Equine Aging and the Oocyte: A Potential Model for Reproductive Aging in Women

Numerous similarities in reproductive aging have been documented between the mare and woman. Aging is associated with a decline in fertility. In mares and women, oocyte transfer procedures were initially used to establish that oocyte donor age is associated with oocyte quality. Age-associated differences in oocytes include altered morphology, gene expression, and developmental potential. Reactive oxygen species and mitochondrial dysfunction are thought to be important contributors to loss of oocyte quality. In the woman, aneuploidy is a primary consideration with maternal aging. Although misalignment of chromosomes during meiosis has been observed in the mare, less is known in this area. Reproductive aging will be reviewed in the mare and compared with the woman with emphasis on factors that affect oocyte quality and developmental potential. Areas in which the mare could be used as a research model to study reproductive aging in women will be highlighted.

Enhancement or inhibition of tumor growth by interferon: dependence on treatment protocol

MSC cells are tumor cells originally induced in BALB/c mice by Moloney sarcoma virus. In these studies we demonstrated that, although these tumor cells are sensitive in vitro both to lysis by NK or NK-like cells and to the growth-inhibitory effect of murine L-cell interferon (IFN), the growth of the tumor in vivo could be either inhibited or enhanced by IFN. The outcome of in vivo IFN treatment was dependent on the timing and route of IFN administration relative to tumor challenge. IFN given systematically at the same time as tumor challenge resulted in enhancement of primary tumor formation, rate of tumor growth and subsequent progressive tumor growth. In contrast, IFN administered at the site of tumor inoculation on days 1-3 after tumor challenge inhibited tumor formation and growth. Histopathology of tissue sections obtained from the site of tumor challenge confirmed these results. Similar studies performed in mice given 450 rads of X-irradiation showed that IFN could still inhibit tumor growth when administered at the site of tumor inoculation on days 1-3 after tumor challenge. IFN administered simultaneously with tumor challenge, however, did not enhance tumor growth in irradiated mice. These results are consistent with the interpretation that 1) inhibition of MSC-induced tumor growth by IFN has a radioresistant component and 2) the enhancement of MSC-induced tumor formation by IFN is dependent on interaction with a radiosensitive population of cells, possibly lymphoid cells.

Intracellular mechanisms of lymphoid cell activation

Activation of lymphocytes for proliferation is associated with the appearance of an intracellular factor (ADR) that can induce DNA synthesis in isolated quiescent nuclei. ADR plays a role in the sequence of intracellular events leading to activation for IL-2-mediated proliferation. Because of the nature of the defining assay, the locus of ADR action appears to be near the terminal end of the transduction pathway. Interestingly, although lymphocytes from aged individuals respond poorly to proliferative stimuli, they appear to produce normal to above-normal levels of ADR. In contrast, their nuclei are only poorly responsive to stimulation by ADR. Preparations rich in ADR activity have proteolytic activity as well. In addition, aprotinin, as well as a variety of other protease inhibitors, suppresses ADR-induced DNA synthesis in a dose-dependent manner. ADR activity can be removed from active extracts by absorption with aprotinin-conjugated agarose beads, and can be removed from the beads by elution at pH 5.0. This latter suggests that ADR itself is a protease. However, its endogenous substrate is not yet known. We have also detected an inhibitor of ADR activity in the cytoplasm of resting lymphocytes. This is a heat-stable protein of approximately 60,000 Da. In addition to suppressing the interaction of ADR with quiescent nuclei, the inhibitor can suppress DNA synthetic activity of replicative nuclei isolated from mitogen-activated lymphocytes. Interestingly, these preparations had little or no activity on replicative nuclei derived from several neoplastic cell lines. The resistance of tumor cell nuclei to spontaneously occurring cytoplasmic inhibitory factors such as the one described here may provide one explanation for the loss of growth control in neoplastic cells.

Modulation of topoisomerase activities by tumor necrosis factor

A number of chemotherapeutic agents which inhibit the DNA topoisomerases markedly potentiate cell death mediated by tumor necrosis factor, suggesting a role for these enzymes in the TNF cytotoxic mechanism. To investigate this possibility, topoisomerase I and II activities were assayed following TNF addition to murine L929 cells. Topoisomerase I and II activities increased within 15 min of TNF addition and returned to baseline levels within 1 and 2 hr, respectively. The increases in both topoisomerase activities were blocked by H-7 (but not H-8) and similar increases were seen following PMA addition. However, concentrations of H-7 which blocked the increased topoisomerase activities had no effect on TNF cytotoxicity nor on the enhancement of TNF cytotoxicity by topoisomerase inhibitors. Thus, in these cells topoisomerase activities are directly modified by TNF during the initial phases of a cytotoxic response. However, neither TNF cytotoxicity nor the enhancement of TNF cytotoxicity by topoisomerase inhibitors appears to require the TNF-mediated increases in topoisomerase activities.

IMSIS: An instrumented microphysiological system with integrated sensors for monitoring cellular metabolic activities

Well plates are widely used in biological experiments, particularly in pharmaceutical sciences and cell biology. Its popularity stems from its versatility to support a variety of fluorescent markers for high throughput monitoring of cellular activities. However, using fluorescent markers in traditional well plates has its own challenges, namely, they can be potentially toxic to cells, and thus, may perturb their biological functions; and it is difficult to monitor multiple analytes concurrently and in real-time inside each well. This paper presents a fully instrumented microphysiological system with integrated sensors (IMSIS) with a similar well format. Each well in the microphysiological system has a set of sensors for monitoring multiple metabolic analytes in real-time. The IMSIS platform is supported by integrated bioelectronic circuits and a graphical user interface for easy user configuration and monitoring. The system has integrated microfluidics to maintain its microphysiological environment within each well. The IMSIS platform currently incorporates O2, H2O2, and pH sensors inside each well, allowing up to six wells to perform concurrent measurements in real-time. Furthermore, the architecture is scalable to achieve an even higher level of throughput. The miniaturized design ensures portability, suitable for small offices and field applications. The IMSIS platform was successfully used to monitor in real-time the mitochondrial functions of live bovine embryos in O2 consumption, H2O2 release as an indication of ROS production, and extracellular acidity changes before and after the introduction of external substrates.

Adiposity in mares induces insulin dysregulation and mitochondrial dysfunction which can be mitigated by nutritional intervention

Obesity is a complex disease associated with augmented risk of metabolic disorder development and cellular dysfunction in various species. The goal of the present study was to investigate the impacts of obesity on the metabolic health of old mares as well as test the ability of diet supplementation with either a complex blend of nutrients designed to improve equine metabolism and gastrointestinal health or L-carnitine alone to mitigate negative effects of obesity. Mares (n = 19, 17.9 ± 3.7 years) were placed into one of three group: normal-weight (NW, n = 6), obese (OB, n = 7) or obese fed a complex diet supplement for 12 weeks (OBD, n = 6). After 12 weeks and completion of sample collections, OB mares received L-carnitine alone for an additional 6 weeks. Obesity in mares was significantly associated with insulin dysregulation, reduced muscle mitochondrial function, and decreased skeletal muscle oxidative capacity with greater ROS production when compared to NW. Obese mares fed the complex diet supplement had better insulin sensivity, greater cell lipid metabolism, and higher muscle oxidative capacity with reduced ROS production than OB. L-carnitine supplementation alone did not significantly alter insulin signaling, but improved lipid metabolism and muscle oxidative capacity with reduced ROS. In conclusion, obesity is associated with insulin dysregulation and altered skeletal muscle metabolism in older mares. However, dietary interventions are an effective strategy to improve metabolic status and skeletal muscle mitochondrial function in older mares.