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Biomedical subjects

T Poulsen

Publications and source records attributed to T Poulsen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Hearing aid measurements with speech and noise signals.

An increasing number of hearing aid types include one or more features which are intentionally non-linear. In such devices measurement of frequency response and distortion using sweep tone measurements are typically of little relevance. Five different non-linear hearing aid types were used to evaluate three different broad-band measuring methods. The results revealed that these methods were meaningful in estimating average frequency response obtained with a specific input signal, but none of the three methods used in the study was able to evaluate separately the effects of the most important signal modifications: memoryless non-linearity like peak clipping, time-varying gain from AGC and additive internal noise.

Equipment Design↗
PubMed1993

Laser induced wounds and scarring modified by antiinflammatory drugs: a murine model.

Scarring is a well-known side effect to cutaneous laser treatment. Therefore we investigated if wounds and scarring could be decreased by pharmacological interference in the acute inflammatory reaction following laser therapy. A copper vapor laser operating at 578 nm was used at three different intensities and doses. The antiinflammatory drugs methylprednisolone (1 mg/kg/24 h) and indomethacin (2 mg/kg/24 h) were administered through the drinking water. The laser induced wounds were evaluated daily and histologic and biochemical analyses were used to estimate scarring. The administration of antiinflammatory drugs resulted at some laser intensities in increased scores of maximum wound area, healing time, cumulated wound area, fibrosis, hydroxyproline, and hydroxylysine, being mostly pronounced for indomethacin at 0.8 W/spot. The maximum wound area and the wound healing time could be used as a predictor of scarring. A dose response was shown between the laser intensities and the mentioned parameters. We recommend carefulness in the laser treatment of patients receiving indomethacin and disrecommend use of the drug in the prophylaxis against laser induced scarring.

Administration, Oral↗
PubMed1993

Side effects of laser therapy, modified by ultraviolet irradiation and para-aminobenzoic acid in mice.

Scarring is a well-known side-effect of cutaneous laser treatment and exposure to solar ultraviolet radiation is suspected to increase scar formation. We investigated how wounds and scarring were modified by interfering in the laser-induced inflammation using ultraviolet radiation and para-aminobenzoic acid. A copper vapour laser operating at 578 nm was used at three different intensities and doses. The ultraviolet radiation was administered three times weekly prior to and four times weekly after the laser treatment. The daily dose was 21.5 kJ/m2 equivalent to 3.5 Basic-MED. The laser-induced wounds were evaluated daily and histological and biochemical analyses were used to estimate scarring. Ultraviolet irradiation resulted at some of the used laser intensities in decreased scores of maximum wound area, wound healing time, cumulated wound area, and a decreased skin content of hydroxyproline, whereas the degree of the chronic fibrosis tended to increase. Application of para-aminobenzoic acid before the solar ultraviolet irradiation did not change the acute wound scores but reduced, although not significantly, the degree of fibrosis.

4-Aminobenzoic Acid↗
PubMed1993

UV-induced alterations in skin and lymphocytes during a one-week holiday in the Canary Islands in May.

The effect of solar exposure during a one-week sunbathing vacation in May at 29 degrees N latitude was investigated in 22 volunteers. The following end-points were measured before and after the holiday: skin reflectance at 507 nm, transmission of radiation from 289 nm to 448 nm through the epidermis, epidermal thickness, minimal erythema dose (MED), total white cell, neutrophil, lymphocyte, and lymphocyte subpopulation counts in blood, spontaneous DNA synthesis, DNA strand breaks and sister-chromatid exchange in lymphocytes, and the UVC tolerance of lymphocytes. There was a statistically significant decrease in skin reflectance (p < 0.001) and epidermal transmission (p < 0.01) after the holiday, reflecting increased pigmentation and epidermal thickening. There was a statistically significant increase in epidermal thickness (p < 0.001), MED (p < 0.05), spontaneous DNA synthesis (p < 0.01) and DNA strand breaks in lymphocytes (p < 0.02) after the holiday. The other end-points were not significantly changed. We report that changes in skin pigmentation and epidermal thickness occur after one week of UV exposure. It was also observed that a one-week UV exposure increased both spontaneous DNA repair and the amount of DNA strand breaks in the lymphocytes of the volunteers, while no changes in T-cell subsets were detected.

Adult↗
PubMed1992

UVA tanning devices interact with solar-simulated UV radiation in skin tumor development in hairless mice.

The carcinogenic effect of three UVA tanning sources was studied in lightly pigmented hairless mice. The three tanning sources (Bellarium-S SA-1-12, Philips TL 09R and Philips TL 10R) have different emission spectra, and emit different amounts of UVB. Radiation from the tanning sources was administered for 20 min/day, 5 day/week in daily doses equivalent to those used in suntan salons. The radiation was given alone or after 12 weeks of exposure to solar-simulated UV radiation (SOLAR UV) (10 min/day, 4 day/week; daily dose, 19.5 kJ/m2 UVA and 3.9 kJ/m2 UVB). Irradiation with Bellarium-S SA-1-12 for 47 weeks and Philips TL 09R for 74 weeks induced skin tumours in 20/20 and 13/20 of the animals, respectively. When irradiation with Bellarium-S SA-1-12 and PHilips TL 09R was administered after 12 weeks of SOLAR-UV exposure, a strong enhancement of SOLAR-UV-induced photocarcinogenesis was observed (p < 0.001). Irradiation with Philips TL 10R was only slightly carcinogenic, and during 85 weeks of irradiation only one skin tumor appeared in a group of 20 mice. However, when irradiation with Philips TL 10R was administered after 12 weeks of exposure to SOLAR UV, an enhancement of SOLAR-UV-induced carcinogenesis was observed (p < 0.001). Our results suggest that the hazards of exposure to commercial tanning devices are increased when they are used after a period of natural sun exposure. Even tanning sources with a low carcinogenic potential are able to increase SOLAR-UV-induced carcinogenesis significantly.

Animals↗
PubMed1991

Speech recognition in young and elderly normal-hearing listeners in a closed response test.

Speech recognition has been measured in a group of elderly (age range 55-70 years) subjects with normal hearing. The results from this group were compared with the results from a young, normal-hearing group (age 19-36 years). The two groups were matched as regards education, occupation and dialect. The test material used was a four-alternative closed-response speech test composed of monosyllabic words. Each word was presented in a carrier sentence and masked by a speech-spectrum shaped modulated background noise. No significant difference was found between the speech recognition in the two groups.

Aged↗
PubMed1991

Reference thresholds for EARTONE 3A insert earphones.

Hearing threshold determinations have been performed with EARTONE 3A insert earphones and compared with threshold measurements performed with TDH 39 supra-aural earphones. 22 normal hearing subjects participated. Results are given as SPL values measured in an acoustic coupler (IEC 126) and an occluded-ear simulator (IEC 711).

Adult↗
PubMed1991

Photocarcinogenesis in hairless mice induced by ultraviolet A tanning devices with or without subsequent solar-simulated ultraviolet irradiation.

The carcinogenic effect of 3 commercially available ultraviolet A (UVA) tanning sources was studied in lightly pigmented hairless mice. The tanning sources (Bellarium-S SA-1-12 and Philips TL 09R and TL 10R) have different emission spectra and emit different quantities of UVB. The tanning sources were administered either alone, or before irradiation with solar-simulated UV (solar UV). All 3 UVA tanning sources were able to induce skin tumors when administered in daily doses resembling those used in tanning salons (20 min/d, 5 d/week). Irradiation with Bellarium-S during 32 weeks induced skin tumors in all mice; a similar response was seen after 66 weeks of irradiation with Philips TL 09R. Irradiation with Philips TL 10R during 98 weeks induced tumors in 6 of 20 mice. Nine groups of 20 mice were pretreated 20 min/d, 5 d/week during 13 weeks with one of the UVA tanning sources. Three groups were irradiated with Bellarium-S, 3 groups with Philips TL 09R and 3 groups with Philips TL 10R in daily doses ranging from 0.2 to 1.8 minimum erythema doses (MED). The highest daily doses were equivalent to the doses received during one session in a commercial solarium. Subsequently all 9 groups were irradiated with 3.1 MED/d solar UV 10 min/d, 4 d/week until all mice had died. Time to first tumor was compared. All groups pretreated with Bellarium-S and Philips TL 09R showed an enhanced tumor development compared with a group irradiated with solar UV only. Pretreatment with Philips TL 10R did not enhance the carcinogenic effect of solar UV.

Animals↗
PubMed1990

Prediction of intelligibility of non-linearly processed speech.

Speech in various noise backgrounds was processed through four different non-linear devices and the intelligibility of the processed signals was predicted from the Speech Transmission Index (STI). A novel calculation method was applied in order to avoid artifacts. Running speech was used as input signal and STI was calculated from the envelopes of the squared, noise-free speech signal and of the processed, squared, noisy signal in 23 critical bands. In situations with linearly processed speech and a stationary background noise, this calculation method gives results identical with the procedure described by Steeneken & Houtgast (6). However, in a number of situations with non-linearly processed speech, or a time varying background noise level, the calculation method used here is preferable. The predictions were evaluated in a psycho-acoustic listening test and the predictions agreed well with the listening test results.

Hearing Aids↗
PubMed1989

Tattoo removal by overtattooing with tannic acid.

Removal of tattoos was studied in the guinea pig. Professional tattoos were made, and two different solutions of tannic acid were injected intradermally into the tattoos four times. The macroscopic end result was formation of a slight fibrosis with little visible pigment. Histologic examination after treatment showed a moderate fibrosis with little visible pigment situated deeper in the dermis than in the untreated tattoo.

Animals↗
PubMed1989

Narrow-band UV radiation and induction of dermal elastosis and skin cancer.

A narrow-band UV light source with emission peaks at 292, 300, 307, 317, and 336 nm was developed and used to irradiate whole cages of hairless mice. The purpose was to obtain experimental information on the action spectrum for photocarcinogenesis and dermal elastosis. Groups of 20 mice were irradiated with 500 J/m2 daily, 5 times per week during one year. The total dose was 130 kJ/m2. All mice irradiated with 292 nm and 300 nm developed squamous cell carcinomas. None in the other groups developed malignant skin tumors. Elastosis was estimated quantitatively. The elastic fibers covered 3% of a representative microscopic section of dermis in the control group. In the groups irradiated with peaks at 336 nm, 317 nm, 307 nm, 300 nm, and 292 nm the corresponding percentages were 6%, 13%, 28%, 32%, and 36%, respectively. The shorter the wavelengths the more pronounced was a subepidermal zone replacing the elastotic tissue to the deeper dermis. This zone stained corresponding to a content of glycosaminoglycans (GAG), sulphated GAG, hyaluronic acid, mature collagen, and new reticulin.

Animals↗
PubMed1988

Sound attenuation of TDH-39 earphones in a standard headset and in a noise-excluding headset.

The sound attenuation of TDH-39 earphones with MX-41/AR cushions has been measured in two different configurations: 1) earphones attached to the usual audiometric headband, and 2) earphones mounted in a noise-excluding headset, ME-70 from Madsen Electronics. The measurement method was in accordance with ISO 4869-1981 for hearing protectors, using 1/3-octave noise bands in a diffuse field. For almost all frequencies, the attenuation results (config. 1) are lower than the guidance values given in the audiometric test method standard, ISO/DIS 8253. The noise-excluding headset (config. 2) provides a 7-10 dB better attenuation.

Audiometry↗
PubMed1988

Mucoepidermoid tumors of salivary glands. A long term follow-up study.

Mucoepidermoid tumors of salivary glands are relative rare and it has often been difficult to correlate the pathologic features and clinical aspects. The literature recommends long term follow-up studies. The object of the present study was therefore to follow this recommendation. The clinico-pathological features of 39 mucoepidermoid tumors are presented. The material was retrieved from the files of the pathological institute, Rigshospitalet, Copenhagen, during the period 1941-75. All patients, 24 males, 15 females, were followed for a minimum of 5 years. The lesions were classified into low grade (13 cases), intermediate grade (14 cases) and high grade (12 cases). The corresponding 5, 10 and 15 years cumulative survival rates were 92%, 92%, 92% for low grade, 47.4%, 47.4%, 35.5% for intermediate grade and 0%, 0%, 0% for high grade tumors. Thus we found a close correlation between pathology and clinical course. Furthermore, a 5 year observation period appeared an acceptable approach, because 17 of the 18 patients who succumbed of the disease, did so within 4 years following surgery. We consider all grades of mucoepidermoid tumors to be potential malignant. In our study one patient with a low grade tumor died of the disease.

Adolescent↗
PubMed1988

Pretreatment with long-wave ultraviolet light inhibits ultraviolet-induced skin tumor development in hairless mice.

The carcinogenic effects of long-wave ultraviolet radiation (UV-A) (320 to 400 nm) irradiation followed by exposure to broad-spectrum ultraviolet (UV) irradiation were studied in 200 lightly pigmented, hairless, hr/hr C3H/Tif mice. No skin tumors were observed in the group irradiated with UV-A for four weeks (total dose, 4050 kJ/m2, observed for 57 weeks). Ultraviolet exposure induced skin tumors in a dose-dependent manner. In a group exposed to UV irradiation for 13 weeks, 35% of the mice had developed tumors after 57 weeks. Twenty-six weeks of exposure resulted in 88% of the animals being affected. In contrast it was found that treatment with UV-A irradiation (four weeks, total dose up to 4200 kJ/m2) preceding exposure to UV irradiation (13 or 26 weeks) resulted in a significantly delayed tumor development. Exposure with UV-A induced no visible changes of the skin, and subsequent microscopic examination revealed no measurable changes in epidermal thickness or melanin content. Our results suggest that, depending on the exposure schedule, UV-A in addition to previously reported carcinogenic properties also may act as an antitumor agent.

Animals↗
PubMed1983

The carcinogenic effect of UVA irradiation.

The carcinogenic effect of UVA radiation (from Philips black light tubes filtered through a 2 mm-thick glass plate to eliminate the radiation below 320 nm) was studied in 7 groups of 25 lightly pigmented hairless mice. Irradiation with a moderate daily dose of combined UVB and UVA for 3 months induced a tumor incidence of 0.22 after 58 weeks. When the combined UVB and UVA irradiation was followed by filtered UVA for 2, 4, or 6 months, the tumor incidence was marginally significantly increased to 0.42, 0.48, and 0.50 (p less than 0.05), respectively. However, irradiation with the moderate dose of combined UVB and UVA induced a slight but not significantly lower tumor incidence as compared to UVB alone (0.22 vs 0.30, p greater than 0.1). UVA alone induced no tumors. It thus appears that in hairless mice initially exposed to a combination of UVB and UVA, subsequent continued irradiation with UVA increases tumor incidence. While only marginally statistically significant, tumor incidence in these animals seems to increase with duration and hence total UVA exposure. Furthermore, it is suggested that the photoaugmentative carcinogenic effect of UVA irradiation from unfiltered UVA bulbs can be reduced by attenuating the shorter wavelengths of the radiation.

Animals↗