ABSTRACT
Penile erection is mediated by nitric oxide (NO) synthesized by the neuronal nitric oxide synthase (nNOS). In the rat penis, the main nNOS mRNA variant, PnNOS, differs from cerebellar nNOS (CnNOS) by a 102 base pair insert encoding a 34-amino acid sequence. In the mouse, two nNOS mRNAs have been identified: nNOSalpha, encoding a 155-kDa protein, and an exon 2-deletion variant, nNOSbeta, encoding a 135-kDa protein that lacks a domain where a protein inhibitor of nNOS (PIN) binds. We wished to determine whether PnNOSalpha and beta are expressed in the rat penis and are located in the nerves and whether the beta form persists in the potent nNOS knock-out mouse (nNOS( big up tri, open big up tri, open)). A PnNOS antibody against the insert common to both PnNOSalpha and beta detected the expected 155-kDa protein in PnNOSalpha-transfected cells. This antibody, and the one common to PnNOS/CnNOS, showed (on Western blots) the 155- and 135-kDa nNOS variants in rat penile tissue during development and aging. PnNOSalpha mRNA and its subvariants were found as the main nNOS in the penile corpora, the cavernosal nerve, and the pelvic ganglia, with lower levels of PnNOSbeta mRNA. In tissue sections, PnNOS protein was immunodetected in the penile nerve endings in the rat and in the nNOS wild-type and nNOS( big up tri, open big up tri, open) mice. An antibody against the sequence encoded by exon 2 did not react (on Western blots) with the 135-kDa band, which confirms that this protein is the beta form. In conclusion, both PnNOSalpha and beta are expressed in the rat penis at all ages and are located in the nerves. The beta form may allow nitric oxide synthesis during erection to be partially insensitive to PIN. The residual expression of PnNOS, and possibly CnNOS, in the penis of the nNOS( big up tri, open big up tri, open) mouse occurs through transcription of the beta mRNA, and this may explain the retention of erectile function when the expression of nNOSalpha is disrupted.
Subject(s)
Gene Expression , Nitric Oxide Synthase/genetics , Penis/innervation , Amino Acid Sequence , Animals , Genetic Variation , Immunohistochemistry , Male , Mice , Mice, Knockout , Molecular Sequence Data , Nitric Oxide Synthase/chemistry , Nitric Oxide Synthase/deficiency , Nitric Oxide Synthase Type I , RNA, Messenger/analysis , Rats , Rats, Inbred BN , Rats, Inbred F344 , TransfectionABSTRACT
Evaluation of motor unit recruitment is an important component of the clinical EMG exam. Typically this is assessed qualitatively using auditory features and estimates of the visual complexity of the EMG waveform. Recent advances in nonlinear dynamics have led to the development of the concept of fractals which can be used to quantify complexity and space filling features of various structures. This study was undertaken to determine if the normal EMG interference pattern (IP) has fractal characteristics that might be helpful in quantitative analysis. EMG activity was recorded from the 9 normal biceps muscles as force was varied from 10 to 90% of maximal. Using a box count algorithm, the fractal dimension was calculated. The EMG IP displays fractal characteristics with a dimension that is highly correlated with force and ranges from 1.1 to 1.4 as force increases from 10 to 90% MVC. The fractal dimension (FD)-force relationship is similar to that observed with other methods of IP analysis and suggests that the fractal dimension can be used to quantify and capture the essence of the 'complexity' of motor unit recruitment patterns.
