Serine-specific tRNAs in Escherichia coli: relative abundance and sequence

Serine isoaccepting tRNAs were isolated from bulk tRNA of Escherichia coli by affinity chromatography on immobilized bacterial elongation factor Tu and their relative abundance was determined. The three major species, which are sufficient to read all six serine codons, were identified by sequencing. The sequence of a novel tRNASer with the anticodon GGA was elucidated.     

Expression of monoclonal antibody-defined cell surface antigens during rat brain development

Using single-cell suspensions of mechanically dissociated, prenatal BDIX-rat brain cells (13th, 15th, and 21st days after fertilization) for immunization, we have established a collection of 37 monoclonal antibodies (Mabs) directed against neural cell surface determinants. The developmental-stage-dependent expression of cell-surface antigens recognized by these Mabs was analyzed both on plasma membranes isolated from whole brains of BDIX rats (prenatal days 13-22 and adults) using an indirect 125I solid-phase radioimmunoassay, and on intact BDIX-rat brain cells (prenatal days 13-22) using a fluorescence-activated cell sorter. Different types of developmental stage-dependent profiles of Mab binding were found, these being indicative of the presence of neural cell surface determinants whose expression increases, decreases, or does not change with brain development. Some of the Mab-binding profiles showed transient changes as a function of developmental stage. These Mabs are currently being used for the characterization, reproducible identification, and isolation of neural cell subpopulations of the developing rat brain, with the aim of investigating the cell type dependence and developmental (differentiation) stage dependence of malignant transformation following pulse exposure to the carcinogen N-ethyl-N-nitrosourea at defined stages of brain development.     

Isolation and characterization of a new thermophilic and autotrophic methane producing bacterium:Methanobacterium thermoaggregans spec. nov.

Methanobacterium thermoaggregans is a new thermophilic autotrophic rod-shaped methane producing bacterium. The organism likes to form aggregates during growth and utilizes only H₂ and CO₂ as substrates. Growth optimum is at 65°C with a doubling time of 3.5 h. Optimal growth occurs at pH-values between 7 and 7.5. The addition of yeast extract to the mineral salt medium stimulates growth. The DNA base composition is 42 mol% G+C. The organism was isolated from mud taken from a cattle pasture. Because of its optimal growth temperature and its tendency to form aggregates the nameMethanobacterium thermoaggregans is suggested.Abbreviations G+C Guanine+cytosine     

Synthesis and phosphorylation of cytoskeleton components in foetal,regenerating and adult normal rat hepatocytes during culture

Summary Detergent insoluble material (DIM) was prepared by gentle treatment with detergent from foetal, regenerating and adult normal rat hepatocytes cultured for various times. It retained to some degree the morphology of the cells. After incubation of intact cells with ³⁵S-methionine, most of the labelled DIM proteins were found to be components of the cytoskeleton. They included several cytokeratins, vimentin and actin. The synthesis rate varied with the age of animals and culture conditions. The high synthetic rate of vimentin in foetal and regenerating hepatocytes could be associated with cell proliferation. No correlation was found between cytokeratin synthesis and hepatocyte growth. Most of the cytoskeleton proteins could be phosphorylated in intact cells and in DIM from cultured hepatocytes. However the degree of phosphorylation of these proteins was not related to their synthetic rate. The decreased phosphorylation level in cultured adult rat hepatocytes could be related to the rapid loss of specific functions.     

Production and release of peptidoglycan and wall teichoic acid polymers in pneumococci treated with beta-lactam antibiotics

Autolysin-defective pneumococci treated with inhibitory concentrations of penicillin and other beta-lactam antibiotics continued to produce non-cross-linked peptidoglycan and cell wall teichoic acid polymers, the majority of which were released into the surrounding medium. The released cell wall polymers were those synthesized by the pneumococci after the addition of the antibiotics. The peptidoglycan and wall teichoic acid chains released were not linked to one another; they could be separated by affinity chromatography on an agarose-linked phosphorylcholine-specific myeloma protein column. Omission of choline, a nutritional requirement and component of the pneumococcal teichoic acid, from the medium inhibited both teichoic acid and peptidoglycan synthesis and release. These observations are discussed in terms of plausible mechanisms for the coordination between the biosynthesis of peptidoglycan and cell wall teichoic acids.     

Investigations on karyotype evolution in patients with chronic myeloid leukemia (CML)

In an attempt to relate karyotype evolution to clinical and hematological data serial chromosomal analyses were performed in 31 patients with chronic myeloid leukemia (CML), both in chronic and acute phases. Our results in Philadelphia chromosome (Ph1)-positive CML are in line with karyotype profiles described in the literature. In addition, we report on chromosomal findings in 4 cases of Ph1-negative disease, one presenting with an iso17q chromosome in the positive CML. The same chromosomal abnormality was observed in a small population of Ph1-negative cells present in one of two patients with mixed Ph1-positive/Ph1-negative CML. The first case of a female patient with the loss of a sex chromosome in Ph1-positive cells is reported. Two patients with unusually long and mild chronic phases despite the presence of trisomy 8 in their karyotypes are described. Our findings suggest that the order of appearance of additional chromosomal changes of CML is of prognostic significance for the progression and the clinical picture of the disease.     

l- andd-alanine transport in brush border membrane vesicles from lepidopteran midgut: Evidence for two transport systems

Summary In brush border membrane vesicles from the midgut ofPhilosamia cynthia larvae (Lepidoptera) thel- andd-alanine uptake is dependent on a potassium gradient and on transmembrane electrical potential difference. Each isomer inhibits the uptake of the other form: inhibition ofl-alanine uptake byd-alanine is competitive, whereas inhibition ofd-alanine uptake byl-alanine is noncompetitive. Transstimulation experiments as well as the different pattern of specificity to cations suggest the existence of two transport systems. Kinetic parameters for the two transporters have been calculated both when K_out>K_in and K_out=K_in.d-alanine is actively transported also by the whole midgut, but it is not metabolized by the intestinal tissue.     

Dietary docosahexaenoic acid is retroconverted in man to eicosapentaenoic acid, which can be quickly transformed to prostaglandin I3

In a 24 h kinetic study docosahexaenoic acid (DCHA, C22:6n-3) or eicosapentaenoic acid (EPA, C20:5n-3) were given in a single dose to healthy male volunteers. PGI₃-M, the main urinary metabolite of prostaglandin I₃ was below the detection limit in the control periods, but was excreted already in the first 4 h after ingestion of DCHA or EPA and decreased thereafter. Excretion of PGI₂-M did not change significantly. In a second dietary trial DCHA and EPA were given cross-over to 7 healthy male volunteers for 6 days. PGI₃-M was formed after DCHA and EPA in amounts of 35 and 20 % of PGI₂-M and showed a considerable interindividual variation. The structure of PGI₃-M was verified by independant biochemical synthesis. Our data indicate that dietary DCHA is retroconverted to EPA in man, which is quickly transformed - like dietary EPA itself - to prostaglandin I₃. DCHA may therefore serve as a precursor fatty acid for EPA and its cyclooxygenated and lipoxygenated products.