Freeze-preservation of rice cells: A physiological study of freeze-thawed cells

Rice ( Oryza sativa L.) cells returning to in vitro culture after preservation at superlow temperature in liquid nitrogen are characterized by a number of physiological alterations. These include: reduction in respiration and glucose uptake, loss of intracellular potassium, decrease in the cellular level of key metabolites (ATP, glucose-6-phosphate and pyruvate) and fragility of protoplasts following the action of cell wall-degrading enzymes.
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time.     

The molecular basis of disorders of human hemoglobin synthesis

Summary The structure and organization of the human globin genes at the nucleotide level has been established by restriction endonuclease digestion of cellular DNA, and by the isolation and purification of these. genes in phage vectors. With this approach it has been possible to define alterations at the DNA level resulting in a group of inherited diseases of man known as the thalassemia syndromes, and related disorders. Combined with other known genetic and biochemical data, these studies provide a framework for understanding the pathogenesis of these disorders at the molecular level.     

Sterols from three Lactarius species

The sterol composition of three fungi was determined. Ergosterol is the major sterol, accompanied by other closely related sterols.     

Enhanced erythroid burst formation in mice after testosterone treatment

A single administration of testosterone propionate (TP) in ex-hypoxic polycythemic mice induces, at 24 hr after androgen, an amplification of the erythroid burst-forming unit (BFU-E or B) pool in marrow. This phenomenon is not associated with an amplification of the erythroid colony-forming unit (CFU-E or E) compartment and is followed by its depletion. In the other hand, the 36–49 hr rise of erythropoietin (Ep) levels in serum is followed by a 60-hr amplification of the E pool. It is suggested that the latter phenomenon is mediated by enhanced Ep production, whereas the early amplification of the B compartment may derive from a direct influence of TP at the stem cell level.     

Amino acid composition of zein molecular components

Zein extracted from maize endosperm has been fractionated into four polypeptide chains, having the following MWs 23 000, 21 000, 13 500 and 9600. By amino acid analysis the two smaller MW chains (representing 30% of total zeins) have been found to be zein-type molecules. These two chains are thought to be responsible for zein granule formation via -S-S- bridges. Zein is also highly heterogeneous in charge, and is resolved into at least 15 components, with pI's in the pH range 5–9. As demonstrated by amino acid analysis, part of this heterogeneity is due to spot mutations in some of the genes responsible for zein synthesis.     

MK-801 Prevents 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Induced Parkinsonism in Primates

In cynomologus monkeys, systemic administration of MK-801, a noncompetitive antagonist for the N-methyl-D-aspartate receptor, prevented the development of the parkinsonian syndrome induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MK-801 also attenuated dopamine depletion in the caudate and putamen and protected dopaminergic neurons in the substantia nigra from the degeneration induced by the neurotoxin. Nevertheless, 7 days after MPTP administration in the caudate and putamen of monkeys also receiving MK-801, the levels of toxic 1-methyl-4-phenylpyridinium were even higher than those measured in monkeys receiving MPTP alone. This indicates that the protective action of MK-801 is not related to MPTP metabolism and strongly suggests that, in primates, the excitatory amino acids could play a crucial role in the mechanism of the selective neuronal death induced by MPTP.     

The R1 gene conferring race-specific resistance to Phytophthora infestans in potato is located on potato chromosome V.

Summary Late blight in potato is caused by the fungusPhytophthora infestans and can inflict severe damage on the potato crop. Resistance toP. infestans is either based on major dominantR genes conferring vertical, race-specific resistance or on minor genes inducing horizontal, unspecific resistance. A dihaploid potato line was identified which carried theR1 gene, conferring vertical resistance to allP. infestans races, with the exception of those homozygous for the recessive virulence allele of the locusV1. The F₁ progeny of a cross between this resistant parent P(R1) and P(r), a line susceptible to all races, was analysed for segregation ofR1 and of restriction fragment length polymorphism (RFLP) markers distributed on the potato RFLP map comprising more than 300 loci. TheR1 locus was mapped to chromosome V in the interval between RFLP markers GP21 and GP179. The map position ofR1 was found to be very similar to the one ofRx2, a dominant locus inducing extreme resistance to potato virus X.     

Determination of the chirality of amino acid residues in the course of subtractive Edman degradation of peptides.

A chiral reagent, 1-fluoro-2,4-dinitro-5-L-alanine, was synthesized for the analysis of enantiomeric mixtures of amino acids after precolumn derivatization. The resulting diastereomers can be separated and quantitated by microbore RP-HPLC. These derivatives are relatively stable under the conditions used for acid hydrolysis of peptide bonds. Thus, this reagent was included in the protocol of a subtractive Edman degradation procedure of peptides to determine the sequence position of amino acid residues with concomitant identification of their chirality at a nanomolar level.     

Proteinase isoinhibitors from bovine spleen: primary structure of an intermediate in the processing of the precursor

The complete amino acid sequence of the proteinase inhibitor III from bovine spleen is reported. It consists of 62 amino acid residues and is identical to that of spleen inhibitor II (an isoinhibitor of the bovine pancreatic trypsin inhibitor, which shares with the latter 89% of sequence identity), except for four extra residues at the C-terminal side. Inhibitor III appears to be an intermediate in the processing of the putative 100-residue primary expression product, which leads to the mature inhibitor II. These results and those previously obtained for another intermediate, isoinhibitor I, are indicative of the following order for the last steps of the precursor processing inhibitor I----inhibitor III----inhibitor II. The mature protein and the two intermediates isolated have a very similar antiproteolytic activity. However, their in vivo target enzyme(s) are not yet known, as also the target enzyme of the bovine pancreatic trypsin inhibitor is not known. Thus, the available data would indicate that either the three isoinhibitors have a distinct functional role, by inhibiting different target enzymes, or inhibitors I and III are obligatory intermediates for directing the final targeting of the mature, functionally relevant inhibitor II.     

A tetrameric iron superoxide dismutase from the eucaryote Tetrahymena pyriformis

An iron-containing superoxide dismutase has been purified from the protozoan Tetrahymena pyriformis. It has a molecular weight of 85,000 and is composed of four subunits of equal size. The tetramer contains 2.5 g atoms of ferric iron. Visible absorption and electron spin resonance spectra closely resemble those of other iron-containing superoxide dismutases. The amino acid sequence of the iron superoxide dismutase was determined. Each subunit is made up of 196 residues, corresponding to a molecular weight of 22,711. Comparison of the primary structure with the known sequences of other iron-containing superoxide dismutases reveals a relatively low degree of identity (33-34%). However, a higher percentage identity is found with mammalian manganese-containing superoxide dismutases (41-42%). The amino acid sequence is discussed in consideration of residues that may distinguish iron from manganese or dimeric from tetrameric superoxide dismutases.