Biosynthesis of candicidin by phosphate-limited resting cells ofStreptomyces griseus

Summary A phosphate-limited resting cell system ofStreptomyces griseus in a synthetic medium has been developed in which biosynthesis of the polyene macrolide, candicidin, is linear for at least 36 h without cell growth. Glucose and to a lesser degree sucrose, but not lactose, support antibiotic synthesis. Glucose is utilized at a constant rate for antibiotic synthesis without affecting mycelial dry weight. Acetate and propionate, the building units of the macrolide aglycone, stimulate candicidin biosynthesis in cultures supplemented with glucose but do not support its synthesis in the absence of glucose. Maximal stimulation of candicidin biosynthesis was produced by 40 mM propionate or 250 mM acetate. The biosynthetic intermediate, methyl malonate, and the analog, 1-propanol, were more stimulatory than propionate at the same concentration.     

Aryl hydrocarbon hydroxylase activity in the fungus Cunninghamella bainieri: evidence for the presence of cytochrome P-450.

The aryl hydrocarbon hydroxylase (AHH) enzyme from the fungus Cunninghamella bainieri has been characterized. It is NADPH dependent and exhibits a pH optimum near 7.8. It is inhibited by CO, SKF 525-A, and metyrapone, but cyanide shows no inhibitory effect. These data, together with the pattern of inhibition and stimulation shown by metal ions, suggest that the fungal AHH activity is due to a cytochrome P-450. About 25% of the hydroxylase activity remains in the supernatant while the remainder precipitates after centrifugation at 100,00g for 2.5 h. The 100,000g supernatant was further fractionated by (NH₄)₂SO₄ precipitation. A NADPH-dependent cytochrome c reductase is concentrated mainly in the 100,000g supernatant, and a cytochrome c oxidase is present mainly in the 100,000g pellet. The cytochrome c reductase is essential for AHH activity as shown by the inhibition of AHH activity with cytochrome c and dichloroindophenol. Solubilization of a portion of the 100,000g pellet in aqueous digitonin followed by dithionite reduction and addition of CO resulted in the observation of a maximum absorbance at 450 nm characteristic of cytochrome P-450.     

Genetic variants of serum alpha1-antitrypsin (Pi types) in Portuguese.

The results of Pi typing on 330 Portuguese from the area of Lisbon are reported. We found six phenotypes and four alleles out of the 24 described in the literature. The allele PiM is the most frequent as in other populations, PiS shows a high frequency (0.1152), and PiF is absent, which agrees satisfactorily with former studies carried out in Spain. These results are compared with others and the entity of the Iberian population is evoked.     

Hospitalization for mental illness: evaluation of admission trends from 1941 to 1971.

A study of the diagnostic composition of the inpatient population of Ontario and Canadian psychiatric facilities has shown an important change in hospital-treated illness over the period 1941-71. Patients with nonpsychotic disorders accounted for 54% of all admissions to Ontario public mental hospitals in 1971, compared with only 8% in 1941. The trend was similar for both first admissions and proportion of readmissions, and was similar for psychiatric units of general hospitals. In contrast, the overall rate of first admission for psychotic disorders to inpatient facilities remained remarkably constant over time, as did the proportion of readmissions among all admissions. The findings dispel the notion that the increasing proportion of readmissions is due largely to a rapid turnover of former long-stay psychotic patients (the "revolving-door phenomenon"). The findings could not be attributed to a changing prevalence of types of psychiatric illness, increased availability of psychiatric inpatient facilities or comprehensive medical insurance.     

Evidence contrary to the protein error hypothesis for in vitro senescence.

A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 +/- 1%, S.E.), in comparison with that in 19 old cultures (4.9 +/- 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H]thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H]thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directes specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylameimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.     

Increased PRPP synthetase activity in cultured rat hepatoma cells containing mutations in the hypoxanthine-guanine phosphoribosyltransferase gene.

Nine independently derived clones of mutagenized rat hepatoma cells selected for resistance to 6-mercaptopurine (6-MP) or 6-thioguanine (6-ThioG) have been isolated. Each has severely reduced catalytic activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and seven of them possess significantly increased activities of phosphoribosylpyrophosphate (PRPP) synthetase. The degrees of elevations of PRPP synthetase activities do not correlate with the degrees of deficiencies of HPRT activities. The cells from one of these clones, 1020/12, posses 40% of the normal HPRT catalytic activity and overproduce purines. We have extensively examined the cells from this clone. Immunotration studies of 1020/12 cells indicate that there is a mutation in the structural gene for HPRT. Although they possess increased specific catalytic activities of the enzyme. PRPP synthetase, the catalytic parameters, heat stability, and isoelectric pH of PRPP synthetase from 1020/12 cells are indistinguishable from those of the enzyme from wild-type cells. The cause of purine overproduction by 1020/12 cells appears to be the elevated PRPP synthetase activity, rather than a PRPP "sparing" effect stemming from reduced HPRT activity. Support for this idea is provided by the observation that the complete loss of HPRT activity in a clone derived from 1020/12 cells does not further enhance the levels of PRPP synthetase or purine overproduction. We propose that the elevated levels of PRPP synthetase activity in these HPRT deficient cells result from a mutational event in the structural gene for HPRT, and that this causes the disruption of a previously undescribed regulatory function of this gene on the expression of the PRPP synthetase gene.     

some aspects of the biochemical and mineral composition of marine plankton

A natural population of phytoplankton and two species of zooplankton, Calanus finmarchicus (Gunnerus) (stage V) and Sagitta elegans (Verrill) (mature), were analysed for their biochemical and mineral composition. Comparison with published data for the same categories of plankton shows that the distribution of both organic and mineral fractions is highly variable, the causes of which are not equally understood. The composition of the organic fraction is affected by the duality of function of the biochemical constituents and by the large number of ecological factors which influence their concentration. Whether this applies to the mineral fraction remains uncertain; nevertheless it appears that plankton concentrate trace metals, that phytoplankton has a greater ability to concentrate them than zooplankton, and that the ability of zooplankton to concentrate various metals varies with the species.     

Undersulfated chondroitin sulfate in the cartilage matrix of brachymorphic mice.

Homozygous brachymorphic ($\text{bm}\text{bm}$) mice have a disproportionately short stature, similar to human achondroplasia. We previously showed that each zone of growth in young $\text{bm}\text{bm}$ epiphyseal cartilages is smaller than normal and that the extracellular matrix appears to contain normal collagen fibrils, but smaller and reduced numbers of proteoglycan matrix granules. Our studies reported here indicate that mutant, like normal cartilage, synthesizes type II collagen and contains normal quantities of glycosaminoglycans as judged by uronic acid content. However, the glycosaminoglycans from the mutant differ from the normal in their chromatographic and electrophoretic properties. Further studies established that glycosaminoglycans from cartilages of brachymorphic animals were undersulfated. Whereas chondroitinase digests of glycosaminoglycans from cartilage of normal $\text{C57Bl}\text{6J}$ 5-day-old mice contained predominantly disaccharides sulfated in the 4-position, that of the mutant contained appreciable unsulfated disaccharides as well.