Identification of natural tricetin-derived C-glycosides through synthesis

C-Glycosylation of 5,7-dihydroxy-3′,4′,5′-trimethoxyflavone was carried out with acetobromo-α-d-glucose, -α-d-galactose, -α-d-xylose, -β-l-arabinose and -αt-L-rhamnose. The respective 6-C-glycosides and 6, 8-di-C-glycosides (excepted for galactose) were isolated and permethylated. MS and TLC comparison confirmed the proposed structures of five natural tricetin-derived C-glycosides.     

Isolation and long-term serial cultivation of endothelial cells from the microvessels of the adult human dermis

A method to isolate and maintain microvascular endothelial cells from the cutaneous vessels of adult human skin in long-term culture has been developed. Endothelial cells lining the microvessels of the papillary dermis are released from surrounding tissue during a brief trypsin incubation (0.3% trypsin, 1% EDTA). Cells are plated onto a fibronectin substrate and maintained in Leibovitz (L15) culture medium containing pooled human serum (50%) and antibiotics. Proliferation is dependent upon the presence of several additional growth factors, cholera enterotoxin (1 X 10(-9) M), isobutyl methylxanthine (3.3 X 10(-5) M), and medium conditioned by explant culture of the mouse EHS sarcoma. Using this supplemented medium, cells proliferate readily and can be cultivated serially for more than 6 passages (3 months in vitro). These cells retain their characteristic endothelial cell morphology, stain positively for Factor VIII antigen, and contain Weibel-Palade bodies.     

On a simple epidemic model with a heterogeneous infective population

This paper is concerned with a generalization of the simple epidemic model in which the infective population is partitioned intom classes, each of specific infectiousness. Attention is restricted, however, to the case where all the meeting rates between two individuals are equal to each other. Both deterministic and stochastic versions are examined. In either case the development in time of the epidemic process is investigated by exploiting a connection with the standard simple epidemic model. Finally, it is shown that the technique used also applies to a similar model for the spread of information.     

Characterization of a new class of circular DNA molecules in yeast

This paper describes the isolation of a pure population of covalently closed circular twisted DNA molecules from yeast. These molecules are homogeneous in size, that is consist of monomers of 2.2μ and of multiple length oligomers of n x 2.2μ. While no data rule out the mitochondrial origin of this DNA, its actual intracellular localization remains unknown; it displays the same buoyant density as the main nuclear DNA and therefore is not the heavy nuclear satellite DNA (γ-DNA described by Moustacchi and Williamson (1966)); although circular molecules represent only 1 to 5 % of the total DNA, they can be prepared in sizable and reproducible amounts by a method based on the use of mechanical disruption of yeast cells rather than lysis by snail gut juice.     

Agar Plate Method for Detecting Microorganisms Which Produce Equilin and Other Estrogens from Various Steroids

The intense red color produced by a reagent specific for xi(7)-estrogens is used to directly detect microorganisms which produce these estrogens from various steroids.     

Influence of cell culture conditions on aromatase activity in human genital skin fibroblasts

Summary Because the measurement of aromatase activity in cultured human genital skin fibroblasts has been proposed as a means of studying estrogen production in men, we investigated the influence of culture conditions on aromatase activity. Genital skin fibroblasts were seeded onto culture plates at a density of 1×10⁶ cells/plate and aromatase activity was determined over a 1-mo. period. Enzyme activity rose slowly over the first 14 d but then rose rapidly to a 10-fold higher plateau by Day 28. The rise in aromatase activity was similar whether activity was normalized for protein or for DNA content. When cells were seeded at the usual density of 1×10⁶ or at 0.25×10⁶ cells/plate, aromatase activity was consistently lower during the first 2 wk in cells plated at lower density, but thereafter the levels of enzyme activity in the two groups converged. In cells plated at the lower density, the lower activity observed in the first 2 wk was associated with a lower V _max . Preincubation of cells plated at one density with conditoned medium from cells plated at the other density did not change the relatve levels of activity in the two groups. By contrast, dihydrotestosterone (DHT) receptor binding and 5α-reductase activity were similar at all time points, despite differences in plating density. In additional experiments, the culture medium was replaced daily rather than every 3rd d, and aromatase activity was assayed on Day 7. In cells fed daily, DNA and protein content were twice that of cells fed every 3rd d. By contrast, aromatase activity declined to 30% of the in the latter group. DHT and dexamethasone receptor binding and 5α-reductase activity were similar in the two groups. In summary, factors such as plating density, culture density, and frequency of media replacement dramatically influence aromatase activity in cultured human genital skin fibroblasts. Therefore, the interpretation of aromatase activity data obtained from cultured cells in relation to physiologic or pathologic states should be viewed with appropriate caution. The work was supported in part by grants R01 DK 35339 and R01 DK 00180 from the National Institutes of Health, Bethesda, MD, and by RR 00035 from CLINFO Systems at the Johns Hopkins University School of Medicine, Baltimore, MD.