Inhibition of neuronal nitric oxide synthase increases aggressive behavior in mice.

BACKGROUND: Mice with targeted disruption of the gene for the neuronal isoform of nitric oxide synthase (nNOS) display exaggerated aggression. Behavioral studies of mice with targeted gene deletions suffer from the criticism that the gene product is missing not only during the assessment period but also throughout development when critical processes, including activation of compensatory mechanisms, may be affected. To address this criticism, we have assessed aggressive behavior in mice treated with a specific pharmacological inhibitor of nNOS. MATERIALS AND METHODS: Aggressive behavior, as well as brain citrulline levels, were monitored in adult male mice after treatment with a specific nNOS inhibitor, 7-nitroindazole (7-NI) (50 mg/kg i.p.), which is known to reduce NOS activity in brain homogenates by > 90%. As controls, animals were treated with a related indazole, 3-indazolinone (3-I) (50 mg/kg i.p.) that does not affect nNOS or with on oil vehicle. RESULTS: Mice treated with 7-NI displayed substantially increased aggression as compared with oil- or 3-I-injected animals when tested in two different models of aggression. Drug treatment did not affect nonspecific locomotor activities or body temperature. Immunohistochemical staining for citrulline in the brain revealed a dramatic reduction in 7-NI-treated animals. CONCLUSIONS: 7-NI augmented aggression in WT mice to levels displayed by nNOS- mice, strongly implying that nNOS is a major mediator of aggression. NOS inhibitors may have therapeutic roles in inflammatory, cardiovascular, and neurologic diseases. The substantial aggressive behavior soon after administration of an nNOS inhibitor raises concerns about adverse behavioral sequelae of such pharmacological agents.     

A hyperelastic fibre-reinforced continuum model of healing tendons with distributed collagen fibre orientations

The healing process of ruptured tendons is problematic due to scar tissue formation and deteriorated material properties, and in some cases, it may take nearly a year to complete. Mechanical loading has been shown to positively influence tendon healing; however, the mechanisms remain unclear. Computational mechanobiology methods employed extensively to model bone healing have achieved high fidelity. This study aimed to investigate whether an established hyperelastic fibre-reinforced continuum model introduced by Gasser, Ogden and Holzapfel (GOH) can be used to capture the mechanical behaviour of the Achilles tendon under loading during discrete timepoints of the healing process and to assess the model’s sensitivity to its microstructural parameters. Curve fitting of the GOH model against experimental tensile testing data of rat Achilles tendons at four timepoints during the tendon repair was used and achieved excellent fits (\(0.9903 < R^{2 }<0.9986\)). A parametric sensitivity study using a three-level central composite design, which is a fractional factorial design method, showed that the collagen-fibre-related parameters in the GOH model—\(\kappa , {k_{{1}}}^{{\prime }}\) and \({k_{{2}}}^{{\prime }}\)—had almost equal influence on the fitting. This study demonstrates that the GOH hyperelastic fibre-reinforced model is capable of describing the mechanical behaviour of healing tendons and that further experiments should focus on establishing the structural and material parameters of collagen fibres in the healing tissue.     

Quantitation of M antigen in Lancefield extracts of group A streptococci type 12 using electro-immuno assay

Anti-type 12 serum incorporated in agarose-polyethylene glycol gel in a concentration of 1.5% (vol/vol) was found to enable a distinct "rocket" precipitate in electro-immuno assay using hot hydrochloric acid extract of type 12 group A streptococci. This precipitate was removed by trypsin treatment of the extract and on addition of anti-M12 typing serum but not of five other typing sera to the extract. The streptococcal component responsible for this precipitate was eluted from a CM-cellulose ion exchange column at pH 6.5. These findings demonstrated that the precipitate was caused by the M12 antigen. Crossed immuno-electrophoresis of hot hydrochloric acid extracts of three different type 12 group A streptococci showed that the electrophoretic mobility of the M12 antigens was similar in the three extracts. A linear correlation was obtained between the concentration of the M12-antigen and the height of the precipitate obtained in the electro-immuno assay using different dilutions of a standard type 12 extract. M12 antigen could thus be quantitated by the electro-immuno assay. In quantitation experiments, uniformly prepared extracts of five randomly selected, freshly-isolated type 12 strains were found to contain from 130 to 1850% of M12 antigen, respectively (expressed in % of the content of the standard type 12 extract).     

Dependence of Root Growth on Photosynthesis in Populus tremula

Hoot elongation of rooted cuttings of aspen, Populus tremula L., was followed on moist filter paper. The time course of root growth during treatments which decrease or interrupt the supply of carbohydrates to the roots was studied. At light intensities below 4000 lux the rate of root elongation was found to berelated to the light intensity over the leaves. In the dark, root growth decreased within 24 hours and the roots stopped growing completely during the second or third day. Excision of the leaves or steam-killing of the tissue in a stem section below the leaves was followed by root growth stoppage within 24 hours. These results imply that the rate of root growth under certain conditions is determined by the supply of carbohydrates from the leaves.     

Enzymatic regulation of the radical content of the small subunit of Escherichia coli ribonucleotide reductase involving reduction of its redox centers

The active form of protein B2, a homodimeric subunit of Escherichia coli ribonucleotide reductase, contains a diferric iron center and a cationic free radical localized to tyrosine 122 of one of the two polypeptide chains. Hydroxyurea scavenges this radical but leaves the iron center intact. The resulting metB2 (earlier named B2/HU) is enzymatically inactive. Crude extracts of E. coli catalyze the interconversion of metB2 and B2. Radical introduction into metB2 requires a flavin reductase together with a second poorly defined protein fraction ("Fraction b") as well as dioxygen, NAD(P)H, and a flavin (Fontecave, M., Eliasson, R., and Reichard, P. (1987) J. Biol. Chem. 262, 12325-12331). We now find that ferrous ions can substitute for Fraction b and that the diferric center of metB2 is reduced during anaerobic incubation of the system with reduced flavin and ferrous ions. Spectroscopic evidence and isotope experiments suggest an in situ reduction of the diferric to a diferrous center. Admission of oxygen then results in the instantaneous oxidation of tyrosine 122 to the cationic radical coupled to the reformation of the diferric center, giving enzymatically active B2. These data suggest that reduced diferrous B2 is an intermediate between metB2 and B2 during radical introduction. In addition, we find that anaerobic incubation of B2 with reduced flavin results in the loss of the tyrosyl radical and the formation of metB2. This reaction occurs in the absence of Fraction b or ferrous ions. Our experiments reconstitute with defined reagents the interconversion between metB2 and B2 observed earlier in the E. coli extract. The flavin reductase system catalyzes the interconversion in both directions with dioxygen as the critical factor deciding whether activation or inactivation of ribonucleotide reductase occurs.     

Clinical,Morphological and Endocrinological Studies in Gilts with Delayed Puberty

Thirty-six gilts which had not shown oestrus at about 8 months of age or more were transported from the pig research station to the clinic, a journey of 12 km. The gilts were examined by laparoscopy and those which had only small follicles in the ovaries were catheterized and placed in pens, with sexually mature boars kept in adjacent pens. Oestrus detection was done twice daily and blood was sampled three times a day. After 7 days the laparoscopy was repeated and gilts which still had only small follicles in their ovaries were given 250 μg GnRH intravenously the following day. Blood samples were taken frequently before and after GnRH treatment. One week. after administration of GnRH the ovaries were inspected by laparoscopy once more. The first laparoscopic examination showed that 42 % of the gilts were sexually mature. One gilt had no uterus or ovaries. Twenty gilts had only small follicles in the ovaries and fourteen of these gilts showed ovulatory oestrus 5.5 days (4-7.5 days) after arrival. In these fourteen gilts a rise in the oestradiol-17B level (>30 pmol/1) was seen at an average time of 1.9 days and a rise in LH (preovulatory peak) was seen at an averaged 4.5 days after the start of blood sampling. Six gilts were given 250 ug GnRH. An immediate rise in LH could be seen in all the gilts (mean peak level was 6.18 μg/l) and the elevated levels had a duration of 4 hours. None of the GnRH-treated gilts responded with oestrus symptoms or increased ovarian activity.