Microbial fermentative preparation of L-[15N2]lysine and its tracer: application to serum amino acid kinetic studies

The microorganism Brevibacterium flavum 21129 has been used to produce multigram batches of L-[15N2]lysine of high purity and isotopic enrichment by supplementation of the growth medium with (15NH4)2SO4 of 98.0 atom% excess. The doubly 15N-labeled lysine can be detected at dilutions 10 times greater than singly labeled lysine when isotope dilution curves are analyzed by gas chromatography-mass spectrometry. This enhanced sensitivity permits kinetic measurements of plasma free-lysine isotope content over a 300-fold dilution during 6 h following a single oral bolus of 5 mg/kg body wt. This inexpensive preparation method lends itself to the production of highly useful biochemical compounds for kinetic studies of human nutrition.     

Regulation of Rat Pineal Hydroxyindole-O-Methyltransferase in Neonatal and Adult Rats

The relative importance of neural, and some nonneural, mechanisms in the control of pineal hydroxyindole-O-methyltransferase (HIOMT) activity during development and in the adult rat was studied. In neonatal rats, guanethidine-treatment, bilateral superior cervical ganglionectomy (SCGX), or exposure to constant light did not prevent the initial appearance of HIOMT activity, indicating that neural stimulation of the gland is not essential for the development of HIOMT activity. In adult rats, decentralization or removal of the SCG led to a slow fall in HIOMT activity, to about 30% of control activity, indicating that the enzyme is largely under neural control. Additionally, adrenalectomy or hypophysectomy had no effect on HIOMT activity, refuting the suggestion that adrenal and/or gonadal steroids are of major importance in the regulation of this enzyme. The fall in activity of the enzyme after SCGX or exposure to constant light probably does not represent a shift in the K_m of the enzyme nor the selective disappearance of a distinct molecular species. Similar changes in HIOMT activity and cyclic GMP responsiveness occur in response to alterations in the length of the daily dark period, adding further evidence to our earlier speculation that there may be a functional relationship between these two.     

Microinjection of human cell extracts corrects xeroderma pigmentosum defect

Cultured fibroblasts of patients with the DNA repair syndrome xeroderma pigmentosum (XP) were injected with crude cell extracts from various human cells. Injected fibroblasts were then assayed for unscheduled DNA synthesis (UDS) to see whether the injected extract could complement their deficiency in the removal of u.v.-induced thymidine dimers from their DNA. Microinjection of extracts from repair-proficient cells (such as HeLa, placenta) and from cells belonging to XP complementation group C resulted in a temporary correction of the DNA repair defect in XP-A cells but not in cells from complementation groups C, D or F. Extracts prepared from XP-A cells were unable to correct the XP-A repair defect. The UDS of phenotypically corrected XP-A cells is u.v.-specific and can reach the level of normal cells. The XP-A correcting factor was found to be sensitive to the action of proteinase K, suggesting that it is a protein. It is present in normal cells in high amounts, it is stable on storage and can still be detected in the injected cells 8 h after injection. The microinjection assay described in this paper provides a useful tool for the purification of the XP-A (and possibly other) factor(s) involved in DNA repair.     

Le genisteto-carlinetum macrocephalae ass. nov. De l'étage montagnard et le ligusticetum corsici ass. nov. De l'étage subalpin des massifs du cinto et du campotile orientale

Sans résuméJe tiens à remercier M. le Dr. J. Braun-Blanquet de la généreuse hospitalité qu'il m'a offerte à la S.I.G.M.A. et des précieux conseils qu'il m'a dispensés pour la définition de ces associations. C'est la raison pour laquelle il m'a paru nécessaire de l'associer à l'une des Associations originales que j'ai décrites.Je suis également reconnaissant à mes amis M. et G. Roux d'avoir permis le traitement de mes données floristiques par l'analyse factorielle des correspondances.     

Le Genisteto-Carlinetum macrocephalae ass. nov. de l'étage montagnard et le Ligusticetum corsici ass. nov. de l'étage subalpin des Massifs du Cinto et du Campotile orientale

Sans résuméJe tiens à remercier M. le Dr.J. Braun-Blanquet de la généreuse hospitalité qu'il m'a offerte à la S.I.G.M.A. et des précieux conseils qu'il m'a dispensés pour la définition de ces associations. C'est la raison pour laquelle il m'a paru nécessaire de l'associer à l'une des Associations originales que j'ai décrites.Je suis également reconnaissant à mes amisM. et G. Roux d'avoir permis le traitement de mes données floristiques par l'analyse factorielle des correspondances.     

DNA-dependent in vitro synthesis of enzymes of the galactose operon of Escherichia coli

Summary Two active enzymes of the galactose operon of Escherichia coli, uridyl transferase and galactokinase have been synthesized with high yields in a DNA dependent system for protein synthesis. The unspecific blank values amount to less than two percent of the rate obtained under optimal conditions and permit the accurate determination of even a small fraction of the maximum synthesis rate. Therefore this system provides a sensitive assay for the biological activity of DNA that contains the intact galactose operon of Escherichia coli.The synthesis of these galactose enzymes is to a high extent dependent on the presence of cyclic adenosine-3:5-monophosphate.D-fucose, known as an inducer of the galactose operon in vivo, stimulates the synthesis of galactokinase, indicating that the repressor of the galactose operon in active under these conditions. This stimulation is not observed, if the bacterial extract is prepared from a strain defective for the galactose repressor or if the DNA carries an operator constitutive mutation in the galactose operon. Therefore the stimulation by D-fucose is true derepression.     

Phycobilisomes in Blue-Green Algae

Fifteen species of freshwater blue-green algae, including unicellular, filamentous, and colonial forms, were subjected to a variety of fixatives, fixation conditions, and stains for comparison of the preservation of phycobilisomes. Absorption spectra of the corresponding in vivo and released photosynthetic pigments, in 10 of the species that were maintained in culture, demonstrated the presence of phycocyanin in all 10 species and phycoerythrin in only 2 of them. Spectroscope and electron microscope evidence was obtained for localization of phycobiliproteins in phycobilisomes of Nostoc muscorum. Phycobilisomes were observed in all species examined in situ, strenghening the hypothesis that phycobilisomes are common to all phycobiliprotein-containing photosynthetic blue-green algae.     

Antibody-induced redistribution of normal and tumor associated surface antigens

Redistribution (capping) of normal and tumor-associated surface antigens was studied on murine and human cells by the indirect membrane immunofluorescence (MIF) technique. The capping of H-2 isoantigens was compared on normal mouse T-lymphocytes and on YAC cells, a Moloney leukemia virus (MLV) induced lymphoma. H-2 and Moloney virus induced cell surface antigen (MCSA) capping was compared on three YAC lines with different MCSA concentrations. H-2 and tumor-associated surface antigen capping was compared on two polyoma induced sarcoma lines and five methylcholanthrene induced sarcoma lines. In the human system, IgM-capping was compared on normal lymphocytes and on the Burkitt lymphoma derived Daudi line. Capping of HL-A and the Epstein-Barr virus (EBV) determined membrane antigen (MA) was compared on the Burkitt lymphoma derived line Maku and on EBV-superinfected Daudi cells. H-2 antigens on normal murine cells capped more promptly and on a larger fraction of the cell population on the various tumor cells. Surface associated IgM showed a better capping on normal lymphocytes than on Daudi cells. All tumor associated antigens except MCSA, showed good capping. MCSA was almost completely refractory to capping. Increasing concentrations of MCSA appeared to inhibit the capping of H-2 on the YAC sublines with different concentrations of MCSA. The polyoma induced ascites sarcoma (SEWA) did not cap either with regard to H-2 or the polyoma determined surface antigen.