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Biomedical subjects

R Hofer

Publications and source records attributed to R Hofer.

At least 19 recordsLinked to original sources
PubMed2005

Accumulation of toxicants in tadpoles of the common frog (Rana temporaria) in high mountains.

We analyzed the accumulation of inorganic and organic toxicants in tadpoles from nine populations of the common frog (Rana temporaria) at different altitudes of the Hohe Tauern National Park in Austria). Lead and cadmium concentrations in tadpoles increased with the acidity and metal-to-HCO3(-) ratio in the water exceeding those found in tadpoles from agricultural areas. Organochlorines (DDTs, polychlorinated biphenyls, lindane) and polyaromatic hydrocarbons were present in all of the populations, but only DDTs accumulated significantly compared with the concentrations in their diet.

Altitude↗
PubMed2004

Dating of ballpoint pen ink.

In this paper we describe a case in which a cash book, dated of the year 2000, was sent to the Forensic Science Division, Document Laboratory, Zurich Canton Police in March 2003. The questioned document was a list of 29 pages containing a consecutive handwritten numbering and dated entries (payments) made of blue ballpoint pen ink. By definition, a cash book has to be written by hand and the entries have to be made daily. The questioned document was suspected to have been written within a short period (e.g., a few hours) and backdated. The document lab was asked to determine the date of the entries of the questioned list. On one hand, we were asked, if the cash book had been kept on account consecutively during the period of one year, and on the other hand, the judges were interested in knowing, if the document could have been written in 2003 and back dated to 2000. To answer these questions, the document was examined for latent elements by electrostatic detection device (ESDA). The relative dating of the entries was performed by the quantification of the ballpoint pen ink dyes and their degradation products using HPLC. Results show that it is possible to determine the relative age of entries written by ballpoint pen within a relatively short time scale, if storage and supporting material of the different samples are the same or at least similar.

Journal Article↗
PubMed2003

Anomia for people names in DAT--evidence for semantic and post-semantic impairments.

Proper name anomia is a frequent finding among patients in the early stages of Alzheimer's disease. The present study investigates naming of famous persons in a group of DAT patients, a group of persons with mild cognitive impairment (MCI) and healthy controls. The study is aimed at distinguishing the relative contributions of semantic and post-semantic factors to difficulties in proper name retrieval. As shown by a significantly lower score in answering semantic questions, DAT patients retrieve less biographical knowledge related to famous persons than healthy elderly subjects and persons with mild cognitive impairment. This finding is in line with the frequent observation of semantic deficits in early and moderate DAT. The high number of Tip-of-the-Tongue (TOT) answers in DAT found in relation to few spontaneously named items shows that post-semantic deficits are as important as semantic deficits in determining anomia for people names in DAT. Moreover, DAT patients were less sensitive to phonological cueing than healthy persons or persons with mild cognitive impairment. These findings suggest that proper name anomia in DAT is not only due to semantic deficits, but also to problems in accessing the phonological representation, as well as to a degradation of phonological representations. Thus, naming deficits in DAT differ not only quantitatively, but also qualitatively from the difficulties of healthy elderly persons. No significant differences were found between persons with mild cognitive impairment and healthy controls in proper name retrieval.

Aged↗
PubMed2001

Selective trapping of organochlorine compounds in mountain lakes of temperate areas.

The study of fish concentrations and sediment inventories in 19 European high mountain lakes (40-67 degrees N) shows that a fraction of organochlorine compounds (OCs), the less volatile compounds (LVC; subcooled liquid vapor pressure < or = 10(-2.5) Pa), are trapped in the higher locations. This general trend is not significantly influenced by possible local sources. Compound distribution is related to average air temperatures. The phase-change pseudoenthalpies calculated from the sediment inventories closely match the summed theoretical volatilization and dissolution enthalpies. This fractionation effect is responsible for the accumulation of high concentrations of the LVC, the more persistent and toxic according to literature data, in organisms inhabiting sites far from the locations of synthesis or use.

Air Pollutants↗
PubMed2000

[Perimetry findings and driving performance. "How much visual field" does a motorist need?].

OBJECTIVE: On 01-01-99 the new driving licence regulations came into force. Are the visual field criteria mentioned there sufficient for an adequate evaluation of driving fitness? METHODS: Typical (binocular) visual field defects were digitally superimposed onto photographs of traffic scenes to show the influence of such scotomata on visual perception. RESULTS: Exemplary cases clearly show that evaluation of visual field borders alone is not sufficient for evaluating driving fitness. They also prove that binocular scotomata affecting the (para-)central region of the visual field are of special importance to driving performance. The actual guidelines given by the traffic commission of the German Ophthalmological Society (DOG) and the legally defined limits will be critically discussed. CONCLUSION: From the ophthalmological point of view the actual visual field criteria of the new driving licence regulations do not seem to be sufficient for the evaluation of driving fitness: An additional consideration of (para-)central scotoma is mandatory. This publication provides recommendations for execution and interpretation of perimetric examinations for traffic ophthalmological purposes.

Automobile Driver Examination↗
PubMed2000

Photoprotection in tadpoles of the common frog, Rana temporaria.

The common frog, Rana temporaria, spawning at altitudes up to 2600 m, is potentially threatened by UVB radiation. In laboratory experiments we found a specifically UVB absorbing substance (UVAS) in the skin of tadpoles with maximum absorption between 290 and 300 nm. The production of UVAS is induced by both visible light and ultraviolet radiation. The concentrations of UVAS found in tadpoles from the field are about as high as those found in tadpoles from laboratory experiments with UVB radiation under simulated mid-summer conditions. The existence of two powerful sun screen factors (UVAS and melanin pigmentation) may explain the high resistance of R. temporaria tadpoles to the intensive UVB radiation at high altitudes.

Animals↗
PubMed1998

Origin of cadmium and lead in clear softwater lakes of high-altitude and high-latitude, and their bioavailability and toxicity to fish.

As a consequence of atmospheric deposition, effects of pollutants such as acidification and metal contamination are evident even in remote aquatic ecosystems of mountain and polar regions. Due to similar environmental characteristics (e.g., oligotrophy, low buffering capacity, long ice-cover, high precipitation rates), clearwater high altitude and high latitude lakes represent very sensitive ecosystems, which are extremely susceptible to even slight changes of the environment. Thus, the environmental relevance of Cd and Pb for both types of lakes is discussed in relation to their extraordinary sensitivity to environmental changes. The impact of Cd and Pb on fish from high altitude and high latitude lakes is reviewed and biotic and abiotic factors controlling bioavailability and toxicity of metals to fish are summarized. Apart from direct toxic effects of low pH, acidification increases the bioavailability of metals for fish. Furthermore, low concentrations of dissolved organic carbon and suspended particles take influence on the uptake and toxicity of metals in fish from clear high altitude and high latitude lakes. Since even very low concentrations of Cd and Pb may result in high metal concentrations in fish, evaluation of critical metal loads for clear high altitude and high latitude lakes is of major importance.

Altitude↗
PubMed1997

Analysis of immunoglobulin classes and subclasses in response to infection of Balb/cJ and C57BL/6J mice with Coxiella burnetii.

In order to establish defined immunological parameters for Q fever infection models, a microtitre enzyme-linked immunosorbent fluorescence assay (ELISA) was used for the first time to analyse the humoral immune response of Balb/cJ and C57BL/6J mice after experimental infection with Coxiella burnetii strain 'Nine Mile' in phase I. The experimental infection evoked a seroconversion in all mice within 10 days. Typically, the immune response measured against the whole-cell antigen showed an early increase of immunoglobulin (Ig) M followed by a later increase of the IgG subclasses. The IgA was low during the entire investigation period. Within the IgG subclasses only IgG2a and IgG2b gained higher values, whereby C57BL/6J mice produced high IgG2b titres and significantly lower IgG2a titres. In contrast, Balb/cJ mice developed IgG2a and IgG2b at equal levels. The use of partial antigens of C. burnetii demonstrated that the dominating IgG2b reaction of the C57BL/6J mice was directed against the lipopolysaccharide (LPS) of C. burnetii. This reaction was almost absent in Balb/cJ mice. In contrast, the SP27 protein antigen did not evoke different IgG2b reactions within the two breeds. No significant influence was observed within the two breeds in regard to sex or between hormone synchronized and non-hormone synchronized animals.

Animals↗
PubMed1992

[What improvements can be gained by additional boring in hearing aid fitting?].

In several investigations the authors tried to find a objective correlation to the subjective positive reactions after venting an earmold. There was no notable effect neither on insertion gain nor on speech intelligibility in different background noise situations. In this study the most comfortable hearing level has been used. This stimulus is influenced by the suprathreshold loudness growth. The measurement has been carried out with and without venting. Comparing the results there can be seen only a little effect of venting at all frequencies. Might be that patient's report about improvement after venting results from the direct input of low frequencies through the vent to the eardrum. These frequency region plays a special part of hearing comfort to reach a comfortable sound quality.

Adult↗
PubMed1990

Effects of domestic wastewater on serum enzyme activities of brown trout (Salmo trutta).

1. Chronic injuries of kidney and liver tissue of brown trout caused by domestic wastewater were not accompanied by increased activities of serum enzymes (GOT, GPT). 2. Increased enzyme activities were only observed in fish with acute Saproloegnia infection. 3. It is important to distinguish between acute and chronic responses of serum enzymes in diseased fish.

Alanine Transaminase↗
PubMed1988

Electroretinography in rats.

Basic mechanisms of the rat ERG were reinvestigated with contemporary methods of recording and photic stimulation via an optic fiber system connected with a contact lens. Flash stimulation and background illuminance were performed with photometrically defined light stimuli. ERGs recorded in darkness, from dark adapted rats, were similar with those observed in earlier work in which light flashes of much longer duration had been used. Flash stimulation carried out under stepwise increased background illuminance gave new information on the characteristics of oscillatory potentials of the ERG. In general the present observations agreed with the notion that the rods of the rat retina are as sensitive as in man, whereas the cones are functionally less efficient with respect to light sensitivity and temporal resolution. Differences in function of the cones from rat to man have to be kept in mind when using the rat ERG as a model for risk assessment in safety studies.

Animals↗
PubMed1987

The preoptic-suprachiasmatic nuclei though morphologically heterogeneous are equally affected by streptozotocin diabetes.

Pituitary and gonadal disorders consistent with abnormal LHRH and LH secretion occur in streptozotocin-diabetic rats. A key role in the synthesis and regulation of LHRH and in the phasic LH release is played by the preoptic-suprachiasmatic region which is mainly formed by the medial preoptic area, the sexually dimorphic nucleus of the medial preoptic area, and the suprachiasmatic nucleus. Therefore we have studied this region by morphology and morphometry in normal and streptozotocin-diabetic rats. In normal animals, the neurons of the above mentioned nuclei were morphologically and morphometrically dissimilar. Independent of their localization, reduced cytoplasmic and nuclear areas were observed in the neurons of diabetic animals. These lesions are consistent with hypotrophied neurons. Consequently, diabetes may impair both synthesis and regulation of LHRH and may therefore account for pituitary disorders, testicular atrophy, and lacking preovulatory LH peaks. The structural differences of the neurons of the three nuclei in normal animals underline their different physiological role. Yet, the similarity of the changes found in all three nuclei suggests a generalized hypofunction of the whole preoptic-suprachiasmatic region under diabetic condition.

Animals↗
PubMed1982

Protein digestion and proteolytic activity in the digestive tract of an omnivorous cyprinid.

1. In adult and juvenile roach (Rutilus rutilus) feeding on meal worms or grass and acclimated to temperatures between 6 and 20 degrees C the following variables were determined: pH, protein and proteolytic activity of gut fluid and faeces, food consumption, duration of gut passage and efficiency of protein assimilation. 2. Proteolytic enzymes of fish are very stable against autolysis but they disappear in posterior portions of the intestine, suggesting the existence of a pinocytotic process. 3. In herbivorous roach as well as in adult carnivorous roach feeding at 20 degrees C this results in very low proteolytic activities in the faeces, whereas in juvenile fish and in adults feeding on meal worms at lower temperatures, the process of reabsorption seems to be less efficient. 4. Daily production of proteases as well as "daily proteolytic duration" are higher in herbivorous than in carnivorous roach. 5. For the same amount of protein consumed, fish feeding on grass require 10 times higher proteolytic activities than fish feeding on meal worms.

Animals↗