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Biomedical subjects

H Michna

Publications and source records attributed to H Michna.

66 records · Page 4Linked to original sources
PubMed1988

Dynamic moisture permeation through clothing.

Dynamic moisture permeation through clothing often occurs during thermal transience, causing an imbalance between evaporative heat loss from the skin (Esk) and that from the clothing surface (Ecl). A device was designed to observe Esk and Ecl simultaneously. It consists of two relative humidity sensors coupled with thermistors so that densities of water vapor at two points within the boundary layer can be calculated. The rate of local evaporation is then estimated from Fick's law of diffusion. Local evaporation rates from the skin and clothing surface at the chest, arm, and thigh were measured during exposure to controlled ambient temperatures varying from 20 degrees-40 degrees C. The subjects wore four different types of helicopter pilot suits: Nomex/Neoprene, Goretex, cotton ventile, and Nomex/Insulite. For the Goretex and cotton ventile suits, consisting of relatively permeable and hygroscopic fabrics, a sudden increase in Esk, exponential decay of Esk, and a gradual increase in Ecl were observed. These appear to be associated with, respectively, the onset of sweat secretion, moisture build-up within the clothing, and water gain in the fabric. Thus, the device may be useful for observing dynamic moisture permeation through clothing.

Adult↗
PubMed1988

Human macrophages from skin: I. Isolation and culture.

Coarsely ground Lytta vesicatoria FABRICIUS (meloideae/coleoptera), with a cantharidine content of 0.5-1% was dissolved in ethanol and worked into a powdery solution. 1-2 cm2 large swabs were dissolved in the tincture, and with the help of a Karaya plate and an occlusive dressing was administered to the skin in the antebrachii anterior region. This led to a severe inflammation, which after a further 10 h was accompanied by pemphigus and vesiculation. The vesicular liquid was aspirated, centrifuged, the cells resuspended and coated on a small cover-glass in a petri-dish and incubated. The human macrophages were kept in a moisture-saturated atmosphere with 5% CO2 at a temperature of 37 degrees C. The blisters healed quickly and without scaring after a correct dressing of the wounds was administered. The safety of this method was thus tested on human subjects, at first on the author, and proven successful.

Cell Separation↗
PubMed1988

Human macrophages from skin: II. Histochemical, cytochemical and scanning electron microscopical identification.

The recent development of a simple not invasive method for isolating macrophages from the skin of normal subjects has also provided a unique opportunity for morphological studies. Human macrophages isolated from skin blisters (n = 34) (Michna 1988) are identified as substratum using the proof of unspecific esterase with alpha-naphthyl-butyrate. The typical morphological features of human macrophages are demonstrated in a transmission and scanning electron microscopic study. In a cytochemical part the lysosomal potenties of these human macrophages are displayed.

Acid Phosphatase↗
PubMed1987

Tendon injuries induced by exercise and anabolic steroids in experimental mice.

The purpose of this study was to examine the effect of anabolic steroid hormones and exercise training on skeletal tendons. Female mice were exercised for 1 and 10 weeks in an endurance running programme on a treadmill. The altered ultrastructure of tendons caused by simultaneously administered anabolic steroid hormone was investigated by electron microscopy. A stereoscopic analysis of collagen fibrils was performed in order to reveal the changes in the architecture of tendons and to quantify the extent of possible injuries to their functional structure. The occurrence of tendon injuries was detected by the appearance of a collagen dysplasia. The morphometric analysis of the degree of the collagen dysplasia in the different experimental groups reveals that it becomes even more conspicuous in the tendons of the mice which were both exercised and given anabolic steroids. The overall picture and the architecture of the tendons provide tentative evidence that anabolic steroid hormones may induce tendon injuries, depending on the duration of treatment. The direct effect of anabolic steroids on tendons has to be taken into account when considering the clinical disorders of tendons and ligaments which occur in high-class athletes.

Animals↗
PubMed1987

Clothing surface area as related to body volume and clothing microenvironment volume.

The evaluation of clothing surface area becomes important in analyses of heat exchange between the clothed body and its environment. The evidence accumulated in the studies of radiation area has led to the conclusion that the ratio of clothing surface area to body surface area (fcl) may be defined as a function of clothing insulation. However, the effects of clothing fit have been disregarded. Radiation area factors (Ar/AD) were derived from pictures of five subjects wearing four different helicopter pilot suits. While sitting on a seat suspended in the center of a box-shaped frame, photographs were taken of the subjects with a fish-eye lens at 90 equidistant points on the six sides of the frame. The derived Ar/AD of 0.7 +/- 0.18 for the unclothed subjects closely agreed with that reported by Fanger, while it scattered in a relatively wide range for a given suit. The present study proposes a new approach for predicting fcl as related to body volume and the clothing microenvironment volume. The predictions show a good correlation with the values derived from the photographs. It is, therefore, suggested that improvement in the prediction of fcl has been achieved by incorporating clothing fit.

Anthropometry↗
PubMed1986

Organisation of collagen fibrils in tendon: changes induced by an anabolic steroid. I. Functional and ultrastructural studies.

The organisation of tendon collagen fibrils has been studied by electron microscopy after treatment with an anabolic steroid hormone in a short-term and a long-term study. The effect of anabolic steroids is of interest because of their use in competitive sports and in clinical therapy. In a functional experimental model the unexpected occurrence of dysplastic as well as ruptured and dissociated collagen fibrils was revealed. The striking time-dependent collagen dysplasia and other pathological findings strongly suggest that in mice anabolic steroid treatment predisposes to tendon rupture especially when the animals are exercised. The possible underlying mode of action of anabolic steroid hormone on connective tissue is discussed.

Anabolic Agents↗
PubMed1986

Organisation of collagen fibrils in tendon: changes induced by an anabolic steroid. II. A morphometric and stereologic analysis.

Morphometric and stereologic analysis of the organisation of collagen fibrils in tendon tissue after a treatment with an anabolic steroid hormone allowed the following observations: In a short-term study stereological data revealed a potent accumulation of collagen fibrils in the extra-cellular matrix after the administration of an anabolic steroid. Compared with controls, the anabolic steroid significantly increased the number of dysplastic collagen fibrils dependent on duration of treatment. Inter- and intrafibrillary dysplastic collagen fibrils possess characteristic diameter distributions which differ considerably from those of normal collagen fibrils. The functional significance of the changes in mean diameter, diameter distribution, numerical density and volume fraction of collagen fibrils in tendons following hormone treatment may be relevant to the use of these drugs in clinical practice and in competitive sports.

Anabolic Agents↗
PubMed1984

Morphometric analysis of loading-induced changes in collagen-fibril populations in young tendons.

This study was designed to gain more detailed morphological information on skeletal tendons in the course of adaptation to physical loading. The effect on collagen fibrils was investigated in 6-week-old mice by means of electron microscopy. Physical loading was performed on a treadmill 5 days a week for 1, 3, 5, 7 and 10 weeks. Morphometric analysis of collagen fibrils revealed the mean diameter, the diameter distribution, the number and the cross-sectional area. The principal observations included: 1. After one week of physical loading an increase in mean fibril diameter (30%, p less than or equal to 0.01), in number (15%, p less than or equal to 0.05), and in cross-sectional area (15%, p less than or equal to 0.05), as well as a change in mean fibril diameter distribution. 2. From the third to the seventh week a fall under the level of the controls in mean diameter (26%, p less than or equal to 0.01), in number (26%, p less than or equal to 0.01), and a reduced cross-sectional area (17%, p less than or equal to 0.01), accompanied by signs of splitting of individual collagen fibrils. 3. In the long-term study an increase in fibril number (29%, p less than or equal to 0.01), a fall in mean diameter from 189 nm in the controls to 179 nm (p less than or equal to 0.05) but no statistically significant change in the relative cross-sectional area (32%) per unit in comparison to unloaded tendons. The possible physiological implications of the findings are discussed in the light of several regulatory mechanisms known to appear during the course of physical loading in connective tissues.

Adaptation, Physiological↗
PubMed1983

A peculiar myofibrillar pattern in the murine muscle-tendon junction.

The muscle-tendon junctions of adult mice show a special arrangement of myofibrils. Essentially, the myofibrils are oriented in an anchor-like manner in the large finger-shaped processes of the muscle fiber, which contain "mitochondrial sacks" (Demmel et al. 1979) in a subsarcolemmal position. Furthermore, the single myofibril frequently branches out into smaller fibrils. It is suggested that due to the three-dimensional arrangement, these processes gain a high rigidity during contraction, thus maintaining their shape and preserving the "mitochondrial sacks".

Animals↗
PubMedDate not supplied

Progesterone receptor repression by estrogens in rat uterine epithelial cells.

Measurements performed using cell lines or animal tissues have shown that the progesterone receptor (PR) can be induced by estrogens. By use of immunohistochemistry we studied the effects of estrogens on the PR levels in the individual cell types of the target organs uterus and breast. In the uteri of rats, ovariectomy induced a decrease in PR immunoreactivity within the myometrium and outer stromal cell layers. In contrast, in the uterine luminal and glandular epithelium and surrounding stromal cell layers the PR immunoreactivity was significantly enhanced. The same picture emerged when intact rats were treated with the pure estrogen receptor antagonist, ZM 182780 (10 mg/kg/d). Treatment of ovariectomized rats with estradiol resulted in high PR levels in the myometrium and stroma cells but low PR immunoreactivity in the epithelial cells. The ER-mediated repression of the PR immunoreactivity was evidently restricted to the uterine epithelium, as we found that in the epithelial cells of the mammary gland and in cells of N-nitrosomethylurea-induced mammary carcinomas the PR expression was induced by estrogens and was blocked by the pure antiestrogen ZM 182780. These results clearly show that in the rat the activated ER induces diverging effects on PR expression in different cell types even within the same organ.

Animals↗
PubMedDate not supplied

Tumor-inhibiting potential of ZK 112.993, a new progesterone antagonist, in hormone-sensitive, experimental rodent and human mammary tumors.

The progesterone antagonists Onapristone (ZK 98.299) and Mifepristone (RU 486) proved to be strong inhibitors of various rodent mammary tumors. Therefore, a further potent antiprogestin, ZK 112.993, and 11 beta-(4-acetyl-phenyl)-analog of Mifepristone, with a high progesterone receptor affinity was tested in experimental rodent and human breast cancer models. In the hormone-dependent MXT(+) mammary tumor of the mouse, treatment of tumors immediately after implantation with 5 mg/kg for 6 weeks led to an inhibition of growth by 95%, being significantly superior to that caused by tamoxifen, diethylstilbestrol and Onapristone. Treatment of established MXT(+) tumors by ZK 112.993 at doses of 0.5, 1.0 and 2.0 mg/kg led to a strong inhibition that equalled that of ovariectomy and surpassed that of Onapristone in the lower doses. In the human, receptor positive mammary carcinoma T61 implanted in male, castrated nude mice, ZK 112.993 (10 mg/kg) significantly retarded tumor growth. Its effect was again superior to Onapristone though weaker than that of tamoxifen. The NMU-induced mammary carcinoma of the rat (established tumors) was inhibited by ZK 112.993 (5 and 10 mg/kg) in a dose-dependent manner slightly superior to Onapristone but weaker than after ovariectomy. Due to its strong antitumor activity and because of the innovative mechanism of action of antiprogesterones in tumor treatment, ZK 112.993 could be of great value for the treatment of breast cancer.

Animals↗