Protein metal-binding sites.

Metal ions have a role in a variety of important functions in proteins including protein folding, assembly, stability, conformational change, and catalysis. The presence or absence of a given metal ion is crucial to the conformation or activity of over one third of all proteins. Recent developments have been made in the understanding and design of metal-binding sites in proteins, an important and rapidly advancing area of protein engineering.     

Maleylated-BSA suppresses IFN-gamma-mediated Ia expression in murine peritoneal macrophages

Maleylated bovine serum albumin (maleyl-BSA) and other polyanionic polymers that are recognized by cell surface receptors on macrophages have been shown to induce chemotaxis, protease secretion, and tumoricidal function in this cell type. In this paper the effect of maleyl-BSA on Ia antigen expression has been evaluated. In a fashion similar to LPS, maleyl-BSA suppressed IFN-gamma-induced expression of Ia in a time- and dose-dependent manner. Also like LPS, maleyl-BSA stimulated the production and secretion of substantial amounts of PGE2 over a 24-hr period. This did not, however, appear to be the primary mechanism by which expression of Ia was suppressed, because co-treatment of the cells with indomethacin, which totally inhibited the production of PGE2, only minimally affected the suppressive activity. Surprisingly, the suppressive activity of both maleyl-BSA and LPS could be largely abrogated by co-treatment of the cells with cyclohexamide during the time period when Ia expression was sensitive to suppression. This effect was selective in that PGE2- or dibutyryl cyclic AMP-induced suppression of Ia expression was not affected by cyclohexamide treatment. The data support the concept that there are multiple molecular mechanisms involved in the negative regulation of IFN-gamma-induced Ia expression in macrophages. Such mechanisms may include, in addition to the synthesis of PGE2 and consequent elevation in intracellular levels of cyclic AMP, one or more proteins made early after treatment with either maleyl-BSA or LPS. Thus the function of some of these early gene products may be to regulate expression of functional genes such as that encoding Ia antigen.     

Interrelation of the changes in the blood rheological properties and the microcirculatory disorders in the early and late stages of experimental hyperlipoproteinemia

Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked.     

Membrane chloride transport measured using a chloride-sensitive fluorescent probe

Transport of chloride across cell membranes through exchange, cotransport, or conductive pathways is a subject of great biological importance. Current methods of measurement are restricted in their sensitivity, time resolution, and applicability. A new transport measurement technique has been developed on the basis of the fluorescence quenching by chloride of the dye 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ). SPQ fluorescence quenching by chloride is rapid (less than 1 ms) and sensitive, with a greater than 50% decrease in fluorescence at 10 mM chloride. SPQ fluorescence is not altered by other physiological anions or by pH and can be used to measure both neutral and conductive transport processes. The high water solubility and membrane permeability properties of SPQ make it ideal for use in both membrane vesicles and cells. Chloride transport determined with SPQ was validated by measurement of erythrocyte chloride/anion exchange and membrane vesicle chloride conductance.     

Cat satellite DNA. Isolation using netropsin with CsCl gradients

The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.     

Absolute configuration and conformation of the pure opioid antagonist (+)-2,9 alpha-dimethyl-5-(m-hydroxyphenyl)morphan.

(+)-2,9 alpha-Dimethyl-5-(m-hydroxyphenyl)morphan is the only phenylmorphan analog whose affinity for opioid kappa-receptors is greater than its affinity for opioid mu-receptors. Pharmacologically, the compound is a pure opioid antagonist devoid of agonist activity in in vivo assays of antinociception. The absolute configuration of the compound has been determined to be (1R,5S,9R) from an X-ray crystallographic study of the chloride salt. Thus, the absolute configuration corresponds to that of the atypical opioid agonist (-)-phenylmorphan while the weak atypical agonist (-)-2,9 alpha-dimethyl-5-(m- hydroxyphenyl)morphan corresponds to the potent morphine-like (+)-phenylmorphan. The preferred orientations of the phenyl ring for the two stereoisomers were determined using the molecular mechanics program MM2-87 and found to vary from that of the two parent compounds. The atypical properties of the two 9 alpha-methyl analogs is consistent with an opioid ligand model which proposes that morphine-like properties require a particular range of phenyl orientations. There was good agreement between the structure obtained from X-ray crystallography and computed with the MM2-87 program.     

Protective reaction of the myocardium in poisoning

Intensive synthesis of collagen-like substance was revealed in the rabbit myocardium during experimental diphtheria intoxication. It was more marked in the right ventricle 24 hours after the injection of diphtheria toxin. Since similar changes (the substance was mainly formed around blood vessels) have been observed in other cases of toxic myocardial alterations (i.e. ethanol intoxication, injection of pharmacological agents, etc.), it can be assumed that it is a standard protective reaction of the altered heart to the penetration of toxic agents from the blood into the myocardial tissue.     

Characteristics of destructive-regenerative processes in the kidneys of albino rats in conditions of necronephrosis caused by corrosive sublimate

Study of serial semi-thin (0.5 micron) metacrylate and paraffinic (8 microns) of rat kidney sections 6, 12, 24 and 48 h after subcutaneous injection of mercury bichloride at a dose of 0.6 mg/100 g bw has revealed that injury to different parts of the canalicular nephron is of heterogeneous character. The proximal part of the nephron demonstrates both complete and partial necrosis of nephrocyte cytoplasm. The distal parts of the nephron and collecting tubules are characterized by partial necrosis of the apical cytoplasm. Within the period between 12 and 24 h after the mercury bichloride injection, intracellular reparative processes are observed, in addition to destruction, in partially damaged but viable nephrocytes, which is confirmed by the enlargement of the nucleolic size. Regeneration of the tubular epithelium due to cellular restoration was unmarked 24 h after the mercury bichloride injection.     

Circumsporozoite protein of Plasmodium berghei: gene cloning and identification of the immunodominant epitopes.

The gene encoding the circumsporozoite (CS) protein of the rodent malaria parasite Plasmodium berghei was cloned and characterized. A cDNA library made from P. berghei sporozoite RNA was screened with a monoclonal antibody for expression of CS protein epitopes. The resulting cDNA clone was used to isolate the CS protein gene from a lambda library containing parasite blood-stage DNA. The CS protein gene contains a central region encoding two types of tandemly repeated amino acid units, flanked by nonrepeated regions encoding amino- and carboxy-terminal signal and anchorlike sequences, respectively. One of the central repeated amino acid unit types contains the immunodominant epitopes.     

Modulation of ornithine decarboxylase activity in the normal and regenerating rat liver by different doses of hydra peptide morphogen

The authors studied the anabolic effect of peptide morphogen of the hydra undecapeptide on normal and regenerating rat liver. Ornithine decarboxylase (EC 4.1.1.17) activity served as a marker. Intraperitoneal injection of the peptide into intact animals stimulated ornithine decarboxylase activity in a dose-dependent manner. In partially hepatectomized rats the peptide stimulated ornithine decarboxylase activity in the dose of 20 micrograms/kg body weight while greater doses inhibited the enzyme activity.