Linkage data suggesting allelic heterogeneity for paramyotonia congenita and hyperkalemic periodic paralysis on chromosome 17

Summary Paramyotonia congenita (PC), an autosomal dominant non-progressive muscle disorder, is characterised by cold-induced stiffness followed by muscle weakness. The weakness is caused by a dysfunction of the sodium channel in muscle fibre. Parts of the gene coding for the -subunit of the sodium channel of the adult human skeletal muscle (SCN4A) have been localised on chromosome 17. To investigate the role of this gene in the etiology of PC, a linkage analysis in 17 well-defined families was carried out. The results (z=20.61, =0.001) show that the mutant gene responsible for the disorder is indeed tightly linked to the SCN4A gene. The mutation causing hyperkalemic periodic paralysis (HyperPP) with myotonia has previously been mapped to this gene locus by the same candidate gene approach. Thus, our data suggest that PC and HyperPP are caused by allelic mutations at a single locus on chromosome 17.Dedicated to Professor P. E. Becker on the occasion of his 83rd birthday.     

No evidence for linkage of autosomal dominant proximal spinal muscular atrophies to chromosome 5q markers

Summary Two recent articles have reported the linkage of a gene for recessive spinal muscular atrophy (SMA) on the chromosome region 5q11.2–13.3. Our data show no linkage of the dominantly inherited forms of SMA to this chromosome region.     

Evidence for a 13,14-Cis Cycle in Bacteriorhodopsin

We discuss to what extent the vibrational spectra of bacteriorhodopsin that have been observed and assigned by Smith et al. (1, 2) by means of resonance Raman and by Gerwert and Siebert (EMBO (Eur. Mol. Biol. Organ.) J. In press) by means of infrared absorption experiments are in agreement with a photo-cycle of bacteriorhodopsin that involves the sequence BR, IO(all-trans) → K(13,14-cis) → L(13,14-cis) → M(13-cis) → N(13-cis) → O(all-trans). Our discussion is based on a quantumchemical modified neglect of diatomic overlap [MNDO] calculation of the vibrational spectra of the relevant isomers of the protonated retinal Schiff base. In particular, we investigated in these calculations the effects of different charge environments on the frequencies of the relevant C-C single bond stretching vibrations of these isomers.     

A new method for the reconstitution of the anion transport system of the human erythrocyte membrane

Summary The anion transport protein of the human erythrocyte membrane, band 3, was solubilized and purified in solutions of the non-ionic detergent Triton X-100. It was incorporated into spherical lipid bilayers by the following procedure: (1) Dry phosphatidylcholine was suspended in the protein solution. Octylglucopyranoside was added until the milky suspension became clear. (2) The sample was dialyzed overnight against detergentfree buffer. (3) Residual Triton X-100 was removed from the opalescent vesicle suspension by sucrose density gradient centrifugation and subsequent dialysis. Sulfate efflux from the vesicles was studied, under exchange conditions, using a filtration method. Three vesicle subpopulations could be distinguished by analyzing the time course of the efflux. One was nearly impermeable to sulfate, and efflux from another was due to leaks. The largest subpopulation, however, showed transport characteristics very similar to those of the anion transport system of the intact erythrocyte membrane: transport numbers (at 30°C) close to 20 sulfate molecules per band 3 and min, an activation energy of approx. 140 kJ/mol, a pH maximum at pH 6.2, saturation of the sulfate flux at sulfate concentrations around 100mm, inhibition of the flux by H₂DIDS and flufenamate (approx.K _l-values at 30°C: 0.1 and 0.7 m, respectively), and right-side-out orientation of the transport protein (as judged from the inhibition of sulfate efflux by up to 98% by externally added H₂DIDS). Thus, the system represents, for the first time, a reconstitution of all the major properties of the sulfate transport across the erythrocyte membrane.     

Age changes of skull dimensions

At cranial level, external apposition during ageing has been postulated by some authors. In longitudinal studies, a gradual increase of cranial diameters has been shown by cephalometry (Kendrick et al. 1967) or by lateral radiography (Israel 1968, 1970). However, these results are contested at methodological level by other longitudinal studies (Tallgren 1974). It is the aim of this study to analyse, in a cross-sectional sample, the effects of senescence on several cephalic dimensions. A series of skulls of known age and sex has been selected for this purpose.     

A plasmodial alpha-tubulin cDNA from Physarum polycephalum. Nucleotide sequence and comparative analysis

As the first step towards correlating structure and function of tubulin in the slime mold Physarum polycephalum we have elucidated the nucleotide sequence of a cDNA that appears to code for all but the last 25 to 30 C-terminal amino acids of a plasmodial alpha-tubulin. Differences in amino acid sequence from those of other alpha-tubulins are distributed fairly evenly throughout the sequence, although a relatively extensive conserved region is found in position 396 to 426 near the C terminus. A small region in position 298 to 307 contains a cluster of amino acid residues unique to Physarum alpha-tubulin. The sequence is 70% homologous to two yeast alpha-tubulins and about 83% homologous to five animal alpha-tubulins. A comparison of the homologies of all the known alpha-tubulins indicates that a large decrease in the accepted point mutation rate has occurred during the evolution of the metazoa, suggesting a major functional specialization of microtubules.     

Is the initiation of macronuclear DNA synthesis in Euplotes dependent on micronuclear functions?

To determine whether the micronucleus makes essential contributions during asexual reproduction, observations were made on cells of Euplotes octocarinatus from which the micronucleus had been removed with a micropipette. Most cells underwent one postenucleation division, then became arrested in macronuclear G1, slowed down in food uptake, developed macronuclear deformations, and finally died. Such cells could be rescued if a micronucleus was reimplanted before macronuclear deformations had developed. When provided with a new micronucleus, cells initiated macronuclear DNA synthesis about 12-16 h later. The data suggest that the micronucleus is involved in the control of the cell's transition from macronuclear G1 to S, and a model is proposed which postulates that in Euplotes macronuclear DNA synthesis is initiated when a micronucleus-encoded "initiator protein" has accumulated to a critical amount.     

Simultaneous and independent effects of abscisic acid on stomata and the photosynthetic apparatus in whole leaves

(±)-Abscisic acid (ABA) at 10^-5 M was added to the transpiration stream of leaves of 16 species (C₃ and C₄, monocotyledons and dicotyledons). Stomatal responses followed one of three patterns: i) stomata that were wide and insensitive to CO₂ initially, closed partially and became sensitive to CO₂; ii) for stomata that were sensitive to CO₂ before the application of ABA, the range of highest sensitivity to CO₂ shifted from high to low intercellular partial pressures of CO₂, for instance in leaves of Zea mays from 170–350 to 70–140 bar; iii) when stomata responded strongly to ABA, their conductance was reduced to a small fraction of the initial conductance, and sensitivity to CO₂ was lost. The photosynthetic apparatus was affected by applications of ABA to various degrees, from no response at all (in agreement with several previous reports on the absence of effects of ABA on photosynthesis) through a temporary decrease of its activity to a lasting reduction. Saturation curves of photosynthesis with respect to the partial pressure of CO₂ in the intercellular spaces indicated that application of ABA could produce three phenomena: i) a reduction of the initial slope of the saturation curve (which indicates a diminished carboxylation efficiency); ii) a reduction of the level of the CO₂-saturated rate of assimilation (which indicates a reduction of the ribulose-1,5-bisphosphate regeneration capacity); and iii) an increase of the CO₂ compensation point. Photosynthesis of isolated mesophyll cells was not affected by ABA treatments. Responses of the stomatal and photosynthetic apparatus were usually synchronous and often proportional to each other, with the result that the partial pressure of CO₂ in the intercellular spaces frequently remained constant in spite of large changes in conductance and assimilation rate. Guard cells and the photosynthetic apparatus were able to recover from effects of ABA applications while the ABA supply continued. Recovery was usually partial, in the case of the photosynthetic apparatus occasionally complete. Abscisic acid did not cause stomatal closure or decreases in the rate of photosynthesis when it was applied during a phase of stomatal opening and induction of photosynthesis that followed a transition from darkness to light.Abbreviations and symbols A rate of CO₂ assimilation - ABA (±)-abscisic acid - c _a partial pressure of CO₂ in the ambient air or in the gas supplied to the leaf chambers - c _i partial pressure of CO₂ in the intercellular spaces of a leaf - e _a partial pressure of H₂O in the air - g conductance for water vapor - J quantum flux - T ₁ leaf temperature     

Chemotherapy and trace element levels in blood and tissue of rats implanted with prostate tumor cells

Male Copenhagen rats with transplanted prostatic adeno-carcinoma were treated with different polyamine synthesis inhibitors, such as methylglyoxal-bis-guanylhydrazone (MGBG), erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) combined with 9-β-d-arabin-ofuranosyl-adenine (ARA-A), α-difluoromethyl-ornithine (DFMO), and some of their combinations. Levels of the essential trace elements—copper, zinc, magnesium, iron, selenium, and manganese —have been determined in blood, tumor, kidney, and liver of these animals and are discussed in terms of efficiency of the treatment. MGBG had the strongest effect on trace element levels in tissues of treated animals. MGBG combined with DFMO exhibited the highest antitumor activity of all treatment protocols. Selenium given as selenite with drinking water was used as an adjuvant with the most toxic combination, (ARA-A/EHNA, MGBG). Selenite reduced the toxicity of these therapeutic agents.     

The potential use of silicon compounds as oxygen carriers for free and immobilized cells containing l-amino acid oxidase

Summary The relatively low solubility of oxygen in water presents a problem in particular when immobilized cells are used or enzymes are applied for oxygen dependent reactions. The other main purpose is the requirement of oxygen for the increase of biomass. In this investigation the usefulness of silicon emulsions as oxygen carriers is demonstrated.In case of l-amino acid oxidase activity of immobilized cells, an increase by a factor of four was found in the presence of silicon emulsions. Likewise, growth medium enriched with silicon emulsions showed a significantly increased growth of cells inside alginate beads compared to normal growth medium.