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Biomedical subjects

D B Stein

Publications and source records attributed to D B Stein.

17 recordsLinked to original sources
PubMed1992

Structural rearrangements of the chloroplast genome provide an important phylogenetic link in ferns.

The chloroplast genome of most land plants is highly conserved. In contrast, physical and gene mapping studies have revealed a highly rearranged chloroplast genome in species representing four families of ferns. In all four, there has been a rare duplication of the psbA gene and the order of the psbA, 16S, and 23S rRNA genes has been inverted. Our analysis shows that the described rearrangement results from a minimum of two inversions within the inverted repeat. This chloroplast DNA structure provides unambiguous evidence that phylogenetically links families of ferns once thought to belong to different major evolutionary lineages.

Chloroplasts↗
PubMed1990

The "REST" program: a new treatment system for the oppositional defiant adolescent.

This study compared the REST (Real Economy System for Teens) program with traditional talk therapy in the treatment of oppositional defiant adolescents. The REST program uses rules for five target behaviors: room care, personal hygiene, completion of chores, abusiveness, and safety violations. Objective measures and subjective parental ratings were taken. Twenty-five adolescents were assigned to each therapy group. In the REST program the adolescent was provided with only food and shelter. The adolescent had to earn money through the REST allowance program to pay for everything else. Earning the allowance was made contingent upon compliance with all rules for the five target behaviors. The results showed significantly greater improvement on all target behaviors for the REST program than for traditional therapy. In addition, parents of adolescents in the REST group reported that their adolescents seemed happier, more relaxed, and closer to them.

Adolescent↗
PubMed1988

The development of acetylcholinesterase activity in the embryonic nervous system of the frog, Xenopus laevis.

Histochemical detection of acetylcholinesterase (AChE) activity in Xenopus embryos was found first in primary motoneurons, Rohon-Beard neurons and somitic myotubes at early tail bud stages. At late tail bud stages all primary neurons, including primary interneurons, cranial ganglion cells and ventral brainstem cells expressed this enzyme. The onset of detectable AChE activity in some primary neurons occurred near the time of initial axon outgrowth, whereas in others it occurred at much later stages. At early independent-feeding and continuous-swimming stages nearly all seemingly postmitotic neurons began to express AChE activity, and by the beginning of limb bud stages, when many secondary neuronal populations were going through their final rounds of mitosis, nearly all CNS cells outside the ventricular zone were intensely stained. Thus, the onset of detectable AChE activity in secondary neurons occurred near the time of their final mitoses. In trunk somites the enzyme activity initially was located diffusely throughout the myotube, and with progressing development it became localized to the myocommata. From the onset of AChE activity both head somites and head muscles had discrete patches of reaction product all over their surfaces. The onset of detectable AChE activity occurred in muscles near the time that they were contacted by motor axons. These data demonstrate that the primary neurons are the first to express AChE activity, and that as the secondary neurons begin to proliferate, AChE is expressed by nearly all embryonic neuronal populations.

Acetylcholinesterase↗
PubMed1988

A fern spore storage protein is genetically similar to the 1.7 S seed storage protein of Brassica napus.

The ostrich fern, Matteuccia struthiopteris L., contains two globulin spore storage proteins of 2.2 S and 11.3 S, with physical characteristics similar to those of seed storage proteins of Brassica napus (rapeseed) and Raphanus sativus (radish). By the use of a cloned cDNA that encodes the 1.7 S B. napus storage protein (napin), gene sequences that hybridized with napin were detected in fern nuclear DNA, and a 900-nucleotide homologous mRNA was detected in developing spores. In vitro translation of this fern mRNA produced a 22-kD polypeptide comparable in size to the 21-kD precursor polypeptide identified in Brassica. No hybridizations were observed between the Brassica 12 S clone and either fern DNA or developing spore mRNA.

Blotting, Southern↗
PubMed1988

Chloroplast DNA evolution and systematics of Phanerophlebia (Dryopteridaceae) and related fern genera.

Restriction site variation in chloroplast DNA was examined in the neotropical fern genus Phanerophlebia and in selected species of the related Asiatic genus Cyrtomium and the cosmopolitan progenitor of these two, Polystichum. A total of 103 restriction site mutations was identified; these were used to construct phylogenetic networks and trees based on Wagner and Dollo parsimony and Fitch-Margoliash distance algorithms. The analyses provided evidence that Phanerophlebia did not arise from Cyrtomium. Both genera are convergent descendants from different progenitor groups in Polystichum, and Asiatic Cyrtomium is more closely related to temperate New World Polystichum than it is to neotropical Phanerophlebia. Reticulate venation, previously considered an important taxonomic character for infrageneric classification in Phanerophlebia, most likely evolved independently twice within the genus. Diploid maternal progenitors are suggested for two of four tetraploid species analyzed, and species-level distinctions for two closely related taxa of Phanerophlebia are questioned.

Journal Article↗
PubMed1987

Promotion of Stomatal Opening by Indoleacetic Acid and Ethrel in Epidermal Strips of Vicia faba L.

Indole-3-acetic acid (IAA), at concentrations of 0.01 to 1.0 millimolar, and ethephon (0.3% v/v Ethrel) promote stomatal opening when applied to epidermal peels of Vicia faba L. in light or dark. The effect of ethylene is seen by 30 minutes and maximal opening (over two times that of untreated controls) occurs after only 60 to 90 minutes in the light. Stomatal opening by IAA and Ethrel in both light and dark is prevented by 0.14 millimolar AgCl. It is suggested that the effect of added IAA, but not that of light, is linked to ethylene production. The possible role of ethylene in stomatal opening during fungal infection is discussed. The stomates of Vicia faba provide a new system to study the effects of ethylene on certain membrane-regulated processes.

Journal Article↗
PubMed1980

Nucleoprotein subunit structure in an unusual prokaryotic organism: Thermoplasma acidophilum.

The freeliving thermophilic mycoplasma, Thermoplasma acidophilum, has a small acid-soluble protein tightly bound to its DNA. This protein is similar to eukaryotic histones in both size and amino acid composition. Here we report that the protein condenses DNA into globular particles that are about half the size of eukaryotic nucleosomes. Our conclusions are based primarily upon the following observations: (1) Nuclease digestion produced DNA fragments of 40 base-pairs. (2) The ratio of protein to DNA was such that 4--5 molecules of protein were associated with each 40 base-pair segment of DNA. (3) Protein crosslinking reagents produced tetramers of the histone-like protein. (4) Electron microscopy revealed globular particles 5--6 nm in diameter. (5) Each globular particle reduced the apparent contour length of the DNA by 40 base-pairs. Thus, each nucleoprotein particle is apparently composed of 40 base-pairs of DNA coiled around four molecules of proteins.

Cross-Linking Reagents↗
PubMed1979

Studies on DNA sequences in the Osmundaceae.

Phylogenetic relationships of Osmunda cinnamomea, O. claytoniana, and O. regalis were explored by means of DNA sequence comparisons. Hydroxyapatite thermal elution profiles of self-reassociated repetitive DNA fragments were very similar, indicating the absence of gross differences in the amount of recent amplification or addition of repetitive DNA in any of these three genomes. Interspecific DNA sequence comparisons showed, in contrast to our earlier interpretation, that repeated DNA sequences of O. claytoniana are nearly equally diverged from those of O. cinnamomea and O. regalis. Differences between repetitive sequences of the three species can be interpreted as reflecting amplification events which occurred subsequent to speciation. The data obtained suggest that the three Osmunda species most likely arose more or less simultaneously from a common ancestor. These findings were verified in experiments with tracer DNA preparations enriched for single copy sequences. On the basis of the hydridization data presented here and of the fossil record, the rate of single copy sequence divergence in the ferns is comparable to that in the primates, although slower than that observed in other animal taxa. From this first evaluation of rates of DNA evolution in plants it would seem that the rates for plants and animals are roughly comparable. The evidence suggests that species divergence is accompanied by further reiteration of preexisting repeat sequences. The rate of addition of repetitive sequences probably is slower in ferns than in angiosperms. This difference might be attributable to the much larger effective generation time in ferns.

Base Sequence↗
PubMed1978

Physiologically important stabilization of DNA by a prokaryotic histone-like protein.

The thermophilic mycoplasma Thermoplasma acidophilum has tightly bound to its DNA a protein that closely resembles the histones of eukaryotes. DNA associated with this protein is more stable than free DNA against thermal denaturation by about 40 degrees C, as shown in both native nucleoprotein and in hybrid nucleoprotein reconstituted in vitro with calf DNA. Since only about 20 percent of the DNA in this organism is associated with the histone-like protein, we suggest that its physiological function is to prevent complete separation of the DNA strands during brief exposures of the organism to denaturing conditions, and thus to facilitate rapid renaturation when normal environmental conditions return.

Bacterial Proteins↗
PubMed1978

Phylogenetic affinities between eukaryotic cells and a thermophilic mycoplasma.

Thermoplasma acidophilum, a thermophilic mycoplasma, has several unusual features suggesting a possible relationship to eukaryotic cells. One feature is a histone-like protein that is associated with the DNA, condensing it into subunits similar to those in eukaryotic chromatin. A second feature is an association of cytoplasmic proteins that resembles eukaryotic actin and myosin. These two components are widely distributed in different groups of eukaryotic cells, but are typically lacking in prokaryotic cells. Furthermore, T. acidophilum lacks cytochromes and respires by enzymes that apparently are not coupled to oxidative phosphorylation. This primitive type of respiration resembles that of microbodies, another feature which is represented in the cytoplasm of all groups of eukaryotic cells. Furthermore, since T. acidophilum lacks a cell wall and appears to have a primitive correlate of endocytosis, it would appear to be mechanically capable of acquiring a symbiotic mitochondrion. Thus, our observations are consistent with the symbiotic hypothesis for the origin of eukaryotic cells. We suggest that an organism similar to T. acidophilum was the host cell for the original symbiosis, becoming the nucleus and cytoplasm of modern eukaryotic cells.

Actomyosin↗
PubMed1971

Gibberellin-induced Fertility in the Fern Ceratopteris thalictroides (L.) Brongn.

Treatment of the homosporous fern Ceratopteris thalictroides L. sporophyte with gibberellic acid results in fertile fronds appearing 3 to 5 weeks after treatment. The hetero-blastic leaf sequence is markedly reduced, and the entire life cycle can be completed in 3 months on defined medium. Treatment with gibberellic acid also stimulates the accumulation of starch in mature leaves.

Journal Article↗