Influence of Temperature of Incubation and Type of Growth Medium on Pigmentation in Serratia marcescens

Maximal amounts of prodigiosin were synthesized in either minimal or complete medium after incubation of cultures at 27 C for 7 days. Biosynthesis of prodigiosin began earlier and the range of temperature for formation was greater in complete medium. No prodigiosin was formed in either medium when cultures were incubated at 38 C; however, after a shift to 27 C, pigmentation ensued, provided the period of incubation at 38 C was not longer than 36 hr for minimal medium or 48 hr for complete medium. Washed, nonpigmented cells grown in either medium at 38 C for 72 hr could synthesize prodigiosin when suspended in saline at 27 C when casein hydrolysate was added. These suspensions produced less prodigiosin at a slower rate than did cultures growing in casein hydrolysate at 27 C without prior incubation at 38 C. Optimal concentration of casein hydrolysate for pigment formation by suspensions was 0.4%; optimal temperature was 27 C. Anaerobic incubation, shift back to 38 C, killing cells by heating, or chloramphenicol (25 mug/ml) inhibited pigmentation. Suspensions of washed cells forming pigment reached pH 8.0 to 8.3 rapidly and maintained this pH throughout incubation for 7 days. Measurements of viable count and of protein, plus other data, indicated that cellular multiplication did not occur in suspensions of washed cells during pigment formation. By this procedure utilizing a shift down in temperature, biosynthesis of prodigiosin by washed cells could be separated from multiplication of bacteria.     

Androgen dynamics in vitro in the normal and hyperplastic human prostate gland

The dynamics of uptake and metabolism in vitro of androgens by normal and hyperplastic human prostate glands was studied by means of a new experimental design proposed by Gurpide & Welch (1969). Prostate slices were perfused with a medium containing [(3)H]testosterone and [(14)C]androstenedione, or 5alpha-dihydro-[(3)H]testosterone and [(14)C]testosterone. The entry into the slices, the irreversible metabolism, the conversion between the compounds and the tissue retention or ;uptake' of the steroids were measured at the steady state. A similar portion of the three androgens entered the tissue and was irreversibly metabolized. Conversion of testosterone into 5alpha-dihydrotestosterone was much greater than the interconversion of testosterone and androstenedione. The prostate slices retained 5alpha-dihydrotestosterone at a concentration three times that in the medium, whereas testosterone and androstenedione were retained to a smaller extent. At a steroid concentration of 0.11mumol/l in the medium, the various parameters did not differ significantly in experiments performed with slices from normal and hyperplastic glands. When the steroid concentration in the medium was increased tenfold, however, a difference between normal and hyperplastic glands was evident. The normal glands increased the uptake and metabolism proportionally to the elevation of the steroid concentration in the medium. In the hyperplastic glands the entry and metabolism lagged behind the increase in steroid supply, whereas the tissue uptake became disproportionately high. The possible causes of this finding are discussed.     

Ultrastructural analysis of the human cerebral ventricular system

Summary The ultrastructural organization of the human fetal choroid plexus was assessed with scanning electron microscopy. The membranous modifications of choroidal ependymal cells differ remarkably between 11 and 20 weeks of intrauterine development and suggest a variable functional capacity at different times of ontogenesis. Based upon existing data coupled with the ultra-architectural organization of cilia, clavate and linear microvilli are seen with scanning electron microscopy, a multiple functional role is hypothesized for choroidal ependymal cells.supported by USPH grant NS 08171.career development awardee K04 GM 70001     

Biosynthesis of polyketides. Purification and inhibition studies of 6-methylsalicylic acid synthase

6-MSA³ synthase has been purified 190-fold with 33% yield. The purification was found to be dependent on the presence of glycerol. The acetylenic inhibitors 3-pentynoyl- and 2-hexynoyl-NAC completely inhibit 6-MSA production at concentrations in which fatty acid synthesis, TAL production as well as NADPH oxidation are only partially affected. These results confirm earlier studies on the specificity of inhibition by acetylenic inhibitors and support a mechanism wherein the NADPH-mediated reduction step occurs on a 6-carbon rather than on an 8-carbon intermediate.