Immunohistochemical detection of factor XIII subunit a in histiocytes of human uterus

As spontaneous abortion is a frequent finding in females with Factor XIII (FXIII) deficiency it has been presumed that this clotting factor is essential to normal pregnancy. FXIII subunit a (FXIII A) has been demonstrated in the homogenate of human uterus, but no information on its cellular distribution has been published, so far. In the present study first FXIII A was detected in paraformaldehyde-fixed, paraffin-embedded sections of human uterus by immunoperoxidase technique. Cells containing FXIII A were localized between collagen fibrils stained by Picrosirius Red F3B in the connective tissue. To characterize them the immunofluorescent detection of FXIII A was combined by the visualization of different marker antigens of monocytes and macrophages recognized by Leu-M3, RFD7, anti-HLA-DR and DAKO-anti-macrophage monoclonal antibodies on frozen sections. The coexpression of FXIII A with monocyte and macrophage differentiation marker antigens clearly proves that cells containing FXIII A in the uterus are monocyte-derived tissue macrophages. The results well agree with our previous findings demonstrating FXIII A in human monocytes and different types of macrophages. On the basis of these results, the presence of FXIII A does not seem to be a specificity of the uterus but a characteristic of monocyte/macrophage cell line including tissue macrophages, in general.     

Disturbed lipid metabolism in diabetic coronary vessels

The aim of this study was to clarify whether or not arachidonic acid metabolic disorders are caused by a substrate inavailability and whether such disorders might contribute to circulatory disturbances in the diabetic myocardium. Norepinephrine induced a decrease in the conductivity of both coronary arterial bed and myocardial microcirculation in alloxan-diabetic dogs. It was markedly (p < 0.05) attenuated both by indomethacin and acetylsalicylic acid pretreatments indicating an imbalance among the vasoactive prostanoids in diabetes. TXA₂ release from the diabetic coronary rings was found to be elevated and could be normalized after the blockade of vascular adrenoceptors by phentolamine (p < 0.05). PGIZ synthesis was also enhanced by adrenergic blockade in the diabetic arterial rings. After pretreatment with ^l4C arachidonic acid, in order to measure substrate availability, the arachidonic acid metabolic rate was less in the diabetic coronary arteries than in healthy vessels (p < 0.05). Ten µmol/1 norepinephrine decreased arachidonic acid metabolism in the presence of prelabelled substrate in the diabetic animals, compared to an increase observed in metabolically healthy dogs. Therefore diabetes appears to diminish arachidonic acid metabolism and uptake independent of adrenoceptors and to induce an imbalance between vasoconstrictor and vasodilator cyclooxygenase products, resulting in elevated TXA₂ release controlled by adrenergic mechanisms which may contribute to an impairment in myocardial microcirculation.Abbreviations 6-oxo-PGF₁ 6-oxo prostaglandin F₁ - HPLC High Pressure Liquid Chromatograph - LAD Left Anterior Descending (coronary artery) - PGI₂ Prostacyclin - TXA₂ Thromboxane     

Subcellular localization of creatine kinase in Torpedo electrocytes: association with acetylcholine receptor-rich membranes

Creatine kinase (CK, EC 2.7.3.2) has recently been identified as the intermediate isoelectric point species (pl 6.5-6.8) of the Mr 40,000-43,000 nonreceptor, peripheral v-proteins in Torpedo marmorata acetylcholine receptor-rich membranes (Barrantes, F. J., G. Mieskes, and T. Wallimann, 1983, Proc. Natl. Acad. Sci. USA, 80: 5440-5444). In the present study, this finding is substantiated at the cellular and subcellular level of the T. marmorata electric organ by immunofluorescence and by protein A-gold labeling of either ultrathin cryosections of electrocytes or purified receptor-membrane vesicles that use subunit-specific anti-chicken creatine kinase antibodies. The muscle form of the kinase, on the one hand, is present throughout the entire T. marmorata electrocyte except in the nuclei. The brain form of the kinase, on the other hand, is predominantly located on the ventral, innervated face of the electrocyte, where it is closely associated with both surfaces of the postsynaptic membrane, and secondarily in the synaptic vesicles at the presynaptic terminal. Labeling of the noninnervated dorsal membrane is observed at the invaginated sac system. In the case of purified acetylcholine receptor-rich membranes, antibodies specific for chicken B-CK label only one face of the isolated vesicles. No immunoreaction is observed with anti-chicken M-CK antibodies. A discussion follows on the possible implications of these localizations of creatine kinase in connection with the function of the acetylcholine receptor at the postsynaptic membrane, the Na/K ATPase at the dorsal electrocyte membrane, and the ATP-dependent transmitter release at the nerve ending.     

Further characterization of the structural and functional properties of the cross-linked complex between F-actin and myosin S-1

Several structural and functional properties of the covalent complex, formed upon cross-linking of the myosin heads (S-1) to F-actin with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, were characterized. The elevated Mg2+-ATPase activity was measured during a 1-month storage of the complex under various conditions. In aqueous medium it showed a rapid time-dependent decrease but it was significantly more stable in the presence of 50% ethylene glycol at -20 degrees C. The ATPase loss most likely reflects a progressive conformational change within the S-1 ATPase site resulting from its greater exposure to the medium, induced by the permanently bound F-actin. The covalent acto-S1 complex was submitted to depolymerization-repolymerization experiments using different depolymerizing agents (0.6 M KI; 4.7 M NH4Cl; low-ionic-strength solution). The depolymerization led to an immediate loss of the enhanced Mg2+-ATPase activity; this activity was almost entirely recovered upon repolymerization of the complex. The protein material formed upon depolymerization of the covalent acto-S1 was analyzed by gel chromatography, gel electrophoresis, analytical ultracentrifugation and electron microscopy. It comprised mainly small-sized actin oligomers associated with the covalently bound S-1 and only a limited amount of free G-actin. The results illustrate the relationships between the filamentous state of actin and its ability to stimulate the Mg2+-ATPase activity of S-1. They also indicate that the binding of S-1 to F-actin is transmitted to several neighbouring actin subunits and strengthens the interactions between actin monomers. Acto-S1 cross-linked complexes were prepared in the presence of tropomyosin and the tropomyosin-troponin system. Under the conditions employed, the regulatory proteins were not cross-linked to actin or S-1 and did not affect the extent or the pattern of S-1 cross-linking to F-actin. Measurements of the elevated Mg2+-ATPase activity of the cross-linked preparations revealed that tropomyosin and the tropomyosin-troponin complex, in the absence of Ca2+, inhibit ATP hydrolysis; the extent of ATPase inhibition (up to 50%) was dependent on the amount of covalently bound S-1, being larger at low level of S-1 cross-linking; the addition of Ca2+ restored the ATPase activity to the control value. The data provide direct evidence that the regulatory proteins can modulate directly the kinetics of ATP hydrolysis by the covalent acto-S1 complex as has earlier been suggested for the reversible complex [Chalovich, J. M. and Eisenberg, E. (1982) J. Biol. Chem. 257, 2432-2437].(ABSTRACT TRUNCATED AT 400 WORDS)     

Magnetic interaction of manganese with pheophytin anion-radical and chlorophyll cation-radical in reaction centers of the photosystem II

The influence of Mn on saturation curves of ESR spectra of Ph(-) and P(+)(680) at 1-200K in samples with different content of Mn has been studied. An analysis of these data and those on photoinduced changes of fluorescence yield of chlorophyll leads to the conclusion that the Mn-containing centre in Photosystem 2 is a cluster of 4 Mn atoms, two of which can be replaced by Mg(2+) or any other divalent metal. The distances between Mn Na Ph as well as between Mn and P(680) have been estimated.