Dipeptidyl peptidase IV inhibits the polymerization of fibrin monomers

A highly purified dipeptidyl peptidase IV from human placenta cleaves glycylproline from the N-terminal end of the fibrin α chain and inhibits the clotting of fibrin monomers. This result underlines the importance of the amino terminus of the fibrin α chain as an aggregation site masked by fibrinopeptide A. We speculate that the peptidase may hinder blood coagulation in intact vessels in vivo, because it is located on the surface of the capillary endothelium.     

Comparative study of the cellular replication kinetics of rat mammary epithelial cells in vivo and in vitro

Ts-131b, one of the temperature-sensitive (ts) mutants isolated from mouse FM3A cells, was found to be defective in DNA replication at a non-permissive temperature. After the cells were transferred to 39.5 °C, the cell number increased by only 10% and the rate of incorporation of precursors into cellular DNA decreased rapidly. Cell cycle analysis by a flow cytometric method with the cells incubated at 39.5 °C revealed that progression of the cells through the S phase was inhibited and most of the cells were arrested in the S phase. To study the defect in DNA replication of this ts-mutant at 39.5 °C, DNA-fiber autoradiography was performed to measure the rate of DNA-chain elongation. The results showed that the rate of DNA-chain elongation was decreased at 6 h after the temperature shift. However, since the decrease in the rate of DNA-chain elongation was not sufficient to account for the decrease in the rate of incorporation of the precursors, it was suggested that there was also a decrease in the rate of initiation of DNA replication at some of the replicon origins.     

Intrinsic PEEP monitored in the ventilated ARDS patient with a mathematical method.

Under mechanical volume-controlled ventilation, the intensive care patient can develop intrinsic positive end-expiratory pressure (iPEEP); that is, the passive expiration is terminated by the following inspiration before the alveolar pressure comes to its physical equilibrium value. We present a mathematical method to estimate this alveolar dynamic iPEEP breath by breath, without the need of a maneuver. We tested it in paralyzed patients ventilated for adult respiratory distress syndrome after multiple trauma and/or sepsis, and we compared the results obtained with the new mathematical method with those from the occlusion method introduced by Pepe and Marini. The results agreed well (median difference of 0.8 mbar in 201 investigations in 12 patients). However, the mathematically determined values, representing dynamic iPEEP, are systematically slightly smaller than those measured by the occlusion maneuver. A variation of expiratory time suggests that this difference might be due to mechanical time-constant inhomogeneity, viscoelastic processes, or other mechanisms showing time dependence.     

Multifrequency EPR evidence for a bimetallic center at the CuA site in cytochrome c oxidase

Multifrequency electron paramagnetic resonance (EPR) spectra of the Cu(II) site in bovine heart cytochrome c oxidase (COX) and nitrous oxide reductase (N2OR) from Pseudomonas stutzeri confirm the existence of Cu-Cu interaction in both enzymes. C-band (4.5 GHz) proves to be a particularly good frequency complementing the spectra of COX and N2OR recorded at 2.4 and 3.5 GHz. Both the high and low field region of the EPR spectra show the presence of a well-resolved 7-line pattern consistent with the idea of a binuclear Cu center in COX and N2OR. Based on this assumption consistent g-values are calculated for gz and gx at four frequencies. No consistent g-values are obtained with the assumption of a 4-line pattern indicative for a mononuclear Cu site.     

Studies on cytochrome c oxidase, IX. The primary structure of polypeptide VIa

The complete amino acid sequence of the cytoplasmic polypeptide VIa of cytochrome c oxidase from beef heart is described. The primary structure of this component of complex IV of the respiratory chain is elucidated by isolation and sequencing of overlapping glutamic acid, arginine, tryptophan and methionine fragments obtained by cleavage with Staphylococcus aureus protease, protease from submaxillaris glands of mice, 2-iodosylbenzoic acid and cyanogen bromide. The chain length of polypeptide VIa is 98 amino acids, the resulting molecular mass of 10670 Da. The hydrophilic protein does not contain a hydrophobic membrane penetrating sequence domain. Its function in the respiratory complex IV is unknown.     

Light-controlled inhibition of hypocotyl growth inSinapis alba L. seedlings

Fluence rate-response curves were determined for the inhibition of hypocotyl growth in 54 h old dark-grownSinapis alba L. seedlings by continuous or hourly 5 min red light irradiation (24 h). In both cases a fluence rate-dependence was observed. More than 90% of the continuous light effect could be substituted for by hourly light pulses if the total fluence of the two different light regimes was the same. Measurements of the far red absorbing form of phytochrome ([P _fr]) and [P _fr]/[P tot] (total phytochrome) showed a strong fluence rate-dependence under continuous and pulsed light which partially paralleled the fluence rate-response curves for the inhibition of the hypocotyl growth.Abbreviations R red - HIR high irradiance response - P _rfr phytochrome in its red, far-red absorbing form - [P _tot]=[P _r]+[P _fr] =k ₁/(k ₁+k ₂): photoequilibrium of phytochrome at wavelength , wherebyk _1,2 rate constants ofP _rP _fr,P _frP _r photoconversion - [P _fr]/[P _tot]     

Inhibition of [3H]Diazepam and [3H]3-Carboethoxy-β-Carboline Binding by Irazepine: Evidence for Multiple "Domains" of the Benzodiazepine Receptor

The binding of [3H]diazepam and [3H]3-carboethoxy-beta-carboline was examined in rat brain synaptosomal membranes treated with irazepine, an alkylating benzodiazepine. Under incubation conditions that resulted in a 25-33% reduction in the Bmax of [3H]diazepam binding, only modest (less than 8.5%) reductions in the Bmax of [3H]3-carboethoxy-beta-carboline were observed. The differential effects of irazepine on the binding of these two compounds may be explained by the presence of multiple areas or "domains" on the benzodiazepine receptor.     

Body movements and retinal pattern displacements while approaching a stationary object in the walking fly,Calliphora erythrocephala

When a walking fly approaches a stationary object two types of body movements are distinguishable. Type I body movements are characterized by low frequencies (0.4–1.3 Hz) and large amplitudes (28–65°). Superimposed on these movements are type II body movements which are characterized by high frequencies (7.3–10.6 Hz) and small amplitudes (5.9–8.2°) (Figs. 3–6; Table 1). Type II movements occur no matter whether the fly is fixating a pattern or orientating itself in homogeneous surroundings without any pattern. In contrast, only 72% of the flies with immobilized heads and 62% of the flies with movable heads make type I body movements. The amplitude of type I and type II body movements increases slightly after immobilization of the head. Binocular as well as monocular pattern projection occurs for the whole walking trajectory (Fig. 7–9). Monocular pattern projection seems to be more frequent in flies with immobilized heads than in those with movable heads. The degree of pattern fluctuations in the visual field of the flies increases slightly along the walking trajectory. Near the starting point in the centre of the arena it amounts to 5–7°, while at the end of the walking trajectory it amounts to 8–10° (Table 2). The following conclusions and hypothesis can be drawn from these experiments. 1. The graph BT for the direction of the fly's logitudinal axis can be approximated by the first derivative of the walking trajectory WT, that means, dWT(x)/dxBT(x) (Fig. 11). 2. The amplitudes of type II body movements are caused by the alternating movements of the legs during forward motion, while type I body movements are classified as exploring movements. During evolution of visually guided behaviour it is possible that blowflies have adapted their elementary movement detector system to type II body movements. 3. The types of pattern projection into the visual field of the fly while approaching an object can be explained by a simple neuronal network characterized by either inhibitory and/or excitatory influences of the visually activated neurones on the motor neurones generating the propulsive forces, that means the forward motion. In addition it is postulated that the large frontal and antero-lateral receptive fields of these neurones are not coupled with the motor centres on the same side of the body (Fig. 12).     

Inhibition of cytochrome c oxidase function by dicyclohexylcarbodiimide

Dicyclohexylcarbodiimide (DCCD) reacted with beef heart cytochrome c oxidase in inhibit the proton-pumping function of this enzyme and to a lesser extent to inhibit electron transfer. The modification of cytochrome c oxidase in detergent dispersion or in vesicular membranes was in subunits II-IV. Labelling followed by fragmentation studies showed that there is one major site of modification in subunit III. DCCD was also incorporated into several sites in subunit II and at least one site of subunit IV. The major site in subunit III has a specificity for DCCD at least one order of magnitude greater than that of other sites (in subunits II and IV). Its modification could account for all of the observed effects of the reagent, at least for low concentrations of DCCD. Labelling of subunit II by DCCD was blocked by prior covalent attachment of arylazidocytochrome c, a cytochrome c derivative which binds to the high-affinity binding site for the substrate. The major site of DCCD binding in subunit III was sequenced. The label was found in glutamic acid 90 which is in a sequence of eight amino acids remarkably similar to the DCCD-binding site within the proteolipid protein of the mitochondrial ATP synthetase.