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Biomedical subjects

D E Buetow

Publications and source records attributed to D E Buetow.

At least 19 recordsLinked to original sources
PubMed2000

Oral immunization of mice with transgenic tomato fruit expressing respiratory syncytial virus-F protein induces a systemic immune response.

Respiratory syncytial virus (RSV) is one of the most important pathogens of infancy and early childhood. Here a fruit-based edible subunit vaccine against RSV was developed by expressing the RSV fusion (F) protein gene in transgenic tomato plants. The F-gene was expressed in ripening tomato fruit under the control of the fruit-specific E8 promoter. Oral immunization of mice with ripe transgenic tomato fruits led to the induction of both serum and mucosal RSV-F specific antibodies. The ratio of immunoglobulin subclasses produced in response to immunization suggested that a type 1 T-helper cell immune response was preferentially induced. Serum antibodies showed an increased titer when the immunized mice were exposed to inactivated RSV antigen.

Administration, Oral↗
PubMed1991

Genes for insulin-like growth factors I and II are expressed in senescent rat tissues.

Insulin-like growth factor IGF-I and IGF-II gene expression was measured for the first time in rat liver, brain and heart during the later stages of life, i.e., young adulthood (6 months) to senescence (25 months). IGF-I mRNA was detected in all three tissues at all ages. Its relative level decreased the most in the liver with advancing age. IGF-II mRNA was detected in the brain and heart but not the liver at all ages. The level of IGF-II mRNA decreased only slightly in the brain from young adulthood to senescence.

Aging↗
PubMed1990

RNA synthesis by nuclei and chromatin isolated from adult and senescent Wistar rat liver.

Nuclei isolated from senescent (22-26 months) female Wistar rat liver show a decreased RNA synthesis compared to nuclei from adult (12 months) liver. Kinetic analyses demonstrate a decreased rate (25-42%) and maximal incorporation (41-54%) of labeled uridine triphosphate into both rRNA and mRNA in senescent nuclei. Chromatin-bound RNA polymerase activity is decreased by 36%, whereas free RNA polymerase activity, i.e., not bound to chromatin, is increased by 41% in senescent nuclei, but the total bound plus free activity is the same in senescent and adult nuclei. Isolated senescent chromatin shows reduced transcriptional capacity and requires a higher temperature to initiate melting. A decreased ability of chromatin to bind RNA polymerases appears to underlie the observed decreased RNA synthesis in senescent liver nuclei.

Aging↗
PubMed1990

RNA synthesis by hepatocytes isolated from adult and senescent Wistar rat liver.

The rates of synthesis of total RNA, poly(A)+ RNA and poly(A)+ RNA are decreased by 41, 49 and 42%, respectively, in hepatocytes isolated from senescent (25 months) compared to adult (12 months) female Wistar rats. Results from transcription run-on assays indicate that an impaired ability to initiate transcription largely accounts for the decreased synthesis of RNA by the senescent hepatocytes.

Aging↗
PubMed1982

The complement of cytoplasmic tRNAs, including queuosine-containing tRNAs, in adult and senescent Wistar rat liver and their levels of aminoacylation.

Our previous studies showed that both total cytoplasmic tRNAs and aminoacyl-tRNA synthetases isolated from senescent (24-30 month) female Wistar rat liver were less capable of supporting cell-free protein synthesis than were the same fractions isolated from adult (10-13 month) rat liver. The present study investigates the molecular basis for this age-related result. No significant age-related differences were found in the extent of aminoacylation of the liver cytoplasmic tRNA population, the total tRNA synthetase activity, the rate of aminoacylation of individual tRNAs, or in the overall complement of tRNA species as detected by two-dimensional gel electrophoresis. In homologous senescent aminoacylation assays, consisting of tRNAs and tRNA synthetases from senescent animals, alanine, arginine and aspartic acid were charged to a greater extent and methionine to a lesser extent compared to homologous adult assays. In heterologous assays, adult synthetases were significantly more active than senescent synthetases when charging isoleucine, methionine, phenylalanine, proline and glutamic acid, and less active when charging alanine, aspartic acid and serine. Also, senescent synthetases charged both adult and senescent tRNAs with methionine to a lesser extent than did adult synthetases. In homologous senescent assays with queuosine-containing tRNAs, asparagine, aspartic acid and histidine were charged to a greater extent and tyrosine to a lesser extent compared to homologous adult assays. Results with queuosine-tRNAs are discussed in terms of their potential ability to lower the efficiency of translation in senescent liver.

Aging↗
PubMed1982

Polypeptide composition of thylakoid membranes: two-dimensional gel analysis during development of Euglena chloroplasts.

Two-dimensional gel electrophoresis is used to analyse the polypeptide composition of thylakoid membranes during chloroplast development in Euglena gracilis. The number of polypeptide spots resolved on the two-dimensional gels is 3-4 times the number of bands previously resolved on one-dimensional gels. Groups of multiple polypeptides with the same Mr but with differing isoelectric points are detected throughout the period of chloroplast development. The pattern of polypeptide synthesis and insertion into the forming thylakoid membranes of dark-grown Euglena exposed to light conforms with previous biochemical measurements on the assembly of the electron transport chain located in these membranes.

Chloroplasts↗
PubMed1981

Decreased protein synthesis by polysomes, tRNA and aminoacyl-tRNA synthetases isolated from senescent rat liver.

A cell-free in vitro protein-synthesizing system isolated from adult(10-13-month) and senescent(24-30-month) female Wistar rat liver is described. Optimal concentrations of polysomes, aminoacyl-tRNA synthetases, tRNA, Mg 2+, K+, and labeled amino acids are reported for this in vitro system. Both are rate and extent of protein synthesis are lower with the system from senescent liver compared to that from adult liver. Senescent polysomes, tRNA synthetases, and tRNA all contribute to this decrease. Free adult or senescent polysomes support protein synthesis to the same extent. However, compared to adult polysomes, senescent membrane-bound polysomes support less protein synthesis and account for an increased proportion of the total polysome fraction. Ribonuclease and protease activities are low in the adult and the senescent in vitro systems and do not account for the decreased protein synthesis with the latter.

Aging↗
PubMed1981

In vitro reconstruction of the mitochondrial translation system of yeast.

We have isolated the translation system from yeast mitochondria and have reconstructed it in vitro. This submitochondrial system, composed of mitochondrial ribosomes, tRNA, pH 5 fraction and mRNA, is maximally active at 10 mM Mg2+ and 100 mM KCl or NH4Cl. NH4+ is more stimulatory than K+. Added Escherichia coli tRNA gives less than half the activity obtained with added mitochondrial tRNA. Activity is enhanced with protease inhibitors but not with Ca2+, spermine, or spermidine. In contrast to heterologous translation systems, the present system produces products with molecular weights similar to those of products synthesized by yeast mitochondria in vivo and by intact yeast mitochondria in vitro. The results support the idea that the unique coding features of the mitochondrial genome require a unique translation system for accurate translation of mitochondrial mRNAs.

Cell-Free System↗
PubMed1978

Total free amino acid levels in adult and senescent rat liver.

The total free amino acid content per gram of liver wet weight does not differ significantly between adult and senescent female rats, being 28.8 +/- 3.3 mumol in adult (13-17 months) and 26.2 +/- 2.2 mumol in senescent (23-29 months) animals. This is the first study in which these two age-groups of rats have been so compared. These results combined with a survey of the literature show that amino acid levels in rat liver do not change much, if at all, throughout the lifespan of the animal.

Aging↗
PubMed1976

Phylogenetic origin of the chloroplast.

The 16S ribosomal RNA of the chloroplast of Euglena gracilis strain Z has been characterized in terms of its 2-dimensional electrophoretic "fingerprint" (T1 ribonuclease). Over 100 spots were resolved on the "fingerprint" and each spot was characterized as to which RNA oligonucleotide fragment(s) is contained. When compared to similar analyses of prokaryotic 16S rRNAs and eukaryotic cytoplasmic 18S rRNAs, the chloroplast 16S rRNA was a typically prokaryotic RNA, but bore little if any relationship to eukaryotic 18S rRNAs. Therefore, the cistrons for chloroplast 16S rRNA are related to the equivalent prokaryotic cistrons, but, apparently, are not related to the equivalent eukaryotic cistrons. Among the organisms available for comparison, the Euglena chloroplast 16S rRNA appears most closely related to the 16S rRNA of the eukaryote, Porphyridium cruentum (a red alga), and at least distantly related to the 16S rRNAs of the blue-green algae and perhaps also to the bacilli.

Animals↗
PubMed1976

Hydrolytic enzymes of Euglena gracilis: characterization and activity as a function of culture age and carbon deprivation.

Optimal assay conditions are described for 8 hydrolases of Euglena gracilis var. bacillaris, SM-L1 (streptomycin-bleached) strain, 7 of which have an acid pH-optimum. Acid-phosphatase, beta-galactosidase, beta-glucosidase, b-fucosidase, cathepsin D, RNase, DNase, and an esterase are active in cell homogenates. Amylase has very low activity, and beta-glucuronidase, arylsulfatase, beta, N-acetyl-glucosaminidase, alpha-fucosidase, and alpha- and beta-mannosidase are inactive.

Acetates↗
PubMed1975

Phylogenetic origin of the chloroplast and prokaryotic nature of its ribosomal RNA.

The 16S ribosomal RNA of the Euglena gracilis chloroplast has been characterized in terms of its two-dimensional electrophoretic "fingerprint" (T1 ribonuclease). Results show it to be a typically prokaryotic 16 S rRNA. By the present criterion, different chloroplasts are shown to be related to one another and at least distantly to blue-green algae and perhaps to Bacillaceae. These results argue in favor of an endosymbiont origin of the chloroplast.

Base Sequence↗