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Biomedical subjects

H Hartman

Publications and source records attributed to H Hartman.

At least 19 recordsLinked to original sources
PubMed1990

Stress and coping patterns of participants and non-participants in self-help groups for parents of the mentally ill.

The authors examined differences in stress and coping patterns as well as in situationally-related variables between participants and non-participants in self-help groups for parents of the mentally ill in Israel. Participants, who were higher on socio-economic status indicators, reported coping patterns that tended to be both more active and interactive. They also reported greater concerns around psycho-social issues than non-participants. The authors discuss the possible interrelationships among these findings.

Adaptation, Psychological↗
PubMed1990

Contrasting evolutionary histories of chloroplast thioredoxins f and m.

Fourteen thioredoxin sequences were used to construct a minimal phylogenetic tree by using parsimony. The bacterial thioredoxins clustered into three groups: one containing the photosynthetic purple bacteria, Escherichia and Corynebacterium; a second containing the photosynthetic green bacterium, Chlorobium; and a third containing cyanobacteria. These groupings are similar to those generated from earlier 16s RNA analyses. Animal thioredoxins formed a fourth group. The two thioredoxins of chloroplasts (f and m) showed contrasting phylogenetic patterns. As predicted from prior studies, spinach chloroplast thioredoxin m grouped with its counterparts from cyanobacteria and eukaryotic algae, but, unexpectedly, thioredoxin f grouped with the animal thioredoxins. The results indicate that, during evolution, thioredoxin m of contemporary photosynthetic eukaryotic cells was derived from a prokaryotic symbiont, whereas thioredoxin f descended from an ancestral eukaryote common to plants and animals. The findings illustrate the potential of thioredoxin as a phylogenetic marker and suggest a relationship between the animal and f-type thioredoxins.

Amino Acid Sequence↗
PubMed1989

Classical plant taxonomic ambiguities extend to the molecular level.

The molecular evolution of cytochrome c from angiosperms is compared to that from vertebrates. On the basis of a cladistic analysis from 26 plant species, compared to that from 27 vertebrate species, we find that although the vertebrate sequences yield reasonably well-defined minimal trees that are congruent with the biological tree, the plant sequences yield multiple minimal trees that are not only highly incongruent with each other, but none of which is congruent with any reasonably biological tree. That is, the plant sequence set is much more homoplastic than that of the animal. However, as judged by the relative rate test, the extent of divergence, and degree of functional constraint, cytochrome c evolution in plants does not appear to differ from that of vertebrates.

Animals↗
PubMed1978

Synthesis of organic compounds from carbon monoxide and water by UV photolysis.

The photolysis of water vapor with carbon monoxide at 1849 A yields alcohols, aldehydes and organic acids, with an overall quantum yield of 3.3 x 10(-2). This rather high quantum yield could have led to a contribution of approximately 10(11) organic molecules cm-2 sec-1 to the pool of organic material on the primitive Earth. The reactions are initiated by the photolysis of water molecules and the resulting hydrogen atoms reduce the carbon monoxide to a variety of one and two carbon compounds. The organic molecules are dissolved in water and thus escape destruction by photolysis. Photolysis of water vapor with carbon dioxide did not yield organic compounds under these conditions.

Carbon Monoxide↗
PubMed1978

Speculations on the evolution of the genetic code. II.

An evolutionary scheme is postulated in which a primitive code, involving only guanine and cytosine, would code for glycine (GG), alanine (GC), arginine (CG) and proline (CC). From each of these amino acids and their codons, there evolves a family of related amino acids as the code expands. The four families are: (1) alanine valine, leucine, isoleucine, phenylalanine, tyrosine, methionine and tryptophane; (2) proline, threonine and serine; (3) arginine, lysine, and histidine; (4) glycine, serine cysteine, glutamic acid, glutamine, aspartic acid and asparagine. Except for the glycine relation to glutamic acid and aspartic acid, all amino acids are related by chemical similarities in their side chains. Glycine not having a side chain would permit a more complex set of substitutions.

Amino Acids↗
PubMed1975

Speculations on the origin and evolution of metabolism.

An autotrophic origin of metabolism is described, which requires clays, transition state metals, disulfide and dithiols, U.V. and cyanide ion. A general scheme is proposed, involving the fixation of CO2 and N2, for the evolution of intermediary metabolism based on the evolution of a complex system from a simple one. The basic conclusion is that metabolism could have evolved from a simple environment rather than from a complex one.

Aluminum Silicates↗
PubMed1975

Speculations on the evolution of the genetic code.

An evolutionary scheme is postulated in which the bases enter the genetic code in a definite temporal sequence and the correlated amino acids are assigned definite functions in the evolving system. The scheme requires a singlet code (guanine coding for glycine) evolving into a doublet code (guanine-cytosine doublet coding for gly (GG), ala (GC), arg (CG), pro (CC). The doublet code evolves into a triplet code. Polymerization of nucleotides is thought to have been by block polymerization rather than by a template mechanism. The proteins formed at first were simple structural peptides. No direct nucleotide-amino acid stereo-chemical interaction was required. Rather an adaptor-type indirect mechanism is thought to have been functioning since the origin.

Biological Evolution↗