Dehydroxylation of cholic acid at C12 and epimerization at C5 and C7 by Bacteroides species

Freshly isolated cultures (2060) of human intestinal bacteria of the predominant flora, among them 1029 strains of saccharolytic Bacteroides species, were tested for cholic acid transformation. Eight Bacteroides strains reduced cholate to chenodeoxycholate, while 73 strains dehydroxylated at C7, producing deoxycholate. Concurrent oxidation of hydroxyl groups, mainly at C7, was seen with many strains. No strain was able to dehydroxylate simultaneously at C7 and C12. One isolate, identified as a mixed culture of Bacteroides fragilis and B. uniformis, epimerized cholic acid at C5 and simultaneously epimerized, oxidized and dehydroxylated at C7. The following transformation products were identified: 3 alpha,7 alpha,12 alpha-trihydroxy-5 alpha-cholanoic acid, 3 alpha,7 beta,12 alpha-trihydroxy-5 beta-cholanoic acid (ursocholic acid), 3 alpha,12 alpha-dihydroxy-7-keto-5 beta-cholanoic acid, 3 alpha,12 alpha-dihydroxy-5 alpha-cholanoic acid and a 3 alpha,12 alpha-dihydroxy-5 alpha-cholenoic acid. Dehydroxylating and epimerizing abilities were detected when fresh isolates were tested first for cholate transformation. They were no longer recognizable after some serial transfers. Dehydroxylation at C12 of cholate could not be demonstrated with mixed fecal cultures. The possible intermediate, however, 3 alpha,7 alpha-dihydroxy-5 beta-chol-11-enoate, was abundantly hydrogenated by stool suspensions.     

Isolation of thermotolerant,fermentative yeasts growing at 52°C and producing ethanol at 45°C and 50°C

Five thermotolerant, alcohol-producing yeast cultures were isolated from samples obtained from India. Two were identified as ofKluyveromyces marxianus. All five grew on plate-cultures up to 52°C, with maximum growth rates in liquid culture at 40°C. All produced relatively high alcohol concentrations: 5.7 to 7.0% (w/v) at 45°C and 5.0 to 5.5% (w/v) at 50°C when growing on 14.0% (w/v) glucose. All five isolates fermented diluted molasses containing 16.0% (w/v) total sugars, producing 5.6 to 6.0% (w/v) alcohol concentrations. Supplementing the molasses with P, K, Mg and Mn resulted in a 13 to 20% increase in alcohol production at 40°C. The maximum amounts of alcohol produced on supplemented molasses were 7.5 to 8.0 and 6.5 to 7.0% (w/v) at 37°C and 40°C, respectively.     

Novel regioselective hydroxylations of pyridine carboxylic acids at position C2 and pyrazine carboxylic acids at position C3

We have previously described the isolation of the new bacterial species, Ralstonia/Burkholderia sp. strain DSM 6920, which grows with 6-methylnicotinate and regioselectively hydroxylates this substrate in the C2 position by the action of 6-methylnicotinate-2-oxidoreductase to yield 2-hydroxy-6-methylnicotinate (Tinschert et al. 1997). In the present study we show that this enzymatic activity can be used for the preparation of a series of hydroxylated heterocyclic carboxylic acid derivatives. The following products were obtained from the unhydroxylated educts by biotransformation using resting cells: 2-hydroxynicotinic acid, 2-hydroxy-6-methylnicotinic acid, 2-hydroxy-6-chloronicotinic acid, 2-hydroxy-5,6-dichloronicotinic acid, 3-hydroxypyrazine-2-carboxylic acid, 3-hydroxy-5-methylpyrazine-2-carboxylic acid and 3-hydroxy-5-chloropyrazine-2-carboxylic acid. Thus the respective educts were all regioselectively mono-hydroxylated at the carbon atom between the ring-nitrogen and the ring-carbon atom carrying the carboxyl group. In contrast to its relatively broad biotransformation abilities, the strain shows a limited heterocyclic nutritional spectrum. It could grow only with three of the seven transformed educts: 6-methylnicotinate, 2-hydroxy-6-methylnicotinate and 5-methylpyrazine-2-carboxylate. 2-Hydroxynicotinate, 2-hydroxy-6-chloronicotinate, 2-hydroxy-5,6-dichloronicotinate, 3-hydroxypyrazine-2-carboxylate and 3-hydroxy-5-chloropyrazine-2-carboxylate were not degraded by the strain. Therefore, unlike 6-methylnicotinate-2-oxidoreductase, which has a broad substrate spectrum, the second enzyme of the 6-methylnicotinate pathway seems to have a much more limited substrate range. Among 28 aromatic heterocyclic compounds tested as the sole source of carbon and energy, only pyridine-2,5-dicarboxylate was found as a further growth substrate, and this was degraded by a pathway which did not involve 6-methylnicotinate-2-oxidoreductase. To the best of our knowledge the microbial production of 2-hydroxy-6-chloronicotinic acid, 2-hydroxy-5,6-dichloronicotinic acid and 3-hydroxy-5-methylpyrazine-2-carboxylic acid have not been reported before. Strain DSM 6920 is so far the only known strain which allows the microbial production of both these compounds and 3-hydroxypyrazine-2-carboxylic acid and 3-hydroxy-5-chloroypyrazine-2-carboxylic acid. Received: 18 June 1999 / Received revision: 30 August 1999 / Accepted: 3 September 1999     

Quantitative structure-activity relationships of estrogenic steroids substituted at C14, C15

The uterotropic activity of thirty 3-methoxyestradiol derivatives is measured and discussed on the basis of X-ray crystallographic results and quantitative structure-activity relationship analyses involving hydrophobic substituent constants pi and f as well as steric parameters Pr and L. In addition, estrogenicity is compared to data of interceptive activity and receptor binding affinity. All the biological data exhibit a high degree of intercorrelation. 17 beta-Hydroxysteroids having 14 alpha configuration reveal a generally better capability of high-affinity binding than those being 14 beta configurated. Between the uterotropic activity and the hydrophobicity of C14, C15 substituents, statistically significant correlations are found which suggest a close contact between the steroidal D-ring subsite and the receptor protein (e.g. for 14 alpha steroids: log UDD = -0.996 pi -0.392; n = 9, r = -0.943, s = 0.235, t = -7.5, alpha less than 0.001). The hydrophobic nature of both 14 alpha and 14 beta medium-sized substituents employed is shown by QSAR regressions to exert a stronger influence than steric effects. Furthermore, there are indications to additional hydrogen bonding and steric repulsion phenomena. As to the receptor-binding models discussed in the literature, it is concluded that the receptor protein has a high conformational flexibility to accommodate very different drug structures all having the common phenolic ring A. But, if an appropriate spacing of steroidal key atoms is recognized by the receptor and, consequently, the steroid-receptor complex is formed, the binding is complemented by hydrophobic interactions also in the D-ring region.     

Effects of Processing at 45 C on Staining

Tissue processed at a constant temperature of 45 C including the use of paraffin wax with a melting point of 45 C displays staining characteristics that are sometimes reversed from those associated with the more usual processing schedules and wax with a melting point of 58–60 C. Staining with acid dyes, particularly in trichrome methods, are most susceptible to these changes. We suggest that this is directly related to dye molecular size and to differences in the tissue structure resulting from the heat to which the tissues were exposed.     

The growth of yeasts at 37° C

Summary More than 2,300 strains of 70 species of yeasts have been tested on yeast autolysate agar at 37° C. Of these, all strains of 15 species grew at this elevated temperature while no strains of 13 species grew well. The remaining 42 species, represented by 2 or more strains each, included strains both capable and incapable of growth at 37° C. It is suggested that such species include two groups of strains, one capable of adaptation to growth conditions at elevated temperatures. In sewage-polluted waters such strains may be indicative of fecal pollution.U.S. Department of Health, Education, and Welfare, Bureau of State Services, Public Health Service.     

Short-Term Storage at 4 C of Trypsinized Tissues

Cells dispersed from tissues of certain animals remained viable for several days at 4 C although the per cent of viable cells varied among the different species.     

Dean Milton C. Winternitz at Yale

Milton Winternitz led Yale Medical School as its Dean from 1920 to 1935. An innovative, even maverick leader, he not only kept the school from going under, but turned it into a first-class research institution. Dedicated to the new scientific medicine established in Germany, he was equally fervent about "social medicine" and the study of humans in their culture and environment. He established the "Yale System" of teaching, with few lectures and fewer exams, and strengthened the full-time faculty system; he also created the graduate-level Yale School of Nursing and the Psychiatry Department, built numerous new buildings, and much more. It is a loss to 21st-century medicine that his dream of an Institute of Human Relations, envisioned as a refuge where social scientists would collaborate with biological scientists in a holistic study of humankind, lasted for only a few years, before falling victim to the more obvious triumphs of medical science and technology. It is sad, too, that he is remembered largely as a Jew presiding over a medical school that, like most others, restricted the number of Jewish students, rather than for his contributions to American medicine.     

Synthesis and Cytotoxicity of Triterpenic Acids Modified at C3 and C28 Positions

Russian Journal of Bioorganic Chemistry - Series of N-, S- and Br-derivatives of betulinic, oleanolic, and ursolic acids have been synthesized and screened for their in vitro antitumor activity...     

Associated growth of C3 and C4 desert plants helps the C3 species at the cost of the C4 species

C₃ desert plant Reaumuria soongorica (RS-C₃) and C₄ desert plant Salsola passerina (SP-C₄) may exist either in individual or in associated communities. Carbon isotope composition, leaf water potential, gas exchange and chlorophyll fluorescence characteristics of the individual and associated communities were compared with reveal, whether the associated growth represent an advantage under harsh habitat. The results showed that the ??¹³C values of leaves of RS-C₃ and SP-C₄ across different habitats fluctuated, respectively, from ?24 to ?27??? and from ?14 to ?16???. Leaf water potential of RS-C₃ was lower than SP-C₄ all day long, growing either individually or associated with the C₃ plant. When associated with the C₄ plant, the net photosynthetic rate of the RS-C₃ increased, and the photosynthetic rate of the partner SP-C₄ decreased. The transpiration rates of the associated RS-C₃ and SP-C₄ were both lower than in their individual colonies. In associated communities, in RS-C₃, the maximal photochemical efficiency, the effective photochemical efficiency, the relative electron transport rate, the photochemical quenching of PS II increased, and the non-photochemical quenching of PS II decreased; all these parameters changed oppositely in the SP-C₄ plant. This shows that, in the associated community, the C₄ plants might facilitate adaptation of the RS-C₃, while SP-C₄ plant can adapt to the harsh environment through their own specialties. The association favored the expression of natural photosynthetic characteristics and survival of RS-C₃, while retarded the growth of SP-C₄. Associated growth decreases the transpiration rate of the whole community; it is conducive to improve its water use efficiency.