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Biomedical subjects

W Meyer

Publications and source records attributed to W Meyer.

At least 271 records · Page 15Linked to original sources
PubMed1987

A comparative scanning electron microscopic view of the integument of domestic mammals.

Scanning electron microscopy (SEM) demonstrates efficiently species-specific differences of hairy skin (integumentum commune) of domestic mammals (pig, cat, dog, horse, cattle, sheep, goat). This technique is very helpful in characterizing the typical structural features of the epidermal layers, the arrangement of the collagen fibre bundles and the elastic fibre network in the dermis, the external and internal construction of hair follicles and hair shafts, and the functional development of skin glands. It is also possible to observe certain domestication effects, especially where the hair coat is concerned. SEM supplements the knowledge about the integument as available from conventional transmission electron microscopy, light microscopy or histochemistry. Thus, comparative morphology can be the basis for the development of specific functional models of the different integumentary layers and derivatives or their tissues involved.

Animals↗
PubMed1986

Structural and histochemical aspects of epidermis development of fetal porcine skin.

Epidermal development of fetal porcine skin was studied in fetuses from 41 days of gestation until birth with scanning and electron microscopy techniques as well as histochemical methods, including immunohistochemistry. The porcine fetus develops a relatively thick and solid multilayered cover of epidermal cells, which is not lost before birth. It consists of tightly packed cells of the periderm and the stratum intermedium. The periderm cells are totally filled with filamentous proteins; in the intermediate cells, the filamentous proteins are concentrated in the cell periphery, forming a thick marginal zone. Immunohistochemically, the cytofilaments could be identified as cytokeratins of lower and higher molecular weights. The first thin stratum corneum lamellae are formed below the stratum intermedium at about 80-85 days of gestation.

Animals↗
PubMed1986

Biochemical and histochemical aspects of lead exposure in dragonfly larvae (Odonata: Anisoptera).

The effects of lead exposure on the oxidative properties of different organs of dragonfly larvae (advanced instars) (Odonata: Anisoptera) were estimated by biochemical and histochemical methods. The lead load of the water was 20 micrograms/liter during 6 weeks at a temperature of 15 degrees C and a normal diurnal rhythm. Lead was not accumulated in the brain, but in considerable amounts in the midgut, fat body, rectum, and cuticula of the test animals, while the control larvae showed astonishing concentrations of the heavy metal in the cuticula. The activities of the oxidative enzymes studied were significantly lowered only in the brain. Histochemically, lead could be visualized in all the organ tissues, apart from the brain, of the test animals, the controls exhibiting lead only in the cuticula. The enzyme histochemical evaluation of succinic dehydrogenase demonstrated typical changes of reaction intensities within the organs of the test animals, as compared to the controls. The results obtained are discussed in view of the specific biology of the tested animals and their normal biotope.

Animals↗
PubMed1986

First trimester diagnosis of Pompe's disease (glycogenosis type II) with normal outcome: assay of acid alpha-glucosidase in chorionic villous biopsy using antibodies.

Prenatal diagnosis of glycogenosis type II was performed by direct assay of acid alpha-glucosidase (EC 3.2.1.20) in chorionic villous biopsy obtained by transcervical cannula aspiration from a pregnancy at risk in the 10th week of gestation. The exact value of the enzyme activity estimated by the use of antibody preparations for purified human liver acid alpha-glucosidase was in the heterozygous range, and so the homozygous enzyme deficiency could be excluded. The subsequent analysis of cells cultured from amniocentesis sampling in the 18th week of gestation resulted in a similar outcome. The study with antibodies showed that in 23 control chorionic villi obtained during gestational ages between 7-13 weeks, 1-15% of the total alpha-glucosidase activity at pH 4.0 were due to renal or neutral enzyme. This indicates that it may be important to employ antibodies for prenatal diagnosis using chorionic villous sampling. A healthy and unaffected boy was born. The biochemical values obtained from an umbilical blood specimen were in accordance with the results of the prenatal diagnosis.

Adult↗
PubMed1986

Phosphodiesterase-inhibiting properties of newer inotropic agents.

The positive inotropic effects of the bipyridine derivatives amrinone and milrinone and of the benzimidazole compounds sulmazole, pimobendane, and UD-CG 212 Cl are due at least in part to inhibition of cardiac phosphodiesterase activity and hence to an increase in myocardial cyclic AMP (cAMP) content. Compared with the other agents, the contribution of the cAMP system appears to be relatively small in the case of pimobendane and UD-CG 212 Cl. This reduced effect is probably advantageous because an increase in cAMP leads not only to positive inotropic but also to positive chronotropic effects and possibly to arrhythmogenesis. The latter in particular may limit the usefulness of new cardiotonic agents, although--at least theoretically--a cAMP-dependent arrhythmogenic action might be overcome by additional "antiarrhythmic" properties, e.g., prolongation of the action potential, depression of transient depolarizations, or depression of the fast Na+ inward current. Sulmazole and pimobendane have been shown to have an additional effect on the contractile properties in that they increase the sensitivity of the myofibrils to Ca++.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Some observations on dermis development in fetal porcine skin.

The study describes dermis development in fetal porcine skin between 40 d GA and birth. The first fibroblast arrangement occurs about 47 d GA, while between 60-65 d GA the first fibres are visible. They can be identified as collagen about 67 d GA, somewhat later the dermis shows 2 strata. At the end of median gestional life, the first birefringent lattice pattern of collagen fibre bundles is formed. The first elastic fibres cannot be demonstrated before 100 d GA.A clear increase in fibrocyte numbers occurs about 70-80 d GA, the next one at birth. The thickness development of the fetal porcine dermis is closely correlated with the increase in body weight. Additionally RNA and glycogen content developments have been studied in the fetal dermis.

Animals↗
PubMed1986

Development of hair coat and skin glands in fetal porcine integument.

The prenatal development of the hair coat and skin glands was studied in skin samples of ten body regions of porcine fetuses (German Landrace) ranging between 40 and 114 days (birth) of gestation (15-1000 g body weight), using light microscopy and scanning electron microscopy. During the development of hair follicles, central and lateral primary hair follicles as well as secondary hair follicles can be distinguished. Initiation of primary hair follicles begins at 40-41 days of gestational age (15 g BW) and has finished at 73 days (300 g BW). The structural development of the primary hair follicle is described in detail, and is divided into twelve stages, in general agreement with those of other mammals. The secondary hair follicles formed later remain rudimentary and disappear during the birth period. The length, depth, density and angle of slope of the primary hair follicles, and the depth of the apocrine skin glands were measured. The development of hair follicle length is closely correlated with the increase in body weight. There is a similar but changing correlation for the development of hair follicle density, especially in connection with hair follicle initiation. In the development of the apocrine skin glands, a branching of the secretory tubule is conspicuous. Secretion does not begin before birth. The development of the sebaceous glands is closely related to hair follicle maturation, i.e. the formation of the first hair canal. The results are discussed in relation to findings from corresponding studies in small laboratory animals, other domestic mammals and man.

Animals↗
PubMed1985

Functional evidence for the existence of adenosine receptors in the human heart.

Adenosine added to isolated electrically driven preparations of human ventricular heart muscle antagonized the positive inotropic effect of isoprenaline (mean EC50 19 mumol 1(-1), n = 9). Similar effects were observed with the adenosine receptor agonist (-)-N6-phenylisopropyladenosine (mean EC50 0.5 mumol 1(-1), n = 7). These data provide functional evidence for the existence of adenosine receptors in the human myocardium which may modulate the force of contraction during beta-adrenergic stimulation and thus could be involved in the autoregulation of myocardial contractility.

Adenosine↗
PubMed1985

Positive inotropic effect of Bay K 8644: cAMP-independence and lack of inhibitory effect of adenosine.

The aim of the present study was to characterize the positive inotropic effect of the Ca2+ channel activator Bay K 8644. In isolated guinea-pig papillary muscles we investigated whether adenosine and the R site adenosine receptor agonist (-)-N6-phenylisopropyladenosine (PIA) were able to antagonize the positive inotropic effect of Bay K 8644. The effect of Bay K 8644 and adenosine or PIA on myocardial cAMP content was also measured. The influence of adenosine and PIA on the positive inotropic effect of the beta-adrenoceptor agonist isoprenaline and of the phosphodiesterase inhibitor amrinone was studied for comparison. Adenosine and PIA antagonized the positive inotropic effects of isoprenaline and amrinone in a concentration-dependent manner. In contrast, adenosine or PIA did not affect the positive inotropic effect of Bay K 8644. The positive inotropic effect of Bay K 8644 was not accompanied by a change in the cAMP content of the papillary muscles. Additionally applied adenosine or PIA also failed to affect the cAMP content. It is concluded that an increased myocardial cAMP content is not involved in the positive inotropic effect of Bay K 8644. Moreover, the results support the view that adenosine and PIA only antagonize the positive inotropic effects of drugs known to increase myocardial cAMP content and that an increased myocardial cAMP content is a prerequisite for the manifestation of a negative inotropic effect of the nucleosides in ventricular cardiac muscle.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1985

Evidence for adenosine receptor-mediated isoprenaline-antagonistic effects of the adenosine analogs PIA and NECA on force of contraction in guinea-pig atrial and ventricular cardiac preparations.

The effects of the adenosine agonists (-)-N6-phenylisopropyladenosine (PIA) and 5'-N-ethylcarboxamideadenosine (NECA) on force of contraction, adenylate cyclase activity and normal as well as slow action potentials were studied in guinea-pig isolated atrial (left auricles) and ventricular preparations (papillary muscles). In auricles PIA and NECA exerted concentration-dependent negative inotropic effects with similar potencies (mean EC50:0.05 mumol l-1 for PIA and 0.03 mumol l-1 for NECA). Similar results were obtained in the presence of isoprenaline. In papillary muscles PIA and NECA alone had no effect on force of contraction but produced negative inotropic effects in the presence of isoprenaline (mean EC50:0.19 mumol l-1 for PIA and 0.10 mumol l-1 for NECA). In both preparations, the negative inotropic effects of PIA and NECA in the presence of isoprenaline were antagonized by the adenosine receptor antagonist 8-phenyltheophylline. In both preparations, PIA and NECA did not affect adenylate cyclase activity, both in the absence and presence of isoprenaline. In auricles the negative inotropic effects of both nucleosides were accompanied by a shortening of the action potential. This effect was also observed in the presence of isoprenaline. In papillary muscles the adenosine analogs did not detectably alter the shape of the normal action potential. Ca2+-dependent slow action potentials elicited in potassium-depolarized preparations also remained unaltered in the presence of PIA or NECA alone. However, the isoprenaline-induced enhancement of the maximal rate of depolarization of slow action potentials was attenuated by PIA or NECA.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗