Antibody-targeted photolysis: in vitro immunological, photophysical, and cytotoxic properties of monoclonal antibody-dextran-Sn(IV) chlorin e6 immunoconjugates.

A set of anti-melanoma immunoconjugates were prepared which contained chlorin e6: antibody molar ratios of 18.9:1, 11.2:1, 6.8:1, and 1.7:1. All immunoconjugates retained antigen binding activity regardless of the chromophore:antibody substitution ratio that was attained. In contrast, the ground-state absorption spectra of the immunoconjugates showed features which appeared to be dependent on the chromophore:antibody molar ratio. In addition, the quantum yield of singlet oxygen generated by the conjugated chromophores was observed to be significantly less than that observed with the unbound dye. Time-resolved absorbance spectroscopy of the chromophore excited triplet state indicated that the loss of singlet oxygen quantum yield resulted from diminished chromophore triplet yield. Analysis of data obtained from in vitro photolysis of target melanoma cells, in combination with that obtained from the immunochemical and photochemical studies, indicates that the observed immunoconjugate phototoxicity can be reasonably quantitatively represented by (1) the ability of the immunoconjugate to bind SK-MEL-2 cell surface antigen, (2) the amount of chromophore localized at the target cells by immunoconjugate binding, (3) the delivered dose of light at 634 nm, and (4) the singlet oxygen quantum yield of the antibody-bound photosensitizer. Though these data argue strongly for photolysis by the cumulative dosage of singlet oxygen at the cell membrane, nonetheless, the concurrent photoinduced release of other cytotoxic agents should not be ruled out.     

Molecular modelling of the interactions of tetra-(4-N-methylpyridyl) porphin with TA and CG sites on DNA.

The molecular structure of the DNA-intercalating ligand tetra-(4-N-methylpyridyl) porphin has been determined by X-ray crystallography. The porphyrin has a precise centre of symmetry; the central core is planar, with the N-methylpyridyl groups inclined to it at angles of 66-72 degrees. Molecular modelling of this structure into TpA and CpG sites of intercalated DNA, has been performed, and approximate energetics calculated. It has been shown that only the CpG site can have full ligand intercalation, since the thymine methyl group sterically hinders such geometry at TpA sites. Modelling indicates the importance of electrostatic effects in the low-energy forms of intercalated and part-intercalated complexes at both sequences.     

Influence of SLA haplotype on preimplantation embryonic cell number in miniature pigs

Embryonic cell number in miniature pigs inbred for specific SLA haplotypes (a, c, and d) was determined on Day 6 by nuclear staining and, on Days 9 and 11, by DNA analyses (first day of oestrus = Day 0). Pigs exhibiting first behavioural oestrus at 08:00 h were hand-mated to an SLA homozygous boar 12 and 24 h later. Numbers of embryos flushed from uteri at 08:00-10:00 h on Days 6, 9 and 11 were greater (P less than 0.05) for SLAd females than for SLAa or SLAc females, which did not differ (8.2 vs 6.8 and 6.2, respectively). Recovery rates (embryos recovered/CL number) were similar, averaging 75.8% for all three SLA haplotypes. Embryos from SLAd dams contained fewer blastomeres (23 cells) on Day 6 than did embryos from SLAa (89 cells) or SLAc (79 cells) females. The reduced cell numbers of SLAd vs SLAa or SLAc embryos continued to Day 9 (28 vs 107 and 67 ng DNA/embryo) and Day 11 (167 vs 674 and 586 ng DNA/embryo). These results suggest an effect of the SLA complex on preimplantation embryonic development.     

5'-Nucleotidase of human placental trophoblastic microvilli possesses cobalt-stimulated FAD pyrophosphatase activity

An enzyme with FAD pyrophosphatase activity was extracted from human placental syncytiotrophoblast microvilli and purified to near-homogeneity. The enzyme has been identified as 5'-nucleotidase by several criteria. Throughout purification, parallel increases in the specific activities of FAD pyrophosphatase and AMP phosphatase were observed. The enzyme was a glycoprotein with a subunit molecular weight of 74,000. EDTA treatment resulted in a marked decline in both activities, and restoration of FAD pyrophosphatase activity but not 5'-nucleotidase activity was accomplished by the addition of Co2+ or, to a lesser extent, Mn2+. The substrate specificity of the 5'-nucleotidase activity that we observed agreed closely with the results of others. The pyrophosphatase activity was relatively specific for FAD. ADP, ATP, NAD(H), and FMN were not hydrolyzed, and ADP strongly inhibited both activities. For FAD pyrophosphatase activity, a Km of 1.2 x 10(-5) M and a Vmax of 1.1 mumol/min/mg protein were determined in assays performed in the presence of Co2+. In the absence of added Co2+, the Vmax declined but the Km was unchanged. For 5'-nucleotidase (AMP as substrate) the Km was 4.1 x 10(-5) M and the Vmax 109 mumol/min/mg protein. Hydrolysis of FMN to riboflavin was observed in partially purified detergent extracts of microvilli that contained alkaline phosphatase activity and lacked FAD pyrophosphatase and 5'-nucleotidase activity. The presence of both FAD pyrophosphatase and FMN phosphatase activities in syncytiotrophoblast microvilli supports the view that the placental uptake of vitamin B2 involves the hydrolysis of FAD and FMN to riboflavin which is then absorbed, a sequence postulated for intestinal absorption and liver uptake.     

Developmental expression of bovine adrenocortical steroid hydroxylases. Regulation of P-450(17 alpha) expression leads to episodic fetal cortisol production

The developmental expression of adrenocortical steroid hydroxylases was studied in bovine fetuses from 40 to 280 days gestational age. The expression of P-450(17 alpha) is first detected at a gestational age of 50 days and reaches a maximum at 60-70 days. The expression of P-450(17 alpha) then declines and is nondetectable at a gestational age of 100 days. P-450(17 alpha) is not expressed again until about 240 days, i.e. shortly before birth (approximately 280 days). P-450scc, P-450c21, P-450(11 beta) and adrenodoxin were present in fetal adrenals throughout gestation. This "on-off-on" pattern of P-450(17 alpha) expression during fetal development was associated with a corresponding episodic production of cortisol. Immunoreactive corticotropin (ACTH) levels in fetal plasma were elevated in small fetuses (corresponding to less than or equal to 100 days) and in near-term fetuses (corresponding to greater than 250 days) compared with those in mid-gestation fetuses. In primary culture, adrenal cells from mid-gestation fetuses contained no detectable P-450(17 alpha) but rapidly responded to ACTH with an increase in P-450(17 alpha) protein and mRNA. The tissue specificity of the developmental patterns is emphasized by the fact that both P-450(17 alpha) and P-450scc were detectable throughout the development of the fetal testes, whereas only P-450scc was detectable in fetal bovine ovary prior to 200 days. Thus, in fetal bovine adrenal it appears that ACTH is the major regulatory factor effecting the intermittent presence of P-450(17 alpha), whereas the presence of the other steroid hydroxylases is either regulated by additional factors or shows a much different sensitivity to ACTH.     

Emotional and behavioral reactions to facially deformed patients before and after craniofacial surgery

The present experiment investigated whether observers' emotional and behavioral reactions to facially deformed patients could be substantially improved by surgical procedures conducted by well-trained specialists in an experienced multidisciplinary team. Also investigated was the hypothesis that emotional states mediate the effects of physical attractiveness and facial deformity on social interaction. Twenty patients between the ages of 3 months and 17 years were randomly selected from over 2000 patients' files of Kenneth E. Salyer of Dallas, Texas. Patient diagnoses included facial clefts, hypertelorism, Treacher Collins syndrome, and craniofacial dysostoses (Crouzon's and Apert's syndromes). Rigorously standardized photographs of patients taken before and after surgery were shown to 22 "naive" raters ranging in age from 18 to 54 years. Raters were asked to predict their emotional and behavioral responses to the patients. These ratings indicated that observers' behavioral reactions to facially deformed children and adolescents would be more positive following craniofacial surgery. Similarly, the ratings indicated that observers' emotional reactions to these patients would be more positive following surgery. The results are discussed in terms of current sociopsychologic theoretical models for the effects of attractiveness on social interaction. A new model is presented that implicates induced emotional states as a mediating process in explaining the effects of attractiveness and facial deformity on the quality of social interactions. Limitations of the current investigation and directions for future research are also discussed.