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Biomedical subjects

A Dietrich

Publications and source records attributed to A Dietrich.

At least 127 records · Page 7Linked to original sources
PubMed1990

Fungal elicitor triggers rapid, transient, and specific protein phosphorylation in parsley cell suspension cultures.

Treatment of suspension-cultured parsley (Petroselinum crispum) cells with fungal elicitor triggers rapid, transient and sequential phosphorylation of a number of proteins, as shown by electrophoretic analysis on two-dimensional gels. This response is rapidly reversed by removal of the elicitor from the medium and appears to be specific. It is not observed in cells exposed to other environmental stress factors, such as heat shock, UV irradiation or treatment with mercuric chloride. Pronase digestion of the elicitor has the same negative effect on protein phosphorylation as its previously demonstrated effect on the activation of some pathogen defense-related genes, suggesting a link between these two phenomena. Some of the changes in protein phosphorylation are among the earliest known events following elicitation. The phosphorylation of a neutral 45-kDa protein, which is found in both the microsomal and cytoplasmic fractions, can be observed as early as 1 min after the onset of elicitor treatment. The phosphorylation of a 26-kDa nuclear protein also starts increasing very early. The changes in protein phosphorylation in response to the elicitor are dependent on the presence of Ca2+ in the medium. Our data are compatible with the hypothesis that protein phosphorylation is involved in the signal transduction processes following elicitor recognition by parsley cells.

Cell Membrane↗
PubMed1990

A nuclear-encoded potato (Solanum tuberosum) mitochondrial tRNA(Leu) and its cytosolic counterpart have identical nucleotide sequences.

Sequencing of potato mitochondrial (mt) tRNA(Leu)(NAA) and of its cytosolic (cyt) counterpart revealed that these tRNAs are identical, except for a post-transcriptional modification: a Gm is present at position 18 in mt tRNA(Leu), instead of a G in cyt tRNA(Leu). Hybridization studies have shown that potato mt tRNA(Leu)(NAA) has a nuclear origin and must therefore be imported from the cytosol.

Base Sequence↗
PubMed1989

A phenylalanine ammonia-lyase gene from parsley: structure, regulation and identification of elicitor and light responsive cis-acting elements.

We demonstrate that phenylalanine ammonia-lyase (PAL) in parsley (Petroselinum crispum) is encoded by a small family of at least four genes. The levels of mRNA from three identified PAL genes increase considerably upon treatment of cultured parsley cells with UV light or fungal elicitor and upon wounding of parsley leaves or roots. In cultured cells these changes were shown to involve transcriptional activation. We present the first primary structure of a plant PAL gene (parsley PAL-1) and the deduced amino acid sequence of the enzyme. Inducible in vivo footprints in the PAL-1 promoter define two nucleotide sequences, within the motifs CTCCAACAAACCCCTTC and ATTCTCACCTACCA, involved in the responses to both UV irradiation and elicitor application. These motifs are conserved at similar positions in several elicitor or light-responsive genes from different species. In two cases they are found within short regions known to confer elicitor or UV-light inducibility. The conserved motifs in the parsley 4-coumarate:CoA ligase gene, which is coordinately regulated with PAL, also display UV-light inducible in vivo footprints. Taken together, our findings suggest a general role of these putative cis-acting elements in the responses of plants to such stresses.

Amino Acid Sequence↗
PubMed1989

Nucleolar structures in chromosome and SC preparations from human oocytes at first meiotic prophase.

We describe a comparative study of the behavior of nucleolar structures and their relationship with nucleolar chromosomes and synaptonemal complexes at first meiotic prophase of human oocytes in an attempt to elucidate the nature of this cellular organization and to learn more about maternal nondisjunction. The number of main nucleoli varies along the different stages of prophase I and is usually low. It shows an increase from leptotene to pachytene and a decrease from pachytene to diplotene related to a decrease and an increase of main nucleoli volume, respectively. The methodology employed has enabled us to analyze in detail dark bodies, round bodies, dense bodies, and main nucleoli in chromosome or synaptonemal complex spreads. The relationship between nucleolar chromosomes or synaptonemal complexes and the nucleoli implies the existence, in a very reduced space, of chromosomal regions that contain homologous sequences and that are often unpaired. This situation may facilitate the production of heterologous pairing and chromosomal exchanges between nonhomologous chromosomes and finally result in aneuploidy. Thus, the situation explained above together with the differences between the oocyte and spermatocyte NOR cycles could be one of the reasons for the higher incidence of aneuploidies of maternal origin at meiosis I.

Cell Nucleolus↗
PubMed1989

Short time action of antirheumatic substances on the liver of rat. Protective effect of tryptophan + methionine.

1. A large number of drugs, including some antirheumatic substances, cause liver damage. 2. Only a little information is available, so far, on the causes of such damage and their prevention. 3. From studies on a number of antirheumatic drugs as to their effect upon the liver, three categories could be differentiated: (a) large effect (b) low effect (c) no effect. 4. Judging from our results, the liver damage is induced via a disturbance of the NAD-adenoribosylation metabolism.

Alanine Transaminase↗
PubMed1989

Orally active aldose reductase inhibitors derived from bioisosteric substitutions on tolrestat.

A series of aldose reductase inhibitors was prepared in which structural modifications were made to three positions of the potent, orally active inhibitor tolrestat (1), namely, the 6-methoxy substituent, thioamide sulfur, and the N-methyl moiety. These compounds were evaluated in two in vitro systems: an isolated enzyme preparation from bovine lens to assess their intrinsic inhibitory activity and an isolated rat sciatic nerve assay to determine their ability to penetrate membranes of nerve tissue. These compounds were also evaluated in vivo as inhibitors of galactitol accumulation in the lens, sciatic nerve, and diaphragm of galactose-fed rats. Bioisosteric replacement of the 6-methoxy group of 1 with a methylthio substituent gave 5, and replacement of the thioamide substituent of 1 with a cyanoamidine gave 7. Both 5 and 7 retained high in vitro potency but were less potent in vivo than 1. Replacement of the tolrestat N-methyl group by a carbomethoxy moiety gave 10 and led to a substantial reduction in activity in each of the three assays employed. However, this same structural modification on oxo-tolrestat (2) led to 11 and resulted in an enhancement of the intrinsic activity and a comparable in vivo potency. The isolated nerve data suggest that some compounds in these series do not readily penetrate into peripheral nerves, and this presumably is a factor in their lack of oral activity.

Aldehyde Reductase↗
PubMed1989

Expression of the kinase domain of mouse protein kinase C in E. coli.

The kinase domain of mouse protein kinase C type alpha has been expressed at high levels in E. coli. The protein has been purified 500-fold taking advantage of the fact that highly expressed fusion proteins precipitate out in the bacterial cell and can be solubilized in 7 M urea. The purified protein can be detected with an antibody generated against a PKC alpha derived synthetic peptide. The purified kinase domain exhibits no measurable kinase activity in a protamin phosphorylation assay. This could be an indication that post-translational modifications of the protein kinase domain which do not happen in bacteria are a requirement for functional enzyme activity or that the regulatory domain of protein kinase C is indispensable for kinase function.

Animals↗
PubMed1988

Molecular cloning of mouse protein kinase C (PKC) cDNA from Swiss 3T3 fibroblasts.

A set of complementary DNAs (cDNAs) that encode the complete 672-amino acid sequence for mouse protein kinase C (PKC) type alpha have been isolated from a mouse Swiss 3T3 cDNA library. Extensive rescreening of this cDNA library only resulted in the isolation of clones of the same PKC species, indicating that Swiss 3T3 fibroblasts express exclusively PKC-alpha. This enzyme is encoded by two different mRNAs that exhibit a substantial heterogeneity in their 3'-noncoding regions. This heterogeneity could have been derived from alternative splicing of the pre-mRNAs or be due to differential usage of the polyadenylation motif. The expression of PKC mRNA in fibroblasts is very low and it is not influenced by treatment with the tumor promoter 12-O-tetradecanoyl-13-phorbol-acetate.

Animals↗
PubMed1987

In vitro synthesis and processing of a bean pathogenesis-related (PR4) protein.

When bean plants (Phaseolus vulgaris var. Saxa) are treated with mercuric chloride or infected with alfalfa mosaic virus, they produce pathogenesis-related (PR) proteins. We report here that functional mRNA encoding bean PR4 protein is only present when synthesis of this protein has been induced. Treatment with mercuric chloride results in a rapid induction of functional bean PR4 mRNA (within 2-3 h), whereas in virus-infected plants this mRNA can only be detected the second day following the infection. Bean PR4 protein is synthesized in vitro, using this mRNA in a rabbit reticulocyte lysate system, as a precursor of 35 kDa. This precursor can be processed into a polypeptide having the same molecular mass (33.5 kDa) as the in vivo PR4 protein by the addition to the cell-free translation system of canine pancreatic microsomal membranes.

Electrophoresis, Polyacrylamide Gel↗
PubMed1987

In vitro synthesis of bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases. Characterization and processing of a precursor polypeptide for the chloroplast enzyme.

Bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases differ in their structural and catalytic properties and do not share common antigenic determinants. Polyadenylated mRNAs, prepared from young bean leaves, have been translated in vitro in a rabbit reticulocyte lysate cell-free system. The newly synthesized polypeptides have been submitted to immunoadsorption on protein A-Sepharose in the presence of the antibodies raised against the chloroplastic or the cytoplasmic leucyl-tRNA synthetase. The specificity of the immunoadsorption has been checked by competition experiments involving the pure enzymes. Bean chloroplastic leucyl-tRNA synthetase is synthesized in vitro from a polyadenylated mRNA as a precursor polypeptide of 130 kDa, which is somewhat larger than the mature enzyme of 120 kDa. Bean cytoplasmic leucyl-tRNA synthetase is synthesized in vitro as a polypeptide which has the size of the mature monomer (130 kDa). Processing of the precursor polypeptide of the chloroplastic leucyl-tRNA synthetase, yielding the mature enzyme, has been obtained by performing the in vitro translation in the presence of canine pancreatic microsomal membranes. These results suggest that in vivo bean chloroplastic leucyl-tRNA synthetase could be synthesized in the cytoplasm as a precursor which would be transported into the chloroplasts.

Amino Acyl-tRNA Synthetases↗
PubMed1987

A qualitative study on vanadate effects in the tetrahydrofolate-dependent formate transfer in vitro and in vivo in mice.

Parenteral administration of sodium vanadate (NaVO3, 22 mg/kg b.w., i.p.) to mice depresses the oxidation rate of [14C]formate to [14C]CO2, as determined by radioactive breath analysis. The heavy metal-induced inhibition is relatively fast in onset, fairly intense (up to 80% inhibition), of short duration (about 2 h) and strongly correlated to the presence of vanadate (in the pentavalent state) in plasma. The [14C]CO2 exhalation rate from [14C]bicarbonate is less affected by vanadate in vivo, thereby suggesting a specific interference of vanadium in the intermediate step of formate oxidation to HCO3-. In vitro in mouse liver cytosolic fractions vanadate inhibits the enzymatic transfer of formate to tetrahydrofolic acid. The inhibition is accomplished by a vanadate-dependent oxidative degradation of tetrahydrofolate. In contrast, the concentrations of N5-methyltetrahydrofolate, dihydrofolate and folate remain unchanged upon in vitro-exposure to vanadate. The in vitro studies thus might explain the observed inhibition of formate oxidation to carbon dioxide in vivo by a vanadate-evoked depletion of its biological carrier tetrahydrofolic acid. Whether the interference in tetrahydrofolate metabolism also occurs under in vivo conditions, remains to be elucidated.

Animals↗
PubMed1987

Influence of oxypangam upon the induction of tyrosine aminotransferase, the NAD content and the ADPR transferase activity in several organs of the rat.

Oxypangam is a substance applied therapeutically against a number of diseases, such as chronic liver damages, angina pectoris, and psychosomatic disturbances. The mode of action of oxypangam has not yet conclusively been described. The only well-known properties of this substance are its intensive methylating and lipolytic effects. The present paper serves to elucidate the influence of oxypangam on the induction of the tyrosine aminotransferase, on the NAD content and on the activity of the ADPR transferase in the liver. Our studies showed that in normal animals, increasing doses of oxypangam support the induction of tyrosine aminotransferase. Up to a concentration of 100 mg/kg oxypangam enhances also the induction of tyrosine aminotransferase by tryptophan. In both cases, however, it does not work in adrenalectomized animals. Under the influence of oxypangam the NAD content of the liver remained unchanged, while the activity of the ADPR transferase was influenced only slightly.

Animals↗
PubMed1987

Assessment of function in routine clinical practice: description of the COOP Chart method and preliminary findings.

The COOP Project, a primary care research network, has begun development of a Chart method to screen function quickly. The COOP Charts, analogous to Snellen Charts, were pretested in two practices on adult patients (N = 117) to test feasibility, clinical utility, and validity. Patients completed questionnaires containing validated health status scales and sociodemographic variables. Practice staff filled out forms indicating COOP Chart scores and clinical data. We held debriefing interviews with staff who administered the Charts. The results indicate the Charts take 1-2 minutes to administer, are easy to use, and produce important clinical data. The patterns of correlations between the Charts and validity indicator variables provide evidence for both convergent and discriminant validity. We conclude that new measures are needed to assess function in a busy office practice and that the COOP Chart system represents one promising strategy.

Activities of Daily Living↗
PubMed1986

House calls by New Hampshire family practitioners.

We surveyed current activities and attitudes regarding house calls among New Hampshire family physicians. Fifty of a random sample of 72 eligible participants returned a brief questionnaire. They reported on 134 house calls they made during the two weeks prior to the survey. Eighty-four percent of participants offered house calls, averaging 2.68 house calls per physician over the two week study period. Most house calls were to the elderly or homebound for management purposes. Physicians thought house calls were important, but often an inefficient use of their time. Financial and time constraints were the most commonly cited limiting factors. The decision to make a house call is based on clinical judgment regarding the individual case and broader issues involving the physician's whole practice. Unless external constraints change, house calls will continue to be an uncommon event.

Adult↗
PubMed1985

Nutritional rickets in breast-fed infants.

A ten-year literature review was prompted by the fortuitous discovery of nutritional rickets in a "well child." Sixty-three cases were identified, suggesting that this disease is not so rare as thought. Rickets should be considered in the differential diagnosis of nonspecific musculoskeletal complaints and poor growth. Vitamin D supplementation in breast-fed children should be prescribed more often.

Adult↗
PubMed1983

Large scale purification and structural properties of yeast aspartyl-tRNA synthetase.

A large scale purification procedure of baker's yeast aspartyl-tRNA synthetase is described which yields more than 200 mg pure protein starting from 30 Kg of wet commercial cells. The synthetase is an alpha 2 dimer of Mr = 125,000 +/- 5,000 which can be crystallized (J. Mol. Biol. 138, 1980, 129-135). The enzyme has an elongated shape with a Stokes radius of 50 A and a frictional ratio of 1.5. The synthetase has a tendency to aggregate but methods are described where this effect is overcome.

Amino Acyl-tRNA Synthetases↗
PubMed1983

Phaseolus vulgaris cytoplasmic leucyl-tRNA synthetase. Purification and comparison of its catalytic, structural, and immunological properties with those of the chloroplastic enzyme.

The cytoplasmic leucyl-tRNA synthetase was purified from bean (Phaseolus vulgaris) leaves. After ammonium sulfate fractionation and chromatography on Sephadex G-50, DEAE-cellulose, hydroxylapatite, and phosphocellulose, complete purification was achieved by blue Sepharose CL-6B chromatography using specific elution with pure yeast tRNALeu1. The enzyme was purified 1050-fold and had a specific activity of 940 nmol of leucyl-tRNA formed/min/mg of protein. Polyacrylamide gel electrophoresis of the native enzyme showed one band, but the denatured enzyme showed two bands. These two protein bands are structurally related. The smallest protein appears to be a cleavage product from the largest one, suggesting the presence of a sensitive cleavage site in the cytoplasmic leucyl-tRNA synthetase. The cytoplasmic enzyme is a monomer (Mr = 130,000), larger than its chloroplastic counterpart (Mr = 120,000). The two enzymes differ in their substrate (tRNA) specificity, tryptic peptide map, and amino acid composition. Antibodies were raised against the cytoplasmic enzyme and against the chloroplastic enzyme and no cross-immunological reaction was detected, showing that the two enzymes do not share any antigenic determinant. Taken together, these results suggest that P. vulgaris cytoplasmic and chloroplastic leucyl-tRNA synthetases are coded for by different genes.

Amino Acids↗