Nutrient and mineral composition during shoot growth in seven species of Phyllostachys and Pseudosasa bamboo consumed by giant panda.

During the annual period of bamboo shoot growth in spring, free-ranging giant pandas feed almost exclusively on the shoots while ignoring the leaves and full- height culm. Little is known about the nutritional changes that occur during bamboo shoot growth, if nutritional changes differ among species, or how these changes might influence forage selection. Our objective was to examine the nutrient and mineral composition during three phases of shoot growth (<60, 90-150 and >180 cm) for seven species of bamboo (Phyllostachys (P.) aurea, P. aureosulcata, P. bissetii, P. glauca, P. nuda, P. rubromarginata, Pseudosasa japonica) fed to captive giant pandas at the Memphis Zoo. Total dietary fiber content of bamboo shoots increased (p < 0.0001) from an overall species average of 61% dry matter (DM) at < 60 cm to 75% DM at shoot heights > 180 cm, while crude protein, fat and ash exhibited significant declines (p < 0.05). Phyllostachys nuda had the overall greatest (p = 0.007) crude protein (21% DM) and fat (4% DM) content, and lowest overall total fibre (61% DM) content compared to the other species examined. In contrast, Pseudosasa japonica had the overall lowest crude protein and fat, and relatively higher fibre content (9%, 3% and 74% respectively). Concentrations of Zn and Fe were highest in shoots <60 cm (10-50 µg/g DM) and decreased (p < 0.05) during growth in all species examined. Concentrations of Ca, Cu, Mn, Na and K varied among species and were largely unaffected by growth stage. Due to their higher concentrations of nutrients and lower fibre content in comparison to culm and leaf, bamboo shoots should be a major component of captive giant panda diets when available.

Effect of the aromatase inhibitor vorozole on estrogen and progesterone receptor content of rat mammary carcinomas induced by 1-methyl-1-nitrosourea.

Vorozole, a nonsteroidal aromatase inhibitor, impedes the post-initiation stage of chemically induced mammary carcinogenesis. While various aspects of vorozole's effects on mammary carcinoma development have been investigated, little attention has been directed to determining the estrogen receptor (ER) and progesterone receptor (PR) content of mammary carcinomas that arise despite vorozole treatment. Female Sprague-Dawley rats were given an i.p. injection of 50mg MNU/kg body weight at 21 days of age and placed on diet supplemented with 0 or 3 mg vorozole/kg, which had no effect on mammary tumor development. Histologically confirmed carcinomas were evaluated for ER and PR by immunohistochemistry. In the control group, 78.8% of carcinomas were ER positive with an ER content ranging from 13.8 to 40.0%, similar to ER content of mammary ductal epithelial cells from non-carcinogen treated animals. PR content ranged from 4.4 to 45.2% and also was similar to levels of PR observed in ductal epithelial cells. ER was not correlated with PR in mammary carcinomas (r = 0.05, p > 0.80), whereas there was a significant correlation in ductal epithelium (r = 0.86, p = 0.006). In vorozole-treated rats, no ER negative carcinomas were observed and overall ER expression by vorozole was elevated (p < 0.03). All carcinomas from vorozole-treated rats expressed PR (2.5-60.2%) and correlation between ER and PR content was numerically greater in carcinomas from vorozole-treated animals (r = 0.42, p = 0.09). These data, which are considered hypothesis generating, provide evidence that low doses of vorozole in the diet select for mammary carcinomas with an increased ER positive phenotype.

Effect of fixation and epitope retrieval on BrdU indices in mammary carcinomas.

Studies in which 5-bromo-2'-deoxyuridine (BrdU) is used to quantify rates of cell proliferation are conducted prospectively. Therefore, the opportunity exists to select conditions that optimize detection of the BrdU epitope. The objective of this study was to quantify the extent to which the BrdU epitope was masked by formalin vs methacarn fixation in the assessment of cell proliferation. Mammary carcinomas from animals pulse-labeled with BrdU were trisected. A portion was frozen and the remaining two portions were fixed in 10% neutral buffered formalin or methacarn for 24 hr, processed, embedded in paraffin, and sections stained for incorporated BrdU using a peroxidase immunohistochemical staining technique. Antigen retrieval techniques also were applied to formalin-fixed sections. Fixation in methacarn gave the highest labeling index (16.4%), which was comparable to that observed in unfixed frozen sections (17.5%). Formalin fixation alone dramatically suppressed the labeling index (0.3%), which was only partially recovered using various antigen retrieval techniques (2.1-8.1%). Methacarn fixation is recommended for prospective studies in which BrdU detection is planned because of the quantitative recovery of epitope and the simplicity of the approach.

Relationship of dietary cholesterol and cellulose in the prevention of colon cancer.

To study the effect of dietary cholesterol and cellulose on fecal sterol output and colon tumors in dimethylhydrazine-treated animals, rats were fed a basal diet supplemented with cholesterol (0.07% w/w) and/or cellulose (20% w/w). The addition of cholesterol alone to the basal diet failed to modify bile acid excretion or colon carcinogenesis. The addition of cellulose alone also failed to modify colon carcinogenesis, although it significantly decreased fecal bile acid concentration and increased daily bile acid excretion. However, when dietary cellulose was added to a cholesterol-containing diet, there was a significant decrease in colon tumor incidence (47% vs. 80%, P less than .05), accompanied by a significant increase in excretion of unmetabolized cholesterol. These data suggest that 1) the protective effect of certain fibers in colon carcinogenesis may be dependent on other dietary variables and 2) certain fecal neutral sterol profiles may be associated with colon tumor inhibition.