Modification of the agar overlay assay: assessment of the influence of acrylics used in orthodontics on proliferation and differentiation of primary and transformed fibroblasts

For most menopausal women, the benefits of hormone replacement therapy outweigh the risks, despite the fears aroused by the unproven link to breast cancer. If the goal is solely to relieve menopausal symptoms, the treatment duration is generally 2 to 3 years and then gradually tapered off. If the goal is to provide cardiac protection and prevent osteoporosis, long-term, possibly lifetime, treatment is needed.     

Two cases of esophageal carcinoma metastatic to the pineal region with a review of the literature

BACKGROUND: Metastasis to the pineal region is rare, and there are no previously reported cases of esophageal carcinoma metastatic to the pineal region. CASE DESCRIPTION: We now present two cases of solitary esophageal carcinoma metastatic to the pineal region. In each case there was no evidence of disease progression at the primary site at the time of presentation, and neurologic symptoms were the first indication of recurrent disease. Both patients underwent infratentorial/supracerebellar resection of the pineal lesions and were subsequently referred for radiation therapy. CONCLUSIONS: These two cases emphasize that metastatic disease must be a likely differential consideration in a patient with a CNS lesion and a history of previous malignancy, even if the lesion is in an unusual location.     

The mechanism of action of phenylalanine ammonia-lyase: the role of prosthetic dehydroalanine

Phenylalanine ammonia-lyase (EC 4.3.1.5) from parsley is posttranslationally modified by dehydrating its Ser-202 to the catalytically essential dehydroalanine prosthetic group. The codon of Ser-202 was changed to those of alanine and threonine by site-directed mutagenesis. These mutants and the recombinant wild-type enzyme, after treatment with sodium borohydride, were virtually inactive with L-phenylalanine as substrate but catalyzed the deamination of L-4-nitrophenylalanine, which is also a substrate for the wild-type enzyme. Although the mutants reacted about 20 times slower with L-4-nitrophenylalanine than the wild-type enzyme, their Vmax for L-4-nitrophenylalanine was two orders of magnitude higher than for L-phenylalanine. In contrast to L-tyrosine, which was a poor substrate, DL-3-hydroxyphenylalanine (DL-m-tyrosine) was converted by phenylalanine ammonia-lyase at a rate comparable to that of L-phenylalanine. These results suggest a mechanism in which the crucial step is an electrophilic attack of the prosthetic group at position 2 or 6 of the phenyl group. In the resulting carbenium ion, the beta-HSi atom is activated in a similar way as it is in the nitro analogue. Subsequent elimination of ammonia, concomitant with restoration of both the aromatic ring and the prosthetic group, completes the catalytic cycle.