The rat suprachiasmatic nucleus: the master clock ticks at 30?Hz

AbstractThe suprachiasmatic nucleus (SCN) of the hypothalamus has an essential role in orchestrating circadian rhythms of behaviour and physiology. In the present study, we recorded from single SCN neurons in urethane‐anaesthetized rats, categorized them by the statistical features of their electrical activity and by their responses to light, and examined how activity in the light phase differs from activity in the dark phase. We classified cells as light‐on cells or light‐off cells according to how their firing rate changed in acute response to light, or as non‐responsive cells. In both sets of light‐responsive neurons, responses to light were stronger at subjective night than in subjective day. Neuronal firing patterns were analysed by constructing hazard functions from interspike interval data. For most light‐responsive cells, the hazard functions showed a multimodal distribution, with a harmonic sequence of modes, indicating that spike activity was driven by an oscillatory input with a fundamental frequency of close to 30 Hz; this harmonic pattern was rarely seen in non‐responsive SCN cells. The frequency of the rhythm was the same in light‐on cells as in light‐off cells, was the same in subjective day as at subjective night, and was unaffected by exposure to light. Paired recordings indicated that the discharge of adjacent light‐responsive neurons was very tightly synchronized, consistent with electrical coupling.     

Renal damage in obstructive nephropathy is decreased in Skp2-deficient mice

Ubiquitin-dependent degradation of the cyclin-dependent kinase inhibitor p27 mediated by SCF-Skp2 ubiquitin ligase is involved in cell cycle regulation. Proliferation of tubular cells is a characteristic feature in obstructed kidneys of unilateral ureteral obstruction. Comparing Skp2(+/+) mice with Skp2(-/-) mice, we investigated the involvement of Skp2, a component of SCF-Skp2 ubiquitin ligase for p27, in the progression of renal lesions in unilateral ureteral obstructed kidneys. mRNA expression of Skp2 was markedly increased in the obstructed kidneys from Skp2(+/+) mice and peaked 3 days after unilateral ureteral obstruction. Renal atrophy, tubular dilatation, tubulointerstitial fibrosis, and increases in alpha-smooth muscle actin expression, the number of tubular cells, and proliferating tubular cells positive for Ki67 were observed in the obstructed kidneys from Skp2(+/+) mice; however, these findings were significantly attenuated in Skp2(-/-) mice. The p27 protein level was increased in the obstructed kidneys but was significantly greater in Skp2(-/-) mice. The number of Ki67-positive p27-negative cells was lower in obstructed kidneys from Skp2(-/-) mice than Skp2(+/+) mice, whereas that of Ki67-negative p27-positive cells was greater in Skp2(-/-) mice. These findings suggest that p27 accumulation, which results from SCF-Skp2 ubiquitin ligase deficiency in Skp2(-/-) mice, is involved in the amelioration of renal damage induced by obstructive nephropathy.     

IL-15 exacerbates collagen-induced arthritis with an enhanced CD4+ T cell response to produce IL-17

IL-15 is thought to be involved in the pathogenesis of rheumatoid arthritis (RA). We found that IL-15 plays an important role in the development of murine collagen-induced arthritis (CIA). The incidence and severity of CIA were slightly decreased in IL-15 KO mice but were increased in IL-15 Tg mice compared with wild-type (WT) mice. The levels of type II collagen (CII)-specific IL-17 production were significantly increased in IL-15 Tg mice compared with WT mice with CIA. Expression of IL-23R was up-regulated in CD4(+) T cells in IL-15 Tg mice but down-regulated in IL-15 KO mice compared with WT mice. In correlation with the expression levels of IL-23R, IL-17 production by CD4(+) T cells in response to exogenous IL-23 was increased in IL-15 Tg mice compared with WT mice. Furthermore, exogenous IL-15 synergized with IL-23 to induce CII-specific IL-17 production by CD4(+) T cells in vitro. Taken together, these results indicate that IL-15 plays an important role in the progression of CIA through increasing antigen-specific IL-17 production by CD4(+) T cells.     

Disruption of paired-associate learning in rat offspring perinatally exposed to dioxins

The prevalence of cognitive abnormalities in children has partly been ascribed to environmental chemical exposure. Appropriate animal models and tools for evaluating higher brain function are required to examine this problem. A recently developed behavioral test in which rats learn six unique flavor-location pairs in a test arena was used to evaluate paired-associate learning, a hallmark of the higher cognitive function that is essential to language learning in humans. Pregnant Long-Evans rats were dosed by gavage with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) at a dose of  0, 200, or 800 ng/kg (referred as Control, TCDD-200, TCDD-800, TBDD-200, or TBDD-800, hereafter) on gestational day 15, and the offspring was tested during adulthood. Paired-associate learning was found to be impaired in the TCDD-200 and TBDD-200 groups, but not in either group exposed to 800 ng/kg, the observations of which were ensured by non-cued trials. As for the emotional aspect, during habituation, the TCDD-200 and TBDD-200 groups showed significantly longer latencies to enter the test arena from a start box than the Control, TCDD-800, and TBDD-800 groups, suggesting that the TCDD-200 and TBDD-200 groups manifested anxiety-like behavior. Thus, both the chlorinated dioxin and its brominated congener affected higher brain function to a similar extent in a nearly identical manner. Use of the behavioral test that can evaluate paired-associate learning in rats demonstrated that in utero and lactational exposure to not only TCDD but also TBDD perturbed higher brain function in rat offspring in a nonmonotonic manner.     

Carotid intima-media thickness is increased in subjects with ischemic heart disease having a familial incidence

OBJECTIVES: A family history of ischemic heart disease (IHD) is an independent risk factor for cardiovascular events. However, the mechanisms underlying this susceptibility have not been fully elucidated. The authors hypothesized that an important mediator of the familial incidence of IHD is subclinical atherosclerosis, which is detectable by noninvasive imaging. METHODS: One hundred forty-seven consecutive subjects (mean age 61.9 years, 57% men) were studied for one year using carotid ultra-sonogrophy for general medical screening, and familial IHD events were validated. Using a 7.5 MHz linear array transducer, carotid intima-media thickness (IMT) and carotid plaque were assessed. Subjects were subsequently divided into four groups based on the severity of IMT. RESULTS: The familial incidence of IHD and incidence of plaque were associated with the severity of IMT. No significant differences in risk factors were found between subjects with and without a family history of IHD. CONCLUSIONS: These findings suggest that subclinical atherosclerosis, as assessed in the carotid arteries, is more prevalent in individuals with a family history of IHD.     

Endonasal flap suture-dacryocystorhinostomy (eFS-DCR): a new surgical technique for nasolacrimal duct obstruction (NLDO)

Conclusion: Endonasal flap suture-dacryocystorhinostomy (eFS- DCR) is a new and valuable technique for the treatment of nasolacrimal duct obstruction (NLDO). This technique could improve the success rate of endonasal DCR in comparison to external DCR. Objective: The standard procedure for NLDO is DCR. DCR can be performed via either an external or endonasal approach. External DCR is now regarded as the gold standard in the treatment of NLDO because of its higher success rate. However, we report a new endonasal surgical technique, eFS-DCR, and assess its efficacy by comparison with the standard endonasal DCR. Methods: We prospectively investigated a series of 62 consecutive patients with NLDO undergoing endonasal DCR. There were two surgical intervention groups: group 1 (24 patients, 28 sites) undergoing endonasal DCR without eFS; and group 2 (38 patients, 47 sites) undergoing eFS-DCR. Study end points were success rate, the ostium diameter (OD) of the lacrimal sac after DCR, and the duration of stent placement. We compared the two groups on these three points. Results: The success rate was 78.6% (22 of 28 sites) for group 1 (DCR without eFS) and 97.9% (46 of 47 sites) for group 2 (eFS-DCR). The ostium size in patients in group 2 was larger than that in group 1. The median time for the duration of stent placement was 42.5 days for group 1 and 31.5 days for group 2. There was a statistical difference (p < 0.01) in all these parameters between the two groups.     

Therapy with immunoglobulin in patients with acute myocarditis and cardiomyopathy: analysis of leukocyte balance

Intravenous immunoglobulin (IVIG) therapy has been used to treat several autoimmune or inflammatory diseases. We conducted a clinical trial of immunoglobulin therapy for acute myocarditis. The study consisted of two projects: (1) a comparison of prognosis between patients treated with and those not treated with IVIG in a multi-center study; (2) analyses of inflammatory cytokines and blood cell profiles in a substudy. In (1), 15 patients were treated with IVIG (1–2 g/kg, over 2 days), whereas 26 were untreated. There was a statistically significant difference between the survival curves of the patients treated with IVIG and the survival curves of those not treated with IVIG. There was no significant difference between the IVIG-treated and untreated groups in terms of clinical parameters of the acute and chronic phases. In (2), 10 patients were treated with IVIG and 6 were untreated. In both groups, all of the data except for changes in the fraction of lymphocytes and the fraction of monocytes decreased due to the treatment or during the course. In patients in the IVIG group, the percentage of peripheral eosinophils was decreased and the percentage of peripheral monocytes was increased by this treatment when they were compared with the pretreatment data. Therefore, therapy with IVIG seems to be a promising treatment for acute myocarditis given that it improves the clinical course, which may be due to modulation of inflammatory cytokines and the peripheral leukocyte balance.