Effects of L-proline and post-plating temperature treatment on Maize (Zea mays L.) anther culture

Summary Comparison of different post-plating temperature regimes with a control treatment (27° C) revealed that a short-term cold (8/14°C:2/2 days or 14°C:4 days) as well as a heat treatment (30°C:14 days) increased the production of embryro-like-structures (ELS) from cultured maize anthers. The beneficial effects of short-term cold treatments were magnified 2–3 times when L-proline (PROL) was added to the induction medium (125–500 mg/L). In the best treatment (14°C:4 days, 125 mg/L L-proline) one genotype produced 143.5 ELS/100 anthers. Anthers subjected to high temperature (30°C:4 days, 30°C:7 days, 30°C:14 days) generally showed a lower response than did cold treated anthers, although genotypic differences were observed. Regeneration frequency did not appear to be affected by the presence of L-proline in the induction medium.Abbreviations ELS Embryo-like-structures - PROL L-proline     

Base sequence studies of 300 nucleotide renatured repeated human DNA clones

A band of 300 nucleotide long duplex DNA is released by treating renatured repeated human DNA with the single strand-specific endonuclease S₁. Since many of the interspersed repeated sequences in human DNA are 300 nucleotides long, this band should be enriched in such repeats. We have determined the nucleotide sequences of 15 clones constructed from these 300 nucleotide S₁-resistant repeats. Ten of these cloned sequences are members of the Alu family of interspersed repeats. These ten sequences share a recognizable consensus sequence from which individual clones have an average divergence of 12.8%. The 300 nucleotide Alu family consensus sequence has a dimeric structure and was evidently formed from a head to tail duplication of an ancestral monomeric sequence. Three of the remaining clones are variations on a simple pentanucleotide sequence previously reported for human satellite III DNA. Two of the 15 clones have distinct and complex sequences and may represent other families of interspersed repeated sequences.     

Trisomy for the distal third of the long arm of chromosome 19 in brother and sister

Summary Trisomy for the distal third of the long arm of chromosome 19 was observed in a 12-year-old boy and his 9-year-old sister. Both are affected by extremely severe statural and psychomotor retardation. The physical symptoms common to both are dwarfism, micro- and brachycephaly, antimongoloid slant of the eyes, hypertelorism, ptosis, short nose, short philtrum, poorly formed ears, short neck with excess skin, barrel-shaped thorax, diastasis of rectus muscles, kyphosis, sacral dimple, excess of digital arches, pedes valgi, laterally curved big toes, epilepsy and muscular hypotonia. The chromosomal anomaly was transmitted by the mother, who is the carrier of a translocation t(19;20)(19q133;20pter). In the pedigree, extending over four generations, among 30 pregnancies fathered or mothered by 5 carriers resulted in: 6 individuals with normal karyotype, 9 carriers, 2 confirmed and 2 presumptive unbalanced abnormal children, and 10 abortions.     

Current-voltage studies on the thylakoid membrane in the presence of ionophores

The reversibility of the binding of ionophores to the thylakoid membrane is studied. While gramicidin binds practically irreversibly, valinomycin and nonactin bind reversibly, however, only a small fraction (about 1 %) of the membrane-bound valinomycin or nonactin is active in ion transport. The current-voltage relationship is evaluated under these circumstances. We have found that it is practically linear. This together with the relationship between current and ion concentration agrees qualitatively with the results reported for bimolecular lipid membranes, which contain a large fraction of negatively charged lipids. For the ionophores, valinomycin and nonactin, the binding equilibria (K ≈ 10⁴) and the turnover numbers (≈ 3 · 10⁴/s) are evaluated for their action on the thylakoid membrane. Possible reasons for the inactivity of the majority of membrane-bound ionophore molecules are discussed.     

The use of several energy-coupling reactions in characterizing mutants of Escherichia coli K12 defective in oxidative phosphorylation.

Oxidative phosphorylation, ATP-32Pi exchange, ATP-dependent quenching of acridine-dye fluorescence, ATP-dependent transhydrogenase and ATP-dependent transport of thiomethyl beta-D-galactoside are shown to be experimentally equivalent tools to study the functional state of the ATPase complex in Escherichia coli wild-type and mutant strains defective in oxidative phosphorylation. According to these criteria ten mutants in the ATPase complex were classified having lesions in the unc A,B region of the chromosome. The first mutant type lacks ATPase activity, but the membrane-integrated part of the complex remains functional (class I). The second mutant type lacks a functional membrane-integrated part, but retains ATPase activity (class II). The third mutant type is shown to be defective in both parts of the ATPase complex (class III).