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W Köhler

Publications and source records attributed to W Köhler.

At least 127 records · Page 7Linked to original sources
PubMed1986

Does filtering and smoothing of average evoked potentials really pay? A statistical comparison.

Averaging of sweeps to obtain evoked potentials provides an unsatisfactory reduction of the background activity for a small number of stimuli. A posteriori Wiener filtering, time varying filtering, and smoothing of the average EP have been proposed to meet this problem. As to a posteriori Wiener filtering, a controversy regarding its merits has been going on for several years. The present paper gives a statistical comparison of the above methods, based on real data of two groups of subjects (flash evoked potentials in 41 subjects, pattern reversal evoked potentials in 9 subjects). It is shown that most of the improvement of the filtering approaches was due to an attenuation effect, without any improvement in smoothness of the potentials. The strength of the attenuation introduced by the filtering approaches depended on the specific underlying signal-to-noise ratio. This effect led to an artificially enhanced interindividual variability and could intraindividually lead to biased topographical distribution, when several electrodes are considered. The smoothing method did not show this undesired feature, but, when applying strong smoothing, this method also rendered sizable distortions of the potentials.

Adolescent↗
PubMed1986

Albumin bound to the surface of M protein-positive streptococci increased their phagocytosis by human polymorphonuclear leukocytes in the absence of complement and bactericidal antibodies.

Using a phagocytosis assay (Leijh 1980, Infect. Immun. 30, 421), determination of chemiluminescence, and transmission electron microscopy, the influence of the binding of albumin to M protein-positive group A streptococci on their phagocytosis by human polymorphonuclear leukocytes (PMNL) was investigated. Coating of streptococci with albumin in the absence of other serum components enhanced phagocytosis but not killing of the bacteria. Complement had no additional effect on engulfment. Fibrinogen reduced the enhancing effect of albumin. Albumin had no additional effect on the high phagocytosis rate of an M-protein-negative strain. It could be demonstrated that human PMNL bound human serum albumin-gold conjugate. The results are discussed with regard to the role of plasma proteins in the phagocytosis of streptococci under in vivo-conditions.

Antibodies, Bacterial↗
PubMed1986

[Oto-acoustic emissions and their significance for inner ear research].

In contrast to the formerly held opinion it is now clear that the spontaneous oto-acoustic emissions (OAEs) are pure sinus tones. Frequency shifting (small oscillations and a drifting in one of the two directions) causes broadening of the image in Fourier's transformation, especially when being averaged. These spontaneous OAEs can be observed in ears with minimal disturbance--often not yet detectable by means of pure tone threshold. In such ears the synchronisation of the hair-cells is out of order and this leads to the spontaneous OAEs. With increasing sensitivity of the microphones OAEs can be found in more and more ears. A connection between spontaneous and evoked OAEs can be shown when calculating a FFT from the image of an evoked emission: the spectrum is similar to that of spontaneous OAEs from the same ear. TTS situations in spontaneous OAEs: the reduction of the ability of synchronisation cancels the emission, which will reappear after some time (shifted in frequency). To explain the frequency resolution in the cochlea an active filter has been postulated and the OAEs are claimed to be a reflection of the same; in fact, they are one of the proverbial keyholes through which we might gain a glimpse of what is taking place in the cochlea.

Animals↗
PubMed1986

Our present experience on spontaneous cochlear emissions.

Spontaneous otoacoustic emissions (SOAEs) consist of one or several sinusoid-like signals. Small broadening of the spectra of SOAEs, are likely due only to some small oscillations and shifts of their center frequency. Presence of a detectable SOAE seems to be attributable to hearing losses of minor severity associated with abnormal synchronization. A part from some amplitude variations, SOAEs, remain consistently the same over prolonged periods of time and for this reason have been called finger-print-like in the literature. They seem to reflect physiological and exposure-related shifts in tonal projection. SOAEs are one of the proverbial key holes through which we can have a glimpse of what is happening into the cochlea.

Acoustic Stimulation↗
PubMed1986

[Isolation and characterization of erythrogenic toxins. VIII. Purification of a biologically active protein of the molecular weight 10,000 (LMP-10k) from filtrates of Streptococcus pyogenes, strain NY-5. Relationship to erythrogenic toxin type A].

The "classical" method for purification of erythrogenic toxin type A results in two products: erythrogenic toxin type A and a low molecular weight protein, m.w. 10,000 (LMP-10k) with mitogenic activities. LMP-10k was purified from culture supernatants of S. pyogenes (group A) by CM-Sepharose CL-6B chromatography and Sephacryl S-200 and Sephadex G75 gel filtration to a high degree of purity with minimal amounts of residual erythrogenic toxin A. The isoelectric point of LMP-10k is the same as for erythrogenic toxin A: 5.2. The immunogenic activity is low, only one of two rabbits produced anti-LMP-10k-antibodies after a prolonged course of immunization. On the other hand it is possible to induce antierythrogenic toxin A-antibodies by immunization with LMP-10k preparations contaminated with small amounts of erythrogenic toxin A. Possibly the data given by some authors for the m.w. of erythrogenic toxin type A as 8 000 D are the results of a mix-up with co-purified LMP-10k.

Amino Acids↗
PubMed1985

[Continuous intragastric pH-metry].

Ambulatory intragastric pH-metry is a suitable method of assessing gastric acidity under conditions of normal daily life. A detailed profile of intragastric acidity is given which is a reproducible individual characteristic. There is a circadian rhythm of gastric acidity in which pH rises during the night and after meals. pH-metry was used to determine the effects of H2-antagonists and antacids, and the results are the basis for the clinical use of intragastric pH-metry.

Antacids↗
PubMed1985

Frequency composition of spontaneous cochlear emissions.

Spontaneous cochlear emissions consist of one or more sinus tones. Oscillations and frequency shifts clearly widen averaged traces. Multiple peaks, if present, are spaced at intervals of 2-3% of the frequency, and increase with frequency. A frequency jump by the same amount was seen in one case. This appears to represent the distance between hair cells, and suggests that individual hair cells play a leading role in these oscillations.

Adult↗
PubMed1985

Temporary threshold shift frequency profiles after low-tone exposure.

Low-tone exposure elicits four distinct dips in hearing thresholds: one octave above the exposure frequency, in the permanent threshold shift (PTS) range, at about 10-11 kHz, and at 14-15 kHz. While dips 1, 2 and 3 decay as a function of the time log, dip 4 has a much longer decay time.

Adolescent↗
PubMed1985

Haptoglobin: an immunoregulatory role in tuberculosis?

A significant correlation was found between levels of haptoglobin in sera from Indonesian patients with tuberculosis and the extent to which these sera suppressed mitogen-driven activation of normal lymphocytes in vitro. As in a previous study we showed that there was an inverse relationship between haptoglobin levels and the circulating lymphocyte count in the same group of patients, it is now suggested that this protein has an immunoregulatory role in tuberculosis. Similar observations have been made by other workers on patients with cancer. There was no difference in the distribution of the 3 allotypes of haptoglobin in patients and healthy subjects nor was there any association between such allotypes and the lymphocyte count, the dermal reactivity to tuberculin or the degree of suppression.

Agglutination Tests↗
PubMed1985

Tissue cages for study of experimental streptococcal infection in rabbits. II. Humoral and cell-mediated immune response to erythrogenic toxins.

Infection of rabbits with erythrogenic toxin producing streptococcal strains caused a marked increase of humoral antibodies, which was detected by immunoprecipitation and ELISA. An antibody response directed towards the erythrogenic toxin type A was demonstrated by fused rocket immunoelectrophoresis. All toxinogenic reference strains produced ET type A under in vivo conditions despite that this toxin was not always demonstrated under in vitro conditions. The infection resulted in an increase of mitogenic response of peripheral lymphocytes to the initial nonspecific mitogenic erythrogenic toxins, whereas the Con A stimulation was depressed starting 14 days after infection and lasting during a period of 90 days. Since a normal antibody response was evoked, it seems likely that the T helper cell function was not affected.

Animals↗
PubMed1985

Interaction of group A type 1 streptococcal M protein with fibrinogen.

Adsorption chromatography of streptococcal extracts on immobilized fibrinogen allows isolation of components that are linked to the corresponding receptors. In this study it is shown by an indirect bactericidal test that fibrinogen binds the M proteins of the streptococcal strains used. Phage-associated lysin extracts of group A type 1 streptococci precipitated with fibrinogen in a double-diffusion test. Fibrinogen reactive components of other streptococcal types inhibited this precipitation reaction. This suggests that the fibrinogen receptors in different types of group A streptococci have identical activity. The interaction between M protein and fibrinogen does not interfere with the interaction between M protein and the corresponding type specific antibodies. The streptococcal antigen components isolated by immobilized fibrinogen showed mitogenic activity in a lymphocyte transformation test.

Adsorption↗
PubMed1984

Binding of five monoclonal anti-CEA antibodies with different epitope specificities to various carcinoma tissues.

Five monoclonal antibodies that recognize different epitopes on carcinoembryonic antigen (CEA) were reacted with tissue sections of various carcinoma specimens. The vital, non-necrotic tissues of those carcinomas of the oesophagus, pancreas, colon and rectum, medullary thyroid, ovary and cervix in which CEA related epitopes were detectable bound all five antibodies to a similar degree. In 3/5 lung carcinomas, 2/10 mammary carcinomas and 1/5 gastric carcinomas, a significantly different binding of the monoclonal antibodies by vital tumour tissue was present as determined by three independent investigators. In necrotic tissue areas, heterogeneity of antibody binding was more common. In a previous investigation, it was shown that normal granulocytes and liver tissue differentially bind the monoclonal anti-CEA antibodies, indicating the presence of crossreacting antigens. The equivalent binding of the five monoclonal anti-CEA antibodies to most of the carcinomas tested suggests that this binding is due to the presence of complete CEA molecules and not only of cross-reacting antigens.

Antibodies, Monoclonal↗
PubMed1984

Expression of a streptokinase gene from Streptococcus equisimilis in Streptococcus sanguis.

Using recombinant DNA techniques, we introduced a previously cloned streptokinase gene from Streptococcus equisimilis into the Challis strain of S. sanguis (group H). The gene was expressed in the new host under the control of its own promoter and the gene product had biological properties identical to authentic streptokinase. However, the molecular weight of cloned streptokinase (42 K) as expressed by S. sanguis was substantially lower than that of authentic streptokinase (47 K). Since the cloned streptokinase gene encoded a 47 K mature protein, the lowered molecular weight of S. sanguis streptokinase may reflect posttranslational proteolytic cleavage, which leaves the biological activity of the gene product and its serological reactivity unimpaired.

Cloning, Molecular↗