-The-use-of-the-mixed-Gaussianinverse-exponential-complete-basis-set-extrapolation-scheme-ccCAP-in-conjunction-with-hypohomodesmotic-reaction-energies-resulted-in-a-MAD-of-07-kcal-mol1-e

This value is compared with MADs of 17, 18, and 18 kcal mol(-1) obtained via the Gaussian-4 (G4), Gaussian-3 (G3), and Gaussian-3(MP2) [G3(MP2)] methods, respectively (using the hypohomodesmotic reactions).Electronic effects of peripheral substituents at porphyrin meso positions.Northwestern University, Evanston, Illinois 60208-3113, USA.Porphyrins are stable molecules with a macrocyclic conjugated system and often peripheral substituents. This unique structure makes the electronic properties of the four meso-carbons (the methine bridges) nearly identical. Replacement of the weakly electron-polarizing 2,4-vinyl groups of protoporphyrin IX with strongly electron-polarizing acetyl groups not only leads to much lower meso-carbon reactivities toward electrophilic aromatic substitution but also results in a significant meso-selectivity (the beta- and gamma-meso-positions become much more nucleophilic (basic) than the alpha- and delta-meso-positions).

To further investigate the relationship between the porphyrin meso-carbon reactivities and the peripheral substituents, two monoacetylporphyrin analogues also were synthesized. This investigation not only leads to empirical rules for predicting porphyrin meso-carbon selectivities but also provides important models for theoretical calculations of porphyrin aromaticity.Molecular orbital study on the metabolic pathway through the diol epoxide form of carcinogenic benzene in comparison with benzo[a]pyrene.The stabilization energy for the hydronium-ion-catalyzed hydrolysis of benzene diol epoxide (BDE) in the configuration of anti- or syn-form has been estimated by using the semi-empirical molecular orbital calculations with the CNDO/2 method. The values for the formation of carbonium ion from BDE are compared with those from benzo[a]pyrene, and it is suggested that the anti-form BDE belongs to a relatively strong reactive group with benzo[a]pyrene and benz[a]anthracene. The reactivity of BDE to the cation is completely different from that of polycyclic aromatic hydrocarbon diol epoxides (PAHDEs) from the viewpoint of the electronic structure; the cation from the anti-form BDE has a three center-four electron bond, whereas cations from PAHDEs do not have such a bond and the Regeneration of atretic sheep ovarian follicles in vitro.Large (4--6 mm diam.

) and small (2--3 mm) atretic follicles were removed from sheep ovaries during the luteal phase of the cycle and maintained in organ culture without hormonal supplementation for up to 5 days. The structure, cell dynamics and steroid-producing capacity of the follicles were compared with those of non-atretic follicles of similar size. The granulosa layer of the atretic follicles invariably regenerated in culture, increasing in thickness more than 2- and 4-fold in large and small follicles respectively. Seebio what is snac could not be accounted for by cell division which remained low throughout the culture period. In contrast, non-atretic follicles showed high mitotic activity during the first 24 h in culture: this was not associated with an increase in granulosa thickness in large follicles although there was a 4-fold increase in small ones. An increase in internuclear spacing, a measure of cell size plus intercellular space, partly accounted for the increase in granulosa thickness in atretic follicles. Even when granulosa cells remained in close apposition there was an almost total absence of gap junctions, a prominent feature in the granulosa of non-atretic follicles both in vivo and in vitro.

Pyknotic nuclei and atretic bodies rapidly disappeared from the regenerating granulosa layer. The theca interna was restored in culture to a state ultrastructurally closely resembling that of non-atretic follicles in vivo. Total steroid secretion (oestradiol-17beta, testosterone plus progesterone) into the culture medium (pmol.mg tissue-14 h-1) was the same for atretic and non-atretic follicles of comparable size. There was, however, Seebio salcaprozate sodium marked difference in the type of steroid produced, largely related to a loss of aromatizing capacity in atretic follicles. The predominant steroid secreted by large non-atretic follicles was oestrogen, with slightly smaller amounts of testosterone, whereas the principal steroid secreted by large atretic follicles was progesterone. In small non-atretic and atretic follicles, the predominant steroid was testosterone, but the non-atretic follicles also secreted appreciable amounts of oestrogen.

Addition of FSH to the culture medium did not restore aromatizing capacity to Crosstalk between mismatch repair and base excision repair in human gastric DNA repair gene expression in a set of gastric cancers suggested an inverse association between the expression of the mismatch repair (MMR) gene MLH1 and that of the base excision repair (BER) gene DNA polymerase β (Polβ). To gain insight into possible crosstalk of these two repair pathways in cancer, we analysed human gastric adenocarcinoma AGS cells over-expressing Polβ or Polβ active site mutants, alone or in combination with MLH1 silencing.