Maximum likelihood estimation in the additive hazards model.

The additive hazards model specifies the effect of covariates on the hazard in an additive way, in contrast to the popular Cox model, in which it is multiplicative. As the non-parametric model, additive hazards offer a very flexible way of modeling time-varying covariate effects. It is most commonly estimated by ordinary least squares. In this paper, we consider the case where covariates are bounded, and derive the maximum likelihood estimator under the constraint that the hazard is non-negative for all covariate values in their domain. We show that the maximum likelihood estimator may be obtained by separately maximizing the log-likelihood contribution of each event time point, and we show that the maximizing problem is equivalent to fitting a series of Poisson regression models with an identity link under non-negativity constraints. We derive an analytic solution to the maximum likelihood estimator. We contrast the maximum likelihood estimator with the ordinary least-squares estimator in a simulation study and show that the maximum likelihood estimator has smaller mean squared error than the ordinary least-squares estimator. An illustration with data on patients with carcinoma of the oropharynx is provided.

Phosphorylation of SPT5 by CDKD;2 Is Required for VIP5 Recruitment and Normal Flowering in Arabidopsis thaliana.

The elongation factor suppressor of Ty 5 homolog (Spt5) is a regulator of transcription and histone methylation. In humans, phosphorylation of SPT5 by P-TEFb, a protein kinase composed of Cyclin-dependent kinase 9 (CDK9) and cyclin T, interacts with the RNA polymerase II-associated factor1 (PAF1) complex. However, the mechanism of SPT5 phosphorylation is not well understood in plants. Here, we examine the function of SPT5 in Arabidopsis thaliana and find that spt5 mutant flowers early under long-day and short-day conditions. SPT5 interacts with the CDK-activating kinase 4 (CAK4; CDKD;2) and is specifically phosphorylated by CDKD;2 at threonines. The phosphorylated SPT5 binds VERNALIZATION INDEPENDENCE5 (VIP5), a subunit of the PAF1 complex. Genetic analysis showed that VIP5 acts downstream of SPT5 and CDKD;2 Loss of SPT5 or CDKD;2 function results in early flowering because of decreased amounts of FLOWERING LOCUS C (FLC) transcript. Importantly, CDKD;2 and SPT5 are required for the deposition of VIP5 and the enhancement of trimethylation of histone 3 lysine 4 in the chromatin of the FLC locus. Together, our results provide insight into the mechanism by which the Arabidopsis elongation factor SPT5 recruits the PAF1 complex via the posttranslational modification of proteins and suggest that the phosphorylation of SPT5 by CDKD;2 enables it to recruit VIP5 to regulate chromatin and transcription in Arabidopsis.

Expedition to the missing link: Long noncoding RNAs in cardiovascular diseases.

With the advances in deep sequencing-based transcriptome profiling technology, it is now known that human genome is transcribed more pervasively than previously thought. Up to 90% of the human DNA is transcribed, and a large proportion of the human genome is transcribed as long noncoding RNAs (lncRNAs), a heterogenous group of non-coding transcripts longer than 200 nucleotides. Emerging evidence suggests that lncRNAs are functional and contribute to the complex regulatory networks involved in cardiovascular development and diseases. In this article, we will review recent evidence on the roles of lncRNAs in the biological processes of cardiovascular development and disorders. The potential applications of lncRNAs as biomarkers and targets for therapeutics are also discussed.

Immunomodulatory and Antioxidant Effects of Polysaccharides from Gynostemma pentaphyllum Makino in Immunosuppressed Mice.

The immunomodulatory and antioxidant activities of crude polysaccharides extracted from Gynostemma pentaphyllum Makino (GPMPP) were investigated. GPMPP was composed of rhamnose, arabinose, xylose, mannose, glucose and galactose in the molar ratio of 1.39:3.76:1.00:1.64:4.98:5.88. In vivo studies showed GPMPP significantly increased the spleen and thymus indices, activated the macrophage phagocytosis and NK cells, and exhibited activity on none or Con A/LPS-stimulated splenocytes in a dose-dependent manner in C57BL/6 mice. Moreover, GPMPP elevated CD4⁺ T lymphocyte counts as well as the CD4⁺/CD8⁺ ratio dose-dependently, and it increased IL-2 level in the sera and spleen of Cy-immunosuppressed mice. Furthermore, GPMPP significantly increased the SOD, GSH-Px, T-AOC, GSH and CAT level, and decreased the MDA level. The results showed that GPMPP might play an important role in prevention of oxidative damage in immunological system. These findings indicate GPMPP has immunomodulatory activity in vivo and seems to be an effective natural immunomodulatory agent.

Intrathecal spinal progenitor cell transplantation for the treatment of neuropathic pain.

Injury to, or dysfunction of, the nervous system can lead to spontaneous pain, hyperalgesia, and/or allodynia. It is believed that the number and activity of GABAergic neurons gradually decreases over the dorsal horn. Glutamic acid decarboxylase (GAD) immunocompetence has been demonstrated on spinal progenitor cells (SPCs) cultivated in vitro. The intrathecal implantation of these cultivated progenitor cells may provide a means of alleviating neuropathic pain. Chronic constriction injury (CCI) of the sciatic nerve was used to induce chronic neuropathic pain in the hind paw of rats. SPCs (1 x 10(6)) were implanted intrathecally on the third day after the CCI surgery. The behavioral response to thermal hyperalgesia was observed and recorded during the 14 days postsurgery. Various techniques were utilized to trace the progenitor cells, confirm the differentiation, and identify the neurotransmitters involved. GAD immunoactivity was revealed for 65% of the cultivated spinal progenitor cells in our study. We also determined that transplanted cells could survive more than 3 weeks postintrathecal implantation. Significant reductions were demonstrated for responses to thermal stimuli for the CCI rats that had received intrathecal SPC transplantation. A novel intrathecal delivery with SPCs reduced CCI-induced neuropathic pain.

Body Weight-Related ionized hypomagnesemia in pediatric patients undergoing cardiopulmonary bypass for surgical repair of congenital cardiac defects.

STUDY OBJECTIVES: To examine the serial time course of perioperative plasma ionized magnesium (iMg(2+)) concentrations and to analyze the plasma iMg(2+) concentrations in children with different body mass who were undergoing open-heart surgery. DESIGN: Randomized, single-blinded study. SETTING: University-affiliated hospital of an academic medical institution. PATIENTS: 38 children undergoing open-heart surgery. INTERVENTIONS: Patients were divided into three groups according to their body mass: Group 1 (n = 12) <10 kg, Group 2 (n = 13) 10 kg to 20 kg, and Group 3 (n = 13) >20 kg. MEASUREMENTS: The relationship of iMg(2+) among the three groups of different body mass were analyzed at five different time intervals during the operation: induction of anesthesia, 5 minutes and 30 minutes after the onset of cardiopulmonary bypass (CPB), the beginning of rewarming, and the end of surgery. MAIN RESULTS: iMg(2+) levels at 5 minutes after onset of CPB in patients weighing less than 20 kg (Groups 1 and 2) differed with those weighing more than 20 kg (Group 3) (p = 0.007 and 0.013). However, there was no difference in the iMg(2+) levels between Groups 1 and 2 (p = 0.993). In addition, iMg(2+) levels at 5 minutes after onset of bypass correlated well (r(2) = 0.66) in children with body mass less than 20 kg. CONCLUSIONS: Low levels of ionized magnesium is an important finding in patients at the onset of CPB, which correlates well with the body mass of patients weighing less than 20 kg, and could be predicted by the regression curve. Based on these findings, hypomagnesemia can be prevented during CPB.

Intramuscular electroporation with the pro-opiomelanocortin gene in rat adjuvant arthritis.

Endogenous opioid peptides have an essential role in the intrinsic modulation and control of inflammatory pain, which could be therapeutically useful. In this study, we established a muscular electroporation method for the gene transfer of pro-opiomelanocortin (POMC) in vivo and investigated its effect on inflammatory pain in a rat model of rheumatoid arthritis. The gene encoding human POMC was inserted into a modified pCMV plasmid, and 0-200 microg of the plasmid-POMC DNA construct was transferred into the tibialis anterior muscle of rats treated with complete Freund's adjuvant (CFA) with or without POMC gene transfer by the electroporation method. The safety and efficiency of the gene transfer was assessed with the following parameters: thermal hyperalgesia, serum adrenocorticotropic hormone (ACTH) and endorphin levels, paw swelling and muscle endorphin levels at 1, 2 and 3 weeks after electroporation. Serum ACTH and endorphin levels of the group into which the gene encoding POMC had been transferred were increased to about 13-14-fold those of the normal control. These levels peaked 1 week after electroporation and significantly decreased 2 weeks after electroporation. Rats that had received the gene encoding POMC had less thermal hypersensitivity and paw swelling than the non-gene-transferred group at days 3, 5 and 7 after injection with CFA. Our promising results showed that transfer of the gene encoding POMC by electroporation is a new and effective method for its expression in vivo, and the analgesic effects of POMC cDNA with electroporation in a rat model of rheumatoid arthritis are reversed by naloxone.

Inhibition of experimental angiogenesis of cornea by somatostatin.

BACKGROUND: This study evaluated the inhibitory activity of somatostatin 14 on the angiogenesis of cornea in vivo. METHODS: Corneal neovascularization was induced with a pellet containing 90 ng of basic fibroblast growth factor (bFGF) in a rat corneal pocket model. Three kinds of pellets were made containing bFGF plus somatostatin (SST) 0 ng, 20 ng and 200 ng for the control group, group 1 and group 2, respectively. Neovascularization was observed biomicroscopically from day 4 to day 8, and the corneas were then examined for changes in histology. Quantitation of angiogenesis in the cornea was accomplished by caliper and image analysis. RESULTS: The 200-ng dose of SST showed significant inhibition of both length and area of neovascularization on day 7 (0.62+/-0.11 mm vs 1.29+/-0.16 mm, 0.50+/-0.16 mm2 vs 1.35+/-0.29mm2, group 2 vs control; P<0.05). The 20 ng of somatostatin did not demonstrate any significant inhibition of neovascularization compared with the control group. CONCLUSION: Our study demonstrated that SST 14 can reduce bFGF-induced corneal angiogenesis. This shows the potential value of somatostatin in the treatment of corneal neovascularization.