In vivo ionizing irradiations produce deletions in the hprt gene of human T-lymphocytes

The hprt T-lymphocyte cloning assay, which detects mutations occurring in vivo in humans, has been used to examine mutants induced in patients receiving radioimmunoglobulin therapy (RIT) for cancer. Samples from 13 patients before treatment (controls) and 15 samples from 12 patients after treatment were studied for both mutant frequencies and molecular changes in the hprt mutant T-cell clones. Patients were studied up to 48 months after treatment. Post-RIT patients showed increased mutant frequencies as compared to pre-treatment values. T-cell receptor (TCR) gene analysis of mutant T-cell clones demonstrated that 84% arose independently, both pre- and post-treatment, which is the same proportion as seen in normal individuals. However, several individuals did show large sets of mutants with the same TCR gene rearrangement patterns. Molecular analysis of mutants demonstrated a greater proportion of mutations with hprt gene changes on Southern blots after RIT treatment than before (40% versus 20%). RIT increases the proportion of mutations with total rather than partial gene deletions or other gross structural changes compared to normal individuals or pre-treatment patients. These studies are defining the spectrum for radiation-induced hprt gene mutations in vivo in human T-lymphocytes.     

Stimulation by auxin of phospholipase A in membrane vesicles from an auxin-sensitive tissue is mediated by an auxin receptor

Microsomal vesicles were prepared from zucchini (Cucurbita pepo L.) hypocotyls containing radioactive phosphatidylethanolamine or phosphatidylcholine, and these lipids were used as substrates by phospholipase A which is activated by auxins. Phospholipase D and phospholipase C hydrolysed the same substrates but were not influenced by auxin. Phospholipase A was activated by the auxins indolyl-3-acetic acid, 2,4-dichlorophenoxyacetic acid and, to a lesser extent, by -naphthaleneacetic acid whereas the weak auxins 2,3-dichlorophenoxyacetic acid and -naphthaleneacetic acid were almost inactive. This hormone specificity was also found in growth tests with etiolated zucchini hypocotyls. Phospholipase A activation by auxin was blocked by a polyclonal antibody against the maize auxin-binding protein. We propose that phospholipase A activation is a primary reaction in the signal transduction leading from hormone-binding to the growth response.Abbreviations IAA indolyl-3-acetic acid - 2,3-D, 2,4-D 2,3- and 2,4-dichlorophenoxyacetic acid - -NAA; -NAA - and -naphthaleneacetic acid This work was supported by the Deutsche Forchungsgemeinschaft. We thank D. Klämbt (Botanical Institute, University of Bonn, FRG) for a generous gift of polyclonal antibody (IgG fraction) against auxin-binding protein and U. Kutschera (Botanical Institute, University of Bonn, FRG) for advice with the growth tests.     

Group size and stability: Why do gibbons and spider monkeys differ?

Gibbons and spider monkeys have similar diets, body size, and locomotor patterns. They are therefore expected to be subject to similar socioecological rules. However their grouping patterns differ. Gibbons live in small stable groups, whereas spider monkey form unstable sub-groups that vary from small to large during different seasons. If similar principles apply to the two species, food abundance should vary more for spider monkeys than for gibbons; food density should be similar for the two species when spider monkey sub-groups are the same size as gibbon groups; and the highest level of food abundance should be higher for spider monkeys than for gibbons. These predictions are upheld for a comparison of particular populations ofHylobates muelleri andAteles geoffroyi.     

Optimal hunting group size: the need for lions to defend their kills against loss to spotted hyaenas

This paper presents preliminary evidence that kleptoparasitism by spotted hyaenas may influence optimal hunting group size of lions. In the absence of adult male lions, hyaenas can drive female and subadult lions off their kills provided they outnumber the lions by a factor of four. Hence the larger the group of lions on the kill, the greater their chance of defending their food against invading hyaenas. At Savuti, where there was a shortage of adult male lions, the groups of female and subadult lions lost almost 20% of their food to hyaenas. Losses were most frequent for those living in small groups. These lions were often satiated by the time the hyaenas acquired the kill, so the hyaenas did not cause immediate need, yet constituted a constant energy drain on lions by forcing them to hunt more frequently. The implications of these observations for modelling optimal hunting group size of lions are discussed.     

Foundations of vectorial metabolism and osmochemistry

Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially-directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.     

A simple model relating photoinhibitory fluorescence quenching in chloroplasts to a population of altered Photosystem II reaction centers

A model is presented describing the relationship between chlorophyll fluorescence quenching and photoinhibition of Photosystem (PS) II-dependent electron transport in chloroplasts. The model is based on the hypothesis that excess light creates a population of inhibited PS II units in the thylakoids. Those units are supposed to posses photochemically inactive reaction centers which convert excitation energy to heat and thereby quench variable fluorescence. If predominant photoinhibition of PS II and cooperativity in energy transfer between inhibited and active units are presumed, a quasi-linear correlation between PS II activity and the ratio of variable to maximum fluorescence, F_VF_M, is obtained. However, the simulation does not result in an inherent linearity of the relationship between quantum yield of PS II and F_VF_M ratio. The model is used to fit experimental data on photoinhibited isolated chloroplasts. Results are discussed in view of current hypotheses of photoinhibition.Abbreviations F_M maximum total fluorescence - F₀ initial fluorescence - F_V maximum variable fluorescence - PS Photosystem - Q_A, Q_B primary and secondary electron acceptors of Photosystem II     

Anther-specific,developmentally regulated expression of genes encoding a new class of proline-rich proteins in sunflower

We have used RNA gel blot analysis to demonstrate the anther-specific expression of three genes in sunflower. Expression of these genes was first detected shortly before flower opening, which occurs sequentially on the sunflower inflorescence, and continues during pollination. In contrast, these genes are not expressed (or only weakly expressed) in a male-sterile line in which anther development aborts. In situ hybridization experiments showed that these genes are only expressed in the single cell layer of the sunflower anther epidermis. In the case of one of these genes, which codes for an abundant mRNA, we report the peptide sequences deduced from the sequence of two similar but non identical cDNAs. These proteins contain a potential signal peptide and are characterized by the presence of a proline-rich region which reads KPSTPAPPPPPP(PP)K. Our results also suggest that several proline-rich proteins of unknown functions are specifically synthesized during the maturation of anthers in sunflower.     

Increasing in vitro germination of Musa balbisiana seed

Seeds of Musa balbisiana were soaked in water for five days prior to excision of embryos. Embryos with their longitudinal axis laid flat and half-way embedded on agar-solidified medium produced the highest germination and the most desirable plantlet characteristics. Germination in vitro was 94% within 7 days compared to 50% after 54 days for greenhouse-sown seeds.     

Effect of potassium humate on apple cv. ‘Golden Delicious’ cultured in vitro

The effects of humic substances on in vitro culture of Golden Delicious apple are reported. Potassium humate (KH) when used in proliferation showed a negative interaction with BA while it enhanced rooting when IBA was not present in the culture medium. In the presence of IBA, KH increased root number and reduced root growth. The highest concentration tested, 500 mg l^-1, caused a drastic reduction in root system development. 50 mg l^-1 KH hastened rooting and plants grew more rapidly when transferred to soil.     

Culture of soybean fruit explants: growth conditions and efficiency of nitrogen sources for reserve protein synthesis

A system was devised for the in vitro culture of soybean fruits. The culture system consisted of a single fruit attached to a short piece of stem through which the nutrients were supplied. The fruit explants were taken when pods were fully expanded and the seeds at initial stages of growth. During a 7-day culture period, the seeds accumulated dry matter and protein in quantities comparable to those in situ. Omission of the C source (sucrose) from the medium resulted in no dry matter accumulation in the seeds, but omission of the N source (glutamine) still led to some protein accumulation, indicating mobilization of N from other parts of the fruit explant. Optimum protein accumulation occurred when glutamine was supplied at 1.2 mg N ml^-1. Protein accumulation in the seeds was highly dependent on the nature of the N source. Glutamine, asparagine and the ureide, allantoin, were equally the most efficient sources, whereas several other amino acids tested showed lower degrees of efficiency. The data indicate a high metabolic capacity of the fruit tissues for principal N transport compounds of soybean, namely allantoin, asparagine and glutamine. The culture system described should prove useful for developmental and metabolic studies where the complex influence of the rest of the plant is to be avoided.Abbreviations ALN allantoin - ALC allantoic acid Preliminary report presented at the IV World Soybean Research Conference, Buenos Aires, Arggentina, March 1989.