Loss of calcineurin from the medial preoptic area of primiparous rats

Western blot analyses reveal that calcineurin A (CNA), which is present in the hippocampus, basolateral amygdala, parietal cortex, and MPOA of virgin males and females, is undetectable only in the MPOA of primiparous females regardless of whether they had postpartum pup contact or not. In contrast, CNB was expressed at unchanging levels in the PC and MPOA. Similarly, G(alphao) and PKA(RI) were expressed at high levels in all of the brain regions of virgin males, virgin females, and primiparous females, supporting the concept that this loss of CNA is a specific event. Understanding how and why the expression of CNA, the sole neuronal Ca2+/CaM-dependent protein phosphatase, is down-regulated specifically in the MPOA of primiparous females may yield some insight into the signal transduction events that mediate the onset of mammalian maternal behavior.

Effect of methoxychlor on implantation and embryo development in the mouse

Methoxychlor (MXC) has been shown to have adverse effects on reproductive functions. However, it has not been fully determined whether the effects of MXC on reproduction are due to its estrogenic or antiestrogenic effects. Therefore, to further elucidate the estrogenic action of this pesticide in the mouse, we studied the effect of MXC on implantation and embryo development. MXC was found to initiate implantation in most delayed implanting mice at 400 microg/g body weight. However, at the higher dose of 800 microg/g body weight, MXC initiated implantation in only 50% of animals and the number of embryos implanting was significantly decreased (P < 0.05). It was determined that MXC inhibited implantation in intact pregnant mice only when given on Day 1 or Day 2 at 800 microg/g but not at lower doses or later in the preimplantation period. Embryonic development and transport were delayed on Days 3 and 4 in these animals. Finally, reciprocal embryo transfers with donor embryos recovered from MXC-treated animals (800 microg/g body weight on Day 1) transferred to untreated recipients resulted in no implantation compared to 79% implantation when donor embryos were treated with vehicle. These data indicate that MXC acts as an estrogen agonist at the level of the uterus and oviduct but as an antiestrogen in the ovary. In addition, MXC appears to alter normal preimplantation embryonic development. These results suggest the need for further studies to assess the mechanism of action of MXC in preimplantation embryos.

Predictive correlates of shoot regeneration from potato protoplast culture

Adaptation of protoplast regeneration systems for use on untested or recalcitrant potato genotypes can be a time-consuming exercise. Callus growth and xylogenesis were evaluated as early correlates of shooting potential to shorten this process. Callus growth was of limited value for predicting organogenesis but a linear relationship was observed between xylogenesis and shooting frequency. Increases in xylem content above a minimum threshold corresponded with increases in shooting frequency. The predictive value of the relationship was tested using a simple protocol modification (the culture of calli on a filter paper base). Calli on filter paper produced more xylem elements and shoots than those plated directly on medium. The potential of xylem content as a predictive test of shooting frequency is discussed.

An inhibitor of catalase induced by cold in chilling-sensitive plants

An inhibitor of catalase accumulated when leaves of chilling-sensitive species were stored in the dark at 0 degrees C. The inhibitor could be removed from crude extracts by passing them through a column of Sephadex G-25. After this treatment, the catalase activity of extracts of chilled tissues was found to be equal to that of extracts from unchilled leaves. When chilled tissues were incubated at 20 degrees C, the inhibitor of catalase was lost, unless the tissues had been irreversibly damaged. It specifically inhibited plant catalase, and had no effect on mammalian catalase, plant malic dehydrogenase, or plant superoxide dismutase.Despite the presence of catalase inhibitor in extracts of chilled plants, no increase in the level of H(2)O(2) in chilled tissues was found, suggesting either that the inhibitor is compartmentalized and not in contact with catalase in vivo, or that the level of H(2)O(2) is controlled by means other than through catalase activity. Plant tissues normally contain H(2)O(2) which is destroyed by catalase when they are damaged. After chilling, H(2)O(2) leaking from already injured cells would not be so readily removed by the inhibited catalase, and could contribute to further injury by acting as a source of free radical oxidants.