and training. All the dogs showed an increase in shy behavior with a stranger after training (P % 0.01). Labradors were more confident that German shepherd dogs. Differences before and after training were calculated for platelets 5-HT and 5-HIAA levels and lower levels were found after training (P % 0.01; P % 0.05) (Jiansong et al., 2009). Plasma L-DOPA level revealed significant differences between sexes (P % 0.05), with higher concentrations in males. The results show the effects of training, sex and breed on behavioral reactivity and neurotransmitters level underlining the importance of an accurate selection of dogs for drugs detection training (Rooney et al., 2007).

Acetyl‐L‐carnitine and α‐lipoic acid supplementation of aged beagle dogs improves learning in two landmark discrimination tests

Beagle dogs between 7.6 and 8.8 years of age administered a twice daily supplement of alpha-lipoic acid (LA) and acetyl-L-carnitine (ALC) over approximately 2 months made significantly fewer errors in reaching the learning criterion on two landmark discrimination tasks compared to controls administered a methylcellulose placebo. Testing started after a 5 day wash-in. The dogs were also tested on a variable delay version of a previously acquired spatial memory task; results were not significant. The improved performance on the landmark task of dogs supplemented with LA + ALC provides evidence of the effectiveness of this supplement in improving discrimination and allocentric spatial learning. We suggest that long-term maintenance on LA and ALC may be effective in attenuating age-associated cognitive decline by slowing the rate of mitochondrial decay and cellular aging.

A longitudinal study of brain morphometrics using serial magnetic resonance imaging analysis in a canine model of aging

Longitudinal changes in cortical atrophy, ventricular enlargement, and lesion development in serial MRI scans collected from 47 healthy dogs from 1999 (8–11 years old) to 2002 (11–14 years old) were studied. The first method involved manual region of interest volumetric analysis to examine changes in cerebral and ventricular volume during the three years. No change in cerebral volume was detected but ventricular volume increased significantly each year in 2000, 2001, and 2002. Increased ventricular volume parallels early studies of age-dependent ventricular enlargement in the brain of aging beagle dogs. The second method involved a visual analysis of co-registered serial MRIs for each subject. Consistent with the volumetric results, there was no visible change in cortical thickness indicating no cerebral atrophy, but a significant increase in ventricular size was noted. Visual examination also revealed a significant increase in number of dogs who developed aging lesions over the last 2 years in 2001 and 2002. Additionally, a disproportionate number of lesions were recorded in the frontal cortex and caudate nucleus compared to other brain regions. These lesion findings are consistent with other studies in the aging dog that suggest that the frontal lobes may be particularly vulnerable to age-related changes.

Learning ability in aged beagle dogs is preserved by behavioral enrichment and dietary fortification: a two-year longitudinal study

The effectiveness of two interventions, dietary fortification with antioxidants and a program of behavioral enrichment, was assessed in a longitudinal study of cognitive aging in beagle dogs. A baseline protocol of cognitive testing was used to select four cognitively equivalent groups: control food-control experience (C-C), control food-enriched experience (C-E), antioxidant fortified food-control experience (A-C), and antioxidant fortified food-enriched experience(A-E). We also included two groups of young behaviorally enriched dogs, one receiving the control food and the other the fortified food. Discrimination learning and reversal was assessed after one year of treatment with a size discrimination task, and again after two years with a black/white discrimination task. The four aged groups were comparable at baseline. At one and two years, the aged combined treatment group showed more accurate learning than the other aged groups. Discrimination learning was significantly improved by behavioral enrichment. Reversal learning was improved by both behavioral enrichment and dietary fortification. By contrast, the fortified food had no effect on the young dogs. These results suggest that behavioral enrichment or dietary fortification with antioxidants over a long-duration can slow age-dependent cognitive decline, and that the two treatments together are more effective than either alone in older dogs.

Learning ability in aged beagle dogs is preserved by behavioral enrichment and dietary fortification: a two-year longitudinal study

The effectiveness of two interventions, dietary fortification with antioxidants and a program of behavioral enrichment, was assessed in a longitudinal study of cognitive aging in beagle dogs. A baseline protocol of cognitive testing was used to select four cognitively equivalent groups: control food-control experience (C-C), control food-enriched experience (C-E), antioxidant fortified food-control experience (A-C), and antioxidant fortified food-enriched experience(A-E). We also included two groups of young behaviorally enriched dogs, one receiving the control food and the other the fortified food. Discrimination learning and reversal was assessed after one year of treatment with a size discrimination task, and again after two years with a black/white discrimination task. The four aged groups were comparable at baseline. At one and two years, the aged combined treatment group showed more accurate learning than the other aged groups. Discrimination learning was significantly improved by behavioral enrichment. Reversal learning was improved by both behavioral enrichment and dietary fortification. By contrast, the fortified food had no effect on the young dogs. These results suggest that behavioral enrichment or dietary fortification with antioxidants over a long-duration can slow age-dependent cognitive decline, and that the two treatments together are more effective than either alone in older dogs.

Adrafinil disrupts performance on a delayed nonmatching-to-position task in aged beagle dogs

Previous studies in humans and dogs have reported beneficial effects of adrafinil on specific cognitive functions. The effects in dogs are limited to a single study examining discrimination learning. We wanted to further explore the cognitive effects of adrafinil in dogs. The purpose of the present study was to determine the effect of oral administration of adrafinil on visuospatial function in dogs. Eighteen aged beagle dogs were tested on a delayed nonmatching-to-position (DNMP) task 2 h following one of three possible treatments; 20 mg/kg of adrafinil, 10 mg/kg of adrafinil or a placebo control. All dogs were tested under each treatment for eight test sessions. A 2-day washout period was given between treatments and the order of treatments was varied. Treatment with 20 mg/kg of adrafinil produced a significant impairment in working memory as indicated by an increase in the number of errors over the 8-day test period. The disturbance of memory functions from adrafinil could be a result of increased noradrenergic transmission in the prefrontal cortex.

Visuospatial impairments in aged canines (Canis familiaris): The role of cognitive-behavioral flexibility.

This study used a novel delayed nonmatching-to-position task to compare visuospatial learning and memory in young and aged beagle dogs (Canis familiaris). The task used 3, rather than 2, spatial locations, which markedly increased difficulty. There were striking age differences in acquisition. Most of the aged canines did not learn the task, and those that did showed impaired learning when compared with the young canines. The aged canines also showed reduced maximal working memory capacity compared with the young canines. Analysis of the response patterns of individual canines indicated that the deficits were related to the use of ineffective strategies and inflexibility in strategy modification.

Visuospatial impairments in aged canines (Canis familiaris): The role of cognitive-behavioral flexibility.

This study used a novel delayed nonmatching-to-position task to compare visuospatial learning and memory in young and aged beagle dogs (Canis familiaris). The task used 3, rather than 2, spatial locations, which markedly increased difficulty. There were striking age differences in acquisition. Most of the aged canines did not learn the task, and those that did showed impaired learning when compared with the young canines. The aged canines also showed reduced maximal working memory capacity compared with the young canines. Analysis of the response patterns of individual canines indicated that the deficits were related to the use of ineffective strategies and inflexibility in strategy modification.

Effect of age and level of cognitive function on spontaneous and exploratory behaviors in the beagle dog.

Cognitively characterized young and aged beagle dogs were administered six different spontaneous behavior tests, which provided measures of locomotion, exploration, and social interaction. Consistent with our previous findings, we obtained no overall effect of age on locomotion. We did find, however, that for the aged dogs locomotion correlated with level of cognitive function, being lowest in age-unimpaired dogs and highest in impaired dogs. Exploratory behavior, as measured by response to novelty, varied with age, with young dogs scoring the highest. Young dogs spent more time with novel toys and a person, responded more to a silhouette of a dog, and interacted more with a model dog compared to aged dogs. Among the aged dogs, age-unimpaired dogs spent the greatest amount of time sitting or standing beside a person whereas age-impaired dogs spent the most time reacting to a reflection in a mirror. The age-impaired dogs show undirected, stereotypical types of behavioral patterns. These differences in activity patterns may be linked to underlying age-associated neuropathology.

Oral Administration of Adrafinil Improves Discrimination Learning in Aged Beagle Dogs

Aged beagle dogs were trained on either a size or intensity discrimination task 2 h following treatment with either 20 mg/kg of adrafinil or a placebo control. Training continued until the dogs reached a predetermined criterion level of performance, or failed to acquire the task after 40 sessions. The treatments and tasks were then reversed, with both the test order and treatment order counterbalanced. Thus, half of the animals were first tested on the intensity discrimination, and half of these were first tested under adrafinil. Treatment with adrafinil produced significant improvement in learning, as indicated by a decrease in both errors and trials to criterion. An effect of adrafinil on motivation may partially account for these findings; however, adrafinil did not significantly affect response latency. Adrafinil is believed to serve as an alpha-1 adrenoceptor agonist. The improved learning may also result from enhancement of vigilance due to facilitation of noradrenergic transmission in the central nervous system.

Effects of Mepartricin (S–160) on Spontaneous Canine Benign Prostatic Hyperplasia

Objective: The effects of mepartricin (S–160) on spontaneous canine benign prostatic hyperplasia (BPH) were investigated by histological, histochemical and biochemical analysis.Methods: Aged beagle dogs (5–9 years old) with spontaneously developed BPH were treated orally with a placebo or S–160 (5, 10 or 20 mg/kg/day) for 8 weeks. The methodology included measurement of prostatic volume by transrectal ultrasonography, qualitative evaluation of prostatic morphology, determination of plasma and intraprostatic estradiol level by radioimmunoassay and immunohistochemical detection of estrogen receptors and androgen receptors in the prostate.Results: S–160 significantly reduced the prostatic volume and regressed histologically the hyperplastic grade of prostate, and also fairly decreased the plasma and intraprostatic estradiol concentration and the estrogen and androgen receptors in the prostate.Conclusions: These results suggest that the reduction of estradiol and estrogen receptors in the prostate may play a crucial role in the regression of BPH by S–160.

Comparison of arterial blood gases and acid-base balance in young and aged beagle dogs, with regard to postprandial alkaline tide.

Arterial blood pH and blood gas tensions were measured before and after feeding in seven young (1-year-old) and 6 aged (10 to 12 year-old) conscious beagle dogs with a portable "i-STAT" blood gas analyzer to obtain the fundamental physiological data on the laboratory dogs. Before feeding, arterial blood pH, HCO3- and base excess (BE) were 7.395 +/- 0.022, 20 +/- 1.0 mmol/L and -4 +/- 1.1 mmol/L in young dogs, and 7.408 +/- 0.031, 23 +/- 1.5 mmol/L and -2 +/- 1.8 mmol/L in aged ones. After feeding, the above values changed to 7.449 +/- 0.021, 25 +/- 1.1 and 1 +/- 1.3 in young dogs, and 7.456 +/- 0.022, 28 +/- 1.7 and 4 +/- 1.9 in aged ones. After feeding, each of the values for pH, HCO3- and BE was increased in comparison with those before feeding in both young and aged dogs, and alkalinization of blood, the alkaline tide, was observed in all healthy dogs. The values for PCO2 also rose from 33.6 +/- 1.91 to 36.7 +/- 1.95 (mmHg) in young dogs, and 36.4 +/- 2.97 to 40.3 +/- 3.06 (mmHg) in aged ones, and in 3 of 6 aged dogs slight hypoxia (PO2 < 80 mmHg) was noted. These changes in PCO2 and PO2 were considered to be due to compensatory hypoventilation for the alkalinization of blood. To confirm the cause of the alkaline tide phenomenon, we investigated the association of the alkaline tide with gastric acid secretion by cimetidine, an H2-blocker; and found that it was effective to inhibit postprandial alkaline tide in dogs. After feeding, ionized Ca concentration (iCa) was decreased inversely with an arterial blood pH increase in both young and aged dogs. The mean values of iCa in aged dogs after feeding was lower than those in young dogs. In the present experiments, it was demonstrated that in beagle dogs the acid-base balance and blood gas values were largely affected by feeding, especially in aged dogs. In case blood gases would be evaluated in toxicity studies, we should consider the influence of feeding and aging.

Assessing the effects of deprenyl on longevity and antioxidant defenses in different animal models.

Among many pharmaceuticals that have been tested for their effects on longevities of different animal rodents, deprenyl is unique in that its effects on longevity has been tested in at least four different animal species by independent research groups and that the effect has been postulated to be due to its effect of raising such antioxidant enzyme activities as superoxide dismutase (SOD) and catalase (CAT) in selective brain regions. Thus far, in all four species of animals examined (rats, mice, hamsters, and dogs), a positive effect was demonstrated, although the extent of its effect is quite variable. Our group has examined the effect on longevities in rats and mice and on antioxidant enzymes in rats, mice, and dogs. Although in rats of both sexes, we have obtained positive effects on longevity, two studies with different doses in mice did not reveal a significantly positive effect. We have observed, however, significantly positive effects on SOD (in Cu, Zn-, and Mn-) as well as CAT (but not glutathione peroxidase) activities in the brain dopaminergic system such as in the S. nigra and striatum (but not in hippocampus) in all rats, mice, and dogs, although the effects were quite variable, depending on the doses used. In mice, however, a long-term administration (3x/w, 3 months) caused a remarkable decrease in the magnitude of activity as well as a narrowing of the effective dose range, which may explain a relatively weak effect of the drug on mouse longevity. Further, a recent study on aging beagle dogs by Ruehl et al. showed a remarkable effect on longevity, which agrees with our SOD study in dogs. Although deprenyl has been claimed to have several other effects, such as a radical scavenging effect and a neuroprotective effect, past reports on its effects on longevities and antioxidant defenses are compatible with the notion that the drug prolongs the life span of animals by reducing the oxidative damage to the brain dopaminergic system during aging. Further, our studies on F-344 rats as well as a dog study by Ruehl et al. suggest that the drug may at least partially prolong the life span of animals by enhancing immune system function and preventing tumor development in animals.

Prussian Blue Decorporation of 137Cs in Humans and Beagle Dogs

Prussian blue (PB) was used to enhance the elimination of 137 Cs from 46 individuals contaminated in an accident in Goiânia, Brazil, in 1987, PB dosages administered to the victims varied from I to 3 g.d -1 for children and from 3 to 10 g.d -1 for adolescents and adults. To complement human data in the evaluation of the effectiveness of PB and its relation to age, a 41 day study was conducted using immature (4.7 months old). young adult (2.4 year old) and aged (13.5 years old) male beagle dogs. The mean biological half-times for the Goiânia people under PB treatment were 24 ± 3 days, 30 ± 12 days and 25 ± 11 days, for children, adolescents and adults, respectively. The mean reductions of half-times were 43%, 46% and 69%, respectively. The effect of PB was shown to be independent of age and the administered dose. Similar results were found in dogs: the mean biological half-times related to the second component of the equation were 11, 15 and 13 days for the immature, young adult and aged dogs. respectively. indicating a reduction of the clearance half-times of 45%, 45% and 63%. The experiment in dogs has shown that when the PB is administered immediately after a caesium intake. its effectiveness is greater in immature than in aged dogs. The percentages of the initial body burden remaining 41 days after caesium intake were 4%, 12% and 8% for the immature, young adult and aged dogs. repectively. This age-related effect correlates with the increased fraction of 137 Cs eliminated with the fast clearance half-time, and was greater in immature than in aged dogs.

Primary vascular neoplasms of lymph nodes in the dog.

Primary vascular neoplasms of lymph nodes are rare, and appear not to have previously been reported in domestic animals. This report describes hemangiomas and a lymphangioma in lymph nodes of aged Beagle dogs. Eight hemangiomas (4.8%) and one lymphangioma were present in 165 examined popliteal lymph nodes, and one hemangioma occurred in a hepatic lymph node. The hemangiomas were cavernous and benign.

A biokinetic model for 137Cs.

An improved biokinetic model for 137Cs in humans was developed based on an analysis of data obtained from individuals internally contaminated during an accident in Goiania, Brazil, and other data. Seventeen children (ten girls and seven boys 1-10 y old), ten adolescents (four females and six males), and thirty adults, (fifteen females and fifteen males contaminated in the accident in Goiânia contributed to this study. 137Cs retention was determined through periodic measurements in a whole-body counter. In addition to the data on 137Cs retention from these individuals, data from a study on the metabolism of 137Cs in immature, adult, and aged Beagle dogs and data from the literature were used in the formulation of the 137Cs biokinetic model presented. Mathematically, the retention of cesium is described by three exponential terms, and the retention model is based on a step function of body weight. When the ICRP Publication 56 model for cesium was compared to the model suggested in this paper, it was determined that the ICRP model predicts lower effective doses in 5-y-old children and higher effective doses in infants, adolescents, and adults.

Effects of intermittent hPTH(1-34) alone and in combination with 1,25(OH)(2)D(3) or risedronate on endosteal bone remodeling in canine cancellous and cortical bone.

Therapies utilizing intermittent human parathyroid hormone(1-34) (hPTH[1-34]) in combination with other agents have recently been proposed as possible anabolic regimens for the treatment of osteoporosis. We conducted a 24 week study in aged beagle dogs to determine the effects of intermittent hPTH(1-34) administered alone or in combination with 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) on the endosteal remodeling in cancellous and cortical bone. Additionally, we tested the interaction between hPTH(1-34) and a new potent bisphosphonate, risedronate. The three treatment groups were compared with a vehicle control group. Kinetic reconstruction of the remodeling unit revealed substantial differences between the groups in resorption and formation at the basic multicellular unit level. Although the estimates of final erosion depth were unaffected by treatment, tunneling resorption was noted in six of the eight dogs administered hPTH(1-34) alone. These qualitative morphological changes in the resorption lacunae were attenuated or absent in dogs administered hPTH(1-34) in combination with either 1,25(OH)(2)D(3) or risedronate. Functional periods for resorption were significantly increased, and the resorption rates were significantly decreased in the hPTH(1-34) + risedronate group. Analyses of the formative site demonstrated that the wall thickness was significantly increased and the bone balance significantly more positive in all three hPTH(1-34) treatment groups. The most positive bone balance was achieved in the combined hPTH(1-34) + risedronate group (+ 15.6 + or - 14.2 mm, p <0.05). Increases in the mineral apposition rate in the early phases of the formative period suggest that an increase in osteoblastic activity (number or function) may contribute to the increase in wall thickness. Treatment with hPTH(1-34) alone or in combination with 1,25(OH)(2)D(3) caused an approximately 2-fold increase in the activation frequency in cancellous bone, which was essentially normalized to control values by the coadministration of risedronate. The impact of these changes on the cancellous bone microstructure was significant only in the combined hPTH(1-34) + risedronate group where normalized bone turnover in the face of a positive bone balance effected a significant increase in the trabecular thickness. Analyses of sequential fluorochrome labels, administered to reconstruct the temporal changes in intracortical activation, demonstrated the presence of an apparent cyclic pattern of activation in the cortex of placebo-treated dogs. Generally, activation was increased throughout the study in dogs administered hPTH(1-34) alone or in combination. However, in the hPTH(1-34) + risedronate group, activation was significantly blunted toward the end of the study, and the cyclic pattern of activation was modulated. These data suggest that intermittent hPTH(1-34) in combination with risedronate may be superior to hPTH(1-34) in combination with 1,25(OH)(2)D(3) as a therapeutic regimen for osteoporosis due to the protective effect of this bisphosphonate on the cortical and endocortical envelope.

Carboxy terminal of β-amyloid deposits in aged human, canine, and polar bear brains

Immunocytochemistry, using antibodies specific for different carboxy termini of β-amyloid, Aβ40 and Aβ42(43), was used to compare β-amyloid deposits in aged animal models to nondemented and demented Alzheimer's disease human cases. Aged beagle dogs exhibit diffuse plaques in the absence of neurofibrillary pathology and the aged polar bear brains contain diffuse plaques and PHF-1-positive neurofibrillary tangles. The brains of nondemented human subjects displayed abundant diffuse plaques, whereas the AD cases had both diffuse and mature (cored) neuritic plaques. Diffuse plaques were positively immunostained with an antibody against Aβ42(43) in all examined species, whereas A(340 immunopositive mature plaques were observed only in the human brain. Anti-Aβ40 strongly immunolabeled cerebrovascular β-amyloid deposits in each of the species examined, although some deposits in the polar bear brain were preferentially labeled with anti-Aβ42(43). β-Amyloid deposition was evident in the outer molecular layer of the dentate gyrus in the aged dog, polar bear, and human. Within this layer, Aβ42 was present as diffuse deposits, although these deposits were morphologically distinct in each of the examined animal models. In dogs, Aβ42 was cloud-like in nature; the polar bear demonstrated a more aggregated type of deposition, and the nondemented human displayed well-defined deposits. Alzheimer's disease cases were most frequently marked by neuritic plaques in this region. Taken together, the data indicate that β-amyloid deposition in aged mammals is similar to the earliest stages observed in human brain. In each species, Aβ42(43) is the initially deposited isoform in diffuse plaques.

Single and 4-week oral toxicity studies of prulifloxacin (NM441) in aged dogs

Single-dose and repeated dose toxicity studies of prulifloxacin, a new antibacterial agent, were conducted in aged beagle dogs. I. A single-dose toxicity study Prulifloxacin was administered orally to aged female dogs at a single dose of 2500 and 5000 mg/kg. No death occurred in any group. Vomiting was observed in one of two animals at 2500 mg/kg and in both animals at 5000 mg/kg 3-4 hr after dosing. At 5000 mg/kg, vomiting was observed in both animals after feeding on the day after dosing. One animal also showed soft stool. Thereafter, no abnormalities were observed in any animal. No test article related changes were noted in food consumption, water consumption, body weight or pathological examination in any group. The results show that the lethal dose of prulifloxacin is judged to be greater than 5000 mg/kg in aged female dogs. II. A repeated dose toxicity study Aged male and female dogs were given the test article orally for 4 weeks at doses of 0 (control), 20, 100 and 500 mg/kg. No death occurred in any group. At 500 mg/kg, vomiting was observed every day or intermittently throughout the dosing period and salivation was observed almost every day from day 6 to the end of the dosing onward. Decreases or lack of food and water consumption, and decrease of body weight were noted at 500 mg/kg. At 100 mg/kg, slight decreases in food consumption and body weight were noted in the females. No abnormalities were noted in ophthalmoscopic or electrocardio-graphic examination. In urinalysis, decreases in Na+, K+ and Cl- concentrations and the total excretion amount were noted mostly at 500 mg/kg. A low specific gravity was noted in males at 500 mg/kg. In hematology and serum biochemistry, high GPT, BUN and creatinine, and decreases in WBC were noted in both sexes at 500 mg/kg. A high GOT was noted in males, and low Cl- in females at 500 mg/kg. At 100 mg/kg, a high GPT was noted. Rough surface in the kidney and chronic interstitial nephritis (basophilic change of tubule, atrophy of tubule, thickening of tubular basement membrane, interstitial mononuclear cell infiltration, interstitial focal fibrosis) were increased at 500 mg/kg. No toxicological findings were seen in the 20 mg/kg group. The results show that the NOAEL of prulifloxacin is 20 mg/kg for 4-week repeated dose toxicity in aged dogs.

Periodontal repair in dogs: evaluation of the natural disease model

Animal models are frequently consulted for histometric analysis of periodontal reconstructive therapy. Such models include surgical, periodontitis-simulating and natural disease defects in canines or non-human primates. Our studies suggest that homogeneity in defect height is critical for sensitivity of surgical and periodontitis-simulating supraalevolar defect models in discriminating treatment effects. We herein evaluate this model aspect for natural disease defects. Buccal-lingual histologic sections from the 2nd, 3rd, and 4th mandibular premolar teeth (P2, P3, P4) from 6 aged beagle dogs with advanced natural periodontal disease were used. Defect heights from the reduced alveolar bone to the cemento-enamel junction were recorded in central step-serial sections at the buccal and lingual surfaces of the mesial and distal roots for the premolar teeth. Mean defect height, standard deviation and coefficient of variation were calculated for tooth types and jaw quadrants, separately, and for all teeth. Confidence intervals were calculated for teeth in left and right jaw quadrants. Mean defect height and standard deviation for left and right jaw quadrants was 3.6 +/- 0.9 and 3.3 +/- 0.6 mm for P2, 3.3 +/- 0.9 and 2.3 +/- 0.9 mm for P3, and 3.3 +/- 1.0 and 4.5 +/- 1.6 mm for P4, respectively. Coefficient of variation for defects for left and right jaw quadrants was 26 and 40%, respectively. Using confidence intervals for mean differences between jaw quadrants, it was determined that a mean treatment effect may be as large as 0.8, 1.1 and 1.9 mm for P2, P3 and P4, respectively, before being detected as statistically significant (p < or = 0.05; N = 6).(ABSTRACT TRUNCATED AT 250 WORDS)