Predictive models for reduction of Salmonella Hadar on chicken skin during single and double sequential spraying treatments with acetic acid

AIMS: The response surface methodology was used to evaluate the effect of acetic acid concentration, spraying time and temperature on the reduction of Salmonella Hadar on poultry skin in a laboratory spraying process, and to identify the best conditions required to develop this operation. METHODS AND RESULTS: A comparative analysis was carried out to ascertain the effects of the application of single (SS) and double sequential decontamination (DSS) treatments on skin samples inoculated with Salm. Hadar. While on the SS treatment, the linear and quadratic acid concentration terms and the interaction of the temperature and time term of the model are statistically significant at P < or = 0.001, P < or = 0.01 and P < or = 0.05, respectively, the other terms do not significantly affect (P > 0.05) the reduction of Salm. Hadar. On the DSS model the acid concentration and time linear terms significantly affected (P < or = 0.001 and P < or = 0.01) the Salm. Hadar reduction within the experimental range assayed. CONCLUSION: Any of the models could be used as an approach to optimize spray washing during chicken processing. SIGNIFICANCE AND IMPACT OF THE STUDY: Neither the SS or the DSS treatment has the capability of eliminating Salm. Hadar from carcasses. However, reductions of approx. 99% initial load could be attained if DSS treatment were put into practice.     

Relationship between inactivation kinetics of a Listeria monocytogenes suspension by chlorine and its chlorine demand

AIMS: Chlorine demand by Listeria monocytogenes cells and inactivation of L. monocytogenes by chlorine (0.6-1.0 mg l(-1)) at different temperatures (4, 20 and 30 degrees C) have been investigated in a batch reactor. METHODS AND RESULTS: Chlorine demand depended on the microbial concentration and was independent on the initial chlorine concentration and temperature. Chlorine decay was modelled by the addition of two first-order decay equations. Inactivation of L. monocytogenes by chlorine depended on the initial microbial concentration, initial chlorine concentration and temperature. A mathematical model based on a biphasic inactivation properly described survival curves of L. monocytogenes and a tertiary model was developed that satisfactorily predicted the inactivation of L. monocytogenes by different concentrations of initial chlorine at different temperatures. CONCLUSIONS: Both available chlorine decay and inactivation of L. monocytogenes by chlorine were biphasic and can be modelled by a two-term exponential model. SIGNIFICANCE AND IMPACT OF THE STUDY: The biphasic nature of survival curves of L. monocytogenes did not reflect the effect of a change of available chlorine concentration during the treatment. The microbial inactivation was caused by successive reactions that occur after the consumption of the chlorine by the bacterial cell components.     

The effects of cleaning and disinfection in reducing Salmonella contamination in a laboratory model kitchen

AIMS: To establish a laboratory model to compare the effectiveness of detergent-based disinfection procedures for reducing cross-contamination risks during handling of contaminated chicken. METHODS AND RESULTS: During handling of chickens, artificially contaminated with Salmonella enteritidis PT4, the organism was widely spread to hands, cloths, and hand- and food-contact surfaces. Hygiene procedures were assessed on the basis of their ability to reduce the number of recoverable salmonellas to <1 CFU. Although detergent-based cleaning using a typical bowl-wash routine without rinsing produced some risk reduction (from 100 to 61.4% of contaminated surfaces), it was insufficient to consistently restore surfaces to a hygienic state. By combining detergent-based cleaning with a rinsing step or with hypochlorite at 500 ppm (of available chlorine) some further reduction in microbial risk was achieved, but was not considered satisfactory for food hygiene purposes. By contrast the risk reduction produced by hypochlorite at 5000 ppm was highly significant and was sufficient to reduce the number of contaminated surfaces to 2.9%. CONCLUSIONS: A key step in achieving a hygienic state through detergent-based cleaning is rinsing but even this will not produce a 'hygienic' result for difficult surfaces such as the chopping board or the dishcloth. Disinfectant compounds should be considered in order to reduce the potential for foodborne cross infection within the home environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Although tests are available to determine the performance of disinfectants, there are no quantitative procedures available to compare the risk reduction achieved by disinfection with that produced by detergent-based procedures. This study describes a reproducible laboratory method which can be used to differentiate the effectiveness of different hygiene procedures for reducing cross-contamination risks during food handling.     

Effect of pH, application technique, and chlorine-to-nitrogen ratio on disinfectant activity of inorganic chloramines with pure culture bacteria.

The influence of pH, application technique, and chlorine-to-nitrogen weight ratio on the bactericidal activity of inorganic chloramine compounds was determined with stock and environmental strains of Escherichia coli, Salmonella spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter cloacae. The rate of inactivation increased from 1.5 to 2 times as the chlorine-to-nitrogen weight ratio was adjusted from 2:1 to 5:1, 5 to 6 times as the pH was decreased from 8 to 6, and 5 to 6 times as the concentration was increased from 1 to 5 mg/liter. Separate additions of free chlorine and ammonia (concurrent addition and preammoniation) into seeded water at or below pH 7.5 resulted in killing comparable to that observed with free chlorine (99% inactivation in less than 20 s). At pH 8, inactivation by separate additions was considerably slower and was comparable to that by prereacted chloramine compounds (99% inactivation in 25 to 26 min). Determination of the effectiveness of inorganic chloramine compounds as primary disinfectants for drinking water must consider the method of application, pH and concentrations of chlorine and ammonia.     

Efficacy of chlorine and heat treatment in killing Salmonella stanley inoculated onto alfalfa seeds and growth and survival of the pathogen during sprouting and storage.

The efficacy of chlorine and hot water treatments in killing Salmonella stanley inoculated onto alfalfa seeds was determined. Treatment of seeds containing 10(2) to 10(3) CFU/g in 100-micrograms/ml active chlorine solution for 5 or 10 min caused a significant (P < or = 0.05) reduction in population, and treatment in 290-micrograms/ml chlorine solution resulted in a significant reduction compared with treatment in 100 micrograms of chlorine per ml. However, concentrations of chlorine of up to 1,010 micrograms/ml failed to result in further significant reductions. Treatment of seeds containing 10(1) to 10(2) CFU of S. stanley per g for 5 min in a solution containing 2,040 micrograms of chlorine per ml reduced the population to undetectable levels (< 1 CFU/g). Treatment of seeds in water for 5 or 10 min at 54 degrees C caused a significant reduction in the S. stanley population, and treatment at > or = 57 degrees C reduced populations to < or = 1 CFU/g. However, treatment at > or = 54 degrees C for 10 min caused a substantial reduction in viability of the seeds. Treatment at 57 or 60 degrees C for 5 min appears to be effective in killing S. stanley without substantially decreasing germinability of seeds. Storage of seeds for 8 to 9 weeks at 8 and 21 degrees C resulted in reductions in populations of S. stanley of about 1 log10 and 2 log10 CFU/g, respectively. The behavior of S. stanley on seeds during soaking germination, sprouting, and refrigerated storage of sprouts was determined. An initial population of 3.29 log10 CFU/g increased slightly during 6 h of soaking, by about 10(3) CFU/g during a 24-h germination period, and by an additional 10 CFU/g during a 72-h sprouting stage. A population of 10(7) CFU/g of mature alfalfa sprouts was detected throughout a subsequent 10-day storage period at 5 degrees C. These studies indicate that while populations of S. stanley can be greatly reduced, elimination of this organism from alfalfa seeds may not be reliably achieved with traditional disinfection procedures. If S. stanley is present on seeds at the initiation of the sprout production process, populations exceeding 10(7) CFU/g can develop and survive on mature sprouts exposed to handling practices used in commercial production and marketing.     

X-ray microanalysis of cockroach fat body in relation to ion and water regulation

X-Ray microanalysis of fat body from the cockroach (Periplaneta americana) showed that the crystals in the urate cells sequestered potassium and sodium during water deprivation. Postassium sequestration appeared to occur by the formation of additional crystals whereas sodium appeared to be taken up by pre-existing crystals of the “amorphous granule” type. Urate cells increased in cytoplasmic density i.e. mass per unit volume as a result of water deprivation and lost potassium from the cytoplasm but not from the nucleus. Trophocyte cells also showed an increase in density and a loss of potassium from the cytoplasm. The nucleus in trophocyte cells however, did not increase in density and showed an increase in chlorine concentration. A previously undescribed type of crystal in the trophocyte cell cytoplasm also increased markedly in chlorine concentration. The mycetocyte cells did not appear to increase in density but chlorine concentration was elevated in symbionts, cytoplasm and nucleus. An increase in density is considered to be a consequence of a reduction in volume due to water loss. It is confirmed that the fat body plays a major role in the maintenance of ion balance during water deprivation.     

Effectiveness of chlorine washing disinfection and effects on the appearance of artichoke and borage

AIM: Optimal conditions for chlorine application to obtain a reasonable decrease in the microbial counts without damaging the appearance of artichoke and borage have been established. METHODS AND RESULTS: The influence of chlorine concentration (0-200 mg l(-1)), pH, addition of organic acids, contact time and presence of protective structures on the microflora and vegetal appearance were studied. When pH was not controlled the effect of chlorine depended on its concentration until the pH increase caused by addition of chlorine reached 8.8. Any further increase in chlorine concentration was nullified by the pH increase. When pH was adjusted to 4.5 with acetic acid, the effectiveness increased with concentration. However, the use of citric acid to control pH caused a sharp decrease in effectiveness at concentration about 250 mg l(-1). The higher effectiveness of chlorine on homogenized plant extracts compared with the whole plant showed the impact of the vegetal structures on the resistance of the microorganisms. For artichoke, a relationship between the effectiveness of chlorine disinfection and its structures was also found. Extended washing times did not affect the total counts. However, in both vegetables, the appearance was affected by the extended contact times. CONCLUSIONS: The solutions rendering the highest microbial reduction with minimum damages were: 50 mg l(-1) free chlorine without pH control for artichoke and 100 mg l(-1) free chlorine at pH 7.0 for borage. SIGNIFICANCE AND IMPACT OF THE STUDY: Specific conditions for chlorine disinfection of artichoke and borage were determined to reduce the microorganisms in minimally processed artichoke and borage without damaging their appearance.     

Seasonal variations in serum levels of thyroid hormones and their relation with seminal quality and libido in buffalo bulls

Blood samples from 15 Murrah buffalo bulls, (10- to 15- years-old) were collected during the summer, monsoon and winter seasons. The serum samples were analysed for thyroxine (T4) and triiodothyronine (T3) by RIA. Semen samples from these bulls were evaluated for various attributes. Sexual behaviour of these bulls was also recorded during the different seasons and was expressed as reaction time and refusal response. T4, T3, (T4 + T3) level and T4:T3 ratio did not reveal significant difference between seasons. Similarly, seminal characteristics did not exhibit any seasonal variation except for the percentage of live spermatozoa. However, the refusal response (no interest in mounting and ejaculating) was highest during summer months. T4 was significantly correlated to T(3) (r=0.53). Overall, T4 showed a positive correlation with seminal volume and initial motility while T3 exhibited a positive correlation with total sperm concentration and percentage of live spermatozoa. T3 was negatively correlated with refusal response only during the monsoon season. Correlation with other seminal and behavioural characteristics were not significant. The results indicated that although the sexual interest of buffalo bulls is reduced during the summer, the bulls can produce semen throughout the year under appropriate feeding and management conditions.     

Steady-state approximation of enzyme activation and inhibition

This article deals with the effects of the initial concentration of effector (inhibitor or activator) on the steady-state approximation of enzyme kinetics. The results could be summarized as follows: (1) In competitive inhibition, the increase in the initial concentration of inhibitor led to the reduction of steady state time. (2) In noncompetitive and uncompetitive inhibitions, the steady state time was not changed with the increase in the initial concentration of inhibitor. (3) In nonessential activation, the increase in the initial concentration of activator led to the reduction of steadystate time. (4) It was specially noted that in nonessential activation, even if the reaction is in the steady-state, activation constant (K(A)) can not be determined exactly unless the initial concentration of activator is very small.     

The effect of exercise on the production and clearance of testosterone in well trained young men

Tritium-labelled testosterone was infused into four well-trained subjects at rest and during one hour of exercise at about 60% of their maximum aerobic power. This exercise regime led to a mean increase of 27% (range 10-51%) in plasma testosterone concentration. At the same time there were significant decreases in the estimated hepatic plasma flow (EHPF) (45%; range 28-67%), metabolic clearance rate of testosterone (MCRT) (29%; range 18-37%) and plasma volume (8.2%; range 3-10%). The production rate of testosterone decreased by 10% (range 9-22%) but this was not statistically significant. The ratio MCRT:EHPF increased in 3 out of 4 subjects in response to exercise but there was considerable inter-subject variation both at rest and during exercise. These findings suggest that the exercise-induced elevation of testosterone level is due solely to the reduction in the rate at which testosterone is cleared from the plasma. The principal cause of the reduction in MCRT is probably the reduction in EHPF but the variation in the ratio MCRT:EHPF suggests that changes in the extrahepatic clearance of testosterone may also be involved.     

Application of antimicrobial ice for reduction of foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes) on the surface of fish

AIMS: The efficacy of antimicrobial ice was evaluated for the reduction of foodborne pathogens on the surface of fish. METHODS AND RESULTS: Antimicrobial ice containing chlorine dioxide (ClO2) was utilized to control foodborne pathogens in laboratory media and on fish skin. Escherichia coli O157:H7, Salmonella serotype Typhimurium and Listeria monocytogenes strains were treated with antimicrobial ice for 30 min on plates of selective agar and for 120 min on fish skin at room temperature, and then incubated for enumeration. After treatment with 100 ppm ClO2 for 30 min, 5.4, 4.4 and 3.2 log10 reduction was obtained with E. coli O157:H7, Salm. Typhimurium and L. monocytogenes on laboratory media, respectively. When antimicrobial ice (100 ppm ClO2) was applied to fish skin for 120 min, total reduction of E. coli O157:H7, Salm. Typhimurium and L. monocytogenes was 4.8, 2.6 and 3.3 log10, respectively. CONCLUSION: The initial load of foodborne pathogens was reduced by antimicrobial ice and the lowered microbial level was maintained during treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: The application of antimicrobial ice is a simple and effective method for the safe preservation of fish.     

Enhanced inactivation of salmonella and pseudomonas biofilms on stainless steel by use of T-128, a fresh-produce washing aid, in chlorinated wash solutions

The effect of the washing aid T-128 (generally recognized as safe [GRAS] formulation, composed mainly of phosphoric acid and propylene glycol) on inactivation of Salmonella and Pseudomonas populations in biofilms on stainless steel was evaluated under conditions of increasing organic matter loads in chlorinated wash solutions dominated by hypochlorous acid. Biofilms were formed statically on stainless steel coupons suspended in 2% lettuce extract after inoculation with Salmonella enterica serovar Thompson or Newport or with Pseudomonas fluorescens. Coupons with biofilms were washed in chlorine solutions (0, 0.5, 1, 2, 5, 10, or 20 mg/liter at pH 6.5, 5.0 and 2.9), with or without T-128, and with increasing loads of organic matter (0, 0.25, 0.5, 0.75, or 1.0% lettuce extract). Cell populations on coupons were dispersed using intermittent, pulsed ultrasonication and vortexing and enumerated by colony counts on XLT-4 or Pseudomonas agars. Cell responses to fluorescent viability staining of biofilm treatment washing solutions were examined using confocal laser scanning microscopy. Results showed that 0.1% T-128 (without chlorine) reduced P. fluorescens biofilm populations by 2.5 log(10) units but did not reduce Salmonella populations. For both Salmonella and Pseudomonas, the sanitizing effect of free chlorine (1.0 to 5.0 mg/liter) was enhanced (P < 0.05) when it was combined with T-128. Application of T-128 decreased the free chlorine depletion rate caused by increasing organic matter in wash waters and significantly (P < 0.05) augmented inactivation of bacteria in biofilms compared to treatments without T-128. Image analysis of surfaces stained with SYTO and propidium iodide corroborate the cultural assay results showing that T-128 can aid in reducing pathogen viability in biofilms and thus can aid in sanitizing stainless steel contact surfaces during processing of fresh-cut produce.     

Seed Film Coating with Uniconazole Improves Rape Seedling Growth in Relation to Physiological Changes Under Waterlogging Stress

Waterlogging is an important constraint of global production of rape. The effects of seed film coating with 0.0075% uniconazole on the growth and physiology was investigated using seedlings from three varieties of rape (Brassica napus L.) subjected to waterlogging. While seed coating with uniconazole had no significant effect on germination percentage during waterlogging stress, it enhanced root vigour, increased root length, root volume and root dry weight. It also significantly enhanced leaf dry weight and ratio of root to shoot, but induced a significant decrease in shoot height and stem dry weight. Seed film coating with uniconazole also significantly increased the activities of the antioxidant enzymes, POD, CAT and SOD, and soluble sugar concentration during waterlogging. Thus, it suggests that seed film coating with uniconazole at a suitable concentration can improve rape seedling growth and increase seedling establishment during waterlogging.     

Effect of adenosine and glucagon on hepatic blood volume responses to sympathetic nerves

Hepatic blood volume responses were studied in cats using in vivo plethysmography. The maximal response (Rmax) to sympathetic nerve stimulation and to infusions of norepinephrine into the hepatic artery or portal vein was similar (12-14 mL expelled per liver in 2.9-kg cats; average liver weight, 76.8 +/- 6.8 g). The ED50 for norepinephrine intraportal (0.44 +/- 0.13) and intrahepatic arterial infusions (0.33 +/- 0.08 micrograms.kg-1.min-1) were similar indicating equal access of both blood supplies to the capacitance vessels. Adenosine (2.0 mg.kg-1.min-1) did not cause significant volume changes but produced a mild (27%) suppression of Rmax due to nerve stimulation with no change in the frequency (3.4 Hz) needed to produce 50% of Rmax. Rmax tended (not statistically significant) to decrease during glucagon (1.0 micrograms.kg-1.min-1) infusion but the nerve frequency needed to produce 50% of Rmax rose to 5.6 Hz. Thus both adenosine and glucagon produced modulation of sympathetic nerve-induced capacitance responses without having significant effects on basal blood volume. Adenosine, by virtue of its marked effects on arterial resistance vessels (at substantially lower doses than those used here) and the relative lack of effect on venous capacitance vessels, may be useful for producing clinical afterload reduction without venous pooling.     

Bactericidal effect of chlorine on motile Aeromonas spp. in drinking water supplies and influence of temperature on disinfection efficacy

The susceptibility of toxigenic Aeromonas spp. to free chlorine in drinking water supplies, and the influence of environmental temperature on the bactericidal activity of the oxidant, were evaluated. The results showed inactivation curves characterized by an initial phase of rapid reduction of viable cells followed by a slow inactivation of bacteria. The effect of the chlorine compound was markedly influenced by water temperature. At a summer water temperature (20 °C), the efficacy of the chlorine concentrations tested was found to be two to three times lower compared to that found at a winter temperature (5 °C). Resistance was moderately, but significantly, greater in Aer. hydrophila vs Aer. caviae and Aer. sobria , but all Aeromonas spp. were more susceptible than Escherichia coli . Selective pressure with free chlorine did not produce Aeromonas cells with higher levels of chlorine resistance.     

Chlorine inactivation of human norovirus,murine norovirus and poliovirus in drinking water

Aims: To evaluate the reduction of human norovirus (HuNoV) by chlorine disinfection under typical drinking water treatment conditions. Methods and Results: HuNoV, murine norovirus (MNV) and poliovirus type 1 (PV1) were inoculated into treated water before chlorination, collected from a drinking water treatment plant, and bench‐scale free chlorine disinfection experiments were performed for two initial free chlorine concentrations, 0·1 and 0·5 mg l^?1. Inactivation of MNV reached more than 4 log₁₀ after 120 and 0·5 min contact time to chlorine at the initial free chlorine concentrations of 0·1 and 0·5 mg l^?1, respectively. Conclusions: MNV was inactivated faster than PV1, and there was no significant difference in the viral RNA reduction rate between HuNoV and MNV. The results suggest that appropriate water treatment process with chlorination can manage the risk of HuNoV infection via drinking water supply systems. Significance and Impact of the Study: The data obtained in this study would be useful for assessing or managing the risk of HuNoV infections from drinking water exposure.     

Effect of retrotestosterone on accessory sex organs & spermatogenesis of rat

Retrotestosterone (17beta-hydroxy 9beta 10alpha androst 4-en 3 one) (RT), testosterone propionate (TP), and a combination of TP and RT were administered to adult male rats in order to study the effects of such treatment on male sex organs and spermatogenesis. Although TP treatment did not produce significant reduction in testis weight, RT and RT+TP did. Seminal vesicle (SV) weight was increased by TP treatment and TP+RT treatment, but it was decreased with the RT treatment. Ventral prostate (VP) weight was increased significantly by TP and TP+RT treatment, whereas RT did not alter VP weight. The The pituitary weight of RT- and RT+TP-treated rats was significantly reduced but that of the TP rats was unaltered. Resting spermatocytes, pachytene spermatocytes, Stage 7 spermatids, and spermatogonia were increased in all treatment groups. In castrated rats, the increase in VP and SV weight was significant in the group treated with TP, but in the RT-treated group, S V and VP weights were significantly reduced. Simultaneous administration of TP and RT in 1:1, 1:4, and 1:8 ratios failed to produce statistically significant increases in SV and VP weight. The group treated with 1:20 ratio of RT:TP produced highly significant incre ases in SV and VP weights. In the spermatodynamic study, results showed that RT is comparatively more potent than TP in stimulating spermatogenesis. RT+TP treatment produced maximum increase in the count of resting and pachytene spermatocytes, whereas spermatogonia and Stage 7 spermatids were more than in the TP-treated group but less than in the RT-treated group. The findings indicate that RT is weakly androgenic and unable to stimulate accessory organs but that it is able to block the effect of endogenous androgen on the target tissue.     

The effect of weight loss on serum concentration of interleukine-6 (IL-6) and insulin resistance

INTRODUCTION: Interleukine-6 (IL-6) is one of the cytokines, excreting by adipocytes, which increases in obesity. These cytokines participate in very complicated mechanisms of developing insulin resistance that accompany obesity. The aim of the study was to: 1) evaluate the influence of weight loss on insulin resistance and serum concentration of IL-6, 2) evaluate the hypothetical association between serum concentration of IL-6 and the improvement of insulin sensitivity in obese women after weight loss. MATERIAL AND METHODS: The study involved 27 obese women (age 40.3 +/- 11.1 year; BMI 37.4 +/- 5.2 kg/m(2)) with insulin resistance diagnosed using HOMA index, without concomitant diseases and without any medication. All the patients participated in complex weight reduction treatment (diet, physical activity and psychotherapy). Before and after weight reduction therapy weight and height were measured, body composition was determined using bioimpedance analysis. Serum concentration of glucose was determined by enzymatic procedure, serum concentration of insulin was measured by radioimmunoassay, serum concentration of IL-6 was measured by ELISA. HOMA index was calculated with formula. RESULTS: The mean weight loss after 3-month was 9.2 +/- 4.5 kg (approximately 10% of initial weight). After weight reduction significant decreases in HOMA index, insulin and IL-6 concentrations was observed. However, no correlations between changes in insulin concentrations, HOMA index and decrease of IL-6 concentration were showed. We observed significant correlations between DeltaHOMA and DeltaBMI (r = 0.48; p = 0.012) and Delta percentage fat mass (r = 0.39; p < 0.05). CONCLUSIONS: A moderate weight loss improves insulin sensitivity and decreases serum concentrations of IL-6. However improvement of insulin sensitivity is the effect of fat mass reduction and does not change serum concentration of IL-6.     

The cell in starvation; physiological and chemical observations

Observations made on Amoeba proteus during total inanition revealed the following changes: Dry weight declined progressively, but at a decreasing rate to about 45 per cent of the initial levels when determined in surviving members of a dying population. Protein fell to about 70 per cent of the initial level. A hexane-alcohol extractable component fell during early starvation then rose to about its initial absolute level in the dying cells. While initially most of this component is probably lipide, it is not certain that other materials are not extracted during cell degeneration. Survival as a function of cell size was studied. No advantage in survival was apparent for any size class. Nucleate cell "halves" likewise showed no survival time differential, unlike a highly significant decrease in the survival of enucleate portions. The maintenance of the initial variance about the mean population weight (after hexane-alcohol extraction) during starvation, likewise supports the idea that survival depends largely on concentration parameters.     

Adiponectin is regulated differently by chronic exercise than by weight-matched food restriction in hyperphagic and obese OLETF rats

This study was intended to investigate the effects of chronic exercise on blood adiponectin level. Male Otsuka Long Evans Tokushima Fatty (OLETF) rats (26 weeks old) were divided to undergo either regular 12-week wheel running exercise (EX) or to have food restriction (FR) that resulted in body weight reduction similar to that in EX. Both EX and FR induced similar reductions in body weight, abdominal fat volume and plasma leptin concentration compared with ad libitum control. At the end of the study, although plasma adiponectin level was increased in FR, the adiponectin level did not change in EX. Plasma testosterone level was higher in EX than in either of the other two groups. A significant inverse relationship existed between plasma levels of adiponectin and testosterone for all groups. Our results suggested that 12-week voluntary wheel running exercise induces different effects on plasma adiponectin level than does food restriction, despite similar reduction in body weight, fat tissue mass and plasma leptin concentration. We speculate that the elevated plasma testosterone concentration might offset any hyperadiponectinemic effect of body weight and fat volume reduction in exercising rats.