Synchronisation of hyperchaotic oscillators

The authors present three different examples demonstrating the possibility of synchronising hyperchaotic oscillators via a single variable     

Peptide YY inhibition of rat gastric enterochromaffin-like cell function

The present study determined tumorigenicity, tumor classification and DNA damage induced in infant mice by benzo[a]pyrene (B[a]P) or Manufactured Gas Plant (MGP) residues after a single exposure. Male and female B6C3F1 mice were exposed to B[a]P or MGP residue from a single environmental site (MGP-4) and males were also exposed to MGP residue composite from seven different sites (MGP-M7). At 26, 39 and 52 weeks after exposure tumorigenesis was assessed in lung, forestomach and liver. Formation and persistence of DNA adducts were quantified by 32P-postlabeling. Exposure of males to B[a]P induced liver tumors in a dose and time dependent manner. MGP induced more advanced tumors than B[a]P. Only a single liver tumor was found in MGP-4 treated females. No forestomach and few pulmonary adenomas were induced in males or females. MGP-4, MGP-M7 or B[a]P induced DNA adducts in males and females. Adducts in liver, lung and forestomach peaked on different days and decreased at different rates. At 24 h post-exposure, no significant differences in initial DNA adduct levels occurred in males and females exposed to MGP-4 or B[a]P. Lack of DNA damage (adducted DNA) did not account for non-responsiveness of lung and forestomach in B6C3F1 genders as well as in liver in females. MGP tumorigenicity could not be accounted for solely by B[a]P content nor did it reflect additivity of B[a]P and other carcinogenic polycyclic aromatic hydrocarbons (PAHs) in MGP. Synergy among MGP-PAHs, presence of unidentified carcinogens and/or promoters in MGP may account for MGP potency. The B6C3F1 infant male model is a convenient and rapid assay for assessing MGP liver tumorigenicity and potency.     

In vitro mutagenesis of PH-20 hyaluronidase from human sperm

The cDNA encoding PH-20 hyaluronidase from human sperm has been mutated at five positions by in vitro mutagenesis. We have changed three acidic amino acids and two arginine residues that are conserved in the sequence of mammalian PH-20 polypeptides as well as in the hyaluronidases from bee and hornet venom. Of the former, the mutants [Gln113]PH-20 and [Gln249]PH-20 had no detectable enzymatic activity; the mutant [Asn111]PH-20 had about 3% activity. The mutant [Thr252]PH-20 was also inactive, while [Gly176]PH-20 had only about 1% activity. This indicates that the PH-20 hyaluronidases, like numerous enzymes that hydrolyze glycosidic bonds, have acidic amino acids in their active site. Moreover, for the binding of the substrate, the polyanion hyaluronan, arginine residues appear to be essential.     

The effects of limbic lesions on locomotion and stereotypy elicited by dopamine agonists in the rat

The purpose of this experiment was to investigate the functional contributions of various limbic structures to locomotion and stereotypy induced by dopaminergic drugs. Female rats were randomly assigned to one of 5 groups (n = 10-14 rats/group) that received either a lesion of the hippocampus (colchicine + kainic acid), basolateral amygdala (quinolinic acid), frontal cortex (aspiration), nucleus accumbens (ibotenic acid), or served as unoperated controls. Beginning at least 2 weeks following surgery locomotion (measured as photocell beam breaks) elicited by D-amphetamine (0.0, 0.32, 1.0 and 3.2 mg/kg), SKF 82958 (0.0, 0.04, 0.08 and 0.16 mg/kg) or quinpirole (0.0, 0.25, 0.1 and 0.5 mg/kg) was determined. In agreement with previous results rats with hippocampal lesions were hyperactive in response to amphetamine. In comparison to these changes in drug-induced locomotion, lesions of the basolateral amygdala, and frontal cortex had only minor effects on drug-induced locomotion. Lesions of the nucleus accumbens produced consistent hyperactivity that was suppressed by doses of amphetamine or quinpirole that elicited behavioral stereotypy. These results provide evidence suggesting that, in comparison to other limbic structures that have substantial inputs to the nucleus accumbens, the hippocampus play a relatively prominent role in the modulation of drug-induced locomotion.     

A stereoselective cobalt-containing nitrile hydratase

Nitrile hydratase from Pseudomonas putida NRRL-18668 has been purified and characterized. The purified enzyme catalyzes the hydration of 2(S)-(4'-chlorophenyl)-3-methylbutyronitrile at least fifty times faster than that of 2(R)-(4'-chlorophenyl)-3-methylbutyronitrile. This enzyme is a member of the class of nitrile hydratase that contains cobalt. Visible absorption and CD spectra suggest the cobalt exists as a non-corrin low-spin Co3+ ion in a tetragonally-distorted octahedral ligand field. Chemical reduction of the native enzyme results in a species with the EPR signature of a low-spin Co2+ complex. Like the other cobalt-containing nitrile hydratases, this enzyme is relatively stable, maintaining its activity below 35 degrees C, and it shows a broad activity optimum between pH 7.2 and 7.8. The structural genes for this enzyme have been cloned and sequenced. The deduced amino acid sequences for the alpha and beta subunits show 48-63% and 35-41% homology, respectively, to other sequenced nitrile hydratases. In particular, the cysteine residues in the alpha subunit that have been suggested to coordinate the metal ion in the iron-containing nitrile hydratases [Brennan, B. A., Cummings, J. G., Chase, D. B., Turner, I. M., Jr., & Nelson, M. J. (1996) Biochemistry 35, 10068-10077] are conserved in this enzyme, suggesting that this nitrile hydratase, like the enzyme from Rhodococcus rhodochrous J1, is a member of a newly described class of metalloenzymes with Co3+-thiolate ligation [Brennan, B. A., Alms, G., Nelson, M. J., Durney, L. T., & Scarrow, R. C. (1996) J. Am. Chem. Soc. 118, 9194-9195].     

Effect of sinus surgery on pulmonary function in patients with cystic fibrosis

The rare case of neurilemmoma of the larynx was presented. The difficulties in histopathologic diagnosis of such tumors were emphasized. The tumor was removed by surgery from external approach.     

The Solution kinetics of zirconium in liquid steel

Zirconium cylinders were immersed into liquid steel and their mass-transfer rates were measured under static and dynamic conditions. The cylinders were suspended from a load cell, and the apparent weight of the dissolving specimen as well as temperatures at various locations in the samples were measured continuously during immersion and recorded with a data acquisition System. From the weight measurements, the mass-transfer rate was deduced. In the assimilation of zirconium in liquid steel two periods were identified, i.e. the steel shell period and the free dissolution period. Immediately upon immersion the steel shell period Starts and when this period ends the free dissolution period commences. During the steel shell period, a shell of frozen steel wraps around the cylinder following its initial immersion. When zirconium cylinders were immersed into liquid steel, a reaction was detected at the steel shell/zirconium interface. This reaction took place almost immediately after immersion. The intermetallic Compounds Fe₂Zr and FeZr₂ were identified as reaction products. The experimentally measured mass transfer rates during the free dissolution, under quiescent and inductively stirred steel baths, were very similar. Under the experimental conditions used, the rate Controlling step of zirconium dissolution in liquid steel is reaction controlled.