Amino Acid incorporation in developing fucus embryos

The incorporation of ¹⁴C-leucine and ¹⁴C-amino acid mixture into protein in unfertilized eggs and developing embryos of the brown alga Fucus vesiculosus L. was studied. Bacterial contamination was initially a problem, but it was found that the addition of 40 μg/ml chloramphenicol to the incubation medium would inhibit bacterial protein synthesis without affecting early development of the Fucus embryos. The kinetics of uptake and incorporation of ¹⁴C-leucine into the trichloroacetic acid-soluble and -insoluble fractions indicated that the exogenous precursor did not equilibrate with the main soluble leucine pool before incorporation into protein. Uptake and incorporation of leucine by embryos 90 to 175 minutes old were proportional to exogenous leucine concentration over the range 5 × 10⁻⁶ m to 5 × 10⁻³ m. Unfertilized eggs will incorporate ¹⁴C-leucine into protein. The rate of this incorporation increases dramatically in newly fertilized eggs with a maximum rate at 3.5 hours, a period of cell wall formation and increasing metabolic rates. Thereafter, the rate of incorporation declines until approximately 15 to 17 hours when it increases again concurrently with the onset of rhizoid initiation and cell division.     

Phenylketonuria—Experience at One Center in the First Year of Screening in California

One year''s experience with phenylketonuria during the calendar year 1966, the first year for compulsory newborn screening in California, was reviewed. The over-all prevalence rate from reported cases in California during this period was one case per 19,500 persons tested. Fifty-seven persons suspected of having pku were evaluated, and 25 of them were determined to be phenylketonuric. Eleven of the 25 were infants in whom the abnormality was detected through the newborn screening program or because it was detected in a sibling through a screening program. All the newborn phenylketonuric patients were developing normally at the time of last report (although the follow-up periods were short).In nine of the other children, pku was detected because they were retarded. Five retarded children who were diagnosed as phenylketonuric at another clinic were given dietary assistance.Five additional infants had elevated serum phenylalanines but did not have the classic biochemical findings of pku and are being evaluated further. Nine infants with positive screening tests exhibited biochemical and clinical findings consistent with transient tyrosinemia. Eighteen other children were evaluated and found to have no metabolic abnormality.The newborn screening program for pku is of decided benefit in early identification of a group of infants who have a high rate of potentially serious metabolic disease. Early identification permits treatment soon enough to prevent mental retardation. Newly identified patients should be evaluated in a medical setting capable of careful pediatric, biochemical and nutritional surveillance.     

Plasma concentrations of pituitary hormones in 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated male rats

Experiments were conducted to test the hypothesis that acute TCDD toxicity is associated with pituitary hypofunction. Sexually mature male Sprague-Dawley rats were given graded doses of TCDD (0-100 micrograms/kg) and evaluated 7 days later. Despite pronounced hypophagia and body weight loss, plasma concentrations of growth hormone (GH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were not significantly affected by any dose of TCDD. Only prolactin (PRL) concentrations were reduced, while, as previously reported, thyroid-stimulating hormone concentrations were elevated. Also, plasma LH, PRL, and adrenocorticotropic hormone (ACTH) concentrations were not significantly affected 1, 2, 3, 4, 5, or 7 days after a single dose of TCDD (50 micrograms/kg). We conclude that (1) pituitary hypofunction is not a major cause of the initial stages of acute TCDD toxicity, (2) growth retardation in TCDD-treated rats is not the result of a deficiency of GH, (3) alterations in plasma corticosterone concentrations are due to altered responsiveness of the adrenal to ACTH stimulation rather than to changes in plasma ACTH concentrations, and (4) that impaired spermatogenesis is not associated with a decrease in plasma FSH concentrations. In addition, the lack of a consistent effect on plasma PRL concentrations suggests that alterations in plasma PRL concentrations do not play a critical role in the toxicity of TCDD. Finally, because TCDD treatment causes a serious androgenic deficiency without increasing the rates at which androgens are catabolized or excreted, the fact that plasma LH concentrations were unaffected indicates that TCDD treatment must reduce the responsiveness of the testis to LH stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fatty acid monooxygenation by cytochrome P-450BM-3

Cytochrome P-450BM-3 is a catalytically self-sufficient enzyme which monooxygenates saturated and unsaturated fatty acids, alcohols, and amides. The protein has two domains: one which contains heme and is P-450-like and the other which contains FAD and FMN and is P-450 reductase-like. Both domains are on a single polypeptide chain. Utilizing a plasmid containing the gene encoding P-450BM-3, we have transformed the Escherichia coli strain DH5 alpha. This clone overexpresses P-450BM-3 to make approximately 20% of the soluble protein of this organism under optimal conditions. P-450BM-3 can be purified to homogeneity from the soluble fraction of the protein of these cells with a recovery of 50% making this cell line an excellent source of this important enzyme. Purified preparations of P-450BM-3 hydroxylate palmitic acid at a rate of 1600 mol/min/mol of heme at 25 degrees C. The stoichiometry of NADPH to oxygen utilized was 1 for all conditions; however, the ratio of oxygen or NADPH utilized per molecule of fatty acid substrate metabolized was different for different homologs of saturated fatty acids, when low concentrations (less than 100 microM) of substrate were used. Lauric and myristic acids were metabolized to two hydroxylated products, irrespective of the initial concentration of fatty acid in the reaction mixture, and the ratio of oxygen consumed to fatty acid hydroxylated was 1. High concentrations of palmitic acid (greater than 200 microM) led to the formation of three polar metabolites and a stoichiometry of 1:1 was observed for oxygen and palmitic acid utilization. These results indicate that a single hydroxyl group was inserted into each of these molecules. Lower concentrations (less than 50 microM) of palmitic acid were metabolized to additional polar metabolites, and the ratio of oxygen consumed to fatty acid substrate consumed approximated 3:1. These results can be explained best by a hypothesis that the initial hydroxylated compounds, which accumulate during the oxidation of palmitic acid by P-450BM-3, can be further oxidized by this enzyme to polyhydroxy- or hydroxy-ketone products.     

The role of litter in an old-field community: impact of litter quantity in different seasons on plant species richness and abundance

Summary We studied the effect of removing and adding plant litter in different seasons on biomass, density, and species richness in a Solidago dominated old-field community in New Jersey, USA. We removed all the naturally accumulated plant litter in November (658 g/m²) and in May (856 g/m²) and doubled the amount of litter in November and May in replicated plots (1 m²). An equal number of plots were left as controls. Litter removal and addition had little impact on total plant biomass or individual species biomass in the growing season following the manipulations. Litter removal, however, significantly increased plant densities but this varied depending upon the season of litter removal, species, and life history type. Specifically, the fall litter removal had a much greater impact than the spring litter removal suggesting that litter has its greatest impact after plant senescence in the fall and prior to major periods of early plant growth in spring. Annual species showed the greatest response, especially early in the growing season. Both spring and fall litter removal significantly increased species richness throughout the study. Litter additions in both spring and fall reduced both plant densities and species richness in June, but these differences disappeared near the end of the growing season in September. We concluded than in productive communities where litter accumulation may be substantial, litter may promote low species richness and plant density. This explanation does not invoke resource competition for the decline in species richness. Finally, we hypothesize that there may be broad thresholds of litter accumulation in different community types that may act to either increase or decrease plant yield and diversity.     

Atriopeptin does not augment the transvascular flux of macromolecules in the hamster cheek pouch.

Natriuretic peptides elaborated by atrial myocytes promote marked renal sodium and water excretion as a mechanism for fluid and electrolyte balance. Recent evidence suggests that atriopeptin (ANP) also targets the non-renal vasculature as a site for enhanced fluid exchange. It remains unclear whether ANP alters microvascular integrity to facilitate the efflux of both plasma and proteins across the endothelial barrier, or if fluid exchange is selectively enhanced. This study evaluated the influence of ANP on macromolecular transport through the direct observation of microvessels in the hamster cheek pouch using fluorescent intravital microscopy. Fluorescein isothiocyanate conjugated to either bovine serum albumin or dextran 150,000 Mw was utilized as a permeability probe. Macromolecular efflux was quantified as fluorochrome clearance. The clearance of fluorescein-conjugated bovine serum albumin (57.94 +/- 7.03) or fluorescein-conjugated dextran 150 (4.09 +/- 1.35) remained unaltered by intravascular injection of 1 microgram/kg ANP. Topical application of 40 ng to cheek pouch microvessels produced similar results. All pouches demonstrated positive leakage response to histamine 2.5 x 10(-6) M, increasing fluorochrome clearance approximately 2- to 11-fold. Bolus injection of 1 microgram/kg ANP reduced mean arterial pressure, increased urine flow from 6.63 +/- 2.59 microliters/min to 8.20 +/- 6.13 microliters/min, and elevated sodium excretion from 1.37 +/- 0.49 microEq/min to 2.54 +/- 0.99 microEq/min. These results suggest that ANP fails to significantly alter the integrity of the protein-transporting channels in the microvascular exchange barrier.