Portrait of a canine probiotic Bifidobacterium--from gut to gut.

The gastrointestinal environment is a complex interactive system involving the host, ingested dietary components, and numerous microbial species. We hypothesized that isolation and screening of Lactobacilli and Bifidobacteria adherent to healthy canine gastrointestinal tissue would yield strains with commensal activity in canines. The aims of this study were (1) to isolate a bank of commensal organisms from the canine gastrointestinal tract; (2) to screen these novel microbial isolates for potential probiotic effects; (3) to select one organism from these screens and test its impact on the canine microbiota. Lactic acid bacteria (LAB) were isolated from resected canine gastrointestinal tissue and screened in vitro for putative probiotic activities. Murine studies examined gastrointestinal transit and inhibition of Salmonella typhimurium translocation. One strain was progressed to a canine study where its impact on the gastrointestinal microbiota was determined. Of the 420 isolates from the canine gut, 62 strains were characterised as LAB. Following assessment of the strain bank with regard to pH sensitivity, bile resistance, pathogen inhibition and survival following freeze-drying, four Lactobacillus strains and two Bifidobacteria strains were selected for further examination. Bifidobacterium animalis AHC7 adhered to epithelial cells, transited the murine gastrointestinal tract to high numbers and significantly reduced S. typhimurium translocation. B. animalis AHC7 consumption significantly reduced the carriage of Clostridia, in particular Clostridium difficile, in dogs. This study describes the isolation and screening of canine-derived bacterial strains with commensal traits. The results demonstrate that B. animalis AHC7 has significant potential for improving canine gastrointestinal health.

Metabolic activity of probiotics-oxalate degradation.

Urinary tract stones are an important clinical problem in human and veterinary medicine. Hyperoxaluria is the single strongest promoter of kidney stone formation. The aims of the present study were to (a) evaluate oxalate degradation by a range of Bifidobacteria species and Lactobacillus species isolated from the canine and feline gastrointestinal tract in vitro and (b) to determine the impact of oxalate degradation by selected strains in vivo. The bacteria were grown in oxalate-containing media and their ability to degrade oxalate in vitro was determined using reverse-phased HPLC. Bifidobacteria species and Lactobacillus species that degraded oxalate in vitro and survived gastric transit were selected for further examination. The selected probiotics were fed to rats for 4 weeks. Urine was collected at week's 0, 2 and 4 and oxalate levels determined by HPLC. In vitro degradation was detected for 11/18 of the Lactobacillus species. In contrast, the capacity to degrade oxalate was not detected for any of the 13 Bifidobacterium species tested. Lactobacillus animalis 223C, Lactobacillus murinus 1222, L. animalis 5323 and L. murinus 3133 were selected for further investigation in a rat model. Urinary oxalate levels were significantly reduced (p<0.05) in animals fed L. animalis 5323 and L. animalis 223C but were unaltered when fed L. murinus 1222, L. murinus 3133 or placebo. Probiotic organisms vary widely in their capacity to degrade oxalate. In vitro degradation does not uniformly translate to an impact in vivo. The results have therapeutic implications and may influence the choice of probiotic, particularly in the setting of enteric hyperoxaluria.

Testosterone and food restriction modulate hepatic lycopene isomer concentrations in male F344 rats.

We previously demonstrated that the castration of male rats profoundly increases hepatic lycopene compared with intact controls. Here we further characterized the role of testosterone in modulating hepatic lycopene accumulation and isomer patterns in male rats. Furthermore, because castration significantly decreases ad libitum food consumption, we investigated the influence of food restriction on lycopene metabolism. Forty male F344 rats 8 wk of age were randomly assigned to one of four treatments (n = 10/group): 1) intact, free access to food, 2) castration, free access to food, 3) castration plus testosterone implants, free access to food and 4) intact, 20% food restricted. All rats were fed an AIN-based diet with 0.25 g lycopene (as 10% water-soluble beadlets)/kg diet for 3 wk. Serum testosterone was 5.31 +/- 1.46 nmol/L in intact controls allowed free access to food, reduced in castrated animals (0.52 +/- 0.10, P < 0.0001 versus controls) and intact, food-restricted rats (1.53 +/- 0.49 nmol/L, P < 0.0001 versus controls) and greater (17.23 +/- 3.09 nmol/L) in castrated rats administered testosterone (P < 0.0001 versus controls). Castrated rats accumulated approximately twice as much liver lycopene (74.5 +/- 8.5 nmol/g; P < 0.01 versus controls) as intact rats allowed free access to food (39.5 +/- 5.0) despite 13% lower dietary lycopene intake (P < 0.001; 3.38 +/- 0.07 versus 3.95 +/- 0.06 mg lycopene/d). Testosterone replacement in castrated rats returned liver lycopene concentrations (32.5 +/- 5.5 nmol lycopene/g with 3.76 +/- 0.05 mg dietary lycopene/d) to those observed in intact rats. Food restriction resulted in a 20% decrease in lycopene intake but significantly increased liver lycopene by 68% (66.3 +/- 7.9 nmol lycopene/g with 3.38 +/- 0.00 mg lycopene/d) compared with controls and castrated rats administered testosterone. These results suggest that androgen depletion and 20% food restriction increase hepatic lycopene accumulation. We hypothesize an endocrine and dietary interaction, where higher androgen concentrations and greater energy intake may stimulate lycopene metabolism and degradation.

beta-Carotene stability and uptake by prostate cancer cells are dependent on delivery vehicle.

Cell culture systems provide an opportunity to evaluate the effects of carotenoids on molecular and cellular processes involved in proliferation and differentiation of prostate cancer cells. The stability and cellular uptake of beta-carotene (BC) by prostate cancer cells were investigated in vitro by use of various delivery methods and three human prostate adenocarcinoma cell lines: PC-3, DU 145, and LNCaP. Recovery of BC from the media (prepared from water-dispersible BC beadlets) significantly (p < 0.05) decreased after 12 hours in culture and continued to significantly decrease (p < 0.05) after 24, 48, 72, and 96 hours, an observation primarily attributed to BC degradation rather than isomerization, metabolism, or cellular uptake. The uptake of BC by prostate cancer cells was compared when delivered by tetrahydrofuran, BC-enriched bovine serum, water-dispersible BC beadlets, and artificial liposomes. Recovery of BC after three days in culture from enriched bovine serum medium was significantly (p < 0.05) greater than recovery from medium prepared by beadlets, tetrahydrofuran, or artificial liposomes. We conclude that BC is relatively unstable in vitro and that degradation products may contribute to biological responses. Furthermore, our studies indicate that enriched bovine serum provides a stable and physiological approach to carotenoid treatment of cells in culture.

Tissue lycopene concentrations and isomer patterns are affected by androgen status and dietary lycopene concentration in male F344 rats.

Diets rich in lycopene from tomato products as well as greater concentrations of blood lycopene have been associated with a decreased risk for prostate cancer in epidemiologic studies. However, little is known about factors modulating lycopene absorption, metabolism and tissue distribution in humans and animal models of prostate cancer. A 2 x 4 factorial design was used to measure the effects of androgen status (castrated vs. intact), dietary lycopene concentration (0.00-5.00 g/kg lycopene) and their interaction on tissue lycopene accumulation and isomer patterns in male F344 rats. Male F344 rats ( 14 wk old; 44 castrated, 44 intact) were randomly assigned to one of four diets containing total lycopene concentrations of 0.00, 0.05, 0.50 or 5.00 g/kg as beadlets and fed for 8 wk. Tissue total lycopene and cis/trans lycopene profiles were determined by HPLC. Tissue and serum lycopene concentrations increased significantly (P < 0.01) as dietary lycopene levels increased between 0.00 and 0.50 g/kg. No further increases in serum or tissue concentrations were seen in rats fed dietary lycopene between 0.50 and 5.00 g/kg. As dietary lycopene increased, so did the percentage of cis lycopene in the liver (P < 0.05), due primarily to an increase in the 5-cis isomer. Castrated rats accumulated twice (P < 0.01) the liver lycopene as compared to intact controls, with no effect of castration on serum lycopene or adrenal, kidney, adipose, or lung tissue concentration. Livers from castrated rats had a greater proportion of cis-lycopene than those of intact rats (P < 0.05). A significant interaction between dietary lycopene concentration and androgen status was seen for liver lycopene concentration (P < 0.01). We conclude that serum and tissue lycopene reaches a plateau between 0.05 and 0.50 g/kg dietary lycopene, the tissue cis/trans lycopene ratio increases with greater dietary lycopene and androgens modulate hepatic lycopene metabolism.

Beta-carotene modulates human prostate cancer cell growth and may undergo intracellular metabolism to retinol.

Epidemiologic and animal studies provide support for a relationship between high intakes of carotenoids from fruits and vegetables with reduced risk of several malignancies including prostate cancer. The highly controlled environments of in vitro systems provide an opportunity to investigate the cellular and molecular effects of carotenoids. The effects of beta-carotene (BC) on in vitro growth rates, p21(WAF1) and p53 gene expression, as well as the conversion of BC to retinol were investigated in three human prostate adenocarcinoma cell lines: PC-3, DU 145 and LNCaP. In these experiments, media concentrations of 30 micromol BC/L for 72 h significantly (P < 0.05) slowed in vitro growth rates in all three cell lines, independently of p53 or p21(WAF1) status or expression. (14)C-labeled retinol was detected in prostate tumor cells incubated with (14)C-labeled BC, suggesting metabolic conversion of BC to retinol. Conversely, no (14)C-labeled retinol was detected in media incubated without prostate cancer cells. These studies support a hypothesis that in vitro biological effects of BC on prostate cells may result in part from the conversion of BC to retinol or other metabolites. The possibility that prostate cancer cells in vivo locally metabolize provitamin A carotenoids to retinol and other related metabolites may have implications for our understanding of prostate cancer etiology and the design of future prevention studies.

Review of animal models in carotenoid research.

Foods containing provitamin A carotenoids are the primary source of vitamin A in many countries, despite the poor bioavailability of carotenoids. In addition, epidemiologic studies suggest that dietary intake of carotenoids influences the risk for certain types of cancer, cardiovascular disease and other chronic diseases. Although it would be ideal to use humans directly to answer critical questions regarding carotenoid absorption, metabolism and effects on disease progression, appropriate animal models offer many advantages. This paper will review recent progress in the development of animal models with which to study this class of nutrients. Each potential model has strengths and weaknesses. Like humans, gerbils, ferrets and preruminant calves all absorb beta-carotene (betaC) intact, but only gerbils and calves convert betaC to vitamin A with efficiency similar to that of humans. Mice and rats efficiently convert betaC to vitamin A but absorb carotenoids intact only when they are provided in the diet at supraphysiologic levels. Mice, rats and ferrets can be used to study cancer, whereas primates and gerbils are probably more appropriate for studies on biomarkers of heart disease. No one animal model completely mimics human absorption and metabolism of carotenoids; thus the best model must be chosen with consideration of the specific application being studied, characteristics of the model, and the available funding and facilities.

Women in pediatrics: the experience in Quebec.

OBJECTIVES: To compare the practice patterns of female pediatricians in Quebec with those of their male counterparts and to identify specific factors influencing these practice patterns. DESIGN: Matched cohort questionnaire survey. SETTING: Primary, secondary and tertiary care pediatric practices in Quebec. PARTICIPANTS: All 146 female pediatricians and 133 of the 298 male pediatricians, matched for age as well as type and site of practice; 119 (82%) of the female and 115 (86%) of the male pediatricians responded. MAIN OUTCOME MEASURES: Demographic and family data as well as detailed information about the practice profile. RESULTS: The two groups were comparable regarding demographic data, professional work and patient care. Compared with the male respondents, the female pediatricians were younger and saw more outpatients. The mean number of hours worked per week, excluding on-call duty, was 40.5 (standard deviation [SD] 12.4) for the women and 48.9 (SD 12.0) for the men (p < 0.001). The female pediatricians were more likely than their male counterparts to have spouses who were also physicians (40%) or in another profession (45%). The female pediatricians without children worked significantly fewer hours than the male pediatricians with or without children (p < 0.001). Children (p = 0.006), but not the number of children (p = 0.452), had a significant effect on the number of hours worked by the female pediatricians. CONCLUSION: The duality of the role of female physicians as mothers and professional caregivers must be considered during workload evaluations. If the same style of practice and the increase in the proportion of female pediatricians continue, about 20% more pediatricians will be needed in 10 years to accomplish the same workload.

Drug monitoring in the perinatal patient: uses and abuses.

Measurements of concentrations for drugs from plasma or biological fluids taken together with the clinical status of the newborn infant may provide better assurance of avoiding potentially dangerous over- or underdosing. They are also useful as guidelines in requisite clinical trials and study designs. To the developmental biologist and pharmacologist, they serve as potent biological probes for various events underlying biochemical differentiation or maturation in the human fetus and newborn infant. Future research developments in neonatal drug monitoring should include improvement of micro-methods for drug assays and refinement of noninvasive techniques for monitoring drug concentrations from biological fluids and for evaluation of drug effects.