350m氦氧模拟饱和潜水过程中潜水员坐位踏车时心缩间期的变化

在350m氦氧模拟饱和潜水过程中,对4名男性潜水员采用耳密度图导数图方法观察坐位踏车时心缩间期变化。在压力(300、230、135m)下和减压后的主要变化是等容收缩期、射血前期(PEP)和PEP/左室射血时间加大,与加压前比较有显著差异,尤其在踏车负荷加重时更为明显。提示心肌收缩力受高气压的影响而降低。     

Differentiation of extracutaneous melanocytes in embryos of the turtle, Trionyx sinensis japonicus.

The present study investigates the mode of differentiation of neural crest-derived melanocytes in the embryos of the soft-shell turtle, Trionyx sinensis japonicus. DOPA reaction-positive melanoblasts were first detected in 10-day-old embryos. Melanocyte differentiation in terms of pigmentation takes place from the day 16 of development. Melanin pigments were found in the dorsal integument as well as in various extracutaneous tissues such as skeletal muscle, dorsal aorta, peritoneum, blood vessels, choroid, lung, bone marrow, fat tissues and in the connective tissue of the nose. These results suggest the presence of a specific environmental regulation of the melanoblast differentiation in the soft-shell turtle.     

Role of minor subunits in the structural asymmetry of the Escherichia coli F1-ATPase

The beta subunits of the Escherichia coli F1-ATPase react independently with chemical reagents (Stan-Lotter, H. and Bragg, P.D. (1986) Arch. Biochem. Biophys. 248, 116-120). Thus, one beta subunit is readily crosslinked to the epsilon subunit, another reacts with N-N'-dicyclohexylcarbodiimide (DCCD), and a third one is modified by 4-chloro-7-nitrobenzofurazan (NbfCl). This asymmetric behaviour is not due to the association of the delta and epsilon subunits of the ATPase molecule with specific beta subunits since it is maintained in a delta, epsilon-deficient form of the enzyme.     

Reaction of membrane-bound F1-adenosine triphosphatase of Escherichia coli with chemical ligands and the asymmetry of beta subunits

The three beta subunits of the isolated Escherichia coli F1-ATPase react independently with chemical reagents (Stan-Lotter, H. and Bragg, P.D. (1986) Arch. Biochem. Biophys. 284, 116-120). Thus, one beta subunit is readily cross-linked to the epsilon subunit, Another reacts with N,N'-dicyclohexylcarbodiimide (DCCD), and the third one is modified on a lysine residue by 4-chloro-7-nitrobenzofurazan (NbfCl). The binding site for the ATP analog, 2-azido-ATP, was not associated with a specific type of beta subunit (Bragg, P.D. and Hou, C. (1989) Biochim. Biophys. Acta 974, 24-29). We now show that this binding site is a catalytic site as opposed to a noncatalytic nucleotide-binding site. NbfCl reacted with a tyrosine residue on the DCCD-reacting beta subunit in contrast to the different subunit location of the lysine residue labeled by the reagent. Thus, O to N transfer of the Nbf group in the free F1-ATPase involves transfer between subunits. The chemical labelling pattern of membrane-bound F1-ATPase differed from that of free F1. The strict asymmetry of labeling of the free F1-ATPase was not observed. Thus, double labeling of beta subunits by several reagents was found. This suggests that the asymmetry was not induced by chemical modification, but is inherent in the structure of the ATPase.     

Microbial oxidation of methanol: Properties of crystallized alcohol oxidase from a yeast, Pichia sp

Alcohol oxidase (alcohol:oxygen oxidoreductase) was crystallized from a methanolgrown yeast, Pichia sp. The crystalline enzyme is homogenous as judged from polyacrylamide gel electrophoresis. Alcohol oxidase catalyzed the oxidation of short-chain primary alcohols (C₁ to C₆), substituted primary alcohols (2-chloroethanol, 3-chloro-1-propanol, 4-chlorobutanol, isobutanol), and formaldehyde. The general reaction with an oxidizable substrate is as follows: Primary alcohol + O₂ → aldehyde + H₂O₂ Formaldehyde + O₂ → formate + H₂O₂. Secondary alcohols, tertiary alcohols, cyclic alcohols, aromatic alcohols, and aldehydes (except formaldehyde) were not oxidized. The K_m values for methanol and formaldehyde are 0.5 and 3.5 mm, respectively. The stoichiometry of substrate oxidized (alcohol or formaldehyde), oxygen consumed, and product formed (aldehyde or formate) is 1:1:1. The purified enzyme has a molecular weight of 300,000 as determined by gel filtration and a subunit size of 76,000 as determined by sodium dodecyl sulfate-gel electrophoresis, indicating that alcohol oxidase consists of four identical subunits. The purified alcohol oxidase has absorption maxima at 460 and 380 nm which were bleached by the addition of methanol. The prosthetic group of the enzyme was identified as a flavin adenine dinucleotide. Alcohol oxidase activity was inhibited by sulfhydryl reagents (p-chloromercuribenzoate, mercuric chloride, 5,5′-dithiobis-2-nitrobenzoate, iodoacetate) indicating the involvement of sulfhydryl groups(s) in the oxidation of alcohols by alcohol oxidase. Hydrogen peroxide (product of the reaction), 2-aminoethanol (substrate analogue), and cupric sulfate also inhibited alcohol oxidase activity.     

Capture of latex beads, bacteria, endotoxin, and viruses by charge-modified filters.

This report demonstrates how electropositive filters can be used to enhance the removal of microorganisms and other negatively charged particles from water. It was shown that electropositive depth filters were capable of adsorbing viruses and endotoxins many times smaller than the average pore size of the filter. Electronegative filters of similar porosity or electropositive filters that had been treated to destroy the positive charge were almost ineffective under similar conditions for the removal of viruses and small latex spheres. The results of this study indicate that electropositive filters are highly effective in the removal of a wide range of contaminants over a wide range of pH values and ionic conditions.     

Characterization of dicyclohexylcarbodiimide binding sites in beef-heart mitochondria.

Binding studies with [¹⁴C]-dicyclohexylcarbodiimide showed the presence of binding sites in the beef-heart mitochondrial membrane at a concentration of 1.8 nmol/mg protein (1.4 sites per cytochrome a+a₃). Saturation of these sites correlated with the inhibition of the ATPase activity. The maximum binding capacity could be related with the amount of F₁-ATPase in mitochondria from various tissues.