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Biomedical subjects

T Steffens

Publications and source records attributed to T Steffens.

5 recordsLinked to original sources
PubMed1994

Hemorrhagic tumor necrosis during a pilot trial of tumor necrosis factor-alpha and anti-GD3 ganglioside monoclonal antibody in patients with metastatic melanoma.

Hemorrhagic tumor necrosis is an inflammatory event that leads to selective destruction of malignant tissues, with both potentially toxic and beneficial consequences. A pilot clinical trial was undertaken combining tumor necrosis factor-alpha (TNF-alpha) with the monoclonal antibody R24 (MoAb R24) against GD3 ganglioside in patients with metastatic melanoma. Patients received MoAb R24 to recruit leukocytes to the tumor followed by low doses of recombinant TNF-alpha to activate leukocytes. Eight patients were treated and seven patients had mild toxicity. One patient with extensive metastatic melanoma developed tumor lysis syndrome within hours after treatment with almost complete necrosis of bulky tumors in multiple visceral sites. To our knowledge, this is the first documented case of hemorrhagic tumor necrosis in a patient with metastatic cancer in multiple visceral sites.

Adult↗
PubMed1993

Comparison of a programmable 3-channel compression hearing system with single-channel AGC instruments.

A commercially available programmable BTE hearing aid with 3-channel AGC (Siemens, Triton 3000) was compared to the subjects' own single-channel compression aids in a group of experienced hearing aid wearers. Two cross-over frequencies, three AGC onset levels, and three channel amplifications were programmable. The maximum output level was controlled by conventional peak clipping. The frequency response of the multichannel system was matched to the individuals' own aids which had been fitted in the two years prior to this study. Frequency response shaping was accomplished by real ear measurement monitoring. The performance of the hearing instruments was measured by (1) speech audiometry in noise and (2) subjective judgement of sound quality and speech intelligibility. Speech recognition was tested using rhyme test material in noise in a group of 10 subjects with sloping high-frequency hearing loss as well as in a group of 16 individuals with nearly flat audiograms. In both subgroups speech recognition scores (S/N: -5 to 15 dB) were 7 to 20% higher for the 3-channel AGC device compared to the single-channel AGC instruments. This finding is equivalent to an improvement of the S/N ratio of about 7 dB for the user. The results of the subjective judgements were similar for both subgroups. Sound quality and speech intelligibility were mostly rated as "very good" or "good" on a 5-point-scale. The subjects were also asked to compare the performance of their own hearing aids with the 3-channel AGC instrument; the latter generally turned out to be preferable.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1991

Clinical evaluation of a programmable three-channel automatic gain control amplification system.

This paper reports on the clinical evaluation of a commercially available head-worn programmable 3-channel automatic gain control (AGC) hearing instrument (Siemens, Triton 3000). A preliminary fitting procedure is developed for the 3-channel AGC amplification system, which is compared by 26 experienced hearing instrument wearers with their own single-channel AGC instruments. The benefits of both amplification systems are assessed by speech audiometry at different signal-to-noise ratios utilizing German rhyme test speech material. In addition, subjective judgements concerning sound quality, speech intelligibility and comparison with the subject's own instrument are evaluated. The results indicate that the multichannel compression instrument is superior to single-channel aids in competitive speech situations. If the 3-channel AGC instrument is used as an automatic noise reduction system in patients requiring a certain amount of low-frequency gain, a markedly better speech recognition can be achieved compared to the subject's personal aids.

Audiometry, Speech↗
PubMed1986

22Na and 86Rb effluxes from bull spermatozoa.

Active transport of sodium and potassium has been postulated for bull sperms by various authors. In the present paper the sodium and rubidium efflux was determined by tracer kinetics. For uninhibited sodium and rubidium efflux a rate constant of 8.9 +/- 2.13/min and 13.9 +/- 3.89 min, respectively, was found for a bull sperm suspension (20 vol.%, 310 K). After ouabain treatment (0.1 mM), a reduction of the rate constant of sodium efflux to 5.1 +/- 1.06/min was found. After cryopreserving (pelletizing process) the majority of samples investigated did not exhibit any inhibition of sodium and rubidium efflux as compared with fresh bull sperms. The inhibition of sodium efflux observed in some cases corresponds to the reduction of the rate constant of sodium efflux caused by ouabain. At storage in seminal plasma (24 h, 278 K) the rate constant of sodium efflux is reduced to 2.7 +/- 0.25/min. Both after ouabain treatment and after cryopreserving of sperms having a reduced rate constant the motility of bull sperms is reduced. It is concluded from the results that in bull sperms there exists an ouabain-sensitive sodium efflux, the inhibition of which reduces the rate constant of sodium efflux by 42%. The ouabain-sensitive sodium efflux is related to the motility of the bull sperm cell.

Animals↗