Folic Acid Supplementation Promotes Mammary Tumor Progression in a Rat Model

Folic acid supplementation may prevent the development of cancer in normal tissues but may promote the progression of established (pre)neoplastic lesions. However, whether or not folic acid supplementation can promote the progression of established (pre)neoplastic mammary lesions is unknown. This is a critically important issue because breast cancer patients and survivors in North America are likely exposed to high levels of folic acid owing to folic acid fortification and widespread supplemental use after cancer diagnosis. We investigated whether folic acid supplementation can promote the progression of established mammary tumors. Female Sprague-Dawley rats were placed on a control diet and mammary tumors were initiated with 7,12-dimethylbenza[a]anthracene at puberty. When the sentinel tumor reached a predefined size, rats were randomized to receive a diet containing the control, 2.5x, 4x, or 5x supplemental levels of folic acid for up to 12 weeks. The sentinel mammary tumor growth was monitored weekly. At necropsy, the sentinel and all other mammary tumors were analyzed histologically. The effect of folic acid supplementation on the expression of proteins involved in proliferation, apoptosis, and mammary tumorigenesis was determined in representative sentinel adenocarcinomas. Although no clear dose-response relationship was observed, folic acid supplementation significantly promoted the progression of the sentinel mammary tumors and was associated with significantly higher sentinel mammary tumor weight and volume compared with the control diet. Furthermore, folic acid supplementation was associated with significantly higher weight and volume of all mammary tumors. The most significant and consistent mammary tumor-promoting effect was observed with the 2.5x supplemental level of folic acid. Folic acid supplementation was also associated with an increased expression of BAX, PARP, and HER2. Our data suggest that folic acid supplementation may promote the progression of established mammary tumors. The potential tumor-promoting effect of folic acid supplementation in breast cancer patients and survivors needs further clarification.     

Spontaneous Osteonecrosis of the Knee in <Emphasis Type="Italic">Macaca mulatta</Emphasis>

Spontaneous osteonecrosis of the knee (SONK) is a common disease in elderly humans. Clinically, SONK presents with the sudden onset of severe knee joint pain, usually in the load-bearing area of the medial compartment of the knee. Articular cartilage lesions are secondary to subchondral trabecular bone necrosis. These biochemical and structural changes in the bone and cartilage alter the biomechanics of the joint, which may then lead to secondary osteoarthritis and ultimately joint destruction. We observed 3 cases of osteonecrosis affecting the knee joint of free-ranging Macaca mulatta (rhesus macaques). The histopathology of these cases consists of defects in the subchondral bone with articular cartilage necrosis and repair. The defects were associated histologically with secondary osteoarthritis in 2 cases. The osteonecrotic lesions in the macaques resemble closely spontaneous osteonecrosis of the knee as seen in humans. This is the first report of spontaneous osteonecrosis of the knee in nonhuman primates.     

Rhesus monkeys (Macaca mulatta) as a model for calcium pyrophosphate dihydrate crystal deposition disease

Calcium pyrophosphate dihydrate crystal deposition disease (CPDD) was recognized in 4 of 30 free-ranging rhesus macaques. By means of tissue radiography, focal radiodensities were noted in lumbar intervertebral discs, menisci, and articular cartilage. Crystal deposits were identified as calcium pyrophosphate dihydrate (Ca2P2O7 X 2H2O) by means of X-ray diffraction. The pathogenesis of calcium pyrophosphate dihydrate arthropathy in man remains elusive. However, with the recognition of this arthritis in a well defined population of aged nonhuman primates, a model now exists to facilitate the study of this disease.     

Struvite urolithiasis in a B6C3F1 mouse.

In a 2 year carcinogenicity bioassay using B6C3F1 mice, one male mouse developed clinical signs near termination of the study, comprising skin sores around the prepuce, penile prolapse and urine scalding. The predominant finding at necropsy was a markedly distended urinary bladder filled with numerous crystallized particles. Microscopically, there was subacute cystitis with marked hyperplasia of the transitional epithelium. X-ray diffraction analysis of the crystals showed a diffraction pattern characteristic of struvite (ammonium magnesium phosphate). The implications of the spontaneous occurrence of bladder stones in rodents on long-term toxicology studies are discussed.     

Cardiovascular response to exercise in younger and older men

Measurements of cardiac performance for humans at various ages is influenced by the variable examined, the population and techniques employed, and the factors that co-vary with age, including the presence of disease and physical conditioning. Interstudy differences in the extent to which occult coronary disease is present in older subjects and in the level of physical conditioning among subjects may underlie the variable perspectives contained in the literature of how aging affects cardiovascular function. In carefully screened, highly motivated but not athletically trained community-dwelling subjects, resting cardiovascular parameters are not age related except for systolic blood pressure, which increases with age. During vigorous exercise the mechanisms used to achieve a high level of cardiac output shift from a dependence on a catecholamine-mediated increase in heart rate and inotropy to a dependence on the Frank Starling mechanism. One reason for the age difference in cardiovascular response to exercise may be a diminished responsiveness to beta-adrenergic stimulation in these subjects. In other elderly subjects who cannot exercise to high work loads, a decline in stroke volume as well as heart rate at peak exercise has been observed. Whether the inability of these individuals to augment stroke volume is caused by a decrease in the ability of the heart to increase diastolic filling, by a decrease in systolic pump function caused by an increased afterload, by intrinsic myocardial contractile defects, or by a greater diminution of the cardiovascular response to beta-adrenergic stimuli is presently unknown.     

Micropurification and amino acid sequence of β-casomorphin-8 in milk from a woman with postpartum psychosis

Milk was obtained from a woman with acute postpartum psychosis and with ongoing lactation. Defatted samples were subjected to micropurification and collected fractions were analyzed by means of their β-casomorphin-8 immunoreactivity. Immunoreactive material with the same chromatographic properties as synthetic human β-casomorphin-8 was determined by amino acid sequence analysis to be Tyr-Pro-Phe-Val-Glu-Pro-Ile-Pro. Its molecular mass was determined by fast atom bombardment-mass spectrometry to be 962.3 Da. These determinations, which ultimately identify the immunoreactive material as human β-casomorphin-8, represent the first structural identification of a β-casomorphin peptide from a body fluid.     

Isolation and characterization of sulphated and nonsulphated forms of cholecystokinin-58 and their action on gallbladder contraction.

Cholecystokinin (CCK) exists in multiple molecular forms with different polypeptide lengths and the absence or presence of sulphation. We have isolated sulphated and nonsulphated forms of CCK-58 from porcine intestine and have determined their bioactivities in a guinea-pig gallbladder contraction assay. Both forms co-eluted in cation-exchange chromatography and in several rounds of reverse-phase (RP)-HPLC, but separated upon RP-HPLC using a water/acetonitrile system with heptafluorobutyric acid as counter ion. Nonsulphated CCK-58 was the form detected by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry because of desulphation in that process. The biological activity of CCK-58 and CCK-33 is equipotent, although the kinetics of the response differ. Sulphated CCK-58 was found to be 35 times more potent than nonsulphated CCK-58. In contrast, sulphated CCK-8 is 150 times more potent than nonsulphated CCK-8, and for sulphated and nonsulphated CCK-33, the activities differ by a factor of 100. This type of correlation indicates that the N-terminal end of CCK-58 partially compensates for the decrease in activity arising from the lack of sulphated tyrosine. Given its fairly high bioactivity, nonsulphated CCK-58 may have a physiological significance.