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Biomedical subjects

D Heinrich

Publications and source records attributed to D Heinrich.

At least 19 recordsLinked to original sources
PubMed1979

Intercellular junctions in the full term human placenta. I. Syncytiotrophoblastic layer.

Inter- and intrasyncytiotrophoblastic junctions within the human full term placenta were electronmicroscopically investigated using thin sections and freeze-fracturing. Narrow clefts were occasionally situated between surface areas where adjacent chorionic villi exhibited close contact. Within these clefts, extensive zonulae and maculae occludentes and numerous maculae adherentes were found. The zonulae occludentes showed a continuous and irregular course on the membrane surface, and the maculae occludentes were irregularly distributed over extended membrane areas. Besides these areas, maculae occludentes and maculae adherentes were observed on infoldings and invaginations of the synctiotrophoblastic surface membrane. Investigations of the inner surface of the syncytiotrophoblastic layer, that is, the layer facing the villous stroma, also revealed invaginations joined by maculae adherentes. The functional significance of the inter- and intrasyncytiotrophoblastic junctions is discussed with respect to the differentiation of the trophoblast.

Female↗
PubMed1978

In vivo performance of the pH tissue electrode during acute acid-base changes in the dog.

The ROCHE tissue pH-electrode was tested in acute animal experiments under various metabolic conditions. In anesthetized dogs an electrode was placed in the subcutaneous tissue of the scalp, neck, and axilla. Simultaneous with the continuous measurement of tissue pH, the overall acid-base balance of the animal was measured discontinuously at 5-min intervals by means of indwelling arterial and venous catheters. Various forms of acidosis and hypoxia were produced in the experimental animal and the sensitivity of the electrodes in relation to their site was tested. A high correlation between the continuously measured tissue pH values and the corresponding arterial and venous actual blood pH values were found in the physiologic pH range. With acute changes of acid-base balance no correlation could be found in the acidotic range.

Acid-Base Imbalance↗
PubMed1978

Continuous measurement of tissue pH in the human fetus.

The ROCHE pH electrode was tested clinically in 20 fetuses and one nonviable newborn with severe malformations. The proper fixation of the electrode in the fetal scalp is difficult. In the physiologic pH range a good correlation between capillary blood pH and tissue pH exists. The situation is less clear for the acidotic range.

Capillaries↗
PubMed1977

Specific interaction of HLA antibodies (eluates) with washed platelets.

The mechanism of complement-independent action of HLA-A2 antibodies (eluates) on washed platelets was investigated. HLA-specific alteration was confirmed by serological (platelet micro-complement fixation), morphological (platelet spreading) and functional parameters (platelet aggregation, inhibition of collagen-induced platelet aggregation, [14C]serotonin release). In the presence of fibrinogen and calcium ions, HLA antibodies induced instantaneous platelet aggregation and release. Although no morphological (spreading) and functional changes (collagen-induded aggregation) were seen, these platelets did not aggregate or release when fibrinogen was subsequently added. When platelets--in the presence of fibrinogen--were incubated with antibody concentrations too low to induce platelet aggregation or release, specific reduction of platelet reactivity was observed by subsequent collagen aggregation. HLA-specific action of antibodies on washed platelets was inhibited by apyrase and acetyl-salicylic acid, indicating an active participation of platelets in HLA antibody-induced platelet alteration.

Antibodies↗
PubMed1977

A comparative analysis of methods suitable for detection of platelet alloantibodies: inhibition of 14C-serotonin uptake, 14C-serotonin release and microcomplement fixation.

Three HLA-specific antisera were comparatively analyzed by platelet microcomplement fixation and 14C-serotonin uptake and/or 14C-serotonin release studies with platelets. In general, there was a good correlation of HLA antibody specificity exhibited in all 3 test systems. Quantitative differences in the response of platelets to HLA antisera were observed and accounted for by differences in antigen density and different types of antibodies involved. Platelet autoantibodies could not be detected by means of 14C-serotonin release from platelets in plasma.

Antibody Specificity↗
PubMed1977

HLA-antibody-induced 14C-serotonin release from platelets. A methodological analysis.

The prerequisites and kinetics of HLA-antibody-induced 14C-serotonin release from platelets were investigated with five HLA-specific antisera. By studying the influence of incubation time, temperature, pH, platelet count, stirring and extent of platelet labeling, optimal results were obtained after 30 (to 60) min of incubation at 37 degrees C, pH 7.5-8.0, under constant stirring (400 rpm). Optimal platelet counts varied between 160,000 and 400,000/microliter depending on the antiserum applied. A comparison of the amount of 14C-serotonin released by different antisera from washed platelets and from platelets in platelet-rich plasma suggests that plasma components--most likely complement--may additionally influence the results. Based on these experiments, a standardized microtechnique of HLA-antibody-induced 14C-serotonin release is recommended.

Antibody Specificity↗
PubMed1977

The problem of platelet autoantibodies. II. The applicability of the 14C-serotonin release test.

To evaluate the applicability of the 14C-serotonin release test for the demonstration of platelet autoantibodies, normal test material (sera, plasmas, globulin fractions), HLA-specific complement-fixing platelet antibodies and aggregated human gamma-globulin (agammaG) were tested in comparison to sera (plasmas, globulin fractions) of 101 thrombocytopenic patients including 46 cases of idiopathic thrombocytopenic purpura. Whereas defined immunological stimuli (HLA antibodies, agammaG) were detected with satisfactory precision, platelet autoantibodies could not be demonstrated. Only sera containing HLA antibodies due to previous immunization induced reproducible 14C-serotonin release. Results with test material from thrombocytopenic patients were analyzed by 2 x 2 tables and inconsistencies were shown to be caused by methodological variations.

Autoantibodies↗
PubMed1977

[The pattern of distribution of free amino acids in human amniotic fluid related to the duration of pregnancy. Part II: Changes in concentration in pathological pregnancy (author's transl)].

18 free amino acids from 196 specimens of amniotic fluid of pathological pregnancies between the 28th and 41st week of pregnancy were measured by gaschromatography. The concentrations of the amino acids in amniotic fluid in normal and pathological pregnancies were analysed by statistical methods. There were only minor differencies of concentration of free amino acids in the amniotic fluid between normal and pathological pregnancies with the exception of hydroxyproline. This was found in a significantly higher concentration in the amniotic fluid of the pathological group. Supposing that the materno-fetal as well as the feto-maternal amino acid exchange may be reduced by the placenta insufficiency, the significantly higher concentration of hydroxyproline in the amniotic fluid during pathological pregnancies may be caused higher fetal urine excretion of hydroxyproline into the amniotic fluid. The increase of hydroxyproline in the amniotic fluid of pathological pregnancies is probably an early diagnostic parameter of an impaired transplacental exchange -- placenta insufficiency.

Amino Acid Metabolism, Inborn Errors↗
PubMed1976

Ultrastructure of perfusion-fixed fetal capillaries in the human placenta.

The ultrastructure of human placental capillaries was investigated using perfusion fixation and the freeze-fracturing technique. The capillaries have a continuous endothelium especially rich in microfilaments, whereas micropinocytotic vesicles are exceedingly scarce. The endothelial cells are connected by three types of junctions: (1) zonulae occludentes characterized by 2 to 4 focal regions of membrane contact in thin-sectioned specimens and an equal number of ridges on the membrane E-face in freeze-fractured specimens; (2) small gap junctions associated with the zonula occludens. (3) attachment plaques resembling zonulae adhaerentes in their fine structure. Endothelial cells are provided with long, circularly oriented pseudopodial extensions, which may be responsible for intermittent constrictions of the vessel lumen. These findings indicate that diaplacental transport at the level of the fetal capillary is controlled by the cytoplasm of the endothelial cells and probably occurs only to a very limited extent by way of micropinocytotic vesicles.

Capillaries↗
PubMed1976

Gap junctions in hemodichorial and hemotrichorial placentae.

Gap junctions were found to be a constant feature of chorioallantoic placentae with two or three trophoblastic layers. The gap junctions connect layers I and II in hemodichorial and layers II and III in hemotrichorial placentae. Although the gap junctions vary in form and in the packing density of membrane-associated particles, they cover an extensive surface area in all species examined. The gap junctions always connect adjacent membranes of two trophoblastic layers, which show no evidence of micropinocytotic activity; at least one of these trophoblastic layers is syncytial. It is therefore concluded that the gap junctions play an important role in diaplacental transport. We consider that gap junctions act as molecular sieves, resulting in limitations in the transport of large molecules. The passage of small molecules, on the contrary, would be facilitated by the gap junctions.

Animals↗