[Hearing with combined electric acoustic stimulation]. / Hören mit kombinierter elektrischer und akustischer Stimulation.

After cochlear implantation, individuals with sufficient residual hearing in the lower frequency region are able to successfully combine acoustic and electrical stimulation patterns to improve speech perception, especially in noise, and to improve music appraisal as well. These improvements occur through enhanced transmission of fine structure information by more accurate mapping of the fundamental frequency contour through acoustic hearing. In current cochlear implant systems, the transfer of frequency and melodic contour is very coarse, and the correct detection of pitch contour requires large frequency differences. It is assumed that the acoustically transferred part of the signal enables the cochlear implant recipient to better segregate between speech signals and interfering sounds. The detection and following of a speech signal emitted by a single talker in a multitalker babble situation is improved when fundamental frequencies as grouping cues are present. The preservation of hearing in the implanted ear must be considered a major surgical challenge. The development of very flexible and soft electrode carriers in combination with surgical approaches that minimally traumatize the inner ear enable hearing preservation in nearly all cases.

Three stages in the evolution of the genetic code.

A diversification of the genetic code based on the number of codons available for the proteinous amino acids is established. Three groups of amino acids during evolution of the code are distinguished. On the basis of their chemical complexity those amino acids emerging later in a translation process are derived. Codon number and chemical complexity indicate that His, Phe, Tyr, Cys and either Lys or Asn were introduced in the second stage, whereas the number of codons alone gives evidence that Trp and Met were introduced in the third stage. The amino acids of stage 1 use purine-rich codons, while all the amino acids introduced in the second stage, in contrast, use pyrimidines in the third position of their codons. A low abundance of pyrimidines during early translation is derived. This assumption is supported by experiments on non-enzymatic replication and interactions of hairpin loops with a complementary strand. A back extrapolation concludes a high purine content of the first nucleic acids, which gradually decreased during their evolution. Amino acids independently available from prebiotic synthesis were thus correlated to purine-rich codons. Implications on the prebiotic replication are discussed also in the light of recent codon usage data.

Hypnotizability in bulimic patients and controls. A pilot study.

Various studies have indicated that bulimics are more easily hypnotized and dissociate more readily than control groups and patients with other eating disorders. A comparison is reported of 15 inpatients with bulimia nervosa (DSM III-R) with 15 subjects in a control group comparable in age and education. The instrument used was the Harvard Group Scale of Hypnotic Susceptibility/Form A (HSGHS:A), which includes 12 standardized test suggestions. The results show that bulimics have higher scores in hypnotizability than the control group. A method study (comparison of self-evaluation with a video recording) shows that this is a result of the behaviour itself and not of the answering pattern used by the subjects in the questionnaire. It is possible that differing expectations regarding the experiment may have influenced the results. Considerations concerning the increased ability of bulimics to dissociate as a causal factor versus an accompanying phenomenon of the disorder are discussed.

Interaction of DNA hairpin loops and a complementary strand by a triplet of base pairs.

Hypothesis of non-enzymatic recognition of primordial tRNA and mRNA precursors is experimentally approached. DNA hairpins containing a different number of deoxyguanosine residues in the loop are analyzed for their binding ability to a chemically fixed single-strand of oligo(dC). In presence of small Mg2+ concentration a hairpin with five dG residues in the loop is adsorbed to affinity matrix. Comparison of elution temperatures of hairpin oligonucleotides with those of single-stranded oligoguanylic acids with length of the loop indicates, that smallest loop able to bind forms a triplet of base pairs.

Complexes of DNA hairpins and a single-stranded oligonucleotide detected by affinity chromatography and mung bean nuclease cleavage.

The emergence of a simple translation device consisting of an assembler strand (primordial mRNA) and RNA hairpins (primordial tRNA) is presumed to be an important step leading to the origin of life. The assumption of a non-enzymatic interaction of primordial tRNA and mRNA is experimentally approached. DNA hairpins containing five or more adenosine residues in the loop are able to bind to complementary oligonucleotides covalently bound to cellulose. The exact number of base pairs formed between the hairpins and the assembler strand is determined by two methods applied to DNA hairpin/assembler complexes. The melting temperature of a complex is measured and the cleavage pattern by nuclease from mung bean is determined. The loop of the smallest hairpin able to bind consists of five adenosine residues and only three base pairs are formed. This supports the idea of a primordial recognition similar to the contemporary codon-anticodon interaction.

Conformational analysis of hairpin oligodeoxyribonucleotides by a single-strand-specific nuclease.

Hairpin-forming oligodeoxynucleotides d[ATCCTA(A)NTAGGAT] with n = 3-6 were subjected to nuclease digestion with the nuclease from mung bean. Cleavage occurs only in the loop region of the hairpin molecules. In detail, the number and intensity of cleavage sites were determined in relation to the length of the loop, the temperature and the salt concentration. The restricted accessibility of mung bean nuclease to the loop bases adjacent to the helical region of all hairpins is due to a reduced exposure of these bases in presence of a certain Mg2+ concentration. With increasing temperature the exposure of these bases is increased. It is deduced that the bases adjacent to the helix increase the length of the latter by stacking, the degree of which is dependent on the number of loop bases.

[Development of drug, alcohol and tobacco consumption. Comparison between 2 studies from 1971 and 1974 in the canton Zurich]. / Entwicklung des Drogen-, Alkoholund Tabakkonsums Vergleich zweier Untersuchungen von 1971 und 1974 im Kanton Zürich

Consumption of drugs, alcohol and tobacco has been compared in two populations of 19-year-old men, of 1971 (2785) and 1974 (1617), drawn from three different geographical regions of the Canton of Zurich. The hypothesis that the percentage of drug users has risen over the last three years was not confirmed: as previously, 25% have had experience of drugs. As expected, however, there was more regular and heavy drug users in 1974 than in 1971. Also, there is a more marked trend towards extension of drug consumption to rural areas than in 1971. The percentage of cigarette smokers has remained stable, but per capita cigarette consumption has increased. Contrary to expectation, alcohol consumption showed the sharpest rise in all three regions. The study suggests that drug consumption is not to be considered in isolation but in conjunction with the use of alcohol and tobacco.