M. Nichols

Nonlinear optical imaging to evaluate the impact of obesity on mammary gland and tumor stroma.

Obesity is an established risk factor for breast cancer incidence and mortality. However, the mechanism that links obesity to tumorigenesis is not well understood. Here we combined nonlinear optical imaging technologies with an early-onset diet-induced obesity breast cancer animal model to evaluate the impact of obesity on the composition of mammary gland and tumor stroma. Using coherent anti-Stokes Raman scattering and second harmonic generation on the same platform, we simultaneously imaged mammary adipocytes, blood capillaries, collagen fibrils, and tumor cells without any labeling. We observed that obesity increases the size of lipid droplets of adipocytes in mammary gland and collagen content in mammary tumor stroma, respectively. Such impacts of obesity on mammary gland and tumor stroma could not be analyzed using standard two-dimensional histologic evaluation. Given the importance of mammary stroma to the growth and migration of tumor cells, our observation provides the first imaging evidence that supports the relationship between obesity and breast cancer risk.

An ex vivo co-culture model system to evaluate stromal–epithelial interactions in breast cancer

Breast cancer is the most commonly diagnosed cancer among women worldwide. High breast cancer incidence and mortality rates, especially in obese patients, emphasize the need for a better biological understanding of this disease. Previous studies provide substantial evidence for a vital role of the local extracellular environment in multiple steps of tumor progression, including proliferation and invasion. Current evidence supports the role of adipocytes as an endocrine organ, which produces steroid hormones, pro‐inflammatory cytokines and adipokines, such as leptin. To further define the role of the mammary microenvironment on tumorigenesis, we have developed an adipose‐tumor epithelial cell co‐culture system designed to reproduce the in vivo mammary environment. We validate this model through use of coherent anti‐Stokes Raman scattering (CARS) microscopy, a label‐free vibrational imaging technique. CARS analysis demonstrates the sustained viability of the adipocytes, and that mammary cancer cell morphology parallels that of tumors in vivo. Also, characterized was the influence of mammary adipose tissue on tumor cell growth and migration. Adipose tissue co‐cultured with mammary tumor epithelial cells, in the absence of any serum or supplemental growth factors, resulted in substantial increases in growth and migration of tumor cells. In conclusion, this novel co‐culture system provides an ideal model to study epithelial–stromal interactions in the mammary gland. Understanding the relationship between adipose tissue, the most abundant and least studied component of the breast stroma and tumor epithelial cells is critical to clarifying the influence of obesity on the development, progression and prognosis of breast cancer.

Effects of environmental temperature on hypothermia and neuroendocrine changes induced by soman

The effects of environmental temperature on body temperature and neuroendocrine parameters were evaluated following a single acute dose (60 micrograms/kg) of soman. Plasma levels of corticosterone, glucose, and free fatty acids, as well as acetylcholinesterase activity in plasma, erythrocytes, and brain were determined over a 96-hr time course in rats maintained at 23-25, 14-16, and 3-5 degrees C. Considerable inhibition of plasma and erythrocyte acetylcholine hydrolysis activity was observed after administration of soman at all three environmental temperatures. The degree of hypothermia in all soman-treated rats in each environment tested was associated with the amount of brain acetylcholinesterase inhibition. In animals maintained at 23-25 and 14-16 degrees C, changes in plasma corticosterone levels were influenced by central acetylcholine hydrolysis. Hyperglycemia was found only in rats with greater than 45% brain inhibition regardless of environmental temperature. However, the plasma concentration of glucose over the 96 hr test period varied in relation to the hydrolysis of acetylcholine in soman-treated rats. Recovery of plasma acetylcholinesterase was more rapid at lower environmental temperatures. A greater inhibition of central acetylcholinesterase was found in soman-treated rats exposed to 3-5 degrees C. Soman may be more toxic at low environmental temperatures.

Antagonism of physostigmine induced hypothermia and neuroendocrine changes following exposure to different environmental temperatures.

1. The magnitude of physostigmine-induced hypothermia increased with decreasing environmental temperature. 2. The hypothermic response was accompanied by significant changes in plasma levels of corticosterone, glucose and fatty acids. 3. Central cholinergic mediation appears to be a significant component of physostigmine-induced hypothermia and neuroendocrine changes at moderate temperature. 4. At lower ambient temperatures cholinergic blockers produced less antagonism of physostigmine-induced effects. 5. The decreased effectiveness of cholinergic blockers at low environmental temperatures and the increased plasma fatty acid levels under almost all conditions studied may be of importance in considering long term therapy with cholinergic agonists.

Time course of physostigmine effects on neuroendocrine responding at varying environmental temperatures

1. Hypothermia was found to be related to both the dose of physostigmine and the environmental temperature. 2. Plasma corticosterone levels were elevated above controls regardless of dose of physostigmine or environmental temperature. 3. Plasma free fatty acid levels appeared to be inversely related to physostigmine-induced hypothermia. 4. A hyperglycemic response was observed under all experimental conditions at 0.5 hours and 1.0 hour post injection. 5. Significant inhibition of brain acetylcholinesterase was observed, whereas, plasma and erythrocyte acetylcholinesterase activity was inconsistent.

Amphetamine enantiomers and rat consummatory behavior: a new perspective

The anorectic actions of amphetamine have been known for over forty years, yet the precise relationship(s) between the enantiomeric forms of the drug and anorexia is not clearly understood. Previous studies have utilized primarily racemic amphetamine or its d-isomer in the analysis of feeding behavior. In the present investigation, a detailed examination of the effects of single and repeated equiactive doses of d- and l-amphetamine on food consumption by adult male rats was undertaken with emphasis on aspects of tolerance development. Weight loss and pattern of daily food intake differed depending upon the isomer, dose, and degree of tolerance. Two types of tolerance were seen with both isomers, an initial tolerance with a decrease in efficacy between days 1 and 2, and a later gradual decrease in efficacy over 12 days of repeated dosage. Rats tolerant to the anorectic effects of d-amphetamine were only minimally affected when challenged with an equiactive anorectic dose of l-amphetamine, while rats tolerant to the anorectic effects of l-amphetamine showed a significantly depressed food intake and modified eating pattern when challenged with an equiactive dose of d-amphetamine. Therefore two-way cross tolerance, as previously assumed, does not completely exist between low equiactive doses of d- and l-amphetamine.