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Biomedical subjects

H Hertel

Publications and source records attributed to H Hertel.

At least 19 recordsLinked to original sources
PubMed1992

The spectral input systems of hymenopteran insects and their receptor-based colour vision.

Spectral sensitivity functions S(lambda) of single photoreceptor cells in 43 different hymenopteran species were measured intracellularly with the fast spectral scan method. The distribution of maximal sensitivity values (lambda max) shows 3 major peaks at 340 nm, 430 nm and 535 nm and a small peak at 600 nm. Predictions about the colour vision systems of the different hymenopteran species are derived from the spectral sensitivities by application of a receptor model of colour vision and a model of two colour opponent channels. Most of the species have a trichromatic colour vision system. Although the S(lambda) functions are quite similar, the predicted colour discriminability curves differ in their relative height of best discriminability in the UV-blue or blue-green area of the spectrum, indicating that relatively small differences in the S(lambda) functions may have considerable effects on colour discriminability. Four of the hymenopteran insects tested contain an additional R-receptor with maximal sensitivity around 600 nm. The R-receptor of the solitary bee Callonychium petuniae is based on a pigment (P596) with a long lambda max, whereas in the sawfly Tenthredo campestris the G-receptor appears to act as filter to a pigment (P570), shifting its lambda max value to a longer wavelength and narrowing its bandwidth. Evolutionary and life history constraints (e.g. phylogenetic relatedness, social or solitary life, general or specialized feeding behaviour) appear to have no effect on the S(lambda) functions. The only effect is found in UV receptors, for which lambda max values at longer wavelengths are found in bees flying predominantly within the forest.

Animals↗
PubMed1992

Opponent colour coding is a universal strategy to evaluate the photoreceptor inputs in Hymenoptera.

Behavioural tests were carried out with 9 hymenopteran insect species, which ranked certain sets of coloured stimuli according to their subjective similarity to a previously memorized stimulus. Kendall's tau co-efficient is employed for the analysis of correlation between these similarity rankings and the colour distance rankings predicted by various models of neural colour computation. The models are based on the measured spectral sensitivities of photoreceptor colour types and use a variety of simple colour coding systems to derive hypothetical colour distances. The correlation between the predictions of the models and the behavioural results serves as a measure for the likelihood of existence of a colour coding system. In all species, the similarity rankings can be best explained by assuming that colour is coded on a perceptual level by two colour opponent mechanisms. Brightness differences are ignored, indicating that an intensity-coding sub-system is not used in colour discrimination by the insects investigated. The weighting factors of the colour opponent mechanisms differ between species in detail, but not in the principles involved. It is thus possible to employ a standard measure of perceptual colour distance (colour hexagon distance) to predict the capacities of colour discrimination adequately in all the tested insects.

Agonistic Behavior↗
PubMed1989

[Low dosage retinol and L-cystine combination improve alopecia of the diffuse type following long-term oral administration].

In a pilot study (I) the efficacy of a new combination therapy for hair loss of the diffuse type was tested in 36 patients, followed by a double blind study with 47 patients. The daily dosage was 18,000 IE retinol, 70 mg L-cystine and 7000 mg gelatin. The clinical efficacy was evaluated by standard methods, such as the preparation of trichograms and measurement of the hair density before and after treatment. The pilot study demonstrated a significant improvement, with reduction of the telogen rate by 8.3%, an increase of the anagen rate by 11%, and an increase of the hair density by 6.9%. In the double blind study (II) the trichogram showed a significant decrease of the telogen rate by 13.5% compared with pathological baseline values. There was no change in the placebo group. The lowered anagen rate of 47.2% was improved by 8%, whereas the mean value in the placebo group decreased from 47.7% to 39.9%. In addition, the percentage of dysplastic anagen hairs improved by 7.4%, as against further impairment with an increase of 26% in the placebo group. During oral therapy no systemic side-effects were detected. We conclude that long-term oral therapy with high doses of L-cystine and gelatin in combination with vitamin A may have beneficial effects on diffuse hair loss.

Administration, Oral↗
PubMed1988

[Disorder of hair growth in hyperprolactinemia].

Functional hyperprolactinemia was found in five female patients, 25-35 years old, seeking medical consultation for hair loss, together with hypertrichosis (4x), disturbances of cyclic bleeding periods (4x), secondary amenorrhea (2x), galactorrhea (2x), seborrhea (2x) and persisting acne (1x). Other hormonal parameters including testosterone levels and thyroid gland function tests were unchanged. Prolactinoma was excluded by x-ray diagrams, partly also by computer tomograms of the sella. In two patients increased telogen effluvium was found by trichogram examination with some dystrophic hairs; in one patient only dystrophic hairs were seen, whereas, in two cases, hair loss was not present at the time of our clinical examination. These observations indicate that cutaneous symptoms such as seborrhea, acne, hypertrichosis/hirsutism, alopecia(= SAHA syndrome) may evidently occur in hyperprolactinemia, representing or mimicking androgen-induced skin symptoms. In such cases, therefore, evaluation of prolactin levels together with androgen blood levels and thyroid gland function tests should be performed to exclude underlying endocrinopathy.

Acne Vulgaris↗
PubMed1987

Marking and recording of monopolar cells in the bee lamina.

Monopolar cells in the lamina ganglionaris of the honeybee, Apis mellifera, were marked individually for the first time and intracellular recordings made. The electrophysiological responses were mainly hyperpolarizing with peaks and descending plateaux; one specific cell gave depolarizing responses, sustained in UV, and phasic at other wavelengths. Spectral sensitivity curves obtained by the spectral scanning method showed maximum sensitivity at 520 nm. Three morphological cell types were encountered, all of which differ considerably from those described by Ribi (1).

Animals↗
PubMed1985

[Rectoscopy: rigid or flexible? A comparative study].

The customary rigid rectoscope was compared prospectively, with a new, flexible one (prototypes of Olympus Opt. and Fuji) in each of 114 patients selected at random. Maximal depth of introduction was reached on average after 1 min with the rigid instruments, after 1 min 40 sec with the flexible one. Mean depth of introduction was 16 cm for the rigid and 33 cm for the flexible one. In 21 patients (18.4%) additional information was obtained with the flexible rectoscope. 80% of patients reported that the flexible instrument caused them no or only slight discomfort. Skill in using the flexible instrument can be quickly acquired.

Fiber Optic Technology↗