Heparin treatment of vascular smooth muscle cells results in the synthesis of the dual‐specificity phosphatase MKP‐1

The ability of heparin to block proliferation of vascular smooth muscle cells has been well documented. It is clear that heparin treatment can decrease the level of ERK activity in vascular smooth muscle cells that are sensitive to heparin. In this study, the mechanism by which heparin induces decreases in ERK activity was investigated by evaluating the dual specificity phosphatase, MKP‐1, in heparin treated cells. Heparin induced MKP‐1 synthesis in a time and concentration dependent manner. The time‐course of MKP‐1 expression correlated with the decrease in ERK activity. Over the same time frame, heparin treatment did not result in decreases in MEK‐1 activity which could have, along with constitutive phosphatase activity, accounted for the decrease in ERK activity. Antibodies against a heparin receptor also induced the synthesis of MKP‐1 along with decreasing ERK activity. Blocking either phosphatase activity or synthesis also blocked heparin‐induced decreases in ERK activity. Consistent with a role for MKP‐1, a nuclear phosphatase, heparin treated cells exhibited decreases in nuclear ERK activity more rapidly than cells not treated with heparin. The data support MKP‐1 as a heparin‐induced phosphatase that dephosphorylates ERK, decreasing ERK activity, in vascular smooth muscle cells. J. Cell. Biochem. 110: 382–391, 2010. © 2010 Wiley‐Liss, Inc.     

Organization and chromosomal locations of Rap1a/Krev sequences in the mouse

The human RAP1A gene encodes a protein that apparently can antagonize the function of oncogenic ras genes in gene transfer experiments, but its normal function is unknown. To understand the function of this gene, we have undertaken a study of the mouse homolog, Rap1a. The complete coding sequence of a mouse Rap1a cDNA has been determined, and genomic clones representing three distinct Rap1a species were recovered. We find that Rap1a is located on distal mouse Chromosome (Chr) 3 near Nras, Ampd-1, Tshb, Ngfb, and Atp1a1. Two related sequences (Rap1a-rs1 and Rap1a-rs2) were also characterized. Rap1a-rs1, which was not localized, has a sequence very similar to the Rap1a cDNA, suggesting that it has been recently acquired by the mouse genome. Rap1a-rs2 is more distantly related to the gene sequence and is located on Chr 2 near Actc-1.     

Performance of African elephants (Loxodonta africana) and California sea lions (Zalophus californianus) on a two-choice object discrimination task

This study documents the ability of African elephants (Loxodonta africana) and California sea lions (Zalophus californianus) to perform a two-choice object discrimination task. Both species were able to perform this task. However, California sea lions took fewer trials overall to reach a criterion of 10 consecutively correct responses than did African elephants. The performance of California sea lions did not change significantly during this study. However, African elephants showed a gradual learning of the task, as exhibited by a gradual decrease in the number of trials needed to reach criterion. This performance difference may reflect differences in either visual abilities or cognitive functioning, which in turn may be influenced by either different evolutionary pressures exerted on herbivores and carnivores, or by the context in which visual information is used in the lives of these animals. © 1994 Wiley-Liss, Inc.