Adrenaline increases the rate of cross-bridge cycling in rat cardiac muscle

To characterize the myocardial cross-bridge dynamics in catecholamine-induced positive inotropic state, we studied the effects of adrenaline (6 X 10(-6) M) on the transient central segment length (SL) response to step decrease in tension in rat right ventricular papillary muscle in barium contracture. The time course of this response is thought to reflect the kinetics of actin-myosin interaction. The muscle was released stepwise from the steady contracture tension (Tc) to new steady tension levels (Tr) of varying magnitudes at 22 degrees C. When the tension decrease was less than 0.7 Tc, the SL transient responses comprised, in most cases, four phases. The first phase was a rapid and minute shortening during tension reduction; the second was a slow further shortening; the third, a slow lengthening; and the fourth, an extremely slow shortening toward a new steady length under the new tension. Adrenaline showed almost no effect on Tc and the amplitude of SL transients, but markedly reduced the duration of the second (D2) and third (D3) phases of SL transient regardless of the amplitude of tension reduction. The reduction of duration was 14 +/- 3% in D2 and 26 +/- 5% in D3 at Tr/Tc of 0.84 +/- 0.03 on the average (mean +/- S.D.) in nine preparations. The velocity measured from the quasi-steady SL shortening in the second phase increased with the addition of adrenaline, regardless of the amplitude of tension reduction. The increase in the shortening velocity was 16 +/- 6% (mean +/- S.D., n = 9) at Tr/Tc of 0.18 +/- 0.04. These results suggest that adrenaline increases the rate of cross-bridge cycling in cardiac muscle independent of activation level.     

Using a High-Speed Movie Camera to Evaluate Slice Dropping in Clinical Image Interpretation with Stack Mode Viewers

The purpose of this study is to verify objectively the rate of slice omission during paging on picture archiving and communication system (PACS) viewers by recording the images shown on the computer displays of these viewers with a high-speed movie camera. This study was approved by the institutional review board. A sequential number from 1 to 250 was superimposed on each slice of a series of clinical Digital Imaging and Communication in Medicine (DICOM) data. The slices were displayed using several DICOM viewers, including in-house developed freeware and clinical PACS viewers. The freeware viewer and one of the clinical PACS viewers included functions to prevent slice dropping. The series was displayed in stack mode and paged in both automatic and manual paging modes. The display was recorded with a high-speed movie camera and played back at a slow speed to check whether slices were dropped. The paging speeds were also measured. With a paging speed faster than half the refresh rate of the display, some viewers dropped up to 52.4 % of the slices, while other well-designed viewers did not, if used with the correct settings. Slice dropping during paging was objectively confirmed using a high-speed movie camera. To prevent slice dropping, the viewer must be specially designed for the purpose and must be used with the correct settings, or the paging speed must be slower than half of the display refresh rate.     

Induction of Mutant Sik3Sleepy Allele in Neurons in Late Infancy Increases Sleep Need

Sleep is regulated in a homeostatic manner. Sleep deprivation increases sleep need, which is compensated mainly by increased EEG δ power during non-rapid eye movement sleep (NREMS) and, to a lesser extent, by increased sleep amount. Although genetic factors determine the constitutive level of sleep need and sleep amount in mice and humans, the molecular entity behind sleep need remains unknown. Recently, we found that a gain-of-function Sleepy (Slp) mutation in the salt-inducible kinase 3 (Sik3) gene, which produces the mutant SIK3(SLP) protein, leads to an increase in NREMS EEG δ power and sleep amount. Since Sik3^Slp mice express SIK3(SLP) in various types of cells in the brain as well as multiple peripheral tissues from the embryonic stage, the cell type and developmental stage responsible for the sleep phenotype in Sik3^Slp mice remain to be elucidated. Here, we generated two mouse lines, synapsin1^CreERT2 and Sik3^ex13flox mice, which enable inducible Cre-mediated, conditional expression of SIK3(SLP) in neurons on tamoxifen administration. Administration of tamoxifen to synapsin1^CreERT2 mice during late infancy resulted in higher recombination efficiency than administration during adolescence. SIK3(SLP) expression after late infancy increased NREMS and NREMS δ power in male synapsin1^CreERT2; Sik3^ex13flox/+ mice. The expression of SIK3(SLP) after adolescence led to a higher NREMS δ power without a significant change in NREMS amounts. Thus, neuron-specific expression of SIK3(SLP) after late infancy is sufficient to increase sleep.SIGNIFICANCE STATEMENT The propensity to accumulate sleep need during wakefulness and to dissipate it during sleep underlies the homeostatic regulation of sleep. However, little is known about the developmental stage and cell types involved in determining the homeostatic regulation of sleep. Here, we show that Sik3^Slp allele induction in mature neurons in late infancy is sufficient to increase non-rapid eye movement sleep amount and non-rapid eye movement sleep δ power. SIK3 signaling in neurons constitutes an intracellular mechanism to increase sleep.     

Generation and characterization of a novel shoulder contracture mouse model

Frozen shoulder is a relatively common disorder that leads to severe pain and stiffness in the shoulder joint. Although this disorder is self‐limiting in nature, the symptoms often persist for years, resulting in severe disability. Recent studies using human specimens and animal models have shown distinct changes in the gene expression patterns in frozen shoulder tissue, indicating that novel therapeutic intervention could be achieved by controlling the genes that are potentially involved in the development of frozen shoulder. To achieve this goal, it is imperative to develop a reliable animal joint contracture model in which gene expression can be manipulated by gene targeting and transgenic technologies. Here, we describe a novel shoulder contracture mouse model. We found that this model mimics the clinical presentation of human frozen shoulder and recapitulates the changes in the gene expression pattern and the histology of frozen shoulder and joint contracture in humans and other larger animal models. The model is highly reproducible, without any major complications. Therefore, the present model may serve as a useful tool for investigating frozen shoulder etiology and for identifying its potential target genes. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1732–1738, 2015.     

Primary structure, synthesis, and biological activity of rat endothelin, an endothelium-derived vasoconstrictor peptide.

Endothelin is a potent vasoconstrictor/pressor peptide, which we recently characterized from the conditioned culture medium of porcine aortic endothelial cells. We report here the cloning and partial sequencing of the rat endothelin gene. The nucleotide sequence predicted a 21-residue peptide similar to, but distinct from, porcine endothelin; 15 residues of rat endothelin were identical and 3 residues were substitutions by chemically similar amino acid residues to those in the porcine peptide. Synthetic rat endothelin was then prepared according to its deduced amino acid sequence. This synthetic peptide had (i) potent vasoconstrictor activity in the rat aortic strip and in perfused rat heart and (ii) a characteristically long-lasting in vivo pressor activity by intraaortic bolus injection in the conscious rat.     

Excessive zinc intake elevates systemic blood pressure levels in normotensive rats--potential role of superoxide-induced oxidative stress

OBJECTIVES: The present study was designed to examine whether or not excessive Zn intake affects systemic blood pressure (BP) levels in a normotensive state. METHODS: Systolic BP (SBP) and mean arterial pressure (MAP) before and after administration of the nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME) or the exogenous superoxide scavenger, tempol and the activity of the endogenous superoxide scavenger, Cu/Zn-superoxide dismutase (SOD) and levels of endothelial type (e)NOS mRNA and protein in the thoracic aorta were analyzed in male Sprague-Dawley rats fed a standard diet containing 0.005% Zn or a high Zn diet containing 0.5% Zn for 8 weeks. RESULTS: SBP and MAP levels observed at the end of dietary conditioning were significantly elevated in rats fed a high Zn diet relative to rats fed a standard diet. Administration of L-NAME caused an increase in MAP levels in rats fed a standard and a high Zn diet, demonstrating the involvement of the vasodilator, nitric oxide (NO) in the regulation of systemic BP in the two groups of rats. However, the expression of eNOS mRNA and protein in the thoracic aorta was not significantly different between rats fed a standard and a high Zn diet. On the other hand, administration of tempol led to a decrease in MAP levels in rats fed a standard and a high Zn diet, indicating the participation of the oxygen free radical, superoxide in the modification of systemic BP in the two groups of rats. As reported recently, the mechanism involved is due likely to a decrease in the action of the vasodilator, NO through the formation of peroxynitrite based on the non-enzymatic reaction of superoxide and NO. In addition, tempol treatment dramatically restored MAP levels in rats fed a high Zn diet to levels comparable with those observed in rats fed a standard diet, indicating that an elevation in systemic BP levels seen in rats fed a high Zn versus a standard diet is presumably brought by a reduction in the action of the vasodilator, NO resulting from an increase in the action of superoxide. The activity of Cu/Zn-SOD in the thoracic aorta was significantly reduced in rats fed a high Zn diet relative to rats fed a standard diet, appearing to at least in part, play a role in an increase in the action of superoxide in the vessel wall of rats fed a high Zn diet. CONCLUSIONS: Excessive Zn intake may be a factor to elevate systemic BP levels in a normotensive state presumably through the oxidative stress caused by superoxide.