Photoaffinity labeling studies of the rat renal sodium bile salt cotransport system

The uptake of a photolabile taurocholate derivative, (7,7-azo-3 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonate, 7,7-azo-TC, into rat renal brush-border membrane vesicles was stimulated by Na+ and inhibited by taurocholate indicating an interaction with the Na+/bile salt cotransport system. Irradiation of membrane vesicles in the presence of 7,7-azo-TC inhibited Na+-dependent taurocholate uptake irreversibly. Photoaffinity labeling with [3H]7,7-azo-TC resulted in a predominant incorporation of radioactivity into a polypeptide with apparent molecular weight of 99,000. These results suggest that the proteins involved in Na+/bile salt cotransport are similar in renal and ileal brush-border membranes, but differ from those in hepatocytes.     

Indole alkaloid production by hairy root cultures of Catharanthus roseus

Hairy root cultures of Catharanthus roseus were established by infection with six different Agrobacterium rhizogenes strains. Two plant varieties were used and found to exhibit significantly different responses to infection. Forty-seven hairy root clones derived from normal plants and two derived from the flowerless variety were screened for their growth and indole alkaloid production. The growth rate and morphological appearance showed wide variations between the clones. The alkaloid spectra observed were qualitatively but not quantitatively very similar to that of the corresponding normal plant roots. No vindoline or deacetyltransferase activity could be detected in any of the cultures studied. O-acetylval-lesamine, an alkaloid which has not been previously observed in C. roseus was identified from extracts of hairy root clone No. 8. Two root clones were examined for their growth and alkaloid accumulation during a 26-day culture period. Alkaloid accumulation parallelled growth in both clones with ca. 2 mg ajmalicine and catharanthine per g dry weight being observed.Dedicated to Dr. Friedrich Constabel on the occasion of his 60th birthday     

A colorimetric method for DNA hybridization.

A general method has been developed which allows crosslinks to be produced between proteins and single-stranded DNA. Such single-stranded DNA protein complexes have been tested for blot hybridization using two colorimetrically detectable enzymes, namely peroxidase and alkaline phosphatase, as the protein moiety of the probe. After hybridization and incubation with a substrate solution sequences complementary to the probe can be visualized directly without the need of tedious cytochemical sandwich methods. This procedure will detect target sequences, a few kilobases long, in the 1- to 5-pg range.     

Cryopreservation of Alkaloid-Producing Cell Cultures of Periwinkle (Catharanthus roseus)

A procedure for cryogenic storage of alkaloid producing cell lines of periwinkle, Catharanthus roseus (L.) G. Don., has been developed. The procedure differs from established cryopreservation protocols in several aspects. Specifically, 4-day-old suspension subcultures of three cell lines were precultured in nutrient media supplemented with 1 molar sorbitol for 6 to 20 hours. The cells were then incubated in nutrient media with 1 molar sorbitol plus 5% DMSO in an ice bath for 1 hour and, thereafter, were frozen in this solution at a cooling rate of 0.5°C per minute to −40°C prior to immersion in liquid nitrogen (LN). After rapid thawing in a 40°C water bath, the regrowth of LN stored cells was achieved by transferring them without washing onto filter paper discs over nutrient media solidified with agar for a period of 4 to 5 hours. The filter paper discs with the cells were then transferred to fresh media of the same composition for regrowth. The viability immediately after thawing as evaluated by the 2,3,5-triphenyl tetrazolium chloride method was about 60% of controls. Suspension cultures established from LN stored cells retained the capability for alkaloid synthesis and accumulation.     

Comment on the use of linear free-energy slopes as criteria for distinguishing hydride-ion from hydrogen-atom transfer in reactions of pyridine-nucleotide coenzymes.

For reductions by dihydropyridines, the slopes of plots of log k vs the standard reduction potential of the dihydropyridine are not direct indicators of whether the rate-determining step is hydride-ion or hydrogen-atom transfer. When there is no substituent effect on the reverse rate, those slopes are independent of mechanism and equal to about (30mV)-1.     

Cranial Anatomy of the Earliest Marsupials and the Origin of Opossums

Background

The early evolution of living marsupials is poorly understood in part because the early offshoots of this group are known almost exclusively from jaws and teeth. Filling this gap is essential for a better understanding of the phylogenetic relationships among living marsupials, the biogeographic pathways that led to their current distribution as well as the successive evolutionary steps that led to their current diversity, habits and various specializations that distinguish them from placental mammals.

Methodology/Principal Findings

Here we report the first skull of a 55 million year old peradectid marsupial from the early Eocene of North America and exceptionally preserved skeletons of an Oligocene herpetotheriid, both representing critical groups to understand early marsupial evolution. A comprehensive phylogenetic cladistic analysis of Marsupialia including the new findings and close relatives of marsupials show that peradectids are the sister group of living opossums and herpetotheriids are the sister group of all living marsupials.

Conclusions/Significance

The results imply that North America played an important role in early Cenozoic marsupial evolutionary history and may have even been the center of origin of living marsupials and opossums. New data from the herpetotheriid postcranium support the view that the ancestral morphotype of Marsupialia was more terrestrial than opossums are. The resolution of the phylogenetic position of peradectids reveals an older calibration point for molecular estimates of divergence times among living marsupials than those currently used.     

Autophagy of HSP70 and chelation of lysosomal iron in a non-redox-active form

Lysosomes contain most of the cell's supply of labile iron, which makes them sensitive to oxidative stress. To keep lysosomal labile iron at a minimum, a cellular strategy might be to autophagocytose iron binding proteins that temporarily would chelate iron in a non-redox-active form. Previously we have shown that autophagy of metallothioneins, as well as of non-Fe-saturated ferritin, meets this goal. Here we add another stress-regulated protein to the list, namely HSP70.