Uptake of 22Na+ by cultured dog kidney cells (MDCK).

22Na+ uptake measurements were conducted on the dog kidney cell line, MDCK, to determine the mechanism of ouabain-insensitive sodium transport. The radioisotope was found to be taken up into monolayer cultures via an ATP-independent, saturable process (Km = 40 mM). The presence of sodium on the opposite side of the membrane gave rise to a transstimulation of the 22Na+ flux. Studies utilizing potassium and valinomycin suggested that the transport system was insensitive to changes in the membrane potential. Replacement of chloride in the assay buffer with other anions did not decrease the rate of 22Na+ uptake at 14 mMNa+, but bicarbonate and acetate were stimulatory. Potassium and rubidium increased the rate of 22Na+ influx (Ka = 13mM with 14 mM NaCL in the medium). Lithium (Ki = 7.5mM) and amiloride (Ki = 1.7 x 10(-5) M) were competitive and partially (or mixed) competitive inhibitors, respectively. The data are consistent with a mechanism of sodium uptake that includes a carrier(s) capable of catalyzing net sodium uptake and sodium-sodium exchange.     

Structural requirements for the binding of prostaglandins

The binding of prostaglandins and analogs to the lipocyte PGE receptor was shown to exhibit a high degree of structural specificity. Small changes, particularly at the 9-keto or 15-hydroxy position, were found to drastically diminish interaction with the receptor. Studies of a rather substantial number of compounds revealed a close relationship between affinity for the lipocyte PGE receptor and the ability to stimulate cyclic AMP synthesis in the isolated mouse ovary. In general, activities in these two parameters follow the biological potencies generally recognized for these compounds.     

Large, rapidly evolving intergenic spacers in the mitochondrial DNA of the salamander family Ambystomatidae (Amphibia: Caudata)

We report the presence, in the mitochondrial DNA (mtDNA) of all of the sexual species of the salamander family Ambystomatidae, of a shared 240- bp intergenic spacer between tRNAThr and tRNAPro. We place the intergenic spacer in context by presenting the sequence of 1,746 bp of mtDNA from Ambystoma tigrinum tigrinum, describe the nucleotide composition of the intergenic spacer in all of the species of Ambystomatidae, and compare it to other coding and noncoding regions of Ambystoma and several other vertebrate mtDNAs. The nucleotide substitution rate of the intergenic spacer is approximately three times faster than the substitution rate of the control region, as shown by comparisons among six Ambystoma macrodactylum sequences and eight members of the Ambystoma tigrinum complex. We also found additional inserts within the intergenic spacers of five species that varied from 87-444 bp in length. The presence of the intergenic spacer in all sexual species of Ambystomatidae suggests that it arose at least 20 MYA and has been a stable component of the ambystomatid mtDNA ever since. As such, it represents one of the few examples of a large and persistent intergenic spacer in the mtDNA of any vertebrate clade.      

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GALNT11 as a new molecular marker in chronic lymphocytic leukemia

Aberrant mucin O-glycosylation often occurs in different cancers and is characterized by immature expression of simple mucin-type carbohydrates. At present, there are some controversial reports about the Tn antigen (GalNAcα-O-Ser/Thr) expression and there is a great lack of information about the [UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-Ts)] expression in chronic lymphocytic leukemia (CLL). To gain insight in these issues we evaluated the Tn antigen expression in CLL patient samples using two Tn binding proteins with different fine specificity. We also studied the expression from 14 GalNAc-Ts genes in CLL patients by RT-PCR. Our results have provided additional information about the expression level of the Tn antigen, suggesting that a low density of Tn residues is expressed in CLL cells. We also found that GALNT11 was expressed in CLL cells and normal T cell whereas little or no expression was found in normal B cells. Based on these results, GALNT11 expression was assessed by qPCR in a cohort of 50 CLL patients. We found significant over-expression of GALNT11 in 96% of B–CLL cells when compared to normal B cells. Moreover, we confirmed the expression of this enzyme at the protein level. Finally we found that GALNT11 expression was significantly associated with the mutational status of the immunoglobulin heavy chain variable region (IGHV), [?²(1) = 18.26; P < 0.0001], lipoprotein lipase expression [?²(1) = 13.72; P = 0.0002] and disease prognosis [?²(1) = 15.49; P < 0.0001]. Our evidence suggests that CLL patient samples harbor aberrant O-glycosylation highlighted by Tn antigen expression and that the over-expression of GALNT11 constitutes a new molecular marker for CLL.