Biotransformation of tabersonine in cell suspension cultures of Catharanthus roseus.

To investigate the reactions involved in the biosynthesis of vindoline from tabersonine, the bioconversion products formed when the latter compound was fed to cell suspension cultures of Catharanthus roseus were isolated and characterized. Two biotransformation products of tabersonine were isolated and shown to be lochnericine, which is formed by epoxidation of tabersonine at positions 14, 15, and lochnerinine, the 11-methoxylation product of lochnericine. The bioconversion ratio of the main biotransformation product, lochnericine, reached a value of 80.6% within three days.     

Explant organ culture: A review

Organ explant culture models offer several significant advantages for studies of patho-physiologic mechanisms like cell injury, secretion, differentiation and structure development. Organs or small explants/slices can be removed in vivo and maintained in vitro for extended periods of time if careful attention is paid to the media composition, substrate selection, and atmosphere. In the case of human tissues obtained from autopsy or surgery, additional attention must be paid to the postmortem interval, temperature, hydration, and cause of death. Explant organ culture has been effectively utilized to establish outgrowth cell cultures and characterize the histiotypic relationships between the various cell types within an organ or tissue.J. Resau is a visiting scientist at the NCI-LMO-DCE in Frederick, MD 21702, U.S.A.K. Sakamoto is a visiting scientist from the Department of Surgery, Gunma University School of Medicine, Maebashi, Japan     

Inhibition of epidermal growth factor-induced DNA synthesis by tyrosine kinase inhibitors

We prepared methyl 2,5-dihydroxycinnamate as a stable analogue of erbstatin, a tyrosine kinase inhibitor. This analogue was about 4 times more stable than erbstatin in calf serum. It inhibited epidermal growth factor receptor-associated tyrosine kinase in vitro with an IC₅₀ of 0.15 μg/ml. It also inhibited in situ autophosphorylation of epidermal growth factor receptor in A431 cells. Methyl 2,5-dihydroxycinnamate was shown to delay the S-phase induction by epidermal growth factor in quiescent normal rat kidney cells, without affecting the total amount ofDNA synthesis. The effect of erbstatin on S-phase induction was smaller, possibly because of its shorter life time.     

Organomercurial-volatilizing bacteria in the mercury-polluted sediment of Minamata Bay, Japan.

A total of 4,604 bacterial strains isolated from the sediments of Minamata Bay and nearby low-level-mercury stations (control stations) were screened for the ability to volatilize mercury from inorganic and organic mercurial compounds. The strains that volatilize mercury from several kinds of organomercurials were found only in the sediments of Minamata Bay.     

An extra idic(15p)(q11) chromosome in Prader-Willi syndrome

Using a nonfluorescent AT-specific oligopeptide antibiotic, Distamycin A, on DAPI fluorescent banding of human chromosome (DA-DAPI) as described by Schweizer et al. (1978), we have detected an additional idic(15p) chromosome in a patient with typical Prader-Willi syndrome. On the basis of the evidence available in previous studies and of our own present results, we suspect that the fundamental genetic error in the syndrome is not caused by a chromosome aberration but by a gene aberration on chromosome 15.     

Study of oxytocin receptor: II. Gestational changes in oxytocin activity in the human myometrium

This study was designed to investigate the oxytocin (OT) specific binding receptors in 20,000 x g pellets of nonpregnant, first trimester and term human myometria. The receptor analysis was done using the lower uterine segment at term and the lower portion of the anterior uterine body in nonpregnant and first trimester subjects, and no difference was found in the myometrial receptor concentrations in the various uteri. The mean +/- S.D. values of the receptor dissociation constants were 3.33 +/- 0.50, 2.71 +/- 1.03 and 1.87 +/- 0.30 nM and the number of binding sites was 0.30 +/- 0.10, 0.50 +/- 0.10 and 1.50 +/- 0.50 pmol/mg protein at each stage studied, indicating that the gestational increase of uterine sensitivity to OT is due to the increase in myometrial OT binding sites as well as its binding affinity. Further, myometrial OT binding before and after the onset of labor was studied and a marked decrease in total myometrial OT binding was noticed; 35.6 +/- 13.0% before and 20.2 +/- 5.0% after. This decrease was thought to be due to the decrease in the number of binding sites from 1.50 +/- 0.50 to 0.74 +/- 0.21 pmol/mg protein after the onset of labor (p less than 0.01). No changes were found in the dissociation constants. Thus it seems that OT and its receptor coupling triggers labor or is involved in the early steps of labor.     

Dielectric relaxation of DNA solutions. III. Effects of DNA concentration, protein contamination, and mixed solvents

As a continuation of previous papers [Biopolymers (1976) 15 , 879; (1978) 17 , 1508], the low-frequency dielectric relaxation of DNA solutions was studied with a four-electrode cell and the simultaneous two-frequency measurement. Below a critical concentration, the dielectric relaxation time agrees with the rotational relaxation time estimated from the reduced viscosity and is almost independent of DNA concentration C_p, and the dielectric increment is proportional to C_p. The critical concentration is approximately 0.02% of DNA for molecular weight M_r 2 × 10⁶ and 0.2% for M_r 4.5 × 10⁵ in 1 mM NaCl. Dielectric relaxations are compared for samples before and after deproteinization, and the protein contamination is found to have a minor effect on the dipole moment of DNA. The effect of a mixed solvent of water and ethanol on the dielectric relaxation of DNA is well interpreted in terms of changes in viscosity and the dielectric constant of the solvent, assuming that the relaxation arises from rotation of the molecule with a quasi-permanent dipole due to counterion fluctuation.