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Biomedical subjects

H Schell

Publications and source records attributed to H Schell.

At least 91 records · Page 5Linked to original sources
PubMed1981

Evidence of diurnal variation of human epidermal cell proliferation. I. Epidermal 3H-labeling index and serum cortisol rhythm.

Performing two longitudinal studies over 48 and 66 h, respectively, in 12 healthy male adult volunteers the epidermal LI were measured by in vitro 3H-thymidine labeling technique every 6 h and serum cortisol levels simultaneously by RIA examination. While serum cortisol showed a circadian rhythm over the whole test period, a circadian rhythmic pattern of epidermal LI yet became evident 12 h after the onset of experiments. This initial time lag in appearance of LI periodicity may be due to some temporal desynchronization in the cell cycle of keratinocytes. Circadian peaks and minima of both cortisol and LI were found to be inversely correlated, with a time-shifting of 6 h according to the experimental conditions. The present results reveal strong evidence that circadian fluctuation of endogenous cortisol secretion does influence the regulation of epidermal DNA-synthesis in man.

Adult↗
PubMed1981

Evidence of diurnal variation of human epidermal cell proliferation. II. Duration of epidermal DNA synthesis.

In the epidermis of six healthy male volunteers the DNA synthesis time was measured by in vitro double labeling technique in a longitudinal study (48 h) with taking skin punch biopsies every 6 h. The external conditions of the experiments and one group of volunteers were identical to those of a previous study on LI of the epidermal keratinocytes. 14C-thymidine and 3H-thymidine were used for double labeling the DNA-synthesizing nuclei of keratinocytes. The duration of DNA replication time proved to be nearly constant, with minor fluctuation, during the entire time span of experiments (mean 6.19 +/- 0.3 h). Thus, the present results are in accordance with the conception that a periodically changing entrance rate of G1-cells into the S-phase of the generation cycle of keratinocytes is predominantly responsible for circadian variations in the number of DNA-synthesizing epidermal keratinocytes.

Adult↗
PubMed1981

Variations of cAMP in epidermis and plasma of male adult subjects.

Over a time span of 66 h (sampling time at every 6th hour) the cAMP content in superficial skin punch biopsies of 8 male volunteers (medical students aged 20-30 years) and simultaneously the cAMP level in plasma were measured. By means of autocorrelation (2 alpha less than or equal to 5%) a circadian rhythm in the epidermal cAMP could be demonstrated. Sharp maxima were detected at midnight, whereas minima (not so clearly expressed) were seen at 6 a.m. A variation in plasma cAMP during the day was also established but no significant hint for a circadian rhythm could be found by autocorrelation.

Adult↗
PubMed1981

[Consideration of biorhythms in systemic dermatotherapy with corticosteroids].

Rhythmic, in particular circadian, variations of body functions can be found in, or at least supposed for, almost all functions of the skin. The periodicity of physiological properties, some of which occur phase shifted to each other, represents the main reason for circadian differences of both the bioavailability and susceptibility to equal doses of drugs given at different day times. With regard to the well known circadian rhythm of ACTH and cortisol secretion, which can be suppressed by high dose administration of corticoids, every systemic corticoid treatment should, as a rule, be restricted to the morning hours, i.e. during the acrophase of endogenous cortisol secretion. Since after systemic or even topic corticoid therapy the rhythm of ACTH-cortisol feedback system may normalize with marked delay, skin reactivity tests as well as immunodiagnostic in vitro measures should be done just after appropriate poststeroid time lapse to avoid erroneous results. Some alteration of the circadian cortisol rhythm without foregoing corticoid treatment has also been found in cases of generalized atopic dermatitis as well as progressive systemic sclerosis of acrosclerotic type.

Adrenal Cortex Hormones↗
PubMed1980

Human epidermal cell proliferation with regard to circadian variation of plasma cortisol.

This study was performed in 6 healthy young men under analogous experimental conditions to investigate whether or not the epidermal proliferative activity is influenced by the physiological circadian rhythmicity of cortisol concentration in blood. Every 6 h of total duration of the experiments, blood samples were taken for radioimmunoassay of serum cortisol and skin punch biopsies (upper arm inside) were labelled in vitro by 3H-thymidine. In 4 out of 6 individuals, an inverse and time-shifted correlation between the combined serum cortisol levels and the epidermal 3H-LI could be found, i.e., a rise or decline of serum cortisol were followed by a lowered or elevated rate of epidermal LI 6 h later. In particular, a steep increase of serum cortisol from midnight to 6 a.m. correlated to a decrease of 3H-LI from 6 a.m. to noon. This indicates that in man the rate of the epidermal proliferative activity inversely depends, apart from other mechanisms of regulation, on the concentration and circadian periodicity of endogenous cortisol in blood. However, we failed to demonstrate a clear circadian rhythm of the epidermal proliferation, possibly due to the short duration of the experiments extended in each individual to 48 h only.

Adult↗
PubMed1979

[Oral candidiasis in leukoplakia and carcinoma of the oral cavity (author's transl)].

The incidence of Candida albicans and other candida species were examined by mycological culture and histologically in 193 patients with various forms of oral leukoplakia and 14 patients with carcinoma of the oral mucosa, the results being compared with a control group of 137 subjects with a normal mucosa. Comparing the leukoplakia groups one with the other and with the control group revealed definite, usually statistically significant, differences in the incidence of fungi: 46.4% of patients, 29.2% among controls. The incidence of oral fungi was 35.4% among those with noxigenic leukoplakia, 50% in precancerous leukoplakia, 71.5% in mucosal carcinoma, and 49% in nosogenic leukoplakia (mainly lichen planus mucosae). The fungal elements could be demonstrated histologically much less frequently than by culture, but the difference of demonstration was statistically more significant between the different forms of leukoplakia. It is probable that chronic candidiasis in leukoplakia is not carcinogenic as such but is the microbiological and indicator of a local or systemic disorder of the cellular immune system.

Candida↗
PubMed1979

An autoradiographic analysis of the mode of proliferation in the buccal mucosa of rats incubated up to 5 hours.

This study was concerned with the course of DNA synthetic activity (3H-TdR-LI-method) in the buccal mucosa of adult male. Sprague Dawley rats over an incubation period of 5 h. Interest was focussed on the influences of different media and, in particular, on temoporary changes in the proliferative activity. 3H-LI were compared in specimens (a) kept in active (= i.e., 3H-thymidine containing) medium throughout their respective incubation period and (b) pre-incubated in inactive medium for varying, but clearly defined periods before being transferred into active medium for 30 min (actual 3H-LI). Independent of the medium used the rate of DNA synthesis was markedly lowered at 60 min, the reduction being more or less significant in the different media. This was due to a temporary inhibition of DNA synthesis, which was restored after 120-180 min. In contrast, the blockade of G2-phase and/or mitosis persisted up to the end of incubation, as indicated by the unchanged number of labelled mitotic figures after 120 min. Addition of glutamine to Mc Coy's 5A markedly enhanced the activity of 3H-thymidine incorporation, but could not prevent the temporary inhibition of DNA synthesis. The biochemical mechanisms relevant for cell proliferation have been reviewed and correlated to the present results.

Animals↗
PubMed1977

[Some measures of proliferative activity in normal and leukoplakic buccal mucosa (author's transl)].

In 29 patients, the DNA synthesis rate of clinically healthy buccal mucosa epithelium in comparison to benign buccal leukoplakias has been studied by in vitro-autoradiography. The proliferative activity has been determined by means of the 3H-labelling indices of basal cells (LBC) and suprabasal cells (LSBC) including the total of labelled epithelium cells and the quotient of LBC:LSBC as well. The progenitor compartment of both leukoplakic and normal buccal epithelium comprises the stratum basale and the adjacent 2-3 layers of suprabasal cells. Around 70% of the DNA synthesis of normal mucosa was found in the suprabasal nuclei of the progenitor compartment. In the leukoplakic mucosa, some displacement of the labelled nuclei in the progenitor compartment resulting in a statistically significant change of the quotient of LBC:LSBC in favour of LBC was determined. Moreover, the leukoplakic specimens showed a moderate decrease of the mean proliferative activity of the total of labelled epithelial cells which may be due to a diminished exfoliation of cornified cells from the hyper(ortho)keratotic surface. It is supposed that in chronic oral leukoplakias some variation of the steady state between renewal and desquamative loss of epithelial cells is operating as far as no precancerous condition is present.

Adult↗
PubMed1977

[Comparative histological and autoradiographic investigations on benign oral leukoplakias (author's transl)].

Proliferation was studied in 18 patients with benign oral leukoplakias of the buccal mucosa by in vitro labelling with 3H-TdR. Identical investigations were performed in clinically normal mucosa of the same patients. Significant differences were found between the LI of both groups. On the other hand the total of labelled cells per 100 micron length of the basal membrane was approximately equal in leukoplakias and normal mucosa. In the majority of cases the LI was increased in leukoplakic regions whereas the number of labelled suprabasal cells was lowered compared to normal. These findings are supposed to be a consequence of shifting of epithelial keratinization to the lower stratum spinosum. From that results an increased proliferation in the basal cell layer.

Adult↗
PubMed1977

Autoradiographic in vitro studies on diurnal variation in human epidermal cell proliferation.

Five men with healthy skin ranging in age from 24 to 37 years were investigated for the presence of diurnal variation in epidermal cell proliferation by the in vitro 3H-thymidine labeling technique. The following parameters were studied: The basal cell LI; the numbers of labeled basas and supra-basal cell nuclei as well as the total number of labeled nuclei situated above a basal membrane length of 100 mum. All autoradiographic parameters showed marked diurnal variations, the amplitudes of which differed individually. The basal 3H labeling index always showed the highest diurnal variation. In all patients diurnal variations of the basal and suprabasal cell proliferation occurred simultaneously and in equal direction. However, each test person showed maxima and minima of epidermal DNA synthesis at different times. No synchronism could be found when comparing the individual variations of cell proliferation. Several possible reasons for the asynchronous in vitro behaviour of epidermal cells will be discussed.

Adult↗
PubMed1975

Comparative study on the 3H-thymidine index of dorsal epidermis, buccal mucosa, and seminal vesicles in senile male rats.

To supplement previous investigations on endogenous fluctuations of DNA synthesis in male rat dorsal epidermis, buccal mucosa and seminal vesicle epithelium from birth to sexual maturity, the labelling indices (L.I.) of these tissues in senile male rats from the same breed, studied under analogous experimental conditions, were evaluated as well as compared to the data obtained from rats in puberal and early mature age. In the dorsal epidermis and buccal mucosa of the old animals the medium L.I. were found to be at about the same level as those measured after puberty. In the aged seminal vesicle epithelium the medium L.I. was found to be decreased. The maintenance of epidermal and buccal DNA synthesis in senile rats as well as the results of previous studies with male rats subjected to castration or long-term administration of cyproteron acetate furnish evidence that a deficiency of testosteron does not diminish the rate of DNA synthesis in epidermis and buccal mucosa. However, from the decreased L.I. in seminal vesicle epithelium a reduced blood level or stimulating capacity, respectively, of testosteron in senile rats can be concluded. Furthermore, withdrawal of testosteron by orchidectomy or administration of cyproteron acetate is appropriate to suppress significantly the proliferative activity of seminal vesicles epithelium.

Aging↗